Polycyclic aromatic hydrocarbons (PAHs) in the water column and sediment core of Deep Bay, South China

NASA Astrophysics Data System (ADS)

Qiu, Yao-Wen; Zhang, Gan; Liu, Guo-Qing; Guo, Ling-Li; Li, Xiang-Dong; Wai, Onyx

2009-06-01

The levels of 15 polycyclic aromatic hydrocarbons (PAHs) were determined in seawater, suspended particulate matter (SPM), surface sediment and core sediment samples of Deep Bay, South China. The average concentrations Σ 15PAHs were 69.4 ± 24.7 ng l -1 in seawater, 429.1 ± 231.8 ng g -1 in SPM, and 353.8 ± 128.1 ng g -1 dry weight in surface sediment, respectively. Higher PAH concentrations were observed in SPM than in surface sediment. Temporal trend of PAH concentrations in core sediment generally increased from 1948 to 2004, with higher concentrations in top than in sub-surface, implying a stronger recent input of PAHs owing to the rapid economic development in Shenzhen. Compared with historical data, the PAH levels in surface sediment has increased, and this was further confirmed by the increasing trend of PAHs in the core sediment. Phenanthrene, fluoranthene and pyrene dominated in the PAH composition pattern profiles in the Bay. Compositional pattern analysis suggested that PAHs in the Deep Bay were derived from both pyrogenic and petrogenic sources, and diesel oil leakage, river runoff and air deposition may serve as important pathways for PAHs input to the Bay. Significant positive correlations between partition coefficient in surface sediment to that in water ( KOC) of PAH and their octanol/water partition coefficients ( KOW) were observed, suggesting that KOC of PAHs in sediment/water of Deep Bay may be predicted by the corresponding KOW.

Surface hydration amplifies single-well protein atom diffusion propagating into the macromolecular core

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

Hong, Liang; Cheng, Xiaolin; Glass, Dennis C.

2012-06-05

The effect of surface hydration water on internal protein motion is of fundamental interest in molecular biophysics. Here, by decomposing the picosecond to nanosecond atomic motion in molecular dynamics simulations of lysozyme at different hydration levels into three components localized single-well diffusion, methyl group rotation, and nonmethyl jumps we show that the effect of surface hydration is mainly to increase the volume of the localized single-well diffusion. As a result, these diffusive motions are coupled in such a way that the hydration effect propagates from the protein surface into the dry core.

High resolution photoemission investigation: The oxidation of W

NASA Astrophysics Data System (ADS)

Morar, J. F.; Himpsel, F. J.; Hughes, G. J.; Jordan, J. L.; McFeely, F. R.; Hollinge, G.

High resolution photoemission measurements of surface oxide layers on tungsten has revealed a set of well resolved core level shifts characteristic of individual metal oxidation states. Measurement and analysis of this type of data can provide specific and quantitative chemical information about surface oxides. The formation of bonds between transition metals and strongly electronegative elements such as oxygen and fluorine results in charge transfer with the effect of shifting the metal core electron binding energies. The magnitude of such shifts depends primarily on two factors; the amount of charge transfer and the screening ability of the metals electrons. The size of core-level shifts tend to increase with additional charge transfer and be decreased by screening. In the case of tungsten the amount of screening should be a function of oxygen content since the oxygen ties up free electrons which are effective at screening. A continuous change in the tungsten core level shifts is observed with increasing oxygen content, i.e., as the screening changes from that characteristic of a metal screened to that characteristic of an insulator unscreened.

Deep Coherent Vortices and Their Sea Surface Expressions

NASA Astrophysics Data System (ADS)

Ienna, Federico; Bashmachnikov, Igor; Dias, Joaquim; Peliz, Alvaro

2017-04-01

Mediterranean Water eddies, known as Meddies, are an important dynamic process occurring at depths of 1000-meters in the Northeast Atlantic Ocean. Meddies occur as a direct result of the Mediterranean Outflow exiting through the Gibraltar Strait, and represent a prevalent mechanism that can be found extensively throughout the ocean. Moreover, Meddy cores are known to produce measurable expressions at the sea surface in the form of rotating coherent vortices, not only affecting the sea surface from beneath, but also allowing for the possibility to remotely study these deep phenomena through data gathered at the sea surface. While many past studies have focused on the properties of Meddy cores, only a handful of studies focus on the physical characteristics and behavior of the surface expressions produced. Are Meddy surface expressions different from other like vortices that dominate the physical ocean surface? What are the relationships between deep and surface mechanisms, and do any feedbacks exist? To shed light on these questions, we investigate the relationship between Meddies and their sea-surface expressions through observations using in-situ float and drifter profiles and satellite altimetry. A total of 782 Meddy cores were examined in the Northeast Atlantic using temperature and salinity data obtained by CTD and Argo during the Mecanismos de transporte e de dispersão da Água Mediterrânica no Atlântico Nordeste (MEDTRANS) project, and their corresponding sea-level expressions were geo-temporally matched in satellite altimetry data. We report several statistical properties of the sea-surface expressions of Meddies, including their mean diameter and vertical magnitude, and compare the properties of their surface features to the underlying Meddy cores. We investigate how the deep core affects the surface, and whether surface expressions may in return yield information about the underlying cores. Additionally, we examine the variability of the surface expressions, including seasonal and geographical variability.

Ice Core Records of West Greenland Melt and Climate Forcing

NASA Astrophysics Data System (ADS)

Graeter, K. A.; Osterberg, E. C.; Ferris, D. G.; Hawley, R. L.; Marshall, H. P.; Lewis, G.; Meehan, T.; McCarthy, F.; Overly, T.; Birkel, S. D.

2018-04-01

Remote sensing observations and climate models indicate that the Greenland Ice Sheet (GrIS) has been losing mass since the late 1990s, mostly due to enhanced surface melting from rising summer temperatures. However, in situ observational records of GrIS melt rates over recent decades are rare. Here we develop a record of frozen meltwater in the west GrIS percolation zone preserved in seven firn cores. Quantifying ice layer distribution as a melt feature percentage (MFP), we find significant increases in MFP in the southernmost five cores over the past 50 years to unprecedented modern levels (since 1550 CE). Annual to decadal changes in summer temperatures and MFP are closely tied to changes in Greenland summer blocking activity and North Atlantic sea surface temperatures since 1870. However, summer warming of 1.2°C since 1870-1900, in addition to warming attributable to recent sea surface temperature and blocking variability, is a critical driver of high modern MFP levels.

Gamma thermometer based reactor core liquid level detector

DOEpatents

Burns, Thomas J.

1983-01-01

A system is provided which employs a modified gamma thermometer for determining the liquid coolant level within a nuclear reactor core. The gamma thermometer which normally is employed to monitor local core heat generation rate (reactor power), is modified by thermocouple junctions and leads to obtain an unambiguous indication of the presence or absence of coolant liquid at the gamma thermometer location. A signal processor generates a signal based on the thermometer surface heat transfer coefficient by comparing the signals from the thermocouples at the thermometer location. The generated signal is a direct indication of loss of coolant due to the change in surface heat transfer when coolant liquid drops below the thermometer location. The loss of coolant indication is independent of reactor power at the thermometer location. Further, the same thermometer may still be used for the normal power monitoring function.

Formation of an Anti-Core–Shell Structure in Layered Oxide Cathodes for Li-Ion Batteries

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

Zhang, Hanlei; Omenya, Fredrick; Whittingham, M. Stanley

The layered → rock-salt phase transformation in the layered dioxide cathodes for Li-ion batteries is believed to result in a “core-shell” structure of the primary particles, in which the core region maintains as the layered phase while the surface region undergoes the phase transformation to the rock-salt phase. Using transmission electron microscopy, here we demonstrate the formation of an “anti-core-shell” structure in cycled primary particles with a formula of LiNi0.80Co0.15Al0.05O2, in which the surface and subsurface regions remain as the layered structure while the rock-salt phase forms as domains in the bulk with a thin layer of the spinel phasemore » between the rock-salt core and the skin of the layered phase. Formation of this anti-core-shell structure is attributed to the oxygen loss at the surface that drives the migration of oxygen from the bulk to the surface, thereby resulting in localized areas of significantly reduced oxygen levels in the bulk of the particle, which subsequently undergoes the phase transformation to the rock-salt domains. The formation of the anti-core-shell rock-salt domains is responsible for the reduced capacity, discharge voltage and ionic conductivity in cycled cathode.« less

Oxidation and thermal reduction of the Cu(1 0 0) surface as studied using positron annihilation induced Auger electron spectroscopy (PAES)

NASA Astrophysics Data System (ADS)

Fazleev, N. G.; Nadesalingam, M. P.; Maddox, W.; Mukherjee, S.; Rajeshwar, K.; Weiss, A. H.

2010-01-01

Changes in the surface of an oxidized Cu(1 0 0) single crystal resulting from vacuum annealing have been investigated using positron annihilation induced Auger electron spectroscopy (PAES). PAES measurements show a large increase in the intensity of the annihilation induced Cu M 2,3VV Auger peak as the sample is subjected to a series of isochronal anneals in vacuum up to annealing temperature 300 °C. The intensity then decreases monotonically as the annealing temperature is increased to ˜600 °C. Experimental probabilities of annihilation of surface-trapped positrons with Cu 3p and O 1s core-level electrons are estimated from the measured intensities of the positron annihilation induced Cu M 2,3VV and O KLL Auger transitions. Experimental PAES results are analyzed by performing calculations of positron surface states and annihilation probabilities of surface-trapped positrons with relevant core electrons taking into account the charge redistribution at the surface, surface reconstructions, and electron-positron correlations effects. The effects of oxygen adsorption on localization of positron surface state wave function and annihilation characteristics are also analyzed. Possible explanation is proposed for the observed behavior of the intensity of positron annihilation induced Cu M 2,3VV and O KLL Auger peaks and probabilities of annihilation of surface-trapped positrons with Cu 3p and O 1s core-level electrons with changes of the annealing temperature.

A Chemical View on X-ray Photoelectron Spectroscopy: the ESCA Molecule and Surface-to-Bulk XPS Shifts.

PubMed

Delesma, Francisco A; Van den Bossche, Maxime; Grönbeck, Henrik; Calaminici, Patrizia; Köster, Andreas M; Pettersson, Lars G M

2018-01-19

In this paper we remind the reader of a simple, intuitive picture of chemical shifts in X-ray photoelectron spectroscopy (XPS) as the difference in chemical bonding between the probed atom and its neighbor to the right in the periodic table, the so called Z+1 approximation. We use the classical ESCA molecule, ethyl trifluoroacetate, and 4d-transition metals to explicitly demonstrate agreement between core-level shifts computed as differences between final core-hole states and the approach where each core-ionized atom is replaced by a Z+1 atom. In this final state, or total energy picture, the XPS shift arises due to the more or less unfavorable chemical bonding of the effective nitrogen in the carbon geometry for the ESCA molecule. Surface core level shifts in metals are determined by whether the Z+1 atom as an alloy segregates to the surface or is more soluble in the bulk. As further illustration of this more chemical picture, we compare the geometry of C 1s and O 1s core-ionized CO with that of, respectively, NO + and CF + . The scope is not to propose a new method to compute XPS shifts but rather to stress the validity of this simple interpretation. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Exploring the core level shift origin of sulfur and thiolates on Pd(111) surfaces.

PubMed

Salvarezza, Roberto Carlos; Carro, Pilar

2015-10-07

Thiol molecules on planar metal surfaces are widely used for building sensing and electronic devices and also as capping agents to protect and to control the size and shape of nanoparticles. In the case of Pd the thiol molecules exhibit a complex behavior because C-S bond scission is possible, resulting in a significant amount of co-adsorbed S. Therefore identification of these species on Pd is a key point for many applications, a task that is usually achieved by XPS. Here we show, from DFT calculations, that the core level shift (CLS) of the S 2p binding energy (BE) of thiol and sulfur on different thiol-Pd(111) surface models strongly depends on the adsorbed or subsurface state of sulfur atoms. Our results reflect the complexity of S 2p BE behavior and contribute to understanding and reanalyzing the experimental data of thiolated Pd surfaces.

Direct work function measurement by gas phase photoelectron spectroscopy and its application on PbS nanoparticles.

PubMed

Axnanda, Stephanus; Scheele, Marcus; Crumlin, Ethan; Mao, Baohua; Chang, Rui; Rani, Sana; Faiz, Mohamed; Wang, Suidong; Alivisatos, A Paul; Liu, Zhi

2013-01-01

Work function is a fundamental property of a material's surface. It is playing an ever more important role in engineering new energy materials and efficient energy devices, especially in the field of photovoltaic devices, catalysis, semiconductor heterojunctions, nanotechnology, and electrochemistry. Using ambient pressure X-ray photoelectron spectroscopy (APXPS), we have measured the binding energies of core level photoelectrons of Ar gas in the vicinity of several reference materials with known work functions (Au(111), Pt(111), graphite) and PbS nanoparticles. We demonstrate an unambiguously negative correlation between the work functions of reference samples and the binding energies of Ar 2p core level photoelectrons detected from the Ar gas near the sample surface region. Using this experimentally determined linear relationship between the surface work function and Ar gas core level photoelectron binding energy, we can measure the surface work function of different materials under different gas environments. To demonstrate the potential applications of this ambient pressure XPS technique in nanotechnology and solar energy research, we investigate the work functions of PbS nanoparticles with various capping ligands: methoxide, mercaptopropionic acid, and ethanedithiol. Significant Fermi level position changes are observed for PbS nanoparticles when the nanoparticle size and capping ligands are varied. The corresponding changes in the valence band maximum illustrate that an efficient quantum dot solar cell design has to take into account the electrochemical effect of the capping ligand as well.

Positron probes of the Ge(1 0 0) surface: The effects of surface reconstructions and electron positron correlations on positron trapping and annihilation characteristics

NASA Astrophysics Data System (ADS)

Fazleev, N. G.; Jung, E.; Weiss, A. H.

2007-08-01

Positron annihilation induced Auger electron spectroscopy (PAES) has been applied to study the Ge(1 0 0) surface. The high-resolution PAES spectrum from the Ge(1 0 0) surface displays several strong Auger peaks corresponding to M4,5N1N2,3, M2,3M4,5M4,5, M2,3M4,5V and M1M4,5M4,5 Auger transitions. The integrated peak intensities of Auger transitions are used to obtain experimental annihilation probabilities for the Ge 3d and 3p core level electrons. These experimental results are analyzed by performing calculations of positron surface states and annihilation characteristics of surface trapped positrons with relevant Ge core-level electrons for the non-reconstructed and reconstructed Ge(1 0 0)-p(2 × 1), Ge(1 0 0)-p(2 × 2) and Ge(1 0 0)-c(4 × 2) surfaces. It is found that the positron surface state wave function extends into the Ge lattice in the regions where atoms are displaced from their ideal terminated positions due to reconstructions. Estimates of the positron binding energy and the positron annihilation characteristics reveal their sensitivity to the specific atomic structure of the topmost layers of Ge(1 0 0). A comparison with PAES data reveals an agreement with theoretical core annihilation probabilities for the Auger transitions considered.

Salt influence on surface microorganisms and ripening of soft ewe cheese.

PubMed

Tabla, Rafael; Gómez, Antonia; Rebollo, José E; Roa, Isidro

2015-05-01

The effect of different brining treatments on salt uptake and diffusion during the first 30 d of ripening was determined in soft ewe cheese. Additionally, salt influence on surface microorganisms and physicochemical parameters was evaluated. Cheeses were placed into different brine solutions (14, 18 and 24°Bé) at 5 and 10 °C for 1, 2 or 3 h. Samples from rind, outer core and inner core were analysed at 0, 7, 15 and 30 d. Complete salt diffusion from rind to the inner core took about 15 d. The resulting salt gradient favoured the development of a pH gradient from the surface to the inner core. Salt concentration also had a significant effect on the growth of surface microorganisms (mesophiles, pseudomonads and halotolerants). However, mould and yeasts were not affected throughout ripening by the salt levels achieved. Brine salting by immersion for 3 h at 10 °C in 24°B brine was found to be the most suitable treatment to control pseudomonads in cheese rind, as spoilage microorganism.

Core stability training: applications to sports conditioning programs.

PubMed

Willardson, Jeffrey M

2007-08-01

In recent years, fitness practitioners have increasingly recommended core stability exercises in sports conditioning programs. Greater core stability may benefit sports performance by providing a foundation for greater force production in the upper and lower extremities. Traditional resistance exercises have been modified to emphasize core stability. Such modifications have included performing exercises on unstable rather than stable surfaces, performing exercises while standing rather than seated, performing exercises with free weights rather than machines, and performing exercises unilaterally rather than bilaterally. Despite the popularity of core stability training, relatively little scientific research has been conducted to demonstrate the benefits for healthy athletes. Therefore, the purpose of this review was to critically examine core stability training and other issues related to this topic to determine useful applications for sports conditioning programs. Based on the current literature, prescription of core stability exercises should vary based on the phase of training and the health status of the athlete. During preseason and in-season mesocycles, free weight exercises performed while standing on a stable surface are recommended for increases in core strength and power. Free weight exercises performed in this manner are specific to the core stability requirements of sports-related skills due to moderate levels of instability and high levels of force production. Conversely, during postseason and off-season mesocycles, Swiss ball exercises involving isometric muscle actions, small loads, and long tension times are recommended for increases in core endurance. Furthermore, balance board and stability disc exercises, performed in conjunction with plyometric exercises, are recommended to improve proprioceptive and reactive capabilities, which may reduce the likelihood of lower extremity injuries.

Historic CH4 Records from Antarctic and Greenland Ice Cores, Antarctic Firn Data, and Archived Air Samples from Cape Grim, Tasmania

DOE Data Explorer

Etheridge, D. M. [Division of Atmospheric Research, CSIRO, Aspendale, Victoria, Australia; Steele, L. P. [Division of Atmospheric Research, CSIRO, Aspendale, Victoria, Australia; Francey, R. J. [Division of Atmospheric Research, CSIRO, Aspendale, Victoria, Australia; Langenfelds, R. L. [Division of Atmospheric Research, CSIRO, Aspendale, Victoria, Australia

2002-01-01

The Antarctic CH4 records presented here are derived from three ice cores obtained at Law Dome, East Antarctica (66°44'S, 112°50'E, 1390 meters above mean sea level). Law Dome has many qualities of an ideal ice core site for the reconstruction of past concentrations of atmospheric gases; these qualities include: negligible melting of the ice sheet surface, low concentrations of impurities, regular stratigraphic layering undisturbed by wind stress at the surface or differential ice flow at depth, and a high snow accumulation rate. Further details on the site, drilling, and cores are provided by Etheridge et al. (1998), Etheridge et al. (1996), Etheridge and Wookey (1989), and Morgan et al. (1997). The two Greenland ice cores are from the Summit region (72°34' N, 37°37' W, 3200 meters above mean sea level). Lower snow accumulation rate there results in lower air-age resolution, and measurements presented here cover only the pre-industrial period (until 1885). More details about these measurements are presented in Etheridge et al. (1998). Additionally, this site contains firn data from Core DE08-2, and archived air samples from Cape Grim, Tasmania, for comparison.

Evaporation from a sphagnum moss surface

Treesearch

D.S. Nichols; J.M. Brown

1980-01-01

Peat cores, 45 cm in diameter, were collected from a sphagnum bog in northern Minnesota, and used to measure the effects of different temperatures and water levels on evaporation from a sphagnum moss surface in a growth chamber. Under all conditions, evaporation from the moss surface was greater than that from a free-water surface. Evaporation from the moss increased...

Landslide investigations, southern Cianjur Regency, West Java Province, Indonesia; a progress report

USGS Publications Warehouse

Ege, John R.

1983-01-01

Two landslide-monitoring sites have been established for a minimum 2-year investigation near the villages of Pasirpari and Cibacang in southern Cianjur Regency, West Java, Indonesia. Surveyed-in lines will measure amounts of surface movement and tilt, borings that produced exploratory cores now serve as slip-surface detectors and open-pipe piezometers, and rain gages will record rainfall at both sites. Exploratory cores and field observations located upper slip surfaces ranging in depth between 4 and 14 m. Rises of borehole-water levels of as much as 63 cm during drilling suggest that pore pressures exist at the inferred-slip surfaces. Sliding along slip surfaces and slope failures occurred during the rainy season between November 1980 and April 1981.

Newly designed silver coated-magnetic, monodisperse polymeric microbeads as SERS substrate for low-level detection of amoxicillin

NASA Astrophysics Data System (ADS)

Kibar, Güneş; Topal, Ahmet Emin; Dana, Aykutlu; Tuncel, Ali

2016-09-01

We report the preparation of silver-coated magnetic polymethacrylate core-shell nanoparticles for use in surface-enhanced Raman scattering based drug detection. Monodisperse porous poly (mono-2-(methacryloyloxy)ethyl succinate-co-glycerol dimethacrylate), poly (MMES-co-GDMA) microbeads of ca. 5 μm diameter were first synthesized through a multistage microsuspension polymerization technique to serve as a carboxyl-bearing core region. Microspheres were subsequently magnetized by the co-precipitation of ferric ions, aminated through the surface hydroxyl groups and decorated with Au nanoparticles via electrostatic attraction. An Ag shell was then formed on top of the Au layer through a seed-mediated growth process, resulting in micron-sized monodisperse microbeads that exhibit Raman enhancement effects due to the roughness of the Ag surface layer. The core-shell microspheres were used as a new substrate for the detection of amoxicillin at trace concentrations up to 10-8 M by SERS. The proposed SERS platform can be evaluated as a useful tool for the follow-up amoxicillin pollution and low-level detection of amoxicillin in aqueous media.

Structural and electronic properties of CdS/ZnS core/shell nanowires: A first-principles study

NASA Astrophysics Data System (ADS)

Kim, Hyo Seok; Kim, Yong-Hoon

2015-03-01

Carrying out density functional theory (DFT) calculation, we studied the relative effects of quantum confinement and strain on the electronic structures of II-IV semiconductor compounds with a large lattice-mismatch, CdS and ZnS, in the core/shell nanowire geometry. We considered different core radii and shell thickness of the CdS/ZnS core/shell nanowire, different surface facets, and various defects in the core/shell interface and surface regions. To properly describe the band level alignment at the core/shell boundary, we adopted the self-interaction correction (SIC)-DFT scheme. Implications of our findings in the context of device applications will be also discussed. This work was supported by the Basic Science Research Grant (No. 2012R1A1A2044793), Global Frontier Program (No. 2013-073298), and Nano-Material Technology Development Program (2012M3A7B4049888) of the National Research Foundation funded by the Ministry of Education, Science and Technology of Korea. Corresponding author

Hawaiian lava flows in the third dimension: Identification and interpretation of pahoehoe and 'a'a distribution in the KP-1 and SOH-4 cores

NASA Astrophysics Data System (ADS)

Katz, Melissa G.; Cashman, Katharine V.

2003-02-01

Hawaiian lava flows are classified as pahoehoe or 'a'a by their surface morphology. As surface morphology reflects flow emplacement conditions, the surface distribution of morphologic flow types has been used to study the evolution and eruptive history of basaltic volcanoes. We extend this analysis to the third dimension by determining the distribution of flow types in two deep drill cores, the Scientific Observation Hole-4 (SOH-4) core, drilled near Kilauea's East Rift Zone (ERZ), and the pilot hole (Kahi Puka-1 (KP-1)) for the Hawaiian Scientific Drilling Project (HSDP), drilled through distal flows from Mauna Loa and Mauna Kea. Flows are classified using both internal structures and groundmass textures, with the latter useful when identification based on mesoscopic flow features (e.g., surface morphology and vesicle content and distribution) is ambiguous. We then examine the temporal distribution of pahoehoe and 'a'a flows in proximal (SOH-4) and distal (KP-1) settings. Sequence analysis shows that the two flow types are not randomly distributed in either core but instead are strongly clustered. The proximal SOH-4 core is dominated by thin pahoehoe flows (˜60% by volume), consistent with the common occurrence of surface-fed pahoehoe flows in near-vent settings. The distal KP-1 core has a high proportion of 'a'a (˜58% by volume), although the proportion of pahoehoe and 'a'a varies dramatically throughout the Mauna Kea sequence. Thick inflated pahoehoe flows dominate when the drill site was near sea level, consistent with the numerous inflated pahoehoe fields on the current coastal plains of Kilauea and Mauna Loa. 'A'a flows are abundant when the site was far above sea level. As slope increases from the coastal plains to Mauna Kea's flank, this correlation may reflect the combined effect of long transport distances and increased slopes on flow emplacement. These results demonstrate that flow type and thickness variations in cores provide valuable information about both vent location and local site environment. Observed variations in flow type within the KP-1 core raise interesting questions about feedback between volcano evolution and flow morphology and suggest that flow type is an important variable in models of volcano growth and related models for lava flow hazard assessment.

Shiga toxin-producing Escherichia coli in meat: a preliminary simulation study on detection capabilities for three sampling methods

USDA-ARS?s Scientific Manuscript database

The objective of this simulation study is to determine which sampling method (Cozzini core sampler, core drill shaving, and N-60 surface excision) will better detect Shiga Toxin-producing Escherichia coli (STEC) at varying levels of contamination when present in the meat. 1000 simulated experiments...

Impacts of pollution derived from ship wrecks on the marine environment on the basis of s/s "Stuttgart" (Polish coast, Europe).

PubMed

Rogowska, Justyna; Wolska, Lidia; Namieśnik, Jacek

2010-11-01

In 1943 the German hospital ship s/s Stuttgart (Lazaretschiff "C") was sunk close to the port of Gdynia (Gulf of Gdańsk - Polish coast). This and other actions (undertaken after the war to remove the wreck) led to pollution of the sea bottom with oil derivatives. During our studies (2009) 11 surface sediment and water samples were collected as well as sediment core samples at 4 locations in order to determine the concentration levels of priority pollutants belonging to polycyclic aromatic hydrocarbons (PAH) and polychlorinated biphenyls (PCB). The concentrations of 16 PAH and 7 PCB were analysed with GC-MS. ΣPAH varied between 11.54 ± 0.39 and 206.7 ± 6.5mg/kg dry weight in the surface sediments, and from 0.686 ± 0.026 to 1291 ± 53 mg/kg dry weight in the core samples. Contamination in the core samples collected may reach a depth of at least 230-240 cm (deepest sample studied). The PAH-group profiles in all surface sediment samples suggest a pyrolytic source of PAH, while the results obtained for core samples indicate a mixed pattern of pyrolytic and petrogenic inputs of PAH. Results obtained may suggest also that fuel residues being present at sea bottom is not crude oil derived but results from coal processing (synthetic fuel). The sum of PCB in surface sediments ranged from 0.761 ± 0.068 to 6.82 ± 0.28 μg/kg dry weight (except for sampling point W2, where ΣPCB was 108.8 ± 4.4 μg/kg dry weight). The strong correlation between PAH and PCB levels, and the fact that PCB are present only in the surface sediments, suggest that the compounds in these sediments got there as a result of emission from urban areas, entering the aquatic environment via atmospheric deposition. PCB levels in the sediment core samples were generally very low and in most cases did not exceed the method quantification limit. Copyright © 2010 Elsevier B.V. All rights reserved.

Occurrence, compositional distribution, and toxicity assessment of pyrethroid insecticides in sediments from the fluvial systems of Chaohu Lake, Eastern China.

PubMed

Wang, Ji-Zhong; Bai, Ya-Shu; Wu, Yakton; Zhang, Shuo; Chen, Tian-Hu; Peng, Shu-Chuan; Xie, Yu-Wei; Zhang, Xiao-Wei

2016-06-01

Surface sediment-associated synthetic pyrethroid insecticides (SPs) are known to pose high risks to the benthic organisms in Chaohu Lake, a shallow lake of Eastern China. However, the pollution status of the lake's tributaries and estuaries is still unknown. The present study was conducted to investigate the occurrence, compositional distribution, and toxicity of 12 currently used SPs in the surface sediments from four important tributaries, as well as in the sediment cores at their estuaries, using GC-MS for quantification. All SPs selected were detectable, with cypermethrin, es/fenvalerate, and permethrin dominant in both surface and core sediments, suggesting that these compounds were extensively applied. Urban samples contained the highest summed concentrations of the 12 SPs analyzed (Σ12SP) in both surface and core sediments compared with rural samples, suggesting that urban areas near aquatic environments posed high risks for SPs. The mean concentration of Σ12SP in surface sediments of each river was generally higher than that found in core sediments from its corresponding estuary, perhaps implying recent increases in SP usage. Surface sediments were significantly dominated by cypermethrin and permethrin, whereas core sediments were dominated by permethrin and es/fenvalerate. The compositional distributions demonstrated a spatial variation for surface sediments because urban sediments generally contained greater percentages of permethrin and cypermethrin, but rural sediments had significant levels of es/fenvalerate and cypermethrin. In all sediment cores, the percentage of permethrin gradually increased, whereas es/fenvalerate tended to decrease, from the bottom sediments to the top, indicating that the former represented fresh input, whereas the latter represented historical residue. Most urban samples would be expected to be highly toxic to benthic organisms due to the residue of SPs based on a calculation of toxic units (TUs) using toxicity data of the amphipod Hyalella azteca. However, low TU values were found for the samples from rural areas. These results indicate that the bottom sediments were exposed to high risk largely by the residual SPs from urban areas. The summed TUs were mostly attributable to cypermethrin, followed by λ-cyhalothrin and es/fenvalerate. Despite permethrin contributing ∼28.7 % of the Σ12SP concentration, it only represented 6.34 % of the summed TUs. Therefore, our results suggest that high levels of urbanization can increase the accumulation of SPs in aquatic environments.

Influence of light intensity on surface free energy and dentin bond strength of core build-up resins.

PubMed

Shimizu, Y; Tsujimoto, A; Furuichi, T; Suzuki, T; Tsubota, K; Miyazaki, M; Platt, J A

2015-01-01

We examined the influence of light intensity on surface free energy characteristics and dentin bond strength of dual-cure direct core build-up resin systems. Two commercially available dual-cure direct core build-up resin systems, Clearfil DC Core Automix with Clearfil Bond SE One and UniFil Core EM with Self-Etching Bond, were studied. Bovine mandibular incisors were mounted in acrylic resin and the facial dentin surfaces were wet ground on 600-grit silicon carbide paper. Adhesives were applied to dentin surfaces and cured with light intensities of 0 (no irradiation), 200, 400, and 600 mW/cm(2). The surface free energy of the adhesives (five samples per group) was determined by measuring the contact angles of three test liquids placed on the cured adhesives. To determine the strength of the dentin bond, the core build-up resin pastes were condensed into the mold on the adhesive-treated dentin surfaces according to the methods described for the surface free energy measurement. The resin pastes were cured with the same light intensities as those used for the adhesives. Ten specimens per group were stored in water maintained at 37°C for 24 hours, after which they were shear tested at a crosshead speed of 1.0 mm/minute in a universal testing machine. Two-way analysis of variance (ANOVA) and a Tukey-Kramer test were performed, with the significance level set at 0.05. The surface free energies of the adhesive-treated dentin surfaces decreased with an increase in the light intensity of the curing unit. Two-way ANOVA revealed that the type of core build-up system and the light intensity significantly influence the bond strength, although there was no significant interaction between the two factors. The highest bond strengths were achieved when the resin pastes were cured with the strongest light intensity for all the core build-up systems. When polymerized with a light intensity of 200 mW/cm(2) or less, significantly lower bond strengths were observed. CONClUSIONS: The data suggest that the dentin bond strength of core build-up systems are still affected by the light intensity of the curing unit, which is based on the surface free energy of the adhesives. On the basis of the results and limitations of the test conditions used in this study, it appears that a light intensity of >400 mW/cm(2) may be required for achieving the optimal dentin bond strength.

The effects of therapeutic hip exercise with abdominal core activation on recruitment of the hip muscles.

PubMed

Chan, Mandy Ky; Chow, Ka Wai; Lai, Alfred Ys; Mak, Noble Kc; Sze, Jason Ch; Tsang, Sharon Mh

2017-07-21

Core stabilization has been utilized for rehabilitation and prevention of lower limb musculoskeletal injuries. Previous studies showed that activation of the abdominal core muscles enhanced the hip muscle activity in hip extension and abduction exercises. However, the lack of the direct measurement and quantification of the activation level of the abdominal core muscles during the execution of the hip exercises affect the level of evidence to substantiate the proposed application of core exercises to promote training and rehabilitation outcome of the hip region. The aim of the present study was to examine the effects of abdominal core activation, which is monitored directly by surface electromyography (EMG), on hip muscle activation while performing different hip exercises, and to explore whether participant characteristics such as gender, physical activity level and contractile properties of muscles, which is assessed by tensiomyography (TMG), have confounding effect to the activation of hip muscles in enhanced core condition. Surface EMG of bilateral internal obliques (IO), upper gluteus maximus (UGMax), lower gluteus maximus (LGMax), gluteus medius (GMed) and biceps femoris (BF) of dominant leg was recorded in 20 young healthy subjects while performing 3 hip exercises: Clam, side-lying hip abduction (HABD), and prone hip extension (PHE) in 2 conditions: natural core activation (NC) and enhanced core activation (CO). EMG signals normalized to percentage of maximal voluntary isometric contraction (%MVIC) were compared between two core conditions with the threshold of the enhanced abdominal core condition defined as >20%MVIC of IO. Enhanced abdominal core activation has significantly promoted the activation level of GMed in all phases of clam exercise (P < 0.05), and UGMax in all phases of PHE exercise (P < 0.05), LGMax in eccentric phases of all 3 exercises (P < 0.05), and BF in all phases of all 3 exercises except the eccentric phase of PHE exercise (P < 0.05). The %MVIC of UGMax was significantly higher than that of LGMax in all phases of clam and HABD exercises under both CO and NC conditions (P < 0.001) while the %MVIC of LGMax was significantly higher than UGMax in concentric phase of PHE exercise under NC condition (P = 0.003). Gender, physical activity level and TMG parameters were not major covariates to activation of hip muscles under enhanced core condition. Abdominal core activation enhances the hip muscles recruitment in Clam, HABD and PHE exercises, and this enhancement is correlated with higher physical activity and stiffer hip muscle. Our results suggest the potential application of abdominal core activation for lower limb rehabilitation since the increased activation of target hip muscles may enhance the therapeutic effects of hip strengthening exercises.

a Photoemission Study of the Electronic Structure Induced by Potassium Adsorption on TiO2(110)

NASA Astrophysics Data System (ADS)

Heise, Rainer; Courths, Ralf

Electronic structure effects induced by potassium adsorption up to one monolayer (ML) on a nearly stoichiometric TiO2(110) surface has been studied by means of angle-resolved photoemission spectroscopy (ARUPS and ARXPS) from valence states and core levels. In agreement with the observations on K/TiO2(100) [P.J. Hardman et al., Surf. Sci. 269/270, 677 (1992)], potassium adsorption at room temperature leads—due to K-to-substrate charge transfer—to the reduction of surface Ti ions (to nominally Ti3+ ions), evidenced by lowered Ti 2p core-level binding energy (ΔBE=-1.6 eV) and occupation of Ti 3d-like band-gap states centered at 0.9 eV BE. The gap-state intensity exhibits a pronounced maximum at 0.37 ML coverage, where the work function has a weak minimum. This behavior is in agreement with a ionic-to-neutral transition of the K-substrate bonding with increasing K coverage, as suggested recently [Souda et al., Surf. Sci. 285, 265 (1993)]. Annealing of a surface precovered with 0.27 ML potassium up to 1000 K results in metallization of the surface, evidenced by (i) the occupation of a second gap-state centered at 0.4 BE and with a considerable state-density at the Fermi energy, and (ii) Ti 2p core-levels lowered by 3.2 eV in BE (nominally “Ti2+” ions). This dramatic reduction of the surface is healed out with complete desorption of potassium. A discussion in terms of desorption of KOx species and oxygen diffusion from the bulk to the surface is given.

Core-level spectra and binding energies of transition metal nitrides by non-destructive x-ray photoelectron spectroscopy through capping layers

NASA Astrophysics Data System (ADS)

Greczynski, G.; Primetzhofer, D.; Lu, J.; Hultman, L.

2017-02-01

We present the first measurements of x-ray photoelectron spectroscopy (XPS) core level binding energies (BE:s) for the widely-applicable group IVb-VIb polycrystalline transition metal nitrides (TMN's) TiN, VN, CrN, ZrN, NbN, MoN, HfN, TaN, and WN as well as AlN and SiN, which are common components in the TMN-based alloy systems. Nitride thin film samples were grown at 400 °C by reactive dc magnetron sputtering from elemental targets in Ar/N2 atmosphere. For XPS measurements, layers are either (i) Ar+ ion-etched to remove surface oxides resulting from the air exposure during sample transfer from the growth chamber into the XPS system, or (ii) in situ capped with a few nm thick Cr or W overlayers in the deposition system prior to air-exposure and loading into the XPS instrument. Film elemental composition and phase content is thoroughly characterized with time-of-flight elastic recoil detection analysis (ToF-E ERDA), Rutherford backscattering spectrometry (RBS), and x-ray diffraction. High energy resolution core level XPS spectra acquired with monochromatic Al Kα radiation on the ISO-calibrated instrument reveal that even mild etching conditions result in the formation of a nitrogen-deficient surface layer that substantially affects the extracted binding energy values. These spectra-modifying effects of Ar+ ion bombardment increase with increasing the metal atom mass due to an increasing nitrogen-to-metal sputter yield ratio. The superior quality of the XPS spectra obtained in a non-destructive way from capped TMN films is evident from that numerous metal peaks, including Ti 2p, V 2p, Zr 3d, and Hf 4f, exhibit pronounced satellite features, in agreement with previously published spectra from layers grown and analyzed in situ. In addition, the N/metal concentration ratios are found to be 25-90% higher than those obtained from the corresponding ion-etched surfaces, and in most cases agree very well with the RBS and ToF-E ERDA values. The N 1 s BE:s extracted from capped TMN films, thus characteristic of a native surface, show a systematic trend, which contrasts with the large BE spread of literature "reference" values. Hence, non-destructive core level XPS employing capping layers provides an opportunity to obtain high-quality spectra, characteristic of virgin in situ grown and analyzed TMN films, although with larger versatility, and allows for extracting core level BE values that are more reliable than those obtained from sputter-cleaned N-deficient surfaces. Results presented here, recorded from a consistent set of binary TMN's grown under the same conditions and analyzed in the same instrument, provide a useful reference for future XPS studies of multinary materials systems allowing for true deconvolution of complex core level spectra.

Photoemission studies of CdTe(100) and the Ag-CdTe(100) interface: Surface structure, growth behavior, Schottky barrier, and surface photovoltage

NASA Astrophysics Data System (ADS)

John, P.; Miller, T.; Hsieh, T. C.; Shapiro, A. P.; Wachs, A. L.; Chiang, T.-C.

1986-11-01

The clean CdTe(100) surface prepared by sputtering and annealing was studied with high-energy electron diffraction (HEED) and photoemission. HEED showed the surface to be a one-domain, (2×1) reconstruction. Photoemission spectra showed two surface-shifted components for the Cd 4d core level, with an intensity ratio of about 1:3, accounting for nearly an entire atomic layer. No surface-induced shifts for the Te 4d core level were detected. A model is proposed for the surface structure in which the surface layer is free of Te, and Cd atoms form dimers resulting in a (2×1) reconstruction; in addition, about (1/4) of the surface area is covered by excess loosely attached Cd atoms. Ag was evaporated on the surface at room temperature and found to grow three dimensionally in the [111] direction. The Ag was found to interact only weakly with the substrate, although the Cd atoms originally loosely bound on top of the surface were found to float on the evaporated Ag islands. A small coverage-dependent surface photovoltage, induced by the synchrotron radiation used for photoemission, was observed; with this effect taken into account, band bending was monitored, the final Fermi-level position being near 0.96 eV above the valence-band maximum. This corresponds to a Schottky-barrier height of about 0.60 eV for the n-type sample used in this experiment. The mechanism for generation of the surface photovoltage will be discussed.

gC1qR expression in chimpanzees with resolved and chronic infection: Potential role of HCV core/gC1qR-mediated T cell suppression in the outcome of HCV infection

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

Yao Zhiqang; Shata, Mohamed Tarek; Tricoche, Nancy

2006-03-15

Chimpanzee is a unique animal model for HCV infection, in which about 50% of infections resolve spontaneously. It has been reported that the magnitude of T cell responses to HCV core in recovered chimpanzees is greater than that in chronically infected ones. However, the mechanism(s) by which the chimpanzees with resolved infection overcome core-mediated immunosuppression remains unknown. In this study, we examined the effect of HCV core on T cell responsiveness in chimpanzees with resolved and chronic HCV infection. We found that core protein strongly inhibited T cell activation and proliferation in chimpanzees with chronic infection, while this inhibition wasmore » limited in chimpanzees with resolved infection. Notably, the level of gC1qR, as well as the binding of core protein, on the surface of T cells was lower in recovered chimpanzees when compared to chimpanzees with chronic HCV infection. Intriguingly, the observed differences in gC1qR expression levels and susceptibility to core-induced suppression amongst HCV-chronically infected and recovered chimpanzees were observed prior to HCV challenge, suggesting a possible genetic determination of the outcome of infection. These findings suggest that gC1qR expression on the surface of T cells is crucial for HCV core-mediated T cell suppression and viral clearance, and that represents a novel mechanism by which a virus usurps host machinery for persistence.« less

Modelling of magnetostriction of transformer magnetic core for vibration analysis

NASA Astrophysics Data System (ADS)

Marks, Janis; Vitolina, Sandra

2017-12-01

Magnetostriction is a phenomenon occurring in transformer core in normal operation mode. Yet in time, it can cause the delamination of magnetic core resulting in higher level of vibrations that are measured on the surface of transformer tank during diagnostic tests. The aim of this paper is to create a model for evaluating elastic deformations in magnetic core that can be used for power transformers with intensive vibrations in order to eliminate magnetostriction as a their cause. Description of the developed model in Matlab and COMSOL software is provided including restrictions concerning geometry and properties of materials, and the results of performed research on magnetic core anisotropy are provided. As a case study modelling of magnetostriction for 5-legged 200 MVA power transformer with the rated voltage of 13.8/137kV is conducted, based on which comparative analysis of vibration levels and elastic deformations is performed.

Dating young geomorphic surfaces using age of colonizing Douglas fir in southwestern Washington and northwestern Oregon, USA

USGS Publications Warehouse

Pierson, T.C.

2007-01-01

Dating of dynamic, young (<500 years) geomorphic landforms, particularly volcanofluvial features, requires higher precision than is possible with radiocarbon dating. Minimum ages of recently created landforms have long been obtained from tree-ring ages of the oldest trees growing on new surfaces. But to estimate the year of landform creation requires that two time corrections be added to tree ages obtained from increment cores: (1) the time interval between stabilization of the new landform surface and germination of the sampled trees (germination lag time or GLT); and (2) the interval between seedling germination and growth to sampling height, if the trees are not cored at ground level. The sum of these two time intervals is the colonization time gap (CTG). Such time corrections have been needed for more precise dating of terraces and floodplains in lowland river valleys in the Cascade Range, where significant eruption-induced lateral shifting and vertical aggradation of channels can occur over years to decades, and where timing of such geomorphic changes can be critical to emergency planning. Earliest colonizing Douglas fir (Pseudotsuga menziesii) were sampled for tree-ring dating at eight sites on lowland (<750 m a.s.l.), recently formed surfaces of known age near three Cascade volcanoes - Mount Rainier, Mount St. Helens and Mount Hood - in southwestern Washington and northwestern Oregon. Increment cores or stem sections were taken at breast height and, where possible, at ground level from the largest, oldest-looking trees at each study site. At least ten trees were sampled at each site unless the total of early colonizers was less. Results indicate that a correction of four years should be used for GLT and 10 years for CTG if the single largest (and presumed oldest) Douglas fir growing on a surface of unknown age is sampled. This approach would have a potential error of up to 20 years. Error can be reduced by sampling the five largest Douglas fir instead of the single largest. A GLT correction of 5 years should be added to the mean ring-count age of the five largest trees growing on the surface being dated, if the trees are cored at ground level. This correction would have an approximate error of ??5 years. If the trees are cored at about 1.4 m above the round surface (breast height), a CTG correction of 11 years should be added to the mean age of the five sampled trees (with an error of about ??7 years).

Surface states and annihilation characteristics of positrons trapped at the oxidized Cu(100) surface

NASA Astrophysics Data System (ADS)

Fazleev, N. G.; Weiss, A. H.

2013-06-01

In this work we present the results of theoretical studies of positron surface and bulk states and annihilation probabilities of surface-trapped positrons with relevant core electrons at the oxidized Cu(100) surface under conditions of high oxygen coverage. Oxidation of the Cu(100) surface has been studied by performing an ab-initio investigation of the stability and electronic structure of the Cu(100) missing row reconstructed surface at various on-surface and subsurface oxygen coverages ranging from 0.5 to 1.5 monolayers using density functional theory (DFT). All studied structures have been found to be energetically more favorable as compared to structures formed by purely on-surface oxygen adsorption. The observed decrease in the positron work function when oxygen atoms occupy on-surface and subsurface sites has been attributed to a significant charge redistribution within the first two layers, buckling effects within each layer and an interlayer expansion. The computed positron binding energy, positron surface state wave function, and annihilation probabilities of the surface trapped positrons with relevant core electrons demonstrate their sensitivity to oxygen coverage, atomic structure of the topmost layers of surfaces, and charge transfer effects. Theoretical results are compared with experimental data obtained from studies of oxidation of the Cu(100) surface using positron annihilation induced Auger electron spectroscopy (PAES). The results presented provide an explanation for the changes observed in the probability of annihilation of surface trapped positrons with Cu 3p core-level electrons as a function of annealing temperature.

Recent Rise in West Greenland Surface Melt and Firn Density Driven by North Atlantic SSTs and Blocking Events

NASA Astrophysics Data System (ADS)

Osterberg, E. C.; Graeter, K.; Hawley, R. L.; Marshall, H. P.; Ferris, D. G.; Lewis, G.; Birkel, S. D.; Meehan, T.; McCarthy, F.

2017-12-01

The Greenland Ice Sheet (GrIS) has been losing mass since at least the early 2000s, mostly due to enhanced surface melt. Approximately 40% of the surface melt currently generated on the GrIS percolates into the snow/firn and refreezes, where it has no immediate impact on GrIS mass balance or sea-level rise. However, in situ observations of surface melt are sparse, and thus it remains unclear how melt water percolation and refreezing are modifying the GrIS percolation zone under recent warming. In addition, understanding the climatic drivers behind the recent increase in melt is critical for accurately predicting future GrIS surface melt rates and contributions to sea-level rise. Here we show that there have been significant increases in melt refreeze and firn density over the past 30-50 years along a 250 km-long region of the Western Greenland percolation zone (2137 - 2218 m elevation). We collected seven shallow firn cores as part of the 2016 Greenland Traverse for Accumulation and Climate Studies (GreenTrACS), analyzed each for melt layer stratigraphy and density, and developed timescales for each based on annual layer counting of seasonal chemical oscillations (e.g. δ18O, dust, and biogenic sulfur). The cores indicate that refrozen melt layers have increased 2- to 9-fold since 1970, with statistically significant (p < 0.05) linear trends at the five southernmost core sites. Comparisons of two GreenTrACS cores to co-located PARCA cores collected in 1998 reveal significant (p < 0.05) increases in density averaged over the top 10 m of firn ranging from 32-42 kg/m3. Recent density increases closely correspond with the locations of refrozen melt water. We use output from the MARv3.7 Regional Climate Model to assess climatic forcing of surface melt at GreenTrACS sites, and find significant summer-to-summer correlations between melt generation and the frequency of blocking high pressure centers over Greenland (represented by the Greenland Blocking Index; GBI), and with North Atlantic sea surface temperatures (represented by the Atlantic Multidecadal Oscillation; AMO). Thus, future surface melt rates in Western Greenland depend on the complex evolution of the GBI and AMO under anthropogenic forcing, both of which remain poorly constrained in 21st century model projections.

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

Dhaka, R. S.; Barman, S. R.

Ne 1s core-level photoelectron spectra from Ne nanobubbles implanted in aluminum exhibit two peaks whose binding energies and relative intensities change with implantation energy, isochronal annealing, and sputtering. These changes in the core-level spectra are manifestations of the nanometer size of the bubbles since the screening of the photohole by the Al conduction electrons depends on the bubble size. Existence of a bimodal depth and size distribution of Ne nanobubbles is demonstrated in this work: smaller bubbles of about 4 A in radius are formed close to the Al(111) surface while the larger sized bubbles of 20 A in radiusmore » exist deeper below in the beneath subsurface region. A general relation between the radius of the rare-gas bubbles and their core-level binding energies is established.« less

Reactions of Atmospheric Species with Clean and H, C, and O Implanted Species

DTIC Science & Technology

1989-07-27

energy shifts of the XFS core level spectra. Atomic concentration measurements were used to estimate the surface compositions. These results are...of the target surface, desorption of adsorbate atoms by hyperthermal physical/chemical interaction, and accumulation of a high surface concentration ...8217chemrical interactiosn, and accumulation of a high surface concentration of the pruijettile spCies. Vi1 film depsistion t-hcse studies investigate the

Surface composition changes in massive star evolution with mass loss

NASA Technical Reports Server (NTRS)

Noels, A.; Gabriel, M.; Vreux, J.-M.; Conti, P. S.

1980-01-01

A series of evolutionary models of 40-100 solar mass objects undergoing mass loss are constructed with the explicit inclusion of the surface composition of H, He, C, N, O elements. Mass loss rates similar to those observed in Of stars, 4 to 7 x 10 to the -6th solar masses/yr, result in an appearance at the surface of equilibrium CNO products, i.e. enhanced nitrogen and diminished carbon, while that star is still burning hydrogen in the core. This result obtains because the initial convection core is a relatively large fraction of the total mass and rather modest loss exposes levels of anomalous composition. It is suggested that these objects might reasonably be identified as those luminous late type WN stars still containing surface hydrogen.

Predictable Particle Engineering: Programming the Energy Level, Carrier Generation, and Conductivity of Core-Shell Particles.

PubMed

Yuan, Conghui; Wu, Tong; Mao, Jie; Chen, Ting; Li, Yuntong; Li, Min; Xu, Yiting; Zeng, Birong; Luo, Weiang; Yu, Lingke; Zheng, Gaofeng; Dai, Lizong

2018-06-20

Core-shell structures are of particular interest in the development of advanced composite materials as they can efficiently bring different components together at nanoscale. The advantage of this structure greatly relies on the crucial design of both core and shell, thus achieving an intercomponent synergistic effect. In this report, we show that decorating semiconductor nanocrystals with a boronate polymer shell can easily achieve programmable core-shell interactions. Taking ZnO and anatase TiO 2 nanocrystals as inner core examples, the effective core-shell interactions can narrow the band gap of semiconductor nanocrystals, change the HOMO and LUMO levels of boronate polymer shell, and significantly improve the carrier density of core-shell particles. The hole mobility of core-shell particles can be improved by almost 9 orders of magnitude in comparison with net boronate polymer, while the conductivity of core-shell particles is at most 30-fold of nanocrystals. The particle engineering strategy is based on two driving forces: catechol-surface binding and B-N dative bonding and having a high ability to control and predict the shell thickness. Also, this approach is applicable to various inorganic nanoparticles with different components, sizes, and shapes.

Core body temperature, skin temperature, and interface pressure. Relationship to skin integrity in nursing home residents.

PubMed

Knox, D M

1999-06-01

To ascertain the effects of 1-, 1 1/2-, and 2-hour turning intervals on nursing home residents' skin over the sacrum and trochanters. (1) the higher the core body temperature, the higher the skin surface temperature; (2) the 2-hour turning interval would have significantly higher skin surface temperature; (3) there would be no relationship between skin surface temperature and interface pressure; and (4) the sacrum would have the lowest skin surface temperature. Modified Latin-square. For-profit nursing home. Convenience sample of 26 residents who scored < 3 on the Short Portable Mini-Mental Status Questionnaire and did not have (1) open wounds; (2) albumin levels < 3.3 mg/dL; (3) severe arthritis; (4) cortisone, anticoagulation, insulin therapy or 3 medications for hypertension; and/or (5) were totally bedridden. First Temp measured core temperature; a disposable thermistor temperature probe, skin temperature; and a digital interface pressure evaluator, the interface pressure. Negative correlation (r = -.33, P = .003) occurred between core body temperature and skin surface temperature. Skin surface temperature rose at the end of the 2-hour turning interval but was not significant (F = (2.68) = .73, P = .49). Weak negative relationship (r = -12, P = .29) occurred between skin surface temperature and interface pressure, and sacral skin surface temperature was significantly lower for the left trochanter only (F = (8.68) = 7.05, P = .002). Although hypotheses were not supported, more research is needed to understand how time in position and multiple chronic illnesses interact to affect skin pressure tolerance.

Effect of different surface treatments on microtensile bond strength of two resin cements to aged simulated composite core materials.

PubMed

Esmaeili, Behnaz; Alaghehmand, Homayoon; Shakerian, Mohadese

2015-01-01

Roughening of the aged composite resin core (CRC) surface seems essential for durable adhesion. The aim of this study was to investigate the influence of various surface treatments and different resin cements on microtensile bond strength (µ TBS) between two aged core build-up composites (CBCs) and feldspathic ceramic. A total of 16 composite blocks made of two CBCs, Core.it and Build-it were randomly assigned to four surface treatment groups after water storage and thermocycling (2 weeks and 500 cycles). Experimental groups included surface roughening with air abrasion (AA), hydrofluoric acid, pumice, and laser and then were bonded to computer-aided design/computer-aided manufacturing feldspathic ceramic blocks using two resin cements, Panavia F2 (PF), and Duo-link (DL). The µ TBS was tested, and the fracture mode was assessed. The data were analyzed with multiple analysis of variance to estimate the contribution of different surface treatments, resin cements, and two aged CRCs on µ TBS. Statistical significance level was set at α < 0.05. Surface treatment and cement type significantly affected bond strength (P < 0.001) but the type of CRC did not (P = 0.468). Between roughening methods, the highest and the lowest values of µ TBS were sequentially obtained in AA and Er.YAG laser groups. The highest bond strength was in AA group cemented with PF (31.83 MPa). The most common failure mode was cohesive fracture in the cement. Different surface treatments had different effects on µ TBS of aged CRCs to feldspathic ceramics. PF was significantly better than DL.

Reaction of Rb and oxygen overlayers with single-crystalline Bi2Sr2CaCu2O8+δ superconductors

NASA Astrophysics Data System (ADS)

Lindberg, P. A. P.; Shen, Z.-X.; Wells, B. O.; Dessau, D. S.; Mitzi, D. B.; Lindau, I.; Spicer, W. E.; Kapitulnik, A.

1989-02-01

Single crystals of Bi2Sr2CaCu2O8+δ superconductors, in situ cleaved and modified by Rb and oxygen overlayers, have been studied using ultraviolet and x-ray photoemission spectroscopy. The core-level results show that Rb strongly reacts with the Bi and O states, while the Cu and Sr states are left unchanged. This observation strongly indicates that the Bi-O plane forms the surface layer. Subsequent exposure to oxygen results in new oxygen states at the surface as monitored by the O 1s core-level data. For both Rb and oxygen overlayers the valence-band spectra are severely altered. In particular, new valence-band states, presumably of oxygen character, are formed.

Photoelectron spectroscopy study of the electronic structures at CoPc/Bi(111) interface

NASA Astrophysics Data System (ADS)

Sun, Haoliang; Liang, Zhaofeng; Shen, Kongchao; Hu, Jinbang; Ji, Gengwu; Li, Zheshen; Li, Haiyang; Zhu, Zhiyuan; Li, Jiong; Gao, Xingyu; Han, Huang; Jiang, Zheng; Song, Fei

2017-07-01

Self-assembly of functional molecules on solid substrate has been recognized as an appealing approach for the fabrication of diverse nanostructures for nanoelectronics. Herein, we investigate the growth of cobalt phthalocyanine (CoPc) on a Bi(111) surface with focus on the interface electronic structures utilizing photoelectron spectroscopy. While charge transfer from bismuth substrate to the molecule results in the emergence of an interface component in the Co 3p core level at lower binding energy, core-levels associated to the molecular ligand (C 1s and N 1s) are less influenced by the adsorption. In addition, density functional theory (DFT) calculations also support the empirical inference that the molecule-substrate interaction mainly involves the out-of-plane empty Co 3d orbital and bismuth states. Finally, valence band spectra demonstrate the molecule-substrate interaction is induced by interface charge transfer, agreeing well with core level measurements. Charge transfer is shown to be mainly from the underlying bismuth substrate to the empty states located at the central Co atom in the CoPc molecules. This report may provide a fundamental basis to the on-surface engineering of interfaces for molecular devices and spintronics.

Distinct effects of Cr bulk doping and surface deposition on the chemical environment and electronic structure of the topological insulator Bi2Se3

NASA Astrophysics Data System (ADS)

Yilmaz, Turgut; Hines, William; Sun, Fu-Chang; Pletikosić, Ivo; Budnick, Joseph; Valla, Tonica; Sinkovic, Boris

2017-06-01

In this report, it is shown that Cr doped into the bulk and Cr deposited on the surface of Bi2Se3 films produced by molecular beam epitaxy (MBE) have strikingly different effects on both the electronic structure and chemical environment. Angle resolved photoemission spectroscopy (ARPES) shows that Cr doped into the bulk opens a surface state energy gap which can be seen at room temperature; much higher than the measured ferromagnetic transition temperature of ≈10 K. On the other hand, similar ARPES measurements show that the surface states remain gapless down to 15 K for films with Cr surface deposition. In addition, core-level photoemission spectroscopy of the Bi 5d, Se 3d, and Cr 3p core levels show distinct differences in the chemical environment for the two methods of Cr introduction. Surface deposition of Cr results in the formation of shoulders on the lower binding energy side for the Bi 5d peaks and two distinct Cr 3p peaks indicative of two Cr sites. These striking differences suggests an interesting possibility that better control of doping at only near surface region may offer a path to quantum anomalous Hall states at higher temperatures than reported in the literature.

Nutrient loss with runoff from fairway turf: an evaluation of core cultivation practices and their environmental impact.

PubMed

Rice, Pamela J; Horgan, Brian P

2011-11-01

The presence of excess nutrients in surface waters can result in undesirable environmental and economic consequences, including nuisance algal blooms and eutrophication. Fertilizer use in highly managed turf systems has raised questions concerning the contribution of nutrients to surrounding surface waters. Experiments were designed to quantify phosphorus and nitrogen transport with runoff from turf plots maintained as a golf course fairway to identify which cultural practice, solid tine (ST) or hollow tine (HT) core cultivation, maximized phosphorus and nitrogen retention at the site of fertilizer application. Simulated precipitation and collection of resulting runoff were completed 26 ± 13 h following granular fertilizer application (18-3-18: N-P₂O₅-K₂O) and 63 d and 2 d following core cultivation. Runoff volumes were reduced in fairway turf plots aerated with HT relative to ST (63 d: 10%, 2 d: 55% reduction). Analysis of the runoff revealed a reduction in soluble phosphorus, ammonium nitrogen, and nitrate nitrogen losses with runoff from plots managed with HT; a 5 to 27% reduction after 63 d; and a 39 to 77% reduction at 2 d. Golf course runoff-to-surface water scenarios were used to calculate estimated environmental concentrations (EECs) of nitrogen and phosphorus in surface water receiving runoff from turf managed with ST or HT core cultivation. Surface water concentrations of phosphorus remained above the U.S. Environmental Protection Agency's water quality criteria to limit eutrophication, with the exception of concentrations associated with HT core cultivation at 2 d. Regardless of management practice (ST or HT) and time between core cultivation and runoff (63 d or 2 d), all EECs of nitrogen were below levels associated with increased algal growth. Understanding nutrient transport with runoff and identifying strategies that reduce off-site transport will increase their effectiveness at intended sites of application and minimize undesirable effects to surrounding surface water resources. Copyright © 2011 SETAC.

Positron-annihilation-induced ion desorption from TiO2(110)

NASA Astrophysics Data System (ADS)

Tachibana, T.; Hirayama, T.; Nagashima, Y.

2014-05-01

We have investigated the positron-stimulated desorption of ions from a TiO2(110) surface. Desorbed O+ ions were detected in coincidence with the emission of annihilation γ rays. The energy dependence of the ion yields shows that the O+ ions were detected at energies much lower than the previously reported threshold for electron impact desorption corresponding to the excitation energy of Ti(3p) core electrons. These results provide evidence that core-hole creation by positron annihilation with electrons in the core levels leads to ion desorption.

Studies of Positrons Trapped at Quantum-Dot Like Particles Embedded in Metal Surfaces

NASA Astrophysics Data System (ADS)

Fazleev, N. G.; Nadesalingam, M. P.; Weiss, A. H.

2009-03-01

Experimental studies of the positron annihilation induced Auger electron (PAES) spectra from the Fe-Cu alloy surfaces with quantum-dot like Cu nanoparticles embedded in Fe show that the PAES signal from Cu increase rapidly as the concentration of Cu is enhanced by vacuum annealing. These measurements indicate that almost 75% of positrons that annihilate with core electrons due so with Cu even though the surface concentration of Cu as measured by EAES is only 6%. This result suggests that positrons become localized at sites at the surface containing high concentration of Cu atoms before annihilation. These experimental results are investigated theoretically by performing calculations of the "image-potential" positron surface states and annihilation characteristics of the surface trapped positrons with relevant Fe and Cu core-level electrons for the clean Fe(100) and Cu(100) surfaces and for the Fe(100) surface with quantum-dot like Cu nanoparticles embedded in the top atomic layers of the host substrate. Estimates of the positron binding energy and positron annihilation characteristics reveal their strong sensitivity to the nanoparticle coverage. Computed core annihilation probabilities are compared with experimental ones estimated from the measured Auger peak intensities. The observed behavior of the Fe and Cu PAES signal intensities is explained by theoretical calculations as being due to trapping of positrons in the regions of Cu nanoparticles embedded in the top atomic layers of Fe.

[Spatial variations of biogenic elements in coastal wetland sediments of the Jiulong River Estuary].

PubMed

Yu, Xiao-Qing; Yang, Jun; Liu, Le-Mian; Tian, Yuan; Yu, Zheng; Wang, Chang-Fu

2012-11-01

To reveal the spatial distribution of biogenic elements and their influencing factors in the typical subtropical coastal wetland, both surface and core sediment samples were collected from the Jiulong River Estuary, southeast China in summer 2009. The biogenic elements including carbon, nitrogen, phosphorus, sulfur (C, N, P, S) were determined by Element Analyzer and Flow Injection Analyzer. The concentrations of TC, TN, TP, and TS were (12.64 +/- 2.66) g x kg(-1), (1.57 +/- 0.29) g x kg(-1), (0.48 +/- 0.06) g x kg(-1), and (2.61 +/- 1.37) g x kg(-1), respectively. Further, these biogenic elements showed a distinct spatial pattern which closely related with the vegetation type and tide level. Values of TC, TN, TP in the surface sediment of mangrove vegetation zones were higher than those in the cord-grass and mudflat zones, while TC, TN, TP concentrations in the high tide level regions were higher than those in the middle and low tide level regions. The TS concentration was the highest in cord-grass vegetation and middle tidal level zones. The TC and TN values in sedimentary core decreased gradually with depth, and they were the highest in the mangrove sites, followed by cord-grass and mudflat sites at the same depth. In mudflat sedimentary core, the average content of TP was the lowest, whereas TS was the highest. Redundancy analysis revealed that vegetation type, pH and tide level were the main factors influencing the distribution of biogenic elements in surface sediments of the Jiulong River Estuary, by explaining 24.0%, 19.0% and 11.6% of total variation in the four biogenic elements (C, N, P and S), respectively.

Core-Level Photoemission Investigations of the CADMIUM-TELLURIDE(100) and INDIUM-ANTIMONY(100) Surface and Interfacial Structures.

NASA Astrophysics Data System (ADS)

John, Peter James

1988-12-01

Photoemission techniques, utilizing a synchrotron light source, were used to analyze the clean (100) surfaces of the zinc-blende semiconductor materials CdTe and InSb. Several interfacial systems involving the surfaces of these materials were also studied, including the CdTe(100)-Ag interface, the CdTe(100)-Sb system, and the InSb(100)-Sn interface. High -energy electron diffraction was also employed to acquire information about of surface structure. A one-domain (2x1) structure was observed for the CdTe(100) surface. Analysis of photoemission spectra of the Cd 4d core level for this surface structure revealed two components resulting from Cd surface atoms. The total intensity of these components accounts for a full monolayer of Cd atoms on the surface. A structural model is discussed commensurate with these results. Photoemission spectra of the Cd and Te 4d core levels indicate that Ag or Sb deposited on the CdTe(100)-(2x1) surface at room temperature do not bound strongly to the surface Cd atoms. The room temperature growth characteristics for these two elements on the CdTe(100)-(2x1) are discussed. The growth at elevated substrate temperatures was also studied for Sb deposition. The InSb(100) surface differed from the CdTe(100) surface. Using molecular beam epitaxy, several structures could be generated for the InSb(100) surface, including a c(8x2), a c(4x4), an asymmetric (1x3), a symmetric (1x3), and a (1x1). Analysis of photoemission intensities and line shapes indicates that the c(4x4) surface is terminated with 1{3 over 4} monolayers of Sb atoms. The c(8x2) surface is found to be terminated with {3over 4} monolayer of In atoms. Structural models for both of these surfaces are proposed based upon the photoemission results and upon models of the similar GaAs(100) structures. The room temperature growth characteristics of grey Sn on the InSb(100)-c(4x4) and InSb(100)-c(8x2) surfaces were studied with photoemission. The discontinuity in the valence band maximum for this semiconductor heterojunction system is measured to be 0.40 eV, independent of the starting surface structure and stoichiometry. This result is reconciled with theoretical predictions for heterostructure behavior.

Modern foraminifera assemblages in the Amundsen Sea Embayment

NASA Astrophysics Data System (ADS)

Ewa Jernas, Patrycja; Kuhn, Gerhard; Hillenbrand, Claus-Dieter; Lander Rasmussen, Tine; Forwick, Matthias; Mackensen, Andreas; Schröder, Michael; Smith, James; Klages, Johann Philipp

2015-04-01

The West Antarctic Ice Sheet (WAIS) is considered the most unstable part of the Antarctic Ice Sheet. As the WAIS is mostly grounded below sea level, its stability is of great concern. A collapse of large parts of the WAIS would result in a significant global sea-level rise. At present, the WAIS shows dramatic ice loss in its Amundsen Sea sector, especially in Pine Island Bay. Pine Island Glacier (PIG) is characterised by fast flow, major thinning and rapid grounding-line retreat. Its mass los over recent decades is generally attributed to melting caused by the inflow of warm Circumpolar Deep Water (CDW). Future melting of PIG may result in a sea level tipping point, because it could trigger widespread collapse of the WAIS, especially when considering ongoing climate change. Our research project aims to establish proxies (integration of foraminifera, sediment properties and oceanographic data) for modern environmental conditions by analysing seafloor surface sediments along a transect from the glacier proximal settings to the middle-outer shelf in the eastern Amundsen Sea Embayment. These proxies will then be applied on sediment records spanning the Holocene back to the Last Glacial Maximum for reconstructing spatial and temporal variations of CDW upwelling and ice-ocean interactions during the past c. 23,000 years. We will present preliminary results from the analyses of ten short marine sediment cores (multi and box cores) collected during expeditions JR179 (2008) and ANT-XXVI/3 (2010) along a transect from inner Pine Island Bay to the middle-outer shelf part of the Abbot Palaeo-Ice Stream Trough at water depths ranging from 458 m (middle shelf) to 1444 m (inner shelf). The sediment cores are currently investigated for distribution patterns of planktonic and benthic foraminifera and grain-size distribution at 1 cm resolution. Core tops (0-10 cm) were stained with Rose Bengal for living benthic foraminifera investigations. The chronology of the cores will be based on 210Pb and calibrated 14C dates. First results reveal the presence of living benthic foraminifera in surface sediments of all investigated cores suggesting that modern seabed surfaces were recovered. Moreover, a core retrieved from a water depth of 793 m in the Abbot Palaeo-Ice Stream Trough shows particularly high abundances of planktonic foraminifera Neogloboquadrina pachyderma.

Core and body surface temperatures of nesting leatherback turtles (Dermochelys coriacea).

PubMed

Burns, Thomas J; McCafferty, Dominic J; Kennedy, Malcolm W

2015-07-01

Leatherback turtles (Dermochelys coriacea) are the largest species of marine turtle and the fourth most massive extant reptile. In temperate waters they maintain body temperatures higher than surrounding seawater through a combination of insulation, physiological, and behavioural adaptations. Nesting involves physical activity in addition to contact with warm sand and air, potentially presenting thermal challenges in the absence of the cooling effect of water, and data are lacking with which to understand their nesting thermal biology. Using non-contact methods (thermal imaging and infrared thermometry) to avoid any stress-related effects, we investigated core and surface temperature during nesting. The mean±SE core temperature was 31.4±0.05°C (newly emerged eggs) and was not correlated with environmental conditions on the nesting beach. Core temperature of leatherbacks was greater than that of hawksbill turtles (Eretmochelys imbricata) nesting at a nearby colony, 30.0±0.13°C. Body surface temperatures of leatherbacks showed regional variation, the lateral and dorsal regions of the head were warmest while the carapace was the coolest surface. Surface temperature increased during the early nesting phases, then levelled off or decreased during later phases with the rates of change varying between body regions. Body region, behavioural phase of nesting and air temperature were found to be the best predictors of surface temperature. Regional variation in surface temperature were likely due to alterations in blood supply, and temporal changes in local muscular activity of flippers during the different phases of nesting. Heat exchange from the upper surface of the turtle was dominated by radiative heat loss from all body regions and small convective heat gains to the carapace and front flippers. Copyright © 2015 Elsevier Ltd. All rights reserved.

Assessing environmental impact from gas and oil exploration in the SW Barents Sea using benthic foraminiferal assemblages

NASA Astrophysics Data System (ADS)

Dijkstra, N.; Junttila, J.; Husum, K.; Carroll, J.; Hald, M.

2012-04-01

During the last decades petroleum industry and shipping activities have increased in the SW Barents Sea. Oil exploration wells were drilled in the 1980s with production starting in 2007. These activities are projected to expand in the coming years. As part of the Northern Environmental Waste Management (EWMA) project, a competence cluster for petroleum industry related waste handling, we investigate the impacts of enhanced anthropogenic activities on benthic foraminiferal assemblages in the SW Barents Sea. Sediment cores (0-20 cm) from sites in proximity to two oil- and gas fields are under investigation. These sediment cores, dated with the 210Pb method, represent the last 90 to 150 years. Both dead and living benthic foraminifera (100 µm-1 mm) were counted to elucidate differences in foraminiferal assemblages between pre-impact and recent conditions. In addition, the heavy metal concentrations, persistent organic pollutant (POP) concentrations, grain size and total organic content (TOC) of the sediment cores have been analyzed. Pollution levels of the surface sediments (0-1 cm) are of background to good level (level I-II) according to the definitions of the Water Framework Directorate (WFD). Patterns in living benthic foraminiferal assemblages identified in the sea floor surface sediments, are the result of natural environmental changes such as depth, water mass and sediment composition. Further downcore (1-20 cm) pollution levels are in general of background environmental status (WFD level I). However, at some depth intervals, especially in sediment cores from the near proximity of the oil- and gas- fields, pollution levels are slightly enhanced (WFD level II). Further work will include statistical comparison of dead and living foraminiferal assemblages with sediment pollution levels, sediment properties, and oceanographic conditions. This research contributes to the development of foraminifera as a useful bio-monitoring technique for the Arctic region as industrial activities increase in the coming years.

Rare-earth-doped optical-fiber core deposition using full vapor-phase SPCVD process

NASA Astrophysics Data System (ADS)

Barnini, A.; Robin, T.; Cadier, B.; Aka, G.; Caurant, D.; Gotter, T.; Guyon, C.; Pinsard, E.; Guitton, P.; Laurent, A.; Montron, R.

2017-02-01

One key parameter in the race toward ever-higher power fiber lasers remains the rare earth doped optical core quality. Modern Large Mode Area (LMA) fibers require a fine radial control of the core refractive index (RI) close to the silica level. These low RI are achieved with multi-component materials that cannot be readily obtained using conventional solution doping based Modified Chemical Vapor Deposition (MCVD) technology. This paper presents a study of such optical material obtained through a full-vapor phase Surface Plasma Chemical Vapor Deposition (SPCVD). The SPCVD process generates straight glassy films on the inner surface of a thermally regulated synthetic silica tube under vacuum. The first part of the presented results points out the feasibility of ytterbium-doped aluminosilicate fibers by this process. In the second part we describe the challenge controlling the refractive index throughout the core diameter when using volatile fluorine to create efficient LMA fiber profiles. It has been demonstrated that it is possible to counter-act the loss of fluorine at the center of the core by adjusting the core composition locally. Our materials yielded, when used in optical fibers with numerical apertures ranging from 0.07 to 0.09, power conversion efficiency up to 76% and low background losses below 20 dB/km at 1100nm. Photodarkening has been measured to be similar to equivalent MCVD based fibers. The use of cerium as a co-dopant allowed for a complete mitigation of this laser lifetime detrimental effect. The SPCVD process enables high capacity preforms and is particularly versatile when it comes to radial tailoring of both rare earth doping level and RI. Large core diameter preforms - up to 4mm - were successfully produced.

Effective surface Debye temperature for NiMnSb(100) epitaxial films

NASA Astrophysics Data System (ADS)

Borca, C. N.; Komesu, Takashi; Jeong, Hae-kyung; Dowben, P. A.; Ristoiu, D.; Hordequin, Ch.; Pierre, J.; Nozières, J. P.

2000-07-01

The surface Debye temperature of the NiMnSb (100) epitaxial films has been obtained using low energy electron diffraction, inverse photoemission, and core-level photoemission. The normal dynamic motion of the (100) surface results in a value for the effective surface Debye temperature of 145±13 K. This is far smaller than the bulk Debye temperature of 312±5 K obtained from wave vector dependent inelastic neutron scattering. The large difference between these measures of surface and bulk dynamic motion indicates a soft and compositionally different (100) surface.

Electronic properties of core-shell nanowire resonant tunneling diodes

PubMed Central

2014-01-01

The electronic sub-band structure of InAs/InP/InAs/InP/InAs core-shell nanowire resonant tunneling diodes has been investigated in the effective mass approximation by varying the core radius and the thickness of the InP barriers and InAs shells. A top-hat, double-barrier potential profile and optimal energy configuration are obtained for core radii and surface shells >10 nm, InAs middle shells <10 nm, and 5 nm InP barriers. In this case, two sub-bands exist above the Fermi level in the InAs middle shell which belongs to the m = 0 and m = 1 ladder of states that have similar wave functions and energies. On the other hand, the lowest m = 0 sub-band in the core falls below the Fermi level but the m = 1 states do not contribute to the current transport since they reside energetically well above the Fermi level. We compare the case of GaAs/AlGaAs/GaAs/AlGaAs/GaAs which may conduct current with smaller applied voltages due to the larger effective mass of electrons in GaAs and discuss the need for doping. PMID:25288912

Electronic properties of core-shell nanowire resonant tunneling diodes.

PubMed

Zervos, Matthew

2014-01-01

The electronic sub-band structure of InAs/InP/InAs/InP/InAs core-shell nanowire resonant tunneling diodes has been investigated in the effective mass approximation by varying the core radius and the thickness of the InP barriers and InAs shells. A top-hat, double-barrier potential profile and optimal energy configuration are obtained for core radii and surface shells >10 nm, InAs middle shells <10 nm, and 5 nm InP barriers. In this case, two sub-bands exist above the Fermi level in the InAs middle shell which belongs to the m = 0 and m = 1 ladder of states that have similar wave functions and energies. On the other hand, the lowest m = 0 sub-band in the core falls below the Fermi level but the m = 1 states do not contribute to the current transport since they reside energetically well above the Fermi level. We compare the case of GaAs/AlGaAs/GaAs/AlGaAs/GaAs which may conduct current with smaller applied voltages due to the larger effective mass of electrons in GaAs and discuss the need for doping.

Distinct effects of Cr bulk doping and surface deposition on the chemical environment and electronic structure of the topological insulator Bi 2 Se 3

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

Yilmaz, Turgut; Hines, William; Sun, Fu-Chang

In this report, it is shown that Cr doped into the bulk and Cr deposited on the surface of Bi2Se3 films produced by molecular beam epitaxy (MBE) have strikingly different effects on both the electronic structure and chemical environment. Angle resolved photoemission spectroscopy (ARPES) shows that Cr doped into the bulk opens a surface state energy gap which can be seen at room temperature; much higher than the measured ferromagnetic transition temperature of ≈ 10 K. On the other hand, similar ARPES measurements show that the surface states remain gapless down to 15 K for films with Cr surface deposition.more » In addition, core-level photoemission spectroscopy of the Bi 5d, Se 3d, and Cr 3p core levels show distinct differences in the chemical environment for the two methods of Cr introduction. Surface deposition of Cr results in the formation of shoulders on the lower binding energy side for the Bi 5d peaks and two distinct Cr 3p peaks indicative of two Cr sites. These striking differences suggests an interesting possibility that better control of doping at only near surface region may offer a path to quantum anomalous Hall states at higher temperatures than reported in the literature.« less

Distinct effects of Cr bulk doping and surface deposition on the chemical environment and electronic structure of the topological insulator Bi 2 Se 3

DOE PAGES

Yilmaz, Turgut; Hines, William; Sun, Fu-Chang; ...

2017-02-21

In this report, it is shown that Cr doped into the bulk and Cr deposited on the surface of Bi2Se3 films produced by molecular beam epitaxy (MBE) have strikingly different effects on both the electronic structure and chemical environment. Angle resolved photoemission spectroscopy (ARPES) shows that Cr doped into the bulk opens a surface state energy gap which can be seen at room temperature; much higher than the measured ferromagnetic transition temperature of ≈ 10 K. On the other hand, similar ARPES measurements show that the surface states remain gapless down to 15 K for films with Cr surface deposition.more » In addition, core-level photoemission spectroscopy of the Bi 5d, Se 3d, and Cr 3p core levels show distinct differences in the chemical environment for the two methods of Cr introduction. Surface deposition of Cr results in the formation of shoulders on the lower binding energy side for the Bi 5d peaks and two distinct Cr 3p peaks indicative of two Cr sites. These striking differences suggests an interesting possibility that better control of doping at only near surface region may offer a path to quantum anomalous Hall states at higher temperatures than reported in the literature.« less

Experimental Evaluation of the Thermal Performance of a Water Shield for a Surface Power Reactor

NASA Technical Reports Server (NTRS)

Pearson, J. Boise; Stewart, Eric T.; Reid, Robert S.

2007-01-01

A water based shielding system is being investigated for use on initial lunar surface power systems. The use of water may lower overall cost (as compared to development cost for other materials) and simplify operations in the setup and handling. The thermal hydraulic performance of the shield is of significant interest. The mechanism for transferring heat through the shield is natural convection. Natural convection in a representative lunar surface reactor shield design is evaluated at various power levels in the Water Shield Testbed (WST) at the NASA Marshall Space Flight Center. The experimental data from the WST is used to anchor a CFD model. Performance of a water shield on the lunar surface is then predicted by CFD models anchored to test data. The accompanying viewgraph presentation includes the following topics: 1) Testbed Configuration; 2) Core Heater Placement and Instrumentation; 3) Thermocouple Placement; 4) Core Thermocouple Placement; 5) Outer Tank Thermocouple Placement; 6) Integrated Testbed; 7) Methodology; 8) Experimental Results: Core Temperatures; 9) Experimental Results; Outer Tank Temperatures; 10) CFD Modeling; 11) CFD Model: Anchored to Experimental Results (1-g); 12) CFD MOdel: Prediction for 1/6-g; and 13) CFD Model: Comparison of 1-g to 1/6-g.

On the violation of gradient wind balance at the top of tropical cyclones

NASA Astrophysics Data System (ADS)

Cohen, Yair; Harnik, Nili; Heifetz, Eyal; Nolan, David S.; Tao, Dandan; Zhang, Fuqing

2017-08-01

The existence of physical solutions for the gradient wind balance is examined at the top of 12 simulated tropical cyclones. The pressure field at the top of these storms, which depends on the vertically integrated effect of the warm core and the near surface low, is found to violate the gradient wind balance—termed here as a state of nonbalance. Using a toy model, it is shown that slight changes in the relative location and relative widths of the warm core drastically increase the isobaric curvature at the upper level pressure maps leading to nonbalance. While idealized storms return to balance within several days, simulations of real-world tropical cyclones retain a considerable degree of nonbalance throughout the model integration. Comparing mean and maximum values of different storms shows that peak nonbalance correlates with either peak intensity or intensification, implying the possible importance of nonbalance at upper levels for the near surface winds.

Global Precipitation Measurement (GPM) Mission: Precipitation Processing System (PPS) GPM Mission Gridded Text Products Provide Surface Precipitation Retrievals

NASA Technical Reports Server (NTRS)

Stocker, Erich Franz; Kelley, O.; Kummerow, C.; Huffman, G.; Olson, W.; Kwiatkowski, J.

2015-01-01

In February 2015, the Global Precipitation Measurement (GPM) mission core satellite will complete its first year in space. The core satellite carries a conically scanning microwave imager called the GPM Microwave Imager (GMI), which also has 166 GHz and 183 GHz frequency channels. The GPM core satellite also carries a dual frequency radar (DPR) which operates at Ku frequency, similar to the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar, and a new Ka frequency. The precipitation processing system (PPS) is producing swath-based instantaneous precipitation retrievals from GMI, both radars including a dual-frequency product, and a combined GMIDPR precipitation retrieval. These level 2 products are written in the HDF5 format and have many additional parameters beyond surface precipitation that are organized into appropriate groups. While these retrieval algorithms were developed prior to launch and are not optimal, these algorithms are producing very creditable retrievals. It is appropriate for a wide group of users to have access to the GPM retrievals. However, for researchers requiring only surface precipitation, these L2 swath products can appear to be very intimidating and they certainly do contain many more variables than the average researcher needs. Some researchers desire only surface retrievals stored in a simple easily accessible format. In response, PPS has begun to produce gridded text based products that contain just the most widely used variables for each instrument (surface rainfall rate, fraction liquid, fraction convective) in a single line for each grid box that contains one or more observations.This paper will describe the gridded data products that are being produced and provide an overview of their content. Currently two types of gridded products are being produced: (1) surface precipitation retrievals from the core satellite instruments GMI, DPR, and combined GMIDPR (2) surface precipitation retrievals for the partner constellation satellites. Both of these gridded products are generated for a.25 degree x.25 degree hourly grid, which are packaged into daily ASCII (American Standard Code for Information Interchange) files that can downloaded from the PPS FTP (File Transfer Protocol) site. To reduce the download size, the files are compressed using the gzip utility.This paper will focus on presenting high-level details about the gridded text product being generated from the instruments on the GPM core satellite. But summary information will also be presented about the partner radiometer gridded product. All retrievals for the partner radiometer are done using the GPROF2014 algorithmusing as input the PPS generated inter-calibrated 1C product for the radiometer.

