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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. Energy landscapes and persistent minima

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    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.

  3. Recent Minima of 193 Eclipsing Binary Stars

    NASA Astrophysics Data System (ADS)

    Samolyk, G.

    2016-06-01

    This paper continues the publication of times of minima for eclipsing binary stars from observations reported to the AAVSO Eclipsing Binary section. Times of minima from CCD observations received by the author from November 2015 through January 2016 are presented.

  4. 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.

  5. Implications of Extended Solar Minima

    NASA Technical Reports Server (NTRS)

    Adams, Mitzi L.; Davis, J. M.

    2009-01-01

    Since the discovery of periodicity in the solar cycle, the historical record of sunspot number has been carefully examined, attempting to make predictions about the next cycle. Much emphasis has been on predicting the maximum amplitude and length of the next cycle. Because current space-based and suborbital instruments are designed to study active phenomena, there is considerable interest in estimating the length and depth of the current minimum. We have developed criteria for the definition of a minimum and applied it to the historical sunspot record starting in 1749. In doing so, we find that 1) the current minimum is not yet unusually long and 2) there is no obvious way of predicting when, using our definition, the current minimum may end. However, by grouping the data into 22- year cycles there is an interesting pattern of extended minima that recurs every fourth or fifth 22-year cycle. A preliminary comparison of this pattern with other records, suggests the possibility of a correlation between extended minima and lower levels of solar irradiance.

  6. Minima Times of Selected Eclipsing Binaries

    NASA Astrophysics Data System (ADS)

    Parimucha, S.; Dubovsky, P.; Kudak, V.; Perig, V.

    2016-05-01

    We present 221 CCD minima times of the 76 selected eclipsing binaries obtained during 2013-2016 at Observatory at Kolonica Saddle in Slovakia and Observatory of Laboratory of Space Research, Uzhhorod National University in Ukraine

  7. Finding pathways between distant local minima.

    PubMed

    Carr, Joanne M; Trygubenko, Semen A; Wales, David J

    2005-06-15

    We report a new algorithm for constructing pathways between local minima that involve a large number of intervening transition states on the potential energy surface. A significant improvement in efficiency has been achieved by changing the strategy for choosing successive pairs of local minima that serve as endpoints for the next search. We employ Dijkstra's algorithm [E. W. Dijkstra, Numer. Math. 1, 269 (1959)] to identify the "shortest" path corresponding to missing connections within an evolving database of local minima and the transition states that connect them. The metric employed to determine the shortest missing connection is a function of the minimized Euclidean distance. We present applications to the formation of buckminsterfullerene and to the folding of various biomolecules: the B1 domain of protein G, tryptophan zippers, and the villin headpiece subdomain. The corresponding pathways contain up to 163 transition states and will be used in future discrete path sampling calculations. PMID:16008483

  8. Finding pathways between distant local minima

    NASA Astrophysics Data System (ADS)

    Carr, Joanne M.; Trygubenko, Semen A.; Wales, David J.

    2005-06-01

    We report a new algorithm for constructing pathways between local minima that involve a large number of intervening transition states on the potential energy surface. A significant improvement in efficiency has been achieved by changing the strategy for choosing successive pairs of local minima that serve as endpoints for the next search. We employ Dijkstra's algorithm [E. W. Dijkstra, Numer. Math. 1, 269 (1959)] to identify the "shortest" path corresponding to missing connections within an evolving database of local minima and the transition states that connect them. The metric employed to determine the shortest missing connection is a function of the minimized Euclidean distance. We present applications to the formation of buckminsterfullerene and to the folding of various biomolecules: the B1 domain of protein G, tryptophan zippers, and the villin headpiece subdomain. The corresponding pathways contain up to 163 transition states and will be used in future discrete path sampling calculations.

  9. 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.

  10. 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.

  11. Global ozone minima in the historical record

    NASA Technical Reports Server (NTRS)

    Rood, Richard B.

    1986-01-01

    The magnitude and structure of the global total ozone minimum between 1958 and 1962 is similar to that observed between 1979 and 1983. Analysis of the single station data that exhibit the most pronounced minima suggest that the spatial structure of the global minimum is different from the currently observed reduction. Very low north polar values were observed, but there is no indication of anomalously low ozone in Antarctica. The temporal relationship to the sun spot cycle is similar in both time periods. Rather than solar terrestrial interaction, however, a more likely explanation of the early 1960's reduction is normal climatology caused by a persistent period of planetary wave activity. Such a natural explanation may also be appropriate for the current depletion.

  12. Relationships between bond dissociation energies, electron density minima and electrostatic potential minima

    NASA Astrophysics Data System (ADS)

    Wiener, John J. M.; Murray, Jane S.; Grice, M. Edward; Politzer, Peter

    The experimental dissociation energies of a group of homonuclear diatomic molecules are found to correlate with computed electron densities pho(r) and electrostatic potentials V (r) at the bond midpoints, supporting an earlier prediction based on density functional arguments (N. H. March, P. M. Kozlowski and F. Perrot 1990, J. molec. Struct. Theochem, 209, 433). The relationships are generalized to 45 molecules of various types, focusing upon the minima of pho(r) and V (r) along internuclear axes. Dissociation energies are shown to be related distinctly more closely to the minimum values of V (r) than to those of pho(r). This complements previous findings for negative monatomic ions as well as the recent observation that the V (r) minima provide the more realistic boundary points between bonded atoms (relative to literature values of covalent radii), and thus further establishes the significance of electrostatic potential axial minima with respect to covalent bonding. In the present work, all calculations were carried out by a density functional procedure (Becke exchange, Lee, Yang and Parr correlation, 6-31G** basis sets).

  13. 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...

  14. 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...

  15. 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...

  16. 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...

  17. 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...

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  19. Aquasols: on the role of secondary minima.

    PubMed

    Hahn, Melinda W; Abadzic, Dean; O'Melia, Charles R

    2004-11-15

    Experiments are presented that test the hypothesis of deposition into and reentrainment from secondary minima during flow through porous media. The release of deposited particles following a decrease in ionic strength is inconsistent with deposition in the primary minimum of either simple DLVO interaction energy curves (which suggest that deposition is irreversible) or Born-DLVO interaction energy curves (which create a finite primary minimum that deepens with decreasing ionic strength). The observed release of particles is, on the other hand, consistent with deposition in the secondary minimum because this energy minimum decreases and can disappear with decreasing ionic strength. The implications for colloid transport of a reversible deposition process in the secondary minimum are very different from those of a process involving irreversible deposition in the primary minimum. First, particles that are continually captured and released will travel much farther in the subsurface than might be expected if the classic irreversible filtration model is applied. Second, and perhaps more significantly, deposition in the secondary well can increase with increasing particle size. Although particle transport by convective diffusion increases as particle size decreases, particle "attachment" in secondary minima decreases with decreasing particle size. Thus, smaller particles (those with diameters in the order of a few tens of nanometers) would be more effective in the facilitated transport of highly sorbing contaminants such as hydrophobic organic molecules, metals, and radionuclides. Other contaminants are themselves particles, such as viruses (tens of nanometers in diameter) and bacteria (near 1 microm in diameter). Due to this difference in size, viruses could be transported over much larger distances than bacteria. Third, the transport of colloids and, hence, the transport of contaminants associated with them, depends on the Hamaker constant of the particle

  20. 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.

  1. 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.

  2. O-C Gateway, a Collection of Minima Timings

    NASA Astrophysics Data System (ADS)

    Paschke, A.; Brat, L.

    2006-02-01

    The huge world-wide database of minima timings maintained by A. Paschke is presented. There is described another similar databases and their availability. The O-C Gateway is freely available at http://var.astro.cz/ocgate and users can plot O-C diagrams and extract the source data (list of minima timings). The web based application was created by L. Brat.

  3. The Earth's climate at minima of Centennial Gleissberg Cycles

    NASA Astrophysics Data System (ADS)

    Ruzmaikin, Alexander; Feynman, Joan

    2015-10-01

    The recent extended, 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 and at the Earth. The Earth's climate response to these prolonged low solar radiation inputs involves heat transfer to the deep ocean causing a time lag longer than a decade. The spatial pattern of the climate response, which allows distinguishing the CGC forcing from other climate forcings, is dominated by the Pacific North American pattern (PNA). 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.

  4. Fullerene valence photoemission time delay near ionization cavity minima

    NASA Astrophysics Data System (ADS)

    Magrakvelidze, Maia; Anstine, Dylan; Dixit, Gopal; Madjet, Mohamed; Chakraborty, Himadri

    2015-05-01

    We investigate photoemission quantum phases and associated Wigner-Smith time delays for HOMO and HOMO-1 electrons of a C60 molecule using time-dependent local density approximation (TDLDA). The interference oscillations in C60 valence emissions produce series of minima whose energy separation depends on the molecular size. We show that the quantum phase associated with these minima exhibits rapid variations due to electron correlations, causing rich structures in the photoemission time delay. Besides fullerenes, the detection of photoemission minima in metal clusters suggests a possible universality of the phenomenon in cluster systems, or even quantum dots, that confine finite-sized electron gas. The work predicts a new research direction to apply attosecond metrology, such as RABITT, in the world of nanosystems. This work was supported by the U.S. National Science Foundation.

  5. 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

  6. Historical records of solar grand minima: a review

    NASA Astrophysics Data System (ADS)

    Vaquero, José M.

    2012-07-01

    Knowing solar activity during the past centuries is of great interest for many purposes. Historical documents can help us to know about the behaviour of the Sun during the last centuries. The observation of aurorae and naked-eye sunspots provides us with continuous information through the last few centuries that can be used to improve our knowledge of the long-term solar activity including solar Grand Minima. We have more or less detailed information on only one Grand minimum (the Maunder minimum in the second half of 17th century), which serves as an archetype for Grand minima in general. Telescopic sunspot records and measurements of solar diameter during Maunder minimum are available. In this contribution, I review some recent progress on these issues.

  7. Differences Between the Current Solar Minimum and Earlier Minima

    NASA Astrophysics Data System (ADS)

    Basu, S.; Broomhall, A.-M.; Chaplin, W. J.; Elsworth, Y.; Fletcher, S.; New, R.

    2010-06-01

    The Birmingham Solar-Oscillations Network (BiSON) has collected helioseismic data over three solar cycles. We use these data to determine how the internal properties of the Sun during this minimum differ from the previous two minima. The Cycle 24 data show oscillatory differences with respect to the other two sets, indicating relatively localized changes in the solar interior. Analysis of MDI data from Cycle 23 and Cycle 24 also show significant signs of differences.

  8. 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.

  9. Observations of Hoppel Minima in CCN Spectra in Oklahoma

    NASA Astrophysics Data System (ADS)

    Tabor, Samantha S.

    Aerosols are one of the most fundamental keys to understanding the future state of the climate. Aerosols impact the radiation budget of the Earth in numerous ways and are poorly understood. Some aerosols can act as cloud condensation nuclei (CCN) and can significantly change the properties of clouds; this is known as the Indirect Aerosol Effect (IAE) and it remains the largest climate change uncertainty. Most studies concerning CCN and the impacts of the CCN distributions occur over the ocean, leaving questions about the processing occurring over the continents. Eleven days of measurements from the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site were taken from an Aerosol Intensive Operational Period (IOP) during May 2003. A ground based CCN spectrometer and differential mobility analyzer (DMA) were deployed to study the distributions of the CCN spectra and dry aerosol size distributions. 268 measurement periods were sorted by their spectral shapes by using two rating systems. Case studies of the characteristics of the spectra observed during specific times of day or particular meteorological conditions were created and it was shown that meteorological conditions have a significant impact on the shapes of the CCN distributions. Back trajectories were also analyzed and shown to have an even larger impact on the observations of the Hoppel Minima, a minima located between the processed and unprocessed CCN modes. Using vertical velocity and back trajectories along with numerous meteorological measurements it can be shown that cloud processing is not only occurring over the continent but transport of the cloud processed air to the surface is also occurring. The Hoppel Minima during this Oklahoma project had a mean critical supersaturation (Sc) of 0.68%.

  10. 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.

  11. Estimation procedures for the GEV distribution for the minima

    NASA Astrophysics Data System (ADS)

    Raynal-Villasenor, Jose A.; Raynal-Gutierrez, M. Elena

    2014-11-01

    The biased and unbiased moments (MOM1 and MOM2), maximum likelihood (ML), sextiles (SEX1 and SEX2) and probability weighted moments (PWM) methods for the estimation the parameters and quantiles of the General Extreme Value (GEV) Distribution for the minima were analyzed and compared by using data generation techniques of the type of distribution sampling experiments. Considering bias, variance and mean square error criteria of estimates of parameters and quantiles, it is concluded that in general for the values of the shape parameter considered: -0.1, -0.3, and -0.5 and 0.1, 0.3 and 0.5, the sample sizes analyzed: 9 ⩽ N ⩽ 99 and non-exceedance probabilities: 0.01 ⩽ Π(x) ⩽ 0.10, the ML method performed better than the other five. However, for sample sizes bigger than 49, most of the methods, with the exception of SEX1, produced similar results. As a general conclusion of the study reported here, it can be stated that the ML method resulted to be better to the other five when estimating the parameters and quantiles of the GEV distribution for the minima, for the cases analyzed in this study.

