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Sample records for root density dynamics

  1. Seasonal dynamics of fine root biomass, root length density, specific root length, and soil resource availability in a Larix gmelinii plantation

    Institute of Scientific and Technical Information of China (English)

    CHENG Yunhuan; HAN Youzhi; WANG Qingcheng; WANG Zhengquan

    2006-01-01

    Fine root tumover is a major pathway for carbon and nutrient cycling in terrestrial ecosystems and is most likely sensitive to many global change factors.Despite the importance of fine root turnover in plant C allocation and nutrient cycling dynamics and the tremendous research efforts in the past,our understanding of it remains limited.This is because the dynamics processes associated with soil resources availability are still poorly understood.Soil moisture,temperature,and available nitrogen are the most important soil characteristics that impact fine root growth and mortality at both the individual root branch and at the ecosystem level.In temperate forest ecosystems,seasonal changes of soil resource availability will alter the pattern of carbon allocation to belowground.Therefore,fine root biomass,root length density(RLD)and specific root length(SRL)vary during the growing season.Studying seasonal changes of fine root biomass,RLD,and SRL associated with soil resource availability will help us understand the mechanistic controls of carbon to fine root longevity and turnover.The objective of this study was to understand whether seasonal variations of fine root biomass,RLD and SRL were associated with soil resource availability,such as moisture,temperature,and nitrogen,and to understand how these soil components impact fine root dynamics in Larix gmelinii plantation.We used a soil coring method to obtain fine root samples(≤2 mm in diameter)every month from Mav to October in 2002 from a 17-year-old L.gmelinii plantation in Maoershan Experiment Station,Northeast Forestry University,China.Seventy-two soil cores(inside diameter 60 mm;depth intervals:0-10 cm,10-20 cm,20-30 cm)were sampled randomly from three replicates 25 m×30 m plots to estimate fine root biomass(live and dead),and calculate RLD and SRL.Soil moisture,temperature,and nitrogen(ammonia and nitrates)at three depth intervals were also analyzed in these plots.Results showed that the average standing fine

  2. Effects of fine root length density and root biomass on soil preferential flow in forest ecosystems

    Directory of Open Access Journals (Sweden)

    Yinghu Zhang

    2015-04-01

    Full Text Available Aim of study: The study was conducted to characterize the impacts of plant roots systems (e.g., root length density and root biomass on soil preferential flow in forest ecosystems. Area of study: The study was carried out in Jiufeng National Forest Park, Beijing, China. Material and methods: The flow patterns were measured by field dye tracing experiments. Different species (Sophora japonica Linn,Platycladus orientalis Franco, Quercus dentata Thunbwere quantified in two replicates, and 12 soil depth were applied. Plant roots were sampled in the sieving methods. Root length density and root biomass were measured by WinRHIZO. Dye coverage was implied in the image analysis, and maximum depth of dye infiltration by direct measurement. Main results: Root length density and root biomass decreased with the increasing distance from soil surface, and root length density was 81.6% higher in preferential pathways than in soil matrix, and 66.7% for root biomass with respect to all experimental plots. Plant roots were densely distributed in the upper soil layers. Dye coverage was almost 100% in the upper 5-10 cm, but then decreased rapidly with soil depth. Root length density and root biomass were different from species: Platycladus orientalis Franco > Quercus dentata Thunb > Sophora japonica Linn. Research highlights: The results indicated that fine roots systems had strong effects on soil preferential flow, particularly root channels enhancing nutrition transport across soil profiles in forest dynamics.

  3. Plant root tortuosity: an indicator of root path formation in soil with different composition and density

    Science.gov (United States)

    Popova, Liyana; van Dusschoten, Dagmar; Nagel, Kerstin A.; Fiorani, Fabio; Mazzolai, Barbara

    2016-01-01

    Background and Aims Root soil penetration and path optimization are fundamental for root development in soil. We describe the influence of soil strength on root elongation rate and diameter, response to gravity, and root-structure tortuosity, estimated by average curvature of primary maize roots. Methods Soils with different densities (1·5, 1·6, 1·7 g cm−3), particle sizes (sandy loam; coarse sand mixed with sandy loam) and layering (monolayer, bilayer) were used. In total, five treatments were performed: Mix_low with mixed sand low density (three pots, 12 plants), Mix_medium - mixed sand medium density (three pots, 12 plants), Mix_high - mixed sand high density (three pots, ten plants), Loam_low sandy loam soil low density (four pots, 16 plants), and Bilayer with top layer of sandy loam and bottom layer mixed sand both of low density (four pots, 16 plants). We used non-invasive three-dimensional magnetic resonance imaging to quantify effects of these treatments. Key Results Roots grew more slowly [root growth rate (mm h–1); decreased 50 %] with increased diameters [root diameter (mm); increased 15 %] in denser soils (1·7 vs. 1·5 g cm–3). Root response to gravity decreased 23 % with increased soil compaction, and tortuosity increased 10 % in mixed sand. Response to gravity increased 39 % and tortuosity decreased 3 % in sandy loam. After crossing a bilayered–soil interface, roots grew more slowly, similar to roots grown in soil with a bulk density of 1·64 g cm–3, whereas the actual experimental density was 1·48±0·02 g cm–3. Elongation rate and tortuosity were higher in Mix_low than in Loam_low. Conclusions The present study increases our existing knowledge of the influence of physical soil properties on root growth and presents new assays for studying root growth dynamics in non-transparent media. We found that root tortuosity is indicative of root path selection, because it could result from both mechanical deflection and

  4. Character sums for primitive root densities

    CERN Document Server

    Lenstra, H W; Stevenhagen, P

    2011-01-01

    It follows from the work of Artin and Hooley that, under assumption of the generalized Riemann hypothesis, the density of the set of primes $q$ for which a given non-zero rational number $r$ is a primitive root modulo $q$ can be written as an infinite product $\\prod_p \\delta_p$ of local factors $\\delta_p$ reflecting the degree of the splitting field of $X^p-r$ at the primes $p$, multiplied by a somewhat complicated factor that corrects for the `entanglement' of these splitting fields. We show how the correction factors arising in Artin's original primitive root problem and some of its generalizations can be interpreted as character sums describing the nature of the entanglement. The resulting description in terms of local contributions is so transparent that it greatly facilitates explicit computations, and naturally leads to non-vanishing criteria for the correction factors.

  5. Methane and Root Dynamics in Arctic Soil

    DEFF Research Database (Denmark)

    D'Imperio, Ludovica

    on the global climate. We investigated two aspects of arctic ecosystem dynamics which are not well represented in climatic models: i) soil methane (CH4) oxidation in dry heath tundra and barren soils and ii) root dynamics in wetlands. Field measurements were carried out during the growing season in Disko Island......, West Greenland, and CH4 and root dynamics were assessed in response to experimentally increased winter snow precipitation, summer warming and their interaction to better understand their contribution to the C balance of the Arctic. Our results indicate that both the dry heath and barren soils have...... from wetlands in a future warmer climate. At the wet fen increased winter snow precipitation delayed the onset of the growing season of about a week and reduced the relative fine root production. The use of minirhizotrons improved our understanding of root growth and phenology. Total root number...

  6. Systems approaches to study root architecture dynamics

    Directory of Open Access Journals (Sweden)

    Candela eCuesta

    2013-12-01

    Full Text Available The plant root system is essential for providing anchorage to the soil, supplying minerals and water, and synthesizing metabolites. It is a dynamic organ modulated by external cues such as environmental signals, water and nutrients availability, salinity and others. Lateral roots are initiated from the primary root post-embryonically, after which they progress through discrete developmental stages which can be independently controlled, providing a high level of plasticity during root system formation.Within this review, main contributions are presented, from the classical forward genetic screens to the more recent high-throughput approaches, combined with computer model predictions, dissecting how lateral roots and thereby root system architecture is established and developed.

  7. Methane and Root Dynamics in Arctic Soil

    DEFF Research Database (Denmark)

    D'Imperio, Ludovica

    on the global climate. We investigated two aspects of arctic ecosystem dynamics which are not well represented in climatic models: i) soil methane (CH4) oxidation in dry heath tundra and barren soils and ii) root dynamics in wetlands. Field measurements were carried out during the growing season in Disko Island...

  8. Compensation in Root Water Uptake Models Combined with Three-Dimensional Root Length Density Distribution

    NARCIS (Netherlands)

    Heinen, M.

    2014-01-01

    A three-dimensional root length density distribution function is introduced that made it possible to compare two empirical uptake models with a more mechanistic uptake model. Adding a compensation component to the more empirical model resulted in predictions of root water uptake distributions

  9. Density of the continental roots: Compositional and thermal contributions

    Science.gov (United States)

    Kaban, M.K.; Schwintzer, P.; Artemieva, I.M.; Mooney, W.D.

    2003-01-01

    The origin and evolution of cratonic roots has been debated for many years. Precambrian cratons are underlain by cold lithospheric roots that are chemically depleted. Thermal and petrologic data indicate that Archean roots are colder and more chemically depleted than Proterozoic roots. This observation has led to the hypothesis that the degree of depletion in a lithospheric root depends mostly on its age. Here we test this hypothesis using gravity, thermal, petrologic, and seismic data to quantify differences in the density of cratonic roots globally. In the first step in our analysis we use a global crustal model to remove the crustal contribution to the observed gravity. The result is the mantle gravity anomaly field, which varies over cratonic areas from -100 to +100 mGal. Positive mantle gravity anomalies are observed for cratons in the northern hemisphere: the Baltic shield, East European Platform, and the Siberian Platform. Negative anomalies are observed over cratons in the southern hemisphere: Western Australia, South America, the Indian shield, and Southern Africa. This indicates that there are significant differences in the density of cratonic roots, even for those of similar age. Root density depends on temperature and chemical depletion. In order to separate these effects we apply a lithospheric temperature correction using thermal estimates from a combination of geothermal modeling and global seismic tomography models. Gravity anomalies induced by temperature variations in the uppermost mantle range from -200 to +300 mGal, with the strongest negative anomalies associated with mid-ocean ridges and the strongest positive anomalies associated with cratons. After correcting for thermal effects, we obtain a map of density variations due to lithospheric compositional variations. These maps indicate that the average density decrease due to the chemical depletion within cratonic roots varies from 1.1% to 1.5%, assuming the chemical boundary layer has the same

  10. Impact factors on fine root seasonal dynamics in Fraxinus mandshurica plantations

    Institute of Scientific and Technical Information of China (English)

    MEI Li; HAN Youzhi; YU Shuiqiang; SHI Jianwei; WANG Zhengquan

    2007-01-01

    Fine root turnover plays important roles in carbon allocation and nutrient cycling in forest ecosystems.Seasonal dynamics of fine roots is critical for understanding the processes of fine root turnover.From May to October 2002,soil core method was used for estimating the seasonal pattern of fine root (diameter < 1 mm) parameters (biomass,specific root length (SRL) and root length density (RLD)) in a Manchurian ash (Fraxinus mandshurica) plantation located at the Maoershan Experiment Station,Heilongjiang Province,northeast of China.The relationships of fine root biomass,SRL and RLD with available nitrogen in soil,average soil temperature per month in 10 cm depth and soil moisture content were analyzed.Seasonal variation of fine root biomass was significant (P < 0.05).The peak values of fine root biomass were observed both in spring and in autumn,but SRL and RLD were the highest in spring and lowest in autumn.Specific root length and root length density were higher in spring and summer,which means that fine root diameter was thinner.In autumn,both parameters decreased significantly due to secondary incrassation of fine root diameter or the increase of tissue density.Seasonal dynamics of fine roots was associated with available nitrogen in soil,soil temperature in 10 cm depth and moisture content.Fine root biomass has a significant relationship with available NH4+-N in soil.Available NO3--N in soil,soil temperature in 10-cm depth and moisture content have a positive correlation with fine root biomass,SRL and RLD,although these correlations are not significant (P >0.05).But the compound effects of soil available N,soil temperature and soil moisture content are significant to every root parameter.The variations of these three root parameters in different seasons show different physiological and ecological functions in different growing periods.

  11. Dynamics of heterorhizic root systems: protoxylem groups within the fine-root system of Chamaecyparis obtusa.

    Science.gov (United States)

    Hishi, Takuo; Takeda, Hiroshi

    2005-08-01

    To understand the physiology of fine-root functions in relation to soil organic sources, the heterogeneity of individual root functions within a fine-root system requires investigation. Here the heterogeneous dynamics within fine-root systems are reported. The fine roots of Chamaecyparis obtusa were sampled using a sequential ingrowth core method over 2 yr. After color categorization, roots were classified into protoxylem groups from anatomical observations. The root lengths with diarch and triarch groups fluctuated seasonally, whereas the tetrarch root length increased. The percentage of secondary root mortality to total mortality increased with increasing amounts of protoxylem. The carbon : nitrogen ratio indicated that the decomposability of primary roots might be greater than that of secondary roots. The position of diarch roots was mostly apical, whereas tetrarch roots tended to be distributed in basal positions within the root architecture. We demonstrate the heterogeneous dynamics within a fine-root system of C. obtusa. Fine-root heterogeneity should affect soil C dynamics. This heterogeneity is determined by the branching position within the root architecture.

  12. [Seasonal dynamics of quantitative and morphological traits of poplar fine roots and their differences between successive rotation plantations].

    Science.gov (United States)

    Wang, Yan-ping; Xu, Tan; Zhu, Wan-rui; Wang, Qi-tong; Liu, Meng-ling; Wang, Hua-tian; Li, Chuan-rong; Dong, Yu-feng

    2016-02-01

    Based on the fine root samples of the first and second generations of poplar (Populus x euramericana ' Neva'), this study examined the response of quantitative and morphological traits of fine roots of different orders and the difference between generations. The results showed that, the quantitative traits of fine roots, such as root length, root surface area and root biomass, presented obvious seasonal variation, and the fine root traits had obvious difference among root orders. The quantitative traits of lower-order fine roots showed significant seasonal difference, and the fine root biomass increased in the growing season and then decreased significantly. The specific root length (SRL) of higher-order roots also showed significant change with season, while the root length density (RLD) and root tissue density (RTD) changed a little. The successive rotation resulted in the significant increase of root length, root biomass, SRL and RLD of 1-2 orders in the growing season. The quantitative traits of first order root significantly positively correlated with soil temperature and moisture, and significantly negatively correlated with the soil organic matter and soil available nitrogen content. However, the quantitative traits of second order root only showed significant correlation with soil nutrient content. The seasonal dynamics of poplar fine roots and the difference between successive rotation plantations implied carbon investment change of poplar to roots. Soil nutrient deficiency induced more carbon investment into roots, and this carbon allocation pattern might affect the aboveground productivity of poplar plantation.

  13. Root dynamics and global change: seeking an ecosystem perspective

    National Research Council Canada - National Science Library

    NORBY, RICHARD J; JACKSON, ROBERT B

    2000-01-01

    ...? What are the consequences of root responses to plant physiological processes? What are the implications of root dynamics to soil microbial communities and the fate of carbon in soil? Ecosystem...

  14. Capturing Arabidopsis root architecture dynamics with ROOT-FIT reveals diversity in responses to salinity.

    Science.gov (United States)

    Julkowska, Magdalena M; Hoefsloot, Huub C J; Mol, Selena; Feron, Richard; de Boer, Gert-Jan; Haring, Michel A; Testerink, Christa

    2014-11-01

    The plant root is the first organ to encounter salinity stress, but the effect of salinity on root system architecture (RSA) remains elusive. Both the reduction in main root (MR) elongation and the redistribution of the root mass between MRs and lateral roots (LRs) are likely to play crucial roles in water extraction efficiency and ion exclusion. To establish which RSA parameters are responsive to salt stress, we performed a detailed time course experiment in which Arabidopsis (Arabidopsis thaliana) seedlings were grown on agar plates under different salt stress conditions. We captured RSA dynamics with quadratic growth functions (root-fit) and summarized the salt-induced differences in RSA dynamics in three growth parameters: MR elongation, average LR elongation, and increase in number of LRs. In the ecotype Columbia-0 accession of Arabidopsis, salt stress affected MR elongation more severely than LR elongation and an increase in LRs, leading to a significantly altered RSA. By quantifying RSA dynamics of 31 different Arabidopsis accessions in control and mild salt stress conditions, different strategies for regulation of MR and LR meristems and root branching were revealed. Different RSA strategies partially correlated with natural variation in abscisic acid sensitivity and different Na(+)/K(+) ratios in shoots of seedlings grown under mild salt stress. Applying root-fit to describe the dynamics of RSA allowed us to uncover the natural diversity in root morphology and cluster it into four response types that otherwise would have been overlooked.

  15. Dynamical maps and density matrices

    Energy Technology Data Exchange (ETDEWEB)

    Asorey, M [Departamento de Fisica Teorica. Facultad de Ciencias. Universidad de Zaragoza, 50009 Zaragoza (Spain); Kossakowski, A [Institute of Physics, Nicolaus Copernicus University Torun 87-100 (Poland); Marmo, G [Dipartimento di Scienze Fisiche, Universita Federico II di Napoli and INFN, Sezione di Napoli Complesso University di Monte Sant' Angelo, Via Cintia, 80125 Napoli (Italy); Sudarshan, E C G [Department of Physics. University of Texas at Austin Austin, Texas 78712-1081 (United States)

    2009-11-01

    The relations between dynamical maps and quantum states of bipartite systems are analyzed from the perspective of quantum conditional probability. In particular, we explore new interesting relations between completely positive maps, which correspond to quantum channels, and states of bipartite systems which correspond to correlations between the initial and final states. The new connection emerges in a natural way from the generalisation of the classical concept of conditional probability. We develop applications of these relations which prove to be very useful in both directions, either for the classification of positive maps which are not completely positive, the classification of non-decomposable dynamical maps or for the classification of positive partial transpose and entangled states.

  16. Particle conservation in dynamical density functional theory.

    Science.gov (United States)

    de Las Heras, Daniel; Brader, Joseph M; Fortini, Andrea; Schmidt, Matthias

    2016-06-22

    We present the exact adiabatic theory for the dynamics of the inhomogeneous density distribution of a classical fluid. Erroneous particle number fluctuations of dynamical density functional theory are absent, both for canonical and grand canonical initial conditions. We obtain the canonical free energy functional, which yields the adiabatic interparticle forces of overdamped Brownian motion. Using an exact and one of the most advanced approximate hard core free energy functionals, we obtain excellent agreement with simulations. The theory applies to finite systems in and out of equilibrium.

  17. Dynamic root uptake model for neutral lipophilic organics

    DEFF Research Database (Denmark)

    Trapp, Stefan

    2002-01-01

    and output to stem with the transpiration stream plus first-order metabolism and dilution by exponential growth. For chemicals with low or intermediate lipophilicity (log Kow , 2), there was no relevant difference between dynamic model and equilibrium approach. For lipophilic compounds, the dynamic model...... approach. Very lipophilic compounds (e.g., DDT) diffuse very slowly into plant tissue, so they are likely to remain in the peel of root vegetables. In addition, a dynamic (steady-state) flux model for uptake with transpiration water into thick roots is presented. The model considers input from soil...

  18. Dynamical quorum sensing: Population density encoded in cellular dynamics

    Science.gov (United States)

    De Monte, Silvia; d'Ovidio, Francesco; Danø, Sune; Sørensen, Preben Graae

    2007-01-01

    Mutual synchronization by exchange of chemicals is a mechanism for the emergence of collective dynamics in cellular populations. General theories exist on the transition to coherence, but no quantitative, experimental demonstration has been given. Here, we present a modeling and experimental analysis of cell-density-dependent glycolytic oscillations in yeast. We study the disappearance of oscillations at low cell density and show that this phenomenon occurs synchronously in all cells and not by desynchronization, as previously expected. This study identifies a general scenario for the emergence of collective cellular oscillations and suggests a quorum-sensing mechanism by which the cell density information is encoded in the intracellular dynamical state. PMID:18003917

  19. Increased root hair density by loss of WRKY6 in Arabidopsis thaliana

    Directory of Open Access Journals (Sweden)

    Markus G. Stetter

    2017-01-01

    Full Text Available Root hairs are unicellular elongations of certain rhizodermal cells that improve the uptake of sparingly soluble and immobile soil nutrients. Among different Arabidopsis thaliana genotypes, root hair density, length and the local acclimation to low inorganic phosphate (Pi differs considerably, when analyzed on split agar plates. Here, genome-wide association fine mapping identified significant single nucleotide polymorphisms associated with the increased root hair density in the absence of local phosphate on chromosome 1. A loss-of-functionmutant of the candidate transcription factor gene WRKY6, which is involved in the acclimation of plants to low phosphorus, had increased root hair density. This is partially explained by a reduced cortical cell diameter in wrky6-3, reducing the rhizodermal cell numbers adjacent to the cortical cells. As a consequence, rhizodermal cells in positions that are in contact with two cortical cells are found more often, leading to higher hair density. Distinct cortical cell diameters and epidermal cell lengths distinguish other Arabidopsis accessions with distinct root hair density and −Pi response from diploid Col-0, while tetraploid Col-0 had generally larger root cell sizes, which explain longer hairs. A distinct radial root morphology within Arabidopsis accessions and wrky6-3explains some, but not all, differences in the root hair acclimation to –Pi.

  20. Increased root hair density by loss of WRKY6 in Arabidopsis thaliana

    Science.gov (United States)

    Benz, Martin

    2017-01-01

    Root hairs are unicellular elongations of certain rhizodermal cells that improve the uptake of sparingly soluble and immobile soil nutrients. Among different Arabidopsis thaliana genotypes, root hair density, length and the local acclimation to low inorganic phosphate (Pi) differs considerably, when analyzed on split agar plates. Here, genome-wide association fine mapping identified significant single nucleotide polymorphisms associated with the increased root hair density in the absence of local phosphate on chromosome 1. A loss-of-functionmutant of the candidate transcription factor gene WRKY6, which is involved in the acclimation of plants to low phosphorus, had increased root hair density. This is partially explained by a reduced cortical cell diameter in wrky6-3, reducing the rhizodermal cell numbers adjacent to the cortical cells. As a consequence, rhizodermal cells in positions that are in contact with two cortical cells are found more often, leading to higher hair density. Distinct cortical cell diameters and epidermal cell lengths distinguish other Arabidopsis accessions with distinct root hair density and −Pi response from diploid Col-0, while tetraploid Col-0 had generally larger root cell sizes, which explain longer hairs. A distinct radial root morphology within Arabidopsis accessions and wrky6-3explains some, but not all, differences in the root hair acclimation to –Pi. PMID:28149680

  1. Phenotyping for the dynamics of field wheat root system architecture

    Science.gov (United States)

    Chen, Xinxin; Ding, Qishuo; Błaszkiewicz, Zbigniew; Sun, Jiuai; Sun, Qian; He, Ruiyin; Li, Yinian

    2017-01-01

    We investigated a method to quantify field-state wheat RSA in a phenotyping way, depicting the 3D topology of wheat RSA in 14d periods. The phenotyping procedure, proposed for understanding the spatio-temporal variations of root-soil interaction and the RSA dynamics in the field, is realized with a set of indices of mm scale precision, illustrating the gradients of both wheat root angle and elongation rate along soil depth, as well as the foraging potential along the side directions. The 70d was identified as the shifting point distinguishing the linear root length elongation from power-law development. Root vertical angle in the 40 mm surface soil layer was the largest, but steadily decreased along the soil depth. After 98d, larger root vertical angle appeared in the deep soil layers. PAC revealed a stable root foraging potential in the 0-70d period, which increased rapidly afterwards (70-112d). Root foraging potential, explained by MaxW/MaxD ratio, revealed an enhanced gravitropism in 14d period. No-till post-paddy wheat RLD decreased exponentially in both depth and circular directions, with 90% roots concentrated within the top 20 cm soil layer. RER along soil depth was either positive or negative, depending on specific soil layers and the sampling time.

  2. Fine Root Productivity and Dynamics on a Forested Floodplain in South Carolina

    Science.gov (United States)

    Terrell T. Baker; William Conner; H. B. Graeme Lockaby; John A. Stanturf; Marianne K. Burke

    2001-01-01

    The highly dynamic, fine root component of forested wetland ecosystems fine root dynamics is a challenging endeavor in any system, but the difficulties are particularly evident in forested floodplains where frequent hydrologic fluctuations directly influence fine root dynamics. Fine root (53 mm) biomass, production, and turnover were estimated for three soils...

  3. Dynamic imaging of cytosolic zinc in Arabidopsis roots combining FRET sensors and RootChip technology.

    Science.gov (United States)

    Lanquar, Viviane; Grossmann, Guido; Vinkenborg, Jan L; Merkx, Maarten; Thomine, Sébastien; Frommer, Wolf B

    2014-04-01

    Zinc plays a central role in all living cells as a cofactor for enzymes and as a structural element enabling the adequate folding of proteins. In eukaryotic cells, metals are highly compartmentalized and chelated. Although essential to characterize the mechanisms of Zn(2+) homeostasis, the measurement of free metal concentrations in living cells has proved challenging and the dynamics are difficult to determine. Our work combines the use of genetically encoded Förster resonance energy transfer (FRET) sensors and a novel microfluidic technology, the RootChip, to monitor the dynamics of cytosolic Zn(2+) concentrations in Arabidopsis root cells. Our experiments provide estimates of cytosolic free Zn(2+) concentrations in Arabidopsis root cells grown under sufficient (0.4 nM) and excess (2 nM) Zn(2+) supply. In addition, monitoring the dynamics of cytosolic [Zn(2+) ] in response to external supply suggests the involvement of high- and low-affinity uptake systems as well as release from internal stores. In this study, we demonstrate that the combination of genetically encoded FRET sensors and microfluidics provides an attractive tool to monitor the dynamics of cellular metal ion concentrations over a wide concentration range in root cells. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

  4. Applicability of optical scanner method for fine root dynamics

    Science.gov (United States)

    Kume, Tomonori; Ohashi, Mizue; Makita, Naoki; Khoon Kho, Lip; Katayama, Ayumi; Matsumoto, Kazuho; Ikeno, Hidetoshi

    2016-04-01

    Fine root dynamics is one of the important components in forest carbon cycling, as ~60 % of tree photosynthetic production can be allocated to root growth and metabolic activities. Various techniques have been developed for monitoring fine root biomass, production, mortality in order to understand carbon pools and fluxes resulting from fine roots dynamics. The minirhizotron method is now a widely used technique, in which a transparent tube is inserted into the soil and researchers count an increase and decrease of roots along the tube using images taken by a minirhizotron camera or minirhizotron video camera inside the tube. This method allows us to observe root behavior directly without destruction, but has several weaknesses; e.g., the difficulty of scaling up the results to stand level because of the small observation windows. Also, most of the image analysis are performed manually, which may yield insufficient quantitative and objective data. Recently, scanner method has been proposed, which can produce much bigger-size images (A4-size) with lower cost than those of the minirhizotron methods. However, laborious and time-consuming image analysis still limits the applicability of this method. In this study, therefore, we aimed to develop a new protocol for scanner image analysis to extract root behavior in soil. We evaluated applicability of this method in two ways; 1) the impact of different observers including root-study professionals, semi- and non-professionals on the detected results of root dynamics such as abundance, growth, and decomposition, and 2) the impact of window size on the results using a random sampling basis exercise. We applied our new protocol to analyze temporal changes of root behavior from sequential scanner images derived from a Bornean tropical forests. The results detected by the six observers showed considerable concordance in temporal changes in the abundance and the growth of fine roots but less in the decomposition. We also examined

  5. Fluid dynamics of aortic root dilation in Marfan syndrome

    CERN Document Server

    Querzoli, Giorgio; Espa, Stefania; Costantini, Martina; Sorgini, Francesca

    2014-01-01

    Aortic root dilation and propensity to dissection are typical manifestations of the Marfan Syndrome (MS), a genetic defect leading to the degeneration of the elastic fibres. Dilation affects the structure of the flow and, in turn, altered flow may play a role in vessel dilation, generation of aneurysms, and dissection. The aim of the present work is the investigation in-vitro of the fluid dynamic modifications occurring as a consequence of the morphological changes typically induced in the aortic root by MS. A mock-loop reproducing the left ventricle outflow tract and the aortic root was used to measure time resolved velocity maps on a longitudinal symmetry plane of the aortic root. Two dilated model aortas, designed to resemble morphological characteristics typically observed in MS patients, have been compared to a reference, healthy geometry. The aortic model was designed to quantitatively reproduce the change of aortic distensibility caused by MS. Results demonstrate that vorticity released from the valve ...

  6. Nitrogen Additions Affect Root Dynamics in a Boreal Forest Ecosystem

    Science.gov (United States)

    Turner, K. M.; Treseder, K. K.

    2004-12-01

    As with many ecosystems, North American boreal forests are increasingly subjected to anthropogenic nitrogen deposition. To examine potential effects on plant growth, we created nitrogen fertilization plots in three sites along an Alaskan fire chronosequence composed of forests aged 5, 17, and 80 years. Each site had been exposed to two years of nitrogen fertilization, with four control plots and four nitrogen plots per site. General observations indicate that aboveground net primary productivity appears to be nitrogen limited in each site. We hypothesized that nitrogen fertilization would positively influence root dynamics as well, with nitrogen additions resulting in an increase in standing root biomass and length. To test our hypothesis, we used a minirhizotron camera to collect sequential images of roots in the top 10 cm of soil in both nitrogen fertilized and control plots in each site. Images were collected monthly during the growing season, with a total of five sampling times between May 2003 and May 2004. We then analyzed the images with WinRhizotron root measurement software. Nitrogen fertilization had varying effects on root biomass among the three sites, with a significant site by N interaction (P = 0.039). A decrease in root biomass was observed in the 5 and 80 year old sites, dropping from 207 g/m2 to 79 g/m2 and from 230 g/m2 to 129 g/m2 for the youngest and oldest sites, respectively. In contrast, root biomass increased from 52 g/m2 to 107 g/m2 in the 17 year old site. (Values are for the top 10 cm of soil only, and likely underestimate total root stocks.) Patterns in standing root lengths diverged from those of root biomass, with a 2.5-fold overall increase under nitrogen fertilization across all sites (P = 0.004). There were no significant differences among sites in nitrogen response. Standing root biomass and length differed from one another in their responses to nitrogen fertilization because nitrogen additions decreased specific root weight (as g

  7. Root density of cherry trees grafted on prunus mahaleb in a semi-arid region

    Science.gov (United States)

    Paltineanu, Cristian; Septar, Leinar; Gavat, Corina; Chitu, Emil; Oprita, Alexandru; Moale, Cristina; Lamureanu, Gheorghe; Vrinceanu, Andrei

    2016-07-01

    Root density was investigated using the trench method in a cherry (Prunus avium grafted on Prunus mahaleb) orchard with clean cultivation in inter-rows and in-row. Trenches of 1 m width and 1.2 m depth were dug up between neighbouring trees. The objectives of the paper were to clarify the spatial distribution of root density of cherry trees under the soil and climate conditions of the region to expand knowledge of optimum planting distance and orchard management for a broad area of chernozems. Some soil physical properties were significantly worsened in inter-rows versus in-row, mainly due to soil compaction, and there were higher root density values in in-row versus inter-rows. Root density decreased more intensely with soil depth than with distance from trees. The pattern of root density suggests that the cherry tree density and fruit yield could be increased. However, other factors concerning orchard management and fruit yield should also be considered. The results obtained have a potential impact to improve irrigation and fertilizer application by various methods, considering the soil depth and distance from trees to wet soil, in accordance with root development.

  8. Genotype and Planting Density Effects on Rooting Traits and Yield in Cotton (Gossypium hirsutum L.)

    Institute of Scientific and Technical Information of China (English)

    Li-Zhen Zhang; Bao-Guo Li; Gen-Tu Yan; Wopke van der Werf; JHJ Spiertz; Si-Ping Zhang

    2006-01-01

    Root density distribution of plants is a major indicator of competition between plants and determines resource capture from the soil. This experiment was conducted in 2005 at Anyang, located in the Yellow River region, Henan Province, China. Three cotton (Gossypium hirsutum L.) cultivars were chosen: hybrid Bt-cultivar CRI46, conventional Bt-cultivars CRI44 and CRI45. Six planting densities were designed, ranging from 1.5 to 12.0 plants/m2. Root parameters such as surface area, diameter and length were analyzed by using the DT-SCAN image analysis method. The root length density (RLD), root average diameter and root area index (RAI), root surface area per unit land area, were studied. The results showed that RLD and RAI differed between genotypes; hybrid CRI46 had significantly higher (P < 0.05) RLD and RAI values than conventional cultivars, especially under low planting densities, less than 3.0 plants/m2. The root area index (RAI) of hybrid CRI46 was 61% higher than of CRI44 and CRI45 at the flowering stage. The RLD and RAI were also significantly different (P= 0.000) between planting densities. The depth distribution of RAI showed that at increasing planting densities RAI was increasingly distributed in the soil layers below 50 cm. The RAI of hybrid CRI46 was for all planting densities, obviously higher than other cultivars during the flowering and boll stages. It was concluded that the hybrid had a strong advantage in root maintenance preventing premature senescence of roots. The root diameter of hybrid CRI46 had a genetically higher root diameter at planting densities lower than 6.0 plants/m2. Good associations were found between yield and RAI in different stages. The optimum planting density ranged from 4.50 plants/m2 to 6.75 plants/m2 for conventional cultivars and around 4.0-5.0 plants/m2 for hybrids.

  9. Sowing Density: A Neglected Factor Fundamentally Affecting Root Distribution and Biomass Allocation of Field Grown Spring Barley (Hordeum Vulgare L.).

    Science.gov (United States)

    Hecht, Vera L; Temperton, Vicky M; Nagel, Kerstin A; Rascher, Uwe; Postma, Johannes A

    2016-01-01

    Studies on the function of root traits and the genetic variation in these traits are often conducted under controlled conditions using individual potted plants. Little is known about root growth under field conditions and how root traits are affected by agronomic practices in particular sowing density. We hypothesized that with increasing sowing density, root length density (root length per soil volume, cm cm(-3)) increases in the topsoil as well as specific root length (root length per root dry weight, cm g(-1)) due to greater investment in fine roots. Therefore, we studied two spring barley cultivars at ten different sowing densities (24-340 seeds m(-2)) in 2 consecutive years in a clay loam field in Germany and established sowing density dose-response curves for several root and shoot traits. We took soil cores for measuring roots up to a depth of 60 cm in and between plant rows (inter-row distance 21 cm). Root length density increased with increasing sowing density and was greatest in the plant row in the topsoil (0-10 cm). Greater sowing density increased specific root length partly through greater production of fine roots in the topsoil. Rooting depth (D50) of the major root axes (root diameter class 0.4-1.0 mm) was not affected. Root mass fraction decreased, while stem mass fraction increased with sowing density and over time. Leaf mass fraction was constant over sowing density but greater leaf area was realized through increased specific leaf area. Considering fertilization, we assume that light competition caused plants to grow more shoot mass at the cost of investment into roots, which is partly compensated by increased specific root length and shallow rooting. Increased biomass per area with greater densities suggest that density increases the efficiency of the cropping system, however, declines in harvest index at densities over 230 plants m(-2) suggest that this efficiency did not translate into greater yield. We conclude that plant density is a

  10. There's a World Going on Underground: Imaging Technologies to Understand Root Growth Dynamics and Rhizosphere Interactions

    Science.gov (United States)

    Topp, C. N.

    2016-12-01

    Our ability to harness the power of plant genomics for basic and applied science depends on how well and how fast we can quantify the phenotypic ramifications of genetic variation. Plants can be considered from many vantage points: at scales from cells to organs, over the course of development or evolution, and from biophysical, physiological, and ecological perspectives. In all of these ways, our understanding of plant form and function is greatly limited by our ability to study subterranean structures and processes. The limitations to accessing this knowledge are well known - soil is opaque, roots are morphologically complex, and root growth can be heavily influenced by a myriad of environmental factors. Nonetheless, recent technological innovations in imaging science have generated a renewed focus on roots and thus new opportunities to understand the plant as a whole. The Topp Lab is interested in crop root system growth dynamics and function in response to environmental stresses such as drought, rhizosphere interactions, and as a consequence of artificial selection for agronomically important traits such as nitrogen uptake and high plant density. Studying roots requires the development of imaging technologies, computational infrastructure, and statistical methods that can capture and analyze morphologically complex networks over time and at high-throughput. The lab uses several imaging tools (optical, X-ray CT, PET, etc.) along with quantitative genetics and molecular biology to understand the dynamics of root growth and physiology. We aim to understand the relationships among root traits that can be effectively measured both in controlled laboratory environments and in the field, and to identify genes and gene networks that control root, and ultimately whole plant architectural features useful for crop improvement.

  11. Regulation of length and density of Arabidopsis root hairs by ammonium and nitrate.

    Science.gov (United States)

    Vatter, Thomas; Neuhäuser, Benjamin; Stetter, Markus; Ludewig, Uwe

    2015-09-01

    Root hairs expand the effective root surface to increase the uptake of nutrients and water from the soil. Here the local effects of the two major nitrogen sources, ammonium and nitrate, on root hairs were investigated using split plates. In three contrasting accessions of A. thaliana, namely Col-0, Tsu-0 and Sha, root hairs were differentially affected by the nitrogen forms and their concentration. Root hairs in Sha were short in the absence of nitrate. In Col-0, hair length was moderately decreased with increasing nitrate or ammonium. In all accessions, the root hair density was insensitive to 1,000-fold changes in the ammonium concentrations, when supplied locally as the exclusive nitrogen form. In contrast, the root hair density generally increased with nitrate as the exclusive local nitrogen source. The nitrate sensitivity was reduced at mM concentrations in a loss-of-function mutant of the nitrate transporter and sensor gene NRT1;1 (NPF6.3). Little differences with respect to ammonium were found in a mutant lacking four high affinity AMT-type ammonium transporters, but interestingly, the response to high nitrate was reduced and may indicate a general defect in nitrogen signaling in that mutant. Genetic diversity and the presence of the nitrogen transceptor NRT1;1 explain heterogeneity in the responses of root hairs to different nitrogen forms in Arabidopsis accessions.

  12. Anisotropic dynamic mass density for fluidsolid composites

    KAUST Repository

    Wu, Ying

    2012-10-01

    By taking the low frequency limit of multiple-scattering theory, we obtain the dynamic effective mass density of fluidsolid composites with a two-dimensional rectangular lattice structure. The anisotropic mass density can be described by an angle-dependent dipole solution, to the leading-order of solid concentration. The angular dependence vanishes for the square lattice, but at high solid concentrations there is a structure-dependent factor that contributes to the leading-order solution. In all cases, Woods formula is found to be accurately valid for the effective bulk modulus, independent of the structures. Numerical evaluations from the solutions are shown to be in excellent agreement with finite-element simulations. © 2012 Elsevier B.V.

  13. Effect of planting density on root lodging resistance and its relationship to nodal root growth characteristics in maize (Zea mays L.)

    DEFF Research Database (Denmark)

    Liu, Shengqun; Song, Fengbin; Liu, Fulai

    2012-01-01

    Increase of planting density has been widely used to increase grain yield in maize. However, it may lead to higher risk of root lodging hence causing significant yield loss of the crop. The objective of this study was to investigate the effect of planting density on maize nodal root growth...

  14. MEASUREMENT OF ROOT LENGTH DENSITY IN INTACT SAMPLES USING X-RADIOGRAPHY AND IMAGE ANALYSIS

    Directory of Open Access Journals (Sweden)

    Alain Pierret

    2011-05-01

    Full Text Available Measurement of root system attributes is of critical importance to understand and model plant growth. Root length density, the length of roots per unit volume of soil, is one of the important parameters required to understand plant performance. Measuring techniques currently in use to assess this parameter, such as for example core washing, are notoriously imprecise and labour-intensive. Roots and soil being inextricably linked, it is virtually impossible to separate them without loosing a significant amount of the root sample to be measured. This noticeably compromises the accuracy of washing techniques. For this reason, non-invasive measurement approaches are highly desirable. Here, a method based on the combination of X-radiography and image analysis is proposed as a new alternative for the measurement of root length density from intact samples. The successive steps of the method, from sampling to image acquisition are briefly described. A specific measurement algorithm, designed to account for the complex spatial arrangement of the roots within the samples is then presented and discussed in detail.

  15. Lateral migration of a foundering high-density root: Insights from numerical modeling applied to the southern Sierra Nevada

    Science.gov (United States)

    Valera, J. L.; Negredo, A. M.; Billen, M. I.; Jiménez-Munt, I.

    2014-02-01

    The southern Sierra Nevada is a geodynamically complex region where several models have been proposed to explain the rapid removal of lithospheric mantle occurring sometime between 8.0 and 3.5 Ma. Tomographic studies show the presence of an east-dipping slab-shaped fast seismic anomaly reaching to about 300 km depth below the western Sierras and Great Valley, and receiver function studies indicate a broad region of lithosphere removal. This work presents thermo-mechanical modeling of asymmetric foundering of a high-density batholithic root with lateral intrusion of asthenospheric material. The predicted evolution is controlled by: a) the upwelling of buoyant asthenosphere facilitated by the presence of a weakened lithospheric mantle adjacent to a dense batholitic root, b) the westward inflow enabled by a low viscosity lower crust, and c) negative buoyancy of a batholithic dense root. The dynamics of these models can be characterized as a slowly migrating lithosphere foundering process driven by the density anomaly of the ultramafic root, but controlled by the magnitude of the lower crustal viscosity, which determines the rate at which asthenospheric material can flow into the opening lower crustal gap. Final model-predicted upper-mantle structure is compatible with existing tomographic images and the observed V-shape geometry of the Moho below the western margin of the southern Sierra Nevada. Model-predicted topography is also generally consistent with observations, and shows a monotonous uplift of the high region since 7 Ma and presently ongoing, and an area of maximum subsidence west of the area of the V-shaped Moho, due to the pull exerted by the sinking of the high-density root.

  16. Combining Molecular Dynamics and Density Functional Theory

    Science.gov (United States)

    Kaxiras, Efthimios

    2015-03-01

    The time evolution of a system consisting of electrons and ions is often treated in the Born-Oppenheimer approximation, with electrons in their instantaneous ground state. This approach cannot capture many interesting processes that involved excitation of electrons and its effects on the coupled electron-ion dynamics. The time scale needed to accurately resolve the evolution of electron dynamics is atto-seconds. This poses a challenge to the simulation of important chemical processes that typically take place on time scales of pico-seconds and beyond, such as reactions at surfaces and charge transport in macromolecules. We will present a methodology based on time-dependent density functional theory for electrons, and classical (Ehrenfest) dynamics for the ions, that successfully captures such processes. We will give a review of key features of the method and several applications. These illustrate how the atomic and electronic structure evolution unravels the elementary steps that constitute a chemical reaction. In collaboration with: G. Kolesov, D. Vinichenko, G. Tritsaris, C.M. Friend, Departments of Physics and of Chemistry and Chemical Biology.

  17. Plant growth, phosphorus nutrition, and root morphological responses to arbuscular mycorrhizas, phosphorus fertilization, and intraspecific density.

    Science.gov (United States)

    Schroeder, M S; Janos, D P

    2005-05-01

    We examined the effects of arbuscular mycorrhizas (AM), phosphorus fertilization, intraspecific density, and their interaction, on the growth, phosphorus uptake, and root morphology of three facultative mycotrophic crops (Capsicum annuum, Zea mays, and Cucurbita pepo). Plants were grown in pots with or without AM at three densities and four phosphorus availabilities for 10 weeks. AM colonization, plant weight, and shoot phosphorus concentration were measured at harvest. Root morphology was assessed for C. annuum and Z. mays. Phosphorus fertilization reduced but did not eliminate AM colonization of all species. AM, phosphorus, and density interacted significantly to modify growth of C. annuum and C. pepo such that increased density and phosphorus diminished beneficial effects of AM. Increased density reduced positive effects of AM on C. annuum and C. pepo shoot phosphorus concentrations. AM altered both Z. mays and C. annuum root morphology in ways that complemented potential phosphorus uptake by mycorrhizas, but increased density and phosphorus diminished these effects. We infer that increased density predominantly influenced plant responses by affecting whether or not carbon (photosynthate) or phosphorus limited plant growth. By exacerbating carbon limitation, high density reduced the benefit/cost ratio of mycorrhizas and minimized their effects.

  18. Effects of grapevine root density and reinforcement on slopes prone to shallow slope instability

    Science.gov (United States)

    Meisina, Claudia; Bordoni, Massimiliano; Bischetti, Gianbattista; Vercesi, Alberto; Chiaradia, Enrico; Cislaghi, Alessio; Valentino, Roberto; Bittelli, Marco; Vergani, Chiara; Chersich, Silvia; Giuseppina Persichillo, Maria; Comolli, Roberto

    2016-04-01

    Slope erosion and shallow slope instabilities are the major factors of soil losses in cultivated steep terrains. These phenomena also cause loss of organic matter and plants nutrients, together with the partial or total destruction of the structures, such as the row tillage pattern of the vineyards, which allow for the plants cultivation. Vegetation has long been used as an effective tool to decrease the susceptibility of a slope to erosion and to shallow landslides. In particular, the scientific research focused on the role played by the plant roots, because the belowground biomass has the major control on the potential development of soil erosion and of shallow failures. Instead, a comprehensive study that analyzes the effects of the roots of agricultural plants on both soil erosion and slope instability has not been carried out yet. This aspect should be fundamental where sloped terrains are cultivated with plants of great economical relevance, as grapevine. To contribute to fill this gap, in this study the features of root density in the soil profile have been analyzed in slopes cultivated with vineyards, located on a sample hilly area of Oltrepò Pavese (northern Italy). In this area, the viticulture is the most important branch of the local economy. Moreover, several events of rainfall-induced slope erosion and shallow landslides have occurred in this area in the last 6 years, causing several economical damages linked to the destruction of the vineyards and the loss of high productivity soils. Grapevine root distribution have been measured in different test-site slopes, representative of the main geological, geomorphological, pedological, landslides distribution, agricultural features, in order to identify particular patterns on root density that can influence the development of slope instabilities. Roots have been sampled in each test-site for characterizing their strength, in terms of the relation between root diameter and root force at rupture. Root

  19. Fine root dynamics in lodgepole pine and white spruce stands along productivity gradients in reclaimed oil sands sites.

    Science.gov (United States)

    Jamro, Ghulam Murtaza; Chang, Scott X; Naeth, M Anne; Duan, Min; House, Jason

    2015-10-01

    Open-pit mining activities in the oil sands region of Alberta, Canada, create disturbed lands that, by law, must be reclaimed to a land capability equivalent to that existed before the disturbance. Re-establishment of forest cover will be affected by the production and turnover rate of fine roots. However, the relationship between fine root dynamics and tree growth has not been studied in reclaimed oil sands sites. Fine root properties (root length density, mean surface area, total root biomass, and rates of root production, turnover, and decomposition) were assessed from May to October 2011 and 2012 using sequential coring and ingrowth core methods in lodgepole pine (Pinus contorta Dougl.) and white spruce (Picea glauca (Moench.) Voss) stands. The pine and spruce stands were planted on peat mineral soil mix placed over tailings sand and overburden substrates, respectively, in reclaimed oil sands sites in Alberta. We selected stands that form a productivity gradient (low, medium, and high productivities) of each tree species based on differences in tree height and diameter at breast height (DBH) increments. In lodgepole pine stands, fine root length density and fine root production, and turnover rates were in the order of high > medium > low productivity sites and were positively correlated with tree height and DBH and negatively correlated with soil salinity (P productivity gradient and was negatively correlated with soil compaction. In conclusion, fine root dynamics along the stand productivity gradients were closely linked to stand productivity and were affected by limiting soil properties related to the specific substrate used for reconstructing the reclaimed soil. Understanding the impact of soil properties on fine root dynamics and overall stand productivity will help improve land reclamation outcomes.

  20. Improving root-zone soil moisture estimations using dynamic root growth and crop phenology

    Science.gov (United States)

    Hashemian, Minoo; Ryu, Dongryeol; Crow, Wade T.; Kustas, William P.

    2015-12-01

    Water Energy Balance (WEB) Soil Vegetation Atmosphere Transfer (SVAT) modelling can be used to estimate soil moisture by forcing the model with observed data such as precipitation and solar radiation. Recently, an innovative approach that assimilates remotely sensed thermal infrared (TIR) observations into WEB-SVAT to improve the results has been proposed. However, the efficacy of the model-observation integration relies on the model's realistic representation of soil water processes. Here, we explore methods to improve the soil water processes of a simple WEB-SVAT model by adopting and incorporating an exponential root water uptake model with water stress compensation and establishing a more appropriate soil-biophysical linkage between root-zone moisture content, above-ground states and biophysical indices. The existing WEB-SVAT model is extended to a new Multi-layer WEB-SVAT with Dynamic Root distribution (MWSDR) that has five soil layers. Impacts of plant root depth variations, growth stages and phenological cycle of the vegetation on transpiration are considered in developing stages. Hydrometeorological and biogeophysical measurements collected from two experimental sites, one in Dookie, Victoria, Australia and the other in Ponca, Oklahoma, USA, are used to validate the new model. Results demonstrate that MWSDR provides improved soil moisture, transpiration and evaporation predictions which, in turn, can provide an improved physical basis for assimilating remotely sensed data into the model. Results also show the importance of having an adequate representation of vegetation-related transpiration process for an appropriate simulation of water transfer in a complicated system of soil, plants and atmosphere.

  1. Capturing Arabidopsis Root Architecture Dynamics with root-fit Reveals Diversity in Responses to Salinity

    NARCIS (Netherlands)

    Julkowska, M.M.; Hoefsloot, H.C.J.; Mol, S.; Feron, R.; de Boer, G.J.; Haring, M.A.; Testerink, C.

    2014-01-01

    The plant root is the first organ to encounter salinity stress, but the effect of salinity on root system architecture (RSA) remains elusive. Both the reduction in main root (MR) elongation and the redistribution of the root mass between MRs and lateral roots (LRs) are likely to play crucial roles i

  2. Dynamic QTL and epistasis analysis on seedling root traits in upland cotton.

    Science.gov (United States)

    Liang, Qingzhi; Li, Pengbo; Hu, Cheng; Hua, Hua; Li, Zhaohu; Rong, Yihua; Wang, Kunbo; Hua, Jinping

    2014-04-01

    Roots are involved in acquisition of water and nutrients, as well as in providing structural support to plant. The root system provides a dynamic model for developmental analysis. Here, we investigated quantitative trait loci (QTL), dynamic conditional QTL and epistatic interactions for seedling root traits using an upland cotton F2 population and a constructed genetic map. Totally, 37 QTLs for root traits, 35 dynamic conditional QTLs based on the net increased amount of root traits (root tips, forks, length, surface area and volume) (i) after transplanting 10 days compared to 5 days, and (ii) after transplanting 15 days to 10 days were detected. Obvious dynamic characteristic of QTL and dynamic conditional QTL existed at different developmental stages of root because QTL and dynamic conditional QTL had not been detected simultaneously. We further confirmed that additive and dominance effects of QTL qRSA-chr1-1 in interval time 5 to 10 DAT (days after transplant) offset the effects in 10 to 15 DAT. Lots of two-locus interactions for root traits were identified unconditionally or dynamically, and a few epistatic interactions were only detected simultaneously in interval time of 5-10 DAT and 10-15 DAT, suggesting different interactive genetic mechanisms on root development at different stages. Dynamic conditional QTL and epistasis effects provide new attempts to understand the dynamics of roots and provide clues for root architecture selection in upland cotton.

  3. Advances on the Responses of Root Dynamics to Increased Atmospheric CO2 and Global Climate Change

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Plant roots dynamics responses to elevated atmospheric CO2 concentration, increased temperature and changed precipitation can be a key link between plant growth and long-term changes in soil organic matter and ecosystem carbon balance. This paper reviews some experiments and hypotheses developed in this area, which mainly include plant fine roots growth, root turnover, root respiration and other root dynamics responses to elevated CO2 and global climate change. Some recent new methods of studying root systems were also discussed and summarized. It holds herein that the assemblage of information about root turnover patterns, root respiration and other dynamic responses to elevated atmospheric CO2 and global climatic change can help to better understand and explore some new research areas. In this paper, some research challenges in the plant root responses to the elevated CO2 and other environmental factors during global climate change were also demonstrated.

  4. The Dynamics of DNA Methylation in Maize Roots under Pb Stress

    Directory of Open Access Journals (Sweden)

    Haiping Ding

    2014-12-01

    Full Text Available Plants adapt to adverse conditions through a series of physiological, cellular, and molecular processes, culminating in stress tolerance. However, little is known about the associated regulatory mechanisms at the epigenetic level in maize under lead (Pb stress. Therefore, in this study, we aimed to compare DNA methylation profiles during the dynamic development of maize roots following Pb treatment to identify candidate genes involved in the response to Pb stress. Methylated DNA immunoprecipitation-sequencing (MeDIP-seq was used to investigate the genome-wide DNA methylation patterns in maize roots under normal condition (A1 and 3 mM Pb(NO32 stress for 12 h (K2, 24 h (K3 and 48 h (K4. The results showed that the average methylation density was the highest in CpG islands (CGIs, followed by the intergenic regions. Within the gene body, the methylation density of the introns was higher than those of the UTRs and exons. In total, 3857 methylated genes were found in 4 tested samples, including 1805 differentially methylated genes for K2 versus A1, 1508 for K3 versus A1, and 1660 for K4 versus A1. Further analysis showed that 140 genes exhibited altered DNA methylation in all three comparisons, including some well-known stress-responsive transcription factors and proteins, such as MYB, AP2/ERF, bZIP, serine-threonine/tyrosine-proteins, pentatricopeptide repeat proteins, RING zinc finger proteins, F-box proteins, leucine-rich repeat proteins and tetratricopeptide repeat proteins. This study revealed the genome-scale DNA methylation patterns of maize roots in response to Pb exposure and identified candidate genes that potentially regulate root dynamic development under Pb stress at the methylation level.

  5. Patterns in soil fertility and root herbivory interact to influence fine-root dynamics.

    Science.gov (United States)

    Stevens, Glen N; Jones, Robert H

    2006-03-01

    Fine-scale soil nutrient enrichment typically stimulates root growth, but it may also increase root herbivory, resulting in trade-offs for plant species and potentially influencing carbon cycling patterns. We used root ingrowth cores to investigate the effects of microsite fertility and root herbivory on root biomass in an aggrading upland forest in the coastal plain of South Carolina, USA. Treatments were randomly assigned to cores from a factorial combination of fertilizer and insecticide. Soil, soil fauna, and roots were removed from the cores at the end of the experiment (8-9 mo), and roots were separated at harvest into three diameter classes. Each diameter class responded differently to fertilizer and insecticide treatments. The finest roots (root biomass, were the only ones to respond significantly to both treatments, increasing when fertilizer and when insecticide were added (each P root-feeding insects have a strong influence on root standing crop with stronger herbivore impacts on finer roots and within more fertile microsites. Thus, increased vulnerability to root herbivory is a potentially significant cost of root foraging in nutrient-rich patches.

  6. Mesoscopic dynamics of copolymer melts : From density dynamics to external potential dynamics using nonlocal kinetic coupling

    NARCIS (Netherlands)

    Maurits, N.M; Fraaije, J.G E M

    1997-01-01

    In this paper we apply nonlocal kinetic coupling to the dynamic mean-field density functional method, which is derived from generalized time-dependent Ginzburg-Landau theory. The method is applied to the mesoscopic dynamics of copolymer melts, which was previously simulated using a local coupling ap

  7. Mesoscopic dynamics of copolymer melts : From density dynamics to external potential dynamics using nonlocal kinetic coupling

    NARCIS (Netherlands)

    Maurits, NM; Fraaije, JGEM

    1997-01-01

    In this paper we apply nonlocal kinetic coupling to the dynamic mean-field density functional method, which is derived from generalized time-dependent Ginzburg-Landau theory. The method is applied to the mesoscopic dynamics of copolymer melts, which was previously simulated using a local coupling ap

  8. Root structural and functional dynamics in terrestrial biosphere models--evaluation and recommendations.

    Science.gov (United States)

    Warren, Jeffrey M; Hanson, Paul J; Iversen, Colleen M; Kumar, Jitendra; Walker, Anthony P; Wullschleger, Stan D

    2015-01-01

    There is wide breadth of root function within ecosystems that should be considered when modeling the terrestrial biosphere. Root structure and function are closely associated with control of plant water and nutrient uptake from the soil, plant carbon (C) assimilation, partitioning and release to the soils, and control of biogeochemical cycles through interactions within the rhizosphere. Root function is extremely dynamic and dependent on internal plant signals, root traits and morphology, and the physical, chemical and biotic soil environment. While plant roots have significant structural and functional plasticity to changing environmental conditions, their dynamics are noticeably absent from the land component of process-based Earth system models used to simulate global biogeochemical cycling. Their dynamic representation in large-scale models should improve model veracity. Here, we describe current root inclusion in models across scales, ranging from mechanistic processes of single roots to parameterized root processes operating at the landscape scale. With this foundation we discuss how existing and future root functional knowledge, new data compilation efforts, and novel modeling platforms can be leveraged to enhance root functionality in large-scale terrestrial biosphere models by improving parameterization within models, and introducing new components such as dynamic root distribution and root functional traits linked to resource extraction.

  9. Chiral dynamics and peripheral transverse densities

    Energy Technology Data Exchange (ETDEWEB)

    Granados, Carlos G. [Uppsala University (Sweden); Weiss, Christian [JLAB, Newport News, VA (United States)

    2014-01-01

    In the partonic (or light-front) description of relativistic systems the electromagnetic form factors are expressed in terms of frame-independent charge and magnetization densities in transverse space. This formulation allows one to identify the chiral components of nucleon structure as the peripheral densities at transverse distances b = O(M{sub {pi}}{sup -1}) and compute them in a parametrically controlled manner. A dispersion relation connects the large-distance behavior of the transverse charge and magnetization densities to the spectral functions of the Dirac and Pauli form factors near the two--pion threshold at timelike t = 4 M{ sub {pi}}{sup 2}, which can be computed in relativistic chiral effective field theory. Using the leading-order approximation we (a) derive the asymptotic behavior (Yukawa tail) of the isovector transverse densities in the "chiral" region b = O(M{sub {pi}}{sup -1}) and the "molecular" region b = O(M{sub N}{sup 2}/M{sub {pi}}{sup 3}); (b) perform the heavy-baryon expansion of the transverse densities; (c) explain the relative magnitude of the peripheral charge and magnetization densities in a simple mechanical picture; (d) include Delta isobar intermediate states and study the peripheral transverse densities in the large-N{ sub c} limit of QCD; (e) quantify the region of transverse distances where the chiral components of the densities are numerically dominant; (f) calculate the chiral divergences of the b{sup 2}-weighted moments of the isovector transverse densities (charge and anomalous magnetic radii) in the limit M{sub {pi}} -> 0 and determine their spatial support. Our approach provides a concise formulation of the spatial structure of the nucleon's chiral component and offers new insights into basic properties of the chiral expansion. It relates the information extracted from low-t elastic form factors to the generalized parton distributions probed in peripheral high-energy scattering processes.

  10. Differentiating Wheat Genotypes by Bayesian Hierarchical Nonlinear Mixed Modeling of Wheat Root Density.

    Science.gov (United States)

    Wasson, Anton P; Chiu, Grace S; Zwart, Alexander B; Binns, Timothy R

    2017-01-01

    Ensuring future food security for a growing population while climate change and urban sprawl put pressure on agricultural land will require sustainable intensification of current farming practices. For the crop breeder this means producing higher crop yields with less resources due to greater environmental stresses. While easy gains in crop yield have been made mostly "above ground," little progress has been made "below ground"; and yet it is these root system traits that can improve productivity and resistance to drought stress. Wheat pre-breeders use soil coring and core-break counts to phenotype root architecture traits, with data collected on rooting density for hundreds of genotypes in small increments of depth. The measured densities are both large datasets and highly variable even within the same genotype, hence, any rigorous, comprehensive statistical analysis of such complex field data would be technically challenging. Traditionally, most attributes of the field data are therefore discarded in favor of simple numerical summary descriptors which retain much of the high variability exhibited by the raw data. This poses practical challenges: although plant scientists have established that root traits do drive resource capture in crops, traits that are more randomly (rather than genetically) determined are difficult to breed for. In this paper we develop a hierarchical nonlinear mixed modeling approach that utilizes the complete field data for wheat genotypes to fit, under the Bayesian paradigm, an "idealized" relative intensity function for the root distribution over depth. Our approach was used to determine heritability: how much of the variation between field samples was purely random vs. being mechanistically driven by the plant genetics? Based on the genotypic intensity functions, the overall heritability estimate was 0.62 (95% Bayesian confidence interval was 0.52 to 0.71). Despite root count profiles that were statistically very noisy, our approach led

  11. Differentiating Wheat Genotypes by Bayesian Hierarchical Nonlinear Mixed Modeling of Wheat Root Density

    Science.gov (United States)

    Wasson, Anton P.; Chiu, Grace S.; Zwart, Alexander B.; Binns, Timothy R.

    2017-01-01

    Ensuring future food security for a growing population while climate change and urban sprawl put pressure on agricultural land will require sustainable intensification of current farming practices. For the crop breeder this means producing higher crop yields with less resources due to greater environmental stresses. While easy gains in crop yield have been made mostly “above ground,” little progress has been made “below ground”; and yet it is these root system traits that can improve productivity and resistance to drought stress. Wheat pre-breeders use soil coring and core-break counts to phenotype root architecture traits, with data collected on rooting density for hundreds of genotypes in small increments of depth. The measured densities are both large datasets and highly variable even within the same genotype, hence, any rigorous, comprehensive statistical analysis of such complex field data would be technically challenging. Traditionally, most attributes of the field data are therefore discarded in favor of simple numerical summary descriptors which retain much of the high variability exhibited by the raw data. This poses practical challenges: although plant scientists have established that root traits do drive resource capture in crops, traits that are more randomly (rather than genetically) determined are difficult to breed for. In this paper we develop a hierarchical nonlinear mixed modeling approach that utilizes the complete field data for wheat genotypes to fit, under the Bayesian paradigm, an “idealized” relative intensity function for the root distribution over depth. Our approach was used to determine heritability: how much of the variation between field samples was purely random vs. being mechanistically driven by the plant genetics? Based on the genotypic intensity functions, the overall heritability estimate was 0.62 (95% Bayesian confidence interval was 0.52 to 0.71). Despite root count profiles that were statistically very noisy, our

  12. Control of high velocity lithosphere roots on crustal scale density variations seen in Gondwana reconstructions

    Science.gov (United States)

    Braitenberg, C. F.; Mariani, P.

    2015-12-01

    The GOCE gravity field is globally homogeneous at the resolution of about 80km or better allowing for the first time to identify tectonic structures at continental scale. The large scale structures are presumably controlled by the rheology of the underlying crust down to the base of the lithosphere. Seismic tomography identifies the presence of the deep lithosphere roots by increased velocity. The joint analysis of the tomography results and the GOCE gravity reveals that at global scale the two data have some common patterns. The correlations are enhanced by applying geodynamic plate reconstructions to the GOCE gravity field and to the tomography models which places today's observed fields at the Gondwana pre-breakup position. There are several examples for which it is found that the deep lithospheric roots, as those found below cratons, control the position of the positive gravity values outboard of the deep roots. This could be explained by the deep lithospheric roots focusing asthenospheric upwelling outboard of the root protecting the overlying craton from magmatic intrusions. Over several of the deep roots the gravity is systematically negative, which could be due to a compositional effect, with deep roots of increased velocity having reduced density. The study is carried out globally, with focus on the African and South American continents. The background for the study can be found in the following publications where the techniques which have been used are described: Braitenberg, C., Mariani, P. and De Min, A. (2013). The European Alps and nearby orogenic belts sensed by GOCE, Boll. Bollettino di Geofisica Teorica ed Applicata, 54(4), 321-334. doi:10.4430/bgta0105 Braitenberg, C. and Mariani, P. (2015). Geological implications from complete Gondwana GOCE-products reconstructions and link to lithospheric roots. Proceedings of 5th International GOCE User Workshop, 25 - 28 November 2014. Braitenberg, C. (2015). Exploration of tectonic structures with GOCE in

  13. Controlling complex Langevin dynamics at finite density

    Energy Technology Data Exchange (ETDEWEB)

    Aarts, Gert; Bongiovanni, Lorenzo [Swansea University, Department of Physics, College of Science, Swansea (United Kingdom); Seiler, Erhard [Max-Planck-Institut fuer Physik (Werner-Heisenberg-Institut), Muenchen (Germany); Sexty, Denes [Universitaet Heidelberg, Institut fuer Theoretische Physik, Heidelberg (Germany); Stamatescu, Ion-Olimpiu [Universitaet Heidelberg, Institut fuer Theoretische Physik, Heidelberg (Germany); FEST, Heidelberg (Germany)

    2013-07-15

    At nonzero chemical potential the numerical sign problem in lattice field theory limits the use of standard algorithms based on importance sampling. Complex Langevin dynamics provides a possible solution, but it has to be applied with care. In this review, we first summarise our current understanding of the approach, combining analytical and numerical insight. In the second part we study SL(N,C) gauge cooling, which was introduced recently as a tool to control complex Langevin dynamics in nonabelian gauge theories. We present new results in Polyakov chain models and in QCD with heavy quarks and compare various adaptive cooling implementations. (orig.)

  14. Relative weights approach to dynamical fermions at finite densities

    CERN Document Server

    Greensite, Jeff

    2016-01-01

    The method of relative weights, coupled with mean field theory, is applied to the problem of simulating gauge theories with dynamical staggered fermions at finite densities. We present initial results and discuss issues so far encountered.

  15. Thermoelectric studies of charge density wave dynamics.

    Science.gov (United States)

    McDonald, Ross; Harrison, Neil; Singleton, John

    2008-03-01

    The conventional pyroelectric effect is intimately connected to the symmetry, or rather lack of center of symmetry, of the material. Although the experiments we discuss involve studies of low symmetry materials, the pyroelectric currents observed are of an entirely new origin. Systems with broken-translational-symmetry phases that incorporate orbital quantization can exhibit significant departures from thermodynamic equilibrium due to a change in magnetic induction. For charge density wave systems, this metastable state consists of a balance between the density-wave pinning force and the Lorentz force on the extended currents due to the drift of cyclotron orbits. In this way the density wave pinning potential plays a similar role to the edge potential in a two-dimensional electron gas, leading to a large Hall angle and quantization of the Hall resistance. A thermal perturbation that reduces the pinning potential returns the system towards thermal equilibrium, via a phason avalanche orthogonal to the sample surface. The observation of this new form of pyroelectric effect in the high magnetic field phase (B > 30 T) of the organic charge transfer salt α-(BEDT-TTF)2KHg(SCN)4, thus provides a measure of the phason thermopower.

  16. Evolution of geometrically necessary dislocation density from computational dislocation dynamics

    Science.gov (United States)

    Guruprasad, P. J.; Benzerga, A. A.

    2009-07-01

    This paper presents a method for calculating GND densities in dislocation dynamics simulations. Evolution of suitably defined averages of GND density as well as maps showing the spatial nonuniform distribution of GNDs are analyzed under uniaxial loading. Focus is laid on the resolution dependence of the very notion of GND density, its dependence upon physical dimensions of plastically deformed specimens and its sensitivity to initial conditions. Acknowledgments Support from the National Science Foundation (CMMI-0748187) is gratefully acknowledged.

  17. Power Spectral Density Conversions and Nonlinear Dynamics

    Directory of Open Access Journals (Sweden)

    Mostafa Rassaian

    1994-01-01

    Full Text Available To predict the vibration environment of a payload carried by a ground or air transporter, mathematical models are required from which a transfer function to a prescribed input can be calculated. For sensitive payloads these models typically include linear shock isolation system stiffness and damping elements relying on the assumption that the isolation system has a predetermined characteristic frequency and damping ratio independent of excitation magnitude. In order to achieve a practical spectral analysis method, the nonlinear system has to be linearized when the input transportation and handling vibration environment is in the form of an acceleration power spectral density. Test data from commercial isolators show that when nonlinear stiffness and damping effects exist the level of vibration input causes a variation in isolator resonant frequency. This phenomenon, described by the stationary response of the Duffing oscillator to narrow-band Gaussian random excitation, requires an alternative approach for calculation of power spectral density acceleration response at a shock isolated payload under random vibration. This article details the development of a plausible alternative approach for analyzing the spectral response of a nonlinear system subject to random Gaussian excitations.

  18. Soil resistivity over root area ratio, soil humidity, and bulk density: laboratory tests

    Science.gov (United States)

    Guastini, Enrico; Giambastiani, Yamuna; Preti, Federico

    2015-04-01

    Knowledge about root system distribution covers an important role in slope shallow stability stud-ies, as this factor grants an increase in soil geotechnical properties (soil cohesion and friction an-gle) and determines a different underground water circulation. Published studies (Amato et al., 2008 and 2011; Censini et al., 2014) about in situ application of ERT (Electrical Resistivity Tomo-graphy) analysis show how the root presence affects the measurable soil resistivity values, confirm-ing the suitability to investigate the application of such technique, aiming to estimate root density in soil with an indirect and non-invasive method. This study, laboratory-based and led on reconstructed samples in controlled condition, aim to find a correlation between the resistivity variations and the various factors that can affect them (humid-ity, bulk density, presence of foreign bodies, temperature). The tests involved a clay-loam soil (USDA classification) taken from Quaracchi (Florence, Italy), in an experimental fir-wood (Picea abies) owned by the Department of Agricultural, Food and For-estry System, Florence University, a previously chosen site for field ERT applications. The row ma-terial has been dried out in a lab stove, grounded and sieved at 2 mm, and then placed in a lexan box (30 x 20 x 20 cm) without compaction. Inside the sample have been inserted 3 series of 4 iron electrodes, insulated along the shaft and with the conductive end placed at three different depth: 2 cm from surface, in the middle of the sample and in contact with the bottom of the box; resistivity measures are conducted on the three levels using a Syscal R2 with electrodes connected in a dipole-dipole configuration. Root presence is simulated inserting bamboo spits (simple geometry, replicable "R.A.R.") in varying number from 0 to 16 in every area between two contiguous electrodes. The tests are repeated in time, monitoring the natural variations in humidity (evapotranspiration) and bulk

  19. Relation between Growth and Vertical Distribution of Fine Roots and Soil Density in the Weibei Loess Plateau

    Institute of Scientific and Technical Information of China (English)

    Zhao Zhong; Li Peng; Xue Wenpeng; Guo Shengwu

    2006-01-01

    The influence of woodland soil bulk density on the growth and distribution of fine root system of main planting tree species in the Weibei Loess Plateau was investigated by means of pot culture and field survey.Results indicated that in the woodland of Pinus tabulaeformis,soil bulk density increased with the depth at different sites,while in the woodland of Robinia pseudoacacia,soil bulk density was higher than that in P.tabulaeformis,and there was no clear difference across the profile.Further analysis implied that there existed negative correlations between soil bulk density and fine root length in the woodland of P.tabulaeformis.Results from pot culture indicated that although the effects of pot culture media on the free root growth and development of different tree species seedlings were different,all treated seedlings grew better in the soil matter with medium bulk density and porosity and with the biggest biomass.Bulk density of pot culture media had clear effects on the growth and development of P.tabulaeformis and R.pseudoacacia seedling roots,especially on the former,whereas it had little effect on that of Platycladus orientalis and Prunus armeniaca var.ansu,whose fine root biomass changed little in different pot culture media.

