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1

Unraveling the electronic structure of azolehemiporphyrazines: direct spectroscopic observation of magnetic dipole allowed nature of the lowest ?-?* transition of 20?-electron porphyrinoids.  

PubMed

Hemiporphyrazines are a large family of phthalocyanine analogues in which two isoindoline units are replaced by other rings. Here we report unambiguous identification of 20?-electron structure of triazolehemiporphyrazines (1, 2) and thiazolehemiporphyrazine (3) by means of X-ray analysis, various spectroscopic methods, and density functional theory (DFT) calculations. The hemiporphyrazines were compared in detail with dibenzotetraazaporphyrin (4), a structurally related 18?-electron molecule. X-ray analysis revealed that tetrakis(2,6-dimethylphenyloxy)triazolehemiporphyrazine (1b) adopted planar geometry in the solid state. A weak absorption band with a pronounced vibronic progression, observed for all the hemiporphyrazines, was attributed to the lowest ?-?* transition with the electric-dipole-forbidden nature. In the case of intrinsically chiral vanadyl triazolehemiporphyrazine (2), a large dissymmetry (g) factor was detected for the CD signal corresponding to the lowest ?-?* transition with the magnetic-dipole-allowed nature. Molecular orbital analysis and NICS calculations showed that the azolehemiporphyrazines have a 20?-electron system with a weak paratropic ring current. PMID:24866729

Muranaka, Atsuya; Ohira, Shino; Toriumi, Naoyuki; Hirayama, Machiko; Kyotani, Fumiko; Mori, Yukie; Hashizume, Daisuke; Uchiyama, Masanobu

2014-06-26

2

Markov models for community dynamics allowing for observation error.  

PubMed

Markov models are dynamic models that characterize transitions among discrete ecological states with transition probability matrices. Such models are widely used to infer community dynamics of sessile organisms because transition probabilities (the elements of transition probability matrices) can be estimated with time series data from "grid sampling," where species occupancy states are assessed at multiple fixed points in a quadrat or transect. These estimates, however, are known to be biased when resampling error exists. In this study, we used the perspective of multistate dynamic occupancy models to develop a new Markov model that is structured hierarchically such that transitions among occupancy states and observation processes are considered explicitly at each fixed point. We show that, by adopting a hierarchical Bayesian approach, our model provides estimates for transition probabilities that are robust to sampling error. We also show that error rate may be estimated without additional data obtained from rapid repeated sampling. Considerations for the analysis for the application to real data set and potential extensions of the proposed model are discussed. PMID:24597214

Fukaya, Keiichi; Royle, J Andrew

2013-12-01

3

Direct observation of time reversal violation  

SciTech Connect

A direct evidence for Time Reversal Violation (TRV) means an experiment that, considered by itself, clearly shows TRV independent of, and unconnected to, the results for CP Violation. No existing result before the recent BABAR experiment with entangled neutral B mesons had demonstrated TRV in this sense. There is a unique opportunity for a search of TRV with unstable particles thanks to the Einstein-Podolsky-Rosen (EPR) Entanglement between the two neutral mesons in B, and PHI, Factories. The two quantum effects of the first decay as a filtering measurement and the transfer of information to the still living partner allow performing a genuine TRV asymmetry with the exchange of 'in' and 'out' states. With four independent TRV asymmetries, BABAR observes a large deviation of T-invariance with a statistical significance of 14 standard deviations, far more than needed to declare the result as a discovery. This is the first direct observation of TRV in the time evolution of any system.

Bernabeu, J. [Department of Theoretical Physics, University of Valencia, and IFIC, Joint Centre Univ. Valencia-CSIC (Spain)

2013-06-12

4

Direct chromatin PCR (DC-PCR): hypotonic conditions allow differentiation of chromatin states during thermal cycling.  

PubMed

Current methods to study chromatin configuration are not well suited for high throughput drug screening since they require large cell numbers and multiple experimental steps that include centrifugation for isolation of nuclei or DNA. Here we show that site specific chromatin analysis can be achieved in one step by simply performing direct chromatin PCR (DC-PCR) on cells. The basic underlying observation was that standard hypotonic PCR buffers prevent global cellular chromatin solubilization during thermal cycling while more loosely organized chromatin can be amplified. Despite repeated heating to >90 °C, 41 of 61 tested 5' sequences of silenced genes (CDKN2A, PU.1, IRF4, FOSB, CD34) were not amplifiable while 47 could be amplified from expressing cells. Two gene regions (IRF4, FOSB) even required pre-heating of cells in isotonic media to allow this differentiation; otherwise none of 19 assayed sequences yielded PCR products. Cells with baseline expression or epigenetic reactivation gave similar DC-PCR results. Silencing during differentiation of CD34 positive cord blood cells closed respective chromatin while treatment of myeloma cells with an IRF4 transcriptional inhibitor opened a site to DC-PCR that was occupied by RNA polymerase II and NF?B as determined by ChIP. Translation into real-time PCR can not be achieved with commercial real-time PCR buffers which potently open chromatin, but even with simple ethidium bromide addition to standard PCR mastermix we were able to identify hits in small molecules screens that suppressed IRF4 expression or reactivated CDKN2A in myeloma cells using densitometry or visual inspection of PCR plates under UV light. While need in drug development inspired this work, application to genome-wide analysis appears feasible using phi29 for selective amplification of open cellular chromatin followed by library construction from supernatants since such supernatants yielded similar results as gene specific DC-PCR. PMID:22984542

Vatolin, Sergei; Khan, Shahper N; Reu, Frederic J

2012-01-01

5

Observe how the monsoon changes direction  

NSDL National Science Digital Library

This Earth science animation shows high school students how changes in wind speed and direction are associated with the Asian monsoon. The introduction explains how seasonal movement of air pressure belts cause winds to change direction. The animation uses a map to present the average April to December precipitation in Asia during the years 1985-1989. Color-enhancement indicates precipitation, and wind speed and direction are designated by arrows. Movie controls allow students to repeat, pause, or step through the animation, which can give students more time to analyze the images. Copyright 2005 Eisenhower National Clearinghouse

TERC. Center for Earth and Space Science Education

2003-01-01

6

Direct observation of chemical bond dynamics on surfaces.  

PubMed

The dynamics of chemisorbed species as they swing to-and-fro on their adsorption sites may be directly observed with electron-stimulated desorption. The observation of the thermal disorder in adsorbate chemical bond directions, through studies of the thermal excitation of librational modes, allows one to visualize the potential energy surfaces controlling the structure and dynamics of adsorbates on single crystal metal and semiconductor surfaces. This information may be useful in understanding surface diffusion as well as the spatial aspects of surface chemical reactions. PMID:17801228

Yates, J T; Alvey, M D; Dresser, M J; Henderson, M A; Kiskinova, M; Ramsier, R D; Szabó, A

1992-03-13

7

First direct observation of muon antineutrino disappearance  

E-print Network

This letter reports the first direct observation of muon antineutrino disappearance. The MINOS experiment has taken data with an accelerator beam optimized for muon antineutrino production, accumulating an exposure of $1.71\\times 10^{20}$ protons on target. In the Far Detector, 97 charged current muon antineutrino events are observed. The no-oscillation hypothesis predicts 156 events and is excluded at $6.3\\sigma$. The best fit to oscillation yields $\\Delta \\bar{m}^{2}=(3.36^{+0.46}_{-0.40}\\trm{(stat.)}\\pm0.06\\trm{(syst.)})\\times 10^{-3}\\,\\eV^{2}$, $\\sin^{2}(2\\bar{\\theta})=0.86^{+0.11}_{-0.12}\\trm{(stat.)}\\pm0.01\\trm{(syst.)}$. The probability that the underlying muon neutrino and muon antineutrino parameters are identical is 2.0%.

Adamson, P; Auty, D J; Ayres, D S; Backhouse, C; Barr, G; Bishai, M; Blake, A; Bock, G J; Boehnlein, D J; Bogert, D; Cavanaugh, S; Cherdack, D; Childress, S; Choudhary, B C; Coelho, J A B; Coleman, S J; Corwin, L; Cronin-Hennessy, D; Danko, I Z; de Jong, J K; Devenish, N E; Diwan, M V; Dorman, M; Escobar, C O; Evans, J J; Falk, E; Feldman, G J; Frohne, M V; Gallagher, H R; Gomes, R A; Goodman, M C; Gouffon, P; Graf, N; Gran, R; Grant, N; Grzelak, K; Habig, A; Harris, D; Hartnell, J; Hatcher, R; Himmel, A; Holin, A; Huang, X; Hylen, J; Ilic, J; Irwin, G M; Isvan, Z; Jaffe, D E; James, C; Jensen, D; Kafka, T; Kasahara, S M S; Koizumi, G; Kopp, S; Kordosky, M; Kreymer, A; Lang, K; Lefeuvre, G; Ling, J; Litchfield, P J; Loiacono, L; Lucas, P; Mann, W A; Marshak, M L; Mayer, N; McGowan, A M; Mehdiyev, R; Meier, J R; Messier, M D; Miller, W H; Mishra, S R; Mitchell, J; Moore, C D; Morfín, J; Mualem, L; Mufson, S; Musser, J; Naples, D; Nelson, J K; Newman, H B; Nichol, R J; Nicholls, T C; Nowak, J A; Ochoa-Ricoux, J P; Oliver, W P; Orchanian, M; Ospanov, R; Paley, J; Patterson, R B; Pawloski, G; Pearce, G F; Petyt, D A; Phan-Budd, S; Plunkett, R K; Qiu, X; Ratchford, J; Raufer, T M; Rebel, B; Rodrigues, P A; Rosenfeld, C; Rubin, H A; Sanchez, M C; Schneps, J; Schreiner, P; Shanahan, P; Sousa, A; Stamoulis, P; Strait, M; Tagg, N; Talaga, R L; Tetteh-Lartey, E; Thomas, J; Thomson, M A; Tinti, G; Toner, R; Tzanakos, G; Urheim, J; Vahle, P; Viren, B; Weber, A; Webb, R C; White, C; Whitehead, L; Wojcicki, S G; Yang, T; Zwaska, R

2011-01-01

8

First direct observation of muon antineutrino disappearance  

SciTech Connect

This letter reports the first direct observation of muon antineutrino disappearance. The MINOS experiment has taken data with an accelerator beam optimized for ??? production, accumulating an exposure of 1.71 x 1020 protons on target. In the Far Detector, 97 charged current ??? events are observed. The no-oscillation hypothesis predicts 156 events and is excluded at 6.3?. The best fit to oscillation yields |?m?2| = (3.36-0.40 +0.46(stat.) ± 0.06(syst.)) x 10-3 eV2, sin2(2 ??) = 0.86-0.12+0.11 (stat.) ± 0.01(syst.). The MINOS ?? and ??? measurements are consistent at the 2.0% confidence level, assuming identical underlying oscillation parameters.

Adamson, P [Fermilab; Andreopoulos, C [Rutherford; Auty, D J [Sussex U.; Ayres, D S [Argonne; Backhouse, C [Oxford U.; Barr, G [Oxford U.; Bishai, M [Brookhaven; Blake, A [Cambridge U.; Bock, G J [Fermilab; Boehnlein, D J [/Fermilab; Bogert, D [Fermilab; Harvard U., Phys. Dept.

2011-07-05

9

Direct observation of sub-binomial light.  

PubMed

Nonclassical states of light are necessary resources for quantum technologies such as cryptography, computation and the definition of metrological standards. Observing signatures of nonclassicality generally requires inferring either the photon number distribution or a quasiprobability distribution indirectly from a set of measurements. Here, we report an experiment in which the nonclassical character of families of quantum states is assessed by direct inspection of the outcomes from a multiplexed photon counter. This scheme does not register the actual photon number distribution; the statistics of the detector clicks alone serve as a witness of nonclassicality, as proposed by Sperling et al. [Phys. Rev. Lett. 109, 093601 (2012)]. Our work paves a way for the practical characterization of increasingly sophisticated states and detectors. PMID:23679726

Bartley, Tim J; Donati, Gaia; Jin, Xian-Min; Datta, Animesh; Barbieri, Marco; Walmsley, Ian A

2013-04-26

10

A General Ligand Design for Gold Catalysis allowing Ligand-Directed Anti Nucleophilic Attack of Alkynes  

PubMed Central

Most homogenous gold catalyses demand ?0.5 mol % catalyst loading. Due to the high cost of gold, these reactions are unlikely to be applicable in medium or large scale applications. Here we disclose a novel ligand design based on the privileged biphenyl-2-phosphine framework that offers a potentially general approach to dramatically lowering catalyst loading. In this design, an amide group at the 3’ position of the ligand framework directs and promotes nucleophilic attack at the ligand gold complex-activated alkyne, which is unprecedented in homogeneous gold catalysis considering the spatial challenge of using ligand to reach antiapproaching nucleophile in a linear P-Au-alkyne centroid structure. With such a ligand, the gold(I) complex becomes highly efficient in catalyzing acid addition to alkynes, with a turnover number up to 99,000. Density functional theory calculations support the role of the amide moiety in directing the attack of carboxylic acid via hydrogen bonding. PMID:24704803

Wang, Yanzhao; Wang, Zhixun; Li, Yuxue; Wu, Gongde; Cao, Zheng; Zhang, Liming

2014-01-01

11

New directions in childhood obesity research: how a comprehensive biorepository will allow better prediction of outcomes  

PubMed Central

Background Childhood obesity is associated with the early development of diseases such as type 2 diabetes and cardiovascular disease. Unfortunately, to date, traditional methods of research have failed to identify effective prevention and treatment strategies, and large numbers of children and adolescents continue to be at high risk of developing weight-related disease. Aim To establish a unique 'biorepository' of data and biological samples from overweight and obese children, in order to investigate the complex 'gene × environment' interactions that govern disease risk. Methods The 'Childhood Overweight BioRepository of Australia' collects baseline environmental, clinical and anthropometric data, alongside storage of blood samples for genetic, metabolic and hormonal profiles. Opportunities for longitudinal data collection have also been incorporated into the study design. National and international harmonisation of data and sample collection will achieve required statistical power. Results Ethical approval in the parent site has been obtained and early data indicate a high response rate among eligible participants (71%) with a high level of compliance for comprehensive data collection (range 56% to 97% for individual study components). Multi-site ethical approval is now underway. Conclusions In time, it is anticipated that this comprehensive approach to data collection will allow early identification of individuals most susceptible to disease, as well as facilitating refinement of prevention and treatment programs. PMID:20969745

2010-01-01

12

Bacterial RTX toxins allow acute ATP release from human erythrocytes directly through the toxin pore.  

PubMed

ATP is as an extracellular signaling molecule able to amplify the cell lysis inflicted by certain bacterial toxins including the two RTX toxins ?-hemolysin (HlyA) from Escherichia coli and leukotoxin A (LtxA) from Aggregatibacter actinomycetemcomitans. Inhibition of P2X receptors completely blocks the RTX toxin-induced hemolysis over a larger concentration range. It is, however, at present not known how the ATP that provides the amplification is released from the attacked cells. Here we show that both HlyA and LtxA trigger acute release of ATP from human erythrocytes that preceded and were not caused by cell lysis. This early ATP release did not occur via previously described ATP-release pathways in the erythrocyte. Both HlyA and LtxA were capable of triggering ATP release in the presence of the pannexin 1 blockers carbenoxolone and probenecid, and the HlyA-induced ATP release was found to be similar in erythrocytes from pannexin 1 wild type and knock-out mice. Moreover, the voltage-dependent anion channel antagonist TRO19622 had no effect on ATP release by either of the toxins. Finally, we showed that both HlyA and LtxA were able to release ATP from ATP-loaded lipid (1-palmitoyl-2-oleoyl-phosphatidylcholine) vesicles devoid of any erythrocyte channels or transporters. Again we were able to show that this happened in a non-lytic fashion, using calcein-containing vesicles as controls. These data show that both toxins incorporate into lipid vesicles and allow ATP to be released. We suggest that both toxins cause acute ATP release by letting ATP pass the toxin pores in both human erythrocytes and artificial membranes. PMID:24860098

Skals, Marianne; Bjaelde, Randi G; Reinholdt, Jesper; Poulsen, Knud; Vad, Brian S; Otzen, Daniel E; Leipziger, Jens; Praetorius, Helle A

2014-07-01

13

Direct Observation of Paramagnons in Palladium  

SciTech Connect

We report an inelastic neutron scattering study of the spin fluctuations in the nearly ferromagnetic element palladium. Dispersive over-damped collective magnetic excitations or 'paramagnons' are observed up to 128 meV. We analyze our results in terms of a Moriya-Lonzarich-type spin-fluctuation model and estimate the contribution of the spin fluctuations to the low-temperature heat capacity. In spite of the paramagnon excitations being relatively strong, their relaxation rates are large. This leads to a small contribution to the low-temperature electronic specific heat.

Doubble, R. [University of Bristol, UK; Hayden, S M. [University of Bristol, UK; Dai, Pengcheng [University of Tennessee, Knoxville (UTK); Mook Jr, Herbert A [ORNL; Thompson, James R [ORNL; Frost, C. [ISIS Facility, Rutherford Appleton Laboratory

2010-01-01

14

Type I interferons directly inhibit regulatory T cells to allow optimal antiviral T cell responses during acute LCMV infection  

PubMed Central

Regulatory T (T reg) cells play an essential role in preventing autoimmunity but can also impair clearance of foreign pathogens. Paradoxically, signals known to promote T reg cell function are abundant during infection and could inappropriately enhance T reg cell activity. How T reg cell function is restrained during infection to allow the generation of effective antiviral responses remains largely unclear. We demonstrate that the potent antiviral type I interferons (IFNs) directly inhibit co-stimulation–dependent T reg cell activation and proliferation, both in vitro and in vivo during acute infection with lymphocytic choriomeningitis virus (LCMV). Loss of the type I IFN receptor specifically in T reg cells results in functional impairment of virus-specific CD8+ and CD4+ T cells and inefficient viral clearance. Together, these data demonstrate that inhibition of T reg cells by IFNs is necessary for the generation of optimal antiviral T cell responses during acute LCMV infection. PMID:24711580

Srivastava, Shivani; Koch, Meghan A.; Pepper, Marion

2014-01-01

15

Enabling direct nanoscale observations of biological reactions with dynamic TEM  

SciTech Connect

Biological processes can occur over a wide range of spatial and temporal scales; from femtoseconds to hours and from angstroms to meters. Although no single experimental method can fully cover this entire phase space, many new biological insights can be expected from a better understanding of the processes that occur on the very fast timescales and very small length scales. In this regard, new instruments that use fast x-ray or electron pulses are now available that are expected to reveal new mechanistic insights for macromolecular protein dynamics. To ensure that any observed conformational change is physiologically relevant and not constrained by three-dimensional crystal packing, it would be preferable for experiments to utilize smaller protein samples such as single particles or two-dimensional crystals that mimic the target protein’s native environment. These samples aren’t typically amenable to x-ray analysis, but transmission electron microscopy has successfully imaged such sample geometries for over 40 years and permits data acquisition using both direct imaging and diffraction modes. While conventional transmission electron microscopes (TEM) have only visualized biological samples with atomic resolution in an arrested or frozen state, the recent development of the dynamic TEM (DTEM) extends electron microscopy capabilities into dynamics. A new 2nd generation DTEM that is currently being constructed has the potential to observe live biological processes with unprecedented spatiotemporal resolution by using pulsed electron packets to probe the sample on the micro- and nanosecond timescale. In addition to the enhanced temporal resolution, the DTEM also operates in the pump-probe regime that can permit visualizing reactions propagating in real-time. This article reviews the experimental parameters necessary for coupling DTEM with in situ liquid microscopy to allow direct imaging of protein conformational dynamics in a fully hydrated environment.

Evans, James E.; Browning, Nigel D.

2013-02-18

16

Plasmon Surface Polariton Dispersion by Direct Optical Observation.  

ERIC Educational Resources Information Center

Describes several simple experiments that can be used to observe directly the dispersion curve of plasmon surface polaritons (PSP) on flat metal surfaces. A method is described of observing the increonental change in the wave vector of the PSP due to coatings that differ in thickness by a few nanometers. (Author/CS)

Swalen, J. D.; And Others

1980-01-01

17

Evaluation of Handheld Computers for Direct Systematic Classroom Observation  

ERIC Educational Resources Information Center

Through this study the authors evaluate outcomes associated with the use of handheld computers by interventionists in improving the efficiency of direct systematic classroom observation. Information from observations is used by interventionists for treatment planning and evaluation. In this study, interventionists were trained to use personal…

Bahr, Michael W.; Gouwens, Donald A.; Schuh, Genevieve

2012-01-01

18

Positively charged nanogold label allows the observation of fine cell filopodia and flagella in solution by atmospheric scanning electron microscopy.  

PubMed

Optical microscopy is generally the first choice to observe microbes and cells. However, its resolution is not always sufficient to reveal specific target structures, such as flagella and pili, which are only nanometers wide. ASEM is an attractive higher resolution alternative, as the sample is observed in aqueous solution at atmospheric pressure. Sample pretreatment for ASEM only comprises simple tasks including fixation, gold labeling, and reagent exchange, taking less than 1 h in total. The lengthy sample pretreatments often required for more classical electron microscopies, such as embedding and dehydration, are unnecessary, and native morphology is preserved. In this study, positively charged nanogold particles were used to label the surfaces of bacteria and cultured animal cells, exploiting their net negative surface charge. After gold enhancement to increase the size of the nanogold particles, ASEM imaging of the bacteria in aqueous solution revealed pili and delicate spiral flagella. This natural shape contrasts starkly with images of dried flagella recorded by standard SEM. Positively charged nanogold labeled the plasma membrane of cultured COS7 cells, and after enhancement allowed filopodia as thin as 100 nm in diameter to be clearly visualized. Based on these studies, ASEM combined with positively charged nanogold labeling promises to become an important tool for the study of cell morphology and dynamics in the near future. PMID:24343867

Nishiyama, Hidetoshi; Teramoto, Kanae; Suga, Mitsuo; Sato, Chikara

2014-02-01

19

Retinex Image Processing: Improved Fidelity To Direct Visual Observation  

NASA Technical Reports Server (NTRS)

Recorded color images differ from direct human viewing by the lack of dynamic range compression and color constancy. Research is summarized which develops the center/surround retinex concept originated by Edwin Land through a single scale design to a multi-scale design with color restoration (MSRCR). The MSRCR synthesizes dynamic range compression, color constancy, and color rendition and, thereby, approaches fidelity to direct observation.

Jobson, Daniel J.; Rahman, Zia-Ur; Woodell, Glenn A.

1996-01-01

20

Abstract--Remotely operated crawlers are specialized vehicles that allow for underwater intervention by staying in direct  

E-print Network

operated vehicle crawler for multiple research activities such as underwater archaeology documentation -- Remotely Operated Vehicle, ROV, Remotely Operated Crawler, Robotics, Underwater Archaeology, Marine1 Abstract-- Remotely operated crawlers are specialized vehicles that allow for underwater

Wood, Stephen L.

21

The Behavior Observation Instrument: a method of direct observation for program evaluation.  

PubMed Central

The background and development of a multicategory direct observation system, the Behavior Observation Instrument (BOI), is described. This time-sampling procedure for recording the behavior of persons is demonstrated in several treatment settings and the results applied to issues of program evaluation. Elements that have prevented direct observation from being widely adopted, such as costs, manpower, and training requirements, are systematically analyzed. A basic psychometric analysis of the instrument is used to determine optimum frequency and duration of observation intervals as well as observer agreement. The results imply that direct observation methods, once assumed by some to belong to the special province of the single-subject design, can be used to assess the effects of programs on groups of psychiatric clients in an efficient and economic manner. PMID:97258

Alevizos, P; DeRisi, W; Liberman, R; Eckman, T; Callahan, E

1978-01-01

22

Experimental observations of shear patterns in direct shear tests  

Microsoft Academic Search

A series of simple experiments were performed using direct shear apparatus in order to study the rupture patterns in sands. Measurements of internal displacements were made by observing with X-rays the positions of lead shot placed in a regular array within the sample. Shear displacement was applied manually and radiographs were taken after each increment of horizontal movement in order

G. Scarpelli; D. M. Wood

1982-01-01

23

Quantifying predation on soybean aphid through direct field observations  

E-print Network

Quantifying predation on soybean aphid through direct field observations Alejandro C. Costamagna Received 8 August 2006; accepted 5 April 2007 Available online 12 April 2007 Abstract The soybean aphid. glycines populations using predator exclusion cages and correlating predator and aphid abundances. However

Landis, Doug

24

Demo: Sound to Picture Logic has a sound to picture feature allowing you to import a QuickTime movie directly into  

E-print Network

Time movie directly into the logic timeline. This allows you to score the video directly while using the video as an immediate reference. First step: find FPS rate of video to be scored · Open movie in Quicktime Player o Window > Show Movie Inspector o Write down FPS value for Logic Pro setting later Open

Stowell, Michael

25

New Directions: Emerging Satellite Observations of Above-cloud Aerosols and Direct Radiative Forcing  

NASA Technical Reports Server (NTRS)

Spaceborne lidar and passive sensors with multi-wavelength and polarization capabilities onboard the A-Train provide unprecedented opportunities of observing above-cloud aerosols and direct radiative forcing. Significant progress has been made in recent years in exploring these new aerosol remote sensing capabilities and generating unique datasets. The emerging observations will advance the understanding of aerosol climate forcing.

Yu, Hongbin; Zhang, Zhibo

2013-01-01

26

Direct Observation of Thymine Dimer Repair in DNA by Photolyase  

NASA Astrophysics Data System (ADS)

Departments of Physics, Chemistry, and Biochemistry, Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University, Columbus, 191 West Woodruff Avenue, OH 43210. Photolyase uses light energy to split ultraviolet-induced cyclobutane pyrimidine dimers in damaged DNA, but its molecular mechanism has never been directly revealed. We report here the direct mapping of catalytic processes through femtosecond synchronization of the enzymatic dynamics with the repair function. We observed direct electron transfer from the excited flavin cofactor to the dimer in 170 ps and back electron transfer from the repaired thymines in 560 ps. Both reactions are strongly modulated by active-site solvation to achieve maximum repair efficiency. These results show that the photocycle of DNA repair by photolyase is through a radical mechanism and completed on subnanosecond time scale at the dynamic active site with no net electron change in redox states of the flavin cofactor.

Zhong, Dongping

2006-03-01

27

Direct Observations of the Evolution of Polar Cap Ionization Patches  

NASA Astrophysics Data System (ADS)

Patches of ionization are common in the polar ionosphere where their motion and associated density gradients give variable disturbances to High Frequency (HF) radio communications, over-the-horizon radar location errors, and disruption and errors to satellite navigation and communication. Their formation and evolution are poorly understood, particularly under disturbed space weather conditions. We report direct observations of the full evolution of patches during a geomagnetic storm, including formation, polar cap entry, transpolar evolution, polar cap exit, and sunward return flow. Our observations show that modulation of nightside reconnection in the substorm cycle of the magnetosphere helps form the gaps between patches where steady convection would give a 'tongue' of ionization (TOI).

Zhang, Q.; Zhang, B.; Lockwood, M. M.; Hu, H.; Moen, J. I.; Ruohoniemi, J.; Thomas, E. G.; Zhang, S.; Yang, H.; Liu, R.; McWilliams, K. A.; Baker, J. B.

2013-12-01

28

Direct observation of single kinesin molecules moving along microtubules  

Microsoft Academic Search

KINESIN is a two-headed motor protein that powers organelle transport along microtubules1. Many ATP molecules are hydro-lysed by kinesin for each diffusional encounter with the micro-tubule2,3. Here we report the development of a new assay in which the processive movement of individual fluorescently labelled kinesin molecules along a microtubule can be visualized directly; this observation is achieved by low-background total

Ronald D. Vale; Takashi Funatsu; Daniel W. Pierce; Laura Romberg; Yoshie Harada; Toshio Yanagida

1996-01-01

29

Responses to the advanced notice of proposed rulemaking EPA published on June 6, 1996 regarding changes to the EPA allowance auctions and elimination of the direct sale  

SciTech Connect

On June 6, 1996, EPA`s Acid Rain Program published an advance notice of proposed rulemaking (ANPRM) in the Federal Register seeking comment on: (1) whether to change the design of the annual sulfur dioxide (SO{sub 2}) allowance auctions; (2) whether to change the timing of the allowance auctions; (3) whether to change the requirement that the minimum price of offered allowances must be in whole dollars, and (4) whether EPA should propose the ability to submit allowance transfers electronically. EPA also published on that day a proposed and direct final rule on whether to eliminate the direct sale. This paper documents the issues addressed in the ANPRM, the comments EPA received, and EPA`s responses to those comments. EPA received comments from 14 separate commenters.

Critchfield, L.R. [EPA Acid Rain Division, Washington, DC (United States)

1997-12-31

30

A general ligand design for gold catalysis allowing ligand-directed anti-nucleophilic attack of alkynes.  

PubMed

Most homogenous gold catalyses demand ? 0.5 mol% catalyst loading. Owing to the high cost of gold, these reactions are unlikely to be applicable in medium- or large-scale applications. Here we disclose a novel ligand design based on the privileged (1,1'-biphenyl)-2-ylphosphine framework that offers a potentially general approach to dramatically lowering catalyst loading. In this design, an amide group at the 3'-position of the ligand framework directs and promotes nucleophilic attack at the ligand gold complex-activated alkyne, which is unprecedented in homogenous gold catalysis considering the spatial challenge of using ligand to reach anti-approaching nucleophile in a linear P-Au-alkyne centroid structure. With such a ligand, the gold(I) complex becomes highly efficient in catalysing acid addition to alkynes, with a turnover number up to 99,000. Density functional theory calculations support the role of the amide moiety in directing the attack of carboxylic acid via hydrogen bonding. PMID:24704803

Wang, Yanzhao; Wang, Zhixun; Li, Yuxue; Wu, Gongde; Cao, Zheng; Zhang, Liming

2014-01-01

31

Microcrack closure in rocks under stress - Direct observation  

NASA Technical Reports Server (NTRS)

Direct observations of the closure of microcracks in rocks under increasing stress are reported. Uniaxial stresses up to 300 bars were applied to untreated and previously heated samples of Westerly granite and Frederick diabase by a small hydraulic press which fit entirely within a scanning electron microscope. Crack closure characteristics are found to depend on crack orientation, with cracks perpendicular to the applied stress closing and those parallel tending to open, as well as crack aspect ratio, crack intersection properties, stress concentrations and surface roughness. Uniaxial and hydrostatic stress measurements are found to be strongly dependent on fracture content as observed by SEM, and the observed hysteresis in strain measurements in the first stress cycles is also related to microscopic processes

Batzle, M. L.; Simmons, G.; Siegfried, R. W.

1980-01-01

32

Direct Observation of the Strange b Baryon ?b-  

NASA Astrophysics Data System (ADS)

We report the first direct observation of the strange b baryon ?b-(?¯b+). We reconstruct the decay ?b-?J/??-, with J/???+?-, and ?-???-?p?-?- in pp¯ collisions at s=1.96TeV. Using 1.3fb-1 of data collected by the D0 detector, we observe 15.2±4.4(stat)-0.4+1.9(syst) ?b- candidates at a mass of 5.774±0.011(stat)±0.015(syst)GeV. The significance of the observed signal is 5.5?, equivalent to a probability of 3.3×10-8 of it arising from a background fluctuation. Normalizing to the decay ?b?J/??, we measure the relative rate (?(?b-)×B(?b-?J/??-))/(?(?b)×B(?b?J/??))=0.28±0.09(stat)-0.08+0.09(syst).

Abazov, V. M.; Abbott, B.; Abolins, M.; Acharya, B. S.; Adams, M.; Adams, T.; Aguilo, E.; Ahn, S. H.; Ahsan, M.; Alexeev, G. D.; Alkhazov, G.; Alton, A.; Alverson, G.; Alves, G. A.; Anastasoaie, M.; Ancu, L. S.; Andeen, T.; Anderson, S.; Andrieu, B.; Anzelc, M. S.; Arnoud, Y.; Arov, M.; Arthaud, M.; Askew, A.; Åsman, B.; Assis Jesus, A. C. S.; Atramentov, O.; Autermann, C.; Avila, C.; Ay, C.; Badaud, F.; Baden, A.; Bagby, L.; Baldin, B.; Bandurin, D. V.; Banerjee, S.; Banerjee, P.; Barberis, E.; Barfuss, A.-F.; Bargassa, P.; Baringer, P.; Barreto, J.; Bartlett, J. F.; Bassler, U.; Bauer, D.; Beale, S.; Bean, A.; Begalli, M.; Begel, M.; Belanger-Champagne, C.; Bellantoni, L.; Bellavance, A.; Benitez, J. A.; Beri, S. B.; Bernardi, G.; Bernhard, R.; Berntzon, L.; Bertram, I.; Besançon, M.; Beuselinck, R.; Bezzubov, V. A.; Bhat, P. C.; Bhatnagar, V.; Biscarat, C.; Blazey, G.; Blekman, F.; Blessing, S.; Bloch, D.; Bloom, K.; Boehnlein, A.; Boline, D.; Bolton, T. A.; Borissov, G.; Bos, K.; Bose, T.; Brandt, A.; Brock, R.; Brooijmans, G.; Bross, A.; Brown, D.; Buchanan, N. J.; Buchholz, D.; Buehler, M.; Buescher, V.; Burdin, S.; Burke, S.; Burnett, T. H.; Buszello, C. P.; Butler, J. M.; Calfayan, P.; Calvet, S.; Cammin, J.; Caron, S.; Carvalho, W.; Casey, B. C. K.; Cason, N. M.; Castilla-Valdez, H.; Chakrabarti, S.; Chakraborty, D.; Chan, K. M.; Chan, K.; Chandra, A.; Charles, F.; Cheu, E.; Chevallier, F.; Cho, D. K.; Choi, S.; Choudhary, B.; Christofek, L.; Christoudias, T.; Cihangir, S.; Claes, D.; Clément, C.; Clément, B.; Coadou, Y.; Cooke, M.; Cooper, W. E.; Corcoran, M.; Couderc, F.; Cousinou, M.-C.; Crépé-Renaudin, S.; Cutts, D.; ?wiok, M.; da Motta, H.; Das, A.; Davies, G.; de, K.; de Jong, S. J.; de Jong, P.; de La Cruz-Burelo, E.; de Oliveira Martins, C.; Degenhardt, J. D.; Déliot, F.; Demarteau, M.; Demina, R.; Denisov, D.; Denisov, S. P.; Desai, S.; Diehl, H. T.; Diesburg, M.; Dominguez, A.; Dong, H.; Dudko, L. V.; Duflot, L.; Dugad, S. R.; Duggan, D.; Duperrin, A.; Dyer, J.; Dyshkant, A.; Eads, M.; Edmunds, D.; Ellison, J.; Elvira, V. D.; Enari, Y.; Eno, S.; Ermolov, P.; Evans, H.; Evdokimov, A.; Evdokimov, V. N.; Ferapontov, A. V.; Ferbel, T.; Fiedler, F.; Filthaut, F.; Fisher, W.; Fisk, H. E.; Ford, M.; Fortner, M.; Fox, H.; Fu, S.; Fuess, S.; Gadfort, T.; Galea, C. F.; Gallas, E.; Galyaev, E.; Garcia, C.; Garcia-Bellido, A.; Gavrilov, V.; Gay, P.; Geist, W.; Gelé, D.; Gerber, C. E.; Gershtein, Y.; Gillberg, D.; Ginther, G.; Gollub, N.; Gómez, B.; Goussiou, A.; Grannis, P. D.; Greenlee, H.; Greenwood, Z. D.; Gregores, E. M.; Grenier, G.; Gris, Ph.; Grivaz, J.-F.; Grohsjean, A.; Grünendahl, S.; Grünewald, M. W.; Guo, J.; Guo, F.; Gutierrez, P.; Gutierrez, G.; Haas, A.; Hadley, N. J.; Haefner, P.; Hagopian, S.; Haley, J.; Hall, I.; Hall, R. E.; Han, L.; Hanagaki, K.; Hansson, P.; Harder, K.; Harel, A.; Harrington, R.; Hauptman, J. M.; Hauser, R.; Hays, J.; Hebbeker, T.; Hedin, D.; Hegeman, J. G.; Heinmiller, J. M.; Heinson, A. P.; Heintz, U.; Hensel, C.; Herner, K.; Hesketh, G.; Hildreth, M. D.; Hirosky, R.; Hobbs, J. D.; Hoeneisen, B.; Hoeth, H.; Hohlfeld, M.; Hong, S. J.; Hooper, R.; Hossain, S.; Houben, P.; Hu, Y.; Hubacek, Z.; Hynek, V.; Iashvili, I.; Illingworth, R.; Ito, A. S.; Jabeen, S.; Jaffré, M.; Jain, S.; Jakobs, K.; Jarvis, C.; Jesik, R.; Johns, K.; Johnson, C.; Johnson, M.; Jonckheere, A.; Jonsson, P.; Juste, A.; Käfer, D.; Kahn, S.; Kajfasz, E.; Kalinin, A. M.; Kalk, J. R.; Kalk, J. M.; Kappler, S.; Karmanov, D.; Kasper, J.; Kasper, P.; Katsanos, I.; Kau, D.; Kaur, R.; Kaushik, V.; Kehoe, R.; Kermiche, S.; Khalatyan, N.; Khanov, A.; Kharchilava, A.; Kharzheev, Y. M.; Khatidze, D.; Kim, H.; Kim, T. J.; Kirby, M. H.; Kirsch, M.; Klima, B.; Kohli, J. M.; Konrath, J.-P.; Kopal, M.; Korablev, V. M.; Kothari, B.; Kozelov, A. V.; Krop, D.; Kryemadhi, A.; Kuhl, T.; Kumar, A.; Kunori, S.; Kupco, A.; Kur?a, T.; Kvita, J.; Lacroix, F.; Lam, D.; Lammers, S.; Landsberg, G.; Lazoflores, J.; Lebrun, P.; Lee, W. M.; Leflat, A.; Lehner, F.; Lellouch, J.; Lesne, V.; Leveque, J.; Lewis, P.; Li, J.; Li, Q. Z.; Li, L.; Lietti, S. M.; Lima, J. G. R.; Lincoln, D.; Linnemann, J.; Lipaev, V. V.; Lipton, R.; Liu, Y.; Liu, Z.; Lobo, L.; Lobodenko, A.; Lokajicek, M.; Lounis, A.; Love, P.; Lubatti, H. J.; Lyon, A. L.; Maciel, A. K. A.; Mackin, D.; Madaras, R. J.; Mättig, P.; Magass, C.; Magerkurth, A.; Makovec, N.; Mal, P. K.; Malbouisson, H. B.; Malik, S.; Malyshev, V. L.; Mao, H. S.; Maravin, Y.; Martin, B.; McCarthy, R.; Melnitchouk, A.; Mendes, A.; Mendoza, L.; Mercadante, P. G.; Merekov, Y. P.; Merkin, M.; Merritt, K. W.; Meyer, J.; Meyer, A.; Michaut, M.; Millet, T.; Mitrevski, J.; Molina, J.; Mommsen, R. K.; Mondal, N. K.; Moore, R. W.; Moulik, T.; Muanza, G. S.; Mulders, M.; Mulhearn, M.; Mundal, O.; Mundim, L.

2007-08-01

33

Direct Observation of Teacher and Student Behavior in School Settings: Trends, Issues and Future Directions  

ERIC Educational Resources Information Center

Across the modern history of the field of special education and emotional/behavioral disorders (EBD), direct observation of student and educator behavior has been an essential component of the diagnostic process, student progress monitoring, and establishing functional and statistical relationships within research. This article provides an…

Lewis, Timothy J.; Scott, Terrance M.; Wehby, Joseph H.; Wills, Howard P.

2014-01-01

34

Direct observation of Kelvin waves excited by quantized vortex reconnection.  

PubMed

Quantized vortices are key features of quantum fluids such as superfluid helium and Bose-Einstein condensates. The reconnection of quantized vortices and subsequent emission of Kelvin waves along the vortices are thought to be central to dissipation in such systems. By visualizing the motion of submicron particles dispersed in superfluid (4)He, we have directly observed the emission of Kelvin waves from quantized vortex reconnection. We characterize one event in detail, using dimensionless similarity coordinates, and compare it with several theories. Finally, we give evidence for other examples of wavelike behavior in our system. PMID:24704878

Fonda, Enrico; Meichle, David P; Ouellette, Nicholas T; Hormoz, Sahand; Lathrop, Daniel P

2014-03-25

35

Direct observation of local atomic order in a metallic glass  

NASA Astrophysics Data System (ADS)

The determination of the atomic configuration of metallic glasses is a long-standing problem in materials science and solid-state physics. So far, only average structural information derived from diffraction and spectroscopic methods has been obtained. Although various atomic models have been proposed in the past fifty years, a direct observation of the local atomic structure in disordered materials has not been achieved. Here we report local atomic configurations of a metallic glass investigated by nanobeam electron diffraction combined with ab initio molecular dynamics simulation. Distinct diffraction patterns from individual atomic clusters and their assemblies, which have been theoretically predicted as short- and medium-range order, can be experimentally observed. This study provides compelling evidence of the local atomic order in the disordered material and has important implications in understanding the atomic mechanisms of metallic-glass formation and properties.

Hirata, Akihiko; Guan, Pengfei; Fujita, Takeshi; Hirotsu, Yoshihiko; Inoue, Akihisa; Yavari, Alain Reza; Sakurai, Toshio; Chen, Mingwei

2011-01-01

36

Direct observations of the evolution of polar cap ionization patches.  

PubMed

Patches of ionization are common in the polar ionosphere, where their motion and associated density gradients give variable disturbances to high-frequency (HF) radio communications, over-the-horizon radar location errors, and disruption and errors to satellite navigation and communication. Their formation and evolution are poorly understood, particularly under disturbed space weather conditions. We report direct observations of the full evolution of patches during a geomagnetic storm, including formation, polar cap entry, transpolar evolution, polar cap exit, and sunward return flow. Our observations show that modulation of nightside reconnection in the substorm cycle of the magnetosphere helps form the gaps between patches where steady convection would give a "tongue" of ionization (TOI). PMID:23539601

Zhang, Qing-He; Zhang, Bei-Chen; Lockwood, Michael; Hu, Hong-Qiao; Moen, Jøran; Ruohoniemi, J Michael; Thomas, Evan G; Zhang, Shun-Rong; Yang, Hui-Gen; Liu, Rui-Yuan; McWilliams, Kathryn A; Baker, Joseph B H

2013-03-29

37

Direct observation of small cluster mobility and ripening  

NASA Technical Reports Server (NTRS)

Direct evidence is reported for the simultaneous occurrence of Ostwald ripening and short-distance cluster mobility during annealing of discontinuous metal films on clean amorphous substrates. The annealing characteristics of very thin particulate deposits of silver on amorphized clean surfaces of single-crystalline thin graphite substrates have been studied by in situ transmission electron microscopy (TEM) under controlled environmental conditions in the temperature range from 25 to 450 C. It was possible to monitor all stages of the experiments by TEM observation of the same specimen area. Slow Ostwald ripening was found to occur over the entire temperature range, but the overriding surface transport mechanism was short-distance cluster mobility. This was concluded from in situ observations of individual particles during annealing and from measurements of cluster size distributions, cluster number densities, area coverages, and mean cluster diameters.

Heinemann, K.; Poppa, H.

1976-01-01

38

Direct observation of thitherto unobservable quantum phenomena by using electrons  

PubMed Central

Fundamental aspects of quantum mechanics, which were discussed only theoretically as “thought experiments” in the 1920s and 1930s, have begun to frequently show up in nanoscopic regions owing to recent rapid progress in advanced technologies. Quantum phenomena were once regarded as the ultimate factors limiting further miniaturization trends of microstructured electronic devices, but now they have begun to be actively used as the principles for new devices such as quantum computers. To directly observe what had been unobservable quantum phenomena, we have tried to develop bright and monochromatic electron beams for the last 35 years. Every time the brightness of an electron beam improved, fundamental experiments in quantum mechanics became possible, and quantum phenomena became observable by using the wave nature of electrons. PMID:16150719

Tonomura, Akira

2005-01-01

39

Directly observable optical properties of sprites in Central Europe  

NASA Astrophysics Data System (ADS)

Luminous optical emissions accompanying streamer-based natural electric breakdown processes initiating in the mesosphere are called sprites. 489 sprite events have been observed with a TV frame rate video system in Central Europe from Sopron (47.68N, 16.58E, 230 m MSL), Hungary between 2007 and 2009. On the basis of these observations, characteristic morphological properties of sprites, i.e. basic forms (e.g. column, carrot, angel, etc.) as well as common morphological features (e.g. tendrils, glows, puffs, beads, etc.), have been identified. Probable time sequences of streamer propagation directions were associated with each of the basic sprite forms. It is speculated that different sequences of streamer propagation directions can result in very similar final sprite shapes. The number and type variety of sprite elements appearing in an event as well as the total optical duration of an event was analyzed statistically. Jellyfish and dancing sprite events were considered as special subsets of sprite clusters. It was found that more than 90% of the recorded sprite elements appeared in clusters rather than alone and more than half of the clusters contained more than one basic sprite forms. The analysis showed that jellyfish sprites and clusters of column sprites featuring glows and tendrils do not tend to have optical lifetimes longer than 80 ms. Such very long optical lifetimes have not been observed in sprite clusters containing more than 25 elements of any type, either. In contrast to clusters containing sprite entities of only one form, sprite events showing more sprite forms seem to have extended optical durations more likely. The need for further investigation and for finding theoretical concepts to link these observations to electric conditions ambient for sprite formation is emphasized.

Bór, József

2013-04-01

40

Direct observation of capacitor switching using planar electrodes  

SciTech Connect

Ferroelectric polarization switching in epitaxial (110) BiFeO{sub 3} films is studied using piezoresponse force microscopy of a model in-plane capacitor structure. The electrode orientation is chosen such that only two active domain variants exist. Studies of the kinetics of domain evolution allows clear visualization of nucleation sites, as well as forward and lateral growth stages of domain formation. It is found that the location of the reverse-domain nucleation is correlated with the direction of switching in a way that the polarization in the domains nucleated at an electrode is always directed away from it. The role of interface charge injection and surface screening charge on switching mechanisms is explored, and the nucleation is shown to be controllable by the bias history of the sample. Finally, the manipulation of domain nucleation through domain structure engineering is illustrated. These studies pave the way for the engineering and design of the ferroelectric device structures through control of individual steps of the switching process.

Balke, Nina [ORNL; Gajek, Martin [University of California, Berkeley; Tagantsev, ALexander [EPFL, Lausanne, Switzerland; Martin, Lane W. W. [University of California, Berkeley; Chu, Ying-Hao [National Chiao Tung University, Hsinchu, Taiwan; Ramesh, R. [University of California, Berkeley; Kalinin, Sergei V [ORNL

2010-01-01

41

Genetic-algorithm discovery of a direct-gap and optically allowed superstructure from indirect-gap Si and Ge semiconductors.  

PubMed

Combining two indirect-gap materials-with different electronic and optical gaps-to create a direct gap material represents an ongoing theoretical challenge with potentially rewarding practical implications, such as optoelectronics integration on a single wafer. We provide an unexpected solution to this classic problem, by spatially melding two indirect-gap materials (Si and Ge) into one strongly dipole-allowed direct-gap material. We leverage a combination of genetic algorithms with a pseudopotential Hamiltonian to search through the astronomic number of variants of Si(n)/Ge(m)/…/Si(p)/Ge(q) superstructures grown on (001) Si(1-x)Ge(x). The search reveals a robust configurational motif-SiGe(2)Si(2)Ge(2)SiGe(n) on (001) Si(x)Ge(1-x) substrate (x?0.4) presenting a direct and dipole-allowed gap resulting from an enhanced ?-X coupling at the band edges. PMID:22324706

d'Avezac, Mayeul; Luo, Jun-Wei; Chanier, Thomas; Zunger, Alex

2012-01-13

42

Direct observation of photoinduced bent nitrosyl excited-state complexes  

SciTech Connect

Ground state structures with side-on nitrosyl ({eta}{sup 2}-NO) and isonitrosyl (ON) ligands have been observed in a variety of transition-metal complexes. In contrast, excited state structures with bent-NO ligands have been proposed for years but never directly observed. Here we use picosecond time-resolved infrared spectroscopy and density functional theory (DFT) modeling to study the photochemistry of Co(CO){sub 3}(NO), a model transition-metal-NO compound. Surprisingly, we have observed no evidence for ON and {eta}{sup 2}-NO structural isomers, but have observed two bent-NO complexes. DFT modeling of the ground and excited state potentials indicates that the bent-NO complexes correspond to triplet excited states. Photolysis of Co(CO){sub 3}(NO) with a 400-nm pump pulse leads to population of a manifold of excited states which decay to form an excited state triplet bent-NO complex within 1 ps. This structure relaxes to the ground triplet state in ca. 350 ps to form a second bent-NO structure.

Sawyer, Karma R.; Steele, Ryan P.; Glascoe, Elizabeth A.; Cahoon, James F.; Schlegel, Jacob P.; Head-Gordon, Martin; Harris, Charles B.

2008-06-28

43

Direct observation of the strange b baryon Xib-.  

PubMed

We report the first direct observation of the strange b baryon Xi(b)- (Xi(b)+). We reconstruct the decay Xi(b)- -->J/psiXi-, with J/psi-->mu+mu-, and Xi--->Lambdapi--->ppi-pi- in pp collisions at square root of s =1.96 TeV. Using 1.3 fb(-1) of data collected by the D0 detector, we observe 15.2 +/- 4.4(stat)(-0.4)(+1.9)(syst) Xi(b)- candidates at a mass of 5.774 +/- 0.011(stat) +/- 0.015(syst) GeV. The significance of the observed signal is 5.5 sigma, equivalent to a probability of 3.3 x 10(-8) of it arising from a background fluctuation. Normalizing to the decay Lambda(b)-->J/psiLambda, we measure the relative rate sigma(Xi(b-) x B(Xi)b})- -->J/psiXi-)/sigma(Lambda(b)) x B(Lambda(b)-->J/psiLambda) = 0.28+/-0.09(stat)(-0.08)(+0.09)(syst). PMID:17930744

Abazov, V M; Abbott, B; Abolins, M; Acharya, B S; Adams, M; Adams, T; Aguilo, E; Ahn, S H; Ahsan, M; Alexeev, G D; Alkhazov, G; Alton, A; Alverson, G; Alves, G A; Anastasoaie, M; Ancu, L S; Andeen, T; Anderson, S; Andrieu, B; Anzelc, M S; Arnoud, Y; Arov, M; Arthaud, M; Askew, A; Asman, B; Assis Jesus, A C S; Atramentov, O; Autermann, C; Avila, C; Ay, C; Badaud, F; Baden, A; Bagby, L; Baldin, B; Bandurin, D V; Banerjee, S; Banerjee, P; Barberis, E; Barfuss, A-F; Bargassa, P; Baringer, P; Barreto, J; Bartlett, J F; Bassler, U; Bauer, D; Beale, S; Bean, A; Begalli, M; Begel, M; Belanger-Champagne, C; Bellantoni, L; Bellavance, A; Benitez, J A; Beri, S B; Bernardi, G; Bernhard, R; Berntzon, L; Bertram, I; Besançon, M; Beuselinck, R; Bezzubov, V A; Bhat, P C; Bhatnagar, V; Biscarat, C; Blazey, G; Blekman, F; Blessing, S; Bloch, D; Bloom, K; Boehnlein, A; Boline, D; Bolton, T A; Borissov, G; Bos, K; Bose, T; Brandt, A; Brock, R; Brooijmans, G; Bross, A; Brown, D; Buchanan, N J; Buchholz, D; Buehler, M; Buescher, V; Burdin, S; Burke, S; Burnett, T H; Buszello, C P; Butler, J M; Calfayan, P; Calvet, S; Cammin, J; Caron, S; Carvalho, W; Casey, B C K; Cason, N M; Castilla-Valdez, H; Chakrabarti, S; Chakraborty, D; Chan, K M; Chan, K; Chandra, A; Charles, F; Cheu, E; Chevallier, F; Cho, D K; Choi, S; Choudhary, B; Christofek, L; Christoudias, T; Cihangir, S; Claes, D; Clément, C; Clément, B; Coadou, Y; Cooke, M; Cooper, W E; Corcoran, M; Couderc, F; Cousinou, M-C; Crépé-Renaudin, S; Cutts, D; Cwiok, M; da Motta, H; Das, A; Davies, G; De, K; de Jong, S J; de Jong, P; De La Cruz-Burelo, E; De Oliveira Martins, C; Degenhardt, J D; Déliot, F; Demarteau, M; Demina, R; Denisov, D; Denisov, S P; Desai, S; Diehl, H T; Diesburg, M; Dominguez, A; Dong, H; Dudko, L V; Duflot, L; Dugad, S R; Duggan, D; Duperrin, A; Dyer, J; Dyshkant, A; Eads, M; Edmunds, D; Ellison, J; Elvira, V D; Enari, Y; Eno, S; Ermolov, P; Evans, H; Evdokimov, A; Evdokimov, V N; Ferapontov, A V; Ferbel, T; Fiedler, F; Filthaut, F; Fisher, W; Fisk, H E; Ford, M; Fortner, M; Fox, H; Fu, S; Fuess, S; Gadfort, T; Galea, C F; Gallas, E; Galyaev, E; Garcia, C; Garcia-Bellido, A; Gavrilov, V; Gay, P; Geist, W; Gelé, D; Gerber, C E; Gershtein, Y; Gillberg, D; Ginther, G; Gollub, N; Gómez, B; Goussiou, A; Grannis, P D; Greenlee, H; Greenwood, Z D; Gregores, E M; Grenier, G; Gris, Ph; Grivaz, J-F; Grohsjean, A; Grünendahl, S; Grünewald, M W; Guo, J; Guo, F; Gutierrez, P; Gutierrez, G; Haas, A; Hadley, N J; Haefner, P; Hagopian, S; Haley, J; Hall, I; Hall, R E; Han, L; Hanagaki, K; Hansson, P; Harder, K; Harel, A; Harrington, R; Hauptman, J M; Hauser, R; Hays, J; Hebbeker, T; Hedin, D; Hegeman, J G; Heinmiller, J M; Heinson, A P; Heintz, U; Hensel, C; Herner, K; Hesketh, G; Hildreth, M D; Hirosky, R; Hobbs, J D; Hoeneisen, B; Hoeth, H; Hohlfeld, M; Hong, S J; Hooper, R; Hossain, S; Houben, P; Hu, Y; Hubacek, Z; Hynek, V; Iashvili, I; Illingworth, R; Ito, A S; Jabeen, S; Jaffré, M; Jain, S; Jakobs, K; Jarvis, C; Jesik, R; Johns, K; Johnson, C; Johnson, M; Jonckheere, A; Jonsson, P; Juste, A; Käfer, D; Kahn, S; Kajfasz, E; Kalinin, A M; Kalk, J R; Kalk, J M; Kappler, S; Karmanov, D; Kasper, J; Kasper, P; Katsanos, I; Kau, D; Kaur, R; Kaushik, V; Kehoe, R; Kermiche, S; Khalatyan, N; Khanov, A; Kharchilava, A; Kharzheev, Y M; Khatidze, D; Kim, H; Kim, T J; Kirby, M H; Kirsch, M; Klima, B; Kohli, J M; Konrath, J-P; Kopal, M; Korablev, V M; Kothari, B; Kozelov, A V; Krop, D; Kryemadhi, A; Kuhl, T; Kumar, A; Kunori, S; Kupco, A; Kurca, T; Kvita, J; Lacroix, F; Lam, D; Lammers, S; Landsberg, G; Lazoflores, J; Lebrun, P; Lee, W M; Leflat, A; Lehner, F; Lellouch, J; Lesne, V; Leveque, J; Lewis, P; Li, J; Li, Q Z; Li, L; Lietti, S M; Lima, J G R; Lincoln, D; Linnemann, J; Lipaev, V V; Lipton, R; Liu, Y; Liu, Z; Lobo, L; Lobodenko, A; Lokajicek, M; Lounis, A; Love, P; Lubatti, H J; Lyon, A L; Maciel, A K A; Mackin, D; Madaras, R J; Mättig, P; Magass, C; Magerkurth, A; Makovec, N; Mal, P K; Malbouisson, H B; Malik, S; Malyshev, V L; Mao, H S; Maravin, Y; Martin, B; McCarthy, R; Melnitchouk, A; Mendes, A; Mendoza, L; Mercadante, P G; Merekov, Y P; Merkin, M; Merritt, K W; Meyer, J; Meyer, A; Michaut, M; Millet, T; Mitrevski, J; Molina, J; Mommsen, R K; Mondal, N K; Moore, R W; Moulik, T; Muanza, G S; Mulders, M; Mulhearn, M; Mundal, O; Mundim, L; Nagy, E; Naimuddin, M; Narain, M; Naumann, N A; Neal, H A; Negret, J P; Neustroev, P; Nilsen, H; Nomerotski, A; Novaes, S F; Nunnemann, T; O'Dell, V; O'Neil, D C; Obrant, G; Ochando, C; Onoprienko, D; Oshima, N; Osta, J; Otec, R; Otero y Garzón, G J; Owen, M; Padley, P; Pangilinan, M; Panov, G; Parashar, N; Park, S-J; Park, S K; Parsons, J; Partridge, R; Parua, N; Patwa, A; Pawloski, G; Penning, B; Perea, P M; Peters, K; Peters, Y; Pétroff, P; Petteni, M; Piegaia, R; Piper, J; Pleier, M-A; Podesta-Lerma, P L M; Podstavkov, V M

2007-08-01

44

Direct observation of athermal photofluidisation in azo-polymer films.  

PubMed

The surface relief gratings (SRGs) can be generated when azo-polymer films are exposed to laser beam interference as a result of mass migration. Despite considerable research effort over the past two decades this complex phenomenon remains incompletely understood. Here we show, for the first time, the athermal photofluidisation of azo-polysiloxane films exposed to 488 nm light, directly monitored by optical microscopy. A process of surface relief erasure occurring in parallel with its inscription was also observed during laser irradiation. We therefore propose a new mechanism of SRG formation, based on three different processes: (1) the polymer photo-fluidization in illuminated regions, (2) the mass displacement from illuminated to dark regions and (3) the inverse mass displacement, from dark to illuminated regions. The mechanical properties of the films during UV light irradiation were investigated by classical rheology and, for the first time, by using amplitude modulation-frequency modulation atomic force microscopy (AM-FM AFM). PMID:24833017

Hurduc, Nicolae; Donose, Bogdan C; Macovei, Alina; Paius, Cristina; Ibanescu, Constanta; Scutaru, Dan; Hamel, Matthieu; Branza-Nichita, Norica; Rocha, Licinio

2014-07-14

45

Direct observation of ordered configurations of hydrogen adatoms on graphene.  

PubMed

Ordered configurations of hydrogen adatoms on graphene have long been proposed, calculated, and searched for. Here, we report direct observation of several ordered configurations of H adatoms on graphene by scanning tunneling microscopy. On the top side of the graphene plane, H atoms in the configurations appear to stick to carbon atoms in the same sublattice. Scanning tunneling spectroscopy measurements revealed a substantial gap in the local density of states in H-contained regions as well as in-gap states below the conduction band due to the incompleteness of H ordering. These findings can be well explained by density functional theory calculations based on double-sided H configurations. In addition, factors that may influence H ordering are discussed. PMID:25621539

Lin, Chenfang; Feng, Yexin; Xiao, Yingdong; Dürr, Michael; Huang, Xiangqian; Xu, Xiaozhi; Zhao, Ruguang; Wang, Enge; Li, Xin-Zheng; Hu, Zonghai

2015-02-11

46

Enabling direct nanoscale observations of biological reactions with dynamic TEM  

PubMed Central

Biological processes occur on a wide range of spatial and temporal scales: from femtoseconds to hours and from angstroms to meters. Many new biological insights can be expected from a better understanding of the processes that occur on these very fast and very small scales. In this regard, new instruments that use fast X-ray or electron pulses are expected to reveal novel mechanistic details for macromolecular protein dynamics. To ensure that any observed conformational change is physiologically relevant and not constrained by 3D crystal packing, it would be preferable for experiments to utilize small protein samples such as single particles or 2D crystals that mimic the target protein's native environment. These samples are not typically amenable to X-ray analysis, but transmission electron microscopy has imaged such sample geometries for over 40 years using both direct imaging and diffraction modes. While conventional transmission electron microscopes (TEM) have visualized biological samples with atomic resolution in an arrested or frozen state, the recent development of the dynamic TEM (DTEM) extends electron microscopy into a dynamic regime using pump-probe imaging. A new second-generation DTEM, which is currently being constructed, has the potential to observe live biological processes with unprecedented spatiotemporal resolution by using pulsed electron packets to probe the sample on micro- and nanosecond timescales. This article reviews the experimental parameters necessary for coupling DTEM with in situ liquid microscopy to enable direct imaging of protein conformational dynamics in a fully hydrated environment and visualize reactions propagating in real time. PMID:23315566

Evans, James E.; Browning, Nigel D.

