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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

Periodic reversal of direction allows Myxobacteria to swarm  

PubMed Central

Many bacteria can rapidly traverse surfaces from which they are extracting nutrient for growth. They generate flat, spreading colonies, called swarms because they resemble swarms of insects. We seek to understand how members of any dense swarm spread efficiently while being able to perceive and interfere minimally with the motion of others. To this end, we investigate swarms of the myxobacterium, Myxococcus xanthus. Individual M. xanthus cells are elongated; they always move in the direction of their long axis; and they are in constant motion, repeatedly touching each other. Remarkably, they regularly reverse their gliding directions. We have constructed a detailed cell- and behavior-based computational model of M. xanthus swarming that allows the organization of cells to be computed. By using the model, we are able to show that reversals of gliding direction are essential for swarming and that reversals increase the outflow of cells across the edge of the swarm. Cells at the swarm edge gain maximum exposure to nutrient and oxygen. We also find that the reversal period predicted to maximize the outflow of cells is the same (within the errors of measurement) as the period observed in experiments with normal M. xanthus cells. This coincidence suggests that the circuit regulating reversals evolved to its current sensitivity under selection for growth achieved by swarming. Finally, we observe that, with time, reversals increase the cell alignment, and generate clusters of parallel cells. PMID:19164578

Wu, Yilin; Kaiser, A. Dale; Jiang, Yi; Alber, Mark S.

2009-01-01

3

Direct observation detonator operation  

NASA Astrophysics Data System (ADS)

The analysis of detonator-timing performance has involved the use of rotating-mirror cameras (RMC) used in the streak mode and high-speed film. Fiducial timing marks are applied to the film to provide temporal references. The use of a RMC for detonator analysis requires aligning the camera, performing an exposure test, capturing light from the detonation and then processing the film. This procedure can take up to an hour for two technicians. After the film is possessed another technician compares each light streak on the film with the fiducial timing marks also recorded on the film. Capturing light from a detonator and recording it directly to a digitizer can improve detonator-timing measurement in several ways. The digitized signals can then be directly analyzed with software. The direct recording method reduces the need for expensive rotating mirror cameras, film processing and subjective optical measurement comparison. Furthermore, an extensive support facility requiring several specialized technicians is reduced to a single technician in a modest laboratory. This technician is then capable of performing several tests an hour. Tests were preformed to measure light intensity at detonation. An optical method of capturing the light was designed using a remote microscope coupled to optical fiber to bring the light to an optical/electrical converter and a digitizer then records the signal. This system is presently used in parallel with a RMC. The results are compared for accuracy.

Hall, Charles R.

2001-11-01

4

Direct observation of time reversal violation  

NASA Astrophysics Data System (ADS)

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.

Bernabéu, J.

2013-06-01

5

Animal models of impact injury allow a direct correla-tion between in vivo tissue deformation  

E-print Network

Animal models of impact injury allow a direct correla- tion between in vivo tissue deformation, neural cell permeability, regional neuronal loss in the hippocampus and white matter axonal damage in TBI not only for intra- operative MRI updat- ing, but also for pre- surgical planning. Phone: 313.577.0252 Fax

Berdichevsky, Victor

6

Direct observations of solar-wind particles  

Microsoft Academic Search

Direct observations of solar-wind particles are discussed in detail. A well-defined ‘quiet state’ of the solar wind is indicated by observations made from 1962 to 1967. The plasma properties in this quiet state are compared with those predicted by hydrodynamic models of the coronal expansion. While the basic flow parameters are predicted with reasonable accuracy by these models, the thermal

A. J. Hundhausen

1968-01-01

7

Metabolic oligosaccharide engineering of Plasmodium falciparum intraerythrocytic stages allows direct glycolipid analysis by mass spectrometry.  

PubMed

A recent addition to the arsenal of tools for glycome analysis is the use of metabolic labels that allow covalent tagging of glycans with imaging probes. In this work we show that N-azidoglucosamine was successfully incorporated into glycolipidic structures of Plasmodium falciparum intraerythrocytic stages. The ability to tag glycoconjugates selectively with a fluorescent reporter group permits TLC detection of the glycolipids providing a new method to quantify dynamic changes in the glycosylation pattern and facilitating direct mass spectrometry analyses. Presence of glycosylphosphatidylinositol and glycosphingolipid structures was determined in the different extracts. Furthermore, the fluorescent tag was used as internal matrix for the MALDI experiment making even easier the analysis. PMID:22245334

Piñero, Tamara; Peres, Valnice J; Katzin, Alejandro; Couto, Alicia S

2012-01-01

8

Direct Observation of Coherent Interorbital Spin-Exchange Dynamics  

NASA Astrophysics Data System (ADS)

We report on the first direct observation of fast spin-exchange coherent oscillations between different long-lived electronic orbitals of ultracold Yb173 fermions. We measure, in a model-independent way, the strength of the exchange interaction driving this coherent process. This observation allows us to retrieve important information on the interorbital collisional properties of Yb173 atoms and paves the way to novel quantum simulations of paradigmatic models of two-orbital quantum magnetism.

Cappellini, G.; Mancini, M.; Pagano, G.; Lombardi, P.; Livi, L.; Siciliani de Cumis, M.; Cancio, P.; Pizzocaro, M.; Calonico, D.; Levi, F.; Sias, C.; Catani, J.; Inguscio, M.; Fallani, L.

2014-09-01

9

Direct observation of coherent interorbital spin-exchange dynamics.  

PubMed

We report on the first direct observation of fast spin-exchange coherent oscillations between different long-lived electronic orbitals of ultracold ^{173}Yb fermions. We measure, in a model-independent way, the strength of the exchange interaction driving this coherent process. This observation allows us to retrieve important information on the interorbital collisional properties of ^{173}Yb atoms and paves the way to novel quantum simulations of paradigmatic models of two-orbital quantum magnetism. PMID:25279608

Cappellini, G; Mancini, M; Pagano, G; Lombardi, P; Livi, L; Siciliani de Cumis, M; Cancio, P; Pizzocaro, M; Calonico, D; Levi, F; Sias, C; Catani, J; Inguscio, M; Fallani, L

2014-09-19

10

Direct observation limits on antimatter gravitation  

SciTech Connect

The proposed Antihydrogen Gravity experiment at Fermilab (P981) will directly measure the gravitational attraction g between antihydrogen and the Earth, with an accuracy of 1% or better. The following key question has been asked by the PAC: Is a possible 1% difference between g and g already ruled out by other evidence? This memo presents the key points of existing evidence, to answer whether such a difference is ruled out (a) on the basis of direct observational evidence; and/or (b) on the basis of indirect evidence, combined with reasoning based on strongly held theoretical assumptions. The bottom line is that there are no direct observations or measurements of gravitational asymmetry which address the antimatter sector. There is evidence which by indirect reasoning can be taken to rule out such a difference, but the analysis needed to draw that conclusion rests on models and assumptions which are in question for other reasons and are thus worth testing. There is no compelling evidence or theoretical reason to rule out such a difference at the 1% level.

Fischler, Mark; Lykken, Joe; Roberts, Tom; /Fermilab

2008-06-01

11

First direct observation of muon antineutrino disappearance  

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

12

First Direct Observation of Muon Antineutrino Disappearance  

NASA Astrophysics Data System (ADS)

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 1.71×1020 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)]×10-3eV2, sin?2(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.; Andreopoulos, C.; 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.; Howcroft, C.; 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.

2011-07-01

13

A new type of remote sensors which allow directly forming certain statistical estimates of images  

NASA Astrophysics Data System (ADS)

A new approach to the problems of statistical and structural pattern recognition, a signal processing and image analysis techniques has been considered. These problems are extremely important for tasks being solved by airborne and space borne remote sensing systems. Development of new remote sensors for image and signal processing is inherently connected with a possibility of statistical processing of images. Fundamentally new optoelectronic sensors "Multiscan" have been suggested in the present paper. Such sensors make it possible to form directly certain statistical estimates, which describe completely enough the different types of images. The sensors under discussion perform the Lebesgue-Stieltjes signal integration rather than the Cauchy-Riemann one. That permits to create integral functionals for determining statistical features of images. The use of the integral functionals for image processing provides a good agreement of obtained statistical estimates with required image information features. The Multiscan remote sensors allows to create a set of integral moments of an input image right up to high-order integral moments, to form a quantile representation of an input image, which provides a count number limited texture, to form a median, which provides a localisation of a low-contrast horizon line in fog, localisation of water flow boundary etc. This work presents both the description of the design concept of the new remote sensor and mathematical apparatus providing the possibility to create input image statistical features and integral functionals.

Podlaskin, Boris; Guk, Elena; Karpenko, Andrey

2010-10-01

14

WMAP Haze: Directly Observing Dark Matter?  

E-print Network

In this paper we show that dark matter in the form of dense matter/antimatter nuggets could provide a natural and unified explanation for several distinct bands of diffuse radiation from the core of the Galaxy spanning over 12 orders of magnitude in frequency. We fix all of the phenomenological properties of this model by matching to x-ray observations in the keV band, and then calculate the unambiguously predicted thermal emission in the microwave band, at frequencies smaller by 10 orders of magnitude. Remarkably, the intensity and spectrum of the emitted thermal radiation are consistent with--and could entirely explain--the so-called "WMAP haze": a diffuse microwave excess observed from the core of our Galaxy by the Wilkinson Microwave Anisotropy Probe (WMAP). This provides another strong constraint of our proposal, and a remarkable nontrivial validation. If correct, our proposal identifies the nature of the dark matter, explains baryogenesis, and provides a means to directly probe the matter distribution in our Galaxy by analyzing several different types of diffuse emissions.

Michael McNeil Forbes; Ariel R. Zhitnitsky

2008-02-26

15

30 CFR 1220.011 - Schedule of allowable direct and allocable joint costs and credits.  

Code of Federal Regulations, 2012 CFR

...that do not directly benefit NPSL operations. ...records showing the nature of the task and the...bonds, and other benefit plans of a like nature that are made available...paying the salaries and benefits defined in this...

2012-07-01

16

30 CFR 220.011 - Schedule of allowable direct and allocable joint costs and credits.  

Code of Federal Regulations, 2010 CFR

...members of his immediate family and transportation of...matter, its direct relationship to NPSL operations...equipment that may be mobile or semimobile and also...Bulldozers Hour. Mobile cranes Hour. Trailer-mounted...a)(3). (k) Communications. Costs of...

2010-07-01

17

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

18

Direct observation of microbubbles in directional solidification of salol  

SciTech Connect

Dynamic light scattering at the crystal-melt interface of solidifying salol was followed for 14 days. The hydrodynamic radius deduced from intensity correlation data increased continuously from {approx}1 to {approx}100 {mu}m. When the scattering layer was trapped by the advancing crystal front, microscopic observation revealed bubbles as inclusions whose size agreed with the light-scattering value. Scattering was also observed to disappear after prolonged pumping on the sample.

Williams, L.M.; Srinivasan, M.R.; Cummins, H.Z. (Department of Physics, City College of the City University of New York, New York, New York 10031 (USA))

1990-03-26

19

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

20

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

21

Emerging feed-forward inhibition allows the robust formation of direction selectivity in the developing ferret visual cortex.  

PubMed

The computation of direction selectivity requires that a cell respond to joint spatial and temporal characteristics of the stimulus that cannot be separated into independent components. Direction selectivity in ferret visual cortex is not present at the time of eye opening but instead develops in the days and weeks following eye opening in a process that requires visual experience with moving stimuli. Classic Hebbian or spike timing-dependent modification of excitatory feed-forward synaptic inputs is unable to produce direction-selective cells from unselective or weakly directionally biased initial conditions because inputs eventually grow so strong that they can independently drive cortical neurons, violating the joint spatial-temporal activation requirement. Furthermore, without some form of synaptic competition, cells cannot develop direction selectivity in response to training with bidirectional stimulation, as cells in ferret visual cortex do. We show that imposing a maximum lateral geniculate nucleus (LGN)-to-cortex synaptic weight allows neurons to develop direction-selective responses that maintain the requirement for joint spatial and temporal activation. We demonstrate that a novel form of inhibitory plasticity, postsynaptic activity-dependent long-term potentiation of inhibition (POSD-LTPi), which operates in the developing cortex at the time of eye opening, can provide synaptic competition and enables robust development of direction-selective receptive fields with unidirectional or bidirectional stimulation. We propose a general model of the development of spatiotemporal receptive fields that consists of two phases: an experience-independent establishment of initial biases, followed by an experience-dependent amplification or modification of these biases via correlation-based plasticity of excitatory inputs that compete against gradually increasing feed-forward inhibition. PMID:24598528

Van Hooser, Stephen D; Escobar, Gina M; Maffei, Arianna; Miller, Paul

2014-06-01

22

[Calculation of allowable pollution loads for lake and reservoir based on bi-direction algorithm and its case study].  

PubMed

Based on the reviews and summaries of water environment carrying capacity researches and practices, the main problems of allowable pollutants load estimation and its allocation in China were analyzed. Then a bi-direction algorithm for allowable pollutants loads calculation was proposed to support the pollutants loads management in the lake and reservoir control units. It was the combination of forward algorithm and backward algorithm. The two major steps were modeling and scenario analysis. Firstly, the basic scenario was proposed using the estimation model. Then the basic scenario was analyzed using the water quality simulation model to assess the compliance of water quality objectives. The allowable pollutant loads were calculated after several loops of scenario simulation, result analysis and scenario optimization. Finally, the Chaihe Reservoir in Liaoning Province, China was used as a case study using Environmental Fluid Dynamic Code (EFDC) model as the kernel model. The results demonstrated that the algorithm proposed provided an efficient and appropriate methodology for allowable pollutant load calculation. PMID:24812947

Jia, Hai-Feng; Guo, Yu

2014-02-01

23

Direct Behavioral Observation in School Settings: Bringing Science to Practice  

ERIC Educational Resources Information Center

Schools provide a useful, controlled setting for evaluating child behavior problems, yet direct observational coding procedures evaluated by child researchers have not been widely incorporated by practicing clinicians. This article provides a summary of procedures useful to clinicians performing direct behavioral observation in school settings. We…

Nock, Matthew K.; Kurtz, Steven M. S.

2005-01-01

24

Objectively Optimized Observation Direction System Providing Situational Awareness for a Sensor Web  

Microsoft Academic Search

There is great utility in having a flexible and automated objective observation direction system for the decadal survey missions and beyond. Such a system allows us to optimize the observations made by suite of sensors to address specific goals from long term monitoring to rapid response. We have developed such a prototype using a network of communicating software elements to

O. Aulov; D. J. Lary

2010-01-01

25

Direct Observation of Postadsorption Aggregation of Antifreeze Glycoproteins on Silicates  

E-print Network

different silicate minerals, muscovite mica and amorphous silica-titania, has been directly observed typically freeze between -0.5 and -0.9 °C (and at -0.01 °C after dialysis), essentially due to the familiar in the cell wall in certain bacteria8 ). Observations of ice crystal growth under freezing conditions

Cheng, Chi-Hing Christina

26

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

27

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

28

Applying Direct Observation to Model Workflow and Assess Adoption  

PubMed Central

Lack of understanding about workflow can impair health IT system adoption. Observational techniques can provide valuable information about clinical workflow. A pilot study using direct observation was conducted in an outpatient chronic disease clinic. The goals of the study were to assess workflow and information flow and to develop a general model of workflow and information behavior. Over 55 hours of direct observation showed that the pilot site utilized many of the features of the informatics systems available to them, but also employed multiple non-electronic artifacts and workarounds. Gaps existed between clinic workflow and informatics tool workflow, as well as between institutional expectations of informatics tool use and actual use. Concurrent use of both paper-based and electronic systems resulted in duplication of effort and inefficiencies. A relatively short period of direct observation revealed important information about workflow and informatics tool adoption. PMID:17238450

Unertl, Kim M.; Weinger, Matthew B.; Johnson, Kevin B.

2006-01-01

29

Combined use of leaf size and economics traits allows direct comparison of hydrophyte and terrestrial herbaceous adaptive strategies  

PubMed Central

Background and Aims Hydrophytes generally exhibit highly acquisitive leaf economics. However, a range of growth forms is evident, from small, free-floating and rapidly growing Lemniden to large, broad-leaved Nymphaeiden, denoting variability in adaptive strategies. Traits used to classify adaptive strategies in terrestrial species, such as canopy height, are not applicable to hydrophytes. We hypothesize that hydrophyte leaf size traits and economics exhibit sufficient overlap with terrestrial species to allow a common classification of plant functional types, sensu Grime's CSR theory. Methods Leaf morpho-functional traits were measured for 61 species from 47 water bodies in lowland continental, sub-alpine and alpine bioclimatic zones in southern Europe and compared against the full leaf economics spectrum and leaf size range of terrestrial herbs, and between hydrophyte growth forms. Key Results Hydrophytes differed in the ranges and mean values of traits compared with herbs, but principal components analysis (PCA) demonstrated that both groups shared axes of trait variability: PCA1 encompassed size variation (area and mass), and PCA2 ranged from relatively dense, carbon-rich leaves to nitrogen-rich leaves of high specific leaf area (SLA). Most growth forms exhibited trait syndromes directly equivalent to herbs classified as R adapted, although Nymphaeiden ranged between C and SR adaptation. Conclusions Our findings support the hypothesis that hydrophyte adaptive strategy variation reflects fundamental trade-offs in economics and size that govern all plants, and that hydrophyte adaptive strategies can be directly compared with terrestrial species by combining leaf economics and size traits. PMID:22337079

Pierce, Simon; Brusa, Guido; Sartori, Matteo; Cerabolini, Bruno E. L.

2012-01-01

30

First direct observations of daytime NO3 during TEXAQS 2000  

Microsoft Academic Search

The importance of nitrate radical (NO3) chemistry at night is well known. NO3 has not been directly observed during the day thus far, and has therefore been considered insignificant. Here we present the first direct daytime detection of NO3 by Differential Optical Absorption Spectroscopy at LaPorte, Texas during the Texas Air Quality Study 2000. On three consecutive days NO3 mixing

A. Geyer; B. Alicke; R. Ackermann; J. Stutz; M. Martinez; H. Harder; W. Brune; E. Williams; T. Jobson; R. Shetter; S. Hall

2002-01-01

31

Time-gated luminescence microscopy allowing direct visual inspection of lanthanide-stained microorganisms in background-free condition.  

PubMed

Application of standard immuno-fluorescence microscopy techniques for detection of rare-event microorganisms in dirty samples is severely limited by autofluorescence of nontarget organisms or other debris. Time-gated detection using gateable array detectors in combination with microsecond-lifetime luminescent bioprobes (usually lanthanide-based) is highly effective in suppression of (nanosecond-lifetime) autofluorescence background; however, the complexity and cost of the instrumentation is a major barrier to application of these techniques to routine diagnostics. We report a practical, low-cost implementation of time-gated luminescence detection in a standard epifluorescence microscope which has been modified to include a high-power pulsed UV light-emitting diode (LED) illumination source and a standard fast chopper inserted in the focal plane behind a microscope eyepiece. Synchronization of the pulsed illumination/gated detection cycle is driven from the clock signal from the chopper. To achieve time-gated luminescence intensities sufficient for direct visual observation, we use high cycle rates, up to 2.5 kHz, taking advantage of the fast switching capabilities of the LED source. We have demonstrated real-time direct-visual inspection of europium-labeled Giardia lamblia cysts in dirty samples and Cryptosporidium parvum oocysts in fruit juice concentrate. The signal-to-background ratio has been enhanced by a factor of 18 in time-gated mode. The availability of low-cost, robust time-gated microscopes will aid development of long-lifetime luminescence bioprobes and accelerate their application in routine laboratory diagnostics. PMID:21344865

Jin, Dayong; Piper, James A

2011-03-15

32

Uni- and Bi-directional Electron Conics Observed by Cluster  

NASA Astrophysics Data System (ADS)

Heated and accelerated electrons are often observed on perigee passes of Cluster near 5-6 RE. On a typical pass through the mid-altitude plasma sheet, one observes the incoming and mirrored plasma sheet electron population. Depressed fluxes are observed at 0 o and 180 o with a width greater than the atmospheric loss cone. These fluxes appear to be modulated at frequencies that are in the ULF band. Similar magnetic fluctuations are observed in magnetometer data. At energies below this near-Maxwellian plasma sheet population, electrons are observed to have rapid variations spatially, temporally, and in energy. These variations in the lower energy population are correlated with ULF waves. No clear occurrence correlation is seen with higher frequency waves, including solitary waves. PEACE has a 15 o angular resolution. This makes it difficult to distinguish between a true parallel heated flux and a perpendicularly heated population. One observes both upward and downward uni-directional beams and bi-directional beams. On February 23, 2001, there is clear evidence that at least at times, these beams are unresolved, folded electron conics. Conics are even observed at 90 o, suggesting that the heating mechanism moves up to the satellite from lower altitudes. Four spacecraft field, wave, and particle data are presented to investigate the wave-particle relationships associated with these events, especially the 90 o conics. The goal is to identify possible heating mechanisms.

Winningham, D.; Goldstein, M. L.; Fazakerley, A.; Balogh, A.; Acuna, M.; Khurana, K.; Kivelson, M.; Reme, H.; Kistler, L.; Parks, G.

2002-05-01

33

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

34

Direct Observation of Ion-irradiation-induced Chemical Mixing  

SciTech Connect

Irradiation-induced dissolution of particles and mixing at heterogeneous interfaces in materials is of importance for ion beam processing and radiation materials sciences. Modeling has predicted dissolution of particles and homogenization at sharp chemical interfaces; imaging and depth profiling techniques have also been used to observe damage and mixing resulting from ion or neutron bombardment. Analytical scanning transmission electron microscopy has been used to directly observe the ion-irradiation induced elemental mixing and dissolution of {approx}25-50 nm titanium oxycarbonitrides in a nanostructured ferritic alloy irradiated at 173 K. The magnitude of the mixed zone is consistent with radiation damage theory.

Parish, Chad M.; Edmondson, P. D.; Zhang, Yanwen; Miller, Michael K.

2011-11-01

35

Direct observation of ion-irradiation-induced chemical mixing  

SciTech Connect

Irradiation-induced dissolution of particles and mixing at heterogeneous interfaces in materials is of importance for ion beam processing and radiation materials sciences. Modeling has predicted dissolution of particles and homogenization at sharp chemical interfaces; imaging and depth profiling techniques have also been used to observe damage and mixing resulting from ion or neutron bombardment. Analytical scanning transmission electron microscopy has been used to directly observe the ion-irradiation induced elemental mixing and dissolution of {approx}25-50 nm titanium oxycarbonitrides in a nanostructured ferritic alloy irradiated at 173 K. The magnitude of the mixed zone is consistent with radiation damage theory.

Edmondson, Philip D [ORNL; Miller, Michael K [ORNL; Parish, Chad M [ORNL; Zhang, Yanwen [ORNL

2011-01-01

36

Direct observation of the strange b baryon Xi_b^{-}  

E-print Network

We report the first direct observation of the strange b baryon Xi_b^{-}. We reconstruct the decay Xi_b^{-} to J/psi Xi^{-}, with J/psi to dimuons and Xi^{-} to Lambda pion, in ppbar collisions at sqrt(s) = 1.96 TeV. Using 1.3 fb^{-1} of data collected by the D0 detector, we observe 15.2 +/- 4.4(stat.)+ 1.9/-0.4(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 sigmas, equivalent to a probability of 3.3 X 10^{-8} of it arising from a background fluctuation. Normalizing to the decay Lambda_b to J/psi Lambda, we measure the relative rate to be 0.28 +/- 0.09(stat.)+ 0.09/-0.08 (syst.).

Abazov, V M; Abolins, M; Acharya, B S; Adams, M; Adams, T; Aguiló, 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; Benítez, 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; Böhnlein, 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; Bühler, M; Büscher, 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; Clement, B; Coadou, Y; Cooke, M; Cooper, W E; Corcoran, M; Couderc, F; Cousinou, M C; Crepe-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; García, C; García-Bellido, A; Gavrilov, V; Gay, P; Geist, W; Gelé, D; Gerber, C E; Gershtein, Yu; Gillberg, D; Ginther, G; Gollub, N; Gómez, B; Goussiou, A; Grannis, P D; Greenlee, H; Greenwood, Z D; Gregores, E M; Grenier, G; Gris, P; Grivaz, J F; Grohsjean, A; Grünendahl, S; Grünewald, M W; Guo, J; Guo, F; Gutíerrez, P; Gutíerrez, 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, Yu 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; Kühl, T; Kumar, A; Kunori, S; Kupco, A; Kurca, T; Kvita, J; Lacroix, F; Lam, D; Lammers, S; Landsberg, G L; Lazoflores, J; Lebrun, P; Lee, W M; Leflat, A; Lehner, F; Lellouch, J; Lesne, V; Lévêque, 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; Lokajícek, 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; Oteroy-Garzon, 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; Petroff, P; Petteni, M; Piegaia, R; Piper, J; Pleier, M A; Podesta-Lerma, P L M; Podstavkov, V M

2007-01-01

37

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

38

Direct Observation of the Strange b Baryon Xib-  

Microsoft Academic Search

We report the first direct observation of the strange b baryon Xib-(Xi¯b+). We reconstruct the decay Xib--->J\\/psiXi-, with J\\/psi-->mu+mu-, and Xi--->Lambdapi--->ppi-pi- 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) Xib- candidates at a mass of 5.774±0.011(stat)±0.015(syst)GeV. The significance of the observed signal is 5.5sigma, equivalent to a probability of 3.3×10-8 of

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

2007-01-01

39

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

40

Direct observation of intermolecular interactions mediated by hydrogen bonding.  

PubMed

Although intermolecular interactions are ubiquitous in physicochemical phenomena, their dynamics have proven difficult to observe directly, and most experiments rely on indirect measurements. Using broadband two-dimensional infrared spectroscopy (2DIR), we have measured the influence of hydrogen bonding on the intermolecular vibrational coupling between dimerized N-methylacetamide molecules. In addition to strong intramolecular coupling between N-H and C=O oscillators, cross-peaks in the broadband 2DIR spectrum appearing upon dimerization reveal strong intermolecular coupling that changes the character of the vibrations. In addition, dimerization changes the effects of intramolecular coupling, resulting in Fermi resonances between high and low-frequency modes. These results illustrate how hydrogen bonding influences the interplay of inter- and intramolecular vibrations, giving rise to correlated nuclear motions and significant changes in the vibrational structure of the amide group. These observations have direct impact on modeling and interpreting the IR spectra of proteins. In addition, they illustrate a general approach to direct molecular characterization of intermolecular interactions. PMID:25053321

De Marco, Luigi; Thämer, Martin; Reppert, Mike; Tokmakoff, Andrei

2014-07-21

41

Complete control, direct observation and study of molecular super rotors  

E-print Network

Extremely fast rotating molecules carrying significantly more energy in their rotation than in any other degree of freedom are known as "super rotors". It has been speculated that super rotors may exhibit a number of unique and intriguing properties. Theoretical studies showed that ultrafast molecular rotation may change the character of molecular scattering from solid surfaces, alter molecular trajectories in external fields, make super rotors surprisingly stable against collisions, and lead to the formation of gas vortices. New ways of molecular cooling and selective chemical bond breaking by ultrafast spinning have been proposed. Owing to the fundamental laws of nature, bringing a large number of molecules to fast, directional and synchronous rotation is rather challenging. As a result, only indirect evidence of super rotors has been reported to date. Here we demonstrate the first controlled creation, direct observation and study of molecular super rotors. Using intense laser pulses tailored to produce an ...

Korobenko, Aleksey; Milner, Valery

2013-01-01

42

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

43

Direct observation of Kelvin waves excited by quantized vortex reconnection  

PubMed Central

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 4He, 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.

2014-01-01

44

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

45

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

46

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

47

First direct observations of daytime NO3 during TEXAQS 2000  

NASA Astrophysics Data System (ADS)

The importance of nitrate radical (NO3) chemistry at night is well known. NO3 has not been directly observed during the day thus far, and has therefore been considered insignificant. Here we present the first direct daytime detection of NO3 by Differential Optical Absorption Spectroscopy at LaPorte, Texas during the Texas Air Quality Study 2000. On three consecutive days NO3 mixing ratios reached ¯ 5 ppt three hours before sunset, increasing to 31 ppt around sunset. These elevated daytime NO3 levels have important implications for the atmospheric chemistry: 1. Although daytime NO3 has no significant effect on the photostationary state between O3 and NOx, it drastically accelerates NO-to- NO2 conversion during the last hour before sunset. 2. Daytime NO3 plays an important role in the Ox (= O3 + NO2) budget: On August 31, NO3 chemistry contributed 10 +/- 7 % to the total Ox loss during the day (destroying 8 (+/- 4) ppb), and 28 +/- 18 % integrated over a 24-hour period (destroying 27 (+/- 6) ppb). 3. NO3 contributes significantly to the daytime oxidation of hydrocarbons such as monoterpenes and phenol in Houston. The observed daytime NO3 concentrations 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 show that elevated (> 1ppt) NO3 levels are present whenever ozone mixing ratios exceed 100 ppb.

Geyer, A.; Alicke, B.; Ackermann, R.; Stutz, J.; Martinez, M.; Harder, H.; Brune, W.; Williams, E.; Jobson, T.; Shetter, R.; Hall, S.

2002-12-01

48

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

E-print Network

-cm long remotely operated vehicle (ROV) flyer with a 1.0-m high, 1.52-m wide, 2.8-m long remotely or to fly over sensitive regions such as reefs. The ROV-flyer piggy-backs on the ROV-crawler and can separate to become an "eye-in-the-sky" to observe from above the activities of the ROV-crawler. Index Terms

Wood, Stephen L.

49

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

50

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

51

Direct Observation of Smectic Layers in Thermotropic Liquid Crystals  

NASA Astrophysics Data System (ADS)

We demonstrate subnanometer resolution cryo-TEM imaging of smectic layers in the smectic and nematic phases of two bent-core liquid crystals. Our results show perfect periodicity over several hundred layers in the smectic phase and also provide the first direct evidence of smectic clusters on length scales of 30-50 nm in a nematic liquid crystal. The results are corroborated with small angle x-ray scattering measurements. The observation of smectic clusters in the nematic phase is of special interest in bent-core liquid crystals, where the smectic clusters are stable over wide temperature ranges, in contrast to the well-known pretransitional “cybotactic” clusters that appear only in the vicinity of a bulk smectic phase. The means to characterize and manipulate this nanoscale molecular order could open up completely new liquid crystal-based technologies.

Zhang, C.; Gao, M.; Diorio, N.; Weissflog, W.; Baumeister, U.; Sprunt, S.; Gleeson, J. T.; Jákli, A.

2012-09-01

52

Direct Imaging Observations of Protoplanetary Disks with TMT  

NASA Astrophysics Data System (ADS)

We present possible science cases of the direct imaging observations of protoplanetary disks by TMT. With TMT equipped with an extreme adoptive optics system, we expect to obtain the diffraction-limited images with the spatial resolution of ~0.01 asec, which is about 1-2AU at the distance of nearby star forming region of 140 pc. With such spatial resolution, TMT can reveal disk structures at the 'planet-forming region' in protoplanetary disks. For instance, TMT can reveal spiral density wave launched by a planet orbiting at 30 AU (close to the Neptune orbit) from the central star. TMT can also resolve the surface water snow line that is expected to reside at several AU from the central star. We also discuss how the synergy with ALMA in its full capability can lead to the new insights on the protoplanetary disks and planet formation.

Muto, Takayuki

2014-07-01

53

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

54

Brownian motion in shear flow: direct observation of anomalous diffusion.  

PubMed

Brownian motion in a simple shear flow has been experimentally investigated by using a different method for observation and analysis. A number of polystyrene spheres dispersed in sheared water were tracked with a confocal scanning laser microscope, and the time dependences of their coordinates were obtained. Since in the usual mean-square displacement in the flow direction the contribution from the Brownian motion is overwhelmed by that due to the convection, we considered an alternative displacement for which the convection effect could be removed. We found that the new mean-square displacement consists of the normal Einstein diffusion term, which is linear in t, and an anomalous t(3) term arising from the coupling between the diffusion along the velocity gradient and the convection. PMID:22304053

Orihara, Hiroshi; Takikawa, Yoshinori

2011-12-01

55

Direct Observation of Cotranscriptional Folding in an Adenine Riboswitch  

PubMed Central

Growing RNA chains fold cotranscriptionally as they are synthesized by RNA polymerase (RNAP). Riboswitches, which regulate gene expression by adopting alternative RNA folds, are sensitive to cotranscriptional events. We developed an optical-trapping assay to follow the cotranscriptional folding of a nascent RNA, and used it to monitor individual transcripts of the pbuE adenine riboswitch, visualizing distinct folding transitions. We report a particular folding signature for the riboswitch aptamer whose presence directs the gene-regulatory transcription outcome, and we measured the termination frequency as a function of adenine level and tension applied to the RNA. Our results demonstrate that the outcome is kinetically controlled. These experiments furnish a means to observe conformational switching in real time, and enable the precise mapping of events during cotranscriptional folding. PMID:23087247

Frieda, Kirsten L.; Block, Steven M.

2012-01-01

56

Direct observation of atomic network migration in glass  

NASA Astrophysics Data System (ADS)

Many physical properties of glasses are still far from being understood at the atomic level. The lack of experimental methods capable of studying glassy dynamics at this scale has impeded the development of a complete model for atomic transport processes. Here we apply the new technique of atomic-scale x-ray photon correlation spectroscopy to directly observe single atomic motion in lead silicate glass. We show that dynamics change significantly depending on the glass composition, from single jump processes between inhomogeneous regions to multiple jump processes along network paths and through voids. Up until now, such measurements were far out of reach for temperatures below the glass transition. Our findings suggest that the method and the model introduced here will also help understanding atomic diffusion in a wide range of other glass systems.

Ross, Manuel; Stana, Markus; Leitner, Michael; Sepiol, Bogdan

2014-09-01

57

An Earth-Directed CME not Observed in LASCO Images  

NASA Astrophysics Data System (ADS)

The COR1 coronagraphs on STEREO-A and -B observed an Earth-directed CME originating from N09W15 at 02:20 UT on 2010/07/09. The apparent CME speed is only 291 km/s, and the angular width is 60 degrees. The CME is somewhat slower than the average LASCO CME (average speed ~450 km/s) but not narrow. The CME was expected to be seen as a halo CME because of the geometry and large width. However, the CME could not be identified in the LASCO running difference movie because of the visibility of the white-light coronagraph. On the other hand, EUV images taken by SDO/AIA show a clear dimming to the northwest of the source region and a wave-like feature propagating to the east. Faint Earth-directed CMEs, seem to be better indicated by surface eruptive signatures such as dimming and EUV waves. We discuss how to estimate CME parameters using the EUV data alone.

Yashiro, S.; Gopalswamy, N.; Akiyama, S.

2010-12-01

58

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

59

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

60

Direct observation of single kinesin molecules moving along microtubules  

NASA Astrophysics Data System (ADS)

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 internal reflection fluorescence microscopy4 in the absence of attachment of the motor to a cargo (for example, an organelle or bead). The average distance travelled after a binding encounter with a microtubule is 600 nm, which reflects a ˜ 1% probability of detachment per mechanical cycle. Surprisingly, processive movement could still be observed at salt concentrations as high as 0.3 M NaCl. Truncated kinesin molecules having only a single motor domain do not show detectable processive movement, which is consistent with a model in which kinesin's two force-generating heads operate by a hand-over-hand mechanism.

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

1996-04-01

61

Direct observation of brownian motion of lipids in a membrane.  

PubMed Central

Nanovid microscopy, which uses 30- to 40-nm colloidal gold probes combined with video-enhanced contrast, can be used to examine random and directed movements of individual molecules in the plasma membrane of living cells. To validate the technique in a model system, the movements of lipid molecules were followed in a supported, planar bilayer containing fluorescein-conjugated phosphatidylethanolamine (Fl-PtdEtn) labeled with 30-nm gold anti-fluorescein (anti-Fl). Multivalent gold probes were prepared by conjugating only anti-Fl to the gold. Paucivalent probes were prepared by mixing an irrelevant antibody with the anti-Fl prior to conjugation. The membrane-bound gold particles moved in random patterns that were indistinguishable from those produced by computer simulations of two-dimensional random motion. The multivalent gold probes had an average lateral diffusion coefficient (D) of 0.26 x 10(-8) cm2/sec, and paucivalent probes had an average D of 0.73 x 10(-8) cm2/sec. Sixteen percent of the multivalent and 50% of the paucivalent probes had values for D in excess of 0.6 x 10(-8) cm2/sec, which, after allowance for stochastic variation, are consistent with the D of 1.3 x 10(-8) cm2/sec measured by fluorescence recovery after photobleaching of Fl-PtdEtn in the planar bilayer. The effect of valency on diffusion suggests that the multivalent gold binds several lipids forming a disk up to 30-40 nm in diameter, resulting in reduced diffusion with respect to the paucivalent gold, which binds one or a very few lipids. Provided the valency of the gold probe is considered in the interpretation of the results. Nanovid microscopy is a valid method for analyzing the movements of single or small groups of molecules within membranes. Images PMID:1712486

Lee, G M; Ishihara, A; Jacobson, K A

1991-01-01

62

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

63

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

64

Direct observation of SU(N) orbital magnetism  

E-print Network

Symmetries play a fundamental role in the laws of nature. SU(N) symmetry can emerge in a quantum system with N single-particle spin states when the spin degree of freedom is decoupled from interactions. Such a system is anticipated to exhibit large degeneracy and exotic many-body behaviors. Owing to the strong decoupling between electronic-orbital and nuclear-spin degrees of freedom, alkaline-earth atoms (AEAs), prepared in the two lowest electronic states (clock states), are predicted to obey an accurate SU(N=2I+1) symmetry arising from the nuclear spin (I). So far, only indirect evidence for this symmetry exists, and the scattering parameters remain largely unknown. Here we report the first direct observation of SU(N=10) symmetry in 87Sr (I=9/2) using the state-of-the-art measurement precision offered by an ultra-stable laser. By encoding the electronic orbital degree of freedom in the two clock states, while keeping the system open to all 10 nuclear spin sublevels, we probe the non-equilibrium two-orbital ...