  20. Soil aggregation and slope stability related to soil density, root length, and mycorrhiza

    Science.gov (United States)

    Graf, Frank; Frei, Martin

    2013-04-01

    Eco-engineering measures combine the use of living plants and inert mechanical constructions to protect slopes against erosion and shallow mass movement. Whereas in geotechnical engineering several performance standards and guidelines for structural safety and serviceability of construction exist, there is a lack of comparable tools in the field of ecological restoration. Various indicators have been proposed, including the fractal dimension of soil particle size distribution, microbiological parameters, and soil aggregate stability. We present results of an soil aggregate stability investigation and compare them with literature data of the angle of internal friction ?' which is conventionally used in slope stability analysis and soil failure calculation. Aggregate stability tests were performed with samples of differently treated moraine, including soil at low (~15.5 kN/m³) and high (~19.0 kN/m³) dry unit weight, soil planted with Alnus incana (White Alder) as well as the combination of soil planted with alder and inoculated with the mycorrhizal fungus Melanogaster variegatus s.l. After a 20 weeks growth period in a greenhouse, a total of 100 samples was tested and evaluated. Positive correlations were found between the soil aggregate stability and the three variables dry unit weight, root length per soil volume, and degree of mycorrhization. Based on robust statistics it turned out that dry unit weight and mycorrhization degree were strongest correlated with soil aggregate stability. Compared to the non-inoculated control plants, mycorrhized White Alder produced significantly more roots and higher soil aggregate stability. Furthermore, the combined biological effect of plant roots and mycorrhizal mycelia on aggregate stability on soil with low density (~15.5 kN/m³) was comparable to the compaction effect of the pure soil from 15.5 to ~19.0 kN/m³. Literature data on the effect of vegetation on the angle of internal friction ?' of the same moraine showed

  1. Effects of soil moisture on cotton root length density and yield under drip irrigation with plastic mulch in Aksu Oasis farmland

    Institute of Scientific and Technical Information of China (English)

    Yilihamu; Yimamu

    2010-01-01

    Effects of soil moisture on cotton root length density (total root length per unit soil volume) and yield under drip irrigation with plastic mulch were studied through field experiments. The results indicate that spatial distributions of root length density of cotton under various water treatments were basically similar. Horizontally, both root length densities of cotton in wide and narrow rows were similar, and higher than that between mulches. Vertically, root length density of cotton decreased with increasing soil depth. The distribution of root length density is different under different irrigation treatments. In conditions of over-irrigation, the root length density of cotton between mulches would increase. However, it would decrease in both the wide rows and narrow rows. The mean root length density of cotton increased with increasing irrigation water. Water stress caused the root length density to increase in lower soil layers. There is a significant correlation between root length density and yields of cotton at the flower-boll and wadding stages. The regression between irrigation amount and yield of cotton can be expressed as y = -0.0026x2+18.015x-24845 (R2 = 0.959). It showed that the irrigation volume of 3,464.4 m3/hm2 led to op-timal root length density. The yield of cotton was 6,360 .8 kg/hm2 under that amount of irrigation.

  2. Long-term habitat selection and chronic root herbivory: explaining the relationship between periodical cicada density and tree growth.

    Science.gov (United States)

    Yang, Louie H; Karban, Richard

    2009-01-01

    Periodical cicadas (Magicicada spp.) are insect herbivores that feed on host tree roots, but their distribution among hosts is determined largely by the oviposition of female cicadas in the previous generation. A pattern of decreasing tree growth rates with increasing cicada densities is predicted when considering the costs of chronic root herbivory, but the opposite pattern is expected when considering adaptive habitat selection. Here, we report observations indicating that the relationship between periodical cicada densities and host tree growth rates is hump shaped. We suggest that both herbivory and habitat selection are likely to be key processes explaining this pattern, resulting in regions of positive and negative correlation. These results suggest that the effects of cicada herbivory are most apparent at relatively high cicada densities, while habitat selection tends to distribute cicada herbivory on host trees that are able to compensate for cicada root herbivory up to threshold cicada densities.

  3. Crystallization induced by multiple seeds: dynamical density functional approach.

    Science.gov (United States)

    Neuhaus, T; Schmiedeberg, M; Löwen, H

    2013-12-01

    Using microscopic dynamical density functional theory, we calculate the dynamical formation of polycrystals by following the crystal growth around multiple crystalline seeds imposed to an undercooled fluid. Depending on the undercooling and the size ratio as well as the relative crystal orientation of two neighboring seeds, three possibilities of the final state emerge, namely no crystallization at all, formation of a monocrystal, or two crystallites separated by a curved grain boundary. Our results, which are obtained for two-dimensional hard disk systems using a fundamental-measure density functional, shed new light on the particle-resolved structure and growth of polycrystalline material in general.

  4. Fine root dynamics of mature European beech (Fagus sylvatica L.) as influenced by elevated ozone concentrations

    Energy Technology Data Exchange (ETDEWEB)

    Mainiero, Raphael, E-mail: raphael.mainiero@iap.c [Department for Systematic Botany and Ecology, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm (Germany); Kazda, Marian, E-mail: marian.kazda@uni-ulm.d [Department for Systematic Botany and Ecology, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm (Germany); Haeberle, Karl-Heinz, E-mail: haeberle@wzw.tum.d [Technische Universitaet Muenchen, Ecophysiology of Plants, Department of Ecology, Am Hochanger 13, 85354 Freising (Germany); Nikolova, Petia Simeonova, E-mail: nikolova@wzw.tum.d [Technische Universitaet Muenchen, Ecophysiology of Plants, Department of Ecology, Am Hochanger 13, 85354 Freising (Germany); Matyssek, Rainer, E-mail: matyssek@wzw.tum.d [Technische Universitaet Muenchen, Ecophysiology of Plants, Department of Ecology, Am Hochanger 13, 85354 Freising (Germany)

    2009-10-15

    Fine root dynamics (diameter < 1 mm) in mature Fagus sylvatica, with the canopies exposed to ambient or twice-ambient ozone concentrations, were investigated throughout 2004. The focus was on the seasonal timing and extent of fine root dynamics (growth, mortality) in relation to the soil environment (water content, temperature). Under ambient ozone concentrations, a significant relationship was found between fine root turnover and soil environmental changes indicating accelerated fine root turnover under favourable soil conditions. In contrast, under elevated ozone, this relationship vanished as the result of an altered temporal pattern of fine root growth. Fine root survival and turnover rate did not differ significantly between the different ozone regimes, although a delay in current-year fine root shedding was found under the elevated ozone concentrations. The data indicate that increasing tropospheric ozone levels can alter the timing of fine root turnover in mature F. sylvatica but do not affect the turnover rate. - Doubling of ozone concentrations in mature European beech affected the seasonal timing of fine root turnover rather than the turnover rate.

  5. Asymptotic Analysis of Invariant Density of Randomly Perturbed Dynamical Systems

    OpenAIRE

    Mikami, Toshio

    1990-01-01

    The invariant density of diffusion processes which are small random perturbations of dynamical systems can be expanded in W.K.B. type, as the random effect disappears, in the set in which the Freidlin-Wentzell quasipotential $V(\\cdot)$ is of $C^\\infty$-class and each coefficient which appears in the expansion is of $C^\\infty$-class.

  6. The population dynamical consequences of density-dependent prophylaxis.

    Science.gov (United States)

    Reynolds, Jennifer J H; White, Andrew; Sherratt, Jonathan A; Boots, Mike

    2011-11-07

    When infectious disease transmission is density-dependent, the risk of infection will tend to increase with host population density. Since host defence mechanisms can be costly, individual hosts may benefit from increasing their investment in immunity in response to increasing population density. Such "density-dependent prophylaxis" (DDP) has now indeed been demonstrated experimentally in several species. However, it remains unclear how DDP will affect the population dynamics of the host-pathogen interaction, with previous theoretical work making conflicting predictions. We develop a general host-pathogen model and assess the role of DDP on the population dynamics. The ability of DDP to drive population cycles is critically dependent on the time delay between the change in density and the subsequent phenotypic change in the level of resistance. When the delay is absent or short, DDP destabilises the system. As the delay increases, its destabilising effect first diminishes and then DDP becomes increasingly stabilising. Our work highlights the significance of the time delay and suggests that it must be estimated experimentally or varied in theoretical investigations in order to understand the implications of DDP for the population dynamics of particular systems.

  7. The Dynamic Density Bottle: A Make-and-Take, Guided Inquiry Activity on Density

    Science.gov (United States)

    Kuntzleman, Thomas S.

    2015-01-01

    An activity is described wherein students observe dynamic floating and sinking behavior of plastic pieces in various liquids. The liquids and solids are all contained within a plastic bottle; the entire assembly is called a "density bottle". After completing a series of experiments that guides students to think about the relative…

  8. The Dynamic Density Bottle: A Make-and-Take, Guided Inquiry Activity on Density

    Science.gov (United States)

    Kuntzleman, Thomas S.

    2015-01-01

    An activity is described wherein students observe dynamic floating and sinking behavior of plastic pieces in various liquids. The liquids and solids are all contained within a plastic bottle; the entire assembly is called a "density bottle". After completing a series of experiments that guides students to think about the relative…

  9. Plant density-dependent variations in bioactive markers and root yield in Australian-grown Salvia miltiorrhiza Bunge.

    Science.gov (United States)

    Li, Chun Guang; Sheng, Shu Jun; Pang, Edwin C K; May, Brian; Xue, Charlie Chang Li

    2011-04-01

    The plant density-dependent variations in the root yield and content, and the yield of biomarkers in Australian grown Salvia miltiorrhiza Bunge, a commonly used Chinese medicinal herb for the treatment of cardiovascular diseases, were investigated in a field trial involving six different plant densities. The key biomarker compounds cryptotanshinone, tanshinone I, tanshinone IIA, and salvianolic acid B were quantified by a validated RP-HPLC method, and the root yields were determined per plant pair or unit area. There were significant variations (pplant densities. Positive linear correlations were observed between the contents of the three tanshinones, whereas negative linear correlations were revealed between the contents of the tanshinones and salvianolic acid B. The highest root yield per plant pair was achieved when the plants were grown at 45×30 cm or 45×40 cm, whereas the highest root production par unit area was obtained for a plant density of 30×30 cm. The highest contents of the three tanshinones and the most abundant production of these tanshinones per unit area were achieved when the plants were grown at 30×30 cm. However, the highest content of salvianolic acid B was found for a density of 45×40 cm, while its highest yield per unit area was obtained for densities of 30×40 cm or 45×30 cm. The findings suggest that the plant density distinctly affects the root yield and content and the yield of tanshinones and salvianolic acid B in Australian grown S. miltiorrhiza, which may be used as a guide for developing optimal agricultural procedures for cultivating this herb.

  10. Root responses to soil physical conditions; growth dynamics from field to cell.

    Science.gov (United States)

    Bengough, A Glyn; Bransby, M Fraser; Hans, Joachim; McKenna, Stephen J; Roberts, Tim J; Valentine, Tracy A

    2006-01-01

    Root growth in the field is often slowed by a combination of soil physical stresses, including mechanical impedance, water stress, and oxygen deficiency. The stresses operating may vary continually, depending on the location of the root in the soil profile, the prevailing soil water conditions, and the degree to which the soil has been compacted. The dynamics of root growth responses are considered in this paper, together with the cellular responses that underlie them. Certain root responses facilitate elongation in hard soil, for example, increased sloughing of border cells and exudation from the root cap decreases friction; and thickening of the root relieves stress in front of the root apex and decreases buckling. Whole root systems may also grow preferentially in loose versus dense soil, but this response depends on genotype and the spatial arrangement of loose and compact soil with respect to the main root axes. Decreased root elongation is often accompanied by a decrease in both cell flux and axial cell extension, and recent computer-based models are increasing our understanding of these processes. In the case of mechanical impedance, large changes in cell shape occur, giving rise to shorter fatter cells. There is still uncertainty about many aspects of this response, including the changes in cell walls that control axial versus radial extension, and the degree to which the epidermis, cortex, and stele control root elongation. Optical flow techniques enable tracking of root surfaces with time to yield estimates of two-dimensional velocity fields. It is demonstrated that these techniques can be applied successfully to time-lapse sequences of confocal microscope images of living roots, in order to determine velocity fields and strain rates of groups of cells. In combination with new molecular approaches this provides a promising way of investigating and modelling the mechanisms controlling growth perturbations in response to environmental stresses.

  11. Dynamic density functional theory of solid tumor growth: Preliminary models

    Directory of Open Access Journals (Sweden)

    Arnaud Chauviere

    2012-03-01

    Full Text Available Cancer is a disease that can be seen as a complex system whose dynamics and growth result from nonlinear processes coupled across wide ranges of spatio-temporal scales. The current mathematical modeling literature addresses issues at various scales but the development of theoretical methodologies capable of bridging gaps across scales needs further study. We present a new theoretical framework based on Dynamic Density Functional Theory (DDFT extended, for the first time, to the dynamics of living tissues by accounting for cell density correlations, different cell types, phenotypes and cell birth/death processes, in order to provide a biophysically consistent description of processes across the scales. We present an application of this approach to tumor growth.

  12. Fine root dynamics in moso bamboo and Japanese cedar forest by scanner method in central Taiwan

    Science.gov (United States)

    Chen, Zhi-Wei; Lin, Po-Hsuan; Kume, Tomonori

    2017-04-01

    Phyllostachys pubescens is one of the most important economic plant in the world. Phyllostachys pubescens originates from China and it had been introduced to neighbor countries about three hundred ago due to its economic value. But substantial bamboo forests were abandoned due to declines in demand. These unmanaged bamboo forests have been expanding to adjacent original forests in northern Taiwan. This vegetation alternation may not only decrease the local biodiversity but also affect the carbon cycle. Fine roots are responsible for water and nutrients acquisition and forming the most active part of the whole root system. The characteristics of fine roots are non-woody, small diameter and short lifespan. When roots keep producing new roots and replacing old roots, carbon and nutrients was transported into soil. Consequently, fine root production is one of the important component to understand the below-ground carbon cycle. However, there is few studies about fine root production in moso bamboo forests. We still lack effective method to obtain quantitative and objective data in Taiwan. It severely limits us to understand the below-ground carbon dynamics there. Minirhizotrons method has been used to investigate fine root dynamics by inserting transparent tubes into soil and by comparing changes in root length in images taken by micro-camera. But this method has some shortcomings; i.e. Most of image analysis are conducted manually and time-consuming. And it is difficult to estimate the stand level fine root production from small observation view. A new method "scanner method", which collect A4-size image (bigger than minirhizotrons) can overcome some parts of the shortcoming of minirhizotrons. The transparent acrylic box with A4-box view is inserted into soil and the interface between soil and box is scanned by commercial scanner. We can monitor the total projected root area, growth and decomposition separately by series of images. The primary objective of this study

  13. Macrophomina phaseolina: density and longevity of microsclerotia in soybean root tissues and free on the soil, and competitive saprophytic ability

    Directory of Open Access Journals (Sweden)

    Erlei Melo Reis

    2014-06-01

    Full Text Available In field experiments, the density of Macrophomina phaseolina microsclerotia in root tissues of naturally colonized soybean cultivars was quantified. The density of free sclerotia on the soil was determined for plots of crop rotation (soybean-corn and soybean monoculture soon after soybean harvest. M. phaseolina natural infection was also determined for the roots of weeds grown in the experimental area. To verify the ability of M. phaseolina to colonize dead substrates, senesced stem segments from the main plant species representing the agricultural system of southern Brazil were exposed on naturally infested soil for 30 and 60 days. To quantify the sclerotia, the methodology of Cloud and Rupe (1991 and Mengistu et al. (2007 was employed. Sclerotium density, assessed based on colony forming units (CFU, ranged from 156 to 1,108/g root tissue. Sclerotium longevity, also assessed according to CFU, was 157 days for the rotation and 163 days for the monoculture system. M. phaseolina did not colonize saprophytically any dead stem segment of Avena strigosa,Avena sativa,Hordeum vulgare,Brassica napus,Gossypium hirsutum,Secale cereale,Helianthus annus,Triticosecalerimpaui, and Triticum aestivum. Mp was isolated from infected root tissues of Amaranthus viridis,Bidens pilosa,Cardiospermum halicacabum,Euphorbia heterophylla,Ipomoea sp., and Richardia brasiliensis. The survival mechanisms of M. phaseolina studied in this paper met the microsclerotium longevity in soybean root tissues, free on the soil, as well as asymptomatic colonization of weeds.

  14. Root carbon reserve dynamics in aspen seedlings: does simulated drought induce reserve limitation?

    Science.gov (United States)

    Galvez, David A; Landhäusser, S M; Tyree, M T

    2011-03-01

    In a greenhouse study we quantified the gradual change of gas exchange, water relations and root reserves of aspen (Populus tremuloides Michx.) seedlings growing over a 3-month period of severe water stress. The aim of the study was to quantify the complex interrelationship between growth, water and gas exchange, and root carbon (C) dynamics. Various growth, gas exchange and water relations variables in combination with root reserves were measured periodically on seedlings that had been exposed to a continuous drought treatment over a 12-week period and compared with well-watered seedlings. Although gas exchange and water relations parameters significantly decreased over the drought period in aspen seedlings, root reserves did not mirror this trend. During the course of the experiment roots of aspen seedlings growing under severe water stress showed a two orders of magnitude increase in sugar and starch content, and roots of these seedlings contained more starch relative to sugar than those in non-droughted seedlings. Drought resulted in a switch from growth to root reserves storage which indicates a close interrelationship between growth and physiological variables and the accumulation of root carbohydrate reserves. Although a severe 3-month drought period created physiological symptoms of C limitation, there was no indication of a depletion of root C reserve in aspen seedlings.

  15. Anharmonic densities of states: A general dynamics-based solution

    Science.gov (United States)

    Jellinek, Julius; Aleinikava, Darya

    2016-06-01

    Density of states is a fundamental physical characteristic that lies at the foundation of statistical mechanics and theoretical constructs that derive from them (e.g., kinetic rate theories, phase diagrams, and others). Even though most real physical systems are anharmonic, the vibrational density of states is customarily treated within the harmonic approximation, or with some partial, often limited, account for anharmonicity. The reason for this is that the problem of anharmonic densities of states stubbornly resisted a general and exact, yet convenient and straightforward in applications, solution. Here we formulate such a solution within both classical and quantum mechanics. It is based on actual dynamical behavior of systems as a function of energy and as observed, or monitored, on a chosen time scale, short or long. As a consequence, the resulting anharmonic densities of states are fully dynamically informed and, in general, time-dependent. As such, they lay the ground for formulation of new statistical mechanical frameworks that incorporate time and are ergodic, by construction, with respect to actual dynamical behavior of systems.

  16. Dynamics of localized particles from density functional theory

    Science.gov (United States)

    Reinhardt, J.; Brader, J. M.

    2012-01-01

    A fundamental assumption of the dynamical density functional theory (DDFT) of colloidal systems is that a grand-canonical free-energy functional may be employed to generate the thermodynamic driving forces. Using one-dimensional hard rods as a model system, we analyze the validity of this key assumption and show that unphysical self-interactions of the tagged particle density fields, arising from coupling to a particle reservoir, are responsible for the excessively fast relaxation predicted by the theory. Moreover, our findings suggest that even employing a canonical functional would not lead to an improvement for many-particle systems, if only the total density is considered. We present several possible schemes to suppress these effects by incorporating tagged densities. When applied to confined systems, we demonstrate, using a simple example, that DDFT necessarily leads to delocalized tagged particle density distributions, which do not respect the fundamental geometrical constraints apparent in Brownian dynamics simulation data. The implication of these results for possible applications of DDFT to treat the glass transition are discussed.

  17. Dynamic root growth and architecture responses to limiting nutrient availability: linking physiological models and experimentation.

    Science.gov (United States)

    Postma, Johannes A; Schurr, Ulrich; Fiorani, Fabio

    2014-01-01

    In recent years the study of root phenotypic plasticity in response to sub-optimal environmental factors and the genetic control of these responses have received renewed attention. As a path to increased productivity, in particular for low fertility soils, several applied research projects worldwide target the improvement of crop root traits both in plant breeding and biotechnology contexts. To assist these tasks and address the challenge of optimizing root growth and architecture for enhanced mineral resource use, the development of realistic simulation models is of great importance. We review this research field from a modeling perspective focusing particularly on nutrient acquisition strategies for crop production on low nitrogen and low phosphorous soils. Soil heterogeneity and the dynamics of nutrient availability in the soil pose a challenging environment in which plants have to forage efficiently for nutrients in order to maintain their internal nutrient homeostasis throughout their life cycle. Mathematical models assist in understanding plant growth strategies and associated root phenes that have potential to be tested and introduced in physiological breeding programs. At the same time, we stress that it is necessary to carefully consider model assumptions and development from a whole plant-resource allocation perspective and to introduce or refine modules simulating explicitly root growth and architecture dynamics through ontogeny with reference to key factors that constrain root growth. In this view it is important to understand negative feedbacks such as plant-plant competition. We conclude by briefly touching on available and developing technologies for quantitative root phenotyping from lab to field, from quantification of partial root profiles in the field to 3D reconstruction of whole root systems. Finally, we discuss how these approaches can and should be tightly linked to modeling to explore the root phenome.

  18. Dynamical density functional theory with hydrodynamic interactions in confined geometries

    Science.gov (United States)

    Goddard, B. D.; Nold, A.; Kalliadasis, S.

    2016-12-01

    We study the dynamics of colloidal fluids in both unconfined geometries and when confined by a hard wall. Under minimal assumptions, we derive a dynamical density functional theory (DDFT) which includes hydrodynamic interactions (HI; bath-mediated forces). By using an efficient numerical scheme based on pseudospectral methods for integro-differential equations, we demonstrate its excellent agreement with the full underlying Langevin equations for systems of hard disks in partial confinement. We further use the derived DDFT formalism to elucidate the crucial effects of HI in confined systems.

  19. Root Architecture Diversity and Meristem Dynamics in Different Populations of Arabidopsis thaliana

    OpenAIRE

    Aceves-García, Pamela; Álvarez-Buylla, Elena R; Garay-Arroyo, Adriana; García-Ponce, Berenice; Muñoz, Rodrigo; Sánchez, María de la Paz

    2016-01-01

    Arabidopsis thaliana has been an excellent model system for molecular genetic approaches to development and physiology. More recently, the potential of studying various accessions collected from diverse habitats has been started to exploit. Col-0 has been the best-studied accession but we now know that several traits show significant divergences among them. In this work, we focused in the root that has become a key system for development. We studied root architecture and growth dynamics of 12...

  20. [Simulation of soil water dynamics in triploid Populus tomentosa root zone under subsurface drip irrigation].

    Science.gov (United States)

    Xi, Ben-Ye; Jia, Li-Ming; Wang, Ye; Li, Guang-De

    2011-01-01

    Based on the observed data of triploid Populus tomentosa root distribution, a one-dimensional root water uptake model was proposed. Taking the root water uptake into account, the soil water dynamics in triploid P. tomentosa root zone under subsurface drip irrigation was simulated by using HYDRUS model, and the results were validated with field experiment. Besides, the HYDRUS model was used to study the effects of various irrigation technique parameters on soil wetting patterns. The RMAE for the simulated soil water content by the end of irrigation and approximately 24 h later was 7.8% and 6.0%, and the RMSE was 0.036 and 0.026 cm3 x cm(-3), respectively, illustrating that the HYDRUS model performed well in simulating the short-term soil water dynamics in triploid P. tomentosa root zone under drip irrigation, and the root water uptake model was reasonable. Comparing with 2 and 4 L x h(-1) of drip discharge and continuous irrigation, both the 1 L x h(-1) of drip discharge and the pulsed irrigation with water applied intermittently in 30 min periods could increase the volume of wetted soil and reduce deep percolation. It was concluded that the combination of 1 L x h(-1) of drip discharge and pulsed irrigation should be the first choice when applying drip irrigation to triploid P. tomentosa root zone at the experiment site.

  1. Uncovering genes and ploidy involved in the high diversity in root hair density, length and response to local scarce phosphate in Arabidopsis thaliana.

    Directory of Open Access Journals (Sweden)

    Markus G Stetter

    Full Text Available Plant root hairs increase the root surface to enhance the uptake of sparingly soluble and immobile nutrients, such as the essential nutrient phosphorus, from the soil. Here, root hair traits and the response to scarce local phosphorus concentration were studied in 166 accessions of Arabidopsis thaliana using split plates. Root hair density and length were correlated, but highly variable among accessions. Surprisingly, the well-known increase in root hair density under low phosphorus was mostly restricted to genotypes that had less and shorter root hairs under P sufficient conditions. By contrast, several accessions with dense and long root hairs even had lower hair density or shorter hairs in local scarce phosphorus. Furthermore, accessions with whole-genome duplications developed more dense but phosphorus-insensitive root hairs. The impact of genome duplication on root hair density was confirmed by comparing tetraploid accessions with their diploid ancestors. Genome-wide association mapping identified candidate genes potentially involved in root hair responses tp scarce local phosphate. Knock-out mutants in identified candidate genes (CYR1, At1g32360 and RLP48 were isolated and differences in root hair traits in the mutants were confirmed. The large diversity in root hair traits among accessions and the diverse response when local phosphorus is scarce is a rich resource for further functional analyses.

  2. Modeling wave-like dynamics of oligotrophic and copiotrophic bacteria along wheat roots in response to nutrient input from a growing root tip

    NARCIS (Netherlands)

    Zelenev, V.V.; Bruggen, van A.H.C.; Semenov, A.M.

    2005-01-01

    Dynamics of oligotrophic bacteria (OB) have not been modeled in soil nor along roots. We extended a spatial¿temporal model ¿BACWAVE¿, describing wave-like dynamics of copiotrophic bacteria (CB) isolated on C-rich media to include dynamics of OB isolated on C-poor media and broad-range bacteria (BRB)

  3. Unraveling protein dynamics through fast spectral density mapping.

    Science.gov (United States)

    Ropars, Virginie; Bouguet-Bonnet, Sabine; Auguin, Daniel; Barthe, Philippe; Canet, Daniel; Roumestand, Christian

    2007-03-01

    Spectral density mapping at multiple NMR field strengths is probably the best method to describe the dynamical behavior of a protein in solution through the analysis of 15N heteronuclear relaxation parameters. Nevertheless, such analyses are scarcely reported in the literature, probably because this method is excessively demanding in spectrometer measuring time. Indeed, when using n different magnetic fields and assuming the validity of the high frequency approximation, the discrete sampling of the spectral density function with 2n + 1 points needs the measurement of 3n 15N heteronuclear relaxation measurements (n R1, n R2, and n15N{1H}NOEs). Based on further approximations, we proposed a new strategy that allows us to describe the spectral density with n + 2 points, with the measurement of a total of n + 2 heteronuclear relaxation parameters. Applied to the dynamics analysis of the protein p13( MTCP1) at three different NMR fields, this approach allowed us to divide by nearly a factor of two the total measuring time, without altering further results obtained by the "model free" analysis of the resulting spectral densities. Furthermore, simulations have shown that this strategy remains applicable to any low isotropically tumbling protein (tauc>3 ns), and is valid for the types of motion generally envisaged for proteins.

  4. Effects of water salinity on the correlation scale of Root density and Evapotranspiration fluxes

    Science.gov (United States)

    Ajeel, Ali; Saeed, Ali; Dragonetti, Giovanna; Comegna, Alessandro; Lamaddalena, Nicola; Coppola, Antonio

    2015-04-01

    Spatial pattern and the correlation of different soil and plant parameters were examined in a green bean field experiment carried out at the Mediterranean Agronomic Institute of Bari, Italy. The experiment aimed to evaluate the role of local processes of salt accumulation and transport which mainly influences the evapotranspiration (and thus the root uptake) processes under different water salinity levels. The experiment consisted of three transects of 30m length and 4.2 m width, irrigated with three different salinity levels (1dSm-1, 3dSm-1, 6dSm-1). Soil measurements (electrical conductivity and soil water content) were monitored along transects in 24 sites, 1 m apart by using TDR probes and Diviner 2000. Water storage measured by TDR and Diviner sensor were coupled for calculating directly the evapotranspiration fluxes along the whole soil profile under the different salinity levels imposed during the experiment. In the same sites, crop monitoring involved measurements of Leaf Area Index (LAI), Osmotic Potential (OP), Leaf Water Potential (LWP), and Root length Density (RlD). Soil and plant properties were analyzed by classical statistics, geostatistics methods and spectral analysis. Results indicated moderate to large spatial variability across the field for soil and plant parameters under all salinity treatments. Furthermore, cross-semivariograms exhibited a strong positive spatial interdependence between electrical conductivity of soil solution ECw with ET and RlD in transect treated with 3dSm-1 as well as with LAI in transect treated with 6dSm-1 at all 24 monitoring sites. Spectral analysis enabled to identify the observation window to sample the soil salinity information responsible for a given plant response (ET, OP, RlD). It is also allowed a clear identification of the spatial scale at which the soil water salinity level and distribution and the crop response in terms of actual evapotranspiration ET, RlD and OP, are actually correlated. Additionally

  5. A Langevin model for low density pedestrian dynamics

    Science.gov (United States)

    Corbetta, Alessandro; Lee, Chung-Min; Benzi, Roberto; Muntean, Adrian; Toschi, Federico

    The dynamics of pedestrian crowds shares deep connections with statistical physics and fluid dynamics. Reaching a quantitative understanding, not only of the average behaviours but also of the statistics of (rare) fluctuations would have major impact, for instance, on the design and safety of civil infrastructures. A key feature of pedestrian dynamics is its strong intrinsic variability, that we can already observe at the single individual level. In this work we aim at a quantitative characterisation of this statistical variability by studying individual fluctuations. We consider experimental observations of low-density pedestrian flows in a corridor within a building at Eindhoven University of Technology. Few hundreds of thousands of pedestrian trajectories with high space and time resolutions have been collected via a Microsoft Kinect 3D-range sensor and automatic head tracking techniques. From these observations we model pedestrians as active Brownian particles by means of a generalised Langevin equation. With this model we can quantitatively reproduce the observed dynamics including the statistics of ordinary pedestrian fluctuations and of rarer U-turn events. Low density, pair-wise interactions between pedestrians are also discussed.

  6. Electron density and plasma dynamics of a colliding plasma experiment

    Energy Technology Data Exchange (ETDEWEB)

    Wiechula, J., E-mail: wiechula@physik.uni-frankfurt.de; Schönlein, A.; Iberler, M.; Hock, C.; Manegold, T.; Bohlender, B.; Jacoby, J. [Plasma Physics Group, Institute of Applied Physics, Goethe University, 60438 Frankfurt am Main (Germany)

    2016-07-15

    We present experimental results of two head-on colliding plasma sheaths accelerated by pulsed-power-driven coaxial plasma accelerators. The measurements have been performed in a small vacuum chamber with a neutral-gas prefill of ArH{sub 2} at gas pressures between 17 Pa and 400 Pa and load voltages between 4 kV and 9 kV. As the plasma sheaths collide, the electron density is significantly increased. The electron density reaches maximum values of ≈8 ⋅ 10{sup 15} cm{sup −3} for a single accelerated plasma and a maximum value of ≈2.6 ⋅ 10{sup 16} cm{sup −3} for the plasma collision. Overall a raise of the plasma density by a factor of 1.3 to 3.8 has been achieved. A scaling behavior has been derived from the values of the electron density which shows a disproportionately high increase of the electron density of the collisional case for higher applied voltages in comparison to a single accelerated plasma. Sequences of the plasma collision have been taken, using a fast framing camera to study the plasma dynamics. These sequences indicate a maximum collision velocity of 34 km/s.

  7. Twenty Years of Litter and Root Manipulations: Insights into Multi-Decadal SOM Dynamics and Controls

    Science.gov (United States)

    Wig, J.; Lajtha, K.; Nadelhoffer, K. J.

    2012-12-01

    Reforestation, reducing deforestation, and sustainable forest management are often recommended by policy makers to mitigate the greenhouse gas contributions of the forestry sector. However, underlying many of these policy recommendations is the assumption that increasing above-ground carbon stocks corresponds to long-term increases in ecosystem carbon stocks, the majority of which is stored in soils. We analyzed soil carbon and nitrogen dynamics in forest soils that had undergone twenty years of continuous manipulations of above- and below-ground organic inputs as part of the Detritus Input and Removal Treatment (DIRT) network. Although we expected that increased C inputs would correspond to significantly elevated C in surface mineral soils, our data suggest that increasing above-ground litter inputs has had a positive priming effect in this soil. Positive priming occurs when increased rates of litter addition to soil lead to disproportionate increases in microbial respiration rates of native soil C, resulting in a net decrease of soil C. Soil respiration rates in a year-long laboratory incubation support this theory: increased above-ground litter inputs led to decreased respiration rates, suggesting a relative deficit of labile organic matter. Removal of below ground inputs, either with or without above-ground litter inputs, also led to decreased respiration in laboratory incubations, demonstrating the importance of fresh root inputs to labile C. Trends in non-hydrolyzable C fractions, a proxy for the more stable C pool, agree with our respiration measurements. Data from sequential density fractionation are consistent with the hypotheses that priming has occurred in response to increased above-ground litter inputs and that root inputs are an important control of the labile C pool. The importance of roots inputs for C stabilization is well documented in the literature, and our hypothesis that increased above-ground litter inputs leads to priming is supported by

  8. Water Dynamics at the Root of Metamorphosis in Living Organisms

    Directory of Open Access Journals (Sweden)

    Paola Rosa Spinetti

    2010-09-01

    Full Text Available Liquid water has been recognized long ago to be the matrix of many processes, including life and also rock dynamics. Interactions among biomolecules occur very differently in a non-aqueous system and are unable to produce life. This ability to make living processes possible implies a very peculiar structure of liquid water. According to modern Quantum Field Theory (QFT, a complementary principle (in the sense of Niels Bohr holds between the number N of field quanta (including the matter field whose quanta are just the atoms/molecules and the phase Ф. This means that when we focus on the atomic structure of matter it loses its coherence properties and, vice versa, when we examine the phase dynamics of the system its atomic structure becomes undefined. Superfluid liquid Helium is the first example of this peculiar quantum dynamics. In the present paper we show how consideration of the phase dynamics of liquid water makes the understanding of its peculiar role in the onset of self-organization in living organisms and in ecosystems possible.

  9. Root Architecture Diversity and Meristem Dynamics in Different Populations of Arabidopsis thaliana

    Science.gov (United States)

    Aceves-García, Pamela; Álvarez-Buylla, Elena R.; Garay-Arroyo, Adriana; García-Ponce, Berenice; Muñoz, Rodrigo; Sánchez, María de la Paz

    2016-01-01

    Arabidopsis thaliana has been an excellent model system for molecular genetic approaches to development and physiology. More recently, the potential of studying various accessions collected from diverse habitats has been started to exploit. Col-0 has been the best-studied accession but we now know that several traits show significant divergences among them. In this work, we focused in the root that has become a key system for development. We studied root architecture and growth dynamics of 12 Arabidopsis accessions. Our data reveal a wide variability in root architecture and root length among accessions. We also found variability in the root apical meristem (RAM), explained mainly by cell size at the RAM transition domain and possibly by peculiar forms of organization at the stem cell niche in some accessions. Contrary to Col-0 reports, in some accessions the RAM size not always explains the variations in the root length; indicating that elongated cell size could be more relevant in the determination of root length than the RAM size itself. This study contributes to investigations dealing with understanding the molecular and cellular basis of phenotypic variation, the role of plasticity on adaptation, and the developmental mechanisms that may restrict phenotypic variation in response to contrasting environmental conditions. PMID:27379140

  10. Root Architecture Diversity and Meristem Dynamics in Different Populations of Arabidopsis thaliana.

    Science.gov (United States)

    Aceves-García, Pamela; Álvarez-Buylla, Elena R; Garay-Arroyo, Adriana; García-Ponce, Berenice; Muñoz, Rodrigo; Sánchez, María de la Paz

    2016-01-01

    Arabidopsis thaliana has been an excellent model system for molecular genetic approaches to development and physiology. More recently, the potential of studying various accessions collected from diverse habitats has been started to exploit. Col-0 has been the best-studied accession but we now know that several traits show significant divergences among them. In this work, we focused in the root that has become a key system for development. We studied root architecture and growth dynamics of 12 Arabidopsis accessions. Our data reveal a wide variability in root architecture and root length among accessions. We also found variability in the root apical meristem (RAM), explained mainly by cell size at the RAM transition domain and possibly by peculiar forms of organization at the stem cell niche in some accessions. Contrary to Col-0 reports, in some accessions the RAM size not always explains the variations in the root length; indicating that elongated cell size could be more relevant in the determination of root length than the RAM size itself. This study contributes to investigations dealing with understanding the molecular and cellular basis of phenotypic variation, the role of plasticity on adaptation, and the developmental mechanisms that may restrict phenotypic variation in response to contrasting environmental conditions.

  11. Graph Theory Roots of Spatial Operators for Kinematics and Dynamics

    Science.gov (United States)

    Jain, Abhinandan

    2011-01-01

    Spatial operators have been used to analyze the dynamics of robotic multibody systems and to develop novel computational dynamics algorithms. Mass matrix factorization, inversion, diagonalization, and linearization are among several new insights obtained using such operators. While initially developed for serial rigid body manipulators, the spatial operators and the related mathematical analysis have been shown to extend very broadly including to tree and closed topology systems, to systems with flexible joints, links, etc. This work uses concepts from graph theory to explore the mathematical foundations of spatial operators. The goal is to study and characterize the properties of the spatial operators at an abstract level so that they can be applied to a broader range of dynamics problems. The rich mathematical properties of the kinematics and dynamics of robotic multibody systems has been an area of strong research interest for several decades. These properties are important to understand the inherent physical behavior of systems, for stability and control analysis, for the development of computational algorithms, and for model development of faithful models. Recurring patterns in spatial operators leads one to ask the more abstract question about the properties and characteristics of spatial operators that make them so broadly applicable. The idea is to step back from the specific application systems, and understand more deeply the generic requirements and properties of spatial operators, so that the insights and techniques are readily available across different kinematics and dynamics problems. In this work, techniques from graph theory were used to explore the abstract basis for the spatial operators. The close relationship between the mathematical properties of adjacency matrices for graphs and those of spatial operators and their kernels were established. The connections hold across very basic requirements on the system topology, the nature of the component

  12. Activated expression of an Arabidopsis HD-START protein confers drought tolerance with improved root system and reduced stomatal density.

    Science.gov (United States)

    Yu, Hong; Chen, Xi; Hong, Yuan-Yuan; Wang, Yao; Xu, Ping; Ke, Sheng-Dong; Liu, Hai-Yan; Zhu, Jian-Kang; Oliver, David J; Xiang, Cheng-Bin

    2008-04-01

    Drought is one of the most important environmental constraints limiting plant growth and agricultural productivity. To understand the underlying mechanism of drought tolerance and to identify genes for improving this important trait, we conducted a gain-of-function genetic screen for improved drought tolerance in Arabidopsis thaliana. One mutant with improved drought tolerance was isolated and designated as enhanced drought tolerance1. The mutant has a more extensive root system than the wild type, with deeper roots and more lateral roots, and shows a reduced leaf stomatal density. The mutant had higher levels of abscisic acid and Pro than the wild type and demonstrated an increased resistance to oxidative stress and high levels of superoxide dismutase. Molecular genetic analysis and recapitulation experiments showed that the enhanced drought tolerance is caused by the activated expression of a T-DNA tagged gene that encodes a putative homeodomain-START transcription factor. Moreover, overexpressing the cDNA of the transcription factor in transgenic tobacco also conferred drought tolerance associated with improved root architecture and reduced leaf stomatal density. Therefore, we have revealed functions of the homeodomain-START factor that were gained upon altering its expression pattern by activation tagging and provide a key regulator that may be used to improve drought tolerance in plants.

  13. Population Dynamics of Biota on the Roots of Azolla microphylla Kaulfuss

    Directory of Open Access Journals (Sweden)

    NITA ETIKAWATI

    2000-01-01

    Full Text Available Azolla was a special fern that their associations with Anabaena azollae able to fix free nitrogen from air, to produce protein. Although by the ages, biota diversity those habits on the roots of Azolla increased and effected to protein concentration. The research was to find out population dynamics of biota on the roots of Azolla microphylla Kaulfuss and the growth peak. This study used Completely Randomized Design with 10 kinds of biota, i.e. bacteria, Fungi, Actinomycetes, Protozoa, Alga, Crustacean, Rotifers, Coelenterate, Insect and Molluscs, and it was used 3 replications. Research was conducted within 4 weeks and the populations of biota were observed every week. Data were statistically analyzed using Analysis Variant and Duncan’s Multiple Range Test. The population dynamics of biota on the roots of Azolla microphylla Kaulfuss were influenced on its quantity and composition, and the growth peak is done in 2nd week.

  14. Functional thermo-dynamics: a generalization of dynamic density functional theory to non-isothermal situations.

    Science.gov (United States)

    Anero, Jesús G; Español, Pep; Tarazona, Pedro

    2013-07-21

    We present a generalization of Density Functional Theory (DFT) to non-equilibrium non-isothermal situations. By using the original approach set forth by Gibbs in his consideration of Macroscopic Thermodynamics (MT), we consider a Functional Thermo-Dynamics (FTD) description based on the density field and the energy density field. A crucial ingredient of the theory is an entropy functional, which is a concave functional. Therefore, there is a one to one connection between the density and energy fields with the conjugate thermodynamic fields. The connection between the three levels of description (MT, DFT, FTD) is clarified through a bridge theorem that relates the entropy of different levels of description and that constitutes a generalization of Mermin's theorem to arbitrary levels of description whose relevant variables are connected linearly. Although the FTD level of description does not provide any new information about averages and correlations at equilibrium, it is a crucial ingredient for the dynamics in non-equilibrium states. We obtain with the technique of projection operators the set of dynamic equations that describe the evolution of the density and energy density fields from an initial non-equilibrium state towards equilibrium. These equations generalize time dependent density functional theory to non-isothermal situations. We also present an explicit model for the entropy functional for hard spheres.

  15. Analysis of correlation between initial alveolar bone density and apical root resorption after 12 months of orthodontic treatment without extraction

    Directory of Open Access Journals (Sweden)

    Paula Cabrini Scheibel

    2014-10-01

    Full Text Available OBJECTIVE: The aim of the present study was to investigate the correlation between initial alveolar bone density of upper central incisors (ABD-UI and external apical root resorption (EARR after 12 months of orthodontic movement in cases without extraction. METHODS: A total of 47 orthodontic patients 11 years old or older were submitted to periapical radiography of upper incisors prior to treatment (T1 and after 12 months of treatment (T2. ABD-UI and EARR were measured by means of densitometry. RESULTS: No statistically significant correlation was found between initial ABD-UI and EARR at T2 (r = 0.149; p = 0.157. CONCLUSION: Based on the present findings, alveolar density assessed through periapical radiography is not predictive of root resorption after 12 months of orthodontic treatment in cases without extraction.

  16. Dictionary learning on the manifold of square root densities and application to reconstruction of diffusion propagator fields.

    Science.gov (United States)

    Sun, Jiaqi; Xie, Yuchen; Ye, Wenxing; Ho, Jeffrey; Entezari, Alireza; Blackband, Stephen J; Vemuri, Baba C

    2013-01-01

    In this paper, we present a novel dictionary learning framework for data lying on the manifold of square root densities and apply it to the reconstruction of diffusion propagator (DP) fields given a multi-shell diffusion MRI data set. Unlike most of the existing dictionary learning algorithms which rely on the assumption that the data points are vectors in some Euclidean space, our dictionary learning algorithm is designed to incorporate the intrinsic geometric structure of manifolds and performs better than traditional dictionary learning approaches when applied to data lying on the manifold of square root densities. Non-negativity as well as smoothness across the whole field of the reconstructed DPs is guaranteed in our approach. We demonstrate the advantage of our approach by comparing it with an existing dictionary based reconstruction method on synthetic and real multi-shell MRI data.

  17. Carrier density driven lasing dynamics in ZnO nanowires

    CERN Document Server

    Wille, Marcel; Michalsky, Tom; Röder, Robert; Ronning, Carsten; Schmidt-Grund, Rüdiger; Grundmann, Marius

    2016-01-01

    We report on the temporal lasing dynamics of high quality ZnO nanowires using time-resolved micro-photoluminescence technique. The temperature dependence of the lasing characteristics and of the corresponding decay constants demonstrate the formation of an electron-hole plasma to be the underlying gain mechanism in the considered temperature range from 10 K to 300 K. We found that the temperature dependent emission onset-time ($t_{\\text{on}}$) strongly depends on the excitation power and becomes smallest in the lasing regime, with values below 5 ps. Furthermore, the observed red shift of the dominating lasing modes in time is qualitatively discussed in terms of the carrier density induced change of the refractive index dispersion after the excitation laser pulse. This theory is supported by extending an existing model for the calculation of the carrier density dependent complex refractive index for different temperatures. This model coincides with the experimental observations and reliably describes the evolu...

  18. Time-dependent density-functional description of nuclear dynamics

    CERN Document Server

    Nakatsukasa, Takashi; Matsuo, Masayuki; Yabana, Kazuhiro

    2016-01-01

    We present the basic concepts and recent developments in the time-dependent density functional theory (TDDFT) for describing nuclear dynamics at low energy. The symmetry breaking is inherent in nuclear energy density functionals (EDFs), which provides a practical description of important correlations at the ground state. Properties of elementary modes of excitation are strongly influenced by the symmetry breaking and can be studied with TDDFT. In particular, a number of recent developments in the linear response calculation have demonstrated their usefulness in description of collective modes of excitation in nuclei. Unrestricted real-time calculations have also become available in recent years, with new developments for quantitative description of nuclear collision phenomena. There are, however, limitations in the real-time approach; for instance, it cannot describe the many-body quantum tunneling. Thus, we treat the quantum fluctuations associated with slow collective motions assuming that time evolution of...

  19. Online traffic flow model applying dynamic flow-density relation

    CERN Document Server

    Kim, Y

    2002-01-01

    This dissertation describes a new approach of the online traffic flow modelling based on the hydrodynamic traffic flow model and an online process to adapt the flow-density relation dynamically. The new modelling approach was tested based on the real traffic situations in various homogeneous motorway sections and a motorway section with ramps and gave encouraging simulation results. This work is composed of two parts: first the analysis of traffic flow characteristics and second the development of a new online traffic flow model applying these characteristics. For homogeneous motorway sections traffic flow is classified into six different traffic states with different characteristics. Delimitation criteria were developed to separate these states. The hysteresis phenomena were analysed during the transitions between these traffic states. The traffic states and the transitions are represented on a states diagram with the flow axis and the density axis. For motorway sections with ramps the complicated traffic fl...

  20. Dynamical density fluctuations of superfluids near the critical velocity.

    Science.gov (United States)

    Kato, Yusuke; Watabe, Shohei

    2010-07-16

    We propose a stability criterion of superfluids in condensed Bose-Einstein systems, which incorporates the spectral function or the autocorrelation function of the local density. Within the Gross-Pitaevskii-Bogoliubov theory, we demonstrate the validity of our criterion for the soliton-emission instability, with use of explicit forms of zero modes of the Bogoliubov equation and a dynamical scaling near the saddle-node bifurcation. We also show that the criterion is applicable to the Landau phonon instability and the Landau roton instability within the single-mode approximation.

  1. Satellite Aerodynamics and Density Determination from Satellite Dynamic Response

    Science.gov (United States)

    Karr, G. R.

    1972-01-01

    The aerodynamic drag and lift properties of a satellite are first expressed as a function of two parameters associated with gas-surface interaction at the satellite surface. The dynamic response of the satellite as it passes through the atmosphere is then expressed as a function of the two gas-surface interaction parameters, the atmospheric density, the satellite velocity, and the satellite orientation to the high speed flow. By proper correlation of the observed dynamic response with the changing angle of attack of the satellite, it is found that the two unknown gas-surface interaction parameters can be determined. Once the gas-surface interaction parameters are known, the aerodynamic properties of the satellite at all angles of attack are also determined.

  2. Ab initio molecular dynamics using hybrid density functionals

    Science.gov (United States)

    Guidon, Manuel; Schiffmann, Florian; Hutter, Jürg; Vandevondele, Joost

    2008-06-01

    Ab initio molecular dynamics simulations with hybrid density functionals have so far found little application due to their computational cost. In this work, an implementation of the Hartree-Fock exchange is presented that is specifically targeted at ab initio molecular dynamics simulations of medium sized systems. We demonstrate that our implementation, which is available as part of the CP2K/Quickstep program, is robust and efficient. Several prescreening techniques lead to a linear scaling cost for integral evaluation and storage. Integral compression techniques allow for in-core calculations on systems containing several thousand basis functions. The massively parallel implementation respects integral symmetry and scales up to hundreds of CPUs using a dynamic load balancing scheme. A time-reversible multiple time step scheme, exploiting the difference in computational efficiency between hybrid and local functionals, brings further time savings. With extensive simulations of liquid water, we demonstrate the ability to perform, for several tens of picoseconds, ab initio molecular dynamics based on hybrid functionals of systems in the condensed phase containing a few thousand Gaussian basis functions.

  3. 3D reconstruction and dynamic modeling of root architecture in situ and its application to crop phosphorus research.

    Science.gov (United States)

    Fang, Suqin; Yan, Xiaolong; Liao, Hong

    2009-12-01

    Root architecture plays important roles in plant water and nutrient acquisition. However, accurate modeling of the root system that provides a realistic representation of roots in the soil is limited by a lack of appropriate tools for the non-destructive and precise measurement of the root system architecture in situ. Here we describe a root growth system in which the roots grow in a solid gel matrix that was used to reconstruct 3D root architecture in situ and dynamically simulate its changes under various nutrient conditions with a high degree of precision. A 3D laser scanner combined with a transparent gel-based growth system was used to capture 3D images of roots. The root system skeleton was extracted using a skeleton extraction method based on the Hough transformation, and mesh modeling using Ball-B spline was employed. We successfully used this system to reconstruct rice and soybean root architectures and determine their changes under various phosphorus (P) supply conditions. Our results showed that the 3D root architecture parameters that were dynamically calculated based on the skeletonization and simulation of root systems were significantly correlated with the biomass and P content of rice and soybean based on both the simulation system and previous reports. Therefore, this approach provides a novel technique for the study of crop root growth and its adaptive changes to various environmental conditions.

  4. Population dynamics of host-specific root-feeding cyst nematode and resource quantity in the root zone of a clonal grass

    NARCIS (Netherlands)

    Stoel, C.D.; Duyts, H.; Putten, van der W.H.

    2006-01-01

    Recent studies have suggested that root-feeding nematodes influence plant community dynamics, but few studies have investigated the population dynamics of the nematodes. In coastal foredunes, feeding-specialist cyst nematodes (Heterodera spp.) are dominant in the soil nematode community and

  5. Population dynamics of a host-specific root-feeding cyst nematode and resource quantity in the root zone of a clonal grass

    NARCIS (Netherlands)

    Van der Stoel, C.D.; Duyts, H.; Van der Putten, W.H.

    2006-01-01

    Recent studies have suggested that root-feeding nematodes influence plant community dynamics, but few studies have investigated the population dynamics of the nematodes. In coastal foredunes, feeding-specialist cyst nematodes (Heterodera spp.) are dominant in the soil nematode community and

  6. Effects of Soil Moisture on Dynamic Distribution of Dry Matter Between Winter Wheat Root and Shoot

    Institute of Scientific and Technical Information of China (English)

    CHEN Xiao-yuan; LIU Xiao-ying; LUO Yuan-pei

    2003-01-01

    The dynamic relationship of dry matter accumulation and distribution between winter wheatroot and shoot was studied under different soil water conditions. The dry matter accumulation in root wasgreatly influenced by water stress, so as to the final root weight of the treatment with 40 % field moisturecapacity (FMC) was less than 1/4 of that of the treatment with 80 % FMC on average. Water stress duringthe 3-leaf stage to the tillering stage had the greatest influence on root, and the influence of water stressduring the jointing stage to the booting stage on shoot was greater than root. However, water stress duringthe tillering stage to the booting stage had a balanced effect on root and shoot, and the proportion of drymatter that distributed to root and shoot was almost the same after rewatering. Water recovery during thejointing stage to booting stage could promote R/S, but the increasing degree was related to the duration ofwater limitation. Soil water condition had the lowest effect on R/S during the flowering stage to the fillingstage and the maximal effect on R/S during the jointing stage to the heading stage, R/S of 40% FMCtreatment was 20.93 and 126.09 % higher than that of 60 % FMC and 80 % FMC treatments respectivelyat this period.

  7. Dynamic change of organic acids secreted from wheat roots in Mn deficiency

    Institute of Scientific and Technical Information of China (English)

    Zheng FANG; Zhenfeng AN; Yingli LI

    2008-01-01

    Through solution culture experiment and liquid chromatogram technique, two wheat (Triticum aestivum L.) genotypes with different tolerances to Mn deficiency were used to study the dynamic change of organic acids secreted from wheat root in the conditions of no Mn, low Mn and normal Mn supply. Nine kinds of organic acids were measured in wheat root exudate. The results showed that there were significant differences of organic acids in root exudate between tolerant genotype and susceptible genotype under Mn-stressed conditions. Tolerant genotype 9023 secreted more organic acids from the plant roots than susceptible genotype CM28. The main organic acid exudate included tartaric acid, malic acid, acetic acid, maleic acid and fumaric acid. Of all these acids, the amounts of tartaric acid and malic acid in root exudate showed significant differences between the tolerant genotype and susceptible genotype under Mn-stressed conditions. The results also indicated that secreting organic acids into root rhizosphere was an active response to Mn deficiency for the tolerant genotype of wheat.

  8. Dynamic density functional theory with hydrodynamic interactions and fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Donev, Aleksandar, E-mail: donev@courant.nyu.edu; Vanden-Eijnden, Eric, E-mail: eve2@courant.nyu.edu [Courant Institute of Mathematical Sciences, New York University, New York, New York 10012 (United States)

    2014-06-21

    We derive a closed equation for the empirical concentration of colloidal particles in the presence of both hydrodynamic and direct interactions. The ensemble average of our functional Langevin equation reproduces known deterministic Dynamic Density Functional Theory (DDFT) [M. Rex and H. Löwen, “Dynamical density functional theory with hydrodynamic interactions and colloids in unstable traps,” Phys. Rev. Lett. 101(14), 148302 (2008)], and, at the same time, it also describes the microscopic fluctuations around the mean behavior. We suggest separating the ideal (non-interacting) contribution from additional corrections due to pairwise interactions. We find that, for an incompressible fluid and in the absence of direct interactions, the mean concentration follows Fick's law just as for uncorrelated walkers. At the same time, the nature of the stochastic terms in fluctuating DDFT is shown to be distinctly different for hydrodynamically-correlated and uncorrelated walkers. This leads to striking differences in the behavior of the fluctuations around Fick's law, even in the absence of pairwise interactions. We connect our own prior work [A. Donev, T. G. Fai, and E. Vanden-Eijnden, “A reversible mesoscopic model of diffusion in liquids: from giant fluctuations to Fick's law,” J. Stat. Mech.: Theory Exp. (2014) P04004] on fluctuating hydrodynamics of diffusion in liquids to the DDFT literature, and demonstrate that the fluid cannot easily be eliminated from consideration if one wants to describe the collective diffusion in colloidal suspensions.

  9. Transitory effects of elevated atmospheric CO₂ on fine root dynamics in an arid ecosystem do not increase long-term soil carbon input from fine root litter.

    Science.gov (United States)

    Ferguson, Scot D; Nowak, Robert S

    2011-06-01

    Experimental increases in atmospheric CO₂ often increase root production over time, potentially increasing soil carbon (C) sequestration. Effects of elevated atmospheric CO₂ on fine root dynamics in a Mojave desert ecosystem were examined for the last 4.5 yr of a long-term (10-yr) free air CO₂ enrichment (FACE) study at the Nevada desert FACE facility (NDFF). Sets of minirhizotron tubes were installed at the beginning of the NDFF experiment to characterize rooting dynamics of the dominant shrub Larrea tridentata, the codominant shrub Ambrosia dumosa and the plant community as a whole. Although significant treatment effects occurred sporadically for some fine root measurements, differences were transitory and often in opposite directions during other time-periods. Nonetheless, earlier root growth under elevated CO₂ helped sustain increased assimilation and shoot growth. Overall CO₂ treatment effects on fine root standing crop, production, loss, turnover, persistence and depth distribution were not significant for all sampling locations. These results were similar to those that occurred near the beginning of the NDFF experiment but unlike those in other ecosystems. Thus, increased C input into soils is unlikely to occur from fine root litter under elevated atmospheric CO₂ in this arid ecosystem.

  10. A Markovian Growth Dynamics on Rooted Binary Trees Evolving According to the Gompertz Curve

    Science.gov (United States)

    Landim, C.; Portugal, R. D.; Svaiter, B. F.

    2012-08-01

    Inspired by biological dynamics, we consider a growth Markov process taking values on the space of rooted binary trees, similar to the Aldous-Shields (Probab. Theory Relat. Fields 79(4):509-542, 1988) model. Fix n≥1 and β>0. We start at time 0 with the tree composed of a root only. At any time, each node with no descendants, independently from the other nodes, produces two successors at rate β( n- k)/ n, where k is the distance from the node to the root. Denote by Z n ( t) the number of nodes with no descendants at time t and let T n = β -1 nln( n/ln4)+(ln2)/(2 β). We prove that 2- n Z n ( T n + nτ), τ∈ℝ, converges to the Gompertz curve exp(-(ln2) e - βτ ). We also prove a central limit theorem for the martingale associated to Z n ( t).

  11. The effect of mycorrhizal inoculation on hybrid poplar fine root dynamics in hydrocarbon contaminated soils

    Energy Technology Data Exchange (ETDEWEB)

    Gunderson, J.; Knight, J.D.; Van Rees, K.C.J. [Saskatchewan Univ., Saskatoon, SK (Canada). Dept. of Soil Science

    2006-07-01

    The biological remediation of contaminated soils using plants was discussed. Hybrid poplars are good candidates for phytoremediation because they root deeply, cycle large amounts of water and grow quickly. Their fine root system is pivotal in nutrient and water acquisition. Therefore, in order to maximize the phytoremediation potential, it is important to understand the response of the fine root system. In addition to degrading organic chemicals, ectomycorrhizal (ECM) fungi provide the host with greater access to nutrients. This study determined the relationship between residual soil hydrocarbons and soil properties at a field site. The effects of residual contamination on hybrid poplar fine root dynamics was also examined along with the effect of ectomycorrhizal colonization on hybrid poplar fine root dynamics when grown in diesel contaminated soil under controlled conditions. A minirhizotron camera inside a growth chamber captured images of mycorrhizal inoculation on hybrid poplar fine root production. Walker hybrid poplar seedlings were grown for 12 weeks in a control soil and also in a diesel contaminated soil. Seedlings were also grown in control and diesel contaminated, ectomycorrhizal inoculated soils. The inoculum was a mycorrhizal mix containing Pisolithus tinctorius and Rhizopogon spp. The images showed that colonization by ECM fungi increased hybrid poplar fine root production and aboveground biomass in a diesel contaminated soil compared to non-colonized trees in the same soil. Root:shoot ratios were much higher in the diesel contaminated/non-inoculated treatment than in either of the control soil treatments. Results of phytoremediation in diesel contaminated soil were better in the non-colonized treatment than in the colonized treatment. Both treatments removed more contaminants from the soil than the unplanted control. Much higher quantities of hydrocarbons were found sequestered in the roots from the inoculated treatment than from the non

  12. Effect of root density on erosion and erodibility of a loamy soil under simulated rain

    DEFF Research Database (Denmark)

    Katuwal, Sheela; Vermang, J.; Cornelis, W. M.

    2013-01-01

    Though both above- and belowground components of vegetation act together in reducing soil erosion, mainly the aboveground component has received attention in past research. Therefore, the aim of this research was to evaluate the contribution of roots in soil erosion control. Perennial ryegrass (L...

  13. Out of Equilibrium Fields in Inflationary Dynamics Density Fluctuations

    CERN Document Server

    Boyanovsky, D; De Vega, H J; Holman, R; Kumar, S P

    1998-01-01

    The energy and time scales during the inflationary stage of the universe calls for an out of equilibrium quantum field treatment. Moreover, the high energy densities involved make necessary the use of non-perturbative approaches as large N and Hartree methods. We start these lectures by introducing such non-perturbative out of equilibrium methods in cosmological universes. We discuss the renormalization procedure and the choice of initial conditions. We then study the nonlinear dynamics of quantum fields in matter and radiation dominated FRW and de Sitter universes. For a variety of initial conditions, we compute the evolution of the inflaton,its quantum fluctuations and the equation of state. We investigate the explosive particle production due to spinodal unstabilities and parametric amplification in FRW and de Sitter universes with and without symmetry breaking.We find that the particle production is sensitive to the expansion of the universe.For symmetry breaking scenarios, we determine generic late time ...

  14. Dynamical eigenfunctions and critical density in loop quantum cosmology

    CERN Document Server

    Craig, David A

    2012-01-01

    We offer a new, physically transparent argument for the existence of the critical, universal maximum matter density in loop quantum cosmology for the case of a flat Friedmann-Lemaitre-Robertson-Walker cosmology with scalar matter. The argument is based on the existence of a sharp exponential ultraviolet cutoff in momentum space on the eigenfunctions of the quantum cosmological dynamical evolution operator (the gravitational part of the Hamiltonian constraint), attributable to the fundamental discreteness of spatial volume in loop quantum cosmology. The existence of the cutoff is proved directly from recently found exact solutions for the eigenfunctions for this model. As a consequence, the operators corresponding to the momentum of the scalar field and the spatial volume approximately commute. The ultraviolet cutoff then implies that the scalar momentum, though not a bounded operator, is in effect bounded on subspaces of constant volume, leading to the upper bound on the expectation value of the matter densit...

  15. Human impacts on soil carbon dynamics of deep-rooted Amazonian forests

    Science.gov (United States)

    Nepstad, Daniel C.; Stone, Thomas A.; Davidson, Eric A.

    1994-01-01

    Deforestation and logging degrade more forest in eastern and southern Amazonia than in any other region of the world. This forest alteration affects regional hydrology and the global carbon cycle, but our current understanding of these effects is limited by incomplete knowledge of tropical forest ecosystems. It is widely agreed that roots are concentrated near the soil surface in moist tropical forests, but this generalization incorrectly implies that deep roots are unimportant in water and C budgets. Our results indicate that half of the closed-canopy forests of Brazilian Amazonic occur where rainfall is highly seasonal, and these forests rely on deeply penetrating roots to extract soil water. Pasture vegetation extracts less water from deep soil than the forest it replaces, thus increasing rates of drainage and decreasing rates of evapotranspiration. Deep roots are also a source of modern carbon deep in the soil. The soils of the eastern Amazon contain more carbon below 1 m depth than is present in above-ground biomass. As much as 25 percent of this deep soil C could have annual to decadal turnover times and may be lost to the atmosphere following deforestation. We compared the importance of deep roots in a mature, evergreen forest with an adjacent man-made pasture, the most common type of vegetation on deforested land in Amazonia. The study site is near the town of Paragominas, in the Brazilian state of Para, with a seasonal rainfall pattern and deeply-weathered, kaolinitic soils that are typical for large portions of Amazonia. Root distribution, soil water extraction, and soil carbon dynamics were studied using deep auger holes and shafts in each ecosystem, and the phenology and water status of the leaf canopies were measured. We estimated the geographical distribution of deeply-rooting forests using satellite imagery, rainfall data, and field measurements.

  16. A new framework for predicting how roots and microbes influence soil organic matter dynamics in forests

    Science.gov (United States)

    Phillips, R.; Midgley, M.; Brzostek, E. R.

    2012-12-01

    While it is well-established that tree species modify soil organic matter (SOM) through differences in leaf litter chemistry, far less is known about the role of roots and their microbial associates in influencing SOM dynamics. We investigated the extent to which temperate hardwood trees which associate with arbuscular mycorrhizal (AM) fungi differ in their effects on SOM turnover from those associating with ectomycorrhizal (EM) fungi using 1) root and fungal ingrowth cores, 2) experimental tree girdling and 3) fertilization additions. We conducted our research in the central hardwood forests of southern Indiana where a rich assemblage of AM (e.g. maples, ashes, tulip poplar, black cherry) and EM (e.g. oaks, hickories, beech, pine) tree species co-occur on soils developed from similar parent materials. Our results indicate that EM trees likely play a greater role in contributing to SOM turnover than AM trees as rhizosphere enzyme activities were greater in EM soils than AM soils, and both girdling and fertilization reduced enzyme activities in EM soils but not in AM soils. Although girdling and fertilization had little effect on enzyme activities in AM soils, soil respiration decreased suggesting that much of the carbon (C) allocated belowground was likely derived from roots rather than from mycorrhizal fungi. Collectively our results suggest AM and EM trees influence SOM dynamics in fundamentally unique ways, and that categorizing forests based on the relative abundance of AM and EM trees may provide a useful framework for predicting complex biogeochemical interactions between roots, microbes and SOM.

  17. Carrier density driven lasing dynamics in ZnO nanowires.

    Science.gov (United States)

    Wille, Marcel; Sturm, Chris; Michalsky, Tom; Röder, Robert; Ronning, Carsten; Schmidt-Grund, Rüdiger; Grundmann, Marius

    2016-06-01

    We report on the temporal lasing dynamics of high quality ZnO nanowires using the time-resolved micro-photoluminescence technique. The temperature dependence of the lasing characteristics and of the corresponding decay constants demonstrate the formation of an electron-hole plasma to be the underlying gain mechanism in the considered temperature range from 10 K to 300 K. We found that the temperature-dependent emission onset-time ([Formula: see text]) strongly depends on the excitation power and becomes smallest in the lasing regime, with values below 5 ps. Furthermore, the observed red shift of the dominating lasing modes in time is qualitatively discussed in terms of the carrier density induced change of the refractive index dispersion after the excitation laser pulse. This theory is supported by extending an existing model for the calculation of the carrier density dependent complex refractive index for different temperatures. This model coincides with the experimental observations and reliably describes the evolution of the refractive index after the excitation laser pulse.

  18. The influence of residual root number and bone density on combined implant-residual tooth supported prosthesis after tooth hemisection: A finite element study.

    Science.gov (United States)

    He, Yun; Hasan, Istabrak; Chen, Junliang; Keilig, Ludger; Bourauel, Christoph

    2016-11-01

    The aim of the present study has been to analyze the influence of residual root number and bone density on the loading distribution of restorations combining implant and residual tooth after tooth hemisection using finite element analysis. Based on the image data of two patients, one has one distal root and the other has two distal roots in the mandibular right first molar, eight models were created (four models for each patient): a single crown was placed on the implant and residual tooth in two different bone densities; two separate crowns for the implant and residual tooth in two different bone densities. Vertical force of 100-N was applied on the crowns. The results show that the increase in number of residual roots decreased the magnitude of all biomechanical parameters. Higher values were observed in models with low bone density, especially in one distal root models. The maximum values of strains in spongious bone with the model (one distal root, low spongious bone density, a single crown was placed on the implant and residual tooth) even reached 9000μstrain. From a biomechanical point of view, when two residual roots exist, a single crown placed on the implant and distal half of the molar or two separate crowns for them seem to be an acceptable treatment option, regardless of the bone density. If there is one residual root and the bone density is low, the prosthesis which combines implant with the root might not be used. Copyright © 2016 Elsevier GmbH. All rights reserved.

  19. Algebraic roots of Newtonian mechanics: correlated dynamics of particles on a unique worldline

    CERN Document Server

    Kassandrov, Vladimir V

    2012-01-01

    In development of the old ideas of Stueckelberg-Wheeler-Feynman on "one-electron Universe", we study purely algebraic dynamics of (two kinds of) identical pointlike particles. These are represented by (real and complex conjugate) roots of a generic polynomial system of equations that implicitly defines a single "Worldline". The dynamics includes, in particular, events of "merging" of some two particles modelling the processes of annihilation/creation and the "exchange of quantum" as well. Correlations in the location and motion of the particles-roots relate, in particular, to the Vieta's formulas. After special choice of the inertial-like reference frame, the linear Vieta's formula ensures satisfaction of the law of (non-relativistic) momentum conservation and reproduces thus general structure of the Newtonian mechanics. Some considerations on relativization of the scheme are presented.

  20. Spatial and temporal dynamics of root exudation: how important is heterogeneity in allelopathic interactions?

    Science.gov (United States)

    Weidenhamer, Jeffrey D; Mohney, Brian K; Shihada, Nader; Rupasinghe, Maduka

    2014-08-01

    Understanding allelopathy has been hindered by the lack of methods available to monitor the dynamics of allelochemicals in the soil. Previous work has demonstrated the feasibility of using polydimethylsiloxane (PDMS) microtubing (silicone tubing microextraction, or STME) to construct sampling devices to monitor the release of lipophilic allelochemicals from plant roots. The objective of this study was to use such sampling devices to intensively monitor thiophene fluxes beneath marigolds over several weeks to gain insight into the magnitude of temporal and spatial heterogeneity in these fluxes. Marigolds were grown in rhizoboxes (20.5 x 20.5 x 3.0 cm) with 16 individual STME samplers per box. Thiophene sampling and HPLC analysis began 45 days after planting. At the end of the study, roots around each sampler were analyzed by HPLC. Results confirmed the tremendous spatial and temporal heterogeneity in thiophene production seen in our previous studies. STME probes show that thiophene concentrations generally increase over time; however, these effects were sampling-port specific. When sampling ports were monitored at 12 h intervals, fluxes at each port ranged from 0 to 2,510 ng day(-1). Fluxes measured over daylight hr averaged 29 % higher than those measured overnight. Fluxes were less than 1 % on average of the total thiophene content of surrounding roots. While the importance of such heterogeneity, or "patchiness", in the root zone has been recognized for soil nutrients, the potential importance in allelopathic interactions has seldom been considered. The reasons for this variability are unclear, but are being investigated. Our results demonstrate that STME can be used as a tool to provide a more finely-resolved picture of allelochemical dynamics in the root zone than has previously been available.