2013-01-01

47

Direct observation of electron dynamics in the attosecond domain.  

PubMed

Dynamical processes are commonly investigated using laser pump-probe experiments, with a pump pulse exciting the system of interest and a second probe pulse tracking its temporal evolution as a function of the delay between the pulses. Because the time resolution attainable in such experiments depends on the temporal definition of the laser pulses, pulse compression to 200 attoseconds (1 as = 10(-18) s) is a promising recent development. These ultrafast pulses have been fully characterized, and used to directly measure light waves and electronic relaxation in free atoms. But attosecond pulses can only be realized in the extreme ultraviolet and X-ray regime; in contrast, the optical laser pulses typically used for experiments on complex systems last several femtoseconds (1 fs = 10(-15) s). Here we monitor the dynamics of ultrafast electron transfer--a process important in photo- and electrochemistry and used in solid-state solar cells, molecular electronics and single-electron devices--on attosecond timescales using core-hole spectroscopy. We push the method, which uses the lifetime of a core electron hole as an internal reference clock for following dynamic processes, into the attosecond regime by focusing on short-lived holes with initial and final states in the same electronic shell. This allows us to show that electron transfer from an adsorbed sulphur atom to a ruthenium surface proceeds in about 320 as. PMID:16034414

Föhlisch, A; Feulner, P; Hennies, F; Fink, A; Menzel, D; Sanchez-Portal, D; Echenique, P M; Wurth, W

2005-07-21

48

Using direct clinical observation to assess the quality of cesarean delivery in Afghanistan: an exploratory study  

PubMed Central

Background As part of a National Emergency Obstetric and Newborn Care (EmONC) Needs Assessment, a special study was undertaken in July 2010 to examine the quality of cesarean deliveries in Afghanistan and examine the utility of direct clinical observation as an assessment method in low-resource settings. Methods This cross-sectional assessment of the quality of cesareans at 14 facilities in Afghanistan included a survey of surgeons regarding their routine cesarean practices, direct observation of 29 cesarean deliveries and comparison of observations with facility records for 34 additional cesareans conducted during the 3 days prior to the observation period at each facility. For both observed cases and record reviews, we assessed time intervals between specified points of care-arrival to the ward, first evaluation, detection of a complication, decision for cesarean, incision, and birth. Results All time intervals with the exception of “decision to skin incision” were longer in the record reviews than in observed cases. Prior cesarean was the most common primary indication for all cases. All mothers in both groups observed survived through one hour postpartum. Among newborns there were two stillbirths (7%) in observed births and seven (21%) record reviews. Although our sample is too small to show statistical significance, the difference is noteworthy. In six of the reviewed cesareans resulting in stillbirth, a fetal heart rate was recorded in the operating theater, although four were recorded as macerated. For the two fresh stillbirths, the cesarean surgeries were recorded as scheduled and not urgent. Conclusions Direct observation of cesarean deliveries enabled us to assess a number of preoperative, postoperative, and intraoperative procedures that are often not described in medical records in low resource settings. Comparison of observations with findings from provider interviews and facility records allowed us to infer whether observed practices were typical of providers and facilities and detect potential Hawthorne effects. PMID:24886143

2014-01-01

49

THEMIS Observations of Directly-Driven Pi2 Pulsations  

NASA Technical Reports Server (NTRS)

The THEMIS tail seasons have provided an unprecedented opportunity to examine the causal relationship between midtail plasma flows and low latitude Pi2 pulsations. We present several events where multiple THEMIS spacecraft observed magnetotail flow bursts which were followed up to several minutes later by ground Pi2 pulsations. We find good agreement with the waveforms of the flow bursts and flank Pi2, in agreement with the hypothesis that Pi2 at low-latitude on the flank are directly-driven by periodic variations in the flow bursts. For at least I event we are able to follow the Pi2 impulses from the periodic flow bursts on the nightside. to ground Pi2 at the flanks, and finally through the dayside magnetosphere as observed by GOES. We further place the physical mechanism generating these Pi2 into the context of sub storm onset. We conclude by discussing the sequence and coupling of events that are necessary to explain the correlation, and the constraints this places on models of transient magnetospheric transport.

Kepko, L.; Angelopoulos, V.; Russell, C. T.; Yumoto, K.; Singer, H.; Glassmeier, K.-H.; McFadden, J.

2010-01-01

50

Direct Observation, Study, and Control of Molecular Superrotors  

NASA Astrophysics Data System (ADS)

Extremely fast rotating molecules whose rotational energy is comparable with the molecular bond strength are known as "superrotors." It has been speculated that superrotors may exhibit a number of unique properties, yet only indirect evidence of these molecular objects has been reported to date. Here we demonstrate the first direct observation of molecular superrotors by detecting coherent unidirectional molecular rotation with extreme frequencies exceeding 10 THz. The technique of an "optical centrifuge" is used to control the degree of rotational excitation in an ultrabroad range of rotational quantum numbers, reaching as high as N =95 in oxygen and N=60 in nitrogen. State-resolved detection enables us to determine the shape of the excited rotational wave packet and quantify the effect of centrifugal distortion on the rotational spectrum. Femtosecond time resolution reveals coherent rotational dynamics with increasing coherence times at higher angular momentum. We demonstrate that molecular superrotors can be created and observed in dense samples under normal conditions where the effects of ultrafast rotation on many-body interactions, intermolecular collisions, and chemical reactions can be readily explored.

Korobenko, Aleksey; Milner, Alexander A.; Milner, Valery

2014-03-01

51

Direct observation, study, and control of molecular superrotors.  

PubMed

Extremely fast rotating molecules whose rotational energy is comparable with the molecular bond strength are known as "superrotors." It has been speculated that superrotors may exhibit a number of unique properties, yet only indirect evidence of these molecular objects has been reported to date. Here we demonstrate the first direct observation of molecular superrotors by detecting coherent unidirectional molecular rotation with extreme frequencies exceeding 10 THz. The technique of an "optical centrifuge" is used to control the degree of rotational excitation in an ultrabroad range of rotational quantum numbers, reaching as high as N = 95 in oxygen and N = 60 in nitrogen. State-resolved detection enables us to determine the shape of the excited rotational wave packet and quantify the effect of centrifugal distortion on the rotational spectrum. Femtosecond time resolution reveals coherent rotational dynamics with increasing coherence times at higher angular momentum. We demonstrate that molecular superrotors can be created and observed in dense samples under normal conditions where the effects of ultrafast rotation on many-body interactions, intermolecular collisions, and chemical reactions can be readily explored. PMID:24702361

Korobenko, Aleksey; Milner, Alexander A; Milner, Valery

2014-03-21

52

The cosmic microwave background: observing directly the early universe  

NASA Astrophysics Data System (ADS)

The Cosmic Microwave Background (CMB) is a relict of the early universe. Its perfect 2.725K blackbody spectrum demonstrates that the universe underwent a hot, ionized early phase; its anisotropy (about 80 µK rms) provides strong evidence for the presence of photon-matter oscillations in the primeval plasma, shaping the initial phase of the formation of structures; its polarization state (about 3 µK rms), and in particular its rotational component (less than 0.1 µK rms) might allow to study the inflation process in the very early universe, and the physics of extremely high energies, impossible to reach with accelerators. The CMB is observed by means of microwave and mm-wave telescopes, and its measurements drove the development of ultra-sensitive bolometric detectors, sophisticated modulators, and advanced cryogenic and space technologies. Here we focus on the new frontiers of CMB research: the precision measurements of its linear polarization state, at large and intermediate angular scales, and the measurement of the inverse-Compton effect of CMB photons crossing clusters of Galaxies. In this framework, we will describe the formidable experimental challenges faced by ground-based, near-space and space experiments, using large arrays of detectors. We will show that sensitivity and mapping speed improvement obtained with these arrays must be accompanied by a corresponding reduction of systematic effects (especially for CMB polarimeters), and by improved knowledge of foreground emission, to fully exploit the huge scientific potential of these missions.

de Bernardis, Paolo; Masi, Silvia

2012-09-01

53

Direct observation of liquid-like behavior of a single Au grain boundary  

NASA Astrophysics Data System (ADS)

Behavior of matter at the nanoscale differs from that of the bulk due to confinement and surface effects. Here, we report a direct observation of liquid-like behavior of a single grain boundary formed by cold-welding Au nanoparticles, 40 nm in size, by mechanical manipulation in situ TEM. The grain boundary rotates almost freely due to the free surfaces and can rotate about 90 degrees. The grain boundary sustains more stress than the bulk, confirming a strong bonding between the nanoparticles. Moreover, this technique allows the measurement of the surface diffusion coefficient from experimental observations, which we compute for the Au nanoparticles. This methodology can be used for any metal, oxide, semiconductor or combination of them.Behavior of matter at the nanoscale differs from that of the bulk due to confinement and surface effects. Here, we report a direct observation of liquid-like behavior of a single grain boundary formed by cold-welding Au nanoparticles, 40 nm in size, by mechanical manipulation in situ TEM. The grain boundary rotates almost freely due to the free surfaces and can rotate about 90 degrees. The grain boundary sustains more stress than the bulk, confirming a strong bonding between the nanoparticles. Moreover, this technique allows the measurement of the surface diffusion coefficient from experimental observations, which we compute for the Au nanoparticles. This methodology can be used for any metal, oxide, semiconductor or combination of them. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr01501g

Casillas, Gilberto; Ponce, Arturo; Velázquez-Salazar, J. Jesús; José-Yacamán, Miguel

2013-06-01

54

Microcrack closure in rocks under stress: direct observation  

SciTech Connect

Microcrack closure in rocks under increasing stress was observed directly with a scanning electron microscope. Uniaxial stresses to 300 bars were applied with a small hydraulic press to specimens of Westerly (RI) granite, both unheated and previously heat cycled to 500/sup 0/C, and of Frederick (MD) diabase, heat cycled to 700/sup 0/C. Closure characteristics (rate, final closure pressure, etc.) depend on crack orientation, shape, surface roughness, and on the nature of fracture intersections and interactions. Cracks perpendicular to the applied stress closed while those parallel to the stress tended to open. Long, narrow cracks (low aspect ratio) closed at relatively low pressures. At some intersections, one fracture would open while another simultaneously closed, depending upon their orientations. Many fractures closed uniformly even though offset by other fractures. Local stress concentrations often caused new fracturing at low applied stress. Some fractures were propped open until material lodged inside was crushed. Significant irreversible damage occurred during the first stress cycle. Closure characteristics varied significantly among the samples. The unheated granite has cracks with rough, pitted, and mismatched walls. Only partial closure occurred under stress with many sections remaining open. Crack porosity is reduced but continues to be interconnected. Fractures in the preheated granite and diabase are also irregular, but the walls are well-matched and closure is nearly complete. The cracks in the heated granite closed at lower stresses than in the diabase. As the maximum stress was approached for the heated granite, new transgranular cracks formed and preexisting cracks were enlarged. The variations in closure rate and character were also observed in strain measurements.

Batzle, M.L.; Simmons, G.; Siegfried, R.W.

1980-12-10

55

Direct observation of interface instability during crystal growth  

NASA Technical Reports Server (NTRS)

The general aim of this investigation was to study interface stability and solute segregation phenomena during crystallization of a model system. Emphasis was to be placed on direct observational studies partly because this offered the possibility at a later stage of performing related experiments under substantially convection-free conditions in the space shuttle. The major achievements described in this report are: (1) the development of a new model system for fundamental studies of crystal growth from the melt and the measurement of a range of material parameters necessary for comparison of experiment with theory. (2) The introduction of a new method of measuring segregation coefficient using absorption of a laser beam by the liquid phase. (3) The comparison of segregation in crystals grown by gradient freezing and by pulling from the melt. (4) The introduction into the theory of solute segregation of an interface field term and comparison with experiment. (5) The introduction of the interface field term into the theories of constitutional supercooling and morphological stability and assessment of its importance.

Tiller, W. A.; Feigelson, R. S.; Elwell, D.

1982-01-01

56

Genetic-Algorithm Discovery of a Direct-Gap and Optically Allowed Superstructure from Indirect-Gap Si and Ge Semiconductors  

SciTech Connect

Combining two indirect-gap materials - with different electronic and optical gaps - to create a direct gap material represents an ongoing theoretical challenge with potentially rewarding practical implications, such as optoelectronics integration on a single wafer. We provide an unexpected solution to this classic problem, by spatially melding two indirect-gap materials (Si and Ge) into one strongly dipole-allowed direct-gap material. We leverage a combination of genetic algorithms with a pseudopotential Hamiltonian to search through the astronomic number of variants of Si{sub n}/Ge{sub m}/.../Si{sub p}/Ge{sub q} superstructures grown on (001) Si{sub 1-x}Ge{sub x}. The search reveals a robust configurational motif - SiGe{sub 2}Si{sub 2}Ge{sub 2}SiGe{sub n} on (001) Si{sub x}Ge{sub 1-x} substrate (x {le} 0.4) presenting a direct and dipole-allowed gap resulting from an enhanced {Gamma}-X coupling at the band edges.

d'Avezac, M.; Luo, J. W.; Chanier, T.; Zunger, A.

2012-01-13

57

Direct observation of optical precursors in a cold potassium gas  

NASA Astrophysics Data System (ADS)

This thesis considers how an electromagnetic field propagates through a dispersive linear dielectric in the case when the field is turned on suddenly. It has been predicted nearly 100 years ago that the point in the waveform where the field first turns on (the front) propagates precisely at the speed of light in vacuum. Furthermore, it is predicted that distinct wave-packets develop after the front, but before the arrival of the main part of the field (the main signal). These wave-packets are known as optical precursors. It was believed that precursors are an ultra-fast phenomena, persisting only for a few optical cycles, and that they have an exceedingly small amplitude. I describe a method to increase the duration of optical precursors into the nanosecond range using a dielectric with a narrow resonance. I also show how to increase the precursor amplitude by tuning the carrier frequency of the field near the resonance frequency of the oscillators making up the dielectric medium. The field emerging from the dielectric consists of a several-nanosecond-long spike occurring immediately after the front with near 100% transmission, which subsequently decays to a constant value expected from Beer's Law of absorption. I demonstrate, using a modern asymptotic theory, that the spike consists of both the Sommerfeld and Brillouin precursors. Thus, my measurement is the first direct observation of optical precursors. The precursor research might be useful for imaging applications requiring penetrating optical radiation, such as in biological systems, or in optical communication systems. While the asymptotic theory explains qualitatively my observations, I find that there are large quantitative disagreements. I hypothesize that these errors are due to the fact that I use a weakly-dispersive narrow-resonance medium for which this theory has never been tested. I suggest empirical fixes to the theory by comparison to my data. I also compare the asymptotic theory and data to a second theory that is known to describe well my experimental conditions, but was believed by some researchers not to predict optical precursors. I demonstrate that this belief is incorrect.

Jeong, Heejeong

58

Determination of acceleration mechanism characteristics directly and nonparametrically from observations: Application to supernova remnants  

NASA Astrophysics Data System (ADS)

We have developed an inversion method for determination of the characteristics of the acceleration mechanism directly and nonparametrically from observations, in contrast to the usual forward fitting of parametric model variables to observations. In two recent papers [V. Petrosian and Q. Chen, Astrophys. J. 712, L131 (2010); Q. Chen and V. Petrosian, Astrophys. J. 777, 33 (2013)], we demonstrated the efficacy of this inversion method by its application to acceleration of electrons in solar flares based on stochastic acceleration by turbulence. Here we explore its application for determining the characteristics of shock acceleration in supernova remnants (SNRs) based on the electron spectra deduced from the observed nonthermal radiation from SNRs and the spectrum of the cosmic ray electrons observed near the Earth. These spectra are related by the process of escape of the electrons from SNRs and energy loss during their transport in the Galaxy. Thus, these observations allow us to determine spectral characteristics of the momentum and pitch angle diffusion coefficients, which play crucial roles in both direct acceleration by turbulence and in high Mach number shocks. Assuming that the average electron spectrum deduced from a few well-known SNRs is representative of those in the solar neighborhood, we find interesting discrepancies between our deduced forms for these coefficients and those expected from well-known wave-particle interactions. This may indicate that the standard assumptions made in the treatment of shock acceleration need revision. In particular, the escape of particles from SNRs may be more complex than generally assumed.

Petrosian, Vahé; Chen, Qingrong

2014-05-01

59

Direct observation of metastable hot trions in an individual quantum dot  

NASA Astrophysics Data System (ADS)

Magnetophotoluminescence and excitation spectroscopy are used to probe the excited-state spectrum of negatively charged trions in an InGaAs quantum dot. A single dot optical charging device allows us to selectively prepare a specific few (1e, 2e) electron states and stabilize hot trions against decay via electron tunneling from excited orbital states. The spin structure of the excited state results in the formation of metastable trions with strong optical activity that are directly observed in luminescence. Excitation spectroscopy is employed to map the excited singlet and triplet states of the two-electron wave function, and fine-structure splittings are measured for the lowest-lying and excited orbital states. Magneto-optical measurements allow us to compare the g factors and diamagnetic response of different trion states.

Jovanov, V.; Kapfinger, S.; Bichler, M.; Abstreiter, G.; Finley, J. J.

2011-12-01

60

Observation of direct processes in photoproduction at HERA  

Microsoft Academic Search

Jets in photoproduction events have been studied with the ZEUS detector for gammap centre-of-mass energies ranging from 130 to 250 GeV. The inclusive jet distributions give evidence for the dominance of resolved photon interactions. In the di-jet sample the direct processes are for the first time clearly isolated. Di-jet cross sections for the resolved and direct processes are given in

M. Derrick; D. Krakauer; S. Magill; B. Musgrave; J. Repond; S. Repond; R. Stanek; R. L. Talaga; J. Thron; F. Arzarello; R. Ayad; G. Bari; M. Basile; L. Bellagamba; D. Boscherini; A. Bruni; G. Bruni; P. Bruni; G. Cara Romeo; G. Castellini; M. Chiarini; L. Cifarelli; F. Cindolo; F. Ciralli; A. Contin; C. del Papa; S. D'Auria; F. Frasconi; P. Giusti; G. Iacobucci; G. Laurenti; G. Levi; Q. Lin; G. Maccarrone; A. Margotti; T. Massam; R. Nania; C. Nemoz; F. Palmonari; G. Sartorelli; R. Timellini; Y. Zamora Garcia; A. Zichichi; A. Bargende; J. Crittenden; K. Desch; B. Diekmann; T. Doeker; L. Feld; A. Frey; M. Geerts; G. Geitz; H. Hartmann; D. Haun; K. Heinloth; E. Hilger; H.-P. Jakob; U. F. Katz; S. Kramarczyk; M. Kückes; A. Mass; S. Mengel; J. Mollen; H. Müsch; E. Paul; R. Schattevoy; J.-L. Schneider; D. Schramm; R. Wedemeyer; A. Cassidy; D. G. Cussans; N. Dyce; B. Foster; S. George; R. Gilmore; G. P. Heath; H. F. Heath; M. Lancaster; T. J. Llewellyn; C. J. S. Morgado; J. A. O'Mara; R. J. Tapper; S. S. Wilson; R. Yoshida; R. R. Rau; M. Arneodo; M. Schioppa; G. Susinno; A. Bernstein; A. Caldwell; I. Gialas; J. A. Parsons; S. Ritz; F. Sciulli; P. B. Straub; L. Wai; S. Yang; P. Borzemski; J. Chwastowski; A. Eskreys; K. Piotrzkowski; M. Zachara; L. Zawiejski; L. Adamczyk; B. Bednarek; K. Eskreys; K. Jelen; D. Kisielewska; T. Kowalski; E. Rulikowska-Zarebska; L. Suszycki; J. Zajc; T. Kedzierski; A. Kotanski; M. Przybycien; L. A. T. Bauerdick; U. Behrens; J. K. Bienlein; S. Böttcher; C. Coldewey; G. Drews; M. Flasinski; I. Fleck; D. J. Gilkinson; P. Göttlicher; B. Gutjahr; T. Haas; L. Hagge; W. Hain; D. Hasell; H. Heßling; H. Hultschig; P. Joos; M. Kasemann; R. Klanner; W. Koch; L. Köpke; U. Kötz; H. Kowalski; W. Kröger; J. Krüger; J. Labs; A. Ladage; M. Löhr; M. Löwe; D. Lüke; J. Mainusch; O. Manczak; M. Momayezi; J. S. T. Ng; S. Nickel; D. Notz; K.-U. Pösnecker; M. Rohde; J. Roldán; U. Schneekloth; J. Schroeder; W. Schulz; F. Selonke; E. Stiliaris; T. Tsurugai; W. Vogel; D. Westphal; G. Wolf; C. Youngman; H. J. Grabosch; A. Leich; A. Meyer; C. Rethfeldt; S. Schlenstedt; G. Barbagli; M. Nuti; P. Pelfer; G. Anzivino; S. de Pasquale; S. Qian; L. Votano; A. Bamberger; A. Freidhof; T. Poser; S. Söldner-Rembold; G. Theisen; T. Trefzger; N. H. Brook; P. J. Bussey; A. T. Doyle; J. R. Forbes; V. A. Jamieson; C. Raine; D. H. Saxon; M. Stavrianakou; A. S. Wilson; H. Brückmann; A. Dannemann; U. Holm; D. Horstmann; H. Kammerlocher; B. Krebs; T. Neumann; R. Sinkus; K. Wick; A. Fürtjes; E. Lohrmann; J. Milewski; M. Nakahata; N. Pavel; G. Poelz; W. Schott; J. Terron; F. Zetsche; T. C. Bacon; R. Beuselinck; I. Butterworth; E. Gallo; V. L. Harris; K. R. Long; D. B. Miller; A. Prinias; J. K. Sedgbeer; A. Vorvolakos; A. Whitfield; T. Bienz; H. Kreutzmann; U. Mallik; E. McCliment; M. Roco; M. Z. Wang; P. Cloth; D. Filges; S. H. An; S. M. Hong; C. O. Kim; T. Y. Kim; S. W. Nam; S. K. Park; M. H. Suh; S. H. Yon; R. Imlay; S. Kartik; H.-J. Kim; R. R. McNeil; W. Metcalf; V. K. Nadendla; F. Barreiro; G. Cases; L. Hervás; L. Labarga; J. del Peso; J. F. de Trocóniz; F. Ikraiam; J. K. Mayer; G. R. Smith; F. Corriveau; D. S. Hanna; J. Hartmann; L. W. Hung; J. N. Lim; C. G. Matthews; J. W. Mitchell; P. M. Patel; L. E. Sinclair; D. G. Stairs; M. St. Laurent; R. Ullmann; G. L. Bashindzhagyan; P. F. Ermolov; L. K. Gladilin; Y. A. Golubkov; V. A. Kuzmin; E. N. Kuznetsov; A. A. Savin; A. G. Voronin; N. P. Zotov; S. Bentvelsen; M. Botje; A. Dake; J. Engelen; P. de Jong; M. de Kamps; P. Kooijman; A. Kruse; H. van der Lugt; V. O'dell; A. Tenner; H. Tiecke; H. Uijterwaal; M. Vreeswijk; L. Wiggers; E. de Wolf; R. van Woudenberg; B. Bylsma; L. S. Durkin; K. Honscheid; C. Li; T. Y. Ling; K. W. McLean; W. N. Murray; I. H. Park; T. A. Romanowski; R. Seidlein; D. Bailey; G. A. Blair; A. Byrne; R. J. Cashmore; A. M. Cooper-Sarkar; R. C. E. Devenish; N. Harnew; T. Khatri; P. Luffman; P. Morawitz; J. Nash; N. C. Roocroft; R. Walczak; F. F. Wilson; T. Yip; G. Abbiendi; A. Bertolin; R. Brugnera; R. Carlin; F. dal Corso; M. de Giorgi; U. Dosselli; F. Gasparini; S. Limentani; M. Morandin; M. Posocco; L. Stanco; R. Stroili; C. Voci; J. Bulmahn; J. M. Butterworth; R. G. Feild; B. Y. Oh; J. J. Whitmore; U. Contino; G. D'Agostini; M. Guida; M. Iori; S. M. Mari; G. Marini; M. Mattioli; A. Nigro; J. C. Hart; N. A. McCubbin; K. Prytz; T. P. Shah; T. L. Short; E. Barberis; N. Cartiglia; C. Heusch; M. van Hook; B. Hubbard; W. Lockman; H. F.-W. Sadrozinski; A. Seiden; D. Zer-Zion; E. Badura; J. Biltzinger; R. J. Seifert; A. H. Walenta; G. Zech; S. Dagan; A. Levy; T. Hasegawa; M. Hazumi; T. Ishii; S. Kasai; M. Kuze; S. Mine; Y. Nagasawa; T. Nagira; M. Nakao; H. Okuno; I. Suzuki; K. Tokushuku; S. Yamada; Y. Yamazaki; M. Chiba; R. Hamatsu; T. Hirose; K. Homma; S. Kitamura; S. Nagayama; Y. Nakamitsu; R. Cirio; M. Costa; M. I. Ferrero

1994-01-01

61

Direct Observation of Magnetic Vortices in Superconductors Using Electron Waves  

Microsoft Academic Search

The development of a coherent field-emission electron beam has made it possible to observe microscopic magnetic lines of force by detecting the electron-wave phase shifts that are due to vector potentials. Electron-holographic interference microscopy has been used to observe magnetic lines of force of magnetic vortices in superconductors, and Lorentz microscopy has been used to observe the dynamics of the

Akira Tonomura

1998-01-01

62

Advanced chemistry-transport modeling and observing systems allow daily air quality observations, short-term forecasts, and real-time analyses of air quality at the global and  

E-print Network

Advanced chemistry-transport modeling and observing systems allow daily air quality observations, short-term forecasts, and real-time analyses of air quality at the global and European scales control measures that could be taken for managing such episodes, European-scale air quality forecasting

Paris-Sud XI, Université de

63

Direct observation of liquid-like behavior of a single Au grain boundary.  

PubMed

Behavior of matter at the nanoscale differs from that of the bulk due to confinement and surface effects. Here, we report a direct observation of liquid-like behavior of a single grain boundary formed by cold-welding Au nanoparticles, 40 nm in size, by mechanical manipulation in situ TEM. The grain boundary rotates almost freely due to the free surfaces and can rotate about 90 degrees. The grain boundary sustains more stress than the bulk, confirming a strong bonding between the nanoparticles. Moreover, this technique allows the measurement of the surface diffusion coefficient from experimental observations, which we compute for the Au nanoparticles. This methodology can be used for any metal, oxide, semiconductor or combination of them. PMID:23760664

Casillas, Gilberto; Ponce, Arturo; Velázquez-Salazar, J Jesús; José-Yacamán, Miguel

2013-07-21

64

Direct observation of liquid-like behavior of a single Au grain boundary  

PubMed Central

Behavior of matter at the nanoscale differs from that of the bulk due to confinement and surface effects. Here, we report a direct observation of liquid-like behavior of a single grain boundary formed by cold-welding Au nanoparticles, 40 nm in size, by mechanical manipulation in-situ TEM. The grain boundary rotates almost freely due to the free surfaces and can rotate about 90 degrees. The grain boundary sustains more stress than the bulk, confirming a strong bonding between the nanoparticles. Moreover, this technique allows the measurement of the surface diffusion coefficient from experimental observations, which we compute for the Au nanoparticles. This methodology can be used for any metal, oxide, semiconductor or combination of them. PMID:23760664

Casillas, Gilberto; Ponce, Arturo; Velázquez-Salazar, J. Jesús; Jose-Yacaman, Miguel

2014-01-01

65

The direct observation of cosmic ray composition in JACEE  

SciTech Connect

No significant changes in spectral index for protons up to 500 TeV and higher intensity for helium above 2 TeV were observed. For heavier elements, a general tendency of intensity enhancement of medium heavies in the relative abundance above about 10 TeV/amu was observed.

Burnett, T.H.; Iwai, J.; Lord, J.J. (Department of Physics, University of Washington, Seattle, WA 98105 (USA)); Dake, S.; Oda, H. (Department of Physics, Kobe University, Kobe 657 (Japan)); Derrickson, J.H.; Fountain, W.F. (Space Science Laboratory, NASA/Marshall Space Flight Center, Huntsville, AL (USA)); Fuki, M. (Matsusho Gakuen Junior College, Matsumoto 390-12 (Japan)); Gregory, J.C.; Hayashi, T. (College of Science, University of Alabama in Huntsville, Huntsville, AL 35899 (USA)); Holynski, R.; Jurak, A. (Institute of Nuclear Physics, PL-30-055 Krakow (Poland)); Jones, W.V. (Department of Physics and Astronomy, Louisiana State University, Baton Rouge LA 70803 (USA)); Miyamura, O. (Department of Applied Mathematics, Osaka University, Osaka 560 (Japan))

1989-03-01

66

Direct Observations of Interstellar H, He, and O by the Interstellar Boundary Explorer (Invited)  

NASA Astrophysics Data System (ADS)

Due to the motion of the Sun relative to its neighborhood, the neutral gas of the local in-terstellar medium (LISM) flows through the inner heliosphere where it is subject to ioni-zation, the Sun’s gravity, and radiation pressure. Observing the resulting spatial distribu-tion and flow pattern of several interstellar gas species with UV backscatter, pickup ion, and neutral atom imaging techniques allows us to unravel the physical conditions of the LISM and its interaction with the heliosphere. Imaging of the neutral gas flow directly with energetic neutral atom (ENA) cameras yields the most accurate account of the ki-netic parameters of the interstellar gas, but so far this has been carried out only for He using Ulysses GAS. IBEX, which was launched in October 2008, provides the capability for simultaneous flow observations of several interstellar species with its triple-time-of-flight IBEX-Lo sensor. Because H and O are strongly affected by the heliospheric inter-face while He is not, a direct comparison between these species enables an independent assessment of the slowdown and heating processes in the outer heliosheath. Likewise, IBEX observations will constrain models of the heliospheric interaction and provide a test of the heliospheric asymmetry - recently inferred from Voyager and SOHO SWAN observations - that is seen as an indicator for the interstellar magnetic field direction. During the first half year of its mission IBEX has observed the interstellar He, O, and H flow. We will present an overview and preliminary analysis of these first interstellar mul-tispecies scans of the interstellar gas flow in spring and fall 2009.

Moebius, E.; Bochsler, P. A.; Bzowski, M.; Crew, G. B.; Funsten, H. O.; Fuselier, S. A.; Ghielmetti, A.; Heirtzler, D.; Izmodenov, V.; Kubiak, M.; Kucharek, H.; Lee, M. A.; Leonard, T.; McComas, D. J.; Petersen, L.; Saul, L. A.; Scheer, J.; Schwadron, N. A.; Witte, M.; Wurz, P.

2009-12-01

67

Physical Activity Surveillance in Parks Using Direct Observation  

PubMed Central

Introduction Primary features of observational public health surveillance instruments are that they are valid, can reliably estimate physical activity behaviors, and are useful across diverse geographic settings and seasons by different users. Previous studies have reported the validity and reliability of Systematic Observation of Play and Recreation in Communities (SOPARC) to estimate park and user characteristics. The purpose of this investigation was to establish the use of SOPARC as a surveillance instrument and to situate the findings from the study in the context of the previous literature. Methods We collected data by using SOPARC for more than 3 years in 4 locations: Philadelphia, Pennsylvania; Columbus, Ohio; Chapel Hill/Durham, North Carolina; and Albuquerque, New Mexico during spring, summer, and autumn. Results We observed a total of 35,990 park users with an overall observer reliability of 94% (range, 85%–99%) conducted on 15% of the observations. We monitored the proportion of park users engaging in moderate-to-vigorous physical activity (MVPA) and found marginal differences in MVPA by both city and season. Park users visited parks significantly more on weekend days than weekdays and visitation rates tended to be lower during summer than spring. Conclusion SOPARC is a highly reliable observation instrument that can be used to collect data across diverse geographic settings and seasons by different users and has potential as a surveillance system. PMID:24384304

McKenzie, Thomas L.; Cohen, Deborah; Evenson, Kelly R.; Golinelli, Daniela; Hillier, Amy; Lapham, Sandra C.; Williamson, Stephanie

2014-01-01

68

The First Direct Observation of Double-Beta Decay  

NASA Astrophysics Data System (ADS)

The possibility of double-beta (??) decay was recognized in the mid 1930s, and by 1939 something of its potential to reveal fundamental properties of the neutrino was known as well. But experimental observation of the phenomenon was out of reach. Despite numerous attempts over the next 30 years, and strong suggestions of its existence from geochemical experiments, ?? decay had not been observed to occur in the laboratory. Our group at UC Irvine took up the search in the early 1970s, first with a cloud chamber and then with a time-projection chamber. The following narrative traces a discovery process that unfolded over the ensuing 15 years—a sequence of setbacks and false starts punctuated by occasional victories and, ultimately, by a definitive laboratory observation of two-neutrino ?? decay, in August 1987.

Moe, Michael

2014-10-01

69

Direct Observation of CIO from Chlorine Nitrate Photolysis  

NASA Astrophysics Data System (ADS)

Chlorine nitrate photolysis has been investigated with the use of a molecular beam technique. Excitation at both 248 and 193 nanometers led to photodissociation by two pathways, CIONO_2 --> CIO + NO_2 and CIONO_2 --> CI + NO_3, with comparable yields. This experiment provides a direct measurement of the CIO product channel and consequently raises the possibility of an analogous channel in CIO dimer photolysis. Photodissociation of the CIO dimer is a critical step in the catalytic cycle that is presumed to dominate polar stratospheric ozone destruction. A substantial yield of CIO would reduce the efficiency of this cycle.

Minton, Timothy K.; Nelson, Christine M.; Moore, Teresa A.; Okumura, Mitchio

1992-11-01

70

Direct Observations of Nucleation in a Nondilute Multicomponent Alloy  

NASA Technical Reports Server (NTRS)

The chemical pathways leading to gamma'(L1(sub 2)) nucleation from nondilute Ni-5.2 Al-14.2 Cr at. %, gama(fcc), at 873 K are followed with radial distribution functions and isoconcentration surface analyses of direct-space atom-probe tomographic images. Although Cr atoms initially are randomly distributed, a distribution of congruent Ni3Al short-range-order domains (SRO), [R] approx. equals 0.6 nm, results from Al diffusion during quenching. Domain site occupancy develops as their number density increases leading to Al-rich phase separation by gamma'-nucleation, [R]=0.75 nm, after SRO occurs.

Sudbrack, Chantal K.; Noebe, Ronald D.; Seidman, David N.

2006-01-01

71

Clear Direction. The Montessori Observer. Volume 32, Number 2  

ERIC Educational Resources Information Center

"The Montessori Observer" is mailed four times each year, in March, May, September and November, to Society members throughout the world. The purpose is to provide news and information about the Society's work in Montessori education, and to extend awareness of Montessori principles throughout the world. This issue contains a feature article,…

International Montessori Society (NJ3), 2011

2011-01-01

72

Relation between Direct Observation of Relaxation and Self-Reported Mindfulness and Relaxation States  

ERIC Educational Resources Information Center

Forty-four individuals, 18-47 (MN 21.8, SD 5.63) years of age, took part in a study examining the magnitude and direction of the relationship between self-report and direct observation measures of relaxation and mindfulness. The Behavioral Relaxation Scale (BRS), a valid direct observation measure of relaxation, was used to assess relaxed behavior…

Hites, Lacey S.; Lundervold, Duane A.

2013-01-01

73

Spectroscopic observation of simultaneous bi-directional reconnection outflows in a laboratory plasma  

E-print Network

Spectroscopic observation of simultaneous bi-directional reconnection outflows in a laboratory;Spectroscopic observation of simultaneous bi-directional reconnection outflows in a laboratory plasma M. R; accepted 6 August 2012; published online 27 August 2012) We report a precise, direct spectroscopic

Brown, Michael R.

74

Direct observation of warping in the plasma sheet of Saturn  

NASA Astrophysics Data System (ADS)

The ENA images from the Ion Neutral CAmera (INCA) on the Cassini spacecraft are projected onto the noon-midnight plane of Sun-Saturn orbital coordinates, and a composite ``image'' of Saturn's plasma sheet is constructed from dawn-side observations of 20-50 keV hydrogens obtained from days 352 to 361 in 2004. The maxima in the intensity contours define the center of the plasma sheet in the noon-midnight plane. This plasma sheet surface displays a distinct bending or ``warping'' above Saturn's equatorial plane at radial distances of beyond ~15 RS on the nightside. On the dayside, the plasma sheet lies close to the equator all the way to the magnetopause. The observed warping agrees with the ``bowl'' model derived from measurements of Saturn's magnetic field, but fits more closely a simple third-order polynomial.

Carbary, J. F.; Mitchell, D. G.; Paranicas, C.; Roelof, E. C.; Krimigis, S. M.

2008-12-01

75

Direct observation of interstitial dislocation loop coarsening in ?-iron.  

PubMed

Interstitial loop coarsening by Ostwald ripening can provide insight into single point defects but is very difficult to observe in ?-iron and many other metals where nanoscale vacancy clusters dissociate and annihilate loops. We show that by implanting helium in the samples at a carefully chosen energy, it is possible to observe Ostwald ripening of loops by transmission electron microscopy during in situ isochronal annealings. This coarsening of loops results in a sharp increase of the mean loop radius at around 850 K. Using cluster dynamics simulations, we demonstrate that loops evolve due to vacancy emission and that such experiments give a robust estimation of the sum of the formation and migration free energies of vacancies. In particular, our results are in good agreement with self-diffusion experiments and confirm that entropic contributions are large for the vacancy in ?-iron. PMID:23863013

Moll, S; Jourdan, T; Lefaix-Jeuland, H

2013-07-01

76

Direct Observation of Nanoparticle-Cancer Cell Nucleus Interactions  

PubMed Central

We report the direct visualization of interactions between drug-loaded nanoparticles and the cancer cell nucleus. Nanoconstructs composed of nucleolin-specific aptamers and gold nanostars were actively transported to the nucleus and induced major changes to the nuclear phenotype via nuclear envelope invaginations near the site of the construct. The number of local deformations could be increased by ultra-fast, light-triggered release of the aptamers from the surface of the gold nanostars. Cancer cells with more nuclear envelope folding showed increased caspase 3 and 7 activity (apoptosis) as well as decreased cell viability. This newly revealed correlation between drug-induced changes in nuclear phenotype and increased therapeutic efficacy could provide new insight for nuclear-targeted cancer therapy. PMID:22424173

Dam, Duncan Hieu M.; Lee, Jung Heon; Sisco, Patrick N.; Co, Dick T.; Zhang, Ming; Wasielewski, Michael R.; Odom, Teri W.

2012-01-01

77

Galileo NIMS Direct Observations of the SL-9 Fireballs  

NASA Technical Reports Server (NTRS)

The Galileo spacecraft was situated 1.8 AU from Jupiter, at a phase angle of 51 deg, providing a direct view of the impacts of the comet fragments with the planet. Low resolution infrared spectra in the 1 to 5 micron range were recorded for several of the events, which can be used to study the early evolution of the fireballs. Preliminary analysis of the data received for the G event show an initial fireball temperature of greater than 5000 K and an effective source diameter of less than 10 km. These spectra show absorption by molecular hydrogen and methane which place the upper emitting surface in the stratosphere, above the ammonia cloud level. As time progresses, the fireball cools and the effective diameter of the radiating area increases at roughly 2 km/sec. In 30 seconds, the fireball cools to approximately 1000 k and exhibits a diameter of about 100 km.

Carlson, R. W.; Weissman, P. R.; Hui, J.; Segura, M.; Johnson, T. V.; Smythe, W. D.; Baines, K. H.; Drossart, P.; Encrenaz, T.; Leader, F.; Mehlman, R.

1995-01-01

78

Direct observation of tetrahedrally coordinated Fe(III) in ferrihydrite.  

PubMed

Ferrihydrite is a common iron hydroxide nanomineral commonly found in soils, sediments, and surface waters. Reactivity with this important environmental surface often controls the fate and mobility of both essential nutrients and inorganic contaminants. Despite the critical role of ferrihydrite in environmental geochemistry, its structure is still debated. In this work, we apply bulk sensitive Fe L edge X-ray absorption spectroscopy to study the crystal field environment of the Fe in ferrihydrite and other Fe oxides of known structure. This direct probe of the local electronic structure provides verification of the presence of tetrahedrally coordinated Fe(III) in the structure of ferrihydrite and puts to rest the controversy on this issue. PMID:22369094

Peak, Derek; Regier, Tom

2012-03-20

79

Direct observation of large temperature fluctuations during DNA thermal denaturation  

E-print Network

In this paper we report direct measurement of large low frequency temperature fluctuations in double stranded (ds) DNA when it undergoes thermal denaturation transition. The fluctuation, which occurs only in the temperature range where the denaturation occurs, is several orders more than the expected equilibrium fluctuation. It is absent in single stranded (ss) DNA of the same sequence. The fluctuation at a given temperature also depends on the wait time and vanishes in a scale of few hours. It is suggested that the large fluctuation occurs due to coexisting denaturated and closed base pairs that are in dynamic equilibrium due to transition through a potential barrier in the scale of 25-30k_{B}T_{0}(T_{0}=300K).

K. S. Nagapriya; A. K. Raychaudhuri; Dipankar Chatterji

2006-02-10

80

Direct Observation of Critical Point Wetting in Microgravity  

NASA Technical Reports Server (NTRS)

The objective of this program is to observe the interface shape in single and multicomponent systems at the onset of critical wetting in microgravity using the MSFC drop tower and KC-135 aircraft. Test cells for the drop facility were built and tested up to critical point of CCl. Low temperature drops were conducted for two-component systems near the critical consolute point. Contact angle seems to approach 90 deg near the critical consolute temperature contrary to expectations. It is suspected that since the interfacial energy becomes vanishingly small at the critical consolute temperature, the interface shape has not reached equilibrium in the available low-gravity time.

Kaukler, W. F.

1985-01-01

81

Development of a Direct Observation Instrument to Measure Environmental Characteristics of Parks for Physical Activity  

Technology Transfer Automated Retrieval System (TEKTRAN)

The study's purpose is to describe the development and evaluate the reliability (inter-observer agreement) and validity (rater agreement with a gold standard) of a direct observation instrument to assess park characteristics that may be related to physical activity. A direct observation instrument ...

82

The cosmic Mach number - Direct comparisons of observations and models  

NASA Technical Reports Server (NTRS)

A robust method is used to derive the cosmic Mach number, M, from existing peculiar velocity data sets. For the IR Tully-Fisher distances of spirals in the Local Supercluster of Aaronson et al. (1979, 1982), M of 1.03 and a characteristic distance from the Local Group of 1464 km/s are found. For the elliptical galaxy sample of Faber et al. (1987, 1988), M of 0.57, with a characteristic distance of 2572 km/s is found. These results are compared with Monte Carlo simulations of the observational realizations drawn from numerical simulations of the universe based on various scenarios, including the standard cold dark matter (CDM) scenario. The effect of velocity bias on the derived Mach number is found to be small. Only 5 percent of the CDM simulations have M as large as or larger than that derived for the Aaronson et al. sample.

Strauss, Michael A.; Cen, Renyue; Ostriker, Jeremiah P.

1993-01-01

83

Direct Observation of Completely Processed Calcium Carbonate Dust Particles  

SciTech Connect

This study presents, for the first time, field evidence of complete, irreversible processing of solid calcium carbonate (calcite)-containing particles and quantitative formation of liquid calcium nitrate particles apparently as a result of heterogeneous reaction of calcium carbonate-containing mineral dust particles with gaseous nitric acid. Formation of nitrates from individual calcite and sea salt particles was followed as a function of time in aerosol samples collected at Shoresh, Israel. Morphology and compositional changes of individual particles were observed using conventional scanning electron microscopy with energy dispersive analysis of X-rays (SEM/EDX) and computer controlled SEM/EDX. Environmental scanning electron microscopy (ESEM) was utilized to determine and demonstrate the hygroscopic behavior of calcium nitrate particles found in some of the samples. Calcium nitrate particles are exceptionally hygroscopic and deliquesce even at very low relative humidity (RH) of 9 -11% which is lower than typical atmospheric environments. Transformation of non-hygroscopic dry mineral dust particles into hygroscopic wet aerosol may have substantial impacts on light scattering properties, the ability to modify clouds and heterogeneous chemistry.

Laskin, Alexander; Iedema, Martin J.; Ichkovich, Aviad; Graber, Ellen R.; Taraniuk, Ilya; Rudich, Yinon

2005-05-27

84

Direct Observation of Long-Lived Isomers in Bi212  

NASA Astrophysics Data System (ADS)

Long-lived isomers in Bi212 have been studied following U238 projectile fragmentation at 670 MeV per nucleon. The fragmentation products were injected as highly charged ions into a storage ring, giving access to masses and half-lives. While the excitation energy of the first isomer of Bi212 was confirmed, the second isomer was observed at 1478(30) keV, in contrast to the previously accepted value of >1910keV. It was also found to have an extended Lorentz-corrected in-ring half-life >30min, compared to 7.0(3) min for the neutral atom. Both the energy and half-life differences can be understood as being due a substantial, though previously unrecognized, internal decay branch for neutral atoms. Earlier shell-model calculations are now found to give good agreement with the isomer excitation energy. Furthermore, these and new calculations predict the existence of states at slightly higher energy that could facilitate isomer deexcitation studies.

Chen, L.; Walker, P. M.; Geissel, H.; Litvinov, Yu. A.; Beckert, K.; Beller, P.; Bosch, F.; Boutin, D.; Caceres, L.; Carroll, J. J.; Cullen, D. M.; Cullen, I. J.; Franzke, B.; Gerl, J.; Górska, M.; Jones, G. A.; Kishada, A.; Knöbel, R.; Kozhuharov, C.; Kurcewicz, J.; Litvinov, S. A.; Liu, Z.; Mandal, S.; Montes, F.; Münzenberg, G.; Nolden, F.; Ohtsubo, T.; Patyk, Z.; Plaß, W. R.; Podolyák, Zs.; Rigby, S.; Saito, N.; Saito, T.; Scheidenberger, C.; Simpson, E. C.; Shindo, M.; Steck, M.; Sun, B.; Williams, S. J.; Weick, H.; Winkler, M.; Wollersheim, H.-J.; Yamaguchi, T.

2013-03-01

85

Initiation of simian virus 40 DNA replication in vitro: aphidicolin causes accumulation of early-replicating intermediates and allows determination of the initial direction of DNA synthesis.  

PubMed

Aphidicolin, a specific inhibitor of DNA polymerase alpha, provided a novel method for distinguishing between initiation of DNA synthesis at the simian virus 40 (SV40) origin of replication (ori) and continuation of replication beyond ori. In the presence of sufficient aphidicolin to inhibit total DNA synthesis by 50%, initiation of DNA replication in SV40 chromosomes or ori-containing plasmids continued in vitro, whereas DNA synthesis in the bulk of SV40 replicative intermediate DNA (RI) that had initiated replication in vivo was rapidly inhibited. This resulted in accumulation of early RI in which most nascent DNA was localized within a 600- to 700-base-pair region centered at ori. Accumulation of early RI was observed only under conditions that permitted initiation of SV40 ori-dependent, T-antigen-dependent DNA replication and only when aphidicolin was added to the in vitro system. Increasing aphidicolin concentrations revealed that DNA synthesis in the ori region was not completely resistant to aphidicolin but simply less sensitive than DNA synthesis at forks that were farther away. Since DNA synthesized in the presence of aphidicolin was concentrated in the 300 base pairs on the early gene side of ori, we conclude that the initial direction of DNA synthesis was the same as that of early mRNA synthesis, consistent with the model proposed by Hay and DePamphilis (Cell 28:767-779, 1982). The data were also consistent with initiation of the first DNA chains in ori by CV-1 cell DNA primase-DNA polymerase alpha. Synthesis of pppA/G(pN)6-8(pdN)21-23 chains on a single-stranded DNA template by a purified preparation of this enzyme was completely resistant to aphidicolin, and further incorporation of deoxynucleotide monophosphates was inhibited. Therefore, in the presence of aphidicolin, this enzyme could initiate RNA-primed DNA synthesis at ori first in the early gene direction and then in the late gene direction, but could not continue DNA synthesis for an extended distance. PMID:3025613

Decker, R S; Yamaguchi, M; Possenti, R; DePamphilis, M L

1986-11-01

86

Initiation of simian virus 40 DNA replication in vitro: aphidicolin causes accumulation of early-replicating intermediates and allows determination of the initial direction of DNA synthesis.  

PubMed Central

Aphidicolin, a specific inhibitor of DNA polymerase alpha, provided a novel method for distinguishing between initiation of DNA synthesis at the simian virus 40 (SV40) origin of replication (ori) and continuation of replication beyond ori. In the presence of sufficient aphidicolin to inhibit total DNA synthesis by 50%, initiation of DNA replication in SV40 chromosomes or ori-containing plasmids continued in vitro, whereas DNA synthesis in the bulk of SV40 replicative intermediate DNA (RI) that had initiated replication in vivo was rapidly inhibited. This resulted in accumulation of early RI in which most nascent DNA was localized within a 600- to 700-base-pair region centered at ori. Accumulation of early RI was observed only under conditions that permitted initiation of SV40 ori-dependent, T-antigen-dependent DNA replication and only when aphidicolin was added to the in vitro system. Increasing aphidicolin concentrations revealed that DNA synthesis in the ori region was not completely resistant to aphidicolin but simply less sensitive than DNA synthesis at forks that were farther away. Since DNA synthesized in the presence of aphidicolin was concentrated in the 300 base pairs on the early gene side of ori, we conclude that the initial direction of DNA synthesis was the same as that of early mRNA synthesis, consistent with the model proposed by Hay and DePamphilis (Cell 28:767-779, 1982). The data were also consistent with initiation of the first DNA chains in ori by CV-1 cell DNA primase-DNA polymerase alpha. Synthesis of pppA/G(pN)6-8(pdN)21-23 chains on a single-stranded DNA template by a purified preparation of this enzyme was completely resistant to aphidicolin, and further incorporation of deoxynucleotide monophosphates was inhibited. Therefore, in the presence of aphidicolin, this enzyme could initiate RNA-primed DNA synthesis at ori first in the early gene direction and then in the late gene direction, but could not continue DNA synthesis for an extended distance. Images PMID:3025613

Decker, R S; Yamaguchi, M; Possenti, R; DePamphilis, M L

1986-01-01

87

Direct Observation of the Cooling of the Cassiopeia A Neutron Star  

NASA Astrophysics Data System (ADS)

The cooling rate of young neutron stars (NSs) gives direct insight into their internal makeup. Although the temperatures of several young NSs have been measured, until now a young NS has never been observed to decrease in temperature over time. We fit nine years of archival Chandra ACIS spectra of the likely NS in the ~330 yr old Cassiopeia A supernova remnant with our non-magnetic carbon atmosphere model. Our fits show a relative decline in the surface temperature by 4% (5.4?, from (2.12 ± 0.01) × 106 K in 2000 to (2.04 ± 0.01) × 106 K in 2009) and the observed flux by 21%. Using a simple model for NS cooling, we show that this temperature decline could indicate that the NS became isothermal sometime between 1965 and 1980, and constrains some combinations of neutrino emission mechanisms and envelope compositions. However, the NS is likely to have become isothermal soon after formation, in which case the temperature history suggests episodes of additional heating or more rapid cooling. Observations over the next few years will allow us to test possible explanations for the temperature evolution.

Heinke, Craig O.; Ho, Wynn C. G.

2010-08-01

88

Direct observation of mobility state transitions in RNA trajectories by sensitive single molecule feedback tracking.  

PubMed

Observation and tracking of fluorescently labeled molecules and particles in living cells reveals detailed information about intracellular processes on the molecular level. Whereas light microscopic particle observation is usually limited to two-dimensional projections of short trajectory segments, we report here image-based real-time three-dimensional single particle tracking in an active feedback loop with single molecule sensitivity. We tracked particles carrying only 1-3 fluorophores deep inside living tissue with high spatio-temporal resolution. Using this approach, we succeeded to acquire trajectories containing several hundred localizations. We present statistical methods to find significant deviations from random Brownian motion in such trajectories. The analysis allowed us to directly observe transitions in the mobility of ribosomal (r)RNA and Balbiani ring (BR) messenger (m)RNA particles in living Chironomus tentans salivary gland cell nuclei. We found that BR mRNA particles displayed phases of reduced mobility, while rRNA particles showed distinct binding events in and near nucleoli. PMID:25414330

Spille, Jan-Hendrik; Kaminski, Tim P; Scherer, Katharina; Rinne, Jennifer S; Heckel, Alexander; Kubitscheck, Ulrich

2015-01-30

89

Capturing intraoperative process deviations using a direct observational approach: the glitch method  

PubMed Central

Objectives To develop a sensitive, reliable tool for enumerating and evaluating technical process imperfections during surgical operations. Design Prospective cohort study with direct observation. Setting Operating theatres on five sites in three National Health Service Trusts. Participants Staff taking part in elective and emergency surgical procedures in orthopaedics, trauma, vascular and plastic surgery; including anaesthetists, surgeons, nurses and operating department practitioners. Outcome measures Reliability and validity of the glitch count method; frequency, type, temporal pattern and rate of glitches in relation to site and surgical specialty. Results The glitch count has construct and face validity, and category agreement between observers is good (?=0.7). Redundancy between pairs of observers significantly improves the sensitivity over a single observation. In total, 429 operations were observed and 5742 glitches were recorded (mean 14 per operation, range 0–83). Specialty-specific glitch rates varied from 6.9 to 8.3/h of operating (ns). The distribution of glitch categories was strikingly similar across specialties, with distractions the commonest type in all cases. The difference in glitch rate between specialty teams operating at different sites was larger than that between specialties (range 6.3–10.5/h, p<0.001). Forty per cent of glitches occurred in the first quarter of an operation, and only 10% occurred in the final quarter. Conclusions The glitch method allows collection of a rich dataset suitable for analysing the changes following interventions to improve process safety, and appears reliable and sensitive. Glitches occur more frequently in the early stages of an operation. Hospital environment, culture and work systems may influence the operative process more strongly than the specialty. PMID:24282244

Morgan, Lauren; Robertson, Eleanor; Hadi, Mohammed; Catchpole, Ken; Pickering, Sharon; New, Steve; Collins, Gary; McCulloch, Peter

2013-01-01

90

Light sheet direct Raman imaging technique for observation of mixing of solvents.  

PubMed

The light sheet direct Raman (LSDR) imaging technique is used to obtain wide scope, simultaneous images of samples emitting Raman scattered light, without mapping their point-to-point Raman scattering intensities. A prototype system consisting of a background-free electronically tuned Ti:sapphire laser (BF-ETL), band-pass (BP) filters, and a charge-coupled device (CCD) detector is developed in the present study. The LS excitation method enables us to obtain a wide field of Raman view. The BF-ETL allows us to obtain direct Raman images with multiple Raman bands without the need for rearranging the optical settings. The system is used to observe the mixing of pure solvents: carbon tetrachloride (CCl(4)) and chloroform (CHCl(3)), and ethylene glycol (EG) and polyethylene glycol (PEG). LSDR images are successfully obtained within an exposure time of 0.5 s. EG and PEG, whose Raman spectra appear similar, can be distinguished clearly in the images, suggesting that the system has high spectral resolution. PMID:19843361

Oshima, Yusuke; Furihata, Chie; Sato, Hidetoshi

2009-10-01

91

Mid-depth recirculation observed in the interior Labrador and Irminger seas by direct velocity measurements  

PubMed

The Labrador Sea is one of the sites where convection exports surface water to the deep ocean in winter as part of the thermohaline circulation. Labrador Sea water is characteristically cold and fresh, and it can be traced at intermediate depths (500-2,000 m) across the North Atlantic Ocean, to the south and to the east of the Labrador Sea. Widespread observations of the ocean currents that lead to this distribution of Labrador Sea water have, however, been difficult and therefore scarce. We have used more than 200 subsurface floats to measure directly basin-wide horizontal velocities at various depths in the Labrador and Irminger seas. We observe unanticipated recirculations of the mid-depth (approximately 700 m) cyclonic boundary currents in both basins, leading to an anticyclonic flow in the interior of the Labrador basin. About 40% of the floats from the region of deep convection left the basin within one year and were rapidly transported in the anticyclonic flow to the Irminger basin, and also eastwards into the subpolar gyre. Surprisingly, the float tracks did not clearly depict the deep western boundary current, which is the expected main pathway of Labrador Sea water in the thermohaline circulation. Rather, the flow along the boundary near Flemish Cap is dominated by eddies that transport water offshore. Our detailed observations of the velocity structure with a high data coverage suggest that we may have to revise our picture of the formation and spreading of Labrador Sea water, and future studies with similar instrumentation will allow new insights on the intermediate depth ocean circulation. PMID:10993072

Lavender; Davis; Owens

2000-09-01

92

The art major at Stetson is designed to allow students to develop their personal styles and directions on the base of a strong foundation  

E-print Network

Art The art major at Stetson is designed to allow students to develop their personal styles and contemporary artistic theories. Because this process takes place in the context of a liberal arts college to work outside of class. The studio art program at Stetson has particular strengths in painting, drawing

Miles, Will

93

Direct observation of Rydberg-Rydberg transitions via CPmmW spectroscopy  

E-print Network

Rydberg-Rydberg transitions of BaF molecules have been directly observed in our lab. The key to the experimental success is our ability to combine two powerful and new technologies, Chirped-Pulse millimeter-Wave spectroscopy ...

Zhou, Yan, Ph. D. Massachusetts Institute of Technology

2014-01-01

94

Direct observation of electron propagation and dielectric screening on the atomic length scale.  

PubMed

The propagation and transport of electrons in crystals is a fundamental process pertaining to the functioning of most electronic devices. Microscopic theories describe this phenomenon as being based on the motion of Bloch wave packets. These wave packets are superpositions of individual Bloch states with the group velocity determined by the dispersion of the electronic band structure near the central wavevector in momentum space. This concept has been verified experimentally in artificial superlattices by the observation of Bloch oscillations--periodic oscillations of electrons in real and momentum space. Here we present a direct observation of electron wave packet motion in a real-space and real-time experiment, on length and time scales shorter than the Bloch oscillation amplitude and period. We show that attosecond metrology (1 as = 10(-18) seconds) now enables quantitative insight into weakly disturbed electron wave packet propagation on the atomic length scale without being hampered by scattering effects, which inevitably occur over macroscopic propagation length scales. We use sub-femtosecond (less than 10(-15) seconds) extreme-ultraviolet light pulses to launch photoelectron wave packets inside a tungsten crystal that is covered by magnesium films of varied, well-defined thicknesses of a few ångströms. Probing the moment of arrival of the wave packets at the surface with attosecond precision reveals free-electron-like, ballistic propagation behaviour inside the magnesium adlayer--constituting the semi-classical limit of Bloch wave packet motion. Real-time access to electron transport through atomic layers and interfaces promises unprecedented insight into phenomena that may enable the scaling of electronic and photonic circuits to atomic dimensions. In addition, this experiment allows us to determine the penetration depth of electrical fields at optical frequencies at solid interfaces on the atomic scale. PMID:25592539

Neppl, S; Ernstorfer, R; Cavalieri, A L; Lemell, C; Wachter, G; Magerl, E; Bothschafter, E M; Jobst, M; Hofstetter, M; Kleineberg, U; Barth, J V; Menzel, D; Burgdörfer, J; Feulner, P; Krausz, F; Kienberger, R

2015-01-15

95

Direct observation of asymmetric domain wall motion in a ferroelectric capacitor  

E-print Network

Direct observation of asymmetric domain wall motion in a ferroelectric capacitor Ja Kyung Lee a,1 observations of the 180° polarization switching process of a PbZr0.2Ti0.8O3 (PZT) capacitor. The preferential capacitors, switching between two bistable polarization states that are related by a 180° rotation

Chen, Long-Qing

96

Direct Observation of the Transition from Calcite to Aragonite Growth as Induced by Abalone Shell Proteins  

E-print Network

Direct Observation of the Transition from Calcite to Aragonite Growth as Induced by Abalone Shell are known to cause the nucleation and growth of aragonite on calcite seed crystals in supersaturated with calcite crystals did not observe this transition because no information about the crystal polymorph

Fygenson, Deborah Kuchnir

97

Direct observation of confined states in metallic single-walled carbon nanotubes  

E-print Network

Direct observation of confined states in metallic single-walled carbon nanotubes Theophilos metallic single-walled carbon nanotubes using low-temperature scanning tunneling spectroscopy. We observed Institute of Physics. DOI: 10.1063/1.1598282 Single-walled carbon nanotubes SWCNTs are consid- ered

Dekker, Cees

98

Observations of nonlinear interactions in directionally spread shoaling surface gravity waves  

NASA Technical Reports Server (NTRS)

Shoaling wave fields generated in laboratory experiments were analyzed to determine the sensitivity of nonlinear interactions to the directional distributions of incident waves. Peaks in the directional spectra observed in shallow water were consistent with near resonating, quadratic interactions between two primary waves transferring energy to a third wave with the sum frequency and vector sum wavenumber of the primary waves. Directionally colinear waves forced a higher-frequency wave propagating in the same direction as the primary waves, while directionally spread (i.e., noncolinear) primary waves forced a higher-frequency wave that propagated in a direction between those of the interacting primary waves. Deepwater wave fields with similar frequency spectra but different directional spectra evolved to different shallow-water directional spectra, yet their shallow-water frequency spectra were remarkably similar. This result suggests that the shape of the directional spectrum of the incident wave field has only a small effect on the magnitudes of nonlinear energy transfer during shoaling. The principal effect of directionality in the incident wave field is on the directions, not the amplitudes, of the nonlinearly generated waves. The laboratory data demonstrate clearly the importance of triad interactions between noncolinear and colinear shoaling waves.