GPM Mission Gridded Text Products Providing Surface Precipitation Retrievals

NASA Astrophysics Data System (ADS)

Stocker, Erich Franz; Kelley, Owen; Huffman, George; Kummerow, Christian

2015-04-01

In February 2015, the Global Precipitation Measurement (GPM) mission core satellite will complete its first year in space. The core satellite carries a conically scanning microwave imager called the GPM Microwave Imager (GMI), which also has 166 GHz and 183 GHz frequency channels. The GPM core satellite also carries a dual frequency radar (DPR) which operates at Ku frequency, similar to the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar), and a new Ka frequency. The precipitation processing system (PPS) is producing swath-based instantaneous precipitation retrievals from GMI, both radars including a dual-frequency product, and a combined GMI/DPR precipitation retrieval. These level 2 products are written in the HDF5 format and have many additional parameters beyond surface precipitation that are organized into appropriate groups. While these retrieval algorithms were developed prior to launch and are not optimal, these algorithms are producing very creditable retrievals. It is appropriate for a wide group of users to have access to the GPM retrievals. However, for reseachers requiring only surface precipitation, these L2 swath products can appear to be very intimidating and they certainly do contain many more variables than the average researcher needs. Some researchers desire only surface retrievals stored in a simple easily accessible format. In response, PPS has begun to produce gridded text based products that contain just the most widely used variables for each instrument (surface rainfall rate, fraction liquid, fraction convective) in a single line for each grid box that contains one or more observations. This paper will describe the gridded data products that are being produced and provide an overview of their content. Currently two types of gridded products are being produced: (1) surface precipitation retrievals from the core satellite instruments - GMI, DPR, and combined GMI/DPR (2) surface precipitation retrievals for the partner constellation satellites. Both of these gridded products are generated for a .25 degree x .25 degree hourly grid, which are packaged into daily ASCII files that can downloaded from the PPS FTP site. To reduce the download size, the files are compressed using the gzip utility. This paper will focus on presenting high-level details about the gridded text product being generated from the instruments on the GPM core satellite. But summary information will also be presented about the partner radiometer gridded product. All retrievals for the partner radiometer are done using the GPROF2014 algorithm using as input the PPS generated inter-calibrated 1C product for the radiometer.

Greenland-Wide Seasonal Temperatures During the Last Deglaciation

NASA Astrophysics Data System (ADS)

Buizert, C.; Keisling, B. A.; Box, J. E.; He, F.; Carlson, A. E.; Sinclair, G.; DeConto, R. M.

2018-02-01

The sensitivity of the Greenland ice sheet to climate forcing is of key importance in assessing its contribution to past and future sea level rise. Surface mass loss occurs during summer, and accounting for temperature seasonality is critical in simulating ice sheet evolution and in interpreting glacial landforms and chronologies. Ice core records constrain the timing and magnitude of climate change but are largely limited to annual mean estimates from the ice sheet interior. Here we merge ice core reconstructions with transient climate model simulations to generate Greenland-wide and seasonally resolved surface air temperature fields during the last deglaciation. Greenland summer temperatures peak in the early Holocene, consistent with records of ice core melt layers. We perform deglacial Greenland ice sheet model simulations to demonstrate that accounting for realistic temperature seasonality decreases simulated glacial ice volume, expedites the deglacial margin retreat, mutes the impact of abrupt climate warming, and gives rise to a clear Holocene ice volume minimum.

Oxidation of InP nanowires: a first principles molecular dynamics study.

PubMed

Berwanger, Mailing; Schoenhalz, Aline L; Dos Santos, Cláudia L; Piquini, Paulo

2016-11-16

InP nanowires are candidates for optoelectronic applications, and as protective capping layers of III-V core-shell nanowires. Their surfaces are oxidized under ambient conditions which affects the nanowire physical properties. The majority of theoretical studies of InP nanowires, however, do not take into account the oxide layer at their surfaces. In this work we use first principles molecular dynamics electronic structure calculations to study the first steps in the oxidation process of a non-saturated InP nanowire surface as well as the properties of an already oxidized surface of an InP nanowire. Our calculations show that the O 2 molecules dissociate through several mechanisms, resulting in incorporation of O atoms into the surface layers. The results confirm the experimental observation that the oxidized layers become amorphous but the non-oxidized core layers remain crystalline. Oxygen related bonds at the oxidized layers introduce defective levels at the band gap region, with greater contributions from defects involving In-O and P-O bonds.

Mid-Holocene hydrologic model of the Shingobee watershed, Minnesota

USGS Publications Warehouse

Filby, S.K.; Locke, Sharon M.; Person, M.A.; Winter, T.C.; Rosenberry, D.O.; Nieber, J.L.; Gutowski, W.J.; Ito, E.

2002-01-01

A hydrologifc model of the Shingobee Watershed in north-central Minnesota was developed to reconstruct mid-Holocene paleo-lake levels for Williams Lake, a surface-water body located in the southern portion of the watershed. Hydrologic parameters for the model were first estimated in a calibration exercise using a 9-yr historical record (1990-1998) of climatic and hydrologic stresses. The model reproduced observed temporal and spatial trends in surface/groundwater levels across the watershed. Mid-Holocene aquifer and lake levels were then reconstructed using two paleoclimatic data sets: CCM1 atmospheric general circulation model output and pollen-transfer functions using sediment core data from Williams Lake. Calculated paleo-lake levels based on pollen-derived paleoclimatic reconstructions indicated a 3.5-m drop in simulated lake levels and were in good agreement with the position of mid-Holocene beach sands observed in a Williams Lake sediment core transect. However, calculated paleolake levels based on CCM1 climate forcing produced only a 0.05-m drop in lake levels. We found that decreases in winter precipitation rather than temperature increases had the largest effect on simulated mid-Holocene lake levels. The study illustrates how watershed models can be used to critically evaluate paleoclimatic reconstructions by integrating geologic, climatic, limnologic, and hydrogeologic data sets. ?? 2002 University of Washington.

Novel Organically Modified Core-Shell Clay for Epoxy Composites-"SOBM Filler 1".

PubMed

Iheaturu, Nnamdi Chibuike; Madufor, Innocent Chimezie

2014-01-01

Preparation of a novel organically modified clay from spent oil base drilling mud (SOBM) that could serve as core-shell clay filler for polymers is herein reported. Due to the hydrophilic nature of clay, its compatibility with polymer matrix was made possible through modification of the surface of the core clay sample with 3-aminopropyltriethoxysilane (3-APTES) compound prior to its use. Fourier transform infrared (FT-IR) spectroscopy was used to characterize clay surface modification. Electron dispersive X-ray diffraction (EDX) and scanning electron microscopy (SEM) were used to expose filler chemical composition and morphology, while electrophoresis measurement was used to examine level of filler dispersion. Results show an agglomerated core clay powder after high temperature treatment, while EDX analysis shows that the organically modified clay is composed of chemical inhomogeneities, wherein elemental compositions in weight percent vary from one point to the other in a probe of two points. Micrographs of the 3-APTES coupled SOBM core-shell clay filler clearly show cloudy appearance, while FT-IR indicates 25% and 5% increases in fundamental vibrations band at 1014 cm(-1) and 1435 cm(-1), respectively. Furthermore, 3-APTES coupled core-shell clay was used to prepare epoxy composites and tested for mechanical properties.

Novel Organically Modified Core-Shell Clay for Epoxy Composites—“SOBM Filler 1”

PubMed Central

Iheaturu, Nnamdi Chibuike; Madufor, Innocent Chimezie

2014-01-01

Preparation of a novel organically modified clay from spent oil base drilling mud (SOBM) that could serve as core-shell clay filler for polymers is herein reported. Due to the hydrophilic nature of clay, its compatibility with polymer matrix was made possible through modification of the surface of the core clay sample with 3-aminopropyltriethoxysilane (3-APTES) compound prior to its use. Fourier transform infrared (FT-IR) spectroscopy was used to characterize clay surface modification. Electron dispersive X-ray diffraction (EDX) and scanning electron microscopy (SEM) were used to expose filler chemical composition and morphology, while electrophoresis measurement was used to examine level of filler dispersion. Results show an agglomerated core clay powder after high temperature treatment, while EDX analysis shows that the organically modified clay is composed of chemical inhomogeneities, wherein elemental compositions in weight percent vary from one point to the other in a probe of two points. Micrographs of the 3-APTES coupled SOBM core-shell clay filler clearly show cloudy appearance, while FT-IR indicates 25% and 5% increases in fundamental vibrations band at 1014 cm−1 and 1435 cm−1, respectively. Furthermore, 3-APTES coupled core-shell clay was used to prepare epoxy composites and tested for mechanical properties. PMID:27355022

Modified Y-TZP Core Design Improves All-ceramic Crown Reliability

PubMed Central

Silva, N.R.F.A.; Bonfante, E.A.; Rafferty, B.T.; Zavanelli, R.A.; Rekow, E.D.; Thompson, V.P.; Coelho, P.G.

2011-01-01

This study tested the hypothesis that all-ceramic core-veneer system crown reliability is improved by modification of the core design. We modeled a tooth preparation by reducing the height of proximal walls by 1.5 mm and the occlusal surface by 2.0 mm. The CAD-based tooth preparation was replicated and positioned in a dental articulator for core and veneer fabrication. Standard (0.5 mm uniform thickness) and modified (2.5 mm height lingual and proximal cervical areas) core designs were produced, followed by the application of veneer porcelain for a total thickness of 1.5 mm. The crowns were cemented to 30-day-aged composite dies and were either single-load-to-failure or step-stress-accelerated fatigue-tested. Use of level probability plots showed significantly higher reliability for the modified core design group. The fatigue fracture modes were veneer chipping not exposing the core for the standard group, and exposing the veneer core interface for the modified group. PMID:21057036

Distributions, Early Diagenesis, and Spatial Characteristics of Amino Acids in Sediments of Multi-Polluted Rivers: A Case Study in the Haihe River Basin, China.

PubMed

Zhao, Yu; Shan, Baoqing; Tang, Wenzhong; Zhang, Hong; Rong, Nan; Ding, Yuekui

2016-02-19

The Haihe River Basin, which is one of the most water-scarce and polluted river basins in China, has abnormally high nitrogen levels. In this study, total hydrolyzable amino acids (THAAs) were measured in surface sediment and sediment core samples in the Haihe River Basin to determine if amino acids were potential sources of ammonium, organic nitrogen, and organic carbon. The rivers were found to be in a state of hypoxia and contain abnormally high levels of ammonium and organic nitrogen. Additionally, NH₃-N was the predominant form of inorganic nitrogen in the surface sediments, while organic nitrogen accounted for 92.53% of sedimentary nitrogen. THAAs-C accounted for 14.92% of the total organic carbon, while THAAs-N accounted for more than 49.59% of organic nitrogen and 45.68% of total nitrogen. The major fraction of THAAs were protein amino acids. Three sediment cores of the most heavily polluted rivers also showed high levels of THAAs. Evaluation of the degradation index (DI) of sedimentary organic matter in sediments evaluated based on the THAAs revealed that most positive DI values were found in the downstream portion of the Ziya River Watershed. Additionally, the DI of surface sediment was correlated with THAAs (r² = 0.763, p < 0.001), as was the DI of sediment cores (r² = 0.773, p < 0.001). Overall, amino acids in sediments were found to be an important potential source of ammonium, organic nitrogen, and organic carbon.

Distributions, Early Diagenesis, and Spatial Characteristics of Amino Acids in Sediments of Multi-Polluted Rivers: A Case Study in the Haihe River Basin, China

PubMed Central

Zhao, Yu; Shan, Baoqing; Tang, Wenzhong; Zhang, Hong; Rong, Nan; Ding, Yuekui

2016-01-01

The Haihe River Basin, which is one of the most water-scarce and polluted river basins in China, has abnormally high nitrogen levels. In this study, total hydrolyzable amino acids (THAAs) were measured in surface sediment and sediment core samples in the Haihe River Basin to determine if amino acids were potential sources of ammonium, organic nitrogen, and organic carbon. The rivers were found to be in a state of hypoxia and contain abnormally high levels of ammonium and organic nitrogen. Additionally, NH3-N was the predominant form of inorganic nitrogen in the surface sediments, while organic nitrogen accounted for 92.53% of sedimentary nitrogen. THAAs-C accounted for 14.92% of the total organic carbon, while THAAs-N accounted for more than 49.59% of organic nitrogen and 45.68% of total nitrogen. The major fraction of THAAs were protein amino acids. Three sediment cores of the most heavily polluted rivers also showed high levels of THAAs. Evaluation of the degradation index (DI) of sedimentary organic matter in sediments evaluated based on the THAAs revealed that most positive DI values were found in the downstream portion of the Ziya River Watershed. Additionally, the DI of surface sediment was correlated with THAAs (r2 = 0.763, p < 0.001), as was the DI of sediment cores (r2 = 0.773, p < 0.001). Overall, amino acids in sediments were found to be an important potential source of ammonium, organic nitrogen, and organic carbon. PMID:26907310

Water immersion for post incident cooling of firefighters; a review of practical fire ground cooling modalities.

PubMed

Brearley, Matt; Walker, Anthony

2015-01-01

Rapidly cooling firefighters post emergency response is likely to increase the operational effectiveness of fire services during prolonged incidents. A variety of techniques have therefore been examined to return firefighters core body temperature to safe levels prior to fire scene re-entry or redeployment. The recommendation of forearm immersion (HFI) in cold water by the National Fire and Protection Association preceded implementation of this active cooling modality by a number of fire services in North America, South East Asia and Australia. The vascularity of the hands and forearms may expedite body heat removal, however, immersion of the torso, pelvis and/or lower body, otherwise known as multi-segment immersion (MSI), exposes a greater proportion of the body surface to water than HFI, potentially increasing the rates of cooling conferred. Therefore, this review sought to establish the efficacy of HFI and MSI to rapidly reduce firefighters core body temperature to safe working levels during rest periods. A total of 38 studies with 55 treatments (43 MSI, 12 HFI) were reviewed. The core body temperature cooling rates conferred by MSI were generally classified as ideal (n = 23) with a range of ~0.01 to 0.35 °C min(-1). In contrast, all HFI treatments resulted in unacceptably slow core body temperature cooling rates (~0.01 to 0.05 °C min(-1)). Based upon the extensive field of research supporting immersion of large body surface areas and comparable logistics of establishing HFI or MSI, it is recommended that fire and rescue management reassess their approach to fireground rehabilitation of responders. Specifically, we question the use of HFI to rapidly lower firefighter core body temperature during rest periods. By utilising MSI to restore firefighter Tc to safe working levels, fire and rescue services would adopt an evidence based approach to maintaining operational capability during arduous, sustained responses. While the optimal MSI protocol will be determined by the specifics of an individual response, maximising the body surface area immersed in circulated water of up to 26 °C for 15 min is likely to return firefighter Tc to safe working levels during rest periods. Utilising cooler water temperatures will expedite Tc cooling and minimise immersion duration.

The history of hexachlorobenzene accumulation in Svalbard fjords.

PubMed

Pouch, A; Zaborska, A; Pazdro, K

2018-05-24

In the present study, we investigated the spatial and historical trends of hexachlorobenzene (HCB) contamination in dated sediments of three Svalbard fjords (Kongsfjorden, Hornsund, Adventfjorden) differing in environmental conditions and human impact. HCB concentrations ranging from below limit of quantification (6.86 pg/g d.w.) to 143.99 pg/g d.w. were measured. The highest concentrations were measured in two surface sediment layers of the core collected in Hornsund near the melting glacier. The lowest concentrations of HCB were measured in Adventfjorden, suggesting that local source of HCB is not significant and global transport processes are the major transport pathways. The history of HCB deposition did not fully reflect the history of HCB emission (largest in 1950s and 1960s). In case of several sediment cores, the HCB enrichment in surface (recent) sediments was noticed. This can indicate importance of secondary sources of HCB, e.g., the influx of HCB accumulated over decades on the surface of glaciers. Detected levels of HCB were generally low and did not exceed background concentration levels; thus, a negative effect on benthic organisms is not expected.

Penetrator Coring Apparatus for Cometary Surfaces

NASA Technical Reports Server (NTRS)

Braun, David F.; Heinrich, Michael; Ai, Huirong Anita; Ahrens, Thomas J.

2004-01-01

Touch and go impact coring is an attractive technique for sampling cometary nuclei and asteroidal surface on account of the uncertain strength properties and low surface gravities of these objects. Initial coring experiments in low temperature (approx. 153K polycrystalline ice) and porous rock demonstrate that simultaneous with impact coring, measurements of both the penetration strength and constraints on the frictional properties of surface materials can be obtained upon core penetration and core sample extraction. The method of sampling an asteroid, to be deployed, on the now launched MUSES-C mission, employs a small gun device that fires into the asteroid and the resulted impact ejecta is collected for return to Earth. This technique is well suited for initial sampling in a very low gravity environment and deployment depends little on asteroid surface mechanical properties. Since both asteroids and comets are believed to have altered surface properties a simple sampling apparatus that preserves stratigraphic information, such as impact coring is an attractive alternate to impact ejecta collection.

Radionuclide activities and metal concentrations in sediments of the Sebou Estuary, NW Morocco, following a flooding event.

PubMed

Laissaoui, A; Mas, J L; Hurtado, S; Ziad, N; Villa, M; Benmansour, M

2013-06-01

This study presents metal concentrations (Fe, Mg, Mn, Co, Cu, Zn, Pb, As, Sr and V) and radionuclide activities ((40)K, (137)Cs, (210)Pb, (226)Ra, (228)Ac, (234)Th and (212)Pb) in surface deposits and a sediment core from the Sebou Estuary, Northwest Morocco. Samples were collected in April 2009, about 2 months after a flooding event, and analysed using a well-type coaxial gamma-ray detector and inductively coupled plasma-quadrupole mass spectrometry. Activities of radionuclides and concentrations of almost all elements in surface samples displayed only moderate spatial variation, suggesting homogenous deposition of eroded local soil in response to intense precipitation. Excess (210)Pb displayed relatively constant activity throughout the sediment core, preventing dating and precluding determination of the historical accumulation rates of pollutants at the core site. Some elements showed non-systematic trends with depth and displayed local maxima and minima. Other elements presented relatively systematic concentration trends or relatively constant levels with discrete maxima and/or minima. Except for Mn, Sr and Cr, all metal concentrations in sediment were below levels typical of polluted systems, suggesting little human impact or losses of metals from sediment particles.

Chemically directing d-block heterometallics to nanocrystal surfaces as molecular beacons of surface structure

DOE PAGES

Rosen, Evelyn L.; Gilmore, Keith; Sawvel, April M.; ...

2015-07-28

Our understanding of structure and bonding in nanoscale materials is incomplete without knowledge of their surface structure. Needed are better surveying capabilities responsive not only to different atoms at the surface, but also their respective coordination environments. We report here that d-block organometallics, when placed at nanocrystal surfaces through heterometallic bonds, serve as molecular beacons broadcasting local surface structure in atomic detail. This unique ability stems from their elemental specificity and the sensitivity of their d-orbital level alignment to local coordination environment, which can be assessed spectroscopically. Re-surfacing cadmium and lead chalcogenide nanocrystals with iron- or ruthenium-based molecular beacons ismore » readily accomplished with trimethylsilylated cyclopentadienyl metal carbonyls. For PbSe nanocrystals with iron-based beacons, we show how core-level X-ray spectroscopies and DFT calculations enrich our understanding of both charge and atomic reorganization at the surface when beacons are bound.« less

Correlation of reaction sites during the chlorine extraction by hydrogen atom from Cl /Si(100)-2×1

NASA Astrophysics Data System (ADS)

Hsieh, Ming-Feng; Chung, Jen-Yang; Lin, Deng-Sung; Tsay, Shiow-Fon

2007-07-01

The Cl abstraction by gas-phase H atoms from a Cl-terminated Si(100) surface was investigated by scanning tunneling microscopy (STM), high-resolution core level photoemission spectroscopy, and computer simulation. The core level measurements indicate that some additional reactions occur besides the removal of Cl. The STM images show that the Cl-extracted sites disperse randomly in the initial phase of the reaction, but form small clusters as more Cl is removed, indicating a correlation between Cl-extracted sites. These results suggest that the hot-atom process may occur during the atom-adatom collision.

Flow throughout the Earth's core inverted from geomagnetic observations and numerical dynamo models

NASA Astrophysics Data System (ADS)

Aubert, Julien

2013-02-01

This paper introduces inverse geodynamo modelling, a framework imaging flow throughout the Earth's core from observations of the geomagnetic field and its secular variation. The necessary prior information is provided by statistics from 3-D and self-consistent numerical simulations of the geodynamo. The core method is a linear estimation (or Kalman filtering) procedure, combined with standard frozen-flux core surface flow inversions in order to handle the non-linearity of the problem. The inversion scheme is successfully validated using synthetic test experiments. A set of four numerical dynamo models of increasing physical complexity and similarity to the geomagnetic field is then used to invert for flows at single epochs within the period 1970-2010, using data from the geomagnetic field models CM4 and gufm-sat-Q3. The resulting core surface flows generally provide satisfactory fits to the secular variation within the level of modelled errors, and robustly reproduce the most commonly observed patterns while additionally presenting a high degree of equatorial symmetry. The corresponding deep flows present a robust, highly columnar structure once rotational constraints are enforced to a high level in the prior models, with patterns strikingly similar to the results of quasi-geostrophic inversions. In particular, the presence of a persistent planetary scale, eccentric westward columnar gyre circling around the inner core is confirmed. The strength of the approach is to uniquely determine the trade-off between fit to the data and complexity of the solution by clearly connecting it to first principle physics; statistical deviations observed between the inverted flows and the standard model behaviour can then be used to quantitatively assess the shortcomings of the physical modelling. Such deviations include the (i) westwards and (ii) hemispherical character of the eccentric gyre. A prior model with angular momentum conservation of the core-mantle inner-core system, and gravitational coupling of reasonable strength between the mantle and the inner core, is shown to produce enough westward drift to resolve statistical deviation (i). Deviation (ii) is resolved by a prior with an hemispherical buoyancy release at the inner-core boundary, with excess buoyancy below Asia. This latter result suggests that the recently proposed inner-core translational instability presently transports the solid inner-core material westwards, opposite to the seismologically inferred long-term trend but consistently with the eccentricity of the geomagnetic dipole in recent times.

Understanding Mississippi Delta Subsidence through Stratigraphic and Geotechnical Analysis of a Continuous Holocene Core at a Subsidence Superstation

NASA Astrophysics Data System (ADS)

Bridgeman, J.; Tornqvist, T. E.; Jafari, N.; Allison, M. A.

2017-12-01

Land-surface subsidence can be a major contributor to the relative sea-level rise that is threatening coastal communities. Loosely constrained subsidence rate estimates across the Mississippi Delta make it difficult to differentiate between subsidence mechanisms and complicate modeling efforts. New data from a nearly 40 m long, 12 cm diameter core taken during the installation of a subsidence monitoring superstation near the Mississippi River, SW of New Orleans, provides insight into the stratigraphic and geotechnical properties of the Holocene succession. Stratigraphically, the core can be grouped into three sections. The top 12 m is dominated by clastic overbank sediment with interspersed organic-rich layers. The middle section, 12-35 m consists predominately of mud, and the bottom section, 35-38.7 m, is marked by a transition into a Holocene-aged basal peat (11,350-11,190 cal BP) which overlies densely packed Pleistocene sediment. Radiocarbon and OSL ages show up to 6 m of vertical displacement since 3,000 cal BP. We infer that most of this was due to compaction of the thick underlying mud package. The top ­­­­­ 70 cm of the core is a peat that represents the modern marsh surface and is inducing minimal surface loading. This is consistent with the negligible shallow subsidence rate as seen at a nearby rod-surface elevation table - marker horizon station and the initial strainmeter data. Future compaction scenarios for the superstation can be modeled from the stratigraphic and geotechnical properties of the core, including the loading from the planned Mid-Barataria sediment diversion which is expected to dramatically change the coastal landscape in this region.

Effect of core ceramic grinding on fracture behaviour of bilayered zirconia veneering ceramic systems under two loading schemes.

PubMed

Jian, Yu-Tao; Tang, Tian-Yu; Swain, Michael V; Wang, Xiao-Dong; Zhao, Ke

2016-12-01

The aim of this in vitro study was to evaluate the effect of core ceramic grinding on the fracture behaviour of bilayered zirconia under two loading schemes. Interfacial surfaces of sandblasted zirconia disks (A) were ground with 80 (B), 120 (C) and 220 (D) grit diamond discs, respectively. Surface roughness and topographic analysis were performed using a confocal scanning laser microscope (CSLM) and a scanning electron microscopy (SEM). Relative monoclinic content was evaluated using X-ray diffraction analysis (XRD) then reevaluated after simulated veneer firing. Biaxial fracture strength (σ) and Weibull modulus (m) were calculated either with core in compression (subgroup Ac-Dc) or in tension (subgroup At-Dt). Facture surfaces were examined by SEM and energy dispersive X-ray spectroscopy (EDS). Maximum tensile stress at fracture was estimated by finite element analysis. Statistical data analysis was performed using Kruskal-Wallis and one-way ANOVA at a significance level of 0.05. As grit size of the diamond disc increased, zirconia surface roughness decreased (p<0.001). Thermal veneering treatment reversed the transformation of monoclinic phase observed after initial grinding. No difference in initial (p=0.519 for subgroups Ac-Dc) and final fracture strength (p=0.699 for subgroups Ac-Dc; p=0.328 for subgroups At-Dt) was found among the four groups for both loading schemes. While coarse grinding slightly increased final fracture strength reliability (m) for subgroups Ac-Dc. Two different modes of fracture were observed according to which material was on the bottom surface. Components of the liner porcelain remained on the zirconia surface after fracture for all groups. Technician grinding changed surface topography of zirconia ceramic material, but was not detrimental to the bilayered system strength after veneer application. Coarse grinding slightly improved the fracture strength reliability of the bilayered system tested with core in compression. It is recommended that veneering porcelain be applied directly after routine lab grinding of zirconia ceramic, and its application on rough zirconia cores may be preferred to enhance bond strength. Copyright © 2016. Published by Elsevier Ltd.

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

NASA Astrophysics Data System (ADS)

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

2016-10-01

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

Non-synchronous climate change along the western margin of North America during glacial terminations

NASA Astrophysics Data System (ADS)

Herbert, T. D.; Liu, Z.; Barron, J.; Heusser, L.; Lyle, M.; Mix, A.; Ravelo, A. C.

2003-04-01

A regional set of cores now exists to study the evolution of ocean surface temperatures and other paleoclimatic signals along the west coast of North America. Core locations range from Vancouver Island to the north, to the tip of Baja California to the south. We report on the evolution of sea surface temperatures and marine productivity, as recorded by alkenones. Several sites also have pollen records, allowing us to compare marine and terrestrial responses. We find that surface climate signals covary tightly with global climate, as represented by benthic d18O, through 80% of a typical glacial-interglacial cycle. However, the associations during glacial maxima and terminations break into three regional patterns. North of Point Conception (heart of the California Current), SST patterns are very similar to benthic d18O and to Greenland ice core surface temperature data to at least 30 ka (ODP Site 1019). In the California borderland region, warmings begin during peak glacial conditions, and significantly precede the deglacial sea level rise. Off Baja California, SST follows benthic d18O, but without the high frequency oscillations of temperature observed in Greenland. These changes outline regional reorganizations of surface winds and currents during times of maximum ice volume. Our data suggests that the geographic extent and intensity of the California Current system was much reduced during glacial maxima in comparison to modern conditions.

Bond strength of the porcelain repair system to all-ceramic copings and porcelain.

PubMed

Lee, Sang J; Cheong, Chan Wook; Wright, Robert F; Chang, Brian M

2014-02-01

The purpose of this study was to investigate the shear bond strength of the porcelain repair system on alumina and zirconia core ceramics, comparing this strength with that of veneering porcelain. Veneering ceramic (n = 12), alumina core (n = 24), and zirconia core (n = 24) blocks measuring 10 × 5 × 5 mm(3) were fabricated. Veneering ceramic blocks were used as the control. Alumina and zirconia core blocks were divided into 2 groups (n = 12 each), and a slot (2 × 2 × 4 mm(3)) filled with veneering ceramics was prepared into one of the alumina and zirconia core groups (n = 12). Followed by surface treatments of micro-abrasion with 30 μm alumina particles, etching with 35% phosphoric acid and silane primer and bond, composite resin blocks (2 × 2 × 2 mm(3)) were built up and light polymerized onto the treated surfaces by 3 configurations: (a) composite blocks bonded onto veneering ceramic surface alone, (b) composite blocks bonded onto alumina core or zirconia core surfaces, (c) a 50% surface area of the composite blocks bonded to veneering ceramics and the other 50% surface area of the composite blocks to alumina core or zirconia core surfaces. The shear bond strength of the composite to each specimen was tested by a universal testing machine at a 0.5 mm/min crosshead speed. The shear bond strength was analyzed by unpaired t-tests for within the configuration groups and ANOVA for among the different configuration groups. When the mean shear bond strength was compared within groups of the same configuration, there were no statistically significant differences. Comparison of the shear bond strength among groups of different configurations revealed statistically significant differences. The mean shear bond strength of composite onto 100% veneering ceramic surface and composite onto 50% veneering 50% all-ceramic cores was statistically higher than that of composite onto 100% all-ceramic cores; however, the differences of the shear bond strength of composite bonded only onto the veneering ceramic surface were not statistically significant from those of 50% surface area of composite bonded onto all-ceramic cores. No statistically significant differences in the bond strength of a porcelain repair system to alumina and zirconia copings were observed. Increasing the surface of veneering ceramics to a porcelain repair system improved the repair material's bond strength. © 2013 by the American College of Prosthodontists.

O 1s core levels in Bi2Sr2CaCu2O8+δ single crystals

NASA Astrophysics Data System (ADS)

Parmigiani, F.; Shen, Z. X.; Mitzi, D. B.; Lindau, I.; Spicer, W. E.; Kapitulnik, A.

1991-02-01

High-quality Bi2Sr2CaCu2O8+δ superconducting single crystals, annealed at different oxygen partial pressures, have been studied using angular-resolved x-ray photoelectron spectroscopy with a resolution higher than that used in any previous study. Two states of the oxygen, separated by ~=0.7 eV, are unambiguously observed. Examining these components at different angles makes it possible to distinguish bulk from surface components. Using this capability we discover that annealing under lower oxygen partial pressure (1 atm) results in oxygen intercalation beneath the Bi-O surface layer of the crystal, whereas for higher-pressure anneals (12 atm) additional oxygen is found on the Bi-O surfaces. This steplike intercalation mechanism is also confirmed by the changes observed in the Cu and Bi core lines as a function of the annealing oxygen partial pressure.

Historical sediment record and levels of PCBs in sediments and mangroves of Jobos Bay, Puerto Rico.

PubMed

Alegria, Henry; Martinez-Colon, Michael; Birgul, Askin; Brooks, Gregg; Hanson, Lindsey; Kurt-Karakus, Perihan

2016-12-15

Polychlorinated biphenyls (PCBs) were quantified in 18 surface sediment samples, 1 sediment core, and several mangrove tissue samples collected in Jobos Bay, Puerto Rico in September 2013. Total PCBs in surface sediments ranged from 0.42 to 1232ngg -1 dw. Generally, higher levels were observed near-shore close to urban and industrial areas. The levels suggest significant pollution in Jobos Bay with respect to PCBs. Two-thirds of the sites were dominated by lighter PCB congeners (tri- to penta-chlorinated PCBs) while one-third had heavy PCB congeners (hexa- to octa-chlorinated PCBs) dominant. Total PCBs in a sediment core indicated levels fluctuating according to historical usage patterns. Total PCBs were measured in mangal leaves (14-747ngg -1 dw), roots (0.26-120ngg -1 dw), and seeds (16-93ngg -1 dw), suggesting bioaccumulation from sediments. This is the first report of a historical profile of PCBs in the study area and of PCB bioaccumulation in mangroves. This article provides new and useful information on PCBs in the Caribbean area of the GRULAC region. Copyright © 2016 Elsevier B.V. All rights reserved.

Current status and historical variations of DDT-related contaminants in the sediments of Lake Chaohu in China and their influencing factors.

PubMed

Kang, Lei; He, Qi-Shuang; He, Wei; Kong, Xiang-Zhen; Liu, Wen-Xiu; Wu, Wen-Jing; Li, Yi-Long; Lan, Xin-Yu; Xu, Fu-Liu

2016-12-01

The temporal-spatial distributions of DDT-related contaminants (DDXs), including DDT (dichlorodiphenyltrichloroethane), DDE (dichlorodiphenyldichloroethylene) and DDD (dichlorodiphenyldichloroethane), in the sediments of Lake Chaohu and their influencing factors were studied. p,p-DDE and p,p-DDD were found to be the two dominant components of DDXs in both surface and core sediments. The parent DDT compounds were still detectable in sediment cores after the late 1930s. Historical usage of technical DDT was identified as the primary source of DDXs in sediments, as indicated by DDT/(DDD + DDE) ratios of less than one. The residual levels of DDXs were higher in the surface and core sediments in the western lake area than in other lake areas, which might be due to the combined inflow effects of municipal sewage, industrial wastewater and agricultural runoff. The DDX residues in the sediment cores reached peak values in the late 1970s or early 1980s. There were significant positive relationships between DDX residues in sediment cores with annual DDT production and with fine particulate sizes (<4.5 μm). The relationship between the DDXs and TOC in sediment was complex, as indicated by the significant differences among the surface and core sediments. The algae-derived organic matter significantly influenced the amount of residue, composition and distribution of DDXs in the sediments. The DDD/DDE ratios responded well to the anaerobic conditions in the sediments that were caused by algal blooms after the late 1970s in the western lake area. This suggests that the algae-derived organic matter was an important factor and served as a biomarker of eutrophication and also affected the DDX residues and lifecycle in the lake ecosystem. Copyright © 2016 Elsevier Ltd. All rights reserved.

Temporal Change of Seismic Earth's Inner Core Phases: Inner Core Differential Rotation Or Temporal Change of Inner Core Surface?

NASA Astrophysics Data System (ADS)

Yao, J.; Tian, D.; Sun, L.; Wen, L.

2017-12-01

Since Song and Richards [1996] first reported seismic evidence for temporal change of PKIKP wave (a compressional wave refracted in the inner core) and proposed inner core differential rotation as its explanation, it has generated enormous interests in the scientific community and the public, and has motivated many studies on the implications of the inner core differential rotation. However, since Wen [2006] reported seismic evidence for temporal change of PKiKP wave (a compressional wave reflected from the inner core boundary) that requires temporal change of inner core surface, both interpretations for the temporal change of inner core phases have existed, i.e., inner core rotation and temporal change of inner core surface. In this study, we discuss the issue of the interpretation of the observed temporal changes of those inner core phases and conclude that inner core differential rotation is not only not required but also in contradiction with three lines of seismic evidence from global repeating earthquakes. Firstly, inner core differential rotation provides an implausible explanation for a disappearing inner core scatterer between a doublet in South Sandwich Islands (SSI), which is located to be beneath northern Brazil based on PKIKP and PKiKP coda waves of the earlier event of the doublet. Secondly, temporal change of PKIKP and its coda waves among a cluster in SSI is inconsistent with the interpretation of inner core differential rotation, with one set of the data requiring inner core rotation and the other requiring non-rotation. Thirdly, it's not reasonable to invoke inner core differential rotation to explain travel time change of PKiKP waves in a very small time scale (several months), which is observed for repeating earthquakes in Middle America subduction zone. On the other hand, temporal change of inner core surface could provide a consistent explanation for all the observed temporal changes of PKIKP and PKiKP and their coda waves. We conclude that the observed temporal changes of the inner core phases are caused by temporal changes of inner core surface. The temporal changes of inner core surface are found to occur in some localized regions within a short time scale (years to months), a phenomenon that should provide important clues to a potentially fundamental change of our understanding of core dynamics.

NUCLEAR REACTOR CORE

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

Preece, G.E.; Bell, F.R.; Page, R.W.

1963-03-01

A nuclear reactor core is described. It contains fuel in the form of blocks or pellets that have a grooved, wrinkled, or corrugated surface to provide a greater radiating surface area. The surfaces of spaces in the core are correspondingly corrugated for maximum heat exchange area. (C.E.S.)

Surface studies of novel oxide-free biocompatible coatings on metals

NASA Astrophysics Data System (ADS)

GAO, FENG

The valence band and core-level X-ray Photoelectron Spectroscopy (XPS) was used to probe biocompatible films formed on the surface of metals. The key to the successful adhesion of these biocompatible films is shown to be the initial formation of a thin, oxide free, etidronate film on the metal. It was not found possible to prepare the biocompatible films directly on the metal surfaces. These films formed on metals may find application in medical implants. The biocompatible films were exposed to air, water and sodium chloride for corrosion studies. The thin hydroxyapatite and etidronate film on the metal show differential charging effects that caused a doubling of the peaks in some core level spectra. This shows the coating has some electric properties such as dielectric or piezoelectric characters. This coating may have application in the insulating materials of electronic circuits or dielectric/ piezoelectric layer in bio-sensors. Experiment and calculation method of X-ray Photoelectron Spectroscopy is one powerful technology in surface and interface analysis. The valence band spectra proved especially valuable in the identification of the surface chemistry of the films, and these spectra were interpreted by comparing the experimental spectra with spectra calculated using band structure calculations which showed good agreement with experiment. The calculated spectrum could also be used to compare with the difference of experiment spectra for the investigation of the interface layers.

Near Edge X-Ray Absorption and X-Ray Photoelectron Diffraction Studies of the Structural Environment of Ge-Si Systems

NASA Astrophysics Data System (ADS)

Castrucci, P.; Gunnella, R.; Pinto, N.; Bernardini, R.; de Crescenzi, M.; Sacchi, M.

Near edge X-ray absorption spectroscopy (XAS), X-ray photoelectron diffraction (XPD) and Auger electron diffraction (AED) are powerful techniques for the qualitative study of the structural and electronic properties of several systems. The recent development of a multiple scattering approach to simulating experimental spectra opened a friendly way to the study of structural environments of solids and surfaces. This article reviews recent X-ray absorption experiments using synchrotron radiation which were performed at Ge L edges and core level electron diffraction measurements obtained using a traditional X-ray source from Ge core levels for ultrathin Ge films deposited on silicon substrates. Thermodynamics and surface reconstruction have been found to play a crucial role in the first stages of Ge growth on Si(001) and Si(111) surfaces. Both techniques show the occurrence of intermixing processes even for room-temperature-grown Ge/Si(001) samples and give a straightforward measurement of the overlayer tetragonal distortion. The effects of Sb as a surfactant on the Ge/Si(001) interface have also been investigated. In this case, evidence of layer-by-layer growth of the fully strained Ge overlayer with a reduced intermixing is obtained when one monolayer of Sb is predeposited on the surface.

Current status and historical trends of organochlorine pesticides in the ecosystem of Deep Bay, South China

NASA Astrophysics Data System (ADS)

Qiu, Yao-Wen; Zhang, Gan; Guo, Ling-Li; Cheng, Hai-Rong; Wang, Wen-Xiong; Li, Xiang-Dong; Wai, Onyx W. H.

2009-11-01

To characterize the current status and historical trends in organochlorine pesticides (OCPs) contamination in Deep Bay, an important water body between Hong Kong and mainland China with a Ramsar mangrove wetland (Maipo), samples from seawater, suspended particulate matter (SPM), surface sediment, sediment core and fish were collected to determine the OCPs concentrations. Sediment core dating was accomplished using the 210Pb method. The average concentrations of DDTs, HCHs and chlordanes in water were 1.96, 0.71, 0.81 ng l -1, while in SPM were 36.5, 2.5, 35.7 ng g -1 dry weight, in surface sediment were 20.2, 0.50, 2.4 ng g -1 dry weight, and in fish were 125.4, 0.43, 13.1 ng g -1 wet weight, respectively. DDTs concentrations in various matrices of Deep Bay were intermediate compared with those in other areas. Temporal trends of the targeted OCPs levels in sediment core generally increased from 1948 to 2004, with the highest levels in top or sub-surface sediment. Both DDT composition and historical trends indicated an ongoing fresh DDT input. A positive relationship between the bioconcentration factor (BCF) of target chemicals and the corresponding octanol-water partition coefficient ( Kow), and between the biota-sediment accumulation factors (BSAF) and the Kow were observed in the Bay. The risk assessment indicated that there were potential ecological and human health risks for the target OCPs in Deep Bay.

Heterotopic bone formation around sintered porous-surfaced Ti-6Al-4V implants coated with native bone morphogenetic proteins.

PubMed

Simon, Ziv; Deporter, Douglas A; Pilliar, Robert M; Clokie, Cameron M

2006-09-01

Coating endosseous dental implants with growth factors such as bone morphogenetic proteins (BMPs) may be one way to accelerate and/or enhance the quality of osseointegration. The purpose of this study was to investigate in the murine muscle pouch model whether sintered porous-surfaced titanium alloy implants coated with BMPs would lead to heterotopic bone formation around and within the implant surface geometry. Porous-surfaced dental implants were coated with partially purified native human BMPs, with or without a carrier of Poloxamer 407 (BASF Corp., Parsippany, NJ), placed in gelatin capsules and implanted into the hindquarter muscles of mice. Mice were euthanized after 28 days. Sections of retrieved specimens were subsequently prepared for morphometric analysis of bone formation using backscatter electron microscopic images. Human BMPs, either with or without the carrier of Poloxamer 407, led to bone formation within and outside of the sintered porous implant surface. When the sintered implant surface region was subdivided into inner and outer halves, similar levels of bone ingrowth and contact were seen in the 2 halves. Evidence of bone formation to the depth of the solid implant core (i.e., the deepest level possible) also was seen. Sintered porous-surfaced dental implants can be used as substrate for partially purified BMPs in the murine muscle pouch model. With the addition of these osteoinductive factors, the porous implant surface supported bone formation within the surface porosity provided, in some instances, all the way to the solid implant core. The addition of growth factors to a sintered porous surface may be an efficient method for altering locally the healing sequence and quality of bone associated with osseointegration of bone-interfacing implants.

Surface Melt and Firn Density Evolution in the Western Greenland Percolation Zone Over the Past 50 Years

NASA Astrophysics Data System (ADS)

Graeter, K.; Osterberg, E. C.; Hawley, R. L.; Thundercloud, Z. R.; Marshall, H. P.; Ferris, D. G.; Lewis, G.

2016-12-01

Predictions of the Greenland Ice Sheet's (GIS) contribution to sea-level rise in a warming climate depend on our ability to model the surface mass balance (SMB) processes occurring across the ice sheet. These processes are poorly constrained in the percolation zone, the region of the ice sheet where surface melt refreezes in the firn, thus preventing that melt from directly contributing to GIS mass loss. In this way, the percolation zone serves as a buffer to higher temperatures increasing mass loss. However, it is unknown how the percolation zone is evolving in a changing climate and to what extent the region will continue to serve as a buffer to future runoff. We collected seven shallow ( 22-30 m) firn cores from the Western Greenland percolation zone in May-June 2016 as part of the Greenland Traverse for Accumulation and Climate Studies (GreenTrACS) project. Here we present data on melt layer stratigraphy, density, and annual accumulation for each core to determine: (1) the temporal and spatial accumulation and melt refreeze patterns in the percolation zone of W. Greenland over the past 40 - 55 years, and (2) the impacts of changing melt and refreeze patterns on the near-surface density profile of the percolation zone. Three of the GreenTrACS firn cores re-occupy firn core sites collected in the 1970's-1990's, allowing us to more accurately quantify the evolution of the percolation zone surface melt and firn density during the most recent decades of summertime warming. This work is the basis for broader investigations into how changes in W. Greenland summertime climate are impacting the SMB of the Greenland Ice Sheet.

Distribution of selenium, molybdenum and uranium in sediment cores from the Colorado River delta, Baja California, Mexico.

PubMed

Orozco-Durán, A; Daesslé, L W; Gutiérrez-Galindo, E A; Muñoz-Barbosa, A

2012-01-01

The distribution of selenium, molybdenum and uranium was studied in ~1.5 m sediment cores from the Colorado River delta, at the Colorado (CR) and Hardy (HR) riverbeds. Core HR2 showed highest Se, Mo and U concentrations at its bottom (2.3, 0.95 and 1.8 μg g(-1)) within a sandy-silt layer deposited prior to dam construction. In CR5 the highest concentrations of these elements (0.9, 1.4 and 1.7 μg g(-1) respectively) were located at the top of the core within a surface layer enriched in organic carbon. A few samples from HR2 had Se above the probable toxic effect level guidelines.

δ18O and Carbonate Clumped Isotopes as Proxies of Lake Level Change: Mono Lake Modern Sediments Inform Pleistocene Interpretations

NASA Astrophysics Data System (ADS)

Westacott, S.; Ingalls, M.; Meixnerova, J.; Betts, M.; Lloyd, M. K.; Miller, L. G.; Sessions, A. L.; Trower, L.; Geobiology Course, A.

2017-12-01

In 1941 LA County began diverting water from the Mono Lake basin, causing lake level to fall dramatically until 1994 when diversion was substantially discontinued. High sedimentation rate (0.7 cm/yr) in combination with rapid, well-documented environmental change offers a unique opportunity to investigate the isotopic fingerprint of lake level change at a much finer scale than is typically accessible in the geologic record. δ18Ocarb can record lake level in a closed-basin system, but relies on knowing the relative contributions from carbonate precipitated from lake water and from authigenic carbonates, both of which are expected to exist in alkaline lake sediments. Here, we combine δ18Ocarb with clumped isotope thermometry (T(Δ47)) on a 70 cm sediment core to "unmix" the carbonate sources and reconstruct δ18Owater of Mono Lake over the past 116 years. Carbonate from the upper 10 cm of the sediment core yields a T(Δ47) of 26°C, reflecting surface water carbonate precipitation during late summer. Carbonates from sediment depths greater than 10cm yield a consistent T(Δ47) of 9.6°C, warmer than today's bottom waters, suggesting dissolution and reprecipitation of originally "warm" carbonate deposited from the water column alongside "cold" water of a different δ18Ow than Mono Lake surface water. A clumped isotope mixing model (Defliese & Lohmann, 2015) used to calculate the relative contributions of the two carbonate precipitates, corroborated by mirrored shifts in δ13Corg and δ13Ccarb down-core, suggests that about half of the carbonate found in the lower 60 cm of the sediment core is authigenic. As an example of how this strategy can be applied to older strata with looser constraints on primary composition, we also analysed the Pleistocene Wilson Creek Formation—lake sediments from Mono Lake's predecessor, Lake Russell. Although Pleistocene Lake Russell should have been cooler than modern Mono Lake, T(Δ47) values were similar to those of modern sediments, suggesting that potentially more of Lake Russell carbonates formed at or near the surface. Clumped isotope analysis thus holds significant potential to improve our interpretation of sedimentary carbonates as proxies for lake level and other paleo-environmental conditions.

Foam Core Particleboards with Intumescent FRT Veneer: Cone Calorimeter Testing With Varying Adhesives, Surface Layer Thicknesses, and Processing Conditions

Treesearch

Mark A. Dietenberger; Johannes Welling; Ali Shalbafan

2014-01-01

Intumescent FRT Veneers adhered to the surface of foam core particleboard to provide adequate fire protection were evaluated by means of cone calorimeter tests (ASTM E1354). The foam core particleboards were prepared with variations in surface layer treatment, adhesives, surface layer thicknesses, and processing conditions. Ignitability, heat release rate profile, peak...

Coastal landscape evolution on the western margin of the Bahía Blanca Estuary (Argentina) mirrors a non-uniform sea-level fall after the mid-Holocene highstand

NASA Astrophysics Data System (ADS)

Pratolongo, Paula; Piovan, María Julia; Cuadrado, Diana G.; Gómez, Eduardo A.

2017-08-01

Sedimentary descriptions and radiocarbon ages from two cores obtained from coastal plains along the western margin of the Bahía Blanca Estuary (Argentina) were integrated with previous information on landscape patterns and plant associations to infer landscape evolution during the mid-to-late Holocene. The study area comprises at least two marine terraces of different elevations. The old marine plain (OMP), at an average elevation of 5 m above mean tidal level (MTL), is a nearly continuous flat surface. The Recent marine plain (RMP), 2 to 3 m above MTL, is a mosaic of topographic highs and elongated depressions that may correspond to former tidal channels. Mollusks at the base of the OMP core (site elevation 5.09 m above MTL), with ages between 5,660 ± 30 and 5,470 ± 30 years BP, indicate a subtidal setting near the inland limits of the marine ingression. The sandy bottom of the core is interpreted as the last stage of the transgressive phase, followed by a tight sequence of dark laminated muds topped by a thick layer of massive gray muds. The RMP core (site elevation 1.80 m above MTL) has a similar sedimentary sequence, but unconformities appear at lower elevations and the massive mud deposits are less developed. The thickness of the grayish mud layer is a major difference between the OMP and RMP cores, but deeper layers have similar ages, suggesting a common origin at the end of the transgressive phase. The overlying massive muds would correspond to rapid sedimentation during a high sea-level stillstand or slow regression. It is proposed that, after a rapid sea-level drop to about 3 m above MTL, a flat and continuous surface corresponding to the OMP emerged, and more recent coastal dynamics shaped the dissected landscape of the RMP. For the Bahía Blanca Estuary, smooth regressive trends have been proposed after the mid-Holocene highstand, but also stepped curves. A stillstand or slowly dropping sea level was described around 3,850 ± 100 years BP, as well as negative relative sea-level oscillations. In this study, the differentiation between the OMP and the RMP supports the occurrence of a stepped regressive trend that, at least locally, presented two different stages.

High performance of PbSe/PbS core/shell quantum dot heterojunction solar cells: short circuit current enhancement without the loss of open circuit voltage by shell thickness control.

PubMed

Choi, Hyekyoung; Song, Jung Hoon; Jang, Jihoon; Mai, Xuan Dung; Kim, Sungwoo; Jeong, Sohee

2015-11-07

We fabricated heterojunction solar cells with PbSe/PbS core shell quantum dots and studied the precisely controlled PbS shell thickness dependency in terms of optical properties, electronic structure, and solar cell performances. When the PbS shell thickness increases, the short circuit current density (JSC) increases from 6.4 to 11.8 mA cm(-2) and the fill factor (FF) enhances from 30 to 49% while the open circuit voltage (VOC) remains unchanged at 0.46 V even with the decreased effective band gap. We found that the Fermi level and the valence band maximum level remain unchanged in both the PbSe core and PbSe/PbS core/shell with a less than 1 nm thick PbS shell as probed via ultraviolet photoelectron spectroscopy (UPS). The PbS shell reduces their surface trap density as confirmed by relative quantum yield measurements. Consequently, PbS shell formation on the PbSe core mitigates the trade-off relationship between the open circuit voltage and the short circuit current density. Finally, under the optimized conditions, the PbSe core with a 0.9 nm thick shell yielded a power conversion efficiency of 6.5% under AM 1.5.

The Shape of Enceladus' Core: Predictions for Degree-2 Nonhydrostatic Gravity, and Role in Survival of the Subsurface Ocean

NASA Astrophysics Data System (ADS)

McKinnon, W. B.

2011-10-01

The global shape of Enceladus is not consistent with a simultaneously hydrostatic and fully differentiated body, but hypotheses that Enceladus is either undifferentiated or preserves a globally unrelaxed figure from an earlier position closer to Saturn are implausible. Enceladus' geophysical activity (and surface) is best understood in the context of a differentiated (rock separated from ice) interior. Topographic profiles indicate that Enceladus' surface conforms to a triaxial shape, consistent with relaxation to a global geoid. Enceladus' rocky core need not be hydrostatic, however. A modestly "lumpy" core, either in terms of topography or density, and dynamically aligned, will act to enhance the global geoid. Explaining the global shape of Enceladus requires ~12 km of excess core polar ellipticity and ~5 km of excess core equatorial ellipticity, for a uniform density core. The stresses in Enceladus' core associated with this modest level of dynamically excess topography can be sustained indefinitely. Enceladus' icy shell should be isostatic with respect to the satellite's degree-2 gravity, but because the rocky core is not hydrostatic, Enceladus' degree-2 gravity coefficients J2 and C22 should not conform to the hydrostatic ratio of 10/3. The moments-of-inertia implied also indicate that Enceladus could be near a low-order spin-orbit librational resonance, and thus tidal heating associated with this resonance type could have contributed to the moon's phenomenal heat flow. Finally, the core c-axis will be depressed by some 8 km with respect to a hydrostatic shape. This true topographic variation can help preserve polar ocean remnants against freezing (and grounding elsewhere) during epochs of low tidal heating.

Sprayed skin turbine component

DOEpatents

Allen, David B

2013-06-04

Fabricating a turbine component (50) by casting a core structure (30), forming an array of pits (24) in an outer surface (32) of the core structure, depositing a transient liquid phase (TLP) material (40) on the outer surface of the core structure, the TLP containing a melting-point depressant, depositing a skin (42) on the outer surface of the core structure over the TLP material, and heating the assembly, thus forming both a diffusion bond and a mechanical interlock between the skin and the core structure. The heating diffuses the melting-point depressant away from the interface. Subsurface cooling channels (35) may be formed by forming grooves (34) in the outer surface of the core structure, filling the grooves with a fugitive filler (36), depositing and bonding the skin (42), then removing the fugitive material.

Unconventional secretory processing diversifies neuronal ion channel properties

PubMed Central

Hanus, Cyril; Geptin, Helene; Tushev, Georgi; Garg, Sakshi; Alvarez-Castelao, Beatriz; Sambandan, Sivakumar; Kochen, Lisa; Hafner, Anne-Sophie; Langer, Julian D; Schuman, Erin M

2016-01-01

N-glycosylation – the sequential addition of complex sugars to adhesion proteins, neurotransmitter receptors, ion channels and secreted trophic factors as they progress through the endoplasmic reticulum and the Golgi apparatus – is one of the most frequent protein modifications. In mammals, most organ-specific N-glycosylation events occur in the brain. Yet, little is known about the nature, function and regulation of N-glycosylation in neurons. Using imaging, quantitative immunoblotting and mass spectrometry, we show that hundreds of neuronal surface membrane proteins are core-glycosylated, resulting in the neuronal membrane displaying surprisingly high levels of glycosylation profiles that are classically associated with immature intracellular proteins. We report that while N-glycosylation is generally required for dendritic development and glutamate receptor surface expression, core-glycosylated proteins are sufficient to sustain these processes, and are thus functional. This atypical glycosylation of surface neuronal proteins can be attributed to a bypass or a hypo-function of the Golgi apparatus. Core-glycosylation is regulated by synaptic activity, modulates synaptic signaling and accelerates the turnover of GluA2-containing glutamate receptors, revealing a novel mechanism that controls the composition and sensing properties of the neuronal membrane. DOI: http://dx.doi.org/10.7554/eLife.20609.001 PMID:27677849

A last glacial and deglacial pollen record from the northern South China Sea: New insight into coastal-shelf paleoenvironment

NASA Astrophysics Data System (ADS)

Yu, Shaohua; Zheng, Zhuo; Chen, Fang; Jing, Xia; Kershaw, Peter; Moss, Patrick; Peng, Xuechao; Zhang, Xin; Chen, Chixin; Zhou, Yang; Huang, Kangyou; Gan, Huayang

2017-02-01

This study presents a marine palynological record of the Asian summer monsoon and sea level change in the Last Glacial Maximum (LGM) and the deglacial period in the northern South China Sea (SCS). A fossil core STD 235 (855 cm in length) and 273 surface sediment samples from the northern SCS were pollen analysed to reconstruct the paleoenvironment of the continental shelf during the last glacial period. Results from fossil pollen show that the main pollen source region fundamentally changed from the LGM to the deglacial period as sea level rapidly rose. The modern marine surface samples show that pollen concentrations in the estuary of the Pearl River are extremely high, and modern pollen assemblages are in good agreement with the regional vegetation. However, wind transport becomes more important in the deeper ocean as the percentages of Pinus, a taxon with very high pollen production and dispersal capacity, is highest in these sediments, which otherwise have very low pollen concentrations. The concentration of total pollen between surface and fossil pollen samples is compared in order to determine the possible vegetation sources areas for the marine core. Pollen concentration as high as >100 grains/g at the LGM suggested that the paleo-shoreline was located within 80 km of the core. Consequently, pollen would mostly have derived from the exposed continental shelf in the northern SCS. By contrast, pollen concentrations were very low due to a much greater transport distance (318 km at present, core STD 235) under higher sea levels, and windblown pollen played a more important role because of the limitation of riverine input into the deep ocean during this highstand period. Such alternation of pollen flux and source distance should be repeated during all glacial-interglacial cycles, reflecting closely sea level and climate dynamics. According to fossil pollen assemblages from Core STD 235, we conclude that wetland and/or grassland communities with sparse subtropical trees dominated most of the exposed shelf during the LGM rather than forest that characterizes the region today. The existence of a predominantly open landscape on the exposed continental shelf suggests lower precipitation during the LGM, which in turn indicates a weaker Asian summer monsoon. This finding is supported by other records from the Okinawa Trough and the East China Sea, suggesting that a weaker summer monsoon was a key characteristic of the LGM in East Asia.

Systematic vertical and lateral changes in quality and time resolution of the macrofossil record: insights from Holocene transgressive deposits, Po coastal plain, Italy

NASA Astrophysics Data System (ADS)

Azzarone, Michele; Scarponi, Daniele; Kusnerik, Kristopher; Amorosi, Alessandro; Bohacs, Kevin M.; Drexler, Tina M.; Kowalewski, Michał

2017-04-01

In siliciclastic marine settings, skeletal concentrations are a characteristic feature of transgressive intervals that provide insights into paleobiology and sequence stratigraphy. To investigate taphonomic signatures of transgressive intervals, we analyzed three cores from a Holocene depositional profile of the Po coastal plain, in northern Italy. Coupled multivariate taphonomic and bathymetric trends delineate spatial and temporal gradients in sediment starvation/bypassing, suggesting that quality and resolution of the fossil record vary predictably along the studied depositional profile. Moreover, joint consideration of taphonomic, bathymetric, and fossil density trends across the study area reveals distinctive signatures that are useful in characterizing facies associations and recognizing surfaces and intervals of sequence stratigraphic significance. Within the southern Po plain succession, taphonomic degradation of macroskeletal remains increases from proximal—nearshore to distal—offshore locations. This trend is discernible for both biologically-driven (bioerosion) and chemically/physically-driven (e.g., dissolution, abrasion) shell alterations. Compared to the up-dip (most proximal) core, the down-dip core is distinguished by shell-rich lithosomes affected by ecological condensation (co-occurrence of environmentally non-overlapping taxa) and by higher taphonomic alteration. The onshore-offshore taphonomic trend likely reflects variation in sediment-supply along the depositional profile of the Holocene Northern Adriatic shelf, with surface/near-surface residence-time of macroskeletal remains increasing down dip due to lower accumulation rates. These results indicate that, during transgressive phases, changes in sea-level (base level) are likely to produce down-dip taphonomic gradients across shelves, where the quality and resolution of the fossil record both deteriorate distally. The amino acid radiometrically calibrated dates on bivalves and the chronostratigraphic framework for this profile suggest that the high levels of taphonomic degradation observed distally developed over millennial time scales ( 8ky). The patterns documented here may be characteristic of siliciclastic-dominated depositional systems that experience high-frequency, base-level fluctuations.

Role of Surface Charge Density in Nanoparticle-templated Assembly of Bromovirus Protein Cages

PubMed Central

Daniel, Marie-Christine; Tsvetkova, Irina B.; Quinkert, Zachary T.; Murali, Ayaluru; De, Mrinmoy; Rotello, Vincent M.; Kao, C. Cheng; Dragnea, Bogdan

2010-01-01

Self-assembling icosahedral protein cages have potencially useful physical and chemical characteristics for a variety of nanotechnology applications, ranging from therapeutic or diagnostic vectors to building blocks for hierarchical materials. For application-specific functional control of protein cage assemblies, a deeper understanding of the interaction between the protein cage and its payload is necessary. Protein-cage encapsulated nanoparticles, with their well-defined surface chemistry, allow for systematic control over key parameters of encapsulation such as the surface charge, hydrophobicity, and size. Independent control over these variables allows experimental testing of different assembly mechanism models. Previous studies done with Brome mosaic virus capsids and negatively-charged gold nanoparticles indicated that the result of the self-assembly process depends on the diameter of the particle. However, in these experiments, the surface-ligand density was maintained at saturation levels, while the total charge and the radius of curvature remained coupled variables, making the interpretation of the observed dependence on the core size difficult. The current work furnishes evidence of a critical surface charge density for assembly through an analysis aimed at decoupling the surface charge the core size. PMID:20575505

Osteocyte viability and regulation of osteoblast function in a 3D trabecular bone explant under dynamic hydrostatic pressure.

PubMed

Takai, Erica; Mauck, Robert L; Hung, Clark T; Guo, X Edward

2004-09-01

A new trabecular bone explant model was used to examine osteocyte-osteoblast interactions under DHP loading. DHP loading enhanced osteocyte viability as well as osteoblast function measured by osteoid formation. However, live osteocytes were necessary for osteoblasts to form osteoids in response to DHP, which directly show osteoblast-osteocyte interactions in this in vitro culture. A trabecular bone explant model was characterized and used to examine the effect of osteocyte and osteoblast interactions and dynamic hydrostatic pressure (DHP) loading on osteocyte viability and osteoblast function in long-term culture. Trabecular bone cores obtained from metacarpals of calves were cleaned of bone marrow and trabecular surface cells and divided into six groups, (1) live cores + dynamic hydrostatic pressure (DHP), (2) live cores + sham, (3) live cores + osteoblast + DHP, (4) live cores + osteoblast + sham, (5) devitalized cores + osteoblast + DHP, and (6) devitalized cores + osteoblast + sham, with four culture durations (2, 8, 15, and 22 days; n = 4/group). Cores from groups 3-6 were seeded with osteoblasts, and cores from groups 5 and 6 were devitalized before seeding. Groups 1, 3, and 5 were subjected to daily DHP loading. Bone histomorphometry was performed to quantify osteocyte viability based on morphology and to assess osteoblast function based on osteoid surface per bone surface (Os/Bs). TUNEL staining was performed to evaluate the mode of osteocyte death under various conditions. A portion of osteocytes remained viable for the duration of culture. DHP loading significantly enhanced osteocyte viability up to day 8, whereas the presence of seeded osteoblasts significantly decreased osteocyte viability. Cores with live osteocytes showed higher Os/Bs compared with devitalized cores, which reached significant levels over a greater range of time-points when combined with DHP loading. DHP loading did not increase Os/Bs in the absence of live osteocytes. The percentage of apoptotic cells remained the same regardless of treatment or culture duration. Enhanced osteocyte viability with DHP suggests the necessity of mechanical stimulation for osteocyte survival in vitro. Furthermore, osteocytes play a critical role in the transmission of signals from DHP loading to modulate osteoblast function. This explant culture model may be used for mechanotransduction studies in long-term cultures.

Cone Calorimeter Analysis of FRT Intumescent and Untreated Foam Core Particleboards

Treesearch

Mark A. Dietenberger; Ali Shalbafan; Johannes Welling; Charles Boardman

2012-01-01

The effectiveness of treatments of the surface layer of novel foam core particleboards were evaluated by means of Cone calorimeter tests. Foam core particleboards with variations of surface layer treatment, adhesives and surface layer thicknesses under similar processing conditions were used to produce the test specimen for the Cone calorimeter tests. Ignitability,...

IMPACT OF OIL PRODUCTION RELEASES ON SOME SOIL CHEMICAL PROPERTIES AT THE OSPER SITES

EPA Science Inventory

Surface and soil core samples were collected at two field sites in an old oil production area near Skiatook Lake in Oklahoma. The soil samples were analyzed for nitrates, organic matter, total petroleum hydrocarbons, conductivity, chlorides and dehydrogenase activity. Low level...

Controlling the surface photovoltage on WSe2 by surface chemical modification

NASA Astrophysics Data System (ADS)

Liu, Ro-Ya; Ozawa, Kenichi; Terashima, Naoya; Natsui, Yuto; Feng, Baojie; Ito, Suguru; Chen, Wei-Chuan; Cheng, Cheng-Maw; Yamamoto, Susumu; Kato, Hiroo; Chiang, Tai-Chang; Matsuda, Iwao

2018-05-01

The surface photovoltage (SPV) effect is key to the development of opto-electronic devices such as solar-cells and photo-detectors. For the prototypical transition metal dichalcogenide WSe2, core level and valence band photoemission measurements show that the surface band bending of pristine cleaved surfaces can be readily modified by adsorption with K (an electron donor) or C60 (an electron acceptor). Time-resolved pump-probe photoemission measurements reveal that the SPV for pristine cleaved surfaces is enhanced by K adsorption, but suppressed by C60 adsorption, and yet the SPV relaxation time is substantially shortened in both cases. Evidently, adsorbate-induced electronic states act as electron-hole recombination centers that shorten the carrier lifetime.

Hydrogen bonding in malonaldehyde: a density functional and reparametrized semiempirical approach

NASA Astrophysics Data System (ADS)

Kovačević, Goran; Hrenar, Tomica; Došlić, Nadja

2003-08-01

Intramolecular proton transfer in malonaldehyde (MA) has been investigated by density functional theory (DFT). The DFT results were used for the construction of a high quality semiempirical potential energy surface with a reparametrized PM3 Hamiltonian. A two-step reparameterization procedure is proposed in which (i) the PM3-MAIS core-core functions for the O-H and H-H interactions were used and a new functional form for the O-O correction function was proposed and (ii) a set of specific reaction parameters (SRP) has been obtained via genetic algorithm optimization. The quality of the reparametrized semiempirical potential energy surfaces was tested by calculating the tunneling splitting of vibrational levels and the anharmonic vibrational frequencies of the system. The applicability to multi-dimensional dynamics in large molecular systems is discussed.

Zirconium(IV) oxide: New coating material for nanoresonators for shell-isolated nanoparticle-enhanced Raman spectroscopy

NASA Astrophysics Data System (ADS)

Krajczewski, Jan; Abdulrahman, Heman Burhanalden; Kołątaj, Karol; Kudelski, Andrzej

2018-03-01

One tool that can be used for determining the structure and composition of surfaces of various materials (even in in situ conditions) is shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS). In SHINERS measurements, the surface under investigation is covered with a layer of surface-protected plasmonic nanoparticles, and then the Raman spectrum of the surface analysed is recorded. The plasmonic cores of the used core-shell structures act as electromagnetic nanoresonators, significantly locally enhancing the intensity of the electric field of the incident radiation, leading to a large increase in the efficiency of the generation of the Raman signal from molecules in the close proximity to the deposited SHINERS nanoresonators. A protective layer (from transparent dielectrics such as SiO2, Al2O3 or TiO2) prevents direct interaction between the plasmonic metal and the analysed surface (such interactions may lead to changes in the structure of the surface) and, in the case of plasmonic cores other than gold cores, the dielectric layer increases the chemical stability of the metal core. In this contribution, we show for the first time that core-shell nanoparticles having a silver core (both a solid and hollow one) and a shell of zirconium(IV) oxide are very efficient SHINERS nanoresonators that are significantly more stable in acidic and alkaline media than the silver-silica core-shell structures typically used for SHINERS experiments.

Vertical velocity in oceanic convection off tropical Australia

NASA Technical Reports Server (NTRS)

Lucas, Christopher; Zipser, Edward J.; Lemone, Margaret A.

1994-01-01

Time series of 1-Hz vertical velocity data collected during aircraft penetrations of oceanic cumulonimbus clouds over the western Pacific warm pool as part of the Equatorial Mesoscale Experiment (EMEX) are analyzed for updraft and downdraft events called cores. An updraft core is defined as occurring whenever the vertical velocity exceeds 1 m/sec for at least 500 m. A downdraft core is defined analogously. Over 19,000 km of straight and level flight legs are used in the analysis. Five hundred eleven updraft cores and 253 downdraft cores are included in the dataset. Core properties are summarized as distributions of average and maximum vertical velocity, diameter, and mass flux in four altitude intervals between 0.2 and 5.8 km. Distributions are approximately lognormal at all levels. Examination of the variation of the statistics with height suggests a maximum in vertical velocity between 2 and 3 km; slightly lower or equal vertical velocity is indicated at 5 km. Near the freezing level, virtual temperature deviations are found to be slightly positive for both updraft and downdraft cores. The excess in updraft cores is much smaller than that predicted by parcel theory. Comparisons with other studies that use the same analysis technique reveal that EMEX cores have approximately the same strength as cores of other oceanic areas, despite warmer sea surface temperatures. Diameter and mass flux are greater than those in the Global Atmospheric Research Program (GATE) but smaller than those in hurricane rainbands. Oceanic cores are much weaker and appear to be slightly smaller than those observed over land during the Thunderstorm Project. The markedly weaker oceanic vertical velocities below 5.8 km (compared to the continental cores) cannot be attributed to smaller total convective available potential energy or to very high water loading. Rather, it is suggested that water loading, although less than adiabatic, is more effective in reducing buoyancy of oceanic cores because of the smaller potential buoyancy below 5.8 km. Entrainment appears to be more effective in reducing buoyancy to well below adiabatic values in oceanic cores, a result consistent with the smaller oceanic core diameters in the lower cloud layer. It is speculated further that core diameters are related to boundary layer depth, which is clearly smaller over the oceans.

Gold core@silver semishell Janus nanoparticles prepared by interfacial etching

NASA Astrophysics Data System (ADS)

Chen, Limei; Deming, Christopher P.; Peng, Yi; Hu, Peiguang; Stofan, Jake; Chen, Shaowei

2016-07-01

Gold core@silver semishell Janus nanoparticles were prepared by chemical etching of Au@Ag core-shell nanoparticles at the air/water interface. Au@Ag core-shell nanoparticles were synthesized by chemical deposition of a silver shell onto gold seed colloids followed by the self-assembly of 1-dodecanethiol onto the nanoparticle surface. The nanoparticles then formed a monolayer on the water surface of a Langmuir-Blodgett trough, and part of the silver shell was selectively etched away by the mixture of hydrogen peroxide and ammonia in the water subphase, where the etching was limited to the side of the nanoparticles that was in direct contact with water. The resulting Janus nanoparticles exhibited an asymmetrical distribution of silver on the surface of the gold cores, as manifested in transmission electron microscopy, UV-vis absorption, and X-ray photoelectron spectroscopy measurements. Interestingly, the Au@Ag semishell Janus nanoparticles exhibited enhanced electrocatalytic activity in oxygen reduction reactions, as compared to their Au@Ag and Ag@Au core-shell counterparts, likely due to a synergistic effect between the gold cores and silver semishells that optimized oxygen binding to the nanoparticle surface.Gold core@silver semishell Janus nanoparticles were prepared by chemical etching of Au@Ag core-shell nanoparticles at the air/water interface. Au@Ag core-shell nanoparticles were synthesized by chemical deposition of a silver shell onto gold seed colloids followed by the self-assembly of 1-dodecanethiol onto the nanoparticle surface. The nanoparticles then formed a monolayer on the water surface of a Langmuir-Blodgett trough, and part of the silver shell was selectively etched away by the mixture of hydrogen peroxide and ammonia in the water subphase, where the etching was limited to the side of the nanoparticles that was in direct contact with water. The resulting Janus nanoparticles exhibited an asymmetrical distribution of silver on the surface of the gold cores, as manifested in transmission electron microscopy, UV-vis absorption, and X-ray photoelectron spectroscopy measurements. Interestingly, the Au@Ag semishell Janus nanoparticles exhibited enhanced electrocatalytic activity in oxygen reduction reactions, as compared to their Au@Ag and Ag@Au core-shell counterparts, likely due to a synergistic effect between the gold cores and silver semishells that optimized oxygen binding to the nanoparticle surface. Electronic supplementary information (ESI) available: Additional TEM, UV-vis, XPS, and electrochemical data. See DOI: 10.1039/c6nr03368g

ALARA efforts in nordic BWRs

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

Ingemansson, T.; Lundgren, K.; Elkert, J.

1995-03-01

Some ALARA-related ABB Atom projects are currently under investigation. One of the projects has been ordered by the Swedish Radiation Protection Institute, and two others by the Nordic BWR utilities. The ultimate objective of the projects is to identify and develop methods to significantly decrease the future exposure levels in the Nordic BWRS. As 85% to 90% of the gamma radiation field in the Nordic BWRs originates from Co-60, the only way to significantly decrease the radiation doses is to effect Co and Co-60. The strategy to do this is to map the Co sources and estimate the source strengthmore » of Co from these sources, and to study the possibility to affect the release of Co-60 from the core surfaces and the uptake on system surfaces. Preliminary results indicate that corrosion/erosion of a relatively small number of Stellite-coated valves and/or dust from grinding of Stellite valves may significantly contribute to the Co input to the reactors. This can be seen from a high measured Co/Ni ratio in the feedwater and in the reactor water. If stainless steel is the only source of Co, the Co/Ni ratio would be less than 0.02 as the Co content in the steel is less than 0.2%. The Co/Ni ratio in the reactor water, however, is higher than 0.1, indicating that the major fraction of the Co originates from Stellite-coated valves. There are also other possible explanations for an increase of the radiation fields. The Co-60 inventory on the core surfaces increases approximately as the square of the burn-up level. If the burn-up is increased from 35 to 5 MWd/kgU, the Co-60 inventory on the core surfaces will be doubled. Also the effect on the behavior of Co-60 of different water chemistry and materials conditions is being investigated. Examples of areas studied are Fe and Zn injection, pH-control, and different forms of surface pre-treatments.« less

The dipole moment surface for hydrogen sulfide H2S

NASA Astrophysics Data System (ADS)

Azzam, Ala`a. A. A.; Lodi, Lorenzo; Yurchenko, Sergey N.; Tennyson, Jonathan

2015-08-01

In this work we perform a systematic ab initio study of the dipole moment surface (DMS) of H2S at various levels of theory and of its effect on the intensities of vibration-rotation transitions; H2S intensities are known from the experiment to display anomalies which have so far been difficult to reproduce by theoretical calculations. We use the transition intensities from the HITRAN database of 14 vibrational bands for our comparisons. The intensities of all fundamental bands show strong sensitivity to the ab initio method used for constructing the DMS while hot, overtone and combination bands up to 4000 cm-1 do not. The core-correlation and relativistic effects are found to be important for computed line intensities, for instance affecting the most intense fundamental band (ν2) by about 20%. Our recommended DMS, called ALYT2, is based on the CCSD(T)/aug-cc-pV(6+d)Z level of theory supplemented by a core-correlation/relativistic corrective surface obtained at the CCSD[T]/aug-cc-pCV5Z-DK level. The corresponding computed intensities agree significantly better (to within 10%) with experimental data taken directly from original papers. Worse agreement (differences of about 25%) is found for those HITRAN intensities obtained from fitted effective dipole models, suggesting the presence of underlying problems in those fits.

Seismic Velocity Anomalies in the Outer Core: The Final Frontier

NASA Astrophysics Data System (ADS)

Stevenson, D. J.

2008-12-01

Variation in density along outer core geoid surfaces must be very small (of order one part in a billion) since the resulting fluid motions and buoyancy fluxes would otherwise be prohibitively large for any reasonable choice of outer core viscosity. In any situation where seismic velocity variations are proportional to density variations (a generalized Birch's "law") this means that the resulting seismic travel time variations in the outer core would be unobservable. The largest lateral variations in the outer core are thus likely to arise from the distortion of geoid surfaces caused by density anomalies in the mantle or inner core. However, these do not change on decadal timescales and would be very difficult to separate from the inner core or mantle variations that cause them. Nonetheless, a recent study (Dai and Song, GRL, vol. 35, L16311, doi:10.1029/2008GL034895) provides evidence for time-variable outer core seismic velocity at the level of ten parts per million. Assuming this is real, I argue that the best candidate explanation is that all or part of the outer core is a two-phase medium consisting of a small mass fraction of small (ten or 100 micron-sized) particles of exsolving silicate material suspended in the convecting liquid. The seismic velocity of this two phase medium can vary at the desired level should the size distribution of particles vary from place to place (and with time) as one would expect in a convecting system, even though the mean density of the medium is invariant at the level of a part per billion, as required by dynamical considerations (thus invalidating Birch's "law"). The seismic velocity variation depends on the ratio of diffusion times to seismic periods, where the diffusion times are thermal or compositional for the particles or the particle spacing. This idea is not new (cf. Stevenson, JGR, 1983) but gains increased impetus from recent work on the nature of core formation and the desirability of an additional energy source for driving the geodynamo, as would arise if of order 10km of mantle underplating occurred over all of geologic time. The amount of suspended material will be tiny at any one time, illustrating the remarkable sensitivity of seismic waves to the microstructure of the medium. Consequences of this picture include some dissipation (finite Q) in the outer core and a significant frequency dependence of this effect, but precise predictions are difficult because of uncertainties in particle kinetics and convective velocities. The two-phase region may also influence radial seismic velocity profiles, particularly in the layers immediately adjacent to the boundaries (e.g., the layer just below the core-mantle boundary), an effect that has been suggested in the literature on many occasions. Even so, this explanation for lateral variability remains marginal at best, suggesting that the claimed observation is either not real or that some other explanation still awaits discovery.

Long-term recovery of PCB-contaminated surface sediments at the Sangamo-westonl Twelvemile Creek/lake Hartwell Superfund Site.

PubMed

Brenner, Richard C; Magar, Victor S; Ickes, Jennifer A; Foote, Eric A; Abbott, James E; Bingler, Linda S; Crecelius, Eric A

2004-04-15

Natural recovery of contaminated sediments relies on burial of contaminated sediments with increasingly clean sediments over time (i.e., natural capping). Natural capping reduces the risk of resuspension of contaminated surface sediments, and it reduces the potential for contaminant transport into the food chain by limiting bioturbation of contaminated surface or near-surface sediments. This study evaluated the natural recovery of surface sediments contaminated with polychlorinated biphenyls (PCBs) at the Sangamo-Weston/Twelvemile Creek/Lake Hartwell Superfund Site (Lake Hartwell), Pickens County, SC. The primary focus was on sediment recovery resulting from natural capping processes. Total PCB (t-PCB), lead-210 (210Pb), and cesium-137 (137Cs) sediment core profiles were used to establish vertical t-PCB concentration profiles, age date sediments, and determine surface sedimentation and surface sediment recovery rates in 18 cores collected along 10 transects. Four upgradient transects in the headwaters of Lake Hartwell were impacted by historical sediment releases from three upgradient sediment impoundments. These transects were characterized by silt/ clay and sand layering. The highest PCB concentrations were associated with silt/clay layers (1.8-3.5% total organic carbon (TOC)), while sand layers (0.05-0.32% TOC) contained much lower PCB concentrations. The historical sediment releases resulted in substantial burial of PCB-contaminated sediment in the vicinity of these four cores; each core contained less than 1 mg/kg t-PCBs in the surface sand layers. Cores collected from six downgradient Lake Hartwell transects consisted primarily of silt and clay (0.91-5.1% TOC) and were less noticeably impacted by the release of sand from the impoundments. Vertical t-PCB concentration profiles in these cores began with relatively low PCB concentrations at the sediment-water interface and increased in concentration with depth until maximum PCB concentrations were measured at approximately 30-60 cm below the sediment-water interface, ca. 1960-1980. Maximum t-PCB concentrations were followed by progressively decreasing concentrations with depth until the t-PCB concentrations approached the detection limit, where sediments were likely deposited before the onset of PCB use at the Sangamo-Weston plant. The sediments containing the maximum PCB concentrations are associated with the period of maximum PCB release into the watershed. Sedimentation rates averaged 2.1 +/- 1.5 g/(cm2 yr) for 12 of 18 cores collected. The 1994 Record of Decision cleanup requirement is 1.0 mg/kg; two more goals (0.4 and 0.05 mg/kg t-PCBs) also were identified. Average surface sedimentation requirements to meet the three goals were 1.4 +/- 3.7, 11 +/- 4.2, and 33 +/- 11 cm, respectively. Using the age dating results, the average recovery dates to meet these goals were 2000.6 +/- 2.7, 2007.4 +/- 3.5, and 2022.7 +/- 11 yr, respectively. (The 95% prediction limits for these values also are provided.) Despite the reduction in surface sediment PCB concentrations, PCB concentrations measured in largemouth bass and hybrid bass filets continue to exceed the 2.0 mg/kg FDA fish tolerance level.

Metal-phthalocyanine ordered layers on Au(110): Metal-dependent adsorption energy

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

Massimi, Lorenzo, E-mail: lorenzo.massimi@uniroma1.it; Angelucci, Marco; Gargiani, Pierluigi

2014-06-28

Iron-phthalocyanine and cobalt-phthalocyanine chains, assembled along the Au(110)-(1×2) reconstructed channels, present a strong interaction with the Au metallic states, via the central metal ion. X-ray photoemission spectroscopy from the metal-2p core-levels and valence band high-resolution ultraviolet photoelectron spectroscopy bring to light signatures of the interaction of the metal-phthalocyanine single-layer with gold. The charge transfer from Au to the molecule causes the emerging of a metal-2p core level component at lower binding energy with respect to that measured in the molecular thin films, while the core-levels associated to the organic macrocycle (C and N 1s) are less influenced by the adsorption,more » and the macrocycles stabilize the interaction, inducing a strong interface dipole. Temperature Programmed Desorption experiments and photoemission as a function of temperature allow to estimate the adsorption energy for the thin-films, mainly due to the molecule-molecule van der Waals interaction, while the FePc and CoPc single-layers remain adsorbed on the Au surface up to at least 820 K.« less

A high-resolution core-level photoemission study of the Au/4H-SiC(0001)-([Formula: see text]) interface.

PubMed

Stoltz, D; Stoltz, S E; Johansson, L S O

2007-07-04

We present a systematic study of different reconstructions obtained after deposition of Au on the [Formula: see text]-4H-SiC(0001) surface. For 1-2 monolayers (ML) Au and annealing temperature T(anneal)∼675 °C, a 3 × 3 reconstruction was observed. For 4 ML Au and T(anneal)∼650 °C, a [Formula: see text] reconstruction appeared, while 5 ML Au annealed at 700 °C reconstructed to give a [Formula: see text] pattern. From the Si 2p and Au 4f core-level components, we propose interface models, depending on the amount of Au on the surface and the annealing temperature. For 1-4 ML Au annealed at 650-675 °C, gold diffuses under the topmost Si into the SiC and forms a silicide. An additional Si component in our Si 2p spectra is related to the interface between the silicide and SiC. For 5 ML Au annealed at 700 °C, silicide is also formed at the surface, covering unreacted Au on top of the SiC substrate. The interface Si component is also observed in the Si 2p spectra of this surface. The key role in [Formula: see text]-4H-SiC(0001) interface formation is played by diffusion and the silicon-richness of the surface.