  1. Mathematical Modeling of the Dynamics of Shoot-Root Interactions and Resource Partitioning in Plant Growth.

    Directory of Open Access Journals (Sweden)

    Chrystel Feller

    Full Text Available Plants are highly plastic in their potential to adapt to changing environmental conditions. For example, they can selectively promote the relative growth of the root and the shoot in response to limiting supply of mineral nutrients and light, respectively, a phenomenon that is referred to as balanced growth or functional equilibrium. To gain insight into the regulatory network that controls this phenomenon, we took a systems biology approach that combines experimental work with mathematical modeling. We developed a mathematical model representing the activities of the root (nutrient and water uptake and the shoot (photosynthesis, and their interactions through the exchange of the substrates sugar and phosphate (Pi. The model has been calibrated and validated with two independent experimental data sets obtained with Petunia hybrida. It involves a realistic environment with a day-and-night cycle, which necessitated the introduction of a transitory carbohydrate storage pool and an endogenous clock for coordination of metabolism with the environment. Our main goal was to grasp the dynamic adaptation of shoot:root ratio as a result of changes in light and Pi supply. The results of our study are in agreement with balanced growth hypothesis, suggesting that plants maintain a functional equilibrium between shoot and root activity based on differential growth of these two compartments. Furthermore, our results indicate that resource partitioning can be understood as the emergent property of many local physiological processes in the shoot and the root without explicit partitioning functions. Based on its encouraging predictive power, the model will be further developed as a tool to analyze resource partitioning in shoot and root crops.

  2. Mathematical Modeling of the Dynamics of Shoot-Root Interactions and Resource Partitioning in Plant Growth.

    Science.gov (United States)

    Feller, Chrystel; Favre, Patrick; Janka, Ales; Zeeman, Samuel C; Gabriel, Jean-Pierre; Reinhardt, Didier

    2015-01-01

    Plants are highly plastic in their potential to adapt to changing environmental conditions. For example, they can selectively promote the relative growth of the root and the shoot in response to limiting supply of mineral nutrients and light, respectively, a phenomenon that is referred to as balanced growth or functional equilibrium. To gain insight into the regulatory network that controls this phenomenon, we took a systems biology approach that combines experimental work with mathematical modeling. We developed a mathematical model representing the activities of the root (nutrient and water uptake) and the shoot (photosynthesis), and their interactions through the exchange of the substrates sugar and phosphate (Pi). The model has been calibrated and validated with two independent experimental data sets obtained with Petunia hybrida. It involves a realistic environment with a day-and-night cycle, which necessitated the introduction of a transitory carbohydrate storage pool and an endogenous clock for coordination of metabolism with the environment. Our main goal was to grasp the dynamic adaptation of shoot:root ratio as a result of changes in light and Pi supply. The results of our study are in agreement with balanced growth hypothesis, suggesting that plants maintain a functional equilibrium between shoot and root activity based on differential growth of these two compartments. Furthermore, our results indicate that resource partitioning can be understood as the emergent property of many local physiological processes in the shoot and the root without explicit partitioning functions. Based on its encouraging predictive power, the model will be further developed as a tool to analyze resource partitioning in shoot and root crops.

  3. Modeling Root Length Density of Field Grown Potatoes under Different Irrigation Strategies and Soil Textures Using Artificial Neural Networks

    DEFF Research Database (Denmark)

    Ahmadi, Seyed Hamid; Sepaskhah, A R; Andersen, Mathias Neumann

    2014-01-01

    Root length density (RLD) is a highly wanted parameter for use in crop growth modeling but difficult to measure under field conditions. Therefore, artificial neural networks (ANNs) were implemented to predict the RLD of field grown potatoes that were subject to three irrigation strategies and three......) of the eight input variables: soil layer intervals (D), percentages of sand (Sa), silt (Si), and clay (Cl), bulk density of soil layers (Bd), weighted soil moisture deficit during the irrigation strategies period (SMD), geometric mean particle size diameter (dg), and geometric standard deviation (σg...... under a range of soil physical conditions with a high degree of accuracy and may be used in crop growth modeling....

  4. The effect of root canal taper on the irrigant flow: evaluation using an unsteady Computational Fluid Dynamics model

    NARCIS (Netherlands)

    Boutsioukis, C.; Gogos, C.; Verhaagen, B.; Versluis, M.; Kastrinakis, E.; van der Sluis, L.W.M.

    2010-01-01

    Aim  To evaluate the effect of root canal taper on irrigant flow inside a prepared root canal during final irrigation with a syringe and two types of needles, using a Computational Fluid Dynamics (CFD) model. Methodology  A validated CFD model was used to simulate irrigant flow from either a side-ve

  5. The effect of root canal taper on the irrigant flow: evaluation using an unsteady Computational Fluid Dynamics model

    NARCIS (Netherlands)

    Boutsioukis, C.; Gogos, C.; Verhaagen, B.; Versluis, M.; Kastrinakis, E.; Sluis, van der L.W.M.

    2010-01-01

    Aim  To evaluate the effect of root canal taper on irrigant flow inside a prepared root canal during final irrigation with a syringe and two types of needles, using a Computational Fluid Dynamics (CFD) model. Methodology  A validated CFD model was used to simulate irrigant flow from either a side-v

  6. Dynamics of shoot vs. root C assessed by natural 13C abundance of their biomarkers

    Science.gov (United States)

    Mendez-Millan, Mercedes; Dignac, Marie-France; Rumpel, Cornelia; Rasse, Daniel P.; Derenne, Sylvie

    2010-05-01

    Cutins and suberins are biopolyesters that have been suggested to significantly contribute to the stable pool of soil organic matter (SOM). They might be used as tracers for the above- or belowground origin of plant material. The aim of this study was to evaluate the dynamics of shoot and root-derived biomarkers in soils using a wheat/maize (C3/C4) chronosequence. Our results suggest that α,?-alkanedioic acids can be considered as root specific markers and mid-chain hydroxy acids as shoot specific markers of wheat and maize in this agricultural soil. The changes of the 13C isotopic signatures of these markers with years of maize cropping after wheat evidenced their contrasted behaviour in soil. After 12 years of maize cropping, shoot markers present in soils probably originated from old C3 vegetation suggesting that new maize cutin added to soils was mostly degraded within a year. The reasons for long-term stabilisation of shoot biomarkers remain unclear. By contrast, maize root markers were highly incorporated into SOM during the first six years of maize crop, which suggested a selective preservation of root biomass when compared to shoots, possibly due to physical protection. The contrasting distribution of the plant-specific monomers in plants and soils might be explained by different chemical mechanisms leading to selective degradation or stabilization of some biomarkers.

  7. Microfilament Dynamics is Required for Root Growth under Alkaline Stress in Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    Yue Zhou; Zijun Yang; Guangqin Guo; Yan Guo

    2010-01-01

    The microfilament (MF) cytoskeleton has crucial functions in plant development. Recent studies have revealed the function of MFs in diverse stress response. Alkaline stress is harmful to plant growth;however, it remains unclear whether the MFs play a role in alkaline stress. In the present study, we find that blocking MF assembly with latrunculin B (Lat B) leads to inhibition of plant root growth, and stabilization of MFs with phalloidin does not significantly affect plant root growth under normal conditions. In high external pH conditions, MF de-polymerization is induced and that associates with the reduction of root growth; phalloidin treatment partially rescues this reduction. Moreover, Lat B treatment further decreases the survival rate of seedlings growing in high external pH conditions. However, a high external pH (8.0) does not affect MF stability in vitro. Taken together, our results suggest that alkaline stress may trigger a signal that leads the dynamics of MFs and in turn regulates root growth.

  8. Topics in the Dynamics of Charge-Density

    Science.gov (United States)

    Ramakrishna, Sathyanarayan (Satish).

    This dissertation is an investigation into some interesting transport properties of charge-density-waves (CDWs). The field of CDW dynamics is an arena for the battle between mathematical analysis and random disorder. It is a very difficult physical situation to analyze. The theoretical study of CDW dynamics dates to the prescient suggestion of John Bardeen (in the 70s) that the nonlinear I-V characteristic of the quasi one-dimensional material TTF-TCNQ was a consequence of collective transport of condensate resulting from a Peierls instability. This instability, described first by Peierls, is studied in Chapter 1. Once the underlying physics of the instability was understood, the effects of coupling the CDW to impurities and to electric and magnetic fields were studied. The most striking effect of impurities is to produce CDW pinning, so that collective-mode transport ceases to occur if the applied electric field is smaller than a threshold field. Intensive research led to the Fukuyama-Lee-Rice model of CDW pinning. Experiments in the field are complicated by the difficulty in preparing well characterized samples of the relevant materials, among which are the trichalco-genides NbSe_3, TaS_3, the dichalcogenides (TaSe_4)_2I, TaS_2, NbSe_2 and blue bronze K_{0.3}MoO _3. Over the last decade, growth techniques have been perfected and intensive comparison between the various theoretical models and experiment is feasible. An outline of the dissertation is as follows. First, we review the theoretical ideas that underlie the subject. Then we discuss each new piece of work separately. First, this thesis presents one important theoretical approach to the study of CDW dynamics. The approach builds upon previous work on the microscopic theory of superconductors and results in a new formulation of the problem that seems likely to lend itself to non-perturbative approaches. The perturbative approach cannot provide answers to the question of what happens near the depinning

  9. Electric field diagnostics of the dynamics of equatorial density depletions

    Science.gov (United States)

    Laakso, H.; Maynard, N. C.; Pfaff, R. F.; Aggson, T. L.; Coley, W. R.; Janhunen, P.; Herrero, F. A.

    1997-09-01

    During its life of 10 months, the San Marco D satellite crossed a large number of plasma density depletion channels in the nightside F-region equatorial ionosphere. In-situ measurements of vector electric fields from San Marco D reveal convection velocity variations inside such channels and thus can be used as diagnostics of the dynamics of these plasma depleted regions. Furthermore, in some cases, the temporal evolution of the channel can be inferred from the measurements. In this paper the electric field data are converted to plasma drift velocities in order to illustrate cases where the plasma flow is directed upward or downward in the channel, the channel itself is oriented vertically upward or tilted eastward/westward, or the channel is experiencing a bifurcation or pinching-off process. Although the E × B plasma drift velocities within the depleted channels are commonly a few hundred m s-1, on some occasions electric fields corresponding to speeds as large as 2-3 km s-1 have been observed. The implications for such highly supersonic convection are discussed, including the possible constriction of such high-speed depletion channels at higher altitudes.

  10. Earthworm effects on native grassland root system dynamics under natural and increased rainfall

    Directory of Open Access Journals (Sweden)

    John A. Arnone

    2014-04-01

    Full Text Available Earthworms (EWs can modify soil structure and nutrient availability, and hence alter conditions for plant growth through their burrowing and casting activities. However, few studies have specifically quantified EW effects by experimentally manipulating EW densities (EWDs. In an earlier field study in native grassland ecosystems exposed to ambient and experimentally elevated rainfall (+280 mm year-1, projected under some climate change scenarios, we found no effects of EWDs (37, 114, 169 EW m-2 and corresponding EW activity on aboveground net primary productivity (ANPP, even though soil nutrient availability likely increased with increasing EWDs. The lack of effects of EWDs on ANPP suggested that EWs may have adversely affected root systems in that study in some way. The objective of the present study was to quantify responses of root length density (RLD, using data collected from the same grassland plots during the earlier study. RLDs were highest in plots with low EWDs and decreased in plots with higher EWDs. Elevated rainfall primarily increased RLDs in the low EWD treatment (by almost +40%. Reductions in RLDs resulting from increased EWDs did not affect ANPP. Our results indicate that elevating EWDs above ambient levels may limit root growth through large increases in soil bioturbation, but concurrent increases in cast production and nutrient availability may compensate for the suppression of root nutrient absorbing surface area leaving ANPP unchanged, but with shifts in growth (biomass allocation toward shoots. Similarly, reductions in EWDs appeared to promote higher RLDs that increased soil nutrient foraging in soil with lower amounts of nutrients because of reduced casting activity. Amplified responses observed when rainfall during the growing season was increased suggest that EWDs may mainly affect RLDs and above- vs. belowground growth (biomass allocation under climate changes that include more frequent wetter-than-average growing

  11. A mechanistic analysis of density dependence in algal population dynamics

    Directory of Open Access Journals (Sweden)

    Adrian eBorlestean

    2015-04-01

    Full Text Available Population density regulation is a fundamental principle in ecology, but the specific process underlying functional expression of density dependence remains to be fully elucidated. One view contends that patterns of density dependence are largely fixed across a species irrespective of environmental conditions, whereas another is that the strength and expression of density dependence are fundamentally variable depending on the nature of exogenous or endogenous constraints acting on the population. We conducted a study investigating the expression of density dependence in Chlamydomonas spp. grown under a gradient from low to high nutrient density. We predicted that the relationship between per capita growth rate (pgr and population density would vary from concave up to concave down as nutrient density became less limiting and populations experienced weaker density regulation. Contrary to prediction, we found that the relationship between pgr and density became increasingly concave-up as nutrient levels increased. We also found that variation in pgr increased, and pgr levels reached higher maxima in nutrient-limited environments. Most likely, these results are attributable to population growth suppression in environments with high intraspecific competition due to limited nutrient resources. Our results suggest that density regulation is strongly variable depending on exogenous and endogenous processes acting on the population, implying that expression of density dependence depends extensively on local conditions. Additional experimental work should reveal the mechanisms influencing how the expression of density dependence varies across populations through space and time.

  12. Dynamic finite element analysis of the aortic root from MRI-derived parameters.

    Science.gov (United States)

    Conti, Carlo A; Votta, Emiliano; Della Corte, Alessandro; Del Viscovo, Luca; Bancone, Ciro; Cotrufo, Maurizio; Redaelli, Alberto

    2010-03-01

    An understanding of aortic root biomechanics is pivotal for the optimisation of surgical procedures aimed at restoring normal root function in pathological subjects. For this purpose, computational models can provide important information, as long as they realistically capture the main anatomical and functional features of the aortic root. Here we present a novel and realistic finite element (FE) model of the physiological aortic root, which simulates its function during the entire cardiac cycle. Its geometry is based on magnetic resonance imaging (MRI) data obtained from 10 healthy subjects and accounts for the geometrical differences between the leaflet-sinus units. Morphological realism is combined with the modelling of the leaflets' non-linear and anisotropic mechanical response, in conjunction with dynamic boundary conditions. The results show that anatomical differences between leaflet-sinus units cause differences in stress and strain patterns. These are notably higher for the leaflets and smaller for the sinuses. For the maximum transvalvular pressure value, maximum principal stresses on the leaflets are equal to 759, 613 and 603 kPa on the non-coronary, right and left leaflet, respectively. For the maximum aortic pressure, average maximum principal stresses values are equal to 118, 112 and 111 kPa on the right, non-coronary and left sinus, respectively. Although liable of further improvements, the model seems to reliably reproduce the behaviour of the real aortic root: the model's leaflet stretches, leaflet coaptation lengths and commissure motions, as well as the timings of aortic leaflet closures and openings, all matched with the experimental findings reported in the literature.

  13. Dynamic aspects of soil water availability for isohydric plants: Focus on root hydraulic resistances

    Science.gov (United States)

    Couvreur, V.; Vanderborght, J.; Draye, X.; Javaux, M.

    2014-11-01

    Soil water availability for plant transpiration is a key concept in agronomy. The objective of this study is to revisit this concept and discuss how it may be affected by processes locally influencing root hydraulic properties. A physical limitation to soil water availability in terms of maximal flow rate available to plant leaves (Qavail) is defined. It is expressed for isohydric plants, in terms of plant-centered variables and properties (the equivalent soil water potential sensed by the plant, ψs eq; the root system equivalent conductance, Krs; and a threshold leaf water potential, ψleaf lim). The resulting limitation to plant transpiration is compared to commonly used empirical stress functions. Similarities suggest that the slope of empirical functions might correspond to the ratio of Krs to the plant potential transpiration rate. The sensitivity of Qavail to local changes of root hydraulic conductances in response to soil matric potential is investigated using model simulations. A decrease of radial conductances when the soil dries induces earlier water stress, but allows maintaining higher night plant water potentials and higher Qavail during the last week of a simulated 1 month drought. In opposition, an increase of radial conductances during soil drying provokes an increase of hydraulic redistribution and Qavail at short term. This study offers a first insight on the effect of dynamic local root hydraulic properties on soil water availability. By better understanding complex interactions between hydraulic processes involved in soil-plant hydrodynamics, better prospects on how root hydraulic traits mitigate plant water stress might be achieved.

  14. A Rhizosphere-Scale Investigation of Root Effects on Wetland Methane Dynamics

    Science.gov (United States)

    Waldo, N.; Hunt, B. K.; Gough, H. L.; Fadely, E. C.; Chistoserdova, L.; Beck, D.; Neumann, R. B.

    2016-12-01

    Methane (CH4) is a greenhouse gas emitted by wetlands. In the anoxic soils of wetlands, CH4 is produced by anaerobic methanogens from acetate and hydrogen produced by anaerobic fermenters. However, much of this CH4 is oxidized to CO2 as it passes through oxic zones before emission to the atmosphere. A key region for microbial processes is the rhizosphere, where roots introduce organic carbon and O2 belowground allowing aerobic heterotrophs to compete with fermenters for organic substrates and with aerobic methanotrophs for O2. These microbial interactions control rates of CH4 production and oxidation. This study tracked the belowground movement of organic carbon and O2 from plants to quantitatively understand rhizosphere microbial processes key to wetland CH4 dynamics. Fluxes of CO2 and CH4 from boxes of peat containing Carex aquatilis were used to determine net primary productivity (NPP), belowground respiration, and total production, oxidation and emission of CH4. We tracked O2 concentrations around the roots using optical O2 sensors (optodes). Twice, the plants were exposed to headspace 13CO2: at mid-growth and when fully grown. The plants fixed the 13C, some of which was exuded through the roots and used by microbes. We tracked the isotope ratio of emitted CO2 and CH4 to establish the timing and extent of 13C being respired and fermented to CH4. Soils samples for microbial DNA analyses were collected at multiple time points after labeling using optode data guide collection from zones of differing oxygenation. Labeled (13C ) DNA was separated from unlabeled DNA using ultracentrifugation to identify microbial populations that had used the root exudate carbon, providing insight into how microbial competition and substrate selection vary with root inputs of oxygen and carbon. Together, data from the experiment will elucidate the plant-microbe interactions that control rates of methane production and oxidation in the rhizosphere of wetland plants.

  15. Plasma Processes : Arc root dynamics in high power plasma torches – Evidence of chaotic behavior

    Indian Academy of Sciences (India)

    A K Das

    2000-11-01

    Although plasma torches have been commercially available for about 50 years, areas such as plasma gun design, process efficiency, reproducibility, plasma stability, torch lives etc. have remained mostly unattended. Recent torch developments have been focusing on the basic understanding of the plasma column and its dynamics inside the plasma torch, the interaction of plasma jet and the powders, the interaction of the plasma jet with surroundings and the impingement of the jet on the substrate. Two of the major causes of erratic and poor performance of a variety of thermal plasma processes are currently identified as the fluctuations arising out of the arc root movement on the electrodes inside the plasma torch and the fluid dynamic instabilities arising out of entrainment of the air into the plasma jet. This paper reviews the current state of understanding of these fluctuations as well as the dynamics of arc root movement in plasma torches. The work done at the author’s laboratory on studying the fluctuations in arc voltage, arc current, acoustic emissions and optical emissions are also presented. These fluctuations are observed to be chaotic and interrelated. Real time monitoring and controlling the arc instabilities through chaos characterization parameters can greatly contribute to the understanding of electrode erosion as well as improvement of plasma torch lifetime.

  16. High-density lipoprotein proteome dynamics in human endotoxemia

    Directory of Open Access Journals (Sweden)

    Stroes Erik SG

    2011-06-01

    Full Text Available Abstract Background A large variety of proteins involved in inflammation, coagulation, lipid-oxidation and lipid metabolism have been associated with high-density lipoprotein (HDL and it is anticipated that changes in the HDL proteome have implications for the multiple functions of HDL. Here, SELDI-TOF mass spectrometry (MS was used to study the dynamic changes of HDL protein composition in a human experimental low-dose endotoxemia model. Ten healthy men with low HDL cholesterol (0.7+/-0.1 mmol/L and 10 men with high HDL cholesterol levels (1.9+/-0.4 mmol/L were challenged with endotoxin (LPS intravenously (1 ng/kg bodyweight. We previously showed that subjects with low HDL cholesterol are more susceptible to an inflammatory challenge. The current study tested the hypothesis that this discrepancy may be related to differences in the HDL proteome. Results Plasma drawn at 7 time-points over a 24 hour time period after LPS challenge was used for direct capture of HDL using antibodies against apolipoprotein A-I followed by subsequent SELDI-TOF MS profiling. Upon LPS administration, profound changes in 21 markers (adjusted p-value Conclusions This study shows that the semi-quantitative differences in the HDL proteome as assessed by SELDI-TOF MS cannot explain why subjects with low HDL cholesterol are more susceptible to a challenge with LPS than those with high HDL cholesterol. Instead the results indicate that hierarchical clustering could be useful to predict HDL functionality in acute phase responses towards LPS.

  17. Incorporation of a dynamic root distribution into CLM4.5: Evaluation of carbon and water fluxes over the Amazon

    Science.gov (United States)

    Wang, Yuanyuan; Xie, Zhenghui; Jia, Binghao

    2016-09-01

    Roots are responsible for the uptake of water and nutrients by plants and have the plasticity to dynamically respond to different environmental conditions. However, most land surface models currently prescribe rooting profiles as a function only of vegetation type, with no consideration of the surroundings. In this study, a dynamic rooting scheme, which describes root growth as a compromise between water and nitrogen availability, was incorporated into CLM4.5 with carbon-nitrogen (CN) interactions (CLM4.5-CN) to investigate the effects of a dynamic root distribution on eco-hydrological modeling. Two paired numerical simulations were conducted for the Tapajos National Forest km83 (BRSa3) site and the Amazon, one using CLM4.5-CN without the dynamic rooting scheme and the other including the proposed scheme. Simulations for the BRSa3 site showed that inclusion of the dynamic rooting scheme increased the amplitudes and peak values of diurnal gross primary production (GPP) and latent heat flux (LE) for the dry season, and improved the carbon (C) and water cycle modeling by reducing the RMSE of GPP by 0.4 g C m-2 d-1, net ecosystem exchange by 1.96 g C m-2 d-1, LE by 5.0 W m-2, and soil moisture by 0.03 m3 m-3, at the seasonal scale, compared with eddy flux measurements, while having little impact during the wet season. For the Amazon, regional analysis also revealed that vegetation responses (including GPP and LE) to seasonal drought and the severe drought of 2005 were better captured with the dynamic rooting scheme incorporated.

  18. Irrigation of human prepared root canal – ex vivo based computational fluid dynamics analysis

    Science.gov (United States)

    Šnjarić, Damir; Čarija, Zoran; Braut, Alen; Halaji, Adelaida; Kovačević, Maja; Kuiš, Davor

    2012-01-01

    Aim To analyze the influence of the needle type, insertion depth, and irrigant flow rate on irrigant flow pattern, flow velocity, and apical pressure by ex-vivo based endodontic irrigation computational fluid dynamics (CFD) analysis. Methods Human upper canine root canal was prepared using rotary files. Contrast fluid was introduced in the root canal and scanned by computed tomography (CT) providing a three-dimensional object that was exported to the computer-assisted design (CAD) software. Two probe points were established in the apical portion of the root canal model for flow velocity and pressure measurement. Three different CAD models of 27G irrigation needles (closed-end side-vented, notched open-end, and bevel open-end) were created and placed at 25, 50, 75, and 95% of the working length (WL). Flow rates of 0.05, 0.1, 0.2, 0.3, and 0.4 mL/s were simulated. A total of 60 irrigation simulations were performed by CFD fluid flow solver. Results Closed-end side-vented needle required insertion depth closer to WL, regarding efficient irrigant replacement, compared to open-end irrigation needle types, which besides increased velocity produced increased irrigant apical pressure. For all irrigation needle types and needle insertion depths, the increase of flow rate was followed by an increased irrigant apical pressure. Conclusions The human root canal shape obtained by CT is applicable in the CFD analysis of endodontic irrigation. All the analyzed values –irrigant flow pattern, velocity, and pressure – were influenced by irrigation needle type, as well as needle insertion depth and irrigant flow rate. PMID:23100209

  19. Dynamic Model of a Rotating Flexible Arm-Flexible Root Mechanism Driven by a Shaft Flexible in Torsion

    Directory of Open Access Journals (Sweden)

    S.Z. Ismail

    2006-01-01

    Full Text Available This paper presents a dynamic model of a rotating flexible beam carrying a payload at its tip. The model accounts for the driving shaft and the arm root flexibilities. The finite element method and the Lagrangian dynamics are used in deriving the equations of motion with the small deformation theory assumptions and the Euler-Bernoulli beam theory. The obtained model is a nonlinear-coupled system of differential equations. The model is simulated for different combinations of shaft and root flexibilities and arm properties. The simulation results showed that the root flexibility is an important factor that should be considered in association with the arm and shaft flexibilities, as its dynamics influence the motor motion. Moreover, the effect of system non-linearity on the dynamic behavior is investigated by simulating the equivalent linearized system and it was found to be an important factor that should be considered, particularly when designing a control strategy for practical implementation.

  20. 不同根构型玉米的根系形态及其对密度的响应%Root Morphology and Its Response to Planting Density in Different Genotypes with Root Architecture

    Institute of Scientific and Technical Information of China (English)

    蔡红光; 刘剑钊; 张秀芝; 闫孝贡; 张洪喜; 袁静超; 盖嘉慧; 任军

    2014-01-01

    在两种种植密度下对8个测交种的根系形态及在0~60 cm土壤剖面的分布进行测定。结果表明,根长、根干重和根拔拉力均具有显著的基因型差异,其中,L105和L109属于大根系基因型;L172和L224属于小根系基因型。L132、L160、L224对密度的反应较为敏感,L219对密度的反应较为迟钝。在增加种植密度后,各基因型根系均有纵向延伸的特征,不同基因型根长和根干重在不同土壤层次间分布比例差异较大,且其对密度的反应仅表现在特定的土层内。%An experiment was conducted to evaluate the root morphology of eight genotypes and their distribu-tion in 0-60 cm soil layer in different planting density treatments. The results indicated that there were significant differences for root length, root dry weight, and vertical root pulling resistance. L105 and L109 had the larger root system, L172 and L224 had the smaller root system. L132, L160 and L224 were more sensitive toplanting density except for L219. The root presented the vertical extension with the increasing of density. There were significant geno-typic differences in different soil layers for root length and root dry weight. The reaction of genotypes on root system was in specific soil layers in different planting density treatments.

  1. Algebraic roots of Newtonian mechanics: correlated dynamics of particles on a unique worldline

    Science.gov (United States)

    Kassandrov, Vladimir V.; Khasanov, Ildus Sh

    2013-05-01

    In the development of the old ideas of Stueckelberg-Wheeler-Feynman on the ‘one-electron Universe’, we study the purely algebraic dynamics of the ensemble of (two kinds of) identical point-like particles. These are represented by the (real and complex conjugate) roots of a generic polynomial system of equations that implicitly defines a single ‘worldline’. The dynamics includes events of ‘merging’ of a pair of particles modelling the annihilation/creation processes. Correlations in the location and motion of the particles-roots relate, in particular, to the Vieta formulas. After a special choice of the inertial-like reference frame, the linear Vieta formulas guarantee that, for any worldline, the law of (non-relativistic) momentum conservation is identically satisfied. Thus, the general structure of Newtonian mechanics follows from the algebraic properties of a worldline alone. A simple example of, unexpectedly rich, ‘polynomial dynamics’ is retraced in detail and illustrated via an animation (available from stacks.iop.org/JPhysA/46/175206/mmedia).

  2. Maize varieties released in different eras have similar root length density distributions in the soil, which are negatively correlated with local concentrations of soil mineral nitrogen.

    Directory of Open Access Journals (Sweden)

    Peng Ning

    Full Text Available Larger, and deeper, root systems of new maize varieties, compared to older varieties, are thought to have enabled improved acquisition of soil resources and, consequently, greater grain yields. To compare the spatial distributions of the root systems of new and old maize varieties and their relationships with spatial variations in soil concentrations of available nitrogen (N, phosphorus (P and potassium (K, two years of field experiments were performed using six Chinese maize varieties released in different eras. Vertical distributions of roots, and available N, P and K in the 0-60 cm soil profile were determined in excavated soil monoliths at silking and maturity. The results demonstrated that new maize varieties had larger root dry weight, higher grain yield and greater nutrient accumulation than older varieties. All varieties had similar total root length and vertical root distribution at silking, but newer varieties maintained greater total root length and had more roots in the 30-60 cm soil layers at maturity. The spatial variation of soil mineral N (Nmin in each soil horizon was larger than that of Olsen-P and ammonium-acetate-extractable K, and was inversely correlated with root length density (RLD, especially in the 0-20 cm soil layer. It was concluded that greater acquisition of mineral nutrients and higher yields of newer varieties were associated with greater total root length at maturity. The negative relationship between RLD and soil Nmin at harvest for all varieties suggests the importance of the spatial distribution of the root system for N uptake by maize.

  3. Maize varieties released in different eras have similar root length density distributions in the soil, which are negatively correlated with local concentrations of soil mineral nitrogen.

    Science.gov (United States)

    Ning, Peng; Li, Sa; White, Philip J; Li, Chunjian

    2015-01-01

    Larger, and deeper, root systems of new maize varieties, compared to older varieties, are thought to have enabled improved acquisition of soil resources and, consequently, greater grain yields. To compare the spatial distributions of the root systems of new and old maize varieties and their relationships with spatial variations in soil concentrations of available nitrogen (N), phosphorus (P) and potassium (K), two years of field experiments were performed using six Chinese maize varieties released in different eras. Vertical distributions of roots, and available N, P and K in the 0-60 cm soil profile were determined in excavated soil monoliths at silking and maturity. The results demonstrated that new maize varieties had larger root dry weight, higher grain yield and greater nutrient accumulation than older varieties. All varieties had similar total root length and vertical root distribution at silking, but newer varieties maintained greater total root length and had more roots in the 30-60 cm soil layers at maturity. The spatial variation of soil mineral N (Nmin) in each soil horizon was larger than that of Olsen-P and ammonium-acetate-extractable K, and was inversely correlated with root length density (RLD), especially in the 0-20 cm soil layer. It was concluded that greater acquisition of mineral nutrients and higher yields of newer varieties were associated with greater total root length at maturity. The negative relationship between RLD and soil Nmin at harvest for all varieties suggests the importance of the spatial distribution of the root system for N uptake by maize.

  4. Changes in wood density, wood anatomy and hydraulic properties of the xylem along the root-to-shoot flow path in tropical rainforest trees.

    Science.gov (United States)

    Schuldt, Bernhard; Leuschner, Christoph; Brock, Nicolai; Horna, Viviana

    2013-02-01

    It is generally assumed that the largest vessels are occurring in the roots and that vessel diameters and the related hydraulic conductance in the xylem are decreasing acropetally from roots to leaves. With this study in five tree species of a perhumid tropical rainforest in Sulawesi (Indonesia), we searched for patterns in hydraulic architecture and axial conductivity along the flow path from small-diameter roots through strong roots and the trunk to distal sun-canopy twigs. Wood density differed by not more than 10% across the different flow path positions in a species, and branch and stem wood density were closely related in three of the five species. Other than wood density, the wood anatomical and xylem hydraulic traits varied in dependence on the position along the flow path, but were unrelated to wood density within a tree. In contrast to reports from conifers and certain dicotyledonous species, we found a hump-shaped variation in vessel diameter and sapwood area--specific conductivity along the flow path in all five species with a maximum in the trunk and strong roots and minima in both small roots and twigs; the vessel size depended on the diameter of the organ. This pattern might be an adaptation to the perhumid climate with a low risk of hydraulic failure. Despite a similar mean vessel diameter in small roots and twigs, the two distal organs, hydraulically weighted mean vessel diameters were on average 30% larger in small roots, resulting in ∼ 85% higher empirical and theoretical specific conductivities. Relative vessel lumen area in percent of sapwood area decreased linearly by 70% from roots to twigs, reflecting the increase in sclerenchymatic tissue and tracheids in acropetal direction in the xylem. Vessel size was more closely related to the organ diameter than to the distance along the root-to-shoot flow path. We conclude that (i) the five co-occurring tree species show convergent patterns in their hydraulic architecture despite different growth

  5. Probing Electron Dynamics with the Laplacian of the Momentum Density

    Energy Technology Data Exchange (ETDEWEB)

    Sukumar, N.; MacDougall, Preston J. [Middle Tennessee State University; Levit, M. Creon [Nasa Ames Research Center

    2012-09-24

    This chapter in the above-titled monograph presents topological analysis of the Laplacian of the electron momentum density in organic molecules. It relates topological features in this distribution to chemical and physical properties, particularly aromaticity and electron transport.

  6. Effects of phase transition induced density fluctuations on pulsar dynamics

    Directory of Open Access Journals (Sweden)

    Partha Bagchi

    2015-07-01

    Full Text Available We show that density fluctuations during phase transitions in pulsar cores may have non-trivial effects on pulsar timings, and may also possibly account for glitches and anti-glitches. These density fluctuations invariably lead to non-zero off-diagonal components of the moment of inertia, leading to transient wobbling of star. Thus, accurate measurements of pulsar timing and intensity modulations (from wobbling may be used to identify the specific pattern of density fluctuations, hence the particular phase transition, occurring inside the pulsar core. Changes in quadrupole moment from rapidly evolving density fluctuations during the transition, with very short time scales, may provide a new source for gravitational waves.

  7. Comparison of radiographic density and compaction index of root canal obturation using nickel titanium or stainless-steel spreaders

    Directory of Open Access Journals (Sweden)

    M. Adel

    2016-08-01

    Full Text Available Background: Both nickel titanium and stainless-steel spreaders are available. The obvious advantage of nickel titanium spreader over stainless steel spreaders is greater penetration in curved canals. Objective: To compare the radiographic density and compaction index of root canal obturation using nickel-titanium or stainless-steel spreaders in curved canals. Methods: In this experimental study the primary weight of 30 acrylic blocks with 45o degrees of apical curvature were measured by a scale (W1. After canals were prepared by step back master apical up to file #30 all blocks were weighed again (W2 and randomly divided in two groups of 15each. All canals were obturated by Cold lateral compaction technique (with nickel-titanium in one group and stainless-steel finger spreaders in another group. After all blocks were reweighed (W3, compaction index (W3-W2/W1-W2 was calculated. One radiograph was taken for each sample. Apical density of the apical third of each canal was measured by digital transmission densitometer. Data were analyzed statistically using T-test. Findings: Mean compaction index for nickel-titanium group was 7.67±2.38 and for stainless-steel group was 9.14±4.06. There was no significant difference between two groups. Mean radiographic density of obturation was 2.05±0.14 in nickel-titanium group and was 2.07±0.21 in stainless-steel group. There was no significant difference between two groups. Conclusion: It is concluded that nickel-titanium spreaders are not superior than stainless-steel spreaders in obturating curved canal.

  8. A molecular dynamics study of structure and dynamics in high-density liquids

    Science.gov (United States)

    Variyar, Jayasankar E.; Noro, Massimo; Kivelson, Daniel

    By means of molecular dynamics simulations we have investigated increasing configurational ordering and decreasing particle mobility with increasing density ρ of a three-dimensional equilibrated liquid composed of soft discs. The equal-time correlation function h(n)3 (0) which includes two-, three- and four-body correlations is introduced as a measure of structural order; this function is related to the dipole-induced-dipole equal-time correlation function and its sensitivity to structural order in the liquid is associated with the cancellation effect, i.e. the cancellation of the positive contributions of the two- and four- body correlations by the negative contribution of the three-body correlations. The analogous time-dependent correlation function h(4)3 (t) is also studied. The possible implications of these results to the study of supercooled liquids and glasses is discussed.

  9. Adaptive partitioning by local density-peaks: An efficient density-based clustering algorithm for analyzing molecular dynamics trajectories.

    Science.gov (United States)

    Liu, Song; Zhu, Lizhe; Sheong, Fu Kit; Wang, Wei; Huang, Xuhui

    2017-01-30

    We present an efficient density-based adaptive-resolution clustering method APLoD for analyzing large-scale molecular dynamics (MD) trajectories. APLoD performs the k-nearest-neighbors search to estimate the density of MD conformations in a local fashion, which can group MD conformations in the same high-density region into a cluster. APLoD greatly improves the popular density peaks algorithm by reducing the running time and the memory usage by 2-3 orders of magnitude for systems ranging from alanine dipeptide to a 370-residue Maltose-binding protein. In addition, we demonstrate that APLoD can produce clusters with various sizes that are adaptive to the underlying density (i.e., larger clusters at low-density regions, while smaller clusters at high-density regions), which is a clear advantage over other popular clustering algorithms including k-centers and k-medoids. We anticipate that APLoD can be widely applied to split ultra-large MD datasets containing millions of conformations for subsequent construction of Markov State Models. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  10. The correlations of ions density with geomagnetic activity and solar dynamic pressure in cusp region

    Institute of Scientific and Technical Information of China (English)

    GUO JianGuang; SHI JianKui; ZHANG TieLong; LIU ZhenXing; A. FAZAKERLEY; H. R(E)ME; Ⅰ. DANDOURAS; E. LUCEK

    2007-01-01

    A statistical study of the properties of ions (O+, He+ and H+) measured by the Cluster-Ⅱ in cusp region as a function of the solar wind dynamic pressure and geomagnetic index Kp respectively was made during the summer and fall of 2001 -2003. The main results are that: (1) O+ ion density responds in a significant way to geomagnetic index Kp, and He+ ion density is not correlated with geomagnetic index Kp,both of them have a significant positive correlation with solar wind dynamic pressure; (2) H+ ion density is also observed to increase with solar wind dynamic pressure, and not correlated with geomagnetic index Kp.

  11. Finite baryon density effects on gauge field dynamics

    CERN Document Server

    Bödeker, Dietrich

    2001-01-01

    We discuss the effective action for QCD gauge fields at finite temperatures and densities, obtained after integrating out the hardest momentum scales from the system. We show that a non-vanishing baryon density induces a charge conjugation (C) odd operator to the gauge field action, proportional to the chemical potential. Even though it is parametrically smaller than the leading C even operator, it could have an important effect on C odd observables. The same operator appears to be produced by classical kinetic theory, allowing in principle for a non-perturbative study of such processes.

  12. Abscisic acid dynamics in roots detected with genetically encoded FRET sensors.

    Science.gov (United States)

    Jones, Alexander M; Danielson, Jonas Ah; Manojkumar, Shruti N; Lanquar, Viviane; Grossmann, Guido; Frommer, Wolf B

    2014-04-15

    Cytosolic hormone levels must be tightly controlled at the level of influx, efflux, synthesis, degradation and compartmentation. To determine ABA dynamics at the single cell level, FRET sensors (ABACUS) covering a range ∼0.2-800 µM were engineered using structure-guided design and a high-throughput screening platform. When expressed in yeast, ABACUS1 detected concentrative ABA uptake mediated by the AIT1/NRT1.2 transporter. Arabidopsis roots expressing ABACUS1-2µ (Kd∼2 µM) and ABACUS1-80µ (Kd∼80 µM) respond to perfusion with ABA in a concentration-dependent manner. The properties of the observed ABA accumulation in roots appear incompatible with the activity of known ABA transporters (AIT1, ABCG40). ABACUS reveals effects of external ABA on homeostasis, that is, ABA-triggered induction of ABA degradation, modification, or compartmentation. ABACUS can be used to study ABA responses in mutants and quantitatively monitor ABA translocation and regulation, and identify missing components. The sensor screening platform promises to enable rapid fine-tuning of the ABA sensors and engineering of plant and animal hormone sensors to advance our understanding of hormone signaling. DOI: http://dx.doi.org/10.7554/eLife.01741.001.

  13. Space-time dynamics of fine root biomass of six forests in the Maoershan forest region,northeast China

    Institute of Scientific and Technical Information of China (English)

    ZHOU Biao; ZHU Shengying; MAO Zijun; WANG Xiuwei; ZHAO Xizhu; SUN Yuanfa

    2007-01-01

    The Maoershan forestry centre is situated in the Zhangguangcai Mountain of the Changbai mountain range.The main forest types in the Maoershan region are plantation (Pinus sylvestris var.mongolica,Pinus koraiensis and Larix gmelinii) and natural secondary forests (Fraxinus mandshurica,Quercus mongolica and Populus davidiana).Fine roots have enormous surface areas,growing and turning over quickly,which plays an important role in terms of substance cycling and energy flow in the forest ecosystem.This study deals with the dynamics of live,dead,and total fine roots (≤ mm) biomass in the 0-30 cm soil layer using the soil core method.Differences between the six stands in the Maoershan region showed the following results:1) the fine root biomass in the various stands showed obvious differences.The total fine root biomass of six stands from high to low were F.mandshurica (1,030.0 g/m2) > Q.mongolica (973.4 g/m2) > Pinus koraiensis (780.9 g/m2) >L.gmelinii (718.2 g/m2) > Populusdavidiana(709.1 g/m2) > Pinus sylvestris var.mongolica (470.4 g/m2);2) except for L.gmelinii,the development of live fine root biomass agreed with the trend of total fine root biomass.The maximum biomass of live fine roots in Pinus koraiensis or L.gmelinii stand appeared in May,others in June;in the F.mandshurica stand,the minimum biomass of live fine roots occurred in September,others in July or August;3) the proportions of dead fine root biomass varied in different stands;4) the vertical distribution of fine roots was affected by temperature,water,and nutrients;the proportion of fine root biomass was concentrated in the 0-10 cm soil layer.The fine root biomass of six stands in the 0-10 cm soil layer was over 40% of the total fine root biomass;this proportion was 60.3% in F.mandshurica. Space-time dynamics of the various stands had different characteristics.When investigating the substance cycling and energy flows of all forest ecosystems,we should consider the characteristics of

  14. [Population of entophytic bacteria in maize roots and its dynamic analysis].

    Science.gov (United States)

    Gao, Zenggui; Zhuang, Jinghua; Chen, Jie; Liu, Xian; Tang, Shuge

    2004-08-01

    In 2001-2002, 14 maize cultivars in Liaoning Province were used for the analysis of their entophytic bacteria population. The entophytic bacteria strains with a higher frequency in maize roots were Bacillus spp., Enterobacter spp., Serratia spp., Pseudomonas spp., Xanthomonas spp., Clavibacter spp., Bacillus spp., Enterobacter spp. and Serratia spp. Comparatively, Bacillus spp. was the most prevalent entophytic bacterium, including 8 species, B. subtilis, B. megaterium, B. cereus, B. licheniformis, B. anthracis, B. mycoides, B. pumilus and B. circulans, and with an average isolation frequency of 75.5% at seedling stage and 77.6% at adult stage. There existed significant differences in the population and dynamics of endophytic bacteria among maize cultivars and growth periods, and a significant correlation was found between maize genetic background and entophytic bacteria population.

  15. Calcium dynamics in root cells of Arabidopsis thaliana visualized with selective plane illumination microscopy.

    Directory of Open Access Journals (Sweden)

    Alex Costa

    Full Text Available Selective Plane Illumination Microscopy (SPIM is an imaging technique particularly suited for long term in-vivo analysis of transparent specimens, able to visualize small organs or entire organisms, at cellular and eventually even subcellular resolution. Here we report the application of SPIM in Calcium imaging based on Förster Resonance Energy Transfer (FRET. Transgenic Arabidopsis plants expressing the genetically encoded-FRET-based Ca(2+ probe Cameleon, in the cytosol or nucleus, were used to demonstrate that SPIM enables ratiometric fluorescence imaging at high spatial and temporal resolution, both at tissue and single cell level. The SPIM-FRET technique enabled us to follow nuclear and cytosolic Ca(2+ dynamics in Arabidopsis root tip cells, deep inside the organ, in response to different stimuli. A relevant physiological phenomenon, namely Ca(2+ signal percolation, predicted in previous studies, has been directly visualized.

  16. Influence of plasma density and plasma sheath dynamics on the ion implantation by plasma immersion technique

    OpenAIRE

    Ensinger, Wolfgang

    1996-01-01

    Influence of plasma density and plasma sheath dynamics on the ion implantation by plasma immersion technique / B. Rauschenbach ... - In: Nuclear instruments and methods in physics research. B. 113. 1996. S. 266-269

  17. Density dependence and population dynamics of black rhinos (Diceros bicornis michaeli) in Kenya's rhino sanctuaries

    NARCIS (Netherlands)

    Ouma, B.O.; Amin, R.; Langevelde, van F.; Leader-Williams, N.

    2010-01-01

    Density-dependent feedback mechanisms provide insights into the population dynamics and interactions of large herbivores with their ecosystem. Sex ratio also has particularly important implications for growth rates of many large mammal populations through its influence on reproductive potential.

  18. Growth dynamics of fine roots in a coniferous fern forest site close to Forsmark in the central part of Sweden

    Energy Technology Data Exchange (ETDEWEB)

    Persson, Hans; Stadenberg, Ingela (SLU, Dept. of Ecology and Environmental Research, Uppsala (Sweden))

    2007-12-15

    The seasonal growth dynamics of live and dead roots for trees and the field layer species (g/m2, varying diameter fractions) and live/dead ratios were analysed at a fresh/moist coniferous fern forest site close to the nuclear power plant at Forsmark in the central eastern parts of Sweden. The changes in depth distribution of fine roots were observed at depth intervals of the top humus horizon down to 40 cm in the mineral soil profile. The bulk of living fine roots of trees (< 1 mm in diameter) were found in the mineral soil horizon the total profile down to 40 cm of the mineral soil, where 89, 82, 83 and 89% of the total amount in the whole profile were found. The upper 2.5 cm part of the humus layer contained 83, 81, 100 and 100% of all roots of the humus layer on the four different sampling occasions. High amounts of living fine roots were found in the upper 10 cm of the mineral soil horizon viz. 84, 76, 91 and 69% of the total mineral soil layer. Consequently, both the top soil horizons of the humus and the mineral soil layers were heavily penetrated by living fine roots. The highest proportion of living fine roots was found in the top 2.5 cm of the humus layer. Accordingly, the live/dead ratio of fine roots (< 1 mm in diameter) decreased from the top of the humus layer to the lower part of mineral soil horizon from 8.0-0.3, 0.8-0.2, 4.4-0.4 and 3.3-0.7 (g g-1) for the four sampling occasions, respectively. We concluded that the decrease in the live/ dead ratio was related to decreased vitality with depth of the fine roots in the soil profile. The highest live/dead ratio was found in the upper 2.5 cm of the humus layer for both the tree and field-layer species. This distribution pattern was most evident for tree fine roots < 1 mm in diameter. The mean fine-root biomass (live tissue < 1 mm in diameter) of tree species for the total profile varied on the four sampling occasions between 317, 113, 139 and 248 g m-2. The related fine root necromass (dead tissue

  19. Density matrix renormalization group with efficient dynamical electron correlation through range separation

    Energy Technology Data Exchange (ETDEWEB)

    Hedegård, Erik Donovan, E-mail: erik.hedegard@phys.chem.ethz.ch; Knecht, Stefan; Reiher, Markus, E-mail: markus.reiher@phys.chem.ethz.ch [Laboratorium für Physikalische Chemie, ETH Zürich, Vladimir-Prelog-Weg 2, CH-8093 Zürich (Switzerland); Kielberg, Jesper Skau; Jensen, Hans Jørgen Aagaard, E-mail: hjj@sdu.dk [Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, Odense (Denmark)

    2015-06-14

    We present a new hybrid multiconfigurational method based on the concept of range-separation that combines the density matrix renormalization group approach with density functional theory. This new method is designed for the simultaneous description of dynamical and static electron-correlation effects in multiconfigurational electronic structure problems.

  20. Density matrix renormalization group with efficient dynamical electron correlation through range separation

    DEFF Research Database (Denmark)

    Hedegård, Erik D.; Knecht, Stefan; Kielberg, Jesper Skau

    2015-01-01

    We present a new hybrid multiconfigurational method based on the concept of range-separation that combines the density matrix renormalization group approach with density functional theory. This new method is designed for the simultaneous description of dynamical and static electroncorrelation...

  1. Density Matrix Renormalization Group with Efficient Dynamical Electron Correlation Through Range Separation

    CERN Document Server

    Hedegård, Erik Donovan; Kielberg, Jesper Skau; Jensen, Hans Jørgen Aagaard; Reiher, Markus

    2015-01-01

    We present a new hybrid multiconfigurational method based on the concept of range-separation that combines the density matrix renormalization group approach with density functional theory. This new method is designed for the simultaneous description of dynamical and static electron-correlation effects in multiconfigurational electronic structure problems.

  2. Molecular dynamics simulation for the baryon-quark phase transition at finite baryon density

    Energy Technology Data Exchange (ETDEWEB)

    Akimura, Y. [Saitama University, Department of physics, Sakura-Ku, Saitama City (Japan); Japan Atomic Energy Research Institute, Advanced Science Research Center, Tokai (Japan); Maruyama, T.; Chiba, S. [Japan Atomic Energy Research Institute, Advanced Science Research Center, Tokai (Japan); Yoshinaga, N. [Saitama University, Department of physics, Sakura-Ku, Saitama City (Japan)

    2005-09-01

    We study the baryon-quark phase transition in the molecular dynamics (MD) of the quark degrees of freedom at finite baryon density. The baryon state at low baryon density, and the deconfined quark state at high baryon density are reproduced. We investigate the equations of state of matters with different u-d-s compositions. It is found that the baryon-quark transition is sensitive to the quark width. (orig.)

  3. Irrigant flow in the root canal: experimental validation of an unsteady Computational Fluid Dynamics model using high-speed imaging

    NARCIS (Netherlands)

    Boutsioukis, C.; Verhaagen, B.; Versluis, M.; Kastrinakis, E.; Sluis, van der L.W.M.

    2010-01-01

    Aim  To compare the results of a Computational Fluid Dynamics (CFD) simulation of the irrigant flow within a prepared root canal, during final irrigation with a syringe and a needle, with experimental high-speed visualizations and theoretical calculations of an identical geometry and to evaluate the

  4. Irrigant flow in the root canal: experimental validation of an unsteady computational fluid dynamics model using high-speed imaging

    NARCIS (Netherlands)

    C. Boutsioukis; B. Verhaagen; M. Versluis; E. Kastrinakis; L.W.M. van der Sluis

    2010-01-01

    Aim  To compare the results of a Computational Fluid Dynamics (CFD) simulation of the irrigant flow within a prepared root canal, during final irrigation with a syringe and a needle, with experimental high-speed visualizations and theoretical calculations of an identical geometry and to evaluate the

  5. The effect of apical preparation size on irrigant flow in root canals evaluated using an unsteady Computational Fluid Dynamics model

    NARCIS (Netherlands)

    Boutsioukis, C.; Gogos, C.; Verhaagen, B.; Versluis, M.; Kastrinakis, E.; van der Sluis, L.W.M.

    2010-01-01

    Aim  To evaluate the effect of apical preparation size on irrigant flow inside a root canal during final irrigation with a syringe and two different needles types, using a Computational Fluid Dynamics (CFD) model. Methodology  A validated CFD model was used to simulate the irrigant flow from either

  6. Evaluation of irrigant flow in the root canal using different needle types by an unsteady computational fluid dynamics model

    NARCIS (Netherlands)

    Boutsioukis, C.; Verhaagen, B.; Versluis, M.; Kastrinakis, E.; Wesselink, P.R.; van der Sluis, L.W.M.

    2010-01-01

    Introduction The aim of this study was to evaluate the effect of needle tip design on the irrigant flow inside a prepared root canal during final irrigation with a syringe using a validated Computational Fluid Dynamics (CFD) model. Methods A CFD model was created to simulate the irrigant flow inside

  7. Evaluation of Irrigant Flow in the Root Canal Using Different Needle Types by an Unsteady Computational Fluid Dynamics Model

    NARCIS (Netherlands)

    Boutsioukis, Christos; Verhaagen, Bram; Versluis, Michel; Kastrinakis, Eleftherios; Wesselink, Paul R.; Sluis, van der Lucas W.M.

    2010-01-01

    Introduction: The aim of this study was to evaluate the effect of needle tip design on the irrigant flow inside a prepared root canal during final irrigation with a syringe using a validated Computational Fluid Dynamics (CFD) model. Methods: A CFD model was created to simulate the irrigant flow insi

  8. Dynamic behavior of chemical reactivity indices in density functional theory: A Bohn-Oppenheimer quantum molecular dynamics study

    Indian Academy of Sciences (India)

    Shubin Liu

    2005-09-01

    Dynamic behaviors of chemical concepts in density functional theory such as frontier orbitals (HOMO/LUMO), chemical potential, hardness, and electrophilicity index have been investigated in this work in the context of Bohn-Oppenheimer quantum molecular dynamics in association with molecular conformation changes. Exemplary molecular systems like CH$^{+}_{5}$ , Cl- (H2O)30 and Ca2+ (H2O)15 are studied at 300 K in the gas phase, demonstrating that HOMO is more dynamic than LUMO, chemical potential and hardness often fluctuate concurrently. It is argued that DFT concepts and indices may serve as a good framework to understand molecular conformation changes as well as other dynamic phenomena.

  9. Improving AODV Performance using Dynamic Density Driven Route Request Forwarding

    CERN Document Server

    Kanakaris, Venetis; Ovaliadis, Kyriakos

    2011-01-01

    Ad-hoc routing protocols use a number of algorithms for route discovery. Some use flooding in which a route request packet (RREQ) is broadcasted from a source node to other nodes in the network. This often leads to unnecessary retransmissions, causing congestion and packet collisions in the network, a phenomenon called a broadcast storm. This paper presents a RREQ message forwarding scheme for AODV that reduces routing overheads. This has been called AODV_EXT. Its performance is compared to that of AODV, DSDV, DSR and OLSR protocols. Simulation results show that AODV_EXT achieves 3% energy efficiency, 19.5% improvement in data throughput and 69.5% reduction in the number of dropped packets for a network of 50 nodes. Greater efficiency is achieved in high density network and marginal improvement in networks with a small number of nodes.

  10. Soil moisture causes dynamic adjustments to root reinforcement that reduce slope stability

    Science.gov (United States)

    Tristram C. Hales; Chelcy F. Miniat

    2017-01-01

    In steep soil-mantled landscapes, the initiation of shallow landslides is strongly controlled by the distribution of vegetation, whose roots reinforce the soil. The magnitude of root reinforcement depends on the number, diameter distribution, orientation and the mechanical properties of roots that cross potential failure planes. Understanding how these...

  11. Hormonal dynamics during recovery from drought in two Eucalyptus globulus genotypes: from root to leaf.

    Science.gov (United States)

    Correia, Barbara; Pintó-Marijuan, Marta; Castro, Bruno B; Brossa, Ricard; López-Carbonell, Marta; Pinto, Glória

    2014-09-01

    Drought is a limiting environmental stress that represents a growing constraint to the forestry sector. Eucalyptus globulus is a widely planted coppice species, which capacity to cope with water deficit has already been described. However, the capacity of this species to recover is still poorly understood. In this study, we aimed to investigate the changes in abscisic acid (ABA), ABA-glucose ester (ABA-GE) and jasmonic acid (JA) content in leaves, xylem sap and roots of two genotypes (AL-10 and AL-18) during rewatering (2 h, 4 h, 24 h, and 168 h), after a drought stress period (0 h). We wished to clarify the role of these hormones in the recovery from drought and to determine whether these hormonal relations were related to specific genotype metabolisms. Our results showed that drought caused an increased in ABA and ABA-GE levels in all analysed plant parts, while JA content decreased in leaves, increased in xylem sap and did not change in roots. Some of these responses were genotype specific. During rewatering, ABA and ABA-GE content decreased in both genotypes and all plant parts, but at different time scales, and JA levels did not greatly change. Again, the genotypes responded differently. Altogether, our results characterised the response pattern of clone AL-10 as more responsive and defended that leaf should be used in preliminary screening methods of stress tolerance. The hormonal dynamics were related to the previously documented responses of these genotypes and sustain further physiological and molecular studies of water stress in this and other tree species.

  12. Density decrease in vanadium-base alloys irradiated in the dynamic helium charging experiment

    Energy Technology Data Exchange (ETDEWEB)

    Chung, H.M.; Galvin, T.M.; Smith, D.L. [Argonne National Laboratory, Chicago, IL (United States)

    1996-04-01

    Combined effects of dynamically charged helium and neutron damage on density decrease (swelling) of V-4Cr-4Ti, V-5Ti, V-3Ti-1Si, and V-8Cr-6Ti alloys have been determined after irradiation to 18-31 dpa at 425-600{degrees}C in the Dynamic helium Charging Experiment (DHCE). To ensure better accuracy in density measurement, broken pieces of tensile specimens {approx} 10 times heavier than a transmission electron microscopy (TEM) disk were used. Density increases of the four alloys irradiated in the DHCE were <0.5%. This small change seems to be consistent with the negligible number density of microcavities characterized by TEM. Most of the dynamically produced helium atoms seem to have been trapped in the grain matrix without significant cavity nucleation or growth.

  13. On stochastic modelling of groundwater uptake in semi-arid water-limited systems: root density and seasonality effects

    NARCIS (Netherlands)

    Vervoort, R.W.; Zee, van der S.E.A.T.M.

    2012-01-01

    In recent ecohydrological modelling, a common basis has been found in methodology and axiomas, such as the minimalist, systems analysis approach and a piecewise linear root zone water loss function. In this paper, we consider the loss function for root zones in contact with ground water through capi

  14. Light-front representation of chiral dynamics in peripheral transverse densities

    CERN Document Server

    Granados, C

    2015-01-01

    The nucleon's electromagnetic form factors are expressed in terms of the transverse densities of charge and magnetization at fixed light-front time. At peripheral transverse distances $b = O(M_\\pi^{-1})$ the densities are governed by chiral dynamics and can be calculated model-independently using chiral effective field theory (EFT). We represent the leading-order chiral EFT results for the peripheral transverse densities as overlap integrals of chiral light-front wave functions, describing the transition of the initial nucleon to soft pion-nucleon intermediate states and back. The new representation (a) explains the parametric order of the peripheral transverse densities; (b) establishes an inequality between the spin-independent and -dependent densities; (c) exposes the role of pion orbital angular momentum in chiral dynamics; (d) reveals a large left-right asymmetry of the current in a transversely polarized nucleon and suggests a simple interpretation. The light-front representation enables a first-quantiz...

  15. The demography of climate-driven and density-regulated population dynamics in a perennial plant

    DEFF Research Database (Denmark)

    Dahlgren, Johan; Bengstsson, Karin; Ehrlén, Johan

    2016-01-01

    Identifying the internal and external drivers of population dynamics is a key objective in ecology, currently accentuated by the need to forecast the effects of climate change on species distributions and abundances. The interplay between environmental and density effects is one particularly...... to be driven solely by the environment can overestimate extinction risks if there is density dependence. We conclude that density regulation can dampen effects of climate change on Fumana population size, and discuss the need to quantify density dependence in predictions of population responses...... important aspect of such forecasts. We examined the simultaneous impact of climate and intraspecific density on vital rates of the dwarf shrub Fumana procumbens over 20 yr, using generalized additive mixed models. We then analyzed effects on population dynamics using integral projection models...

  16. Efficient estimation of dynamic density functions with an application to outlier detection

    KAUST Repository

    Qahtan, Abdulhakim Ali Ali

    2012-01-01

    In this paper, we propose a new method to estimate the dynamic density over data streams, named KDE-Track as it is based on a conventional and widely used Kernel Density Estimation (KDE) method. KDE-Track can efficiently estimate the density with linear complexity by using interpolation on a kernel model, which is incrementally updated upon the arrival of streaming data. Both theoretical analysis and experimental validation show that KDE-Track outperforms traditional KDE and a baseline method Cluster-Kernels on estimation accuracy of the complex density structures in data streams, computing time and memory usage. KDE-Track is also demonstrated on timely catching the dynamic density of synthetic and real-world data. In addition, KDE-Track is used to accurately detect outliers in sensor data and compared with two existing methods developed for detecting outliers and cleaning sensor data. © 2012 ACM.

  17. Discharge dynamics and plasma density recovery by on/off switches of additional gas

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hyo-Chang, E-mail: lhc@kriss.re.kr [Center for Vacuum Technology, Korea Research Institute of Standard and Science, Daejeon 305-340 (Korea, Republic of); Department of Electrical Engineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul 04763 (Korea, Republic of); Kwon, Deuk-Chul [Plasma Technology Research Center, Nation Fusion Research Institute, Gunsan 573-540 (Korea, Republic of); Oh, SeungJu; Kang, Hyun-Ju; Kim, Yu-Sin; Chung, Chin-Wook, E-mail: joykang@hanyang.ac.kr [Department of Electrical Engineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul 04763 (Korea, Republic of)

    2016-06-15

    Measurement of the plasma density is investigated to study plasma dynamics by adding reactive gas (O{sub 2}) or rare gas (He) in Ar plasmas. When the O{sub 2} or He gas is added, plasma density is suddenly decreased, while the plasma density recovers slowly with gas off. It is found that the recovery time is strongly dependent on the gas flow rate, and it can be explained by effect of gas residence time. When the He gas is off in the Ar plasma, the plasma density is overshot compared to the case of the O{sub 2} gas pulsing due to enhanced ionizations by metastable atoms. Analysis and calculation for correlation between the plasma density dynamics and the gas pulsing are also presented in detail.

  18. Momentum density of spacetime and the gravitational dynamics

    CERN Document Server

    Padmanabhan, T

    2015-01-01

    I introduce a covariant four-vector $\\mathcal{G}^a[v]$, which can be interpreted as the momentum density attributed to the spacetime geometry by an observer with velocity $v^a$, and describe its properties: (a) Demanding that the total momentum of matter plus geometry is conserved for all observers, leads to the gravitational field equations. Thus, how matter curves spacetime is entirely determined by this principle of momentum conservation. (b) The $\\mathcal{G}^a[v]$ can be related to the gravitational Lagrangian in a manner similar to the usual definition of Hamiltonian in, say, classical mechanics. (c) Geodesic observers in a spacetime will find that the conserved total momentum vanishes on-shell. (d) The on-shell, conserved, total energy in a region of space, as measured by the comoving observers, will be equal to the total heat energy of the boundary surface. (e) The off-shell gravitational energy in a region will be the sum of the ADM energy in the bulk plus the thermal energy of the boundary. These res...

  19. Momentum density of spacetime and the gravitational dynamics

    Science.gov (United States)

    Padmanabhan, T.

    2016-01-01

    I introduce a covariant four-vector G^a[v], which can be interpreted as the momentum density attributed to the spacetime geometry by an observer with velocity v^a, and describe its properties: (a) Demanding that the total momentum of matter plus geometry is conserved for all observers, leads to the gravitational field equations. Thus, how matter curves spacetime is entirely determined by this principle of momentum conservation. (b) The G^a[v] can be related to the gravitational Lagrangian in a manner similar to the usual definition of Hamiltonian in, say, classical mechanics. (c) Geodesic observers in a spacetime will find that the conserved total momentum vanishes on-shell. (d) The on-shell, conserved, total energy in a region of space, as measured by comoving observers, will be equal to the total heat energy of the boundary surface. (e) The off-shell gravitational energy in a region will be the sum of the ADM energy in the bulk plus the thermal energy of the boundary. These results suggest that G^a[v] can be a useful physical quantity to probe the gravitational theories.

  20. Dynamical charge density waves rule the phase diagram of cuprates

    Science.gov (United States)

    Caprara, S.; Di Castro, C.; Seibold, G.; Grilli, M.

    2017-06-01

    In the last few years, charge density waves (CDWs) have been ubiquitously observed in high-temperature superconducting cuprates and are now the most investigated among the competing orders in the still hot debate on these systems. A wealth of new experimental data raises several fundamental issues that challenge the various theoretical proposals. We here relate our mean-field instability line TCDW0 of a strongly correlated Fermi liquid to the pseudogap T*(p ) line, marking in this way the onset of CDW-fluctuations. These fluctuations reduce strongly the mean-field critical line. Controlling this reduction via an infrared frequency cutoff related to the characteristic time of the probes, we account for the complex experimental temperature versus doping phase diagram. We provide a coherent scenario explaining why different CDW onset curves are observed by different experimental probes and seem to extrapolate at zero temperature into seemingly different quantum critical points (QCPs) in the intermediate and overdoped region. The nearly singular anisotropic scattering mediated by these fluctuations also accounts for the rapid changes of the Hall number seen in experiments and provides the first necessary step for a possible Fermi surface reconstruction fully establishing at lower doping. Finally, we show that phase fluctuations of the CDWs, which are enhanced in the presence of strong correlations near the Mott insulating phase, naturally account for the disappearance of the CDWs at low doping with yet another QCP as seen by the experiments.

  1. Density-dependent population dynamics in larvae of the dragonfly Pachydiplax longipennis: a field experiment.

    Science.gov (United States)

    Van Buskirk, J

    1987-05-01

    Several features of dragonfly population biology suggest that population regulation occurs in the larval stage. This study was designed to determine if density-dependent interactions among larval odonates can affect survival, growth and emergence. First-instar larvae of the dragonfly Pachydiplax longipennis were raised in outdoor experimental ponds at initial densities of 38, 152, and 608 larvae · m(-2), under two levels of food availability. Food availability was supplemented in half the pools by volumetric addition of zooplankton every other day. Pools in the low food treatment did not receive the zooplankton supplement.There was a strong negative effect of density on the mean growth rate of survivors, which included both emerging tenerals and individuals overwintering in the larval stage. A higher proportion emerged from low density than high density pools. Metamorphs from high density populations were smaller and emerged slightly later than those from low density, but the absolute number of metamorphs did not differ significantly among density treatments. Food supplementation significantly increased the proportion of overwintering larvae. There were no significant food-by-density interactions, indicating that food and density acted independently on larval population dynamics. Density-dependent mechanisms can clearly contribute to odonate population regulation, especially by controlling the number of larvae which emerge and the average age at reproduction. Population-level responses to density may be a result of interference among larvae.

  2. Root dynamics in an artificially constructed regenerating longleaf pine ecosystem are affected by atmospheric CO(2) enrichment.

    Science.gov (United States)

    Pritchard, S G.; Davis, M A.; Mitchell, R J.; Prior, S A.; Boykin, D L.; Rogers, H H.; Runion, G B.

    2001-08-01

    Differential responses to elevated atmospheric CO(2) concentration exhibited by different plant functional types may alter competition for above- and belowground resources in a higher CO(2) world. Because C allocation to roots is often favored over C allocation to shoots in plants grown with CO(2) enrichment, belowground function of forest ecosystems may change significantly. We established an outdoor facility to examine the effects of elevated CO(2) on root dynamics in artificially constructed communities of five early successional forest species: (1) a C(3) evergreen conifer (longleaf pine, Pinus palustris Mill.); (2) a C(4) monocotyledonous bunch grass (wiregrass, Aristida stricta Michx.); (3) a C(3) broadleaf tree (sand post oak, Quercus margaretta); (4) a C(3) perennial herbaceous legume (rattlebox, Crotalaria rotundifolia Walt. ex Gemel); and (5) an herbaceous C(3) dicotyledonous perennial (butterfly weed, Asclepias tuberosa L.). These species are common associates in early successional longleaf pine savannahs throughout the southeastern USA and represent species that differ in life-form, growth habit, physiology, and symbiotic relationships. A combination of minirhizotrons and soil coring was used to examine temporal and spatial rooting dynamics from October 1998 to October 1999. CO(2)-enriched plots exhibited 35% higher standing root crop length, 37% greater root length production per day, and 47% greater root length mortality per day. These variables, however, were enhanced by CO(2) enrichment only at the 10-30 cm depth. Relative root turnover (flux/standing crop) was unchanged by elevated CO(2). Sixteen months after planting, root biomass of pine was 62% higher in elevated compared to ambient CO(2) plots. Conversely, the combined biomass of rattlebox, wiregrass, and butterfly weed was 28% greater in ambient compared to high CO(2) plots. There was no difference in root biomass of oaks after 16 months of exposure to elevated CO(2). Using root and shoot

  3. Molecular dynamics simulation for baryon-quark phase transition at finite temperature and density

    CERN Document Server

    Akimura, Y; Yoshinaga, N; Chiba, S; Akimura, Yuka; Maruyama, Toshiki; Yoshinaga, Naotaka; Chiba, Satoshi

    2005-01-01

    We study the baryon-quark phase transition in a molecular dynamics (MD) of quark degrees of freedom at finite temperature and density. The baryon state at low density and temperature, and the deconfined quark state at high density and temperature are reproduced. We investigate the equations of state of matters with different $u$-$d$-$s$ compositions. Then we draw phase diagrams in the temperature-density plane by this simulation. It is found that the baryon-quark transition is sensitive to the quark width.