Elgar, Steve; Guza, R. T.; Freilich, M. H.

1993-01-01

99

Direct Observation of Multiple Tautomers of Oxythiamine and their Recognition by the Thiamine Pyrophosphate Riboswitch  

PubMed Central

Structural diversification of canonical nucleic acid bases and nucleotide analogues by tautomerism has been proposed to be a powerful on/off switching mechanism allowing regulation of many biological processes mediated by RNA enzymes and aptamers. Despite the suspected biological importance of tautomerism, attempts to observe minor tautomeric forms in nucleic acid or hybrid nucleic acid-ligand complexes have met with challenges due to the lack of sensitive methods. Here, a combination of spectroscopic, biochemical and computational tools probed tautomerism in the context of an RNA aptamer-ligand complex; studies involved a model ligand, oxythiamine pyrophosphate (OxyTPP), bound to the thiamine pyrophosphate (TPP) riboswitch (an RNA aptamer) as well as its unbound non-phosphorylated form, oxythiamine (OxyT). OxyTPP, like canonical heteroaromatic nucleic acid bases, has a pyrimidine ring that forms hydrogen bonding interactions with the riboswitch. Tautomerism was established using two-dimensional infrared (2D IR) spectroscopy, variable temperature FTIR and NMR spectroscopies, binding isotope effects (BIEs) and computational methods. All three possible tautomers of OxyT, including the minor enol tautomer, were directly identified and their distributions were quantitated. In the bound form, BIE data suggested that OxyTPP existed as a 4'-keto tautomer that was likely protonated at the N1'-position. These results also provide a mechanistic framework for understanding the activation of riboswitch in response to deamination of the active form of vitamin B1 (or TPP). The combination of methods reported here revealing the fine details of tautomerism can be applied to other systems where the importance of tautomerism is suspected. PMID:24252063

Singh, Vipender; Peng, Chunte Sam; Li, Deyu; Mitra, Koyel; Silvestre, Katherine J.; Tokmakoff, Andrei; Essigmann, John M.

2014-01-01

100

Metabolic profiling of plant extracts using direct-injection electrospray ionization mass spectrometry allows for high-throughput phenotypic characterization according to genetic and environmental effects.  

PubMed

In comparison to the exponential increase of genotyping methods, phenotyping strategies are lagging behind in agricultural sciences. Genetic improvement depends upon the abundance of quantitative phenotypic data and the statistical partitioning of variance into environmental, genetic, and random effects. A metabolic phenotyping strategy was adapted to increase sample throughput while saving reagents, reducing cost, and simplifying data analysis. The chemical profiles of stem extracts from maize plants grown under low nitrogen (LN) or control trial (CT) were analyzed using optimized protocols for direct-injection electrospray ionization mass spectrometry (DIESI-MS). Specific ions significantly decreased or increased because of environmental (LN versus CT) or genotypic effects. Biochemical profiling with DIESI-MS had a superior cost-benefit compared to other standard analytical technologies (e.g., ultraviolet, near-infrared reflectance spectroscopy, high-performance liquid chromatography, and gas chromatography with flame ionization detection) routinely used for plant breeding. The method can be successfully applied in maize, strawberry, coffee, and other crop species. PMID:25588121

García-Flores, Martín; Juárez-Colunga, Sheila; García-Casarrubias, Adrián; Trachsel, Samuel; Winkler, Robert; Tiessen, Axel

2015-01-28

101

Direct observation of molecularly-aligned molecules in the second physisorbed layer-CO/Ag(110)  

SciTech Connect

We report the direct observation of oriented second-layer physisorbed molecules on a single crystal surface by electron stimulated desorption. Experiments and simulations show that the orientation of the second-layer physisorbed CO molecules on Ag(110) is the result of both electrostatic and dispersion forces from the underlying chemisorbed CO and Ag atoms. At 25 K, the physisorbed C-O bond is tilted and azimuthally oriented with the C-O bond axis inclined in an azimuthal plane at 45° to the principal Ag( 110) azimuthal crystallographic directions. The O atom in CO is directed outward, giving an O+ beam at 43° to the normal.

Lee, J.-G. (Chevron Science Center, Pittsburgh, PA); Hong, S.-H. (Chevron Science Center, Pittsburgh, PA); Ahner, J. (Chevron Science Center, Pittsburgh, PA); Zhao, X. (Univ. of Pittsburgh, PA); Chen, L.; Johnson, J.K.; Yates, J.T., Jr. (Chevron Science Center, Pittsburgh, PA)

2006-01-25

102

Directional surface plasmon coupled chemiluminescence from nickel thin films: Fixed angle observation  

NASA Astrophysics Data System (ADS)

Directional surface plasmon coupled chemiluminescence (SPCC) from nickel thin films is demonstrated. Free-space and angular-dependent SPCC emission from blue, green and turquoise chemiluminescent solutions placed onto nickel thin films attached to a hemispherical prism were measured. SPCC emission was found to be highly directional and preferentially p-polarized, in contrast to the unpolarized and isotropic chemiluminescence emission. The largest SPCC emission for all chemiluminescence solutions was observed at a fixed observation angle of 60°, which was also predicted by theoretical Fresnel calculations. It was found that nickel thin films did not have a catalytic effect on chemiluminescence emission.

Weisenberg, Micah; Aslan, Kadir; Hortle, Elinor; Geddes, Chris D.

2009-04-01

103

Direct observation of grain growth from molten silicon formed by micro-thermal-plasma-jet irradiation  

SciTech Connect

Phase transformation of amorphous-silicon during millisecond annealing using micro-thermal-plasma-jet irradiation was directly observed using a high-speed camera with microsecond time resolution. An oval-shaped molten-silicon region adjacent to the solid phase crystallization region was clearly observed, followed by lateral large grain growth perpendicular to a liquid-solid interface. Furthermore, leading wave crystallization (LWC), which showed intermittent explosive crystallization, was discovered in front of the moving molten region. The growth mechanism of LWC has been investigated on the basis of numerical simulation implementing explosive movement of a thin liquid layer driven by released latent heat diffusion in a lateral direction.

Hayashi, Shohei; Fujita, Yuji; Kamikura, Takahiro; Sakaike, Kohei; Akazawa, Muneki; Ikeda, Mitsuhisa; Hanafusa, Hiroaki; Higashi, Seiichiro [Department of Semiconductor Electronics and Integration Science, Graduate School of Advanced Sciences of Matter, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8530 (Japan)

2012-10-22

104

RECYCLING PROGRAM TYPE LOCATION ALLOWED NOT ALLOWED  

E-print Network

RECYCLING PROGRAM TYPE LOCATION ALLOWED NOT ALLOWED Batteries, toner, ink cartridges & cell phones Aerosol cans Window glass The University of Miami strives to create a more sustainable campus environment and recycling is an important part of that effort. Below is a guide to on-campus recycling at RSMAS: Visit http

Miami, University of

105

Five spacecraft observations of oppositely directed exhaust jets from a magnetic reconnection X-line extending > 4.26 106  

E-print Network

Five spacecraft observations of oppositely directed exhaust jets from a magnetic reconnection X] Observations of oppositely directed plasma jets within an extended, bifurcated current sheet in the solar wind. Russell, and K. D. Simunac (2007), Five spacecraft observations of oppositely directed exhaust jets from

California at Berkeley, University of

106

Direct observation of liquid crystals using cryo-TEM: specimen preparation and low-dose imaging.  

PubMed

Liquid crystals (LCs) represent a challenging group of materials for direct transmission electron microscopy (TEM) studies due to the complications in specimen preparation and the severe radiation damage. In this paper, we summarize a series of specimen preparation methods, including thin film and cryo-sectioning approaches, as a comprehensive toolset enabling high-resolution direct cryo-TEM observation of a broad range of LCs. We also present comparative analysis using cryo-TEM and replica freeze-fracture TEM on both thermotropic and lyotropic LCs. In addition to the revisits of previous practices, some new concepts are introduced, e.g., suspended thermotropic LC thin films, combined high-pressure freezing and cryo-sectioning of lyotropic LCs, and the complementary applications of direct TEM and indirect replica TEM techniques. The significance of subnanometer resolution cryo-TEM observation is demonstrated in a few important issues in LC studies, including providing direct evidences for the existence of nanoscale smectic domains in nematic bent-core thermotropic LCs, comprehensive understanding of the twist-bend nematic phase, and probing the packing of columnar aggregates in lyotropic chromonic LCs. Direct TEM observation opens ways to a variety of TEM techniques, suggesting that TEM (replica, cryo, and in situ techniques), in general, may be a promising part of the solution to the lack of effective structural probe at the molecular scale in LC studies. PMID:25045045

Gao, Min; Kim, Young-Ki; Zhang, Cuiyu; Borshch, Volodymyr; Zhou, Shuang; Park, Heung-Shik; Jákli, Antal; Lavrentovich, Oleg D; Tamba, Maria-Gabriela; Kohlmeier, Alexandra; Mehl, Georg H; Weissflog, Wolfgang; Studer, Daniel; Zuber, Benoît; Gnägi, Helmut; Lin, Fang

2014-10-01

107

Earth-bound observations of asteroid 19 Fortuna as support to HST imaging: lightcurves, pole direction and shape  

NASA Astrophysics Data System (ADS)

To support the 19 Fortuna imaging work performed by the Hubble Space Telescope, this asteroid was photoelectrically observed in September 1993 at Mt. John, Lake Tekapo and Serra la Nave observatories, covering a complete rotational cycle. These observations and the unpublished ones, collected in November 1986 at Torino Observatory, allowed us to compute the value of the synodic rotational period, which results in accordance with that already known. The spin axis direction and the shape of 19 Fortuna were determined by applying the amplitude-magnitude method (Zappalà et al., in Asteroids, Comets, Meteors (edited by C.-I. Lagerkvist and H. Rickman), pp. 73-76. Uppsala Univeritet, Reprocentralen, HSC, Uppsala, 1983) to our data and to those reported in the literature. The values of the pole coordinates are in agreement with the previous determinations, while the ratio between the semi-axes a and b is larger than about 0.1.

Blanco, C.; Di Martino, M.; Dotto, E.; Gilmore, A. C.; Kilmartin, P. M.; Riccioli, D.

1996-02-01

108

Ethical aspects of directly observed treatment for tuberculosis: a cross-cultural comparison  

PubMed Central

Background Tuberculosis is a major global public health challenge, and a majority of countries have adopted a version of the global strategy to fight Tuberculosis, Directly Observed Treatment, Short Course (DOTS). Drawing on results from research in Ethiopia and Norway, the aim of this paper is to highlight and discuss ethical aspects of the practice of Directly Observed Treatment (DOT) in a cross-cultural perspective. Discussion Research from Ethiopia and Norway demonstrates that the rigid enforcement of directly observed treatment conflicts with patient autonomy, dignity and integrity. The treatment practices, especially when imposed in its strictest forms, expose those who have Tuberculosis to extra burdens and costs. Socially disadvantaged groups, such as the homeless, those employed as day labourers and those lacking rights as employees, face the highest burdens. Summary From an ethical standpoint, we argue that a rigid practice of directly observed treatment is difficult to justify, and that responsiveness to social determinants of Tuberculosis should become an integral part of the management of Tuberculosis. PMID:23819555

2013-01-01

109

Parallel electric fields in the upward current region of the aurora: Indirect and direct observations  

E-print Network

Parallel electric fields in the upward current region of the aurora: Indirect and direct current region of the aurora focusing on the structure of electric fields at the boundary between account of the electric fields in the upward current region of the aurora as observed by the Fast Auroral

California at Berkeley, University of

110

The Impact of Observation Duration on the Accuracy of Data Obtained from Direct Behavior Rating (DBR)  

ERIC Educational Resources Information Center

In this study, evaluation of direct behavior rating (DBR) occurred with regard to two primary areas: (a) accuracy of ratings with varied instrumentation (anchoring: proportional or absolute) and procedures (observation length: 5 min, 10 min, or 20 min) and (b) one-week test-retest reliability. Participants viewed video clips of a typical third…

Riley-Tillman, T. Chris; Christ, Theodore J.; Chafouleas, Sandra M.; Boice-Mallach, Christina H.; Briesch, Amy

2011-01-01

111

From Directly Observed Therapy to Accompagnateurs: Enhancing AIDS Treatment Outcomes in Haiti and in Boston  

Microsoft Academic Search

Like tuberculosis, human immunodeficiency virus (HIV) disease is associated with poverty and social ine- qualities, conditions that hamper the delivery of care. Like tuberculosis, treatment of HIV infection requires multidrug regimens, and the causative agent acquires drug resistance, which can be transmitted to others. A pilot project in rural Haiti introduced DOT-HAART (directly observed therapy with highly active antiretroviral therapy)

H. L. Behforouz; P. E. Farmer; J. S. Mukherjee

2004-01-01

112

Direct Observation of Slow Light in the Noise Spectrum of a Laser  

E-print Network

. A thick glass etalon is inserted inside the cavity to make the laser single mode. The noise spectrumDirect Observation of Slow Light in the Noise Spectrum of a Laser A. El Amili1, B.-X. Miranda1,2, F oscillations is evidenced in the noise spectrum of an ultra-low noise laser. The coherent population

Boyer, Edmond

113

Direct Observation of Protein Folding, Aggregation, and a Prion-like Conformational Conversion*  

E-print Network

Direct Observation of Protein Folding, Aggregation, and a Prion-like Conformational Conversion to -sheets precedes aggregation of proteins implicated in many diseases, including Alzheimer and prion, S. B. (1998) Proc. Natl. Acad. Sci. U. S. A. 95, 13363­ 13383) to account for prion infectivity

Dokholyan, Nikolay V.

114

Direct observation of electron thermalization and electron-phonon coupling in photoexcited bismuth  

E-print Network

Direct observation of electron thermalization and electron-phonon coupling in photoexcited bismuth: September 5, 2013) Abstract We investigate the ultrafast response of the bismuth (111) surface by means bismuth. PACS numbers: 73.20.Mf, 71.15.Mb,73.20.At,78.47.jb 1 hal-00856065,version1-9Sep2013 Author

Paris-Sud XI, Université de

115

Direct in Situ Observation of Synergism between Cellulolytic Enzymes during the Biodegradation of Crystalline Cellulose Fibers  

E-print Network

Direct in Situ Observation of Synergism between Cellulolytic Enzymes during the Biodegradation types of T. reesei cellulolytic enzymes TrCel6A, TrCel7A, and TrCel7Band their mixtures. TrCel6A and Tr. When acting alone on native cellulose fibers, each of the three enzymes is incapable of significant

Dutcher, John

116

Analysis of multidimensional difference-of-Gaussians filters in terms of directly observable parameters  

PubMed Central

The difference-of-Gaussians (DOG) filter is a widely used model for the receptive field of neurons in the retina and lateral geniculate nucleus and is a potential model in general for responses modulated by an excitatory center with an inhibitory surrounding region. A DOG filter is defined by three standard parameters: the center and surround sigmas (which define the variance of the radially symmetric Gaussians) and the balance (which defines the linear combination of the two Gaussians). These parameters are not directly observable and are typically determined by nonlinear parameter estimation methods applied to the frequency response function. DOG filters show both low-pass (optimal response at zero frequency) and band-pass (optimal response at a non-zero frequency) behavior. This paper reformulates the DOG filter in terms of a directly observable parameter, the zero-crossing radius, and two new (but not directly observable) parameters. In the new two-dimensional parameter space, the exact region corresponding to band-pass behavior is determined. A detailed description of the frequency response characteristics of the DOG filter is obtained. It is also found that the directly observable optimal frequency and optimal gain (the ratio of the response at optimal frequency to the response at zero frequency) provide an alternate coordinate system for the band-pass region. Altogether, the DOG filter and its three standard implicit parameters can be determined by three directly observable values. The two-dimensional band-pass region is a potential tool for the analysis of populations of DOG filters (for example, populations of neurons in the retina or lateral geniculate nucleus) because the clustering of points in this parameter space may indicate an underlying organizational principle. This paper concentrates on circular Gaussians, but the results generalize to multidimensional radially symmetric Gaussians and are given as an appendix. PMID:23695334

Cope, Davis; Blakeslee, Barbara; McCourt, Mark E.

2013-01-01

117

Direct laboratory observation of fluid distribution and its influence on acoustic properties of patchy saturated rocks  

NASA Astrophysics Data System (ADS)

Porous rocks in hydrocarbon reservoirs are often saturated with a mixture of two or more fluids. Interpretation of exploration seismograms requires understanding of the relationship between distribution of the fluids patches and acoustic properties of rocks. The sizes of patches as well as their distribution affect significantly the seismic response. If the size of the fluid patch is smaller than the diffusion wavelength then pressure equilibration is achieved and the bulk modulus of the rock saturated with a mixture is defined by the Gassmann equations (Gassmann, 1951) with the saturation-weighted average of the fluid bulk modulus given by Wood's law (Wood, 1955, Mavko et al., 1998). If the fluid patch size is much larger than the diffusion wavelength then there is no pressure communication between different patches. In this case, fluid-flow effects can be neglected and the overall rock may be considered equivalent to an elastic composite material consisting of homogeneous parts whose properties are given by Gassmann theory with Hill's equation for the bulk modulus (Hill, 1963, Mavko et al., 1998). At intermediate values of fluid saturation the velocity-saturation relationship is significantly affected by the fluid patch distribution. In order to get an improved understanding of factors influencing the patch distribution and the resulting seismic wave response we performed simultaneous measurements of P-wave velocities and rock sample CT imaging. The CT imaging allows us to map the fluid distribution inside rock sample during saturation (water imbibition). We compare the experimental results with theoretical predictions. In this paper we will present results of simultaneous measurements of longitudinal wave velocities and imaging mapping of fluid distribution inside rock sample during sample saturation. We will report results of two kinds of experiments: "dynamic" and "quasi static" saturation. In both experiments Casino Cores Otway Basin sandstone, Australia core samples (38 mm in diameter, approximately 60 mm long) were dried in oven under reduced pressure. In dynamic saturation experiments, samples were jacketed in the experimental cell, made from transparent for X-radiation material (PMMA). Distillate water was injected into the sample from the one side. Fluid distribution in such "dynamic" experiment: both spatial and time dependant was measured using X-ray Computer Tomograph (CT) with resolution 0.2 x 0.2 x 1 mm3. Velocities (Vp, and Vs) at ultrasonic frequency of 1 MHz, were measured in the direction perpendicular to initial direction of the fluid flow injection. Sample saturation was estimated from the CT results. In "quasi static" experiments samples were saturated during long period of time (over 2 weeks) to achieve uniform distribution of liquid inside the sample. Saturation was determined by measurement of the weight of water fraction. All experiments were performed at laboratory environments at temperature 25 C. Ultrasonic velocities and fluid saturations were measured simultaneously during water injection into sandstone core samples. The experimental results obtained on low-permeability samples show that at low saturation values the velocity-saturation dependence can be described by the Gassmann-Wood relationship. However, with increasing saturation a sharp increase of P-wave velocity is observed, eventually approaching the Gassmann-Hill relationship. We connect the characteristics of the transition behavior of the velocity-saturation relationships to the increasing size of the patches inside the rock sample. In particular, we show that for relatively large fluid injection rate this transition occurs at smaller degrees of saturation as compared with high injection rate. We model the experimental data using the so-called White model (Toms 2007) that assumes fluid patch distribution as a periodic assemblage of concentric spheres. We can observe reasonable agreement between experimental results and theoretical predictions of White's model. The results illustrate the non

Lebedev, M.; Clennell, B.; Pervukhina, M.; Shulakova, V.; Mueller, T.; Gurevich, B.

2009-04-01

118

THE STRUCTURE OF A SELF-GRAVITATING PROTOPLANETARY DISK AND ITS IMPLICATIONS FOR DIRECT IMAGING OBSERVATIONS  

SciTech Connect

We consider the effects of self-gravity on the hydrostatic balance in the vertical direction of a gaseous disk and discuss the possible signature of the self-gravity that may be captured by direct imaging observations of protoplanetary disks in the future. In this paper, we consider a vertically isothermal disk in order to isolate the effects of self-gravity. The specific disk model we consider in this paper is the one with a radial surface density gap, at which the Toomre's Q-parameter of the disk varies rapidly in the radial direction. We calculate the vertical structure of the disk including the effects of self-gravity. We then calculate the scattered light and the dust thermal emission. We find that if the disk is massive enough and the effects of self-gravity come into play, a weak bump-like structure at the gap edge appears in the near-infrared (NIR) scattered light, while no such bump-like structure is seen in the submillimeter (sub-mm) dust continuum image. The appearance of the bump is caused by the variation of the height of the surface in the NIR wavelength. If such a bump-like feature is detected in future direct imaging observations, combined with sub-mm observations, it will give us useful information about the physical states of the disk.

Muto, Takayuki, E-mail: muto@geo.titech.ac.jp [Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Oh-okayama, Meguro-ku, Tokyo 152-8551 (Japan)

2011-09-20

119

VERITAS Observations of the Arrival Directions of the Highest Energy Cosmic Rays  

E-print Network

The recent discovery by the Pierre Auger collaboration of anisotropy in the arrival directions of the highest energy cosmic rays, correlated with the positions of nearby active galactic nuclei, encourages the search for counterpart TeV gamma-ray emission. Approximately half of the sky viewed by the southern hemisphere Pierre Auger experiment is also visible at reasonable elevations for the northern hemisphere gamma-ray telescope array, VERITAS. We report on first observations by VERITAS of regions associated with the arrival directions of ultra-high energy cosmic ray events.

J. Holder; for the VERITAS Collaboration

2008-10-02

120

Mid-Cretaceous charred fossil flowers reveal direct observation of arthropod feeding strategies  

PubMed Central

Although plant–arthropod relationships underpin the dramatic rise in diversity and ecological dominance of flowering plants and their associated arthropods, direct observations of such interactions in the fossil record are rare, as these ephemeral moments are difficult to preserve. Three-dimensionally preserved charred remains of Chloranthistemon flowers from the Late Albian to Early Cenomanian of Germany preserve scales of mosquitoes and an oribatid mite with mouthparts inserted into the pollen sac. Mosquitoes, which today are frequent nectar feeders, and the mite were feeding on pollen at the time wildfire consumed the flowers. These findings document directly arthropod feeding strategies and their role in decomposition. PMID:21900310

Hartkopf-Fröder, Christoph; Rust, Jes; Wappler, Torsten; Friis, Else Marie; Viehofen, Agnes

2012-01-01

121

Direct Observation of the Dzyaloshinskii-Moriya Interaction in a Pt/Co/Ni Film  

NASA Astrophysics Data System (ADS)

The interfacial Dzyaloshinskii-Moriya interaction in an in-plane anisotropic Pt (4 nm )/Co (1.6 nm )/Ni (1.6 nm ) film has been directly observed by Brillouin spectroscopy. It is manifested as the asymmetry of the measured magnon dispersion relation, from which the Dzyaloshinskii-Moriya interaction constant has been evaluated. Linewidth measurements reveal that the lifetime of the magnons is asymmetric with respect to their counter-propagating directions. The lifetime asymmetry is dependent on the magnon frequency, being more pronounced, the higher the frequency. Analytical calculations of the magnon dispersion relation and linewidth agree well with experiments.

Di, Kai; Zhang, Vanessa Li; Lim, Hock Siah; Ng, Ser Choon; Kuok, Meng Hau; Yu, Jiawei; Yoon, Jungbum; Qiu, Xuepeng; Yang, Hyunsoo

2015-01-01

122

Diffusion of a Highly-Charged Supramolecular Assembly: Direct Observation of Ion-Association in Water  

SciTech Connect

Understanding the solution behavior of supramolecular assemblies is essential for a full understanding of the formation and chemistry of synthetic host-guest systems. While the interaction between host and guest molecules is generally the focus of mechanistic studies of host-guest complexes, the interaction of the host-guest complex with other species in solution remains largely unknown, although in principle accessible by diffusion studies. Several NMR techniques are available to monitor diffusion and have recently been reviewed. Pulsed gradient spin-echo (PGSE) NMR methods have attracted increasing interest, since they allow diffusion coefficients to be measured with high accuracy; they have been successfully used with observation of {sup 7}Li and {sup 31}P nuclei as well as with {sup 1}H NMR. We report here the direct measurement of diffusion coefficients to observe ion-association interactions by counter cations with a highly-charged supramolecular assembly. Raymond and coworkers have described the design and chemistry of a class of metal-ligand supramolecular assemblies over the past decade. The [Ga{sub 4}L{sub 6}]{sup 12-} (L = 1,5-bis(2,3-dihydroxybenzamido)naphthalene) (1) (Figure 1) assembly has garnered the most attention, with the exploration of the dynamics and mechanism of guest exchange as well as the ability of 1 to achieve either stoichiometric or catalytic reactions inside its interior cavity. Recent studies have revealed the importance of counter cations in solution on the chemistry of 1. During the mechanistic study of the C-H bond activation of aldehydes by [Cp*Ir(PMe{sub 3})(olefin){sup +} {contained_in} 1]{sup 11-} a stepwise guest dissociation mechanism with an ion-paired intermediate was proposed. Similarly, in the mechanism for the hydrolysis of iminium cations generated from the 3-aza Cope rearrangement of enammonium cations in 1, the presence of an exterior ion association was part of the kinetic model. To further substantiate the indirect kinetic evidence for such ion-paired species, we sought to explore the solution behavior of 1 by studying the diffusion of 1 with varying alkali and tetraalkyl ammonium cations. For large molecules in solution, such as synthetic supramolecular assemblies, the diffusion behavior of host and guest molecules can provide valuable information on host-guest interaction. One characteristic feature of a stable host-guest complex is that the host and guest molecules diffuse at the same rate in solution; this has been observed in a number of supramolecular systems. In order to confirm that this system was suitable for study by diffusion NMR spectroscopy, a PGSE-DOSY spectrum was acquired of [NEt{sub 4} {contained_in} 1]{sup 11-} (Figure 2), which shows that the host and guest molecules diffuse at the same rate. Quantitative analysis of the data, from monitoring the integral of host and guest resonances as a function of applied gradient strength, gave identical diffusion coefficients, confirming that the host and guest molecules diffuse together.

University of California, Berkeley; Lawrence Berkeley National Laboratory; Raymond, Kenneth; Pluth, Michael D.; Tiedemann, Bryan E.F.; van Halbeek, Herman; Nunlist, Rudi; Raymond, Kenneth N.

2007-10-22

123

Direct Observation of Field and Temperature Induced Domain Replication in Dipolar Coupled Perpendicular Anisotropy Films  

SciTech Connect

Dipolar interactions in a soft/Pd/hard [CoNi/Pd]{sub 30}/Pd/[Co/Pd]{sub 20} multilayer system, where a thick Pd layer between two ferromagnetic units prevents direct exchange coupling, are directly revealed by combining magnetometry and state-of-the-art layer resolving soft x-ray imaging techniques with sub-100-nm spatial resolution. The domains forming in the soft layer during external magnetic field reversal are found to match the domains previously trapped in the hard layer. The low Curie temperature of the soft layer allows varying its intrinsic parameters via temperature and thus studying the competition with dipolar fields due to the domains in the hard layer. Micromagnetic simulations elucidate the role of [CoNi/Pd] magnetization, exchange, and anisotropy in the duplication process. Finally, thermally driven domain replication in remanence during temperature cycling is demonstrated.

Hauet, T.; Gunther, C.M.; Pfau, B.; Eisebitt, S.; Fischer, P.; Rick, R. L.; Thiele, J.-U.; Hellwig, O.; Schabes, M.E.

2007-07-01

124

Direct reconstruction of spherical harmonics from interferometer observations of the CMB polarization  

E-print Network

Interferometric observation of the CMB polarization can be expressed as a linear sum of spherical harmonic coefficients $a_{\\pm 2,lm}$ of the CMB polarization. The linear weight for $a_{\\pm 2,lm}$ depends on the observational configuration such as antenna pointing, baseline orientation, and spherical harmonic number $l,m$. Since an interferometer is sensitive over a finite range of multipoles, $a_{\\pm 2,lm}$ in the range can be determined by fitting $a_{\\pm 2,lm}$ for visibilities of various observational configurations. The formalism presented in this paper enables the determination of $a_{\\pm 2,lm}$ directly from spherical harmonic spaces without spherical harmonic transformation of pixellized maps. The result of its application to a simulated observation is presented with the formalism.

Jaiseung Kim

2009-04-06

125

Direct spectroscopic observation of a shallow hydrogenlike donor state in insulating SrTiO3.  

PubMed

We present a direct spectroscopic observation of a shallow hydrogenlike muonium state in SrTiO(3) which confirms the theoretical prediction that interstitial hydrogen may act as a shallow donor in this material. The formation of this muonium state is temperature dependent and appears below ? 70K. From the temperature dependence we estimate an activation energy of ? 50 meV in the bulk and ? 23 meV near the free surface. The field and directional dependence of the muonium precession frequencies further supports the shallow impurity state with a rare example of a fully anisotropic hyperfine tensor. From these measurements we determine the strength of the hyperfine interaction and propose that the muon occupies an interstitial site near the face of the oxygen octahedron in SrTiO(3). The observed shallow donor state provides new insight for tailoring the electronic and optical properties of SrTiO(3)-based oxide interface systems. PMID:25375730

Salman, Z; Prokscha, T; Amato, A; Morenzoni, E; Scheuermann, R; Sedlak, K; Suter, A

2014-10-10

126

Direct Spectroscopic Observation of a Shallow Hydrogenlike Donor State in Insulating SrTiO3  

NASA Astrophysics Data System (ADS)

We present a direct spectroscopic observation of a shallow hydrogenlike muonium state in SrTiO3 which confirms the theoretical prediction that interstitial hydrogen may act as a shallow donor in this material. The formation of this muonium state is temperature dependent and appears below ˜70 K. From the temperature dependence we estimate an activation energy of ˜50 meV in the bulk and ˜23 meV near the free surface. The field and directional dependence of the muonium precession frequencies further supports the shallow impurity state with a rare example of a fully anisotropic hyperfine tensor. From these measurements we determine the strength of the hyperfine interaction and propose that the muon occupies an interstitial site near the face of the oxygen octahedron in SrTiO3. The observed shallow donor state provides new insight for tailoring the electronic and optical properties of SrTiO3-based oxide interface systems.

Salman, Z.; Prokscha, T.; Amato, A.; Morenzoni, E.; Scheuermann, R.; Sedlak, K.; Suter, A.

2014-10-01

127

Direct observation of pulse dynamics and self-compression along a femtosecond filament.  

PubMed

We report on the direct experimental observation of pulse-splitting dynamics along a femtosecond filament. The fundamental pulse experiences a significant self-shortening during the propagation leading to pulse durations of 5.3 fs, corresponding to sub-3 cycles, which is measured without external pulse compression. A compression factor of eight could be achieved in a single filamentary stage. Theoretical modeling of the fundamental pulse propagation confirms our observed pulse structures and durations and gives further insight into the nonlinear dynamics during filamentation. PMID:25321761

Kretschmar, Martin; Brée, Carsten; Nagy, Tamas; Demircan, Ayhan; Kurz, Heiko G; Morgner, Uwe; Kova?ev, Milutin

2014-09-22

128

Controllability and observability analysis for vertex domination centrality in directed networks.  

PubMed

Topological centrality is a significant measure for characterising the relative importance of a node in a complex network. For directed networks that model dynamic processes, however, it is of more practical importance to quantify a vertex's ability to dominate (control or observe) the state of other vertices. In this paper, based on the determination of controllable and observable subspaces under the global minimum-cost condition, we introduce a novel direction-specific index, domination centrality, to assess the intervention capabilities of vertices in a directed network. Statistical studies demonstrate that the domination centrality is, to a great extent, encoded by the underlying network's degree distribution and that most network positions through which one can intervene in a system are vertices with high domination centrality rather than network hubs. To analyse the interaction and functional dependence between vertices when they are used to dominate a network, we define the domination similarity and detect significant functional modules in glossary and metabolic networks through clustering analysis. The experimental results provide strong evidence that our indices are effective and practical in accurately depicting the structure of directed networks. PMID:24954137

Wang, Bingbo; Gao, Lin; Gao, Yong; Deng, Yue; Wang, Yu

2014-01-01

129

Controllability and observability analysis for vertex domination centrality in directed networks  

NASA Astrophysics Data System (ADS)

Topological centrality is a significant measure for characterising the relative importance of a node in a complex network. For directed networks that model dynamic processes, however, it is of more practical importance to quantify a vertex's ability to dominate (control or observe) the state of other vertices. In this paper, based on the determination of controllable and observable subspaces under the global minimum-cost condition, we introduce a novel direction-specific index, domination centrality, to assess the intervention capabilities of vertices in a directed network. Statistical studies demonstrate that the domination centrality is, to a great extent, encoded by the underlying network's degree distribution and that most network positions through which one can intervene in a system are vertices with high domination centrality rather than network hubs. To analyse the interaction and functional dependence between vertices when they are used to dominate a network, we define the domination similarity and detect significant functional modules in glossary and metabolic networks through clustering analysis. The experimental results provide strong evidence that our indices are effective and practical in accurately depicting the structure of directed networks.

Wang, Bingbo; Gao, Lin; Gao, Yong; Deng, Yue; Wang, Yu

2014-06-01

130

Direct observation of the orientational Kerr effect in the self-focusing of picosecond pulses.  

NASA Technical Reports Server (NTRS)

Direct measurements of the relaxation time of the birefringence within the self-focusing region of mode-locked laser pulses in several anisotropic liquids establish the importance of the orientational Kerr effect in the picosecond time regime. This result leads to some speculation as to the origin of the high degree of symmetry in the phase-modulated filament spectra observed with picosecond pulses.

Reintjes, J.; Carman, R. L.

1972-01-01

131

Direct observation of porous SiC formed by anodization in HF  

NASA Technical Reports Server (NTRS)

A process for forming porous SiC from single-crystal SiC wafers has been demonstrated. Porous SiC can be fabricated by anodizing n-type 6H-SiC in HF under UV illumination. TEM reveals pores of sizes 10-30 nm with interpore spacings ranging from roughly 5 to 150 nm. This is the first reported direct observation of porous SiC formation.

Shor, Joseph S.; Grimberg, Ilana; Weiss, Ben-Zion; Kurtz, Anthony D.

1993-01-01

132

Direct observations of basin-wide acidification of the North Pacific Ocean  

Microsoft Academic Search

Global ocean acidification is a prominent, inexorable change associated with rising levels of atmospheric CO2. Here we present the first basin-wide direct observations of recently declining pH, along with estimates of anthropogenic and non-anthropogenic contributions to that signal. Along 152°W in the North Pacific Ocean (22–56°N), pH changes between 1991 and 2006 were essentially zero below about 800 m depth.

Robert H. Byrne; Sabine Mecking; Richard A. Feely; Xuewu Liu

2010-01-01

133

Direct solar radiation pressure on the orbits of small near-Earth asteroids: observable effects?  

NASA Astrophysics Data System (ADS)

We consider the perturbations of Near-Earth Asteroid orbits due to direct solar radiation pressure (both the absorption and the reflection components). When the body is spherical and the surface albedo homogeneous the effect is small (and only short-periodic). However, when at least one of these restrictive and unrealistic assumptions is relaxed, long-term orbital effects appear and they may potentially lead to observable displacement of the orbit. We illustrate this conclusion by computing the orbital perturbations due to radiation pressure for objects with an odd-zonal distribution of albedo and for objects with ellipsoidal shape. Especially in the first case the effects are large, due to the long-term perturbations of the semimajor axis. For high-eccentricity orbits observed over a long interval of time, the (v/c)-correction of the direct radiation pressure, known as Poynting-Robertson effect, should be also considered. As an example we demonstrate that for the asteroid 1566 Icarus, during its next close approach to the Earth, the orbit displacement due to the direct solar radiation forces might be, under reasonable assumptions, comparable to the orbit determination uncertainty, thus potentially observable.

Vokrouhlický, D.; Milani, A.

2000-10-01

134

Direct observation and mapping of spin waves emitted by spin-torque nano-oscillators.  

PubMed

Dynamics induced by spin-transfer torque is a quickly developing topic in modern magnetism, which has initiated several new approaches to magnetic nanodevices. It is now well established that a spin-polarized electric current injected into a ferromagnetic layer through a nanocontact exerts a torque on the magnetization, leading to microwave-frequency precession detectable through the magnetoresistance effect. This phenomenon provides a way for the realization of tunable nanometre-size microwave oscillators, the so-called spin-torque nano-oscillators (STNOs). Present theories of STNOs are mainly based on pioneering works predicting emission of spin waves due to the spin torque. Despite intense experimental studies, until now this spin-wave emission has not been observed. Here, we report the first experimental observation and two-dimensional mapping of spin waves emitted by STNOs. We demonstrate that the emission is strongly directional, and the direction of the spin-wave propagation is steerable by the magnetic field. The information about the emitted spin waves obtained in our measurements is of key importance for the understanding of the physics of STNOs, and for the implementation of coupling between individual oscillators mediated by spin waves. Analysis shows that the observed directional emission is a general property inherent to any dynamical system with strongly anisotropic dispersion. PMID:20972428

Demidov, Vladislav E; Urazhdin, Sergei; Demokritov, Sergej O

2010-12-01

135

Direction-sensitive codes for observed head turns in human superior temporal sulcus.  

PubMed

Humans and other primates are adept at using the direction of another's gaze or head turn to infer where that individual is attending. Research in macaque neurophysiology suggests that anterior superior temporal sulcus (STS) contains a direction-sensitive code for such social attention cues. By contrast, most human functional Magnetic resonance imaging (fMRI) studies report that posterior STS is responsive to social attention cues. It is unclear whether this functional discrepancy is caused by a species difference or by experimental design differences. Furthermore, social attention cues are dynamic in naturalistic social interaction, but most studies to date have been restricted to static displays. In order to address these issues, we used multivariate pattern analysis of fMRI data to test whether response patterns in human right STS distinguish between leftward and rightward dynamic head turns. Such head turn discrimination was observed in right anterior STS/superior temporal gyrus (STG). Response patterns in this region were also significantly more discriminable for head turn direction than for rotation direction in physically matched ellipsoid control stimuli. Our findings suggest a role for right anterior STS/STG in coding the direction of motion in dynamic social attention cues. PMID:21709175

Carlin, Johan D; Rowe, James B; Kriegeskorte, Nikolaus; Thompson, Russell; Calder, Andrew J

2012-04-01

136

Increasing Reliability of Direct Observation Measurement Approaches in Emotional and/or Behavioral Disorders Research Using Generalizability Theory  

ERIC Educational Resources Information Center

Reliability of direct observation outcomes ensures the results are consistent, dependable, and trustworthy. Typically, reliability of direct observation measurement approaches is assessed using interobserver agreement (IOA) and the calculation of observer agreement (e.g., percentage of agreement). However, IOA does not address intraobserver…

Gage, Nicholas A.; Prykanowski, Debra; Hirn, Regina

2014-01-01

137

Direct observation of ionic structure at solid-liquid interfaces: a deep look into the Stern Layer  

NASA Astrophysics Data System (ADS)

The distribution of ions and charge at solid-water interfaces plays an essential role in a wide range of processes in biology, geology and technology. While theoretical models of the solid-electrolyte interface date back to the early 20th century, a detailed picture of the structure of the electric double layer has remained elusive, largely because of experimental techniques have not allowed direct observation of the behaviour of ions, i.e. with subnanometer resolution. We have made use of recent advances in high-resolution Atomic Force Microscopy to reveal, with atomic level precision, the ordered adsorption of the mono- and divalent ions that are common in natural environments to heterogeneous gibbsite/silica surfaces in contact with aqueous electrolytes. Complemented by density functional theory, our experiments produce a detailed picture of the formation of surface phases by templated adsorption of cations, anions and water, stabilized by hydrogen bonding.

Siretanu, Igor; Ebeling, Daniel; Andersson, Martin P.; Stipp, S. L. Svane; Philipse, Albert; Stuart, Martien Cohen; van den Ende, Dirk; Mugele, Frieder

2014-05-01

138

Direct observation of imprinted antiferromagnetic vortex state in CoO/Fe/Ag(001) disks  

SciTech Connect

In magnetic thin films, a magnetic vortex is a state in which the magnetization vector curls around the center of a confined structure. A vortex state in a thin film disk, for example, is a topological object characterized by the vortex polarity and the winding number. In ferromagnetic (FM) disks, these parameters govern many fundamental properties of the vortex such as its gyroscopic rotation, polarity reversal, core motion, and vortex pair excitation. However, in antiferromagnetic (AFM) disks, though there has been indirect evidence of the vortex state through observations of the induced FM-ordered spins in the AFM disk, they have never been observed directly in experiment. By fabricating single crystalline NiO/Fe/Ag(001) and CoO/Fe/Ag(001) disks and using X-ray Magnetic Linear Dichroism (XMLD), we show direct observation of the vortex state in an AFM disk of AFM/FM bilayer system. We observe that there are two types of AFM vortices, one of which has no analog in FM structures. Finally, we show that a frozen AFM vortex can bias a FM vortex at low temperature.

Wu, J.; Carlton, D.; Park, J. S.; Meng, Y.; Arenholz, E.; Doran, A.; Young, A.T.; Scholl, A.; Hwang, C.; Zhao, H. W.; Bokor, J.; Qiu, Z. Q.

2010-12-21

139

Home Videophones Improve Direct Observation in Tuberculosis Treatment: A Mixed Methods Evaluation  

PubMed Central

Background The use of direct observation to monitor tuberculosis treatment is controversial: cost, practical difficulties, and lack of patient acceptability limit effectiveness. Telehealth is a promising alternative delivery method for improving implementation. This study aimed to evaluate the clinical and cost-effectiveness of a telehealth service delivering direct observation, compared to an in-person drive-around service. Methodology/Principal Findings The study was conducted within a community nursing service in South Australia. Telehealth patients received daily video calls at home on a desktop videophone provided by the nursing call center. A retrospective cohort study assessed the effectiveness of the telehealth and traditional forms of observation, defined by the proportion of missed observations recorded in case notes. This data was inputted to a model, estimating the incremental cost-effectiveness ratio (ICER) of telehealth. Semi-structured interviews were conducted with current patients, community nursing and Chest Clinic staff, concerning service acceptability, usability and sustainability. The percentage of missed observations for the telehealth service was 12.1 (n?=?58), compared to 31.1 for the in-person service (n?=?70). Most of the difference of 18.9% (95% CI: 12.2 – 25.4) was due to fewer pre-arranged absences. The economic analysis calculated the ICER to be AUD$1.32 (95% CI: $0.51 – $2.26) per extra day of successful observation. The video service used less staff time, and became dominant if implemented on a larger scale and/or with decreased technology costs. Qualitative analysis found enabling factors of flexible timing, high patient acceptance, staff efficiency, and Chest Clinic support. Substantial technical problems were manageable, and improved liaison between the nursing service and Chest Clinic was an unexpected side-benefit. Conclusions/Significance Home video observation is a patient-centered, resource efficient way of delivering direct observation for TB, and is cost-effective when compared with a drive-around service. Future research is recommended to determine applicability and effectiveness in other settings. PMID:23226243

Wade, Victoria A.; Karnon, Jonathan; Eliott, Jaklin A.; Hiller, Janet E.

2012-01-01

140

Direct Determination of Wind Shears from the Gradients of Satellite Radiance Observations.  

NASA Astrophysics Data System (ADS)

To the extent that the stratosphere wind field is close to geostrophic, the thermal wind is a good approximation to the vertical wind shear (vertical variation of the horizontal wind). And since the thermal wind is proportional to the horizontal temperature gradient, the possibility exists of determining it from satellite radiance observations. Several different methods are developed here for retrieving thermal winds directly from the horizontal gradients of satellite radiance observations, without first retrieving the horizontal temperature gradient. The methods are applied to the determination of thermal winds in the upper troposphere and lower stratosphere over the White Sands Missile Range area. A special series of about 30 concurrent sets of radiance observations from the NDAA-4 VTPR instrument and wind shears from radiosonde observations (for ground truth) distributed throughout one year, is used for these tests. The results obtained with these direct methods are compared with results obtained with 1) a traditional method, in which temperature profiles are first retrieved from the satellite radiances and the thermal winds are then obtained from the horizontal gradients of the retrieved temperatures; and 2) a linear regression between observed radiance gradients and observed wind shears. The latter method serves as an estimate of the upper limit of accuracy to be obtained by any method based on a linear combination of radiance gradients.The results indicate that the direct methods may be divided into two groups, with much better retrievals for one of these groups. The probable reasons for these differences are identified. The best direct methods yield results comparable to the traditional method. In comparison with ground truth none of the methods is particularly skillful. The lack of skill in these particular cases is attributed mainly to the modest wind shears contained in the sample. Errors associated with trying to measure relatively small horizontal radiance gradients over relatively small horizontal distances result in residual uncertainty nearly as large as the variance of the sample. it is suggested that much better results would be obtained if some of the better methods were to be applied over greater horizontal distances or to regions with larger wind shears.

Ohring, George; Neeman, Binyamin; Duncan, Louis D.

1981-11-01

141

Direct observation of Anderson localization of matter-waves in an optical disorder  

NASA Astrophysics Data System (ADS)

In 1958, P.W. Anderson predicted the localization^1 of electronic wave functions in disordered crystals, and the resulting absence of diffusion. It has been realized later that Anderson Localization is ubiquitous in wave physics^2, and this has prompted an intense activity to observe it with light, microwaves, sound waves, and electron gases, but to our knowledge there was no direct observation of exponential spatial localization of matter-waves (electrons or others). We have observed directly^3 exponential localization of the wave function of ultracold atoms released into a one-dimensional waveguide in the presence of a controlled disorder created by laser speckle. We will present this work, and the prospects of extending that experimental scheme to quantum gases in higher dimensions (2D and 3D), and with controlled interactions. We will also discuss its significance in the rapidly growing field of quantum simulators. 1 Anderson, P.W. Absence of diffusion in certain random lattices. Phys. Rev. 109, 1492-1505 (1958). 2 Van Tiggelen, B. Anderson localization of waves. In Wave diffusion in complex media 1998, edited by J.P. Fouque, Les Houches Lectures (Kluwer, Dordrecht, 1999). 3 Juliette Billy, Vincent Josse, Zhanchun Zuo, Alain Bernard, Ben Hambrecht, Pierre Lugan, David Cl'ement, Laurent Sanchez-Palencia, Philippe Bouyer^ & Alain Aspect. Direct observation of Anderson localization of matter-waves in a controlled disorder Nature, 453, 891 (2008). Work published back to back with a related work in the Inguscio's group in Florence: G. Roati et al., Nature, 453, 895 (2008).

Aspect, Alain

2009-03-01

142

Observations of black carbon induced semi direct effect over Northeast India  

NASA Astrophysics Data System (ADS)

This article reports observational evidence of Black Carbon (BC) induced cloud burning effect (Semi direct effect) for the first time over a mountainous location in North east India. Simultaneous aircraft observations of Black Carbon (BC) mass concentrations and cloud microphysical parameters were carried out over Guwahati, in Northeast India during Cloud Aerosol Interactions and Precipitation Enhancement Experiment (CAIPEEX) Phase-I in 2009. Elevated pollution layers of BC (concentration exceeding 1 ?g m-3) were observed over the site up to 7 km on different experimental days (August 30, September 4 and 6 in 2009) in the cloud regime. The vertical heating rate and radiative forcing induced by elevated BC layers in the cloud regime were estimated using an optical model along with a radiative transfer model. The instantaneous vertical heating rate induced by BC in cloud layers is found to be as high as 2.65 K/day. The instantaneous vertical heating by BC is found to be inducing a significant reduction in the measured cloud liquid water content (LWC) over the site. Subsequently, the BC stimulated heating has been found to be reducing the cloud fraction (CFR) and thus inducing a “cloud burning effect (Semi direct effect)”, over the region. The estimated instantaneous BC induced radiative forcing in the cloud regime is found to be +12.7-+45.1 W m-2 during the experimental periods. This large warming and reduction in cloudiness can decrease the precipitation over the region. However, more simultaneous BC-cloud observations and further research are necessary to establish a stable “semi-direct effect” over the region.

Panicker, A. S.; Pandithurai, G.; Safai, P. D.; Dipu, S.; Prabha, T. V.; Konwar, M.

2014-12-01

143

Direct observation of keyhole plasma characteristics in deep penetration laser welding of aluminum alloy 6016  

NASA Astrophysics Data System (ADS)

Deep penetration laser welding is associated with violent plasma generation which consists of metal vapour, ionized ions and electrons. The plasma resides both outside and inside the keyhole, known as the plasma plume and keyhole plasma, respectively. Plasma plumes have been studied extensively due to the convenience of observing them. However, very little work has been carried out on the investigation of keyhole plasmas. In this paper, a novel experimental set-up is designed to observe the keyhole plasma directly in CW and PW deep penetration laser welding of aluminum alloy 6016. Then on the basis of the experimentally obtained spectra, the electron temperature distribution of the keyhole plasma both in the radial and depth directions of the keyhole is calculated, and the effects of processing parameters such as laser power, welding velocity and defocus on the keyhole plasma temperature are studied. The results show that the electron temperature of the keyhole plasma both in the radial and depth directions is not uniformly distributed. The temperature increases as the laser power increases, decreases as the welding velocity increases and decreases as the location of the laser beam focal point is moved from within to above the keyhole.

Jin, Xiangzhong; Zeng, Licheng; Cheng, Yuanyong

2012-06-01

144

Capturing the complexity of first opinion small animal consultations using direct observation  

PubMed Central

Various different methods are currently being used to capture data from small animal consultations. The aim of this study was to develop a tool to record detailed data from consultations by direct observation. A second aim was to investigate the complexity of the consultation by examining the number of problems discussed per patient. A data collection tool was developed and used during direct observation of small animal consultations in eight practices. Data were recorded on consultation type, patient signalment and number of problems discussed. During 16?weeks of data collection, 1901 patients were presented. Up to eight problems were discussed for some patients; more problems were discussed during preventive medicine consultations than during first consultations (P<0.001) or revisits (P<0.001). Fewer problems were discussed for rabbits than cats (P<0.001) or dogs (P<0.001). Age was positively correlated with discussion of specific health problems and negatively correlated with discussion of preventive medicine. Consultations are complex with multiple problems frequently discussed, suggesting comorbidity may be common. Future research utilising practice data should consider how much of this complexity needs to be captured, and use appropriate methods accordingly. The findings here have implications for directing research and education as well as application in veterinary practice. PMID:25262057

Robinson, N. J.; Brennan, M. L.; Cobb, M.; Dean, R. S.

2015-01-01

145

Capturing the complexity of first opinion small animal consultations using direct observation.  

PubMed

Various different methods are currently being used to capture data from small animal consultations. The aim of this study was to develop a tool to record detailed data from consultations by direct observation. A second aim was to investigate the complexity of the consultation by examining the number of problems discussed per patient. A data collection tool was developed and used during direct observation of small animal consultations in eight practices. Data were recorded on consultation type, patient signalment and number of problems discussed. During 16?weeks of data collection, 1901 patients were presented. Up to eight problems were discussed for some patients; more problems were discussed during preventive medicine consultations than during first consultations (P<0.001) or revisits (P<0.001). Fewer problems were discussed for rabbits than cats (P<0.001) or dogs (P<0.001). Age was positively correlated with discussion of specific health problems and negatively correlated with discussion of preventive medicine. Consultations are complex with multiple problems frequently discussed, suggesting comorbidity may be common. Future research utilising practice data should consider how much of this complexity needs to be captured, and use appropriate methods accordingly. The findings here have implications for directing research and education as well as application in veterinary practice. PMID:25262057

Robinson, N J; Brennan, M L; Cobb, M; Dean, R S

2014-09-26

146

Video Allows Young Scientists New Ways to Be Seen  

ERIC Educational Resources Information Center

Science is frequently a visual endeavor, dependent on direct or indirect observations. Teachers have long employed motion pictures in the science classroom to allow students to make indirect observations, but the capabilities of digital video offer opportunities to engage students in active science learning. Not only can watching a digital video…

Park, John C.

2009-01-01

147

Direct observation of aggregative nanoparticle growth: kinetic modeling of the size distribution and growth rate.  

PubMed

Direct observations of solution-phase nanoparticle growth using in situ liquid transmission electron microscopy (TEM) have demonstrated the importance of "non-classical" growth mechanisms, such as aggregation and coalescence, on the growth and final morphology of nanocrystals at the atomic and single nanoparticle scales. To date, groups have quantitatively interpreted the mean growth rate of nanoparticles in terms of the Lifshitz-Slyozov-Wagner (LSW) model for Ostwald ripening, but less attention has been paid to modeling the corresponding particle size distribution. Here we use in situ fluid stage scanning TEM to demonstrate that silver nanoparticles grow by a length-scale dependent mechanism, where individual nanoparticles grow by monomer attachment but ensemble-scale growth is dominated by aggregation. Although our observed mean nanoparticle growth rate is consistent with the LSW model, we show that the corresponding particle size distribution is broader and more symmetric than predicted by LSW. Following direct observations of aggregation, we interpret the ensemble-scale growth using Smoluchowski kinetics and demonstrate that the Smoluchowski model quantitatively captures the mean growth rate and particle size distribution. PMID:24325680

Woehl, Taylor J; Park, Chiwoo; Evans, James E; Arslan, Ilke; Ristenpart, William D; Browning, Nigel D

2014-01-01

148

Direct observations of microscale turbulence and thermohaline structure in the Kuroshio Front  

NASA Astrophysics Data System (ADS)

Direct observations of microstructure near the Kuroshio Front were conducted in August 2008 and October 2009. These show negative potential vorticity (PV) in the mixed layer south of the front, where directly measured turbulent kinetic energy dissipation rates are an order magnitude larger than predicted by wind-scaling. These elevated dissipation rates scale better with an empirical scaling, which considers local wind and Ekman buoyancy flux driven by downfront wind. Near-zero PV in the thermocline under the Kuroshio mainstream is observed at 200-300 m depth, with dissipation exceeding open ocean thermocline values by factors of 10-100. Overall, the large turbulent dissipation rates measured in the Kuroshio can be categorized into two groups, one characterized by low Richardson number along the Kuroshio Front thermocline, and the other characterized by high stratification away from the Kuroshio mainstream. The former is attributed to mixing by unbalanced frontal ageostrophic flows, and the latter is attributed to internal wave breaking. On average, both groups appear in regions of large horizontal density gradients. Observed thermohaline structure shows low salinity tongues from the surface to over 300 m depth and deep cold tongues, extending upward from 500 to 100 m depth in a narrow (20 km) zone, suggesting down and upwelling driven by geostrophic straining, which is confirmed by Quasigeostrophic-Omega equation solutions. This implies that adiabatic along isopycnal subduction and diabatic diapycnal turbulent mixing acting in tandem at the Kuroshio Front likely contribute to NPIW formation.

Nagai, Takeyoshi; Tandon, Amit; Yamazaki, Hidekatsu; Doubell, Mark J.; Gallager, Scott

149

Direct observation of a highly spin-polarized organic spinterface at room temperature  

PubMed Central

Organic semiconductors constitute promising candidates toward large-scale electronic circuits that are entirely spintronics-driven. Toward this goal, tunneling magnetoresistance values above 300% at low temperature suggested the presence of highly spin-polarized device interfaces. However, such spinterfaces have not been observed directly, let alone at room temperature. Thanks to experiments and theory on the model spinterface between phthalocyanine molecules and a Co single crystal surface, we clearly evidence a highly efficient spinterface. Spin-polarised direct and inverse photoemission experiments reveal a high degree of spin polarisation at room temperature at this interface. We measured a magnetic moment on the molecule's nitrogen ? orbitals, which substantiates an ab-initio theoretical description of highly spin-polarised charge conduction across the interface due to differing spinterface formation mechanisms in each spin channel. We propose, through this example, a recipe to engineer simple organic-inorganic interfaces with remarkable spintronic properties that can endure well above room temperature. PMID:23412079

Djeghloul, F.; Ibrahim, F.; Cantoni, M.; Bowen, M.; Joly, L.; Boukari, S.; Ohresser, P.; Bertran, F.; Le Fèvre, P.; Thakur, P.; Scheurer, F.; Miyamachi, T.; Mattana, R.; Seneor, P.; Jaafar, A.; Rinaldi, C.; Javaid, S.; Arabski, J.; Kappler, J. -P; Wulfhekel, W.; Brookes, N. B.; Bertacco, R.; Taleb-Ibrahimi, A.; Alouani, M.; Beaurepaire, E.; Weber, W.

2013-01-01

150

Statistical study of muons counts rates in differents directions, observed at the Brazilian Southern Space Observatory  

NASA Astrophysics Data System (ADS)

Cosmic ray are charged particles, at the most time protons, that reach the earth's magne-tosphere from interplanetary space with velocities greater than the solar wind. When these impinge the atmosphere, they interact with atmosphere constituents and decay into sub-particles forming an atmospheric shower. The muons are the sub-particles which normally maintain the originated direction of the primary cosmic ray. A multi-directional muon detec-tor (MMD) was installed in 2001 and upgraded in 2005, through an international cooperation between Brazil, Japan and USA, and operated since then at the Southern Space Observatory -SSO/CRS/CCR/INPE -MCT, (29,4° S, 53,8° W, 480m a.s.l.), São Martinho da Serra, RS, a Brazil. The main objetive of this work is to present a statistical analysis of the intensity of muons, with energy between 50 and 170 GeV, in differents directions, measured by the SSO's multi-directional muon detector. The analysis was performed with data from 2006 and 2007 collected by the SSO's MMD. The MMD consists of two layers of 4x7 detectors with a total observation area of 28 m2 . The counting of muons in each directional channel is made by a coincidence of pulses pair, one from a detector in the upper layer and the other from a detector in the lower layer. The SSO's MMD is equipped with 119 directional channels for muon count rate measurement and is capable of detecting muons incident with zenithal angle between 0° and 75,53° . A statistical analysis was made with the MMD muon count rate for all the di-rectional channels. The average and the standard deviation of the muon count rate in each directional component were calculated. The results show lower cont rate for the channels with larger zenith, and higher cont rate with smaller zenith, as expected from the production and propagation of muons in the atmosphere. It is also possible to identify the Stormer cone. The SSO's MMD is also a detector component of the Global Muon Detector Network (GMDN), which has been developed in an international collaboration lead by Shinshu University, Japan.

Grams, Guilherme; Schuch, Nelson Jorge; Braga, Carlos Roberto; Purushottam Kane, Rajaram; Echer, Ezequiel; Ronan Coelho Stekel, Tardelli

151

International Journal of Applied Earth Observation and Geoinformation 33 (2014) 4756 Contents lists available at ScienceDirect  

E-print Network

International Journal of Applied Earth Observation and Geoinformation 33 (2014) 47­56 Contents lists available at ScienceDirect International Journal of Applied Earth Observation and Geoinformation May 2014 Keywords: Hyperspectral remote sensing Coastal wetlands Soil properties Particulate organic

Lajeunesse, Marc J.