  12. Symmetry-protected local minima in infinite DMRG

    NASA Astrophysics Data System (ADS)

    Pfeifer, Robert N. C.

    2015-11-01

    The infinite density matrix renormalization group (iDMRG) algorithm is a highly successful numerical algorithm for the study of low-dimensional quantum systems, and is also frequently used to initialize the more popular finite DMRG algorithm. Implementations of both finite and infinite DMRG frequently incorporate support for the protection and exploitation of symmetries of the Hamiltonian. In common with other variational tensor network algorithms, convergence of iDMRG to the ground state is not guaranteed, with the risk that the algorithm may become stuck in a local minimum. In this paper, I demonstrate the existence of a particularly harmful class of physically irrelevant local minima affecting both iDMRG and to a lesser extent also infinite time-evolving block decimation (iTEBD), for which the ground state is compatible with the protected symmetries of the Hamiltonian but cannot be reached using the conventional iDMRG or iTEBD algorithms. I describe a modified iDMRG algorithm which evades these local minima, and which also admits a natural interpretation on topologically ordered systems with a boundary.

  13. 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.

  14. 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. PMID:25933136

  15. 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.

  16. The cosmic radiation in the heliosphere at successive solar minima

    NASA Technical Reports Server (NTRS)

    Mcdonald, Frank B.; Moraal, Harm; Reinecke, J. P. L.; Lal, Nand; Mcguire, Robert E.

    1992-01-01

    Cosmic ray observations at 1 AU are compared for the last three solar minimum periods along with the 1977/1989 and 1987 Pioneer 10 and Voyager 1 and 2 data from the outer heliosphere. There is good agreement between the 1965 and 1987 Galactic cosmic ray H and He spectra at 1 AU. Significant and complex differences are found between the 1977/1978 and 1987 measurements of the Galactic and anomalous cosmic ray components at 1 and 15 AU. In the outer heliosphere there are negative latitudinal gradients that reach their maximum magnitude when the inclination of the outer heliosphere current sheet is at a minimum. The radial gradients decrease with heliocentric distance as about 1/r exp 0.7 and do not differ significantly at the successive solar minima. The measured radial and latitudinal gradients are used to estimate the particle transport parameters in the outer heliosphere. Using the local interstellar He spectrum of Webber et al. (1987), it is estimated that the modulation boundary is of the order of 160 AU.

  17. Competition between Salvinia minima and Spirodela polyrhiza mediated by nutrient levels and herbivory.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We investigated the effects of initial biomass, nutrients, herbivory, and competition with Spirodela polyrhiza on Salvinia minima biomass and density. Salvinia minima populations were subjected to two levels of herbivory from the weevil Cyrtobagous salviniae and various levels of competition from S...

  18. 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. PMID:21715277

  19. 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.

  20. Minima in generalized oscillator strengths for initially excited hydrogen-like atoms

    NASA Technical Reports Server (NTRS)

    Matsuzawa, M.; Omidvar, K.; Inokuti, M.

    1976-01-01

    Generalized oscillator strengths for transitions from an initially excited state of a hydrogenic atom to final states (either discrete or continuum) have complicated structures, including minima and shoulders, as functions of the momentum transfer. Extensive calculations carried out in the present work have revealed certain systematics of these structures. Some implications of the minima to the energy dependence of the inner-shell ionization cross section of heavy atoms by proton impact are discussed.

  1. Grand Minima of Solar Activity and the Mean-Field Dynamo

    NASA Astrophysics Data System (ADS)

    Usoskin, I. G.; Sokoloff, D.; Moss, D.

    2009-02-01

    We demonstrate that a simple solar dynamo model, in the form of a Parker migratory dynamo with random fluctuations of the dynamo governing parameters and algebraic saturation of dynamo action, can at least qualitatively reproduce all the basic features of solar Grand Minima as they are known from direct and indirect data. In particular, the model successfully reproduces such features as an abrupt transition into a Grand Minimum and the subsequent gradual recovery of solar activity, as well as mixed-parity butterfly diagrams during the epoch of the Grand Minimum. The model predicts that the cycle survives in some form during a Grand Minimum, as well as the relative stability of the cycle inside and outside of a Grand Minimum. The long-term statistics of simulated Grand Minima appears compatible with the phenomenology of the Grand Minima inferred from the cosmogenic isotope data. We demonstrate that such ability to reproduce the Grand Minima phenomenology is not a general feature of the dynamo models but requires some specific assumption, such as random fluctuations in dynamo governing parameters. In general, we conclude that a relatively simple and straightforward model is able to reproduce the Grand Minima phenomenology remarkably well, in principle providing us with a possibility of studying the physical nature of Grand Minima.

  2. 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. PMID:22575872

  3. Long-Term Changes in Sunspot Activity, Occurrence of Grand Minima, and Their Future Tendencies

    NASA Astrophysics Data System (ADS)

    Mordvinov, A. V.; Kramynin, A. P.

    2010-06-01

    Long-term changes in the magnetic activity of the Sun were studied in terms of the empirical mode decomposition that revealed their essential modes. The occurrence of grand minima was also studied in their relation to long-term changes in sunspot activity throughout the past 11 000 yr. Characteristic timescales of long-term changes in solar activity manifest themselves in the occurrence of grand minima. A quantitative criterion has been defined to identify epochs of grand minima. This criterion reveals the important role of secular and bicentennial activity variations in the occurrence of grand minima and relates their amplitudes with the current activity level, which is variable on a millennial timescale. We have revealed specific patterns in the magnetic activity between successive grand minima which tend to recur approximately every 2300 yr but occasionally alternate with irregular changes. Such intermittent activity behavior indicates low dimensional chaos in the solar dynamo due to the interplay of its dominant modes. The analysis showed that in order to forecast activity level in forthcoming cycles, one should take into account long-term changes in sunspot activity on a ≈2300-yr timescale. The regularities revealed suggest solar activity to decrease in the foreseeable future.

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

    PubMed

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

    2016-09-01

    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

  5. 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.

  6. Influence of multiple orbital effect on shifts of minima in harmonic spectra

    NASA Astrophysics Data System (ADS)

    Wu, Yan; Li, Chaorong; Gong, Cheng; Yu, Yongli; Gong, Shangqing

    2014-09-01

    Using the Lewenstein model combined with the molecular Ammosov-Delone-Krainov ionization theory, laser induced harmonics generated from aligned N2 molecules are calculated. We focus attention on shifts in minima of the harmonic spectra due to interference between harmonics generated from different molecular orbitals (MOs). When harmonic spectra generated from different MOs are of the same intensity (i.e., the “cross” region of the harmonic spectra), interference is most pronounced. We find that contributions to the harmonic spectrum from different MOs respond differently to the change of the laser intensity. This difference in response results in two phenomena. On the one hand, by changing the laser intensity, harmonics generated from an individual MO may become more or less prominent, thus, structure-induced minima can appear. On the other hand, when the laser intensity increases, the “cross” region shifts, and multiple-orbital-interference-induced minima appear at different energies.

  7. 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.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  9. Multiple local minima in radiotherapy optimization problems with dose-volume constraints.

    PubMed

    Deasy, J O

    1997-07-01

    The cause of multiple local minima in beam weight optimization problems subject to dose-volume constraints is analyzed. Three objective functions were considered: (a) maximization of tumor control probability (TCP), (b) maximization of the minimum target dose, and (c) minimization of the mean-squared-deviation of the target dose from the prescription dose. It is shown that: (a) TCP models generally result in strongly quasiconvex objective functions; (b) maximization of the minimum target dose results in a strongly quasiconvex objective function; and (c) minimizing the root-mean-square dose deviation results in a convex objective function. Dose-volume constraints are considered such that, for each region at risk (RAR), the volume of tissue whose dose exceeds a certain tolerance dose (DTol) is kept equal to or below a given fractional level (VTol). If all RARs lack a "volume effect" (i.e., VTol = 0 for all RARs) then there is a single local minimum. But if volume effects are present, then the feasible space is possibly nonconvex and therefore possibly leads to multiple local minima. These conclusions hold for all three objective functions. Hence, possible local minima come not from the nonlinear nature of the objective functions considered, but from the "either this volume or that volume but not both" nature of the volume effect. These observations imply that optimization algorithms for dose-volume constraint types of problems should have effective strategies for dealing with multiple local minima. PMID:9243478

  10. Evaluation of Docking Target Functions by the Comprehensive Investigation of Protein-Ligand Energy Minima

    PubMed Central

    Oferkin, Igor V.; Katkova, Ekaterina V.; Sulimov, Alexey V.; Kutov, Danil C.; Sobolev, Sergey I.; Voevodin, Vladimir V.; Sulimov, Vladimir B.

    2015-01-01

    The adequate choice of the docking target function impacts the accuracy of the ligand positioning as well as the accuracy of the protein-ligand binding energy calculation. To evaluate a docking target function we compared positions of its minima with the experimentally known pose of the ligand in the protein active site. We evaluated five docking target functions based on either the MMFF94 force field or the PM7 quantum-chemical method with or without implicit solvent models: PCM, COSMO, and SGB. Each function was tested on the same set of 16 protein-ligand complexes. For exhaustive low-energy minima search the novel MPI parallelized docking program FLM and large supercomputer resources were used. Protein-ligand binding energies calculated using low-energy minima were compared with experimental values. It was demonstrated that the docking target function on the base of the MMFF94 force field in vacuo can be used for discovery of native or near native ligand positions by finding the low-energy local minima spectrum of the target function. The importance of solute-solvent interaction for the correct ligand positioning is demonstrated. It is shown that docking accuracy can be improved by replacement of the MMFF94 force field by the new semiempirical quantum-chemical PM7 method. PMID:26693223

  11. A combined method for determining reaction paths, minima, and transition state geometries

    NASA Astrophysics Data System (ADS)

    Ayala, Philippe Y.; Schlegel, H. Bernhard

    1997-07-01

    Mapping out a reaction mechanism involves optimizing the reactants and products, finding the transition state and following the reaction path connecting them. Transition states can be difficult to locate and reaction paths can be expensive to follow. We describe an efficient algorithm for determining the transition state, minima and reaction path in a single procedure. Starting with an approximate path represented by N points, the path is iteratively relaxed until one of the N points reached the transition state, the end points optimize to minima and the remaining points converged to a second order approximation of the steepest descent path. The method appears to be more reliable than conventional transition state optimization algorithms, and requires only energies and gradients, but not second derivative calculations. The procedure is illustrated by application to a number of model reactions. In most cases, the reaction mechanism can be described well using 5 to 7 points to represent the transition state, the minima and the path. The computational cost of relaxing the path is less than or comparable to the cost of standard techniques for finding the transition state and the minima, determining the transition vector and following the reaction path on both sides of the transition state.

  12. Biological control of common salvinia (Salvinia minima) in Louisiana using Cyrtobagous salviniae (Coleoptera: curculionidae)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Common salvinia, Salvinia minima Baker, is an aquatic invasive fern that obstructs waterways and impacts water quality throughout the southeastern United States. In an effort to establish populations for classical biological control, the weevil, Cyrtobagous salviniae Calder and Sands, was released a...

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  15. 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

  16. 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

  17. Dust around young stars. Observations of the polarization of UX Ori in deep minima

    SciTech Connect

    Voshchinnikov, N.V.; Grinin, V.P.; Kiselev, N.N.; Minikulov, N.K.

    1988-09-01

    Photometric and polarimetric monitoring observations of UX Ori begun in 1986 in the Crimea and Bolivia have resulted in the observation of two deep minima of the brightness during which a growth of the linear polarization (to approx. =7%) was observed, together with a tendency for the circular polarization to increase (up to approx. =1%). Analysis of the observational data shows that the main source of the polarized radiation in the deep minima is the emission of the star scattered by grains of circumstellar dust. On the basis of Mie's theory for a polydisperse graphite-silicate mixtures of particles the optical properties of ellipsoidal dust envelopes have been calculated and a model of the Algol-like minimum constructed.

  18. The 2p photoionization of ground-state sodium in the vicinity of Cooper minima

    NASA Astrophysics Data System (ADS)

    Liu, Xiaobin; Shi, Yinglong; Dong, Chenzhong

    2016-07-01

    The photoionization processes of ground-state sodium have been investigated with the multiconfiguration Dirac–Fock method. The results are in good or at least reasonable agreement with available experimental and theoretical data. In the energy region near the threshold, the cross sections show non-monotonic changes because of Cooper minima, which due to the sign changes of dominant dipole matrix elements and are very sensitive to electron correlations. As the energy increases continuously, the radial wave functions of the photoelectrons will move towards the nucleus. The values of the cross sections, and hence the Cooper minima, mainly depend on the relative positions of the one-electron radial wave functions of the initial bound electrons 2{p}1/{2,3/2} and the continuum photoelectrons.

