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Sample records for blidingia minima ulvales

  1. Exploring bacteria-induced growth and morphogenesis in the green macroalga order Ulvales (Chlorophyta)

    PubMed Central

    Wichard, Thomas

    2015-01-01

    Green macroalgae, such as Ulvales, lose their typical morphology completely when grown under axenic conditions or in the absence of the appropriate microbiome. As a result, slow growing aberrant phenotypes or even callus-like morphotypes are observed in Ulvales. The cross-kingdom interactions between marine algae and microorganisms are hence not only restricted by the exchange of macronutrients, including vitamins and nutrients, but also by infochemicals such as bacterial morphogenetic compounds. The latter are a fundamental trait mediating the mutualism within the chemosphere where the organisms interact with each other via compounds in their surroundings. Approximately 60 years ago, pilot studies demonstrated that certain bacteria promote growth, whereas other bacteria induce morphogenesis; this is particularly true for the order of Ulvales. However, only slow progress was made towards the underlying mechanism due to the complexity of, for example, algal cultivation techniques, and the lack of standardized experiments in the laboratory. A breakthrough in this research was the discovery of the morphogenetic compound thallusin, which was isolated from an epiphytic bacterium and induces normal germination restoring the foliaceous morphotypes of Monostroma. Owing to the low concentration, the purification and structure elucidation of highly biologically active morphogenetic compounds are still challenging. Recently, it was found that only the combination of two specific bacteria from the Rhodobacteraceae and Flavobacteriaceae can completely recover the growth and morphogenesis of axenic Ulva mutabilis cultures forming a symbiotic tripartite community by chemical communication. This review combines literature detailing evidences of bacteria-induced morphogenesis in Ulvales. A set of standardized experimental approaches is further proposed for the preparation of axenic algal tissues, bacteria isolation, co-cultivation experiments, and the analysis of the chemosphere

  2. Exploring bacteria-induced growth and morphogenesis in the green macroalga order Ulvales (Chlorophyta).

    PubMed

    Wichard, Thomas

    2015-01-01

    Green macroalgae, such as Ulvales, lose their typical morphology completely when grown under axenic conditions or in the absence of the appropriate microbiome. As a result, slow growing aberrant phenotypes or even callus-like morphotypes are observed in Ulvales. The cross-kingdom interactions between marine algae and microorganisms are hence not only restricted by the exchange of macronutrients, including vitamins and nutrients, but also by infochemicals such as bacterial morphogenetic compounds. The latter are a fundamental trait mediating the mutualism within the chemosphere where the organisms interact with each other via compounds in their surroundings. Approximately 60 years ago, pilot studies demonstrated that certain bacteria promote growth, whereas other bacteria induce morphogenesis; this is particularly true for the order of Ulvales. However, only slow progress was made towards the underlying mechanism due to the complexity of, for example, algal cultivation techniques, and the lack of standardized experiments in the laboratory. A breakthrough in this research was the discovery of the morphogenetic compound thallusin, which was isolated from an epiphytic bacterium and induces normal germination restoring the foliaceous morphotypes of Monostroma. Owing to the low concentration, the purification and structure elucidation of highly biologically active morphogenetic compounds are still challenging. Recently, it was found that only the combination of two specific bacteria from the Rhodobacteraceae and Flavobacteriaceae can completely recover the growth and morphogenesis of axenic Ulva mutabilis cultures forming a symbiotic tripartite community by chemical communication. This review combines literature detailing evidences of bacteria-induced morphogenesis in Ulvales. A set of standardized experimental approaches is further proposed for the preparation of axenic algal tissues, bacteria isolation, co-cultivation experiments, and the analysis of the chemosphere.

  3. Collection of minima

    NASA Astrophysics Data System (ADS)

    Zasche, P.; Uhlar, R.; Kucakova, H.; Svoboda, P.

    2011-12-01

    We present CCD times of minima for selected eclipsing binaries. Besides our own data as obtained at various observatories, also the photometric surveys (ASAS, SuperWASP, NSVS), as well as space telescopes (COROT, OMC) were used. The discovery of pulsations in V887 Aql, SU Aqr and V389 Cas and eccentric orbit in KO Nor are announced.

  4. Microscopic observation of pyrenoids in Order Ulvales (Chlorophyta) collected from Qingdao coast

    NASA Astrophysics Data System (ADS)

    Teng, Linhong; Ding, Lanping; Lu, Qinqin

    2011-09-01

    Pyrenoids found in green algae Order Ulvales have taxonomical significance. Their morphology, microstructure, and the location and number in the cells have been widely used as identification criteria. As these traits can be affected by environmental conditions, it is necessary to look for other different characteristics. Here pyrenoids in several algae species collected along the Qingdao coast were studied for such purpose. The morphology and distribution of pyrenoids in the cells, as well as their change in different parts of the frond and at different times were studied with light microscope. The results are as follows. Pyrenoids appeared to be spherical or oval in observed Ulvales' algae cells. They were embedded in chloroplasts with the number of 1-3 per cell on average. The number of pyrenoids for Ulva pertusa could change drastically with continuing culture and could reach up to 10-20 per cell in late-growth stages. Generally, the pyrenoids in the marginal part were more observable than those in the central part for Ulva pertusa. In addition, the basal part of frond had more distinct pyrenoids with an average diameter of 2.42 μm for Enteromorpha linza. For some species the pyrenoids were difficult to be observed while dark treatment made them more distinguishable. The apoptosis rate of pyrenoids in different species varied under continuing dark treatment, which could be used to identify different species. Pyrenoids disappeared faster in E. linza than those in E. intestinalis.

  5. Seeking Global Minima

    NASA Astrophysics Data System (ADS)

    Tajuddin, Wan Ahmad

    1994-02-01

    Ease in finding the configuration at the global energy minimum in a symmetric neural network is important for combinatorial optimization problems. We carry out a comprehensive survey of available strategies for seeking global minima by comparing their performances in the binary representation problem. We recall our previous comparison of steepest descent with analog dynamics, genetic hill-climbing, simulated diffusion, simulated annealing, threshold accepting and simulated tunneling. To this, we add comparisons to other strategies including taboo search and one with field-ordered updating.

  6. Energy landscapes and persistent minima

    SciTech Connect

    Carr, Joanne M.; Wales, David J.; Mazauric, Dorian; Cazals, Frédéric

    2016-02-07

    We consider a coarse-graining of high-dimensional potential energy landscapes based upon persistences, which correspond to lowest barrier heights to lower-energy minima. Persistences can be calculated efficiently for local minima in kinetic transition networks that are based on stationary points of the prevailing energy landscape. The networks studied here represent peptides, proteins, nucleic acids, an atomic cluster, and a glassy system. Minima with high persistence values are likely to represent some form of alternative structural morphology, which, if appreciably populated at the prevailing temperature, could compete with the global minimum (defined as infinitely persistent). Threshold values on persistences (and in some cases equilibrium occupation probabilities) have therefore been used in this work to select subsets of minima, which were then analysed to see how well they can represent features of the full network. Simplified disconnectivity graphs showing only the selected minima can convey the funnelling (including any multiple-funnel) characteristics of the corresponding full graphs. The effect of the choice of persistence threshold on the reduced disconnectivity graphs was considered for a system with a hierarchical, glassy landscape. Sets of persistent minima were also found to be useful in comparing networks for the same system sampled under different conditions, using minimum oriented spanning forests.

  7. A MOLECULAR PHYLOGENY OF ACROCHAETE AND OTHER ENDOPHYTIC GREEN ALGAE (ULVALES, CHLOROPHYTA)(1).

    PubMed

    Rinkel, Barbara E; Hayes, Paul; Gueidan, Cécile; Brodie, Juliet

    2012-08-01

    A molecular phylogeny was reconstructed from a culture collection of >150 isolates of epi-endophytic and endophytic green algae, based on nucleotide sequences of the plastid tufA and nuclear ITS2 loci. The cultures were isolated from a variety of algal hosts, notably the red algae Chondrus crispus, Mastocarpus stellatus, and Osmundea species, and the brown algae Chorda filum and Fucus serratus. The phylogeny revealed that in the Ulvales the majority of isolates fell into Acrochaete (Ulvellaceae), Ulva (Ulvaceae), Bolbocoleon (Bolbocoleaceae), and at least two unknown genera provisionally assigned to the Kornmanniaceae. Acrochaete was monophyletic. The genus was also more specious than previously described with 12 species, including up to six new species awaiting formal description. Isolates identified as Acrochaete repens, the type species of the genus, were polyphyletic. The remainder of the isolates were placed in the Ulotrichales. The results confirm that the endophytic habit supports a broad diversity of algal taxa and suggest that blade formation is a relatively recent innovation within the green algae. © 2012 Phycological Society of America.

  8. Ulva (Chlorophyta, Ulvales) Biodiversity in the North Adriatic Sea (Mediterranean, Italy): Cryptic Species and New Introductions.

    PubMed

    Wolf, Marion A; Sciuto, Katia; Andreoli, Carlo; Moro, Isabella

    2012-12-01

    Ulva Linnaeus (Ulvophyceae, Ulvales) is a genus of green algae widespread in different aquatic environments. Members of this genus show a very simple morphology and a certain degree of phenotypic plasticity, heavily influenced by environmental conditions, making difficult the delineation of species by morphological features alone. Most studies dealing with Ulva biodiversity in Mediterranean waters have been based only on morphological characters and a modern taxonomic revision of this genus in the Mediterranean is not available. We report here the results of an investigation on the diversity of Ulva in the North Adriatic Sea based on molecular analyses. Collections from three areas, two of which subject to intense shipping traffic, were examined, as well as historical collections of Ulva stored in the Herbarium Patavinum of the University of Padova, Italy. Molecular analyses based on partial sequences of the rbcL and tufA genes revealed the presence of six different species, often with overlapping morphologies: U. californica Wille, U. flexuosa Wulfen, U. rigida C. Agardh, U. compressa Linnaeus, U. pertusa Kjellman, and one probable new taxon. U. californica is a new record for the Mediterranean and U. pertusa is a new record for the Adriatic. Partial sequences obtained from historical collections show that most of the old specimens are referable to U. rigida. No specimens referable to the two alien species were found among the old herbarium specimens. The results indicate that the number of introduced seaweed species and their impact on Mediterranean communities have been underestimated, due to the difficulties in species identification of morphologically simple taxa as Ulva. © 2012 Phycological Society of America.

  9. Antileishmanial physalins from Physalis minima.

    PubMed

    Choudhary, M Iqbal; Yousaf, Sammer; Ahmed, Shakil; Yasmeen, Kauser

    2005-09-01

    Three new physalins (1-3) and a new withanolide 7 have been isolated from the whole plant of Physalis minima, along with three known physalins: physalin H (4), isophysalin B (5), and 5beta,6beta-epoxyphysalin B (6). Their structures were deduced on the basis of in-depth spectroscopic analyses. Compounds 1-6 showed significant in vitro leishmanicidal activities (0.92-19.4 microg/ml) against promastigotes of Leishmania major.

  10. Recent Minima of 171 Eclipsing Binary Stars

    NASA Astrophysics Data System (ADS)

    Samolyk, G.

    2015-12-01

    This paper continues the publication of times of minima for 171 eclipsing binary stars from observations reported to the AAVSO EB section. Times of minima from observations received by the author from March 2015 thru October 2015 are presented.

  11. Franck-Condon breakdown from Cooper minima.

    NASA Astrophysics Data System (ADS)

    Rao, R. M.; Poliakoff, E. D.; Wang, K.; McKoy, V.

    1996-05-01

    We report Cooper minima-induced Franck-Condon breakdown for N2 2σ_u-1 photoionization. The measurements are over an extended energy range (230 eV), and we find that the v^+= 2/v^+= 0 and v^+= 1/v^+= 0 vibrational branching ratios vary strongly over a 100 eV range. This is a dramatic deviation from Franck-Condon predictions, and calculations show that this coupling between vibrational and electronic motion arises from a dependence of Cooper minima on molecular bond length. To our knowledge, this is the only example of a broad-range Franck-Condon breakdown due to a non-resonant mechanism, and is the broadest deviation from Franck-Condon behavior observed to date. The ubiquitous nature of Cooper minima suggests this effect to be common in molecular systems.

  12. Occurrence of Knudsen minima in diverging microchannels

    SciTech Connect

    Hemadri, Vadiraj; Bhandarkar, Upendra; Agrawal, Amit

    2014-12-09

    Rarefied gas flow is gaining increasing importance with the emergence of Micro Electro Mechanical Systems (MEMS). Knudsen minima is one of the characteristic feature of such rarefied flows and has been observed in uniform cross section channels such as plane channel, cylindrical tube and annulus. However, data pertaining to gaseous flow in varying cross section channel is relatively sparse. Channels of varying cross section are frequently encountered in MEMS devices and are fundamental to the design of micro-scale nozzles and micro-valves. In this context, rarefied gas flow through a diverging microchannel (divergence angle – 12 degree) is studied experimentally with three different gases (argon, nitrogen and oxygen). The experiments are performed over a wide range with the mean Knudsen number varying from slip to the transitional regime (0.07 to 1.2). It is found that the effect of molecular weight of the gas on the non-dimensional mass flow rate is negligible. The Knudsen minima is experimentally observed for the first time in microchannel of non-uniform cross section.

  13. Cloud supersaturations from CCN spectra Hoppel minima

    NASA Astrophysics Data System (ADS)

    Hudson, James G.; Noble, Stephen; Tabor, Samantha

    2015-04-01

    High-resolution cloud condensation nucleus (CCN) spectral measurements in two aircraft field projects, Marine Stratus/Stratocumulus Experiment (MASE) and Ice in Clouds Experiment-Tropical (ICE-T), often showed bimodality that had previously been observed in submicrometer aerosol size distributions obtained by differential mobility analyzers. However, a great deal of spectral shape variability from very bimodal to very monomodal was observed in close proximity. Cloud supersaturation (S) estimates based on critical S, Sc, at minimal CCN concentrations between two modes (Hoppel minima) were ascertained for 63% of 325 measured spectra. These cloud S were lower than effective S (Seff) determined by comparing ambient CCN spectra with nearby cloud droplet concentrations (Nc). Averages for the polluted MASE stratus were 0.15 and 0.23% and for the cumulus clouds of ICE-T 0.44 and 1.03%. This cloud S disagreement between the two methods might in part be due to the fact that Hoppel minima include the effects of cloud processing, which push CCN spectra toward lower S. Furthermore, there is less cloud processing by the smaller cloud droplets, which might be related to smaller droplets evaporating more readily. Significantly lower concentrations within the more bimodal spectra compared with the monomodal spectra indicated active physical processes: Brownian capture of interstitial CCN and droplet coalescence. Chemical cloud processing also contributed to bimodality, especially in MASE.

  14. New leishmanicidal physalins from Physalis minima.

    PubMed

    Choudhary, M Iqbal; Yousuf, Sammer; Samreen; Ahmed, Shakil; Atta-Ur-Rahman

    2007-08-01

    Two new physalins, 16,24-cyclo-13,14-secoergosta-2-ene-18,26-dioic acid-14 : 17,14 : 27-diepoxy-11beta,13,20,22-tetrahydroxy-5alpha-methoxy-1,15-dioxo-gamma-lactone delta-lactone (1), and 16,24-cyclo-13,14-secoergosta-2-ene-18,26-dioic acid-14 : 17,14 : 27-diepoxy-5alpha,11beta,13,20,22-pentahydroxy-1,6,15-trioxo-gamma-lactone delta-lactone (2), have been isolated from the whole plant of Physalis minima Linn. (var. indica). Their structures were deduced on the basis of spectroscopic analysis. Both of these compounds have shown potent leishmanicidal activity against the promastigotes of Leishmania major.

  15. Solar Twins and Stellar Maunder Minima

    NASA Astrophysics Data System (ADS)

    Hall, Jeffrey C.

    2012-05-01

    In 1966, Olin C. Wilson undertook an answer to the question “Does the chromospheric activity of main-sequence stars vary with time, and if so, how?”, initiating the so-called HK Project at Mount Wilson Observatory, which resulted in a magnificent 43-year data set and which has spawned a number of complementary synoptic programs in both hemispheres. Subsequent developments, in particular the realization that activity controls angular momentum evolution in the stars and Sun, that solar activity modulates irradiance, and that there was a pronounced response of terrestrial climate to the Maunder Minimum, spurred efforts to identify solar twins, stars that Giusa Cayrel de Strobel required to possess “fundamental physical parameters very similar, if not identical to those of the Sun.” Non-cycling states appear to occur in the Mount Wilson stars and in other synoptic data with about the same frequency that the Sun’s grand minima occur in the long-term proxy record, suggesting that stellar analogs of the Maunder Minimum may be used to guide understanding of the Sun’s state in the late seventeenth century and, as appears possible given the extended Cycle 23/24 minimum, in the near future. However, the magnitude limits of the existing surveys have kept the sample of solar twins small and long-term monitoring programs have only recently begun to accumulate good time-domain data beyond the canonical HK-index. Addressing these and other issues toward understanding prolonged stellar minima is therefore a key area of inquiry in solar-stellar connection work for the next decade. I will summarize the state of the field and the most promising lines of work for the immediate future. I and my colleagues Wes Lockwood and Brian Skiff sincerely appreciate the National Science Foundation’s long-time support of stellar cycles work at Lowell Observatory.

  16. Geocoronal hydrogen observations spanning three solar minima

    NASA Astrophysics Data System (ADS)

    Nossal, S. M.; Mierkiewicz, E. J.; Roesler, F. L.; Haffner, L. M.; Reynolds, R. J.; Woodward, R. C.

    2008-11-01

    The 11-year solar cycle is a dominant source of natural variability in the upper atmosphere, and its effect on atomic hydrogen distributions and emissions must be understood to investigate possible signs of longer-term climatic trends in this region. We present midlatitude geocoronal hydrogen Balmer α observations from solar cycle 23 (1997-2006) and three solar minimum periods, 1985, 1997, and 2006. The 1997 through 2006 observations were taken with the Wisconsin H-α Mapper Fabry-Perot (WHAM), a ground-based CCD-annular summing instrument that began observations at the Kitt Peak Observatory in Arizona in 1997. The 1985 observations were made with a similarly designed "pre-WHAM" Fabry-Perot Interferometer utilizing photomultiplier detection and located in Wisconsin. WHAM has consistently observed higher column emission intensities during solar maximum periods than during solar minimum conditions, with the ratio dependent upon the viewing geometry. The observations from three solar minimum periods agree to within 18% uncertainties over most of the shadow altitude range. An analysis of recent Fabry-Perot observations of upper atmospheric hydrogen during solar cycle 23 and during three solar minima (1985, 1997, 2006) established a reference data set of highly precise, consistently calibrated, thermospheric plus exospheric hydrogen column emission observations from northern midlatitudes that can be used to compare with future observations.

  17. Ecology of common salvinia, Salvinia minima, in southern Florida

    USDA-ARS?s Scientific Manuscript database

    The floating macrophyte, Salvinia minima, grows in a variety of freshwater habitats in Florida. We conducted a 39-month study at four sites in southern Florida to elucidate the abiotic and biotic factors that influenced the density, nutritional profile, and size of S. minima. These factors include...

  18. 14 CFR 121.625 - Alternate Airport weather minima.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 3 2012-01-01 2012-01-01 false Alternate Airport weather minima. 121.625... Alternate Airport weather minima. Except as provided in § 121.624 for ETOPS Alternate Airports, no person may list an airport as an alternate in the dispatch or flight release unless the appropriate weather...

  19. 14 CFR 121.625 - Alternate Airport weather minima.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 3 2013-01-01 2013-01-01 false Alternate Airport weather minima. 121.625... Alternate Airport weather minima. Except as provided in § 121.624 for ETOPS Alternate Airports, no person may list an airport as an alternate in the dispatch or flight release unless the appropriate weather...

  20. 14 CFR 121.625 - Alternate Airport weather minima.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 3 2014-01-01 2014-01-01 false Alternate Airport weather minima. 121.625... Alternate Airport weather minima. Except as provided in § 121.624 for ETOPS Alternate Airports, no person may list an airport as an alternate in the dispatch or flight release unless the appropriate weather...

  1. 14 CFR 121.625 - Alternate Airport weather minima.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 3 2010-01-01 2010-01-01 false Alternate Airport weather minima. 121.625... Alternate Airport weather minima. Except as provided in § 121.624 for ETOPS Alternate Airports, no person may list an airport as an alternate in the dispatch or flight release unless the appropriate weather...

  2. 14 CFR 121.625 - Alternate Airport weather minima.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 3 2011-01-01 2011-01-01 false Alternate Airport weather minima. 121.625... Alternate Airport weather minima. Except as provided in § 121.624 for ETOPS Alternate Airports, no person may list an airport as an alternate in the dispatch or flight release unless the appropriate weather...

  3. GRAND MINIMA AND NORTH-SOUTH ASYMMETRY OF SOLAR ACTIVITY

    SciTech Connect

    Olemskoy, S. V.; Kitchatinov, L. L.

    2013-11-01

    A solar-type dynamo model in a spherical shell is developed with allowance for random dependence of the poloidal field generation mechanism on time and latitude. The model shows repeatable epochs of a strongly decreased amplitude of magnetic cycles similar to the Maunder minimum of solar activity. Random dependence of dynamo parameters on latitude breaks the equatorial symmetry of generated fields. The model shows the correlation of the occurrence of grand minima with deviations in the dynamo field from dipolar parity. An increased north-south asymmetry of magnetic activity can, therefore, be an indicator of transitions to grand minima. Qualitative interpretation of this correlation is suggested. Statistics of grand minima in the model are close to the Poisson random process, indicating that the onset of a grand minimum is statistically independent of preceding minima.

  4. CCD Times of Minima of Selected Eclipsing Binaries

    NASA Astrophysics Data System (ADS)

    Zejda, Miloslav

    2004-12-01

    682 CCD minima observations of 259 eclipsing binaries made mainly by author are presented. The observed stars were chosen mainly from catalogue BRKA of observing programme of BRNO-Variable Star Section of CAS.

  5. Taboo search: an approach to the multiple minima problem.

    PubMed

    Cvijovicacute, D; Klinowski, J

    1995-02-03

    Described here is a method, based on Glover's taboo search for discrete functions, of solving the multiple minima problem for continuous functions. As demonstrated by model calculations, the algorithm avoids entrapment in local minima and continues the search to give a near-optimal final solution. Unlike other methods of global optimization, this procedure is generally applicable, easy to implement, derivative-free, and conceptually simple.

  6. Taboo Search: An Approach to the Multiple Minima Problem

    NASA Astrophysics Data System (ADS)

    Cvijovic, Djurdje; Klinowski, Jacek

    1995-02-01

    Described here is a method, based on Glover's taboo search for discrete functions, of solving the multiple minima problem for continuous functions. As demonstrated by model calculations, the algorithm avoids entrapment in local minima and continues the search to give a near-optimal final solution. Unlike other methods of global optimization, this procedure is generally applicable, easy to implement, derivative-free, and conceptually simple.

  7. Connection between solar activity cycles and grand minima generation

    NASA Astrophysics Data System (ADS)

    Vecchio, A.; Lepreti, F.; Laurenza, M.; Alberti, T.; Carbone, V.

    2017-03-01

    Aims: The revised dataset of sunspot and group numbers (released by WDC-SILSO) and the sunspot number reconstruction based on dendrochronologically dated radiocarbon concentrations have been analyzed to provide a deeper characterization of the solar activity main periodicities and to investigate the role of the Gleissberg and Suess cycles in the grand minima occurrence. Methods: Empirical mode decomposition (EMD) has been used to isolate the time behavior of the different solar activity periodicities. A general consistency among the results from all the analyzed datasets verifies the reliability of the EMD approach. Results: The analysis on the revised sunspot data indicates that the highest energy content is associated with the Schwabe cycle. In correspondence with the grand minima (Maunder and Dalton), the frequency of this cycle changes to longer timescales of 14 yr. The Gleissberg and Suess cycles, with timescales of 60-120 yr and 200-300 yr, respectively, represent the most energetic contribution to sunspot number reconstruction records and are both found to be characterized by multiple scales of oscillation. The grand minima generation and the origin of the two expected distinct types of grand minima, Maunder and longer Spörer-like, are naturally explained through the EMD approach. We found that the grand minima sequence is produced by the coupling between Gleissberg and Suess cycles, the latter being responsible for the most intense and longest Spörer-like minima (with typical duration longer than 80 yr). Finally, we identified a non-solar component, characterized by a very long scale oscillation of 7000 yr, and the Hallstatt cycle ( 2000 yr), likely due to the solar activity. Conclusions: These results provide new observational constraints on the properties of the solar cycle periodicities, the grand minima generation, and thus the long-term behavior of the solar dynamo.

  8. Study on the antibacterial potential of physalis minima linn.

    PubMed

    Patel, T; Shah, K; Jiwan, K; Shrivastava, Neeta

    2011-01-01

    Physalis minima is an important medicinal plant of Indian System of Medicine. This plant is reported for its diuretic, laxative and antiinflammatory activities. However, the plant is not well scrutinized for its antimicrobial potential. The major chemical constituents reported from the plant are phenolics and alkaloids, which suggest that the plant may turn out to be a potent antiinfective agent. The aim of the study was to find out the antibacterial potential of mature berries of P. minima using streak plate, well diffusion, determination of minimum inhibitory concentration and bioautographic methods against a battery of Gram positive and Gram negative bacterial strains. Results of the study showed that methanol and chloroform extracts of P. minima exhibited potent inhibitory activity against all the bacterial strains tested. Minimum inhibitory concentration found out was 100 μg in both the extracts. Bioautography assay showed polar compounds present in the crude extract are responsible for the antimicrobial action.

  9. Study on the Antibacterial Potential of Physalis Minima Linn

    PubMed Central

    Patel, T.; Shah, K.; Jiwan, K.; Shrivastava, Neeta

    2011-01-01

    Physalis minima is an important medicinal plant of Indian System of Medicine. This plant is reported for its diuretic, laxative and antiinflammatory activities. However, the plant is not well scrutinized for its antimicrobial potential. The major chemical constituents reported from the plant are phenolics and alkaloids, which suggest that the plant may turn out to be a potent antiinfective agent. The aim of the study was to find out the antibacterial potential of mature berries of P. minima using streak plate, well diffusion, determination of minimum inhibitory concentration and bioautographic methods against a battery of Gram positive and Gram negative bacterial strains. Results of the study showed that methanol and chloroform extracts of P. minima exhibited potent inhibitory activity against all the bacterial strains tested. Minimum inhibitory concentration found out was 100 μg in both the extracts. Bioautography assay showed polar compounds present in the crude extract are responsible for the antimicrobial action. PMID:22131635

  10. Chemopreventive Agents from Physalis minima Function as Michael Reaction Acceptors.

    PubMed

    Men, Ruizhi; Li, Ning; Ding, Chihong; Tang, Yingzhan; Xing, Yachao; Ding, Wanjing; Ma, Zhongjun

    2016-05-01

    The fruits of some varieties of genus Physalis have been used as delicious fruits and functional food in the Northeast of China. To reveal the functional material basis, we performed bioactivity-guided phytochemical research and chemopreventive effect assay of the constituents from Physalis minima. It was demonstrated that the ethyl acetate extract of P. minima L. (EEPM) had potential quinone reductase (QR) inducing activity with induction ratio (IR, QR induction activity) value of 1.47 ± 0.24, and glutathione binding property as potential Michael reaction acceptors (with an α, β-unsaturated ketone moiety). Furthermore, bioactivity-guided phytochemical research led eight compounds (1-8), which were elucidated as 3-isopropyl-5-acetoxycyclohexene-2-one-1 (1), isophysalin B (2), physalin G (3), physalin D (4), physalin I (5), physordinose B (6), stigmasterol-3-O-β-D-glucopyranoside (7) and 5α-6β-dihydroxyphysalin R (8) on the basis of nuclear magnetic resonance spectroscopy analyses and HRESIMS. Then, isophysalin B (2) and physordinose B (6) showed significant QR inducing activity with IR value of 2.80 ± 0.19 and 2.38 ± 0.46, respectively. An ultra-performance liquid chromatographic method with glutathione as the substrate was used to detect the Michael reaction acceptors in extracts of Physalis minima (EPM)We investigated the chemical constituents of EPM guided by biological activity methodIsophysalin B (1) and physordinose B (6) showed strong quinone reductase inducing activity with induction ratio values of 2.80 ± 0.19 and 2.38 ± 0.46This study generated useful information for consumers and many encourage researchers to utilize edible fruits from Physalis as a source of phytochemicals Abbreviations used: EPM: Extracts of Physalis minima, EEPM: Ethyl acetate extract of Physalis minima L., GSH: Glutathione, MRAs: Michael reaction acceptors, QR: Quinone reductase.

  11. Chemopreventive Agents from Physalis minima Function as Michael Reaction Acceptors

    PubMed Central

    Men, Ruizhi; Li, Ning; Ding, Chihong; Tang, Yingzhan; Xing, Yachao; Ding, Wanjing; Ma, Zhongjun

    2016-01-01

    Background: The fruits of some varieties of genus Physalis have been used as delicious fruits and functional food in the Northeast of China. Materials and Methods: To reveal the functional material basis, we performed bioactivity-guided phytochemical research and chemopreventive effect assay of the constituents from Physalis minima. Results: It was demonstrated that the ethyl acetate extract of P. minima L. (EEPM) had potential quinone reductase (QR) inducing activity with induction ratio (IR, QR induction activity) value of 1.47 ± 0.24, and glutathione binding property as potential Michael reaction acceptors (with an α, β-unsaturated ketone moiety). Furthermore, bioactivity-guided phytochemical research led eight compounds (1–8), which were elucidated as 3-isopropyl-5-acetoxycyclohexene-2-one-1 (1), isophysalin B (2), physalin G (3), physalin D (4), physalin I (5), physordinose B (6), stigmasterol-3-O-β-D-glucopyranoside (7) and 5α-6β-dihydroxyphysalin R (8) on the basis of nuclear magnetic resonance spectroscopy analyses and HRESIMS. Then, isophysalin B (2) and physordinose B (6) showed significant QR inducing activity with IR value of 2.80 ± 0.19 and 2.38 ± 0.46, respectively. SUMMARY An ultra-performance liquid chromatographic method with glutathione as the substrate was used to detect the Michael reaction acceptors in extracts of Physalis minima (EPM)We investigated the chemical constituents of EPM guided by biological activity methodIsophysalin B (1) and physordinose B (6) showed strong quinone reductase inducing activity with induction ratio values of 2.80 ± 0.19 and 2.38 ± 0.46This study generated useful information for consumers and many encourage researchers to utilize edible fruits from Physalis as a source of phytochemicals Abbreviations used: EPM: Extracts of Physalis minima, EEPM: Ethyl acetate extract of Physalis minima L., GSH: Glutathione, MRAs: Michael reaction acceptors, QR: Quinone reductase. PMID:27279713

  12. Comparative analysis of solar minima with EUV tomography

    NASA Astrophysics Data System (ADS)

    Lloveras, D. G.; Nuevo, F. A.; Vásquez, A. M.; Frazin, R. A.

    2016-08-01

    Due to the dynamo mechanism of the Sun, the magnetic activity of its atmosphere presents a periodic cycle about 11 years long. The last three solar cycles have shown a systematic decrease of activity, with the last minimum (2008/2009) being considerably more quiet than the previous one (1996), as well as magnetically weaker. We present a comparative analysis of three--dimensional thermodynamical structure of the lower corona for last two minimima, based on differential emission measure tomography. The study is combined with potential extrapolations of the coronal magnetic field. To study the minima of 1996 and 2009 we use data taken by the instruments EIT/SOHO y EUVI/STEREO, respectively. The aim of the work is to establish if there were systematic thermodynamical differences in the lower corona during the two minima.

  13. "Compressing liquid": an efficient global minima search strategy for clusters.

    PubMed

    Zhou, R L; Zhao, L Y; Pan, B C

    2009-07-21

    In this paper we present a new global search strategy named as "compressing liquid" for atomic clusters. In this strategy, a random fragment of liquid structure is adopted as a starting geometry, followed by iterative operations of "compressing" and Monte Carlo adjustment of the atom positions plus structural optimization. It exhibits fair efficiency when it is applied to seeking the global minima of Lennard-Jones clusters. We also employed it to search the low-lying candidates of medium silicon clusters Si(n)(n=40-60), where the global search is absent. We found the best candidates for most sizes. More importantly, we obtained non-fullerene-based structures for some sized clusters, which were not found from the endohedral-fullerene strategy. These results indicate that the "compressing-liquid" method is highly efficient for global minima search of clusters.

  14. B.R.N.O. Contributions #39 Times of minima

    NASA Astrophysics Data System (ADS)

    Honkova, K.; Jurysek, J.; Lehky, M.; Smelcer, L.; Masek, M.; Mazanec, J.; Hanzl, D.; Urbanik, M.; Magris, M.; Vrastak, M.; Walter, F.; Hladik, B.; Medulka, T.; Bilek, F.; Trnka, J.; Jacobsen, J.; Benacek, J.; Kuchtak, B.; Audejean, M.; Ogmen, Y.; Zibar, M.; Fatka, P.; Marchi, F.; Poddany, S.; Quinones, C.; Tapia, L.; Scaggiante, F.; Zardin, D.; Corfini, G.; Hajek, P.; Lomoz, F.; Mravik, J.; Grnja, J.; Campos, F.; Caloud, J.; Esseiva, N.; Jaks, S.; Hornik, M.; Filip, J.; Uhlar, R.; Mina, F.; Artola, R.; Zalazar, J.; Muller, D.; Pintr, P.; Divisova, L.

    2015-02-01

    This paper presents 1463 times of minima for 455 objects acquired by 46 members and cooperating observers of the Variable Star and Exoplanet Section of the Czech Astronomical Society (B.R.N.O. Observing project). Observations were carried out between October 2013 - September 2014. Some neglected southern eclipsing binaries and newly discovered stars by the observers of project B.R.N.O. are included in the list.

  15. B.R.N.O. Contributions #40 Times of minima

    NASA Astrophysics Data System (ADS)

    Juryšek, J.; Hoňková, K.; Šmelcer, L.; Mašek, M.; Lehký, M.; Bílek, F.; Mazanec, J.; Hanžl, D.; Magris, M.; Nosál, P.; Bragagnolo, U.; Medulka, T.; Vraš&tacute; ák, M.; Urbaník, M.; Auer, R. F.; Sergey, I.; Jacobsen, J.; Alessandroni, M. R.; Andreatta, C.; Antonio, Ch. F.; Artola, R.; Audejean, M.; Balanzino, L.; Banfi, M.; Bazán, R. S.; Borgonovo, M.; Cagaš, P.; Čaloud, J.; Campos, F.; Čapková, H.; Černíková, V.; Červinka, L.; Chiavassa, A.; Dřevěný, R.; Durantini, L. H.; Ferraro, M. E.; Ferrero, G.; Girardini, C.; Gudmundsson, S.; Guzzo, P.; Guevara, N.; Hladík, B.; Horník, M.; Jakš, S.; Janoštiak, L.; Jelínek, M.; Kalášek, J.; Kalmbach, R.; Kubica, T.; Kučáková, H.; Liška, J.; Lomoz, F.; López, O. Ch.; Lovato, B. M.; Morero, S.; Mrllák, R.; Mrňák, P.; Persha, G.; Pignata, R.; Pintr, P.; Popov, A.; Portillo, L. F. T.; Quiñones, C.; Rodriguez, E.; Ruocco, N.; Scaggiante, F.; Scavuzzo, A.; Šebela, P.; Šimkovič, S.; Školník, V.; Skubák, P.; Smolka, M.; Špecián, M.; Šuchaň, J.; Tornatore, M.; Trnka, J.; Tylšar, M.; Walter, F.; Zardin, D.; Zejda, M.; Zíbar, M.; Ziková, A.

    2017-03-01

    This paper presents 3394 times of minima for 1096 objects acquired by 82 members and cooperating observers of the Variable Star and Exoplanet Section of the Czech Astronomical Society (B.R.N.O. Observing project). Observations were carried out between October 2014 and November 2016. Some newly discovered stars by the observers of project B.R.N.O. are included in the list.

  16. Efficient Accommodation of Local Minima in Watershed Model Calibration

    DTIC Science & Technology

    2006-02-02

    of information if it does not display a currently valid OMB control number. 1. REPORT DATE 2006 2. REPORT TYPE 3. DATES COVERED 00-00-2006 to...should notify the user of this, and of the fact that parameter estimates forthcom- ing from the calibration process are nonunique . Whether or not an...challenges posed by parameter nonuniqueness and local objective function minima will lead to the necessity to carry out more model runs than that

  17. Grand minima of solar activity and sociodynamics of culture

    NASA Astrophysics Data System (ADS)

    Vladimirsky, B. M.

    2012-12-01

    Indices of creative productivity introduced by C. Murrey were used to verify S. Ertel's conclusion about a global increase in creative productivity during the prolonged minimum of solar activity in 1640-1710. It was found that these indices for mathematicians, philosophers, and scientists increase in the Maunder era by factor of 1.6 in comparison with intervals of the same length before and after the minimum. A similar effect was obtained for mathematicians and philosophers for five earlier equitype minima in total (an increase by a factor of 1.9). The regularity that is revealed is confirmed by the fact that the most important achievements of high-ranking mathematicians and philosophers during the whole time period (2300 years) considered in this study fall on epochs of reduced levels of solar activity. The rise in the probability of the generation of rational ideas during grand minima is reflected also in the fact that they precede the appearance of written language and farming. Ultra-low-frequency electromagnetic fields appear to serve as a physical agent stimulating the activity of the brain's left hemisphere during the epochs of minima.

  18. The Earth's Climate at Minima of the Centennial Gleissberg Cycles

    NASA Astrophysics Data System (ADS)

    Ruzmaikin, A.; Feynman, J.

    2016-12-01

    The recent extended and deep minimum of solar variability and the extended minima in the 19th and 20th centuries (1810-1830 and 1900-1920) are consistent with minima of the Centennial Gleissberg Cycle (CGC), a 90-100 year variation of the amplitude of the 11-year sunspot cycle observed on the Sun, solar wind, and at the Earth. The CGC has been identified in the Total Solar Irradiance reconstructed for over three centuries. The Earth's climate response to the prolonged low solar irradiance involves heat transfer to the deep ocean with a time lag longer than a decade. The CGC minima, sometimes coincidently in combination with volcanic forcing, are associated with severe weather extremes. Thus the 19th century CGC minimum, coexisted with volcanic eruptions, led to especially cold conditions in United States, Canada and Western Europe ("a year without summer"). Using the reconstructed solar forcing and modeled and reconstructed Earth's temperature data we identify the timing and spatial pattern of the Earth's climate response that allows distinguishing the solar forcing from other climate forcings.

  19. Dynamical characterization of the last prolonged solar minima

    NASA Astrophysics Data System (ADS)

    Cionco, Rodolfo Gustavo; Compagnucci, Rosa Hilda

    2012-11-01

    The planetary hypothesis of the solar cycle is an old idea in which the gravitational influence of the planets has a non-negligible effect on the causes of the solar magnetic cycle. The advance of this hypothesis is based on phenomenological correlations between dynamical parameters of the Sun's movement around the barycentre of the Solar System and sunspots time series; and more especially, identifying relationships linking solar barycentric dynamics with prolonged minima (especially Grand Minima events). However, at present there is no clear physical mechanism relating these phenomena. The possible celestial influence on solar cycle modulation is of great importance not only in solar physics but also in Earth sciences, because prolonged solar minima have associated important climatic and telluric variations, in particular, during the Maunder and Dalton Minimum. In this work we looked for a possible causal link in relation with solar barycentric dynamics and prolonged minima events. We searched for particular changes in the Sun's acceleration and concentrated on long-term variations of the solar cycle. We show how the orbital angular momentum of the Sun evolves and how the inclination of the solar barycentric orbit varies during the epochs of orbital retrogressions. In particular, at these moments, the radial component of the Sun's acceleration (i.e., in the barycentre-Sun direction) had an exceptional magnitude. These radial impulses occurred at the very beginning of the Maunder Minimum, during the Dalton Minimum and also at the maximum of cycle 22 before the present extended minimum. We also found a strong correlation between the planetary torque and the observed sunspots international number around that maximum. We apply our results in a novel theory of Sun-planets interaction that it is sensitive to Sun barycentric dynamics and found a very important effect on the Sun's capability of storing hypothetical reservoirs of potential energy that could be released by

  20. B.R.N.O. Contributions #38 Times of minima

    NASA Astrophysics Data System (ADS)

    Hoňková, K.; Juryšek, J.; Lehký, M.; Šmelcer, L.; Trnka, J.; Mašek, M.; Urbaník, M.; Auer, R.; Vrašták, M.; Kučáková, H.; Ruocco, N.; Magris, M.; Polák, J.; Brát, L.; Audejean, M.; Banfi, M.; Moudrá, M.; Lomoz, F.; Přibík, V.; Dřevěný, R.; Scaggiante, F.; Kocián, R.; Cagaš, P.; Poddaný, S.; Zíbar, M.; Jacobsen, J.; Marek, P.; Colazo, C.; Zardin, D.; Sobotka, P.; Starzomski, J.; Hladík, B.; Vincenzi, M.; Skarka, M.; Walter, F.; Chapman, A.; Díaz, N. D.; Aceti, P.; Singh, P.; Kalista, L.; Kamenec, M.; Zejda, M.; Marchi, F.; Bílek, R.; Guzzo, P.; Corfini, G.; Onderková, K.; Hečko, A.; Mina, F.; Vítek, M.; Barsa, R.; Quinones, C.; Taormina, M.; Melia, R.; Schneiter, M.; Scavuzzo, A.; Marcionni, N.; Ehrenberger, R.; Tapia, L.; Fasseta, G.; Suarez, N.; Scaggiante, D.; Artusi, E.; Garcia, R.; Grnja, J.; Fišer, A.; Hynek, T.; Vilášek, M.; Rozehnal, J.; Kalisch, T.; Lang, K.; Gorková, S.; Novysedlák, R.; Salvaggio, F.; Smyčka, T.; Spurný, M.; Wikander, T.; Mravik, J.; Šuchaň, J.; Čaloud, J.

    2013-12-01

    This paper presents observations of eclipsing binaries acquired by members and cooperating observers of the Variable Star and Exoplanet Section of Czech Astronomical Society (B.R.N.O. observing project). Paper contains 3417 times of minima for 969 objects. It was obtained by 80 observers during 2011 ± 2013 period. Some neglected southern eclipsing binaries and newly discovered stars by the observers of project B.R.N.O. are included in the list. New accurate ephemerides have been found for 447 binary systems. Time of primary minimum of long period variable eps Aur is presented as well.

  1. Very extended minima in the A=180 mass region

    NASA Astrophysics Data System (ADS)

    Chasman, R. R.

    1993-03-01

    A search for very extended nuclear shapes in the A=180 mass region has been carried out in a three dimensional deformation space, using the cranked Strutinsky procedure. Many such minima have been found and their properties are described in detail. I thank P.H. Heenen for informing me of the Hartree-Fock calculations of VEMs and R.V.F. Janssens for a helpful discussion on this problem. The calculations reported here were carried out on the NERSC computer facility at Livermore.

  2. Global Franck-Condon Breakdown Resulting from Cooper Minima

    NASA Astrophysics Data System (ADS)

    Rao, R. M.; Poliakoff, E. D.; Wang, Kwanghsi; McKoy, V.

    1996-04-01

    Using N2 2σ-1u photoionization as an example, we present the first measurements and calculations of photoion vibrational distributions for an extended energy range ( 5<=Ek<=230 eV). The results show a striking breakdown of the Franck-Condon approximation over a 100 eV range. We show that this coupling between vibrational and electronic motion arises from a dependence of Cooper minima on molecular bond length. Based on this mechanism, the effect is expected to be common for molecular systems.

  3. Effect of correlations between minima on a complex energy landscape

    NASA Astrophysics Data System (ADS)

    Pusuluri, Sai Teja; Lang, Alex H.; Mehta, Pankaj; Castillo, Horacio E.

    We recently modeled cellular interconvertion dynamics by using an epigenetic landscape model inspired by neural network models. Given an arbitrary set of patterns, the model can be used to construct an energy landscape in which those patterns are the global minima. We study the possible stable states and metastable states of the landscapes thus constructed. We consider three different cases: i) choosing the patterns to be random and independently distributed ii) choosing a set of patterns directly derived from the experimental cellular transcription factor expression data for a representative set of cell types in an organism and iii) choosing randomly generated trees of hierarchically correlated patterns, inspired by biology. For each of the three cases, we study the energy landscapes. In particular we study the basins of attraction of both the stable states and the metastable states, we compute the configurational entropy as a function of energy, and we demonstrate how those results depend on the correlations between the patterns.

  4. Viscosity minima in binary mixtures of ionic liquids + molecular solvents.

    PubMed

    Tariq, M; Shimizu, K; Esperança, J M S S; Canongia Lopes, J N; Rebelo, L P N

    2015-05-28

    The viscosity (η) of four binary mixtures (ionic liquids plus molecular solvents, ILs+MSs) was measured in the 283.15 < T/K < 363.15 temperature range. Different IL/MS combinations were selected in such a way that the corresponding η(T) functions exhibit crossover temperatures at which both pure components present identical viscosity values. Consequently, most of the obtained mixture isotherms, η(x), exhibit clear viscosity minima in the studied T-x range. The results are interpreted using auxiliary molecular dynamics (MD) simulation data in order to correlate the observed η(T,x) trends with the interactions in each mixture, including the balance between electrostatic forces and hydrogen bonding.

  5. Potential energy stored by planets and grand minima events

    NASA Astrophysics Data System (ADS)

    Cionco, Rodolfo G.

    2012-07-01

    Recently, Wolff & Patrone (2010), have developed a simple but very interesting model by which the movement of the Sun around the barycentre of the Solar system could create potential energy that could be released by flows pre-existing inside the Sun. The authors claim that it is the first mechanism showing how planetary movements can modify internal structure in the Sun that can be related to solar cycle. In this work we point out limitations of mentioned mechanism (which is based on interchange arguments), which could be inapplicable to a real star. Then, we calculate the temporal evolution of potential energy stored in zones of Sun's interior in which the potential energy could be most efficiently stored taking into account detailed barycentric Sun dynamics. We show strong variations of potential energy related to Maunder Minimum, Dalton Minimum and the maximum of Cycle 22, around 1990. We discuss briefly possible implications of this putative mechanism to solar cycle specially Grand Minima events.

  6. SOLAR ROTATION EFFECTS ON THE HELIOSHEATH FLOW NEAR SOLAR MINIMA

    SciTech Connect

    Borovikov, Sergey N.; Pogorelov, Nikolai V.; Ebert, Robert W.

    2012-05-01

    The interaction between fast and slow solar wind (SW) due to the Sun's rotation creates corotating interaction regions (CIRs), which further interact with each other creating complex plasma structures at large heliospheric distances. We investigate the global influence of CIRs on the SW flow in the inner heliosheath between the heliospheric termination shock (TS) and the heliopause. The stream interaction model takes into account the major global effects due to slow-fast stream interaction near solar minima. The fast and slow wind parameters are derived from the Ulysses observations. We investigate the penetration of corotating structures through the TS and their further propagation through the heliosheath. It is shown that the heliosheath flow structure may experience substantial modifications, including local decreases in the radial velocity component observed by Voyager 1.

  7. All Solar Minima are not Alike: Consequences at Earth

    NASA Astrophysics Data System (ADS)

    Kozyra, J. U.; Gibson, S. E.; de Toma, G.; Emery, B. A.; Onsager, T. G.; Sojka, J. J.; Thompson, B. J.

    2009-05-01

    New observations that were collected as part of the IHY Whole Heliosphere Campaign are changing our present understanding of solar quiet intervals and the solar minimum sun-Earth system. These observations indicate that significant differences in coronal hole distribution can occur at the Sun from one solar minimum to the next. The high-speed coronal hole wind is the primary source of space weather disturbances that perturb the Earth's upper atmosphere and create reactive species. The broad low-latitude coronal holes that developed this solar minimum produced strong, long-lived and recurring high-speed streams. This is in contrast to the weaker and more sporadic streams last solar minimum produced by narrow equatorward extensions from polar coronal holes. Since the speed, duration and southward magnetic field component determine the severity of space weather effects, the geospace environment responds quite differently to these two coronal hole distributions. Despite the fact that the present solar minimum is exceptionally quiet with sunspot numbers the lowest in 75 years, solar wind density and IMF strength at the lowest values ever observed and with geomagnetic indices and solar EUV fluxes the lowest in three solar cycles, magnetic activity at Earth is showing new features and has remained surprisingly strong. The details of newly discovered geospace and upper atmospheric effects are described and possible reasons behind them discussed. What these new data sets demonstrate is that the distribution of low-latitude open magnetic flux on the Sun is a key factor in determining how the Earth will respond to a given solar minimum. If the low sunspot conditions of solar minima have analogies to conditions during solar "grand minima" (where sunspots all but disappear for extended periods), then these new results imply that high-speed solar wind streams may introduce complexities to the Earth's response during these times as well.

  8. Thermal Conductivity Minima in Superlattices and Localization-like Phenomena

    NASA Astrophysics Data System (ADS)

    Venkatasubramanian, Rama

    2007-03-01

    It is becoming clear in many 2-dimensional superlattice (SL) material systems that there exists a minimum lattice thermal conductivity for an optimal SL period. These have been first observed and reported in the Bi2Te3/Sb2Te3, PbTe/PbTeSe and Si/Ge SL systems by us in RTI. These minima become evident when the electronic thermal conductivity, using Lorentz parameter, is subtracted from the total thermal conductivity to monitor the lattice thermal conductivity as a function of SL period. The basis for the numerical value of Lorentz parameter, observed from many facets of material and device characteristics, will be presented. Such a lattice thermal conductivity minimum has also been recently observed in other SL material systems. Recently, a similar behavior has also been observed in the thermal conductivity of superlattices embedded with an ordered array of nanoparticles. We will explore the commonality of these results in terms of a localization-like behavior for phonons. The arguments for the complex relationship between the SL period and the low-frequency cut-off wavelength, traceable to a cut-off frequency originating from diffusive transport of a temperature wave, will be presented. The physics behind what triggers the localization-like phenomena of phonons in such nanostructures will be discussed.

  9. The supercenturial solar minima and their preceding phenomena

    NASA Astrophysics Data System (ADS)

    Komitov, Boris P.

    The main aim of this study is to find different observational characteristics of sunspot cycles, which could be used as precursors of forthcoming supercenturial solar minima. A data set of indirect records for solar activity (so called Schove's series) between 214 BC - AD 2000 has been analyzed. Two potential precursors of the further behaviour of the solar activity have been pointed out - the violation of Gnevyshev-Ohl's rule in even-odd numbered pairs of Schwabe-Wolf's cycles and the increasing of the cycles duration. A third method for prediction, based on two-factor regression model has been applied too. In this method the magnitudes of both even-odd sunspot cycles are used as predictors. On the base of the actual data for the current pair of the Zurich cycles No.22 and 23 a prediction for a relatively weak sunspot cycle No. 24 with expected maximum about AD 2012/13 and Wolf's index W_{max}≈ 90 was made. A prediction of forthcoming supercenturial solar minimum in the period AD 2030-2080, like the Dalton minimum in AD 1795-1830, is given also. Some climatic effects may be expected in the period of the supercenturial solar minimum. As a result a "global cooling" climatic effect in the range of 0.4-0.7° C could be expected.

  10. INTERPLANETARY MAGNETIC FLUX DEPLETION DURING PROTRACTED SOLAR MINIMA

    SciTech Connect

    Connick, David E.; Smith, Charles W.; Schwadron, Nathan A. E-mail: Charles.Smith@unh.edu

    2011-01-20

    We examine near-Earth solar wind observations as assembled within the Omni data set over the past 15 years that constitute the latest solar cycle. We show that the interplanetary magnetic field continues to be depleted at low latitudes throughout the protracted solar minimum reaching levels below previously predicted minima. We obtain a rate of flux removal resulting in magnetic field reduction by 0.5 nT yr{sup -1} at 1 AU when averaged over the years 2005-2009 that reduces to 0.3 nT yr{sup -1} for 2007-2009. We show that the flux removal operates on field lines that follow the nominal Parker spiral orientation predicted for open field lines and are largely unassociated with recent ejecta. We argue that the field line reduction can only be accomplished by ongoing reconnection of nominally open field lines or very old closed field lines and we contend that these two interpretations are observationally equivalent and indistinguishable.

  11. Polar Magnetic Fields Observed During the Last Four Solar Minima

    NASA Astrophysics Data System (ADS)

    Sun, X.; Liu, Y.; Hoeksema, J. T.

    2008-12-01

    The Sun's polar fields during the current minimum are the weakest in at least four solar cycles. The field strengths are fairly symmetric, unlike at least the two previous minima. We compare data from the Wilcox Solar Observatory (WSO) and Michelson Doppler Imager (MDI) to follow the polar field changes since 1976. The polar field is never observed well from Earth because the ecliptic lies near the Sun's equator, and each year the view of the north (south) is completely hidden for several months around March 7 (September 7). Analysis of the most favorably oriented MDI synoptic maps each year allows us to derive the fairly slowly evolving large-scale polar magnetic field pattern from 1996 to the present. We account for differential rotation and other geometric effects. The analysis allows us to provide a useful interpolated or extrapolated correction that can be smoothly incorporated into the global synoptic or synchronic maps above about 70 degrees latitude. The polar field is important in modeling the large-scale coronal and heliospheric field, particularly at minimum. Even though there has been extremely little solar activity over the last several months, at the current solar minimum the structure of the corona is much less equatorial than usual, in part because the polar fields are relatively weak.

  12. Relativistic electrons in the magnetospheric tail during solar activity minima

    NASA Astrophysics Data System (ADS)

    Daibog, Elena; Kecskemety, Karoly; Logachev, Yurii

    Measurements of energetic particle fluxes in the Earth magnetosphere at large distances from the Earth (10 Re and more) are still sparse, and registering instruments usually have high background, that does not permit to determine low particle fluxes accurately, in particular those of subrelativistic electrons. Information on these fluxes and their dynamics are very important for understanding the structure of the magnetosphere, direction of particle drifts, mechanisms of the penetration of solar particles into the magnetosphere and other details of particle-field interaction. The orbit and instrumentation of the Earth satellite IMP-8 allows to fill up this gap to some extent. IMP-8 had a nearly circular orbit with a radius of about 35 Re. The orbital period was 12 days, of which 4 days was spent in the magnetospheric tail. The fluxes of 0.2-10 MeV electrons between 1974 and 2001 are analyzed in different parts of the IMP-8 orbit: at the entrance-exit from the magnetosphere, outside of the magnetosphere and in the near- magnetospheric space. It is shown that during quite periods of solar activity, even during solar minima, electron flux enhancements in the magnetospheric tail were observed due to acceleration mechanisms in the magnetosphere, penetration of solar particles and electrons from the Jovian magnetosphere.

  13. VizieR Online Data Catalog: Minima and maxima of 299 variables (Hubscher+, 2009)

    NASA Astrophysics Data System (ADS)

    Hubscher, J.; Steinbach, H.-M.; Walter, F.

    2009-03-01

    In this 61th compilation of BAV results, photoelectric observations obtained in the year 2008 are presented on 299 variable stars giving 655 minima on eclipsing binaries and maxima on pulsating stars. All moments of minima and maxima are heliocentric. (3 data files).

  14. Anti lipid peroxidation activity of Piper trioicum Roxb. and Physalis minima L. extracts.

    PubMed

    Dinakaran, Sathis Kumar; Saraswathi, Narasimha Raju; Nalini, Venkata Rama Rao; Srisudharson; Bodanapu, Venkat Ram Reddy; Avasarala, Harani; Banji, David

    2011-07-01

    Attempt has been made to evaluate free radical scavenging activity of ethanolic extract of Piper trioicum Roxb. and Physalis minima L. individually. In this study goat liver has been used as lipid source. This in vitro evaluation was done by measuring the malondialdehyde (MDA) of tissue homogenates. The results suggest that the ethanolic extract of the Piper trioicum Roxb. and Physalis minima L. has the ability to suppress the lipid peroxidation and it was also found that Piper trioicum Roxb. extract has more activity than Physalis minima L. extract.

  15. Erratum: "B.R.N.O. Contributions #38 Times of minima of eclipsing binary" (OEJV #160, [2013])

    NASA Astrophysics Data System (ADS)

    Honková, K.; Juryšek, J.; Lehký, M.; Šmelcer, L.; Trnka, J.; Mašek, M.; Urbaník, M.; Auer, R.; Vrašták, M.; Kučáková, H.; Ruocco, N.; Magris, M.; Polák, J.; Brát, L.; Audejean, M.; Banfi, M.; Moudrá, M.; Lomoz, F.; Přibík, V.; Dřevěný, R.; Scaggiante, F.; Kocián, R.; Cagaš, P.; Poddaný, S.; Zíbar, M.; Jacobsen, J.; Marek, P.; Colazo, C.; Zardin, D.; Sobotka, P.; Starzomski, J.; Hladík, B.; Vincenzi, M.; Skarka, M.; Walter, F.; Chapman, A.; Díaz, N. D.; Aceti, P.; Singh, P.; Kalista, L.; Kamenec, M.; Zejda, M.; Marchi, F.; Bílek, R.; Guzzo, P.; Corfini, G.; Onderková, K.; Hečko, A.; Mina, F.; Vítek, M.; Barsa, R.; Quinones, C.; Taormina, M.; Melia, R.; Schneiter, M.; Scavuzzo, A.; Marcionni, N.; Ehrenberger, R.; Tapia, L.; Fasseta, G.; Suarez, N.; Scaggiante, D.; Artusi, E.; Garcia, R.; Grnja, J.; Fišer, A.; Hynek, T.; Vilášek, M.; Rozehnal, J.; Kalisch, T.; Lang, K.; Gorková, S.; Novysedlák, R.; Salvaggio, F.; Smyčka, T.; Spurný, M.; Wikander, T.; Mravik, J.; Šuchań, J.; Čaloud, J.

    2014-08-01

    Due to an errors in calculated heliocentric corrections, there are 404 wrong HJD minima timings (with larger Difference than Min error; see header of the Table) in "B.R.N.O. Contributions #38 Times of minima of eclipsing binary" paper. The correct minima timings are presented hereafter.

  16. More on conditions of local and global minima coincidence in discrete optimization problems

    SciTech Connect

    Lebedeva, T.T.; Sergienko, I.V.; Soltan, V.P.

    1994-05-01

    In some areas of discrete optimization, it is necessary to isolate classes of problems whose target functions do not have local or strictly local minima that differ from the global minima. Examples include optimizations on discrete metric spaces and graphs, lattices and partially ordered sets, and linear combinatorial problems. A unified schema that to a certain extent generalizes the convexity models on which the above-cited works are based has been presented in articles. This article is a continuation of that research.

  17. Global minima for rare gas clusters containing one alkali metal ion

    NASA Astrophysics Data System (ADS)

    Hernández-Rojas, Javier; Wales, David J.

    2003-10-01

    We present candidate structures for the global minima of N-atom rare gas clusters containing one additional alkali metal ion, LJNM. Lennard-Jones and Mason-Schamp potentials are used to represent the rare gas-rare gas and rare gas-alkali metal ion interactions, respectively. Results are presented for parameters appropriate to both Ar-K+ and Xe-Cs+ systems. When the ion is closer in size to the rare gas atoms (for XeNCs+) the global minima tend to be based on icosahedral packing. However, when the ion is relatively small (for ArNK+) the global minima below a certain size threshold are based on structures where the ion has lower coordination numbers. For larger clusters the global minima are again based on icosahedral packing. The latter structures can be found with minimal computational effort using the known global minima for clusters bound by Lennard-Jones or Morse potentials, substituting one atom at a time by the ion and minimizing.

  18. Coupled factors influencing detachment of nano- and micro-sized particles from primary minima

    NASA Astrophysics Data System (ADS)

    Shen, Chongyang; Lazouskaya, Volha; Jin, Yan; Li, Baoguo; Ma, Zhiqiang; Zheng, Wenjuan; Huang, Yuanfang

    2012-06-01

    This study examined the detachments of nano- and micro-sized colloids from primary minima in the presence of cation exchange by laboratory column experiments. Colloids were initially deposited in columns packed with glass beads at 0.2 M CaCl2 in the primary minima of Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energies. Then, the columns were flushed with NaCl solutions with different ionic strengths (i.e., 0.001, 0.01, 0.1 and 0.2 M). Detachments were observed at all ionic strengths and were particularly significant for the nanoparticle. The detachments increased with increasing electrolyte concentration for the nanoparticle whereas increased from 0.001 M to 0.01 M and decreased with further increasing electrolyte concentration for the micro-sized colloid. The observations were attributed to coupled influence of cation exchange, short-range repulsion, surface roughness, surface charge heterogeneity, and deposition in the secondary minima. The detachments of colloids from primary minima challenge the common belief that colloid interaction in primary minimum is irreversible and resistant to disturbance in solution ionic strength and composition. Although the significance of surface roughness, surface charge heterogeneity, and secondary minima on colloid deposition has been widely recognized, our study implies that they also play important roles in colloid detachment. Whereas colloid detachment is frequently associated with decrease of ionic strength, our results show that increase of ionic strength can also cause detachment due to influence of cation exchange.

  19. Fast-Flowering Mini-Maize: Seed to Seed in 60 Days

    PubMed Central

    McCaw, Morgan E.; Wallace, Jason G.; Albert, Patrice S.; Buckler, Edward S.; Birchler, James A.

    2016-01-01

    Two lines of Zea mays were developed as a short-generation model for maize. The Fast-Flowering Mini-Maize (FFMM) lines A and B are robust inbred lines with a significantly shorter generation time, much smaller stature, and better greenhouse adaptation than traditional maize varieties. Five generations a year are typical. FFMM is the result of a modified double-cross hybrid between four fast-flowering lines: Neuffer’s Early ACR (full color), Alexander’s Early Early Synthetic, Tom Thumb Popcorn, and Gaspe Flint, followed by selection for early flowering and desirable morphology throughout an 11-generation selfing regime. Lines A and B were derived from different progeny of the initial hybrid, and crosses between Mini-Maize A and B exhibit heterosis. The ancestry of each genomic region of Mini-Maize A and B was inferred from the four founder populations using genotyping by sequencing. Other genetic and genomic tools for these lines include karyotypes for both lines A and B, kernel genetic markers y1 (white endosperm) and R1-scm2 (purple endosperm and embryo) introgressed into Mini-Maize A, and ∼24× whole-genome resequencing data for Mini-Maize A. PMID:27440866

  20. Time spans between price maxima and price minima in stock markets

    NASA Astrophysics Data System (ADS)

    Zou, Yongjie; Li, Honggang

    2014-02-01

    We empirically investigate the distribution of time spans between price maxima and price minima in international stock markets, where a time span is defined as the time interval between a local price minimum and a local price maximum, and local price extrema are identified by a method introduced by Preis and Stanley (Preis et al. (2011), Preis (2011), Preis and Stanley (2011, 2010), Preis (2010), Preis and Stanley (2010), Stanley et al. (2010), Preis and Stanley (2009)). The empirical results show that both the tail distributions of time spans from local price maxima to local price minima and the tail distributions of time spans from local price minima to local price maxima yield an exponential distribution. In addition, price rise/fall asymmetry is observed by comparing the values of the exponents of the distribution curves. These results are robust across eight representative stock markets.

  1. VizieR Online Data Catalog: Minima and maxima of 389 variables (Hubscher+, 2007)

    NASA Astrophysics Data System (ADS)

    Hubscher, J.; Walter, F.

    2008-11-01

    In this 57th compilation of BAV results, photoelectric observations obtained in the year 2006 are presented on 389 variable stars giving 611 minima on eclipsing binaries and maxima on pulsating stars. All moments of minima and maxima are heliocentric. The errors are tabulated in column '+/-'. The values in column 'O-C' are determined without incorporation of nonlinear terms. The references are given in the section 'Remarks'. All information about photometers and filters are specified in the column 'Rem'. The observations were made at private observatories. The photoelectric measurements and all the light-curves with evaluations can be obtained from the office of the BAV for inspection. (3 data files).

  2. VizieR Online Data Catalog: Minima and maxima of 380 variables (Hubscher+, 2009)

    NASA Astrophysics Data System (ADS)

    Hubscher, J.; Steinbach, H.-M.; Walter, F.

    2011-03-01

    In this 63rd compilation of BAV results, photoelectric observations obtained in the year 2008 are presented on 380 variable stars giving 591 minima on eclipsing binaries and maxima on pulsating stars. All moments of minima and maxima are heliocentric. The errors are tabulated in column '+/-'. The values in column 'O-C' are determined without incorporation of nonlinear terms. The references are given in the section 'Remarks'. All information about photometers and filters are specified in the column 'Rem'. The observations were made at private observatories. The photoelectric measurements and all the light curves with evaluations can be obtained from the office of the BAV for inspection. (3 data files).

  3. VizieR Online Data Catalog: Minima and maxima of 436 variables (Huebscher+, 2011)

    NASA Astrophysics Data System (ADS)

    Huebscher, J.; Monninger, G.

    2011-08-01

    In this 68th compilation of BAV results, photoelectric observations obtained in the year 2010 are presented on 436 variable stars giving 784 minima on eclipsing binaries and maxima on pulsating stars. All moments of minima and maxima are heliocentric. The errors are tabulated in column '+/-'. The values in column 'O-C' are determined without incorporation of nonlinear terms.The references are given in the section 'Remarks'. All information about photometers and filters are specified in the column 'Rem'. The observations were made at private observatories. The photoelectric measurements and all the lightcurves with evaluations can be obtained from the office of the BAV for inspection. (3 data files).

  4. VizieR Online Data Catalog: Minima and maxima of 292 variables (Hubscher+, 2008)

    NASA Astrophysics Data System (ADS)

    Hubscher, J.; Steinbach, H.-M.; Walter, F.

