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1

Psychometrics of Direct Observation  

ERIC Educational Resources Information Center

Direct observation plays an important role in the assessment practices of school psychologists and in the development of evidence-based practices in general and special education. The defining psychometric features of direct observation are presented, the contributions to assessment practice reviewed, and a specific proposal is offered for…

Hintze, John M.

2005-01-01

2

Directional drilling allows quick exit from petrochemical plant  

SciTech Connect

Horizontal directional drilling uses specialty tools and techniques largely taken from the oil field and the mining industry to very accurately install pipelines, utilities and other conduits under obstacles such as rivers, beaches, environmentally sensitive areas, roadways, railroads, airfields, and congested pipeline corridors. In the early part of 1990, a particularly interesting problem confronted the pipeline engineers at Union Carbides 2,500-acre Seadrift plant near Port Lavaca, Texas. Having started up in 1954, the plant today is a major supplier of chemicals and plastics to industry, shipping more than two billion pounds per year. Since very large volumes of cooling water are needed for the operation of a petrochemical complex of this magnitude, years of expansion and modifications have caused the plant to become nearly surrounded by a number of rather large segmented ponds.

Halderman, R.G. [BERCO Services, Inc., Houston, TX (United States)

1994-12-31

3

Markov models for community dynamics allowing for observation error.  

PubMed

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

Fukaya, Keiichi; Royle, J Andrew

2013-12-01

4

Direct observation of Josephson capacitance.  

PubMed

The effective capacitance has been measured in the split Cooper-pair box (CPB) over its phase-gate bias plane. Our low-frequency reactive measurement scheme allows us to probe purely the capacitive susceptibility due to the CPB band structure. The data are quantitatively explained using parameters determined independently by spectroscopic means. In addition, we show in practice that the method offers an efficient way to do nondemolition readout of the CPB quantum state. PMID:16384085

Sillanpää, M A; Lehtinen, T; Paila, A; Makhlin, Yu; Roschier, L; Hakonen, P J

2005-11-11

5

Polynomial Synthesis of Supervisor for Partially Observed Discrete Event Systems by allowing  

E-print Network

Polynomial Synthesis of Supervisor for Partially Observed Discrete Event Systems by allowing of discrete event systems under partial ob- servation using nondeterministic supervisors. We formally define a nondeterministic control policy and also a control & observation compatible nondeterministic state ma- chine

Kumar, Ratnesh

6

Direct observation of the direction of motion for spherical catalytic swimmers.  

PubMed

Nonconductive Janus particle swimmers made by coating fluorescent polymer beads with hemispheres of platinum have been fully characterized using video microscopy to reveal that they undergo propulsion in hydrogen peroxide fuel away from the catalytic platinum patch. The platinum coating shadows the fluorescence signal from half of each swimmer to allow the orientation to be observed directly and correlated quantitatively with the resulting swimming direction. The observed swimmer direction is consistent with both the bubble release and diffusiophoretic propulsion mechanisms. PMID:21928845

Ebbens, Stephen J; Howse, Jonathan R

2011-10-18

7

Direct Observation of Polymer Sheathing in Carbon  

E-print Network

Direct Observation of Polymer Sheathing in Carbon Nanotube-Polycarbonate Composites W. Ding, A (MWCNT)-polycarbonate composites are presented. This sheathing was observed in images of the composite behavior of nanotube-polycarbonate composites, and their SEM observation of the fracture surface showed

8

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

PubMed

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

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

2012-01-01

9

Observe how the monsoon changes direction  

NSDL National Science Digital Library

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

TERC. Center for Earth and Space Science Education

2003-01-01

10

Direct Observation of Born-Oppenheimer Approximation  

E-print Network

Direct Observation of Born-Oppenheimer Approximation Breakdown in Carbon Nanotubes Adam W of the theoretically predicted breakdown of the Born-Oppenheimer approximation in individual single-walled carbon nanotubes. The Born-Oppenheimer (BO) or adiabatic approximation is widely used to simplify the very complex

Cronin, Steve

11

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

12

First direct observation of muon antineutrino disappearance  

DOE PAGESBeta

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

13

Direct observation of sub-binomial light.  

PubMed

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

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

2013-04-26

14

WMAP haze: Directly observing dark matter?  

SciTech Connect

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 13 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 11 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.

Forbes, Michael McNeil; Zhitnitsky, Ariel R. [Nuclear Theory Group, Department of Physics, University of Washington, Seattle, Washington 98195-1560 (United States); University of British Columbia, Department of Physics and Astronomy, Vancouver, B.C., V6T 1Z1 (Canada)

2008-10-15

15

Direct observation of amyloid nucleation under nanomechanical stretching  

NASA Astrophysics Data System (ADS)

Self-assembly of amyloid nanofiber is associated with functional and pathological processes such as in neurodegenerative diseases. Despite intensive studies, stochastic nature of the process has made it difficult to elucidate molecular mechanisms for the key amyloid nucleation. Here, we investigated the amyloid nucleation of silk-elastin-like peptide (SELP) using time-lapse lateral force microscopy (LFM). By repeated scanning a single line on a SELP-coated mica surface, we observed sudden stepwise height increases, corresponds to nucleation of an amyloid fiber. The lateral force profiles followed either a worm-like chain model or an exponential function, suggesting that the atomic force microscopy (AFM) tip stretches a single or multiple SELP molecules along the scanning direction, serves as the template for further self-assembly perpendicular to the scan direction. Such mechanically induced nucleation of amyloid fibrils allows positional and directional control of amyloid assembly in vitro , which we demonstrate by generating single nanofibers at predetermined nucleation sites.

Varongchayakul, Nitinun

16

Catalytic carbene transfer allows the direct customization of cyclic purine dinucleotides.  

PubMed

We describe a simple method for the direct modification of nucleobases in cyclic purine dinucleotides, important signalling molecules in both prokaryotes and eukaryotes. The method tolerates all members of the cyclic dinucleotide family and could be used to modulate their function or introduce useful side-chains such as fluorophores and photo-crosslinking groups. PMID:24946836

Fei, Na; Häussinger, Daniel; Blümli, Seraina; Laventie, Benoît-Joseph; Bizzini, Lorenzo D; Zimmermann, Kaspar; Jenal, Urs; Gillingham, Dennis

2014-08-11

17

Direct observation of fast protein conformational switching  

PubMed Central

Folded proteins can exist in multiple conformational substates. Each substate reflects a local minimum on the free-energy landscape with a distinct structure. By using ultrafast 2D-IR vibrational echo chemical-exchange spectroscopy, conformational switching between two well defined substates of a myoglobin mutant is observed on the ?50-ps time scale. The conformational dynamics are directly measured through the growth of cross peaks in the 2D-IR spectra of CO bound to the heme active site. The conformational switching involves motion of the distal histidine/E helix that changes the location of the imidazole side group of the histidine. The exchange between substates changes the frequency of the CO, which is detected by the time dependence of the 2D-IR vibrational echo spectrum. These results demonstrate that interconversion between protein conformational substates can occur on very fast time scales. The implications for larger structural changes that occur on much longer time scales are discussed. PMID:18562286

Ishikawa, Haruto; Kwak, Kyungwon; Chung, Jean K.; Kim, Seongheun; Fayer, Michael D.

2008-01-01

18

Trehalose glycopolymer resists allow direct writing of protein patterns by electron-beam lithography.  

PubMed

Direct-write patterning of multiple proteins on surfaces is of tremendous interest for a myriad of applications. Precise arrangement of different proteins at increasingly smaller dimensions is a fundamental challenge to apply the materials in tissue engineering, diagnostics, proteomics and biosensors. Herein, we present a new resist that protects proteins during electron-beam exposure and its application in direct-write patterning of multiple proteins. Polymers with pendant trehalose units are shown to effectively crosslink to surfaces as negative resists, while at the same time providing stabilization to proteins during the vacuum and electron-beam irradiation steps. In this manner, arbitrary patterns of several different classes of proteins such as enzymes, growth factors and immunoglobulins are realized. Utilizing the high-precision alignment capability of electron-beam lithography, surfaces with complex patterns of multiple proteins are successfully generated at the micrometre and nanometre scale without requiring cleanroom conditions. PMID:25791943

Bat, Erhan; Lee, Juneyoung; Lau, Uland Y; Maynard, Heather D

2015-01-01

19

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

PubMed Central

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

2010-01-01

20

Direct observation of stepwise movement of a synthetic molecular transporter  

NASA Astrophysics Data System (ADS)

Controlled motion at the nanoscale can be achieved by using Watson-Crick base-pairing to direct the assembly and operation of a molecular transport system consisting of a track, a motor and fuel, all made from DNA. Here, we assemble a 100-nm-long DNA track on a two-dimensional scaffold, and show that a DNA motor loaded at one end of the track moves autonomously and at a constant average speed along the full length of the track, a journey comprising 16 consecutive steps for the motor. Real-time atomic force microscopy allows direct observation of individual steps of a single motor, revealing mechanistic details of its operation. This precisely controlled, long-range transport could lead to the development of systems that could be programmed and routed by instructions encoded in the nucleotide sequences of the track and motor. Such systems might be used to create molecular assembly lines modelled on the ribosome.

Wickham, Shelley F. J.; Endo, Masayuki; Katsuda, Yousuke; Hidaka, Kumi; Bath, Jonathan; Sugiyama, Hiroshi; Turberfield, Andrew J.

2011-03-01

21

Sensor calibration for multiple direction reflectance observations  

NASA Technical Reports Server (NTRS)

Spectral and radiometric calibrations of a pointable airborne spectroradiometer called ASAS are discussed. A laboratory integrating hemisphere is used to characterize the radiometric respones of ASAS detectors. Radiometric responses are linear except for an initial build-up lag in response to low levels of radiance. Assuming radiometric stability in flight, raw ASAS digital counts can be transformed to absolute spectral radiance values with an uncertainty of 5.5 percent attributable to the laboratory calibration. The calibrations are being applied to radiometrically correct ASAS data acquired from multiple view directions over a tall grass prairie during the 1987 growing season.

Irons, James R.; Irish, Richard R.

1988-01-01

22

Bonding of SU-8 to glass for gastight picoliter reactors allowing in situ optical observation  

NASA Astrophysics Data System (ADS)

Experimental tasks in chemistry and biology require large experiment statistics, small solution volumes, and no gas or vapor exchange with the environment. Microfluidics devices built of the epoxy-based polymer SU-8 comply with these requirements. However, the additional constraints of reactor thickness of several micrometers, localized temperature control, and optical access for high-resolution observation provide a challenge. We developed a device consisting of top and bottom glass plates separated by a layer of cross-linked SU-8, with a resistive microheater deposited at the bottom. Picoliter reactor volumes are achieved by suspending aqueous solution droplets in silicone oil held in a channel with cross-section 5 × 40 µm2. The narrow channels lead to large capillary resistance and, in turn, high injection pressures. To achieve bonding of SU-8 to glass capable of withstanding such pressures, we optimized the oxygen plasma treatment of the polymer surface by monitoring the evolution of the treated surface with atomic force microscopy. We found that the plasma effect was fully determined by its power. The hydrophilicity of the treated surfaces was characterized by their contact angles with water. The treated surfaces were bonded to glass bottoms using a torque-controlled clamp with a 3 µm smoothness of the holding plates. The bonding pressure and temperature were chosen in the gap between those for the glass transition of the SU-8 layer and fracture of the glass bottom.

Petrova, Elena V.; Aich, Anupam; Byington, Michael C.; Vekilov, Peter G.

2013-10-01

23

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

24

[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

25

Direct observations of field-induced assemblies in magnetite ferrofluids  

NASA Astrophysics Data System (ADS)

Evolution of microstructures in magnetite-based ferrofluids with weak dipolar moments (particle size ? 10 nm) is studied with an emphasis on examining the effects of particle concentration (?) and magnetic field strength (H) on the structures. Nanoparticles are dispersed in water at three different concentrations, ? = 0.15%, 0.48%, and 0.59% (w/v) [g/ml%] and exposed to uniform magnetic fields in the range of H = 0.05-0.42 T. Cryogenic transmission electron microscopy is employed to provide in-situ observations of the field-induced assemblies in such systems. As the magnetic field increases, the Brownian colloids are observed to form randomly distributed chains aligned in the field direction, followed by head-to-tail chain aggregation and then lateral aggregation of chains termed as zippering. By increasing the field in low concentration samples, the number of chains increases, though their length does not change dramatically. Increasing concentration increases the length of the linear particle assemblies in the presence of a fixed external magnetic field. Thickening of the chains due to zippering is observed at relatively high fields. Through a systematic variation of concentration and magnetic field strength, this study shows that both magnetic field strength and change in concentration can strongly influence formation of microstructures even in weak dipolar systems. Additionally, the results of two commonly used support films on electron microscopy grids, continuous carbon and holey carbon films, are compared. Holey carbon film allows us to create local regions of high concentrations that further assist the development of field-induced assemblies. The experimental observations provide a validation of the zippering effect and can be utilized in the development of models for thermophysical properties such as thermal conductivity.

Mousavi, N. S. Susan; Khapli, Sachin D.; Kumar, Sunil

2015-03-01

26

Enabling direct nanoscale observations of biological reactions with dynamic TEM  

SciTech Connect

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

Evans, James E.; Browning, Nigel D.

2013-02-18

27

Direct Observation of Two Proton Radioactivity Using Digital Photography  

SciTech Connect

Recently the observation of a new type of spontaneous radioactive decay has been claimed in which two protons are simultaneously ejected by an atomic nucleus from the ground state1,2,3. Experimental data obtained for the extremely neutron-deficient nuclei 45Fe and 54Zn, were interpreted as the first evidence of such a decay mode which has been sought since 1960.4 However, the technique applied in those studies allowed only measurements of the decay time and the total energy released. Particles emitted in the decay were not identified and the conclusions had to be supported by theoretical arguments. Here we show for the first time, directly and unambiguously, that 45Fe indeed disintegrates by two-proton decay. Furthermore, we demonstrate that the decay branch of this isotope leads to various particle emission channels including two-proton and three-proton emission. To achieve this result we have developed a new type of detector V the Optical Time Projection Chamber (OTPC) in which digital photography is applied to nuclear physics for the first time. The detector records images of tracks from charged particles, allowing for their unambiguous identification and the reconstruction of decay events in three dimensions. This new and simple technique provides a powerful method to identify exotic decay channels involving emission of charged particles. It is expected that further studies with the OTPC device will yield important information on nuclei located at and beyond the proton drip-line, thus providing new material for testing and improving models of very unstable atomic nuclei.