Podoplanin requires sialylated O-glycans for stable expression on lymphatic endothelial cells and for interaction with platelets

PubMed Central

Pan, Yanfang; Yago, Tadayuki; Fu, Jianxin; Herzog, Brett; McDaniel, J. Michael; Mehta-D’Souza, Padmaja; Cai, Xiaofeng; Ruan, Changgeng; McEver, Rodger P.; West, Christopher; Dai, Kesheng; Chen, Hong

2014-01-01

O-glycosylation of podoplanin (PDPN) on lymphatic endothelial cells is critical for the separation of blood and lymphatic systems by interacting with platelet C-type lectin-like receptor 2 during development. However, how O-glycosylation controls endothelial PDPN function and expression remains unclear. In this study, we report that core 1 O-glycan–deficient or desialylated PDPN was highly susceptible to proteolytic degradation by various proteases, including metalloproteinases (MMP)-2/9. We found that the lymph contained activated MMP-2/9 and incubation of the lymph reduced surface levels of PDPN on core 1 O-glycan–deficient endothelial cells, but not on wild-type ECs. The lymph from mice with sepsis induced by cecal ligation and puncture, which contained bacteria-derived sialidase, reduced PDPN levels on wild-type ECs. The MMP inhibitor, GM6001, rescued these reductions. Additionally, GM6001 treatment rescued the reduction of PDPN level on lymphatic endothelial cells in mice lacking endothelial core 1 O-glycan or cecal ligation and puncture-treated mice. Furthermore, core 1 O-glycan–deficient or desialylated PDPN impaired platelet interaction under physiological flow. These data indicate that sialylated O-glycans of PDPN are essential for platelet adhesion and prevent PDPN from proteolytic degradation primarily mediated by MMPs in the lymph. PMID:25336627

Liquid molded hollow cell core composite articles

NASA Technical Reports Server (NTRS)

Bernetich, Karl R. (Inventor)

2005-01-01

A hollow core composite assembly 10 is provided, including a hollow core base 12 having at least one open core surface 14, a bondable solid film 22 applied to the open core surface 14, at least one dry face ply 30 laid up dry and placed on top of the solid film 22, and a liquid resin 32 applied to the at least one dry face ply 30 and then cured.

Intraparticle reduction of arsenite (As(III)) by nanoscale zerovalent iron (nZVI) investigated with In Situ X-ray absorption spectroscopy.

PubMed

Yan, Weile; Vasic, Relja; Frenkel, Anatoly I; Koel, Bruce E

2012-07-03

While a high efficiency of contaminant removal by nanoscale zerovalent iron (nZVI) has often been reported for several contaminants of great concern, including aqueous arsenic species, the transformations and translocation of contaminants at and within the nanoparticles are not clearly understood. By analysis using in situ time-dependent X-ray absorption spectroscopy (XAS) of the arsenic core level for nZVI in anoxic As(III) solutions, we have observed that As(III) species underwent two stages of transformation upon adsorption at the nZVI surface. The first stage corresponds to breaking of As-O bonds at the particle surface, and the second stage involves further reduction and diffusion of arsenic across the thin oxide layer enclosing the nanoparticles, which results in arsenic forming an intermetallic phase with the Fe(0) core. Extended X-ray absorption fine-structure (EXAFS) data from experiments conducted at different iron/arsenic ratios indicate that the reduced arsenic species tend to be enriched at the surface of the Fe(0) core region and had limited mobility into the interior of the metal core within the experimental time frame (up to 22 h). Therefore, there was an accumulation of partially reduced arsenic at the Fe(0)/oxide interface when a relatively large arsenic content was present in the solid phase. These results illuminate the role of intraparticle diffusion and reduction in affecting the chemical state and spatial distribution of arsenic in nZVI materials.

Transport of perfluoroalkyl substances (PFAS) from an arctic glacier to downstream locations: implications for sources.

PubMed

Kwok, Karen Y; Yamazaki, Eriko; Yamashita, Nobuyoshi; Taniyasu, Sachi; Murphy, Margaret B; Horii, Yuichi; Petrick, Gert; Kallerborn, Roland; Kannan, Kurunthachalam; Murano, Kentaro; Lam, Paul K S

2013-03-01

Perfluoroalkyl substances (PFAS) have been globally detected in various environmental matrices, yet their fate and transport to the Arctic is still unclear, especially for the European Arctic. In this study, concentrations of 17 PFAS were quantified in two ice cores (n=26), surface snow (n=9) and surface water samples (n=14) collected along a spatial gradient in Svalbard, Norway. Concentrations of selected ions (Na(+), SO4(2-), etc.) were also determined for tracing the origins and sources of PFAS. Perfluorobutanoate (PFBA), perfluorooctanoate (PFOA) and perfluorononanoate (PFNA) were the dominant compounds found in ice core samples. Taking PFOA, PFNA and perfluorooctane-sulfonate (PFOS) as examples, higher concentrations were detected in the middle layers of the ice cores representing the period of 1997-2000. Lower concentrations of C8-C12 perfluorocarboxylates (PFCAs) were detected in comparison with concentrations measured previously in an ice core from the Canadian Arctic, indicating that contamination levels in the European Arctic are lower. Average PFAS concentrations were found to be lower in surface snow and melted glacier water samples, while increased concentrations were observed in river water downstream near the coastal area. Perfluorohexanesulfonate (PFHxS) was detected in the downstream locations, but not in the glacier, suggesting existence of local sources of this compound. Long-range atmospheric transport of PFAS was the major deposition pathway for the glaciers, while local sources (e.g., skiing activities) were identified in the downstream locations. Copyright © 2012 Elsevier B.V. All rights reserved.

Core level line shapes and surface band structures of Sn/Ge(111) and Sn/Si(111)

NASA Astrophysics Data System (ADS)

Uhrberg, Roger

2001-03-01

We have performed a comparative study of Sn/Ge(111) and the closely related Sn/Si(111) system, using photoelectron spectroscopy (PES) and low energy electron diffraction (LEED). In similarity with the results from the Sn/Ge(111) surface, the Sn 4d spectra from Sn/Si(111) exhibit two major components and the valence band spectra show two surface state bands at both room temperature (RT) and 70 K. These features, which have been associated with the low temperature 3x3 phase in the case of Sn/Ge(111), are not expected for the rt3xrt3 RT surfaces. In contrast to Sn/Ge(111), we do not observe any transition to a 3x3 phase in LEED for Sn/Si(111) at temperatures down to 70 K (the lowest temperature in this study). Despite the absence of a 3x3 phase for Sn/Si(111) the core-level and the valence band data are very similar to those of Sn/Ge(111). The Sn 4d spectra show, however, one interesting difference. The intensity ratio of the two Sn 4d components is reversed for the Sn/Si(111) surface compared the Ge counterpart. This and the other PES results will be discussed in terms of the two different types of 3x3 periodicities that have been reported to be induced by substitutional defects on the Sn/Ge(111) surface [1]. [1] A.V. Melechko et al., Phys. Rev. B61, 2235 (2000)

NUCLEAR REACTOR CONTROL SYSTEM

DOEpatents

Howard, D.F.; Motta, E.E.

1961-06-27

A method for controlling the excess reactivity in a nuclear reactor throughout the core life while maintaining the neutron flux distribution at the desired level is described. The control unit embodies a container having two electrodes of different surface area immersed in an electrolytic solution of a good neutron sbsorbing metal ion such as boron, gadolinium, or cadmium. Initially, the neutron absorber is plated on the larger electrode to control the greater neutron flux of a freshly refueled core. As the fuel burns up, the excess reactivity decreases and the neutron absorber is then plated onto the smaller electrode so that the number of neutrons absorbed also decreases. The excess reactivity in the core may thus be maintained without the introduction of serious perturbations in the neutron flux distributibn.

Tritium, deuterium, and oxygen-18 in water collected from unsaturated sediments near a low-level radioactive-waste burial site south of Beatty, Nevada

USGS Publications Warehouse

Prudic, David E.; Stonestrom, David A.; Striegl, Robert G.

1997-01-01

Pore water was extracted in March 1996 from cores collected from test holes UZB-1 and UZB-2 drilled November 1992 and September 1993, respectively, in the Amargosa Desert south of Beatty, Nevada. The test holes are part of a study to determine factors affecting water and gas movement through unsaturated sediments. The holes are about 100 meters south of the southwest corner of the fence enclosing a commercial burial area for low-level radioactive waste. Water vapor collected from test hole UZB-2 in April 1994 and July 1995 had tritium concentrations greater than would be expected from atmospheric deposition. An apparatus was built in which pore water was extracted by cryodistillation from the previously obtained core samples. The extracted core water was analyzed for the radioactive isotope tritium and for the stable isotopes deuterium (D) and oxygen-18 (18O). The isotopic composition of core water was compared with that of water vapor previously collected from air ports in test hole UZB-2 and to additional samples collected during May 1996. Core water becomes increasingly depleted in D and 18O from the land surface to a depth of 30 meters, indicating that net evaporation of water is occurring near the land surface. Below a depth of 30 meters the stable-isotopic composition of core water becomes nearly constant and roughly equal to that of ground water. The stable isotopes plot on an evaporation trend. The source of the partly evaporated water could be either ground water or past precipitation having the same average isotopic composition as ground water but not modern precipitation, based on 18 months of record. Profiles of D and 18O in water vapor roughly parallel those in core water. The stable isotopes of core water appear to be in isotopic equilibrium with water vapor from UZB-2 when temperature-dependent fractionation is considered. The data are consistent with the hypothesis of evaporative discharge of ground water at the land surface. The concentration of tritium in core water from depths less than 50 meters was higher than that of present-day atmospheric air, indicating that elevated tritium concentrations preceded the drilling. The concentrations of tritium in core water from the deepest sample (85 meters) and in UZB-2 groundwater (110 meters) were below detection. Thus, tritium in the unsaturated zone is not being introduced through ground water. The shape of the tritium profile for core water was similar to the shape of the tritium profile for water vapor collected April 1994, except that concentrations were consistently lower in core water than in water vapor. Tritium concentrations in water vapor increased from April 1994 to May 1996. Similar to the stable isotopes, the highest tritium concentrations were measured at shallow depths. Concentrations of tritium in water vapor during core collection were estimated assuming isotopic equilibrium with core water. The computed concentrations for November 1992 and September 1993 form consistent temporal trends with subsequent tritium concentrations in water vapor collected April 1994, July 1995, and May 1996. Observations of a bimodal distribution of tritium, in which the highest concentrations are in a gravel layer at a depth of 1-2 meters, indicate lateral migration of tritium through the vicinity of UZB-2.

Effect of core diameter and surface treatment on the retention of resin composite cores to prefabricated endodontic posts.

PubMed

Artopoulou, Ioli-Ioanna; O'Keefe, Kathy L; Powers, John M

2006-01-01

With advances in adhesive dentistry and current emphasis on esthetic restorations, dowel systems have been developed to take advantage of these new techniques. Of interest when using these systems is the interaction between core materials and post materials. This investigation compared the tensile retentive force of two resin composite core materials to two metallic and one non-metallic prefabricated endodontic posts. Two dimensions of core build-up and two post-surface treatments were tested. One hundred twenty posts (stainless steel, titanium alloy, and glass fiber-impregnated resin) were secured in a jig with 4 mm of the post extending into a cylindrical matrix. The matrix formed cylinders with diameters of 3 and 5 mm into which resin composite was inserted. The posts were treated or not treated with a bonding agent. After storage for 24 hours at 100% humidity, five specimens per condition were tested in an Instron testing machine at a crosshead speed of 0.5 mm/min. Failure loads were recorded in kilograms and failure modes were observed under light microscopy (40 x). Four-way analysis of variance and multiple comparison testing were used to compare means at the 0.05 level of significance. The means and standard deviations of tensile loads were calculated. All variables were significant in either main effects or interactions ( p<0.05). Fisher's PLSD intervals for post, core, treatment, and diameter were 2.0, 1.6, 1.6, and 1.6 kg, respectively. In most cases, the retentive force recorded for metallic posts was higher than that of glass fiber posts. Titanium posts had higher retentive forces than did the stainless steel posts. For metallic posts, 5-mm cores provided higher forces than 3-mm cores. In the glass fiber group, core diameter was not significant. For core materials, Build-It gave higher results with stainless steel posts, and FluoroCore gave higher results with the titanium ones. The surface treatment results were mixed. In the metallic post groups the adhesive failure data ranged between 80% and 100%, whereas in the glass fiber post groups, adhesive failures ranged between 60% and 70%. Within the limitations of this study, the metallic post groups always provided higher tensile retentive forces, with the titanium post groups showing higher retentive forces than the stainless steel ones. In the glass fiber post groups, different core diameters did not affect retention values.

Effect of abalone farming on sediment geochemistry in the Shallow Sea near Wando, South Korea

NASA Astrophysics Data System (ADS)

Kang, Jeongwon; Lee, Yeon Gyu; Jeong, Da Un; Lee, Jung Sick; Choi, Yang Ho; Shin, Yun Kyung

2015-12-01

Wando County has grown up to 93% of the total abalone produced in South Korea since the late 1990s; however, this production has been decreasing in recent years. The objectives of this study were to understand the potential contamination risks of abalone farming and to examine the influence of intensive abalone farming on sediment quality by analyzing grain-size composition, organic matter (total organic carbon (TOC), total nitrogen (TN), total sulfur (TS)) and heavy metal content, pH, and 210Pb geochronology. The results of organic matter analysis from surface and core sediment (length: 64 cm) showed that the area around the abalone farm had oxic marine-to-brackish conditions, but that the area directly below an abalone cage (location 7) had reductive conditions, with a C/S ratio of ~2. The average TN levels in the surface and core sediments were 0.25% and 0.29%, respectively, and this was predominantly due to the use of seaweed for feed. The low sediment pH (surface, 7.23; core, 7.04), indicates that acidification of the bottom sediment has gradually increased since the initiation of abalone farming and is likely due to the continuous accumulation of uneaten feed and feces. Heavy metal pollution was not apparent based on the examination of EF and Igeo, although the excess metal flux of Ni, Pb, Cu, Co, As, and Cd increased toward surface of the sediment core. These sediment changes may be caused by the rapid accumulation (sedimentation rate: 1.45 cm/year) of sludge discharged from the abalone farm and may be controlled by tidal currents, physiography, water depth, and tidal ranges.

Diamond /111/ studied by electron energy loss spectroscopy in the characteristic loss region

NASA Technical Reports Server (NTRS)

Pepper, S. V.

1982-01-01

Unoccupied surface states on diamond (111) annealed at greater than 900 C are studied by electron energy loss spectroscopy with valence band excitation. A feature found at 2.1 eV loss energy is attributed to an excitation from occupied surface states into unoccupied surface states of energy within the bulk band gap. A surface band gap of approximately 1 eV is estimated. This result supports a previous suggestion for unoccupied band gap states based on core level energy loss spectroscopy. Using the valence band excitation energy loss spectrosocpy, it is also suggested that hydrogen is removed from the as-polished diamond surface by a Menzel-Gomer-Redhead mechanism.

Green synthesis of CuInS2/ZnS core-shell quantum dots by facile solvothermal route with enhanced optical properties

NASA Astrophysics Data System (ADS)

Jindal, Shikha; Giripunje, Sushama M.; Kondawar, Subhash B.; Koinkar, Pankaj

2018-03-01

We report an eco-friendly green synthesis of highly luminescent CuInS2/ZnS core-shell quantum dots (QDs) with average particle size ∼ 3.9 nm via solvothermal process. The present study embodies the intensification of CuInS2/ZnS QDs properties by the shell growth on the CuInS2 QDs. The as-prepared CuInS2 core and CuInS2/ZnS core-shell QDs have been characterized using a range of optical and structural techniques. By adopting a low temperature growth of CuInS2 core and high temperature growth of CuInS2/ZnS core-shell growth, the tuning of absorption and photoluminescence emission spectra were observed. Optical absorption and photoluminescence spectroscopy probe the effect of ZnS passivation on the electronic structure of the CuInS2 dots. In addition, QDs have been scrutinized using ultra violet photoelectron spectroscopy (UPS) to explore their electronic band structure. The band level positions of CuInS2 and CuInS2/ZnS QDs suffices the demand of non-toxic acceptor material for electronic devices. The variation in electronic energy levels of CuInS2 core with the coating of wide band gap ZnS shell influence the removal of trap assisted recombination on the surface of the core. QDs exhibited tunable emission from red to orange region. These studies reveal the feasibility of QDs in photovoltaic and light emitting diodes.

Hydrogeologic and water-quality data for the main site, Naval Surface Warfare Center, Dahlgren Laboratory, Dahlgren, Virginia

USGS Publications Warehouse

Bell, Clifton F.; Bolles, Thomas P.; Harlow, George E.

1994-01-01

Hydrogeologic and water-quality data were collected at the Naval Surface Warfare Center, Dahlgren Laboratory at Dahlgren, Virginia, as part of a hydrogeologic assessment of the shallow aquifer system begun in 1992. The U.S. Geological Survey conducted this study to provide the Navy with hydrogeologic data to meet the requirements of a Spill Contingency Plan. This report describes the ground-water observation-well network, hydro- geologic, and water-quality data collected between August 1992 and September 1993. The report includes a description of the locations and con- struction of 35 observation wells on the Main Site. Hydrologic data include lithologic core samples, geophysical logs, and vertical hydraulic conductivity measurements of selected core intervals. Hydrologic data include synoptic and hourly measurements of ground-water levels, observation-well slug tests to determine horizontal hydraulic conductivity, and tide data. Water-quality data include analyses of major dissolved constituents in ground water and surface water.

Spectral engineering of LaF3:Ce3+ nanoparticles: The role of Ce3+ in surface sites

NASA Astrophysics Data System (ADS)

Jacobsohn, L. G.; Toncelli, A.; Sprinkle, K. B.; Kucera, C. J.; Ballato, J.

2012-04-01

Due to the high surface-to-volume ratio, luminescence centers on the surface have relative dominance in the overall spectral response of nanoparticles. The luminescence of LaF3:Ce3+ nanoparticles was investigated in the spectral and temporal domains with a particular focus on the role of Ce3+ on the surface. These nanoparticles present two luminescence bands at 4.10 eV and 4.37 eV attributed to Ce3+ transitions from the 5d level to the spin-orbit split 4f ground levels 2F5/2 and 2F7/2, in addition to a low-energy band at 3.62 eV that has been attributed to Ce3+ ions residing in perturbed sites. The growth of up to three undoped shells, ca. 0.9 nm thick each, around the core promoted a progressive enhancement of luminescence output, concomitant with an increase in the fluorescence lifetime due to the weakening of energy transfer through multipolar interaction between Ce3+ in the core and quenching defects on the surface. Also, the growth of the first shell led to a decrease in the relative intensity of the low-energy band and a 0.23 eV shift to higher energies. These results were interpreted as being due to the existence of two types of perturbed sites, one on the surface that is eliminated by the growth of the first shell, and another within the volume of the nanoparticle, similar to observations in bulk single crystals. This work demonstrates how surface engineering can affect and control the luminescence behavior of this nanomaterial.

The Surface Velocity Structure of the Florida Current in a Jet Coordinate Frame

NASA Astrophysics Data System (ADS)

Archer, Matthew R.; Shay, Lynn K.; Johns, William E.

2017-11-01

The structure and variability of the Florida Current between 25° and 26°N are investigated using HF radar ocean current measurements to provide the most detailed view of the surface jet to date. A 2-D jet coordinate analysis is performed to define lateral displacements of the jet in time (meandering), and associated structural variations over a 2 year period (2005-2006). In the jet coordinate frame, core speed has a median value of ˜160 cm s-1 at the central latitude of the array (25.4°N), with a standard deviation (STD) of 35 cm s-1. The jet meanders at timescales of 3-30 days, with a STD of 8 km, and a downstream phase speed of ˜80 km d-1. Meandering accounts for ˜45% of eddy kinetic energy computed in a fixed (geographical) reference frame. Core speed, width, and shear undergo the same dominant 3-30 day variability, plus an annual cycle that matches seasonality of alongshore wind stress. Jet transport at 25.4°N exhibits a different seasonality to volume transport at 27°N, most likely driven by input from the Northwest Providence Channel. Core speed correlates inversely with Miami sea level fluctuations such that a 40 cm s-1 deceleration is associated with a ˜10 cm elevation in sea level, although there is no correlation of sea level to jet meandering or width. Such accurate quantification of the Florida Current's variability is critical to understand and forecast future changes in the climate system of the North Atlantic, as well as local impacts on coastal circulation and sea level variability along south Florida's coastline.

Acute Warm-up Effects in Submaximal Athletes: An EMG Study of Skilled Violinists.

PubMed

McCrary, J Matt; Halaki, Mark; Sorkin, Evgeny; Ackermann, Bronwen J

2016-02-01

Warm-up is commonly recommended for injury prevention and performance enhancement across all activities, yet this recommendation is not supported by evidence for repetitive submaximal activities such as instrumental music performance. The objective of this study is to quantify the effects of cardiovascular, core muscle, and musical warm-ups on muscle activity levels, musical performance, and subjective experience in skilled violinists. Fifty-five undergraduate, postgraduate, or professional violinists performed five randomly ordered 45-s musical excerpts of varying physical demands both before and after a randomly assigned 15-min, moderate-intensity cardiovascular, core muscle, musical (technical violin exercises), or inactive control warm-up protocol. Surface EMG data were obtained for 16 muscles of the trunk, shoulders, and right arm during each musical performance. Sound recording and perceived exertion (RPE) data were also obtained. Sound recordings were randomly ordered and rated for performance quality by blinded adjudicators. Questionnaire data regarding participant pain sites and fitness levels were used to stratify participants according to pain and fitness levels. Data were analyzed using two- and three-factor ANCOVA (surface EMG and sound recording) and Wilcoxon matched pairs tests (RPE). None of the three warm-up protocols had significant effects on muscle activity levels (P ≥ 0.10). Performance quality did not significantly increase (P ≥ 0.21). RPE significantly decreased (P < 0.05) after warm-up for each of the three experimental warm-ups; control condition RPE did not significantly decrease (P > 0.23). Acute physiological and musical benefits from cardiovascular, core muscle, and musical warm-ups in skilled violinists are limited to decreases in RPE. This investigation provides data from the performing arts in support of sports medical evidence suggesting that warm-up only effectively enhances maximal strength and power performance.

Sequence stratigraphic principles applied to the Miocene Hawthorn Group, west-central Florida

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

Norton, V.L.; Randazzo, A.F.

1993-03-01

Sequence boundaries for the Miocene Hawthorn Group in the ROMP 20 drill core from Osprey, Sarasota County, FL were generally delineated by lithologic variations recognized from core slabs, thin section analysis, and geophysical logs. At least six depositional sequences representing third order sea level fluctuations were identified. Depositional environments were determined on the basis of the characteristic lithologic constituents including rip-up clasts, pellets, fossils, laminations, burrow, degree of induration, and grain sorting. The sequence boundaries appear to have formed when the rate of the eustatic fall exceeded basin subsidence rates producing a relative sea level fall at a depositional shorelinemore » break. As a result of the basinward facies shift associated with this sequence type, peritidal facies may directly overlie deeper water facies. Subaerial exposure and erosion can be expected. The sequence of facies representing progressively deeper water depositional environments, followed by a progressive shallowing, were present between bounding surfaces. Among the six sequences recognized, four were clearly delineated as representative of regression, subaerial exposure, and subsequent transgression. Two sequences were less clearly defined and probably represent transitional facies which had exposure surfaces developed. Comparison of the petrologically established sequence stratigraphy with published sea level curves resulted in a strong correlation between the number of sequences recognized and the number of coastal on-lap/off-lap cycles depicted for the early to middle Miocene. This correlation suggests that petrologic examination of core slabs, with supplemental thin section data, can provide useful information regarding the recognition of stratigraphic sequences and relative sea level fluctuations, particularly, in situations where seismic data may not be available.« less

Gold core@silver semishell Janus nanoparticles prepared by interfacial etching.

PubMed

Chen, Limei; Deming, Christopher P; Peng, Yi; Hu, Peiguang; Stofan, Jake; Chen, Shaowei

2016-08-14

Gold core@silver semishell Janus nanoparticles were prepared by chemical etching of Au@Ag core-shell nanoparticles at the air/water interface. Au@Ag core-shell nanoparticles were synthesized by chemical deposition of a silver shell onto gold seed colloids followed by the self-assembly of 1-dodecanethiol onto the nanoparticle surface. The nanoparticles then formed a monolayer on the water surface of a Langmuir-Blodgett trough, and part of the silver shell was selectively etched away by the mixture of hydrogen peroxide and ammonia in the water subphase, where the etching was limited to the side of the nanoparticles that was in direct contact with water. The resulting Janus nanoparticles exhibited an asymmetrical distribution of silver on the surface of the gold cores, as manifested in transmission electron microscopy, UV-vis absorption, and X-ray photoelectron spectroscopy measurements. Interestingly, the Au@Ag semishell Janus nanoparticles exhibited enhanced electrocatalytic activity in oxygen reduction reactions, as compared to their Au@Ag and Ag@Au core-shell counterparts, likely due to a synergistic effect between the gold cores and silver semishells that optimized oxygen binding to the nanoparticle surface.

Divertor tungsten tile melting and its effect on core plasma performance

NASA Astrophysics Data System (ADS)

Lipschultz, B.; Coenen, J. W.; Barnard, H. S.; Howard, N. T.; Reinke, M. L.; Whyte, D. G.; Wright, G. M.

2012-12-01

For the 2007 and 2008 run campaigns, Alcator C-Mod operated with a full toroidal row of tungsten tiles in the high heat flux region of the outer divertor; tungsten levels in the core plasma were below measurement limits. An accidental creation of a tungsten leading edge in the 2009 campaign led to this study of a melting tungsten source: H-mode operation with strike point in the region of the melting tile was immediately impossible due to some fraction of tungsten droplets reaching the main plasma. Approximately 15 g of tungsten was lost from the tile over ˜100 discharges. Less than 1% of the evaporated tungsten was found re-deposited on surfaces, the rest is assumed to have become dust. The strong discharge variability of the tungsten reaching the core implies that the melt layer topology is always varying. There is no evidence of healing of the surface with repeated melting. Forces on the melted tungsten tend to lead to prominences that extend further into the plasma. A discussion of the implications of melting a divertor tungsten monoblock on the ITER plasma is presented.

Concentration of Antifouling Biocides and Metals in Sediment Core Samples in the Northern Part of Hiroshima Bay

PubMed Central

Tsunemasa, Noritaka; Yamazaki, Hideo

2014-01-01

Accumulation of Ot alternative antifoulants in sediment is the focus of this research. Much research had been done on surface sediment, but in this report, the accumulation in the sediment core was studied. The Ot alternative antifoulants, Diuron, Sea-Nine211, and Irgarol 1051, and the latter’s degradation product, M1, were investigated in five samples from the northern part of Hiroshima Bay. Ot compounds (tributyltin (TBT) and triphenyltin (TPT)) were also investigated for comparison. In addition, metal (Pb, Cu, Zn, Fe and Mn) levels and chronology were measured to better understand what happens after accumulation on the sea floor. It was discovered that Ot alternative antifoulant accumulation characteristics in sediment were like Ot compounds, with the concentration in the sediment core being much higher than surface sediment. The concentration in sediment seems to have been affected by the regulation of Ot compounds in 1990, due to the concentration of Ot alternative antifoulants and Ot compounds at the survey point in front of the dock, showing an increase from almost the same layer after the regulation. PMID:24901529

The Last Interglacial History of the Antarctic Ice sheet

NASA Astrophysics Data System (ADS)

Bradley, Sarah; Siddall, Mark; Milne, Glenn A.; Masson-Delmotte, Valerie; Wolff, Eric; Hindmarsh, Richard C. A.

2014-05-01

In this paper we present a summary of the work which was conducted as part of the 'PAST4FUTURE -WP4.1: Sea Level and Ice sheets' project. The overall aim of this study was to understand the response of the Antarctic Ice sheet (AIS) to climate forcing during the Last interglacial (LIG) and its contribution to the observed higher than present sea level during this period. The study involved the application and development of a novel technique which combined East Antarctic stable isotope ice core data with the output from a Glacial Isostatic Adjustment (GIA) model [Bradley et al., 2012]. We investigated if the stable isotope ice core data are sensitive to detecting isostatically driven changes in the surface elevation driven by changes in the ice-loading history of the AIS and if so, could we address some key questions relating to the LIG history of the AIS. Although it is believed that the West Antarctic Ice sheet (WAIS) reduced in size during the LIG compared to the Holocene, major uncertainties and unknowns remain unresolved: Did the WAIS collapse? What would the contribution of such a collapse be the higher than present LIG eustatic sea level (ESL)? We will show that a simulated collapse of the WAIS does not generate a significant elevation driven signal at the EAIS LIG ice core sites, and as such, these ice core records cannot be used to assess WAIS stability over this period. However, we will present 'treasure maps' [Bradley et al., 2012] to identify regions of the AIS where results from geological studies and/or new paleoclimate data may be sensitive to detecting a WAIS collapse. These maps can act as a useful tool for the wider science community/field scientists as a guide to highlight sites suitable to constrain the evolution of the WAIS during the LIG. Studies have proposed that the surface temperature across the East Antarctic Ice Sheet (EAIS) was significantly warmer, 2-5°C during the LIG compared to present [Lang and Wolff, 2011]. These higher temperatures are estimated primarily using the difference in the δD peak in the LIG stable isotope ice core data relative to the records for the present interglacial; a feature which is referred to as the 'LIG overshoot'. Generally studies have attributed most of this signal to changes in the Antarctic climate [Masson-Delmotte et al., 2011]. However, a previously overlooked contribution is the influence of changes in surface elevation driven by changes in ice-loading history of the EAIS [Bradley et al., 2013]. We will show that introducing a relatively moderate reduction in the amount of thickening of the EAIS over the LIG, can generate a significant elevation driven δD signal at the EAIS ice core sites, and as such elevation effects can account for a significant fraction of the LIG overshoot. We will conclude that the potential contribution of this process must be considered when using the EAIS stable isotope ice core data to make estimated of the LIG surface temperature. Finally, we will provide estimates of the contribution of the AIS to both ESL and to the higher than observed relative sea level during the LIG. Bradley, S. L., M. Siddall, G. A. Milne, V. Masson-Delmotte, and E. Wolff (2012), Where might we find evidence of a Last Interglacial West Antarctic Ice Sheet collapse in Antarctic ice core records?, Global and Planetary Change, 88-89(0), 64-75. Bradley, S. L., M. Siddall, G. A. Milne, V. Masson-Delmotte, and E. Wolff (2013), Combining ice core records and ice sheet models to explore the evolution of the East Antarctic Ice sheet during the Last Interglacial period, Global and Planetary Change, 100, 278-290. Lang, N., and E. W. Wolff (2011), Interglacial and glacial variability from the last 800 ka in marine, ice and terrestrial archives, Clim. Past., 7(2), 361-380. Masson-Delmotte, V., et al. (2011), A comparison of the present and last interglacial periods in six Antarctic ice cores, Clim. Past., 7(2), 397-423.

Tropical cyclone warm core analyses with FY-3 microwave temperature sounder data

NASA Astrophysics Data System (ADS)

Liu, Zhe; Bai, Jie; Zhang, Wenjun; Yan, Jun; Zhou, Zhuhua

2014-05-01

Space-borne microwave instruments are well suited to analyze Tropical Cyclone (TC) warm core structure, because certain wavelengths of microwave energy are able to penetrate the cirrus above TC. With the vector discrete-ordinate microwave radiative transfer model, the basic atmospheric parameters of Hurricane BOB are used to simulate the upwelling brightness temperatures on each channel of the Microwave Temperature Sounder (MWTS) onboard FY-3A/3B observation. Based on the simulation, the characteristic of 1109 super typhoon "Muifa" warm core structure is analyzed with the MWTS channel 3. Through the radiative and hydrostatic equation, TC warm core brightness temperature anomalies are related to surface pressure anomalies. In order to correct the radiation attenuation caused by MWTS scan geometric features, and improve the capability in capturing the relatively complete warm core radiation, a proposed algorithm is devised to correct the bias from receiving warm core microwave radiation, shows similar time-variant tendency with "Muifa" minimal sea level pressure as described by TC best track data. As the next generation of FY-3 satellite will be launched in 2012, this method will be further verified

[Difference analysis of muscle fatigue during the exercises of core stability training].

PubMed

Xiao, Jinzhuang; Sun, Jinli; Wang, Hongrui; Yang, Xincai; Zhao, Jinkui

2017-04-01

The present study was carried out with the surface electromyography signal of subjects during the time when subjects did the exercises of the 6 core stability trainings. We analyzed the different activity level of surface electromyography signal, and finally got various fatigue states of muscles in different exercises. Thirty subjects completed exercises of 6 core stability trainings, which were prone bridge, supine bridge, unilateral bridge (divided into two trainings, i.e. the left and right sides alternatively) and bird-dog (divided into two trainings, i.e. the left and right sides alternatively), respectively. Each exercise was held on for 1 minute and 2 minutes were given to relax between two exercises in this test. We measured both left and right sides of the body's muscles, which included erector spina, external oblique, rectus abdominis, rectus femoris, biceps femoris, anterior tibial and gastrocnemius muscles. We adopted the frequency domain characteristic value of the surface electromyography signal, i.e . median frequency slope to analyze the muscle fatigue in this study. In the present paper, the results exhibit different fatigue degrees of the above muscles during the time when they did the core stability rehabilitation exercises. It could be concluded that supine bridge and unilateral bridge can cause more fatigue on erector spina muscle, prone bridge caused Gastrocnemius muscle much fatigue and there were statistical significant differences ( P <0.05) between prone bridge and other five rehabilitation exercises in the degree of rectus abdominis muscle fatigue. There were no statistical significant differences ( P >0.05) between all the left and right sides of the same-named muscles in the median frequency slope during all the exercises of the six core stability trainings, i.e. the degree which the various kinds of rehabilitation exercises effected the left and right side of the same-named muscle had no statistical significant difference ( P >0.05). In this research, the conclusion presents quantized guidelines on the effects of core stability trainings on different muscles.

Core flow inversion tested with numerical dynamo models

NASA Astrophysics Data System (ADS)

Rau, Steffen; Christensen, Ulrich; Jackson, Andrew; Wicht, Johannes

2000-05-01

We test inversion methods of geomagnetic secular variation data for the pattern of fluid flow near the surface of the core with synthetic data. These are taken from self-consistent 3-D models of convection-driven magnetohydrodynamic dynamos in rotating spherical shells, which generate dipole-dominated magnetic fields with an Earth-like morphology. We find that the frozen-flux approximation, which is fundamental to all inversion schemes, is satisfied to a fair degree in the models. In order to alleviate the non-uniqueness of the inversion, usually a priori conditions are imposed on the flow; for example, it is required to be purely toroidal or geostrophic. Either condition is nearly satisfied by our model flows near the outer surface. However, most of the surface velocity field lies in the nullspace of the inversion problem. Nonetheless, the a priori constraints reduce the nullspace, and by inverting the magnetic data with either one of them we recover a significant part of the flow. With the geostrophic condition the correlation coefficient between the inverted and the true velocity field can reach values of up to 0.65, depending on the choice of the damping parameter. The correlation is significant at the 95 per cent level for most spherical harmonic degrees up to l=26. However, it degrades substantially, even at long wavelengths, when we truncate the magnetic data sets to l <= 14, that is, to the resolution of core-field models. In some of the latter inversions prominent zonal currents, similar to those seen in core-flow models derived from geomagnetic data, occur in the equatorial region. However, the true flow does not contain this flow component. The results suggest that some meaningful information on the core-flow pattern can be retrieved from secular variation data, but also that the limited resolution of the magnetic core field could produce serious artefacts.

Transient calcite fracture fillings in a welded tuff, Snowshoe Mountain, Colorado

USGS Publications Warehouse

Hoch, A.R.; Reddy, M.M.; Heymans, M.J.

2000-01-01

The core from two boreholes (13.1 and 19.2 m depth) drilled 500 m apart in the fractured, welded tuff near the summit of the Snowshoe Mountain, Colorado (47??30'N, 106??55'W) had unique petrographic and hydrodynamic properties. Borehole SM-4 had highly variable annual water levels, in contrast to SM-1a, whose water level remained near the land surface. Core samples from both boreholes (n = 10 and 11) were examined petrographically in thin sections impregnated with epoxy containing rhodamine to mark the pore system features, and were analyzed for matrix porosity and permeability. Core from the borehole sampling the vadose zone was characterized by open fractures with enhanced porosity around phenocrysts due to chemical weathering. Fractures within the borehole sampling the phreatic zone were mineralized with calcite and had porosity characteristics similar to Unweathered and unfractured rock. At the top of the phreatic zone petrography indicates that calcite is dissolving, thereby changing the hydrogeochemical character of the rock (i.e. permeability, porosity, reactive surface area, and mineralogy). Radiocarbon ages and C and O stable isotopes indicate that calcite mineralization occurred about 30 to 40 ka ago and that there was more than one mineralization event. Results of this study also provide some relationships between primary porosity development from 3 types of fracture in a welded tuff. (C) 2000 Elsevier Science Ltd.

Utilization of fluorescent microspheres and a green fluorescent protein-marked strain for assessment of microbiological contamination of permafrost and ground ice core samples from the Canadian High Arctic.

PubMed

Juck, D F; Whissell, G; Steven, B; Pollard, W; McKay, C P; Greer, C W; Whyte, L G

2005-02-01

Fluorescent microspheres were applied in a novel fashion during subsurface drilling of permafrost and ground ice in the Canadian High Arctic to monitor the exogenous microbiological contamination of core samples obtained during the drilling process. Prior to each drill run, a concentrated fluorescent microsphere (0.5-microm diameter) solution was applied to the interior surfaces of the drill bit, core catcher, and core tube and allowed to dry. Macroscopic examination in the field demonstrated reliable transfer of the microspheres to core samples, while detailed microscopic examination revealed penetration levels of less than 1 cm from the core exterior. To monitor for microbial contamination during downstream processing of the permafrost and ground ice cores, a Pseudomonas strain expressing the green fluorescent protein (GFP) was painted on the core exterior prior to processing. Contamination of the processed core interiors with the GFP-expressing strain was not detected by culturing the samples or by PCR to detect the gfp marker gene. These methodologies were quick, were easy to apply, and should help to monitor the exogenous microbiological contamination of pristine permafrost and ground ice samples for downstream culture-dependent and culture-independent microbial analyses.

Utilization of Fluorescent Microspheres and a Green Fluorescent Protein-Marked Strain for Assessment of Microbiological Contamination of Permafrost and Ground Ice Core Samples from the Canadian High Arctic

PubMed Central

Juck, D. F.; Whissell, G.; Steven, B.; Pollard, W.; McKay, C. P.; Greer, C. W.; Whyte, L. G.

2005-01-01

Fluorescent microspheres were applied in a novel fashion during subsurface drilling of permafrost and ground ice in the Canadian High Arctic to monitor the exogenous microbiological contamination of core samples obtained during the drilling process. Prior to each drill run, a concentrated fluorescent microsphere (0.5-μm diameter) solution was applied to the interior surfaces of the drill bit, core catcher, and core tube and allowed to dry. Macroscopic examination in the field demonstrated reliable transfer of the microspheres to core samples, while detailed microscopic examination revealed penetration levels of less than 1 cm from the core exterior. To monitor for microbial contamination during downstream processing of the permafrost and ground ice cores, a Pseudomonas strain expressing the green fluorescent protein (GFP) was painted on the core exterior prior to processing. Contamination of the processed core interiors with the GFP-expressing strain was not detected by culturing the samples or by PCR to detect the gfp marker gene. These methodologies were quick, were easy to apply, and should help to monitor the exogenous microbiological contamination of pristine permafrost and ground ice samples for downstream culture-dependent and culture-independent microbial analyses. PMID:15691963

Anthropogenic tritium in the Loire River estuary, France

NASA Astrophysics Data System (ADS)

Péron, O.; Gégout, C.; Reeves, B.; Rousseau, G.; Montavon, G.; Landesman, C.

2016-12-01

This work is carried out in the frame of a radioecological monitoring of anthropogenic tritium from upstream and downstream of several nuclear power plants along the Loire River to its estuary. This paper studies the variation of anthropogenic tritium species in the Loire River system from upstream to the mouth of the estuary. Tritiated water (HTO and HTO in sediment pore water) and organically bound tritium (OBT) forms were analysed after dedicated pre-treatments. The collected environmental samples consist in (i) surface-sediment and core samples from the river floor, (ii) surface and water column samples. A maximum 3H activity concentration of 26 ± 3 Bq·L- 1 in the Loire River estuary is obtained whereas an environmental background level around 1 Bq·L- 1 is determined for a non influenced continental area by anthropogenic activities. The European follow-up indicator used as a screening value is 100 Bq·L- 1. The conservative tritium behaviour was used in order to characterize the tidal regime and river flow influences in the mixing zone of the Loire River estuary. Furthermore, OBT levels and total organically carbon (TOC) content are explored. Finally, ratios of OBT relative to HTO in sediment pore water in surface-sediment and core samples are also discussed.

Pollution levels of DDTs and their spatiotemporal trend from sediment records in the Southern Yellow Sea, China.

PubMed

Zhao, Zongshan; Jia, Jiaojiao; Wang, Jiaokai; Liu, Aifeng; Lan, Jing; Zhang, Hailong; Zhao, Meixun

2018-02-01

In order to study the pollution levels and spatiotemporal trend of Dichlorodiphenyltrichloroethanes (DDTs) in the Southern Yellow Sea (SYS), thirty-two surface sediment samples and a sediment core have been analyzed, and our results have been compared with previous reports. DDTs contents in our samples ranged from below detection limit to 5.1ng/gdry weight (d.w.), which presented lower ecological risks in the SYS. Surface sediment results show a seaward increasing trend with high values in the northern region of the central basin of the SYS. Our reconstructed core record and historical data from previous reports reveal an increasing trend from 1905 to 1955 but a decline trend since 1985 for DDTs, which is consistent of the production, usage and banning of DDTs in China. The source identification, based on (DDE+DDD)/DDTs, suggested that aged DDTs were the major contributor, though there were some inputs of fresh DDTs from the usage of 1,1-bis(p-Chlorophenyl)-2,2,2-trichloroethanol (dicofol). Copyright © 2017 Elsevier Ltd. All rights reserved.

Free Surface Properties of III-V Compound Semiconductor Surfaces.

DTIC Science & Technology

1980-06-01

selvage. Most important is the fact that atomic displacements also occur up to two layers into the substrate in the IaSb (ll0) selvage, presumably because of...result is that the interaction is of a disordering nature. 1 2,1 3 We took LEED measurements for a very large range of exposure to molecular oxygen (103...which the Al replaces the Ga. Arguments in favor of this reaction are given by measured photoemission peak shifts: 1 8󈧗 the Ga 3-d core level shifts

A relic coral fauna threatened by global changes and human activities, Eastern Brazil.

PubMed

Leão, Zelinda M A N; Kikuchi, Ruy K P

2005-01-01

Coral species composition of drilled cores from emergent bank reefs, and coral cover of the surface of old and living reefs located along the coast of the state of Bahia, Eastern Brazil, revealed that there is a marked change in the occurrence of the major building coral species in different time intervals of the reef structure, as well as in the living surface of reefs located in two different geographical sites. Holocene core sections from two reef areas (12 degrees 40'S-38 degrees 00'W and 18 degrees 00'S-39 degrees 00'W) have as major reef builders, on its topmost core interval (3 to 4 ky old), the endemic coral Mussismilia braziliensis Verrill, 1868, which also dominate on the 2.5-3.5 ky old surfaces of truncated reef tops. At the base of the cores (the 2m lower interval, older than 4 ky BP), another endemic coral Mussismilia harttii Verrill, 1868 is the dominant reef component. The relative abundance of M. braziliensis on the living surfaces of shallow reefs from both areas, shows that in the southern area, it is up to 98% on reefs located 60 km off the coast, in depths between 3 and 4m, but do not exceed 1.3% on the surface of the northern reefs located 1-2 km off the coast in depths 4-5m. The Holocene falling sea level that occurred along the coast of Brazil since 5.1 ky BP, causes an increasing runoff into the area of coastal reefs. This phenomenon may have affected the nearshore reef building fauna, replacing a more susceptive coral fauna with one better adapted to low light levels and higher sediment influx. The high turbidity associated with early Holocene shelf flooding, should also be responsible for the absence of M. braziliensis during the initial stages of reef buildup in Brazil. At the present time, the rapidly increasing human pressure, due to changes in land uses of the coastal zone (increasing sedimentation rate, nutrification of coastal waters, industrial pollution) and underwater practices, such as overfishing and an intense tourism, is aggravating the recovery capacity of this already naturally threatened coral community. If this situation coupled with increasing sea surface temperature persists, modern coral reef growth, in Brazil cannot be maintained and the major reef building coral species of the reefs in Bahia, a remnant endemic coral fauna will very soon appear in the list of endangered species.

Denali Ice Core Record of North Pacific Sea Surface Temperatures and Marine Primary Productivity

NASA Astrophysics Data System (ADS)

Polashenski, D.; Osterberg, E. C.; Kreutz, K. J.; Winski, D.; Wake, C. P.; Ferris, D. G.; Introne, D.; Campbell, S. W.

2016-12-01

Chemical analyses of precipitation preserved in glacial ice cores provide a unique opportunity to study changes in atmospheric circulation patterns and ocean surface conditions through time. In this study, we aim to investigate changes in both the physical and biological parameters of the north-central Pacific Ocean and Bering Sea over the twentieth century using the deuterium excess (d-excess) and methanesulfonic acid (MSA) records from the Mt. Hunter ice cores drilled in Denali National Park, Alaska. These parallel, 208 m-long ice cores were drilled to bedrock during the 2013 field season on the Mt. Hunter plateau (63° N, 151° W, 3,900 m above sea level) by a collaborative research team consisting of members from Dartmouth College and the Universities of Maine and New Hampshire. The cores were sampled on a continuous melter system at Dartmouth College and analyzed for the concentrations major ions (Dionex IC) and trace metals (Element2 ICPMS), and for stable water isotope ratios (Picarro). The depth-age scale has been accurately dated to 400 AD using annual layer counting of several chemical species and further validated using known historical volcanic eruptions and the Cesium-137 spike associated with nuclear weapons testing in 1963. We use HYSPLIT back trajectory modeling to identify likely source areas of moisture and aerosol MSA being transported to the core site. Satellite imagery allows for a direct comparison between chlorophyll a concentrations in these source areas and MSA concentrations in the core record. Preliminary analysis of chlorophyll a and MSA concentrations, both derived almost exclusively from marine biota, suggest that the Mt. Hunter ice cores reflect changes in North Pacific and Bering Sea marine primary productivity. Analysis of the water isotope and MSA data in conjunction with climate reanalysis products shows significant correlations (p<0.05) between d-excess and MSA in the ice record and sea surface temperatures in the Bering Sea and North Central Pacific. These findings, coupled with the HYSPLIT storm track analysis, suggest the chemical records preserved in the Mt. Hunter cores are sensitive to Pacific Decadal Oscillation variability over the 20th century and may provide a robust proxy of PDO fluctuations prior to the instrumental record.

Defining the healthy "core microbiome" of oral microbial communities

PubMed Central

2009-01-01

Background Most studies examining the commensal human oral microbiome are focused on disease or are limited in methodology. In order to diagnose and treat diseases at an early and reversible stage an in-depth definition of health is indispensible. The aim of this study therefore was to define the healthy oral microbiome using recent advances in sequencing technology (454 pyrosequencing). Results We sampled and sequenced microbiomes from several intraoral niches (dental surfaces, cheek, hard palate, tongue and saliva) in three healthy individuals. Within an individual oral cavity, we found over 3600 unique sequences, over 500 different OTUs or "species-level" phylotypes (sequences that clustered at 3% genetic difference) and 88 - 104 higher taxa (genus or more inclusive taxon). The predominant taxa belonged to Firmicutes (genus Streptococcus, family Veillonellaceae, genus Granulicatella), Proteobacteria (genus Neisseria, Haemophilus), Actinobacteria (genus Corynebacterium, Rothia, Actinomyces), Bacteroidetes (genus Prevotella, Capnocytophaga, Porphyromonas) and Fusobacteria (genus Fusobacterium). Each individual sample harboured on average 266 "species-level" phylotypes (SD 67; range 123 - 326) with cheek samples being the least diverse and the dental samples from approximal surfaces showing the highest diversity. Principal component analysis discriminated the profiles of the samples originating from shedding surfaces (mucosa of tongue, cheek and palate) from the samples that were obtained from solid surfaces (teeth). There was a large overlap in the higher taxa, "species-level" phylotypes and unique sequences among the three microbiomes: 84% of the higher taxa, 75% of the OTUs and 65% of the unique sequences were present in at least two of the three microbiomes. The three individuals shared 1660 of 6315 unique sequences. These 1660 sequences (the "core microbiome") contributed 66% of the reads. The overlapping OTUs contributed to 94% of the reads, while nearly all reads (99.8%) belonged to the shared higher taxa. Conclusions We obtained the first insight into the diversity and uniqueness of individual oral microbiomes at a resolution of next-generation sequencing. We showed that a major proportion of bacterial sequences of unrelated healthy individuals is identical, supporting the concept of a core microbiome at health. PMID:20003481

Observed Evolution of the Upper-level Thermal Structure in Tropical Cyclones

NASA Astrophysics Data System (ADS)

Rivoire, L.; Birner, T.; Knaff, J. A.

2016-12-01

Tropical cyclones (TCs) are associated with tropopause-level cooling above the well-known tropospheric warm core. While the investigation of tropopause-level structures started as early as 1951, there is no clear consensus on the mechanisms involved. In addition, the large-scale average vertical and radial structure of the tropopause-level cooling is yet to be examined. Tropopause-level cooling destabilizes the upper atmosphere to convection, which potentially allows existing convection to reach higher altitudes. This is of particular importance during the early stages of tropical cyclogenesis. Other important characteristics of the tropopause-level cooling include its amplitude, its position relative to that of the warm core, its radial extent, and its evolution during the lifetime of TCs. These potentially influence TC structure, surface pressure gradients and maximum winds, intensity evolution, and outflow entropy. We use the 322 hurricane-strength TCs from the best-track archive in 2007-2014, along with high vertical resolution temperature measurements from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC). These measurements are composited about the Lifetime Maximum Intensity (LMI) to examine the evolution of the fine-scale upper-level thermal structure inside TCs. We find that the tropopause-cooling has an amplitude similar to that of the warm core. Relative to the far-field structure (the area average between 1300-1500 km radii), tropopause-level cooling is found to occur several days before the warm core is established. Cold anomalies extend up to 1000 km away from the storm center, and may take part in a large-scale poleward transport of cold, dry air in the UTLS. Lastly, cold air masses move away from the storm center (and warm core) after LMI, and their remains lie around the 400-700 km radius -essentially inward of the radius of maximum tangential anticyclonic winds in the outflow layer. We discuss these results in the light of the previously cited TC characteristics, and highlight the importance of an improved description of the upper-level thermal structure in TCs. We also discuss the likely mechanisms involved in TC-induced tropopause-level cooling.

Neutral Mass Spectrometry for Venus Atmosphere and Surface

NASA Technical Reports Server (NTRS)

Mahaffy, Paul

2005-01-01

The assignment is to make precise (better than 1 %) measurements of isotope ratios and accurate (5-10%) measurements of abundances of noble gas and to obtain vertical profiles of trace chemically active gases from above the clouds all the way down to the surface. Science measurement objectives are as follows: 1) Determine the composition of Venus atmosphere, including trace gas species and light stable isotopes; 2) Accurately measure noble-gas isotopic abundance in the atmosphere; 3) Provide descent, surface, and ascent meteorological data; 4) Measure zonal cloud-level winds over several Earth days; 5) Obtain near-IR descent images of the surface from 10-km altitude to the surface; 6) Accurately measure elemental abundances & mineralogy of a core from the surface; and 7) Evaluate the texture of surface materials to constrain weathering environment.

Influence of water table on carbon dioxide, carbon monoxide, and methane fluxes from taiga bog microcosms

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

Funk, D.W.; Pullmann, E.R.; Peterson, K.M.

1994-09-01

Hydrological changes, particularly alterations in water table level, may largely overshadow the more direct effects of global temperature increase upon carbon cycling in arctic and subarctic wetlands. Frozen cores (n=40) of intact soils and vegetation were collected from a bog near Fairbanks, Alaska, and fluxes of CO{sub 2}, CH{sub 4}, and Co in response to water table variation were studied under controlled conditions in the Duke University phytotron. Core microcosms thawed to a 20-cm depth over 30 days under a 20 hour photoperiod with a day/night temperature regime of 20/10{degrees}C. After 30 days the water table in 20 microcosms wasmore » decreased from the soil surface to -15 cm and maintained at the soil surface in 20 control cores. Outward fluxes of CO{sub 2} (9-16 g m{sup -2}d{sup -1}) and CO (3-4 mg m{sup -2}d{sup -1}) were greatest during early thaw and decreased to near zero for both gases before the water table treatment started. Lower water table tripled CO{sub 2} flux to the atmosphere when compared with control cores. Carbon monoxide was emitted at low rates from high water table cores and consumed by low water table cores. Methane fluxes were low (<1 mg m{sup -2}d{sup -1}) in all cores during thaw. High water table cores increased CH{sub 4} flux to 8-9 mg m{sup -2}d{sup -1} over 70 days and remained high relative to the low water table cores (<0.74 mg m{sup -2}d{sup -1}). Although drying of wetland taiga soils may decrease CH{sub 4} emissions to the atmosphere, the associated increase in CO{sub 2} due to aerobic respiration will likely increase the global warming potential of gas emissions from these soils. 43 refs., 4 figs.« less

Dynamical Core in Atmospheric Model Does Matter in the Simulation of Arctic Climate

NASA Astrophysics Data System (ADS)

Jun, Sang-Yoon; Choi, Suk-Jin; Kim, Baek-Min

2018-03-01

Climate models using different dynamical cores can simulate significantly different winter Arctic climates even if equipped with virtually the same physics schemes. Current climate simulated by the global climate model using cubed-sphere grid with spectral element method (SE core) exhibited significantly warmer Arctic surface air temperature compared to that using latitude-longitude grid with finite volume method core. Compared to the finite volume method core, SE core simulated additional adiabatic warming in the Arctic lower atmosphere, and this was consistent with the eddy-forced secondary circulation. Downward longwave radiation further enhanced Arctic near-surface warming with a higher surface air temperature of about 1.9 K. Furthermore, in the atmospheric response to the reduced sea ice conditions with the same physical settings, only the SE core showed a robust cooling response over North America. We emphasize that special attention is needed in selecting the dynamical core of climate models in the simulation of the Arctic climate and associated teleconnection patterns.

Biosorption of cationic dyes on breadfruit ( Artocarpus altilis) peel and core

NASA Astrophysics Data System (ADS)

Priyantha, Namal; Lim, Linda B. L.; Tennakoon, D. T. B.; Liaw, Elaine T. Z.; Ing, Chieng Hei; Liyandeniya, Anushka B.

2018-03-01

The purpose of this research is to investigate biosorption characteristics of two cationic dyes, methylene blue (MB) and methyl violet 2B (MV), on breadfruit ( Artocarpus altilis) peel and core. Characterization of breadfruit waste was conducted using surface titrations, thermogravimetry, and Fourier transform infrared spectroscopy. The extent of interaction between dyes and each biosorbent was monitored by absorbance measurements, which was then used in isotherm, thermodynamics, and kinetics analysis. Biosorption of MB and MV on breadfruit peel and core reaches equilibrium in 150-180 min. All four systems under investigation (MB-breadfruit peel, MB-breadfruit core, MV-breadfruit peel, and MV-breadfruit core) show similar extent of dye removal of about 80% under the conditions employed. Biosorption of both dyes on both biosorbents follow the Langmuir adsorption isotherm model at the ambient pH, at which the breadfruit surface bears a negative charge. Kinetics of biosorption of MB on breadfruit waste is so fast that it is not possible to determine the order of adsorption kinetics at the concentration level employed. The rate of biosorption of MV on breadfruit waste is smaller and follows pseudo second order kinetics with rate constants of 153.5 and 31.7 g mmol-1 min-1 for peel and core, respectively. Thermodynamics studies conducted for each biosorption system provide negative Δ G Θ, Δ H Θ and Δ S Θ values with the maximum biosorption for MB at the ambient temperature of 24 °C, while that for MV is obtained between 40 and 50 °C. All four biosorption systems show spontaneity and exothermic behaviour to varying degrees.

Electron band bending of polar, semipolar and non-polar GaN surfaces

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

Bartoš, I.; Romanyuk, O., E-mail: romanyuk@fzu.cz; Houdkova, J.

2016-03-14

The magnitudes of the surface band bending have been determined by X-ray photoelectron spectroscopy for polar, semipolar, and non-polar surfaces of wurtzite GaN crystals. All surfaces have been prepared from crystalline GaN samples grown by the hydride-vapour phase epitaxy and separated from sapphire substrates. The Ga 3d core level peak shifts have been used for band bending determination. Small band bending magnitudes and also relatively small difference between the band bendings of the surfaces with opposite polarity have been found. These results point to the presence of electron surface states of different amounts and types on surfaces of different polaritymore » and confirm the important role of the electron surface states in compensation of the bound surface polarity charges in wurtzite GaN crystals.« less

Influence of Nonfused Cores on the Photovoltaic Performance of Linear Triphenylamine-Based Hole-Transporting Materials for Perovskite Solar Cells.

PubMed

Wu, Yungen; Wang, Zhihui; Liang, Mao; Cheng, Hua; Li, Mengyuan; Liu, Liyuan; Wang, Baiyue; Wu, Jinhua; Prasad Ghimire, Raju; Wang, Xuda; Sun, Zhe; Xue, Song; Qiao, Qiquan

2018-05-30

The core plays a crucial role in achieving high performance of linear hole transport materials (HTMs) toward the perovskite solar cells (PSCs). Most studies focused on the development of fused heterocycles as cores for HTMs. Nevertheless, nonfused heterocycles deserve to be studied since they can be easily synthesized. In this work, we reported a series of low-cost triphenylamine HTMs (M101-M106) with different nonfused cores. Results concluded that the introduced core has a significant influence on conductivity, hole mobility, energy level, and solubility of linear HTMs. M103 and M104 with nonfused oligothiophene cores are superior to other HTMs in terms of conductivity, hole mobility, and surface morphology. PSCs based on M104 exhibited the highest power conversion efficiency of 16.50% under AM 1.5 sun, which is comparable to that of spiro-OMeTAD (16.67%) under the same conditions. Importantly, the employment of M104 is highly economical in terms of the cost of synthesis as compared to that of spiro-OMeTAD. This work demonstrated that nonfused heterocycles, such as oligothiophene, are promising cores for high performance of linear HTMs toward PSCs.

Mountain Lake, Presidio National Park, San Francisco: Paleoenvironment, heavy metal contamination, sedimentary record rescue, remediation, and public outreach

NASA Astrophysics Data System (ADS)

Myrbo, A.; Rodysill, J. R.; Jones, K.; Reidy, L. M.

2014-12-01

Sediment cores from Mountain Lake, a small natural lake in Presidio National Park, San Francisco, CA, provide a record of Bay Area environmental change spanning the past 2000 years, and of unusually high heavy metal contamination in the last century (Reidy 2001). In 2013, partial dredging of the lake removed the upper two meters of lake sediment as part of a remediation effort. Prior to dredging, long and short cores spatially covering the lake and representing deep and shallow environments were recovered from the lake to preserve the paleoenvironmental record of one of the only natural lakes on the San Francisco Peninsula. The cores are curated at LacCore and are available for research by the scientific community. Mountain Lake formed in an interdunal depression and was shallow and fluctuating in its first few hundred years. Lake level rise and inundation of a larger area was followed by lowstands under drier conditions around 550-700 and 1300 CE. Nonnative taxa and cultivars appeared at the time of Spanish settlement in the late 18th century, and the lake underwent eutrophication due to livestock pasturing. U.S. Army landscaping introduced trees to the watershed in the late 19th century. The upper ~1m of sediments document unusually high heavy metal contamination, especially for lead and zinc, caused by the construction and heavy use of Highway 1 on the lake shore. Lead levels peak in 1975 and decline towards the surface, reflecting the history of leaded gasoline use in California. Zinc is derived mainly from automobile tires, and follows a pattern similar to that of lead, but continues to increase towards the surface. Ongoing research includes additional radiocarbon dating and detailed lithological analysis to form the basis of lake-level reconstruction and archeological investigations. Because the Presidio archaeological record does not record human habitation in the area until approximately 1300 years before present, the core analysis also has the potential to determine whether people lived at the tip of the SF peninsula as early as 2000 BP. In October 2014 the Presidio Trust opened a Heritage Gallery that interprets the cultural and natural history of the park for the public. The Mountain Lake sedimentary record is an important component of this exhibit, which includes an epoxy-embedded core from the lake.

The host galaxy/AGN connection in nearby early-type galaxies. Is there a miniature radio-galaxy in every "core" galaxy?

NASA Astrophysics Data System (ADS)

Balmaverde, B.; Capetti, A.

2006-02-01

This is the second of a series of three papers exploring the connection between the multiwavelength properties of AGN in nearby early-type galaxies and the characteristics of their hosts. We selected two samples with 5 GHz VLA radio flux measurements down to 1 mJy, reaching levels of radio luminosity as low as 1036 erg s-1. In Paper I we presented a study of the surface brightness profiles for the 65 objects with available archival HST images out of the 116 radio-detected galaxies. We classified early-type galaxies into "core" and "power-law" galaxies, discriminating on the basis of the slope of their nuclear brightness profiles, following the Nukers scheme. Here we focus on the 29 core galaxies (hereafter CoreG). We used HST and Chandra data to isolate their optical and X-ray nuclear emission. The CoreG invariably host radio-loud nuclei, with an average radio-loudness parameter of Log R = L5 {GHz} / LB ˜ 3.6. The optical and X-ray nuclear luminosities correlate with the radio-core power, smoothly extending the analogous correlations already found for low luminosity radio-galaxies (LLRG) toward even lower power, by a factor of ˜ 1000, covering a combined range of 6 orders of magnitude. This supports the interpretation of a common non-thermal origin of the nuclear emission also for CoreG. The luminosities of the nuclear sources, most likely dominated by jet emission, set firm upper limits, as low as L/L_Edd ˜ 10-9 in both the optical and X-ray band, on any emission from the accretion process. The similarity of CoreG and LLRG when considering the distributions host galaxies luminosities and black hole masses, as well as of the surface brightness profiles, indicates that they are drawn from the same population of early-type galaxies. LLRG represent only the tip of the iceberg associated with (relatively) high activity levels, with CoreG forming the bulk of the population. We do not find any relationship between radio-power and black hole mass. A minimum black hole mass of M_BH = 108 M⊙ is apparently associated with the radio-loud nuclei in both CoreG and LLRG, but this effect must be tested on a sample of less luminous galaxies, likely to host smaller black holes. In the unifying model for BL Lacs and radio-galaxies, CoreG likely represent the counterparts of the large population of low luminosity BL Lac now emerging from the surveys at low radio flux limits. This suggests the presence of relativistic jets also in these quasi-quiescent early-type "core" galaxies.

Effects of Oxidation on Oxidation-Resistant Graphite

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

Windes, William; Smith, Rebecca; Carroll, Mark

2015-05-01

The Advanced Reactor Technology (ART) Graphite Research and Development Program is investigating doped nuclear graphite grades that exhibit oxidation resistance through the formation of protective oxides on the surface of the graphite material. In the unlikely event of an oxygen ingress accident, graphite components within the VHTR core region are anticipated to oxidize so long as the oxygen continues to enter the hot core region and the core temperatures remain above 400°C. For the most serious air-ingress accident which persists over several hours or days the continued oxidation can result in significant structural damage to the core. Reducing the oxidationmore » rate of the graphite core material during any air-ingress accident would mitigate the structural effects and keep the core intact. Previous air oxidation testing of nuclear-grade graphite doped with varying levels of boron-carbide (B4C) at a nominal 739°C was conducted for a limited number of doped specimens demonstrating a dramatic reduction in oxidation rate for the boronated graphite grade. This report summarizes the conclusions from this small scoping study by determining the effects of oxidation on the mechanical strength resulting from oxidation of boronated and unboronated graphite to a 10% mass loss level. While the B4C additive did reduce mechanical strength loss during oxidation, adding B4C dopants to a level of 3.5% or more reduced the as-fabricated compressive strength nearly 50%. This effectively minimized any benefits realized from the protective film formed on the boronated grades. Future work to infuse different graphite grades with silicon- and boron-doped material as a post-machining conditioning step for nuclear components is discussed as a potential solution for these challenges in this report.« less

Chlorinated hydrocarbon pesticides and polychlorinated biphenyls in sediment cores from San Francisco Bay

USGS Publications Warehouse

Venkatesan, M.I.; De Leon, R. P.; VanGeen, A.; Luoma, S.N.

1999-01-01

Sediment cores of known chronology from Richardson and San Pablo Bays in San Francisco Bay, CA, were analyzed for a suite of chlorinated hydrocarbon pesticides and polychlorinated biphenyls to reconstruct a historic record of inputs. Total DDTs (DDT = 2,4'- and 4,4'-dichlorodiphenyltrichloroethane and the metabolites, 2,4'- and 4,4'-DDE, -DDD) range in concentration from 4-21 ng/g and constitute a major fraction (> 84%) of the total pesticides in the top 70 cm of Richardson Bay sediment. A subsurface maximum corresponds to a peak deposition date of 1969-1974. The first measurable DDT levels are found in sediment deposited in the late 1930's. The higher DDT inventory in the San Pablo relative to the Richardson Bay core probably reflects the greater proximity of San Pablo Bay to agricultural activities in the watershed of the Sacramento and San Joaquin rivers. Total polychlorinated biphenyls (PCBs) occur at comparable levels in the two Bays (< 1-34 ng/g). PCBs are first detected in sediment deposited during the 1930's in Richardson Bay, about a decade earlier than the onset of detectable levels of DDTs. PCB inventories in San Pablo Bay are about a factor of four higher in the last four decades than in Richardson Bay, suggesting a distribution of inputs not as strongly weighed towards the upper reaches of the estuary as DDTs. The shallower subsurface maximum in PCBs compared to DDT in the San Pablo Bay core is consistent with the imposition of drastic source control measures four these constituents in 1970 and 1977 respectively. The observed decline in DDT and PCB levels towards the surface of both cores is consistent with a dramatic drop in the input of these pollutants once the effect of sediment resuspension and mixing is taken into account.

Solar reflection panels

DOEpatents

Diver, Jr., Richard B.; Grossman, James W [Albuquerque, NM; Reshetnik, Michael [Boulder, CO

2006-07-18

A solar collector comprising a glass mirror, and a composite panel, wherein the back of the mirror is affixed to a front surface of the composite panel. The composite panel comprises a front sheet affixed to a surface of a core material, preferably a core material comprising a honeycomb structure, and a back sheet affixed to an opposite surface of the core material. The invention may further comprise a sealing strip, preferably comprising EPDM, positioned between the glass mirror and the front surface of the composite panel. The invention also is of methods of making such solar collectors.

Lateral temperature variations at the core-mantle boundary deduced from the magnetic field

NASA Technical Reports Server (NTRS)

Bloxham, Jeremy; Jackson, Andrew

1990-01-01

Recent studies of the secular variation of the earth's magnetic field over periods of a few centuries have suggested that the pattern of fluid motion near the surface of earth's outer core may be strongly influenced by lateral temperature variations in the lowermost mantle. This paper introduces a self-consistent method for finding the temperature variations near the core surface by assuming that the dynamical balance there is geostrophic and that lateral density variations there are thermal in origin. As expected, the lateral temperature variations are very small. Some agreement is found between this pattern and the pattern of topography of the core-mantle boundary, but this does not conclusively answer to what extent core surface motions are controlled by the mantle, rather than being determined by processes in the core.

Origin of the anomalies in light and middle REE in sediments of an estuary affected by phosphogypsum wastes (south-western Spain).

PubMed

Borrego, J; López-González, N; Carro, B; Lozano-Soria, O

2004-12-01

Sc, Y, Th, Cu and rare earth elements (REE) concentrations have been analyzed in 14 samples of surface sediments and in two gravity cores by means of ICP-MS. Mean concentrations of Sc, Y and Th in surface sediments are 6.23, 4.76 and 16.30 ppm, respectively, lower than those present in the Upper Continental Crust (UCC). Cu concentration in these sediments is very high, 1466 ppm, and is caused by inputs from the Odiel and Tinto rivers, affected by acid mine drainage. SigmaREE mean concentration is 106.8 ppm, lower than that observed in other rivers and estuaries. In the cores, Sc, Y and Th concentrations show a significant increase in the intermediate levels, between 10 and 40 cm depth. The same pattern exists with Cu, where concentrations of 4440 ppm can be reached. Vertical evolution patterns for Sc, Y, Cu and heavy REE (HREE) are similar, and contrary to those shown by Th, light REE (LREE) and middle REE (MREE). Plots of North American Shale Composite (NASC)-normalized REE data of surface sediments show a slight depletion in REE concentrations. Most samples present with middle REE enrichment relative to light REE and heavy REE. Conversely, samples of the intermediate levels of the cores show significant enrichment of REE relative to NASC and high values in the (La/Gd)NASC and (La/Yb)NASC ratios. These anomalies in the fractionation patterns caused by enrichments in LREE and MREE concentrations is related to the presence of high concentrations of Th. They were generated by effluents from fertilizer factories between 1968 and 1998 which used phosphorite as source material.

Adjustable shear stress erosion and transport flume

DOEpatents

Roberts, Jesse D.; Jepsen, Richard A.

2002-01-01

A method and apparatus for measuring the total erosion rate and downstream transport of suspended and bedload sediments using an adjustable shear stress erosion and transport (ASSET) flume with a variable-depth sediment core sample. Water is forced past a variable-depth sediment core sample in a closed channel, eroding sediments, and introducing suspended and bedload sediments into the flow stream. The core sample is continuously pushed into the flow stream, while keeping the surface level with the bottom of the channel. Eroded bedload sediments are transported downstream and then gravitationally separated from the flow stream into one or more quiescent traps. The captured bedload sediments (particles and aggregates) are weighed and compared to the total mass of sediment eroded, and also to the concentration of sediments suspended in the flow stream.

Studies of proteoglycan involvement in CPP-mediated delivery.

PubMed

Wittrup, Anders; Zhang, Si-He; Belting, Mattias

2011-01-01

Cell-penetrating peptides (CPPs) are widely used to deliver macromolecular cargoes to intracellular sites of action. Many CPPs have been demonstrated to rely on cell surface heparan sulfate proteoglycans (HSPGs) for efficient cellular entry and delivery. In this chapter, we describe methods for the study of PG involvement in CPP uptake. We provide descriptions of how to determine whether uptake of a CPP of interest is dependent on PGs. We also provide detailed protocols for the purification of PGs by anion-exchange chromatography as well as the characterization of the HSPG core protein composition of a cell line of interest. Finally, we present methods for modulating the expression level of specific HSPG core proteins as a means to determine the core protein specificity in the uptake of a particular CPP.

First results from IODP Expedition 325 to the Great Barrier Reef: unlocking climate and sea level secrets since the Last Glacial Maximum

NASA Astrophysics Data System (ADS)

Webster, J. M.; Yokoyama, Y.; Cotterill, C.; Expedition 325 Scientists

2010-12-01

Integrated Ocean Drilling Program (IODP) Exp. 325 (GBREC: Great Barrier Reef Environmental Change) that investigated fossil reefs on the shelf edge of the Great Barrier Reef (GBR), was the fourth IODP expedition to use a mission-specific platform, and was conducted by the European Consortium for Ocean Research Drilling (ECORD) Science Operator (ESO). The scientific objectives are to establish the course of sea level change, define sea-surface temperature variations, and to analyze the impact of these environmental changes on reef growth and geometry over the period of 20-10 ka. Exp.325 complements and extends the findings of the 2005 Exp. 310 (Tahiti Sea Level) that recovered Postglacial coral reef cores from the flanks of Tahiti from 41.6-117.5 meters below sea level and spanned ~16 to ~8 ka. Preliminary data confirms that Exp. 325 recovered truly unique and valuable fossil coral reef material from key periods in Earth's sea level and climate history from 30 to 9 ka. On Exp. 325 a succession of fossil reef structures preserved on the shelf edge seaward of the modern barrier reef were cored at three geographic locations (Hydrographers Passage, Noggin Pass and Ribbon Reef) from a dynamically positioned vessel in February-April 2010. A total of 34 boreholes were cored from 17 sites in four transects at depths ranging from 42.2 to 167.2 meters below sea level. Borehole logging of four boreholes provided continuous geophysical information about the drilled strata. The cores were split and described during the Onshore Science Party at the IODP Bremen Core Repository (Germany) in July 2010, where minimum and some standard measurements were made. Initial lithologic and biologic observations identified high-quality fossil coralgal frameworks, consistent with shallow, high energy reef settings - crucial for precise reconstructions of sea level and paleoclimate change. Preliminary C14-AMS and U-Th age interpretations from 60 core catcher samples confirmed that the cores span ages from >30 to 9 ka. This chronology, combined with their recovered depths, clearly demonstrates that Exp. 325 recovered coral reef material from key periods of interest for sea level change and environmental reconstruction, including the Last Glacial Maximum, Heinrich Events 1 and 2, 19ka-MWP, Bølling-Allerød, MWP1A, the Younger Dryas and MWPB. The new Exp. 325 cores are especially important because few fossil coral records span these intervals, and even fewer are from stable, passive margin settings far from the confounding influences of ice sheets or tectonic activity. This paper summarizes Exp. 325’s first results and their broader implications for understanding global sea-level and paleoclimate changes, and provides a first interpretation of how these reefs responded to environmental stress.

Podoplanin requires sialylated O-glycans for stable expression on lymphatic endothelial cells and for interaction with platelets.

PubMed

Pan, Yanfang; Yago, Tadayuki; Fu, Jianxin; Herzog, Brett; McDaniel, J Michael; Mehta-D'Souza, Padmaja; Cai, Xiaofeng; Ruan, Changgeng; McEver, Rodger P; West, Christopher; Dai, Kesheng; Chen, Hong; Xia, Lijun

2014-12-04

O-glycosylation of podoplanin (PDPN) on lymphatic endothelial cells is critical for the separation of blood and lymphatic systems by interacting with platelet C-type lectin-like receptor 2 during development. However, how O-glycosylation controls endothelial PDPN function and expression remains unclear. In this study, we report that core 1 O-glycan-deficient or desialylated PDPN was highly susceptible to proteolytic degradation by various proteases, including metalloproteinases (MMP)-2/9. We found that the lymph contained activated MMP-2/9 and incubation of the lymph reduced surface levels of PDPN on core 1 O-glycan-deficient endothelial cells, but not on wild-type ECs. The lymph from mice with sepsis induced by cecal ligation and puncture, which contained bacteria-derived sialidase, reduced PDPN levels on wild-type ECs. The MMP inhibitor, GM6001, rescued these reductions. Additionally, GM6001 treatment rescued the reduction of PDPN level on lymphatic endothelial cells in mice lacking endothelial core 1 O-glycan or cecal ligation and puncture-treated mice. Furthermore, core 1 O-glycan-deficient or desialylated PDPN impaired platelet interaction under physiological flow. These data indicate that sialylated O-glycans of PDPN are essential for platelet adhesion and prevent PDPN from proteolytic degradation primarily mediated by MMPs in the lymph. © 2014 by The American Society of Hematology.

Effects of hydrogen treatment on ohmic contacts to p-type GaN films

NASA Astrophysics Data System (ADS)

Huang, Bohr-Ran; Chou, Chia-Hui; Ke, Wen-Cheng; Chou, Yi-Lun; Tsai, Chia-Lung; Wu, Meng-chyi

2011-06-01

This study investigated the effects of hydrogen (H 2) treatment on metal contacts to Mg-doped p-GaN films by Hall-effect measurement, current-voltage ( I- V) analyzer and X-ray photoemission spectra (XPS). The interfacial oxide layer on the p-GaN surface was found to be the main reason for causing the nonlinear I- V behavior of the untreated p-GaN films. The increased nitrogen vacancy (V N) density due to increased GaN decomposition rate at high-temperature hydrogen treatment is believed to form high density surface states on the surface of p-GaN films. Compared to untreated p-GaN films, the surface Fermi level determined by the Ga 2p core-level peak on 1000 °C H 2-treated p-GaN films lies about ˜2.1 eV closer to the conduction band edge (i.e., the surface inverted to n-type behavior). The reduction in barrier height due to the high surface state density pinned the surface Fermi level close to the conduction band edge, and allowed the electrons to easily flow over the barrier from the metal into the p-GaN films. Thus, a good ohmic contact was achieved on the p-GaN films by the surface inversion method.

Toward a computational and experimental model of a poly-epoxy surface

NASA Astrophysics Data System (ADS)

Duguet, Thomas; Bessaguet, Camille; Aufray, Maëlenn; Esvan, Jérôme; Charvillat, Cédric; Vahlas, Constantin; Lacaze-Dufaure, Corinne

2015-01-01

A model poly-epoxy surface formed by the reaction of DGEBA and EDA is studied by the combination of experiments and DFT calculations. A special synthesis protocol is presented leading to the formation of a surface that is smooth (Sa < 1 nm), chemically homogeneous, and that presents a low-defect density (0.21 μm-2), as shown by AFM characterizations. Then, XPS is used for the determination of the elemental and functional groups' surface composition. DFT allows the identification and assignment of individual bonds contributions to the experimental 1s core-level peaks. Overall, we demonstrate that such a model sample is perfectly suitable for a use as a template for the study of poly-epoxy surface functionalization.

Group IV nanocrystals with ion-exchangeable surface ligands and methods of making the same

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

Wheeler, Lance M.; Nichols, Asa W.; Chernomordik, Boris D.

Methods are described that include reacting a starting nanocrystal that includes a starting nanocrystal core and a covalently bound surface species to create an ion-exchangeable (IE) nanocrystal that includes a surface charge and a first ion-exchangeable (IE) surface ligand ionically bound to the surface charge, where the starting nanocrystal core includes a group IV element.

Isostructural solid-solid phase transition in monolayers of soft core-shell particles at fluid interfaces: structure and mechanics.

PubMed

Rey, Marcel; Fernández-Rodríguez, Miguel Ángel; Steinacher, Mathias; Scheidegger, Laura; Geisel, Karen; Richtering, Walter; Squires, Todd M; Isa, Lucio

2016-04-21

We have studied the complete two-dimensional phase diagram of a core-shell microgel-laden fluid interface by synchronizing its compression with the deposition of the interfacial monolayer. Applying a new protocol, different positions on the substrate correspond to different values of the monolayer surface pressure and specific area. Analyzing the microstructure of the deposited monolayers, we discovered an isostructural solid-solid phase transition between two crystalline phases with the same hexagonal symmetry, but with two different lattice constants. The two phases corresponded to shell-shell and core-core inter-particle contacts, respectively; with increasing surface pressure the former mechanically failed enabling the particle cores to come into contact. In the phase-transition region, clusters of particles in core-core contacts nucleate, melting the surrounding shell-shell crystal, until the whole monolayer moves into the second phase. We furthermore measured the interfacial rheology of the monolayers as a function of the surface pressure using an interfacial microdisk rheometer. The interfaces always showed a strong elastic response, with a dip in the shear elastic modulus in correspondence with the melting of the shell-shell phase, followed by a steep increase upon the formation of a percolating network of the core-core contacts. These results demonstrate that the core-shell nature of the particles leads to a rich mechanical and structural behavior that can be externally tuned by compressing the interface, indicating new routes for applications, e.g. in surface patterning or emulsion stabilization.

Effects of surface and groundwater interactions on phosphorus transport within streambank sediments.

PubMed

Thompson, Carol A; McFarland, Anne M S

2010-01-01

Understanding internal stream P transfers is important in controlling eutrophication. To determine the direction of groundwater and surface water interactions and evaluate P retention within streambank sediments, groundwater well pairs, about 5-m deep, were installed at three locations along a second-order, eutrophic stream in north-central Texas. Well cores were analyzed for P, and groundwater levels were monitored for about 2 yr. Water levels in wells furthest upstream always indicated a losing stream, while wells further downstream showed a gaining stream except during flow reversals with storm events and periods with reservoir backwater. Total-P from well cores ranged from 54 to 254 mg kg(-1) and was typically high near surface, decreased downward until redoximorphic features were encountered and then increased notably with depth to near or above surface concentrations. Very little extractable P occurred in sediments from the two upstream well sets; however, the set furthest downstream showed extractable P throughout with a high of 21 mg kg(-1) near the bottom. Repeated wetting-drying at sites A and B as noted by redoximorphic features may have shifted P into more stable sediment-bound forms. The decrease in extractable P at sites A and B compared to site C may be explained by conditions at C that were wetter and potentially anaerobic. Because the overall stream reach was more often losing than gaining, there appears to be a mass flow of P into streambank sediments. Streambank erosion may then transport this P downstream if not controlled.

Interfacial chemical and electronic structure of cobalt deposition on 2,7-dioctyl[1]benzothieno[3,2-b]benzothiophene (C8-BTBT)

NASA Astrophysics Data System (ADS)

Zhu, Menglong; Lyu, Lu; Niu, Dongmei; Zhang, Hong; Zhang, Yuhe; Liu, Peng; Gao, Yongli

2017-04-01

Interfacial chemical and electronic structure of Co deposition on 2,7-dioctyl[1]benzothieno[3,2-b]benzothiophene(C8-BTBT) was investigated by ultraviolet photoemission spectroscopy (UPS) and X-ray photoemission spectroscopy (XPS). Chemical reaction of cobalt with C8-BTBT at the interface is confirmed by a new component of S 2s peak which is electron-rich compared to the original one of C8-BTBT molecules. Intensity evolution of the core level in XPS indicates that the adsorption of Co atoms is mainly at the surface without deeper diffusion into C8-BTBT layer. Initial deposition of Co atoms downward shifts the core levels of C8-BTBT by electron transfer from isolated Co atoms or clusters to the C8-BTBT. Further deposition of Co upward shifts the core levels of C8-BTBT because of the neutralization of the thicker metal Co film. Our investigation suggests an inert buffer layer inserted to protect organic layer from reaction or decomposition and to lower the carrier barriers for both the electron and hole to improve the performance of Co/C8-BTBT-based OFETs.

A near ambient pressure XPS study of subnanometer silver clusters on Al 2O 3 and TiO 2 ultrathin film supports

DOE PAGES

Mao, Bao -Hua; Chang, Rui; Shi, Lei; ...