  19. The solar wind during current and past solar minima and maxima

    NASA Astrophysics Data System (ADS)

    Zerbo, J.-L.; Richardson, J. D.

    2015-12-01

    This paper presents solar wind data from the last five solar cycles. We review solar wind parameters over the four solar minima and five maxima for which spacecraft data are available and show the recovery from the last very weak minimum to the current solar maximum. The solar wind magnetic field, speed, and density have remained anomalously low in this time period. However, the distributions of these parameters about the (lower than normal) average are similar to those from previous solar minima and maxima. This result suggests that the acceleration mechanism for the recent weak solar wind is probably not significantly different from earlier solar cycles. The He++/H+ ratio variation with solar cycle continues to be a function of speed, but the most recent solar minimum has significantly lower ratios than in the previous solar cycle.

  20. 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.

  1. 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.

  2. 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.

  3. Theoretical analysis of the single-particle states in the secondary minima of fissioning nuclei

    NASA Astrophysics Data System (ADS)

    Dudek, J.; Nazarewicz, W.; Faessler, A.

    1984-01-01

    The structure of the single-particle levels in the secondary minima of fissioning nuclei is analysed with the help of the deformed Woods-Saxon potential. The parametrisation of the spin-orbit part of the potential at large elongations is analysed in detail. A set of parameters is found which reproduces simultaneously results of the g-factor measurements for 239mPu, 237mpu and 239mAm, the data on single-particle resonances in the secondary minima of 231Th, 233Th, and which also gives rise to a significant energy gap at the neutron magic number N0 = 146 ( ΔE~ 1.3 MeV). The structure of the single-particle states around N0 = 146 is analysed and the results are compared with the existing experimental information. The total enegy surfaces are recalculated with the new-found parametrisation of the potential; an overall improvement of the barrier characteristics is found. Decoupling parameters and g-factors are tabulated for deformations corresponding to the secondary minima.

  4. 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

  5. Grand solar minima and maxima deduced from 10Be and 14C: magnetic dynamo configuration and polarity reversal

    NASA Astrophysics Data System (ADS)

    Inceoglu, F.; Simoniello, R.; Knudsen, M. F.; Karoff, C.; Olsen, J.; Turck-Chiéze, S.; Jacobsen, B. H.

    2015-05-01

    Aims: This study aims to improve our understanding of the occurrence and origin of grand solar maxima and minima. Methods: We first investigate the statistics of peaks and dips simultaneously occurring in the solar modulation potentials reconstructed using the Greenland Ice Core Project (GRIP) 10Be and IntCal13 14C records for the overlapping time period spanning between ~1650 AD to 6600 BC. Based on the distribution of these events, we propose a method to identify grand minima and maxima periods. By using waiting time distribution analysis, we investigate the nature of grand minima and maxima periods identified based on the criteria as well as the variance and significance of the Hale cycle during these kinds of events throughout the Holocene epoch. Results: Analysis of grand minima and maxima events occurring simultaneously in the solar modulation potentials, reconstructed based on the 14C and the 10Be records, shows that the majority of events characterized by periods of moderate activity levels tend to last less than 50 years: grand maxima periods do not last longer than 100 years, while grand minima can persist slightly longer. The power and the variance of the 22-year Hale cycle increases during grand maxima and decreases during grand minima, compared to periods characterized by moderate activity levels. Conclusions: We present the first reconstruction of the occurrence of grand solar maxima and minima during the Holocene based on simultaneous changes in records of past solar variability derived from tree-ring 14C and ice-core 10Be, respectively. This robust determination of the occurrence of grand solar minima and maxima periods will enable systematic investigations of the influence of grand solar minima and maxima episodes on Earth's climate.

  6. 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.

  7. Polar and Equatorial Coronal Hole Winds at Solar Minima: From the Heliosphere to the Inner Corona

    NASA Astrophysics Data System (ADS)

    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.

  8. Times of Minima and New Ephemerides for Southern Hemisphere Eclipsing Binary Stars Observed in 2015

    NASA Astrophysics Data System (ADS)

    Pavlov, H.; Mallama, A.; Loader, B.; Kerr, S.

    2016-06-01

    Observers from Australia and New Zealand used video equipment to time eclipses of short-period binary stars. The objects were typically south of -20o declination and had periods of less than a day. Many of those systems had very few observations since their discovery and some of them had not been observed for 50 or more years. We present 44 times of minima of 42 stars, provide revised ephemerides for 7 of these systems and characterize an orbital period change for RW PsA.

  9. Times of Minima and New Ephemerides for Southern Hemisphere Eclipsing Binary Stars Observed in 2015

    NASA Astrophysics Data System (ADS)

    Pavlov, H.; Mallama, A.; Loader, B.; Kerr, S.

    2016-04-01

    Observers from Australia and New Zealand used video equipment to time eclipses of short-period binary stars. The objects were typically south of -20o declination and had periods of less than a day. Many of those systems had very few observations since their discovery and some of them had not been observed for 50 or more years. We present 44 times of minima of 42 stars, provide revised ephemerides for 7 of these systems and characterize an orbital period change for RW PsA.

  10. 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.

  11. Enhanced docking with the mining minima optimizer: acceleration and side-chain flexibility.

    PubMed

    Kairys, Visvaldas; Gilson, Michael K

    2002-12-01

    The ligand-protein docking algorithm based on the Mining Minima method has been substantially enhanced. First, the basic algorithm is accelerated by: (1) adaptively determining the extent of each energy well to help avoid previously discovered energy minima; (2) biasing the search away from ligand positions at the surface of the receptor to prevent the ligand from staying at the surface when large sampling regions are used; (3) quickly testing multiple different ligand positions and orientations for each ligand conformation; and (4) tuning the source code to increase computational efficiency. These changes markedly shorten the time needed to discover an accurate result, especially when large sampling regions are used. The algorithm now also allows user-selected receptor sidechains to be treated as mobile during the docking procedure. The energies associated with the mobile side chains are computed as if they belonged to the ligand, except that atoms at the boundary between side chains and the rigid backbone are treated specially. This new capability is tested for several well-known ligand/protein systems, and preliminary application to an enzyme whose substrate is unknown--the recently solved hypothetical protein YecO (HI0319) from Haemophilus influenzae--indicates that side-chains relaxations allow candidate substrates of various sizes to be accommodated. PMID:12395431

  12. 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.

  13. 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.

  14. 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.

  15. Ultrasound-Assisted Extraction, Antioxidant and Anticancer Activities of the Polysaccharides from Rhynchosia minima Root.

    PubMed

    Jia, Xuejing; Zhang, Chao; Hu, Jie; He, Muxue; Bao, Jiaolin; Wang, Kai; Li, Peng; Chen, Meiwan; Wan, Jianbo; Su, Huanxing; Zhang, Qingwen; He, Chengwei

    2015-01-01

    Box-Behnken design (BBD), one of the most common response surface methodology (RSM) methods, was used to optimize the experimental conditions for ultrasound-assisted extraction of polysaccharides from Rhynchosia minima root (PRM). The antioxidant abilities and anticancer activity of purified polysaccharide fractions were also measured. The results showed that optimal extraction parameters were as follows: ultrasound exposure time, 21 min; ratio of water to material, 46 mL/g; ultrasound extraction temperature, 63 °C. Under these conditions, the maximum yield of PRM was 16.95%±0.07%. Furthermore, the main monosaccharides of purified fractions were Ara and Gal. PRM3 and PRM5 exhibited remarkable DPPH radical scavenging activities and reducing power in vitro. PRM3 showed strong inhibitory activities on the growth of MCF-7 cells in vitro. The above results indicate that polysaccharides from R. minima root have the potential to be developed as natural antioxidants and anticancer ingredients for the food and pharmaceutical industries. PMID:26610456

  16. 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.

  17. 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

  18. 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

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

    PubMed

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

    2003-01-21

    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

  20. 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.

  1. Polar cap magnetic field reversals during solar grand minima: could pores play a role?

    NASA Astrophysics Data System (ADS)

    Švanda, Michal; Brun, Allan Sacha; Roudier, Thierry; Jouve, Laurène

    2016-02-01

    We study the magnetic flux carried by pores located outside active regions with sunspots and investigate their possible contribution to the reversal of the global magnetic field of the Sun. We find that they contain a total flux of comparable amplitude to the total magnetic flux contained in polar caps. The pores located at distances of 40-100 Mm from the closest active region systematically have the correct polarity of the magnetic field to contribute to the polar cap reversal. These pores can be found predominantly in bipolar magnetic regions. We propose that during grand minima of solar activity, such a systematic polarity trend, which is akin to a weak magnetic (Babcock-Leighton-like) source term, could still be operating but was missed by the contemporary observers because of the limited resolving power of their telescopes.

  2. 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.

  3. Shear-deformation-potential constant of the conduction-band minima of Si: Pseudopotential calculations

    NASA Astrophysics Data System (ADS)

    Li, Ming-Fu; Gu, Zong-Quan; Wang, Jian-Qing

    1990-09-01

    We have calculated the value of the shear-deformation-potential constant Ξu of the conduction-band minima of Si and its temperature coefficient dΞu/dT. The value of Ξu is 9.0 eV for an ab initio pseudopotential calculation and 10.8 eV by the empirical-pseudopotential method (EPM), in good agreement with our experiment. The EPM calculations of the temperature dependence of Ξu yield the values of (dΞu/dT)||DW=-0.04 meV/K due to the Debye-Waller contribution, and (dΞu/dT)||TE=-0.04 meV/K for thermal expansion. We suspect and suggest that the existing experimental value of dΞu/dT~=+3 meV/K is unreliable due to large experimental uncertainty.

  4. Global energy minima of molecular clusters computed in polynomial time with semidefinite programming.

    PubMed

    Kamarchik, Eugene; Mazziotti, David A

    2007-12-14

    The global energy minima of pure and binary molecular clusters with 5-12 particles interacting pairwise are computed in polynomial time as a function of only the two-particle reduced density function (2-RDF). We derive linear matrix inequalities from the classical analogue of quantum N-representability constraints to ensure that the 2-RDF represents realistic N-particle configurations. The 2-RDF reformulation relaxes a combinatorial optimization into a convex optimization that scales polynomially in computer time. Clusters are optimized with a code for large-scale semidefinite programming developed for the quantum representability problem [D. A. Mazziotti, Phys. Rev. Lett. 93, 213001 (2004)10.1103/PhysRevLett.93.213001]. PMID:18233446

  5. Accurate prediction of interference minima in linear molecular harmonic spectra by a modified two-center model

    NASA Astrophysics Data System (ADS)

    Xin, Cui; Di-Yu, Zhang; Gao, Chen; Ji-Gen, Chen; Si-Liang, Zeng; Fu-Ming, Guo; Yu-Jun, Yang

    2016-03-01

    We demonstrate that the interference minima in the linear molecular harmonic spectra can be accurately predicted by a modified two-center model. Based on systematically investigating the interference minima in the linear molecular harmonic spectra by the strong-field approximation (SFA), it is found that the locations of the harmonic minima are related not only to the nuclear distance between the two main atoms contributing to the harmonic generation, but also to the symmetry of the molecular orbital. Therefore, we modify the initial phase difference between the double wave sources in the two-center model, and predict the harmonic minimum positions consistent with those simulated by SFA. Project supported by the National Basic Research Program of China (Grant No. 2013CB922200) and the National Natural Science Foundation of China (Grant Nos. 11274001, 11274141, 11304116, 11247024, and 11034003), and the Jilin Provincial Research Foundation for Basic Research, China (Grant Nos. 20130101012JC and 20140101168JC).

  6. Comparison of solar activity during last two minima on turn of Activity Cycles 22/23 and 23/24

    NASA Astrophysics Data System (ADS)

    Gryciuk, Magdalena; Gburek, Szymon; Siarkowski, Marek; Podgorski, Piotr; Sylwester, Janusz; Farnik, Frantisek

    2013-07-01

    The subject of our work is the review and comparison of solar activity during the last two solar minima that occurred between recent activity cycles. We use the soft X-ray global solar corona observations covering the two nine-months long time intervals in 1997/98 and 2009. Data from RF15-I multichannel photometer are used for the penultimate minimum. For the last unusually deep and prolonged solar activity minimum in 2009 the data from SphinX spectrophotometer are used. Comparison of measurements from both minima takes place in the overlapping energy range 2-15 keV. We focus on the active region formation, evolution and flaring productivity during respective minima.

  7. 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.