Rykaczewski, Krzysztof Piotr [ORNL; Pfutzner, M. [IEP, Warsaw University; Dominik, Wojciech [Warsaw University; Janas, Z. [IEP, Warsaw University; Miernik, K. [IEP, University of Warsaw; Bingham, C. R. [University of Tennessee, Knoxville (UTK); Czyrkowski, Henryk [Warsaw University; Cwiok, Mikolaj [Warsaw University; Darby, Iain [University of Tennessee, Knoxville (UTK); Dabrowski, Ryszard [Warsaw University; Ginter, T. N. [NSCL Michigan State University; Grzywacz, Robert Kazimierz [ORNL; Karny, M. [IEP, Warsaw University; Korgul, A. [IEP, Warsaw University; Kusmierz, Waldemar [Warsaw University; Liddick, Sean [University of Tennessee, Knoxville (UTK); Rajabali, Mustafa [University of Tennessee, Knoxville (UTK); Stolz, A. [NSCL Michigan State University

2007-01-01

28

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

29

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

30

Retinex Image Processing: Improved Fidelity To Direct Visual Observation  

NASA Technical Reports Server (NTRS)

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

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

1996-01-01

31

Directionality of solar flare hard X rays - Venera 13 observations  

SciTech Connect

An analysis of 79 flares detected by the Venera 13 SIGNE 2 MS gamma-ray telescope is performed to indirectly search for directional effects in the hard (50-300 keV) X rays of solar flares. X-ray spectra were reconstructed assuming a power law fit. From the distribution of X-ray flares with respect to angle of observation and spectral index it is found that the primary-plus-albedo radiation is directive, and that the observed flare spectrum hardens toward the solar limb. 21 references.

Bogovalov, S.V.; Kotov, IU.D.; Zenchenko, V.M.; Vedrenne, G.; Niel, M.

1985-10-01

32

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

PubMed

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

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

2014-02-01

33

Direct Observation of Postadsorption Aggregation of Antifreeze Glycoproteins on Silicates  

E-print Network

Direct Observation of Postadsorption Aggregation of Antifreeze Glycoproteins on Silicates Ph Form: March 13, 2000 The adsorption of antifreeze glycoproteins (AFGP) from aqueous solution onto two of these results to the adsorption of the AFGP on ice is discussed. Introduction Antifreeze glycoproteins (AFGP

Cheng, Chi-Hing Christina

34

Direct observation of a local structural mechanism for dynamic arrest  

E-print Network

ARTICLES Direct observation of a local structural mechanism for dynamic arrest C. PATRICK ROYALL1 2008; doi:10.1038/nmat2219 The mechanism by which a liquid may become arrested, forming a glass or gel been thought to play a key role in dynamical arrest. Here, we propose a definition of LFSs which we

Weeks, Eric R.

35

The Validity of Direct Observation Measures of Pupil Classroom Behavior.  

ERIC Educational Resources Information Center

An evaluation of the validity of direct observation measures of pupil classroom behaviors is presented. Three types of measures are discussed: molar, molecular, and molecular-composite. Consistent support for the validity of molar and molecular-composite types of measures is revealed. (Author/LMO)

Hoge, Robert D.

1985-01-01

36

Quantifying predation on soybean aphid through direct field observations  

E-print Network

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

Landis, Doug

37

Observations of aerosol semi-direct effects at multiple scales  

NASA Astrophysics Data System (ADS)

The semi-direct radiative forcing of absorbing aerosols such as soot and smoke is generally regarded as a positive forcing whereby tropospheric heating owing to aerosol absorption of sunlight reduces cloud cover. The responses of cloud systems to tropospheric heating, however, may be more varied depending upon the vertical and geographic relationship between the aerosol direct forcing and the clouds, as well as depending upon the scales of the cloud systems. This presentation will explore techniques for applying satellite and in-situ observations to the diagnosis of semi-direct effects on cloud systems ranging from trade cumulus clouds to the inter-tropical convergence zone. Examples are shown of semi-direct effects yielding a negative radiative forcing, as well as large-scale shifts of cloud and precipitation patterns. These studies seek to evaluate the results of controlled model experiments where the radiative effects of aerosols are isolated from other modifications to the environment that influence cloud systems.

Wilcox, E. M.

2013-05-01

38

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

39

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

E-print Network

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

Wood, Stephen L.

40

Direct Observation of Nonaffine Tube Deformation in Strained Polymer Networks  

NASA Astrophysics Data System (ADS)

We present a one-to-one comparison of polymer segmental fluctuations as measured by small angle neutron scattering in a network under deformation with those obtained by neutron spin echo spectroscopy. This allows an independent proof of the strain dependence of the chain entanglement length. The experimentally observed nonaffine square-root dependence of the tube channel on strain is in excellent agreement with theoretical predictions and permits us to exclude an often invoked nondeformed as well as affinely deformed tube.

Pyckhout-Hintzen, W.; Westermann, S.; Wischnewski, A.; Monkenbusch, M.; Richter, D.; Straube, E.; Farago, B.; Lindner, P.

2013-05-01

41

Direct Observations of the Evolution of Polar Cap Ionization Patches  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

42

Direct observation of single kinesin molecules moving along microtubules  

Microsoft Academic Search

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

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

1996-01-01

43

Microcrack closure in rocks under stress - Direct observation  

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

44

Allowing cycle-stealing direct memory access I\\/O concurrent with hard-real-time programs  

Microsoft Academic Search

Abstract: Hard-real-time schedulability analysis is carried outbased on the assumption that the worst-case executiontime (WCET) of each task is known. CyclestealingDirect Memory Access (DMA) I\\/O steals buscycles from an executing program and prolongs theexecution time of the program. Because of the difficultyin bounding the interference on the executingprogram, cycle-stealing DMA I\\/O is often disabled inhard-real-time systems. This paper presents an

Tai-yi Huang; Jane W.-S. Liu; Jen-yao Chung

1996-01-01

45

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

46

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

47

Direct observation of Kelvin waves excited by quantized vortex reconnection.  

PubMed

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

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

2014-03-25

48

Direct Observation of Correlated Interdomain Motion in Alcohol Dehydrogenase  

SciTech Connect

Interdomain motions in proteins are essential to enable or promote biochemical function. Neutron spin-echo spectroscopy is used to directly observe the domain dynamics of the protein alcohol dehydrogenase. The collective motion of domains as revealed by their coherent form factor relates to the cleft opening dynamics between the binding and the catalytic domains enabling binding and release of the functional important cofactor. The cleft opening mode hardens as a result of an overall stiffening of the domain complex due to the binding of the cofactor.

Biehl, Ralf; Monkenbusch, Michael; Richter, Dieter [Institut fuer Festkoerperforschung, Forschungszentrum Juelich, D-52425 Juelich (Germany); Hoffmann, Bernd; Merkel, Rudolf [Institut fuer Bio- und Nanosysteme, Forschungszentrum Juelich, D-52425 Juelich (Germany); Falus, Peter [Institut Laue Langevin, F-38042 Grenoble (France); Preost, Sylvain [Hahn Meitner Institut, D-14109 Berlin (Germany)

2008-09-26

49

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

50

Experimental observations of shear patterns in direct shear tests  

NASA Astrophysics Data System (ADS)

A series of simple experiments were performed using direct shear apparatus in order to study the rupture patterns in sands. Measurements of internal displacements were made by observing with X-rays the positions of lead shot placed in a regular array within the sample. Shear displacement was applied manually and radiographs were taken after each increment of horizontal movement in order to observe the incremental strain field. The sand used was 30/52 Leighton Buzzard sand with a grain size between 0.3mm and 0.5mm. It was concluded that, while caution should be exercised in extrapolating the results of these low stress tests, the results matched some theoretical estimates for the orientation of shear bands. It was suggested that characteristic lengths and thicknessess of shear bands might be related to the average particle size of the sand.

Scarpelli, G.; Wood, D. M.

51

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

52

Direct observations of the evolution of polar cap ionization patches.  

PubMed

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

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

2013-03-29

53

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

54

Direct microscopic observation of forward osmosis membrane fouling.  

PubMed

This study describes the application of a noninvasive direct microscopic observation method for characterizing fouling of a forward osmosis (FO) membrane. The effect of the draw solution concentration, membrane orientation, and feed spacer on FO fouling was systematically investigated in a cross-flow setup using latex particles as model foulant in the feedwater. Higher draw solution (DS) concentrations (and thus increased flux levels) resulted in dramatic increase in the surface coverage by latex particles, suggesting that the critical flux concept might be applicable even for the osmotically driven FO process. Under identical draw solution concentrations, the active-layer-facing-the-feed-solution orientation (AL-FS) experienced significantly less fouling compared to the alternative orientation. This may be explained by the lower water flux in AL-FS, which is consistent with the critical flux concept. The use of a feed spacer not only dramatically enhanced the initial flux of the FO membrane, but also significantly improved the flux stability during FO fouling. Despite such beneficial effects of using the feed spacer, a significant amount of particle accumulation was found near the spacer filament, suggesting further opportunities for improved spacer design. To the best of the authors' knowledge, this is the first direct microscopic observation study on FO fouling. PMID:20735033

Wang, Yining; Wicaksana, Filicia; Tang, Chuyang Y; Fane, Anthony G

2010-09-15

55

Direct and Semi-direct Radiative Responses to Observation-Constrained Aerosol Absorption over S Asia  

NASA Astrophysics Data System (ADS)

Climate impacts of aerosols over S. Asia have been studied extensively in both models and observations. However, discrepancies between observed and modeled aerosol concentrations and optical properties have hindered our understanding of the aerosol influences on the regional monsoon circulation and rainfall. We present an in-depth examination of direct and semi-direct radiative responses due to aerosols on the latitudinal heating gradient and cloud distribution, with observational constraints on solar absorption by aerosols. Regional distributions of aerosol concentration are simulated with a 12-km regional climate model (WRF-Chem) driven by the NCEP analysis data from August 2011 to March 2012. During this time period, the ground-based measurements of aerosols and clouds, surface radiation, water vapor, and temperature were taken at Nainital (29.38°N, 79.45°E) during the DOE Ganges Valley Experiment (GVAX). This data set, which is available at high temporal resolution (hourly), is used to evaluate and constrain the simulated wavelength dependence of aerosol absorption and the correlation with changes in surface radiation, cloud base height and liquid water content for the entire post-monsoon period. The analysis is extended to a regional scale by comparing with satellite observation of absorbing aerosol optical depth (OMI) and cloud properties (MODIS). Preliminary results show good agreement in monthly variations of simulated and observed aerosol optical depth (AOD) except during periods of high observed AOD. Initial analysis indicates a possible local origin for the aerosols that is not captured in the model at present. Furthermore, analysis of the spectrally resolved aerosol absorption measurements indicates that these local aerosols exhibit strong absorption in near-UV and visible wavelengths. A large fraction of increased absorption during October and November (local fall harvest season) is attributable to the super-micron sized aerosol particles. In addition, much higher ceilometer lowest cloud base height (>5 km) is observed coincident with high aerosol absorption coefficient (>50 Mm-1 at 528nm), which may be indicative of the semi-direct 'burning off' effect due to absorbing aerosols, as the prevailing lowest cloud base height observed is below 3km from the ground. In comparison, the model-simulated aerosol absorption is significantly lower around 15 Mm-1 during these time periods and the model calculated OC/BC ratios are about 2~4 also smaller than observations. This may likely suggest an underestimate of absorbing organics from the biomass burning or biogenic sources. In the presentation, we will present the model sensitivity studies of aerosol absorption constrained by the observed absorption AOD and spectral dependence, and discuss the subsequent changes in the simulated atmospheric heating rates and cloud distributions over this region.

Feng, Y.; Kotamarthi, V. R.; Manoharan, V.

2013-12-01

56

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

57

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

58

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

59

Enabling direct nanoscale observations of biological reactions with dynamic TEM  

PubMed Central

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

Evans, James E.; Browning, Nigel D.

2013-01-01

60

Direct Observation, Study, and Control of Molecular Superrotors  

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

61

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

62

The cosmic microwave background: observing directly the early universe  

E-print Network

The Cosmic Microwave Background (CMB) is a relict of the early universe. Its perfect 2.725K blackbody spectrum demonstrates that the universe underwent a hot, ionized early phase; its anisotropy (about 80 \\mu K rms) provides strong evidence for the presence of photon-matter oscillations in the primeval plasma, shaping the initial phase of the formation of structures; its polarization state (about 3 \\mu K rms), and in particular its rotational component (less than 0.1 \\mu K rms) might allow to study the inflation process in the very early universe, and the physics of extremely high energies, impossible to reach with accelerators. The CMB is observed by means of microwave and mm-wave telescopes, and its measurements drove the development of ultra-sensitive bolometric detectors, sophisticated modulators, and advanced cryogenic and space technologies. Here we focus on the new frontiers of CMB research: the precision measurements of its linear polarization state, at large and intermediate angular scales, and the m...

de Bernardis, Paolo

2012-01-01

63

Microcrack closure in rocks under stress: direct observation  

SciTech Connect

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

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

1980-12-10

64

Direct observation of subunit exchange along mature vimentin intermediate filaments.  

PubMed

Actin filaments, microtubules, and intermediate filaments (IFs) are central elements of the metazoan cytoskeleton. At the molecular level, the assembly mechanism for actin filaments and microtubules is fundamentally different from that of IFs. The former two types of filaments assemble from globular proteins. By contrast, IFs assemble from tetrameric complexes of extended, half-staggered, and antiparallel oriented coiled-coils. These tetramers laterally associate into unit-length filaments; subsequent longitudinal annealing of unit-length filaments yields mature IFs. In vitro, IFs form open structures without a fixed number of tetramers per cross-section along the filament. Therefore, a central question for the structural biology of IFs is whether individual subunits can dissociate from assembled filaments and rebind at other sites. Using the fluorescently labeled IF-protein vimentin for assembly, we directly observe and quantitatively determine subunit exchange events between filaments as well as with soluble vimentin pools. Thereby we demonstrate that the cross-sectional polymorphism of donor and acceptor filaments plays an important role. We propose that in segments of donor filaments with more than the standard 32 molecules per cross-section, subunits are not as tightly bound and are predisposed to be released from the filament. PMID:25517157

Nöding, Bernd; Herrmann, Harald; Köster, Sarah

2014-12-16

65

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

66

Direct Observations Of Microbial Activity At Extreme Pressures  

NASA Astrophysics Data System (ADS)

Microbial communities adapt to a wide range of pressures, temperatures, salinities, pH, and oxidation states. Although, significant attention has been focused on the effects of high and low temperature on physiology, there is some evidence that elevated pressure may also manifest interesting effects on cellular physiology, such as enzyme inactivation, cell-membrane breach, and suppression of protein interactions with various substrates. However, exactly how these factors affect intact cells is not well understood. In this study, we have adapted diamond anvil cells to explore the effects of high pressure on microbial life. We used the rate of microbial formate oxidation as a probe of metabolic viability. The utilization of formate by microorganisms is a fundamental metabolic process in anaerobic environments. We monitored in-situ microbial formate oxidation via molecular spectroscopy for Shewanella oneidensis strain MR1 and Escherichia coli strain MG1655 at high pressures (68 to 1060 MPa). At pressures of 1200 to 1600 MPa, living bacteria resided in fluid inclusions in ice-VI crystals and continued to be viable upon subsequent release to ambient pressures (0.1 MPa). Furthermore, direct microscopic observations indicate that these cells maintain their ability for cellular division upon decompression from such high pressures. Evidence of microbial viability and activity at these extreme pressures expands by an order of magnitude the range of conditions representing the habitable zone in the solar system. These results imply that pressure may not be a significant impediment to life. The maximum pressure explored in this work is equivalent to a depth of ~ 50 km below Earth's crust, or ~ 160 km in a hypothetical ocean. The pressures encountered at the depths of thick ice caps and deep crustal subsurface may not be a limiting factor for the existence of life. This suggests that deep (water/ice) layers of Europa, Callisto, or Ganymede, subduction zones on Earth, and the polar ice caps of Mars might provide viable settings for life unhindered by the high pressures.