Zhang, X; Bromley, S L; Kraus, C V; Safronova, M S; Zoller, P; Rey, A M; Ye, J

2014-01-01

65

Minimally invasive knee arthroplasty with the subvastus approach allows rapid rehabilitation: a prospective, biomechanical and observational study.  

PubMed

[Purpose] To study the recovery of patients treated with minimally invasive total knee arthroplasty (TKA) performed via the subvastus approach, and to develop an optimal rehabilitation program for these patients. [Methods] Twenty-two patients (17 females and 5 males; mean age 69.2?years), who received unilateral minimally invasive TKA for osteoarthritis, underwent isometric and isokinetic muscle testing and completed a quality of life questionnaire, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), before and after surgery. Muscle strength and ultrasound tests were repeated 1, 2, 6, and 12 months after surgery. [Results] Strength and range of motion were initially lower in the operated knees but demonstrated no significant difference from the healthy knees after 12 months. Sonographically, joint effusion was greater in the osteoarthritic knees than in the healthy knees at baseline, but no significant difference was observed after 12 months. The mean WOMAC pain, stiffness and function scores all decreased from baseline to 6 months, and then slightly increased at 12 months, but only the function score showed a significant difference compared to baseline. [Conclusions] One year after minimally invasive TKA using a subvastus approach, patients had a good overall prognosis, with prompt functional recovery. PMID:24259801

Lin, Tsung-Ching; Wang, Hsing-Kuo; Chen, Jia-Wine; Chiu, Cheng-Ming; Chou, Hsiu-Ling; Chang, Chih-Hung

2013-05-01

66

Degassing-induced crystallization in basalts: direct experimental observations  

NASA Astrophysics Data System (ADS)

Degassing of magma increases its liquidus temperature and can thus trigger crystal growth. This can drastically increase magma viscosity and exert a key control on eruptive dynamics in a range of magma compositions. To investigate the process we have used a microscope and heated stage to obtain the first direct observations of degassing-driven crystal growth in natural basaltic melts at magmatic temperatures. We heated samples from Mt. Etna, Italy (0.39 wt.% H2O), and Kilauea, Hawaii (0.18 wt.% H2O) in air at atmospheric pressure to temperatures between 1190 and 1270 °C. Samples were held isothermally for 0.5 to 17 hours before cooling to sub-solidus temperatures. Bubble growth above 900 °C indicated volatile exsolution during heating. Isothermal conditions produced numerous new plagioclase crystals in the Etna sample, which grew to ?160 ?m at maximum rates of 5.2 x 10-6 to 1.8 x 10-5 cm s-1. The dwell temperature determined both crystal growth rates and morphologies (tabular to spherulitic). As equilibrium was approached after 20 minutes crystal growth slowed dramatically. Few new crystals appeared in the H2O-poor Kilauea sample, and maximum growth rates of 1.7 to 6.5 x 10-6 cm s-1 were determined. Pre-existing crystal textures strongly influenced crystal nucleation and growth during cooling, which highlights the importance of studying natural rather than experimental samples. Our results indicate that, when melts are sufficiently H2O-rich, degassing can indeed trigger rapid crystal growth. The resultant changes in the texture, and hence rheology, of erupting magma could exert important controls on eruption dynamics.

Applegarth, L. J.; Tuffen, H.; James, M. R.; Cashman, K.; Pinkerton, H.

2012-12-01

67

Observe how the Coriolis effect influences wind direction  

NSDL National Science Digital Library

This animated series of satellite images shows Earth science students how the Coriolis effect causes winds in the Northern Hemisphere to veer to the right of their predicted course. 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

Education, Terc. C.; Littell, Mcdougal

2003-01-01

68

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

69

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

70

Part 5: Concluding observations: New Directions for Understanding Systemic Risk  

Microsoft Academic Search

The Federal Reserve Bank of New York released a report -- New Directions for Understanding Systemic Risk -- that presents key findings from a cross-disciplinary conference that it cosponsored in May 2006 with the National Academy of Sciences' Board on Mathematical Sciences and Their Applications. ; The pace of financial innovation over the past decade has increased the complexity and

John Kambhu; Scott Weidman; Neel Krishnan

2007-01-01

71

Direct UV observations of the circumstellar envelope of alpha Orionis  

NASA Technical Reports Server (NTRS)

Observations were made in the IUE LWP camera, low dispersion mode, with alpha Ori being offset various distances from the center of the Long Wavelength Large Aperture along its major axis. Signal was acquired at all offset positions and is comprised of unequal components of background/dark counts, telescope-scattered light, and scattered light emanating from the extended circumstellar shell. The star is known from optical and infrared observations to possess an extended, arc-minute sized, shell of cool material. Attempts to observe this shell with the IUE are described, although the deconvolution of the stellar signal from the telescope scattered light requires further calibration effort.

Stencel, R. E.; Carpenter, K. G.; Pesce, J. E.; Skinner, S.; Brown, A.; Judge, P.

1988-01-01

72

Direct observation of defect structure in protein crystals by atomic force and transmission electron microscopy  

SciTech Connect

We have examined the structure of S-layers isolated from {ital Sulfolobus} {ital acidocaldarius} using atomic force microscopy (AFM) and transmission electron microscopy (TEM). From the AFM images, we were able to directly observe individual dimers of the crystal, defects in the crystal structure, and twin boundaries. We have identified two types of boundaries, one defined by a mirror plane and the other by a glide plane. This work shows that twin boundaries are highly structured regions that are directly related to the organization of units within each crystal domain. Projection maps from TEM images have shown that there are significant differences in the final average maps, depending on which side of the sample is adsorbed to the carbon support film. Comparison of AFM images to TEM projection maps has allowed us to relate high magnification views obtained by AFM to the relatively high resolution information obtained by electron microscopy and image processing.

Devaud, G. (Department of Physics, University of Colorado, Boulder, Colorado 80309 (United States)); Furcinitti, P.S. (Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado 80309 (United States)); Fleming, J.C.; Lyon, M.K.; Douglas, K. (Department of Physics, University of Colorado, Boulder, Colorado 80309 (United States))

1992-09-01

73

Imaging radar observations of directional properties of ocean waves  

Microsoft Academic Search

SEASAT-A synthetic aperture radar (SAR) and side-looking airborne radar (SLAR) images of ocean waves are examined in the form of normalized directional distributions of backscatter variance at series of frequencies. This method provides a more detailed description of radar results than have contoured two-dimensional wave number spectra and reduces some of the uncertainties in relating radar measurements to the waves.

William McLeish; Duncan B. Ross

1983-01-01

74

Observations of directional gamma prime coarsening during engine operation  

Microsoft Academic Search

Two alloys, NASAIR 100 and a modified NASAIR 100 called Alloy 3, were run as turbine blades in an experimental ground-based\\u000a Garrett TFE731 engine for up to 200 hours. The stress induced directional coarsening of ?? (rafting) that developed during\\u000a engine testing was analyzed and compared to previous research from laboratory tests. The blades were found to have formed\\u000a a

S. Draper; D. Hull; R. Dreshfield

1989-01-01

75

Direct Observation of the Dynamics of Jahn-Teller Fluctuations  

Microsoft Academic Search

(La\\/Sr)CoO3 serves as a prototype for studying lattice dynamic effects associated with Jahn-Teller type distortions prevalent in ABO3 perovskites. Earlier pair density function analysis of pulsed neutron diffraction data provided strong evidence for local lattice distortions associated with a Jahn-Teller active state (intermediate spin configuration), that is directly correlated to the change in the magnetic\\/conductive states of this system. Recent

Despina Louca

2001-01-01

76

DIRECT OBSERVATION OF A COROTATING INTERACTION REGION BY THREE SPACECRAFT  

SciTech Connect

White-light observations of interplanetary disturbances have been dominated by interplanetary coronal mass ejections (ICMEs). This is because the other type of disturbance, the corotating interaction region (CIR), has proved difficult to detect using white-light imagers. Recently, a number of papers have appeared presenting CIR observations using the Solar Terrestrial Relations Observatory (STEREO) Heliospheric Imagers (HIs), but have mostly only focused on a single spacecraft and imager. In this paper, we present observations of a single CIR that was observed by all three current white-light heliospheric imagers (SMEI and both STEREO HIs), as well as the in situ instruments on both STEREO satellites and ACE. We begin with a discussion of the geometry of the CIR structure, and show how the apparent leading edge structure is expected to change as it corotates relative to the observer. We use these calculations to predict elongation-time profiles for CIRs of different speeds for each of the imagers, and also to predict the arrival times at the in situ instruments. We show that although all three measured different parts, they combine to produce a self-consistent picture of the CIR. Finally, we offer some thoughts on why CIRs have proved so difficult to detect in white-light heliospheric images.

Tappin, S. J. [Air Force Research Laboratory, National Solar Observatory, Sunspot, NM 88349 (United States)], E-mail: jtappin@nso.edu; Howard, T. A

2009-09-10

77

Cryogenic Transmission Electron Microscopy for Direct Observation of Polymer and Small-Molecule Materials and Structures in Solution  

Microsoft Academic Search

The application of cryogenic transmission electron microscopy (cryo-TEM) in the study of molecular self-assembly of amphiphilic macromolecules, lipid\\/surfactants, peptides, and other hybrid material systems is quickly growing in popularity as a standard characterization technique. Cryo-TEM allows the direct visualization of nanostructures and microstructures embedded in a thin film of vitrified solvent at liquid nitrogen temperature. This direct observation technique provides

Sheng Zhong; Darrin J. Pochan

2010-01-01

78

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

79

Observations of directional gamma prime coarsening during engine operation  

NASA Technical Reports Server (NTRS)

Two alloys with negative mismatch parameters, NASAIR 100 and a modified NASAIR 100 called Alloy 3 were run as turbine blades in an experimental ground based Garret TFE731 engine for up to 200 hr. The directional coarsening of gamma prime (rafting) that developed during engine testing was analyzed and compared to previous research from laboratory tests. The blades were found to be rafted normal to the centrifugal stress axis over much of the span, but near the surfaces, the blades were found to be rafted parallel to the centrifugal stress axis for certain cycles. Representative photomicrographs of the blades and the effects of stress and temperature on raft formation are shown.

Draper, Susan L.; Hull, David R.; Dreshfield, Robert L.

1987-01-01

80

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

81

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

82

Direct observation of disulfide isomerization in a single protein  

NASA Astrophysics Data System (ADS)

Photochemical uncaging techniques use light to release active molecules from otherwise inert compounds. Here we expand this class of techniques by demonstrating the mechanical uncaging of a reactive species within a single protein. We proved this novel technique by capturing the regiospecific reaction between a thiol and a vicinal disulfide bond. We designed a protein that includes a caged cysteine and a buried disulfide. The mechanical unfolding of this protein in the presence of an external nucleophile frees the single reactive cysteine residue, which now can cleave the target disulfide via a nucleophilic attack on either one of its two sulfur atoms. This produces two different and competing reaction pathways. We used single-molecule force spectroscopy to monitor the cleavage of the disulfides, which extends the polypeptide by a magnitude unambiguously associated with each reaction pathway. This allowed us to measure, for the first time, the kinetics of disulfide-bond isomerization in a protein.

Alegre-Cebollada, Jorge; Kosuri, Pallav; Rivas-Pardo, Jaime Andrés; Fernández, Julio M.

2011-11-01

83

Direct Observation of a Self-Affine Crack Propagation  

SciTech Connect

We study experimentally the propagation of an in-plane crack through a transparent Plexiglas block. The toughness is controlled artificially and fluctuates spatially like uncorrelated random noise. The system is loaded by an imposed displacement and cracks in mode I at low speed (10{sup -7}{endash}5{times}10{sup -5} m/s). The crack front is observed optically with a microscope and a high resolution digital camera. During the propagation, the front is pinned and becomes rough. Roughness of the crack front is analyzed in terms of self-affinity. The roughness exponent is shown to be 0.55{plus_minus}0.05 in a static regime. No evolution of the roughness exponent is observed during the propagation even if the crack speed changes. {copyright} {ital 1997} {ital The American Physical Society}

Schmittbuhl, J. [Laboratoire de Geologie, URA 1316, Ecole Normale Superieure, 24 Rue Lhomond, 75231 Paris Cedex 05 (France)] [Laboratoire de Geologie, URA 1316, Ecole Normale Superieure, 24 Rue Lhomond, 75231 Paris Cedex 05 (France); Malo/y, K.J. [Fysisk Institutt, Universitetet i Oslo, P.O. Boks 1048 Blindern, N-0316 Oslo 3 (Norway)

1997-05-01

84

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

85

Direct Observation of a Self-Affine Crack Propagation  

Microsoft Academic Search

We study experimentally the propagation of an in-plane crack through a transparent Plexiglas block. The toughness is controlled artificially and fluctuates spatially like uncorrelated random noise. The system is loaded by an imposed displacement and cracks in mode I at low speed ( 10-7-5×10-5 m\\/s). The crack front is observed optically with a microscope and a high resolution digital camera.

Jean Schmittbuhl; Knut Jørgen Måløy

1997-01-01

86

Observations of directional gamma prime coarsening during engine operation  

NASA Technical Reports Server (NTRS)

Two alloys, NASAIR 100 and a modified NASAIR 100 called Alloy 3, were run as turbine blades in an experimental ground-based Garrett TFE731 engine for up to 200 hours. The stress induced directional coarsening of gamma-prime (rafting) that developed during engine testing was analyzed and compared to previous research from laboratory tests. The blades were found to have formed a lamellar structure, the lamellae being normal to the centrifugal stress axis over much of the span. However, near the surfaces, the blades were found to have formed lamellae parallel to the centrifugal stress axis for certain cycles. Representative photomicrographs of the blades and the effects of stress and temperature on lamellae formation are shown.

Draper, S.; Hull, D.; Dreshfield, R.

1989-01-01

87

Internal waves in the Aral Sea: the first direct observations  

NASA Astrophysics Data System (ADS)

At present time the Aral sea represents an ultrahaline basin (maximum of salinity is about 120 g/kg) characterized with sharp vertical stratification, which implies development of baroclinic processes. In October 2013 during the latest expedition of the Institute of Oceanology at Large Aral Sea observations aimed specifically at investigating the internal waves were conducted for the first time. The measurements were performed using 4 moored stations equipped with thermistor chains. Moored stations were located at the vertices of a rectangle with sides 10 and 13 km, so that 2 stations were situated at the western and 2 stations at the eastern shores of the basin. The stations were installed at a depth of 23-25 m. Recording was carried out continuously with sampling rate of 30 seconds during 6 days. During the observation, the position of thermocline was at a depth of 20-21 m, with a maximum depth of the sea 37 m. According to the wind conditions, all measurement period was divided into 3 parts. At first, the weather was calm, but after a few days there was a 1 day long intensification of the southwestern wind. Then there was a period of calm wind again. Both long-period and short-period internal waves were identified in the data record. In particular, we observed internal seiche oscillations with a period of 10-11 hours and vertical displacements of about 5 m. Short-period internal waves with periods from several minutes and heights of 1 m and less were also registered. After the period of strong wind, at one station periodically appearing and disappearing temperature inversions were observed. Temperature records of thermistors were analyzed in detail. Frequency and spatial spectral analysis of internal waves was performed. Dispersion curves for the real stratification of the Aral Sea were calculated and compared with the experimental data. This work was partly supported by the Ministry of science and education of the Russian Federation and Russian Foundation for Basic Research (project 13-05-01106).

Khymchenko, Ielizaveta; Serebryany, Andrey; Zavialov, Peter

2014-05-01

88

Direct observation of spiropyran phosphorescence in imidazolium ionic liquids  

NASA Astrophysics Data System (ADS)

Emission spectroscopy is used to investigate the photochromism of a spiropyran ester in imidazolium ionic liquids. While the spiropyran exhibits positive photochromism, the ring-opening reaction is slowed such that both fluorescence from the merocyanine form and phosphorescence from the spiro form are observed. These results illustrate the first example of spiropyran phosphorescence in ionic liquids and suggest that this system could be used to design a robust two-color emitting molecular device that depends on the state of the photochrome, where the state can be modulated by internal (the medium) and external (irradiation wavelength) factors.

Naughton, Sean P.; Gaudet, Robyn M.; Leslie, Anne A.; Keirstead, Amy E.

2013-01-01

89

Direct observation of ballistic Brownian motion on a single particle  

E-print Network

At fast timescales, the self-similarity of random Brownian motion is expected to break down and be replaced by ballistic motion. So far, an experimental verification of this prediction has been out of reach due to a lack of instrumentation fast and precise enough to capture this motion. With a newly developed detector, we have been able to observe the Brownian motion of a single particle in an optical trap with 75 MHz bandwidth and sub-{AA}ngstrom spatial precision. We report the first measurements of ballistic Brownian motion as well as the first determination of the velocity autocorrelation function of a Brownian particle. The data are in excellent agreement with theoretical predictions taking into account the inertia of the particle and the surrounding fluid as well as hydrodynamic memory effects.

Rongxin Huang; Branimir Lukic; Sylvia Jeney; Ernst-Ludwig Florin

2010-03-09

90

Methodological Issues in the Direct Observation of Parent–Child Interaction: Do Observational Findings Reflect the Natural Behavior of Participants?  

Microsoft Academic Search

This review examines evidence for the utility and validity of direct observational techniques for answering particular research and clinical questions. Observational techniques often involve recording behavior in settings that are relatively unnatural for families. However, it is argued that construct validity of observational methods depends partly on whether the findings are representative of participants' typical everyday behavior. Evidence is reviewed

Frances Gardner

2000-01-01

91

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

Menut, Laurent

92

Direct observation of long-lived isomers in $^{212}$Bi  

E-print Network

Long-lived isomers in 212Bi have been studied following 238U projectile fragmentation at 670 MeV per nucleon. The fragmentation products were injected as highly charged ions into the GSI storage ring, giving access to masses and half-lives. While the excitation energy of the first isomer of 212Bi was confirmed, the second isomer was observed at 1478(30) keV, in contrast to the previously accepted value of >1910 keV. It was also found to have an extended Lorentz-corrected in-ring halflife >30 min, 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 unrecognised, 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 de-excitation studies.

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

2013-06-03

93

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

94

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

95

Direct observations of pandanus-tool manufacture and use by a New Caledonian crow ( Corvus moneduloides )  

Microsoft Academic Search

New Caledonian crows are reported to have impressive pandanus-tool manufacture abilities. These claims are based on an extensive artefact record. However, inferring behavioural and cognitive abilities without direct observation of tool manufacture is problematic. Here we report (and document on video) direct observations of a crow making and using stepped pandanus tools at Pic Ningua. We observed (1) a bias

Gavin R. Hunt; Russell D. Gray

2004-01-01

96

DIRECT OBSERVATION OF THE COOLING OF THE CASSIOPEIA A NEUTRON STAR  

SciTech Connect

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 {approx}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{sigma}, from (2.12 {+-} 0.01) x 10{sup 6} K in 2000 to (2.04 {+-} 0.01) x 10{sup 6} 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. [Department of Physics, University of Alberta, Room 238 CEB, Edmonton, AB T6G 2G7 (Canada); Ho, Wynn C. G., E-mail: heinke@ualberta.c, E-mail: wynnho@slac.stanford.ed [School of Mathematics, University of Southampton, Southampton SO17 1BJ (United Kingdom)

2010-08-20

97

Direct observation of dangling bond motion in disordered silicon N. H. Nickel  

E-print Network

Direct observation of dangling bond motion in disordered silicon N. H. Nickel Hahn-Meitner-Institut and hydrogen-passivated polycrystalline silicon. This observation invalidates the identification largely control the electronic properties of disor- dered silicons--amorphous, polycrystalline

Schiff, Eric A.

98

Direct Observations of Coherent Backscatter of Radar Waves in Precipitation A. R. JAMESON  

E-print Network

Direct Observations of Coherent Backscatter of Radar Waves in Precipitation A. R. JAMESON RJH the authors now present direct observations of radar coherent backscattered signals in precipitation, hereafter JK10a) the presence of radar coherent signals backscattered by precipitation was inferred from

Kostinski, Alex

99

First direct observation of self-imaging effect in active multimode-interference semiconductor laser diodes  

Microsoft Academic Search

We report the first direct observation of the self-imaging effect in active multimode-interference semiconductor laser diodes (MMI-SLDs). Interference patterns inside laser diode waveguides were obtained by using the electroluminescence (EL) method. To the best of our knowledge, this result is the first direct observation of the self-imaging effect in self-photon-emitting active waveguides such as laser diodes. The observed EL pattern

Syogo Shimizu; Mohd Dannial Bin Razali; Kenichi Kasahara; Kiichi Hamamoto; Masaki Ohya

2006-01-01

100

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

101

Direct retrieval of ocean surface evaporation and latent heat flux from the spacebased observations  

NASA Technical Reports Server (NTRS)

The Tropical Rain Measuring Mission (TRMM) provides the opportunity to improve the spacebased estimation of evaporation. An algorithm for retrieving evaporation directly from the radiances observed by the TRMM Microwave Imager and its validation results are described.

Liu, W. T.; Tang, W.

2000-01-01

102

Direct observation of correlations between individual photon emission events of a microcavity laser.  

PubMed

Lasers are recognized for coherent light emission, the onset of which is reflected in a change in the photon statistics. For many years, attempts have been made to directly measure correlations in the individual photon emission events of semiconductor lasers. Previously, the temporal decay of these correlations below or at the lasing threshold was considerably faster than could be measured with the time resolution provided by the Hanbury Brown/Twiss measurement set-up used. Here we demonstrate a measurement technique using a streak camera that overcomes this limitation and provides a record of the arrival times of individual photons. This allows us to investigate the dynamical evolution of correlations between the individual photon emission events. We apply our studies to micropillar lasers with semiconductor quantum dots as the active material, operating in the regime of cavity quantum electrodynamics. For laser resonators with a low cavity quality factor, Q, a smooth transition from photon bunching to uncorrelated emission with increasing pumping is observed; for high-Q resonators, we see a non-monotonic dependence around the threshold where quantum light emission can occur. We identify regimes of dynamical anti-bunching of photons in agreement with the predictions of a microscopic theory that includes semiconductor-specific effects. PMID:19587766

Wiersig, J; Gies, C; Jahnke, F; Assmann, M; Berstermann, T; Bayer, M; Kistner, C; Reitzenstein, S; Schneider, C; Höfling, S; Forchel, A; Kruse, C; Kalden, J; Hommel, D

2009-07-01

103

Direct observation of blocked nanoscale surface evaporation on SiO2 nanodroplets  

NASA Astrophysics Data System (ADS)

Nano-scale surface evaporation of SiO2 nanodroplets from a volcano-shaped tip (tip diameter d ˜ 20 nm to 70 nm) was observed directly using an in situ transmission electron microscopy method. Au nanoparticles, those precipitated in the SiO2 matrix after an Au catalyzed growth, diffused and pinned onto the evaporation surface, which induced blocked evaporation dynamics. Our observations provide direct evidences of blocked evaporation dynamics caused by small-sized nanoparticles at the nanometer scale.

Wan, Neng; Xu, Jun; Sun, Li-Tao; Martini, Matteo; Huang, Qing-An; Hu, Xiao-Hui; Xu, Tao; Bi, Heng-Chang; Sun, Jun

2012-10-01

104

"It's important to provide direction with compassion and concern. At times I've found it difficult to allow those trainees to select paths of experimentation or career  

E-print Network

"It's important to provide direction with compassion and concern. At times I've found it difficult regularly with stu- dent in the lab. Dr. David Taylor, PhD Mentoring with Compassion division of research

105

Scheme for directly observing the non-commutativity of the position and the momentum operators with interference  

E-print Network

Although non-commutativity of a certain set of quantum operators (e.g., creation/annihilation operators and Pauli spin operators) has been shown experimentally in recent years, the commu- tation relation for the position and the momentum operators has not been directly demonstrated to date. In this paper, we propose and analyze an experimental scheme for directly observing the non-commutativity of the position and the momentum operators using single-photon quantum in- terference. While the scheme is studied for the single-photon state as the input quantum state, the analysis applies equally to matter-wave interference, allowing a direct test of the position-momentum commutation relation with a massive particle.

Jong-Chan Lee; Yong-Su Kim; Young-Sik Ra; Hyang-Tag Lim; Yoon-Ho Kim

2012-07-10

106

Generalizability of Classroom Behavior Problem and On-Task Scores from the Direct Observation Form  

ERIC Educational Resources Information Center

The present study used generalizability theory to investigate the dependability of systematic observations of students' problem behavior and on-task behavior in classrooms. The Direct Observation Form (McConaughy & Achenbach, 2009) was used with a sample of 24, 6- to-11-year-old children attending 18 different elementary schools. The participants…

Volpe, Robert J.; McConaughy, Stephanie H.; Hintze, John M.

2009-01-01

107

The direct observation of hindered rotation of a chemisorbed molecule: PF3 on Ni(111)  

Microsoft Academic Search

By using the bond direction imaging capabilities of the electron stimulated desorption ion angular distribution (ESDIAD) technique, we have observed a thermally induced azimuthal disorder effect due to the thermal population of unbound hindered rotor states in chemisorbed PF3 on Ni(111). The six beam F+ ESDIAD patterns observed for PF3 on Ni(111) are interpreted as evidence for a weak barrier

Mark D. Alvey; John T. Yates; Kevin J. Uram

1987-01-01

108

Direct Observation of Pinning and Bowing of a Single Ferroelectric Domain Wall  

Microsoft Academic Search

We have made a direct optical observation of pinning and bowing of a single 180° ferroelectric domain wall under a uniform applied electric field using a collection mode near-field scanning optical microscope. The domain wall is observed to curve between the pinning defects, with a radius of curvature determined by the material parameters and the applied electric field. The change

T. J. Yang; U. Mohideen; V. Gopalan; P. J. Swart

1999-01-01

109

Direct Observation of Pinning and Bowing of a Single Ferroelectric Domain Wall  

Microsoft Academic Search

We have made a direct optical observation of pinning and bowing of a single 180° ferroelectric domain wall under a uniform applied electric field using a collection mode near-field scanning optical microscope. The domain wall is observed to curve between the pinning defects, with a radius of curvature determined by the material parameters and the applied electric field. The change

T. J. Yang; Venkatraman Gopalan; P. J. Swart; U. Mohideen

1999-01-01

110

Direct observation of biting for studying grazing behavior of goats and llamas on garrigue rangelands  

Microsoft Academic Search

In any heterogeneous environment, classical methods used to estimate daily DMI and daily diets of grazing animals are difficult to implement. To investigate the grazing behavior of a goat and a llama, feeding on the garrigue in their respective flock, we therefore used a technique based on direct observation of biting. The observations were carried out in spring and early

B. Dumont; M. Meuret; M. Prud'hon

1995-01-01

111

Direct observation of cavitation fields at 23 and 515 kHz.  

PubMed

Direct observation of cavitation fields using photography, sonoluminescence and luminol "mapping" is reported for a 23 kHz horn sonicator and a 515 kHz plate transducer system. The effect of sound intensity and added surfactant on the cavitation fields is described. The observations support previously reported results suggesting significant differences in the cavitation fields between the two sonication systems. PMID:19464940

Price, Gareth J; Harris, Naomi K; Stewart, Alison J

2010-01-01

112

OBSERVATIONS OF BI-DIRECTIONAL FIELD ALIGNED ELECTRONS AND SOLITARY WAVES IN  

E-print Network

OBSERVATIONS OF BI-DIRECTIONAL FIELD ALIGNED ELECTRONS AND SOLITARY WAVES IN THE PLASMA SHEET M. O, observations of low frequency broadband electrostatic noise (BEN) in the plasma sheet [Scarf et al., 1974 solitary waves (ESW) [Matsumoto et al., 1994]. Simulations have suggested that these wave forms can

Fillingim, Matthew

113

Observations of nonlinear interactions in directionally spread shoaling surface gravity waves  

NASA Astrophysics Data System (ADS)

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-resonant, 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 transfers 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

114

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

115

The Stochastic Engine Initiative: Improving Prediction of Behavior in Geologic Environments We Cannot Directly Observe  

SciTech Connect

The stochastic engine uses modern computational capabilities to combine simulations with observations. We integrate the general knowledge represented by models with specific knowledge represented by data, using Bayesian inferencing and a highly efficient staged Metropolis-type search algorithm. From this, we obtain a probability distribution characterizing the likely configurations of the system consistent with existing data. The primary use will be optimizing knowledge about the configuration of a system for which sufficient direct observations cannot be made. Programmatic applications include underground systems ranging from environmental contamination to military bunkers, optimization of complex nonlinear systems, and timely decision-making for complex, hostile environments such as battlefields or the detection of secret facilities. We create a stochastic ''base representation'' of system configurations (states) from which the values of measurable parameters can be calculated using forward simulators. Comparison of these predictions to actual measurements drives embedded Bayesian inferencing, updating the distributions of states in the base representation using the Metropolis method. Unlike inversion methods that generate a single bestcase deterministic solution, this method produces all the likely solutions, weighted by their likelihoods. This flexible method is best applied to highly non-linear, multi-dimensional problems. Staging of the Metropolis searches permits us to run the simplest model systems, such as lithology estimators, at the lower stages. The majority of possible configurations are thus eliminated from further consideration by more complex simulators, such as flow and transport models. Because the method is fully automated, large data sets of a variety of types can be used to refine the system configurations. The most important prerequisites for optimal use of this method are well-characterized forward simulators, realistic base representations, and most importantly an ability to obtain disparate data sets that are directly affected by the system configuration. Our initial earth-sciences application uses models for lithology, flow and transport, geochemistry, and geophysical imaging; the system configuration (base representation) being refined is the rock type at each underground location. In the initial stages of this initiative we demonstrated a two-stage analysis of synthetic Electrical Resistance Tomography (ERT) data and hydraulic flow information (Newmark et al., 2002). We used these results to develop algorithms that improve efficiency of the Metropolis search and provide accurate diagnostic evaluation during the search. Using actual data from a highly contaminated A/M outfall and solvent tank storage areas at the Savannah River Site (SRS), we used the stochastic engine to resolve lithology using ERT data. SRS will use these methods in their design and implementation of steam cleanup of the largest trichloroethylene (TCE) source in the Department of Energy (DOE) complex. We have implemented ''soft conditioning'' algorithms that allow us to use a variety of data types to control the initial representations, and most importantly, to use the final distribution resulting from one stochastic engine analysis as the initial distribution for a subsequent analysis. We have created a web-based interface that will allow collaborators like SRS to enter data and observe results of calculations on Lawrence Livermore National Laboratory (LLNL) supercomputers in an interactive mode. All engine functions operate in three dimensions, and a parallel implementation on Linux cluster machines is in initial testing. The method will be extended to include active process analysis, in which an ongoing data stream is used to continuously update the understanding of the system configuration. Applications to other types of state spaces, such as chemical parameters in a reacting system or atmospheric plume movement, are being evaluated.

Aines, R; Nitao, J; Newmark, R; Carle, S; Ramirez, A; Harris, D; Johnson, J; Johnson, V; Ermak, D; Sugiyama, G; Hanley, W; Sengupta, S; Daily, W; Glaser, R; Dyer, K; Fogg, G; Zhang, Y; Yu, Z; Levine, R

2002-05-09

116

Direct observations of higher frequency density fluctuations in the interplanetary plasma  

NASA Technical Reports Server (NTRS)

Direct observations from the plasma spectrometers on Pioneer 6 at 1 AU in December, 1965, have been used to obtain the power associated with fluctuations in the number density of solar-wind protons in the frequency range from .001 to .01 Hz. A power-law spectrum is obtained in this frequency range. The extension of the power-law density spectrum based on direct observations to these higher frequencies is consistent with previous extrapolations of both spacecraft and interplanetary scintillation observations and with the dominance of large-scale turbulence in the solar wind. This result is also consistent with direct observations of the solar-wind proton speed and the interplanetary magnetic field.

Intriligator, D. S.

1975-01-01

117

Direct observation of the transition from indirect to direct bandgap in atomically thin epitaxial MoSe2.  

PubMed

Quantum systems in confined geometries are host to novel physical phenomena. Examples include quantum Hall systems in semiconductors and Dirac electrons in graphene. Interest in such systems has also been intensified by the recent discovery of a large enhancement in photoluminescence quantum efficiency and a potential route to valleytronics in atomically thin layers of transition metal dichalcogenides, MX2 (M = Mo, W; X = S, Se, Te), which are closely related to the indirect-to-direct bandgap transition in monolayers. Here, we report the first direct observation of the transition from indirect to direct bandgap in monolayer samples by using angle-resolved photoemission spectroscopy on high-quality thin films of MoSe2 with variable thickness, grown by molecular beam epitaxy. The band structure measured experimentally indicates a stronger tendency of monolayer MoSe2 towards a direct bandgap, as well as a larger gap size, than theoretically predicted. Moreover, our finding of a significant spin-splitting of ? 180 meV at the valence band maximum of a monolayer MoSe2 film could expand its possible application to spintronic devices. PMID:24362235

Zhang, Yi; Chang, Tay-Rong; Zhou, Bo; Cui, Yong-Tao; Yan, Hao; Liu, Zhongkai; Schmitt, Felix; Lee, James; Moore, Rob; Chen, Yulin; Lin, Hsin; Jeng, Horng-Tay; Mo, Sung-Kwan; Hussain, Zahid; Bansil, Arun; Shen, Zhi-Xun

2014-02-01

118

Boundary Layer Ozone Dynamics: Direct Observations over Arctic and Ocean Locations  

NASA Astrophysics Data System (ADS)

Influences of anthropogenic emissions from the northern hemisphere mid-latitudes can be seen in remote arctic and oceanic regions previously thought to be removed from the effects of pollution. Direct observations of surface layer ozone have been underrepresented above the hydrosphere and cryosphere. With oceans covering two thirds of the Earth's surface, the air-sea exchange plays an important role in the surface energy budget and in the transfer of ozone to the ocean surface. Recent developments of a fast response ozone instrument have allowed for ozone flux measurements over the open ocean. I investigated the quenching effect due to water vapor on the ozone instrument and quantified the corrections required for accurate measurements. A method for removing water vapor while leaving ozone unchanged was described. Mean water vapor concentrations were reduced by 77% and fast fluctuations of the water vapor signal were reduced by 97%. The transport of ozone over the open ocean was examined at island monitoring stations and from ship-board measurements. It has been speculated that ozone ocean uptake is determined by chemical enhancements. Currently, limited concurrent measurements of ozone flux and ocean surface chemistry have occurred. This work examined the use of satellite derived ocean surface chemistry measurements. In-situ and satellite derived measurements of chlorophyll agreed within 1 ?g l-1 when the wind speed was greater than 6 m s-1. The fast response ozone instrument was deployed during a two month long field campaign to study ozone depletion events in Barrow, Alaska. During the campaign, seven ozone depletion events (ODE) where the ozone would drop below 1.0 ppbv were observed. The longest ODE lasted over 72 hours with residual ozone varying between 0.1 to 0.8 ppbv. Ozone surface deposition rates were relatively low, ? 0.02-0.05 cm s-1 during most times. There was no clear evidence of ozone in interstitial air being influenced by photochemical processes. Concurrent atmospheric turbulence measurements from seven sonic anemometers showed general agreement except when winds were disturbed by the location of a nearby building. A composite boundary layer height was defined during the campaign, based on atmospheric turbulence measurements and validated against over 100 radiosonde observations. Sustained periods of boundary layer heights below 50 m were seen for several days. There was not a clear correlation between ozone depletion events and boundary layer height.