  8. Anti-angiogenic Activity and Mechanism of Sesquiterpene Lactones from Centipeda minima.

    PubMed

    Huang, Weihuan; Yu, Xiaobin; Liang, Ning; Ge, Wei; Kwok, Hin Fai; Lau, Clara Bik-San; Li, Yaolan; Chung, Hau Yin

    2016-04-01

    Centipeda minima is a Chinese herbal medicine used in the treatment of various diseases including cancer. An ethanol extract of the herb, its four fractions with different polarities, and two volatile oils prepared by steam distillation (SD) and supercritical fluid extraction (SFE) were investigated for their anti-angiogenic activity in a wild-type zebrafish model using a quantitative endogenous alkaline phosphatase (EAP) assay. The SFE oil displayed potent anti-angiogenic activity. Fifteen sesquiterpene lactones (SLs; compounds 1-15) isolated from the SFE oil were evaluated for their anti-angiogenic effect. Results revealed that pseudoguaianolide type SLs (1-8) inhibited vessel formation in the zebrafish embryos while guaianolide type SLs (9-15) showed little effect. Among the active ones, 6-O-angeloylenolin (1), a major component of SFE oil, possessed the strongest effect by reducing vessel formation in zebrafish embryos to 40% of the control value at 29.7 µM. Further study using the Tg (fli1a:EGFP) y1-type zebrafish model revealed that it blocked both intersegmental blood vessels (ISVs) and subintestinal vessels plexus (SIVs) formation in zebrafish embryos. Real-time polymerase chain reaction assay on the wild-type zebrafish embryos suggested that 6-O-angeloylenolin affected multiple molecular targets related to angiogenesis including VEGF receptor, angiopoietin, and its receptors. Taken together, our findings demonstrate that C. minima possesses anti-angiogenic activity, and 6-O-angeloylenolin is a promising candidate for the development of an anti-angiogenic agent. PMID:27396185

  9. First-year PSA kinetics and minima after prostate cancer radiotherapy are predictive of overall survival

    SciTech Connect

    Cheung, Rex . E-mail: mrcheung@mdanderson.org; Tucker, Susan L.; Kuban, Deborah A.

    2006-09-01

    Purpose: We analyzed whether first-year prostate-specific antigen (PSA) kinetics and minima are predictive of overall survival (OS). Methods and Materials: The data set contained 1,174 patients treated with external beam radiotherapy (RT) from 1987 to 2001. The relative rate of change ({lambda}) in post-RT PSA values during the first year (13.5 months) was computed using regression analysis of ln(PSA) vs. time. We also computed the PSA minimum (mPSA) reached during the same period. Recursive partitioning analysis was used to identify the relevant cutpoints for the factors being investigated for its association with survival: age, pretreatment PSA, radiation dose, relative rate of change in PSA post-RT, and 1-year PSA minimum. For each of the other factors stage, Gleason score and risk group, all possible cutpoints were considered in the multivariate analyses. Significant factors were considered in the multivariate analyses to identify independent predictors for overall survival. Results: The median value of {lambda} was -1.0 years{sup -1} (range, -11.0-5.1 years{sup -1}). The 1-year minimum had a median of 0.8 ng/mL (range, 0.01-30.9 ng/mL). Recursive partitioning analysis and Cox proportional hazards analyses identified the following pretreatment or treatment factors adversely related to OS: age, Gleason score, stage, and dose. First-year mPSA {>=} 4 ng/mL and {lambda} > 0 were post-RT independent prognostic factors for worse OS. Conclusion: First-year post-RT PSA kinetics and minima are early response parameters predictive of overall survival for prostate cancer patients. These factors may be useful in selecting patients for early salvage therapy.

  10. 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

  11. Leaching of lead by ammonium salts and EDTA from Salvinia minima biomass produced during aquatic phytoremediation.

    PubMed

    Núñez-López, Roberto Aurelio; Meas, Yunny; Gama, Silvia Citlalli; Borges, Raúl Ortega; Olguín, Eugenia J

    2008-06-15

    Plant biomass harvested after heavy-metal phytoremediation must be considered as a hazardous waste that should be contained or treated appropriately before disposal or reuse. As a potential method to detoxify the biomass and to convert this material to a suitable fertilizer or mulch, leaching of lead (Pb) from Salvinia minima biomass was studied by testing water, several aqueous ammonium salts, and EDTA solution as lead extractants. The research was carried out in two phases: (i) a leaching study to determine the lead-extraction efficiency of the different leachants, and (ii) a thermodynamic analysis to identify the likely reactions and stable Pb(II) species formed in the leaching systems of the most efficient leachants. Experimentally, lead concentrations measured in leached biomass and in leachates were significantly different among the various leachants. It was determined that the extraction strength of the leachants followed the order: EDTA>ammonium oxalate>water approximately ammonium nitrate>ammonium acetate, achieving Pb extraction efficiencies of 99%, 70%, 7.2%, 6.9% and 1.3%, respectively, in single-stage extractions. The thermodynamic study indicated that the dominant species produced by the leaching process should be the soluble species PbEDTA2- for EDTA system, and the insoluble Pb(COO)2S precipitate for the oxalate system. PMID:18078711

  12. Space climate. On geoeffective solar activity during Maunder and Dalton grand minima

    NASA Astrophysics Data System (ADS)

    Demetrescu, Crisan; Stefan, Cristiana; Dobrica, Venera

    2014-05-01

    The study of geomagnetic phenomena known as geomagnetic activity has long contributed to progress in solar-terrestrial science. The long geomagnetic time series recorded at geomagnetic observatories have provided means to characterize the Sun-Earth interaction at times prior to space era, via geomagnetic indices (e.g. aa, going back to 1868). For times prior to geomagnetic observatory era, we looked for information at the main geomagnetic field model gufm1 (1590-1990) (Jackson et al., 2000). We show first the presence in the time series provided by this model of a solar-activity-related signal, of 10-20 nT. Then the characteristics of this signal for times to 1600 are discussed. A significant geomagnetic activity at the 22-year time scale is found during the the Maunder and Dalton minima. The signal we discuss also corroborates the so-called excursions in the reconstructed sunspot number based on 10Be determinations on polar ice cores (Usoskin et al., 2003).

  13. 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.

  14. 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.

  15. 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.

  16. 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

    , together 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

  17. 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

    , together 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

  18. Rapid sampling of local minima in protein energy surface and effective reduction through a multi-objective filter

    PubMed Central

    2013-01-01

    Background Many problems in protein modeling require obtaining a discrete representation of the protein conformational space as an ensemble of conformations. In ab-initio structure prediction, in particular, where the goal is to predict the native structure of a protein chain given its amino-acid sequence, the ensemble needs to satisfy energetic constraints. Given the thermodynamic hypothesis, an effective ensemble contains low-energy conformations which are similar to the native structure. The high-dimensionality of the conformational space and the ruggedness of the underlying energy surface currently make it very difficult to obtain such an ensemble. Recent studies have proposed that Basin Hopping is a promising probabilistic search framework to obtain a discrete representation of the protein energy surface in terms of local minima. Basin Hopping performs a series of structural perturbations followed by energy minimizations with the goal of hopping between nearby energy minima. This approach has been shown to be effective in obtaining conformations near the native structure for small systems. Recent work by us has extended this framework to larger systems through employment of the molecular fragment replacement technique, resulting in rapid sampling of large ensembles. Methods This paper investigates the algorithmic components in Basin Hopping to both understand and control their effect on the sampling of near-native minima. Realizing that such an ensemble is reduced before further refinement in full ab-initio protocols, we take an additional step and analyze the quality of the ensemble retained by ensemble reduction techniques. We propose a novel multi-objective technique based on the Pareto front to filter the ensemble of sampled local minima. Results and conclusions We show that controlling the magnitude of the perturbation allows directly controlling the distance between consecutively-sampled local minima and, in turn, steering the exploration towards

  19. Blind prediction of SAMPL4 cucurbit[7]uril binding affinities with the mining minima method

    PubMed Central

    Muddana, Hari S.; Yin, Jian; Sapra, Neil V.; Fenley, Andrew T.; Gilson, Michael K.

    2014-01-01

    Accurate methods for predicting protein-ligand binding affinities are of central interest to computer-aided drug design for hit identification and lead optimization. Here, we used the mining minima (M2) method to predict cucurbit[7]uril binding affinities from the SAMPL4 blind prediction challenge. We tested two different energy models, an empirical classical force field, CHARMm with VCharge charges, and the Poisson-Boltzmann Surface Area (PBSA) solvation model; and a semiempirical quantum mechanical Hamiltonian, PM6-DH+, coupled with the COSMO solvation model and a surface area term for nonpolar solvation free energy. Binding affinities based on the classical force field correlated strongly with the experiments with a correlation coefficient (R2) of 0.74. On the other hand, binding affinities based on the quantum mechanical energy model correlated poorly with experiments (R2 = 0.24), due largely to two major outliers. As we used extensive conformational search methods, these results point to possible inaccuracies in the PM6-DH+ energy model or the COSMO solvation model. Furthermore, the different binding free energy components, solute energy, solvation free energy, and configurational entropy showed significant deviations between the classical M2 and quantum M2 calculations. Comparison of different classical M2 free energy components to experiments show that the change in the total energy, i.e. the solute energy plus the solvation free energy, is the key driving force for binding, with a reasonable correlation to experiment (R2 = 0.56); however, accounting for configurational entropy further improves the correlation. PMID:24510191

  20. 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.

  1. 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.

  2. A population-based evolutionary search approach to the multiple minima problem in de novo protein structure prediction

    PubMed Central

    2013-01-01

    Background Elucidating the native structure of a protein molecule from its sequence of amino acids, a problem known as de novo structure prediction, is a long standing challenge in computational structural biology. Difficulties in silico arise due to the high dimensionality of the protein conformational space and the ruggedness of the associated energy surface. The issue of multiple minima is a particularly troublesome hallmark of energy surfaces probed with current energy functions. In contrast to the true energy surface, these surfaces are weakly-funneled and rich in comparably deep minima populated by non-native structures. For this reason, many algorithms seek to be inclusive and obtain a broad view of the low-energy regions through an ensemble of low-energy (decoy) conformations. Conformational diversity in this ensemble is key to increasing the likelihood that the native structure has been captured. Methods We propose an evolutionary search approach to address the multiple-minima problem in decoy sampling for de novo structure prediction. Two population-based evolutionary search algorithms are presented that follow the basic approach of treating conformations as individuals in an evolving population. Coarse graining and molecular fragment replacement are used to efficiently obtain protein-like child conformations from parents. Potential energy is used both to bias parent selection and determine which subset of parents and children will be retained in the evolving population. The effect on the decoy ensemble of sampling minima directly is measured by additionally mapping a conformation to its nearest local minimum before considering it for retainment. The resulting memetic algorithm thus evolves not just a population of conformations but a population of local minima. Results and conclusions Results show that both algorithms are effective in terms of sampling conformations in proximity of the known native structure. The additional minimization is shown to be

  3. 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.

  4. A Novel Approach to Decoy Set Generation: Designing a Physical Energy Function Having Local Minima with Native Structure Characteristics

    PubMed Central

    Keasar, Chen; Levitt, Michael

    2009-01-01

    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. PMID:12742025

  5. 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.

  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. PMID:26941790

  7. 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. PMID:24211828

  8. cluster: Searching for Unique Low Energy Minima of Structures Using a Novel Implementation of a Genetic Algorithm.

    PubMed

    Kanters, René P F; Donald, Kelling J

    2014-12-01

    A new flexible implementation of a genetic algorithm for locating unique low energy minima of isomers of clusters is described and tested. The strategy employed can be applied to molecular or atomic clusters and has a flexible input structure so that a system with several different elements can be built up from a set of individual atoms or from fragments made up of groups of atoms. This cluster program is tested on several systems, and the results are compared to computational and experimental data from previous studies. The quality of the algorithm for locating reliably the most competitive low energy structures of an assembly of atoms is examined for strongly bound Si-Li clusters, and ZnF2 clusters, and the more weakly interacting water trimers. The use of the nuclear repulsion energy as a duplication criterion, an increasing population size, and avoiding mutation steps without loss of efficacy are distinguishing features of the program. For the Si-Li clusters, a few new low energy minima are identified in the testing of the algorithm, and our results for the metal fluorides and water show very good agreement with the literature. PMID:26583254

  9. 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. PMID:25628115

  10. 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

  11. Solar Wind Structure at 1 AU: Comparison between Solar Minima 22/23 and 23/24

    NASA Astrophysics Data System (ADS)

    Jian, L.; Russell, C.; Luhmann, J. G.; Galvin, A. B.; Skoug, R. M.; Schroeder, P. C.

    2009-12-01

    The current solar minimum 23/24 has been unusually long and deep, compared with the solar minima in the space era. In order to see the consequence of the extremely quiet Sun on the solar wind, we compare the solar wind structure during the current solar minimum with the last solar minimum 22/23, which represents the case of a short and shallow solar minimum. Based on ACE, Wind, and STEREO in situ plasma and magnetic field observations, we identify and characterize stream interaction regions (SIRs), interplanetary CMEs (ICMEs), interplanetary shocks, sector boundaries, and other structures in the solar wind at 1 AU for 1995 - 1997 and 2007 - 2009. The properties of these structures, such as the occurrence rate, SIR and ICME scale and interaction strength, shock Mach number, correlation between sector boundary and SIR, will be studied. In addition to the statistical study, we will present some case studies of events from this deep solar minimum.

  12. 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.