    2008-11-01

    In this 60th compilation of BAV results, photoelectric observations obtained in the years 2007 are presented on 292 variable stars giving 399 minima on eclipsing binaries and maxima on pulsating stars. All moments of minima and maxima are heliocentric. The errors are tabulated in column '+/-'. The values in column 'O-C' are determined without incorporation of nonlinear terms. The references are given in the section 'Remarks'. All information about photometers and filters are specified in the column 'Rem'. The observations were made at private observatories. The photoelectric measurements and all the lightcurves with evaluations can be obtained from the office of the BAV for inspection. (3 data files).

  5. VizieR Online Data Catalog: Minima and maxima of 452 variables (Hubscher+, 2010)

    NASA Astrophysics Data System (ADS)

    Hubscher, J.; Lehmann, P. B.; Monninger, G.; Steinbach, H.-M.; Walter, F.

    2011-03-01

    In this 65th compilation of BAV results, photoelectric observations obtained in the year 2009 are presented on 521 variable stars giving 871 minima on eclipsing binaries and maxima on pulsating stars. All moments of minima and maxima are heliocentric. The errors are tabulated in column '+/-'. The values in column 'O-C' are determined without incorporation of nonlinear terms. The references are given in the section 'Remarks'. All information about photometers and filters are specified in the column 'Rem'. The observations were made at private observatories. The photoelectric measurements and all the light curves with evaluations can be obtained from the office of the BAV for inspection. (3 data files).

  6. VizieR Online Data Catalog: Minima and maxima of 503 variables (Hubscher, 2011)

    NASA Astrophysics Data System (ADS)

    Hubscher, J.

    2011-09-01

    In this 69th compilation of BAV results, photoelectric observations obtained in the year 2010 and 2011 are presented on 503 variable stars giving 767 minima on eclipsing binaries and maxima on pulsating stars. All moments of minima and maxima are heliocentric. The errors are tabulated in column '+/-'. The values in column 'O-C' are determined without incorporation of nonlinear terms. The references are given in the section 'Remarks'. All information about photometers and filters are specified in the column 'Rem'. The observations were made at private observatories. The photoelectric measurements and all the light curves with evaluations can be obtained from the office of the BAV for inspection. (3 data files).

  7. VizieR Online Data Catalog: Minima and maxima of 735 variables (Hubscher+, 2007)

    NASA Astrophysics Data System (ADS)

    Hubscher, J.

    2008-11-01

    In this 58th compilation of BAV results, photoelectric observations obtained in the years 2006 and 2007 are presented on 473 variable stars giving 735 minima and maxima on eclipsing binaries and pulsating stars. All moments of minima and maxima are heliocentric. The errors are tabulated in column '+/-'. The values in column 'O-C' are determined without incorporation of nonlinear terms. The references are given in the section 'Remarks'. All information about photometers and filters are specified in the column 'Rem'. The observations were made at private observatories. The photoelectric measurements and all the light curves with evaluations can be obtained from the office of the BAV for inspection. (3 data files).

  8. Coherent and dissipative wave packet dynamics in cyclic model systems with four equivalent potential minima

    NASA Astrophysics Data System (ADS)

    Brackhagen, O.; Kühn, O.; Manz, J.; May, V.; Meyer, R.

    1994-06-01

    The dynamics of cyclic systems with four equivalent potential minima is studied here from two different points of view. The solution of the time-dependent Schrödinger equation provides insight into the coherent wave packet motion. The resulting reaction mechanism involves relocalization between opposite, not neighboring potential minima. The inclusion of an environment within a density matrix description leads to dissipation and therefore to a transition from coherent to incoherent dynamics. The theoretical considerations are applied to a simple model of the cyclic motion of a proton in a molecular framework.

  9. Restricted random search method based on taboo search in the multiple minima problem

    NASA Astrophysics Data System (ADS)

    Hong, Seung Do; Jhon, Mu Shik

    1997-03-01

    The restricted random search method is proposed as a simple Monte Carlo sampling method to search minima fast in the multiple minima problem. This method is based on taboo search applied recently to continuous test functions. The concept of the taboo region instead of the taboo list is used and therefore the sampling of a region near an old configuration is restricted in this method. This method is applied to 2-dimensional test functions and the argon clusters. This method is found to be a practical and efficient method to search near-global configurations of test functions and the argon clusters.

  10. Source of level dependent minima in rabbit distortion product otoacoustic emissions

    PubMed Central

    Fahey, P. F.; Stagner, B. B.; Martin, G. K.

    2008-01-01

    Sharp level dependent minima (commonly called nulls or notches) in the distortion product otoacoustic emissions (DPOAEs) have been postulated to be due to two different mechanisms. It is shown here that the level dependent nulls in rabbit 2f1−f2 DPOAEs carry the signature of the mixing of a third order nonlinear term with a fifth order nonlinear term. This suggests that the minima are not due to the mixing of signals from two different physical sites of origin, but rather are due to the nature of the nonlinearity itself. Model simulations show that null production is indifferent to several properties of nonlinear input∕output functions. PMID:19206797

  11. Studies of the location of azimuth modulation minima for Ku band ocean radar backscatter

    NASA Technical Reports Server (NTRS)

    Li, F.; Neumann, G.; Shaffer, S.; Durden, S. L.

    1988-01-01

    An extensive data set of radar backscatter measurements at 14 GHz was used to evaluate the locations of the azimuthal modulation minima relative to the cross-wind directions. It was found that the minima were significantly offset from the cross-wind directions toward the downwind direction for the horizontal polarization data. These offsets were substantially smaller for the vertical polarization data. Simple scattering model calculations, based on the two-scale scattering approach, also show similar offsets. Implications of these results for the goephysical model function are discussed.

  12. Spontaneous Detachment of Colloids from Primary Energy Minima by Brownian Diffusion.

    PubMed

    Wang, Zhan; Jin, Yan; Shen, Chongyang; Li, Tiantian; Huang, Yuanfang; Li, Baoguo

    2016-01-01

    The Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energy profile has been frequently used to interpret the mechanisms controlling colloid attachment/detachment and aggregation/disaggregation behavior. This study highlighted a type of energy profile that is characterized by a shallow primary energy well (i.e., comparable to the average kinetic energy of a colloid) at a small separation distance and a monotonic decrease of interaction energy with separation distance beyond the primary energy well. This energy profile is present due to variations of height, curvature, and density of discrete physical heterogeneities on collector surfaces. The energy profile indicates that colloids can be spontaneously detached from the shallow primary energy well by Brownian diffusion. The spontaneous detachment from primary minima was unambiguously confirmed by conducting laboratory column transport experiments involving flow interruptions for two model colloids (polystyrene latex microspheres) and engineered nanoparticles (fullerene C60 aggregates). Whereas the spontaneous detachment has been frequently attributed to attachment in secondary minima in the literature, our study indicates that the detached colloids could be initially attached at primary minima. Our study further suggests that the spontaneous disaggregation from primary minima is more significant than spontaneous detachment because the primary minimum depth between colloid themselves is lower than that between a colloid and a collector surface.

  13. Spontaneous Detachment of Colloids from Primary Energy Minima by Brownian Diffusion

    PubMed Central

    Wang, Zhan; Jin, Yan; Shen, Chongyang; Li, Tiantian; Huang, Yuanfang; Li, Baoguo

    2016-01-01

    The Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energy profile has been frequently used to interpret the mechanisms controlling colloid attachment/detachment and aggregation/disaggregation behavior. This study highlighted a type of energy profile that is characterized by a shallow primary energy well (i.e., comparable to the average kinetic energy of a colloid) at a small separation distance and a monotonic decrease of interaction energy with separation distance beyond the primary energy well. This energy profile is present due to variations of height, curvature, and density of discrete physical heterogeneities on collector surfaces. The energy profile indicates that colloids can be spontaneously detached from the shallow primary energy well by Brownian diffusion. The spontaneous detachment from primary minima was unambiguously confirmed by conducting laboratory column transport experiments involving flow interruptions for two model colloids (polystyrene latex microspheres) and engineered nanoparticles (fullerene C60 aggregates). Whereas the spontaneous detachment has been frequently attributed to attachment in secondary minima in the literature, our study indicates that the detached colloids could be initially attached at primary minima. Our study further suggests that the spontaneous disaggregation from primary minima is more significant than spontaneous detachment because the primary minimum depth between colloid themselves is lower than that between a colloid and a collector surface. PMID:26784446

  14. Release and evaluation of Cyrtobagous salviniae on common salvinia minima in southern Louisiana

    USDA-ARS?s Scientific Manuscript database

    Common salvinia (Salvinia minima) is one of the most widespread, non-native invasive species at the Barataria Preserve of Jean Lafitte National Historical Park and Preserve in southern Louisiana and currently infests more than 3,600 ha and 48 km of navigable waterways. A proven biological control a...

  15. Checklist of insects associated with Salvinia minima (Baker) in Louisiana, USA

    USDA-ARS?s Scientific Manuscript database

    his study presents a list of adult insects (excluding Diptera and Lepidoptera) collected from an infestation of an invasive aquatic weed, common salvinia (Salvinia minima Baker), in southern Louisiana, USA. Insects were sampled from May – November of 2009 and 2010 using floating pitfall traps. A to...

  16. Solar Cycle Variability and Grand Minima Induced by Joy's Law Scatter

    NASA Astrophysics Data System (ADS)

    Karak, Bidya Binay; Miesch, Mark S.

    2017-08-01

    The strength of the solar cycle varies from one cycle to another in an irregular manner and the extreme example of this irregularity is the Maunder minimum when Sun produced only a few spots for several years. We explore the cause of these variabilities using a 3D Babcock--Leighton dynamo. In this model, based on the toroidal flux at the base of the convection zone, bipolar magnetic regions (BMRs) are produced with flux, tilt angle, and time of emergence all obtain from their observed distributions. The dynamo growth is limited by a tilt quenching.The randomnesses in the BMR emergences make the poloidal field unequal and eventually cause an unequal solar cycle. When observed fluctuations of BMR tilts around Joy's law, i.e., a standard deviation of 15 degrees, are considered, our model produces a variation in the solar cycle comparable to the observed solar cycle variability. Tilt scatter also causes occasional Maunder-like grand minima, although the observed scatter does not reproduce correct statistics of grand minima. However, when we double the tilt scatter, we find grand minima consistent with observations. Importantly, our dynamo model can operate even during grand minima with only a few BMRs, without requiring any additional alpha effect.

  17. Influence of shape resonances on minima in cross sections for photoionization of excited atoms

    SciTech Connect

    Felfli, Z.; Manson, S.T. Department of Astronomy, Georgia State University, Atlanta, Georgia 30303 )

    1990-02-01

    A relationship between the location of Cooper minima and the difference between the quantum defect of the initial state and the threshold phase shift (in units of {pi}) of the final state in excited photoionization has been suggested earlier (Phys. Rev. Lett. 48, 473 (1982)). The existence of a shape resonance in the final state is shown to modify this relationship.

  18. Fast-flowering mini-maize: seed to seed in 60 days

    USDA-ARS?s Scientific Manuscript database

    Two lines of Zea mays were developed as a short-generation model for maize. The Fast-Flowering Mini-Maize (FFMM) lines A and B are robust inbred lines with a significantly shorter generation time, much smaller stature, and better greenhouse adaptation than traditional maize varieties. Five generatio...

  19. A new heuristic method for approximating the number of local minima in partial RNA energy landscapes.

    PubMed

    Albrecht, Andreas A; Day, Luke; Abdelhadi Ep Souki, Ouala; Steinhöfel, Kathleen

    2016-02-01

    The analysis of energy landscapes plays an important role in mathematical modelling, simulation and optimisation. Among the main features of interest are the number and distribution of local minima within the energy landscape. Granier and Kallel proposed in 2002 a new sampling procedure for estimating the number of local minima. In the present paper, we focus on improved heuristic implementations of the general framework devised by Granier and Kallel with regard to run-time behaviour and accuracy of predictions. The new heuristic method is demonstrated for the case of partial energy landscapes induced by RNA secondary structures. While the computation of minimum free energy RNA secondary structures has been studied for a long time, the analysis of folding landscapes has gained momentum over the past years in the context of co-transcriptional folding and deeper insights into cell processes. The new approach has been applied to ten RNA instances of length between 99 nt and 504 nt and their respective partial energy landscapes defined by secondary structures within an energy offset ΔE above the minimum free energy conformation. The number of local minima within the partial energy landscapes ranges from 1440 to 3441. Our heuristic method produces for the best approximations on average a deviation below 3.0% from the true number of local minima.

  20. Metastable minima of the Heisenberg spin glass in a random magnetic field

    NASA Astrophysics Data System (ADS)

    Sharma, Auditya; Yeo, Joonhyun; Moore, M. A.

    2016-11-01

    We have studied zero-temperature metastable minima in classical m -vector component spin glasses in the presence of m -component random fields for two models, the Sherrington-Kirkpatrick (SK) model and the Viana-Bray (VB) model. For the SK model we have calculated analytically its complexity (the log of the number of minima) for both the annealed case where one averages the number of minima before taking the log and the quenched case where one averages the complexity itself, both for fields above and below the de Almeida-Thouless (AT) field, which is finite for m >2 . We have done numerical quenches starting from a random initial state (infinite temperature state) by putting spins parallel to their local fields until there is no further decrease of the energy and found that in zero field it always produces minima that have zero overlap with each other. For the m =2 and m =3 cases in the SK model the final energy reached in the quench is very close to the energy Ec at which the overlap of the states would acquire replica symmetry-breaking features. These minima have marginal stability and will have long-range correlations between them. In the SK limit we have analytically studied the density of states ρ (λ ) of the Hessian matrix in the annealed approximation. Despite the fact that in the presence of a random field there are no continuous symmetries, the spectrum extends down to zero with the usual √{λ } form for the density of states for fields below the AT field. However, when the random field is larger than the AT field, there is a gap in the spectrum, which closes up as the AT field is approached. The VB model behaves differently and seems rather similar to studies of the three-dimensional Heisenberg spin glass in a random vector field.

  1. Coupled factors influencing detachment of nano- and micro-sized particles from primary minima.

    PubMed

    Shen, Chongyang; Lazouskaya, Volha; Jin, Yan; Li, Baoguo; Ma, Zhiqiang; Zheng, Wenjuan; Huang, Yuanfang

    2012-06-01

    This study examined the detachments of nano- and micro-sized colloids from primary minima in the presence of cation exchange by laboratory column experiments. Colloids were initially deposited in columns packed with glass beads at 0.2 M CaCl(2) in the primary minima of Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energies. Then, the columns were flushed with NaCl solutions with different ionic strengths (i.e., 0.001, 0.01, 0.1 and 0.2 M). Detachments were observed at all ionic strengths and were particularly significant for the nanoparticle. The detachments increased with increasing electrolyte concentration for the nanoparticle whereas increased from 0.001 M to 0.01 M and decreased with further increasing electrolyte concentration for the micro-sized colloid. The observations were attributed to coupled influence of cation exchange, short-range repulsion, surface roughness, surface charge heterogeneity, and deposition in the secondary minima. The detachments of colloids from primary minima challenge the common belief that colloid interaction in primary minimum is irreversible and resistant to disturbance in solution ionic strength and composition. Although the significance of surface roughness, surface charge heterogeneity, and secondary minima on colloid deposition has been widely recognized, our study implies that they also play important roles in colloid detachment. Whereas colloid detachment is frequently associated with decrease of ionic strength, our results show that increase of ionic strength can also cause detachment due to influence of cation exchange. Copyright © 2012 Elsevier B.V. All rights reserved.

  2. The method of intercepts in parameter space for the analysis of local minima caused by dose-volume constraints.

    PubMed

    Wu, Chuan; Jeraj, Robert; Mackie, Thomas R

    2003-06-07

    The local minima problem in radiotherapy optimization has been a concern for both researchers and physicians. In this work, local minima induced by dose-volume histogram (DVH) constraints are discussed. The non-convex property of the feasible set formed by DVH constraints is discussed in beam weight space. An intuitive explanation of the origin of this type of local minima is given by a two-beam model setup. Some interesting properties and insights about the DVH-induced local minima are found. Based on this, a heuristic non-random initial guess sampling method is proposed and applied to a clinical nasopharyngeal case, where some significantly different local minima are located.

  3. Third Minima in Thorium and Uranium Isotopes in a Self-Consistent Theory

    SciTech Connect

    McDonnell, J. D.

    2013-01-01

    Background: Well-developed third minima, corresponding to strongly elongated and reflection-asymmetric shapes associated with dimolecular configurations, have been predicted in some non-self-consistent models to impact fission pathways of thorium and uranium isotopes. These predictions have guided the interpretation of resonances seen experimentally. On the other hand, self-consistent calculations consistently predict very shallow potential-energy surfaces in the third minimum region.

    Purpose: We investigate the interpretation of third-minimum configurations in terms of dimolecular (cluster) states. We study the isentropic potential-energy surfaces of selected even-even thorium and uranium isotopes at several excitation energies. In order to understand the driving effects behind the presence of third minima, we study the interplay between pairing and shell effects.

    Methods: We use the finite-temperature superfluid nuclear density functional theory. We consider two Skyrme energy density functionals: a traditional functional SkM and a recent functional UNEDF1 optimized for fission studies.

    Results: We predict very shallow or no third minima in the potential-energy surfaces of 232Th and 232U. In the lighter Th and U isotopes with N = 136 and 138, the third minima are better developed. We show that the reflection-asymmetric configurations around the third minimum can be associated with dimolecular states involving the spherical doubly magic 132Sn and a lighter deformed Zr or Mo fragment. The potential-energy surfaces for 228,232Th and 232U at several excitation energies are presented. We also study isotopic chains to demonstrate the evolution of the depth of the third minimum with neutron number.

    Conclusions: We show that the neutron shell effect that governs the existence of the dimolecular states around the third minimum is consistent with the spherical-to-deformed shape transition in the Zr andMo isotopes around N = 58.We demonstrate that the depth of

  4. Third minima in thorium and uranium isotopes in a self-consistent theory

    NASA Astrophysics Data System (ADS)

    McDonnell, J. D.; Nazarewicz, W.; Sheikh, J. A.

    2013-05-01

    Background: Well-developed third minima, corresponding to strongly elongated and reflection-asymmetric shapes associated with dimolecular configurations, have been predicted in some non-self-consistent models to impact fission pathways of thorium and uranium isotopes. These predictions have guided the interpretation of resonances seen experimentally. On the other hand, self-consistent calculations consistently predict very shallow potential-energy surfaces in the third minimum region.Purpose: We investigate the interpretation of third-minimum configurations in terms of dimolecular (cluster) states. We study the isentropic potential-energy surfaces of selected even-even thorium and uranium isotopes at several excitation energies. In order to understand the driving effects behind the presence of third minima, we study the interplay between pairing and shell effects.Methods: We use the finite-temperature superfluid nuclear density functional theory. We consider two Skyrme energy density functionals: a traditional functional SkM* and a recent functional UNEDF1 optimized for fission studies.Results: We predict very shallow or no third minima in the potential-energy surfaces of 232Th and 232U. In the lighter Th and U isotopes with N=136 and 138, the third minima are better developed. We show that the reflection-asymmetric configurations around the third minimum can be associated with dimolecular states involving the spherical doubly magic 132Sn and a lighter deformed Zr or Mo fragment. The potential-energy surfaces for 228,232Th and 232U at several excitation energies are presented. We also study isotopic chains to demonstrate the evolution of the depth of the third minimum with neutron number.Conclusions: We show that the neutron shell effect that governs the existence of the dimolecular states around the third minimum is consistent with the spherical-to-deformed shape transition in the Zr and Mo isotopes around N=58. We demonstrate that the depth of the third minimum

  5. VizieR Online Data Catalog: Minima and maxima of 292 variables (Hubscher+, 2010)

    NASA Astrophysics Data System (ADS)

    Hubscher, J.; Lehmann, P. B.; Monninger, G.; Steinbach, H.-M.; Walter, F.

    2011-03-01

    In this 66th compilation of BAV results, photoelectric observations obtained in the years 2009 and 2010 are presented on 452 variable stars giving 838 minima on eclipsing binaries and maxima on pulsating stars. All moments of minima and maxima are heliocentric. The errors are tabulated in column '+/-'. The values in column 'O-C' are determined without incorporation of nonlinear terms.The references are given in the section 'Remarks'. All information about photometers and filters are specified in the column `Rem'. The observations were made at private observatories. The photoelectric measurements and all the light curves with evaluations can be obtained from the office of the BAV for inspection. (3 data files).

  6. Anti-inflammatory, analgesic and antipyretic activities of Physalis minima Linn.

    PubMed

    Khan, Murad Ali; Khan, Haroon; Khan, Sarwar; Mahmood, Tahira; Khan, Pir Mohammad; Jabar, Abdul

    2009-06-01

    In our present investigation, the crude methanol extract and chloroform fraction of the whole plant of Physalis minima Linn (Solanaceae) was investigated for anti-inflammatory, analgesic and antipyretic activities in NMRI mice and Wistar rats of either sex at 200 and 400 mg/kg, respectively. Various established in-vivo model's were used during the study. Both crude extract and chloroform fraction showed marked anti-inflammatory and analgesic activities as compared to a control at tested doses. The antipyretic potential of the crude extract and chloroform were insignificant in the Brewer's yeast fever model. Therefore, the whole plant of Physalis minima Linn could be considered as a potential candidate for bioactivity-guided isolation of natural anti-inflammatory and analgesic agents.

  7. [Preliminary study on molluscicidal effect of active components from Centipeda minima].

    PubMed

    Ni, Hong; Ma, An-Ning; Zhang, Yun; Geng, Peng

    2009-08-01

    The active components from Centipeda minima were extracted by water or ethanol, and identified by FTIR spectroscopy and UV-visible spectrophotometer. The molluscicidal effect of aqueous extract and ethanol extract from Centipeda minima against Oncomelania hupensis was determined as referring to the WHO guidelines for laboratory molluscicidal test. Treated with over 2.0 g/L aqueous extract and ethanol extract for five days, the mortality of O. hupensis was up to 100%, and their LC50, for snails was 0.50 g/L and 0.62 g/L, respectively. The molluscicidal activity of aqueous extract was higher than that of ethanol extract. The main components of aqueous extract and ethanol extract were sesquiterpenes lactones and sterols.

  8. Antibiotic activity of Emerimicin IV isolated from Emericellopsis minima from Talcahuano Bay, Chile.

    PubMed

    Inostroza, Alejandro; Lara, Liliana; Paz, Cristian; Perez, Andrés; Galleguillos, Felipe; Hernandez, Victor; Becerra, José; González-Rocha, Gerardo; Silva, Mario

    2017-07-03

    Due to the increasing emergence of resistance of bacterial pathogens to current antibiotics, we have examined the marine fungi present in sea sediments obtained 200 m offshore to discover new antibacterial compounds active against multidrug-resistant bacteria. One strain, identified as Emericellopsis minima, was isolated from sediments of Talcahuano Bay (Chile). From the liquid culture of E. minima, we isolated Emerimicin IV, a unique fungal peptaibol that exhibited antibacterial activity. The structure of this compound was assigned by interpretation of (1)H NMR and HR-LCMS data. Emerimicin IV showed bacteriostatic activity against clinical isolates of methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecalis with MIC values ranging between 100 and 12.5 μg/mL.

  9. Minima of Higgs potentials corresponding to non-maximal isotropy subgroups

    NASA Astrophysics Data System (ADS)

    Abud, M.; Anastaze, G.; Eckert, P.; Ruegg, H.

    1985-06-01

    Results are presented of the minimization of the Higgs potential for the irreducible representation 75 of SU(5). Isotropy groups of minima are determined using a geometrical method developed recently by Abud and Sartori. Minima with the maximal isotropy algebras su(3) + su(2) + u(1), sp(4) + u(1), su(2) + su(2) + u(1) and su(2) were found as well as a minimum with a non-maximal isotropy algebra su(2) + su(2) + u(1) + u(1) and discrete symmetry. A minimum having a non-maximal isotropy group SU(2) ⊗ U(1) ⊗ U(1) was also found, contrary to Michel's conjecture. A detailed analysis of the results is presented and the limits of Michel's conjecture are pointed out.

  10. Physalindicanols, New Biogenetic Precursors of C28-Steroidal Lactones from Physalis minima var. indica.

    PubMed

    Sinha, S C; Ali, A; Bagchi, A; Sahai, M; Ray, A B

    1987-02-01

    The structures of two isomeric C (28)-sterols isolated from PHYSALIS MINIMA Linn. var. INDICA were elucidated as ergosta-5,25-dien-3beta,24zeta,-diol and ergosta-5,24(28)-dien-3beta,25-diol on the basis of detailed spectral analysis. The isolated sterols are regarded as precursors in the elaboration of complex C (28)-steroidal lactones, native in this plant and related species.

  11. Solasodine glycoside production by hairy root cultures of Physalis minima Linn.

    PubMed

    Putalun, Waraporn; Prasamsiwamai, Preeyaporn; Tanaka, Hiroyuki; Shoyama, Yukihiro

    2004-04-01

    Hairy root cultures of Physalis minima L. were developed using Agrobacterium rhizogenes, strain ATCC 15834 mediated transformation and grown in half strength of Murashige and Skoog medium containing 8% (w/v) sucrose. Media supplementation with 1 mg naphthalenacetic acid l(-1) and 1 mg benzyladenine increased solasodine glycoside up to 900 g dry wt, which was 20 times higher than that in the native root.

  12. Cooper minima and Young-type interferences in the photoionization of H{sub 2}{sup +}

    SciTech Connect

    Della Picca, R.; Fainstein, P. D.; Dubois, A.

    2011-09-15

    We present a detailed study of the partial and total cross sections for photon-induced electron emission from H{sub 2}{sup +}. By comparing the results employing exact and approximate, bounded and continuum wave functions, for one- and two-center basis functions, we find the origin and position of the Cooper-like minima in the partial cross sections and their relationship with the Young-type interference pattern.

  13. Quantification of colloid retention and release by straining and energy minima in variably saturated porous media.

    PubMed

    Sang, Wenjing; Morales, Verónica L; Zhang, Wei; Stoof, Cathelijne R; Gao, Bin; Schatz, Anna Lottie; Zhang, Yalei; Steenhuis, Tammo S

    2013-08-06

    The prediction of colloid transport in unsaturated porous media in the presence of large energy barrier is hampered by scant information of the proportional retention by straining and attractive interactions at surface energy minima. This study aims to fill this gap by performing saturated and unsaturated column experiments in which colloid pulses were added at various ionic strengths (ISs) from 0.1 to 50 mM. Subsequent flushing with deionized water released colloids held at the secondary minimum. Next, destruction of the column freed colloids held by straining. Colloids not recovered at the end of the experiment were quantified as retained at the primary minimum. Results showed that net colloid retention increased with IS and was independent of saturation degree under identical IS and Darcian velocity. Attachment rates were greater in unsaturated columns, despite an over 3-fold increase in pore water velocity relative to saturated columns, because additional retention at the readily available air-associated interfaces (e.g., the air-water-solid [AWS] interfaces) is highly efficient. Complementary visual data showed heavy retention at the AWS interfaces. Retention by secondary minima ranged between 8% and 46% as IS increased, and was greater for saturated conditions. Straining accounted for an average of 57% of the retained colloids with insignificant differences among the treatments. Finally, retention by primary minima ranged between 14% and 35% with increasing IS, and was greater for unsaturated conditions due to capillary pinning.

  14. Scale-estimation of quantum coherent energy transport in multiple-minima systems.

    PubMed

    Farrow, Tristan; Vedral, Vlatko

    2014-07-01

    A generic and intuitive model for coherent energy transport in multiple minima systems coupled to a quantum mechanical bath is shown. Using a simple spin-boson system, we illustrate how a generic donor-acceptor system can be brought into resonance using a narrow band of vibrational modes, such that the transfer efficiency of an electron-hole pair (exciton) is made arbitrarily high. Coherent transport phenomena in nature are of renewed interest since the discovery that a photon captured by the light-harvesting complex (LHC) in photosynthetic organisms can be conveyed to a chemical reaction centre with near-perfect efficiency. Classical explanations of the transfer use stochastic diffusion to model the hopping motion of a photo-excited exciton. This accounts inadequately for the speed and efficiency of the energy transfer measured in a series of recent landmark experiments. Taking a quantum mechanical perspective can help capture the salient features of the efficient part of that transfer. To show the versatility of the model, we extend it to a multiple minima system comprising seven-sites, reminiscent of the widely studied Fenna-Matthews-Olson (FMO) light-harvesting complex. We show that an idealised transport model for multiple minima coupled to a narrow-band phonon can transport energy with arbitrarily high efficiency.

  15. Dynamics of driven transitions between minima of a complex energy landscapes

    NASA Astrophysics Data System (ADS)

    Pusuluri, Sai Teja; Lang, Alex H.; Mehta, Pankaj; Castillo, Horacio E.

    We recently modeled cellular interconvertion dynamics by using an epigenetic landscape model inspired by neural network models. Given an arbitrary set of patterns, the model can be used to construct an energy landscape in which those patterns are the global minima. Here we study the transitions between stable states of the landscapes thus constructed, under the effect of an external driving force. We consider three different cases: i) choosing the patterns to be random and independendently distributed ii) choosing a set of patterns directly derived from the experimental cellular transcription factor expression data for a representative set of cell types in an organism and iii) choosing randomly generated trees of hierarchically correlated patterns, inspired by biology. For each of the three cases, we study the stability of the global minima against thermal fluctuations and external driving forces, and the dynamics of the driven transitions away from global minima. We compare the results obtained in the three cases defined above, and in particular we explore to what degree the correlations between patterns affect the transition dynamics.

  16. Coronal transients during two solar minima: their source regions and interplanetary counterparts

    NASA Astrophysics Data System (ADS)

    Cremades, Hebe; Mandrini, Cristina H.; Dasso, Sergio

    2012-07-01

    We have investigated two full solar rotations belonging to two distinct solar minima, in the frame of two coordinated observational and research campaigns. The nearly uninterrupted gathering of solar coronal data since the beginning of the SOHO era offers the exceptional possibility of comparing two solar minima for the first time, with regard to coronal transients. This study characterizes the variety of outward-travelling transients observed in the solar corona during both time intervals, from very narrow jet-like events to coronal mass ejections (CMEs). Their solar source regions and ensuing interplanetary structures were identified and characterized. Multi-wavelength images from the space missions SOHO, Yohkoh and STEREO, and ground-based observatories were studied for coronal ejecta and their solar sources, while in situ data registered by the ACE spacecraft were inspected for interplanetary CMEs and magnetic clouds. Instrumental aspects such as dissimilar resolution, cadence, and fields of view are considered in order to discern instrumentally-driven disparities from inherent differences between solar minima.

  17. Scale-estimation of quantum coherent energy transport in multiple-minima systems

    PubMed Central

    Farrow, Tristan; Vedral, Vlatko

    2014-01-01

    A generic and intuitive model for coherent energy transport in multiple minima systems coupled to a quantum mechanical bath is shown. Using a simple spin-boson system, we illustrate how a generic donor-acceptor system can be brought into resonance using a narrow band of vibrational modes, such that the transfer efficiency of an electron-hole pair (exciton) is made arbitrarily high. Coherent transport phenomena in nature are of renewed interest since the discovery that a photon captured by the light-harvesting complex (LHC) in photosynthetic organisms can be conveyed to a chemical reaction centre with near-perfect efficiency. Classical explanations of the transfer use stochastic diffusion to model the hopping motion of a photo-excited exciton. This accounts inadequately for the speed and efficiency of the energy transfer measured in a series of recent landmark experiments. Taking a quantum mechanical perspective can help capture the salient features of the efficient part of that transfer. To show the versatility of the model, we extend it to a multiple minima system comprising seven-sites, reminiscent of the widely studied Fenna-Matthews-Olson (FMO) light-harvesting complex. We show that an idealised transport model for multiple minima coupled to a narrow-band phonon can transport energy with arbitrarily high efficiency. PMID:24980547

  18. Minima of the fluctuations of the order parameter of global seismicity

    NASA Astrophysics Data System (ADS)

    Sarlis, N. V.; Christopoulos, S.-R. G.; Skordas, E. S.

    2015-06-01

    It has been recently shown [N. V. Sarlis, Phys. Rev. E 84, 022101 (2011) and N. V. Sarlis and S.-R. G. Christopoulos, Chaos 22, 023123 (2012)] that earthquakes of magnitude M greater or equal to 7 are globally correlated. Such correlations were identified by studying the variance κ1 of natural time which has been proposed as an order parameter for seismicity. Here, we study the fluctuations of this order parameter using the Global Centroid Moment Tensor catalog for a magnitude threshold Mthres = 5.0 and focus on its behavior before major earthquakes. Natural time analysis reveals that distinct minima of the fluctuations of the order parameter of seismicity appear within almost five and a half months on average before all major earthquakes of magnitude larger than 8.4. This phenomenon corroborates the recent finding [N. V. Sarlis et al., Proc. Natl. Acad. Sci. U.S.A. 110, 13734 (2013)] that similar minima of the seismicity order parameter fluctuations had preceded all major shallow earthquakes in Japan. Moreover, on the basis of these minima a statistically significant binary prediction method for earthquakes of magnitude larger than 8.4 with hit rate 100% and false alarm rate 6.67% is suggested.

  19. Minima of the fluctuations of the order parameter of global seismicity.

    PubMed

    Sarlis, N V; Christopoulos, S-R G; Skordas, E S

    2015-06-01

    It has been recently shown [N. V. Sarlis, Phys. Rev. E 84, 022101 (2011) and N. V. Sarlis and S.-R. G. Christopoulos, Chaos 22, 023123 (2012)] that earthquakes of magnitude M greater or equal to 7 are globally correlated. Such correlations were identified by studying the variance κ1 of natural time which has been proposed as an order parameter for seismicity. Here, we study the fluctuations of this order parameter using the Global Centroid Moment Tensor catalog for a magnitude threshold Mthres = 5.0 and focus on its behavior before major earthquakes. Natural time analysis reveals that distinct minima of the fluctuations of the order parameter of seismicity appear within almost five and a half months on average before all major earthquakes of magnitude larger than 8.4. This phenomenon corroborates the recent finding [N. V. Sarlis et al., Proc. Natl. Acad. Sci. U.S.A. 110, 13734 (2013)] that similar minima of the seismicity order parameter fluctuations had preceded all major shallow earthquakes in Japan. Moreover, on the basis of these minima a statistically significant binary prediction method for earthquakes of magnitude larger than 8.4 with hit rate 100% and false alarm rate 6.67% is suggested.

  20. [Supercomputer investigation of the protein-ligand system low-energy minima].

    PubMed

    Oferkin, I V; Sulimov, A V; Katkova, E V; Kutov, D K; Grigoriev, F V; Kondakova, O A; Sulimov, V B

    2015-01-01

    The accuracy of the protein-ligand binding energy calculations and ligand positioning is strongly influenced by the choice of the docking target function. This work demonstrates the evaluation of the five different target functions used in docking: functions based on MMFF94 force field and functions based on PM7 quantum-chemical method accounting or without accounting the implicit solvent model (PCM, COSMO or SGB). For these purposes the ligand positions corresponding to the minima of the target function and the experimentally known ligand positions in the protein active site (crystal ligand positions) were compared. Each function was examined on the same test-set of 16 protein-ligand complexes. The new parallelized docking program FLM based on Monte Carlo search algorithm was developed to perform the comprehensive low-energy minima search and to calculate the protein-ligand binding energy. This study demonstrates that the docking target function based on the MMFF94 force field can be used to detect the crystal or near crystal positions of the ligand by the finding the low-energy local minima spectrum of the target function. The importance of solvent accounting in the docking process for the accurate ligand positioning is also shown. The accuracy of the ligand positioning as well as the correlation between the calculated and experimentally determined protein-ligand binding energies are improved when the MMFF94 force field is substituted by the new PM7 method with implicit solvent accounting.

  1. Minima of the fluctuations of the order parameter of global seismicity

    SciTech Connect

    Sarlis, N. V. Christopoulos, S.-R. G.; Skordas, E. S.

    2015-06-15

    It has been recently shown [N. V. Sarlis, Phys. Rev. E 84, 022101 (2011) and N. V. Sarlis and S.-R. G. Christopoulos, Chaos 22, 023123 (2012)] that earthquakes of magnitude M greater or equal to 7 are globally correlated. Such correlations were identified by studying the variance κ{sub 1} of natural time which has been proposed as an order parameter for seismicity. Here, we study the fluctuations of this order parameter using the Global Centroid Moment Tensor catalog for a magnitude threshold M{sub thres} = 5.0 and focus on its behavior before major earthquakes. Natural time analysis reveals that distinct minima of the fluctuations of the order parameter of seismicity appear within almost five and a half months on average before all major earthquakes of magnitude larger than 8.4. This phenomenon corroborates the recent finding [N. V. Sarlis et al., Proc. Natl. Acad. Sci. U.S.A. 110, 13734 (2013)] that similar minima of the seismicity order parameter fluctuations had preceded all major shallow earthquakes in Japan. Moreover, on the basis of these minima a statistically significant binary prediction method for earthquakes of magnitude larger than 8.4 with hit rate 100% and false alarm rate 6.67% is suggested.

  2. Coronal Transient Events During Two Solar Minima: Their Solar Source Regions and Interplanetary Counterparts

    NASA Astrophysics Data System (ADS)

    Cremades, H.; Mandrini, C. H.; Dasso, S.

    2011-12-01

    In the frame of two coordinated observational and research efforts, two full solar rotations were investigated in the times of two distinct solar minima. These two campaigns were dubbed Whole Sun Month (WSM; 10 August - 8 September 1996) and Whole Heliosphere Interval (WHI; 20 March - 16 April 2008). The nearly uninterrupted gathering of solar coronal data since the beginning of the Solar and Heliospheric Observatory (SOHO) era offers the exceptional possibility of comparing two solar minima for the first time, with regard to the coronal transient aspect. This study characterizes the variety of outward-traveling transients observed in the solar corona during both time intervals, from very narrow jet-like events to coronal mass ejections (CMEs). Their solar source regions and ensuing interplanetary structures were identified and characterized as well, toward a global-scale description of their role in determining the heliosphere’s conditions. Multi-wavelength images provided by the space missions SOHO, Yohkoh (only WSM), and Solar-Terrestrial Relations Observatory (STEREO; only WHI) and ground-based observatories were analyzed for coronal ejecta and their solar sources, while data registered by the Advanced Composition Explorer (ACE) spacecraft were inspected for interplanetary CMEs and magnetic clouds. Notable differences arise from the analysis of the detailed survey of events: more (fewer) ejecta during WHI (WSM), 12% (40%) were produced by active regions during WHI (WSM), and nearly no (high) deflection from the radial direction was observed during WHI (WSM). Instrumental aspects such as dissimilar resolution, cadence, and fields of view are considered in order to discern instrumentally driven disparities from inherent differences between solar minima.

  3. Polar and equatorial coronal hole winds at solar minima: From the heliosphere to the inner corona

    SciTech Connect

    Zhao, L.; Landi, E.

    2014-02-01

    Fast solar wind can be accelerated from at least two different sources: polar coronal holes and equatorial coronal holes. Little is known about the relationship between the wind coming from these two different latitudes and whether these two subcategories of fast wind evolve in the same way during the solar cycle. Nineteen years of Ulysses observations, from 1990 to 2009, combined with ACE observations from 1998 to the present provide us with in situ measurements of solar wind properties that span two entire solar cycles. These missions provide an ideal data set to study the properties and evolution of the fast solar wind originating from equatorial and polar holes. In this work, we focus on these two types of fast solar wind during the minima between solar cycles 22 and 23 and 23 and 24. We use data from SWICS, SWOOPS, and VHM/FGM on board Ulysses and SWICS, SWEPAM, and MAG on board ACE to analyze the proton kinetic, thermal, and dynamic characteristics, heavy ion composition, and magnetic field properties of these two fast winds. The comparison shows that: (1) their kinetic, thermal, compositional, and magnetic properties are significantly different at any time during the two minima and (2) they respond differently to the changes in solar activity from cycle 23 to 24. These results indicate that equatorial and polar fast solar wind are two separate subcategories of fast wind. We discuss the implications of these results and relate them to remote-sensing measurements of the properties of polar and equatorial coronal holes carried out in the inner corona during these two solar minima.

  4. Theoretical studies of the global minima and polarizabilities of small lithium clusters

    NASA Astrophysics Data System (ADS)

    Hu, Han-Shi; Zhao, Ya-Fan; Hammond, Jeff R.; Bylaska, Eric J.; Aprà, Edoardo; van Dam, Hubertus J. J.; Li, Jun; Govind, Niranjan; Kowalski, Karol

    2016-01-01

    Lithium clusters Lin (n = 1⿿20) have been investigated with density functional theory (DFT) and coupled-cluster (CC) methods. The global minima are located via an improved basin-hopping algorithm. Simulated polarizabilities are in good agreement with the measured data generally. The simulated polarizabilities for Li6, Li12 and Li19 are in reasonable agreement when thermal effects are included, except the Li3 cluster. A linear correlation for the inverse relationship between the CCSD calculated polarizabilities and ionization potential (IP) has been reported to have the linear coefficient of 0.996, which further strengthens our simulations.

  5. A genetic survey of Salvinia minima in the southern United States

    USGS Publications Warehouse

    Madeira, Paul T.; Jacono, C.C.; Tipping, Phil; Van, Thai K.; Center, Ted D.

    2003-01-01

    The genetic relationships among 68 samples of Salvinia minima (Salviniaceae) were investigated using RAPD analysis. Neighbor joining, principle components, and AMOVA analyses were used to detect differences among geographically referenced samples within and outside of Florida. Genetic distances (Nei and Li) range up to 0.48, although most are under 0.30, still relatively high levels for an introduced, clonally reproducing plant. Despite the diversity AMOVA analysis yielded no indication that the Florida plants, as a group, were significantly different from the plants sampled elsewhere in its adventive, North American range. A single, genetically dissimilar population probably exists in the recent (1998) horticultural introduction to Mississippi. When the samples were grouped into 10 regional (but artificial) units and analyzed using AMOVA the between region variance was only 7.7%. Genetic similarity among these regions may indicate introduction and dispersal from common sources. The reduced aggressiveness of Florida populations (compared to other states) may be due to herbivory. The weevil Cyrtobagous salviniae, a selective feeder, is found in Florida but not other states. The genetic similarity also suggests that there are no obvious genetic obstacles to the establishment or efficacy of C. salviniae as a biological control agent on S. minima outside of Florida.

  6. STRUCTURE IN THE 3D GALAXY DISTRIBUTION. II. VOIDS AND WATERSHEDS OF LOCAL MAXIMA AND MINIMA

    SciTech Connect

    Way, M. J.; Gazis, P. R.; Scargle, Jeffrey D. E-mail: PGazis@sbcglobal.net

    2015-01-20

    The major uncertainties in studies of the multi-scale structure of the universe arise not from observational errors but from the variety of legitimate definitions and detection methods for individual structures. To facilitate the study of these methodological dependencies, we have carried out 12 different analyses defining structures in various ways. This has been done in a purely geometrical way by utilizing the HOP algorithm as a unique parameter-free method of assigning groups of galaxies to local density maxima or minima. From three density estimation techniques (smoothing kernels, Bayesian blocks, and self-organizing maps) applied to three data sets (the Sloan Digital Sky Survey Data Release 7, the Millennium simulation, and randomly distributed points) we tabulate information that can be used to construct catalogs of structures connected to local density maxima and minima. We also introduce a void finder that utilizes a method to assemble Delaunay tetrahedra into connected structures and characterizes regions empty of galaxies in the source catalog.

  7. Systematic Phase Diagram of LiSi and LiAl compounds from Minima Hopping Method

    NASA Astrophysics Data System (ADS)

    Romero, Aldo; Marques, Miguel; Botti, Silvana; Sarmiento-Pérez, Rafael; Valencia-Jaime, Irais; Amsler, Max; Goedecker, Stefan

    2014-03-01

    We performed an extensive theoretical exploration of the structural phase diagram of LiSi and LiAl alloys through global structural prediction. These compounds have very interesting properties. For example, LiSi alloys have been considered for high energy density anodes for future rechargeable battery technology, while LiAl alloys are expected to have applications in the field of structural components due to its light weight and maleability. The global structural prediction was performed with the minima hopping method. In this method the low energy structures are obtained by solving a set of dynamical equations of motion that allows efficient visits to local minima on the Born Oppenheimer surface. We found very good agreement between our simulations and previously reported stoichiometries. Moreover, we were able to identify several novel thermodynamically stable compositions that have not been previously synthesized. The ground-state structures were further characterized both structurally and electronically. Our calculations show that global structural prediction is a very powerful tool to predict new thermodynamically stable materials, and that it consistently outperforms other methods commonly used. Support from ACS-PRF #54075-ND10 is recognized.

  8. Iterative h-minima-based marker-controlled watershed for cell nucleus segmentation.

    PubMed

    Koyuncu, Can Fahrettin; Akhan, Ece; Ersahin, Tulin; Cetin-Atalay, Rengul; Gunduz-Demir, Cigdem

    2016-04-01

    Automated microscopy imaging systems facilitate high-throughput screening in molecular cellular biology research. The first step of these systems is cell nucleus segmentation, which has a great impact on the success of the overall system. The marker-controlled watershed is a technique commonly used by the previous studies for nucleus segmentation. These studies define their markers finding regional minima on the intensity/gradient and/or distance transform maps. They typically use the h-minima transform beforehand to suppress noise on these maps. The selection of the h value is critical; unnecessarily small values do not sufficiently suppress the noise, resulting in false and oversegmented markers, and unnecessarily large ones suppress too many pixels, causing missing and undersegmented markers. Because cell nuclei show different characteristics within an image, the same h value may not work to define correct markers for all the nuclei. To address this issue, in this work, we propose a new watershed algorithm that iteratively identifies its markers, considering a set of different h values. In each iteration, the proposed algorithm defines a set of candidates using a particular h value and selects the markers from those candidates provided that they fulfill the size requirement. Working with widefield fluorescence microscopy images, our experiments reveal that the use of multiple h values in our iterative algorithm leads to better segmentation results, compared to its counterparts. © 2016 International Society for Advancement of Cytometry. © 2016 International Society for Advancement of Cytometry.

  9. Minima in generalized oscillator strengths of atomic transitions and the approach to the high-energy limit

    SciTech Connect

    Avdonina, N.B.; Fursa, D.; Msezane, A.Z.; Pratt, R.H.

    2005-06-15

    Minima in the generalized oscillator strength (GOS) and the convergence of the GOS to the first Born approximation (FBA) limit for the Ba 6s {sup 1}S{yields}6p {sup 1}P optically allowed transition are investigated. The random-phase approximation with exchange, which takes into account correlation effects among the atomic electrons themselves, and the convergent close-coupling (CCC) approximation are used for the calculations. We find the following. (1) The GOS as a function of the momentum transfer squared K{sup 2} is characterized by a complex structure of multiple minima, significantly different in the two approximations and approaches the high-energy FBA limit only at small K{sup 2} values (less than about 0.5 a.u.). (2) The number of minima calculated in the CCC approximation increases with increase in energy, but does not correspond to the number obtained in the FBA, even at high energy {approx}1 keV. The CCC and FBA minima are in general not directly related. The FBA minima, except for the first, do not correspond to physical observables at these energies. (3) At high energy the interaction between the incident electron and the target remains significant, resulting in slowing down the convergence of the CCC GOS to the corresponding nonrelativistic FBA results.

  10. Annual ionospheric variations of the critical frequency foF2 at the equatorial stations during the solar minima

    NASA Astrophysics Data System (ADS)

    Biktash, Lilia

    2016-07-01

    We have analyzed annual ionospheric variations of the critical frequency foF2 at the equatorial stations during the solar minima. There are essential distinctions between the global TEC (total electron content) and foF2 annual variations during the last two solar minima. Many authors concluded that the annual means of foF2 and the global TEC were reduced, while others investigations no found essential variations as compared with the previous solar minimum. Most if not all of authors suppose that the possible source of this phenomenon is the low level of the EUV (extreme ultraviolet) during the solar minima. The aim of our paper is to amplify these conclusions or to propose new factor which can change ionosphere parameters during the solar minima. We calculated annual variations of foF2 at the equatorial stations and compared these data with Dst annual variations. We found that in addition to low level of the EUV during the solar minima, geomagnetic storms effects have to be included as the influencing factor on annual ionospheric variations.

  11. MinFinder: Locating all the local minima of a function

    NASA Astrophysics Data System (ADS)

    Tsoulos, Ioannis G.; Lagaris, Isaac E.

    2006-01-01

    A new stochastic clustering algorithm is introduced that aims to locate all the local minima of a multidimensional continuous and differentiable function inside a bounded domain. The accompanying software (MinFinder) is written in ANSI C++. However, the user may code his objective function either in C++, C or Fortran 77. We compare the performance of this new method to the performance of Multistart and Topographical Multilevel Single Linkage Clustering on a set of benchmark problems. Program summaryTitle of program:MinFinder Catalogue identifier:ADWU Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADWU Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Computer for which the program is designed and others on which is has been tested:The tool is designed to be portable in all systems running the GNU C++ compiler Installation:University of Ioannina, Greece Programming language used:GNU-C++, GNU-C, GNU Fortran 77 Memory required to execute with typical data:200 KB No. of bits in a word:32 No. of processors used:1 Has the code been vectorized or parallelized?:no No. of lines in distributed program, including test data, etc.:5797 No. of bytes in distributed program, including test data, etc.:588 121 Distribution format:gzipped tar file Nature of the physical problem:A multitude of problems in science and engineering are often reduced to minimizing a function of many variables. There are instances that a local optimum does not correspond to the desired physical solution and hence the search for a better solution is required. Local optimization techniques can be trapped in any local minimum. Global optimization is then the appropriate tool. For example, solving a non-linear system of equations via optimization, employing a "least squares" type of objective, one may encounter many local minima that do not correspond to solutions, i.e. they are far from zero. Method of solution:Using a uniform pdf, points are sampled from the

  12. Absence of multiple local minima effects in intensity modulated optimization with dose-volume constraints

    NASA Astrophysics Data System (ADS)

    Llacer, Jorge; Deasy, Joseph O.; Bortfeld, Thomas R.; Solberg, Timothy D.; Promberger, Claus

    2003-01-01

    This paper reports on the analysis of intensity modulated radiation treatment optimization problems in the presence of non-convex feasible parameter spaces caused by the specification of dose-volume constraints for the organs-at-risk (OARs). The main aim was to determine whether the presence of those non-convex spaces affects the optimization of clinical cases in any significant way. This was done in two phases: (1) Using a carefully designed two-dimensional mathematical phantom that exhibits two controllable minima and with randomly initialized beamlet weights, we developed a methodology for exploring the nature of the convergence characteristics of quadratic cost function optimizations (deterministic or stochastic). The methodology is based on observing the statistical behaviour of the residual cost at the end of optimizations in which the stopping criterion is progressively more demanding and carrying out those optimizations to very small error changes per iteration. (2) Seven clinical cases were then analysed with dose-volume constraints that are stronger than originally used in the clinic. The clinical cases are two prostate cases differently posed, a meningioma case, two head-and-neck cases, a spleen case and a spine case. Of the 14 different sets of optimizations (with and without the specification of maximum doses allowed for the OARs), 12 fail to show any effect due to the existence of non-convex feasible spaces. The remaining two sets of optimizations show evidence of multiple minima in the solutions, but those minima are very close to each other in cost and the resulting treatment plans are practically identical, as measured by the quality of the dose-volume histograms (DVHs). We discuss the differences between fluence maps resulting from those similar treatment plans. We provide a possible reason for the observed results and conclude that, although the study is necessarily limited, the annealing characteristics of a simulated annealing method may not be

  13. Capturing the solubility minima of n-alkanes in water by soft-SAFT.

    PubMed

    Vega, Lourdes F; Llovell, Fèlix; Blas, Felipe J

    2009-05-28

    The purpose of this work is twofold: (1) to provide an accurate molecular model for water within the soft-SAFT equation of state [Blas, F.J.; Vega, L.F. Mol. Phys. 1997, 92, 135; Llovell, F., et al. J. Chem. Phys. 2004, 121, 10715] and (2) to check the capability of this molecular-based equation of state for capturing the solubility minima of n-alkanes in water experimentally found at room temperature for these mixtures. Water was modeled as a Lennard-Jones sphere with four associating sites, with parameters obtained by fitting to experimental vapor-liquid equilibrium data. Special care was taken to the value of these parameters depending on the range of applicability of the equation, which turned out to be essential for accurate predictions for mixtures. A correlation available in the literature was used for the molecular parameters of the n-alkane series. The crossover soft-SAFT equation was able to accurately describe the phase behavior of water near to and far from the critical point, up to 350 K. If instead of obtaining an overall good agreement one is interested in a more precise description of the near-ambient conditions, a more refined fitting of the parameters is needed. The model was used to describe the water+methane up to water+n-decane binary mixtures. The equation was able to predict the mutual solubilities in almost quantitative agreement with experimental data, including the presence of the solubility minima at ambient temperature, with a single transferable energy binary parameter, independent of temperature and chain length. Predictions obtained from the soft-SAFT approach are clearly superior than those obtained from the Huang and Radosz version of the SAFT equation [Economou, I. G.; Tsonopoulos, C. Chem. Eng. Sci. 1997, 52, 511], due to the more refined reference term and the more accurate radial distribution function used in the chain and association terms. This is the first time a SAFT approach is able to describe this minima.

  14. Properties of Supergranulation During the Solar Minima of Cycles 22/23 and 23/24

    NASA Technical Reports Server (NTRS)

    Williams, Peter E.; Pesnell, W. Dean

    2011-01-01

    The solar minimum at the transition from cycle 23 to 24 was notable for its low level of activity and its extended duration. Among the various fields of study, the evolution of the solar convection zone may provide insight into the causes and consequences of this recent minimum. This study continues previous investigations of the characteristics of solar supergranulation, a convection component strongly linked to the structure of the magnetic field, namely the time-evolution of the global mean of supergranule cell size, determined from spectral analysis of MDI Dopplergrams from the two previous solar minima. Analyses of the global mean of supergranule sizes show a quasi-oscillatory nature to the evolution of this particular supergranule characteristic. Performing similar analyses on realistic, synthetic Doppler images show similar time-dependent characteristics. We conclude that the observed fluctuations are not observational artifacts, and that an underlying trend exists within the evolution of the supergranulation network.

  15. A concept for reducing oceanic separation minima through the use of a TCAS-derived CDTI

    NASA Technical Reports Server (NTRS)

    Love, W. D.; Mcfarland, A. L.; Ludwick, J. S.

    1984-01-01

    A concept for using a cockpit display of traffic information (CDTI), as derived from a modified version of the Traffic Alert and Collision Avoidance System 2 (TCAS 2), to support reductions in air traffic separation minima for an oceanic track system is presented. The concept, and the TCAS modifications required to support it, are described. The feasibility of the concept is examined from a number of standpoints, including expected benefits, maximum alert rates, and possible transition strategies. Various implementation issues are analyzed. Pilot procedures are suggested for dealing with alert situations. Possible variations of the concept are also examined. Finally, recommendations are presented for other studies and simulation experiments which can be used to further verify the feasibility of the concept.

  16. Prediction of a reconstructed α-boron (111) surface by the minima hopping method

    NASA Astrophysics Data System (ADS)

    Amsler, Maximilian; Goedecker, Stefan; Botti, Silvana; Marques, Miguel A. L.

    2014-03-01

    Boron exhibits an impressive structural variety and immense efforts have recently been made to explore boron structures of low dimensionality, such as boron fullerenes, two-dimensional boron sheets or boron nanotubes which are theoretically predicted to exhibit superior electronic properties compared to their carbon analogues. By performing an extensive and systematic ab initio structural search for the (111) surface of α-boron (111) using the minima hopping structure prediction method we found very strong reconstructions that lead to two-dimensional surface layers. The topmost layer of these low energy reconstructions is a conductive, nearly perfectly planar boron sheet. If exfoliation was experimentally possible, promising precursors for a large variety of boron nano-structures such as single walled boron nanotubes and boron fullerenes could be obtained.

  17. Withanolides from Physalis minima and their inhibitory effects on nitric oxide production.

    PubMed

    Guan, Yu-Zhou; Shan, Si-Ming; Zhang, Wei; Luo, Jian-Guang; Kong, Ling-Yi

    2014-04-01

    Six new withanolides (1-6), including two uncommon 1,10-seco withanolides (1 and 2), together with five known withanolides (7-11), were isolated from the whole plants of Physalis minima Linn.. The structures of new compounds were elucidated through spectroscopic methods, including (1)H, (13)C NMR, 2D-NMR, HRESIMS and circular dichroism (CD). Inhibitory effects of the isolates on nitric oxide (NO) production in lipopolysaccaride-activated RAW264.7 macrophages were evaluated. Compounds 2 and 5 showed strong inhibitory activities with IC50 values of 8.04 and 10.01 μM, respectively. Compounds 1, 9 and 10 exhibited moderate inhibitory activities with IC50 values from 25.54 to 43.58 μM. Copyright © 2014 Elsevier Inc. All rights reserved.

  18. Invertebrate and fish assemblage relations to dissolved Oxygen minima in lowland streams of southwestern Louisiana

    USGS Publications Warehouse

    Justus, B.G.; Mize, Scott V.; Kroes, Daniel; Wallace, James E.

    2012-01-01

    Dissolved oxygen (DO) concentrations in lowland streams are naturally lower than those in upland streams; however, in some regions where monitoring data are lacking, DO criteria originally established for upland streams have been applied to lowland streams. This study investigated the DO concentrations at which fish and invertebrate assemblages at 35 sites located on lowland streams in southwestern Louisiana began to demonstrate biological thresholds.Average threshold values for taxa richness, diversity and abundance metrics were 2.6 and 2.3 mg/L for the invertebrate and fish assemblages, respectively. These thresholds are approximately twice the DO concentration that some native fish species are capable of tolerating and are comparable with DO criteria that have been recently applied to some coastal streams in Louisiana and Texas. DO minima >2.5 mg/L were favoured for all but extremely tolerant taxa. Extremely tolerant taxa had respiratory adaptations that gave them a competitive advantage, and their success when DO minima were <2 mg/L could be related more to reductions in competition or predation than to DO concentration directly.DO generally had an inverse relation to the amount of agriculture in the buffer area; however, DO concentrations at sites with both low and high amounts of agriculture (including three least-disturbed sites) declined to <2.5 mg/L. Thus, although DO fell below a concentration that was identified as an approximate biological threshold, sources of this condition were sometimes natural (allochthonous material) and had little relation to anthropogenic activity.

  19. Unveiling the nature of the He II λ4686 periodic minima in η Carinae

    NASA Astrophysics Data System (ADS)

    Teodoro, Mairan; Damineli, Augusto; Richardson, Noel; Moffat, Anthony F. J.; St-Jean, Lucas; Russell, Christopher Michael Post; Gull, Theodore R.; Madura, Thomas; Pollard, Karen; Walter, Frederick M.; Coimbra, Adriano; Prates, Rodrigo; Fernández-Lajús, Eduardo; gamen, roberto; Hickel, Gabriel; Henrique, William; Navarete, Felipe; Andrade, Thiago; Jablonski, Francisco; Corcoran, Michael F.; Hamaguchi, Kenji; Groh, Jose H.; Hillier, Desmond John; Gerd, Weigelt; SASER Team Members; Heathcote, Bernard; Luckas, Paul; Locke, Malcolm; Powles, Jonathan; Bohlsen, Terry

    2016-01-01

    η Carinae is known to be a massive binary system, but some of the orbital parameters remain uncertain. The nature of the periodic minima seen in several spectral features are associated with periastron passages near stellar conjunction, but its nature has been interpreted either as a low excitation event or as an eclipse of the hotter secondary star by the dense inner wind of the primary. We conducted an intense spectroscopic monitoring of the He II λ4686 emission line across the 2014.6 event using ground- and space-based telescopes. Comparison with results from the past two events confirmed the stability of the equivalent width and radial velocity of this line, as well as the strict periodicity of its minima. In combination with different other measurements, the orbital period is 2022.7 (±0.3) d. We adopted a power law model in combination with the total opacity in the line of sight to the apex of the wind-wind collision region obtained from hydrodynamic simulations to reproduce the observed He II λ4686 equivalent width curve. We constrained the orbital inclination to 135°-153° and the longitude of periastron to 234°-252°. Periastron passage occurred on T0(2014.6)=2456874.4 (±1.3) d. With these orbital elements, we successfully reproduced both the equivalent width curve observed from our direct view of the central source and the polar view. This suggests that the He II λ4686 minimum is ultimately caused by an increase in the opacity in the line of sight to the emitting region as the secondary star moves behind the primary star and plunges into denser regions of its wind.

  20. Atlantic forcing of Western Mediterranean winter rain minima during the last 12,000 years

    NASA Astrophysics Data System (ADS)

    Zielhofer, Christoph; Fletcher, William J.; Mischke, Steffen; De Batist, Marc; Campbell, Jennifer F. E.; Joannin, Sebastien; Tjallingii, Rik; El Hamouti, Najib; Junginger, Annett; Stele, Andreas; Bussmann, Jens; Schneider, Birgit; Lauer, Tobias; Spitzer, Katrin; Strupler, Michael; Brachert, Thomas; Mikdad, Abdeslam

    2017-02-01

    The limited availability of high-resolution continuous archives, insufficient chronological control, and complex hydro-climatic forcing mechanisms lead to many uncertainties in palaeo-hydrological reconstructions for the Western Mediterranean. In this study we present a newly recovered 19.63 m long core from Lake Sidi Ali in the North African Middle Atlas, a transition zone of Atlantic, Western Mediterranean and Saharan air mass trajectories. With a multi-proxy approach based on magnetic susceptibility, carbonate and total organic C content, core-scanning and quantitative XRF, stable isotopes of ostracod shells, charcoal counts, Cedrus pollen abundance, and a first set of diatom data, we reconstruct Western Mediterranean hydro-climatic variability, seasonality and forcing mechanisms during the last 12,000 yr. A robust chronological model based on AMS 14C dated pollen concentrates supports our high-resolution multi-proxy study. Long-term trends reveal low lake levels at the end of the Younger Dryas, during the mid-Holocene interval 6.6 to 5.4 cal ka BP, and during the last 3000 years. In contrast, lake levels are mostly high during the Early and Mid-Holocene. The record also shows sub-millennial- to centennial-scale decreases in Western Mediterranean winter rain at 11.4, 10.3, 9.2, 8.2, 7.2, 6.6, 6.0, 5.4, 5.0, 4.4, 3.5, 2.9, 2.2, 1.9, 1.7, 1.5, 1.0, 0.7, and 0.2 cal ka BP. Early Holocene winter rain minima are in phase with cooling events and millennial-scale meltwater discharges in the sub-polar North Atlantic. Our proxy parameters do not show so far a clear impact of Saharan air masses on Mediterranean hydro-climate in North Africa. However, a significant hydro-climatic shift at the end of the African Humid Period (∼5 ka) indicates a change in climate forcing mechanisms. The Late Holocene climate variability in the Middle Atlas features a multi-centennial-scale NAO-type pattern, with Atlantic cooling and Western Mediterranean winter rain maxima generally

  1. Antioxidant and anti-inflammatory activities of aqueous extract of Centipeda minima.

    PubMed

    Huang, Shyh-Shyun; Chiu, Chuan-Sung; Lin, Tsung-Hui; Lee, Min-Min; Lee, Chao-Ying; Chang, Shu-Jen; Hou, Wen-Chi; Huang, Guan-Jhong; Deng, Jeng-Shyan

    2013-05-20

    Centipeda minima (L.) is traditionally used in Chinese folk medicine for the treatments of rhinitis, sinusitis, relieving pain, reducing swelling, and treating cancer for a long history in Taiwan. However, there is no scientific evidence which supports the use in the literature. The aim of this study was to evaluate the antioxidant and anti-inflammatory activities of the aqueous extract of Centipeda minima (ACM). The following activities were investigated: antioxidant activities [2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), DPPH (1,1-diphenyl-2-picrylhydrazyl)], and anti-inflammatory [lipopolysaccharide (LPS) induced nitric oxide (NO) production in RAW264.7 macrophages and paw-edema induced by λ-carrageenan (Carr)]. We also investigated the anti-inflammatory mechanism of ACM via studies of the activities of catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) and the levels of malondialdehyde (MDA) in the edema paw. Serum NO, tumor necrosis factor α (TNF-α), and interleukin-1β (IL-1β) were also measured in vivo. In HPLC analysis, the fingerprint chromatogram of ACM was established. ACM showed the highest TEAC and DPPH radical scavenging activities, respectively. ACM also had highest contents of polyphenol and flavonoid contents. We evaluated that ACM and the reference compound of protocatechualdehyde and caffeic acid decreased the LPS-induced NO production in RAW264.7 cells. Administration of ACM showed a concentration dependent inhibition on paw edema development after Carr treatment in mice. The anti-inflammatory effects of ACM could be via NO, TNF-α, and IL-1β suppressions and associated with the increase in the activities of antioxidant enzymes. Western blotting revealed that ACM decreased Carr-induced inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expressions. Anti-inflammatory mechanisms of ACM might be correlated to the decrease in the level of Malondialdehyde (MDA), iNOS, and COX-2 via

  2. Solar activity during the Holocene: the Hallstatt cycle and its consequence for grand minima and maxima

    NASA Astrophysics Data System (ADS)

    Usoskin, I. G.; Gallet, Y.; Lopes, F.; Kovaltsov, G. A.; Hulot, G.