Boylan, Patrick Joseph

119

Objectively Optimized Observation Direction System Providing Situational Awareness for a Sensor Web  

NASA Astrophysics Data System (ADS)

There is great utility in having a flexible and automated objective observation direction system for the decadal survey missions and beyond. Such a system allows us to optimize the observations made by suite of sensors to address specific goals from long term monitoring to rapid response. We have developed such a prototype using a network of communicating software elements to control a heterogeneous network of sensor systems, which can have multiple modes and flexible viewing geometries. Our system makes sensor systems intelligent and situationally aware. Together they form a sensor web of multiple sensors working together and capable of automated target selection, i.e. the sensors “know” where they are, what they are able to observe, what targets and with what priorities they should observe. This system is implemented in three components. The first component is a Sensor Web simulator. The Sensor Web simulator describes the capabilities and locations of each sensor as a function of time, whether they are orbital, sub-orbital, or ground based. The simulator has been implemented using AGIs Satellite Tool Kit (STK). STK makes it easy to analyze and visualize optimal solutions for complex space scenarios, and perform complex analysis of land, sea, air, space assets, and shares results in one integrated solution. The second component is target scheduler that was implemented with STK Scheduler. STK Scheduler is powered by a scheduling engine that finds better solutions in a shorter amount of time than traditional heuristic algorithms. The global search algorithm within this engine is based on neural network technology that is capable of finding solutions to larger and more complex problems and maximizing the value of limited resources. The third component is a modeling and data assimilation system. It provides situational awareness by supplying the time evolution of uncertainty and information content metrics that are used to tell us what we need to observe and the priority we should give to the observations. A prototype of this component was implemented with AutoChem. AutoChem is NASA release software constituting an automatic code generation, symbolic differentiator, analysis, documentation, and web site creation tool for atmospheric chemical modeling and data assimilation. Its model is explicit and uses an adaptive time-step, error monitoring time integration scheme for stiff systems of equations. AutoChem was the first model to ever have the facility to perform 4D-Var data assimilation and Kalman filter. The project developed a control system with three main accomplishments. First, fully multivariate observational and theoretical information with associated uncertainties was combined using a full Kalman filter data assimilation system. Second, an optimal distribution of the computations and of data queries was achieved by utilizing high performance computers/load balancing and a set of automatically mirrored databases. Third, inter-instrument bias correction was performed using machine learning. The PI for this project was Dr. David Lary of the UMBC Joint Center for Earth Systems Technology at NASA/Goddard Space Flight Center.

Aulov, O.; Lary, D. J.

2010-12-01

120

Observation of coherent anti-Stokes Raman scattering in the phase-mismatched direction  

NASA Astrophysics Data System (ADS)

We have experimentally demonstrated coherent anti-Stokes Raman scattering in both forward and backward directions from thin samples of dipicolinic acid crystalline. The signal observed in the backscattered, phased-mismatched direction is 3 orders of magnitude stronger than would be expected without scattering from the crystal's inhomogeneities. We present a theoretical explanation of these results, based on the theory of random diffraction gratings and discuss possible applications.

Hanna, Sherif F.; Wang, Lei; Sariyanni, Zoe-Elizabeth; Kalugin, Nikolai G.; Lucht, Robert P.; Sautenkov, Vladimir A.; Sokolov, Alexei V.; Rostovtsev, Yuri; Scully, Marlan O.

2005-09-01

121

Unimolecular thermal decomposition of phenol and d5-phenol: Direct observation of cyclopentadiene formation via cyclohexadienone  

NASA Astrophysics Data System (ADS)

The pyrolyses of phenol and d5-phenol (C6H5OH and C6D5OH) have been studied using a high temperature, microtubular (?tubular) SiC reactor. Product detection is via both photon ionization (10.487 eV) time-of-flight mass spectrometry and matrix isolation infrared spectroscopy. Gas exiting the heated reactor (375 K-1575 K) is subject to a free expansion after a residence time in the ?tubular reactor of approximately 50-100 ?s. The expansion from the reactor into vacuum rapidly cools the gas mixture and allows the detection of radicals and other highly reactive intermediates. We find that the initial decomposition steps at the onset of phenol pyrolysis are enol/keto tautomerization to form cyclohexadienone followed by decarbonylation to produce cyclopentadiene; C6H5OH --> c-C6H6 = O --> c-C5H6 + CO. The cyclopentadiene loses a H atom to generate the cyclopentadienyl radical which further decomposes to acetylene and propargyl radical; c-C5H6 --> c-C5H5 + H --> HC?CH + HCCCH2. At higher temperatures, hydrogen loss from the PhO-H group to form phenoxy radical followed by CO ejection to generate the cyclopentadienyl radical likely contributes to the product distribution; C6H5O-H --> C6H5O + H --> c-C5H5 + CO. The direct decarbonylation reaction remains an important channel in the thermal decomposition mechanisms of the dihydroxybenzenes. Both catechol (o-HO-C6H4-OH) and hydroquinone (p-HO-C6H4-OH) are shown to undergo decarbonylation at the onset of pyrolysis to form hydroxycyclopentadiene. In the case of catechol, we observe that water loss is also an important decomposition channel at the onset of pyrolysis.

Scheer, Adam M.; Mukarakate, Calvin; Robichaud, David J.; Nimlos, Mark R.; Carstensen, Hans-Heinrich; Barney Ellison, G.

2012-01-01

122

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

123

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

PubMed Central

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. PMID:23185095

Hayashi, Shohei; Fujita, Yuji; Kamikura, Takahiro; Sakaike, Kohei; Akazawa, Muneki; Ikeda, Mitsuhisa; Hanafusa, Hiroaki; Higashi, Seiichiro

2012-01-01

124

Estimating nonlinear mixing effects for arid vegetation scenes with MISR channels and observation directions  

SciTech Connect

A Monte-Carlo ray-trace model has been applied to simulated sparse vegetation desert canopies in an effort to quantify the spectral mixing (both linear and nonlinear) occurring as a result of radiative interactions between vegetation and soil. This work is of interest as NASA is preparing to launch new instruments such as MISR and MODIS. MISR will observe each ground pixel from nine different directions in three visible channels and one near-infrared channel. It is desired to study angular variations in spectral mixing by quantifying the amount of nonlinear spectral mixing occurring in the MISR observing directions.

Villeneuve, P.V.; Gerstl, S.A. [Los Alamos National Lab., NM (United States); Asner, G.P. [Univ. of Colorado, Boulder, CO (United States)

1998-12-01

125

Directional Variation of 5 GeV Muon Flux Observed in the Underground Muon Telescope  

Microsoft Academic Search

The small muon telescope is placed in the underground lab oratory. The muon energy threshold is about 5 GeV which corresp onds to primary CR energies above 15 GeV (maximal contribution at 100 GeV). We have observed a number of Forbush Decrease events which made a 1-2 percent fall in observed counting rate. The telescope has 2 degrees directional accuracy.

J. Szabelski; Michael Alania; Karol Jedrzejczak; Karczmarczyk; Jozef Swarzyuski; Barbara Szabelska; Tadeusz Wibig

2003-01-01

126

Direct satellite observations on bremsstrahlung radiation as a technique to investigate its role in meteorological processes  

NASA Technical Reports Server (NTRS)

Satellite observations on bremsstrahlung produced in the atmosphere by precipitating energetic electrons are reported. This type of observation affords the possibility of directly monitoring the bremsstrahlung energy input to the lower atmosphere over large segments of the earth and at frequent intervals. From comparison of the ion production rates from cosmic rays with those calculated for bremsstrahlung from precipitating energetic electrons, it is concluded that bremsstrahlung is a negligible contributor to the ionization near the 300-mb level.

Johnson, R. G.; Imhof, W. L.

1974-01-01

127

Direct observation of Coulomb interactions in highly conducting [2,5-dimethyl-dicyanoquinonediimine]2Ag  

NASA Astrophysics Data System (ADS)

Valence-band photoelectron spectroscopy and scanning-tunneling microscopy demonstrate the significance of Coulomb interactions for the semiconducting state of single crystalline [2,5-dimethyl-dicyanoquinonediimine]2Ag. Direct evidence for the electron-electron interactions is deduced from the spectroscopic observation of a pseudogap in the density of states near the Fermi energy and from the dimerization in real space observed by tunneling microscopy.

Schmeisser, D.; Göpel, W.; Fuchs, H.; Graf, K.; Erk, P.

1993-08-01

128

Observations of nonlinear effects in directional spectra of shoaling gravity waves  

NASA Astrophysics Data System (ADS)

The spatial evolution of a directionally spread wave field on a near-planar natural beach is examined using data from longshore arrays of pressure sensors and wave staffs at 10.3 m and 4.1 m depth. High-resolution frequency-directional spectra from the deeper array are used to initialize a linear refraction model, and the resulting model predictions are compared with frequency-directional measurements at the shallow array. Linear theory inaccurately predicts both the shapes of directional spectra in shallow water and the total variances in some frequency bands. The discrepancies are largest for frequencies associated with maxima in the bicoherence spectrum, suggesting the importance of nonlinear effects. Furthermore, the measured directional spectrum at energetic low frequencies (0.05-0.11 Hz) and the vector resonance conditions for triads of long waves can be used to predict accurately the directions of observed peaks in directional spectra at higher frequencies (0.12-0.21 Hz). Prominent features in the measured directional spectra at the shallow array are thus consistent with energy transfers resulting from near-resonant triad interactions in the shoaling wave field.

Freilich, M. H.; Guza, R. T.; Elgar, S. L.

1990-06-01

129

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. Microsc. Res. Tech. 77:754-772, 2014. © 2014 Wiley Periodicals, Inc. 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

130

A Method to Remove Differences in Frequency Response Between Commercial Hearing Aids to Allow Direct Comparison of the Sound Quality of Hearing-Aid Features  

PubMed Central

Goal: We want to remove differences in frequency response between different commercial hearing aids so that we can compare the sound quality of signal processing features from different hearing-aid in a future paired-comparison set-up. More specifically, we want to control for the confounding effects of the linear hearing aid response when evaluating nonlinear processing. This article presents a control procedure and evaluates its effectiveness. Method: We increased the similarity of hearing-aid recordings in three steps and used both an objective quality metric and listening tests to investigate if the recordings from different hearing aids were perceptually similar. Results: Neither was it sufficient to manually adjust the hearing-aid insertion gain, nor was it sufficient to add an additional bandwidth limitation to the recordings. Only after the application of an inverse filter the perceptual differences between recordings were removed adequately. Conclusion: It was possible to level the ground between different hearing devices, so to speak. This will allow future research to evaluate the sound quality of nonlinear signal processing features. PMID:22068224

Brons, Inge; Dreschler, Wouter A.

2011-01-01

131

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

132

Affective Evaluations of Objects Are Influenced by Observed Gaze Direction and Emotional Expression  

ERIC Educational Resources Information Center

Gaze direction signals another person's focus of interest. Facial expressions convey information about their mental state. Appropriate responses to these signals should reflect their combined influence, yet current evidence suggests that gaze-cueing effects for objects near an observed face are not modulated by its emotional expression. Here, we…

Bayliss, Andrew P.; Frischen, Alexandra; Fenske, Mark J.; Tipper, Steven P.

2007-01-01

133

Direct observation of biofouling in cross-flow microfiltration: mechanisms of deposition and release  

Microsoft Academic Search

A laboratory-scale membrane filtration cell was constructed to enable direct microscopic observation of microbial cell deposition and release in cross-flow microfiltration. Initial deposition rates determined from microscopic images were interpreted through an interaction force model. Experimentally derived deposition rates and model calculations confirmed that initial cell and particle deposition was governed by permeation drag and electrostatic double layer forces. Microbial

Seok-Tae Kang; Arun Subramani; Eric M. V. Hoek; Marc A. Deshusses; Mark R. Matsumoto

2004-01-01

134

Journal of Membrane Science xxx (2004) xxxxxx Direct observation of biofouling in cross-flow microfiltration  

E-print Network

Journal of Membrane Science xxx (2004) xxx­xxx Direct observation of biofouling in cross; Fouling; Water treatment; Particle deposition; Biofouling 1. Introduction Microbial cells attach firmly to as biofouling. Bio- fouling is a major problem in environmental membrane sep- arations because it leads

135

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

E-print Network

at the cathode/organic interface and expand or grow as a result of exposure to atmosphere. We propose a mechanism-based devices is associated with changes at the cathode/Alq3 interface. In their study, they operatedDirect observation of structural changes in organic light emitting devices during degradation

136

Direct Observation of Broadband Coating Thermal Noise in a Suspended Interferometer  

E-print Network

We have directly observed broadband thermal noise in silica/tantala coatings in a high-sensitivity Fabry-Perot interferometer. Our result agrees well with the prediction based on indirect, ring-down measurements of coating mechanical loss, validating that method as a tool for the development of advanced interferometric gravitational-wave detectors.

Eric D. Black; Akira Villar; Kyle Barbary; Adam Bushmaker; Jay Heefner; Seiji Kawamura; Fumiko Kawazoe; Luca Matone; Sharon Meidt; Shanti R. Rao; Kevin Schulz; Michael Zhang; Kenneth G. Libbrecht

2004-01-09

137

Three-Item Direct Observation Screen (TIDOS) for Autism Spectrum Disorder  

ERIC Educational Resources Information Center

We compared ratings on the Three-Item Direct Observation Screen test for autism spectrum disorders completed by pediatric residents with the Social Communication Questionnaire parent reports as an augmentative tool for improving autism spectrum disorder screening performance. We examined three groups of children (18-60 months) comparable in age…

Oner, Pinar; Oner, Ozgur; Munir, Kerim

2014-01-01

138

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

139

Directly Observed Interaction within Adolescent Romantic Relationships: What Have We Learned?  

ERIC Educational Resources Information Center

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…

Welsh, Deborah P.; Shulman, Shmuel

2008-01-01

140

UV Plasmonic Structures: Direct Observations of UV Extraordinary Optical Transmission and Localized Field Enhancement Through Nanoslits  

Microsoft Academic Search

The ultraviolet (UV) extraordinary optical transmission through nanoslit structures in the far field and the localized field enhancement in the near field are directly observed and compared with each other. Numerical modeling results are also presented, and the distribution properties of the UV Surface Plasmon polaritons (SPPs) are analyzed, showing agreement with the experiment results. These phenomena may enrich the

Qiaoqiang Gan; Liangcheng Zhou; Volkmar Dierolf; Filbert J. Bartoli

2009-01-01

141

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

142

Single-Molecule Magnets on Gold Direct Observation of Single-Molecule Magnets  

E-print Network

,2] In the last decade, it was discovered that single molecules can, in principle, be used to store magneticSingle-Molecule Magnets on Gold Direct Observation of Single-Molecule Magnets Organized on Gold, and Herre S. J. Van der Zant An aim of molecular electronics is to use single (or a few) molecules as active

143

Direct observation of ballistic Brownian motion on a single particle Rongxin Huang,1  

E-print Network

1 Direct observation of ballistic Brownian motion on a single particle Rongxin Huang,1 Branimir and be replaced by ballistic motion. So far, an experimental verification of this prediction has been out of reach with 75 MHz bandwidth and sub-Ã?ngstrom spatial precision. We report the first measurements of ballistic

Texas at Austin. University of

144

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.

145

Direct Observation of Multiferroic Vortex Domains in YMnO3  

E-print Network

Direct Observation of Multiferroic Vortex Domains in YMnO3 Qinghua Zhang1 , Guotai Tan2 , Lin Gu1 of multiferroic vortex domains in YMnO3 at atomic scale using state-of-the-art aberration-corrected scanning of topological behaviors and unusual properties of the multiferroic vortex. T opological defects are widespread

Wang, Wei Hua

146

A Review of Direct Observation Research within the Past Decade in the Field of Emotional and Behavioral Disorders  

ERIC Educational Resources Information Center

This study reviewed prominent journals within the field of emotional and behavioral disorders to identify direct observation approaches, reported reliability statistics, and key features of direct observation. Selected journals were systematically reviewed for the past 10 years identifying and quantifying specific direct observation systems and…

Adamson, Reesha M.; Wachsmuth, Sean T.

2014-01-01

147

Direct observation of quasi-coherent thermal emission by a three-dimensional metallic photonic crystal.  

PubMed

We report a direct observation of a quasi-coherent thermal emission from a heated three-dimensional photonic-crystal sample. While the sample was under Joule heating, we observed multiple oscillations in its emission interferogram and deduced a coherent length of L(coh)?(20-40) ?m, 5-10 times longer than that of a blackbody at comparable wavelengths. The observed, relatively long coherent length is attributed to coupling of thermal emission into lossy Bloch modes that oscillate coherently over a distance determined by decay length and the slow light nature of Bloch modes at the band-edges. PMID:23503257

Hsieh, Mei-Li; Bur, James; Kim, Yong-Sung; Lin, Shawn-Yu

2013-03-15

148

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

PubMed

The difference-of-Gaussians (DOG) filter is a widely used model for the receptive field of neurons in the retina and lateral geniculate nucleus (LGN) 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 bandpass (optimal response at a nonzero 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 two-dimensional parameter space, the exact region corresponding to bandpass 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 bandpass region. Altogether, the DOG filter and its three standard implicit parameters can be determined by three directly observable values. The two-dimensional bandpass region is a potential tool for the analysis of populations of DOG filters (for example, populations of neurons in the retina or LGN), 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

2013-05-01

149

A direct observation the asteroid's structure from deep interior to regolith: why and how do it?  

NASA Astrophysics Data System (ADS)

The internal structure of asteroids is still poorly known and has never been measured directly. Our knowledge is relying entirely on inferences from remote sensing observations of the surface, and theoretical modeling. Is the body a monolithic piece of rock or a rubble-pile, an aggregate of boulders held together by gravity and how much porosity it contains, both in the form of micro-scale or macro-scale porosity? What is the typical size of the constituent blocs? Are these blocs homogeneous or heterogeneous? Is the body a defunct or dormant comet and such MBC can become active? The body is covered by a regolith from whose properties remains largely unknown in term of depth, size distribution and spatial variation. Is resulting from fine particles re-accretion or from thermal fracturing? What are its coherent forces? How to model is thermal conductivity while this parameter is so important to estimate Yarkowsky and Yorp effects? Knowing asteroid deep interior and regolith structure is a key point for a better understanding of the asteroid accretion and dynamical evolution. There is no way to determine this from ground-based observation. Radar operating from a spacecraft is the only technique capable of achieving this science objective of characterizing the internal structure and heterogeneity from submetric to global scale for the science benefit as well as for the planetary defence and human exploration. The deep interior structure tomography requires low-frequency radar to penetrate throughout the complete body. The radar wave propagation delay and the received power are related to the complex dielectric permittivity (i.e to the composition and microporosity) and the small scale heterogeneities (scattering losses) while the spatial variation of the signal and the multiple paths provide information on the presence of heterogeneities (variations in composition or porosity), layers, ice lens. A partial coverage will provide "cuts" of the body when a dense coverage will allow a complete tomography. Two instruments concepts can be envisaged: A monostatic radar like Marsis/Mars Express (ESA) that will analyze radar waves transmitted by the orbiter and received after reflection by the asteroid, its surface and its internal structures. A bistatic radar like Consert/Rosetta (ESA that will analyze radar waves transmitted by a lander, propagated through the body and received by the orbiter. Imaging the first ~50 meters of the subsurface with a decimetric resolution to identify layering and to reconnect surface measurement to internal structure requires a higher frequency radar on Orbiter only, like Wisdom developed for ExoMars Rover (ESA) with a frequency ranging from 300 MHz up to 2.7 GHz. This paper reviews the science benefit of direct measurement of asteroid interior. Then radar concepts for both deep interior and near surface sounding and their science return are shown.

Herique, A.; Kofman, W. W.

2013-12-01

150

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

151

Unimolecular Thermal Decomposition of Phenol and d5-Phenol: Direct Observation of Cyclopentadiene Formation via Cyclohexadienone  

SciTech Connect

The pyrolyses of phenol and d{sub 5}-phenol (C{sub 6}H{sub 5}OH and C{sub 6}D{sub 5}OH) have been studied using a high temperature, microtubular ({mu}tubular) SiC reactor. Product detection is via both photon ionization (10.487 eV) time-of-flight mass spectrometry and matrix isolation infrared spectroscopy. Gas exiting the heated reactor (375 K-1575 K) is subject to a free expansion after a residence time in the {mu}tubular reactor of approximately 50-100 {micro}s. The expansion from the reactor into vacuum rapidly cools the gas mixture and allows the detection of radicals and other highly reactive intermediates. We find that the initial decomposition steps at the onset of phenol pyrolysis are enol/keto tautomerization to form cyclohexadienone followed by decarbonylation to produce cyclopentadiene; C{sub 6}H{sub 5}OH {yields} c-C{sub 6}H{sub 6} = O {yields} c-C{sub 5}H{sub 6} + CO. The cyclopentadiene loses a H atom to generate the cyclopentadienyl radical which further decomposes to acetylene and propargyl radical; c-C{sub 5}H{sub 6} {yields} c-C{sub 5}H{sub 5} + H {yields} HC {triple_bond} CH + HCCCH{sub 2}. At higher temperatures, hydrogen loss from the PhO-H group to form phenoxy radical followed by CO ejection to generate the cyclopentadienyl radical likely contributes to the product distribution; C{sub 6}H{sub 5}O-H {yields} C{sub 6}H{sub 5}O + H {yields} c-C{sub 5}H{sub 5} + CO. The direct decarbonylation reaction remains an important channel in the thermal decomposition mechanisms of the dihydroxybenzenes. Both catechol (o-HO-C{sub 6}H{sub 4}-OH) and hydroquinone (p-HO-C{sub 6}H{sub 4}-OH) are shown to undergo decarbonylation at the onset of pyrolysis to form hydroxycyclopentadiene. In the case of catechol, we observe that water loss is also an important decomposition channel at the onset of pyrolysis.

Scheer, A. M.; Mukarakate, C.; Robichaud, D. J.; Nimlos, M. R.; Carstensen, H. H.; Barney, E. G.

2012-01-28

152

Direct observation of sn adatoms dynamical fluctuations at the Sn/Ge(111) surface.  

PubMed

The well-known low-temperature phase transition sqrt[3]xsqrt[3] to 3x3 for the 1/3 monolayer of Sn adatoms on the Ge(111) surface has been studied by scanning tunneling microscopy. The STM tip was used as a probe to record the tunneling current as a function of time on top of the Sn adatoms. The presence of steps on the current-time curves allowed the detection of fluctuating Sn atoms along the direction vertical to the substrate. We discuss the effect of temperature and surface defects on the frequency of the motion, finding consistency with the dynamical fluctuations model. PMID:16241741

Ronci, Fabio; Colonna, Stefano; Thorpe, Stephen D; Cricenti, Antonio; Le Lay, Guy

2005-10-01

153

Direct observation of shear deformation during equal channel angular pressing of pure aluminum  

SciTech Connect

Equal Channel Angular (ECA) pressing is a method through which intense plastic strain can be introduced into materials by simple shear. It is suggested that during ECA pressing, only simple shear deformation is introduced into the specimen. The degree of shear deformation can be well predicted by theory and is assumed to be uniform across the specimen except the top and end part. The theory had been proved to be correct by observation of ECA pressing of plasticine with a transparent plexiglass tool and by finite element modeling. However, direct observation of shear deformation had not yet been conducted in metallic materials. One difficulty in observing the shear deformation is that marks or scratches on the surface of the specimen will be erased or destroyed by severe surface deformation caused by friction. In this research, a special method is employed to eliminate the surface friction effect so that a clear shear deformation figure can be observed.

Shan, A. [Shanghai Jiao Tong Univ. (China)] [Shanghai Jiao Tong Univ. (China); Moon, I.G.; Ko, H.S.; Park, J.W. [Korean Inst. of Science and Technology, Seoul (Korea, Republic of). Div. of Metals] [Korean Inst. of Science and Technology, Seoul (Korea, Republic of). Div. of Metals

1999-07-23

154

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

155

Microbunching Instability in Relativistic Electron Bunches: Direct Observations of the Microstructures Using Ultrafast YBCO Detectors  

NASA Astrophysics Data System (ADS)

Relativistic electron bunches circulating in accelerators are subjected to a dynamical instability leading to microstructures at millimeter to centimeter scale. Although this is a well-known fact, direct experimental observations of the structures, or the field that they emit, remained up to now an open problem. Here, we report the direct, shot-by-shot, time-resolved recording of the shapes (including envelope and carrier) of the pulses of coherent synchrotron radiation that are emitted, and that are a "signature" of the electron bunch microstructure. The experiments are performed on the UVSOR-III storage ring, using electrical field sensitive YBa2Cu3O7-x thin-film ultrafast detectors. The observed patterns are subjected to permanent drifts, that can be explained from a reasoning in phase space, using macroparticle simulations.

Roussel, E.; Evain, C.; Szwaj, C.; Bielawski, S.; Raasch, J.; Thoma, P.; Scheuring, A.; Hofherr, M.; Ilin, K.; Wünsch, S.; Siegel, M.; Hosaka, M.; Yamamoto, N.; Takashima, Y.; Zen, H.; Konomi, T.; Adachi, M.; Kimura, S.; Katoh, M.

2014-08-01

156

Direct observation of amplified spontaneous emission of surface plasmon polaritons at metal/dielectric interfaces  

NASA Astrophysics Data System (ADS)

We report on direct observation of amplified spontaneous emission (ASE) of surface plasmon polaritons (SPPs) at the interface of a silver film and a gain medium. Based on a typical Kretschmann configuration incorporated with Rhodamine 6G molecules, the growing ASE spectra of SPPs have been clearly identified by carefully conducting a pump-dependent angle-resolved spectral measurement. Spectral narrowing effects induced by the SPP amplification are also demonstrated. The observed phenomena are helpful in understanding the fundamental interactions between SPPs and gain medium, which could enable wide applications on plasmonic sources and sensors.

Chen, Yu-Hui; Li, Jiafang; Ren, Ming-Liang; Wang, Ben-Li; Fu, Jin-Xin; Liu, Si-Yun; Li, Zhi-Yuan

2011-06-01

157

Direct Observation of Pinning and Bowing of a Single Ferroelectric Domain Wall  

SciTech Connect

We have made a direct optical observation of pinning and bowing of a single 180{degree} ferroelectric domain wall under a uniform applied electric field using a collection mode near-field scanning optical microscope. The domain wall is observed to curve between the pinning defects, with a radius of curvature determined by the material parameters and the applied electric field. The change in birefringence with applied field is used to infer the orientation of the internal field at the domain wall. {copyright} {ital 1999} {ital The American Physical Society}

Yang, T.J.; Mohideen, U. [Department of Physics, University of California, Riverside, California 92521 (United States)] [Department of Physics, University of California, Riverside, California 92521 (United States); Gopalan, V. [Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)] [Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Swart, P.J. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

1999-05-01

158

Earth Science System of the Future: Observing, Processing, and Delivering Data Products Directly to Users  

NASA Technical Reports Server (NTRS)

Advancement of our predictive capabilities will require new scientific knowledge, improvement of our modeling capabilities, and new observation strategies to generate the complex data sets needed by coupled modeling networks. New observation strategies must support remote sensing from a variety of vantage points and will include "sensorwebs" of small satellites in low Earth orbit, large aperture sensors in Geostationary orbits, and sentinel satellites at L1 and L2 to provide day/night views of the entire globe. Onboard data processing and high speed computing and communications will enable near real-time tailoring and delivery of information products (i.e., predictions) directly to users.

Crisp, David; Komar, George (Technical Monitor)

2001-01-01

159

Direct observation of depth-dependent atomic displacements associated with dislocations in gallium nitride.  

PubMed

We demonstrate that the aberration-corrected scanning transmission electron microscope has a sufficiently small depth of field to observe depth-dependent atomic displacements in a crystal. The depth-dependent displacements associated with the Eshelby twist of dislocations in GaN normal to the foil with a screw component of the Burgers vector are directly imaged. We show that these displacements are observed as a rotation of the lattice between images taken in a focal series. From the sense of the rotation, the sign of the screw component can be determined. PMID:25302902

Lozano, J G; Yang, H; Guerrero-Lebrero, M P; D'Alfonso, A J; Yasuhara, A; Okunishi, E; Zhang, S; Humphreys, C J; Allen, L J; Galindo, P L; Hirsch, P B; Nellist, P D

2014-09-26

160

Direct Observation of Depth-Dependent Atomic Displacements Associated with Dislocations in Gallium Nitride  

NASA Astrophysics Data System (ADS)

We demonstrate that the aberration-corrected scanning transmission electron microscope has a sufficiently small depth of field to observe depth-dependent atomic displacements in a crystal. The depth-dependent displacements associated with the Eshelby twist of dislocations in GaN normal to the foil with a screw component of the Burgers vector are directly imaged. We show that these displacements are observed as a rotation of the lattice between images taken in a focal series. From the sense of the rotation, the sign of the screw component can be determined.

Lozano, J. G.; Yang, H.; Guerrero-Lebrero, M. P.; D'Alfonso, A. J.; Yasuhara, A.; Okunishi, E.; Zhang, S.; Humphreys, C. J.; Allen, L. J.; Galindo, P. L.; Hirsch, P. B.; Nellist, P. D.

2014-09-01

161

Three-dimensional atomic force microscopy: interaction force vector by direct observation of tip trajectory.  

PubMed

The prospect of a robust three-dimensional atomic force microscope (AFM) holds significant promise in nanoscience. Yet, in conventional AFM, the tip-sample interaction force vector is not directly accessible. We scatter a focused laser directly off an AFM tip apex to rapidly and precisely measure the tapping tip trajectory in three-dimensional space. This data also yields three-dimensional cantilever spring constants, effective masses, and hence, the tip-sample interaction force components via Newton's second law. Significant lateral forces representing 49 and 13% of the normal force (Fz = 152 ± 17 pN) were observed in common tapping mode conditions as a silicon tip intermittently contacted a glass substrate in aqueous solution; as a consequence, the direction of the force vector tilted considerably more than expected. When addressing the surface of a lipid bilayer, the behavior of the force components differed significantly from that observed on glass. This is attributed to the lateral mobility of the lipid membrane coupled with its elastic properties. Direct access to interaction components Fx, Fy, and Fz provides a more complete view of tip dynamics that underlie force microscope operation and can form the foundation of a three-dimensional AFM in a plurality of conditions. PMID:24099456

Sigdel, Krishna P; Grayer, Justin S; King, Gavin M

2013-11-13

162

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

163

Influence of Parenting Factors on Childhood Social Anxiety: Direct Observation of Parental Warmth and Control  

Microsoft Academic Search

The purpose of the present study is to determine the association of parenting behaviors and social anxiety in children. Three parental factors—including parental socialization, control, and warmth—were investigated in a sample of 31 two-parent families. Rather than solely relying upon retrospective questionnaires, this study incorporated direct observation and a Daily Activity Log to assess the qualities of social interaction. Moderate

Kristine E. Rork; Tracy L. Morris

2009-01-01

164

Attitudes to directly observed antiretroviral treatment in a workplace HIV care programme in South Africa  

Microsoft Academic Search

Objective: To investigate attitudes to directly observed antiretroviral therapy (DOT ART) among HIV infected adults attending a workplace HIV care programme in South Africa.Methods: Clients attending workplace HIV clinics in two regions were interviewed using a semi-structured questionnaire.Results: 100 individuals (99% male, mean age 40.2 years) participated, 61% were already taking ART by self administration. 71% had previous tuberculosis (TB)

Liesl S Page-Shipp; Salome Charalambous; Surita Roux; Belinda Dias; Clement Sefuti; Gavin J Churchyard; Alison D Grant

2007-01-01

165

Object-Recognition with oblique observation directions Based on Biomimetic Pattern Recognition  

Microsoft Academic Search

In this paper, we propose a new scheme for omnidirectional object-recognition in free space. The proposed scheme divides above problem into several omnidirectional object-recognition with different depression angles. An omnidirectional object-recognition system with oblique observation directions based on a new recognition theory-biomimetic pattern recognition (BPR) is discussed in detail. Based on it, we can get the size of training samples

Wang Shoujue; Chen Xu; Li Weijun

2005-01-01

166

Direct Observation of Ferroelectric Domains in LiTaO3 Using Environmental Scanning Electron Microscopy  

Microsoft Academic Search

Direct observation of ferroelectric domain structures in LiTaO3 crystal, without etching or surface coating, has been realized by using environmental scanning electron microscopy in secondary electron emission mode. The new method can nondestructively provide domain contrast image at submicron resolution, and the domain contrast image is very stable. Conditions for best domain contrast of LiTaO3 crystals have been established.

Shining Zhu; Wenwu Cao

1997-01-01

167

Direct Observation of Charge Transfer in Double-Perovskite-Like RbMn[Fe(CN)6  

Microsoft Academic Search

The charge density distribution has been determined for a transition metal cyanide, RbMn[Fe(CN)6], by means of the maximum entropy Rietveld method combined with the highly angularly resolved synchrotron radiation x-ray powder diffraction at SPring-8 BL02B2. We directly observed a charge transfer from the Mn site to the Fe site in the low-temperature phase. On the basis of a local density

K. Kato; Y. Moritomo; M. Takata; M. Sakata; M. Umekawa; N. Hamada; S. Ohkoshi; H. Tokoro; K. Hashimoto

2003-01-01

168

Direct observation of intracluster reactions induced in (CF3I) n clusters by femtosecond ultraviolet radiation  

NASA Astrophysics Data System (ADS)

Intracluster reactions that are induced in (CF3I) n clusters by femtosecond ultraviolet radiation, including the reaction of the formation of the I{2/+} molecular ion, have been directly observed. It has been shown that there are two channels of the formation of I{2/+} ions with the characteristic times ?1 ? 1 ps and ?2 ? 7 ps. A model of these reactions has been proposed that is in good agreement with the experimental data.

Apatin, V. M.; Kompanets, V. O.; Lokhman, V. N.; Ogurok, N.-D. D.; Poydashev, D. G.; Ryabov, E. A.; Chekalin, S. V.

2011-12-01

169

RECYCLING PROGRAM TYPE LOCATION ALLOWED NOT ALLOWED  

E-print Network

RECYCLING PROGRAM TYPE LOCATION ALLOWED NOT ALLOWED Batteries, toner, ink cartridges & cell phones and recycling is an important part of that effort. Below is a guide to on-campus recycling at RSMAS: Visit http://www.rsmas.miami.edu/msgso/ for map of recycling bin locations. NOTE: This is not an exhaustive list. If unauthorized items are found

Miami, University of

170

Does prey size matter? Novel observations of feeding in the leatherback turtle (Dermochelys coriacea) allow a test of predator-prey size relationships.  

PubMed

Optimal foraging models predict that large predators should concentrate on large prey in order to maximize their net gain of energy intake. Here, we show that the largest species of sea turtle, Dermochelys coriacea, does not strictly adhere to this general pattern. Field observations combined with a theoretical model suggest that a 300 kg leatherback turtle would meet its energetic requirements by feeding for 3-4 h a day on 4 g jellyfish, but only if prey were aggregated in high-density patches. Therefore, prey abundance rather than prey size may, in some cases, be the overriding parameter for foraging leatherbacks. This is a classic example where the presence of small prey in the diet of a large marine predator may reflect profitable foraging decisions if the relatively low energy intake per small individual prey is offset by high encounter rates and minimal capture and handling costs. This study provides, to our knowledge, the first quantitative estimates of intake rate for this species. PMID:22090203

Fossette, Sabrina; Gleiss, Adrian C; Casey, James P; Lewis, Andrew R; Hays, Graeme C

2012-06-23

171

Accuracy and reliability of direct observations of home-packed lunches in elementary schools by trained nutrition students.  

PubMed

Increased attention has been directed toward the school food environment because children consume important contributions toward their daily food intake while at school. In Canada, most elementary school students bring a lunch to school and there are minimal data on the composition and consumption of these lunches. Dietary assessment of home-packed lunches is challenging compared with assessment of standardized school meals due to greater diversity of items, nonstandard portions, and opaque containers. We assessed accuracy and reliability of a food observation method whereby upper-year nutrition students (n=15) were trained to assess packed lunch contents and intake in elementary schools. Accuracy and reliability was assessed during 2010-2011 in three observational phases: sample lunches, volunteer-consumed lunches, and elementary school students' lunches (n=32). Observers accurately identified 96% and 95% of items in the sample and volunteer lunches, respectively. Similarly, they accurately reported portion sizes for 86% and 94% of the items in the sample and volunteer lunches, thus showing improvements in successive phases. Interobserver reliability for amount consumed, by portion size and macronutrient content, ranged from 0.79 to 0.88 in the volunteer-consumed lunches and 0.78 to 0.86 in the students' lunches, with a majority ?0.80. It is noteworthy that the analyses for the amount consumed were conducted as absolute amounts with no allowances for discrepancies, which differs from other interobserver reliability assessments where as much as 25% discrepancy is considered agreement. Observers with prior nutrition knowledge assessed packed lunch contents and intake accurately and reliably by direct observation in an elementary school setting. PMID:23017569

Richter, Shannon L; Vandervet, Laura M; Macaskill, Lesley A; Salvadori, Marina I; Seabrook, Jamie A; Dworatzek, Paula D N

2012-10-01

172

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

173

Direct observation of syringeal muscle function in songbirds and a parrot.  

PubMed

The role of syringeal muscles in controlling the aperture of the avian vocal organ, the syrinx, was evaluated directly for the first time by observing and filming through an endoscope while electrically stimulating different muscle groups of anaesthetised birds. In songbirds (brown thrashers, Toxostoma rufum, and cardinals, Cardinalis cardinalis), direct observations of the biomechanical effects of contraction largely confirm the functions of the intrinsic syringeal muscles proposed from indirect studies. Contraction of the dorsal muscles, m. syringealis dorsalis (dS) and m. tracheobronchialis dorsalis, constricts the syringeal lumen and thus reduces airflow by adducting connective tissue masses, the medial (ML) and lateral (LL) labia. Activity of the medial portion of the dS appears to affect the position of the ML and, consequently, plays a previously undescribed role in aperture control. Under the experimental conditions used in this study, full constriction of the syringeal lumen could not be achieved by stimulating adductor muscles. Full closure may require simultaneous activation of extrinsic syringeal muscles or the supine positioning of the bird may have exerted excessive tension on the syrinx. Contraction of m. tracheobronchialis ventralis enlarges the syringeal lumen and thus increases airflow by abducting the LL but does not affect the ML. The largest syringeal muscle, m. syringealis ventralis, plays a minor role, if any, in direct aperture control and thus in gating airflow. In parrots (cockatiels, Nymphicus hollandicus), direct observations show that even during quiet respiration the lateral tympaniform membranes (LTMs) are partially adducted into the tracheal lumen to form a narrow slot. Contraction of the superficial intrinsic muscle, m. syringealis superficialis, adducts the LTMs further into the tracheal lumen but does not close the syringeal aperture fully. The intrinsic deep muscle, m. syringealis profundus, abducts the LTMs through cranio-lateral movement of a paired, protruding half-ring. The weakly developed extrinsic m. sternotrachealis seems to increase tension in the ipsilateral LTM but does not move it in or out of the syringeal lumen. PMID:11818409

Larsen, Ole Naesbye; Goller, Franz

2002-01-01

174

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

175

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

176

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

177

Direct Observation of a Nonheme Iron(IV)-Oxo Complex That Mediates Aromatic C-F Hydroxylation.  