152

In Situ Observation of Directed Nanoparticle Aggregation During the Synthesis of Ordered Nanoporous Metal in Soft Templates  

SciTech Connect

The prevalent approach to developing new nanomaterials is a trial-and-error process of iteratively altering synthesis procedures and then characterizing the resulting nanostructures. This is fundamentally limited in that the growth processes that occur during synthesis can be inferred only from the final synthetic structure. Directly observing real-time nanomaterial growth provides unprecedented insight into the relationship between synthesis conditions and product evolution and facilitates a mechanistic approach to nanomaterial development. Here, we use in situ liquid-stage scanning transmission electron microscopy to observe the growth of mesoporous palladium in a solvated block copolymer (BCP) template under various synthesis conditions, and we ultimately determined a refined synthesis procedure that yields extended structures with ordered pores. We found that after sufficient drying time of the casting solvent (tetrahydrofuran, THF), the BCP assembles into a rigid, cylindrical micelle array with a high degree of short-range order but poor long-range order. Upon slowing the THF evaporation rate using a solvent-vapor anneal step, the long-range order was greatly improved. The electron beam induces nucleation of small particles in the aqueous phase around the micelles. The small particles then flocculate and grow into denser structures that surround, but do not overgrow, the micelles, forming an ordered mesoporous structure. The microscope observations revealed that pore disorder can be addressed prior to metal reduction and is not invariably induced by the Pd growth process itself, allowing for more rapid optimization of the synthetic method.

Parent, Lucas R.; Robinson, David B.; Cappillino, Patrick J.; Hartnett, Ryan J.; Abellan, Patricia; Evans, James E.; Browning, Nigel D.; Arslan, Ilke

2014-01-17

153

Direct Observation of Coherent Oscillations in Solution due to Microheterogeneous Environment  

PubMed Central

We report, for the first time, direct observation of coherent oscillations in the ground-state of IR775 dye due to microheterogeneous environment. Using ultrafast near-infrared degenerate pump-probe technique centered at 800?nm, we present the dynamics of IR775 in a binary mixture of methanol and chloroform at ultra-short time resolution of 30?fs. The dynamics of the dye in binary mixtures, in a time-scale of a few fs to ~740?ps, strongly varies as a function of solvent composition (volume fraction). Multi-oscillation behavior of the coherent vibration was observed, which increased with decreasing percentage of methanol in the dye mixture. Maximum number of damped oscillations were observed in 20% methanol. The observed vibrational wavepacket motion in the ground-state is periodic in nature. We needed two cosine functions to fit the coherent oscillation data as two different solvents were used. Dynamics of the dye molecule in binary mixtures can be explained by wavepacket motion in the ground potential energy surface. More is the confinement of the dye molecule in binary mixtures, more is the number of damped oscillations. The vibrational cooling time, ?2, increases with increase in the confinement of the system. The observed wavepacket oscillations in ground-state dynamics continued until 1.6?ps. PMID:25130204

Das, Dipak Kumar; Makhal, Krishnandu; Bandyopadhyay, Soumendra Nath; Goswami, Debabrata

2014-01-01

154

A flexible reporter system for direct observation and isolation of cancer stem cells.  

PubMed

Many tumors are hierarchically organized with a minority cell population that has stem-like properties and enhanced ability to initiate tumorigenesis and drive therapeutic relapse. These cancer stem cells (CSCs) are typically identified by complex combinations of cell-surface markers that differ among tumor types. Here, we developed a flexible lentiviral-based reporter system that allows direct visualization of CSCs based on functional properties. The reporter responds to the core stem cell transcription factors OCT4 and SOX2, with further selectivity and kinetic resolution coming from use of a proteasome-targeting degron. Cancer cells marked by this reporter have the expected properties of self-renewal, generation of heterogeneous offspring, high tumor- and metastasis-initiating activity, and resistance to chemotherapeutics. With this approach, the spatial distribution of CSCs can be assessed in settings that retain microenvironmental and structural cues, and CSC plasticity and response to therapeutics can be monitored in real time. PMID:25497455

Tang, Binwu; Raviv, Asaf; Esposito, Dominic; Flanders, Kathleen C; Daniel, Catherine; Nghiem, Bao Tram; Garfield, Susan; Lim, Langston; Mannan, Poonam; Robles, Ana I; Smith, William I; Zimmerberg, Joshua; Ravin, Rea; Wakefield, Lalage M

2015-01-13

155

A Flexible Reporter System for Direct Observation and Isolation of Cancer Stem Cells  

PubMed Central

Summary Many tumors are hierarchically organized with a minority cell population that has stem-like properties and enhanced ability to initiate tumorigenesis and drive therapeutic relapse. These cancer stem cells (CSCs) are typically identified by complex combinations of cell-surface markers that differ among tumor types. Here, we developed a flexible lentiviral-based reporter system that allows direct visualization of CSCs based on functional properties. The reporter responds to the core stem cell transcription factors OCT4 and SOX2, with further selectivity and kinetic resolution coming from use of a proteasome-targeting degron. Cancer cells marked by this reporter have the expected properties of self-renewal, generation of heterogeneous offspring, high tumor- and metastasis-initiating activity, and resistance to chemotherapeutics. With this approach, the spatial distribution of CSCs can be assessed in settings that retain microenvironmental and structural cues, and CSC plasticity and response to therapeutics can be monitored in real time. PMID:25497455

Tang, Binwu; Raviv, Asaf; Esposito, Dominic; Flanders, Kathleen C.; Daniel, Catherine; Nghiem, Bao Tram; Garfield, Susan; Lim, Langston; Mannan, Poonam; Robles, Ana I.; Smith, William I.; Zimmerberg, Joshua; Ravin, Rea; Wakefield, Lalage M.

2014-01-01

156

Direct observation of domain wall evolution at a bifurcation in magnetic network structures  

NASA Astrophysics Data System (ADS)

We report on the magnetization dynamics at a bifurcation in a dual-branch magnetic network structure. When a transverse domain wall (DW) propagates through the network, interaction with an edge defect at the bifurcation leads to the transformation of the DW from transverse to vortex. The topological charge is conserved as the DW moves through the bifurcation, and this charge conservation is intrinsically linked to a ?1/2 topological defect in the system. Magnetic force microscopy (MFM) imaging enables the direct observation of defect displacement during DW transformation, which induces a selective switching in the branch of the network structure.

Murapaka, Chandrasekhar; Sethi, Pankaj; Goolaup, Sarjoosing; Maddu, Ramu; Chen, Yunjie; Leong, Siang Huei; Siang Lew, Wen

2014-11-01

157

Direct Reconstruction of dynamical dark energy from observational Hubble Parameter data  

E-print Network

Reconstructing the evolution history of the equation of state parameter $w(z)$ directly from observational data is highly valuable in cosmology, since it holds substantial clues in understanding the origin of the accelerated expansion of the Universe. Contrast to a wealth of works on reconstructing $w(z)$ from supernova data, few work pay attention to Hubble parameter data. We analyze the merit of Hubble parameter data and make an attempt on reconstructing $w(z)$ from them, using the PCA approach introduced. We find that current Hubble parameter data does well in reconstructing w(z), though compared to supernova data, they are scant and their quality is much poor.

Liu, Zhi-E; Zhang, Tong-Jie; Wang, Bao-Quan; Bi, Shao-Lan

2015-01-01

158

Direct Observation of Resonant Scattering Phase Shifts and Their Energy Dependence  

NASA Astrophysics Data System (ADS)

We scan the collision energy of two clouds of cesium atoms between 12 and 50?K in an atomic fountain clock. By directly detecting the difference of s-wave scattering phase shifts, we observe a rapid variation of a scattering phase shift through a series of Feshbach resonances. At the energies we use, resonances that overlap at threshold become resolved. Our statistical phase uncertainty of 8 mrad can be improved in future precision measurements of Feshbach resonances to accurately determine the Cs-Cs interactions, which may provide stringent limits on the time variation of fundamental constants.

Gensemer, Stephen D.; Martin-Wells, Ross B.; Bennett, Aaron W.; Gibble, Kurt

2012-12-01

159

Directly observed interaction within adolescent romantic relationships: What have we learned?  

PubMed Central

Review and conceptual analysis of the papers in this special issue calls attention to several important methodological and conceptual issues surrounding the direct observation of adolescent romantic couples. It also provides an important new foundation of knowledge about the nature of adolescents' romantic relationships. Connections with previous family relationships, new understandings of the distinctive nature of adolescent romantic relationships, and gender issues are clarified by this body of papers. Together, these papers move the scholarly field forward and generate new lines of questions for future investigators. PMID:18986697

Welsh, Deborah P; Shulman, Shmuel

2008-01-01

160

Direct Observation of Magnetochiral Effects through a Single Metamolecule in Microwave Regions.  

PubMed

We report direct observation of magnetochiral (MCh) effects for the X-band microwaves through a single metamolecule consisting of a copper chiral structure and ferrite rod. A fictitious interaction between chirality and magnetism is realized in the metamolecule without intrinsic electronic interactions. The MCh effects are induced at the resonant optical activities by applying a weak dc magnetic field of 1 mT, and are increased with the magnetic field. The nonreciprocal differences in refractive indices are evaluated to be 10^{-3} at 200 mT. PMID:25526133

Tomita, Satoshi; Sawada, Kei; Porokhnyuk, Andrey; Ueda, Tetsuya

2014-12-01

161

Direct observation of Oersted-field-induced magnetization dynamics in magnetic nanostripes  

SciTech Connect

We have used time-resolved x-ray photoemission electron microscopy to investigate the magnetization dynamics induced by nanosecond current pulses in NiFe/Cu/Co nanostripes. A large tilt of the NiFe magnetization in the direction transverse to the stripe is observed during the pulses. We show that this effect cannot be quantitatively understood from the amplitude of the Oersted field and the shape anisotropy. High-frequency oscillations observed at the onset of the pulses are attributed to precessional motion of the NiFe magnetization about the effective field. We discuss the possible origins of the large magnetization tilt and the potential implications of the static and dynamic effects of the Oersted field on current-induced domain-wall motion in such stripes.

Uhlir, V. [Institut Neel, Centre national de la recherche scientifique and Universite Joseph Fourier, BP166, F-38042 Grenoble (France); Institute of Physical Engineering, Brno University of Technology, CZ-61669 Brno (Czech Republic); Pizzini, S.; Rougemaille, N.; Ranno, L.; Fruchart, O.; Wagner, E.; Vogel, J. [Institut Neel, Centre national de la recherche scientifique and Universite Joseph Fourier, BP166, F-38042 Grenoble (France); Cros, V. [Unite Mixte de Physique CNRS-Thales, Route departementale 128, F-91767 Palaiseau Cedex (France); Jimenez, E.; Camarero, J. [Departamento Fisica de la Materia Condensada, Instituto ''Nicolas Cabrera'' and Instituto Madrileno de Estudios Avanzados-Nanociencia, Campus Universidad Autonoma de Madrid, E-28049 Madrid (Spain); Urbanek, M. [Institute of Physical Engineering, Brno University of Technology, CZ-61669 Brno (Czech Republic); Gaudin, G. [SPINTEC, UMR8191 CEA/CNRS/UJF/Grenoble INP, INAC, F-38045 Grenoble (France); Tieg, C. [European Synchrotron Radiation Facility, BP200, F-38043 Grenoble (France); Sirotti, F. [Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, F-91192 Gif-sur-Yvette (France)

2011-01-15

162

Direct experimental observation of stacking fault scattering in highly oriented pyrolytic graphite meso-structures.  

PubMed

Stacking fault defects are thought to be the root cause for many of the anomalous transport phenomena seen in high-quality graphite samples. In stark contrast to their importance, direct observation of stacking faults by diffractive techniques has remained elusive due to fundamental experimental difficulties. Here we show that the stacking fault density and resistance can be measured by analyzing the non-Gaussian scatter observed in the c-axis resistivity of mesoscopic graphite structures. We also show that the deviation from Ohmic conduction seen at high electrical field strength can be fit to a thermally activated transport model, which accurately reproduces the stacking fault density inferred from the statistical analysis. From our measurements, we conclude that the c-axis resistivity is entirely determined by the stacking fault resistance, which is orders of magnitude larger than the inter-layer resistance expected from a Drude model. PMID:25510583

Koren, E; Knoll, A W; Lörtscher, E; Duerig, U

2014-01-01

163

Direct Observation of the Opening and Closing of Inelastic Scattering Channels  

NASA Astrophysics Data System (ADS)

We observe the abrupt changes of scattering phase shifts as a function of collision energy and magnetic field. Scattering atoms form a multi-channel system, where a distinction can be made between energetically open and closed channels. When the collision energy increases, inelastic collision channels open, yielding an abrupt change in the scattering phase shift at the threshold. We directly observe the difference of s-wave scattering phase shifts in our juggling cesium fountain clock by detecting only the scattered part of the atomic wavefunctions ootnotetextR. A. Hart, X. Xu, R. Legere, & K. Gibble, Nature 446, 892-895 (2007).. Here, we study the scattering of the cesium clock states scattering off of cesium atoms prepared in F=3,mF.

Gensemer, S. D.; Martin, R. B.; Gibble, K.; Kokkelmans, S. J. J. M. F.

2008-05-01

164

Direct observation of frictional contacts: New insights for state-dependent properties  

USGS Publications Warehouse

Rocks and many other materials display a rather complicated, but characteristic, dependence of friction on sliding history. These effects are well-described by empirical rate- and state-dependent constitutive formulations which have been utilized for analysis of fault slip and earthquake processes. We present a procedure for direct quantitative microscopic observation of frictional contacts during slip. The observations reveal that frictional state dependence represents an increase of contact area with contact age. Transient changes of sliding resistance correlate with changes in contact area and arise from shifts of contact population age. Displacement-dependent replacement of contact populations is shown to cause the diagnostic evolution of friction over a characteristic sliding distance that occurs whenever slip begins or sliding conditions change. ?? 1994 Birkha??user Verlag.

Dieterich, J.H.; Kilgore, B.D.

1994-01-01

165

Direct observation of nonlinear acoustoelastic hysteresis in kinking nonlinear elastic solids  

NASA Astrophysics Data System (ADS)

Herein we report on direct experimental observation of nonlinear hysteretic ultrasonic wave transmission through the kinking nonlinear elastic solids Ti3SiC2 and Ti3AlC2 under bias-stress loading. We observed two characteristic regimes; up to strain ?2×10-4, the ultrasound attenuation increased strongly and linearly with strain. At higher strains, the attenuation was fully reversible and hysteretic as the compressive stresses were cycled. This hysteretic behavior was attributed to interaction of the acoustic waves with dislocations in the incipient kink bands, the micromechanism believed to be responsible for the concomitant hysteretic stress-strain loops. The relevance of these findings to possible sensor applications is briefly discussed.

Finkel, P.; Zhou, A. G.; Basu, S.; Yeheskel, O.; Barsoum, M. W.

2009-06-01

166

Direct observation of temporal coherence by weak projective measurements of photon arrival time  

NASA Astrophysics Data System (ADS)

We show that a weak projective measurement of photon arrival time can be realized by controllable two-photon interferences with photons from short-time reference pulses at a polarization beam splitter. The weak value of the projector on the arrival time defined by the reference pulse can be obtained from the coincidence rates conditioned by a specific output measurement. If the weak measurement is followed by a measurement of frequency, the coincidence counts reveal the complete temporal coherence of the single-photon wave function. Significantly, the weak values of the input state can also be obtained at higher measurement strengths, so that correlations between weak measurements on separate photons can be observed and evaluated without difficulty. The method can thus be used to directly observe the nonclassical statistics of time-energy entangled photons.

Hofmann, Holger F.; Ren, Changliang

2013-06-01

167

Direct observation of Dirac cones and a flatband in a honeycomb lattice for polaritons.  

PubMed

Two-dimensional lattices of coupled micropillars etched in a planar semiconductor microcavity offer a workbench to engineer the band structure of polaritons. We report experimental studies of honeycomb lattices where the polariton low-energy dispersion is analogous to that of electrons in graphene. Using energy-resolved photoluminescence, we directly observe Dirac cones, around which the dynamics of polaritons is described by the Dirac equation for massless particles. At higher energies, we observe p orbital bands, one of them with the nondispersive character of a flatband. The realization of this structure which holds massless, massive, and infinitely massive particles opens the route towards studies of the interplay of dispersion, interactions, and frustration in a novel and controlled environment. PMID:24702392

Jacqmin, T; Carusotto, I; Sagnes, I; Abbarchi, M; Solnyshkov, D D; Malpuech, G; Galopin, E; Lemaître, A; Bloch, J; Amo, A

2014-03-21

168

Direct experimental observation of stacking fault scattering in highly oriented pyrolytic graphite meso-structures  

NASA Astrophysics Data System (ADS)

Stacking fault defects are thought to be the root cause for many of the anomalous transport phenomena seen in high-quality graphite samples. In stark contrast to their importance, direct observation of stacking faults by diffractive techniques has remained elusive due to fundamental experimental difficulties. Here we show that the stacking fault density and resistance can be measured by analyzing the non-Gaussian scatter observed in the c-axis resistivity of mesoscopic graphite structures. We also show that the deviation from Ohmic conduction seen at high electrical field strength can be fit to a thermally activated transport model, which accurately reproduces the stacking fault density inferred from the statistical analysis. From our measurements, we conclude that the c-axis resistivity is entirely determined by the stacking fault resistance, which is orders of magnitude larger than the inter-layer resistance expected from a Drude model.

Koren, E.; Knoll, A. W.; Lörtscher, E.; Duerig, U.

2014-12-01

169

Direct observations of aluminosilicate weathering in the hyporheic zone of an Antarctic Dry Valley stream  

NASA Astrophysics Data System (ADS)

This study focused on chemical weathering and bacterial ecology in the hyporheic zone of Green Creek, a McMurdo Dry Valley (Antarctica) stream. An in situ microcosm approach was used to observe dissolution features on the basal-plane surface of muscovite mica. Four mica chips were buried in December 1999 and dug up 39 d later. Atomic force microscopy (AFM) of the basal-plane surfaces revealed small, anhedral ˜10-Å-deep etch pits covering ˜4% of the surfaces, from which an approximate basal-plane dissolution rate of 8.3 × 10 -18 mol muscovite cm -2 s -1 was calculated (on the basis of the geometric surface area) for the study period. This is an integrated initial dissolution rate on a fresh surface exposed for a relatively brief period over the austral summer and should not be compared directly to other long-term field rates. The observation of weathering features on mica agrees with previous stream- and watershed-scale studies in the Dry Valleys, which have demonstrated that weathering occurs where liquid water is present, despite the cold temperatures. AFM imaging of mica surfaces revealed biofilms including numerous small (<1 ?m long), rounded, oblong bacteria. The AFM observations agreed well with X-ray photoelectron microscopy results showing increased organic C and N. Bacteriologic analysis of the hyporheic zone sediments also revealed <1-?m-long bacteria. ?-Proteobacteria were observed, consistent with the oligotrophic conditions of the hyporheic zone. Nitrate-reducing bacteria were found, in agreement with a previous tracer test at Green Creek that suggested nitrate reduction occurs in the hyporheic zone. The results of this study thus provide direct evidence of dynamic geochemical and microbial processes in the hyporheic zone of a Dry Valley stream despite the extreme conditions; such processes were inferred previously from stream-scale hydrogeochemical studies.

Maurice, Patricia A.; McKnight, Diane M.; Leff, Laura; Fulghum, Julia E.; Gooseff, Michael

2002-04-01

170

IMF Direction Derived from Cycloid-Like Ion Distributions Observed by Mars Express  

NASA Astrophysics Data System (ADS)

Although the Mars Express (MEX) does not carry a magnetometer, it is in principle possible to derive the interplanetary magnetic field (IMF) orientation from the three dimensional velocity distribution of pick-up ions measured by the Ion Mass Analyser (IMA) on board MEX because pick-up ions' orbits, in velocity phase space, are expected to gyrate around the IMF when the IMF is relatively uniform on a scale larger than the proton gyroradius. During bow shock outbound crossings, MEX often observed cycloid distributions (two dimensional partial ring distributions in velocity phase space) of protons in a narrow channel of the IMA detector (only one azimuth for many polar angles). We show two such examples. Three different methods are used to derive the IMF orientation from the observed cycloid distributions. One method is intuitive (intuitive method), while the others derive the minimum variance direction of the velocity vectors for the observed ring ions. These velocity vectors are selected either manually (manual method) or automatically using simple filters (automatic method). While the intuitive method and the manual method provide similar IMF orientations by which the observed cycloid distribution is well arranged into a partial circle (representing gyration) and constant parallel velocity, the automatic method failed to arrange the data to the degree of the manual method, yielding about a 30° offset in the estimated IMF direction. The uncertainty of the derived IMF orientation is strongly affected by the instrument resolution. The source population for these ring distributions is most likely newly ionized hydrogen atoms, which are picked up by the solar wind.

Yamauchi, M.; Futaana, Y.; Fedorov, A.; Dubinin, E.; Lundin, R.; Sauvaud, J.-A.; Winningham, D.; Frahm, R.; Barabash, S.; Holmstrom, M.; Woch, J.; Fraenz, M.; Budnik, E.; Borg, H.; Sharber, J. R.; Coates, A. J.; Soobiah, Y.; Koskinen, H.; Kallio, E.; Asamura, K.; Hayakawa, H.; Curtis, C.; Hsieh, K. C.; Sandel, B. R.; Grande, M.; Grigoriev, A.; Wurz, P.; Orsini, S.; Brandt, P.; McKenna-Lawler, S.; Kozyra, J.; Luhmann, J.

2006-10-01

171

IMF Direction Derived from Cycloid-Like Ion Distributions Observed by Mars Express  

NASA Astrophysics Data System (ADS)

Although the Mars Express (MEX) does not carry a magnetometer, it is in principle possible to derive the interplanetary magnetic field (IMF) orientation from the three dimensional velocity distribution of pick-up ions measured by the Ion Mass Analyser (IMA) on board MEX because pick-up ions' orbits, in velocity phase space, are expected to gyrate around the IMF when the IMF is relatively uniform on a scale larger than the proton gyroradius. Upstream of bow shock, MEX often observed cycloid distributions (two dimensional partial ring distributions in velocity phase space) of protons in a narrow channel of the IMA detector (only one azimuth for many polar angles). We show two such examples. Three different methods are used to derive the IMF orientation from the observed cycloid distributions. One method is intuitive (intuitive method), while the others derive the minimum variance direction of the velocity vectors for the observed ring ions. These velocity vectors are selected either manually (manual method) or automatically using simple filters (automatic method). While the intuitive method and the manual method provide similar IMF orientations by which the observed cycloid distribution is well arranged into a partial circle (representing gyration) and constant parallel velocity, the automatic method failed to arrange the data to the degree of the manual method, yielding about a 30° offset in the estimated IMF direction. The uncertainty of the derived IMF orientation is strongly affected by the instrument resolution. The source population for these ring distributions is most likely newly ionized hydrogen atoms, which are picked up by the solar wind.

Yamauchi, M.; Futaana, Y.; Fedorov, A.; Dubinin, E.; Lundin, R.; Sauvaud, J.-A.; Winningham, D.; Frahm, R.; Barabash, S.; Holmstrom, M.; Woch, J.; Fraenz, M.; Budnik, E.; Borg, H.; Sharber, J. R.; Coates, A. J.; Soobiah, Y.; Koskinen, H.; Kallio, E.; Asamura, K.; Hayakawa, H.; Curtis, C.; Hsieh, K. C.; Sandel, B. R.; Grande, M.; Grigoriev, A.; Wurz, P.; Orsini, S.; Brandt, P.; McKenna-Lawler, S.; Kozyra, J.; Luhmann, J.

172

Direct observation of the mechanochemical coupling in myosin-V during processive movement  

PubMed Central

Myosin-Va transports intracellular cargos along actin filaments in cells1. This processive two-headed motor takes multiple 36-nm steps in which the two heads swing forward alternately towards the barbed end of actin driven by ATP hydrolysis2. The ability of myosin-Va to move processively is a function of its long lever arm, the high duty ratio of its kinetic cycle and the gating of the kinetics between the two heads such that ADP release from the lead head is greatly retarded3-10. Mechanical studies at the multiple and single molecule level suggest that there is tight coupling (i.e. one ATP is hydrolyzed per power stroke), but this has not been directly demonstrated4,5,11. We therefore investigated the coordination between the ATPase mechanism of the two heads of myosin-Va and directly visualized the binding and dissociation of single fluorescently-labelled nucleotide molecules while simultaneously observing the stepping motion of the fluorescently labelled myosin-V as it moves along an actin filament. Here we show that preferential ADP dissociation from the trail head of myosin Va is followed by ATP binding and a synchronous 36-nm step. Even at low ATP concentrations, the myosin-V molecule retains at least one nucleotide (ADP in the lead head position) while moving. Thus we directly demonstrate tight coupling between myosin Va movement and the binding and dissociation of nucleotide by simultaneously imaging with nanometer precision. PMID:18668042

Sakamoto, Takeshi; Webb, Martin R.; Forgacs, Eva; White, Howard D.; Sellers, James R.

2009-01-01

173

Direct radiative forcing of anthropogenic aerosols over oceans from satellite observations  

NASA Astrophysics Data System (ADS)

Anthropogenic aerosols play an important role in the atmospheric energy balance. Anthropogenic aerosol optical depth (AOD) and its accompanying shortwave radiative forcing (RF) are usually simulated by numerical models. Recently, with the development of space-borne instruments and sophisticated retrieval algorithms, it has become possible to estimate aerosol radiative forcing based on satellite observations. In this study, we have estimated shortwave direct radiative forcing due to anthropogenic aerosols over oceans in all-sky conditions by combining clouds and the Single Scanner Footprint data of the Clouds and Earth's Radiant Energy System (CERES/SSF) experiment, which provide measurements of upward shortwave fluxes at the top of atmosphere, with Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol and cloud products. We found that globally averaged aerosol radiative forcing over oceans in the clear-sky conditions and all-sky conditions were -1.03±0.48 W m-2 and -0.34 ±0.16 W m-2, respectively. Direct radiative forcing by anthropogenic aerosols shows large regional and seasonal variations. In some regions and in particular seasons, the magnitude of direct forcing by anthropogenic aerosols can be comparable to the forcing of greenhouse gases. However, it shows that aerosols caused the cooling effect, rather than warming effect from global scale, which is different from greenhouse gases.

Chen, Lin; Shi, Guangyu; Qin, Shiguang; Yang, Su; Zhang, Peng

2011-07-01

174

Competing Two-phase Coexistence in Doped Manganites: Direct Observations by in situ Lorentz Electron Microscopy  

SciTech Connect

We examined thin epitaxial films La{sub 5/8-y}Pr{sub y}Ca{sub 3/8}MnO{sub 3} (LPCMO:y=0.275-0.3) in situ by Lorentz transmission electron microscopy (TEM) and other microscopy methods. Clear evidence was obtained for the competing two-phase coexistence of antiferromagnetic charge-ordered (CO) and ferromagnetic (FM) phases that exhibit mesoscale phase separation below the metal-to-insulator transition (MIT) at -164 K. In addition, we observed some regions of mixed CO- and FM-domain contrast attributed earlier to formation of the new CO-FM phase. Using in situ heating/cooling TEM experiments, we interpret this effect as the interfacial wetting phenomenon inherent to the first-order CO-FM phase transition, rather than to the formation of new CO-FM phase. It is evidenced by the partial magnetic melting of CO phase at interfaces with the FM phase, thereby creating charge-disordered spin-glass metastates. For coexisting CO- and FM-domain configurations, we directly refined the relationship between charge-orbital and spin-ordering vectors, consistent with FM moments pinned by (101)-crystal twins in LPCMO films. We also discuss the striking linear dependence observed below MIT for the log-resistance behavior and the CO fraction in LPCMO directly measured by TEM. Such linear dependence does not follow typical percolation equations, suggesting that percolation model needs further revisions for transport description of manganites.

He, J.Q.; Volkov, V.; Asaka, T.; Chaudhuri, S.; Budhani, R.C.; Zhu, Y.

2010-12-01

175

Direct observation of a local thermal vibration anomaly in a quasicrystal.  

PubMed

Quasicrystals have long-range order with symmetries that are incompatible with periodicity, and are often described with reference to a higher-dimensional analogue of a periodic lattice. Within the context of this 'hyperspace' crystallography, lattice dynamics of quasicrystals can be described by a combination of lattice vibrations and atomic fluctuations--phonons and phasons. However, it is difficult to see localized fluctuations in a real-space quasicrystal structure, and so the nature of phason-related fluctuations and their contribution to thermodynamic stability are still not fully understood. Here we use atomic-resolution annular dark-field scanning transmission electron microscopy to map directly the change in thermal diffuse scattering intensity distribution in the quasicrystal, through in situ high-temperature observation of decagonal Al72Ni20Co8. We find that, at 1,100 K, a local anomaly of atomic vibrations becomes significant at specific atomic sites in the structure. The distribution of these localized vibrations is not random but well-correlated, with a quasiperiodic length scale of 2 nm. We are able to explain this feature by an anomalous temperature (Debye-Waller) factor for the Al atoms that sit at the phason-related sites defined within the framework of hyperspace crystallography. The present results therefore provide a direct observation of local thermal vibration anomalies in a solid. PMID:12540895

Abe, Eiji; Pennycook, S J; Tsai, A P

2003-01-23

176

Direct estimation of QBO-related gravity wave drag from satellite observations  

NASA Astrophysics Data System (ADS)

The quasi-biennial oscillation (QBO) of the zonal wind in the tropical stratosphere is an important process in atmospheric dynamics. Effects of the QBO are found also in the mesosphere and in the extra-tropics. The QBO even has influence on the surface weather and climate, for example during winter in the northern hemisphere at midlatitudes. Still, climate models have large difficulties in reproducing a realistic QBO. The QBO is driven by atmospheric waves. Both global scale waves and mesoscale gravity waves (GWs) contribute. It has been proposed that the driving of the QBO by GWs is more important than that of the global scale waves. The relative importance of GWs is however still highly uncertain, and a direct estimation of the QBO driving by GWs from global observations is still missing. We derive GW temperature variances, GW momentum fluxes and GW drag from three years of High Resolution Dynamics Limb Sounder (HIRDLS) and from 11 years of Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite data. These observations are compared with the drag that is still missing in the tropical momentum budget of the ECMWF ERA Interim (ERAI) reanalysis after considering zonal wind tendency, Coriolis force, advection terms and drag of resolved global-scale waves. The meteorological fields of ERAI are quite realistic because ERAI is strongly constrained by data assimilation. Therefore this missing drag can be attributed to GWs not resolved by the model. We find good qualitative agreement between observed GW drag and the missing drag in ERAI. During eastward QBO wind shear even the magnitude of observed and ERAI missing drag are in good agreement. During westward shear, however, observed drag is much lower than the ERAI missing drag. This asymmetry might hint at uncertainties in the advection terms of ERAI. Further, observed GW spectra indicate that QBO-related GW dissipation is mainly due to critical level filtering.

Ern, Manfred; Ploeger, Felix; Preusse, Peter; Kalisch, Silvio; Riese, Martin

2014-05-01

177

Direct in situ observation of synergism between cellulolytic enzymes during the biodegradation of crystalline cellulose fibers.  

PubMed

High-resolution atomic force microscopy (AFM) was used to image the real-time in situ degradation of crystalline by three types of T. reesei cellulolytic enzymes-TrCel6A, TrCel7A, and TrCel7B-and their mixtures. TrCel6A and TrCel7A are exo-acting cellobiohydrolases processing cellulose fibers from the nonreducing and reducing ends, respectively. TrCel7B is an endoglucanase that hydrolyzes amorphous cellulose within fibers. When acting alone on native cellulose fibers, each of the three enzymes is incapable of significant degradation. However, mixtures of two enzymes exhibited synergistic effects. The degradation effects of this synergism depended on the order in which the enzymes were added. Faster hydrolysis rates were observed when TrCel7A (exo) was added to fibers pretreated first with TrCel7B (endo) than when adding the enzymes in the opposite order. Endo-acting TrCel7B removed amorphous cellulose, softened and swelled the fibers, and exposed single microfibrils, facilitating the attack by the exo-acting enzymes. AFM images revealed that exo-acting enzymes processed the TrCel7B-pretreated fibers preferentially from one specific end (reducing or nonreducing). The most efficient (almost 100%) hydrolysis was observed with the mixture of the three enzymes. In this mixture, TrCel7B softened the fiber and TrCel6A and TrCel7A were directly observed to process it from the two opposing ends. This study provides high-resolution direct visualization of the nature of the synergistic relation between T. reesei exo- and endo-acting enzymes digesting native crystalline cellulose. PMID:24195649

Wang, Jingpeng; Quirk, Amanda; Lipkowski, Jacek; Dutcher, John R; Clarke, Anthony J

2013-12-01

178

Evaluation of flow direction methods against field observations of overland flow dispersion  

NASA Astrophysics Data System (ADS)

Despite the broad effort made in grid-based distributed catchment modeling to account for planar overland flow dispersion, actual dispersion experienced by overland flow along a natural slope has not been measured so far, and the ability of terrain analysis methods to reproduce this dispersion has not been evaluated. In the present study, the D8, D8-LTD, D? -LTD, D? , MD? , and MD8 flow direction methods are evaluated against field observations of overland flow dispersion obtained from novel experimental methods. Thin flows of cold (2--10oC) water were released at selected points on a warmer (15--30oC) slope and individual overland flow patterns originating from each of these points were observed using a terrestrial laser scanner and a thermal imaging camera. Prior to each experimental water release, a ScanStation C10 terrestrial laser scanner by Leica Geosystems was used to acquire a point cloud having average density of 25~points/cm2. This point cloud was used to generate alternative grid-based digital elevation models having resolution h ranging from 1~cm to 2~m. During the experiments, an Avio Advanced Thermo TVS-500EX camera by Nippon Avionics was used to monitor land surface temperature with resolution better than 0.05oC. The overland flow patterns were also found to be discernible in terrestrial laser scanner reflectance signal acquired immediately following the flow experiments. Overland flow patterns were determined by considering contrasted temperature and reflectance of the dry and wetted land surface portions. Predicted propagation patterns and observed flow patterns were compared by considering the fractions of flow released at the point source that propagates through the grid cells. Predictions of these quantities were directly provided by flow direction methods and by related flow accumulation algorithms. Suitable data for the comparison were derived from observed overland flow patterns by assuming a uniform distribution of flow along each cross section. Planar overland flow dispersion is found to play an important role in the region lying immediately downslope of the point source, but attenuates rapidly as flow propagates downslope displaying a nearly constant width of about 50~cm. In contrast, existing dispersive flow direction methods are found to provide a continued dispersion with distance downslope. Predicted propagation patterns, for all methods considered here, depend critically on h. All methods are found to be poorly sensitive in extremely fine grids (h ? 2~cm), and to be poorly specific in coarse grids (h = 2~m). Satisfactory results are, however, obtained when h approaches the average flow width, with the best performances in terms of Pearson correlation coefficient displayed by the MD8 method in the finest grids (5~cm ? h ? 20~cm), and by the MD? , D? , and D? -LTD methods in the coarsest grids (20~cm < h ? 1~m). The results obtained in this study suggest further testing of terrain analysis methods with longer flow patterns and coarser grids. Scale issues affecting the relation between land surface microtopography, dispersion, and size of grid cells involved need then to be addressed to provide a hydrologic model of flow partitioning along the slope directions identified by terrain analysis methods.

Orlandini, S.; Moretti, G.; Corticelli, M. A.; Santangelo, P. E.; Capra, A.; Rivola, R.; Albertson, J. D.

2012-12-01

179

Direct observation of reaction intermediates for a well defined heterogeneous alkene metathesis catalyst  

PubMed Central

Grafting of [W(?NAr)(=CHtBu)(2,5-Me2NC4H2)2] on a silica partially dehydroxylated at 700°C (SiO2- (700)) generates the corresponding monosiloxy complex [(?SiO)W(?NAr)(=CHtBu)(2,5-Me2NC4H2)] as the major species (?90%) along with [(?SiO)W(?NAr)(CH2tBu)(2,5-Me2NC4H2)2], according to mass balance analysis, IR, and NMR studies. This heterogeneous catalyst displays good activity and stability in the metathesis of propene. Very importantly, solid state NMR spectroscopy allows observation of the propagating alkylidene as well as stable metallacyclobutane intermediates. These species have the same reactivity as the initial surface complex [(?SiO)W(?NAr)(=CHtBu)(2,5-Me2NC4H2)], which shows that they are the key intermediates of alkene metathesis. PMID:18723685

Blanc, Frédéric; Berthoud, Romain; Copéret, Christophe; Lesage, Anne; Emsley, Lyndon; Singh, Rojendra; Kreickmann, Thorsten; Schrock, Richard R.

2008-01-01

180

Direct observations of the influence of solution composition on magnesite dissolution  

NASA Astrophysics Data System (ADS)

In situ observations during atomic force microscopy experiments and ex situ observations after static and flow-through experiments were used to explore the effect of three different electrolytes on magnesite (MgCO3) dissolution at pH 2. The experiments showed that the magnesite dissolution rate varied in the order NO3->Cl>SO42- when these anions were present in solution. Under the experimental conditions magnesite dissolution occurred via the removal of successive single surface layers, where changes in magnesite reactivity in the presence of different electrolytes could be observed as variations in the cycle length for the removal of one unit cell layer. The cycles began with the formation of sporadically distributed etch pits followed by the nucleation of homogeneously distributed etch pits. Coalescence of the etch pits formed isolated sections of the remnant surface, which then dissolved away. The timing of sporadic and homogeneous etch pit nucleation was constant despite the presence of different anions. However, the cycles in surface roughness and etch pit spreading rates indicate that the different anions affect step retreat rates and hence dissolution rates. Differences in magnesite reactivity can be attributed to the direct interaction of sulphate with the magnesite surface and the indirect effects of chloride and nitrate on the magnesite surface hydration and hydration of the Mg2+ ion in solution. In all experiments during the dissolution process evidence for the precipitation of a new phase was observed, either directly as precipitates forming on the magnesite surface in the AFM and after the experiments, seen in SEM analysis, or as changes in the Mg outlet concentration during flow-through experiments. EDX and Raman spectroscopy were used to analyse the composition of the precipitate and although it could not be definitively identified, considering previous observations the precipitate is most likely a hydrated Mg-carbonate phase with a MgCO3·xH2O composition. Thus, the formation of a precipitate can facilitate further magnesite dissolution by increasing the undersaturation of the interfacial solution.

King, Helen E.; Putnis, Christine V.

2013-05-01

181

Direct observation of hole transfer from semiconducting polymer to carbon nanotubes.  

PubMed

Carbon nanotubes have been proven to play significant roles in polymer-based solar cells. However, there is intensive debate on whether carbon nanotube behaves as a donor or acceptor in the semiconducting polymer:carbon nanotube composite. In this paper, we report a direct observation via Kelvin probe force microscopy (KPFM) that single walled carbon nanotubes (SWNTs) behave as hole transporting channels in poly(3-hexylthiophene-2,5-diyl) (P3HT)/SWNT heterojunctions. By comparing the surface potential (SP) change of SWNT in dark and under illumination, we observed that electrons are blocked from SWNT while holes are transferred to SWNT. This observation can be well-explained by our proposed band alignment model of P3HT/SWNT heterojunction. The finding is further verified by hole mobility measurement using the space charge limited current (SCLC) method. SCLC results indicate that the existence of small amount of SWNT (wt 0.5%) promotes device hole mobility to around 15-fold, indicating SWNT act as hole transfer channel. Our finding of hole transporting behavior of SWNT in P3HT/SWNT blend will provide a useful guidance for enhancing the performance of polymer solar cells by carbon nanotubes. PMID:23574570

Lan, Fei; Li, Guangyong

2013-05-01

182

Chemotaxis study using optical tweezers to observe the strength and directionality of forces of Leishmania amazonensis  

NASA Astrophysics Data System (ADS)

The displacements of a dielectric microspheres trapped by an optical tweezers (OT) can be used as a force transducer for mechanical measurements in life sciences. This system can measure forces on the 50 femto Newtons to 200 pico Newtons range, of the same order of magnitude of a typical forces induced by flagellar motion. The process in which living microorganisms search for food and run away from poison chemicals is known is chemotaxy. Optical tweezers can be used to obtain a better understanding of chemotaxy by observing the force response of the microorganism when placed in a gradient of attractors and or repelling chemicals. This report shows such observations for the protozoa Leishmania amazomenzis, responsible for the leishmaniasis, a serious tropical disease. We used a quadrant detector to monitor the movement of the protozoa for different chemicals gradient. This way we have been able to observe both the force strength and its directionality. The characterization of the chemotaxis of these parasites can help to understand the infection mechanics and improve the diagnosis and the treatments employed for this disease.

Pozzo, Liliana d. Y.; Fontes, Adriana; de Thomaz, André A.; Barbosa, Luiz C.; Ayres, Diana C.; Giorgio, Selma; Cesar, Carlos L.

2006-08-01

183

Deadbeat flux level control of direct-field-oriented high-horsepower induction servo motor using adaptive rotor flux observer  

Microsoft Academic Search

A method for the deadbeat flux level control of direct-field-oriented high-power induction servo motor drives has been developed that employs an adaptive rotor flux observer. The observer is a full-order type and is used not only in the direct-field-oriented controller, but also to determine the stator and rotor resistances of the servo motor. The observer reduces the sensitivity of a

Lipei Huang; Yasuki Tadokoro; Kouki Matsuse

1994-01-01

184

Observing and improving hand hygiene compliance: implementation and refinement of an electronic-assisted direct-observer hand hygiene audit program.  

PubMed

We implemented a direct-observer hand hygiene audit program that used trained observers, wireless data entry devices, and an intranet portal. We improved the reliability and utility of the data by standardizing audit processes, regularly retraining auditors, developing an audit guidance tool, and reporting weighted composite hand hygiene compliance scores. PMID:23295569

Chen, Luke F; Carriker, Charlene; Staheli, Russell; Isaacs, Pamela; Elliott, Brandon; Miller, Becky A; Anderson, Deverick J; Moehring, Rebekah W; Vereen, Sheila; Bringhurst, Judie; Rhodes, Lisa; Strittholt, Nancy; Sexton, Daniel J

2013-02-01

185

Observing and Improving Hand Hygiene Compliance: Implementation and Refinement of an Electronic-Assisted Direct-Observer Hand Hygiene Audit Program  

PubMed Central

We implemented a direct-observer hand hygiene audit program that used trained observers, wireless data entry devices, and an intranet portal. We improved the reliability and utility of the data by standardizing audit processes, regularly retraining auditors, developing an audit guidance tool, and reporting weighted composite hand hygiene compliance scores. PMID:23295569

Chen, Luke F.; Carriker, Charlene; Staheli, Russell; Isaacs, Pamela; Elliott, Brandon; Miller, Becky A.; Anderson, Deverick J.; Moehring, Rebekah W.; Vereen, Sheila; Bringhurst, Judie; Rhodes, Lisa; Strittholt, Nancy; Sexton, Daniel J.

2013-01-01

186

Direct observation of resistive heating at graphene wrinkles and grain boundaries  

SciTech Connect

We directly measure the nanometer-scale temperature rise at wrinkles and grain boundaries (GBs) in functioning graphene devices by scanning Joule expansion microscopy with 50 nm spatial and 0.2K temperature resolution. We observe a small temperature increase at select wrinkles and a large (100 K) temperature increase at GBs between coalesced hexagonal grains. Comparisons of measurements with device simulations estimate the GB resistivity (8 150 X lm) among the lowest reported for graphene grown by chemical vapor deposition. An analytical model is developed, showing that GBs can experience highly localized resistive heating and temperature rise, most likely affecting the reliability of graphene devices. Our studies provide an unprecedented view of thermal effects surrounding nanoscale defects in nanomaterials such as graphene.

Grosse, Kyle L. [University of Illinois Urbana-Champaign; Dorgan, Vincent E. [University of Illinois at Urbana-Champaign, Urbana-Champaign; Estrada, David [University of Illinois at Urbana-Champaign, Urbana-Champaign; Wood, Joshua D. [University of Illinois at Urbana-Champaign, Urbana-Champaign; Vlassiouk, Ivan V [ORNL; Eres, Gyula [ORNL; Lyding, Joseph W [University of Illinois at Urbana-Champaign, Urbana-Champaign; King, William P. [University of Illinois at Urbana-Champaign, Urbana-Champaign; Pop, Eric [Stanford University

2014-01-01

187

Direct observation of half-metallicity in the Heusler compound Co2MnSi.  

PubMed

Ferromagnetic thin films of Heusler compounds are highly relevant for spintronic applications owing to their predicted half-metallicity, that is, 100% spin polarization at the Fermi energy. However, experimental evidence for this property is scarce. Here we investigate epitaxial thin films of the compound Co2MnSi in situ by ultraviolet-photoemission spectroscopy, taking advantage of a novel multi-channel spin filter. By this surface sensitive method, an exceptionally large spin polarization of (93(-11)(+7)) % at room temperature is observed directly. As a more bulk sensitive method, additional ex situ spin-integrated high energy X-ray photoemission spectroscopy experiments are performed. All experimental results are compared with advanced band structure and photoemission calculations which include surface effects. Excellent agreement is obtained with calculations, which show a highly spin polarized bulk-like surface resonance ingrained in a half metallic bulk band structure. PMID:24875774

Jourdan, M; Minár, J; Braun, J; Kronenberg, A; Chadov, S; Balke, B; Gloskovskii, A; Kolbe, M; Elmers, H J; Schönhense, G; Ebert, H; Felser, C; Kläui, M

2014-01-01

188

Direct observation of half-metallicity in the Heusler compound Co2MnSi  

NASA Astrophysics Data System (ADS)

Ferromagnetic thin films of Heusler compounds are highly relevant for spintronic applications owing to their predicted half-metallicity, that is, 100% spin polarization at the Fermi energy. However, experimental evidence for this property is scarce. Here we investigate epitaxial thin films of the compound Co2MnSi in situ by ultraviolet-photoemission spectroscopy, taking advantage of a novel multi-channel spin filter. By this surface sensitive method, an exceptionally large spin polarization of () % at room temperature is observed directly. As a more bulk sensitive method, additional ex situ spin-integrated high energy X-ray photoemission spectroscopy experiments are performed. All experimental results are compared with advanced band structure and photoemission calculations which include surface effects. Excellent agreement is obtained with calculations, which show a highly spin polarized bulk-like surface resonance ingrained in a half metallic bulk band structure.

Jourdan, M.; Minár, J.; Braun, J.; Kronenberg, A.; Chadov, S.; Balke, B.; Gloskovskii, A.; Kolbe, M.; Elmers, H. J.; Schönhense, G.; Ebert, H.; Felser, C.; Kläui, M.

2014-05-01

189

Direct observation of rare-earth ions in ?-sialon:Ce phosphors.  

PubMed

Doping structures of Ce(3+) into the refractory ?-sialon crystal lattice have been examined via an atom-resolved Cs-corrected scanning transmission electron microscope. The location and coordination of the rare-earth ions are well-defined through direct observation in conjunction with structural modeling and image simulation. The stability and solubility of Ce(3+) ions could be remarkably enhanced via congregation into the planar defects formed by a 1/3 (210)-type lattice displacement along with an inversion operation. The formation of cylindrical chambers near the defects is believed to provide effective structural relaxation upon doping of large rare-earth ions into the interstices in their neighborhoods. The as-revealed structural information could be useful for understanding the luminescence properties of the promising rare-earth doped sialon materials. PMID:21370828

Xu, Fangfang; Sourty, Erwan; Shi, Wei; Mou, Xinliang; Zhang, Linlin

2011-04-01

190

Direct Observation of Ion Distributions near Electrodes in Ionic Polymer Actuators Containing Ionic Liquids  

PubMed Central

The recent boom of energy storage and conversion devices, exploiting ionic liquids (ILs) to enhance the performance, requires an in-depth understanding of this new class of electrolytes in device operation conditions. One central question critical to device performance is how the mobile ions accumulate near charged electrodes. Here, we present the excess ion depth profiles of ILs in ionomer membrane actuators (Aquivion/1-butyl-2,3-dimethylimidazolium chloride (BMMI-Cl), 27??m thick), characterized directly by Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) at liquid nitrogen temperature. Experimental results reveal that for the IL studied, cations and anions are accumulated at both electrodes. The large difference in the total volume occupied by the excess ions between the two electrodes cause the observed large bending actuation of the actuator. Hence we demonstrate that ToF-SIMS experiment provides great insights on the physics nature of ionic devices. PMID:23512124

Liu, Yang; Lu, Caiyan; Twigg, Stephen; Ghaffari, Mehdi; Lin, Junhong; Winograd, Nicholas; Zhang, Q. M.

2013-01-01

191

Direct neutron scattering-based observation of spin excitons in LaCoO3  

NASA Astrophysics Data System (ADS)

We report temperature-dependent small angle neutron scattering (SANS) results on undoped LaCoO3 single crystals. The data reveal two main scattering components; a high q signal increasing with T above 50 K, and a low q component that turns on sharply below 60 K. The former is shown to be due to inelastic scattering quantitatively consistent with the excitations associated with the spin-state transition. Of greater interest, the low q scattering is shown to be of Guinier form, revealing scattering from a dilute assembly of magnetic objects of size approximately 15-20 nm. The abrupt onset of this scattering at 60 K, i.e. very close to the point at which prior work provided evidence of formation of interacting magnetic excitons, suggests that this represents the first direct scattering-based observation of magnetic excitons forming around O defects in LaCoO3.

El-Khatib, S.; Phelan, D.; Borchers, J. A.; Barker, J.; Butler, P.; Zheng, H.; Mitchell, J. F.; Leighton, C.

2012-02-01

192

The directivity of high-energy emission from solar flares - Solar Maximum Mission observations  

NASA Technical Reports Server (NTRS)

The data base consisting of flares detected by the gamma-ray spectrometer (GRS) on board the Solar Maximum Mission (SMM) satellite is used to study the directivity of high-energy radiation. A number of observations are presented that, strongly indicate that the high-energy emission from flares is anisotropic. They are the following: (1) the fraction of events detected at energies above 300 keV near the limb is higher than is expected for isotropically emitting flares; (2) there is a statistically significant center-to-limb variation in the 300 keV to 1 MeV spectra of flares detected by the SMM GRS; (3) the 25-200 keV hard X-ray spectra measured during the impulsive phase by the SMM GRS show a center-to-limb variation; and (4) nearly all of the events detected at above 10 MeV are located near the limb.

Vestrand, W. Thomas; Forrest, D. J.; Chupp, E. L.; Rieger, E.; Share, G. H.

1987-01-01

193

Direct observation of half-metallicity in the Heusler compound Co2MnSi  

PubMed Central

Ferromagnetic thin films of Heusler compounds are highly relevant for spintronic applications owing to their predicted half-metallicity, that is, 100% spin polarization at the Fermi energy. However, experimental evidence for this property is scarce. Here we investigate epitaxial thin films of the compound Co2MnSi in situ by ultraviolet-photoemission spectroscopy, taking advantage of a novel multi-channel spin filter. By this surface sensitive method, an exceptionally large spin polarization of () % at room temperature is observed directly. As a more bulk sensitive method, additional ex situ spin-integrated high energy X-ray photoemission spectroscopy experiments are performed. All experimental results are compared with advanced band structure and photoemission calculations which include surface effects. Excellent agreement is obtained with calculations, which show a highly spin polarized bulk-like surface resonance ingrained in a half metallic bulk band structure. PMID:24875774

Jourdan, M.; Minár, J.; Braun, J.; Kronenberg, A.; Chadov, S.; Balke, B.; Gloskovskii, A.; Kolbe, M.; Elmers, H.J.; Schönhense, G.; Ebert, H.; Felser, C.; Kläui, M.

2014-01-01

194

First observational estimates of global clear sky shortwave aerosol direct radiative effect over land  

NASA Astrophysics Data System (ADS)

Using one year (2000-2001) of merged Multiangle Imaging SpectroRadiometer (MISR), Moderate Resolution Imaging SpectroRadiometer (MODIS) and Clouds and the Earth's Radiant Energy System (CERES) data sets from NASA's Terra satellite, we estimate the top of atmosphere cloud-free direct radiative effect (DRE) of aerosols over global land areas. The global mean shortwave DRE is -5.1 +/- 1.1 Wm-2 although substantial regional variability in DRE over land exists due to differences in aerosol properties and land cover types. This value is consistent with those reported in the literature although this is the first observational estimate of the global DRE over land using satellite data alone. Future studies need to separate the anthropogenic component of aerosols from satellite data to examine aerosol climate forcing over global scales.

Patadia, Falguni; Gupta, Pawan; Christopher, Sundar A.

2008-02-01

195

Copernicus observations of neutral hydrogen and deuterium in the direction of HR 1099  

NASA Technical Reports Server (NTRS)

High-resolution Copernicus U1 scans were obtained of the bright RS CVn binary HR 1099 (d = 33 pc, galactic longitude = 185 deg, galactic latitude = -41 deg) in October 1977. Strong emission at L-alpha was detected. The interstellar L-alpha absorption features of H I and D I were also observed. Analyses of these interstellar lines are reported in this paper. The average density of neutral H in the direction of this system is found to be 0.006-0.012 per cu cm, which, because the local density is higher, requires a marked inhomogeneity along this line of sight. This result, when combined with other recent studies of the local interstellar medium, suggests the sun is located within a moderate-density H I region.

Anderson, R. C.; Weiler, E. J.

1979-01-01

196

Copernicus observations of interstellar matter in the direction of HR 1099  

NASA Technical Reports Server (NTRS)

Results are reported for high-resolution Copernicus U1 and V2 scans of the bright RS CVn spectroscopic binary HR 1099. The observations reveal strong UV emission lines at L-alpha and Mg II h and k from the stars as well as interstellar H I and D I L-alpha absorption lines and interstellar Mg II h and k absorption in the direction of the binary system. Column densities, bulk velocities, and temperatures are derived for the interstellar features. A comparison of the derived number density of interstellar H I with data for the nearby star Epsilon Eri indicates an inhomogeneous distribution of interstellar hydrogen along the line of sight. The range of values obtained for the D/H ratio is shown to be consistent with results of other studies. A depletion factor of at least 5 with respect to the solar abundance is estimated for the interstellar magnesium.

Anderson, R. C.; Weiler, E. J.

1978-01-01

197

Direct observation of hierarchical nucleation of martensite and size-dependent superelasticity in shape memory alloys.  

PubMed

Martensitic transformation usually creates hierarchical internal structures beyond mere change of the atomic crystal structure. Multi-stage nucleation is thus required, where nucleation (level-1) of the underlying atomic crystal lattice does not have to be immediately followed by the nucleation of higher-order superstructures (level-2 and above), such as polysynthetic laths. Using in situ transmission electron microscopy (TEM), we directly observe the nucleation of the level-2 superstructure in a Cu-Al-Ni single crystal under compression, with critical super-nuclei size L2c around 500 nm. When the sample size D decreases below L2c, the superelasticity behavior changes from a flat stress plateau to a continuously rising stress-strain curve. Such size dependence definitely would impact the application of shape memory alloys in miniaturized MEMS/NEMS devices. PMID:24384687

Liu, Lifeng; Ding, Xiangdong; Li, Ju; Lookman, Turab; Sun, Jun

2014-02-21

198

Direct Observation of Morphological Tranformation from Twisted Ribbons into Helical Ribbons  

SciTech Connect

We report on the direct observation of a nanostructural transformation from a twisted ribbon to a helical ribbon in supramolecular assemblies of peptide amphiphiles. Using cryogenic electron microscopy, a peptide amphiphile molecule containing aromatic residues was found to first assemble into short twisted ribbons in the time range of seconds, which then elongate in the time scale of minutes, and finally transform into helical ribbons over the course of weeks. By synthesizing an analogous molecule without the aromatic side groups, it was found that a cylindrical nanostructure is formed that does not undergo any transitions during the same time period. The study of metastable states in peptide aggregation can contribute to our understanding of amyloid-related diseases, such as Alzheimer's disease.

Pashuck, E.Thomas; Stupp, Samuel I. (NWU)

2010-07-01

199

Direct observations of gas-hydrate formation in natural porous media on the micro-scale  

NASA Astrophysics Data System (ADS)

Gas hydrates (GH) are crystalline, inclusion compounds consisting of hydrogen-bonded water network encaging small gas molecules such as methane, ethane, CO2, etc (Sloan and Koh 2008). Natural gas hydrates are found worldwide in marine sediments and permafrost regions as a result of a reaction of biogenic or thermogenic gas with water under elevated pressure. Although a large amount of research on GH has been carried out over the years, the micro-structural aspects of GH growth, and in particular the contacts with the sedimentary matrix as well as the details of the distribution remain largely speculative. The present study was undertaken to shed light onto the well-established but not fully understood seismic anomalies, in particular the unusual attenuation of seismic waves in GH-bearing sediments, which may well be linked to micro-structural features. Observations of in-situ GH growth have been performed in a custom-build pressure cell (operating pressures up to several bar) mounted at the TOMCAT beam line of SLS/ PSI. In order to provide sufficient absorption contrast between phases and reduce pressure requirements for the cell we have used Xe instead of CH4. To the best of our knowledge this represents the first direct observation of GH growth in natural porous media with sub-micron spatial resolution and gives insight into the nucleation location and growth process of GH. The progress of the formation of sI Xe-hydrate in natural quartz sand was observed with a time-resolution of several minutes; the runs were conducted with an excess of a free-gas phase and show that the nucleation starts at the gas-water interface. Initially, a GH film is formed at this interface with a typical thickness of several ?m; this film may well be permeable to gas as suggested in the past - which would explain the rapid transport of gas molecules for further conversion of water to hydrate, completed in less than 20 min. Clearly, initially the growth is directed mainly into the liquid (and not into the gas phase as sometimes suggested). The observations of the 2D slices after full transformation show for all systems studied that hydrates tend to concentrate in the center of pore spaces and do not adhere in a systematic manner to quartz grains. Whether or not a thin film of water remained at the quartz-GH interface after completion of the reaction is presently under investigation. Sloan, E.D., Koh, C.A., (2008) Clathrate hydrates of natural gases. CRC Press, Boca Raton, FL.

Chaouachi, M.; Sell, K.; Falenty, A.; Enzmann, F.; Kersten, M.; Pinzer, B.; Saenger, E. H.; Kuhs, W. F.

2013-12-01

200

Direct observation of zirconium segregation to dislocations and grain boundaries in NiAl  

SciTech Connect

Segregation of zirconium to dislocations in microalloyed NiAl has been directly observed in the atom probe field ion microscopy (APFIM). Approximately two thirds of the <100> dislocations in the NiAl matrix exhibited zirconium segregation. Zirconium-rich regions with ribbon-like morphology were also detected in the NiAl matrix. It is suggested that these regions are associated with dislocations. These results support the suggestion that the substantial increase in ductile-to-brittle transition temperature (DBTT) of the zirconium-doped alloy is due to pinning of dislocations by zirconium. Since the mechanism underlying the DBTT in binary NiAl is not understood, it would be of interest to examine the possibility of a similar pinning of dislocations by trace interstitial and other impurities in the undoped alloy. Segregation of zirconium to grain boundaries has also been observed in the APFIM. This result indicates the possible strengthening of grain boundaries has also been observed in the APFIM. This result indicates the possible strengthening of grain boundaries due to zirconium segregation and is consistent with the change in the fracture mode from intergranular in the undoped NiAl to a mixture of intergranular and transgranular mode in zirconium-doped NiAl. The NiAl matrix was heavily depleted of both solutes molybdenum and zirconium. Small Mo-rich precipitates observed in the matrix and at grain boundaries and the ribbon-like Zr-rich regions are likely to contributed to the increase in yield stress through precipitation hardening.

Jayaram, R. [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Materials Science and Engineering] [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Materials Science and Engineering; Miller, M.K. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Division] [Oak Ridge National Lab., TN (United States). Metals and Ceramics Division

1995-07-01

201

Direct observation of microcavitation in underwater adhesion of mushroom-shaped adhesive microstructure.  