    2016-03-01

    Aims: Cosmogenic isotopes provide the only quantitative proxy for analyzing the long-term solar variability over a centennial timescale. While essential progress has been achieved in both measurements and modeling of the cosmogenic proxy, uncertainties still remain in the determination of the geomagnetic dipole moment evolution. Here we aim at improving the reconstruction of solar activity over the past nine millennia using a multi-proxy approach. Methods: We used records of the 14C and 10Be cosmogenic isotopes, current numerical models of the isotope production and transport in Earth's atmosphere, and available geomagnetic field reconstructions, including a new reconstruction relying on an updated archeo- and paleointensity database. The obtained series were analyzed using the singular spectrum analysis (SSA) method to study the millennial-scale trends. Results: A new reconstruction of the geomagnetic dipole field moment, referred to as GMAG.9k, is built for the last nine millennia. New reconstructions of solar activity covering the last nine millennia, quantified in terms of sunspot numbers, are presented and analyzed. A conservative list of grand minima and maxima is also provided. Conclusions: The primary components of the reconstructed solar activity, as determined using the SSA method, are different for the series that are based on 14C and 10Be. This shows that these primary components can only be ascribed to long-term changes in the terrestrial system and not to the Sun. These components have therefore been removed from the reconstructed series. In contrast, the secondary SSA components of the reconstructed solar activity are found to be dominated by a common ≈2400-year quasi-periodicity, the so-called Hallstatt cycle, in both the 14C and 10Be based series. This Hallstatt cycle thus appears to be related to solar activity. Finally, we show that the grand minima and maxima occurred intermittently over the studied period, with clustering near lows and highs

  3. A gentic survey of Salvinia minima in the southern United States

    USGS Publications Warehouse

    Madeira, Paul T.; Jacono, Colette C.; Tipping, Phil; Van, Thai K.; Center, Ted D.

    2003-01-01

    The genetic relationships among 68 samples of Salvinia minima (Salviniaceae) were investigated using RAPD analysis. Neighbor joining, principle components, and AMOVA analyses were used to detect differences among geographically referenced samples within and outside of Florida. Genetic distances (Nei and Li) range up to 0.48, although most are under 0.30, still relatively high levels for an introduced, clonally reproducing plant. Despite the diversity AMOVA analysis yielded no indication that the Florida plants, as a group, were significantly different from the plants sampled elsewhere in its adventive, North American range. A single, genetically dissimilar population probably exists in the recent (1998) horticultural introduction to Mississippi. When the samples were grouped into 10 regional (but artificial) units and analyzed using AMOVA the between region variance was only 7.7%. Genetic similarity among these regions may indicate introduction and dispersal from common sources. The reduced aggressiveness of Florida populations (compared to other states) may be due to herbivory. The weevilCyrtobagous salviniae, a selective feeder, is found in Florida but not other states. The genetic similarity also suggests that there are no obvious genetic obstacles to the establishment or efficacy of C. salviniae as a biological control agent on S. minimaoutside of Florida.

  4. [Adam Christian Thebesius (1686-1732) and the discovery of the Vasa Cordis Minima].

    PubMed

    Mettenleiter, A

    2001-01-01

    In first years of the 18th century, Raymond Vieussens (1635-1713) and Adam Christian Thebesius (1686-1732) discovered the Vasa cordis minima, today known as Vasa Thebesii; in 1868, Odilon Marc Lannelongue (1840-1911) described the so-called crypts of Lannelongue in the right atrium. The present study gives a historical survey over the research on the cardiac vascularization before 1700 and presents these three authors and their works on the Thebesian vessels with a biographical introduction and a commented translation. As for the biography of the Silesian anatomist Thebesius large, mostly inedited materials from Polish archives and from family archives were studied, among them, poems, a handwritten biography and a pedigree of the family. A schedule tables the studies and articles on the Thebesian vessels and the Thebesian valve published since 1708. As a commentary to the bibliography, the present stage of knowledge on the Thebesian vessels is shortly summarized. Although a compensatory function of the Thebesian vessels in coronary sclerosis and other pathological conditions has been discussed repeatedly, methodical difficulties still do not allow a reliable judgement on the role of the Thebesian vessels in physiological and pathological conditions. This study shows the contradictory results and summarizes all statements which have been published on the embryology, comparative anatomy, macroscopical and (electron-)microscopical anatomy, physiology, pathophysiology and cardio-surgery. The aim is to encourage an interdiscplinary discussion on the base of the thorough literature study.

  5. The mobility minima in pulsed-field capillary electrophoresis of large DNA.

    PubMed Central

    Sudor, J; Novotny, M

    1995-01-01

    Pulsed-field capillary electrophoresis represents a new tool for rapid and highly efficient separations of large biopolymers. The method has been utilized here to study dependencies of the electrophoretic mobility upon the frequency and pulse shape of applied voltage for large, double-stranded DNA molecules (5-100 kb) migrating in neutral polymer solutions. Two different shapes of alternating electric field (sine- and square-wave impulses) were examined with the frequency values ranging from 1 to 30 Hz. The linear dependence between duration of the forward pulse (at which the DNA molecule experiences a minimum mobility) and the product N.In(N) (where N is the number of base pairs) was experienced in field-inversion gel electrophoresis, while exponential dependence was found with the sinusoidal electric field. The mobility minima were lower in field-inversion electrophoresis than with the biased sinusoidal-field technique. The DNA (5 kb concatamers) was adequately separated using a ramp of frequency in the square-wave electric field, in approximately 1 h. The migration order of DNA fragments was referenced through adding a monodisperse DNA (48.5 kb) into the sample. The band inversion phenomena were not observed under any experimental conditions used in this work. PMID:7630733

  6. Coeval dust accumulation minima in Greenland and East Central Europe over 31-23 ka

    NASA Astrophysics Data System (ADS)

    Újvári, Gábor; Stevens, Thomas; Varga, György; Kovács, János; Molnár, Mihály

    2016-04-01

    with the bulk loess median grain size (D50bulk) that is considered an integrated proxy of wind strength, dust source distance, aridity and vegetation cover. While an increase of dust flux and D50bulk with time is apparent, such a trend cannot be seen in the quartz grain size measures (D50quartz). This observation may imply that wind speeds were relatively constant in the studied time interval, while the turbulence of the flow may have been extremely varying (i.e. strong/rapid changes in the frequency/magnitude of dust storm events). A striking feature of the MAR record is that accumulation minima in the Dunaszekcsö record are synchronous with the Greenland Interstadials (GI-5.1 to GI-3). Subsequent Ca2+ minima in the NGRIP record at 26.22 and 25.02 ka (b2k) are also coeval with the MAR minima in the studied loess sequence. At the same time, these patterns are barely visible in the bulk and quartz grain size records. We speculate that the synchronous changes in the NGRIP Ca2+ and the Dunaszekcsö MAR records are results of millennial scale variations in the activity of Northern Hemisphere dust emitting regions shown in two archives from different environments. The very similar timing of MAR minima (and also some of the maxima) suggest a rapid aeolian system response in East Central Europe to abrupt climatic changes in the North Atlantic. Although such a synchronicity does not prove a Central European dust source to Greenland, it is consistent with this possibility. This study was supported by the OTKA PD-108639 grant and the Bolyai János Research Fellowship (both to GÚ). [1] Dansgaard, W., et al. (1993). Evidence for general instability of past climate from a 250-kyr ice-core record. Nature 364, 218-220. [2] Johnsen, S.J., et al. (1992). Irregular glacial interstadials recorded in a new Greenland ice core. Nature 359, 311-313. [3] Rasmussen, S.O., et al. (2014). A stratigraphic framework for abrupt climatic changes during the Last Glacial period based on three

  7. Synonymous Mutations and Ribosome Stalling Can Lead to Altered Folding Pathways and Distinct Minima

    PubMed Central

    Tsai, Chung-Jung; Sauna, Zuben E.; Kimchi-Sarfaty, Chava; Ambudkar, Suresh V.; Gottesman, Michael M.; Nussinov, Ruth

    2008-01-01

    How can we understand a case where a given amino acid sequence folds into structurally and functionally distinct molecules? Synonymous single-nucleotide polymorphisms (SNPs) in the multidrug resistance 1 (MDR1 or ABCB1) gene involving frequent to rare codon substitutions lead to identical protein sequences. Remarkably these alternative sequences give a protein product with similar but different structures and functions. Here we propose that long-enough ribosomal pause time-scales may lead to alternate folding pathways and distinct minima on the folding free energy surface. While the conformational and functional differences between the native and alternate states may be minor, the MDR1 case illustrates that the barriers may nevertheless constitute sufficiently high hurdles in physiological time-scales, leading to kinetically trapped states with altered structures and functions. Different folding pathways leading to conformationally-similar trapped states may be due to swapping of (fairly symmetric) segments. Domain swapping is more likely in the no-pause case where the chain elongates and folds simulaneously; on the other hand, sufficiently long pause times between such segments may be expected to lessen the chances of swapping events. Here, we review the literature in this light. PMID:18722384

  8. Processes controlling mid-water column oxygen minima over the Texas-Louisiana shelf

    NASA Astrophysics Data System (ADS)

    Zhang, Wenxia; Hetland, Robert D.; DiMarco, Steven F.; Fennel, Katja

    2015-04-01

    We investigate distributions of dissolved oxygen over the Texas-Louisiana shelf using spatially highly resolved observations in combination with a regional circulation model with simple oxygen dynamics. The observations were collected using a towed, undulating CTD during the Mechanisms Controlling Hypoxia (MCH) program. Mid-water oxygen minimum layers (dissolved oxygen lower than 3.2 mL L-1) were detected in many transects. These oxygen minimum layers are connected with the bottom boundary layer and follow the pycnocline seaward as a tongue of low oxygen into the mid-water column. T-S diagrams highlighting the low oxygen minima in both observations and simulations imply direct connections between low-oxygen bottom water and the oxygen minimum layer. The dynamics of these oxygen minimum layers in the mid-water column are examined using a three-dimensional hydrodynamic model, based on the Regional Ocean Modeling System (ROMS). Convergence within the bottom boundary layer relative to density surfaces is calculated, results show that there is a convergence in the bottom boundary layer at the location where the pycnocline intersects the bottom. Buoyancy advection forced by bottom Ekman transport creates this convergent flow, and the corresponding low-oxygen intrusion. Similar intrusions of near-bottom water into the pycnocline are observed in other regions. The presence of hypoxia within the bottom boundary layer in the northern Gulf of Mexico creates a unique situation in which these intrusions are also associated with low dissolved oxygen.

  9. Depth-dose equivalent relationship for cosmic rays at various solar minima

    NASA Technical Reports Server (NTRS)

    Badhwar, G. D.; Cucinotta, F. A.; O'Neill, P. M.

    1993-01-01

    Galactic cosmic rays (GCR) pose a serious radiation hazard for long-duration missions. In designing a lunar habitat or a Mars transfer vehicle, the radiation exposure determines the GCR shielding thickness, and hence the weight of spacecraft. Using the spherically symmetric diffusion theory of the solar modulation of GCR, and data on the differential energy spectra of H, He, O, and Fe, from 1965 to 1989, it has been shown that (1) the flux is determined by the diffusion parameter which is a function of the time in the solar cycle, and (2) the fluxes in the 1954 and 1976-1977 solar minima were similar and higher than those in 1965. In this paper, we have extended the spherical solar modulation theory back to 1954. The 1954-1955 GCR flux was nearly the same as that from 1976 to 1977; the 1965 flux values were nearly the same as those in 1986. Using this theory we have obtained the GCR spectra for all the nuclei, and calculated the depth dose as a function of Al thickness. It is shown that the shielding required to stay below 0.5 Sv is 17.5 -3/+8 g/sq cm of Al, and 9 -1.5/+5 g/sq cm to stay below 0.6 Sv. The calculated dose equivalent using the ICRP 60 values for quality factors is about 15 percent higher than that calculated using the ICRP 26 value.

  10. Ultrastructure of the Feeding Apparatus of Rhabdodemania minima Chitwood, 1936 (Enoplida: Rhabdodemaniidae)

    PubMed Central

    Hope, W. Duane

    1988-01-01

    The feeding apparatus of the marine nematode Rhabdodemania minima Chitwood, 1936 has been examined with light and transmission electron microscopy. The buccal capsule consists of a posterior region with smooth walls bearing three sets of three minute denticles at its posterior end and three large onchia in its mid region; a middle region with grooved walls; and an anterior region with costae and six odontia. The anterior and middle portions of the buccal capsule are enveloped by the cephalic cuticle, whereas the posterior region, which is set off from the middle region by a buccal seam, is partially enveloped by the anterior end of the esophagus. Two subventral esophageal glands open into the lumen of the esophagus. Secretions of each of three paraesophageal glands are conveyed through a duct in each of the three corresponding corners of the buccal wall to an opening between labia. A pair of wing-like thickenings, termed pterons, embraces the duct of each paraesophageal gland in the posterior and middle regions of the buccal capsule. A model of how the buccal capsule operates is proposed and tested. Morphological and functional aspects of the buccal apparatus and cephalic cuticle are compared with those of other taxa of the Enoplida, and their phylogenetic implications are discussed. PMID:19290194

  11. Identity of Ṭaṅkārī (Physalis Minima Linn.) in Ayurvedic Classics: A Literature Review.

    PubMed

    Kallianpur, Supriya S; Gokarn, Rohit A; Rajashekhar, N

    2016-01-01

    Proper identification of drugs and their use in proper doses are important for successful treatment. Physalis minima Linn commonly known as country gooseberry has anti-cancerous, anti-diabetic, analgesic, antipyretic and anti-inflammatory potentials. The present paper is aimed to ascertain the proper identity of Ṭaṅkārī (Physalis minima Linn.) in Ayurvedic classics by a meticulous search and hence a review of the drug Ṭaṅkārī (Physalis minima Linn) was carried out in the texts of Ayurveda, modern literature, journals and online publications. The result of the search showed that the name "Ṭaṅkārī" is not found in Vedic lore. In Saṃhitās, it is mentioned in Bhāvaprakāśa. Reference of the drug "Śārṅgeṣṭhā" is found in Bṛhattrayī, Bhela, Kāśyapa, Cakradatta and Vaṅgasena. It is variously named as Cirapoṭikā, Kākatikta, and Vāyasī by ḍalhaṇa and he describes it as gaura (pale), vartula (round), and as having avaguṇṭhita/veṣṭhita (covered) fruit which matches the description of Ṭaṅkārī (P. minima Linn). A search for terms Kākatikta and Vāyasī showed Kākatikta to be synonymous to Śārṅgeṣṭhā and Vāyasī to be synonymous to both Kākatikta and Kākamācī (Solanum nigrum). Madanapāla and Śāligrāma Nighaṇṭus have mentioned the name Cirapoṭikā to be synonymous with Ṭaṅkārī. Śodhala has used the term Parpoṭī as a synonym of Ṭaṅkārī, which is the Gujarati name of P. minima Linn. Recent authors have considered Śārṅgeṣṭhā as either P. minima or Cardiospermum helicabum. The regional names of P. minima are Cirpoṭi (Hindi), Cirboli (Marathi), also the folklore uses and pharmacological activities of P. minima are in accordance with the indications of Śārṅgeṣṭhā in classics. Thus with a complete review of both Ayurveda and modern literatures, it can be concluded that the drug mentioned as Ṭaṅkārī in Bhāvaprakāśa is the same as

  12. Identity of Ṭaṅkārī (Physalis Minima Linn.) in Ayurvedic Classics: A Literature Review

    PubMed Central

    Kallianpur, Supriya S; Gokarn, Rohit A; Rajashekhar, N

    2016-01-01

    Proper identification of drugs and their use in proper doses are important for successful treatment. Physalis minima Linn commonly known as country gooseberry has anti-cancerous, anti-diabetic, analgesic, antipyretic and anti-inflammatory potentials. The present paper is aimed to ascertain the proper identity of Ṭaṅkārī (Physalis minima Linn.) in Ayurvedic classics by a meticulous search and hence a review of the drug Ṭaṅkārī (Physalis minima Linn) was carried out in the texts of Ayurveda, modern literature, journals and online publications. The result of the search showed that the name “Ṭaṅkārī” is not found in Vedic lore. In Saṃhitās, it is mentioned in Bhāvaprakāśa. Reference of the drug “Śārṅgeṣṭhā” is found in Bṛhattrayī, Bhela, Kāśyapa, Cakradatta and Vaṅgasena. It is variously named as Cirapoṭikā, Kākatikta, and Vāyasī by ḍalhaṇa and he describes it as gaura (pale), vartula (round), and as having avaguṇṭhita/veṣṭhita (covered) fruit which matches the description of Ṭaṅkārī (P. minima Linn). A search for terms Kākatikta and Vāyasī showed Kākatikta to be synonymous to Śārṅgeṣṭhā and Vāyasī to be synonymous to both Kākatikta and Kākamācī (Solanum nigrum). Madanapāla and Śāligrāma Nighaṇṭus have mentioned the name Cirapoṭikā to be synonymous with Ṭaṅkārī. Śodhala has used the term Parpoṭī as a synonym of Ṭaṅkārī, which is the Gujarati name of P. minima Linn. Recent authors have considered Śārṅgeṣṭhā as either P. minima or Cardiospermum helicabum. The regional names of P. minima are Cirpoṭi (Hindi), Cirboli (Marathi), also the folklore uses and pharmacological activities of P. minima are in accordance with the indications of Śārṅgeṣṭhā in classics. Thus with a complete review of both Ayurveda and modern literatures, it can be concluded that the drug mentioned as Ṭaṅkārī in Bhāvaprakāśa is the same as

  13. Short-Term Variations of Cosmic-Ray Intensity During the Recent Deep Solar Minimum and the Previous Four Solar Minima: A Wavelet Analysis

    NASA Astrophysics Data System (ADS)

    Singh, Y. P.; Badruddin

    2015-10-01

    The recent, unusual solar cycle and solar minima between Cycles 23 and 24 have been studied extensively. Wavelet analysis of hourly cosmic-ray intensity during the last five solar minima reveals a number of short-term variations with few temporal shifts in the periods. This study suggests that deviations with a one-solar-rotation period and its harmonics are small during the recent minimum. However, deviations are considerably larger during the other minima. Analysis also demonstrates that the behavior of active regions is nearly the same during the minima of Cycles 19, 20, 21, and 22. The results also suggest that regions outside the streamer stalk are significantly larger in the recent solar minimum as opposed to the other minima.

  14. Is the Sun heading for another Maunder Minimum? - Precursors of the grand solar minima

    NASA Astrophysics Data System (ADS)

    Miyahara, H.; Kitazawa, K.; Nagaya, K.; Yokoyama, Y.; Matsuzaki, H.; Masuda, K.; Nakamura, T.; Muraki, Y.

    2010-06-01

    The Sun shows a quasi-periodic ~200-year cycle of activity that causes sporadic intervals of minimal sunspot activity and prolonged sunspot absence lasting for several decades. Such long-term sunspot absence may influence global climate and appears to be associated with periods of global cooling and little ice ages. Long-lasting sunspot absences since the 13th century are specifically linked to periods of increased glaciation and colder temperatures world wide and the development of "Little Ice Ages". These include the Wolf (AD 1282-342), Spoerer (AD 1416-534), Maunder (AD 1645-1715), and Dalton (AD 1795-1825) periods of sunspot minima. By contrast, increased solar activity may be linked to periods of global warming. Consequently, it is important to establish a methodology that enables predictions of near-future, long-term reductions in solar activity. However, it remains difficult to predict even the timing of onset and amplitude of the next 11-year solar cycle. To address this problem, we examined the features of precursory solar cycles related to three prolonged intervals of sunspot absence that occurred during the past ~600 years. Carbon-14 based analyses of the evolution of solar cycles around the onset of two prolonged periods of sunspot absence, the Maunder Minimum and the Spoerer Minimum, reveal that at least the two preceding solar cycles were longer than usual by several years, as were the cycles during the periods of sunspot absence. The solar cycle is likely to show characteristic precursory features leading up to intervals of sunspot absence, and which can be differentiated by events of different durations.

  15. Mitigating local minima in full-waveform inversion by expanding the search space

    NASA Astrophysics Data System (ADS)

    van Leeuwen, Tristan; Herrmann, Felix J.

    2013-10-01

    Wave equation based inversions, such as full-waveform inversion and reverse-time migration, are challenging because of their computational costs, memory requirements and reliance on accurate initial models. To confront these issues, we propose a novel formulation of wave equation based inversion based on a penalty method. In this formulation, the objective function consists of a data-misfit term and a penalty term, which measures how accurately the wavefields satisfy the wave equation. This new approach is a major departure from current formulations where forward and adjoint wavefields, which both satisfy the wave equation, are correlated to compute updates for the unknown model parameters. Instead, we carry out the inversions over two alternating steps during which we first estimate the wavefield everywhere, given the current model parameters, source and observed data, followed by a second step during which we update the model parameters, given the estimate for the wavefield everywhere and the source. Because the inversion involves both the synthetic wavefields and the medium parameters, its search space is enlarged so that it suffers less from local minima. Compared to other formulations that extend the search space of wave equation based inversion, our method differs in several aspects, namely (i) it avoids storage and updates of the synthetic wavefields because we calculate these explicitly by finding solutions that obey the wave equation and fit the observed data and (ii) no adjoint wavefields are required to update the model, instead our updates are calculated from these solutions directly, which leads to significant computational savings. We demonstrate the validity of our approach by carefully selected examples and discuss possible extensions and future research.

  16. Comparative study of the equatorial ionosphere over Jicamarca during recent two solar minima

    NASA Astrophysics Data System (ADS)

    Liu, Libo; Yang, Jun; Le, Huijun; Chen, Yiding; Wan, Weixing; Lee, Chien-Chih

    2012-01-01

    It is a critical issue that whether or not the extremely deep solar minimum of solar cycle 23/24 brought serious influences on the Earth's space environment. In this study, we collected and manually scaled the ionograms recorded by a DPS ionosonde at Jicamarca (12.0°S, 283.2°E) to retrieve F layer parameters and electron density (Ne) profiles. A comparative study is performed to evaluate the equatorial ionosphere in solar minima of cycle 22/23 (1996-1997) and 23/24 (2008-2009). The seasonal median values of the critical frequency of F2 layer (foF2) were remarkably reduced in four seasons during the deep solar minimum, compared to those in 1996-1997. It is the first time to find that lower values prevail at most times in 2008-2009 in the F2 layer peak height (hmF2) and Chapman scale height (Hm). The bottomside profile thickness (B0) shows higher values in 2008-2009 than that in 1996-1997 at some daytime intervals, although it also becomes smaller during the rest times. Furthermore, the ionosphere in 2008-2009 is contracted strongly at altitudes above hmF2 and more perceptible in the afternoon hours. The decrease in Ne is strongest in September equinox and weakest in June solstice. The ionospheric responses from solar minimum to minimum are mainly caused by the reduction in solar extreme ultraviolet intensity, and the contribution from dynamical processes competes and is variable. Analysis reveals that semiannual and longer-scale components are certainly reduced during the deep solar minimum, while shorter scale (e.g., 4 month) components may disrupt the decline picture at some times.

  17. Are both symmetric and buckled dimers on Si(100) minima? Density functional and multireference perturbation theory calculations

    SciTech Connect

    Jung, Yousung; Shao, Yihan; Gordon, Mark S.; Doren, Douglas J.; Head-Gordon, Martin

    2003-08-29

    We report a spin-unrestricted density functional theory (DFT) solution at the symmetric dimer structure for cluster models of Si(100). With this solution, it is shown that the symmetric structure is a minimum on the DFT potential energy surface, although higher in energy than the buckled structure. In restricted DFT calculations the symmetric structure is a saddle point connecting the two buckled minima. To further assess the effects of electron correlation on the relative energies of symmetric versus buckled dimers on Si(100), multireference second order perturbation theory (MRMP2) calculations are performed on these DFT optimized minima. The symmetric structure is predicted to be lower in energy than the buckled structure via MRMP2, while the reverse order is found by DFT. The implications for recent experimental interpretations are discussed.

  18. Spectroscopic Evidence of Sporadic Gas Accretion onto the Herbig AE Stars with Non-Periodic Algol-Type Minima

    NASA Astrophysics Data System (ADS)

    Kozlova, O. V.; Grinin, V. P.; Rostopchina, A. N.

    We present the results of simultaneous spectroscopic and photometric observations for six isolated Herbig Ae stars with non-periodic Algol-like minima: UX Ori, BF Ori, CQ Tau, SV Cep, VX Gas, and WW Vul. In all cases the Ha line has the profile typical for axially symmetric accretion. In the spectra of five stars (CQ Tau is the exception) the strong He I 5876 Å line has been observed in absorption which is not typical of normal A stars. In three cases: UX Ori, VX Cas, and WW Vul, variability of this line is found. We did not observe any correlation between the strength of this line and the brightness of the stars. These observational facts are considered as evidence for gas accretion, which is probably an important property of young stars with non-periodic Algol-type minima.

  19. Quantum Dynamics Study of the Potential Energy Minima Effect on Energy Efficiency for the F(-) + CH3Cl → FCH3 + Cl(-) Reaction.

    PubMed

    Li, Yida; Wang, Yuping; Wang, Dunyou

    2017-04-13

    The Polanyi rules on the energy efficiency on reactivity are summarized solely from the locations of barriers on the potential energy surfaces. Here, our quantum dynamics study for the F(-) + CH3Cl → FCH3 + Cl(-) reaction shows that the two potential energy minima in the entrance channel on the potential energy surface play an essential role in energy efficiency on reactivity. The reactivity of this reaction is dominated by the low collision energies where two distinctive reaction mechanisms involve the two minima in the entrance channel. Overall, the Cl-CH3 stretching motion and C-H3 umbrella motion both are more efficient than the translational motion in promoting this reaction. Although this reaction has a negative energy barrier, our study shows that it is the minima in the entrance channel, together with the energy barrier relative to these minima, that determine the energy efficacy on reactivity.

  20. The adventive status of Salvinia minima and S. molestain the southern United States and the related distribution of the weevil Cyrtobagous salviniae

    USGS Publications Warehouse

    Jacono, Colette C.; Davern, Tracy R.; Center, Ted D.

    2001-01-01

    The recent introduction of Salvinia molesta constitutes a serious threat to aquatic systems in the warm temperate regions of the United States. Salvinia minima, the only other member of Salviniaceae present in North America, is considered native by current floras. Evidence is presented which suggests that Salvinia minima was also introduced to North America, probably during the late 1920s and early 1930s. Likely sites of introduction and subsequent range expansions are identified. The accidentally introduced salvinia weevil, putatively Cyrtobagous salviniae, was found to occur widely on S. minima in Florida but is not established in other states. The disparate distribution of this Salvinia herbivore may account for the reduced aggressiveness of S. minima in Florida as compared to its troublesome growth in Texas and LOUisiana, where the weevil is not yet known.

  1. Pinpointing Gap Minima in Ba(Fe0:94Co0:06)2 via Band Structure Calculations and Electronic Raman Scattering

    DTIC Science & Technology

    2010-08-03

    for the Raman vertices, it is shown that the location of the gap minima may occur on loops stretching over a portion of the c-axis in Ba(Fe0.94Co0.06...the value of B1g Raman vertex is larger than the average are shaded red. The gold ellipses mark the area where the deep gap minima or nodes are

  2. A novel approach to decoy set generation: designing a physical energy function having local minima with native structure characteristics.

    PubMed

    Keasar, Chen; Levitt, Michael

    2003-05-23

    We suggest a new approach to the generation of candidate structures (decoys) for ab initio prediction of protein structures. Our method is based on random sampling of conformation space and subsequent local energy minimization. At the core of this approach lies the design of a novel type of energy function. This energy function has local minima with native structure characteristics and wide basins of attraction. The current work presents our motivation for deriving such an energy function and also tests the derived energy function. Our approach is novel in that it takes advantage of the inherently rough energy landscape of proteins, which is generally considered a major obstacle for protein structure prediction. When local minima have wide basins of attraction, the protein's conformation space can be greatly reduced by the convergence of large regions of the space into single points, namely the local minima corresponding to these funnels. We have implemented this concept by an iterative process. The potential is first used to generate decoy sets and then we study these sets of decoys to guide further development of the potential. A key feature of our potential is the use of cooperative multi-body interactions that mimic the role of the entropic and solvent contributions to the free energy. The validity and value of our approach is demonstrated by applying it to 14 diverse, small proteins. We show that, for these proteins, the size of conformation space is considerably reduced by the new energy function. In fact, the reduction is so substantial as to allow efficient conformational sampling. As a result we are able to find a significant number of near-native conformations in random searches performed with limited computational resources.

  3. Comparison of PSF maxima and minima of multiple annuli coded aperture (MACA) and complementary multiple annuli coded aperture (CMACA) systems

    NASA Astrophysics Data System (ADS)

    Ratnam, Challa; Lakshmana Rao, Vadlamudi; Lachaa Goud, Sivagouni

    2006-10-01

    In the present paper, and a series of papers to follow, the Fourier analytical properties of multiple annuli coded aperture (MACA) and complementary multiple annuli coded aperture (CMACA) systems are investigated. First, the transmission function for MACA and CMACA is derived using Fourier methods and, based on the Fresnel-Kirchoff diffraction theory, the formulae for the point spread function are formulated. The PSF maxima and minima are calculated for both the MACA and CMACA systems. The dependence of these properties on the number of zones is studied and reported in this paper.

  4. Solving Local Minima Problem in Back Propagation Algorithm Using Adaptive Gain, Adaptive Momentum and Adaptive Learning Rate on Classification Problems

    NASA Astrophysics Data System (ADS)

    Hamid, Norhamreeza Abdul; Nawi, Nazri Mohd; Ghazali, Rozaida; Salleh, Mohd Najib Mohd

    This paper presents a new method to improve back propagation algorithm from getting stuck with local minima problem and slow convergence speeds which caused by neuron saturation in the hidden layer. In this proposed algorithm, each training pattern has its own activation functions of neurons in the hidden layer that are adjusted by the adaptation of gain parameters together with adaptive momentum and learning rate value during the learning process. The efficiency of the proposed algorithm is compared with the conventional back propagation gradient descent and the current working back propagation gradient descent with adaptive gain by means of simulation on three benchmark problems namely iris, glass and thyroid.

  5. Mars: The Origin of the 3.58- and 3.69-Micron Minima in the Infrared Spectra.

    PubMed

    Rea, D G; O'leary, B T; Sinton, W M

    1965-03-12

    The 3- to 4-micron spectra of Mars, recorded with the 200-inch telescope in 1958, were reexamined in order to ascertain whether the minima at 3.58 and 3.69 microns are due to telluric HDO molecules. Solar spectra obtained at Denver and water vapor abundances derived from radiosonde flights during the observing period were used. There seems to be a correlation between the intensities of the 3.58- and 3.69-micron features and the amount of telluric water vapor in the optical path. An important corollary is that there is no evidence for attributing these spectral features to Mars.

  6. Methanolic Extract of Ceplukan Leaf (Physalis minima L.) Attenuates Ventricular Fibrosis through Inhibition of TNF-α in Ovariectomized Rats.

    PubMed

    Lestari, Bayu; Permatasari, Nur; Rohman, Mohammad Saifur

    2016-01-01

    The increase of heart failure prevalence on menopausal women was correlated with the decrease of estrogen level. The aim of this study is to investigate the effects of ceplukan leaf (Physalis minima L.), which contains phytoestrogen physalin and withanolides, on ventricular TNF-α level and fibrosis in ovariectomized rats. Wistar rats were divided into six groups (control (-); OVX 5: 5-week ovariectomy (OVX); OVX 9: 9-week ovariectomy; treatments I, II, and III: 9-weeks OVX + 4-week ceplukan leaf's methanolic extract doses 500, 1500, and 2500 mg/kgBW, resp.). TNF-α levels were measured with ELISA. Fibrosis was counted as blue colored tissues percentage using Masson's Trichrome staining. This study showed that prolonged hypoestrogen increases ventricular fibrosis (p < 0.05). Ceplukan leaf treatment also resulted in a decrease of ventricular fibrosis and TNF-α level in dose dependent manner compared to without treatment group (p < 0.05). Furthermore, the TNF-α level was normalized in 2500 mg/kgBW Physalis minima L. (p < 0.05) treatment. The reduction of fibrosis positively correlated with TNF-α level (p < 0.05, r = 0.873). Methanolic extract of ceplukan leaf decreases ventricular fibrosis through the inhibition of ventricular TNF-α level in ovariectomized rats.

  7. Thermodynamic properties of supercritical n-m Lennard-Jones fluids and isochoric and isobaric heat capacity maxima and minima

    NASA Astrophysics Data System (ADS)

    Mairhofer, Jonas; Sadus, Richard J.

    2013-10-01

    Molecular dynamics simulations are reported for the thermodynamic properties of n-m Lennard-Jones fluids, where n = 10 and 12, and m = 5 and 6. Results are reported for the thermal expansion coefficient, isothermal and adiabatic compressibilities, isobaric and isochoric heat capacities, Joule-Thomson coefficient, and speed of sound at supercritical conditions covering a wide range of fluid densities. The thermodynamic criteria for maxima/minima in the isochoric and isobaric heat capacities are identified and the simulation results are also compared with calculations from Lennard-Jones equations of state. The Johnson et al. [Mol. Phys. 78, 591 (1993)] equation of state can be used to reproduce all heat capacity phenomena reported [T. M. Yigzawe and R. J. Sadus, J. Chem. Phys. 138, 194502 (2013)] from molecular dynamics simulations for the 12-6 Lennard-Jones potential. Significantly, these calculations and molecular dynamics results for other n-m Lennard-Jones potentials support the existence of Cp minima at supercritical conditions. The values of n and m also have a significant influence on many other thermodynamic properties.

  8. Thermodynamic properties of supercritical n-m Lennard-Jones fluids and isochoric and isobaric heat capacity maxima and minima.

    PubMed

    Mairhofer, Jonas; Sadus, Richard J

    2013-10-21

    Molecular dynamics simulations are reported for the thermodynamic properties of n-m Lennard-Jones fluids, where n = 10 and 12, and m = 5 and 6. Results are reported for the thermal expansion coefficient, isothermal and adiabatic compressibilities, isobaric and isochoric heat capacities, Joule-Thomson coefficient, and speed of sound at supercritical conditions covering a wide range of fluid densities. The thermodynamic criteria for maxima∕minima in the isochoric and isobaric heat capacities are identified and the simulation results are also compared with calculations from Lennard-Jones equations of state. The Johnson et al. [Mol. Phys. 78, 591 (1993)] equation of state can be used to reproduce all heat capacity phenomena reported [T. M. Yigzawe and R. J. Sadus, J. Chem. Phys. 138, 194502 (2013)] from molecular dynamics simulations for the 12-6 Lennard-Jones potential. Significantly, these calculations and molecular dynamics results for other n-m Lennard-Jones potentials support the existence of Cp minima at supercritical conditions. The values of n and m also have a significant influence on many other thermodynamic properties.

  9. Methanolic Extract of Ceplukan Leaf (Physalis minima L.) Attenuates Ventricular Fibrosis through Inhibition of TNF-α in Ovariectomized Rats

    PubMed Central

    Lestari, Bayu; Permatasari, Nur; Rohman, Mohammad Saifur

    2016-01-01

    The increase of heart failure prevalence on menopausal women was correlated with the decrease of estrogen level. The aim of this study is to investigate the effects of ceplukan leaf (Physalis minima L.), which contains phytoestrogen physalin and withanolides, on ventricular TNF-α level and fibrosis in ovariectomized rats. Wistar rats were divided into six groups (control (—); OVX 5: 5-week ovariectomy (OVX); OVX 9: 9-week ovariectomy; treatments I, II, and III: 9-weeks OVX + 4-week ceplukan leaf's methanolic extract doses 500, 1500, and 2500 mg/kgBW, resp.). TNF-α levels were measured with ELISA. Fibrosis was counted as blue colored tissues percentage using Masson's Trichrome staining. This study showed that prolonged hypoestrogen increases ventricular fibrosis (p < 0.05). Ceplukan leaf treatment also resulted in a decrease of ventricular fibrosis and TNF-α level in dose dependent manner compared to without treatment group (p < 0.05). Furthermore, the TNF-α level was normalized in 2500 mg/kgBW Physalis minima L. (p < 0.05) treatment. The reduction of fibrosis positively correlated with TNF-α level (p < 0.05, r = 0.873). Methanolic extract of ceplukan leaf decreases ventricular fibrosis through the inhibition of ventricular TNF-α level in ovariectomized rats. PMID:26941790

  10. Biosynthesis of gold nanoparticles by the living freshwater diatom Eolimna minima, a species developed in river biofilms.

    PubMed

    Feurtet-Mazel, Agnès; Mornet, Stéphane; Charron, Laëtitia; Mesmer-Dudons, Nathalie; Maury-Brachet, Régine; Baudrimont, Magalie

    2016-03-01

    Testing biotransformation capacities of living aquatic microalgae diatoms to naturally synthetize gold nanoparticles (AuNP) from gold salts and assessing aftereffects on their viability by microscope observations is a great challenge. In this work, a laboratory experiment was conducted, which aimed to observe (i) directly by transmission electronic and light microscopy and (ii) through indirect measurements (UV-visible spectroscopy) the periphytic freshwater diatom Eolimna minima exposed to gold salts. This work revealed the capacity of E. minima to intracellularly biosynthetize AuNP and to tolerate it. AuNP synthesis appears as a mechanism of detoxification to protect diatom from gold salt contamination. We also pointed out the risks associated with the spread of diatoms full of AuNP, through the trophic web of freshwater ecosystems. The preponderant part of the diatoms in natural biofilms associated with their position at the basis of the trophic webs in rivers could then make them responsible for the contamination of their consumers (grazer animals) and consequently for the potential release of AuNP through the entire food web.

  11. The Pb-hyperaccumulator aquatic fern Salvinia minima Baker, responds to Pb(2+) by increasing phytochelatins via changes in SmPCS expression and in phytochelatin synthase activity.

    PubMed

    Estrella-Gómez, N; Mendoza-Cózatl, D; Moreno-Sánchez, R; González-Mendoza, D; Zapata-Pérez, O; Martínez-Hernández, A; Santamaría, J M

    2009-03-09

    The relationship between accumulation of Pb(2+) and the activation of chelation and metal sequestration mechanisms mediated by phytochelatins (PC) was analyzed in the Pb(2+) hyperaccumulator aquatic fern Salvinia minima, after exposure to 40microM Pb(NO(3))(2). The tissue accumulation pattern of lead and the phytochelatin biosynthesis responses were analyzed in both, S. minima submerged root-like modified fronds (here named "roots"), and in its aerial leaf-like fronds ("leaves"). S. minima roots accumulated a significantly higher concentrations of Pb(+2) than leaves did. Accumulation of Pb(2+) in roots was bi-phasic with a first uptake phase reached after 3h exposure and a second higher uptake phase reached after 24h exposure. In leaves, a single delayed, smaller uptake phase was attained only after 9h of exposure. In roots lead accumulation correlated with an increased phytochelatin synthase (PCS) activity and an enhanced PC production. A higher proportion of polymerized PC(4) was observed in both tissues of exposed S. minima plants relative to unexposed ones, although a higher concentration of PC(4) was found in roots than in leaves. PCS activity and Pb(2+) accumulation was also higher in roots than in leaves. The expression levels of the S. minima PCS gene (SmPCS), in response to Pb(2+) treatment, were also evaluated. In S. minima leaves, the accumulation of Pb(2+) correlated with a marked increase in expression of SmPCS, suggesting a transcriptional regulation in the PCS activation and PC accumulation in this S. minima tissue. However, in roots, the basal expression of SmPCS was down-regulated after Pb(2+) treatment. This fact did not correlate with the later but strong increase in both, PCS activity and PC production; suggesting that the PC biosynthesis activation in S. minima roots occurs only by post-translational activation of PCS. Taken together, our data suggest that the accumulation of PC in S. minima is a direct response to Pb(2+) accumulation, and

  12. Capacity of the aquatic fern (Salvinia minima Baker) to accumulate high concentrations of nickel in its tissues, and its effect on plant physiological processes.

    PubMed

    Fuentes, Ignacio I; Espadas-Gil, Francisco; Talavera-May, Carlos; Fuentes, Gabriela; Santamaría, Jorge M

    2014-10-01

    An experiment was designed to assess the capacity of Salvinia minima Baker to uptake and accumulate nickel in its tissues and to evaluate whether or not this uptake can affect its physiology. Our results suggest that S. minima plants are able to take up high amounts of nickel in its tissues, particularly in roots. In fact, our results support the idea that S. minima might be considered a hyper-accumulator of nickel, as it is able to accumulate 16.3 mg g(-1) (whole plant DW basis). Our results also showed a two-steps uptake pattern of nickel, with a fast uptake of nickel at the first 6 to 12h of being expose to the metal, followed by a slow take up phase until the end of the experiment at 144 h. S. minima thus, may be considered as a fern useful in the phytoremediation of residual water bodies contaminated with this metal. Also from our results, S. minima can tolerate fair concentrations of the metal; however, at concentrations higher than 80 μM Ni (1.5 mg g(-1) internal nickel concentration), its physiological performance can be affected. For instance, the integrity of cell membranes was affected as the metal concentration and exposure time increased. The accumulation of high concentrations of internal nickel did also affect photosynthesis, the efficiency of PSII, and the concentration of photosynthetic pigments, although at a lower extent. Copyright © 2014 Elsevier B.V. All rights reserved.

  13. Interference minima effect of high-order harmonic generation from H2+ with different full width at half maximum

    NASA Astrophysics Data System (ADS)

    Pan, Xue-Fei; Zhang, Jun; Du, Hui; Liu, Hai-Feng; Zhang, Hong-Dan; Liu, Xue-Shen

    2017-01-01

    We investigate the effect of the interference minima of the high-order harmonic generation (HHG) in H2+ molecule with varying the full width at half maximum (FWHM) of the laser field by solving the one-dimensional (1D) time-dependent Schrödinger equation (TDSE) within the non-Born-Oppenheimer approximation. The numerical results show that the probability of the electron recombined with the two nuclei is different with the variation of the FWHM. The HHG spectrum of H2+ molecule is separated into two parts according to the electronic coordinate z (z > 0 and z < 0), which illustrate the contributions of the two nuclei to the harmonic generation. In addition, we investigate the time-evolution electron wave packet distributions to illustrate the underlying physical mechanism.

  14. Qualitative and quantitative analysis of chemical constituents of Centipeda minima by HPLC-QTOF-MS & HPLC-DAD.

    PubMed

    Chan, Chi-On; Jin, Deng-Ping; Dong, Nai-Ping; Chen, Si-Bao; Mok, Daniel Kam Wah

    2016-06-05

    A high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (HPLC-QTOF-MS) method in both positive and negative ion modes was established to investigate the major constituents in the ethanolic extract of Centipeda minima (EBSC). Twelve common components including flavones and their glycosides, phenolic and polyphenolic acids, and sesquiterpene lactone were identified in ten batches of samples based on comparison with the retention time and accurate mass of external standards (mass accuracy within 3ppm) or the fragmentation patterns of tandem MS. Meanwhile, a simple, accurate and reliable HPLC-DAD method was also developed to determine the content of 10 chemical markers simultaneously. Results obtained from method validations including linearity, accuracy and precision showed that this new method is reliable and robust. Isochlorogenic acid A and brevilin A were found to be the most abundant in the ethanol extract of EBSC and could be served as markers for quality control of EBSC.

  15. Hybrid functional for correlated electrons in the projector augmented-wave formalism: Study of multiple minima for actinide oxides

    NASA Astrophysics Data System (ADS)

    Jollet, F.; Jomard, G.; Amadon, B.; Crocombette, J. P.; Torumba, D.

    2009-12-01

    Exact (Hartree-Fock) exchange for correlated electrons is implemented to describe correlated orbitals in the projector augmented-waves (PAW) framework, as suggested recently in another context [P. Novák , Phys. Status Solidi B 243, 563 (2006)]. Hartree-Fock exchange energy is applied to strongly correlated electrons only inside the PAW atomic spheres. This allows the use of PBE0 hybrid exchange-correlation functional for correlated electrons. This method is tested on NiO and results agree well with already published results and generalized gradient approximation, GGA+U calculations. It is then applied to plutonium oxides and UO2 for which the results are comparable with the ones of GGA+U calculations but without adjustable parameter. As evidenced in the uranium oxide case, the occurrence of multiple energy minima may lead to very different results depending on the initial electronic configurations and on the symmetries taken into account in the calculation.

  16. 13,14-seco-Withanolides from Physalis minima with Potential Anti-inflammatory Activity.

    PubMed

    Lin, Ru; Guan, Yu-Zhou; Li, Rui-Jun; Xu, Xiao-Ming; Luo, Jian-Guang; Kong, Ling-Yi

    2016-07-01

    Four new 13,14-seco-withanolides, minisecolides A - D (1 - 4), together with three known analogues 5 - 7, were isolated from the whole plants of Physalis minima. The structures of new compounds were determined on the basis of spectroscopic analysis, including (1) H-, (13) C-NMR, 2D-NMR (HMBC, HSQC, ROESY), and HR-ESI-MS. Evaluation of all isolates for their inhibitory effects on nitric oxide (NO) production was conducted on lipopolysaccaride-activated RAW264.7 macrophages. Compounds 2, 3, 5, and 6 showed inhibitory activities, especially for compound 5 with IC50 value of 3.87 μm. © 2016 Wiley-VHCA AG, Zürich.

  17. Differential Expression of Antioxidant Enzymes During Degradation of Azo Dye Reactive black 8 in Hairy roots of Physalis minima L.

    PubMed

    Jha, Pamela; Modi, Nikita; Jobby, Renitta; Desai, Neetin

    2015-01-01

    The enzymes involved in the protection of plant metabolism in presence of azo dye was characterized by studying activities of the role of antioxidant enzymes in the hairy roots (HRs) of Physalis minima L. during degradation of an azo dye, Reactive Black 8 (RB8). When the HRs were exposed to RB8 (30 mg L(-1)), a  nine fold increase in SOD activity was observed after 24 h, while 22 and 50 fold increase in activity was observed for POX and APX respectively after 72 h, whereas there was no significant change in activity of CAT. The activation of different antioxidant enzymes at different time intervals under dye stress suggests the synchronized functioning of antioxidant machinery to protect the HRs from oxidative damage. FTIR analysis confirmed the degradation of dye and the non-toxic nature of metabolites formed after dye degradation was confirmed by phytotoxicity study.

  18. 3D Electron Density Distributions in the Solar Corona during Solar Minima: Assessment for More Realistic Solar Wind Modeling

    NASA Astrophysics Data System (ADS)

    de Patoul, Judith; Foullon, Claire; Riley, Pete

    2015-11-01

    Knowledge of the electron density distribution in the solar corona put constraints on the magnetic field configurations for coronal modeling and on initial conditions for solar wind modeling. We work with polarized SOHO/LASCO-C2 images from the last two recent minima of solar activity (1996-1997 and 2008-2010), devoid of coronal mass ejections. The goals are to derive the 4D electron density distributions in the corona by applying a newly developed time-dependent tomographic reconstruction method and to compare the results between the two solar minima and with two magnetohydrodynamic models. First, we confirm that the values of the density distribution in thermodynamic models are more realistic than in polytropic ones. The tomography provides more accurate distributions in the polar regions, and we find that the density in tomographic and thermodynamic solutions varies with the solar cycle in both polar and equatorial regions. Second, we find that the highest-density structures do not always correspond to the predicted large-scale heliospheric current sheet or its helmet streamer but can follow the locations of pseudo-streamers. We deduce that tomography offers reliable density distributions in the corona, reproducing the slow time evolution of coronal structures, without prior knowledge of the coronal magnetic field over a full rotation. Finally, we suggest that the highest-density structures show a differential rotation well above the surface depending on how they are magnetically connected to the surface. Such valuable information on the rotation of large-scale structures could help to connect the sources of the solar wind to their in situ counterparts in future missions such as Solar Orbiter and Solar Probe Plus.

  19. Biosynthesis of lead nanoparticles by the aquatic water fern, Salvinia minima Baker, when exposed to high lead concentration.

    PubMed

    Castro-Longoria, E; Trejo-Guillén, K; Vilchis-Nestor, A R; Avalos-Borja, M; Andrade-Canto, S B; Leal-Alvarado, D A; Santamaría, J M

    2014-02-01

    Salvinia minima Baker is a small floating aquatic fern that is efficient for the removal and storage of heavy metals such as lead and cadmium. In this study, we report that lead removal by S. minima causes large accumulation of lead inside the cells in the form of nanoparticles (PbNPs). The accumulation pattern of lead was analyzed in both, submerged root-like modified fronds (here named "roots"), and in its aerial leaf-like fronds ("leaves"). Analysis by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) confirmed the biosynthesis of PbNPs by the plant. In both, roots and leaves, PbNPs were found to accumulate almost exclusively at the cell wall and closely associated to the cell membrane. Two types of PbNPs shapes were found in cells of both tissues, those associated to the cell wall were quasi-spherical with 17.2±4.2 nm of diameter, while those associated to the cell membrane/cytoplasm were elongated. Elongated particles were 53.7±29.6 nm in length and 11.1±2.4 nm wide. Infrared spectroscopy (IR) results indicate that cellulose, lignin and pectin are the major components that may be acting as the reducing agents for lead ions; these findings strongly suggest the potential use of this fern to further explore the bio-assisted synthesis of heavy metal nanostructures. Copyright © 2013 Elsevier B.V. All rights reserved.

  20. Study of minima of the fluctuations of the order parameter of seismicity using GCMT catalogue in global scale.

    NASA Astrophysics Data System (ADS)

    Christopoulos, Stavros-Richard G.; Sarlis, Nicholas V.; Skordas, Efthimios S.

    2016-04-01

    It has been recently shown [1,2] that earthquakes of magnitude M greater or equal to 7 are globally correlated. The identification of this correlation became possible when studying the variance κ1 of natural time which has been proposed as an order parameter for seismicity[3,4]. In the present study, we focus on the behaviour of the fluctuations of κ1 before major earthquakes using the Global Centroid Moment Tensor catalogue for a magnitude threshold Mthres=5.0 as in Ref.[5]. Natural time analysis reveals that distinct minima of the fluctuations κ1of seismicity appear within almost five and a half months on average before all major earthquakes of magnitude larger than M8.4. This phenomenon corroborates the recent finding [6] that similar minima of seismicity order parameter fluctuations had been observed before all major shallow earthquakes in Japan. Finally, we examine the statistical significance of the results by using ROC graphs [7,8] and the proposed prediction method has a p-value to occur by chance well below 0.1%. The hit rate is 100% with a false alarm rate only 6.67%. An attempt to lower the target earthquake magnitude threshold will be also presented. REFERENCES [1] N. V. Sarlis, Phys. Rev. E 84, 022101 (2011). [2] N. V. Sarlis and S.-R. G. Christopoulos, Chaos 22, 023123 (2012) [3] P. A. Varotsos, N. V. Sarlis, and E. S. Skordas, Practica of Athens Acad. 76, 294 (2001). [4] P. A. Varotsos, N. V. Sarlis, and E. S. Skordas, Phys. Rev. E 66, 011902 (2002). [5] N.V. Sarlis, S.-R. G. Christopoulos, and E. S. Skordas, Chaos 25, 063110 (2015) [6] N. V. Sarlis et al., Proc. Natl. Acad. Sci. U.S.A. 110, 13734 (2013) [7] T. Fawcett, Pattern Recognit. Lett. 27, 861 (2006). [8] N. V. Sarlis and S.-R. G. Christopoulos, Comput. Phys. Commun. 185, 1172 (2014).

  1. 3D ELECTRON DENSITY DISTRIBUTIONS IN THE SOLAR CORONA DURING SOLAR MINIMA: ASSESSMENT FOR MORE REALISTIC SOLAR WIND MODELING

    SciTech Connect

    Patoul, Judith de; Foullon, Claire; Riley, Pete E-mail: c.foullon@exeter.ac.uk

    2015-11-20

    Knowledge of the electron density distribution in the solar corona put constraints on the magnetic field configurations for coronal modeling and on initial conditions for solar wind modeling. We work with polarized SOHO/LASCO-C2 images from the last two recent minima of solar activity (1996–1997 and 2008–2010), devoid of coronal mass ejections. The goals are to derive the 4D electron density distributions in the corona by applying a newly developed time-dependent tomographic reconstruction method and to compare the results between the two solar minima and with two magnetohydrodynamic models. First, we confirm that the values of the density distribution in thermodynamic models are more realistic than in polytropic ones. The tomography provides more accurate distributions in the polar regions, and we find that the density in tomographic and thermodynamic solutions varies with the solar cycle in both polar and equatorial regions. Second, we find that the highest-density structures do not always correspond to the predicted large-scale heliospheric current sheet or its helmet streamer but can follow the locations of pseudo-streamers. We deduce that tomography offers reliable density distributions in the corona, reproducing the slow time evolution of coronal structures, without prior knowledge of the coronal magnetic field over a full rotation. Finally, we suggest that the highest-density structures show a differential rotation well above the surface depending on how they are magnetically connected to the surface. Such valuable information on the rotation of large-scale structures could help to connect the sources of the solar wind to their in situ counterparts in future missions such as Solar Orbiter and Solar Probe Plus.

  2. Comparison of the extended solar minimum of 2006-2009 with the Spoerer, Maunder, and Dalton Grand Minima in solar activity in the past

    NASA Astrophysics Data System (ADS)

    McCracken, K. G.; Beer, J.

    2014-04-01

    We use cosmic radiation records (neutron monitor and the cosmogenic radionuclides, 10Be and 14C) as a proxy to compare the solar activity during the extended solar minimum 2006-2009, with that during the Grand Solar Minima and Maxima that occurred between 1391 and 2010. The inferred cosmic ray intensities during the Spoerer, Maunder, and Dalton Grand Minima were significantly greater than those during 2006-2009. The onset phases of the three Grand Minima extended over between two and five Schwabe (sunspot) cycles, the cosmic ray intensity at the Schwabe minima increasing from a value approximating that of 2006-2009, to substantially higher values later in the Grand Minimum. The minimum estimated strengths of the heliospheric magnetic field near Earth during the Grand Minima were 2.4 nT (Spoerer), <2.0 nT (Maunder), and 2.6 nT (Dalton), compared to 3.9 nT in 2009. We conclude that the periods of highest solar activity during the Maunder Minimum approximated those near the sunspot minima between 1954 and 1996. The average ratio of the maximum to minimum estimated HMF in the six Schwabe cycles in the Maunder Minimum is 1.54 (range 1.30-1.85) compared to 1.52 (1.31-1.63) for the modern epoch suggesting similar operation of the solar dynamo in both intervals. The onset phase of the Maunder Minimum extending over five Schwabe cycles, and the large increase in cosmic ray flux (and decrease in estimated heliospheric magnetic field), leads us to speculate that the magnetohydrodynamic amplification in the solar dynamo exhibits a relaxation time well in excess of the 11 year period of the Schwabe cycle.

  3. A phenomenological study of the timing of solar activity minima of the last millennium through a physical modeling of the Sun-Planets Interaction

    NASA Astrophysics Data System (ADS)

    Cionco, Rodolfo Gustavo; Soon, Willie

    2015-01-01

    We numerically integrate the Sun’s orbital movement around the barycenter of the solar system under the persistent perturbation of the planets from the epoch J2000.0, backward for about one millennium, and forward for another millennium to 3000 AD. Under the Sun-Planets Interaction (SPI) framework and interpretation of Wolff and Patrone (2010), we calculated the corresponding variations of the most important storage of the specific potential energy (PE) within the Sun that could be released by the exchanges between two rotating, fluid-mass elements that conserve its angular momentum. This energy comes about as a result of the roto-translational dynamics of the cell around the solar system barycenter. We find that the maximum variations of this PE storage correspond remarkably well with the occurrences of well-documented Grand Minima (GM) solar events throughout the available proxy solar magnetic activity records for the past 1000 yr. It is also clear that the maximum changes in PE precede the GM events in that we can identify precursor warnings to the imminent weakening of solar activity for an extended period. The dynamical explanation of these PE minima is connected to the minima of the Sun’s position relative to the barycenter as well as the significant amount of time the Sun’s inertial motion revolving near and close to the barycenter. We presented our calculation of PE forward by another 1000 yr until 3000 AD. If the assumption of the solar activity minima corresponding to PE minima is correct, then we can identify quite a few significant future solar activity GM events with a clustering of PE minima pulses starting at around 2150 AD, 2310 AD, 2500 AD, 2700 AD and 2850 AD.

  4. Global minima and energetics of Li +(H 2O) n and Ca 2+(H 2O) n clusters for n ⩽ 20

    NASA Astrophysics Data System (ADS)

    González, Briesta S.; Hernández-Rojas, Javier; Wales, David J.

    2005-08-01

    We present candidate structures for the global potential energy minima of X(H 2O) n (X = Li +, Ca 2+) clusters with n ⩽ 20. The TIP4P rigid body water-water potential is employed, together with cation-water interactions that are represented as a sum of Coulomb and Lennard-Jones terms. We find that in the Li + global minima the cation tends to be located on the cluster surface with a preferred coordination number of four water molecules in tetrahedral positions. In contrast, for Ca 2+ clusters the cation occupies an interior site surrounded by eight water molecules in a square anti-prismatic arrangement.

  5. A Change in the Solar He II EUV Global Network Structure as an Indicator of the Geo-Effectiveness of Solar Minima

    NASA Technical Reports Server (NTRS)

    Didkovsky, L.; Gurman, J. B.

    2013-01-01

    Solar activity during 2007 - 2009 was very low, causing anomalously low thermospheric density. A comparison of solar extreme ultraviolet (EUV) irradiance in the He II spectral band (26 to 34 nm) from the Solar Extreme ultraviolet Monitor (SEM), one of instruments on the Charge Element and Isotope Analysis System (CELIAS) on board the Solar and Heliospheric Observatory (SOHO) for the two latest solar minima showed a decrease of the absolute irradiance of about 15 +/- 6 % during the solar minimum between Cycles 23 and 24 compared with the Cycle 22/23 minimum when a yearly running-mean filter was used. We found that some local, shorter-term minima including those with the same absolute EUV flux in the SEM spectral band show a higher concentration of spatial power in the global network structure from the 30.4 nm SOHO/Extreme ultraviolet Imaging Telescope (EIT) images for the local minimum of 1996 compared with the minima of 2008 - 2011.We interpret this higher concentration of spatial power in the transition region's global network structure as a larger number of larger-area features on the solar disk. These changes in the global network structure during solar minima may characterize, in part, the geo-effectiveness of the solar He II EUV irradiance in addition to the estimations based on its absolute levels.

  6. Adults of the Waterfern Weevil, Stenopelmus rufinasus Gyllenhal (Coleoptera: Curculionidae) feed on a Non-Host Plant Salvinia minima Baker, in Louisiana

    USDA-ARS?s Scientific Manuscript database

    The waterfern weevil, Stenopelmus refinasus Gyllenhal, has previously been reported as host-specific, only feeding on plants in the genus Azolla. We report the first observations of S. rufinasus feeding on a non-host plant, Salvinia minima Baker, within the United States....

  7. SOHO/CELIAS Solar EUV Monitor (SEM) Absolute Solar EUV Irradiance Measurements Spanning Two Solar Minima (Invited)

    NASA Astrophysics Data System (ADS)

    Wieman, S. R.; Didkovsky, L. V.; Judge, D.

    2010-12-01

    The SOHO/CELIAS Solar EUV Monitor (SEM) has measured absolute EUV solar irradiance nearly continuously over a 15 year period that includes both the cycle 22/23 (1996) and cycle 23/24 (2008) solar minima. These measurements indicate that irradiance in the 26-34 nm spectral range, including the dominant He II 30.4 nm spectral line, was about 15% ± 6% lower during the more recent minimum compared to the previous minimum. The SEM data have been verified against measurements from seven sounding rocket calibration underflights that included a NIST calibrated SEM clone instrument as well as a Rare Gas Ionization Cell (RGIC) absolute extreme ultraviolet (EUV) detector. Additionally, the SEM measurements are in good agreement with measurements from the EUV Spectrophotomer (ESP) part of the EUV Variability Experiment (EVE) on SDO. ESP measurements from the EVE sounding rocket flight (2008) confirmed the very low solar EUV irradiance observed during the 23/24 minimum. A comparison of SEM and ESP data in the 30.4 nm spectral windows is presented.

  8. Application of ''Protocollo di Minima per l'ictus'' (PMIC- Minimal Protocol for Stroke) for inpatient rehabilitation setting.

    PubMed

    Piazzini, D B; Ferrara, P E; Maggi, L; Frasca, G; Aprile, I; Rabini, A; Specchia, A; Bertolini, C

    2008-09-01

    The aim of this study was to describe the baseline characteristics of a sample of stroke patients admitted to rehabilitation settings with the use of a standardised stroke assessment named ''Protocollo di Minima per l'ictus cerebrale'' (PMIC), to verify the usefulness of the application of PMIC and to compare the data of the authors with the international literature. An observational cross sectional study was conducted on a sample of 102 first-time stroke patients (mean age: 71.9 [+/-11.6], 54 men), in three inpatient rehabilitation centres. PMIC. Most patients were enrolled within 14 days of stroke onset. PMIC assessment took on average 20 minutes and provided the following information: 35% had architectural barriers in their homes; 82% of the cases had 1 or more family assistants; the educational level was low for 53%; 72% were retired; most cases were ischemic stroke without any side predominance being shown; 44% had partial anterior circulation infarcts (PACI) ischemic stroke; 18.6% presented dysphagia; 73% had sphincteral incontinence; there was no hypertone in more than 50% of the cases; 87% required assistance; the median Motricity Index Side Score (Miss) value was 44.1; 38% was affected by mood tone alteration. PMIC appeared to be a useful tool for a standardized evaluation of stroke patients. These results provide data with a high correspondence in international reports.

  9. Curvature and the visual perception of shape: theory on information along object boundaries and the minima rule revisited.

    PubMed

    Lim, Ik Soo; Leek, E Charles

    2012-07-01

    Previous empirical studies have shown that information along visual contours is known to be concentrated in regions of high magnitude of curvature, and, for closed contours, segments of negative curvature (i.e., concave segments) carry greater perceptual relevance than corresponding regions of positive curvature (i.e., convex segments). Lately, Feldman and Singh (2005, Psychological Review, 112, 243-252) proposed a mathematical derivation to yield information content as a function of curvature along a contour. Here, we highlight several fundamental errors in their derivation and in its associated implementation, which are problematic in both mathematical and psychological senses. Instead, we propose an alternative mathematical formulation for information measure of contour curvature that addresses these issues. Additionally, unlike in previous work, we extend this approach to 3-dimensional (3D) shape by providing a formal measure of information content for surface curvature and outline a modified version of the minima rule relating to part segmentation using curvature in 3D shape. Copyright 2012 APA, all rights reserved.

  10. Salinity minima, water masses and surface circulation in the Eastern Tropical Pacific off Mexico and surrounding areas

    NASA Astrophysics Data System (ADS)

    Portela, Esther; Beier, Emilio; Godínez, Victor; Castro, Rubén; Desmond Barton, Eric

    2016-04-01

    The seasonal variations of the water masses and their interactions are analyzed in the Tropical Pacific off Mexico (TPOM) and four contiguous areas of on the basis of new extensive hydrographic database. The regional water masses intervals are redefined in terms of Absolute Salinity (SA) in g kg-1 and Conservative Temperature (Θ) according to TEOS - 10. The California Current System Water (CCSW) mass is introduced as an improved description of the former California Current Water (CCW) together with the Subarctic Water (SAW) to describe better the characteristics of the components of the California Current System. Hydrographic data, Precipitation-Evaporation balance and geostrophic currents were used to investigate the origin and seasonality of two salinity minima in the area. The shallow salinity minimum of around 33.5 g kg-1 originated in the California Current System and became saltier but less dense water as it traveled to the southeast. It can be identified as a mixture of CCSW and tropical waters. The surface salinity minimum of 32 - 33 g kg-1 was seen as a sharp surface feature in the TPOM from August to November. It was produced by the arrival of tropical waters from the south in combination with the net precipitation in the area during these months. This result provides new evidence of the presence of the poleward-flowing Mexican Coastal Current and, for the first time, of its seasonal pattern of variation.

  11. Signatures of the Primordial Universe from Its Emptiness: Measurement of Baryon Acoustic Oscillations from Minima of the Density Field

    NASA Astrophysics Data System (ADS)

    Kitaura, Francisco-Shu; Chuang, Chia-Hsun; Liang, Yu; Zhao, Cheng; Tao, Charling; Rodríguez-Torres, Sergio; Eisenstein, Daniel J.; Gil-Marín, Héctor; Kneib, Jean-Paul; McBride, Cameron; Percival, Will J.; Ross, Ashley J.; Sánchez, Ariel G.; Tinker, Jeremy; Tojeiro, Rita; Vargas-Magana, Mariana; Zhao, Gong-Bo

    2016-04-01

    Sound waves from the primordial fluctuations of the Universe imprinted in the large-scale structure, called baryon acoustic oscillations (BAOs), can be used as standard rulers to measure the scale of the Universe. These oscillations have already been detected in the distribution of galaxies. Here we propose to measure BAOs from the troughs (minima) of the density field. Based on two sets of accurate mock halo catalogues with and without BAOs in the seed initial conditions, we demonstrate that the BAO signal cannot be obtained from the clustering of classical disjoint voids, but it is clearly detected from overlapping voids. The latter represent an estimate of all troughs of the density field. We compute them from the empty circumsphere centers constrained by tetrahedra of galaxies using Delaunay triangulation. Our theoretical models based on an unprecedented large set of detailed simulated void catalogues are remarkably well confirmed by observational data. We use the largest recently publicly available sample of luminous red galaxies from SDSS-III BOSS DR11 to unveil for the first time a >3 σ BAO detection from voids in observations. Since voids are nearly isotropically expanding regions, their centers represent the most quiet places in the Universe, keeping in mind the cosmos origin and providing a new promising window in the analysis of the cosmological large-scale structure from galaxy surveys.

  12. Study of the Formation and Evolution of Precipitation Induced Sea Surface Salinity Minima in the Tropical Pacific Using HYCOM

    NASA Astrophysics Data System (ADS)

    Gallagher, R. L.