PubMed

The synthesis of a pentadentate ligand with strategically designed fluorinated arene groups in the second coordination sphere of a nonheme iron center is reported. The oxidatively resistant fluorine substituents allow for the trapping and characterization of an Fe(IV)(O) complex at -20 °C. Upon warming of the Fe(IV)(O) complex, an unprecedented arene C-F hydroxylation reaction occurs. Computational studies support the finding that substrate orientation is a critical factor in the observed reactivity. This work not only gives rare direct evidence for the participation of an Fe(IV)(O) species in arene hydroxylation but also provides the first example of a high-valent iron-oxo complex that mediates aromatic C-F hydroxylation. PMID:25246108

Sahu, Sumit; Quesne, Matthew G; Davies, Casey G; Dürr, Maximilian; Ivanovi?-Burmazovi?, Ivana; Siegler, Maxime A; Jameson, Guy N L; de Visser, Sam P; Goldberg, David P

2014-10-01

178

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

PubMed Central

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. PMID:24850566

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

2014-01-01

179

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

180

Direct observation of microtubule pushing by cortical dynein in living cells  

PubMed Central

Microtubules are under the influence of forces mediated by cytoplasmic dynein motors associated with the cell cortex. If such microtubules are free to move, they are rapidly transported inside cells. Here we directly observe fluorescent protein–labeled cortical dynein speckles and motile microtubules. We find that several dynein complex subunits, including the heavy chain, the intermediate chain, and the associated dynactin subunit Dctn1 (also known as p150glued) form spatially resolved, dynamic speckles at the cell cortex, which are preferentially associated with microtubules. Measurements of bleaching and dissociation kinetics at the cell cortex reveal that these speckles often contain multiple labeled dynein heavy-chain molecules and turn over rapidly within seconds. The dynamic behavior of microtubules, such as directional movement, bending, or rotation, is influenced by association with dynein speckles, suggesting a direct physical and functional interaction. Our results support a model in which rapid turnover of cell cortex–associated dynein complexes facilitates their search to efficiently capture and push microtubules directionally with leading plus ends. PMID:24173713

Mazel, Tomas; Biesemann, Anja; Krejczy, Magda; Nowald, Janos; Muller, Olga; Dehmelt, Leif

2014-01-01

181

Orbit evolution of disk-embedded masses: Directly observed in Saturn's rings  

NASA Astrophysics Data System (ADS)

Disk-embedded masses are thought to exist and evolve in many astrophysical contexts, including protoplanetary and protosatellite disks, stellar debris disks, and galaxies. The only known "ground truth" for these theorized objects is found in Saturn's rings. The "propeller" moons within Saturn's rings are the first objects ever to have their orbits tracked while embedded in a disk, rather than moving through empty space (Tiscareno etal. 2010, ApJL). The embedded masses are not seen directly; rather, their locations are inferred by means of the propeller-shaped disturbances they create in the surrounding ring material (Tiscareno etal. 2006, Nature). Their observed orbits are primarily Keplerian, but with clear excursions in longitude on the order of +-0.15 degrees longitude for the largest and best-studied example, and +-several degrees longitude for others. Most theories that have been proposed to explain the non-Keplerian motion of propeller moons rely on gravitational and/or collisional interactions between the moon and the surrounding disk, and thus hold out the prospect for directly observing processes that are important in other astrophysical disk systems. The different models make different predictions, and future data will likely distinguish among them. The Cassini spacecraft, currently orbiting Saturn, is monitoring the propeller moons whenever possible. We will report the latest results of that observing campaign.

Tiscareno, Matthew S.; Moran, A. E.

2014-01-01

182

Investigations on the mechanism of superlubricity achieved with phosphoric acid solution by direct observation  

NASA Astrophysics Data System (ADS)

In this work, the contact region between a Si3N4 ball and a SiO2 plate with the lubrication of phosphoric acid solution is observed directly by an optical microscope combined with a Raman microscope to understand the superlubricity mechanism. It is found that the wear on the friction surfaces mainly occurs at the beginning of the test and nearly disappears after the friction coefficient reduces to 0.05. When the superlubricity appears (? = 0.004), there is only a limited amount of solution available to the contact (forming starvation state), resulting in an "H" distribution surrounding the contact region. Moreover, it is observed that the hydrogen bond effect in the solution is enhanced with time going by, and finally a thin film with hydrogen bond network among H3PO4, H2PO4-, and H2O is formed on the friction surfaces, leading to the superlubricity. By employing this direct observation approach, the structure of the confined solution and the superlubricity mechanism of phosphoric acid solution are finally investigated and discussed.

Li, Jinjin; Ma, Liran; Zhang, Shaohua; Zhang, Chenhui; Liu, Yuhong; Luo, Jianbin

2013-09-01

183

Directional trends in thermospheric neutral winds observed at Arecibo during the past three solar cycles  

NASA Astrophysics Data System (ADS)

Since 1980, we have observed the thermospheric neutral wind at the Arecibo Observatory using a Fabry-Perot interferometer to measure the O(1D) 630 nm emission. Burnside and Tepley (1989) examined the first 8 years of this extended data set and found that there were no significant or systematic solar cycle influences on the magnitude or direction of the neutral wind field, nor on its horizontal gradients. Such affects have been observed previously at other locations around the globe, and their absence at Arecibo may have been due to the limited data set. Thus, we have extended the period of acquisition and analysis of our neutral wind measurements to include nearly three complete solar cycles (or approximately 30 years) and will present our results within the framework of the earlier work. While the earlier conclusion that no major systematic solar cycle influence on the neutral winds at Arecibo generally remains intact, we did find a slight increase in wind magnitude and a gradual, yet consistent rotation of the thermospheric neutral wind vector from a general southeast to a more eastward flow during 30 years of observation. We explain the magnitude and directional variations in terms of long-term changes in the density and temperature of the upper atmosphere and their possible dissimilar influences on each wind component that appear as a rotation of the neutral wind vector.

Tepley, C. A.; Robles, E.; García, R.; Santos, P. T.; Brum, C. M.; Burnside, R. G.

2011-06-01

184

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

PubMed

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

185

Direct observation of chemical reactions on single gold nanocrystals using surface plasmon spectroscopy.  

PubMed

Heterogeneous catalysts have been pivotal to the development of the modern chemical industry and are essential for catalysing many industrial reactions. However, reaction rates are different for every individual catalyst particle and depend upon each particle's morphology and size, crystal structure and composition. Measuring the rates of reaction on single nanocrystals will enable the role of catalyst structure to be quantified. Here, using surface plasmon spectroscopy, we have directly observed the kinetics of atomic deposition onto a single gold nanocrystal and also monitored electron injection and extraction during a redox reaction involving the oxidation of ascorbic acid on a gold nanocrystal surface. These results constitute the first direct measurement of the rates of redox catalysis on single nanocrystals. PMID:18838998

Novo, Carolina; Funston, Alison M; Mulvaney, Paul

2008-10-01

186

First direct observation of two protons in the decay of $^{45}$Fe with a TPC  

E-print Network

The decay of the ground-state two-proton emitter 45Fe was studied with a time-projection chamber and the emission of two protons was unambiguously identified. The total decay energy and the half-life measured in this work agree with the results from previous experiments. The present result constitutes the first direct observation of the individual protons in the two-proton decay of a long-lived ground-state emitter. In parallel, we identified for the first time directly two-proton emission from 43Cr, a known beta-delayed two-proton emitter. The technique developped in the present work opens the way to a detailed study of the mechanism of ground-state as well as beta-delayed two-proton radioactivity.

J. Giovinazzo; B. Blank; C. Borcea; G. Canchel; C. E. Demonchy; F. de Oliveira Santos; C. Dossat; S. Grevy; L. Hay; J. Huikari; S. Leblanc; I. Matea; J. -L. Pedroza; L. Perrot; J. Pibernat; L. Serani; C. Stodel; J. -C. Thomas

2007-03-05

187

Direct Observation of Coherent Oscillations in Solution due to Microheterogeneous Environment  

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

188

Airborne hyperspectral observations of surface and cloud directional reflectivity using a commercial digital camera  

NASA Astrophysics Data System (ADS)

Spectral radiance measurements by a digital single-lens reflex camera were used to derive the directional reflectivity of clouds and different surfaces in the Arctic. The camera has been calibrated radiometrically and spectrally to provide accurate radiance measurements with high angular resolution. A comparison with spectral radiance measurements with the Spectral Modular Airborne Radiation measurement sysTem (SMART-Albedometer) showed an agreement within the uncertainties of both instruments (6% for both). The directional reflectivity in terms of the hemispherical directional reflectance factor (HDRF) was obtained for sea ice, ice-free ocean and clouds. The sea ice, with an albedo of ? = 0.96 (at 530 nm wavelength), showed an almost isotropic HDRF, while sun glint was observed for the ocean HDRF (? = 0.12). For the cloud observations with ? = 0.62, the cloudbow - a backscatter feature typically for scattering by liquid water droplets - was covered by the camera. For measurements above heterogeneous stratocumulus clouds, the required number of images to obtain a mean HDRF that clearly exhibits the cloudbow has been estimated at about 50 images (10 min flight time). A representation of the HDRF as a function of the scattering angle only reduces the image number to about 10 (2 min flight time). The measured cloud and ocean HDRF have been compared to radiative transfer simulations. The ocean HDRF simulated with the observed surface wind speed of 9 m s-1 agreed best with the measurements. For the cloud HDRF, the best agreement was obtained by a broad and weak cloudbow simulated with a cloud droplet effective radius of Reff = 4 ?m. This value agrees with the particle sizes derived from in situ measurements and retrieved from the spectral radiance of the SMART-Albedometer.

Ehrlich, A.; Bierwirth, E.; Wendisch, M.; Herber, A.; Gayet, J.-F.

2012-04-01

189

Implementing a directly observed therapy program in an urban community hospital.  

PubMed

St. Clare's Health and Hospital Center has implemented a directly observed therapy (DOT) program for a challenging urban population of largely HIV+ patients in response to a need for the prevention of the spread of multidrug-resistant tuberculosis in the population. Identified treatment barriers are needs of patient subgroups within the population. Issues in the implementation include: patient compliance, effectiveness of patient identification and follow-up, and continuity of care. Challenges to continuity of care include patients signing out of the hospital against medical advice and missed clinic appointments. Patient identification and follow-up is enhanced by coordinating DOT treatment with the methadone maintenance treatment program. PMID:10186639

Sharp, V; Bray, D; Carey, J

1995-01-01

190

Hydrogen Atoms under Magnification: Direct Observation of the Nodal Structure of Stark States  

NASA Astrophysics Data System (ADS)

To describe the microscopic properties of matter, quantum mechanics uses wave functions, whose structure and time dependence is governed by the Schrödinger equation. In atoms the charge distributions described by the wave function are rarely observed. The hydrogen atom is unique, since it only has one electron and, in a dc electric field, the Stark Hamiltonian is exactly separable in terms of parabolic coordinates (?, ?, ?). As a result, the microscopic wave function along the ? coordinate that exists in the vicinity of the atom, and the projection of the continuum wave function measured at a macroscopic distance, share the same nodal structure. In this Letter, we report photoionization microscopy experiments where this nodal structure is directly observed. The experiments provide a validation of theoretical predictions that have been made over the last three decades.

Stodolna, A. S.; Rouzée, A.; Lépine, F.; Cohen, S.; Robicheaux, F.; Gijsbertsen, A.; Jungmann, J. H.; Bordas, C.; Vrakking, M. J. J.

2013-05-01

191

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

192

Direct Observation of Two Protons in the Decay of {sup 54}Zn  

SciTech Connect

The two protons emitted in the decay of {sup 54}Zn have been individually observed for the first time in a time projection chamber. The total decay energy and the half-life measured in this work agree with the results obtained in a previous experiment. Angular and energy correlations between the two protons are determined and compared to theoretical distributions of a three-body model. Within the shell model framework, the relative decay probabilities show a strong contribution of the p{sup 2} configuration for the two-proton emission. After {sup 45}Fe, the present result on {sup 54}Zn constitutes only the second case of a direct observation of the ground state two-proton decay of a long-lived isotope.

Ascher, P.; Audirac, L.; Blank, B.; Delalee, F.; Demonchy, C. E.; Giovinazzo, J.; Grevy, S.; Kurtukian-Nieto, T.; Leblanc, S.; Pedroza, J.-L.; Pibernat, J.; Serani, L. [Centre d'Etudes Nucleaires de Bordeaux Gradignan--Universite Bordeaux 1--UMR 5797 CNRS/IN2P3, Chemin du Solarium, BP 120, 33175 Gradignan (France); Adimi, N. [Centre d'Etudes Nucleaires de Bordeaux Gradignan--Universite Bordeaux 1--UMR 5797 CNRS/IN2P3, Chemin du Solarium, BP 120, 33175 Gradignan (France); Faculte de Physique, USTHB, B.P.32, El Alia, 16111 Bab Ezzouar, Alger (Algeria); Borcea, C.; Companis, I. [National Institute for Physics and Nuclear Engineering, P.O. Box MG6, Bucharest-Margurele (Romania); Brown, B. A. [Department of Physics and Astronomy, and National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824-1321 (United States); Oliveira Santos, F. de; Perrot, L.; Thomas, J.-C. [Grand Accelerateur National d'Ions Lourds, CEA/DSM-CNRS/IN2P3, 14076 Caen Cedex 05 (France); Grigorenko, L. V. [Flerov Laboratory of Nuclear Reactions, JINR, Dubna 141980 (Russian Federation)

2011-09-02

193

Aerosol characterization in Northern Africa, Northeastern Atlantic, Mediterranean Basin and Middle East from direct-sun AERONET observations  

NASA Astrophysics Data System (ADS)

We provide an atmospheric aerosol characterization for North Africa, Northeastern Atlantic, Mediterranean and Middle East based on the analysis of quality-assured direct-sun observations of 39 stations of the AErosol RObotic NETwork (AERONET) which include at least an annual cycle within the 1994-2007 period. We extensively test and apply the recently introduced graphical method of Gobbi and co-authors in order to track and discriminate different aerosol types and quantify the contribution of mineral dust. The method relies on the combined analysis of the Ångstrøm exponent (?) and its spectral curvature. Plotting data in these coordinates allows to infer aerosol fine mode size (Rf) and fractional contribution (?) to total Aerosol Optical Depth (AOD) and separate AOD growth due to fine-mode aerosol humidification and/or coagulation from AOD growth due to the increase in coarse particles or cloud contamination. Our results confirm the robustness of this graphical method. Large mineral dust is the most important constituent in Northern Africa and Middle East; and under specific meteorological conditions, its transport to Europe is observed from spring to autumn. Small pollution particles are abundant in sites close to urban and industrial areas of Continental and Eastern Europe and Middle East; as well as, important contributions of biomass burning are observed in the sub-Sahel region in winter. Dust is usually found to mix with these fine, pollution aerosols.

Basart, S.; Pérez, C.; Cuevas, E.; Baldasano, J. M.; Gobbi, G. P.

2009-03-01

194

A multimethod investigation including direct observation of 3751 patient visits to 120 dental offices  

PubMed Central

This report defines verbal interactions between practitioners and patients as core activities of dental practice. Trained teams spent four days in 120 Ohio dental practices observing 3751 patient encounters with dentists and hygienists. Direct observation of practice characteristics, procedures performed, and how procedure and nonprocedure time was utilized during patient visits was recorded using a modified Davis Observation Code that classified patient contact time into 24 behavioral categories. Dentist, hygienist, and patient characteristics were gathered by questionnaire. The most common nonprocedure behaviors observed for dentists were chatting, evaluation feedback, history taking, and answering patient questions. Hygienists added preventive counseling. We distinguish between preventive procedures and counseling in actual dental offices that are members of a practice-based research network. Almost a third of the dentist’s and half of the hygienist’s patient contact time is utilized for nonprocedure behaviors during patient encounters. These interactions may be linked to patient and practitioner satisfaction and effectiveness of self-care instruction. PMID:23662080

Wotman, Stephen; Demko, Catherine A; Victoroff, Kristin; Sudano, Joseph J; Lalumandier, James A

2010-01-01

195

Direct observation of multiple misfolding pathways in a single prion protein molecule  

PubMed Central

Protein misfolding is a ubiquitous phenomenon associated with a wide range of diseases. Single-molecule approaches offer a powerful tool for deciphering the mechanisms of misfolding by measuring the conformational fluctuations of a protein with high sensitivity. We applied single-molecule force spectroscopy to observe directly the misfolding of the prion protein PrP, a protein notable for having an infectious misfolded state that is able to propagate by recruiting natively folded PrP. By measuring folding trajectories of single PrP molecules held under tension in a high-resolution optical trap, we found that the native folding pathway involves only two states, without evidence for partially folded intermediates that have been proposed to mediate misfolding. Instead, frequent but fleeting transitions were observed into off-pathway intermediates. Three different misfolding pathways were detected, all starting from the unfolded state. Remarkably, the misfolding rate was even higher than the rate for native folding. A mutant PrP with higher aggregation propensity showed increased occupancy of some of the misfolded states, suggesting these states may act as intermediates during aggregation. These measurements of individual misfolding trajectories demonstrate the power of single-molecule approaches for characterizing misfolding directly by mapping out nonnative folding pathways. PMID:22421432

Yu, Hao; Liu, Xia; Neupane, Krishna; Gupta, Amar Nath; Brigley, Angela M.; Solanki, Allison; Sosova, Iveta; Woodside, Michael T.

2012-01-01

196

Direct observation of bosonic quantum interference of surface plasmon polaritons using photon-number-resolving detectors  

NASA Astrophysics Data System (ADS)

Quantum plasmonics is a field of research combining plasmonics with quantum optics and investigates interactions between photons and metallic nanostructures. So far, it has been proven that quantum properties of single photons to excite single surface plasmon polaritons (SPPs) are preserved in the process of photon-SPP-photon mode conversion in plasmonic nanostructures, which suggests the potential application of SPPs to the quantum information processing (QIP). Recently the Hong-Ou-Mandel (HOM) interference of single SPPs was observed in a plasmonic circuitry. However, the visibility was below the classical limit (50%) due to the simultaneous excitation of distinguishable SPP modes. We employed a directional coupler based on long-range surface-plasmon-polariton waveguides (LRSPP-DC) and superconducting photon-number-resolving detectors to directly observe the bosonic quantum interference of single SPPs beyond the classical limit. In addition, we demonstrated the indistinguishability of photons that excite single SPPs is well preserved in the process of photon-SPP mode conversion.

Fujii, Go; Fukuda, Daiji; Inoue, Shuichiro

2014-08-01

197

The Exozodiacal Dust Problem for Direct Observations of ExoEarths  

NASA Technical Reports Server (NTRS)

Debris dust in the habitable zones of stars otherwise known as exozodiacal dust comes from extrasolar asteroids and comets and is thus an expected part of a planetary system. Background flux from the Solar Systems zodiacal dust and the exozodiacal dust in the target system is likely to be the largest source of astrophysical noise in direct observations of terrestrial planets in the habitable zones of nearby stars. Furthermore, dust structures like clumps, thought to be produced by dynamical interactions with exoplanets, are a possible source of confusion. In this paper, we qualitatively assess the primary impact of exozodical dust on high-contrast direct imaging at optical wavelengths, such as would be performed with a coronagraph. Then we present the sensitivity of previous, current, and near-term facilities to thermal emission from debris dust at all distances from nearby solar-type stars, as well as our current knowledge of dust levels from recent surveys. Finally, we address the other method of detecting debris dust, through high-contrast imaging in scattered light. This method is currently far less sensitive than thermal emission observations, but provides high spatial resolution for studying dust structures. This paper represents the first report of NASA's Exoplanet Exploration Program Analysis Group (ExoPAG).

Roberge, Aki; Chen, Christine H.; Millan-Gabet, Rafael; Weinberger, Alycia J.; Hinz, Philip M.; Stapelfeldt, Karl R.; Absil, Olivier; Kuchner, Marc J.; Bryden, Geoffrey

2012-01-01

198

Direct observation of pentacene-thiol interaction using x-ray spectroscopy  

NASA Astrophysics Data System (ADS)

There has been an intense interest in the surface modification of the source-drain electrodes for organic field effect transistors (OFETs) to improve their performance. A number of thiol based self assembled monolayers demonstrated improvements to the contact resistance and channel performance. Morphological improvements at the contacts, a change in the effective work function, and charge transfer between the thiols and the semiconductor have all been credited with the observed performance improvements. Using in-situ semiconductor deposition together with x-ray photoelectron spectroscopy and near-edge x-ray absorption fine structure, we are able to directly probe two technologically relevant OFET stacks. This work directly measures the interaction between pentacene and two thiols which have been associated to contact improvement: an electroneutral thiol (1-hexadecanethiol) and an electronegative thiol (pentafluorobenzenethiol). Based on our results we observe no chemical interaction between pentacene and the thiol. The electrical improvements to transistor performance, based on these systems, can be attributed to work function shifts of the contacts and morphological improvements of the organic semiconductor.

Jia, Zhang; Lee, Vincent; Floreano, Luca; Verdini, Alberto; Cossaro, Albano; Morgante, Alberto; Kymissis, Ioannis

2010-03-01

199

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

200

Direct observation of Anderson localization of matter waves in a controlled disorder.  

PubMed

In 1958, Anderson predicted the localization of electronic wavefunctions in disordered crystals and the resulting absence of diffusion. It is now recognized that Anderson localization is ubiquitous in wave physics because it originates from the interference between multiple scattering paths. Experimentally, localization has been reported for light waves, microwaves, sound waves and electron gases. However, there has been no direct observation of exponential spatial localization of matter waves of any type. Here we observe exponential localization of a Bose-Einstein condensate released into a one-dimensional waveguide in the presence of a controlled disorder created by laser speckle. We operate in a regime of pure Anderson localization, that is, with weak disorder-such that localization results from many quantum reflections of low amplitude-and an atomic density low enough to render interactions negligible. We directly image the atomic density profiles as a function of time, and find that weak disorder can stop the expansion and lead to the formation of a stationary, exponentially localized wavefunction-a direct signature of Anderson localization. We extract the localization length by fitting the exponential wings of the profiles, and compare it to theoretical calculations. The power spectrum of the one-dimensional speckle potentials has a high spatial frequency cutoff, causing exponential localization to occur only when the de Broglie wavelengths of the atoms in the expanding condensate are greater than an effective mobility edge corresponding to that cutoff. In the opposite case, we find that the density profiles decay algebraically, as predicted in ref. 13. The method presented here can be extended to localization of atomic quantum gases in higher dimensions, and with controlled interactions. PMID:18548065

Billy, Juliette; Josse, Vincent; Zuo, Zhanchun; Bernard, Alain; Hambrecht, Ben; Lugan, Pierre; Clément, David; Sanchez-Palencia, Laurent; Bouyer, Philippe; Aspect, Alain

2008-06-12

201

Aerosol characterization in Northern Africa, Northeastern Atlantic, Mediterranean Basin and Middle East from direct-sun AERONET observations  

NASA Astrophysics Data System (ADS)

We provide an atmospheric aerosol characterization for North Africa, Northeastern Atlantic, Mediterranean and Middle East based on the analysis of quality-assured direct-sun observations of 39 stations of the AErosol RObotic NETwork (AERONET) which include at least an annual cycle within the 1994-2007 period. We extensively test and apply the recently introduced graphical method of Gobbi and co-authors to track and discriminate different aerosol types and quantify the contribution of mineral dust. The method relies on the combined analysis of the Ångström exponent (?) and its spectral curvature ??. Plotting data in these coordinates allows to infer aerosol fine mode radius (Rf) and fractional contribution (?) to total Aerosol Optical Depth (AOD) and separate AOD growth due to fine-mode aerosol humidification and/or coagulation from AOD growth due to the increase in coarse particles or cloud contamination. Our results confirm the robustness of this graphical method. Large mineral dust is found to be the most important constituent in Northern Africa and Middle East. Under specific meteorological conditions, its transport to Southern Europe is observed from spring to autumn and decreasing with latitude. We observe "pure Saharan dust" conditions to show AOD>0.7 (ranging up to 5), ?<0.3 and ??<0 corresponding to ?<40% and (Rf)~0.13 ?m. Small pollution particles are abundant in sites close to urban and industrial areas of Continental and Eastern Europe and Middle East, as well as, important contributions of biomass burning are observed in the sub-Sahel region in winter. These small aerosols are associated to AOD<1, ?>1.5 and ??~-0.2 corresponding to ?>70% and Rf~0.13 ?m. Here, dust mixed with fine pollution aerosols shifts the observations to the region ?<0.75, in which the fine mode contribution is less than 40%.

Basart, S.; Pérez, C.; Cuevas, E.; Baldasano, J. M.; Gobbi, G. P.

2009-11-01

202

Direct Observation of Ultrafast Excited State Dynamics in Condensed Phase Photochemical Reactions  

NASA Astrophysics Data System (ADS)

Tunable ultrashort pulses of 23-70 fs at peak wavelengths ranging from 268 nm to 690 nm are being used to investigate excited electronic state dynamics in a variety of different systems. The use of such short pulses permits, for the first time, direct observation of the initial photochemical and photophysical dynamics in complicated molecules in condensed phase environments. Several different systems are being investigated for which results will be presented here. The femtosecond excited state internal conversion dynamics of simple polyenes are being investigated by using ultrashort (40-70 fs) pulses in the deep ultraviolet. Measurements were performed in alcohol and alkane solvents on cis- and trans-1,3,5-hexatriene, 1,3-cyclohexadiene, and the related molecule 7-dehydrocholesterol (Provitamin D3). These measurements permit direct observation of the internal conversion from the initially excited state (S2) to the lower energy S1 state and the subsequent internal conversion from the S1 state to the ground state. In a related study, tunable ultrashort visible pulses, 23-40 fs at 520 nm, are being used to investigate the excited state dynamics of B12 cofactors, including ultrafast internal conversion processes, and picosecond bond-cleavage. Wavelength dependent photochemistry (400 nm to 520 nm) has been observed for several cobalamins including the biologically active coenzyme methylcobalamin. Ultrashort pulses are being used to investigate the partitioning between reaction pathways, and the time scales for the initial bond cleavage process. Finally, ultrashort pulses of 23-40 fs with peak wavelengths between 650 nm and 690 nm are being used to study the ultrafast energy transfer and electron transfer processes in the photosystem II reaction center of green plants. These pulses permit coherent excitation of the entire Qy absorption band. The subsequent dynamics reflect ultrafast charge separation, excited state localization, and protein relaxation. A substantial percentage of the total charge separation occurs on a truly ultrafast, sub 100 fs, time scale.

Sension, Roseanne

2000-03-01

203

Direct Observations of the Composition of Sub-20 Nanometer Ambient Aerosol  

NASA Astrophysics Data System (ADS)

Understanding new particle formation in the atmosphere depends upon many factors including detailed knowledge of their chemical composition. The chemical composition of sub-20 nanometer ambient aerosol particles, however, is typically inferred from observations of the aerosol behavior when subjected to varying conditions during sampling. Direct observations of aerosol chemical composition are usually limited to or dominated by larger particles of higher mass. Recently a new instrument has been developed - the Thermal Desorption Chemical Ionization Mass Spectrometer (TDCIMS) - which can directly measure the chemical composition of sub-20 nanometer aerosol particles. Briefly, the front end of the TDCIMS functions as an electrostatic precipitator using a strong electric field to collect charged aerosol particles onto a sample wire. After volatilization by heating, the component species of the collected particles are subjected to chemical ionization prior to introduction into the mass spectrometer for analysis. Detection limits on the order of picograms permit sample collection periods as small as five minutes for ambient aerosol concentrations providing near "real-time" resolution. For selected periods from April through June 2002, we used the TDCIMS to measure the chemical composition of ambient aerosol for the first time. We investigated both the positive and negative ion spectrums produced by sub-20 nanometer ambient aerosol particles at the National Center for Atmospheric Research in Boulder, Colorado. Principal species identified include ammonium, sulfate and nitrate although additional peaks consistent with particle-phase origin were readily observed. Diurnal concentration profiles appear to be present and the relative proportion of sulfate and nitrate to each other can vary appreciably over several hours and between days. Validation of the TDCIMS' performance and the interpretation of its results will also be discussed.

Moore, K. F.; Smith, J. N.; Eisele, F. L.; McMurry, P. H.

2002-12-01

204

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, Frederic; Berthoud, Romain; Coperet, Christophe; Lesage, Anne; Emsley, Lyndon; Singh, Rojendra; Kreickmann, Thorsten; Schrock, Richard R.

2008-01-01

205

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

206

A new filter for the Mean Dynamic Topography of the ocean derived directly from satellite observations  

NASA Astrophysics Data System (ADS)

The Mean Dynamic Topography (MDT) of the ocean provides valuable information about the ocean's surface currents. Therefore the MDT is computed from satellite observations and then assimilated into ocean models in order to improve the ocean circulation estimates. However, the computation of the MDT from satellite observations of sea surface height and the Earth's gravity field is not straightforward and requires additional filtering of the data combination. The choice of the filter is crucial as it determines the amount of small-scale noise in the data and the resolution of the final MDT. There exist various approaches for the determination of an "optimal" filter. However, they all have in common the more or less subjective choice of the filter type and filter width. Here, a new filter is presented that is determined directly from the geodetic normal equations. By its construction, this filter accurately accounts for the correlations within the MDT data and requires no subjective choice about the filter radius. The new filtered MDT is assimilated into an inverse ocean model. Modifications in the meridional overturning circulation and in the poleward heat transports can be observed, compared to the result of the assimilation using the unfiltered MDT.

Freiwald, G.

2013-12-01

207

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

208

Direct observation of the spin polarization in Au atomic wires on Si(553)  

NASA Astrophysics Data System (ADS)

The spin-resolved electronic band structure of Au-induced metallic atomic wires on a vicinal silicon surface, Si(553), was investigated using spin- and angle-resolved photoelectron spectroscopy. We directly measured the spin polarization of three partially filled one-dimensional metallic bands, a one-third-filled band, and the doublet of nearly half-filled bands. For the half-filled doublet, the strong apparent spin polarization was observed near the Fermi energy with a minor out-of-plane spin component. This observation is consistent with the Rashba-type spin-orbit splitting and with a recent experiment on a similar doublet of Si(557)-Au. In contrast, the one-third-filled band does not show a substantial spin polarization within the experimental accuracy, indicating a much smaller spin splitting, if any. These results are discussed for the origin of the partially filled bands and for the intriguing broken-symmetry ground state observed at low temperature.

Yeom, H. W.; Jung, S. W.; Shin, J. S.; Kim, J.; Kim, K. S.; Miyamoto, K.; Okuda, T.; Namatame, H.; Kimura, A.; Taniguchi, M.

2014-09-01

209

Direct Observation of a Majorana Quasiparticle Heat Capacity in 3He  

NASA Astrophysics Data System (ADS)

The Majorana fermion, which acts as its own antiparticle, was suggested by Majorana in 1937 (Nuovo Cimento 14:171). While no stable particle with Majorana properties has yet been observed, Majorana quasiparticles (QP) may exist at the boundaries of topological insulators. Here we report the preliminary results of direct observation of Majorana QPs by a precise measurements of superfluid 3He heat capacity. The bulk superfluid 3He heat capacity falls exponentially with cooling at the temperatures significantly below the energy gap. Owing to the zero energy gap mode the Majorana heat capacity falls in a power law. The Majorana heat capacity can be larger than bulk one at some temperature, which depends on surface to volume ratio of the experimental cell. Some times ago we developed the Dark matter particles detector (DMD) on a basis of superfluid 3He which is working at the frontier of extremely low temperatures (Winkelmann et al., Nucl. Instrum. Meth. A 559:384-386, 2006). Here we report the observation of zero gap mode of Majorana, follows from the new analyses of DMD heat capacity, published early. We have found a 10 % deviation from the bulk superfluid 3He heat capacity at the temperature of 135 ?K. This deviation corresponds well to the theoretical value for Majorana heat capacity at such low temperature. (Note, there were no fitting parameters).

Bunkov, Y. M.

2014-04-01

210

Direct Observation of the Fourth Star in the Zeta Cancri System  

E-print Network

Direct imaging of the zeta Cnc system has resolved the fourth star in the system, which is in orbit around zeta Cnc C. The presence of the fourth star has been inferred for many years from irregularities in the motion of star C, and recently from C's spectroscopic orbit. However, its mass is close to that of C, making its non-detection puzzling. Observing at wavelengths of 1.2, 1.7, and 2.2 microns with the adaptive-optics system of the CFHT, we have obtained images which very clearly reveal star D and show it to have the color of an M2 star. Its brightness is consonant with its being two M stars, which are not resolved in our observations but are likely to be in a short-period orbit, thereby accounting for the large mass and the difficulty of detection at optical wavelengths, where the magnitude difference is much larger. The positions and colors of all four stars in the system are reported and are consistent with the most recent astrometric observations.

J. B. Hutchings; R. F. Griffin; F. Menard

2000-04-19

211

Direct nanoscale observations of CO2 sequestration during brucite [Mg(OH)2] dissolution.  

PubMed

The dissolution and carbonation of brucite on (001) cleavage surfaces was investigated in a series of in situ and ex situ atomic force microscopy (AFM) experiments at varying pH (2-12), temperature (23-40 °C), aqueous NaHCO(3) concentration (10(-5)-1 M), and PCO(2) (0-1 atm). Dissolution rates increased with decreasing pH and increasing NaHCO(3) concentration. Simultaneously with dissolution of brucite, the growth of a Mg-carbonate phase (probably dypingite) was directly observed. In NaHCO(3) solutions (pH 7.2-9.3,), precipitation of Mg-carbonates was limited. Enhanced precipitation was, however, observed in acidified NaHCO(3) solutions (pH 5, DIC ? 25.5 mM) and in solutions that were equilibrated under a CO(2) atmosphere (pH 4, DIC ? 25.2 mM). Nucleation predominantly occurred in areas of high dissolution such as deep step edges suggesting that the carbonation reaction is locally diffusion-transport controlled. More extensive particle growth was also observed after ex situ experiments lasting for several hours. This AFM study contributes to an improved understanding of the mechanism of aqueous brucite carbonation at low temperature and pressure conditions and has implications for carbonation reactions in general. PMID:22500652

Hövelmann, J; Putnis, C V; Ruiz-Agudo, E; Austrheim, H

2012-05-01

212

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

213

A novel approach to directly observed therapy for tuberculosis in an HIV-endemic area.  

PubMed Central

OBJECTIVES: This study evaluated a novel approach to the delivery of directly observed therapy (DOT) for tuberculosis in Haiti. METHODS: A total of 194 patients (152 HIV seropositive, 42 HIV seronegative) received daily unsupervised triple-drug therapy for 4 to 8 weeks, followed by twice-weekly 2-drug therapy for the remainder of the 6-month period. DOT was deferred until initiation of the twice-weekly phase. RESULTS: A total of 169 of 194 patients (87.1%) completed the 6-month course. The program of deferred DOT had an effectiveness of 85%. Overall cost was reduced by approximately 40%. CONCLUSIONS: Flexible approaches to DOT, integrating behavioral knowledge, cost considerations, and practicality may improve completion rates and program effectiveness. PMID:11189809

Desvarieux, M; Hyppolite, P R; Johnson, W D; Pape, J W

2001-01-01

214

Direct observation of the degree of correlations using photon-number-resolving detectors  

NASA Astrophysics Data System (ADS)

Optical parametric down-conversion is a common source for the generation of nonclassical correlated photonic states. Using a parametric down-conversion source and photon-number-resolving detectors, we measure the two-mode photon-number distribution of up to 10 photons for different degrees of correlation. The degree of correlation is controlled by collecting different spatial and spectral single modes for each polarization and varying the amount of spectral and spatial overlap between them. Clear evidence for photon-number correlations is presented despite detector imperfections such as low detection efficiency and other distorting effects. Two criteria, derived directly from the raw data, are shown to be good measures for the degree of correlation. Additionally, using a fitting technique, we find a connection between the measured photon-number distribution and the degree of correlation of the reconstructed original two-mode state. These observations are only possible as a result of the detection of high photon number events.

Dovrat, L.; Bakstein, M.; Istrati, D.; Megidish, E.; Halevy, A.; Cohen, L.; Eisenberg, H. S.