PubMed

In this work we report on experiments aimed at testing the cavitation hypothesis [Varenberg, M.; Gorb, S. J. R. Soc., Interface 2008, 5, 383-385] proposed to explain the strong underwater adhesion of mushroom-shaped adhesive microstructures (MSAMSs). For this purpose, we measured the pull-off forces of individual MSAMSs by detaching them from a glass substrate under different wetting conditions and simultaneously video recording the detachment behavior at very high temporal resolution (54,000-100,000 fps). Although microcavitation was observed during the detachment of individual MSAMSs, which was a consequence of water inclusions present at the glass-MSAMS contact interface subjected to negative pressure (tension), the pull-off forces were consistently lower, around 50%, of those measured under ambient conditions. This result supports the assumption that the recently observed strong underwater adhesion of MSAMS is due to an air layer between individual MSAMSs [Kizilkan, E.; Heepe, L.; Gorb, S. N. Underwater adhesion of mushroom-shaped adhesive microstructure: An air-entrapment effect. In Biological and biomimetic adhesives: Challenges and opportunities; Santos, R.; Aldred, N.; Gorb, S. N.; Flammang, P., Eds.; The Royal Society of Chemistry: Cambridge, U.K., 2013; pp 65-71] rather than by cavitation. These results obtained due to the high-speed visualisation of the contact behavior at nanoscale-confined interfaces allow for a microscopic understanding of the underwater adhesion of MSAMSs and may aid in further development of artificial adhesive microstructures for applications in predominantly liquid environments. PMID:24991528

Heepe, Lars; Kovalev, Alexander E; Gorb, Stanislav N

2014-01-01

202

Direct observation of microcavitation in underwater adhesion of mushroom-shaped adhesive microstructure  

PubMed Central

Summary In this work we report on experiments aimed at testing the cavitation hypothesis [Varenberg, M.; Gorb, S. J. R. Soc., Interface 2008, 5, 383–385] proposed to explain the strong underwater adhesion of mushroom-shaped adhesive microstructures (MSAMSs). For this purpose, we measured the pull-off forces of individual MSAMSs by detaching them from a glass substrate under different wetting conditions and simultaneously video recording the detachment behavior at very high temporal resolution (54,000–100,000 fps). Although microcavitation was observed during the detachment of individual MSAMSs, which was a consequence of water inclusions present at the glass–MSAMS contact interface subjected to negative pressure (tension), the pull-off forces were consistently lower, around 50%, of those measured under ambient conditions. This result supports the assumption that the recently observed strong underwater adhesion of MSAMS is due to an air layer between individual MSAMSs [Kizilkan, E.; Heepe, L.; Gorb, S. N. Underwater adhesion of mushroom-shaped adhesive microstructure: An air-entrapment effect. In Biological and biomimetic adhesives: Challenges and opportunities; Santos, R.; Aldred, N.; Gorb, S. N.; Flammang, P., Eds.; The Royal Society of Chemistry: Cambridge, U.K., 2013; pp 65–71] rather than by cavitation. These results obtained due to the high-speed visualisation of the contact behavior at nanoscale-confined interfaces allow for a microscopic understanding of the underwater adhesion of MSAMSs and may aid in further development of artificial adhesive microstructures for applications in predominantly liquid environments. PMID:24991528

Kovalev, Alexander E; Gorb, Stanislav N

2014-01-01

203

Direct Determination of Auroral Kilomeric Radiation Burst Locations Using Cluster VLBI Delay Observations  

NASA Astrophysics Data System (ADS)

We have used the Wideband Data (WBD) instrument on Cluster to determine source locations of auroral kilometric radiation (AKR) bursts using multiple spacecraft in a very long baseline interferometry (VLBI) mode. The technique involves measuring the delays of AKR impulsive bursts on each of several independent baselines between pairs of spacecraft with sub-millisecond accuracy. The delays are combined to solve for source location by triangulation. The accuracy of the technique depends on the Cluster orientation and distance from Earth, but typical uncertainties are 200-1000 km in a plane perpendicular to the source-Cluster line of sight, and somewhat larger along this direction. We have analyzed AKR burst locations for more than 30 events, and have compared the derived positions with contemporaneous images of auroral taken by imagers on the POLAR and Image spacecraft. We find that the AKR locations are consistent with emission occurring at or near the local gyrofrequency, and the bursts tend to occur along magnetic field lines located above regions of bright regions in the auroral oval. These observations are the first direct 3-dimensional measurement of AKR source location. >http://denali.physics.uiowa.edu/rlm/research/vlbi-akr

Mutel, R. L.; Gurnett, D. A.; Christopher, I.

2001-12-01

204

Ultrasound Open Channel Flow-Speed Measurement Based on the Lateral Directional Echo Observations  

NASA Astrophysics Data System (ADS)

Conventional ultrasonic flowmeters have a problem in measuring the small open channel fluid flow. To solve this problem, a lateral observation technique using a single transmitter/receiver transducer attached at the bottom of the pipe was proposed. Pulse echo signals scattered from the particles in the medium were repetitively recorded with a constant time interval. From the slope of the correlation peak amplitude with the variation in pulse echo excitation time, the flow speed of the medium was estimated. The method has an advantage in that the variation in flow speed in the vertical depth direction is directly measured with a minimum measurement space. Moreover, the fluctuations caused by the turbulent water can be avoided compared with the case of a conventional method based on the time estimation method. Bubbles were generated by an aspirator and flour powder was mixed with water as scatterers in the imitated drainage water. The flow speed of water was measured with respect to the inflowing fluid volume. Moreover, vertical flow speed profiles were measured and compared with fluid flow simulation results. The results showed that the precision of the measured flow speed was satisfactory and tolerant against the turbulence of the water flow medium.

Nishimura, Ichiro; Ishigamori, Mitsuhide; Yamada, Akira

2012-07-01

205

Directionality and variability of energetic neutral hydrogen fluxes observed by Mars Express  

NASA Astrophysics Data System (ADS)

Using data collected by the neutral particle detector of the analyzer of space plasmas and energetic atoms on board Mars Express, we establish the global morphology of hydrogen energetic neutral atom (ENA) fluxes. The observations were conducted in March-July 2004 and reveal that low flux ENAs (<5×105cm-2s-1sr-1) are emitted roughly isotropically from the dayside of the planet. These ENA emissions originate from the backscattering of the hydrogen ENAs produced by the charge exchange of the upstream solar wind in the extended Martian exosphere. ENAs of higher fluxes are emitted preferentially in the directions perpendicular to the undisturbed solar wind velocity. This population is due to the charge exchange of the magnetosheath plasma. At a great distance, these ENA emissions resemble a thick layer or a wall. The emissions are enhanced in the direction opposite to the convective electric field (Ec). This enhancement reflects the asymmetric shape of the induced magnetic boundary that is close to the planet hemisphere where the Ec points toward the Sun-Mars line (-Ec hemisphere). The ENA flux shows a positive correlation with the solar wind dynamic pressure. The asymmetry in the ENA emissions is modest during quiet solar wind conditions but becomes more pronounced when the solar wind dynamic pressure increases.

Wang, X.-D.; Barabash, S.; Futaana, Y.; Grigoriev, A.; Wurz, P.

2013-12-01

206

Microscopic Observations on the Origin of Defects During Machining of Direct Aged (DA) Inconel 718 Superalloy  

NASA Astrophysics Data System (ADS)

Surface quality of advanced superalloys after machining is one of the major issues in the aerospace industry because it directly affects service characteristics of the machined part. Tool life of cemented carbide inserts with the TiAlN coating during machining of direct aged DA 718 alloys under roughing and finishing conditions has been under study. The defect origin on the surface of the machined part was investigated. Metallographic observations of the DA 718 were made using optical metallography and SEM/EDS. To find out the origins of surface defect formation, the morphology of machined parts and cross sections of the machined surfaces have been investigated. Two major categories of defects were detected on the surface of the machined part: cracks and tears. The origin of the cracks on the machined surface is related to shearing of the primary complex TiC/NbC carbide revealed in a structure of DA 718 alloy. At the same time, Nb-rich regions of the primary complex carbide interact with the environment (oxygen from air) during machining with further formation of low strength oxide layer on the surface, forming tears.

Dosbaeva, G. K.; Veldhuis, S. C.; Elfizy, A.; Fox-Rabinovich, G.; Wagg, T.

2010-11-01

207

Efficacy of directly observed treatment short-course intermittent regimen in spinal tuberculosis  

PubMed Central

Background: Most important cause of treatment failure and emergence of drug resistance in the treatment of tuberculosis is noncompliance. Compliance can be improved by direct observation of drug intake, intermittent therapy, and short-course treatment. The efficacy of Directly Observed Treatment Short Course (DOTS) strategy advocated by World Health Organization (WHO) in spinal tuberculosis is not yet proven. We conducted a prospective clinical study on a consecutive series of patients with spinal tuberculosis treated by Category I Revised National Tuberculosis Control Programme (RNTCP) regimen based on DOTS strategy of WHO from 2004 to 2007 to evaluate the efficacy. Materials and Methods: Forty-nine consecutive patients of spinal tuberculosis were treated with short-course intermittent chemotherapy under Category I RNTCP/DOTS strategy. Patients were followed up for a minimum period of 2 years. Surgery was done if the patient presented with significant neurologic deficit or when the drug treatment failed. Outcome was assessed by clinical, radiologic, and laboratory criteria, and graded into excellent, good, fair, and poor based on various parameters. Results: 63.4% (n=26) of the patients had excellent results. 14.6% (n=6) of the patients had good and fair results. Three patients (7.3%) had poor results 48.7% (n=20) of the patients had but only one of them was severe enough to warrant change of drug. Conclusions: Efficacy of DOTS was comparable with other standard regimens. There was a significant reduction in adverse side effects when compared with daily regimens. Study showed that the outcome was better in those treated early. PMID:22448050

Valsalan, Rejith; Purushothaman, Rajesh; Raveendran, MK; Zacharia, Balaji; Surendran, Sibin

2012-01-01

208

Effects of the observation method (direct v. from video) and of the presence of an observer on behavioural results in veal calves.  

PubMed

This study aimed at assessing the effect of the observation method (direct or from video) and the effect of the presence of an observer on the behavioural results in veal calves kept on a commercial farm. To evaluate the effect of the observation method, 20 pens (four to five calves per pen) were observed by an observer for 60 min (two observation sessions of 30 min) and video-recorded at the same time. To evaluate the effect of the presence of the observer in front of the pen, 24 pens were video-recorded on 4 consecutive days and an observer was present in front of each pen for 60 min (two observation sessions of 30 min) on the third day. Behaviour was recorded using instantaneous scan sampling. For the study of the observer's effect, the analysis was limited to the posture, abnormal oral behaviour and manipulation of substrates. The two observation methods gave similar results for the time spent standing, but different results for all other behaviours. The presence of an observer did not affect the behaviour of calves at day level; however, their behaviour was affected when the observer was actually present in front of the pens. A higher percentage of calves were standing and were manipulating substrate in the presence of the observer, but there was no effect on abnormal oral behaviour. In conclusion, direct observations are a more suitable observation method than observations from video recordings for detailed behaviours in veal calves. The presence of an observer has a short-term effect on certain behaviours of calves that will have to be taken into consideration when monitoring these behaviours. PMID:23916373

Leruste, H; Bokkers, E A M; Sergent, O; Wolthuis-Fillerup, M; van Reenen, C G; Lensink, B J

2013-11-01

209

Direct NMR observation of a substrate protein bound to the chaperonin GroEL  

PubMed Central

The reaction cycle and the major structural states of the molecular chaperone GroEL and its cochaperone, GroES, are well characterized. In contrast, very little is known about the nonnative states of the substrate polypeptide acted on by the chaperonin machinery. In this study, we investigated the substrate protein human dihydrofolate reductase (hDHFR) while bound to GroEL or to a single-ring analog, SR1, by NMR spectroscopy in solution under conditions where hDHFR was efficiently recovered as a folded, enzymatically active protein from the stable complexes upon addition of ATP and GroES. By using the NMR techniques of transverse relaxation-optimized spectroscopy (TROSY), cross-correlated relaxation-induced polarization transfer (CRIPT), and cross-correlated relaxation-enhanced polarization transfer (CRINEPT), bound hDHFR could be observed directly. Measurements of the buildup of hDHFR NMR signals by different magnetization transfer mechanisms were used to characterize the dynamic properties of the NMR-observable parts of the bound substrate. The NMR data suggest that the bound state includes random coil conformations devoid of stable native-like tertiary contacts and that the bound hDHFR might best be described as a dynamic ensemble of randomly structured conformers. PMID:16116078

Horst, Reto; Bertelsen, Eric B.; Fiaux, Jocelyne; Wider, Gerhard; Horwich, Arthur L.; Wüthrich, Kurt

2005-01-01

210

Direct observation of small cluster mobility and ripening. [during annealing of metal films on amorphous substrates  

NASA Technical Reports Server (NTRS)

Direct evidence is reported for the simultaneous occurrence of Ostwald ripening and short-distance cluster mobility during annealing of discontinuous metal films on clean amorphous substrates. The annealing characteristics of very thin particulate deposits of silver on amorphized clean surfaces of single crystalline thin graphite substrates were studied by in-situ transmission electron microscopy (TEM) under controlled environmental conditions (residual gas pressure of 10 to the minus 9th power torr) in the temperature range from 25 to 450 C. Sputter cleaning of the substrate surface, metal deposition, and annealing were monitored by TEM observation. Pseudostereographic presentation of micrographs in different annealing stages, the observation of the annealing behavior at cast shadow edges, and measurements with an electronic image analyzing system were employed to aid the visual perception and the analysis of changes in deposit structure recorded during annealing. Slow Ostwald ripening was found to occur in the entire temperature range, but the overriding surface transport mechanism was short-distance cluster mobility.

Heinemann, K.; Poppa, H.

1975-01-01

211

Direct observations of evolving subglacial drainage beneath the Greenland Ice Sheet  

NASA Astrophysics Data System (ADS)

Seasonal acceleration of the Greenland Ice Sheet is influenced by the dynamic response of the subglacial hydrologic system to variability in meltwater delivery to the bed via crevasses and moulins (vertical conduits connecting supraglacial water to the bed of the ice sheet). As the melt season progresses, the subglacial hydrologic system drains supraglacial meltwater more efficiently, decreasing basal water pressure and moderating the ice velocity response to surface melting. However, limited direct observations of subglacial water pressure mean that the spatiotemporal evolution of the subglacial hydrologic system remains poorly understood. Here we show that ice velocity is well correlated with moulin hydraulic head but is out of phase with that of nearby (0.3-2 kilometres away) boreholes, indicating that moulins connect to an efficient, channelized component of the subglacial hydrologic system, which exerts the primary control on diurnal and multi-day changes in ice velocity. Our simultaneous measurements of moulin and borehole hydraulic head and ice velocity in the Paakitsoq region of western Greenland show that decreasing trends in ice velocity during the latter part of the melt season cannot be explained by changes in the ability of moulin-connected channels to convey supraglacial melt. Instead, these observations suggest that decreasing late-season ice velocity may be caused by changes in connectivity in unchannelized regions of the subglacial hydrologic system. Understanding this spatiotemporal variability in subglacial pressures is increasingly important because melt-season dynamics affect ice velocity beyond the conclusion of the melt season.

Andrews, Lauren C.; Catania, Ginny A.; Hoffman, Matthew J.; Gulley, Jason D.; Lüthi, Martin P.; Ryser, Claudia; Hawley, Robert L.; Neumann, Thomas A.

2014-10-01

212

Magnetic fields in the Venus ionosphere: Dependence on the IMF direction—Venus express observations  

NASA Astrophysics Data System (ADS)

The structure of the magnetized ionosphere of Venus is investigated using the magnetometer and plasma (Analyzer of Space Plasmas and Energetic Atoms 4) data from the Venus Express spacecraft. Observations surveying the low-altitude (h ? 250 km) ionosphere were made at solar zenith angles ? 75°. The magnetic field permeating the Venus ionosphere at solar minimum conditions increases at low altitudes and reaches a maximum at an altitude of ˜200 km. The orientation of the magnetic field in the peak is almost insensible to the magnetic field direction in the solar wind. For both sector polarities of the IMF, the magnetic field vector has a dominant dawn-dusk component. The topology of the magnetic field also occurs different for different signs of the cross-flow component of the IMF revealing either a sudden straightening with liberation of the magnetic field stresses or a closing into a loop. We discuss different mechanisms of the peak formation including local magnetization, a weak intrinsic planetary field, a dipole field induced by eddy currents, a remnant origin, or giant flux ropes. All of them fail to explain most of the observed features. We suggest that a decoupling of ion and electron motion at low altitudes due to ion-neutral collisions results in currents which produce different field configurations depending on the IMF orientation.

Dubinin, E.; Fraenz, M.; Zhang, T. L.; Woch, J.; Wei, Y.

2014-09-01

213

Experimental Technique for Direct Observation of Onset of Reaction in Shocked Powder Mixtures  

NASA Astrophysics Data System (ADS)

A new experimental technique was developed to directly observe the onset of shock initiation in powder mixtures contained in recovery capsules over time scales ranging from hundreds of nanoseconds to at least hundreds of milliseconds. Simultaneously with a thermocouple embedded in the test mixture to monitor bulk temperature changes, a photomultiplier tube detected light emissions produced by the reacting sample. A particular window/optic fiber system was developed that remained intact and did not move during the experiment. A T-shaped polycarbonate window was placed into a steel recovery capsule, which was held solidly in place in a heavy steel anvil designed to protect the fiber optic and to prevent motion of the polycarbonate window. Samples of as-blended 5Ti+3Si powders and ball-milled mixtures 5Ti+3Si were tested in this setup. In all experiments, a weak light emission peak was observed upon shock passage followed by much more intense light emissions beginning a few milliseconds to a few hundreds of milliseconds later. The intense light emissions occurred at approximately the same time as a bulk temperature increase measured with the thermocouple. These results suggest that only a very small fraction of the sample was initiated by the shock. This setup shows promise for further studies of shock initiation in reactive powders.

Jetté, François-Xavier; Goroshin, Sam; Higgins, Andrew; Frost, David; Lee, Julian

2011-06-01

214

Experimental technique for direct observation of onset of reaction in shocked powder mixtures  

NASA Astrophysics Data System (ADS)

A new experimental technique was developed to directly observe the onset of shock initiation in powder mixtures contained in recovery capsules over time scales ranging from hundreds of nanoseconds to at least hundreds of milliseconds. Simultaneously with a thermocouple embedded in the test mixture to monitor bulk temperature changes, a photomultiplier tube detected light emissions produced by the reacting sample. A window/optic fiber system was developed that remained intact and did not move during the experiment. A polycarbonate window was placed into a steel recovery capsule, which was held solidly in place in a steel anvil designed to protect the fiber optic and to prevent motion of the window. Samples of as-blended 5Ti+3Si powders and ball-milled mixtures 5Ti+3Si were tested in this setup. In all experiments, a weak light emission peak was observed upon shock passage followed by much more intense light beginning a few milliseconds to a few hundreds of milliseconds later. The intense light emissions occurred at approximately the same time as a bulk temperature increase measured with the thermocouple. These results suggest that only a very small fraction of the sample was initiated by the shock.

Jetté, Francois-Xavier; Goroshin, Sam; Higgins, Andrew; Frost, David; Lee, Julian

2012-03-01

215

Graphene as Transparent Electrode for Direct Observation of Hole Photoemission from Silicon to Oxide  

E-print Network

The outstanding electrical and optical properties of graphene make it an excellent alternative as a transparent electrode. Here we demonstrate the application of graphene as collector material in internal photoemission (IPE) spectroscopy; enabling the direct observation of both electron and hole injections at a Si/Al2O3 interface and successfully overcoming the long-standing difficulty of detecting holes injected from a semiconductor emitter in IPE measurements. The observed electron and hole barrier heights are 3.5 eV and 4.1 eV, respectively. Thus the bandgap of Al2O3 can be further deduced to be 6.5 eV, in close agreement with the valued obtained by vacuum ultraviolet spectroscopic ellipsometry analysis. The detailed optical modeling of a graphene/Al2O3/Si stack reveals that by using graphene in IPE measurements the carrier injection from the emitter is significantly enhanced and the contribution of carrier injection from the collector electrode is minimal. The method can be readily extended to various IPE...

Yan, Rusen; Kirillov, Oleg A; Li, Wei; Basham, James; Boosalis, Alex; Liang, Xuelei; Jena, Debdeep; Richter, Curt A; Seabaugh, Alan; Gundlach, David J; Xing, Huili G; Nguyen, N V

2012-01-01

216

Medication-administration errors in an urban mental health hospital: A direct observation study.  

PubMed

In the present study, we aimed to identify the incidence, type, and potential clinical consequence of medication-administration errors made in a mental health hospital, and to investigate factors that might increase the risk of error. A prospective, direct observational technique was used to collect data from nurse medication rounds on each of the hospital's 43 inpatient wards. Regression analysis was used to identify potential error predictors. During the 172 medication rounds observed, 139 errors were detected in 4177 (3.3%) opportunities. The most common error was incorrect dose omission (52/139, 37%). Other common errors included incorrect dose (25/139, 18%), incorrect form (16/139, 12%), and incorrect time (12/139, 9%). Fifteen (11%) of the errors were of serious clinical severity; the rest were of negligible or minor severity. Factors that increased the risk of error included the nurse interrupting the medication round to attend to another activity, an increased number of 'when required' doses of medication administered, a higher number of patients on the ward, and an increased number of doses of medication due. These findings suggest that providers of inpatient mental health-care services should adopt medicine-administration systems that minimize task interruption and the use of 'when required' medication, as well as taking steps to reduce nursing workload. PMID:25394525

Cottney, Alan; Innes, James

2014-11-14

217

Direct observations of evolving subglacial drainage beneath the Greenland Ice Sheet.  

PubMed

Seasonal acceleration of the Greenland Ice Sheet is influenced by the dynamic response of the subglacial hydrologic system to variability in meltwater delivery to the bed via crevasses and moulins (vertical conduits connecting supraglacial water to the bed of the ice sheet). As the melt season progresses, the subglacial hydrologic system drains supraglacial meltwater more efficiently, decreasing basal water pressure and moderating the ice velocity response to surface melting. However, limited direct observations of subglacial water pressure mean that the spatiotemporal evolution of the subglacial hydrologic system remains poorly understood. Here we show that ice velocity is well correlated with moulin hydraulic head but is out of phase with that of nearby (0.3-2 kilometres away) boreholes, indicating that moulins connect to an efficient, channelized component of the subglacial hydrologic system, which exerts the primary control on diurnal and multi-day changes in ice velocity. Our simultaneous measurements of moulin and borehole hydraulic head and ice velocity in the Paakitsoq region of western Greenland show that decreasing trends in ice velocity during the latter part of the melt season cannot be explained by changes in the ability of moulin-connected channels to convey supraglacial melt. Instead, these observations suggest that decreasing late-season ice velocity may be caused by changes in connectivity in unchannelized regions of the subglacial hydrologic system. Understanding this spatiotemporal variability in subglacial pressures is increasingly important because melt-season dynamics affect ice velocity beyond the conclusion of the melt season. PMID:25279921

Andrews, Lauren C; Catania, Ginny A; Hoffman, Matthew J; Gulley, Jason D; Lüthi, Martin P; Ryser, Claudia; Hawley, Robert L; Neumann, Thomas A

2014-10-01

218

Influence of Observed Diurnal Cycles of Aerosol Optical Depth on Aerosol Direct Radiative Effect  

NASA Technical Reports Server (NTRS)

The diurnal variability of aerosol optical depth (AOD) can be significant, depending on location and dominant aerosol type. However, these diurnal cycles have rarely been taken into account in measurement-based estimates of aerosol direct radiative forcing (ADRF) or aerosol direct radiative effect (ADRE). The objective of our study was to estimate the influence of diurnal aerosol variability at the top of the atmosphere ADRE estimates. By including all the possible AERONET sites, we wanted to assess the influence on global ADRE estimates. While focusing also in more detail on some selected sites of strongest impact, our goal was to also see the possible impact regionally.We calculated ADRE with different assumptions about the daily AOD variability: taking the observed daily AOD cycle into account and assuming diurnally constant AOD. Moreover, we estimated the corresponding differences in ADREs, if the single AOD value for the daily mean was taken from the the Moderate Resolution Imaging Spectroradiometer (MODIS) Terra or Aqua overpass times, instead of accounting for the true observed daily variability. The mean impact of diurnal AOD variability on 24 h ADRE estimates, averaged over all AERONET sites, was rather small and it was relatively small even for the cases when AOD was chosen to correspond to the Terra or Aqua overpass time. This was true on average over all AERONET sites, while clearly there can be much stronger impact in individual sites. Examples of some selected sites demonstrated that the strongest observed AOD variability (the strongest morning afternoon contrast) does not typically result in a significant impact on 24 h ADRE. In those cases, the morning and afternoon AOD patterns are opposite and thus the impact on 24 h ADRE, when integrated over all solar zenith angles, is reduced. The most significant effect on daily ADRE was induced by AOD cycles with either maximum or minimum AOD close to local noon. In these cases, the impact on 24 h ADRE was typically around 0.1-0.2W/sq m (both positive and negative) in absolute values, 5-10% in relative ones.

Arola, A.; Eck, T. F.; Huttunen, J.; Lehtinen, K. E. J.; Lindfors, A. V.; Myhre, G.; Smirinov, A.; Tripathi, S. N.; Yu, H.

2013-01-01

219

Search for Higher Order Effects in Allowed beta Transitions  

Microsoft Academic Search

The beta-gamma directional correlations of several allowed beta transitions with unusually large ft values (ft>7) were measured. Effects of second-forbidden beta components are expected to manifest themselves in small observable anisotropies if second-forbidden matrix elements are not reduced appreciably by those nuclear-structure effects that cause the reduction of the allowed matrix elements. The experimental results for the anisotropy factor A22(W)

Z. W. Grabowski; R. S. Raghavan; R. M. Steffen

1965-01-01

220

Direct comparison of pulsating aurora observed simultaneously by the FAST satellite and from the ground at Syowa  

E-print Network

Direct comparison of pulsating aurora observed simultaneously by the FAST satellite and from September 2002; published 15 November 2002. [1] We have made a direct comparison of a pulsating aurora: a poleward moving pulsation and a standing mode pulsation, each with a period of $5 sec. The aurora occurs

California at Berkeley, University of

221

Toward an Environmental Assessment of Social Determinants of Health: Direct Observations of Latino Neighborhoods in Kansas City  

E-print Network

Toward an Environmental Assessment of Social Determinants of Health: Direct Observations of Latino Neighborhoods in Kansas City CaraSmith (FacultyAdvisor: Stephen Fawcett) Applied Behavioral Science ABSTRACT The environment - including exposure... environmental features - exposures related to social determinants - can be assessed by direct observation. A checklist and measurement protocol was created for this purpose. This two-page environmental assessment was used to document the occurrence or non...

Smith, Cara

2012-04-01

222

Direct observation of Guanine radical cation deprotonation in g-quadruplex DNA.  

PubMed

Although numerous studies have been devoted to the charge transfer through double-stranded DNA (dsDNA), one of the major problems that hinder their potential applications in molecular electronics is the fast deprotonation of guanine cation (G(+•)) to form a neutral radical that can cause the termination of hole transfer. It is thus of critical importance to explore other DNA structures, among which G-quadruplexes are an emerging topic. By nanosecond laser flash photolysis, we report here the direct observation and findings of the unusual deprotonation behavior (loss of amino proton N2-H instead of imino proton N1-H) and slower (1-2 orders of magnitude) deprotonation rate of G(+•) within G-quadruplexes, compared to the case in the free base dG or dsDNA. Four G-quadruplexes AG3(T2AG3)3, (G4T4G4)2, (TG4T)4, and G2T2G2TGTG2T2G2 (TBA) are measured systematically to examine the relationship of deprotonation with the hydrogen-bonding surroundings. Combined with in depth kinetic isotope experiments and pKa analysis, mechanistic insights have been further achieved, showing that it should be the non-hydrogen-bonded free proton to be released during deprotonation in G-quadruplexes, which is the N2-H exposed to solvent for G bases in G-quartets or the free N1-H for G base in the loop. The slower N2-H deprotonation rate can thus ensure less interruption of the hole transfer. The unique deprotonation features observed here for G-quadruplexes open possibilities for their interesting applications as molecular electronic devices, while the elucidated mechanisms can provide illuminations for the rational design of G-quadruplex structures toward such applications and enrich the fundamental understandings of DNA radical chemistry. PMID:25506785

Wu, Lidan; Liu, Kunhui; Jie, Jialong; Song, Di; Su, Hongmei

2015-01-14

223

Quantifying aerosol direct effects from broadband irradiance and spectral aerosol optical depth observations  

NASA Astrophysics Data System (ADS)

outline a methodology using broadband and spectral irradiances to quantify aerosol direct effects on the surface diffuse shortwave (SW) irradiance. Best Estimate Flux data span a 13 year timeframe at the Department of Energy Atmospheric Radiation Measurement Program's Southern Great Plains (SGP) site. Screened clear-sky irradiances and aerosol optical depth (AOD), for solar zenith angles ? 65°, are used to estimate clear-sky diffuse irradiances. We validate against detected clear-sky observations from SGP's Basic Radiation System (BRS). BRS diffuse irradiances were in accordance with estimates, producing a root-mean-square error and mean bias errors of 4.0 W/m2 and -1.4 W/m2, respectively. Absolute differences show 99% of estimates within ±10 W/m2 (10%) of the mean BRS observations. Clear-sky diffuse estimates are used to derive quantitative estimates of aerosol radiative effects, represented as the aerosol diffuse irradiance (ADI). ADI is the contribution of diffuse SW to global SW, attributable to scattering of atmospheric transmission by natural plus anthropogenic aerosols. Estimated slope for the ADI as a function of AOD indicates an increase of ~22 W/m2 in diffuse SW for every 0.1 increase in AOD. Such significant increases in the diffuse fraction could possibly increase photosynthesis. Annual mean ADI is 28.2 W/m2, and heavy aerosol loading at SGP provides up to a maximum increase of 120 W/m2 in diffuse SW over background conditions. With regard to seasonal variation, the mean diffuse forcings are 17.2, 33.3, 39.0, and 23.6 W/m2 for winter, spring, summer, and fall, respectively.

Creekmore, Torreon N.; Joseph, Everette; Long, Charles N.; Li, Siwei

2014-05-01

224

Direct observation of ?-actinin tension and recruitment at focal adhesions during contact growth.  

PubMed

Adherent cells interact with extracellular matrix via cell-substrate contacts at focal adhesions. The dynamic assembly and disassembly of focal adhesions enables cell attachment, migration and growth. While the influence of mechanical forces on the formation and growth of focal adhesions has been widely observed, the force loading on specific proteins at focal adhesion complex is not clear. By co-expressing force sensitive ?-actinin FRET probes and fluorescence labeled paxillin in MDCK cells, we have simultaneously observed the time-dependent changes in tension in ?-actinin and the dynamics of focal adhesion during cell migration. We show that increase in tension in ?-actinin at the focal adhesion coincides with elongation of the adhesion in its growth phase. The enlargement of focal adhesion is through a force sensitive recruitment of ?-actinin and paxillin to the adhesion sites. Changes in ?-actinin tension and correlated relocation of ?-actinin in an active adhesion also guide the growth direction of the adhesion. The results support the model that cytoskeletal tension is coupled to focal adhesion via the linking protein, ?-actinin at the adhesion complex. Lysophosphatidic acid caused an immediate increase in ?-actinin tension followed by drastic focal adhesion formation and elongation. Application of Rho-ROCK inhibitor, Y27632, resulted in reversible reduction in tension in ?-actinin and disassociation of focal adhesion, suggesting the involvement of myosin-II mediated contractile force in the focal adhesion dynamics. These findings suggest that ?-actinin not only serves as a physical linker between cytoskeleton and integrin, but also participates in force transmission at adhesion sites to facilitate adhesion?s growth. PMID:25088253

Ye, Nannan; Verma, Deepika; Meng, Fanjie; Davidson, Michael W; Suffoletto, Kevin; Hua, Susan Z

2014-09-10

225

Quantifying Aerosol Direct Effects from Broadband Irradiance and Spectral Aerosol Optical Depth Observations  

SciTech Connect

We outline a methodology using broadband and spectral irradiances to quantify aerosol direct effects on the surface diffuse shortwave (SW) irradiance. Best Estimate Flux data span a 13 year timeframe at the Department of Energy Atmospheric Radiation Measurement Program’s Southern Great Plains (SGP) site. Screened clear-sky irradiances and aerosol optical depth (AOD), for solar zenith angles ? 65°, are used to estimate clear-sky diffuse irradiances. We validate against detected clear-sky observations from SGP’s Basic Radiation System (BRS). BRS diffuse irradiances were in accordance with estimates, producing a root-mean-square error and mean bias errors of 4.0 W/m2 and -1.4 W/m2, respectively. Absolute differences show 99% of estimates within ±10 W/m2 (10%) of the mean BRS observations. Clear-sky diffuse estimates are used to derive quantitative estimates of aerosol radiative effects, represented as the aerosol diffuse irradiance (ADI). ADI is the contribution of diffuse SW to global SW, attributable to scattering of atmospheric transmission by natural plus anthropogenic aerosols. Estimated slope for the ADI as a function of AOD indicates an increase of ~22 W/m2 in diffuse SW for every 0.1 increase in AOD. Such significant increases in the diffuse fraction could possibly increase photosynthesis. Annual mean ADI is 28.2 W/m2, and heavy aerosol loading at SGP provides up to a maximum increase of 120 W/m2 in diffuse SW over background conditions. With regard to seasonal variation, the mean diffuse forcings are 17.2, 33.3, 39.0, and 23.6 W/m2 for winter, spring, summer, and fall, respectively.

Creekmore, Torreon N.; Joseph, Everette; Long, Charles N.; Li, Siwei

2014-05-16

226

Investigation of droplet jumping on superhydrophobic coatings during dew condensation by the observation from two directions  

NASA Astrophysics Data System (ADS)

Superhydrophobic coatings with nanoscale random roughness structure were prepared onto a Si substrate using boehmite (AlOOH) particles and hydrophobic silanes. The samples were cooled by a Peltier cooling element. Then spontaneous jumping behavior of the water droplets that had condensed on the coatings was observed from two directions (top-view and side-view) using high-speed camera systems. Spontaneous jumping of water droplets occurred subsequent to the coalescence of more than two water droplets, deformation, and shape recovery. Small droplets exhibited high initial jumping velocity, which decreased concomitantly with increasing difference in droplet size before coalescence. The actual jumping velocity was lower than the theoretical one, suggesting the existence of energy dissipation. When the sample was declined at 30°, the jumping frequency of water droplets fluctuated against the cooling time with repetition of the increasing-decreasing cycle, and sustained a certain value. The water droplet jumping height was increased remarkably under an external electric field. The droplet possessed positive charge. Coulombic force was expected to contribute to this phenomenon.

Yanagisawa, Kosuke; Sakai, Munetoshi; Isobe, Toshihiro; Matsushita, Sachiko; Nakajima, Akira

2014-10-01

227

Adaptive optics operation with focal wavefront sensor in a coronagraph for direct observation of exoplanets  

NASA Astrophysics Data System (ADS)

A stellar coronagraph system for direct observations of extra solar planets is under development by combining unbalanced nulling interferometer (UNI), adaptive optics, and a focal plane mask coronagraph1,2,3,4,5,6. It can reach a high contrast as using ?/10000 precision optics by ?/1000 quality ones. However, a sufficient high contrast is not obtained yet in the experiment before. It is thought that the remained speckle noise at the final coronagraph focal plane detector are produced by a "non-common path error" of ?/100 level, which is a wavefront error of the coronagraph different from that of a wavefront sensor (WFS) of adaptive optics, even when the WFS indicates ?/1000 conversion. The non-common path error can be removed by the dark zone method that is the way of wavefront correction by wavefront sensing at the final focal plane detector, although it has an issue of operation for very faint targets because of a slow feedback loop. In the present paper, we describe that our coronagraph system becomes practically higher contrast by upgrading the control method of deformable mirror (DM) with the WFS assisted by final focal plane wavefront sensing method. We accomplished contrast of 8×10-7 relative to the star in experiment.

Oya, Masahito; Nishikawa, Jun; Horie, Masaaki; Sato, Kazuma; Fukase, Masao; Murakami, Naoshi; Kotani, Takayuki; Kumagai, Shiomi; Tamura, Motohide; Tanaka, Yosuke; Kurokawa, Takashi

2014-08-01

228

Direct observation of crystal growth from solution using optical investigation of a growing crystal face  

NASA Technical Reports Server (NTRS)

The first technical report for the period 1 Jan. 1993 till 31 Dec. 1993 for the research entitled, 'Direct observation of crystal growth from solution using Optical Investigation of a growing crystal Face' is presented. The work on the project did not start till 1 June 1993 due to the non-availability of the required personnel. The progress of the work during the period 1 June 1993 till the end of 1993 is described. Significant progress was made for testing various optical diagnostic techniques for monitoring crystal solution. Some of the techniques that are being tested are: heterodyne detection technique, in which changes in phase are measured as a interferometric function of time/crystal growth; a conventional technique, in which a fringe brightness is measured as a function of crystal growth/time; and a Mach-Zehnder interferometric technique in which a fringe brightness is measured as a function of time to obtain information on concentration changes. During the second year it will be decided to incorporate the best interferometric technique along with the ellipsometric technique, to obtain real time in-situ growth rate measurements. A laboratory mock-up of the first two techniques were made and tested.

Lal, Ravindra

1994-01-01

229

[Longitudinal observation of pulmonary tuberculosis patients by Gen-Probe Mycobacterium tuberculosis direct test (MTD)].  

PubMed

To study the clinical significance of conducting Gen-Probe Mycobacterium tuberculosis Direct Test (MTD) during the course of the disease, sputum specimens from 19 pulmonary tuberculosis patients were smeared, cultured, and tested by MTD, once a month for five months from the initiation of chemotherapy. 1) MTD-positive rates declined in parallel with decreased pulmonary tuberculosis activity, and the MTD findings of 16 patients who presented mild to moderate pulmonary tuberculosis at admission became negative by four months after the beginning of treatment. Three patients (15.8%) who were consistently positive for MTD during five months after the beginning of treatment were serious pulmonary tuberculosis patients, excreting a large number of organisms at admission. 2) During the course, a total of 43 MTD negative findings were observed, of which one (2.3%) was positive for Ogawa medium culture and the other 42 (92.7%) were negative. MTD was useful in briefly determining the absence of infection, provided that a negative culture on Ogawa medium means no infection. 3) Eleven of the 12 specimens (91.7%) showing positive smears and negative cultures on Ogawa medium were positive for MTD. Since MTD shows negative results for atypical mycobacteria, this is a very useful test in identifying acid fast bacilli which shows a positive smear and a negative culture. PMID:7745308

Toyoda, T; Aoyagi, T; Osumi, M; Kawashiro, T

1995-03-01

230

Direct Observation and Analysis of Bacterial Growth on an Antimicrobial Surface?  

PubMed Central

Cells of Escherichia coli NBRC 3972 and Staphylococcus aureus NBRC 12732 were inoculated onto an agar (1.5%) medium varying in nutrient concentration from full strength of the nutrient broth (NB) to 1/10 NB. Immediately thereafter, the inoculated agar was placed on antimicrobial and nonantimicrobial surfaces in such a way that the microbial cells came into contact with these surfaces. Cell growth was directly observed under a microscope, and the growth rate constant of the cells was measured based on the increase in the area of the colonies formed by the growing cells. On the antimicrobial surface, the growth rate constant decreased at lower nutrient concentrations for both E. coli and S. aureus cells, whereas it showed little change on the nonantimicrobial surface. It was supposed that either the nutrient uptake or the nutrient utilization efficiency was retarded by the antimicrobial surface. At the lowest nutrient concentration examined in the present study, 1/10 NB, the cells could hardly grow on the antimicrobial surface, indicating that the surface would be sufficiently active in preventing bacterial growth under normal usage conditions, such as the wet areas of a kitchen. It was also revealed that the antimicrobial surface could prevent the division of cells either during the growth stage or before the onset of growth. PMID:20562272

Yamada, Hiroyuki; Takahashi, Nobuyuki; Okuda, Shujiro; Tsuchiya, Yuki; Morisaki, Hisao

2010-01-01

231

Direct observation of polymer network structure in macroporous N-isopropylacrylamide gel by Raman microscopy  

NASA Astrophysics Data System (ADS)

Raman microscopy technique is used to directly observe the pore structures of a macroporous N-isopropylacrylamide (NIPA) gel as a function of temperature. The gel is synthesized using a suspension of 45-wt. % toluene and 55-wt. % pre-gel NIPA solution. The intensity of the band due to the CH2 bending vibration, centered at 1445 cm-1, is used to monitor the distribution of the polymer chains density in the lateral plane. It is found that the macroporous gel consists of water-rich areas, which can be interpreted as the pores, and polymer-rich areas. At room temperature, the average size of the pores and the width of polymer-rich areas are 75 microns, and 20 microns, respectively. Both the pores and their surrounding polymer-rich areas have random geometry as demonstrated by the three-dimensional Raman microimaging. With increased temperature the size of the pores decreases. This process is accompanied by a narrowing of the polymer-rich areas. At higher temperatures polymer chains bunch together and this process accelerates rapidly near the volume phase transition temperature (307 K). Above 309 K, the pore sizes become too small to be resolved using Raman microscopy.

Appel, R.; Wei, X.; Zerda, T. W.; Hu, Z.

1997-10-01

232

Autocompensation of torque ripple of direct drive motor by torque observer  

Microsoft Academic Search

Since a direct drive motor (DDM) does not require a reduction gear, the drive system can be made simple, and therefore it is used in high-precision robot and machine tool applications. However, without reduction gear, a disturbance torque is directly reflected to the motor shaft, and a torque ripple generated by the motor is directly transmitted to the load, causing

Nobuyuki Matsui; Tatsuo Makino; Hirokazu Satoh

1993-01-01

233

Direct real-space observation of nearly stochastic behavior in magnetization reversal process on a nanoscale  

SciTech Connect

We report a non-deterministic nature in the magnetization reversal of nanograins of CoCrPt alloy film. Magnetization reversal process of CoCrPt alloy film is investigated using high resolution soft X-ray microscopy which provides real space images with a spatial resolution of 15 nm. Domain nucleation sites mostly appear stochastically distributed within repeated hysteretic cycles, where the correlation increases as the strength of the applied magnetic field increases in the descending and ascending branches of the major hysteresis loop. In addition, domain configuration is mostly asymmetric with inversion of an applied magnetic field in the hysteretic cycle. Nanomagnetic simulation considering thermal fluctuations of the magnetic moments of the grains explains the nearly stochastic nature of the domain nucleation behavior observed in CoCrPt alloy film. With the bit size in high-density magnetic recording media approaching nanometer length scale, one of the fundamental and crucial issues is whether the domain nucleation during magnetization reversal process exhibits a deterministic behavior. Repeatability of local domain nucleation and deterministic switching behavior are basic and essential factors for achieving high performance in high-density magnetic recording [1-3]. Most experimental studies on this issue reported so far have been mainly performed by indirect probes through macroscopic hysteresis loop and Barkhausen pattern measurements, which provide the ensemble-average magnetization. Thus, they are inadequate to gain insight into the domain-nucleation behavior on a nanometer length scale during the magnetization reversal process [4-6]. Very recently, coherent X-ray speckle metrology, where the speckle pattern observed in reciprocal space acts as a fingerprint of the domain configurations, was adopted to investigate stochastic behavior in the magnetization reversal of a Co/Pt multilayer film [7,8]. However, no direct observation on the stochastic behavior of domain nucleation during magnetization reversal in real space at the nanometer scale has yet been reported. The main reason is due to limitations of the microscopic measurement techniques employed. Thus, experimental confirmation for stochastic behavior of domain nucleation together with its clarification has to date remained a scientific challenge.

Im, M.-Y.; Kim, D.-H.; Lee, K.-D.; Fischer, P.; Shin, S.-C.

2007-06-01

234

Direct observation of extrasolar planets and the development of the gemini planet imager integral field spectrograph  

NASA Astrophysics Data System (ADS)

This thesis is focused on the development and testing of a new instrument capable of finding and characterizing recently-formed Jupiter-sized planets orbiting other stars. To observe these planets, I present the design, construction and testing of the Gemini Planet Imager (GPI) Integral Field Spectrograph (IFS). GPI is a facility class instrument for the Gemini Observatory with the primary goal of directly detecting young Jovian planets. The GPI IFS utilizes an infrared transmissive lenslet array to sample a rectangular 2.7 x 2.7 arcsecond field of view and provide low-resolution spectra across five bands between 1 and 2.5 mum. The dispersing element can be replaced with a Wollaston prism to provide broadband polarimetry across the same five filter bands. The IFS construction was based at the University of California, Los Angeles in collaboration with the Universite de Montreal, Immervision and Lawrence Livermore National Laboratory. I will present performance results, from in-lab testing, of the Integral Field Spectrograph (IFS) for the Gemini Planet Imager (GPI). The IFS is a large, complex, cryogenic, optical system requiring several years of development and testing. I will present the design and integration of the mechanical and optical performance of the spectrograph optics. The IFS passed its pre-ship review in 2011 and was shipped to University of California, Santa Cruz for integration with the remaining sub-systems of GPI. The UCLA built GPI IFS was integrated with the rest of GPI and is delivering high quality spectral datacubes of GPI's coronagraphic field. Using the NIRC2 instrument located at the Keck Observatory, my collaborators and I observed the planetary companion to beta Pictoris in L' (3.5--4.1mum). Observations taken in the fall of 2009 and 2012 are used to find the location and inclination of the planet relative to the massive debris disk orbiting beta Pictoris. We find that the planet's orbit has a position angle on the sky of 211.9+/-0.4 degrees, making the planet misaligned by 2.9+/-0.5 degrees from the main disk, consistent with other observations that beta Pic b is misaligned with the main disk, and part of the misaligned inner disk. In 2009 & 2012 we find a projected orbital separation of 312.8 +/- 18.3 and 466.35 +/- 8.4 milliarcseconds consistent with an orbital period of ˜ 20 years, and a semi-major axis of ˜ 9 AU as found by Macintosh et al. (2014). During the first commissioning observations with the Gemini Planet Imager (GPI), my collaborators and I took the first H-band spectrum of the planetary companion to the nearby young star beta Pictoris. The spectrum has a resolving power of ˜ 45 and demonstrates the distinctive triangular shape of a cool substellar object with low surface gravity. Using atmospheric models, we find an effective temperature of 1650 +/- 50K and a surface gravity of log(g) = 4.0 +/- 0.25 (cgs units). These values agree well with predictions from planetary evolution models for a gas giant with mass between 10 and 12 MJup and age between 10 and 20 Myrs. The spectrum is very similar to a known low mass field brown dwarf but has more flux at the long wavelength end of the filters compared to models. Given the very high signal-to-noise of our spectrum this likely indicates additional physics such as patchy clouds that need to be included in the model.

Chilcote, Jeffrey Kaplan

235

International Journal of Applied Earth Observation and Geoinformation 26 (2014) 387398 Contents lists available at ScienceDirect  

E-print Network

International Journal of Applied Earth Observation and Geoinformation 26 (2014) 387­398 Contents lists available at ScienceDirect International Journal of Applied Earth Observation and Geoinformation eigenvectors for remote sensing image transformations Derek Roggea, , Martin Bachmanna , Benoit Rivardb , Allan

236

International Journal of Applied Earth Observation and Geoinformation 34 (2015) 188197 Contents lists available at ScienceDirect  

E-print Network

International Journal of Applied Earth Observation and Geoinformation 34 (2015) 188­197 Contents lists available at ScienceDirect International Journal of Applied Earth Observation and Geoinformation,c , Hankui Zhange , George Alan Blackburnf , Jing Yang , Jianhong Liuh a Institute of Applied Remote Sensing

Blackburn, Alan

237

International Journal of Applied Earth Observation and Geoinformation 30 (2014) 3041 Contents lists available at ScienceDirect  

E-print Network

International Journal of Applied Earth Observation and Geoinformation 30 (2014) 30­41 Contents lists available at ScienceDirect International Journal of Applied Earth Observation and Geoinformation: Received 24 August 2013 Accepted 15 January 2014 Keywords: Landsat MODIS Rangeland Remote sensing STARFM

Lawrence, Rick L.

238

Observations of fast protons above 1 MeV produced in direct-drive laser-fusion experiments  

E-print Network

Observations of fast protons above 1 MeV produced in direct-drive laser-fusion experiments D. G observed on previous, single-beam experiments at the same I 2 . The total energy in the proton spectrum high-intensity laser interactions with solids has been ob- served in many previous experiments.1

239

29 CFR 15.22 - Allowable claims.  

Code of Federal Regulations, 2010 CFR

...be allowed for damage to, or loss of, property as a direct consequence...be allowed for damage to, or loss, of property when used for...be allowed for damage to, or loss of, clothing and accessories...person, such as eyeglasses, hearing aids, or dentures....

2010-07-01

240

Measuring Learning Styles with Questionnaires Versus Direct Observation of Preferential Choice Behavior in Authentic Learning Situations: The Visualizer\\/Verbalizer Behavior Observation Scale (VV-BOS)  

Microsoft Academic Search

Research on learning styles and their assessment has been the focus of growing interest due to rapid advances in educational multimedia applications. As an alternative to conventional questionnaires, the VV-BOS, a computer-based instrument for direct observation of students' preference for visual or verbal learning material in an authentic learning situation, was developed. A study with 103 second language learners was

Detlev Leutner; Jan L. Plass

1998-01-01

241

The Photochemical Reflectance Index from Directional Cornfield Reflectances: Observations and Simulations  

NASA Technical Reports Server (NTRS)

The two-layer Markov chain Analytical Canopy Reflectance Model (ACRM) was linked with in situ hyperspectral leaf optical properties to simulate the Photochemical Reflectance Index (PRI) for a corn crop canopy at three different growth stages. This is an extended study after a successful demonstration of PRI simulations for a cornfield previously conducted at an early vegetative growth stage. Consistent with previous in situ studies, sunlit leaves exhibited lower PRI values than shaded leaves. Since sunlit (shaded) foliage dominates the canopy in the reflectance hotspot (coldspot), the canopy PRI derived from field hyperspectral observations displayed sensitivity to both view zenith angle and relative azimuth angle at all growth stages. Consequently, sunlit and shaded canopy sectors were most differentiated when viewed along the azimuth matching the solar principal plane. These directional PRI responses associated with sunlit/shaded foliage were successfully reproduced by the ACRM. As before, the simulated PRI values from the current study were closer to in situ values when both sunlit and shaded leaves were utilized as model input data in a two-layer mode, instead of a one-layer mode with sunlit leaves only. Model performance as judged by correlation between in situ and simulated values was strongest for the mature corn crop (r = 0.87, RMSE = 0.0048), followed by the early vegetative stage (r = 0.78; RMSE = 0.0051) and the early senescent stage (r = 0.65; RMSE = 0.0104). Since the benefit of including shaded leaves in the scheme varied across different growth stages, a further analysis was conducted to investigate how variable fractions of sunlit/shaded leaves affect the canopy PRI values expected for a cornfield, with implications for 20 remote sensing monitoring options. Simulations of the sunlit to shaded canopy ratio near 50/50 +/- 10 (e.g., 60/40) matching field observations at all growth stages were examined. Our results suggest in the importance of the sunlit/shaded fraction and canopy structure in understanding and interpreting PRI.

Cheng, Yen-Ben; Middleton, Elizabeth M.; Zhang, Qingyuan; Corp, Lawrence A.; Dandois, Jonathan; Kustas, William P.

2012-01-01

242

All-sky Aerosol Direct Radiative Effect from Merged CALIOP and A-train Observations  

NASA Astrophysics Data System (ADS)

Observation-based estimates of global aerosol radiative effects have been hampered by satellite aerosol retrievals restricted to clear-sky conditions. Assumptions or model estimates are then required to extend the clear-sky estimates to all-sky conditions. In addition to aerosol optical properties, the cloudy-sky effects depend in part on the relative vertical distribution of aerosol and cloud. This represents a major uncertainty in model estimates of aerosol forcing, as the aerosol vertical distribution is poorly constrained and there is a large diversity between models. These uncertainties can be reduced using observations from the CALIOP lidar, on the CALIPSO satellite, which retrieves the vertical distribution of aerosol extinction in both clear and cloudy skies. Estimates of the direct radiative effect (DRE) of the total aerosol (natural plus anthropogenic) have been performed, making use of the CERES-MODIS-CALIPSO-CloudSat (C3M) product. C3M contains profiles of SW and LW irradiance computed from instantaneous, collocated MODIS aerosol/cloud data and profiles from CALIPSO and CloudSat, all matched to CERES footprints. Aerosol extinction profiles in both clear and cloudy skies come from CALIOP. Aerosol absorption, which is not retrieved by either CALIOP or MODIS, is estimated using a combination of aerosol type information from CALIOP and the MATCH global aerosol model. Diurnally averaged fluxes are derived and used to estimate annual and seasonal mean DRE. Global mean all-sky SW TOA DRE is found to be reduced in magnitude relative to clear-sky DRE, due to a combination of cloud-masking of low-altitude aerosol and enhanced warming of aerosol above cloud. The reduced cooling effect of absorbing aerosol in cloudy skies significantly offsets the clear-sky aerosol cooling in several regions: southern Africa, south and east Asia, South America, and the subtropical Atlantic, due primarily to aerosol absorption by pollution, smoke from biomass burning, and Sahara dust, respectively. The largest uncertainty in these estimates of DRE comes from uncertainty in aerosol absorption. Sensitivity studies have been performed to estimate uncertainties. Details of the approach will be presented, along with a discussion of results and uncertainties.

Winker, D. M.; Kato, S.; Tackett, J. L.; Omar, A. H.

2012-12-01

243

Major outcomes of patients with tuberculous meningitis on directly observed thrice a week regime  

PubMed Central

Background: Revised National Tuberculosis Control Programme (RNTCP) of Government of India provides intermittent thrice-a-week directly observed treatment short course (RNTCP regimen). Objective: Assessments of all-cause mortality and nine-month morbidity outcomes of patients with tuberculous meningitis (TBM) on RNTCP regimen. Materials and Methods: We prospectively followed up patients registered with RNTCP center, with a diagnosis of TBM from January 1st, 2010 to December 31st, 2011. Morbidity was assessed using modified Rankin Scale (mRS). Results: We had 43 patients with median duration for follow-up of 396 days and that of survivors of 425 days. Two patients defaulted. Fourteen patients (32.5%) had mRS score of 4 to 6 and 29 had mRS of 0 to 3 after 9-month treatment. Severe disability was not related to any factor on logistic regression. Severe disability was seen in one patient (6.66%) among the 15 patients with stage 1, nine (37.5%) out of 24 patients with stage 2 and three (75%) out of 4 patients with stage 3 disease. Eight patients died (18.6%) of whom 4 died during the intensive phase and 4 during the continuation phase of RNTCP regimen. Mortality was independently related to treatment failure with adjusted Hazard ratio of 8.29 (CI: 1.38-49.78) (P = 0.02). One patient (6.66%) died out of the 15 patients with stage 1 disease, 5 (20.8%) out of 24 patients with stage 2 disease and 2 (50%) out of the 4 with stage 3 disease. Discussion and Conclusion: RNTCP regimen was associated with good compliance, comparable mortality and morbidity. PMID:25221396

Iype, Thomas; Pillai, Ayyappan Kunjukrishna; Cherian, Ajith; Nujum, Zinia T.; Pushpa, Chithra; Dae, Dalus; Krishnapillai, Vijayakumar

2014-01-01

244

Estimation of aerosol direct radiative effects for all-sky conditions from CERES and MODIS observations  

NASA Astrophysics Data System (ADS)

Satellite observations have shown the global average of the aerosol direct radiative effect (DRE) at the top of the atmosphere to be approximately -5.0 W m-2. Although there is a general consensus on this quantity, it is essentially biased toward clear-sky conditions. To circumvent this limitation, the present study introduces a new method for retrieving the global DRE of aerosol over the region of 60°S-60°N for all-sky conditions (both clear and cloudy skies). The all-sky DRE was calculated on a monthly basis by combining the measured DRE for a clear sky and the simulated DRE for a cloudy sky in 1°×1° grids. For the measured clear-sky DRE, we employed aerosol, cloud, and radiation fluxes from the Cloud and Earth's Radiant Energy System (CERES) instrument and the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the Terra satellite for May 2000-December 2005. For the simulated cloudy-sky DRE, we performed radiative transfer modeling with the MODIS cloud properties in addition to the aerosol optical properties independently estimated in this study that include asymmetry factor and single scattering albedo. The results show that the global mean±standard deviation of DRE for the all-sky scene is -3.1±1.0 W m-2, which is weaker than that for the clear-sky only. This is in good agreement with the global estimates from previous studies based on different methods. The main advantage of our method is near-real-time estimation of monthly global all-sky DRE that has physical consistency with the CERES data.

Oh, Hye-Ryun; Choi, Yong-Sang; Ho, Chang-Hoi; Jeong, Myeong-Jae

2013-09-01

245

Direct observation of increasing CO 2 in the Weddell Gyre along the Prime Meridian during 1973-2008  

NASA Astrophysics Data System (ADS)

The World Ocean takes up a large portion of the anthropogenic CO 2 emitted into the atmosphere. Determining the resulting increase in dissolved inorganic carbon ( CT, expressed in ?mol kg -1) is challenging, particularly in the sub-surface and deep Southern Ocean where the time rate of change of CT (in ?mol kg -1 decade -1) is commonly expected to be low. We present a determination of this time trend of CT in a dataset of measurements that spans 35 years comprising 10 cruises in the 1973-2008 period along the 0°-meridian in the Weddell Gyre. The inclusion of many cruises aims to generate results that are more robust than may be obtained by taking the difference between only one pair of cruises, each of which may suffer from errors in accuracy. To further improve consistency between cruises, data were adjusted in order to obtain time-invariant values of CT (and other relevant parameters) over the 35 years in the least ventilated local water body, this comprising the deeper Warm Deep Water (WDW) and upper Weddell Sea Deep Water (WSDW). It is assumed that this normalization procedure will allow trends in CT in the more intensely ventilated water masses to be more clearly observed. Time trends were determined directly in measurements of CT, and alternatively in back-calculated values of preformed CT ( CT0; i.e., the CT of the water at the time that it lost contact with the atmosphere). The determined time trends may be attributed to a combination of natural variability (in hydrography or biogeochemistry) and increased uptake of anthropogenic CO 2 from the atmosphere. In order to separate these natural and anthropogenic components, an analysis of the residuals of a multivariate linear regression (MLR), involving the complete time series of all 10 cruises, was additionally performed. This approach is referred to as the Time Series Residuals (TSR) approach. Using the direct method, the time trends of CT in the WSDW are quite small and non-significant at +0.176±0.321 ?mol kg -1 decade -1. On the other hand, the measured concentration of CT in the Weddell Sea Bottom Water (WSBW) is shown to rise slowly but significantly over the period from 1973 to 2008 at a rate of +1.151±0.563 ?mol kg -1 decade -1. The spatial distribution of these determined increases of CT in the deep Weddell Gyre closely resembles that of the increase of the anthropogenic tracer CFC-12, this strong similarity supporting a mostly anthropogenic cause for the increasing trend of CT. Time trends in back-calculated values of CT0 appear to be obscured due to uncertainties in the measurements of O 2. Finally, the shallow waters (<200 m depth) do not allow for interpretation since these are strongly affected by seasonality. Due to the small time trend signal in the WSBW, the TSR approach does not allow for unambiguous attribution of the observed trend in CT in the WSBW. The residuals of the TSR method do exhibit a time trend (considered representative of the time trend of Cant) of +0.445±0.405 ?mol kg -1 decade -1 (i.e., only 38% of the direct observed time trend in CT) thus only partly supporting the attribution of the measured time trend of CT to uptake of anthropogenic CO 2. Another TSR-derived result suggests that there is no significant time trend of biogeochemical changes. A time trend in hydrography of mixing between two deep water masses does exist, as evidenced by a slight positive time trend in the temperature of the WSBW, but is inadequate to explain the time trend of CT. After all, the time trend in measured CT is most straightforwardly ascribed entirely to uptake of Cant, and assuming an exponentially growing history of storage, the observed increase of CT in the WSBW suggests that a total amount of Cant of 6±3 ?mol kg -1 has accumulated in this water mass between the onset of the Industrial Revolution and 1995. Extrapolating the determined time trend, the rate of storage of Cant in the deep Weddell Gyre (>3000 m, west of 20°E) is calculated to be about 12±6 TgC yr -1 over the 1973-2008 period. This rate of storage is likely somewha

van Heuven, Steven M. A. C.; Hoppema, Mario; Huhn, Oliver; Slagter, Hans A.; de Baar, Hein J. W.