  4. Modeling of neutral gas dynamics in high-density plasmas

    Science.gov (United States)

    Canupp, Patrick Wellington

    This thesis describes a physical model of chemically reactive neutral gas flow and discusses numerical solutions of this model for the flow in an inductively coupled plasma etch reactor. To obtain these solutions, this research develops an efficient, implicit numerical method. As a result of the enhanced numerical stability of the scheme, large time steps advance the solution from initial conditions to a final steady state in fewer iterations and with less computational expense than simpler explicit methods. This method would incorporate suitably as a module in currently existing large scale plasma simulation tools. In order to demonstrate the accuracy of the numerical technique, this thesis presents results from two simulations of flows that possess theoretical solutions. The first case is the inviscid flow of a gas through a converging nozzle. A comparison of the numerical solution to isentropic flow theory shows that the numerical technique capably captures the essential flow features of this environment. The second case is the Couette flow of a gas between two parallel plates. The simulation results compare well with the exact solution for this flow. After establishing the accuracy of the numerical technique, this thesis discusses results for the flow of chemically reactive gases in a chlorine plasma etch reactor. This research examines the influence of the plasma on the neutral gas and the dynamics exhibited by the neutral gas in the reactor. This research finds that the neutral gas temperature strongly depends on the rate at which inelastic, electron-impact dissociation reactions occur and on atomic chlorine wall recombination rates. Additionally, the neutral gas Aow in the reactor includes a significant mass flux of etch product from the wafer surface. Resolution of these effects is useful for neutral gas simulation. Finally, this thesis demonstrates that continuum fluid models provide reasonable accuracy for these low pressure reactor flows due to the fact

  5. Dynamic transcriptional profiling provides insights into tuberous root development in Rehmannia glutinosa

    Directory of Open Access Journals (Sweden)

    Peng eSun

    2015-06-01

    Full Text Available Rehmannia glutinosa, a herb of the Scrophulariaceae family, is widely cultivated in the Northern part of China. The tuberous root has well known medicinal properties; however, yield and quality are threatened by abiotic and biotic stresses. Understanding the molecular process of tuberous root development may help identify novel targets for its control. In the present study, we used Illumina sequencing and de novo assembly strategies to obtain a reference transcriptome that is relevant to tuberous root development. We then conducted RNA-seq quantification analysis to determine gene expression profiles of the adventitious root (AR, thickening adventitious root (TAR, and the developing tuberous root (DTR. Expression profiling identified a total of 6,974 differentially expressed unigenes during root developmental. Bioinformatics analysis and gene expression profiling revealed changes in phenylpropanoid biosynthesis, starch and sucrose metabolism, and plant hormone biosynthesis during root development. Moreover, we identified and allocated putative functions to the genes involved in tuberous root development, including genes related to major carbohydrate metabolism, hormone metabolism, and transcription regulation. The present study provides the initial description of gene expression profiles of AR, TAR, and DTR, which facilitates identification of genes of interest. Moreover, our work provides insights into the molecular mechanisms underlying tuberous root development and may assist in the design and development of improved breeding schemes for different R. glutinosa varieties through genetic manipulation.

  6. Root cooling strongly affects diel leaf growth dynamics, water and carbohydrate relations in Ricinus communis.

    Science.gov (United States)

    Poiré, Richard; Schneider, Heike; Thorpe, Michael R; Kuhn, Arnd J; Schurr, Ulrich; Walter, Achim

    2010-03-01

    In laboratory and greenhouse experiments with potted plants, shoots and roots are exposed to temperature regimes throughout a 24 h (diel) cycle that can differ strongly from the regime under which these plants have evolved. In the field, roots are often exposed to lower temperatures than shoots. When the root-zone temperature in Ricinus communis was decreased below a threshold value, leaf growth occurred preferentially at night and was strongly inhibited during the day. Overall, leaf expansion, shoot biomass growth, root elongation and ramification decreased rapidly, carbon fluxes from shoot to root were diminished and carbohydrate contents of both root and shoot increased. Further, transpiration rate was not affected, yet hydrostatic tensions in shoot xylem increased. When root temperature was increased again, xylem tension reduced, leaf growth recovered rapidly, carbon fluxes from shoot to root increased, and carbohydrate pools were depleted. We hypothesize that the decreased uptake of water in cool roots diminishes the growth potential of the entire plant - especially diurnally, when the growing leaf loses water via transpiration. As a consequence, leaf growth and metabolite concentrations can vary enormously, depending on root-zone temperature and its heterogeneity inside pots.

  7. Dynamical density functional theory for molecular and colloidal fluids: a microscopic approach to fluid mechanics.

    Science.gov (United States)

    Archer, A J

    2009-01-07

    In recent years, a number of dynamical density functional theories (DDFTs) have been developed for describing the dynamics of the one-body density of both colloidal and atomic fluids. In the colloidal case, the particles are assumed to have stochastic equations of motion and theories exist for both the case when the particle motion is overdamped and also in the regime where inertial effects are relevant. In this paper, we extend the theory and explore the connections between the microscopic DDFT and the equations of motion from continuum fluid mechanics. In particular, starting from the Kramers equation, which governs the dynamics of the phase space probability distribution function for the system, we show that one may obtain an approximate DDFT that is a generalization of the Euler equation. This DDFT is capable of describing the dynamics of the fluid density profile down to the scale of the individual particles. As with previous DDFTs, the dynamical equations require as input the Helmholtz free energy functional from equilibrium density functional theory (DFT). For an equilibrium system, the theory predicts the same fluid one-body density profile as one would obtain from DFT. Making further approximations, we show that the theory may be used to obtain the mode coupling theory that is widely used for describing the transition from a liquid to a glassy state.

  8. A New Calculation Method of Dynamic Kill Fluid Density Variation during Deep Water Drilling

    Directory of Open Access Journals (Sweden)

    Honghai Fan

    2017-01-01

    Full Text Available There are plenty of uncertainties and enormous challenges in deep water drilling due to complicated shallow flow and deep strata of high temperature and pressure. This paper investigates density of dynamic kill fluid and optimum density during the kill operation process in which dynamic kill process can be divided into two stages, that is, dynamic stable stage and static stable stage. The dynamic kill fluid consists of a single liquid phase and different solid phases. In addition, liquid phase is a mixture of water and oil. Therefore, a new method in calculating the temperature and pressure field of deep water wellbore is proposed. The paper calculates the changing trend of kill fluid density under different temperature and pressure by means of superposition method, nonlinear regression, and segment processing technique. By employing the improved model of kill fluid density, deep water kill operation in a well is investigated. By comparison, the calculated density results are in line with the field data. The model proposed in this paper proves to be satisfactory in optimizing dynamic kill operations to ensure the safety in deep water.

  9. EVALUATION OF TREATED SEWAGE DEODORIZATION IN ROOT-ZONE WETLANDS THROUGH DYNAMIC OLFACTOMETRY

    Directory of Open Access Journals (Sweden)

    Waldir Nagel Schirmer

    2012-12-01

    Full Text Available The wastewater treatment station (WWTS by wetlands consists of a physic-biological system with part of the filtering formed by plants and projected according to the filtering soil principle. The elements that constitute the medium, in this case the soil, microorganisms and plants, are responsible for the organic matter and the sewage odor compounds degradation. This study employed the static and dynamic olfactometry methodologies to evaluate the treated effluents odor removal in two stations by root-zone wetlands in rural communities in Irati (PR. Olfactometry results were compared to the effluents physic-chemical analysis, and parameters such as dissolved oxygen (DO, chemical oxygen demand (COD and pH were taken into account. Results revealed DO increase and COD removal in the treated effluents. Olfactometric analyses pointed to noticeable levels of odor in the treated effluents; however, there was significant reduction in the odor intensity of exit effluents in relation to the entrance ones. In general, the wastewater treatment station through wetlands showed efficient to the removal of odor compounds, as well as the removal or organic matter from the medium.

  10. Mitochondrial morphology and dynamics in Triticum aestivum roots in response to rotenone and antimycin A.

    Science.gov (United States)

    Rakhmatullina, Daniya; Ponomareva, Anastasiya; Gazizova, Natalia; Minibayeva, Farida

    2016-09-01

    Mitochondria are dynamic organelles, capable of fusion and fission as a part of cellular responses to various signals, such as the shifts in the redox status of a cell. The mitochondrial electron transport chain (ETC.) is involved in the generation of reactive oxygen species (ROS), with complexes I and III contributing the most to this process. Disruptions of ETC. can lead to increased ROS generation. Here, we demonstrate the appearance of giant mitochondria in wheat roots in response to simultaneous application of the respiratory inhibitors rotenone (complex I of mitochondrial ETC.) and antimycin A (complex III of mitochondrial ETC.). The existence of such megamitochondria was temporary, and following longer treatment with inhibitors mitochondria resumed their conventional size and oval shape. Changes in mitochondrial morphology were accompanied with a decrease in mitochondrial potential and an unexpected increase in oxygen consumption. Changes in mitochondrial morphology and activity may result from the fusion and fission of mitochondria induced by the disruption of mitochondrial ETC. Results from experiments with the inhibitor of mitochondrial fission Mdivi-1 suggest that the retarded fission may facilitate plant mitochondria to appear in a fused shape. The processes of mitochondrial fusion and fission are involved in the regulation of the efficacy of the functions of the respiratory chain complexes and ROS metabolism during stresses. The changes in morphology of mitochondria, along with the changes in their functional activity, can be a part of the strategy of the plant adaptation to stresses.

  11. Phosphate DIstribution and Movement in Soil—Root Interface Zone:Ⅲ.Dynamics

    Institute of Scientific and Technical Information of China (English)

    XUMING-GANG; ZHANGYI-PING; 等

    1995-01-01

    The depletion rate of phosphate in the soil-root interface zone increased along with growth and phosphate uptske of wheat or maize,which indicated that the phosphate distribution in soil near the root surface agreed well with the phosphate movement in rhizosphere and phosphate uptake by plant,The relative accumulation zone of phosphate within 0.5mm apart from the root surface developed at the 15th day or so after cultivating wheat or maize since the root phosphate secretion increased gradually in this stage.The phosphate distribution in the soil-root interface zone against the growing time(t)and the distance from the root plane(x) could be described by the non-linear regression equation with the third powers of x and t.

  12. Nutrient Dynamics of Fine Roots in the Mixed Plantation of Poplar and Black Locust

    Institute of Scientific and Technical Information of China (English)

    Zhai Mingpu; Jiang Sannai; Jia Liming

    2006-01-01

    The mixed plantation of poplar (Populus spp.)and black locust (Robinia pseudoacacia) is one of the typical mixed stands with nitrogen-fixing and non-nitrogen-fixing species.Interaction between the two species in the mixed stand is harmonious and productivity is high,making this kind of mixed plantation a very successful pattern on poor sandy sites in north China.In this study,the fine root decomposition of the two species was investigated in the mixed plantation of 27-year-old Canadian poplar (P.canadansis)and 22-year-old black locust on sandy sites along the Chaobai River in Beijing.Mechanism of harmonious interaction between the two species was observed in the view of the nutrient cycle of fine roots.Results showed that:(1) the fine root decomposition of Canadian poplar and black locust trees was different.Concentrations of N,Ca and Mg gradually increased and those of P and K gradually decreased in the fine roots of poplar during the period of decomposition.Concentrations of N,P and K gradually decreased in the fine roots of black locust during decomposition.The speed of nutrient decomposition in mixed fine roots of the two species fell between the speed of the two pure samples.(2) During decomposition,the annual return amount of N,K and Mg in fine roots of black locust was highest,followed by the mixed fine roots of the two species,and then the fine roots of poplar.(3) The increased return amount of N in mixed fine roots could improve the N nutrient condition of poplar trees.The return amount of P in poplar Fine roots was greater than that of black locust,which could improve the P nutrient of black locust trees.The interaction of mutual supplements of N and P nutrient cycle of fine roots between these two species formed.

  13. Influences of canopy photosynthesis and summer rain pulses on root dynamics and soil respiration in a young ponderosa pine forest.

    Science.gov (United States)

    Misson, Laurent; Gershenson, Alexander; Tang, Jianwu; McKay, Megan; Cheng, Weixin; Goldstein, Allen

    2006-07-01

    Our first objective was to link the seasonality of fine root dynamics with soil respiration in a ponderosa pine (Pinus ponderosa P. & C. Lawson) plantation located in the Sierra Nevada of California. The second objective was to examine how canopy photosynthesis influences fine root initiation, growth and mortality in this ecosystem. We compared CO2 flux measurements with aboveground and belowground root dynamics. Initiation of fine root growth coincided with tree stem thickening and shoot elongation, preceding new needle growth. In the spring, root, shoot and stem growth occurred simultaneously with the increase in canopy photosynthesis. Compared with the other tree components, initial growth rate of fine roots was the highest and their growing period was the shortest. Both above and belowground components completed 90% of their growth by the end of July and the growing season lasted approximately 80 days. The period for optimal growth is short at the study site because of low soil temperatures during winter and low soil water content during summer. High photosynthetic rates were observed following unusual late-summer rains, but tree growth did not resume. The autotrophic contribution to soil respiration was 49% over the whole season, with daily contributions ranging between 18 and 87%. Increases in soil and ecosystem respiration were observed during spring growth; however, the largest variation in soil respiration occurred during summer rain events when no growth was observed. Both the magnitude and persistence of the soil respiration pulses were positively correlated with the amount of rain. These pulses accounted for 16.5% of soil respiration between Days 130 and 329.

  14. Effective model hierarchies for dynamic and static classical density functional theories

    Energy Technology Data Exchange (ETDEWEB)

    Majaniemi, S [Department of Applied Physics, Aalto University School of Science and Technology, PO Box 11100, FI-00076 Aalto (Finland); Provatas, N [Department of Materials Science and Engineering, McMaster University, 1280 Main Street West, Hamilton, ON, L8S-4L7 (Canada); Nonomura, M, E-mail: maj@fyslab.hut.f [Department of Physics, Graduate School of Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan)

    2010-09-15

    The origin and methodology of deriving effective model hierarchies are presented with applications to solidification of crystalline solids. In particular, it is discussed how the form of the equations of motion and the effective parameters on larger scales can be obtained from the more microscopic models. It will be shown that tying together the dynamic structure of the projection operator formalism with static classical density functional theories can lead to incomplete (mass) transport properties even though the linearized hydrodynamics on large scales is correctly reproduced. To facilitate a more natural way of binding together the dynamics of the macrovariables and classical density functional theory, a dynamic generalization of density functional theory based on the nonequilibrium generating functional is suggested.

  15. Dynamical friction in constant density cores: a failure of the Chandrasekhar formula

    CERN Document Server

    Read, J I; Moore, B; Pontzen, A P; Lake, J S G; Goerdt, Tobias; Moore, Ben; Lake, Joachim Stadel & George

    2006-01-01

    Using analytic calculations and N-body simulations we show that in constant density (harmonic) cores, sinking satellites undergo an initial phase of very rapid (super-Chandrasekhar) dynamical friction, after which they experience no dynamical friction at all. For density profiles with a central power law profile of log-slope, $-\\alpha$, the infalling satellite heats the background and causes $\\alpha$ to decrease. For $\\alpha < 0.5$ initially, the satellite generates a small central constant density core and stalls as in the $\\alpha = 0$ case. We discuss some astrophysical applications of our results to decaying satellite orbits, galactic bars and mergers of supermassive black hole binaries. In a companion paper we show that a central constant density core can provide a natural solution to the timing problem for Fornax's globular clusters.

  16. Investigating the Dynamics and Density Evolution of Returning Plasma Blobs from the 2011 June 7 Eruption

    CERN Document Server

    Carlyle, Jack; van Driel-Gesztelyi, Lidia; Innes, Davina; Hillier, Andrew; Matthews, Sarah

    2014-01-01

    This work examines infalling matter following an enormous Coronal Mass Ejection (CME) on 2011 June 7. The material formed discrete concentrations, or blobs, in the corona and fell back to the surface, appearing as dark clouds against the bright corona. In this work we examined the density and dynamic evolution of these blobs in order to formally assess the intriguing morphology displayed throughout their descent. The blobs were studied in five wavelengths (94, 131, 171, 193 and 211 \\AA) using the Solar Dynamics Observatory Atmospheric Imaging Assembly (SDO/AIA), comparing background emission to attenuated emission as a function of wavelength to calculate column densities across the descent of four separate blobs. We found the material to have a column density of hydrogen of approximately 2 $\\times$ 10$^{19}$ cm$^{-2}$, which is comparable with typical pre-eruption filament column densities. Repeated splitting of the returning material is seen in a manner consistent with the Rayleigh-Taylor instability. Furthe...

  17. Dynamic investigation on the coupled changing process of moisture and density fields in freezing soil

    Institute of Scientific and Technical Information of China (English)

    张立新; 蒲毅彬; 廖全荣; 顾同欣

    1999-01-01

    The data reflecting the change in density are obtained, with computer tomograph scanning through the sample of freezing soil section by section at intervals without destruction. Combined with the changing characteristics of water content along the sample during test, the dynamic coupled process of moisture and density fields under the effect of temperature gradient on the freezing soil in closed system is discussed. The result reflects the internal process of frost heave improvement resulting from the transfer of mass and heat.

  18. Dynamics of biomass and population density of fucus algae of the Kola Bay, Barents Sea

    Directory of Open Access Journals (Sweden)

    Malavenda S. S.

    2016-03-01

    Full Text Available The long-term dynamics of biomass and population density of Fucus distichus and F. vesiculosus in the southern and middle knees of the Kola Bay have been analyzed. The feedbacks between these parameters and their changes over several years have been revealed for the first time. Changing the prevalence of biomass and population density can be considered as an adaptation at the population level to maintain the stability of algae communities in chronic pollution

  19. Probing heterogeneous dynamics from spatial density correlation in glass-forming liquids

    Science.gov (United States)

    Li, Yan-Wei; Zhu, You-Liang; Sun, Zhao-Yan

    2016-12-01

    We numerically investigate the connection between spatial density correlation and dynamical heterogeneity in glass-forming liquids. We demonstrate that the cluster size defined by the spatial aggregation of densely packed particles (DPPs) can better capture the difference between the dynamics of the Lennard-Jones glass model and the Weeks-Chandler-Andersen truncation model than the commonly used pair correlation functions. More interestingly, we compare the mobility of DPPs and loosely packed particles, and we find that high local density correlates well with slow dynamics in systems with relatively hard repulsive interactions but links to mobile ones in the system with soft repulsive interactions at one relaxation time scale. Our results show clear evidence that the above model dependence behavior stems from the hopping motion of DPPs at the end of the caging stage due to the compressive nature of soft repulsive spheres, which activates the dynamics of DPPs in the α relaxation stage.

  20. A consumer-resource approach to the density-dependent population dynamics of mutualism.

    Science.gov (United States)

    Holland, J Nathaniel; DeAngelis, Donald L

    2010-05-01

    Like predation and competition, mutualism is now recognized as a consumer-resource (C-R) interaction, including, in particular, bi-directional (e.g., coral, plant-mycorrhizae) and uni-directional (e.g., ant-plant defense, plant-pollinator) C-R mutualisms. Here, we develop general theory for the density-dependent population dynamics of mutualism based on the C-R mechanism of interspecific interaction. To test the influence of C-R interactions on the dynamics and stability of bi- and uni-directional C-R mutualisms, we developed simple models that link consumer functional response of one mutualistic species with the resources supplied by another. Phase-plane analyses show that the ecological dynamics of C-R mutualisms are stable in general. Most transient behavior leads to an equilibrium of mutualistic coexistence, at which both species densities are greater than in the absence of interactions. However, due to the basic nature of C-R interactions, certain density-dependent conditions can lead to C-R dynamics characteristic of predator-prey interactions, in which one species overexploits and causes the other to go extinct. Consistent with empirical phenomena, these results suggest that the C-R interaction can provide a broad mechanism for understanding density-dependent population dynamics of mutualism. By unifying predation, competition, and mutualism under the common ecological framework of consumer-resource theory, we may also gain a better understanding of the universal features of interspecific interactions in general.

  1. A consumer-resource approach to the density-dependent population dynamics of mutualism

    Science.gov (United States)

    Holland, J. Nathaniel; DeAngelis, Donald L.

    2010-01-01

    Like predation and competition, mutualism is now recognized as a consumer resource (C-R) interaction, including, in particular, bi-directional (e.g., coral, plant- mycorrhizae) and uni-directional (e.g., ant-plant defense, plant-pollinator) C-R mutualisms. Here, we develop general theory for the density-dependent population dynamics of mutualism based on the C-R mechanism of interspecific interaction. To test the influence of C-R interactions on the dynamics and stability of bi- and uni-directional C-R mutualisms, we developed simple models that link consumer functional response of one mutualistic species with the resources supplied by another. Phase-plane analyses show that the ecological dynamics of C-R mutualisms are stable in general. Most transient behavior leads to an equilibrium of mutualistic coexistence, at which both species densities are greater than in the absence of interactions. However, due to the basic nature of C-R interactions, certain density-dependent conditions can lead to C-R dynamics characteristic of predator-prey interactions, in which one species overexploits and causes the other to go extinct. Consistent with empirical phenomena, these results suggest that the C-R interaction can provide a broad mechanism for understanding density-dependent population dynamics of mutualism. By unifying predation, competition, and mutualism under the common ecological framework of consumer-resource theory, we may also gain a better understanding of the universal features of interspecific interactions in general.

  2. Interaction between stocking density and settlement on population dynamics in suspended mussel culture

    Science.gov (United States)

    Cubillo, Alhambra M.; Fuentes-Santos, Isabel; Labarta, Uxío

    2015-01-01

    Population dynamics on mussels growing on suspended culture depend mainly on the balance of several processes: mortality and/or dislodgements from the ropes, recruitment and growth. The negative effect of overcrowding on mussel growth and survival has been widely studied. Other works have addressed the effect of population size on recruitment on bottom beds. This study aims to provide insight into the processes underlying population dynamics. To this purpose, we analyzed the effect of stocking density on mussel growth, survival and seed settlement, and the post-settlement interaction between adults and recruits in suspended culture. The temporal pattern of the variables involved in population dynamics was fitted by GAM models, which in contrast with parametric models does not assume any prior relationships between variables. Our results show that mussel growth and survival depend on a trade-off between competition for resources at high densities and the risk of great settlements in less crowded adult mussel populations. Intracohort competition increased with stocking density, while seed settlement, which increases the risk of mussel dislodgements and leads to intercohort competition, was higher at moderate stocking densities. Post-settlement competitive pressures were driven by total population density and size composition. Both intracohort competition in adults and asymmetric competition between adults and recruits increase with higher adult-recruit ratios. All these density-dependent processes should be considered in future management strategies and research experimental designs.

  3. Dynamic intratubular biomineralization following root canal obturation with pozzolan‐based mineral trioxide aggregate sealer cement

    Science.gov (United States)

    Yoo, Yeon‐Jee; Baek, Seung‐Ho; Kum, Kee‐Yeon; Shon, Won‐Jun; Woo, Kyung‐Mi

    2015-01-01

    Summary The application of mineral trioxide aggregates (MTA) cement during the root canal obturation is gaining concern due to its bioactive characteristic to form an apatite in dentinal tubules. In this regard, this study was to assess the biomineralization of dentinal tubules following root canal obturation by using pozzolan‐based (Pz‐) MTA sealer cement (EndoSeal MTA, Maruchi). Sixty curved roots (mesiobuccal, distobuccal) from human maxillary molars were instrumented and prepared for root canal obturation. The canals were obturated with gutta‐percha (GP) and Pz‐MTA sealer by using continuous wave of condensation technique. Canals obturated solely with ProRoot MTA (Dentsply Tulsa Dental) or Pz‐MTA sealer were used for comparison. In order to evaluate the biomineralization ability under different conditions, the PBS pretreatment before the root canal obturation was performed in each additional samples. At dentin‐material interfaces, the extension of intratubular biomineralization was analyzed using scanning electron microscopy (SEM) and energy dispersive spectroscopy. When the root canal was obturated with GP and Pz‐MTA sealer, enhanced biomineralization of the dentinal tubules beyond the penetrated sealer tag was confirmed under the SEM observation (p cement can be used as a promising bioactive root canal sealer to enhance biomineralization of dentinal tubules under controlled environment. SCANNING 38:50–56, 2016. © 2015 The Authors. Scanning Published by Wiley Periodicals, Inc. PMID:26179659

  4. Dynamic intratubular biomineralization following root canal obturation with pozzolan-based mineral trioxide aggregate sealer cement.

    Science.gov (United States)

    Yoo, Yeon-Jee; Baek, Seung-Ho; Kum, Kee-Yeon; Shon, Won-Jun; Woo, Kyung-Mi; Lee, WooCheol

    2016-01-01

    The application of mineral trioxide aggregates (MTA) cement during the root canal obturation is gaining concern due to its bioactive characteristic to form an apatite in dentinal tubules. In this regard, this study was to assess the biomineralization of dentinal tubules following root canal obturation by using pozzolan-based (Pz-) MTA sealer cement (EndoSeal MTA, Maruchi). Sixty curved roots (mesiobuccal, distobuccal) from human maxillary molars were instrumented and prepared for root canal obturation. The canals were obturated with gutta-percha (GP) and Pz-MTA sealer by using continuous wave of condensation technique. Canals obturated solely with ProRoot MTA (Dentsply Tulsa Dental) or Pz-MTA sealer were used for comparison. In order to evaluate the biomineralization ability under different conditions, the PBS pretreatment before the root canal obturation was performed in each additional samples. At dentin-material interfaces, the extension of intratubular biomineralization was analyzed using scanning electron microscopy (SEM) and energy dispersive spectroscopy. When the root canal was obturated with GP and Pz-MTA sealer, enhanced biomineralization of the dentinal tubules beyond the penetrated sealer tag was confirmed under the SEM observation (p cement can be used as a promising bioactive root canal sealer to enhance biomineralization of dentinal tubules under controlled environment.

  5. A shift from exploitation to interference competition with increasing density affects population and community dynamics.

    Science.gov (United States)

    Holdridge, Erica M; Cuellar-Gempeler, Catalina; terHorst, Casey P

    2016-08-01

    Intraspecific competition influences population and community dynamics and occurs via two mechanisms. Exploitative competition is an indirect effect that occurs through use of a shared resource and depends on resource availability. Interference competition occurs by obstructing access to a resource and may not depend on resource availability. Our study tested whether the strength of interference competition changes with protozoa population density. We grew experimental microcosms of protozoa and bacteria under different combinations of protozoan density and basal resource availability. We then solved a dynamic predator-prey model for parameters of the functional response using population growth rates measured in our experiment. As population density increased, competition shifted from exploitation to interference, and competition was less dependent on resource levels. Surprisingly, the effect of resources was weakest when competition was the most intense. We found that at low population densities, competition was largely exploitative and resource availability had a large effect on population growth rates, but the effect of resources was much weaker at high densities. This shift in competitive mechanism could have implications for interspecific competition, trophic interactions, community diversity, and natural selection. We also tested whether this shift in the mechanism of competition with protozoa density affected the structure of the bacterial prey community. We found that both resources and protozoa density affected the structure of the bacterial prey community, suggesting that competitive mechanism may also affect trophic interactions.

  6. Controls on groundwater dynamics and root zone aeration of a coastal fluvial delta island, Wax Lake, Louisiana

    Science.gov (United States)

    O'Connor, M.; Hardison, A. K.; Moffett, K. B.

    2013-12-01

    Louisiana coastal wetlands are thought to function as buffers, filtering nutrient-rich terrestrial runoff as it travels to the Gulf of Mexico. While surface water filtration by these wetlands is a large and active area of research, flow through subsurface portions of the wetlands and possible nutrient cycling in the root zone has been largely overlooked. Specifically for Louisiana's coastal deltas, the physics and chemistry of island groundwater systems is unknown.To characterize these subsurface hydraulic dynamics at Pintail Island in the Wax Lake Delta, Louisiana, we collected sediment core samples and penetrometer measurements, monitored surface water and groundwater levels and chemistry, and analyzed meteorological, tidal, and river discharge data. As a first step, we focused on identifying wetland sediment properties and the relative influence of the major hydrologic controls, tides, delta outlet discharge, rainfall, and evapotranspiration, on water table dynamics. Pintail Island is a two-layer system with fine sediments and organic matter overlying sandy deltaic deposits. The sediment layer interface occurs approximately 60 cm below ground surface, around the mean surface water level. The vegetation root zone is concentrated in the surficial layer, although willow roots can extend into the deeper, higher-permeability sandy layer. Groundwater data from the upper portion of this sandy layer (~1m deep) is most strongly influenced by tides but also responds to long-term changes in discharge. While the tides are damped as they propagate into the island sediments, they also flood interior island lagoons, setting up groundwater gradients to potentially drive fluid and nutrient fluxes through the islands. Although the tidally oscillating water table causes significant temporal variation in root zone fluid potentials, evapotranspiration dynamics do not appear to strongly influence groundwater dynamics at depth, consistent with the shallow concentration of roots

  7. Patterns in hydraulic architecture from roots to branches in six tropical tree species from cacao agroforestry and their relation to wood density and stem growth

    Directory of Open Access Journals (Sweden)

    Martyna Malgorzata Kotowska

    2015-03-01

    Full Text Available For decades it has been assumed that the largest vessels are generally found in roots and that vessel size and corresponding sapwood area-specific hydraulic conductivity are acropetally decreasing towards the distal twigs. However, recent studies from the perhumid tropics revealed a hump-shaped vessel size distribution. Worldwide tropical perhumid forests are extensively replaced by agroforestry systems often using introduced species of various biogeographical and climatic origins. Nonetheless, it is unknown so far what kind of hydraulic architectural patterns are developed in those agroforestry tree species and which impact this exerts regarding important tree functional traits, such as stem growth, hydraulic efficiency and wood density. We investigated wood anatomical and hydraulic properties of the root, stem and branch wood in Theobroma cacao and five common shade tree species in agroforestry systems on Sulawesi (Indonesia; three of these were strictly perhumid tree species, and the other three tree species are tolerating seasonal drought. The overall goal of our study was to relate these properties to stem growth and other tree functional traits such as foliar nitrogen content and sapwood to leaf area ratio. Our results confirmed a hump-shaped vessel size distribution in nearly all species. Drought-adapted species showed divergent patterns of hydraulic conductivity, vessel density and relative vessel lumen area between root, stem and branch wood compared to wet forest species. Confirming findings from natural old-growth forests in the same region, wood density showed no relationship to specific conductivity. Overall, aboveground growth performance was better predicted by specific hydraulic conductivity than by foliar traits and wood density. Our study results suggest that future research on conceptual trade-offs of tree hydraulic architecture should consider biogeographical patterns underlining the importance of anatomical adaptation

  8. Glycolysis Is Dynamic and Relates Closely to Respiration Rate in Stored Sugarbeet Roots

    Directory of Open Access Journals (Sweden)

    Clarice A. Megguer

    2017-05-01

    Full Text Available Although respiration is the principal cause of the loss of sucrose in postharvest sugarbeet (Beta vulgaris L., the internal mechanisms that control root respiration rate are unknown. Available evidence, however, indicates that respiration rate is likely to be controlled by the availability of respiratory substrates, and glycolysis has a central role in generating these substrates. To determine glycolytic changes that occur in sugarbeet roots after harvest and to elucidate relationships between glycolysis and respiration, sugarbeet roots were stored for up to 60 days, during which activities of glycolytic enzymes and concentrations of glycolytic substrates, intermediates, cofactors, and products were determined. Respiration rate was also determined, and relationships between respiration rate and glycolytic enzymes and metabolites were evaluated. Glycolysis was highly variable during storage, with 10 of 14 glycolytic activities and 14 of 17 glycolytic metabolites significantly altered during storage. Changes in glycolytic enzyme activities and metabolites occurred throughout the 60 day storage period, but were greatest in the first 4 days after harvest. Positive relationships between changes in glycolytic enzyme activities and root respiration rate were abundant, with 10 of 14 enzyme activities elevated when root respiration was elevated and 9 glycolytic activities static during periods of unchanging respiration rate. Major roles for pyruvate kinase and phosphofructokinase in the regulation of postharvest sugarbeet root glycolysis were indicated based on changes in enzymatic activities and concentrations of their substrates and products. Additionally, a strong positive relationship between respiration rate and pyruvate kinase activity was found indicating that downstream TCA cycle enzymes were unlikely to regulate or restrict root respiration in a major way. Overall, these results establish that glycolysis is not static during sugarbeet root

  9. Dynamic Graphics in Excel for Teaching Statistics: Understanding the Probability Density Function

    Science.gov (United States)

    Coll-Serrano, Vicente; Blasco-Blasco, Olga; Alvarez-Jareno, Jose A.

    2011-01-01

    In this article, we show a dynamic graphic in Excel that is used to introduce an important concept in our subject, Statistics I: the probability density function. This interactive graphic seeks to facilitate conceptual understanding of the main aspects analysed by the learners.

  10. TREATMENT OF NONADIABATIC TRANSITIONS BY DENSITY-MATRIX EVOLUTION AND MOLECULAR-DYNAMICS SIMULATIONS

    NARCIS (Netherlands)

    MAVRI, J; BERENDSEN, HJC

    1994-01-01

    A density matrix evolution (DME) method (H.J.C. Berendsen and J. Mavri, J. Phys. Chem., 97 (1993) 13469) to simulate the dynamics of quantum systems embedded in a classical environment is presented. The DME method allows treatment of nonadiabatic transitions. As numerical examples the collinear coll

  11. Density dependence and population dynamics of black rhinos (Diceros bicornis michaeli) in Kenya's rhino sanctuaries

    NARCIS (Netherlands)

    Ouma, B.O.; Amin, R.; Langevelde, van F.; Leader-Williams, N.

    2010-01-01

    Density-dependent feedback mechanisms provide insights into the population dynamics and interactions of large herbivores with their ecosystem. Sex ratio also has particularly important implications for growth rates of many large mammal populations through its influence on reproductive potential. The

  12. Dynamics and density distributions in a capillary-discharge waveguide with an embedded supersonic jet

    Energy Technology Data Exchange (ETDEWEB)

    Matlis, N. H., E-mail: nmatlis@gmail.com; Gonsalves, A. J.; Steinke, S.; Tilborg, J. van; Shaw, B.; Mittelberger, D. E.; Geddes, C. G. R. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Matlis, E. H. [Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Leemans, W. P. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Department of Physics, University of California, Berkeley, California 94720 (United States)

    2015-11-28

    We present an analysis of the gas dynamics and density distributions within a capillary-discharge waveguide with an embedded supersonic jet. This device provides a target for a laser plasma accelerator which uses longitudinal structuring of the gas-density profile to enable control of electron trapping and acceleration. The functionality of the device depends sensitively on the details of the density profile, which are determined by the interaction between the pulsed gas in the jet and the continuously-flowing gas in the capillary. These dynamics are captured by spatially resolving recombination light from several emission lines of the plasma as a function of the delay between the jet and the discharge. We provide a phenomenological description of the gas dynamics as well as a quantitative evaluation of the density evolution. In particular, we show that the pressure difference between the jet and the capillary defines three regimes of operation with qualitatively different longitudinal density profiles and show that jet timing provides a sensitive method for tuning between these regimes.

  13. Impact of tapping and soil water status on fine root dynamics in a rubber tree plantation in Thailand

    Directory of Open Access Journals (Sweden)

    Naruenat eChairungsee

    2013-12-01

    Full Text Available Fine roots (FR play a major role in the water and nutrient uptake of plants and contribute significantly to the carbon and nutrient cycles of ecosystems through their annual production and turnover. FR growth dynamics were studied to understand the endogenous and exogenous factors driving these processes in a 14 year-old plantation of rubber trees located in eastern Thailand. FR dynamics were observed using field rhizotrons from Oct. 2007 to Oct. 2009. This period covered two complete dry seasons (Nov.-Mar. and two complete rainy seasons (Apr.-Oct., allowing us to study the effect of rainfall seasonality on FR dynamics. Rainfall and its distribution during the two successive years showed strong differences with 1500 mm and 950 mm in 2008 and 2009, respectively. Fine root production (FRP completely stopped during the dry seasons and resumed quickly after the first rains. During the rainy seasons, FRP and the daily root elongation rate (RER were highly variable and exhibited strong annual variations with a total FRP of 139.8 and 40.4 m m-² and an average RER of 0.16 and 0.12 cm d-1 in 2008 and 2009, respectively. The significant positive correlations found between FRP, RER, the appearance of new roots and rainfall at monthly intervals revealed the impact of rainfall seasonality on FR dynamics. However, the rainfall patterns failed to explain the weekly variations of FR dynamics observed particularly during the rainy seasons. At this time step, FRP, RER and the appearance of new FR were negatively correlated to the average soil matric potential measured at a depth of between 30 and 60 cm. In addition, our study revealed a significant negative correlation between FR dynamics and the monthly production of dry rubber. Consequently, latex harvesting might disturb carbon dynamics in the whole tree, far beyond the trunk where the tapping was performed. These results exhibit the impact of climatic conditions and tapping system in the carbon budget of

  14. Recovering root system traits using image analysis exemplified by two-dimensional neutron radiography images of lupine.

    Science.gov (United States)

    Leitner, Daniel; Felderer, Bernd; Vontobel, Peter; Schnepf, Andrea

    2014-01-01

    Root system traits are important in view of current challenges such as sustainable crop production with reduced fertilizer input or in resource-limited environments. We present a novel approach for recovering root architectural parameters based on image-analysis techniques. It is based on a graph representation of the segmented and skeletonized image of the root system, where individual roots are tracked in a fully automated way. Using a dynamic root architecture model for deciding whether a specific path in the graph is likely to represent a root helps to distinguish root overlaps from branches and favors the analysis of root development over a sequence of images. After the root tracking step, global traits such as topological characteristics as well as root architectural parameters are computed. Analysis of neutron radiographic root system images of lupine (Lupinus albus) grown in mesocosms filled with sandy soil results in a set of root architectural parameters. They are used to simulate the dynamic development of the root system and to compute the corresponding root length densities in the mesocosm. The graph representation of the root system provides global information about connectivity inside the graph. The underlying root growth model helps to determine which path inside the graph is most likely for a given root. This facilitates the systematic investigation of root architectural traits, in particular with respect to the parameterization of dynamic root architecture models.

  15. Investigating the dynamics and density evolution of returning plasma blobs from the 2011 June 7 eruption

    Energy Technology Data Exchange (ETDEWEB)

    Carlyle, Jack; Williams, David R.; Van Driel-Gesztelyi, Lidia; Matthews, Sarah [Mullard Space Science Laboratory, University College London, Holmbury St Mary, Surrey, RH5 6NT (United Kingdom); Innes, Davina [Max-Planck Institut für Sonnensystemforschung, D-37191 Katlenburg-Lindau (Germany); Hillier, Andrew, E-mail: j.carlyle@ucl.ac.uk [Kwasan and Hida Observatories, Kyoto University, Kyoto 607-8471 (Japan)

    2014-02-20

    This work examines in-falling matter following an enormous coronal mass ejection on 2011 June 7. The material formed discrete concentrations, or blobs, in the corona and fell back to the surface, appearing as dark clouds against the bright corona. In this work we examined the density and dynamic evolution of these blobs in order to formally assess the intriguing morphology displayed throughout their descent. The blobs were studied in five wavelengths (94, 131, 171, 193, and 211 Å) using the Solar Dynamics Observatory Atmospheric Imaging Assembly, comparing background emission to attenuated emission as a function of wavelength to calculate column densities across the descent of four separate blobs. We found the material to have a column density of hydrogen of approximately 2 × 10{sup 19} cm{sup –2}, which is comparable with typical pre-eruption filament column densities. Repeated splitting of the returning material is seen in a manner consistent with the Rayleigh-Taylor instability. Furthermore, the observed distribution of density and its evolution is also a signature of this instability. By approximating the three-dimensional geometry (with data from STEREO-A), volumetric densities were found to be approximately 2 × 10{sup –14} g cm{sup –3}, and this, along with observed dominant length scales of the instability, was used to infer a magnetic field of the order 1 G associated with the descending blobs.

  16. Universal dynamics of density correlations at the transition to the many-body localized state

    Science.gov (United States)

    Mierzejewski, M.; Herbrych, J.; Prelovšek, P.

    2016-12-01

    Within one-dimensional disordered models of interacting fermions, we perform a numerical study of several dynamical density correlations, which can serve as hallmarks of the transition to the many-body localized state. The results confirm that density-wave correlations exhibit quite an abrupt change with increasing disorder, with a nonvanishing long-time value characteristic for the nonergodic phase. In addition, our results reveal a logarithmic variation of correlations in time in a wide time window, which we can bring in connection with the anomalous behavior of the dynamical conductivity near the transition. Our results support the view that the transition to many-body localization can be characterized by universal dynamical exponents.

  17. Water dynamics: relation between hydrogen bond bifurcations, molecular jumps, local density & hydrophobicity.

    Science.gov (United States)

    Titantah, John Tatini; Karttunen, Mikko

    2013-10-21

    Structure and dynamics of water remain a challenge. Resolving the properties of hydrogen bonding lies at the heart of this puzzle. We employ ab initio Molecular Dynamics (AIMD) simulations over a wide temperature range. The total simulation time was ≈ 2 ns. Both bulk water and water in the presence of a small hydrophobic molecule were simulated. We show that large-angle jumps and bond bifurcations are fundamental properties of water dynamics and that they are intimately coupled to both local density and hydrogen bond strength oscillations in scales from about 60 to a few hundred femtoseconds: Local density differences are the driving force for bond bifurcations and the consequent large-angle jumps. The jumps are intimately connected to the recently predicted hydrogen bond energy asymmetry. Our analysis also appears to confirm the existence of the so-called negativity track provided by the lone pairs of electrons on the oxygen atom to enable water rotation.

  18. The development dynamics of the maize root transcriptome responsive to heavy metal Pb pollution.

    Science.gov (United States)

    Gao, Jian; Zhang, Yongzhong; Lu, Chaolong; Peng, Hua; Luo, Mao; Li, Gaoke; Shen, Yaou; Ding, Haiping; Zhang, Zhiming; Pan, Guangtang; Lin, Haijian

    2015-03-01

    Lead (Pb), as a heavy metal element, has become the most important metal pollutant of the environment. With allocating a relatively higher proportion of its biomass in roots, maize could be a potential important model to study the phytoremediation of Pb-contaminated soil. Here we analyzed the maize root transcriptome of inbred lines 9782 under heavy metal lead (Pb) pollution, which was identified as a non-hyperaccumulator for Pb in roots. In the present study, more than 98 millions reads were mapped to define gene structure and detect polymorphism, thereby to qualify transcript abundance along roots development under Pb treatment. A total of 17,707, 17,440, 16,998 and 16,586 genes were identified in maize roots at four developmental stages (0, 12 h, 24 h and 48 h) respectively and 2,825, 2,626, 2161 and 2260 stage-specifically expressed genes were also identified respectively. In addition, based on our RNA-Seq data, transcriptomic changes during maize root development responsive to Pb were investigated. A total of 384 differentially expressed genes (DEGs) (log2Ratio ≥ 1, FDR ≤ 0.001) were identified, of which, 36 genes with significant alteration in expression were detected in four developmental stages; 12 DEGs were randomly selected and successful validated by qRT-PCR. Additionally, many transcription factor families might act as the important regulators at different developmental stages, such as bZIP, ERF and GARP et al. These results will expand our understanding of the complex molecular and cellular events in maize root development and provide a foundation for future study on root development in maize under heavy metal pollution and other cereal crops.

  19. Densidade do sistema radicular da bananeira 'Pacovan' sob irrigação por aspersão Root system density of 'Pacovan' banana plant under sprinkler irrigation

    Directory of Open Access Journals (Sweden)

    Raimundo Lacerda Filho

    2004-12-01

    Full Text Available O presente trabalho foi realizado no município de Governador Dix-Sept Rosado, microrregião Açu-Apodi, no Estado do Rio Grande do Norte, tendo como objetivo verificar os efeitos do sistema de irrigação por aspersão na densidade do sistema radicular da bananeira 'Pacovan'. O delineamento experimental utilizado foi o de blocos casualizados, em esquema de parcelas subdivididas, com cinco repetições. Os tratamentos foram duas amostragens por planta, realizadas do lado contrário ao da emissão da inflorescência, formando um ângulo de 45º. Em cada amostragem, foram realizadas quatro retiradas do material de solo a distâncias de 20 cm, sendo a primeira a 30 cm e a última a 90 cm do pseudocaule. A análise dos dados demonstrou que ocorreu redução linear no peso fresco e na densidade de comprimento de raízes da bananeira em função da profundidade do solo. Em relação à distância do pseudocaule da bananeira, tanto o peso fresco quanto a densidade de comprimento de raízes não mostraram resultados significativos.The present work was conducted at Governador Dix-Sept Rosado County, microregion Açu-Apodi, in the state of Rio Grande do Norte and its objective was to study the effects of sprinkler irrigation system on the density of the root system of 'Pacovan' banana plants. The experiment followed a completely randomized block design, in a split-plot scheme, with five replications. The treatments were two sampling groups, taken per plant, and in the opposite side of the inflorescence emission, forming between them an angle of 45°. In each sampling group, four samples containing soil material were collected at intervals of 20 cm, so the first was distant 30 cm and the last 90 cm from the pseudostem. Data analysis showed that occurred a linear reduction in root fresh weight and in lenght of roots density, in replications to soil depth. For the distance from the plant pseudostem there were no significant differences between samples, both

  20. Decomposition and nitrogen dynamics of (15)N-labeled leaf, root, and twig litter in temperate coniferous forests.

    Science.gov (United States)

    van Huysen, Tiff L; Harmon, Mark E; Perakis, Steven S; Chen, Hua

    2013-12-01

    Litter nutrient dynamics contribute significantly to biogeochemical cycling in forest ecosystems. We examined how site environment and initial substrate quality influence decomposition and nitrogen (N) dynamics of multiple litter types. A 2.5-year decomposition study was installed in the Oregon Coast Range and West Cascades using (15)N-labeled litter from Acer macrophyllum, Picea sitchensis, and Pseudotsuga menziesii. Mass loss for leaf litter was similar between the two sites, while root and twig litter exhibited greater mass loss in the Coast Range. Mass loss was greatest from leaves and roots, and species differences in mass loss were more prominent in the Coast Range. All litter types and species mineralized N early in the decomposition process; only A. macrophyllum leaves exhibited a net N immobilization phase. There were no site differences with respect to litter N dynamics despite differences in site N availability, and litter N mineralization patterns were species-specific. For multiple litter × species combinations, the difference between gross and net N mineralization was significant, and gross mineralization was 7-20 % greater than net mineralization. The mineralization results suggest that initial litter chemistry may be an important driver of litter N dynamics. Our study demonstrates that greater amounts of N are cycling through these systems than may be quantified by only measuring net mineralization and challenges current leaf-based biogeochemical theory regarding patterns of N immobilization and mineralization.

  1. Decomposition and nitrogen dynamics of 15N-labeled leaf, root, and twig litter in temperate coniferous forests

    Science.gov (United States)

    van Huysen, Tiff L.; Harmon, Mark E.; Perakis, Steven S.; Chen, Hua

    2013-01-01

    Litter nutrient dynamics contribute significantly to biogeochemical cycling in forest ecosystems. We examined how site environment and initial substrate quality influence decomposition and nitrogen (N) dynamics of multiple litter types. A 2.5-year decomposition study was installed in the Oregon Coast Range and West Cascades using 15N-labeled litter from Acer macrophyllum, Picea sitchensis, and Pseudotsuga menziesii. Mass loss for leaf litter was similar between the two sites, while root and twig litter exhibited greater mass loss in the Coast Range. Mass loss was greatest from leaves and roots, and species differences in mass loss were more prominent in the Coast Range. All litter types and species mineralized N early in the decomposition process; only A. macrophyllum leaves exhibited a net N immobilization phase. There were no site differences with respect to litter N dynamics despite differences in site N availability, and litter N mineralization patterns were species-specific. For multiple litter × species combinations, the difference between gross and net N mineralization was significant, and gross mineralization was 7–20 % greater than net mineralization. The mineralization results suggest that initial litter chemistry may be an important driver of litter N dynamics. Our study demonstrates that greater amounts of N are cycling through these systems than may be quantified by only measuring net mineralization and challenges current leaf-based biogeochemical theory regarding patterns of N immobilization and mineralization.

  2. Chaotic dynamics dependence on doping density in weakly coupled GaAs/AlAs superlattices

    Science.gov (United States)

    Gui, Yang; Yuanhong, Li; Fengying, Zhang; Yuqi, Li

    2012-09-01

    A discrete sequential tunneling model is used for studying the influence of the doping density on the dynamical behaviors in weakly coupled GaAs/AlAs superlattices. Driven by the DC bias, the system exhibits self-sustained current oscillations induced by the period motion of the unstable electric field domain, and an electrical hysteresis in the loop of current density voltage curve is deduced. It is found that the hysteresis range strongly depends on the doping density, and the width of the hysteresis loop increases with increasing the doping density. By adding an external driving ac voltage, more complicated nonlinear behaviors are observed including quasiperiodicity, period-3, and the route of an inverse period-doubling to chaos when the driving frequency changes.

  3. Chaotic dynamics dependence on doping density in weakly coupled GaAs/AlAs superlattices

    Institute of Scientific and Technical Information of China (English)

    Yang Gui; Li Yuanhong; Zhang Fengying; Li Yuqi

    2012-01-01

    A discrete sequential tunneling model is used for studying the influence of the doping density on the dynamical behaviors in weakly coupled GaAs/AlAs superlattices.Driven by the DC bias,the system exhibits selfsustained current oscillations induced by the period motion of the unstable electric field domain,and an electrical hysteresis in the loop of current density voltage curve is deduced.It is found that the hysteresis range strongly depends on the doping density,and the width of the hysteresis loop increases with increasing the doping density.By adding an external driving ac voltage,more complicated nonlinear behaviors are observed including quasiperiodicity,period-3,and the route of an inverse period-doubling to chaos when the driving frequency changes.

  4. Disentangling the effects of climate, density dependence, and harvest on an iconic large herbivore's population dynamics

    DEFF Research Database (Denmark)

    Koons, David; Colchero, Fernando; Hersey, Kent

    2015-01-01

    Understanding the relative effects of climate, harvest, and density dependence on population dynamics is critical for guiding sound population management, especially for ungulates in arid and semi-arid environments experiencing climate change. To address these issues for bison in southern Utah, we...... applied a Bayesian state-space model to a 72-year time series of abundance counts. While accounting for known harvest (as well as live removal) from the population, we found that the bison population in southern Utah exhibited strong potential to grow from low density (β0 = 0.26; Bayesian credible...... interval based on 95% of the highest posterior density: BCI = 0.19 to 0.33), and weak but statistically significant density dependence (β1 = -0.02, BCI = -0.04 to -0.004). Early spring temperatures also had strong positive effects on population growth (βfebaprtemp1 = 0.09, BCI = 0.04 to 0.14), much more so...

  5. Effect of Stem Density on Leaf Nutrient Dynamics and Nutrient Use Efficiency of Dwarf Bamboo

    Institute of Scientific and Technical Information of China (English)

    WU Fu-Zhong; YANG Wan-Qin; WANG Kai-Yun; WU Ning; LU Ye-Jiang

    2009-01-01

    The monthly dynamics of nitrogen (N) and phosphorus (P) concentrations and stocks in leaves,resorption efficiency,and resorption proficiency as well as leaf-level use efficiency,nutrient productivity,and mean residence time were studied to understand the effect of stem density of dwarf bamboo (Fargesia denudata Yi) on leaf-level N and P use efficiency in three dwarf bamboo stands with different stem densities under bamboo-fir (Picea purpurca Mast.) forest over one growing period in the Wanglang National Nature Reserve,Sichuan,China.Dwarf bamboo density had little effect on the dynamics pattern of both N and P concentrations,stocks,resorption efficiency,and resorption proficiency,but strongly affected their absolute values and leaf-level use efficiency.Higher density stands stored more nutrients but had lower concentrations.There was a clear difference in the resorption of limiting nutrient (N) and non-limiting nutrient (P) among the stands.Phosphorus resorption efficiency,N resorption proficiency,and P resorption proficiency increased with increase of stem density,but no significant variation of N resorption efficiency was found among the stands.Moreover,the higher density stands used both N and P more efficiently with higher N productivity and higher P mean residence time,respectively.Higher P productivity was found in the lower density stands,but there was no clear variation in the N mean residence time among stands.These suggested that the higher density stands may have more efficient strategies for utilizing nutrients,especially those which axe limiting.

  6. Calculation of static and dynamic linear magnetic response in approximate time-dependent density functional theory.

    Science.gov (United States)

    Krykunov, Mykhaylo; Autschbach, Jochen

    2007-01-14

    We report implementations and results of time-dependent density functional calculations (i) of the frequency-dependent magnetic dipole-magnetic dipole polarizability, (ii) of the (observable) translationally invariant linear magnetic response, and (iii) of a linear intensity differential (LID) which includes the dynamic dipole magnetizability. The density functional calculations utilized density fitting. For achieving gauge-origin independence we have employed time-periodic magnetic-field-dependent basis functions as well as the dipole velocity gauge, and have included explicit density-fit related derivatives of the Coulomb potential. We present the results of calculations of static and dynamic magnetic dipole-magnetic dipole polarizabilities for a set of small molecules, the LID for the SF6 molecule, and dispersion curves for M-hexahelicene of the origin invariant linear magnetic response as well as of three dynamic polarizabilities: magnetic dipole-magnetic dipole, electric dipole-electric dipole, and electric dipole-magnetic dipole. We have also performed comparison of the linear magnetic response and magnetic dipole-magnetic dipole polarizability over a wide range of frequencies for H2O and SF6.

  7. Molecular dynamics, density functional theory of the metal--electrolyte interface

    Energy Technology Data Exchange (ETDEWEB)

    Price, D.L. [Department of Physics, University of Memphis, Memphis Tennessee 38152 (United States); Halley, J.W. [School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

    1995-04-22

    Quantitative, predictive theories for metal--electrolyte interfaces require an atomic-scale representation of the interface, which must include an accurate statistical description of a polar fluid in contact with a solid surface; and also a description of the electronic density and structure of a metal surface in contact with a fluid. Such a complex system presents a difficult computational problem, and has been dealt with in the past essentially by parts; either by molecular dynamics calculations of the fluid structure, or density functional calculations of the metal--surface electronic structure. A complete and self-consistent determination of the surface structure would, however, involve a simultaneous calculation of both the atomic and electronic structure of the interface. This suggests a combination of these two calculational techniques, and it is just this sort of molecular dynamics and density functional combination which comprises the Car--Parrinello, and related, methods. We have developed a Car--Parrinello type combination of molecular dynamics and density functional methods, suitable for application to the metal--electrolyte interface. We briefly describe this calculation and discuss our initial results for a fairly simple metal--water interface.

  8. Effect of difference of cupula and endolymph densities on the dynamics of semicircular canal.

    Science.gov (United States)

    Kondrachuk, A V; Sirenko, S P; Boyle, R

    2008-01-01

    The effect of different densities of a cupula and endolymph on the dynamics of the semicircular canals is considered within the framework of a simplified one-dimensional mathematical model where the canal is approximated by a torus. If the densities are equal, the model is represented by Steinhausen's phenomenological equation. The difference of densities results in the complex dynamics of the cupulo-endolymphatic system, and leads to a dependence on the orientation of both the gravity vector relative to the canal plane and the axis of rotation, as well as on the distance between the axis of rotation and the center of the semicircular canal. Our analysis focused on two cases of canal stimulation: rotation with a constant velocity and a time-dependent (harmonically oscillating) angular velocity. Two types of spatial orientation of the axis of rotation, the axis of canal symmetry, and the vector of gravity were considered: i) the gravity vector and axis of rotation lie in the canal plane, and ii) the axis of rotation and gravity vector are normal to the canal plane. The difference of the cupula and endolymph densities reveals new features of cupula dynamics, for instance--a shift of the cupula to a new position of equilibrium that depends on the gravity vector and the parameters of head rotation, and the onset of cupula oscillations with multiple frequencies that results in the distortion of cupula dynamics relative to harmonic stimulation. Factors that might influence the density difference effects and the conditions under which these effects occur are discussed.

  9. A compact fast ionization gauge for in situ measurement of high-density neutral flow dynamics.

    Science.gov (United States)

    Weber, T E; Intrator, T P

    2014-04-01

    A compact ionization gauge has been developed to carry out in situ measurements of high density (10(20)-10(22) m(-3)) neutral gas flow dynamics with high temporal and spatial resolution. Key design aspects are discussed including gauge sensitivity and time response scaling with decreased probe dimensions, high-pressure operation, improved driver circuit bandwidth, and techniques for constructing a miniaturized probe head. Gas adsorption was discovered to significantly alter emission current and gauge sensitivity over timescales of several seconds. This effect must be taken into consideration when making time-resolved, high-density measurements. Over short timescales gauge response was predicted by scaling the sensitivity of a nominal Bayard-Alpert gauge to account for variations in probe dimensions and species-dependent ionization cross-section. Time-resolved neutral density profiles have been acquired in the Magnetized Shock Experiment at Los Alamos National Laboratory, providing data on the initial conditions of the ionization, plasmoid formation, and translation processes. It is shown that the desired density profiles can be achieved using a dynamic gas fill and that density can be scaled independently of the spatial profile.

  10. Path Integral Molecular Dynamics for Hydrogen with Orbital-Free Density Functional Theory

    Science.gov (United States)

    Runge, Keith; Karasiev, Valentin; Deymier, Pierre

    2014-03-01

    The computational bottleneck for performing path-integral molecular dynamics (PIMD) for nuclei on a first principles electronic potential energy surface has been the speed with which forces from the electrons can be generated. Recent advances in orbital-free density functional theory (OF-DFT) not only allow for faster generation of first principles forces but also include the effects of temperature on the electron density. We will present results of calculations on hydrogen in warm dense matter conditions where the protons are described by PIMD and the electrons by OF-DFT. Work supported by U.S. Dept. of Energy, grant DE-SC0002139.

  11. Multiformity of inherent randomicity and visitation density in n symbolic dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Yagang [Department of Applied Mathematics, School of Mathematics and Physics, North China Electric Power University, Box 205, Baoding, Hebei 071003 (China) and Center for Nonlinear Complex Systems, Department of Physics, Yunnan University, Kunming, Yunnan 650091 (China)]. E-mail: ygzhg@163.com; Wang Changjiang [Center for Nonlinear Complex Systems, Department of Physics, Yunnan University, Kunming, Yunnan 650091 (China)

    2007-07-15

    The multiformity of inherent randomicity and visitation density in n symbolic dynamics will be clarified in this paper. These stochastic symbolic sequences bear three features. The distribution of frequency, inter-occurrence times and the alignment of two random sequences are amplified in detail. The features of visitation density in surjective maps presents catholicity and the catholicity in n letters randomicity has the same measure foundation. We hope to offer a symbolic platform that satisfies these stochastic properties and to attempt to study certain properties of DNA base sequences, 20 amino acids symbolic sequences of proteid structure, and the time series that can be symbolic in finance market et al.

  12. Modeling of Soil Water and Salt Dynamics and Its Effects on Root Water Uptake in Heihe Arid Wetland, Gansu, China

    Directory of Open Access Journals (Sweden)

    Huijie Li

    2015-05-01

    Full Text Available In the Heihe River basin, China, increased salinity and water shortages present serious threats to the sustainability of arid wetlands. It is critical to understand the interactions between soil water and salts (from saline shallow groundwater and the river and their effects on plant growth under the influence of shallow groundwater and irrigation. In this study, the Hydrus-1D model was used in an arid wetland of the Middle Heihe River to investigate the effects of the dynamics of soil water, soil salinization, and depth to water table (DWT as well as groundwater salinity on Chinese tamarisk root water uptake. The modeled soil water and electrical conductivity of soil solution (ECsw are in good agreement with the observations, as indicated by RMSE values (0.031 and 0.046 cm3·cm−3 for soil water content, 0.037 and 0.035 dS·m−1 for ECsw, during the model calibration and validation periods, respectively. The calibrated model was used in scenario analyses considering different DWTs, salinity levels and the introduction of preseason irrigation. The results showed that (I Chinese tamarisk root distribution was greatly affected by soil water and salt distribution in the soil profile, with about 73.8% of the roots being distributed in the 20–60 cm layer; (II root water uptake accounted for 91.0% of the potential maximal value when water stress was considered, and for 41.6% when both water and salt stress were considered; (III root water uptake was very sensitive to fluctuations of the water table, and was greatly reduced when the DWT was either dropped or raised 60% of the 2012 reference depth; (IV arid wetland vegetation exhibited a high level of groundwater dependence even though shallow groundwater resulted in increased soil salinization and (V preseason irrigation could effectively increase root water uptake by leaching salts from the root zone. We concluded that a suitable water table and groundwater salinity coupled with proper irrigation

  13. Nitrogen fertilization and root growth dynamics of durum wheat for a sustainable production

    Directory of Open Access Journals (Sweden)

    Donato De Giorgio

    2012-07-01

    Full Text Available In an area of the Apulian Tavoliere (southern Italy, the effects of three levels of nitrogen fertilization (0, 50 and 100 kg N ha–1 on root development, growth analysis and yield parameters of durum wheat were evaluated. The research was conducted over a four-year period (1994-97. The non-destructive mini-rhizotron method was used to study the root system at stem extension and at the beginning of heading and ripening stages. At the end of tillering and at boot and flowering stages, samples of wheat biomass were taken and subjected to growth analysis. Yield data and the main biometric parameters were collected at harvest time. The doses of nitrogen (N fertilizer 50 and 100 kg N ha–1 had a greater effect on root development in the 20-30 cm soil layer and on epigeal biomass than the control test (N0 without nitrogen fertilization. In the test (N0 the growth of root and epigeal biomass was slower during the first vegetative phases, however, afterwards both of them recovered and the root system was mainly developed in the 30-40 cm soil layer. A better development of root system in deeper soil layers, without nitrogen supply, has allowed the plant to overcome more easily the water-deficit and thermal stresses during the ripening stage. The results of this research have shown that the production of grain with 50 kg ha–1 of N is similar to those of 100 kg ha–1 of N doses and higher than the test without nitrogen fertilization. In this kind of environment can be recommended a nitrogen dose of 50 kg ha–1 for obtaining an increase in grain production with low costs and reduced agricultural sources of pollution.

  14. Density Fluctuations in the Yukawa One Component Plasma: An accurate model for the dynamical structure factor

    CERN Document Server

    Mithen, James P; Crowley, Basil J B; Gregori, Gianluca

    2011-01-01

    Using numerical simulations, we investigate the equilibrium dynamics of a single component fluid with Yukawa interaction potential. We show that, for a wide range of densities and temperatures, the dynamics of the system are in striking agreement with a simple model of generalized hydrodynamics. Since the Yukawa potential can describe the ion-ion interactions in a plasma, the model has significant applicability for both analyzing and interpreting the results of x-ray scattering data from high power lasers and fourth generation light sources.

  15. Response and reliability analysis of nonlinear uncertain dynamical structures by the probability density evolution method

    DEFF Research Database (Denmark)

    Nielsen, Søren R. K.; Peng, Yongbo; Sichani, Mahdi Teimouri

    2016-01-01

    The paper deals with the response and reliability analysis of hysteretic or geometric nonlinear uncertain dynamical systems of arbitrary dimensionality driven by stochastic processes. The approach is based on the probability density evolution method proposed by Li and Chen (Stochastic dynamics...... of structures, 1st edn. Wiley, London, 2009; Probab Eng Mech 20(1):33–44, 2005), which circumvents the dimensional curse of traditional methods for the determination of non-stationary probability densities based on Markov process assumptions and the numerical solution of the related Fokker–Planck and Kolmogorov......–Feller equations. The main obstacle of the method is that a multi-dimensional convolution integral needs to be carried out over the sample space of a set of basic random variables, for which reason the number of these need to be relatively low. In order to handle this problem an approach is suggested, which...

  16. Spatially heterogeneous dynamics investigated via a time-dependent four-point density correlation function

    DEFF Research Database (Denmark)

    Lacevic, N.; Starr, F. W.; Schrøder, Thomas

    2003-01-01

    two-point time-dependent density correlation functions, while providing information about the transient "caging" of particles on cooling, are unable to provide sufficiently detailed information about correlated motion and dynamical heterogeneity. Here, we study a four-point, time-dependent density...... simulations of a binary Lennard-Jones mixture approaching the mode coupling temperature from above. We find that the correlations between particles measured by g4(r,t) and S4(q,t) become increasingly pronounced on cooling. The corresponding dynamical correlation length xi4(t) extracted from the small......-q behavior of S4(q,t) provides an estimate of the range of correlated particle motion. We find that xi4(t) has a maximum as a function of time t, and that the value of the maximum of xi4(t) increases steadily from less than one particle diameter to a value exceeding nine particle diameters in the temperature...

  17. The demography of climate-driven and density-regulated population dynamics in a perennial plant

    DEFF Research Database (Denmark)

    Dahlgren, Johan; Bengstsson, Karin; Ehrlén, Johan

    2016-01-01

    Identifying the internal and external drivers of population dynamics is a key objective in ecology, currently accentuated by the need to forecast the effects of climate change on species distributions and abundances. The interplay between environmental and density effects is one particularly...... important aspect of such forecasts. We examined the simultaneous impact of climate and intraspecific density on vital rates of the dwarf shrub Fumana procumbens over 20 yr, using generalized additive mixed models. We then analyzed effects on population dynamics using integral projection models....... The population projection models accurately captured observed fluctuations in population size. Our analyses suggested the population was intrinsically regulated but with annual fluctuations in response to variation in weather. Simulations showed that implicitly assuming variation in demographic rates...

  18. Low amounts of herbivory by root-knot nematodes affect microbial community dynamics and carbon allocation in the rhizosphere.

    Science.gov (United States)

    Poll, Julia; Marhan, Sven; Haase, Susan; Hallmann, Johannes; Kandeler, Ellen; Ruess, Liliane

    2007-12-01

    Increased carbon translocation to the rhizosphere via 'leakage' induced by low amounts of plant parasitic nematodes can foster microorganisms. The effects of the root-knot nematode Meloidogyne incognita on microbial biomass (C(mic)) and community structure (phospholipid fatty acids) in the rhizosphere of barley were studied. Inoculation densities of 2000, 4000, and 8000 nematodes were well below the threshold level for plant damage. A (13)CO(2) pulse-labelling was performed to assess the distribution of assimilated (13)C in the rhizosphere. Infection with M. incognita increased the carbon concentration in shoots, and enhanced root biomass slightly. The presence of nematodes did not affect microbial biomass, but significantly changed the allocation of the recent photosynthate. Less plant carbon was sequestered by microorganisms with increasing nematode abundance. Microbial community structure was distinctly altered in the early stages of the plant-nematode interactions. Both, bacteria and fungi, showed a positive response with 2000, and a negative one with 4000 and 8000 M. incognita added. The results suggest that low-level root herbivory still imposes a considerable carbon demand, and that proliferation of microorganisms due to increased rhizodeposition may be short-termed. The carbon flow to rhizosphere microbial communities is likely dependent on the specific nematode-plant association and the developmental stage of the nematode in the host.

  19. KDE-Track: An Efficient Dynamic Density Estimator for Data Streams

    KAUST Repository

    Qahtan, Abdulhakim Ali Ali

    2016-11-08

    Recent developments in sensors, global positioning system devices and smart phones have increased the availability of spatiotemporal data streams. Developing models for mining such streams is challenged by the huge amount of data that cannot be stored in the memory, the high arrival speed and the dynamic changes in the data distribution. Density estimation is an important technique in stream mining for a wide variety of applications. The construction of kernel density estimators is well studied and documented. However, existing techniques are either expensive or inaccurate and unable to capture the changes in the data distribution. In this paper, we present a method called KDE-Track to estimate the density of spatiotemporal data streams. KDE-Track can efficiently estimate the density function with linear time complexity using interpolation on a kernel model, which is incrementally updated upon the arrival of new samples from the stream. We also propose an accurate and efficient method for selecting the bandwidth value for the kernel density estimator, which increases its accuracy significantly. Both theoretical analysis and experimental validation show that KDE-Track outperforms a set of baseline methods on the estimation accuracy and computing time of complex density structures in data streams.

  20. StreamMap: Smooth Dynamic Visualization of High-Density Streaming Points.

    Science.gov (United States)

    Li, Chenhui; Baciu, George; Yu, Han

    2017-02-13

    Interactive visualization of streaming points for real-time scatterplots and linear blending of correlation patterns is increasingly becoming the dominant mode of visual analytics for both big data and streaming data from active sensors and broadcasting media. To better visualize and interact with inter-stream patterns, it is generally necessary to smooth out gaps or distortions in the streaming data. Previous approaches either animate the points directly or present a sampled static heatmap. We propose a new approach, called StreamMap, to smoothly blend high-density streaming points and create a visual flow that emphasizes the density pattern distributions. In essence, we present three new contributions for the visualization of high-density streaming points. The first contribution is a density-based method called super kernel density estimation that aggregates streaming points using an adaptive kernel to solve the overlapping problem. The second contribution is a robust density morphing algorithm that generates several smooth intermediate frames for a given pair of frames. The third contribution is a trend representation design that can help convey the flow directions of the streaming points. The experimental results on three datasets demonstrate the effectiveness of StreamMap when dynamic visualization and visual analysis of trend patterns on streaming points are required.

  1. Evaluation of Biomass Yield and Water Treatment in Two Aquaponic Systems Using the Dynamic Root Floating Technique (DRF)

    OpenAIRE

    Laura Silva; Eucario Gasca-Leyva; Edgardo Escalante; Kevin M Fitzsimmons; David Valdés Lozano

    2015-01-01

    The experiment evaluates the food production and water treatment of TAN, NO2−–N, NO3−–N, and PO43− in two aquaponics systems using the dynamic root floating technique (DRF). A separate recirculation aquaculture system (RAS) was used as a control. The fish cultured was Nile tilapia (Oreochromis niloticus). The hydroponic culture in one treatment (PAK) was pak choy (Brassica chinensis,) and in the other (COR) coriander (Coriandrum sativum). Initial and final weights were determined for the fis...

  2. Vortex Dynamics in Selfdual Maxwell-Higgs Systems with Uniform Background Electric Charge Density

    CERN Document Server

    Lee, K M

    1994-01-01

    We introduce selfdual Maxwell-Higgs systems with uniform background electric charge density and show that the selfdual equations satisfied by topological vortices can be reduced to the original Bogomol'nyi equations without any background. These vortices are shown to carry no spin but to feel the Magnus force due to the shielding charge carried by the Higgs field. We also study the dynamics of slowly moving vortices and show that the spin-statistics theorem holds to our vortices.