  13. Complex Orbitals, Multiple Local Minima, and Symmetry Breaking in Perdew-Zunger Self-Interaction Corrected Density Functional Theory Calculations.

    PubMed

    Lehtola, Susi; Head-Gordon, Martin; Jónsson, Hannes

    2016-07-12

    Implentation of seminumerical stability analysis for calculations using the Perdew-Zunger self-interaction correction is described. It is shown that real-valued solutions of the Perdew-Zunger equations for gas phase atoms are unstable with respect to imaginary orbital rotations, confirming that a proper implementation of the correction requires complex-valued orbitals. The orbital density dependence of the self-interaction corrected functional is found to lead to multiple local minima in the case of the acrylic acid, H6, and benzene molecules. In the case of benzene, symmetry breaking that results in incorrect ground state geometry is found to occur, erroneously leading to alternating bond lengths in the molecule. PMID:27232582

  14. 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. PMID:27258922

  15. 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

    2016-06-01

    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. PMID:27131150

  16. 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).

  17. Comparisons of Supergranule Characteristics 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

    Supergranulation is a component of solar convection that manifests itself on the photosphere as a cellular network of around 35 Mm across, with a turnover lifetime of 1 2 days. It is strongly linked to the structure of the magnetic field. The horizontal, divergent flows within supergranule cells carry local field lines to the cell boundaries, while the rotational properties of supergranule upflows may contribute to the restoration of the poloidal field as part of the dynamo mechanism, which controls the solar cycle. The solar minimum at the transition from cycle 23 to 24 was notable for its low level of activity and its extended length. It is of interest to study whether the convective phenomena that influence the solar magnetic field during this time differed in character from periods of previous minima. This study investigates three characteristics (velocity components, sizes and lifetimes) of solar supergranulation. Comparisons of these characteristics are made between the minima of cycles 22/23 and 23/24 using MDI Doppler data from 1996 and 2008, respectively. It is found that whereas the lifetimes are equal during both epochs (around 18 h), the sizes are larger in 1996 (35.9 plus or minus 0.3 Mm) than in 2008 (35.0 plus or minus 0.3 Mm), while the dominant horizontal velocity flows are weaker (139 plus or minus m per second in 1996; 141 plus or minus 1 m per second in 2008). Although numerical differences are seen, they are not conclusive proof of the most recent minimum being inherently unusual.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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....

  19. 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.

  20. A ~0.1 bar Rule for Tropopause Temperature Minima in Thick Atmospheres of Planets and Large Moons

    NASA Astrophysics Data System (ADS)

    Robinson, T. D.; Catling, D. C.

    2013-12-01

    Tropopause temperature minima are fundamental for understanding planetary atmospheric structure. A number of shortwave absorbers (e.g., ozone, organic hazes) produce temperature inversions in the stratospheres of Earth, Jupiter, Saturn, Titan, Uranus and Neptune. These inversions lead to temperature minima that, remarkably, all occur near 0.1 bar, despite very different insolation, atmospheric composition, gravity, and internal heat flux. We examined the atmospheric thermal structure of solar system worlds with thick atmospheres using an analytic 1-D radiative-convective model, which assumes gray thermal radiative transfer. Shortwave radiative transfer is divided into a stratospheric channel, which allows for inversions, and a tropospheric channel for solar heating at depth and at the surface. We assume that a convective profile, which is adjusted to account for condensation, sits below the portion of the atmosphere that is in radiative equilibrium. The model ensures that the temperature and upwelling thermal flux are continuous across the radiative-convective boundary. Finally, the model uses a power-law scaling between the gray infrared optical depth and pressure, which is physically justified for tropospheres and lower stratospheres where opacity is dominated by collision-induced absorption and/or strong pressure broadening. For the worlds of the solar system, the tropopause temperature minimum always lies above the radiative-convective boundary. Thus, the shared 0.1 bar tropopause arises from the common physics of infrared radiative transfer. Model fits to solar system worlds show that the gray infrared optical depth where the tropopause minimum occurs is ~0.1. Furthermore, the gray infrared optical depths at a pressure of 1 bar are typically of order a few. These, along with the aforementioned scaling between pressure and infrared optical depth, set the tropopause pressure to be near 0.1 bar. Moving beyond the solar system, we show that the typical gray

  1. 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.

  2. 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.

  3. 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. PMID:27176512

  4. 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

  5. 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.

    PubMed

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

    2013-09-21

    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 coupled-cluster including single, double, and full perturbative triple excitations (CCSD(T))/aug-cc-pVDZ level of theory. All five examined hexamer isomer minima previously reported by Møller-Plesset perturbation theory (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) frequencies 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 CCSD(T) and MP2 are observed for the harmonic hydrogen bonded frequencies, for which the former produces larger absolute values than the latter. Their CCSD(T) redshifts from the monomer values (Δω) are smaller than the MP2 ones, due to the fact that CCSD(T) produces shorter elongations (ΔR) of the respective hydrogen bonded OH lengths from the monomer value with respect to MP2. Both

  6. 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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

    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 coupled-cluster including single, double, and full perturbative triple excitations (CCSD(T))/aug-cc-pVDZ level of theory. All five examined hexamer isomer minima previously reported by Møller-Plesset perturbation theory (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) frequencies 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 CCSD(T) and MP2 are observed for the harmonic hydrogen bonded frequencies, for which the former produces larger absolute values than the latter. Their CCSD(T) redshifts from the monomer values (Δω) are smaller than the MP2 ones, due to the fact that CCSD(T) produces shorter elongations (ΔR) of the respective hydrogen bonded OH lengths from the monomer value with respect to MP2

  7. 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

  8. New findings on increasing solar trend that can change Earth climate: are we entering new great solar minima?

    NASA Astrophysics Data System (ADS)

    Rozelot, J. P.

    2009-10-01

    Studies of the Sun-Earth relationships during the past years have dramatically changed our view on Solar- Terrestrial Physics. Neither is the interplanetary medium unstructured or quasi-static, nor is it a simple magnetic stratified object. Thus, the interaction of the solar electromagnetic radiation (photons), hot plasma (electrons, protons and other ions), cosmic rays, microscopic dust particles, and magnetic fields (primarily from the Sun) with the upper environment of our Earth leads to a complex physics which is far to be understandable. This new science is growing rapidly, as well as for the physical problems which arise as for its growing impact on our societies. This last case is well illustrated by the emergence of the so-called Space Weather. In spite of a great number of papers and books written on this subject and on a broader one devoted to Solar-Terrestrial links, the different terms deserve to be clarified. In this paper, we will first establish a clear distinction between Space Weather, Space Climate, Space Physics, Sun-Earth connections, and Helioclimatology, this last word being introduced to describe the role of the Sun in the Earth's climate forcing. In a second step, we will emphasize the key role of the ranging time on which the effects may act. We will then underline the necessity to better predict solar activity showing the physical difficulties for such an exercise, yielding the extreme complexity for forecasting specific events. The three dataset, past Earth's temperature (since AD 630), solar shape variability (since AD 1600) and strength of umbral/sunspots magnetic field (since AD 1995) lead all to a Next Grand Minima predictable for 2015-2018. We will conclude by giving some imprints for the future.

  9. Shear-deformation-potential constant of the conduction-band minima of Si: Experimental determination by the deep-level capacitance transient method

    NASA Astrophysics Data System (ADS)

    Li, Ming-Fu; Zhao, Xue-Shu; Gu, Zong-Quan; Chen, Jian-Xin; Li, Yan-Jin; Wang, Jian-Qing

    1991-06-01

    The shear-deformation-potential constant Ξu of the conduction-band minima of Si has been measured by a method which we called deep-level capacitance transient under uniaxial stress. The uniaxial-stress (F) dependence of the electron emission rate en from deep levels to the split conduction-band minima of Si has been analyzed. Theoretical curves are in good agreement with experimental data for the S0 and S+ deep levels in Si. The values of Ξu obtained by the method are 11.1+/-0.3 eV at 148.9 K and 11.3+/-0.3 eV at 223.6 K. The analysis and the Ξu values obtained are also valuable for symmetry determination of deep electron traps in Si.

  10. Brachyopa minima (Diptera: Syrphidae), a new species from Greece with notes on the biodiversity and conservation of the genus Brachyopa Meigen in the Northern Aegean Islands.

    PubMed

    Pérez-Bañón, Celeste; Radenković, Snezana; Vujić, Ante; Petanidou, Theodora

    2016-01-01

    An on-going study of the hoverfly fauna of the Northern Aegean Islands (Greece) has revealed the presence of four species of the genus Brachyopa Meigen. During the survey the following species were found: B. bicolor (Fallén), B. quadrimaculosa Thompson in Kaplan & Thompson, B. minima Vujić & Pérez-Bañón sp. nov. and an unidentified species very close to B. pilosa (Collin). Morphological characters and mitochondrial COI barcodes were used to link different life stages of B. minima, and to identify a larval specimen of B. bicolor. In this study adult and larval morphology and habitat preferences for B. minima are described. The description of larval morphology of B. bicolor and Brachyopa sp. aff. pilosa is amended too. An identification key to the adults of the B. quadrimaculosa group sensu Kassebeer (2002) in the Eastern Mediterranean (Greece, Israel and Turkey) is provided. The importance of specific microhabitats for the continued existence of these taxa is discussed. PMID:27395920

  11. Ultrastructural studies of the mandibular glands of the minima, media and soldier ants of Atta sexdens rubropilosa (Forel 1908) (Hymenoptera: Formicidae).

    PubMed

    Pavon, Lorena Favaro; Mathias, Maria Izabel Camargo

    2005-01-01

    The mandibular glands of Hymenoptera are structures associated with the mandibles and constitute part of the salivary glands system. Histological studies in workers of Atta sexdens rubropilosa revealed that this gland contains two portions: a secretory and a storage portion or reservoir. Both portions are connected by means of canaliculi. The object of the present work was the study of the ultratructure of the mandibular glands of minima, media and soldier ant of A. s. rubropilosa by TEM techniques. The glands, in the three castes studied, possess a reservoir, constituted by a simple pavementous epithelium surrounded by the cuticular intima and the secretory portion is constituted by cells of rounded shape. The secretory cells, mainly of minima and soldier, were rich in smooth endoplasmic reticulum. The media worker and soldier presented a large number of mitochondria, of varying shape. Well-developed Golgi complexes were also present in the soldiers. The secretory cells in minima, media and soldier were provided with collecting intracellular canaliculi, which were linked to the reservoir through the extracellular portion. The cytoplasm of the canaliculi-forming cell was poor in organelles. In the individuals of the three castes of A. s. rubropilosa, the presence of lipid secretion granules suggested, beyond the other functions, also a possible pheromonal action. The different roles executed by the different insect castes are directly dependent on the glandular products and, consequently, on the secretory cellular characteristics. PMID:15935305

  12. 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.

  13. 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

  14. 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

  15. 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

  16. A study of the properties of the Grand Solar Minima throughout the past 13,000 years and the implications for Space Weather.

    NASA Astrophysics Data System (ADS)

    McCracken, Ken; Beer, Juerg

    2016-04-01

    The intensity of the cosmic radiation reaching the orbit of Earth is primarily controlled by the strength of the heliomagnetic field, which itself is largely determined by the level of solar activity. The paleo-cosmic ray (PCR) record therefore provides the output from a "cosmic magnetometer", and a proxy for solar activity in the past. Using 10Be (ice-cores) and 14C (tree rings) data we investigate the wide variations in the PCR and solar activity that have occurred during the past 13,000 years. In particular, we study the occurrence and properties of "Grand Minima"- the periods of very low solar activity similar to the Maunder Minimum (1645-1715) for which solar and geophysical data are available. There was a sequence of five GM between 950-1830CE; there were three similar sequences of similar duration in the preceding millennia; interspersed with intervals of ~1000 year essentially devoid of GM. The four sequences of GM correspond to the minima of the 2300 y Hallstatt periodicity. The PCR increases by ~50% during "Grand Solar Minima" and we use the PCR intensity to quantify the relative significance of the Grand Minima in the past. On the basis that the terrestrial and heliospheric consequences of a GM will depend on both the amplitude of the change in PCR intensity, and its duration, we have defined a parameter, the GM index, as the product of the amplitude and duration of a GM. We conclude that there have been 22 GM of geophysical significance equal to, or greater than that of the Wolf GM (1230-1350CE). The Sun is in a "Grand Minimum" condition for ~45% of the time during a GM sequence; and for only ~5% of the time in the intervening 1000y intervals of high solar activity. We discuss the implications of these observations in respect of space weather and climate. In conclusion, we speculate that the sun may now be entering one of its extended periods of high activity which will persist for ~1000 y.

  17. 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

  18. 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. PMID:26742090

  19. The difference in the energy spectra of galactic cosmic rays at the minima of the 19th and 20th solar activity cycles

    NASA Technical Reports Server (NTRS)

    Svirzhevskaya, A. K.; Stozhkov, Y. I.; Svirzhevsky, N. S.; Charakhchyan, T. N.