Sharma, A.; Scott, J. H.; Cody, G. D.; Fogel, M.; Hazen, R. M.; Hemley, R. J.; Huntress, W. T.

2002-12-01

67

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

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

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

70

Observation of direct processes in photoproduction at HERA  

Microsoft Academic Search

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

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

1994-01-01

71

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

TERC. Center for Earth and Space Science Education

2003-01-01

72

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

PubMed Central

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

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

2014-01-01

73

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

74

The direct observation of cosmic ray composition in JACEE  

NASA Technical Reports Server (NTRS)

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

Burnett, T. H.; Dake, S.; Derrickson, J. H.; Fountain, W. F.; Fuki, M.

1989-01-01

75

The direct observation of cosmic ray composition in JACEE  

SciTech Connect

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

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

1989-03-01

76

Direct observation of the Aharonov-Casher phase.  

PubMed

Ring structures fabricated from HgTe/HgCdTe quantum wells have been used to study Aharonov-Bohm type conductance oscillations as a function of Rashba spin-orbit splitting strength. We observe nonmonotonic phase changes indicating that an additional phase factor modifies the electron wave function. We associate these observations with the Aharonov-Casher effect. This is confirmed by comparison with numerical calculations of the magnetoconductance for a multichannel ring structure within the Landauer-Büttiker formalism. PMID:16606124

König, M; Tschetschetkin, A; Hankiewicz, E M; Sinova, Jairo; Hock, V; Daumer, V; Schäfer, M; Becker, C R; Buhmann, H; Molenkamp, L W

2006-02-24

77

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

E-print Network

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

Paris-Sud XI, Université de

78

Physical Activity Surveillance in Parks Using Direct Observation  

PubMed Central

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

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

2014-01-01

79

Van Allen Probes Observations of Direct Wave Particle Interactions  

NASA Astrophysics Data System (ADS)

We present observations of wave-particle interactions observed on the Van Allen Probes during an interval of sporadic increases or bursts of 20-30 keV electron fluxes observed in conjunction with bursts of chorus activity. The electron flux and chorus burst occurred on a nearly one for one basis during an hour interval on January 13, 2013. The electron angular distributions changed during the burst events such that flux increases evolved from Sinn(?) type angular distributions to form maxima in the electron angular distributions at 75-80° local pitch angle with the fluxes at 90° and <60° remaining the same as in the pre and post burst distributions. These events occurred well outside the plasmasphere following a minor plasma injection. They were observed on both Van Allen Probes spacecraft, which were relatively close together. The plasma density, electron gyro-frequency and pitch angle of peak flux in a burst was used to estimate the resonant electron energy. The result of ~25 keV is consistent with the energies of the electrons showing the flux enhancements observed by the ECT/MagEIS and ECT/HOPE spectrometers. These results will be described in detail and questions concerning the source of such events will be discussed.

Fennell, J. F.; Roeder, J. L.; Kurth, W. S.; Henderson, M. G.; Larsen, B.; Hospodarsky, G. B.; Blake, J. B.; Claudepierre, S. G.; Clemmons, J. H.; Spence, H.; Funsten, H. O.; Reeves, G. D.; Kletzing, C.; Wygant, J. R.

2013-12-01

80

Fluorophore labeling of native FKBP12 by ligand-directed tosyl chemistry allows detection of its molecular interactions in vitro and in living cells.  

PubMed

Introducing synthetic fluorophores into specific endogenous proteins and analyzing their function in living cells are a great challenge in chemical biology. Toward this end, we demonstrate the target-selective and site-specific fluorescent labeling of native FKBP12 (FK506-binding protein 12) in vitro and in living cells using ligand-directed tosyl (LDT) chemistry. The LDT-mediated labeling yielded a semisynthetic FKBP12 containing the Oregon green (OG) dye near the catalytic pocket. The OG-labeled FKBP12 (OG-FKBP12) acted as a fluorescent reporter that allows monitoring of its interaction with rapamycin and FRB (FKBP-rapamycin-binding domain) in vitro. We also successfully demonstrated the visualization of the rapamycin-mediated complexation of the OG-FKBP12 and FRB inside of living cells by the combined use with fluorescent protein-tag technology and Förster resonance energy-transfer imaging. PMID:23611728

Tamura, Tomonori; Kioi, Yoshiyuki; Miki, Takayuki; Tsukiji, Shinya; Hamachi, Itaru

2013-05-01

81

The First Direct Observation of Double-Beta Decay  

NASA Astrophysics Data System (ADS)

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

Moe, Michael

2014-10-01

82

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

83

Direct observations of hydrogen enhanced crack propagation in iron  

Microsoft Academic Search

Investigation of hydrogen enhanced fracture of iron and steel has given rise to numerous theoretical explanations for the observed phenomena. Despite this effort, the basic parameters of the explanation, whether H affects the ''''cohesive energy'' of the solid, whether it affects the surface energy, whether it influences the plastic processes at the crack tip or some combination of these have

T. Tabata; H. K. Birnbaum

1984-01-01

84

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

85

Direct Observations of Reaction Zone Structure in Propagating Detonations  

E-print Network

of the detonation cell width. The structure of the triple point was studied in a narrow channel using schlieren it propagates in a narrow channel, as shown by Strehlow and Crooker [7]. Schlieren images of detonations in non structure, schlieren images show similar shock configurations to those observed in narrow channels, when

Barr, Al

86

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

87

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

88

Direct observation of muon pair production by cosmic ray muons  

Microsoft Academic Search

Experimental data collected in a long-term exposition of the big liquid-argon spectrometer BARS in horizontal cosmic ray flux have been analysed to select the events corresponding to muon pair production by muons in the inner fiducial volume of the detector. The observed number of such events (7 among 1.9 million muons passing through the setup) is in agreement with recent

V. B. Anikeev; S. P. Denisov; S. N. Gurzhiev; S. R. Kelner; T. M. Kirina; R. P. Kokoulin; V. V. Lipaev; A. A. Petrukhin; A. M. Rybin; F. Sergiampietri; E. E. Yanson; O. S. Zolina

2001-01-01

89

Directional Observations of Radio Noise from the Outer Atmosphere  

Microsoft Academic Search

ALTHOUGH many observations have been made in the past of the spectra of the radio emissions of the Earth's outer atmosphere in the frequency band 2-40 Kc.\\/s.1,2, it is only recently that a technique has been developed for continuously monitoring the occurrence of these phenomena3. This has revealed that radio noise bursts lasting some hours are normally associated with disturbances

G. R. A. Ellis; D. G. Cartwright

1959-01-01

90

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

91

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

92

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

93

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

94

Observability Analysis of Conewise Linear Systems via Directional Derivative and Positive Invariance  

E-print Network

Observability Analysis of Conewise Linear Systems via Directional Derivative and Positive estimation of nonsmooth switched systems in applications, we exploit directional derivative and positive Abstract Belonging to the broad framework of hybrid systems, conewise linear systems (CLSs) form a class

Shen, Jinglai

95

Direct observation of time.reversal violation in B mesons at BABAR  

NASA Astrophysics Data System (ADS)

Although CP violation in the B meson system has been well established by the B factories, there has been no direct observation of time-reversal violation. The decays of entangled neutral B mesons into definite flavour states (B0 or bar B0), and J/?K0L or cbar cK0s final states (referred to as B+ or B-), allow comparisons between the probabilities of four pairs of T-conjugated transitions, for example, bar B0 ? B- and B- ? bar B0, as a function of the time difference between the two B decays. Using 468 million Bbar B pairs produced in Upsilon(4S) decays collected by the BABAR detector at SLAC, T-violating parameters in the time evolution of neutral B mesons have been measured, yielding ?S+T = -1.37 ± 0.14 (stat.) ± 0.06 (syst.) and ?S-T = 1.17 ± 0.18 (stat.) ± 0.11 (syst.) [1]. These non-zero results represent the first direct observation of T violation through the exchange of initial and final states in transitions that can only be connected by a T-symmetry transformation.

Villanueva-Pérez, Pablo

2013-07-01

96

Direct Observation of a Semi-Bare Electron Coulomb Field Recover  

NASA Astrophysics Data System (ADS)

The problem of "semi-bare electron" was first considered in frame of quantum electrodynamics by E.L. Feinberg in 1980. In theory in frame of classical electrodynamics this problem was touched on in articles of N.F. Shul'ga and X. Artru. In 2008 the experimental investigations of this phenomenon in millimeter wavelength region were started by the group of scientists, including authors of this article. Used technique allowed us to study this effect in macroscopic mode. In this paper we present the results of direct observation of a semi-bare electron coulomb field recovery. The semi-bare state was obtained by passing of electron beam through the hole in a conductive screen. Measured spatial distribution of electromagnetic field shows the process of recover of the electron coulomb field, which is followed by a forward radiation. The experiments were performed on the relativistic electron beam of the microtron of Tomsk Polytechnic University.

Naumenko, G.; Popov, Yu; Shevelev, M.

2012-05-01

97

Direct observation of cloud forcing by ground-based thermal imaging  

NASA Astrophysics Data System (ADS)

Instantaneous surface Cloud Radiative Forcing (CRF) in the 7.5-13 ?m region is observed for the first time, using a thermal infrared camera. The sampling of clear sky and cloudy radiances from images of broken cloud fields allows cloud cover, CRF and effective cloud emission to be directly calculated, all within a consistent field of view. Analysis of 1300 images taken over more than two months in Central England shows that surface CRF is a nonlinear function of cloud cover, with daytime forcings larger and less linear than those at night. This nonlinearity is caused both by the increase in cloud optical thickness and the more frequent occurrence of low altitude (warm) cloud as the cloud cover increases. Even for nearly complete cloud cover, effective cloud emission remains significantly less than that of widely assumed homogeneous, optically thick cloud. Possible clear sky sampling errors associated with traditional methods of measuring CRF are also investigated.

Smith, Stephen; Toumi, Ralf

2008-04-01

98

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

99

Direct observation of substrate induced exciton in carbon nanotube  

NASA Astrophysics Data System (ADS)

We have successfully measured the electroluminescence spectra of a single-walled carbon nanotube (CNT) grown to serpentine shape on quartz substrate. We observe two emission peaks: One locates at 0.85 eV and is identified as the usual E11 exciton peak, and the other locates at slightly higher energy of 0.94 eV with similar symmetrical line shape and comparable intensity. However, the extra peak is substantially wider and it broadens with increasing current at unusually faster speed. We show that the extra peak is not from interband transitions, and ascribe it to a type of exciton induced by the formation of substrate-CNT superlattice. The periodic surface potential of the substrate modulates the CNT band structure, causes degeneracy lifting and band flattering at the Brillouin zone, and generates the higher energy exciton. For confirmation, a similar device is fabricated using amorphous SiO2 substrate to avoid the formation of the superlattice. Indeed, the extra emission peak disappears.

Ye, Lin-Hui; Yu, Dang-Min; Wang, Sheng; Zhang, Zhiyong; Peng, Lian-Mao

2013-11-01

100

Direct Observation of Long-Lived Isomers in Bi212  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

101

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

102

Direct observation of OH formation from stabilised Criegee intermediates.  

PubMed

The syn-CH3CHOO Criegee intermediate formed from the ozonolysis of propene and (E)-2-butene was detected via unimolecular decomposition and subsequent detection of OH radicals by a LIF-FAGE instrument. An observed time dependent OH concentration profile was analysed using a detailed model focusing on the speciated chemistry of Criegee intermediates based on the recent literature. The absolute OH concentration was found to depend on the steady state concentration of syn-CH3CHOO at the injection point while the time dependence of the OH concentration profile was influenced by the sum of the rates of unimolecular decomposition of syn-CH3CHOO and wall loss. By varying the most relevant parameters influencing the SCI chemistry in the model and based on the temporal OH concentration profile, the unimolecular decomposition rate k (293 K) of syn-CH3CHOO was shown to lie within the range 3-30 s(-1), where a value of 20 ± 10 s(-1) yields the best agreement with the CI chemistry literature. PMID:25119645

Novelli, A; Vereecken, L; Lelieveld, J; Harder, H

2014-10-01

103

High-resolution cryo-SEM allows direct identification of F-actin at the inner nuclear membrane of Xenopus oocytes by virtue of its structural features.  

PubMed

The nuclear envelope of Xenopus laevis stage VI oocytes was studied in a high-resolution field emission cryo-scanning electron microscope to compare the level of structural preservation obtainable by different procedures of specimen preparation. All approaches generally allowed frequent detection of long filaments of about 10 nm in diameter that were attached to the nuclear envelope's inner membrane facing the nuclear interior. Structural details of these 10-nm filaments, however, could not be unveiled by standard procedures of specimen preparation and analysis, including critical point drying and imaging at room temperature. In contrast, after freeze-drying and imaging at -100 degrees C, the 10-nm filament type was found to be composed of distinct globular subunits of approximately 5 nm in diameter that were arranged in a helical manner with right-handed periodicity. Stereoscopic images showed that some of these filaments were lying directly on the membrane whereas others appeared to hover at a certain distance above the nuclear envelope. The appearance of these filaments was highly similar to that of in vitro polymerized F-actin analysed in parallel, and closely resembled the structural characteristics of F-actin filaments described earlier. By virtue of their structural features we therefore conclude that these filaments at the nuclear periphery represent F-actin. The high level of structural resolution obtainable by field emission cryo-SEM illustrates the potential of this method for studying details of biological structures in a subcellular context. PMID:19017237

Walther, P

2008-11-01

104

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

PubMed

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

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

2015-01-01

105

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

PubMed Central

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

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

2015-01-01

106

Some Pragmatics in the Valid and Reliable Recording of Directly Observed Behavior  

ERIC Educational Resources Information Center

This article examines issues in developing valid and reliable direct observation of behavior. Suggestions are made to minimize the problems that threaten validity and reliability. The discussion is concluded by an examination of costs and benefits of direct observation and who pays them and who benefits from them. (Contains 5 tables and 2 figures.)