2011-12-01

246

Direct observation of microtubule dynamics at kinetochores in Xenopus extract spindles: implications for spindle mechanics  

Microsoft Academic Search

icrotubule plus ends dynamically attach to kineto- chores on mitotic chromosomes. We directly im- aged this dynamic interface using high resolution fluorescent speckle microscopy and direct labeling of kinetochores in Xenopus extract spindles. During meta- phase, kinetochores were stationary and under tension while plus end polymerization and poleward microtubule flux (flux) occurred at velocities varying from 1.5-2.5 ? m\\/ min.

Paul Maddox; Aaron Straight; Peg Coughlin; Timothy J. Mitchison; Edward D. Salmon

2003-01-01

247

Direct observation of driving, self reports of driver behaviour, and accident involvement  

Microsoft Academic Search

Forty-eight drivers answered a set of written questions about their driving style and drove a pre-defined, mixed urban and motorway route under observation. For 20 drivers there was a second observer in the car to check on inter-observer reliability. Relationships were examined between self-reports of driver behaviour and observers' reports, and between both of these and the number of accidents

ROBERT WEST; DAVINA FRENCH; RICHARD KEMP; JAMES ELANDER

1993-01-01

248

Nano-aquarium for dynamic observation of aquatic microorganisms fabricated by femtosecond laser direct writing of photostructurable glass  

NASA Astrophysics Data System (ADS)

We demonstrate the fabrication of three-dimensional (3-D) hollow microstructures embedded in photostructurable glass by a femtosecond (fs) laser direct writing. Fs laser direct writing followed by annealing and successive wet etching in dilute hydrofluoric (HF) acid solution resulted in the rapid manufacturing of microchips with 3-D hollow microstructures for the dynamic observation of living microorganisms in fresh water. The embedded microchannel structure enables us to analyze the continuous motion of Euglena gracilis. A microchamber with a movable microneedle demonstrates its ability for the elucidation of the information transmission process in Pleurosira laevis. Such microchips, referred to as nano-aquariums realize the efficient and highly functional observation of microorganisms.

Hanada, Y.; Sugioka, K.; Kawano, H.; Ishikawa, I.; Miyawaki, A.; Midorikawa, K.

2008-02-01

249

Observations on direct and cross tolerance with LSD and d-amphetamine in man  

Microsoft Academic Search

1.Within the limits of this experimental design in man:a)the spectrum of LSD effects is different from that of d-amphetamine in single doses to nontolerant subjectsb)following the daily administration of LSD for 14 days, direct tolerance develops to LSD (1.5 mcg\\/kg) with respect to pupillary dilatation and mental excitationc)following the daily administration of d-amphetamine for 14 days, direct tolerance develops to

D. E. Rosenberg; A. B. Wolbach; E. J. Miner; Harris Isbell

1963-01-01

250

Anna Freud: the Hampstead War Nurseries and the role of the direct observation of children for psychoanalysis.  

PubMed

The psychoanalytic tradition of direct observation of children has a long history, going back to the early 20th century, when psychoanalysis and the emerging field of 'child studies' came into fruitful contact in Freud's Vienna. As a leading figure in the attempted integration of direct observation with the new psychoanalytic knowledge emerging from the consulting room, Anna Freud played a crucial role in the emergence of this field. But her major contribution to the theory and practice of observing children came during the Second World War, when she founded the Hampstead War Nurseries. The author describes in detail this important period of Anna Freud's career, and discusses the impact it had on later work. He explores the theoretical contribution that Anna Freud made in the post-war years to the debate about the place of direct observation in psychoanalysis, and concludes that Anna Freud's 'double approach' (direct observation plus analytic reconstruction) still has a great deal to offer as a method of both psychoanalytic research and education. PMID:17681901

Midgley, Nick

2007-08-01

251

Simultaneous and two-directional high speed schlieren observation of effects of ignition points on vortex-flame interaction  

Microsoft Academic Search

To observe and analyze detailed processes of the vortex-flame interaction in the two-dimensional coherent structure, a premixed flame is generated by a spark ignition either at the center of an organized eddy or at the midpoint between two adjacent eddies, and the initial propagation stage of the spark-ignited flame is optically observed using the simultaneous and two-directional high speed schlieren

Norio Ohiwa; Yojiro Ishino; Motonobu Ikari; Shigeki Yamaguchi

2003-01-01

252

Near-field scanning optical microscopy enables direct observation of Moiré effects at the nanometer scale.  

PubMed

This work reports probing the Moiré effect directly at the nanometer scale via near-field scanning optical microscopy (NSOM). Periodic metal nanostructures of Au and Cu have been produced sequentially using particle lithography, and the overlapped regions serve as Moiré patterns at nanometer scale. The Moiré effect in these regions can be directly visualized from NSOM images, from which periodicity and structural details are accurately determined. In addition, the near-field Moiré effect was found to be very sensitive to structural changes, such as lateral displacement and/or rotations of the two basic arrays with respect to each other. Further, nanostructures of Cu exhibited higher photon transmission than Au from NSOM images. Collectively, NSOM enables direct visualization of the Moiré effect at nanoscale levels, from optical read out, and without enhancements or modification of the structures. The results demonstrate the feasibility to extend applications of the Moiré effect-based techniques to nanometer levels. PMID:22973942

Lin, Wei-feng; Li, Jie-Ren; Liu, Gang-yu

2012-10-23

253

Direct Observation Of Nanoparticle-Surfactant Interactions Using Small Angle Neutron Scattering  

NASA Astrophysics Data System (ADS)

Interactions of anionic silica nanoparticles with anionic, cationic and nonionic surfactants have directly been studied by contrast variation small angle neutron scattering (SANS). The measurements are performed on 1 wt% of both silica nanoparticles and surfactants of anionic sodium dodecyle sulphate (SDS), cationic dodecyltrimethyl ammonium bromide (DTAB) and non-ionic polyoxyethylene 10 lauryl ether (C12E10) in aqueous solution. We show that there is no direct interaction in the case of SDS with silica particles, whereas strong interaction for DTAB leads to the aggregation of silica particles. The interaction of C12E10 is found through the micelles adsorbed on the silica particles.

Kumar, Sugam; Aswal, V. K.

2010-12-01

254

Direct Evidence for Dynamical Evolution of Luminosity Functions of Globular Cluster Systems: HST/ACS observations of the 3-Gyr-old merger remnant NGC 1316  

E-print Network

Recent observations of globular clusters (GCs) in intermediate-age (2-4 Gyr old), early-type merger remnants have provided the hitherto `missing link' between young merger remnants and `normal' elliptical galaxies in the form of a GC subsystem with colors and luminosities consistent with population synthesis model predictions for those ages and ~solar metallicity. Here we present new, deep observations of the GC system of the intermediate-age merger remnant NGC 1316, using the ACS camera aboard Hubble Space Telescope, which allowed us to create luminosity functions (LFs) as a function of galactocentric radius. We find that the inner 50% of the `red' GC system shows a clear turnover in its LF, at about 1 mag fainter than that of the `old' blue GCs. This constitutes direct, dynamical evidence that metal-rich GC populations formed during a gas-rich merger can evolve into the `red', metal-rich GC populations that are ubiquitous in `normal' giant ellipticals.

Paul Goudfrooij

2004-04-08

255

Direct Observation of a Breit-Wigner Phase of a Wave Function  

NASA Astrophysics Data System (ADS)

The Breit-Wigner phase of a wave function was obtained by measuring the interference between two independent ionization paths of a molecule. The state of interest was present in only one of the paths, thereby producing a phase shift in the observed signal. An analytical theory was used to determine the phase of the wave function from the observable.

Fiss, Jeanette A.; Khachatrian, Ani; Truhins, Kaspars; Zhu, Langchi; Gordon, Robert J.; Seideman, Tamar

2000-09-01

256

PHYSICAL REVIEW B 88, 144307 (2013) Direct observation of the phonon dispersion of a three-dimensional solid/solid  

E-print Network

of the Brillouin zone. Theoretical calculations, based on the finite element method and the finite-difference time) and finite-difference time-domain (FDTD) methods offer tremendous insights on the phonon dispersion relationsPHYSICAL REVIEW B 88, 144307 (2013) Direct observation of the phonon dispersion of a three-dimensional

Deymier, Pierre

257

ERNE observations of energetic particles associated with Earth-directed coronal mass ejections in April and May, 1997  

E-print Network

ERNE observations of energetic particles associated with Earth-directed coronal mass ejections most eective in energetic ($1± 50 MeV) particle acceleration during the ®rst 18 months since the Solar we have deconvoluted the injection spectrum of energetic protons by using the method described

Paris-Sud XI, Université de

258

Direct observation of superconducting vortex clusters pinned by a periodic array of magnetic dots in ferromagnetic/superconducting hybrid structures  

E-print Network

Direct observation of superconducting vortex clusters pinned by a periodic array of magnetic dots flux quanta by a square array of 1- m-sized ferromagnetic dots in a magnetic-vortex state magnetoresistance measurements on the hybrid structures but suggest a modified picture of the pinning mechanism. DOI

Metlushko, Vitali

259

Bi-directional streaming of halo electrons in interplanetary plasma clouds observed between 0.3 and 1 AU  

NASA Technical Reports Server (NTRS)

The solar wind data obtained from the two Helios solar probes in the years 1974 to 1986 were systematically searched for the occurrence of bi-directional electron events. Most often these events are found in conjunction with shock associated magnetic clouds. The implications of these observations for the topology of interplanetary plasma clouds are discussed.

Ivory, K.; Schwenn, R.

1995-01-01

260

Direct observation of single molecule mobility in semidilute polymer solutions Heiko Zettl,* Ute Zettl, and Georg Krausch  

E-print Network

Direct observation of single molecule mobility in semidilute polymer solutions Heiko Zettl,* Ute that FCS is uniquely suited to explore polymer dynamics in solution. The mobility of the chains.061804 PACS number s : 61.25.Hq I. INTRODUCTION Diffusion and transport in polymer solutions is among

Enderlein, Jörg

261

Direct Observation of delta -crystallin Accumulation by Laser Light-Scattering Spectroscopy in the Chicken Embryo Lens  

Microsoft Academic Search

By using the technique of laser light-scattering spectroscopy, direct observation has been made on the intracellular accumulation of a crystallin protein within the cells of chicken embryo lens during the process of development. Appearance of delta -crystallin has been detected as early as day 4, and its concentration reaches a plateau at day 19. The measurements constitute a noninvasive determination

Shao-Tang Sun; Toyoichi Tanaka; Izumi Nishio; Joyce Peetermans; Jacob V. Maizel; Joram Piatigorsky

1984-01-01

262

DOI: 10.1002/adfm.200700162 Direct Observation of Super-Plasticity of Beta-SiC Nanowires  

E-print Network

] bending technique have shown low-temperature large strain plasticity of single- crystal SiC NW. HoweverDOI: 10.1002/adfm.200700162 Direct Observation of Super-Plasticity of Beta-SiC Nanowires at Low.[2,3] SiC, as a rein- forcing material behave with high hardness, high strength and high stiffness

Wang, Zhong L.

263

Solar Physics (2004) 224: 34 C Springer 2005 The topical issue of "Space Climate: Direct and Indirect Observations of  

E-print Network

Solar Physics (2004) 224: 3­4 C Springer 2005 PREFACE The topical issue of "Space Climate: Direct and Indirect Observations of Long-Term Solar Activity" is based on contributions presented at the First of solar activity, and their effects in the near-Earth environment and technoculture. As an analogy

Usoskin, Ilya G.

264

Establishing the Feasibility of Direct Observation in the Assessment of Tics in Children with Chronic Tic Disorders  

ERIC Educational Resources Information Center

Behavior analysis has been at the forefront in establishing effective treatments for children and adults with chronic tic disorders. As is customary in behavior analysis, the efficacy of these treatments has been established using direct-observation assessment methods. Although behavior-analytic treatments have enjoyed acceptance and integration…

Himle, Michael B.; Chang, Susanna; Woods, Douglas W.; Pearlman, Amanda; Buzzella, Brian; Bunaciu, Liviu; Piacentini, John C.

2006-01-01

265

The underlying magnetic field direction in Ulysses observations of the southern polar heliosphere  

SciTech Connect

Magnetic field data provided by the Ulysses spacecraft between May 1993 and January 1995 are presented for the south latitudes 30-80 dg. The deflections of the magnetic field direction are attributed to the intense Alfven waves. {copyright} {bold 1997 American Institute of Physics.}

Forsyth, R.J.; Balogh, A. [The Blackett Laboratory, Imperial College, London (United Kingdom); Smith, E.J.; Murphy, N. [Jet Propulsion Laboratory, Pasadena, California (United States); McComas, D.J. [Los Alamos National Laboratory, Los Alamos, New Mexico (United States)

1996-07-01

266

A scheme for direct observation of entanglement for Gaussian continuous variables  

E-print Network

We suggest an experimentally realizable scheme to test entanglement of a mixed Gaussian continuous variable state. We find that the entanglement condition is simplified for the family of Gaussian states which are relevant to experimental realization. The entanglement condition is then shown to be directly related to joint homodyne measurements. We show how robust the proposed test of entanglement is against imperfect detection efficiency.

M. S. Kim; Jinhyoung Lee

2002-03-29

267

Direct spectroscopic observation of charge-exchange recombination of medium-Z elements in the PLT tokamak  

SciTech Connect

We report the first observation of line emission resulting directly from charge-exchange recombination of medium-Z elements (Al, Sc) injected into a PLT discharge. Transitions due to the radiative cascade immediately following charge-exchange of He-like Al and Sc were observed by a VUV spectrograph and two air monochromators. In two cases, AlXI 3209 A and ScXIX 112.1 A, the observed transition had not previously been experimentally identified. Spatial scans provided information on the profile of the neutral beam in the plasma.

Skinner, C.H.; Suckewer, S.; Cohen, S.A.; Schilling, G.; Wilson, R.; Stratton, B.

1984-03-01

268

Direct observation of the mass renormalization in SrVO3 by angle resolved photoemission spectroscopy  

SciTech Connect

We have performed an angle-resolved photoemission study of the three-dimensional perovskite-type SrVO{sub 3}. Observed spectral weight distribution of the coherent part in the momentum space shows cylindrical Fermi surfaces consisting of the V 3d t{sub 2g} orbitals as predicted by local-density approximation (LDA) band-structure calculation. The observed energy dispersion shows a moderately enhanced effective mass compared to the LDA results, corresponding to the effective mass enhancement seen in the thermodynamic properties. Contributions from the bulk and surface electronic structures to the observed spectra are discussed based on model calculations.

Yoshida, t.

2010-05-03

269

Direct observation of keyhole characteristics in deep penetration laser welding with a 10 kW fiber laser.  

PubMed

Keyhole formation is a prerequisite for deep penetration laser welding. Understanding of the keyhole dynamics is essential to improve the stability of the keyhole. Direct observation of the keyhole during deep penetration laser welding of a modified "sandwich" specimen with a 10 kW fiber laser is presented. A distinct keyhole wall and liquid motion along the wall are observed directly for the first time. The moving liquid "shelf" on the front keyhole wall and the accompanying hydrodynamic and vapor phenomena are observed simultaneously. Micro-droplets torn off the keyhole wall and the resultant bursts of vapor are also visualized. The hydrodynamics on the keyhole wall has a dominant effect on the weld defects. The emission spectrum inside the keyhole is captured accurately using a spectrometer to calculate the characteristics of the keyhole plasma plume. PMID:24105546

Zhang, Mingjun; Chen, Genyu; Zhou, Yu; Li, Shichun

2013-08-26

270

Direct electrical observation of plasma wave-related effects in GaN-based two-dimensional electron gases  

NASA Astrophysics Data System (ADS)

In this work, signatures of plasma waves in GaN-based high electron mobility transistors were observed by direct electrical measurement at room temperature. Periodic grating-gate device structures were fabricated and characterized by on-wafer G-band (140-220 GHz) s-parameter measurements as a function of gate bias voltage and device geometry. A physics-based equivalent circuit model was used to assist in interpreting the measured s-parameters. The kinetic inductance extracted from the measurement data matches well with theoretical predictions, consistent with direct observation of plasma wave-related effects in GaN-channel devices at room temperature. This observation of electrically significant room-temperature plasma-wave effects in GaN-channel devices may have implications for future millimeter-wave and THz device concepts and designs.

Zhao, Y.; Chen, W.; Li, W.; Zhu, M.; Yue, Y.; Song, B.; Encomendero, J.; Sensale-Rodriguez, B.; Xing, H.; Fay, P.

2014-10-01

271

A DTN-ready application for the real-time dissemination of Earth Observation data received by Direct Readout stations  

NASA Astrophysics Data System (ADS)

The majority of Earth observation satellites operate in low Earth sun-synchronous orbit and transmit data captured by a variety of sensors. The effective dissemination of satellite data in real-time is a crucial parameter for disaster monitoring in particular. Generally, a spacecraft collects data and then stores it on-board until it passes over dedicated ground stations to transmit the data. Additionally, some satellites (e.g. Terra, Aqua, Suomi-NPP, NOAA series satellites) have the so-called Direct Broadcast (DB) capability, which is based on a real-time data transmission sub-system. Compatible Direct Readout (DR) stations in direct line of sight are able to receive these transmissions. To date data exchange between DR stations have not been fully exploited for real-time data dissemination. Stations around the world store data locally, which is then disseminated on demand via Internet gateways based on the standard TCP-IP protocols. On the other hand, Delay Tolerant Networks (DTNs), which deliver data by enabling store-and-forward transmission in order to cope with link failures, service disruptions and network congestion, could prove as an alternative/complementary transmission mechanism for the efficient dissemination of data. The DTN architecture allows for efficient utilization of the network, using in-network storage and taking advantage of the network availability among the interconnected nodes. Although DTNs were originally developed for high-propagation delay, challenged connectivity environments such as deep space, the broader research community has investigated possible architectural enhancements for various emerging applications (e.g., terrestrial infrastructure, ground-to-air communications, content retrieval and dissemination). In this paper, a scheme for the effective dissemination of DB data is conceptualized, designed and implemented based on store-and-forward transmission capabilities provided by DTNs. For demonstration purposes, a set-up has been designed and implemented which emulates the interconnection and data transmission of various HRPT/AVHRR DR stations based on pre-scheduled contacts via the DTN architecture. According to the scheme adopted, as soon as the satellite scans the earth and after image reception, a contact is established with a DTN node and data transmission is initiated. These DR stations form a DTN overlay, taking advantage of the routing, transport and security mechanisms developed. Most importantly, data received at a station can automatically be forwarded to any other station belonging to the same "interest" group through a flexible DTN multicasting mechanism. Thus, a composite image of an extended area (or potentially an image of the entire globe, depending on the interest groups formed is constructed in each node in an imperceptible way. Upon processing of the received data streams, stations are able to further disseminate new products to other interested third party entities exploiting the DTN overlay and the filtering capabilities provided by a web-based tool. The work leading to this paper has received funding from the European Union's Seventh Framework Programme (FP7-SPACE-2010-1) under grant agreement no. 263330 for the SDR (Space-Data Routers for Exploiting Space Data) collaborative research project. This paper reflects only the authors' views and the Union is not liable for any use that may be made of the information contained therein.

Paronis, Dimitris; Daglis, Ioannis A.; Diamantopoulos, Sotirios; Tsaoussidis, Vassilis; Tsigkanos, Antonis; Ghita, Bogdan; Evans, Michael

2014-05-01

272

Direct Observation of Multiphoton Processes in Laser-Induced Free-Free Transitions  

Microsoft Academic Search

Multiphoton processes are detected in the scattering of electrons on argon atoms in the presence of a strong CO2-laser field. The observations are in accordance with a recently developed semiclassical model.

A. Weingartshofer; J. K. Holmes; G. Caudle; E. M. Clarke; H. Krueger

1977-01-01

273

Direct Observations of Lunar Pickup Ions in the Magnetosphere Tail-Lobes by ARTEMIS  

NASA Astrophysics Data System (ADS)

We present ARTEMIS observations of pickup ions on the dayside of the Moon in the terrestrial magnetotail lobes. We attempt to determine the composition of these ions, presumably from either the surface or the exosphere, via ion tracing simulations.

Samad, R. L.; Poppe, A. R.; Halekas, J. S.; Delory, G. T.; Angelopoulos, V.; Farrell, W. M.

2012-03-01

274

Direct /TEM/ observation of the catalytic oxidation of amorphous carbon by Pd particles  

NASA Technical Reports Server (NTRS)

The catalytic oxidation of amorphous carbon substrates by Pd particles is observed by in situ transmission electron microscopy. Various modes of selective attack of the carbon substrate in the immediate neighborhood of Pd particles are observed, which can be correlated with different degrees of particle mobility. Using amorphous substrates we have been able to demonstrate that the particle-substrate interaction is influenced by the structure of the particle. This has not previously been noted.

Moorhead, R. D.; Poppa, H.; Heinemann, K.

1980-01-01

275

Direct observation and analysis of indentation cracking on glasses and ceramics  

Microsoft Academic Search

A review of the observations of indentation-induced fracture suggests that there is no simple generalization which may be made concerning crack initiation sequences. A detailed consideration of the stress fields arising during indentation contact predicts material-dependent initiation sequences, in agreement with observations, particularly those of radial crack formation on loading for materials with large modulus-to-hardness ratios. In addition, a new,

Robert F. Cook; George M. Pharr

1990-01-01

276

Direct Observation of Domain Wall Motion in Co/Pt Wire under Gate Electric Field  

NASA Astrophysics Data System (ADS)

In this study, we have investigated magnetic domain wall motion under gate electric fields in a perpendicularly magnetized Co/Pt wire. The motion under a transparent gate electrode was directly monitored using a magneto-optical Kerr effect microscope. The domain wall velocity was determined as a function of temperature and gate voltage. It was found that this velocity could be modulated by up to two orders of magnitude by changing the gate voltage.

Kakizakai, Haruka; Yamada, Kihiro; Kawaguchi, Masashi; Shimamura, Kazutoshi; Fukami, Shunsuke; Ishiwata, Nobuyuki; Chiba, Daichi; Ono, Teruo

2013-07-01

277

The direct observation of solidification as a function of gravity level. [for space manufacturing  

NASA Technical Reports Server (NTRS)

A saturated solution of NH4Cl was solidified on earth at 1 g and in a suborbital rocket flight at .00001 g. In the 1 g experiments, macrosegregation caused by the gravitational acceleration was marked. Nucleation started at the cold walls after which dendrites and dendritic debris were swept into the center of the cuvette by convective fluid flow. Secondary dendrite arms were oriented toward the cold wall. When solidified in low g, only four nuclei grew to form the complete casting. There were no free floating crystals or visible dendrite remelting. The lack of fluid flow allowed symmetrical dendrite growth into the fluid.

Johnston, M. H.; Griner, C. S.

1977-01-01

278

Direct Observations of Plasma Upflows and Condensation in a Catastrophically Cooling Solar Transition Region Loop  

NASA Astrophysics Data System (ADS)

Minimal observational evidence exists for fast transition region (TR) upflows in the presence of cool loops. Observations of such occurrences challenge notions of standard solar atmospheric heating models as well as their description of bright TR emission. Using the EUV Imaging Spectrometer on board Hinode, we observe fast upflows (v ? <= -10 km s-1) over multiple TR temperatures (5.8 <=log T <= 6.0) at the footpoint sites of a cool loop (log T <= 6.0). Prior to cool loop energizing, asymmetric flows of +5 km s-1 and -60 km s-1 are observed at footpoint sites. These flows, speeds, and patterns occur simultaneously with both magnetic flux cancellation (at the site of upflows only) derived from the Solar Dynamics Observatory's Helioseismic Magnetic Imager's line-of-sight magnetogram images, and a 30% mass influx at coronal heights. The incurred non-equilibrium structure of the cool loop leads to a catastrophic cooling event, with subsequent plasma evaporation indicating that the TR is the heating site. From the magnetic flux evolution, we conclude that magnetic reconnection between the footpoint and background field is responsible for the observed fast TR plasma upflows.

Orange, N. B.; Chesny, D. L.; Oluseyi, H. M.; Hesterly, K.; Patel, M.; Champey, P.

2013-12-01

279

42 CFR 405.2468 - Allowable costs.  

Code of Federal Regulations, 2010 CFR

...direct graduate medical education costs are those costs...activities associated with patient care services of an...direct graduate medical education. (ii) The following...allowable graduate medical education costs— (A) Costs...but not related to patient care services....

2010-10-01

280

Direct observation of the structural and electronic changes of Li2MnO3 during electron irradiation  

NASA Astrophysics Data System (ADS)

This study focuses on the effects of electron beam induced irradiation to the layered oxide Li2MnO3. Aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy are used to characterize structural and electronic transitions in the material during irradiation, with a focus on changes in Mn valence and O content. This truly in situ irradiation allows for specific particle tracking, dose quantification, and real-time observation, while demonstrating many parallels to the oxide's structure evolution observed during electrochemical cycling. Furthermore, it is demonstrated that typical imaging conditions are not severe enough to induce damage to the pristine oxide.

Phillips, Patrick J.; Iddir, Hakim; Abraham, Daniel P.; Klie, Robert F.

2014-09-01

281

Direct observation of closed magnetic flux trapped in the high-latitude magnetosphere.  

PubMed

The structure of Earth's magnetosphere is poorly understood when the interplanetary magnetic field is northward. Under this condition, uncharacteristically energetic plasma is observed in the magnetotail lobes, which is not expected in the textbook model of the magnetosphere. Using satellite observations, we show that these lobe plasma signatures occur on high-latitude magnetic field lines that have been closed by the fundamental plasma process of magnetic reconnection. Previously, it has been suggested that closed flux can become trapped in the lobe and that this plasma-trapping process could explain another poorly understood phenomenon: the presence of auroras at extremely high latitudes, called transpolar arcs. Observations of the aurora at the same time as the lobe plasma signatures reveal the presence of a transpolar arc. The excellent correspondence between the transpolar arc and the trapped closed flux at high altitudes provides very strong evidence of the trapping mechanism as the cause of transpolar arcs. PMID:25525244

Fear, R C; Milan, S E; Maggiolo, R; Fazakerley, A N; Dandouras, I; Mende, S B

2014-12-19

282

Instructions for observing air temperature, humidity, and direction and force of wind  

USGS Publications Warehouse

Description of instruments.-The temperature and humidity of the air are obtained from the simultaneous observation of a pair of mercurial thermometers termed the dry and the wet bulb. The air temperature is given by the dry-bulb thermometer, and the humidity is obtained from the combined readings of both. The wet-bulb thermometer differs from the dry-bulb thermometer only in having its bulb covered with thin muslin, which is wetted in pure water at each observation.The two thermometers are fastened in a light metal 'or wooden frame. To this frame is to be attached a stout cord for the whirling of the thermometers, which is an essential part of every observation.

U.S. Geological Survey

1892-01-01

283

Direct Observation of Multiple Pathways of Single-Stranded DNA Stretching  

NASA Astrophysics Data System (ADS)

We observed multiple pathways of stretching single-stranded polydeoxynucleotides, poly(dA). Poly(dA) has been shown to undergo unique transitions under mechanical force, and such transitions were attributed to the stacking characteristics of poly(dA). Using single-molecule manipulation studies, we found that poly(dA) has two stretching pathways at high forces. The previously observed pathway has a free energy that is less than what is expected of single-stranded DNA with a random sequence, indicating the existence of a novel conformation of poly(dA) at large extensions. We also observed stepwise transitions between the two pathways by pulling the molecule with constant force, and found that the transitions are cooperative. These results suggest that the unique mechanical property of poly(dA) may play an important role in biological processes such as gene expression.

Chen, Wuen-Shiu; Chen, Wei-Hung; Chen, Zephan; Gooding, Ashton A.; Lin, Kuan-Jiuh; Kiang, Ching-Hwa

2010-11-01

284

Direct observation of closed magnetic flux trapped in the high-latitude magnetosphere  

NASA Astrophysics Data System (ADS)

The structure of Earth’s magnetosphere is poorly understood when the interplanetary magnetic field is northward. Under this condition, uncharacteristically energetic plasma is observed in the magnetotail lobes, which is not expected in the textbook model of the magnetosphere. Using satellite observations, we show that these lobe plasma signatures occur on high-latitude magnetic field lines that have been closed by the fundamental plasma process of magnetic reconnection. Previously, it has been suggested that closed flux can become trapped in the lobe and that this plasma-trapping process could explain another poorly understood phenomenon: the presence of auroras at extremely high latitudes, called transpolar arcs. Observations of the aurora at the same time as the lobe plasma signatures reveal the presence of a transpolar arc. The excellent correspondence between the transpolar arc and the trapped closed flux at high altitudes provides very strong evidence of the trapping mechanism as the cause of transpolar arcs.

Fear, R. C.; Milan, S. E.; Maggiolo, R.; Fazakerley, A. N.; Dandouras, I.; Mende, S. B.

2014-12-01

285

Direct and remotely-sensed observations of water vapor isotopes in the North American Monsoon domain  

NASA Astrophysics Data System (ADS)

The climate models that make up the current IPCC ensemble do not accurately represent the predominant spatial and temporal features of the North American Monsoon (NAM) system. This leads to large uncertainty in predicting the response of the NAM to both anthropogenic and natural forcings. One method of diagnosing model deficiencies in capturing summertime precipitation patterns in the Southwestern US is to assess how the atmospheric moisture budget of a model compares to observed budgets created using water isotope data. We present an analysis of continuous in situ ground and tower-based observations of the isotopic composition of water vapor (?D and ?18O) and remotely-sensed satellite retrievals of the column-integrated isotopic composition of water vapor (?D) from the Greenhouse Gases Observing Satellite over the southwestern US. The isotopic data capture a strong seasonal transition between winter and summer seasons, which is associated with a change between predominately northwesterly and southwesterly moisture sources. On synoptic timescales during the monsoon season, the isotopes also serve as a lucid tracer of "Gulf Surges" providing observational confirmation on the importance of this moisture source; a finding that had previously been gleaned through "painted water" simulations and wind pattern analysis. While Gulf Surges are observable from analysis of water vapor concentration alone, observations of the isotopic composition of this phenomenon provides a unique capacity to trace the northerly extent of this moisture, which is difficult to discern from looking at non-isotopic humidity data alone. The new data also show that from a budgetary standpoint the significance of continental moisture fluxes (evaporation and transpiration) is quite large. This result therefore suggests that progress on modeling the NAM and ultimately in understandings its response to forcing cannot only be focused on large-scale SST and atmospheric circulation fields but also must better address the surface moisture dynamics and land-atmosphere coupling.

Berkelhammer, M. B.; Langford, S.; Buenning, N. H.; Yoshimura, K.; Frankenberg, C.; Kaushik, A.; Noone, D. C.

2012-12-01

286

Direct observation of high-speed plasma outflows produced by magnetic reconnection in solar impulsive events  

E-print Network

Spectroscopic observations of a solar limb flare recorded by SUMER on SOHO reveal, for the first time, hot fast magnetic reconnection outflows in the corona. As the reconnection site rises across the SUMER spectrometer slit, significant blue- and red-shift signatures are observed in sequence in the Fe XIX line, reflecting upflows and downflows of hot plasma jets, respectively. With the projection effect corrected, the measured outflow speed is between 900-3500 km/s, consistent with theoretical predictions of the Alfvenic outflows in magnetic reconnection region in solar impulsive events. Based on theoretic models, the magnetic field strength near the reconnection region is estimated to be 19-37 Gauss.

Tongjiang Wang; Linhui Sui; Jiong Qiu

2007-09-14

287

Cognitive Correlates of Functional Performance in Older Adults: Comparison of Self-Report, Direct Observation, and Performance-Based Measures  

PubMed Central

Neuropsychologists are often asked to answer questions about the effects of cognitive deficits on everyday functioning. This study examined the relationship between and the cognitive correlates of self-report, performance-based, and direct observation measures commonly used as proxy measures for everyday functioning. Participants were 88 community-dwelling, cognitively healthy older adults (age 50–86 years). Participants completed standardized neuropsychological tests and questionnaires, and performed eight activities of daily living (e.g., water plants, fill a medication dispenser) while under direct observation in a campus apartment. All proxy measures of everyday function were sensitive to the effects of healthy cognitive aging. After controlling for age, cognitive predictors explained a unique amount of the variance for only the performance-based behavioral simulation measure (i.e., Revised Observed Tasks of Daily Living). The self-report instrumental activities of daily living (IADL) and the performance-based everyday problem-solving test (i.e., EPT) did not correlate with each other; however, both were unique predictors of the direct observation measure. These findings suggest that neuropsychologists must be cautious in making predictions about the quality of everyday activity completion in cognitively healthy older adults from specific cognitive functions. The findings further suggest that a self-report of IADLs and the performance-based EPT may be useful measures for assessing everyday functional status in cognitively healthy older adults. PMID:21729400

Schmitter-Edgecombe, Maureen; Parsey, Carolyn; Cook, Diane J.

2013-01-01

288

Wave normal direction and spectral properties of whistler mode hiss observed on the DE 1 satellite  

NASA Technical Reports Server (NTRS)

Hiss is represented by a field distribution function in order to investigate magnetospheric hiss as a spatially and temporally enduring phenomenon. The study takes into account the whistler mode relationships and the linear and spin motion of the satellite. Hiss signals received on September 23, 1983 by the DE-1 electric and magnetic field antennas are analyzed. A wave normal angle of 60 + or - 5 deg with respect to the local geomagnetic field is found near the geomagnetic equator, and wave normal directions from 30-80 deg with respect to the local geomagnetic field are found away from the equator.

Sonwalkar, Vikas S.; Inan, Umran S.

1988-01-01

289

Direct observation of enhanced residual thermal energy coupling to solids in femtosecond laser ablation  

SciTech Connect

We perform direct measurement of the thermal energy remaining in the bulk of Cu, Mg, Au, and Si samples following multi-pulse femtosecond laser ablation. In contrast to the previous belief that the thermal energy remaining in the ablated sample is negligible using femtosecond pulses, we show a significant amount of residual thermal energy deposited in various materials. In fact, with a sufficiently large number of pulses at high fluence, virtually all the incident laser energy can be retained in the sample. Several possible mechanisms are investigated for their role in residual heating, including laser-induced surface modification, exothermic chemical processes, and pressure effects.

Vorobyev, A.Y.; Guo Chunlei [Institute of Optics, University of Rochester, Rochester, New York 14627 (United States)

2005-01-03

290

Direct observation of structural changes in organic light emitting devices during degradation  

E-print Network

crystallization of either the hole transporting8 or electron transporting9 layer, or indium tin oxide ITODirect observation of structural changes in organic light emitting devices during degradation microscopy. Structural changes, such as degradation of organic materials and the cathode surface, occur well

291

Some direct observations on the ecology and behaviour of the Norway lobster Nephrops norvegicus  

Microsoft Academic Search

A detailed investigation of a small area of sea bed occupied by the Norway lobster Nephrops norvegicus (L.) was carried out by diving and television observations at depths of 30 m in Loch Torridon, Scotland. The density of burrows was 1\\/2 m2, but only a proportion of these were occupied by N. norvegicus. Although about 70% of the larger burrows

C. J. Chapman; A. L. Rice

1971-01-01

292

Direct and Remote Sensing Observations of the Effects of Ships on Clouds  

Microsoft Academic Search

Under certain conditions ships can affect the structure of shallow layer clouds. Simultaneous observations of two ship track signatures in stratus clouds from a satellite and in situ from an aircraft show that in the ship tracks the droplet sizes were reduced and total concentrations of both droplets and particles were substantially increased from those in adjacent clouds. In situ

LAWRENCE F. UDKE; JAMES A. COAKLEY; MICHAEL D. KING

1989-01-01

293

XXV. The direct observation of dislocation nets in rock salt single crystals  

Microsoft Academic Search

A method for decorating dislocation lines in rocksalt single crystals is described. The method consists in colouring the crystals additively by means of sodium metal. It is found that specks are formed along the dislocation lines, which are, as a consequence, visible in ultra microscopic observation. It is thought that the specks are colloidal sodium particles, and an explanation is

S. Amelinckx

1956-01-01

294

New Directions in Earth Observing: Scientific Applications of Multiangle Remote Sensing  

Microsoft Academic Search

The physical interpretation of simultaneous multiangle observations represents a relatively new approach to remote sensing of terrestrial geophysical and biophysical parameters. Multiangle measurements enable retrieval of physical scene characteristics, such as aerosol type, cloud morphology and height, and land cover (e.g., vegetation canopy type), providing improved albedo accuracies as well as compositional, morphological, and structural information that facilitates addressing many

David J. Diner; Gregory P. Asner; Roger Davies; Yuri Knyazikhin; Jan-Peter Muller; Anne W. Nolin; Bernard Pinty; Crystal B. Schaaf; Julienne Stroeve

1999-01-01

295

A Direct Method to Self-Calibrate a Surveillance Camera by Observing a Walking Pedestrian  

Microsoft Academic Search

Recent efforts show that it is possible to calibrate a surveillance camera simply from observing a walking hu- man. This procedure can be seen as a special application of the camera self-calibration technique. Several methods have been proposed along this line, but most of them have certain restrictions, such as require the human walking at a constant speed, or require

Worapan Kusakunniran; Hongdong Li; Jian Zhang

2009-01-01

296

Direct Observations of Plasma Upflows and Condensation in a Catastrophically Cooling Solar Transition Region Looop  

E-print Network

Minimal observational evidence exists for fast transition region (TR) upflows in the presence of cool loops. Observations of such occurrences challenge notions of standard solar atmospheric heating models, as well as their description of bright TR emission. Using the {\\it EUV Imaging Spectrometer} (EIS) onboard {\\it Hinode}, we observe fast upflows ($v_\\lambda$\\,$\\le$\\,$-$10 km s$^{-1}$) over multiple TR temperatures (5.8\\,$\\le$\\,$\\log T$\\,$\\le$ 6.0) at the footpoint sites of a cool loop ($\\log T$\\,$\\le$\\,6.0). Prior to cool loop energizing, asymmetric flows of $+$\\,5 km s$^{-1}$ and $-$\\,60 km s$^{-1}$ are observed at footpoint sites. These flows speeds and patterns occur simultaneously with both magnetic flux cancellation (at site of upflows only) derived from the {\\it Solar Dynamics Observatory}'s (SDOs) { \\it Helioseismic Magnetic Imager}'s (HMI) line-of-sight magnetogram images, and a 30\\% mass in-flux at coronal heights. The incurred non-equilibrium structure of the cool loop leads to a catastrophic coo...

Orange, N B; Oluseyi, H M; Hesterly, K; Patel, M; Champey, P R

2015-01-01

297

Observations of bi-directional leader development in a triggered lightning flash  

NASA Technical Reports Server (NTRS)

Observations of a modified form of rocket triggered lightning are described. A flash triggered during the summer of 1989 is studied as part of an effort to model bidirectional discharge. It is suggested that the altitude triggering technique provides a realistic means of studying the attachment process.

Laroche, P.; Idone, V.; Eybert-Berard, A.; Barret, L.

1991-01-01

298

Alignment of micro-crystals of Mn12-acetate and direct observation of single molecules thereof  

E-print Network

films were fabricated and characterized by AFM and STM. Finally, magnetization of the film material was also studied. Enhanced alignment of Mn12-acetate micro-crystals as compared to prior studies was verified by observation of several sharp steps in low...

Seo, Dongmin

2009-05-15

299

Direct observation of oil consumption mechanisms in a production spark ignition engine using fluorescence techniques  

NASA Astrophysics Data System (ADS)

The oil consumption characteristics of a four cylinder, normally aspirated spark-ignition engine were investigated for different piston ring end-gap configurations. A radiotracer was used to perform direct measurement of the oil consumption while Laser-induced Fluorescence (LIF) was used to perform the oil film thickness measurements for consumption predictions using the 'Puddle Theory of Oil Consumption,' which relates oil consumption to second land film thickness and reverse flow through top ring gap. The consumption data was evaluated to determine the impact of top ring end-gap azimuthal location on oil consumption. The film thickness data was used to evaluate the extent to which the oil Puddle Theory predicts variations seen in the actual oil consumption. A tritium radiotracer oil consumption measurement system with an accuracy of 94.6 percent was designed and constructed. This was used to perform direct measurements of the test engine oil consumption in two different test matrices. The first evaluated a piston ring configuration with the rings free to rotate. The second evaluated configurations with the top ring and second piston rings pinned to fix the azimuthal location of the end-gap; the azimuth of the top ring was varied. In the second test matrix, the oil film thickness on the piston's second land was measured, and predictions were made on the basis of that measurement.

Lusted, Roderick M.

1994-05-01

300

Direct observation of dynamic charge stripes in La2 xSrxNiO4  

SciTech Connect

The insulator-to-metal transition continues to be a challenging subject, especially when electronic correlations are strong. In layered compounds, such as La2 xSrxNiO4 and La2 xBaxCuO4, the doped charge carriers can segregate into periodically spaced charge stripes separating narrow domains of antiferromagnetic order. Although there have been theoretical proposals of dynamically fluctuating stripes, direct spectroscopic evidence of charge-stripe fluctuations has been lacking. Here we report the detection of critical lattice fluctuations, driven by charge-stripe correlations, in La2 xSrxNiO4 using inelastic neutron scattering. This scattering is detected at large momentum transfers where the magnetic form factor suppresses the spin fluctuation signal. The lattice fluctuations associated with the dynamic charge stripes are narrow in q and broad in energy. They are strongest near the charge-stripe melting temperature. Our results open the way towards the quantitative theory of dynamic stripes and for directly detecting dynamical charge stripes in other strongly correlated systems, including high-temperature superconductors such as La2 xSrxCuO4.

Anissimova, S. [University of Colorado, Boulder] [University of Colorado, Boulder; Parshall, D [University of Colorado, Boulder] [University of Colorado, Boulder; Gu, Genda [Brookhaven National Laboratory (BNL)] [Brookhaven National Laboratory (BNL); Marty, K. [Oak Ridge National Laboratory (ORNL)] [Oak Ridge National Laboratory (ORNL); Lumsden, Mark D [ORNL] [ORNL; Chi, Songxue [ORNL] [ORNL; Fernandez-Baca, Jaime A [ORNL] [ORNL; Abernathy, D. [Oak Ridge National Laboratory (ORNL)] [Oak Ridge National Laboratory (ORNL); Lamago, D. [Laboratoire Leon Brillouin, France] [Laboratoire Leon Brillouin, France; Tranquada, John M. [Brookhaven National Laboratory (BNL)] [Brookhaven National Laboratory (BNL); Reznik, Dmitry [University of Colorado, Boulder] [University of Colorado, Boulder

2014-01-01

301

Direct observation of dynamic charge stripes in La2-xSrxNiO4.  

PubMed

The insulator-to-metal transition continues to be a challenging subject, especially when electronic correlations are strong. In layered compounds, such as La2-xSrxNiO4 and La2-xBaxCuO4, the doped charge carriers can segregate into periodically spaced charge stripes separating narrow domains of antiferromagnetic order. Although there have been theoretical proposals of dynamically fluctuating stripes, direct spectroscopic evidence of charge-stripe fluctuations has been lacking. Here we report the detection of critical lattice fluctuations, driven by charge-stripe correlations, in La2-xSrxNiO4 using inelastic neutron scattering. This scattering is detected at large momentum transfers where the magnetic form factor suppresses the spin fluctuation signal. The lattice fluctuations associated with the dynamic charge stripes are narrow in q and broad in energy. They are strongest near the charge-stripe melting temperature. Our results open the way towards the quantitative theory of dynamic stripes and for directly detecting dynamical charge stripes in other strongly correlated systems, including high-temperature superconductors such as La2-xSrxCuO4. PMID:24632780

Anissimova, S; Parshall, D; Gu, G D; Marty, K; Lumsden, M D; Chi, Songxue; Fernandez-Baca, J A; Abernathy, D L; Lamago, D; Tranquada, J M; Reznik, D

2014-01-01

302

Direct observation of prefreezing at the interface melt–solid in polymer crystallization  

PubMed Central

Crystallization is almost always initiated at an interface to a solid. This observation is classically explained by the assumption of a reduced barrier for crystal nucleation at the interface. However, an interface can also induce crystallization by prefreezing (i.e., the formation of a crystalline layer that is already stable above the bulk melting temperature). We present an atomic force microscopy (AFM)-based in situ observation of a prefreezing process at the interface of a polymeric model system and a crystalline solid. Explicitly, we show an interfacial ordered layer that forms well above the bulk melting temperature with thickness that increases on approaching melt–solid coexistence. Below the melting temperature, the ordered layer initiates crystal growth into the bulk, leading to an oriented, homogeneous semicrystalline structure. PMID:25422447

Löhmann, Ann-Kristin; Henze, Thomas; Thurn-Albrecht, Thomas

2014-01-01

303

Surface plasmon coupled chemiluminescence from iron thin films: Directional and approaching fixed angle observation  

NASA Astrophysics Data System (ADS)

We report the observation of surface plasmon coupled chemiluminescence (SPCC) from iron thin films. Theoretical Fresnel calculations were employed to determine the optimum thickness of iron thin films to be 15 nm, which is assessed by the value of minimum reflectivity curves for incident light upon the thin film. An overlayer 10 nm thick SiO2 was used to protect the iron thin films from oxidation by air or physical changes induced by chemiluminescent solutions. SPCC emission from blue, green, and chartreuse chemiluminescent solutions on iron films can be observed at a fixed angle of 60° for all the chemiluminescent solutions, while free-space emission was isotropic. Iron thin films do not have a catalytic effect on chemiluminescence emission.

Aslan, Kadir; Weisenberg, Micah; Hortle, Elinor; Geddes, Chris D.

2009-07-01

304

Direct observations of thermally induced structural changes in amorphous silicon carbide  

SciTech Connect

Thermally induced structural relaxation in amorphous silicon carbide (SiC) has been examined by means of in situ transmission electron microscopy (TEM). The amorphous SiC was prepared by high-energy ion-beam-irradiation into a single crystalline 4H-SiC substrate. Cross-sectional TEM observations and electron energy-loss spectroscopy measurements revealed that thermal annealing induces a remarkable volume reduction, so-called densification, of amorphous SiC. From radial distribution function analyses using electron diffraction, notable changes associated with structural relaxation were observed in chemical short-range order. On the basis of the alteration of chemical short-range order, we discuss the origin of thermally induced densification in amorphous SiC.

Ishimaru, Manabu; Hirata, Akihiko; Naito, Muneyuki; Bae, In-Tae; Zhang, Yanwen; Weber, William J.

2008-08-01

305

Direct observation of spin-like reaction fronts in planar energetic multilayer foils.  

SciTech Connect

Propagating reactions in initially planar cobalt/aluminum exothermic multilayer foils have been investigated using high-speed digital photography. Real-time observations of reactions indicate that unsteady (spinlike) reaction propagation leads to the formation of highly periodic surface morphologies with length scales ranging from 1 {micro}m to 1 mm. The characteristics of propagating spinlike reactions and corresponding reacted foil morphologies depend on the bilayer thickness of multilayer foils.

Adams, David Price; Hodges, V. Carter; Jones, Eric D., Jr.; McDonald, Joel Patrick

2008-10-01

306

Direct radiative forcing of anthropogenic aerosols over oceans from satellite observations  

Microsoft Academic Search

Anthropogenic aerosols play an important role in the atmospheric energy balance. Anthropogenic aerosol optical depth (AOD)\\u000a and its accompanying shortwave radiative forcing (RF) are usually simulated by numerical models. Recently, with the development\\u000a of space-borne instruments and sophisticated retrieval algorithms, it has become possible to estimate aerosol radiative forcing\\u000a based on satellite observations. In this study, we have estimated shortwave

Lin Chen; Guangyu Shi; Shiguang Qin; Su Yang; Peng Zhang

2011-01-01

307

Direct constraint on the distance of y2 Velorum from AMBER/VLTI observations  

E-print Network

In this work, we present the first AMBER observations, of the Wolf-Rayet and O (WR+O) star binary system y2 Velorum. The AMBER instrument was used with the telescopes UT2, UT3, and UT4 on baselines ranging from 46m to 85m. It delivered spectrally dispersed visibilities, as well as differential and closure phases, with a resolution R = 1500 in the spectral band 1.95-2.17 micron. We interpret these data in the context of a binary system with unresolved components, neglecting in a first approximation the wind-wind collision zone flux contribution. We show that the AMBER observables result primarily from the contribution of the individual components of the WR+O binary system. We discuss several interpretations of the residuals, and speculate on the detection of an additional continuum component, originating from the free-free emission associated with the wind-wind collision zone (WWCZ), and contributing at most to the observed K-band flux at the 5% level. The expected absolute separation and position angle at the time of observations were 5.1±0.9mas and 66±15° respectively. However, we infer a separation of 3.62+0.11-0.30 mas and a position angle of 73+9-11°. Our analysis thus implies that the binary system lies at a distance of 368+38-13 pc, in agreement with recent spectrophotometric estimates, but significantly larger than the Hipparcos value of 258+41-31 pc.

F. Millour; R. G. Petrov; O. Chesneau; D. Bonneau; L. Dessart; C. Bechet; I. Tallon-Bosc; M. Tallon; E. Thiébaut; F. Vakili; F. Malbet; D. Mourard; G. Zins; A. Roussel; S. Robbe-Dubois; P. Puget; K. Perraut; F. Lisi; E. Le Coarer; S. Lagarde; P. Kern; L. Glück; G. Duvert; A. Chelli; Y. Bresson; U. Beckmann; P. Antonelli; G. Weigelt; N. Ventura; M. Vannier; J. -C. Valtier; L. Testi; E. Tatulli; D. Tasso; P. Stefanini; P. Stee; W. Solscheid; D. Schertl; P. Salinari; M. Sacchettini; A. Richichi; F. Reynaud; S. Rebattu; Y. Rabbia; T. Preibisch; C. Perrier; F. Pacini; K. Ohnaka; E. Nussbaum; D. Mouillet; J. -L. Monin; P. Mège; P. Mathias; G. Martinot-Lagarde; G. Mars; A. Marconi; Y. Magnard; B. Lopez; D. Le Contel; J. -M. Le Contel; S. Kraus; D. Kamm; K. -H. Hofmann; O. Hernandez Utrera; M. Heininger; M. Heiden; C. Gil; E. Giani; A. Glentzlin; S. Gennari; A. Gallardo; D. Fraix-Burnet; R. Foy; E. Fossat; T. Forveille; D. Ferruzzi; P. Feautrier; M. Dugué; T. Driebe; A. Domiciano De Souza; A. Delboulbé; C. Connot; J. Colin; J. -M. Clausse; F. Cassaing; S. Busoni; S. Bonhomme; T. Blöcker; J. Behrend; C. Baffa; E. Aristidi; B. Arezki; K. Agabi; B. Acke; M. Accardo; M. Kiekebusch; F. Rantakyrö; Markus Schoeller

2006-10-31

308

Direct observation of a 'devil's staircase' in wave-particle interaction  

SciTech Connect

We report the experimental observation of a 'devil's staircase' in a time-dependent system considered as a paradigm for the transition to large-scale chaos in the universality class of Hamiltonian systems. A test electron beam is used to observe its non-self-consistent interaction with externally excited wave(s) in a traveling wave tube (TWT). A trochoidal energy analyzer records the beam energy distribution at the output of the interaction line. An arbitrary waveform generator is used to launch a prescribed spectrum of waves along the slow wave structure (a 4 m long helix) of the TWT. The resonant velocity domain associated to a single wave is observed, as well as the transition to large-scale chaos when the resonant domains of two waves and their secondary resonances overlap. This transition exhibits a 'devil's staircase' behavior for increasing excitation amplitude, due to the nonlinear forcing by the second wave on the pendulum-like motion of a charged particle in one electrostatic wave.

Doveil, Fabrice; Macor, Alessandro; Elskens, Yves [Physique des interactions ioniques et moleculaires, Unite 6633 CNRS-Universite de Provence, Equipe turbulence plasma, case 321, Centre de Saint-Jerome, F-13397 Marseille cedex 20 (France)

2006-09-15

309

Value-directed human behavior analysis from video using partially observable Markov decision processes.  

PubMed

This paper presents a method for learning decision theoretic models of human behaviors from video data. Our system learns relationships between the movements of a person, the context in which they are acting, and a utility function. This learning makes explicit that the meaning of a behavior to an observer is contained in its relationship to actions and outcomes. An agent wishing to capitalize on these relationships must learn to distinguish the behaviors according to how they help the agent to maximize utility. The model we use is a partially observable Markov decision process, or POMDP. The video observations are integrated into the POMDP using a dynamic Bayesian network that creates spatial and temporal abstractions amenable to decision making at the high level. The parameters of the model are learned from training data using an a posteriori constrained optimization technique based on the expectation-maximization algorithm. The system automatically discovers classes of behaviors and determines which are important for choosing actions that optimize over the utility of possible outcomes. This type of learning obviates the need for labeled data from expert knowledge about which behaviors are significant and removes bias about what behaviors may be useful to recognize in a particular situation. We show results in three interactions: a single player imitation game, a gestural robotic control problem, and a card game played by two people. PMID:17496372

Hoey, Jesse; Little, James J

2007-07-01

310

Direct atomic-scale observation of layer-by-layer oxide growth during magnesium oxidation  

SciTech Connect

The atomic-scale oxide growth dynamics are directly revealed by in situ high resolution transmission electron microscopy during the oxidation of Mg surface. The oxidation process is characterized by the layer-by-layer growth of magnesium oxide (MgO) nanocrystal via the adatom process. Consistently, the nucleated MgO crystals exhibit faceted surface morphology as enclosed by (200) lattice planes. It is believed that the relatively lower surface energies of (200) lattice planes should play important roles, governing the growth mechanism. These results facilitate the understanding of the nanoscale oxide growth mechanism that will have an important impact on the development of magnesium or magnesium alloys with improved resistance to oxidation.

Zheng, He; Wu, Shujing; Sheng, Huaping; Liu, Chun; Liu, Yu; Cao, Fan; Zhou, Zhichao; Zhao, Dongshan, E-mail: wang@whu.edu.cn, E-mail: dszhao@whu.edu.cn; Wang, Jianbo, E-mail: wang@whu.edu.cn, E-mail: dszhao@whu.edu.cn [School of Physics and Technology, Center for Electron Microscopy and MOE Key Laboratory of Artificial Micro- and Nano-structures, Wuhan University, Wuhan 430072 (China); Zhao, Xingzhong [School of Physics and Technology, Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Wuhan University, Wuhan 430072 (China)

2014-04-07

311

Direct observation of ClO from chlorine nitrate photolysis. [as mechanism of polar ozone depletion  

NASA Technical Reports Server (NTRS)

Chlorine nitrate photolysis has been investigated with the use of a molecular beam technique. Excitation at both 248 and 193 nanometers led to photodissociation by two pathways, ClONO2 yields ClO + NO2 and ClONO2 yields Cl + NO3, with comparable yields. This experiment provides a direct measurement of the ClO product channel and consequently raises the possibility of an analogous channel in ClO dimer photolysis. Photodissociation of the ClO dimer is a critical step in the catalytic cycle that is presumed to dominate polar stratospheric ozone destruction. A substantial yield of ClO would reduce the efficiency of this cycle.

Minton, Timothy K.; Nelson, Christine M.; Moore, Teresa A.; Okumura, Mitchio

1992-01-01

312

Experimental Observation of Direct Particle Acceleration by Stimulated Emission of Radiation  

NASA Astrophysics Data System (ADS)

We report the first experimental evidence for direct particle acceleration by stimulated emission of radiation. In the framework of this proof-of-principle experiment, a 45 MeV electron macrobunch was modulated by a high-power CO2 laser and then injected into an excited CO2 gas mixture. The emerging microbunches experienced a 0.15% relative change in the kinetic energy, in a less than 40 cm long interaction region. According to our experimental results, a fraction of these electrons have gained more than 200 keV each, implying that such an electron has undergone an order of magnitude of 2×106 collisions of the second kind.

Banna, Samer; Berezovsky, Valery; Schächter, Levi

2006-09-01

313

Direct structural observation of a molecular junction by high-energy x-ray reflectometry  

PubMed Central

We report a direct angstrom resolution measurement of the structure of a molecular-size electronic junction comprising a single (or a double) layer of alkyl-thiol and alkyl-silane molecules at the buried interface between solid silicon and liquid mercury. The high-energy synchrotron x-ray measurements reveal densely packed layers comprising roughly interface-normal molecules. The monolayer’s thickness is found to be 3–4 Å larger than that of similar layers at the free surfaces of both mercury and silicon. The origins of this and the other unusual features detected are discussed in this article. Measurements of the bilayer junction with an applied potential did not show visible changes in the surface normal structure. PMID:16467139

Lefenfeld, Michael; Baumert, Julian; Sloutskin, Eli; Kuzmenko, Ivan; Pershan, Peter; Deutsch, Moshe; Nuckolls, Colin; Ocko, Benjamin M.

2006-01-01

314

Direct Observation of Room-Temperature Polar Ordering in Colloidal GeTe Nanocrystals  

SciTech Connect

Ferroelectrics and other materials that exhibit spontaneous polar ordering have demonstrated immense promise for applications ranging from non-volatile memories to microelectromechanical systems. However, experimental evidence of polar ordering and effective synthetic strategies for accessing these materials are lacking for low-dimensional nanomaterials. Here, we demonstrate the synthesis of size-controlled nanocrystals of the polar material germanium telluride (GeTe) using colloidal chemistry and provide the first direct evidence of room-temperature polar ordering in nanocrystals less than 5 nm in size using aberration-corrected transmission electron microscopy. Synchrotron x-ray diffraction and Raman studies demonstrate a sizeable polar distortion and a reversible size-dependent polar phase transition in these nanocrystals. The stability of polar ordering in solution-processible nanomaterials suggests an economical avenue to Tbit/in2-density non-volatile memory devices and other applications.

Polking, Mark J.; Zheng, Haimei; Urban, Jeffrey J.; Milliron, Delia J.; Chan, Emory; Caldwell, Marissa A.; Raoux, Simone; Kisielowski, Christian F.; Ager III, Joel W.; Ramesh, Ramamoorthy; Alivisatos, A.P.

2009-12-07

315

Direct Observation of Multiferroic Vortex Domains in YMnO3  

PubMed Central

Topological vortices with swirling ferroelectric, magnetic and structural anti-phase relationship in hexagonal RMnO3 (R = Ho to Lu, Y, and Sc) have attracted much attention because of their intriguing behaviors. Herein, we report the structure of multiferroic vortex domains in YMnO3 at atomic scale using state-of-the-art aberration-corrected scanning transmission electron microscopy (STEM). Two types of displacements were identified among six domain walls (DWs); six translation-ferroelectric domains denoted by ?+, ??, ?+, ??, ?+ and ??, respectively, were recognized, demonstrating the interlocking nature of the anti-vortex domain. We found that the anti-vortex core is about four unit cells wide. In addition, we reconstructed the vortex model with three swirling pairs of DWs along the [001] direction. These results are very critical for the understanding of topological behaviors and unusual properties of the multiferroic vortex. PMID:24061552

Zhang, Qinghua; Tan, Guotai; Gu, Lin; Yao, Yuan; Jin, Changqing; Wang, Yanguo; Duan, Xiaofeng; Yu, Richeng

2013-01-01

316

Experimental observation of direct particle acceleration by stimulated emission of radiation.  

PubMed

We report the first experimental evidence for direct particle acceleration by stimulated emission of radiation. In the framework of this proof-of-principle experiment, a 45 MeV electron macrobunch was modulated by a high-power CO2 laser and then injected into an excited CO2 gas mixture. The emerging microbunches experienced a 0.15% relative change in the kinetic energy, in a less than 40 cm long interaction region. According to our experimental results, a fraction of these electrons have gained more than 200 keV each, implying that such an electron has undergone an order of magnitude of 2 x 10(6) collisions of the second kind. PMID:17026038

Banna, Samer; Berezovsky, Valery; Schächter, Levi

2006-09-29

317

Direct observation of two-step crystallization in nanoparticle superlattice formation  

SciTech Connect

Direct imaging of nanoparticle solutions by liquid phase transmission electron microscopy has enabled unique in-situ studies of nanoparticle motion and growth. In the present work, we report on real-time formation of two-dimensional nanoparticle arrays in the very low diffusive limit, where nanoparticles are mainly driven by capillary forces and solvent fluctuations. We find that superlattice formation appears to be segregated into multiple regimes. Initially, the solvent front drags the nanoparticles, condensing them into an amorphous agglomerate. Subsequently, the nanoparticle crystallization into an array is driven by local fluctuations. Following the crystallization event, superlattice growth can also occur via the addition of individual nanoparticles drawn from outlying regions by different solvent fronts. The dragging mechanism is consistent with simulations based on a coarse-grained lattice gas model at the same limit.