  3. Dynamic kinetic energy potential for orbital-free density functional theory.

    Science.gov (United States)

    Neuhauser, Daniel; Pistinner, Shlomo; Coomar, Arunima; Zhang, Xu; Lu, Gang

    2011-04-14

    A dynamic kinetic energy potential (DKEP) is developed for time-dependent orbital-free (TDOF) density function theory applications. This potential is constructed to affect only the dynamical (ω ≠ 0) response of an orbital-free electronic system. It aims at making the orbital-free simulation respond in the same way as that of a noninteracting homogenous electron gas (HEG), as required by a correct kinetic energy, therefore enabling extension of the success of orbital-free density functional theory in the static case (e.g., for embedding and description of processes in bulk materials) to dynamic processes. The potential is constructed by expansions of terms, each of which necessitates only simple time evolution (concurrent with the TDOF evolution) and a spatial convolution at each time-step. With 14 such terms a good fit is obtained to the response of the HEG at a large range of frequencies, wavevectors, and densities. The method is demonstrated for simple jellium spheres, approximating Na(9)(+) and Na(65)(+) clusters. It is applicable both to small and large (even ultralarge) excitations and the results converge (i.e., do not blow up) as a function of time. An extension to iterative frequency-resolved extraction is briefly outlined, as well as possibly numerically simpler expansions. The approach could also be extended to fit, instead of the HEG susceptibility, either an experimental susceptibility or a theoretically derived one for a non-HEG system. The DKEP potential should be a powerful tool for embedding a dynamical system described by a more accurate method (such as time-dependent density functional theory, TDDFT) in a large background described by TDOF with a DKEP potential. The type of expansions used and envisioned should be useful for other approaches, such as memory functionals in TDDFT. Finally, an appendix details the formal connection between TDOF and TDDFT.

  4. A shift from exploitation to interference competition with increasing density affects population and community dynamics

    OpenAIRE

    Holdridge, Erica M.; Cuellar‐Gempeler, Catalina; terHorst, Casey P.

    2016-01-01

    Abstract Intraspecific competition influences population and community dynamics and occurs via two mechanisms. Exploitative competition is an indirect effect that occurs through use of a shared resource and depends on resource availability. Interference competition occurs by obstructing access to a resource and may not depend on resource availability. Our study tested whether the strength of interference competition changes with protozoa population density. We grew experimental microcosms of ...

  5. Patterns in hydraulic architecture from roots to branches in six tropical tree species from cacao agroforestry and their relation to wood density and stem growth.

    Science.gov (United States)

    Kotowska, Martyna M; Hertel, Dietrich; Rajab, Yasmin Abou; Barus, Henry; Schuldt, Bernhard

    2015-01-01

    For decades it has been assumed that the largest vessels are generally found in roots and that vessel size and corresponding sapwood area-specific hydraulic conductivity are acropetally decreasing toward the distal twigs. However, recent studies from the perhumid tropics revealed a hump-shaped vessel size distribution. Worldwide tropical perhumid forests are extensively replaced by agroforestry systems often using introduced species of various biogeographical and climatic origins. Nonetheless, it is unknown so far what kind of hydraulic architectural patterns are developed in those agroforestry tree species and which impact this exerts regarding important tree functional traits, such as stem growth, hydraulic efficiency and wood density (WD). We investigated wood anatomical and hydraulic properties of the root, stem and branch wood in Theobroma cacao and five common shade tree species in agroforestry systems on Sulawesi (Indonesia); three of these were strictly perhumid tree species, and the other three tree species are tolerating seasonal drought. The overall goal of our study was to relate these properties to stem growth and other tree functional traits such as foliar nitrogen content and sapwood to leaf area ratio. Our results confirmed a hump-shaped vessel size distribution in nearly all species. Drought-adapted species showed divergent patterns of hydraulic conductivity, vessel density, and relative vessel lumen area between root, stem and branch wood compared to wet forest species. Confirming findings from natural old-growth forests in the same region, WD showed no relationship to specific conductivity. Overall, aboveground growth performance was better predicted by specific hydraulic conductivity than by foliar traits and WD. Our study results suggest that future research on conceptual trade-offs of tree hydraulic architecture should consider biogeographical patterns underlining the importance of anatomical adaptation mechanisms to environment.

  6. Proline accumulation, ions dynamics and sodium root-shoot partition and compartmentation

    Directory of Open Access Journals (Sweden)

    Jesus Emanuel eBojorquez Quintal

    2014-11-01

    Full Text Available Despite its economic relevance, little is known about salt tolerance mechanisms in pepper plants. To address this question, we compared differences in responses to NaCl in two Capsicum chinense varieties: Rex (tolerant and Chichen-Itza (sensitive. Under salt stress (150 mM NaCl over 7 days roots of Rex variety accumulated 50 times more compatible solutes such as proline compared to Chichen-Itza. Mineral analysis indicated that Na+ is restricted to roots by preventing its transport to leaves. Fluorescence analysis suggested an efficient Na+ compartmentalization in vacuole-like structures and in small intracellular compartments in roots of Rex variety. At the same time, Na+ in Chichen-Itza plants was compartmentalized in the apoplast, suggesting substantial Na+ extrusion. Rex variety was found to retain more K+ in its roots under salt stress according to a mineral analysis and microelectrode ion flux estimation (MIFE. Vanadate-sensitive H+ efflux was higher in Chichen-Itza variety plants, suggesting a higher activity of the plasma membrane H+-ATPase, which fuels the extrusion of Na+, and, possibly, also the re-uptake of K+. Our results suggest a combination of stress tolerance mechanisms, in order to alleviate the salt-induced injury. Furthermore, Na+ extrusion to apoplast does not appear to be an efficient strategy for salt tolerance in pepper plants.

  7. Dual permeability soil water dynamics and water uptake by roots in irrigated potato fields

    DEFF Research Database (Denmark)

    Dolezal, Frantisek; Zumr, David; Vacek, Josef

    2007-01-01

    Water movement and uptake by roots in a drip-irrigated potato field was studied by combining field experiments, outputs of numerical simulations and summary results of an EU project (www.fertorganic.org). Detailed measurements of soil suction and weather conditions in the Bohemo-Moravian highland...

  8. Fine Root Dynamics and Forest Production Across a Calcium Gradient in Northern Hardwood and Conifer Ecosystems

    Science.gov (United States)

    Byung Bae Park; Ruth D. Yanai; Timothy J. Fahey; Scott W. Bailey; Thomas G. Siccama; James B. Shanley; Natalie L. Cleavitt

    2008-01-01

    Losses of soil base cations due to acid rain have been implicated in declines of red spruce and sugar maple in the northeastern USA. We studied fine root and aboveground biomass and production in five northern hardwood and three conifer stands differing in soil Ca status at Sleepers River, VT; Hubbard Brook, NH; and Cone Pond, NH. Neither aboveground biomass and...

  9. Simulation of the fluid dynamics in artificial aortic roots: comparison of two different types of prostheses.

    Science.gov (United States)

    Bara, Christoph L; Verhey, Janko F

    2008-01-01

    As a consequence of the growing number of elderly people, the incidence of degenerative aortic diseases continues to increase. Often, artificial aortic roots are needed to replace the native tissue. Some physical characteristics of the artificial aortic root, however, are quite different from native aorta and need to be optimized. The supposed benefit of a prosthesis with artificial sinuses of Valsalva could first be checked by numerical calculations. Two simplified base geometries were used for simulating the flow and pressure distributions, especially in the coronary arteries. One model approximates the ascending aorta as a tube, and the other uses a design with toroidal dilation of the aortic root to approximate the native geometry of the sinuses of Valsalva. The flow and pressure distributions in both models were compared in the ascending aorta as well as in the right and the left coronary arteries. Both the pressure and the velocity distribution in the coronary artery region were not significantly higher in the model with the sinus design compared to the tube model. The sinus design only slightly increased the mean pressures and the velocities in both the ascending aorta and in the coronary arteries. Higher pressure in the coronary arteries should improve the blood circulation and decrease the risk of a surgery-related coronary incident. The sinus design did not show the hoped-for benefits, and therefore it is only a minor factor in optimizing future aortic root prostheses.

  10. Glycolysis is dynamic and relates closely to respiration rate in stored sugarbeet roots

    Science.gov (United States)

    Although respiration is the principal cause of postharvest sugarbeet (Beta vulgaris L.) sucrose loss, the internal mechanisms that control sugarbeet root respiration have not been established. Available evidence, however, indicates that respiration is likely to be controlled by the availability of r...

  11. Root growth dynamics linked to aboveground growth in walnuts (Juglans regia L.)

    Science.gov (United States)

    Background and Aims: Examination of belowground plant responses to canopy and soil moisture manipulation is scant compared to that aboveground but needed to understand whole plant responses to environmental factors. Plasticity in the seasonal timing and vertical distribution of root growth in respon...

  12. Fine root dynamics for forests on contrasting soils in the colombian Amazon

    Directory of Open Access Journals (Sweden)

    E. M. Jiménez

    2009-03-01

    Full Text Available It has been hypothesized that in a gradient of increase of soil resources carbon allocated to belowground production (fine roots decreases. To evaluate this hypothesis, we measured the mass and production of fine roots (<2 mm by two methods: 1 ingrowth cores and, 2 sequential soil coring, during 2.2 years in two lowland forests with different soils in the colombian Amazon. Differences of soil resources were determined by the type and physical and chemical properties of soil: a forest on loamy soil (Ultisol at the Amacayacu National Natural Park and, the other on white sands (Spodosol at the Zafire Biological Station, located in the Forest Reservation of the Calderón River. We found that mass and production of fine roots was significantly different between soil depths (0–10 and 10–20 cm and also between forests. White-sand forest allocated more carbon to fine roots than the clayey forest; the production in white-sand forest was twice (2.98 and 3.33 Mg C ha−1 year−1, method 1 and 2, respectively as much as in clayey forest (1.51 and 1.36–1.03 Mg C ha−1 year−1, method 1 and 2, respectively; similarly, the average of fine root mass was higher in the white-sand forest (10.94 Mg C ha−1 than in the forest on clay soils (3.04–3.64 Mg C ha−1. The mass of fine roots also showed a temporal variation related to rainfall, such that production of fine roots decreased substantially in the dry period of the year 2005. Our results suggest that soil resources play an important role in patterns of carbon allocation in these forests; carbon allocated to above-and belowground organs is different between forest types, in such a way that a trade-off above/belowground seems to exist; as a result, it is probable that there are not differences in total net primary productivity between these two forests: does belowground offset lower aboveground production in poorer soils?

  13. Colorectal carcinoma evaluated by incremental dynamic CT; Comparison of CT density, histology, and tumor size

    Energy Technology Data Exchange (ETDEWEB)

    Furukawa, Hiroyoshi; Hara, Tsuyoshi; Taniguchi, Tetsushi (Shimizu Kosei Hospital, Shizuoka (Japan))

    1992-06-01

    Evaluation of incremental dynamic CT scan and histologic findings were compared in order to clarify the cause of the differences in colorectal carcinoma as observed on CT after administration of contrast medium. In 48 cases demonstrated on postcontrast dynamic CT scan, the CT density of the tumor was homogeneous (Type 1) in 26 (54.2%) cases and heterogeneous (Type 2) in 22 (45.8%) cases. Well differentiated adenocarcinoma was seen as Type 1 in 11 of 13 (84.6%) cases while moderately differentiated adenocarcinoma was of Type 1 in 15 of 29 (51.7%) cases. Poorly differentiated and mucinous adenocarcinoma were detected as Type 2 in all cases. A comparison of CT types and tumor size showed that as tumor size increased, the number of Type 1 cases decreased while Type 2 cases increased. Histologically, high density areas consisted mainly of well-developed tubular, branching glands of adenocarcinoma, while low density areas were composed of fibrous or mucinous stroma or necrosis. Dynamic CT scans for colorectal cancer are useful not only for preoperative staging but also for tissue characterization. (author).

  14. Dynamic Reliability Analysis Method of Degraded Mechanical Components Based on Process Probability Density Function of Stress

    Directory of Open Access Journals (Sweden)

    Peng Gao

    2014-01-01

    Full Text Available It is necessary to develop dynamic reliability models when considering strength degradation of mechanical components. Instant probability density function (IPDF of stress and process probability density function (PPDF of stress, which are obtained via different statistical methods, are defined, respectively. In practical engineering, the probability density function (PDF for the usage of mechanical components is mostly PPDF, such as the PDF acquired via the rain flow counting method. For the convenience of application, IPDF is always approximated by PPDF when using the existing dynamic reliability models. However, it may cause errors in the reliability calculation due to the approximation of IPDF by PPDF. Therefore, dynamic reliability models directly based on PPDF of stress are developed in this paper. Furthermore, the proposed models can be used for reliability assessment in the case of small amount of stress process samples by employing the fuzzy set theory. In addition, the mechanical components in solar array of satellites are chosen as representative examples to illustrate the proposed models. The results show that errors are caused because of the approximation of IPDF by PPDF and the proposed models are accurate in the reliability computation.

  15. Disentangling the effects of climate, density dependence, and harvest on an iconic large herbivore's population dynamics

    DEFF Research Database (Denmark)

    Koons, David; Colchero, Fernando; Hersey, Kent

    2015-01-01

    Understanding the relative effects of climate, harvest, and density dependence on population dynamics is critical for guiding sound population management, especially for ungulates in arid and semi-arid environments experiencing climate change. To address these issues for bison in southern Utah, we...... spring temperature could have a greater ‘relative effect’ on equilibrium abundance than either harvest or the strength of density dependence. Our findings highlight the utility of incorporating elasticity analyses into state-space population models, and the need to include climatic processes in wildlife...... applied a Bayesian state-space model to a 72-year time series of abundance counts. While accounting for known harvest (as well as live removal) from the population, we found that the bison population in southern Utah exhibited strong potential to grow from low density (β0 = 0.26; Bayesian credible...

  16. Genetic Based Plant Resistance and Susceptibility Traits to Herbivory Influence Needle and Root Litter Nutrient Dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Classen, Aimee T [ORNL; Chapman, Samantha K. [Smithsonian Environmental Research Center, Edgewater, MD; Whitham, Thomas G [Northern Arizona University; Hart, Stephen C [Northern Arizona University; Koch, George W [Northern Arizona University

    2007-01-01

    It is generally assumed that leaf and root litter decomposition have similar drivers and that nutrient release from these substrates is synchronized. Few studies have examined these assumptions, and none has examined how plant genetics (i.e., plant susceptibility to herbivory) could affect these relationships. Here we examine the effects of herbivore susceptibility and resistance on needle and fine root litter decomposition of pi on pine, Pinus edulis. The study population consists of individual trees that are either susceptible or resistant to herbivory by the pi on needle scale, Matsucoccus acalyptus, or the stem-boring moth, Dioryctria albovittella. Genetic analyses and experimental removals and additions of these insects have identified trees that are naturally resistant and susceptible to these insects. These herbivores increase the chemical quality of litter inputs and alter soil microclimate, both of which are important decomposition drivers. Our research leads to four major conclusions: Herbivore susceptibility and resistance effects on 1) needle litter mass loss and phosphorus (P) retention in moth susceptible and resistant litter are governed by microclimate, 2) root litter nitrogen (N) and P retention, and needle litter N retention are governed by litter chemical quality, 3) net nutrient release from litter can reverse over time, 4) root and needle litter mass loss and nutrient release are determined by location (above- vs. belowground), suggesting that the regulators of needle and root decomposition differ at the local scale. Understanding of decomposition and nutrient retention in ecosystems requires consideration of herbivore effects on above- and belowground processes and how these effects may be governed by plant genotype. Because an underlying genetic component to herbivory is common to most ecosystems of the world and herbivory may increase in climatic change scenarios, it is important to evaluate the role of plant genetics in affecting carbon and

  17. Density fluctuation dynamics in a dissipative self-gravitating dilute gas revisited

    Science.gov (United States)

    Méndez, A. R.; García-Perciante, A. L.

    2016-11-01

    The analysis of the behavior of density fluctuations in a dissipative self gravitating gas in the linear regime is revisited. A factorization for the dispersion relation given by approximate roots is proposed, which is analogous to the one introduced in the case without gravitational field. The threshold for the onset of a gravitational instability, namely Jeans wavenumber, is found to be unaltered by the presence of thermal and viscous dissipation. However, the behavior of damped modes does not correspond to the usual Rayleigh-Brillouin spectrum when the gravitational field is taken into account. Additional to the usual central Rayleigh peak and Brillouin doublet, both corrected due to the presence of the field, non-Lorentizan terms are included in the structure factor. These terms are larger in the presence of the gravitational field and may lead in principle to relevant differences in the general properties of the spectrum. The possible mathematical origin of these modifications is briefly discussed.

  18. Structural, Electronic and Dynamical Properties of Curium Monopnictides: Density Functional Calculations

    Science.gov (United States)

    Roondhe, Basant; Upadhyay, Deepak; Som, Narayan; Pillai, Sharad B.; Shinde, Satyam; Jha, Prafulla K.

    2017-03-01

    The structural, electronic, dynamical and thermodynamical properties of CmX (X = N, P, As, Sb, and Bi) compounds are studied using first principles calculations within density functional theory. The Perdew-Burke-Ernzerhof spin polarized generalized gradient approximation and Perdew-Wang (PW) spin polarized local density approximation as the exchange correlational functionals are used in these calculations. There is a good agreement between the present and previously reported data. The calculated electronic density of states suggests that the curium monopnictides are metallic in nature, which is consistent with earlier studies. The significant values of magnetic moment suggest their magnetic nature. The phonon dispersion curves and phonon density of states are also calculated, which depict the dynamical stability of these compounds. There is a significant separation between the optical and acoustical phonon branches. The temperature dependence of the thermodynamical functions are also calculated and discussed. Internal energy and vibrational contribution to the Helmholtz free energy increases and decreases, respectively, with temperature. The entropy increases with temperature. The specific heat at constant volume and Debye temperature obey Debye theory. The temperature variation of the considered thermodynamical functions is in line with those of other crystalline solids.

  19. Experimental characterization of active acoustic metamaterial cell with controllable dynamic density

    Science.gov (United States)

    Akl, Wael; Baz, Amr

    2012-10-01

    Controlling wave propagation pattern within acoustic fluid domains has been the motivation for the acoustic metamaterials developments to target applications ranging from acoustic cloaking to passive noise control techniques. Currently, various numerical and analytical approaches exist to predict the fluid domain material properties necessary for specific propagation pattern. Physical attempts to realize such material properties have revealed engineered material constructions that are focused on predefined wave propagation patterns. In the current paper, coupled fluid-structure one-dimensional metamaterial cell, in which piezoelectric active ingredient has been introduced, is manufactured to achieve controllable dynamic density. The density-controllable cell has been manufactured by coupling a water-filled cavity with piezoelectric elements in a cell of 4.5 cm length and 4.1 cm diameter subject to impulse excitation. A finite element model of the cell has been developed and its predictions are validated against the experimental results. The validated model is utilized to predict the changes in the pressure gradient inside the developed cell which is a direct measure of the changes introduced to the dynamic density of the acoustic metamaterial domain. With such predictions, it is demonstrated that densities as high as 3.2 gm/cm3 and as low as 0.72 gm/cm3 can be achieved experimentally for excitation frequencies ranging between 100 Hz and 500 Hz.

  20. Dissipative particle dynamics simulation for the density currents of polymer fluids

    Science.gov (United States)

    Li, Yanggui; Geng, Xingguo; Liu, Zhijun; Liu, Qingsheng; Ouyang, Jie

    2016-11-01

    In this work, the two-dimensional lock-exchange density currents of polymer fluids are numerically investigated using dissipative particle dynamics (DPD) at the mesoscale particle level. A modified finitely extensible nonlinear elastic (FENE) chain model is chosen to describe the polymer system, which perfectly depicts not only the elastic tension but also the elastic repulsion between the adjacent beads with bond length as the equilibrium length of one segment. Through the model and numerical simulation, we analyze the dynamics behavior of the density currents of polymer fluids. A comparison with its Newtonian counterpart suggests that the interface between two polymer fluids is more smoothed, and the front structure is different from the Newtonian case because the Kelvin-Helmholtz instability and cleft instability are suppressed by the polymer. Besides, we also probe the influences of polymer volume concentration, chain length and extensibility on the density currents. These simulation results show that increasing any of the parameters, concentration, chain length, and extensibility, the inhibiting effect of polymer on the density currents becomes more significant.

  1. Density, structure, and dynamics of water: the effect of van der Waals interactions.

    Science.gov (United States)

    Wang, Jue; Román-Pérez, G; Soler, Jose M; Artacho, Emilio; Fernández-Serra, M-V

    2011-01-14

    It is known that ab initio molecular dynamics (AIMD) simulations of liquid water at ambient conditions, based on the generalized gradient approximation (GGA) to density functional theory (DFT), with commonly used functionals fail to produce structural and diffusive properties in reasonable agreement with experiment. This is true for canonical, constant temperature simulations where the density of the liquid is fixed to the experimental density. The equilibrium density, at ambient conditions, of DFT water has recently been shown by Schmidt et al. [J. Phys. Chem. B, 113, 11959 (2009)] to be underestimated by different GGA functionals for exchange and correlation, and corrected by the addition of interatomic pair potentials to describe van der Waals (vdW) interactions. In this contribution we present a DFT-AIMD study of liquid water using several GGA functionals as well as the van der Waals density functional (vdW-DF) of Dion et al. [Phys. Rev. Lett. 92, 246401 (2004)]. As expected, we find that the density of water is grossly underestimated by GGA functionals. When a vdW-DF is used, the density improves drastically and the experimental diffusivity is reproduced without the need of thermal corrections. We analyze the origin of the density differences between all the functionals. We show that the vdW-DF increases the population of non-H-bonded interstitial sites, at distances between the first and second coordination shells. However, it excessively weakens the H-bond network, collapsing the second coordination shell. This structural problem is partially associated to the choice of GGA exchange in the vdW-DF. We show that a different choice for the exchange functional is enough to achieve an overall improvement both in structure and diffusivity.

  2. Impact of biochar and root-induced changes on metal dynamics in the rhizosphere of Agrostis capillaris and Lupinus albus.

    Science.gov (United States)

    Houben, David; Sonnet, Philippe

    2015-11-01

    Rhizosphere interactions are deemed to play a key role in the success of phytoremediation technologies. Here, the effects of biochar and root-induced changes in the rhizosphere of Agrostis capillaris L. and Lupinus albus L. on metal (Cd, Pb and Zn) dynamics were investigated using a biotest on a 2mm soil layer and a sequential extraction procedure (Tessier's scheme). In the bulk soil, the application of 5% biochar significantly reduced the exchangeable pool of metals primarily due to a liming effect which subsequently promoted the metal shift into the carbonate-bound pool. However, metals were re-mobilized in the rhizosphere of both A. capillaris and L. albus due to root-induced acidification which counteracted the liming effect of biochar. As a result, the concentrations of metals in roots and shoots of both plants were not significantly reduced by the application of biochar. Although the study should be considered a worst-case scenario because experimental conditions induced the intensification of rhizosphere processes, the results highlight that changes in rhizosphere pH can impact the effectiveness of biochar to immobilize metals in soil. Biochar has thus a potential as amendment for reducing metal uptake by plants, provided the acidification of the rhizosphere is minimized.

  3. Dynamics of two-phase interfaces and surface tensions: A density-functional theory perspective

    Science.gov (United States)

    Yatsyshin, Petr; Sibley, David N.; Duran-Olivencia, Miguel A.; Kalliadasis, Serafim

    2016-11-01

    Classical density functional theory (DFT) is a statistical mechanical framework for the description of fluids at the nanoscale, where the inhomogeneity of the fluid structure needs to be carefully accounted for. By expressing the grand free-energy of the fluid as a functional of the one-body density, DFT offers a theoretically consistent and computationally accessible way to obtain two-phase interfaces and respective interfacial tensions in a ternary solid-liquid-gas system. The dynamic version of DFT (DDFT) can be rigorously derived from the Smoluchowsky picture of the dynamics of colloidal particles in a solvent. It is generally agreed that DDFT can capture the diffusion-driven evolution of many soft-matter systems. In this context, we use DDFT to investigate the dynamic behaviour of two-phase interfaces in both equilibrium and dynamic wetting and discuss the possibility of defining a time-dependent surface tension, which still remains in debate. We acknowledge financial support from the European Research Council via Advanced Grant No. 247031 and from the Engineering and Physical Sciences Research Council of the UK via Grants No. EP/L027186 and EP/L020564.

  4. Fine root dynamics for forests on contrasting soils in the Colombian Amazon

    Directory of Open Access Journals (Sweden)

    E. M. Jiménez

    2009-12-01

    Full Text Available It has been hypothesized that as soil fertility increases, the amount of carbon allocated to below-ground production (fine roots should decrease. To evaluate this hypothesis, we measured the standing crop fine root mass and the production of fine roots (<2 mm by two methods: (1 ingrowth cores and, (2 sequential soil coring, during 2.2 years in two lowland forests growing on different soils types in the Colombian Amazon. Differences of soil resources were defined by the type and physical and chemical properties of soil: a forest on clay loam soil (Endostagnic Plinthosol at the Amacayacu National Natural Park and, the other on white sand (Ortseinc Podzol at the Zafire Biological Station, located in the Forest Reservation of the Calderón River. We found that the standing crop fine root mass and the production was significantly different between soil depths (0–10 and 10–20 cm and also between forests. The loamy sand forest allocated more carbon to fine roots than the clay loam forest with the production in loamy sand forest twice (mean±standard error=2.98±0.36 and 3.33±0.69 Mg C ha−1 yr−1, method 1 and 2, respectively as much as for the more fertile loamy soil forest (1.51±0.14, method 1, and from 1.03±0.31 to 1.36±0.23 Mg C ha−1 yr−1, method 2. Similarly, the average of standing crop fine root mass was higher in the white-sands forest (10.94±0.33 Mg C ha−1 as compared to the forest on the more fertile soil (from 3.04±0.15 to 3.64±0.18 Mg C ha−1. The standing crop fine root mass also showed a temporal pattern related to rainfall, with the production of fine roots decreasing substantially in the dry period of the year 2005. These results suggest that soil resources may play an important role in patterns of carbon allocation to the production of fine roots in these forests as the proportion of carbon allocated to above- and below-ground organs is different

  5. The influence of dynamical friction on the collapse of spherical density pertubation

    CERN Document Server

    Popolo, A D; Antonuccio-Delogu, V

    1996-01-01

    We solve numerically the equations of motion for the collapse of a shell of baryonic matter falling into the central regions of a cluster of galaxies, taking into account of the presence of the substructure inducing dynamical friction. The evolution of the expansion parameter a(t) of the perturbation is calculated in spherical systems. The effect of dynamical friction is to reduce the binding radius and the total mass accreted by the central regions. Using a peak density profile given by Bardeen et al. (1986) we show how the binding radius of the perturbation is modified by dinamical friction. We show how dynamical friction modifies the collapse parameter of the perturbation slowing down the collapse.

  6. Dynamic density functional theory of protein adsorption on polymer-coated nanoparticles

    CERN Document Server

    Angioletti-Uberti, Stefano; Dzubiella, Joachim

    2014-01-01

    We present a theoretical model for the description of the adsorption kinetics of globular proteins onto charged core-shell microgel particles based on Dynamic Density Functional Theory (DDFT). This model builds on a previous description of protein adsorption thermodynamics [Yigit \\textit{et al}, Langmuir 28 (2012)], shown to well interpret the available calorimetric experimental data of binding isotherms. In practice, a spatially-dependent free-energy functional including the same physical interactions is built, and used to study the kinetics via a generalised diffusion equation. To test this model, we apply it to the case study of Lysozyme adsorption on PNIPAM coated nanoparticles, and show that the dynamics obtained within DDFT is consistent with that extrapolated from experiments. We also perform a systematic study of the effect of various parameters in our model, and investigate the loading dynamics as a function of proteins' valence and hydrophobic adsorption energy, as well as their concentration and th...

  7. Revealing structural and dynamical properties of high density lipoproteins through molecular simulations

    DEFF Research Database (Denmark)

    Koivuniemi, A.; Vattulainen, I.

    2012-01-01

    The structure and function of high density lipoprotein (HDL) particles have intrigued the scientific community for decades because of their crucial preventive role in coronary heart disease. However, it has been a taunting task to reveal the precise molecular structure and dynamics of HDL. Further......, because of the complex composition of HDL, understanding the impact of its structure and dynamics on the function of HDL in reverse cholesterol transport has also been a major issue. Recent progress in molecular simulation methodology and computing power has made a difference, as it has enabled...... essentially atomistic considerations of HDL particles over microsecond time scales, thereby proving substantial added value to experimental research. In this article, we discuss recent highlights concerning the structure and dynamics of HDL particles as revealed by atomistic and coarse-grained molecular...

  8. Doppler Spectrometry for Ultrafast Temporal Mapping of Density Dynamics in Laser-Induced Plasmas

    Science.gov (United States)

    Mondal, S.; Lad, Amit D.; Ahmed, Saima; Narayanan, V.; Pasley, J.; Rajeev, P. P.; Robinson, A. P. L.; Kumar, G. Ravindra

    2010-09-01

    We present high resolution measurements of the ultrafast temporal dynamics of the critical surface in moderately overdense, hot plasma by using two-color, pump-probe Doppler spectrometry. Our measurements clearly capture the initial inward motion of the plasma inside the critical surface of the pump laser which is followed by outward expansion. The measured instantaneous velocity and acceleration profiles are very well reproduced by a hybrid simulation that uses a 1D electromagnetic particle-in-cell simulation for the initial evolution and a hydrodynamics simulation for the later times. The combination of high temporal resolution and dynamic range in our measurements clearly provides quantitative unraveling of the dynamics in this important region, enabling this as a powerful technique to obtain ultrafast snapshots of plasma density and temperature profiles for providing benchmarks for simulations.

  9. A dynamic genetic-hormonal regulatory network model explains multiple cellular behaviors of the root apical meristem of Arabidopsis thaliana.

    Science.gov (United States)

    García-Gómez, Mónica L; Azpeitia, Eugenio; Álvarez-Buylla, Elena R

    2017-04-01

    The study of the concerted action of hormones and transcription factors is fundamental to understand cell differentiation and pattern formation during organ development. The root apical meristem of Arabidopsis thaliana is a useful model to address this. It has a stem cell niche near its tip conformed of a quiescent organizer and stem or initial cells around it, then a proliferation domain followed by a transition domain, where cells diminish division rate before transiting to the elongation zone; here, cells grow anisotropically prior to their final differentiation towards the plant base. A minimal model of the gene regulatory network that underlies cell-fate specification and patterning at the root stem cell niche was proposed before. In this study, we update and couple such network with both the auxin and cytokinin hormone signaling pathways to address how they collectively give rise to attractors that correspond to the genetic and hormonal activity profiles that are characteristic of different cell types along A. thaliana root apical meristem. We used a Boolean model of the genetic-hormonal regulatory network to integrate known and predicted regulatory interactions into alternative models. Our analyses show that, after adding some putative missing interactions, the model includes the necessary and sufficient components and regulatory interactions to recover attractors characteristic of the root cell types, including the auxin and cytokinin activity profiles that correlate with different cellular behaviors along the root apical meristem. Furthermore, the model predicts the existence of activity configurations that could correspond to the transition domain. The model also provides a possible explanation for apparently paradoxical cellular behaviors in the root meristem. For example, how auxin may induce and at the same time inhibit WOX5 expression. According to the model proposed here the hormonal regulation of WOX5 might depend on the cell type. Our results

  10. Smoothness and asymptotic estimates of densities for SDEs with locally smooth coefficients and applications to square root-type diffusions

    CERN Document Server

    De Marco, Stefano

    2011-01-01

    We study smoothness of densities for the solutions of SDEs whose coefficients are smooth and nondegenerate only on an open domain $D$. We prove that a smooth density exists on $D$ and give upper bounds for this density. Under some additional conditions (mainly dealing with the growth of the coefficients and their derivatives), we formulate upper bounds that are suitable to obtain asymptotic estimates of the density for large values of the state variable ("tail" estimates). These results specify and extend some results by Kusuoka and Stroock [J. Fac. Sci. Univ. Tokyo Sect. IA Math. 32 (1985) 1--76], but our approach is substantially different and based on a technique to estimate the Fourier transform inspired from Fournier [Electron. J. Probab. 13 (2008) 135--156] and Bally [Integration by parts formula for locally smooth laws and applications to equations with jumps I (2007) The Royal Swedish Academy of Sciences]. This study is motivated by existing models for financial securities which rely on SDEs with non-...

  11. Effect of NGF, BDNF, bFGF, aFGF and cell density on NPY expression in cultured rat dorsal root ganglion neurones.

    Science.gov (United States)

    Kerekes, N; Landry, M; Lundmark, K; Hökfelt, T

    2000-07-01

    The effect of neurotrophic factors on neuropeptide Y (NPY) expression was studied in adult rat dispersed dorsal root ganglion (DRG) cultures. Nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), acidic fibroblast growth factor (aFGF) or basic FGF was included in the culture medium during incubation for 72 h. In untreated cultures, around 18% of all neurones (visualized by antibodies to PGP 9.5) expressed NPY-like immunoreactivity (LI). In contrast, in vivo uninjured neurones do not contain detectable levels of NPY-LI. In the immunohistochemical analysis aFGF increased the percentage of NPY-immunoreactive (-IR) neurones 1.8-fold, while NGF, BDNF or bFGF had no significant effect on NPY expression. When the effect of these growth factors was monitored with non-radioactive in situ hybridization, both aFGF and bFGF caused a significant increase (2.25- and 1.8-fold, respectively), whereas, again, NGF and BDNF had no effect. The results also showed an effect of cell density on NPY expression, whereby fewer neurones expressed NPY in high than in low density cultures. This difference was seen in untreated as well as growth factor-treated cultures. The present results support the hypothesis that DRG neurones in culture are in an axotomized state, since they express NPY to about the same extent as axotomized DRG neurones in vivo. Surprisingly, two growth factors of the FGF family enhance NPY expression in DRG neurones, which is in apparent contrast to a published in vivo study [Ji, R.-R., Zhang, Q., Pettersson, R.F., Hökfelt, T., 1996. aFGF, bFGF and NGF differentially regulate neuropeptide expression in dorsal root ganglia after axotomy and induce autotomy. Reg. Pept. 66, 179-189.]. Finally, NPY expression was also influenced by cell density.

  12. High-resolution quantification of root dynamics in split-nutrient rhizoslides reveals rapid and strong proliferation of maize roots in response to local high nitrogen.

    Science.gov (United States)

    in 't Zandt, Dina; Le Marié, Chantal; Kirchgessner, Norbert; Visser, Eric J W; Hund, Andreas

    2015-09-01

    The plant's root system is highly plastic, and can respond to environmental stimuli such as high nitrogen (N) in patches. A root may respond to an N patch by selective placement of new lateral roots, and therewith increases root N uptake. This may be a desirable trait in breeding programmes, since it decreases NO3(-) leaching and N2O emission. Roots of maize (Zea mays L.) were grown without N in split-nutrient rhizoslides. One side of the slides was exposed to high N after 15 d of root development, and root elongation was measured for another 15 d, described in a time course model and parameterized. The elongation rates of crown axile roots on the N-treated side of the plant followed a logistic increase to a maximum of 5.3cm d(-1); 95% of the maximum were reached within 4 d. At the same time, on the untreated side, axile root elongation dropped linearly to 1.2cm d(-1) within 6.4 d and stayed constant thereafter. Twice as many lateral roots were formed on the crown axis on the N side compared to the untreated side. Most strikingly, the elongation rates of laterals of the N side increased linearly with most of the roots reaching an asymptote ~8 d after start of the N treatment. By contrast, laterals on the side without N did not show any detectable elongation beyond the first day after their emergence. We conclude that split-nutrient rhizoslides have great potential to improve our knowledge about nitrogen responsiveness and selection for contrasting genotypes.

  13. Ion channel density and threshold dynamics of repetitive firing in a cortical neuron model.

    Science.gov (United States)

    Arhem, Peter; Blomberg, Clas

    2007-01-01

    Modifying the density and distribution of ion channels in a neuron (by natural up- and down-regulation, by pharmacological intervention or by spontaneous mutations) changes its activity pattern. In the present investigation, we analyze how the impulse patterns are regulated by the density of voltage-gated channels in a model neuron, based on voltage clamp measurements of hippocampal interneurons. At least three distinct oscillatory patterns, associated with three distinct regions in the Na-K channel density plane, were found. A stability analysis showed that the different regions are characterized by saddle-node, double-orbit, and Hopf bifurcation threshold dynamics, respectively. Single strongly graded action potentials occur in an area outside the oscillatory regions, but less graded action potentials occur together with repetitive firing over a considerable range of channel densities. The presently found relationship between channel densities and oscillatory behavior may be relevance for understanding principal spiking patterns of cortical neurons (regular firing and fast spiking). It may also be of relevance for understanding the action of pharmacological compounds on brain oscillatory activity.

  14. Consistent schemes for non-adiabatic dynamics derived from partial linearized density matrix propagation.

    Science.gov (United States)

    Huo, Pengfei; Coker, David F

    2012-12-14

    Powerful approximate methods for propagating the density matrix of complex systems that are conveniently described in terms of electronic subsystem states and nuclear degrees of freedom have recently been developed that involve linearizing the density matrix propagator in the difference between the forward and backward paths of the nuclear degrees of freedom while keeping the interference effects between the different forward and backward paths of the electronic subsystem described in terms of the mapping Hamiltonian formalism and semi-classical mechanics. Here we demonstrate that different approaches to developing the linearized approximation to the density matrix propagator can yield a mean-field like approximate propagator in which the nuclear variables evolve classically subject to Ehrenfest-like forces that involve an average over quantum subsystem states, and by adopting an alternative approach to linearizing we obtain an algorithm that involves classical like nuclear dynamics influenced by a quantum subsystem state dependent force reminiscent of trajectory surface hopping methods. We show how these different short time approximations can be implemented iteratively to achieve accurate, stable long time propagation and explore their implementation in different representations. The merits of the different approximate quantum dynamics methods that are thus consistently derived from the density matrix propagator starting point and different partial linearization approximations are explored in various model system studies of multi-state scattering problems and dissipative non-adiabatic relaxation in condensed phase environments that demonstrate the capabilities of these different types of approximations for treating non-adiabatic electronic relaxation, bifurcation of nuclear distributions, and the passage from nonequilibrium coherent dynamics at short times to long time thermal equilibration in the presence of a model dissipative environment.

  15. Silicate melts density, buoyancy relations and the dynamics of magmatic processes in the upper mantle

    Science.gov (United States)

    Sanchez-Valle, Carmen; Malfait, Wim J.

    2016-04-01

    Although silicate melts comprise only a minor volume fraction of the present day Earth, they play a critical role on the Earth's geochemical and geodynamical evolution. Their physical properties, namely the density, are a key control on many magmatic processes, including magma chamber dynamics and volcanic eruptions, melt extraction from residual rocks during partial melting, as well as crystal settling and melt migration. However, the quantitative modeling of these processes has been long limited by the scarcity of data on the density and compressibility of volatile-bearing silicate melts at relevant pressure and temperature conditions. In the last decade, new experimental designs namely combining large volume presses and synchrotron-based techniques have opened the possibility for determining in situ the density of a wide range of dry and volatile-bearing (H2O and CO2) silicate melt compositions at high pressure-high temperature conditions. In this contribution we will illustrate some of these progresses with focus on recent results on the density of dry and hydrous felsic and intermediate melt compositions (rhyolite, phonolite and andesite melts) at crustal and upper mantle conditions (up to 4 GPa and 2000 K). The new data on felsic-intermediate melts has been combined with in situ data on (ultra)mafic systems and ambient pressure dilatometry and sound velocity data to calibrate a continuous, predictive density model for hydrous and CO2-bearing silicate melts with applications to magmatic processes down to the conditions of the mantle transition zone (up to 2773 K and 22 GPa). The calibration dataset consist of more than 370 density measurements on high-pressure and/or water-and CO2-bearing melts and it is formulated in terms of the partial molar properties of the oxide components. The model predicts the density of volatile-bearing liquids to within 42 kg/m3 in the calibration interval and the model extrapolations up to 3000 K and 100 GPa are in good agreement

  16. Molecular markers indicate different dynamics of leaves and roots during litter decomposition

    Science.gov (United States)

    Altmann, Jens; Jansen, Boris; Palviainen, Marjo; Kalbitz, Karsten

    2010-05-01

    Up to now there is only a poor understanding of the sources contributing to organic carbon in forest soils, especially the contribution of leaves and roots. Studies of the last 2 decades have shown that methods like pyrolysis and CuO oxidation are suitable tools to trace back the main contributors of organic matter in water, sediments and soils. Lignin derived monomers, extractable lipids, cutin and suberin derived compounds have been used frequently for identification of plant material. However, for the selection of suitable biomarker the decomposition patterns and stability of these compounds are of high importance but they are only poorly understood. In this study we focused on following questions: (I) Which compounds are characteristic to identify certain plant parts and plant species? (II) How stable are these compounds during the first 3 years of litter decomposition? We studied the chemical composition of samples from a 3-year litterbag decomposition experiment with roots and leaves of spruce, pine and birch which was done in Finland. Additionally to mass loss, carbon and nitrogen contents, free lipids were extracted; by alkaline hydrolysis non extractable lipids were gained. The extracts were analyzed afterwards by GC-MS, the insoluble residues were analyzed by curie-point Pyrolysis GC-MS. In addition to the identification and quantification of a variety of different compounds and compound ratios we used statistical classification methods to get deeper insights into the patterns of leaf and root-derived biomarkers during litter decomposition. The mass loss was largely different between the litter species and we always observed larger mass loss for leaf-derived litter in comparison to root derived litter. This trend was also observed by molecular analysis. The increase of the ratio of vanillic acid to vanillin was correlated to the mass loss of the samples over time. This shows that the degree of decomposition of plant material was linked with the degree of

  17. Recovering Root System Traits Using Image Analysis Exemplified by Two-Dimensional Neutron Radiography Images of Lupine1[C][W][OPEN

    Science.gov (United States)

    Leitner, Daniel; Felderer, Bernd; Vontobel, Peter; Schnepf, Andrea

    2014-01-01

    Root system traits are important in view of current challenges such as sustainable crop production with reduced fertilizer input or in resource-limited environments. We present a novel approach for recovering root architectural parameters based on image-analysis techniques. It is based on a graph representation of the segmented and skeletonized image of the root system, where individual roots are tracked in a fully automated way. Using a dynamic root architecture model for deciding whether a specific path in the graph is likely to represent a root helps to distinguish root overlaps from branches and favors the analysis of root development over a sequence of images. After the root tracking step, global traits such as topological characteristics as well as root architectural parameters are computed. Analysis of neutron radiographic root system images of lupine (Lupinus albus) grown in mesocosms filled with sandy soil results in a set of root architectural parameters. They are used to simulate the dynamic development of the root system and to compute the corresponding root length densities in the mesocosm. The graph representation of the root system provides global information about connectivity inside the graph. The underlying root growth model helps to determine which path inside the graph is most likely for a given root. This facilitates the systematic investigation of root architectural traits, in particular with respect to the parameterization of dynamic root architecture models. PMID:24218493

  18. Density functional approaches to collective phenomena in nuclei: Time-dependent density-functional theory for perturbative and non-perturbative nuclear dynamics

    CERN Document Server

    Nakatsukasa, Takashi

    2012-01-01

    We present the basic concepts and our recent developments in the density functional approaches with the Skyrme functionals for describing nuclear dynamics at low energy. The time-dependent density-functional theory (TDDFT) is utilized for the exact linear response with an external perturbation. For description of collective dynamics beyond the perturbative regime, we present a theory of a decoupled collective submanifold to describe for a slow motion based on the TDDFT. Selected applications are shown to demonstrate the quality of their performance and feasibility. Advantages and disadvantages in the numerical aspects are also discussed.

  19. Protein dynamics governed by interfaces of high polarity and low packing density.

    Directory of Open Access Journals (Sweden)

    Vladimir Espinosa Angarica

    Full Text Available The folding pathway, three-dimensional structure and intrinsic dynamics of proteins are governed by their amino acid sequences. Internal protein surfaces with physicochemical properties appropriate to modulate conformational fluctuations could play important roles in folding and dynamics. We show here that proteins contain buried interfaces of high polarity and low packing density, coined as LIPs: Light Interfaces of high Polarity, whose physicochemical properties make them unstable. The structures of well-characterized equilibrium and kinetic folding intermediates indicate that the LIPs of the corresponding native proteins fold late and are involved in local unfolding events. Importantly, LIPs can be identified using very fast and uncomplicated computational analysis of protein three-dimensional structures, which provides an easy way to delineate the protein segments involved in dynamics. Since LIPs can be retained while the sequences of the interacting segments diverge significantly, proteins could in principle evolve new functional features reusing pre-existing encoded dynamics. Large-scale identification of LIPS may contribute to understanding evolutionary constraints of proteins and the way protein intrinsic dynamics are encoded.

  20. Effect of Physicochemical Characteristics of Soil on Population Density of Arbuscular Mycorrhizal Fungi in the Roots of Grapevine in Urmia

    Directory of Open Access Journals (Sweden)

    A. Mahdavi Bileh Savar

    2015-01-01

    Full Text Available Relationship of is one of the most useful interactions in terrestrial ecosystems that its positive effects on growth, physiology and ecology of different plants has been documented. This study investigated the relationship between important physicochemical characteristics of soils such as pH, electrical conductivity (EC, soil texture, organic carbon percentage, soil potassium percentage and the amount of accessible phosphorus with population of mycorrhizal fungi. After dividing the study region into four areas, 43 samples of soil were collected. The results of statistical analysis on physico-chemical characteristics of soil and their relation with population density of spores of arbuscular mycorrhizal fungi showed that there was a negative correlation between electrical conductivity (EC, pH, clay percent, and percent of soil available phosphorus, potassium percent, and percentage of organic carbon with the mean number of fungi. There were positive correlations between silt and sand percentages and mean number of spores present in the soil. Based on the coefficien of determination and based on study conditions, the best model for the rhizosphere was found tobe the one in wich available phosphorus percent of soil was the independent variable, and mean population of fungi as the dependant variable. The correlation between available phosphorus percent in soil samples with average fungi population density negative (P<0/05, but there was not a meaningful correlation between other traits and population density of fungi

  1. The role of riparian vegetation density, channel orientation and water velocity in determining river temperature dynamics

    Science.gov (United States)

    Garner, Grace; Malcolm, Iain A.; Sadler, Jonathan P.; Hannah, David M.

    2017-10-01

    A simulation experiment was used to understand the importance of riparian vegetation density, channel orientation and flow velocity for stream energy budgets and river temperature dynamics. Water temperature and meteorological observations were obtained in addition to hemispherical photographs along a ∼1 km reach of the Girnock Burn, a tributary of the Aberdeenshire Dee, Scotland. Data from nine hemispherical images (representing different uniform canopy density scenarios) were used to parameterise a deterministic net radiation model and simulate radiative fluxes. For each vegetation scenario, the effects of eight channel orientations were investigated by changing the position of north at 45° intervals in each hemispheric image. Simulated radiative fluxes and observed turbulent fluxes drove a high-resolution water temperature model of the reach. Simulations were performed under low and high water velocity scenarios. Both velocity scenarios yielded decreases in mean (≥1.6 °C) and maximum (≥3.0 °C) temperature as canopy density increased. Slow-flowing water resided longer within the reach, which enhanced heat accumulation and dissipation, and drove higher maximum and lower minimum temperatures. Intermediate levels of shade produced highly variable energy flux and water temperature dynamics depending on the channel orientation and thus the time of day when the channel was shaded. We demonstrate that in many reaches relatively sparse but strategically located vegetation could produce substantial reductions in maximum temperature and suggest that these criteria are used to inform future river management.

  2. Dynamic structure factor of a strongly correlated Fermi superfluid within a density functional theory approach

    Science.gov (United States)

    Zou, Peng; Dalfovo, Franco; Sharma, Rishi; Liu, Xia-Ji; Hu, Hui

    2016-11-01

    We theoretically investigate the dynamic structure factor of a strongly interacting Fermi gas at the crossover from Bardeen-Cooper-Schrieffer superfluids to Bose-Einstein condensates, by developing an improved random phase approximation within the framework of a density functional theory (DFT)—the so-called superfluid local density approximation. Compared with the previous random-phase-approximation studies based on the standard Bogoliubov-de Gennes equations, the use of the DFT greatly improves the accuracy of the equation of state at the crossover, and leads to a better description of both collective Bogoliubov-Anderson-Goldstone phonon mode and single-particle fermionic excitations at small transferred momentum. Near unitarity, where the s-wave scattering length diverges, we show that the single-particle excitations start to significantly contribute to the spectrum of dynamic structure factor once the frequency is above a threshold of the energy gap at 2{{Δ }}. The sharp rise in the spectrum at this threshold can be utilized to measure the pairing gap Δ. Together with the sound velocity determined from the phonon branch, the dynamic structure factor provides us some key information of the crossover Fermi superfluid. Our predictions could be examined in experiments with 6Li or 40K atoms using Bragg spectroscopy.

  3. The dynamical masses, densities, and star formation scaling relations of Lyα galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Rhoads, James E.; Malhotra, Sangeeta; Richardson, Mark L. A.; McLinden, Emily M. [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 (United States); Finkelstein, Steven L. [Department of Astronomy, University of Texas at Austin, 1 University Station C1400, Austin, TX 78712 (United States); Fynbo, Johan P. U. [DARK Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø (Denmark); Tilvi, Vithal S., E-mail: James.Rhoads@asu.edu [George P. and Cynthia W. Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics, Texas A and M University, College Station, TX 77843 (United States)

    2014-01-01

    We present the first dynamical mass measurements for Lyα galaxies at high redshift, based on velocity dispersion measurements from rest-frame optical emission lines and size measurements from Hubble Space Telescope imaging, for nine galaxies drawn from four surveys. We use these measurements to study Lyα galaxies in the context of galaxy scaling relations. The resulting dynamical masses range from 10{sup 9} to 10{sup 10} M {sub ☉}. We also fit stellar population models to our sample and use them to place the Lyα sample on a stellar mass versus line width relation. The Lyα galaxies generally follow the same scaling relation as star-forming galaxies at lower redshift, although, lower stellar mass fits are also acceptable in ∼1/3 of the Lyα galaxies. Using the dynamical masses as an upper limit on gas mass, we show that Lyα galaxies have unusually active star formation for their gas mass surface density. This behavior is consistent with what is observed in starburst galaxies, despite the typically smaller masses and sizes of the Lyα galaxy population. Finally, we examine the mass densities of these galaxies and show that their future evolution likely requires dissipational ('wet') merging. In short, we find that Lyα galaxies are low-mass cousins of larger starbursts.

  4. Functions for biomass and basic density of stem, crown and root system of Norway spruce (Picea abies (L.) Karst.) in Denmark

    Energy Technology Data Exchange (ETDEWEB)

    Skovsgaard, Jens Peter (Swedish Univ. of Agricultural Sciences (SLU), Southern Swedish Forest Research Centre, Alnarp (Sweden)); Bald, Caroline (Danish Nature Agency, Koebenhavn Oe (Denmark)); Nord-Larsen, Thomas (Forest and Landscape, Univ. of Copenhagen, Frederiksberg (Denmark))

    2011-04-15

    Models for predicting the biomass of forest trees are becoming increasingly important for assessing forest resources and carbon sequestration in forests. We developed functions for predicting the biomass and basic density of above and below ground parts of Norway spruce (Picea abies (L.) Karst.) in Denmark. Separate models were developed for branches (including foliage), stem and the below-ground stump and root system as well as for the aggregate components of total above-ground biomass and total tree biomass. Trees were sampled in 14 forest stands, reflecting the range of growth conditions and thinning practises of Norway spruce in Denmark. Because of inclusion of experimental plots, data reflected a wider range of thinning practices than commonly used in forestry practice. The data included measurements of biomass and basic density from 114 trees, two of which were regarded as outliers and consequently excluded in the final model estimation. The final models reflected known properties of tree growth and allocation of biomass among different tree components of even-aged Norway spruce. The models were successful in predicting biomass, basic density and biomass expansion factors across a wide variety of tree sizes, stand treatments and growth conditions. The models are believed to substantially improve national estimates of carbon sequestration and biomass resources

  5. Imaging pH and oxygen at the soil-root interface by planar optodes: a challenging technology to study dynamic rhizosphere processes.

    Science.gov (United States)

    Daudin, Gabrielle; Oburger, Eva; Schmidt, Hannes; Borisov, Sergey; Pradier, Céline; Jourdan, Christophe; Marsden, Claire; Obermaier, Daniela; Woebken, Dagmar; Richter, Andreas; Wenzel, Walter; Hinsinger, Philippe

    2017-04-01

    Roots do not only take up water and nutrients from surrounding soil but they also release a wide range of exudates, such as low molecular weight organic compounds, CO2 or protons. Root-soil interactions trigger heterogeneous rhizosphere processes based on differences in root activity along the root axis and with distance from the root surface. Elucidating their temporal and spatial dynamics is of crucial importance for a better understanding of these interrelated biogeochemical processes in the rhizosphere. Therefore, monitoring key parameters at a fine scale and in a non-invasive way at the root-soil interface is essential. Planar optodes are an emerging technology that allows in situ and non-destructive imaging of mainly pH, CO2 and O2. Originated in limnology, planar optodes have recently been applied to soil-root systems in laboratory conditions. This presentation will highlight advantages and challenges of using planar optodes to image pH and O2 dynamics in the rhizosphere, focusing on two RGB (red-green-blue) approaches: a commercially available system (PreSens) and a custom-made one. Important insights into robustness, accuracy, potentials and limitations of the two systems applied to different laboratory/greenhouse-based experimental conditions (flooded and aerobic rhizobox systems, plant species) will be addressed. Furthermore, challenges of optode measurements in the field, including a first case study with Eucalyptus grandis in Brazil, will be discussed.

  6. Dynamics of phenolic acids and lignin accumulation in metal-treated Matricaria chamomilla roots.

    Science.gov (United States)

    Kovácik, Jozef; Klejdus, Borivoj

    2008-03-01

    Phenylalanine ammonia-lyase (PAL) activity, 11 phenolic acids and lignin accumulation in Matricaria chamomilla roots exposed to low (3 microM) and high (60 and 120 microM) levels of cadmium (Cd) or copper (Cu) for 7 days were investigated. Five derivatives of cinnamic acid (chlorogenic, p-coumaric, caffeic, ferulic and sinapic acids) and six derivatives of benzoic acid (protocatechuic, vanillic, syringic, p-hydroxybenzoic, salicylic acids and protocatechuic aldehyde) were detected. Accumulation of glycoside-bound phenolics (revealed by acid hydrolysis) was enhanced mainly towards the end of the experiment, being more expressive in Cu-treated roots. Interestingly, chlorogenic acid was extremely elevated by the highest Cu dose (21-fold higher than control) suggesting its involvement in antioxidative protection. All compounds, with the exception of chlorogenic acid, were detected in the cell wall bound fraction, but only benzoic acids were found in the ester-bound fraction (revealed by alkaline hydrolysis). Soluble phenolics were present in substantially higher amounts in Cu-treated roots and more Cu was retained there in comparison to Cd. Cu strongly elevated PAL activity (by 5.4- and 12.1-fold in 60 and 120 microM treatment, respectively) and lignin content (by 71 and 148%, respectively) after one day of treatment, indicating formation of a barrier against metal entrance. Cd had slighter effects, supporting its non-redox active properties. Taken together, different forms of phenolic metabolites play an important role in chamomile tolerance to metal excess and participate in active antioxidative protection.

  7. Functions for biomass and basic density of stem, crown and root system of Norway spruce (Picea abies (L.) Karst.) in Denmark

    DEFF Research Database (Denmark)

    Skovsgaard, Jens Peter; Bald, Caroline; Nord-Larsen, Thomas

    2011-01-01

    Models for predicting the biomass of forest trees are becoming increasingly important for assessing forest resources and carbon sequestration in forests. We developed functions for predicting the biomass and basic density of above- and below-ground parts of Norway spruce (Picea abies (L.) Karst...... variety of tree sizes, stand treatments and growth conditions. The models are believed to substantially improve national estimates of carbon sequestration and biomass resources........) in Denmark. Separate models were developed for branches (including foliage), stem and the below-ground stump and root system as well as for the aggregate components of total above-ground biomass and total tree biomass. Trees were sampled in 14 forest stands, reflecting the range of growth conditions...

  8. Dynamic Adaptive Median Filter (DAMF for Removal of High Density Impulse Noise

    Directory of Open Access Journals (Sweden)

    Punyaban Patel

    2012-10-01

    Full Text Available This paper proposes a novel adaptive filtering scheme to remove impulse noise from images. The scheme replaces the corrupted test pixel with the median value of non-corrupted neighboring pixels selected from a window dynamically. If the number of non-corrupted pixels in the selected window is not sufficient, a window of next higher size is chosen. Thus window size is automatically adapted based on the density of noise in the image as well as the density of corruption local to a window. As a result window size may vary pixel to pixel while filtering. The scheme is simple to implement and do not require multiple iterations. The efficacy of the proposed scheme is evaluated with respect to subjective as well as objective parameters on standard images on various noise densities. Comparative analysis reveals that the proposed scheme has improved performance over other schemes, preferably in high density impulse noise cases. Further, the computational overhead is also less as compared its competent scheme.

  9. The Relation between Stellar and Dynamical Surface Densities in the Central Regions of Disk Galaxies

    CERN Document Server

    Lelli, Federico; Schombert, James M; Pawlowski, Marcel S

    2016-01-01

    We use the SPARC (Spitzer Photometry & Accurate Rotation Curves) database to study the relation between the central surface density of stars Sstar and dynamical mass Sdyn in 135 disk galaxies (S0 to dIrr). We find that Sdyn correlates tightly with Sstar over 4 dex. This central density relation can be described by a double power law. High surface brightness galaxies are consistent with a 1:1 relation, suggesting that they are self-gravitating and baryon dominated in the inner parts. Low surface brightness galaxies systematically deviate from the 1:1 line, indicating that the dark matter contribution progressively increases but remains tightly coupled to the stellar one. The observed scatter is small (~0.2 dex) and largely driven by observational uncertainties. The residuals show no correlations with other galaxy properties like stellar mass, size, or gas fraction.

  10. Quadrupole Collective Dynamics from Energy Density Functionals: Collective Hamiltonian and the Interacting Boson Model

    CERN Document Server

    Nomura, K; Otsuka, T; Shimizu, N; Vretenar, D

    2011-01-01

    Microscopic energy density functionals (EDF) have become a standard tool for nuclear structure calculations, providing an accurate global description of nuclear ground states and collective excitations. For spectroscopic applications this framework has to be extended to account for collective correlations related to restoration of symmetries broken by the static mean field, and for fluctuations of collective variables. In this work we compare two approaches to five-dimensional quadrupole dynamics: the collective Hamiltonian for quadrupole vibrations and rotations, and the Interacting Boson Model. The two models are compared in a study of the evolution of non-axial shapes in Pt isotopes. Starting from the binding energy surfaces of $^{192,194,196}$Pt, calculated with a microscopic energy density functional, we analyze the resulting low-energy collective spectra obtained from the collective Hamiltonian, and the corresponding IBM-2 Hamiltonian. The calculated excitation spectra and transition probabilities for t...

  11. Structure of solvent-free grafted nanoparticles: Molecular dynamics and density-functional theory

    KAUST Repository

    Chremos, Alexandros

    2011-01-01

    The structure of solvent-free oligomer-grafted nanoparticles has been investigated using molecular dynamics simulations and density-functional theory. At low temperatures and moderate to high oligomer lengths, the qualitative features of the core particle pair probability, structure factor, and the oligomer brush configuration obtained from the simulations can be explained by a density-functional theory that incorporates the configurational entropy of the space-filling oligomers. In particular, the structure factor at small wave numbers attains a value much smaller than the corresponding hard-sphere suspension, the first peak of the pair distribution function is enhanced due to entropic attractions among the particles, and the oligomer brush expands with decreasing particle volume fraction to fill the interstitial space. At higher temperatures, the simulations reveal effects that differ from the theory and are likely caused by steric repulsions of the expanded corona chains. © 2011 American Institute of Physics.

  12. Path Integral Monte Carlo and Density Functional Molecular Dynamics Simulations of Warm Dense Matter

    Science.gov (United States)

    Militzer, Burkhard; Driver, Kevin

    2011-10-01

    We analyze the applicability of two first-principles simulation techniques, path integral Monte Carlo (PIMC) and density functional molecular dynamics (DFT-MD), to study the regime of warm dense matter. We discuss the advantages as well as the limitations of each method and propose directions for future development. Results for dense, liquid helium, where both methods have been applied, demonstrate the range of each method's applicability. Comparison of the equations of state from simulations with analytical theories and free energy models show that DFT is useful for temperatures below 100000 K and then PIMC provides accurate results for all higher temperatures. We characterize the structure of the liquid in terms of pair correlation functions and study the closure of the band gap with increasing density and temperature. Finally, we discuss simulations of heavier elements and demonstrate the reliability are both methods in such cases with preliminary results.

  13. Simulating the frontal instability of lock-exchange density currents with dissipative particle dynamics

    Science.gov (United States)

    Li, Yanggui; Geng, Xingguo; Wang, Heping; Zhuang, Xin; Ouyang, Jie

    2016-06-01

    The frontal instability of lock-exchange density currents is numerically investigated using dissipative particle dynamics (DPD) at the mesoscopic particle level. For modeling two-phase flow, the “color” repulsion model is adopted to describe binary fluids according to Rothman-Keller method. The present DPD simulation can reproduce the flow phenomena of lock-exchange density currents, including the lobe-and-cleft instability that appears at the head, as well as the formation of coherent billow structures at the interface behind the head due to the growth of Kelvin-Helmholtz instability. Furthermore, through the DPD simulation, some small-scale characteristics can be observed, which are difficult to be captured in macroscopic simulation and experiment.

  14. Postcatastrophe population dynamics and density dependence of an endemic island duck

    Science.gov (United States)

    Seavy, N.E.; Reynolds, M.H.; Link, W.A.; Hatfield, J.S.

    2009-01-01

    Laysan ducks (Anas laysanensis) are restricted to approximately 9 km2 in the Northwestern Hawaiian Islands, USA. To evaluate the importance of density dependence for Laysan ducks, we conducted a Bayesian analysis to estimate the parameters of a Gompertz model and the magnitude of process variation and observation error based on the fluctuations in Laysan duck abundance on Laysan Island from 1994 to 2007. This model described a stationary distribution for the population at carrying capacity that fluctuates around a long-term mean of 456 ducks and is between 316 to 636 ducks 95% of the time. This range of expected variability can be used to identify changes in population size that warn of catastrophic events. Density-dependent population dynamics may explain the recovery of Laysan duck from catastrophic declines and allow managers to identify population monitoring thresholds.

  15. Comparison between Fermion Bag Approach and Complex Langevin Dynamics for Massive Thirring Model at Finite Density in 0 + 1 Dimensions

    CERN Document Server

    Li, Daming

    2016-01-01

    We consider the massive Thirring model at finite density in 0+1 dimension. The fermion bag approach, Langevin dynamics and complex Langevin dynamics are adopted to attack the sign problem for this model. Compared with the complex Langevin dynamics, both fermion bag approach and Langvin dynamics avoid the sign problem. The fermion density and chiral condensate, which are obtained by these numerical methods, are compared with the exact results. The advantages of the fermion bag approach over the other numerical methods are also discussed.

  16. Correlated electron dynamics and memory in time-dependent density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Thiele, Mark

    2009-07-28

    Time-dependent density functional theory (TDDFT) is an exact reformulation of the time-dependent many-electron Schroedinger equation, where the problem of many interacting electrons is mapped onto the Kohn-Sham system of noninteracting particles which reproduces the exact electronic density. In the Kohn-Sham system all non-classical many-body effects are incorporated in the exchange-correlation potential which is in general unknown and needs to be approximated. It is the goal of this thesis to investigate the connection between memory effects and correlated electron dynamics in strong and weak fields. To this end one-dimensional two-electron singlet systems are studied. At the same time these systems include the onedimensional helium atom model, which is an established system to investigate the crucial effects of correlated electron dynamics in external fields. The studies presented in this thesis show that memory effects are negligible for typical strong field processes. Here the approximation of the spatial nonlocality is of primary importance. For the photoabsorption spectra on the other hand the neglect of memory effects leads to qualitative and quantitative errors, which are shown to be connected to transitions of double excitation character. To develop a better understanding of the conditions under which memory effects become important quantum fluid dynamics has been found to be especially suitable. It represents a further exact reformulation of the quantum mechanic many-body problem which is based on hydrodynamic quantities such as density and velocity. Memory effects are shown to be important whenever the velocity field develops strong gradients and dissipative effects contribute. (orig.)

  17. A convergent scheme for a non-local coupled system modelling dislocations densities dynamics

    Science.gov (United States)

    Hajj, A. El; Forcadel, N.

    2008-06-01

    In this paper, we study a non-local coupled system that arises in the theory of dislocations densities dynamics. Within the framework of viscosity solutions, we prove a long time existence and uniqueness result for the solution of this model. We also propose a convergent numerical scheme and we prove a Crandall-Lions type error estimate between the continuous solution and the numerical one. As far as we know, this is the first error estimate of Crandall-Lions type for Hamilton-Jacobi systems. We also provide some numerical simulations.

  18. Probabilistic density function method for nonlinear dynamical systems driven by colored noise

    Energy Technology Data Exchange (ETDEWEB)

    Barajas-Solano, David A.; Tartakovsky, Alexandre M.

    2016-05-01

    We present a probability density function (PDF) method for a system of nonlinear stochastic ordinary differential equations driven by colored noise. The method provides an integro-differential equation for the temporal evolution of the joint PDF of the system's state, which we close by means of a modified Large-Eddy-Diffusivity-type closure. Additionally, we introduce the generalized local linearization (LL) approximation for deriving a computable PDF equation in the form of the second-order partial differential equation (PDE). We demonstrate the proposed closure and localization accurately describe the dynamics of the PDF in phase space for systems driven by noise with arbitrary auto-correlation time. We apply the proposed PDF method to the analysis of a set of Kramers equations driven by exponentially auto-correlated Gaussian colored noise to study the dynamics and stability of a power grid.

  19. Micromagnetic model for studies on Magnetic Tunnel Junction switching dynamics, including local current density

    Energy Technology Data Exchange (ETDEWEB)

    Frankowski, Marek, E-mail: mfrankow@agh.edu.pl; Czapkiewicz, Maciej; Skowronski, Witold; Stobiecki, Tomasz

    2014-02-15

    We present a model introducing the Landau–Lifshitz–Gilbert equation with a Slonczewski's Spin-Transfer-Torque (STT) component in order to take into account spin polarized current influence on the magnetization dynamics, which was developed as an Object Oriented MicroMagnetic Framework extension. We implement the following computations: magnetoresistance of vertical channels is calculated from the local spin arrangement, local current density is used to calculate the in-plane and perpendicular STT components as well as the Oersted field, which is caused by the vertical current flow. The model allows for an analysis of all listed components separately, therefore, the contribution of each physical phenomenon in dynamic behavior of Magnetic Tunnel Junction (MTJ) magnetization is discussed. The simulated switching voltage is compared with the experimental data measured in MTJ nanopillars.

  20. [Determination of myclobutanil 25% WG degradation dynamics in ginseng root, stem, leaf and soil by HPLC-MS/MS].

    Science.gov (United States)

    Wang, Yan; Wang, Chun-Wei; Gao, Jie; Cui, Li-Li; Xu, Yun-Cheng

    2014-07-01

    A high performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) method was developed for determining degradation dynamics and final residues of myclobutanil 25% WG in ginseng root, stem, leaf and soil. The samples were extracted with acetonitrile, cleaned-up with primary secondary amine (PSA) solid phase extraction cartridge, separated by Kromasil Eternity-5-C18 (2.1 mm x 150 mm, 5 microm) column with a gradient of acetonitrile and 0.1% formate in water as mobile phases, and analyzed with the multiple reaction monitoring (MRM) in positive ion mode by employing the external standard method. The average recoveries and the relative standard derivations (RSDs) of myclobutanil at the spiked level of 0.01-0.20 mg x kg(-1) were 80.9%-90.7% and 5.54%-9.29%, respectively, and the limit of quantification (LOQ) was 0.005 mg x kg(-1). The method with good reproducible, high precision and low detection limit could meet the requirements of residual analysis on ginseng production. The half-lives of myclobutanil were from 6.25 days to 9.94 days in ginseng root, stem, leaf and soil at spraying dosage of 1 152 g x hm(-2) The final residues were below 0.060 1 mg x kg(-1) in root, below 0.081 7 mg x kg(-1) in stem, 0.006 0-0.102 2 mg x kg(-1) in leaf and below 0.037 6 mg x kg(-1) in soil at spraying dosage range from 576 to 1 152 g x hm(-2). It is recommended that the MRLs of myclobutanil in dried ginseng may be suggested to be 0.10 mg x kg(-1) temporarily, and the preharvest interval was set at 35 days.

  1. Efficient Estimation of Dynamic Density Functions with Applications in Streaming Data

    KAUST Repository

    Qahtan, Abdulhakim

    2016-05-11

    Recent advances in computing technology allow for collecting vast amount of data that arrive continuously in the form of streams. Mining data streams is challenged by the speed and volume of the arriving data. Furthermore, the underlying distribution of the data changes over the time in unpredicted scenarios. To reduce the computational cost, data streams are often studied in forms of condensed representation, e.g., Probability Density Function (PDF). This thesis aims at developing an online density estimator that builds a model called KDE-Track for characterizing the dynamic density of the data streams. KDE-Track estimates the PDF of the stream at a set of resampling points and uses interpolation to estimate the density at any given point. To reduce the interpolation error and computational complexity, we introduce adaptive resampling where more/less resampling points are used in high/low curved regions of the PDF. The PDF values at the resampling points are updated online to provide up-to-date model of the data stream. Comparing with other existing online density estimators, KDE-Track is often more accurate (as reflected by smaller error values) and more computationally efficient (as reflected by shorter running time). The anytime available PDF estimated by KDE-Track can be applied for visualizing the dynamic density of data streams, outlier detection and change detection in data streams. In this thesis work, the first application is to visualize the taxi traffic volume in New York city. Utilizing KDE-Track allows for visualizing and monitoring the traffic flow on real time without extra overhead and provides insight analysis of the pick up demand that can be utilized by service providers to improve service availability. The second application is to detect outliers in data streams from sensor networks based on the estimated PDF. The method detects outliers accurately and outperforms baseline methods designed for detecting and cleaning outliers in sensor data. The

  2. [Effects nutrients on the seedlings root hair development and root growth of Poncirus trifoliata under hydroponics condition].