2014-10-29

Here, we have investigated model systems of silver clusters with different sizes (3 and 15 atoms) deposited on alumina and titania supports using ambient pressure X-ray photoelectron spectroscopy. The electronic structures of silver clusters and support materials are studied upon exposure to various atmospheres (ultrahigh vacuum, O 2 and CO) at different temperatures. Compared to bulk silver, the binding energies of silver clusters are about 0.55 eV higher on TiO 2 and 0.95 eV higher on Al 2O 3 due to the final state effect and the interaction with supports. No clear size effect of the silver XPS peak ismore » observed on different silver clusters among these samples. Silver clusters on titania show better stability against sintering. Al 2p and Ti 2p core level peak positions of the alumina and titania support surfaces change upon exposure to oxygen while the Ag 3d core level position remains unchanged. We discuss the origin of these core level shifts and their implications for catalytic properties of Ag clusters.« less

The effect of mining on the sediment - trace element geochemistry of cores from the Cheyenne River arm of Lake Oahe, South Dakota, U.S.A.

USGS Publications Warehouse

Horowitz, A.J.; Elrick, K.A.; Callender, E.

1988-01-01

Six cores, ranging in length from 1 to 2 m, were collected in the Cheyenne River arm of Lake Oahe, South Dakota, to investigate potential impacts from gold-mining operations around Lead, South Dakota. Sedimentation rates in the river arm appear to be event-dominated and rapid, on the order of 6-7 cm yr.-1. All the chemical concentrations in the core samples fall within the wide ranges previously reported for the Pierre Shale of Cretaceous age and with the exception of As, generally are similar to bed sediment levels in the Cheyenne River, Lake Oahe and Foster Bay. Based on the downcore distribution of Mn, it appears that reducing conditions exist in the sediment column of the river arm below 2-3 cm. The reducing conditions do not appear to be severe enough to produce differentiation of Fe and Mn throughout the sediment column in the river arm. Cross-correlations for high-level metal-bearing strata within the sediment column can be made for several strata and for several cores; however, cross-correlations for all the high-level metal-bearing strata are not feasible. As is the only element which appears enriched in the core samples compared to surface sediment levels. Well-crystallized arsenopyrite was found in high-As bearing strata from two cores and probably was transported in that form from reducing sediment-storage sites in the banks or floodplains of Whitewood Creek and the Belle Fourche River. It has not oxidized due to the reducing conditions in the sediment column of the Cheyenne River arm. Some As may also be transported in association with Fe- and Mn-oxides and -hydroxides, remobilized under the reducing conditions in the river arm, and then reprecipitated in authigenic sulfide phases. In either case, the As appears to be relatively immobile in the sediment column. ?? 1988.

Research on Earth's rotation and the effect of atmospheric pressure on vertical deformation and sea level variability

NASA Technical Reports Server (NTRS)

Wahr, John

1993-01-01

The work done under NASA grant NAG5-485 included modelling the deformation of the earth caused by variations in atmospheric pressure. The amount of deformation near coasts is sensitive to the nature of the oceanic response to the pressure. The PSMSL (Permanent Service for Mean Sea Level) data suggest the response is inverted barometer at periods greater than a couple months. Green's functions were constructed to describe the perturbation of the geoid caused by atmospheric and oceanic loading and by the accompanying load-induced deformation. It was found that perturbation of up to 2 cm are possible. Ice mass balance data was used for continental glaciers to look at the glacial contributions to time-dependent changes in polar motion, the lod, the earth's gravitational field, the position of the earth's center-of-mass, and global sea level. It was found that there can be lateral, non-hydrostatic structure inside the fluid core caused by gravitational forcing from the mantle, from the inner core, or from topography at the core/mantle or inner core/outer core boundaries. The nutational and tidal response of a non-hydrostatic earth with a solid inner core was modeled. Monthly, global tide gauge data from PSMSL was used to look at the 18.6-year ocean tide, the 14-month pole tide, the oceanic response to pressure, the linear trend and inter-annual variability in the earth's gravity field, the global sea level rise, and the effects of post glacial rebound. The effects of mantle anelasticity on nutations, earth tides, and tidal variation in the lod was modeled. Results of this model can be used with Crustal Dynamics observations to look at the anelastic dissipation and dispersion at tidal periods. The effects of surface topography on various components of crustal deformation was also modeled, and numerical models were developed of post glacial rebound.

Mean-field and linear regime approach to magnetic hyperthermia of core-shell nanoparticles: can tiny nanostructures fight cancer?

NASA Astrophysics Data System (ADS)

Carrião, Marcus S.; Bakuzis, Andris F.

2016-04-01

The phenomenon of heat dissipation by magnetic materials interacting with an alternating magnetic field, known as magnetic hyperthermia, is an emergent and promising therapy for many diseases, mainly cancer. Here, a magnetic hyperthermia model for core-shell nanoparticles is developed. The theoretical calculation, different from previous models, highlights the importance of heterogeneity by identifying the role of surface and core spins on nanoparticle heat generation. We found that the most efficient nanoparticles should be obtained by selecting materials to reduce the surface to core damping factor ratio, increasing the interface exchange parameter and tuning the surface to core anisotropy ratio for each material combination. From our results we propose a novel heat-based hyperthermia strategy with the focus on improving the heating efficiency of small sized nanoparticles instead of larger ones. This approach might have important implications for cancer treatment and could help improving clinical efficacy.The phenomenon of heat dissipation by magnetic materials interacting with an alternating magnetic field, known as magnetic hyperthermia, is an emergent and promising therapy for many diseases, mainly cancer. Here, a magnetic hyperthermia model for core-shell nanoparticles is developed. The theoretical calculation, different from previous models, highlights the importance of heterogeneity by identifying the role of surface and core spins on nanoparticle heat generation. We found that the most efficient nanoparticles should be obtained by selecting materials to reduce the surface to core damping factor ratio, increasing the interface exchange parameter and tuning the surface to core anisotropy ratio for each material combination. From our results we propose a novel heat-based hyperthermia strategy with the focus on improving the heating efficiency of small sized nanoparticles instead of larger ones. This approach might have important implications for cancer treatment and could help improving clinical efficacy. Electronic supplementary information (ESI) available: Unit cells per region calculation; core-shell Hamiltonian; magnetisation description functions; energy argument of Brillouin function; polydisperse models; details of experimental procedure; LRT versus core-shell model; model calculation software; and shell thickness study. See DOI: 10.1039/C5NR09093H

Facet-Dependent Deposition of Highly Strained Alloyed Shells on Intermetallic Nanoparticles for Enhanced Electrocatalysis

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

Wang, Chenyu; Sang, Xiahan; Gamler, Jocelyn T. L.

Compressive surface strains can enhance the performance of platinum-based core@shell electrocatalysts for the oxygen reduction reaction (ORR). Bimetallic core@shell nanoparticles (NPs) are widely studied nanocatalysts but often have limited lattice mismatch and surface compositions; investigations of core@shell NPs with greater compositional complexity and lattice misfit are in their infancy. Here, a new class of multimetallic NPs composed of intermetallic cores and random alloy shells is reported. Specifically, face-centered cubic (fcc) Pt- Cu random alloy shells were deposited non-epitaxially on PdCu B2 intermetallic seeds, giving rise to faceted core@shell NPs with highly strained surfaces. In fact, high resolution transmission electron microscopymore » (HRTEM) revealed orientation-dependent surface strains, where the compressive strains were minimal on Pt-Cu {111} facets but greater on {200} facets. These core@shell NPs provide higher specific and mass activities for the ORR when compared to conventional Pt-Cu NPs. Moreover, these intermetallic@random alloy NPs displayed high endurance, undergoing 10,000 cycles with only a slight decay in activity and no apparent structural changes.« less

Facet-Dependent Deposition of Highly Strained Alloyed Shells on Intermetallic Nanoparticles for Enhanced Electrocatalysis

DOE PAGES

Wang, Chenyu; Sang, Xiahan; Gamler, Jocelyn T. L.; ...

2017-08-25

Compressive surface strains can enhance the performance of platinum-based core@shell electrocatalysts for the oxygen reduction reaction (ORR). Bimetallic core@shell nanoparticles (NPs) are widely studied nanocatalysts but often have limited lattice mismatch and surface compositions; investigations of core@shell NPs with greater compositional complexity and lattice misfit are in their infancy. Here, a new class of multimetallic NPs composed of intermetallic cores and random alloy shells is reported. Specifically, face-centered cubic (fcc) Pt- Cu random alloy shells were deposited non-epitaxially on PdCu B2 intermetallic seeds, giving rise to faceted core@shell NPs with highly strained surfaces. In fact, high resolution transmission electron microscopymore » (HRTEM) revealed orientation-dependent surface strains, where the compressive strains were minimal on Pt-Cu {111} facets but greater on {200} facets. These core@shell NPs provide higher specific and mass activities for the ORR when compared to conventional Pt-Cu NPs. Moreover, these intermetallic@random alloy NPs displayed high endurance, undergoing 10,000 cycles with only a slight decay in activity and no apparent structural changes.« less

Geomagnetic South Atlantic Anomaly and global sea level rise: A direct connection?

NASA Astrophysics Data System (ADS)

de Santis, A.; Qamili, E.; Spada, G.; Gasperini, P.

2012-01-01

We highlight the existence of an intriguing and to date unreported relationship between the surface area of the South Atlantic Anomaly (SAA) of the geomagnetic field and the current trend in global sea level rise. These two geophysical variables have been growing coherently during the last three centuries, thus strongly suggesting a causal relationship supported by some statistical tests. The monotonic increase of the SAA surface area since 1600 may have been associated with an increased inflow of radiation energy through the inner Van Allen belt with a consequent warming of the Earth's atmosphere and finally global sea level rise. An alternative suggestive and original explanation is also offered, in which pressure changes at the core-mantle boundary cause surface deformations and relative sea level variations. Although we cannot establish a clear connection between SAA dynamics and global warming, the strong correlation between the former and global sea level supports the idea that global warming may be at least partly controlled by deep Earth processes triggering geomagnetic phenomena, such as the South Atlantic Anomaly, on a century time scale.

Tonsillar Surface Micro Flora: Does it Truly Represent Pathological Tonsillar Flora?

PubMed

Haq, Syed Nadeem Ul; Ayub, Zeeshan; Ahmed, Azeema

2017-01-01

To determine the best method of identifying core tonsillar flora. Quasi-experimental study. ENT Department, Combined Military Hospital, Lahore, from September 2013 to October 2015. Eighty-seven patients of recurrent tonsillitis undergoing tonsillectomy were included. All the patients, after being anaesthetised, had surface swabs taken from the tonsillar surface followed by tonsillar aspiration with a 5cc syringe. Following tonsillectomy, the tonsils were sent for culture of core flora. All three specimens from each patient were cultured according to established criteria. The patient population had 33 (37%) female and 54 (62%) male patients. Flora of 12 (13.8%) surface swabs and 68 (78.2%) tonsillar aspirates matched the flora cultured from core of the tonsils. Chi-square test showed this difference to be significant (p-value <0.001). Tonsillar aspiration gave a much more realistic picture of the tonsillar core flora as compared to surface swabs.

Examining Model Atmospheric Particles Inside and Out

NASA Astrophysics Data System (ADS)

Wingen, L. M.; Zhao, Y.; Fairhurst, M. C.; Perraud, V. M.; Ezell, M. J.; Finlayson-Pitts, B. J.

2017-12-01

Atmospheric particles scatter incoming solar radiation and act as cloud condensation nuclei (CCN), thereby directly and indirectly affecting the earth's radiative balance and reducing visibility. These atmospheric particles may not be uniform in composition. Differences in the composition of a particle's outer surface from its core can arise during particle growth, (photo)chemical aging, and exchange of species with the gas phase. The nature of the surface on a molecular level is expected to impact growth mechanisms as well as their ability to act as CCN. Model laboratory particle systems are explored using direct analysis in real time-mass spectrometry (DART-MS), which is sensitive to surface composition, and contrasted with average composition measurements using high resolution, time-of-flight aerosol mass spectrometry (HR-ToF-AMS). Results include studies of the heterogeneous reactions of amines with solid dicarboxylic acid particles, which are shown to generate aminium dicarboxylate salts at the particle surface, leaving an unreacted core. Combination of both mass spectrometric techniques reveals a trend in reactivity of C3-C7 dicarboxylic acids with amines and allows calculation of the DART probe depth into the particles. The results of studies on additional model systems that are currently being explored will also be reported.

Spatio-Temporal Variability of Recent Snow Accumulation Across the West Antarctic Ice Sheet Divide Using Ultra-High Frequency Radar and Shallow Firn Cores

NASA Astrophysics Data System (ADS)

Keeler, D. G.; Rupper, S.; Forster, R. R.; Miège, C.; Brewer, S.; Koenig, L.

2017-12-01

The West Antarctic Ice Sheet (WAIS) could be a substantial source of future sea level rise, with 3+ meters of potential increase stored in the ice sheet. Adequate predictions of WAIS contributions, however, depend on well-constrained surface mass balance estimates for the region. Given the sparsity of available data, such estimates are tenuous. Although new data are periodically added, further research (both to collect more data and better utilize existing data) is critical to addressing these issues. Here we present accumulation data from 9 shallow firn cores and 600 km of Ku band radar traces collected as part of the Satellite Era Antarctic Traverse (SEAT) 2011/2012 field season. Using these data, combined with similar data collected during the SEAT 2010/2011 field season, we investigate the spatial variability in accumulation across the WAIS Divide and surrounding regions. We utilize seismic interpretation and 3D visualization tools to investigate the extent and variations of laterally continuous internal horizons in the radar profiles, and compare the results to nearby firn cores. Previous results show that clearly visible, laterally continuous horizons in radar returns in this area do not always represent annual accumulation isochrones, but can instead represent multi-year or sub-annual events. The automated application of Bayesian inference techniques to averaged estimates of multiple adjacent radar traces, however, can estimate annually-resolved independent age-depth scales for these radar data. We use these same automated techniques on firn core isotopic records to infer past snow accumulation rates, allowing a direct comparison with the radar-derived results. Age-depth scales based on manual annual-layer counting of geochemical and isotopic species from these same cores provide validation for the automated approaches. Such techniques could theoretically be applied to additional radar/core data sets in polar regions (e.g. Operation IceBridge), thereby increasing the number of high resolution accumulation records available in these data-sparse regions. An increased understanding of the variability in magnitude and past rates of surface mass balance can provide better constraints on sea level projections and more precise context for present-day and future observations in these regions.

Core-shell fuel cell electrodes

DOEpatents

Adzic, Radoslav; Bliznakov, Stoyan; Vukmirovic, Miomir

2017-07-25

Embodiments of the disclosure relate to electrocatalysts. The electrocatalyst may include at least one gas-diffusion layer having a first side and a second side, and particle cores adhered to at least one of the first and second sides of the at least one gas-diffusion layer. The particle cores includes surfaces adhered to the at least one of the first and second sides of the at least one gas-diffusion layer and surfaces not in contact with the at least one gas-diffusion layer. Furthermore, a thin layer of catalytically atoms may be adhered to the surfaces of the particle cores not in contact with the at least one gas-diffusion layer.

Tunable optofluidic microring laser based on a tapered hollow core microstructured optical fiber.

PubMed

Li, Zhi-Li; Zhou, Wen-Yuan; Luo, Ming-Ming; Liu, Yan-Ge; Tian, Jian-Guo

2015-04-20

A tunable optofluidic microring dye laser within a tapered hollow core microstructured optical fiber was demonstrated. The fiber core was filled with a microfluidic gain medium plug and axially pumped by a nanosecond pulse laser at 532 nm. Strong radial emission and low-threshold lasing (16 nJ/pulse) were achieved. Lasing was achieved around the surface of the microfluidic plug. Laser emission was tuned by changing the liquid surface location along the tapered fiber. The possibility of developing a tunable laser within the tapered simplified hollow core microstructured optical fiber presents opportunities for developing liquid surface position sensors and biomedical analysis.

Interaction of gold and silver nanoparticles with human plasma: Analysis of protein corona reveals specific binding patterns.

PubMed

Lai, Wenjia; Wang, Qingsong; Li, Lumeng; Hu, Zhiyuan; Chen, Jiankui; Fang, Qiaojun

2017-04-01

Determining how nanomaterials interact with plasma will assist in understanding their effects on the biological system. This work presents a systematic study of the protein corona formed from human plasma on 20nm silver and gold nanoparticles with three different surface modifications, including positive and negative surface charges. The results show that all nanoparticles, even those with positive surface modifications, acquire negative charges after interacting with plasma. Approximately 300 proteins are identified on the coronas, while 99 are commonly found on each nanomaterial. The 20 most abundant proteins account for over 80% of the total proteins abundance. Remarkably, the surface charge and core of the nanoparticles, as well as the isoelectric point of the plasma proteins, are found to play significant roles in determining the nanoparticle coronas. Albumin and globulins are present at levels of less than 2% on these nanoparticle coronas. Fibrinogen, which presents in the plasma but not in the serum, preferably binds to negatively charged gold nanoparticles. These observations demonstrate the specific plasma protein binding pattern of silver and gold nanoparticles, as well as the importance of the surface charge and core in determining the protein corona compositions. The potential downstream biological impacts of the corona proteins were also investigated. Copyright © 2017 Elsevier B.V. All rights reserved.

Photoemission study of electronic structure of the half-metallic ferromagnet Co3Sn2S2

NASA Astrophysics Data System (ADS)

Holder, M.; Dedkov, Yu. S.; Kade, A.; Rosner, H.; Schnelle, W.; Leithe-Jasper, A.; Weihrich, R.; Molodtsov, S. L.

2009-05-01

Surface electronic structure of polycrystalline and single-crystalline samples of the half-metallic ferromagnet Co3Sn2S2 was studied by means of angle-resolved and core-level photoemissions. The experiments were performed in temperature regimes both above and below a Curie temperature of 176.9 K. The spectroscopic results are compared to local-spin density approximation band-structure calculations for the bulk samples. It is found that the surface sensitive experimental data are generally reproduced by the bulk computation suggesting that the theoretically predicted half-metallic properties of Co3Sn2S2 are retained at the surface.

Postcollision interaction in noble gas clusters: observation of differences in surface and bulk line shapes.

PubMed

Lindblad, A; Fink, R F; Bergersen, H; Lundwall, M; Rander, T; Feifel, R; Ohrwall, G; Tchaplyguine, M; Hergenhahn, U; Svensson, S; Björneholm, O

2005-12-01

The surface and bulk components of the x-ray photoelectron spectra of free noble gas clusters are shown to display differences in the influence of postcollision interaction between the photoelectron and the Auger electron on the spectral line shape; the bulk component is observed to be less affected than the surface and atomic parts of the spectra. A model for postcollision interaction in nonmetallic solids and clusters is also provided which takes the polarization screening into account. Core-level photoelectron spectra of Ar, Kr, and Xe have been recorded to verify the dependence of the postcollision interaction effect on the polarizability of the sample.

Electronic Interactions of Size-Selected Oxide Clusters on Metallic and Thin Film Oxide Supports

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

Xue, Meng; Nakayama, Miki; Liu, Ping

The interfacial electronic structure of various size-selected metal oxide nanoclusters (M 3O x; M = Mo, Nb, Ti) on Cu(111) and a thin film of Cu 2O supports were investigated in this paper by a combination of experimental methods and density functional theory (DFT). These systems explore electron transfer at the metal–metal oxide interface which can modify surface structure, metal oxidation states, and catalytic activity. Electron transfer was probed by measurements of surface dipoles derived from coverage dependent work function measurements using two-photon photoemission (2PPE) and metal core level binding energy spectra from X-ray photoelectron spectroscopy (XPS). The measured surfacemore » dipoles are negative for all clusters on Cu(111) and Cu 2O/Cu(111), but those on the Cu 2O surface are much larger in magnitude. In addition, sub-stoichiometric or “reduced” clusters exhibit smaller surface dipoles on both the Cu(111) and Cu 2O surfaces. Negative surface dipoles for clusters on Cu(111) suggest Cu → cluster electron transfer, which is generally supported by DFT-calculated Bader charge distributions. For Cu 2O/Cu(111), calculations of the surface electrostatic potentials show that the charge distributions associated with cluster adsorption structures or distortions at the cluster–Cu 2O–Cu(111) interface are largely responsible for the observed negative surface dipoles. Changes observed in the XPS spectra for the Mo 3d, Nb 3d, and Ti 2p core levels of the clusters on Cu(111) and Cu 2O/Cu(111) are interpreted with help from the calculated Bader charges and cluster adsorption structures, the latter providing information about the presence of inequivalent cation sites. Finally, the results presented in this work illustrate how the combined use of different experimental probes along with theoretical calculations can result in a more realistic picture of cluster–support interactions and bonding.« less

Electronic Interactions of Size-Selected Oxide Clusters on Metallic and Thin Film Oxide Supports

DOE PAGES

Xue, Meng; Nakayama, Miki; Liu, Ping; ...

2017-09-13

The interfacial electronic structure of various size-selected metal oxide nanoclusters (M 3O x; M = Mo, Nb, Ti) on Cu(111) and a thin film of Cu 2O supports were investigated in this paper by a combination of experimental methods and density functional theory (DFT). These systems explore electron transfer at the metal–metal oxide interface which can modify surface structure, metal oxidation states, and catalytic activity. Electron transfer was probed by measurements of surface dipoles derived from coverage dependent work function measurements using two-photon photoemission (2PPE) and metal core level binding energy spectra from X-ray photoelectron spectroscopy (XPS). The measured surfacemore » dipoles are negative for all clusters on Cu(111) and Cu 2O/Cu(111), but those on the Cu 2O surface are much larger in magnitude. In addition, sub-stoichiometric or “reduced” clusters exhibit smaller surface dipoles on both the Cu(111) and Cu 2O surfaces. Negative surface dipoles for clusters on Cu(111) suggest Cu → cluster electron transfer, which is generally supported by DFT-calculated Bader charge distributions. For Cu 2O/Cu(111), calculations of the surface electrostatic potentials show that the charge distributions associated with cluster adsorption structures or distortions at the cluster–Cu 2O–Cu(111) interface are largely responsible for the observed negative surface dipoles. Changes observed in the XPS spectra for the Mo 3d, Nb 3d, and Ti 2p core levels of the clusters on Cu(111) and Cu 2O/Cu(111) are interpreted with help from the calculated Bader charges and cluster adsorption structures, the latter providing information about the presence of inequivalent cation sites. Finally, the results presented in this work illustrate how the combined use of different experimental probes along with theoretical calculations can result in a more realistic picture of cluster–support interactions and bonding.« less

Assessment of heavy metal contamination in the sediments of Nansihu Lake Catchment, China.

PubMed

Liu, Enfeng; Shen, Ji; Yang, Liyuan; Zhang, Enlou; Meng, Xianghua; Wang, Jianjun

2010-02-01

At present, anthropogenic contribution of heavy metals far exceeds natural input in some aquatic sediment, but the proportions are difficult to differentiate due to the changes in sediment characters. In this paper, the metal (Al, Fe, K, Mg, Ca, Cr, Cu, Ni, and Zn) concentrations, grain size, and total organic carbon (TOC) content in the surface and core sediments of Nansihu Lake Catchment (the open lake and six inflow rivers) were determined. The chemical speciations of the metals (Al, Fe, Cr, Cu, Ni, and Zn) in the surface sediments were also analyzed. Approaches of factor analysis, normalized enrichment factor (EF) and the new non-residual fractions enrichment factor (K(NRF)) were used to differentiate the sources of the metals in the sediments, from detrital clastic debris or anthropogenic input, and to quantify the anthropogenic contamination. The results indicate that natural processes were more dominant in concentrating the metals in the surface and core sediments of the open lake. High concentration of Ca and deficiency of other metals in the upper layers of the sediment core were attributed to the input of carbonate minerals in the catchment with increasing human activities since 1980s. High TOC content magnified the deficiency of the metals. Nevertheless, the EF and K(NRF) both reveal moderate to significant anthropogenic contamination of Cr, Cu, Ni, and Zn in the surface sediments of Laoyun River and the estuary and Cr in the surface sediments of Baima River. The proportion of non-residual fractions (acid soluble, reducible, and oxidizable fractions) of Cr, Cu, Ni, and Zn in the contaminated sediments increased to 37-99% from the background levels less than 30%.

Multivariate geostatistical analysis and source identification of heavy metals in the sediment of Poyang Lake in China.

PubMed

Dai, Lijun; Wang, Lingqing; Li, Lianfang; Liang, Tao; Zhang, Yongyong; Ma, Chuanxin; Xing, Baoshan

2018-04-15

Heavy metals in lake sediment have become a great concern because their remobilization has frequently occurred under hydrodynamic disturbance in shallow lakes. In this study, heavy metals (Cr, Cu, Cd, Pb, and Zn) concentrations in the surface and core sediments of the largest freshwater lake in China, Poyang Lake, were investigated. Geostatistical prediction maps of heavy metals distribution in the surface sediment were completed as well as further data mining. Based on the prediction maps, the ranges of Cr, Cu, Cd, Pb, and Zn concentrations in the surface sediments of the entire lake were 96.2-175.2, 38.3-127.6, 0.2-2.3, 22.5-77.4, and 72.3-254.4mg/kg, respectively. A self-organizing map (SOM) was applied to find the inner element relation of heavy metals in the sediment cores. K-means clustering of the self-organizing map was also completed to define the Euclidian distance of heavy metals in the sediment cores. The geoaccumulation index (I geo ) for Poyang Lake indicated a varying degree of heavy metal contamination in the surface sediment, especially for Cu. The heavy metal contamination in the sediment profiles had similar pollution levels as those of surface sediment, except for Cd. Correlation matrix mapping and principal component analysis (PCA) were used to support the idea that Cr, Pb, and Zn may be mainly derived from both lithogenic and human activities, such as atmospheric and river inflow transportation, whereas Cu and Cd may be mainly contributed from anthropogenic sources, such as mining activities and fertilizer application. Copyright © 2017 Elsevier B.V. All rights reserved.

The COMMD Family Regulates Plasma LDL Levels and Attenuates Atherosclerosis Through Stabilizing the CCC Complex in Endosomal LDLR Trafficking.

PubMed

Fedoseienko, Alina; Wijers, Melinde; Wolters, Justina C; Dekker, Daphne; Smit, Marieke; Huijkman, Nicolette; Kloosterhuis, Niels; Klug, Helene; Schepers, Aloys; Willems van Dijk, Ko; Levels, Johannes H M; Billadeau, Daniel D; Hofker, Marten H; van Deursen, Jan; Westerterp, Marit; Burstein, Ezra; Kuivenhoven, Jan Albert; van de Sluis, Bart

2018-06-08

COMMD (copper metabolism MURR1 domain)-containing proteins are a part of the CCC (COMMD-CCDC22 [coiled-coil domain containing 22]-CCDC93 [coiled-coil domain containing 93]) complex facilitating endosomal trafficking of cell surface receptors. Hepatic COMMD1 inactivation decreases CCDC22 and CCDC93 protein levels, impairs the recycling of the LDLR (low-density lipoprotein receptor), and increases plasma low-density lipoprotein cholesterol levels in mice. However, whether any of the other COMMD members function similarly as COMMD1 and whether perturbation in the CCC complex promotes atherogenesis remain unclear. The main aim of this study is to unravel the contribution of evolutionarily conserved COMMD proteins to plasma lipoprotein levels and atherogenesis. Using liver-specific Commd1 , Commd6 , or Commd9 knockout mice, we investigated the relation between the COMMD proteins in the regulation of plasma cholesterol levels. Combining biochemical and quantitative targeted proteomic approaches, we found that hepatic COMMD1, COMMD6, or COMMD9 deficiency resulted in massive reduction in the protein levels of all 10 COMMDs. This decrease in COMMD protein levels coincided with destabilizing of the core (CCDC22, CCDC93, and chromosome 16 open reading frame 62 [C16orf62]) of the CCC complex, reduced cell surface levels of LDLR and LRP1 (LDLR-related protein 1), followed by increased plasma low-density lipoprotein cholesterol levels. To assess the direct contribution of the CCC core in the regulation of plasma cholesterol levels, Ccdc22 was deleted in mouse livers via CRISPR/Cas9-mediated somatic gene editing. CCDC22 deficiency also destabilized the complete CCC complex and resulted in elevated plasma low-density lipoprotein cholesterol levels. Finally, we found that hepatic disruption of the CCC complex exacerbates dyslipidemia and atherosclerosis in ApoE3*Leiden mice. Collectively, these findings demonstrate a strong interrelationship between COMMD proteins and the core of the CCC complex in endosomal LDLR trafficking. Hepatic disruption of either of these CCC components causes hypercholesterolemia and exacerbates atherosclerosis. Our results indicate that not only COMMD1 but all other COMMDs and CCC components may be potential targets for modulating plasma lipid levels in humans. © 2018 American Heart Association, Inc.

Bonding core mating surfaces improves transformer

NASA Technical Reports Server (NTRS)

Mclyman, W. T.

1978-01-01

Modifications to assembly procedures for C-core transformers virtually eliminates changes in core end gaps due to temperature cycling during impregnation and potting stages, thus stabilizing magnetization properties of core.

Hepatitis B Virus Core Gene Mutations Which Block Nucleocapsid Envelopment

PubMed Central

Koschel, Matthias; Oed, Daniela; Gerelsaikhan, Tudevdagwa; Thomssen, Reiner; Bruss, Volker

2000-01-01

Recently we generated a panel of hepatitis B virus core gene mutants carrying single insertions or deletions which allowed efficient expression of the core protein in bacteria and self-assembly of capsids. Eleven of these mutations were introduced into a eukaryotic core gene expression vector and characterized by trans complementation of a core-negative HBV genome in cotransfected human hepatoma HuH7 cells. Surprisingly, four mutants (two insertions [EFGA downstream of A11 and LDTASALYR downstream of R39] and two deletions [Y38-R39-E40 and L42]) produced no detectable capsids. The other seven mutants supported capsid formation and pregenome packaging/viral minus- and plus-strand-DNA synthesis but to different levels. Four of these seven mutants (two insertions [GA downstream of A11 and EHCSP downstream of P50] and two deletions [S44 and A80]) allowed virion morphogenesis and secretion. The mutant carrying a deletion of A80 at the tip of the spike protruding from the capsid was hepatitis B virus core antigen negative but wild type with respect to virion formation, indicating that this site might not be crucial for capsid-surface protein interactions during morphogenesis. The other three nucleocapsid-forming mutants (one insertion [LS downstream of S141] and two deletions [T12 and P134]) were strongly blocked in virion formation. The corresponding sites are located in the part of the protein forming the body of the capsid and not in the spike. These mutations may alter sites on the particle which contact surface proteins during envelopment, or they may block the appearance of a signal for the transport or the maturation of the capsid which is linked to viral DNA synthesis and required for envelopment. PMID:10590084

Evolution of a compound droplet attached to a core-shell nozzle under the action of a strong electric field

NASA Astrophysics Data System (ADS)

Reznik, S. N.; Yarin, A. L.; Zussman, E.; Bercovici, L.

2006-06-01

The shape evolution of small compound droplets at the exit of a core-shell system in the presence of a sufficiently strong electric field is studied both experimentally and theoretically. It is shown that the jetting effect at the tip of the shell nozzle does not necessarily cause entrainment of the core fluid, in which case the co-electrospinning process fails to produce core-shell nanofibers. The remedy lies in extending the core nozzle outside its shell counterpart by about half the radius of the latter. The results also show that the free charges migrate very rapidly from both fluids and their interface to the free surface of the shell. This reflects the fact that most of the prejetting evolution of the droplet can be effectively described in terms of the perfect conductor model, even though the fluids can be characterized as leaky dielectrics. The stress level at the core-shell interface is of the order of 5×103g/(cms2), the relevant value in assessing the viability of viruses, bacteria, DNA molecules, drugs, enzymes, chromophores, and proteins to be encapsulated in nanofibers via co-electrospinning.

Sedimentological, mineralogical, and geochemical results from surface sediments and the sediment record from Site 2 of the ICDP drilling project at Lake Towuti, Indonesia

NASA Astrophysics Data System (ADS)

Hasberg, A. K.; Melles, M.; Wennrich, V.; Vogel, H.; Just, J.; Russell, J. M.; Bijaksana, S.; Morlock, M.; Opitz, S.

2017-12-01

More than 1000 m of sediment core were recovered in spring 2015 from three different drill sites in tropical Lake Towuti (2.5°S, 121°E), Indonesia, during the Towuti Drilling Project (TDP) of the International Continental Scientific Drilling Program (ICDP). Furthermore, a set of 84 lake surface sediment samples, distributed over the entire lake, was collected in order to better understand modern sedimentary processes. The surface samples were investigated for physical, chemical, mineralogical, and biological properties at the University of Cologne (UoC), Germany. On the sediment cores macro- and microscopical lithological descriptions, line-scan imaging, logging of physical properties (MSCL), and subsampling was conducted at the National Lacustrine Core Facility of the University of Minnesota, USA, in November 2015 and January 2016. Afterwards, the archive core halves and 672 subsamples of TDP Site 2 were shipped to the UoC for X-Ray Fluorescence (XRF) scanning and sedimentological, geochemical, and mineralogical analyses, respectively, supplemented by visible to near-infrared spectroscopy (VNIR) at Brown University, USA. The data from the surface samples evidence that allochthonous sedimentation in Lake Towuti today is dominated by fluvial supply from five distinguishable source areas: (i) the Mahalona River to the north, which drains lakes Mahalona and Matano, (ii) inlets around the village of Timampu to the northwest, (iii) the Loeha River to the east, (iv) the Lengke River to the south, and (v) the Lemo-Lemo River to the northeast of Lake Towuti. Of these, source areas (ii) and (iii) as well as (iv) and (v) have similar geochemical compositions, respectively. In addition, the lake sedimentation is significantly influenced by gravitational sediment supply from steep slopes as well as lake-internal gravitational and density-driven processes. The uppermost 41 m of sediment core 2A consist of pelagic sediments (totaling 11 m) and event layers from mass movement ( 30 m) that were formed during the past 50 cal kyr. In this period, the data reflect significant climatic and environmental changes, in particular in precipitation and lake level. These changes seem to be coupled to prominent paleoclimatic events.

Constraints on Mercury's Core-Mantle Boundary Region

NASA Astrophysics Data System (ADS)

Hauck, S. A., II; Chabot, N. L.; Sun, P.; Jing, Z.; Johnson, C. L.; Margot, J. L.; Padovan, S.; Peale, S. J.; Phillips, R. J.; Solomon, S. C.

2014-12-01

Understanding the boundary between a planet's metallic core and silicate mantle is important for constraining processes that dominate on either side of this boundary. Geophysical measurements of the planet Mercury by the MESSENGER spacecraft have provided evidence of a core larger than earlier, less-constrained estimates. Further, these results, taken in concert with measurements of the elemental composition of the surface by MESSENGER, have led to the suggestion that the uppermost layer of the outer core may be highly enriched in sulfur, and the top of the core may consist of a solid sulfide layer. The low iron and relatively large sulfur contents of the surface indicate highly reducing conditions during planet formation, placing constraints on the potential composition of Mercury's core. Recent metal-silicate partitioning experiments have developed new limits on the amount of sulfur and silicon that may partition into the core as a function of sulfur abundance at the surface. Models for the planet's internal structure constrained by the current best estimates of the bulk density, normalized polar moment of inertia, and fraction of the polar moment of inertia of the solid layer that extends from the surface to the top of the liquid outer core provide an important view of the layering and bulk composition of Mercury. By combining the results of these internal structure models with the experimental relationship between core and mantle composition we place new limits on core composition and structure. Further, imposing measured compositional constraints on the miscibility of iron-sulfur-silicon alloys yields important limits on the presence or absence of an immiscible sulfur-rich liquid layer or a solid sulfide layer at the top of the core.

Enhanced nitrogen diffusion induced by atomic attrition

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

Ochoa, E.A.; Figueroa, C.A.; Czerwiec, T.

2006-06-19

The nitrogen diffusion in steel is enhanced by previous atomic attrition with low energy xenon ions. The noble gas bombardment generates nanoscale texture surfaces and stress in the material. The atomic attrition increases nitrogen diffusion at lower temperatures than the ones normally used in standard processes. The stress causes binding energy shifts of the Xe 3d{sub 5/2} electron core level. The heavy ion bombardment control of the texture and stress of the material surfaces may be applied to several plasma processes where diffusing species are involved.

Gravity Scaling of a Power Reactor Water Shield

NASA Technical Reports Server (NTRS)

Reid, Robert S.; Pearson, J. Boise

2008-01-01

Water based reactor shielding is being considered as an affordable option for use on initial lunar surface power systems. Heat dissipation in the shield from nuclear sources must be rejected by an auxiliary thermal hydraulic cooling system. The mechanism for transferring heat through the shield is natural convection between the core surface and an array of thermosyphon radiator elements. Natural convection in a 100 kWt lunar surface reactor shield design has been previously evaluated at lower power levels (Pearson, 2007). The current baseline assumes that 5.5 kW are dissipated in the water shield, the preponderance on the core surface, but with some volumetric heating in the naturally circulating water as well. This power is rejected by a radiator located above the shield with a surface temperature of 370 K. A similarity analysis on a water-based reactor shield is presented examining the effect of gravity on free convection between a radiation shield inner vessel and a radiation shield outer vessel boundaries. Two approaches established similarity: 1) direct scaling of Rayleigh number equates gravity-surface heat flux products, 2) temperature difference between the wall and thermal boundary layer held constant on Earth and the Moon. Nussult number for natural convection (laminar and turbulent) is assumed of form Nu = CRa(sup n). These combined results estimate similarity conditions under Earth and Lunar gravities. The influence of reduced gravity on the performance of thermosyphon heat pipes is also examined.

Fe{sub 2}O{sub 3} nanowires on HOPG as precursor of new carbon-based anode for high-capacity lithium ion batteries

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

Angelucci, Marco; Frau, Eleonora; Betti, Maria Grazia

Iron Oxides nanostructures are very promising systems for new generation of anode material for Lithium-Ion batteries because of their high capacity associated to their surface area. A core-level photoemission study of Fe{sub 2}O{sub 3} nanowires deposited on highly-oriented pyrolitic graphite (HOPG) under Li exposure is presented. The Fe-2p, Fe-3p, and Li-1s core-level lineshape evolution upon Li exposure in ultra-high-vacuum conditions clearly brings to light the Fe ion reduction from fully trivalent to prevalently divalent at saturation. Furthermore, the graphite substrate allows allocation of a large amount of Li ions surrounding the iron-oxide nanowires, opening a new scenario towards the usemore » of graphene for improving the ionic charge exchange.« less

A model of Saturn inferred from its measured gravitational field

NASA Astrophysics Data System (ADS)

Kong, Dali; Zhang, Keke; Schubert, Gerald; Anderson, John D.

2018-04-01

We present an interior model of Saturn with an ice-rock core, a metallic region, an outer molecular envelope and a thin transition layer between the metallic and molecular regions. The shape of Saturn’s 1 bar surface is irregular and determined fully self-consistently by the required equilibrium condition. While the ice-rock core is assumed to have a uniform density, three different equations of state are adopted for the metallic, molecular and transition regions. The Saturnian model is constrained by its known mass, its known equatorial and polar radii, and its known zonal gravitational coefficients, J 2n , n = 1, 2, 3. The model produces an ice-rock core with equatorial radius 0.203 R S, where R S is the equatorial radius of Saturn at the 1-bar pressure surface; the core density ρ c = 10388.1 kgm‑3 corresponding to 13.06 Earth masses; and an analytical expression describing the Saturnian irregular shape of the 1-bar pressure level. The model also predicts the values of the higher-order gravitational coefficients, J 8, J 10 and J 12, for the hydrostatic Saturn and suggests that Saturn’s convective dynamo operates in the metallic region approximately defined by 0.2 R S < r e < 0.7 R S, where r e denotes the equatorial radial distance from the Saturnian center of figure.

Germanium–Tin/Cadmium Sulfide Core/Shell Nanocrystals with Enhanced Near-Infrared Photoluminescence

DOE PAGES

Boote, Brett W.; Men, Long; Andaraarachchi, Himashi P.; ...

2017-06-27

Ge 1–xSn x alloy nanocrystals and Ge 1–xSn x/CdS core/shell nanocrystals were prepared via solution phase synthesis, and their size, composition, and optical properties were characterized. We found that the diameter of the nanocrystal samples ranged from 6 to 13 nm. Furthermore, the crystal structure of the Ge 1–xSn x materials was consistent with a cubic diamond phase, while the CdS shell was consistent with the zinc blende polytype. Inclusion of Sn alone does not result in enhanced photoluminescence intensity; however, adding an epitaxial CdS shell onto the Ge 1–xSn x nanocrystals does enhance the photoluminescence up to 15-fold versusmore » that of Ge/CdS nanocrystals with a pure Ge core. There is more effective passivation of surface defects, and a consequent decrease in the level of surface oxidation, by the CdS shell as a result of improved epitaxy (smaller lattice mismatch) is the most likely explanation for the increased photoluminescence observed for the Ge 1–xSn x/CdS materials. With enhanced photoluminescence in the near-infrared region, Ge 1–xSn x core/shell nanocrystals might be useful alternatives to other materials for energy capture and conversion applications and as imaging probes.« less

Tetraphenylporphyrin electronic properties: a combined theoretical and experimental study of thin films deposited by SuMBD.

PubMed

Nardi, Marco; Verucchi, Roberto; Corradi, Claudio; Pola, Marco; Casarin, Maurizio; Vittadini, Andrea; Iannotta, Salvatore

2010-01-28

Porphyrins and their metal complexes are particularly well suitable for applications in photoelectronics, sensing, energy production, because of their chemical, electronic and optical properties. The understanding of the electronic properties of the pristine molecule is of great relevance for the study and application of the wide class of these compounds. This is notably important for the recently achieved in-vacuo synthesis of organo-metallic thin films directly from the pure free base organic-inorganic precursors in the vapor phase, and its interpretation by means of surface electron spectroscopies. We report on a combined experimental and theoretical study of the physical/chemical properties of tetraphenylporphyrin, H(2)TPP, deposited on the SiO(2)/Si(100) native oxide surface by supersonic molecular beam deposition (SuMBD). Valence states and 1s core level emissions of carbon and nitrogen have been investigated with surface photoelectron spectroscopies by using synchrotron radiation light. The interpretation of the spectra has been guided by density functional numerical experiments on the gas-phase molecule. Non-relativistic calculations were carried out for the valence states, whereas a two component relativistic approach in the zeroth-order regular approximation was used to investigate the core levels. The good agreement between theoretical and experimental analysis results in a comprehensive overview of the chemical properties of the H(2)TPP molecule, highly improving reliability in the interpretation of experimental photoemission spectra.

Dependence of Hurricane intensity and structures on vertical resolution and time-step size

NASA Astrophysics Data System (ADS)

Zhang, Da-Lin; Wang, Xiaoxue

2003-09-01

In view of the growing interests in the explicit modeling of clouds and precipitation, the effects of varying vertical resolution and time-step sizes on the 72-h explicit simulation of Hurricane Andrew (1992) are studied using the Pennsylvania State University/National Center for Atmospheric Research (PSU/NCAR) mesoscale model (i.e., MM5) with the finest grid size of 6 km. It is shown that changing vertical resolution and time-step size has significant effects on hurricane intensity and inner-core cloud/precipitation, but little impact on the hurricane track. In general, increasing vertical resolution tends to produce a deeper storm with lower central pressure and stronger three-dimensional winds, and more precipitation. Similar effects, but to a less extent, occur when the time-step size is reduced. It is found that increasing the low-level vertical resolution is more efficient in intensifying a hurricane, whereas changing the upper-level vertical resolution has little impact on the hurricane intensity. Moreover, the use of a thicker surface layer tends to produce higher maximum surface winds. It is concluded that the use of higher vertical resolution, a thin surface layer, and smaller time-step sizes, along with higher horizontal resolution, is desirable to model more realistically the intensity and inner-core structures and evolution of tropical storms as well as the other convectively driven weather systems.

Sequence stratigraphy of the subaqueous Changjiang (Yangtze River) delta since the Last Glacial Maximum

NASA Astrophysics Data System (ADS)

Xu, Taoyu; Wang, Guoqing; Shi, Xuefa; Wang, Xin; Yao, Zhengquan; Yang, Gang; Fang, Xisheng; Qiao, Shuqing; Liu, Shengfa; Wang, Xuchen; Zhao, Quanhong

2016-01-01

This study focuses on sedimentary research at the subaqueous Changjiang (Yangtze River) delta, based on five high-resolution seismic profiles and seven borehole cores with accurate AMS 14C datings. Three distinct seismic units were identified from the seismic profiles according to seismic reflection characteristics, and five sedimentary facies were recognized from borehole cores. These facies constituted a fining upward sedimentary sequence in relation to postglacial sea-level transgression. Three sequence surfaces (sequence boundary (SB), transgressive surface (TS), and maximum flooding surface (MFS)) demarcate the boundaries between early transgressive system tract (E-TST), late transgressive system tract (L-TST), early highstand system tract (E-HST) and late highstand system tract (L-HST), which constitute the sixth order sequence. These system tracts were developed coevally with postglacial sea-level rise. E-TST (~ 19-12 ka BP) corresponds to an incised-valley infilling in the early stages of postglacial transgression whereas L-TST (~ 12-7.5 ka BP) was formed during the last stage of postglacial transgression. The progradational structure of L-TST reflected in seismic profiles is possibly related to the intensification of the East Asian summer monsoon. E-HST (~ 7.5-2 ka BP) was deposited in response to the highstand after maximum postglacial transgression was reached, while L-HST (~ 2 ka BP-present) was initiated by accelerated progradation of the Changjiang delta.

Spring design for use in the core of a nuclear reactor

DOEpatents

Willard, Jr., H. James

1993-01-01

A spring design particularly suitable for use in the core of a nuclear reactor includes one surface having a first material oriented in a longitudinal direction, and another surface having a second material oriented in a transverse direction. The respective surfaces exhibit different amounts of irraditation induced strain.

Determination of the core temperature of a Li-ion cell during thermal runaway

NASA Astrophysics Data System (ADS)

Parhizi, M.; Ahmed, M. B.; Jain, A.

2017-12-01

Safety and performance of Li-ion cells is severely affected by thermal runaway where exothermic processes within the cell cause uncontrolled temperature rise, eventually leading to catastrophic failure. Most past experimental papers on thermal runaway only report surface temperature measurement, while the core temperature of the cell remains largely unknown. This paper presents an experimentally validated method based on thermal conduction analysis to determine the core temperature of a Li-ion cell during thermal runaway using surface temperature and chemical kinetics data. Experiments conducted on a thermal test cell show that core temperature computed using this method is in good agreement with independent thermocouple-based measurements in a wide range of experimental conditions. The validated method is used to predict core temperature as a function of time for several previously reported thermal runaway tests. In each case, the predicted peak core temperature is found to be several hundreds of degrees Celsius higher than the measured surface temperature. This shows that surface temperature alone is not sufficient for thermally characterizing the cell during thermal runaway. Besides providing key insights into the fundamental nature of thermal runaway, the ability to determine the core temperature shown here may lead to practical tools for characterizing and mitigating thermal runaway.

Deformation Behavior of Al/a-Si Core-shell Nanostructures

NASA Astrophysics Data System (ADS)

Fleming, Robert

Al/a-Si core-shell nanostructures (CSNs), consisting of a hemispherical Al core surrounded by a hard shell of a-Si, have been shown to display unusual mechanical behavior in response to compression loading. Most notably, these nanostructures exhibit substantial deformation recovery, even when loaded much beyond the elastic limit. Nanoindentation measurements revealed a unique mechanical response characterized by discontinuous signatures in the load-displacement data. In conjunction with the indentation signatures, nearly complete deformation recovery is observed. This behavior is attributed to dislocation nucleation and annihilation events enabled by the 3-dimensional confinement of the Al core. As the core confinement is reduced, either through an increase in confined core volume or a change in the geometrical confinement, the indentation signatures and deformation resistance are significantly reduced. Complimentary molecular dynamics simulations show that a substantial amount of dislocation egression occurs in the core of CSNs during unloading as dislocations annihilate at the core/shell interface. Smaller core diameters correlate with the development of a larger back-stress within the core during unloading, which further correlates with improved dislocation annihilation after unloading. Furthermore, dislocations nucleated in the core of core-shell nanorods are not as effectively removed as compared to CSNs. Nanostructure-textured surfaces (NSTSs) composed of Al/a-Si CSNs have improved tribological properties compared surfaces patterned with Al nanodots and a flat (100) Si surface. NSTSs have a coefficient of friction (COF) as low as 0.015, exhibit low adhesion with adhesion forces on the order of less than 1 microN, and are highly deformation resistant, with no apparent surface deformation after nanoscratch testing, even at contact forces up to 8000 microN. In comparison, (100) Si has substantially higher adhesion and COF ( 10 microN and 0.062, respectively), while the Al nanodots have both higher friction (COF 0.044) and are deformed when subjected to contact loads as low as 250 microN. This integrated experimental and computational study elucidates the mechanisms that contribute to the novel properties of Al/a-Si CSNs and characterizes the tribological properties of surface composed of these nanostructures, which provides a foundation for the rational design of novel technologies based on CSNs.

Hard X-ray photoemission study of the Fabre salts (TMTTF)2X (X = SbF6 and PF6)

NASA Astrophysics Data System (ADS)

Medjanik, Katerina; de Souza, Mariano; Kutnyakhov, Dmytro; Gloskovskii, Andrei; Müller, Jens; Lang, Michael; Pouget, Jean-Paul; Foury-Leylekian, Pascale; Moradpour, Alec; Elmers, Hans-Joachim; Schönhense, Gerd

2014-11-01

Core-level photoemission spectra of the Fabre salts with X = SbF6 and PF6 were taken using hard X-rays from PETRA III, Hamburg. In these salts TMTTF layers show a significant stack dimerization with a charge transfer of 1 e per dimer to the anion SbF6 or PF6. At room temperature and slightly below the core-level spectra exhibit single lines, characteristic for a well-screened metallic state. At reduced temperatures progressive charge localization sets in, followed by a 2nd order phase transition into a charge-ordered ground state. In both salts groups of new core-level signals occur, shifted towards lower kinetic energies. This is indicative of a reduced transverse-conductivity across the anion layers, visible as layer-dependent charge depletion for both samples. The surface potential was traced via shifts of core-level signals of an adsorbate. A well-defined potential could be established by a conducting cap layer of 5 nm aluminum which appears "transparent" due to the large probing depth of HAXPES (8-10 nm). At the transition into the charge-ordered phase the fluorine 1 s line of (TMTTF)2SbF6 shifts by 2.8 eV to higher binding energy. This is a spectroscopic fingerprint of the loss of inversion symmetry accompanied by a cooperative shift of the SbF6 anions towards the more positively charged TMTTF donors. This shift does not occur for the X = PF6 compound, most likely due to smaller charge disproportion or due to the presence of charge disorder.

Positron annihilation induced Auger electron spectroscopy

NASA Technical Reports Server (NTRS)

Weiss, Alex; Koymen, A. R.; Mehl, David; Jensen, K. O.; Lei, Chun; Lee, K. H.

1990-01-01

Recently, Weiss et al. have demonstrated that it is possible to excite Auger transitions by annihilating core electrons using a low energy (less than 30eV) beam of positrons. This mechanism makes possible a new electron spectroscopy, Positron annihilation induced Auger Electron Spectroscopy (PAES). The probability of exciting an Auger transition is proportional to the overlap of the positron wavefunction with atomic core levels. Since the Auger electron energy provides a signature of the atomic species making the transition, PAES makes it possible to determine the overlap of the positron wavefunction with a particular element. PAES may therefore provide a means of detecting positron-atom complexes. Measurements of PAES intensities from clean and adsorbate covered Cu surfaces are presented which indicate that approx. 5 percent of positrons injected into CU at 25eV produce core annihilations that result in Auger transitions.

Annually resolved ice core records of tropical climate variability over the past ~1800 years.

PubMed

Thompson, L G; Mosley-Thompson, E; Davis, M E; Zagorodnov, V S; Howat, I M; Mikhalenko, V N; Lin, P-N

2013-05-24

Ice cores from low latitudes can provide a wealth of unique information about past climate in the tropics, but they are difficult to recover and few exist. Here, we report annually resolved ice core records from the Quelccaya ice cap (5670 meters above sea level) in Peru that extend back ~1800 years and provide a high-resolution record of climate variability there. Oxygen isotopic ratios (δ(18)O) are linked to sea surface temperatures in the tropical eastern Pacific, whereas concentrations of ammonium and nitrate document the dominant role played by the migration of the Intertropical Convergence Zone in the region of the tropical Andes. Quelccaya continues to retreat and thin. Radiocarbon dates on wetland plants exposed along its retreating margins indicate that it has not been smaller for at least six millennia.

Theoretical and Experimental Studies of Epidermal Heat Flux Sensors for Measurements of Core Body Temperature

PubMed Central

Zhang, Yihui; Webb, Richard Chad; Luo, Hongying; Xue, Yeguang; Kurniawan, Jonas; Cho, Nam Heon; Krishnan, Siddharth; Li, Yuhang; Huang, Yonggang

2016-01-01

Long-term, continuous measurement of core body temperature is of high interest, due to the widespread use of this parameter as a key biomedical signal for clinical judgment and patient management. Traditional approaches rely on devices or instruments in rigid and planar forms, not readily amenable to intimate or conformable integration with soft, curvilinear, time-dynamic, surfaces of the skin. Here, materials and mechanics designs for differential temperature sensors are presented which can attach softly and reversibly onto the skin surface, and also sustain high levels of deformation (e.g., bending, twisting, and stretching). A theoretical approach, together with a modeling algorithm, yields core body temperature from multiple differential measurements from temperature sensors separated by different effective distances from the skin. The sensitivity, accuracy, and response time are analyzed by finite element analyses (FEA) to provide guidelines for relationships between sensor design and performance. Four sets of experiments on multiple devices with different dimensions and under different convection conditions illustrate the key features of the technology and the analysis approach. Finally, results indicate that thermally insulating materials with cellular structures offer advantages in reducing the response time and increasing the accuracy, while improving the mechanics and breathability. PMID:25953120

Core thermal response and hydrogen generation of the N Reactor hydrogen mitigation design basis accident

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

White, M.D.; Lombardo, N.J.; Heard, F.J.

1988-04-01

Calculations were performed to determine core heatup, core damage, and subsequent hydrogen production of a hypothetical loss-of-cooling accident at the Department of Energy's N Reactor. The thermal transient response of the reactor core was solved using the TRUMP-BD computer program. Estimates of whole-core thermal damage and hydrogen production were made by weighting the results of multiple half-length pressure tube simulations at various power levels. The Baker-Just and Wilson parabolic rate equations for the metal-water chemical reactions modeled the key phenomena of chemical energy and hydrogen evolution. Unlimited steam was assumed available for continuous oxidation of exposed Zircaloy-2 surfaces and formore » uranium metal with fuel cladding beyond the failure temperature (1038 C). Intact fuel geometry was modeled. Maximum fuel temperatures (1181 C) in the cooled central regions of the core were predicted to occur one-half hour into the accident scenario. Maximum fuel temperatures of 1447 C occurred in the core GSCS-regions at the end of the 10-h transient. After 10-h 26% of the fuel inventory was predicted to have failed. Peak hydrogen evolution equaled 42 g/s, while 10-h integrated hydrogen evolution equaled 167 kg. 12 refs., 12 figs., 2 tabs.« less

Structure, Dynamics, and Deuterium Fractionation of Massive Pre-stellar Cores

NASA Astrophysics Data System (ADS)

Goodson, Matthew D.; Kong, Shuo; Tan, Jonathan C.; Heitsch, Fabian; Caselli, Paola

2016-12-01

High levels of deuterium fraction in N2H+ are observed in some pre-stellar cores. Single-zone chemical models find that the timescale required to reach observed values ({D}{frac}{{{N}}2{{{H}}}+}\\equiv {{{N}}}2{{{D}}}+/{{{N}}}2{{{H}}}+≳ 0.1) is longer than the free-fall time, possibly 10 times longer. Here, we explore the deuteration of turbulent, magnetized cores with 3D magnetohydrodynamics simulations. We use an approximate chemical model to follow the growth in abundances of N2H+ and N2D+. We then examine the dynamics of the core using each tracer for comparison to observations. We find that the velocity dispersion of the core as traced by N2D+ appears slightly sub-virial compared to predictions of the Turbulent Core Model of McKee & Tan, except at late times just before the onset of protostar formation. By varying the initial mass surface density, the magnetic energy, the chemical age, and the ortho-to-para ratio of H2, we also determine the physical and temporal properties required for high deuteration. We find that low initial ortho-to-para ratios (≲ 0.01) and/or multiple free-fall times (≳ 3) of prior chemical evolution are necessary to reach the observed values of deuterium fraction in pre-stellar cores.

Luminescence study of Eu3+ doped GdVO4 nanoparticles: Concentration, particle size, and core/shell effects

NASA Astrophysics Data System (ADS)

Singh, N. Shanta; Ningthoujam, R. S.; Devi, L. Romila; Yaiphaba, N.; Sudarsan, V.; Singh, S. Dorendrajit; Vatsa, R. K.; Tewari, R.

2008-11-01

Nanoparticles of GdVO4 doped with Eu3+ and core/shell of GdVO4:Eu3+/GdVO4 are prepared by urea hydrolysis method using ethylene glycol as capping agent as well as reaction medium at 130 °C. Unit cell volume increases when GdVO4 is doped with Eu3+ indicating the substitution of Gd3+ lattice sites by Eu3+. From luminescence study, it is confirmed that there is no particle size effect on emission positions of Eu3+. Optimum luminescence intensity is found to be in 5-10 at. % Eu3+. Above these concentrations, luminescence intensity decreases due to concentration quenching effect. There is an enhancement in luminescence intensity of core/shell nanoparticles. This has been attributed to the reduction in surface inhomogenities of Eu3+ surroundings by bonding to GdVO4 shell. The lifetime for D50 level increases with annealing and core/shell formation.

A diurnal resonance in the ocean tide and in the earth's load response due to the resonant free 'core nutation'

NASA Technical Reports Server (NTRS)

Wahr, J. M.; Sasao, T.

1981-01-01

The effects of the oceans, which are subject to a resonance due to a free rotational eigenmode of an elliptical, rotating earth with a fluid outer core having an eigenfrequency of (1 + 1/460) cycle/day, on the body tide and nutational response of the earth to the diurnal luni-tidal force are computed. The response of an elastic, rotating, elliptical, oceanless earth with a fluid outer core to a given load distribution on its surface is first considered, and the tidal sea level height for equilibrium and nonequilibrium oceans is examined. Computations of the effects of equilibrium and nonequilibrium oceans on the nutational and deformational responses of the earth are then presented which show small but significant perturbations to the retrograde 18.6-year and prograde six-month nutations, and more important effects on the earth body tide, which is also resonant at the free core notation eigenfrequency.

Tuning electrocatalytic activity of Pt monolayer shell by bimetallic Ir-M (M=Fe, Co, Ni or Cu) cores for the oxygen reduction reaction

DOE PAGES

Kuttiyiel, Kurian A.; Choi, YongMan; Sasaki, Kotaro; ...

2016-05-18

Here, platinum monolayer electrocatalyst are known to exhibit excellent oxygen reduction reaction (ORR) activity depending on the type of substrate used. Here we demonstrate a relationship between the ORR electrocatalytic activity and the surface electronic structure of Pt monolayer shell induced by various IrM bimetallic cores (M=Fe, Co, Ni or Cu). The relationship is rationalized by comparing density functional theory calculations and experimental results. For an efficient Pt monolayer electrocatalyst, the core should induce sufficient contraction to the Pt shell leading to a downshift of the d-band center with respect to the Fermi level. Depending on the structure of themore » IrM, relative to that of pure Ir, this interaction not only alters the electronic and geometric structure but also induces segregation effects. Combined these effects significantly enhance the ORR activities of the Pt monolayer shell on bimetallic Ir cores electrocatalysts.« less

Influence of surface displacement on solid state flow induced by horizontally heterogeneous Joule heating in the inner core of the Earth

NASA Astrophysics Data System (ADS)

Takehiro, Shin-ichi

2015-04-01

We investigate the influence of surface displacement on fluid motions induced by horizontally heterogeneous Joule heating in the inner core. The difference between the governing equations and those of Takehiro (2011) is the boundary conditions at the inner core boundary (ICB). The temperature disturbance at the ICB coincides with the melting temperature, which varies depending on the surface displacement. The normal component of stress equalizes with the buoyancy induced by the surface displacement. The toroidal magnetic field and surface displacement with the horizontal structure of Y20 spherical harmonics is given. The flow fields are calculated numerically for various amplitudes of surface displacement with the expected values of the parameters of the core. Further, by considering the heat balance at the ICB, the surface displacement amplitude is related to the turbulent velocity amplitude in the outer core, near the ICB. The results show that when the turbulent velocity is on the order of 10-1 -10-2 m/s, the flow and stress fields are similar to those of Takehiro (2011), where the surface displacement vanishes. As the amplitude of the turbulent velocity decreases, the amplitude of the surface displacement increases, and counter flows from the polar to equatorial regions emerge around the ICB, while flow in the inner regions is directed from the equatorial to polar regions, and the non-zero radial component of velocity at the ICB remains. When the turbulent velocity is on the order of 10-4 -10-5 m/s, the radial component of velocity at the ICB vanishes, the surface counter flows become stronger than the flow in the inner region, and the amplitude of the stress field near the ICB dominates the inner region, which might be unsuitable for explaining the elastic anisotropy in the inner core.

Core-shell fuel cell electrodes

DOEpatents

Adzic, Radoslav; Bliznakov, Stoyan; Vukmirovic, Miomir

2017-12-26

Embodiments of the disclosure relate to membrane electrode assemblies. The membrane electrode assembly may include at least one gas-diffusion layer having a first side and a second side, and particle cores adhered to at least one of the first and second sides of the at least one gas-diffusion layer. The particle cores includes surfaces adhered to the at least one of the first and second sides of the at least one gas-diffusion layer and surfaces not in contact with the at least one gas-diffusion layer. Furthermore, a thin layer of catalytically atoms may be adhered to the surfaces of the particle cores not in contact with the at least one gas-diffusion layer.

A metallicity recipe for rocky planets

NASA Astrophysics Data System (ADS)

Dawson, Rebekah I.; Chiang, Eugene; Lee, Eve J.

2015-10-01

Planets with sizes between those of Earth and Neptune divide into two populations: purely rocky bodies whose atmospheres contribute negligibly to their sizes, and larger gas-enveloped planets possessing voluminous and optically thick atmospheres. We show that whether a planet forms rocky or gas-enveloped depends on the solid surface density of its parent disc. Assembly times for rocky cores are sensitive to disc solid surface density. Lower surface densities spawn smaller planetary embryos; to assemble a core of given mass, smaller embryos require more mergers between bodies farther apart and therefore exponentially longer formation times. Gas accretion simulations yield a rule of thumb that a rocky core must be at least 2M⊕ before it can acquire a volumetrically significant atmosphere from its parent nebula. In discs of low solid surface density, cores of such mass appear only after the gas disc has dissipated, and so remain purely rocky. Higher surface density discs breed massive cores more quickly, within the gas disc lifetime, and so produce gas-enveloped planets. We test model predictions against observations, using planet radius as an observational proxy for gas-to-rock content and host star metallicity as a proxy for disc solid surface density. Theory can explain the observation that metal-rich stars host predominantly gas-enveloped planets.

Comparative DFT study of structure, reactivity and IR spectra of phosphorus-containing dendrons with Pdbnd Nsbnd Pdbnd S linkages, vinyl and azide functional groups

NASA Astrophysics Data System (ADS)

Furer, V. L.; Vandyukov, A. E.; Majoral, J. P.; Caminade, A. M.; Gottis, S.; Laurent, R.; Kovalenko, V. I.

2015-07-01

Fourier transform IR spectra of the first generation dendrons built from thiophosphoryl core with terminal Psbnd Cl groups, vinyl (G1) and azide (G2) functional group at the level of the core have been recorded. The optimized geometries of low energy isomers of G1 and G2 have been calculated by density functional (DFT) method at the PBE/TZ2P level of theory. DFT is used for analyzing the properties of each structural part (core, branches, surface). It was found that the repeated branching units of G1 and G2 contain planar sbnd Osbnd C6H4sbnd CHdbnd Nsbnd N(CH3)sbnd Prbond2 fragments. DFT results for the structure of G1 and G2 are in good agreement with X-ray diffraction measurements. A complete vibrational assignment is proposed for different parts of G1 and G2. The global and local reactivity descriptors have been used to characterize the reactivity pattern of the core functional and terminal groups. Natural bond orbital (NBO) analysis has been applied to comparative study of charge delocalization. Our study reveals why azide group linked to phosphorus has a different reactivity when compared to organic azides.

Radionuclides (210Po and 210Pb) and Some Heavy Metals in Fish and Sediments in Lake Bafa, Turkey, and the Contribution of 210Po to the Radiation Dose.

PubMed

Manav, Ramazan; Uğur Görgün, Aysun; Filizok, Işık

2016-11-09

The pollution level of Lake Bafa was investigated by collecting fish samples { Dicentrarchus labrax (sea bass), Liza ramada (mullet) and Anguilla anguilla (eel)}, surface sediment, and core samples. In all these samples, 210 Po and 210 Pb concentrations were estimated, and total annual dose rates were obtained for each species. Some heavy metal (Cr, Ni, Pb, Cd, Mn, Fe, and Zn) concentration levels were obtained for the fish and a core sample. The sediment mass accumulation rate was found to be 3.27 g·m -2 ·day -1 (0.119 g·cm -2 ·y -1 ) from a core sample. The heavy metal concentrations in the vertical profile of samples from the core were also observed. The measured concentration of Zn, Pb, Cd, and Cr were between the ERL (effects range low) and ERM (effects range median) limits, while Ni concentrations were higher than the ERM limit. The observed concentrations of Cd, Pb, and Zn in fish samples did not exceed the limits in accordance with Turkish Food Regulations. Further, the maximum effective dose equivalent of 210 Po in the area was found to be 1.169 µSv·y -1 .

One-dimensional cuts through multidimensional potential-energy surfaces by tunable x rays

NASA Astrophysics Data System (ADS)

Eckert, Sebastian; da Cruz, Vinícius Vaz; Gel'mukhanov, Faris; Ertan, Emelie; Ignatova, Nina; Polyutov, Sergey; Couto, Rafael C.; Fondell, Mattis; Dantz, Marcus; Kennedy, Brian; Schmitt, Thorsten; Pietzsch, Annette; Odelius, Michael; Föhlisch, Alexander

2018-05-01

The concept of the potential-energy surface (PES) and directional reaction coordinates is the backbone of our description of chemical reaction mechanisms. Although the eigenenergies of the nuclear Hamiltonian uniquely link a PES to its spectrum, this information is in general experimentally inaccessible in large polyatomic systems. This is due to (near) degenerate rovibrational levels across the parameter space of all degrees of freedom, which effectively forms a pseudospectrum given by the centers of gravity of groups of close-lying vibrational levels. We show here that resonant inelastic x-ray scattering (RIXS) constitutes an ideal probe for revealing one-dimensional cuts through the ground-state PES of molecular systems, even far away from the equilibrium geometry, where the independent-mode picture is broken. We strictly link the center of gravity of close-lying vibrational peaks in RIXS to a pseudospectrum which is shown to coincide with the eigenvalues of an effective one-dimensional Hamiltonian along the propagation coordinate of the core-excited wave packet. This concept, combined with directional and site selectivity of the core-excited states, allows us to experimentally extract cuts through the ground-state PES along three complementary directions for the showcase H2O molecule.

Comparative hazard analysis and toxicological modeling of diverse nanomaterials using the embryonic zebrafish (EZ) metric of toxicity

NASA Astrophysics Data System (ADS)

Harper, Bryan; Thomas, Dennis; Chikkagoudar, Satish; Baker, Nathan; Tang, Kaizhi; Heredia-Langner, Alejandro; Lins, Roberto; Harper, Stacey

2015-06-01

The integration of rapid assays, large datasets, informatics, and modeling can overcome current barriers in understanding nanomaterial structure-toxicity relationships by providing a weight-of-the-evidence mechanism to generate hazard rankings for nanomaterials. Here, we present the use of a rapid, low-cost assay to perform screening-level toxicity evaluations of nanomaterials in vivo. Calculated EZ Metric scores, a combined measure of morbidity and mortality in developing embryonic zebrafish, were established at realistic exposure levels and used to develop a hazard ranking of diverse nanomaterial toxicity. Hazard ranking and clustering analysis of 68 diverse nanomaterials revealed distinct patterns of toxicity related to both the core composition and outermost surface chemistry of nanomaterials. The resulting clusters guided the development of a surface chemistry-based model of gold nanoparticle toxicity. Our findings suggest that risk assessments based on the size and core composition of nanomaterials alone may be wholly inappropriate, especially when considering complex engineered nanomaterials. Research should continue to focus on methodologies for determining nanomaterial hazard based on multiple sub-lethal responses following realistic, low-dose exposures, thus increasing the availability of quantitative measures of nanomaterial hazard to support the development of nanoparticle structure-activity relationships.

A Nonequilibrium Figure of Saturn's Satellite Iapetus and the Origin of the Equatorial Ridge on Its Surface

NASA Astrophysics Data System (ADS)

Kondratyev, B. P.

2018-03-01

The structure, dynamical equilibrium, and evolution of Saturn's moon Iapetus are studied. It has been shown that, in the current epoch, the oblateness of the satellite ɛ2 ≈ 0.046 does not correspond to its angular velocity of rotation, which causes the secular spherization behavior of the ice shell of Iapetus. To study this evolution, we apply a spheroidal model, containing a rock core and an ice shell with an external surface ɛ2, to Iapetus. The model is based on the equilibrium finite-difference equation of the Clairaut theory, while the model parameters are taken from observations. The mean radius of the rock core and the oblateness of its level surface, ɛ1 ≈ 0.028, were determined. It was found that Iapetus is covered with a thick ice shell, which is 56.6% of the mean radius of the figure. We analyze a role of the core in the evolution of the shape of a gravitating figure. It was determined that the rock core plays a key part in the settling of the ice masses of the equatorial bulge, which finally results in the formation of a large circular equatorial ridge on the surface of the satellite. From the known mean altitude of this ice ridge, it was found that, in the epoch of its formation, the rotation period of Iapetus was 166 times shorter than that at present, as little as T ≈ 11h27m. This is consistent with the fact that a driving force of the evolution of the satellite in our model was its substantial despinning. The model also predicts that the ice ridge should be formed more intensively in the leading (dark and, consequently, warmer) hemisphere of the satellite, where the ice is softer. This inference agrees with the observations: in the leading hemisphere of Iapetus, the ridge is actually high and continuous everywhere, while it degenerates into individual ice peaks in the opposite colder hemisphere.

Role of surface energy on the morphology and optical properties of GaP micro & nano structures grown on polar and non-polar substrates

NASA Astrophysics Data System (ADS)

Roychowdhury, R.; Kumar, Shailendra; Wadikar, A.; Mukherjee, C.; Rajiv, K.; Sharma, T. K.; Dixit, V. K.

2017-10-01

Role of surface energy on the morphology, crystalline quality, electronic structure and optical properties of GaP layer grown on Si (001), Si (111), Ge (111) and GaAs (001) is investigated. GaP layers are grown on four different substrates under identical growth kinetics by metal organic vapour phase epitaxy. The atomic force microscopy images show that GaP layer completely covers the surface of GaAs substrate. On the other hand, the surfaces of Si (001), Si (111), Ge (111) substrates are partially covered with crystallographically morphed GaP island type micro and nano-structures. Origin of these crystallographically morphed GaP island is explained by the theoretical calculation of surface energy of the layer and corresponding substrates respectively. The nature of GaP island type micro and nano-structures and layers are single crystalline with existence of rotational twins on Si and Ge (111) substrates which is confirmed by the phi, omega and omega/2theta scans of high resolution x-ray diffraction. The electronic valence band offsets between the GaP and substrates have been determined from the valence band spectra of ultraviolet photoelectron spectroscopy. The valence electron plasmon of GaP are investigated by studying the energy values of Ga (3d) core level along with loss peaks in the energy dependent photoelectron spectra. The peak observed within the range of 3-6 eV from the Ga (3d) core level in the photoelectron spectra are associated to inter band transitions as their energy values are estimated from the pseudo dielectric function by the spectroscopic ellipsometry.

Thermal barriers for compartments

DOEpatents

Kreutzer, Cory J.; Lustbader, Jason A.

2017-10-17

An aspect of the present disclosure is a thermal barrier that includes a core layer having a first surface, a second surface, and a first edge, and a first outer layer that includes a third surface and a second edge, where the third surface substantially contacts the first surface, the core layer is configured to minimize conductive heat transfer through the barrier, and the first outer layer is configured to maximize reflection of light away from the barrier.

Fractographic logging for determination of pre-core and core-induced fractures: Nicholas Combs No. 7239 well, Hazard, Kentucky

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

Kulander, B.R.; Dean, S.L.; Barton, C.C.

1977-01-01

Methods results, and conclusions formulated during a prototype fractographic logging study of seventy-five feet of oriented Devonian shale core are summarized. The core analyzed is from the Nicholas Combs No. 7239 well located twelve miles due north of Hazard, Kentucky. The seventy-five foot core length was taken from a cored section lying between 2369.0 feet (subsea) and 2708.0 feet (subsea). Total core length is 339.0 feet. The core was extracted from the upper Devonian Ohio and Olentangy shale formations. Results indicate that there are few tectonic (pre-core) fractures within the studied core section. The region may nevertheless be cut atmore » core sample depth by well-defined vertical or inclined tectonic fractures that the vertically drilled test core didn't intersect. This is likely since surface Plateau systematic fractures in other Plateau areas are vertical to sub-vertical and seldom have a frequency of less than one major fracture per foot. The remarkable directional preference of set three fractures about strikes of N 40/sup 0/ E, N 10/sup 0/ W, N 45/sup 0/ W, suggests some incipient pre-core rock anisotropy or stored directional strain energy. If this situation exists, the anisotropy strike change or stored strain variance from N 40/sup 0/ E to N 45/sup 0/ W downcore remains an unanswered question. Tectonic features, indicating local and/or regional movement plans, are present on and within the tectonichorizontal fracture set one. Slickensides had a preferred orientation within several core levels, and fibrous-nonfibrous calcite serves as fracture fillings.« less

Seed-Surface Grafting Precipitation Polymerization for Preparing Microsized Optically Active Helical Polymer Core/Shell Particles and Their Application in Enantioselective Crystallization.

PubMed

Zhao, Biao; Lin, Jiangfeng; Deng, Jianping; Liu, Dong

2018-05-14

Core/shell particles constructed by polymer shell and silica core have constituted a significant category of advanced functional materials. However, constructing microsized optically active helical polymer core/shell particles still remains as a big academic challenge due to the lack of effective and universal preparation methods. In this study, a seed-surface grafting precipitation polymerization (SSGPP) strategy is developed for preparing microsized core/shell particles with SiO 2 as core on which helically substituted polyacetylene is covalently bonded as shell. The resulting core/shell particles exhibit fascinating optical activity and efficiently induce enantioselective crystallization of racemic threonine. Taking advantage of the preparation strategy, novel achiral polymeric and hybrid core/shell particles are also expected. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Preparation and recognition of surface molecularly imprinted core-shell microbeads for protein in aqueous solutions

NASA Astrophysics Data System (ADS)

Lu, Yan; Yan, Chang-Ling; Gao, Shu-Yan

2009-04-01

In this paper, a surface molecular imprinting technique was reported for preparing core-shell microbeads of protein imprinting, and bovine hemoglobin or bovine serum albumin were used as model proteins for studying the imprinted core-shell microbeads. 3-Aminophenylboronic acid (APBA) was polymerized onto the surface of polystyrene microbead in the presence of the protein templates to create protein-imprinted core-shell microbeads. The various samples were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) methods. The effect of pH on rebinding of the template hemoglobin, the specific binding and selective recognition were studied for the imprinted microbeads. The results show that the bovine hemoglobin-imprinted core-shell microbeads were successfully created. The shell was a sort of imprinted thin films with porous structure and larger surface areas. The imprinted microbeads have good selectivity for templates and high stability. Due to the recognition sites locating at or closing to the surface, these imprinted microbeads have good property of mass-transport. Unfortunately, the imprint technology was not successfully applied to imprinting bovine serum albumin (BSA).

Drilling, construction, geophysical log data, and lithologic log for boreholes USGS 142 and USGS 142A, Idaho National Laboratory, Idaho

USGS Publications Warehouse

Twining, Brian V.; Hodges, Mary K.V.; Schusler, Kyle; Mudge, Christopher

2017-07-27

Starting in 2014, the U.S. Geological Survey in cooperation with the U.S. Department of Energy, drilled and constructed boreholes USGS 142 and USGS 142A for stratigraphic framework analyses and long-term groundwater monitoring of the eastern Snake River Plain aquifer at the Idaho National Laboratory in southeast Idaho. Borehole USGS 142 initially was cored to collect rock and sediment core, then re-drilled to complete construction as a screened water-level monitoring well. Borehole USGS 142A was drilled and constructed as a monitoring well after construction problems with borehole USGS 142 prevented access to upper 100 feet (ft) of the aquifer. Boreholes USGS 142 and USGS 142A are separated by about 30 ft and have similar geology and hydrologic characteristics. Groundwater was first measured near 530 feet below land surface (ft BLS) at both borehole locations. Water levels measured through piezometers, separated by almost 1,200 ft, in borehole USGS 142 indicate upward hydraulic gradients at this location. Following construction and data collection, screened water-level access lines were placed in boreholes USGS 142 and USGS 142A to allow for recurring water level measurements.Borehole USGS 142 was cored continuously, starting at the first basalt contact (about 4.9 ft BLS) to a depth of 1,880 ft BLS. Excluding surface sediment, recovery of basalt, rhyolite, and sediment core at borehole USGS 142 was approximately 89 percent or 1,666 ft of total core recovered. Based on visual inspection of core and geophysical data, material examined from 4.9 to 1,880 ft BLS in borehole USGS 142 consists of approximately 45 basalt flows, 16 significant sediment and (or) sedimentary rock layers, and rhyolite welded tuff. Rhyolite was encountered at approximately 1,396 ft BLS. Sediment layers comprise a large percentage of the borehole between 739 and 1,396 ft BLS with grain sizes ranging from clay and silt to cobble size. Sedimentary rock layers had calcite cement. Basalt flows ranged in thickness from about 2 to 100 ft and varied from highly fractured to dense, and ranged from massive to diktytaxitic to scoriaceous, in texture.Geophysical logs were collected on completion of drilling at boreholes USGS 142 and USGS 142A. Geophysical logs were examined with available core material to describe basalt, sediment and sedimentary rock layers, and rhyolite. Natural gamma logs were used to confirm sediment layer thickness and location; neutron logs were used to examine basalt flow units and changes in hydrogen content; gamma-gamma density logs were used to describe general changes in rock properties; and temperature logs were used to understand hydraulic gradients for deeper sections of borehole USGS 142. Gyroscopic deviation was measured to record deviation from true vertical at all depths in boreholes USGS 142 and USGS 142A.

Treated and Untreated foam core particleboards with intumescent veneer

Treesearch

Mark A. Dietenberger; Ali Shalbafan; Johannes Welling; Charles Boardman

2013-01-01

The effectiveness of treatments for the surface layer of novel foam core particleboards was evaluated by means of Cone calorimeter tests, Foam cote particleboards with variations of surface layer treatment, adhesives, and surface layer thicknesses under similar processing conditions were used to produce the test specimen for the Cone calorimeter tests. Ignitability,...

Benthic foraminiferal census data from Mobile Bay, Alabama--counts of surface samples and box cores

USGS Publications Warehouse

Richwine, Kathryn A.; Osterman, Lisa E.

2012-01-01

A study was undertaken in order to understand recent environmental change in Mobile Bay, Alabama. For this study a series of surface sediment and box core samples was collected. The surface benthic foraminiferal data provide the modern baseline conditions of the bay and can be used as a reference for changing paleoenvironmental parameters recorded in the box cores. The 14 sampling locations were chosen in the bay to cover the wide diversity of fluvial and marine-influenced environments on both sides of the shipping channel.

Changes in Body Temperature in Incomplete Spinal Cord Injury by Digital Infrared Thermographic Imaging

PubMed Central

Song, Yun-Gyu; Won, Yu Hui; Park, Sung-Hee; Ko, Myoung-Hwan

2015-01-01

Objective To investigate changes in the core temperature and body surface temperature in patients with incomplete spinal cord injuries (SCI). In incomplete SCI, the temperature change is difficult to see compared with complete spinal cord injuries. The goal of this study was to better understand thermal regulation in patients with incomplete SCI. Methods Fifty-six SCI patients were enrolled, and the control group consisted of 20 healthy persons. The spinal cord injuries were classified according to International Standards for Neurological Classification of Spinal Cord Injury. The patients were classified into two groups: upper (neurological injury level T6 or above) and lower (neurological injury level T7 or below) SCIs. Body core temperature was measured using an oral thermometer, and body surface temperature was measured using digital infrared thermographic imaging. Results Twenty-nine patients had upper spinal cord injuries, 27 patients had lower SCIs, and 20 persons served as the normal healthy persons. Comparing the skin temperatures of the three groups, the temperatures at the lower abdomen, anterior thigh and anterior tibia in the patients with upper SCIs were lower than those of the normal healthy persons and the patients with lower SCIs. No significant temperature differences were observed between the normal healthy persons and the patients with lower SCIs. Conclusion In our study, we found thermal dysregulation in patients with incomplete SCI. In particular, body surface temperature regulation was worse in upper SCIs than in lower injuries. Moreover, cord injury severity affected body surface temperature regulation in SCI patients. PMID:26605167

Fluorescent solute-partitioning characterization of layered soft contact lenses.

PubMed

Dursch, T J; Liu, D E; Oh, Y; Radke, C J

2015-03-01

Partitioning of aqueous packaging, wetting, and care-solution agents into and out of soft contact lenses (SCLs) is important for improving wear comfort and also for characterizing lens physico-chemical properties. We illustrate both features of partitioning by application of fluorescent-solute partitioning into DAILIES TOTAL1® (delefilcon A) water-gradient SCLs, which exhibit a layered structure of a silicone-hydrogel (SiHy) core sandwiched between thin surface-gel layers. Two-photon fluorescence confocal laser-scanning microscopy and attenuated total-reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) characterize the lens and assess uptake profiles of six prototypical fluorescent solutes. Comparison of solute uptake in a SiHy-core prototype lens (i.e., O2OPTIX(TM)) validates the core SiHy structure of DAILIESTOTAL1®. To establish surface-layer charge, partition coefficients and water contents are obtained for aqueous pH values of 4 and 7.4. Solute fluorescence-intensity profiles clearly confirm a layered structure for the DAILIES TOTAL1® lenses. In all cases, aqueous solute partition coefficients are greater in the surface layers than in the SiHy core, signifying higher water in the surface gels. ATR-FTIR confirms surface-layer mass water contents of 82±3%. Water uptake and hydrophilic-solute uptake at pH 4 compared with that at pH 7.4 reveal that the surface-gel layers are anionic at physiologic pH 7.4, whereas both the SiHy core and O2OPTIX™ (lotrafilcon B) are nonionic. We successfully confirm the layered structure of DAILIES TOTAL1®, consisting of an 80-μm-thick SiHy core surrounded by 10-μm-thick polyelectrolyte surface-gel layers of significantly greater water content and aqueous solute uptake compared with the core. Accordingly, fluorescent-solute partitioning in SCLs provides information on gel structure and composition, in addition to quantifying uptake and release amounts and rates. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Hepatitis B core-related antigen (HBcrAg) levels in the natural history of hepatitis B virus infection in a large European cohort predominantly infected with genotypes A and D.