    1985-01-01

    The absorption curves of the cosmic ray charged component for solar minima in 1965 and 1975 to 1977 are analyzed on the basis of daily stratospheric measurements in Murmansk, Moscow, Alma-Ata and Mirny (Antarctic). Two distinct features in the energy spectra of galactic cosmic rays are revealed during these periods. At the 20th solar activity minimum there was the additional short range component of cosmic rays. Additional fluxes in the stratosphere at high latitudes caused by this component are probably protons and He nuclei with the energy 100 to 500 MeV/n. The fluxes are estimates as Approx. 300 sq m/s/sr. At the minimum in 1975 to 1977 the proton intensity in the energy range 1 to 15 GeV is 10 to 15% lower than that in the 1965 solar activity minimum.

  20. 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. PMID:20562212

  1. 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.

  2. 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

  3. 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. PMID:27007320

  4. Ion-Stockmayer clusters: Minima, classical thermodynamics, and variational ground state estimates of Li+(CH3NO2)n (n = 1-20)

    NASA Astrophysics Data System (ADS)

    Curotto, E.

    2015-12-01

    Structural optimizations, classical NVT ensemble, and variational Monte Carlo simulations of ion Stockmayer clusters parameterized to approximate the Li+(CH3NO2)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.

  5. 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.

  6. 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. PMID:26908369

  7. 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. PMID:24915501

  8. 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.

  9. Quadratic minima and modular forms II

    NASA Astrophysics Data System (ADS)

    Brent, Barry

    We give upper bounds on the size of the gap between a non-zero constant term and the next non-zero Fourier coefficient of an entire level two modular form. We give upper bounds for the minimum positive integer represented by a level two even positive-definite quadratic form. These bounds extend partial results in part I.

  10. 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.

  11. 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%.

  12. 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.

  13. 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

  14. 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. PMID:25329833

  15. 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).

  16. 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.

  17. Deciphering Solar Magnetic Activity: On Grand Minima in Solar Activity

    NASA Astrophysics Data System (ADS)

    Mcintosh, Scott; Leamon, Robert

    2015-07-01

    The Sun provides the energy necessary to sustain our existence. While the Sun provides for us, it is also capable of taking away. The weather and climatic scales of solar evolution and the Sun-Earth connection are not well understood. There has been tremendous progress in the century since the discovery of solar magnetism - magnetism that ultimately drives the electromagnetic, particulate and eruptive forcing of our planetary system. There is contemporary evidence of a decrease in solar magnetism, perhaps even indicators of a significant downward trend, over recent decades. Are we entering a minimum in solar activity that is deeper and longer than a typical solar minimum, a "grand minimum"? How could we tell if we are? What is a grand minimum and how does the Sun recover? These are very pertinent questions for modern civilization. In this paper we present a hypothetical demonstration of entry and exit from grand minimum conditions based on a recent analysis of solar features over the past 20 years and their possible connection to the origins of the 11(-ish) year solar activity cycle.

  18. The 11-year solar cycle continues during prolonged sunspot minima

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2012-12-01

    Streaming into the solar system at nearly the speed of light, galactic cosmic rays (GCRs) are a high-energy mix of protons, electrons, and atomic nuclei. As they pass into reach of the outflowing solar wind, the propagation of GCRs is inhibited. Galactic cosmic rays that make it to Earth interact with the atmosphere, creating a shower of heavy isotopes including beryllium-10. Beryllium-10 isotope concentrations recorded in ice cores provide a long-term, high temporal resolution record of galactic cosmic ray flux.

  19. 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.

  20. 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.

  1. 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.

  2. 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).

  3. Two-center minima in harmonic spectra from aligned polar molecules

    SciTech Connect

    Etches, Adam; Gaarde, Mette B.; Madsen, Lars Bojer

    2011-08-15

    We extend a model of two-center interference to include the superposition of opposite orientations in aligned polar molecules. We show that the position of the minimum in the harmonic spectrum from both aligned and oriented CO depends strongly on the relative recombination strength at different atoms, not just the relative phase. We reinterpret the minimum in aligned CO as an interference between opposite orientations, and obtain good agreement with numerical calculations. Inclusion of the first-order Stark effect shifts the position of the interference minimum in aligned CO even though aligned molecules do not posses total permanent dipoles. We explain the shift in terms of the phase that the electron of oriented CO accumulates due to the Stark effect.

  4. 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=26Mȯ). 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).

  5. 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.

  6. Global Solar Convective Dynamo with Cycles, Equatorward Propagation and Grand Minima

    NASA Astrophysics Data System (ADS)

    Toomre, Juri; Augustson, Kyle C.; Brun, Allan Sacha; Miesch, Mark S.

    2016-05-01

    The 3-D MHD Anelastic Spherical Harmonic (ASH) code, using slope-limited diffusion, is used to study the interaction of turbulent convection, rotation and magnetism in a full spherical shell comparable to the solar convection zone. Here a star of one solar mass, with a solar luminosity, is considered that is rotating at three times the solar rate. The dynamo generated magnetic field forms large-scale toroidal wreaths, whose formation is tied to the low Rossby number of the convection in this simulation which we have labeled K3S. This case displays prominent polarity cycles with regular reversals occurring roughly every 6.2 years. These reversals are linked to the weakened differential rotation and a resistive collapse of the large-scale magnetic field. Distinctive equatorial migration of the strong magnetic wreaths is seen, arising from modulation of the differential rotation rather than a dynamo wave. As the wreaths approach the equator, cross-equatorial magnetic flux is achieved that permits the low-latitude convection to generate poloidal magnetic field with opposite polarity. Poleward migration of such magnetic flux from the equator eventually leads to the reversal of the polarity of the high-latitude magnetic field. This K3S 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 striking grand minimum reveals that it likely arises through the interplay of symmetric and antisymmetric dynamo families.

  7. Grand Minima and Equatorward Propagation in a Cycling Stellar Convective Dynamo

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    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.

  8. Grand Minima and Equatorward Propagation in a Cycling Stellar Convective Dynamo

    NASA Astrophysics Data System (ADS)

    Augustson, Kyle C.; Brun, Allan Sacha; Miesch, Mark; Toomre, Juri

    2015-08-01

    The 3-D magnetohydrodynamic (MHD) Anelastic Spherical Harmonic (ASH) 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 time scales, 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 simulations relatively low magnetic Prandtl number. A mean-field-based analysis of this dynamo simulation demonstrates that it is of the α-Ω type. The time scales that appear to be relevant to the magnetic polarity reversal are also identified.

  9. VizieR Online Data Catalog: Time minima of EP Aur (Li+, 2015)

    NASA Astrophysics Data System (ADS)

    Li, H.-L.; Wei, J.-Y.; Yang, Y.-G.; Li, K.; Zhang, X.-B.

    2015-07-01

    From 2003 December to 2014 January, the photometry of EP Aur was performed by using the 60-cm telescope and the 85-cm telescope at the Xinglong station (XLs) of National Astronomical Observatories of China (NAOC), and the 1.0-m telescope at the Weihai Observatory (WHO) of Shandong University. The three telescopes were equipped with standard Johnson-Cousins UBVRcIc systems. All observed images were reduced by using the IMREDIMRED and APPHOTAPPHOT packages in IRAF in a standard fashion. The multi-color photometry of EP Aur was carried out on 2013 December 1, 2, 3, and 5, 2009 January 3, 4 and 5 using the 60-cm telescope at XLs. TYC 2420-434-1 and TYC 2420-193-1 were taken as the comparison and check stars respectively. (2 data files).

  10. The role of the oceanic oxygen minima in generating biodiversity in the deep sea

    NASA Astrophysics Data System (ADS)

    Rogers, Alex D.

    2000-01-01

    Many studies on the deep-sea benthic biota have shown that the most species-rich areas lie on the continental margins between 500 and 2500 m, which coincides with the present oxygen-minimum in the world's oceans. Some species have adapted to hypoxic conditions in oxygen-minimum zones, and some can even fulfil all their energy requirements through anaerobic metabolism for at least short periods of time. It is, however, apparent that the geographic and vertical distribution of many species is restricted by the presence of oxygen-minimum zones. Historically, cycles of global warming and cooling have led to periods of expansion and contraction of oxygen-minimum layers throughout the world's oceans. Such shifts in the global distribution of oxygen-minimum zones have presented many opportunities for allopatric speciation in organisms inhabiting slope habitats associated with continental margins, oceanic islands and seamounts. On a smaller scale, oxygen-minimum zones can be seen today as providing a barrier to gene-flow between allopatric populations. Recent studies of the Arabian Sea and in other regions of upwelling also have shown that the presence of an oxygen-minimum layer creates a strong vertical gradient in physical and biological parameters. The reduced utilisation of the downward flux of organic material in the oxygen-minimum zone results in an abundant supply of food for organisms immediately below it. The occupation of this area by species exploiting abundant food supplies may lead to strong vertical gradients in selective pressures for optimal rates of growth, modes of reproduction and development and in other aspects of species biology. The presence of such strong selective gradients may have led to an increase in habitat specialisation in the lower reaches of oxygen-minimum zones and an increased rate of speciation.

  11. VizieR Online Data Catalog: HL Aur light curves and minima (Zhang+ 1997)

    NASA Astrophysics Data System (ADS)

    Zhang, R. X.; Fang, M. J.; Zhai, D. S.

    1996-11-01

    Photoelectric observations of HL Aur were carried out with the 60cm reflector of Beijing Astronomical Observatory in 1990 and 1994, and the first photoelectric BV light curves were obtained along with a newly derived ephemeris. The period of the system appears to be constant over the past 65-years. Using the Wilson-Devinney program a photometric analysis of the B and V light curves is performed. It is evident that HL Aur is a near-contact binary with a mass ratio of q=m2/m1=0.722+/-0.011. The primary component of the system is essentially in contact with its Roche lobe, while the secondary is detached but nearly in contact with its lobe. It is found that the components of the system are slightly evolved and located near the terminal-age main sequence. The binary is consistent with the general evolutionary picture for near-contact systems. (3 data files).

  12. 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).

  13. Comparison of Coronal Streamer Properties to Solar Wind Models For The Last Two Solar Cycle Minima

    NASA Astrophysics Data System (ADS)

    Miralles, Mari Paz; Landi, E.; Cranmer, S. R.; Raymond, J. C.; Cohen, O.; Oran, R.

    2013-07-01

    We characterize the physical properties of two coronal streamers during Earth/Ulysses quadrature configurations for the previous two solar minimum periods. Comparisons between coronal remote-sensing observations and in situ measurements of solar wind plasma properties are being used to characterize the origin of slow wind streams. In order to investigate slow solar wind heating and acceleration, we compare the measurements with predictions from MHD models. We aim to use the empirical measurements to distinguish between different proposed physical processes for the slow solar wind. This work is supported by NASA grant NNX10AQ58G to the Smithsonian Astrophysical Observatory.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  15. 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.

  16. 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,…

  17. Binary complexes of ammonia with phenylacetylenes: a combined experimental and computational approach to explore multiple minima on intermolecular potentials.

    PubMed

    Dey, Arghya; Mondal, Sohidul Islam; Patwari, G Naresh

    2013-03-18

    The hydrogen-bonded complexes of phenylacetylene, 4-fluorophenylacetylene, 2-fluorophenylacetylene, and 2,6-difluorophenylacetylene with ammonia are investigated using IR-UV double resonance spectroscopy in combination with high-level ab initio calculations at the CCSD(T)/CBS level of theory. The C-H···N hydrogen-bonded complex, which involves an interaction of ammonia with the acetylenic CH group is the global minimum and is observed in all four cases investigated. In addition, phenylacetylene and 4-fluorophenylacetylene form a quasi-planar cyclic complexes with ammonia incorporating N-H···π and C-H···N hydrogen bonds, wherein the π-electron density of the acetylenic C≡C bond acts as an acceptor to the N-H group of ammonia. A third ammonia complex is observed for 4-fluorophenylacetylene in which ammonia interacts with the fluorine atom once again, leading to the formation of a quasi-planar cyclic complex. The substitution of the fluorine atom on the phenyl ring of phenylacetylene modulates the intermolecular potentials, which are dependent on the position of the substitution. PMID:23281120

  18. 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.

  19. Constraints from color and/or charge breaking minima in the supersymmetric standard model with right-handed neutrinos

    SciTech Connect

    Kobayashi, Tatsuo; Shimomura, Takashi

    2010-08-01

    We consider a model where right-handed neutrinos and sneutrinos are introduced to the minimal supersymmetric standard model. In the scalar potential of this model, there exist trilinear and quartic terms in scalar potential that are proportional to Yukawa couplings of neutrinos. Because of these trilinear and quartic terms, color and/or charge breaking (CCB) and unbounded-from-below (UFB) directions appear along which sneutrinos have a vacuum expectation value, making the vacuum of the electroweak symmetry breaking unstable. We analyze the scalar potential of this model and derive necessary conditions for color and/or charge breaking and unbounded-from-below directions to vanish.