2013-05-01

215

Direct Observation of Fatigue Cracking in the Fuel Plate Using the Scanning Electron Microscope  

NASA Astrophysics Data System (ADS)

Safety and environmental considerations play the important role in selecting and processing fusion materials. Fatigue impairs the reliability of the components utilized in the fusion reactor. In this paper, we described the fatigue cracking mechanism of the sandwich structure of dispersion U3Si2-Al fuel plates using the in situ scanning electron microscope. Direct observations indicated that the failure originates in the vicinal clad-meat interface under tensile-tensile cyclic and three points bending loading. The fatigue crack occurs in two typical fracture modes — Mode-I and the mixed-mode of I and II. The effect of the process of U3Si2-Al fuel meat on the fatigue behaviors of the sandwich structure is obvious.

Wang, Xi-Shu; Xu, Yong; Xu, Xian-Qi

2004-05-01

216

Direct observation of Young's double-slit interferences in vibrationally resolved photoionization of diatomic molecules  

PubMed Central

Vibrationally resolved valence-shell photoionization spectra of H2, N2 and CO have been measured in the photon energy range 20–300 eV using third-generation synchrotron radiation. Young’s double-slit interferences lead to oscillations in the corresponding vibrational ratios, showing that the molecules behave as two-center electron-wave emitters and that the associated interferences leave their trace in the angle-integrated photoionization cross section. In contrast to previous work, the oscillations are directly observable in the experiment, thereby removing any possible ambiguity related to the introduction of external parameters or fitting functions. A straightforward extension of an original idea proposed by Cohen and Fano [Cohen HD, Fano U (1966) Phys Rev 150:30] confirms this interpretation and shows that it is also valid for diatomic heteronuclear molecules. Results of accurate theoretical calculations are in excellent agreement with the experimental findings.

Canton, Sophie E.; Plesiat, Etienne; Bozek, John D.; Rude, Bruce S.; Decleva, Piero; Martin, Fernando

2011-01-01

217

Direct observation of dispersive Kondo resonance peaks in a heavy-fermion system.  

PubMed

Ce 4d-4f resonant angle-resolved photoemission spectroscopy was carried out to study the electronic structure of strongly correlated Ce 4f electrons in a quasi-two-dimensional nonmagnetic heavy-fermion system CeCoGe1.2Si0.8. For the first time, dispersive coherent peaks of an f state crossing the Fermi level, the so-called Kondo resonance, are directly observed together with the hybridized conduction band. Moreover, the experimental band dispersion is quantitatively in good agreement with a simple hybridization-band picture based on the periodic Anderson model. The obtained physical quantities, i.e., coherent temperature, Kondo temperature, and mass enhancement, are comparable to the results of thermodynamic measurements. These results manifest an itinerant nature of Ce 4f electrons in heavy-fermion systems and clarify their microscopic hybridization mechanism. PMID:18518313

Im, H J; Ito, T; Kim, H-D; Kimura, S; Lee, K E; Hong, J B; Kwon, Y S; Yasui, A; Yamagami, H

2008-05-01

218

Direct Observations of the Charge States of Low Energy Solar Particles  

NASA Technical Reports Server (NTRS)

The charge states of carbon and oxygen of solar origin were measured directly in interplanetary space. At 100 keV per nucleon the C(+5)/C(+6) and O(+7)/O(+8) ratios are 1.8 and 1.6 respectively. It was found that the abundance ratios of low energy heavy nuclei to He is significantly larger than corresponding photospheric values: the enhancement of O/He is 35 and both Si/He and Fe/He are overabundant by a factor of 100. To explain these observations a mechanism is proposed which first preferentially accelerates heavy ions and is followed by either storage of these ions in the coronal regions or strong adiabatic deceleration.

Gloeckler, G.; Fan, C. Y.; Hovestadt, D.

1973-01-01

219

Direct observations of the charge states of low energy solar particles  

NASA Technical Reports Server (NTRS)

The charge states of carbon and oxygen of solar origin have been measured directly in interplanetary space. At 100 keV per nucleon the C(+5)/C(+6) and O(+7)/O(+8) ratios are 1.8 and 1.6, respectively. Abundance ratios of low energy heavy nuclei to He are found which are significantly larger than the corresponding photospheric values. The enhancement of O/He is 35, and both Si/He and Fe/He are overabundant by a factor of 100. To explain these observations a mechanism is proposed which first preferentially accelerates heavy ions and is followed by either storage of these ions in the coronal regions or strong adiabatic deceleration.

Gloeckler, G.; Fan, C. Y.; Hovestadt, D.

1974-01-01

220

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

221

Direct observation of electron leakage in InGaAsP/InP double heterostructure  

NASA Astrophysics Data System (ADS)

The electron leakage through the heterobarrier consisting of a thin InGaAsP active layer and a p-InP confining layer was directly observed by using a novel InGaAsP/InP light-emitting diode (LED) structure. In the present structure, electrons leaking from the active layer were confined in a subsidiary quaternary layer having a crystal composition different from that of the active layer, and the recombination emission caused by these electrons was optically detected. Experimental results showed that significant electron leakage can occur in the present InGaAsP/InP double heterostructure (DH) system, suggesting a possibility of the electron leakage being one of the dominant mechanisms of sublinearity in the light intensity-current characteristics in InGaAsP/InP DH LED's operating at wavelengths shorter than 1.3 ?m and also of the temperature dependence of threshold current in laser diodes.

Yamakoshi, S.; Sanada, T.; Wada, O.; Umebu, I.; Sakurai, T.

1982-01-01

222

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

223

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

224

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

225

Direct observation of resistive heating at graphene wrinkles and grain boundaries  

NASA Astrophysics Data System (ADS)

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 ˜0.2 K 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 ? ?m) 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.; Dorgan, Vincent E.; Estrada, David; Wood, Joshua D.; Vlassiouk, Ivan; Eres, Gyula; Lyding, Joseph W.; King, William P.; Pop, Eric

2014-10-01

226

Direct observation of spin-polarized bulk bands in an inversion-symmetric semiconductor  

NASA Astrophysics Data System (ADS)

Methods to generate spin-polarized electronic states in non-magnetic solids are strongly desired to enable all-electrical manipulation of electron spins for new quantum devices. This is generally accepted to require breaking global structural inversion symmetry. In contrast, here we report the observation from spin- and angle-resolved photoemission spectroscopy of spin-polarized bulk states in the centrosymmetric transition-metal dichalcogenide WSe2. Mediated by a lack of inversion symmetry in constituent structural units of the bulk crystal where the electronic states are localized, we show how spin splittings up to ~0.5 eV result, with a spin texture that is strongly modulated in both real and momentum space. Through this, our study provides direct experimental evidence for a putative locking of the spin with the layer and valley pseudospins in transition-metal dichalcogenides, of key importance for using these compounds in proposed valleytronic devices.

Riley, J. M.; Mazzola, F.; Dendzik, M.; Michiardi, M.; Takayama, T.; Bawden, L.; Granerød, C.; Leandersson, M.; Balasubramanian, T.; Hoesch, M.; Kim, T. K.; Takagi, H.; Meevasana, W.; Hofmann, Ph.; Bahramy, M. S.; Wells, J. W.; King, P. D. C.

2014-11-01

227

From directly observed therapy to accompagnateurs: enhancing AIDS treatment outcomes in Haiti and in Boston.  

PubMed

Like tuberculosis, human immunodeficiency virus (HIV) disease is associated with poverty and social inequalities, 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) for the care of patients with advanced acquired immune deficiency syndrome. A similar DOT-HAART effort was launched in Boston for patients with drug-resistant HIV disease who had experienced failure of unsupervised therapy. In both settings, community health promoters or accompagnateurs provide more than DOT: they offer psychosocial support and link patients to clinical staff and available resources. DOT-HAART in these 2 settings presents both challenges and opportunities. These models of care can be applied to other poverty-stricken populations in resource-poor settings. PMID:15156434

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

2004-06-01

228

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

229

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

230

Direct single-molecule observation of calcium-dependent misfolding in human neuronal calcium sensor-1  

PubMed Central

Neurodegenerative disorders are strongly linked to protein misfolding, and crucial to their explication is a detailed understanding of the underlying structural rearrangements and pathways that govern the formation of misfolded states. Here we use single-molecule optical tweezers to monitor misfolding reactions of the human neuronal calcium sensor-1, a multispecific EF-hand protein involved in neurotransmitter release and linked to severe neurological diseases. We directly observed two misfolding trajectories leading to distinct kinetically trapped misfolded conformations. Both trajectories originate from an on-pathway intermediate state and compete with native folding in a calcium-dependent manner. The relative probability of the different trajectories could be affected by modulating the relaxation rate of applied force, demonstrating an unprecedented real-time control over the free-energy landscape of a protein. Constant-force experiments in combination with hidden Markov analysis revealed the free-energy landscape of the misfolding transitions under both physiological and pathological calcium concentrations. Remarkably for a calcium sensor, we found that higher calcium concentrations increased the lifetimes of the misfolded conformations, slowing productive folding to the native state. We propose a rugged, multidimensional energy landscape for neuronal calcium sensor-1 and speculate on a direct link between protein misfolding and calcium dysregulation that could play a role in neurodegeneration. PMID:25157171

Heidarsson, Pétur O.; Naqvi, Mohsin M.; Otazo, Mariela R.; Mossa, Alessandro; Kragelund, Birthe B.; Cecconi, Ciro

2014-01-01

231

Ultrafast electron diffraction and direct observation of transient structures in a chemical reaction  

PubMed Central

Ultrafast electron diffraction is a unique method for the studies of structural changes of complex molecular systems. In this contribution, we report direct ultrafast electron diffraction study of the evolution of short-lived intermediates in the course of a chemical change. Specifically, we observe the transient intermediate in the elimination reaction of 1,2-diiodotetrafluoroethane (C2F4I2) to produce the corresponding ethylene derivative by the breakage of two carbon–iodine, C—I, bonds. The evolution of the ground-state intermediate (C2F4I radical) is directly revealed in the population change of a single chemical bond, namely the second C—I bond. The elimination of two iodine atoms was shown to be nonconcerted, with reaction time of the second C—I bond breakage being 17 ± 2 ps. The structure of the short-lived C2F4I radical is more favorable to the classical radical structure than to the bridged radical structure. This leap in our ability to record structural changes on the ps and shorter time scales bodes well for many future applications in complex molecular systems. PMID:9892634

Cao, Jianming; Ihee, Hyotcherl; Zewail, Ahmed H.

1999-01-01

232

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

NASA Astrophysics Data System (ADS)

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.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. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr05258c

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

2014-01-01

233

Direct observation of intermediates formed during steady-state electrocatalytic O2 reduction by iron porphyrins  

PubMed Central

Heme/porphyrin-based electrocatalysts (both synthetic and natural) have been known to catalyze electrochemical O2, H+, and CO2 reduction for more than five decades. So far, no direct spectroscopic investigations of intermediates formed on the electrodes during these processes have been reported; and this has limited detailed understanding of the mechanism of these catalysts, which is key to their development. Rotating disk electrochemistry coupled to resonance Raman spectroscopy is reported for iron porphyrin electrocatalysts that reduce O2 in buffered aqueous solutions. Unlike conventional single-turnover intermediate trapping experiments, these experiments probe the system while it is under steady state. A combination of oxidation and spin-state marker bands and metal ligand vibrations (identified using isotopically enriched substrates) allow in situ identification of O2-derived intermediates formed on the electrode surface. This approach, combining dynamic electrochemistry with resonance Raman spectroscopy, may be routinely used to investigate a plethora of metalloporphyrin complexes and heme enzymes used as electrocatalysts for small-molecule activation. PMID:23650367

Sengupta, Kushal; Chatterjee, Sudipta; Samanta, Subhra; Dey, Abhishek

2013-01-01

234

The breakup of large tabular icebergs - direct observations and theoretical considerations  

NASA Astrophysics Data System (ADS)

Peter Wadhams and Till Wagner Dept. of Applied Mathematics and Theoretical Physics (DAMTP), University of Cambridge. We review the factors governing the stability, dynamics and decay of icebergs and describe areas where current models are inadequate. These include questions such as draft changes in capsizing icebergs; iceberg trajectory modelling; the melt rate of the ice underside and ways of reducing it; and wave-induced flexure and its role in the break-up of tabular icebergs. In July 2012 the authors worked on a very large (42 sq km) tabular iceberg in Baffin Bay, which had calved from the Petermann Glacier in NW Greenland. We measured incoming swell spectrum and the iceberg response; also the role of buoyancy forces due to erosion of a waterline wave cut and the creation of an underwater ram. The iceberg broke up while we were on it, allowing an instrumental measurement of the calving event. The experiments were included in the BBC-2 film 'Operation Iceberg' shown on Nov 1 2012 and repeated on Nov 18. We conclude that two processes interacted in the break-up event: increased bending stress due to buoyancy of underwater rams; and direct flexural strain due to incidence of ocean swell. Implications for icebergs in the open sea are estimated.

Wadhams, P.

2013-12-01

235

Direct observation of the hole protonation state and hole localization site in DNA-oligomers  

PubMed Central

In this work, it is shown that the incorporation of an 8-deuteroguanine (G*) moiety in DNA-oligomers allows for direct determination at 77 K of (i) the location of holes (i.e., the radical site) within dsDNA at specific base sites, even within stacks of G, as well as (ii) the protonation state of the hole at that site. These findings are based on our work and demonstrate that selective deuteration at C-8 on guanine moiety in dGuo results in an ESR signal from the guanine cation radical (G*•+) which is easily distinguishable from that of the undeuterated guanine cation radical (G•+). G*•+ is also found to be easily distinguishable from its conjugate base, the N1-deprotonated radical, G*(?H)•. Our ESR results clearly establish that at 77 K (i) one-electron oxidized guanine in double stranded DNA-oligomers exists as the deprotonated neutral radical G(?H)• as a result of facile proton transfer to the hydrogen bonded cytosine, and (ii) the hole is preferentially located at the 5?-end in several ds DNA-oligomers with a GGG sequence. PMID:19469533

Adhikary, Amitava; Khanduri, Deepti; Sevilla, Michael D.

2009-01-01

236

Direct Observation of Controlled Melting and Resolidification of Succinonitrile Mixtures in a Microgravity Environment  

NASA Technical Reports Server (NTRS)

In support of the Pore Formation and Mobility Investigation (PFMI) direct observation of experiments on the controlled melting and subsequent resolidification of succinonitrile were conducted in the glovebox facility (GBX) of the International Space Station (ISS). Samples were prepared on ground by filling glass tubes, 1 cm ID and approximately 30 cm in length, with pure succinonitrile (SCN) and SCN-Water mixtures under 450 millibar of nitrogen. Experimental processing parameters of temperature gradient and translation speed, as well as camera settings, were remotely monitored and manipulated from the ground Telescience Center (TSC) at the Marshall Space Flight Center. Sample temperatures are monitored by six in situ thermocouples. Real time visualization during melt back revealed bubbles of different sizes initiating at the solid/liquid interface, their release, interactions, and movement into the temperature field ahead of them. Subsequent re-solidification examined planar interface breakdown and the transition to steady-state dendritic growth. A preliminary analysis of the observed phenomena and its implication to future microgravity experiments is presented and discussed.

Grugel, R. N.; Anilkumar, A. V.; Lee, C. P.

2004-01-01

237

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

238

Direct observation and control of supported lipid bilayer formation with interferometric scattering microscopy.  

PubMed

Supported lipid bilayers (SLB) are frequently used to study processes associated with or mediated by lipid membranes. The mechanism by which SLBs form is a matter of debate, largely due to the experimental difficulty associated with observing the adsorption and rupture of individual vesicles. Here, we used interferometric scattering microscopy (iSCAT) to directly visualize membrane formation from nanoscopic vesicles in real time. We observed a number of previously proposed phenomena such as vesicle adsorption, rupture, movement, and a wave-like bilayer spreading. By varying the vesicle size and the lipid-surface interaction strength, we rationalized and tuned the relative contributions of these phenomena to bilayer formation. Our results support a model where the interplay between bilayer edge tension and the overall interaction energy with the surface determine the mechanism of SLB formation. The unique combination of sensitivity, speed, and label-free imaging capability of iSCAT provides exciting prospects not only for investigations of SLB formation, but also for studies of assembly and disassembly processes on the nanoscale with previously unattainable accuracy and sensitivity. PMID:24251388

Andrecka, Joanna; Spillane, Katelyn M; Ortega-Arroyo, Jaime; Kukura, Philipp

2013-12-23

239

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.; Wuthrich, Kurt

2005-01-01

240

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

241

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

242

Direct observation of protein secondary structure in gas vesicles by atomic force microscopy.  

PubMed

The protein that forms the gas vesicle in the cyanobacterium Anabaena flos-aquae has been imaged by atomic force microscopy (AFM) under liquid at room temperature. The protein constitutes "ribs" which, stacked together, form the hollow cylindrical tube and conical end caps of the gas vesicle. By operating the microscope in deflection mode, it has been possible to achieve sub-nanometer resolution of the rib structure. The lateral spacing of the ribs was found to be 4.6 +/- 0.1 nm. At higher resolution the ribs are observed to consist of pairs of lines at an angle of approximately 55 degrees to the rib axis, with a repeat distance between each line of 0.57 +/- 0.05 nm along the rib axis. These observed dimensions and periodicities are consistent with those determined from previous x-ray diffraction studies, indicating that the protein is arranged in beta-chains crossing the rib at an angle of 55 degrees to the rib axis. The AFM results confirm the x-ray data and represent the first direct images of a beta-sheet protein secondary structure using this technique. The orientation of the GvpA protein component of the structure and the extent of this protein across the ribs have been established for the first time. PMID:9172769

McMaster, T J; Miles, M J; Walsby, A E

1996-05-01

243

THE EFFECTIVENESS OF CLOSED CIRCUIT TELEVISION OBSERVATION AND OF DIRECT OBSERVATION OF CHILDREN'S ART CLASSES FOR IMPLEMENTING ELEMENTARY TEACHERS' TRAINING IN ART EDUCATION.  

ERIC Educational Resources Information Center

AN EXPERIMENTAL STUDY WAS DESIGNED TO MEASURE THE EXTENT TO WHICH CLOSED CIRCUIT TELEVISION OBSERVATIONS AND DIRECT OBSERVATIONS OF CHILDREN'S ART CLASSES CONTRIBUTE SIGNIFICANTLY TO THE ABILITY OF ELEMENTARY EDUCATION MAJORS TO DISCRIMINATE BETWEEN DESIRABLE AND UNDESIRABLE SOLUTIONS TYPICALLY OCCURRING IN TEACHING ART TO ELEMENTARY SCHOOL…

SYKES, RONALD E.

244

An instrument for direct observations of seismic and normal-mode rotational oscillations of the Earth  

PubMed Central

The rotations around the vertical axis associated with the normal mode oscillations of the Earth and those induced by the seismic and other disturbances have been very difficult to observe directly. Such observations will provide additional information for 3D modeling of the Earth and for understanding earthquakes and other underground explosions. In this paper, we describe the design of an instrument capable of measuring the rotational motions associated with the seismic oscillations of the Earth, including the lowest frequency normal mode at ? ? 3.7 × 10?4 Hz. The instrument consists of a torsion balance with a natural frequency of ?0 ? 1.6 × 10?4 Hz, which is observed by an autocollimating optical lever of high angular resolution and dynamic range. Thermal noise limits the sensitivity of the apparatus to amplitudes of ? 1.5 × 10?9 rad at the lowest frequency normal mode and the sensitivity improves as ??3/2 with increasing frequency. Further improvements in sensitivity by about two orders of magnitude may be achieved by operating the balance at cryogenic temperatures. Alternatively, the instrument can be made more robust with a reduced sensitivity by increasing ?0 to ?10?2 Hz. This instrument thus complements the ongoing effort by Igel and others to study rotational motions using ring laser gyroscopes and constitutes a positive response to the clarion call for developments in rotation seismology by Igel, Lee, and Todorovska [H. Igel, W.H.K. Lee and M.I. Todorovska, AGU Fall Meeting 2006, Rotational Seismology Sessions: S22A,S23B, Inauguration of the International Working Group on Rotational Seismology (IWGoRS)]. PMID:17438268

Cowsik, R.

2007-01-01

245

On Quasi-Periodic Variations of Cosmic Rays Observed at Earth: Direct Measurements  

NASA Astrophysics Data System (ADS)

Important role in space weather related studies play cosmic rays (CR). Their temporal variability, both of quasi-periodic character as well as of irregular one, is studied on the ground from direct measurements as well as from cosmogenic nuclides, over long time. We attempt to describe the current knowledge on selected quasi-periodicities in CR flux, especially in energy range above the atmospheric threshold, from direct measurement. Quasi-periodicities in relativistic electron flux near Earth is discussed shortly too. The power spectrum density (PSD) of the CR time series at a single station has rather complicated character. Along with the shape (slope) of PSD the knowledge of contribution of quasi-periodic variations to the CR signal is of importance for the modulation as well as for the checking the links of CR to space weather and/or space climate effects. Rotation of the Earth and solar rotation cause two types of mechanisms behind the certain quasi-periodicities observed in secondary CR on the Earth's surface. Solar activity and solar magnetic field cyclicities contribute to the quasi-periodic signals in CR if studied over longer time periods. The complexity of spatial structure of IMF and its evolution within the heliosphere as well as the changes in the geomagnetic field cause variability in contributions of the quasi-periodicities in CR. Wavelet spectra are useful tool for checking the fine strucure of quasi-periodicities and their temporal behaviour. Over long time the neutron monitors and muon telescopes provide the informations about quasi-periodicities in CR. In addition to that, in recent years there are new installations on the ground from which the unique information about CR variability can be deduced (higher statistical accuracy, different response function to primaries). The unsolved questions and few tasks for the future studies are listed.

Kudela, K.; Perez-Peraza, J. A.

2013-05-01

246

Constraining nova observables: Direct measurements of resonance strengths in 33S(p,?)34Cl  

NASA Astrophysics Data System (ADS)

The 33S(p,?)34Cl reaction is important for constraining predictions of certain isotopic abundances in oxygen-neon novae. Models currently predict as much as 150 times the solar abundance of 33S in oxygen-neon nova ejecta. This overproduction factor may vary by orders of magnitude due to uncertainties in the 33S(p,?)34Cl reaction rate at nova peak temperatures. Depending on this rate, 33S could potentially be used as a diagnostic tool for classifying certain types of presolar grains. Better knowledge of the 33S(p,?)34Cl rate would also aid in interpreting nova observations over the S-Ca mass region and contribute to the firm establishment of the maximum endpoint of nova nucleosynthesis. Additionally, the total S elemental abundance which is affected by this reaction has been proposed as a thermometer to study the peak temperatures of novae. Previously, the 33S(p,?)34Cl reaction rate had only been studied directly down to resonance energies of 432 keV. However, for nova peak temperatures of 0.2-0.4 GK there are seven known states in 34Cl both below the 432-keV resonance and within the Gamow window that could play a dominant role. Direct measurements of the resonance strengths of these states were performed using the DRAGON (Detector of Recoils And Gammas of Nuclear reactions) recoil separator at TRIUMF. Additionally two new states within this energy region are reported. Several hydrodynamic simulations have been performed, using all available experimental information for the 33S(p,?)34Cl rate, to explore the impact of the remaining uncertainty in this rate on nucleosynthesis in nova explosions. These calculations give a range of ?20-150 for the expected 33S overproduction factor, and a range of ?100-450 for the 32S/33S ratio expected in ONe novae.

Fallis, J.; Parikh, A.; Bertone, P. F.; Bishop, S.; Buchmann, L.; Chen, A. A.; Christian, G.; Clark, J. A.; D'Auria, J. M.; Davids, B.; Deibel, C. M.; Fulton, B. R.; Greife, U.; Guo, B.; Hager, U.; Herlitzius, C.; Hutcheon, D. A.; José, J.; Laird, A. M.; Li, E. T.; Li, Z. H.; Lian, G.; Liu, W. P.; Martin, L.; Nelson, K.; Ottewell, D.; Parker, P. D.; Reeve, S.; Rojas, A.; Ruiz, C.; Setoodehnia, K.; Sjue, S.; Vockenhuber, C.; Wang, Y. B.; Wrede, C.

2013-10-01

247

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

248

A study of the aerosol direct forcing using ESSP/CALIPSO observation and GCM simulation  

NASA Astrophysics Data System (ADS)

Shortwave direct aerosol radiative forcing (SWDARF) at the top-of the atmosphere (TOA) under clear-sky, cloudy-sky, and all-sky conditions are calculated using data of space-borne CALIOP lidar and MODIS sensor and simulation result of a global aerosol model, SPRINTARS. We investigate four scenarios for evaluating the SWDARF using both an observational and model approach: clear-sky, the case that aerosols exist above clouds, the case that aerosols exist below high-level clouds, and the case that aerosols are not detected by CALIOP in cloudy-sky condition. The cloudy-sky SWDARF is estimated by the latter three scenarios. The all-sky SWDARF is the combination of clearsky and cloudy-sky SWDARF weighted by the cloud occurrence. The results show that the TOA forcing over desert regions caused by dust with single scattering albedo (SSA) of 0.92 is positive regardless of cloud existence, due to high solar surface albedo. Off southern Africa, smoke aerosols with SSA of 0.84 above low-level clouds are observed and simulated and the annual mean cloudy-sky SWDARF is estimated at more than +2 Wm-2, as consistent with past studies. Annual zonal averages of SWDARF from 60°S to 60°N under clear-sky, cloudy-sky, and all-sky are -3.72, -1.13, and -2.07 Wm-2 from CALIOP, and -2.78, +1.07, and -0.58 Wm-2 from SPRINTARS. The difference of aerosol loading and occurrence probability in the case that aerosols exist above clouds changes the sign of all-sky and cloudy-sky SWDARF.

Oikawa, Eiji; Nakajima, Teruyuki; Inoue, Toshiro; Winker, David

2013-05-01

249

Direct observation of heat dissipation in individual suspended carbon nanotubes using a two-laser technique  

SciTech Connect

A two-laser technique is used to investigate heat spreading along individual single walled carbon nanotube (SWCNT) bundles in vacuum and air environments. A 532 nm laser focused on the center of a suspended SWCNT bundle is used as a local heat source, and a 633 nm laser is used to measure the spatial temperature profile along the SWCNT bundle by monitoring the G band downshifts in the Raman spectra. A constant temperature gradient is observed when the SWCNT bundle is irradiated in vacuum, giving direct evidence of diffusive transport of the phonons probed by the Raman laser. In air, however, we observe an exponentially decaying temperature profile with a decay length of about 7 {mu}m, due to heat dissipation from the SWCNT bundle to the surrounding gas molecules. The thermal conductivity of the suspended carbon nanotube (CNT) is determined from its electrical heating temperature profile as measured in vacuum and the nanotube bundle diameter measured via transmission electron microscopy. Based on the exponential decay curves measured in three different CNTs in air, the heat transfer coefficient between the SWCNTs and the surrounding air molecules is found to range from 1.5 x 10{sup 3} to 7.9 x 10{sup 4} W/m{sup 2} K, which is smaller than the 1 x 10{sup 5} W/m{sup 2} K thermal boundary conductance value calculated using the kinetic theory of gases. This measurement is insensitive to the thermal contact resistance, as no temperature drops occur at the ends of the nanotube. It is also insensitive to errors in the calibration of the G band temperature coefficient. The optical absorption is also obtained from these results and is on the order of 10{sup -5}.

Hsu, I-Kai; Hung, Wei-Hsuan [Department of Materials Science, University of Southern California, Los Angeles, California 90089 (United States); Pettes, Michael T.; Shi Li [Department of Mechanical Engineering and Center for Nano and Molecular Science and Technology, Texas Materials Institute, University of Texas of Austin, Austin, Texas 78712 (United States); Aykol, Mehmet; Theiss, Jesse; Cronin, Stephen B. [Department of Electrical Engineering, University of Southern California, Los Angeles, California 90089 (United States); Chang, Chia-Chi [Department of Physics, University of Southern California, Los Angeles, California 90089 (United States)

2011-08-15

250

Direct observation of heat dissipation in individual suspended carbon nanotubes using a two-laser technique  

NASA Astrophysics Data System (ADS)

A two-laser technique is used to investigate heat spreading along individual single walled carbon nanotube (SWCNT) bundles in vacuum and air environments. A 532 nm laser focused on the center of a suspended SWCNT bundle is used as a local heat source, and a 633 nm laser is used to measure the spatial temperature profile along the SWCNT bundle by monitoring the G band downshifts in the Raman spectra. A constant temperature gradient is observed when the SWCNT bundle is irradiated in vacuum, giving direct evidence of diffusive transport of the phonons probed by the Raman laser. In air, however, we observe an exponentially decaying temperature profile with a decay length of about 7 ?m, due to heat dissipation from the SWCNT bundle to the surrounding gas molecules. The thermal conductivity of the suspended carbon nanotube (CNT) is determined from its electrical heating temperature profile as measured in vacuum and the nanotube bundle diameter measured via transmission electron microscopy. Based on the exponential decay curves measured in three different CNTs in air, the heat transfer coefficient between the SWCNTs and the surrounding air molecules is found to range from 1.5 × 103 to 7.9 × 104 W/m2 K, which is smaller than the 1 × 105 W/m2 K thermal boundary conductance value calculated using the kinetic theory of gases. This measurement is insensitive to the thermal contact resistance, as no temperature drops occur at the ends of the nanotube. It is also insensitive to errors in the calibration of the G band temperature coefficient. The optical absorption is also obtained from these results and is on the order of 10-5.

Hsu, I.-Kai; Pettes, Michael T.; Aykol, Mehmet; Chang, Chia-Chi; Hung, Wei-Hsuan; Theiss, Jesse; Shi, Li; Cronin, Stephen B.

2011-08-01

251

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

252

Direct pore-level observation of permeability increase in two-phase flow by shaking  

NASA Astrophysics Data System (ADS)

Increases in permeability of natural reservoirs and aquifers by passing seismic waves have been well documented. If the physical causes of this phenomenon can be understood, technological applications would be possible for controlling the flow in hydrologic systems or enhancing production from oil reservoirs. The explanation of the dynamically increased mobility of underground fluids must lie at the pore level. The natural fluids can be viewed as two-phase systems, composed of water as the wetting phase and of dispersed non-wetting globules of gas or organic fluids, flowing through tortuous constricted channels. Capillary forces prevent free motion of the suspended non-wetting droplets, which tend to become immobilized in capillary constrictions. The capillary entrapment significantly reduces macroscopic permeability. In a controlled experiment with a constricted capillary channel, we immobilize the suspended ganglia and test the model of capillary entrapment: it agrees precisely with the experiment. We then demonstrate by direct optical pore-level observation that the vibrations applied to the wall of the channel liberate the trapped ganglia if a predictable critical acceleration is reached. When the droplet begins to progressively advance, the permeability is restored. The mobilizing acceleration in the elastic wave, needed to “unplug” an immobile flow, is theoretically calculated within a factor of 1-5 of the experimental value. Overcoming the capillary entrapment in porous channels is hypothesized to be one of the principal pore-scale mechanisms by which natural permeabilities are enhanced by the passage of elastic waves.

Beresnev, Igor; Gaul, William; Vigil, R. Dennis

2011-10-01

253

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

254

Directly observed care: can unannounced standardized patients address a gap in performance measurement?  

PubMed

There are three potential sources of information for evaluating a clinician's performance: documentation, patient report, and directly observed care. Current measures draw on just two of these: data recorded in the medical record and surveys of patients. Neither captures an array of performance characteristics, including clinician attention to symptoms and signs while taking a history or conducting a physical exam, accurate recording in the medical record of information obtained during the encounter, evidence based communication strategies for preventive care counseling, and effective communication behavior. Unannounced Standardized Patients (USPs) have been widely deployed as a research strategy for systematically uncovering significant performance deficits in each of these areas, but have not been adopted for quality improvement. Likely obstacles include concerns about the ethics of sending health professionals sham patients, the technical challenges of the subterfuge, and concerns about the relatively small sample sizes and substantial costs involved. However, the high frequency of significant and remediable performance deficits unmasked by USPs, and the potential to adapt registration and record keeping systems to accommodate their visits, suggest that their selective and purposeful deployment could be a cost effective and powerful strategy for addressing a gap in performance measurement. PMID:24756945

Weiner, Saul J; Schwartz, Alan

2014-08-01

255

Comparison of advection and steam fogs: From direct observation over the sea  

NASA Astrophysics Data System (ADS)

Sea fog occurs frequently over the Yellow Sea in spring and summer, which causes costly or even catastrophic events including property damage, marine accidents, public health and financial losses. Case studies of advection and steam fogs using direct observation over the sea are constructed to better understand their formation, evolution and dissipation. A southerly wind supplies moisture to initiate advection fog events (AFs). Approximately -100 to -200 W m -2 of latent heat flux and -70 W m -2 of sensible heat flux during mature AFs are characterized with stable stratification which maintains dense fog by limiting downward mixing of dryer air. Steam fogs (SFs) develop from flow of cold air over warmer water, but are normally of limited persistence. During the SFs, a northerly wind decreases the air temperature below the sea surface temperature, which increases the relative humidity through evaporation from the warmer ocean. During mature SF, 360 W m -2 of latent heat flux and 150 W m -2 of sensible heat flux are characterized with neutral and unstable atmospheric conditions. The increase in wind speed and wind shear mixes dry air downward to the surface and limits the duration of the SF.

Heo, Ki-Young; Ha, Kyung-Ja; Mahrt, Larry; Shim, Jae-Seol

2010-11-01

256

Build a Better Mouse: Directly-Observed Issues in Computer Use for Adults with SMI  

PubMed Central

Integrating information technology into healthcare has the potential to bring treatment to hard-to-reach people. Individuals with serious mental illness (SMI), however, may derive limited benefit from these advances in care because of lack of computer ownership and experience. To date, conclusions about the computer skills and attitudes of adults with SMI have been based primarily on self-report. In the current study, 28 psychiatric outpatients with co-occurring cocaine use were interviewed about their computer use and opinions, and 25 were then directly observed using task analysis and think aloud methods as they navigated a multi-component health informational website. Participants reported low rates of computer ownership and use, and negative attitudes towards computers. Self-reported computer skills were higher than demonstrated in the task analysis. However, some participants spontaneously expressed more positive attitudes and greater computer self-efficacy after navigating the website. Implications for increasing access to computer-based health information are discussed. PMID:22711454

Black, Anne C.; Serowik, Kristin L.; Schensul, Jean J.; Bowen, Anne M.; Rosen, Marc I.

2014-01-01

257

Directly observed treatment, short-course strategy and multidrug-resistant tuberculosis: are any modifications required?  

PubMed Central

Multidrug-resistant tuberculosis (MDRTB) should be defined as tuberculosis with resistance to at least isoniazid and rifampicin because these drugs are the cornerstone of short-course chemotherapy, and combined isoniazid and rifampicin resistance requires prolonged treatment with second-line agents. Short-course chemotherapy is a key ingredient in the tuberculosis control strategy known as directly observed treatment, short-course (DOTS). For populations in which multidrug-resistant tuberculosis is endemic, the outcome of the standard short-course chemotherapy regimen remains uncertain. Unacceptable failure rates have been reported and resistance to additional agents may be induced. As a consequence there have been calls for well-functioning DOTS programmes to provide additional services in areas with high rates of multidrug-resistant tuberculosis. These "DOTS-plus for MDRTB programmes" may need to modify all five elements of the DOTS strategy: the treatment may need to be individualized rather than standardized; laboratory services may need to provide facilities for on-site culture and antibiotic susceptibility testing; reliable supplies of a wide range of expensive second-line agents would have to be supplied; operational studies would be required to determine the indications for and format of the expanded programmes; financial and technical support from international organizations and Western governments would be needed in addition to that obtained from local governments. PMID:10743297

Bastian, I.; Rigouts, L.; Van Deun, A.; Portaels, F.

2000-01-01

258

Directly Observing the Motion of DNA Molecules near Solid-State Nanopores  

PubMed Central

We investigate the diffusion and the drift motion of ? DNA molecules near solid-state nanopores prior to their translocation though the nanopores using fluorescence microscopy. The radial dependence of the electric field near a nanopore generated by an applied voltage in ionic solution can be estimated quantitatively in 3D by analyzing the motion of negatively charged DNA molecules. We find that the electric field is approximately spherically symmetric around the nanopore under the conditions investigated. In addition, DNA clogging at the nanopore was directly observed. Surprisingly, the probability of the clogging event increases with increasing external bias voltage. We also find that DNA molecules clogging the nanopore reduce the electric field amplitude at the nanopore membrane surface. To better understand these experimental results, analytical method with Ohm’s law and computer simulation with Poisson and Nernst-Planck (PNP) equations are used to calculate the electric field near the nanopore. These results are of great interest in both experimental and theoretical considerations of the motion of DNA molecules near voltage-biased nanopores. These findings will also contribute to the development of solid-state nanopore based DNA sensing devices. PMID:23046052

Ando, Genki; Hyun, Changbae; Li, Jiali; Mitsui, Toshiyuki

2012-01-01

259

Direct observation of stick-slip movements of water nanodroplets induced by an electron beam  

PubMed Central

Dynamics of the first few nanometers of water at the interface are encountered in a wide range of physical, chemical, and biological phenomena. A simple but critical question is whether interfacial forces at these nanoscale dimensions affect an externally induced movement of a water droplet on a surface. At the bulk-scale water droplets spread on a hydrophilic surface and slip on a nonwetting, hydrophobic surface. Here we report the experimental description of the electron beam-induced dynamics of nanoscale water droplets by direct imaging the translocation of 10- to 80-nm-diameter water nanodroplets by transmission electron microscopy. These nanodroplets move on a hydrophilic surface not by a smooth flow but by a series of stick-slip steps. We observe that each step is preceded by a unique characteristic deformation of the nanodroplet into a toroidal shape induced by the electron beam. We propose that this beam-induced change in shape increases the surface free energy of the nanodroplet that drives its transition from stick to slip state. PMID:22517747

Mirsaidov, Utkur M.; Zheng, Haimei; Bhattacharya, Dipanjan; Casana, Yosune; Matsudaira, Paul

2012-01-01

260

Direct observation of stick-slip movements of water nanodroplets induced by an electron beam.  