    Science.gov (United States)

    Cao, Xiu; Xia, Ren-Xue; Zhang, De-Jian; Shu, Bo

    2013-06-01

    Ahydroponics experiment was conducted to study the effects of nutrients (N, P, K, Ca, Mg, Fe, and Mn) deficiency on the length of primary root, the number of lateral roots, and the root hair density, length, and diameter on the primary root and lateral roots of Poncirus trifoliata seedlings. Under the deficiency of each test nutrient, root hair could generate, but was mainly concentrated on the root base and fewer on the root tip. The root hair density on lateral roots was significantly larger than that on primary root, but the root hair length was in adverse. The deficiency of each test nutrient had greater effects on the growth and development of root hairs, with the root hair density on primary root varied from 55.0 to 174.3 mm(-2). As compared with the control, Ca deficiency induced the significant increase of root hair density and length on primary root, P deficiency promoted the root hair density and length on the base and middle part of primary root and on the lateral roots significantly, Fe deficiency increased the root hair density but decreased the root hair length on the tip of primary root significantly, K deficiency significantly decreased the root hair density, length, and diameter on primary root and lateral roots, whereas Mg deficiency increased the root hair length of primary root significantly. In all treatments of nutrient deficiency, the primary root had the similar growth rate, but, with the exceptions of N and Mg deficiency, the lateral roots exhibited shedding and regeneration.

  3. The Impact of Spinal Cord Nerve Roots and Denticulate Ligaments on Cerebrospinal Fluid Dynamics in the Cervical Spine

    Science.gov (United States)

    Heidari Pahlavian, Soroush; Yiallourou, Theresia; Tubbs, R. Shane; Bunck, Alexander C.; Loth, Francis; Goodin, Mark; Raisee, Mehrdad; Martin, Bryn A.

    2014-01-01

    Cerebrospinal fluid (CSF) dynamics in the spinal subarachnoid space (SSS) have been thought to play an important pathophysiological role in syringomyelia, Chiari I malformation (CM), and a role in intrathecal drug delivery. Yet, the impact that fine anatomical structures, including nerve roots and denticulate ligaments (NRDL), have on SSS CSF dynamics is not clear. In the present study we assessed the impact of NRDL on CSF dynamics in the cervical SSS. The 3D geometry of the cervical SSS was reconstructed based on manual segmentation of MRI images of a healthy volunteer and a patient with CM. Idealized NRDL were designed and added to each of the geometries based on in vivo measurments in the literature and confirmation by a neuroanatomist. CFD simulations were performed for the healthy and patient case with and without NRDL included. Our results showed that the NRDL had an important impact on CSF dynamics in terms of velocity field and flow patterns. However, pressure distribution was not altered greatly although the NRDL cases required a larger pressure gradient to maintain the same flow. Also, the NRDL did not alter CSF dynamics to a great degree in the SSS from the foramen magnum to the C1 level for the healthy subject and CM patient with mild tonsillar herniation (∼6 mm). Overall, the NRDL increased fluid mixing phenomena and resulted in a more complex flow field. Comparison of the streamlines of CSF flow revealed that the presence of NRDL lead to the formation of vortical structures and remarkably increased the local mixing of the CSF throughout the SSS. PMID:24710111

  4. The impact of spinal cord nerve roots and denticulate ligaments on cerebrospinal fluid dynamics in the cervical spine.

    Directory of Open Access Journals (Sweden)

    Soroush Heidari Pahlavian

    Full Text Available Cerebrospinal fluid (CSF dynamics in the spinal subarachnoid space (SSS have been thought to play an important pathophysiological role in syringomyelia, Chiari I malformation (CM, and a role in intrathecal drug delivery. Yet, the impact that fine anatomical structures, including nerve roots and denticulate ligaments (NRDL, have on SSS CSF dynamics is not clear. In the present study we assessed the impact of NRDL on CSF dynamics in the cervical SSS. The 3D geometry of the cervical SSS was reconstructed based on manual segmentation of MRI images of a healthy volunteer and a patient with CM. Idealized NRDL were designed and added to each of the geometries based on in vivo measurments in the literature and confirmation by a neuroanatomist. CFD simulations were performed for the healthy and patient case with and without NRDL included. Our results showed that the NRDL had an important impact on CSF dynamics in terms of velocity field and flow patterns. However, pressure distribution was not altered greatly although the NRDL cases required a larger pressure gradient to maintain the same flow. Also, the NRDL did not alter CSF dynamics to a great degree in the SSS from the foramen magnum to the C1 level for the healthy subject and CM patient with mild tonsillar herniation (∼ 6 mm. Overall, the NRDL increased fluid mixing phenomena and resulted in a more complex flow field. Comparison of the streamlines of CSF flow revealed that the presence of NRDL lead to the formation of vortical structures and remarkably increased the local mixing of the CSF throughout the SSS.

  5. The impact of spinal cord nerve roots and denticulate ligaments on cerebrospinal fluid dynamics in the cervical spine.

    Science.gov (United States)

    Heidari Pahlavian, Soroush; Yiallourou, Theresia; Tubbs, R Shane; Bunck, Alexander C; Loth, Francis; Goodin, Mark; Raisee, Mehrdad; Martin, Bryn A

    2014-01-01

    Cerebrospinal fluid (CSF) dynamics in the spinal subarachnoid space (SSS) have been thought to play an important pathophysiological role in syringomyelia, Chiari I malformation (CM), and a role in intrathecal drug delivery. Yet, the impact that fine anatomical structures, including nerve roots and denticulate ligaments (NRDL), have on SSS CSF dynamics is not clear. In the present study we assessed the impact of NRDL on CSF dynamics in the cervical SSS. The 3D geometry of the cervical SSS was reconstructed based on manual segmentation of MRI images of a healthy volunteer and a patient with CM. Idealized NRDL were designed and added to each of the geometries based on in vivo measurments in the literature and confirmation by a neuroanatomist. CFD simulations were performed for the healthy and patient case with and without NRDL included. Our results showed that the NRDL had an important impact on CSF dynamics in terms of velocity field and flow patterns. However, pressure distribution was not altered greatly although the NRDL cases required a larger pressure gradient to maintain the same flow. Also, the NRDL did not alter CSF dynamics to a great degree in the SSS from the foramen magnum to the C1 level for the healthy subject and CM patient with mild tonsillar herniation (∼ 6 mm). Overall, the NRDL increased fluid mixing phenomena and resulted in a more complex flow field. Comparison of the streamlines of CSF flow revealed that the presence of NRDL lead to the formation of vortical structures and remarkably increased the local mixing of the CSF throughout the SSS.

  6. Nitrogen dynamics in the soil-plant system under deficit and partial root-zone drying irrigation strategies in potatoes

    DEFF Research Database (Denmark)

    Shahnazari, Ali; Ahmadi, Seyed Hamid; Lærke, Poul Erik

    2008-01-01

    Experiments were conducted in lysimeters with sandy soil under an automatic rain-out shelter to study the effects of subsurface drip irrigation treatments, full irrigation (FI), deficit irrigation (DI) and partial root-zone drying (PRD), on nitrogen (N) dynamics in the soil-plant system of potatoes....... In 2005, FI and PRD2 were investigated, where FI plants received 100% of evaporative demands, while PRD2 plants received 70% water of FI at each irrigation event after tuber initiation. In 2006, besides FI and PRD2 treatments, DI and PRDI receiving 70% water of FI during the whole season were also studied....... Crop N uptake and residual NH (4)-N and NO3-N to a depth of 0-50 cm, at 10 cm intervals were analyzed. For both years, the PRD2 treatment resulted in 30% water saving and maintained yield as compared with the FI treatment, while when investigated in 2006 only, DI and PRDI treatments resulted...

  7. A real-time extension of density matrix embedding theory for non-equilibrium electron dynamics

    CERN Document Server

    Kretchmer, Joshua S

    2016-01-01

    We introduce the real-time density matrix embedding theory (DMET), a dynamical quantum embedding theory for computing non-equilibrium electron dynamics. As in the previously developed static DMET, real-time DMET partitions the system into an impurity corresponding to the region of interest coupled to the surrounding environment. The environment is efficiently represented by a quantum bath of the same size as the impurity. The equations of motion of the coupled impurity and bath embedding problem are then derived using the time-dependent variational principle. The accuracy of real-time DMET is benchmarked through comparisons with reference time-dependent density matrix renormalization group (DMRG) calculations for a variety of quantum quenches in the single impurity Anderson model (SIAM). We find that real-time DMET is able to correctly capture the non-trivial behavior in the Kondo regime of the SIAM and is able to simulate system sizes beyond those that can be treated by time-dependent DMRG. Our results demon...

  8. Wolbachia-Host Interactions: Host Mating Patterns Affect Wolbachia Density Dynamics.

    Science.gov (United States)

    Zhao, Dong-Xiao; Zhang, Xiang-Fei; Chen, Da-Song; Zhang, Yan-Kai; Hong, Xiao-Yue

    2013-01-01

    Wolbachia are maternally inherited intracellular bacteria that infect a wide range of arthropods and cause an array of effects on host reproduction, fitness and mating behavior. Although our understanding of the Wolbachia-associated effects on hosts is rapidly expanding, our knowledge of the host factors that mediate Wolbachia dynamics is rudimentary. Here, we explore the interactions between Wolbachia and its host, the two-spotted spider mite Tetranychus urticae Koch. Our results indicate that Wolbachia induces strong cytoplasmic incompatibility (CI), increases host fecundity, but has no effects on the longevity of females and the mating competitiveness of males in T. urticae. Most importantly, host mating pattern was found to affect Wolbachia density dynamics during host aging. Mating of an uninfected mite of either sex with an infected mite attenuates the Wolbachia density in the infected mite. According to the results of Wolbachia localization, this finding may be associated with the tropism of Wolbachia for the reproductive tissue in adult spider mites. Our findings describe a new interaction between Wolbachia and their hosts.

  9. Effects of Density and Moisture Variation on Dynamic Deformation Properties of Compacted Lateritic Soil

    Directory of Open Access Journals (Sweden)

    Weizheng Liu

    2016-01-01

    Full Text Available A series of repeated load triaxial tests were conducted in this study to investigate the influences of compaction density and postcompaction moisture variation on the dynamic elastic modulus (Ed and plastic permanent strain (PPS of compacted lateritic soil. Specimens were compacted at optimum moisture content (OMC and three degrees of compaction (90%, 93%, and 96%. Then the specimens were dried or wetted to different moisture contents (OMC, OMC±3%, OMC±6%, and OMC+9% prior to testing for Ed and PPS. Results show that moisture content has greater influence on the Ed and PSS than compaction degree, and the increase in moisture content leads to a decrease of Ed and an increase of PPS. Furthermore, an empirical relationship between Ed and applied cyclic stress (σd is developed that incorporates density and moisture variations. Three different evolution types of PPS with number of load cycles, plastic stable, plastic creep, and incremental collapse, are identified as the increase of moisture content. In addition, the critical dynamic stress (σdc separating stable and unstable deformation is determined based on the shakedown concept. The envelope curves of σdc-moisture of lateritic soil with different degrees of compaction are also determined to provide reference for the pavement design.

  10. Dynamics of depletion and replenishment of water storage in stem and roots of black spruce measured by dendrometers

    Directory of Open Access Journals (Sweden)

    Audrey eTurcotte

    2011-06-01

    Full Text Available In the short term, trees rely on the internal storage of water because it affects their ability to sustain photosynthesis and growth. However, water is not rapidly available for transpiration from all the compartments of the plant and the living tissues of the stem act as a buffer to preclude low water potentials during peaks of transpiration. In this paper, electronic dendrometers were used from mid-June to mid-September 2008 to compare the radius variations in stem and roots of black spruce [Picea mariana (Mill. B.S.P.] in two sites of the boreal forest of Quebec, Canada, with different soil characteristics and water retention. The duration of the daily cycles was similar between sites and measurement heights but greater amplitudes of contraction and expansion were observed on the stem and in the site with the shallowest soil organic layer. The expansion phase had higher amplitudes and lasted longer than contraction. On average, the contraction phase occurred between 07:00 and 16:30 (legal time, while expansion lasted 14.5 h. The roots in the site with the deepest organic layer showed a wider variation in the onset of contraction, which could be as late as 13:00. The probability of observing the contraction phase depended on precipitation. With a precipitation <0.5 mm h-1, the bivariate posterior probabilities estimated >60% probability of observing contraction between 05:00 and 21:00, decreasing to 20% with precipitation >1.1 mm h-1. These findings demonstrated that the depth of the organic layer plays an important role in maintaining the internal water reserve of trees. The dynamics of water depletion and replenishment can modify the water potential of xylem and cell turgor during the enlargement phase, thus affecting radial growth. Changes in temperature and precipitation regime could influence the dynamics of internal water storage in trees growing on shallower and drier soils.

  11. [Effects of water temperature and edible algal density on the population dynamics and sexual reproduction of Moina irrasa].

    Science.gov (United States)

    Li, Yu-Ying; Deng, Dao-Gui; Lei, Juan; Xi, Yi-Long

    2011-12-01

    This paper studied the population dynamics and sexual reproduction of Moina irrasa at different water temperature and edible algal density. The population density of M. irrasa was obviously higher at high than at medium and low densities of edible algae, with the maximum at high edible algal density and 20 degrees C. At the same temperatures, the average number of the offsprings first produced by per female M. irrasa declined with decreasing edible algal density, and the maximum value appeared at 25 degrees C and at high edible algal density. The male offsprings produced were obviously higher at high than at medium and low edible algal densities. There was a significant correlation between the male density and the population density of M. irrasa. The number of ephippia produced by M. irrasa declined with decreasing edible algal density, and was higher at 25 degrees C than at other temperatures. Edible algal density had larger effects on the population dynamics and sexual reproduction of M. irrasa, as compared with temperature.

  12. Universal MOND relation between the baryonic and `dynamical' central surface densities of disc galaxies

    CERN Document Server

    Milgrom, Mordehai

    2016-01-01

    I derive a new MOND relation for pure-disc galaxies: The `dynamical' central surface density, $\\Sigma^0_D$, deduced from the measured velocities, is a universal function of only the true, `baryonic' central surface density, $\\Sigma^0_B$: $\\Sigma^0_D=\\Sigma_M \\mathcal{S}(\\Sigma^0_B/\\Sigma_M)$, where $\\Sigma_M\\equiv a_0/2\\pi G$ is the MOND surface density constant. This surprising result is shown to hold in both existing, nonrelativistic MOND theories (the nonlinear Poisson formulation, and QUMOND). $\\mathcal{S}(y)$ is derived, giving in the two limits: $\\Sigma^0_D=\\Sigma^0_B$ for very high arguments, and $\\Sigma^0_D=(4\\Sigma_M\\Sigma^0_B)^{1/2}$ for $\\Sigma^0_B/\\Sigma_M\\ll 1$. This study was prompted by the recent finding of a correlation between related attributes in a large sample of disc galaxies by Lelli et al. (2016). The MOND relation is shown to agree very well with these results.

  13. Practical technique to quantify small, dense low-density lipoprotein cholesterol using dynamic light scattering

    Science.gov (United States)

    Trirongjitmoah, Suchin; Iinaga, Kazuya; Sakurai, Toshihiro; Chiba, Hitoshi; Sriyudthsak, Mana; Shimizu, Koichi

    2016-04-01

    Quantification of small, dense low-density lipoprotein (sdLDL) cholesterol is clinically significant. We propose a practical technique to estimate the amount of sdLDL cholesterol using dynamic light scattering (DLS). An analytical solution in a closed form has newly been obtained to estimate the weight fraction of one species of scatterers in the DLS measurement of two species of scatterers. Using this solution, we can quantify the sdLDL cholesterol amount from the amounts of the low-density lipoprotein cholesterol and the high-density lipoprotein (HDL) cholesterol, which are commonly obtained through clinical tests. The accuracy of the proposed technique was confirmed experimentally using latex spheres with known size distributions. The applicability of the proposed technique was examined using samples of human blood serum. The possibility of estimating the sdLDL amount using the HDL data was demonstrated. These results suggest that the quantitative estimation of sdLDL amounts using DLS is feasible for point-of-care testing in clinical practice.

  14. Path integral Monte Carlo and density functional molecular dynamics simulations of hot, dense helium

    Science.gov (United States)

    Militzer, B.

    2009-04-01

    Two first-principles simulation techniques, path integral Monte Carlo (PIMC) and density functional molecular dynamics (DFT-MD), are applied to study hot, dense helium in the density-temperature range of 0.387-5.35gcm-3 and 500K-1.28×108K . One coherent equation of state is derived by combining DFT-MD data at lower temperatures with PIMC results at higher temperatures. Good agreement between both techniques is found in an intermediate-temperature range. For the highest temperatures, the PIMC results converge to the Debye-Hückel limiting law. In order to derive the entropy, a thermodynamically consistent free-energy fit is used that reproduces the internal energies and pressure derived from the first-principles simulations. The equation of state is presented in the form of a table as well as a fit and is compared with different free-energy models. Pair-correlation functions and the electronic density of states are discussed. Shock Hugoniot curves are compared with recent laser shock-wave experiments.

  15. The influence of velocity and density ratio on the dynamics of spatially developing mixing layers

    Science.gov (United States)

    Strykowski, P. J.; Niccum, D. L.

    1992-04-01

    The dynamics of countercurrent mixing is examined in the shear layer of an axisymmetric jet. Experiments were designed to establish conditions of absolute instability in a spatially developing shear layer and to document how the instability influences the jet development. By applying suction around the jet periphery, shear-layer velocity ratios R greater than 1 could be studied. Here, R=(U1-U2)/(U1+U2), where U1 is the velocity of the forward jet stream and U2 is the velocity of the counterflowing stream created by suction. The density ratio S=ρ1/ρ2 of the mixing layer was also varied to determine the stability boundary in the S-R plane. The density of the forward stream ρ1 was increased by adding sulfur hexafluoride to the air jet, which provided density ratios between 1 and 5.1. Hot-wire anemometry and flow visualization revealed that a global transition occurs when conditions of absolute instability are established in the jet shear layers. One consequence of this transition is an abrupt decrease in the jet spread rate. The experimentally determined transition between globally stable and globally unstable flow regimes in the S-R plane agrees quite well with predictions of the convective/absolute instability boundary based on the linear stability theory [Pavithran and Redekopp, Phys. Fluids A 1, 1736 (1989)].

  16. Molecular Rayleigh Scattering Diagnostic for Dynamic Temperature, Velocity, and Density Measurements

    Science.gov (United States)

    Mielke, Amy R.; Elam, Kristie A.; Sung, Chi-Jen

    2006-01-01

    A molecular Rayleigh scattering technique is developed to measure dynamic gas temperature, velocity, and density in unseeded turbulent flows at sampling rates up to 16 kHz. A high power CW laser beam is focused at a point in an air jet plume and Rayleigh scattered light is collected and spectrally resolved. The spectrum of the light, which contains information about the temperature and velocity of the flow, is analyzed using a Fabry-Perot interferometer. The circular interference fringe pattern is divided into four concentric regions and sampled at 1 and 16 kHz using photon counting electronics. Monitoring the relative change in intensity within each region allows for measurement of gas temperature and velocity. Independently monitoring the total scattered light intensity provides a measure of gas density. A low speed heated jet is used to validate the measurement of temperature fluctuations and an acoustically excited nozzle flow is studied to validate velocity fluctuation measurements. Power spectral density calculations of the property fluctuations, as well as mean and fluctuating quantities are presented. Temperature fluctuation results are compared with constant current anemometry measurements and velocity fluctuation results are compared with constant temperature anemometry measurements at the same locations.

  17. Soil acidification effects on fine root growth of Douglas-fir on sandy soils.

    NARCIS (Netherlands)

    Olsthoorn, A.F.M.

    1998-01-01

    The ammonium sulphate deposited in forest ecosystems in the Netherlands as a result of air pollution currently exceeds 80 kg N ha -1yr -1locally. To study the influence of this air pollution on fine root density and its dynamics, fine root growth was monitored for three years i

  18. The Effect of Needle-insertion Depth on the Irrigant Flow in the Root Canal : Evaluation Using an Unsteady Computational Fluid Dynamics Model

    NARCIS (Netherlands)

    Boutsioukis, Christos; Lambrianidis, Theodor; Verhaagen, Bram; Versluis, Michel; Kastrinakis, Eleftherios; Wesselink, Paul R.; van der Sluis, Lucas W. M.

    2010-01-01

    Introduction: The aim of this study was to evaluate the effect of needle-insertion depth on the irrigant flow inside a prepared root canal during final irrigation with a syringe and two different needle types using a Computational Fluid Dynamics (CFD) model. Methods: A validated CFD model was used t

  19. The effect of needle-insertion depth on the irrigant flow in the root canal: evaluation using an unsteady computational fluid dynamics model

    NARCIS (Netherlands)

    Boutsioukis, C.; Lambrianidis, T.; Verhaagen, B.; Versluis, M.; Kastrinakis, E.; Wesselink, P.R.; van der Sluis, L.W.M.

    2010-01-01

    Introduction The aim of this study was to evaluate the effect of needle-insertion depth on the irrigant flow inside a prepared root canal during final irrigation with a syringe and two different needle types using a Computational Fluid Dynamics (CFD) model. Methods A validated CFD model was used to

  20. The Effects of Hydroperiod and Nutrient Levels on Root Dynamics in a Seasonally Flooded Swamp Ecosystem 1986

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The major objectives of this study were; 1) to test and evaluate several modified methods for measuring root production and decay, 2) to measure root production and...

  1. Dynamics of electron injection and acceleration driven by laser wakefield in tailored density profiles

    Science.gov (United States)

    Lee, P.; Maynard, G.; Audet, T. L.; Cros, B.; Lehe, R.; Vay, J.-L.

    2016-11-01

    The dynamics of electron acceleration driven by laser wakefield is studied in detail using the particle-in-cell code WARP with the objective to generate high-quality electron bunches with narrow energy spread and small emittance, relevant for the electron injector of a multistage accelerator. Simulation results, using experimentally achievable parameters, show that electron bunches with an energy spread of ˜11 % can be obtained by using an ionization-induced injection mechanism in a mm-scale length plasma. By controlling the focusing of a moderate laser power and tailoring the longitudinal plasma density profile, the electron injection beginning and end positions can be adjusted, while the electron energy can be finely tuned in the last acceleration section.

  2. Incremental Density-Based Link Clustering Algorithm for Community Detection in Dynamic Networks

    Directory of Open Access Journals (Sweden)

    Fanrong Meng

    2016-01-01

    Full Text Available Community detection in complex networks has become a research hotspot in recent years. However, most of the existing community detection algorithms are designed for the static networks; namely, the connections between the nodes are invariable. In this paper, we propose an incremental density-based link clustering algorithm for community detection in dynamic networks, iDBLINK. This algorithm is an extended version of DBLINK which is proposed in our previous work. It can update the local link community structure in the current moment through the change of similarity between the edges at the adjacent moments, which includes the creation, growth, merging, deletion, contraction, and division of link communities. Extensive experimental results demonstrate that iDBLINK not only has a great time efficiency, but also maintains a high quality community detection performance when the network topology is changing.

  3. Kinetic theory of correlated fluids: from dynamic density functional to Lattice Boltzmann methods.

    Science.gov (United States)

    Marconi, Umberto Marini Bettolo; Melchionna, Simone

    2009-07-07

    Using methods of kinetic theory and liquid state theory we propose a description of the nonequilibrium behavior of molecular fluids, which takes into account their microscopic structure and thermodynamic properties. The present work represents an alternative to the recent dynamic density functional theory, which can only deal with colloidal fluids and is not apt to describe the hydrodynamic behavior of a molecular fluid. The method is based on a suitable modification of the Boltzmann transport equation for the phase space distribution and provides a detailed description of the local structure of the fluid and its transport coefficients. Finally, we propose a practical scheme to solve numerically and efficiently the resulting kinetic equation by employing a discretization procedure analogous to the one used in the Lattice Boltzmann method.

  4. Crystal and electronic structures of substituted halide perovskites based on density functional calculation and molecular dynamics

    Science.gov (United States)

    Takaba, Hiromitsu; Kimura, Shou; Alam, Md. Khorshed

    2017-03-01

    Durability of organo-lead halide perovskite are important issue for its practical application in a solar cells. In this study, using density functional theory (DFT) and molecular dynamics, we theoretically investigated a crystal structure, electronic structure, and ionic diffusivity of the partially substituted cubic MA0.5X0.5PbI3 (MA = CH3NH3+, X = NH4+ or (NH2)2CH+ or Cs+). Our calculation results indicate that a partial substitution of MA induces a lattice distortion, resulting in preventing MA or X from the diffusion between A sites in the perovskite. DFT calculations show that electronic structures of the investigated partially substituted perovskites were similar with that of MAPbI3, while their bandgaps slightly decrease compared to that of MAPbI3. Our results mean that partial substitution in halide perovskite is effective technique to suppress diffusion of intrinsic ions and tune the band gap.

  5. High density gas state at water/graphite interface studied by molecular dynamics simulation

    Institute of Scientific and Technical Information of China (English)

    Wang Chun-Lei; Li Zhao-Xia; Li Jing-Yuan; Xiu Peng; Hu Jun; Fang Hai-Ping

    2008-01-01

    In this paper molecular dynamics simulations are performed to study the accumulation behaviour of N2 and H2 at water/graphite interface under ambient temperature and pressure. It finds that both N2 and H2 molecules can accumulate at the interface and form one of two states according to the ratio of gas molecules number to square of graphite surface from our simulation results: gas films (pancake-like) for a larger ratio and nanobubbles for a Smaller ratio. In addition, we discuss the stabilities of nanobubbles at different environment temperatures. Surprisingly, it is found that the density of both kinds of gas states can be greatly increased, even comparable with that of the liquid N2 and liquid H2. The present results are expected to be helpful for the understanding of the stable existence of gas film (pancake-like) and nanobubbles.

  6. Low density lipoprotein: structure, dynamics, and interactions of apoB-100 with lipids

    DEFF Research Database (Denmark)

    Murtola, T.; Vuorela, T. A.; Hyvonen, M. T.;

    2011-01-01

    Low-density lipoprotein (LDL) transports cholesterol in the bloodstream and plays an important role in the development of cardiovascular diseases, in particular atherosclerosis. Despite its importance to health, the structure of LDL is not known in detail. This is worrying since the lack of LDL......'s structural information makes it more difficult to understand its function. In this work, we have combined experimental and theoretical data to construct LDL models comprised of the apoB-100 protein wrapped around a lipid droplet of about 20 nm in size. The models are considered by near-atomistic multi......-microsecond simulations to unravel structural as well as dynamical properties of LDL, with particular attention paid to lipids and their interactions with the protein. We find that the distribution and the ordering of the lipids in the LDL particle are rather complex. The previously proposed 2- and 3- layer models turn...

  7. Time-dependent density functional theory scheme for efficient calculations of dynamic (hyper)polarizabilities

    Science.gov (United States)

    Andrade, Xavier; Botti, Silvana; Marques, Miguel A. L.; Rubio, Angel

    2007-05-01

    The authors present an efficient perturbative method to obtain both static and dynamic polarizabilities and hyperpolarizabilities of complex electronic systems. This approach is based on the solution of a frequency-dependent Sternheimer equation, within the formalism of time-dependent density functional theory, and allows the calculation of the response both in resonance and out of resonance. Furthermore, the excellent scaling with the number of atoms opens the way to the investigation of response properties of very large molecular systems. To demonstrate the capabilities of this method, they implemented it in a real-space (basis-set-free) code and applied it to benchmark molecules, namely, CO, H2O, and para-nitroaniline. Their results are in agreement with experimental and previous theoretical studies and fully validate their approach.

  8. Effect of rooting depth, plant density and planting date on maize (Zea Mays L.) yield and water use efficiency in semi-arid Zimbabwe: Modelling with AquaCrop

    NARCIS (Netherlands)

    Nyakudya, I.W.; Stroosnijder, L.

    2014-01-01

    Under low and poorly distributed rainfall higher food production can be achieved by increasing crop water use efficiency (WUE) through optimum soil fertility management and selection of deep-rooting cultivars, appropriate plant density and planting dates. We explored AquaCrop's applicability in sele

  9. Effect of rooting depth, plant density and planting date on maize (Zea Mays L.) yield and water use efficiency in semi-arid Zimbabwe: Modelling with AquaCrop

    NARCIS (Netherlands)

    Nyakudya, I.W.; Stroosnijder, L.

    2014-01-01

    Under low and poorly distributed rainfall higher food production can be achieved by increasing crop water use efficiency (WUE) through optimum soil fertility management and selection of deep-rooting cultivars, appropriate plant density and planting dates. We explored AquaCrop's applicability in

  10. Dynamic Responses of Root, Mycorrhizal and Soil Heterotrophic Respiration to Temperature Increases in an Arid System of Southeast Spain.

    Science.gov (United States)

    Estruch, C.; Pugnaire, F. I.

    2014-12-01

    Mycorrhizal and heterotrophic respiration may represent up to 80% of total soil respiration in temperate environments; however little is known about arid environments where the dynamics of carbon cycling is less known. To improve models of CO2 efflux to the atmosphere in these environments it is necessary to quantify the contribution of soil components (roots, mycorrhizas and heterotrophic respiration) to soil respiration and their response to temperature increases. We settled up a soil partitioning experiment in December 2013 to address this topic. Using a mesh-collar design we quantified soil respiration of the tree main components (roots, mycorrhiza and heterotrophic respiration) in a Mediterranean arid location dominated by the shrub Rethama sphaerocarpa under two temperature regimes, an increased air temperature using open-top chambers (OTC) and a control. For the firths 6 months of measurements, we recorded a decrease in annual species cover with increased temperature; total soil respiration varied between treatments, being higher in the control treatment while, contrary to our expectations, mycorrhizal and soil heterotrophic respiration did not vary between treatments. When looking at the relative contribution of the different soil components, the treatment enclosing both mycorrhizal and soil heterotrophic respiration represented more than half the total soil respiration. These results show that temperature affects total soil respiration and that, in our case, mycorrhizal and soil heterotrophic community were not major drivers of soil respiration responses to temperature. However, these data correspond to an abnormal dry period and data to be collected during the wet season would help us to better understand the contribution of the different soil components to temperature increases in arid environments.

  11. Dynamic stall development in the near-root region of a model wind turbine blade

    Science.gov (United States)

    Melius, Matthew; Cal, Raul Bayoan; Mulleners, Karen

    2014-11-01

    The dynamic behavior of atmospheric flows create highly variable operational conditions which affect the life expectancy of the turbine components and the power output of the turbine. To gain insight into the unsteady aerodynamics of wind turbine blades, wind tunnel experiments were conducted with a scaled three-dimensional NREL 5MW wind turbine blade model in the 2.2 m × 1.8 m cross-section closed loop wind tunnel DLR in Göttingen. The development of dynamic stall in response to a sudden change in the blades angle of attack are studied by means of time-resolved stereoscopic PIV in span-wisely distributed planes capturing the suction side of the blade. The change in angle of attack was obtained by varying the blade pitch angle to simulate a sudden change in wind speed or pitch angle regulation. Resulting time scales associated with flow separation and reattachment are determined at different radial positions ranging from r / R = 0 . 19 to r / R = 0 . 38 . The influence of the three-dimensionality of the blade geometry on the corresponding aerodynamic effects is captured by analyzing the radial flow component in neighboring measurement fields during stall development.

  12. Coupling density functional theory to polarizable force fields for efficient and accurate Hamiltonian molecular dynamics simulations.

    Science.gov (United States)

    Schwörer, Magnus; Breitenfeld, Benedikt; Tröster, Philipp; Bauer, Sebastian; Lorenzen, Konstantin; Tavan, Paul; Mathias, Gerald

    2013-06-28

    Hybrid molecular dynamics (MD) simulations, in which the forces acting on the atoms are calculated by grid-based density functional theory (DFT) for a solute molecule and by a polarizable molecular mechanics (PMM) force field for a large solvent environment composed of several 10(3)-10(5) molecules, pose a challenge. A corresponding computational approach should guarantee energy conservation, exclude artificial distortions of the electron density at the interface between the DFT and PMM fragments, and should treat the long-range electrostatic interactions within the hybrid simulation system in a linearly scaling fashion. Here we describe a corresponding Hamiltonian DFT/(P)MM implementation, which accounts for inducible atomic dipoles of a PMM environment in a joint DFT/PMM self-consistency iteration. The long-range parts of the electrostatics are treated by hierarchically nested fast multipole expansions up to a maximum distance dictated by the minimum image convention of toroidal boundary conditions and, beyond that distance, by a reaction field approach such that the computation scales linearly with the number of PMM atoms. Short-range over-polarization artifacts are excluded by using Gaussian inducible dipoles throughout the system and Gaussian partial charges in the PMM region close to the DFT fragment. The Hamiltonian character, the stability, and efficiency of the implementation are investigated by hybrid DFT/PMM-MD simulations treating one molecule of the water dimer and of bulk water by DFT and the respective remainder by PMM.

  13. Absolute densities, masses, and radii of the WASP-47 system determined dynamically

    CERN Document Server

    Almenara, J M; Bonfils, X; Udry, S

    2016-01-01

    We present a self-consistent modelling of the available light curve and radial velocity data of WASP-47 that takes into account the gravitational interactions between all known bodies in the system. The joint analysis of light curve and radial velocity data in a multi-planetary system allows deriving absolute densities, radii, and masses without the use of theoretical stellar models. For WASP-47 the precision is limited by the reduced dynamical information that is due to the short time span of the K2 light curve. We achieve a precision of around 22% for the radii of the star and the transiting planets, between 40% and 60% for their masses, and between 1.5% and 38% for their densities. All values agree with previously reported measurements. When theoretical stellar models are included, the system parameters are determined with a precision that exceeds that achieved by previous studies, thanks to the self-consistent modelling of light curve and radial velocity data.

  14. Protein backbone dynamics revealed by quasi spectral density function analysis of amide N-15 nuclei.

    Science.gov (United States)

    Ishima, R; Nagayama, K

    1995-03-14

    Spectral density functions J(0), J(omega N), and J(omega H + omega N) of individual amide N-15 nuclei in proteins were approximated by a quasi spectral density function (QSDF). Using this function, the backbone dynamics were analyzed for seven protein systems on which data have been published. We defined J(0; omega N) as the difference between the J(0) and the J(omega N) values, which describes motions slower than 50 (or 60) MHz, and J(omega N; omega H+N) as the difference between the J(omega N) and the J(omega H + omega N) values, which describes motions slower than 450 (or 540) MHz. The QSDF analysis can easily extract the J(0; omega N) of protein backbones, which have often some relation to biologically relevant reactions. Flexible N-terminal regions in eglin c and glucose permease IIA and a loop region in eglin c showed smaller values of both the J(0; omega N) and the J(omega N; omega H+N) as compared with the other regions, indicating increases in motions faster than nanosecond. The values of the J(0; omega N) for the backbone of the FK506 binding protein showed a large variation in the apoprotein but fell in a very narrow range after the binding of FK506. Characteristic increase or decrease in the values of J(0) and J(omega N) was observed in two or three residues located between secondary structures.

  15. Maximum-Likelihood Sequence Detector for Dynamic Mode High Density Probe Storage

    CERN Document Server

    Kumar, Naveen; Ramamoorthy, Aditya; Salapaka, Murti

    2009-01-01

    There is an ever increasing need for storing data in smaller and smaller form factors driven by the ubiquitous use and increased demands of consumer electronics. A new approach of achieving a few Tb per in2 areal densities, utilizes a cantilever probe with a sharp tip that can be used to deform and assess the topography of the material. The information may be encoded by means of topographic profiles on a polymer medium. The prevalent mode of using the cantilever probe is the static mode that is known to be harsh on the probe and the media. In this paper, the high quality factor dynamic mode operation, which is known to be less harsh on the media and the probe, is analyzed for probe based high density data storage purposes. It is demonstrated that an appropriate level of abstraction is possible that obviates the need for an involved physical model. The read operation is modeled as a communication channel which incorporates the inherent system memory due to the intersymbol interference and the cantilever state ...

  16. Switching dynamics of the spin density wave in superconducting CeCoIn5

    Science.gov (United States)

    Kim, Duk Y.; Lin, Shi-Zeng; Bauer, Eric D.; Ronning, Filip; Thompson, J. D.; Movshovich, Roman

    2017-06-01

    The ordering wave vector Q of a spin density wave (SDW), stabilized within the superconducting state of CeCoIn5 in a high magnetic field, has been shown to be hypersensitive to the direction of the field. Q can be switched from a nodal direction of the d -wave superconducting order parameter to a perpendicular node by rotating the in-plane magnetic field through the antinodal direction within a fraction of a degree. Here, we address the dynamics of the switching of Q . We use a free-energy functional based on the magnetization density, which describes the condensation of magnetic fluctuations of nodal quasiparticles, and show that the switching process includes closing of the SDW gap at one Q and then reopening the SDW gap at another Q perpendicular to the first one. The magnetic field couples to Q through the spin-orbit interaction. Our calculations show that the width of the hysteretic region of switching depends linearly on the deviation of magnetic field from the critical field associated with the SDW transition, consistent with our thermal conductivity measurements. The agreement between theory and experiment supports our scenario of the hypersensitivity of the Q phase on the direction of magnetic field, as well as the magnon condensation as the origin of the SDW phase in CeCoIn5.

  17. Absolute densities, masses, and radii of the WASP-47 system determined dynamically

    Science.gov (United States)

    Almenara, J. M.; Díaz, R. F.; Bonfils, X.; Udry, S.

    2016-10-01

    We present a self-consistent modelling of the available light curve and radial velocity data of WASP-47 that takes into account the gravitational interactions between all known bodies in the system. The joint analysis of light curve and radial velocity data in a multi-planetary system allows deriving absolute densities, radii, and masses without the use of theoretical stellar models. For WASP-47 the precision is limited by the reduced dynamical information that is due to the short time span of the K2 light curve. We achieve a precision of around 22% for the radii of the star and the transiting planets, between 40% and 60% for their masses, and between 1.5% and 38% for their densities. All values agree with previously reported measurements. When theoretical stellar models are included, the system parameters are determined with a precision that exceeds that achieved by previous studies, thanks to the self-consistent modelling of light curve and radial velocity data.

  18. Dynamic simulation for tempo-spatial distribution of strain energy density in inhomogeneous stratified crust

    Institute of Scientific and Technical Information of China (English)

    CHEN Yu-kun; NIE Yong-an

    2000-01-01

    Through simulating the research on dynamic variations of strain energy density (SED) in seismogenic model with hard inclusion, the authors have gained further knowledge to such problems as the process of earthquake preparation, initial rupture, conditions of the initial rupture and fracture propagation direction, etc. Results of the research show that SED (strain energy density) in soft inclusion is very high during the initial period of earthquake preparation. And the increment of SED in the soft area decreases at the later stage of the process. Meanwhile, the increment increases quickly in hard inclusion and in the intersection zone of the inclusion with an erecting fault, where the increment of SED is maximum. Thus, the intersection zone between hard inclusion with larger elastic modulus and erecting fault becomes the place where the initial rupture or earthquake occurs. The fracture in the end part of the hard inclusion spreads along a direction nearly vertical to the erecting fault, so the theoretical fracture direction is consistent with that calculated by digital simulation.

  19. Dynamics of supercritical methanol of varying density from first principles simulations: hydrogen bond fluctuations, vibrational spectral diffusion, and orientational relaxation.

    Science.gov (United States)

    Yadav, Vivek Kumar; Chandra, Amalendu

    2013-06-14

    A first principles study of the dynamics of supercritical methanol is carried out by means of ab initio molecular dynamics simulations. In particular, the fluctuation dynamics of hydroxyl stretch frequencies, hydrogen bonds, dangling hydroxyl groups, and orientation of methanol molecules are investigated for three different densities at 523 K. Apart from the dynamical properties, various equilibrium properties of supercritical methanol such as the local density distributions and structural correlations, hydrogen bonding aspects, frequency-structure correlations, and dipole distributions of methanol molecules are also investigated. In addition to the density dependence of various equilibrium and dynamical properties, their dependencies on dispersion interactions are also studied by carrying out additional simulations using a dispersion corrected density functional for all the systems. It is found that the hydrogen bonding between methanol molecules decreases significantly as we move to the supercritical state from the ambient one. The inclusion of dispersion interactions is found to increase the number of hydrogen bonds to some extent. Calculations of the frequency-structure correlation coefficient reveal that a statistical correlation between the hydroxyl stretch frequency and the nearest hydrogen-oxygen distance continues to exist even at supercritical states of methanol, although it is weakened with increase of temperature and decrease of density. In the supercritical state, the frequency time correlation function is found to decay with two time scales: One around or less than 100 fs and the other in the region of 250-700 fs. It is found that, for supercritical methanol, the times scales of vibrational spectral diffusion are determined by an interplay between the dynamics of hydrogen bonds, dangling OD groups, and inertial rotation of methanol molecules and the roles of these various components are found to vary with density of the supercritical solvent. Effects

  20. The Integrated Role of Water Availability, Nutrient Dynamics, and Xylem Hydraulic Dysfunction on Plant Rooting Strategies in Managed and Natural Ecosystems

    Science.gov (United States)

    Mackay, D. S.; Savoy, P.; Pleban, J. R.; Tai, X.; Ewers, B. E.

    2015-12-01

    Plants adapt or acclimate to changing environments in part by allocating biomass to roots and leaves to strike a balance between water and nutrient uptake requirements on the one hand and growth and hydraulic safety on the other hand. In a recent study examining experimental drought with the TREES model, which couples plant ecophysiology with rhizosphere-and-xylem hydraulics, we hypothesized that the asynchronous nature of soil water availability and xylem repair supported root-to-leaf area (RLA) proportionality that favored long-term survival over short-term carbon gain or water use. To investigate this as a possible general principal of plant adjustment to changing environmental conditions, TREES was modified to allocate carbon to fine and coarse roots organized in ten orders differing in biomass allocated per unit absorbing root area, root lifespan, and total absorbing root area in each of several soil-root zones with depth. The expanded model allowed for adjustment of absorbing root area and rhizosphere volume based on available carbohydrate production and nitrogen (N) availability, resulting in dynamic expansion and contraction of the supply-side of the rhizosphere-plant hydraulics and N uptake capacity in response to changing environmental conditions and plant-environment asynchrony. The study was conducted partly in a controlled experimental setting with six genotypes of a widely grown crop species, Brassica rapa. The implications for forests were investigated in controlled experiments and at Fluxnet sites representing temperate mixed forests, semi-arid evergreen needle-leaf, and Mediterranean biomes. The results showed that the effects of N deficiency on total plant growth was modulated by a relative increase in fine root biomass representing a larger absorbing root volume per unit biomass invested. We found that the total absorbing root area per unit leaf area was consistently lower than that needed to maximize short-term water uptake and carbohydrate gain

  1. Neuronal actin dynamics, spine density and neuronal dendritic complexity are regulated by CAP2

    Directory of Open Access Journals (Sweden)

    Atul Kumar

    2016-07-01

    Full Text Available Actin remodeling is crucial for dendritic spine development, morphology and density. CAP2 is a regulator of actin dynamics through sequestering G-actin and severing F-actin. In a mouse model, ablation of CAP2 leads to cardiovascular defects and delayed wound healing. This report investigates the role of CAP2 in the brain using Cap2gt/gt mice. Dendritic complexity, the number and morphology of dendritic spines were altered in Cap2gt/gt with increased number of excitatory synapse. This was accompanied by increased F-actin content and F-actin accumulation in cultured Cap2gt/gt neurons. Moreover, reduced surface GluA1 was observed in mutant neurons under basal condition and after induction of chemical LTP. Additionally, we show an interaction between CAP2 and n-cofilin, presumably mediated through the C-terminal domain of CAP2 and dependent on cofilin ser3 phosphorylation. In vivo, the consequences of this interaction were altered phosphorylated cofilin levels and formation of cofilin aggregates in the neurons. Thus, our studies identify a novel role of CAP2 in neuronal development and neuronal actin dynamics.

  2. High hydrostatic pressure specifically affects molecular dynamics and shape of low-density lipoprotein particles

    Science.gov (United States)

    Golub, M.; Lehofer, B.; Martinez, N.; Ollivier, J.; Kohlbrecher, J.; Prassl, R.; Peters, J.

    2017-04-01

    Lipid composition of human low-density lipoprotein (LDL) and its physicochemical characteristics are relevant for proper functioning of lipid transport in the blood circulation. To explore dynamical and structural features of LDL particles with either a normal or a triglyceride-rich lipid composition we combined coherent and incoherent neutron scattering methods. The investigations were carried out under high hydrostatic pressure (HHP), which is a versatile tool to study the physicochemical behavior of biomolecules in solution at a molecular level. Within both neutron techniques we applied HHP to probe the shape and degree of freedom of the possible motions (within the time windows of 15 and 100 ps) and consequently the flexibility of LDL particles. We found that HHP does not change the types of motion in LDL, but influences the portion of motions participating. Contrary to our assumption that lipoprotein particles, like membranes, are highly sensitive to pressure we determined that LDL copes surprisingly well with high pressure conditions, although the lipid composition, particularly the triglyceride content of the particles, impacts the molecular dynamics and shape arrangement of LDL under pressure.

  3. Decay of aftershock density with distance indicates triggering by dynamic stress.

    Science.gov (United States)

    Felzer, K R; Brodsky, E E

    2006-06-01

    The majority of earthquakes are aftershocks, yet aftershock physics is not well understood. Many studies suggest that static stress changes trigger aftershocks, but recent work suggests that shaking (dynamic stresses) may also play a role. Here we measure the decay of aftershocks as a function of distance from magnitude 2-6 mainshocks in order to clarify the aftershock triggering process. We find that for short times after the mainshock, when low background seismicity rates allow for good aftershock detection, the decay is well fitted by a single inverse power law over distances of 0.2-50 km. The consistency of the trend indicates that the same triggering mechanism is working over the entire range. As static stress changes at the more distant aftershocks are negligible, this suggests that dynamic stresses may be triggering all of these aftershocks. We infer that the observed aftershock density is consistent with the probability of triggering aftershocks being nearly proportional to seismic wave amplitude. The data are not fitted well by models that combine static stress change with the evolution of frictionally locked faults.

  4. Probabilistic density function method for nonlinear dynamical systems driven by colored noise.

    Science.gov (United States)

    Barajas-Solano, David A; Tartakovsky, Alexandre M

    2016-05-01

    We present a probability density function (PDF) method for a system of nonlinear stochastic ordinary differential equations driven by colored noise. The method provides an integrodifferential equation for the temporal evolution of the joint PDF of the system's state, which we close by means of a modified large-eddy-diffusivity (LED) closure. In contrast to the classical LED closure, the proposed closure accounts for advective transport of the PDF in the approximate temporal deconvolution of the integrodifferential equation. In addition, we introduce the generalized local linearization approximation for deriving a computable PDF equation in the form of a second-order partial differential equation. We demonstrate that the proposed closure and localization accurately describe the dynamics of the PDF in phase space for systems driven by noise with arbitrary autocorrelation time. We apply the proposed PDF method to analyze a set of Kramers equations driven by exponentially autocorrelated Gaussian colored noise to study nonlinear oscillators and the dynamics and stability of a power grid. Numerical experiments show the PDF method is accurate when the noise autocorrelation time is either much shorter or longer than the system's relaxation time, while the accuracy decreases as the ratio of the two timescales approaches unity. Similarly, the PDF method accuracy decreases with increasing standard deviation of the noise.

  5. Dynamic density functional theory for nucleation: Non-classical predictions of mesoscopic nucleation theory

    Science.gov (United States)

    Duran-Olivencia, Miguel A.; Yatsyshin, Peter; Lutsko, James F.; Kalliadasis, Serafim

    2016-11-01

    Classical density functional theory (DFT) for fluids and its dynamic extension (DDFT) provide an appealing mean-field framework for describing equilibrium and dynamics of complex soft matter systems. For a long time, homogeneous nucleation was considered to be outside the limits of applicability of DDFT. However, our recently developed mesoscopic nucleation theory (MeNT) based on fluctuating hydrodynamics, reconciles the inherent randomness of the nucleation process with the deterministic nature of DDFT. It turns out that in the weak-noise limit, the most likely path (MLP) for nucleation to occur is determined by the DDFT equations. We present computations of MLPs for homogeneous and heterogeneous nucleation in colloidal suspensions. For homogeneous nucleation, the MLP obtained is in excellent agreement with the reduced order-parameter description of MeNT, which predicts a multistage nucleation pathway. For heterogeneous nucleation, the presence of impurities in the fluid affects the MLP, but remarkably, the overall qualitative picture of homogeneous nucleation persists. Finally, we highlight the use of DDFT as a simulation tool, which is especially appealing as there are no known applications of MeNT to heterogeneous nucleation. We acknowledge financial support from the European Research Council via Advanced Grant No. 247031 and from EPSRC via Grants No. EP/L020564 and EP/L025159.

  6. Extracting functional components of neural dynamics with Independent Component Analysis and inverse Current Source Density.

    Science.gov (United States)

    Lęski, Szymon; Kublik, Ewa; Swiejkowski, Daniel A; Wróbel, Andrzej; Wójcik, Daniel K

    2010-12-01

    Local field potentials have good temporal resolution but are blurred due to the slow spatial decay of the electric field. For simultaneous recordings on regular grids one can reconstruct efficiently the current sources (CSD) using the inverse Current Source Density method (iCSD). It is possible to decompose the resultant spatiotemporal information about the current dynamics into functional components using Independent Component Analysis (ICA). We show on test data modeling recordings of evoked potentials on a grid of 4 × 5 × 7 points that meaningful results are obtained with spatial ICA decomposition of reconstructed CSD. The components obtained through decomposition of CSD are better defined and allow easier physiological interpretation than the results of similar analysis of corresponding evoked potentials in the thalamus. We show that spatiotemporal ICA decompositions can perform better for certain types of sources but it does not seem to be the case for the experimental data studied. Having found the appropriate approach to decomposing neural dynamics into functional components we use the technique to study the somatosensory evoked potentials recorded on a grid spanning a large part of the forebrain. We discuss two example components associated with the first waves of activation of the somatosensory thalamus. We show that the proposed method brings up new, more detailed information on the time and spatial location of specific activity conveyed through various parts of the somatosensory thalamus in the rat.

  7. Dissipative particle dynamics for systems with high density of charges: Implementation of electrostatic interactions

    Science.gov (United States)

    Gavrilov, A. A.; Chertovich, A. V.; Kramarenko, E. Yu.

    2016-11-01

    In this work, we study the question of how to introduce electrostatic interactions in dissipative particle dynamics (DPD) method in order to correctly reproduce the properties of systems with high density of charges, including those with inhomogeneous charge distribution. To this end, we formulate general requirements for the electrostatic force in DPD and propose a new functional form of the force which suits better for satisfying these requirements than the previously used ones. In order to verify the proposed model, we study the problem of a single polyelectrolyte chain collapse and compare the results with molecular dynamics (MD) simulations in which the exact Coulomb force is used. We show that an excellent quantitative agreement between MD and DPD models is observed if the length parameter D of the proposed electrostatic force is chosen properly; the recommendations concerning the choice of this parameter value are given based on the analysis of a polyelectrolyte chain collapse behavior. Finally, we demonstrate the applicability of DPD with the proposed electrostatic force to studying microphase separation phenomenon in polyelectrolyte melts and show that the same values of D as in the case of single chain collapse should be used, thus indicating universality of the model. Due to the charge correlation attraction, a long-range order in such melts can be observed even at zero Flory-Huggins parameter.

  8. Cell receptor and surface ligand density effects on dynamic states of adhering circulating tumor cells.

    Science.gov (United States)

    Zheng, Xiangjun; Cheung, Luthur Siu-Lun; Schroeder, Joyce A; Jiang, Linan; Zohar, Yitshak

    2011-10-21

    Dynamic states of cancer cells moving under shear flow in an antibody-functionalized microchannel are investigated experimentally and theoretically. The cell motion is analyzed with the aid of a simplified physical model featuring a receptor-coated rigid sphere moving above a solid surface with immobilized ligands. The motion of the sphere is described by the Langevin equation accounting for the hydrodynamic loadings, gravitational force, receptor-ligand bindings, and thermal fluctuations; the receptor-ligand bonds are modeled as linear springs. Depending on the applied shear flow rate, three dynamic states of cell motion have been identified: (i) free motion, (ii) rolling adhesion, and (iii) firm adhesion. Of particular interest is the fraction of captured circulating tumor cells, defined as the capture ratio, via specific receptor-ligand bonds. The cell capture ratio decreases with increasing shear flow rate with a characteristic rate. Based on both experimental and theoretical results, the characteristic flow rate increases monotonically with increasing either cell-receptor or surface-ligand density within certain ranges. Utilizing it as a scaling parameter, flow-rate dependent capture ratios for various cell-surface combinations collapse onto a single curve described by an exponential formula.

  9. Optical excitation and electron relaxation dynamics at semiconductor surfaces: a combined approach of density functional and density matrix theory applied to the silicon (001) surface

    Energy Technology Data Exchange (ETDEWEB)

    Buecking, N.

    2007-11-05

    In this work a new theoretical formalism is introduced in order to simulate the phononinduced relaxation of a non-equilibrium distribution to equilibrium at a semiconductor surface numerically. The non-equilibrium distribution is effected by an optical excitation. The approach in this thesis is to link two conventional, but approved methods to a new, more global description: while semiconductor surfaces can be investigated accurately by density-functional theory, the dynamical processes in semiconductor heterostructures are successfully described by density matrix theory. In this work, the parameters for density-matrix theory are determined from the results of density-functional calculations. This work is organized in two parts. In Part I, the general fundamentals of the theory are elaborated, covering the fundamentals of canonical quantizations as well as the theory of density-functional and density-matrix theory in 2{sup nd} order Born approximation. While the formalism of density functional theory for structure investigation has been established for a long time and many different codes exist, the requirements for density matrix formalism concerning the geometry and the number of implemented bands exceed the usual possibilities of the existing code in this field. A special attention is therefore attributed to the development of extensions to existing formulations of this theory, where geometrical and fundamental symmetries of the structure and the equations are used. In Part II, the newly developed formalism is applied to a silicon (001)surface in a 2 x 1 reconstruction. As first step, density-functional calculations using the LDA functional are completed, from which the Kohn-Sham-wave functions and eigenvalues are used to calculate interaction matrix elements for the electron-phonon-coupling an the optical excitation. These matrix elements are determined for the optical transitions from valence to conduction bands and for electron-phonon processes inside the

  10. Effects of laser power density on static and dynamic mechanical properties of dissimilar stainless steel welded joints

    Institute of Scientific and Technical Information of China (English)

    Yan-Peng Wei; Mao-Hui Li; Gang Yu; Xian-Qian Wu; Chen-Guang Huang; Zhu-Ping Duan

    2012-01-01

    The mechanical properties of laser welded joints under impact loadings such as explosion and car crash etc.are critical for the engineering designs. The hardness,static and dynamic mechanical properties of AISI304 and AISI316L dissimilar stainless steel welded joints by CO2 laser were experimentally studied. The dynamic strain-stress curves at the strain rate around 103 s-1 were obtained by the split Hopkinson tensile bar (SHTB).The static mechanical properties of the welded joints have little changes with the laser power density and all fracture occurs at 316 L side.However,the strain rate sensitivity has a strong dependence on laser power density.The value of strain rate factor decreases with the increase of laser power density.The welded joint which may be applied for the impact loading can be obtained by reducing the laser power density in the case of welding quality assurance.

  11. Estimating groundwater evapotranspiration from irrigated cropland incorporating root zone soil texture and moisture dynamics

    Science.gov (United States)

    Wang, Xingwang; Huo, Zailin; Feng, Shaoyuan; Guo, Ping; Guan, Huade

    2016-12-01

    Estimating evapotranspiration from groundwater (ETg) is of importance to understanding water cycle and agricultural water management. Traditional ETg estimation was developed for regional steady condition and is difficult to be used for cropland where ETg changes with crop growth and irrigation schemes. In the present study, a new method estimating daily ETg during the crop growing season was developed. In this model, the effects of crop growth stage, climate condition, groundwater depth and soil moisture are considered. The method was tested with controlled lysimeter experiments of winter wheat including five controlled water table depths and four soil profiles of different textures. The simulated ETg is in good agreement with the measured data for four soil profiles and different depths to groundwater table. Coefficient of determination (R2) and coefficient of efficiency (NSE) are mostly larger than 0.85 and 0.70, respectively. This result suggests that the new method incorporating both soil texture and moisture dynamics can be used to estimate average daily groundwater evapotranspiration in cropland and contribute to quantifying the field water cycle.

  12. Void structure and density change of vanadium-base alloys irradiated in the dynamic helium charging experiment

    Energy Technology Data Exchange (ETDEWEB)

    Chung, H.M.; Nowicki, L.; Gazda, J. [Argonne National Lab., Chicago, IL (United States)] [and others

    1995-04-01

    The objective of this work is to determine void structure, distribution, and density changes of several promising vanadium-base alloys irradiated in the Dynamic Helium Charging Experiment (DHCE). Combined effects of dynamically charged helium and neutron damage on density change, void distribution, and microstructural evolution of V-4Cr-4Ti alloy have been determined after irradiation to 18-31 dpa at 425-600{degree}C in the DHCE, and the results compared with those from a non-DHCE in which helium generation was negligible.

  13. Evaluation of Biomass Yield and Water Treatment in Two Aquaponic Systems Using the Dynamic Root Floating Technique (DRF

    Directory of Open Access Journals (Sweden)

    Laura Silva

    2015-11-01

    Full Text Available The experiment evaluates the food production and water treatment of TAN, NO2−–N, NO3−–N, and PO43− in two aquaponics systems using the dynamic root floating technique (DRF. A separate recirculation aquaculture system (RAS was used as a control. The fish cultured was Nile tilapia (Oreochromis niloticus. The hydroponic culture in one treatment (PAK was pak choy (Brassica chinensis, and in the other (COR coriander (Coriandrum sativum. Initial and final weights were determined for the fish culture. Final edible fresh weight was determined for the hydroponic plant culture. TAN, NO2−–N, NO3−–N, and PO43− were measured in fish culture and hydroponic culture once a week at two times, morning (9:00 a.m. and afternoon (3:00 p.m.. The fish biomass production was not different in any treatment (p > 0.05 and the total plant yield was greater (p < 0.05 in PAK than in COR. For the hydroponic culture in the a.m., the PO43− was lower (p < 0.05 in the PAK treatment than in COR, and in the p.m. NO3−–N and PO43− were lower (p < 0.05 in PAK than in COR. The PAK treatment demonstrated higher food production and water treatment efficiency than the other two treatments.

  14. Flow Transformation in Pyroclastic Density Currents: Entrainment and Granular Dynamics during the 2006 eruption of Tungurahua

    Science.gov (United States)

    Dufek, J.; Benage, M. C.; Geist, D.; Harpp, K. S.

    2013-12-01

    Pyroclastic density currents are ground hugging flows composed of hot gases, fragments of juvenile magmatic material, and entrained clasts from the conduit or the edifice over which the flows have traveled. The interior of these flows are opaque to observation due to their large ash content, but recent investigations have highlighted that there are likely strong gradients in particle concentration and segregation of particle sizes in these particle-laden gravity currents. Pyroclastic density currents refer to a broad range of phenomena from dense flows in which the dynamics are dominated by frictional interaction between particles (dense granular flows), to gas fluidized flows, to dilute flows dominated by particle-gas turbulent interaction. However, abrupt flow transformation (e.g. from dense to dilute pyroclastic density currents) can arise due to energy exchange across multiple length scales and phases, and understanding these flow transformations is important in delineating the entrainment and erosion history of these flows, interpretations of their deposits, and in better understanding the hazards they present. During the 2006 eruption of Tungurahua, Ecuador numerous, dense pyroclastic density currents descended the volcano as result of boiling-over or low column collapse eruptions. The deposits of these flows typically have pronounced snouts and levees, and are often dominated by large, clasts (meter scale in some locations). There is an exceptional observational record of these flows and their deposits, permitting detailed field constraints of their dynamics. A particularly interesting set of flows occurred on Aug. 17, 2006 during the paroxysmal phase of the eruption that descended the slope of the volcano, filled in the river channel of the Chambo river, removing much of the larger clasts from the flow, and resulting in a dilute ';surge' that transported finer material across the channel and uphill forming dune features on the opposite bank of the river. We

  15. Dynamic probe selection for studying microbial transcriptome with high-density genomic tiling microarrays

    Directory of Open Access Journals (Sweden)

    Chen Tsute

    2010-02-01

    Full Text Available Abstract Background Current commercial high-density oligonucleotide microarrays can hold millions of probe spots on a single microscopic glass slide and are ideal for studying the transcriptome of microbial genomes using a tiling probe design. This paper describes a comprehensive computational pipeline implemented specifically for designing tiling probe sets to study microbial transcriptome profiles. Results The pipeline identifies every possible probe sequence from both forward and reverse-complement strands of all DNA sequences in the target genome including circular or linear chromosomes and plasmids. Final probe sequence lengths are adjusted based on the maximal oligonucleotide synthesis cycles and best isothermality allowed. Optimal probes are then selected in two stages - sequential and gap-filling. In the sequential stage, probes are selected from sequence windows tiled alongside the genome. In the gap-filling stage, additional probes are selected from the largest gaps between adjacent probes that have already been selected, until a predefined number of probes is reached. Selection of the highest quality probe within each window and gap is based on five criteria: sequence uniqueness, probe self-annealing, melting temperature, oligonucleotide length, and probe position. Conclusions The probe selection pipeline evaluates global and local probe sequence properties and selects a set of probes dynamically and evenly distributed along the target genome. Unique to other similar methods, an exact number of non-redundant probes can be designed to utilize all the available probe spots on any chosen microarray platform. The pipeline can be applied to microbial genomes when designing high-density tiling arrays for comparative genomics, ChIP chip, gene expression and comprehensive transcriptome studies.

  16. Dynamic observation on bone mineral density of unsexed rabbits with QCT

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    Objective: The purpose of this tudy was to dynamicly observe the weight and the bone mineral density (BMD) of the unsexed rabbits with a few self-made standardized phantoms. Methods:The eighteen healthy adult female rabbits were measured for their weight and BMD in preunsexed and postunsexed 5 months, 10 months with quantitative CT(QCT). Results:There were 61.1% of rabbits whose weight and BMD decreased after 5 months of the postunsexed and 100% of rabbits whose weight and BMD decreased after 10 months of the operation. Conclusion:QCT can be used to dynamicly observe curative effect of drugs in various periods as well,and it is a good method to study osteoporosis.%目的:用自制标准件动态观察去势兔的体重、骨密度(BMD).方法:用定量CT(QCT)方法测量了18只健康成年雌兔去势前和去势后5个月、10个月的体重和骨密度.结果:去势后5个月有61.1%兔体重和BMD下降,而去势后10个月则100%体重和骨密度明显下降.结论:QCT可以对临床药物疗效的不同时期进行较精确的数字化动态观察,对骨质疏松的研究是较好的方法.

  17. Effects of water transportation on subduction dynamics: Roles of viscosity and density reduction

    Science.gov (United States)

    Nakao, Atsushi; Iwamori, Hikaru; Nakakuki, Tomoeki

    2016-11-01

    The effects of water on subduction dynamics, e.g., plate migration rate, slab geometry, stress field, and back-arc spreading, are investigated by using a 2-D self-consistent model for lithosphere subduction and whole mantle convection. We solve water transportation coupled with hydrous mineral phase changes. Mantle flows and water transportation are interactive through constitutive and state equations for hydrous rocks. Our model has successfully reproduced the water distribution in a mantle wedge and along the slab with sufficient resolution comparable to that of previous models that focus on the mantle wedge structure. As a result, low density owing to hydration reduces subduction rates, back-arc spreading, and slab stagnation on the phase boundary at 660-km depth, whereas low viscosity owing to hydration enhances rapid subduction, trench migration, and slab stagnation. We attribute these results to mechanisms that cause the hydrous buoyancy of subducting plates to reduce the slab pull force and the accompanying tensile stress on overlying lithosphere. In addition, hydrous weakening diminishes the mechanical coupling of the subducted slab with the wedge mantle and overriding lithosphere. Thus, water is capable of generating two opposite situations in the stress field of the overlying lithosphere and the subduction rate. Water is therefore expected to be an important mechanism for generating broad styles of the subduction structure and kinematics, as observed in actual subduction zones such as Tonga and Mariana. Such observed variation in the subduction mode can be caused by variation in buoyancy corresponding to the water content from relatively dry to several thousands of parts per million for the wedge mantle and slab surface, whereas the extremely buoyant case does not appear to occur in nature. Water in the mantle is thus key to better understand the whole-mantle-scale slab dynamics as well as island arc volcanic processes.

  18. Introducing PROFESS 3.0: An advanced program for orbital-free density functional theory molecular dynamics simulations

    Science.gov (United States)

    Chen, Mohan; Xia, Junchao; Huang, Chen; Dieterich, Johannes M.; Hung, Linda; Shin, Ilgyou; Carter, Emily A.

    2015-05-01

    Orbital-free density functional theory (OFDFT) is a linear-scaling first-principles quantum mechanics method used to calculate the ground-state energy of a given system. Here we present a new version of PRinceton Orbital-Free Electronic Structure Software (PROFESS) with new features. First, PROFESS 3.0 provides a set of new kinetic energy density functionals (KEDFs) which are designed to model semiconductors or transition metals. Specifically, PROFESS 3.0 includes the Huang-Carter (HC) KEDF [1], a density decomposition method with fixed localized electronic density [2], the Wang-Govind-Carter (WGC) decomposition KEDF [3], and the Enhanced von Weizsäcker (EvW)-WGC KEDF [4]. Other major new functions are included, such as molecular dynamics with different statistical mechanical ensembles and spin-polarized density optimizers.

  19. The effect of fracture density and stress state on the static and dynamic bulk moduli of Westerly granite

    Science.gov (United States)

    Blake, O. O.; Faulkner, D. R.

    2016-04-01

    Elastic properties are key parameters during the deformation of rocks. They can be measured statically or dynamically, but the two measurements are often different. In this study, the static and dynamic bulk moduli (Kstatic and Kdynamic) were measured at varying effective stress for dry and fluid-saturated Westerly granite with controlled fracture densities under isotropic and differential stress states. Isotropic fracturing of different densities was induced in samples by thermal treatment to 250, 450, 650, and 850°C. Results show that fluid saturation does not greatly affect static moduli but increases dynamic moduli. Under isotropic loading, high fracture density and/or low effective pressure results in a low Kstatic/Kdynamic ratio. For dry conditions Kstatic/Kdynamic approaches 1 at low fracture densities when the effective pressure is high, consistent with previous studies. Stress-induced anisotropy exists under differential stress state that greatly affects Kstatic compared to Kdynamic. As a result, the Kstatic/Kdynamic ratio is higher than that for the isotropic stress state and approaches 1 with increasing axial loading. The effect of stress-induced anisotropy increases with increasing fracture density. A key omission in previous studies comparing static and dynamic properties is that anisotropy has not been considered. The standard methods for measuring static elastic properties, such as Poisson's ratio, Young's and shear modulus, involve subjecting the sample to a differential stress state that promotes anisotropy. Our results show that stress-induced anisotropy resulting from differential stress state is a major contributor to the difference between static and dynamic elasticity and is dominant with high fracture density.

  20. Electroactive and High Dielectric Folic Acid/PVDF Composite Film Rooted Simplistic Organic Photovoltaic Self-Charging Energy Storage Cell with Superior Energy Density and Storage Capability.

    Science.gov (United States)

    Roy, Swagata; Thakur, Pradip; Hoque, Nur Amin; Bagchi, Biswajoy; Sepay, Nayim; Khatun, Farha; Kool, Arpan; Das, Sukhen

    2017-07-19

    Herein we report a simplistic prototype approach to develop an organic photovoltaic self-charging energy storage cell (OPSESC) rooted with biopolymer folic acid (FA) modified high dielectric and electroactive β crystal enriched poly(vinylidene fluoride) (PVDF) composite (PFA) thin film. Comprehensive and exhaustive characterizations of the synthesized PFA composite films validate the proper formation of β-polymorphs in PVDF. Significant improvements of both β-phase crystallization (F(β) ≈ 71.4%) and dielectric constant (ε ≈ 218 at 20 Hz for PFA of 7.5 mass %) are the twosome realizations of our current study. Enhancement of β-phase nucleation in the composites can be thought as a contribution of the strong interaction of the FA particles with the PVDF chains. Maxwell-Wagner-Sillars (MWS) interfacial polarization approves the establishment of thermally stable high dielectric values measured over a wide temperature spectrum. The optimized high dielectric and electroactive films are further employed as an active energy storage material in designing our device named as OPSESC. Self-charging under visible light irradiation without an external biasing electrical field and simultaneous remarkable self-storage of photogenerated electrical energy are the two foremost aptitudes and the spotlight of our present investigation. Our as fabricated device delivers an impressively high energy density of 7.84 mWh/g and an excellent specific capacitance of 61 F/g which is superior relative to the other photon induced two electrode organic self-charging energy storage devices reported so far. Our device also proves the realistic utility with good recycling capability by facilitating commercially available light emitting diode.

  1. Statistics of initial density perturbations in heavy ion collisions and their fluid dynamic response

    Science.gov (United States)

    Floerchinger, Stefan; Wiedemann, Urs Achim

    2014-08-01

    An interesting opportunity to determine thermodynamic and transport properties in more detail is to identify generic statistical properties of initial density perturbations. Here we study event-by-event fluctuations in terms of correlation functions for two models that can be solved analytically. The first assumes Gaussian fluctuations around a distribution that is fixed by the collision geometry but leads to non-Gaussian features after averaging over the reaction plane orientation at non-zero impact parameter. In this context, we derive a three-parameter extension of the commonly used Bessel-Gaussian event-by-event distribution of harmonic flow coefficients. Secondly, we study a model of N independent point sources for which connected n-point correlation functions of initial perturbations scale like 1 /N n-1. This scaling is violated for non-central collisions in a way that can be characterized by its impact parameter dependence. We discuss to what extent these are generic properties that can be expected to hold for any model of initial conditions, and how this can improve the fluid dynamical analysis of heavy ion collisions.

  2. Dynamical density functional theory for arbitrary-shape colloidal fluids including inertia and hydrodynamic interactions

    Science.gov (United States)

    Duran-Olivencia, Miguel A.; Goddard, Ben; Kalliadasis, Serafim

    2015-11-01

    Over the last few decades the classical density-functional theory (DFT) and its dynamic extensions (DDFTs) have become a remarkably powerful tool in the study of colloidal fluids. Recently there has been extensive research to generalise all previous DDFTs finally yielding a general DDFT equation (for spherical particles) which takes into account both inertia and hydrodynamic interactions (HI) which strongly influence non-equilibrium properties. The present work will be devoted to a further generalisation of such a framework to systems of anisotropic particles. To this end, the kinetic equation for the Brownian particle distribution function is derived starting from the Liouville equation and making use of Zwanzig's projection-operator techniques. By averaging over all but one particle, a DDFT equation is finally obtained with some similarities to that for spherical colloids. However, there is now an inevitable translational-rotational coupling which affects the diffusivity of asymmetric particles. Lastly, in the overdamped (high friction) limit the theory is notably simplified leading to a DDFT equation which agrees with previous derivations. We acknowledge financial support from European Research Council via Advanced Grant No. 247031.