Baer, Donald M.; Harrison, Richard; Fradenburg, Linda; Petersen, Dan; Milla, Susan

2005-01-01

107

Rationale and design of a randomized controlled trial of varenicline directly observed therapy delivered in methadone clinics  

PubMed Central

Background Tobacco cessation medication adherence is one of the few factors shown to improve smoking cessation rates among methadone-maintained smokers, but interventions to improve adherence to smoking cessation medications have not yet been tested among methadone treatment patients. Methadone clinic-based, directly observed therapy (DOT) programs for HIV and tuberculosis improve adherence and clinical outcomes, but have not been evaluated for smoking cessation. We describe a randomized controlled trial to evaluate whether a methadone clinic-based, directly observed varenicline therapy program increases adherence and tobacco abstinence among opioid-dependent drug users receiving methadone treatment. Methods/Design We plan to enroll 100 methadone-maintained smokers and randomize them to directly observed varenicline dispensed with daily methadone doses or treatment as usual (self-administered varenicline) for 12 weeks. Our outcome measures are: 1) pill count adherence and 2) carbon monoxide-verified tobacco abstinence. We will assess differences in adherence and abstinence between the two treatment arms using repeated measures models. Discussion This trial will allow for rigorous evaluation of the efficacy of methadone clinic-based, directly observed varenicline for improving adherence and smoking cessation outcomes. This detailed description of trial methodology can serve as a template for the development of future DOT programs and can guide protocols for studies among opioid-dependent smokers receiving methadone treatment. Trial Registration clinicaltrials.gov NCT01378858 PMID:24928218

2014-01-01

108

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

109

Direct observation of Rydberg-Rydberg transitions via CPmmW spectroscopy  

E-print Network

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

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

2014-01-01

110

Slip and flow in pastes of soft particles: Direct observation and rheology  

E-print Network

Slip and flow in pastes of soft particles: Direct observation and rheology Steven P. Meeker due to wall slip. By directly imaging the deformation of pastes and from rheological measurements, we received 9 July 2004) Synopsis Microgel pastes and concentrated emulsions are shown to exhibit a generic

111

Instructional Interactions of Kindergarten Mathematics Classrooms: Validating a Direct Observation Instrument  

ERIC Educational Resources Information Center

In this paper, the authors report research focused directly on the validation of the Coding of Academic Teacher-Student interactions (CATS) direct observation instrument. They use classroom information gathered by the CATS instrument to better understand the potential mediating variables hypothesized to influence student achievement. Their study's…

Doabler, Christian; Smolkowski, Keith; Fien, Hank; Kosty, Derek B.; Cary, Mari Strand

2010-01-01

112

Direct observation of individual endogenous protein complexes in situ by proximity ligation  

E-print Network

Direct observation of individual endogenous protein complexes in situ by proximity ligation Ola So of the recently developed proximity ligation method to examine the subcellular localization of protein-protein to monitor interactions of endogenous proteins directly in individual cells and tissues to reveal

Cai, Long

113

Direct observation of roaming radicals in the thermal decomposition of acetaldehyde.  

SciTech Connect

The thermal dissociation of acetaldehyde has been studied with the reflected shock tube technique using H(D)-atom atomic resonance absorption spectrometry detection. The use of an unreversed light source yields extraordinarily sensitive H atom detection. As a result, we are able to measure both the total decomposition rate and the branching to radical versus molecular channels. This branching provides a direct measure of the contribution from the roaming radical mechanism since the contributions from the usual tight transition states are predicted by theory to be negligible. The experimental observations also provide a measure of the rate coefficient for H + CH{sub 3}CHO. Another set of experiments employing C{sub 2}H{sub 5}I as an H-atom source provides additional data for this rate coefficient that extends to lower temperature. An evaluation of the available experimental results for H + CH{sub 3}CHO can be expressed by a three-parameter Arrhenius expression as k = 7.66 x 10{sup -20}T{sup 2.75} exp((-486 K)/T) cm{sup 3} molecule{sup -1} s{sup -1} (298-1415 K). Analogous experiments employing C{sub 2}D{sub 5}I as a D-atom source allow for the study of the isotopically substituted reaction. The present experiments are the only direct measure for this reaction rate constant, and the results can be expressed by an Arrhenius expression as k = 5.20 x 10{sup -10} exp((-4430 K)/T) cm{sup 3} molecule{sup -1} s{sup -1} (1151-1354 K). The H/D + CH{sub 3}CHO reactions are also studied with ab initio transition-state theory, and the results are in remarkably good agreement with the current experimental data.

Sivaramakrishnan, R.; Michael, J. V.; Klippenstein, S. J.; Chemical Sciences and Engineering Division

2010-01-21

114

Direct observation of single flexible polymers using single stranded DNA Christopher Brockman,a  

E-print Network

). In addition, we used epifluorescence microscopy to image single ssDNA polymer molecules stretching in flow of experimental and theoretical tools.1,2 Single molecule techniques allow for the direct obser- vation of chain to study single polymer dynamics using fluorescence microscopy.3 In particular, dsDNA has been extensively

Schroeder, Charles

115

Nature of Fluctuations on Directional Discontinuities Inside a Solar Ejection: Wind and IMP 8 Observations  

NASA Technical Reports Server (NTRS)

A solar ejection passed the Wind spacecraft between December 23 and 26, 1996. On closer examination, we find a sequence of ejecta material, as identified by abnormally low proton temperatures, separated by plasmas with typical solar wind temperatures at 1 AU. Large and abrupt changes in field and plasma properties occurred near the separation boundaries of these regions. At the one boundary we examine here, a series of directional discontinuities was observed. We argue that Alfvenic fluctuations in the immediate vicinity of these discontinuities distort minimum variance normals, introducing uncertainty into the identification of the discontinuities as either rotational or tangential. Carrying out a series of tests on plasma and field data including minimum variance, velocity and magnetic field correlations, and jump conditions, we conclude that the discontinuities are tangential. Furthermore, we find waves superposed on these tangential discontinuities (TDs). The presence of discontinuities allows the existence of both surface waves and ducted body waves. Both probably form in the solar atmosphere where many transverse nonuniformities exist and where theoretically they have been expected. We add to prior speculation that waves on discontinuities may in fact be a common occurrence. In the solar wind, these waves can attain large amplitudes and low frequencies. We argue that such waves can generate dynamical changes at TDs through advection or forced reconnection. The dynamics might so extensively alter the internal structure that the discontinuity would no longer be identified as tangential. Such processes could help explain why the occurrence frequency of TDs observed throughout the solar wind falls off with increasing heliocentric distance. The presence of waves may also alter the nature of the interactions of TDs with the Earth's bow shock in so-called hot flow anomalies.

Vasquez, Bernard J.; Farrugia, Charles J.; Markovskii, Sergei A.; Hollweg, Joseph V.; Richardson, Ian G.; Ogilvie, Keith W.; Lepping, Ronald P.; Lin, Robert P.; Larson, Davin; White, Nicholas E. (Technical Monitor)

2001-01-01

116

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

PubMed

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

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

2015-01-15

117

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

118

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

119

Direct Observation of Nitrosylated Heme in Myoglobin and Hemoglobin by Electrospray Ionization Mass Spectrometry  

E-print Network

for Mass Spectrometry and Gaseous Ion Chemistry, The Rockefeller UniVersity, New York, New York, 10021 ionization mass spectrometry (ESI-MS), we demonstrate the direct observation of NO attached to the heme spectrometry were unsuccessful. For Mb and Hb, mass shifts are observed that are consistent

Chait, Brian T.

120

Direct Surface Thermodynamic Observations within the Rear-Flank Downdrafts of Nontornadic and Tornadic Supercells  

Microsoft Academic Search

Despite the long-surmised importance of the hook echo and rear-flank downdraft (RFD) in tornadogenesis, only a paucity of direct observations have been obtained at the surface within hook echoes and RFDs. In this paper, in situ surface observations within hook echoes and RFDs are analyzed. These ''mobile mesonet'' data have unprecedented horizontal spatial resolution and were obtained from the Verifications

Paul M. Markowski; Jerry M. Straka; Erik N. Rasmussen

2002-01-01

121

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

122

Direct Observation of Sub-Poissonian Number Statistics in a Degenerate Bose Gas  

E-print Network

We report the direct observation of sub-Poissonian number fluctuation for a degenerate Bose gas confined in an optical trap. Reduction of number fluctuations below the Poissonian limit is observed for average numbers that range from 300 to 60 atoms.

C. -S. Chuu; F. Schreck; T. P. Meyrath; J. L. Hanssen; G. N. Price; M. G. Raizen

2005-12-21

123

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

124

Direct in situ observation of structural transition driven actuation in VO2 utilizing electron transparent cantilevers.  

PubMed

Direct imaging and quantification of actuation in nanostructures that undergo structural phase transitions could advance our understanding of collective phenomena in the solid state. Here, we demonstrate visualization of structural phase transition induced actuation in a model correlated insulator vanadium dioxide by in situ Fresnel contrast imaging of electron transparent cantilevers. We quantify abrupt, reversible cantilever motion occurring due to the stress relaxation across the structural transition from a monoclinic to tetragonal phase with increasing temperature. Deflections measured in such nanoscale cantilevers can be directly correlated with macroscopic stress measurements by wafer curvature studies as well as temperature dependent electrical conduction allowing one to interrogate lattice dynamics across length scales. PMID:23832192

Viswanath, B; Ramanathan, Shriram

2013-08-21

125

Direct observation of markovian behavior of the mechanical unfolding of individual proteins.  

PubMed

Single-molecule force-clamp spectroscopy is a valuable tool to analyze unfolding kinetics of proteins. Previous force-clamp spectroscopy experiments have demonstrated that the mechanical unfolding of ubiquitin deviates from the generally assumed Markovian behavior and involves the features of glassy dynamics. Here we use single molecule force-clamp spectroscopy to study the unfolding kinetics of a computationally designed fast-folding mutant of the small protein GB1, which shares a similar beta-grasp fold as ubiquitin. By treating the mechanical unfolding of polyproteins as the superposition of multiple identical Poisson processes, we developed a simple stochastic analysis approach to analyze the dwell time distribution of individual unfolding events in polyprotein unfolding trajectories. Our results unambiguously demonstrate that the mechanical unfolding of NuG2 fulfills all criteria of a memoryless Markovian process. This result, in contrast with the complex mechanical unfolding behaviors observed for ubiquitin, serves as a direct experimental demonstration of the Markovian behavior for the mechanical unfolding of a protein and reveals the complexity of the unfolding dynamics among structurally similar proteins. Furthermore, we extended our method into a robust and efficient pseudo-dwell-time analysis method, which allows one to make full use of all the unfolding events obtained in force-clamp experiments without categorizing the unfolding events. This method enabled us to measure the key parameters characterizing the mechanical unfolding energy landscape of NuG2 with improved precision. We anticipate that the methods demonstrated here will find broad applications in single-molecule force-clamp spectroscopy studies for a wide range of proteins. PMID:18375518

Cao, Yi; Kuske, Rachel; Li, Hongbin

2008-07-01

126

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

PubMed Central

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

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

2014-01-01

127

Direct observation of multiple tautomers of oxythiamine and their recognition by the thiamine pyrophosphate riboswitch.  

PubMed

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

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

2014-01-17

128

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

129

Direct observation method of individual single-stranded DNA molecules using fluorescent replication protein A.  

PubMed

Direct observation studies of single molecules have revealed molecular behaviors usually hidden in the ensemble and time-averaging of bulk experiments. Direct single DNA molecule analysis of DNA metabolism reactions such as DNA replication, repair, and recombination is necessary to fully understand these essential processes. Intercalation of fluorescent dyes such as YOYO-1 and SYTOX Orange has been the standard method for observing single molecules of double-stranded DNA (dsDNA), but effective fluorescent dyes for observing single molecules of single-stranded DNA (ssDNA) have not been found. To facilitate direct single-molecule observations of DNA metabolism reactions, it is necessary to establish methods for discriminating ssDNA and dsDNA. To observe ssDNA directly, we prepared a fusion protein consisting of the 70 kDa DNA-binding domain of replication protein A and enhanced yellow fluorescent protein (RPA-YFP). This fusion protein had ssDNA-binding activity. In our experiments, dsDNA was stained by SYTOX Orange and ssDNA by RPA-YFP, and we succeeded in staining ssDNA and dsDNA by using RPA-YFP and SYTOX Orange simultaneously. PMID:21225324

Oshige, Masahiko; Kawasaki, Shohei; Takano, Hiroki; Yamaguchi, Kouji; Kurita, Hirofumi; Mizuno, Takeshi; Matsuura, Shun-ichi; Mizuno, Akira; Katsura, Shinji

2011-05-01

130

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

PubMed

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

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

2014-10-01

131

An analysis of the soil moisture-rainfall feedback, based on direct observations from Illinois  

Microsoft Academic Search

Many global and regional climate modeling studies have demonstrated the importance of the initial soil water condition in their simulations of regional rainfall distribution. However, none of these modeling studies has been tested against directly observed data. This study tests the hypothesis that soil saturation is positively correlated with subsequent precipitation by analyzing a 14-year soil moisture data set from

Kirsten L. Findell; Elfatih A. B. Eltahir

1997-01-01

132

Comparison of Teacher Estimates and Direct Observation of Spontaneous Language in Preschool Handicapped Children.  

ERIC Educational Resources Information Center

Compares teachers' estimates of spontaneous language with direct observations of performance of developmentally delayed preschool children in classroom situations. Teachers tended to be more accurate in their estimation of children with higher spontaneous language frequencies and to underestimate the frequency of spontaneous language in other…

Raver, Sharon A.; Peterson, Ann M.

1988-01-01

133

Female lemon sharks return to their birth waters to deliver offspring --the first direct observation  

E-print Network

Female lemon sharks return to their birth waters to deliver offspring -- the first direct observation of such behaviour in any shark species. Kevin Feldheim at the Field Museum in Chicago, Illinois, and his colleagues collected and analysed DNA from lemon sharks (Negaprion brevirostris; pictured

Cai, Long

134

Direct porelevel observation of permeability increase in twophase flow by shaking  

E-print Network

of water as the wetting phase and of dispersed nonwetting globules of gas or organic fluids, flowing acceleration in the elastic wave, needed to "unplug" an immobile flow, is theoretically calculated withinDirect porelevel observation of permeability increase in twophase flow by shaking Igor Beresnev,1

Beresnev, Igor

135

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

136

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-Ångstrom spatial precision. We report the first measurements of ballistic

Texas at Austin. University of

137

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

138

Direct observations of a medium-intensity inflow into the Baltic Sea  

E-print Network

Direct observations of a medium-intensity inflow into the Baltic Sea Jü rgen Sellschoppa , Lars a ship cruise into the Arkona Sea (Western Baltic) happened to start just prior to a mediumsize inflow-salinity Baltic surface water and a small amount of higher salinity water at the bottom. After a few days

Mohrholz, Volker

139

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

Microsoft Academic Search

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

Webster C. Cash

2009-01-01

140

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

Microsoft Academic Search

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

Webster C. Cash Jr.