Park, Jungwon; Zheng, Haimei; Lee, Won Chul; Geissler, Phillip L.; Rabani, Eran; Alivisatos, A. Paul

2011-10-06

318

Direct observation of the oxygenated species during oxygen reduction on a platinum fuel cell cathode  

NASA Astrophysics Data System (ADS)

The performance of polymer electrolyte membrane fuel cells is limited by the reduction at the cathode of various oxygenated intermediates in the four-electron pathway of the oxygen reduction reaction. Here we use ambient pressure X-ray photoelectron spectroscopy, and directly probe the correlation between the adsorbed species on the surface and the electrochemical potential. We demonstrate that, during the oxygen reduction reaction, hydroxyl intermediates on the cathode surface occur in several configurations with significantly different structures and reactivities. In particular, we find that near the open-circuit potential, non-hydrated hydroxyl is the dominant surface species. On the basis of density functional theory calculations, we show that the removal of hydration enhances the reactivity of oxygen species. Tuning the hydration of hydroxyl near the triple phase boundary will be crucial for designing more active fuel cell cathodes.

Casalongue, Hernan Sanchez; Kaya, Sarp; Viswanathan, Venkatasubramanian; Miller, Daniel J.; Friebel, Daniel; Hansen, Heine A.; Nørskov, Jens K.; Nilsson, Anders; Ogasawara, Hirohito

2013-12-01

319

Direct-sun total ozone data from a Bentham spectroradiometer: methodology and comparison with satellite observations  

NASA Astrophysics Data System (ADS)

A methodology to obtain the total ozone column (TOC) from the direct-solar spectral measurements of a Bentham spectroradiometer located at Granada (Spain) is presented in this paper. The method relies on the differential absorption technique using two pairs of direct irradiance at adjacent wavelengths between 305 and 340 nm. The extraterrestrial constant was determined from the extrapolation to zero air mass of each wavelength pair (Langley plot method). We checked the strong influence of the cloud cover on the Bentham TOC measurements using simultaneous sky images taken with an All-sky camera. Thus, reliable TOC data are exclusively obtained during cloud-free conditions or partly cloudy conditions without the solar disk obstructed. In this work, the hourly TOC averages retrieved by the Bentham instrument with a~standard deviation smaller than 3% (~ 10 Dobson Unit) are selected as high-quality TOC data. The analysis of the diurnal TOC variations during cloud-free days showed a differential behavior between the morning and afternoon periods. Thus, while the mornings exhibit an almost stable pattern, the afternoons displays a monotonic TOC increase which could be related to photochemical processes in the lower troposphere associated with the formation of surface ozone. Finally, the Bentham TOC measurements were validated against the satellite data derived from three satellite instruments: OMI, GOME and SCIAMACHY. The mean absolute values of the relative differences between satellite and ground-based data were smaller than 3% which highlight the high reliability of the retrieval method proposed in this paper to derive TOC data.

Antón, M.; Román, R.; Valenzuela, A.; Olmo, F. J.; Alados-Arboledas, L.

2012-11-01

320

Direct-sun total ozone data from a spectroradiometer: methodology and comparison with satellite observations  

NASA Astrophysics Data System (ADS)

A methodology to obtain the total ozone column (TOC) from the direct-sun spectral measurements of a Bentham spectroradiometer located at Granada (Spain) is presented in this paper. The method relies on the differential absorption technique using two pairs of direct irradiance at adjacent wavelengths between 305 and 340 nm. The extraterrestrial constant was determined from the extrapolation to zero air mass of each wavelength pair (Langley plot method). We checked the strong influence of the cloud cover on the Bentham TOC measurements using simultaneous sky images taken with an all-sky camera. Thus, reliable TOC data are exclusively obtained during cloud-free conditions or partly cloudy conditions without the solar disk obstructed. In this work, the hourly TOC averages retrieved by the Bentham instrument with a standard deviation smaller than 3% (~ 10 Dobson Unit) are selected as high-quality TOC data. The analysis of the diurnal TOC variations during cloud-free days in late spring and summer showed different TOC values between the morning and afternoon periods. Thus, while the mornings exhibit an almost stable pattern, the afternoons display a monotonic TOC increase which could be partially related to photochemical processes in the lower troposphere associated with the formation of surface ozone. Finally, the Bentham TOC measurements were compared against the satellite data derived from three satellite instruments: OMI, GOME and SCIAMACHY. The mean absolute values of the relative differences between satellite and ground-based data were smaller than 3%, highlighting the high reliability of the retrieval method proposed in this paper to derive TOC data.

Antón, M.; Román, R.; Valenzuela, A.; Olmo, F. J.; Alados-Arboledas, L.

2013-03-01

321

Direct Observations of Explosive Eruptive Activity at a Submarine Volcano, NW Rota-1, Mariana Arc  

NASA Astrophysics Data System (ADS)

In April 2006, a series of extraordinary observations of a deep-sea volcanic eruption were made at NW Rota-1, located at 14^{circ}36'N in the Mariana arc, western Pacific. This is a conical, basaltic-andesite submarine volcano with a summit depth of 517 m. Explosive eruptive activity at NW Rota-1 was discovered in 2004 and was witnessed again in 2005, but the activity in 2006 was especially vigorous and well documented. During six dives with the remotely operated vehicle Jason II over a period of 7 days, video observations made at close range documented a diverse and increasingly energetic range of volcanic activity that culminated in explosive bursts with flashes of glowing red lava propelled by violently expanding gases. Other notable activity included discreet degassing events, extrusion of sluggish lava flows, explosions that formed dilute density currents and/or expelled rocks and ash tens of meters from the vent, and rapid pressure oscillations apparently caused by the repeated formation and condensation of steam. During the last dive when the highest extrusion rates were observed, quasi-periodic bursts from the vent, each lasting 1-10 minutes, were separated by pauses lasting 10 seconds to a few minutes. Each burst started as a plug of crusted-over lava rose in the vent and was blown apart by expanding gases, producing large lava bombs with distinctly flat, disc-like shapes. A remarkable aspect of these observations was how close Jason II could be to the vent during the eruptions. This was because the pressure of the overlying seawater dampened the energy of the explosions and slowed the velocity of volcanic ejecta. Also, lava degassing could be visualized with great clarity underwater as either clear bubbles (CO2) or opaque yellow clouds (dominated by SO2 and H2S). A portable hydrophone with a 30-hour recording capacity was deployed twice by Jason II at the summit of NW Rota-1 during the 2006 dive series. The hydrophone data extends the visual observations made at the vent and quantifies the temporal pattern and intensity of the eruptive activity. The expedition to NW Rota-1 in 2006 was supported by the NOAA Ocean Exploration Program.

Chadwick, W. W.; Embley, R. W.; de Ronde, C. E.; Deardorff, N.; Matsumoto, H.; Cashman, K. V.; Dziak, R. P.; Merle, S. G.

2006-12-01

322

Preliminary Results on Direct Observation of True Ternary fission in the reaction 232Th+d (10 MeV)  

NASA Astrophysics Data System (ADS)

Results of the first direct observation of the true ternary fission of 234Pa* nucleus are presented. The yield of the effect depending of the experimental geometry is about 10-5/binary fission. Mass of the lightest fragment in the triplet lies mainly in the range of (20÷40) a.m.u. Connection between the effect and known heavy ion or lead radioactivity is discussed.

Pyatkov, Yu.; Kamanin, D.; Krasznohorkay, A.; Alexandrov, A.; Alexandrova, I.; Csatlós, M.; Csige, L.; Gulyás, J.; Naqvi, F.; Kondratyev, N.; Kuznetsova, E.; Tyukavkin, A.; Tornyi, T.; Zhuchko, V.

2010-04-01

323

Observation of an ionospheric acceleration mechanism producing energetic (keV) ions primarily normal to the geomagnetic field direction  

Microsoft Academic Search

O\\/sup +\\/ ions with energies of approximately 1 keV have been observed flowing upward out of the ionosphere with a pitch angle distribution having a minimum along the magnetic field direction and maxima in about 130°⁻⁻¹⁴°sup 0\\/ range. The measurements were obtained with an energetic ion mass spectrometer experiment on the satellite 1976-65B at an altitude of about 7600 km

R. D. Sharp; R. G. Johnson; E. G. Shelley

1977-01-01

324

Nano-aquarium for dynamic observation of living cells fabricated by femtosecond laser direct writing of photostructurable glass  

Microsoft Academic Search

We demonstrate the fabrication of three-dimensional (3-D) hollow microstructures embedded in photostructurable glass by a\\u000a nonlinear multiphoton absorption process using a femtosecond (fs) laser. Fs laser direct writing followed by annealing and\\u000a successive wet etching in dilute hydrofluoric (HF) acid solution resulted in the rapid manufacturing of microchips with 3-D\\u000a hollow microstructures for the dynamic observation of living microorganisms and

Yasutaka Hanada; Koji Sugioka; Hiroyuki Kawano; Ikuko Shihira Ishikawa; Atsushi Miyawaki; Katsumi Midorikawa

2008-01-01

325

Direct observation of stress accumulation and relaxation in small bundles of superconducting vortices in tungsten thin-films  

E-print Network

We study the behavior of bundles of superconducting vortices when increasing the magnetic field using scanning tunneling microscopy and spectroscopy (STM/S) at 100 mK. Pinning centers are given by features on the surface corrugation. We find strong net vortex motion in a bundle towards a well defined direction. We observe continuos changes of the vortex arrangements, and identify small displacements, which stress and deform the vortex bundle, separated by larger re-arrangements or avalanches, which release accumulated stress.

I. Guillamon; H. Suderow; S. Vieira; J. Sese; R. Cordoba; J. M. De Teresa; M. R. Ibarra

2011-01-12

326

Direct observation of the topological charge of a terahertz vortex beam generated by a Tsurupica spiral phase plate  

SciTech Connect

A terahertz (THz) spiral phase plate with high transmission (>90% after Fresnel correction) and low dispersion has been developed based on the Tsurupica olefin polymer. Direct observations of the topological charge (both magnitude and sign) of a THz vortex beam are performed by using a THz camera with tilted lens focusing and radial defect introduction. The vortex outputs with a topological charge of ±1 (or ±2) are obtained at a frequency of 2 (or 4) THz.

Miyamoto, K., E-mail: k-miyamoto@faculty.chiba-u.jp [Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); Suizu, K.; Akiba, T. [Department of Electrical, Electronics and Computer Engineering, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, Chiba 275-0016 (Japan); Omatsu, T. [Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); CREST Japan Science and Technology Agency, Sanbancho, Chiyoda-ku, Tokyo 102-0075 (Japan)

2014-06-30

327

Direct observations of flow path evolution during reactive transport in porous media using clinical nuclear imaging tomography  

NASA Astrophysics Data System (ADS)

Changes in the physical structure of a porous medium associated with heterogeneous reactivity are extremely difficult to observe directly. We require the ability to monitor, quantify and predict these changes in order to optimize contaminant sequestration and remediation strategies, develop carbon storage methods and preserve groundwater resources. Field-scale detection of chemically induced permeability alteration is often accomplished by multiple hydrogeophysical observations and pumping tests, whereas direct analysis of the structural changes in a porous medium are limited to small sample sizes that do not capture the range of length scales describing heterogeneity. Here we present a novel application of medical imaging techniques to directly observe variations in flow field structure associated with mineral precipitation in real time. We use a Single Photon Emission Computed Tomography (SPECT) scanner to observe the movement of a conservative 99mTc-DTPA tracer introduced to a through-flowing column of packed sediment recovered from the Old Rifle aquifer in Western Colorado. Nine individual imaging studies were carried out over the course of 112 days of continuous flow in the 30 cm long, 10 cm diameter column. During this time, organic carbon was supplied to the influent, leading to microbially mediated reduction of Fe(III) (hyrdo)oxides and sulfate. Permeability reduction associated with this reactivity is known to occur as a result of biomass accumulation and precipitation of FeS and carbonate minerals. The nine imaging datasets each yielded intensity values over a 24 hour period at a resolution of 4.42 mm3. These images were corrected for decay and attenuation to produce 4D datasets directly proportional to Tc-DTPA concentration. These data provide a highly accurate observation of the flow field during each imaging study, and are used to assign property values to the elements of a geostatistical model using the iTOUGH2 code. Permeability distributions obtained from these inverse techniques demonstrate substantial changes in flow field structure over the 112 days of continuous reactive flow, providing a direct observation of the coupling between heterogeneous reactivity and variable permeability at a scale relevant to field applications.

Druhan, J. L.; Finsterle, S.; Vandehey, N. T.; Boutchko, R.; O'Neil, J.; Moses, W. W.; Nico, P. S.

2012-12-01

328

Direct observation of electrogenic NH4+ transport in ammonium transport (Amt) proteins  

PubMed Central

Ammonium transport (Amt) proteins form a ubiquitous family of integral membrane proteins that specifically shuttle ammonium across membranes. In prokaryotes, archaea, and plants, Amts are used as environmental NH4+ scavengers for uptake and assimilation of nitrogen. In the eukaryotic homologs, the Rhesus proteins, NH4+/NH3 transport is used instead in acid–base and pH homeostasis in kidney or NH4+/NH3 (and eventually CO2) detoxification in erythrocytes. Crystal structures and variant proteins are available, but the inherent challenges associated with the unambiguous identification of substrate and monitoring of transport events severely inhibit further progress in the field. Here we report a reliable in vitro assay that allows us to quantify the electrogenic capacity of Amt proteins. Using solid-supported membrane (SSM)-based electrophysiology, we have investigated the three Amt orthologs from the euryarchaeon Archaeoglobus fulgidus. Af-Amt1 and Af-Amt3 are electrogenic and transport the ammonium and methylammonium cation with high specificity. Transport is pH-dependent, with a steep decline at pH values of ?5.0. Despite significant sequence homologies, functional differences between the three proteins became apparent. SSM electrophysiology provides a long-sought-after functional assay for the ubiquitous ammonium transporters. PMID:24958855

Wacker, Tobias; Garcia-Celma, Juan J.; Lewe, Philipp; Andrade, Susana L. A.

2014-01-01

329

Direct observation of electrogenic NH4(+) transport in ammonium transport (Amt) proteins.  

PubMed

Ammonium transport (Amt) proteins form a ubiquitous family of integral membrane proteins that specifically shuttle ammonium across membranes. In prokaryotes, archaea, and plants, Amts are used as environmental NH4(+) scavengers for uptake and assimilation of nitrogen. In the eukaryotic homologs, the Rhesus proteins, NH4(+)/NH3 transport is used instead in acid-base and pH homeostasis in kidney or NH4(+)/NH3 (and eventually CO2) detoxification in erythrocytes. Crystal structures and variant proteins are available, but the inherent challenges associated with the unambiguous identification of substrate and monitoring of transport events severely inhibit further progress in the field. Here we report a reliable in vitro assay that allows us to quantify the electrogenic capacity of Amt proteins. Using solid-supported membrane (SSM)-based electrophysiology, we have investigated the three Amt orthologs from the euryarchaeon Archaeoglobus fulgidus. Af-Amt1 and Af-Amt3 are electrogenic and transport the ammonium and methylammonium cation with high specificity. Transport is pH-dependent, with a steep decline at pH values of ?5.0. Despite significant sequence homologies, functional differences between the three proteins became apparent. SSM electrophysiology provides a long-sought-after functional assay for the ubiquitous ammonium transporters. PMID:24958855

Wacker, Tobias; Garcia-Celma, Juan J; Lewe, Philipp; Andrade, Susana L A

2014-07-01

330

Direct observation of magnetic monopole defects in an artificial spin-ice system  

NASA Astrophysics Data System (ADS)

Frustration is the inability to satisfy the bonding requirements of all pairs in a system. Spin-ice materials have proven to be a model system to study frustration, and more recently they have been shown both theoretically and experimentally to be home to exotic excitations, whereby the atomic magnetic moments fractionalize into monopoles. Two-dimensional Kagome and square lattice systems have been shown to capture the physics of frustration and reproduce the ice-rules. In this study we have carried out magnetic force microscopy (MFM) at remanence in order to understand the magnetic reversal of an artificial kagome ice structure. We find that during the switching process ice-rule violating defects which carry magnetic charge are created and hop through the lattice with further increments to the magnetic field. These defects are the two-dimensional equivalent of magnetic monopoles in bulk spin-ice and hence are defined as monopole defects. The dynamics of the monopole defects through the artificial spin ice system will be discussed. High resolution MFM imaging at vertices and OOMMF simulations allow the micro-magnetic configuration of a monopole defect to be resolved.

Ladak, Sam; Read, Dan; Perkins, Garry; Branford, Will; Cohen, Lesley

2010-03-01

331

Direct Observation of Phase Transition Dynamics in Suspensions of Soft Colloidal Hydrogel Particles  

NASA Astrophysics Data System (ADS)

Due to the tunability of their softness and volume as a function of temperature, poly(N-isopropylacrylamide) (pNIPAm) hydrogel particles have emerged as a model system for soft colloidal spheres. By introducing AAc as comonomer, one can also tune the particle volume via pH. We report on the phase behavior of these stimuli-responsive colloids as measured with a microdialysis cell. This device, which integrates microfluidics with Particle Tracking Video-microscopy allows for simple and quick investigation of the phase behavior of suspensions the soft colloidal hydrogel as a function of pH as well as its packing density. In particular, we demonstrate the existence of an unusually broad liquid/crystal coexistence region as a function of effective particle volume fraction. Additionally, we reveal that nonequilibrium jammed states can be created in the coexistence region upon sudden large changes of pH. The phase diagram is indicative of complex interparticle interactions with weakly attractive components.

Cho, Jae Kyu; Meng, Zhiyong; Lyon, L. Andrew; Breedveld, Victor

2008-07-01

332

Direct Observation of the Coherent Nuclear Response after the Absorption of a Photon  

NASA Astrophysics Data System (ADS)

How molecules convert light energy to perform a specific transformation is a fundamental question in photophysics. Ultrafast spectroscopy reveals the kinetics associated with electronic energy flow, but little is known about how absorbed photon energy drives nuclear motion. Here we used ultrabroadband transient absorption spectroscopy to monitor coherent vibrational energy flow after photoexcitation of the retinal chromophore. In the proton pump bacteriorhodopsin, we observed coherent activation of hydrogen-out-of-plane wagging and backbone torsional modes that were replaced by unreactive coordinates in the solution environment, concomitant with a deactivation of the reactive relaxation pathway.

Liebel, M.; Schnedermann, C.; Bassolino, G.; Taylor, G.; Watts, A.; Kukura, P.

2014-06-01

333

Direct Observations of Three Dimensional Growth of Hydrates Hosted in Porous Media  

SciTech Connect

The visualization of time-resolved three-dimensional growth of tetrahydrofuran hydrates with glass spheres of uniform size as porous media using synchrotron x-ray computed microtomography is presented. The images of hydrate patches, formed from excess tetrahydrofuran in aqueous solution, show random nucleation and growth concomitant with grain movement but independent of container-wall effect. Away from grain surfaces, hydrate surface curvature was convex showing that liquid, not hydrate, was the wetting phase, similar to ice growth in porous media. The extension of the observed behavior to methane hydrates could have implications in understanding their role in seafloor stability and climate change.

Kerkar, P.; Jones, K; Kleinberg, R; Lindquist, W; Tomov, S; Feng, H; Mahajan, D

2009-01-01

334

Singlet fission in rubrene single crystal: direct observation by femtosecond pump-probe spectroscopy.  

PubMed

The excited state dynamics of rubrene in solution and in the single crystal were studied by femtosecond pump-probe spectroscopy under various excitation conditions. Singlet fission was demonstrated to play a predominant role in the excited state relaxation of the rubrene crystal in contrast to rubrene in solution. Upon 500 nm excitation, triplet excitons form on the picosecond time scale via fission from the lowest excited singlet state. Upon 250 nm excitation, fission from upper excited singlet states is observed within 200 fs. PMID:22510785

Ma, Lin; Zhang, Keke; Kloc, Christian; Sun, Handong; Michel-Beyerle, Maria E; Gurzadyan, Gagik G

2012-06-21

335

Direct observation of the coherent nuclear response after the absorption of a photon.  

PubMed

How molecules convert light energy to perform a specific transformation is a fundamental question in photophysics. Ultrafast spectroscopy reveals the kinetics associated with electronic energy flow, but little is known about how absorbed photon energy drives nuclear motion. Here we used ultrabroadband transient absorption spectroscopy to monitor coherent vibrational energy flow after photoexcitation of the retinal chromophore. In the proton pump bacteriorhodopsin, we observed coherent activation of hydrogen-out-of-plane wagging and backbone torsional modes that were replaced by unreactive coordinates in the solution environment, concomitant with a deactivation of the reactive relaxation pathway. PMID:24972232

Liebel, M; Schnedermann, C; Bassolino, G; Taylor, G; Watts, A; Kukura, P

2014-06-13

336

Direct Observation of the Phenomenology of a Solid Thermal Explosion Using Time-Resolved Proton Radiography  

NASA Astrophysics Data System (ADS)

We present a new phenomenology for burn propagation inside a thermal explosion based on dynamic radiography. Radiographic images were obtained of an aluminum cased solid cylindrical sample of a plastic bonded formulation of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine. The phenomenology observed is ignition followed by cracking in the solid accompanied by the propagation of a radially symmetric front of increasing proton transmission. This is followed by a further increase in transmission through the sample, ending after approximately 100?s. We show that these processes are consistent with the propagation of a convective burn front followed by consumption of the remaining solid by conductive particle burning.

Smilowitz, L.; Henson, B. F.; Romero, J. J.; Asay, B. W.; Schwartz, C. L.; Saunders, A.; Merrill, F. E.; Morris, C. L.; Kwiatkowski, K.; Hogan, G.; Nedrow, P.; Murray, M. M.; Thompson, T. N.; McNeil, W.; Rightley, P.; Marr-Lyon, M.

2008-06-01

337

Direct observation of lipid bilayer disruption by poly(amidoamine) dendrimers.  

PubMed

Atomic force microscopy (AFM) is employed to observe the effect of poly(amidoamine) (PAMAM) dendrimers on 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) lipid bilayers. Aqueous solutions of generation 7 PAMAM dendrimers cause the formation of holes 15-40 nm in diameter in previously intact bilayers. This effect is observed for two different branch end-groups--amine and carboxyl. In contrast, carboxyl-terminated core-shell tectodendrimer clusters do not create holes in the lipid membrane but instead show a strong affinity to adsorb to the edges of existing bilayer defects. A possible mechanism for the formation of holes in the lipid bilayer is proposed. The dendrimers remove lipid molecules from the substrate and form aggregates consisting of a dendrimer surrounded by lipid molecules. Dynamic light scattering (DLS) measurements as well as 31P NMR data support this explanation. The fact that tectodendrimers behave differently suggests that their cluster-like architecture plays an important role in their interaction with the lipid bilayer. PMID:15530443

Mecke, Almut; Uppuluri, Srinivas; Sassanella, Timothy M; Lee, Dong-Kuk; Ramamoorthy, A; Baker, James R; Orr, Bradford G; Banaszak Holl, Mark M

2004-11-01

338

Direct observation of a borane–silane complex involved in frustrated Lewis-pair-mediated hydrosilylations  

NASA Astrophysics Data System (ADS)

Perfluorarylborane Lewis acids catalyse the addition of silicon–hydrogen bonds across C=C, C=N and C=O double bonds. This ‘metal-free’ hydrosilylation has been proposed to occur via borane activation of the silane Si–H bond, rather than through classical Lewis acid/base adducts with the substrate. However, the key borane/silane adduct had not been observed experimentally. Here it is shown that the strongly Lewis acidic, antiaromatic 1,2,3-tris(pentafluorophenyl)-4,5,6,7-tetrafluoro-1-boraindene forms an observable, isolable adduct with triethylsilane. The equilibrium for adduct formation was studied quantitatively through variable-temperature NMR spectroscopic investigations. The interaction of the silane with the borane occurs through the Si–H bond, as evidenced by trends in the Si–H coupling constant and the infrared stretching frequency of the Si–H bond, as well as by X-ray crystallography and theoretical calculations. The adduct's reactivity with nucleophiles demonstrates conclusively the role of this species in metal-free ‘frustrated-Lewis-pair’ hydrosilylation reactions.

Houghton, Adrian Y.; Hurmalainen, Juha; Mansikkamäki, Akseli; Piers, Warren E.; Tuononen, Heikki M.

2014-11-01

339

Direct observation of a borane-silane complex involved in frustrated Lewis-pair-mediated hydrosilylations.  

PubMed

Perfluorarylborane Lewis acids catalyse the addition of silicon-hydrogen bonds across C=C, C=N and C=O double bonds. This 'metal-free' hydrosilylation has been proposed to occur via borane activation of the silane Si-H bond, rather than through classical Lewis acid/base adducts with the substrate. However, the key borane/silane adduct had not been observed experimentally. Here it is shown that the strongly Lewis acidic, antiaromatic 1,2,3-tris(pentafluorophenyl)-4,5,6,7-tetrafluoro-1-boraindene forms an observable, isolable adduct with triethylsilane. The equilibrium for adduct formation was studied quantitatively through variable-temperature NMR spectroscopic investigations. The interaction of the silane with the borane occurs through the Si-H bond, as evidenced by trends in the Si-H coupling constant and the infrared stretching frequency of the Si-H bond, as well as by X-ray crystallography and theoretical calculations. The adduct's reactivity with nucleophiles demonstrates conclusively the role of this species in metal-free 'frustrated-Lewis-pair' hydrosilylation reactions. PMID:25343603

Houghton, Adrian Y; Hurmalainen, Juha; Mansikkamäki, Akseli; Piers, Warren E; Tuononen, Heikki M

2014-11-01

340

Direct observations of oxygen-induced platinum nanoparticle ripening studied by in situ TEM.  

PubMed

This study addresses the sintering mechanism of Pt nanoparticles dispersed on a planar, amorphous Al(2)O(3) support as a model system for a catalyst for automotive exhaust abatement. By means of in situ transmission electron microscopy (TEM), the model catalyst was monitored during the exposure to 10 mbar air at 650 degrees C. Time-resolved image series unequivocally reveal that the sintering of Pt nanoparticles was mediated by an Ostwald ripening process. A statistical analysis of an ensemble of Pt nanoparticles shows that the particle size distributions change shape from an initial Gaussian distribution via a log-normal distribution to a Lifshitz-Slyozov-Wagner (LSW) distribution. Furthermore, the time-dependency of the ensemble-averaged particle size and particle density is determined. A mean field kinetic description captures the main trends in the observed behavior. However, at the individual nanoparticle level, deviations from the model are observed suggesting in part that the local environment influences the atom exchange process. PMID:20481529

Simonsen, Søren B; Chorkendorff, Ib; Dahl, Søren; Skoglundh, Magnus; Sehested, Jens; Helveg, Stig

2010-06-16

341

A direct observation of solar neutrons following the 0118 UT flare on 1980 June 21  

NASA Technical Reports Server (NTRS)

The Gamma Ray Spectrometer on the Solar Maximum Mission satellite has observed energetic solar neutrons (greater than 50 MeV) at the earth following a solar flare that occurred on the west limb on June 21, 1980 at 01:18:20 UT. Impulsive photon emission from 10 keV to greater than 65 MeV lasting over a period of about 66 s was followed by a transient flux of 50-600 MeV neutrons incident over a 17 minute period. The peak counting rate corresponds to an average flux at the earth of (3.8 + or - 0.6) x 10 to the -2nd neutrons/sq cm s at 130 MeV. These observations indicate the emission of 3 x 10 to the 28th neutrons/sr with energies greater than 50 MeV, requiring the rapid acceleration (much less than 60 s) of protons to GeV energies during the impulsive phase of the flare.

Chupp, E. L.; Forrest, D. J.; Ryan, J. M.; Heslin, J.; Reppin, C.; Pinkau, K.; Kanbach, G.; Rieger, E.; Share, G. H.

1982-01-01

342

A microfluidic imaging chamber for the direct observation of chemotactic transmigration  

PubMed Central

To study the roles of nonmuscle myosin II (NM-II) during invasive cell migration, microfluidic migration chambers have been designed and fabricated using photo- and soft-lithography microfabrication techniques. The chamber consists of two channels separated by a vertical barrier with multiple bays of pores with widths varying from 6 µm to 16 µm, and lengths varying from 25µm to 50µm. The cells are plated in the channel on one side of the barrier while a chemoattractant is flowed through the channel on the other side of the barrier. In these chambers, cells can be observed with transmitted light or fluorescence optics while they chemotax through various sized pores that impose differential mechanical resistance to transmigration. As an initial test of this device, we compared breast-cancer cell chemotactic transmigration through different pore sizes with and without inhibition of NM-II. Two distinct rates were observed as cells attempted to pull their nucleus through the smaller pores, and the faster nuclear transit mode was critically dependent on NM-II motor activity. The ability to monitor cells as they chemotax through pores of different dimensions within a single experimental system provides novel information on how pore size affects cell morphology and migration rate, providing a dramatic improvement of imaging potential relative to other in vitro transmigration systems such as Boyden chambers. PMID:20309736

Breckenridge, Mark T.; Egelhoff, Thomas T.; Baskaran, Harihara

2010-01-01

343

Direct observation of cesium at the interlayer region in phlogopite mica.  

PubMed

To investigate the sorption mechanism of cesium (Cs) into clay minerals, high-resolution (scanning) transmission electron microscopy (TEM/STEM) imaging of Cs in mica (phlogopite) has been conducted. Platy phlogopite powders were immersed in a cesium chloride (CsCl) solution to achieve Cs(+)-K(+) ion-exchange at the interlayer regions in phlogopite. To observe many phlogopite particles with the incident electron beam parallel to the mica layers, cross-sectional thin specimens were prepared from sedimented particles using a focused ion beam. High-angle annular dark-field imaging with STEM is superior to conventional high-resolution TEM (HRTEM) for visualizing Cs at interlayer sites even in thicker crystal regions and/or at lower magnification due to the intense Z-contrast of Cs. However, HRTEM is also practical for estimating the concentration of Cs at the interlayer site from the thickness dependence of the contrast at the interlayer region. Cs sorption of micas was previously thought to be localized mainly at the frayed-edge sites of mica crystals. However, the present observations indicate that Cs substitution of K occurs not around crystal edges but deep inside the crystals along specific interlayer regions. PMID:24291667

Okumura, Taiga; Tamura, Kenji; Fujii, Eiko; Yamada, Hirohisa; Kogure, Toshihiro

2014-02-01

344

Epidemiologic Studies of Cancer in Agricultural Populations: Observations and Future Directions  

PubMed Central

This paper reviews epidemiologic studies of cancer among agricultural populations to identify possible associations and to provide a focus for future investigations. Meta-analyses of mortality surveys of farmers find excesses of several cancers, including connective tissue, non-Hodgkin lymphoma, Hodgkin disease, and multiple myeloma and cancers of the skin, stomach and brain and deficits for total mortality, heart disease, total cancer, and cancers of the esophagus, colon, lung and bladder. Meta-analyses of studies of individual cancers also support these findings indicating a need to identify exposures and lifestyle factors that might account for this mortality pattern. Although cancer studies of other occupations that might have pesticide exposures in common with farmers show some similarities with observations among farmers, the overall patterns are quite different. This suggests that pesticides are not likely to fully explain the cancer and other disease patterns observed among farmers. Because exposures vary by type of farm operation, exposures for individual farmers can differ considerably. Studies in the future need to focus on the full range of exposures to fully understand the cancer pattern in farmers. PMID:19437268

Blair, Aaron; Freeman, Laura Beane

2009-01-01

345

The direct observation of alkali vapor species in biomass combustion and gasification  

SciTech Connect

This report summarizes new data from screening various feedstocks for alkali vapor release under combustion conditions. The successful development of a laboratory flow reactor and molecular beam, mass spectrometer interface is detailed. Its application to several herbaceous and woody feedstocks, as well as a fast-pyrolysis oil, under 800 and 1,100{degrees}C batch combustion, is documented. Chlorine seems to play a large role in the facile mobilization of potassium. Included in the report is a discussion of relevant literature on the alkali problem in combustors and turbines. Highlighted are the phenomena identified in studies on coal and methods that have been applied to alkali speciation. The nature of binding of alkali in coal versus biomass is discussed, together with the implications for the ease of release. Herbaceous species and many agricultural residues appear to pose significant problems in release of alkali species to the vapor at typical combustor temperatures. These problems could be especially acute in direct combustion fired turbines, but may be ameliorated in integrated gasification combined cycles.

French, R.J.; Dayton, D.C.; Milne, T.A.

1994-01-01

346

What is the probability that direct detection experiments have observed Dark Matter?  

E-print Network

In Dark Matter direct detection we are facing the situation of some experiments reporting positive signals which are in conflict with limits from other experiments. Such conclusions are subject to large uncertainties introduced by the poorly known local Dark Matter distribution. We present a method to calculate an upper bound on the joint probability of obtaining the outcome of two potentially conflicting experiments under the assumption that the Dark Matter hypothesis is correct, but completely independent of assumptions about the Dark Matter distribution. In this way we can quantify the compatibility of two experiments in an astrophysics independent way. We illustrate our method by testing the compatibility of the hints reported by DAMA and CDMS-Si with the limits from the LUX and SuperCDMS experiments. The method does not require Monte Carlo simulations but is mostly based on using Poisson statistics. In order to deal with signals of few events we introduce the so-called "signal length" to take into account energy information. The signal length method provides a simple way to calculate the probability to obtain a given experimental outcome under a specified Dark Matter and background hypothesis.

Nassim Bozorgnia; Thomas Schwetz

2014-11-17

347

Direct Brillouin light scattering observation of dark spin-wave envelope solitons in magnetic films  

NASA Astrophysics Data System (ADS)

The formation and evolution of dark spin-wave envelope solitons have been studied in a yttrium iron garnet (YIG) film. The Brillouin light scattering (BLS) technique has been used to map the propagation and evolution of the excited dark solitons. Experiments have been carried out using (1) a YIG-film delay-line structure supporting propagation of backward volume spin waves, (2) time- and space-resolved forward-scattering BLS, (3) a fixed magnetic field of 1000 Oe applied along the propagation direction, and (4) a soliton excitation technique based on the nonlinear interaction of two large amplitude cw input signals with fixed frequency enabling an induced modulation instability. Theoretical interpretation of the experiments based on numerical solution of the Ginzburg-Landau equation taking into account the conditions of nonlinear spin-wave dissipation is given. It is found that the dark soliton formation process involves competition between effects of nonlinearity and dispersion, and that nonlinear damping effects play an important role.

Ordóñez-Romero, César L.; Cherkasskii, Mikhail A.; Qureshi, Naser; Kalinikos, Boris A.; Patton, Carl E.

2013-05-01

348

Direct observation of two-electron Ag(I)/Ag(III) redox cycles in coupling catalysis.  

PubMed

Silver is extensively used in homogeneous catalysis for organic synthesis owing to its Lewis acidity, and as a powerful one-electron oxidant. However, two-electron redox catalytic cycles, which are most common in noble metal organometallic reactivity, have never been considered. Here we show that a Ag(I)/Ag(III) catalytic cycle is operative in model C-O and C-C cross-coupling reactions. An aryl-Ag(III) species is unequivocally identified as an intermediate in the catalytic cycle and we provide direct evidence of aryl halide oxidative addition and C-N, C-O, C-S, C-C and C-halide bond-forming reductive elimination steps at monometallic silver centres. We anticipate our study as the starting point for expanding Ag(I)/Ag(III) redox chemistry into new methodologies for organic synthesis, resembling well-known copper or palladium cross-coupling catalysis. Furthermore, findings described herein provide unique fundamental mechanistic understanding on Ag-catalysed cross-coupling reactions and dismiss the generally accepted conception that silver redox chemistry can only arise from one-electron processes. PMID:25014317

Font, Marc; Acuña-Parés, Ferran; Parella, Teodor; Serra, Jordi; Luis, Josep M; Lloret-Fillol, Julio; Costas, Miquel; Ribas, Xavi

2014-01-01

349

Direct observation of individual particle armored bubble interaction, stability, and coalescence dynamics.  

PubMed

The interactions between two individual particle-stabilized bubbles were investigated, in the absence of surfactant, using a combination of coalescence rig and high-speed video camera. This combination allows the visualization of bubble coalescence dynamics which provide information on bubble stability. Experimental data suggested that bubble stability is enhanced by both the adsorption of particles at the interface as indicated by the long induction time and the increase in damping coefficient at high surface coverage. The interaction between an armored bubble and a bare bubble (asymmetric interaction) can be destabilized through the addition of a small amount of salt, which suggested that electrostatic interactions play a significant role in bubble stability. Interestingly, the DLVO theory cannot be used to describe the bubble stability in the case of a symmetric interaction as coalescence was inhibited at 0.1 M KCl in both the absence and presence of particles at the interfaces. Furthermore, bubbles can also be destabilized by increasing the particle hydrophobicity. This behavior is due to thinner liquid films between bubbles and an increase in film drainage rate. The fraction of particles detached from the bubble surface after film rupture was found to be very similar within the range of solution ionic strength, surface coverage, and particle hydrophobicity studied. This lack of dependence implies that the kinetic energy generated by the coalescing bubbles is larger than the attachment energy of the particles and dominates the detachment process. This study illuminates the stability behavior of individual particle-stabilized bubbles and has potential impact on processes which involve their interaction. PMID:23796213

Tan, Sin-Ying; Ata, Seher; Wanless, Erica J

2013-07-18

350

Amplified Doppler shift observed in diffraction images as function of the COBE "ether drift" direction  

E-print Network

We report results on an ``one-way light path'' laser diffraction experiment as a function of the laser beam alignment relative to the Earth's velocity vector obtained by COBE measurements of the Doppler shift in the cosmic microwave background radiation (CMBR). An amplified Doppler shift is observed in the diffraction images, and the effect is compatible with a ``dipole'' speed of light anisotropy due to Earth's motion relative to the ``CMBR rest frame'', with an amplitude of $\\delta c/\\bar{c}=0.00123$. This amplitude coincides with the value of the dipole temperature anisotropy $\\delta T/\\bar{T}=0.00123$ of the CMBR obtained by COBE. Our results point out that it is not possible to neglect the preferred frame imposed by the cosmology and they are well described by the Ether Gauge Theory (an extension of the Lorentz's ether theory) and it satisfies the cosmological time boundary condition.

C. E. Navia; C. R. A. Augusto

2006-04-06

351

New Results from Space and Field Observations on the Aerosol Direct and Indirect Radiative Forcing  

NASA Technical Reports Server (NTRS)

New space observations from the MODIS instrument on board the Terra satellite and analysis of POLDER data flown on the ADEOS satellite, show in great details the spatial and seasonal variability of the global aerosol system. These spaceborne instruments distinguish fine aerosol from man-made regional pollution and biomass burning from mostly natural coarse dust and sea salt aerosol. E.g. fine regional pollution in and around the Indian sub-continent, Europe and North America; smoke from biomass burning in Southern Africa and Southern America; coarse dust from West Africa and mixed dust pollution and smoke from West and central Africa and East Asia. These regions were also studied extensively in focused field experiments and by the distributed AERONET network. The results generate the first climatologies of the aerosol system, are used to derive the aerosol radiative effects and to estimate the anthropogenic component. The measurements are also used to evaluate each other and constrain aerosol transport models.

Kaufman, Yoram J.; Remer, Lorraine; Tanre, Didier; Boucher, Olivier; Chin, Mian; Dubovik, Oleg; Holben, Brent

2002-01-01

352

Direct observation of vacuum fluctuations in a spinor Bose-Einstein condensate  

E-print Network

The nature of the vacuum state and its fluctuations constitutes one of the most fascinating aspects of modern physics. Despite their non-intuitive character, vacuum fluctuations play an important role for our understanding of nature. Specifically, the parametric amplification of such fluctuations is crucial for phenomena ranging from optical parametric down-conversion to stimulated positronium annihilation, and boson creation in Universe inflation. Spinor Bose-Einstein condensates, consisting of atoms with non-zero total spin, provide an optimal system for the investigation of the vacuum state, since vacuum fluctuations can dominate classical fluctuations in the spin dynamics of these magnetic superfluids. Here we explore the amplification of vacuum fluctuations in gaseous spinor condensates in an unstable spin configuration. We observe strong instability resonances in the spinor condensate, induced by the confinement of the atomic ensemble. Our work shows that it is crucial for the understanding of spinor dy...

Klempt, Carsten; Gebreyesus, Gebremedhn; Scherer, Manuel; Henninger, Thorsten; Hyllus, Philipp; Ertmer, Wolfgang; Santos, Luis; Arlt, Jan

2009-01-01

353

Direct observation of the collapse of the delocalized excess electron in water.  

PubMed

It is generally assumed that the hydrated electron occupies a quasi-spherical cavity surrounded by only a few water molecules in its equilibrated state. However, in the very moment of its generation, before water has had time to respond to the extra charge, it is expected to be significantly larger in size. According to a particle-in-a-box picture, the frequency of its absorption spectrum is a sensitive measure of the initial size of the electronic wavefunction. Here, using transient terahertz spectroscopy, we show that the excess electron initially absorbs in the far-infrared at a frequency for which accompanying ab initio molecular dynamics simulations estimate an initial delocalization length of ? 40 Å. The electron subsequently shrinks due to solvation and thereby leaves the terahertz observation window very quickly, within ? 200 fs. PMID:25054939

Savolainen, Janne; Uhlig, Frank; Ahmed, Saima; Hamm, Peter; Jungwirth, Pavel

2014-08-01

354

Direct observation of cationic ordering in double perovskite Sr?FeReO? crystals.  

PubMed

Two kinds of Sr?FeReO? (SFRO) samples, pristine SFRO and Re-excess SFRO, were prepared and we visualized the local atomic structure in terms of cationic ordering in the prepared SFRO samples via high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM). HAADF-STEM results demonstrated the high degree of cationic ordering maintains in both the pristine SFRO and Re-excess SFRO samples. On the other hand, defective structures such as antiphase boundary and Re-deficient phase were observed dominantly in the pristine SFRO, and thus the poor magnetic property in the pristine SFRO is attributed to those defective structures related with the frustrated Fe/Re ordering. PMID:23920168

Choi, Si-Young; Lim, Jong Bong; Ikuhara, Yuichi; Suvorov, Danilo; Jeon, Jae-Ho

2013-08-01

355

Direct Observation of Differences of Carotenoid Polyene Chain cis/trans Isomers Resulting from Structural Topology  

PubMed Central

In the present paper, trapped ion mobility spectrometry (TIMS) and theoretical calculations have been used to study carotenoid geometrical motifs generated by photoisomerization from the all-trans geometry. Multiple geometric isomers of the carotenoids lutein and zeaxanthin were separated using TIMS (R > 110) for [M]+, [M + H]+, and [M – 18]+ molecular species. Comparison of observed cross sections with those obtained from molecular dynamics calculations showed that the number of cis double bonds and s-cis single bonds in the polyene chain determine the topology space of the carotenoid. The intensities of IMS signals are correlated with the relative stability of these geometric isomers.1,2 The most stable isomer is the all-trans geometry regardless of the ionization state ([M – 18]+, [M]+, and [M + H]+), and structural stability decreases with the increasing number of cis and/or s-cis bonds in the polyene chain. PMID:24428664

2015-01-01

356

Direct observation of differences of carotenoid polyene chain cis/trans isomers resulting from structural topology.  

PubMed

In the present paper, trapped ion mobility spectrometry (TIMS) and theoretical calculations have been used to study carotenoid geometrical motifs generated by photoisomerization from the all-trans geometry. Multiple geometric isomers of the carotenoids lutein and zeaxanthin were separated using TIMS (R > 110) for [M](+), [M + H](+), and [M - 18](+) molecular species. Comparison of observed cross sections with those obtained from molecular dynamics calculations showed that the number of cis double bonds and s-cis single bonds in the polyene chain determine the topology space of the carotenoid. The intensities of IMS signals are correlated with the relative stability of these geometric isomers.1,2 The most stable isomer is the all-trans geometry regardless of the ionization state ([M - 18](+), [M](+), and [M + H](+)), and structural stability decreases with the increasing number of cis and/or s-cis bonds in the polyene chain. PMID:24428664

Schenk, Emily R; Mendez, Vanesa; Landrum, John T; Ridgeway, Mark E; Park, Melvin A; Fernandez-Lima, Francisco

2014-02-18

357

Direct observation of electro-optic modulation in a single split-ring resonator  

NASA Astrophysics Data System (ADS)

We study experimentally and numerically the electro-optic (EO) effect in a single metamaterial cell incorporating a nonlinear crystal. A metal split-ring fabricated on a ZnTe substrate resonating at 3 GHz was excited with a tunable microwave source. A linearly polarized laser beam probed the EO effect. Enhanced EO modulation was observed in the split-gap at the resonant frequency proportional to Q-factor. The electric field surrounding the metamaterial element in the ZnTe was mapped by the EO effect and agrees well with simulation. We show that high-Q metamaterials incorporating an EO crystal in the split-gap could lead to improved EO devices.

Shchegolkov, Dmitry Yu.; Reiten, Matthew T.; O'Hara, John F.; Azad, Abul K.

2013-03-01

358

Complex Observation in Electron Microscopy. II. Direct Visualization of Phases and Amplitudes of Exit Wave Functions  

NASA Astrophysics Data System (ADS)

We report microscopic observation of complex waves emitted from objects. Two images sequentially detected at the image plane with two transmission electron microscopic (TEM) methods, the conventional and the phase-contrasted, are numerically combined to reproduce complex wave functions, which are holding complete optical information. The long lasting issue in conventional TEM that the contrast and the resolution of images are difficult to be simultaneously optimized was settled with the complex wave functions. The aberration-corrected phase images of ferritin (at 400 kV) and TMV (at 100 kV) did show an extraordinary high contrast free from image distortion without sacrificing the resolution compared with that obtained by conventional TEM.

Danev, Radostin; Nagayama, Kuniaki

2001-03-01

359

Direct observation of intermediates in a thermodynamically controlled solid-state dynamic covalent reaction.  

PubMed

We present the first polymorph interconversion study that uses solid-state dynamic covalent chemistry (DCC). This system exhibits unexpected and rich behavior, including the observation that under appropriate conditions the polymorph interconversion of a heterodimer proceeds through reversible covalent chemistry intermediates, and this route is facilitated by one of the two disulfide homodimers involved in the reaction. Furthermore, we demonstrate experimentally that in all cases a dynamic equilibrium is reached, meaning that changing the milling conditions affects the free energy difference between the two polymorphs and thus their relative stability. We suggest that this effect is due to the surface solvation energy combined with the high surface to volume ratio of the nanocrystalline powder. PMID:25314624

Belenguer, Ana M; Lampronti, Giulio I; Wales, David J; Sanders, Jeremy K M

2014-11-19

360

Extreme-Ultraviolet Spectroscopic Observation of Direct Coronal Heating During a C-Class Solar Flare  

NASA Technical Reports Server (NTRS)

With the Coronal Diagnostic Spectrometer operating in rapid cadence (9.8 s) stare mode during a C6.6 flare on the solar disk, we observed a sudden brightening of Fe xix line emission (formed at temperature T ˜ 8 MK) above the pre-flare noise without a corresponding brightening of emission from ions formed at lower temperatures, including He i (0.01 MK), Ov (0.25 MK), and Si xii (2 MK). The sudden brightening persisted as a plateau of Fe xix intensity that endured more than 11 minutes. The Fe xix emission at the rise and during the life of the plateau showed no evidence of significant bulk velocity flows, and hence cannot be attributed to chromospheric evaporation. However, the line width showed a significant broadening at the rise of the plateau, corresponding to nonthermal velocities of at least 89 km s-1 due to reconnection outflows or turbulence. During the plateau He i, Ov, and Si xii brightened at successively later times starting about 3.5 minutes after Fe xix, which suggests that these brightenings were produced by thermal conduction from the plasma that produced the Fe xix line emission; however, we cannot rule out the possibility that they were produced by a weak beam of nonthermal particles. We interpret an observed shortening of the Ov wavelength for about 1.5 minutes toward the middle of the plateau to indicate new upward motions driven by the flare, as occurs during gentle chromospheric evaporation; relative to a quiescent interval shortly before the flare, the Ov upward velocity was around -10 km s-1.

Brosius, Jeffrey W.

2012-01-01

361

Direct Observation of Phosphate Inhibiting the Force-Generating Capacity of a Miniensemble of Myosin Molecules  

PubMed Central

Elevated levels of phosphate (Pi) reduce isometric force, providing support for the notion that the release of Pi from myosin is closely associated with the generation of muscular force. Pi is thought to rebind to actomyosin in an ADP-bound state and reverse the force-generating steps, including the rotation of the lever arm (i.e., the powerstroke). Despite extensive study, this mechanism remains controversial, in part because it fails to explain the effects of Pi on isometric ATPase and unloaded shortening velocity. To gain new insight into this process, we determined the effect of Pi on the force-generating capacity of a small ensemble of myosin (?12 myosin heads) using a three-bead laser trap assay. In the absence of Pi, myosin pulled the actin filament out of the laser trap an average distance of 54 ± 4 nm, translating into an average peak force of 1.2 pN. By contrast, in the presence of 30 mM Pi, myosin generated only enough force to displace the actin filament by 13 ± 1 nm, generating just 0.2 pN of force. The elevated Pi also caused a >65% reduction in binding-event lifetime, suggesting that Pi induces premature detachment from a strongly bound state. Definitive evidence of a Pi-induced powerstroke reversal was not observed, therefore we determined if a branched kinetic model in which Pi induces detachment from a strongly bound, postpowerstroke state could explain these observations. The model was able to accurately reproduce not only the data presented here, but also the effects of Pi on both isometric ATPase in muscle fibers and actin filament velocity in a motility assay. The ability of the model to capture the findings presented here as well as previous findings suggests that Pi-induced inhibition of force may proceed along a kinetic pathway different from that of force generation. PMID:24268149

Debold, Edward P.; Walcott, Sam; Woodward, Mike; Turner, Matthew A.

2013-01-01

362

Direct observation of unstained wet biological samples by scanning-electron generation X-ray microscopy  

SciTech Connect

Analytical tools of nanometre-scale resolution are indispensable in the fields of biology, physics and chemistry. One suitable tool, the soft X-ray microscope, provides high spatial resolution of visible light for wet specimens. For biological specimens, X-rays of water-window wavelength between carbon (284 eV; 4.3 nm) and oxygen (540 eV; 2.3 nm) absorption edges provide high-contrast imaging of biological samples in water. Among types of X-ray microscope, the transmission X-ray microscope using a synchrotron radiation source with diffractive zone plates offers the highest spatial resolution, approaching 15-10 nm. However, even higher resolution is required to measure proteins and protein complexes in biological specimens; therefore, a new type of X-ray microscope with higher resolution that uses a simple light source is desirable. Here we report a novel scanning-electron generation X-ray microscope (SGXM) that demonstrates direct imaging of unstained wet biological specimens. We deposited wet yeasts in the space between two silicon nitride (Si{sub 3}N{sub 4}) films. A scanning electron beam of accelerating voltage 5 keV and current 1.6 nA irradiates the titanium (Ti)-coated Si{sub 3}N{sub 4} film, and the soft X-ray signal from it is detected by an X-ray photodiode (PD) placed below the sample. The SGXM can theoretically achieve better than 5 nm resolution. Our method can be utilized easily for various wet biological samples of bacteria, viruses, and protein complexes.

Ogura, Toshihiko, E-mail: t-ogura@aist.go.jp [Neuroscience Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Central 2, Umezono, Tsukuba, Ibaraki 305-8568 (Japan)] [Neuroscience Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Central 2, Umezono, Tsukuba, Ibaraki 305-8568 (Japan)

2010-01-01

363

Direct observation of ON and OFF pathways in the Drosophila visual system.  

PubMed

Visual motion perception is critical to many animal behaviors, and flies have emerged as a powerful model system for exploring this fundamental neural computation. Although numerous studies have suggested that fly motion vision is governed by a simple neural circuit [1-3], the implementation of this circuit has remained mysterious for decades. Connectomics and neurogenetics have produced a surge in recent progress, and several studies have shown selectivity for light increments (ON) or decrements (OFF) in key elements associated with this circuit [4-7]. However, related studies have reached disparate conclusions about where this selectivity emerges and whether it plays a major role in motion vision [8-13]. To address these questions, we examined activity in the neuropil thought to be responsible for visual motion detection, the medulla, of Drosophila melanogaster in response to a range of visual stimuli using two-photon calcium imaging. We confirmed that the input neurons of the medulla, the LMCs, are not responsible for light-on and light-off selectivity. We then examined the pan-neural response of medulla neurons and found prominent selectivity for light-on and light-off in layers of the medulla associated with two anatomically derived pathways (L1/L2 associated) [14, 15]. We next examined the activity of prominent interneurons within each pathway (Mi1 and Tm1) and found that these neurons have corresponding selectivity for light-on or light-off. These results provide direct evidence that motion is computed in parallel light-on and light-off pathways, demonstrate that this selectivity emerges in neurons immediately downstream of the LMCs, and specify where crucial elements of motion computation occur. PMID:24704075

Strother, James A; Nern, Aljoscha; Reiser, Michael B

2014-05-01

364

Direct observations of sympathetic cholinergic vasodilatation of skeletal muscle small arteries in the cat.  

PubMed Central

1. The aim of this study was to examine the actual changes of the internal diameter (i.d.) of arterial vessels of skeletal muscle evoked by activation of sympathetic cholinergic nerve fibres during stimulation of the hypothalamic defence area in anaesthetized cats. 2. For this purpose, we have used our novel X-ray TV system for visualizing small arteries (100-500 microm i.d.) of the triceps surae muscle and larger extramuscular arteries (500-1400 microm i.d.) of the hindlimb (the femoral (FA), popliteal (PA) and distal caudal femoral (DCFA) arteries). The passage of a contrast medium from the large extramuscular arteries to the smaller intramuscular arteries was serially measured before and during hypothalamic stimulation. 3. Hypothalamic stimulation increased mean arterial blood pressure, heart rate and femoral vascular conductance. The i.d. of FA, PA, and DCFA did not change during the hypothalamic stimulation, whereas the i.d. of small arteries in the triceps surae muscle increased by 48 +/- 2% (mean +/- S.E.M.) and the cross-sectional area increased concomitantly by 118%. The maximum increase in i.d. of 78 +/- 6%, was observed in arteries of 100-200 microm. These increases in diameter were markedly reduced by intra-arterial injection of atropine or by cutting the sciatic nerve, but not by phentolamine and propranolol given together. 4. The vasodilatation evoked by hypothalamic stimulation was seen in almost all the sections of the small arteries observed under control conditions and was distributed along the entire length of the vessel. In addition, the number of arterial vessels that could be detected increased by 42% during hypothalamic stimulation. The newly detected arterial branches, which ranged from 100 to 300 microm in diameter, mostly arose from the branching points. 5. It is concluded that stimulation of sympathetic cholinergic nerve fibres dilates the small arteries of skeletal muscle ranging from 100 to 500 microm, but not the larger extramuscular arteries. Images Figure 4 Figure 8 PMID:9097945

Matsukawa, K; Shindo, T; Shirai, M; Ninomiya, I

1997-01-01

365

Direct observation of 1000m deep convection in the Irminger Sea by Argo-02 floats  

NASA Astrophysics Data System (ADS)

Deep convection is an important process for intermediate and deep-water masses formation and for deep ocean ventilation. Deep convection is particularly important in the North Atlantic Ocean because it contributes at setting the density of the lower limb of the Meridional Overturning Circulation. The Labrador Sea is the most famous place in the North Atlantic Ocean where deep convection occurs, forming the intermediate Labrador Sea Water (LSW). Recent studies have suggested that the Irminger Sea is also a convection site where LSW could also be formed locally. Argo floats provide a regular sampling of the Irminger Sea since the early 2000s, in particular during the winter season. Thus, the Argo dataset provides opportunities to investigate, through a study of the winter mixed layers, whether deep convection in the Irminger Sea is isolated or occurs at a broad spatial scale firstly and to investigate local formation of LSW in the Irminger Sea secondly. The present analysis of Argo data highlights a deep convection event occurring in the Irminger Sea during winter 2011-2012. Intense convective activity at basin scale has been observed for the first time in the Irminger Sea. From mid-January to mid-March, 31 Argo profiles exhibited a mixed layer depth exceeding 700m over a wide area located east of the southern tip of Greenland. Over the period 2002-2010, the deepest observed mixed layers in the Irminger Sea did not exceed 600m, except for the winters 2007-2008 and 2008-2009 during which a few localized mixed layer depths reached 1000m. Among those 31 profiles, the mixed layer depth recorded by 4 different floats reached about 1000m, which is deep enough to feed the pool of LSW located in the Irminger Sea. A lagrangian study along the trajectory of those 4 floats, shows that there is a good agreement between heat loss at the air-sea interface and the heat content variations in the mixed layer. Those results clearly demonstrate that LSW was formed in the Irminger Sea in winter 2001-2012, which is further confirmed by oxygen data provided by one Argo float equipped with an oxygen sensor. Finally, the properties of the 2011-2012 LSW formed in the Irminger Sea are compared to those formed in the Labrador Sea.

Piron, Anne; Mercier, Herlé; Thierry, Virginie; Caniaux, Guy

2014-05-01

366

Direct observations of the upper layer circulation in the southern Gulf of Mexico  

NASA Astrophysics Data System (ADS)

The upper layer circulation in the Bay of Campeche is analyzed with three years of data recorded by surface drifters, current meter moorings, and satellite altimetry. The measurements show that the mean cyclonic circulation observed by previous authors extends below 1000 m, and that its size and location are delimited by the particular topography of the region: a deep basin to the west, and a shallower and gentle sloping submarine fan to the east. An Empirical Orthogonal Function analysis and large correlations of the surface flow with the deeper currents suggest that the topographic constraint is the result of potential vorticity conservation for an equivalent barotropic flow. The variability of the surface currents in the western basin is mostly due to changes in the size, form, position and intensity of the cyclonic gyre due to its interaction with northern Gulf of Mexico eddies, particularly Loop Current Eddies traveling the southern route towards the western boundary. By contrast, the eastern basin is characterized by a weak northward drift, with the occasional generation of anticyclones in the southeastern boundary, the genesis of which remains to be understood. This suggests that the variability in the eastern basin is mostly driven by locally generated disturbances, rather than by an influx of northern Gulf of Mexico eddies. Strong northward flows in the central and eastern basins result from the flow convergence between locally generated anticyclones and the cyclonic gyre.

Pérez-Brunius, Paula; García-Carrillo, Paula; Dubranna, Jean; Sheinbaum, Julio; Candela, Julio

2013-01-01

367

Direct observation of DNA motions into solid state nanopore under applied electrical potentials on conductive surface  

NASA Astrophysics Data System (ADS)

Solid state nanopore is one of emerging methods for rapid single DNA molecule detection because the translocation of the DNA though nanopore produces ionic current changes. One of issues in this method is clogging long DNA molecules. Once DNA molecules clogged, the molecules are rarely removed by varying or switching the polarity of applied bias voltages across the nanopore. We develop a modified nanopore by 50nm Au coating on top of the nanopore surface to be able to remove the clogged DNA molecules during the DNA translocation experiment. Fluorescence microscopy was implemented for observation of stained DNA molecules. The nanopores with diameters near 100 nm can be used initially. DNA translocation rates changes dramatically by tuning the applied electrical potentials on surface higher or lower than the potentials across the nanopore. Furthermore, the Au potentials modifies IV characteristic of the ionic current across the nanopore which is similar to the gate voltages controlling the SD current in FET. We will discuss the influence of surface potential on DNA motion and translocation and clogged DNA molecules. Finally, we will present the recent results of DNA translocation into the SiN-Au-SiO2 nanopore and discuss the effect of applied voltages on Au.