PubMed

Dynamics of the first few nanometers of water at the interface are encountered in a wide range of physical, chemical, and biological phenomena. A simple but critical question is whether interfacial forces at these nanoscale dimensions affect an externally induced movement of a water droplet on a surface. At the bulk-scale water droplets spread on a hydrophilic surface and slip on a nonwetting, hydrophobic surface. Here we report the experimental description of the electron beam-induced dynamics of nanoscale water droplets by direct imaging the translocation of 10- to 80-nm-diameter water nanodroplets by transmission electron microscopy. These nanodroplets move on a hydrophilic surface not by a smooth flow but by a series of stick-slip steps. We observe that each step is preceded by a unique characteristic deformation of the nanodroplet into a toroidal shape induced by the electron beam. We propose that this beam-induced change in shape increases the surface free energy of the nanodroplet that drives its transition from stick to slip state. PMID:22517747

Mirsaidov, Utkur M; Zheng, Haimei; Bhattacharya, Dipanjan; Casana, Yosune; Matsudaira, Paul

2012-05-01

261

Direct microscopic observation of localized protein bindings in topographically patterned lipid rafts  

NASA Astrophysics Data System (ADS)

Signal transductions through binding of ligands to cell membrane receptors are the most fundamental way of cell-to-cell communications in multicellular organisms. Important classes of the cell membrane receptors are predominantly concentrated at the phase-separated domains of membranes, the lipid rafts. By localizing lipid rafts at predetermined sites on membranes, cells control the distribution of the ligand bindings to membrane receptors, thereby manipulating the position and intensity of the signal transductions. Thus, prescribed localization of lipid rafts in model membranes could become an important biomimetic methodology of studying cell-to-cell signaling and its engineering in laboratory environments. Here, we demonstrate that topographical nano structures incorporated in supported membranes control the organization processes of lipid rafts; formation, growth, and clustering, by generating elastic energy barriers. We made direct microscopic observations of localized protein bindings in topographically patterned lipid rafts that were prepared by micro-fabrication and nano-corrugation technologies. This topographical concept of controlling the distribution of ligand-membrane receptor binding processes, not disrupting the integral structure of lipid membranes, should provide a viable platform to study human diseases and drug delivery systems.

Yoon, Tae-Young; Kim, Joon Heon

2005-03-01

262

Direct observation of turbulent magnetic fields in hot, dense laser produced plasmas  

PubMed Central

Turbulence in fluids is a ubiquitous, fascinating, and complex natural phenomenon that is not yet fully understood. Unraveling turbulence in high density, high temperature plasmas is an even bigger challenge because of the importance of electromagnetic forces and the typically violent environments. Fascinating and novel behavior of hot dense matter has so far been only indirectly inferred because of the enormous difficulties of making observations on such matter. Here, we present direct evidence of turbulence in giant magnetic fields created in an overdense, hot plasma by relativistic intensity (1018W/cm2) femtosecond laser pulses. We have obtained magneto-optic polarigrams at femtosecond time intervals, simultaneously with micrometer spatial resolution. The spatial profiles of the magnetic field show randomness and their k spectra exhibit a power law along with certain well defined peaks at scales shorter than skin depth. Detailed two-dimensional particle-in-cell simulations delineate the underlying interaction between forward currents of relativistic energy “hot” electrons created by the laser pulse and “cold” return currents of thermal electrons induced in the target. Our results are not only fundamentally interesting but should also arouse interest on the role of magnetic turbulence induced resistivity in the context of fast ignition of laser fusion, and the possibility of experimentally simulating such structures with respect to the sun and other stellar environments. PMID:22566660

Mondal, Sudipta; Narayanan, V.; Ding, Wen Jun; Lad, Amit D.; Hao, Biao; Ahmad, Saima; Wang, Wei Min; Sheng, Zheng Ming; Sengupta, Sudip; Kaw, Predhiman; Das, Amita; Kumar, G. Ravindra

2012-01-01

263

Direct spectroscopic observation of ion deceleration accompanying laser plasma-wall interaction  

NASA Astrophysics Data System (ADS)

Interactions of plasma jets with solid surfaces are extensively studied in context with development of future fusion devices. In experiments carried out on the iodine laser system PALS, the energetic ions were produced at double-foil Al/Mg targets irradiated by one or two counter-propagating laser beams. The plasma jets from the rear surface of the laser-exploded Al foil streamed towards the Mg target representing the wall preheated by the action of the high-energy photons, particle and/or laser beams. Instead of being trapped by the cold secondary-target material, the forward-accelerated Al ions collided with the counter-propagating matter ejected from the wall. The environmental conditions in near-wall plasmas were analyzed with the high-resolution x-ray spectroscopy and temporally-resolved x-ray imaging. The deceleration of the incident Al ions in the near-wall region was directly observed and quantitatively characterized via Doppler shifts of the J-satellite from the Al Lya spectral group. The interaction scenario was modelled using the 2D arbitrary Lagrangian Eulerian hydrocode PALE and the multifluid code MULTIF.

Renner, O.; Krouský, E.; Liska, R.; Šmíd, M.; Larroche, O.; Dalimier, E.; Rosmej, F. B.

2010-08-01

264

Direct observation of turbulent magnetic fields in hot, dense laser produced plasmas.  

PubMed

Turbulence in fluids is a ubiquitous, fascinating, and complex natural phenomenon that is not yet fully understood. Unraveling turbulence in high density, high temperature plasmas is an even bigger challenge because of the importance of electromagnetic forces and the typically violent environments. Fascinating and novel behavior of hot dense matter has so far been only indirectly inferred because of the enormous difficulties of making observations on such matter. Here, we present direct evidence of turbulence in giant magnetic fields created in an overdense, hot plasma by relativistic intensity (10(18) W/cm(2)) femtosecond laser pulses. We have obtained magneto-optic polarigrams at femtosecond time intervals, simultaneously with micrometer spatial resolution. The spatial profiles of the magnetic field show randomness and their k spectra exhibit a power law along with certain well defined peaks at scales shorter than skin depth. Detailed two-dimensional particle-in-cell simulations delineate the underlying interaction between forward currents of relativistic energy "hot" electrons created by the laser pulse and "cold" return currents of thermal electrons induced in the target. Our results are not only fundamentally interesting but should also arouse interest on the role of magnetic turbulence induced resistivity in the context of fast ignition of laser fusion, and the possibility of experimentally simulating such structures with respect to the sun and other stellar environments. PMID:22566660

Mondal, Sudipta; Narayanan, V; Ding, Wen Jun; Lad, Amit D; Hao, Biao; Ahmad, Saima; Wang, Wei Min; Sheng, Zheng Ming; Sengupta, Sudip; Kaw, Predhiman; Das, Amita; Kumar, G Ravindra

2012-05-22

265

Direct Observation of Reversible Electronic Energy Transfer Involving an Iridium Center  

PubMed Central

A cyclometalated iridium complex is reported where the core complex comprises naphthylpyridine as the main ligand and the ancillary 2,2?-bipyridine ligand is attached to a pyrene unit by a short alkyl bridge. To obtain the complex with satisfactory purity, it was necessary to modify the standard synthesis (direct reaction of the ancillary ligand with the chloro-bridged iridium dimer) to a method harnessing an intermediate tetramethylheptanolate-based complex, which was subjected to acid-promoted removal of the ancillary ligand and subsequent complexation. The photophysical behavior of the bichromophoric complex and a model complex without the pendant pyrene were studied using steady-state and time-resolved spectroscopies. Reversible electronic energy transfer (REET) is demonstrated, uniquely with an emissive cyclometalated iridium center and an adjacent organic chromophore. After excited-state equilibration is established (5 ns) as a result of REET, extremely long luminescence lifetimes of up to 225 ?s result, compared to 8.3 ?s for the model complex, without diminishing the emission quantum yield. As a result, remarkably high oxygen sensitivity is observed in both solution and polymeric matrices. PMID:24555716

2014-01-01

266

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

267

Observation of directional exitance and retrieval of soil and foliage component temperatures: case studies with biangular ATSR radiometric data  

Microsoft Academic Search

A mixture of foliage and soil is thermally heterogeneous, so the radiometric temperature of the mixture depends on view direction. A simple linear mixture model was applied to estimate the component surface temperatures of foliage and soil temperatures. The potential of directional observations in the thermal infrared region for land surface studies is a largely uncharted area of research. The

Li Jia; Massimo Menenti; Zhongbo Su; Zhao-Liang Li

2002-01-01

268

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

269

Drainage of single Plateau borders: Direct observation of rigid and mobile interfaces Stephan A. Koehler,1,3  

E-print Network

Drainage of single Plateau borders: Direct observation of rigid and mobile interfaces Stephan A drainage varies with surfactant. We present direct measurements of the flow velocity profiles across single importance of surface rheology on the drainage behavior. DOI: 10.1103/PhysRevE.66.040601 PACS number s : 68

Weeks, Eric R.

270

Direct observation of ferroelectric domain switching in varying electric field regimes using in situ TEM.  

PubMed

In situ Transmission Electron Microscopy (TEM) techniques can potentially fill in gaps in the current understanding interfacial phenomena in complex oxides. Select multiferroic oxide materials, such as BiFeO(3) (BFO), exhibit ferroelectric and magnetic order, and the two order parameters are coupled through a quantum-mechanical exchange interaction. The magneto-electric coupling in BFO allows control of the ferroelectric and magnetic domain structures via applied electric fields. Because of these unique properties, BFO and other magneto-electric multiferroics constitute a promising class of materials for incorporation into devices such as high-density ferroelectric and magnetoresistive memories, spin valves, and magnetic field sensors. The magneto-electric coupling in BFO is mediated by volatile ferroelastically switched domains that make it difficult to incorporate this material into devices. To facilitate device integration, an understanding of the microstructural factors that affect ferroelastic relaxation and ferroelectric domain switching must be developed. In this article, a method of viewing ferroelectric (and ferroelastic) domain dynamics using in situ biasing in TEM is presented. The evolution of ferroelastically switched ferroelectric domains in BFO thin films during many switching cycles is investigated. Evidence of partial domain nucleation, propagation, and switching even at applied electric fields below the estimated coercive field is revealed. Our observations indicate that the occurrence of ferroelastic relaxation in switched domains and the stability of these domains is influenced the applied field as well as the BFO microstructure. These biasing experiments provide a real time view of the complex dynamics of domain switching and complement scanning probe techniques. Quantitative information about domain switching under bias in ferroelectric and multiferroic materials can be extracted from in situ TEM to provide a predictive tool for future device development. PMID:22459251

Winkler, C R; Damodaran, A R; Karthik, J; Martin, L W; Taheri, M L

2012-11-01

271

Direct nano-scale observations of CO2 sequestration during brucite (Mg(OH)2) dissolution  

NASA Astrophysics Data System (ADS)

Mineralization of CO2 is regarded as the safest and most permanent option for carbon sequestration (e.g., O'Connor et al. 2005). So far, research has been concentrated on the carbonation of silicates such as olivine ((Mg,Fe)2SiO4) and serpentine (Mg3Si2O5(OH)4). However, also the less common hydroxide mineral brucite (Mg(OH)2) has recently become a focus of interest, owing to its much higher reactivity relative to silicate minerals at low temperature and P CO2 conditions(e.g., Zhao et al. 2010; Schaef et al. 2011). Utilization of brucite for carbon sequestration requires an in-depth understanding of the associated reaction mechanisms from the macro- to the nano-scale. Therefore, we have conducted a series of in-situ and ex-situ Atomic Force Microscopy (AFM) experiments enabling direct nano-scale observations of dissolution and precipitation features on brucite (001) cleavage surfaces. In particular, we tested the effects of pH (2-12), aqueous NaHCO3 concentration (1?M - 1M) and P CO2 (0-1 bar) on brucite dissolution and carbonation. Brucite dissolution proceeded by the formation and spreading of etch pits with equilateral triangular shapes. Measured etch pit spreading rates increased with decreasing pH (from 0.030±0.008 nm/s at pH 9 to 0.70±0.07 nm/s at pH 2) and increasing NaHCO3 concentration (from 0.038±0.004 nm/s in 1?M to 0.38±0.07 nm/s in 1M solution). In pure NaHCO3 solutions (pH 7.2-9.3) secondary phase precipitation was relatively minor. Enhanced precipitation was observed in slightly acidified NaHCO3 solutions (pH 5) as well as in solutions that were equilibrated with 1 bar CO2 (pH 4). Nucleation predominantly occurred in areas of high dissolution such as larger step edges. Initially, nucleating particles were only 1-2 nm and weakly attached to the brucite surface as they could be easily pushed away by the scanning tip during in-situ AFM experiments. Growth of the particles was observed after ex-situ AFM experiments lasting for several hours. The size of individual particles increased to about 100 nm within 16 h. Lateral spreading of the particles was rather limited. Instead, we observed the formation of particle clusters reaching total heights of up to 1 ?m after 32 h. SEM-EDX investigations confirmed that the precipitate is an Mg-rich carbonate phase (probably hydromagnesite). Our results contribute to an improved understanding of the mechanism of aqueous brucite carbonation at low temperature and P CO2 conditions and to a further understanding of carbonation reactions in general.

Hövelmann, J.; Putnis, C. V.; Austrheim, H.; Ruiz-Agudo, E.

2012-04-01

272

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

273

The New Worlds Observer: An Optimal Path to Direct Study of Earth-like Planets  

NASA Astrophysics Data System (ADS)

Direct detection and spectroscopic study of the planets around the nearby stars is generally recognized as a prime goal of astronomy. The New Worlds Observer mission concept is being studied as an Astrophysics Strategic Mission Concept Study for this purpose. NWO features two spacecraft: a general purpose 4m telescope that operates from the UV to the Near IR, and a starshade, a flower-shaped occulter about 50m in diameter flying in alignment about 70,000km away. Our study shows this is the most effective way to map nearby planetary systems. In this poster we will show that NWO can return much more science than any of the competing approaches at any given price point. Images will show dust and debris down to a fraction of our zodiacal light level. Planets fainter than the Earth can be seen from the Habitable Zone outward, at distances up to 20pc. High throughput and low noise enable immediate follow-up spectroscopy of discovered planets. NWO can discover many more Earth-like planets than all competing approaches including astrometric, interferometric, and internal coronagraphic. Within hours of discovery, a high quality spectrum can determine the true nature of the exoplanet and open the search for biomarkers and life. Over half of the time will be spent with the starshade in transit to the next target. During those times the telescope will be available to for general astrophysics purposes. Operating from the ultraviolet to the near infrared, this will be a true HST follow-on. The study shows all needed technologies already exist. The cost scales primarily with telescope size. The mission is definitely within the financial and technical reach of NASA for the coming decade.

Cash, Webster C., Jr.; New Worlds Study Team

2009-01-01

274

The New Worlds Observer: Direct Detection and Study of Exoplanets from the Habitable Zone Outward  

NASA Astrophysics Data System (ADS)

Direct detection and spectroscopic study of the planets around the nearby stars is generally recognized as a prime goal of astronomy. The New Worlds Observer mission concept is being studied as an Astrophysics Strategic Mission Concept Study for this purpose. NWO features two spacecraft: a general purpose 4m telescope that operates from the UV to the Near IR, and a starshade, a flower-shaped occulter about 50m in diameter flying in alignment about 70,000km away. Our study shows this is the most effective way to map nearby planetary systems. Images will show dust and debris down to a fraction of our zodiacal light level. Planets fainter than the Earth can be seen from the Habitable Zone outward, at distances up to 20pc. High throughput and low noise enable immediate follow-up spectroscopy of discovered planets. NWO can discover many more Earth-like planets than all competing approaches including astrometric, interferometric, and internal coronagraphic. Within hours of discovery, a high quality spectrum can determine the true nature of the exoplanet and open the search for biomarkers and life. Over half of the time will be spent with the starshade in transit to the next target. During those times the telescope will be available to for general astrophysics purposes. Operating from the ultraviolet to the near infrared, this will be a true HST follow-on. The study shows all needed technologies already exist. The cost scales primarily with telescope size. The mission is definitely within the financial and technical reach of NASA for the coming decade.

Cash, Webster C.; New Worlds Study Team

2009-01-01

275

A study of the shortwave direct aerosol forcing using ESSP/CALIPSO observation and GCM simulation  

NASA Astrophysics Data System (ADS)

Shortwave direct aerosol radiative forcing (DARF) is derived at the top of the atmosphere (TOA) and at the surface under clear-sky, cloudy-sky, and all-sky conditions using data of space-borne CALIOP lidar and MODIS sensor. We investigate four scenarios for evaluating the DARF: clear-sky, the case that aerosols exist above clouds, the case that aerosols exist below high-level clouds, and the case that aerosols are not detected by CALIOP in cloudy-sky condition. The cloudy-sky DARF is estimated by the latter three scenarios. The all-sky DARF is the combination of clear-sky and cloudy-sky DARF weighted by the cloud occurrence. They are then compared with DARF calculated by a global aerosol model, SPRINTARS. The results show that the TOA forcing over desert regions caused by dust with single scattering albedo (SSA) of 0.92 is positive regardless of cloud existence, due to high solar surface albedo. Off southern Africa, smoke aerosols with SSA of 0.84 above low-level clouds are observed and simulated and the annual mean TOA cloudy-sky DARF is estimated at more than +3 Wm-2, consistent with past studies. Aerosols with SSA of 0.96 within optically thin clouds cause a TOA negative forcing, while that within optically thick clouds cause a TOA positive forcing. This indicates that aerosols within optically thick clouds cause positive forcing in our radiative transfer calculation, regardless of SSA. Annual zonal averages of DARF from 60°S to 60°N under clear-sky, cloudy-sky, and all-sky are -2.97, +0.07, and -0.61 Wm-2 from CALIOP and -2.78, +1.07, and -0.58 Wm-2 from SPRINTARS.

Oikawa, Eiji; Nakajima, Teruyuki; Inoue, Toshiro; Winker, David

2013-05-01

276

Lattice Boltzmann simulation and direct observation of pore fluid flow around irregularly shaped grains  

NASA Astrophysics Data System (ADS)

An accurate velocity model of porous flow plays an important role in the prediction of the ground water pollution.To clarify the behavior of porous flow passing through irregularly shaped grains, we have been performed CFD simulation and direct observation based on the Lattice Boltzmann Method and the LAT-PIV visuallization technique respectively. The Lattice Boltzmann simulator, which works on a graphics processing unit(GPU), is employed to evaluate the pore fluid velocity distribution in an accurate three dimensional digital model involving Toyoura sand. From the simulation results, the pore fluid velocity distributions converge into a unique non-gaussian distribution under various Reynolds numbers ranging from 2 to 10. The features of the non-gaussian distribution are summarized as follows: (1)It has a long tail until sextuple of the mean velocity magnitude. (2)It has a peak frequency close to zero velocity magnitude. (3)It slightly contains negative velocities. The LAT-PIV visuallization technique, a kind of laser slicing visualization method combined LAT(Laser-Aided Tomography) and PIV (Particle Image Velocimetry), visualizes both grain edges and pore fluid behavior inside specimen which is composed of crashed glass grains and specially blended silicone oil. The pore fluid velocity distributions captured by the LAT-PIV images indicate a similar tendency compared with those measured by the LBM simulations. This supports that the LBM simulation has sufficient ability to predict the pore fluid flow even if the porous medium is composed of irregularly shaped grains. GPU accelerated LBM simulation for Toyoura sand model Pore fluid velocity magnitude distributions for several Reynolds numbers

Saomoto, H.; Kase, Y.; Matsushima, T.; Yamada, Y.

2012-12-01

277

Direct observation of substitutional Au atoms in SrTi O3  

NASA Astrophysics Data System (ADS)

Ion implantation and subsequent high-temperature annealing is an effective way to prepare metal nanoclusters dispersed in a dielectric for useful optical and electrical properties. However, there is very little understanding of the nucleation and growth process of these nanoclusters, their correlations with the sites of the implanted ions, and the behavior of defects (such as vacancies) generated during the ion-implantation process. Using high-angle annular dark-field imaging in aberration-corrected scanning transmission electron microscopy, we have directly observed that, at a dilute concentration, Au atoms implanted in SrTiO3 are in a substitutional lattice position for both Sr and Ti. The congregation of Au atoms by diffusion to a critical concentration leads to the nucleation of an Au lattice within the SrTiO3 . The Au nanocluster and SrTiO3 were found to maintain an orientation relationship of Au[001]//SrTiO3[001] and Au(100)//SrTiO3(100) , which corroborated the results of a first-principles total-energy calculation. The interface between the Au cluster and SrTiO3 was bridged by an O/Ti plane. The Au-O bond length was found to be 2.2Å , which is the same as the Au-O bond length in AuO. Furthermore, the atomic planes adjacent to the interface in both Au and SrTiO3 were found to be slightly stretched. The high concentration of vacancies generated during the Au implantation aggregated to form cavities in the SrTiO3 lattice, and were faceted mostly along the SrTiO3 {100} and (110) planes. The Au and vacancy clusters were spatially associated, indicating a strong interaction. Thus, the formation of cavities in Au-implanted materials indicates that the vacancy-clustering process prevails over the Frenkel-pair recombination.

Wang, C. M.; Shutthanandan, V.; Zhang, Y.; Thevuthasan, S.; Duscher, G.

2004-11-01

278

Identification of an androgen response element in intron 8 of the sterol regulatory element-binding protein cleavage-activating protein gene allowing direct regulation by the androgen receptor.  

PubMed

Sterol regulatory element-binding proteins (SREBPs) are transcription regulators that play a pivotal role in intracellular lipid homeostasis. They are synthesized as inactive precursor proteins in the endoplasmic reticulum, where they are retained by SREBP cleavage-activating protein (SCAP), a sterol sensing protein that in turn is linked to a retention protein complex. Low intracellular sterol concentrations weaken the interaction of SCAP with its retention proteins and allow translocation of the SREBP.SCAP complex to the Golgi compartment where SREBP is proteolytically cleaved and activated. Previous studies on the mechanisms by which androgens provoke a coordinated activation of lipogenic pathways in prostate cancer cells have suggested an alternative pathway of activation in which androgens increase the expression of SCAP and favor translocation of the SREBP.SCAP complex to the Golgi apparatus by disturbing the balance between SCAP and its retention proteins. Here we show that the SCAP gene contains an androgen-responsive region located in intron 8. This region interacts directly with the androgen receptor and confers androgen responsiveness to promoter-reporter constructs transfected in LNCaP cells. It contains a noncanonical androgen response element GGAAGAaaaTGTACC that interacts not only with the androgen receptor but also with the glucocorticoid receptor and that also confers glucocorticoid responsiveness. The identification of a steroid response element in intron 8 of the SCAP gene further supports the contention that SCAP is a direct target for steroid hormone action. PMID:15133039

Heemers, Hannelore; Verrijdt, Guy; Organe, Sophie; Claessens, Frank; Heyns, Walter; Verhoeven, Guido; Swinnen, Johannes V

2004-07-16

279

Hand Hygiene Practices among Nursing Staff in Public Secondary Care Hospitals in Kuwait: Self-Report and Direct Observation  

Microsoft Academic Search

Objective: To assess the compliance with hand hygiene guidelines among nursing staff in secondary care hospitals in Kuwait. Subjects and Methods: A cross-sectional study was conducted through direct observation using the Lewisham observation tool and self-administered questionnaire in six major public secondary care hospitals in Kuwait. Only patient care activities that are described as ‘dirty contacts’ by the Fulkerson scale

Batool Al-Wazzan; Yasmeen Salmeen; Eisa Al-Amiri; Ala’a Abul; Manal Bouhaimed; Abdullah Al-Taiar

2011-01-01

280

49 CFR 40.67 - When and how is a directly observed collection conducted?  

Code of Federal Regulations, 2012 CFR

...must ensure that the observer is the same gender as the employee. You must never permit an opposite gender person to act as the observer. The observer...e.g., in order to ensure a same gender observer), you must verbally...

2012-10-01

281

49 CFR 40.67 - When and how is a directly observed collection conducted?  

Code of Federal Regulations, 2011 CFR

...must ensure that the observer is the same gender as the employee. You must never permit an opposite gender person to act as the observer. The observer...e.g., in order to ensure a same gender observer), you must verbally...

2011-10-01

282

49 CFR 40.67 - When and how is a directly observed collection conducted?  

Code of Federal Regulations, 2013 CFR

...must ensure that the observer is the same gender as the employee. You must never permit an opposite gender person to act as the observer. The observer...e.g., in order to ensure a same gender observer), you must verbally...

2013-10-01

283

Direct observation of the glue pairing the halo of the nucleus 11Li  

E-print Network

With the help of a unified description of the nuclear structure and of the direct reaction mechanism we show that a recent 1H(11Li,9Li)3H experiment provides, for the first time in nuclear physics, direct evidence of phonon mediated pairing.

G. Potel; F. Barranco; E. Vigezzi; R. A. Broglia

2009-12-04

284

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

285

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

286

The implementation of a mobile problem-specific electronic CEX for assessing directly observed student--patient encounters  

PubMed Central

Background Facilitating direct observation of medical students' clinical competencies is a pressing need. Methods We developed an electronic problem-specific Clinical Evaluation Exercise (eCEX) based on a national curriculum. We assessed its feasibility in monitoring and recording students' competencies and the impact of a grading incentive on the frequency of direct observations in an internal medicine clerkship. Students (n = 56) at three clinical sites used the eCEX and comparison students (n = 56) at three other clinical sites did not. Students in the eCEX group were required to arrange 10 evaluations with faculty preceptors. Students in the second group were required to document a single, faculty observed ‘Full History and Physical’ encounter with a patient. Students and preceptors were surveyed at the end of each rotation. Results eCEX increased students' and evaluators' understanding of direct-observation objectives and had a positive impact on the evaluators' ability to provide feedback and assessments. The grading incentive increased the number of times a student reported direct observation by a resident preceptor. Conclusions eCEX appears to be an effective means of enhancing student evaluation. PMID:20174616

Ferenchick, Gary S.; Foreback, Jami; Towfiq, Basim; Kavanaugh, Kevin; Solomon, David; Mohmand, Asad

2010-01-01

287

10 CFR 26.115 - Collecting a urine specimen under direct observation.  

Code of Federal Regulations, 2013 CFR

...observer shall instruct the donor to adjust his or her clothing to ensure that the area of the donor's body between the waist and knees is exposed; (2) The observer shall watch the donor urinate into the collection container. Specifically, the...

2013-01-01

288

10 CFR 26.115 - Collecting a urine specimen under direct observation.  

...observer shall instruct the donor to adjust his or her clothing to ensure that the area of the donor's body between the waist and knees is exposed; (2) The observer shall watch the donor urinate into the collection container. Specifically, the...

2014-01-01

289

DIRECT OBSERVATIONS OF CHILDREN AT RISK FOR ACADEMIC FAILURE: BENEFITS OF AN INTERGENERATIONAL VISITING PROGRAM  

Microsoft Academic Search

Ten elementary school students in need of a positive self-image and\\/or a sense of appropriate social conduct took part in a monthly intergenerational visiting program at an assisted living facility. In comparison to systematic observations obtained in their classrooms, the children were observed to be significantly less anxious, more interested, and participating more during the intergenerational program. Outcomes of a

S. Marx Marcia; R. Pannell Alicia; Aleksandra Parpura-Gill; Jiska Cohen-Mansfield

2004-01-01

290

Direct observation of the microstructure and defects in KBe2BO3F2 crystals by TEM.  

PubMed

We apply for the first time transmission electron microscopy to the direct observation of the deep-UV nonlinear optical crystal KBe2BO3F2 (KBBF) grown using different methods. Two kinds of electron diffraction patterns were observed in the hydrothermally synthesized KBBF along the [120] direction, which resulted from the coexistence of two structures with space groups R32 and R3[combining macron]c. As a comparison, the flux grown KBBF crystals show uniform R32 structures. Furthermore we observed a twin boundary in flux KBBF which corresponds to the (21[combining macron]3)R32 crystallographic plane. Two structure models are proposed here for the twin boundary. These observations on the microstructure and defects were not disclosed in previous powder XRD and optical microscopy experiments and shed new light on the understanding of the structure and defects of KBBF crystals. PMID:25247734

Xu, Tao; Liu, Lijuan; Wang, Xiaoyang; Chen, Chuangtian; Zhou, Haitao; He, Xiaoling; Zhang, Changlong; Sun, Junliang

2014-10-14

291

Direct Behavior Rating (DBR): Generalizability and Dependability across Raters and Observations  

ERIC Educational Resources Information Center

Generalizability theory was used to examine the generalizability and dependability of outcomes from two single-item Direct Behavior Rating (DBR) scales: DBR of actively manipulating and DBR of visually distracted. DBR is a behavioral assessment tool with specific instrumentation and procedures that can be used by a variety of service delivery…

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

2010-01-01

292

Ocean wave directional spectra estimation from an HF ocean radar with a single antenna array: Observation  

Microsoft Academic Search

A method of estimating ocean wave directional spectra using a]high-frequency (HF) radar with a single antenna array was applied to actual ocean data. This method incorporates the wave energy balance equation and the continuity equation of wind vectors into the inversion method to solve the integral equation which relates a Doppler spectrum to wave spectra. This method uses dynamic extrapolation

Yukiharu Hisaki

2005-01-01

293

Participant observation of time allocation, direct patient contact and simultaneous activities in hospital physicians  

Microsoft Academic Search

BACKGROUND: Hospital physicians' time is a critical resource in medical care. Two aspects are of interest. First, the time spent in direct patient contact – a key principle of effective medical care. Second, simultaneous task performance ('multitasking') which may contribute to medical error, impaired safety behaviour, and stress. There is a call for instruments to assess these aspects. A preliminary

Matthias Weigl; Andreas Müller; Andrea Zupanc; Peter Angerer

2009-01-01

294

DIRECT OBSERVATIONAL EVIDENCE OF FILAMENT MATERIAL WITHIN INTERPLANETARY CORONAL MASS EJECTIONS  

SciTech Connect

Coronal mass ejections (CMEs) are explosive events that escape the Sun's corona carrying solar material and energy into the heliosphere. The classic picture of a CME observed in the corona presents a 'three-part structure', including a bright front at the leading edge indicating dense plasma, a low-density cavity, the possible signature of an embedded magnetic flux rope, and the so-called core, a high-density region observed to be associated with an erupting filament. Although there are experimental analogs to the first two parts of the CME when observed in situ, there are only a handful of in situ observations of cold, filament-type plasma. This has been a source of major uncertainty and qualitative disagreement between remote and in situ observations of these ejecta. We present the first comprehensive and long-term survey of such low charge states observed by the Advanced Composition Explorer Solar Wind Ion Composition Spectrometer, using a novel data analysis process developed to identify ions with low ionic charge states. Using a very stringent set of observational signatures, we find that more than 4% of detected interplanetary CMEs have significant contributions of ions with low charge states. These time periods of low-charge ions often occur concurrent with some of the hottest ions, previously interpreted to be affected by flare heating during the CME initiation.

Lepri, S. T.; Zurbuchen, T. H., E-mail: slepri@umich.ed, E-mail: thomasz@umich.ed [Department of Atmospheric, Oceanic, and Space Sciences University of Michigan, Ann Arbor, MI 48109-2143 (United States)

2010-11-01

295

Direct observation of lattice constant variations depending on layer structures in an InGaN\\/GaN MQW LED  

Microsoft Academic Search

We have directly observed that InGaN quantum well layers were incoherently grown on 5-nm-thick GaN barrier layers in an InGaN\\/GaN multiple quantum well (MQW) system of a blue light-emitting diode by using a lattice image obtained by high-resolution transmission electron microscopy and fast Fourier transform mapping (FFTM) analysis of the lattice image. The lattice disorder was observed in the middle

Shigeya Kimura; Koichi Tachibana; Toshiyuki Oka; Hajime Nago; Hisashi Yoshida; Shinya Nunoue

2011-01-01

296

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

297

OBSERVATIONAL EVIDENCE OF A CORONAL MASS EJECTION DISTORTION DIRECTLY ATTRIBUTABLE TO A STRUCTURED SOLAR WIND  

SciTech Connect

We present the first observational evidence of the near-Sun distortion of the leading edge of a coronal mass ejection (CME) by the ambient solar wind into a concave structure. On 2007 November 14, a CME was observed by coronagraphs onboard the STEREO-B spacecraft, possessing a circular cross section. Subsequently the CME passed through the field of view of the STEREO-B Heliospheric Imagers where the leading edge was observed to distort into an increasingly concave structure. The CME observations are compared to an analytical flux rope model constrained by a magnetohydrodynamic solar wind solution. The resultant bimodal speed profile is used to kinematically distort a circular structure that replicates the initial shape of the CME. The CME morphology is found to change rapidly over a relatively short distance. This indicates an approximate radial distance in the heliosphere where the solar wind forces begin to dominate over the magnetic forces of the CME influencing the shape of the CME.

Savani, N. P.; Owens, M. J.; Forsyth, R. J. [The Blackett Laboratory, Imperial College London, London (United Kingdom); Rouillard, A. P. [College of Science, George Mason University, Fairfax, VA 22030 (United States); Davies, J. A. [Space Science and Technology Department, Rutherford Appleton Laboratory, Didcot (United Kingdom)], E-mail: neel.savani02@imperial.ac.uk

2010-05-01

298

Instrumentation for direct observation of frozen hydrated specimens in the electron microscope.  

PubMed

Instrumentation and techniques are described for the transfer and observation of frozen hydrated specimens in the transmission electron microscope. The transfer is accomplished without the complexity of a vacuum transfer device but also without significant sublimation of specimen ice or frosting. Examples are given of the transfer and observation of thin sections of rapidly frozen muscle and of rapidly frozen thin film preparations of isolated cells. PMID:734786

Hutchinson, T E; Johnson, D E; MacKenzie, A P

1978-01-01

299

Analyzing the contribution of aerosols to an observed increase in direct normal irradiance in Oregon  

SciTech Connect

Annual average total irradiance increases by 1-2% per decade at three monitoring stations in Oregon over the period from 1980 to 2007. Direct normal irradiance measurements increase by 5% per decade over the same time period. The measurements show no sign of a dimming before 1990. Clear-sky periods from this long direct normal time series are used in conjunction with radiative transfer calculations to look for changes in anthropogenic aerosols. Stratospheric aerosols from the volcanic eruptions of El Chichon and Mt. Pinatubo are clearly seen in the measurements. The period from 1987 to 2007 shows no detectable change in aerosols not explained by the volcanic aerosols. All three sites show relatively low clear-sky measurements before the eruption of El Chichon in 1982, suggesting higher aerosol loads during this period.

Riihimaki, L. D.; Vignola, F.; Long, Charles N.

2009-01-22

300

DIRECT OBSERVATION OF THE TURBULENT emf AND TRANSPORT OF MAGNETIC FIELD IN A LIQUID SODIUM EXPERIMENT  

SciTech Connect

For the first time, we have directly measured the transport of a vector magnetic field by isotropic turbulence in a high Reynolds number liquid metal flow. In analogy with direct measurements of the turbulent Reynolds stress (turbulent viscosity) that governs momentum transport, we have measured the turbulent electromotive force (emf) by simultaneously measuring three components of velocity and magnetic fields, and computed the correlations that lead to mean-field current generation. Furthermore, we show that this turbulent emf tends to oppose and cancel out the local current, acting to increase the effective resistivity of the medium, i.e., it acts as an enhanced magnetic diffusivity. This has important implications for turbulent transport in astrophysical objects, particularly in dynamos and accretion disks.

Rahbarnia, Kian; Brown, Benjamin P.; Clark, Mike M.; Kaplan, Elliot J.; Nornberg, Mark D.; Rasmus, Alex M.; Taylor, Nicholas Zane; Forest, Cary B. [Department of Physics, University of Wisconsin-Madison, 1150 University Ave, Madison, WI 53706 (United States); Jenko, Frank; Limone, Angelo [Max-Planck-Institut fuer Plasmaphysik (IPP), EURATOM Association, D-85748 Garching (Germany); Pinton, Jean-Francois; Plihon, Nicolas; Verhille, Gautier, E-mail: kian.rahbarnia@ipp.mpg.de [Laboratoire de Physique de l'Ecole Normale Superieure de Lyon, CNRS and Universite de Lyon, F-69364 Lyon (France)

2012-11-10

301

Direct Observation of Dark Excitons in Individual Carbon Nanotubes: Inhomogeneity in the Exchange Splitting  

E-print Network

bright excitons due to the Aharonov- Bohm effect [17­19]. Previous temperature (T)-dependent magneto-optical the Aharonov-Bohm effect and intervalley Coulomb mixing. The directly measured dark-bright splitting valuesRevLett.101.087402 PACS numbers: 78.67.Ch, 71.35.Ji, 78.55.�m Optical properties of single-walled carbon

Kono, Junichiro

302

Analyzing the contribution of aerosols to an observed increase in direct normal irradiance in Oregon  

NASA Astrophysics Data System (ADS)

Annual average total irradiance increases by 1-2% per decade at three monitoring stations in Oregon over the period from 1980 to 2007. Direct normal irradiance measurements increase by 5% per decade over the same time period. The measurements show no sign of a dimming before 1990. The impact of high concentrations of stratospheric aerosols following the volcanic eruptions of El Chichón and Mount Pinatubo are clearly seen in the measurements. Removing these years from the annual average all-sky time series reduces the trends in both total and direct normal irradiance. Clear-sky periods from this long direct normal time series are used in conjunction with radiative transfer calculations to test whether part of the increase could be caused by anthropogenic aerosols. All three sites show relatively low clear-sky measurements before the eruption of El Chichón in 1982, suggesting higher aerosol loads during this period. After removing the periods most strongly impacted by volcanic eruptions, two of the sites show statistically significant increases in clear-sky direct normal irradiance from 1987 to 2007. Radiative transfer calculations of the impact of volcanic aerosols and tropospheric water vapor indicate that only about 20% of that clear-sky increase between background aerosol periods before and after the eruption of Mount Pinatubo can be explained by these two factors. Thus a statistically significant clear-sky trend remains between 1987 and 2007 that is consistent with the hypothesis that at least some of the increase in surface irradiance could be caused by a reduction of anthropogenic aerosols.