2009-01-01

141

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

142

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

143

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

144

Developing Single-Molecule TPM Experiments for Direct Observation of Successful RecA-Mediated Strand  

E-print Network

Developing Single-Molecule TPM Experiments for Direct Observation of Successful Rec particle motion (TPM) to investigate the fates of the invading and the outgoing strands during E. coli RecA-mediated pairing and strand exchange at the single-molecule level in the absence of force. TPM experiments measure

Cox, Michael M.

145

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

146

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

E-print Network

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

California at Berkeley, University of

147

Direct observation of standing wave formation at surface steps using scanning tunneling spectroscopy  

Microsoft Academic Search

Using scanning tunneling microscopy and spectroscopy, we have observed the formation of standing waves by the scattering of surface state electrons at steps and defects on the Au(111) surface. From the periods, peak positions, and intensities of the standing waves, the energy dispersion of the surface states, the scattering phase shifts as a function of energy and crystallographic direction, and

Y. Hasegawa; Ph. Avouris

1993-01-01

148

A comparison of in situ and airborne radar observations of ocean wave directionality  

NASA Technical Reports Server (NTRS)

The directional spectrum of a fully arisen, about 3 m sea as measured by an experimental airborne radar, the NASA K(u)-band radar ocean wave spectrometer (ROWS), is compared to reference pitch-roll buoy data and to the classical SWOP (stereo wave observations project) spectrum for fully developed conditions. The ROWS spectrum, inferred indirectly from backscattered power measurements at 5-km altitude, is shown to be in excellent agreement with the buoy spectrum. Specifically, excellent agreement is found between the two nondirectional height spectra, and mean wave directions and directional spreads as functions of frequency. A comparison of the ROWS and SWOP spectra shows the two spectra to be very similar, in detailed shape as well as in terms of the gross spreading characteristics. Both spectra are seen to exhibit bimodal structures which accord with the Phillips' (1958) resonance mechanism. This observation is thus seen to support Phillips' contention that the SWOP modes were indeed resonance modes, not statistical artifacts.

Jackson, F. C.; Walton, W. T.; Peng, C. Y.

1985-01-01

149

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

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

150

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

151

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

152

Direct Observations and Modelling of Clear-Sky Aerosol Radiative Forcing at Surface over Peninsular India  

NASA Astrophysics Data System (ADS)

Accurate estimates of the radiative impact of aerosols on the earth-atmosphere system have paramount importance in climate research. Though the aerosol radiative forcing has been extensively investigated in the past, most of them were estimates obtained by integrating the observed aerosol properties into radiation transfer models. In this study, direct observations of the dependence of instantaneous aerosol direct radiative forcing efficiency (IADRFE) at surface on solar zenith angle (SZA), diurnal mean aerosol direct radiative forcing efficiency (ADRFE) and diurnal mean aerosol direct radiative forcing (ADRF) at surface during the Asian dry season over Thumba (8.5(°) N, 77(°) E), a coastal station located in the southwest Peninsular India are estimated. These observations pertain to the perennial continental aerosol plume that spread over the east Arabian Sea during the dry season. The observed values of IADRFE, ADRFE and ADRF at surface are compared with those estimated using radiation transfer model computations; sensitivity of the model-derived radiative forcing on aerosol properties is also estimated. Absolute magnitudes and SZA-dependence of IADRFE during December to March are comparable; IADRFE increase significantly with cosine of SZA to attain a peak value of -165±10 Wm(-2}tau_{500}({-1)) at SZA ˜60±7(°) . Absolute magnitudes and SZA-dependence of the observed IADRFE compare well with the model estimates for the aerosol model with single scattering albedo (omega_a) ˜0.90±0.03. The observed mean values of ADRFE vary between -70 and -74 Wm(-2) during December to March, which is in agreement with the model estimate of -72 Wm(-2) . The diurnal mean ADRF at surface during December, January, February and March are -27, -26, -25, and -36 Wm(-2) respectively, which are almost 10 to 14 % of the diurnal mean downwelling SW flux at surface during the dry period at this location, indicating the significant role of aerosols in regulating energetics of the surface.

Mishra, Manoj; Rajeev, Kunjukrishnapillai; Gupta, Ashok

153

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

154

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

PubMed Central

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

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

2012-01-01

155

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

156

Direct observation of the dzyaloshinskii-moriya interaction in a pt/co/ni film.  

PubMed

The interfacial Dzyaloshinskii-Moriya interaction in an in-plane anisotropic Pt(4??nm)/Co(1.6??nm)/Ni(1.6??nm) film has been directly observed by Brillouin spectroscopy. It is manifested as the asymmetry of the measured magnon dispersion relation, from which the Dzyaloshinskii-Moriya interaction constant has been evaluated. Linewidth measurements reveal that the lifetime of the magnons is asymmetric with respect to their counter-propagating directions. The lifetime asymmetry is dependent on the magnon frequency, being more pronounced, the higher the frequency. Analytical calculations of the magnon dispersion relation and linewidth agree well with experiments. PMID:25679905

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

2015-01-30

157

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

E-print Network

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

J. Holder; for the VERITAS Collaboration

2008-10-02

158

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

159

Direct observations of polarization reversal process in ferroelectric thin films using high speed piezoresponse force microscopy  

NASA Astrophysics Data System (ADS)

Ferroelectric thin films have been widely implicated for use in future ultra-high-density memory devices, using atomic force microscopy (AFM) related techniques for the read/write operations of ferroelectric memory media where formation of a single domain structure with a defined polarization direction acts as a distinct memory bit. Therefore, it is important to understand the mechanisms and kinetics involved in the polarization switching process, which includes the nucleation and growth of ferroelectric domains at the nanoscale. In recent years, the piezoresponse force microscopy (PFM) technique has been widely been used to image, characterize and modify the domain structures in ferroelectric films with this spatial resolution. However, operating speeds for PFM (and AFM in general) remain a continuing limitation for imaging dynamic processes such as domain switching and read/write operations. A simple method to increase PFM characterization speeds by several orders of magnitude is presented here based on standard commercial equipment and AFM probes. Essentially, an AC voltage at a high resonance frequency is applied to a conducting AFM tip, which is in contact with a ferroelectric surface. The tip is rapidly rastered across a surface without force feedback, while the amplitude and phase of the high frequency resonances are detected with a lock-in amplifier. Although the topography is not reliably recorded, stable contrast related to ferroelectric properties is accurately mapped due to the relative insensitivity of many dynamic AFM contrast mechanisms to variations in repulsive contact forces. Images with nanoscale contrast of ferroelectric domains are presented, acquired at complete frame rates as low as 6 seconds per 256x256 pixel image. The mechanism and kinetics involved in the dynamic domain switching process of PZT thin films are therefore uniquely presented with nanoscale and nanosecond resolution. It was found that domain dynamics processes are governed by the spatial distribution of inhomogeneities present in the film. This allowed a spatially resolved analysis of nucleation and growth kinetics based on tracking thousands of individual domain locations, areas, nucleation times, and growth rates. Finally, an exponential behavior is observed for individual domain growth, and inversely for nucleation time, as a function of electric field.

Premnath, Ramesh Nath

160

Protein structure. Direct observation of structure-function relationship in a nucleic acid-processing enzyme.  

PubMed

The relationship between protein three-dimensional structure and function is essential for mechanism determination. Unfortunately, most techniques do not provide a direct measurement of this relationship. Structural data are typically limited to static pictures, and function must be inferred. Conversely, functional assays usually provide little information on structural conformation. We developed a single-molecule technique combining optical tweezers and fluorescence microscopy that allows for both measurements simultaneously. Here we present measurements of UvrD, a DNA repair helicase, that directly and unambiguously reveal the connection between its structure and function. Our data reveal that UvrD exhibits two distinct types of unwinding activity regulated by its stoichiometry. Furthermore, two UvrD conformational states, termed "closed" and "open," correlate with movement toward or away from the DNA fork. PMID:25883359

Comstock, Matthew J; Whitley, Kevin D; Jia, Haifeng; Sokoloski, Joshua; Lohman, Timothy M; Ha, Taekjip; Chemla, Yann R

2015-04-17

161

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

E-print Network

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

Jaiseung Kim

2009-04-06

162

Bi-directional reflectance and other radiation parameters of cirrus from ER-2 observations  

NASA Technical Reports Server (NTRS)

Passive and active remote sensing of cirrus were acquired from the ER-2 high altitude aircraft in the 1991 Cirrus Experiment. The observations include direct measurements of cirrus bi-directional reflectance from a new translinear scanning radiometer and the previously employed measurements by lidar and visible-infrared imaging radiometers. For any cirrus radiative transfer application, it is necessary to know the appropriate model for visible reflectance in relation to angle and also the optical thickness and infrared emissivity of the clouds. At a more complicated level, for remote sensing and overall cloud effects it is ultimately required to understand effects from multiple cloud layers, broken clouds, and variable microphysics. Our overall data set from the scanning radiometers and lidar is intended to provide the necessary observations to investigate these problems.

Spinhime, James

1993-01-01

163

Microbunching instability in relativistic electron bunches: direct observations of the microstructures using ultrafast YBCO detectors.  

PubMed

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 YBa2Cu3O(7-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. PMID:25215987

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

2014-08-29

164

Direct observation of charge mediated lattice distortions in complex oxide solid solutions  

NASA Astrophysics Data System (ADS)

Using aberration corrected scanning transmission electron microscopy combined with advanced imaging methods, we directly observe atom column specific, picometer-scale displacements induced by local chemistry in a complex oxide solid solution. Displacements predicted from density functional theory were found to correlate with the observed experimental trends. Further analysis of bonding and charge distribution was used to clarify the mechanisms responsible for the detected structural behavior. By extending the experimental electron microscopy measurements to previously inaccessible length scales, we identified correlated atomic displacements linked to bond differences within the complex oxide structure.

Sang, Xiahan; Grimley, Everett D.; Niu, Changning; Irving, Douglas L.; LeBeau, James M.

2015-02-01

165

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

166

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

167

Controllability and observability analysis for vertex domination centrality in directed networks  

PubMed Central

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

168

Controllability and observability analysis for vertex domination centrality in directed networks  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

169

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

170

Directivity of high-energy emission from solar flares: solar-maximum mission observations  

Microsoft Academic Search

The data base consisting of flares detected by the gamma-ray spectrometer (GRS) on board the Solar Maximum Mission (SMM) satellite is used to study the directivity of high-energy radiation. A number of observations strongly indicate that the high-energy emission from flares is anisotropic. They are the following: the fraction of events detected at energies > 300 keV near the limb

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

1987-01-01

171

Calibration and Validation of Direction-Finding High-Frequency Radar Ocean Surface Current Observations  

Microsoft Academic Search

This paper focuses on the validation of remotely sensed ocean surface currents from SeaSonde-type high-frequency (HF) radar systems. Hourly observations during the period July 22, 2003 through September 9, 2003 are used from four separate radar sites deployed around the shores of Monterey Bay, CA. Calibration of direction-finding techniques is addressed through the comparisons of results obtained using measured and

Jeffrey D. Paduan; Kyung Cheol Kim; Michael S. Cook; Francisco P. Chavez

2006-01-01

172

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

PubMed Central

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.

2012-01-01

173

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

174

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

PubMed

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

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

2010-12-01

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

Energy relaxation during hot-exciton transport in quantum wells: Direct observation by spatially resolved phonon-sideband spectroscopy  

E-print Network

, originating from the LO-phonon assisted recombination of hot excitons, is measured directly. By calculating the LO-phonon assisted recombination probability, we obtain the nonthermal energy distribution of excitons and observe directly the energy relaxation...

Zhao, Hui; Moehl, Sebastian; Kalt, Heinz

2002-10-01

177

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

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 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

180

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

181

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

182

Direct observation of organic contaminant uptake, storage, and metabolism within plant roots.  

PubMed

Two-photon excitation microscopy (TPEM) is used to visualize and track the uptake and movement of anthracene and phenanthrene from a contaminated growth medium into living unmodified roots of maize and wheat over a 56-day period. The degradation of anthracene was also directly observed within the cortex cells of both species. The power of this technique is that neither the plant nor the compound require altering (staining or sectioning) to visualize them, meaning they are in their natural form throughout the experiment. Initially both compounds bound to the epidermis along the zone of elongation, passing through the epidermal cells to reach the cortex within the root hair, and branching zones of the root. The PAHs entered the epidermis radially; however, once within the cortex cells this movement was dominated by slow lateral movement of both compounds toward the shoot. Highly focused "streams" of compound were observed to form over time; zones where phenanthrene concentrated extended up to 1500 microm in length over a 56-day period, for example, passing through several adjoining cells, and were detectable in cell walls and cell vacuoles. Radial movement was not observed to extend beyond the cortex cells to reach the vascular tissues of the plant. The longitudinal movement of both compounds was not observed to extend beyond the root base into the stem or vegetative parts of the plant. The lateral movement of both compounds within the cortex cells was dominated by movement within the cell walls, suggesting apoplastic flow through multiple cell walls, but with a low level of symplastic movement to transport compound into the cellular vacuoles. Degradation of anthracene to the partial breakdown products anthrone, anthraquinone, and hydroxyanthraquinone was observed directly in the zones of root elongation and branching. The technique and observations have important applications to the fields of agrochemistry and phytoremediation. PMID:15952374

Wild, Edward; Dent, John; Thomas, Gareth O; Jones, Kevin C

2005-05-15

183

Observations of black carbon induced semi direct effect over Northeast India  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

184

Direct observation and quantification of extracellular long-range electron flow in anaerobic bacteria  

NASA Astrophysics Data System (ADS)

Some anaerobic microorganisms are capable of transporting electrons outside their cell to distant electron acceptors such as metals, minerals or partner species. Previous studies have focused primarily on transport over short distances (1 ?m) via diffusion of molecular intermediates, or alternatively via tunneling or thermally-activated hopping across biomolecules. However, we have found that Geobacter sulfurreducens can transport electrons over long distances (10 ?m) using pili filaments that show organic metal-like conductivity [1]. Pili also enable direct exchange of electrons among syntrophic Geobacter co-cultures [2]. In order to establish the physical principles underlying this remarkable electron transport, we have employed a novel scanning probe microscopy-based method to perform quantitative measurements of electron flow at a single cell level under physiological conditions. Using this nanoscopic approach, we have directly observed the propagation and distribution of injected electrons in individual native bacterial extracellular proteins. Our direct measurements demonstrate unambiguously for the first time that the pili of G. sulfurreducens are a novel class of electronically functional proteins that can sustain electron flow in a surprising manner that has not been observed previously in any other natural protein.[4pt] [1] Nature Nanotechnology, 6, 573 (2011)[0pt] [2] Science, 330, 1413 (2010)

Malvankar, Nikhil; Yalcin, Sibel; Vargas, Madeline; Tuominen, Mark; Lovley, Derek

2013-03-01

185

Direct observation of microtubule pushing by cortical dynein in living cells.  