    2016-02-01

    During heavy rain events in the tropics, areas of relatively low salinity water collect on the ocean surface. Rainfall events increase the buoyancy of the ocean surface and impact upper ocean salinity and temperature profiles. This resists downward mixing and as a result can persist (SPURS II planning group, 2012; Oceanography 28(1) 150-159). Salinity at the surface adjusts through advective and diffusive mixing processes (Scott, J. et al, 2013; AGU Fall meeting abstracts). This project investigates the upper ocean salinity response in both advection and diffusion dominated regions. The changes in ocean surface salinity are tracked before, during, and after rainfall events. Data from a standard oceanographic model, HYCOM, are used to identify areas where each surface process is significant. Rainfall events are identified using a TRMM dataset. It provides a tropical rainfall analysis which uses amalgamated satellite data to develop detailed global precipitation grids between 50 o north and south latitude. TRMM is useful due its high temporal and spatial resolutions. The salinity response in HYCOM is tested against simple theoretical advective and diffusive mixing models. The magnitude of sea surface salinity minima, their persistence and the precision by which HYCOM can resolve these phenomena are of interest.

  13. Paravannella minima n. g. n. sp. (Discosea, Vannellidae) and distinction of the genera in the vannellid amoebae.

    PubMed

    Kudryavtsev, Alexander

    2014-06-01

    Paravannella minima n. g. n. sp. (Amoebozoa, Vannellidae) isolated from a freshwater aquarium, possesses all light-microscopic and ultrastructural characteristics of the genus Vannella, being one of the smallest species among the vannellid amoebae (cell size during locomotion usually between 4.5 and 10μm). At the same time, sequence analysis of the genes encoding for nuclear SSU rRNA, actin and mitochondrial Cox1 shows this species as the earliest-branching vannellid that appears to be sister to the rest of this clade. This is correlated with the presence of some plesiomorphic characters; in particular, the secondary structure of the hypervariable helices E23-1-E23-7 in the studied species is shared with Vannella and most of the genera of Dactylopodida. The cell coat structure of the studied species corresponds to the hypothesis that vannellid amoebae were ancestrally enclosed in a cell coat consisting of pentagonal glycostyles that have undergone multiple independent losses in various clades of Vannellidae.

  14. Signatures of the Primordial Universe from Its Emptiness: Measurement of Baryon Acoustic Oscillations from Minima of the Density Field.

    PubMed

    Kitaura, Francisco-Shu; Chuang, Chia-Hsun; Liang, Yu; Zhao, Cheng; Tao, Charling; Rodríguez-Torres, Sergio; Eisenstein, Daniel J; Gil-Marín, Héctor; Kneib, Jean-Paul; McBride, Cameron; Percival, Will J; Ross, Ashley J; Sánchez, Ariel G; Tinker, Jeremy; Tojeiro, Rita; Vargas-Magana, Mariana; Zhao, Gong-Bo

    2016-04-29

    Sound waves from the primordial fluctuations of the Universe imprinted in the large-scale structure, called baryon acoustic oscillations (BAOs), can be used as standard rulers to measure the scale of the Universe. These oscillations have already been detected in the distribution of galaxies. Here we propose to measure BAOs from the troughs (minima) of the density field. Based on two sets of accurate mock halo catalogues with and without BAOs in the seed initial conditions, we demonstrate that the BAO signal cannot be obtained from the clustering of classical disjoint voids, but it is clearly detected from overlapping voids. The latter represent an estimate of all troughs of the density field. We compute them from the empty circumsphere centers constrained by tetrahedra of galaxies using Delaunay triangulation. Our theoretical models based on an unprecedented large set of detailed simulated void catalogues are remarkably well confirmed by observational data. We use the largest recently publicly available sample of luminous red galaxies from SDSS-III BOSS DR11 to unveil for the first time a >3σ BAO detection from voids in observations. Since voids are nearly isotropically expanding regions, their centers represent the most quiet places in the Universe, keeping in mind the cosmos origin and providing a new promising window in the analysis of the cosmological large-scale structure from galaxy surveys.

  15. Optimal geometries and harmonic vibrational frequencies of the global minima of water clusters (H2O)n, n = 2–6, and several hexamer local minima at the CCSD(T) level of theory

    SciTech Connect

    Miliordos, Evangelos; Aprà, Edoardo; Xantheas, Sotiris S.

    2013-01-01

    We report the first optimum geometries and harmonic vibrational frequencies for the ring pentamer and several water hexamer (prism, cage, cyclic and two book) at the CCSD(T)/aug-cc-pVDZ level of theory. All five hexamer isomer minima previously reported by MP2 are also minima on the CCSD(T) potential energy surface (PES). In addition, all CCSD(T) minimum energy structures for the n=2-6 cluster isomers are quite close to the ones previously obtained by MP2 on the respective PESs, as confirmed by a modified Procrustes analysis that quantifies the difference between any two cluster geometries. The CCSD(T) results confirm the cooperative effect of the homodromic ring networks (systematic contraction of the nearest-neighbor (nn) intermolecular separations with cluster size) previously reported by MP2, albeit with O-O distances shorter by ~0.02 Å, indicating that MP2 overcorrects this effect. The harmonic frequencies at the minimum geometries were obtained by the double differentiation of the CCSD(T) energy using an efficient scheme based on internal coordinates that reduces the number of required single point energy evaluations by ~15% when compared to the corresponding double differentiation using Cartesian coordinates. Negligible differences between MP2 and CCSD(T) are found for the librational modes, while uniform increases of ~15 and ~25 cm-1 are observed for the bending and “free” OH harmonic frequencies. The largest differences between MP2 and CCSD(T) are observed for the harmonic hydrogen bonded frequencies. The CCSD(T) red shifts from the monomer frequencies (Δω) are smaller than the MP2 ones, due to the fact that the former produces shorter elongations (ΔR) of the respective hydrogen bonded OH lengths from the monomer value with respect to the latter. Both the MP2 and CCSD(T) results for the hydrogen bonded frequencies were found to closely follow the relation - Δω = s · ΔR, with a rate of s = 20.3 cm-1 / 0.001 Å. The CCSD

  16. Variability of surface water dynamics during eccentricity minima interglacials of the last 1 Myr in the North Atlantic

    NASA Astrophysics Data System (ADS)

    Palumbo, Eliana; Emanuele, Dario; Ferretti, Patrizia; Flores, José-Abel; Perugia, Carmen; Petrillo, Zaccaria; Ornella Amore, Filomena

    2014-05-01

    Eccentricity minima occurred only three times during the last 1 Myr in correspondence of Marine Isotope Stages (MIS) 1 (last 11 ka), 11 (425-360 ka) and 19 (791-763 ka). All these stages are characterised by similar orbital configurations and the Pleistocene eccentricity minima interglacials are considered, by several authors, as possible analogues for the Holocene and its future evolution. Surface water dynamics were reconstructed through quantitative analyses performed on coccolithophore assemblages in two key-sites of the North Atlantic: MD03-2699 core, retrieved off Iberian Margin (IM), and IODP Site U1313, located in the upper western flank of the Mid-Atlantic Ridge. Nowadays, IODP Site U1313 is under the influence of a northern ramification of the Gulf Stream, the North Atlantic Current (NAC). This current forms a transitional zone between the productive cold polar system and the oligotrophic warm subtropical system. In addition, the NAC represents the northern boundary of the Portugal Current (PC) system which influences the modern surface oceanography off the IM at MD03-2699 site. Coccolithophore data were carried out by sediments of MD03-2699 core for MIS 11 and MIS 1(Amore et al., 2012; Palumbo et al., 2013a,b) and by IODP Site U1313 for MIS 19 (Emanuele, 2013). The mean sampling resolution for MIS 1 is 140 yrs, for MIS 11 about 400 yrs and for MIS 19 about 220 yrs. The high samples resolution allowed reconstructing long term changes at orbital timescale as well as rapid changes at millennial scale. Data from coccolithophore assemblages were compared with available proxy for the studied cores such as alkenones, lithics, oxygen and carbon isotopes. Coccolithophores belong to phytoplankton group and they are widely used as proxy of surface water dynamics thanks to their attitude to record the smallest paleoclimatic changes and because they directly depend on sea surface temperature and salinity, sunlight and availability of nutrients. Through the use of

  17. 3D electron density distributions in the solar corona during solar minima: assessment for more realistic solar wind modeling

    NASA Astrophysics Data System (ADS)

    de Patoul, J.; Foullon, C.; Riley, P.

    2015-12-01

    Knowledge of the electron density distribution in the solar corona put constraints on the magnetic field configurations for coronal modeling, and on initial conditions for solar wind modeling. We work with polarized SOHO/LASCO-C2 images from the last two recent minima of solar activity (1996-1997 and 2008-2010), devoid of coronal mass ejections. We derive the 4D electron density distributions in the corona by applying a newly developed time-dependent tomographic reconstruction method. First we compare the density distributions obtained from tomography with magnetohydrodynamic (MHD) solutions. The tomography provides more accurate distributions of electron densities in the polar regions, and we find that the observed density varies with the solar cycle in both polar and equatorial regions. Second, we find that the highest-density structures do not always correspond to the predicted large-scale heliospheric current sheet or its helmet streamer but can follow the locations of pseudo-streamers. We conclude that tomography offers reliable density distribution in the corona, reproducing the slow time evolution of coronal structures, without prior knowledge of the coronal magnetic field over a full rotation. Finally, we suggest that the highest-density structures show a differential rotation well above the surface depending on how it is magnetically connected to the surface. Such valuable information on the rotation of large-scale structures could help to connect the sources of the solar wind to their in-situ counterparts in future missions such as Solar Orbiter and Solar Probe Plus. This research combined with the MHD coronal modeling efforts has the potential to increase the reliability for future space weather forecasting.

  18. Delayed build-up of Arctic ice sheets during 400,000-year minima in insolation variability.

    PubMed

    Hao, Qingzhen; Wang, Luo; Oldfield, Frank; Peng, Shuzhen; Qin, Li; Song, Yang; Xu, Bing; Qiao, Yansong; Bloemendal, Jan; Guo, Zhengtang

    2012-10-18

    Knowledge of the past variability of climate at high northern latitudes during astronomical analogues of the present interglacial may help to inform our understanding of future climate change. Unfortunately, long-term continuous records of ice-sheet variability in the Northern Hemisphere only are scarce because records of benthic (18)O content represent an integrated signal of changes in ice volume in both polar regions. However, variations in Northern Hemisphere ice sheets influence the Siberian High (an atmospheric pressure system), so variations in the East Asian winter monsoon (EAWM)--as recorded in the aeolian dust deposits on the Chinese Loess Plateau--can serve as a useful proxy of Arctic climate variability before the ice-core record begins. Here we present an EAWM proxy record using grain-size variations in two parallel loess sections representative of sequences across the whole of the Chinese Loess Plateau over the past 900,000 years. The results show that during periods of low eccentricity and precessional variability at approximately 400,000-year intervals, the grain-size-inferred intensity of the EAWM remains weak for up to 20,000 years after the end of the interglacial episode of high summer monsoon activity and strong pedogenesis. In contrast, there is a rapid increase in the EAWM after the end of most other interglacials. We conclude that, for both the 400,000-year interglacials, the weak EAWM winds maintain a mild, non-glacial climate at high northern latitudes for much longer than expected from the conventional loess and marine oxygen isotope records. During these times, the less-severe summer insolation minima at 65° N (ref. 4) would have suppressed ice and snow accumulation, leading to a weak Siberian High and, consequently, weak EAWM winds.

  19. Defect mediated room temperature ferromagnetism and resistance minima study in epitaxial ZnGa0.002Al0.02O transparent conducting oxide films

    NASA Astrophysics Data System (ADS)

    Temizer, Namik K.; Nori, Sudhakar; Kumar, D.; Narayan, Jagdish

    2016-09-01

    We report on the micro-structural, transport, optical and magnetic properties in ZnGa0.002Al0.02O (AGZO) films grown by pulsed laser deposition under different growth conditions. AGZO films grown at substrate temperatures of 600 °C show metal-like behavior with a resistivity minima at lower temperatures, whereas films grown at 300 °C and ambient oxygen partial pressure of 1 mTorr show metallic nature with resistivity values on the order of 100 µΩ · cm at room temperature. The most interesting features are the concomitant occurrence of high temperature resistivity minima and room temperature ferromagnetism with a saturation magnetic moment of 1000 A m-1 and with coercivity in the range 100-240 Oe. The temperature dependent resistivity data has been interpreted in the light of quantum corrections to conductivity in disordered systems, suggesting that the e-e interactions is the dominant mechanism in the weak-localization (WL) limit in the case of films showing resisitivity minima. The simultaneous ferromagnetic ordering coupled with the enhancements in electrical conductivity in AGZO system should have their origin in native point defects in the form of oxygen and zinc vacancies and interstitials and their complexes. We propose that formation of oxygen vacancy-zinc interstitial defect complex (V O-I Zn) is responsible for the enhancement in n-type conductivity, and zinc vacancies (V Zn) for the observed room temperature ferromagnetism.

  20. Delayed build-up of Arctic ice sheets during 400, 000-year minima in insolation variability confirmed by Chinese loess

    NASA Astrophysics Data System (ADS)

    Hao, Q.; Wang, L.; Oldfield, F.; Peng, S.; Qin, L.; Song, Y.; Xu, B.; Qiao, Y.; Bloemendal, J.; Guo, Z.

    2013-12-01

    The growth and decay of the Northern Hemisphere ice volume led to alternations of glacial and interglacial climate and major changes in sea level during the Quaternary period. Unfortunately, long-term continuous records of ice-sheet variability in the Northern during the Quaternary period Hemisphere only are scarce because benthic δ18O records represent an integrated signal of changes in ice volume in both polar regions. Direct sedimentary records of Northern Hemisphere polar ice sheets exist only for the late Quaternary and longer term records are scarce. However, variations in Northern Hemisphere ice sheets influence the Siberian High (an atmospheric pressure system), so variations in the East Asian winter monsoon (EAWM)--as recorded in the aeolian dust deposits on the Chinese Loess Plateau--can serve as a useful proxy of Arctic climate variability. Here we present an EAWM proxy record using grain-size variations in two parallel loess sections over the past 900 kyr to address the timing of build-up of Northern hemisphere ice sheets around 413 kyr mimina in eccentricity and precessional variability. These periods are regarded as the astronomical analogues of the present interglacial. The results show that during periods of low eccentricity and precessional variability around 400 kyr and 800 kyr ago, the grain-size-inferred intensity of the EAWM remains weak for up to 20 kyr after the end of the interglacial episodes MIS 11, MIS 19 and MIS 21. In contrast, there is a rapid increase in the EAWM after the end of most other interglacials. We conclude that, for these interglacials at 400 kyr intervals, the weak EAWM winds maintain a non-glacial climate at high northern latitudes for much longer than expected from the conventional loess and marine oxygen isotope records. During these times, the less severe summer insolation minima at 65° N (modulated by 413-kyr eccentricity cycles) would have suppressed ice and snow accumulation, leading to a weak Siberian High and

  1. VizieR Online Data Catalog: TU UMa light curves and maxima, CL Aur minima (Liska+, 2016)

    NASA Astrophysics Data System (ADS)

    Liska, J.; Skarka, M.; Mikulasek, Z.; Zejda, M.; Chrastina, M.

    2016-02-01

    Differential photometry for RR Lyrae star TU UMa in the 1st and 2nd file. The measurements were obtained using 24-inch and 1-inch telescopes, respectively. The observations were performed at the Masaryk University Observatory in Brno (3 nights, 24-inch), and at the private observatory in Brno (16 nights, 1-inch) in the Czech Republic from December 2013 to June 2014. Observing equipments consisted of 24-inch Newtonian telescope (600/2780mm, diameter/focal length) and a Moravian Instruments CCD camera G2-4000 with Stromgren photometric filters vby, and of 1-inch refractor (a photographic lens Sonnar 4/135mm, lens focal ratio/focal length) and ATIK 16IC CCD camera with green photometric filter with similar throughput as the Johnson V filter. Exposures were v - 60s, b - 30s, y - 30s, green - 30s. For the small aperture telescope, five frames were combined to a single image to achieve a better signal-to-noise ratio. The time resolution of a such combined frame is about 170s. CCD images were calibrated in a standard way (dark frame and flat field corrections). The C-Munipack software (Motl 2009) was used for this processing as well as for differential photometry. The comparison star BD+30 2165 was the same for both instruments, but the control stars were BD+30 2164 (for the 24-inch telescope) and HD 99593 (for the 1-inch telescope). The 3rd file contains maxima timings of TU UMa adopted from the GEOS RR Lyr database, from the latest publications, together with maxima timings determined in our study. Times of maxima were calculated from our observations, sky-surveys data (Hipparcos, NSVS, Pi of the Sky, SuperWASP), photographic measurements (project DASCH), and from several published datasets, in which the maxima were omitted or badly determined - Boenigk (1958AcA.....8...13B), Liakos, Niarchos (2011IBVS.6099....1L, 2011IBVS.5990....1L), Liu, Janes (1989ApJS...69..593L), Preston et al. (1961ApJ...133..484P). The 4th file contains minima timings of eclipsing binary CL Aur

  2. Delayed build-up of Arctic ice sheets during 400, 000-year minima in insolation variability confirmed by Chinese loess

    NASA Astrophysics Data System (ADS)

    Hao, Qingzhen; Wang, Luo; Oldfield, Frank; Peng, Shuzhen; Qin, Li; Song, Yang; Xu, Bing; Qiao, Yansong; Bloemendal, Jan; Guo, Zhengtang

    2014-05-01

    The growth and decay of the Northern Hemisphere ice volume led to alternations of glacial and interglacial climate. Unfortunately, long-term continuous records of ice-sheet variability in the Northern Hemisphere during the Quaternary period only are scarce because benthic δ18O records represent an integrated signal of changes in ice volume in both polar regions. However, variations in Northern Hemisphere ice sheets influence the Siberian High (an atmospheric pressure system), so variations in the East Asian winter monsoon (EAWM)—as recorded in the aeolian dust deposits on the Chinese Loess Plateau—can serve as a useful proxy of Arctic climate variability. Here we present an EAWM proxy record using grain-size variations in two parallel loess sections over the past 900 kyr to address the timing of build-up of Northern hemisphere ice sheets around 413 kyr mimina in eccentricity and precessional variability. These periods are regarded as the astronomical analogues of the present interglacial. The grain-size-inferred intensity of the EAWM records shows that the wind strength of EAWM increased rapidly after the end of most interglacials. However, during periods of low eccentricity and precessional variability around 400 kyr and 800 kyr ago, EAWM remains weak for up to 20 kyr after the end of the interglacial episodes MIS 11, MIS 19 and MIS 21. We conclude that the delayed increase in wind strength of the EAWM was caused by delayed buildup of Arctic ice sheets at the ends of the interglacials at 400 kyr intervals, which had led to much longer climate of interglacial mode at high northern latitudes than expected from the marine oxygen isotope records. During these times, the less severe summer insolation minima at 65° N (modulated by 413-kyr eccentricity cycles) would have suppressed ice and snow accumulation, leading to a weak Siberian High and, consequently, weak EAWM winds. Astronomically driven insolation during the present interglacial and in the near future is

  3. NmF2 trends at low and mid latitudes for the recent solar minima and comparison with IRI-2012 model

    NASA Astrophysics Data System (ADS)

    Perna, L.; Pezzopane, M.; Ezquer, R.; Cabrera, M.; Baskaradas, J. A.

    2017-07-01

    The ionospheric electron density peak (NmF2) is analyzed for the recent minima of solar activity for two mid-latitude stations, Rome (41.8°N, 12.5°E, geomagnetic latitude 41.7°N, Italy) and Gibilmanna (37.9°N, 14.0°E, geomagnetic latitude 37.6°N, Italy), and for the low-latitude station of Tucumán (26.9°S, 294.6°E, geomagnetic latitude 17.2°S, Argentina), located in the south ridge of the equatorial ionization anomaly. An inter-minima comparison reveals that from an ionospheric point of view the last minimum of solar activity (minimum 23/24) was peculiar, with values of NmF2 lower than those recorded during the previous minima for all the stations and all the hours of the day. A more pronounced decrease is observed at Tucumán than at Rome and Gibilmanna. The study of the winter and semi-annual anomaly shows that at mid-latitude stations the winter anomaly is not visible only for the years 2008 and 2009, which represent the deeper part of the prolonged and anomalous last solar minimum. The same is for the semi-annual anomaly. A comparison with the version 2012 of the International Reference Ionosphere model (IRI) is also carried out. The results reveal that for low solar activity the model works better at mid latitudes than at low latitudes, confirming the problems of IRI in correctly representing the low-latitude ionosphere. Nevertheless, using as input updated values of the solar and geomagnetic indices, no loss of accuracy is detected in the IRI performances for the last solar minimum with respect to the previous ones, both at mid and low latitudes.

  4. Opportunities and challenges to conserve water on the landscape in snow-dominated forests: The quest for the radiative minima and more...

    NASA Astrophysics Data System (ADS)

    Link, T. E.; Kumar, M.; Pomeroy, J. W.; Seyednasrollah, B.; Ellis, C. R.; Lawler, R.; Essery, R.

    2012-12-01

    In mountainous, forested environments, vegetation exerts a strong control on snowcover dynamics that affect ecohydrological processes, streamflow regimes, and riparian health. Snowcover deposition and ablation patterns in forests are controlled by a complex combination of canopy interception processes coupled with radiative and turbulent heat flux patterns related to topographic and canopy cover variations. In seasonal snow environments, snowcover ablation dynamics in forests are dominated by net radiation. Recent research indicates that in small canopy gaps a net radiation minima relative to both open and forested environments can occur, but depends strongly on solar angle, gap size, slope, canopy height and stem density. The optimal gap size to minimize radiation to snow was estimated to have a diameter between 1 and 2 times the surrounding vegetation height. Physically-based snowmelt simulations indicate that gaps may increase SWE and desynchronize snowmelt by approximately 3 weeks between north and south facing slopes, relative to undisturbed forests. On east and west facing slopes, small gaps cause melt to be slightly delayed relative to intact forests, and have a minimal effect on melt synchronicity between slopes. Recent research focused on canopy thinning also indicates that a net radiation minima occurs in canopies of intermediate densities. Physically-based radiative transfer simulations using a discrete tree-based model indicate that in mid-latitude level forests, the annually-integrated radiative minima occurs at a tree spacing of 2.65 relative to the canopy height. The radiative minima was found to occur in denser forests on south-facing slopes and sparser forests on north-facing slopes. The radiative minimums in thinned forests are controlled by solar angle, crown geometry and density, tree spacing, slope, and aspect. These results indicate that both gap and homogeneous forest thinning may be used to reduce snowmelt rates or alter melt synchronicity

  5. Major geophysical events and transitions of heliospheric magnetic field in the beginning, middle and end phase of the Maunder solar minima

    NASA Astrophysics Data System (ADS)

    Casati, Michele; Straser, Valentino; Feron, Alessandro

    2016-04-01

    In recent decades we are moving towards the hypothesis that electromagnetic (EM) processes inside the solar system (not yet fully understood from a physical point of view), may be linked with the energy released during major geophysical events (energy expressed in magnitude or Volcanic Explosivity Index). This research has focused on analysis of the temporal relationship between EM processes inside the solar system and major geophysical events around the crucial phase of the Maunder solar minima (1645-1715). To carry out this study thirty-five limit values of the heliospheric magnetic field strength HMF (minimum and/or maximum) were compared, in terms of time, with twenty-one major geophysical events which occurred between 1600 and 1729. In the solar-terrestrial interaction, the concomitant conditions necessary for the amplification of the energy of the geophysical event, are two: i. low solar activity during a long period (from decades to centuries), for example, the historical solar minima: Wolf, Sporer, Maunder, Dalton, etc. and ii. fast and impulsive EM solar dynamo reorganizations in the short-term (one year or two years), are characteristic in the two periods of the solar cycle border, the incoming or outgoing of the solar minima or solar maximum. The reconstructed intensity of the heliospheric magnetic field (HMF) was the main set of data used to carry out the present study. HMF evaluated by the annual cosmogenic 10Be ice core data from Dye 3 and North GRIP, in Greenland [McCracken;Beer,Sol.Phys.,2015 in press]. Analysis of the data shows that all the major geophysical events, with magnitude and volcanic explosivity index: 8.7

  6. Effects in the radiation belts caused by the second adiabatic invariant violation in the presence of dayside off-equatorial magnetic field minima

    NASA Astrophysics Data System (ADS)

    Antonova, A. E.; Gubar', Yu. I.; Kropotkin, A. P.

    Recent experiments (INTERBALL, POLAR) provided new substantial information concerning particle populations in the high-latitude near-magnetopause cusp regions with highly depressed magnetic field. We have studied adiabaticity violation of energetic particle bounce motion in those regions, which is due to nonmonotonous change in magnetic field intensity along field lines near the dayside magnetopause. The violation takes place at the separatrix dividing a region of transequatorial bounce oscillations from that of oscillations about high-latitude field minima. An invariant `jump' is evaluated. Diffusion over the second invariant associated with that jump can result in particle phase space redistribution during magnetic storms.

  7. Apoptotic effects of Physalis minima L. chloroform extract in human breast carcinoma T-47D cells mediated by c-myc-, p53-, and caspase-3-dependent pathways.

    PubMed

    Ooi, Kheng Leong; Tengku Muhammad, Tengku Sifzizul; Lim, Chui Hun; Sulaiman, Shaida Fariza

    2010-03-01

    The chloroform extract of Physalis minima produced a significant growth inhibition against human T-47D breast carcinoma cells as compared with other extracts with an EC(50) value of 3.8 microg/mL. An analysis of cell death mechanisms indicated that the extract elicited an apoptotic cell death. mRNA expression analysis revealed the coregulation of apoptotic genes, that is, c-myc , p53, and caspase-3. The c-myc was significantly induced by the chloroform extract at the earlier phase of treatment, followed by p53 and caspase-3. Biochemical assay and ultrastructural observation displayed typical apoptotic features in the treated cells, including DNA fragmentation, blebbing and convolution of cell membrane, clumping and margination of chromatin, and production of membrane-bound apoptotic bodies. The presence of different stages of apoptotic cell death and phosphatidylserine externalization were further reconfirmed by annexin V and propidium iodide staining. Thus, the results from this study strongly suggest that the chloroform extract of P. minima induced apoptotic cell death via p53-, caspase-3-, and c-myc-dependent pathways.

  8. CAl2Be3(2-) and its salt complex LiCAl2Be3-: anionic global minima with planar pentacoordinate carbon.

    PubMed

    Wu, Yan-Bo; Duan, Yan; Lu, Hai-Gang; Li, Si-Dian

    2012-03-29

    Following the isoelectronic relationship in global minima planar pentacoordinate carbon (ppC) species (cationic CAl(5)(+), neutral CAl(4)Be, and monoanionic CAl(3)Be(2)(-)), we designed a dianionic ppC species C(2v) CAl(2)Be(3)(2-) (1a) and its salt complex C(2v) LiCAl(2)Be(3)(-) (2a) in this work. In combination with DFT and high-level ab initio calculations (CCSD(T)), the extensive exploration on their potential energy surfaces indicates that they are the global minima. Their kinetic stability was proved by two sets of 100 ps ab initio Born-Oppenheimer molecular dynamic simulations at the B3LYP/6-31+G(d) level. The detailed analyses indicate that the introduction of Li(+) into 1a only influences the electrovalent bonding (through changing of the charge distribution) and the σ aromaticity (through changing of the in-plane ring current), while the structures, the bonding properties, the π aromaticity, and so forth are almost unchanged. Nevertheless, the MO energy levels, the HOMO-LUMO gaps, and the values of vertical detachment energies (VDEs) all verify that the lithiation significantly improves the stability. We think the ppC dianion 1a is possible to detect directly in the gas-phase experiments, but it can be detected as its salt complex 2a more easily.

  9. Lead accumulation reduces photosynthesis in the lead hyper-accumulator Salvinia minima Baker by affecting the cell membrane and inducing stomatal closure.

    PubMed

    Leal-Alvarado, Daniel A; Espadas-Gil, Francisco; Sáenz-Carbonell, Luis; Talavera-May, Carlos; Santamaría, Jorge M

    2016-02-01

    Salvinia minima Baker accumulates a fair amount of lead in its tissues; however, no studies have investigated the effect of lead on the physiological processes that affect photosynthesis in this species. The objective of the present study was to assess whether the high amounts of lead accumulated by S. minima can affect its photosynthetic apparatus. The physiological changes in the roots and leaves in response to lead accumulation were analyzed. An exposure to 40 μM Pb(NO3)2 for 24 h (first stage) was sufficient to reduce the photosynthetic rate (Pn) by 44%. This reduction in Pn was apparently the result of processes at various levels, including damage to the cell membranes (mainly in roots). Interestingly, although the plants were transferred to fresh medium without lead for an additional 24 h (second stage), Pn not only remained low, but was reduced even further, which was apparently related to stomatal closure, and may have led to reduced CO2 availability. Therefore, it can be concluded that lead exposure first decreases the photosynthetic rate by damaging the root membrane and then induces stomatal closure, resulting in decreased CO2 availability.

  10. Growth arrest and induction of apoptotic and non-apoptotic programmed cell death by, Physalis minima L. chloroform extract in human ovarian carcinoma Caov-3 cells.

    PubMed

    Ooi, Kheng Leong; Muhammad, Tengku Sifzizul Tengku; Sulaiman, Shaida Fariza

    2010-03-02

    The decoction of the whole plant of Physalis minima L. is traditionally consumed to treat cancer. Its anticancer property has been previously verified (using in vitro cytotoxicity assays) against NCI-H23 lung, CORL23 lung and MCF7 breast cancer cell lines but the mechanism underlying the anticancer potency towards ovarian carcinoma cells remain unclear. The present study is aimed to systematically determine the cytotoxicity and possible cell death mechanism elicited by the chloroform extract of Physalis minima in human ovarian Caov-3 carcinoma. Cytotoxicity of the extract was measured using the methylene blue assay. The mechanism of cell death was determined using four independent methods, namely DeadEnd assay to label the DNA fragmentation nuclei cells, RT-PCR analysis to determine the mRNA expression level of three apoptotic genes (c-myc, p53 and caspase-3 genes), Transmission Electron Microscope (TEM) analysis to describe the ultra structural characteristics and annexin V and propidium iodide staining to confirm the types and stages of cell deaths. Cytotoxicity screening of the extract on Caov-3 cells exhibited concentration- and time-dependent inhibitory effects. A combination of apoptotic and autophagic programmed cell death was detected. The apoptotic characteristic was initially determined by DNA fragmentation followed by the expression of c-myc and p53 genes that was much earlier than caspase-3. Apoptotic ultra structural changes (including clumping and magination of chromatin, blebbing and convolution of nucleus membrane and formation of apoptotic bodies) and autophagy (Type II non-apoptotic programmed cell death) with distinct vacuolated morphology were detected in TEM analysis. The existence of these programmed cell deaths was then corroborated using annexin V and propidium iodide staining. The chloroform extract of Physalis minima exerted anticancer effect due to a combination of apoptotic and autophagic cell death mechanisms on Caov-3 cells. The

  11. Global minima of (C 60) nCa 2+, (C 60) nF - and (C 60) nI - clusters

    NASA Astrophysics Data System (ADS)

    Hernández-Rojas, J.; Bretón, J.; Llorente, J. M. Gomez; Wales, D. J.

    2005-07-01

    Likely candidates for the lowest potential energy minima of (C 60) nCa 2+, (C 60) nF - and (C 60) nI - clusters are located using basin-hopping global optimisation. In each case, the potential energy surface is constructed using the Girifalco form for the C 60 intermolecular interaction, an averaged Lennard-Jones C 60-ion interaction, and a polarisation potential, which depends on the first few non-vanishing C 60 multipole polarisabilities. We find that the ions generally occupy the interstitial sites of a (C 60) n cluster, the coordination shell being tetrahedral for Ca 2+ and F -. The I - ion has an octahedral coordination shell in the global minimum for (C 60) 6I -, however for 12 ⩾ n ⩾ 8 the preferred coordination geometry is trigonal prismatic.

  12. Spectroscopic evidence for the coexistence of tetragonal and trigonal minima within the exited state adiabatic potential energy surfaces of hexachlorotellurate and -selenate complexes

    NASA Astrophysics Data System (ADS)

    Cremers, C.; Degen, J.

    1998-11-01

    Coexistence of Jahn-Teller minima resulting from the coupling to different accepting modes within the adiabatic potential energy surface (APES) is not possible within the framework of linear vibronic coupling theory. For the lowest exited triplet state 3T1u of inorganic complexes with s2 electronic ground-state configuration, such a coexistence, due to quadratic coupling effects, is discussed. As a direct experimental evidence two vibronic progressions with different accepting modes in the emission spectra resulting from a single electronic state are observed in the emission spectra of the title compounds. The observation of vibronic finestructure in the emission spectra of [TeCl6]2- is reported for the first time.

  13. Cost-effective, species-specific microsatellite development for the endangered Dwarf Bulrush (Typha minima) using next-generation sequencing technology.

    PubMed

    Csencsics, Daniela; Brodbeck, Sabine; Holderegger, Rolf

    2010-01-01

    The dwarf bulrush (Typha minima Funck ex Hoppe) is an endangered pioneer plant species of riparian flood plains. In Switzerland, only 3 natural populations remain, but reintroductions are planned. To identify suitable source populations for reintroductions, we developed 17 polymorphic microsatellite markers with perfect repeats using the 454 pyrosequencing technique and tested them on 20 individuals with low-cost M13 labeling. We detected 2 to 7 alleles per locus and found expected and observed heterozygosities of 0.05-0.76 and 0.07-1, respectively. The whole process was finished in less than 6 weeks and cost approximately USD 5000. Due to low costs and reduced expenditure of time, the use of next-generation sequencing techniques for microsatellite development represent a powerful tool for population genetic studies in nonmodel species, as we show in this first application of the approach to a plant species of conservation importance.

  14. Critical behavior of the number of minima of a random landscape at the glass transition point and the Tracy-Widom distribution.

    PubMed

    Fyodorov, Yan V; Nadal, Celine

    2012-10-19

    We exploit a relation between the mean number N(m) of minima of random Gaussian surfaces and extreme eigenvalues of random matrices to understand the critical behavior of N(m) in the simplest glasslike transition occuring in a toy model of a single particle in an N-dimensional random environment, with N>1. Varying the control parameter μ through the critical value μ(c) we analyze in detail how N(m)(μ) drops from being exponentially large in the glassy phase to N(m)(μ)~1 on the other side of the transition. We also extract a subleading behavior of N(m)(μ) in both glassy and simple phases. The width δμ/μ(c) of the critical region is found to scale as N(-1/3) and inside that region N(m)(μ) converges to a limiting shape expressed in terms of the Tracy-Widom distribution.

  15. Amylase production by Preussia minima, a fungus of endophytic origin: optimization of fermentation conditions and analysis of fungal secretome by LC-MS

    PubMed Central

    2014-01-01

    Background Environmental screening programs are used to find new enzymes that may be utilized in large-scale industrial processes. Among microbial sources of new enzymes, the rationale for screening fungal endophytes as a potential source of such enzymes relates to the hypothesised mutualistic relationship between the endophyte and its host plant. There is a need for new microbial amylases that are active at low temperature and alkaline conditions as these would find industrial applications as detergents. Results An α-amylase produced by Preussia minima, isolated from the Australian native plant, Eremophilia longifolia, was purified to homogeneity through fractional acetone precipitation and Sephadex G-200 gel filtration, followed by DEAE-Sepharose ion exchange chromatography. The purified α-amylase showed a molecular mass of 70 kDa which was confirmed by zymography. Temperature and pH optima were 25°C and pH 9, respectively. The enzyme was activated and stabilized mainly by the metal ions manganese and calcium. Enzyme activity was also studied using different carbon and nitrogen sources. It was observed that enzyme activity was highest (138 U/mg) with starch as the carbon source and L-asparagine as the nitrogen source. Bioreactor studies showed that enzyme activity was comparable to that obtained in shaker cultures, which encourages scale-up fermentation for enzyme production. Following in-gel digestion of the purified protein by trypsin, a 9-mer peptide was sequenced and analysed by LC-ESI-MS/MS. The partial amino acid sequence of the purified enzyme presented similarity to α-amylase from Magnaporthe oryzae. Conclusions The findings of the present study indicate that the purified α-amylase exhibits a number of promising properties that make it a strong candidate for application in the detergent industry. To our knowledge, this is the first amylase isolated from a Preussia minima strain of endophytic origin. PMID:24602289

  16. Physalin F from Physalis minima L. triggers apoptosis-based cytotoxic mechanism in T-47D cells through the activation caspase-3- and c-myc-dependent pathways.

    PubMed

    Ooi, Kheng Leong; Muhammad, Tengku Sifzizul Tengku; Sulaiman, Shaida Fariza

    2013-10-28

    Physalin F (a secosteroid derivative), is well recognized as a potent anticancer compound from Physalis minima L., a plant that is traditionally used to treat cancer. However, the exact molecular anticancer mechanism remains to be elucidated. We have recently reported the apoptosis-based cytotoxic effect of the chloroform extract of this plant. Here, we investigated the cytotoxicity and possible cell death mechanism elicited by the active constituent, physalin F on human breast T-47D carcinoma. Cytotoxic-guided fractionation of the chloroform extract of Physalis minima has led to the isolation of physalin F. The cytotoxicity activity was assayed using MTS assay. The effect of the compound to induce apoptosis was determined by biochemical and morphological observations through DeadEnd Colorimetric and annexin V assays, respectively, and RT-PCR analysis of mRNA expression of the apoptotic-associated genes. Cytotoxicity screening of physalin F displayed a remarkable dose-dependent inhibitory effect on T-47D cells with lower EC50 value (3.60 μg/ml) than the crude extract. mRNA expression analysis revealed the co-regulation of c-myc- and caspase-3-apoptotic genes in the treated cells with the peak expression at 9 and 12h of treatment, respectively. This apoptotic mechanism is reconfirmed by DNA fragmentation and phosphatidylserine externalization. These findings indicate that physalin F may potentially act as a chemopreventive and/or chemotherapeutic agent by triggering apoptosis mechanism via the activation of caspase-3 and c-myc pathways in T-47D cells. © 2013 Elsevier Ireland Ltd. All rights reserved.

  17. Amylase production by Preussia minima, a fungus of endophytic origin: optimization of fermentation conditions and analysis of fungal secretome by LC-MS.

    PubMed

    Zaferanloo, Bita; Bhattacharjee, Shatabdi; Ghorbani, Mahmood M; Mahon, Peter J; Palombo, Enzo A

    2014-03-07

    Environmental screening programs are used to find new enzymes that may be utilized in large-scale industrial processes. Among microbial sources of new enzymes, the rationale for screening fungal endophytes as a potential source of such enzymes relates to the hypothesised mutualistic relationship between the endophyte and its host plant. There is a need for new microbial amylases that are active at low temperature and alkaline conditions as these would find industrial applications as detergents. An α-amylase produced by Preussia minima, isolated from the Australian native plant, Eremophilia longifolia, was purified to homogeneity through fractional acetone precipitation and Sephadex G-200 gel filtration, followed by DEAE-Sepharose ion exchange chromatography. The purified α-amylase showed a molecular mass of 70 kDa which was confirmed by zymography. Temperature and pH optima were 25°C and pH 9, respectively. The enzyme was activated and stabilized mainly by the metal ions manganese and calcium. Enzyme activity was also studied using different carbon and nitrogen sources. It was observed that enzyme activity was highest (138 U/mg) with starch as the carbon source and L-asparagine as the nitrogen source. Bioreactor studies showed that enzyme activity was comparable to that obtained in shaker cultures, which encourages scale-up fermentation for enzyme production. Following in-gel digestion of the purified protein by trypsin, a 9-mer peptide was sequenced and analysed by LC-ESI-MS/MS. The partial amino acid sequence of the purified enzyme presented similarity to α-amylase from Magnaporthe oryzae. The findings of the present study indicate that the purified α-amylase exhibits a number of promising properties that make it a strong candidate for application in the detergent industry. To our knowledge, this is the first amylase isolated from a Preussia minima strain of endophytic origin.

  18. Detoxification of Cr(VI) in Salvinia minima is related to seasonal-induced changes of thiols, phenolics and antioxidative enzymes.

    PubMed

    Prado, Carolina; Pagano, Eduardo; Prado, Fernando; Rosa, Mariana

    2012-11-15

    In this study, protein- and non-protein-thiol-containing compounds (THCC), soluble phenolics (SP), proline (Pro), proteins and malondialdehyde (MDA) contents, and antioxidative enzyme activities were analyzed in floating and submerged leaves of Salvinia minima to establish their role against Cr-induced oxidative stress. We analyzed relationships among biochemical responses to different Cr(VI) concentrations to explore underlying mechanisms of Cr detoxification in plants growing under field conditions during summer and winter seasons. Significant increases in THCC were observed in submerged leaves from both seasons, while in floating leaves THCC increased only in summer being decreased in winter. Contrarily SP increased in floating leaves and decreased in submerged ones. MDA increased significantly in winter-leaves, but in summer-leaves remained unchanged. Antioxidative enzymes, i.e. guaiacol peroxidase (G-POD), superoxide dismutase (SOD) and catalase (CAT) showed different activity patterns. G-POD significantly increased in Cr-treated leaves from both seasons, while SOD increased in submerged leaves only, remaining practically unchanged in floating ones. CAT activity increased in floating leaves from both seasons, whereas in submerged ones was decreased or increased. Proteins increased in both leaf types during summer whereas decreased or remained unchanged in winter. Pro increased in winter-submerged leaves only. Results show that seasonal-induced changes occur in all measured parameters. Copyright © 2012 Elsevier B.V. All rights reserved.

  19. Cytotoxic Activities of Physalis minima L. Chloroform Extract on Human Lung Adenocarcinoma NCI-H23 Cell Lines by Induction of Apoptosis.

    PubMed

    Leong, Ooi Kheng; Muhammad, Tengku Sifzizul Tengku; Sulaiman, Shaida Fariza

    2011-01-01

    Physalis minima L. is reputed for having anticancer property. In this study, the chloroform extract of this plant exhibited remarkable cytotoxic activities on NCI-H23 (human lung adenocarcinoma) cell line at dose- and time-dependent manners (after 24, 48 and 72 h of incubation). Analysis of cell-death mechanism demonstrated that the extract exerted apoptotic programed cell death in NCI-H23 cells with typical DNA fragmentation, which is a biochemical hallmark of apoptosis. Morphological observation using transmission electron microscope (TEM) also displayed apoptotic characteristics in the treated cells, including clumping and margination of chromatins, followed by convolution of the nuclear and budding of the cells to produce membrane-bound apoptotic bodies. Different stages of apoptotic programed cell death as well as phosphatidylserine externalization were confirmed using annexin V and propidium iodide staining. Furthermore, acute exposure to the extract produced a significant regulation of c-myc, caspase-3 and p53 mRNA expression in this cell line. Due to its apoptotic effect on NCI-H23 cells, it is strongly suggested that the extract could be further developed as an anticancer drug.

  20. Correlation between the variation in observed melting temperatures and structural motifs of the global minima of gallium clusters: an ab initio study.

    PubMed

    Susan, Anju; Kibey, Aniruddha; Kaware, Vaibhav; Joshi, Kavita

    2013-01-07

    We have investigated the correlation between the variation in the melting temperature and the growth pattern of small positively charged gallium clusters. Significant shift in the melting temperatures was observed for a change of only few atoms in the size of the cluster. Clusters with size between 31-42 atoms melt between 500-600 K whereas those with 46-48 atoms melt around 800 K. Density functional theory based first principles simulations have been carried out on Ga(n)(+) clusters with n = 31, ..., 48. At least 150 geometry optimizations have been performed towards the search for the global minima for each size resulting in about 3000 geometry optimizations. For gallium clusters in this size range, the emergence of spherical structures as the ground state leads to higher melting temperature. The well-separated core and surface shells in these clusters delay isomerization, which results in the enhanced stability of these clusters at elevated temperatures. The observed variation in the melting temperature of these clusters therefore has a structural origin.

  1. Cytotoxic Activities of Physalis minima L. Chloroform Extract on Human Lung Adenocarcinoma NCI-H23 Cell Lines by Induction of Apoptosis

    PubMed Central

    Leong, Ooi Kheng; Muhammad, Tengku Sifzizul Tengku; Sulaiman, Shaida Fariza

    2011-01-01

    Physalis minima L. is reputed for having anticancer property. In this study, the chloroform extract of this plant exhibited remarkable cytotoxic activities on NCI-H23 (human lung adenocarcinoma) cell line at dose- and time-dependent manners (after 24, 48 and 72 h of incubation). Analysis of cell-death mechanism demonstrated that the extract exerted apoptotic programed cell death in NCI-H23 cells with typical DNA fragmentation, which is a biochemical hallmark of apoptosis. Morphological observation using transmission electron microscope (TEM) also displayed apoptotic characteristics in the treated cells, including clumping and margination of chromatins, followed by convolution of the nuclear and budding of the cells to produce membrane-bound apoptotic bodies. Different stages of apoptotic programed cell death as well as phosphatidylserine externalization were confirmed using annexin V and propidium iodide staining. Furthermore, acute exposure to the extract produced a significant regulation of c-myc, caspase-3 and p53 mRNA expression in this cell line. Due to its apoptotic effect on NCI-H23 cells, it is strongly suggested that the extract could be further developed as an anticancer drug. PMID:19541726

  2. Analytic evaluation of nonadiabatic coupling terms at the MR-CI level. II. Minima on the crossing seam: formaldehyde and the photodimerization of ethylene.

    PubMed

    Dallos, Michal; Lischka, Hans; Shepard, Ron; Yarkony, David R; Szalay, Peter G

    2004-04-22

    The method for the analytic calculation of the nonadiabatic coupling vector at the multireference configuration-interaction (MR-CI) level and its program implementation into the COLUMBUS program system described in the preceding paper [Lischka et al., J. Chem. Phys. 120, 7322 (2004)] has been combined with automatic searches for minima on the crossing seam (MXS). Based on a perturbative description of the vicinity of a conical intersection, a Lagrange formalism for the determination of MXS has been derived. Geometry optimization by direct inversion in the iterative subspace extrapolation is used to improve the convergence properties of the corresponding Newton-Raphson procedure. Three examples have been investigated: the crossing between the 1(1)B1/2(1)A1 valence states in formaldehyde, the crossing between the 2(1)A1/3(1)A1 pi-pi* valence and ny-3py Rydberg states in formaldehyde, and three crossings in the case of the photodimerization of ethylene. The methods developed allow MXS searches of significantly larger systems at the MR-CI level than have been possible before and significantly more accurate calculations as compared to previous complete-active space self-consistent field approaches.

  3. Effect of seasonality and Cr(VI) on starch-sucrose partitioning and related enzymes in floating leaves of Salvinia minima.

    PubMed

    Rosa, Mariana; Prado, Carolina; Chocobar-Ponce, Silvana; Pagano, Eduardo; Prado, Fernando

    2017-09-01

    Effects of seasonality and increasing Cr(VI) concentrations on leaf starch-sucrose partitioning, sucrose- and starch-related enzyme activities, and carbon allocation toward leaf development were analyzed in fronds (floating leaves) of the floating fern Salvinia minima. Carbohydrates and enzyme activities of Cr-exposed fronds showed different patterns in winter and summer. Total soluble sugars, starch, glucose and fructose increased in winter fronds, while sucrose was higher in summer ones. Starch and soluble carbohydrates, except glucose, increased under increasing Cr(VI) concentrations in winter fronds, while in summer ones only sucrose increased under Cr(VI) treatment. In summer fronds starch, total soluble sugars, fructose and glucose practically stayed without changes in all assayed Cr(VI) concentrations. Enzyme activities related to starch and sucrose metabolisms (e.g. ADPGase, SPS, SS and AI) were higher in winter fronds than in summer ones. Total amylase and cFBPase activities were higher in summer fronds. Cr(VI) treatment increased enzyme activities, except ADPGase, in both winter and summer fronds but no clear pattern changes were observed. Data of this study show clearly that carbohydrate metabolism is differently perturbed by both seasonality and Cr(VI) treatment in summer and winter fronds, which affects leaf starch-sucrose partitioning and specific leaf area (SLA) in terms of carbon investment. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  4. Correlation between the variation in observed melting temperatures and structural motifs of the global minima of gallium clusters: An ab initio study

    NASA Astrophysics Data System (ADS)

    Susan, Anju; Kibey, Aniruddha; Kaware, Vaibhav; Joshi, Kavita

    2013-01-01

    We have investigated the correlation between the variation in the melting temperature and the growth pattern of small positively charged gallium clusters. Significant shift in the melting temperatures was observed for a change of only few atoms in the size of the cluster. Clusters with size between 31-42 atoms melt between 500-600 K whereas those with 46-48 atoms melt around 800 K. Density functional theory based first principles simulations have been carried out on Ga+n clusters with n = 31, …, 48. At least 150 geometry optimizations have been performed towards the search for the global minima for each size resulting in about 3000 geometry optimizations. For gallium clusters in this size range, the emergence of spherical structures as the ground state leads to higher melting temperature. The well-separated core and surface shells in these clusters delay isomerization, which results in the enhanced stability of these clusters at elevated temperatures. The observed variation in the melting temperature of these clusters therefore has a structural origin.

  5. Sequencing of small RNAs of the fern Pleopeltis minima (Polypodiaceae) offers insight into the evolution of the microrna repertoire in land plants

    PubMed Central

    Berruezo, Florencia; de Souza, Flávio S. J.; Picca, Pablo I.; Nemirovsky, Sergio I.; Martínez Tosar, Leandro; Rivero, Mercedes; Mentaberry, Alejandro N.

    2017-01-01

    MicroRNAs (miRNAs) are short, single stranded RNA molecules that regulate the stability and translation of messenger RNAs in diverse eukaryotic groups. Several miRNA genes are of ancient origin and have been maintained in the genomes of animal and plant taxa for hundreds of millions of years, playing key roles in development and physiology. In the last decade, genome and small RNA (sRNA) sequencing of several plant species have helped unveil the evolutionary history of land plants. Among these, the fern group (monilophytes) occupies a key phylogenetic position, as it represents the closest extant cousin taxon of seed plants, i.e. gymno- and angiosperms. However, in spite of their evolutionary, economic and ecological importance, no fern genome has been sequenced yet and few genomic resources are available for this group. Here, we sequenced the small RNA fraction of an epiphytic South American fern, Pleopeltis minima (Polypodiaceae), and compared it to plant miRNA databases, allowing for the identification of miRNA families that are shared by all land plants, shared by all vascular plants (tracheophytes) or shared by euphyllophytes (ferns and seed plants) only. Using the recently described transcriptome of another fern, Lygodium japonicum, we also estimated the degree of conservation of fern miRNA targets in relation to other plant groups. Our results pinpoint the origin of several miRNA families in the land plant evolutionary tree with more precision and are a resource for future genomic and functional studies of fern miRNAs. PMID:28494025

  6. Sequencing of small RNAs of the fern Pleopeltis minima (Polypodiaceae) offers insight into the evolution of the microrna repertoire in land plants.

    PubMed

    Berruezo, Florencia; de Souza, Flávio S J; Picca, Pablo I; Nemirovsky, Sergio I; Martínez Tosar, Leandro; Rivero, Mercedes; Mentaberry, Alejandro N; Zelada, Alicia M

    2017-01-01

    MicroRNAs (miRNAs) are short, single stranded RNA molecules that regulate the stability and translation of messenger RNAs in diverse eukaryotic groups. Several miRNA genes are of ancient origin and have been maintained in the genomes of animal and plant taxa for hundreds of millions of years, playing key roles in development and physiology. In the last decade, genome and small RNA (sRNA) sequencing of several plant species have helped unveil the evolutionary history of land plants. Among these, the fern group (monilophytes) occupies a key phylogenetic position, as it represents the closest extant cousin taxon of seed plants, i.e. gymno- and angiosperms. However, in spite of their evolutionary, economic and ecological importance, no fern genome has been sequenced yet and few genomic resources are available for this group. Here, we sequenced the small RNA fraction of an epiphytic South American fern, Pleopeltis minima (Polypodiaceae), and compared it to plant miRNA databases, allowing for the identification of miRNA families that are shared by all land plants, shared by all vascular plants (tracheophytes) or shared by euphyllophytes (ferns and seed plants) only. Using the recently described transcriptome of another fern, Lygodium japonicum, we also estimated the degree of conservation of fern miRNA targets in relation to other plant groups. Our results pinpoint the origin of several miRNA families in the land plant evolutionary tree with more precision and are a resource for future genomic and functional studies of fern miRNAs.

  7. Presence of two emissive minima in the lowest excited state of a push-pull cationic dye unequivocally proved by femtosecond up-conversion spectroscopy and vibronic quantum-mechanical computations.

    PubMed

    Benassi, Enrico; Carlotti, Benedetta; Segado, Mireia; Cesaretti, Alessio; Spalletti, Anna; Elisei, Fausto; Barone, Vincenzo

    2015-05-14

    The long-standing controversy about the presence of two different emissive minima in the lowest excited state of the cationic push-pull dye o-(p-dimethylamino-styryl)-methylpyridinium (DASPMI) was definitively proved through the observation of dual emission, evidenced by both experimental (femtosecond up-conversion measurements) and theoretical (density functional theory calculations) approaches. From the fluorescence up-conversion data of DASPMI in water, the time resolved area normalized spectra (TRANES) were calculated, showing one isoemissive point and therefore revealing the presence of two distinct emissive minima of the excited state potential energy hypersurface with lifetimes of 0.51 and 4.8 ps. These spectroscopic techniques combined with proper data analysis allowed us to discriminate the sub-picosecond emitting state from the occurrence of ultrafast solvation dynamics and to disentangle the overlapping fluorescence (very close in energy) of the two components. Vibronic computations based on TD-DFT potential energy surfaces fully confirm those results and provide deeper insights about the key factors playing a role in determining the overall result. The two emissive minima have different structural and electronic characteristics: on one hand, the locally excited (LE) minimum has a flat geometry and an electric dipole moment smaller than the ground state; on the other hand, the twisted-intramolecular-charge-transfer (TICT) minimum shows a rotation of the methylpyridinium moiety with respect to the rest of the structure, and has an electric dipole moment significantly larger than the ground state.

  8. The Anti-inflammatory Activities of Two Major Withanolides from Physalis minima Via Acting on NF-κB, STAT3, and HO-1 in LPS-Stimulated RAW264.7 Cells.

    PubMed

    Li, Rui-Jun; Gao, Cai-Yun; Guo, Chao; Zhou, Miao-Miao; Luo, Jun; Kong, Ling-Yi

    2016-12-02

    Physalis minima has been traditionally used as a folk herbal medicine in China for the treatment of many inflammatory diseases. However, little is known about its anti-inflammatory constituents and associated molecular mechanisms. In our study, withaphysalin A (WA) and 2, 3-dihydro-withaphysalin C (WC), two major withanolide-type compounds, were obtained from the anti-inflammatory fraction of P. minima. Both WA and WC significantly inhibited the production of nitrite oxide (NO), prostaglandin E2 (PGE2), and several pro-inflammatory cytokines, such as interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α (TNF-α) in lipopolysaccharide (LPS)-activated RAW264.7 macrophages. Further research indicated that they downregulated the LPS-induced expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) at the mRNA and protein levels. In addition, they also suppressed nuclear translocation of NF-κB p65, phosphorylation of STAT3, and upregulated HO-1 expression. Intriguingly, the activation of MAPKs was suppressed by WA but was not altered by WC. Taken together, these data provide scientific evidence for elucidating the major bioactive constituents and related molecular mechanisms for the traditional use of P. minima and suggest that WA and WC can be attractive therapeutic candidates for various inflammatory diseases.

  9. Minima de L'intégrale D'action du Problème Newtoniende 4 Corps de Masses Égales Dans R3: Orbites `Hip-Hop'

    NASA Astrophysics Data System (ADS)

    Chenciner, Alain; Venturelli, Andrea

    2000-09-01

    We consider the problem of 4 bodies of equal masses in R 3 for the Newtonian r-1 potential. We address the question of the absolute minima of the action integral among (anti)symmetric loops of class H 1 whose period is fixed. It is the simplest case for which the results of [4] (corrected in [5]) do not apply: the minima cannot be the relative equilibria whose configuration is an absolute minimum of the potential among the configurations having a given moment of inertia with respect to their center of mass. This is because the regular tetrahedron cannot have a relative equilibrium motion in R 3 (see [2]). We show that the absolute minima of the action are not homographic motions. We also show that if we force the configuration to admit a certain type of symmetry of order 4, the absolute minimum is a collisionless orbit whose configuration ‘hesitates’ between the central configuration of the square and the one of the tetrahedron. We call these orbits ‘hip-hop’. A similar result holds in case of a symmetry of order 3 where the central configuration of the equilateral triangle with a body at the center of mass replaces the square.

  10. Fouling of coarse-clastic sediments with macrophytes depending on the rate of abrasion, Murmansk coast

    NASA Astrophysics Data System (ADS)

    Malavenda, S. V.; Mitayev, M. V.; Malavenda, S. S.; Gerasimova, M. V.

    2017-05-01

    It is shown for the first time that the hydrodynamics and average daily gradient of air temperature affect the rate of abrasion of the coarse-clastic material on the boulder littoral of the Murmansk coast, as well as the density of its fouling by macroalgae. The proportion and biomass of species-explerents vary depending on the hydrological and meteorological conditions. The annual species-explerents ( Acrosiphonia arcta, Blidingia minima, Spongomorpha aeruginosa, Pylaiella littoralis) are the basis for new phytocenoses. In the fucus phytocenoses of the boulder littoral, these groupings represent the intermediate stage of fouling of the coarse-clastic material.

  11. North west area of Tuscany, Italy : Are the solar maximum and solar minima a particular period for increased frequency of floods and local geological destabilization ?

    NASA Astrophysics Data System (ADS)

    Casati, Michele; Straser, Valentino; Feron, Alessandro

    2017-04-01

    river since 1939 (Data provided by Serchio River Authority and Aauthority and Magra Interregional River Authority), we observe that floods and/or local seismic events occur more frequently when there are solar maximum and solar minima.

  12. Molecular and morphological diversity of Narragansett Bay (RI, USA) Ulva (Ulvales, Chlorophyta) populations.

    PubMed

    Guidone, Michele; Thornber, Carol; Wysor, Brian; O'Kelly, Charles J

    2013-10-01

    Macroalgal bloom-forming species occur in coastal systems worldwide. However, due to overlapping morphologies in some taxa, accurate taxonomic assessment and classification of these species can be quite challenging. We investigated the molecular and morphological characteristics of 153 specimens of bloom-forming Ulva located in and around Narragansett Bay, RI, USA. We analyzed sequences of the nuclear internal transcribed spacer 1 region (ITS1) and the chloroplast-encoded rbcL; based on the ITS1 data, we grouped the specimens into nine operational taxonomic units (OTUs). Eight of these OTUs have been previously reported to exist, while one is novel. Of the eight OTUs, all shared sequence identity with previously published sequences or differed by less than 1.5% sequence divergence for two molecular markers. Previously, 10 species names were reported for Ulva in Rhode Island (one blade and nine tube-forming species) based upon morphological classification alone. Of our nine OTUs, three contained blade-forming specimens (U. lactuca, U. compressa, U. rigida), one OTU had a blade with a tubular stipe, and six contained unbranched and/or branched tubular morphologies (one of these six, U. compressa, had both a blade and a tube morphology). While the three blade-forming OTUs in Narragansett Bay can frequently be distinguished by careful observations of morphological characteristics, and spatial/temporal distribution, it is much more difficult to distinguish among the tube-forming specimens based upon morphology or distribution alone. Our data support the molecular species concept for Ulva, and indicate that molecular-based classifications of Ulva species are critical for proper species identification, and subsequent ecological assessment or mitigation of Ulva blooms.

  13. Differences in the Effect of Coal Pile Runoff (Low pH, High Metal Concentrations) Versus Natural Carolina Bay Water (Low pH, Low Metal Concentrations) on Plant Condition and Associated Bacterial Epiphytes of Salvinia minima.

    PubMed

    Lindell, A H; Tuckfield, R C; McArthur, J V

    2016-05-01

    Numerous wetlands and streams have been impacted by acid mine drainage (AMD) resulting in lowered pH and increased levels of toxic heavy metals. Remediation of these contaminated sites requires knowledge on the response of microbial communities (especially epiphytic) and aquatic plants to these altered environmental conditions. We examined the effect of coal pile runoff waters as an example of AMD in contrast to natural water from Carolina Bays with low pH and levels of metals on Salvinia minima, a non-native, metal accumulating plant and associated epiphytic bacteria. Treatments included water from two Carolina Bays, one AMD basin and Hoagland's Solution at two pH levels (natural and adjusted to 5.0-5.5). Using controlled replicated microcosms (N = 64) we determined that the combination of low pH and high metal concentrations has a significant negative impact (p < 0.05) on plant condition and epiphytes. Solution metal concentrations dropped indicating removal from solution by S. minima in all microcosms.

  14. Ion-Stockmayer clusters: Minima, classical thermodynamics, and variational ground state estimates of Li{sup +}(CH{sub 3}NO{sub 2}){sub n} (n = 1–20)

    SciTech Connect

    Curotto, E.

    2015-12-07

    Structural optimizations, classical NVT ensemble, and variational Monte Carlo simulations of ion Stockmayer clusters parameterized to approximate the Li{sup +}(CH{sub 3}NO{sub 2}){sub n} (n = 1–20) systems are performed. The Metropolis algorithm enhanced by the parallel tempering strategy is used to measure internal energies and heat capacities, and a parallel version of the genetic algorithm is employed to obtain the most important minima. The first solvation sheath is octahedral and this feature remains the dominant theme in the structure of clusters with n ≥ 6. The first “magic number” is identified using the adiabatic solvent dissociation energy, and it marks the completion of the second solvation layer for the lithium ion-nitromethane clusters. It corresponds to the n = 18 system, a solvated ion with the first sheath having octahedral symmetry, weakly bound to an eight-membered and a four-membered ring crowning a vertex of the octahedron. Variational Monte Carlo estimates of the adiabatic solvent dissociation energy reveal that quantum effects further enhance the stability of the n = 18 system relative to its neighbors.

  15. VERTEX: manganese transport through oxygen minima

    NASA Astrophysics Data System (ADS)

    Martin, John H.; Knauer, George A.

    1984-01-01

    Manganese transport through a well-developed oxygen minimum was studied off central Mexico (18°N, 108°W) in October-November 1981 as part of the VERTEX (Vertical Transport and Exchange) research program. Refractory, leachable and dissolved Mn fractions associated with particulates caught in traps set at eight depths (120-1950 m) were analyzed. Particles entering the oxygen minimum had relatively large Mn loads; however, as the particulates sank further into the minimum, total Mn fluxes steadily decreased from 190 nmol m -2 day -1 at 120 m to 36 nmol m -2 day -1 at 400 m. Manganese fluxes then steadily increased in the remaining 800-1950 m, reaching rates of up to 230 nmol m -2 day -1 at 1950 m. Manganese concentrations were also measured in the water column. Dissolved Mn levels < 3.0 nmol kg -1 were consistently observed within the 150-600 m depth interval. In contrast, suspended particulate leachable Mn amounts were especially low at those depths, and never exceeded 0.04 nmol kg -1. The combined water column and particle trap data clearly indicate that Mn is released from particles as they sink through the oxygen minimum. Rate-of-change estimates based on trap flux data yield regeneration rates of up to 0.44 nmol kg -1 yr -1 in the upper oxygen minimum (120-200 m). However, only 30% of the dissolved Mn in the oxygen minimum appears to be from sinking particulate regeneration; the other 70% probably results from continental-slope-release-horizontal-transport processes. Dissolved Mn scavenges back onto particles as oxygen levels begin to increase with depth. Scavenging rates ranging from -0.03 to -0.09 nmol kg -1 yr -1 were observed at depths from 700 to 1950 m. These scavenging rates result in Mn residence times of 16-19 years, and scavenging rate constants on the order of 0.057 yr -1. Manganese removal via scavenging on sinking particles below the oxygen minimum is balanced by Mn released along continental boundaries and transported horizontally via advective-diffusive processes. Manganese appears to be very weakly associated with particulates. Nevertheless, the amounts of Mn involved with sinking biogenic particles are large, and the resulting fluxes are on the same order of magnitude as those necessary to explain the excess Mn accumulating on the sea floor. The overall behavior of Mn observed in this, and other, studies strongly suggests some type of equilibrium occurring between dissolved and particulate phases. This equilibrium appears to shift in direct or indirect response to dissolved oxygen levels.

  16. Tunable reflection minima of nanostructured antireflective surfaces

    NASA Astrophysics Data System (ADS)

    Boden, S. A.; Bagnall, D. M.

    2008-09-01

    Broadband antireflection schemes for silicon surfaces based on the moth-eye principle and comprising arrays of subwavelength-scale pillars are applicable to solar cells, photodetectors, and stealth technologies and can exhibit very low reflectances. We show that rigorous coupled wave analysis can be used to accurately model the intricate reflectance behavior of these surfaces and so can be used to explore the effects of variations in pillar height, period, and shape. Low reflectance regions are identified, the extent of which are determined by the shape of the pillars. The wavelengths over which these low reflectance regions operate can be shifted by altering the period of the array. Thus the subtle features of the reflectance spectrum of a moth-eye array can be tailored for optimum performance for the input spectrum of a specific application.

  17. Prevalence and mechanism of polyunsaturated aldehydes production in the green tide forming macroalgal genus Ulva (Ulvales, Chlorophyta).