PubMed

Maasoumy, B; Wiegand, S B; Jaroszewicz, J; Bremer, B; Lehmann, P; Deterding, K; Taranta, A; Manns, M P; Wedemeyer, H; Glebe, D; Cornberg, M

2015-06-01

Hepatitis B core-related antigen (HBcrAg) has been suggested as an additional marker of hepatitis B virus (HBV) infection. HBcrAg combines the antigenic reactivity resulting from denatured hepatitis B e antigen (HBeAg), HBV core antigen and an artificial core-related protein (p22cr). In Asian patients, high levels of HBcrAg have been suggested to be an independent risk factor for hepatocellular carcinoma, while low levels could guide safe cessation of treatment with nucleos(t)ide analogues. We here studied HBcrAg levels in different phases of HBV infection in a large European cohort predominantly infected with genotypes A and D: HBeAg-positive immune tolerance (n = 30), HBeAg-positive immune clearance (IC) (n = 60), HBeAg-negative hepatitis (ENH) (n = 50), HBeAg-negative inactive/quiescent carrier phase (c) (n = 109) and acute hepatitis B (n = 8). Median HBcrAg levels were high in the immune tolerance and immune clearance phases (8.41 and 8.11 log U/mL, respectively), lower in ENH subjects (4.82 log U/mL) but only 2.00 log U/mL in ENQ subjects. Correlation between HBcrAg and HBV DNA varied among the different phases of HBV infection, while HBcrAg moderately correlated with hepatitis B surface antigen in all phases. ENQ patients had HBcrAg levels <3 log U/mL in 79%, in contrast to only 12% in the ENH group. HBcrAg levels vary significantly during the different phases of HBV infection. HBcrAg may serve as valuable marker for virus replication and reflect the transcriptional activity of intrahepatic cccDNA. In HBeAg-negative patients, HBcrAg may help to distinguish between inactive carriers (ENQ) and those with active disease (ENH). Copyright © 2015 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.

Long-term Glacial History of the West Antarctic Ice Sheet from Cosmogenic Nuclides in a Subglacial Bedrock Core

NASA Astrophysics Data System (ADS)

Spector, P. E.; Stone, J.; Hillebrand, T.; Gombiner, J. H.

2017-12-01

To investigate the response of the West Antarctic Ice Sheet (WAIS) to climatic conditions warmer than present, we are analyzing cosmogenic nuclides in a bedrock core from beneath 150 m of ice at a site near the Pirrit Hills. Our aim is to determine whether the WAIS has thinned in the past, exposing bedrock at this site, and if so, when. This will help to determine the vulnerability of the ice sheet to future warming, and identify climatic thresholds capable of inducing WAIS collapse. We selected a site where the ice-sheet surface lies at 1300 m, approximately halfway from the ice-sheet divide to the grounding line. We expect ice thickness at the site to reflect WAIS dynamics, rather than local meteorology or topography. Ice flow speeds are moderate and ice above the core site is thin enough to remain cold-based, limiting the possibility of subglacial erosion which would compromise the cosmogenic nuclide record. We targeted a subglacial ridge adjacent to an exposed granite nunatak. This lithology provides minerals suitable for analysis of multiple cosmogenic nuclides with different half-lives. Although we aimed to collect two cores from different depths to compare exposure histories, hydrofracture of the basal ice prevented us from reaching the bed at the first drill site. The second hole produced 5.5 m of discontinuous ice core above 8 m of bedrock core. Initial analyses of quartz from the bedrock show low levels of Be-10. Further analyses of Be-10, Al-26, Cl-36 and Ne-21 from the full length of the core will be required to determine whether this is because the surface has never been exposed, or because the cosmogenic nuclide profile has been truncated by glacial erosion. We will present comprehensive cosmogenic nuclide data, and discuss implications for WAIS deglaciation history, at the meeting. Supported by US National Science Foundation awards ANT-1142162 and PLR-1341728.

Influence of power density on polymerization behavior and bond strengths of dual-cured resin direct core foundation systems.

PubMed

Oto, Tatsuki; Yasuda, Genta; Tsubota, Keishi; Kurokawa, Hiroyasu; Miyazaki, Masashi; Platt, Jeffrey A

2009-01-01

This study examined the influence of power density on dentin bond strength and polymerization behavior of dual-cured direct core foundation resin systems. Two commercially available dual-cured direct core foundation resin systems, Clearfil DC Core Automix with Clearfil DC Bond and UniFil Core with Self-Etching Bond, were studied. Bovine mandibular incisors were mounted in autopolymerizing resin and the facial dentin surfaces were ground wet on 600-grit SiC paper. Dentin surfaces were treated according to manufacturer's recommendations. The resin pastes were condensed into the mold and cured with the power densities of 0 (no irradiation), 100, 200, 400 and 600 mW/cm2. Ten specimens per group were stored in 37 degrees C water for 24 hours, then shear tested at a crosshead speed of 1.0 mm/minute in a universal testing machine. An ultrasonic measurement device was used to measure the ultrasonic velocities through the core foundation resins. The power densities selected were 0 (no irradiation), 200, and 600 mW/cm2, and ultrasonic velocity was calculated. ANOVA and Tukey HSD tests were performed at a level of 0.05. The highest bond strengths were obtained when the resin pastes were cured with the highest power density for both core foundation systems (16.8 +/- 1.9 MPa for Clearfil DC Core Automix, 15.6 +/- 2.9 MPa for UniFil Core). When polymerized with the power densities under 200 mW/cm2, significantly lower bond strengths were observed compared to those obtained with the power density of 600 mW/cm2. As the core foundation resins hardened, the sonic velocities increased and this tendency differed among the power density of the curing unit. When the sonic velocities at three minutes after the start of measurements were compared, there were no significant differences among different irradiation modes for UniFil Core, while a significant decrease in sonic velocity was obtained when the resin paste was chemically polymerized compared with dual-polymerization for Clearfil DC Core Automix. The data suggests that the dentin bond strengths and polymerization behavior of the dual-cured, direct core foundation systems are still affected by the power density of the curing unit. With a careful choice of the core foundation systems and power density of the curing unit, the benefit of using resin composites to endodontically-treated teeth might be acceptable.

Some aspects of core formation in Mercury

NASA Technical Reports Server (NTRS)

Solomon, S. C.

1976-01-01

Some questions dealing with the nature and history of a large metallic core within Mercury are considered. These include the existence of a core, its size, whether it is fluid or solid, the timescale for core formation, the geological consequences of core formation, and whether such consequences are consistent with the surface geology. Several indirect lines of evidence are discussed which suggest the presence of a large iron-rich core. A core-formation model is examined in which core infall is accompanied by an increase of 17 km in planetary radius, an increase of 700 K in mean internal temperature, and substantial melting of the mantle. It is argued that if the core differentiated from an originally homogeneous planet, that event must have predated the oldest geological units comprising most of the planetary surface. A convective dynamo model for the source of Mercury's magnetic field is shown to conflict with cosmochemical models that do not predict a substantial radiogenic heat source in the core.

Shear bond strength in zirconia veneered ceramics using two different surface treatments prior veneering.

PubMed

Gasparić, Lana Bergman; Schauperl, Zdravko; Mehulić, Ketij

2013-03-01

Aim of the study was to assess the effect of different surface treatments on the shear bond strength (SBS) of the veneering ceramics to zirconia core. In a shear test the influence of grinding and sandblasting of the zirconia surface on bonding were assessed. Statistical analysis was performed using SPSS statistical package (version 17.0, SPSS Inc., Chicago, IL, USA) and Microsoft Office Excel 2003 (Microsoft, Seattle, WA, USA). There was a significant difference between the groups considering shear bond strength (SBS) values, i.e. ground and sandblasted samples had significantly higher SBS values than only ground samples (mean difference = -190.67; df = 10, t = -6.386, p < 0.001). The results of the present study indicate that ground and sandblasted cores are superior to ground cores, allowing significantly higher surface roughness and significantly higher shear bond strength between the core and the veneering material.

Geologic and hydrologic data collected during 1976-1983 at the Sheffield low-level radioactive waste disposal site and adjacent areas, Sheffield, Illinois

USGS Publications Warehouse

Foster, J.B.; Garklavs, George; Mackey, G.W.

1984-01-01

Hydrogeologic studies were conducted at the low-level radioactive-waste disposal site near Sheffield, Illinois, from 1976-84. Data in this report include water levels in wells, lake stages, inorganic, organic, and radiometric chemical analyses of ground and surface water, hydraulic conductivities of glacial materials, grain-size distribution, clay and carbonate mineralogy, and cation exchange capacities of the glacial materials. Also included are results of petrographic analyses, physical measurements of wells, stratigraphy and lithology of cores collected from test wells, and horizontal coordinates of wells.

Mean-field and linear regime approach to magnetic hyperthermia of core-shell nanoparticles: can tiny nanostructures fight cancer?

PubMed

Carrião, Marcus S; Bakuzis, Andris F

2016-04-21

The phenomenon of heat dissipation by magnetic materials interacting with an alternating magnetic field, known as magnetic hyperthermia, is an emergent and promising therapy for many diseases, mainly cancer. Here, a magnetic hyperthermia model for core-shell nanoparticles is developed. The theoretical calculation, different from previous models, highlights the importance of heterogeneity by identifying the role of surface and core spins on nanoparticle heat generation. We found that the most efficient nanoparticles should be obtained by selecting materials to reduce the surface to core damping factor ratio, increasing the interface exchange parameter and tuning the surface to core anisotropy ratio for each material combination. From our results we propose a novel heat-based hyperthermia strategy with the focus on improving the heating efficiency of small sized nanoparticles instead of larger ones. This approach might have important implications for cancer treatment and could help improving clinical efficacy.

Size-Dependent Specific Surface Area of Nanoporous Film Assembled by Core-Shell Iron Nanoclusters

DOE PAGES

Antony, Jiji; Nutting, Joseph; Baer, Donald R.; ...

2006-01-01

Nmore » anoporous films of core-shell iron nanoclusters have improved possibilities for remediation, chemical reactivity rate, and environmentally favorable reaction pathways. Conventional methods often have difficulties to yield stable monodispersed core-shell nanoparticles. We produced core-shell nanoclusters by a cluster source that utilizes combination of Fe target sputtering along with gas aggregations in an inert atmosphere at 7 ∘ C . Sizes of core-shell iron-iron oxide nanoclusters are observed with transmission electron microscopy (TEM). The specific surface areas of the porous films obtained from Brunauer-Emmett-Teller (BET) process are size-dependent and compared with the calculated data.« less

Theory of Auger core-valence-valence processes in simple metals. II. Dynamical and surface effects on Auger line shapes

NASA Astrophysics Data System (ADS)

Almbladh, C.-O.; Morales, A. L.

1989-02-01

Auger CVV spectra of simple metals are generally believed to be well described by one-electron-like theories in the bulk which account for matrix elements and, in some cases, also static core-hole screening effects. We present here detailed calculations on Li, Be, Na, Mg, and Al using self-consistent bulk wave functions and proper matrix elements. The resulting spectra differ markedly from experiment and peak at too low energies. To explain this discrepancy we investigate effects of the surface and dynamical effects of the sudden disappearance of the core hole in the final state. To study core-hole effects we solve Mahan-Nozières-De Dominicis (MND) model numerically over the entire band. The core-hole potential and other parameters in the MND model are determined by self-consistent calculations of the core-hole impurity. The results are compared with simpler approximations based on the final-state rule due to von Barth and Grossmann. To study surface and mean-free-path effects we perform slab calculations for Al but use a simpler infinite-barrier model in the remaining cases. The model reproduces the slab spectra for Al with very good accuracy. In all cases investigated either the effects of the surface or the effects of the core hole give important modifications and a much improved agreement with experiment.

Visual detection of gas shows from coal core and cuttings using liquid leak detector

USGS Publications Warehouse

Barker, C.E.

2006-01-01

Portions of core or cutting samples that have active gas shows can be identified by applying a liquid leak detector to the core surface. Although these gas shows can be caused by manmade changes to the coals' internal structure and surface of the core during the coring process, in many cases, the marked gas shows overlie changes in maceral composition, subtle fractures or coal, coal structure and so forth that seemingly are places where natural primary permeability is higher and gas shows would be favored. Given the limited time available for core description before a core is closed in a canister, using the liquid leak detector method to mark gas shows enhances core description by providing a photographic record of places of apparently increased gas flow likely related to enhanced coal permeability that cannot be easily detected otherwise.

Modelling of surface fluxes and Urban Boundary Layer over an old mediterannean city core

NASA Astrophysics Data System (ADS)

Lemonsu, A.; Masson, V.; Grimmond, Cs. B.

2003-04-01

In the frameworks of the UBL(Urban Boundary Layer)-ESCOMPTE campaign, the Town Energy Balance (TEB) model was run in off-line mode for Marseille. TEB's performance is evaluated with observations of surface temperatures and surface energy balance fluxes collected during the campaign. Parameterization improvements allow to better represent the energy exchanges between the air inside the canyon and the atmosphere above the roof level. Then, high resolution Méso-NH simulations are done to study the 3-D structure and the evolution of the Urban Boundary Layer (UBL) over Marseille. Will will give a special attention to the impact of the seabord effects (sea-breeze circulation) on the UBL.

The Electronic Structure of the Cs/ n-GaN(0001) Nano-Interface

NASA Astrophysics Data System (ADS)

Benemanskaya, G. V.; Lapushkin, M. N.; Marchenko, D. E.; Timoshnev, S. N.

2018-03-01

Electronic structures of the n-GaN(0001) surface and Cs/ n-GaN(0001) interface with submonolayer Cs coverages were studied for the first time in situ by the photoelectron spectroscopy (PES) method. The spectra of photoemission from the valence band, surface electron states, and core levels (Ga 3 d, Cs 4 d, Cs 5 p) under synchrotron excitation were measured in a range of photon energies within 50-150 eV. Evolution of the spectrum of surface states near the valence-band maximum was revealed by PES during the adsorption of Cs atoms. A metallic character of the Cs/ n-GaN(0001) nano-interface is demonstrated.

Performance evaluation of new automated hepatitis B viral markers in the clinical laboratory: two quantitative hepatitis B surface antigen assays and an HBV core-related antigen assay.

PubMed

Park, Yongjung; Hong, Duck Jin; Shin, Saeam; Cho, Yonggeun; Kim, Hyon-Suk

2012-05-01

We evaluated quantitative hepatitis B surface antigen (qHBsAg) assays and a hepatitis B virus (HBV) core-related antigen (HBcrAg) assay. A total of 529 serum samples from patients with hepatitis B were tested. HBsAg levels were determined by using the Elecsys (Roche Diagnostics, Indianapolis, IN) and Architect (Abbott Laboratories, Abbott Park, IL) qHBsAg assays. HBcrAg was measured by using Lumipulse HBcrAg assay (Fujirebio, Tokyo, Japan). Serum aminotransferases and HBV DNA were respectively quantified by using the Hitachi 7600 analyzer (Hitachi High-Technologies, Tokyo, Japan) and the Cobas AmpliPrep/Cobas TaqMan test (Roche). Precision of the qHBsAg and HBcrAg assays was assessed, and linearity of the qHBsAg assays was verified. All assays showed good precision performance with coefficients of variation between 4.5% and 5.3% except for some levels. Both qHBsAg assays showed linearity from 0.1 to 12,000.0 IU/mL and correlated well (r = 0.9934). HBsAg levels correlated with HBV DNA (r = 0.3373) and with HBcrAg (r = 0.5164), and HBcrAg also correlated with HBV DNA (r = 0.5198; P < .0001). This observation could provide impetus for further research to elucidate the clinical usefulness of the qHBsAg and HBcrAg assays.

Shape evolution of a core-shell spherical particle under hydrostatic pressure.

PubMed

Colin, Jérôme

2012-03-01

The morphological evolution by surface diffusion of a core-shell spherical particle has been investigated theoretically under hydrostatic pressure when the shear modulii of the core and shell are different. A linear stability analysis has demonstrated that depending on the pressure, shear modulii, and radii of both phases, the free surface of the composite particle may be unstable with respect to a shape perturbation. A stability diagram finally emphasizes that the roughness development is favored in the case of a hard shell with a soft core.

Comprehensive study of thermal properties of lunar core samples

NASA Technical Reports Server (NTRS)

Langseth, M. G.; Horath, K.

1975-01-01

The feasibility of a technique for measuring the thermal conductivity of lunar core samples was investigated. The thermal conduction equation for a composite cylinder was solved to obtain a mathematical expression for the surface temperature of the core tube filled with lunar material. The sample is heated by radiation from the outside at a known rate, the variation of the temperature at the surface of the core tube is measured, and the thermal conductivity determined by comparing the observed temperature with the theoretically expected one. The apparatus used in the experiment is described.

Oscillatory erosion and transport flume with superimposed unidirectional flow

DOEpatents

Jepsen, Richard A.; Roberts, Jesse D.

2004-01-20

A method and apparatus for measuring erosion rates of sediments and at high shear stresses due to complex wave action with, or without, a superimposed unidirectional current. Water is forced in a channel past an exposed sediment core sample, which erodes sediments when a critical shear stress has been exceeded. The height of the core sample is adjusted during testing so that the sediment surface remains level with the bottom of the channel as the sediments erode. Complex wave action is simulated by driving tandom piston/cylinder mechanisms with computer-controlled stepper motors. Unidirectional flow, forced by a head difference between two open tanks attached to each end of the channel, may be superimposed on to the complex wave action. Sediment traps may be used to collect bedload sediments. The total erosion rate equals the change in height of the sediment core sample divided by a fixed period of time.

Crustal Cooling in the Neutron Star Low-Mass X-Ray Binary KS 1731-260

NASA Astrophysics Data System (ADS)

Merritt, Rachael L.

Neutron stars in binary systems can undergo periods of accretion (outburst), where in- falling material heats the crust of the star out of thermal equilibrium with the core. When accretion stops (quiescence), we can directly observe the thermal relaxation of the crust. Crustal cooling of accretion-heated neutron stars provides insight into the stellar interior of neutron stars. The neutron star X-ray transient, KS 1731-260, was in outburst for 12.5 years before returning to quiescence in 2001. Here, we present a 150 ks Chandra observation of KS 1731-260 taken in August 2015, about 14.5 years into quiescence. We find that the neutron star surface temperature is consistent with the previous observation, suggesting the crust has reached thermal equilibrium with the core. Using a theoretical thermal evolution code, we fit the observed cooling curves and constrain the core temperature, composition, and the required level of extra shallow heating.

Investigation on influence of Wurster coating process parameters for the development of delayed release minitablets of Naproxen.

PubMed

Shah, Neha; Mehta, Tejal; Aware, Rahul; Shetty, Vasant

2017-12-01

The present work aims at studying process parameters affecting coating of minitablets (3 mm in diameter) through Wurster coating process. Minitablets of Naproxen with high drug loading were manufactured using 3 mm multi-tip punches. The release profile of core pellets (published) and minitablets was compared with that of marketed formulation. The core formulation of minitablets was found to show similarity in dissolution profile with marketed formulation and hence was further carried forward for functional coating over it. Wurster processing was implemented to pursue functional coating over core formulation. Different process parameters were screened and control strategy was applied for factors significantly affecting the process. Modified Plackett Burman Design was applied for studying important factors. Based on the significant factors and minimum level of coating required for functionalization, optimized process was executed. Final coated batch was evaluated for coating thickness, surface morphology, and drug release study.

Correlating structural dynamics and catalytic activity of AgAu nanoparticles with ultrafast spectroscopy and all-atom molecular dynamics simulations.

PubMed

Ferbonink, G F; Rodrigues, T S; Dos Santos, D P; Camargo, P H C; Albuquerque, R Q; Nome, R A

2018-05-29

In this study, we investigated hollow AgAu nanoparticles with the goal of improving our understanding of the composition-dependent catalytic activity of these nanoparticles. AgAu nanoparticles were synthesized via the galvanic replacement method with controlled size and nanoparticle compositions. We studied extinction spectra with UV-Vis spectroscopy and simulations based on Mie theory and the boundary element method, and ultrafast spectroscopy measurements to characterize decay constants and the overall energy transfer dynamics as a function of AgAu composition. Electron-phonon coupling times for each composition were obtained from pump-power dependent pump-probe transients. These spectroscopic studies showed how nanoscale surface segregation, hollow interiors and porosity affect the surface plasmon resonance wavelength and fundamental electron-phonon coupling times. Analysis of the spectroscopic data was used to correlate electron-phonon coupling times to AgAu composition, and thus to surface segregation and catalytic activity. We have performed all-atom molecular dynamics simulations of model hollow AgAu core-shell nanoparticles to characterize nanoparticle stability and equilibrium structures, besides providing atomic level views of nanoparticle surface segregation. Overall, the basic atomistic and electron-lattice dynamics of core-shell AgAu nanoparticles characterized here thus aid the mechanistic understanding and performance optimization of AgAu nanoparticle catalysts.

Trace metal concentrations in tropical mangrove sediments, NE Brazil.

PubMed

Miola, Brígida; Morais, Jáder Onofre de; Pinheiro, Lidriana de Souza

2016-01-15

Sediment cores were taken from the mangroves of the Coreaú River estuary off the northeast coast of Brazil. They were analyzed for grain size, CaCO3, organic matter, and trace metal (Cd, Pb, Zn, Cu, Al, and Fe) contents. Mud texture was the predominant texture. Levels of trace metals in surface sediments indicated strong influence of anthropogenic processes, and diagenetic processes controlled the trace metal enrichment of core sediments of this estuary. The positive relationships between trace metals and Al and Fe indicate that Cu, Zn, Pb, and Cd concentrations are associated mainly with Al and Fe oxy-hydroxides and have natural sources. Copyright © 2015 Elsevier Ltd. All rights reserved.

Rise in central west Greenland surface melt unprecedented over the last three centuries

NASA Astrophysics Data System (ADS)

Trusel, Luke; Das, Sarah; Osman, Matthew; Evans, Matthew; Smith, Ben; McConnell, Joe; Noël, Brice; van den Broeke, Michiel

2017-04-01

Greenland Ice Sheet surface melting has intensified and expanded over the last several decades and is now a leading component of ice sheet mass loss. Here, we constrain the multi-century temporal evolution of surface melt across central west Greenland by quantifying layers of refrozen melt within well-dated firn and ice cores collected in 2014 and 2015, as well as from a core collected in 2004. We find significant agreement among ice core, satellite, and regional climate model melt datasets over recent decades, confirming the fidelity of the ice core melt stratigraphy as a reliable record of past variability in the magnitude of surface melt. We also find a significant correlation between the melt records derived from our new 100-m GC-2015 core (2436 m.a.s.l.) and the older (2004) 150-m D5 core (2472 m.a.s.l.) located 50 km to the southeast. This agreement demonstrates the robustness of the ice core-derived melt histories and the potential for reconstructing regional melt evolution from a single site, despite local variability in melt percolation and refreeze processes. Our array of upper percolation zone cores reveals that although the overall frequency of melt at these sites has not increased, the intensification of melt over the last three decades is unprecedented within at least the last 365 years. Utilizing the regional climate model RACMO 2.3, we show that this melt intensification is a nonlinear response to warming summer air temperatures, thus underscoring the heightened sensitivity of this sector of Greenland to further climate warming. Finally, we examine spatial correlations between the ice core melt records and modeled melt fields across the ice sheet to assess the broader representation of each ice core record. This analysis reveals wide-ranging significant correlations, including to modeled meltwater runoff. As such, our ice core melt records may furthermore offer unique, observationally-constrained insights into past variability in ice sheet mass loss.

Aircraft Engine Exhaust Nozzle System for Jet Noise Reduction

NASA Technical Reports Server (NTRS)

Thomas, Russell H. (Inventor); Czech, Michael J. (Inventor); Elkoby, Ronen (Inventor)

2014-01-01

The aircraft exhaust engine nozzle system includes a fan nozzle to receive a fan flow from a fan disposed adjacent to an engine disposed above an airframe surface of the aircraft, a core nozzle disposed within the fan nozzle and receiving an engine core flow, and a pylon structure connected to the core nozzle and structurally attached with the airframe surface to secure the engine to the aircraft.

Non-invasive, transient determination of the core temperature of a heat-generating solid body

PubMed Central

Anthony, Dean; Sarkar, Daipayan; Jain, Ankur

2016-01-01

While temperature on the surface of a heat-generating solid body can be easily measured using a variety of methods, very few techniques exist for non-invasively measuring the temperature inside the solid body as a function of time. Measurement of internal temperature is very desirable since measurement of just the surface temperature gives no indication of temperature inside the body, and system performance and safety is governed primarily by the highest temperature, encountered usually at the core of the body. This paper presents a technique to non-invasively determine the internal temperature based on the theoretical relationship between the core temperature and surface temperature distribution on the outside of a heat-generating solid body as functions of time. Experiments using infrared thermography of the outside surface of a thermal test cell in a variety of heating and cooling conditions demonstrate good agreement of the predicted core temperature as a function of time with actual core temperature measurement using an embedded thermocouple. This paper demonstrates a capability to thermally probe inside solid bodies in a non-invasive fashion. This directly benefits the accurate performance prediction and control of a variety of engineering systems where the time-varying core temperature plays a key role. PMID:27804981

Non-invasive, transient determination of the core temperature of a heat-generating solid body

NASA Astrophysics Data System (ADS)

Anthony, Dean; Sarkar, Daipayan; Jain, Ankur

2016-11-01

While temperature on the surface of a heat-generating solid body can be easily measured using a variety of methods, very few techniques exist for non-invasively measuring the temperature inside the solid body as a function of time. Measurement of internal temperature is very desirable since measurement of just the surface temperature gives no indication of temperature inside the body, and system performance and safety is governed primarily by the highest temperature, encountered usually at the core of the body. This paper presents a technique to non-invasively determine the internal temperature based on the theoretical relationship between the core temperature and surface temperature distribution on the outside of a heat-generating solid body as functions of time. Experiments using infrared thermography of the outside surface of a thermal test cell in a variety of heating and cooling conditions demonstrate good agreement of the predicted core temperature as a function of time with actual core temperature measurement using an embedded thermocouple. This paper demonstrates a capability to thermally probe inside solid bodies in a non-invasive fashion. This directly benefits the accurate performance prediction and control of a variety of engineering systems where the time-varying core temperature plays a key role.

Delayed Geodynamo in Hadean

NASA Astrophysics Data System (ADS)

Arkani-Hamed, J.

2014-12-01

Paleointensity measurements of Archean rocks reveal a strong geodynamo at ~3.45 Ga, while excess nitrogen content of lunar soil samples implies no geodynamo at ~3.9 Ga. Here I propose that initiation of a strong geodynamo is delayed due to accretion style of Earth, involving collision and merging of a few dozen Moon to Mars size planetary embryos. Two accretion scenarios consisting of 25 and 50 embryos are investigated. The collision of an embryo heats the proto-Earth's core differentially and the rotating low-viscosity core stably stratifies, creating a spherically symmetric and radially increasing temperature distribution. Convection starts in the outer core after each impact but is destroyed by the next impact. The iron core of an impacting embryo descends in the mantle and merges to the proto-Earth's core. Both adiabatic and non-adiabatic merging cases are studied. A major part of the gravitational energy released due to core merging is used to lift up the upper portion of the core to emplace the impactor core material at the neutrally buoyant level in the proto-Earth's core. The remaining energy is converted to heat. In the adiabatic case the merging embryo's core retains all of the remaining energy, while in the non-adiabatic merging 50% of the remaining energy is shared with the outer part of the proto-Earth's core where the embryo's core descends. The two merging models result in significantly different temperature distributions in the core at the end of accretion. After the accretion, the convecting shell in the outer core grows monotonically and generates geodynamo gradually. It takes about 50-100 Myr for the convecting shell to generate a strong dipole field at the surface, 50,000 to 100,000 nT, in the presence of a large stably stratified liquid inner core when the convecting outer core thickness exceeds about one half the radius of the Earth's core.

Electronic and Optical Properties of Core/Shell Pb16X16/Cd52X52 (X =S, Se, Te) Quantum Dots

NASA Astrophysics Data System (ADS)

Tamukong, Patrick; Mayo, Michael; Kilina, Svetlana

2015-03-01

The electronic and optoelectronic properties of semiconductor quantum dots (QDs) are mediated by surface defects due to the presence of dangling bonds producing trap states within the HOMO-LUMO energy gap, and contributing to fluorescence quenching. Surface capping ligands are generally used to alleviate this problem and increase the quantum yields of QDs. An alternative way is to synthesize core-shell QD structures; i.e., a QD core with a shell of another semiconductor material. We have investigated the effects of Cd52X52 shells on the photoexcited dynamics of Pb16X16 (X =S, Se, Te) QDs. The thin (~ 0.50 nm) shells were found to result largely in type I core/shell structures and a blue shift of the absorption spectra. Our studies revealed fairly strong core-shell hybridization in the electronic states close to the conduction band (CB) edge for Pb16S16andPb16Se16 cores, whereas for the Pb16Te16 core, such CB states were largely shell-like in nature. Nonadiabatic DFT-based dynamics, coupled with the surface hopping method, was used to study the effects of the core and shell compositions on energy relaxation rates in these systems.

Infrared thermal imaging as a method to evaluate heat loss in newborn lambs.

PubMed

Labeur, L; Villiers, G; Small, A H; Hinch, G N; Schmoelzl, S

2017-12-01

Thermal imaging technology has been identified as a potential method for non-invasive study of thermogenesis in the neonatal lamb. In comparison to measurement of the core body temperature, infrared thermography may observe thermal loss and thermogenesis linked to subcutaneous brown fat depots. This study aimed to identify a suitable method to measure heat loss in the neonatal lamb under a cold challenge. During late pregnancy (day 125), ewes were subjected to either shearing (n=15) or mock handling (sham-shorn for 2min mimicking the shearing movements) (n=15). Previous studies have shown an increase in brown adipose tissue deposition in lambs born to ewes shorn during pregnancy and we hypothesized that the shearing treatment would impact thermoregulatory capacities in newborn lambs. Lambs born to control ewes (n=14; CONTROL) and shorn ewes (n=13; SHORN) were subjected to a cold challenge of 1h duration at 4h after birth. During the cold challenge, thermography images were taken every 10min, from above, at a fixed distance from the dorsal midline. On each image, four fixed-size areas were identified (shoulder, mid loin, hips and rump) and the average and maximum temperatures of each recorded. In all lambs, body surface temperature decreased over time. Overall the SHORN lambs appeared to maintain body surface temperature better than CONTROL lambs, while CONTROL lambs appeared to have higher core temperature. At 30min post cold challenge SHORN lambs tended to have higher body surface temperatures than lambs (P=0.0474). Both average and maximum temperatures were highest at the hips. Average temperature was lowest at the shoulder (P<0.05), while maximum temperatures were lowest at both shoulder and rump (P<0.005). These results indicate that lambs born to shorn ewes maintained their radiated body surface temperature better than CONTROL lambs. In conjunction with core temperature changes under cold challenge, this insight will allow us to understand whether increased body surface temperature contributes to increased overall heat loss or whether increased body surface temperature is indeed a mechanism contributing to maintenance of core body temperature under cold challenge conditions. This study has confirmed the utility of infrared thermography images to capture and identify different levels of thermoregulatory capacity in newborn lambs. Copyright © 2017 Elsevier Ltd. All rights reserved.

Promising critical current density characteristics of Ag-sheathed (Sr,Na)Fe2As2 tape

NASA Astrophysics Data System (ADS)

Suwa, Takahiro; Pyon, Sunseng; Tamegai, Tsuyoshi; Awaji, Satoshi

2018-06-01

We report the fabrication of (Sr,Na)Fe2As2 superconducting tapes by the powder-in-tube technique and their characteristics, including the transport critical current density J c at 4.2 K up to 140 kOe, the magnetic J c estimated from magnetic hysteresis curves, magneto-optical (MO) images, and scanning electron microscopy images. In a tape sintered at 875 °C for 1 h, the transport J c reaches 26 kA/cm2 at 4.2 K and 100 kOe for a field perpendicular to the tape surface. When the field is parallel to the tape surface, the magnetic J c exceeds the practical level of 100 kA/cm2 at 4.2 K below 25 kOe. Analysis of the MO images reveals clear current discontinuity lines in the core, indicating that the current flows homogeneously and the connections between grains are strong in the core.

Optical fiber nanoprobe preparation for near-field optical microscopy by chemical etching under surface tension and capillary action.

PubMed

Mondal, Samir K; Mitra, Anupam; Singh, Nahar; Sarkar, S N; Kapur, Pawan

2009-10-26

We propose a technique of chemical etching for fabrication of near perfect optical fiber nanoprobe (NNP). It uses photosensitive single mode optical fiber to etch in hydro fluoric (HF) acid solution. The difference in etching rate for cladding and photosensitive core in HF acid solution creates capillary ring along core-cladding boundary under a given condition. The capillary ring is filled with acid solution due to surface tension and capillary action. Finally it creates near perfect symmetric tip at the apex of the fiber as the height of the acid level in capillary ring decreases while width of the ring increases with continuous etching. Typical tip features are short taper length (approximately 4 microm), large cone angle (approximately 38 degrees ), and small probe tip dimension (<100 nm). A finite difference time domain (FDTD) analysis is also presented to compare near field optics of the NNP with conventional nanoprobe (CNP). The probe may be ideal for near field optical imaging and sensor applications.

Method and apparatus for producing a carbon based foam article having a desired thermal-conductivity gradient

DOEpatents

Klett, James W [Knoxville, TN; Cameron, Christopher Stan [Sanford, NC

2010-03-02

A carbon based foam article is made by heating the surface of a carbon foam block to a temperature above its graphitizing temperature, which is the temperature sufficient to graphitize the carbon foam. In one embodiment, the surface is heated with infrared pulses until heat is transferred from the surface into the core of the foam article such that the graphitizing temperature penetrates into the core to a desired depth below the surface. The graphitizing temperature is maintained for a time sufficient to substantially entirely graphitize the portion of the foam article from the surface to the desired depth below the surface. Thus, the foam article is an integral monolithic material that has a desired conductivity gradient with a relatively high thermal conductivity in the portion of the core that was graphitized and a relatively low thermal conductivity in the remaining portion of the foam article.

Synoptic characteristics of heavy snowfalls at Busan of Korea caused by polar lows over the East/Japan Sea

NASA Astrophysics Data System (ADS)

Choi, Jae-Won; Cha, Yumi; Kim, Hae-Dong

2018-02-01

The results of the present study prove that snowfall occurred due to the polar low (PL) in the Korean Peninsula and six cases of snowfall exceeding a snow depth of 2 cm over the past 16 years in Busan, South Korea. A strong northwesterly air current with a cold outbreak at the lower level passed through the Korean Peninsula and penetrated into the East/Japan Sea causing the generation and characteristics of a PL. However, a northeasterly air current due to a synoptic low (SL) in East Japan approached the east coast via the East/Japan Sea, which generated a wind field with mesoscale cyclonic circulation. In the center of this cyclone, a strong positive vorticity region was revealed from the lower level to the upper level. The air temperature in the center of the PL was warmer than the surrounding areas at the lower level. As the PL developed and the air temperature decreased, a rapid tropopause drop followed due to the effect of the cold core along with the cutoff low at the mid-level or the higher level. As a result, the stratification became more unstable. The PL moved into Busan as the cold core at the upper level rapidly moved to the lower latitudes, which formed an unstable region around Busan. The PL decayed because the cutoff low, the cold core, and the positive vorticity region at the upper level quickly moved to the east, thereby causing the stratification to stabilize. Also, because the approach to the Japanese Archipelago caused an increase in surface friction, the original structure could no longer be maintained.

Physical property control in core/shell inorganic nanostructures for fluorescence and magnetic targeting applications

NASA Astrophysics Data System (ADS)

Roberts, Stephen K.

Nanomaterials show immense promise for the future in numerous areas of application. Properties that are unique from the bulk material and are tunable allow for innovation in material design. This thesis will focus on controlling the physical properties of core/shell nanostructures to enhance the utility of the materials. The first focus is on the impact of different solvent mixtures during the shell growth phase of SILAR based core/shell quantum dot synthesis is studied. Gaining insight into the mechanism for SILAR growth of core/shell nanoparticles allows improved synthetic yields and precursor binding, providing enhanced control to synthesis of core/shell nanoparticles. The second focus of this thesis is exploring the use of magnetic nanoparticles for magnetic drug targeting for cardiovascular conditions. Magnetic targeting for drug delivery enables increased local drug concentration, while minimizing non-specific interactions. In order to be effective for magnetic targeting, it must be shown that low magnetic strength is sufficient to capture flowing nanoparticles. By demonstrating the binding of a therapeutic agent to the surface at medicinal levels, the viability for use as a nanoparticle drug delivery system is improved.

Rational design of novel, fluorescent, tagged glutamic acid dendrimers with different terminal groups and in silico analysis of their properties

PubMed Central

Martinho, Nuno; Silva, Liana C; Florindo, Helena F; Brocchini, Steve; Zloh, Mire; Barata, Teresa S

2017-01-01

Dendrimers are hyperbranched polymers with a multifunctional architecture that can be tailored for the use in various biomedical applications. Peptide dendrimers are particularly relevant for drug delivery applications due to their versatility and safety profile. The overall lack of knowledge of their three-dimensional structure, conformational behavior and structure–activity relationship has slowed down their development. Fluorophores are often conjugated to dendrimers to study their interaction with biomolecules and provide information about their mechanism of action at the molecular level. However, these probes can change dendrimer surface properties and have a direct impact on their interactions with biomolecules and with lipid membranes. In this study, we have used computer-aided molecular design and molecular dynamics simulations to identify optimal topology of a poly(l-glutamic acid) (PG) backbone dendrimer that allows incorporation of fluorophores in the core with minimal availability for undesired interactions. Extensive all-atom molecular dynamic simulations with the CHARMM force field were carried out for different generations of PG dendrimers with the core modified with a fluorophore (nitrobenzoxadiazole and Oregon Green 488) and various surface groups (glutamic acid, lysine and tryptophan). Analysis of structural and topological features of all designed dendrimers provided information about their size, shape, internal distribution and dynamic behavior. We have found that four generations of a PG dendrimer are needed to ensure minimal exposure of a core-conjugated fluorophore to external environment and absence of undesired interactions regardless of the surface terminal groups. Our findings suggest that NBD-PG-G4 can provide a suitable scaffold to be used for biophysical studies of surface-modified dendrimers to provide a deeper understanding of their intermolecular interactions, mechanisms of action and trafficking in a biological system. PMID:29026301

Rational design of novel, fluorescent, tagged glutamic acid dendrimers with different terminal groups and in silico analysis of their properties.

PubMed

Martinho, Nuno; Silva, Liana C; Florindo, Helena F; Brocchini, Steve; Zloh, Mire; Barata, Teresa S

2017-01-01

Dendrimers are hyperbranched polymers with a multifunctional architecture that can be tailored for the use in various biomedical applications. Peptide dendrimers are particularly relevant for drug delivery applications due to their versatility and safety profile. The overall lack of knowledge of their three-dimensional structure, conformational behavior and structure-activity relationship has slowed down their development. Fluorophores are often conjugated to dendrimers to study their interaction with biomolecules and provide information about their mechanism of action at the molecular level. However, these probes can change dendrimer surface properties and have a direct impact on their interactions with biomolecules and with lipid membranes. In this study, we have used computer-aided molecular design and molecular dynamics simulations to identify optimal topology of a poly(l-glutamic acid) (PG) backbone dendrimer that allows incorporation of fluorophores in the core with minimal availability for undesired interactions. Extensive all-atom molecular dynamic simulations with the CHARMM force field were carried out for different generations of PG dendrimers with the core modified with a fluorophore (nitrobenzoxadiazole and Oregon Green 488) and various surface groups (glutamic acid, lysine and tryptophan). Analysis of structural and topological features of all designed dendrimers provided information about their size, shape, internal distribution and dynamic behavior. We have found that four generations of a PG dendrimer are needed to ensure minimal exposure of a core-conjugated fluorophore to external environment and absence of undesired interactions regardless of the surface terminal groups. Our findings suggest that NBD-PG-G4 can provide a suitable scaffold to be used for biophysical studies of surface-modified dendrimers to provide a deeper understanding of their intermolecular interactions, mechanisms of action and trafficking in a biological system.

NASA CYGNSS Ocean Wind Observations in the 2017 Atlantic Hurricane Season

NASA Astrophysics Data System (ADS)

Ruf, C. S.; Balasubramaniam, R.; Mayers, D.; McKague, D. S.

2017-12-01

The CYGNSS constellation of eight satellites was successfully launched on 15 December 2016 into a low inclination (tropical) Earth orbit to measure ocean surface wind speed in the inner core of tropical cyclones with better than 12 hour refresh rates. Each satellite carries a four-channel bi-static radar receiver that measures GPS signals scattered by the ocean, from which ocean surface roughness, near surface wind speed, and air-sea latent heat flux are estimated. The measurements are unique in several respects, most notably in their ability to penetrate through all levels of precipitation, made possible by the low frequency at which GPS operates, and in the frequent sampling of tropical cyclone intensification, made possible by the large number of satellites. Level 2 science data products have been developed for near surface (10 m referenced) ocean wind speed, ocean surface roughness (mean square slope) and latent heat flux. Level 3 gridded versions of the L2 products have also been developed. A set of Level 4 products have also been developed specifically for direct tropical cyclone overpasses. These include the storm intensity (peak sustained winds) and size (radius of maximum winds), its extent (34, 50 and 64 knot wind radii), and its integrated kinetic energy. Results of measurements made during the 2017 Atlantic hurricane season, including frequent overpasses of Hurricanes Harvey, Irma and Maria, will be presented.

Cone calorimeter testing of foam core sandwich panels treated with intumescent paper underneath the veneer (FRV)

Treesearch

Mark A. Dietenberger; Ali Shalbafan; Johannes Welling

2017-01-01

Surfaces of novel foam core sandwich panels were adhered with intumescent fire‐retardant paper underneath the veneers (FRV) to improve their flammability properties. The panels were evaluated by means of cone calorimeter test (ASTM E 1354). Variables tested were different surface layer treatments, adhesives used for veneering, surface layer thicknesses, and processing...

Capacitively coupled and direct-current resistivity surveys of selected reaches of Cozad, Thirty-Mile, Orchard-Alfalfa, Kearney, and Outlet Canals in Nebraska, 2012-13

USGS Publications Warehouse

Hobza, Christopher M.; Burton, Bethany L.; Lucius, Jeffrey E.; Tompkins, Ryan E.

2014-01-01

Understanding the spatial characteristics of leakage from canals is critical to effectively managing and utilizing water resources for irrigation and hydroelectric purposes. Canal leakage in some parts of Nebraska is the primary source of water for groundwater recharge and helps maintain the base flow of streams. Because surface-water supplies depend on the streamflow of the Platte River and the available water stored in upstream reservoirs, water managers seek to minimize conveyance losses, which can include canal leakage. The U.S. Geological Survey, in cooperation with the Central Platte Natural Resources District and Nebraska Public Power District, used capacitively coupled (CC) and direct-current (DC) resistivity techniques for continuous resistivity profiling to map near-surface lithologies near and underlying the Cozad, Thirty-Mile, Orchard-Alfalfa, Kearney, and Outlet Canals. Approximately 84 kilometers (km) of CC-resistivity data were collected along the five canals. The CC-resistivity data were compared with results from continuous sediment cores and electrical conductivity logs. Generally, the highest resistivities were recorded at the upstream reaches of the Cozad, Thirty-Mile, and Orchard-Alfalfa canals where flood-plain deposits of silt and clay mantle coarser channel deposits of sand and gravel. The finer grained deposits gradually thicken with increasing distance away from the Platte River. Consequently, for many surveyed reaches the thickness of fine-grained deposits exceeded the 8-meter depth of investigation. A detailed geophysical investigation along a 5-km reach of the Outlet Canal southwest of North Platte, Nebraska, used CC and DC resistivity to examine the condition of a compacted-core bank structure and characterized other potential controls on areas of focused seepage. CC-resistivity data, collected along the 5-km study reach, were compared with continuous sediment cores and DC-resistivity data collected near a selected seep near Outlet Canal mile post 15.55 along 5 separate profiles. DC-resistivity results were compared to a schematic cross section of the Outlet Canal north embankment that include the original surfaces and modifications to the compacted-core bank structure. Along the canal road south line, there is a transition from high resistivity at land surface to much lower resistivity near the estimated depth of the northern slope of the original compacted-core bank; however, the surveyed elevation of the water surface in the canal also is at this elevation. Along the canal road north line, there is a transition from high resistivity near land surface to lower resistivity at depth. Although the transition is rapid near the estimated depth of the first-modified bank slope, it also is coincident with the groundwater level measured in piezometer PZ-4. Currently (2013), it is unknown if the indicated changes in resistivity at these elevations was the effect of saturation of the underlying sediments or caused by the compacted-core bank.

Atmospheric Signature of the Agulhas Current

NASA Astrophysics Data System (ADS)

Nkwinkwa Njouodo, Arielle Stela; Koseki, Shunya; Keenlyside, Noel; Rouault, Mathieu

2018-05-01

Western boundary currents play an important role in the climate system by transporting heat poleward and releasing it to the atmosphere. While their influence on extratropical storms and oceanic rainfall is becoming appreciated, their coastal influence is less known. Using satellite and climate reanalysis data sets and a regional atmospheric model, we show that the Agulhas Current is a driver of the observed band of rainfall along the southeastern African coast and above the Agulhas Current. The Agulhas current's warm core is associated with sharp gradients in sea surface temperature and sea level pressure, a convergence of low-level winds, and a co-located band of precipitation. Correlations among wind convergence, sea level pressure, and sea surface temperature indicate that these features show high degree of similarity to those in the Gulf Stream region. Model experiments further indicate that the Agulhas Current mostly impacts convective rainfall.

Controlled Synthesis of Pd/Pt Core Shell Nanoparticles Using Area-selective Atomic Layer Deposition

PubMed Central

Cao, Kun; Zhu, Qianqian; Shan, Bin; Chen, Rong

2015-01-01

We report an atomic scale controllable synthesis of Pd/Pt core shell nanoparticles (NPs) via area-selective atomic layer deposition (ALD) on a modified surface. The method involves utilizing octadecyltrichlorosilane (ODTS) self-assembled monolayers (SAMs) to modify the surface. Take the usage of pinholes on SAMs as active sites for the initial core nucleation, and subsequent selective deposition of the second metal as the shell layer. Since new nucleation sites can be effectively blocked by surface ODTS SAMs in the second deposition stage, we demonstrate the successful growth of Pd/Pt and Pt/Pd NPs with uniform core shell structures and narrow size distribution. The size, shell thickness and composition of the NPs can be controlled precisely by varying the ALD cycles. Such core shell structures can be realized by using regular ALD recipes without special adjustment. This SAMs assisted area-selective ALD method of core shell structure fabrication greatly expands the applicability of ALD in fabricating novel structures and can be readily applied to the growth of NPs with other compositions. PMID:25683469

Resolving Magnetic Flux Patches at the Surface of the Core

NASA Technical Reports Server (NTRS)

OBrien, Michael S.

1996-01-01

The geomagnetic field at a given epoch can be used to partition the surface of the liquid outer core into a finite number of contiguous regions in which the radial component of the magnetic flux density, B (sub r), is of one sign. These flux patches are instrumental in providing detail to surface fluid flows inferred from the changing geomagnetic field and in evaluating the validity of the frozen-flux approximation on which such inferences rely. Most of the flux patches in models of the modem field are small and enclose little flux compared to the total unsigned flux emanating from the core. To demonstrate that such patches are not required to explain the most spatially complete and accurate data presently available, those from the Magsat mission, I have constructed a smooth core field model that fits the Magsat data but does not possess small flux patches. I conclude that our present knowledge of the geomagnetic field does not allow us to resolve these features reliably at the core-mantle boundary; thus we possess less information about core flow than previously believed.

Ferromagnetic resonance and magnetic studies of cores 60009/60010 and 60003 - Compositional and surface-exposure stratigraphy. [of Apollo deep drill lunar samples

NASA Technical Reports Server (NTRS)

Morris, R. V.; Gose, W. A.

1976-01-01

Ferromagnetic resonance and static magnetic measurements were made on 131 samples from core 60009/60010 and on 40 samples from section 60003 of the Apollo 16 deep drill core. These studies provided depth profiles for composition, in terms of the concentration of FeO, and relative surface exposure age (or maturity), in terms of the values of the specific FMR intensity normalized to the FeO content. For core 60009/60010, the concentration of FeO ranged from about 1.6 wt.% to 5.8 wt.% with a mean value of 4.6 wt.% and the maturity ranged from immature to mature with most of the soils being submature. A systematic decrease in maturity from the lunar surface to a depth of about 12.5 cm was observed in core section 60010. For core section 60003, the concentration of FeO ranged from about 5.2 wt.% to 7.5 wt.% with a mean value of 6.4 wt.% and the maturity ranged from submature to mature with most of the soils being mature.

Surface shift of the occupied and unoccupied 4f levels of the rare-earth metals

NASA Astrophysics Data System (ADS)

Aldén, M.; Johansson, B.; Skriver, H. L.

1995-02-01

The surface energy shifts of the occupied and unoccupied 4f levels for the lanthanide metals have been calculated from first principles by means of a Green's-function technique within the tight-binding linear muffin-tin orbitals method. We use the concept of complete screening to identify the occupied and unoccupied 4f energy level shifts as the surface segregation energy of a 4fn-1 and 4fn+1 impurity atom, respectively, in a 4fn host metal. The calculations include both initial- and final-state effects and give values that are considerably lower than those measured on polycrystalline samples as well as those found in previous initial-state model calculations. The present theory agrees well with very recent high-resolution, single-crystal film measurements for Gd, Tb, Dy, Ho, Er, Tm, and Lu. We furthermore utilize the unique possibility offered by the lanthanide metals to clarify the roles played by the initial and the different final states of the core-excitation process, permitted by the fact that the so-called initial-state effect is identical upon 4f removal and 4f addition. Surface energy and work function calculations are also reported.

Atmospheric soluble dust records from a Tibetan ice core: Possible climate proxies and teleconnection with the Pacific Decadal Oscillation

NASA Astrophysics Data System (ADS)

Grigholm, B.; Mayewski, P. A.; Kang, S.; Zhang, Y.; Kaspari, S.; Sneed, S. B.; Zhang, Q.

2009-10-01

In autumn 2005, a joint expedition between the University of Maine and the Institute of Tibetan Plateau Research recovered three ice cores from Guoqu Glacier (33°34'37.8″N, 91°10'35.3″E, 5720 m above sea level) on the northern side of Mt. Geladaindong, central Tibetan Plateau. Isotopes (δ18O), major soluble ions (Na+, K+, Mg2+, Ca2+, Cl-, NO3-, SO42-), and radionuclide (β-activity) measurements from one of the cores revealed a 70-year record (1935-2005). Statistical analysis of major ion time series suggests that atmospheric soluble dust species dominate the chemical signature and that background dust levels conceal marine ion species deposition. The soluble dust time series have interspecies relations and common structure (empirical orthogonal function (EOF) 1), suggesting a similar soluble dust source or transport route. Annual and seasonal correlations between the EOF 1 time series and National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis climate variables (1948-2004) suggest that the Mt. Geladaindong ice core record provides a proxy for local and regional surface pressure. An approximately threefold decrease of soluble dust concentrations in the middle to late 1970s, accompanied by regional increases in pressure and temperature and decreases in wind velocity, coincides with the major 1976-1977 shift of the Pacific Decadal Oscillation (PDO) from a negative to a positive state. This is the first ice core evidence of a potential teleconnection between central Asian atmospheric soluble dust loading and the PDO. Analysis of temporally longer ice cores from Mt. Geladaindong may enhance understanding of the relationship between the PDO and central Asian atmospheric circulation and subsequent atmospheric soluble dust loading.

Basic data report for drillhole WIPP 30 (Waste Isolation Pilot Plant - WIPP)

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

Not Available

1980-04-01

WIPP 30 was drilled in east-central Eddy County, New Mexico, in NW 1/4, Sec. 33, T21S, R31E, to obtain drill core for the study of dissolution of near-surface rocks. The borehole encountered from top to bottom, the Dewey Lake Red Beds (449' including artificial fill for drill pad), Rustler Formation (299'), and the upper 160' of the Salado Formation. Continuous core was cut from the surface to total depth. Geophysical logs were taken the full length of the borehole to measure acoustic velocities, density, and distribution of potassium and other radioactive elements. Information from this borehole will be included inmore » an interpretive report on dissolution in Nash Draw based on combined borehole data, surface mapping and laboratory analyses of rocks and fluids. The WIPP is to demonstrate (through limited operations) disposal technology for transuranic defense wastes and to then be converted to a repository. The WIPP will also provide research facilities for interactions between high-level waste and salt. Administration policy as of February 1980 is to hold the WIPP site in reserve until the first disposal site can be chosen from several potential sites, including the WIPP.« less

The role of local heating in the 2015 Indian Heat Wave.

PubMed

Ghatak, Debjani; Zaitchik, Benjamin; Hain, Christopher; Anderson, Martha

2017-08-09

India faced a major heat wave during the summer of 2015. Temperature anomalies peaked in the dry period before the onset of the summer monsoon, suggesting that local land-atmosphere feedbacks involving desiccated soils and vegetation might have played a role in driving the heat extreme. Upon examination of in situ data, reanalysis, satellite observations, and land surface models, we find that the heat wave included two distinct peaks: one in late May, and a second in early June. During the first peak we find that clear skies led to a positive net radiation anomaly at the surface, but there is no significant sensible heat flux anomaly within the core of the heat wave affected region. By the time of the second peak, however, soil moisture had dropped to anomalously low levels in the core heat wave region, net surface radiation was anomalously high, and a significant positive sensible heat flux anomaly developed. This led to a substantial local forcing on air temperature that contributed to the intensity of the event. The analysis indicates that the highly agricultural landscape of North and Central India can reinforce heat extremes under dry conditions.

Clostridium perfringens in Long Island Sound sediments: An urban sedimentary record

USGS Publications Warehouse

Buchholtz ten Brink, Marilyn R.; Mecray, E.L.; Galvin, E.L.

2000-01-01

Clostridium perfringens is a conservative tracer and an indicator of sewage-derived pollution in the marine environment. The distribution of Clostridium perfringens spores was measured in sediments from Long Island Sound, USA, as part of a regional study designed to: (1) map the distribution of contaminated sediments; (2) determine transport and dispersal paths; (3) identify the locations of sediment and contaminant focusing; and (4) constrain predictive models. In 1996, sediment cores were collected at 58 stations, and surface sediments were collected at 219 locations throughout the Sound. Elevated concentrations of Clostridium perfringens in the sediments indicate that sewage pollution is present throughout Long Island Sound and has persisted for more than a century. Concentrations range from undetectable amounts to 15,000 spores/g dry sediment and are above background levels in the upper 30 cm at nearly all core locations. Sediment focusing strongly impacts the accumulation of Clostridium perfringens spores. Inventories in the cores range from 28 to 70,000 spores/cm2, and elevated concentrations can extend to depths of 50 cm. The steep gradients in Clostridium perfringens profiles in muddier cores contrast with concentrations that are generally constant with depth in sandier cores. Clostridium perfringens concentrations rarely decrease in the uppermost sediment, unlike those reported for metal contaminants. Concentrations in surface sediments are highest in the western end of the Sound, very low in the eastern region, and intermediate in the central part. This pattern reflects winnowing and focusing of Clostridium perfringens spores and fine-grained sediment by the hydrodynamic regime; however, the proximity of sewage sources to the westernmost Sound locally enhances the Clostridium perfringens signals.

Alkyl Chain Ordering of Asymmetric Phosphatidyicholines Adsorbed at a Liquid-Liquid Interface

DTIC Science & Technology

1998-05-30

the blood bind to the PL surface and begin to hydrolyze the triglyceride core and only a small fraction of the phospholipids, such that the core...which surface-adsorbed proteins are able to hydrolyze the triglyceride core has been shown to depend on the acyl chain composition of monolayer PCs...in the commercial use of natural phosphatidylcholines (or lecithins ) as emulsifiers, including their use in delivery of water-insoluble drugs (Davis

In situ reworking /gardening/ of the lunar surface - Evidence from the Apollo cores

NASA Technical Reports Server (NTRS)

Morris, R. V.

1978-01-01

The in situ reworking (gardening) of the lunar surface by impacting projectiles creates an in situ reworking zone extending horizontally over the entire regolith surface and extending vertically from the surface to a depth which varies from place-to-place on the moon. On the basis of available evidence, the 'high-maturity' zones observed at the top of the lunar cores have resulted from the in situ reworking of the present-day lunar surface. The temporal variation of the in situ reworking depth was investigated using depths inferred from maturity I sub s/FeO and Al-26 profiles of Apollo cores. The observed temporal variation of the in situ reworking depth in units of centimeters is equal to 2.2 times the time (in units of million years) to the 0.45th power.

In vitro and in vivo mRNA delivery using lipid-enveloped pH-responsive polymer nanoparticles

PubMed Central

Su, Xingfang; Fricke, Jennifer; Kavanagh, Daniel; Irvine, Darrell J.

2012-01-01

Biodegradable core-shell structured nanoparticles with a poly(β-amino-ester) (PBAE) core enveloped by a phospholipid bilayer shell were developed for in vivo mRNA delivery, with a view toward delivery of mRNA-based vaccines. The pH-responsive PBAE component was chosen to promote endosome disruption, while the lipid surface layer was selected to minimize toxicity of the polycation core. Messenger RNA was efficiently adsorbed via electrostatic interactions onto the surface of these net positively-charged nanoparticles. In vitro, mRNA-loaded particle uptake by dendritic cells (DCs) led to mRNA delivery into the cytosol with low cytotoxicity, followed by translation of the encoded protein in these difficult-to-transfect cells at a frequency of ~30%. Particles loaded with mRNA administered intranasally in mice led to the expression of the reporter protein luciferase in vivo as soon as 6 h after administration, a timepoint when naked mRNA given i.n. showed no expression. At later timepoints, luciferase expression was detected in naked mRNA-treated mice, but this group showed a wide variation in levels of transfection, compared to particle-treated mice. This system may thus be promising for non-invasive delivery of mRNA-based vaccines. PMID:21417235

Theoretical and Experimental Studies of Epidermal Heat Flux Sensors for Measurements of Core Body Temperature.

PubMed

Zhang, Yihui; Webb, Richard Chad; Luo, Hongying; Xue, Yeguang; Kurniawan, Jonas; Cho, Nam Heon; Krishnan, Siddharth; Li, Yuhang; Huang, Yonggang; Rogers, John A

2016-01-07

Long-term, continuous measurement of core body temperature is of high interest, due to the widespread use of this parameter as a key biomedical signal for clinical judgment and patient management. Traditional approaches rely on devices or instruments in rigid and planar forms, not readily amenable to intimate or conformable integration with soft, curvilinear, time-dynamic, surfaces of the skin. Here, materials and mechanics designs for differential temperature sensors are presented which can attach softly and reversibly onto the skin surface, and also sustain high levels of deformation (e.g., bending, twisting, and stretching). A theoretical approach, together with a modeling algorithm, yields core body temperature from multiple differential measurements from temperature sensors separated by different effective distances from the skin. The sensitivity, accuracy, and response time are analyzed by finite element analyses (FEA) to provide guidelines for relationships between sensor design and performance. Four sets of experiments on multiple devices with different dimensions and under different convection conditions illustrate the key features of the technology and the analysis approach. Finally, results indicate that thermally insulating materials with cellular structures offer advantages in reducing the response time and increasing the accuracy, while improving the mechanics and breathability. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Valence charge fluctuations in YBa/sub 2/Cu/sub 3/O/sub 7-//sub delta/ from core-level spectroscopies

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

Balzarotti, A.; De Crescenzi, M.; Motta, N.

1988-10-01

From x-ray photoemission and Auger measurements of the Cu 2p and O 1s core levels of YBa/sub 2/Cu/sub 3/O/sub 7-//sub delta/ as a function of the oxygen concentration delta, the average copper charge is determined. Evidence is found of dynamic charge fluctuations on the oxygen sublattice giving rise to a greater concentration of trivalent copper at the Cu(1) sites with respect to that determined by the analysis of neutron-diffraction data. On the basis of our experimental results, we introduce a molecular cluster description for the Cu states. The lowest final-states configurations of Cu/sup 2+/ and Cu/sup 3+/ are c3d/sup 10/Lmore » and c3d/sup 10/L/sup 2/, respectively, where c and L denote core holes on copper and oxygen atoms. Oxygen holes have high mobility and a Hubbard correlation energy less than 2 eV, a signature of their delocalization. The effect of temperature on the spectra is minor. Surface degradation modifies the relative intensity of the structures, particularly those of the O spectrum.« less

Effects of core strength training using stable versus unstable surfaces on physical fitness in adolescents: a randomized controlled trial.

PubMed

Granacher, Urs; Schellbach, Jörg; Klein, Katja; Prieske, Olaf; Baeyens, Jean-Pierre; Muehlbauer, Thomas

2014-01-01

It has been demonstrated that core strength training is an effective means to enhance trunk muscle strength (TMS) and proxies of physical fitness in youth. Of note, cross-sectional studies revealed that the inclusion of unstable elements in core strengthening exercises produced increases in trunk muscle activity and thus provide potential extra training stimuli for performance enhancement. Thus, utilizing unstable surfaces during core strength training may even produce larger performance gains. However, the effects of core strength training using unstable surfaces are unresolved in youth. This randomized controlled study specifically investigated the effects of core strength training performed on stable surfaces (CSTS) compared to unstable surfaces (CSTU) on physical fitness in school-aged children. Twenty-seven (14 girls, 13 boys) healthy subjects (mean age: 14 ± 1 years, age range: 13-15 years) were randomly assigned to a CSTS (n = 13) or a CSTU (n = 14) group. Both training programs lasted 6 weeks (2 sessions/week) and included frontal, dorsal, and lateral core exercises. During CSTU, these exercises were conducted on unstable surfaces (e.g., TOGU© DYNAIR CUSSIONS, THERA-BAND© STABILITY TRAINER). Significant main effects of Time (pre vs. post) were observed for the TMS tests (8-22%, f = 0.47-0.76), the jumping sideways test (4-5%, f = 1.07), and the Y balance test (2-3%, f = 0.46-0.49). Trends towards significance were found for the standing long jump test (1-3%, f = 0.39) and the stand-and-reach test (0-2%, f = 0.39). We could not detect any significant main effects of Group. Significant Time x Group interactions were detected for the stand-and-reach test in favour of the CSTU group (2%, f = 0.54). Core strength training resulted in significant increases in proxies of physical fitness in adolescents. However, CSTU as compared to CSTS had only limited additional effects (i.e., stand-and-reach test). Consequently, if the goal of training is to enhance physical fitness, then CSTU has limited advantages over CSTS. ClinicalTrials.gov Identifier: NCT02290457 Registered 13 November 2014.

X-ray photoemission analysis of clean and carbon monoxide-chemisorbed platinum(111) stepped surfaces using a curved crystal

DOE PAGES

Walter, Andrew L.; Schiller, Frederik; Corso, Martina; ...

2015-11-12

Surface chemistry and catalysis studies could significantly gain from the systematic variation of surface active sites, tested under the very same conditions. Curved crystals are excellent platforms to perform such systematics, which may in turn allow to better resolve fundamental properties and reveal new phenomena. This is demonstrated here for the carbon monoxide/platinum system. We curve a platinum crystal around the high-symmetry (111) direction and carry out photoemission scans on top. This renders the spatial core-level imaging of carbon monoxide adsorbed on a 'tunable' vicinal surface, allowing a straightforward visualization of the rich chemisorption phenomenology at steps and terraces. Throughmore » such photoemission images we probe a characteristic elastic strain variation at stepped surfaces, and unveil subtle stress-release effects on clean and covered vicinal surfaces. Lastly, these results offer the prospect of applying the curved surface approach to rationally investigate the chemical activity of surfaces under real pressure conditions.« less

X-ray photoemission analysis of clean and carbon monoxide-chemisorbed platinum(111) stepped surfaces using a curved crystal

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

Walter, Andrew L.; Schiller, Frederik; Corso, Martina

Surface chemistry and catalysis studies could significantly gain from the systematic variation of surface active sites, tested under the very same conditions. Curved crystals are excellent platforms to perform such systematics, which may in turn allow to better resolve fundamental properties and reveal new phenomena. This is demonstrated here for the carbon monoxide/platinum system. We curve a platinum crystal around the high-symmetry (111) direction and carry out photoemission scans on top. This renders the spatial core-level imaging of carbon monoxide adsorbed on a 'tunable' vicinal surface, allowing a straightforward visualization of the rich chemisorption phenomenology at steps and terraces. Throughmore » such photoemission images we probe a characteristic elastic strain variation at stepped surfaces, and unveil subtle stress-release effects on clean and covered vicinal surfaces. Lastly, these results offer the prospect of applying the curved surface approach to rationally investigate the chemical activity of surfaces under real pressure conditions.« less

Accumulation and persistence of chlorobiphenyls, organochlorine pesticides and faecal sterols at the Garroch Head sewage sludge disposal site, Firth of Clyde.

PubMed

Kelly, A G

1995-01-01

The sediment concentrations of organic carbon, faecal sterols, individual chlorobiphenyl congeners and organochlorine pesticides have been measured in seabed cores from the sewage sludge disposal area at Garroch Head in the Firth of Clyde. The measurements confirm the accumulative nature of the site with high levels of sedimentary faecal sterols (152 mg kg(-1) coprostanol). Levels of chlorobiphenyls, DDT compounds and dieldrin in surface sediment were elevated by factors of 12, 40 and 120, respectively, over those observed at a site remote from the effects of dumping. Total chlorobiphenyl levels of 515 microg kg(-1) Arochlor 1254 in surface sediment were comparable to levels found in other areas heavily contaminated with sewage sludge. The 20-cm depth of heavily sludge-contaminated sediment overlays a mixed sludge/basal sediment layer some 10 cm in depth. Levels of organochlorine contaminants were elevated to depths of 90 cm in the sediment, suggesting that the surface layer is a source of contaminants to the deeper sediment. Within the upper 15-20 cm sediment in the disposal area, chlorobiphenyls are conservative, the variation in their concentration with respect to depth being related to historical input. Lindane and possibly dieldrin, and hexachlorobenzene are not conservative. Faecal sterols are removed in sub-surface sediment, in contrast to conservative behaviour previously found at other sewage polluted sites.

Numerical evaluation of gas core length in free surface vortices

NASA Astrophysics Data System (ADS)

Cristofano, L.; Nobili, M.; Caruso, G.

2014-11-01

The formation and evolution of free surface vortices represent an important topic in many hydraulic intakes, since strong whirlpools introduce swirl flow at the intake, and could cause entrainment of floating matters and gas. In particular, gas entrainment phenomena are an important safety issue for Sodium cooled Fast Reactors, because the introduction of gas bubbles within the core causes dangerous reactivity fluctuation. In this paper, a numerical evaluation of the gas core length in free surface vortices is presented, according to two different approaches. In the first one, a prediction method, developed by the Japanese researcher Sakai and his team, has been applied. This method is based on the Burgers vortex model, and it is able to estimate the gas core length of a free surface vortex starting from two parameters calculated with single-phase CFD simulations. The two parameters are the circulation and the downward velocity gradient. The other approach consists in performing a two-phase CFD simulation of a free surface vortex, in order to numerically reproduce the gas- liquid interface deformation. Mapped convergent mesh is used to reduce numerical error and a VOF (Volume Of Fluid) method was selected to track the gas-liquid interface. Two different turbulence models have been tested and analyzed. Experimental measurements of free surface vortices gas core length have been executed, using optical methods, and numerical results have been compared with experimental measurements. The computational domain and the boundary conditions of the CFD simulations were set consistently with the experimental test conditions.

Solvent friction effects propagate over the entire protein molecule through low-frequency collective modes.

PubMed

Moritsugu, Kei; Kidera, Akinori; Smith, Jeremy C

2014-07-24

Protein solvation dynamics has been investigated using atom-dependent Langevin friction coefficients derived directly from molecular dynamics (MD) simulations. To determine the effect of solvation on the atomic friction coefficients, solution and vacuum MD simulations were performed for lysozyme and staphylococcal nuclease and analyzed by Langevin mode analysis. The coefficients thus derived are roughly correlated with the atomic solvent-accessible surface area (ASA), as expected from the fact that friction occurs as the result of collisions with solvent molecules. However, a considerable number of atoms with higher friction coefficients are found inside the core region. Hence, the influence of solvent friction propagates into the protein core. The internal coefficients have large contributions from the low-frequency modes, yielding a simple picture of the surface-to-core long-range damping via solvation governed by collective low-frequency modes. To make use of these findings in implicit-solvent modeling, we compare the all-atom friction results with those obtained using Langevin dynamics (LD) with two empirical representations: the constant-friction and the ASA-dependent (Pastor-Karplus) friction models. The constant-friction model overestimates the core and underestimates the surface damping whereas the ASA-dependent friction model, which damps protein atoms only on the solvent-accessible surface, reproduces well the friction coefficients for both the surface and core regions observed in the explicit-solvent MD simulations. Therefore, in LD simulation, the solvent friction coefficients should be imposed only on the protein surface.

Solvent friction effects propagate over the entire protein molecule through low-frequency collective modes

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

Moritsugu, Kei; Kidera, Akinori; Smith, Jeremy C.

2014-06-25

Protein solvation dynamics has been investigated using atom-dependent Langevin friction coefficients derived directly from molecular dynamics (MD) simulations. To determine the effect of solvation on the atomic friction coefficients, solution and vacuum MD simulations were performed for lysozyme and staphylococcal nuclease and analyzed by Langevin mode analysis. The coefficients thus derived are roughly correlated with the atomic solvent-accessible surface area (ASA), as expected from the fact that friction occurs as the result of collisions with solvent molecules. However, a considerable number of atoms with higher friction coefficients are found inside the core region. Hence, the influence of solvent friction propagatesmore » into the protein core. The internal coefficients have large contributions from the low-frequency modes, yielding a simple picture of the surface-to-core long-range damping via solvation governed by collective low-frequency modes. To make use of these findings in implicit-solvent modeling, we compare the all-atom friction results with those obtained using Langevin dynamics (LD) with two empirical representations: the constant-friction and the ASA-dependent (Pastor Karplus) friction models. The constant-friction model overestimates the core and underestimates the surface damping whereas the ASA-dependent friction model, which damps protein atoms only on the solvent-accessible surface, reproduces well the friction coefficients for both the surface and core regions observed in the explicit-solvent MD simulations. Furthermore, in LD simulation, the solvent friction coefficients should be imposed only on the protein surface.« less

Surface drilling technologies for Mars

NASA Technical Reports Server (NTRS)

Blacic, J. D.; Rowley, J. C.; Cort, G. E.

1986-01-01

Rock drilling and coring conceptual designs for the surface activities associated with a manned Mars mission are proposed. Straightforward extensions of equipment and procedures used on Earth are envisioned for the sample coring and shallow high explosive shot holes needed for tunneling and seismic surveying. A novel rocket exhaust jet piercing method is proposed for very rapid drilling of shot holes required for explosive excavation of emergency radiation shelters. Summaries of estimated equipment masses and power requirements are provided, and the indicated rotary coring rigs are scaled from terrestrial equipment and use compressed CO2 from the Martian atmosphere for core bit cooling and cuttings removal. A mass of 120 kg and power of 3 kW(e) are estimated for a 10 m depth capability. A 100 m depth capacity core rig requires about 1150 kg and 32 km(e). The rocket exhaust jet equipment devised for shallow (3m) explosive emplacement shot holes requires no surface power beyond an electrical ignition system, and might have a 15 kg mass.

The synthesis of four-layer gold-silver-polymer-silver core-shell nanomushroom with inbuilt Raman molecule for surface-enhanced Raman scattering

NASA Astrophysics Data System (ADS)

Jiang, Tao; Wang, Xiaolong; Zhou, Jun

2017-12-01

A facial two-step reduction method was proposed to synthesize four-layer gold-silver-polymer-silver (Au@Ag@PSPAA@Ag) core-shell nanomushrooms (NMs) with inbuilt Raman molecule. The surface-enhanced Raman scattering (SERS) intensity of 4MBA adhered on the surface of Au core gradually increased with the modification of middle Ag shell and then Ag mushroom cap due to the formation of two kinds of ultra-small interior nanogap. Compared with the initial Au nanoparticles, the SERS enhancement ratio of the Au@Ag@PSPAA@Ag NMs approached to nearly 40. The novel core-shell NMs also exhibited homogeneous SERS signals for only one sample and reproducible signals for 10 different samples, certified by the low relative standard deviation values of less than 10% and 15% for the character peaks of 4-mercaptobenzoic acid, respectively. Such a novel four-layer core-shell nanostructure with reliable SERS performance has great potential application in quantitative SERS-based immunoassay.

Adaptive multi-GPU Exchange Monte Carlo for the 3D Random Field Ising Model

NASA Astrophysics Data System (ADS)

Navarro, Cristóbal A.; Huang, Wei; Deng, Youjin

2016-08-01

This work presents an adaptive multi-GPU Exchange Monte Carlo approach for the simulation of the 3D Random Field Ising Model (RFIM). The design is based on a two-level parallelization. The first level, spin-level parallelism, maps the parallel computation as optimal 3D thread-blocks that simulate blocks of spins in shared memory with minimal halo surface, assuming a constant block volume. The second level, replica-level parallelism, uses multi-GPU computation to handle the simulation of an ensemble of replicas. CUDA's concurrent kernel execution feature is used in order to fill the occupancy of each GPU with many replicas, providing a performance boost that is more notorious at the smallest values of L. In addition to the two-level parallel design, the work proposes an adaptive multi-GPU approach that dynamically builds a proper temperature set free of exchange bottlenecks. The strategy is based on mid-point insertions at the temperature gaps where the exchange rate is most compromised. The extra work generated by the insertions is balanced across the GPUs independently of where the mid-point insertions were performed. Performance results show that spin-level performance is approximately two orders of magnitude faster than a single-core CPU version and one order of magnitude faster than a parallel multi-core CPU version running on 16-cores. Multi-GPU performance is highly convenient under a weak scaling setting, reaching up to 99 % efficiency as long as the number of GPUs and L increase together. The combination of the adaptive approach with the parallel multi-GPU design has extended our possibilities of simulation to sizes of L = 32 , 64 for a workstation with two GPUs. Sizes beyond L = 64 can eventually be studied using larger multi-GPU systems.

Evaluation of the Pharmacokinetics and Tolerance of Allopurinol Riboside in Human Volunteers.

DTIC Science & Technology

1984-08-06

hepatitis B "e" antigen. In addition, a mononucleosis screen was performed on serum. Urine and blood (buffy coat) were cultured for cytomegalovirus (CMV...study. His enzyme levels returned to norma, in two weeks, and remained normal one week thereafter. The following laboratory tests for infectious ...hepatitis were negative: hepatitis B surface antigen and antibody, hepatitis B core antibody, hepatitis A antibody, mononucleosis spot test, VDRL

Polarity reversals and tilt of the Earth's magnetic dipole

NASA Technical Reports Server (NTRS)

Dolginov, A. Z.

1993-01-01

There is evidence that the terrestrial magnetic field is connected with the Earth's mantle: (1) there are magnetic anomalies that do not take part in the westward drift of the main field, but are fixed with respect to the mantle; (2) the geomagnetic pole position flips in a particular way by preferred meridional paths during a reversal; and (3) magnetic polarity reversals are correlated with the activations of geological processes. These facts may be explained if we take into account that a significant horizontal temperature gradient can exist in the top levels of the liquid core because of the different thermoconductivity of the different areas of the core-mantle boundary. These temperature inhomogeneities can penetrate the core because fluxes along the core boundary (the thermal wind) can be strongly suppressed by a small redistribution of the chemical composition in the top of the core. The nonparallel gradients of the temperature, density, and composition on the top of the core create a curled electric field that produces a current and a magnetic field. This seed-field can be amplified by motions in the core. The resulting field does not forget the seed-field distribution and in this way the field on the Earth surface (that can be created only in regions with high conductivity, i.e. in the core) is connected with the core-mantle boundary. Contrary to the usual approach to the dynamo problem, we will take into account that the seed field of thermoelectric origin is acting not only at some initial moment of time but permanently.

Holocene depositional environments and surface-level changes at Lake Fryxell, Antarctica

USGS Publications Warehouse

Whittaker, T.E.; Hall, B.L.; Hendy, C.H.; Spaulding, S.A.

2008-01-01

We report on Holocene surface-level variations of Lake Fryxell, Antarctica, as determined from multi-proxy analyses of 18 sediment cores. During this time accumulating sediments were predominantly aeolian sand with algal and carbonate laminae. Based on stratigraphy, mineralogy and diatom assemblages we suggest some carbonate laminae were deposited when lake level dropped, leading to concentration and subsequent precipitation of salts. Although lake level appears to have remained relatively stable throughout the Holocene, minor (<4.5 m below present) lowstands occurred at approximately 6400, 4700, 3800 and ??? 1600 cal. yr BP. The stability of Lake Fryxell during the Holocene contrasts with large-scale variability at other Dry Valleys lakes (eg, Lake Vanda) and with suggestions from chemical diffusion models of a near-desiccation at ???1200 cal. yr BP. The reason for the comparative stability of Lake Fryxell is uncertain, but may be the result of basin morphology and the number, aspect and proximity of meltwater sources. ?? 2008 SAGE Publications.

Gold decorated NaYF4:Yb,Er/NaYF4/silica (core/shell/shell) upconversion nanoparticles for photothermal destruction of BE(2)-C neuroblastoma cells

NASA Astrophysics Data System (ADS)

Qian, Li Peng; Zhou, Li Han; Too, Heng-Phon; Chow, Gan-Moog

2011-02-01

Gold decorated NaYF4:Yb,Er/NaYF4/silica (core/shell/shell) upconversion (UC) nanoparticles ( 70-80 nm) were synthesized using tetraethyl orthosilicate and chloroauric acid in a one-step reverse microemulsion method. Gold nanoparticles ( 6 nm) were deposited on the surface of silica shell of these core/shell/shell nanoparticles. The total upconversion emission intensity (green, red, and blue) of the core/shell/shell nanoparticles decreased by 31% after Au was deposited on the surface of silica shell. The upconverted green light was coupled with the surface plasmon of Au leading to rapid heat conversion. These UC/silica/Au nanoparticles were very efficient to destroy BE(2)-C cancer cells and showed strong potential in photothermal therapy.

Fluid flow near the surface of earth's outer core

NASA Technical Reports Server (NTRS)

Bloxham, Jeremy; Jackson, Andrew

1991-01-01

This review examines the recent attempts at extracting information on the pattern of fluid flow near the surface of the outer core from the geomagnetic secular variation. Maps of the fluid flow at the core surface are important as they may provide some insight into the process of the geodynamo and may place useful constraints on geodynamo models. In contrast to the case of mantle convection, only very small lateral variations in core density are necessary to drive the flow; these density variations are, by several orders of magnitude, too small to be imaged seismically; therefore, the geomagnetic secular variation is utilized to infer the flow. As substantial differences exist between maps developed by different researchers, the possible underlying reasons for these differences are examined with particular attention given to the inherent problems of nonuniqueness.

Microstructure of In x Ga1-x N nanorods grown by molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Webster, R. F.; Soundararajah, Q. Y.; Griffiths, I. J.; Cherns, D.; Novikov, S. V.; Foxon, C. T.

2015-11-01

Transmission electron microscopy is used to examine the structure and composition of In x Ga1-x N nanorods grown by plasma-assisted molecular beam epitaxy. The results confirm a core-shell structure with an In-rich core and In-poor shell resulting from axial and lateral growth sectors respectively. Atomic resolution mapping by energy-dispersive x-ray microanalysis and high angle annular dark field imaging show that both the core and the shell are decomposed into Ga-rich and In-rich platelets parallel to their respective growth surfaces. It is argued that platelet formation occurs at the surfaces, through the lateral expansion of surface steps. Studies of nanorods with graded composition show that decomposition ceases for x ≥ 0.8 and the ratio of growth rates, shell:core, decreases with increasing In concentration.

Trends in chlorinated hydrocarbon levels in Hudson River basin sediments.

PubMed

Bopp, R F; Chillrud, S N; Shuster, E L; Simpson, H J; Estabrooks, F D

1998-08-01

Analysis of sections from dated sediment cores were used to establish geographic distributions and temporal trends of chlorinated hydrocarbon contaminant levels in sediments from natural waters of the Hudson River basin. Radiometric dating was based primarily on the depth distribution of 137(Cs) in the cores and on the occurrence of detectable levels of 7(Be) in surface sediment samples. Eighteen sampling sites included several along the main stem of the Hudson, its major tributaries, and components of the New York/New Jersey (NY/NJ) harbor complex. Drinking-water reservoirs were sampled to place upper limits on atmospheric inputs. Core sections were analyzed for polychlorinated biphenyls (PCBs), 1,1,1-trichloro-2,2-bis(p-chlorophenyl) ethane (DDT)-derived compounds, chlordane, and dioxins. Sediment concentrations of most contaminants at most sites have decreased significantly since the mid-1960s. The data provide a basinwide perspective on major point-source inputs of PCBs to the upper Hudson River and of 2,3,7,8-tetrachlorodibenzo-p-dioxin and DDT to the lower Passaic River. Evidence was found for significant but poorly characterized sources of PCBs and chlordane to the western NY/NJ harbor, and of highly chlorinated dioxins to the upstream sites on the main stem of the Hudson. The results indicate that analysis of dated sediment samples is a most effective and efficient monitoring tool for the study of large-scale geographic and temporal trends in levels of particle-associated contaminants.

Depleted uranium investigation at missile impact sites in White Sands Missile Range

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

Van Etten, D.M.; Purtymun, W.D.