PubMed

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, Tomáš; Biesemann, Anja; Krejczy, Magda; Nowald, Janos; Müller, Olga; Dehmelt, Leif

2014-01-01

186

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

PubMed

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

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

2014-01-01

187

Direct Observation of Aggregative Nanoparticle Growth: Kinetic Modeling of the Size Distribution and Growth Rate  

SciTech Connect

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

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

2014-01-08

188

Direct Observation of Coherent Oscillations in Solution due to Microheterogeneous Environment  

PubMed Central

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

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

2014-01-01

189

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

PubMed Central

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

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

2014-01-01

190

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

191

Direct observation of resonant scattering phase shifts and their energy dependence.  

PubMed

We scan the collision energy of two clouds of cesium atoms between 12 and 50???K in an atomic fountain clock. By directly detecting the difference of s-wave scattering phase shifts, we observe a rapid variation of a scattering phase shift through a series of Feshbach resonances. At the energies we use, resonances that overlap at threshold become resolved. Our statistical phase uncertainty of 8 mrad can be improved in future precision measurements of Feshbach resonances to accurately determine the Cs-Cs interactions, which may provide stringent limits on the time variation of fundamental constants. PMID:23368559

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

2012-12-28

192

Direct Reconstruction of dynamical dark energy from observational Hubble Parameter data  

E-print Network

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

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

2015-01-01

193

Direct observation of surface plasmon vortex and subwavelength focusing with arbitrarily-tailored intensity patterns  

NASA Astrophysics Data System (ADS)

Surface plasmon (SP) vortices typically have annular intensity patterns. Here we show that fractional SP vortices with arbitrary, asymmetric intensity patterns can be synthesized via simple geometric arrangements. We provide the direct experimental observations over the existence of fractional SP vortices. Triangular SP vortex intensities are synthesized by circularly polarized plane waves. On the other hand, subwavelength focusing with user-desired patterns is also experimentally demonstrated. The synthesized SP vortex and focusing patterns are experimentally measured using a near-field scanning optical microscope with uncoated fiber probe and are found in good agreements as compared to numerical results.

Ku, Chen-Ta; Lin, Heh-Nan; Huang, Chen-Bin

2015-02-01

194

Direct observation of medium-range crystalline order in granular liquids near the glass transition.  

PubMed

Collective behavior of driven granular matter is often strikingly analogous to that of thermal systems. Here we use a vibrated quasi-two-dimensional granular matter as a model system and investigate the mechanism of the liquid-glass transition. We demonstrate by direct observation the existence of long-lived medium-range crystalline order, which is found to be closely related to both dynamic heterogeneity and slow dynamics. Our findings are remarkably similar to recent numerical results on model thermal liquids and thus open an intriguing possibility of understanding the dynamic arrest in both thermal and athermal systems in a unified manner. PMID:18518153

Watanabe, Keiji; Tanaka, Hajime

2008-04-18

195

Direct Observations of Silver Nanoink Sintering and Eutectic Remelt Reaction with Copper  

SciTech Connect

Ag nanoink sintering kinetics and subsequent melting is studied using in-situ synchrotron based x-ray diffraction. Direct observations of Ag nanoink sintering on Cu demonstrate its potential for materials joining since the Ag nanoink sinters at low temperatures but melts at high temperatures. Results show low expansion coefficient of sintered Ag, non-linear expansion as Ag densifies and interdiffuses with Cu above 500 C, remelting consistent with bulk Ag, and eutectic reaction with Cu demonstrating its usefulness as a high temperature bonding medium

Elmer, J. W. [Lawrence Livermore National Laboratory (LLNL); Specht, Eliot D [ORNL

2010-01-01

196

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

PubMed Central

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

Welsh, Deborah P; Shulman, Shmuel

2008-01-01

197

Video Allows Young Scientists New Ways to Be Seen  

ERIC Educational Resources Information Center

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

Park, John C.

2009-01-01

198

Direct observation of stochastic domain-wall depinning in magnetic nanowires  

SciTech Connect

The stochastic field-driven depinning of a domain wall pinned at a notch in a magnetic nanowire is directly observed using magnetic X-ray microscopy with high lateral resolution down to 15 nm. The depinning-field distribution in Ni{sub 80}Fe{sub 20} nanowires considerably depends on the wire width and the notch depth. The difference in the multiplicity of domain-wall types generated in the vicinity of a notch is responsible for the observed dependence of the stochastic nature of the domain wall depinning field on the wire width and the notch depth. Thus the random nature of the domain wall depinning process is controllable by an appropriate design of the nanowire.

Im, Mi-Young; Bocklage, Lars; Fischer, Peter; Meier, Guido

2008-11-01

199

Direct observation of quark-hadron duality in the free neutron F_2 structure function  

E-print Network

Using data from the recent BONuS experiment at Jefferson Lab, which utilized a novel spectator tagging technique to extract the inclusive electron-free neutron scattering cross section, we obtain the first direct observation of quark-hadron duality in the neutron F_2 structure function. The data are used to reconstruct the lowest few (N=2, 4 and 6) moments of F_2 in the three prominent nucleon resonance regions, as well as the moments integrated over the entire resonance region. Comparison with moments computed from global parametrizations of parton distribution functions suggest that quark--hadron duality holds locally for the neutron in the second and third resonance regions down to Q^2 ~ 1 GeV^2, with violations possibly up to 20% observed in the first resonance region.

Niculescu, I; Melnitchouk, W; Arrington, J; Christy, M E; Ent, R; Griffioen, K A; Kalantarians, N; Keppel, C E; Kuhn, S; Tkachenko, S; Zhang, J

2015-01-01

200

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

201

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

202

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

PubMed

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

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

2014-01-01

203

Direct in Situ Observation of Nanoparticle Synthesis in a Liquid Crystal Surfactant Template  

SciTech Connect

Controlled synthesis of nanostructures is essential for many applications, from energy storage/generation and catalysis to semiconductor and biomedical devices. Normally, nanostructures are characterized after synthesis and growth mechanisms are assumed. Here we show the first direct observation of nanoparticle synthesis in a liquid crystal surfactant template using an electron microscope fluid stage. The nanoparticles first sinter (to ~5nm), then grow connections to each other around the micelles to form clusters. Upon reaching a critical size (>10-15nm), the clusters become highly mobile in the template, displacing micelles to form spherical nanoparticles. This ability to observe and understand fundamental growth mechanisms on the nanoscale in real time and in aqueous environments will impact every branch of nanoscience where precise control over nanostructure is essential. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

Parent, Lucas R.; Robinson, David R.; Woehl, Taylor J.; Ristenpart, William D.; Evans, James E.; Browning, Nigel D.; Arslan, Ilke

2012-04-24

204

Direct torque control with an optimized observer for multi-machine systems  

NASA Astrophysics Data System (ADS)

The first purpose of this work is to design a new observation technique for the Direct Torque Control (DTC). We put emphasis on robustness especially at very low speed, which represents the basic problem of the DTC operating, and on the optimization of the time computing. The reduced order observer is defined by decoupling the full order one in ? and ? axis. The second basic aim of this paper is to apply the DTC strategy to multi-machine multi-inverter industrial systems. Speed and tension controls are designed; their performances and parameter robustness are analyzed and compared with those obtained with a Flux Oriented Control (FOC). Mechanical and electrical couplings constitute the principal operation difficulty of these systems mainly when one of the machines is perturbed.

Belhadj, J.; Belkhodja, I. S.; David, M.; de Fornel, B.

2006-01-01

205

Direct observation of the translocation mechanism of transcription termination factor Rho  

PubMed Central

Rho is a ring-shaped, ATP-fueled motor essential for remodeling transcriptional complexes and R-loops in bacteria. Despite years of research on this fundamental model helicase, key aspects of its mechanism of translocation remain largely unknown. Here, we used single-molecule manipulation and fluorescence methods to directly monitor the dynamics of RNA translocation by Rho. We show that the efficiency of Rho activation is strongly dependent on the force applied on the RNA but that, once active, Rho is able to translocate against a large opposing force (at least 7 pN) by a mechanism involving ‘tethered tracking’. Importantly, the ability to directly measure dynamics at the single-molecule level allowed us to determine essential motor properties of Rho. Hence, Rho translocates at a rate of ?56 nt per second under our experimental conditions, which is 2–5 times faster than velocities measured for RNA polymerase under similar conditions. Moreover, the processivity of Rho (?62 nt at a 7 pN opposing force) is large enough for Rho to reach termination sites without dissociating from its RNA loading site, potentially increasing the efficiency of transcription termination. Our findings unambiguously establish ‘tethered tracking’ as the main pathway for Rho translocation, support ‘kinetic coupling’ between Rho and RNA polymerase during Rho-dependent termination, and suggest that forces applied on the nascent RNA transcript by cellular substructures could have important implications for the regulation of transcription and its coupling to translation in vivo. PMID:25662222

Gocheva, Veronika; Le Gall, Antoine; Boudvillain, Marc; Margeat, Emmanuel; Nollmann, Marcelo

2015-01-01

206

The directivity of solar type III bursts at hectometer and kilometer wavelengths: Wind-Ulysses observations  

NASA Astrophysics Data System (ADS)

We investigate the directivity of solar type III radio bursts at hectometer and kilometer wavelengths using radio data recorded simultaneously by the Wind and Ulysses spacecraft which are widely separated in heliocentric longitude and latitude. From the positions of the associated flares and the solar wind speed and plasma density measured aboard the spacecraft, we estimate the location of the type III radio sources along the approximately spiral magnetic field lines connected to the flare sites. Using the ratios of the radio flux densities measured from 1995 to 2005 at the same frequencies (940-80 kHz) on these spacecraft, we have for the first time derive the average directivity diagram of type III bursts in two dimensions, longitude and latitude relative to the emission source. This diagram is found to exhibit no significant variation with the solar activity. The diagram in longitude is found to shift east of the local magnetic field direction at the source. The angular width and eastward shift of the diagram are observed to increase with decreasing frequencies; around 800 kHz, its full width at maximum/10 level is about 190° and its eastward shift 23°. The diagram in latitude, obtained uniquely thanks to the out-of-ecliptic orbit of Ulysses, shows no significant variation with latitude.

Bonnin, X.; Hoang, S.; Maksimovic, M.

2008-10-01

207

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

208

[Preliminary study on detox in outpatient care units with 18 alcoholic patients in Directly Observed Treatment].  

PubMed

Directly Observed Treatment (TOD-DOT) has been tested in different conditions. The objective of this work is to check whether a UCA-CAB (Centre for Addictive Behaviour) can achieve detox and reduce the risk of early relapse (up to 12 weeks) in alcoholic patients. All patients had an established organic addiction and serious withdrawal syndrome, and had undergone multiple previous treatments. Furthermore, they had not managed to abstain for a 3-month consecutive period over the previous 2 years. The aim of the Directly Observed Treatment was to attain detox and reduce relapse by following a multi-method approach: medical, psychological and personal care, based on a brief daily consultation and pharmacological supervision. The results were as follows: Of the 18 patients included in the study, after 12 weeks, 13 (72 %) were still abstinent and 4 (22 %) had relapsed. Thus, 17 (94 %) were still following the treatment, with just one drop-out. We analysed the profiles of the patients abstaining, of those who relapsed (4) and of the one who dropped out. The average CIWA-Ar was 27.05 (21-36). Any value over 20 is considered to indicate serious withdrawal syndrome, though there were no negative events leading to hospitalization. Level of adherence to the treatment (94 %) meant that the most seriously affected patients and those with fewest financial resources could benefit, not only from any auxiliary social schemes, but also from basic health services, permitting them to improve the quality of their everyday life. PMID:18813775

Lloréns Martínez, Ramón; Calatayud Francés, María; Morales Gallús, Esperanza; Añó Cervera, Consol; Adriá Caballero, Librada

2008-01-01

209

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

SciTech Connect

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

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

2010-12-01

210

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

211

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

PubMed

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

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

2013-12-01

212

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

213

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

214

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

215

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

216

Direct Observation of the Strange b Baryon {xi}{sub b}{sup -}  

SciTech Connect

We report the first direct observation of the strange b baryon {xi}{sub b}{sup -}({xi}{sub b}{sup +}). We reconstruct the decay {xi}{sub b}{sup -}{yields}J/{psi}{xi}{sup -}, with J/{psi}{yields}{mu}{sup +}{mu}{sup -}, and {xi}{sup -}{yields}{lambda}{pi}{sup -}{yields}p{pi}{sup -}{pi}{sup -} in pp collisions at {radical}(s)=1.96 TeV. Using 1.3 fb{sup -1} of data collected by the D0 detector, we observe 15.2{+-}4.4(stat){sub -0.4}{sup +1.9}(syst) {xi}{sub b}{sup -} 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 3.3x10{sup -8} of it arising from a background fluctuation. Normalizing to the decay {lambda}{sub b}{yields}J/{psi}{lambda}, we measure the relative rate ({sigma}({xi}{sub b}{sup -})xB({xi}{sub b}{sup -}{yields}J/{psi}{xi}{sup -})/{sigma}({lambda}{sub b})xB({lambda}{sub b}{yields}J/{psi}{lambda}))=0.28{+-}0.09(stat){sub -0.08}{sup +0.09}(syst)

Abazov, V. M.; Alexeev, G. D.; Kalinin, A. M.; Kharzheev, Y. M.; Malyshev, V. L.; Merekov, Y. P.; Panov, G.; Rozhdestvenski, A.; Tokmenin, V. V.; Vertogradov, L. S.; Vertogradova, Y.; Yatsunenko, Y. A. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Abbott, B.; Gutierrez, P.; Hall, I.; Hossain, S.; Jain, S.; Kopal, M.; Pompos, A.; Severini, H. [University of Oklahoma, Norman, Oklahoma 73019 (United States)] (and others)

2007-08-03

217

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

218

An observation related to directional attenuation of SKS waves propagating in anisotropic media  

NASA Astrophysics Data System (ADS)

Azimuthal anisotropy of attenuation is a physical phenomenon related to the directional change of attenuation. This study examines the frequency properties and directional attenuation of SKS waves. The directional frequency-dependent characteristics of SKS waves are investigated in the frequency band of 0.02-0.5 Hz using data from 53 permanent seismic stations located throughout the northern Yangtze Craton, the southern North China Craton and adjacent areas. In addition to normal splitting behavior, the analysis reveals that many SKS splitting measurements exhibit a lemniscate shape, reflecting frequency differences along fast and slow polarization directions. Frequency analysis shows that spectral ratios between fast/slow components of the lemniscate-type splitting results fluctuate strongly in a higher frequency band of 0.2-0.5 Hz, and fluctuate less within the main frequency band of 0.02-0.2 Hz. For each station, the ratio of the peak amplitude of the fast/slow components can be represented as a cotangential function of event backazimuth multiplying with a constant = 0.42 ± 0.10. This transformation shows that the regional average angles consistently fall within the relatively narrow range of -46.5 ± 3° with respect to the north, suggesting that a regional tectonic controlling factor dictates the relatively uniform directional attenuation of SKS waves within the frequency band of 0.02-0.2 Hz. Further analysis is performed by projecting the SKS waves onto the components along and perpendicular to the regional average angles. The calculation also shows that, in the 0.02-0.2 Hz band, the relationship between amplitude ratio and event backazimuth matches a cotangential functions with the same best matching angles and constant a < 1. Synthetic calculations demonstrate that although different filters influence the splitting parameters, attenuation anisotropy cannot be explained by elastic anisotropic media, including multilayer anisotropy and anisotropy with a tilting symmetrical axis. This observed behavior of the SKS wave may arise from the combined effects of frequency-dependent attenuation anisotropy and small-scale heterogeneities in the crust and the upper mantle.