    PubMed

    Alsufyani, Taghreed; Engelen, Aschwin H; Diekmann, Onno E; Kuegler, Stefan; Wichard, Thomas

    2014-10-01

    Lipoxygenase/hydroperoxide lyase mediated transformations convert polyunsaturated fatty acids into various oxylipins. First, lipoxygenases catalyze fatty acid oxidation to fatty acid hydroperoxides. Subsequently, breakdown reactions result in a wide array of metabolites with multiple physiological and ecological functions. These fatty acid transformations are highly diverse in marine algae and play a crucial rule in e.g., signaling, chemical defense, and stress response often mediated through polyunsaturated aldehydes (PUAs). In this study, green tide-forming macroalgae of the genius Ulva (Chlorophyta) were collected at various sampling sites in the lagoon of the Ria Formosa (Portugal) and were surveyed for PUAs. We demonstrated that sea-lettuce like but not tube-like morphotypes produce elevated amounts of volatile C10-polyunsaturated aldehydes (2,4,7-decatrienal and 2,4-decadienal) upon tissue damage. Moreover, morphogenetic and phylogenetic analyses of the collected Ulva species revealed chemotaxonomic significance of the perspective biosynthetic pathways. The aldehydes are derived from omega-3 and omega-6 polyunsaturated fatty acids (PUFA) with 20 or 18 carbon atoms including eicosapentaenoic acid (C20:5 n-3), arachidonic acid (C20:4 n-6), stearidonic acid (C18:4 n-3), and γ-linolenic acid (C18:3 n-6). We present first evidences that lipoxygenase-mediated (11-LOX and 9-LOX) eicosanoid and octadecanoid pathways catalyze the transformation of C20- and C18-polyunsaturated fatty acids into PUAs and concomitantly into short chain hydroxylated fatty acids.

  18. High-level ab initio calculations for the four low-lying families of minima of (H2O)20. I. Estimates of MP2/CBS binding energies and comparison with empirical potentials.

    PubMed

    Fanourgakis, George S; Aprà, Edoardo; Xantheas, Sotiris S

    2004-08-08

    We report estimates of complete basis set (CBS) limits at the second-order Møller-Plesset perturbation level of theory (MP2) for the binding energies of the lowest-lying isomers within each of the four major families of minima of (H(2)O)(20). These were obtained by performing MP2 calculations with the family of correlation-consistent basis sets up to quadruple zeta quality, augmented with additional diffuse functions (aug-cc-pVnZ, n=D, T, Q). The MP2/CPS estimates are -200.1 (dodecahedron, 30 hydrogen bonds), -212.6 (fused cubes, 36 hydrogen bonds), -215.0 (face-sharing pentagonal prisms, 35 hydrogen bonds), and -217.9 kcal/mol (edge-sharing pentagonal prisms, 34 hydrogen bonds). The energetic ordering of the various (H(2)O)(20) isomers does not follow monotonically the number of hydrogen bonds as in the case of smaller clusters such as the different isomers of the water hexamer. The dodecahedron lies ca. 18 kcal/mol higher in energy than the most stable edge-sharing pentagonal prism isomer. The TIP4P, ASP-W4, TTM2-R, AMOEBA, and TTM2-F empirical potentials also predict the energetic stabilization of the edge-sharing pentagonal prisms with respect to the dodecahedron, albeit they universally underestimate the cluster binding energies with respect to the MP2/CBS result. Among them, the TTM2-F potential was found to predict the absolute cluster binding energies to within <1% from the corresponding MP2/CBS values, whereas the error for the rest of the potentials considered in this study ranges from 3% to 5%.

  19. Low-Lying Energy Isomers and Global Minima of Aqueous Nanoclusters: Structures and Spectroscopic Features of the Pentagonal Dodecahedron (H2O)20 and (H3O)+(H2O)20

    SciTech Connect

    Xantheas, Sotiris S.

    2012-08-01

    We rely on a hierarchy of methods to identify the low-lying isomers for the pentagonal dodecahedron (H2O)20 and the H3O+(H2O)20 clusters. Initial screening of isomers was performed with classical potentials [TIP4P, TTM2-F, TTM2.1-F for (H2O)20 and ASP for H3O+(H2O)20] and the networks obtained with those potentials were subsequently reoptimized at the DFT (B3LYP) and MP2 levels of theory. For the pentagonal dodecahedron (H2O)20 it was found that DFT (B3LYP) and MP2 produced the same global minimum. However, this was not the case for the H3O+(H2O)20 cluster, for which MP2 produced a different network for the global minimum when compared to DFT (B3LYP). All low-lying minima of H3O+(H2O)20 correspond to hydrogen bonding networks having 9 ''free'' OH bonds and the hydronium ion on the surface of the cluster. The fact that DFT (B3LYP) and MP2 produce different results and issues related to the use of a smaller basis set, explains the discrepancy between the current results and the structure previously suggested [Science 304, 1137 (2004)] for the global minimum of the H3O+(H2O)20 cluster. Additionally, the IR spectra of the MP2 global minimum are closer to the experimentally measured ones than the spectra of the previously suggested DFT global minimum. The latter exhibit additional bands in the most red-shifted region of the OH stretching vibrations (corresponding to the ''fingerprint'' of the underlying hydrogen bonding network), which are absent from both the experimental as well as the spectra of the new structure suggested for the global minimum of this cluster.

  20. High-level ab initio calculations for the four low-lying families of minima of (H2O)(20): 1. Estimates of MP2/CBS binding energies and comparison with empirical potentials

    SciTech Connect

    Fanourgakis, Georgios S.; Apra, Edoardo; Xantheas, Sotiris S.

    2004-08-08

    We report estimates of complete basis set (CBS) limits at the second-order Møller-Plesset perturbation level of theory (MP2) for the binding energies of the lowest lying isomers within each of the four major families of minima of (H2O)20. These were obtained by performing MP2 calculations with the family of correlation-consistent basis sets up to quadruple zeta quality, augmented with additional diffuse functions (aug-cc-pVnZ, n=D, T, Q). The MP2/CBS estimates are: -200.1 kcal/mol (dodecahedron, 30 hydrogen bonds), -212.6 kcal/mol (fused cubes, 36 hydrogen bonds), -215.0 (face-sharing pentagonal prisms, 35 hydrogen bonds) and –217.9 kcal/mol (edge-sharing pentagonal prisms, 34 hydrogen bonds). The energetic ordering of the various (H2O)20 isomers does not follow monotonically the number of hydrogen bonds as in the case of smaller clusters such as the different isomers of the water hexamer. The dodecahedron lies ca. 18 kcal/mol higher in energy than the most stable edge-sharing pentagonal prism isomer. The TIP4P, ASP-W4, TTM2-R, AMOEBA and TTM2-F empirical potentials also predict the energetic stabilization of the edge-sharing pentagonal prisms with respect to the dodecahedron, albeit they universally underestimate the cluster binding energies with respect to the MP2/CBS result. Among them, the TTM2-F potential was found to predict the absolute cluster binding energies to within < 1% from the corresponding MP2/CBS values, whereas the error for the rest of the potentials considered in this study ranges from 3-5%.

  1. False minima and the perils of a polar axis in X-ray structure solutions: Molecular structures of W(PMe{sub 3}){sub 4}H{sub 2}X{sub 2} (X = F, Cl, Br) and W(PMe{sub 3}){sub 4}H{sub 2}F{sub 2}(H{sub 2}O)

    SciTech Connect

    Murphy, V.J.; Rabinovich, D.; Parkin, G.

    1995-09-27

    Single-crystal X-ray diffraction is undoubtedly the most common and powerful method for the determination of molecular structures in the solid state. In this paper, we describe how, in specific circumstances, models may refine into extremely deceptive false minima, characterized by well-behaved refinement and displacement parameters, but are grossly distorted from the true structures. The existence of such a phenomenon has serious implications with respect to the interpretation of certain molecular structures as determined by X-ray diffraction. We have demonstrated that molecules which crystallize in polar space groups may suffer from structure solutions that refine into deceptive false minima. Although the existence of false minima is not without precedence, the examples described here are remarkable in the sense that the false structures are dramatically different from their true structures but are nevertheless characterized by low R values and well-behaved displacement parameters. It is likely that this effect will be most pronounced when the X-ray scattering is dominated by a single atom. Thus, in addition to the well-known requirement of ensuring that the correct sense of a polar axis has been selected, it is critical to establish that all of the atoms in the asymmetric unit of a polar space group belong to a single true polar configuration and that the correct molecular geometry is established. 26 refs., 3 figs.

  2. Strong Endemism of bloom-forming tubular Ulva in Indian West Coast, with description of Ulva paschima Sp. Nov. (Ulvales, Chlorophyta).

    PubMed

    Bast, Felix; John, Aijaz Ahmad; Bhushan, Satej

    2014-01-01

    Ulva intestinalis and Ulva compressa are two bloom-forming morphologically-cryptic species of green seaweeds widely accepted as cosmopolitan in distribution. Previous studies have shown that these are two distinct species that exhibit great morphological plasticity with changing seawater salinity. Here we present a phylogeographic assessment of tubular Ulva that we considered belonging to this complex collected from various marine and estuarine green-tide occurrences in a ca. 600 km stretch of the Indian west coast. Maximum Likelihood and Bayesian Inference phylogenetic reconstructions using ITS nrDNA revealed strong endemism of Indian tubular Ulva, with none of the Indian isolates forming part of the already described phylogenetic clades of either U. compressa or U. intestinalis. Due to the straightforward conclusion that Indian isolates form a robust and distinct phylogenetic clade, a description of a new bloom-forming species, Ulva paschima Bast, is formally proposed. Our phylogenetic reconstructions using Neighbor-Joining method revealed evolutionary affinity of this new species with Ulva flexuosa. This is the first molecular assessment of Ulva from the Indian Subcontinent.

  3. Strong Endemism of Bloom-Forming Tubular Ulva in Indian West Coast, with Description of Ulva paschima Sp. Nov. (Ulvales, Chlorophyta)

    PubMed Central

    Bast, Felix; John, Aijaz Ahmad; Bhushan, Satej

    2014-01-01

    Ulva intestinalis and Ulva compressa are two bloom-forming morphologically-cryptic species of green seaweeds widely accepted as cosmopolitan in distribution. Previous studies have shown that these are two distinct species that exhibit great morphological plasticity with changing seawater salinity. Here we present a phylogeographic assessment of tubular Ulva that we considered belonging to this complex collected from various marine and estuarine green-tide occurrences in a ca. 600 km stretch of the Indian west coast. Maximum Likelihood and Bayesian Inference phylogenetic reconstructions using ITS nrDNA revealed strong endemism of Indian tubular Ulva, with none of the Indian isolates forming part of the already described phylogenetic clades of either U. compressa or U. intestinalis. Due to the straightforward conclusion that Indian isolates form a robust and distinct phylogenetic clade, a description of a new bloom-forming species, Ulva paschima Bast, is formally proposed. Our phylogenetic reconstructions using Neighbor-Joining method revealed evolutionary affinity of this new species with Ulva flexuosa. This is the first molecular assessment of Ulva from the Indian Subcontinent. PMID:25329833

  4. High-level ab-initio calculations for the four low-lying families of minima of (H2O)20: II. Spectroscopic signatures of the dodecahedron, fused cubes, face-sharing pentagonal prisms, and edge-sharing pentagonal prisms hydrogen bonding networks

    SciTech Connect

    Fanourgakis, Georgios S.; Apra, Edoardo; De Jong, Wibe A.; Xantheas, Sotiris S.

    2005-04-01

    We report the first harmonic vibrational spectra for each of the lowest lying isomers within the four major families of minima of (H{sub 2}O){sub 20}, namely the dodecahedron, fused cubes, face-sharing pentagonal prisms and edge-sharing pentagonal prisms. These were obtained at the second-order Moeller-Plesset perturbation level of theory (MP2) with the augmented correlation consistent basis set of double zeta quality (aug-cc-pVDZ) at the corresponding minimum energy geometries. The computed infrared (IR) spectra are the first ones obtained from first principles for these clusters. They were found to contain spectral features, which can be directly mapped onto the distinctive spectroscopic signatures of their constituent tetramer, pentamer and octamer fragments. The dodecahedron spectra show the richest structure in the OH stretching region and are associated with the most red-shifted OH vibrations with respect to the monomer. The lowest lying face-sharing pentagonal prism isomer displays intense IR active vibrations that are red-shifted by {approx}600 cm{sup -1} with respect to the water monomer. The zero-point energy corrected MP2/CBS (complete basis set) limit binding energies (D{sub 0}) for the four isomers are -163.1 kcal/mol (face-sharing pentagonal prism), -160.1 kcal/mol (edgesharing pentagonal prism), -157.5 kcal/mol (fused cubes) and -148.1 kcal/mol (dodecahedron).

  5. First observed roost site of Vervain Hummingbird (mellisuga minima)

    Treesearch

    P.B. Hamel

    2012-01-01

    An observation of a roost site of a male Vervain Hummingbird in the Dominican Republic on 7 November 2010 is the first for this species. The bird chose an entirely exposed position on a very thin twig,

  6. Observation of Electronic Structure Minima in High-Harmonic Generation

    SciTech Connect

    Woerner, Hans Jakob; Villeneuve, D. M.; Niikura, Hiromichi; Bertrand, Julien B.; Corkum, P. B.

    2009-03-13

    We report detailed measurements of the high-harmonic spectra generated from argon atoms. The spectra exhibit a deep minimum that is shown to be independent of the laser intensity, and is thus a clear measure of the electronic structure of the atom. We show that exact field-free continuum wave functions reproduce the minimum, but plane wave and Coulomb wave functions do not. This remarkable observation suggests that electronic structure can be accurately determined in high-harmonic experiments despite the presence of the strong laser field. Our results clarify the relation between high-harmonic generation and photoelectron spectroscopy. The use of exact continuum functions also resolves the ambiguity associated with the choice of the dispersion relation.

  7. Activities: Activities to Introduce Maxima-Minima Problems.

    ERIC Educational Resources Information Center

    Pleacher, David

    1991-01-01

    Presented are student activities that involve two standard problems from geometry and calculus--the volume of a box and the bank shot on a pool table. Problem solving is emphasized as a method of inquiry and application with descriptions of the results using graphical, numerical, and physical models. (JJK)

  8. Minimum action transition paths connecting minima on an energy surface.

    PubMed

    Koehl, Patrice

    2016-11-14

    Dynamics is essential to the biological functions of many bio-molecules, yet our knowledge of dynamics remains fragmented. Experimental techniques for studying bio-molecules either provide high resolution information on static conformations of the molecule or provide low-resolution, ensemble information that does not shed light on single molecule dynamics. In parallel, bio-molecular dynamics occur at time scale that are not yet attainable through detailed simulation methods. These limitations are especially noticeable when studying transition paths. To address this issue, we report in this paper two methods that derive meaningful trajectories for proteins between two of their conformations. The first method, MinActionPath, uses approximations of the potential energy surface for the molecule to derive an analytical solution of the equations of motion related to the concept of minimum action path. The second method, RelaxPath, follows the same principle of minimum action path but implements a more sophisticated potential, including a mixed elastic potential and a collision term to alleviate steric clashes. Using this new potential, the equations of motion cannot be solved analytically. We have introduced a relaxation method for solving those equations. We describe both the theories behind the two methods and their implementations, focusing on the specific techniques we have used that make those implementations amenable to study large molecular systems. We have illustrated the performance of RelaxPath on simple 2D systems. We have also compared MinActionPath and RelaxPath to other methods for generating transition paths on a well suited test set of large proteins, for which the end points of the trajectories as well as an intermediate conformation between those end points are known. We have shown that RelaxPath outperforms those other methods, including MinActionPath, in its ability to generate trajectories that get close to the known intermediates. We have also shown that the structures along the RelaxPath trajectories remain protein-like. Open source versions of the two programs MinActionPath and RelaxPath are available by request.

  9. Plural voltage minima in an arc-heated channel flow

    NASA Astrophysics Data System (ADS)

    Sasoh, A.

    2001-04-01

    In flows through a channel with varying cross-sectional area, the impulse and total enthalpy can be increased by superimposing an electrical discharge. The flow field is determined from the inlet flow condition, channel geometry, and discharge specifications. In this study, steady-state, quasi-one-dimensional flows interacting with an arc discharge are computed numerically. Once the arc column configuration is given, the discharge voltage is computed from the solution of flow field variables. For a constant discharge current, there exist plural column configurations which yield a minimum discharge voltage. This result explains the fluid-dynamic mechanisms of the existence of plural voltage modes in an arcjet operation.

  10. Minimum action transition paths connecting minima on an energy surface

    NASA Astrophysics Data System (ADS)

    Koehl, Patrice

    2016-11-01

    Dynamics is essential to the biological functions of many bio-molecules, yet our knowledge of dynamics remains fragmented. Experimental techniques for studying bio-molecules either provide high resolution information on static conformations of the molecule or provide low-resolution, ensemble information that does not shed light on single molecule dynamics. In parallel, bio-molecular dynamics occur at time scale that are not yet attainable through detailed simulation methods. These limitations are especially noticeable when studying transition paths. To address this issue, we report in this paper two methods that derive meaningful trajectories for proteins between two of their conformations. The first method, MinActionPath, uses approximations of the potential energy surface for the molecule to derive an analytical solution of the equations of motion related to the concept of minimum action path. The second method, RelaxPath, follows the same principle of minimum action path but implements a more sophisticated potential, including a mixed elastic potential and a collision term to alleviate steric clashes. Using this new potential, the equations of motion cannot be solved analytically. We have introduced a relaxation method for solving those equations. We describe both the theories behind the two methods and their implementations, focusing on the specific techniques we have used that make those implementations amenable to study large molecular systems. We have illustrated the performance of RelaxPath on simple 2D systems. We have also compared MinActionPath and RelaxPath to other methods for generating transition paths on a well suited test set of large proteins, for which the end points of the trajectories as well as an intermediate conformation between those end points are known. We have shown that RelaxPath outperforms those other methods, including MinActionPath, in its ability to generate trajectories that get close to the known intermediates. We have also shown that the structures along the RelaxPath trajectories remain protein-like. Open source versions of the two programs MinActionPath and RelaxPath are available by request.

  11. Grand Minima: Is The Sun Going To Sleep?

    NASA Astrophysics Data System (ADS)

    Mcintosh, S. W.; Leamon, R. J.

    2014-12-01

    We explore recent observational work which indicate that the energetics of the sun's outer atmosphere have been on a steady decline for the past decade and perhaps longer. Futher, we show that new investigations into evolution of the Sun's global magnetic activity appear to demonstrate a path through which the Sun can go into, and exit from, a grand activity minimum without great difficulty while retaining an activity cycle - only losing sunspots. Are we at the begining of a new grand(-ish) minimum? Naturally, only time will tell, but the observational evidence hint that one may not be far off to what impact on the Sun-Earth Connection.

  12. "Minima Pedagogica": Education, Thinking and Experience in Adorno

    ERIC Educational Resources Information Center

    Snir, Itay

    2017-01-01

    This article attempts to think of thinking as the essence of critical education. While contemporary education tends to stress the conveying of knowledge and skills needed to succeed in the present-day information society, the present article turns to the work of Theodor W. Adorno to develop alternative thinking about education, thinking and the…

  13. Derivative, Maxima and Minima in a Graphical Context

    ERIC Educational Resources Information Center

    Rivera-Figueroa, Antonio; Ponce-Campuzano, Juan Carlos

    2013-01-01

    A deeper learning of the properties and applications of the derivative for the study of functions may be achieved when teachers present lessons within a highly graphic context, linking the geometric illustrations to formal proofs. Each concept is better understood and more easily retained when it is presented and explained visually using graphs.…

  14. Tunneling from super- to normal-deformed minima in nuclei.

    SciTech Connect

    Khoo, T. L.

    1998-01-08

    An excited minimum, or false vacuum, gives rise to a highly elongated superdeformed (SD) nucleus. A brief review of superdeformation is given, with emphasis on the tunneling from the false to the true vacuum, which occurs in the feeding and decay of SD bands. During the feeding process the tunneling is between hot states, while in the decay it is from a cold to a hot state. The {gamma} spectra connecting SD and normal-deformed (ND) states provide information on several physics issues: the decay mechanism; the spin/parity quantum numbers, energies and microscopic structures of SD bands; the origin of identical SD bands; the quenching of pairing with excitation energy; and the chaoticity of excited ND states at 2.5-5 MeV. Other examples of tunneling in nuclei, which are briefly described, include the possible role of tunneling in {Delta}I = 4 bifurcation in SD bands, sub-barrier fusion and proton emitters.

  15. Communities of minima in local optima networks of combinatorial spaces

    NASA Astrophysics Data System (ADS)

    Daolio, Fabio; Tomassini, Marco; Vérel, Sébastien; Ochoa, Gabriela

    2011-05-01

    In this work, we present a new methodology to study the structure of the configuration spaces of hard combinatorial problems. It consists in building the network that has as nodes the locally optimal configurations and as edges the weighted oriented transitions between their basins of attraction. We apply the approach to the detection of communities in the optima networks produced by two different classes of instances of a hard combinatorial optimization problem: the quadratic assignment problem (QAP). We provide evidence indicating that the two problem instance classes give rise to very different configuration spaces. For the so-called real-like class, the networks possess a clear modular structure, while the optima networks belonging to the class of random uniform instances are less well partitionable into clusters. This is convincingly supported by using several statistical tests. Finally, we briefly discuss the consequences of the findings for heuristically searching the corresponding problem spaces.

  16. An ab initio method for locating potential energy minima

    SciTech Connect

    Bock, Nicolas; Peery, Travis; Venneri, Giulia; Chisolm, Eric; Wallace, Duane; Lizarraga, Raquel; Holmstrom, Erik

    2009-01-01

    We study the potential energy landscape underlying the motion of monatomic liquids by quenching from random initial configurations (stochastic configurations) to the nearest local minimum of the potential energy. We show that this procedure reveals the underlying potential energy surface directly. This is in contrast to the common technique of quenching from a molecular dynamics trajectory which does not allow a direct view of the underlying potential energy surface, but needs to be corrected for thermodynamic weighting factors.

  17. Ocean oxygen minima expansions and their biological impacts

    NASA Astrophysics Data System (ADS)

    Stramma, Lothar; Schmidtko, Sunke; Levin, Lisa A.; Johnson, Gregory C.

    2010-04-01

    Climate models with biogeochemical components predict declines in oceanic dissolved oxygen with global warming. In coastal regimes oxygen deficits represent acute ecosystem perturbations. Here, we estimate dissolved oxygen differences across the global tropical and subtropical oceans within the oxygen minimum zone (200-700-dbar depth) between 1960-1974 (an early period with reliable data) and 1990-2008 (a recent period capturing ocean response to planetary warming). In most regions of the tropical Pacific, Atlantic, and Indian Oceans the oxygen content in the 200-700-dbar layer has declined. Furthermore, at 200 dbar, the area with O 2 <70 μmol kg -1, where some large mobile macro-organisms are unable to abide, has increased by 4.5 million km 2. The tropical low oxygen zones have expanded horizontally and vertically. Subsurface oxygen has decreased adjacent to most continental shelves. However, oxygen has increased in some regions in the subtropical gyres at the depths analyzed. According to literature discussed below, fishing pressure is strong in the open ocean, which may make it difficult to isolate the impact of declining oxygen on fisheries. At shallower depths we predict habitat compression will occur for hypoxia-intolerant taxa, with eventual loss of biodiversity. Should past trends in observed oxygen differences continue into the future, shifts in animal distributions and changes in ecosystem structure could accelerate.

  18. High-level ab initio calculations for the four low-lying families of minima of (H2O)20. II. Spectroscopic signatures of the dodecahedron, fused cubes, face-sharing pentagonal prisms, and edge-sharing pentagonal prisms hydrogen bonding networks.

    PubMed

    Fanourgakis, George S; Aprà, Edoardo; de Jong, Wibe A; Xantheas, Sotiris S

    2005-04-01

    We report the first harmonic vibrational spectra for each of the lowest lying isomers within the four major families of minima of (H2O)20, namely, the dodecahedron, fused cubes, face-sharing pentagonal prisms, and edge-sharing pentagonal prisms. These were obtained at the second-order Moller-Plesset perturbation level of theory (MP2) with the augmented correlation consistent basis set of double zeta quality (aug-cc-pVDZ) at the corresponding minimum energy geometries. The computed infrared (IR) spectra are the first ones obtained from first principles for these clusters. They were found to contain spectral features, which can be directly mapped onto the distinctive spectroscopic signatures of their constituent tetramer, pentamer, and octamer fragments. The dodecahedron spectra show the richest structure in the OH stretching region and are associated with the most redshifted OH vibrations with respect to the monomer. The lowest lying edge-sharing pentagonal prism isomer displays intense IR active vibrations that are redshifted by approximately 600 cm(-1) with respect to the water monomer. Furthermore the most redshifted, IR-active OH stretching vibrations for all four networks correspond to hydrogen bonded OH groups, which exhibit the following two common characteristics: (i) they belong to fragments which have a "free" OH stretch and (ii) they act as donors to a neighboring water molecule along a "dimerlike" (strong) hydrogen bond. The zero-point energy corrected MP2/CBS (complete basis set) limit binding energies D(0) for the four isomers are -163.1 kcal/mol (edge-sharing pentagonal prism), -160.1 kcal/mol (face-sharing pentagonal prism), -157.5 kcal/mol (fused cubes), and -148.1 kcal/mol (dodecahedron).

  19. Episodic total ozone minima and associated effects on heterogeneous chemistry and lower stratospheric transport

    NASA Technical Reports Server (NTRS)

    Rood, Richard B.; Nielsen, J. E.; Stolarski, Richard B.; Douglass, Anne R.; Kaye, Jack A.; Allen, Dale J.

    1992-01-01

    Three-dimensional model simulations are used to describe the January 31, 1989 ozone minihole over Stavanger, Norway. This minihole is typical of many transient events in the lower stratosphere that arise because of cyclonic-scale disturbances in the troposphere. Although the ozone reduction is a short-lived reversible dynamical event, through heterogeneous chemical processes there can be a significant transfer of chlorine from reservoir molecules to active radicals. This chemically perturbed air is defined as processed air, and it is found that a single event can produce enough processed air to reduce the HCl in the entire polar vortex. Chemical processing on clouds associated with transient events is shown to be a major source of processed air in the polar vortex in December before background temperatures are cold enough for more uniform heterogeneous conversion.

  20. Transporting and manipulating single electrons in surface-acoustic-wave minima

    NASA Astrophysics Data System (ADS)

    Ford, Christopher J. B.

    2017-03-01

    A surface acoustic wave (SAW) can produce a moving potential wave that can trap and drag electrons along with it. We review work on using a SAW to create moving quantum dots containing single electrons, with the aims of developing a current standard, emitting single photons, transferring single electrons between static quantum dots, and investigating non-adiabatic effects.

  1. VizieR Online Data Catalog: Minima of 41 binaries from entire Kepler mission (Gies+, 2015)

    NASA Astrophysics Data System (ADS)

    Gies, D. R.; Matson, R. A.; Guo, Z.; Lester, K. V.; Orosz, J. A.; Peters, G. J.

    2016-06-01

    We embarked on a search for eclipse timing variations among a subset of 41 eclipsing binaries that were identified prior to the start of Kepler observations (see our first paper, Gies et al. 2012, cat. J/AJ/143/137). Our first paper documented the eclipse times in observations made over quarters Q0-Q9 (2009.3-2011.5). Now with the Kepler mission complete with observations through Q17 (ending 2013.4), we present here the eclipse timings for our sample of 41 binaries over the entire duration of the mission. The associated times given in our first paper were based upon UTC (Coordinated Universal Time) while the current set uses TDB (Barycentric Dynamical Time), and here we report the times in reduced Barycentric Julian Date (BJD-2400000 days). We used the Simple Aperture Photometry (SAP) flux except in the case of KIC04678873. The list of targets appears in Table1. The eclipse timing measurements were made in almost the same way as described in our first paper. Our measurements appear in Table2. (2 data files).

  2. Theoretical studies of the global minima and polarizabilities of small lithium clusters

    SciTech Connect

    Hu, Hanshi; Zhao, Ya-Fan; Hammond, Jeffrey R.; Bylaska, Eric J.; Apra, Edoardo; van Dam, Hubertus JJ; Li, Jun; Govind, Niranjan; Kowalski, Karol

    2016-01-16

    Lithium clusters Lin (n=1-20) have been investigated with density functional theory (DFT) and coupled—cluster (CC) methods. The global-minimum structures are located via an improved basin---hopping algorithm and the lowest energy Lin isomers are confirmed with DFT geometry optimizations, CCSD(T) energy calculations, and by comparing simulated and experimental polarizabilities. The tetrahedral Li4 structure is found to be the basic building block of lithium clusters Lin (n=6-20). Simulated polarizabilities, including thermal effects at room temperature, are in good agreement with measured isotropic polarizabilities.

  3. Many pathways in laboratory evolution can lead to improved enzymes: how to escape from local minima.

    PubMed

    Gumulya, Yosephine; Sanchis, Joaquin; Reetz, Manfred T

    2012-05-07

    Directed evolution is a method to tune the properties of enzymes for use in organic chemistry and biotechnology, to study enzyme mechanisms, and to shed light on darwinian evolution in nature. In order to enhance its efficacy, iterative saturation mutagenesis (ISM) was implemented. This involves: 1) randomized mutation of appropriate sites of one or more residues; 2) screening of the initial mutant libraries for properties such as enzymatic rate, stereoselectivity, or thermal robustness; 3) use of the best hit in a given library as a template for saturation mutagenesis at the other sites; and 4) continuation of the process until the desired degree of enzyme improvement has been reached. Despite the success of a number of ISM-based studies, the question of the optimal choice of the many different possible pathways remains unanswered. Here we considered a complete 4-site ISM scheme. All 24 pathways were systematically explored, with the epoxide hydrolase from Aspergillus niger as the catalyst in the stereoselective hydrolytic kinetic resolution of a chiral epoxide. All 24 pathways were found to provide improved mutants with notably enhanced stereoselectivity. When a library failed to contain any hits, non-improved or even inferior mutants were used as templates in the continuation of the evolutionary pathway, thereby escaping from the local minimum. These observations have ramifications for directed evolution in general and for evolutionary biological studies in which protein engineering techniques are applied. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Design of structure/control systems with transient response constraints exhibiting relative minima

    NASA Technical Reports Server (NTRS)

    Sepulveda, A. E.; Jin, I. M.

    1992-01-01

    Structural optimization problems involving dynamic behavior constraints often exhibit nonconvex design spaces. The direct application of a global optimization algorithm requires a large number of function evaluations which in term require a large number of dynamic structural analyses. This work presents a strategy aimed at finding the global optimum for problems with transient dynamic behavior constraints based on approximation concepts. The method consists of generating and solving a sequence of approximate problems using a global optimizer. The approximations are explicit and capture the inherent nonconvexity of the exact functions. A simple example problem is presented.

  5. Radar Inaccuracies and Mid-Air Collision Risk: Part 2 En Route Radar Separation Minima

    NASA Astrophysics Data System (ADS)

    Brooker, Peter

    2004-01-01

    A review of safety targets for en route ATC radar separation suggests that the existing target level of safety (TLS) is over-cautious. If risk budgeting principles are followed consistently, a ‘radar TLS’ of 1·0×10[minus sign]9 fatal aircraft accidents per flying hour is appropriate. This rate is consistent with Joint Aviation Authorities (JAA) guidance on system failure conditions leading to catastrophic accidents. Dynamic and static calculations using published data are compared. The new methodology shows where there are problems with the traditional static calculations, and how to improve the estimation. A further improvement introduces a simple robust model of the controller's decision processes. The focus is not on describing what controllers would generally do, but on setting criteria based on what they could not reasonably be expected to do. This additional ingredient into the calculation adds realism and ensures that attention is focused on hazardous correlated errors. Focused data collection would be an essential component of new risk estimates. The key information required would be on radar performance and the nature and frequency of use of radar separation, including the relative velocities for proximate events at closest point of approach and the frequency of correlated gross errors (through a conditional probability factor). If this factor is not properly taken into account, then the data collection and analysis could be inefficient.

  6. Teoria de chovitz de segundo orden aplicada a la busqueda de proyecciones cartograficas de minima deformacion

    NASA Astrophysics Data System (ADS)

    Malpica Velasco, Jose Antonio

    The rampant success of quantum theory is the result of applications of the 'new' quantum mechanics of Schrodinger and Heisenberg (1926-7), the Feynman-Schwinger-Tomonaga Quantum Electro-dynamics (1946-51), the electro-weak theory of Salaam, Weinberg, and Glashow (1967-9), and Quantum Chromodynamics (1973-); in fact, this success of 'the' quantum theory has depended on a continuous stream of brilliant and quite disparate mathematical formulations. In this carefully concealed ferment there lie plenty of unresolved difficulties, simply because in churning out fabulously accurate calculational tools there has been no sensible explanation of all that is going on. It is even argued that such an understanding is nothing to do with physics. A long-standing and famous illustration of this is the paradoxical thought-experiment of Einstein, Podolsky and Rosen (1935). Fundamental to all quantum theories, and also their paradoxes, is the location of sub-microscopic objects; or, rather, that the specification of such a location is fraught with mathematical inconsistency. This project encompasses a detailed, critical survey of the tangled history of Position within quantum theories. The first step is to show that, contrary to appearances, canonical quantum mechanics has only a vague notion of locality. After analysing a number of previous attempts at a 'relativistic quantum mechanics', two lines of thought are considered in detail. The first is the work of Wan and students, which is shown to be no real improvement on the iisu.al 'nonrelativistic' theory. The second is based on an idea of Dirac's - using backwards-in-time light-cones as the hypersurface in space-time. There remain considerable difficulties in the way of producing a consistent scheme here. To keep things nicely stirred up, the author then proposes his own approach - an adaptation of Feynman's QED propagators. This new approach is distinguished from Feynman's since the propagator or Green's function is not obtained by Feynman's rule. The type of equation solved is also different: instead of an initial-value problem, a solution that obeys a time-symmetric causality criterion is found for an inhomogeneous partial differential equation with homogeneous boundary conditions. To make the consideration of locality more precise, some results of Fourier transform theory are presented in a form that is directly applicable. Somewhat away from the main thrust of the thesis, there is also an attempt to explain, the manner in which quantum effects disappear as the number of particles increases in such things as experimental realisations of the EPR and de Broglie thought experiments.

  7. First report of leaf rust of blueberry caused by Thekopsora minima in Mexico

    USDA-ARS?s Scientific Manuscript database

    Blueberry (Vaccinium corymbosum L.) is becoming an important crop in the states of Jalisco and Michoacan in Mexico. As the area under blueberry cultivation increases, new diseases causing severe losses are appearing. Leaf rust is one of the most destructive diseases of blueberry in Mexico. Sori on t...

  8. Communication: Effective spectroscopic Hamiltonian for multiple minima with above barrier motion: Isomerization in HO(2).

    PubMed

    Barnes, George L; Kellman, Michael E

    2010-09-14

    We present a two-dimensional potential surface for the isomerization in the hydroperoxyl radical HO(2) and calculate the vibrational spectrum. We then show that a simple effective spectroscopic fitting Hamiltonian is capable of reproducing large scale vibrational spectral structure above the isomerization barrier. Polyad breaking with multiple resonances is necessary to adequately describe the spectral features of the system. Insight into the dynamical nature of isomerization related to the effective Hamiltonian is gained through classical trajectories on the model potential. Contrary to physical intuition, the bend mode is not a "reaction mode," but rather isomerization requires excitation in both stretch and bend. The dynamics reveals a Farey tree formed from the 2:1 and 3:1 resonances, corresponding to the resonance coupling terms in the effective Hamiltonian, with the prominent 5:2 (2:1+3:1) feature dividing the tree into parts that we call the 3:1 and 2:1 portions.

  9. Neural network exponential fitting of a potential energy surface with multiple minima: Application to HFCO

    NASA Astrophysics Data System (ADS)

    Pradhan, Ekadashi; Brown, Alex

    2016-12-01

    We have constructed a (semi)-global six-dimensional potential energy surface (PES) for HFCO, incorporating the equilibrium, cis- and trans- isomers (HOCF) as well as the transition states connecting them. The PES is based on a fit to 15000 CCSD(T)-F12/cc-pVTZ-F12 ab initio energies. The sum-of-products PES, obtained using neural network exponential fitting functions, was used to compute vibrational state frequencies using block improved relaxation with the multiconfiguration time dependent Hartree (MCTDH) approach. The PES is accurate (RMSE = 130 cm-1) up to 40,000 cm-1 above the minimum energy. The equilibrium region of the PES was fit very well based on a comparison of the vibrational frequencies with those from a recent local HFCO PES (Pradhan and Brown, 2016) and experimental measurements (RMSE = 10.9 cm-1 compared to experiment). The vibrational frequencies for the trans- and cis-isomers are computed from the PES and compared to anharmonic MP2/aug-cc-pVTZ and CCSD(T)/aug-cc-pVTZ results; the trans- and cis-isomers have yet to be detected experimentally. Based on the accuracy of the vibrational energies at equilibrium, the present results for the cis- and trans-isomers could facilitate the identification of these species. The PES will also enable the study of intramolecular vibrational energy redistribution and its control leading to the elusive equilibrium HFCO to trans-HOCF conversion.

  10. GRAND MINIMA AND EQUATORWARD PROPAGATION IN A CYCLING STELLAR CONVECTIVE DYNAMO

    SciTech Connect

    Augustson, Kyle; Miesch, Mark; Brun, Allan Sacha

    2015-08-20

    The 3D MHD Anelastic Spherical Harmonic code, using slope-limited diffusion, is employed to capture convective and dynamo processes achieved in a global-scale stellar convection simulation for a model solar-mass star rotating at three times the solar rate. The dynamo-generated magnetic fields possesses many timescales, with a prominent polarity cycle occurring roughly every 6.2 years. The magnetic field forms large-scale toroidal wreaths, whose formation is tied to the low Rossby number of the convection in this simulation. The polarity reversals are linked to the weakened differential rotation and a resistive collapse of the large-scale magnetic field. An equatorial migration of the magnetic field is seen, which is due to the strong modulation of the differential rotation rather than a dynamo wave. A poleward migration of magnetic flux from the equator eventually leads to the reversal of the polarity of the high-latitude magnetic field. This simulation also enters an interval with reduced magnetic energy at low latitudes lasting roughly 16 years (about 2.5 polarity cycles), during which the polarity cycles are disrupted and after which the dynamo recovers its regular polarity cycles. An analysis of this grand minimum reveals that it likely arises through the interplay of symmetric and antisymmetric dynamo families. This intermittent dynamo state potentially results from the simulation’s relatively low magnetic Prandtl number. A mean-field-based analysis of this dynamo simulation demonstrates that it is of the α-Ω type. The timescales that appear to be relevant to the magnetic polarity reversal are also identified.

  11. Accelerating the search for global minima on potential energy surfaces using machine learning

    NASA Astrophysics Data System (ADS)

    Carr, S. F.; Garnett, R.; Lo, C. S.

    2016-10-01

    Controlling molecule-surface interactions is key for chemical applications ranging from catalysis to gas sensing. We present a framework for accelerating the search for the global minimum on potential surfaces, corresponding to stable adsorbate-surface structures. We present a technique using Bayesian inference that enables us to predict converged density functional theory potential energies with fewer self-consistent field iterations. We then discuss how this technique fits in with the Bayesian Active Site Calculator, which applies Bayesian optimization to the problem. We demonstrate the performance of our framework using a hematite (Fe2O3) surface and present the adsorption sites found by our global optimization method for various simple hydrocarbons on the rutile TiO2 (110) surface.

  12. VizieR Online Data Catalog: Massive LMC eclipsing binaries minima timings (Zasche+, 2016)

    NASA Astrophysics Data System (ADS)

    Zasche, P.; Wolf, M.; Vrastil, J.; Pilarcik, L.; Jurysek, J.

    2016-04-01

    For the first time, in this study we derived the relatively short periods of modulation in these systems, which relates to third bodies. The orbital periods resulted from 3.6 to 11.3yr and the eccentricities were found to be up to 0.64. This is the first time that this kind of analysis for the set of extragalactic sources has been performed. The Wolf-Rayet system OGLE-LMC-ECL-08823 is the most mysterious one, owing to the resultant high mass function. Another system, OGLE-LMC-ECL-19996, was found to contain a third body with a very high mass (M3,min=26M⊙). One system (OGLE-LMC-ECL-09971) is suspicious because of its eccentricity, and another one (OGLE-LMC-ECL-20162) shows some light curve variability, with a possible flare-like or microlensing-like event. (2 data files).

  13. VizieR Online Data Catalog: Times of minima for 18 LMC eclipsing binaries (Zasche+, 2015)

    NASA Astrophysics Data System (ADS)

    Zasche, P.; Wolf, M.; Vrastil, J.; Pilarcik, L.

    2016-04-01

    New CCD photometry was obtained at the La Silla Observatory in Chile, where the 1.54m Danish telescope with the CCD camera and R filter was used (remotely operated from the Czech Republic). All new times of minimum are given in Table1. (2 data files).

  14. Comparing the Internal Structure of the Sun During the Cycle 23 and Cycle 24 Minima

    NASA Astrophysics Data System (ADS)

    Basu, S.; Broomhall, A.-M.; Chaplin, W. J.; Elsworth, Y.; Davies, G. R.; Schou, J.; Larson, T. P.

    2013-12-01

    The Birmingham Solar-Oscillations Network (BiSON) has been collecting helioseismic data for the last three solar cycles. We use these data to determine whether the internal properties of the Sun during the minimum preceding cycle 24 was different compared to that preceding cycle 23.

  15. Migration, fidelity, and use of autumn staging grounds in Alaska by Cackling Canada Geese Branta canadensis minima

    USGS Publications Warehouse

    Gill, Robert; Babcock, Christopher; Handel, Colleen M.; Butler, William R.; Raveling, Dennis G.

    1996-01-01

    Cackling Canada Geese were studied annually (1985-88) on autumn migration staging areas in Alaska during a period of rapid population growth. Geese concentrated at two estuaries (Ugashik Bay and Cinder Lagoon) along the north side of the Alaska Peninsula. Birds arrived on the staging areas in late September, numbers peaked during mid-October, and departure occurred by late October or early November. Annual peak counts combined for the two staging areas ranged from 16,000-54,000 geese, or from 23-120% of the autumn population index. Up to 30,000 geese were recorded at each estuary, but relative use of the two staging areas varied among years. Within-year fidelity to staging areas was high; only three of 242 neck-banded geese seen more than once were observed at both areas within a season. Between-year fidelity to staging areas was highest among hatching-year females (11 of 11) and adult males (14 of 17), lowest among hatching-year males (4 of 9), and intermediate among adult females (18 of 28). Use of the two staging areas was independent of family status, reproductive status, and age. Late arrivals on the staging areas consisted of a higher proportion of single and paired birds than of geese in family groups. Most geese departed the staging grounds with the onset of freezing conditions and the passage of low pressure systems that produced winds favourable for migration. Transoceanic flights to the wintering grounds in Oregon and California were completed in about 48 h. During years with mild weather on the breeding grounds and years with early freezing conditions on the staging areas, few geese staged on the Alaska Peninsula, indicating that geese can sometimes obtain sufficient energy reserves to migrate directly from the breeding grounds without stopping on the staging areas. Only 25% of the area used for staging is legally protected. Use of unprotected areas may become increasingly important if the population continues to increase.

  16. Global minima for water clusters (H 2O) n, n ⩽ 21, described by a five-site empirical potential

    NASA Astrophysics Data System (ADS)

    James, Tim; Wales, David J.; Hernández-Rojas, Javier

    2005-11-01

    Candidate global minimum structures are reported for (H 2O) n clusters for n ⩽ 21 described by the rigid-body TIP5P potential. These structures are compared with previously published results for the related TIP4P potential, and with ab initio calculations at the MP2 level. The variation of the energy gap from the putative global minimum to the next-lowest structure as a function of system size is analysed. Comparisons with previously reported structural trends in water clusters are made.

  17. On the crossing points of the Lamb modes and the maxima and minima of displacements observed at the surface☆

    PubMed Central

    Veres, István A.; Berer, Thomas; Grünsteidl, Clemens; Burgholzer, Peter

    2014-01-01

    This article elaborates on the crossing points of the frequency–wavenumber branches for the symmetric and anti-symmetric Lamb modes in a homogeneous plate. It is shown both theoretically as well as experimentally that at these crossing points either the normal or the longitudinal components of modal displacement attain an extreme value, i.e. a maximum or it vanishes. This behavior is assessed herein using a method due to Mindlin, who showed that the dispersion curves for a plate with mixed boundary conditions – which are associated with uncoupled shear and dilatational modes – provide bounds to the spectral lines of the free plate. Therefore, a subset of the crossing points of the symmetric and antisymmetric Lamb modes for a free plate coincide with the crossing points for a plate with mixed boundary conditions. PMID:24268025

  18. Pronounced Minima in Tropospheric Ozone and OH above the Tropical West Pacific and their Role for Stratospheric Composition

    NASA Astrophysics Data System (ADS)

    Rex, M.; Wohltmann, I.; Lehmann, R.; Rosenlof, K. H.; Wennberg, P. O.; Weisenstein, D. K.; Notholt, J.; Krüger, K.; Mohr, V.; Tegtmeier, S.

    2014-12-01

    Hundreds of organic species are emitted into the atmosphere mostly from biogenic processes. The rapid breakdown by reactions with OH radicals prevents most of them from reaching the stratosphere. Hence, the omnipresent layer of OH in the troposphere shields the stratosphere from these emissions and is particularly relevant for those species that do not photolyse efficiently. Reactions involving ozone are a strong source of OH in clean tropical air. Hence the OH concentration is closely coupled to ozone abundances. The Western Pacific warm pool is key for troposphere to stratosphere exchange. We report measurements of 14 ozonesondes launched during the Transbrom ship cruise through the center of the warm pool. During a 2500km portion of the ship track between 10S and 15N we found ozone concentrations below the detection limit of the sondes throughout the troposphere. We will discuss the uncertainties of ozonesonde measurements at very low ozone concentrations, the robustness of our observations and the upper limit of the ozone concentration that would be consistent with our raw data. Based on modelling and measurements of OH on the ER-2 during the STRAT campaign we suggest that there also is a pronounced minimum in the tropospheric column of OH over the tropical West Pacific. We show that this increases the lifetime of chemical species and has the potential to amplify the impact of surface emissions on the stratospheric composition. Specifically, we discuss the role of emissions of biogenic halogenated species from this geographic region for stratospheric ozone depletion. Also, we discuss the potential role of increasing anthropogenic emissions of SO2 in South East Asia or from minor volcanic eruptions for the stratospheric aerosol budget.

  19. Curvature and the Visual Perception of Shape: Theory on Information along Object Boundaries and the Minima Rule Revisited

    ERIC Educational Resources Information Center

    Lim, Ik Soo; Leek, E. Charles

    2012-01-01

    Previous empirical studies have shown that information along visual contours is known to be concentrated in regions of high magnitude of curvature, and, for closed contours, segments of negative curvature (i.e., concave segments) carry greater perceptual relevance than corresponding regions of positive curvature (i.e., convex segments). Lately,…

  20. Limited poleward influence of relative humidity and controls on the positions of the subtropical relative humidity minima

    NASA Astrophysics Data System (ADS)

    O'Gorman, P. A.; Lamquin, N.; Schneider, T.; Singh, M. S.

    2011-12-01

    Dairy manure is a large potential source of agriculturally-derived greenhouse gases, but few studies have compared source locations or management strategies, nor evaluated how well emissions factors capture actual emission rates. We compiled published data on field-scale measurements of greenhouse gas emissions from working and research dairies and compared these to rates predicted by the IPCC Tier 2 approach. Greenhouse gas emissions varied by several orders of magnitude from all sources due to the heterogeneity of surface conditions and manure composition, the length of sampling, and the measurement technique. Anaerobic lagoons were the largest source of methane (1097 × 591 g hd-1 d-1), over twice that from enteric fermentation (~350 g hd-1 d-1). Corrals and manure piles were the largest sources of nitrous oxide. Methane and nitrous oxide emissions from hardstandings and barn floors were negligible. Predicted methane emissions underestimated measured fluxes for slurry tanks, barns, and whole dairies. Predicted nitrous oxide emissions underestimated anaerobic lagoon fluxes but overestimated emissions from slurry tanks and barn floors. Refining these calculations requires: 1) within-site comparisons of measurement techniques, 2) multiple year data sets, 3) within-site comparisons across measurement scales, and 4) better metadata to constrain greenhouse gas emission models.

  1. The GSAM software: A global search algorithm of minima exploration for the investigation of low lying isomers of clusters

    NASA Astrophysics Data System (ADS)

    Marchal, Rémi; Carbonnière, Philippe; Pouchan, Claude

    2015-01-01

    The study of atomic clusters has become an increasingly active area of research in the recent years because of the fundamental interest in studying a completely new area that can bridge the gap between atomic and solid state physics. Due to their specific properties, such compounds are of great interest in the field of nanotechnology [1,2]. Here, we would present our GSAM algorithm based on a DFT exploration of the PES to find the low lying isomers of such compounds. This algorithm includes the generation of an intial set of structure from which the most relevant are selected. Moreover, an optimization process, called raking optimization, able to discard step by step all the non physically reasonnable configurations have been implemented to reduce the computational cost of this algorithm. Structural properties of GanAs m clusters will be presented as an illustration of the method.

  2. The Local Minima Problem in Hierarchical Classes Analysis: An Evaluation of a Simulated Annealing Algorithm and Various Multistart Procedures

    ERIC Educational Resources Information Center

    Ceulemans, Eva; Van Mechelen, Iven; Leenen, Iwin

    2007-01-01

    Hierarchical classes models are quasi-order retaining Boolean decomposition models for N-way N-mode binary data. To fit these models to data, rationally started alternating least squares (or, equivalently, alternating least absolute deviations) algorithms have been proposed. Extensive simulation studies showed that these algorithms succeed quite…

  3. HfO{sub 2} dielectric thickness dependence of electrical properties in graphene field effect transistors with double conductance minima

    SciTech Connect

    Zhang, Cheng; Xie, Dan Xu, Jian-Long; Sun, Yi-Lin; Dai, Rui-Xuan; Li, Xian; Li, Xin-Ming; Zhu, Hong-Wei

    2015-10-14

    We investigate the electrical properties in back-gated graphene field effect transistors (GFETs) with SiO{sub 2} dielectric and different thickness of high-k HfO{sub 2} dielectric. The results show that transform characteristic (I{sub ds}–V{sub gs}) curves of GFETs are uniquely W-shaped with two charge neutrality point (left and right) in both SiO{sub 2} and HfO{sub 2} dielectric (SiO{sub 2}-GFETs and HfO{sub 2}-GFETs). The gate voltage reduces drastically in HfO{sub 2}-GFETs compared with that in SiO{sub 2}-GFETs, and it becomes much smaller with the decline of HfO{sub 2} thickness. The left charge neutrality point in I{sub d}–V{sub g} curves of all HfO{sub 2}-GFETs is negative, compared to the positive ones in SiO{sub 2}-GFETs, which means that there exists n-doping in graphene with HfO{sub 2} as bottom dielectric. We speculate that this n-doping comes from the HfO{sub 2} layer, which brings fixed charged impurities in close proximity to graphene. The carrier mobility is also researched, demonstrating a decreasing trend of hole mobility in HfO{sub 2}-GFETs contrast to that in SiO{sub 2}-GFETs. In a series of HfO{sub 2}-GFETs with different HfO{sub 2} dielectric thickness, the hole mobility shows a tendency of rise when the thickness decreases to 7 nm. The possible reason might be due to the introduced impurities into HfO{sub 2} film from atomic layer deposition process, the concentration of which varies from the thickness of HfO{sub 2} layer.

  4. The GSAM software: A global search algorithm of minima exploration for the investigation of low lying isomers of clusters

    SciTech Connect

    Marchal, Rémi; Carbonnière, Philippe; Pouchan, Claude

    2015-01-22

    The study of atomic clusters has become an increasingly active area of research in the recent years because of the fundamental interest in studying a completely new area that can bridge the gap between atomic and solid state physics. Due to their specific properties, such compounds are of great interest in the field of nanotechnology [1,2]. Here, we would present our GSAM algorithm based on a DFT exploration of the PES to find the low lying isomers of such compounds. This algorithm includes the generation of an intial set of structure from which the most relevant are selected. Moreover, an optimization process, called raking optimization, able to discard step by step all the non physically reasonnable configurations have been implemented to reduce the computational cost of this algorithm. Structural properties of Ga{sub n}Asm clusters will be presented as an illustration of the method.

  5. Curvature and the Visual Perception of Shape: Theory on Information along Object Boundaries and the Minima Rule Revisited

    ERIC Educational Resources Information Center

    Lim, Ik Soo; Leek, E. Charles

    2012-01-01

    Previous empirical studies have shown that information along visual contours is known to be concentrated in regions of high magnitude of curvature, and, for closed contours, segments of negative curvature (i.e., concave segments) carry greater perceptual relevance than corresponding regions of positive curvature (i.e., convex segments). Lately,…

  6. HEMISPHERIC ASYMMETRIES IN THE POLAR SOLAR WIND OBSERVED BY ULYSSES NEAR THE MINIMA OF SOLAR CYCLES 22 AND 23

    SciTech Connect

    Ebert, R. W.; Dayeh, M. A.; Desai, M. I.; McComas, D. J.; Pogorelov, N. V.

    2013-05-10

    We examined solar wind plasma and interplanetary magnetic field (IMF) observations from Ulysses' first and third orbits to study hemispheric differences in the properties of the solar wind and IMF originating from the Sun's large polar coronal holes (PCHs) during the declining and minimum phase of solar cycles 22 and 23. We identified hemispheric asymmetries in several parameters, most notably {approx}15%-30% south-to-north differences in averages for the solar wind density, mass flux, dynamic pressure, and energy flux and the radial and total IMF magnitudes. These differences were driven by relatively larger, more variable solar wind density and radial IMF between {approx}36 Degree-Sign S-60 Degree-Sign S during the declining phase of solar cycles 22 and 23. These observations indicate either a hemispheric asymmetry in the PCH output during the declining and minimum phase of solar cycles 22 and 23 with the southern hemisphere being more active than its northern counterpart, or a solar cycle effect where the PCH output in both hemispheres is enhanced during periods of higher solar activity. We also report a strong linear correlation between these solar wind and IMF parameters, including the periods of enhanced PCH output, that highlight the connection between the solar wind mass and energy output and the Sun's magnetic field. That these enhancements were not matched by similar sized variations in solar wind speed points to the mass and energy responsible for these increases being added to the solar wind while its flow was subsonic.

  7. Of Minima and Maxima: The Social Significance of Minimal Competency Testing and the Search for Educational Excellence.

    ERIC Educational Resources Information Center

    Ericson, David P.

    1984-01-01

    Explores the many meanings of the minimal competency testing movement and the more recent mobilization for educational excellence in the schools. Argues that increasing the value of the diploma by setting performance standards on minimal competency tests and by elevating academic graduation standards may strongly conflict with policies encouraging…

  8. The Local Minima Problem in Hierarchical Classes Analysis: An Evaluation of a Simulated Annealing Algorithm and Various Multistart Procedures

    ERIC Educational Resources Information Center

    Ceulemans, Eva; Van Mechelen, Iven; Leenen, Iwin

    2007-01-01

    Hierarchical classes models are quasi-order retaining Boolean decomposition models for N-way N-mode binary data. To fit these models to data, rationally started alternating least squares (or, equivalently, alternating least absolute deviations) algorithms have been proposed. Extensive simulation studies showed that these algorithms succeed quite…

  9. Emergent phase shift between diurnal transpiration maxima and stream flow minima during base flow as diagnostic of eco-hydrologic interactions in landscapes

    NASA Astrophysics Data System (ADS)

    Zanardo, Stefano; Hilberts, Arno; Foufoula-Georgiou, Efi; Dietrich, William

    2014-05-01

    Diurnal oscillations in river base flow are frequently observed in hydrological datasets, yet have only been examined in a few, exploratory studies. In this work we focus on the oscillation shift between base flow and the forcing signal, which, in the case study at hand, is essentially dominated by the tree transpiration oscillation. This quantity characterizes the propagation time of the forcing throughout the river basin, and will be referred to as Eco-hydrological Phase Shift (EHPS). In principle, it is reasonable to hypothesize that EHPS depends on the combination of hillslope and channel characteristic transport times, however it is unclear whether and how its value varies over a range of spatial scales. This is the central question of the study. We analyzed base flow data collected between 2009 and 2012 in 8 stations within the Eel river basin (Mendocino county, CA), where the typical Mediterranean climate allows for long, undisturbed summer base flow recessions. The drainage areas relative to each gauging station span over four orders of magnitude, ranging from ~10 km2 to ~10000 km2. We found that, despite the wide range of spatial scales, EHPS by late summer tends to a remarkably narrow range of values, between 8 and 11 hours for all the stations considered. This implies that the timing of diurnal oscillations is dominated by hillslope rather than river network processes, even at large spatial scales. We then propose a simple, conceptual model to explore the hillslope controls on EHPS. The framework allows deriving analytical expressions for EHPS under different 'behavioral assumptions' for vegetation water-use. Results show that, within this framework, a delay of 8-11 hours can only be observed if tree roots exclusively use water from the unsaturated zone and variations within that range are due to different signal propagation times in both the unsaturated and the saturated zone. This analysis demonstrates that EHPS represents a scale-invariant signature of river basins and can be used to further explore the eco-hydrological interactions between hillslopes and streams.

  10. The protonation of N2O reexamined - A case study on the reliability of various electron correlation methods for minima and transition states

    NASA Technical Reports Server (NTRS)

    Martin, J. M. L.; Lee, Timothy J.

    1993-01-01

    The protonation of N2O and the intramolecular proton transfer in N2OH(+) are studied using various basis sets and a variety of methods, including second-order many-body perturbation theory (MP2), singles and doubles coupled cluster (CCSD), the augmented coupled cluster (CCSD/T/), and complete active space self-consistent field (CASSCF) methods. For geometries, MP2 leads to serious errors even for HNNO(+); for the transition state, only CCSD/T/ produces a reliable geometry due to serious nondynamical correlation effects. The proton affinity at 298.15 K is estimated at 137.6 kcal/mol, in close agreement with recent experimental determinations of 137.3 +/- 1 kcal/mol.

  11. Exploiting Free-Energy Minima to Design Novel EphA2 Protein-Protein Antagonists: From Simulation to Experiment and Return.

    PubMed

    Russo, Simonetta; Callegari, Donatella; Incerti, Matteo; Pala, Daniele; Giorgio, Carmine; Brunetti, Jlenia; Bracci, Luisa; Vicini, Paola; Barocelli, Elisabetta; Capoferri, Luigi; Rivara, Silvia; Tognolini, Massimiliano; Mor, Marco; Lodola, Alessio

    2016-06-06

    The free-energy surface (FES) of protein-ligand binding contains information useful for drug design. Here we show how to exploit a free-energy minimum of a protein-ligand complex identified by metadynamics simulations to design a new EphA2 antagonist with improved inhibitory potency.

  12. The Jones-Ray effect reinterpreted: Surface tension minima of low ionic strength electrolyte solutions are caused by electric field induced water-water correlations

    NASA Astrophysics Data System (ADS)

    Okur, H. I.; Chen, Y.; Wilkins, D. M.; Roke, S.

    2017-09-01

    The surface tension of electrolyte solutions exhibits a minimum at millimolar electrolyte concentrations and then rises with increasing concentration. This minimum, known as the Jones-Ray effect, has been hotly debated over the past ∼80 years. If not considered as an artifact, it is typically ascribed to a phenomenological rare binding site for ions or ion pairs. Here, we propose an alternative underlying mechanism, namely that the hydrogen bond network of water responds to the collective electrostatic field of ions by increasing its orientational order, supported by recent surface tension measurements of NaCl solutions in H2O and D2O, and second harmonic scattering experiments in combination with ion resonant second harmonic reflection experiments. Recent thermodynamic and purely electrostatic treatments of the surface tension provide support for this interpretation. In addition, concerns related to possible artifacts influencing the measurements are quantified experimentally.

  13. Bromine enrichment in marsh sediments as a marker of environmental changes driven by Grand Solar Minima and anthropogenic activity (Caminha, NW of Portugal).

    PubMed

    Moreno, J; Fatela, F; Leorri, E; Araújo, M F; Moreno, F; De la Rosa, J; Freitas, M C; Valente, T; Corbett, D R

    2015-02-15

    A sediment core collected in Caminha tidal marsh, NW Portugal, was used to assess bromine (Br) signal over the last ca. 1,700 years. The Br temporal variability reflects its close relationship with soil/sediment organic matter (OM) and also alterations in Br biogeochemical recycling in marsh environment. The highest Br enrichment in sediments was found during the Maunder Solar Minimum, a major solar event characterized by lower irradiance (TSI) and temperature, increased cloudiness and albedo. The obtained results suggest that those climate-induced changes weakened the natural mechanisms that promote Br biochemical transformations, driven by both living plants metabolism and plant litter degradation, with the ensuing generation of volatile methyl bromide (CH3Br). It seems that the prevailing climate conditions during the Maunder favoured the retention of more Br in marsh ecosystem, ultimately decreasing the biogenic Br emissions to the atmosphere. During the 20th century, the Br pattern in sediments appears to mirror likewise anthropogenic sources. The significant correlation (p<0.05) between Br/OM ratios and Pb contents in sediments after 1934 suggests a common source. This is most probably related with the rise, massive consumption and prohibition of leaded gasoline, where ethylene dibromide was added as lead scavenger to antiknock mixtures. More regionally, the concerted use of flame retardants on forest fire management, covering the 1980s through mid-1990s in the north of Portugal and Galicia, could be responsible for the observed increase of sediment Br (relatively to Pb) pool of this tidal marsh. Although man-made brominated compounds are being phased-out since the inception of the 1992 Montreal Protocol, the Caminha tidal marsh sedimentary record showed that Br levels only started to decline after 2002.

  14. He II λ4686 Emission from the Massive Binary System in η Car: Constraints to the Orbital Elements and the Nature of the Periodic Minima

    NASA Astrophysics Data System (ADS)

    Teodoro, M.; Damineli, A.; Heathcote, B.; Richardson, N. D.; Moffat, A. F. J.; St-Jean, L.; Russell, C.; Gull, T. R.; Madura, T. I.; Pollard, K. R.; Walter, F.; Coimbra, A.; Prates, R.; Fernández-Lajús, E.; Gamen, R. C.; Hickel, G.; Henrique, W.; Navarete, F.; Andrade, T.; Jablonski, F.; Luckas, P.; Locke, M.; Powles, J.; Bohlsen, T.; Chini, R.; Corcoran, M. F.; Hamaguchi, K.; Groh, J. H.; Hillier, D. J.; Weigelt, G.

    2016-03-01

    Eta Carinae (η Car) is an extremely massive binary system in which rapid spectrum variations occur near periastron. Most notably, near periastron the He ii λ4686 line increases rapidly in strength, drops to a minimum value, then increases briefly before fading away. To understand this behavior, we conducted an intense spectroscopic monitoring of the He ii λ4686 emission line across the 2014.6 periastron passage using ground- and space-based telescopes. Comparison with previous data confirmed the overall repeatability of the line equivalent width (EW), radial velocities, and the timing of the minimum, though the strongest peak was systematically larger in 2014 than in 2009 by 26%. The EW variations, combined with other measurements, yield an orbital period of 2022.7 ± 0.3 days. The observed variability of the EW was reproduced by a model in which the line flux primarily arises at the apex of the wind-wind collision and scales inversely with the square of the stellar separation, if we account for the excess emission as the companion star plunges into the hot inner layers of the primary’s atmosphere, and including absorption from the disturbed primary wind between the source and the observer. This model constrains the orbital inclination to 135°-153°, and the longitude of periastron to 234°-252°. It also suggests that periastron passage occurred on {T}0=2456874.4\\quad (+/- 1.3 days). Our model also reproduced EW variations from a polar view of the primary star as determined from the observed He ii λ 4686 emission scattered off the Homunculus nebula. Based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program numbers 11506, 12013, 12508, 12750, and 13054. Support for program numbers 12013, 12508, and 12750 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

  15. Temperature minima in the average thermal structure of the middle mesosphere (70 - 80 km) from analysis of 40- to 92-km SME global temperature profiles

    NASA Technical Reports Server (NTRS)

    Clancy, R. Todd; Rusch, David W.; Callan, Michael T.

    1994-01-01

    Global temperatures have been derived for the upper stratosphere and mesosphere from analysis of Solar Mesosphere Explorer (SME) limb radiance profiles. The SME temperature represent fixed local time observations at 1400 - 1500 LT, with partial zonal coverage of 3 - 5 longitudes per day over the 1982-1986 period. These new SME temperatures are compared to the COSPAR International Ionosphere Reference Atmosphere 86 (CIRA 86) climatology (Fleming et al., 1990) as well as stratospheric and mesospheric sounder (SAMS); Barnett and Corney, 1984), National Meteorological Center (NMC); (Gelman et al., 1986), and individual lidar and rocket observations. Significant areas of disagreement between the SME and CIRA 86 mesospheric temperatures are 10 K warmer SME temperatures at altitudes above 80 km. The 1981-1982 SAMS temperatures are in much closer agreement with the SME temperatures between 40 and 75 km. Although much of the SME-CIRA 86 disagreement probably stems from the poor vertical resolution of the observations comprising the CIRA 86 modelm, some portion of the differences may reflect 5- to 10-year temporal variations in mesospheric temperatures. The CIRA 86 climatology is based on 1973-1978 measurements. Relatively large (1 K/yr) 5- to 10-year trends in temperatures as functions of longitude, latitude, and altitude have been observed for both the upper stratosphere (Clancy and Rusch, 1989a) and mesosphere (Clancy and Rusch, 1989b; Hauchecorne et al., 1991). The SME temperatures also exhibit enhanced amplitudes for the semiannual oscillation (SAO) of upper mesospheric temperatures at low latitudes, which are not evident in the CIRA 86 climatology. The so-called mesospheric `temperature inversions' at wintertime midlatitudes, which have been observed by ground-based lidar (Hauschecorne et al., 1987) and rocket in situ measurements (Schmidlin, 1976), are shown to be a climatological aspect of the mesosphere, based on the SME observations.