Riihimaki, L. D.; Vignola, F. E.; Long, C. N.

2009-05-01

303

Analyzing the Contribution of Aerosols to an Observed Increase in Direct Normal Irradiance in Oregon  

SciTech Connect

Annual average total irradiance increases by 1-2% per decade at three mon- itoring stations in Oregon over the period from 1980 to 2007. Direct normal irradiance measurements increase by 5% per decade over the same time pe- riod. The measurements show no sign of a dimming before 1990. The impact of high concentrations of stratospheric aerosols following the volcanic erup- tions of El Chich¶on and Mt. Pinatubo are clearly seen in the measurements. Removing these years from the annual average all-sky time series reduces the trends in both total and direct normal irradiance. Clear-sky periods from this long direct normal time series are used in conjunction with radiative trans- fer calculations to test whether part of the increase could be caused by an- thropogenic aerosols. All three sites show relatively low clear-sky measure- ments before the eruption of El Chich¶on in 1982, suggesting higher aerosol loads during this period. After removing the periods most strongly impacted by volcanic eruptions, two of the sites show statistically signi¯cant increases in clear-sky direct normal irradiance from 1987 to 2007. Radiative transfer calculations of the impact of volcanic aerosols and tropospheric water vapor indicate that only about 20% of that clear-sky increase between background aerosol periods before and after the eruption of Mt. Pinatubo can be explained by these two factors. Thus, a statistically signi¯cant clear-sky trend remains between 1987 and 2007 that is consistent with the hypothesis that at least some of the increase in surface irradiance could be caused by a reduction of anthropogenic aerosols. D

Riihimaki, Laura D.; Vignola, F.; Long, Charles N.

2009-01-22

304

An improved method for quantifying intake rate and ingestive behaviour of ruminants in diverse and variable habitats using direct observation  

Microsoft Academic Search

Using heterogeneous vegetation through grazing is a necessary component of de-intensification of livestock systems and conservation of natural environments. Better understanding of the dynamics of animal feeding behaviour is therefore needed, in particular in response to feed diversity and variability. On the basis of three on-farm experiments with ewes and goats, we improved a direct observation method that links intake

C. Agreil; M. Meuret

2004-01-01

305

Direct Observation of Nanoscale Peltier and Joule Effects at Metal-Insulator Domain Walls in Vanadium Dioxide Nanobeams  

E-print Network

localized alternating Peltier heating and cooling as well as Joule heating concentrated at the M-I domain, Joule heating, metal-insulator domain wall Strongly correlated materials share a unique feature whereDirect Observation of Nanoscale Peltier and Joule Effects at Metal- Insulator Domain Walls

Wu, Junqiao

306

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.

307

Direct observation of the alignment of ferromagnetic spins by antiferromagnetic spins  

PubMed

The arrangement of spins at interfaces in a layered magnetic material often has an important effect on the properties of the material. One example of this is the directional coupling between the spins in an antiferromagnet and those in an adjacent ferromagnet, an effect first discovered in 1956 and referred to as exchange bias. Because of its technological importance for the development of advanced devices such as magnetic read heads and magnetic memory cells, this phenomenon has received much attention. Despite extensive studies, however, exchange bias is still poorly understood, largely due to the lack of techniques capable of providing detailed information about the arrangement of magnetic moments near interfaces. Here we present polarization-dependent X-ray magnetic dichroism spectro-microscopy that reveals the micromagnetic structure on both sides of a ferromagnetic-antiferromagnetic interface. Images of thin ferromagnetic Co films grown on antiferromagnetic LaFeO3 show a direct link between the arrangement of spins in each material. Remanent hysteresis loops, recorded for individual ferromagnetic domains, show a local exchange bias. Our results imply that the alignment of the ferromagnetic spins is determined, domain by domain, by the spin directions in the underlying antiferromagnetic layer. PMID:10866191

Nolting; Scholl; Stohr; Seo; Fompeyrine; Siegwart; Locquet; Anders; Luning; Fullerton; Toney; Scheinfein; Padmore

2000-06-15

308

Observation of gravity waves by limb-viewing satellite instruments: Impact of the measuring direction on the observational-filter effect  

NASA Astrophysics Data System (ADS)

Limb-viewing satellite instruments are often used to observe atmospheric gravity waves (GW) on global scales. Derived parameters (amplitudes, wavelengths…) give information about GW activity, for example, as input for models. However, small-scale processes like GWs cannot be completely resolved by remote sensing instruments because they integrate over relatively large air volumes along their ray-of-sight, known as the observational-filter effect. Radiosonde measurements are used as reference to temperature profiles of the satellite-based instrument TIMED/SABER in order to compare signatures of present GWs in both data sets. Results show that among known aspects (e.g. the wavelengths) the measuring direction of the satellite with regard to the direction of wave propagation influences the intensity of the observational-filter effect. If GWs have a prevailing orientation in particular regions, e.g. orographic induced GWs, this leads to systematic errors in observed GW activity derived by satellite instruments. Since the wave orientation cannot be determined solely by the temperature profiles of an instrument, it is not possible to specify a general correction function for this effect. This implies a need for the development of improved techniques concerning the measuring geometry of satellite instruments.

Wendt, Verena; Wüst, Sabine; Bittner, Michael

2013-04-01

309

Direct observation of a nuclear spin excitation in Ho2Ti2O7.  

PubMed

A single nondispersive excitation is observed by means of neutron backscattering, at E_{0}=26.3 microeV in the spin ice Ho2Ti2O7 but not in the isotopically enriched 162Dy2Ti2O7 analogue. The intensity of this excitation is rather small, less, similar0.2% of the elastic intensity. It is clearly observed below 80 K but resolution limited only below approximately 65 K. The application of a magnetic field up to micro_{0}H=4.5 T, at 1.6 K, has no measurable effect on the energy or intensity. This nuclear excitation is believed to perturb the electronic, Ising spin system resulting in the persistent spin dynamics observed in spin ice compounds. PMID:19257221

Ehlers, G; Mamontov, E; Zamponi, M; Kam, K C; Gardner, J S

2009-01-01

310

Direct Observation of a Nuclear Spin Excitation in Ho2Ti2O7  

NASA Astrophysics Data System (ADS)

A single nondispersive excitation is observed by means of neutron backscattering, at E0=26.3?eV in the spin ice Ho2Ti2O7 but not in the isotopically enriched Dy2162Ti2O7 analogue. The intensity of this excitation is rather small, ?0.2% of the elastic intensity. It is clearly observed below 80 K but resolution limited only below ˜65K. The application of a magnetic field up to ?0H=4.5T, at 1.6 K, has no measurable effect on the energy or intensity. This nuclear excitation is believed to perturb the electronic, Ising spin system resulting in the persistent spin dynamics observed in spin ice compounds.

Ehlers, G.; Mamontov, E.; Zamponi, M.; Kam, K. C.; Gardner, J. S.

2009-01-01

311

Direct observations of thermally induced structural changes in amorphous silicon carbide  

NASA Astrophysics Data System (ADS)

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. It was confirmed that the structural changes observed by the in situ TEM study agree qualitatively with those of the bulk material. 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

312

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

313

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

314

Direct injection into the dorsal root ganglion: technical, behavioral, and histological observations.  

PubMed

Direct injection of agents into the dorsal root ganglia (DRGs) offers the opportunity to manipulate sensory neuron function at a segmental level to explore pathophysiology of painful conditions. However, there is no described method that has been validated in detail for such injections in adult rats. We have found that 2 ?l of dye injected through a pulled glass pipette directly into the distal DRG, exposed by a minimal foraminotomy, produces complete filling of the DRG with limited extension into the spinal roots. Injection into the spinal nerve required 3 ?l to achieve comparable DRG filling, produced preferential spread into the ventral root, and was accompanied by substantial leakage of injected solution from the injection site. Injections into the sciatic nerve of volumes up to 10 ?l did not reach the DRG. Transient hypersensitivity to mechanical stimulation at threshold (von Frey) and noxious levels (pin) developed after 2 ?l saline injection directly into the DRG that was in part attributable to the surgical exposure procedure alone. Only minimal astrocyte activation in the spinal dorsal horn was evident after DRG saline injections. Injection of adeno-associated virus (AAV) vector conveying green fluorescent protein (GFP) transgene resulted in expression as soon as 1 day after injection into the DRG, including fibers in the spinal dorsal horn and columns. AAV injection into the DRG produced additional thermal hypersensitivity and withdrawal from the stroke of a brush and compromised motor performance. These findings demonstrate a method for selective injection of agents into single DRGs for anatomically restricted actions. PMID:21540055

Fischer, Gregory; Kostic, Sandra; Nakai, Hiroyuki; Park, Frank; Sapunar, Damir; Yu, Hongwei; Hogan, Quinn

2011-07-15

315

Direct injection into the dorsal root ganglion: Technical, behavioral, and histological observations  

PubMed Central

Direct injection of agents into the dorsal root ganglia (DRGs) offers the opportunity to manipulate sensory neuron function at a segmental level to explore pathophysiology of painful conditions. However, there is no described method that has been validated in detail for such injections in adult rats. We have found that 2 (µl of dye injected through a pulled glass pipette directly into the distal DRG, exposed by a minimal foraminotomy, produces complete filling of the DRG with limited extension into the spinal roots. Injection into the spinal nerve required 3 µl to achieve comparable DRG filling, produced preferential spread into the ventral root, and was accompanied by substantial leakage of injected solution from the injection site. Injections into the sciatic nerve of volumes up to 10 (µl did not reach the DRG. Transient hypersensitivity to mechanical stimulation at threshold (von Frey) and noxious levels (pin) developed after 2 µl saline injection directly into the DRG that was in part attributable to the surgical exposure procedure alone. Only minimal astrocyte activation in the spinal dorsal horn was evident after DRG saline injections. Injection of adeno-associated virus (AAV) vector conveying green fluorescent protein (GFP) transgene resulted in expression as soon as 1 day after injection into the DRG, including fibers in the spinal dorsal horn and columns. AAV injection into the DRG produced additional thermal hypersensitivity and withdrawal from the stroke of a brush and compromised motor performance. These findings demonstrate a method for selective injection of agents into single DRGs for anatomically restricted actions. PMID:21540055

Fischer, Gregory; Kostic, Sandra; Nakai, Hiroyuki; Park, Frank; Sapunar, Damir; Yu, Hongwei; Hogan, Quinn

2013-01-01

316

Direct observation of parallel folding pathways revealed using a symmetric repeat protein system.  

PubMed

Although progress has been made to determine the native fold of a polypeptide from its primary structure, the diversity of pathways that connect the unfolded and folded states has not been adequately explored. Theoretical and computational studies predict that proteins fold through parallel pathways on funneled energy landscapes, although experimental detection of pathway diversity has been challenging. Here, we exploit the high translational symmetry and the direct length variation afforded by linear repeat proteins to directly detect folding through parallel pathways. By comparing folding rates of consensus ankyrin repeat proteins (CARPs), we find a clear increase in folding rates with increasing size and repeat number, although the size of the transition states (estimated from denaturant sensitivity) remains unchanged. The increase in folding rate with chain length, as opposed to a decrease expected from typical models for globular proteins, is a clear demonstration of parallel pathways. This conclusion is not dependent on extensive curve-fitting or structural perturbation of protein structure. By globally fitting a simple parallel-Ising pathway model, we have directly measured nucleation and propagation rates in protein folding, and have quantified the fluxes along each path, providing a detailed energy landscape for folding. This finding of parallel pathways differs from results from kinetic studies of repeat-proteins composed of sequence-variable repeats, where modest repeat-to-repeat energy variation coalesces folding into a single, dominant channel. Thus, for globular proteins, which have much higher variation in local structure and topology, parallel pathways are expected to be the exception rather than the rule. PMID:24988356

Aksel, Tural; Barrick, Doug

2014-07-01

317

Direct Observation of Valley Hybridization and Universal Symmetry of Graphene with Mesoscopic Conductance Fluctuations  

NASA Astrophysics Data System (ADS)

In graphene, the valleys represent spinlike quantities and can act as a physical resource in valley-based electronics to produce novel quantum computation schemes. Here we demonstrate a direct route to tune and read the valley quantum states of disordered graphene by measuring the mesoscopic conductance fluctuations. We show that the conductance fluctuations in graphene at low temperatures are reduced by a factor of 4 when valley triplet states are gapped in the presence of short-range potential scatterers at high carrier densities. We also show that this implies a gate tunable universal symmetry class that outlines a fundamental feature arising from graphene’s unique crystal structure.

Pal, Atindra Nath; Kochat, Vidya; Ghosh, Arindam

2012-11-01

318

Direct Observation and Calipering of the {open_quotes}Webbing{close_quotes} Fermi Surface of Yttrium  

SciTech Connect

The first measurement of both the size and shape of the region of the Fermi surface of yttrium known as the {open_quotes}webbing{close_quotes} is reported. This particular Fermi surface feature is of considerable interest because it is very similar to that found in a number of the heavier rare earth metals, where it is believed to play a vital role in driving the exotic magnetic structures found therein. In this positron study, two-dimensional angular correlation measurements combined with three-dimensional reconstruction provide a direct image of this part of the yttrium Fermi surface. {copyright} {ital 1997} {ital The American Physical Society}

Dugdale, S.B.; Fretwell, H.M.; Alam, M.A. [H.H.Wills Physics Laboratory, University of Bristol,Tyndall Avenue, Bristol, BS8 1TL (United Kingdom)] [H.H.Wills Physics Laboratory, University of Bristol,Tyndall Avenue, Bristol, BS8 1TL (United Kingdom); Kontrym-Sznajd, G. [Polish Academy of Sciences, W. Trzebiatowski Intsitute of Low Temperature and Structure Research, 50-950 Wroclaw 2, P.O.Box 937 (Poland)] [Polish Academy of Sciences, W. Trzebiatowski Intsitute of Low Temperature and Structure Research, 50-950 Wroclaw 2, P.O.Box 937 (Poland); West, R.N.; Badrzadeh, S. [Department of Physics, University of Texas at Arlington, P.O.Box 19059, Arlington, Texas 76019 (United States)] [Department of Physics, University of Texas at Arlington, P.O.Box 19059, Arlington, Texas 76019 (United States)

1997-08-01

319

Replication of Non-Trivial Directional Motion in Multi-Scales Observed by the Runs Test  

NASA Astrophysics Data System (ADS)

Non-trivial autocorrelation in up-down statistics in financial market price fluctuation is revealed by a multi-scale runs test(Wald-Wolfowitz test). We apply two models, a stochastic price model and dealer model to understand this property. In both approaches we successfully reproduce the non-stationary directional price motions consistent with the runs test by tuning parameters in the models. We find that two types of dealers exist in the markets, a short-time-scale trend-follower and an extended-time-scale contrarian who are active in different time periods.

Yura, Yoshihiro; Ohnishi, Takaaki; Yamada, Kenta; Takayasu, Hideki; Takayasu, Misako

320

Direct Observation of Enantiospecific Substitution in a Two-Dimensional Chiral Phase Transition  

E-print Network

to a racemate lattice is observed with increasing coverage. Enantiomers of a homochiral lamella line become. Introduction When a racemic mixture of chiral molecules condenses it may form (i) a racemic compound, in which crystals contain only one enantiomer, but the sample as a whole is racemic; and, quite rarely, (iii

Gao, Hongjun

321

Catecholamine-Induced Leukocytosis: Early Observations, Current Research, and Future Directions  

Microsoft Academic Search

Recent studies demonstrate that acute psychological stress in man affects lymphocyte circulation. It has been suggested that catecholamines are responsible for these changes. The present review summarizes findings regarding catecholamine-induced lympho- and leukocytosis, starting with observations dating back to the beginning of this century. Particular attention is given to the mechanisms of this phenomenon and the potential site of origin

Robert J. Benschop; Mario Rodriguez-Feuerhahn; Manfred Schedlowski

1996-01-01

322

Direct Observation of Subtropical Mode Water in the Western North Atlantic Ocean  

E-print Network

of (left) a conventional Argo float equipped with CTD and dissolved oxygen sensors, and (right) a CLIMODEDirect Observation of Subtropical Mode Water in the Western North Atlantic Ocean David M, nutrients and CO2. Although isolated beneath the stratified upper-ocean at the end of each winter, EDW may

Fratantoni, David

323

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

324

Directly Observed Physical Activity among 3-Year-Olds in Finnish Childcare  

ERIC Educational Resources Information Center

The main purpose of the study was to determine 3-year-olds' physical activity levels and how these vary across season, gender, time of day, location, and the physical and social environment in childcare settings in Finland. A modified version of the Observational System for Recording Physical Activity in Children-Preschool (OSRAC-P) was used…

Soini, Anne; Villberg, Jari; Sääkslahti, Arja; Gubbels, Jessica; Mehtälä, Anette; Kettunen, Tarja; Poskiparta, Marita

2014-01-01

325

Value-Directed Human Behavior Analysis from Video Using Partially Observable Markov Decision Processes  

Microsoft Academic Search

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

Jesse Hoey; James J. Little

2007-01-01

326

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

327

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

328

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

329

Direct observation of solute location in solutions frozen using various methods  

NASA Astrophysics Data System (ADS)

Photochemical reactions in snow and ice impact the transport and fate of organic and inorganic compounds in the snowpack, particularly in polar regions. While photodegradation rate constants have been determined for relatively few reactions on ice, in some cases different studies give significantly different results for the same reaction. Compounds in snow and ice can be located in several different compartments in the frozen matrix, including in bulk ice, at the ice-air interface in quasi-liquid layers (QLLs), or in liquid-like layers (LLLs) or micropockets within the ice matrix. Reaction rate differences may be due to changes in chemical kinetics in the various compartments, or variation in the photochemical reaction environment, such as photon flux. Here we examine various methods to segregate chemical compounds into different ice compartments by visualizing solute locations in the frozen samples. We preferentially segregate solutes into the various ice compartments by varying sample geometry, freezing speed (how quickly heat is removed from the liquid solution), and freezing direction (whether heat is removed from the solution from all sides equally, or preferentially in a single direction). We examine the results of our freezing methods by preparing ice samples containing a fluorescent solute, then using an imaging cryomicrotome to remove thin slices of the sample and image the remaining ice surface. By measuring the fluorescence from the ice surface as a function of depth, we can determine the location and concentration of the solute in various ice compartments.

Hullar, T.; Anastasio, C.

2012-12-01

330

Direct Observation of a Molecular Junction using High-Energy X-ray Reflectometry  

NASA Astrophysics Data System (ADS)

Very little is known about the structure of organic molecular thin films at their rest potential. Further, it is not known whether the structure of these films is modified by an applied potential. We present a new x-ray scattering technique, which allows high-resolution structural studies of buried self-assembled monolayers (SAMs) that are sandwiched between silicon and mercury junctions. The high-energy x-ray beams, utilized in the present studies (32 keV), penetrate through the conducting silicon electrode. The x-ray reflectivity interference pattern thus provides information on the thickness and orientation of the molecules in the electronic junction. Our results, for alkane-thiol and alkane-silane layers, show that the SAMs form homogenous densely packed monolayers within the deeply buried interface. The thickness of these layers is compared with the SAMs prepared at the vapor/vacuum interfaces on mercury and silicon.

Baumert, Julian; Lefenfeld, Michael; Sloutskin, Eli; Deutsch, Moshe; Nuckolls, Colin; Ocko, Ben

2005-03-01

331

Direct observation of hydrogen atom dynamics and interactions by ultrahigh resolution neutron protein crystallography  

PubMed Central

The 1.1 ?, ultrahigh resolution neutron structure of hydrogen/deuterium (H/D) exchanged crambin is reported. Two hundred ninety-nine out of 315, or 94.9%, of the hydrogen atom positions in the protein have been experimentally derived and resolved through nuclear density maps. A number of unconventional interactions are clearly defined, including a potential O?H…? interaction between a water molecule and the aromatic ring of residue Y44, as well as a number of potential C?H…O hydrogen bonds. Hydrogen bonding networks that are ambiguous in the 0.85 ? ultrahigh resolution X-ray structure can be resolved by accurate orientation of water molecules. Furthermore, the high resolution of the reported structure has allowed for the anisotropic description of 36 deuterium atoms in the protein. The visibility of hydrogen and deuterium atoms in the nuclear density maps is discussed in relation to the resolution of the neutron data. PMID:22949690

Chen, Julian C.-H.; Hanson, B. Leif; Fisher, S. Zoe; Langan, Paul; Kovalevsky, Andrey Y.

2012-01-01

332

Direct observation of momentum-dependent exchange interaction in a heisenberg ferromagnet.  

PubMed

We measured the temperature-dependent three-dimensional angle-resolved photoemission spectra of EuO (100) thin film, a typical Heisenberg ferromagnetic semiconductor, to investigate the essential origin of the ferromagnetic transition. We observed sizable energy dispersion and large binding-energy shift of the Eu 4f state below the Curie temperature only near the Gamma and X points, despite the expected Heisenberg-type local magnetism. The band dispersion and temperature dependence of the Eu 4f state indicates that the indirect exchange and superexchange interactions have strong momentum dependence. The observed temperature-dependent energy shift of the 4f state is the essential origin of the magnetism of EuO. PMID:19658899

Miyazaki, H; Ito, T; Im, H J; Yagi, S; Kato, M; Soda, K; Kimura, S

2009-06-01

333

Direct observation of fast protein folding: the initial collapse of apomyoglobin.  

PubMed Central

The rapid refolding dynamics of apomyoglobin are followed by a new temperature-jump fluorescence technique on a 15-ns to 0.5-ms time scale in vitro. The apparatus measures the protein-folding history in a single sweep in standard aqueous buffers. The earliest steps during folding to a compact state are observed and are complete in under 20 micros. Experiments on mutants and consideration of steady-state CD and fluorescence spectra indicate that the observed microsecond phase monitors assembly of an A x (H x G) helix subunit. Measurements at different viscosities indicate diffusive behavior even at low viscosities, in agreement with motions of a solvent-exposed protein during the initial collapse. Images Fig. 1 Fig. 3 PMID:8650166

Ballew, R M; Sabelko, J; Gruebele, M

1996-01-01

334

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

335

TRMM Observed First Direct Evidence of Smoke from Forest Fires Inhibiting Rainfall  

Microsoft Academic Search

Although it has been known that smoke from biomass burning suppresses warm rain processes, it was not known to what extent this occurs. The satellite observations of the Tropical-Rainfall-Measuring-Mission (TRMM), presented here, show that warm rain processes in convective tropical clouds infected by heavy smoke from forest fires are practically shut off. The tops of the smoke-infected clouds must exceed

Daniel Rosenfeld

1999-01-01

336

Direct Observation of Reversible and Irreversible Stomatal Responses of Attached Sunflower Leaves to SO2  

PubMed Central

The effects of SO2 on stomatal aperture of attached sunflower leaves were observed with a remote-control light microscope system that permitted continuous observation of stomatal responses over periods of several hours. The relationship between actual stomatal aperture and stomatal conductance, measured with a porometer, also was examined on leaves before and after exposure to SO2. A distinction between uninjured and injured regions was clearly visible on leaves after exposure to 1.5 microliters per liter SO2 for less than an hour. During the exposure, the mean value of apertures for many stomata, which indicates stomatal conductance and transpiration rate, tended to decrease simultaneously in the uninjured and injured regions. However, the rate of decrease in the injured region was slower than that in the uninjured region because of a transient opening induced by water-soaking in the injured region. The transient opening was less common in stomata near veins and veinlets. There was a good correlation between pore width and stomatal conductance measured with a porometer before exposure to SO2. This correlation continued in leaves exposed to SO2 until visible, irreversible injury occurred, but then it disappeared. The results of these experiments indicate the necessity of continuous observation of individual stomata under the microscope to understand the effects of air pollutants such as SO2 on stomatal behavior. Images Fig. 3 Fig. 5 PMID:16664361

Omasa, Kenji; Hashimoto, Yasushi; Kramer, Paul J.; Strain, Boyd R.; Aiga, Ichiro; Kondo, Jiro

1985-01-01

337

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

PubMed

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. PMID:17014208

Doveil, Fabrice; Macor, Alessandro; Elskens, Yves

2006-09-01

338

Direct Observation of the High Magnetic Field Effect on the Jahn-Teller State in TbVO4  

SciTech Connect

We report the first direct observation of the influence of high magnetic fields on the Jahn-Teller (JT) transition in TbVO{sub 4}. Contrary to spectroscopic and magnetic methods, x-ray diffraction directly measures the JT distortion; the splitting between the (311)/(131) and (202)/(022) pairs of Bragg reflections is proportional to the order parameter. Our experimental results are compared to mean-field calculations, taking into account all possible orientations of the grains relative to the applied field, and qualitative agreement is obtained.

Detlefs, C.; Duc, F.; Kazei, Z.; Vanacken, J.; Frings, P.; Bras, W.; Lorenzo, J.; Canfield, P.; Rikken, G.

2008-02-08

339

Direct observation of ultrafast long-range charge separation at polymer-fullerene heterojunctions  

NASA Astrophysics Data System (ADS)

In polymeric semiconductors, charge carriers are polarons, which means that the excess charge deforms the molecular structure of the polymer chain that hosts it. This results in distinctive signatures in the vibrational modes of the polymer. Here, we probe polaron photogeneration dynamics at polymer:fullerene heterojunctions by monitoring its time-resolved resonance-Raman spectrum following ultrafast photoexcitation. We conclude that polarons emerge within 300?fs. Surprisingly, further structural evolution on ?50-ps timescales is modest, indicating that the polymer conformation hosting nascent polarons is not significantly different from that near equilibrium. We interpret this as suggestive that charges are free from their mutual Coulomb potential because we would expect rich vibrational dynamics associated with charge-pair relaxation. We address current debates on the photocarrier generation mechanism at molecular heterojunctions, and our work is, to our knowledge, the first direct probe of molecular conformation dynamics during this fundamentally important process in these materials.

Provencher, Françoise; Bérubé, Nicolas; Parker, Anthony W.; Greetham, Gregory M.; Towrie, Michael; Hellmann, Christoph; Côté, Michel; Stingelin, Natalie; Silva, Carlos; Hayes, Sophia C.

2014-07-01

340

Paul trapping of radioactive 6He+ions and direct observation of their beta-decay  

E-print Network

We demonstrate that abundant quantities of short-lived beta unstable ions can be trapped in a novel transparent Paul trap and that their decay products can directly be detected in coincidence. Low energy 6He+ (807 ms half-life) ions were extracted from the SPIRAL source at GANIL, then decelerated, cooled and bunched by means of the buffer gas cooling technique. More than 10^8 ions have been stored over a measuring period of six days and about 10^5 decay coincidences between the beta particles and the 6Li^{++} recoiling ions have been recorded. The technique can be extended to other short-lived species, opening new possibilities for trap assisted decay experiments.

X. Flechard; E. Lienard; A. Mery; D. Rodriguez; G. Ban; D. Durand; F. Duval; M. Herbane; M. Labalme; F. Mauger; O. Naviliat-Cuncic; J. C. Thomas; Ph. Velten

2008-10-10

341

Direct Observation of ?-Chloride Elimination from an Isolable ?-Chloroalkyl Complex of Square-Planar Nickel.  

PubMed

Reported here are the isolation, structural characterization, and decomposition kinetics of the four-coordinate pentachloroethyl nickel complex, NiCl(CCl2CCl3)(CNAr(Mes2))2 (Ar(Mes2) = 2,6-(2,4,6-Me3C6H2)2C6H3). This complex is a unique example of a kinetically persistent ?-chloroalkyl in a system relevant to coordination-insertion polymerization of polar olefins. Kinetic analysis of NiCl(CCl2CCl3)(CNAr(Mes2))2 decomposition indicates that ?-chloride (?-Cl) elimination proceeds by a unimolecular mechanism that does not require initial dissociation of a CNAr(Mes2) ligand. The results suggest that a direct ?-Cl elimination pathway is available to four-coordinate, Group 10 metal vinyl chloride polymerization systems. PMID:25317481

Carpenter, Alex E; McNeece, Andrew J; Barnett, Brandon R; Estrada, Alexander L; Mokhtarzadeh, Charles C; Moore, Curtis E; Rheingold, Arnold L; Perrin, Charles L; Figueroa, Joshua S

2014-11-01

342

Direct observation of multiferroic vortex domains in YMnO3.  

PubMed

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

343

Direct observation of dynamic mechanical regulation of DNA condensation by environmental stimuli.  

PubMed

Gene delivery is a promising way to treat hereditary diseases and cancer; however, there is little understanding of DNA:carrier complex mechanical properties, which may be critical for the protection and release of nucleic acids. We applied optical tweezers to directly measure single-molecule mechanical properties of DNA condensed using 19-mer poly-L-lysine (PLL) or branched histidine-lysine (HK) peptides. Force-extension profiles indicate that both carriers condense DNA actively, showing force plateaus during stretching and relaxation cycles. As the environment such as carrier concentration, pH, and the presence of zinc ions changes, DNA:HK complexes showed dynamically regulated mechanical properties at multiple force levels. The fundamental knowledge from this study can be applied to design a mechanically tailored complex which may enhance transfection efficiency by controlling the stability of the complex temporally and spatially. PMID:25146232

Lee, Amy; Karcz, Adam; Akman, Ryan; Zheng, Tai; Kwon, Sara; Chou, Szu-Ting; Sucayan, Sarah; Tricoli, Lucas J; Hustedt, Jason M; Leng, Qixin; Kahn, Jason D; Mixson, A James; Seog, Joonil

2014-09-26

344

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

345

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

346

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

347

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

348

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

349

Direct Observations of Magnetic Flux Rope Formation during a Solar Coronal Mass Ejection  

NASA Astrophysics Data System (ADS)

Coronal mass ejections (CMEs) are the most spectacular eruptive phenomena in the solar atmosphere. It is generally accepted that CMEs are the results of eruptions of magnetic flux ropes (MFRs). However, there is heated debate on whether MFRs exist prior to the eruptions or if they are formed during the eruptions. Several coronal signatures, e.g., filaments, coronal cavities, sigmoid structures, and hot channels (or hot blobs), are proposed as MFRs and observed before the eruption, which support the pre-existing MFR scenario. There is almost no reported observation of MFR formation during the eruption. In this Letter, we present an intriguing observation of a solar eruptive event that occurred on 2013 November 21 with the Atmospheric Imaging Assembly on board the Solar Dynamic Observatory, which shows the formation process of the MFR during the eruption in detail. The process began with the expansion of a low-lying coronal arcade, possibly caused by the flare magnetic reconnection underneath. The newly formed ascending loops from below further pushed the arcade upward, stretching the surrounding magnetic field. The arcade and stretched magnetic field lines then curved in just below the arcade vertex, forming an X-point. The field lines near the X-point continued to approach each other and a second magnetic reconnection was induced. It is this high-lying magnetic reconnection that led to the formation and eruption of a hot blob (~10 MK), presumably an MFR, producing a CME. We suggest that two spatially separated magnetic reconnections occurred in this event, which were responsible for producing the flare and the hot blob (CME).

Song, H. Q.; Zhang, J.; Chen, Y.; Cheng, X.

2014-09-01

350

Direct Observation of Cross-Phase-Modulation-Induced Nonlinear Phase Noise  

NASA Astrophysics Data System (ADS)

This paper reports a quantitative investigation of the nonlinear phase noise (NLPN) in dispersion-shifted and single-mode optical fibers, which is induced by amplified spontaneous emission (ASE) noise through cross-phase modulation. The phase noise power spectral density (PN-PSD) of a probe light, which is transmitted through the fibers and is affected by the copropagating ASE, is precisely measured with the delayed self-heterodyne method. The observed PN-PSDs agree well with the theory that takes account of the group velocity dispersion of the fiber and the polarization states of the propagating lights.

Tsuchida, Hidemi

2013-06-01

351

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

352

Direct observation of stronger flux-line pinning of crossed compared to parallel linear defects  

SciTech Connect

Linear defects were introduced in high-temperature superconductors (HTSC{close_quote}s) by high-energy heavy-ion irradiation. Flux penetration into partly crossed and parallel irradiated HTSC{close_quote}s was observed by magneto- optics. The obtained flux distributions show that the critical current density {ital j}{sub {ital c}} in cross-irradiated HTSC{close_quote}s is larger by a factor up to 14 than in parallel irradiated HTSC{close_quote}s. {copyright} {ital 1996 The American Physical Society.}

Schuster, T.; Kuhn, H. [Max-Planck-Institut fuer Metallforschung, Institut fuer Physik, Postfach 800665, D-70506 Stuttgart (Germany)] [Max-Planck-Institut fuer Metallforschung, Institut fuer Physik, Postfach 800665, D-70506 Stuttgart (Germany); Indenbom, M.V. [Institut de Genie Atomique, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne (Switzerland)] [Institut de Genie Atomique, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne (Switzerland); Kreiselmeyer, G.; Leghissa, M. [III. Physikalisches Institut, Universitaet Erlangen-Nuernberg, Erwin-Rommel-Strasse 1, D-91058 Erlangen (Germany)] [III. Physikalisches Institut, Universitaet Erlangen-Nuernberg, Erwin-Rommel-Strasse 1, D-91058 Erlangen (Germany); Klaumuenzer, S. [Hahn-Meitner-Institut, Postfach 390128, D-14091 Berlin (Germany)] [Hahn-Meitner-Institut, Postfach 390128, D-14091 Berlin (Germany)

1996-02-01

353

Direct observation of interstitial titanium ions in TiO2 substrate with gold nanoparticle  

NASA Astrophysics Data System (ADS)

Interstitial titanium ions in TiO2 substrates with gold nanoparticle (Au/TiO2) are found to be observable by aberration corrected transmission electron microscopy. The local distribution of the interstitial Ti ions was obtained from TEM images. The interstitial ions are found to exist at a perimeter/interface of Au/TiO2, whereas they are deficient in a peripheral region of the gold nanoparticles. The interstitial ions at the perimeter/interface of Au/TiO2 need attention in CO oxidation catalysis.

Tanaka, Takayuki; Sumiya, Ami; Sawada, Hidetaka; Kondo, Yukihito; Takayanagi, Kunio

2014-01-01

354

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

355

Observation of direct soft photon production in ?-p interactions at 280 GeV/ c  

NASA Astrophysics Data System (ADS)

The OMEGA spectrometer, equipped with a hydrogen target and two electromagnetic calorimeters, was used to investigate the production of soft gammas in hadronic collisions. The E? and PT distributions of the measured ?'s are compared with the corresponding distributions of ?'s arising from hadronic decays and of ?'s expected from QED inner bremsstrahlung. An excess of gammas by a factor of 7.9 ± 1.4 over the QED prediction is measured in the low energy (0.2< E?<1.0 GeV) and low PT (< 10 MeV/ c) kinematic region, and confirms the original observation of a similar effect in a bubble chamber experiment.

Banerjee, S.; Barberis, D.; Belogianni, A.; Beusch, W.; Brodbeck, T. J.; French, B. R.; Goldschmidt-Clermont, Y.; Grabowski, M.; Kerres, U.; Knudson, K.; Morris, J. A. G.; Perepelitsa, V.; Quercigh, E.; Sonderegger, P.; Spyropoulou-Stassinaki, M.; Subramanian, A.; Vassiliadis, G.; Vichou, I.; Weigend, A.; Wilson, G. W.; Sophie/Wa83 Collaboration

1993-05-01

356

Direct Observation of Nanocrystallite Buckling in Carbon Fibers under Bending Load  

SciTech Connect

Single carbon fibers are deformed in bending by forming loops with varying radius. Position-resolved x-ray diffraction patterns from the bent fibers are collected from the tension to the compression region with a synchrotron radiation nanobeam of 100 nm size from a waveguide structure. A strain redistribution with a shift of the neutral axis is observed. A significant increase of the misorientation of the graphene sheets in the compression region shows that intense buckling of the nanosized carbon crystallites is the physical origin of different tensile and compressive properties.