Zhao, Liang; Xue, Mei

2015-04-01

219

Observation of Intrinsic Magnus Force and Direct Detection of Chirality in Superfluid 3He-A  

NASA Astrophysics Data System (ADS)

We report details of the observation of the intrinsic Magnus (IM) force acting on negative and positive ions trapped just below a free surface of the A phase of superfluid 3He (3He-A). From the transport measurements of the ions along the surface, we found that the IM force acts on both the negative and positive ions. We also demonstrate that the transport measurements could distinguish whether the surface is composed of a chiral monodomain or multiple chiral domains. For multiple chiral domains, the current of the ions was found to be irreproducible and unstable, which was reasonably explained by the formation of the chiral domain structure and the dynamics of the chiral domain walls. For chiral monodomains, the appearance ratio of chirality emerging upon cooling through the superfluid transition temperature was found to depend on the direction of the external magnetic field, which implies the existence of an unknown coupling between the chirality and the magnetic field.

Ikegami, Hiroki; Tsutsumi, Yasumasa; Kono, Kimitoshi

2015-04-01

220

Preliminary findings of an intervention integrating modified directly observed therapy and risk reduction counseling.  

PubMed

Various interventions have been proposed to address these ongoing needs of HIV-positive patients as they encounter challenges with medication adherence and risk reduction. This report presents the findings of a study that pilots 'DAART+', an intervention that integrates modified directly observed therapy (MDOT), and risk reduction counseling for a population of marginally housed, substance-using persons. The pilot study intended to assess the feasibility of the intervention and to obtain data to assess the intervention's potential effectiveness. The preliminary data reveal that 83% of participants who completed the intervention (n=18) had undetectable viral load (VL) (VL< or =400 copies/mL) which represents a 2.15 log(10) decrease from baseline. Risk behaviors also changed modestly with self-reported increases in condom usage. PMID:17453598

Mitchell, C G; Freels, S; Creticos, C M; Oltean, A; Douglas, R

2007-04-01

221

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

222

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

223

Direct observation of half-metallicity in the Heusler compound Co2MnSi  

PubMed Central

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

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

2014-01-01

224

Carbon radicals. Direct observation and kinetics of a hydroperoxyalkyl radical (QOOH).  

PubMed

Oxidation of organic compounds in combustion and in Earth's troposphere is mediated by reactive species formed by the addition of molecular oxygen (O2) to organic radicals. Among the most crucial and elusive of these intermediates are hydroperoxyalkyl radicals, often denoted "QOOH." These species and their reactions with O2 are responsible for the radical chain branching that sustains autoignition and are implicated in tropospheric autoxidation that can form low-volatility, highly oxygenated organic aerosol precursors. We report direct observation and kinetics measurements of a QOOH intermediate in the oxidation of 1,3-cycloheptadiene, a molecule that offers insight into both resonance-stabilized and nonstabilized radical intermediates. The results establish that resonance stabilization dramatically changes QOOH reactivity and, hence, that oxidation of unsaturated organics can produce exceptionally long-lived QOOH intermediates. PMID:25657245

Savee, John D; Papajak, Ewa; Rotavera, Brandon; Huang, Haifeng; Eskola, Arkke J; Welz, Oliver; Sheps, Leonid; Taatjes, Craig A; Zádor, Judit; Osborn, David L

2015-02-01

225

Direct Insights Into Observational Absorption Line Analysis Methods of the Circumgalactic Medium Using Cosmological Simulations  

NASA Astrophysics Data System (ADS)

We study the circumgalactic medium (CGM) of a z = 0.54 simulated dwarf galaxy using hydroART simulations. We present our analysis methods, which emulate observations, including objective absorption line detection, apparent optical depth (AOD) measurements, Voigt profile (VP) decomposition, and ionization modeling. By comparing the inferred CGM gas properties from the absorption lines directly to the gas selected by low ionization H i and Mg ii, and by higher ionization C iv and O vi absorption, we examine how well observational analysis methods recover the “true” properties of CGM gas. In this dwarf galaxy, low ionization gas arises in sub-kiloparsec “cloud” structures, but high ionization gas arises in multiple extended structures spread over 100 kpc; due to complex velocity fields, highly separated structures give rise to absorption at similar velocities. We show that AOD and VP analysis fails to accurately characterize the spatial, kinematic, and thermal conditions of high ionization gas. We find that H i absorption selected gas and O vi absorption gas arise in totally distinct physical gas structures, calling into question current observational techniques employed to infer metallicities and the total mass of “warm-hot” CGM gas. We present a method to determine whether C iv and O vi absorbing gas is photo or collisionally ionized and whether the assumption of ionization equilibrium is sound. As we discuss, these and additional findings have strong implications for how accurately currently employed observational absorption line methods recover the true gas properties, and ultimately, our ability to understand the CGM and its role in galaxy evolution.

Churchill, Christopher W.; Vander Vliet, Jacob R.; Trujillo-Gomez, Sebastian; Kacprzak, Glenn G.; Klypin, Anatoly

2015-03-01

226

Effects of action observation on corticospinal excitability: Muscle specificity, direction, and timing of the mirror response.  

PubMed

Many human behaviours and pathologies have been attributed to the putative mirror neuron system, a neural system that is active during both the observation and execution of actions. While there are now a very large number of papers on the mirror neuron system, variations in the methods and analyses employed by researchers mean that the basic characteristics of the mirror response are not clear. This review focuses on three important aspects of the mirror response, as measured by modulations in corticospinal excitability: (1) muscle specificity; (2) direction; and (3) timing of modulation. We focus mainly on electromyographic (EMG) data gathered following single-pulse transcranial magnetic stimulation (TMS), because this method provides precise information regarding these three aspects of the response. Data from paired-pulse TMS paradigms and peripheral nerve stimulation (PNS) are also considered when we discuss the possible mechanisms underlying the mirror response. In this systematic review of the literature, we examine the findings of 85 TMS and PNS studies of the human mirror response, and consider the limitations and advantages of the different methodological approaches these have adopted in relation to discrepancies between their findings. We conclude by proposing a testable model of how action observation modulates corticospinal excitability in humans. Specifically, we propose that action observation elicits an early, non-specific facilitation of corticospinal excitability (at around 90ms from action onset), followed by a later modulation of activity specific to the muscles involved in the observed action (from around 200ms). Testing this model will greatly advance our understanding of the mirror mechanism and provide a more stable grounding on which to base inferences about its role in human behaviour. PMID:25281883

Naish, Katherine R; Houston-Price, Carmel; Bremner, Andrew J; Holmes, Nicholas P

2014-10-01

227

Direct Impact of El Nino on East Asian Summer Precipitation in the Observation  

NASA Astrophysics Data System (ADS)

This study investigates the direct impact of El Nino in the tropical Pacific on the East Asian summer precipitation. Generalized equilibrium feedback assessment (GEFA) is used to isolate this direct impact from interrelated ocean forcings in the observations. Results indicate that the El Nino can directly influence the summer precipitation in East China significantly. The precipitation response presents a tri-pole pattern, with anomalous wet in the Southeast and the Northeast China and anomalous dry in the northern China. Amplitude of the precipitation response is around 20% of the total precipitation for 1C El Nino forcing in most area of the East China, with maximal response up to 30%/C. The tri-pole precipitation response is attributed to an El Nino-induced cyclonic anomaly in the Northeast Asia and an anticyclonic anomaly in the western North Pacific (WNP). The anomalous cyclone deepens the East Asian trough southwestward, favoring an air ascending in front of the trough in the Southeast and the Northeast China, and an air descending at the rear of the trough in the northern China. The anomalous anticyclone in the WNP strengthens the WNP subtropical high northeastward, providing adequate water vapor to the Southeast China. The anomalous cyclone and anomalous anticyclone work together to generate the tri-pole precipitation response pattern in the East China. Further investigation suggests that these two key anomalous circulations are part of a northwestward propagating Rossby wave, which is excited by the El Nino warming-induced convection over the subtropical west-central Pacific. This study can serve as a reference for the prediction of the East Asian precipitation in both the developing and decaying summer of El Nino.

Wen, Na; Liu, Zhengyu; Liu, Yinghui

2014-05-01

228

Direct observation of graphene growth and associated copper substrate dynamics by in situ scanning electron microscopy.  

PubMed

This work highlights the importance of in situ experiments for an improved understanding of graphene growth on copper via metal-catalyzed chemical vapor deposition (CVD). Graphene growth inside the chamber of a modified environmental scanning electron microscope under relevant low-pressure CVD conditions allows visualizing structural dynamics of the active catalyst simultaneously with graphene nucleation and growth in an unparalleled way. It enables the observation of a complete CVD process from substrate annealing through graphene nucleation and growth and, finally, substrate cooling in real time and nanometer-scale resolution without the need of sample transfer. A strong dependence of surface dynamics such as sublimation and surface premelting on grain orientation is demonstrated, and the influence of substrate dynamics on graphene nucleation and growth is presented. Insights on the growth mechanism are provided by a simultaneous observation of the growth front propagation and nucleation rate. Furthermore, the role of trace amounts of oxygen during growth is discussed and related to graphene-induced surface reconstructions during cooling. Above all, this work demonstrates the potential of the method for in situ studies of surface dynamics on active metal catalysts. PMID:25584770

Wang, Zhu-Jun; Weinberg, Gisela; Zhang, Qiang; Lunkenbein, Thomas; Klein-Hoffmann, Achim; Kurnatowska, Michalina; Plodinec, Milivoj; Li, Qing; Chi, Lifeng; Schloegl, R; Willinger, Marc-Georg

2015-02-24

229

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

PubMed Central

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

Kovalev, Alexander E; Gorb, Stanislav N

2014-01-01

230

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

231

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

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

Comparison of methods for measurement of smoking behavior: Mouthpiece-based computerized devices versus direct observation  

PubMed Central

Introduction: Understanding factors that influence tobacco use often involves detailed assessment of smoking behavior (i.e., puff topography) via mouthpiece-based, computerized devices. Research suggests that the use of a mouthpiece to evaluate topography may alter natural smoking behavior. This study was designed to compare topography measurement using mouthpiece-based methods (i.e., desktop and portable computerized devices) to methods that do not use a mouthpiece (i.e., direct observation). Methods: A total of 30 smokers (?15 full-flavor or light cigarettes/day) participated in six Latin square–ordered, 2.5-hr experimental sessions that were preceded by at least 8 hr of objectively verified tobacco abstinence (carbon monoxide level ? 10 ppm). Each session consisted of participants smoking four cigarettes (own brand or Merit ultra-light) ad libitum, conventionally or using a desktop or portable device. Sessions were videotaped using a digital camcorder. Results: All three measurement methods were sensitive to oft-reported brand- and bout-induced changes. Topography measurement differed little between methods (across methods, all r values > .68), and each method was reliable (across bouts within each condition, most r values > .78). In contrast, participants perceived the use of either mouthpiece-based device to alter aspects of their smoking behavior (e.g., increased smoking difficulty, reduced enjoyment, altered cigarette taste; p < .05), relative to video recording only. Discussion: Although direct observational methods may be optimal for measuring certain smoking characteristics, logistical challenges posed by this method likely limit its usefulness. Together, these results suggest that mouthpiece-based devices offer a convenient and useful tool for researchers examining smoking topography. PMID:19525207

Blank, Melissa D.; Disharoon, Steven

2009-01-01

234

Twenty-four-hour recall, knowledge-attitude-practice questionnaires, and direct observations of sanitary practices: a comparative study  

PubMed Central

Although responses to 24-hour recall and knowledge—attitude—practice questionnaires are commonly used in water—sanitation studies as surrogates for direct observation of behaviour, the validity of this approach is questionable. We therefore compared questionnaire data with those obtained by direct observation of practices related to water storage, handwashing, and defecation among 247 families in urban Dhaka, Bangladesh. Analysis of the results indicates that accord between the replies to the questionnaires and the data collected by direct observation was poor and that the responses to the two questionnaires were often contradictory. Significant disagreements between the results of questionnaires and observations arose usually because desirable practices were over-reported by the respondents. The results of the study suggest that in urban Bangladesh 24-hour recall and knowledge—attitude—practice questionnaires should not be used as proxies for direct observation of hygiene practices. PMID:3496987

Stanton, B. F.; Clemens, J. D.; Aziz, K. M. A.; Rahman, M.

1987-01-01

235

Direct observations of feeding structures and mechanisms in bivalve molluscs using endoscopic examination and video image analysis  

Microsoft Academic Search

A new technique is described for observing the structures and mechanisms of suspension feeding in bivalves using endoscopic examination and video image analysis. This method permits direct in vivo observations of whole, intact structures of relatively undisturbed specimens. No surgical alterations of shell or tissue are required for most species. Pallial organ activity can be recorded for future observations and

J. E. Ward; P. G. Beninger; B. A. MacDonald; R. J. Thompson

1991-01-01

236

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

237

Direct observations of ligand dynamics in hemoglobin by subpicosecond infrared spectroscopy.  