  20. Variability of ionospheric TEC during solar and geomagnetic minima (2008 and 2009): external high speed stream drivers

    NASA Astrophysics Data System (ADS)

    Verkhoglyadova, O. P.; Tsurutani, B. T.; Mannucci, A. J.; Mlynczak, M. G.; Hunt, L. A.; Runge, T.

    2013-02-01

    We study solar wind-ionosphere coupling through the late declining phase/solar minimum and geomagnetic minimum phases during the last solar cycle (SC23) - 2008 and 2009. This interval was characterized by sequences of high-speed solar wind streams (HSSs). The concomitant geomagnetic response was moderate geomagnetic storms and high-intensity, long-duration continuous auroral activity (HILDCAA) events. The JPL Global Ionospheric Map (GIM) software and the GPS total electron content (TEC) database were used to calculate the vertical TEC (VTEC) and estimate daily averaged values in separate latitude and local time ranges. Our results show distinct low- and mid-latitude VTEC responses to HSSs during this interval, with the low-latitude daytime daily averaged values increasing by up to 33 TECU (annual average of ~20 TECU) near local noon (12:00 to 14:00 LT) in 2008. In 2009 during the minimum geomagnetic activity (MGA) interval, the response to HSSs was a maximum of ~30 TECU increases with a slightly lower average value than in 2008. There was a weak nighttime ionospheric response to the HSSs. A well-studied solar cycle declining phase interval, 10-22 October 2003, was analyzed for comparative purposes, with daytime low-latitude VTEC peak values of up to ~58 TECU (event average of ~55 TECU). The ionospheric VTEC changes during 2008-2009 were similar but ~60% less intense on average. There is an evidence of correlations of filtered daily averaged VTEC data with Ap index and solar wind speed. We use the infrared NO and CO2 emission data obtained with SABER on TIMED as a proxy for the radiation balance of the thermosphere. It is shown that infrared emissions increase during HSS events possibly due to increased energy input into the auroral region associated with HILDCAAs. The 2008-2009 HSS intervals were ~85% less intense than the 2003 early declining phase event, with annual averages of daily infrared NO emission power of ~ 3.3 × 1010 W and 2.7 × 1010 W in 2008 and 2009, respectively. The roles of disturbance dynamos caused by high-latitude winds (due to particle precipitation and Joule heating in the auroral zones) and of prompt penetrating electric fields (PPEFs) in the solar wind-ionosphere coupling during these intervals are discussed. A correlation between geoeffective interplanetary electric field components and HSS intervals is shown. Both PPEF and disturbance dynamo mechanisms could play important roles in solar wind-ionosphere coupling during prolonged (up to days) external driving within HILDCAA intervals.

  1. 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

  2. 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.

  3. 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.

  4. In search of radiation minima for balancing the needs of forest and water management in snow dominated watersheds (Invited)

    NASA Astrophysics Data System (ADS)

    Kumar, M.; Seyednasrollah, B.; Link, T. E.

    2013-12-01

    In upland snowfed forested watersheds, where the majority of melt recharge occurs, there is growing interest among water and forest managers to strike a balance between maximizing forest productivity and minimizing impacts on water resources. Implementation of forest management strategies that involve reduction of forest cover generally result in increased water yield and peak flows from forests, which has potentially detrimental consequences including increased erosion, stream destabilization, water shortages in late melt season, and degradation of water quality and ecosystem health. These ill effects can be partially negated by implementing optimal gap patterns and vegetation densities through forest management, that may minimize net radiation on snow-covered forest floor (NRSF). A small NRSF can moderate peak flows and increase water availability late in the melt season. Since forest canopies reduce direct solar (0.28 - 3.5 μm) radiation but increase longwave (3.5-100 μm) radiation at the snow surface, by performing detailed quantification of individual radiation components for a range of vegetation density and and gap configurations, we identify the optimal vegetation configurations. We also evaluate the role of site location, its topographic setting, local meteorological conditions and vegetation morphological characteristics, on the optimal configurations. The results can be used to assist forest managers to quantify the radiative regime alteration for various thinning and gap-creation scenarios, as a function of latitudinal, topographic, climatic and vegetation characteristics.

  5. 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.

  6. 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…

  7. Program of Measurement of the Asymmetry P at the Minima of the Differential Cross Section for Elastic {pi}{sup +}p Scattering

    SciTech Connect

    Beloglazov, Yu.A.; Kovalev, A.I.; Kruglov, S.P.; Novinsky, D.V.; Sumachev, V.V.; Trautman, V.Yu.; Filimonov, E.A.; Shchedrov, V.A.; Alekseev, I.G.; Budkovsky, P.E.; Zhurkin, V.V.; Kanavets, V.P.; Koroleva, L.I.; Morozov, B.V.; Nesterov, V.M.; Ryltsov, V.V.; Svirida, D.N.; Sulimov, A.D.; Bazhanov, N.A.; Bunyatova, E.I.

    2005-03-01

    A program of measurement of the polarization parameter P in elastic {pi}{sup +}p interaction in the resonance region of backward pion scattering is presented. This program is aimed at determining the bifurcation points of the trajectory of zeros of the pion-nucleon amplitude and, hence, at unambiguously reconstructing the amplitude of {pi}N scattering in the second resonance region. It is planned to perform a relevant experiment in a pion beam from the accelerator of the Institute of Experimental and Theoretical Physics (ITEP, Moscow)

  8. 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.

  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. 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. PMID:25433387

  11. 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.

  12. Quantum chemical and matrix-IR characterization of CH3CN-BCl3: a complex with two distinct minima along the B-N bond potential.

    PubMed

    Wrass, John P; Sadowsky, Daniel; Bloomgren, Kaitlin M; Cramer, Christopher J; Phillips, James A

    2014-08-21

    We have characterized the structural and energetic properties of CH3CN-BCl3via computations and matrix-IR spectroscopy. We find two equilibrium structures of the complex via computations. At the MP2/aug-cc-pVTZ level, the global minimum energy structure has a B-N distance of 1.601 Å, and a binding energy of 12.0 kcal mol(-1). The secondary structure lies 7.1 kcal mol(-1) higher in energy with a B-N distance of 2.687 Å and a binding energy of 4.9 kcal mol(-1). Computational scans of the B-N potential curve using both DFT and post-HF methods indicate that a significant barrier exists between these structures, and that it lies 1 to 2 kcal mol(-1) above the secondary minimum at a B-N distance of about 2.2 Å. We also observed several key, structurally-sensitive IR bands for six isotopic forms of the complex in neon matrices, including: the B-Cl asymmetric stretching band (ν) at 792 cm(-1) and the C-N stretching band (νCN) at 2380 cm(-1) (for the primary isotopomer, CH3C(14)N-(11)BCl3). These frequencies are consistent with computational predictions for the minimum-energy form of the complex. Energy decomposition analyses were conducted for CH3CN-BCl3 and also two related complexes, CH3CN-BF3 and CH3CN-BH3. These provide insight into the trend in Lewis acidity of the BX3 acceptors toward nitriles. Furthermore, these analyses indicate that the barrier along the B-N potential of CH3CN-BCl3 results from Pauli repulsion between the π electrons on the nitrile moiety and the chlorine atoms in BCl3, which is significant at relatively long distances where attractive bonding interactions fail to overcome it. PMID:24984763

  13. 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

    2016-06-01

    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. PMID:27139720

  14. He II λ4686 Emission from the Massive Binary System in λ 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. High Energetic Solar Flares in the Solar Minima Activity in Comparative Study with the Solar Maxima Activity from 1954 to 2014 and Their Effects on the Space Environment

    NASA Astrophysics Data System (ADS)

    Mohamed, Wael

    Solar 11-year cycle of solar activity is characterized by the rise and fall in the numbers and areas of sunspots. On solar maximum activity, many flares and CMEs can affect the near-earth space environment. But on the solar minimum activity, there are sometimes solar proton events, (e.g. High Energetic Solar Proton Flares on the declining phase of solar cycle 22 for M.A.Mosalam Shaltout, 1995), have the same effect for those on the solar maximum activity or more. So, a study must be made for the ascending and descending phases of solar activity for a set of solar cycles (from 1954 to 2014) to confirm the conclusion of Mosalam Shaltout on the light of the present high quality observations from ground and by artificial satellites.

  16. 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. PMID:26987087

  17. 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.

  18. 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.

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

    DOE PAGESBeta

    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 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

  20. 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

  1. 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

  2. Attosecond structures from the molecular cavity in fullerene photoemission time delay

    NASA Astrophysics Data System (ADS)

    Magrakvelidze, Maia; Anstine, Dylan M.; Dixit, Gopal; Madjet, Mohamed El-Amine; Chakraborty, Himadri S.

    2015-05-01

    Photoelectron spectroscopy studies earlier probed oscillations in C60 valence emissions, producing a series of minima whose energy separation depends on the molecular cavity. We show here that the quantum phase at these cavity minima exhibits variations from strong electron correlations in C60 , causing rich structures in the emission time delay. Hence, these minima offer unique spectral zones to directly explore multielectron forces via attosecond RABITT interferometry not only in fullerenes, but also in clusters and nanostructures for which such minima are likely abundant.

  3. 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.

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

    PubMed Central

    Sun, Sang-Mi; Yang, Seung Hwan

    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. PMID:27190985

  5. Alternative electron transports participate in the maintenance of violaxanthin De-epoxidase activity of Ulva sp. under low irradiance.

    PubMed

    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

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

    PubMed

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

    2016-03-11

    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 (1)H 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

  7. O-C Analysis of Selected 3-Body Systems

    NASA Astrophysics Data System (ADS)

    Ogłoza, W.; Kreiner, J. M.; Stachowski, G.; Winiarski, M.; Zakrzewski, B.; Doǧru, S.; Aliçavuş, F.; Demircan, O.; Erdem, A.

    2012-04-01

    This paper presents the results of the analysis of (O-C) diagrams of four eclipsing variables. The diagrams are based on times of minima collected in the Cracow database, which contains times of minima found in the literature, from observations at Mt. Suhora and Ulupinar Observatories, or determined using publicly-available photometric surveys (NSVS, ASAS etc).

  8. 75 FR 62639 - Air Ambulance and Commercial Helicopter Operations, Part 91 Helicopter Operations, and Part 135...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-12

    ... in the Federal Register published on April 11, 2000 (65 FR 19477-78) or you may visit http://Dockets..., and alternate airport weather minima. The changes are intended to provide certificate holders and... Weather Minima (Sec. 135.607) ii. IFR Operations at Airports and Heliports Without Weather Reporting...

  9. 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.

  10. Troughs under threshold modeling of minimum flows in perennial streams

    NASA Astrophysics Data System (ADS)

    Önöz, B.; Bayazit, M.

    2002-02-01

    Troughs under threshold analysis has so far found little application in the modeling of minimum streamflows. In this study, all the troughs under a certain threshold level are considered in deriving the probability distribution of annual minima through the total probability theorem. For the occurrence of minima under the threshold, Poissonian, binomial or negative binomial processes are assumed. The magnitude of minima follows the generalized Pareto, exponential or power distribution. It is shown that asymptotic extreme value distributions for minima or the two-parameter Weibull distribution is obtained for the annual minima, depending on which models are assumed for the occurrence and magnitude of troughs under the threshold. Derived distributions can be used for modeling the minimum flows in streams which do not have zero flows. Expressions for the T-year annual minimum flow are obtained. An example illustrates the application of the troughs under threshold model to the minimum flows observed in a stream.

  11. Geometric Frustration of Colloidal Dimers on a Honeycomb Magnetic Lattice

    NASA Astrophysics Data System (ADS)

    Tierno, Pietro

    2016-01-01

    We study the phase behavior and the collective dynamics of interacting paramagnetic colloids assembled above a honeycomb lattice of triangular shaped magnetic minima. A frustrated colloidal molecular crystal is realized when filling these potential minima with exactly two particles per pinning site. External in-plane rotating fields are used to anneal the system into different phases, including long range ordered stripes, random fully packed loops, labyrinth and disordered states. At a higher amplitude of the annealing field, the dimer lattice displays a two-step melting transition where the initially immobile dimers perform first localized rotations and later break up by exchanging particles across consecutive lattice minima.

  12. Glass transition and random walks on complex energy landscapes.

    PubMed

    Baronchelli, Andrea; Barrat, Alain; Pastor-Satorras, Romualdo

    2009-08-01

    We present a simple mathematical model of glassy dynamics seen as a random walk in a directed weighted network of minima taken as a representation of the energy landscape. Our approach gives a broader perspective to previous studies focusing on particular examples of energy landscapes obtained by sampling energy minima and saddles of small systems. We point out how the relation between the energies of the minima and their number of neighbors should be studied in connection with the network's global topology and show how the tools developed in complex network theory can be put to use in this context. PMID:19792062

  13. Parametric modeling in distributed optical fiber vibration sensing system for position determination

    NASA Astrophysics Data System (ADS)

    Wu, Hongyan; Wang, Jian; Jia, Bo

    2016-04-01

    Distributed optical fiber vibration sensing system is widely used as a monitoring system in communication cable and pipeline of long distances. When a vibration signal occurs at a particular position along the fiber, the response of the system, in the frequency domain, presents a series of periodic maxima and minima (or null frequencies). These minima depend on the position of the vibration signal along the fiber. Power spectral estimation methods are considered to denoise the power spectrum of the system and determine these minima precisely. The experimental results show higher accuracy of the position using a parametric model with appropriate selection of order p and q than just using fast Fourier transform algorithm.