1994-01-01

An investigation for residual depleted uranium was conducted at Pershing missile impact sites on the White Sands Missile Range. Subsurface core soil samples were taken at Chess, Salt Target, and Mine Impact Sites. A sampling pump was installed in a monitoring well at Site 65 where a Pershing earth penetrator was not recovered. Pumping tests and water samples were taken at this site. Chess Site, located in a gypsum flat, was the only location showing elevated levels of depleted uranium in the subsurface soil or perched groundwater. Small fragments can still be found on the surface of the impact sites.more » The seasonal flooding and near surface water has aided in the movement of surface fragments.« less

Williams working on the JAXA MS (Marangoni Surface) Experiment

NASA Image and Video Library

2009-11-05

ISS021-E-020304 (5 Nov. 2009) --- NASA astronaut Jeffrey Williams, Expedition 21 flight engineer, works with Fluid Physics Experiment Facility/Marangoni Surface (FPEF MS) Core hardware in the Kibo laboratory of the International Space Station. Williams first inserted the Marangoni Inside (MI) cassette in the MI Core for a leak check, and then installed the MI Core into the FPEF MI Body. The Marangoni convection experiment in the FPEF examines fluid tension flow in micro-G.

On the Existence of the Logarithmic Surface Layer in the Inner Core of Hurricanes

DTIC Science & Technology

2012-01-01

characteristics of eyewall boundary layer of Hurricane Hugo (1989). Mon. Wea. Rev., 139, 1447-1462. Zhang, JA, Montgomery MT. 2012 Observational...the inner core of hurricanes Roger K. Smitha ∗and Michael T. Montgomeryb a Meteorological Institute, University of Munich, Munich, Germany b Dept. of...logarithmic surface layer”, or log layer, in the boundary layer of the rapidly-rotating core of a hurricane . One such study argues that boundary-layer

Microplastics in Sediment Cores from Asia and Africa as Indicators of Temporal Trends in Plastic Pollution.

PubMed

Matsuguma, Yukari; Takada, Hideshige; Kumata, Hidetoshi; Kanke, Hirohide; Sakurai, Shigeaki; Suzuki, Tokuma; Itoh, Maki; Okazaki, Yohei; Boonyatumanond, Ruchaya; Zakaria, Mohamad Pauzi; Weerts, Steven; Newman, Brent

2017-08-01

Microplastics (<5 mm) were extracted from sediment cores collected in Japan, Thailand, Malaysia, and South Africa by density separation after hydrogen peroxide treatment to remove biofilms were and identified using FTIR. Carbonyl and vinyl indices were used to avoid counting biopolymers as plastics. Microplastics composed of variety of polymers, including polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethyleneterphthalates (PET), polyethylene-polypropylene copolymer (PEP), and polyacrylates (PAK), were identified in the sediment. We measured microplastics between 315 µm and 5 mm, most of which were in the range 315 µm-1 mm. The abundance of microplastics in surface sediment varied from 100 pieces/kg-dry sediment in a core collected in the Gulf of Thailand to 1900 pieces/kg-dry sediment in a core collected in a canal in Tokyo Bay. A far higher stock of PE and PP composed microplastics in sediment compared with surface water samples collected in a canal in Tokyo Bay suggests that sediment is an important sink for microplastics. In dated sediment cores from Japan, microplastic pollution started in 1950s, and their abundance increased markedly toward the surface layer (i.e., 2000s). In all sediment cores from Japan, Thailand, Malaysia, and South Africa, the abundance of microplastics increased toward the surface, suggesting the global occurrence of and an increase in microplastic pollution over time.

Core surface magnetic field evolution 2000-2010

NASA Astrophysics Data System (ADS)

Finlay, C. C.; Jackson, A.; Gillet, N.; Olsen, N.

2012-05-01

We present new dedicated core surface field models spanning the decade from 2000.0 to 2010.0. These models, called gufm-sat, are based on CHAMP, Ørsted and SAC-C satellite observations along with annual differences of processed observatory monthly means. A spatial parametrization of spherical harmonics up to degree and order 24 and a temporal parametrization of sixth-order B-splines with 0.25 yr knot spacing is employed. Models were constructed by minimizing an absolute deviation measure of misfit along with measures of spatial and temporal complexity at the core surface. We investigate traditional quadratic or maximum entropy regularization in space, and second or third time derivative regularization in time. Entropy regularization allows the construction of models with approximately constant spectral slope at the core surface, avoiding both the divergence characteristic of the crustal field and the unrealistic rapid decay typical of quadratic regularization at degrees above 12. We describe in detail aspects of the models that are relevant to core dynamics. Secular variation and secular acceleration are found to be of lower amplitude under the Pacific hemisphere where the core field is weaker. Rapid field evolution is observed under the eastern Indian Ocean associated with the growth and drift of an intense low latitude flux patch. We also find that the present axial dipole decay arises from a combination of subtle changes in the southern hemisphere field morphology.

Earth Core and Inner Core: What Can We Learn From a Bayesian Inversion of Combined Nutation and Surface Gravimetry Data?

NASA Astrophysics Data System (ADS)

Lambert, S. B.; Ziegler, Y.; Rosat, S.; Bizouard, C.

2017-12-01

Nutation time series derived from very long baseline interferometry (VLBI) and time varying surface gravity data recorded by superconducting gravimeters (SG) have long been used separately to assess the Earth's interior via the estimation of the free core and inner core resonance effects on nutation or tidal gravity. The results obtained from these two techniques have shown recently to be consistent, making relevant the combination of VLBI and SG observables and the estimation of Earth's interior parameters in a single inversion. We present here the results of combining nutation and surface gravity time series to improve estimates of the Earth's core and inner core resonant frequencies. We use VLBI nutation time series spanning 1984-2016 derived by several analysis centers affiliated to the International VLBI Service for Geodesy and Astrometry, together with surface gravity data from about 15 SG stations. We address the resonance model used for describing the Earth's interior response to tidal excitation, the data preparation consisting of the error recalibration and amplitude fitting to nutation data, and processing of SG time-varying gravity to remove any gaps, spikes, steps and other disturbances, followed by the tidal analysis with the ETERNA 3.4 software package. New estimates of the resonant periods are proposed and correlations between the parameters are investigated.

Combining nutation and surface gravity observations to estimate the Earth's core and inner core resonant frequencies

NASA Astrophysics Data System (ADS)

Ziegler, Yann; Lambert, Sébastien; Rosat, Séverine; Nurul Huda, Ibnu; Bizouard, Christian

2017-04-01

Nutation time series derived from very long baseline interferometry (VLBI) and time varying surface gravity data recorded by superconducting gravimeters (SG) have long been used separately to assess the Earth's interior via the estimation of the free core and inner core resonance effects on nutation or tidal gravity. The results obtained from these two techniques have been shown recently to be consistent, making relevant the combination of VLBI and SG observables and the estimation of Earth's interior parameters in a single inversion. We present here the intermediate results of the ongoing project of combining nutation and surface gravity time series to improve estimates of the Earth's core and inner core resonant frequencies. We use VLBI nutation time series spanning 1984-2016 derived by the International VLBI Service for geodesy and astrometry (IVS) as the result of a combination of inputs from various IVS analysis centers, and surface gravity data from about 15 SG stations. We address here the resonance model used for describing the Earth's interior response to tidal excitation, the data preparation consisting of the error recalibration and amplitude fitting for nutation data, and processing of SG time-varying gravity to remove any gaps, spikes, steps and other disturbances, followed by the tidal analysis with the ETERNA 3.4 software package, the preliminary estimates of the resonant periods, and the correlations between parameters.

Collecting, preparing, crossdating, and measuring tree increment cores

USGS Publications Warehouse

Phipps, R.L.

1985-01-01

Techniques for collecting and handling increment tree cores are described. Procedures include those for cleaning and caring for increment borers, extracting the sample from a tree, core surfacing, crossdating, and measuring. (USGS)

Intricate Estimation and Assessment of Surface Conditioning of Posts to improve Interfacial Adhesion in Post-core Restorations: An in vitro Study.

PubMed

Gupta, Priyanka; Sharma, Amil; Pathak, Vivek K; Mankeliya, Saurabh; Bhardwaj, Shivanshu; Dhanare, Poorvasha

2017-12-01

Post and core restorations are routinely used for restoring grossly decayed tooth structures. Various chemical agents are known to affect the interfacial adhesions between the post and the core. Hence, we planned the present study to evaluate the effect of various post-surface treatments on the interfacial strength between the posts and composite materials that are used for building up the core portion. The present study included assessment of the effect of surface conditioning of posts on the interfacial adhesion in post-core restorations. A total of 80 clear post-tapers were included and were divided broadly into four study groups based on the type of chemical testing protocols used. Various chemical treatments included alkaline potassium permanganate, hydrogen peroxide, and phosphoric acid. The fourth group was the control group. The composite core material was used for building up the core. Testing of the tensile load was done on a universal testing machine. All the results were analyzed by the Statistical Package for the Social Sciences (SPSS) software. The highest bond strength was observed in the study group treated with alkaline potassium permanganate, while the lowest was observed in the control group followed by the hydrogen peroxide group. While comparing the mean bond strength in between various study groups, significant results were obtained. Chemical treatment protocol significantly alters the mean bond strength of the post and core restoration. Potassium permanganate significantly increases the bond strength between the fiber post and core restoration.

Glacial-interglacial dynamics of Antarctic firn columns: comparison between simulations and ice core air-?15N measurements

NASA Astrophysics Data System (ADS)

Capron, E.; Landais, A.; Buiron, D.; Cauquoin, A.; Chappellaz, J. A.; Debret, M.; Jouzel, J.; Leuenberger, M.; Martinerie, P.; Masson-Delmotte, V.; Mulvaney, R.; Parrenin, F.; Prié, F.

2013-12-01

Correct estimation of the firn lock-in depth is essential for correctly linking gas and ice chronologies in ice core studies. Here, two approaches to constrain the firn depth evolution in Antarctica are presented over the last deglaciation: outputs of a firn densification model, and measurements of δ15N of N2 in air trapped in ice core, assuming that δ15N is only affected by gravitational fractionation in the firn column. Since the firn densification process is largely governed by surface temperature and accumulation rate, we have investigated four ice cores drilled in coastal (Berkner Island, BI, and James Ross Island, JRI) and semi-coastal (TALDICE and EPICA Dronning Maud Land, EDML) Antarctic regions. Combined with available ice core air- δ15N measurements from the EPICA Dome C (EDC) site, the studied regions encompass a large range of surface accumulation rates and temperature conditions. Our δ15N profiles reveal a heterogeneous response of the firn structure to glacial-interglacial climatic changes. While firn densification simulations correctly predict TALDICE δ15N variations, they systematically fail to capture the large millennial-scale δ15N variations measured at BI and the δ15N glacial levels measured at JRI and EDML - a mismatch previously reported for central East Antarctic ice cores. New constraints of the EDML gas-ice depth offset during the Laschamp event (41 ka) and the last deglaciation do not favour the hypothesis of a large convective zone within the firn as the explanation of the glacial firn model- δ15N data mismatch for this site. While we could not conduct an in-depth study of the influence of impurities in snow for firnification from the existing datasets, our detailed comparison between the δ15N profiles and firn model simulations under different temperature and accumulation rate scenarios suggests that the role of accumulation rate may have been underestimated in the current description of firnification models.

Glacial-interglacial dynamics of Antarctic firn columns: comparison between simulations and ice core air-δ15N measurements

NASA Astrophysics Data System (ADS)

Capron, E.; Landais, A.; Buiron, D.; Cauquoin, A.; Chappellaz, J.; Debret, M.; Jouzel, J.; Leuenberger, M.; Martinerie, P.; Masson-Delmotte, V.; Mulvaney, R.; Parrenin, F.; Prié, F.

2013-05-01

Correct estimation of the firn lock-in depth is essential for correctly linking gas and ice chronologies in ice core studies. Here, two approaches to constrain the firn depth evolution in Antarctica are presented over the last deglaciation: outputs of a firn densification model, and measurements of δ15N of N2 in air trapped in ice core, assuming that δ15N is only affected by gravitational fractionation in the firn column. Since the firn densification process is largely governed by surface temperature and accumulation rate, we have investigated four ice cores drilled in coastal (Berkner Island, BI, and James Ross Island, JRI) and semi-coastal (TALDICE and EPICA Dronning Maud Land, EDML) Antarctic regions. Combined with available ice core air-δ15N measurements from the EPICA Dome C (EDC) site, the studied regions encompass a large range of surface accumulation rates and temperature conditions. Our δ15N profiles reveal a heterogeneous response of the firn structure to glacial-interglacial climatic changes. While firn densification simulations correctly predict TALDICE δ15N variations, they systematically fail to capture the large millennial-scale δ15N variations measured at BI and the δ15N glacial levels measured at JRI and EDML - a mismatch previously reported for central East Antarctic ice cores. New constraints of the EDML gas-ice depth offset during the Laschamp event (~41 ka) and the last deglaciation do not favour the hypothesis of a large convective zone within the firn as the explanation of the glacial firn model-δ15N data mismatch for this site. While we could not conduct an in-depth study of the influence of impurities in snow for firnification from the existing datasets, our detailed comparison between the δ15N profiles and firn model simulations under different temperature and accumulation rate scenarios suggests that the role of accumulation rate may have been underestimated in the current description of firnification models.

Generation of surface-wave microwave microplasmas in hollow-core photonic crystal fiber based on a split-ring resonator.

PubMed

Vial, Florian; Gadonna, Katell; Debord, Benoît; Delahaye, Frédéric; Amrani, Foued; Leroy, Olivier; Gérôme, Frédéric; Benabid, Fetah

2016-05-15

We report on a new and highly compact scheme for the generation and sustainment of microwave-driven plasmas inside the core of an inhibited coupling Kagome hollow-core photonic crystal fiber. The microwave plasma generator consists of a split-ring resonator that efficiently couples the microwave field into the gas-filled fiber. This coupling induces the concomitant generation of a microwave surface wave at the fiber core surround and a stable plasma column confined in the fiber core. The scheme allowed the generation of several centimeters long argon microplasma columns with a very low excitation power threshold. This result represents an important step toward highly compact plasma lasers or plasma-based photonic components.

SPECTROSCOPIC INVESTIGATION OF (NH4)2S TREATED GaSeTe FOR RADIATION DETECTOR APPLICATIONS

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

Nelson, A; Laurence, T; Conway, A

2009-08-04

The surface of the layered III-VI chalcogenide semiconductor GaSeTe was treated with (NH{sub 4}){sub 2}S at 60 C to modify the surface chemistry and determine the effect on transport properties. Room temperature photoluminescence (PL) measurements were used to assess the effect of the (NH{sub 4}){sub 2}S treatment on surface defect states. Evaluation of the subsequent surface chemistry was performed with high-resolution core-level photoemission measurements. Metal overlayers were deposited on the (NH{sub 4}){sub 2}S treated surfaces and the I-V characteristics were measured. The measurements were correlated to understand the effect of (NH{sub 4}){sub 2}S modification of the interfacial electronic structure withmore » the goal of optimizing the metal/GaSeTe interface for radiation detector devices.« less

Density functional investigation of the adsorption effects of PH3 and SH2 on the structure stability of the Au55 and Pt55 nanoclusters

NASA Astrophysics Data System (ADS)

Guedes-Sobrinho, Diego; Chaves, Anderson S.; Piotrowski, Maurício J.; Da Silva, Juarez L. F.

2017-04-01

Although several studies have been reported for Pt55 and Au55 nanoclusters, our atomistic understanding of the interplay between the adsorbate-surface interactions and the mechanisms that lead to the formation of the distorted reduced core (DRC) structures, instead of the icosahedron (ICO) structure in gas phase, is still far from satisfactory. Here, we report a density functional theory (DFT) investigation of the role of the adsorption effects of PH3 (one lone pair of electrons) and SH2 (two lone pairs) on the relative stability of the Pt55 and Au55 nanoclusters. In gas phase, we found that the DRC structures with 7 and 9 atoms in the core region are about 5.34 eV (Pt55) and 2.20 eV (Au55) lower in energy than the ICO model with Ih symmetry and 13 atoms in the core region. However, the stability of the ICO structure increases by increasing the number of adsorbed molecules from 1 to 18, in which both DRC and ICO structures are nearly degenerate in energy at the limit of 18 ligands, which can be explained as follows. In gas phase, there is a strong compression of the cationic core region by the anionic surface atoms induced by the attractive Coulomb interactions (core+-surface-), and hence, the strain release is obtained by reducing the number of atoms in the cationic core region, which leads to the 55 atoms distorted reduced core structures. Thus, the Coulomb interactions between the core+ and surface- contribute to break the symmetry in the ICO55 structure. On the other hand, the addition of ligands on the anionic surface reduces the charge transfer between the core and surface, which contributes to decrease the Coulomb interactions and the strain on the core region of the ICO structure, and hence, it stabilizes a compact ICO structure. The same conclusion is obtained by adding van der Waals corrections to the plain DFT calculations. Similar results are obtained by the addition of steric effects, which are considered through the adsorption of triphenylphosphine (PPh3) molecules on Au55, in which the relative stability between ICO and DRC is the same as for PH3 and SH2. However, for Pt55, we found an inversion of stability due to the PPh3 ligand effects, where ICO has higher stability than DRC by 2.40 eV. Our insights are supported by several structural, electronic, and energetic analyses.

Density functional investigation of the adsorption effects of PH3 and SH2 on the structure stability of the Au55 and Pt55 nanoclusters.

PubMed

Guedes-Sobrinho, Diego; Chaves, Anderson S; Piotrowski, Maurício J; Da Silva, Juarez L F

2017-04-28

Although several studies have been reported for Pt 55 and Au 55 nanoclusters, our atomistic understanding of the interplay between the adsorbate-surface interactions and the mechanisms that lead to the formation of the distorted reduced core (DRC) structures, instead of the icosahedron (ICO) structure in gas phase, is still far from satisfactory. Here, we report a density functional theory (DFT) investigation of the role of the adsorption effects of PH 3 (one lone pair of electrons) and SH 2 (two lone pairs) on the relative stability of the Pt 55 and Au 55 nanoclusters. In gas phase, we found that the DRC structures with 7 and 9 atoms in the core region are about 5.34 eV (Pt 55 ) and 2.20 eV (Au 55 ) lower in energy than the ICO model with I h symmetry and 13 atoms in the core region. However, the stability of the ICO structure increases by increasing the number of adsorbed molecules from 1 to 18, in which both DRC and ICO structures are nearly degenerate in energy at the limit of 18 ligands, which can be explained as follows. In gas phase, there is a strong compression of the cationic core region by the anionic surface atoms induced by the attractive Coulomb interactions (core + -surface - ), and hence, the strain release is obtained by reducing the number of atoms in the cationic core region, which leads to the 55 atoms distorted reduced core structures. Thus, the Coulomb interactions between the core + and surface - contribute to break the symmetry in the ICO 55 structure. On the other hand, the addition of ligands on the anionic surface reduces the charge transfer between the core and surface, which contributes to decrease the Coulomb interactions and the strain on the core region of the ICO structure, and hence, it stabilizes a compact ICO structure. The same conclusion is obtained by adding van der Waals corrections to the plain DFT calculations. Similar results are obtained by the addition of steric effects, which are considered through the adsorption of triphenylphosphine (PPh 3 ) molecules on Au 55 , in which the relative stability between ICO and DRC is the same as for PH 3 and SH 2 . However, for Pt 55 , we found an inversion of stability due to the PPh 3 ligand effects, where ICO has higher stability than DRC by 2.40 eV. Our insights are supported by several structural, electronic, and energetic analyses.

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

Lockhart, L.; Ramial, K.; Wilkinson, P.

Mercury concentrations were measured in sediment cores from lakes in central and northern Canada. Typically cores spanned periods of one hundred to several hundred years, as judged by profiles of unsupported lead-210 and cesium-137. Mercury in the uppermost slices of sediment from lakes in more easterly locations was consistently elevated above that in deeper slices from the same lakes. The authors have interpreted this surface enrichment as evidence of increased recent loadings in agreement with similar studies in Ontario, Quebec, USA and Scandinavia. Western sites showed less surface enrichment with mercury, sometimes almost none, in agreement with experience in Alaska.more » Surface grab samples and two deep cores from Lake Winnipeg indicated that mercury in surface sediments exceeded that at depths corresponding to several thousand years in the history of the lake. The current indication from the cores is a regional difference in loadings of mercury with higher enrichments over basal values in the East than in the West. Recent literature, however, has raised the possibility of vertical mobility of mercury in sediments. This has suggested that processes controlling the well-known concentration of iron and manganese in oxidized surface sediments may also concentrate mercury. A number of the cores were analyzed for iron and manganese but mercury (or lead or cadmium) failed to correlate with iron or manganese. Efforts are underway to develop ways to distinguish rigorously between natural mercury and contamination.« less

The surface of 1-euro coins studied by X-ray photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Gou, F.; Gleeson, M. A.; Villette, J.; Kleyn, S. E. F.; Kleyn, A. W.

2004-03-01

The two alloy surfaces (pill and ring) that are present on 1-euro coins have been studied by X-ray photoelectron spectroscopy (XPS). Comparison is made between coins from general circulation and coin surfaces that have been subjected to a variety of cleaning and oxidation treatments. The concentrations and possible oxidation states of the metals (nickel, copper and zinc) at the surface were derived from analysis of the 2p 3/2 core levels. The surface atomic ratios measured for the pill and the ring parts of the euro coins were compared to the official bulk ratios. This study shows a clear nickel enrichment of both pill and ring surfaces. Nickel at surface seems to be present mainly in hydroxide form although the chloride form cannot be excluded. A small concentration of zinc was present on the surface of the pill, even though it is not present in the bulk alloy. Evidence of both nickel and zinc surface enrichment is observed for the ring. No surface enrichment is observed for the atomically clean or oxidized alloy surfaces over a 60-h time scale.

Anatomy of a Plate Boundary at Shallow Crustal Levels: a Composite Section from the Alpine Fault, New Zealand

NASA Astrophysics Data System (ADS)

Barth, N. C.; Toy, V. G.; Boulton, C. J.; Carpenter, B. M.

2010-12-01

New Zealand's Alpine Fault is mostly a moderately SE-dipping dextral reverse plate boundary structure, but at its southern end, strike-slip-normal motion is indicated by offset of recent surfaces, juxtaposition of sediments, and both brittle and ductile shear sense indicators. At the location of uplift polarity reversal fault rocks exhumed from both the hangingwall Pacific and footwall Australian Plates are juxtaposed, offering a remarkably complete cross section of the plate boundary at shallow crustal levels. We describe Alpine Fault damage zone and fault core structures overprinted on Pacific and Australian plate mylonites of a variety of compositions, in a fault-strike perpendicular composite section spanning the reversal in dip-slip polarity. The damage zone is asymmetric; on the Australian Plate 160m of quartzose paragneiss-derived mylonites are overprinted by brittle faults and fractures that increase in density towards the principal slip surface (PSS). This damage zone fabric consists of 1-10m-spaced, moderately to steeply-dipping, 1-20cm-thick gouge-filled faults, overprinted on and sub-parallel to a mylonitic foliation sub-parallel to the PSS. On the Pacific Plate, only 40m of the 330m section of volcaniclastic-derived mylonites have brittle damage in the form of unhealed fractures and faults, as well as a pervasive greenschist facies hydrothermal alteration absent in the footwall. These damage-related structures comprise a network of small-offset faults and fractures with increasing density and intensity towards the PSS. The active Pacific Plate fault core is composed of ~1m of cataclasite grading into folded protocataclasite that is less folded and fractured with increasing distance from the PSS. The active Australian Plate fault core is <1.5m wide and consists of 3 distinct foliated clay gouges, as well as a 4cm thick brittle ultracataclasite immediately adjacent to the active PSS. The Australian Plate foliated clay gouge contains stringers of quartz that become less continuous and more sigmoidal toward the PSS, indicating a strain gradient across the gouge zone. Gouge textures are consistent with deformation by pressure solution. Intact wafers from one of the gouges, experimentally -sheared in a biaxial configuration under true-triaxial loading at σn’= 31MPa and Pf = 10MPa, yielded a friction coefficient, μss = 0.32 and displayed velocity strengthening behavior. No significant re-strengthening was observed during hold periods of slide-hold tests. Well-cemented glacial till (~8000 years old), which caps many outcrops, is a marker that shows that the damage zone is not active in the near-surface, but most of the fault core is. The active near-surface damage zone here is <40m wide and the active fault core is <2.5m wide. Both overprint a much wider, inactive damage zone. The combination of rheologically-weak Australian Plate fault rocks with surface rupture traces indicates distinctly different coseismic and interseismic behaviors along the southern strike-slip-normal segment of the Alpine Fault.

NEUTRONIC REACTOR

DOEpatents

Metcalf, H.E.

1957-10-01

A reactor of the type which preferably uses plutonium as the fuel and a liquid moderator, preferably ordinary water, and which produces steam within the reactor core due to the heat of the chain reaction is described. In the reactor shown the fuel elements are essentially in the form of trays and are ventically stacked in spaced relationship. The water moderator is continuously supplied to the trays to maintain a constant level on the upper surfaces of the fuel element as it is continually evaporated by the heat. The steam passes out through the spaces between the fuel elements and is drawn off at the top of the core. The fuel elements are clad in aluminum to prevent deterioration thereof with consequent contamimation of the water.

The effect of surface-bulk potential difference on the kinetics of intercalation in core-shell active cathode particles

NASA Astrophysics Data System (ADS)

Kazemiabnavi, Saeed; Malik, Rahul; Orvananos, Bernardo; Abdellahi, Aziz; Ceder, Gerbrand; Thornton, Katsuyo

2018-04-01

Surface modification of active cathode particles is commonly observed in battery research as either a surface phase evolving during the cycling process, or intentionally engineered to improve capacity retention, rate capability, and/or thermal stability of the cathode material. Here, a continuum-scale model is developed to simulate the galvanostatic charge/discharge of a cathode particle with core-shell heterostructure. The particle is assumed to be comprised of a core material encapsulated by a thin layer of a second phase that has a different open-circuit voltage. The effect of the potential difference between the surface and bulk phases (Ω) on the kinetics of lithium intercalation and the galvanostatic charge/discharge profiles is studied at different values of Ω, C-rates, and exchange current densities. The difference between the Li chemical potential in the surface and bulk phases of the cathode particle results in a concentration difference between these two phases. This leads to a charge/discharge asymmetry in the galvanostatic voltage profiles, causing a decrease in the accessible capacity of the particle. These effects are more significant at higher magnitudes of surface-bulk potential difference. The proposed model provides detailed insight into the kinetics and voltage behavior of the intercalation/de-intercalation processes in core-shell heterostructure cathode particles.

Diatoms in sediments of perennially ice-covered Lake Hoare, and implications for interpreting lake history in the McMurdo Dry Valleys of Antarctica

USGS Publications Warehouse

Spaulding, S.A.; McKnight, Diane M.; Stoermer, E.F.; Doran, P.T.

1997-01-01

Diatom assemblages in surficial sediments, sediment cores, sediment traps, and inflowing streams of perennially ice-covered Lake Hore, South Victorialand, Antarctica were examined to determine the distribution of diatom taxa, and to ascertain if diatom species composition has changed over time. Lake Hoare is a closed-basin lake with an area of 1.8 km2, maximum depth of 34 m, and mean depth of 14 m, although lake level has been rising at a rate of 0.09 m yr-1 in recent decades. The lake has an unusual regime of sediment deposition: coarse grained sediments accumulate on the ice surface and are deposited episodically on the lake bottom. Benthic microbial mats are covered in situ by the coarse episodic deposits, and the new surfaces are recolonized. Ice cover prevents wind-induced mixing, creating the unique depositional environment in which sediment cores record the history of a particular site, rather than a lake=wide integration. Shallow-water (<1 m) diatom assemblages (Stauroneis anceps, Navicula molesta, Diadesmis contenta var. parallela, Navicula peraustralis) were distinct from mid-depth (4-16 m) assemblages (Diadesmis contenta, Luticola muticopsis fo. reducta, Stauroneis anceps, Diadesmis contenta var. parallela, Luticola murrayi) and deep-water (2-31 m) assemblages (Luticola murrayi, Luticola muticopsis fo. reducta, Navicula molesta. Analysis of a sediment core (30 cm long, from 11 m water depth) from Lake Hoare revealed two abrupt changes in diatom assemblages. The upper section of the sediment core contained the greatest biomass of benthic microbial mat, as well as the greatest total abundance and diversity of diatoms. Relative abundances of diatoms in this section are similar to the surficial samples from mid-depths. An intermediate zone contained less organic material and lower densities of diatoms. The bottom section of core contained the least amount of microbial mat and organic material, and the lowest density of diatoms. The dominant process influencing species composition and abundance of diatom assemblages in the benthic microbial mats is episodic deposition of coarse sediment from the ice surface.

Hepatitis B virus DNA-positive, hepatitis B surface antigen-negative blood donations intercepted by anti-hepatitis B core antigen testing: the Canadian Blood Services experience.

PubMed

O'Brien, Sheila F; Fearon, Margaret A; Yi, Qi-Long; Fan, Wenli; Scalia, Vito; Muntz, Irene R; Vamvakas, Eleftherios C

2007-10-01

The benefit of introducing anti-hepatitis B core antigen (HBc) screening for intercepting potentially infectious donations missed by hepatitis B surface antigen (HBsAg) screening in Canada was studied. Anti-HBc testing of all donations was implemented in April 2005, along with antibody to hepatitis B surface antigen (anti-HBs) and hepatitis B virus (HBV) DNA supplemental testing of anti-HBc repeat-reactive, HBsAg-negative donations. The proportion of potentially infectious donations intercepted by anti-HBc over the initial 18 months of testing was calculated based on three assumptions relating infectivity of HBV DNA-positive units to anti-HBs levels. Lookback was conducted for all DNA-positive donations. Of 493,344 donors, 5,585 (1.13%) were repeat-reactive for the presence of anti-HBc, with 29 (0.52%) being HBV DNA-positive and HBsAg-negative. The proportion of potentially infectious donations intercepted by anti-HBc screening was 1 in 17,800 if all HBV DNA-positive donations were infectious, 1 in 26,900 if infectivity was limited to donations with an anti-HBs level of not more than 100 mIU per mL, and 1 in 69,300 if only donations with undetectable anti-HBs were infectious. For 279 components in the lookback study, no traced recipients were HBsAg-positive and 7 recipients were anti-HBc-reactive in association with 4 donors, 3 of whom had an anti-HBs level of more than 100 mIU per mL and 1 of whom had a level of 61 mIU per mL. Implementation of anti-HBc screening reduced the risk of transfusing potentially infectious units by at least as much as had been expected based on the literature. The lookback did not provide proof of transfusion transmission of HBV from HBV DNA-positive, anti-HBc-reactive, HBsAg-negative donors but it did not establish lack of transmission either.

Angle-resolved and core-level photoemission study of interfacing the topological insulator Bi1.5Sb0.5Te1.7Se1.3 with Ag, Nb, and Fe

NASA Astrophysics Data System (ADS)

de Jong, N.; Frantzeskakis, E.; Zwartsenberg, B.; Huang, Y. K.; Wu, D.; Hlawenka, P.; Sańchez-Barriga, J.; Varykhalov, A.; van Heumen, E.; Golden, M. S.

2015-08-01

Interfaces between a bulk-insulating topological insulator (TI) and metallic adatoms have been studied using high-resolution, angle-resolved, and core-level photoemission. Fe, Nb, and Ag were evaporated onto Bi1 .5Sb0 .5Te1 .7Se1 .3 (BSTS) surfaces both at room temperature and 38 K. The coverage and temperature dependence of the adsorption and interfacial formation process have been investigated, highlighting the effects of the overlayer growth on the occupied electronic structure of the TI. For all coverages at room temperature and for those equivalent to less than 0.2 monolayer at low temperature all three metals lead to a downward shift of the TI bands with respect to the Fermi level. At room temperature Ag appears to intercalate efficiently into the van der Waals gap of BSTS, accompanied by low-level substitution for the Te/Se atoms of the termination layer of the crystal. This Te/Se substitution with silver increases significantly for low temperature adsorption, and can even dominate the electrostatic environment of the Bi/Sb atoms in the BSTS near-surface region. On the other hand, Fe and Nb evaporants remain close to the termination layer of the crystal. On room temperature deposition, they initially substitute isoelectronically for Bi as a function of coverage, before substituting for Te/Se atoms. For low temperature deposition, Fe and Nb are too immobile for substitution processes and show a behavior consistent with clustering on the surface. For both Ag and Fe/Nb, these differing adsorption pathways still lead to the qualitatively similar and remarkable behavior for low temperature deposition that the chemical potential first moves downward (p -type dopant behavior) and then upward (n -type behavior) on increasing coverage.

Kilopower: Small and Affordable Fission Power Systems for Space

NASA Technical Reports Server (NTRS)

Mason, Lee; Palac, Don; Gibson, Marc

2017-01-01

The Nuclear Systems Kilopower Project was initiated by NASA's Space Technology Mission Directorate Game Changing Development Program in fiscal year 2015 to demonstrate subsystem-level technology readiness of small space fission power in a relevant environment (Technology Readiness Level 5) for space science and human exploration power needs. The Nuclear Systems Kilopower Project centerpiece is the Kilopower Reactor Using Stirling Technology (KRUSTY) test, which consists of the development and testing of a fission ground technology demonstrator of a 1 kWe-class fission power system. The technologies to be developed and validated by KRUSTY are extensible to space fission power systems from 1 to 10 kWe, which can enable higher power future potential deep space science missions, as well as modular surface fission power systems for exploration. The Kilopower Project is cofounded by NASA and the Department of Energy National Nuclear Security Administration (NNSA).KRUSTY include the reactor core, heat pipes to transfer the heat from the core to the power conversion system, and the power conversion system. Los Alamos National Laboratory leads the design of the reactor, and the Y-12 National Security Complex is fabricating it. NASA Glenn Research Center (GRC) has designed, built, and demonstrated the balance of plant heat transfer and power conversion portions of the KRUSTY experiment. NASA MSFC developed an electrical reactor simulator for non-nuclear testing, and the design of the reflector and shielding for nuclear testing. In 2016, an electrically heated non-fissionable Depleted Uranium (DU) core was tested at GRC in a configuration identical to the planned nuclear test. Once the reactor core has been fabricated and shipped to the Device Assembly Facility at the NNSAs Nevada National Security Site, the KRUSTY nuclear experiment will be assembled and tested. Completion of the KRUSTY experiment will validate the readiness of 1 to 10 kWe space fission technology for NASAs future requirements for sunlight-independent space power. An early opportunity for demonstration of In-Situ Resource Utilization (ISRU) capability on the surface of Mars is currently being considered for 2026 launch. Since a space fission system is the leading option for power generation for the first Mars human outpost, a smaller version of a planetary surface fission power system could be built to power the ISRU demonstration and ensure its end-to-end validity. Planning is underway to start the hardware development of this subscale flight demonstrator in 2018.

Carbon Solubility in Silicon-Iron-Bearing Metals during Core Formation on Mercury

NASA Technical Reports Server (NTRS)

Vander Kaaden, Kathleen E.; McCubbin, Francis M.; Ross, D. Kent; Rapp, Jennifer F.; Danielson, Lisa R.; Keller, Lindsay P.; Righter, Kevin

2016-01-01

Recent results obtained from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft showed the surface of Mercury has high S abundances (approximately 4 wt%) and low Iron(II) Oxide abundances (less than 2 wt%). Based on these extreme values, the oxygen fugacity of Mercury's surface materials was estimated to be approximately 3 to 7 log(sub 10) units below the IW buffer (Delta IW-3 to Delta IW-7). This highly reducing nature of the planet has resulted in a large core and relatively thin mantle, extending to only approximately 420 km depth (corresponding to a core-mantle boundary pressure of approximately 4-7 GPa) within the planet. Furthermore, MESSENGER results have suggested the presence of carbon on the surface of the planet. Previous experimental results from have also suggested the possibility of a primary floatation crust on Mercury composed of graphite, produced after a global magma ocean event. With these exotic conditions of this compositional end-member planet, it begs the question, what is the core composition of Mercury? Although no definitive conclusion has been reached, previous studies have made advances towards answering this question. Riner et al. and Chen et al. looked at iron sulfide systems and implemented various crystallization and layered core scenarios to try and determine the composition and structure of Mercury's core. Malavergne et al. examined core crystallization scenarios in the presence of sulfur and silicon. Hauck et al. used the most recent geophysical constraints from the MESSENGER spacecraft to model the internal structure of Mercury, including the core, in a iron-sulfur-silicon system. More recently, Chabot et al. conducted a series of metal-silicate partitioning experiments in a iron-sulfur-silicon system. These results showed the core of Mercury has the potential to contain more than 15 wt% silicon. However, with the newest results from MESSENGER's low altitude campaign, carbon is another potential light element that could be incorporated into Mercury's core. The goal of this study is to determine the carbon concentration at graphite saturation in various silicon-iron bearing metals relevant to possible mercurian core compositions. Future experiments will include the addition of sulfur into these metals.

Arsenic and lead distribution and mobility in lake sediments in the south-central Puget Sound watershed: the long-term impact of a metal smelter in Ruston, Washington, USA.

PubMed

Gawel, James E; Asplund, Jessica A; Burdick, Sarah; Miller, Michelle; Peterson, Shawna M; Tollefson, Amanda; Ziegler, Kara

2014-02-15

The American Smelting and Refining Company (ASARCO) smelter in Ruston, Washington, contaminated the south-central Puget Sound region with heavy metals, including arsenic and lead. Arsenic and lead distribution in surface sediments of 26 lakes is significantly correlated with atmospheric model predictions of contaminant deposition spatially, with concentrations reaching 208 mg/kg As and 1,375 mg/kg Pb. The temporal distribution of these metals in sediment cores is consistent with the years of operation of the ASARCO smelter. In several lakes arsenic and lead levels are highest at the surface, suggesting ongoing inputs or redistribution of contaminants. Moreover, this study finds that arsenic is highly mobile in these urban lakes, with maximum dissolved arsenic concentrations proportional to surface sediment levels and reaching almost 90 μg/L As. With 83% of the lakes in the deposition zone having surface sediments exceeding published "probable effects concentrations" for arsenic and lead, this study provides evidence for possible ongoing environmental health concerns. Copyright © 2013 Elsevier B.V. All rights reserved.

Pulse plating of Pt on n-GaAs ( 1 0 0 ) wafer surfaces: Synchrotron induced photoelectron spectroscopy and XPS of wet fabrication processes

NASA Astrophysics Data System (ADS)

Ensling, D.; Hunger, R.; Kraft, D.; Mayer, Th.; Jaegermann, W.; Rodriguez-Girones, M.; Ichizli, V.; Hartnagel, H. L.

2003-01-01

Preparation steps of Pt/n-GaAs Schottky contacts as applied in the fabrication process of varactor diode arrays for THz applications are analysed by photoelectron spectroscopy. Pulsed cathodic deposition of Pt onto GaAs (1 0 0) wafer surfaces from acidic solution has been studied by core level photoelectron spectroscopy using different excitation energies. A laboratory AlKα source as well as synchrotron radiation of hν=130 and 645 eV at BESSY was used. Chemical analyses and semiquantitative estimates of layer thickness are given for the natural oxide of an untreated wafer surface, a surface conditioning NH 3 etching step, and stepwise pulse plating of Pt. The structural arrangement of the detected species and interface potentials are considered.

Design of Aerosol Particle Coating: Thickness, Texture and Efficiency

PubMed Central

Buesser, B.; Pratsinis, S.E.

2013-01-01

Core-shell particles preserve the performance (e.g. magnetic, plasmonic or opacifying) of a core material while modifying its surface with a shell that facilitates (e.g. by blocking its reactivity) their incorporation into a host liquid or polymer matrix. Here coating of titania (core) aerosol particles with thin silica shells (films or layers) is investigated at non-isothermal conditions by a trimodal aerosol dynamics model, accounting for SiO2 generation by gas phase and surface oxidation of hexamethyldisiloxane (HMDSO) vapor, coagulation and sintering. After TiO2 particles have reached their final primary particle size (e.g. upon completion of sintering during their flame synthesis), coating starts by uniformly mixing them with HMDSO vapor that is oxidized either in the gas phase or on the particles’ surface resulting in SiO2 aerosols or deposits, respectively. Sintering of SiO2 deposited onto the core TiO2 particles takes place transforming rough into smooth coating shells depending on process conditions. The core-shell characteristics (thickness, texture and efficiency) are calculated for two limiting cases of coating shells: perfectly smooth (e.g. hermetic) and fractal-like. At constant TiO2 core particle production rate, the influence of coating weight fraction, surface oxidation and core particle size on coating shell characteristics is investigated and compared to pertinent experimental data through coating diagrams. With an optimal temperature profile for complete precursor conversion, the TiO2 aerosol and SiO2-precursor (HMDSO) vapor concentrations have the strongest influence on product coating shell characteristics. PMID:23729833

Surface functionalization of magnetite nanoparticle: A new approach using condensation of alkoxysilanes

NASA Astrophysics Data System (ADS)

Rodriguez, A. F. R.; Costa, T. P.; Bini, R. A.; Faria, F. S. E. D. V.; Azevedo, R. B.; Jafelicci, M.; Coaquira, J. A. H.; Martínez, M. A. R.; Mantilla, J. C.; Marques, R. F. C.; Morais, P. C.

2017-09-01

In this study we report on successful production of two samples (BR15 and BR16) comprising magnetite (Fe3O4) nanoparticles ( 10 nm) surface-functionalized via hydrolysis and condensation of alkoxysilane agents, namely 3-aminopropyl-trimethoxisilane (APTS) and N-propyl-trimethoxisilane (NPTS). The as-produced samples were characterized using transmission electron microscopy (TEM), x-ray diffraction (XRD), magnetization measurements (5 K and 300 K hysteresis cycles and zero field-cooled/field-cooled measurements), and Mössbauer spectroscopy (77 and 297 K). The Mössbauer data supported the model picture of a core-shell magnetite-based system. This material system shows shell properties influenced by the surface-coating design, either APTS-coated (BR15) or APTS+NPTS-coated (sample BR16). Analyses of the Mössbauer spectra indicates that the APTS-coated sample presents Fe(III)-rich core and Fe(II)-rich shell with strong hyperfine field; whereas, the APTS+NPTS-coated sample leads to a mixture of two main nanostructures, one essentially surface-terminated with APTS whereas the other surface-terminated with NPTS, both presenting weak hyperfine fields compared with the single surface-coated sample. Magnetization measurements support the core-shell picture built from the analyses of the Mössbauer data. Our findings emphasize the capability of the Mössbauer spectroscopy in assessing subtle differences in surface-functionalized iron-based core-shell nanostructures.

Internal structure of normal maize starch granules revealed by chemical surface gelatinization.

PubMed

Pan, D D; Jane, J I

2000-01-01

Normal maize starch was fractionated into two sizes: large granules with diameters more than 5 microns and small granules with diameters less than 5 microns. The large granules were surface gelatinized by treating them with an aqueous LiCl solution (13 M) at 22-23 degrees C. Surface-gelatinized remaining granules were obtained by mechanical blending, and gelatinized surface starch was obtained by grinding with a mortar and a pestle. Starches of different granular sizes and radial locations, obtained after different degrees of surface gelatinization, were subjected to scanning electron microscopy, iodine potentiometric titration, gel-permeation chromatography, and amylopectin branch chain length analysis. Results showed that the remaining granules had a rough surface with a lamella structure. Amylose was more concentrated at the periphery than at the core of the granule. Amylopectin had longer long B-chains at the core than at the periphery of the granule. Greater proportions of the long B-chains were present at the core than at the periphery of the granule.

Climate dependent contrast in surface mass balance in East Antarctica over the past 216 kyr

NASA Astrophysics Data System (ADS)

Parrenin, Frédéric; Fujita, Shuji; Abe-Ouchi, Ayako; Kawamura, Kenji; Masson-Delmotte, Valérie; Motoyama, Hideaki; Saito, Fuyuki; Severi, Mirko; Stenni, Barbara; Uemura, Ryu; Wolff, Eric

2016-04-01

Documenting past changes in the East Antarctic surface mass balance is important to improve ice core chronologies and to constrain the ice sheet contribution to global mean sea level change. Here we reconstruct the past changes in the ratio of surface mass balance (SMB ratio) between the EPICA Dome C (EDC) and Dome Fuji (DF) East Antarctica ice core sites, based on a precise volcanic synchronisation of the two ice cores and on corrections for the vertical thinning of layers. During the past 216,000 years, this SMB ratio, denoted SMB_EDC/SMB_DF, varied between 0.7 and 1.1, being small during cold periods and large during warm periods. While past climatic changes have been depicted as homogeneous along the East Antarctic Plateau, our results reveal larger amplitudes of changes in SMB at EDC compared to DF, consistent with previous results showing larger amplitudes of changes in water stable isotopes and estimated surface temperature at EDC compared to DF. Within the last glacial inception (Marine Isotope Stages, MIS-5c and MIS-5d), the SMB ratio deviates by up to 20% from what is expected based on differences in water stable isotope records. Moreover, the SMB ratio is constant throughout the late parts of the current and last interglacial periods, despite contrasting isotopic trends. These SMB ratio changes not reflected in the isotope profiles are one of the possible causes of the observed differences between the ice core chronologies at DF and EDC. Such changes in SMB ratio may have been caused by (i) climatic processes related to changes in air mass trajectories and local climate, (ii) glaciological processes associated with relative elevation changes, or (iii) a combination of climatic and glaciological processes, such as the interaction between changes in accumulation and in the position of the domes. Our inferred SMB ratio history has important implications for ice sheet modeling (for which SMB is a boundary condition) or atmospheric modeling (our inferred SMB ratio could serve as a test).

Climate dependent contrast in surface mass balance in East Antarctica over the past 216 kyr

NASA Astrophysics Data System (ADS)

Parrenin, F.; Fujita, S.; Abe-Ouchi, A.; Kawamura, K.; Masson-Delmotte, V.; Motoyama, H.; Saito, F.; Severi, M.; Stenni, B.; Uemura, R.; Wolff, E.

2015-02-01

Documenting past changes in the East Antarctic surface mass balance is important to improve ice core chronologies and to constrain the ice sheet contribution to global mean sea level. Here we reconstruct the past changes in the ratio of surface mass balance (SMB ratio) between the EPICA Dome C (EDC) and Dome Fuji (DF) East Antarctica ice core sites, based on a precise volcanic synchronisation of the two ice cores and on corrections for the vertical thinning of layers. During the past 216 000 years, this SMB ratio, denoted SMBEDC/SMBDF, varied between 0.7 and 1.1, decreasing during cold periods and increasing during warm periods. While past climatic changes have been depicted as homogeneous along the East Antarctic Plateau, our results reveal larger amplitudes of changes in SMB at EDC compared to DF, consistent with previous results showing larger amplitudes of changes in water stable isotopes and estimated surface temperature at EDC compared to DF. Within interglacial periods and during the last glacial inception (Marine Isotope Stages, MIS-5c and MIS-5d), the SMB ratio deviates by up to 30% from what is expected based on differences in water stable isotope records. Moreover, the SMB ratio is constant throughout the late parts of the current and last interglacial periods, despite contrasting isotopic trends. These SMB ratio changes not closely related to isotopic changes are one of the possible causes of the observed gaps between the ice core chronologies at DF and EDC. Such changes in SMB ratio may have been caused by (i) climatic processes related to changes in air mass trajectories and local climate, (ii) glaciological processes associated with relative elevation changes, or (iii) a combination of climatic and glaciological processes, such as the interaction between changes in accumulation and in the position of the domes. Our inferred SMB ratio history has important implications for ice sheet modeling (for which SMB is a boundary condition) or atmospheric modeling (our inferred SMB ratio could serve as a test).

Depositional and surface exposure history of the Shorty Crater core 74001/2 - FMR and magnetic studies

NASA Technical Reports Server (NTRS)

Morris, R. V.; Gose, W. A.; Lauer, H. V., Jr.

1978-01-01

Surface exposure (maturity) indices and concentrations of FeO and metallic iron were determined at 0.5-cm intervals of the Apollo 17 core section, which sampled a pyroclastic deposit on the rim of Shorty Crater. The determinations showed that all of the soil in the core is extremely immature. An exposure history of the core is proposed: accumulation (about 3.6 billion years ago), shallow burial (during the first 20 million years), deep burial (till about 10-15 million years ago), followed by excavation (10-15 million years ago), and in situ reworking (till the present).

Surface Plasmon Scattering in Exposed Core Optical Fiber for Enhanced Resolution Refractive Index Sensing.

PubMed

Klantsataya, Elizaveta; François, Alexandre; Ebendorff-Heidepriem, Heike; Hoffmann, Peter; Monro, Tanya M

2015-09-29

Refractometric sensors based on optical excitation of surface plasmons on the side of an optical fiber is an established sensing architecture that has enabled laboratory demonstrations of cost effective portable devices for biological and chemical applications. Here we report a Surface Plasmon Resonance (SPR) configuration realized in an Exposed Core Microstructured Optical Fiber (ECF) capable of optimizing both sensitivity and resolution. To the best of our knowledge, this is the first demonstration of fabrication of a rough metal coating suitable for spectral interrogation of scattered plasmonic wave using chemical electroless plating technique on a 10 μm diameter exposed core of the ECF. Performance of the sensor in terms of its refractive index sensitivity and full width at half maximum (FWHM) of SPR response is compared to that achieved with an unstructured bare core fiber with 140 μm core diameter. The experimental improvement in FWHM, and therefore the detection limit, is found to be a factor of two (75 nm for ECF in comparison to 150 nm for the large core fiber). Refractive index sensitivity of 1800 nm/RIU was achieved for both fibers in the sensing range of aqueous environment (1.33-1.37) suitable for biosensing applications.

Why are enteric ganglia so small? Role of differential adhesion of enteric neurons and enteric neural crest cells.

PubMed Central

Rollo, Benjamin N.; Zhang, Dongcheng; Simkin, Johanna E.; Menheniott, Trevelyan R.; Newgreen, Donald F.

2015-01-01

The avian enteric nervous system (ENS) consists of a vast number of unusually small ganglia compared to other peripheral ganglia. Each ENS ganglion at mid-gestation has a core of neurons and a shell of mesenchymal precursor/glia-like enteric neural crest (ENC) cells. To study ENS cell ganglionation we isolated midgut ENS cells by HNK-1 fluorescence-activated cell sorting (FACS) from E5 and E8 quail embryos, and from E9 chick embryos. We performed cell-cell aggregation assays which revealed a developmentally regulated functional increase in ENS cell adhesive function, requiring both Ca 2+ -dependent and independent adhesion. This was consistent with N-cadherin and NCAM labelling. Neurons sorted to the core of aggregates, surrounded by outer ENC cells, showing that neurons had higher adhesion than ENC cells. The outer surface of aggregates became relatively non-adhesive, correlating with low levels of NCAM and N-cadherin on this surface of the outer non-neuronal ENC cells. Aggregation assays showed that ENS cells FACS selected for NCAM-high and enriched for enteric neurons formed larger and more coherent aggregates than unsorted ENS cells. In contrast, ENS cells of the NCAM-low FACS fraction formed small, disorganised aggregates.  This suggests a novel mechanism for control of ENS ganglion morphogenesis where i) differential adhesion of ENS neurons and ENC cells controls the core/shell ganglionic structure and ii) the ratio of neurons to ENC cells dictates the equilibrium ganglion size by generation of an outer non-adhesive surface. PMID:26064478

Effect of surface treatments on the bond strength of CAD/CAM fiberglass posts.

PubMed

Garcia, Paula-Pontes; da Costa, Rogério-Goulart; Garcia, André-Vivan; Gonzaga, Carla-Castiglia; da Cunha, Leonardo-Fernandes; Rezende, Carlos-Eduardo-Edwards; Correr, Gisele-Maria

2018-06-01

There is no ideal protocol for the surface treatment of fiber posts, especially when using a computer-aided design/computer-aided manufacturing (CAD/CAM) experimental fiberglass block. The purpose of this study was to evaluate the bond strength of a CAD/CAM customized glass fiber post and core after applying different surface treatment techniques. Forty premolars were prepared to receive a customized CAD/CAM glass-fiber post and core obtained from an experimental block of glass fiber and epoxy resin. The specimens were randomly distributed in 4 groups (n=10) according to the post and core surface treatment: ETH - 70% ethanol; HP - 24% hydrogen peroxide for 1 minute; ETH/S - 70% ethanol + silane; HP/S - 24% hydrogen peroxide + silane. The universal adhesive containing silane was applied on the posts and prepared post spaces in all groups. The posts were cemented using dual cure resin cement. The specimens were stored in distilled water at 37°C for 24 h, cut (two slices of 1 mm for each root third - coronal, middle, and apical) and subjected to push-out test (0.5 mm/min). Data was subjected to two-way ANOVA (surface treatment and root third) and Tukey's test (α=0,05). There was no significant difference of bond strength values among groups, regardless the surface treatment ( p >0.05). There was significant difference on bond strength values for the different root thirds ( p <0.05) (coronal>middle=apical). The different surface treatment and application of additional silane in the CAD/CAM customized glass-fiber post and core does not interfere on bond strength values. The root dentin third interfered on the bond strength, with higher values for the coronal third. Key words: Post and core technique, cad/cam, shear strength, hydrogen peroxide.

To evaluate and compare the effect of different Post Surface treatments on the Tensile Bond Strength between Fiber Posts and Composite Resin.

PubMed

Shori, Deepa; Pandey, Swapnil; Kubde, Rajesh; Rathod, Yogesh; Atara, Rahul; Rathi, Shravan

2013-10-01

Fiber posts are widely used for restoration of mutilated teeth that lack adequate coronal tooth structure to retain a core for definitive restoration, bond between the fiber post and composite material depends upon the chemical reaction between the post surface and the resin material used for building up the core. In attempt to maximize the resin bonding with fiber post, different post surface conditioning is advocated. Therefore the purpose of the study is to examine the interfacial strength between fiber post and composite, as core build-up material after different surface treatments of fiber posts. Twenty fiber posts were split into four groups off five each according to different surface treatments viz. Group I-(Negative Control), Group II-Silanization (Positive control), Group III-(37% Phosphoric Acid & Silanization) ,Group IV- (10% Hydrogen Peroxide and Silanization). With the preformed plastic mould, a core of dual cure composite resin around the fiber post having the uniform thickness was created. Tensile bond strength of each specimen was measured under Universal Testing Machine (UTM) at the cross head speed of 3mm/min. The results achieved with 10% Hydrogen peroxide had a marked effect on micro tensile bond strength values between the tested materials. Immense enhancement in the silanization efficiency of quartz fiber phase was observed with different surface chemical treatment of the resin phase of fiber posts with the marked increase in the micro-tensile bond strength between fiber post and composite core. Shori D, Pandey S, Kubde R, Rathod Y, Atara R, Rathi S. To evaluate and compare the effect of different Post Surface treatments on the Tensile Bond Strength between Fiber Posts and Composite Resin. J Int Oral Health 2013; 5(5):27-32.

Photoresponse and Field Effect Transport Studies in InAsP-InP Core-Shell Nanowires

NASA Astrophysics Data System (ADS)

Lee, Rochelle; Jo, Min Hyeok; Kim, TaeWan; Kim, Hyo Jin; Kim, Doo Gun; Shin, Jae Cheol

2018-05-01

A ternary InAsyP1-y alloy is suitable for an application to near-infrared (NIR) optical devices as their direct bandgap energy covers the entire NIR band. A nanowire (NW) system allows an epitaxial integration of InAsyP1-y alloy on any type of substrate since the lattice mismatch strain can be relieved through the NW sidewall. Nevertheless, the very large surface to volume ratio feature of the NWs leads to enormous surface states which are susceptible to surface recombination of free carriers. Here, ternary InAs0.75P0.25 NWs are grown with InP passivation layer (i.e., core-shell structure) to minimize the influence of the surface states, thus increasing their optical and electrical properties. A photoresponse study was achieved through the modeled band structure of the grown NWs. The model and experimental results suggest that 5-nm-thick InP shell efficiently passivates the surface states of the InAs0.75P0.25 NWs. The fabricated core-shell photodetectors and field-effect transistors exhibit improved photoresponse and transport properties compared to its counterpart core-only structure.

Photoresponse and Field Effect Transport Studies in InAsP-InP Core-Shell Nanowires

NASA Astrophysics Data System (ADS)

Lee, Rochelle; Jo, Min Hyeok; Kim, TaeWan; Kim, Hyo Jin; Kim, Doo Gun; Shin, Jae Cheol

2018-03-01

A ternary InAsyP1-y alloy is suitable for an application to near-infrared (NIR) optical devices as their direct bandgap energy covers the entire NIR band. A nanowire (NW) system allows an epitaxial integration of InAsyP1-y alloy on any type of substrate since the lattice mismatch strain can be relieved through the NW sidewall. Nevertheless, the very large surface to volume ratio feature of the NWs leads to enormous surface states which are susceptible to surface recombination of free carriers. Here, ternary InAs0.75P0.25 NWs are grown with InP passivation layer (i.e., core-shell structure) to minimize the influence of the surface states, thus increasing their optical and electrical properties. A photoresponse study was achieved through the modeled band structure of the grown NWs. The model and experimental results suggest that 5-nm-thick InP shell efficiently passivates the surface states of the InAs0.75P0.25 NWs. The fabricated core-shell photodetectors and field-effect transistors exhibit improved photoresponse and transport properties compared to its counterpart core-only structure.

Mercury accumulation and attenuation at a rapidly forming delta with a point source of mining waste

PubMed Central

Johnson, Bryce E.; Esser, Bradley K.; Whyte, Dyan C.; Ganguli, Priya M.; Austin, Carrie M.; Hunt, James R.

2009-01-01

The Walker Creek intertidal delta of Tomales Bay, California is impacted by a former mercury mine within the watershed. Eleven short sediment cores (10 cm length) collected from the delta found monomethylmercury (MMHg) concentrations ranging from 0.3 to 11.4 ng/g (dry wt.), with lower concentrations occurring at the vegetated marsh and upstream channel locations. Algal mats common to the delta’s sediment surface had MMHg concentrations ranging from 7.5 to 31.5 ng/g, and the top 1 cm of sediment directly under the mats had two times greater MMHg concentrations compared to adjacent locations without algal covering. Spatial trends in resident biota reflect enhanced MMHg uptake at the delta compared to other bay locations. Eighteen sediment cores, 1 to 2 meters deep, collected from the 1.2 km2 delta provide an estimate of a total mercury (Hg) inventory of 2500 ± 500 kg. Sediment Hg concentrations ranged from pre-mining background conditions of approximately 0.1 μg/g to a post-mining maximum of 5 μg/g. Sediment accumulation rates were determined from three sediment cores using measured differences of 137Cs activity. We estimate a pre-mining Hg accumulation of less than 20 kg/yr, and a period of maximum Hg accumulation in the 1970s and 1980s with loading rates greater than 50 kg/yr, corresponding to the failure of a tailings dam at the mine site. At the time of sampling (2003) over 40 kg/yr of Hg was still accumulating at the delta, indicating limited recovery. We attribute observed spatial evolution of elevated Hg levels to ongoing inputs and sediment re-working, and estimate the inventory of the anthropogenic fraction of total Hg to be at least 1500 ± 300 kg. We suggest ongoing sediment inputs and methylation at the deltaic surface support enhanced mercury levels for resident biota and transfer to higher trophic levels throughout the Bay. PMID:19539980

A highly accurate ab initio potential energy surface for methane.

PubMed

Owens, Alec; Yurchenko, Sergei N; Yachmenev, Andrey; Tennyson, Jonathan; Thiel, Walter

2016-09-14

A new nine-dimensional potential energy surface (PES) for methane has been generated using state-of-the-art ab initio theory. The PES is based on explicitly correlated coupled cluster calculations with extrapolation to the complete basis set limit and incorporates a range of higher-level additive energy corrections. These include core-valence electron correlation, higher-order coupled cluster terms beyond perturbative triples, scalar relativistic effects, and the diagonal Born-Oppenheimer correction. Sub-wavenumber accuracy is achieved for the majority of experimentally known vibrational energy levels with the four fundamentals of (12)CH4 reproduced with a root-mean-square error of 0.70 cm(-1). The computed ab initio equilibrium C-H bond length is in excellent agreement with previous values despite pure rotational energies displaying minor systematic errors as J (rotational excitation) increases. It is shown that these errors can be significantly reduced by adjusting the equilibrium geometry. The PES represents the most accurate ab initio surface to date and will serve as a good starting point for empirical refinement.

Surface electronic properties of polycrystalline bulk and thin film In2O3(ZnO)k compounds

NASA Astrophysics Data System (ADS)

Hopper, E. Mitchell; Zhu, Qimin; Gassmann, Jürgen; Klein, Andreas; Mason, Thomas O.

2013-01-01

The surface electronic potentials of In2O3(ZnO)k compounds were measured by X-ray and ultraviolet photoelectron spectroscopy. Both thin film (k = 2) and bulk specimens (k = 3, 5, 7, 9) were studied. All bulk specimens exhibited In enrichment at the surface. All samples showed an increase of In core level binding energies compared to pure and Sn-doped In2O3. The work functions and Fermi levels spanned a range similar to those of the basis oxides In2O3 and ZnO, and the ionization potential was similar to that of both In2O3 and ZnO processed under similar conditions (7.7 eV). This ionization potential was independent of both composition and post-deposition oxidation and reduction treatments. Kelvin probe measurements of cleaned and UV-ozone treated specimens under ambient conditions were in agreement with the photoelectron spectroscopy measurements.

The performance of cable braids and terminations to lightning induced transients

NASA Technical Reports Server (NTRS)

Crofts, David

1991-01-01

The latest specification detailing the test waveforms for indirect lightning transients as applied to aircraft wiring systems specify very high voltages and currents. Although considerable data exists for measuring cable screen leakage using such methods as surface transfer impedance and bulk cable injection, there is little data on the likely core transient level that is likely to be induced from these threats. In particular, the new Waveform 5 at very high current levels (10 kA) is reputed to cause severe cable damage. A range of representative cables were made with various screen termination techniques and screening levels. These were tested first to determine their relative screening performance and then they were subjected to lightning transient testing to all the specified waveforms. Core voltages were measured for each test. Tests were also performed on bundles with fewer wires to determine the failure criteria with Waveform 5 and these tests also include flat conductor cables. The test showed that correctly terminated cable bundles performed well in all the tests and would provide a high level of protection to the electronic systems. The use of overbraides, provided the individual screens are well terminated, appears to be unnecessary.

Greater sage-grouse population trends across Wyoming

USGS Publications Warehouse

Edmunds, David; Aldridge, Cameron L.; O'Donnell, Michael; Monroe, Adrian

2018-01-01

The scale at which analyses are performed can have an effect on model results and often one scale does not accurately describe the ecological phenomena of interest (e.g., population trends) for wide-ranging species: yet, most ecological studies are performed at a single, arbitrary scale. To best determine local and regional trends for greater sage-grouse (Centrocercus urophasianus) in Wyoming, USA, we modeled density-independent and -dependent population growth across multiple spatial scales relevant to management and conservation (Core Areas [habitat encompassing approximately 83% of the sage-grouse population on ∼24% of surface area in Wyoming], local Working Groups [7 regional areas for which groups of local experts are tasked with implementing Wyoming's statewide sage-grouse conservation plan at the local level], Core Area status (Core Area vs. Non-Core Area) by Working Groups, and Core Areas by Working Groups). Our goal was to determine the influence of fine-scale population trends (Core Areas) on larger-scale populations (Working Group Areas). We modeled the natural log of change in population size ( peak M lek counts) by time to calculate the finite rate of population growth (λ) for each population of interest from 1993 to 2015. We found that in general when Core Area status (Core Area vs. Non-Core Area) was investigated by Working Group Area, the 2 populations trended similarly and agreed with the overall trend of the Working Group Area. However, at the finer scale where Core Areas were analyzed separately, Core Areas within the same Working Group Area often trended differently and a few large Core Areas could influence the overall Working Group Area trend and mask trends occurring in smaller Core Areas. Relatively close fine-scale populations of sage-grouse can trend differently, indicating that large-scale trends may not accurately depict what is occurring across the landscape (e.g., local effects of gas and oil fields may be masked by increasing larger populations). 

Encapsulation of superparamagnetic Fe 3 O 4 @SiO 2 core/shell nanoparticles in MnO 2 microflowers with high surface areas

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

Sun, Yu-Gang; Truong, Tu T.; Liu, Yu-Zi

2015-02-01

Microflowers made of interconnected MnO2 nanosheets have been successfully synthesized in a microwave reactor through a hydrothermal reduction of KMnO4 with aqueous HCl at elevated temperatures in the presence of superparamagnetic Fe3O4@SiO2 core-shell nanoparticles. Due to the chemical compatibility between SiO2 and MnO2, the heterogeneous reaction leads to the spontaneous encapsulation of the Fe3O4@SiO2 core-shell nanoparticles in the MnO2 microflowers. The resulting hybrid particles exhibit multiple properties including high surface area associated with the MnO2 nanosheets and superparamagnetism originated from the Fe3O4@SiO2 core-shell nanoparticles, which are beneficial for applications requiring both high surface area and magnetic separation. (C) 2014 Yu-Gangmore » Sun.« less

Electromyographic response of global abdominal stabilizers in response to stable- and unstable-base isometric exercise.

PubMed

Atkins, Stephen J; Bentley, Ian; Brooks, Darrell; Burrows, Mark P; Hurst, Howard T; Sinclair, Jonathan K

2015-06-01

Core stability training traditionally uses stable-base techniques. Less is known as to the use of unstable-base techniques, such as suspension training, to activate core musculature. This study sought to assess the neuromuscular activation of global core stabilizers when using suspension training techniques, compared with more traditional forms of isometric exercise. Eighteen elite level, male youth swimmers (age, 15.5 ± 2.3 years; stature, 163.3 ± 12.7 cm; body mass, 62.2 ± 11.9 kg) participated in this study. Surface electromyography (sEMG) was used to determine the rate of muscle contraction in postural musculature, associated with core stability and torso bracing (rectus abdominus [RA], external obliques [EO], erector spinae [ES]). A maximal voluntary contraction test was used to determine peak amplitude for all muscles. Static bracing of the core was achieved using a modified "plank" position, with and without a Swiss ball, and held for 30 seconds. A mechanically similar "plank" was then held using suspension straps. Analysis of sEMG revealed that suspension produced higher peak amplitude in the RA than using a prone or Swiss ball "plank" (p = 0.04). This difference was not replicated in either the EO or ES musculature. We conclude that suspension training noticeably improves engagement of anterior core musculature when compared with both lateral and posterior muscles. Further research is required to determine how best to activate both posterior and lateral musculature when using all forms of core stability training.

Semiquantitative analysis of gaps in microbiological performance of fish processing sector implementing current food safety management systems: a case study.

PubMed

Onjong, Hillary Adawo; Wangoh, John; Njage, Patrick Murigu Kamau

2014-08-01

Fish processing plants still face microbial food safety-related product rejections and the associated economic losses, although they implement legislation, with well-established quality assurance guidelines and standards. We assessed the microbial performance of core control and assurance activities of fish exporting processors to offer suggestions for improvement using a case study. A microbiological assessment scheme was used to systematically analyze microbial counts in six selected critical sampling locations (CSLs). Nine small-, medium- and large-sized companies implementing current food safety management systems (FSMS) were studied. Samples were collected three times on each occasion (n = 324). Microbial indicators representing food safety, plant and personnel hygiene, and overall microbiological performance were analyzed. Microbiological distribution and safety profile levels for the CSLs were calculated. Performance of core control and assurance activities of the FSMS was also diagnosed using an FSMS diagnostic instrument. Final fish products from 67% of the companies were within the legally accepted microbiological limits. Salmonella was absent in all CSLs. Hands or gloves of workers from the majority of companies were highly contaminated with Staphylococcus aureus at levels above the recommended limits. Large-sized companies performed better in Enterobacteriaceae, Escherichia coli, and S. aureus than medium- and small-sized ones in a majority of the CSLs, including receipt of raw fish material, heading and gutting, and the condition of the fish processing tables and facilities before cleaning and sanitation. Fish products of 33% (3 of 9) of the companies and handling surfaces of 22% (2 of 9) of the companies showed high variability in Enterobacteriaceae counts. High variability in total viable counts and Enterobacteriaceae was noted on fish products and handling surfaces. Specific recommendations were made in core control and assurance activities associated with sampling locations showing poor performance.

Sulfur Earth

NASA Astrophysics Data System (ADS)

de Jong, B. H.

2007-12-01

Variations in surface tension affect the buoyancy of objects floating in a liquid. Thus an object floating in water will sink deeper in the presence of dishwater fluid. This is a very minor but measurable effect. It causes for instance ducks to drown in aqueous solutions with added surfactant. The surface tension of liquid iron is very strongly affected by the presence of sulfur which acts as a surfactant in this system varying between 1.9 and 0.4 N/m at 10 mass percent Sulfur (Lee & Morita (2002), This last value is inferred to be the maximum value for Sulfur inferred to be present in the liquid outer core. Venting of Sulfur from the liquid core manifests itself on the Earth surface by the 105 to 106 ton of sulfur vented into the atmosphere annually (Wedepohl, 1984). Inspection of surface Sulfur emission indicates that venting is non-homogeneously distributed over the Earth's surface. The implication of such large variation in surface tension in the liquid outer core are that at locally low Sulfur concentration, the liquid outer core does not wet the predominantly MgSiO3 matrix with which it is in contact. However at a local high in Sulfur, the liquid outer core wets this matrix which in the fluid state has a surface tension of 0.4 N/m (Bansal & Doremus, 1986), couples with it, and causes it to sink. This differential and diapiric movement is transmitted through the essentially brittle mantle (1024 Pa.s, Lambeck & Johnson, 1998; the maximum value for ice being about 1030 Pa.s at 0 K, in all likely hood representing an upper bound of viscosity for all materials) and manifests itself on the surface by the roughly 20 km differentiation, about 0.1 % of the total mantle thickness, between topographical heights and lows with concomitant lateral movement in the crust and upper mantle resulting in thin skin tectonics. The brittle nature of the medium though which this movement is transmitted suggests that the extremes in topography of the D" layer are similar in range to those observed on the Earth's surface and are mimicked by lows under the oceans and highs under the altiplanos. Careful and area selective S wave core mantle ellipsometry might be able to discern these core-mantle topographic variations. As such this process demonstrates the validity of the Gaia hypothesis enunciated by Baas Becking(1931) that no ecological niche on our planet is closed off from other niches "nothing in the world is single".

Soft particles at fluid interfaces: wetting, structure, and rheology

NASA Astrophysics Data System (ADS)

Isa, Lucio

Most of our current knowledge concerning the behavior of colloidal particles at fluid interfaces is limited to model spherical, hard and uniform objects. Introducing additional complexity, in terms of shape, composition or surface chemistry or by introducing particle softness, opens up a vast range of possibilities to address new fundamental and applied questions in soft matter systems at fluid interfaces. In this talk I will focus on the role of particle softness, taking the case of core-shell microgels as a paradigmatic example. Microgels are highly swollen and cross-linked hydrogel particles that, in parallel with their practical applications, e.g. for emulsion stabilization and surface patterning, are increasingly used as model systems to capture fundamental properties of bulk materials. Most microgel particles develop a core-shell morphology during synthesis, with a more cross-linked core surrounded by a corona of loosely linked and dangling polymer chains. I will first discuss the difference between the wetting of a hard spherical colloid and a core-shell microgel at an oil-water interface, pinpointing the interplay between adsorption at the interface and particle deformation. I will then move on to discuss the interplay between particle morphology and the microstructure and rheological properties of the interface. In particular, I will demonstrate that synchronizing the compression of a core-shell microgel-laden fluid interface with the deposition of the interfacial monolayer makes it possible to transfer the 2D phase diagram of the particles onto a solid substrate, where different positions correspond to different values of the surface pressure and the specific area. Using atomic force microscopy, we analyzed the microstructure of the monolayer and discovered a phase transition between two crystalline phases with the same hexagonal symmetry, but with two different lattice constants. The two phases correspond to shell-shell or core-core inter-particle contacts, respectively, where with increasing surface pressure the former mechanically fail enabling the particle cores to come into contact. In the phase-transition region, clusters of particles in core-core contacts nucleate, melting the surrounding shell-shell crystal, until the whole monolayer moves into the second phase. We furthermore extended our analysis to measure the interfacial rheology of the monolayers as a function of the surface pressure using an interfacial microdisk rheometer; the interfaces always show a strong elastic response, with a dip in the elastic modulus in correspondence of the melting of the shell-shell phase, followed by a steep increase upon formation of a percolating network of the core-core contacts. The presented results highlight the complex interplay between the wetting and deformation of individual soft particles at fluid interfaces and the overall interface microstructure and mechanics. They show strong connections to fundamental studies on phase transitions in two-dimensional systems and pave the way for novel nanoscale surface patterning routes. The author acknowledges financial support from the Swiss National Science Foundation Grant PP00P2-144646/1.

Sentinel-3 For Land Applications

NASA Astrophysics Data System (ADS)

Goryl, Philippe; Gobron, Nadine; Mecklenburg, Susanne; Donlon, Craig; Bouvet, Marc; Buongiorno, Alessandra; Wilson, Hilary

2016-07-01

The Copernicus Programme, being Europe's Earth Observation and Monitoring Programme led by the European Union, aims to provide, on a sustainable basis, reliable and timely services related to environmental and security issues. The Sentinel-3 mission forms part of the Copernicus Space Component. Its main objectives, building on the heritage and experience of the European Space Agency's (ESA) ERS and ENVISAT missions, are to measure sea-surface topography, sea- and land-surface temperature and ocean- and land-surface colour in support of ocean forecasting systems, and for environmental and climate monitoring. The series of Sentinel-3 satellites will ensure global, frequent and near-real time ocean, ice and land monitoring, with the provision of observation data in a routine, long-term (up to 20 years of operations) and continuous fashion, with a consistent quality and a high level of reliability and availability. The launch of Sentinel-3 was successful last February 2016. The Sentinel-3 missions are jointly operated by ESA and EUMETSAT. ESA will be responsible for the operations, maintenance and evolution of the Sentinel-3 ground segment on land related products and EUMETSAT on the marine products and the satellite monitoring and control. All facilities supporting the Sentinel-3 operations are in place. The Sentinel-3 ground segment systematically acquires, processes and distributes a set of pre-defined core data products to the users. For a detailed description of the core data products please see https://earth.esa.int/web/sentinel/missions/sentinel-3/data-products. On request from the European Commission, ESA and EUMETSAT are presently assessing the possibility to include further core data products, in particular on aerosol optical depth, fire monitoring and synergistic products over land. This paper will provide an update on the status of the mission operations after the initial months in orbit and provide in particular an overview on the status of the Sentinel-3 core land products and their provision in the mission's ramp-up phase.

Glacial-interglacial dynamics of Antarctic firn columns: comparison between simulations and ice core air-δ15N measurements

NASA Astrophysics Data System (ADS)

Capron, E.; Landais, A.; Buiron, D.; Cauquoin, A.; Chappellaz, J.; Debret, M.; Jouzel, J.; Leuenberger, M.; Martinerie, P.; Masson-Delmotte, V.; Mulvaney, R.; Parrenin, F.; Prié, F.

2012-12-01

Correct estimate of the firn lock-in depth is essential for correctly linking gas and ice chronologies in ice cores studies. Here, two approaches to constrain the firn depth evolution in Antarctica are presented over the last deglaciation: output of a firn densification model and measurements of δ15N of N2 in air trapped in ice core. Since the firn densification process is largely governed by surface temperature and accumulation rate, we have investigated four ice cores drilled in coastal (Berkner Island, BI, and James Ross Island, JRI) and semi coastal (TALDICE and EPICA Dronning Maud Land, EDML) Antarctic regions. Combined with available δ15N measurements performed from the EPICA Dome C (EDC) site, the studied regions encompass a large range of surface accumulation rate and temperature conditions. While firn densification simulations are able to correctly represent most of the δ15N trends over the last deglaciation measured in the EDC, BI, TALDICE and EDML ice cores, they systematically fail to capture BI and EDML δ15N glacial levels, a mismatch previously seen for Central East Antarctic ice cores. Using empirical constraints of the EDML gas-ice depth offset during the Laschamp event (~ 41 ka), we can rule out the existence of a large convective zone as the explanation of the glacial firn model-δ15N data mismatch for this site. The good match between modelled and measured δ15N at TALDICE as well as the lack of any clear correlation between insoluble dust concentration in snow and δ15N records in the different ice cores suggest that past changes in loads of impurities are not the only main driver of glacial-interglacial changes in firn lock-in depth. We conclude that firn densification dynamics may instead be driven mostly by accumulation rate changes. The mismatch between modelled and measured δ15N may be due to inaccurate reconstruction of past accumulation rate or underestimated influence of accumulation rate in firnification models.

Hollow-core photonic-crystal fibres for laser dentistry.

PubMed

Konorov, Stanislav O; Mitrokhin, Vladimir P; Fedotov, Andrei B; Sidorov-Biryukov, Dmitrii A; Beloglazov, Valentin I; Skibina, Nina B; Wintner, Ernst; Scalora, Michael; Zheltikov, Aleksei M

2004-04-07

Hollow-core photonic-crystal fibres (PCFs) for the delivery of high-fluence laser radiation capable of ablating tooth enamel are developed. Sequences of picosecond pulses of 1.06 microm Nd:YAG-laser radiation with a total energy of about 2 mJ are transmitted through a hollow-core photonic-crystal fibre with a core diameter of approximately 14 microm and are focused on a tooth surface in vitro to ablate dental tissue. The hollow-core PCF is shown to support the single-fundamental-mode regime for 1.06 microm laser radiation, serving as a spatial filter and allowing the laser beam quality to be substantially improved. The same fibre is used to transmit emission from plasmas produced by laser pulses on the tooth surface in the backward direction for detection and optical diagnostics.

Interaction of sigma 70 with Escherichia coli RNA polymerase core enzyme studied by surface plasmon resonance.

PubMed

Ferguson, A L; Hughes, A D; Tufail, U; Baumann, C G; Scott, D J; Hoggett, J G

2000-09-22

The interaction between the core form of bacterial RNA polymerases and sigma factors is essential for specific promoter recognition, and for coordinating the expression of different sets of genes in response to varying cellular needs. The interaction between Escherichia coli core RNA polymerase and sigma 70 has been investigated by surface plasmon resonance. The His-tagged form of sigma 70 factor was immobilised on a Ni2+-NTA chip for monitoring its interaction with core polymerase. The binding constant for the interaction was found to be 1.9x10(-7) M, and the dissociation rate constant for release of sigma from core, in the absence of DNA or transcription, was 4x10(-3) s(-1), corresponding to a half-life of about 200 s.

Effect of core quantum-dot size on power-conversion-efficiency for silicon solar-cells implementing energy-down-shift using CdSe/ZnS core/shell quantum dots.

PubMed

Baek, Seung-Wook; Shim, Jae-Hyoung; Seung, Hyun-Min; Lee, Gon-Sub; Hong, Jin-Pyo; Lee, Kwang-Sup; Park, Jea-Gun

2014-11-07

Silicon solar cells mainly absorb visible light, although the sun emits ultraviolet (UV), visible, and infrared light. Because the surface reflectance of a textured surface with SiNX film on a silicon solar cell in the UV wavelength region (250-450 nm) is higher than ∼27%, silicon solar-cells cannot effectively convert UV light into photo-voltaic power. We implemented the concept of energy-down-shift using CdSe/ZnS core/shell quantum-dots (QDs) on p-type silicon solar-cells to absorb more UV light. CdSe/ZnS core/shell QDs demonstrated clear evidence of energy-down-shift, which absorbed UV light and emitted green-light photoluminescence signals at a wavelength of 542 nm. The implementation of 0.2 wt% (8.8 nm QDs layer) green-light emitting CdSe/ZnS core/shell QDs reduced the surface reflectance of the textured surface with SiNX film on a silicon solar-cell from 27% to 15% and enhanced the external quantum efficiency (EQE) of silicon solar-cells to around 30% in the UV wavelength region, thereby enhancing the power conversion efficiency (PCE) for p-type silicon solar-cells by 5.5%.

Does core mobility of lumbar total disc arthroplasty influence sagittal and frontal intervertebral displacement? Radiologic comparison with fixed-core prosthesis

PubMed Central

Delécrin, Joël; Allain, Jérôme; Beaurain, Jacques; Steib, Jean-Paul; Chataigner, Hervé; Aubourg, Lucie; Huppert, Jean; Ameil, Marc; Nguyen, Jean-Michel

2009-01-01

Background An artificial disc prosthesis is thought to restore segmental motion in the lumbar spine. However, it is reported that disc prosthesis can increase the intervertebral translation (VT). The concept of the mobile-core prosthesis is to mimic the kinematic effects of the migration of the natural nucleus and therefore core mobility should minimize the VT. This study explored the hypothesis that core translation should influence VT and that a mobile core prosthesis may facilitate physiological motion. Methods Vertebral translation (measured with a new method presented here), core translation, range of motion (ROM), and distribution of flexion-extension were measured on flexion-extension, neutral standing, and lateral bending films in 89 patients (63 mobile-core [M]; 33 fixed-core [F]). Results At L4-5 levels the VT with M was lower than with F and similar to the VT of untreated levels. At L5-S1 levels the VT with M was lower than with F but was significantly different compared to untreated levels. At M levels a strong correlation was found between VT and core translation; the VT decreases as the core translation increases. At F levels the VT increases as the ROM increases. No significant difference was found between the ROM of untreated levels and levels implanted with either M or F. Regarding the mobility distribution with M and F we observed a deficit in extension at L5-S1 levels and a similar distribution at L4-5 levels compared to untreated levels. Conclusion The intervertebral mobility was different between M and F. The M at L4-5 levels succeeded to replicate mobility similar to L4-5 untreated levels. The M at L5-S1 succeeded in ROM, but failed regarding VT and mobility distribution. Nevertheless M minimized VT at L5-S1 levels. The F increased VT at both L4-5 and L5-S1. Clinical Relevance This study validates the concept that the core translation of an artificial lumbar disc prosthesis minimizes the VT. PMID:25802632

Updated procedures for using drill cores and cuttings at the Lithologic Core Storage Library, Idaho National Laboratory, Idaho

USGS Publications Warehouse

Hodges, Mary K.V.; Davis, Linda C.; Bartholomay, Roy C.

2018-01-30

In 1990, the U.S. Geological Survey, in cooperation with the U.S. Department of Energy Idaho Operations Office, established the Lithologic Core Storage Library at the Idaho National Laboratory (INL). The facility was established to consolidate, catalog, and permanently store nonradioactive drill cores and cuttings from subsurface investigations conducted at the INL, and to provide a location for researchers to examine, sample, and test these materials.The facility is open by appointment to researchers for examination, sampling, and testing of cores and cuttings. This report describes the facility and cores and cuttings stored at the facility. Descriptions of cores and cuttings include the corehole names, corehole locations, and depth intervals available.Most cores and cuttings stored at the facility were drilled at or near the INL, on the eastern Snake River Plain; however, two cores drilled on the western Snake River Plain are stored for comparative studies. Basalt, rhyolite, sedimentary interbeds, and surficial sediments compose most cores and cuttings, most of which are continuous from land surface to their total depth. The deepest continuously drilled core stored at the facility was drilled to 5,000 feet below land surface. This report describes procedures and researchers' responsibilities for access to the facility and for examination, sampling, and return of materials.