Hayashi, Yoshitaka; Ando, Genki; Idutsu, Ichiro; Mitsui, Toshiyuki

2011-03-01

368

Direct observation of ultrafast-electron-transfer reactions unravels high effectiveness of reductive DNA damage  

PubMed Central

Both water and electron-transfer reactions play important roles in chemistry, physics, biology, and the environment. Oxidative DNA damage is a well-known mechanism, whereas the relative role of reductive DNA damage is unknown. The prehydrated electron (), a novel species of electrons in water, is a fascinating species due to its fundamental importance in chemistry, biology, and the environment. is an ideal agent to observe reductive DNA damage. Here, we report both the first in situ femtosecond time-resolved laser spectroscopy measurements of ultrafast-electron-transfer (UET) reactions of with various scavengers (KNO3, isopropanol, and dimethyl sulfoxide) and the first gel electrophoresis measurements of DNA strand breaks induced by and OH• radicals co-produced by two-UV-photon photolysis of water. We strikingly found that the yield of reductive DNA strand breaks induced by each is twice the yield of oxidative DNA strand breaks induced by each OH• radical. Our results not only unravel the long-standing mystery about the relative role of radicals in inducing DNA damage under ionizing radiation, but also challenge the conventional notion that oxidative damage is the main pathway for DNA damage. The results also show the potential of femtomedicine as a new transdisciplinary frontier and the broad significance of UET reactions of in many processes in chemistry, physics, biology, and the environment. PMID:21730183

Nguyen, Jenny; Ma, Yuhan; Luo, Ting; Bristow, Robert G.; Jaffray, David A.; Lu, Qing-Bin

2011-01-01

369

Direct observation of the inner structure of unstained atmospheric cells by low-energy electrons  

NASA Astrophysics Data System (ADS)

Imaging at nanometre-scale resolution is indispensable for many scientific fields, such as biology, physics, chemistry, materials science and nanotechnology. Electron microscopy is an important technique to produce high-resolution images of biological samples. Inner structure inspection of cell samples of a few micrometre thickness is enabled using a high-voltage electron beam (EB) of around 1000 kV. However, large and complex equipment is required for such systems. Therefore, a more convenient and simple measurement system is desired. Here, we show clear observations of the inner structure of unstained atmospheric cells using a low-voltage EB of less than 10 kV. Experiments suggest that whole cell imaging by a low-voltage EB is enabled by the transmission electrons (TEs), and TEs are of very low energy of less than 20 eV. Therefore, the damage to the biological samples is very low. Our microscope system can easily be applied for diverse samples, such as cells, bacteria, viruses and other organic samples.

Ogura, Toshihiko

2012-08-01

370

Direct Observation of the Photodegradation of Anthracene and Pyrene Adsorbed onto Mangrove Leaves  

PubMed Central

An established synchronous fluorimetry method was used for in situ investigation of the photodegradation of pyrene (PYR) and anthracene (ANT) adsorbed onto fresh leaves of the seedlings of two mangrove species, Aegiceras corniculatum (L.) Blanco (Ac) and Kandelia obovata (Ko) in multicomponent mixtures (mixture of the ANT and PYR). Experimental results indicated that photodegradation was the main transformation pathway for both ANT and PYR in multicomponent mixtures. The amount of the PAHs volatilizing from the leaf surfaces and entering the inner leaf tissues was negligible. Over a certain period of irradiation time, the photodegradation of both PYR and ANT adsorbed onto the leaves of Ac and Ko followed first-order kinetics, with faster rates being observed on Ac leaves. In addition, the photodegradation rate of PYR on the leaves of the mangrove species in multicomponent mixtures was much slower than that of adsorbed ANT. Compared with the PAHs adsorbed as single component, the photodegradation rate of ANT adsorbed in multicomponent mixtures was slower, while that of PYR was faster. Moreover, the photodegradation of PYR and ANT dissolved in water in multicomponent mixtures was investigated for comparison. The photodegradation rate on leaves was much slower than in water. Therefore, the physical-chemical properties of the substrate may strongly influence the photodegradation rate of adsorbed PAHs. PMID:25144741

Wang, Ping; Wu, Tun-Hua; Zhang, Yong

2014-01-01

371

Direct observation of prompt pre-thermal laser ion sheath acceleration  

PubMed Central

High-intensity laser plasma-based ion accelerators provide unsurpassed field gradients in the megavolt-per-micrometer range. They represent promising candidates for next-generation applications such as ion beam cancer therapy in compact facilities. The weak scaling of maximum ion energies with the square-root of the laser intensity, established for large sub-picosecond class laser systems, motivates the search for more efficient acceleration processes. Here we demonstrate that for ultrashort (pulse duration ~30 fs) highly relativistic (intensity ~1021 W cm?2) laser pulses, the intra-pulse phase of the proton acceleration process becomes relevant, yielding maximum energies of around 20 MeV. Prominent non-target-normal emission of energetic protons, reflecting an engineered asymmetry in the field distribution of promptly accelerated electrons, is used to identify this pre-thermal phase of the acceleration. The relevant timescale reveals the underlying physics leading to the near-linear intensity scaling observed for 100 TW class table-top laser systems. PMID:22673901

Zeil, K.; Metzkes, J.; Kluge, T.; Bussmann, M.; Cowan, T.E.; Kraft, S.D.; Sauerbrey, R.; Schramm, U.

2012-01-01

372

Direct nanoscale observations of the coupled dissolution of calcite and dolomite and the precipitation of gypsum  

PubMed Central

Summary In-situ atomic force microscopy (AFM) experiments were performed to study the overall process of dissolution of common carbonate minerals (calcite and dolomite) and precipitation of gypsum in Na2SO4 and CaSO4 solutions with pH values ranging from 2 to 6 at room temperature (23 ± 1 °C). The dissolution of the carbonate minerals took place at the (104) cleavage surfaces in sulfate-rich solutions undersaturated with respect to gypsum, by the formation of characteristic rhombohedral-shaped etch pits. Rounding of the etch pit corners was observed as solutions approached close-to-equilibrium conditions with respect to calcite. The calculated dissolution rates of calcite at pH 4.8 and 5.6 agreed with the values reported in the literature. When using solutions previously equilibrated with respect to gypsum, gypsum precipitation coupled with calcite dissolution showed short gypsum nucleation induction times. The gypsum precipitate quickly coated the calcite surface, forming arrow-like forms parallel to the crystallographic orientations of the calcite etch pits. Gypsum precipitation coupled with dolomite dissolution was slower than that of calcite, indicating the dissolution rate to be the rate-controlling step. The resulting gypsum coating partially covered the surface during the experimental duration of a few hours. PMID:25161860

Cama, Jordi; Soler, Josep Maria; Putnis, Christine V

2014-01-01

373

Directly imaging damped Ly? galaxies at z > 2 - II. Imaging and spectroscopic observations of 32 quasar fields  

NASA Astrophysics Data System (ADS)

Damped Ly? absorbers (DLAs) are a well-studied class of absorption line systems, and yet the properties of their host galaxies remain largely unknown. To investigate the origin of these systems, we have conducted an imaging survey of 32 quasar fields with intervening DLAs between z ˜ 1.9 and 3.8, leveraging a technique that allows us to image galaxies at any small angular separation from the background quasars. In this paper, we present the properties of the targeted DLA sample, new imaging observations of the quasar fields, and the analysis of new and archival spectra of the background quasars.

Fumagalli, Michele; O'Meara, John M.; Prochaska, J. Xavier; Kanekar, Nissim; Wolfe, Arthur M.

2014-10-01

374

Adhesion Failure at 180 000 Frames per Second: Direct Observation of the Detachment Process of a Mushroom-Shaped Adhesive  

NASA Astrophysics Data System (ADS)

Nature has successfully evolved the mushroom-shaped contact geometry in many organisms in order to solve the attachment problem. We studied the detachment process of individual bioinspired artificial mushroom-shaped adhesive microstructures (MSAMSs) resolving the failure dynamics at high spatiotemporal resolution. The experimental data provide strong evidence for a homogeneous stress distribution in MSAMS, which was recently proposed. Our results allow us to explain the advantage of such contact geometry and provide a suggestion for the widely observed mushroom-shaped contact geometry.

Heepe, Lars; Kovalev, Alexander E.; Filippov, Alexander E.; Gorb, Stanislav N.

2013-09-01

375

The Direct Radiative Effects of Aerosols over Southeast Asia based on Satellite Observations and Modelling Calculations  

NASA Astrophysics Data System (ADS)

The influence of aerosols have been suggested as one of the important reasons for climate change over Southeast Asia (SE Asia, 15S~35N and 75E~155E). Hence, quantification efforts on identifying the impacts of aerosols on regional climate are quite necessary, especially for improvement of the accuracy of climate models. Using the Moderate Resolution Imaging Spectroradiometer (MODIS), Clouds and the Earth's Radiant Energy System (CERES) instrument, and Four-stream Radiative Transfer Models, we provide quantitative evaluation of regional cloud-free diurnally averaged shortwave aerosol radiative effects (SWARE) at both Top of Atmosphere (TOA) and Surface (SFC) over the entire SE Asia. The spatial and temporal variations of annual SWARE are mainly estimated based on satellite and ground-based measurements (e.g. AERONET), supplemented by radiative transfer simulations. During the period of 2001 ~ 2010, our results indicate that the diurnally averaged SWARE at the TOA are -6.61±0.48 Wm-2 over land and -5.10±1.29 Wm-2 over ocean, respectively. We also compare observation- and model-based estimates of clear-sky, annual averaged SWARE with statistic results, which shown that model simulations are quantitatively distinct with measurement-based SWARE, even after accounting for cloud contamination. Our results present significant inter-annual variability of the computed aerosol radiative properties, which is extremely large over major emission outflow areas such as SE Asia. This study suggest an integrated system of satellite data, model calculations, ground-based and meteorological data sets to assess aerosols radiative effects on regional earth-atmosphere energy budgets.

Feng, N.; Christopher, S. A.

2012-12-01

376

Direct Observations of Daytime NO3: Implications for the Urban Boundary Layer Chemistry  

SciTech Connect

The nitrate radical (NO3) is the dominant atmospheric oxidant during the night in most environments. During daytime, however, NO3 has thus far been undetected and considered insignificant. Here, we present the first daytime detection of NO3 by Differential Optical Absorption Spectroscopy near Houston, Texas during the Texas Air Quality Study 2000. On three consecutive days in August/September 2000, NO3 reached levels from » 5 ppt three hours before sunset to 31 ppt around sunset. Daytime NO3 has a negligible effect on the photostationary state (PSS) between O3 and NOx, with the exception of the last hour before sunset, when it significantly accelerates NO-to-NO2 conversion. On August 31 chemical reactions involving NO3 destroyed 8 (±4) ppb Ox (= O3 + NO2) during the day, and 27 (±6) ppb at night. NO3 chemistry contributed 10 (±7)% to the total Ox loss during the daytime, and 28% (±18%) integrated over a 24-hour period. It therefore plays an important role in the Ox budget. NO3 also contributed significantly to the daytime oxidation of hydrocarbons such as monoterpenes and phenol in Houston. The observed daytime NO3 mixing ratios can be described as a function of O3 and NOx. Above NOx/O3 ratios of 3%, daytime NO3 becomes independent of NOx and proportional to the square of O3. Our calculations indicate that elevated (> 1ppt) NO3 levels are present whenever ozone mixing ratios exceed typical urban smog levels of 100 ppb.

Geyer, A.; Alicke, B.; Ackerman, Ralph; Martinez, M.; Harder, H.; Brune, W. H.; di Carlo, Piero; Williams, E. J.; Jobson, B Tom T.; Hall, Samual R.; Shetter, Richard E.; Stutz, Jochen P.

2003-06-27

377

The exit interview as a proxy measure of malaria case management practice: sensitivity and specificity relative to direct observation.  

PubMed

BackgroundThis paper aims to assess the sensitivity and specificity of exit interviews as a measure of malaria case management practice as compared to direct observation.MethodsThe malaria case management of 1654 febrile patients attending 110 health facilities from across Papua New Guinea was directly observed by a trained research officer as part of a repeat cross sectional survey. Patient recall of 5 forms of clinical advice and 5 forms of clinical action were then assessed at service exit and statistical analyses on matched observation/exit interview data conducted.ResultsThe sensitivity of exit interviews with respect to clinical advice ranged from 36.2% to 96.4% and specificity from 53.5% to 98.6%. With respect to clinical actions, sensitivity of the exit interviews ranged from 83.9% to 98.3% and specificity from 70.6% to 98.1%.ConclusionThe exit interview appears to be a valid measure of objective malaria case management practices such as the completion of a diagnostic test or the provision of antimalarial medication, but may be a less valid measure of low frequency, subjective practices such as the provision of malaria prevention advice. PMID:25465383

Pulford, Justin; Siba, Peter M; Mueller, Ivo; Hetzel, Manuel W

2014-12-01

378

Direct observation of periodic swelling and collapse of polymer chain induced by the Belousov-Zhabotinsky reaction.  

PubMed

By utilizing a quartz crystal microbalance with dissipation (QCM-D), we directly observed the self-oscillating behavior of a polymer chain induced by the Belousov-Zhabotinsky (BZ) reaction. We succeeded in measuring self-oscillations of the resonance frequency (?f) and dissipation (?D), which originate in the self-oscillating behavior of the polymer chain on a gold surface induced by the BZ reaction. We synthesized a self-oscillating polymer chain with Ru as the catalyst of the BZ reaction and a chemical adsorption site, so as to directly observe its periodic swelling and collapse on the gold surface. Distinct self-oscillation of ?D synchronized with the self-oscillation ?f was observed. The period of the ?f self-oscillation was about 400 s, and the induction time was about 6.5 h. In QCM-D measurements, we found that the peaks of ?f and ?D oscillations did not coincide in time because the state of the Gaussian chain did not coincide with the maximum value of ?f. Moreover, examination of the relationship between ?f and ?D revealed that their oscillatory waveforms were identical in frequency but differed in phase and amplitude. PMID:24147635

Hara, Yusuke; Mayama, Hiroyuki; Yamaguchi, Yoshinori; Takenaka, Yoshiko; Fukuda, Ryushi

2013-11-21

379

Direct Observation of Dopant Atom Diffusion in a Bulk Semiconductor Crystal Enhanced by a Large Size Mismatch  

NASA Astrophysics Data System (ADS)

Diffusion is one of the fundamental processes that govern the structure, processing, and properties of materials and it plays a crucial role in determining device lifetimes. However, direct observations of diffusion processes have been elusive and limited only to the surfaces of materials. Here we use an aberration-corrected electron microscope to locally excite and directly image the diffusion of single Ce and Mn dopants inside bulk wurtzite-type AlN single crystals, identifying correlated vacancy-dopant and interstitial-dopant kick-out mechanisms. Using a 200 kV electron beam to supply energy, we observe a higher frequency of dopant jumps for the larger and heavier Ce atoms than the smaller Mn atoms. These observations confirm density-functional-theory-based predictions of a decrease in diffusion barrier for large substitutional atoms. The results show that combining depth sensitive microscopy with theoretical calculations represents a new methodology to investigate diffusion mechanisms, not restricted to surface phenomena, but within bulk materials.

Ishikawa, Ryo; Mishra, Rohan; Lupini, Andrew R.; Findlay, Scott D.; Taniguchi, Takashi; Pantelides, Sokrates T.; Pennycook, Stephen J.

2014-10-01

380

Direct observation of mass oscillations due to ablative Richtmyer-Meshkov instability and feedout in planar plastic targets  

NASA Astrophysics Data System (ADS)

Perturbations that seed Rayleigh-Taylor (RT) instability in laser-driven targets form during the early-time period. This time includes a shock wave transit from the front to the rear surface of the target, and a rarefaction wave transit in the opposite direction. During this time interval, areal mass perturbations caused by all sources of nonuniformity (laser imprint, surface ripple) are expected to oscillate. The first direct experimental observations of the areal mass oscillations due to ablative Richtmyer-Meshkov (RM) instability and feedout followed by the RT growth of areal mass modulation are discussed. The experiments were made with 40-99 ?m thick planar plastic targets rippled either on the front or on the rear with a sine wave ripple with either 30 or 45 ?m wavelength and with 0.5, 1, or 1.5 ?m amplitude. Targets were irradiated with 4 ns long Nike KrF laser pulses at ˜50 TW/cm2. The oscillations were observed with our novel diagnostic technique, a monochromatic x-ray imager coupled to a streak camera. For the ablative RM instability (front side ripple), the mass modulation amplitude was typically observed to grow, reach a peak, and then decrease, after which the exponential RT growth started. In some cases, one phase reversal due to the ablative RM instability was observed. For the feedout geometry (rear side ripple), in all cases two phase reversals were observed: a distinct half-oscillation was followed by the onset of the RT growth, resulting in a second phase reversal.

Aglitskiy, Y.; Velikovich, A. L.; Karasik, M.; Serlin, V.; Pawley, C. J.; Schmitt, A. J.; Obenschain, S. P.; Mostovych, A. N.; Gardner, J. H.; Metzler, N.

2002-05-01

381

Protein-induced changes in DNA structure and dynamics observed with noncovalent site-directed spin labeling and PELDOR  

PubMed Central

Site-directed spin labeling and pulsed electron–electron double resonance (PELDOR or DEER) have previously been applied successfully to study the structure and dynamics of nucleic acids. Spin labeling nucleic acids at specific sites requires the covalent attachment of spin labels, which involves rather complicated and laborious chemical synthesis. Here, we use a noncovalent label strategy that bypasses the covalent labeling chemistry and show that the binding specificity and efficiency are large enough to enable PELDOR or DEER measurements in DNA duplexes and a DNA duplex bound to the Lac repressor protein. In addition, the rigidity of the label not only allows resolution of the structure and dynamics of oligonucleotides but also the determination of label orientation and protein-induced conformational changes. The results prove that this labeling strategy in combination with PELDOR has a great potential for studying both structure and dynamics of oligonucleotides and their complexes with various ligands. PMID:22941643

Reginsson, Gunnar W.; Shelke, Sandip A.; Rouillon, Christophe; White, Malcolm F.; Sigurdsson, Snorri Th.; Schiemann, Olav

2013-01-01

382

Direct spectroscopic observation of singlet oxygen emission at 1268 nm excited by sensitizing dyes of biological interest in liquid solution  

PubMed Central

The direct observation of dye-photosensitized 1268-nm emission of the 1?g ? 3?g transition of molecular oxygen in liquid solution at room temperature is reported. Singlet oxygen was photosensitized by UV excitation of perfluorobenzophenone in fluorocarbon solvent, by 3,4-benzpyrene and hematoporphyrin in carbon tetrachloride, and by methylene blue in water. Also reported is the development of an extremely sensitive near-infrared spectrophotometer that uses a thermoelectrically cooled lead sulfide detector, optimized optics, and a boxcar integrator as a data processor. PMID:16592729

Khan, A. U.; Kasha, M.

1979-01-01

383

Direct Observation of Hyperfine Quenching of the (2)3p0 Level in Helium-Like Nickel  

E-print Network

PHYSICAL REVIEW A VOLUME 44, NUMBER 1 I JULY 1991 Direct observation of hyperfine quenching of the 2 I'o level in heliumlike nickel R. W. Dunford, C. J. Liu, J. Last, N. Berrah-Mansour, and R. Vondrasek Physics Division, Argonne National... Laboratory, Argonne, Illinois 60439 D. A. Church Department ofPhysics, Texas A d'cM University, College Station, Texas 77843 L. J. Curtis Department of Physics and Astronomy, University of Toledo, Toledo, Ohio 43606 (Received 11 February 1991) We report...

Dunford, R. W.; Liu, C. J.; Last, J.; Berrahmansour, N.; Vondrasek, R.; Church, David A.; Curtis, L. J.

1991-01-01

384

Direct Observation of Molybdenum Disulfide, MoS2, Domains by Using a Liquid Crystalline Texture Method.  

PubMed

Because the properties of molybdenum disulfide (MoS2) are strongly influenced by the sizes and boundaries of its domains, the direct visualization of large-area MoS2 domains is one of the most important challenges in MoS2 research. In the current study, we developed a simple and rapid method to observe and determine the boundaries of MoS2 domains. The technique, which depends on observations of nematic liquid crystal textures on the MoS2 surface, does not damage the sample and is not limited by domain size. Thus, this approach should significantly aid not only efforts aimed at gaining an understanding of the relationships between grain boundaries and properties of MoS2 but also those focusing on how domain sizes are controlled during large-area synthesis. PMID:25494827

Kim, Dae Woo; Ok, Jong Min; Jung, Woo-Bin; Kim, Jong-Seon; Kim, Seon Joon; Choi, Hyung Ouk; Kim, Yun Ho; Jung, Hee-Tae

2015-01-14

385

Direct observation of copper precipitation in a neutron irradiated FeCu alloy by 3D atomic tomography  

SciTech Connect

Precipitation processes under neutron irradiation are of great interest, of course, because of their importance in nuclear industry but, also, from a theoretical point of view. In this scope, prediction and modelling of the property changes of pressure vessel steels under irradiation require a more in depth knowledge of the microstructural evolution; structural and compositional features of formed precipitates being key parameters. One of the main advantages of the new generation of atom probe that was recently developed, namely the Tomographic Atom Probe (TAP), is that a three-dimensional observation of the spatial distribution of solutes (Cu) can be achieved on a near atomic scale. In this work, the very first three-dimensional (3D) images of neutron irradiated FeCu alloys provided by this new apparatus are presented and discussed. These 3D-reconstructions give for the first time, a direct observation of irradiation induced precipitated particles in these model alloys on a subnanometer scale.

Pareige, P.; Auger, P.; Bas, P.; Blavette, D. [Univ. de Rouen, Mont Saint Aignan (France). Laboratoire de Microscopie Ionique] [Univ. de Rouen, Mont Saint Aignan (France). Laboratoire de Microscopie Ionique

1995-10-01

386

Remote and In Situ Observations of an Unusual Earth-Directed Coronal Mass Ejection from Multiple Viewpoints  

NASA Technical Reports Server (NTRS)

During June 16-21, 2010, an Earth-directed Coronal Mass Ejection (CME) event was observed by instruments onboard STEREO, SOHO, MESSENGER and Wind. This event was the first direct detection of a rotating CME in the middle and outer corona. Here, we carry out a comprehensive analysis of the evolution of the CME in the interplanetary medium comparing in-situ and remote observations, with analytical models and three-dimensional reconstructions. In particular, we investigate the parallel and perpendicular cross section expansion of the CME from the corona through the heliosphere up to 1 AU. We use height-time measurements and the Gradual Cylindrical Shell (GCS) technique to model the imaging observations, remove the projection effects, and derive the 3-dimensional extent of the event. Then, we compare the results with in-situ analytical Magnetic Cloud (MC) models, and with geometrical predictions from past works. We nd that the parallel (along the propagation plane) cross section expansion agrees well with the in-situ model and with the Bothmer & Schwenn [1998] empirical relationship based on in-situ observations between 0.3 and 1 AU. Our results effectively extend this empirical relationship to about 5 solar radii. The expansion of the perpendicular diameter agrees very well with the in-situ results at MESSENGER ( 0:5 AU) but not at 1 AU. We also find a slightly different, from Bothmer & Schwenn [1998], empirical relationship for the perpendicular expansion. More importantly, we find no evidence that the CME undergoes a significant latitudinal over-expansion as it is commonly assumed

Nieves-Chinchilla, T.; Colaninno, R.; Vourlidas, A.; Szabo, A.; Lepping, R. P.; Boardsen, S. A.; Anderson, B. J.; Korth, H.

2012-01-01

387

Direct, intraoperative observation of ?0.1 Hz hemodynamic oscillations in awake human cortex: Implications for fMRI  

PubMed Central

An almost sinusoidal, large amplitude ?0.1 Hz oscillation in cortical hemodynamics has been repeatedly observed in species ranging from mice to humans. However, the occurrence of ‘slow sinusoidal hemodynamic oscillations’ (SSHOs) in human functional magnetic resonance imaging (fMRI) studies is rarely noted or considered. As a result, little investigation into the cause of SSHOs has been undertaken, and their potential to confound fMRI analysis, as well as their possible value as a functional biomarker has been largely overlooked. Here, we report direct observation of large-amplitude, sinusoidal ?0.1 Hz hemodynamic oscillations in the cortex of an awake human undergoing surgical resection of a brain tumor. Intraoperative multispectral optical intrinsic signal imaging (MS-OISI) revealed that SSHOs were spatially localized to distinct regions of the cortex, exhibited wave-like propagation, and involved oscillations in the diameter of specific pial arterioles, confirming that the effect was not the result of systemic blood pressure oscillations. fMRI data collected from the same subject 4 days prior to surgery demonstrates that ?0.1 Hz oscillations in the BOLD signal can be detected around the same region. Intraoperative optical imaging data from a patient undergoing epilepsy surgery, in whom sinusoidal oscillations were not observed, is shown for comparison. This direct observation of the ‘0.1 Hz wave’ in the awake human brain, using both intraoperative imaging and pre-operative fMRI, confirms that SSHOs occur in the human brain, and can be detected by fMRI. We discuss the possible physiological basis of this oscillation and its potential link to brain pathologies, highlighting its relevance to resting-state fMRI and its potential as a novel target for functional diagnosis and delineation of neurological disease. PMID:24185013

Rayshubskiy, Aleksandr; Wojtasiewicz, Teresa J.; Mikell, Charles B.; Bouchard, Matthew B.; Timerman, Dmitriy; Youngerman, Brett E.; McGovern, Robert A.; Otten, Marc L.; Canoll, Peter D.; McKhann, Guy M.; Hillman, Elizabeth M.C.

2014-01-01

388

Direct observation of R-loop formation by single RNA-guided Cas9 and Cascade effector complexes  

PubMed Central

Clustered, regularly interspaced, short palindromic repeats (CRISPR)/CRISPR-associated (Cas) systems protect bacteria and archaea from infection by viruses and plasmids. Central to this defense is a ribonucleoprotein complex that produces RNA-guided cleavage of foreign nucleic acids. In DNA-targeting CRISPR-Cas systems, the RNA component of the complex encodes target recognition by forming a site-specific hybrid (R-loop) with its complement (protospacer) on an invading DNA while displacing the noncomplementary strand. Subsequently, the R-loop structure triggers DNA degradation. Although these reactions have been reconstituted, the exact mechanism of R-loop formation has not been fully resolved. Here, we use single-molecule DNA supercoiling to directly observe and quantify the dynamics of torque-dependent R-loop formation and dissociation for both Cascade- and Cas9-based CRISPR-Cas systems. We find that the protospacer adjacent motif (PAM) affects primarily the R-loop association rates, whereas protospacer elements distal to the PAM affect primarily R-loop stability. Furthermore, Cascade has higher torque stability than Cas9 by using a conformational locking step. Our data provide direct evidence for directional R-loop formation, starting from PAM recognition and expanding toward the distal protospacer end. Moreover, we introduce DNA supercoiling as a quantitative tool to explore the sequence requirements and promiscuities of orthogonal CRISPR-Cas systems in rapidly emerging gene-targeting applications. PMID:24912165

Szczelkun, Mark D.; Tikhomirova, Maria S.; Sinkunas, Tomas; Gasiunas, Giedrius; Karvelis, Tautvydas; Pschera, Patrizia; Siksnys, Virginijus; Seidel, Ralf

2014-01-01

389

Community-based treatment of advanced HIV disease: introducing DOT-HAART (directly observed therapy with highly active antiretroviral therapy).  

PubMed Central

In 2000, acquired immunodeficiency syndrome (AIDS) overtook tuberculosis (TB) as the world's leading infectious cause of adult deaths. In affluent countries, however, AIDS mortality has dropped sharply, largely because of the use of highly active antiretroviral therapy (HAART). Antiretroviral agents are not yet considered essential medications by international public health experts and are not widely used in the poor countries where human immunodeficiency virus (HIV) takes its greatest toll. Arguments against the use of HAART have mainly been based on the high cost of medications and the lack of the infrastructure necessary for using them wisely. We re- examine these arguments in the setting of rising AIDS mortality in developing countries and falling drug prices, and describe a small community-based treatment programme based on lessons gained in TB control. With the collaboration of Haitian community health workers experienced in the delivery of home-based and directly observed treatment for TB, an AIDS-prevention project was expanded to deliver HAART to a subset of HIV patients deemed most likely to benefit. The inclusion criteria and preliminary results are presented. We conclude that directly observed therapy (DOT) with HAART, "DOT-HAART", can be delivered effectively in poor settings if there is an uninterrupted supply of high-quality drugs. PMID:11799447

Farmer, P.; Léandre, F.; Mukherjee, J.; Gupta, R.; Tarter, L.; Kim, J. Y.

2001-01-01

390

Replication protein A: single-stranded DNA's first responder: dynamic DNA-interactions allow replication protein A to direct single-strand DNA intermediates into different pathways for synthesis or repair.  

PubMed

Replication protein A (RPA), the major single-stranded DNA-binding protein in eukaryotic cells, is required for processing of single-stranded DNA (ssDNA) intermediates found in replication, repair, and recombination. Recent studies have shown that RPA binding to ssDNA is highly dynamic and that more than high-affinity binding is needed for function. Analysis of DNA binding mutants identified forms of RPA with reduced affinity for ssDNA that are fully active, and other mutants with higher affinity that are inactive. Single molecule studies showed that while RPA binds ssDNA with high affinity, the RPA complex can rapidly diffuse along ssDNA and be displaced by other proteins that act on ssDNA. Finally, dynamic DNA binding allows RPA to prevent error-prone repair of double-stranded breaks and promote error-free repair. Together, these findings suggest a new paradigm where RPA acts as a first responder at sites with ssDNA, thereby actively coordinating DNA repair and DNA synthesis. PMID:25171654

Chen, Ran; Wold, Marc S

2014-12-01

391

What keeps family physicians busy in Portugal? A multicentre observational study of work other than direct patient contacts  

PubMed Central

Objectives To quantify the time spent by family physicians (FP) on tasks other than direct patient contact, to evaluate job satisfaction, to analyse the association between time spent on tasks and physician characteristics, the association between the number of tasks performed and physician characteristics and the association between time spent on tasks and job satisfaction. Design Cross-sectional, using time-and-motion techniques. Two workdays were documented by direct observation. A significance level of 0.05 was adopted. Setting Multicentric in 104 Portuguese family practices. Participants A convenience sample of FP, with lists of over 1000 patients, teaching senior medical students and first-year family medicine residents in 2012, was obtained. Of the 217 FP invited to participate, 155 completed the study. Main outcomes measured Time spent on tasks other than direct patient contact and on the performance of more than one task simultaneously, the number of direct patient contacts in the office, the number of indirect patient contacts, job satisfaction, demographic and professional characteristics associated with time spent on tasks and the number of different tasks performed, and the association between time spent on tasks and job satisfaction. Results FP (n=155) spent a mean of 143.6?min/day (95% CI 135.2 to 152.0) performing tasks such as prescription refills, teaching, meetings, management and communication with other professionals (33.4% of their workload). FP with larger patient lists spent less time on these tasks (p=0.002). Older FP (p=0.021) and those with larger lists (p=0.011) performed fewer tasks. The mean job satisfaction score was 3.5 (out of 5). No association was found between job satisfaction and time spent on tasks. Conclusions FP spent one-third of their workday in coordinating care, teaching and managing. Time devoted to these tasks decreases with increasing list size and physician age. PMID:24934208

Granja, Mónica; Ponte, Carla; Cavadas, Luís Filipe

2014-01-01

392

Population genetic structure and direct observations reveal sex-reversed patterns of dispersal in a cooperative bird  

PubMed Central

Sex-biased dispersal is pervasive and has diverse evolutionary implications, but the fundamental drivers of dispersal sex biases remain unresolved. This is due in part to limited diversity within taxonomic groups in the direction of dispersal sex biases, which leaves hypothesis testing critically dependent upon identifying rare reversals of taxonomic norms. Here, we use a combination of observational and genetic data to demonstrate a rare reversal of the avian sex bias in dispersal in the cooperatively breeding white-browed sparrow weaver (Plocepasser mahali). Direct observations revealed that (i) natal philopatry was rare, with both sexes typically dispersing locally to breed, and (ii), unusually for birds, males bred at significantly greater distances from their natal group than females. Population genetic analyses confirmed these patterns, as (i) corrected Assignment index (AIc), FST tests and isolation-by-distance metrics were all indicative of longer dispersal distances among males than females, and (ii) spatial autocorrelation analysis indicated stronger within-group genetic structure among females than males. Examining the spatial scale of extra-group mating highlighted that the resulting ‘sperm dispersal’ could have acted in concert with individual dispersal to generate these genetic patterns, but gamete dispersal alone cannot account entirely for the sex differences in genetic structure observed. That leading hypotheses for the evolution of dispersal sex biases cannot readily account for these sex-reversed patterns of dispersal in white-browed sparrow weavers highlights the continued need for attention to alternative explanations for this enigmatic phenomenon. We highlight the potential importance of sex differences in the distances over which dispersal opportunities can be detected. PMID:25346189

Harrison, Xavier A; York, Jennifer E; Young, Andrew J

2014-01-01

393

Population genetic structure and direct observations reveal sex-reversed patterns of dispersal in a cooperative bird.  

PubMed

Sex-biased dispersal is pervasive and has diverse evolutionary implications, but the fundamental drivers of dispersal sex biases remain unresolved. This is due in part to limited diversity within taxonomic groups in the direction of dispersal sex biases, which leaves hypothesis testing critically dependent upon identifying rare reversals of taxonomic norms. Here, we use a combination of observational and genetic data to demonstrate a rare reversal of the avian sex bias in dispersal in the cooperatively breeding white-browed sparrow weaver (Plocepasser mahali). Direct observations revealed that (i) natal philopatry was rare, with both sexes typically dispersing locally to breed, and (ii), unusually for birds, males bred at significantly greater distances from their natal group than females. Population genetic analyses confirmed these patterns, as (i) corrected Assignment index (AIc), FST tests and isolation-by-distance metrics were all indicative of longer dispersal distances among males than females, and (ii) spatial autocorrelation analysis indicated stronger within-group genetic structure among females than males. Examining the spatial scale of extra-group mating highlighted that the resulting 'sperm dispersal' could have acted in concert with individual dispersal to generate these genetic patterns, but gamete dispersal alone cannot account entirely for the sex differences in genetic structure observed. That leading hypotheses for the evolution of dispersal sex biases cannot readily account for these sex-reversed patterns of dispersal in white-browed sparrow weavers highlights the continued need for attention to alternative explanations for this enigmatic phenomenon. We highlight the potential importance of sex differences in the distances over which dispersal opportunities can be detected. PMID:25346189

Harrison, Xavier A; York, Jennifer E; Young, Andrew J

2014-12-01

394

Health Insurance Definitions Allowable Charge  

E-print Network

Health Insurance Definitions Allowable Charge: Also referred to as the Allowed Amount, Approved considered payment-in-full by an insurance company and an associated network of healthcare providers. If the doctor is a member of your health insurance company's network of providers, he or she may be required

Buehrer, R. Michael

395

76 FR 5733 - Clothing Allowance  

Federal Register 2010, 2011, 2012, 2013, 2014

...rejected a claim for a second clothing allowance...garment may wear out faster than if affected...was entitled to a second clothing allowance...clothing to wear out faster, requiring replacement...outergarment at a faster rate, requiring...damage caused by the second appliance...

2011-02-02

396

First Direct Observation of the Interaction between a Comet and a Coronal Mass Ejection Leading to a Complete Plasma Tail Disconnection  

NASA Astrophysics Data System (ADS)

This a discovery report of the first direct imaging of the interaction a comet with a coronal mass ejection (CME) in the inner heliosphere with high temporal and spatial resolution. The observations were obtained by the Sun-Earth Connection Coronal and Heliospheric Investigation (SECCHI) Heliospheric Imager-1 (HI-1) aboard the STEREO mission. They reveal the extent of the plasma tail of comet 2P/Encke to unprecedented lengths and allow us to examine the mechanism behind a spectacular tail disconnection event. Our preliminary analysis suggests that the disconnection is driven by magnetic reconnection between the magnetic field entrained in the CME and the interplanetary field draped around the comet and not by pressure effects. Further analysis is required before we can conclude whether the reconnection occurs on the day side or on the tail side of the comet. However, the observations offer strong support to the idea that large-scale tail disconnections are magnetic in origin. The online movie reveals a wealth of interactions between solar wind structures and the plasma tail beyond the collision with the CME. Future analyses of this data set should provide critical insights on the structure of the inner heliosphere.

Vourlidas, Angelos; Davis, Chris J.; Eyles, Chris J.; Crothers, Steve R.; Harrison, Richard A.; Howard, Russell A.; Moses, J. Daniel; Socker, Dennis G.

2007-10-01

397

Direct Observation of Unstained Biological Specimens in Water by the Frequency Transmission Electric-Field Method Using SEM  

PubMed Central

Scanning electron microscopy (SEM) is a powerful tool for the direct visualization of biological specimens at nanometre-scale resolution. However, images of unstained specimens in water using an atmospheric holder exhibit very poor contrast and heavy radiation damage. Here, we present a new form of microscopy, the frequency transmission electric-field (FTE) method using SEM, that offers low radiation damage and high-contrast observation of unstained biological samples in water. The wet biological specimens are enclosed in two silicon nitride (SiN) films. The metal-coated SiN film is irradiated using a focused modulation electron beam (EB) at a low-accelerating voltage. A measurement terminal under the sample holder detects the electric-field frequency signal, which contains structural information relating to the biological specimens. Our results in very little radiation damage to the sample, and the observation image is similar to the transmission image, depending on the sample volume. Our developed method can easily be utilized for the observation of various biological specimens in water. PMID:24651483

Ogura, Toshihiko

2014-01-01

398

Direct observation of adsorption geometry for the van der Waals adsorption of a single ?-conjugated hydrocarbon molecule on Au(111)  

SciTech Connect

Weak van der Waals adsorption of ?-conjugated hydrocarbon molecules onto the gold surface, Au(111), is one of the essential processes in constructing organic-metal interfaces in organic electronics. Here we provide a first direct observation of adsorption geometry of a single ?-conjugated hydrocarbon molecule on Au(111) using an atomically resolved scanning tunneling microscopy study combined with van der Waals density functional methodology. For the purpose, we utilized a highly symmetric ?-conjugated hydrocarbon molecule, dehydrobenzo[12]annulene (DBA), which has a definite three-fold symmetry, the same as the Au(111) surface. Interestingly, our observations on an atomically resolved scale clearly indicate that the DBA molecule has only one adsorption configuration on Au(111) in spite of the weak van der Waals adsorption system. Based on the precisely determined adsorption geometry of DBA/Au(111), our calculation results imply that even a very small contribution of the interfacial orbital interaction at the organic-metal interface can play a decisive role in constraining the adsorption geometry even in the van der Waals adsorption system of a ?-conjugated hydrocarbon molecule on the noblest Au(111) surface. Our observations provide not only deeper insight into the weak adsorption process, but also new perspectives to organic electronics using ?-conjugated hydrocarbon molecules on the Au surface.

Kim, Ju-Hyung [Department of Advanced Materials Science, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561 (Japan) [Department of Advanced Materials Science, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561 (Japan); Surface and Interface Science Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Jung, Jaehoon; Kim, Yousoo, E-mail: tobe@chem.es.osaka-u.ac.jp, E-mail: ykim@riken.jp, E-mail: maki@k.u-tokyo.ac.jp [Surface and Interface Science Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan)] [Surface and Interface Science Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Tahara, Kazukuni; Tobe, Yoshito, E-mail: tobe@chem.es.osaka-u.ac.jp, E-mail: ykim@riken.jp, E-mail: maki@k.u-tokyo.ac.jp [Division of Frontier Materials Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531 (Japan)] [Division of Frontier Materials Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531 (Japan); Kawai, Maki, E-mail: tobe@chem.es.osaka-u.ac.jp, E-mail: ykim@riken.jp, E-mail: maki@k.u-tokyo.ac.jp [Department of Advanced Materials Science, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561 (Japan)] [Department of Advanced Materials Science, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561 (Japan)

2014-02-21

399

Methods for Observing Microbial Biofilms Directly on Leaf Surfaces and Recovering Them for Isolation of Culturable Microorganisms  

PubMed Central

Epifluorescence microscopy, scanning electron microscopy, and confocal laser scanning microscopy were used to observe microbial biofilms directly on leaf surfaces. Biofilms were observed on leaves of all species sampled (spinach, lettuce, Chinese cabbage, celery, leeks, basil, parsley, and broad-leaved endive), although the epifluorescent images were clearest when pale green tissue or cuticle pieces were used. With these techniques, biofilms were observed that were about 20 (mu)m in depth and up to 1 mm in length and that contained copious exopolymeric matrices, diverse morphotypes of microorganisms, and debris. The epifluorescence techniques described here can be used to rapidly determine the abundance and localization of biofilms on leaves. An additional technique was developed to recover individual biofilms or portions of single biofilms from leaves and to disintegrate them for isolation of the culturable microorganisms they contained. Nineteen biofilms from broad-leaved endive, spinach, parsley, and olive leaves were thus isolated and characterized to illustrate the applications of this technique. PMID:16535579

Morris, C. E.; Monier, J.; Jacques, M.

1997-01-01

400

Direct observation of lattice symmetry breaking at the hidden-order transition in URu2Si2.  

PubMed

Since the 1985 discovery of the phase transition at THO=17.5 K in the heavy-fermion metal URu2Si2, neither symmetry change in the crystal structure nor large magnetic moment that can account for the entropy change has been observed, which makes this hidden order enigmatic. Recent high-field experiments have suggested electronic nematicity that breaks fourfold rotational symmetry, but direct evidence has been lacking for its ground state in the absence of magnetic field. Here we report on the observation of lattice symmetry breaking from the fourfold tetragonal to twofold orthorhombic structure by high-resolution synchrotron X-ray diffraction measurements at zero field, which pins down the space symmetry of the order. Small orthorhombic symmetry-breaking distortion sets in at THO with a jump, uncovering the weakly first-order nature of the hidden-order transition. This distortion is observed only in ultrapure samples, implying a highly unusual coupling nature between the electronic nematicity and underlying lattice. PMID:24943003

Tonegawa, S; Kasahara, S; Fukuda, T; Sugimoto, K; Yasuda, N; Tsuruhara, Y; Watanabe, D; Mizukami, Y; Haga, Y; Matsuda, T D; Yamamoto, E; Onuki, Y; Ikeda, H; Matsuda, Y; Shibauchi, T

2014-01-01

401

Direct observation of lattice symmetry breaking at the hidden-order transition in URu2Si2  

NASA Astrophysics Data System (ADS)

Since the 1985 discovery of the phase transition at THO=17.5 K in the heavy-fermion metal URu2Si2, neither symmetry change in the crystal structure nor large magnetic moment that can account for the entropy change has been observed, which makes this hidden order enigmatic. Recent high-field experiments have suggested electronic nematicity that breaks fourfold rotational symmetry, but direct evidence has been lacking for its ground state in the absence of magnetic field. Here we report on the observation of lattice symmetry breaking from the fourfold tetragonal to twofold orthorhombic structure by high-resolution synchrotron X-ray diffraction measurements at zero field, which pins down the space symmetry of the order. Small orthorhombic symmetry-breaking distortion sets in at THO with a jump, uncovering the weakly first-order nature of the hidden-order transition. This distortion is observed only in ultrapure samples, implying a highly unusual coupling nature between the electronic nematicity and underlying lattice.

Tonegawa, S.; Kasahara, S.; Fukuda, T.; Sugimoto, K.; Yasuda, N.; Tsuruhara, Y.; Watanabe, D.; Mizukami, Y.; Haga, Y.; Matsuda, T. D.; Yamamoto, E.; Onuki, Y.; Ikeda, H.; Matsuda, Y.; Shibauchi, T.

2014-06-01

402

TB treatment outcomes following directly-observed treatment at an urban outpatient specialist TB facility in South Africa.  

PubMed

The treatment of 450 consecutive new patients with pulmonary TB was evaluated to determine outcome following directly-observed treatment. In all, 176 (39.1%) patients were cured, 23 (5.1%) completed treatment, 80 (17.8%) defaulted treatment, 24 (5.3%) died, 54 (12.0%) were lost to follow-up and 93 (20.7%) were transferred out. Increasing age was significant for death. Males were more likely to default and those with negative pretreatment sputum smears and those who were unemployed were more likely to be lost to follow-up. The overall treatment success rate remains low. Our data suggests that greater emphasis is needed to improve TB treatment success. PMID:16483424

Kharsany, A B M; Connolly, C; Olowolagba, A; Abdool Karim, S S; Abdool Karim, Q

2006-01-01

403

Direct observation of Lomer-Cottrell Locks during strain hardening in nanocrystalline nickel by in situ TEM  

NASA Astrophysics Data System (ADS)

Strain hardening capability is critical for metallic materials to achieve high ductility during plastic deformation. A majority of nanocrystalline metals, however, have inherently low work hardening capability with few exceptions. Interpretations on work hardening mechanisms in nanocrystalline metals are still controversial due to the lack of in situ experimental evidence. Here we report, by using an in situ transmission electron microscope nanoindentation tool, the direct observation of dynamic work hardening event in nanocrystalline nickel. During strain hardening stage, abundant Lomer-Cottrell (L-C) locks formed both within nanograins and against twin boundaries. Two major mechanisms were identified during interactions between L-C locks and twin boundaries. Quantitative nanoindentation experiments recorded show an increase of yield strength from 1.64 to 2.29 GPa during multiple loading-unloading cycles. This study provides both the evidence to explain the roots of work hardening at small length scales and the insight for future design of ductile nanocrystalline metals.

Lee, Joon Hwan; Holland, Troy B.; Mukherjee, Amiya K.; Zhang, Xinghang; Wang, Haiyan

2013-01-01

404

Direct observation of localized spin antiferromagnetic transition in PdCrO2 by angle-resolved photoemission spectroscopy.  

PubMed

We report the first case of the successful measurements of a localized spin antiferromagnetic transition in delafossite-type PdCrO2 by angle-resolved photoemission spectroscopy (ARPES). This demonstrates how to circumvent the shortcomings of ARPES for investigation of magnetism involved with localized spins in limited size of two-dimensional crystals or multi-layer thin films that neutron scattering can hardly study due to lack of bulk compared to surface. Also, our observations give direct evidence for the spin ordering pattern of Cr(3+) ions in PdCrO2 suggested by neutron diffraction and quantum oscillation measurements, and provide a strong constraint that has to be satisfied by a microscopic mechanism for the unconventional anomalous Hall effect recently reported in this system. PMID:24419488

Noh, Han-Jin; Jeong, Jinwon; Chang, Bin; Jeong, Dahee; Moon, Hyun Sook; Cho, En-Jin; Ok, Jong Mok; Kim, Jun Sung; Kim, Kyoo; Min, B I; Lee, Han-Koo; Kim, Jae-Young; Park, Byeong-Gyu; Kim, Hyeong-Do; Lee, Seongsu

2014-01-01

405

Direct Observation of Localized Spin Antiferromagnetic Transition in PdCrO2 by Angle-Resolved Photoemission Spectroscopy  

NASA Astrophysics Data System (ADS)

We report the first case of the successful measurements of a localized spin antiferromagnetic transition in delafossite-type PdCrO2 by angle-resolved photoemission spectroscopy (ARPES). This demonstrates how to circumvent the shortcomings of ARPES for investigation of magnetism involved with localized spins in limited size of two-dimensional crystals or multi-layer thin films that neutron scattering can hardly study due to lack of bulk compared to surface. Also, our observations give direct evidence for the spin ordering pattern of Cr3+ ions in PdCrO2 suggested by neutron diffraction and quantum oscillation measurements, and provide a strong constraint that has to be satisfied by a microscopic mechanism for the unconventional anomalous Hall effect recently reported in this system.

Noh, Han-Jin; Jeong, Jinwon; Chang, Bin; Jeong, Dahee; Moon, Hyun Sook; Cho, En-Jin; Ok, Jong Mok; Kim, Jun Sung; Kim, Kyoo; Min, B. I.; Lee, Han-Koo; Kim, Jae-Young; Park, Byeong-Gyu; Kim, Hyeong-Do; Lee, Seongsu

2014-01-01

406

Direct Observation of Localized Spin Antiferromagnetic Transition in PdCrO2 by Angle-Resolved Photoemission Spectroscopy  

PubMed Central

We report the first case of the successful measurements of a localized spin antiferromagnetic transition in delafossite-type PdCrO2 by angle-resolved photoemission spectroscopy (ARPES). This demonstrates how to circumvent the shortcomings of ARPES for investigation of magnetism involved with localized spins in limited size of two-dimensional crystals or multi-layer thin films that neutron scattering can hardly study due to lack of bulk compared to surface. Also, our observations give direct evidence for the spin ordering pattern of Cr3+ ions in PdCrO2 suggested by neutron diffraction and quantum oscillation measurements, and provide a strong constraint that has to be satisfied by a microscopic mechanism for the unconventional anomalous Hall effect recently reported in this system. PMID:24419488

Noh, Han-Jin; Jeong, Jinwon; Chang, Bin; Jeong, Dahee; Moon, Hyun Sook; Cho, En-Jin; Ok, Jong Mok; Kim, Jun Sung; Kim, Kyoo; Min, B. I.; Lee, Han-Koo; Kim, Jae-Young; Park, Byeong-Gyu; Kim, Hyeong-Do; Lee, Seongsu

2014-01-01

407

Is the directly observed therapy short course (DOTS) an effective strategy for tuberculosis control in a developing country?  

PubMed Central

Objective To investigate the effectiveness of the directly observed therapy short course (DOTS) strategy in tuberculosis control in developing countries. Methods Secondary data was searched to identify relevant publications. Databases, organizational websites and search engines were utilized. Sort criteria were then applied to further limit the articles used. Results A total of 50 articles were found. Abstracts of the 50 articles were then scrutinized and 26 that met the inclusion criteria were identified. Full length copies of these articles were obtained and analysed to extract salient details which were relevant to the research question. Conclusions DOTS as a whole remains the cornerstone of tuberculosis control in developing countries. In the setting of high human immunodeficiency virus (HIV) infection rates and HIV/tuberculosis co-infection, there is a pressing need to modify DOTS to increase its relevance.

Out, Akaninyene Asuquo

2013-01-01

408

Direct observations of the kinetics of migrating T cells suggest active retention by endothelial cells with continual bidirectional migration  

PubMed Central

The kinetics and regulatory mechanisms of T cell migration through the endothelium have not been fully defined. In experimental, filter-based assays in vitro, transmigration of lymphocytes takes hours, compared with minutes, in vivo. We cultured endothelial cell (EC) monolayers on filters, solid substrates, or collagen gels and treated them with TNF-?, IFN-?, or both prior to analysis of lymphocyte migration in the presence or absence of flow. PBL, CD4+ cells, or CD8+ cells took many hours to migrate through EC-filter constructs for all cytokine treatments. However, direct microscopic observations of EC filters, which had been mounted in a flow chamber, showed that PBL crossed the endothelial monolayer in minutes and were highly motile in the subendothelial space. Migration through EC was also observed on clear plastic, with or without flow. After a brief settling without flow, PBL and isolated CD3+ or CD4+ cells crossed EC in minutes, but the numbers of migrated cells varied little with time. Close observation revealed that lymphocytes migrated back and forth continuously across endothelium. Under flow, migration kinetics and the proportions migrating back and forth were altered little. On collagen gels, PBL again crossed EC in minutes and migrated back and forth but showed little penetration of the gel over hours. In contrast, neutrophils migrated efficiently through EC and into gels. These observations suggest a novel model for lymphoid migration in which EC support migration but retain lymphocytes (as opposed to neutrophils), and additional signal(s) are required for onward migration. PMID:18948550

McGettrick, Helen M.; Hunter, Kirsty; Moss, Paul A.; Buckley, Christopher D.; Rainger, G. Ed; Nash, Gerard B.

2009-01-01

409

Top-of-Atmosphere Direct Radiative Effect of Aerosols over Global Oceans from Merged CERES and MODIS Observations  

NASA Technical Reports Server (NTRS)

The direct radiative effect of aerosols (DREA) is defined as the difference between radiative fluxes in the absence and presence of aerosols. In this study, the direct radiative effect of aerosols is estimated for 46 months (March, 2000 to December, 2003) of merged CERES and MODIS Terra global measurements over ocean. This analysis includes the contribution from clear regions in both clear and partly cloudy CERES footprints. MODIS-CERES narrow-to-broadband regressions are developed to convert clear-sky MODIS narrowband radiances to broadband SW radiances, and CERES clear-sky Angular Distribution Models (ADMs) are used to estimate the corresponding TOA radiative fluxes needed to determine the DREA. Clear-sky MODIS pixels are identified using two independent cloud masks: (i) the NOAA-NESDIS algorithm used for inferring aerosol properties from MODIS on the CERES Single Scanner Footprint TOA/Surface Fluxes and Clouds (SSF) product (NOAA-SSF); and (ii) the standard algorithm used by the MODIS aerosol group to produce the MODO4 product (MODO4). Over global oceans, direct radiative cooling by aerosols for clear scenes identified from MODO4 is estimated to be 5.5 W m-2, compared to 3.8 W m-2 for clear scenes from NOAA-SSF. Regionally, differences are largest in areas affected by dust aerosol, such as oceanic regions adjacent to the Saharan and Saudi Arabian deserts, and in northern Pacific Ocean regions influenced by dust transported from Asia. The net total-sky (clear and cloudy) DREA is negative (cooling) and is estimated to be -2.0 W m-2 from MOD04, and -1.6 W m-2 from NOAA-SSF. The DREA is shown to have pronounced seasonal cycles in the Northern Hemisphere and large year-to-year fluctuations near deserts. However, no systematic trend in deseasonalized anomalies of the DREA is observed over the 46-month time series considered.

Loeb, N. G.; Smith, N. M.

2004-01-01

410

Direct observation of nanoscale Peltier and Joule effects at metal-insulator domain walls in vanadium dioxide nanobeams.  

PubMed

The metal to insulator transition (MIT) of strongly correlated materials is subject to strong lattice coupling, which brings about the unique one-dimensional alignment of metal-insulator (M-I) domains along nanowires or nanobeams. Many studies have investigated the effects of stress on the MIT and hence the phase boundary, but few have directly examined the temperature profile across the metal-insulating interface. Here, we use thermoreflectance microscopy to create two-dimensional temperature maps of single-crystalline VO2 nanobeams under external bias in the phase coexisting regime. We directly observe highly localized alternating Peltier heating and cooling as well as Joule heating concentrated at the M-I domain boundaries, indicating the significance of the domain walls and band offsets. Utilizing the thermoreflectance technique, we are able to elucidate strain accumulation along the nanobeam and distinguish between two insulating phases of VO2 through detection of the opposite polarity of their respective thermoreflectance coefficients. Microelasticity theory was employed to predict favorable domain wall configurations, confirming the monoclinic phase identification. PMID:24735496

Favaloro, Tela; Suh, Joonki; Vermeersch, Bjorn; Liu, Kai; Gu, Yijia; Chen, Long-Qing; Wang, Kevin X; Wu, Junqiao; Shakouri, Ali

2014-05-14

411

OBSERVATION OF ANISOTROPY IN THE GALACTIC COSMIC-RAY ARRIVAL DIRECTIONS AT 400 TeV WITH ICECUBE  

SciTech Connect

In this paper we report the first observation in the Southern hemisphere of an energy dependence in the Galactic cosmic-ray anisotropy up to a few hundred TeV. This measurement was performed using cosmic-ray-induced muons recorded by the partially deployed IceCube observatory between 2009 May and 2010 May. The data include a total of 33 Multiplication-Sign 10{sup 9} muon events with a median angular resolution of {approx}3 Degree-Sign . A sky map of the relative intensity in arrival direction over the Southern celestial sky is presented for cosmic-ray median energies of 20 and 400 TeV. The same large-scale anisotropy observed at median energies around 20 TeV is not present at 400 TeV. Instead, the high-energy sky map shows a different anisotropy structure including a deficit with a post-trial significance of -6.3{sigma}. This anisotropy reveals a new feature of the Galactic cosmic-ray distribution, which must be incorporated into theories of the origin and propagation of cosmic rays.

Abbasi, R.; Aguilar, J. A.; Andeen, K.; Baker, M. [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States); Abdou, Y. [Department of Physics and Astronomy, University of Gent, B-9000 Gent (Belgium); Abu-Zayyad, T. [Department of Physics, University of Wisconsin, River Falls, WI 54022 (United States); Ackermann, M.; Bazo Alba, J. L. [DESY, D-15735 Zeuthen (Germany); Adams, J. [Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch (New Zealand); Ahlers, M. [Department of Physics, University of Oxford, 1 Keble Road, Oxford OX1 3NP (United Kingdom); Allen, M. M. [Department of Physics, Pennsylvania State University, University Park, PA 16802 (United States); Altmann, D. [III. Physikalisches Institut, RWTH Aachen University, D-52056 Aachen (Germany); Auffenberg, J. [Department of Physics, University of Wuppertal, D-42119 Wuppertal (Germany); Bai, X. [Bartol Research Institute and Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Barwick, S. W. [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Bay, R. [Department of Physics, University of California, Berkeley, CA 94720 (United States); Beattie, K. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Beatty, J. J. [Department of Physics and Center for Cosmology and Astro-Particle Physics, Ohio State University, Columbus, OH 43210 (United States); Bechet, S. [Science Faculty CP230, Universite Libre de Bruxelles, B-1050 Brussels (Belgium); Becker, J. K. [Fakultaet fuer Physik and Astronomie, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany); Collaboration: IceCube Collaboration; and others

2012-02-10

412

Multiple-view spectrally resolved x-ray imaging observations of polar-direct-drive implosions on OMEGA  

NASA Astrophysics Data System (ADS)

We present spatially, temporally, and spectrally resolved narrow- and broad-band x-ray images of polar-direct-drive (PDD) implosions on OMEGA. These self-emission images were obtained during the deceleration phase and bang time using several multiple monochromatic x-ray imaging instruments fielded along two or three quasi-orthogonal lines-of-sight, including equatorial and polar views. The instruments recorded images based on K-shell lines from a titanium tracer located in the shell as well as continuum emission. These observations constitute the first such data obtained for PDD implosions. The image data show features attributed to laser imprinting and zero-order hydrodynamics. Equatorial-view images show a "double bun" structure that is consistent with synthetic images obtained from post-processing 2D and 3D radiation-hydrodynamic simulations of the experiment. Polar-view images show a pentagonal, petal pattern that correlates with the PDD laser illumination used on OMEGA, thus revealing a 3D aspect of PDD OMEGA implosions not previously observed. Differences are noted with respect to a PDD experiment performed at National Ignition Facility.

Mancini, R. C.; Johns, H. M.; Joshi, T.; Mayes, D.; Nagayama, T.; Hsu, S. C.; Baumgaertel, J. A.; Cobble, J.; Krasheninnikova, N. S.; Bradley, P. A.; Hakel, P.; Murphy, T. J.; Schmitt, M. J.; Shah, R. C.; Tregillis, I. L.; Wysocki, F. J.

2014-12-01

413

Direct observation of the reversible unwinding of a single DNA molecule caused by the intercalation of ethidium bromide  

PubMed Central

Ethidium bromide (EtBr) is the conventional intercalator for visualizing DNA. Previous studies suggested that EtBr lengthens and unwinds double-stranded DNA (dsDNA). However, no one has observed the unwinding of a single dsDNA molecule during intercalation. We developed a simple method to observe the twisting motions of a single dsDNA molecule under an optical microscope. A short dsDNA was attached to a glass surface of a flow chamber at one end and to a doublet bead as a rotation marker at the other end. After the addition and removal of EtBr, the bead revolved in opposite directions that corresponded to the unwinding and rewinding of a dsDNA, respectively. The amount of intercalating EtBr was estimated from the revolutions of the bead. EtBr occupied 57% of base pairs on a single dsDNA at 1 mM of EtBr, indicating that EtBr molecules could bind at contiguous sites to each other. The isotherm of intercalation showed that negative cooperativity existed between adjoining EtBr molecules. The association constant of EtBr and dsDNA (1.9 (±0.1) × 105 M?1) was consistent with that of previous results. Our system is useful to investigate the twisting of a single dsDNA interacting with various chemicals and biomolecules. PMID:17905818

Hayashi, Masahito; Harada, Yoshie

2007-01-01

414

Direct Observation of Radiation-Belt Electron Acceleration from Electron-Volt Energies to Megavolts by Nonlinear Whistlers  

NASA Astrophysics Data System (ADS)

The mechanisms for accelerating electrons from thermal to relativistic energies in the terrestrial magnetosphere, on the sun, and in many astrophysical environments have never been verified. We present the first direct observation of two processes that, in a chain, cause this acceleration in Earth's outer radiation belt. The two processes are parallel acceleration from electron-volt to kilovolt energies by parallel electric fields in time-domain structures (TDS), after which the parallel electron velocity becomes sufficiently large for Doppler-shifted upper band whistler frequencies to be in resonance with the electron gyration frequency, even though the electron energies are kilovolts and not hundreds of kilovolts. The electrons are then accelerated by the whistler perpendicular electric field to relativistic energies in several resonant interactions. TDS are packets of electric field spikes, each spike having duration of a few hundred microseconds and containing a local parallel electric field. The TDS of interest resulted from nonlinearity of the parallel electric field component in oblique whistlers and consisted of ˜0.1 msec pulses superposed on the whistler waveform with each such spike containing a net parallel potential the order of 50 V. Local magnet