  14. Geometric Frustration of Colloidal Dimers on a Honeycomb Magnetic Lattice.

    PubMed

    Tierno, Pietro

    2016-01-22

    We study the phase behavior and the collective dynamics of interacting paramagnetic colloids assembled above a honeycomb lattice of triangular shaped magnetic minima. A frustrated colloidal molecular crystal is realized when filling these potential minima with exactly two particles per pinning site. External in-plane rotating fields are used to anneal the system into different phases, including long range ordered stripes, random fully packed loops, labyrinth and disordered states. At a higher amplitude of the annealing field, the dimer lattice displays a two-step melting transition where the initially immobile dimers perform first localized rotations and later break up by exchanging particles across consecutive lattice minima. PMID:26849619

  15. Impacts of Extended Periods of Low Solar Activity on Climate (Abstract)

    NASA Astrophysics Data System (ADS)

    Denig, W. F.

    2016-06-01

    (Abstract only) There has been great interest in determining the length and amplitude of Solar Cycle 24 in recent years, in part due to increasing speculation that the current solar minimum is anomalously quiet and perhaps signaling the beginning of a decreased period of solar activity in the coming decades. We aim to examine the current solar minimum and compare it to previous solar minima in order to: determine if the current minimum shares characteristics with other historically quiet solar minima (sometimes referred to as grand minima); outline the potential consequences of a grand minimum with respect to climate; and predict the future of Solar Cycle 24.

  16. 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

  17. 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). PMID:25849557

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  19. 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.

  20. Multiple Conformational States of Proteins: A Molecular Dynamics Analysis of Myoglobin

    NASA Astrophysics Data System (ADS)

    Elber, R.; Karplus, M.

    1987-01-01

    A molecular dynamics simulation of myoglobin provides the first direct demonstration that the potential energy surface of a protein is characterized by a large number of thermally accessible minima in the neighborhood of the native structure (for example, approximately 2000 minima were sampled in a 300-picosecond trajectory). This is expected to have important consequences for the interpretation of the activity of transport proteins and enzymes. Different minima correspond to changes in the relative orientation of the helices coupled with side-chain rearrangements that preserve the close packing of the protein interior. The conformational space sampled by the simulation is similar to that found in the evolutionary development of the globins. Glasslike behavior is expected at low temperatures. The minima obtained from the trajectory do not satisfy certain criteria for ultrametricity.

  1. 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.

  2. Timing of eclipsing binary V0873 Per: a third body candidate

    NASA Astrophysics Data System (ADS)

    Bogomazov, A. I.; Ibrahimov, M. A.; Satovskii, B. L.; Kozyreva, V. S.; Irsmambetova, T. R.; Krushevska, V. N.; Kuznyetsova, Y. G.; Gaynullina, E. R.; Karimov, R. G.; Ehgamberdiev, S. A.; Tutukov, A. V.

    2016-01-01

    We analyze a set of moments of minima of eclipsing variable V0873 Per. V0873 Per is a short-period low-mass binary star. Data about moments of minima of V0873 Per were taken from the literature and our observations during 2013-2014. Our aim is to test the system on existence of new bodies using timing of minima of eclipses. We found a periodic variation of orbital period of V0873 Per. This variation can be explained by the gravitational influence of a third companion on the central binary star. The mass of the third body candidate is ≈ 0.2 M_{⊙}, and its orbital period is ≈300 days. The paper also includes a table with moments of minima calculated from our observations, which can be used in future investigations of V0873 Per.

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

    SciTech Connect

    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.

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

    DOEpatents

    Kaduchak, Gregory; Ward, Michael D.

    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

    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.

  6. Extreme value statistics of 2D Gaussian free field: effect of finite domains

    NASA Astrophysics Data System (ADS)

    Cao, X.; Rosso, A.; Santachiara, R.

    2016-01-01

    We study minima statistics of the 2D Gaussian free field (GFF) on circles in the unit disk with Dirichlet boundary condition. Free energy distributions of the associated random energy models are exactly calculated in the high temperature phase, and shown to satisfy the duality property, which enables us to predict the minima distribution by assuming the freezing scenario. Numerical tests are provided. Related questions concerning the GFF on a sphere are also considered.

  7. 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.

  8. Screw dislocation-induced growth spirals as emissive exciton localization centers in Al-rich AlGaN/AlN quantum wells

    NASA Astrophysics Data System (ADS)

    Funato, Mitsuru; Banal, Ryan G.; Kawakami, Yoichi

    2015-11-01

    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.

  9. Optical fiber diameter measurement by the diffraction method with digital processing of the light scattering indicatrix

    NASA Astrophysics Data System (ADS)

    Kokodii, N. G.; Natarova, A. O.

    2016-07-01

    Relations between the position of the first diffraction minima and the fiber diameter are derived based on the solution of the problem of electromagnetic wave diffraction on a transparent fiber with a circular cross section. The obtained formulas are used to measure the fiber diameter. The diffraction pattern is recorded with a digital camera. The obtained image is digitally processed to determine the positions of the first two scattering indicatrix minima.

  10. 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.

  11. Vacuum selection on axionic landscapes

    NASA Astrophysics Data System (ADS)

    Wang, Gaoyuan; Battefeld, Thorsten

    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.

  12. 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. PMID:26536353

  13. Hydrocarbon adsorption in an aqueous environment: A computational study of alkyls on Cu(111).

    PubMed

    Montemore, Matthew M; Andreussi, Oliviero; Medlin, J Will

    2016-08-21

    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. PMID:27544118

  14. Molecular phylogeny of the forensically important genus Cochliomyia (Diptera: Calliphoridae).

    PubMed

    Yusseff-Vanegas, Sohath; Agnarsson, Ingi

    2016-01-01

    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

  15. 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

  16. 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.

  17. Random versus Deterministic Descent in RNA Energy Landscape Analysis

    PubMed Central

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

    2016-01-01

    Identifying sets of metastable conformations is a major research topic in RNA energy landscape analysis, and recently several methods have been proposed for finding local minima in landscapes spawned by RNA secondary structures. An important and time-critical component of such methods is steepest, or gradient, descent in attraction basins of local minima. We analyse the speed-up achievable by randomised descent in attraction basins in the context of large sample sets where the size has an order of magnitude in the region of ~106. While the gain for each individual sample might be marginal, the overall run-time improvement can be significant. Moreover, for the two nongradient methods we analysed for partial energy landscapes induced by ten different RNA sequences, we obtained that the number of observed local minima is on average larger by 7.3% and 3.5%, respectively. The run-time improvement is approximately 16.6% and 6.8% on average over the ten partial energy landscapes. For the large sample size we selected for descent procedures, the coverage of local minima is very high up to energy values of the region where the samples were randomly selected from the partial energy landscapes; that is, the difference to the total set of local minima is mainly due to the upper area of the energy landscapes. PMID:27110241

  18. 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".

  19. Heteroaggregation of microparticles with nanoparticles changes the chemical reversibility of the microparticles' attachment to planar surfaces.

    PubMed

    Shen, Chongyang; Wu, Lei; Zhang, Shiwen; Ye, Huichun; Li, Baoguo; Huang, Yuanfang

    2014-05-01

    This study theoretically investigated detachment of homoaggregates and heteroaggregates attached on the planar surfaces at primary minima during transients in solution chemistry. 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 in 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., ⩽0.01M), indicating that the heteroaggregates experience repulsive forces at all separation distances. Therefore, attachment of the heteroaggregates at primary minima can be detached upon reduction in 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 in ionic strength, which challenges the common belief that attachment/aggregation of particles in primary minima is chemically irreversible. PMID:24594038

  20. 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.

  1. Time-resolved photoluminescence and excited state structure of Bi3+ center in YAlO3

    NASA Astrophysics Data System (ADS)

    Krasnikov, A.; Lipińska, L.; Mihokova, E.; Nikl, M.; Shalapska, T.; Suchocki, A.; Zazubovich, S.; Zhydachevskii, Ya.

    2014-08-01

    YAlO3:Bi ceramics prepared from the nanopowders synthesized by the sol-gel (Pechini) method are studied at 8-400 K by the time-resolved spectroscopy methods. An intense dominant ultraviolet luminescence of YAlO3:Bi is shown to arise from the radiative decay of the metastable and radiative minima of the triplet relaxed excited state (RES) of Bi3+ centers related to the 3P0, 3P1 levels of a free Bi3+ ion, respectively. At T < 80 K, the radiative transitions from the metastable minima take place. Thermally stimulated nonradiative transitions between the metastable and radiative minima of the triplet RES appear at T > 80 K in the temperature dependences of the emission spectrum and decay kinetics. From these dependences, the energy separation between the radiative and metastable minima, and the rates of the radiative and nonradiative transitions from these minima, are determined. The excitation bands of the ultraviolet emission, located at 4.425, around 5.6 eV and at the energy higher than 6 eV, are ascribed to the 1S0 → 3P1, 1S0 → 3P2, and 1S0 → 1P1 transitions of a free Bi3+ ion, respectively.

  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. 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

  4. Tight-binding approach to overdamped Brownian motion on a bichromatic periodic potential.

    PubMed

    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. PMID:26986305

  5. Flowing crystals: nonequilibrium structure of foam.

    PubMed

    Garstecki, Piotr; Whitesides, George M

    2006-07-14

    Bubbles pushed through a quasi-two-dimensional channel self-organize into a variety of periodic lattices. The structures of these lattices correspond to local minima of the interfacial energy. The "flowing crystals" are long-lived metastable states, a small subset of possible local minima of confined quasi-two-dimensional foams [P. Garstecki and G. M. Whitesides, Phys. Rev. E 73, 031603 (2006)10.1103/PhysRevE.73.031603]. Experimental results suggest that the choice of the structures that we observe is dictated by the dynamic stability of the cyclic processes of their formation. Thus, the dynamic system that we report provides a unique example of nonequilibrium self-organization that results in structures that correspond to local minima of the relevant energy functional. PMID:16907453

  6. Free energy surfaces from an extended harmonic superposition approach and kinetics for alanine dipeptide

    NASA Astrophysics Data System (ADS)

    Strodel, Birgit; Wales, David J.

    2008-12-01

    Approximate free energy surfaces and transition rates are presented for alanine dipeptide for a variety of force fields and implicit solvent models. Our calculations are based upon local minima, transition states and pathways characterised for each potential energy surface using geometry optimisation. The superposition approach employing only local minima and harmonic densities of states provides a representation of low-lying regions of the free energy surfaces. However, including contributions from the transition states of the potential energy surface and selected points obtained from displacements along the corresponding reaction vectors produces surfaces that compare quite well with results from replica exchange molecular dynamics. Characterising the local minima, transition states, normal modes, pathways, rate constants and free energy surfaces for each force field within this framework typically requires between one and five minutes cpu time on a single processor.

  7. 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.

  8. Registration of range data using a hybrid simulated annealing and iterative closest point algorithm

    SciTech Connect

    LUCK,JASON; LITTLE,CHARLES Q.; HOFF,WILLIAM

    2000-04-17

    The need to register data is abundant in applications such as: world modeling, part inspection and manufacturing, object recognition, pose estimation, robotic navigation, and reverse engineering. Registration occurs by aligning the regions that are common to multiple images. The largest difficulty in performing this registration is dealing with outliers and local minima while remaining efficient. A commonly used technique, iterative closest point, is efficient but is unable to deal with outliers or avoid local minima. Another commonly used optimization algorithm, simulated annealing, is effective at dealing with local minima but is very slow. Therefore, the algorithm developed in this paper is a hybrid algorithm that combines the speed of iterative closest point with the robustness of simulated annealing. Additionally, a robust error function is incorporated to deal with outliers. This algorithm is incorporated into a complete modeling system that inputs two sets of range data, registers the sets, and outputs a composite model.

  9. Supermodulation of the Sun's magnetic activity: the effects of symmetry changes

    NASA Astrophysics Data System (ADS)

    Weiss, N. O.; Tobias, S. M.

    2016-03-01

    In this paper, we argue that the solar activity record, as revealed by telescopic observations and proxy data from the abundances of cosmogenic isotopes, is consistent with the action of a deterministic non-linear chaotic dynamo. In particular, we claim that the long time-scale `supermodulation' apparent in the isotopic record can be ascribed to switching of the dynamo between two different modulational patterns. The first (which is currently in operation) involves deep grand minima and occasional changes in symmetry triggered by these minima. The second, which exhibits only weak modulation and no grand minima, arises as a consequence of symmetry breaking. These processes are demonstrated for highly idealized simple models of the non-linear dynamo equations.

  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.