  3. Modeling Changing Morphology and Density Dependent Groundwater Flow in a Dynamic Environment: case study

    Science.gov (United States)

    Huizer, Sebastian; Bierkens, Marc; Oude Essink, Gualbert

    2015-04-01

    The prospect of sea level rise and increase in extreme weather conditions has led to a new focus on coastal defense in the Netherlands. As an innovative solution for coastal erosion a mega-nourishment named the Sand Motor (or Sand Engine) has been constructed at the Dutch coast. This body of sand will be distributed slowly along the coastline by wind, waves and currents; keeping the coastal defense structures in place and creating a unique, dynamic environment with changing morphology over time. The large size and position of the Sand Motor might lead to a substantial increase of fresh ground water resources. This creates an opportunity to combine coastal protection with an increase of fresh water resources in coastal regions. With a three dimensional, density dependent, groundwater model the effects of changing morphology over time and the potential increase in fresh water availability have been studied. The preliminary model calculations show that in a period of 20 years volume of fresh water gradually increases to ca. 12 Mm3. In the nearby dune area 7-8 Mm3 is abstracted yearly, therefore the first results are promising in increasing fresh groundwater resources. More model calculations will be performed to investigate the sensitivity of the change in the fresh, brackish and salt water distribution.

  4. Linear low-density polyethylene/silica micro- and nanocomposites: dynamic rheological measurements and modelling

    Directory of Open Access Journals (Sweden)

    2010-02-01

    Full Text Available Linear low-density polyethylene (LLDPE based composites were prepared by melt compounding with 1, 2, 3 and 4 vol% of various kinds of amorphous silicon dioxide (SiO2 micro- and nanoparticles. Dynamic rheological tests in parallel plate configuration were conducted in order to detect the role of the filler morphology on the rheological behaviour of the resulting micro- and nanocomposites. A strong dependence of the rheological parameters from the filler surface area was highlighted, with a remarkable enhancement of the storage shear modulus (G′ and of the viscosity (η in fumed silica nanocomposites and in precipitated silica microcomposites, while glass microbeads only marginally affected the rheological properties of the LLDPE matrix. This result was explained considering the formation of a network structure arising from particle-particle interactions due to hydrogen bonding between silanol groups. A detailed analysis of the solid like behaviour for the filled samples at low frequencies was conducted by fitting viscosity data with a new model, based on a modification of the original De Kee-Turcotte expression performed in order to reach a better modelling of the high-frequency region.

  5. Modeling Changing Morphology and Density Dependent Groundwater Flow in a Dynamic Environment: case study

    Science.gov (United States)

    Huizer, S.; Bierkens, M. F.; Oude Essink, G.

    2014-12-01

    In many coastal regions around the world climate change will lead to a sea level rise and an increase in extreme weather conditions. This prospect has resulted in a new focus on coastal protection in the Netherlands, resulting in the initiation of an innovative coastal defence project called the Sand Motor. In this project a large body of sand or so-called mega-nourishment has been constructed along the Dutch coast. This body of sand will be distributed slowly along the coastline by wind, waves and currents. Keeping the coastal defence structures in place and creating a unique, dynamic environment with changing morphology over time. Because of the large size of the body of sand (21.5 million m3) and the position at the coastline and near coastal dunes, the Sand Motor might cause a substantial increase of the fresh water availability by increasing the volume fresh water lens underneath the dunes. This creates an opportunity to combine coastal protection with an increase of fresh water resources in coastal regions. With a three dimensional, density dependent, groundwater model the effects of changing morphology over time and the potential increase in fresh water availability have been studied.

  6. Hematite(001)-liquid water interface from hybrid density functional-based molecular dynamics

    Science.gov (United States)

    Falk von Rudorff, Guido; Jakobsen, Rasmus; Rosso, Kevin M.; Blumberger, Jochen

    2016-10-01

    The atom-scale characterisation of interfaces between transition metal oxides and liquid water is fundamental to our mechanistic understanding of diverse phenomena ranging from crystal growth to biogeochemical transformations to solar fuel production. Here we report on the results of large-scale hybrid density functional theory-based molecular dynamics simulations for the hematite(001)-liquid water interface. A specific focus is placed on understanding how different terminations of the same surface influence surface solvation. We find that the two dominant terminations for the hematite(001) surface exhibit strong differences both in terms of the active species formed on the surface and the strength of surface solvation. According to present simulations, we find that charged oxyanions (-O-) and doubly protonated oxygens (-OH2+ ) can be formed on the iron terminated layer via autoionization of neutral -OH groups. No such charged species are found for the oxygen terminated surface. In addition, the missing iron sublayer in the iron terminated surface strongly influences the solvation structure, which becomes less well ordered in the vicinity of the interface. These pronounced differences are likely to affect the reactivity of the two surface terminations, and in particular the energetics of excess charge carriers at the surface.

  7. Communication: Dynamical density functional theory for dense suspensions of colloidal hard spheres.

    Science.gov (United States)

    Stopper, Daniel; Roth, Roland; Hansen-Goos, Hendrik

    2015-11-14

    We study structural relaxation of colloidal hard spheres undergoing Brownian motion using dynamical density functional theory. Contrary to the partial linearization route [D. Stopper et al., Phys. Rev. E 92, 022151 (2015)] which amounts to using different free energy functionals for the self and distinct part of the van Hove function G(r, t), we put forward a unified description employing a single functional for both components. To this end, interactions within the self part are removed via the zero-dimensional limit of the functional with a quenched self component. In addition, we make use of a theoretical result for the long-time mobility in hard-sphere suspensions, which we adapt to the inhomogeneous fluid. Our results for G(r, t) are in excellent agreement with numerical simulations even in the dense liquid phase. In particular, our theory accurately yields the crossover from free diffusion at short times to the slower long-time diffusion in a crowded environment.

  8. Recent Developments in Modeling Heteroepitaxy/Heterogeneous Nucleation by Dynamical Density Functional Theory

    Science.gov (United States)

    Podmaniczky, Frigyes; Tóth, Gyula I.; Tegze, György; Gránásy, László

    2015-11-01

    Crystallization of supersaturated liquids usually starts by epitaxial growth or by heterogeneous nucleation on foreign surfaces. Herein, we review recent advances made in modeling heteroepitaxy and heterogeneous nucleation on flat/modulated surfaces and nanoparticles within the framework of a simple dynamical density functional theory, known as the phase-field crystal model. It will be shown that the contact angle and the nucleation barrier are nonmonotonous functions of the lattice mismatch between the substrate and the crystalline phase. In continuous cooling studies for substrates with lattice mismatch, we recover qualitatively the Matthews-Blakeslee mechanism of stress release via the misfit dislocations. The simulations performed for particle-induced freezing will be confronted with recent analytical results, exploring thus the validity range of the latter. It will be demonstrated that time-dependent studies are essential, as investigations based on equilibrium properties often cannot identify the preferred nucleation pathways. Modeling of these phenomena is essential for designing materials on the basis of controlled nucleation and/or nano-patterning.

  9. Density matrix based time-dependent configuration interaction approach to ultrafast spin-flip dynamics

    CERN Document Server

    Wang, H; Kühn, O

    2016-01-01

    Recent developments in attosecond spectroscopy yield access to the correlated motion of electrons on their intrinsic time scales. Spin-flip dynamics is usually considered in the context of valence electronic states, where spin-orbit coupling is weak and processes related to the electron spin are usually driven by nuclear motion. However, for core-excited states, where the core hole has a nonzero angular momentum, spin-orbit coupling is strong enough to drive spin-flips on a much shorter time scale. Using density matrix based time-dependent restricted active space configuration interaction including spin-orbit coupling, we address an unprecedentedly short spin-crossover for the example of L-edge (2p$\\rightarrow$3d) excited states of a prototypical Fe(II) complex. This process occurs on a time scale, which is faster than that of Auger decay ($\\sim$4\\,fs) treated here explicitly. Modest variations of carrier frequency and pulse duration can lead to substantial changes in the spin-state yield, suggesting its cont...

  10. Detonation shock dynamics calibration for pBX 9502 with temperature, density, and material lot variations

    Energy Technology Data Exchange (ETDEWEB)

    Hill, Larry G [Los Alamos National Laboratory; Aslam, Tariq D [Los Alamos National Laboratory

    2010-01-01

    We present a methodology for scaling the detonation shock dynamics D{sub n}[{kappa}] calibration function to accommodate variations in the HE starting material. We apply our model to the insensitive TATB-based explosive PBX 9502, for which we have enough front curvature rate stick data to characterize three material attributes: initial temperature T{sub 0}, nominal density {rho}{sub 0}, and manufacturing lot (representing different microstructures). A useful feature of the model is that it returns an absolute estimate for the reaction zone thickness, {delta}. Lacking demonstrated material metrics(s), we express microstructural variation indirectly, in terms of its effect on {delta}. This results in a D{sub n}[{kappa}] function that depends on T{sub 0}, {rho}{sub 0}, and {delta}. After examining the separate effects of each parameter on D{sub n}[{kappa}], we compute an arc geometry as a validation problem. We compare the calculation to a PBX 9502 arc experiment that was pressed from one of the calibrated HE lots. The agreement between the model and experiment is excellent. We compute worst, nominal, and best-performing material parameter combinations to show how much difference accrues throughout the arc.

  11. Nonadiabatic dynamics with intersystem crossings: A time-dependent density functional theory implementation

    Energy Technology Data Exchange (ETDEWEB)

    Franco de Carvalho, F. [Centre Européen de Calcul Atomique et Moléculaire, Ecole Polytechnique Fédérale de Lausanne, Lausanne (Switzerland); Tavernelli, I. [IBM Research GmbH, Zurich Research Laboratory, 8803 Ruschlikon (Switzerland)

    2015-12-14

    In this work, we derive a method to perform trajectory-based nonadiabatic dynamics that is able to describe both nonadiabatic transitions and intersystem crossing events (transitions between states of different spin-multiplicity) at the same level of theory, namely, time-dependent density functional theory (TDDFT). To this end, we combined our previously developed TDDFT-based trajectory surface hopping scheme with an accurate and efficient algorithm for the calculation of the spin-orbit coupling (SOC) matrix elements. More specifically, we designed two algorithms for the calculation of intersystem crossing transitions, one based on an extended Tully’s surface hopping scheme including SOC and the second based on a Landau-Zener approximation applied to the spin sector of the electronic Hilbert space. This development allows for the design of an efficient on-the-fly nonadiabatic approach that can handle, on an equal footing, nonadiabatic and intersystem crossing transitions. The method is applied to the study of the photophysics of sulfur dioxide (SO{sub 2}) in gas and liquid phases.

  12. Electrostatic solvation free energies of charged hard spheres using molecular dynamics with density functional theory interactions

    Science.gov (United States)

    Duignan, Timothy T.; Baer, Marcel D.; Schenter, Gregory K.; Mundy, Chistopher J.

    2017-10-01

    Determining the solvation free energies of single ions in water is one of the most fundamental problems in physical chemistry and yet many unresolved questions remain. In particular, the ability to decompose the solvation free energy into simple and intuitive contributions will have important implications for models of electrolyte solution. Here, we provide definitions of the various types of single ion solvation free energies based on different simulation protocols. We calculate solvation free energies of charged hard spheres using density functional theory interaction potentials with molecular dynamics simulation and isolate the effects of charge and cavitation, comparing to the Born (linear response) model. We show that using uncorrected Ewald summation leads to unphysical values for the single ion solvation free energy and that charging free energies for cations are approximately linear as a function of charge but that there is a small non-linearity for small anions. The charge hydration asymmetry for hard spheres, determined with quantum mechanics, is much larger than for the analogous real ions. This suggests that real ions, particularly anions, are significantly more complex than simple charged hard spheres, a commonly employed representation.

  13. Collision frequency of Lennard–Jones fluids at high densities by equilibrium molecular dynamics simulation

    Indian Academy of Sciences (India)

    G A Adebayo; B C Anusionwu; A N Njah; O J Adeniran; B Mathew; R S Sunmonu

    2010-09-01

    Detailed classical molecular dynamics simulation of transport coefficients and collision frequencies at high densities in rare gases are presented in this paper with a view to investigate the likely cause of discrepancy between theory and experiments. The results, when compared with experiments, showed an underestimation of the viscosity calculated through the Green–Kubo formalism, but the results are in agreement with some other calculations performed by other groups. The origin of the underestimation was considered in the present work. Analyses of the transport coefficients showed a very high collision frequency which suggested that an atom might spend much less time in the neighbourhood of the fields of force of another atom. The distribution of atoms in the systems adjusts itself to a nearly Maxwellian type that resulted in a locally and temporarily slowly varying temperature. We showed that during collision, the time spent by an atom in the fields of force of other atoms is so small compared with its relaxation time, leading to a possible reduction in local velocity autocorrelation between atoms.

  14. DYNAMICAL SIMULATION OF A QUANTUM HARMONIC-OSCILLATOR IN A NOBLE-GAS BATH BY DENSITY-MATRIX EVOLUTION

    NARCIS (Netherlands)

    MAVRI, J; BERENDSEN, HJC

    1994-01-01

    A density-matrix evolution method [Berendsen and Mavri, J. Phys. Chem. 97, 13464 (1993)] coupled to a classical molecular dynamics simulation was applied to study a quantum harmonic oscillator immersed in a bath of Lennard-Jones particles. Eigenfunctions of the three, lowest levels of the unperturbe

  15. DYNAMICAL SIMULATION OF A QUANTUM HARMONIC-OSCILLATOR IN A NOBLE-GAS BATH BY DENSITY-MATRIX EVOLUTION

    NARCIS (Netherlands)

    MAVRI, J; BERENDSEN, HJC

    1994-01-01

    A density-matrix evolution method [Berendsen and Mavri, J. Phys. Chem. 97, 13464 (1993)] coupled to a classical molecular dynamics simulation was applied to study a quantum harmonic oscillator immersed in a bath of Lennard-Jones particles. Eigenfunctions of the three, lowest levels of the unperturbe

  16. Root microbiota dynamics of perennial Arabis alpina are dependent on soil residence time but independent of flowering time.

    Science.gov (United States)

    Dombrowski, Nina; Schlaeppi, Klaus; Agler, Matthew T; Hacquard, Stéphane; Kemen, Eric; Garrido-Oter, Ruben; Wunder, Jörg; Coupland, George; Schulze-Lefert, Paul

    2017-01-01

    Recent field and laboratory experiments with perennial Boechera stricta and annual Arabidopsis thaliana suggest that the root microbiota influences flowering time. Here we examined in long-term time-course experiments the bacterial root microbiota of the arctic-alpine perennial Arabis alpina in natural and controlled environments by 16S rRNA gene profiling. We identified soil type and residence time of plants in soil as major determinants explaining up to 15% of root microbiota variation, whereas environmental conditions and host genotype explain maximally 11% of variation. When grown in the same soil, the root microbiota composition of perennial A. alpina is largely similar to those of its annual relatives A. thaliana and Cardamine hirsuta. Non-flowering wild-type A. alpina and flowering pep1 mutant plants assemble an essentially indistinguishable root microbiota, thereby uncoupling flowering time from plant residence time-dependent microbiota changes. This reveals the robustness of the root microbiota against the onset and perpetual flowering of A. alpina. Together with previous studies, this implies a model in which parts of the root microbiota modulate flowering time, whereas, after microbiota acquisition during vegetative growth, the established root-associated bacterial assemblage is structurally robust to perturbations caused by flowering and drastic changes in plant stature.

  17. Equation of state of warm dense deuterium and its isotopes from density-functional theory molecular dynamics.

    Science.gov (United States)

    Danel, J-F; Kazandjian, L; Piron, R

    2016-04-01

    Of the two approaches of density-functional theory molecular dynamics, quantum molecular dynamics is limited at high temperature by computational cost whereas orbital-free molecular dynamics, based on an approximation of the kinetic electronic free energy, can be implemented in this domain. In the case of deuterium, it is shown how orbital-free molecular dynamics can be regarded as the limit of quantum molecular dynamics at high temperature for the calculation of the equation of state. To this end, accurate quantum molecular dynamics calculations are performed up to 20 eV at mass densities as low as 0.5g/cm^{3} and up to 10 eV at mass densities as low as 0.2g/cm^{3}. As a result, the limitation in temperature so far attributed to quantum molecular dynamics is overcome and an approach combining quantum and orbital-free molecular dynamics is used to construct an equation of state of deuterium. The thermodynamic domain addressed is that of the fluid phase above 1 eV and 0.2g/cm^{3}. Both pressure and internal energy are calculated as functions of temperature and mass density, and various exchange-correlation contributions are compared. The generalized gradient approximation of the exchange-correlation functional, corrected to approximately include the influence of temperature, is retained and the results obtained are compared to other approaches and to experimental shock data; in parts of the thermodynamic domain addressed, these results significantly differ from those obtained in other first-principles investigations which themselves disagree. The equations of state of hydrogen and tritium above 1 eV and above, respectively, 0.1g/cm^{3} and 0.3g/cm^{3}, can be simply obtained by mass density scaling from the results found for deuterium. This ab initio approach allows one to consistently cover a very large domain of temperature on the domain of mass density outlined above.

  18. Effects of subsoil bulk density on root growth and soil enzyme activities during the growth of corn (Zea mays L.)%不同土层容重对玉米根系生长及土壤酶活性的影响

    Institute of Scientific and Technical Information of China (English)

    王群; 赵亚丽; 张学林; 张永恩; 李潮海

    2012-01-01

    The two-year pool-culture and barrel-culture experiments were conducted to study the impacts of subsoil bulk/density on root lenght, root dry weight, soil enzyme activities and yield in corn field on a sandy loam soil at the Experimental Farm of Henan Agricultural University. The results showed that the dynamic changes of root length, root dry weight, soil catalase, invertase, protease, urease, alkaline phosphatase activities and yields were single curve during the growth of corn, and the maximum values of these parameters occurred at the corn silking stage. Root length, root dry weight, yield and its components decreased with increaseing soil bulk density. These enzyme activities decreased with the increasing of both soil bulk density and soil depth. The higher the soil bulk density was the less active the soil enzyme activities were all soil enzyme activities were significantly different among soil bulk densities in the same soil layer, and they were also affected by soil bulk density in the adjacent layers. The bigger the soil bulk density of adjacent layers was the more significant the decrease was. The effect of subsoil bulk density on soil enzyme was more apparant from jointing stage to maturity.%采用微区池栽和桶栽试验,研究了下层(20~40 cm,40 ~ 60 cm)土壤容重改变后,玉米根系生长、产量及生育期间土壤过氧化氢酶、转化酶、蛋白酶、脲酶和碱性磷酸酶活性动态变化规律及其与微生物活性的相关性.结果表明,在玉米生育期内,玉米单株根长度和根干重、土壤过氧化氢酶、转化酶、蛋白酶、脲酶和碱性磷酸酶活性呈单峰曲线,最高值均出现在吐丝期;且随着下层土壤容重增加呈递减趋势.各土层酶活性均随着土层的加深和本土层容重的增大而降低,同时也随着相邻土层容重的增大其降幅加剧;玉米穗粒数、粒重和产量也随着土壤容重的增加而降低.玉米生长期间,土壤酶活性变化受下层

  19. Computation of Raman Spectra from Density Matrix Linear Response Theory in Extended Lagrangian Born-Oppenheimer Molecular Dynamics

    Science.gov (United States)

    Niklasson, Anders; Coe, Joshua; Cawkwell, Marc

    2011-06-01

    Linear response calculations based on density matrix perturbation theory [A. M. N. Niklasson and M. Challacombe, Phys. Rev. Lett. 92, 193001 (2004)] have been developed within a self-consistent tight-binding method for extended Lagrangian Born-Oppenheimer molecular dynamics [A. M. N. Niklasson, Phys. Rev. Lett., 100, 123004 (2008)]. Besides the nuclear coordinates, extended auxiliary electronic degrees of freedom are added to the regular Born-Oppenheimer Lagrangian, both for the electronic ground state and response densities. This formalism enables highly efficient, on-the-fly, analytic computations of the polarizability autocorrelation functions and the Raman spectra during energy conserving Born-Oppenheimer molecular dynamics trajectories. We will illustrate these capabilities via time-resolved Raman spectra computed during explicit, reactive molecular dynamics simulations of the shock compression of methane, benzene, tert-butylacetylene. Comparisons will be made with experimental results where possible.

  20. DMPD: Low density lipoprotein oxidation and its pathobiological significance. [Dynamic Macrophage Pathway CSML Database

    Lifescience Database Archive (English)

    Full Text Available 9261091 Low density lipoprotein oxidation and its pathobiological significance. Ste...in oxidation and its pathobiological significance. PubmedID 9261091 Title Low density lipoprotein oxidation ...and its pathobiological significance. Authors Steinberg D. Publication J Biol Che

  1. Qualidade de raízes de cenoura em sistemas consorciados com alface sob diferentes densidades populacionais Quality of carrot roots in intercropped systems with lettuce under different planting densities

    Directory of Open Access Journals (Sweden)

    Aurélio P. Barros Júnior

    2005-06-01

    densities. The experimental design used was of randomized blocks in a 4 x 4 factorial scheme with three replications. The treatments consisted of the combination of four carrot-planting densities [(40%, 60%, 80% and 100% of the recommended sole crop density (RSCD] with four lettuce-planting densities (40%, 60%, 80% and 100% of RSCD. The evaluated quality characteristics of the carrot roots were: titrable total acidity (TTA, total soluble solids (TSS, total sugars (TSU, pH, and TSS/TSS ratio, besides commercial productivity of carrot roots and lettuce yield. There was a significant interaction between carrot planting-densities and lettuce-planting densities on TSS of carrot roots. The TTS content and pH increased with increasing carrot-planting densities. Commercial productivity of carrot roots and lettuce yield also increased with increasing in planting densities. The variation in the carrot planting density did not influence lettuce yield but the variation in the lettuce planting density negatively influenced commercial productivity of carrot roots. Among the assessed characteristics, TSS and TSS were significantly correlated with commercial productivity, showing that these traits may be representative of carrot root quality.

  2. Density of states and dynamical crossover in a dense fluid revealed by exponential mode analysis of the velocity autocorrelation function

    Science.gov (United States)

    Bellissima, S.; Neumann, M.; Guarini, E.; Bafile, U.; Barocchi, F.

    2017-01-01

    Extending a preceding study of the velocity autocorrelation function (VAF) in a simulated Lennard-Jones fluid [Phys. Rev. E 92, 042166 (2015), 10.1103/PhysRevE.92.042166] to cover higher-density and lower-temperature states, we show that the recently demonstrated multiexponential expansion method allows for a full account and understanding of the basic dynamical processes encompassed by a fundamental quantity as the VAF. In particular, besides obtaining evidence of a persisting long-time tail, we assign specific and unambiguous physical meanings to groups of exponential modes related to the longitudinal and transverse collective dynamics, respectively. We have made this possible by consistently introducing the interpretation of the VAF frequency spectrum as a global density of states in fluids, generalizing a solid-state concept, and by giving to specific spectral components, obtained through the VAF exponential expansion, the corresponding meaning of partial densities of states relative to specific dynamical processes. The clear identification of a high-frequency oscillation of the VAF with the near-top excitation frequency in the dispersion curve of acoustic waves is a neat example of the power of the method. As for the transverse mode contribution, its analysis turns out to be particularly important, because the multiexponential expansion reveals a transition marking the onset of propagating excitations when the density is increased beyond a threshold value. While this finding agrees with the recent literature debating the issue of dynamical crossover boundaries, such as the one identified with the Frenkel line, we can add detailed information on the modes involved in this specific process in the domains of both time and frequency. This will help obtain a still missing full account of transverse dynamics, in both its nonpropagating and propagating aspects which are linked through dynamical transitions depending on both the thermodynamic states and the excitation

  3. Dynamical co-existence of excitons and free carriers in perovskite probed by density-resolved fluorescent spectroscopic method

    CERN Document Server

    Wang, Wei; Wang, Xiangyuan; Lv, Yanping; Wang, Shufeng; Wang, Kai; Shi, Yantao; Xiao, Lixin; Chen, Zhijian; Gong, Qihuang

    2016-01-01

    Using transient fluorescent spectra at time-zero, we develop a density-resolved fluorescent spectroscopic method for investigating photoproducts in CH3NH3PbI3 perovskite and related photophysics. The density dependent dynamical co-existence of excitons and free carriers over a wide density range is experimentally observed for the first time. The exciton binding energy (EB) and the effective mass of electron-hole pair can be estimated based on such co-existence. No ionic polarization is found contributing to photophysical behavior. It also solves the conflict between the large experimentally measured EB and the small predicted values. The spectroscopic method also helps to detect the true free carrier density under continuous illumination without the interference of ionic conductivity. Our methods and results profoundly enrich the study and understanding of the photophysics in perovskite materials for photovoltaic applications.

  4. The model of cupular dynamics in the case of the difference of the cupula and endolymph densities.

    Science.gov (United States)

    Kondrachuk, A V; Sirenko, S P; Boyle, R

    2007-07-01

    The function of semicircular canals (SC) is based on the precise equality of densities of the cupula and endolymph. Otherwise the information provided by SC would depend on the orientation of both the gravity vector relative to canal plane and the axis of rotation. It would also depend on the distance between the axis of rotation and the center of the SC. We believe that the equality of densities is approximate and expect that due to the high sensitivity of the SC, even the small differences of densities (approximately 10(-4) g/cm3) can influence the SC dynamics, and this influence depends on the conditions of canal stimulation. The work aims to examine this hypothesis and analyze the parameters of the SC and mechanical stimulation under which the effect of the difference of densities on the SC functioning could be observed.

  5. Modelling an infinite nucleonic system. Static and dynamical properties. Study of density fluctuations

    Science.gov (United States)

    Idier, D.; Farine, M.; Remaud, B.; Sébille, F.

    For one decade, several fields in physics as well microscopic as macroscopic benefit from the computational particle-models (astrophysics, electronics, fluids mechanics...). In particular, the nuclear matter offers an interesting challenge as many body problem, owing to the quantal nature of its components and the complexity of the in-medium interaction. Using a model derived from semi-classical Vlasov equation and the projection of the Wigner function on a Gaussian coherent states basis (pseudo-particles), static and dynamical properties of nuclear matter are studied, featuring the growing of bulk instabilities in dilute matter. Using different zero and finite range effective interactions, the effect of the model parameters upon the relation total energy - density - temperature and surface energy of the pseudo-particles fluid is pointed out. The dynamical feature is first based upon a model of the 2-body Uehling-Ulhenbeck collisionnal term. A study of the relaxation of a nucleonic system is performed. At last, the pseudo-particle model is used in order to extract time scale for the growing of density fluctuations. This process is supposed to be a possible way to clusterization during heavy nuclei collisions. Depuis une dizaine d'années, plusieurs domaines de la physique aussi bien microscopiques que macroscopiques bénéficient des modèles à particules pour ordinateurs (astrophysique, électronique, plasmas...). En particulier, la matière nucléaire constitue un objet intéressant pour le problème à N corps ; tant par la nature quantique des nucléons que par la complexité des interactions dans ce milieu. A travers un modèle dérivant de l'équation de Vlasov semi-classique et de la projection de la fonction de Wigner sur une base d'état cohérents gaussiens (les pseudo-particules), on étudie les propriétés statiques et dynamiques de la matière nucléaire dont en particulier le développement des instabilités de volume en milieu dilué. Pour diff

  6. Nonlinear dynamics and intermittency in a turbulent reacting wake with density ratio as bifurcation parameter

    Science.gov (United States)

    Suresha, Suhas; Sujith, R. I.; Emerson, Benjamin; Lieuwen, Tim

    2016-10-01

    The flame or flow behavior of a turbulent reacting wake is known to be fundamentally different at high and low values of flame density ratio (ρu/ρb ), as the flow transitions from globally stable to unstable. This paper analyzes the nonlinear dynamics present in a bluff-body stabilized flame, and identifies the transition characteristics in the wake as ρu/ρb is varied over a Reynolds number (based on the bluff-body lip velocity) range of 1000-3300. Recurrence quantification analysis (RQA) of the experimentally obtained time series of the flame edge fluctuations reveals that the time series is highly aperiodic at high values of ρu/ρb and transitions to increasingly correlated or nearly periodic behavior at low values. From the RQA of the transverse velocity time series, we observe that periodicity in the flame oscillations are related to periodicity in the flow. Therefore, we hypothesize that this transition from aperiodic to nearly periodic behavior in the flame edge time series is a manifestation of the transition in the flow from globally stable, convective instability to global instability as ρu/ρb decreases. The recurrence analysis further reveals that the transition in periodicity is not a sudden shift; rather it occurs through an intermittent regime present at low and intermediate ρu/ρb . During intermittency, the flow behavior switches between aperiodic oscillations, reminiscent of a globally stable, convective instability, and periodic oscillations, reminiscent of a global instability. Analysis of the distribution of the lengths of the periodic regions in the intermittent time series and the first return map indicate the presence of type-II intermittency.

  7. Effects of Bulk Density on Root Growth of High Yield Maize and Their Regulation%土壤容重对高产玉米根系生长的影响及调控研究

    Institute of Scientific and Technical Information of China (English)

    郑存德; 依艳丽; 张大庚; 徐龙超

    2012-01-01

    不同土壤容重不同,其稳定性也不同.土壤容重的变化会引起土壤调节水、气、热能力的变化,提高土壤的自动调节能力可以使土壤肥力水平得以提高并满足植物对生长因子的持续需求.为研究土壤物理性质对玉米高产稳产的影响机理,以耕地棕壤为试验材料,采用盆栽方法,研究不同容重对玉米根系生长指标的影响,并进一步研究了施用不同有机肥量及模拟不同耕作深度对玉米根系生长的调控效果.结果表明:在设计容重范围内,容重增加,根系生长指标都表现为下降,容重大于1.2g/m3时,不同处理根系生长指标差异显著;当容重大于1.3g/cm3时,不同处理根系活力差异显著.施用有机肥对高容重土壤调控效果更好,有机质含量为4%与5%的处理差异减小,低容重土壤在所设计的有机质水平内调控效果也都较好.耕层厚度增加可以提高根系生长参数,但与对照相比,差异不显著.所以,对于紧实结构性较差的土壤,改善其调节能力应该通过增施有机肥的方法,紧实结构较好的土壤考虑使用耕翻的办法.%Soil bulk density is one of the important soil physical properties. Different soil with different soil bulk density and stability, at the same time , soil regulation ability of soil-water, soil-gas, soil-heat capacity changed with unstability of soil bulk density. It can improve soil fertility degree and the continuing demand factors of plant growth if the soil's automatically adaptational ability was enhanced, therefore, it is necessary to research how soil bulk density vary and how to regulate and control it. In order to study the mechanism of the impact of soil physical properties on high and stable yield of maize, this paper, with cultivated brown soil and pot experiment, studied the effect of soil bulk density on maize root growth parameters( root length,root area,root volume) ,furthermore,it studied the result of regulation by

  8. Studies on the Effect of Density on the Root-shoot Relationship and Yield in Maize%提高密度对根冠发育及其产量的影响研究

    Institute of Scientific and Technical Information of China (English)

    张凤路; 牛兴奎; 张怡明; 李少昆; 谢瑞芝; 刘鑫; 修文雯

    2012-01-01

    Experiment was conducted at Gongzhuling experimental station of Institute of Crop Sciences,Chinese Academy of Agricultural Sciences,Gongzhuling,Jilin Province during 2009 -2010. Changes of plant and population morphological and physiological index were measured using maize hybrids Zhengdan958( ZD) and Xianyu335 (XY) as experimental materials under 52500 plants/ha ( LD ) and 82500 plants/ha ( HD) conditions. Root characteristics distribution among soil layers and the relationships between shoot and roots were also studied by the field root digging method. The results showed that plant character index decreased but the population quality increased with the densities. There were significant increases in population leaf areas and biomass. Root distribution showed a trend of horizontal contraction and vertical extension under high density conditions compared with low density. Root length density ( RLD)was significantly bigger than that of low density population, so the water and nutrition resources could be absorbed more efficiently under high density conditions. Shoot-root ratio was a character of hybrid and it did not change with density at a certain growing stage. Different varieties had their own optimal density, Xianyu335 was more suitable to high density than Zhengdan958 under this experimental conditions. Based on the result of the experiment it was passible to improve the current maize planting density of 52500 plants/ha to 82500 plants/ha in North-east maize production area. This experiment elucidated the mechanism of high-yield under high density conditions, and it is also of a great meaning for high-yielding maize production.%试验于2009-2010年在吉林省中国农科院公主岭试验站进行.以耐密玉米品种郑单958(ZD)和先玉335(XY)为材料,采用2种密度(52 500株/hm2 (LD)和82 500株/hm2(HD))研究了不同处理单株和群体形态和生理指标的变化动态,通过田间根系挖掘的方法研究了根系性状在不同土层的分

  9. Path integral molecular dynamics method based on a pair density matrix approximation: An algorithm for distinguishable and identical particle systems

    Science.gov (United States)

    Miura, Shinichi; Okazaki, Susumu

    2001-09-01

    In this paper, the path integral molecular dynamics (PIMD) method has been extended to employ an efficient approximation of the path action referred to as the pair density matrix approximation. Configurations of the isomorphic classical systems were dynamically sampled by introducing fictitious momenta as in the PIMD based on the standard primitive approximation. The indistinguishability of the particles was handled by a pseudopotential of particle permutation that is an extension of our previous one [J. Chem. Phys. 112, 10 116 (2000)]. As a test of our methodology for Boltzmann statistics, calculations have been performed for liquid helium-4 at 4 K. We found that the PIMD with the pair density matrix approximation dramatically reduced the computational cost to obtain the structural as well as dynamical (using the centroid molecular dynamics approximation) properties at the same level of accuracy as that with the primitive approximation. With respect to the identical particles, we performed the calculation of a bosonic triatomic cluster. Unlike the primitive approximation, the pseudopotential scheme based on the pair density matrix approximation described well the bosonic correlation among the interacting atoms. Convergence with a small number of discretization of the path achieved by this approximation enables us to construct a method of avoiding the problem of the vanishing pseudopotential encountered in the calculations by the primitive approximation.

  10. Effect of total and pair configurational entropy in determining dynamics of supercooled liquids over a range of densities

    Science.gov (United States)

    Banerjee, Atreyee; Nandi, Manoj Kumar; Sastry, Srikanth; Bhattacharyya, Sarika Maitra

    2016-07-01

    In this paper, we present a study of supercooled liquids interacting with the Lennard Jones potential and the corresponding purely repulsive (Weeks-Chandler-Andersen) potential, over a range of densities and temperatures, in order to understand the origin of their different dynamics in spite of their structures being similar. Using the configurational entropy as the thermodynamic marker via the Adam Gibbs relation, we show that the difference in the dynamics of these two systems at low temperatures can be explained from thermodynamics. At higher densities both the thermodynamical and dynamical difference between these model systems decrease, which is quantitatively demonstrated in this paper by calculating different parameters. The study also reveals the origin of the difference in pair entropy despite the similarity in the structure. Although the maximum difference in structure is obtained in the partial radial distribution function of the B type of particles, the rdf of AA pairs and AB pairs gives rise to the differences in the entropy and dynamics. This work supports the observation made in an earlier study [A. Banerjee et al., Phys. Rev. Lett. 113, 225701 (2014)] and shows that they are generic in nature, independent of density.

  11. Effect of soil bulk density on root morphology and biomass of vetiver grass seedlings%土壤容重对野生香根草幼苗根系形态及其生物量的影响

    Institute of Scientific and Technical Information of China (English)

    刘晚苟; 李良贤; 谢海容; 何泳怡; 刘金祥

    2015-01-01

    香根草因其具有发达的根系而被许多国家用于水土保持,但紧实土壤影响根系的生长,而土壤容重与土壤紧实度密切相关。为了掌握粤西野生香根草对紧实土壤的适应状况,用人工土柱研究了容重分别为1.20 g/cm3(D1.20)、1.35 g/cm3(D1.35)和1.58 g/cm3(D1.58)的土壤对其根系形态和生物量的影响。结果表明:1)随容重增大,根系和地上部生物量下降,根冠比降低,植株的根表面积、根长密度和根体积密度减小,而平均根直径增大。2)容重影响根系的空间分布,D1.20和 D1.35处理的根系在上、下层分布较多,中间层分布少,表明粤西野生香根草具有深根型特性;高容重阻止根向下延伸,D1.58处理的根系主要分布0~6 cm 的土层内。3)D1.20和 D1.35土壤的平均根直径随土层加深减小,而 D1.58的则增加。本实验结果说明粤西野生香根草能耐较紧实(D1.35)的土壤,高紧实土壤(D1.58)虽然限制其生长,但对表土层根系的分布影响小。并就容重对粤西野生香根草固土护坡的影响进行了讨论。%Vetiver grass (Vetiveria zizanioides )has an extensive root system and is consequently used world-wide for water and soil conservation.However,soil compaction resulting in high soil bulk density negatively influences root growth.In order to understand the adaptation of vetiver grass to soil compaction,the effects of soil of different bulk density,1.20 g/cm3 (D1 .20 ),1.35 g/cm3 (D1 .35 )and 1.58 g/cm3 (D1 .58 ),on the root mor-phology and biomass of vetiver seedlings were investigated using soil columns.The results showed that shoot and root dry weight,root:shoot ratio,root surface area,root length density and root volume density decreased with increasing bulk density,but that average root diameter increased.High bulk density influenced the spatial distribution of roots;more roots grew in

  12. Spin-density correlations in the dynamic spin-fluctuation theory: Comparison with polarized neutron scattering experiments

    Energy Technology Data Exchange (ETDEWEB)

    Melnikov, N.B., E-mail: melnikov@cs.msu.su [Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Reser, B.I., E-mail: reser@imp.uran.ru [Miheev Institute of Metal Physics, Ural Branch of Russian Academy of Sciences, Ekaterinburg 620990 (Russian Federation); Paradezhenko, G.V., E-mail: gparadezhenko@cs.msu.su [Lomonosov Moscow State University, Moscow 119991 (Russian Federation)

    2016-08-01

    To study the spin-density correlations in the ferromagnetic metals above the Curie temperature, we relate the spin correlator and neutron scattering cross-section. In the dynamic spin-fluctuation theory, we obtain explicit expressions for the effective and local magnetic moments and spatial spin-density correlator. Our theoretical results are demonstrated by the example of bcc Fe. The effective and local moments are found in good agreement with results of polarized neutron scattering experiment over a wide temperature range. The calculated short-range order is small (up to 4 Å) and slowly decreases with temperature.

  13. Disentangling density-dependent dynamics using full annual cycle models and Bayesian model weight updating

    Science.gov (United States)

    Robinson, Orin J.; McGowan, Conor; Devers, Patrick K.

    2017-01-01

    Density dependence regulates populations of many species across all taxonomic groups. Understanding density dependence is vital for predicting the effects of climate, habitat loss and/or management actions on wild populations. Migratory species likely experience seasonal changes in the relative influence of density dependence on population processes such as survival and recruitment throughout the annual cycle. These effects must be accounted for when characterizing migratory populations via population models.To evaluate effects of density on seasonal survival and recruitment of a migratory species, we used an existing full annual cycle model framework for American black ducks Anas rubripes, and tested different density effects (including no effects) on survival and recruitment. We then used a Bayesian model weight updating routine to determine which population model best fit observed breeding population survey data between 1990 and 2014.The models that best fit the survey data suggested that survival and recruitment were affected by density dependence and that density effects were stronger on adult survival during the breeding season than during the non-breeding season.Analysis also suggests that regulation of survival and recruitment by density varied over time. Our results showed that different characterizations of density regulations changed every 8–12 years (three times in the 25-year period) for our population.Synthesis and applications. Using a full annual cycle, modelling framework and model weighting routine will be helpful in evaluating density dependence for migratory species in both the short and long term. We used this method to disentangle the seasonal effects of density on the continental American black duck population which will allow managers to better evaluate the effects of habitat loss and potential habitat management actions throughout the annual cycle. The method here may allow researchers to hone in on the proper form and/or strength of

  14. Density, dynamic viscosity, and derived properties of binary mixtures of methanol or ethanol with water, ethyl acetate, and methyl acetate at T (293.15, 298.15, and 303.15) K

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, Begona; Calvar, Noelia; Gomez, Elena [Chemical Engineering Department, University of Vigo, 36200 Vigo (Spain); Dominguez, Angeles [Chemical Engineering Department, University of Vigo, 36200 Vigo (Spain)], E-mail: admguez@uvigo.es

    2007-12-15

    Densities and dynamic viscosities for methanol or ethanol with water, ethyl acetate, and methyl acetate at several temperatures T = (293.15, 298.15, and 303.15) K have been measured over the whole composition range and 0.1 MPa, along with the properties of the pure components. Excess molar volumes, viscosity deviations, and excess free energy of activation for the binary systems at the above-mentioned temperatures, were calculated and fitted to the Redlich-Kister equation to determine the fitting parameters and the root-mean-square deviations. UNIQUAC equation was used to correlate the experimental viscosity data. The UNIFAC-VISCO method and ASOG-VISCO method, based on contribution groups, were used to predict the dynamic viscosities of the binary mixtures.

  15. Effect of passive ultrasonic irrigation and manual dynamic irrigation on smear layer removal from root canals in a closed apex in vitro model.

    Science.gov (United States)

    Andrabi, Syed Mukhtar-Un-Nisar; Kumar, Ashok; Zia, Afaf; Iftekhar, Huma; Alam, Sharique; Siddiqui, Shiraz

    2014-08-01

    To compare the effect of passive ultrasonic irrigation with manual dynamic irrigation on smear layer removal from root canals using a closed apex in vitro model. The root canals of 45 freshly-extracted human single-rooted mandibular premolar teeth were prepared by the Pro-Taper rotary system to an apical preparation of F4 size. Prepared teeth were randomly divided into three groups; two experimental groups and one control group (n = 15) on the basis of the type of activation of final irrigation as follows: (a) Group A, 3% sodium hypochlorite (NaOCl) and 17% ethylenediaminetetraacetic acid (EDTA), no activation received; (b) Group B, 3% NaOCl and 17% EDTA, ultrasonic activation with a small file; and (c) Group C, 3% NaOCl and 17% EDTA, manual activation with a master gutta-percha point. The prepared teeth were decoronated and split into two halves longitudinally, and observed under a scanning electron microscope to assess the removal of the smear layer. In the apical-third region, the mean smear scores for groups B and C were significantly less than those of Group A (control group) (P < 0.05). Both activation techniques are important adjuncts in removing the smear layer, with manual dynamic activation being a simpler, safer, and more cost-effective technique. © 2013 Wiley Publishing Asia Pty Ltd.

  16. Point defect dynamics in sodium aluminum hydrides - a combined quasielastic neutron scattering and density functional theory study

    DEFF Research Database (Denmark)

    Shi, Qing; Voss, Johannes; Jacobsen, H.S.

    2007-01-01

    we study hydrogen dynamics in undoped and TiCl3-doped samples of NaAlH4 and Na3AlH6 using a combination of density functional theory calculations and quasielastic neutron scattering. Hydrogen dynamics is found to be limited and mediated by hydrogen vacancies in both alanate phases, requiring......Understanding the catalytic role of titanium-based additives on the reversible hydrogenation of complex metal hydrides is an essential step towards developing hydrogen storage materials for the transport sector. Improved bulk diffusion of hydrogen is one of the proposed catalytic effects, and here...

  17. Hydrogen dynamics in Na3AlH6: A combined density functional theory and quasielastic neutron scattering study

    DEFF Research Database (Denmark)

    Voss, Johannes; Shi, Qing; Jacobsen, Hjalte Sylvest

    2007-01-01

    alanate with TiCl3, and here we study hydrogen dynamics in doped and undoped Na3AlH6 using a combination of density functional theory calculations and quasielastic neutron scattering. The hydrogen dynamics is found to be vacancy mediated and dominated by localized jump events, whereas long-range bulk......Understanding the elusive catalytic role of titanium-based additives on the reversible hydrogenation of complex hydrides is an essential step toward developing hydrogen storage materials for the transport sector. Improved bulk diffusion of hydrogen is one of the proposed effects of doping sodium...

  18. Modeling root reinforcement using root-failure Weibull survival function

    Directory of Open Access Journals (Sweden)

    M. Schwarz

    2013-03-01

    Full Text Available Root networks contribute to slope stability through complicated interactions that include mechanical compression and tension. Due to the spatial heterogeneity of root distribution and the dynamic of root turnover, the quantification of root reinforcement on steep slope is challenging and consequently the calculation of slope stability as well. Although the considerable advances in root reinforcement modeling, some important aspect remain neglected. In this study we address in particular to the role of root strength variability on the mechanical behaviors of a root bundle. Many factors may contribute to the variability of root mechanical properties even considering a single class of diameter. This work presents a new approach for quantifying root reinforcement that considers the variability of mechanical properties of each root diameter class. Using the data of laboratory tensile tests and field pullout tests, we calibrate the parameters of the Weibull survival function to implement the variability of root strength in a numerical model for the calculation of root reinforcement (RBMw. The results show that, for both laboratory and field datasets, the parameters of the Weibull distribution may be considered constant with the exponent equal to 2 and the normalized failure displacement equal to 1. Moreover, the results show that the variability of root strength in each root diameter class has a major influence on the behavior of a root bundle with important implications when considering different approaches in slope stability calculation. Sensitivity analysis shows that the calibration of the tensile force and the elasticity of the roots are the most important equations, as well as the root distribution. The new model allows the characterization of root reinforcement in terms of maximum pullout force, stiffness, and energy. Moreover, it simplifies the implementation of root reinforcement in slope stability models. The realistic quantification of root

  19. Density functional theory and dynamical mean-field theory. A way to model strongly correlated systems

    Energy Technology Data Exchange (ETDEWEB)

    Backes, Steffen

    2017-04-15

    The study of the electronic properties of correlated systems is a very diverse field and has lead to valuable insight into the physics of real materials. In these systems, the decisive factor that governs the physical properties is the ratio between the electronic kinetic energy, which promotes delocalization over the lattice, and the Coulomb interaction, which instead favours localized electronic states. Due to this competition, correlated electronic systems can show unique and interesting properties like the Metal-Insulator transition, diverse phase diagrams, strong temperature dependence and in general a high sensitivity to the environmental conditions. A theoretical description of these systems is not an easy task, since perturbative approaches that do not preserve the competition between the kinetic and interaction terms can only be applied in special limiting cases. One of the most famous approaches to obtain the electronic properties of a real material is the ab initio density functional theory (DFT) method. It allows one to obtain the ground state density of the system under investigation by mapping onto an effective non-interacting system that has to be found self-consistently. While being an exact theory, in practical implementations certain approximations have to be made to the exchange-correlation potential. The local density approximation (LDA), which approximates the exchange-correlation contribution to the total energy by that of a homogeneous electron gas with the corresponding density, has proven quite successful in many cases. Though, this approximation in general leads to an underestimation of electronic correlations and is not able to describe a metal-insulator transition due to electronic localization in the presence of strong Coulomb interaction. A different approach to the interacting electronic problem is the dynamical mean-field theory (DMFT), which is non-perturbative in the kinetic and interaction term but neglects all non

  20. Genetic dissection of maize seedling root system architecture traits using an ultra-high density bin-map and a recombinant inbred line population

    Institute of Scientific and Technical Information of China (English)

    Weibin Song; Baobao Wang; Andrew L Hauck; Xiaomei Dong; Jieping Li; Jinsheng Lai

    2016-01-01

    Maize (Zea mays) root system architecture (RSA) mediates the key functions of plant anchorage and acquisition of nutrients and water. In this study, a set of 204 recombinant inbred lines (RILs) was derived from the widely adapted Chinese hybrid ZD958(Zheng58 ? Chang7-2), genotyped by sequencing (GBS) and evaluated as seedlings for 24 RSA related traits divided into primary, seminal and total root classes. Significant differences between the means of the parental phenotypes were detected for 18 traits, and extensive transgressive segregation in the RIL population was observed for all traits. Moderate to strong relationships among the traits were discovered. A total of 62 quantitative trait loci (QTL) were identified that individually explained from 1.6% to 11.6% (total root dry weight/total seedling shoot dry weight) of the phenotypic variation. Eighteen, 24 and 20 QTL were identified for primary, seminal and total root classes of traits, respectively. We found hotspots of 5, 3, 4 and 12 QTL in maize chromosome bins 2.06, 3.02-03, 9.02-04, and 9.05-06, respectively, implicating the presence of root gene clusters or pleiotropic effects. These results characterized the phenotypic variation and genetic architecture of seedling RSA in a population derived from a successful maize hybrid.

  1. Liquid Water through Density-Functional Molecular Dynamics: Plane-Wave vs Atomic-Orbital Basis Sets

    CERN Document Server

    Miceli, Giacomo; Pasquarello, Alfredo

    2016-01-01

    We determine and compare structural, dynamical, and electronic properties of liquid water at near ambient conditions through density-functional molecular dynamics simulations, when using either plane-wave or atomic-orbital basis sets. In both frameworks, the electronic structure and the atomic forces are self-consistently determined within the same theoretical scheme based on a nonlocal density functional accounting for van der Waals interactions. The overall properties of liquid water achieved within the two frameworks are in excellent agreement with each other. Thus, our study supports that implementations with plane-wave or atomic-orbital basis sets yield equivalent results and can be used indiscriminately in study of liquid water or aqueous solutions.

  2. Ab initio molecular dynamics with nuclear quantum effects at classical cost: ring polymer contraction for density functional theory

    CERN Document Server

    Marsalek, Ondrej

    2015-01-01

    Path integral molecular dynamics simulations, combined with an ab initio evaluation of interactions using electronic structure theory, incorporate the quantum mechanical nature of both the electrons and nuclei, which are essential to accurately describe systems containing light nuclei. However, path integral simulations have traditionally required a computational cost around two orders of magnitude greater than treating the nuclei classically, making them prohibitively costly for most applications. Here we show that the cost of path integral simulations can be dramatically reduced by extending our ring polymer contraction approach to ab initio molecular dynamics simulations. By using density functional tight binding as a reference system, we show that our ab initio ring polymer contraction (AI-RPC) scheme gives rapid and systematic convergence to the full path integral density functional theory result. We demonstrate the efficiency of this approach in ab initio simulations of liquid water and the reactive pro...

  3. Dynamic Predictive Density Combinations for Large Data Sets in Economics and Finance

    NARCIS (Netherlands)

    R. Casarin (Roberto); S. Grassi (Stefano); F. Ravazzolo (Francesco); H.K. van Dijk (Herman)

    2015-01-01

    markdownabstract__Abstract__ A Bayesian nonparametric predictive model is introduced to construct time-varying weighted combinations of a large set of predictive densities. A clustering mechanism allocates these densities into a smaller number of mutually exclusive subsets. Using properties of Aitc

  4. Density-associated recruitment mediates coral population dynamics on a coral reef

    Science.gov (United States)

    Bramanti, Lorenzo; Edmunds, Peter J.

    2016-06-01

    Theory suggests that density-associated processes can modulate community resilience following declines in population size. Here, we demonstrate density-associated processes in two scleractinian populations on the outer reef of Moorea, French Polynesia, that are rapidly increasing in size following the effects of two catastrophic disturbances. Between 2006 and 2010, predation by the corallivorous crown-of-thorns sea star reduced coral cover by 93 %; in 2010, the dead coral skeletons were removed by a cyclone, and in 2011 and 2012, high coral recruitment initiated population recovery. Coral recruitment was associated with coral cover, but the relationship differed between two coral genera that are almost exclusively broadcast spawners in Moorea. Acroporids recruited at low densities, and the density of recruits was positively associated with cover of Acropora, whereas pocilloporids recruited at high densities, and densities of their recruits were negatively associated with cover of Pocillopora. Together, our results suggest that associations between adult cover and density of both juveniles and recruits can mediate rapid coral community recovery after large disturbances. The difference between taxa in sign of the relationships between recruit density and coral cover indicate that they reflect contrasting mechanisms with the potential to mediate temporal shifts in taxonomic composition of coral communities.

  5. Thermodynamic properties and shear viscosity over entropy density ratio of nuclear fireball in a quantum-molecular dynamics model

    CERN Document Server

    Zhou, C L; Fang, D Q; Zhang, G Q

    2013-01-01

    Thermodynamic and transport properties of nuclear fireball created in the central region of heavy-ion collisions below 200 MeV/nucleon are investigated within the isospin-dependent quantum molecular dynamic (IQMD) model. These properties include time evolutions of the density, temperature, chemical potential, entropy density ($s$) and shear viscosity ($\\eta$) as well as density and temperature dependencies of the ratio of shear viscosity over entropy density ($\\eta/s$) etc. Based on the shear viscosity parametrization developed by Danilewicz and entropy density which is obtained by a generalized hot Thomas Fermi formalism, the ratio of shear viscosity over entropy density is calculated in the whole collision process as well as in the freeze-out stage. With the collision goes on, a transient minimal $\\eta/s$ with the value around 5/$4\\pi$ occurs in the largest compression stage. While, the relationship of $\\eta/s$ to tempertaure ($T$) in the freeze-out stage displays a local minimum which is about 9-10 times $...

  6. Root hairs

    NARCIS (Netherlands)

    Grierson, C.; Nielsen, E.; Ketelaar, T.; Schiefelbein, J.

    2014-01-01

    Roots hairs are cylindrical extensions of root epidermal cells that are important for acquisition of nutrients, microbe interactions, and plant anchorage. The molecular mechanisms involved in the specification, differentiation, and physiology of root hairs in Arabidopsis are reviewed here. Root hair

  7. Aliphatic and aromatic plant biopolymer dynamics in soil particles isolated from sequential density fractionation

    Science.gov (United States)

    Caldwell, B.; Filley, T.; Sollins, P.; Lajtha, K.; Swanston, C.; Kleber, M.; Kramer, M.

    2007-12-01

    A recent multi-layer-based soil organic matter-mineral interaction mechanistic model to describe the nature of soil organic matter-mineral surface mechanism for soil organic matter stabilization predicts that proteinaceous and aliphatic materials establish the core of strong binding-interactions upon which other organic matter is layered. A key methodology providing data underpinning this hypothesis is sequential density fractionation where soil is partitioned into particles of increasing density with the assumption that a partial control on organic matter distribution through density series is the thickness of its layering. Four soils of varying mineralogy and texture were investigated for their biopolymer, isotopic, and mineralogical properties. Light fractions (cutin and suberin while heavier fractions, 1.8-2.6 g/cm3, exhibited a progressive decrease in concentration in plant derived biopolymers with density. Extractable lignin phenols exhibited a progressive oxidation state with density. The concentration of biopolymers roughly mirrored the C:N ratio of soil particles which dropped consistently with increasing particle density. Although, in all soils, both lignin phenols and SFA concentration generally decreased with increasing density the ratio SFA/lignin varied with density and depending upon the soil. All soils, except the oxisol, exhibited an increase in SFA with respect to lignin suggesting a selective stabilization of those material with respect to lignin. In the oxisol, which showed little variation in its hematite dominated mineralogy across density, SFA/lignin remained constant, potentially indicating a greater capacity to stabilize lignin in that system. Interestingly, the lignin oxidation state increased with density in the oxisol. Given the variation in soil character, the consistency in these trends it suggests a general phenomenon of progressive decay in plant derived material with thinness of mineral coating but an overall relative increase in

  8. Impact of the pedestal plasma density on dynamics of edge localized mode crashes and energy loss scaling

    Energy Technology Data Exchange (ETDEWEB)

    Xu, X. Q., E-mail: xxu@llnl.gov [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Ma, J. F. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Institute for Fusion Studies, University of Texas, Austin, Texas 78712 (United States); Li, G. Q. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Institute of Plasma Physics, Chinese Academy of Sciences, Hefei (China)

    2014-12-15

    The latest BOUT++ studies show an emerging understanding of dynamics of edge localized mode (ELM) crashes and the consistent collisionality scaling of ELM energy losses with the world multi-tokamak database. A series of BOUT++ simulations are conducted to investigate the scaling characteristics of the ELM energy losses vs collisionality via a density scan. Linear results demonstrate that as the pedestal collisionality decreases, the growth rate of the peeling-ballooning modes decreases for high n but increases for low n (1 < n < 5), therefore the width of the growth rate spectrum γ(n) becomes narrower and the peak growth shifts to lower n. Nonlinear BOUT++ simulations show a two-stage process of ELM crash evolution of (i) initial bursts of pressure blob and void creation and (ii) inward void propagation. The inward void propagation stirs the top of pedestal plasma and yields an increasing ELM size with decreasing collisionality after a series of micro-bursts. The pedestal plasma density plays a major role in determining the ELM energy loss through its effect on the edge bootstrap current and ion diamagnetic stabilization. The critical trend emerges as a transition (1) linearly from ballooning-dominated states at high collisionality to peeling-dominated states at low collisionality with decreasing density and (2) nonlinearly from turbulence spreading dynamics at high collisionality into avalanche-like dynamics at low collisionality.

  9. Numerical Simulation of Hot Accretion Flows (I): A Large Radial Dynamical Range and the Density Profile of Accretion Flow

    CERN Document Server

    Yuan, Feng; Bu, Defu

    2012-01-01

    Numerical simulations of hot accretion flow have shown that the mass accretion rate decreases with decreasing radius; consequently the density profile of accretion flow becomes flatter compared to the case of a constant accretion rate. This result has important theoretical and observational implications. However, because of technical difficulties, the radial dynamic range in almost all previous simulations usually spans at most two orders of magnitude. This small dynamical range, combined with the effects of boundary conditions, makes the simulation results suspectable. Especially, the radial profiles of density and accretion rate may not be precise enough to be used to compare with observations. In this paper we present a "two-zone" approach to expand the radial dynamical range from two to four orders of magnitude. We confirm previous results and find that from $r_s$ to $ 10^4r_s$ the radial profiles of accretion rate and density can be well described by $\\dot{M}(r)\\propto r^s$ and $\\rho\\propto r^{-p}$. The ...

  10. The dynamics of straight vortex filaments in a Bose-Einstein condensate with a Gaussian density profile

    CERN Document Server

    Ruban, V P

    2016-01-01

    The dynamics of interacting quantized vortex filaments in a rotating trapped Bose-Einstein condensate, which is in the Thomas-Fermi regime at zero temperature and described by the Gross-Pitaevskii equation, is considered in the hydrodynamical "anelastic" approximation. In the presence of a smoothly inhomogeneous array of filaments (vortex lattice), a non-canonical Hamiltonian equation of motion is derived for the macroscopically averaged vorticity, with taking into account the spatial non-uniformity of the equilibrium condensate density determined by the trap potential. A minimum of the corresponding Hamiltonian describes a static configuration of deformed vortex lattice against a given density background. The minimum condition is reduced to a vector nonlinear partial differential equation of the second order, for which some approximate and exact solutions are found. It is shown that if the condensate density has an anisotropic Gaussian profile then equation of motion for the averaged vorticity admits solutio...

  11. Gravitational removal of volcanic arc roots in Cordilleran orogens

    Science.gov (United States)

    Currie, C. A.; Ducea, M. N.; DeCelles, P. G.; Beaumont, C.

    2013-12-01

    Cordilleran orogens, such as the central Andes, form above subduction zones and their evolution depends on processes associated with oceanic plate subduction and continental plate shortening. Such orogens are characterized by abundant arc volcanism and the formation of thick (>30 km) granitoid batholiths. The magma composition is consistent with a multi-stage model, in which parental mantle-derived basaltic magmas stagnate within the continental lithosphere and then undergo differentiation. Felsic partial melts rise through the crust, leaving a high-density garnet pyroxenite root in the deep lithosphere. Here, we study the dynamics of gravitational removal of this root using regional two-dimensional thermal-mechanical models of subduction below a continent. In the models, the volcanic arc location is determined dynamically based on subduction zone thermal structure, and formation of the batholith-root complex is simulated by changing the density of the volcanic arc lithosphere over time. For the lithosphere structure used in our models, arc roots that undergo even a small density increase are readily removed through gravitational foundering for a wide range of root strengths and subduction rates. The dynamics of removal depend on the relative rates of downward gravitational growth and horizontal shearing by subduction-induced mantle flow. Gravitational growth dominates for high root densification rates, high root viscosities and low subduction rates, leading to drip-like removal of the root as a single downwelling over 1-3 Myr. At lower growth rates, the root is removed over ~6 Myr through shear entrainment, as it is carried sideways by mantle flow and then subducted on top of the oceanic plate. In all models, >80% of the root is removed, making this an effective way to thin mantle lithosphere in the volcanic arc region. This can help resolve the mass problem in the central Andes, where observations indicate a thin mantle lithosphere, despite significant crustal

  12. The dynamic mean-field density functional method and its application to the mesoscopic dynamics of quenched block copolymer melts

    NARCIS (Netherlands)

    Fraaije, JGEM; vanVlimmeren, BAC; Maurits, NM; Postma, M; Evers, OA; Hoffmann, C; Altevogt, P; GoldbeckWood, G

    1997-01-01

    In this paper we discuss a new generalized time-dependent Ginzburg-Landau theory for the numerical calculation of polymer phase separation kinetics in 3D. The thermodynamic forces are obtained by a mean-field density functional method, using a Gaussian chain as a molecular model. The method is

  13. Full-density, net-shape powder consolidation using dynamic magnetic pulse pressures

    Science.gov (United States)

    Chelluri, Bhanu; Barber, John P.

    1999-07-01

    The full-density consolidation of powders into net-shape parts yields high green strength, low shrinkage, short sinter times, superior mechanical properties, and low manufacturing costs. The conventional lowcost, single-press, single-sinter process typically densifies powders at less than 65 percent green density. This article describes the Magnepress™ process, a powder-processing technique wherein pulsed magnetic pressures consolidate powders into full-density parts without admixed lubricants or binders. The Magnepress technique is especially suitable for producing net-shape products with radial symmetry (e.g., rods, cylindrical parts with internal features, tubular shapes, and high aspect-ratio specimens).

  14. Exact many-body dynamics with stochastic one-body density matrix evolution

    Energy Technology Data Exchange (ETDEWEB)

    Lacroix, D

    2004-05-01

    In this article, we discuss some properties of the exact treatment of the many-body problem with stochastic Schroedinger equation (SSE). Starting from the SSE theory, an equivalent reformulation is proposed in terms of quantum jumps in the density matrix space. The technical details of the derivation a stochastic version of the Liouville von Neumann equation are given. It is shown that the exact Many-Body problem could be replaced by an ensemble of one-body density evolution, where each density matrix evolves according to its own mean-field augmented by a one-body noise. (author)

  15. Dynamics of observables and exactly solvable quantum problems: Using time-dependent density-functional theory to control quantum systems

    Science.gov (United States)

    Farzanehpour, M.; Tokatly, I. V.

    2016-05-01

    We use analytic (current) density-potential maps of time-dependent (current) density-functional theory [TD(C)DFT] to inverse engineer analytically solvable time-dependent quantum problems. In this approach the driving potential (the control signal) and the corresponding solution of the Schrödinger equation are parametrized analytically in terms of the basic TD(C)DFT observables. We describe the general reconstruction strategy and illustrate it with a number of explicit examples. First we consider the real space one-particle dynamics driven by a time-dependent electromagnetic field and recover, from the general TDDFT reconstruction formulas, the known exact solution for a driven oscillator with a time-dependent frequency. Then we use analytic maps of the lattice TD(C)DFT to control quantum dynamics in a discrete space. As a first example we construct a time-dependent potential which generates prescribed dynamics on a tight-binding chain. Then our method is applied to the dynamics of spin-1/2 driven by a time-dependent magnetic field. We design an analytic control pulse that transfers the system from the ground to excited state and vice versa. This pulse generates the spin flip thus operating as a quantum not gate.

  16. Particle visualization in high-power impulse magnetron sputtering. II. Absolute density dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Britun, Nikolay, E-mail: nikolay.britun@umons.ac.be; Palmucci, Maria; Konstantinidis, Stephanos [Chimie des Interactions Plasma-Surface (ChIPS), CIRMAP, Université de Mons, 23 Place du Parc, B-7000 Mons (Belgium); Snyders, Rony [Chimie des Interactions Plasma-Surface (ChIPS), CIRMAP, Université de Mons, 23 Place du Parc, B-7000 Mons (Belgium); Materia Nova Research Center, Parc Initialis, B-7000 Mons (Belgium)

    2015-04-28

    Time-resolved characterization of an Ar-Ti high-power impulse magnetron sputtering discharge has been performed. The present, second, paper of the study is related to the discharge characterization in terms of the absolute density of species using resonant absorption spectroscopy. The results on the time-resolved density evolution of the neutral and singly-ionized Ti ground state atoms as well as the metastable Ti and Ar atoms during the discharge on- and off-time are presented. Among the others, the questions related to the inversion of population of the Ti energy sublevels, as well as to re-normalization of the two-dimensional density maps in terms of the absolute density of species, are stressed.

  17. Growth of bare root Pinus taeda, L. seedlings cultivated under five densities in nursery Crescimento de mudas em raiz nua de Pinus taeda, L. produzidas em cinco densidades no viveiro

    Directory of Open Access Journals (Sweden)

    José Geraldo de Araújo Carneiro

    2007-02-01

    Full Text Available Seedlings compete for nutrients, water and light. The available area for each seedling affects their behavior related to requirements for these resources. This experiment evaluated the influence of five plant densities on the growth of bare root Pinus taeda, L. seedlings in a nursery after outplanting. The analyzed characteristics were: height (H, root collar diameter (D, H/D ratio, and dry matter weight. Higher densities stimulated H growth and the lowest densities increased D average and dry matter weight and lowered the H/D ratio. Seedlings were distributed by H, D and H/D classes. Higher densities had a larger number of seedlings in larger H classes. Larger numbers of seedlings with larger D and lower H/D ratios were found in lower densities. Ten months after outplanting the seedlings grown in lower densities had higher survival percentages and growth. Some saplings of standardized heights were uprooted with the objective of studying their root systems. The lowest densities stimulated higher numbers of first and second order roots as well as fresh and dry matter weights of thin roots with mycorrhizae presence. In both parts of the experiment, the density of 278 seedlings m-2 yielded equivalent averages as compared to the lowest densities.Mudas competem por nutrientes, água e luz. A área de cada muda afeta seu comportamento na exigência destes recursos. Este experimento avaliou a influência de cinco densidades no crescimento de mudas em raiz nua de Pinus taeda, L. no viveiro e no campo. As características analisadas foram: altura da parte aérea (H, diâmetro de colo (D, relação H/D e pesos de matéria seca. Maiores densidades estimularam o crescimento em H, no viveiro. As mais baixas aumentaram as médias de D, pesos de matéria seca e diminuíram a relação H/D. Distribuíram-se as mudas em classes de H, D e relação H/D, para quantificar seu número, em cada classe. Maiores quantidades de mudas com mais elevados valores de D e com

  18. Dynamics of Spontaneous Emission Controlled by Local Density of States in Photonic Crystals

    DEFF Research Database (Denmark)

    Lodahl, Peter; Nikolaev, Ivan S.; van Driel, A. Floris;

    2006-01-01

    We have measured time-resolved spontaneous emission from quantum dots in 3D photonic crystals. Due to the spatially dependent local density of states, the distribution of decay rates varies strongly with the photonic crystal lattice parameter.......We have measured time-resolved spontaneous emission from quantum dots in 3D photonic crystals. Due to the spatially dependent local density of states, the distribution of decay rates varies strongly with the photonic crystal lattice parameter....

  19. Reproducing morphologies of disorderly self-assembling planar molecules with static and dynamic simulation methods by matching density

    Science.gov (United States)

    Bumstead, M.; Arnold, B.; Turak, A.

    2017-04-01

    Monte Carlo and molecular dynamics simulations are the two main numerical approaches to modeling molecular self-assembly and ordering. Conceptually, however, each method explores different paths through the thermodynamic landscape. Molecular dynamics depends on the position and momentum terms. Monte Carlo is a static set, and thus the momentum term is replaced with an energy term that is dependent on the volume and entropy. Until now, it was unclear if a stochastic process of densifying particles would have the same internal structure as morphologies produced from classical mechanics. This paper provides a systematic (i.e., statistical) analysis of the outcomes of 4032 simulations for hard-core circular objects as a function of the number of molecules and the boundary conditions. Structural classification of the resultant ensembles (averaged pair correlation function, bond-order parameter, translational order parameter, and Voronoi diagrams) shows that stochastic and dynamic approaches do not alter the morphology of the steric molecules. We conclude that when the probability density of covering area fractions are matched, the ensembles produced from the two methods will show the same level of structural disorder and positional patterns. The resultant morphology from both models, therefore, is not a product of dynamic unrest, but that of the relaxation of entropic frustration from macromolecular crowding. Although statistically the two methods produce similar configurations, nuances arise from the static and dynamic nature of modeling. As a result, Monte Carlo is slightly better suited to modeling systems when the desired morphology is represented by a metastable state; molecular dynamics on the other hand is more suited to finding defects that can arise in morphologies. Regardless, a fixed density will result in similar morphologies from both techniques, driven by similar configurational entropy.

  20. A molecular dynamics study of dislocation density generation and plastic relaxation during shock of single crystal Cu

    Science.gov (United States)

    Sichani, Mehrdad M.; Spearot, Douglas E.

    2016-07-01

    The molecular dynamics simulation method is used to investigate the dependence of crystal orientation and shock wave strength on dislocation density evolution in single crystal Cu. Four different shock directions , , , and are selected to study the role of crystal orientation on dislocation generation immediately behind the shock front and plastic relaxation as the system reaches the hydrostatic state. Dislocation density evolution is analyzed for particle velocities between the Hugoniot elastic limit ( up H E L ) for each orientation up to a maximum of 1.5 km/s. Generally, dislocation density increases with increasing particle velocity for all shock orientations. Plastic relaxation for shock in the , , and directions is primarily due to a reduction in the Shockley partial dislocation density. In addition, plastic anisotropy between these orientations is less apparent at particle velocities above 1.1 km/s. In contrast, plastic relaxation is limited for shock in the orientation. This is partially due to the emergence of sessile stair-rod dislocations with Burgers vectors of 1/3 and 1/6. The nucleation of 1/6 dislocations at lower particle velocities is mainly due to the reaction between Shockley partial dislocations and twin boundaries. On the other hand, for the particle velocities above 1.1 km/s, the nucleation of 1/3 dislocations is predominantly due to reaction between Shockley partial dislocations at stacking fault intersections. Both mechanisms promote greater dislocation densities after relaxation for shock pressures above 34 GPa compared to the other three shock orientations.