Loidl, D.; Peterlik, H. [Institute of Materials Physics, University of Vienna, Boltzmanngasse 5, A-1090 Vienna (Austria); Paris, O. [Department of Biomaterials, Max-Planck-Institute of Colloids and Interfaces, 14424 Potsdam (Germany); Burghammer, M.; Riekel, C. [European Synchrotron Radiation Facility, 6 Rue Jules Horowitz, B.P. 220, F-38043 Grenoble Cedex 9 (France)

2005-11-25

357

Non-parametric Determination of the Acceleration Mechanisms Directly From RHESSI Solar Flare Observations  

NASA Astrophysics Data System (ADS)

The most common practice of the determination of the characteristics of the radiation and acceleration mechanisms in solar flares are through forward fitting procedures where observed spectra are fitted to those obtained from assumed parametric model. The uniqueness of the result is always questionable. Here we describe a new "Inversion" method for a non-parametric determination of energy dependences of critical characteristics of the acceleration mechanism in the framework of the Fokker-Planck kinetic equation. The assumptions leading to this model and the applicability of the inversion method to both stochastic acceleration by turbulence and/or shock acceleration will be described. We then will present results from application of the method to several solar flares observed by RHESSI with distinct bremsstrahlung hard X-ray emission from the looptop and thick-target footpoint regions of the flaring loop. We present results based on either the so-called regularized inversion from visibility to electron spectra or the traditional hard X-ray imaging spectroscopy. The result show some puzzling aspects for both shock or stochastic acceleration models implications of which will be discussed. We will also briefly discuss potential application of the method to particle acceleration in supernova remnants.

Petrosian, Vahe; Chen, Q.

2013-07-01

358

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

359

Direct observations of parenting and real-time negative affect among adolescent smokers and nonsmokers.  

PubMed

This longitudinal study examined how observations of parental general communication style and control with their adolescents predicted changes in negative affect over time for adolescent smokers and nonsmokers. Participants were 9th- and 10th-grade adolescents (N = 111; 56.8% female) who had all experimented with cigarettes and were thus at risk for continued smoking and escalation; 36% of these adolescents (n = 40) had smoked in the past month at baseline and were considered smokers in the present analyses. Adolescents participated separately with mothers and fathers in observed parent-adolescent problem-solving discussions to assess parenting at baseline. Adolescent negative affect was assessed at baseline, 6 months, and 24 months via ecological momentary assessment. Among both smoking and nonsmoking adolescents, escalating negative affect significantly increased risk for future smoking. Higher quality maternal and paternal communication predicted a decline in negative affect over 1.5 years for adolescent smokers but was not related to negative affect for nonsmokers. Controlling maternal, but not paternal, parenting predicted escalation in negative affect for all adolescents. Findings suggest that reducing negative affect among experimenting youth can reduce risk for smoking escalation. Therefore, family-based prevention efforts for adolescent smoking escalation might consider parental general communication style and control as intervention targets. However, adolescent smoking status and parent gender may moderate these effects. PMID:23153193

Richmond, Melanie J; Mermelstein, Robin J; Wakschlag, Lauren S

2013-01-01

360

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

361

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

362

Direct observation and quantification of nanoscale spinodal decomposition in super duplex stainless steel weld metals.  

PubMed

Three variants of super duplex stainless steel weld metals with the basic composition 29Cr-8Ni-2Mo (wt%) were investigated. The nitrogen content of the three materials was 0.22%, 0.33% and 0.37%, respectively. Isothermal heat treatments were performed at 450 degrees C for times up to 243 h. The hardness evolution of the three materials was found to vary with the overall concentration of the nitrogen. Atom probe field ion microscopy (APFIM) was used to directly detect and quantify the degree of spinodal decomposition in different material conditions. 3-DAP atomic reconstruction clearly illustrate nanoscale variation of iron rich (alpha) and chromium rich (alpha') phases. A longer ageing time produces a coarser microstructure with larger alpha and alpha' domains. Statistical evaluation of APFIM data showed that phase separation was significant already after 1 h of ageing that gradually became more pronounced. Although nanoscale concentration variation was evident, no significant influence of overall nitrogen content on the degree of spinodal decomposition was found. PMID:19504899

Shariq, Ahmed; Hättestrand, Mats; Nilsson, Jan-Olof; Gregori, Andrea

2009-06-01

363

Direct Observation of Protein Unfolded State Compaction in the Presence of Macromolecular Crowding  

PubMed Central

Proteins fold and function in cellular environments that are crowded with other macromolecules. As a consequence of excluded volume effects, compact folded states of proteins should be indirectly stabilized due to destabilization of extended unfolded conformations. Here, we assess the role of excluded volume in terms of protein stability, structural dimensions and folding dynamics using a sugar-based crowding agent, dextran 20, and the small ribosomal protein S16 as a model system. To specifically address dimensions, we labeled the protein with BODIPY at two positions and measured Trp-BODIPY distances under different conditions. As expected, we found that dextran 20 (200 mg/ml) stabilized the variants against urea-induced unfolding. At conditions where the protein is unfolded, Förster resonance energy transfer measurements reveal that in the presence of dextran, the unfolded ensemble is more compact and there is residual structure left as probed by far-ultraviolet circular dichroism. In the presence of a crowding agent, folding rates are faster in the two-state regime, and at low denaturant concentrations, a kinetic intermediate is favored. Our study provides direct evidence for protein unfolded-state compaction in the presence of macromolecular crowding along with its energetic and kinetic consequences. PMID:23442920

Mikaelsson, Therese; Aden, Jorgen; Johansson, Lennart B.-A.; Wittung-Stafshede, Pernilla

2013-01-01

364

Observation of direct sulfenium and selenenium group transfer from thiiranium and seleniranium ions to alkenes.  

PubMed

Sulfenium and selenenium ions undergo a stereospecific transfer from the corresponding three-membered ring species ("-iranium ions") to unactivated alkenes with varying facility. The thiiranium and seleniranium hexafluoroantimonates could be generated by treatment of the corresponding chloro sulfides or selenides with silver hexafluoroantimonate, followed by removal of the silver chloride by filtration. Clean (1)H, (13)C, and (77)Se NMR spectra could be recorded for these species. Treatment of the S-phenylthiiranium ion with an alkene leads to a slow transfer of the sulfenium group at 0 degrees C. However, the S-methylthiiranium ion did not transfer the sulfenium group, even at room temperature. On the other hand, both the Se-phenyl- and Se-butylseleniranium ions transferred the selenenium moiety instantaneously at -70 degrees C. By measuring the equilibrium position for these transfers from both directions, the relative stability of the 1-phenylseleniranium ions could be established: cis-tetramethylene < trans-2,3-dipropyl approximately trans-2,3-diisopropyl < cis-hexamethylene. PMID:19227982

Denmark, Scott E; Collins, William R; Cullen, Matthew D

2009-03-18

365

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

366

Direct observation of dipolar chains in ferrofluids in zero field using cryogenic electron microscopy  

NASA Astrophysics Data System (ADS)

The particle structure of ferrofluids is studied in situ, by cryogenic electron microscopy, on vitrified films of iron and magnetite dispersions. By means of synthesis of iron colloids with controlled particle size and different types of surfactant, dipolar particle interactions can be varied over a broad range, which significantly influences the ferrofluid particle structure. Our experiments on iron dispersions (in contrast to magnetite dispersions) for the first time demonstrate, in ferrofluids in zero field, a transition with increasing particle size from separate particles to linear chains of particles (Butter K, Bomans P H, Frederik P M, Vroege G J and Philipse A P 2003 Nature Mater. 2 88). These chains, already predicted theoretically by de Gennes and Pincus (de Gennes P G and Pincus P A 1970 Phys. Kondens. Mater. 11 189), very much resemble the fluctuating chains found in simulations of dipolar fluids (Weis J J 1998 Mol. Phys. 93 361, Chantrell R W, Bradbury A, Popplewell J and Charles S W 1982 J. Appl. Phys. 53 2742). Decreasing the range of steric repulsion between particles by employing a thinner surfactant layer is found to change particle structures as well. The dipolar nature of the aggregation is confirmed by the alignment of existing chains and individual particles in the field direction upon vitrification of dispersions in a saturating magnetic field. Frequency-dependent susceptibility measurements indicate that particle structures in truly three-dimensional ferrofluids are qualitatively similar to those in liquid films.

Butter, K.; Bomans, P. H.; Frederik, P. M.; Vroege, G. J.; Philipse, A. P.

2003-04-01

367

Direct observation of dipolar chains in iron ferrofluids by cryogenic electron microscopy.  

PubMed

A key issue in research on ferrofluids (dispersions of magnetic colloids) is the effect of dipolar interactions on their structure and phase behaviour, which is not only important for practical applications but gives fundamental insight in dipolar fluids in general. In 1970, de Gennes and Pincus predicted a Van der Waals-like phase diagram and the presence of linear chains of particles in ferrofluids in zero magnetic field. Despite many experimental studies, no direct evidence of the existence of linear chains of dipoles has been reported in the absence of magnetic field, although simulations clearly show the presence of chain-like structures. Here, we show in situ linear dipolar structures in ferrofluids in zero field, visualized on the particle level by electron cryo-microscopy on thin, vitrified films of organic dispersions of monodisperse metallic iron particles. On systematically increasing the particle size, we find an abrupt transition from separate particles to randomly oriented linear aggregates and branched chains or networks. When vitrified in a permanent magnetic field, these chains align and form thick elongated structures, indicating lateral attraction between parallel dipole chains. These findings show that the experimental model used is well suited to study the structural properties of dipolar particle systems. PMID:12612691

Butter, K; Bomans, P H H; Frederik, P M; Vroege, G J; Philipse, A P

2003-02-01

368

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 accoun...

Bozorgnia, Nassim

2014-01-01

369

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

2014-10-22

370

Direct observation of photolysis-induced tertiary structural changes in hemoglobin  

PubMed Central

Human Hb, an ?2?2 tetrameric oxygen transport protein that switches from a T (tense) to an R (relaxed) quaternary structure during oxygenation, has long served as a model for studying protein allostery in general. Time-resolved spectroscopic measurements after photodissociation of CO-liganded Hb have played a central role in exploring both protein dynamical responses and molecular cooperativity, but the direct visualization and the structural consequences of photodeligation have not yet been reported. Here we present an x-ray study of structural changes induced by photodissociation of half-liganded T-state and fully liganded R-state human Hb at cryogenic temperatures (25–35 K). On photodissociation of CO, structural changes involving the heme and the F-helix are more marked in the ? subunit than in the ? subunit, and more subtle in the R state than in the T state. Photodeligation causes a significant sliding motion of the T-state ? heme. Our results establish that the structural basis of the low affinity of the T state is radically different between the subunits, because of differences in the packing and chemical tension at the hemes. PMID:12773618

Adachi, Shin-ichi; Park, Sam-Yong; Tame, Jeremy R. H.; Shiro, Yoshitsugu; Shibayama, Naoya

2003-01-01

371

Direct observation of the formation of liquid protrusions on polymer colloids and their coalescence.  

PubMed

Monodisperse nonspherical poly (methyl methacrylate) (PMMA) particles where a central core particle had grown two extra "lobes", or protrusions, placed opposite each other were successfully synthesized by swelling and subsequent polymerization of cross-linked PMMA spheres with methyl methacrylate and the cross-linker ethylene glycol dimethacrylate. The use of large (~3 ?m) seed particles allowed for real-time monitoring of the swelling and deswelling of the cross-linked particles with optical microscopy. First, a large number of small droplets of swelling monomers formed simultaneously on the surface of the seed particles, and then fused together until under certain conditions two protrusions remained on opposite sides of the seed particles. The yield of such particles could be made up to 90% with a polydispersity of 7.0%. Stirring accelerated the transfer of the swelling monomers to the seed particles. Stirring was also found to induce self-assembly of the swollen seed particles into a wide variety of n-mers, consisting of a certain number, n, of swollen seed particles. The formation of these structures is guided by the minimization of the interfacial free energy between the seed particles, liquid protrusions and aqueous phase, but stirring time and geometrical factors influence it as well. By inducing polymerization the structures could be made permanent. Some control over the topology as well as overall size of the clusters was achieved by varying the stirring time before polymerization. 3D models of possible particle structures were used to identify all projections of the structures obtained by scanning electron microscopy. These models also revealed that the seed particles inside the central coalesced body were slightly compressed after polymerization. By extending the synthesis of the monodisperse particles with n = 1 to (slightly) different monomers and/or different cores, an important class of patchy particles could be realized. PMID:23594337

Peng, Bo; van Blaaderen, Alfons; Imhof, Arnout

2013-05-22

372

Direct observation of N-(group V) bonding defects in dilute nitride semiconductors using hard x-ray photoelectron spectroscopy  

NASA Astrophysics Data System (ADS)

Using bulk sensitive hard x-ray photoelectron spectroscopy, we directly observe a spectrum related to N-As bonding defects in (Ga,In)(N,As)/Ga(N,As) heterostructure. The defects are most likely attributed to split interstitials. Their concentration is in the order of 1019 cm-3, close to the detection limit of the measurement. Rapid thermal annealing eliminates the defects, leading to those undetectable. Similar phenomenon is observed for N-P bonding defects in In(N,P). The results indicate common features in dilute nitride semiconductor system: existence of N-(group V) bonding defects and their behavior on postgrowth annealing.

Ishikawa, F.; Fuyuno, S.; Higashi, K.; Kondow, M.; Machida, M.; Oji, H.; Son, J.-Y.; Trampert, A.; Umeno, K.; Furukawa, Y.; Wakahara, A.

2011-03-01

373

Direct Observation of a Photo-Induced Non-Stabilized Nitrile Imine Structure in the Solid State  

PubMed Central

We report the direct observation of a bent geometry for a non-stabilized nitrile imine in a metal-coordination crystal. The photoinduced tetrazole ring rupture to release N2 appears to depend on the size of voids around the N3-N4 bond in the crystal lattice. We further observed the selective formation of 1,3-addition product when a reactive nitrile imine was photo-generated in water. Taken together, the bent nitrile imine geometry agrees with the 1,3-dipolar structure, a transient reactive species that mediates the photoinduced 1,3-dipolar cycloaddition in the aqueous medium. PMID:19928921

Zheng, Shao-Liang; Wang, Yizhong; Yu, Zhipeng; Lin, Qing; Coppens, Philip

2009-01-01

374

Direct observation of ferroelectric domains created by Wigner crystallization of electrons in ?-[bis(ethylenedithio)tetrathiafulvalene]2I3  

NASA Astrophysics Data System (ADS)

The organic conductor ?-[bis(ethylenedithio)tetrathiafulvalene]2I3 undergoes a ferroelectric transition due to the Wigner-crystal-like charge ordering. The present paper reports the direct observation of 180° polar domains growing in the ferroelectric phase by means of optical second-harmonic generation interferometry. Mapping observation of the nonlinear optical interference revealed the development of large polar domains, illustrating a strong tendency of single-domain growth in the ferroelectric compound. The domain structures were varied when the crystal was annealed above the transition temperature and recooled into the ferroelectric phase. The variation indicates the mobile nature of the domains in the ferroelectric organic conductor.

Yamamoto, Kaoru; Kowalska, Aneta Aniela; Yakushi, Kyuya

2010-03-01

375

Direct observation of supramolecular structures of biorelated materials by atomic force microscopy  

NASA Astrophysics Data System (ADS)

We have prepared DNA catenanes and studied the topological structures of DNA catenanes by atomic force microscopy (AFM) and electrophoresis. Nicked DNA was synthesized by the addition of DNASE I to a solution of plasmid pBR322. Catenated DNA molecules were prepared by the reaction of topoisomerase I with nicked DNA. Catenation reactions were monitored by the agarose gel electrophoresis. A droplet of solution, containing DNA catenanes extracted from the band of 1.0 percent agarose gel electrophoresis by a centrifugal filter device, was applied to a freshly cleaved mica surface. After drying the specimens, AFM measurements were carried out by using a silicon cantilever. The single molecule images of DNA catenanes were clearly observed for the first time by AFM using a tapping mode at room temperature and in an ambient atmosphere.

Yamaguchi, Hiroyasu; Kubota, Kei; Harada, Akira

2000-04-01

376

Comparison of direct observational methods for measuring stereotypic behavior in children with autism spectrum disorders.  

PubMed

We compared partial-interval recording (PIR) and momentary time sampling (MTS) estimates against continuous measures of the actual durations of stereotypic behavior in young children with autism or pervasive developmental disorder-not otherwise specified. Twenty-two videotaped samples of stereotypy were scored using a low-tech duration recording method, and relative durations (i.e., proportions of observation periods consumed by stereotypy) were calculated. Then 10, 20, and 30s MTS and 10s PIR estimates of relative durations were derived from the raw duration data. Across all samples, PIR was found to grossly overestimate the relative duration of stereotypy. Momentary time sampling both over- and under-estimated the relative duration of stereotypy, but with much smaller errors than PIR (Experiment 1). These results were replicated across 27 samples of low, moderate and high levels of stereotypy (Experiment 2). PMID:15026089

Gardenier, Nicole Ciotti; MacDonald, Rebecca; Green, Gina

2004-01-01

377

Direct observation of the collapse of the delocalized excess electron in water  

NASA Astrophysics Data System (ADS)

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.

Savolainen, Janne; Uhlig, Frank; Ahmed, Saima; Hamm, Peter; Jungwirth, Pavel

2014-08-01

378

Pesticide residues in groundwater in The Netherlands: state of observations and future directions of research.  

PubMed

In the first stage of a programme of sampling and analysis for pesticide residues in groundwater in The Netherlands, the upper groundwater below four vulnerable soils was analysed for nearly 2,5 years in eight sampling rounds. Of 18 compounds analysed, including some metabolites, 1,3-dichloropropene, aldicarb, ethoprophos dinoseb, metamitron, atrazine, desethyl- and desisopropylatrazine, metolachlor and ethylenethioureum were repeatedly detected in the groundwater in concentrations above 0.1 micrograms.dm-3, the limit for pesticides in drinking water set by the EC. These observations were made below fields with potatoe-, maize- and bulb flower culture, all on low-humic to moderately humic sandy soils. No residues were found below a cracked light clay on a sandy subsoil. On the locations sampled evidence was found for complete in situ removal in the upper groundwater of 1,3-dichloropropene, high persistence of aldicarb residues and partial in situ degradation of dinoseb. PMID:2756375

Loch, J P; Verdam, B

1989-01-01

379

Direct observation of frequency modulated transcription in single cells using light activation  

PubMed Central

Single-cell analysis has revealed that transcription is dynamic and stochastic, but tools are lacking that can determine the mechanism operating at a single gene. Here we utilize single-molecule observations of RNA in fixed and living cells to develop a single-cell model of steroid-receptor mediated gene activation. We determine that steroids drive mRNA synthesis by frequency modulation of transcription. This digital behavior in single cells gives rise to the well-known analog dose response across the population. To test this model, we developed a light-activation technology to turn on a single steroid-responsive gene and follow dynamic synthesis of RNA from the activated locus. DOI: http://dx.doi.org/10.7554/eLife.00750.001 PMID:24069527

Larson, Daniel R; Fritzsch, Christoph; Sun, Liang; Meng, Xiuhau; Lawrence, David S; Singer, Robert H

2013-01-01

380

Direct observation of interface and nanoscale compositional modulation in ternary III-As heterostructure nanowires  

SciTech Connect

Straight, axial InAs nanowire with multiple segments of Ga{sub x}In{sub 1?x}As was grown. High resolution X-ray energy-dispersive spectroscopy (EDS) mapping reveals the distribution of group III atoms at the axial interfaces and at the sidewalls. Significant Ga enrichment, accompanied by a structural change is observed at the Ga{sub x}In{sub 1?x}As/InAs interfaces and a higher Ga concentration for the early grown Ga{sub x}In{sub 1?x}As segments. The elemental map and EDS line profile infer Ga enrichment at the facet junctions between the sidewalls. The relative chemical potentials of ternary alloys and the thermodynamic driving force for liquid to solid transition explains the growth mechanisms behind the enrichment.

Venkatesan, Sriram; Scheu, Christina [Department of Chemistry and Center for NanoScience, Ludwig-Maximilians-Universität München, Butenandstr 5-13(E), 81377 München (Germany)] [Department of Chemistry and Center for NanoScience, Ludwig-Maximilians-Universität München, Butenandstr 5-13(E), 81377 München (Germany); Madsen, Morten H.; Krogstrup, Peter; Johnson, Erik [Nano-Science Center and Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen (Denmark)] [Nano-Science Center and Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen (Denmark); Schmid, Herbert [INM-Leibniz Institute for New Materials, 66123 Saarbrücken (Germany)] [INM-Leibniz Institute for New Materials, 66123 Saarbrücken (Germany)

2013-08-05

381

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

382

Direct observations of the primary state of radiation damage of ion-irradiated tungsten and platinum  

SciTech Connect

A brief summary was presented of all the Cornell work on the primary state of radiation damage in ion-irradiated tungsten and platinum. The primary research tool for all this research was the field-ion microscope (FIM); the FIM was ideally suited for this research because of its excellent atomic resolution and the ability to examine the interior of the specimens, as a result of the field-evaporation effect. This paper summarized, in outline form, the following items: (1) the principal experimental quantities determined from the analyses performed on all the individual depleted zones (DZs) observed; (2) the main experimental programs; (3) a number of the more important results and conclusions concerning the vacancy structure of DZs; and (4) the three-dimensional spatial distribution of self-interstitial atoms around DZs in tungsten which had been irradiated and examined in situ at 10/sup 0/K.

Seidman, D. N.; Current, M. I.; Pramanik, D.; Wei, C. Y.

1980-07-01

383

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

384

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

385

Direct Observation of Aminoglycoside-RNA Binding by Localized Surface Plasmon Resonance (LSPR) Spectroscopy  

PubMed Central

RNA is involved in fundamental biological functions when bacterial pathogens replicate. Identifying and studying small molecules that can interact with bacterial RNA and interrupt cellular activities is a promising path for drug design. Aminoglycoside (AMG) antibiotics, prominent natural products that recognize RNA specifically, exert their biological functions by binding to prokaryotic ribosomal RNA and interfering with protein translation, ultimately resulting in bacterial cell death. The decoding site, a small internal loop within the 16S rRNA, is the molecular target for the AMG antibiotics. The specificity of neomycin B, a highly potent AMG antibiotic, to the ribosomal decoding RNA site, was previously studied by observing AMG–RNA complexes in solution. Here we study this interaction using localized surface plasmon resonance (LSPR) transducers comprising gold island films prepared by evaporation on glass and annealing. Small molecule AMG receptors were immobilized on the Au islands via PEG-thiol linkers, and the interaction with target RNA in solution was studied by monitoring the change in the LSPR optical response upon binding. The results show high-affinity binding of neomycin to 27-nucleotide model A-site and A-modified RNA sequences in the nanomolar range, while no specific binding is observed for synthetic RNA oligomers (e.g., poly-U). The impact of specific base substitutions in the A-site RNA constructs on binding affinity and selectivity is determined quantitatively. It is concluded that LSPR is a powerful tool for providing molecular insight into small molecule–RNA interactions and for the design and screening of selective antimicrobial drugs. PMID:23368968

Frolov, Ludmila; Dix, Andrew; Tor, Yitzhak; Tesler, Alexander B.; Chaikin, Yulia; Vaskevich, Alexander; Rubinstein, Israel

2013-01-01

386

EXTREME-ULTRAVIOLET SPECTROSCOPIC OBSERVATION OF DIRECT CORONAL HEATING DURING A C-CLASS SOLAR FLARE  

SciTech Connect

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 Almost-Equal-To 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), O V (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{sup -1} due to reconnection outflows or turbulence. During the plateau He I, O V, 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 O V 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 O V upward velocity was around -10 km s{sup -1}.

Brosius, Jeffrey W., E-mail: Jeffrey.W.Brosius@nasa.gov [Catholic University of America at NASA Goddard Space Flight Center, Solar Physics Laboratory, Code 671, Greenbelt, MD 20771 (United States)

2012-07-20

387

Motion of single wandering diblock-macromolecules directed by a PTFE nano-fence: real time SFM observations.  

PubMed

Using SFM we have observed a peculiar twisting motion of diblock macromolecules pre-collapsed in ethanol vapour during their subsequent spreading in water vapour. The intrinsic asymmetry of the diblock macromolecules has been considered to be the reason for such twisting. Further, friction-deposited PTFE nano-stripes have been employed as nano-trails with the purpose of inducing lateral directed motion of the asymmetric diblock macromolecules under cyclic impact from the changing vapour surroundings. Indeed, some of the macromolecules have demonstrated a certain tendency to orient along the PTFE stripes, and some of the oriented ones have moved occasionally in a directed manner along the trail. However, it has been difficult to reliably record such directed motion at the single molecule level due to some mobility of the PTFE nano-trails themselves in the changing vapour environment. In vapours, the PTFE stripes have demonstrated a distinct tendency towards conjunction. This tendency has manifested itself in efficient expelling of groups of the mobile brush-like molecules from the areas between two PTFE stripes joining in a zip-fastener manner. This different kind of vapour-induced cooperative macromolecular motion has been reliably observed as being directed. The PTFE nano-frame experiences some deformation when constraining the spreading macromolecules. We have estimated the possible force causing such deformation of the PTFE fence. The force has been found to be a few pN as calculated by a partial contribution from every single molecule of the constrained group. PMID:19842476

Gallyamov, Marat O; Qin, Shuhui; Matyjaszewski, Krzysztof; Khokhlov, Alexei; Möller, Martin

2009-07-21

388

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

389

Direct sampling and in situ observation of a persistent copepod aggregation in the mesopelagic zone of the Santa Barbara Basin  

Microsoft Academic Search

Observations from a one-person submersible (“Wasp”) in fall, 1982, revealed a persistent aggregation of non-migrating, Stage V copepodites of Calanus pacificus californicus Brodsky in a band 20±3 m thick at a depth of 450 m, about 100 m above the bottom of the Santa Barbara Basin, California. Copepod abundances, calculated from nearest-neighbor distances measured directly from the submersible, yielded maximum

A. L. Alldredge; B. H. Robison; A. Fleminger; J. J. Torres; J. M. King; W. M. Hamner

1984-01-01

390

Journal of Crystal Growth 292 (2006) 395398 Direct observation of ferroelectric domains and phases in (0 0 1)-cut  

E-print Network

Journal of Crystal Growth 292 (2006) 395­398 Direct observation of ferroelectric domains and phases in (0 0 1)-cut Pb(Mg1/3Nb2/3)1�xTixO3 single crystals under electric-field poling R.R. Chiena,�, V. Hugo.33O3 (PMNT33%) single crystal has been performed by polarizing microscopy. A hysteresis loop

391

Direct observation of quantum-confined graphene-like states and novel hybrid states in graphene oxide by transient spectroscopy.  

PubMed

Quantum-confined graphene-like electronic states are directly observed in graphene oxide and photothermally reduced graphene oxide via transient spectroscopy. An unexpected novel hybrid state arising from amorphous carbon-like peripheral structure with high sp(3) /sp(2) carbon ratio in close vicinity of confined graphene-like states is found commonly existent in various carbon nanomaterials, including graphene oxide, graphene quantum dots, and carbon dots. PMID:24030902

Wang, Lei; Wang, Hai-Yu; Wang, Yan; Zhu, Shou-Jun; Zhang, Yong-Lai; Zhang, Jun-Hu; Chen, Qi-Dai; Han, Wei; Xu, Huai-Liang; Yang, Bai; Sun, Hong-Bo

2013-12-01

392

Direct observation of hydrogen spillover on carbon-supported platinum and its influence on the hydrogenation of benzene  

Microsoft Academic Search

A study on the presence of hydrogen spillover on carbon-supported platinum catalysts was conducted. CO and H[sub 2] uptakes were determined at ambient temperature on Pt\\/C catalyst variously dilute with carbon. The effect of H[sub 2] spillover on benzene hydrogenation over Pt\\/C and dilute Pt\\/C was studied. From chemisorption results a direct observation of hydrogen spillover at room temperature was

S. T. Srinivas; P. K. Rao

1994-01-01

393

Aerosol characterization in Northern Africa, Northeastern Atlantic, Mediterranean Basin and Middle East from direct-sun AERONET observations  

Microsoft Academic Search

We provide an atmospheric aerosol characterization for North Africa, Northeastern Atlantic, Mediterranean and Middle East based on the analysis of quality-assured direct-sun observations of 39 stations of the AErosol RObotic NETwork (AERONET) which include at least an annual cycle within the 1994-2007 period. We extensively test and apply the recently introduced graphical method of Gobbi and co-authors in order to

S. Basart; C. Pérez; E. Cuevas; J. M. Baldasano; G. P. Gobbi

2009-01-01

394

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

395

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

396

Apollo 11 and 16 Soil Bi-directional Solar Reflectance Measurements, Models and LRO Diviner Observations  

NASA Astrophysics Data System (ADS)

We have compared laboratory solar reflectance measurements of Apollo 11 and 16 soil samples to Lunar Reconnaissance Orbiter (LRO) Diviner orbital albedo measurements at the Apollo landing sites. The soil samples are two representative end member samples from the moon, low albedo lunar maria (sample 10084) and high albedo lunar highlands (sample 68810). Bidirectional reflectance distribution function (BRDF) measurements of the soil samples were conducted at Bloomsburg University (BUG) and at the University of Arizona [1,2]. We collected two different types of BUG datasets: a standard set of BRDF measurements at incidence angles of 0-60°, emission angles of 0-80°, and phase angles of 3-140°, and a high-incidence angle set of measurements along and perpendicular to the principal plane at incidence angles of 0-75° and phase angles of 3-155°. The BUG measurements generated a total of 765 data points in four different filters 450, 550, 750 and 950 nm. The Blacklab measurements were acquired at incidence angles of 60-88°, emission angles 60-82°, and phase angles of 17-93° at wavelengths of 455, 554, 699, 949nm. The BUG data were fit to two BRDF models: Hapke’s model [3] as described by Johnson et al, 2010 [4], and a simplified empirical function. The fact that both approaches can satisfactorily fit the BUG data is not unexpected, given the similarities between the functions and their input parameters, and the fact that the BRDF for dark lunar soil is dominated by the single scattering phase functions of the individual soil particles. To compare our lunar sample measurements with LRO Diviner data [5], we selected all daytime observations acquired during the first year of operation within 3 km square boxes centered at the landing sites. We compared Diviner Channel 1 (0.3 - 3 µm) Lambert albedos with model calculated Lambert albedos of the lunar samples at the same photometric angles. In general, we found good agreement between the laboratory and Diviner measurements, particularly at intermediate incidence angles. We are currently reconciling any differences observed between our two datasets to provide mutual validation, and to better understand the Diviner solar reflectance measurements in terms of lunar regolith properties. [1] Shepard, M.K., Solar System Remote Sensing Symposium, #4004, LPI, 2002; [2] Biggar, S.F. et al, Proc. Soc. Photo-Opt. Instrum. Eng. 924:232-240, 1988; [3] Hapke, B. Theory of Reflectance and Emittance Spectroscopy, Cambridge University Press, 1993; [4] Johnson J.R. et al, Fall AGU 2010; [5] Paige, D.A. et al, Space Science Reviews, 150:125-160, 2010;

Foote, E. J.; Paige, D. A.; Shepard, M. K.; Johnson, J. R.; Biggar, S. F.; Greenhagen, B. T.; Allen, C.

2010-12-01

397

Direct observation of the formation of surfactant micelles under nonisothermal conditions by synchrotron SAXS.  

PubMed

Self-assembly of amphiphilic molecules into micelles occurs on very short times scales of typically some milliseconds, and the structural evolution is therefore very challenging to observe experimentally. While rate constants of surfactant micelle kinetics have been accessed by spectroscopic techniques for decades, so far no experiments providing detailed information on the structural evolution of surfactant micelles during their formation process have been reported. In this work we show that by applying synchrotron small-angle X-ray scattering (SAXS) in combination with the stopped-flow mixing technique, the entire micelle formation process from single surfactants to equilibrium micelles can be followed in situ. Using a sugar-based surfactant system of dodecyl maltoside (DDM) in dimethylformamide (DMF), micelle formation can be induced simply by adding water, and this can be followed in situ by SAXS. Mixing of water and DMF is an exothermic process where the micelle formation process occurs under nonisothermal conditions with a temperature gradient relaxing from about 40 to 20 °C. A kinetic nucleation and growth mechanism model describing micelle formation by insertion/expulsion of single molecules under nonisothermal conditions was developed and shown to describe the data very well. PMID:23590205

Jensen, Grethe Vestergaard; Lund, Reidar; Gummel, Jérémie; Monkenbusch, Michael; Narayanan, Theyencheri; Pedersen, Jan Skov

2013-05-15

398

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

399

Direct observation of prompt pre-thermal laser ion sheath acceleration  

NASA Astrophysics Data System (ADS)

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.

Zeil, K.; Metzkes, J.; Kluge, T.; Bussmann, M.; Cowan, T. E.; Kraft, S. D.; Sauerbrey, R.; Schramm, U.

2012-06-01

400

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

401

Direct observation of self-assembled chain-like water structures in a nanoscopic water meniscus.  

PubMed

Sawtooth-like oscillatory forces generated by water molecules confined between two oxidized silicon surfaces were observed using a cantilever-based optical interfacial force microscope when the two surfaces approached each other in ambient environments. The humidity-dependent oscillatory amplitude and periodicity were 3-12 nN and 3-4 water diameters, respectively. Half of each period was matched with a freely jointed chain model, possibly suggesting that the confined water behaved like a bundle of water chains. The analysis also indicated that water molecules self-assembled to form chain-like structures in a nanoscopic meniscus between two hydrophilic surfaces in air. From the friction force data measured simultaneously, the viscosity of the chain-like water was estimated to be between 10(8) and 10(10) times greater than that of bulk water. The suggested chain-like structure resolves many unexplained properties of confined water at the nanometer scale, thus dramatically improving the understanding of a variety of water systems in nature. PMID:23927275

Kim, Byung I; Boehm, Ryan D; Bonander, Jeremy R

2013-08-01

402

Motivating health workers for the provision of directly observed treatment to TB patients in rural China: does cash incentive work? A qualitative study.  

PubMed

As a key component of DOTS (directly observed treatment, short course) strategy, DOT is essential in the prevention of drug-resistant tuberculosis. However, DOT had very poor implementation in rural areas of China. One major reason to this problem was the lack of incentives for DOT providers. In 2005, the Chinese Minister of Health released an incentive strategy that aimed to improve the DOT performance of rural health workers by providing allowances. Our study used a qualitative method to explore the practical impact of this incentive strategy in motivating rural DOT providers, and searched for other potential incentive measures as well. A total of 16 focus group discussions were carried out among 102 rural health workers in eight counties of China. A semi-structured theme outline was used to collect the perception, attitude and experiences of health workers toward the DOT implementation as well as the cash incentive strategy. Findings showed that DOT allowance had some incentive effect to DOT providers, but its extent was circumscribed by the small amount and operational problems. Raising DOT allowance and removing existing barriers to DOT provision might result in a greater motivational impact, particularly in less developed areas of China, where health workers were more likely to encounter financial and other obstacles in delivering DOT services to TB patients in rural areas. PMID:23553649

Tao, Tao; Zhao, Qi; Jiang, Shiwen; Ma, Liping; Wan, Liya; Ma, Yongcheng; Xu, Biao

2013-01-01

403

Residue Ionization in LpxC Directly Observed by 67Zn NMR Spectroscopy  

PubMed Central

The pH dependence of the solid-state 67Zn NMR lineshapes has been measured for both wild type (WT) and the H265A mutant of Aquifex aeolicus LpxC, each in the absence of substrate (resting state). The 67Zn NMR spectrum of WT LpxC at pH 6 (prepared at 0 °C) contains two overlapping quadrupole lineshapes with Cq's of 10 and 12.9 MHz, while the spectrum measured for the sample prepared at a pH near 9 (at 0 °C) is dominated by the appearance of a third species with a Cq of 14.3 MHz. These findings are consistent with the two pKa values previously observed by the bell-shaped dependence of the LpxC-catalyzed reaction. Based on comparison of the experimental results with predictions from QM/MM modeling we suggest that pKa1 (low pH) represents the ionization of Glu78 and pKa2 (high pH) reflects the ionization of another active site residue located near the zinc ion, such as His265. These results are also consistent with water being bound to the Zn2+ throughout this pH range. The 67Zn NMR spectra of the H265A mutant appear to be pH independent with a Cq of 9.55 MHz being sufficient to describe both low and high pH data. The QM/MM models of the H265A mutant suggest that over this pH range water is bound to the zinc, while Glu78 is protonated. PMID:18761443

Lipton, Andrew S.; Heck, Robert W.; Hernick, Marcy; Fierke, Carol A.; Ellis, Paul D.

2009-01-01

404

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

405

An empirical model for transient crater growth in granular targets based on direct observations  

NASA Astrophysics Data System (ADS)

The present paper describes observations of crater growth up to the time of transient crater formation and presents a new empirical model for transient crater growth as a function of time. Polycarbonate projectiles were impacted vertically into soda-lime glass sphere targets using a single-stage light-gas gun. Using a new technique with a laser sheet illuminating the target [Barnouin-Jha, O.S., Yamamoto, S., Toriumi, T., Sugita, S., Matsui, T., 2007. Non-intrusive measurements of the crater growth. Icarus, 188, 506-521], we measured the temporal change in diameter of crater cavities (diameter growth). The rate of increase in diameter at early times follows a power law relation, but the data at later times (before the end of transient crater formation) deviates from the power law relation. In addition, the power law exponent at early times and the degree of deviation from a power law at later times depend on the target. In order to interpret these features, we propose