Renewable Decyl-alcohol Templated Synthesis of Si-Cu Core-Shell Nanocomposite

NASA Astrophysics Data System (ADS)

Salim, M. A.; >H Misran, S. Z.; Shah, N. N. H.; Razak, N. A. A.; >A Manap,

2013-06-01

Monodispersed silica spheres with particles size of ca. 450 nm were successfully synthesized using a modified Stöber method. The synthesized monodispersed silica spheres were successfully coated with copper using modified sol-gel method employing nonsurfactant surface modifiers and catalyst. A renewable palm oil based decyl-alcohol (C10) as nonsurfactant surface modifiers and catalyst were used to modify the silica surfaces prior to coating with copper. The X-ray diffraction patterns of Si-Cu core-shell exhibited a broad peak corresponding to amorphous silica networks and monoclinic CuO phase. It was found that samples modified in the presence of 1 ml catalyst exhibited homogeneous deposition. The surface area of core materials (SiO2) was at ca. 7.04 m2/g and Si-Cu core-shell was at ca. 8.21 m2/g. The band gap of samples prepared with and without catalyst was calculated to be ca. 2.45 eV and ca. 3.90 eV respectively based on the UV-vis absorption spectrum of the product.

Application of Intel Many Integrated Core (MIC) accelerators to the Pleim-Xiu land surface scheme

NASA Astrophysics Data System (ADS)

Huang, Melin; Huang, Bormin; Huang, Allen H.

2015-10-01

The land-surface model (LSM) is one physics process in the weather research and forecast (WRF) model. The LSM includes atmospheric information from the surface layer scheme, radiative forcing from the radiation scheme, and precipitation forcing from the microphysics and convective schemes, together with internal information on the land's state variables and land-surface properties. The LSM is to provide heat and moisture fluxes over land points and sea-ice points. The Pleim-Xiu (PX) scheme is one LSM. The PX LSM features three pathways for moisture fluxes: evapotranspiration, soil evaporation, and evaporation from wet canopies. To accelerate the computation process of this scheme, we employ Intel Xeon Phi Many Integrated Core (MIC) Architecture as it is a multiprocessor computer structure with merits of efficient parallelization and vectorization essentials. Our results show that the MIC-based optimization of this scheme running on Xeon Phi coprocessor 7120P improves the performance by 2.3x and 11.7x as compared to the original code respectively running on one CPU socket (eight cores) and on one CPU core with Intel Xeon E5-2670.

The Surface-Tension Method of Visually Inspecting Honeycomb-Core Sandwich Plates

NASA Technical Reports Server (NTRS)

Katzoff, Samuel

1960-01-01

When one face of a metal-honeycomb-core sandwich plate is heated or cooled relative to the other, heat transfer through the core causes the temperature on each face at the lines of contact with the core to be slightly different from that on the rest of the face. If a thin liquid film is applied to the face, the variation of surface tension with temperature causes the liquid to move from warmer to cooler areas and thus to develop a pattern corresponding to the temperature pattern on the face. Irregularities in the pattern identify the locations where the core is not adequately bonded to the face sheet. The pattern is easily observed when a fluorescent liquid is used and illumination is by means of ultraviolet light. Observation in ordinary light is also possible when a very deeply colored liquid is used. A method based on the use of a thermographic phosphor to observe the temperature pattern was found to be less sensitive than the surface-tension method. A sublimation method was found to be not only less sensitive but also far more troublesome.

Multi-physics design and analyses of long life reactors for lunar outposts

NASA Astrophysics Data System (ADS)

Schriener, Timothy M.

Future human exploration of the solar system is likely to include establishing permanent outposts on the surface of the Moon. These outposts will require reliable sources of electrical power in the range of 10's to 100's of kWe to support exploration and resource utilization activities. This need is best met using nuclear reactor power systems which can operate steadily throughout the long ˜27.3 day lunar rotational period, irrespective of location. Nuclear power systems can potentially open up the entire lunar surface for future exploration and development. Desirable features of nuclear power systems for the lunar surface include passive operation, the avoidance of single point failures in reactor cooling and the integrated power system, moderate operating temperatures to enable the use of conventional materials with proven irradiation experience, utilization of the lunar regolith for radiation shielding and as a supplemental neutron reflector, and safe post-operation decay heat removal and storage for potential retrieval. In addition, it is desirable for the reactor to have a long operational life. Only a limited number of space nuclear reactor concepts have previously been developed for the lunar environment, and these designs possess only a few of these desirable design and operation features. The objective of this research is therefore to perform design and analyses of long operational life lunar reactors and power systems which incorporate the desirable features listed above. A long reactor operational life could be achieved either by increasing the amount of highly enriched uranium (HEU) fuel in the core or by improving the neutron economy in the reactor through reducing neutron leakage and parasitic absorption. The amount of fuel in surface power reactors is constrained by the launch safety requirements. These include ensuring that the bare reactor core remains safely subcritical when submerged in water or wet sand and flooded with seawater in the unlikely event of a launch abort accident. Increasing the amount of fuel in the reactor core, and hence its operational life, would be possible by launching the reactor unfueled and fueling it on the Moon. Such a reactor would, thus, not be subject to launch criticality safety requirements. However, loading the reactor with fuel on the Moon presents a challenge, requiring special designs of the core and the fuel elements, which lend themselves to fueling on the lunar surface. This research investigates examples of both a solid core reactor that would be fueled at launch as well as an advanced concept which could be fueled on the Moon. Increasing the operational life of a reactor fueled at launch is exercised for the NaK-78 cooled Sectored Compact Reactor (SCoRe). A multi-physics design and analyses methodology is developed which iteratively couples together detailed Monte Carlo neutronics simulations with 3-D Computational Fluid Dynamics (CFD) and thermal-hydraulics analyses. Using this methodology the operational life of this compact, fast spectrum reactor is increased by reconfiguring the core geometry to reduce neutron leakage and parasitic absorption, for the same amount of HEU in the core, and meeting launch safety requirements. The multi-physics analyses determine the impacts of the various design changes on the reactor's neutronics and thermal-hydraulics performance. The option of increasing the operational life of a reactor by loading it on the Moon is exercised for the Pellet Bed Reactor (PeBR). The PeBR uses spherical fuel pellets and is cooled by He-Xe gas, allowing the reactor core to be loaded with fuel pellets and charged with working fluid on the lunar surface. The performed neutronics analyses ensure the PeBR design achieves a long operational life, and develops safe launch canister designs to transport the spherical fuel pellets to the lunar surface. The research also investigates loading the PeBR core with fuel pellets on the Moon using a transient Discrete Element Method (DEM) analysis in lunar gravity. In addition, this research addresses the post-operation storage of the SCoRe and PeBR concepts, below the lunar surface, to determine the time required for the radioactivity in the used fuel to decrease to a low level to allow for its safe recovery. The SCoRe and PeBR concepts are designed to operate at coolant temperatures ≤ 900 K and use conventional stainless steels and superalloys for the structure in the reactor core and power system. They are emplaced below grade on the Moon to take advantage of the regolith as a supplemental neutron reflector and as shielding of the lunar outpost from the reactors' neutron and gamma radiation.

Simulation of drift wave instability in field-reversed configurations using global magnetic geometry

NASA Astrophysics Data System (ADS)

Fulton, D. P.; Lau, C. K.; Lin, Z.; Tajima, T.; Holod, I.; the TAE Team

2016-10-01

Minimizing transport in the field-reversed configuration (FRC) is essential to enable FRC-based fusion reactors. Recently, significant progress on advanced beam-driven FRCs in C-2 and C-2U (at Tri Alpha Energy) provides opportunities to study transport properties using Doppler backscattering (DBS) measurements of turbulent fluctuations and kinetic particle-in-cell simulations of driftwaves in realistic equilibria via the Gyrokinetic Toroidal Code (GTC). Both measurements and simulations indicate relatively small fluctuations in the scrape-off layer (SOL). In the FRC core, local, single flux surface simulations reveal strong stabilization, while experiments indicate quiescent but finite fluctuations. One possible explanation is that turbulence may originate in the SOL and propagate at very low levels across the separatrix into the core. To test this hypothesis, a significant effort has been made to develop A New Code (ANC) based on GTC physics formulations, but using cylindrical coordinates which span the magnetic separatrix, including both core and SOL. Here, we present first results from global ANC simulations.

Test prediction for the German PKL Test K5A using RELAP4/MOD6

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

Chen, Y.S.; Haigh, W.S.; Sullivan, L.H.

RELAP4/MOD6 is the most recent modification in the series of RELAP4 computer programs developed to describe the thermal-hydraulic conditions attendant to postulated transients in light water reactor systems. The major new features in RELAP4/MOD6 include best-estimate pressurized water reactor (PWR) reflood transient analytical models for core heat transfer, local entrainment, and core vapor superheat, and a new set of heat transfer correlations for PWR blowdown and reflood. These new features were used for a test prediction of the Kraftwerk Union three-loop PRIMAR KREISLAUF (PKL) Reflood Test K5A. The results of the prediction were in good agreement with the experimental thermalmore » and hydraulic system data. Comparisons include heater rod surface temperature, system pressure, mass flow rates, and core mixture level. It is concluded that RELAP4/MOD6 is capable of accurately predicting transient reflood phenomena in the 200% cold-leg break test configuration of the PKL reflood facility.« less

Magnetic Reconnections in Mast

NASA Astrophysics Data System (ADS)

Turri, G.; Buttery, R. J.; Hastie, R. J.; Gimblett, C. G.; Cowley, S. C.; Lehane, I.

2004-11-01

In MAST the appearance of a spontaneous snake in the plasma core has many of the properties of a full reconnection. Analysis of SXR and TS data indicates a strongly radiating core with high impurity levels forming before the onset of the snake. Following the appearance of an x-point (island on the q=1 surface) the former core is hypothesised to move off axis and shrink, appearing as a radiative region with flux-tube-like rotating helical structure (the snake). A code has been developed to compare this with a slow full Kadomtsev type reconnection process including effects of impurities, density and temperature perturbations, current profile evolution and transport. The code reproduces many of the trends and effects seen in the data, confirming the event as consistent with full reconnection. The time-scale of the event is also consistent with estimates of hybrid growth times for such a reconnection process. Further analysis will be presented exploring the physics of this process in more detail.

Sombrero-shaped plasmonic nanoparticles with molecular-level sensitivity and multifunctionality.

PubMed

Wi, Jung-Sub; Barnard, Edward S; Wilson, Robert J; Zhang, Mingliang; Tang, Mary; Brongersma, Mark L; Wang, Shan X

2011-08-23

We demonstrate top-down synthesis of monodisperse plasmonic nanoparticles designed to contain internal Raman hot spots. Our Raman-active nanoparticles are fabricated using nanoimprint lithography and thin-film deposition and are composed of novel internal structures with sublithographic dimensions: a disk-shaped Ag core, a Petri-dish-shaped SiO(2) base whose inner surface is coated with Ag film, and a sub-10 nm scale circular gap between the core and the base. Confocal Raman measurements and electromagnetic simulations show that Raman hot spots appear at the inside perimeter of individual nanoparticles and serve as the source of a 1000-fold improvement of minimum molecular detection level that enables detection of signals from a few molecules near hot spots. A multimodality version of these nanoparticles, which includes the functionality offered by magnetic multilayers, is also demonstrated. These results illustrate the potential of direct fabrication for creating exotic monodisperse nanoparticles, which combine engineered internal nanostructures and multilayer composite materials, for use in nanoparticle-based molecular imaging and detection. © 2011 American Chemical Society

Study of the phase composition of nanostructures produced by the local anodic oxidation of titanium films

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

Avilov, V. I.; Ageev, O. A.; Konoplev, B. G.

2016-05-15

The results of experimental studies of the phase composition of oxide nanostructures formed by the local anodic oxidation of a titanium thin film are reported. The data of the phase analysis of titanium-oxide nanostructures are obtained by X-ray photoelectron spectroscopy in the ion profiling mode of measurements. It is established that the surface of titanium-oxide nanostructures 4.5 ± 0.2 nm in height possesses a binding energy of core levels characteristic of TiO{sub 2} (458.4 eV). By analyzing the titanium-oxide nanostructures in depth by X-ray photoelectron spectroscopy, the formation of phases with binding energies of core levels characteristic of Ti{sub 2}O{submore » 3} (456.6 eV) and TiO (454.8 eV) is established. The results can be used in developing the technological processes of the formation of a future electronic-component base for nanoelectronics on the basis of titanium-oxide nanostructures and probe nanotechnologies.« less

Structure of Arabidopsis leaf starch is markedly altered following nocturnal degradation.

PubMed

Zhu, Fan; Bertoft, Eric; Wang, You; Emes, Michael; Tetlow, Ian; Seetharaman, Koushik

2015-03-06

Little is known about the thermal properties and internal molecular structure of transitory starch. In this study, granule morphology, thermal properties, and the cluster structure of Arabidopsis leaf starch at beginning and end of the light period were explored. The structural properties of building blocks and clusters were evaluated by using diverse chromatographic techniques. On the granular level, starch from end of day had larger granule size, thinner crystalline lamellae thickness, lower free surface energy of crystals, and lower tendency to retrograde than that from end of night. On the molecular level, the starch had lower amylose content, larger cluster size, and higher number of blocks per cluster at the end of day than at end of night. It is concluded that the core of the granules contains a more permanent molecular and less-ordered physical structure different from the transitory layers laid down around the core at daytime. Copyright © 2014 Elsevier Ltd. All rights reserved.

Perfluoroalkyl substances and extractable organic fluorine in surface sediments and cores from Lake Ontario.

PubMed

Yeung, Leo W Y; De Silva, Amila O; Loi, Eva I H; Marvin, Chris H; Taniyasu, Sachi; Yamashita, Nobuyoshi; Mabury, Scott A; Muir, Derek C G; Lam, Paul K S

2013-09-01

Fourteen perfluoroalkyl substances (PFASs) including short-chain perfluorocarboxylates (PFCAs, C4-C6) and perfluoroalkane sulfonates (PFSAs, C4 and C6) were measured in surface sediment samples from 26 stations collected in 2008 and sediment core samples from three stations (Niagara, Mississauga, and Rochester basins) collected in 2006 in Lake Ontario. Perfluorooctanesulfonate (PFOS), perfluorooctanoate (PFOA), perfluorononanoate (PFNA), perfluorodecanoate (PFDA), and perfluoroundecanoate (PFUnDA) were detected in all 26 surface sediment samples, whereas perfluorohexane sulfonate (PFHxS), perfluorooctane sulfonamide (FOSA), perfluorododecanoate (PFDoDA) and perfluorobutanoate (PFBA) were detected in over 70% of the surface sediment samples. PFOS was detected in all of the sediment core samples (range: 0.492-30.1ngg(-1) d.w.) over the period 1952-2005. The C8 to C11 PFCAs, FOSA, and PFBA increased in early 1970s. An overall increasing trend in sediment PFAS concentrations/fluxes from older to more recently deposited sediments was evident in the three sediment cores. The known PFCAs and PFSAs accounted for 2-44% of the anionic fraction of the extractable organic fluorine in surface sediment, suggesting that a large proportion of fluorine in this fraction remained unknown. Sediment core samples collected from Niagara basin showed an increase in unidentified organic fluorine in recent years (1995-2006). These results suggest that the use and manufacture of fluorinated organic compounds other than known PFCAs and PFSAs has diversified and increased. © 2013.

Quantitative hepatitis B core antibody levels in the natural history of hepatitis B virus infection.

PubMed

Song, L-W; Liu, P-G; Liu, C-J; Zhang, T-Y; Cheng, X-D; Wu, H-L; Yang, H-C; Hao, X-K; Yuan, Q; Zhang, J; Kao, J-H; Chen, D-S; Chen, P-J; Xia, N-S

2015-02-01

We previously demonstrated that pretreatment quantitative anti-hepatitis B core protein (qAnti-HBc) levels can predict the treatment response for both interferon and nucleoside analogue therapy, but the characteristics of qAnti-HBc during chronic hepatitis B virus (HBV) infection remain poorly understood. To understand this issue, the qAnti-HBc levels were evaluated in individuals with past HBV infection, occult HBV infection and chronic HBV infection in the immune tolerance phase, immune clearance phase, low-replicative phase and hepatitis B e antigen (HBeAg)-negative hepatitis phase. Individuals with hepatitis B surface antigen (n = 598, 3.74 ± 0.90 log10 IU/mL) had significantly higher (p < 0.001, approximately 1000-fold) serum qAnti-HBc levels than those who had occult HBV, and serum qAnti-HBc levels were significantly higher in the occult HBV group than in the past HBV infection group (p < 0.001). qAnti-HBc levels were positively correlated with alanine aminotransferase levels (R = 0.663, p < 0.001), and subjects with an abnormal alanine aminotransferase level had a higher qAnti-HBc level (p < 0.001). Serum qAnti-HBc level varied in different phases of HBV infection, as determined by host immune status. Serum qAnti-HBc level is strongly associated with hepatitis activity in subjects with chronic HBV infection. Copyright © 2014 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.

Dark matter sterile neutrinos in stellar collapse: Alteration of energy/lepton number transport, and a mechanism for supernova explosion enhancement

NASA Astrophysics Data System (ADS)

Hidaka, Jun; Fuller, George M.

2006-12-01

We investigate matter-enhanced Mikheyev-Smirnov-Wolfenstein (MSW) active-sterile neutrino conversion in the νe⇌νs channel in the collapse of the iron core of a presupernova star. For values of sterile neutrino rest mass ms and vacuum mixing angle θ (specifically, 0.5keV5×10-12) which include those required for viable sterile neutrino dark matter, our one-zone in-fall phase collapse calculations show a significant reduction in core lepton fraction. This would result in a smaller homologous core and therefore a smaller initial shock energy, disfavoring successful shock reheating and the prospects for an explosion. However, these calculations also suggest that the MSW resonance energy can exhibit a minimum located between the center and surface of the core. In turn, this suggests a post-core-bounce mechanism to enhance neutrino transport and neutrino luminosities at the core surface and thereby augment shock reheating: (1) scattering-induced or coherent MSW νe→νs conversion occurs deep in the core, at the first MSW resonance, where νe energies are large (˜150MeV); (2) the high energy νs stream outward at near light speed; (3) they deposit their energy when they encounter the second MSW resonance νs→νe just below the proto-neutron star surface.

The formation of the doubly stable stratification in the Mediterranean Outflow

NASA Astrophysics Data System (ADS)

Bormans, M.; Turner, J. S.

1990-11-01

The Mediterranean Outflow as it exits from the Strait of Gibraltar can be seen as a gravity current flowing down the slope and mixing with Atlantic Water until it reaches its own density level. Typical salinity and temperature profiles through the core region of a Meddy show that the bottom of the core is colder and saltier than the top, leading to a stably stratified core with respect to double-diffusive processes. The bottom of the core is also more enriched with Mediterranean Water than the top, and this behaviour can be explained by a reduced mixing of the source water with the environment close to the rigid bottom. Although the mechanism involved is different from the actual case, we have successfully produced these doubly stable gradient in some laboratory experiments which incorporate the "filling-box" mechanism. Salt and sugar were used as laboratory analogues of temperature and salt, respectively. The laboratory experiments consisted of supplying a dense input fluid at the surface of a linearly salt stratified environment. We suggest that req, the ratio of the initial volume flux at the source to the volume flux at the equilibrium level, is an important parameter, and that in our experiments this must be in general smaller than 0.1 in order to produce a doubly stable region of salt and sugar. The most relevant experiments had a mixed sugar/salt input which is the analogue of the Mediterranean Outflow as it mixes with Atlantic Water outside the Strait of Gibraltar.

Continuum-kinetic-microscopic model of lung clearance due to core-annular fluid entrainment

PubMed Central

Mitran, Sorin

2013-01-01

The human lung is protected against aspirated infectious and toxic agents by a thin liquid layer lining the interior of the airways. This airway surface liquid is a bilayer composed of a viscoelastic mucus layer supported by a fluid film known as the periciliary liquid. The viscoelastic behavior of the mucus layer is principally due to long-chain polymers known as mucins. The airway surface liquid is cleared from the lung by ciliary transport, surface tension gradients, and airflow shear forces. This work presents a multiscale model of the effect of airflow shear forces, as exerted by tidal breathing and cough, upon clearance. The composition of the mucus layer is complex and variable in time. To avoid the restrictions imposed by adopting a viscoelastic flow model of limited validity, a multiscale computational model is introduced in which the continuum-level properties of the airway surface liquid are determined by microscopic simulation of long-chain polymers. A bridge between microscopic and continuum levels is constructed through a kinetic-level probability density function describing polymer chain configurations. The overall multiscale framework is especially suited to biological problems due to the flexibility afforded in specifying microscopic constituents, and examining the effects of various constituents upon overall mucus transport at the continuum scale. PMID:23729842

Continuum-kinetic-microscopic model of lung clearance due to core-annular fluid entrainment

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

Mitran, Sorin, E-mail: mitran@unc.edu

2013-07-01

The human lung is protected against aspirated infectious and toxic agents by a thin liquid layer lining the interior of the airways. This airway surface liquid is a bilayer composed of a viscoelastic mucus layer supported by a fluid film known as the periciliary liquid. The viscoelastic behavior of the mucus layer is principally due to long-chain polymers known as mucins. The airway surface liquid is cleared from the lung by ciliary transport, surface tension gradients, and airflow shear forces. This work presents a multiscale model of the effect of airflow shear forces, as exerted by tidal breathing and cough,more » upon clearance. The composition of the mucus layer is complex and variable in time. To avoid the restrictions imposed by adopting a viscoelastic flow model of limited validity, a multiscale computational model is introduced in which the continuum-level properties of the airway surface liquid are determined by microscopic simulation of long-chain polymers. A bridge between microscopic and continuum levels is constructed through a kinetic-level probability density function describing polymer chain configurations. The overall multiscale framework is especially suited to biological problems due to the flexibility afforded in specifying microscopic constituents, and examining the effects of various constituents upon overall mucus transport at the continuum scale.« less

Continuum-kinetic-microscopic model of lung clearance due to core-annular fluid entrainment

NASA Astrophysics Data System (ADS)

Mitran, Sorin

2013-07-01

The human lung is protected against aspirated infectious and toxic agents by a thin liquid layer lining the interior of the airways. This airway surface liquid is a bilayer composed of a viscoelastic mucus layer supported by a fluid film known as the periciliary liquid. The viscoelastic behavior of the mucus layer is principally due to long-chain polymers known as mucins. The airway surface liquid is cleared from the lung by ciliary transport, surface tension gradients, and airflow shear forces. This work presents a multiscale model of the effect of airflow shear forces, as exerted by tidal breathing and cough, upon clearance. The composition of the mucus layer is complex and variable in time. To avoid the restrictions imposed by adopting a viscoelastic flow model of limited validity, a multiscale computational model is introduced in which the continuum-level properties of the airway surface liquid are determined by microscopic simulation of long-chain polymers. A bridge between microscopic and continuum levels is constructed through a kinetic-level probability density function describing polymer chain configurations. The overall multiscale framework is especially suited to biological problems due to the flexibility afforded in specifying microscopic constituents, and examining the effects of various constituents upon overall mucus transport at the continuum scale.

Inquiry Based Projects Using Student Ozone Measurements and the Status of Using Plants as Bio-Indicators

NASA Astrophysics Data System (ADS)

Ladd, I. H.; Fishman, J.; Pippin, M.; Sachs, S.; Skelly, J.; Chappelka, A.; Neufeld, H.; Burkey, K.

2006-05-01

Students around the world work cooperatively with their teachers and the scientific research community measuring local surface ozone levels using a hand-held optical scanner and ozone sensitive chemical strips. Through the GLOBE (Global Learning and Observations to Benefit the Environment) Program, students measuring local ozone levels are connected with the chemistry of the air they breathe and how human activity impacts air quality. Educational tools have been developed and correlated with the National Science and Mathematics Standards to facilitate integrating the study of surface ozone with core curriculum. Ozone air pollution has been identified as the major pollutant causing foliar injury to plants when they are exposed to concentrations of surface ozone. The inclusion of native and agricultural plants with measuring surface ozone provides an Earth system approach to understanding surface ozone. An implementation guide for investigating ozone induced foliar injury has been developed and field tested. The guide, Using Sensitive Plants as Bio-Indicators of Ozone Pollution, provides: the background information and protocol for implementing an "Ozone Garden" with native and agricultural plants; and, a unique opportunity to involve students in a project that will develop and increase their awareness of surface ozone air pollution and its impact on plants.

Historical CO2 Records from the Law Dome DE08, DE08-2, and DSS Ice Cores (1006 A.D.-1978 A.D)

DOE Data Explorer

Etheridge, D. M. [Commonwealth Scientific and Industrial Research Organization (CSIRO), Aspendale, Australia; Barnola, J. M. [Laboratoire de Glaciologie et Géophysique de l'Environnement, Saint Martin d'Hères-Cedex, France; Morgan, V. I. [Antarctic CRC and Australian Antarctic Division, Hobart, Tasmania, Australia; Steele, L. P. [Commonwealth Scientific and Industrial Research Organization (CSIRO), Aspendale, Australia; Langenfelds, R. L. [Commonwealth Scientific and Industrial Research Organization (CSIRO), Aspendale, Australia; Francey, R. J. [Commonwealth Scientific and Industrial Research Organization (CSIRO), Aspendale, Australia; Martinez, Monica [Oak Ridge National Laboratory, Oak Ridge, TN (USA)

1998-01-01

The CO2 records presented here are derived from three ice cores obtained at Law Dome, East Antarctica from 1987 to 1993. The Law Dome site satisfies many of the desirable characteristics of an ideal ice core site for atmospheric CO2 reconstructions including negligible melting of the ice sheet surface, low concentrations of impurities, regular stratigraphic layering undisturbed at the surface by wind or at depth by ice flow, and high snow accumulation rate. Further details on the site, drilling, and cores are provided in Etheridge et al. (1996), Etheridge and Wookey (1989), and Morgan et al (1997).

Mercury profiles in sediment from the marginal high of Arabian Sea: an indicator of increasing anthropogenic Hg input.

PubMed

Chakraborty, Parthasarathi; Vudamala, Krushna; Chennuri, Kartheek; Armoury, Kazip; Linsy, P; Ramteke, Darwin; Sebastian, Tyson; Jayachandran, Saranya; Naik, Chandan; Naik, Richita; Nath, B Nagender

2016-05-01

Total Hg distributions and its speciation were determined in two sediment cores collected from the western continental marginal high of India. Total Hg content in the sediment was found to gradually increase (by approximately two times) towards the surface in both the cores. It was found that Hg was preferentially bound to sulfide under anoxic condition. However, redox-mediated reactions in the upper part of the core influenced the total Hg content in the sediment cores. This study suggests that probable increase in authigenic and allogenic Hg deposition attributed to the increasing Hg concentration in the surface sediment in the study area.

Polished Downhole Transducer Having Improved Signal Coupling

DOEpatents

Hall, David R.; Fox, Joe

2006-03-28

Apparatus and methods to improve signal coupling in downhole inductive transmission elements to reduce the dispersion of magnetic energy at the tool joints and to provide consistent impedance and contact between transmission elements located along the drill string. A transmission element for transmitting information between downhole tools is disclosed in one embodiment of the invention as including an annular core constructed of a magnetically conductive material. The annular core forms an open channel around its circumference and is configured to form a closed channel by mating with a corresponding annular core along an annular mating surface. The mating surface is polished to provide improved magnetic coupling with the corresponding annular core. An annular conductor is disposed within the open channel.

Phosphine-free synthesis of high-quality reverse type-I ZnSe/CdSe core with CdS/CdxZn1 - xS/ZnS multishell nanocrystals and their application for detection of human hepatitis B surface antigen

NASA Astrophysics Data System (ADS)

Shen, Huaibin; Yuan, Hang; Niu, Jin Zhong; Xu, Shasha; Zhou, Changhua; Ma, Lan; Li, Lin Song

2011-09-01

Highly photoluminescent (PL) reverse type-I ZnSe/CdSe nanocrystals (NCs) and ZnSe/CdSe/CdS/CdxZn1 - xS/ZnS core/multishell NCs were successfully synthesized by a phosphine-free method. By this low-cost, 'green' synthesis route, more than 10 g of high-quality ZnSe/CdSe/CdS/CdxZn1 - xS/ZnS NCs were synthesized in a large scale synthesis. After the overgrowth of a CdS/CdxZn1 - xS/ZnS multishell on ZnSe/CdSe cores, the PL quantum yields (QYs) increased from 28% to 75% along with the stability improvement. An amphiphilic oligomer was used as a surface coating agent to conduct a phase transfer experiment, core/multishell NCs were dissolved in water by such surface modification and the QYs were still kept above 70%. The as-prepared water dispersible ZnSe/CdSe/CdS/CdxZn1 - xS/ZnS core/multishell NCs not only have high fluorescence QYs but also are extremely stable in various physiological conditions. Furthermore, a biosensor system (lateral flow immunoassay system, LFIA) for the detection of human hepatitis B surface antigen (HBsAg) was developed by using this water-soluble core/multishell NCs as a fluorescent label and a nitrocellulose filter membrane for lateral flow. The result showed that such ZnSe/CdSe/CdS/CdxZn1 - xS/ZnS core/multishell NCs were excellent fluorescent labels to detect HBsAg. The sensitivity of HBsAg detection could reach as high as 0.05 ng ml - 1.

Evidence of a Weakening Gulf Stream from In-situ Expendable Bathythermograph Data, 1996-2013

NASA Astrophysics Data System (ADS)

Roupe, L.; Baringer, M. O.

2014-12-01

A weakening of the Gulf Stream, the upper branch of the Atlantic Meridional Overturning Circulation system, has been hypothesized to accelerate sea level rise on the east coast of the United States, caused by changes in the Gulf Stream strength and, hence, sea level difference across the current. It still remains unclear if the Gulf Stream has in fact weakened or remains stable, along with the potential role of natural long-term variability. Tide gauges along the east coast show an accelerated sea level rise from Cape Hatteras to Cape Cod that is 3-4 times higher than global sea level rise. Satellite altimetry shows a weakening gradient in Gulf Stream sea surface height that is highly correlated (r=-0.85) with east coast sea level rise, however, direct velocity measurements showed no significant decrease in Gulf Stream strength over a similar time period. We introduce another in-situ dataset to examine the issues between these conflicting results. Expendable bathythermographs (XBTs) measure temperature at depth directly, and then depth and salinity can be inferred, along with geostrophic velocity and transport. XBT data has been used to measure transport in various current systems, however, the Gulf Stream transport has not been analyzed using the newest high-density XBT data made available since 1996. The trend in sea level difference is determined to be 3.3 +/- 3.2 mm/yr, resulting in an overall decrease of 5.2 cm in sea level from 1996-2013. This result agrees with satellite altimetry results that show a significant decrease in recent years. This data also shows a changing Gulf Stream core position, based on the 15°C isotherm at 200 m, of 0.03°N/yr that is negatively correlated with surface transport (r=-0.25). Issues remain in defining the core and width of the Gulf Stream and with eliminating the possibility of natural variability in the current system.

Nuclear Bombs and Coral: Guam Coral Core Reveals Operation-Specific Radiocarbon Signals from the Pacific Proving Grounds

NASA Astrophysics Data System (ADS)

Andrews, A. H.

2016-12-01

Radiocarbon (14C) analyses on a coral core extracted from the western Central Pacific (Guam) has revealed a series of early peaks in the marine bomb 14C record. The typical marine bomb 14C signal, one that is phase lagged and attenuated relative to atmospheric bomb 14C, is present in the coral core and is consistent with other North Pacific records. However, 14C levels that are well above what can be explained by air-sea diffusion alone punctuate this pattern. This anomaly has been demonstrated to a limited extent in other coral cores of the Indo-Pacific region, but is unmatched relative to the magnitude and temporal resolution recorded in the Guam coral core. Other records have shown an early Δ14C rise on the order of 40-50‰ above pre-bomb levels, with a subsequent decline before continuing the gradual Δ14C rise that is indicative of air-sea diffusion of 14CO2. The Guam coral Δ14C record provided three strong pulses in 1954-55, 1956-57, and 1958-59 that are superimposed on the pre-bomb to initial Δ14C rise from atmospheric bomb 14C. Each of these peaks can be directly linked to testing of thermonuclear devices in the Pacific Proving Grounds at Eniwetok and Bikini Atoll of the Marshall Islands. The measurable lag in reaching Guam can be tied to ocean surface currents and can be traced to other regional Δ14C records from corals, providing a transport timeline to places as distant as the Indonesian throughflow, Okinawa and Palmyra.

Thermal Jeans Fragmentation within ∼1000 au in OMC-1S

NASA Astrophysics Data System (ADS)

Palau, Aina; Zapata, Luis A.; Román-Zúñiga, Carlos G.; Sánchez-Monge, Álvaro; Estalella, Robert; Busquet, Gemma; Girart, Josep M.; Fuente, Asunción; Commerçon, Benoit

2018-03-01

We present subarcsecond 1.3 mm continuum ALMA observations toward the Orion Molecular Cloud 1 South (OMC-1S) region, down to a spatial resolution of 74 au, which reveal a total of 31 continuum sources. We also present subarcsecond 7 mm continuum VLA observations of the same region, which allow further study of fragmentation down to a spatial resolution of 40 au. By applying a method of “mean surface density of companions” we find a characteristic spatial scale at ∼560 au, and we use this spatial scale to define the boundary of 19 “cores” in OMC-1S as groupings of millimeter sources. We find an additional characteristic spatial scale at ∼2800 au, which is the typical scale of the filaments in OMC-1S, suggesting a two-level fragmentation process. We measured the fragmentation level within each core and find a higher fragmentation toward the southern filament. In addition, the cores of the southern filament are also the densest cores (within 1100 au) in OMC-1S. This is fully consistent with previous studies of fragmentation at spatial scales one order of magnitude larger, and suggests that fragmentation down to 40 au seems to be governed by thermal Jeans processes in OMC-1S.

Re-Evaluating the Geological Evidence for Late Holocene Marine Incursion Events along the Guerrero Seismic Gap on the Pacific Coast of Mexico

PubMed Central

Bianchette, Thomas A.

2016-01-01

Despite the large number of tsunamis that impact Mexico’s Pacific coast, stratigraphic studies focusing on geological impacts are scanty, making it difficult to assess the long-term risks for this vulnerable region. Surface samples and six cores were taken from Laguna Mitla near Acapulco to examine sedimentological and geochemical evidence for marine incursion events. Sediment cores collected from behind the beach barrier are dominated by intercalated layers of peat and inorganic sediments, mostly silt and clay, with little or no sand. Sand- and shell-rich clastic layers with high levels of sulfur, calcium, and strontium only occur adjacent to the relict beach ridge remnants near the center of the lagoon. With the exception of one thin fine sand layer, the absence of sand in the near-shore cores and the predominance of the terrigenous element titanium in the inorganic layers, evidently eroded from the surrounding hillslopes, suggests that these large-grained intervals do not represent episodic marine incursions, but rather were likely formed by the erosion and redeposition of older marine deposits derived from the beach ridge remnants when water levels were high. These results do not support the occurrence of a large tsunami event at Laguna Mitla during the Late Holocene. PMID:27571270

Re-Evaluating the Geological Evidence for Late Holocene Marine Incursion Events along the Guerrero Seismic Gap on the Pacific Coast of Mexico.

PubMed

Bianchette, Thomas A; McCloskey, Terrence A; Liu, Kam-Biu

2016-01-01

Despite the large number of tsunamis that impact Mexico's Pacific coast, stratigraphic studies focusing on geological impacts are scanty, making it difficult to assess the long-term risks for this vulnerable region. Surface samples and six cores were taken from Laguna Mitla near Acapulco to examine sedimentological and geochemical evidence for marine incursion events. Sediment cores collected from behind the beach barrier are dominated by intercalated layers of peat and inorganic sediments, mostly silt and clay, with little or no sand. Sand- and shell-rich clastic layers with high levels of sulfur, calcium, and strontium only occur adjacent to the relict beach ridge remnants near the center of the lagoon. With the exception of one thin fine sand layer, the absence of sand in the near-shore cores and the predominance of the terrigenous element titanium in the inorganic layers, evidently eroded from the surrounding hillslopes, suggests that these large-grained intervals do not represent episodic marine incursions, but rather were likely formed by the erosion and redeposition of older marine deposits derived from the beach ridge remnants when water levels were high. These results do not support the occurrence of a large tsunami event at Laguna Mitla during the Late Holocene.

In-flight flow visualization with pressure measurements at low speeds on the NASA F-18 high alpha research vehicle

NASA Technical Reports Server (NTRS)

Delfrate, John H.; Fisher, David F.; Zuniga, Fanny A.

1990-01-01

In-flight results from surface and off-surface flow visualizations and from extensive pressure distributions document the vortical flow on the leading edge extensions (LEX) and forebody of the NASA F-18 high alpha research vehicle for low speeds and angles of attack up to 50 degs. Surface flow visualization data, obtained using the emitted fluid technique, were used to define separation lines and laminar separation bubbles. Off-surface flow visualization data, obtained by smoke injection, were used to document both the path of the vortex cores and the location of vortex core breakdown. The location of vortex core breakdown correlated well with the loss of suction pressure on the LEX and with the flow visualization results from ground facilities. Surface flow separation lines on the LEX and forebody corresponded well with the end of pressure recovery under the vortical flows. Correlation of the pressures with wind tunnel results show fair to good correlation.

Discovery of Cellulose Surface Layer Conformation by Nonlinear Vibrational Spectroscopy

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

Zhang, Libing; Fu, Li; Wang, Hong-fei

2017-03-14

Significant questions remain with respect to the structure and polymorphs of cellulose. These include the cellulose surface layers and the bulk crystalline core as well as the conformational differences. The Total Internal Reflection Sum Frequency Generation Vibrational Spectroscopy (TIR-SFG-VS) combined with the conventional SFG-VS (non-TIR) can help to resolve these questions by selectively characterizing the molecular structures of surface layers and the crystalline core of cellulose. From the SFG spectra in the C-H and O-H regions, we found that the surface layers of Avicel are essentially amorphous; while the surface layers of Iβ cellulose are crystalline but with different structuralmore » and spectroscopic signatures than that of its crystalline core. This work demonstrates the capacity of TIR and Non-TIR SFG-VS tools in selectively studying the structures and polymorphs of cellulose. In addition, these results also suggest that the assignments of major vibrational peaks for cellulose need to be further determined.« less

A Composite Depth Scale for Sediments from Crevice Lake, Montana

USGS Publications Warehouse

Rosenbaum, J.G.; Skipp, G.; Honke, J.; Chapman, C.

2010-01-01

As part of a study to derive records of past environmental change from lake sediments in the western United States, a set of cores was collected from Crevice Lake, Montana, in late February and early March 2001. Crevice Lake (latitude 45.000N, longitude 110.578W, elevation 1,713 meters) lies adjacent to the Yellowstone River at the north edge of Yellowstone National Park. The lake is more than 31 meters deep and has a surface area of 7.76 hectares. The combination of small surface area and significant depth promote anoxic bottom-water conditions that preserve annual laminations (varves) in the sediment. Three types of cores were collected through the ice. The uppermost sediments were obtained in freeze cores that preserved the sediment water interface. Two sites were cored with a 5-centimeter diameter corer. Five cores were taken with a 2-meter-long percussion piston corer. The percussion core uses a plastic core liner with an inside diameter of 9 centimeters. Coring was done at two sites. Because of the relatively large diameter of the percussion cores, samples from these cores were used for a variety of analyses including pollen, charcoal, diatoms, stable isotopes, organic and inorganic carbon, elemental analyses, and magnetic properties.

Preliminary Physical Stratigraphy and Geophysical Data From the USGS Dixon Core, Onslow County, North Carolina

USGS Publications Warehouse

Seefelt, Ellen L.; Gonzalez, Wilma Aleman B.; Self-Trail, Jean M.; Weems, Robert E.; Edwards, Lucy E.; Pierce, Herbert A.; Durand, Colleen T.

2009-01-01

In October through November 2006, scientists from the U. S. Geological Survey (USGS) Eastern Region Earth Surface Processes Team (EESPT) and the Raleigh (N.C.) Water Science Center (WSC), in cooperation with the North Carolina Geological Survey (NCGS) and the Onslow County Water and Sewer Authority (ONWASA), drilled a stratigraphic test hole and well in Onslow County, N.C. The Dixon corehole was cored on ONWASA water utility property north of the town of Dixon, N.C., in the Sneads Ferry 7.5-minute quadrangle at latitude 34deg33'35' N, longitude 77deg26'54' W (decimal degrees 34.559722 and -77.448333). The site elevation is 66.0 feet (ft) above mean sea level as determined using a Paulin precision altimeter. The corehole attained a total depth of 1,010 ft and was continuously cored by the USGS EESPT drilling crew. A groundwater monitoring well was installed in the screened interval between 234 and 254 ft below land surface. The section cored at this site includes Upper Cretaceous, Paleogene, and Neogene sediments. The Dixon core is stored at the NCGS Coastal Plain core storage facility in Raleigh. The Dixon corehole is the fourth and last in a series of planned North Carolina benchmark coreholes drilled by the USGS Coastal Carolina Project. These coreholes explore the physical stratigraphy, facies, and thickness of Cretaceous, Paleogene, and Neogene Coastal Plain sediments in North Carolina. Correlations of lithologies, facies, and sequence stratigraphy can be made with the Hope Plantation corehole, N.C., near Windsor in Bertie County (Weems and others, 2007); the Elizabethtown corehole, near Elizabethtown, N.C., in Bladen County (Self-Trail and others, 2004b); the Smith Elementary School corehole, near Cove City, N.C., in Craven County (Harris and Self-Trail, 2006; Crocetti, 2007); the Kure Beach corehole, near Wilmington, N.C., in New Hanover County (Self-Trail and others, 2004a); the Esso#1, Esso #2, Mobil #1, and Mobil #2 cores in Albermarle and Pamlico Sounds, N.C. (Zarra, 1989); and the Cape Fear River outcrops in Bladen County, N.C. (Farrell, 1998; Farrell and others, 2001). This report contains the lithostratigraphic summary recorded at the drill site, core photographs, geophysical data, and calcareous nannofossil biostratigraphic correlations.

Lipid Bilayer-Enabled Synthesis of Waxberry-like Core/Fluidic Satellite Nanoparticles: toward Ultrasensitive SERS Tags for Bioimaging.

PubMed

Mei, Rongchao; Wang, Yunqing; Liu, Wanhui; Chen, Lingxin

2018-06-25

Herein, we presented waxberry-like core-satellite (C-S) nanoparticles (NPs) prepared by in situ growth of satellite gold NPs on spherical phospholipid bilayer-coated gold cores. The fluidic lipid bilayer cross-linker was reported for the first time, which imparted several novel morphological and optical properties to the C-S NPs. First, it regulated the anisotropic growth of the satellite NPs into vertically oriented nanorods on the core NP surface. Thus, an interesting waxberry-like nanostructure could be obtained, which was different from the conventional raspberry-like C-S structures decorated with spherical satellite NPs. Second, the satellite NPs were "soft-landed" on the lipid bilayer and could move on the core NP surface under certain conditions. The movement induced tunable plasmonic features in the C-S NPs. Furthermore, the fluidic lipid bilayer was capable of not only holding an abundance of reporter molecules but also delivering them to hotspots at junctions between the core and satellite NPs, which made the C-S NPs an excellent candidate for preparing ultrasensitive surface-enhanced Raman scattering (SERS) tags. The bioimaging capabilities of the C-S NP-based SERS tags were successfully demonstrated in living cells and mice. The developed SERS tags hold great potential for bioanalysis and medical diagnostics.

Synthesis of highly monodisperse particles composed of a magnetic core and fluorescent shell.

PubMed

Nagao, Daisuke; Yokoyama, Mikio; Yamauchi, Noriko; Matsumoto, Hideki; Kobayashi, Yoshio; Konno, Mikio

2008-09-02

Highly monodisperse particles composed of a magnetic silica core and fluorescent polymer shell were synthesized with a combined technique of heterocoagulation and soap-free emulsion polymerization. Prior to heterocoagulation, monodisperse, submicrometer-sized silica particles were prepared with the Stober method, and magnetic nanoparticles were prepared with a modified Massart method in which a cationic silane coupling agent of N-trimethoxysilylpropyl- N, N, N-trimethylammonium chloride was added just after coprecipitation of Fe (2+) and Fe (3+). The silica particles with negative surface potential were heterocoagulated with the magnetic nanoparticles with positive surface potential. The magnetic silica particles obtained with the heterocoagulation were treated with sodium silicate to modify their surfaces with silica. In the formation of a fluorescent polymer shell onto the silica-coated magnetic silica cores, an amphoteric initiator of 2,2'-azobis[ N-(2-carboxyethyl)-2-2-methylpropionamidine] (VA-057) was used to control the colloidal stability of the magnetic cores during the polymer coating. The polymerization of St in the presence of a hydrophobic fluorophore of pyrene could coat the cores with fluorescent polymer shells, resulting in monodisperse particles with a magnetic silica core and fluorescent polymer shell. Measurements of zeta potential for the composite particles in different pH values indicated that the composite particles had an amphoteric property originating from VA-057 initiator.

Trends in chlorinated hydrocarbon levels in Hudson River basin sediments.

PubMed Central

Bopp, R F; Chillrud, S N; Shuster, E L; Simpson, H J; Estabrooks, F D

1998-01-01

Analysis of sections from dated sediment cores were used to establish geographic distributions and temporal trends of chlorinated hydrocarbon contaminant levels in sediments from natural waters of the Hudson River basin. Radiometric dating was based primarily on the depth distribution of 137(Cs) in the cores and on the occurrence of detectable levels of 7(Be) in surface sediment samples. Eighteen sampling sites included several along the main stem of the Hudson, its major tributaries, and components of the New York/New Jersey (NY/NJ) harbor complex. Drinking-water reservoirs were sampled to place upper limits on atmospheric inputs. Core sections were analyzed for polychlorinated biphenyls (PCBs), 1,1,1-trichloro-2,2-bis(p-chlorophenyl) ethane (DDT)-derived compounds, chlordane, and dioxins. Sediment concentrations of most contaminants at most sites have decreased significantly since the mid-1960s. The data provide a basinwide perspective on major point-source inputs of PCBs to the upper Hudson River and of 2,3,7,8-tetrachlorodibenzo-p-dioxin and DDT to the lower Passaic River. Evidence was found for significant but poorly characterized sources of PCBs and chlordane to the western NY/NJ harbor, and of highly chlorinated dioxins to the upstream sites on the main stem of the Hudson. The results indicate that analysis of dated sediment samples is a most effective and efficient monitoring tool for the study of large-scale geographic and temporal trends in levels of particle-associated contaminants. Images Figure 1 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 PMID:9703496

A nitride-based epitaxial surface layer formed by ammonia treatment of silicene-terminated ZrB{sub 2}

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

Wiggers, F. B., E-mail: F.B.Wiggers@utwente.nl; Van Bui, H.; Schmitz, J.

We present a method for the formation of an epitaxial  surface layer involving B, N, and Si atoms on a ZrB{sub 2}(0001) thin film on Si(111). It has the potential to be an insulating growth template for 2D semiconductors. The chemical reaction of NH{sub 3} molecules with the silicene-terminated ZrB{sub 2}  surface was characterized by synchrotron-based, high-resolution core-level photoelectron spectroscopy and low-energy electron diffraction. In particular, the dissociative chemisorption of NH{sub 3} at 400 °C leads to surface  nitridation, and subsequent annealing up to 830 °C results in a solid phase reaction with the ZrB{sub 2} subsurface layers. In this way, amore » new nitride-based epitaxial  surface layer is formed with hexagonal symmetry and a single in-plane crystal orientation.« less

High-resolution Auger-electron spectroscopy induced by positron annihilation on Fe, Ni, Cu, Zn, Pd, and Au

NASA Astrophysics Data System (ADS)

Hugenschmidt, C.; Mayer, J.; Schreckenbach, K.

2010-04-01

Positron annihilation induced Auger electron spectroscopy (PAES) enables almost background free, non-destructive surface analysis with high surface selectivity. The Auger-spectrometer at the high intense positron source NEPOMUC now allows to record positron annihilation induced Auger spectra within a short data acquisition time of 10-80 minutes. With a new hemispherical electron energy analyzer and due to the exceptional peak to noise ratio, we succeeded to measure Auger-transitions such as the M2,3V V double peak of nickel with high energy resolution. The relative Auger-electron intensities are obtained by the analysis of the recorded positron annihilation induced Auger spectra for the surfaces of Fe, Ni, Cu, Pd and Au. It is demonstrated, that high-resolution PAES allows to determine experimentally the relative surface core annihilation probability of various atomic levels.

Methods for computing internal flattening, with applications to the Earth's structure and geodynamics

NASA Astrophysics Data System (ADS)

Denis, C.; Amalvict, M.; Rogister, Y.; Tomecka-Suchoń, S.

1998-03-01

After general comments (Section 1) on using variational procedures to compute the oblateness of internal strata in the Earth and slowly rotating planets, we recall briefly some basic concepts about barotropic equilibrium figures (Section 2), and then proceed to discuss several accurate methods to derive the internal flattening. The algorithms given in Section 3 are based on the internal gravity field theory of Clairaut, Laplace and Lyapunov. They make explicit use of the concept of a level surface. The general formulation given here leads to a number of formulae which are of both theoretical and practical use in studying the Earth's structure, dynamics and rotational evolution. We provide exact solutions for the figure functions of three Earth models, and apply the formalism to yield curves for the internal flattening as a function of the spin frequency. Two more methods, which use the general deformation equations, are discussed in Section 4. The latter do not rely explicitly on the existence of level surfaces. They offer an alternative to the classical first-order internal field theory, and can actually be used to compute changes of the flattening on short timescales produced by variations in the LOD. For short durations, the Earth behaves elastically rather than hydrostatically. We discuss in some detail static deformations and Longman's static core paradox (Section 5), and demonstrate that in general no static solution exists for a realistic Earth model. In Section 6 we deal briefly with differential rotation occurring in cylindrical shells, and show why differential rotation of the inner core such as has been advocated recently is incompatible with the concept of level surfaces. In Section 7 we discuss first-order hydrostatic theory in relation to Earth structure, and show how to derive a consistent reference Earth model which is more suitable for geodynamical modelling than are modern Earth models such as 1066-A, PREM or CORE11. An important result is that a consistent application of hydrostatic theory leads to an inertia factor of about 0.332 instead of the value 0.3308 used until now. This change automatically brings `hydrostatic' values of the flattening, the dynamic shape factor and the precessional constant into much better agreement with their observed counterparts than has been assumed hitherto. Of course, we do not imply that non-hydrostatic effects are unimportant in modelling geodynamic processes. Finally, we discuss (Sections 7-8) some implications of our way of looking at things for Earth structure and some current problems of geodynamics. We suggest very significant changes for the structure of the core, in particular a strong reduction of the density jump at the inner core boundary. The theoretical value of the free core nutation period, which may be computed by means of our hydrostatic Earth models CGGM or PREMM, is in somewhat better agreement with the observed value than that based on PREM or 1066-A, although a significant residue remains. We attribute the latter to inadequate modelling of the deformation, and hence of the change in the inertia tensor, because the static deformation equations were used. We argue that non-hydrostatic effects, though present, cannot explain the large observed discrepancy of about 30 days.

Levoglucosan Levels in Alaskan Ice Cores as a Record of Past Wildfires

NASA Astrophysics Data System (ADS)

Dunham, M. E.; Osterberg, E. C.; Kehrwald, N. M.; Kennedy, J.; Ferris, D. G.

2017-12-01

Glaciers in southeast Alaska are significant contributors to global sea-level rise, and therefore understanding the mechanisms driving their recent mass loss is crucial for predicting future sea-level change. Fire activity in Alaska has increased dramatically during the last decade, adding a potential new source of light-absorbing organic material (soot) to the Juneau Icefield that can reduce albedo and enhance surface melt rates. The goal of this project is to create an accurate record of Alaskan wildfires to understand how Alaskan glacial mass balance is affected by the deposition of organic aerosols from wildfires. Previously, oxalate, ammonia, and potassium ion levels have been used as proxies for past wildfire activity, but these ions all have broader emission sources in addition to wildfires. Here we develop a record of past Alaskan fire events and climate from: (1) levels of a biomass burning indicator, levoglucosan, which only forms when cellulose is burned over 300 °C, (2) major ions including oxalate, ammonia, and potassium; (3) the number and size distribution of particles to quantify trace amounts of soot from wildfires; and (4) stable water isotope ratios as a proxy for past temperature in ice cores. We utilize a total of four shallow ice cores, ranging from 7 to 9 m in length, that were collected by a biogeochemistry team during the Juneau Icefield Research Program (JIRP) in 2016. Complications include our limited understanding of the conservation and degradation of levoglucosan over time or during the firnification process. We hypothesize that particle counts will be correlated with levoglucosan peaks, co-varying with wildfire frequency and temperatures over time. Based on previous work, we also expect to find correlations between levoglucosan and oxalate ion concentrations, even though oxalate ions have sources in addition to wildfire activity.

Recent geomagnetic secular variation from Swarm and ground observatories as estimated in the CHAOS-6 geomagnetic field model

NASA Astrophysics Data System (ADS)

Finlay, Christopher C.; Olsen, Nils; Kotsiaros, Stavros; Gillet, Nicolas; Tøffner-Clausen, Lars

2016-07-01

We use more than 2 years of magnetic data from the Swarm mission, and monthly means from 160 ground observatories as available in March 2016, to update the CHAOS time-dependent geomagnetic field model. The new model, CHAOS-6, provides information on time variations of the core-generated part of the Earth's magnetic field between 1999.0 and 2016.5. We present details of the secular variation (SV) and secular acceleration (SA) from CHAOS-6 at Earth's surface and downward continued to the core surface. At Earth's surface, we find evidence for positive acceleration of the field intensity in 2015 over a broad area around longitude 90°E that is also seen at ground observatories such as Novosibirsk. At the core surface, we are able to map the SV up to at least degree 16. The radial field SA at the core surface in 2015 is found to be largest at low latitudes under the India-South-East Asia region, under the region of northern South America, and at high northern latitudes under Alaska and Siberia. Surprisingly, there is also evidence for significant SA in the central Pacific region, for example near Hawaii where radial field SA is observed on either side of a jerk in 2014. On the other hand, little SV or SA has occurred over the past 17 years in the southern polar region. Inverting for a quasi-geostrophic core flow that accounts for this SV, we obtain a prominent planetary-scale, anti-cyclonic, gyre centred on the Atlantic hemisphere. We also find oscillations of non-axisymmetric, azimuthal, jets at low latitudes, for example close to 40°W, that may be responsible for localized SA oscillations. In addition to scalar data from Ørsted, CHAMP, SAC-C and Swarm, and vector data from Ørsted, CHAMP and Swarm, CHAOS-6 benefits from the inclusion of along-track differences of scalar and vector field data from both CHAMP and the three Swarm satellites, as well as east-west differences between the lower pair of Swarm satellites, Alpha and Charlie. Moreover, ground observatory SV estimates are fit to a Huber-weighted rms level of 3.1 nT/year for the eastward components and 3.8 and 3.7 nT/year for the vertical and southward components. We also present an update of the CHAOS high-degree lithospheric field, making use of along-track differences of CHAMP scalar and vector field data to produce a new static field model that agrees well with the MF7 field model out to degree 110.

X-ray photoemission spectroscopy of nonmetallic materials: Electronic structures of boron and BxOy

NASA Astrophysics Data System (ADS)

Ong, C. W.; Huang, H.; Zheng, B.; Kwok, R. W. M.; Hui, Y. Y.; Lau, W. M.

2004-04-01

Although an increasing volume of x-ray photoemission spectroscopic (XPS) data has been accumulated on boron and boron-rich compounds because of their unusual properties, including a unique three-center, two-electron bonding configuration, their common nonmetallic nature has been overlooked. Typically, the measured energy-state data are not clarified by surface Fermi level positions of these nonmetallic samples, which compromises the scientific contents of the data. In the present study, we revisited the XPS studies of sputter-cleaned β-rhombohedral boron (βr-B), the oxidized surface of βr-B, B6O pellet, and polished B2O3, to illustrate the impact and resolution of this scientific issue. These samples were chosen because βr-B is the most thermodynamically stable polytype of pure boron, B2O3 is its fully oxidized form, and B6O is the best known superhard family member of boron-rich compounds. From our XPS measurements, including those from a sputter-cleaned gold as a metal reference, we deduced that our βr-B had a surface Fermi level located at 0.7±0.1 eV from its valence-band maximum (VBM) (referred as EFL) and a binding energy for its B 1s core level at 187.2 eV from VBM (Eb,VBM). The latter attribute, unlike typical XPS binding energy data that are referenced to a sample-dependent Fermi level (Eb,FL), is immune from any uncertainties and variations arising from sample doping and surface charging. For bulk B2O3, we found an Eb,VBM for its B 1s core level at 190.5 eV and an Eb,FL at 193.6 eV. For our βr-B subjected to a surface oxidation treatment, an overlayer structure of ˜1.2 nm B2O3/˜2 nm B2O/B was found. By comparing the data from this sample and those from βr-B and bulk B2O3, we infer that the oxide overlayer carried some negative fixed charge and this induced on the semiconducting βr-B sample an upward surface band bending of ˜0.6 eV. As for our B6O sample, we found an EFL of ˜1.7 eV and two different chemical states having Eb,VBM of 185.4 and 187.2 eV, with the former belonging to boron with no oxygen neighbor and the latter to boron with an oxygen neighbor. The methodology in this work is universally applicable to all nonmetallic samples.

Hydrogeologic and chemical data for the O-Field area, Aberdeen Proving Ground, Maryland

USGS Publications Warehouse

Nemoff, P.R.; Vroblesky, D.A.

1989-01-01

O-Field, located at the Edgewood area of Aberdeen Proving Ground , Maryland, was periodically used for disposal of munitions, waste chemicals, and chemical-warfare agents from World War II through the 1950' s. This report includes various physical, geologic, chemical, and hydrologic data obtained from well-core, groundwater, surface water, and bottom-sediment sampling sites at and near the O-Field disposal area. The data are presented in tables and hydrographs. Three site-location maps are also included. Well-core data include lithologic logs for 11 well- cluster sites, grain-size distributions, various chemical characteristics, and confining unit characteristics. Groundwater data include groundwater chemistry, method blanks for volatile organic carbon, available data on volatile and base/neutral organics, and compilation of corresponding method blanks, chemical-warfare agents, explosive-related products, radionuclides, herbicides, and groundwater levels. Surface-water data include field-measured characteristics; concentrations of various inorganic constituents including arsenic; selected organic constituents with method blanks; detection limits of organics; and a compilation of information on corresponding acids, volatiles, and semivolatiles. Bottom- sediment data include inorganic properties and constituents; organic chemistry; detection limits for organic chemicals; a compilation of information on acids, volatiles, and semivolatiles; and method blanks corresponding to acids, volatiles, and semivolatiles. A set of 15 water- level hydrographs for the period March 1986 through September 1987 also is included in the report. (USGS)

High-level ab initio potential energy surface and dynamics of the F- + CH3I SN2 and proton-transfer reactions.

PubMed

Olasz, Balázs; Szabó, István; Czakó, Gábor

2017-04-01

Bimolecular nucleophilic substitution (S N 2) and proton transfer are fundamental processes in chemistry and F - + CH 3 I is an important prototype of these reactions. Here we develop the first full-dimensional ab initio analytical potential energy surface (PES) for the F - + CH 3 I system using a permutationally invariant fit of high-level composite energies obtained with the combination of the explicitly-correlated CCSD(T)-F12b method, the aug-cc-pVTZ basis, core electron correlation effects, and a relativistic effective core potential for iodine. The PES accurately describes the S N 2 channel producing I - + CH 3 F via Walden-inversion, front-side attack, and double-inversion pathways as well as the proton-transfer channel leading to HF + CH 2 I - . The relative energies of the stationary points on the PES agree well with the new explicitly-correlated all-electron CCSD(T)-F12b/QZ-quality benchmark values. Quasiclassical trajectory computations on the PES show that the proton transfer becomes significant at high collision energies and double-inversion as well as front-side attack trajectories can occur. The computed broad angular distributions and hot internal energy distributions indicate the dominance of indirect mechanisms at lower collision energies, which is confirmed by analyzing the integration time and leaving group velocity distributions. Comparison with available crossed-beam experiments shows usually good agreement.

Geomagnetic inverse problem and data assimilation: a progress report

NASA Astrophysics Data System (ADS)

Aubert, Julien; Fournier, Alexandre

2013-04-01

In this presentation I will present two studies recently undertaken by our group in an effort to bring the benefits of data assimilation to the study of Earth's magnetic field and the dynamics of its liquid iron core, where the geodynamo operates. In a first part I will focus on the geomagnetic inverse problem, which attempts to recover the fluid flow in the core from the temporal variation of the magnetic field (known as the secular variation). Geomagnetic data can be downward continued from the surface of the Earth down to the core-mantle boundary, but not further below, since the core is an electrical conductor. Historically, solutions to the geomagnetic inverse problem in such a sparsely observed system were thus found only for flow immediately below the core mantle boundary. We have recently shown that combining a numerical model of the geodynamo together with magnetic observations, through the use of Kalman filtering, now allows to present solutions for flow throughout the core. In a second part, I will present synthetic tests of sequential geomagnetic data assimilation aiming at evaluating the range at which the future of the geodynamo can be predicted, and our corresponding prospects to refine the current geomagnetic predictions. Fournier, Aubert, Thébault: Inference on core surface flow from observations and 3-D dynamo modelling, Geophys. J. Int. 186, 118-136, 2011, doi: 10.1111/j.1365-246X.2011.05037.x Aubert, Fournier: Inferring internal properties of Earth's core dynamics and their evolution from surface observations and a numerical geodynamo model, Nonlinear Proc. Geoph. 18, 657-674, 2011, doi:10.5194/npg-18-657-2011 Aubert: Flow throughout the Earth's core inverted from geomagnetic observations and numerical dynamo models, Geophys. J. Int., 2012, doi: 10.1093/gji/ggs051

The Replacement of 10 Non-Conserved Residues in the Core Protein of JFH-1 Hepatitis C Virus Improves Its Assembly and Secretion

PubMed Central

Etienne, Loïc; Blanchard, Emmanuelle; Boyer, Audrey; Desvignes, Virginie; Gaillard, Julien; Meunier, Jean-Christophe; Roingeard, Philippe; Hourioux, Christophe

2015-01-01

Hepatitis C virus (HCV) assembly is still poorly understood. It is thought that trafficking of the HCV core protein to the lipid droplet (LD) surface is essential for its multimerization and association with newly synthesized HCV RNA to form the viral nucleocapsid. We carried out a mapping analysis of several complete HCV genomes of all genotypes, and found that the genotype 2 JFH-1 core protein contained 10 residues different from those of other genotypes. The replacement of these 10 residues of the JFH-1 strain sequence with the most conserved residues deduced from sequence alignments greatly increased virus production. Confocal microscopy of the modified JFH-1 strain in cell culture showed that the mutated JFH-1 core protein, C10M, was present mostly at the endoplasmic reticulum (ER) membrane, but not at the surface of the LDs, even though its trafficking to these organelles was possible. The non-structural 5A protein of HCV was also redirected to ER membranes and colocalized with the C10M core protein. Using a Semliki forest virus vector to overproduce core protein, we demonstrated that the C10M core protein was able to form HCV-like particles, unlike the native JFH-1 core protein. Thus, the substitution of a few selected residues in the JFH-1 core protein modified the subcellular distribution and assembly properties of the protein. These findings suggest that the early steps of HCV assembly occur at the ER membrane rather than at the LD surface. The C10M-JFH-1 strain will be a valuable tool for further studies of HCV morphogenesis. PMID:26339783

Magnetohydrodynamic Convection in the Outer Core and its Geodynamic Consequences

NASA Technical Reports Server (NTRS)

Kuang, Weijia; Chao, Benjamin F.; Fang, Ming

2004-01-01

The Earth's fluid outer core is in vigorous convection through much of the Earth's history. In addition to generating and maintaining Earth s time-varying magnetic field (geodynamo), the core convection also generates mass redistribution in the core and a dynamical pressure field on the core-mantle boundary (CMB). All these shall result in various core-mantle interactions, and contribute to surface geodynamic observables. For example, electromagnetic core-mantle coupling arises from finite electrically conducting lower mantle; gravitational interaction occurs between the cores and the heterogeneous mantle; mechanical coupling may also occur when the CMB topography is aspherical. Besides changing the mantle rotation via the coupling torques, the mass-redistribution in the core shall produce a spatial-temporal gravity anomaly. Numerical modeling of the core dynamical processes contributes in several geophysical disciplines. It helps explain the physical causes of surface geodynamic observables via space geodetic techniques and other means, e.g. Earth's rotation variation on decadal time scales, and secular time-variable gravity. Conversely, identification of the sources of the observables can provide additional insights on the dynamics of the fluid core, leading to better constraints on the physics in the numerical modeling. In the past few years, our core dynamics modeling efforts, with respect to our MoSST model, have made significant progress in understanding individual geophysical consequences. However, integrated studies are desirable, not only because of more mature numerical core dynamics models, but also because of inter-correlation among the geophysical phenomena, e.g. mass redistribution in the outer core produces not only time-variable gravity, but also gravitational core-mantle coupling and thus the Earth's rotation variation. They are expected to further facilitate multidisciplinary studies of core dynamics and interactions of the core with other components of the Earth.

The impact of surface-polish on the angular and wavelength dependence of fiber focal ratio degradation

NASA Astrophysics Data System (ADS)

Eigenbrot, Arthur D.; Bershady, Matthew A.; Wood, Corey M.

2012-09-01

We present measurements of how multimode fiber focal-ratio degradation (FRD) and throughput vary with levels of fiber surface polish from 60 to 0.5 micron grit. Measurements used full-beam and laser injection methods at wavelengths between 0.4 and 0.8 microns on 17 meter lengths of Polymicro FBP 300 and 400 μm core fiber. Full-beam injection probed input focal-ratios between f/3 and f/13.5, while laser injection allowed us to isolate FRD at discrete injection angles up to 17 degrees (f/1.6 marginal ray). We find (1) FRD effects decrease as grit size decreases, with the largest gains in beam quality occurring at grit sizes above 5 μm (2) total throughput increases as grit size decreases, reaching 90% at 790 nm with the finest polishing levels; (3) total throughput is higher at redder wavelengths for coarser polishing grit, indicating surface-scattering as the primary source of loss. We also quantify the angular dependence of FRD as a function of polishing level. Our results indicate that a commonly adopted micro-bending model for FRD is a poor descriptor of the observed phenomenon.

Extensive Liquid Meltwater Storage in Firn Within the Greenland Ice Sheet

NASA Technical Reports Server (NTRS)

Forster, Richard R.; Box, Jason E.; vandenBroeke, Michael R.; Miege, Clement; Burgess, Evan W.; vanAngelen, Jan H.; Lenaerts, Jan T. M.; Koenig, Lora S.; Paden, John; Lewis, Cameron;

Effect of Surface Functionalization on Structural and Optical Properties of Luminescent LaF₃:Sm Nanoparticles.

PubMed

Ansari, Anees A

2018-02-01

Samarium (Sm3+)-doped LaF3 nanoparticles (NPs) subsequently encapsulated with inert crystalline LaF3 and amorphous silica layers were prepared by polyol and sol-gel chemical process, respectively. These surface modified core/shell/SiO2-nanostructured were characterized by X-ray diffraction (XRD), FE-transmission electron microscopy (TEM), thermal analysis, FTIR, UV/Vis absorption, bang gap energy and photoluminescence spectroscopy. The FETEM, EDX and FTIR spectral studies clearly revealed that the silica layer has been formed surrounding the core-NPs. Comparative spectral analysis indicated that core/shell/SiO2-NPs revealed high solubility in aqueous and non-aqueous solvents. The decrease in band gap energy after surface growth of an inert LaF3 and silica shells is directly correlated to the increase in grain size. On comparing the emission intensity, a significant enhancement was observed after inert layer coating, whereas, it suppress after silica encapsulation due to the non-radiative transitions. The increase luminescent intensity after inert shell growth indicates that a significant amount of non-radiative centers existing on the surface of core/shell nanoparticles can be eliminated by the shielding effect of LaF3 shells. These observed results indicate that the as-prepared core/shell/SiO2-NPs could be highly useful in broad photonic based applications such as optical sensor/optical bio-probe and light emitting diode.

Laser techniques for spectroscopy of core-excited atomic levels

NASA Technical Reports Server (NTRS)

Harris, S. E.; Young, J. F.; Falcone, R. W.; Rothenberg, J. E.; Willison, J. R.

1982-01-01

We discuss three techniques which allow the use of tunable lasers for high resolution and picosecond time scale spectroscopy of core-excited atomic levels. These are: anti-Stokes absorption spectroscopy, laser induced emission from metastable levels, and laser designation of selected core-excited levels.

Tandem Fusion of Hepatitis B Core Antigen Allows Assembly of Virus-Like Particles in Bacteria and Plants with Enhanced Capacity to Accommodate Foreign Proteins

PubMed Central

Peyret, Hadrien; Gehin, Annick; Thuenemann, Eva C.; Blond, Donatienne; El Turabi, Aadil; Beales, Lucy; Clarke, Dean; Gilbert, Robert J. C.; Fry, Elizabeth E.; Stuart, David I.; Holmes, Kris; Stonehouse, Nicola J.; Whelan, Mike; Rosenberg, William; Lomonossoff, George P.; Rowlands, David J.

2015-01-01

The core protein of the hepatitis B virus, HBcAg, assembles into highly immunogenic virus-like particles (HBc VLPs) when expressed in a variety of heterologous systems. Specifically, the major insertion region (MIR) on the HBcAg protein allows the insertion of foreign sequences, which are then exposed on the tips of surface spike structures on the outside of the assembled particle. Here, we present a novel strategy which aids the display of whole proteins on the surface of HBc particles. This strategy, named tandem core, is based on the production of the HBcAg dimer as a single polypeptide chain by tandem fusion of two HBcAg open reading frames. This allows the insertion of large heterologous sequences in only one of the two MIRs in each spike, without compromising VLP formation. We present the use of tandem core technology in both plant and bacterial expression systems. The results show that tandem core particles can be produced with unmodified MIRs, or with one MIR in each tandem dimer modified to contain the entire sequence of GFP or of a camelid nanobody. Both inserted proteins are correctly folded and the nanobody fused to the surface of the tandem core particle (which we name tandibody) retains the ability to bind to its cognate antigen. This technology paves the way for the display of natively folded proteins on the surface of HBc particles either through direct fusion or through non-covalent attachment via a nanobody. PMID:25830365

Comparison of predicted engine core noise with current and proposed aircraft noise certification requirements

NASA Technical Reports Server (NTRS)

Vonglahn, U. H.; Groesbeck, D. E.

1981-01-01

Predicted engine core noise levels are compared with measured total aircraft noise levels and with current and proposed federal noise certification requirements. Comparisons are made at the FAR-36 measuring stations and include consideration of both full- and cutback-power operation at takeoff. In general, core noise provides a barrier to achieving proposed EPA stage 5 noise levels for all types of aircraft. More specifically, core noise levels will limit further reductions in aircraft noise levels for current widebody commercial aircraft.

The surface stability of Cr 2O 3 (0 0 0 1)

DOE PAGES

Cao, Shi; Wu, Ning; Echtenkamp, William; ...

2015-05-28

The surface of chromia (Cr 2O 3) has a surface electronic structure distinct from the bulk and a packing density distinct from the bulk. More than a demarcation between the solid and the vacuum, the surface differs from the bulk of chromia, not just because of a partial occupancy of chromium sites, but also because of an increased number of unoccupied surface oxygen sites (vacancy sites), evident in angle-resolved core level photoemission. In spite of the structural differences that exist at the surface, there is, as yet, no evidence that these complications affect the surface Debye temperature beyond the mostmore » simple of assumptions regarding the lower coordination of the surface. Using low-energy electron diffraction (LEED), the effective surface Debye temperature (similar to 490 K) is found to be lower than the bulk (similar to 645 K) Debye temperature of Cr 2O 3(0 0 0 1). This surface effective Debye temperature, indicative of vibrations along the surface normal, uncorrected for anharmonic effects, has a value reduced from the effective bulk Debye temperature yet close to the value root 2 expected from a simple mean field argument.« less

Study of positron annihilation with core electrons at the clean and oxygen covered Ag(001) surface

NASA Astrophysics Data System (ADS)

Joglekar, P.; Shastry, K.; Olenga, A.; Fazleev, N. G.; Weiss, A. H.

2013-03-01

In this paper we present measurements of the energy spectrum of electrons emitted as a result of Positron Annihilation Induce Auger Electron Emission from a clean and oxygen covered Ag (100) surface using a series of incident beam energies ranging from 20 eV down to 2 eV. A peak was observed at ~ 40 eV corresponding to the N23VV Auger transition in agreement with previous PAES studies. Experimental results were investigated theoretically by calculations of positron states and annihilation probabilities of surface-trapped positrons with relevant core electrons at the clean and oxygen covered Ag(100) surface. An ab-initio investigation of stability and associated electronic properties of different adsorption phases of oxygen on Ag(100) has been performed on the basis of density functional theory and using DMOl3 code. The computed positron binding energy, positron surface state wave function, and positron annihilation probabilities of surface trapped positrons with relevant core electrons demonstrate their sensitivity to oxygen coverage, elemental content, atomic structure of the topmost layers of surfaces, and charge transfer effects. Theoretical results are compared with experimental data. This work was supported in part by the National Science Foundation Grant # DMR-0907679.

Multi-modality nanoparticles having optically responsive shape

DOEpatents

Chen, Fanqing; Bouchard, Louis-Serge

2015-05-19

In certain embodiments novel nanoparticles (nanowontons) are provided that are suitable for multimodal imaging and/or therapy. In one embodiment, the nanoparticles include a first biocompatible (e.g., gold) layer, an inner core layer (e.g., a non-biocompatible material), and a biocompatible (e.g., gold) layer. The first gold layer includes a concave surface that forms a first outer surface of the layered nanoparticle. The second gold layer includes a convex surface that forms a second outer surface of the layered nanoparticle. The first and second gold layers encapsulate the inner core material layer. Methods of fabricating such nanoparticles are also provided.

[Three-dimensional computer aided design for individualized post-and-core restoration].

PubMed

Gu, Xiao-yu; Wang, Ya-ping; Wang, Yong; Lü, Pei-jun

2009-10-01

To develop a method of three-dimensional computer aided design (CAD) of post-and-core restoration. Two plaster casts with extracted natural teeth were used in this study. The extracted teeth were prepared and scanned using tomography method to obtain three-dimensional digitalized models. According to the basic rules of post-and-core design, posts, cores and cavity surfaces of the teeth were designed using the tools for processing point clouds, curves and surfaces on the forward engineering software of Tanglong prosthodontic system. Then three-dimensional figures of the final restorations were corrected according to the configurations of anterior teeth, premolars and molars respectively. Computer aided design of 14 post-and-core restorations were finished, and good fitness between the restoration and the three-dimensional digital models were obtained. Appropriate retention forms and enough spaces for the full crown restorations can be obtained through this method. The CAD of three-dimensional figures of the post-and-core restorations can fulfill clinical requirements. Therefore they can be used in computer-aided manufacture (CAM) of post-and-core restorations.

Rotation profile flattening and toroidal flow shear reversal due to the coupling of magnetic islands in tokamaks

DOE PAGES

Tobias, B.; Chen, M.; Classen, I. G. J.; ...

2016-04-15

The electromagnetic coupling of helical modes, including those having different toroidal mode numbers, modifies the distribution of toroidal angular momentum in tokamak discharges. This can have deleterious effects on other transport channels as well as on magnetohydrodynamic (MHD) stability and disruptivity. At low levels of externally injected momentum, the coupling of core-localized modes initiates a chain of events, whereby flattening of the core rotation profile inside successive rational surfaces leads to the onset of a large m/n = 2/1 tearing mode and locked-mode disruption. Furthermore, with increased torque from neutral beam injection, neoclassical tearing modes in the core may phase-lockmore » to each other without locking to external fields or structures that are stationary in the laboratory frame. The dynamic processes observed in these cases are in general agreement with theory, and detailed diagnosis allows for momentum transport analysis to be performed, revealing a significant torque density that peaks near the 2/1 rational surface. However, as the coupled rational surfaces are brought closer together by reducing q95, additional momentum transport in excess of that required to attain a phase-locked state is sometimes observed. Rather than maintaining zero differential rotation (as is predicted to be dynamically stable by single-fluid, resistive MHD theory), these discharges develop hollow toroidal plasma fluid rotation profiles with reversed plasma flow shear in the region between the m/n = 3/2 and 2/1 islands. Additional forces expressed in this state are not readily accounted for, and therefore, analysis of these data highlights the impact of mode coupling on torque balance and the challenges associated with predicting the rotation dynamics of a fusion reactor-a key issue for ITER. Published by AIP Publishing.« less

Rotation profile flattening and toroidal flow shear reversal due to the coupling of magnetic islands in tokamaks

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

Tobias, B.; Grierson, B. A.; Okabayashi, M.

2016-05-15

The electromagnetic coupling of helical modes, even those having different toroidal mode numbers, modifies the distribution of toroidal angular momentum in tokamak discharges. This can have deleterious effects on other transport channels as well as on magnetohydrodynamic (MHD) stability and disruptivity. At low levels of externally injected momentum, the coupling of core-localized modes initiates a chain of events, whereby flattening of the core rotation profile inside successive rational surfaces leads to the onset of a large m/n = 2/1 tearing mode and locked-mode disruption. With increased torque from neutral beam injection, neoclassical tearing modes in the core may phase-lock to each othermore » without locking to external fields or structures that are stationary in the laboratory frame. The dynamic processes observed in these cases are in general agreement with theory, and detailed diagnosis allows for momentum transport analysis to be performed, revealing a significant torque density that peaks near the 2/1 rational surface. However, as the coupled rational surfaces are brought closer together by reducing q{sub 95}, additional momentum transport in excess of that required to attain a phase-locked state is sometimes observed. Rather than maintaining zero differential rotation (as is predicted to be dynamically stable by single-fluid, resistive MHD theory), these discharges develop hollow toroidal plasma fluid rotation profiles with reversed plasma flow shear in the region between the m/n = 3/2 and 2/1 islands. The additional forces expressed in this state are not readily accounted for, and therefore, analysis of these data highlights the impact of mode coupling on torque balance and the challenges associated with predicting the rotation dynamics of a fusion reactor—a key issue for ITER.« less

Results from Geothermal Logging, Air and Core-Water Chemistry Sampling, Air Injection Testing and Tracer Testing in the Northern Ghost Dance Fault, YUCCA Mountain, Nevada, November 1996 to August 1998

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

Lecain, G.D.; Anna, L.O.; Fahy, M.F.

1998-08-01

Geothermal logging, air and core-water chemistry sampling, air-injection testing, and tracer testing were done in the northern Ghost Dance Fault at Yucca Mountain, Nevada, from November 1996 to August 1998. The study was done by the U.S. Geological Survey, in cooperation with the U.S. Department of Energy. The fault-testing drill room and test boreholes were located in the crystal-poor, middle nonlithophysal zone of the Topopah Spring Tuff, a tuff deposit of Miocene age. The drill room is located off the Yucca Mountain underground Exploratory Studies Facility at about 230 meters below ground surface. Borehole geothermal logging identified a temperature decreasemore » of 0.1 degree Celsius near the Ghost Dance Fault. The temperature decrease could indicate movement of cooler air or water, or both, down the fault, or it may be due to drilling-induced evaporative or adiabatic cooling. In-situ pneumatic pressure monitoring indicated that barometric pressure changes were transmitted from the ground surface to depth through the Ghost Dance Fault. Values of carbon dioxide and delta carbon-13 from gas samples indicated that air from the underground drill room had penetrated the tuff, supporting the concept of a well-developed fracture system. Uncorrected carbon-14-age estimates from gas samples ranged from 2,400 to 4,500 years. Tritium levels in borehole core water indicated that the fault may have been a conduit for the transport of water from the ground surface to depth during the last 100 years.« less

Writing Bragg Gratings in Multicore Fibers.

PubMed

Lindley, Emma Y; Min, Seong-Sik; Leon-Saval, Sergio G; Cvetojevic, Nick; Lawrence, Jon; Ellis, Simon C; Bland-Hawthorn, Joss

2016-04-20

Fiber Bragg gratings in multicore fibers can be used as compact and robust filters in astronomical and other research and commercial applications. Strong suppression at a single wavelength requires that all cores have matching transmission profiles. These gratings cannot be inscribed using the same method as for single-core fibers because the curved surface of the cladding acts as a lens, focusing the incoming UV laser beam and causing variations in exposure between cores. Therefore we use an additional optical element to ensure that the beam shape does not change while passing through the cross-section of the multicore fiber. This consists of a glass capillary tube which has been polished flat on one side, which is then placed over the section of the fiber to be inscribed. The laser beam enters the fiber through the flat surface of the capillary tube and hence maintains its original dimensions. This paper demonstrates the improvements in core-to-core uniformity for a 7-core fiber using this method. The technique can be generalized to larger multicore fibers.

Writing Bragg Gratings in Multicore Fibers

PubMed Central

Lindley, Emma Y.; Min, Seong-sik; Leon-Saval, Sergio G.; Cvetojevic, Nick; Lawrence, Jon; Ellis, Simon C.; Bland-Hawthorn, Joss

2016-01-01

Fiber Bragg gratings in multicore fibers can be used as compact and robust filters in astronomical and other research and commercial applications. Strong suppression at a single wavelength requires that all cores have matching transmission profiles. These gratings cannot be inscribed using the same method as for single-core fibers because the curved surface of the cladding acts as a lens, focusing the incoming UV laser beam and causing variations in exposure between cores. Therefore we use an additional optical element to ensure that the beam shape does not change while passing through the cross-section of the multicore fiber. This consists of a glass capillary tube which has been polished flat on one side, which is then placed over the section of the fiber to be inscribed. The laser beam enters the fiber through the flat surface of the capillary tube and hence maintains its original dimensions. This paper demonstrates the improvements in core-to-core uniformity for a 7-core fiber using this method. The technique can be generalized to larger multicore fibers. PMID:27167576

Evolution of silver/gold triangular nanoframes from prismatic silver/gold core/shell nanostructures and their SERS properties

NASA Astrophysics Data System (ADS)

Parthiban, P.; Sakar, M.; Balakumar, S.