  1. Structural, electronic, and vibrational properties of high-density amorphous silicon: a first-principles molecular-dynamics study.

    Science.gov (United States)

    Morishita, Tetsuya

    2009-05-21

    We report a first-principles study of the structural, electronic, and dynamical properties of high-density amorphous (HDA) silicon, which was found to be formed by pressurizing low-density amorphous (LDA) silicon (a normal amorphous Si) [T. Morishita, Phys. Rev. Lett. 93, 055503 (2004); P. F. McMillan, M. Wilson, D. Daisenberger, and D. Machon, Nature Mater. 4, 680 (2005)]. Striking structural differences between HDA and LDA are revealed. The LDA structure holds a tetrahedral network, while the HDA structure contains a highly distorted tetrahedral network. The fifth neighboring atom in HDA tends to be located at an interstitial position of a distorted tetrahedron composed of the first four neighboring atoms. Consequently, the coordination number of HDA is calculated to be approximately 5 unlike that of LDA. The electronic density of state (EDOS) shows that HDA is metallic, which is consistent with a recent experimental measurement of the electronic resistance of HDA Si. We find from local EDOS that highly distorted tetrahedral configurations enhance the metallic nature of HDA. The vibrational density of state (VDOS) also reflects the structural differences between HDA and LDA. Some of the characteristic vibrational modes of LDA are dematerialized in HDA, indicating the degradation of covalent bonds. The overall profile of the VDOS for HDA is found to be an intermediate between that for LDA and liquid Si under pressure (high-density liquid Si).

  2. A regional-scale, high resolution dynamical malaria model that accounts for population density, climate and surface hydrology.

    Science.gov (United States)

    Tompkins, Adrian M; Ermert, Volker

    2013-02-18

    The relative roles of climate variability and population related effects in malaria transmission could be better understood if regional-scale dynamical malaria models could account for these factors. A new dynamical community malaria model is introduced that accounts for the temperature and rainfall influences on the parasite and vector life cycles which are finely resolved in order to correctly represent the delay between the rains and the malaria season. The rainfall drives a simple but physically based representation of the surface hydrology. The model accounts for the population density in the calculation of daily biting rates. Model simulations of entomological inoculation rate and circumsporozoite protein rate compare well to data from field studies from a wide range of locations in West Africa that encompass both seasonal endemic and epidemic fringe areas. A focus on Bobo-Dioulasso shows the ability of the model to represent the differences in transmission rates between rural and peri-urban areas in addition to the seasonality of malaria. Fine spatial resolution regional integrations for Eastern Africa reproduce the malaria atlas project (MAP) spatial distribution of the parasite ratio, and integrations for West and Eastern Africa show that the model grossly reproduces the reduction in parasite ratio as a function of population density observed in a large number of field surveys, although it underestimates malaria prevalence at high densities probably due to the neglect of population migration. A new dynamical community malaria model is publicly available that accounts for climate and population density to simulate malaria transmission on a regional scale. The model structure facilitates future development to incorporate migration, immunity and interventions.

  3. Dissolved gas dynamics in wetland soils: Root-mediated gas transfer kinetics determined via push-pull tracer tests

    Science.gov (United States)

    Reid, Matthew C.; Pal, David S.; Jaffé, Peter R.

    2015-09-01

    Gas transfer processes are fundamental to the biogeochemical and water quality functions of wetlands, yet there is limited knowledge of the rates and pathways of soil-atmosphere exchange for gases other than oxygen and methane (CH4). In this study, we use a novel push-pull technique with sulfur hexafluoride (SF6) and helium (He) as dissolved gas tracers to quantify the kinetics of root-mediated gas transfer, which is a critical efflux pathway for gases from wetland soils. This tracer approach disentangles the effects of physical transport from simultaneous reaction in saturated, vegetated wetland soils. We measured significant seasonal variation in first-order gas exchange rate constants, with smaller spatial variations between different soil depths and vegetation zones in a New Jersey tidal marsh. Gas transfer rates for most biogeochemical trace gases are expected to be bracketed by the rate constants for SF6 and He, which ranged from ˜10-2 to 2 × 10-1 h-1 at our site. A modified Damköhler number analysis is used to evaluate the balance between biochemical reaction and root-driven gas exchange in governing the fate of environmental trace gases in rooted, anaerobic soils. This approach confirmed the importance of plant gas transport for CH4, and showed that root-driven transport may affect nitrous oxide (N2O) balances in settings where N2O reduction rates are slow.

  4. Actin-Depolymerizing Factor2-Mediated Actin Dynamics Are Essential for Root-Knot Nematode Infection of Arabidopsis

    NARCIS (Netherlands)

    Clement, M.; Ketelaar, T.; Rodiuc, N.; Banora, M.Y.; Smertenko, A.; Engler, G.; Abad, P.; Hussey, P.J.; Almeida Engler, De J.

    2009-01-01

    Reorganization of the actin and microtubule networks is known to occur in targeted vascular parenchymal root cells upon infection with the nematode Meloidogyne incognita. Here, we show that actin-depolymerizing factor (ADF) is upregulated in the giant feeding cells of Arabidopsis thaliana that devel

  5. Mathematics Teachers' Visualization of Complex Number Multiplication and the Roots of Unity in a Dynamic Geometry Environment

    Science.gov (United States)

    Caglayan, Gunhan

    2016-01-01

    This qualitative research, drawing on the theoretical frameworks by Even (1990, 1993) and Sfard (2007), investigated five high school mathematics teachers' geometric interpretations of complex number multiplication along with the roots of unity. The main finding was that mathematics teachers constructed the modulus, the argument, and the conjugate…

  6. Actin-Depolymerizing Factor2-Mediated Actin Dynamics Are Essential for Root-Knot Nematode Infection of Arabidopsis

    NARCIS (Netherlands)

    Clement, M.; Ketelaar, T.; Rodiuc, N.; Banora, M.Y.; Smertenko, A.; Engler, G.; Abad, P.; Hussey, P.J.; Almeida Engler, De J.

    2009-01-01

    Reorganization of the actin and microtubule networks is known to occur in targeted vascular parenchymal root cells upon infection with the nematode Meloidogyne incognita. Here, we show that actin-depolymerizing factor (ADF) is upregulated in the giant feeding cells of Arabidopsis thaliana that

  7. LM-type tests for idiosyncratic and common unit roots in the exact factor model with AR(1) dynamics

    NARCIS (Netherlands)

    Solberger, M.; Zhou, X.

    2013-01-01

    Recent developments within the panel unit-root literature have illustrated how the exact factor model serves as a parsimonious framework and allows for consistent maximum likelihood inference even when it is misspecified contra the more general approximate factor model. In this paper we consider an

  8. Density dependence of hydrogen bonding and the translational-orientational structural order in supercritical water: a molecular dynamics study.

    Science.gov (United States)

    Ma, Haibo; Ma, Jing

    2011-08-07

    Molecular dynamics simulation have been performed with a wide range of densities along a near critical isotherm of supercritical water (SCW) in order to study the density dependence of the structure order and hydrogen bonding (HB). It is revealed that the translational structure order is nearly invariant while the orientational tetrahedral structure order is very sensitive to the bulk density under supercritical conditions. Meanwhile, some energetically unfavorable intermediate water dimer structures are found to appear under supercritical conditions due to the reduced energy difference and the enhanced energy fluctuation. As a consequence, a general geometrical criterion or the inclusion of a energy-based criterion instead of currently widely adopted pure r(OH)-based geometric criterion is suggested to be used in the HB statistics under supercritical conditions. It is found that the average HB number per H(2)O molecule (n(HB)) reduces with the decreasing SCW bulk density although a given pair of H(2)O molecules are shown to have a stronger ability to form a hydrogen bond under lower SCW bulk densities. Accordingly, the orientational tetrahedral structure order q decreases with the reducing bulk density under supercritical conditions. However, when the fluid is dilute with ρ ≤ 0.19ρ(c) (ρ(c) = 0.322 g/cm(3)), the energy fluctuation increases sharply and the short-range order is destroyed, signifying the supercritical fluid (SCF)-gas state transition. Accordingly, the orientational tetrahedral structure order q gets reversal around ρ = 0.19ρ(c) and approaches zero under very dilute conditions. The sensitivity of the orientational order to the density implies the microscopic origin of the significant dependence of SCF's physicochemical properties on the pressure.

  9. Ab initio molecular dynamics with nuclear quantum effects at classical cost: Ring polymer contraction for density functional theory.

    Science.gov (United States)

    Marsalek, Ondrej; Markland, Thomas E

    2016-02-07

    Path integral molecular dynamics simulations, combined with an ab initio evaluation of interactions using electronic structure theory, incorporate the quantum mechanical nature of both the electrons and nuclei, which are essential to accurately describe systems containing light nuclei. However, path integral simulations have traditionally required a computational cost around two orders of magnitude greater than treating the nuclei classically, making them prohibitively costly for most applications. Here we show that the cost of path integral simulations can be dramatically reduced by extending our ring polymer contraction approach to ab initio molecular dynamics simulations. By using density functional tight binding as a reference system, we show that our ring polymer contraction scheme gives rapid and systematic convergence to the full path integral density functional theory result. We demonstrate the efficiency of this approach in ab initio simulations of liquid water and the reactive protonated and deprotonated water dimer systems. We find that the vast majority of the nuclear quantum effects are accurately captured using contraction to just the ring polymer centroid, which requires the same number of density functional theory calculations as a classical simulation. Combined with a multiple time step scheme using the same reference system, which allows the time step to be increased, this approach is as fast as a typical classical ab initio molecular dynamics simulation and 35× faster than a full path integral calculation, while still exactly including the quantum sampling of nuclei. This development thus offers a route to routinely include nuclear quantum effects in ab initio molecular dynamics simulations at negligible computational cost.

  10. Runout distance and dynamic pressure of pyroclastic density currents: Evidence from 18 May 1980 blast surge of Mount St. Helens

    Science.gov (United States)

    Gardner, J. E.; Andrews, B. J.

    2016-12-01

    Pyroclastic density currents (flows and surges) are one of the most deadly hazards associated with volcanic eruptions. Understanding what controls how far such currents will travel, and how their dynamic pressure evolves, could help mitigate their hazards. The distance a ground hugging, pyroclastic density current travels is partly limited by when it reverses buoyancy and lifts off into the atmosphere. The 1980 blast surge of Mount St. Helens offers an example of a current seen to lift off. Before lofting, it had traveled up to 20 km and leveled more than 600 km3 of thick forest (the blowdown zone). The outer edge of the devastated area - where burned trees that were left standing (the singe zone) - is where the surge is thought to have lifted off. We recently examined deposits in the outer parts of the blowdown and in the singe zone at 32 sites. The important finding is that the laterally moving surge travelled into the singe zone, and hence the change in tree damage does not mark the run out distance of the ground hugging surge. Eyewitness accounts and impacts on trees and vehicles reveal that the surge consisted of a fast, dilute "overcurrent" and a slower "undercurrent", where most of the mass (and heat) was retained. Reasonable estimates for flow density and velocity show that dynamic pressure of the surge (i.e., its ability to topple trees) peaked near the base of the overcurrent. We propose that when the overcurrent began to lift off, the height of peak dynamic pressure rose above the trees and stopped toppling them. The slower undercurrent continued forward, burning trees but it lacked the dynamic pressure needed to topple them. Grain-size variations argue that it slowed from 30 m/s when it entered the singe zone to 3 m/s at the far end. Buoyancy reversal and liftoff are thus not preserved in the deposits where the surge lofted upwards.

  11. Dispersal-mediated effect of microhabitat availability and density dependence determine population dynamics of a forest floor web spider.

    Science.gov (United States)

    Takada, Mayura B; Miyashita, Tadashi

    2014-09-01

    Landscapes in nature can be viewed as a continuum of small total habitable area with high fragmentation to widely spreading habitats. The dispersal-mediated rescue effect predominates in the former landscapes, while classical density-dependent processes generally prevail in widely spread habitats. A similar principle should be applied to populations of organisms utilizing microhabitats in limited supply. To test this hypothesis, we examined the population dynamics of a web spider, Neriene brongersmai, in 16 populations with varying degrees of microhabitat availability, and we explored whether: (i) high microhabitat availability improves survival rate during density-independent movement, while the resultant high density reduces survival rate in a density-dependent manner; and (ii) temporal population stability increases with microhabitat availability at the population level. Furthermore, we conducted two types of field experiments to verify whether high microhabitat availability actually reduces mortality associated with web-site movement. Field observations revealed that demographic change in N. brongersmai populations was affected by three factors at different stages, namely the microhabitat limitation from the early to late juvenile stages, the density dependence from the late juvenile to adult stages and the food limitation from the adult to the next early juvenile stages. In addition, there was a tendency for a positive association between population stability and microhabitat availability at the population level. A small-scale experiment, where the frequency of spider web relocation was equalized artificially, revealed that high microhabitat availability elevated the survival rate during a movement event between web-sites. The larger spatiotemporal scale experiment also revealed an improved spider survival rate following treatment with high microhabitat availability, even though spider density was kept at a relatively low level. The population dynamics of N

  12. Approach to nonadiabatic transitions by density matrix evolution and molecular dynamics simulations

    NARCIS (Netherlands)

    Berendsen, H.J.C.; Mavri, J.

    1996-01-01

    Many biological processes are characterized by an essentially quantum dynamical event, such as electron or proton transfer, in a complex classical environment. To treat such processes properly by computer simulation, allowing nonadiabatic transitions involving excited states, we recently developed a

  13. Transcription co-activator Arabidopsis ANGUSTIFOLIA3 (AN3) regulates water-use efficiency and drought tolerance by modulating stomatal density and improving root architecture by the transrepression of YODA (YDA).

    Science.gov (United States)

    Meng, Lai-Sheng; Yao, Shun-Qiao

    2015-09-01

    One goal of modern agriculture is the improvement of plant drought tolerance and water-use efficiency (WUE). Although stomatal density has been linked to WUE, the causal molecular mechanisms and engineered alternations of this relationship are not yet fully understood. Moreover, YODA (YDA), which is a MAPKK kinase gene, negatively regulates stomatal development. BR-INSENSITIVE 2 interacts with phosphorylates and inhibits YDA. However, whether YDA is modulated in the transcriptional level is still unclear. Plants lacking ANGUSTIFOLIA3 (AN3) activity have high drought stress tolerance because of low stomatal densities and improved root architecture. Such plants also exhibit enhanced WUE through declining transpiration without a demonstrable reduction in biomass accumulation. AN3 negatively regulated YDA expression at the transcriptional level by target-gene analysis. Chromatin immunoprecipitation analysis indicated that AN3 was associated with a region of the YDA promoter in vivo. YDA mutation significantly decreased the stomatal density and root length of an3 mutant, thus proving the participation of YDA in an3 drought tolerance and WUE enhancement. These components form an AN3-YDA complex, which allows the integration of water deficit stress signalling into the production or spacing of stomata and cell proliferation, thus leading to drought tolerance and enhanced WUE.

  14. Phase-space consistency of stellar dynamical models determined by separable augmented densities

    CERN Document Server

    An, J; Baes, M

    2012-01-01

    Assuming the separable augmented density, it is always possible to construct a distribution function of a spherical population with any given density and anisotropy. We consider under what conditions the distribution constructed as such is in fact non-negative everywhere in the accessible phase-space. We first generalize known necessary conditions on the augmented density using fractional calculus. The condition on the radius part R(r^2) (whose logarithmic derivative is the anisotropy parameter) is equivalent to the complete monotonicity of R(1/w)/w. The condition on the potential part on the other hand is given by its derivative up to any order not greater than (3/2-beta) being non-negative where beta is the central anisotropy parameter. We also derive a specialized inversion formula for the distribution from the separable augmented density, which leads to sufficient conditions on separable augmented densities for the non-negativity of the distribution. The last generalizes the similar condition derived earl...

  15. Analysis of surface and root-zone soil moisture dynamics with ERS scatterometer and the hydrometeorological model SAFRAN-ISBA-MODCOU at Grand Morin watershed (France

    Directory of Open Access Journals (Sweden)

    T. Paris Anguela

    2008-12-01

    Full Text Available Spatial and temporal variations of soil moisture strongly affect flooding, erosion, solute transport and vegetation productivity. Its characterization, offers an avenue to improve our understanding of complex land surface-atmosphere interactions. In this paper, soil moisture dynamics at soil surface (first centimeters and root-zone (up to 1.5 m depth are investigated at three spatial scales: local scale (field measurements, 8×8 km2 (hydrological model and 25×25 km2 scale (ERS scatterometer in a French watershed. This study points out the quality of surface and root-zone soil moisture data for SIM model and ERS scatterometer for a three year period. Surface soil moisture is highly variable because is more influenced by atmospheric conditions (rain, wind and solar radiation, and presents RMSE up to 0.08 m3 m−3. On the other hand, root-zone moisture presents lower variability with small RMSE (between 0.02 and 0.06 m3 m−3. These results will contribute to satellite and model verification of moisture, but also to better application of radar data for data assimilation in future.

  16. Analysis of surface and root-zone soil moisture dynamics with ERS scatterometer and the hydrometeorological model SAFRAN-ISBA-MODCOU at Grand Morin watershed (France

    Directory of Open Access Journals (Sweden)

    T. Paris Anguela

    2008-07-01

    Full Text Available Spatial and temporal variations of soil moisture strongly affect flooding, erosion, solute transport and vegetation productivity. Its characterization, offers an avenue to improve our understanding of complex land surface–atmosphere interactions. In this paper, soil moisture dynamics at soil surface (first centimeters and root-zone (up to 1.5 m depth are investigated at three spatial scales: local scale (field measurements, 8×8 km2 (hydrological model and 25×25 km2 scale (ERS scatterometer in a French watershed. This study points out the quality of surface and root-zone soil moisture data for SIM model and ERS scatterometer for a three year period. Surface soil moisture is highly variable because is more influenced by atmospheric conditions (rain, wind and solar radiation, and presents RMS errors up to 0.08 m3 m−3. On the other hand, root-zone moisture presents lower variability with small RMS errors (between 0.02 and 0.06 m3 m-3. These results will contribute to satellite and model verification of moisture, but also to better application of radar data for data assimilation in future.

  17. Plasma dynamics near critical density inferred from direct measurements of laser hole boring.

    Science.gov (United States)

    Gong, Chao; Tochitsky, Sergei Ya; Fiuza, Frederico; Pigeon, Jeremy J; Joshi, Chan

    2016-06-01

    We have used multiframe picosecond optical interferometry to make direct measurements of the hole boring velocity, v_{HB}, of the density cavity pushed forward by a train of CO_{2} laser pulses in a near critical density helium plasma. As the pulse train intensity rises, the increasing radiation pressure of each pulse pushes the density cavity forward and the plasma electrons are strongly heated. After the peak laser intensity, the plasma pressure exerted by the heated electrons strongly impedes the hole boring process and the v_{HB} falls rapidly as the laser pulse intensity falls at the back of the laser pulse train. A heuristic theory is presented that allows the estimation of the plasma electron temperature from the measurements of the hole boring velocity. The measured values of v_{HB}, and the estimated values of the heated electron temperature as a function of laser intensity are in reasonable agreement with those obtained from two-dimensional numerical simulations.

  18. Residual Dynamics of Thiamethoxam in Potato Roots%噻虫嗪种衣剂在马铃薯根中的残留动态分析

    Institute of Scientific and Technical Information of China (English)

    张海英; 陆磊; 胡梅; 郭建国; 刘永刚

    2011-01-01

    An analytical method was developed for determining residues in roots of potatoes grown from the seeds coated with thiamethoxam. This method was characterized by recovery rates between 89.33% and 91.80%, LOD at 0.001 g and sensitivity of 0.001 mg / kg. The residual dynamics of thiamethoxam in potato roots by two different approaches of seed coating was studied in the experiment. The results showed that the degradation rates of thiamethoxam were slow in potato roots by two different approaches of seed coating. The half-lives of thiamethoxam was 17.96 d in roots of potatoes grown from the seeds which were dressed with medicine before cutting, and the half-lives of thiamethoxam was 15.13 d in roots of potatoes from seeds which were cut before dressing with medicine. In a word, thiamethoxam had a long residual activity, but the activity would not exist for a long time in the potato roots.%建立一种高效液相色谱分析方法,用于测定马铃薯根中噻虫嗪种衣剂的残留量,该方法的添加回收率为89.33%~91.80%,最低检出量为0.001 g,最低检出质量分数为0.001 mg/kg。该试验还通过运用两种不同的包衣方式,研究了噻虫嗪在马铃薯根中的残留消解动态。试验结果表明,在两种不同的包衣方式下,噻虫嗪在马铃薯根中的消解速度都较为缓慢,先包衣后切块的半衰期为17.96 d,而先切块后包衣的半衰期为15.13 d,两者持效期都较长,但不会长期存在于马铃薯根中。

  19. Root fractures

    DEFF Research Database (Denmark)

    Andreasen, Jens Ove; Christensen, Søren Steno Ahrensburg; Tsilingaridis, Georgios

    2012-01-01

    The purpose of this study was to analyze tooth loss after root fractures and to assess the influence of the type of healing and the location of the root fracture. Furthermore, the actual cause of tooth loss was analyzed.......The purpose of this study was to analyze tooth loss after root fractures and to assess the influence of the type of healing and the location of the root fracture. Furthermore, the actual cause of tooth loss was analyzed....

  20. Dynamics of photosynthetic photon flux density (PPFD) and estimates in coastal northern California

    Science.gov (United States)

    The seasonal trends and diurnal patterns of Photosynthetically Active Radiation (PAR) were investigated in the San Francisco Bay Area of Northern California from March through August in 2007 and 2008. During these periods, the daily values of PAR flux density (PFD), energy loading with PAR (PARE), a...

  1. Static and Dynamical Valence-Charge-Density Properties of GaAs

    Science.gov (United States)

    Pietsch, Ullrich

    1993-02-01

    Owing to the close neighbourhood of Ga and As in Mendeleev's table, GaAs shows two fundamental classes of X-ray structure amplitudes distinguished by their extremely different scattering power. They are differently sensitive to the valence electron density (VED) redistribution caused by the chemical bond and must be measured by different experimental methods. Using such data, both the VED and the difference electron densities (DED) are calculated here. Comparison with theoret-ical densities shows that the VED is characterized by covalent, ionic and metallic contributions. The DED constructed from GaAs and Ge data demonstrates the electronic response caused by a "protonic" charge transfer between both f.c.c. sublattices as well as the transition from a purely covalent to a mixed covalent-ionic bond. Especially the charge-density accumulation between nearest neighbours (bond charge (BC)) depends on the distance between the bonding atoms and changes under the influence of any lattice deformation. This phenomenon is described by a BC-transfer model. Its direct experimental proof is given by measuring the variation of the scattering power of weak reflections under the influence of an external electric field. This experiment demonstrates that the ionicity of the bond changes in addition to the BC variation.

  2. The Role of Neutral Atmospheric Dynamics in Cusp Density and Ionospheric Patch Formation

    Science.gov (United States)

    2012-10-01

    direction to reduce its exposure to the winds. Fortunately the Stratospheric Warming experiment was running when a CME hit the Earth at 0617UT on...which are shown by the two red blobs between altitudes of 200-300km in Fig 3a. The second, shorter-lived pulse of increased electron density in the F

  3. Dynamics of the spatial electron density distribution of EUV-induced plasmas

    Science.gov (United States)

    van der Horst, R. M.; Beckers, J.; Osorio, E. A.; Banine, V. Y.

    2015-11-01

    We studied the temporal evolution of the electron density distribution in a low pressure pulsed plasma induced by high energy extreme ultraviolet (EUV) photons using microwave cavity resonance spectroscopy (MCRS). In principle, MCRS only provides space averaged information about the electron density. However, we demonstrate here the possibility to obtain spatial information by combining multiple resonant modes. It is shown that EUV-induced plasmas, albeit being a rather exotic plasma, can be explained by known plasma physical laws and processes. Two stages of plasma behaviour are observed: first the electron density distribution contracts, after which it expands. It is shown that the contraction is due to cooling of the electrons. The moment when the density distribution starts to expand is related to the inertia of the ions. After tens of microseconds, the electrons reached the wall of the cavity. The speed of this expansion is dependent on the gas pressure and can be divided into two regimes. It is shown that the acoustic dominated regime the expansion speed is independent of the gas pressure and that in the diffusion dominated regime the expansion depends reciprocal on the gas pressure.

  4. DYNAMIC DENSITY-FUNCTIONAL THEORY FOR MICROPHASE SEPARATION KINETICS OF BLOCK-COPOLYMER MELTS

    NARCIS (Netherlands)

    FRAAIJE, JGEM

    1993-01-01

    In this paper, we describe a numerical method for the calculation of collective diffusion relaxation mechanisms in quenched block copolymer melts. The method entails the repeated calculation of two opposing fields-an external potential field U, conjugate to the density field rho, and an energetic

  5. Non-destructive image analysis of soil surface porosity and bulk density dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Pires, L.F., E-mail: lfpires@uepg.b [Laboratory of Soil Physics and Environmental Sciences, State University of Ponta Grossa, UEPG, C.E.P. 84.030-900, Ponta Grossa, PR (Brazil); Cassaro, F.A.M. [Laboratory of Soil Physics and Environmental Sciences, State University of Ponta Grossa, UEPG, C.E.P. 84.030-900, Ponta Grossa, PR (Brazil); Bacchi, O.O.S.; Reichardt, K. [Laboratory of Soil Physics, Center for Nuclear Energy in Agriculture, USP/CENA, C.P. 96, C.E.P. 13.400-970, Piracicaba, SP (Brazil)

    2011-04-15

    A gamma-ray computed tomography (CT) scanner was used to evaluate changes in the structure of clayey soil samples with surface compaction submitted to wetting and drying (W-D) cycles. The obtained results indicate that W-D cycles promoted an increasing of about 10% in soil porosity with a decreasing of about 6% in soil bulk density of this compacted region. With the use of the CT it was also possible to define the thickness of the compacted region that in our case was of about 8.19 mm. This last information is very important, for instance, to estimate hydraulic parameters in infiltration models. Finally, CT analysis showed that the compacted region remained at the surface samples, even after the application of the W-D cycles. -- Research highlights: {yields} Gamma-ray tomography allowed non-destructive analysis of soil bulk density and porosity changes. {yields} Soil porosity increased about 10% with the wetting and drying cycles. {yields} Soil bulk density in the compacted region decreased about 6% with the wetting and drying cycles. {yields} Detailed bulk density and porosity analysis changes were obtained for layers of 1.17 mm.

  6. Low density lipoprotein : structure, dynamics, and interactions of apoB-100 with lipids

    NARCIS (Netherlands)

    Murtola, Teemu; Vuorela, Timo A.; Hyvonen, Marja T.; Marrink, Siewert-Jan; Karttunen, Mikko; Vattulainen, Ilpo

    2011-01-01

    Low-density lipoprotein (LDL) transports cholesterol in the bloodstream and plays an important role in the development of cardiovascular diseases, in particular atherosclerosis. Despite its importance to health, the structure of LDL is not known in detail. This is worrying since the lack of LDL's st

  7. An experimental investigation of the dynamics of submarine leveed channel initiation as sediment-laden density currents experience sudden unconfinement

    Energy Technology Data Exchange (ETDEWEB)

    Rowland, Joel C [Los Alamos National Laboratory; Hilley, George E [STANFORD UNIV; Fildani, Andrea [CHEVRON ETC

    2009-01-01

    Leveed submarine channels play a critical role in the transfer of sediment from the upper continental slopes to interslope basins and ultimately deepwater settings. Despite a reasonable understanding of how these channels grow once established, how such channels initiate on previously unchannelized portions of the seafloor remains poorly understood. We conducted a series of experiments that elucidate the influence of excess density relative to flow velocity on the dynamics of, and depositional morphologies arising from, density currents undergoing sudden unconfinement across a sloped bed. Experimental currents transported only suspended sediment across a non-erodible substrate. Under flow conditions ranging from supercritical to subcritical (bulk Richardson numbers of 0.02 to 1.2) our experiments failed to produce deposits resembling or exhibiting the potential to evolve into self-formed leveed channels. In the absence of excess density, a submerged sediment-laden flow produced sharp crested lateral deposits bounding the margins of the flow for approximately a distance of two outlet widths down basin. These lateral deposits terminated in a centerline deposit that greatly exceeded marginal deposits in thickness. As excess density increased relative to the outlet velocity, the rate of lateral spreading of the flow increased relative to the downstream propagation of the density current, transitioning from a narrow flow aligned with the channel outlet to a broad radially expanding flow. Coincident with these changes in flow dynamics, the bounding lateral deposits extended for shorter distances, had lower, more poorly defined crests that were increasingly wider in separation than the initial outlet, and progressively became more oblong rather than linear. Based on our results, we conclude that leveed channels cannot initiate from sediment-laden density currents under strictly depositional conditions. Partial confinement of these currents appears to be necessary to

  8. A dynamic growth model of vegetative soya bean plants: model structure and behaviour under varying root temperature and nitrogen concentration

    Science.gov (United States)

    Lim, J. T.; Wilkerson, G. G.; Raper, C. D. Jr; Gold, H. J.

    1990-01-01

    A differential equation model of vegetative growth of the soya bean plant (Glycine max (L.) Merrill cv. Ransom') was developed to account for plant growth in a phytotron system under variation of root temperature and nitrogen concentration in nutrient solution. The model was tested by comparing model outputs with data from four different experiments. Model predictions agreed fairly well with measured plant performance over a wide range of root temperatures and over a range of nitrogen concentrations in nutrient solution between 0.5 and 10.0 mmol NO3- in the phytotron environment. Sensitivity analyses revealed that the model was most sensitive to changes in parameters relating to carbohydrate concentration in the plant and nitrogen uptake rate.

  9. A dynamic growth model of vegetative soya bean plants: model structure and behaviour under varying root temperature and nitrogen concentration

    Science.gov (United States)

    Lim, J. T.; Wilkerson, G. G.; Raper, C. D. Jr; Gold, H. J.

    1990-01-01

    A differential equation model of vegetative growth of the soya bean plant (Glycine max (L.) Merrill cv. Ransom') was developed to account for plant growth in a phytotron system under variation of root temperature and nitrogen concentration in nutrient solution. The model was tested by comparing model outputs with data from four different experiments. Model predictions agreed fairly well with measured plant performance over a wide range of root temperatures and over a range of nitrogen concentrations in nutrient solution between 0.5 and 10.0 mmol NO3- in the phytotron environment. Sensitivity analyses revealed that the model was most sensitive to changes in parameters relating to carbohydrate concentration in the plant and nitrogen uptake rate.

  10. Shallow Subsurface Soil Moisture Dynamics in the Root-Zone and Bulk Soil of Sparsely Vegetated Land Surfaces as Impacted by Near-Surface Atmospheric State

    Science.gov (United States)

    Trautz, A.; Illangasekare, T. H.; Tilton, N.

    2015-12-01

    Soil moisture is a fundamental state variable that provides the water necessary for plant growth and evapotranspiration. Soil moisture has been extensively studied in the context of bare surface soils and root zones. Less attention has focused on the effects of sparse vegetation distributions, such as those typical of agricultural cropland and other natural surface environments, on soil moisture dynamics. The current study explores root zone, bulk soil, and near-surface atmosphere interactions in terms of soil moisture under different distributions of sparse vegetation using multi-scale laboratory experimentation and numerical simulation. This research is driven by the need to advance our fundamental understanding of soil moisture dynamics in the context of improving water conservation and next generation heat and mass transfer numerical models. Experimentation is performed in a two-dimensional 7.3 m long intermediate scale soil tank interfaced with a climate-controlled wind tunnel, both of which are outfitted with current sensor technologies for measuring atmospheric and soil variables. The soil tank is packed so that a sparsely vegetated soil is surrounded by bulk bare soil; the two regions are separated by porous membranes to isolate the root zone from the bulk soil. Results show that in the absence of vegetation, evaporation rates vary along the soil tank in response to longitudinal changes in humidity; soil dries fastest upstream where evaporation rates are highest. In the presence of vegetation, soil moisture in the bulk soil closest to a vegetated region decreases more rapidly than the bulk soil farther away. Evapotranspiration rates in this region are also higher than the bulk soil region. This study is the first step towards the development of more generalized models that account for non-uniformly distributed vegetation and land surfaces exhibiting micro-topology.

  11. Research on the gear root dynamic stress of the planetary gear transmission%行星齿轮传动齿根动应力计算

    Institute of Scientific and Technical Information of China (English)

    蒋立冬; 李应生; 朱振荣; 陈营利

    2012-01-01

    The workload is big to calculate the gear root stress of the planetary gear transmission because of the big contact ratio, so the gear root dynamic stress was studied in the paper. At the same time, the sun gear in the differential stage of the power dividing planetary transmission was taken an example, the finite element model, meshing and loading method were analyzed in detail. File of load was formed by use of APDL language on Ansys software. It was used for controlling loading on locations of several contact lines in a meshing cycle. Method of calculation in the paper can obtain the gear root dynamic stress on a tooth meshing process precisely and quickly.%针对功率分流行星齿轮传动齿轮重合度大,齿根应力计算工作量大的问题,对齿根动应力的计算问题进行了详细的研究.并以功率分流差动级太阳轮为例,对模型的建立方法、网格的划分方法、载荷的施加方法进行了详细的分析.利用Ansys中的APDL语言形成载荷文件,来控制在1个啮合周期内若干对接触线位置上载荷的施加.本文的计算方法可以精确、快速地得到1个齿在啮合过程中齿根的动应力.

  12. Time-dependent reduced density matrix functional theory applied to laser-driven, correlated two-electron dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Brics, Martins; Kapoor, Varun; Bauer, Dieter [Institut fuer Physik, Universitaet Rostock, 18051 Rostock (Germany)

    2013-07-01

    Time-dependent density functional theory (TDDFT) with known and practicable exchange-correlation potentials does not capture highly correlated electron dynamics such as single-photon double ionization, autoionization, or nonsequential ionization. Time-dependent reduced density matrix functional theory (TDRDMFT) may remedy these problems. The key ingredients in TDRDMFT are the natural orbitals (NOs), i.e., the eigenfunctions of the one-body reduced density matrix (1-RDM), and the occupation numbers (OCs), i.e., the respective eigenvalues. The two-body reduced density matrix (2-RDM) is then expanded in NOs, and equations of motion for the NOs can be derived. If the expansion coefficients of the 2-RDM were known exactly, the problem at hand would be solved. In practice, approximations have to be made. We study the prospects of TDRDMFT following a top-down approach. We solve the exact two-electron time-dependent Schroedinger equation for a model Helium atom in intense laser fields in order to study highly correlated phenomena such as the population of autoionizing states or single-photon double ionization. From the exact wave function we calculate the exact NOs, OCs, the exact expansion coefficients of the 2-RDM, and the exact potentials in the equations of motion. In that way we can identify how many NOs and which level of approximations are necessary to capture such phenomena.

  13. PHASE SEPARATION IN BIMODAL MOLECULAR WEIGHT HIGH DENSITY POLYETHYLENE WITH DIFFERING BRANCH CONTENTS BY MOLECULAR DYNAMICS AND MESODYN SIMULATION

    Institute of Scientific and Technical Information of China (English)

    Zhi-jie Zhang; Zhong-yuan Lu; Ze-sheng Li

    2009-01-01

    The phase behavior of bimodal molecular weight high density polyethylene (BHDPE) in solid state was investigated. Hildebrand solubility parameters (δ) were calculated for the models of blends of higher molecular weight branch polyethylene (HBPE) with different branch contents and lower molecular weight linear polyethylene (LLPE), by using molecular dynamics (MD) simulations. These δ values were then used to calculate the corresponding Flory-Huggins interaction parameter (χ) between HBPE and LLPE models. In order to better understand the compatibility between LLPE and various HBPE, Mesodyn simulations were used to show the density profiles of the blends of LLPE with various HBPE at different compositions. The results indicated that the phase behavior of BHDPE was influenced by both the global branch content of the system and the local branch content, I.e., the branch content of HBPE.

  14. Electron-Ion Dynamics with Time-Dependent Density Functional Theory: Towards Predictive Solar Cell Modeling: Final Technical Report

    Energy Technology Data Exchange (ETDEWEB)

    Maitra, Neepa [Hunter College City University of New York, New York, NY (United States)

    2016-07-14

    This project investigates the accuracy of currently-used functionals in time-dependent density functional theory, which is today routinely used to predict and design materials and computationally model processes in solar energy conversion. The rigorously-based electron-ion dynamics method developed here sheds light on traditional methods and overcomes challenges those methods have. The fundamental research undertaken here is important for building reliable and practical methods for materials discovery. The ultimate goal is to use these tools for the computational design of new materials for solar cell devices of high efficiency.

  15. Low Density Supersonic Decelerator (LDSD) Supersonic Flight Dynamics Test (SFDT) Plume Induced Environment Modelling

    Science.gov (United States)

    Mobley, B. L.; Smith, S. D.; Van Norman, J. W.; Muppidi, S.; Clark, I

    2016-01-01

    Provide plume induced heating (radiation & convection) predictions in support of the LDSD thermal design (pre-flight SFDT-1) Predict plume induced aerodynamics in support of flight dynamics, to achieve targeted freestream conditions to test supersonic deceleration technologies (post-flight SFDT-1, pre-flight SFDT-2)

  16. The Dynamical Masses, Densities, and Star Formation Scaling Relations of Lyman Alpha Galaxies

    CERN Document Server

    Rhoads, James E; Finkelstein, Steven L; Fynbo, Johan P U; McLinden, Emily M; Richardson, Mark L A; Tilvi, Vithal S

    2013-01-01

    We present the first dynamical mass measurements for Lyman alpha galaxies at high redshift, based on velocity dispersion measurements from rest-frame optical emission lines and size measurements from HST imaging, for a sample of nine galaxies drawn from four surveys. These measurements enable us to study the nature of Lyman alpha galaxies in the context of galaxy scaling relations. The resulting dynamical masses range from 1e9 to 1e10 solar masses. We also fit stellar population models to our sample, and use them to plot the Lyman alpha sample on a stellar mass vs. line width relation. Overall, the Lyman alpha galaxies follow well the scaling relation established by observing star forming galaxies at lower redshift (and without regard for Lyman alpha emission), though in 1/3 of the Lyman alpha galaxies, lower-mass fits are also acceptable. In all cases, the dynamical masses agree with established stellarmass-linewidth relation. Using the dynamical masses as an upper limit on gas mass, we show that Lyman alpha...

  17. Transport dynamics of a high-power-density matrix-type hydrogen-oxygen fuel cell

    Science.gov (United States)

    Prokopius, P. R.; Hagedorn, N. H.

    1974-01-01

    Experimental transport dynamics tests were made on a space power fuel cell of current design. Various operating transients were introduced and transport-related response data were recorded with fluidic humidity sensing instruments. Also, sampled data techniques were developed for measuring the cathode-side electrolyte concentration during transient operation.

  18. Lane Formation Dynamics of Oppositely Self-Driven Binary Particles: Effects of Density and Finite System Size

    Science.gov (United States)

    Ikeda, Kosuke; Kim, Kang

    2017-04-01

    We examined the lane formation dynamics of oppositely self-driven binary particles by molecular dynamics simulations of a two-dimensional system. Our study comprehensively revealed the effects of the density and system size on the lane formation. The phase diagram distinguishing the no-lane and lane states was systematically determined for various combinations of the anisotropic friction coefficient and the desired velocity. A peculiar clustered structure was observed when the lane was destroyed by considerably increasing the desired velocity. A strong system size effect was demonstrated by the relationship between the temporal and spatial scales of the lane structure. This system size effect can be attributed to an analogy with the driven lattice gas. The transport efficiency was characterized from the scaling relation in terms of the degree of lane formation and the interface thickness between different lanes.

  19. Density Functional Study of the Carbon Dependence of the Structural, Mechanic, Thermodynamic, and Dynamic Properties of SiC Alloys

    Science.gov (United States)

    Langueur, H.; Kassali, K.

    2017-03-01

    Using a density functional scheme, for the first time the carbon dependence on the structural, dynamic, thermodynamic, and dynamic properties of Si_{1-x}Cx alloys (x=0.0 to 1.0 in steps of 0.125) has been investigated. The structural properties of these materials, in particular, the composition dependence of the lattice parameter and bulk modulus, are in excellent agreement with experimental data and follow a quadratic law in ( x). A nonlinear relationship is found between the elastic constants C_{11}, C_{12}, and C_{44} and the carbon concentration ( x). The behavior of the acoustical and optical phonon frequencies at high-symmetry points Γ, X, and L is predicted. Through the quasi-harmonic Debye model, in which the photonic effects are taken into account, the Debye temperature, the heat capacity, the Helmholtz free energy, the internal energy, and the entropy are determined for the Si_{1-x}C_{x } compounds.

  20. Characterization of root response to phosphorus supply from morphology to gene analysis in field-grown wheat.

    Science.gov (United States)

    Teng, Wan; Deng, Yan; Chen, Xin-Ping; Xu, Xiao-Feng; Chen, Ri-Yuan; Lv, Yang; Zhao, Yan-Yan; Zhao, Xue-Qiang; He, Xue; Li, Bin; Tong, Yi-Ping; Zhang, Fu-Suo; Li, Zhen-Sheng

    2013-03-01

    The adaptations of root morphology, physiology, and biochemistry to phosphorus supply have been characterized intensively. However, characterizing these adaptations at molecular level is largely neglected under field conditions. Here, two consecutive field experiments were carried out to investigate the agronomic traits and root traits of wheat (Triticum aestivum L.) at six P-fertilizer rates. Root samples were collected at flowering to investigate root dry weight, root length density, arbusular-mycorrhizal colonization rate, acid phosphatase activity in rhizosphere soil, and expression levels of genes encoding phosphate transporter, phosphatase, ribonucleases, and expansin. These root traits exhibited inducible, inhibitory, or combined responses to P deficiency, and the change point for responses to P supply was at or near the optimal P supply for maximum grain yield. This research improves the understanding of mechanisms of plant adaptation to soil P in intensive agriculture and provides useful information for optimizing P management based on the interactions between soil P dynamics and root processes.

  1. Molecular-dynamics approach for studying the nonequilibrium behavior of x-ray-heated solid-density matter

    Science.gov (United States)

    Abdullah, Malik Muhammad; Anurag, Jurek, Zoltan; Son, Sang-Kil; Santra, Robin

    2017-08-01

    When matter is exposed to a high-intensity x-ray free-electron-laser pulse, the x rays excite inner-shell electrons leading to the ionization of the electrons through various atomic processes and creating high-energy-density plasma, i.e., warm or hot dense matter. The resulting system consists of atoms in various electronic configurations, thermalizing on subpicosecond to picosecond timescales after photoexcitation. We present a simulation study of x-ray-heated solid-density matter. For this we use XMDYN, a Monte Carlo molecular-dynamics-based code with periodic boundary conditions, which allows one to investigate nonequilibrium dynamics. XMDYN is capable of treating systems containing light and heavy atomic species with full electronic configuration space and three-dimensional spatial inhomogeneity. For the validation of our approach we compare for a model system the electron temperatures and the ion charge-state distribution from XMDYN to results for the thermalized system based on the average-atom model implemented in XATOM, an ab initio x-ray atomic physics toolkit extended to include a plasma environment. Further, we also compare the average charge evolution of diamond with the predictions of a Boltzmann continuum approach. We demonstrate that XMDYN results are in good quantitative agreement with the above-mentioned approaches, suggesting that the current implementation of XMDYN is a viable approach to simulate the dynamics of x-ray-driven nonequilibrium dynamics in solids. To illustrate the potential of XMDYN for treating complex systems, we present calculations on the triiodo benzene derivative 5-amino-2,4,6-triiodoisophthalic acid (I3C), a compound of relevance of biomolecular imaging, consisting of heavy and light atomic species.

  2. Spatiotemporal neural dynamics of moral judgment: A high-density ERP study

    OpenAIRE

    Yoder, Keith J.; Decety, Jean

    2014-01-01

    Morality is a pervasive aspect of human nature across all cultures, and neuroscience investigations are necessary for identifying what computational mechanisms underpin moral cognition. The current study used high-density ERPs to examine how moral evaluations are mediated by automatic and controlled processes as well as how quickly information and causal-intentional representations can be extracted when viewing morally laden behavior. The study also explored the extent to which individual dis...

  3. Study of Fusion Dynamics Using Skyrme Energy Density Formalism with Different Surface Corrections

    Institute of Scientific and Technical Information of China (English)

    Ishwar Dutt; Narinder K. Dhiman

    2010-01-01

    @@ Within the framework of Skyrme energy density formalism, we investigate the role of surface corrections on the fusion of colliding nuclei. The coefficient of surface correction is varied between 1/36 and 4/36, and its impact is studied on about 180 reactions. The detailed investigations indicate a linear relationship between the fusion barrier heights and strength of the surface corrections. Our analysis of the fusion barriers advocate the strength of surface correction of 1/36.

  4. Field-Induced Dynamic Diamagnetism in a Charge-Density-Wave System

    Science.gov (United States)

    Harrison, N.; Mielke, C. H.; Christianson, A. D.; Brooks, J. S.; Tokumoto, M.

    2001-02-01

    ac susceptibility measurements of the charge-density-wave (CDW) compound α-\\(BEDT-TTF\\)2-KHg\\(SCN\\)4 at magnetic fields, μ0H>23 T, above its Pauli paramagnetic limit, reveal unambiguously that the magnetic hysteresis observed previously within this CDW phase is diamagnetic and can only be explained by induced currents. It is argued that the ensemble of experimental techniques amounts to a strong case for dissipationless conductivity within this phase.

  5. Complex Langevin Dynamics in 1+1d QCD at Non-Zero Densities

    CERN Document Server

    Schmalzbauer, Sebastian

    2016-01-01

    We present our results obtained from gauge cooled complex Langevin simulations in 1+1d QCD at non-zero densities in the strong coupling regime with unrooted staggered fermions. For small quark masses there are regions of the chemical potential where this method fails to reproduce correct results. In these parameter ranges we studied the effect of different gauge cooling schemes on the distributions of the fermion determinant as well as of observables.

  6. Nuclear single-particle states: dynamical shell model and energy density functional methods

    CERN Document Server

    Bortignon, P F; Sagawa, H

    2010-01-01

    We discuss different approaches to the problem of reproducing the observed features of nuclear single-particle (s.p.) spectra. In particular, we analyze the dominant energy peaks, and the single-particle strength fragmentation, using the example of neutron states in 208Pb. Our main emphasis is the interpretation of that fragmentation as due to particle-vibration coupling (PVC). We compare with recent Energy Density Functional (EDF) approaches, and try to present a critical perspective.

  7. A density matrix functional with occupation number driven treatment of dynamical and nondynamical correlation.

    Science.gov (United States)

    Rohr, Daniel R; Pernal, Katarzyna; Gritsenko, Oleg V; Baerends, Evert Jan

    2008-10-28

    A recently proposed series of corrections to the earliest JK-only functionals has considerably improved the prospects of density matrix functional theory (DMFT). Still, the most advanced of these functionals (correction C3) requires a preselection of the terms in the pair density Gamma(r(1),r(2)) involving the bonding and antibonding natural orbitals (NOs) belonging to an electron pair bond. Ideally, a DMFT functional should only depend on the NOs and their occupation numbers, and we propose a functional with an occupation number driven weighing of terms in the pair density. These are formulated as "damping" for certain ranges of occupation numbers of the two-electron cumulant that arises in the expansion of the two-particle density matrix of the paradigmatic two-electron system. This automatic version of C3, which we denote AC3, provides the correct dissociation limit for electron pair bonds and it excellently reproduces the potential energy curves of the multireference configuration interaction (MRCI) method for the dissociation of the electron pair bond in the series of the ten-electron hydrides CH(4), NH(3), H(2)O, and HF. AC3 reproduces closely the experimental equilibrium distances and at R(e) it yields correlation energies of the ten-electron systems with an average error in the absolute values of only 3.3% compared to the MRCI values. We stress the importance of treatment of strong correlation cases (NO occupation numbers differing significantly from 2.0 and 0.0) by appropriate terms in the cumulant.

  8. High Energy-Density Plasma Dynamics in Plasma-Filled Rod-Pinch Diodes

    Science.gov (United States)

    2013-06-01

    at about 30 eV at the time of maximum energy density, and that the time-averaged ionization is about +17, similar to MHD model predictions [2... MHD model predictions [2]. The plasma mass distribution is inferred from x-ray distribution measurements. The time-dependent mass distribution is used...Previous modeling [2] assumed the tungsten plasma had a time-dependent Gaussian radial profile and a fixed length of 3.5 mm, consistent with time

  9. Wolbachia-Host Interactions: Host Mating Patterns Affect Wolbachia Density Dynamics

    OpenAIRE

    Dong-Xiao Zhao; Xiang-Fei Zhang; Da-Song Chen; Yan-Kai Zhang; Xiao-Yue Hong

    2013-01-01

    Wolbachia are maternally inherited intracellular bacteria that infect a wide range of arthropods and cause an array of effects on host reproduction, fitness and mating behavior. Although our understanding of the Wolbachia-associated effects on hosts is rapidly expanding, our knowledge of the host factors that mediate Wolbachia dynamics is rudimentary. Here, we explore the interactions between Wolbachia and its host, the two-spotted spider mite Tetranychus urticae Koch. Our results indicate th...

  10. The interface of SrTiO3 and H2O from density functional theory molecular dynamics

    Science.gov (United States)

    Holmström, E.; Spijker, P.; Foster, A. S.

    2016-09-01

    We use dispersion-corrected density functional theory molecular dynamics simulations to predict the ionic, electronic and vibrational properties of the SrTiO3/H2O solid-liquid interface. Approximately 50% of surface oxygens on the planar SrO termination are hydroxylated at all studied levels of water coverage, the corresponding number being 15% for the planar TiO2 termination and 5% on the stepped TiO2-terminated surface. The lateral ordering of the hydration structure is largely controlled by covalent-like surface cation to H2O bonding and surface corrugation. We find a featureless electronic density of states in and around the band gap energy region at the solid-liquid interface. The vibrational spectrum indicates redshifting of the O-H stretching band due to surface-to-liquid hydrogen bonding and blueshifting due to high-frequency stretching vibrations of OH fragments within the liquid, as well as strong suppression of the OH stretching band on the stepped surface. We find highly varying rates of proton transfer above different SrTiO3 surfaces, owing to differences in hydrogen bond strength and the degree of dissociation of incident water. Trends in proton dynamics and the mode of H2O adsorption among studied surfaces can be explained by the differential ionicity of the Ti-O and Sr-O bonds in the SrTiO3 crystal.

  11. Dynamics of the Leeuwin Current: Part 1. Coastal flows in an inviscid, variable-density, layer model

    Science.gov (United States)

    Furue, Ryo; McCreary, Julian P.; Benthuysen, Jessica; Phillips, Helen E.; Bindoff, Nathaniel L.

    2013-09-01

    In this paper, we investigate basic dynamics of the Leeuwin Current (LC) using a dynamically "minimal" model, one that lies at the bottom of a planned hierarchy of LC models. The model is a steady-state, inviscid, 2-layer system, in which the upper-layer density is fixed to ρ1(y), all mixing and advection are ignored, and β ≠ 0. As a result, solutions can be obtained analytically. Our model both simplifies and extends prior models of this sort, which include bottom drag in a fundamental way and adopt the f-plane. Solutions are obtained in a semi-infinite domain, x ≤ xe, y ≤ yn, in the southern hemisphere (yn LC deepens poleward; there is downwelling over the shelf, as well as westward flow at the bottom of the upper layer, both associated with the thermal-wind circulation and existing only when β ≠ 0; the speed of the coastal jet is proportional to ∂D/∂x; and its transport is proportional to H12, so that it is strongest farther offshore and is very sensitive to the specified thermocline thickness in the northern basin. When equatorward wind stress is included, an equatorward jet can develop very nearshore provided that the wind stress is strong enough to overcome the density forcing.

  12. Molecular Dynamical Simulation of Ice Phase Transition: Ice Ih to High-Density Amorphous

    Institute of Scientific and Technical Information of China (English)

    DONG Shun-Le; WANG Yan

    2005-01-01

    @@ We put 5kbar and 12kbar on perfect ice Ih lattice at 77K and 180K. After 30000 simulation steps (in units of 10-15 s), high-density amorphous ice is formed. Four-site simple-pair potential TIP4P is used for molecular interactions and the rigid molecular model is employed. Phase transition processes are fitted by an exponential function, and different phase transition times τ are obtained from O-O radial distribution functions (366 and 359fs for 77K and 180K) and O-O-O angle distribution functions (126 and 116fs for 77K and 180K).

  13. A Dynamic Density Functional Theory Approach to Diffusion in White Dwarfs and Neutron Star Envelopes

    Science.gov (United States)

    Diaw, A.; Murillo, M. S.

    2016-09-01

    We develop a multicomponent hydrodynamic model based on moments of the Born-Bogolyubov-Green-Kirkwood-Yvon hierarchy equations for physical conditions relevant to astrophysical plasmas. These equations incorporate strong correlations through a density functional theory closure, while transport enters through a relaxation approximation. This approach enables the introduction of Coulomb coupling correction terms into the standard Burgers equations. The diffusive currents for these strongly coupled plasmas is self-consistently derived. The settling of impurities and its impact on cooling can be greatly affected by strong Coulomb coupling, which we show can be quantified using the direct correlation function.

  14. Modelling of the internal dynamics and density in a tens of joules plasma focus device

    Energy Technology Data Exchange (ETDEWEB)

    Marquez, Ariel [CNEA and Instituto Balseiro, 8402 Bariloche (Argentina); Gonzalez, Jose [INVAP-CONICET and Instituto Balseiro, 8402 Bariloche, Argentina. (Argentina); Tarifeno-Saldivia, Ariel; Pavez, Cristian; Soto, Leopoldo [CCHEN, Comision Chilena de Energia Nuclear, Casilla 188-D, Santiago (Chile); Center for Research and Applications in Plasma Physics and Pulsed Power, P4 (Chile); Clausse, Alejandro [CNEA-CONICET and Universidad Nacional del Centro, 7000 Tandil (Argentina)

    2012-01-15

    Using MHD theory, coupled differential equations were generated using a lumped parameter model to describe the internal behaviour of the pinch compression phase in plasma focus discharges. In order to provide these equations with appropriate initial conditions, the modelling of previous phases was included by describing the plasma sheath as planar shockwaves. The equations were solved numerically, and the results were contrasted against experimental measurements performed on the device PF-50J. The model is able to predict satisfactorily the timing and the radial electron density profile at the maximum compression.

  15. Population dynamics models based on cumulative density dependent feedback: A link to the logistic growth curve and a test for symmetry using aphid data

    NARCIS (Netherlands)

    Matis, J.H.; Kiffe, T.R.; Werf, van der W.; Costamagna, A.C.; Matis, T.I.; Grant, W.E.

    2009-01-01

    Density dependent feedback, based on cumulative population size, has been advocated to explain and mathematically characterize “boom and bust” population dynamics. Such feedback results in a bell-shaped population trajectory of the population density. Here, we note that this trajectory is mathematic

  16. Population dynamics of three songbird species in a nestbox population in Central Europe show effects of density, climate and competitive interactions

    NARCIS (Netherlands)

    Smallegange, I.M.; van der Meer, J.; Fiedler, W.

    2011-01-01

    Unravelling the contributions of density-dependent and density-independent factors in determining species population dynamics is a challenge, especially if the two factors interact. One approach is to apply stochastic population models to long-term data, yet few studies have included interactions

  17. Dynamics of laser-driven proton beam focusing and transport into solid density matter

    Science.gov (United States)

    Kim, J.; McGuffey, C.; Beg, F.; Wei, M.; Mariscal, D.; Chen, S.; Fuchs, J.

    2016-10-01

    Isochoric heating and local energy deposition capabilities make intense proton beams appealing for studying high energy density physics and the Fast Ignition of inertial confinement fusion. To study proton beam focusing that results in high beam density, experiments have been conducted using different target geometries irradiated by a kilojoule, 10 ps pulse of the OMEGA EP laser. The beam focus was measured by imaging beam-induced Cu K-alpha emission on a Cu foil that was positioned at a fixed distance. Compared to a free target, structured targets having shapes of wedge and cone show a brighter and narrower K-alpha radiation emission spot on a Cu foil indicating higher beam focusability. Experimentally observed images with proton radiography demonstrate the existence of transverse fields on the structures. Full-scale simulations including the contribution of a long pulse duration of the laser confirm that such fields can be caused by hot electrons moving through the structures. The simulated fields are strong enough to reflect the diverging main proton beam and pinch a transverse probe beam. Detailed simulation results including the beam focusing and transport of the focused intense proton beam in Cu foil will be presented. This work was supported by the National Laser User Facility Program through Award DE-NA0002034.

  18. Spatiotemporal neural dynamics of moral judgment: a high-density ERP study.

    Science.gov (United States)

    Yoder, Keith J; Decety, Jean

    2014-07-01

    Morality is a pervasive aspect of human nature across all cultures, and neuroscience investigations are necessary for identifying what computational mechanisms underpin moral cognition. The current study used high-density ERPs to examine how moral evaluations are mediated by automatic and controlled processes as well as how quickly information and causal-intentional representations can be extracted when viewing morally laden behavior. The study also explored the extent to which individual dispositions in affective and cognitive empathy as well as justice sensitivity influence the encoding of moral valence when healthy participants make moral judgments about prosocial (interpersonal assistance) and antisocial (interpersonal harm) actions. Moral judgment differences were reflected in differential amplitudes for components associated with cognitive appraisal (LPP) as well as early components associated with emotional salience (N1 and N2). Moreover, source estimation was performed to indicate potential neural generators. A posterior-to-anterior shift was observed, with current density peaks first in right inferior parietal cortex (at the temporoparietal junction), then later in medial prefrontal cortex. Cognitive empathy scores predicted behavioral ratings of blame as well as differential amplitudes in LPP and component activity at posterior sites. Overall, this study offers important insights into the temporal unfolding of moral evaluations, including when in time individual differences in empathy influence neural encoding of moral valence.

  19. Static and Dynamic Electronic (Hyperpolarizabilities of Dimethylnaphthalene Isomers: Characterization of Spatial Contributions by Density Analysis

    Directory of Open Access Journals (Sweden)

    Andrea Alparone

    2013-01-01

    Full Text Available Static and frequency-dependent electronic (hyperpolarizabilities of the dimethylnaphthalene (DMN isomers were computed in vacuum using the Coulomb-attenuating Density Functional Theory method. The nonlinear optical Second Harmonic Generation (SHG and Electro-Optical Pockels Effect (EOPE were investigated at the characteristic Nd:YAG laser wavelength of 1064 nm. The response electric properties especially the longitudinal polarizability, polarizability anisotropy, and first-order hyperpolarizability are significantly affected by the position of the methyl groups. The SHG and EOPE techniques can be potentially useful to discriminate the ,-DMN isomers (2,6-DMN < 2,7-DMN < 2,3-DMN as well as the ,-DMN isomers (1,5-DMN < 1,4-DMN < 1,8-DMN. The (hyperpolarizability differences among the investigated DMNs were elucidated through density analysis calculations. The predicted polarizabilities exhibit good linear relationships with the experimental first-order biomass-normalized rate coefficient, a physicochemical property connected to the rates of biodegradation processes of polycyclic aromatic hydrocarbons.

  20. Application of a single root-scale model to improve macroscopic modeling of root water uptake: focus on osmotic stress

    Science.gov (United States)

    Jorda, Helena; Perelman, Adi; Lazarovitch, Naftali; Vanderborght, Jan

    2017-04-01

    Root water uptake is a fundamental process in the hydrological cycle and it largely regulates the water balance in the soil vadose zone. Macroscopic stress functions are currently used to estimate the effect of salinity on root water uptake. These functions commonly assume stress to be a function of bulk salinity and of the plant sensitivity to osmotic stress expressed as the salinity at which transpiration is reduced by half or so called tolerance value. However, they fail to integrate additional relevant factors such as atmospheric conditions or root architectural traits. We conducted a comprehensive simulation study on a single root using a 3-D physically-based model that resolves flow and transport to individual root segments and that couples flow in the soil and root system. The effect of salt concentrations on root water uptake was accounted for by including osmotic water potential gradients between the solution at the soil root interface and the root xylem sap in the hydraulic gradient between the soil and root. A large set of factors were studied, namely, potential transpiration rate and dynamics, root length density (RLD), irrigation water quality and irrigation frequency, and leaching fraction. Results were fitted to the macroscopic function developed by van Genuchten and Hoffman (1984) and the dependency of osmotic stress and the fitted macroscopic parameters on the studied factors was evaluated. Osmotic stress was found to be highly dependent on RLD. Low RLDs result in a larger stress to the plant due to high evaporative demand per root length unit. In addition, osmotic stress was positively correlated to potential transpiration rate, and sinusoidal potential transpiration lead to larger stress than when imposed as a constant boundary condition. Macroscopic parameters are usually computed as single values for each crop and used for the entire growing season. However, our study shows that both tolerance value and shape parameter p from the van Genuchten

  1. The Rapidity Density Distributions and Longitudinal Expansion Dynamics of Identified Pions from the STAR Beam Energy Scan

    Science.gov (United States)

    Flores, Christopher E.

    2016-12-01

    The Beam Energy Scan (BES) at the Relativistic Heavy-Ion Collider was proposed to characterize the properties of the medium produced in heavy-ion interactions over a broad range of baryon chemical potential. The aptitude of the STAR detector for mid-rapidity measurements has previously been leveraged to measure identified particle yields and spectra to extract bulk properties for the BES energies for | y | ≤ 0.1. However, to extract information on expansion dynamics and full phase space particle production, it is necessary to study identified particle rapidity density distributions. We present the first rapidity density distributions of identified pions from Au+Au collisions at √{sNN} = 7.7 , 11.5, and 19.6 GeV from the BES program as measured by the STAR detector. We use these distributions to obtain the full phase space yields of the pions to provide additional information of the system's chemistry. Further, we report the width of the rapidity density distributions compared to the width expected from Landau hydrodynamics. Finally, we interpret the results as a function of collision energy and discuss them in the context of previous energy scans done at the AGS and SPS.

  2. Dynamics of a low-density tiger population in Southeast Asia in the context of improved law enforcement.

    Science.gov (United States)

    Duangchantrasiri, Somphot; Umponjan, Mayuree; Simcharoen, Saksit; Pattanavibool, Anak; Chaiwattana, Soontorn; Maneerat, Sompoch; Kumar, N Samba; Jathanna, Devcharan; Srivathsa, Arjun; Karanth, K Ullas

    2016-06-01

    Recovering small populations of threatened species is an important global conservation strategy. Monitoring the anticipated recovery, however, often relies on uncertain abundance indices rather than on rigorous demographic estimates. To counter the severe threat from poaching of wild tigers (Panthera tigris), the Government of Thailand established an intensive patrolling system in 2005 to protect and recover its largest source population in Huai Kha Khaeng Wildlife Sanctuary. Concurrently, we assessed the dynamics of this tiger population over the next 8 years with rigorous photographic capture-recapture methods. From 2006 to 2012, we sampled across 624-1026 km(2) with 137-200 camera traps. Cameras deployed for 21,359 trap days yielded photographic records of 90 distinct individuals. We used closed model Bayesian spatial capture-recapture methods to estimate tiger abundances annually. Abundance estimates were integrated with likelihood-based open model analyses to estimate rates of annual and overall rates of survival, recruitment, and changes in abundance. Estimates of demographic parameters fluctuated widely: annual density ranged from 1.25 to 2.01 tigers/100 km(2) , abundance from 35 to 58 tigers, survival from 79.6% to 95.5%, and annual recruitment from 0 to 25 tigers. The number of distinct individuals photographed demonstrates the value of photographic capture-recapture methods for assessments of population dynamics in rare and elusive species that are identifiable from natural markings. Possibly because of poaching pressure, overall tiger densities at Huai Kha Khaeng were 82-90% lower than in ecologically comparable sites in India. However, intensified patrolling after 2006 appeared to reduce poaching and was correlated with marginal improvement in tiger survival and recruitment. Our results suggest that population recovery of low-density tiger populations may be slower than anticipated by current global strategies aimed at doubling the number of wild tigers

  3. Relative weights approach to SU(3) gauge theories with dynamical fermions at finite density

    CERN Document Server

    Höllwieser, Roman

    2016-01-01

    We derive effective Polyakov line actions for SU(3) gauge theories with staggered dynamical fermions, for a small sample of lattice couplings, lattice actions, and lattice extensions in the time direction. The derivation is via the method of relative weights, and the theories are solved at finite chemical potential by mean field theory. We find in some instances that the long-range couplings in the effective action are very important to the phase structure, and that these couplings are responsible for long-lived metastable states in the effective theory. Only one of these states corresponds to the underlying lattice gauge theory.

  4. Advances in experimental methods for root system architecture and root development

    Institute of Scientific and Technical Information of China (English)

    Jun-bang Wang; Xiu-juan Zhang; Chu Wu

    2015-01-01

    Plant roots play important roles in acquisition of water and nutrients, storage, anchoring, transport, and symbiosis with soil microorganisms, thus quantitative researches on root developmental processes are essential to understand root functions and root turnover in ecosystems, and at the same time such researches are the most difficult because roots are hidden underground. Therefore, how to investigate efficiently root functions and root dynamics is the core aspect in underground ecology. In this article, we reviewed some experimental methods used in root resear-ches on root development and root system architecture, and summarized the advantages and shortages of these meth-ods. Based on the analyses, we proposed three new ways to more understand root processes: (1) new experimental materials for root development; (2) a new observatory system comprised of multiple components, including many observatory windows installed in field, analysis software, and automatic data transport devices; (3) new techniques used to analyze quantitatively functional roots.

  5. Dynamics of a recovering Arctic bird population: the importance of climate, density dependence, and site quality.

    Science.gov (United States)

    Bruggeman, Jason E; Swem, Ted; Andersen, David E; Kennedy, Patricia L; Nigro, Debora

    2015-10-01

    Intrinsic and extrinsic factors affect vital rates and population-level processes, and understanding these factors is paramount to devising successful management plans for wildlife species. For example, birds time migration in response, in part, to local and broadscale climate fluctuations to initiate breeding upon arrival to nesting territories, and prolonged inclement weather early in the breeding season can inhibit egg-laying and reduce productivity. Also, density-dependent regulation occurs in raptor populations, as territory size is related to resource availability. Arctic Peregrine Falcons (Falco peregrinus tundrius; hereafter Arctic peregrine) have a limited and northern breeding distribution, including the Colville River Special Area (CRSA) in the National Petroleum Reserve-Alaska, USA. We quantified influences of climate, topography, nest productivity, prey habitat, density dependence, and interspecific competition affecting Arctic peregrines in the CRSA by applying the Dail-Madsen model to estimate abundance and vital rates of adults on nesting cliffs from 1981 through 2002. Arctic peregrine abundance increased throughout the 1980s, which spanned the population's recovery from DDT-induced reproductive failure, until exhibiting a stationary trend in the 1990s. Apparent survival rate (i.e., emigration; death) was negatively correlated with the number of adult Arctic peregrines on the cliff the previous year, suggesting effects of density-dependent population regulation. Apparent survival and arrival rates (i.e., immigration; recruitment) were higher during years with earlier snowmelt and milder winters, and apparent survival was positively correlated with nesting season maximum daily temperature. Arrival rate was positively correlated with average Arctic peregrine productivity along a cliff segment from the previous year and initial abundance was positively correlated with cliff height. Higher cliffs with documented higher productivity (presumably

  6. Interpretation of the Isabella High Wave-Speed Anomaly as the Partially Delaminated High-Density Root of the Southern Sierra Nevada Batholith, California

    Science.gov (United States)

    Saleeby, J.; Le Pourhiet, L.

    2012-12-01

    runs is a chain of events that initiates with the basal thermal perturbation and load of the arclogite root inducing Rayleigh-Taylor (RT) instability within the peridotitic lithosphere, as well as the development of a lower crustal channel along the eastern margin of root, which draws lower crust into the eastern Sierra region from the adjacent Basin and Range. These lead to a lithospheric break-off event that corresponds to the ca. 10 Ma inception of the Sierra Nevada microplate, and which further promotes the east to west delamination of the arclogite root. Initial topography is shown to influence the asymmetry of delamination. Much of our model experimentation consists of testing the influence of crustal rheology on model results. We find that a relatively weak crust for the entire microplate best reproduces rock uplift and tectonic subsidence observations, as well as the timing and source characteristics of observed volcanism. We apply the findings of our 2-D models to 3-D relationships across the southern Sierra region in order to elucidate the time transgressive patterns in uplift, subsidence, volcanism and shallow thermal anomalies in relation to the 3-D delamination of the root, and the production of the higher Vp core of the anomaly. These relations suggest a significant compositional component to the core area of the anomaly (deformed arclogite slab), while the peridotitic envelope produces a broad thermally-induced wave-speed anomaly.

  7. Assessment of dynamic modulus of high density polypropylene waste fiber reinforcement in asphalt concrete

    Directory of Open Access Journals (Sweden)

    Hassan S. OTUOZE

    2015-12-01

    Full Text Available Traditional asphalt tests like Hveem and Marshall tests are at best mere characterization than effective test of pavement field performance because of complex viscoelastic behavior of asphalt. Mechanical properties otherwise called simple performance tests (SPT are performance criteria of asphalt. Dynamic modulus among other SPT’s like permanent deformation, fatigue cracking, thermal cracking, moisture susceptibility, shear and friction properties; determines stress-strain to time-temperature relationships that imparts on strength, service life and durability. The test followed the recommendations of NCHRP 1-37a (2004 and mixes were prepared using 0, 0.5, 1.0 and 1.5% HDPP contents. The parameters tested for dynamic modulus, /E*/, are stiffness, recoverable strain (ε, and phase angle (ξ. Time – temperature superposition (TTS called master curve was fitted using sigmoidal curve to interpolate the parameters beyond measured data set so as to observe the viscoelastic behavior outside the physical properties. The performance of 0.5% HDPP asphalt is better enhanced than the conventional asphalt to improve upon strength, service and durability.