  16. Macroalage as a source of alpha-glucosidase inhibitors

    NASA Astrophysics Data System (ADS)

    Li, Xiancui; Niu, Rongli; Fan, Xiao; Han, Lijun; Zhang, Lixin

    2005-09-01

    Alpha-glucosidase inhibitors were screened from organic solvent extracts of macroalgae by a spectrophotometrical method with p-nitrophenyl-D-glucopyranosidase as the substrate. The result indicates that organic crude extracts from some macroalgae such as Rhodomela confervoides (Huds.) Silva, Gracilaria textorii (Suringar) De Toni, Plocamium telfairiae Harv., Dictyopteris divaricata (Okam.) Okam, Ulval pertusa and Enteromorpha intestinalis (L.) Link et al. show strong inhibitory activity of alpha-glucosidase at concentration of 79.6 μg/ml.

  17. New Ulvaceae (Ulvophyceae, Chlorophyta) from mesophotic ecosystems across the Hawaiian Archipelago.

    PubMed

    Spalding, Heather L; Conklin, Kimberly Y; Smith, Celia M; O'Kelly, Charles J; Sherwood, Alison R

    2016-02-01

    Ulvalean algae (Chlorophyta) are most commonly described from intertidal and shallow subtidal marine environments worldwide, but are less well known from mesophotic environments. Their morphological simplicity and phenotypic plasticity make accurate species determinations difficult, even at the generic level. Here, we describe the mesophotic Ulvales species composition from 13 locations across 2,300 km of the Hawaiian Archipelago. Twenty-eight representative Ulvales specimens from 64 to 125 m depths were collected using technical diving, submersibles, and remotely operated vehicles. Morphological and molecular characters suggest that mesophotic Ulvales in Hawaiian waters form unique communities comprising four species within the genera Ulva and Umbraulva, each with discrete geographic and/or depth-related distributional patterns. Three genetically distinct taxa are supported by both plastid (rbcL and tufA) and nuclear (ITS1) markers, and are presented here as new species: Umbraulva kaloakulau, Ulva ohiohilulu, and Ulva iliohaha. We also propose a new Umbraulva species (Umbraulva kuaweuweu), which is closely related to subtidal records from New Zealand and Australia, but not formally described. To our knowledge, these are the first marine species descriptions from Hawai'i resulting from the collaboration of traditional Hawaiian nomenclature specialists, cultural practitioners and scientists. The difficulty of finding reliable diagnostic morphological characters for these species reflects a common problem worldwide of achieving accurate identification of ulvalean taxa using solely morphological criteria. Mesophotic Ulvales appear to be distinct from shallow-water populations in Hawai'i, but their degree of similarity to mesophotic floras in other locations in the Pacific remains unknown.

  18. A consensus secondary structure of ITS2 in the chlorophyta identified by phylogenetic reconstruction.

    PubMed

    Caisová, Lenka; Marin, Birger; Melkonian, Michael

    2013-07-01

    The definition of species plays a pivotal role in biology. It has been proposed that Compensatory Base Changes (CBCs) in the fast-evolving Internal Transcribed Spacer 2 (ITS2) correlate with speciation and thus can be used to distinguish species. The applicability of CBC - based species concepts using ITS2, however, rests on the homology of the investigated ITS2 positions. We studied the ITS2 molecule of 147 strains of Chlorophyceae (Chlorophyta, Viridiplantae) including 26 new sequences in the order Chaetophorales, and compared their secondary structures to ITS2 in the sister class Ulvophyceae, represented by the order Ulvales. Using a phylogenetic/comparative approach, it was possible to identify 1) the first consensus structure model of the ITS2 molecule that can be applied to two classes of green algae [Ulvophyceae (Ulvales), Chlorophyceae] and 2) landmarks (the spacer regions separating the ITS2 Helices) for more robust prediction of the secondary structures in green algae. Moreover, we found that CBCs in homologous positions in these 147 strains (representing 115 validly described species) are either completely absent or mostly associated with internal branches representing higher order taxonomic levels (genera, families, orders). As reported for the Ulvales, CBCs are not diagnostic at the species level in the dataset used.

  19. Tracking Performance Requirements for Tracking Performance Requirements for Rotorcraft Instrument Approaches to Reduced Minima. Phase 1. Preliminary Study (Exigences Relatives Aux Performances De Suivi D’Approche Aux Instruments D’Un Giravion Afin De Reduire Les)

    DTIC Science & Technology

    1991-02-01

    A l’a~ronautique jug~es importantes, completes et durables en termes de contribution aux connaissances actuelles. CAHIERS D’AERONAUTIQUE (AN...83 large overshoot of pad (50 + feet); late in power application 84 past pad by 10 feet; large flare 85 stopped short - taxied to pad 86 50-75 foot

  20. Specific heat to Hc2: Evidence for nodes or deep minima in the superconducting gap of underdoped and overdoped Ba(Fe1–xCox)₂As₂

    DOE PAGES

    Kim, J. S.; Faeth, B. D.; Wang, Y.; ...

    2012-07-13

    Low-temperature specific heat, C, in magnetic fields up to Hc2 is reported for underdoped Ba(Fe₀.₉₅₅Co₀.₀₄₅)₂As₂ (Tc = 8 K) and for three overdoped samples Ba(Fe₁₋xCox)₂As₂ (x = 0.103, 0.13, and 0.15; Tc = 17.2, 16.5, and 11.7 K, respectively). Previous measurements of thermal conductivity (as a function of temperature and field) and penetration depth on comparable-composition samples gave some disagreement as to whether there was fully gapped/nodal behavior in the under-/overdoped materials, respectively. The present work shows that the measured behavior of the specific heat γ (∝C/T as T → 0, i.e., a measure of the electronic density of statesmore » at the Fermi energy) as a function of field approximately obeys γ ∝ H0.5±0.1, similar to the Volovik effect for nodal superconductors, for both the underdoped and the most overdoped Co samples. However, for the two overdoped compositions x = 0.103 and 0.13, the low-field (H ≤ 10 T) data show a Volovik-like behavior of γ ∝ H0.3–0.4, followed by an inflection point, followed at higher fields by γ ∝ H¹. We argue that, within the two-band theory of superconductivity, an inflection point may occur if the interband coupling is dominant.« less

  1. Specific heat to Hc2: Evidence for nodes or deep minima in the superconducting gap of underdoped and overdoped Ba(Fe1–xCox)₂As₂

    SciTech Connect

    Kim, J. S.; Faeth, B. D.; Wang, Y.; Hirschfeld, P. J.; Stewart, G. R.; Gofryk, K.; Ronning, F.; Sefat, A. S.; Choi, K. Y.; Kim, K. H.

    2012-07-13

    Low-temperature specific heat, C, in magnetic fields up to Hc2 is reported for underdoped Ba(Fe₀.₉₅₅Co₀.₀₄₅)₂As₂ (Tc = 8 K) and for three overdoped samples Ba(Fe₁₋xCox)₂As₂ (x = 0.103, 0.13, and 0.15; Tc = 17.2, 16.5, and 11.7 K, respectively). Previous measurements of thermal conductivity (as a function of temperature and field) and penetration depth on comparable-composition samples gave some disagreement as to whether there was fully gapped/nodal behavior in the under-/overdoped materials, respectively. The present work shows that the measured behavior of the specific heat γ (∝C/T as T → 0, i.e., a measure of the electronic density of states at the Fermi energy) as a function of field approximately obeys γ ∝ H0.5±0.1, similar to the Volovik effect for nodal superconductors, for both the underdoped and the most overdoped Co samples. However, for the two overdoped compositions x = 0.103 and 0.13, the low-field (H ≤ 10 T) data show a Volovik-like behavior of γ ∝ H0.3–0.4, followed by an inflection point, followed at higher fields by γ ∝ H¹. We argue that, within the two-band theory of superconductivity, an inflection point may occur if the interband coupling is dominant.

  2. Comparative Magnetic Minima: Characterizing Quiet Times in the Sun and Stars. Symposium of the International Astronomical Union (286th) Held in Mendoza, Argentina on October 3-7, 2011

    DTIC Science & Technology

    2011-10-01

    Magnetic Turbulent Outer Scale María Emilia Ruiz, S. Dasso, W.H. Matthaeus, et al. (Presentation file) Wednesday 5 October Session 3 – Comparative Solar...53. Joern Warnecke 85. Daniel Gómez 22. Lurdes Mart́ınez Meneses 54. John Linker 86. Maŕıa Emilia Ruiz 23. Lois Linsky 55. Dmitry Sokoloff 87. Ramon

  3. Temporal variation of green macroalgal assemblage on Porphyra aquaculture rafts in the Subei Shoal, China

    NASA Astrophysics Data System (ADS)

    Fan, Shiliang; Fu, Mingzhu; Wang, Zongling; Zhang, Xuelei; Song, Wei; Li, Yan; Liu, Guangxing; Shi, Xiaoyong; Wang, Xiaona; Zhu, Mingyuan

    2015-09-01

    Previous studies showed that Ulva prolifera caused green tides in the Yellow Sea were very possible from the facilities of Porphyra aquaculture. To confirm the origin of green algae, the assemblage of fouling macroalgae growing on rafts were investigated from early March to the middle of May across the growing season. The results showed that the fouling green macroalgae increased rapidly and reached to the maximum in biomass during mid-May. Six species, including Blidingia sp., U. prolifera, Ulva linza, Ulva compressa, Ulva intestinalis and Ulva clathrata were identified from the rafts. In early March, the dominant species were U. compressa, U. intestinalis and U. clathrata; while they shifted to Blidingia sp. and U. prolifera in late March to middle May. This study indicated that the changes in sea temperature might affect the nutrient uptake rate of the green macroalgae, and then affect the temporal variation in the raft-fouling green macroalgae. The biomass of U. prolifera was sufficient to seed a massive green tides, based on its high growth rate.

  4. Investigations on the feeding habits of the rocky-shore mite Hyadesia fusca (Acari: Astigmata: Hyadesiidae): diet range, food preference, food quality, and the implications for distribution patterns

    NASA Astrophysics Data System (ADS)

    Bücking, Jens

    1998-06-01

    Within the food web of estuarine and marine rocky shore ecosystems phytophagous mites of terrestrial and marine origin constitute an important part as grazers on algae and as a food source for certain arthropods, especially zoophagous mites. This investigation deals with the feeding biology of Hyadesia fusca taking as an example a population located on an artificial rocky shore of the middle Weser estuary in Northern Germany. The species is characterized by a broad diet range; in feeding experiments diatoms, lichens, detritus as well as blue, red and green algae were accepted. Even analyses of faecal pellets produced by field specimen suggest a non-specific feeding habit. However, the influence of certain diets on mortality, offspring number and rearing success showed that the food quality differs significantly. The most suitable food, the Ulvaceae Blidingia, was clearly preferred in a series of pairwise choice tests. These findings correlate with the vertical zonation of the field population i.e.: higher population densities in the vegetation zone dominated by Blidingia. It can be concluded that in addition to abiotic factors food supply could play an important role for distribution patterns of phytophagous mites.

  5. Seasonal variations of vegetation patterns and biomass constituents in the rocky eulittoral of Helgoland

    NASA Astrophysics Data System (ADS)

    Munda, I. M.; Markham, J. W.

    1982-06-01

    Seasonal changes in vegetation patterns and biomass of benthic algae were recorded over a 14-month period in the rocky eulittoral of the North Sea island of Helgoland. The area is characterized by the dominance of Fucus serratus throughout most of the eulittoral and this is reflected in higher biomass of F. serratus ranged seasonally from 4.3 kg to 15 kg m-2 in the center of its extensive distribution. Biomass was also recorded monthly, when the plants were present, for Blidingia spp., Enteromorpha spp., Ulva lactuca, Fucus spiralis, F. vesiculosus, Porphyra linearis, P. umbilicalis, Chondrus crispus, Corallina officinalis, Dumontia incrassata, Petalonia fascia, P. zosterifolia and Scytosiphon lomentaria. New generations of several species which reappeared after a destructive winter storm showed a higher protein content than in the previous year. The winter and early spring flora of Helgoland shows several resemblances in species composition to the summer flora of Scandinavia.

  6. Molecular identification of green algae from the rafts based infrastructure of Porphyra yezoensis.

    PubMed

    Shen, Qi; Li, Hongye; Li, Yan; Wang, Zongling; Liu, Jiesheng; Yang, Weidong

    2012-10-01

    To provide more information on the origin of the Ulva prolifera bloom in Qingdao sea area in China from 2007 to 2011, the diversity of green algae growing on the rafts of Porphyra yezoensis on the coast in Jiangsu Province was investigated based on ITS, rbcL and 5S sequences. Eighty-four of green algal samples from various sites and cruises in 2010 and 2011 were collected. According to ITS and rbcL sequences, samples from the rafts of P. yezoensis fell into four clades: Ulva linza-procera-prolifera (LPP) complex, Ulva flexuosa, Blidingia sp. and Urospora spp. However, based on the 5S rDNA, a more resolved DNA marker, only one of the 84 samples belonged to U. prolifera. Combined with the previous reports, it is likely that U. prolifera bloom in Qingdao sea area might consist of more than one origin, and Porphyra cultivation rafts might be one of the causes.

  7. Effects of temperature on the germination of green algae micro-propagules in coastal waters of the Subei Shoal, China

    NASA Astrophysics Data System (ADS)

    Song, Wei; Peng, Keqin; Xiao, Jie; Li, Yan; Wang, Zongling; Liu, Xiangqing; Fu, Mingzhu; Fan, Shiliang; Zhu, Mingyuan; Li, Ruixiang

    2015-09-01

    Since 2007, large-scale green tides that primarily consisted of Ulva prolifera have consecutively invaded the coast of Qingdao (36°06'N, 120°25'E, PR China) in summer. The germination of green algae micro-propagules in the Subei Shoal played a significant role in the formation of these green tides. The change in sea temperature might be the key factor that affects the germination of the micro-propagules because the other environmental factors varied only slightly according to previous studies. This study was designed to investigate the effects of temperature on the germination of micro-propagules via laboratory experiments. The results showed the following: (1) five types of green algae micro-propagules, including U. prolifera, U. linza, U. compressa, Ulva sp. (Clade 6) and Blidingia sp., were detected in the seawater samples collected from the Subei Shoal; (2) at 5 °C, germinated micro-propagules were not detected in any of the samples; at 10 °C, the micro-propagules began to germinate, and the germination quantity markedly changed between 10 °C and 30 °C; (3) the germination numbers of U. prolifera, U. linza, Ulva sp. (Clade 6) and Blidingia sp. were maximized at 15 °C, 10 °C, 25 °C and 20 °C, respectively. This study indicated that the sea temperature played a significant role in the germination of green algae micro-propagules in water and could partly explain the community succession phenomenon of the attached green algae in the Subei Shoal.

  8. The distribution of Elongation Factor-1 Alpha (EF-1alpha), Elongation Factor-Like (EFL), and a non-canonical genetic code in the ulvophyceae: discrete genetic characters support a consistent phylogenetic framework.

    PubMed

    Gile, Gillian H; Novis, Philip M; Cragg, David S; Zuccarello, Giuseppe C; Keeling, Patrick J

    2009-01-01

    The systematics of the green algal class Ulvophyceae have been difficult to resolve with ultrastructural and molecular phylogenetic analyses. Therefore, we investigated relationships among ulvophycean orders by determining the distribution of two discrete genetic characters previously identified only in the order Dasycladales. First, Acetabularia acetabulum uses the core translation GTPase Elongation Factor 1alpha (EF-1alpha) while most Chlorophyta instead possess the related GTPase Elongation Factor-Like (EFL). Second, the nuclear genomes of dasycladaleans A. acetabulum and Batophora oerstedii use a rare non-canonical genetic code in which the canonical termination codons TAA and TAG instead encode glutamine. Representatives of Ulvales and Ulotrichales were found to encode EFL, while Caulerpales, Dasycladales, Siphonocladales, and Ignatius tetrasporus were found to encode EF-1alpha, in congruence with the two major lineages previously proposed for the Ulvophyceae. The EF-1alpha of I. tetrasporus supports its relationship with Caulerpales/Dasycladales/Siphonocladales, in agreement with ultrastructural evidence, but contrary to certain small subunit rRNA analyses that place it with Ulvales/Ulotrichales. The same non-canonical genetic code previously described in A. acetabulum was observed in EF-1alpha sequences from Parvocaulis pusillus (Dasycladales), Chaetomorpha coliformis, and Cladophora cf. crinalis (Siphonocladales), whereas Caulerpales use the universal code. This supports a sister relationship between Siphonocladales and Dasycladales and further refines our understanding of ulvophycean phylogeny.

  9. A close-up view on ITS2 evolution and speciation - a case study in the Ulvophyceae (Chlorophyta, Viridiplantae)

    PubMed Central

    2011-01-01

    Background The second Internal Transcriber Spacer (ITS2) is a fast evolving part of the nuclear-encoded rRNA operon located between the 5.8S and 28S rRNA genes. Based on crossing experiments it has been proposed that even a single Compensatory Base Change (CBC) in helices 2 and 3 of the ITS2 indicates sexual incompatibility and thus separates biological species. Taxa without any CBC in these ITS2 regions were designated as a 'CBC clade'. However, in depth comparative analyses of ITS2 secondary structures, ITS2 phylogeny, the origin of CBCs, and their relationship to biological species have rarely been performed. To gain 'close-up' insights into ITS2 evolution, (1) 86 sequences of ITS2 including secondary structures have been investigated in the green algal order Ulvales (Chlorophyta, Viridiplantae), (2) after recording all existing substitutions, CBCs and hemi-CBCs (hCBCs) were mapped upon the ITS2 phylogeny, rather than merely comparing ITS2 characters among pairs of taxa, and (3) the relation between CBCs, hCBCs, CBC clades, and the taxonomic level of organisms was investigated in detail. Results High sequence and length conservation allowed the generation of an ITS2 consensus secondary structure, and introduction of a novel numbering system of ITS2 nucleotides and base pairs. Alignments and analyses were based on this structural information, leading to the following results: (1) in the Ulvales, the presence of a CBC is not linked to any particular taxonomic level, (2) most CBC 'clades' sensu Coleman are paraphyletic, and should rather be termed CBC grades. (3) the phenetic approach of pairwise comparison of sequences can be misleading, and thus, CBCs/hCBCs must be investigated in their evolutionary context, including homoplasy events (4) CBCs and hCBCs in ITS2 helices evolved independently, and we found no evidence for a CBC that originated via a two-fold hCBC substitution. Conclusions Our case study revealed several discrepancies between ITS2 evolution in the

  10. Circadian Rhythms of Chloroplast Orientation and Photosynthetic Capacity in Ulva123

    PubMed Central

    Britz, Steven J.; Briggs, Winslow R.

    1976-01-01

    Ulva lactuca L. var. latissima (L.) Decandolle and var. rigida (C. Agardh) Le Jolis and U. mutabilis Foyn have a circadian rhythm of chloroplast orientation which results in large changes in the light-absorption properties of the thallus. During the day, the chloroplasts cover the outer face of the cells and absorbance is high. At night, the chloroplasts are along the side walls and absorbance is low. Enteromorpha linza (L.) J. Agardh, E. intestinalis (L.) Link, E. sp., and Monostroma grevillei (Thuret) Wittrock, members of the Ulvales, were not observed to have this rhythmic movement. Chloroplasts, when in the face position, could not be induced to move to the sides by high intensity light up to 80,000 lux. Unrelated to chloroplast position per se and light-absorption efficiency, there is a rhythm of photosynthetic capacity which peaks just before midday and which continues in constant darkness. Images PMID:16659613

  11. Expression of genes involved in redox homeostasis and antioxidant defense in a marine macroalga Ulva fasciata by excess copper.

    PubMed

    Wu, Tsung-Meng; Hsu, Yuan-Ting; Sung, Ming-Shiuan; Hsu, Yi-Ting; Lee, Tse-Min

    2009-10-04

    The expression of genes involved in the control of redox homeostasis and antioxidant defense was studied in macroalga Ulva fasciata Delile in response to 5 and 50 microM CuSO(4). Redox-related genes, methionine sulfoxide reductase A (UfMsrA), thioredoxin (UfTrx), cyclophilin (UfCyp), and ferritin (UfFer) that were up-regulated by excess Cu [Wu, T.M., Lee, T.M., 2008. Regulation of activity and gene expression of antioxidant enzymes in Ulva fasciata Delile (Ulvales, Chlorophyta) in response to excess copper. Phycologia 47, 346-360] were cloned and their expression was compared to superoxide dismutase (UfMnsod and UfFesod), ascorbate peroxidase (UfApx), glutathione reductase (UfGr), and catalase (UfCat). Transcripts of UfMsrA, UfCyp, and UfFer were increased by excess Cu with a peak at 3h and that of UfTrx increased after 6-9h, but not affected by 4-day exposure to excess Cu, except an increase in UfMsrA transcript. Transcripts of UfMnsod, UfFesod, UfApx, UfGr and UfCat can be increased by 4-day exposure to Cu excess [Wu, T.M., Lee, T.M., 2008. Regulation of activity and gene expression of antioxidant enzymes in Ulva fasciata Delile (Ulvales, Chlorophyta) in response to excess copper. Phycologia 47, 346-360] but not by short-term excess Cu treatment, except UfGr whose transcript increased after 3h. Reactive oxygen species involved in up-regulation of antioxidant defense enzymes genes. These results suggest that the expression of genes of antioxidant defense enzymes and UfMsrA are associated with long-term adaptation of U. fasciata to Cu excess and transcription of redox-related genes and UfGr is up-regulated for short-term acclimation.

  12. Mitochondrion-to-Chloroplast DNA Transfers and Intragenomic Proliferation of Chloroplast Group II Introns in Gloeotilopsis Green Algae (Ulotrichales, Ulvophyceae).

    PubMed

    Turmel, Monique; Otis, Christian; Lemieux, Claude

    2016-09-19

    To probe organelle genome evolution in the Ulvales/Ulotrichales clade, the newly sequenced chloroplast and mitochondrial genomes of Gloeotilopsis planctonica and Gloeotilopsis sarcinoidea (Ulotrichales) were compared with those of Pseudendoclonium akinetum (Ulotrichales) and of the few other green algae previously sampled in the Ulvophyceae. At 105,236 bp, the G planctonica mitochondrial DNA (mtDNA) is the largest mitochondrial genome reported so far among chlorophytes, whereas the 221,431-bp G planctonica and 262,888-bp G sarcinoidea chloroplast DNAs (cpDNAs) are the largest chloroplast genomes analyzed among the Ulvophyceae. Gains of non-coding sequences largely account for the expansion of these genomes. Both Gloeotilopsis cpDNAs lack the inverted repeat (IR) typically found in green plants, indicating that two independent IR losses occurred in the Ulvales/Ulotrichales. Our comparison of the Pseudendoclonium and Gloeotilopsis cpDNAs offered clues regarding the mechanism of IR loss in the Ulotrichales, suggesting that internal sequences from the rDNA operon were differentially lost from the two original IR copies during this process. Our analyses also unveiled a number of genetic novelties. Short mtDNA fragments were discovered in two distinct regions of the G sarcinoidea cpDNA, providing the first evidence for intracellular inter-organelle gene migration in green algae. We identified for the first time in green algal organelles, group II introns with LAGLIDADG ORFs as well as group II introns inserted into untranslated gene regions. We discovered many group II introns occupying sites not previously documented for the chloroplast genome and demonstrated that a number of them arose by intragenomic proliferation, most likely through retrohoming. © The Author 2016. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

  13. Kepler-Daten von BR Cyg

    NASA Astrophysics Data System (ADS)

    Pagel, Lienhard

    2015-01-01

    In the Kepler field is the eclipsing binary BR Cyg. He is a BAV program star. In the KIC (Kepler Input Catalogue) he is associated with the identifier kplr009899416 [1]. There have been determined 1084 minima and as many secondary minima. Acknowledgement: This paper makes use of data from the Kepler exoplanetarchive.

  14. Development of a fluorescence in situ hybridization (FISH) method for rapid detection of Ulva prolifera

    NASA Astrophysics Data System (ADS)

    Zhang, Qing-Chun; Liu, Qing; Kang, Zhen-Jun; Yu, Ren-Cheng; Yan, Tian; Zhou, Ming-Jiang

    2015-09-01

    Large-scale green tides have occurred consecutively since 2007 in the Yellow Sea (YS), China. The dominant causative species of the green tides has been identified as Ulva prolifera. The origin of green tides in the YS has been traced back to the Subei Shoal based on the results of remote-sensing, numerical simulations and field investigations. However, it is difficult to study the early development of green tides in the Subei Shoal because of the mixture of multiple green algae and the morphological diversity of U. prolifera when under variable environmental conditions. In this study, a rapid and accurate fluorescence in situ hybridization (FISH) method was developed to detect U. prolifera from the community of green algae targeting the 5S rDNA spacer region of U. prolifera. Two specific probes, 5S-1 and 5S-2, were designed based on the sequences of the 5S rDNA spacer regions of U. prolifera, Ulva linza and Ulva flexuosa. Specificity of the FISH method was tested using the six species of green algae commonly occurring in the Subei Shoal, including U. prolifera, U. linza, U. flexuosa, Ulva compressa, Ulva pertusa and Blidingia sp. The results showed that only U. prolifera could be labeled with both probes. Probe 5S-1, which showed a much higher labeling efficiency on U. prolifera, was ultimately selected as the probe for the FISH detection. The sample preparation method was optimized, particularly for the mature green algae, by the addition of cellulase and proteinase K in the pre-hybridization solution. Labeling efficiency with the probe 5S-1 reached 96% on average under the optimized conditions. The successful development of the FISH method has been applied to qualitative and quantitative analysis of field samples collected from the YS, and the results indicate a potential use in future green algae studies.

  15. Sequences and phylogeny analysis of rbcL gene in marine chlorophyta

    NASA Astrophysics Data System (ADS)

    Shen, Songdong; Li, Yanyan; Wu, Xunjian; Ding, Lanping

    2010-06-01

    The rbcL gene of Ulva pertusa, Enteromorpha prolifera and Monostroma grevillei was amplified, sequenced and analyzed. By comparing the rbcL sequences with seven other Ulvales species retrieved from GenBank, the sequence divergences and the phyletic evolution were analyzed and the phylogenetic tree was constructed. From the phylogenetic tree, it can be found that U. pertusa, E. prolifera and U. californica group in one branch, while E. compressa, U. rigida and U. fenestrata cluster in another clade. Obviously, unlike the Enteomorpha species, the Ulva species do not gather in one branch. Therefore Ulva and Enteomorpha might be affiliates of one genus. E. compressa and E. intestinalis gathered together, which coincided with the morphological characters. However, the thallus of U. pertusa is thick and with many holes, which is different from E. prolifera in morphology. They cluster together in the phylogenetic tree with a genetic distance of 0.005. The results indicate that Ulva and Enteromorpha are not distinguished strictly.

  16. Reconstructing the Phylogeny of Capsosiphon fulvescens (Ulotrichales, Chlorophyta) from Korea Based on rbcL and 18S rDNA Sequences.

    PubMed

    Sun, Sang-Mi; Yang, Seung Hwan; Golokhvast, Kirill S; Le, Bao; Chung, Gyuhwa

    2016-01-01

    Capsosiphon fulvescens is a filamentous green algae in the class Ulvophyceae. It has been consumed as food with unique flavor and soft texture to treat stomach disorders and hangovers, and its economic value justifies studying its nutritional and potential therapeutic effects. In contrast to these applications, only a few taxonomic studies have been conducted on C. fulvescens. In particular, classification and phylogenetic relationships of the C. fulvescens below the order level are controversial. To determine its phylogenetic position in the class, we used rbcL and 18S rDNA sequences as molecular markers to construct phylogenetic trees. The amplified rbcL and 18S rDNA sequences from 4 C. fulvescens isolates (Jindo, Jangheung, Wando, and Koheung, Korea) were used for phylogenetic analysis by employing three different phylogenetic methods: neighbor joining (NJ), maximum parsimony (MP), and maximum likelihood (ML). The rbcL phylogenetic tree showed that all taxa in the order Ulvales were clustered as a monophyletic group and resolved the phylogenetic position of C. fulvescens in the order Ulotrichales. The significance of our study is that the 18S rDNA phylogenetic tree shows the detailed taxonomic position of C. fulvescens. In our result, C. fulvescens is inferred as a member of Ulotrichaceae, along with Urospora and Acrosiphonia.

  17. Comparison of chlorophyll and photosynthesis parameters of floating and attached Ulva prolifera.

    PubMed

    Lin, Apeng; Shen, Songdong; Wang, Guangce; Yi, Qianqian; Qiao, Hongjin; Niu, Jianfeng; Pan, Guanghua

    2011-01-01

    In mid-May 2008 a serious green tide caused mainly by floating Ulva prolifera (Müller) J. Agardh (Chlorophyta, Ulvales) thalli struck the coastal area of Qingdao, China. To understand the present physiological conditions of the floating alga, in this work both laboratory and field investigations were conducted on the floating U. prolifera thalli in comparison with the attached U. prolifera thalli collected from the area. The floating thalli of three distinctively different colors and attached thalli at three different stages of sporangium formation process were characterized under a microscope, while their photosynthetic parameters were determined with chlorophyll fluorescence technology. On the other hand, the sporangium formation status of the floating U. prolifera thalli was surveyed both in the laboratory and in the field. Comparisons showed that both of the paired morphological characteristics and the paired physiological parameters of the floating and attached U. prolifera thalli were consistent. Furthermore, some spores were confirmed in the field and some motile particles were found within the floating thalli. These results suggest that the floating U. prolifera thalli with different colors could be at different stages of sporangium formation. However, our results also showed that the floating alga thalli have only a limited reproductive potential. This might limit the duration and the further geographic expansion of the green algal bloom.

  18. New Family of Ulvan Lyases Identified in Three Isolates from the Alteromonadales Order*

    PubMed Central

    Kopel, Moran; Helbert, William; Belnik, Yana; Buravenkov, Vitaliy; Herman, Asael; Banin, Ehud

    2016-01-01

    Ulvan is the main polysaccharide component of the Ulvales (green seaweed) cell wall. It is composed of disaccharide building blocks comprising 3-sulfated rhamnose linked to d-glucuronic acid (GlcUA), l-iduronic acid (IdoUA), or d-xylose (Xyl). The degradation of ulvan requires ulvan lyase, which catalyzes the endolytic cleavage of the glycoside bond between 3-sulfated rhamnose and uronic acid according to a β-elimination mechanism. The first characterized ulvan lyase was identified in Nonlabens ulvanivorans, an ulvanolytic bacterial isolate. In the current study, we have identified and biochemically characterized novel ulvan lyases from three Alteromonadales isolated bacteria. Two homologous ulvan lyases (long and short) were found in each of the bacterial genomes. The protein sequences have no homology to the previously reported ulvan lyases and therefore are the first representatives of a new family of polysaccharide lyases. The enzymes were heterologously expressed in Escherichia coli to determine their mode of action. The heterologous expressed enzymes were secreted into the milieu subsequent to their signal sequence cleavage. An endolytic mode of action was observed and studied using gel permeation chromatography and 1H NMR. In contrast to N. ulvanivorans ulvan lyase, cleavage occurred specifically at the GlcUA residues. In light of the genomic context and modular structure of the ulvan lyase families identified to date, we propose that two ulvan degradation pathways evolved independently. PMID:26763234

  19. Alternative Electron Transports Participate in the Maintenance of Violaxanthin De-Epoxidase Activity of Ulva sp. under Low Irradiance

    PubMed Central

    Xie, Xiujun; Gu, Wenhui; Gao, Shan; Lu, Shan; Li, Jian; Pan, Guanghua; Wang, Guangce; Shen, Songdong

    2013-01-01

    The xanthophyll cycle (Xc), which involves violaxanthin de-epoxidase (VDE) and the zeaxanthin epoxidase (ZEP), is one of the most rapid and efficient responses of plant and algae to high irradiance. High light intensity can activate VDE to convert violaxanthin (Vx) to zeaxanthin (Zx) via antheraxanthin (Ax). However, it remains unclear whether VDE remains active under low light or dark conditions when there is no significant accumulation of Ax and Zx, and if so, how the ΔpH required for activation of VDE is built. In this study, we used salicylaldoxime (SA) to inhibit ZEP activity in the intertidal macro-algae Ulva sp. (Ulvales, Chlorophyta) and then characterized VDE under low light and dark conditions with various metabolic inhibitors. With inhibition of ZEP by SA, VDE remained active under low light and dark conditions, as indicated by large accumulations of Ax and Zx at the expense of Vx. When PSII-mediated linear electron transport systems were completely inhibited by SA and DCMU, alternative electron transport systems (i.e., cyclic electron transport and chlororespiration) could maintain VDE activity. Furthermore, accumulations of Ax and Zx decreased significantly when SA, DCMU, or DBMIB together with an inhibitor of chlororespiration (i.e., propyl gallate (PG)) were applied to Ulva sp. This result suggests that chlororespiration not only participates in the build-up of the necessary ΔpH, but that it also possibly influences VDE activity indirectly by diminishing the oxygen level in the chloroplast. PMID:24250793

  20. Ubiquitous mechanisms of energy dissipation in noncontact atomic force microscopy.

    PubMed

    Ghasemi, S Alireza; Goedecker, Stefan; Baratoff, Alexis; Lenosky, Thomas; Meyer, Ernst; Hug, Hans J

    2008-06-13

    Atomistic simulations considering larger tip structures than hitherto assumed reveal novel dissipation mechanisms in noncontact atomic force microscopy. The potential energy surfaces of realistic silicon tips exhibit many energetically close local minima that correspond to different structures. Most of them easily deform, thus causing dissipation arising from hysteresis in force versus distance characteristics. Furthermore, saddle points which connect local minima can suddenly switch to connect different minima. Configurations driven into metastability by the tip motion can thus suddenly access lower energy structures when thermal activation becomes allowed within the time required to detect the resulting average dissipation.

  1. Structural evolution of nucleobase clusters using force field models and density functional theory

    NASA Astrophysics Data System (ADS)

    Chiriki, Siva; Dagar, Anuradha; Bulusu, Satya S.

    2015-08-01

    We report global minima for all nucleobase clusters (nucleobase)n, with 2 ≤ n ≤ 4. The global minima are predicted using force field based global optimization methods followed by local optimizations using the dispersion corrected DFT method. In this study, we use both non-polarizable (OPLS-AA) and polarizable (AMOEBA) force fields for global optimization. Here we emphasize on the reliability of AMOEBA force field used for predicting accurate global minima of nucleobase clusters. The average deviation in binding energies using AMOEBA is 3 kcal/mol from the DFT while the average deviation using OPLS-AA is 8 kcal/mol from DFT.

  2. Molecular above-threshold ionization spectra as an evidence of the three-point interference of electron wave packets

    NASA Astrophysics Data System (ADS)

    Hasović, Elvedin; Milošević, Dejan B.; Gazibegović-Busuladžić, Azra; Čerkić, Aner; Busuladžić, Mustafa

    2015-03-01

    We consider high-order above-threshold ionization (HATI) of polyatomic molecules ionized by a strong linearly polarized laser field. Improved molecular strong-field approximation by which the HATI process on polyatomic molecular species can be described is developed. Using this theory we calculate photoelectron angular-energy spectra for different triatomic molecules. Special attention is devoted to the minima that are observed in the calculated high-energy electron spectra of the ozone and carbon dioxide molecules. A key difference between these minima and minima that are observed in the corresponding spectra of diatomic molecules are presented.

  3. Fast Energy Minimization of large Polymers Using Constrained Optimization

    SciTech Connect

    Todd D. Plantenga

    1998-10-01

    A new computational technique is described that uses distance constraints to calculate empirical potential energy minima of partially rigid molecules. A constrained minimuzation algorithm that works entirely in Cartesian coordinates is used. The algorithm does not obey the constraints until convergence, a feature that reduces ill-conditioning and allows constrained local minima to be computed more quickly than unconstrained minima. Computational speedup exceeds the 3-fold factor commonly obtained in constained molecular dynamics simulations, where the constraints must be strictly obeyed at all times.

  4. Apparatus for separating particles utilizing engineered acoustic contrast capture particles

    DOEpatents

    Kaduchak, Gregory [Los Alamos, NM; Ward, Michael D [Los Alamos, NM

    2011-12-27

    An apparatus for separating particles from a medium includes a capillary defining a flow path therein that is in fluid communication with a medium source. The medium source includes engineered acoustic contrast capture particle having a predetermined acoustic contrast. The apparatus includes a vibration generator that is operable to produce at least one acoustic field within the flow path. The acoustic field produces a force potential minima for positive acoustic contrast particles and a force potential minima for negative acoustic contrast particles in the flow path and drives the engineered acoustic contrast capture particles to either the force potential minima for positive acoustic contrast particles or the force potential minima for negative acoustic contrast particles.

  5. Apparatus for separating particles utilizing engineered acoustic contrast capture particles

    DOEpatents

    Kaduchak, Gregory; Ward, Michael D

    2014-10-21

    An apparatus for separating particles from a medium includes a capillary defining a flow path therein that is in fluid communication with a medium source. The medium source includes engineered acoustic contrast capture particle having a predetermined acoustic contrast. The apparatus includes a vibration generator that is operable to produce at least one acoustic field within the flow path. The acoustic field produces a force potential minima for positive acoustic contrast particles and a force potential minima for negative acoustic contrast particles in the flow path and drives the engineered acoustic contrast capture particles to either the force potential minima for positive acoustic contrast particles or the force potential minima for negative acoustic contrast particles.

  6. Apparatus for separating particles utilizing engineered acoustic contrast capture particles

    DOEpatents

    Kaduchak, Gregory; Ward, Michael D

    2016-05-17

    An apparatus for separating particles from a medium includes a capillary defining a flow path therein that is in fluid communication with a medium source. The medium source includes engineered acoustic contrast capture particle having a predetermined acoustic contrast. The apparatus includes a vibration generator that is operable to produce at least one acoustic field within the flow path. The acoustic field produces a force potential minima for positive acoustic contrast particles and a force potential minima for negative acoustic contrast particles in the flow path and drives the engineered acoustic contrast capture particles to either the force potential minima for positive acoustic contrast particles or the force potential minima for negative acoustic contrast particles.

  7. Features of the concentration dependences of the surface tension of water suspensions of bentonites

    NASA Astrophysics Data System (ADS)

    Dadashev, R. Kh.; Dzhambulatov, R. S.; Elimkhanov, D. Z.

    2015-08-01

    The concentration dependence of the surface tension of water suspensions of bentonites is studied experimentally. Possible reasons for the emergence of the minima on isotherms of the surface tensions of dispersed systems are analyzed.

  8. Jan Hudde and the Quotient Rule before Newton and Leibniz

    ERIC Educational Resources Information Center

    Curtin, Daniel J.

    2005-01-01

    This article describes some of the work of Jan Hudde who anticipated some results of calculus. Prior to a career as a Burgomaster of Amsterdam, Hudde engaged in mathematics. His method of finding maxima and minima is especially interesting.

  9. A simple empirical stream flow prediction model for ungauged watersheds

    USDA-ARS?s Scientific Manuscript database

    Knowledge of streamflow is important for estimating groundwater recharge rates, forecasting floods, and designing hydropower structures and irrigation systems. However, many watersheds throughout the developing world remain ungauged. This fact demands a simple hydrological model that requires minima...

  10. A multidimensional generalization of Heilbronn's theorem on the average length of a finite continued fraction

    SciTech Connect

    Illarionov, A A

    2014-03-31

    Heilbronn's theorem on the average length of a finite continued fraction is generalized to the multidimensional case in terms of relative minima of the lattices which were introduced by Voronoy and Minkowski. Bibliography: 21 titles.

  11. Jan Hudde and the Quotient Rule before Newton and Leibniz

    ERIC Educational Resources Information Center

    Curtin, Daniel J.

    2005-01-01

    This article describes some of the work of Jan Hudde who anticipated some results of calculus. Prior to a career as a Burgomaster of Amsterdam, Hudde engaged in mathematics. His method of finding maxima and minima is especially interesting.

  12. Metastable states in homogeneous Ising models

    SciTech Connect

    Achilles, M.; Bendisch, J.; von Trotha, H.

    1987-04-01

    Metastable states of homogeneous 2D and 3D Ising models are studied under free boundary conditions. The states are defined in terms of weak and strict local minima of the total interaction energy. The morphology of these minima is characterized locally and globally on square and cubic grids. Furthermore, in the 2D case, transition from any spin configuration that is not a strict minimum to a strict minimum is possible via non-energy-increasing single flips.

  13. Screw dislocation-induced growth spirals as emissive exciton localization centers in Al-rich AlGaN/AlN quantum wells

    SciTech Connect

    Funato, Mitsuru Banal, Ryan G.; Kawakami, Yoichi

    2015-11-15

    Screw dislocations in Al-rich AlGaN/AlN quantum wells cause growth spirals with an enhanced Ga incorporation, which create potential minima. Although screw dislocations and their surrounding potential minima suggest non-radiative recombination processes within growth spirals, in reality, screw dislocations are not major non-radiative sinks for carriers. Consequently, carriers localized within growth spirals recombine radiatively without being captured by non-radiative recombination centers, resulting in intense emissions from growth spirals.

  14. Differential evolution algorithm for global optimizations in nuclear physics

    NASA Astrophysics Data System (ADS)

    Qi, Chong

    2017-04-01

    We explore the applicability of the differential evolution algorithm in finding the global minima of three typical nuclear structure physics problems: the global deformation minimum in the nuclear potential energy surface, the optimization of mass model parameters and the lowest eigenvalue of a nuclear Hamiltonian. The algorithm works very effectively and efficiently in identifying the minima in all problems we have tested. We also show that the algorithm can be parallelized in a straightforward way.

  15. The complex lightcurve of 1992 NA

    NASA Astrophysics Data System (ADS)

    Wisniewski, Wieslaw Z.; Harris, A. W.

    1994-04-01

    Amor asteroid 1992 NA was monitored during three nights at a large phase angle of -65 deg. The lightcurves obtained did not reveal a repeatable curve with two maxima and two minima. However, some features suggested a periodicity with three maxima and three minima. A satisfactory composite lightcurve of this form was obtained by means of an 'eyeball' fit and by Fourier analysis. Individual and composite lightcurves are presented. The observed colors are consistent with the C class.

  16. Convergence and Energy Landscape for Cheeger Cut Clustering

    DTIC Science & Technology

    2014-12-01

    provably equivalent to the original problem. The `1-relaxation therefore trades convexity for exactness, yielding improved clustering results at the cost of...however, it is convex and leads to a simple optimization problem. The ‘1-relaxation, in contrast, is non-convex but is provably equivalent to the...minima of the combinatorial problem is equivalent to finding local minima of the continuous relaxation. The last section is devoted to numerical

  17. Predictions of Crystal Structures from First Principles

    DTIC Science & Technology

    2007-06-01

    coefficients 2. Computational Details modeling the long-range dispersion and induction interactions were obtained from separate fits of these...Potential Energy Surface induction energy components are much less important, in particular for the second lowest minimum. Moreover, a large part of the...minima on the PES. from second -order Moller-Plesset (MP2) level The energies of the minima range between -12.5 and calculations used in the SRT

  18. Two-Color V and R CCD Photometry of the SW Sex-Type Eclipsing Cataclysmic Variable V1315 Aql

    NASA Astrophysics Data System (ADS)

    Andronov, I. L.; Baklanov, A. V.; Burwitz, V.

    2005-08-01

    The V-R color index shows a complicated behaviour during the eclipse, being largest at the brightness minimum, but showing asymmetric minima at phases -0.07 and +0.13. The hump at the light curve occurs after the eclipse, contrary to systems with the "hot spot". The phases of minima in V and R are 0.0092(17) and 0.0062(17), respectively, for the mean date JD=2453202.

  19. On Solar Cycle Predictions and Reconstructions

    DTIC Science & Technology

    2008-12-01

    for grand solar minima and to reconstruct the relative sunspol number in the Maunder minimum . Methods. We calculate the asymmetry of the ascending...was identified in the asymmetry data. The maximal smoothed monthly sunspot number during the Maunder minimum was reconstructed and found to be in the...cycle, to investigate proxies for grand solar minima and to reconstruct the relative sunspot number in the Maunder minimum . Methods. We calculate the

  20. Evidence of double layer quantum dot formation in a silicon-on-insulator nanowire transistor

    NASA Astrophysics Data System (ADS)

    Cho, K. H.; Choi, B. H.; Son, S. H.; Hwang, S. W.; Ahn, D.; Park, B.-G.; Naser, B.; Lin, J.-F.; Bird, J. P.

    2005-01-01

    We report the observation of a unique example of double-dot transport in a silicon-on-insulator nanowire transistor. The transport at low temperature showed typical characteristics of two parallel quantum dots, and anomalous secondary minima were also observed in the dID/dVDS spectrum. Our transport data, including these secondary minima, were consistent with two parallel quantum dots, each formed at the front and at the back interface.

  1. The complex lightcurve of 1992 NA

    NASA Technical Reports Server (NTRS)

    Wisniewski, Wieslaw Z.; Harris, A. W.

    1994-01-01

    Amor asteroid 1992 NA was monitored during three nights at a large phase angle of -65 deg. The lightcurves obtained did not reveal a repeatable curve with two maxima and two minima. However, some features suggested a periodicity with three maxima and three minima. A satisfactory composite lightcurve of this form was obtained by means of an 'eyeball' fit and by Fourier analysis. Individual and composite lightcurves are presented. The observed colors are consistent with the C class.

  2. Vacuum selection on axionic landscapes

    SciTech Connect

    Wang, Gaoyuan; Battefeld, Thorsten E-mail: tbattefe@astro.physik.uni-goettingen.de

    2016-04-01

    We compute the distribution of minima that are reached dynamically on multi-field axionic landscapes, both numerically and analytically. Such landscapes are well suited for inflationary model building due to the presence of shift symmetries and possible alignment effects (the KNP mechanism). The resulting distribution of dynamically reached minima differs considerably from the naive expectation based on counting all vacua. These differences are more pronounced in the presence of many fields due to dynamical selection effects: while low lying minima are preferred as fields roll down the potential, trajectories are also more likely to get trapped by one of the many nearby minima. We show that common analytic arguments based on random matrix theory in the large D-limit to estimate the distribution of minima are insufficient for quantitative arguments pertaining to the dynamically reached ones. This discrepancy is not restricted to axionic potentials. We provide an empirical expression for the expectation value of such dynamically reached minimas' height and argue that the cosmological constant problem is not alleviated in the absence of anthropic arguments. We further comment on the likelihood of inflation on axionic landscapes in the large D-limit.

  3. Photophysical deactivation pathways in adenine oligonucleotides.

    PubMed

    Spata, Vincent A; Matsika, Spiridoula

    2015-12-14

    In this work we study deactivation processes in adenine oligomers after absorption of UV radiation using Quantum Mechanics combined with Molecular Mechanics (QM/MM). Correlated electronic structure methods appropriate for describing the excited states are used to describe a π-stacked dimer of adenine bases incorporated into (dA)20(dT)20. The results of these calculations reveal three different types of excited state minima which play a role in deactivation processes. Within this set of minima there are minima where the excited state is localized on one adenine (monomer-like) as well as minima where the excited state is delocalized on two adenines, forming different types of excimers and bonded excimers of varying but inter-related character. The proximity of their energies reveals that the minima can decay into one another along a flat potential energy surface dependent on the interbase separation. Additionally, analysis of the emissive energies and other physical properties, including theoretical anisotropy calculations, and comparison with fluorescence experiments, provides evidence that excimers play an important role in long-lived signals in adenine oligonucleotides while the subpicosecond decay is attributed to monomer-like minima. The necessity for a close approach of the nucleobases reveals that the deactivation mechanism is tied to macro-molecular motion.

  4. Looking for order in the optical design landscape

    NASA Astrophysics Data System (ADS)

    Bociort, Florian; van Turnhout, Maarten

    2006-08-01

    In present-day optical system design, it is tacitly assumed that local minima are points in the merit function landscape without relationships between them. We will show however that there is a certain degree of order in the design landscape and that this order is best observed when we change the dimensionality of the optimization problem and when we consider not only local minima, but saddle points as well. We have developed earlier a computational method for detecting saddle points numerically, and a method, then applicable only in a special case, for constructing saddle points by adding lenses to systems that are local minima. The saddle point construction method will be generalized here and we will show how, by performing a succession of one-dimensional calculations, many local minima of a given global search can be systematically obtained from the set of local minima corresponding to systems with fewer lenses. As a simple example, the results of the Cooke triplet global search will be analyzed. In this case, the vast majority of the saddle points found by our saddle point detection software can in fact be obtained in a much simpler way by saddle point construction, starting from doublet local minima.

  5. The complete chloroplast and mitochondrial genomes of the green macroalga Ulva sp. UNA00071828 (Ulvophyceae, Chlorophyta).

    PubMed

    Melton, James T; Leliaert, Frederik; Tronholm, Ana; Lopez-Bautista, Juan M

    2015-01-01

    Sequencing mitochondrial and chloroplast genomes has become an integral part in understanding the genomic machinery and the phylogenetic histories of green algae. Previously, only three chloroplast genomes (Oltmannsiellopsis viridis, Pseudendoclonium akinetum, and Bryopsis hypnoides) and two mitochondrial genomes (O. viridis and P. akinetum) from the class Ulvophyceae have been published. Here, we present the first chloroplast and mitochondrial genomes from the ecologically and economically important marine, green algal genus Ulva. The chloroplast genome of Ulva sp. was 99,983 bp in a circular-mapping molecule that lacked inverted repeats, and thus far, was the smallest ulvophycean plastid genome. This cpDNA was a highly compact, AT-rich genome that contained a total of 102 identified genes (71 protein-coding genes, 28 tRNA genes, and three ribosomal RNA genes). Additionally, five introns were annotated in four genes: atpA (1), petB (1), psbB (2), and rrl (1). The circular-mapping mitochondrial genome of Ulva sp. was 73,493 bp and follows the expanded pattern also seen in other ulvophyceans and trebouxiophyceans. The Ulva sp. mtDNA contained 29 protein-coding genes, 25 tRNA genes, and two rRNA genes for a total of 56 identifiable genes. Ten introns were annotated in this mtDNA: cox1 (4), atp1 (1), nad3 (1), nad5 (1), and rrs (3). Double-cut-and-join (DCJ) values showed that organellar genomes across Chlorophyta are highly rearranged, in contrast to the highly conserved organellar genomes of the red algae (Rhodophyta). A phylogenomic investigation of 51 plastid protein-coding genes showed that Ulvophyceae is not monophyletic, and also placed Oltmannsiellopsis (Oltmannsiellopsidales) and Tetraselmis (Chlorodendrophyceae) closely to Ulva (Ulvales) and Pseudendoclonium (Ulothrichales).

  6. Mudflat surface morphology as a structuring agent of algae and associated macroepifauna communities: A case study in the Ria Formosa

    NASA Astrophysics Data System (ADS)

    Aníbal, J.; Rocha, C.; Sprung, M.

    2007-01-01

    Although mudflats seem relatively planar, closer inspection reveals a succession of meso-topographical features, including consecutive convex and concave meso- and micro-topographical features. The objective of this study was to determine the influence of meso-scale surface sediment morphology on the dynamics of the macroalgae Ulvales (Chlorophyta) and associated macroepifauna in the Ria Formosa tidal lagoon (southern coast of Portugal). Four sites in the Ria Formosa were sampled monthly. Two were located on convex sections (mounds) of the mudflat and the other two on concave sections (depressions). Macroalgae and related macroepifauna were sampled at each station. Biomass was quantified by determination of the ash-free dry weight (AFDW). Data were analysed using the software package 'PRIMER' (Plymouth Routines In Multivariate Ecological Research). Results show a clear distinction between convex and concave areas. In convex sections, Enteromorpha dominated, to the point of being the only algal species present during part of the year. Conversely, biomass and dynamics of Enteromorpha and Ulva were almost the same in concave sections. The associated macroepifauna was also different in protruding or depressed sections of the mudflat. In the convex areas, the macroepifauna population showed less diversity and was dominated by the snail Hydrobia ulvae. In concave areas, the species diversity was larger, but dominated in terms of biomass by the amphipod Melita palmata and the gastropod Nassarius pfeifferi. Results of the study indicate that the benthic communities associated with concave or convex features were different. No relevant differences in texture and sediment physico-chemical characteristics were found between convex and concave sections. The inference is that the morphological nature of the bottom in tidal mudflats can act as a structuring agent of benthic communities.

  7. The Complete Chloroplast and Mitochondrial Genomes of the Green Macroalga Ulva sp. UNA00071828 (Ulvophyceae, Chlorophyta)

    PubMed Central

    Melton, James T.; Leliaert, Frederik; Tronholm, Ana; Lopez-Bautista, Juan M.

    2015-01-01

    Sequencing mitochondrial and chloroplast genomes has become an integral part in understanding the genomic machinery and the phylogenetic histories of green algae. Previously, only three chloroplast genomes (Oltmannsiellopsis viridis, Pseudendoclonium akinetum, and Bryopsis hypnoides) and two mitochondrial genomes (O. viridis and P. akinetum) from the class Ulvophyceae have been published. Here, we present the first chloroplast and mitochondrial genomes from the ecologically and economically important marine, green algal genus Ulva. The chloroplast genome of Ulva sp. was 99,983 bp in a circular-mapping molecule that lacked inverted repeats, and thus far, was the smallest ulvophycean plastid genome. This cpDNA was a highly compact, AT-rich genome that contained a total of 102 identified genes (71 protein-coding genes, 28 tRNA genes, and three ribosomal RNA genes). Additionally, five introns were annotated in four genes: atpA (1), petB (1), psbB (2), and rrl (1). The circular-mapping mitochondrial genome of Ulva sp. was 73,493 bp and follows the expanded pattern also seen in other ulvophyceans and trebouxiophyceans. The Ulva sp. mtDNA contained 29 protein-coding genes, 25 tRNA genes, and two rRNA genes for a total of 56 identifiable genes. Ten introns were annotated in this mtDNA: cox1 (4), atp1 (1), nad3 (1), nad5 (1), and rrs (3). Double-cut-and-join (DCJ) values showed that organellar genomes across Chlorophyta are highly rearranged, in contrast to the highly conserved organellar genomes of the red algae (Rhodophyta). A phylogenomic investigation of 51 plastid protein-coding genes showed that Ulvophyceae is not monophyletic, and also placed Oltmannsiellopsis (Oltmannsiellopsidales) and Tetraselmis (Chlorodendrophyceae) closely to Ulva (Ulvales) and Pseudendoclonium (Ulothrichales). PMID:25849557

  8. An Atlas of O-C Diagrams of Eclipsing Binary Stars

    NASA Astrophysics Data System (ADS)

    Kreiner, Jerzy M.; Kim, Chun-Hwey; Nha, Il-Seong

    The Atlas contains data for 1,138 eclipsing binaries represented by 91,798 minima timings, collected from the usual international and local journals, observatory publications and unpublished minima. Among this source material there is a considerable representation of amateur astronomers. Some timings were found in the card-index catalogue of the Astronomical Observatory of the Jagiellonian University, Cracow. Stars were included in the Atlas provided that they satisfied 3 criteria: (1) at least 20 minima had been times; (2) these minima spanned at least 2,500 cycles; and (3) the 2,500 cycles represented no fewer than 40 years. Some additional stars not strictly satisfying these criteria were also included if useful information was available. For each star, the Atlas contains the (O-C) diagram calculated by the authors and a table of general information containing: binary characteristics; assorted catalogue numbers; the statistics of the collected minima timings; the light elements (light ephemeris); comments and literature references. All of the data and diagrams in the Atlas are also available in electronic form on the Internet at http://www.as.ap.krakow.pl/o- c".

  9. [Interactions of DNA bases with individual water molecules. Molecular mechanics and quantum mechanics computation results vs. experimental data].

    PubMed

    Gonzalez, E; Lino, J; Deriabina, A; Herrera, J N F; Poltev, V I

    2013-01-01

    To elucidate details of the DNA-water interactions we performed the calculations and systemaitic search for minima of interaction energy of the systems consisting of one of DNA bases and one or two water molecules. The results of calculations using two force fields of molecular mechanics (MM) and correlated ab initio method MP2/6-31G(d, p) of quantum mechanics (QM) have been compared with one another and with experimental data. The calculations demonstrated a qualitative agreement between geometry characteristics of the most of local energy minima obtained via different methods. The deepest minima revealed by MM and QM methods correspond to water molecule position between two neighbor hydrophilic centers of the base and to the formation by water molecule of hydrogen bonds with them. Nevertheless, the relative depth of some minima and peculiarities of mutual water-base positions in' these minima depend on the method used. The analysis revealed insignificance of some differences in the results of calculations performed via different methods and the importance of other ones for the description of DNA hydration. The calculations via MM methods enable us to reproduce quantitatively all the experimental data on the enthalpies of complex formation of single water molecule with the set of mono-, di-, and trimethylated bases, as well as on water molecule locations near base hydrophilic atoms in the crystals of DNA duplex fragments, while some of these data cannot be rationalized by QM calculations.

  10. When Gravity Fails: Local Search Topology

    NASA Technical Reports Server (NTRS)

    Frank, Jeremy; Cheeseman, Peter; Stutz, John; Lau, Sonie (Technical Monitor)

    1997-01-01

    Local search algorithms for combinatorial search problems frequently encounter a sequence of states in which it is impossible to improve the value of the objective function; moves through these regions, called {\\em plateau moves), dominate the time spent in local search. We analyze and characterize {\\em plateaus) for three different classes of randomly generated Boolean Satisfiability problems. We identify several interesting features of plateaus that impact the performance of local search algorithms. We show that local minima tend to be small but occasionally may be very large. We also show that local minima can be escaped without unsatisfying a large number of clauses, but that systematically searching for an escape route may be computationally expensive if the local minimum is large. We show that plateaus with exits, called benches, tend to be much larger than minima, and that some benches have very few exit states which local search can use to escape. We show that the solutions (i.e. global minima) of randomly generated problem instances form clusters, which behave similarly to local minima. We revisit several enhancements of local search algorithms and explain their performance in light of our results. Finally we discuss strategies for creating the next generation of local search algorithms.

  11. Heteroaggregation of Microparticles with Nanoparticles Changes the Chemical Reversibility of the Microparticles' Attachment to Planar Surfaces

    NASA Astrophysics Data System (ADS)

    Shen, Chongyang; Jin, Yan; Huang, Yuanfang; Li, Baoguo

    2014-05-01

    Detachment of homoaggregates and heteroaggregates attached on planar surfaces at primary minima during transients in solution chemistry was theoretically investigated. The homoaggregates were represented as small colloidal clusters with well-defined structures or as clusters generated by randomly packing spheres using Monte Carlo method. The heteroaggregates were modeled as microparticles coated with nanoparticles. Surface element integration technique was adopted to calculate Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energies for the homoaggregates and heteroaggregates at different ionic strengths. Results show that attached homoaggregates on the planar surface at primary minima are irreversible to reduction of solution ionic strength whether the primary spheres of the homoaggregates are nano- or micro-sized. Heteroaggregation of nanoparticles with a microparticle can cause DLVO interaction energy to decrease monotonically with separation distance at low ionic strengths (e.g., ≤ 0.01 M), indicating that the heteroaggregates experience repulsive forces at all separation distances. Therefore, attachment of the heteroaggregates at primary minima can be detached upon reduction of ionic strength. Additionally, we showed that the adhesive forces and torques that the aforementioned heteroaggregates experience can be significantly smaller than those experienced by the microspheres without attaching nanoparticles, thus, the heteroaggregates are readily detached via hydrodynamic drag. Results of study provide plausible explanation for the observations in the literature that attached/aggregated particles can be detached/redispersed from primary minima upon reduction of ionic strength, which challenges the common belief that attachment/aggregation of particles in primary minima is chemically irreversible.

  12. Molecular phylogeny of the forensically important genus Cochliomyia (Diptera: Calliphoridae)

    PubMed Central

    Yusseff-Vanegas, Sohath; Agnarsson, Ingi

    2016-01-01

    Abstract Cochliomyia Townsend includes several abundant and one of the most broadly distributed, blow flies in the Americas, and is of significant economic and forensic importance. For decades, Cochliomyia hominivorax (Coquerel) and Cochliomyia macellaria (Fabricius) have received attention as livestock parasites and primary indicator species in forensic entomology. However, Cochliomyia minima Shannon and Cochliomyia aldrichi Del Ponte have only been subject to basic taxonomy and faunistic studies. Here we present the first complete phylogeny of Cochliomyia including numerous specimens per species, collected from 13 localities in the Caribbean. Four genes, the mitochondrial COI and the nuclear EF-1α, 28S rRNA, and ITS2, were analyzed. While we found some differences among gene trees, a concatenated gene matrix recovered a robustly supported monophyletic Cochliomyia with Compsomyiops Townsend as its sister group and recovered the monophyly of Cochliomyia hominivorax, Cochliomyia macellaria and Cochliomyia minima. Our results support a close relationship between Cochliomyia minima and Cochliomyia aldrichi. However, we found Cochliomyia aldrichi containing Cochliomyia minima, indicating recent speciation, or issues with the taxonomy of the group. We provide basic information on habitat preference, distribution and feeding habits of Cochliomyia minima and Cochliomyia aldrichi that will be useful for future forensic studies in the Caribbean. PMID:27563274

  13. Hydrocarbon adsorption in an aqueous environment: A computational study of alkyls on Cu(111)

    NASA Astrophysics Data System (ADS)

    Montemore, Matthew M.; Andreussi, Oliviero; Medlin, J. Will

    2016-08-01

    Hydrocarbon chains are important intermediates in various aqueous-phase surface processes, such as CO2 electroreduction, aqueous Fischer-Tropsch synthesis, and aqueous phase reforming of biomass-derived molecules. Further, the interaction between water and adsorbed hydrocarbons represents a difficult case for modern computational methods. Here, we explore various methods for calculating the energetics of this interaction within the framework of density functional theory and explore trade-offs between the use of low water coverages, molecular dynamics approaches, and minima hopping for identification of low energy structures. An effective methodology for simulating low temperature processes is provided by using a unit cell in which the vacuum space is filled with water, employing the minima hopping algorithm to search for low-lying minima, and including dispersion (van der Waals) interactions. Using this methodology, we show that a high coverage of adsorbed alkyls is destabilized by the presence of water, while a low coverage of alkyls is stabilized. Solvation has a small effect on the energetics of hydrocarbon chain growth, generally decreasing its favorability at low temperatures. We studied higher temperatures by running molecular dynamics simulations starting at the minima found by the minima hopping algorithm and found that increased temperatures facilitate chain growth. The self-consistent continuum solvation method effectively describes the alkyl-water interaction and is in general agreement with the explicit solvation results in most cases, but care should be taken at high alkyl coverage.

  14. Computationally efficient characterization of potential energy surfaces based on fingerprint distances

    NASA Astrophysics Data System (ADS)

    Schaefer, Bastian; Goedecker, Stefan

    2016-07-01

    An analysis of the network defined by the potential energy minima of multi-atomic systems and their connectivity via reaction pathways that go through transition states allows us to understand important characteristics like thermodynamic, dynamic, and structural properties. Unfortunately computing the transition states and reaction pathways in addition to the significant energetically low-lying local minima is a computationally demanding task. We here introduce a computationally efficient method that is based on a combination of the minima hopping global optimization method and the insight that uphill barriers tend to increase with increasing structural distances of the educt and product states. This method allows us to replace the exact connectivity information and transition state energies with alternative and approximate concepts. Without adding any significant additional cost to the minima hopping global optimization approach, this method allows us to generate an approximate network of the minima, their connectivity, and a rough measure for the energy needed for their interconversion. This can be used to obtain a first qualitative idea on important physical and chemical properties by means of a disconnectivity graph analysis. Besides the physical insight obtained by such an analysis, the gained knowledge can be used to make a decision if it is worthwhile or not to invest computational resources for an exact computation of the transition states and the reaction pathways. Furthermore it is demonstrated that the here presented method can be used for finding physically reasonable interconversion pathways that are promising input pathways for methods like transition path sampling or discrete path sampling.

  15. A strategy to find minimal energy nanocluster structures.

    PubMed

    Rogan, José; Varas, Alejandro; Valdivia, Juan Alejandro; Kiwi, Miguel

    2013-11-05

    An unbiased strategy to search for the global and local minimal energy structures of free standing nanoclusters is presented. Our objectives are twofold: to find a diverse set of low lying local minima, as well as the global minimum. To do so, we use massively the fast inertial relaxation engine algorithm as an efficient local minimizer. This procedure turns out to be quite efficient to reach the global minimum, and also most of the local minima. We test the method with the Lennard-Jones (LJ) potential, for which an abundant literature does exist, and obtain novel results, which include a new local minimum for LJ13 , 10 new local minima for LJ14 , and thousands of new local minima for 15≤N≤65. Insights on how to choose the initial configurations, analyzing the effectiveness of the method in reaching low-energy structures, including the global minimum, are developed as a function of the number of atoms of the cluster. Also, a novel characterization of the potential energy surface, analyzing properties of the local minima basins, is provided. The procedure constitutes a promising tool to generate a diverse set of cluster conformations, both two- and three-dimensional, that can be used as an input for refinement by means of ab initio methods.

  16. Conformational Analysis of Retinoic Acids: Effects of Steric Interactions on Nonplanar Conjugated Polyenes

    PubMed Central

    Cox, Bryan D.; Muccio, Donald D.; Hamilton, Tracy P.