2013-02-01

We report the evolution of Ag/Au triangular nanoframes from nano core/shell of Ag/Au and their surface enhanced Raman scattering (SERS) properties. The Ag/Au prismatic core/shell nanostructures were synthesized using chemical reduction method. It was observed that, on the addition of excess gold chloride (HAuCl4) solution, the morphology of nano core/shell was changed to alloy like triangular nanoframes. Accordingly, a shift was found towards higher wavelengths in the UV-Visible absorption peaks of Ag/Au nanoframes compare to Ag/Au nano core/shell. Consequently, the SERS effect of these Ag/Au anisotropic nanostructures were studied on methylene blue. The Ag/Au alloy like prismatic nanoframes showed improved SERS effect than that of prismatic core/shell nanostructures. The experimental findings were revealed that the improved SERS effect could be resulted from the enhanced surface plasmon resonance (SPR) due to the alloy like construction of Ag/Au system.

Platinum-coated non-noble metal-noble metal core-shell electrocatalysts

DOEpatents

Adzic, Radoslav; Zhang, Junliang; Mo, Yibo; Vukmirovic, Miomir

2015-04-14

Core-shell particles encapsulated by a thin film of a catalytically active metal are described. The particles are preferably nanoparticles comprising a non-noble core with a noble metal shell which preferably do not include Pt. The non-noble metal-noble metal core-shell nanoparticles are encapsulated by a catalytically active metal which is preferably Pt. The core-shell nanoparticles are preferably formed by prolonged elevated-temperature annealing of nanoparticle alloys in an inert environment. This causes the noble metal component to surface segregate and form an atomically thin shell. The Pt overlayer is formed by a process involving the underpotential deposition of a monolayer of a non-noble metal followed by immersion in a solution comprising a Pt salt. A thin Pt layer forms via the galvanic displacement of non-noble surface atoms by more noble Pt atoms in the salt. The overall process is a robust and cost-efficient method for forming Pt-coated non-noble metal-noble metal core-shell nanoparticles.

New technique for the direct measurement of core noise from aircraft engines

NASA Technical Reports Server (NTRS)

Krejsa, E. A.

1981-01-01

A new technique is presented for directly measuring the core noise levels from gas turbine aircraft engines. The technique requires that fluctuating pressures be measured in the far-field and at two locations within the engine core. The cross-spectra of these measurements are used to determine the levels of the far-field noise that propagated from the engine core. The technique makes it possible to measure core noise levels even when other noise sources dominate. The technique was applied to signals measured from an AVCO Lycoming YF102 turbofan engine. Core noise levels as a function of frequency and radiation angle were measured and are presented over a range of power settings.

Transmission electron microscopy and ab initio calculations to relate interfacial intermixing and the magnetism of core/shell nanoparticles

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

Chi, C.-C.; Hsiao, C.-H.; Ouyang, Chuenhou, E-mail: houyang@mx.nthu.edu.tw

2015-05-07

Significant efforts towards understanding bi-magnetic core-shell nanoparticles are underway currently as they provide a pathway towards properties unavailable with single-phased systems. Recently, we have demonstrated that the magnetism of γ-Fe2O3/CoO core-shell nanoparticles, in particular, at high temperatures, originates essentially from an interfacial doped iron-oxide layer that is formed by the migration of Co{sup 2+} from the CoO shell into the surface layers of the γ-Fe2O3 core [Skoropata et al., Phys. Rev. B 89, 024410 (2014)]. To examine directly the nature of the intermixed layer, we have used high-resolution transmission electron microscopy (HRTEM) and first-principles calculations to examine the impact ofmore » the core-shell intermixing at the atomic level. By analyzing the HRTEM images and energy dispersive spectra, the level and nature of intermixing was confirmed, mainly as doping of Co into the octahedral site vacancies of γ-Fe2O3. The average Co doping depths for different processing temperatures (150 °C and 235 °C) were 0.56 nm and 0.78 nm (determined to within 5% through simulation), respectively, establishing that the amount of core-shell intermixing can be altered purposefully with an appropriate change in synthesis conditions. Through first-principles calculations, we find that the intermixing phase of γ-Fe2O3 with Co doping is ferromagnetic, with even higher magnetization as compared to that of pure γ-Fe2O3. In addition, we show that Co doping into different octahedral sites can cause different magnetizations. This was reflected in a change in overall nanoparticle magnetization, where we observed a 25% reduction in magnetization for the 235 °C versus the 150 °C sample, despite a thicker intermixed layer.« less

Coring the deep critical zone in the Jemez River Basin Critical Zone Observatory, Valles Caldera National Preserve, Northern New Mexico

NASA Astrophysics Data System (ADS)

Moravec, B. G.; White, A. M.; Paras, B.; Sanchez, A.; McGuffy, C.; Fairbanks, D.; McIntosh, J. C.; Pelletier, J. D.; Gallery, R. E.; Rasmussen, C.; Carr, B.; Holbrook, W. S.; Chorover, J.

2016-12-01

The Critical Zone (CZ) is the focus of current interdisciplinary Earth surface science research that aims to describe the interactions between geological and biological processes that influence ecosystem function, soil formation, nutrient and carbon cycling, hydrologic partitioning, biological activity and diversity, and mineral weathering. Prior research at the Catalina-Jemez (C-J) CZO has focused on the CZ near-surface, including remote sensing, and sampling/analysis of vegetation and soil microbiota, soils and saprolite, and surface water. However, the extent to which weathering, water/rock interaction, and solute mobility along flowpaths in the deep CZ respond to near surface CZ processes (i.e. water, energy, and mass fluxes) is not well understood. The goal of the present research is to understand depth-dependent trends in weathering dynamics from the mobile soil to unweathered bedrock in relation to landscape position (hillslope aspect and downgradient hollow). We used diamond core drilling techniques to excavate three boreholes to depths of 18.9, 41.8, and 46.3 meters in an instrumented forested sub-catchment of the C-J CZO in northern New Mexico. Here we present field methodology and preliminary data collected during the field campaign conducted during summer 2016. Element concentrations were measured during core extractions using portable X-ray fluorescence (XRF), which was subsequently validated against bench-scale XRF. Depth-dependent trends in both regolith depth and chemical depletion patterns show significant variation with landscape position. All three boreholes show complex weathering profiles with differences potentially due to textural controls on weathering, development of preferential flowpaths, and differing hydrologic base levels. Preliminary data indicate that chemical depletion patterns are not monotonic, but rather comprise large excursions that are being investigated for their relation to variation in local mineralogical composition and incongruent weathering reactions.

Fabrication of Cu-Ag core-shell bimetallic superfine powders by eco-friendly reagents and structures characterization

NASA Astrophysics Data System (ADS)

Zhao, Jun; Zhang, Dongming; Zhao, Jie

2011-09-01

Superfine bimetallic Cu-Ag core-shell powders were synthesized by reduction of copper sulfate pentahydrate and silver nitrate with eco-friendly ascorbic acid as a reducing agent and cyclodextrins as a protective agent in an aqueous system. The influence of Ag/Cu ratio on coatings was investigated. Ag was homogeneously distributed on the surface of Cu particles at a mole ratio of Ag/Cu=1. FE-SEM showed an uniformity of Ag coatings on Cu particles. Antioxidation of Cu particles was improved by increasing Ag/Cu ratio. TEM-EDX and UV-vis spectra also revealed that Cu cores were covered by Ag nanoshells on the whole. The surface composition analysis by XPS indicated that only small parts of Cu atoms in the surface were oxidized. It was noted that the hindrance of cyclodextrins chemisorbed on particles plays an important role in forming high quality and good dispersity Cu-Ag (Cu@Ag) core-shell powders.

Analysis of loss-of-coolant accident for a fast-spectrum lithium-cooled nuclear reactor for space-power applications

NASA Technical Reports Server (NTRS)

Turney, G. E.; Petrik, E. J.; Kieffer, A. W.

1972-01-01

A two-dimensional, transient, heat-transfer analysis was made to determine the temperature response in the core of a conceptual space-power nuclear reactor following a total loss of reactor coolant. With loss of coolant from the reactor, the controlling mode of heat transfer is thermal radiation. In one of the schemes considered for removing decay heat from the core, it was assumed that the 4 pi shield which surrounds the core acts as a constant-temperature sink (temperature, 700 K) for absorption of thermal radiation from the core. Results based on this scheme of heat removal show that melting of fuel in the core is possible only when the emissivity of the heat-radiating surfaces in the core is less than about 0.40. In another scheme for removing the afterheat, the core centerline fuel pin was replaced by a redundant, constant temperature, coolant channel. Based on an emissivity of 0.20 for all material surfaces in the core, the calculated maximum fuel temperature for this scheme of heat removal was 2840 K, or about 90 K less than the melting temperature of the UN fuel.

Laser ablation of dental tissues with picosecond pulses of 1.06-microm radiation transmitted through a hollow-core photonic-crystal fiber.

PubMed

Konorov, Stanislav O; Mitrokhin, Vladimir P; Fedotov, Andrei B; Sidorov-Biryukov, Dmitrii A; Beloglazov, Valentin I; Skibina, Nina B; Shcherbakov, Andrei V; Wintner, Ernst; Scalora, Michael; Zheltikov, Aleksei M

2004-04-10

Sequences of picosecond pulses of 1.06-microm Nd:YAG laser radiation with a total energy of approximately 2 mJ are transmitted through a hollow-core photonic-crystal fiber with a core diameter of approximately 14 microm and are focused onto a tooth's surface in vitro to ablate dental tissue. The hollow-core photonic-crystal fiber is shown to support the single-fundamental-mode regime for 1.06-microm laser radiation, serving as a spatial filter and allowing the laser beam's quality to be substantially improved. The same fiber is used to transmit emission from plasmas produced by laser pulses onto the tooth's surface in the backward direction for detection and optical diagnostics.

Methods for computing comet core temperatures

NASA Astrophysics Data System (ADS)

McKay, C. P.; Squyres, S. W.; Reynolds, R. T.

1986-06-01

The temperature profile within the comet nucleus provides the key to an understanding of the history of the volatiles within a comet. Certain difficulties arise in connection with current cometary temperature models. It is shown that the constraint of zero net heat flow can be used to derive general analytical expressions which will allow for the determination of comet core temperature for a spherically symmetric comet, taking into account information about the surface temperature and the thermal conductivity. The obtained results are compared with the expression for comet core temperatures considered by Klinger (1981). Attention is given to analytical results, an example case, and numerical models. The formalization developed makes it possible to determine the core temperature on the basis of the numerical models of the surface temperature.

Understanding the Thermal Stability of Palladium-Platinum Core-Shell Nanocrystals by In Situ Transmission Electron Microscopy and Density Functional Theory.

PubMed

Vara, Madeline; Roling, Luke T; Wang, Xue; Elnabawy, Ahmed O; Hood, Zachary D; Chi, Miaofang; Mavrikakis, Manos; Xia, Younan

2017-05-23

Core-shell nanocrystals offer many advantages for heterogeneous catalysis, including precise control over both the surface structure and composition, as well as reduction in loading for rare and costly metals. Although many catalytic processes are operated at elevated temperatures, the adverse impacts of heating on the shape and structure of core-shell nanocrystals are yet to be understood. In this work, we used ex situ heating experiments to demonstrate that Pd@Pt 4L core-shell nanoscale cubes and octahedra are promising for catalytic applications at temperatures up to 400 °C. We also used in situ transmission electron microscopy to monitor the thermal stability of the core-shell nanocrystals in real time. Our results demonstrate a facet dependence for the thermal stability in terms of shape and composition. Specifically, the cubes enclosed by {100} facets readily deform shape at a temperature 300 °C lower than that of the octahedral counterparts enclosed by {111} facets. A reversed trend is observed for composition, as alloying between the Pd core and the Pt shell of an octahedron occurs at a temperature 200 °C lower than that for the cubic counterpart. Density functional theory calculations provide atomic-level explanations for the experimentally observed behaviors, demonstrating that the barriers for edge reconstruction determine the relative ease of shape deformation for cubes compared to octahedra. The opposite trend for alloying of the core-shell structure can be attributed to a higher propensity for subsurface Pt vacancy formation in octahedra than in cubes.

Disentangling atomic-layer-specific x-ray absorption spectra by Auger electron diffraction spectroscopy

NASA Astrophysics Data System (ADS)

Matsui, Fumihiko; Matsushita, Tomohiro; Kato, Yukako; Hashimoto, Mie; Daimon, Hiroshi

2009-11-01

In order to investigate the electronic and magnetic structures of each atomic layer at subsurface, we have proposed a new method, Auger electron diffraction spectroscopy, which is the combination of x-ray absorption spectroscopy (XAS) and Auger electron diffraction (AED) techniques. We have measured a series of Ni LMM AED patterns of the Ni film grown on Cu(001) surface for various thicknesses. Then we deduced a set of atomic-layer-specific AED patterns in a numerical way. Furthermore, we developed an algorithm to disentangle XANES spectra from different atomic layers using these atomic-layer-specific AED patterns. Surface and subsurface core level shift were determined for each atomic layer.

Mn-silicide nanostructures aligned on massively parallel silicon nano-ribbons

NASA Astrophysics Data System (ADS)

De Padova, Paola; Ottaviani, Carlo; Ronci, Fabio; Colonna, Stefano; Olivieri, Bruno; Quaresima, Claudio; Cricenti, Antonio; Dávila, Maria E.; Hennies, Franz; Pietzsch, Annette; Shariati, Nina; Le Lay, Guy

2013-01-01

The growth of Mn nanostructures on a 1D grating of silicon nano-ribbons is investigated at atomic scale by means of scanning tunneling microscopy, low energy electron diffraction and core level photoelectron spectroscopy. The grating of silicon nano-ribbons represents an atomic scale template that can be used in a surface-driven route to control the combination of Si with Mn in the development of novel materials for spintronics devices. The Mn atoms show a preferential adsorption site on silicon atoms, forming one-dimensional nanostructures. They are parallel oriented with respect to the surface Si array, which probably predetermines the diffusion pathways of the Mn atoms during the process of nanostructure formation.

Mn-silicide nanostructures aligned on massively parallel silicon nano-ribbons.

PubMed

De Padova, Paola; Ottaviani, Carlo; Ronci, Fabio; Colonna, Stefano; Olivieri, Bruno; Quaresima, Claudio; Cricenti, Antonio; Dávila, Maria E; Hennies, Franz; Pietzsch, Annette; Shariati, Nina; Le Lay, Guy

2013-01-09

The growth of Mn nanostructures on a 1D grating of silicon nano-ribbons is investigated at atomic scale by means of scanning tunneling microscopy, low energy electron diffraction and core level photoelectron spectroscopy. The grating of silicon nano-ribbons represents an atomic scale template that can be used in a surface-driven route to control the combination of Si with Mn in the development of novel materials for spintronics devices. The Mn atoms show a preferential adsorption site on silicon atoms, forming one-dimensional nanostructures. They are parallel oriented with respect to the surface Si array, which probably predetermines the diffusion pathways of the Mn atoms during the process of nanostructure formation.

Geologic Map of the Poverty Bay 7.5' quadrangle, King and Pierce counties, Washington

USGS Publications Warehouse

Booth, Derek B.; Waldron, H.H.; Troost, K.G.

2004-01-01

The Poverty Bay quadrangle lies near the center of the region?s intensively developing urban core. Less than 20 km north lies the city of Seattle; downtown Tacoma lies just southwest of the quadrangle. The map area expresses much of the tremendous range of Quaternary environments and deposits found throughout the central Puget Lowland. Much of the ground surface is mantled by a rolling surface of glacial till deposited during the last occupation of the Puget Lowland by a great continental ice sheet about 14,000 years ago. A complex sequence of older unconsolidated sediments extends far below sea level across most of the quadrangle, with no bedrock exposures at all.

One-pot synthesis of iniferter-bound polystyrene core nanoparticles for the controlled grafting of multilayer shells

NASA Astrophysics Data System (ADS)

Marchyk, Nataliya; Maximilien, Jacqueline; Beyazit, Selim; Haupt, Karsten; Sum Bui, Bernadette Tse

2014-02-01

A novel approach using one-pot synthesis for the production of uniform, iniferter-bound polystyrene core nanoparticles of size 30-40 nm is described. Conventional oil-in-water emulsion polymerisation of styrene and divinylbenzene, combining a hybrid initiation system (thermal and UV), triggered sequentially, was employed to form the surface-bound thiocarbamate iniferters in situ. The iniferter cores were then used as seeds for re-initiating further polymerisation by UV irradiation to produce water-compatible core-shell nanoparticles. Grafting of various shell-types is demonstrated: linear polymers of poly(N-isopropylacrylamide) brushes, crosslinked polymers bearing different surface charges and molecularly imprinted polymers. The shell thickness was readily tuned by varying the monomers' concentration and polymerisation time. Our method is straightforward and in addition, gives access to the preparation of fluorescent seeds and the possibility of grafting nanosized multiple shells. The core-shell nanoparticles were fully characterised by dynamic light scattering, transmission electron microscopy, Fourier transform infrared spectroscopy and microelemental analysis.A novel approach using one-pot synthesis for the production of uniform, iniferter-bound polystyrene core nanoparticles of size 30-40 nm is described. Conventional oil-in-water emulsion polymerisation of styrene and divinylbenzene, combining a hybrid initiation system (thermal and UV), triggered sequentially, was employed to form the surface-bound thiocarbamate iniferters in situ. The iniferter cores were then used as seeds for re-initiating further polymerisation by UV irradiation to produce water-compatible core-shell nanoparticles. Grafting of various shell-types is demonstrated: linear polymers of poly(N-isopropylacrylamide) brushes, crosslinked polymers bearing different surface charges and molecularly imprinted polymers. The shell thickness was readily tuned by varying the monomers' concentration and polymerisation time. Our method is straightforward and in addition, gives access to the preparation of fluorescent seeds and the possibility of grafting nanosized multiple shells. The core-shell nanoparticles were fully characterised by dynamic light scattering, transmission electron microscopy, Fourier transform infrared spectroscopy and microelemental analysis. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr05295h

Logging-while-coring method and apparatus

DOEpatents

Goldberg, David S.; Myers, Gregory J.

2007-11-13

A method and apparatus for downhole coring while receiving logging-while-drilling tool data. The apparatus includes core collar and a retrievable core barrel. The retrievable core barrel receives core from a borehole which is sent to the surface for analysis via wireline and latching tool The core collar includes logging-while-drilling tools for the simultaneous measurement of formation properties during the core excavation process. Examples of logging-while-drilling tools include nuclear sensors, resistivity sensors, gamma ray sensors, and bit resistivity sensors. The disclosed method allows for precise core-log depth calibration and core orientation within a single borehole, and without at pipe trip, providing both time saving and unique scientific advantages.

Logging-while-coring method and apparatus

DOEpatents

Goldberg, David S.; Myers, Gregory J.

2007-01-30

A method and apparatus for downhole coring while receiving logging-while-drilling tool data. The apparatus includes core collar and a retrievable core barrel. The retrievable core barrel receives core from a borehole which is sent to the surface for analysis via wireline and latching tool The core collar includes logging-while-drilling tools for the simultaneous measurement of formation properties during the core excavation process. Examples of logging-while-drilling tools include nuclear sensors, resistivity sensors, gamma ray sensors, and bit resistivity sensors. The disclosed method allows for precise core-log depth calibration and core orientation within a single borehole, and without at pipe trip, providing both time saving and unique scientific advantages.

First investigations of an ice core from Eisriesenwelt cave (Austria)

NASA Astrophysics Data System (ADS)

May, B.; Spötl, C.; Wagenbach, D.; Dublyansky, Y.; Liebl, J.

2010-09-01

Investigations into the genesis and dynamical properties of cave ice are essential for assessing the climate significance of these underground glaciers. We drilled an ice core through a 7.1 m thick ice body filling a large cavern of the dynamic ice cave Eisenriesenwelt (Austria). In addition to visual core inspections, quasi-continuous measurements at 2 cm resolution comprised particulate matter, stable water isotope (δ18O, δD) and electrolytic conductivity profiles supplemented by specifically selected samples analysed for tritium and radiocarbon. We found that recent ablation led to an almost complete loss of bomb derived tritium removing any ice accumulated, since at least, the early fifties leaving the actual ice surface even below the natural tritium level. The small particulate organic masses made radiocarbon dating inconclusive, though a crude estimate gave a maximum ice age in the order of several thousand years. The visual stratigraphy and all investigated parameters showed a clear dichotomy between the upper 4 m and the bottom 3 m of the core, which points to a substantial change in the ice formation process. Main features of the core comprise the changing appearance and composition of distinct cyro-calcite layers, a extremely low total ion content and a surprisingly high variability of the isotope signature. Co-isotope evaluation (δD versus δ18O) of the core in comparison with data from precipitation and karst spring water clearly indicate that ice formation is governed by (slow) freezing of dripping water.

First investigations of an ice core from Eisriesenwelt cave (Austria)

NASA Astrophysics Data System (ADS)

May, B.; Spötl, C.; Wagenbach, D.; Dublyansky, Y.; Liebl, J.

2011-02-01

Investigations into the genesis and dynamical properties of cave ice are essential for assessing the climate significance of these underground glaciers. We drilled an ice core through a 7.1 m-thick ice body filling a large cavern of the dynamic ice cave Eisenriesenwelt (Austria). In addition to visual core inspections, quasi-continuous measurements at 2 cm resolution comprised particulate matter, stable water isotope (δ18O, δD) and electrolytic conductivity profiles supplemented by specifically selected samples analyzed for tritium and radiocarbon. We found that recent ablation led to an almost complete loss of bomb-derived tritium removing any ice accumulated since, at least, the early fifties leaving the actual ice surface even below the natural tritium level. The small particulate organic masses rendered radiocarbon dating inconclusive, though a crude estimate gave a basal ice age in the order of several thousand years. The visual stratigraphy and all investigated parameters showed a clear dichotomy between the upper 2 m and the bottom 3 m of the core, which points to a substantial change in the ice formation process. Main features of the core comprise the changing appearance and composition of distinct cryocalcite layers, extremely low total ion content and a surprisingly high variability of the isotope signature. Co-isotope evaluation (δD versus δ18O) of the core in comparison with data from precipitation and karst spring water clearly indicate that ice formation is governed by (slow) freezing of dripping water.

Effect of surface treatments on the bond strength of CAD/CAM fiberglass posts

PubMed Central

Garcia, Paula-Pontes; da Costa, Rogério-Goulart; Garcia, André-Vivan; Gonzaga, Carla-Castiglia; da Cunha, Leonardo-Fernandes; Rezende, Carlos-Eduardo-Edwards

2018-01-01

Background There is no ideal protocol for the surface treatment of fiber posts, especially when using a computer-aided design/computer-aided manufacturing (CAD/CAM) experimental fiberglass block. The purpose of this study was to evaluate the bond strength of a CAD/CAM customized glass fiber post and core after applying different surface treatment techniques. Material and Methods Forty premolars were prepared to receive a customized CAD/CAM glass-fiber post and core obtained from an experimental block of glass fiber and epoxy resin. The specimens were randomly distributed in 4 groups (n=10) according to the post and core surface treatment: ETH - 70% ethanol; HP - 24% hydrogen peroxide for 1 minute; ETH/S - 70% ethanol + silane; HP/S - 24% hydrogen peroxide + silane. The universal adhesive containing silane was applied on the posts and prepared post spaces in all groups. The posts were cemented using dual cure resin cement. The specimens were stored in distilled water at 37°C for 24 h, cut (two slices of 1 mm for each root third - coronal, middle, and apical) and subjected to push-out test (0.5 mm/min). Data was subjected to two-way ANOVA (surface treatment and root third) and Tukey’s test (α=0,05). Results There was no significant difference of bond strength values among groups, regardless the surface treatment (p >0.05). There was significant difference on bond strength values for the different root thirds (p<0.05) (coronal>middle=apical). Conclusions The different surface treatment and application of additional silane in the CAD/CAM customized glass-fiber post and core does not interfere on bond strength values. The root dentin third interfered on the bond strength, with higher values for the coronal third. Key words:Post and core technique, cad/cam, shear strength, hydrogen peroxide. PMID:29930778

Importance of core electrostatic properties on the electrophoresis of a soft particle

NASA Astrophysics Data System (ADS)

De, Simanta; Bhattacharyya, Somnath; Gopmandal, Partha P.

2016-08-01

The impact of the volumetric charged density of the dielectric rigid core on the electrophoresis of a soft particle is analyzed numerically. The volume charge density of the inner core of a soft particle can arise for a dendrimer structure or bacteriophage MS2. We consider the electrokinetic model based on the conservation principles, thus no conditions for Debye length or applied electric field is imposed. The fluid flow equations are coupled with the ion transport equations and the equation for the electric field. The occurrence of the induced nonuniform surface charge density on the outer surface of the inner core leads to a situation different from the existing analysis of a soft particle electrophoresis. The impact of this induced surface charge density together with the double-layer polarization and relaxation due to ion convection and electromigration is analyzed. The dielectric permittivity and the charge density of the core have a significant impact on the particle electrophoresis when the Debye length is in the order of the particle size. We find that by varying the ionic concentration of the electrolyte, the particle can exhibit reversal in its electrophoretic velocity. The role of the polymer layer softness parameter is addressed in the present analysis.

The Effects of Core-Mantle Interactions on Earth Rotation, Surface Deformation, and Gravity Changes

NASA Astrophysics Data System (ADS)

Watkins, A.; Gross, R. S.; Fu, Y.

2017-12-01

The length-of-day (LOD) contains a 6-year signal, the cause of which is currently unknown. The signal remains after removing tidal and surface fluid effects, thus the cause is generally believed to be angular momentum exchange between the mantle and core. Previous work has established a theoretical relationship between pressure variations at the core-mantle boundary (CMB) and resulting deformation of the overlying mantle and crust. This study examines globally distributed GPS deformation data in search of this effect, and inverts the discovered global inter-annual component for the CMB pressure variations. The geostrophic assumption is then used to obtain fluid flow solutions at the edge of the core from the CMB pressure variations. Taylor's constraint is applied to obtain the flow deeper within the core, and the equivalent angular momentum and LOD changes are computed and compared to the known 6-year LOD signal. The amplitude of the modeled and measured LOD changes agree, but the degree of period and phase agreement is dependent upon the method of isolating the desired component in the GPS position data. Implications are discussed, and predictions are calculated for surface gravity field changes that would arise from the CMB pressure variations.

A prevalence of dynamo-generated magnetic fields in the cores of intermediate-mass stars.

PubMed

Stello, Dennis; Cantiello, Matteo; Fuller, Jim; Huber, Daniel; García, Rafael A; Bedding, Timothy R; Bildsten, Lars; Aguirre, Victor Silva

2016-01-21

Magnetic fields play a part in almost all stages of stellar evolution. Most low-mass stars, including the Sun, show surface fields that are generated by dynamo processes in their convective envelopes. Intermediate-mass stars do not have deep convective envelopes, although 10 per cent exhibit strong surface fields that are presumed to be residuals from the star formation process. These stars do have convective cores that might produce internal magnetic fields, and these fields might survive into later stages of stellar evolution, but information has been limited by our inability to measure the fields below the stellar surface. Here we report the strength of dipolar oscillation modes for a sample of 3,600 red giant stars. About 20 per cent of our sample show mode suppression, by strong magnetic fields in the cores, but this fraction is a strong function of mass. Strong core fields occur only in red giants heavier than 1.1 solar masses, and the occurrence rate is at least 50 per cent for intermediate-mass stars (1.6-2.0 solar masses), indicating that powerful dynamos were very common in the previously convective cores of these stars.

Levels of metals and semimetals in sedimentary cores in Bertioga Channel, Brazil

NASA Astrophysics Data System (ADS)

Sartoretto, J. R.; Salaroli, A.; Figueira, R. C.

2013-05-01

The Baixada Santista is one of the most exploited and populated regions of São Paulo state. During the last decades, due to intense industrialization the Baixada Santista has passed through a strong process of environmental degradation. Metals in sediments are persistent, present toxicity in varied concentrations and may be deposited reaching biota habitats. In this context, high concentrations of metals represent environmental concern to costal management. Bertioga Channel is part of this complex system and is known mainly by a wide adjacent mangrove area. The channel is 25 km long, connecting the upstream region of Santos estuary to the adjacent ocean through an inlet located at the city of Bertioga. Urban development generates the concern of potential waste influx from surrounding streams, generating deposits and contaminating surface sediments along the channel, which may lead to adjacent coastal issues. The objective of this study was to characterize the concentration of the following metals at Bertioga Channel sediments: Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Sc, V and Zn. Five sediment cores were sampled along the channel and analyzed. Determination of metals concentration was based on methods SW 846 US EPA 3050B and EPA 7471. High As concentrations were observed at all cores, with considerable concentration similarity between the first and second sampling points. Analytical results showed that cores Bertioga 4 and Bertioga 5 have accumulated high quantity of metals and semimetals, mainly As, Cd and Cr. Normalization of concentration values showed low contamination at the cores. Nevertheless, As and Hg values indicated moderate to significant contamination at a few sampling points. Despite of the low probability of contamination demonstrated by the normalized values, increasing at the sediment surface of Enrichment Factor (ER), Pollution Load Index (PLI) and Sediment Pollution Index (SPI) parameters were observed. Results indicate that industrialization process and environmental degradation at the region are acting for the last decades.

Fluxes to sediments underlying the Rainbow hydrothermal plume at 36°14‧N on the Mid-Atlantic Ridge

NASA Astrophysics Data System (ADS)

Cave, R. R.; German, C. R.; Thomson, J.; Nesbitt, R. W.

2002-06-01

A geochemical investigation has been conducted of a suite of four sediment cores collected from directly beneath the hydrothermal plume at distances of 2 to 25 km from the Rainbow hydrothermal field. As well as a large biogenic component (>80% CaCO3) these sediments record clear enrichments of the elements Fe, Cu, Mn, V, P, and As from hydrothermal plume fallout but only minor detrital background material. Systematic variations in the abundances of ;hydrothermal; elements are observed at increasing distance from the vent site, consistent with chemical evolution of the dispersing plume. Further, pronounced Ni and Cr enrichments at specific levels within each of the two cores collected from closest to the vent site are indicative of discrete episodes of additional input of ultrabasic material at these two near-field locations. Radiocarbon dating reveals mean Holocene accumulation rates for all four cores of 2.7 to 3.7 cm.kyr-1, with surface mixed layers 7 to 10+ cm thick, from which a history of deposition from the Rainbow hydrothermal plume can be deduced. Deposition from the plume supplies elements to the underlying sediments that are either directly hydrothermally sourced (e.g., Fe, Mn, Cu) or scavenged from seawater via the hydrothermal plume (e.g., V, P, As). Holocene fluxes into to the cores' surface mixed layers are presented which, typically, are an order of magnitude greater than ;background; authigenic fluxes from the open North Atlantic. One core, collected closest to the vent site, indicates that both the concentration and flux of hydrothermally derived material increased significantly at some point between 8 and 12 14C kyr ago; the preferred explanation is that this variation reflects the initiation/intensification of hydrothermal venting at the Rainbow hydrothermal field at this time-perhaps linked to some specific tectonic event in this fault-controlled hydrothermal setting.

Morphology of the lingual papillae in the fishing cat.

PubMed

Emura, Shoichi; Okumura, Toshihiko; Chen, Huayue

2014-01-01

We examined the dorsal lingual surface of an adult fishing cat (Prionailurus viverrinus) by scanning electron microscopy. The filiform papillae on the lingual apex had several pointed processes. The connective tissue core of the filiform papillae resembleda a well in shape. The filiform papillae on the anterior part of the lingual body were large and cylindrical in shape. The connective tissue core of the filiform papillae consisted of a large conical papilla. The filiform papillae on the central part of the lingual body were large and conical. The connective tissue core of the filiform papillae consisted of a large main process and some secondary processes. The connective tissue core of the fungiform papillae did not have processes. The vallate papillae were surrounded by a groove and a pad. The top of the connective tissue core of the vallate papillae had a rough surface with no spines.

Enhanced magnetocaloric effect material

DOEpatents

Lewis, Laura J. H.

2006-07-18

A magnetocaloric effect heterostructure having a core layer of a magnetostructural material with a giant magnetocaloric effect having a magnetic transition temperature equal to or greater than 150 K, and a constricting material layer coated on at least one surface of the magnetocaloric material core layer. The constricting material layer may enhance the magnetocaloric effect by restriction of volume changes of the core layer during application of a magnetic field to the heterostructure. A magnetocaloric effect heterostructure powder comprising a plurality of core particles of a magnetostructural material with a giant magnetocaloric effect having a magnetic transition temperature equal to or greater than 150 K, wherein each of the core particles is encapsulated within a coating of a constricting material is also disclosed. A method for enhancing the magnetocaloric effect within a giant magnetocaloric material including the step of coating a surface of the magnetocaloric material with a constricting material is disclosed.

A problem in representing the core magnetic field of the earth using spherical harmonics

NASA Technical Reports Server (NTRS)

Carle, H. M.; Harrison, C. G. A.

1982-01-01

Although there are computational advantages to the representation of the earth's magnetic field by spherical harmonic coefficients of the magnetic potential, up to the thirteenth degree and order, the following disadvantages emerge: (1) the use of spherical harmonics of up to a certain degree does not remove wavelengths greater than a certain value from the surface fields, and (2) the total field magnitudes represented by spherical harmonics up to a certain degree have minimum wavelengths equal to the circumference of the earth divided by twice the maximum degree of the harmonic used. The implications of the ways in which surface fields are separated into core and crustal components are discussed, and it is concluded that since field signals are generated in the core, the representation of the core field by spherical harmonics of potential does not adequately represent all core field components.

Nonlinear saturation of the Rayleigh instability due to oscillatory flow in a liquid-lined tube

NASA Astrophysics Data System (ADS)

Halpern, David; Grotberg, James B.

2003-10-01

In this paper, the stability of core annular flows consisting of two immiscible fluids in a cylindrical tube with circular cross-section is examined. Such flows are important in a wide range of industrial and biomedical applications. For example, in secondary oil recovery, water is pumped into the well to displace the remaining oil. It is also of relevance in the lung, where a thin liquid film coats the inner surface of the small airways of the lungs. In both cases, the flow is influenced by a surface-tension instability, which may induce the breakup of the core fluid into short plugs, reducing the efficiency of the oil recovery, or blocking the passage of air in the lung thus inducing airway closure. We consider the stability of a thin film coating the inner surface of a rigid cylindrical tube with the less viscous fluid in the core. For thick enough films, the Rayleigh instability forms a liquid bulge that can grow to eventually create a plug blocking the tube. The analysis explores the effect of an oscillatory core flow on the interfacial dynamics and particularly the nonlinear stabilization of the bulge. The oscillatory core flow exerts tangential and normal stresses on the interface between the two fluids that are simplified by uncoupling the core and film analyses in the thin-film high-frequency limit of the governing equations. Lubrication theory is used to derive a nonlinear evolution equation for the position of the air liquid interface which includes the effects of the core flow. It is shown that the core flow can prevent plug formation of the more viscous film layer by nonlinear saturation of the capillary instability. The stabilization mechanism is similar to that of a reversing butter knife, where the core shear wipes the growing liquid bulge back on to the tube wall during the main tidal volume stroke, but allows it to grow back as the stoke and shear turn around. To be successful, the leading film thickness ahead of the bulge must be smaller than the trailing film thickness behind it, a requirement necessitating a large enough core capillary number which promotes a large core shear stress on the interface. The core capillary number is defined to be the ratio of core viscous forces to surface tension forces. When this process is tuned correctly, the two phases balance and there is no net growth of the liquid bulge over one cycle. We find that there is a critical frequency above which plug formation does not occur, and that this critical frequency increases as the tidal volume amplitude of the core flow decreases.

Study on surface-enhanced Raman scattering efficiency of Ag core-Au shell bimetallic nanoparticles

NASA Astrophysics Data System (ADS)

Dong, Xiao; Gu, Huaimin; Kang, Jian; Yuan, Xiaojuan

2009-08-01

In this article, the relationship between the states of Ag core-Au shell (core-shell) nanoparticles (NP) and the intensity of Raman scattering of analytes dissolved in the water and adsorbed on the NP was studied. The core-shell NP were synthesised by coating Au layers over Ag seeds by the method of "seed-growth". To highlight the advantage of the core-shell NP, Ag colloid and Au colloid were chosen for contrasting. The analyte that were chosen for this testing were methylene blue (MB) for the reason that MB has very strong signal in surface-enhanced Raman scattering (SERS). The SERS activity of optimalizing states of Ag and Au colloids were compared with that of core-shell NP when MB was used as analyte. In this study, sodium chloride, sodium sulfate and sodium nitrate were used as aggregating agents for Ag, Au colloids and core-shell NP, because anions have a strong influence on the SERS efficiency and the stability of colloids. The results indicate that core-shell NP can obviously enhance the SERS of MB. The aim of this study is to prove that compared with the metal colloid, the core-shell NP is a high efficiency SERS active substrate.

Uranium passivation by C + implantation: A photoemission and secondary ion mass spectrometry study

NASA Astrophysics Data System (ADS)

Nelson, A. J.; Felter, T. E.; Wu, K. J.; Evans, C.; Ferreira, J. L.; Siekhaus, W. J.; McLean, W.

2006-03-01

Implantation of 33 keV C + ions into polycrystalline U 238 with a dose of 4.3 × 10 17 cm -2 produces a physically and chemically modified surface layer that prevents further air oxidation and corrosion. X-ray photoelectron spectroscopy and secondary ion mass spectrometry were used to investigate the surface chemistry and electronic structure of this C + ion implanted polycrystalline uranium and a non-implanted region of the sample, both regions exposed to air for more than a year. In addition, scanning electron microscopy was used to examine and compare the surface morphology of the two regions. The U 4f, O 1s and C 1s core-level and valence band spectra clearly indicate carbide formation in the modified surface layer. The time-of-flight secondary ion mass spectrometry depth profiling results reveal an oxy-carbide surface layer over an approximately 200 nm thick UC layer with little or no residual oxidation at the carbide layer/U metal transitional interface.

Integrating Condensed Matter Physics into a Liberal Arts Physics Curriculum

NASA Astrophysics Data System (ADS)

Collett, Jeffrey

2008-03-01

The emergence of nanoscale science into the popular consciousness presents an opportunity to attract and retain future condensed matter scientists. We inject nanoscale physics into recruiting activities and into the introductory and the core portions of the curriculum. Laboratory involvement and research opportunity play important roles in maintaining student engagement. We use inexpensive scanning tunneling (STM) and atomic force (AFM) microscopes to introduce students to nanoscale structure early in their college careers. Although the physics of tip-surface interactions is sophisticated, the resulting images can be interpreted intuitively. We use the STM in introductory modern physics to explore quantum tunneling and the properties of electrons at surfaces. An interdisciplinary course in nanoscience and nanotechnology course team-taught with chemists looks at nanoscale phenomena in physics, chemistry, and biology. Core quantum and statistical physics courses look at effects of quantum mechanics and quantum statistics in degenerate systems. An upper level solid-state physics course takes up traditional condensed matter topics from a structural perspective by beginning with a study of both elastic and inelastic scattering of x-rays from crystalline solids and liquid crystals. Students encounter reciprocal space concepts through the analysis of laboratory scattering data and by the development of the scattering theory. The course then examines the importance of scattering processes in band structure and in electrical and thermal conduction. A segment of the course is devoted to surface physics and nanostructures where we explore the effects of restricting particles to two-dimensional surfaces, one-dimensional wires, and zero-dimensional quantum dots.

Determination of Mercury Content in a Shallow Firn Core from Summit, Greenland by Isotope Dilution Inductively Coupled Plasma Mass Spectrometry

NASA Technical Reports Server (NTRS)

Mann, Jacqueline L.; Long, Stephen E.; Shuman, Christopher A.; Kelly, W. Robert

2003-01-01

The total mercury Hg content was determined in 6 cm sections of a near-surface 7 m firn core and in surrounding surface snow from Summit, Greenland (elevation: 3238 m, 72.58 N, 38.53 W) in May 2001 by isotope dilution cold-vapor inductively coupled plasma mass spectrometry (ID-CV-ICP-MS). The focus of this research was to evaluate the capability of the ID-CV-ICPMS technique for measuring trace levels of Hg typical of polar snow and firn. Highly enriched Hg-201 isotopic spike is added to approximately 10 ml melted core and thoroughly mixed. The Hg(+2) in the sample is reduced on line with tin (II) chloride (SnCl2) and the elemental Hg (Hg(0)) vapor pre-concentrated on to gold gauze using a commercial amalgam system. The Hg is then thermally desorbed and introduced into a quadrupole ICP-MS. The blank corrected Hg concentrations determined for all samples ranged from 0.25 ng/L to 1.74 ng/L (ppt) (average 0.59 ng/L plus or minus 0.28 ng/L) and fall within the range of those previously determined by Boutron et al., 1998 (less than or equal to 0.05 ng/L to 2.0 ng/L) for the Summit site. The average blank value was 0.19 ng/L plus or minus 0.045 ng/L (n=6). The Hg values specifically for the firn core range from 0.25 ng/L to 0.87 ng/L (average 0.51 ng/L plus or minus 0.13 ng/L) and show both values declining with time and larger variability in concentration in the top 1.8 m.

Theoretical studies of positron states and annihilation characteristics at the oxidized Cu(100) surface

NASA Astrophysics Data System (ADS)

Fazleev, N. G.; Weiss, A. H.

2013-04-01

In this work we present the results of theoretical studies of positron surface and bulk states and annihilation probabilities of surface-trapped positrons with relevant core electrons at the oxidized Cu(100) surface under conditions of high oxygen coverage. An ab-initio study of the electronic properties of the Cu(100) missing row reconstructed surface at various on surface and sub-surface oxygen coverages has been performed on the basis of the density functional theory (DFT) using the Dmol3 code and the generalized gradient approximation (GGA). Surface structures in calculations have been constructed by adding oxygen atoms to various surface hollow and sub-surface octahedral sites of the 0.5 monolayer (ML) missing row reconstructed phase of the Cu(100) surface with oxygen coverages ranging from 0.5 to 1.5 ML. The charge redistribution at the surface and variations in atomic structure and chemical composition of the topmost layers associated with oxidation and surface reconstruction have been found to affect the spatial extent and localization of the positron surface state wave function and annihilation probabilities of surface trapped positrons with relevant core electrons. Theoretical results are compared with experimental data obtained from studies of oxidation of the Cu(100) surface using positron annihilation induced Auger electron spectroscopy (PAES). It has been shown that positron annihilation probabilities with Cu 3s and 3p core electrons decrease when total (on-surface and sub-surface) oxygen coverage of the Cu(100) surface increases up to 1 ML. The calculations show that for high oxygen coverage when total oxygen coverage is 1. 5 ML the positron is not bound to the surface.

Theoretical studies of positron states and annihilation characteristics at the oxidized Cu(100) surface

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

Fazleev, N. G.; Weiss, A. H.

2013-04-19

In this work we present the results of theoretical studies of positron surface and bulk states and annihilation probabilities of surface-trapped positrons with relevant core electrons at the oxidized Cu(100) surface under conditions of high oxygen coverage. An ab-initio study of the electronic properties of the Cu(100) missing row reconstructed surface at various on surface and sub-surface oxygen coverages has been performed on the basis of the density functional theory (DFT) using the Dmol3 code and the generalized gradient approximation (GGA). Surface structures in calculations have been constructed by adding oxygen atoms to various surface hollow and sub-surface octahedral sitesmore » of the 0.5 monolayer (ML) missing row reconstructed phase of the Cu(100) surface with oxygen coverages ranging from 0.5 to 1.5 ML. The charge redistribution at the surface and variations in atomic structure and chemical composition of the topmost layers associated with oxidation and surface reconstruction have been found to affect the spatial extent and localization of the positron surface state wave function and annihilation probabilities of surface trapped positrons with relevant core electrons. Theoretical results are compared with experimental data obtained from studies of oxidation of the Cu(100) surface using positron annihilation induced Auger electron spectroscopy (PAES). It has been shown that positron annihilation probabilities with Cu 3s and 3p core electrons decrease when total (on-surface and sub-surface) oxygen coverage of the Cu(100) surface increases up to 1 ML. The calculations show that for high oxygen coverage when total oxygen coverage is 1. 5 ML the positron is not bound to the surface.« less

Spectroscopic mapping of the white horse alunite deposit, Marysvale volcanic field, Utah: Evidence of a magmatic component

USGS Publications Warehouse

Rockwell, B.W.; Cunningham, C.G.; Breit, G.N.; Rye, R.O.

2006-01-01

Previous studies have demonstrated that the replacement alunite deposits just north of the town of Marysvale, Utah, USA, were formed primarily by low-temperature (100??-170?? C), steam-heated processes near the early Miocene paleoground surface, immediately above convecting hydrothermal plumes. Pyrite-bearing propylitically altered rocks occur mainly beneath the steam-heated alunite and represent the sulfidized feeder zone of the H2S-dominated hydrothermal fluids, the oxidation of which at higher levels led to the formation of the alunite. Maps of surface mineralogy at the White Horse deposit generated from Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data were used in conjunction with X-ray diffraction studies of field samples to test the accuracy and precision of AVIRIS-based mineral mapping of altered rocks and demonstrate the utility of spectroscopic mapping for ore deposit characterization. The mineral maps identified multiple core zones of alunite that grade laterally outward to kaolinite. Surrounding the core zones are dominantly propylitically altered rocks containing illite, montmorillonite, and chlorite, with minor pyrite, kaolinite, gypsum, and remnant potassium feldspar from the parent rhyodacitic ash-flow tuff. The AVIRIS mapping also identified fracture zones expressed by ridge-forming selvages of quartz + dickite + kaolinite that form a crude ring around the advanced argillic core zones. Laboratory analyses identified the aluminum phosphate-sulfate (APS) minerals woodhouseite and svanbergite in one sample from these dickite-bearing argillic selvages. Reflectance spectroscopy determined that the outer edges of the selvages contain more dickite than do the medial regions. The quartz + dickite ?? kaolinite ?? APS-mineral selvages demonstrate that fracture control of replacement processes is more prevalent away from the advanced argillic core zones. Although not exposed at the White Horse deposit, pyrophyllite ?? ordered illite was identified using AVIRIS in localized, superimposed conduits within propylitically altered rocks in nearby alteration systems of similar age and genesis that have been eroded to deeper levels. The fracture zones bearing pyrophyllite, illite, dickite, natroalunite, and/or APS minerals indicate a magmatic component in the dominantly steam-heated system. ?? 2006 Society of Economic Geologists, Inc.

Surface formation, preservation, and history of low-porosity crusts at the WAIS Divide site, West Antarctica

NASA Astrophysics Data System (ADS)

Fegyveresi, John M.; Alley, Richard B.; Muto, Atsuhiro; Orsi, Anaïs J.; Spencer, Matthew K.

2018-01-01

Observations at the West Antarctic Ice Sheet (WAIS) Divide site show that near-surface snow is strongly altered by weather-related processes such as strong winds and temperature fluctuations, producing features that are recognizable in the deep ice core. Prominent glazed surface crusts develop frequently at the site during summer seasons. Surface, snow pit, and ice core observations made in this study during summer field seasons from 2008-2009 to 2012-2013, supplemented by automated weather station (AWS) data with short- and longwave radiation sensors, revealed that such crusts formed during relatively low-wind, low-humidity, clear-sky periods with intense daytime sunshine. After formation, such glazed surfaces typically developed cracks in a polygonal pattern likely from thermal contraction at night. Cracking was commonest when several clear days occurred in succession and was generally followed by surface hoar growth; vapor escaping through the cracks during sunny days may have contributed to the high humidity that favored nighttime formation of surface hoar. Temperature and radiation observations show that daytime solar heating often warmed the near-surface snow above the air temperature, contributing to upward mass transfer, favoring crust formation from below, and then surface hoar formation. A simple surface energy calculation supports this observation. Subsequent examination of the WDC06A deep ice core revealed that crusts are preserved through the bubbly ice, and some occur in snow accumulated during winters, although not as commonly as in summertime deposits. Although no one has been on site to observe crust formation during winter, it may be favored by greater wintertime wind packing from stronger peak winds, high temperatures and steep temperature gradients from rapid midwinter warmings reaching as high as -15 °C, and perhaps longer intervals of surface stability. Time variations in crust occurrence in the core may provide paleoclimatic information, although additional studies are required. Discontinuity and cracking of crusts likely explain why crusts do not produce significant anomalies in other paleoclimatic records.

Interaction of oxygen with ZrC(001) and VC(001): Photoemission and first-principles studies

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

Rodriguez, J.A.; Liu, P.; Gomes, J.

2005-08-15

High-resolution photoemission and first-principles density-functional calculations were used to study the interaction of oxygen with ZrC(001) and VC(001) surfaces. Atomic oxygen is present on the carbide substrates after small doses of O{sub 2} at room temperature. At 500 K, the oxidation of the surfaces is fast and clear features for ZrO{sub x} or VO{sub x} are seen in the O(1s), Zr(3d), and V(2p{sub 3/2}) core levels spectra, with an increase in the metal/carbon ratio of the samples. A big positive shift (1.3-1.6 eV) was detected for the C 1s core level in O/ZrC(001), indicating the existence of strong O{r_reversible}C ormore » C{r_reversible}C interactions. A phenomenon corroborated by the results of first-principles calculations, which show a CZrZr hollow as the most stable site for the adsorption of O. Furthermore, the calculations also show that a C{r_reversible}O exchange is exothermic on ZrC(001), and the displaced C atoms bond to CZrZr sites. In the O/ZrC(001) interface, the surface C atoms play a major role in determining the behavior of the system. In contrast, the adsorption of oxygen induces very minor changes in the C(1s) spectrum of VC(001). The O{r_reversible}V interactions are stronger than the O{r_reversible}Zr interactions, and O{r_reversible}C interactions do not play a dominant role in the O/VC(001) interface. In this system, C{r_reversible}O exchange is endothermic. VC(001) has a larger density of metal d states near the Fermi level than ZrC(001), but the rate of oxidation of VC(001) is slower. Therefore the O/ZrC(001) and O/VC(001) systems illustrate two different types of pathways for the oxidation of carbide surfaces.« less

Photoinduced Changes of Surface Topography in Amorphous, Liquid-Crystalline, and Crystalline Films of Bent-Core Azobenzene-Containing Substance.

PubMed

Bobrovsky, Alexey; Mochalov, Konstantin; Oleinikov, Vladimir; Solovyeva, Daria; Shibaev, Valery; Bogdanova, Yulia; Hamplová, Vĕra; Kašpar, Miroslav; Bubnov, Alexej

2016-06-09

Recently, photofluidization and mass-transfer effects have gained substantial interest because of their unique abilities of photocontrolled manipulation with material structure and physicochemical properties. In this work, the surface topographies of amorphous, nematic, and crystalline films of an azobenzene-containing bent-core (banana-shaped) compound were studied using a special experimental setup combining polarizing optical microscopy and atomic force microscopy. Spin-coating or rapid cooling of the samples enabled the formation of glassy amorphous or nematic films of the substance. The effects of UV and visible-light irradiation on the surface roughness of the films were investigated. It was found that UV irradiation leads to the fast isothermal transition of nematic and crystalline phases into the isotropic phase. This effect is associated with E-Z photoisomerization of the compound accompanied by a decrease of the anisometry of the bent-core molecules. Focused polarized visible-light irradiation (457.9 nm) results in mass-transfer phenomena and induces the formation of so-called "craters" in amorphous and crystalline films of the substance. The observed photofluidization and mass-transfer processes allow glass-forming bent-core azobenzene-containing substances to be considered for the creation of promising materials with photocontrollable surface topographies. Such compounds are of principal importance for the solution of a broad range of problems related to the investigation of surface phenomena in colloid and physical chemistry, such as surface modification for chemical and catalytic reactions, predetermined morphology of surfaces and interfaces in soft matter, and chemical and biochemical sensing.

Three decades of TBT contamination in sediments around a large scale shipyard.

PubMed

Kim, Nam Sook; Shim, Won Joon; Yim, Un Hyuk; Ha, Sung Yong; An, Joon Geon; Shin, Kyung Hoon

2011-08-30

Tributyltin (TBT) contamination in sediments was investigated in the vicinity of a large-scale shipyard in the years after the implementation of a total ban on the use of TBT based antifouling paints in Korea. Extremely high level of TBT (36,292ng Sn/g) in surface sediment was found at a station in front of a drydock and near surface runoff outfall of the shipyard. TBT concentration in surface sediments of Gohyeon Bay, where the shipyard is located, showed an apparent decreased TBT concentration gradient from the shipyard towards the outer bay. The vertical distribution of TBT contamination derived from a sediment core analysis demonstrated a significant positive correlation (r(2)=0.88; p<0.001) with the annual tonnage of ship-construction in the shipyard within the past three decades. TBT concentrations at six stations surveyed before (2003) and seven years after (2010) the total ban showed no significant differences (p>0.05). Despite the ban on the use of TBT, including ocean going vessels, surface sediments are still being heavily contaminated with TBT, and its levels well exceeded the sediment quality guideline or screening values. Copyright © 2011 Elsevier B.V. All rights reserved.

Sea-level and environmental changes since the last interglacial in the Gulf of Carpentaria, Australia: an overview

USGS Publications Warehouse

Chivas, Allan R.; Garcı́a, Adriana; van der Kaars, Sander; Couapel, Martine; Holt, Sabine; Reeves, Jessica M.; Wheeler, David J.; Switzer, Adam D.; Murray-Wallace, Colin V.; Banerjee, Debabrata; Price, David M.; Wang, Sue X.; Pearson, Grant; Edgar, N. Terry; Beaufort, Luc; de Deckker, Patrick; Lawson, Ewan; Cecil, C. Blaine

2001-01-01

The Gulf of Carpentaria is an epicontinental sea (maximum depth 70 m) between Australia and New Guinea, bordered to the east by Torres Strait (currently 12 m deep) and to the west by the Arafura Sill (53 m below present sea level). Throughout the Quaternary, during times of low sea-level, the Gulf was separated from the open waters of the Indian and Pacific Oceans, forming Lake Carpentaria, an isolation basin, perched above contemporaneous sea-level with outlet channels to the Arafura Sea. A preliminary interpretation is presented of the palaeoenvironments recorded in six sediment cores collected by the IMAGES program in the Gulf of Carpentaria. The longest core (approx. 15 m) spans the past 130 ka and includes a record of sea-level/lake-level changes, with particular complexity between 80 and 40 ka when sea-level repeatedly breached and withdrew from Gulf/Lake Carpentaria. Evidence from biotic remains (foraminifers, ostracods, pollen), sedimentology and geochemistry clearly identifies a final marine transgression at about 9.7 ka (radiocarbon years). Before this transgression, Lake Carpentaria was surrounded by grassland, was near full, and may have had a surface area approaching 600 km×300 km and a depth of about 15 m. The earlier rise in sea-level which accompanied the Marine Isotopic Stage 6/5 transgression at about 130 ka is constrained by sedimentological and biotic evidence and dated by optical- and thermoluminescence and amino acid racemisation methods.

Eye surface temperature detects stress response in budgerigars (Melopsittacus undulatus).

PubMed

Ikkatai, Yuko; Watanabe, Shigeru

2015-08-05

Previous studies have suggested that stressors not only increase body core temperature but also body surface temperature in many animals. However, it remains unclear whether surface temperature could be used as an alternative to directly measure body core temperature, particularly in birds. We investigated whether surface temperature is perceived as a stress response in budgerigars. Budgerigars have been used as popular animal models to investigate various neural mechanisms such as visual perception, vocal learning, and imitation. Developing a new technique to understand the basic physiological mechanism would help neuroscience researchers. First, we found that cloacal temperature correlated with eye surface temperature. Second, eye surface temperature increased after handling stress. Our findings suggest that eye surface temperature is closely related to cloacal temperature and that the stress response can be measured by eye surface temperature in budgerigars.

Field alignment of bent-core smectic liquid crystals for analog optical phase modulation

NASA Astrophysics Data System (ADS)

Shen, Y.; Goodhew, L.; Shao, R.; Moran, M.; Korblova, E.; Walba, D. M.; Clark, N. A.; Maclennan, J. E.; Rudquist, P.

2015-05-01

A general method for aligning bent-core smectic liquid crystal materials is described. Alternating electric fields between interdigitated electrodes patterned on one cell surface create torques on the liquid crystal that result in uniform "bookshelf" orientation of the smectic layers. The aligned cell can then be driven in the conventional way by applying an electric field between all of the stripe electrodes connected together and a monolithic electrode on the other cell surface. Fast, analog, optical phase-only modulation is demonstrated in a device containing a polar, bent-core SmAPF material aligned using this technique.

Wetland paleoecological study of southwest coastal Louisiana: sediment cores and diatom calibration dataset

USGS Publications Warehouse

Smith, Kathryn E. L.; Flocks, James G.; Steyer, Gregory D.; Piazza, Sarai C.

2015-01-01

Wetland sediment data were collected in 2009 and 2010 throughout the southwest Louisiana Chenier Plain as part of a pilot study to develop a diatom-based proxy for past wetland water chemistry and the identification of sediment deposits from tropical storms. The complete dataset includes forty-six surface sediment samples and nine sediment cores. The surface sediment samples were collected in fresh, intermediate, and brackish marsh and are located coincident with Coastwide Reference Monitoring System (CRMS) sites. The nine sediment cores were collected at the Rockefeller Wildlife Refuge (RWR) located in Grand Chenier, La.

Synthesis of the RGO/Al2O3 core-shell nanocomposite flakes and characterization of their unique electrostatic properties using zeta potential measurements

NASA Astrophysics Data System (ADS)

Jastrzębska, A. M.; Karcz, J.; Letmanowski, R.; Zabost, D.; Ciecierska, E.; Zdunek, J.; Karwowska, E.; Siekierski, M.; Olszyna, A.; Kunicki, A.

2016-01-01

The aim of this study was to describe the influence of the modification of electrostatic properties of RGO/Al2O3 core-shell nanocomposite flakes. The amount of crystalline form of aluminum oxide was very small. It existed mostly in amorphous phase in the form of covalently bonded to GO surface. The morphological, structural and physicochemical investigations results showed that spherical Al2O3 nanoparticles (ca. 41 nm) in gamma phase completely covered the surface of curly-shaped RGO flakes and acted as a spreader between individual flakes. The high BET specific surface area of the analyzed composite (119.71 m2/g) together with very low open porosity (0.479 cm3/g) indicated that RGO/Al2O3 nanocomposite flakes showed low tendency to agglomeration. The zeta potential curves obtained for RGO/Al2O3 core-shell nanocomposite flakes were differing from curves obtained for GO and Al2O3 suspensions in distilled water and neutral environment. The specific electrostatic properties of the core-shell system of RGO/Al2O3 flakes had an influence on its surface charge (zeta potential) which was measured by applying an external electric field. The FTIR and Raman investigations results also confirmed that the Cdbnd O species were not taking part in the surface amphoteric reactions resulting in the formation of electrostatic surface charge.

Studying the Variation in Gas Permeability of Porous Building Substrates

NASA Astrophysics Data System (ADS)

Townsend, L.; Savidge, C. R.; Hu, L.; Rizzo, D. M.; Hayden, N. J.; Dewoolkar, M.

2009-12-01

Understanding permeability of building materials is important for problems involving studies of contaminant transport. Examples include contamination from fire, acid rain, and chemical and biological weapons. Our research investigates the gas permeability of porous building substrates such as concretes, limestones, sandstones, and bricks. Each sample was cored to produce 70 mm (2.75”) diameter cores approximately 75-130 mm (3-5”) tall. The surface gas permeability was measured on the top surface of these specimens using the AutoScan II device manufactured by New England Research, Inc. The measurements were taken along a 3 mm grid producing a map of surface gas permeability. An example map is shown in Figure 1. The macroscopic measurements were performed along the entire cored specimen. A second set of measurements were made on a 5 mm thick slice cut from the top of each specimen to examine whether these measurements compare better with the surface measurements. The macroscopic gas permeability was measured for all specimens using ASTM D 4525. The results are summarized in Table 1. In general, the surface and macroscopic gas permeability measurements (Table 1) compare reasonably well (within one order of magnitude). The permeability of the 5 mm slices is not significantly different from the entire core for the specimens tested. Figure 1. Results of surface permeability mappingof Ohio Sandstone using the AutoScan II device. a) Map of gas permeability b) Range of gas permeability c) Density function of permeability. Table 1. Gas permeability values (mD)

A Cul-3-BTB ubiquitylation pathway regulates junctional levels and asymmetry of core planar polarity proteins

PubMed Central

Strutt, Helen; Searle, Elizabeth; Thomas-MacArthur, Victoria; Brookfield, Rosalind; Strutt, David

2013-01-01

The asymmetric localisation of core planar polarity proteins at apicolateral junctions is required to specify cell polarity in the plane of epithelia. This asymmetric distribution of the core proteins is proposed to require amplification of an initial asymmetry by feedback loops. In addition, generation of asymmetry appears to require the regulation of core protein levels, but the importance of such regulation and the underlying mechanisms is unknown. Here we show that ubiquitylation acts through more than one mechanism to control core protein levels in Drosophila, and that without this regulation cellular asymmetry is compromised. Levels of Dishevelled at junctions are regulated by a Cullin-3-Diablo/Kelch ubiquitin ligase complex, the activity of which is most likely controlled by neddylation. Furthermore, activity of the deubiquitylating enzyme Fat facets is required to maintain Flamingo levels at junctions. Notably, ubiquitylation does not alter the total cellular levels of Dishevelled or Flamingo, but only that of the junctional population. When junctional core protein levels are either increased or decreased by disruption of the ubiquitylation machinery, their asymmetric localisation is reduced and this leads to disruption of planar polarity at the tissue level. Loss of asymmetry by altered core protein levels can be explained by reference to feedback models for amplification of asymmetry. PMID:23487316

Decontamination and deactivation of the power burst facility at the Idaho National Laboratory.

PubMed

Greene, Christy Jo

2007-05-01

Successful decontamination and deactivation of the Power Burst Facility located at the Idaho National Laboratory was accomplished through the use of extensive planning, job sequencing, engineering controls, continuous radiological support, and the use of a dedicated group of experienced workers. Activities included the removal and disposal of irradiated fuel, miscellaneous reactor components and debris stored in the canal, removal and disposition of a 15.6 curie Pu:Be start-up source, removal of an irradiated in-pile tube, and the removal of approximately 220,000 pounds of lead that was used as shielding primarily in Cubicle 13. The canal and reactor vessel were drained and water was transferred to an evaporation tank adjacent to the facility. The canal was decontaminated using underwater divers, and epoxy was affixed to the interior surfaces of the canal to contain loose contamination. The support structures and concrete or steel frame walls that form the confinement were left in place. The reactor core was left in place and a carbon steel shielding plate was placed over the reactor core to reduce radiation levels. All low-level waste and mixed low level waste generated as a result of the work activities was characterized and disposed.

A SERS-active sensor based on heterogeneous gold nanostar core-silver nanoparticle satellite assemblies for ultrasensitive detection of aflatoxinB1

NASA Astrophysics Data System (ADS)

Li, Aike; Tang, Lijuan; Song, Dan; Song, Shanshan; Ma, Wei; Xu, Liguang; Kuang, Hua; Wu, Xiaoling; Liu, Liqiang; Chen, Xin; Xu, Chuanlai

2016-01-01

A surface-enhanced Raman scattering (SERS) sensor based on gold nanostar (Au NS) core-silver nanoparticle (Ag NP) satellites was fabricated for the first time to detect aflatoxinB1 (AFB1). We constructed the SERS sensor using AFB1 aptamer (DNA1)-modified Ag satellites and a complementary sequence (DNA2)-modified Au NS core. The Raman label (ATP) was modified on the surface of Ag satellites. The SERS signal was enhanced when the satellite NP was attached to the Au core NS. The AFB1 aptamer on the surface of Ag satellites would bind to the targets when AFB1 was present in the system, Ag satellites were then removed and the SERS signal decreased. This SERS sensor showed superior specificity for AFB1 and the linear detection range was from 1 to 1000 pg mL-1 with the limit of detection (LOD) of 0.48 pg mL-1. The excellent recovery experiment using peanut milk demonstrated that the sensor could be applied in food and environmental detection.A surface-enhanced Raman scattering (SERS) sensor based on gold nanostar (Au NS) core-silver nanoparticle (Ag NP) satellites was fabricated for the first time to detect aflatoxinB1 (AFB1). We constructed the SERS sensor using AFB1 aptamer (DNA1)-modified Ag satellites and a complementary sequence (DNA2)-modified Au NS core. The Raman label (ATP) was modified on the surface of Ag satellites. The SERS signal was enhanced when the satellite NP was attached to the Au core NS. The AFB1 aptamer on the surface of Ag satellites would bind to the targets when AFB1 was present in the system, Ag satellites were then removed and the SERS signal decreased. This SERS sensor showed superior specificity for AFB1 and the linear detection range was from 1 to 1000 pg mL-1 with the limit of detection (LOD) of 0.48 pg mL-1. The excellent recovery experiment using peanut milk demonstrated that the sensor could be applied in food and environmental detection. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr08372a

Respiratory potential in sapwood of old versus young ponderosa pine trees in the Pacific Northwest.

PubMed

Pruyn, Michele L; Gartner, Barbara L; Harmon, Mark E

2002-02-01

Our primary objective was to present and test a new technique for in vitro estimation of respiration of cores taken from old trees to determine respiratory trends in sapwood. Our secondary objective was to quantify effects of tree age and stem position on respiratory potential (rate of CO2 production of woody tissue under standardized laboratory conditions). We extracted cores from one to four vertical positions in boles of +200-, +50- and +15-year-old Pinus ponderosa Dougl. ex Laws. trees. Cores were divided into five segments corresponding to radial depths of inner bark; outer, middle and inner sapwood; and heartwood. Data suggested that core segment CO2 production was an indicator of its respiratory activity, and that potential artifacts caused by wounding and extraction were minimal. On a dry mass basis, respiratory potential of inner bark was 3-15 times greater than that of sapwood at all heights for all ages (P < 0.0001). Within sapwood at all heights and in all ages of trees, outer sapwood had a 30-60% higher respiratory potential than middle or inner sapwood (P < 0.005). Heartwood had only 2-10% of the respiratory potential of outer sapwood. For all ages of trees, sapwood rings produced in the same calendar year released over 50% more CO2 at treetops than at bases (P < 0.0001). When scaled to the whole-tree level on a sapwood volume basis, sapwood of younger trees had higher respiratory potential than sapwood of older trees. In contrast, the trend was reversed when using the outer-bark surface area of stems as a basis for comparing respiratory potential. The differences observed in respiratory potential calculated on a core dry mass, sapwood volume, or outer-bark surface area basis clearly demonstrate that the resulting trends within and among trees are determined by the way in which the data are expressed. Although these data are based on core segments rather than in vivo measurements, we conclude that the relative differences are probably valid even if the absolute differences are not.

Developing the Cleanliness Requirements for an Organic-detection Instrument MOMA-MS

NASA Technical Reports Server (NTRS)

Perry, Radford; Canham, John; Lalime, Erin

2015-01-01

The cleanliness requirements for an organic-detection instrument, like the Mars Organic Molecule Analyzer Mass Spectrometer (MOMA-MS), on a Planetary Protection Class IVb mission can be extremely stringent. These include surface molecular and particulate, outgassing, and bioburden. The prime contractor for the European Space Agencys ExoMars 2018 project, Thales Alenia Space Italy, provided requirements based on a standard, conservative approach of defining limits which yielded levels that are unverifiable by standard cleanliness verification methods. Additionally, the conservative method for determining contamination surface area uses underestimation while conservative bioburden surface area relies on overestimation, which results in inconsistencies for the normalized reporting. This presentation will provide a survey of the challenge to define requirements that can be reasonably verified and still remain appropriate to the core science of the ExoMars mission.

Effect of core ceramic grinding on fracture behaviour of bilayered lithium disilicate glass-ceramic under two loading schemes.

PubMed

Wang, Xiao-Dong; Jian, Yu-Tao; Guess, Petra C; Swain, Michael V; Zhang, Xin-Ping; Zhao, Ke

2014-11-01

The purpose of this in vitro study was to evaluate the effect of core ceramic grinding on the fracture behaviour of bilayered lithium disilicate glass-ceramic (LDG) under two loading schemes. Interfacial surfaces of sandblasted LDG disks (A) were ground with 220 (B), 500 (C) and 1200 (D) grit silicon carbide (SiC) sandpapers, respectively. Surface roughness and topographic analysis were performed using a profilometer and a scanning electron microscopy (SEM), and then underwent retesting after veneer firing. Biaxial fracture strength (σf) and Weibull modulus (m) were calculated either with core in tension (subgroup t) or in compression (subgroup c). Failure modes were observed by SEM, and loading induced stress distribution was simulated and analyzed by finite element analysis. Statistical data analysis was performed using Kruskal-Wallis, one-way ANOVA, and paired test at a significance level of 0.05. As the grits size of SiC increased, LDG surface roughness decreased from group A to D (p<0.001), which remained unchanged after veneer firing. No difference in σf (p=0.41 for subgroups At-Dt; p=0.11 for subgroups Ac-Dc), m values as well as failure modes was found among four subgroups for both loading schemes. Specimens in subgroup t showed higher σf (p<0.001) and m values than subgroup c. Stress distribution between loading schemes did not differ from each other. Cracks, as the dominant failure mode initiated from bottom tensile surface. No sign of interfacial cracking or delamination was observed for all groups. Technician grinding changed surface topography of LDG ceramic material, but was not detrimental to the bilayered system strength after veneer application. LDG bilayered system was more sensitive to fracture when loaded with veneer porcelain in tension. Within the limitations of the simulated grinding applied, it is concluded that veneer porcelain can be applied directly after technician grinding of LDG ceramic as it has no detrimental effect on the strength of bilayered structures. The connector areas of LDG fixed dental prosthesis are more sensitive to fracture compared with single crowns, and should be fabricated with more caution. Copyright © 2014 Elsevier Ltd. All rights reserved.

Coaxial Electrospinning and Characterization of Core-Shell Structured Cellulose Nanocrystal Reinforced PMMA/PAN Composite Fibers

PubMed Central

Li, Chao; Li, Qingde; Ni, Xiaohui; Liu, Guoxiang; Cheng, Wanli; Han, Guangping

2017-01-01

A modified coaxial electrospinning process was used to prepare composite nanofibrous mats from a poly(methyl methacrylate) (PMMA) solution with the addition of different cellulose nanocrystals (CNCs) as the sheath fluid and polyacrylonitrile (PAN) solution as the core fluid. This study investigated the conductivity of the as-spun solutions that increased significantly with increasing CNCs addition, which favors forming uniform fibers. This study discussed the effect of different CNCs addition on the morphology, thermal behavior, and the multilevel structure of the coaxial electrospun PMMA + CNCs/PAN composite nanofibers. A morphology analysis of the nanofibrous mats clearly demonstrated that the CNCs facilitated the production of the composite nanofibers with a core-shell structure. The diameter of the composite nanofibers decreased and the uniformity increased with increasing CNCs concentrations in the shell fluid. The composite nanofibrous mats had the maximum thermal decomposition temperature that was substantially higher than electrospun pure PMMA, PAN, as well as the core-shell PMMA/PAN nanocomposite. The BET (Brunauer, Emmett and Teller) formula results showed that the specific surface area of the CNCs reinforced core-shell composite significantly increased with increasing CNCs content. The specific surface area of the composite with 20% CNCs loading rose to 9.62 m2/g from 3.76 m2/g for the control. A dense porous structure was formed on the surface of the electrospun core-shell fibers. PMID:28772933

Barium and calcium analyses in sediment cores using µ-XRF core scanners

NASA Astrophysics Data System (ADS)

Acar, Dursun; Çaǧatay, Namık; Genç, S. Can; Eriş, K. Kadir; Sarı, Erol; Uçarkus, Gülsen

2017-04-01

Barium and Ca are used as proxies for organic productivity in paleooceanographic studies. With its heavy atomic weight (137.33 u), barium is easily detectable in small concentrations (several ppm levels) in marine sediments using XRF methods, including the analysis by µ-XRF core scanners. Calcium has an intermediate atomic weight (40.078 u) but is a major element in the earth's crust and in sediments and sedimentary rocks, and hence it is easily detectable by µ-XRF techniques. Normally, µ-XRF elemental analysis of cores are carried out using split half cores or 1-2 cm thich u-channels with an original moisture. Sediment cores show variation in different water content (and porosity) along their length. This in turn results in variation in the XRF counts of the elements and causes error in the elemental concentrations. We tried µ-XRF elemental analysis of split half cores, subsampled as 1 cm thick u-channels with original moisture and 0.3 mm-thin film slices of the core with original wet sample and after air drying with humidity protector mylar film. We found considerable increase in counts of most elements, and in particular for Ba and Ca, when we used 0.3 mm thin film, dried slice. In the case of Ba, the counts increased about three times that of the analysis made with wet and 1 cm thick u-channels. The higher Ba and Ca counts are mainly due to the possible precipitation of Ba as barite and Ca as gypsum from oxidation of Fe-sulphides and the evaporation of pore waters. The secondary barite and gypsum precipitation would be especially serious in unoxic sediment units, such as sapropels, with considerable Fe-sulphides and bio-barite.It is therefore suggested that reseachers should be cautious of such secondary precipitation on core surfaces when analyzing cores that have long been exposed to the atmospheric conditions.

Proceedings of the Edgewood Chemical Biological Center In-House Laboratory Independent Research and Surface Science Initiative Programs FY12

DTIC Science & Technology

2012-01-01

mind." ECBC views the ILIR as a critical part of its efforts at ensuring a high level of basic science, to foster innovation in the areas of...program solicits innovative proposals from the center’s principal investigators that correspond to ECBC’s critical core capability areas: Inhalation...are compiled and used, with the numerical score, as a critical assessment of the proposal. This written feedback is essential for ECBC’s mentoring

A 10-MJ compact homopolar generator

NASA Astrophysics Data System (ADS)

McKee, B. D.; McNab, I. R.

1986-11-01

The design and initial testing of a lightweight (5 kJ/kg) iron-cored homopolar generator is described. The machine employs an external power supply to motor up to operating speed (12,500 rpm) at which point 10 MJ of energy is stored in the steel rotor. Copper-graphite brushes in the stator, actuated by pneumatic actuators, make contact with the rotor surface and permit the inertial energy to be transferred to a load circuit at current levels up to 1.5 MA and voltages up to 60 V.

Chemical and structural order in silicon oxynitrides by methods of surface physics

NASA Astrophysics Data System (ADS)

Finster, J.; Heeg, J.; Klinkenberg, E.-D.

A large number of thin amorphous layers of SiO xN y and several (crystalline) reference compounds (SiO 2, Si 3N 4, Si 2N 2O) are studied. Although XANES and SEXAFS are well sulted to derive structural and chemical order, for these compounds many problems remain to be solved. We show how core level spectra (XPS, AES) can be used to gain such information (e.g. random bonding structure, N coordination, oxidation behaviour).

Nature of distribution of mercury in the sediments of the river Yamuna (tributary of the Ganges), India.

PubMed

Subramanian, V; Madhavan, N; Saxena, Rajinder; Lundin, Lars-Christer

2003-06-01

Suspended Particulate Matter (SPM), surface (bed sediments) and short length cores of sediments collected from the largest tributary of the river Ganges, namely the river Yamuna, were analysed for total mercury as well as its fractionation in various size and chemical sites in the sediments following standard procedures. Also, attempts were made to determine the vertical distribution in sediments in relation to the recent timescale of a few decades. Our observations indicate that the SPM in general showed higher levels of total mercury compared to the surface sediments while at places the enhancement could be by a factor of 10, say around 25 microg g(-1) in the downstream region that integrates the industrial midstream and agricultural downstream terrain near its confluence with the Ganges. Surface sediments in the upstream direction near the Himalayan foothills and SPM in the lower reaches showed significant high Index of Geoaccumulation (Igeo) as defined by Müller. Size fractionation studies indicate that the finer fraction preferentially showed higher levels of mercury while in the lower reaches of the river, the total mercury is equitably distributed among all size fractions. The proportion of the residual fraction of mercury in relation to mobile fractions, in general decreases downstream towards its confluence with the Ganges river. In sediment cores, the vertical distribution show systematic peaks of mercury indicating that addition of this toxic metal to the aquatic system is in direct proportion to the increase in various types of human activities such as thermal power plants, land use changes (urbanisation) in the midstream region and intensive fertiliser application in lower reaches of this vast river basin.

Fabrication of a polyvinylidene difluoride fiber with a metal core and its application as directional air flow sensor

NASA Astrophysics Data System (ADS)

Bian, Yixiang; Liu, Rongrong; Hui, Shen

2016-09-01

We fabricated a sensitive air flow detector that mimic the sensing mechanism found at the tail of some insects. [see Y. Yang, A. Klein, H. Bleckmann and C. Liu, Appl. Phys. Lett. 99(2) (2011); J. J. Heys, T. Gedeon, B. C. Knott and Y. Kim, J. Biomech. 41(5), 977 (2008); J. Tao and X. Yu, Smart Mat. Struct. 21(11) (2012)]. Our bionic airflow sensor uses a polyvinylidene difluoride (PVDF) microfiber with a molybdenum core which we produced with the hot extrusion tensile method. The surface of the fiber is partially coated with conductive silver adhesive that serve as surface electrodes. A third electrode, the metal core is used to polarize polyvinylidene difluoride (PVDF) under the surface electrodes. The cantilever beam structure of the prepared symmetric electrodes of metal core piezoelectric fiber (SMPF) is used as the artificial hair airflow sensor. The surface electrodes are used to measure output voltage. Our theoretical and experimental results show that the SMPF responds fast to air flow changes, the output charge has an exponential correlation with airflow velocity and a cosine relation with the direction of airflow. Our bionic airflow sensor with directional sensing ability can also measure air flow amplitude. [see H. Droogendijk, R. G. P. Sanders and G. J. M. Krijnen, New J. Phys. 15 (2013)]. By using two surface electrodes, our sensing circuit further improves sensitivity.

Marine historical ecology at the Brijuni Islands, Croatia: preliminary results from down-core changes of foraminiferal assemblages

NASA Astrophysics Data System (ADS)

Vidovic, Jelena; Cosovic, Vlasta; Gallmetzer, Ivo; Haselmair, Alexandra; Zuschin, Martin

2015-04-01

The Late Holocene in the northern Adriatic is characterized by the eustatic peak of the sea-level rise, followed by the equilibrium between the regional tectonic subsidence and hydro-isostatic emergence and relatively stable sea level for a few thousand years. During this period the area experienced changes in sedimentation rate, food/oxygen availability in the benthic ecosystem and eutrophication with seasonal hypoxic and anoxic events. In order to reconstruct the marine paleoecology in the Brijuni Islands area during this period, a multidisciplinary study was carried out, including geochemical (TOC, trace metals, carbonate content), micropaleontological analyses (benthic foraminifera) and dating of sediments and mollusc shells. The principal aim of this study is to observe the effects of ecological shifts on foraminiferal assemblages during the Late Holocene. One core of 1.5 m length was taken at a sampling station south of Veli Brijuni Island, located within a marine protected area with no fishing/dredging pressure (Croatian national park). The core was sliced into smaller subsamples, and four sediment fractions of each subsample (63, 125, 250 and 500 µm) were analyzed for standard properties of the foraminiferal community (species richness, faunal composition, biodiversity indices), in comparison with relevant physical and geochemical properties of the sediment. The results concerning changes in foraminiferal species composition and abundance point to differences within the core: surface sediments are dominated by suspension feeders (Planorbulina mediterranensis, Lobatula lobatula, Cibicides variabilis, Cibicides refulgens), whereas deposit feeders (genera Textularia, Siphonaperta, Adelosina, Trioculina) appear in higher abundances at approximately 30 cm of the sediment depth and dominate down-core. Species richness in the first 30 cm is lower (10 to 34 species per sample) in comparison to the middle part of the core (39 to 53 species), and decreases again at 100 cm to 25 to 42 species per sample. Diversity indices follow the pattern of species richness and point to normal marine conditions. Similarity indices rise with core depth. The radiometric dating of the sediments together with carbon-calibrated amino acid- racemisation of mollusc shells from selected species will help to determine the timing of major ecological changes.

TOPAZ-2 reactor distribution during descent in the atmosphere and at the impact with the Earth surface

NASA Astrophysics Data System (ADS)

Grinberg, Eduard I.; Nikolaev, Vadim S.; Sokolov, Nikolai A.; Doschatov, Vitaly V.; Usov, Veniamin A.; Gulidov, Aleksander I.

1995-01-01

The paper presents results of more accurate computational analysis of the TOPAZ-2 system reactor core aerodynamic disruption at an inadvertent reentry. Given are preliminary results on the pattern of disruption of the core partially burnt during its descent in the atmosphere at its impact on the surface of water and sandstone (medium density concrete).

Effects of Two Types of Melatonin-Loaded Nanocapsules with Distinct Supramolecular Structures: Polymeric (NC) and Lipid-Core Nanocapsules (LNC) on Bovine Embryo Culture Model.

PubMed

Komninou, Eliza Rossi; Remião, Mariana Härter; Lucas, Caroline Gomes; Domingues, William Borges; Basso, Andrea Cristina; Jornada, Denise Soledade; Deschamps, João Carlos; Beck, Ruy Carlos Ruver; Pohlmann, Adriana Raffin; Bordignon, Vilceu; Seixas, Fabiana Kömmling; Campos, Vinicius Farias; Guterres, Silvia Stanisçuaski; Collares, Tiago

2016-01-01

Melatonin has been used as a supplement in culture medium to improve the efficiency of in vitro produced mammalian embryos. Through its ability to scavenge toxic oxygen derivatives and regulate cellular mRNA levels for antioxidant enzymes, this molecule has been shown to play a protective role against damage by free radicals, to which in vitro cultured embryos are exposed during early development. In vivo and in vitro studies have been performed showing that the use of nanocapsules as active substances carriers increases stability, bioavailability and biodistribution of drugs, such as melatonin, to the cells and tissues, improving their antioxidant properties. These properties can be modulated through the manipulation of formula composition, especially in relation to the supramolecular structures of the nanocapsule core and the surface area that greatly influences drug release mechanisms in biological environments. This study aimed to evaluate the effects of two types of melatonin-loaded nanocapsules with distinct supramolecular structures, polymeric (NC) and lipid-core (LNC) nanocapsules, on in vitro cultured bovine embryos. Embryonic development, apoptosis, reactive oxygen species (ROS) production, and mRNA levels of genes involved in cell apoptosis, ROS and cell pluripotency were evaluated after supplementation of culture medium with non-encapsulated melatonin (Mel), melatonin-loaded polymeric nanocapsules (Mel-NC) and melatonin-loaded lipid-core nanocapsules (Mel-LNC) at 10-6, 10-9, and 10-12 M drug concentrations. The highest hatching rate was observed in embryos treated with 10-9 M Mel-LNC. When compared to Mel and Mel-NC treatments at the same concentration (10-9 M), Mel-LNC increased embryo cell number, decreased cell apoptosis and ROS levels, down-regulated mRNA levels of BAX, CASP3, and SHC1 genes, and up-regulated mRNA levels of CAT and SOD2 genes. These findings indicate that nanoencapsulation with LNC increases the protective effects of melatonin against oxidative stress and cell apoptosis during in vitro embryo culture in bovine species.