    2013-01-01

    Retinoic acids and other vitamin A analogs contain a trimethylcyclohexenyl ring in conjugation with a polyene chain joined at carbon-6 (C6) and carbon-7 (C7). A MP2-SCS/cc-pVDZ// B3LYP/6-31G(d) 2-D potential energy surface was computed for all-trans retinoic acid, which had 6 minima (3 enantiomeric pairs). The global minima were distorted s-gauche enantiomers (6–7 = 53°) with half-chair conformations of the ring. Distorted s-gauche enantiomers (6–7 = 55°) with inverted half-chair ring conformations were 1.7 kJ/mol above the global minima. The s-trans enantiomers (6–7 = 164°) were 11.3 kJ/mol above the global minima. Steric energies were computed by the method of Guo and Karplus to identify key structural elements in retinoic acids which determines their conformation. Small molecule crystal structures in the CCDC database with trimethylcyclohexenyl ring and exocyclic double bonds have ring-chain geometries near to one of the 6 energy minima of retinoic acids, except for retinaldehyde iminium cations. PMID:25798372

  17. Conformational Analysis of Retinoic Acids: Effects of Steric Interactions on Nonplanar Conjugated Polyenes.

    PubMed

    Cox, Bryan D; Muccio, Donald D; Hamilton, Tracy P

    2013-05-01

    Retinoic acids and other vitamin A analogs contain a trimethylcyclohexenyl ring in conjugation with a polyene chain joined at carbon-6 (C6) and carbon-7 (C7). A MP2-SCS/cc-pVDZ// B3LYP/6-31G(d) 2-D potential energy surface was computed for all-trans retinoic acid, which had 6 minima (3 enantiomeric pairs). The global minima were distorted s-gauche enantiomers (6-7 = 53°) with half-chair conformations of the ring. Distorted s-gauche enantiomers (6-7 = 55°) with inverted half-chair ring conformations were 1.7 kJ/mol above the global minima. The s-trans enantiomers (6-7 = 164°) were 11.3 kJ/mol above the global minima. Steric energies were computed by the method of Guo and Karplus to identify key structural elements in retinoic acids which determines their conformation. Small molecule crystal structures in the CCDC database with trimethylcyclohexenyl ring and exocyclic double bonds have ring-chain geometries near to one of the 6 energy minima of retinoic acids, except for retinaldehyde iminium cations.

  18. Application of the ARMA model in distributed fiber vibration sensing system

    NASA Astrophysics Data System (ADS)

    Wu, Hongyan; Xu, Haiyan; Peng, HeKuo

    2015-06-01

    Distributed fiber vibration sensing system is widely used in the field of wide area security, communication cable of long distances and pipeline security. The principle of the system is that for a vibration signal applied at a particular position along the fiber, the response, in the frequency domain, presents a series of periodic maxima and minima (or nulls). These minima depend on the position of the vibration along a fiber. Power spectral estimation method is considered to denoise the power spectrum of the system and determine these minima precisely in the paper. The parametric modelling methods such as autoregressive-moving average (ARMA) model is used to improve the positional accuracy of the system. The experimental results show the high accuracy of the position using ARMA model.

  19. Discriminating Between qm and SED with Spin

    NASA Astrophysics Data System (ADS)

    Cavalleri, G.; Tonni, E.

    The complete prediction of diffraction for electrons passing through two slits is obtained by stochastic electrodynamics (SED) implemented by spin. The positions of the maxima and minima of the diffraction pattern turn out to be equal to those given by quantum mechanics (QM). However, when the transversal width Δy of the electron beam is much smaller than the size b of a slit, no diffraction should be present according to QM while a part of the diffraction pattern dependent on the position of the beam should appear according to SED plus spin. A relevant experiment is proposed to discriminate between the two theories. A second proposed experiment regards the form of the diffraction pattern. The intensities of the minima should be almost zero if the wall containing the slit is made of metal but appreciably different from zero if the wall is made of a dielectric. For a dielectric constant ≃ 2 the even maxima should be less than the minima.

  20. WS-BP: An efficient wolf search based back-propagation algorithm

    NASA Astrophysics Data System (ADS)

    Nawi, Nazri Mohd; Rehman, M. Z.; Khan, Abdullah

    2015-05-01

    Wolf Search (WS) is a heuristic based optimization algorithm. Inspired by the preying and survival capabilities of the wolves, this algorithm is highly capable to search large spaces in the candidate solutions. This paper investigates the use of WS algorithm in combination with back-propagation neural network (BPNN) algorithm to overcome the local minima problem and to improve convergence in gradient descent. The performance of the proposed Wolf Search based Back-Propagation (WS-BP) algorithm is compared with Artificial Bee Colony Back-Propagation (ABC-BP), Bat Based Back-Propagation (Bat-BP), and conventional BPNN algorithms. Specifically, OR and XOR datasets are used for training the network. The simulation results show that the WS-BP algorithm effectively avoids the local minima and converge to global minima.

  1. Combined Docking with Classical Force Field and Quantum Chemical Semiempirical Method PM7

    PubMed Central

    Kutov, D. C.; Sulimov, V. B.

    2017-01-01

    Results of the combined use of the classical force field and the recent quantum chemical PM7 method for docking are presented. Initially the gridless docking of a flexible low molecular weight ligand into the rigid target protein is performed with the energy function calculated in the MMFF94 force field with implicit water solvent in the PCM model. Among several hundred thousand local minima, which are found in the docking procedure, about eight thousand lowest energy minima are chosen and then energies of these minima are recalculated with the recent quantum chemical semiempirical PM7 method. This procedure is applied to 16 test complexes with different proteins and ligands. For almost all test complexes such energy recalculation results in the global energy minimum configuration corresponding to the ligand pose near the native ligand position in the crystalized protein-ligand complex. A significant improvement of the ligand positioning accuracy comparing with MMFF94 energy calculations is demonstrated. PMID:28191015

  2. On the origin of a very close similarity between the spectra of the supernova type 1 in NGC 3198 and the absorption of DQ HeR

    NASA Technical Reports Server (NTRS)

    Mustel, E. R.

    1979-01-01

    The type 1 supernova discovered late in 1966 in NGC 3198 has broad minima in its spectrum break down into a number of significantly narrower absorption bands. The broad minima of tau, sigma and mu, which usually show no details in the spectra of type supernovas, contain a number of narrow absorption bands. The reality of most of these absorption bands is demonstrated by comparison of recordings of spectra of the supernova presented for two moments in time. These minima (particularly of tau and mu,) are a result of blending of several broad absorption bands. The minimum of tau should be a blend of intensive and very broad Fe absorption lines, in which the lower level is metastable. The wavelengths of these line are: 5169, 5198, 5235, 5276, 5317, 5363A.

  3. Comparative modelling of chemical ordering in palladium-iridium nanoalloys.

    PubMed

    Davis, Jack B A; Johnston, Roy L; Rubinovich, Leonid; Polak, Micha

    2014-12-14

    Chemical ordering in "magic-number" palladium-iridium nanoalloys has been studied by means of density functional theory (DFT) computations, and compared to those obtained by the Free Energy Concentration Expansion Method (FCEM) using derived coordination dependent bond energy variations (CBEV), and by the Birmingham Cluster Genetic Algorithm using the Gupta potential. Several compositions have been studied for 38- and 79-atom particles as well as the site preference for a single Ir dopant atom in the 201-atom truncated octahedron (TO). The 79- and 38-atom nanoalloy homotops predicted for the TO by the FCEM/CBEV are shown to be, respectively, the global minima and competitive low energy minima. Significant reordering of minima predicted by the Gupta potential is seen after reoptimisation at the DFT level.

  4. Nonlinear optimization simplified by hypersurface deformation

    SciTech Connect

    Stillinger, F.H.; Weber, T.A.

    1988-09-01

    A general strategy is advanced for simplifying nonlinear optimization problems, the ant-lion method. This approach exploits shape modifications of the cost-function hypersurface which distend basins surrounding low-lying minima (including global minima). By intertwining hypersurface deformations with steepest-descent displacements, the search is concentrated on a small relevant subset of all minima. Specific calculations demonstrating the value of this method are reported for the partitioning of two classes of irregular but nonrandom graphs, the prime-factor graphs and the pi graphs. We also indicate how this approach can be applied to the traveling salesman problem and to design layout optimization, and that it may be useful in combination with simulated annealing strategies.

  5. Quantum chemical studies of photochromic properties of benzoxazine compound

    NASA Astrophysics Data System (ADS)

    Toliautas, Stepas; Sulskus, Juozas; Valkunas, Leonas; Vengris, Mikas

    2012-08-01

    Molecular electronic structure of ground and excited states of a photochromic indolo[2,1-b][1,3]benzoxazine compound incorporating closed-ring system, which opens upon UV light excitation, was studied using various quantum chemical methods. Three local minima of the ground electronic state potential energy surface and related transition states were identified along the path of rotation of 4-nitrophenol group. Additionally, three local minima of the excited electronic states were located. The evaluated transition energy barriers between local ground-state minima nearest to the initial structure of the investigated molecule are less than 2 kBT, making open structures likely to revert to the initial structure by thermalization. Results obtained using ab initio GMC-QDPT method were explored and compared to the widely used TD-DFT and semi-empiric ZINDO methods.

  6. Computing Freidlin's Cycles for the Overdamped Langevin Dynamics. Application to the Lennard-Jones-38 Cluster

    NASA Astrophysics Data System (ADS)

    Cameron, M. K.

    2013-08-01

    The large time behavior of a stochastic system with infinitesimally small noise can be described in terms of Freidlin's cycles. We show that if the system is gradient and the potential satisfies certain non-restrictive conditions, the hierarchy of cycles has a structure of a full binary tree, and each cycle is exited via the lowest saddle adjacent to it. Exploiting this property, we propose an algorithm for computing the asymptotic zero-temperature path and building a hierarchy of Freidlin's cycles associated with the transition process between two given local equilibria. This algorithm is suitable for systems with a complex potential energy landscape with numerous minima. We apply it to find the asymptotic zero-temperature path and Freidlin's cycles involved into the transition process between the two lowest minima of the Lennard-Jones cluster of 38 atoms. D. Wales's stochastic network of minima and transition states of this cluster is used as an input.

  7. Tight-binding approach to overdamped Brownian motion on a bichromatic periodic potential

    NASA Astrophysics Data System (ADS)

    Nguyen, P. T. T.; Challis, K. J.; Jack, M. W.

    2016-02-01

    We present a theoretical treatment of overdamped Brownian motion on a time-independent bichromatic periodic potential with spatially fast- and slow-changing components. In our approach, we generalize the Wannier basis commonly used in the analysis of periodic systems to define a basis of S states that are localized at local minima of the potential. We demonstrate that the S states are orthonormal and complete on the length scale of the periodicity of the fast-changing potential, and we use the S-state basis to transform the continuous Smoluchowski equation for the system to a discrete master equation describing hopping between local minima. We identify the parameter regime where the master equation description is valid and show that the interwell hopping rates are well approximated by Kramers' escape rate in the limit of deep potential minima. Finally, we use the master equation to explore the system dynamics and determine the drift and diffusion for the system.

  8. Vibrational energy levels of CH5+

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Gang; Carrington, Tucker

    2008-12-01

    We present a parallelized contracted basis-iterative method for calculating numerically exact vibrational energy levels of CH5+ (a 12-dimensional calculation). We use Radau polyspherical coordinates and basis functions that are products of eigenfunctions of bend and stretch Hamiltonians. The bend eigenfunctions are computed in a nondirect product basis with more than 200×106 functions and the stretch functions are computed in a product potential optimized discrete variable basis. The basis functions have amplitude in all of the 120 equivalent minima. Many low-lying levels are well converged. We find that the energy level pattern is determined in part by the curvature and width of the valley connecting the minima and in part by the slope of the walls of this valley but does not depend on the height or shape of the barriers separating the minima.

  9. Comparative modelling of chemical ordering in palladium-iridium nanoalloys

    SciTech Connect

    Davis, Jack B. A.; Johnston, Roy L.; Rubinovich, Leonid; Polak, Micha

    2014-12-14

    Chemical ordering in “magic-number” palladium-iridium nanoalloys has been studied by means of density functional theory (DFT) computations, and compared to those obtained by the Free Energy Concentration Expansion Method (FCEM) using derived coordination dependent bond energy variations (CBEV), and by the Birmingham Cluster Genetic Algorithm using the Gupta potential. Several compositions have been studied for 38- and 79-atom particles as well as the site preference for a single Ir dopant atom in the 201-atom truncated octahedron (TO). The 79- and 38-atom nanoalloy homotops predicted for the TO by the FCEM/CBEV are shown to be, respectively, the global minima and competitive low energy minima. Significant reordering of minima predicted by the Gupta potential is seen after reoptimisation at the DFT level.

  10. Genetic algorithm optimization of atomic clusters

    SciTech Connect

    Morris, J.R.; Deaven, D.M.; Ho, K.M.; Wang, C.Z.; Pan, B.C.; Wacker, J.G.; Turner, D.E. |

    1996-12-31

    The authors have been using genetic algorithms to study the structures of atomic clusters and related problems. This is a problem where local minima are easy to locate, but barriers between the many minima are large, and the number of minima prohibit a systematic search. They use a novel mating algorithm that preserves some of the geometrical relationship between atoms, in order to ensure that the resultant structures are likely to inherit the best features of the parent clusters. Using this approach, they have been able to find lower energy structures than had been previously obtained. Most recently, they have been able to turn around the building block idea, using optimized structures from the GA to learn about systematic structural trends. They believe that an effective GA can help provide such heuristic information, and (conversely) that such information can be introduced back into the algorithm to assist in the search process.

  11. Combined Docking with Classical Force Field and Quantum Chemical Semiempirical Method PM7.

    PubMed

    Sulimov, A V; Kutov, D C; Katkova, E V; Sulimov, V B

    2017-01-01

    Results of the combined use of the classical force field and the recent quantum chemical PM7 method for docking are presented. Initially the gridless docking of a flexible low molecular weight ligand into the rigid target protein is performed with the energy function calculated in the MMFF94 force field with implicit water solvent in the PCM model. Among several hundred thousand local minima, which are found in the docking procedure, about eight thousand lowest energy minima are chosen and then energies of these minima are recalculated with the recent quantum chemical semiempirical PM7 method. This procedure is applied to 16 test complexes with different proteins and ligands. For almost all test complexes such energy recalculation results in the global energy minimum configuration corresponding to the ligand pose near the native ligand position in the crystalized protein-ligand complex. A significant improvement of the ligand positioning accuracy comparing with MMFF94 energy calculations is demonstrated.

  12. Differential physiological responses of two Salvinia species to hexavalent chromium at a glance.

    PubMed

    Prado, Carolina; Chocobar Ponce, Silvana; Pagano, Eduardo; Prado, Fernando E; Rosa, Mariana

    2016-06-01

    In plants of Salvinia rotundifolia and Salvinia minima the effect of two Cr(VI) concentrations (5 and 20mgL(-1)) applied for 7days was assessed by measuring changes in biomass, photosynthetic pigments, Cr accumulation, malondialdehyde (MDA), membrane stability index (MSI), thiols (TT, NPT and PBT), and phenolics (SP and IP). Biomass in S. minima was decreased at highest Cr(VI) concentration, but there were no changes in S. rotundifolia. Metal accumulation was different in both species. S. minima accumulates more metal in fronds, but S. rotundifolia accumulates more metal in lacinias. Results also showed that S. minima translocates more Cr to fronds than S. rotundifolia, but at the whole plant level higher accumulation occurred in this last. Tolerance index (Ti) was higher in S. rotundifolia. Chl b and carotenoids were decreased only upon exposure to high Cr(VI) concentration in both species. Cr(VI) treatment did not enhance MDA accumulation. Cr exposure had no impact on MSI values when comparing with Cr-untreated values. Thiols in fronds and lacinias showed different distribution patterns between species. IP and NPT were higher in S. rotundifolia lacinias that accumulate more Cr than S. minima lacinias. Whilst SP and NPT were higher in S. minima fronds compared with S. rotundifolia ones. This may indicate that these species can cope with Cr(VI) toxicity, either through metal complexation and/or metal reduction or by the scavenging of ROS derived from Cr-induced oxidative stress. Based on Cr accumulation and biomass production, S. rotundifolia seems more suitable to remove Cr(VI) from polluted waters. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. The Heliosphere in Time

    NASA Astrophysics Data System (ADS)

    McCracken, Ken; Beer, Juerg; Steinhilber, Friedhelm; Abreu, Jose

    2013-06-01

    The paleo-cosmic ray records are used to study the properties of the heliosphere and solar processes over the past 9300 years. They show that both varied greatly over that time, ranging from ˜26 "Grand Minima" of duration 50-100 yr when the Sun was inactive, to periods similar to the past 50 years of strong solar activity. This shows that the detailed information regarding the heliosphere gained during the "space era" represents an extreme case, and is not representative of the majority of the past 9300 yr. The data confirm that the 11 and 22-year cycles of solar activity continued through the Spoerer and Maunder Grand Minima. Throughout the 9300 yr interval, "Grand Minima" usually occurred in groups of 2 to 4, similar to the group of four that occurred in the interval 1000-1800 AD. The groups are separated by ˜1000 yr intervals without Grand Minima. Frequency spectra of the full 9300 yr record show that the heliospheric and solar phenomena exhibit >10 well-defined and persistent periodicities. We speculate that the solar dynamo exhibits a 2300 yr periodicity, wherein it alternates between two different states of activity. In the first (˜800 yr duration) solar activity weakens greatly every 100-200 yr resulting in a sequence of Grand Minima, while in the other, the solar dynamo suffers smaller changes; the centenary scale solar and heliospheric changes are smaller, being similar to those that occurred in the interval 1890-1910. The paleo-cosmic ray evidence suggests that the Sun has now entered this more uniform period of activity, following the sequence of Grand Minima (Wolf, Spoerer, Maunder, and Dalton) that occurred between 1000 and 1800 AD.

  14. Variations of the tropical Atlantic and Pacific SSS minimum zones and their relations to the ITCZ and SPCZ rain bands (1979-2009)

    NASA Astrophysics Data System (ADS)

    Tchilibou, M.; Delcroix, T.; Alory, G.; Arnault, S.; Reverdin, G.

    2015-07-01

    This study focuses on the time-space variability of the low Sea Surface Salinity (SSS) waters extending zonally within 2°N-12°N in the Atlantic and Pacific and within 6°S-16°S in the western third of the Pacific. The analysis is based on a combination of in situ SSS observations collected in the last three decades from voluntary observing ships, TAO/TRITON and PIRATA moorings, Argo floats, and (few) CTD profiles. The mean latitudes of the Atlantic and Pacific low SSS waters appear 1°-3° further poleward than the Evaporation minus Precipitation (E-P) minima linked to the Inter Tropical Convergence Zones (ITCZ) and South Pacific Convergence Zone (SPCZ). At the seasonal time scale, the E-P minima migrate poleward in summer hemispheres, leading the migration of the SSS minima by 2-3 months in the Atlantic ITCZ, Pacific SPCZ, and in the eastern part of the Pacific ITCZ. On the other hand, the seasonal displacements of E-P and SSS minima are in antiphase in the central and western parts of the Pacific ITCZ. At the interannual time scale, the E-P and SSS minima migrate poleward during La Nina events in the Pacific and during the positive phase of the Atlantic Meridional Dipole (AMD) in the Atlantic (and vice versa during El Nino and the negative phase of the AMD). We further document long-term (1979-2009) meridional migrations of the E-P and SSS minima, especially in the SPCZ region, and discuss whether or not they are consistent with documented SST and wind stress trends.

  15. Oxygen-induced recombination centers in as-grown Czochralski silicon crystals

    NASA Technical Reports Server (NTRS)

    Nauka, K.; Gatos, H. C.; Lagowski, J.

    1983-01-01

    Simultaneous quantitative microprofiles of the interstitial oxygen concentration and of the excess carrier lifetime are obtained in Czochralski-grown Si crystals employing double laser absorption scanning. It is found that oxygen concentration maxima and minima along the crystal growth direction coincide with lifetime minima and maxima, respectively. Another finding is that the magnitude of oxygen-induced lifetime changes increases dramatically in going from the center to the periphery of the crystal. The findings discussed imply that 'as-grown' oxygen precipitates figure in lifetime-limiting processes.

  16. Gaussian-mixture umbrella sampling

    PubMed Central

    van der Vaart, Arjan; Karplus, Martin

    2009-01-01

    We introduce the Gaussian-mixture umbrella sampling method (GAMUS), a biased molecular dynamics technique based on adaptive umbrella sampling that efficiently escapes free energy minima in multi-dimensional problems. The prior simulation data are reweighted with a maximum likelihood formulation, and the new approximate probability density is fit to a Gaussian-mixture model, augmented by information about the unsampled areas. The method can be used to identify free energy minima in multi-dimensional reaction coordinates. To illustrate GAMUS, we apply it to the alanine dipeptide (2D reaction coordinate) and tripeptide (4D reaction coordinate). PMID:19284746

  17. On the timing of the next great solar activity minimum

    NASA Astrophysics Data System (ADS)

    Tlatov, A. G.; Pevtsov, A. A.

    2017-09-01

    The long-term variations in solar activity are studied using the dataset comprised of sunspot number and 14C radioisotope timeseries. We use a novel S200 index to identify possible past Grand Minima (GM). The Maunder, Oort, Wolf and Spörer Minima fall in phase with the minimum of S200 index. We also show GM develop in clusters, with a separation of about 400-600 years between individual GM. Extending these found similarities to modern solar activity, it is predicted that next grand solar minimum may occur in about ∼ 2090 ± 20 .

  18. Dust Around Herbig Ae Stars: Additional Constraints from their Photometric and Polarimetric Variability

    NASA Technical Reports Server (NTRS)

    Krivova, N. A.; Ilin, V. B.; Fischer, O.

    1996-01-01

    For the Herbig Ae stars with Algol-like minima (UX Ori, WW Vul, etc), the effects of circumstellar dust include: excess infrared emission, anomalous ultraviolet extinction, the 'blueing' of the stars in minima accompanying by an increase of intrinsic polarization. Using a Monte-Carlo code for polarized radiation transfer we have simulated these effects and compared the results obtained for different models with the observational data available. We found that the photometric and polarimetric behavior of the stars provided essential additional constraints on the circumstellar dust models. The models with spheroidal shell geometry and compact (non-fluffy) dust grains do not appear to be able to explain all the data.

  19. Method and apparatus for thickness measurement using microwaves

    DOEpatents

    Woskov, Paul [Bedford, MA; Lamar, David A [West Richland, WA

    2001-01-01

    The method for measuring the thickness of a material which transmits a detectable amount of microwave radiation includes irradiating the material with coherent microwave radiation tuned over a frequency range. Reflected microwave radiation is detected, the reflected radiation having maxima and minima over the frequency range as a result of coherent interference of microwaves reflected from reflecting surfaces of the material. The thickness of the material is determined from the period of the maxima and minima along with knowledge of the index of refraction of the material.

  20. Acoustic concentration of particles in fluid flow

    DOEpatents

    Ward, Michael D.; Kaduchak, Gregory

    2010-11-23

    An apparatus for acoustic concentration of particles in a fluid flow includes a substantially acoustically transparent membrane and a vibration generator that define a fluid flow path therebetween. The fluid flow path is in fluid communication with a fluid source and a fluid outlet and the vibration generator is disposed adjacent the fluid flow path and is capable of producing an acoustic field in the fluid flow path. The acoustic field produces at least one pressure minima in the fluid flow path at a predetermined location within the fluid flow path and forces predetermined particles in the fluid flow path to the at least one pressure minima.

  1. Solar wind, radiation belt electrons and atmospheric vorticity

    NASA Astrophysics Data System (ADS)

    Mironova, Irina; Tinsley, Brian; Zhou, Limin

    The association of atmospheric vorticity changes with solar wind sector structure explored by John Wilcox and Walter Orr Roberts in the 1970s is examined in terms of the sector related minima in solar wind speed, and associated minima in relativistic electron precipitation from the outer radiation belt. Stronger correlations of atmospheric vorticity with the relativistic electron flux are found than with either solar wind speed or the passage of magnetic sector boundaries over the Earth. This is consistent with changes in the ionosphere-earth current density affecting cloud microphysics, with the ionization from the Bremsstrahlung X-rays from the relativistic electron precipitation increasing the conductivity of the stratosphere.

  2. Computer-aided analysis of signals from a low-coherence Fabry-Perot interferometer used for measurements of biological samples

    NASA Astrophysics Data System (ADS)

    Mrotek, Marcin; Pluciński, Jerzy; Jedrzejewska-Szczerska, Małgorzata

    2016-09-01

    The aim of the study was to develop an automated computer-aided system for analysis of spectrograms obtained from measurements of biological samples performed with a low-coherence Fabry-Pérot interferometer. Information necessary to determine dispersion characteristics of measured materials can be calculated from the positions of the maxima and minima that are present in their spectra. The main challenge faced during the development of the system was reliable detection of these maxima and minima in the presence of noise, without requiring substantial user interaction, and with an acceptable computational complexity.

  3. Ecological-floristic analysis of soil algae and cyanobacteria on the Tra-Tau and Yurak-Tau Mounts, Bashkiria

    NASA Astrophysics Data System (ADS)

    Bakieva, G. R.; Khaibullina, L. S.; Gaisina, L. A.; Kabirov, R. R.

    2012-09-01

    The species composition of the soil algae and cyanobacteria in the Tra-Tau and Yurak-Tau mountains is represented by 136 species belonging to five phyla: Cyanobacteria (56 species), Chlorophyta (52 species), Xanthophyta (13 species), Bacillariophyta (12 species), and Eustigmatophyta (3 species). Hantzschia amphioxys var. amphioxys, Hantzschia amphioxys var. constricta, Klebsormidium flaccidum, Leptolyngbya foveolarum, Luticola mutica, Navicula minima var. minima, Nostoc punctiforme, Phormidium jadinianum, Phormidium autumnale, and Pinnularia borealis were identified more often than other species. The composition of the algal flora depended on the soil properties; the higher plants also had a significant influence on the species composition of the soil algae.

  4. Oxygen-induced recombination centers in as-grown Czochralski silicon crystals

    NASA Technical Reports Server (NTRS)

    Nauka, K.; Gatos, H. C.; Lagowski, J.

    1983-01-01

    Simultaneous quantitative microprofiles of the interstitial oxygen concentration and of the excess carrier lifetime are obtained in Czochralski-grown Si crystals employing double laser absorption scanning. It is found that oxygen concentration maxima and minima along the crystal growth direction coincide with lifetime minima and maxima, respectively. Another finding is that the magnitude of oxygen-induced lifetime changes increases dramatically in going from the center to the periphery of the crystal. The findings discussed imply that 'as-grown' oxygen precipitates figure in lifetime-limiting processes.

  5. Optical Model and Cross Section Uncertainties

    SciTech Connect

    Herman,M.W.; Pigni, M.T.; Dietrich, F.S.; Oblozinsky, P.

    2009-10-05

    Distinct minima and maxima in the neutron total cross section uncertainties were observed in model calculations using spherical optical potential. We found this oscillating structure to be a general feature of quantum mechanical wave scattering. Specifically, we analyzed neutron interaction with 56Fe from 1 keV up to 65 MeV, and investigated physical origin of the minima.We discuss their potential importance for practical applications as well as the implications for the uncertainties in total and absorption cross sections.

  6. Geometry and symmetry presculpt the free-energy landscape of proteins

    PubMed Central

    Hoang, Trinh Xuan; Trovato, Antonio; Seno, Flavio; Banavar, Jayanth R.; Maritan, Amos

    2004-01-01

    We present a simple physical model that demonstrates that the native-state folds of proteins can emerge on the basis of considerations of geometry and symmetry. We show that the inherent anisotropy of a chain molecule, the geometrical and energetic constraints placed by the hydrogen bonds and sterics, and hydrophobicity are sufficient to yield a free-energy landscape with broad minima even for a homopolymer. These minima correspond to marginally compact structures comprising the menu of folds that proteins choose from to house their native states in. Our results provide a general framework for understanding the common characteristics of globular proteins. PMID:15148372

  7. Acoustic concentration of particles in fluid flow

    DOEpatents

    Ward, Michael W.; Kaduchak, Gregory

    2017-08-15

    Disclosed herein is a acoustic concentration of particles in a fluid flow that includes a substantially acoustically transparent membrane and a vibration generator that define a fluid flow path therebetween. The fluid flow path is in fluid communication with a fluid source and a fluid outlet and the vibration generator is disposed adjacent the fluid flow path and is capable of producing an acoustic field in the fluid flow path. The acoustic field produces at least one pressure minima in the fluid flow path at a predetermined location within the fluid flow path and forces predetermined particles in the fluid flow path to the at least one pressure minima.

  8. Interaction modes between asymmetrically and oppositely charged rods

    NASA Astrophysics Data System (ADS)

    Antila, Hanne S.; Van Tassel, Paul R.; Sammalkorpi, Maria

    2016-02-01

    The interaction of oppositely and asymmetrically charged rods in salt—a simple model of (bio)macromolecular assembly—is observed via simulation to exhibit two free energy minima, separated by a repulsive barrier. In contrast to similar minima in the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, the governing mechanism includes electrostatic attraction at large separation, osmotic repulsion at close range, and depletion attraction near contact. A model accounting for ion condensation and excluded volume is shown to be superior to a mean-field treatment in predicting the effect of charge asymmetry on the free-energy profile.

  9. The Scalar Mesons and Z(3) Symmetry

    SciTech Connect

    Toernqvist, Nils A.

    2007-02-27

    It is pointed out that the det{sigma} + det{sigma}{dagger} term, which resolves the UA(1) problem in effective theories, gives rise to three classical minima along the UA(1) circle when Nf = 3. The three minima are related to the center Z(3) of SU(3). This Z(3) symmetry can be retained if the SU(3)L x SU(3)R symmetry breaking is assumed to be trilinear in the fields. The three vacua suggests a connection to the strong CP problem and confinement.

  10. Computational study of the rovibrational spectrum of (CO2)2

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Gang; Carrington, Tucker; Dawes, Richard

    2016-12-01

    An interpolating moving least squares method is used to fit ab initio points to obtain an intermolecular potential energy surface (PES) for (CO2)2. The surface is used in conjunction with the symmetry-adapted Lanczos algorithm to compute rovibrational transition frequencies. The PES has four equivalent minima separated by barriers high enough that tunneling splittings are very small. The lowest energy pathway connecting the minima is a disrotatory channel. The calculations enable us to assign a combination band observed by Dehghany et al. (2010).

  11. Improved Particle Swarm Optimization for Global Optimization of Unimodal and Multimodal Functions

    NASA Astrophysics Data System (ADS)

    Basu, Mousumi

    2016-12-01

    Particle swarm optimization (PSO) performs well for small dimensional and less complicated problems but fails to locate global minima for complex multi-minima functions. This paper proposes an improved particle swarm optimization (IPSO) which introduces Gaussian random variables in velocity term. This improves search efficiency and guarantees a high probability of obtaining the global optimum without significantly impairing the speed of convergence and the simplicity of the structure of particle swarm optimization. The algorithm is experimentally validated on 17 benchmark functions and the results demonstrate good performance of the IPSO in solving unimodal and multimodal problems. Its high performance is verified by comparing with two popular PSO variants.

  12. Atomistic Modeling of Mechanical Loss in Amorphous Oxides

    NASA Astrophysics Data System (ADS)

    Hamdan, Rashid; Trinastic, Jonathan; Cheng, Hai-Ping

    2013-03-01

    The mechanical and optical loss in amorphous solids, described by the internal friction and light scattering susceptibility are investigated using classical, atomistic molecular dynamics simulation. We implemented the trajectory bisection method and the non-local ridge method in DL-POLY molecular dynamics simulation software. These methods were used to locate the different local potential energy minima that a system visits through an MD trajectory and the transition state between any two consecutive minima. From the distributions of the barrier height and asymmetry, and the relaxation time of the different transition states we calculated the internal friction of pure amorphous silica and mixed oxides. Acknowledgment: NSF/PHYS

  13. Variation of the Radiocarbon Content of Tree Rings during the Spoerer Minimum

    NASA Astrophysics Data System (ADS)

    Miyahara, H.; Masuda, Kimiaki; Furuzawa, Hudeki; Muraki, Tasushi; Nakamura, Toshio; Kitagawa, Hiroyuki; Arslanov, Khikmatulla

    2003-07-01

    The radio carbon content of tree rings offers important information on the level of the solar activity in the past. We have fo cused on the variation of solar activity during the grand minima, when solar activity was extremely low. In order to clarify the characteristics of solar activity during the grand minima, we measured the radio carbon content of tree rings from the spo erer Minimum (14151534 AD) annually. The time series was analyzed and periodicities of 7, 11 and 22 years were derived. The 11-year periodicity was dominant, however it was weakened during 1460-1500 AD.

  14. Angle-Resolved Photoelectron Spectrometry Studies of the Autoionization of the 2s{sup 2}2p {sup 2}P Triply Excited State of Atomic Lithium: Experimental Results and R -Matrix Calculations

    SciTech Connect

    Diehl, S.; Cubaynes, D.; Zhou, H. L.; VoKy, L.; Wuilleumier, F. J.; Kennedy, E. T.; Bizau, J. M.; Manson, S. T.; Morgan, T. J.; Blancard, C.

    2000-02-21

    We have measured the angle-resolved energy dependence of the electrons emitted over the energy range of the triply excited 2s{sup 2}2p P{sup 2} lithium resonance using synchrotron radiation. We have also calculated the behavior of the angular distribution parameter {beta} using the R -matrix approximation. Experimental and theoretical results are in good agreement and show deep minima in the 1s2p P{sup 1,} {sup 3} ionic channels. The energy at which the minima occur does not coincide with the resonance energy, but is shifted towards higher energy. (c) 2000 The American Physical Society.

  15. The Muon F-µ+-F Hydrogen Bond-like Complex.

    PubMed

    Blinc, Robert; Lahajnar, Gojmir; Potočnik, Anton

    2011-09-01

    Muon spin rotation (µSR) and relaxation has been used to study the local magnetic structure of K3Fe5F15. A collinear F-µ+-F "hydrogen bond-like" symmetric double minimum type complex with a F...F distance of 2.8 Å and a separation between the two minima of 0.8 Å has been found in the paramagnetic phase. The apparent central position of the muon seems to be the result of fast muon tunneling between two equivalent minima in the F-µ+-F bond.

  16. Validity of the kink approximation to the tunneling action

    NASA Astrophysics Data System (ADS)

    Dutta, Koushik; Hector, Cecelie; Konstandin, Thomas; Vaudrevange, Pascal M.; Westphal, Alexander

    2012-12-01

    Coleman tunneling in a general scalar potential with two nondegenerate minima is known to have an approximation in terms of a piecewise linear triangular-shaped potential with sharp “kinks” at the place of the local minima. This approximate potential has a regime where the existence of the bounce solution needs the scalar field to “wait” for some amount of Euclidean time at one of the kinks. We discuss under which conditions a kink approximation of locally smooth “cap” regions provides a good estimate for the bounce action.

  17. Energy landscape of social balance.

    PubMed

    Marvel, Seth A; Strogatz, Steven H; Kleinberg, Jon M

    2009-11-06

    We model a close-knit community of friends and enemies as a fully connected network with positive and negative signs on its edges. Theories from social psychology suggest that certain sign patterns are more stable than others. This notion of social "balance" allows us to define an energy landscape for such networks. Its structure is complex: numerical experiments reveal a landscape dimpled with local minima of widely varying energy levels. We derive rigorous bounds on the energies of these local minima and prove that they have a modular structure that can be used to classify them.

  18. Energy Landscape of Social Balance

    NASA Astrophysics Data System (ADS)

    Marvel, Seth A.; Strogatz, Steven H.; Kleinberg, Jon M.

    2009-11-01

    We model a close-knit community of friends and enemies as a fully connected network with positive and negative signs on its edges. Theories from social psychology suggest that certain sign patterns are more stable than others. This notion of social “balance” allows us to define an energy landscape for such networks. Its structure is complex: numerical experiments reveal a landscape dimpled with local minima of widely varying energy levels. We derive rigorous bounds on the energies of these local minima and prove that they have a modular structure that can be used to classify them.

  19. Protein folding simulations and structure predictions

    NASA Astrophysics Data System (ADS)

    Okamoto, Yuko

    2001-12-01

    In complex systems such as spin glasses and proteins, conventional simulations in the canonical ensemble will get trapped in states of energy local minima. We employ the simulated annealing method and generalized-ensemble algorithms in order to overcome this multiple-minima problem. Besides simulated annealing, three well-known generalized-ensemble algorithms, namely, multicanonical algorithm, simulated tempering, and replica-exchange method, are described. We then present three new generalized-ensemble algorithms based on the combinations of the three methods.

  20. Photometric geodesy of main-belt asteroids. III. Additional lightcurves

    SciTech Connect

    Weidenschilling, S.J.; Chapman, C.R.; Davis, D.R.; Greenberg, R.; Levy, D.H. )

    1990-08-01

    A total of 107 complete or partial lightcurves are presented for 59 different asteroids over the 1982-1989 period. Unusual lightcurves with unequal minima and maxima at large amplitudes are preferentially seen for M-type asteroids. Some asteroids, such as 16 Psyche and 201 Penelope, exhibit lightcurves combining large amplitude with very unequal brightness for both maxima and both minima, even at small phase angles. An M-type asteroid is believed to consist of a metal core of a differentiated parent body that has had its rocky mantle completely removed by one or more large impacts. 39 refs.

  1. The emergence of a new chlorophytan system, and Dr. Kornmann's contribution thereto

    NASA Astrophysics Data System (ADS)

    van den Hoek, C.; Stam, W. T.; Olsen, J. L.

    1988-09-01

    In traditional chlorophytan systems the organizational level was the primary character for the distinction of main groups (classes and orders). For instance, in Fott (1971), the flagellate level corresponds with the Volvocales, the coccoid level with the Chlorococcales, the filamentous level with the Ulotrichales, the siphonocladous level with the Siphonocladales, and the siphonous level with the Bryopsidales. The new system presented here is an elaboration and emendation of recently proposed taxonomies and their underlying phylogenetic hypotheses, and it is mainly based on ultrastructural features which have become available over the last 15 years. The following criteria are used for the distinction of classes and orders: (1) architecture of the flagellate cell (flagellate cells are considered as the depositories of primitive characters); (2) type of mitosis-cytokinesis; (3) place of meiosis in the life history and, consequently, the sexual life history type; (4) organizational level and thallus architecture; (5) habitat type (marine versus feshwater and terrestrial); (6) chloroplast type. The following classes are presented: Prasinophyceae, Chlamydophyceae, Ulvophyceae (orders Codiolales, Ulvales, Cladophorales, Bryopsidales, Dasycladales), Pleurastrophyceae (?), Chlorophyceae s.s. (orders Cylindrocapsales, Oedogoniales, Chaetophorales), Zygnematophyceae, Trentepohliophyceae, Charophyceae (orders Klebsormidiales, Coleochaetales, Charales). The new system no longer reflects the traditional hypothesis of a stepwise evolutionary progression of organizational levels in which the flagellate level represents the most primitive lineage, the coccoid and sarcinoid levels lineages of intermediate derivation, and the filamentous, siphonocladous and siphonous levels the most derived lineages. Instead, it is now hypothesized that these levels have arisen over and over again in different chlorophytan lineages which are primarily characterized by their type of flagellate cell

  2. Nuclear DNA Content Estimates in Green Algal Lineages: Chlorophyta and Streptophyta

    PubMed Central

    Kapraun, Donald F.

    2007-01-01

    Background and Aims Consensus higher-level molecular phylogenies present a compelling case that an ancient divergence separates eukaryotic green algae into two major monophyletic lineages, Chlorophyta and Streptophyta, and a residuum of green algae, which have been referred to prasinophytes or micromonadophytes. Nuclear DNA content estimates have been published for less than 1% of the described green algal members of Chlorophyta, which includes multicellular green marine algae and freshwater flagellates (e.g. Chlamydomonas and Volvox). The present investigation summarizes the state of our knowledge and adds substantially to our database of C-values, especially for the streptophyte charophycean lineage which is the sister group of the land plants. A recent list of 2C nuclear DNA contents for isolates and species of green algae is expanded by 72 to 157. Methods The DNA-localizing fluorochrome DAPI (4′,6-diamidino-2-phenylindole) and red blood cell (chicken erythrocytes) standard were used to estimate 2C values with static microspectrophotometry. Key Results In Chlorophyta, including Chlorophyceae, Prasinophyceae, Trebouxiophyceae and Ulvophyceae, 2C DNA estimates range from 0·01 to 5·8 pg. Nuclear DNA content variation trends are noted and discussed for specific problematic taxon pairs, including Ulotrichales–Ulvales, and Cladophorales–Siphonocladales. For Streptophyta, 2C nuclear DNA contents range from 0·2 to 6·4 pg, excluding the highly polyploid Charales and Desmidiales, which have genome sizes of up to 14·8 and 46·8 pg, respectively. Nuclear DNA content data for Streptophyta superimposed on a contemporary molecular phylogeny indicate that early diverging lineages, including some members of Chlorokybales, Coleochaetales and Klebsormidiales, have genomes as small as 0·1–0·5 pg. It is proposed that the streptophyte ancestral nuclear genome common to both the charophyte and the embryophyte lineages can be characterized as 1C = 0·2 pg and 1n = 6

  3. De novo sequencing and analysis of the Ulva linza transcriptome to discover putative mechanisms associated with its successful colonization of coastal ecosystems

    PubMed Central

    2012-01-01

    Background The green algal genus Ulva Linnaeus (Ulvaceae, Ulvales, Chlorophyta) is well known for its wide distribution in marine, freshwater, and brackish environments throughout the world. The Ulva species are also highly tolerant of variations in salinity, temperature, and irradiance and are the main cause of green tides, which can have deleterious ecological effects. However, limited genomic information is currently available in this non-model and ecologically important species. Ulva linza is a species that inhabits bedrock in the mid to low intertidal zone, and it is a major contributor to biofouling. Here, we presented the global characterization of the U. linza transcriptome using the Roche GS FLX Titanium platform, with the aim of uncovering the genomic mechanisms underlying rapid and successful colonization of the coastal ecosystems. Results De novo assembly of 382,884 reads generated 13,426 contigs with an average length of 1,000 bases. Contiguous sequences were further assembled into 10,784 isotigs with an average length of 1,515 bases. A total of 304,101 reads were nominally identified by BLAST; 4,368 isotigs were functionally annotated with 13,550 GO terms, and 2,404 isotigs having enzyme commission (EC) numbers were assigned to 262 KEGG pathways. When compared with four other full sequenced green algae, 3,457 unique isotigs were found in U. linza and 18 conserved in land plants. In addition, a specific photoprotective mechanism based on both LhcSR and PsbS proteins and a C4-like carbon-concentrating mechanism were found, which may help U. linza survive stress conditions. At least 19 transporters for essential inorganic nutrients (i.e., nitrogen, phosphorus, and sulphur) were responsible for its ability to take up inorganic nutrients, and at least 25 eukaryotic cytochrome P450s, which is a higher number than that found in other algae, may be related to their strong allelopathy. Multi-origination of the stress related proteins, such as glutamate

  4. De novo sequencing and analysis of the Ulva linza transcriptome to discover putative mechanisms associated with its successful colonization of coastal ecosystems.

    PubMed

    Zhang, Xiaowen; Ye, Naihao; Liang, Chengwei; Mou, Shanli; Fan, Xiao; Xu, Jianfang; Xu, Dong; Zhuang, Zhimeng

    2012-10-25

    The green algal genus Ulva Linnaeus (Ulvaceae, Ulvales, Chlorophyta) is well known for its wide distribution in marine, freshwater, and brackish environments throughout the world. The Ulva species are also highly tolerant of variations in salinity, temperature, and irradiance and are the main cause of green tides, which can have deleterious ecological effects. However, limited genomic information is currently available in this non-model and ecologically important species. Ulva linza is a species that inhabits bedrock in the mid to low intertidal zone, and it is a major contributor to biofouling. Here, we presented the global characterization of the U. linza transcriptome using the Roche GS FLX Titanium platform, with the aim of uncovering the genomic mechanisms underlying rapid and successful colonization of the coastal ecosystems. De novo assembly of 382,884 reads generated 13,426 contigs with an average length of 1,000 bases. Contiguous sequences were further assembled into 10,784 isotigs with an average length of 1,515 bases. A total of 304,101 reads were nominally identified by BLAST; 4,368 isotigs were functionally annotated with 13,550 GO terms, and 2,404 isotigs having enzyme commission (EC) numbers were assigned to 262 KEGG pathways. When compared with four other full sequenced green algae, 3,457 unique isotigs were found in U. linza and 18 conserved in land plants. In addition, a specific photoprotective mechanism based on both LhcSR and PsbS proteins and a C4-like carbon-concentrating mechanism were found, which may help U. linza survive stress conditions. At least 19 transporters for essential inorganic nutrients (i.e., nitrogen, phosphorus, and sulphur) were responsible for its ability to take up inorganic nutrients, and at least 25 eukaryotic cytochrome P450s, which is a higher number than that found in other algae, may be related to their strong allelopathy. Multi-origination of the stress related proteins, such as glutamate dehydrogenase, superoxide

  5. Artificial Neural Network Metamodels of Stochastic Computer Simulations

    DTIC Science & Technology

    1994-08-10

    Networks, Vol. 5 (1992), pp. 207-220. 55 Haykin, Op. Cit., pp. 190-191. 56 Gon, M. and Tesi , A., "On the Problem of Local Minima in Backpropagation," IEEE...Simulation Experiments: Taguchi Methods and Response Surface Metamodels, by J. Ramberg, S. Sanchez , P. Sanchez , and L. Hollick" (Piscataway, New Jersey

  6. Conformational analysis of thiophene analogs of propranolol

    NASA Astrophysics Data System (ADS)

    Corral, Carlos; Donoso, Rosa; Elguero, Jose; Goya, Pilar; Lissavetzky, Jaime; Rozas, Isabel

    1990-10-01

    Conformation of 3-tert-butylamino-1-thienyloxy-2-propanol, a thiophene analogue of propanolol, have been theoretically investigated by molecular mechanics and semiempirical calculations. The conformational minima obtained have been compared with those reported for propranolol using molecular graphics. The good "fit" obtained can account for the similar biological activity of these compounds.

  7. Hydrolysis of Phosphorus Esters: A Computational Study

    DTIC Science & Technology

    2005-04-01

    Bernhard. Reaction Path Following in Mass- Weighted Internal Coordinates. J. Phys. Chem. 1990, 94, pp 5523-7. 18. Onsager , Lars . Electric Moments of...confirm that the transition states did in fact connect their corresponding minima. For the inclusion of solvation on the anionic systems, the Onsager SCRF

  8. Characterization of the dynamics of glass-forming liquids from the properties of the potential energy landscape.

    PubMed

    Banerjee, Sumilan; Dasgupta, Chandan

    2012-02-01

    We develop a framework for understanding the difference between strong and fragile behavior in the dynamics of glass-forming liquids from the properties of the potential energy landscape. Our approach is based on a master equation description of the activated jump dynamics among the local minima of the potential energy (the so-called inherent structures) that characterize the potential energy landscape of the system. We study the dynamics of a small atomic cluster using this description as well as molecular dynamics simulations and demonstrate the usefulness of our approach for this system. Many of the remarkable features of the complex dynamics of glassy systems emerge from the activated dynamics in the potential energy landscape of the atomic cluster. The dynamics of the system exhibits typical characteristics of a strong supercooled liquid when the system is allowed to explore the full configuration space. This behavior arises because the dynamics is dominated by a few lowest-lying minima of the potential energy and the potential energy barriers between these minima. When the system is constrained to explore only a limited region of the potential energy landscape that excludes the basins of attraction of a few lowest-lying minima, the dynamics is found to exhibit the characteristics of a fragile liquid. © 2012 American Physical Society

  9. NextGen Avionics Roadmap, Version 1.2

    DTIC Science & Technology

    2010-09-21

    prediction information. Global Navigation Satellite System ( GNSS ), ADS-B Out, Aircraft Characteristic Database, Aircraft Wake Database, Wake...Aircraft-based wake vortex sensors are leveraged to further improve detection and prediction, reducing wake hazards in high-density operations. GNSS ...through reduction in approach minima for aircraft equipped with some combination of augmented GNSS , EFVS, and SVS capabilities. RNP SAAAR, GLS III

  10. THE IDENTIFICATION OF ALGAE WHICH INTERFERE WITH THE DETECTION OF GIARDIA AND CRYPTOSPORIDIUM AND A METHOD FOR ALLEVIATING THIS INTERFERENCE

    EPA Science Inventory

    Fifty-four algal species were tested for cross-reaction in the American Society for Testing and Materials Giardia/Cryptosporidium indirect immunofluorescence assay, and 24 showed some degree of fluorescence. Two species, Navicula minima and Synechococcus elongatus, exhibited a b...

  11. BAV-Results of Observations

    NASA Astrophysics Data System (ADS)

    Hübscher, Joachim

    2011-01-01

    This 67th compilation contains the results of visual and photographic observations of BAV-members mostly from the years 2009 and 2010. Here we publish altogether 468 minima and maxima of 152 eclipsing binaries and pulsating stars. The data were acquired by 13 observers.

  12. BAV-Results of observations

    NASA Astrophysics Data System (ADS)

    Hübscher, Joachim; Steinbach, Hans-Mereyntje; Vohla, Frank; Walter, Frank

    2009-01-01

    This 62nd compilation contains the results of visual observations of BAV-members from the years 2007 and 2008. Here we publish altogether 337 minima and maxima of 201 eclipsing binaries, pulsating and eruptive stars. The data were acquired by 14 observers. The compilation contains also one photographic- and two ccd-results.

  13. BAV-Results of Observations

    NASA Astrophysics Data System (ADS)

    Hübscher, Joachim

    2010-03-01

    This 64th compilation contains the results of visual and photographic observations of BAV-members from the years 2008 and 2009. Here we publish altogether 193 minima and maxima of 130 eclipsing binaries and pulsating stars. The data were acquired by 13 observers.

  14. VizieR Online Data Catalog: Observations of variable stars (Hubscher+, 2010)

    NASA Astrophysics Data System (ADS)

    Hubscher, J.

    2011-03-01

    This 64th compilation contains the results of visual and photographic observations of BAV-members from the years 2088 and 2009. Here we publish altogether 193 minima and maxima of 130 eclipsing binaries and pulsating stars. The data were acquiered by 13 observers. (3 data files).

  15. The Heat Capacity of Ideal Gases

    ERIC Educational Resources Information Center

    Scott, Robert L.

    2006-01-01

    The heat capacity of an ideal gas has been shown to be calculable directly by statistical mechanics if the energies of the quantum states are known. However, unless one makes careful calculations, it is not easy for a student to understand the qualitative results. Why there are maxima (and occasionally minima) in heat capacity-temperature curves…

  16. Structures of Cl-(H20)n and F-(H2O)n(n=2,3,...15) Clusters. Molecular Dynamics Computer Simulations

    DTIC Science & Technology

    1993-11-01

    basic cubic structure . As always, it is hard to know if our structures represent the global minima, but the similarity of the structures to the cubic ... structure of the established global minim.m indicate that our structures are close to the global minimum structures. Fig. 10 also shows that both F and

  17. USSR Report, Electronics and Electrical Engineering.

    DTIC Science & Technology

    2007-11-02

    results obtained by the thermoluminescence method with an LiF crystal. Both methods agree within their limits of accuracy. The microwave method is...MPa range. The behavior of electric charges was tracked by thermoluminescence measurements. Maxima of thermoluminescence were found to coincide...field intensity, with attendant shifting of thermoluminescence maxima and durability minima toward higher temperatures. Figures 5; references: 3

  18. Recycling, Thermodynamics and Environmental Thrift

    ERIC Educational Resources Information Center

    Berry, R. Stephen

    1972-01-01

    Compares the cost, in terms of thermodynamic potential, of manufacturing automobiles from raw mineral resources or from recycled vehicles, and of the production of extended-life products. Uses this as an example for arguing that new technologies, with efficiencies closer to the theoretical themodynamic minima, are needed if a society is to…

  19. Genetic Diversity Analysis of Indian Bitter Gourd (Momordica Charantia L.) Allows for the Development of Crop Improvement Strategies

    USDA-ARS?s Scientific Manuscript database

    Bitter gourd (Momordica charantia L. var. minima and var. maxima) or bitter melon is one of the most economically important cucurbit species worldwide. Although India is the center of origin of bitter melon, and cultivars and landraces of this species are widely cultivated in Asia, a rigorous asses...

  20. AFLP Analysis Provides Strategies for Improvement of Momordica Charantia L. (Bitter Gourd)

    USDA-ARS?s Scientific Manuscript database

    Monoecious bitter gourd (Momordica charantia L. var. minima and maxima Williams & Ng), a cucurbit of major economic importance, is widely cultivated in India, China, Africa, and South America. Although the morphology (i.e., growth habit and fruit shape, size, color and surface texture) of Indian bi...

  1. Decoding heat capacity features from the energy landscape

    NASA Astrophysics Data System (ADS)

    Wales, David J.

    2017-03-01

    A general scheme is derived to connect transitions in configuration space with features in the heat capacity. A formulation in terms of occupation probabilities for local minima that define the potential energy landscape provides a quantitative description of how contributions arise from competition between different states. The theory does not rely on a structural interpretation for the local minima, so it is equally applicable to molecular energy landscapes and the landscapes defined by abstract functions. Applications are presented for low-temperature solid-solid transitions in atomic clusters, which involve just a few local minima with different morphologies, and for cluster melting, which is driven by the landscape entropy associated with the more numerous high-energy minima. Analyzing these features in terms of the balance between states with increasing and decreasing occupation probabilities provides a direct interpretation of the underlying transitions. This approach enables us to identify a qualitatively different transition that is caused by a single local minimum associated with an exceptionally large catchment volume in configuration space for a machine learning landscape.

  2. Saddle Point Localization of Molecular Wavefunctions

    NASA Astrophysics Data System (ADS)

    Mellau, Georg Ch.; Kyuberis, Aleksandra; Polyansky, Oleg; Zobov, Nikolay Fedorovich; Field, Robert W.

    2016-06-01

    The quantum mechanical description of isomerization is based on bound eigenstates of the molecular potential energy surface. For the near-minimum regions there is a textbook-based relationship between the potential and eigenenergies. Here we show how the saddle point region that connects the two minima is encoded in the energy levels and wave functions of the potential energy surface.

  3. Weiss oscillations and particle-hole symmetry at the half-filled Landau level

    DOE PAGES

    Cheung, Alfred K. C.; Raghu, S.; Mulligan, Michael

    2017-06-15

    Particle-hole symmetry in the lowest Landau level of the two-dimensional electron gas requires the electrical Hall conductivity to equal ± e2/2h at half filling. Here, we study the consequences of weakly broken particle-hole symmetry for magnetoresistance oscillations about half filling in the presence of an applied periodic one-dimensional electrostatic potential using the Dirac composite fermion theory proposed by Son [Son, Phys. Rev. X 5, 031027 (2015)]. At fixed electron density, the oscillation minima are asymmetrically biased towards higher magnetic fields, while at fixed magnetic field the oscillations occur symmetrically as the electron density is varied about half filling. We findmore » an approximate “sum rule” obeyed for all pairs of oscillation minima that can be tested in experiment. The locations of the magnetoresistance oscillation minima for the composite fermion theory of Halperin, Lee, and Read (HLR) and its particle-hole conjugate agree exactly. Within the current experimental resolution, the locations of the oscillation minima produced by the Dirac composite fermion coincide with those of HLR. These results may indicate that all three composite fermion theories describe the same long-wavelength physics.« less

  4. Assessing genotypic diversity and symbiotic efficiency of five rhizobial legume interactions under cadmium stress for soil phytoremediation.

    PubMed

    Guefrachi, I; Rejili, M; Mahdhi, M; Mars, M

    2013-01-01

    In the framework of soil phytoremediation using local legume plants coupled with their native root-nodulating bacteria to increase forage yields and preserve contaminated soils in arid regions of Tunisia, we investigated the diversity of bacteria from root nodules of Lathyrus sativus, Lens culinaris, Medicago marina, M. truncatula, and M. minima and the symbiotic efficiency of these five legume symbiosis under Cadmium stress. Fifty bacterial strains were characterized using physiological and biochemical features such heavy metals resistant, and PCR-RFLP of 16S rDNA. Taxonomically, the isolates nodulating L. sativus, and L. culinaris are species within the genera Rhizobium and the ones associated to Medicago sp, within the genera Sinorhizobium. The results revealed also that the cadmium tolerance of the different legumes-rhizobia interaction was as follows: M. minima < M. truncatula < M. marina < L. sativus < L. culinaris indicating that the effect of Cadmium on root nodulation and biomass production is more deleterious on M. minima-S. meliloti and M. truncatula-S. meliloti than in other symbiosis. Knowledge on genetic and functional diversity of M. marina, L. sativus and L. culinaris microsymbiotes is very useful for inoculant strain selection and can be selected to develop inoculants for soil phytoremediation.

  5. Circulating tumor cell detection using photoacoustic spectral methods

    NASA Astrophysics Data System (ADS)

    Strohm, Eric M.; Berndl, Elizabeth S. L.; Kolios, Michael C.

    2014-03-01

    A method to detect and differentiate circulating melanoma tumor cells (CTCs) from blood cells using ultrasound and photoacoustic signals with frequencies over 100 MHz is presented. At these frequencies, the acoustic wavelength is similar to the dimensions of a cell, which results in unique features in the signal; periodically varying minima and maxima occur throughout the power spectrum. The spacing between minima depends on the ratio of the size to sound speed of the cell. Using a 532 nm pulsed laser and a 375 MHz center frequency wide-bandwidth transducer, the ultrasound and photoacoustic signals were measured from single cells. A total of 80 cells were measured, 20 melanoma cells, 20 white blood cells (WBCs) and 40 red blood cells (RBCs). The photoacoustic spectral spacing Δf between minima was 95 +/- 15 MHz for melanoma cells and greater than 230 MHz for RBCs. No photoacoustic signal was detected from WBCs. The ultrasonic spectral spacing between minima was 46 +/- 9 MHz for melanoma cells and 98 +/- 11 for WBCs. Both photoacoustic and ultrasound signals were detected from melanoma cells, while only ultrasound signals were detected from WBCs. RBCs showed distinct photoacoustic spectral variations in comparison to any other type of cell. Using the spectral spacing and signal amplitudes, each cell type could be grouped together to aid in cell identification. This method could be used for label-free counting and classifying cells in a sample.

  6. Roles of starting geometries in quantum mechanics studies of cellobiose

    USDA-ARS?s Scientific Manuscript database

    A relaxed HF/6 31G(d) energy surface was constructed for the fraction of phi,psi space that contains most geometries from crystals of molecules similar to cellobiose. Two regions around other minima were examined with unconstrained B3LYP/6 31+G(d) minimizations, as were two sub regions covered by th...

  7. Using Cayley's theorem to find the order of a power in a group

    NASA Astrophysics Data System (ADS)

    Dobbs, David E.

    2013-04-01

    It is shown how Cayley's theorem can be used to prove the formula for the order of a power of an element of finite order in a group. Reasoning with disjoint cycles leads to a proof that depends on elementary number theory in some new ways, leading naturally to some new connections involving least common multiples, greatest common divisors and minima.

  8. Four new cestode species from the spiral intestine of the round stingray, Urobatis halleri, in the Northern Gulf of California, Mexico

    Treesearch

    Megan M. Friggens; Donald W. Duszynski

    2005-01-01

    The spiral intestines of 40 specimens of Urobatis halleri from the northern Gulf of California, Mexico, were examined for cestodes. Four new species, Rhinebothrium chollaensis n. sp., Rhinebothrium gravidum n. sp., Eutetrarhynchus cortezensis n. sp., and Prochristianella minima n. sp., are described. This is the first record of these 3 genera in the Gulf of...

  9. Geomagnetic detection of the sectorial solar magnetic field and the historical peculiarity of minimum 23-24

    USGS Publications Warehouse

    Love, Jeffrey J.; Rigler, J.

    2012-01-01

    [1] Analysis is made of the geomagnetic-activityaaindex covering solar cycle 11 to the beginning of 24, 1868–2011. Autocorrelation shows 27.0-d recurrent geomagnetic activity that is well-known to be prominent during solar-cycle minima; some minima also exhibit a smaller amount of 13.5-d recurrence. Previous work has shown that the recent solar minimum 23–24 exhibited 9.0 and 6.7-d recurrence in geomagnetic and heliospheric data, but those recurrence intervals were not prominently present during the preceding minima 21–22 and 22–23. Using annual-averages and solar-cycle averages of autocorrelations of the historicalaadata, we put these observations into a long-term perspective: none of the 12 minima preceding 23–24 exhibited prominent 9.0 and 6.7-d geomagnetic activity recurrence. We show that the detection of these recurrence intervals can be traced to an unusual combination of sectorial spherical-harmonic structure in the solar magnetic field and anomalously low sunspot number. We speculate that 9.0 and 6.7-d recurrence is related to transient large-scale, low-latitude organization of the solar dynamo, such as seen in some numerical simulations.

  10. Soil spectra contributions to grass canopy spectral reflectance

    NASA Technical Reports Server (NTRS)

    Tucker, C. J.; Miller, L. D.

    1977-01-01

    The soil or background spectra contribution to grass canopy spectral reflectance for the 0.35 to 0.80 micron region was investigated using in situ collected spectral reflectance data. Regression analysis was used to estimate accurately the unexposed soil spectral reflectance and to quantify maxima and minima for soil-green vegetation reflection contrasts.

  11. Adult brightness vs. luminance as models of infant photometry: variability, biasability, and spectral characteristics for the two age groups favor the luminance model.

    PubMed

    Teller, Davida Y; Pereverzeva, Maria; Civan, Andrea L

    2003-01-01

    When infants fail to make chromatic discriminations, do the characteristics of their performance minima coincide more closely with the properties of adult luminance matches or heterochromatic brightness matches? In addition to their spectral properties, adult luminance matches are typically characterized by relatively small individual differences, whereas brightness matches are believed to be both more variable and more biasable. Two complementary experiments were carried out on adults and 8-week-old infant subjects. Both groups were tested with small (1.5 degrees to 4 degrees ) red and blue test fields of varying luminances, embedded in a white surround. In adults, heterochromatic brightness matches were measured. Individual differences spanned about 0.5 log units, and brightness matches could be biased by as much as 0.8 log units by varying the range of test field luminances. In infants, the locations of performance minima were measured. Individual differences spanned less than 0.1 log units, the mean performance minima coincided with predictions based on V10(lambda), and the location of the performance minimum was nearly unaffected by the range of test field luminances used. Thus by all three criteria, these data suggest that infants' performance minima are mediated by luminance rather than by brightness signals. To date there remains no evidence that the infant visual system computes a brightness signal.

  12. Double Eclipsing Binary Fitting

    NASA Astrophysics Data System (ADS)

    Cagas, P.; Pejcha, O.

    2012-06-01

    The parameters of the mutual orbit of eclipsing binaries that are physically connected can be obtained by precision timing of minima over time through light travel time effect, apsidal motion or orbital precession. This, however, requires joint analysis of data from different sources obtained through various techniques and with insufficiently quantified uncertainties. In particular, photometric uncertainties are often underestimated, which yields too small uncertainties in minima timings if determined through analysis of a χ2 surface. The task is even more difficult for double eclipsing binaries, especially those with periods close to a resonance such as CzeV344, where minima get often blended with each other. This code solves the double binary parameters simultaneously and then uses these parameters to determine minima timings (or more specifically O-C values) for individual datasets. In both cases, the uncertainties (or more precisely confidence intervals) are determined through bootstrap resampling of the original data. This procedure to a large extent alleviates the common problem with underestimated photometric uncertainties and provides a check on possible degeneracies in the parameters and the stability of the results. While there are shortcomings to this method as well when compared to Markov Chain Monte Carlo methods, the ease of the implementation of bootstrapping is a significant advantage.

  13. The Heat Capacity of Ideal Gases

    ERIC Educational Resources Information Center

    Scott, Robert L.

    2006-01-01

    The heat capacity of an ideal gas has been shown to be calculable directly by statistical mechanics if the energies of the quantum states are known. However, unless one makes careful calculations, it is not easy for a student to understand the qualitative results. Why there are maxima (and occasionally minima) in heat capacity-temperature curves…

  14. 3D Clumped Cell Segmentation Using Curvature Based Seeded Watershed.

    PubMed

    Atta-Fosu, Thomas; Guo, Weihong; Jeter, Dana; Mizutani, Claudia M; Stopczynski, Nathan; Sousa-Neves, Rui

    2016-12-01

    Image segmentation is an important process that separates objects from the background and also from each other. Applied to cells, the results can be used for cell counting which is very important in medical diagnosis and treatment, and biological research that is often used by scientists and medical practitioners. Segmenting 3D confocal microscopy images containing cells of different shapes and sizes is still challenging as the nuclei are closely packed. The watershed transform provides an efficient tool in segmenting such nuclei provided a reasonable set of markers can be found in the image. In the presence of low-contrast variation or excessive noise in the given image, the watershed transform leads to over-segmentation (a single object is overly split into multiple objects). The traditional watershed uses the local minima of the input image and will characteristically find multiple minima in one object unless they are specified (marker-controlled watershed). An alternative to using the local minima is by a supervised technique called seeded watershed, which supplies single seeds to replace the minima for the objects. Consequently, the accuracy of a seeded watershed algorithm relies on the accuracy of the predefined seeds. In this paper, we present a segmentation approach based on the geometric morphological properties of the 'landscape' using curvatures. The curvatures are computed as the eigenvalues of the Shape matrix, producing accurate seeds that also inherit the original shape of their respective cells. We compare with some popular approaches and show the advantage of the proposed method.

  15. Optical Physics of Microcavity Surface Emitting Lasers

    DTIC Science & Technology

    2007-11-02

    in confinement factor balances the change in mirror reflectance. For TM and HEM modes, no minima exists since the mirror reflectance is approximately...Noble. "Model of Intra and Extracavity Photodetection for Planar Resonant Cavity Light Emitting Diodes." 24th International Symposium on Compound

  16. 14 CFR 29.1389 - Position light distribution and intensities.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... maximum intensities in overlapping beams, within dihedral angles, L, R, and A, and must meet the following... overlaps may be used with the use of main beam intensities substantially greater than the minima specified in §§ 29.1391 and 29.1393 if the overlap intensities in relation to the main beam intensities do not...

  17. 14 CFR 27.1389 - Position light distribution and intensities.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... intensities in overlapping beams, within dihedral angles L, R, and A, and must meet the following requirements... overlaps may be used with main beam intensities substantially greater than the minima specified in §§ 27.1391 and 27.1393, if the overlap intensities in relation to the main beam intensities do not adversely...

  18. FLOYDS Classification of ASASSN-14dq as a Young Type II SN

    NASA Astrophysics Data System (ADS)

    Arcavi, I.; Valenti, S.; Howell, D. A.; Sand, D.

    2014-07-01

    We obtained a spectrum of ASASSN-14dq (ATel #6301) on 2014 July 9.5 (UT) with the robotic FLOYDS instrument mounted on the Faulkes Telescope North. The spectrum displays a blue continuum with broad hydrogen p-cygni features having absorption minima at ~10000 km/s.

  19. FLOYDS Classification of ASASSN-14ha as a Young Type II SN

    NASA Astrophysics Data System (ADS)

    Arcavi, I.; Valenti, S.; Hosseinzadeh, G.; Mccully, C.; Howell, D. A.; Sand, D.

    2014-09-01

    We obtained a spectrum of ASASSN-14ha (ATel #6460) on 2014 September 13 (UT) with the robotic FLOYDS instrument mounted on the Faulkes Telescope South. The spectrum displays a blue continuum with H and He I p-cygni features at the redshift of the host galaxy (z~0.05), showing relatively low velocity (~3000-4000 km/s) absorption minima.

  20. Prelimary Photoelectric Light Curve for DHK29=SAO 70629

    NASA Astrophysics Data System (ADS)

    Kaiser, Daniel H.; Gunn, Jerry B.; Lamb, Charles F.; Sullivan, Philip

    The newly discovered eclipsing binary star DHK 29 = SAO 70629 has been observed photoelectrically from October 1992 to October 1993. With the light curve coverage 75% complete, it is apparent that the initial 1.9-day period reported in IB VS 3815 is the half-period. Three times of primary minima have been determined. New light elements are given.

  1. Soil spectra contributions to grass canopy spectral reflectance

    NASA Technical Reports Server (NTRS)

    Tucker, C. J.; Miller, L. D.

    1977-01-01

    The soil or background spectra contribution to grass canopy spectral reflectance for the 0.35 to 0.80 micron region was investigated using in situ collected spectral reflectance data. Regression analysis was used to estimate accurately the unexposed soil spectral reflectance and to quantify maxima and minima for soil-green vegetation reflection contrasts.

  2. Examination of Bursty Electromagnetic Waves Observed During Intervals of Turbulent Magnetosheath Reconnection

    NASA Technical Reports Server (NTRS)

    Adrian, Mark L.; Wendel, D. E.

    2011-01-01

    We investigate observations of intense bursts of electromagnetic waves in association with magnetic reconnection in the turbulent magnetosheath. These structured, broadband bursts occur above 80-Hz, often displaying features reminiscent of absorption bands and are observed at local minima in the magnetic field. We present detailed analyses of these intense bursts of electromagnetic waves and quantify their proximity to X- and O-nulls.

  3. Laplacian Smoothing Splines with Generalized Cross Validation for Objective Analysis of Meteorological Data.

    DTIC Science & Technology

    1985-08-01

    REPOR NUMUERVi ACCESO NO3. RECIPIENT’S CATALOG HUMMER NPS-53-85-0008 __ 4. TITLE (and ,Subite) S. TYPE OF REPORT & PERIOD COVER[’D Technical Report...is best. Though not discernable from the table, the GCV func- tion generally was found to have multiple local minima, especial- ly for the larger data

  4. Increasing synchrony of high temperature and low flow in western North American streams: Double trouble for coldwater biota?

    Treesearch

    Ivan Arismendi; Mohammad Safeeq; Sherri L. Johnson; Jason B Dunham; Roy. Haggerty

    2013-01-01

    Flow and temperature are strongly linked environmental factors driving ecosystem processes in streams. Stream temperature maxima (Tmax_w) and stream flow minima (Qmin) can create periods of stress for aquatic organisms. In mountainous areas, such as western North America, recent shifts toward an earlier spring peak flow and...

  5. "In Situ" Observation of a Soap-Film Catenoid--A Simple Educational Physics Experiment

    ERIC Educational Resources Information Center

    Ito, Masato; Sato, Taku

    2010-01-01

    The solution to the Euler-Lagrange equation is an extremal functional. To understand that the functional is stationary at local extrema (maxima or minima), we propose a physics experiment that involves using a soap film to form a catenoid. A catenoid is a surface that is formed between two coaxial circular rings and is classified mathematically as…

  6. "In Situ" Observation of a Soap-Film Catenoid--A Simple Educational Physics Experiment

    ERIC Educational Resources Information Center

    Ito, Masato; Sato, Taku

    2010-01-01

    The solution to the Euler-Lagrange equation is an extremal functional. To understand that the functional is stationary at local extrema (maxima or minima), we propose a physics experiment that involves using a soap film to form a catenoid. A catenoid is a surface that is formed between two coaxial circular rings and is classified mathematically as…

  7. IDENTIFICATION OF ALGAE WHICH INTERFERE WITH THE DETECTION OF GIARDIA CYSTS AND CRYPTOSPORIDIUM OOCYSTS AND A METHOD FOR ALLEVIATING THIS INTERFERENCE

    EPA Science Inventory

    Fifty-four algal species were tested for cross-reaction in the American Society for Testing and Materials Giardia/Cryptosporidium indirect immunofluorescence assay, and 24 showed some degree of fluorescence. Two species, Navicula minima and Synechococcus elongatus, exhibited a br...

  8. Software for Fermat's Principle and Lenses

    ERIC Educational Resources Information Center

    Mihas, Pavlos

    2012-01-01

    Fermat's principle is considered as a unifying concept. It is usually presented erroneously as a "least time principle". In this paper we present some software that shows cases of maxima and minima and the application of Fermat's principle to the problem of focusing in lenses. (Contains 12 figures.)

  9. Software for Fermat's Principle and Lenses

    ERIC Educational Resources Information Center

    Mihas, Pavlos

    2012-01-01

    Fermat's principle is considered as a unifying concept. It is usually presented erroneously as a "least time principle". In this paper we present some software that shows cases of maxima and minima and the application of Fermat's principle to the problem of focusing in lenses. (Contains 12 figures.)

  10. Higher-Spin Theory of the Magnetorotons

    NASA Astrophysics Data System (ADS)

    Golkar, Siavash; Nguyen, Dung Xuan; Roberts, Matthew M.; Son, Dam Thanh

    2016-11-01

    Fractional quantum Hall liquids exhibit a rich set of excitations, the lowest energy of which are the magnetorotons with dispersion minima at a finite momentum. We propose a theory of the magnetorotons on the quantum Hall plateaux near half filling, namely, at filling fractions ν =N /(2 N +1 ) at large N . The theory involves an infinite number of bosonic fields arising from bosonizing the fluctuations of the shape of the composite Fermi surface. At zero momentum there are O (N ) neutral excitations, each carrying a well-defined spin that runs integer values 2 ,3 ,…. The mixing of modes at nonzero momentum q leads to the characteristic bending down of the lowest excitation and the appearance of the magnetoroton minima. A purely algebraic argument shows that the magnetoroton minima are located at q ℓB=zi/(2 N +1 ), where ℓB is the magnetic length and zi are the zeros of the Bessel function J1, independent of the microscopic details. We argue that these minima are universal features of any two-dimensional Fermi surface coupled to a gauge field in a small background magnetic field.

  11. Material Properties and Defects Characterization Using LLW Data

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Y.; Mal, A.; Chang, Z.

    1998-01-01

    Leaky Lamb Wave (LLW) propagation in composite materials has been studied extensively since it was first observed in 1982. The wave is induced using a pitch-catch arrangement and the plate wave modes are detected by identifying minima in the reflected spectra to obtain the dispersion data.

  12. IDENTIFICATION OF ALGAE WHICH INTERFERE WITH THE DETECTION OF GIARDIA CYSTS AND CRYPTOSPORIDIUM OOCYSTS AND A METHOD FOR ALLEVIATING THIS INTERFERENCE

    EPA Science Inventory

    Fifty-four algal species were tested for cross-reaction in the American Society for Testing and Materials Giardia/Cryptosporidium indirect immunofluorescence assay, and 24 showed some degree of fluorescence. Two species, Navicula minima and Synechococcus elongatus, exhibited a br...

  13. THE IDENTIFICATION OF ALGAE WHICH INTERFERE WITH THE DETECTION OF GIARDIA AND CRYPTOSPORIDIUM AND A METHOD FOR ALLEVIATING THIS INTERFERENCE

    EPA Science Inventory

    Fifty-four algal species were tested for cross-reaction in the American Society for Testing and Materials Giardia/Cryptosporidium indirect immunofluorescence assay, and 24 showed some degree of fluorescence. Two species, Navicula minima and Synechococcus elongatus, exhibited a b...

  14. Molecular photoionization as a probe of vibrational-rotational-electronic correlations

    NASA Astrophysics Data System (ADS)

    Rao, R. M.; Poliakoff, E. D.; Wang, Kwanghsi; McKoy, V.

    1996-06-01

    We determine the rotationally state-resolved 2σu-1 photoionization of N2 into alternative vibrational channels as a function of energy over a 200 eV range. Experiment and theory reveal that Cooper minima highlight the coupling between electronic, vibrational, and rotational degrees of freedom over this very wide range.

  15. Ultrasonic Characterization of Flaws in Composites Using Plate Waves Dispersion Data

    NASA Technical Reports Server (NTRS)

    Shiuh, S.; Bar-Cohen, Y.

    1997-01-01

    Leaky Lamb wave (LLW) propagation in composite materials has been studied extensively since it was first observed in 1982. The wave is induced using a pitch-catch arrangement and the plate wave modes are detected by searching minima in the reflected spectra.

  16. Recycling, Thermodynamics and Environmental Thrift

    ERIC Educational Resources Information Center

    Berry, R. Stephen

    1972-01-01

    Compares the cost, in terms of thermodynamic potential, of manufacturing automobiles from raw mineral resources or from recycled vehicles, and of the production of extended-life products. Uses this as an example for arguing that new technologies, with efficiencies closer to the theoretical themodynamic minima, are needed if a society is to…

  17. Elastic Rod Model of a DNA Loop in the Lac Operon

    NASA Astrophysics Data System (ADS)

    Balaeff, Alexander; Mahadevan, L.; Schulten, Klaus

    1999-12-01

    We use the theory of elasticity to compute the shape of the DNA loop bridging the gap in the crystal structure of the lac repressor-DNA complex. The Kirchhoff system of equations with boundary conditions derived from the crystal structure is solved using a continuation method. This approach can be applied effectively to find coarse-grained conformational minima of DNA loops.

  18. Quasibiennial Periodicity of Solar and Planetary Phenomena

    NASA Astrophysics Data System (ADS)

    Predeanu, Irina

    The quasibiennial oscillation (QBO) of various solar and geophysical parameters is anlysed, taking some planetary configurations as temporal reference points. The incidence of the QBO minima in the proximity of Sun-Mars oppositions is discussed. The increase of this effect when Mars is near the perihelion or Jupiter is conjunct to the Sun is pointed out,

  19. ESTIMATION OF TOTAL DISSOLVED NITRATE LOAD IN NATURAL STREAM FLOWS USING AN IN-STREAM MONITOR

    EPA Science Inventory

    Estuaries respond rapidly to rain events and the nutrients carried by inflowing rivers such that discrete samples at weekly or monthly intervals are inadequate to catch the maxima and minima in nutrient variability. To acquire data with sufficient sampling frequency to realistica...

  20. Weiss oscillations and particle-hole symmetry at the half-filled Landau level

    NASA Astrophysics Data System (ADS)

    Cheung, Alfred K. C.; Raghu, S.; Mulligan, Michael

    2017-06-01

    Particle-hole symmetry in the lowest Landau level of the two-dimensional electron gas requires the electrical Hall conductivity to equal ±e2/2 h at half filling. We study the consequences of weakly broken particle-hole symmetry for magnetoresistance oscillations about half filling in the presence of an applied periodic one-dimensional electrostatic potential using the Dirac composite fermion theory proposed by Son [Son, Phys. Rev. X 5, 031027 (2015), 10.1103/PhysRevX.5.031027]. At fixed electron density, the oscillation minima are asymmetrically biased towards higher magnetic fields, while at fixed magnetic field the oscillations occur symmetrically as the electron density is varied about half filling. We find an approximate "sum rule" obeyed for all pairs of oscillation minima that can be tested in experiment. The locations of the magnetoresistance oscillation minima for the composite fermion theory of Halperin, Lee, and Read (HLR) and its particle-hole conjugate agree exactly. Within the current experimental resolution, the locations of the oscillation minima produced by the Dirac composite fermion coincide with those of HLR. These results may indicate that all three composite fermion theories describe the same long-wavelength physics.

  1. Soil respiration from four aggrading forested watersheds measured over a quarter century

    Treesearch

    David C. Coleman; Mark D. Hunter; John Hutton; Steven Pomeroy; Lloyd Swift

    2002-01-01

    Soil respiration was measured in four aggrading, forested second-growth watersheds in the southern Appalachians using an identical method (alkali absorption) at intervals 23 and 24 years apart. Seasonal trends were similar, with mid-summer maxima and winter minima. Amounts of carbon dioxide evolved were higher in the recent measurements (1995) compared to the earlier...

  2. A measurement by BOOMERANG of multiple peaks in the angular power spectrum of the cosmic microwave background

    NASA Technical Reports Server (NTRS)

    Netterfield, C. B.; Ade, P. A. R.; Bock, J. J.; Bond, J. R.; Borrill, J.; Boscaleri, A.; Coble, K.; Contaldi, C. R.; Crill, B. P.; Bernardis, P. de; Farese, P.; Ganga, K.; Giacometti, M.; Hivon, E.; Hristov, V. V.; Iacoangeli, A.; Jaffe, A. H.; Jones, W. C.; Lange, A. E.; Martinis, L.; Masi, S.; Mason, P.; Mauskopf, P.; Melchiorri, A.; Montroy, T.

    2001-01-01

    This paper presents a measurement of the angular power spectrum of the Cosmic Microwave Background from l = 75 to l = 1025 (10' to 5 degrees) from a combined analysis of four 150 GHz channels in the BOOMERANG experiment. The spectrum contains multiple peaks and minima, as predicted by standard adiabatic-inflationary models in which the primordial plasma undergoes acoustic oscillations.

  3. Diffusion of a protein in configuration space

    SciTech Connect

    Garcia, A.E.; Blumenfeld, R.; Hummer, G.; Sobehart, J.

    1995-09-01

    Simulations of biomolecular dynamics are commonly interpreted in terms of harmonic or quasi-harmonic models for the dynamics of the system. These models assume that biomolecules exhibit oscillations around a single energy minimum. However, spectroscopic data on myoglobin suggest that proteins sample multiple minima. Transitions between minima reveal a broad distribution of energy barriers. This behavior has been observed in other biomolecular systems. To elucidate the nature of protein dynamics the authors have studied a 1.2ns molecular dynamics trajectory of crambin in aqueous solution. This trajectory samples multiple local energy minima. Transitions between minima involve collective motions of amino acids over long distances. The authors show that nonlinear motions are responsible for most of the atomic fluctuations of the protein. These atomic fluctuations are not well described by large motions of individual atoms or a small group of atoms, but rather by concerted motions of many atoms. These nonlinear motions describe transitions between different basins of attraction. The signature of these motions manifests in local and global structural variables. A method for extracting Molecule Optimal Dynamic Coordinates (MODC) is presented.

  4. Molecular shape and the energetics of chemisorption: From simple to complex energy landscapes

    NASA Astrophysics Data System (ADS)

    Huang, David M.; Harrowell, Peter

    2012-07-01

    We enumerate all local minima of the energy landscape for model rigid adsorbates characterized by three or four equivalent binding sites (e.g., thiol groups) on a close-packed (111) surface of a face-centered-cubic crystal. We show that the number of energy minima increases linearly with molecular size with a rate of increase that depends on the degree of registry between the molecule shape and the surface structure. The sparseness of energy minima and the large variations in the center-of-mass positions of these minima vs molecular size for molecules that are incommensurate with the surface suggests a strong coupling in these molecules between surface mobility and shape or size fluctuations resulting from molecular vibrations. We also find that the variation in the binding energy with respect to molecular size decreases more rapidly with molecular size for molecules with a higher degree of registry with the surface. This indicates that surface adsorption should be better able to distinguish molecules by size if the molecules are incommensurate with the surface.

  5. Simple and effective procedure for conformational search of macromolecules. Application to Met- and Leu-Enkephalin

    SciTech Connect

    Meirovitch, H.; Meirovitch, E. ); Michel, A.G. ); Vasquez, M. )

    1994-06-23

    A simple and efficient method for searching the conformational space of macromolecules is presented. With this method an initial set of relatively low-energy structures is generated, and their energies are further minimized with a procedure that enables escaping from local energy minima. Illustrative calculations are described for Met- and Leu-enkephalin. 37 refs., 1 tab.

  6. ESTIMATION OF TOTAL DISSOLVED NITRATE LOAD IN NATURAL STREAM FLOWS USING AN IN-STREAM MONITOR

    EPA Science Inventory

    Estuaries respond rapidly to rain events and the nutrients carried by inflowing rivers such that discrete samples at weekly or monthly intervals are inadequate to catch the maxima and minima in nutrient variability. To acquire data with sufficient sampling frequency to realistica...

  7. 14 CFR 91.169 - IFR flight plan: Information required.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... following: (i) For aircraft other than helicopters. For at least 1 hour before and for 1 hour after the... visibility will be at least 3 statute miles. (ii) For helicopters. At the estimated time of arrival and for 1... to the operator, for that airport, the following minima: (i) For aircraft other than helicopters: The...

  8. 14 CFR 91.169 - IFR flight plan: Information required.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... following: (i) For aircraft other than helicopters. For at least 1 hour before and for 1 hour after the... visibility will be at least 3 statute miles. (ii) For helicopters. At the estimated time of arrival and for 1... to the operator, for that airport, the following minima: (i) For aircraft other than helicopters: The...

  9. 14 CFR 91.169 - IFR flight plan: Information required.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... following: (i) For aircraft other than helicopters. For at least 1 hour before and for 1 hour after the... visibility will be at least 3 statute miles. (ii) For helicopters. At the estimated time of arrival and for 1... to the operator, for that airport, the following minima: (i) For aircraft other than helicopters: The...

  10. Real-Time Characterization of Materials Degradation Using Leaky Lamb Wave

    NASA Technical Reports Server (NTRS)

    Shiuh, S.; Bar-Cohen, Y.

    1997-01-01

    Leaky Lamb wave (LLW) propagation in composite materials has been studied extensively since it was first observed in 1982. The wave is induced using a pitch-catch arrangement and the plate wave modes are detected by searching minima in the reflected spectra.

  11. 2. QUANTUM HALL EFFECT: Magnetocapacitance studies of two-dimensional electron systems with long-range potential fluctuations

    NASA Astrophysics Data System (ADS)

    Dorokhova, M. O.; Dorozhkin, S. I.

    2001-10-01

    We report on magnetocapacitance study of the quantum Hall effect (QHE) states. Capacitance minima width was found to be independent of magnetic field and to be the same for even, odd and fractional QHE states when measured as a function of the average electron density. This result indicates that the width of capacitance minima in the samples investigated are governed by long-range carrier density fluctuations. At low temperatures, the amplitudes of the minima decrease linearly with the temperature increase. All our experimental results for the integer QHE states are quantitatively explained by introducing unbroadened magnetic levels and dispersion of the electron density along the sample. The energy gaps at even filling factors obtained from fitting the experimental data are found to be close to the known cyclotron gaps. At odd fillings v = 1, 3, and 5, the energy gaps appear to be enhanced in comparison with the Zeeman splitting, with the enhancement decreasing with filling factor. The capacitance minima are argued to originate from the motion of incompressible regions along a sample caused by the gate voltage variation. We derive the condition for the appearance and motion of such regions for the case of gated samples with long-range fluctuations of density of charged donors. The appearance of narrow magnetocapacitance peaks when a dc current is passed through the sample is reported. We hypothesize that these peaks are due to the current percolation along incompressible regions.

  12. Cadophora species as trunk pathogens and wood-infecting fungi of grapevine in North America

    USDA-ARS?s Scientific Manuscript database

    Cadophora species, in particular Cadophora luteo-olivacea, are reported from grapevine (Vitis vinifera L.) in California, South Africa, Spain, Uruguay, and Canada. Frequent isolation from vines co-infected with the Esca pathogens (Togninia minima, Phaeomoniella chlamydospora), and confirmation of it...

  13. Relativistic calculations of angle-dependent photoemission time delay

    NASA Astrophysics Data System (ADS)

    Kheifets, Anatoli; Mandal, Ankur; Deshmukh, Pranawa C.; Dolmatov, Valeriy K.; Keating, David A.; Manson, Steven T.

    2016-07-01

    Angular dependence of photoemission time delay for the valence n p3 /2 and n p1 /2 subshells of Ar, Kr, and Xe is studied in the dipole relativistic random phase approximation. Strong angular anisotropy of the time delay is reproduced near respective Cooper minima while the spin-orbit splitting affects the time delay near threshold.

  14. The unusual lightcurve of 1990 TR

    NASA Technical Reports Server (NTRS)

    Wisniewski, Wieslaw Z.

    1992-01-01

    Amor asteroid 1990 TR was monitored during three nights shortly after discovery. Obtained lightcurves did not reveal a repeatable curve with two maxima and two minima. However, some features suggest periodicity, and a synodic rotational period P = 6.25 hours was determined. Individual and composite lightcurves are presented. The colors are best represented by the class S.

  15. The role of solar activities & IMF(Bz) on the severe storm of March 13 - 14 1989.

    NASA Astrophysics Data System (ADS)

    Eucharia; Okoro, Chidinma

    We present the statistical study of the severe geomagnetic activity of the 13 - 14th March 1989 as observed using the World Data Centre Observatories; Kyoto, Japan. Increase of the amplitude sudden commencements with solar minima which was not the case was predicted and IMF points Northward(Southward). Discussion that the effect could be from coronal mass ejection and other parameters were illustrated.

  16. Learning Extrema Problems Using a Non-Differential Approach in a Digital Dynamic Environment: The Case of High-Track yet Low-Achievers

    ERIC Educational Resources Information Center

    Dvir, Assaf; Tabach, Michal

    2017-01-01

    High schools commonly use a differential approach to teach minima and maxima geometric problems. Although calculus serves as a systematic and powerful technique, this rigorous instrument might hinder students' ability to understand the behavior and constraints of the objective function. The proliferation of digital environments allowed us to adopt…

  17. Modeling hardwood crown radii using circular data analysis

    Treesearch

    Paul F. Doruska; Hal O. Liechty; Douglas J. Marshall

    2003-01-01

    Cylindrical data are bivariate data composed of a linear and an angular component. One can use uniform, first-order (one maximum and one minimum) or second-order (two maxima and two minima) models to relate the linear component to the angular component. Crown radii can be treated as cylindrical data when the azimuths at which the radii are measured are also recorded....

  18. Theoretical studies of collisional relaxation of highly excited SO{sub 2} in an Ar bath

    SciTech Connect

    Lendvay, G.; Schatz, G.C.; Harding, L.B.

    1995-12-31

    This paper describes molecular dynamics studies of collisional relaxation of highly excited SO{sub 2} in an Ar bath. Most of the calculations use a newly developed global ab initio potential surface for SO{sub 2} that correctly describes the superoxide (SOO) and ring isomers of SO{sub 2} that occur as secondary minima on the ground state potential surface at high energies (about 75% of the dissociation energy) above the C{sub 2v} minimum. Rate constants for the S + O{sub 2} and O + SO reactions are calculated to test this surface, and to examine the importance of electronically excited states in the O + SO recombination. The Ar + SO{sub 2} collisions are described by summing the ab initio potential with empirical intermolecular potentials. The resulting average vibrational energy transfer <{Delta}E> per collision is in good agreement with direct measurements (done at energies where the secondary minima are not populated) at 1000K, but the agreement is poorer at 300K. The agreement is significantly better than was obtained in a previous theoretical study, and our results indicate that the use of improved intramolecular and intermolecular potentials is crucial to obtaining the better results. The energy dependence of <{Delta}E> is found to be much stronger at energies where the secondary minima on the potential surface are accessible, however much of this effect is reproduced using a potential that has the same dissociation energy but not the secondary minima.

  19. 50 forgotten Miras

    NASA Astrophysics Data System (ADS)

    Karlsson, T.; Bengtsson, H.; Wikander, T.; Holmberg, G.; Wahlström, R.; Allen, C.

    2016-12-01

    We report the results of 4 years observing of 50 poorly studied Mira stars. 247 maxima and 241 minima together with current period elements, ranges and colour indices for the stars are presented. "50 forgotten Miras" is an ongoing observing program run by SAAF/V that started in 2012.

  20. Determination and classification of the aerodynamic properties of wing sections

    NASA Technical Reports Server (NTRS)

    Munk, Max M

    1925-01-01

    The following note, prepared for the NACA, contains several remarks on the possible improvement of the experimental determination of the aerodynamic properties of wing sections. It shows how errors of observation can subsequently be partially eliminated, and how the computation of the maxima or minima of aerodynamic characteristics can be much improved.

  1. Electronic states of GeCl +

    NASA Astrophysics Data System (ADS)

    Dai, Dingguo; Xu, Hua; Balasubramanian, K.

    1995-11-01

    Twenty-eight electronic states of GeCl + are studied using the complete active space self-consistent field (CASSCF) followed by first- and second-order configuration interaction (FOCI, SOCI) methods. Spectroscopic constants of electronic states exhibiting minima are computed.

  2. Shoot regeneration of mesophyll protoplasts transformed by Agrobacterium tumefaciens, not achievable with untransformed protoplasts.

    PubMed

    Steffen, A; Eriksson, T; Schieder, O

    1986-04-01

    Alternative methods for shoot regeneration in protoplast derived cultures were developed in Nicotiana paniculata and Physalis minima. In both species protoplast derived callus is not regeneratable to shoots by conventional methods, e.g. hormone treatment. Leaf discs and stem segments of N. paniculata and P. minima were incubated with Agrobacterium tumefaciens "shooter" strains harbouring pGV 2215 or pGV 2298 or wildtype strain B6S3. After 36 h of co-incubation protoplasts were prepared. (Leaf disc and stem segment cloning). Co-cultivation experiments were also undertaken with protoplasts of both species. Transformed clones, characterized by their hormone independent growth and octopine production, could be isolated after about two months. Transformation frequencies of "leaf disc and stem segment cloning" and co-cultivation experiments varied from 5×10(-3) to 5×10(-5). After about one year of cultivation on hormone-free culture medium, shoots could be recovered from colonies of N. paniculata, transformed by the strain harbouring pGV 2298. In protoplast derived colonies of P. minima, shoot induction was obtained only after transformation by bacteria carrying pGV 2215. This demonstrates the importance of the particular "shooter" mutant, as well as the response of the host plant. Transformed shoots of P. minima produced octopine, whereas octopine production in transformed shoots and callus of N. paniculata was undetectable after one year of cultivation, though T-DNA was still present in the plant genome. Transformed shoots of N. paniculata and P. minima do not produce any roots. Shoots of N. paniculata have an especially tumerous phenotype. Shoots of both species were successfully grafted to normal donor plants of N. tabacum.

  3. Detachment of fullerene nC60 nanoparticles in saturated porous media under flow/stop-flow conditions: Column experiments and mechanistic explanations.

    PubMed

    Wang, Zhan; Wang, Dengjun; Li, Baoguo; Wang, Jizhong; Li, Tiantian; Zhang, Mengjia; Huang, Yuanfang; Shen, Chongyang

    2016-06-01

    This study was aimed at investigating the detachment of fullerene nC60 nanoparticles (NPs) in saturated sand porous media under transient and static conditions. The nC60 NPs were first attached at primary minima of Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energy profiles in electrolyte solutions with different ionic strengths (ISs). The columns were then eluted with deionized water to initiate nC60 NP detachment by decreasing solution IS. Finally, the flow of the columns was periodically interrupted to investigate nC60 NP detachment under static condition. Our results show that the detachment of nC60 NPs occurred under both transient and static conditions. The detachment under transient conditions was attributed to the fact that the attractions acting on the nC60 NPs at primary minima were weakened by nanoscale physical heterogeneities and overcome by hydrodynamic drags at lower ISs. However, a fraction of nC60 NPs remained at shallow primary minima in low flow regions, and detached via Brownian diffusion during flow interruptions. Greater detachment of nC60 NPs occurred under both transient and static conditions if the NPs were initially retained in electrolyte solutions with lower valent cations due to lower attractions between the NPs and collectors. Decrease in collector surface chemical heterogeneities and addition of dissolved organic matter also increased the extent of detachment by increasing electrostatic and steric repulsions, respectively. While particle attachment in and subsequent detachment from secondary minima occur in the same electrolyte solution, our results indicate that perturbation in solution chemistry is necessary to lower the primary minimum depths to initiate spontaneous detachment from the primary minima. These findings have important implications for predicting the fate and transport of nC60 NPs in subsurface environments during multiple rainfall events and accordingly for accurately assessing their environmental risks

  4. Solar extreme ultraviolet variability of the quiet Sun

    NASA Astrophysics Data System (ADS)

    Shakeri, F.; Teriaca, L.; Solanki, S. K.

    2015-09-01

    The last solar minimum has been unusually quiet compared to the previous minima (since space-based radiometric measurements are available). The Sun's magnetic flux was substantially lower during this minimum. Some studies also show that the total solar irradiance during the minimum after cycle 23 may have dropped below the values known from the two minima prior to that. For chromospheric and coronal radiation, the situation is less clear-cut. The Sun's 10.7 cm flux shows a decrease of ~4% during the solar minimum in 2008 compared to the previous minimum, but Ca ii K does not. Here we consider additional wavelengths in the extreme ultraviolet (EUV), specifically transitions of He i at 584.3 Å and O v at 629.7 Å, of which the CDS spectrometer aboard SOHO has been taking regular scans along the solar central meridian since 1996. We analysed this unique dataset to verify if and how the radiance distribution undergoes measurable variations between cycle minima. To achieve this aim we determined the radiance distribution of quiet areas around the Sun centre. Concentrating on the last two solar minima, we found out that there is very little variation in the radiance distribution of the chromospheric spectral line He i between these minima. The same analysis shows a modest, although significant, 4% variation in the radiance distribution of the TR spectral line O v. These results are comparable to those obtained by earlier studies employing other spectral features, and they confirm that chromospheric indices display a small variation, whereas in the transition region a more significant reduction of the brighter features is visible.

  5. What are the consequences of ant-seed interactions on the abundance of two dry-fruited shrubs in a Mediterranean scrub?

    PubMed

    Arnan, Xavier; Rodrigo, A; Retana, J

    2011-12-01

    Strong interactions between dry-fruited shrubs and seed-harvesting ants are expected in early successional scrubs, where both groups have a major presence. We have analysed the implications of the seed characteristics of two dry-fruited shrub species (Coronilla minima and Dorycnium pentaphyllum) on seed predation and dispersal mediated by harvester ants and the consequences of these processes on spatio-temporal patterns of plant abundance in a heterogeneous environment. We found that large C. minima seeds were collected much more (39%) than small D. pentaphyllum seeds (2%). However, not all of the removed seeds of these plant species were consumed, and 12.8% of the seeds were lost along the trails, which increased dispersal distances compared with abiotic dispersal alone. Seed dropping occurred among all microhabitats of the two plant species, but especially in open microhabitats, which are the most suitable ones for plant establishment. The two plant species increased their presence in the study area during the study period: C. minima in open microhabitats and D. pentaphyllum in high vegetation. The large size of C. minima seeds probably limited the primary seed dispersal of this species, but may have allowed strong interaction with ants. Thus, seed dispersal by ants resulted in C. minima seeds reaching more suitable microhabitats by means of increasing dispersal distance and redistribution among microhabitats. In contrast, the smaller size of D. pentaphyllum seeds arguably allows abiotic seed dispersal over longer distances and colonization of all types of microhabitats, although it probably also limits their interaction with ants and, consequently, their redistribution in suitable microhabitats. We suggest that dyszoochory could contribute to the success of plant species with different seed characteristics in scrub habitats where seeds are abundantly collected by seed-harvesting ants.

  6. Hale cycle and long-term trend in variation of galactic cosmic rays related to solar rotation

    NASA Astrophysics Data System (ADS)

    Gil, A.; Mursula, K.

    2017-03-01

    Context. Galactic cosmic ray (GCR) intensities around solar minimum times are modulated by magnetic drifts that depend on the overall solar polarity. GCR intensities reach a higher but more narrow peak during negative minima than during positive minima. However, despite these higher intensities, the variation of GCRs over timescales of solar rotation is smaller during negative minima than during positive minima. Aims: We study the variation of GCR intensity over the 27-day synodic solar rotation and over the 14-day half-rotation, in particular the long-term trend and cyclic pattern of this variation, and propose a unifying explanation for the observations. Methods: We used two high-latitude neutron monitors, Oulu and Apatity, which are most sensitive to the low-energy part of the GCR spectrum and thereby more strongly affected by the changes in the conditions of the local heliosphere. We calculated the yearly mean amplitudes of the GCR intensity variation during the full solar rotation (A27) and half-rotation (A14) in 1964-2016. Results: We verify that the A27 and A14 amplitudes exhibit a clear 22-yr Hale cycle during solar minima at both stations, with larger amplitudes in positive minima. We find that the mean amplitude of the Hale cycle is about 30-45% of the mean amplitude for A14, while is only about 15-30% for A27. We also find that all amplitudes depict a declining long-term trend, which we suggest is due to the weakening of solar polar magnetic fields during the last four solar cycles and the ensuing latitudinal widening of the heliospheric current sheet (HCS) region. An exceptionally wide HCS region during the last solar minimum, when A14 reached its all-time minimum, is demonstrated by Ulysses probe observations. Conclusions: Our results emphasize the effect of polarity-dependent drift and the properties of the HCS in modulating the variation of GCR intensity during solar rotation in solar minimum times. The second rotation harmonic yields a larger Hale

  7. Near-Infrared Photometric Studies of R Canis Majoris

    NASA Astrophysics Data System (ADS)

    Varricatt, Watson P.; Ashok, N. M.

    1999-06-01

    We present here the first light curves of the peculiar Algol binary system R Canis Majoris obtained in the near-infrared photometric bands J and K. The light curves are fitted for a semidetached model with the Wilson-Devinney light-curve synthesis program. The parameters of the system are derived. Published light curves in the optical photometric bands (U, U_n, B, B_n, V, V_n, Hβ_w, and Hβ_n of Guinan, V light curve of Sato, and Hα_w and Hα_n light curves of Edalati, Khalesse, & Riazi) are reanalyzed and the results are compared. The temperature of the secondary component T_2 derived from the light-curve analysis shows an increase toward the near-IR wavelengths, achieving maximum in the K band. The secondary minima are deeper by 0.03 and 0.07 mag and the primary minima are shallower by 0.02 and 0.03 mag in the J and K bands, respectively, than what is expected in these bands from the secondary temperature and primary radius derived from the V band. In the case of the Hα and Hβ light curves, the narrowband light curves yielded higher T_2 than the broadband light curves. The values of T_2 derived from these bands are found to be higher than those derived from the light curves observed in the neighboring wavelengths. We consider the possibility of the difference in the strength of photospheric absorption of Hα and Hβ lines in the primary and the secondary as a reason for the high values of T_2 derived from these light curves. Five epochs of primary minima and four epochs of secondary minima are obtained in the present study. The increased depth of the secondary minima in the near-IR bands compared with the optical bands enabled us to determine the moments of secondary minima with nearly the same accuracy as those of primary minima. All the secondary minima appear at phase 0.5, and the durations are equal for the primary and the secondary eclipses. The epochs of primary minima follow the nearly sinusoidal O-C curve that has been observed for this star in

  8. A finite-temperature Hartree-Fock code for shell-model Hamiltonians

    NASA Astrophysics Data System (ADS)

    Bertsch, G. F.; Mehlhaff, J. M.

    2016-10-01

    The codes HFgradZ.py and HFgradT.py find axially symmetric minima of a Hartree-Fock energy functional for a Hamiltonian supplied in a shell model basis. The functional to be minimized is the Hartree-Fock energy for zero-temperature properties or the Hartree-Fock grand potential for finite-temperature properties (thermal energy, entropy). The minimization may be subjected to additional constraints besides axial symmetry and nucleon numbers. A single-particle operator can be used to constrain the minimization by adding it to the single-particle Hamiltonian with a Lagrange multiplier. One can also constrain its expectation value in the zero-temperature code. Also the orbital filling can be constrained in the zero-temperature code, fixing the number of nucleons having given Kπ quantum numbers. This is particularly useful to resolve near-degeneracies among distinct minima.

  9. Rotation Period Determination for 254 Augusta, 465 Alekto 477 Italia, 515 Athalia, and 1061 Paeonia

    NASA Astrophysics Data System (ADS)

    Pilcher, Frederick

    2015-04-01

    Synodic rotation periods and amplitudes have been found for 254 Augusta 5.8949 ± 0.0001 hours, 0.75 to 0.58 magnitudes; 465 Alekto, 10.936 ± 0.001 hours, 0.14 ± 0.02 magnitudes with 3 maxima and minima per cycle; 477 Italia 19.413 ± 0.001 hours, 0.20 to 0.15 magnitudes with 3 very unequal maxima and minima per cycle; 515 Athalia 10.636 ± 0.001 hours, 0.21 ± 0.02 magnitudes; and 1061 Paeonia, 7.9971 ± 0.0001 hours, 1.00 ± 0.05 magnitudes.

  10. Cross-flow vortex structure and transition measurements using multi-element hot films

    NASA Technical Reports Server (NTRS)

    Agarwal, Naval K.; Mangalam, Siva M.; Maddalon, Dal V.; Collier, Fayette S., Jr.

    1991-01-01

    An experiment on a 45-degree swept wing was conducted to study three-dimensional boundary-layer characteristics using surface-mounted, micro-thin, multi-element hot-film sensors. Cross-flow vortex structure and boundary-layer transition were measured from the simultaneously acquired signals of the hot films. Spanwise variation of the root-mean-square (RMS) hot-film signal show a local minima and maxima. The distance between two minima corresponds to the stationary cross-flow vortex wavelength and agrees with naphthalene flow-visualization results. The chordwise and spanwise variation of amplified traveling (nonstationary) cross-flow disturbance characteristics were measured as Reynolds number was varied. The frequency of the most amplified cross-flow disturbances agrees with linear stability theory.

  11. A bivariate limiting distribution of tumor latency time.

    PubMed

    Rachev, S T; Wu, C; Yakovlev AYu

    1995-06-01

    The model of radiation carcinogenesis, proposed earlier by Klebanov, Rachev, and Yakovlev [8] substantiates the employment of limiting forms of the latent time distribution at high dose values. Such distributions arise within the random minima framework, the two-parameter Weibull distribution being a special case. This model, in its present form, does not allow for carcinogenesis at multiple sites. As shown in the present paper, a natural two-dimensional generalization of the model appears in the form of a Weibull-Marshall-Olkin distribution. Similarly, the study of a randomized version of the model based on the negative binomial minima scheme results in a bivariate Pareto-Marshall-Olkin distribution. In the latter case, an estimate for the rate of convergence to the limiting distribution is given.

  12. Acceleration of the Particle Swarm Optimization for Peierls–Nabarro modeling of dislocations in conventional and high-entropy alloys

    DOE PAGES

    Pei, Zongrui; Max-Planck-Inst. fur Eisenforschung, Duseldorf; Eisenbach, Markus

    2017-02-06

    Dislocations are among the most important defects in determining the mechanical properties of both conventional alloys and high-entropy alloys. The Peierls-Nabarro model supplies an efficient pathway to their geometries and mobility. The difficulty in solving the integro-differential Peierls-Nabarro equation is how to effectively avoid the local minima in the energy landscape of a dislocation core. Among the other methods to optimize the dislocation core structures, we choose the algorithm of Particle Swarm Optimization, an algorithm that simulates the social behaviors of organisms. By employing more particles (bigger swarm) and more iterative steps (allowing them to explore for longer time), themore » local minima can be effectively avoided. But this would require more computational cost. The advantage of this algorithm is that it is readily parallelized in modern high computing architecture. We demonstrate the performance of our parallelized algorithm scales linearly with the number of employed cores.« less

  13. Domains in multiband superconductors

    NASA Astrophysics Data System (ADS)

    Tanaka, Y.; Yanagisawa, T.; Crisan, A.; Shirage, P. M.; Iyo, A.; Tokiwa, K.; Nishio, T.; Sundaresan, A.; Terada, N.

    2011-11-01

    Multiband superconductors can have several types of domains that are inhibited in conventional single-band superconductors. These domains are phase domains and chiral domains and their domain wall are an interband phase difference soliton. In a superconductor with an odd number of electronic bands (five or more) and with positive interband Josephson interactions, we find other types of domains with different interband phase differences. We call these domains configuration domains because pseudo-order parameters for each band are dispersed in the complex plain and several configurations, which have several local minima. Fractional vortices serve as hubs for phase difference solitons (configuration domain walls). The divergence of the number of configurations with local minima would pose a serious problem for the stability of superconductivity.

  14. The analysis of temporal variations in regional models of the Sargasso Sea from GEOS-3 altimetry

    NASA Technical Reports Server (NTRS)

    Mather, R. S.; Coleman, R.; Hirsch, B.

    1978-01-01

    The dense coverage of short pulse mode GEOS-3 altimeter data in the western North Atlantic provides a basis for studying time variations in the sea surface heights in the Sargasso Sea. Two techniques are utilized: the method of regional models, and the analysis of overlapping passes. An 88 percent correlation is obtained between the location of cyclonic eddies obtained from infrared imagery and sea surface height minima in the altimeter models. This figure drops to 59 percent in the case of correlations with maxima and minima of surface temperature fields. The analysis of overlapping passes provides a better picture of instantaneous sea state through wavelengths greater than 30 km. The variability of the Sargasso Sea through wavelengths between 150 km and 5000 km is estimated at + or - 28 cm. This value is in reasonable agreement with oceanographic estimates and is compatible with the eddy kinetic energy of a wind driven circulation.

  15. Acoustic properties of hematite near the orientation phase transitions in magnetic fields and under pressure

    NASA Astrophysics Data System (ADS)

    Migachev, S. A.; Bogdanova, Kh. G.; Kurkin, M. I.

    2015-01-01

    This paper reports on the results of the experimental investigation of the quasi-phonon (quasi-sound) branch of magnetoelastic waves in hematite (α-Fe2O3) in the easy-plane state near the orientation phase transitions in magnetic fields H and under uniaxial pressure P. It has been found that, in an applied external magnetic field H > 1.0 kOe and at a uniaxial pressure P > 40 MPa, the amplitude of the transmitted quasi-sound abruptly increases. The minima of quasi-sound velocities observed at the orientation phase transition points in the magnetic field H are consistent with the predictions of the existing theory of magnetoelastic waves, but their width significantly exceeds the theoretical values. The minima of quasi-sound velocities at a uniaxial pressure P are observed only in magnetic fields H < 3 kOe and, at H > 3 kOe, turn into extended plateaus.

  16. Exchange and polarization effect in high-order harmonic imaging of molecular structures

    SciTech Connect

    Sukiasyan, Suren; Ivanov, Misha Yu.; Patchkovskii, Serguei; Smirnova, Olga; Brabec, Thomas

    2010-10-15

    We analyze the importance of exchange, polarization, and electron-electron correlation in high-order harmonic generation in molecules interacting with intense laser fields. We find that electron exchange can become particularly important for harmonic emission associated with intermediate excitations in the molecular ion. In particular, for orbitals associated with two-hole one-particle excitations, exchange effects can eliminate structure-related minima and maxima in the harmonic spectra. Laser-induced polarization of the neutral molecule may also have major effects on orbital structure-related minima and maxima in the harmonic spectra. Finally, we show how exchange terms in recombination can be viewed as a shakedownlike process induced by sudden electronic excitation in the ion.

  17. Impact of Mg content on native point defects in Mg{sub x}Zn{sub 1−x}O (0 ≤ x ≤ 0.56)

    SciTech Connect

    Perkins, J.; Foster, G. M.; Myer, M.; Mehra, S.; Chauveau, J. M.; Hierro, A.; Windl, W.; Brillson, L. J.

    2015-06-01

    We used depth-resolved cathodoluminescence spectroscopy and surface photovoltage spectroscopy to measure the densities, energy levels, and spatial distributions of zinc/magnesium cation and oxygen vacancies in isostructural, single-phase, non-polar Mg{sub x}Zn{sub 1−x}O alloys over a wide (0 ≤ x ≤ 0.56) range. Within this wide range, both defect types exhibit strong Mg content-dependent surface segregation and pronounced bulk density minima corresponding to unit cell volume minima, which can inhibit defect formation due to electrostatic repulsion. Mg in ZnO significantly reduces native defect densities and their non-polar surface segregation, both major factors in carrier transport and doping of these oxide semiconductors.

  18. A Theoretical Study of NO2 Complexes with Aluminium and Gallium Based on Topological Analysis of Electron Density and Electron Localization Function

    SciTech Connect

    Panek, Jaroslaw; Latajaka, Zdzislaw

    2000-12-26

    Results of DFT and MP4 calculations on AlNO2 and GaNO2 molecules are presented. One Cs and two C2v structures (two minima and one TS) are found and their energies and vibrational frequencies are reported and discussed. The minima are close in energy and lie ca. 70 kcal mol-1 below reactants (M+NO2). More insight is obtained via topological analysis of electron density and electron localization function (ELF). It is shown that the molecules are bound mainly via electrostatic interactions, and there is a significant charge transfer from metal atom to the NO2 moiety. Detailed analysis of the ELF shows that the loss of stability of gallium complexes with respect to aluminium structures is best explained by (antibonding) influence of gallium semi-cored electrons.

  19. Monthly and seasonal occurrences of potential flash flood-producing rains determined from Manually Digitized Radar data

    NASA Technical Reports Server (NTRS)

    Wilson, G. S.

    1980-01-01

    An analysis is conducted of a small 4-year climatological data base of Manually Digitized Radar (MDR) data to infer the monthly and seasonal distributions of the relative frequency of occurrence of potential flash flood-producing rains over the Central and Eastern U.S. Some possible meteorological mechanisms for producing potential flash flooding rains are discussed in terms of the relative maxima and minima in the monthly and seasonal frequency distributions over the MDR network. Frequencies were found to be generally higher in more southern locations and lower farther north in all months and seasons. However, most locations experienced an annual cycle in the frequency of occurrence with maxima in summer and minima in winter. In given seasons and months, local areas of maximum and minimum occurrences may be related to quasi-stationary meteorological processes that trigger and organize intense convection over a common area.

  20. Density effects in a bulk binary Lennard-Jones system

    NASA Astrophysics Data System (ADS)

    Hernández-Rojas, Javier; Wales, David J.

    2003-10-01

    Properties of local minima as a function of density are studied in a binary Lennard-Jones system for temperatures T=1.0 (normal liquid), 0.5 (supercooled liquid), and 0.4 (glass), in reduced units. The number of different local minima sampled, energy, pressure, normal mode angular frequencies, and partial radial distribution functions are presented for simulation times of constant length. In agreement with previous studies by Sastry [Phys. Rev. Lett. 85, 590 (2000)] a limiting density is found at ρl=1.08 with negative pressure, below which the local structure of the glass and the supercooled phases are essentially the same, as evidenced by the partial radial distribution functions.

  1. Coronene molecules in helium clusters: Quantum and classical studies of energies and configurations

    NASA Astrophysics Data System (ADS)

    Rodríguez-Cantano, Rocío; Pérez de Tudela, Ricardo; Bartolomei, Massimiliano; Hernández, Marta I.; Campos-Martínez, José; González-Lezana, Tomás; Villarreal, Pablo; Hernández-Rojas, Javier; Bretón, José

    2015-12-01

    Coronene-doped helium clusters have been studied by means of classical and quantum mechanical (QM) methods using a recently developed He-C24H12 global potential based on the use of optimized atom-bond improved Lennard-Jones functions. Equilibrium energies and geometries at global and local minima for systems with up to 69 He atoms were calculated by means of an evolutive algorithm and a basin-hopping approach and compared with results from path integral Monte Carlo (PIMC) calculations at 2 K. A detailed analysis performed for the smallest sizes shows that the precise localization of the He atoms forming the first solvation layer over the molecular substrate is affected by differences between relative potential minima. The comparison of the PIMC results with the predictions from the classical approaches and with diffusion Monte Carlo results allows to examine the importance of both the QM and thermal effects.

  2. Features of the kinetics of electrical damage of polymers

    NASA Astrophysics Data System (ADS)

    Slutsker, A. I.; Veliev, T. M.; Alieva, I. K.; Alekperov, V. A.; Polikarpov, Yu. I.; Karov, D. D.

    2016-09-01

    The kinetics of electrical damage (breakdown) of polymer films 20-50 μm thick in a constant-sign field of 0.5-0.6 GV/m at 77-300 K has been studied. At elevated temperatures (250-300 K), the exponential temperature dependence of the durability and the above-barrier thermal-fluctuation mechanism of electron emission from traps, i.e., space charge accumulation leading to breakdown, take place. At low temperatures (77-200 K), there are separate local decreases in the durability (minima) at the athermal durability level. The identity of the temperatures of durability minima and measured thermoluminescence maxima of polymers was found. A conclusion is made about the mechanism of thermally stimulated tunneling (subbarrier emission) of electrons from traps.

  3. Combustion characteristics in the transition region of liquid fuel sprays

    NASA Technical Reports Server (NTRS)

    Cernansky, N. P.; Namer, I.; Tidona, R. J.

    1984-01-01

    A number of important effects were observed in the droplet size transition region in spray combustion systems. In this region, where the mechanism of flame propagation is transformed from diffusive to premixed dominated combustion, the following effects have been observed: (1) maxima in burning velocity; (2) extension of flammability limits; (3) minima in ignition energy; and (4) minima in NO(x) formation. Unfortunately, because of differences in experimental facilities and limitations in the ranges of experimental data, a unified description of these transition region effects is not available at this time. Consequently, a fundamental experimental investigation was initiated to study the effect of droplet size, size distribution, and operating parameters on these transition region phenomena in a single well controlled spray combustion facility.

  4. Phase retrapping in a φ Josephson junction: Onset of the butterfly effect

    NASA Astrophysics Data System (ADS)

    Menditto, R.; Sickinger, H.; Weides, M.; Kohlstedt, H.; Žonda, M.; Novotný, T.; Koelle, D.; Kleiner, R.; Goldobin, E.

    2016-05-01

    We investigate experimentally the retrapping of the phase in a φ Josephson junction upon return of the junction to the zero-voltage state. Since the Josephson energy profile U0(ψ ) in φ JJ is a 2 π periodic double-well potential with minima at ψ =±φ mod2 π , the question is at which of the two minima -φ or +φ the phase will be trapped upon return from a finite voltage state during quasistatic decrease of the bias current (tilt of the potential). By measuring the relative population of two peaks in escape histograms, we determine the probability of phase trapping in the ±φ wells for different temperatures. Our experimental results agree qualitatively with theoretical predictions. In particular, we observe an onset of the butterfly effect with an oscillating probability of trapping. Unexpectedly, this probability saturates at a value different from 50% at low temperatures.

  5. Comments on "A robust fuzzy local information C-means clustering algorithm".

    PubMed

    Celik, Turgay; Lee, Hwee Kuan

    2013-03-01

    In a recent paper, Krinidis and Chatzis proposed a variation of fuzzy c-means algorithm for image clustering. The local spatial and gray-level information are incorporated in a fuzzy way through an energy function. The local minimizers of the designed energy function to obtain the fuzzy membership of each pixel and cluster centers are proposed. In this paper, it is shown that the local minimizers of Krinidis and Chatzis to obtain the fuzzy membership and the cluster centers in an iterative manner are not exclusively solutions for true local minimizers of their designed energy function. Thus, the local minimizers of Krinidis and Chatzis do not converge to the correct local minima of the designed energy function not because of tackling to the local minima, but because of the design of energy function.

  6. Modeling of the dielectrophoretic conveyer-belt assembling microparticles into large-scale structures

    NASA Astrophysics Data System (ADS)

    Khusid, Boris; Jacqmin, David; Kumar, Anil; Acrivos, Andreas

    2007-11-01

    A dielectrophoretic conveyor-belt method for assembling negatively polarized microparticles into large-scale structures was recently developed (APL 90, 154104, 2007). To do this, first, an array of microelectrodes is energized to generate a spatially periodic AC electric field that causes the particles to aggregate into boluses in positions of the field intensity- minima, which are located mid-way along the height of the channel. The minima and their associated boluses are then moved by periodically grounding and energizing the electrode array so as to generate an electrical field moving along the electrode array. We simulate this experiment numerically via a two- dimensional electro-hydrodynamic model (PRE 69, 021402, 2004). The numerical results are in qualitative agreement with experiments in that they show similar particle aggregation rates, bolus sizes and bolus transport speeds.

  7. Saddles of the energy landscape and folding of model proteins

    NASA Astrophysics Data System (ADS)

    Angelani, L.; Ruocco, G.

    2009-07-01

    We numerically investigate the Potential Energy Landscape of an off-lattice β-sheet model protein, looking at saddles and minima probed by the system during the folding process. G {\\bar o} - like (with native-state-dependent force field and funnel-like landscape) and non-G {\\bar o} -like models are considered. In the G {\\bar o} -like case, on varying the temperature, we observe: i) a pronounced peak at the collapse/folding temperature T θsimeTf in the energy elevation of visited saddles from underlying minima, ii) a crossover at the same point of the saddle order. Saddles-based quantities seem then to be good candidates as indicators of the funneled shape of the landscape in protein models.

  8. An exploration of the ozone dimer potential energy surface

    SciTech Connect

    Azofra, Luis Miguel; Alkorta, Ibon; Scheiner, Steve

    2014-06-28

    The (O{sub 3}){sub 2} dimer potential energy surface is thoroughly explored at the ab initio CCSD(T) computational level. Five minima are characterized with binding energies between 0.35 and 2.24 kcal/mol. The most stable may be characterized as slipped parallel, with the two O{sub 3} monomers situated in parallel planes. Partitioning of the interaction energy points to dispersion and exchange as the prime contributors to the stability, with varying contributions from electrostatic energy, which is repulsive in one case. Atoms in Molecules analysis of the wavefunction presents specific O⋯O bonding interactions, whose number is related to the overall stability of each dimer. All internal vibrational frequencies are shifted to the red by dimerization, particularly the antisymmetric stretching mode whose shift is as high as 111 cm{sup −1}. In addition to the five minima, 11 higher-order stationary points are identified.

  9. Stochastic optimization with randomized smoothing for image registration.

    PubMed

    Sun, Wei; Poot, Dirk H J; Smal, Ihor; Yang, Xuan; Niessen, Wiro J; Klein, Stefan

    2017-01-01

    Image registration is typically formulated as an optimization process, which aims to find the optimal transformation parameters of a given transformation model by minimizing a cost function. Local minima may exist in the optimization landscape, which could hamper the optimization process. To eliminate local minima, smoothing the cost function would be desirable. In this paper, we investigate the use of a randomized smoothing (RS) technique for stochastic gradient descent (SGD) optimization, to effectively smooth the cost function. In this approach, Gaussian noise is added to the transformation parameters prior to computing the cost function gradient in each iteration of the SGD optimizer. The approach is suitable for both rigid and nonrigid registrations. Experiments on synthetic images, cell images, public CT lung data, and public MR brain data demonstrate the effectiveness of the novel RS technique in terms of registration accuracy and robustness.

  10. Data classification using metaheuristic Cuckoo Search technique for Levenberg Marquardt back propagation (CSLM) algorithm

    NASA Astrophysics Data System (ADS)

    Nawi, Nazri Mohd.; Khan, Abdullah; Rehman, M. Z.

    2015-05-01

    A nature inspired behavior metaheuristic techniques which provide derivative-free solutions to solve complex problems. One of the latest additions to the group of nature inspired optimization procedure is Cuckoo Search (CS) algorithm. Artificial Neural Network (ANN) training is an optimization task since it is desired to find optimal weight set of a neural network in training process. Traditional training algorithms have some limitation such as getting trapped in local minima and slow convergence rate. This study proposed a new technique CSLM by combining the best features of two known algorithms back-propagation (BP) and Levenberg Marquardt algorithm (LM) for improving the convergence speed of ANN training and avoiding local minima problem by training this network. Some selected benchmark classification datasets are used for simulation. The experiment result show that the proposed cuckoo search with Levenberg Marquardt algorithm has better performance than other algorithm used in this study.

  11. Dynamical evolution of domain walls in an expanding universe

    NASA Technical Reports Server (NTRS)

    Press, William H.; Ryden, Barbara S.; Spergel, David N.

    1989-01-01

    Whenever the potential of a scalar field has two or more separated, degenerate minima, domain walls form as the universe cools. The evolution of the resulting network of domain walls is calculated for the case of two potential minima in two and three dimensions, including wall annihilation, crossing, and reconnection effects. The nature of the evolution is found to be largely independent of the rate at which the universe expands. Wall annihilation and reconnection occur almost as fast as causality allows, so that the horizon volume is 'swept clean' and contains, at any time, only about one, fairly smooth, wall. Quantitative statistics are given. The total area of wall per volume decreases as the first power of time. The relative slowness of the decrease and the smoothness of the wall on the horizon scale make it impossible for walls to both generate large-scale structure and be consistent with quadrupole microwave background anisotropy limits.

  12. Simulated annealing in orbital flight planning

    NASA Technical Reports Server (NTRS)

    Soller, Jeffrey

    1990-01-01

    Simulated annealing is used to solve a minimum fuel trajectory problem in the space station environment. The environment is unique because the space station will define the first true multivehicle environment in space. The optimization yields surfaces which are potentially complex, with multiple local minima. Because of the likelihood of these local minima, descent techniques are unable to offer robust solutions. Other deterministic optimization techniques were explored without success. The simulated annealing optimization is capable of identifying a minimum-fuel, two-burn trajectory subject to four constraints. Furthermore, the computational efforts involved in the optimization are such that missions could be planned on board the space station. Potential applications could include the on-site planning of rendezvous with a target craft of the emergency rescue of an astronaut. Future research will include multiwaypoint maneuvers, using a knowledge base to guide the optimization.

  13. Two-dimensional time-dependent vortex regions based on the acceleration magnitude.

    PubMed

    Kasten, Jens; Reininghaus, Jan; Hotz, Ingrid; Hege, Hans-Christian

    2011-12-01

    Acceleration is a fundamental quantity of flow fields that captures Galilean invariant properties of particle motion. Considering the magnitude of this field, minima represent characteristic structures of the flow that can be classified as saddle- or vortex-like. We made the interesting observation that vortex-like minima are enclosed by particularly pronounced ridges. This makes it possible to define boundaries of vortex regions in a parameter-free way. Utilizing scalar field topology, a robust algorithm can be designed to extract such boundaries. They can be arbitrarily shaped. An efficient tracking algorithm allows us to display the temporal evolution of vortices. Various vortex models are used to evaluate the method. We apply our method to two-dimensional model systems from computational fluid dynamics and compare the results to those arising from existing definitions.

  14. Methylene blue adsorption on a DMPA lipid langmuir monolayer.

    PubMed

    Giner Casares, Juan José; Camacho, Luis; Martín-Romero, Maria Teresa; López Cascales, José Javier

    2010-07-12

    Adsorption of methylene blue (MB) onto a dimyristoylphosphatidic acid (DMPA) Langmuir air/water monolayer is studied by molecular dynamics (MD) simulations, UV reflection spectroscopy and surface potential measurements. The free-energy profile associated with MB transfer from water to the lipid monolayer shows two minima of -66 and -60 kJ mol(-1) for its solid and gas phase, respectively, corresponding to a spontaneous thermodynamic process. From the position of the free-energy minima, it is possible to predict the precise location of MB in the interior of the DMPA monolayer. Thus, MB is accommodated in the phosphoryl or carbonyl region of the DMPA Langmuir air/water interface, depending on the isomorphic state (solid or gas phase, respectively). Reorientation of MB, measured from the bulk solution to the interior of the lipid monolayer, passes from a random orientation in bulk solution to an orientation parallel to the surface of the lipid monolayer when MB is absorbed.

  15. Solar forcing of Gulf of California climate during the past 2000 yr suggested by diatoms and silicoflagellates

    USGS Publications Warehouse

    Barron, John A.; Bukry, David

    2007-01-01

    Cores BAM80 E-17 (27.9° N) and NH01-26 (24.3° N) contain longer-duration cycles of diatoms and silicoflagellates. The early part of Medieval Climate Anomaly (∼ A.D. 900 to 1200) is characterized by two periods of reduced productivity (warmer SST) with an intervening high productivity (cool) interval centered at ∼ A.D. 1050. Reduced productivity and higher SST also characterize the record of the last ∼ 100 to 200 yr in these cores. Solar variability appears to be driving productivity cycles, as intervals of increased radiocarbon production (sunspot minima) correlate with intervals of enhanced productivity. It is proposed that increased winter cooling of the atmosphere above southwest U.S. during sunspot minima causes intensification of the northwest winds that blow down the Gulf during the late fall to early spring, leading to intensified overturn of surface waters and enhanced productivity.

  16. Astroid Curves for a Synthetic Antiferromagnetic Stack in AN Applied Magnetic Field

    NASA Astrophysics Data System (ADS)

    Forrester, D. M.; Kovacs, E.; Kürten, K. E.; Kusmartsev, F. V.

    The interaction of two magnetic particles separated by an interlayer is illustrated through the "astroid" curves that represent regions in the magnetic field plane where different numbers of minima associated with stable or metastable states may exist. For a single particle, we describe the astroid curves of the Stoner-Wohlfarth model. The case of two particles is then examined and found to be much more complicated. The energy landscape of the two-particle system contains ferromagnetic, antiferromagnetic and canting states that emerge in response to the level of applied magnetic field. Because of this, up to four energy minima can exist in the system, depending upon the strength of the magnetic field and the material properties of the particles.

  17. Astroid Curves for a Synthetic Antiferromagnetic Stack in AN Applied Magnetic Field

    NASA Astrophysics Data System (ADS)

    Forrester, D. M.; Kovacs, E.; Kürten, K. E.; Kusmartsev, F. V.

    2010-12-01

    The interaction of two magnetic particles separated by an interlayer is illustrated through the "astroid" curves that represent regions in the magnetic field plane where different numbers of minima associated with stable or metastable states may exist. For a single particle, we describe the astroid curves of the Stoner-Wohlfarth model. The case of two particles is then examined and found to be much more complicated. The energy landscape of the two-particle system contains ferromagnetic, antiferromagnetic and canting states that emerge in response to the level of applied magnetic field. Because of this, up to four energy minima can exist in the system, depending upon the strength of the magnetic field and the material properties of the particles.

  18. Asymmetry of projected increases in extreme temperature distributions

    PubMed Central

    Kodra, Evan; Ganguly, Auroop R.

    2014-01-01

    A statistical analysis reveals projections of consistently larger increases in the highest percentiles of summer and winter temperature maxima and minima versus the respective lowest percentiles, resulting in a wider range of temperature extremes in the future. These asymmetric changes in tail distributions of temperature appear robust when explored through 14 CMIP5 climate models and three reanalysis datasets. Asymmetry of projected increases in temperature extremes generalizes widely. Magnitude of the projected asymmetry depends significantly on region, season, land-ocean contrast, and climate model variability as well as whether the extremes of consideration are seasonal minima or maxima events. An assessment of potential physical mechanisms provides support for asymmetric tail increases and hence wider temperature extremes ranges, especially for northern winter extremes. These results offer statistically grounded perspectives on projected changes in the IPCC-recommended extremes indices relevant for impacts and adaptation studies. PMID:25073751

  19. Coronene molecules in helium clusters: Quantum and classical studies of energies and configurations

    SciTech Connect

    Rodríguez-Cantano, Rocío; Pérez de Tudela, Ricardo; Bartolomei, Massimiliano; Hernández, Marta I.; Campos-Martínez, José; González-Lezana, Tomás Villarreal, Pablo; Hernández-Rojas, Javier; Bretón, José

    2015-12-14

    Coronene-doped helium clusters have been studied by means of classical and quantum mechanical (QM) methods using a recently developed He–C{sub 24}H{sub 12} global potential based on the use of optimized atom-bond improved Lennard-Jones functions. Equilibrium energies and geometries at global and local minima for systems with up to 69 He atoms were calculated by means of an evolutive algorithm and a basin-hopping approach and compared with results from path integral Monte Carlo (PIMC) calculations at 2 K. A detailed analysis performed for the smallest sizes shows that the precise localization of the He atoms forming the first solvation layer over the molecular substrate is affected by differences between relative potential minima. The comparison of the PIMC results with the predictions from the classical approaches and with diffusion Monte Carlo results allows to examine the importance of both the QM and thermal effects.

  20. Fundamental limitations of LIGA x-ray lithography : sidewall offset, slope and minimum feature size.

    SciTech Connect

    Griffiths, Stewart K.

    2004-01-01

    Analytical and numerical methods are used to examine photoelectron doses and their effect on the dimensions of features produced by deep x-ray lithography. New analytical models describing electron doses are presented and used to compute dose distributions for several feature geometries. The history of development and final feature dimensions are also computed, taking into account the dose field, dissolution kinetics based on measured development rates, and the transport of PMMA fragments away from the dissolution front. We find that sidewall offsets, sidewall slope and producible feature sizes all exhibit at least practical minima and that these minima represent fundamental limitations of the LIGA process. The minimum values under optimum conditions are insensitive to the synchrotron spectrum, but depend strongly on resist thickness. This dependence on thickness is well approximated by simple analytical expressions describing the minimum offset, minimum sidewall slope, minimum producible size of positive and negative features, maximum aspect ratio and minimum radius of inside and outside corners.