PubMed Central

The photodissociation of CO from HbCO at ambient temperature is studied by means of a femtosecond IR technique. The bleaching of the FeCO absorption and the appearance of a new IR absorption near that of free CO are both observed at 300 fs after optical excitation. The bleach does not recover on the time scale of a few picoseconds but does recover by approximately 4% within 1 ns, which suggests that a barrier to recombination is formed within a few picoseconds. The CO spectrum does not change significantly between 300 fs and 1 ns, suggesting that the CO quickly finds some locations in the heme pocket that are not more than a few angstroms from the iron. The de-ligated CO appears in its ground vibrational level. There is evidence that 85 +/- 10% of this CO remains in the heme pocket at 1 ns; it probably resides there for 50 ns. The flow of excess vibrational energy from the heme to the solvent was directly observed in the IR experiments. The heme cools within 1-2 ps while thermal disruption of the surrounding solvent structure requires approximately 30 ps. PMID:2554314

Anfinrud, P A; Han, C; Hochstrasser, R M

1989-01-01

238

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

239

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

240

Direct observation of the capillary mechanisms of liquid-liquid entrapment and mobilization  

NASA Astrophysics Data System (ADS)

The dissertation develops further insight into the behavior of liquid-liquid flow in porous media. This topic is of great importance with applications in chemical reaction engineering, enhanced oil recovery, and environmental remediation. This work focuses on the experimental observation of invading immiscible drops, the long term behavior of their interface, and their entrapment via capillary pressure and mobilization through vibratory stimulation. Using a simplified capillary physics mechanism several specific predictions can be made. So far these theories have generally agreed with CFD simulations, however a direct comparison to physical experiments is needed. Experiments were conducted using single pore glass capillaries. Straight capillaries were used to study the film thickness left by an invading drop, which is critical for determining realistic initial conditions for the interface theory. A range of constricted capillaries were used in verifying the ``breakup criterion'' was influenced only by the geometric parameters of the capillary and not flow regimes. Additionally, the experiments and theory demonstrates qualitative agreement with respect to the evolution of the liquid-liquid interface. Finally, the theory of vibratory mobilization was verified by trapping single drops with a pressure below their mobilization threshold and observing the drop's mobilization over several oscillations. The level of agreement between experiment, theory and CFD demonstrates the utility of the capillary physics mechanism in terms of reducing computational costs. The next goal is extending the theory to networks of pores so we can further our understanding of the oil mobilization and related processes, leading to useful technical applications.

Gaul, William Gerard

241

Comparison of Direct Numerical Simulation and Experimental Observation of Particle Clustering in Isotropic Turbulence  

NASA Astrophysics Data System (ADS)

Experimental observation of particle clustering in turbulent flow is often complicated by particles of non-uniform in size, and the accuracy of most diagnostic techniques is sensitive to the particle size. To make meaningful comparisons with experiments direct numerical simulations (DNS) must take into consideration the properties of the particles and model the limitations introduced by the diagnostics. We present a series of DNS of inertial particles in turbulence that were designed to match the measurements of Cao et al. In their experiments, the particle radial distribution function (RDF) was obtained from 3-D holographic images of particles in a turbulence box. DNS was done using the same particle size distribution as the particles in the experiments. The parameters of the flow (Re #) and the particles (St #) were matched. In the DNS, we eliminated particles below a specified size and recalculated the RDF to better match the experiments. Trends in the variation of the RDF with size cutoff were found to be non-intuitive, but can be explained based on an extension of the theory of Chun et al. (2005) to polydisperse particles. We optimized the cutoff size based on the comparison of the experimental and numerical RDF at one fan speed and applied the same cutoff to other fan speeds. The results showed good agreement. The comparison highlights the complexity of matching DNS and experimental observations.

Salazar, Juan; de Jong, Jeremy; Cao, Lujie; Woodward, Scott; Meng, Hui; Collins, Lance

2006-11-01

242

The use of direct clinician observation and vignettes for health services quality evaluation in developing countries.  

PubMed

This paper reports the results of a comparison between two different methods of examining quality in outpatient services in a developing country. Data from rural and urban Tanzania are used to compare the measures of quality collected by direct clinician observation (DCO) (where clinicians are observed in the course of their normal consultations) and vignettes (unblind case studies with an actor). The vignettes are shown to exhibit a strong connection between the inputs provided during consultation (rational history taking, physical examination and health education) and the ability of the clinician to properly diagnose the presented illness. However, the inputs provided in vignettes are not well correlated with the inputs provided in DCO, suggesting that the inputs provided in the vignette are not well correlated with the inputs that would be provided in an actual consultation. We conclude that since vignettes do not appear to be measuring what would be provided in an actual consultation they are not a good measure of quality. Instead, we suggest that vignettes and DCO be used simultaneously. We show how the scores obtained using vignettes in conjunction with DCO can be used to improve the reliability of DCO and therefore our estimates of actual clinician quality. PMID:15936863

Leonard, Kenneth L; Masatu, Melkiory C

2005-11-01

243

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

244

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

PubMed

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

Cottney, Alan; Innes, James

2015-02-01

245

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

NASA Technical Reports Server (NTRS)

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

Heinemann, K.; Poppa, H.

1975-01-01

246

Influence of observed diurnal cycles of aerosol optical depth on aerosol direct radiative effect  

NASA Astrophysics Data System (ADS)

The diurnal variability of aerosol optical depth (AOD) can be significant, depending on location and dominant aerosol type. However, these diurnal cycles have rarely been taken into account in measurement-based estimates of aerosol direct radiative forcing (ADRF) or aerosol direct radiative effect (ADRE). The objective of our study was to estimate the influence of diurnal aerosol variability at the top of the atmosphere ADRE estimates. By including all the possible AERONET sites, we wanted to assess the influence on global ADRE estimates. While focusing also in more detail on some selected sites of strongest impact, our goal was to also see the possible impact regionally. We calculated ADRE with different assumptions about the daily AOD variability: taking the observed daily AOD cycle into account and assuming diurnally constant AOD. Moreover, we estimated the corresponding differences in ADREs, if the single AOD value for the daily mean was taken from the the Moderate Resolution Imaging Spectroradiometer (MODIS) Terra or Aqua overpass times, instead of accounting for the true observed daily variability. The mean impact of diurnal AOD variability on 24 h ADRE estimates, averaged over all AERONET sites, was rather small and it was relatively small even for the cases when AOD was chosen to correspond to the Terra or Aqua overpass time. This was true on average over all AERONET sites, while clearly there can be much stronger impact in individual sites. Examples of some selected sites demonstrated that the strongest observed AOD variability (the strongest morning afternoon contrast) does not typically result in a significant impact on 24 h ADRE. In those cases, the morning and afternoon AOD patterns are opposite and thus the impact on 24 h ADRE, when integrated over all solar zenith angles, is reduced. The most significant effect on daily ADRE was induced by AOD cycles with either maximum or minimum AOD close to local noon. In these cases, the impact on 24 h ADRE was typically around 0.1-0.2 W m-2 (both positive and negative) in absolute values, 5-10% in relative ones.

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

2013-08-01

247

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

PubMed

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 nu approximately 3.7 x 10(-4) Hz. The instrument consists of a torsion balance with a natural frequency of nu(0) approximately 1.6 x 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 approximately 1.5 x 10(-9) rad at the lowest frequency normal mode and the sensitivity improves as nu(-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 nu(0) to approximately 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

2007-04-24

248

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

249

Direct observations of DNA provides new insights into how genetic material is copied and repaired News-Medical.Net  

E-print Network

News-Medical.Net · Home Page Direct observations of DNA provides new insights into how genetic material is copied and repaired Medical Research News Published: Thursday, 21-Sep-2006 Printer Friendly Email and repaired. "We can monitor the process directly, and that gives us a different perspective," said Roberto

Kowalczykowski, Stephen C.

250

Direct Observation of the Movement of Vertical Bloch Lines in Ho-Co Sputter-Deposited Films  

Microsoft Academic Search

The presence of two types of a vertical Bloch line pair in a sputter-deposited Ho-Co alloy thin film with a perpendicular magnetic anisotropy are directly observed by high voltage electron microscopy. One type is that in which two Bloch lines of a pair move in the same direction in the wall responding to a magnetic field applied normal to the

Takao Suzuki

1983-01-01

251

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

252

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

253

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

E-print Network

The 33S(p,\\gamma)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, however, vary by orders of magnitude due to uncertainties in the 33S(p,\\gamma)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,\\gamma)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,\\gamma)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 7 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 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,\\gamma)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.

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

2013-09-13

254

Direct Observations of Rapid Diffusion of Cu in Au Thin Films Using In-Situ X-Ray Diffraction  

SciTech Connect

In situ x-ray diffraction was performed while annealing thin film Au/Cu binary diffusion couples to directly observe diffusion at elevated temperatures. The temperature dependence of the interdiffusion coefficient was determined from isothermal measurements at 700, 800, and 900 C, where Cu and Au form a disordered continuous face centered cubic solid solution. Large differences in the lattice parameters of Au and Cu allowed the initial diffraction peaks to be easily identified, and later tracked as they merged into one diffraction peak with increased diffusion time. Initial diffusion kinetics were studied by measuring the time required for the Cu to diffuse through the Au thin film of known thickness. The activation energy for interdiffusion was measured to be 65.4 kJ/mole during this initial stage, which is approximately 0.4x that for bulk diffusion and 0.8x that for grain boundary diffusion. The low activation energy is attributed to the high density of columnar grain boundaries combined with other defects in the sputter deposited thin film coatings. As interdiffusion continues, the two layers homogenize with an activation energy of 111 kJ/mole during the latter stages of diffusion. This higher activation energy falls between the reported values for grain boundary and bulk diffusion, and may be related to grain growth occurring at these temperatures which accounts for the decreasing importance of grain boundaries on diffusion.

Elmer, J. W. [Lawrence Livermore National Laboratory (LLNL); Palmer, T. A. [Lawrence Livermore National Laboratory (LLNL); Specht, Eliot D [ORNL

2006-01-01

255

Direct Observations of Rapid Diffusion of Cu in Au Thin Films using In-Situ X-ray Diffraction  

SciTech Connect

In-situ x-ray diffraction was performed while annealing thin-film Au/Cu binary diffusion couples to directly observe diffusion at elevated temperatures. The temperature dependence of the interdiffusion coefficient was determined from isothermal measurements at 700 C, 800 C, and 900 C, where Cu and Au form a disordered continuous face centered cubic solid solution. Large differences in the lattice parameters of Au and Cu allowed the initial diffraction peaks to be easily identified, and later tracked as they merged into one diffraction peak with increased diffusion time. Initial diffusion kinetics were studied by measuring the time required for the Cu to diffuse through the Au thin film of known thickness. The activation energy for interdiffusion was measured to be 65.4 kJ/mole during this initial stage, which is approximately 0.4x that for bulk diffusion and 0.8x that for grain boundary diffusion. The low activation energy is attributed to the high density of columnar grain boundaries combined with other defects in the sputter deposited thin film coatings. As interdiffusion continues, the two layers homogenize with an activation energy of 111 kJ/mole during the latter stages of diffusion. This higher activation energy falls between the reported values for grain boundary and bulk diffusion, and may be related to grain growth occurring at these temperatures which accounts for the decreasing importance of grain boundaries on diffusion.

Elmer, J W; Palmer, T A; Specht, E D

2005-11-28

256

Direct observation of a noncatalytic growth regime for GaAs nanowires.  

PubMed

We identify a new noncatalytic growth regime for molecular beam epitaxially grown GaAs nanowires (NWs) that may provide a route toward axial heterostructures with discrete material boundaries and atomically sharp doping profiles. Upon increase of the As/Ga flux ratio, the growth mode of self-induced GaAs NWs on SiO(2)-masked Si(111) is found to exhibit a surprising discontinuous transition in morphology and aspect ratio. For effective As/Ga ratios <1, in situ reflection high-energy electron diffraction measurements reveal clear NW growth delay due to formation of liquid Ga droplets since the growth proceeds via the vapor-liquid-solid mechanism. In contrast, for effective As/Ga ratios >1 an immediate onset of NW growth is observed indicating a transition to droplet-free, facet-driven selective area growth with low vertical growth rates. Distinctly different microstructures, facet formation and either the presence or absence of Ga droplets at the apex of NWs, are further elucidated by transmission electron microscopy. The results show that the growth mode transition is caused by an abrupt change from As- to Ga-limited conditions at the (111)-oriented NW growth front, allowing precise tuning of the dominant growth mode. PMID:21823601

Rudolph, Daniel; Hertenberger, Simon; Bolte, Stefanie; Paosangthong, Watcharapong; Spirkoska, Dan?e; Döblinger, Markus; Bichler, Max; Finley, Jonathan J; Abstreiter, Gerhard; Koblmüller, Gregor

2011-09-14

257

Melt electrospinning of poly(?-caprolactone) scaffolds: phenomenological observations associated with collection and direct writing.  

PubMed

Melt electrospinning and its additive manufacturing analogue, melt electrospinning writing (MEW), are two processes which can produce porous materials for applications where solvent toxicity and accumulation in solution electrospinning are problematic. This study explores the melt electrospinning of poly(?-caprolactone) (PCL) scaffolds, specifically for applications in tissue engineering. The research described here aims to inform researchers interested in melt electrospinning about technical aspects of the process. This includes rapid fiber characterization using glass microscope slides, allowing influential processing parameters on fiber morphology to be assessed, as well as observed fiber collection phenomena on different collector substrates. The distribution and alignment of melt electrospun PCL fibers can be controlled to a certain degree using patterned collectors to create large numbers of scaffolds with shaped macroporous architectures. However, the buildup of residual charge in the collected fibers limits the achievable thickness of the porous template through such scaffolds. One challenge identified for MEW is the ability to control charge buildup so that fibers can be placed accurately in close proximity, and in many centimeter heights. The scale and size of scaffolds produced using MEW, however, indicate that this emerging process will fill a technological niche in biofabrication. PMID:25491879

Brown, Toby D; Edin, Fredrik; Detta, Nicola; Skelton, Anthony D; Hutmacher, Dietmar W; Dalton, Paul D

2014-12-01

258

Direct time-resolved observation of tungsten nanostructured growth due to helium plasma exposure  

NASA Astrophysics Data System (ADS)

Determination of the mechanisms underlying the growth of tungsten fuzz is an important step towards mitigation of fuzz formation. Nanostructured tungsten was produced on resistively heated tungsten wires in a helicon plasma source (maximum flux of 2.5 × 1021 m?2 s?1). Asymmetry in the setup allows for investigation of temperature and flux effects in a single sample. An effort at elucidating the mechanism of formation was made by inspecting SEM micrographs of the nanostructured tungsten at successive fluence steps of helium ions up to a fluence of 1 × 1027 m?2. To create these micrographs a single tungsten sample was exposed to the plasma, removed and inspected with an SEM, and replaced into the plasma. The tungsten surface was marked in several locations so that each micrograph is centred within 200 nm of each previous micrograph. Pitting of the surface (diameter 9.5 ± 2.3 nm, fluence (5 ± 2) × 1025 m?2) followed by surface roughening (fluence (9 ± 2) × 1025 m?2) and tendril formation (diameter 30 ± 10 nm, fluence (2 ± 1) × 1026 m?2) is observed, providing evidence of bubble bursting as the mechanism for seeding the growth of the tungsten fuzz.

Fiflis, P.; Curreli, D.; Ruzic, D. N.

2015-03-01

259

CAN-DOO: The Climate Action Network through Direct Observations and Outreach  

NASA Astrophysics Data System (ADS)

The urgency of climate change demands a greater understanding of our climate system, not only by the leaders of today, but by the scientists, policy makers, and citizens of tomorrow. Unfortunately, a large segment of the population currently possesses inadequate knowledge of climate science. In direct response to a need for greater scientific literacy with respect to climate science, researchers from Appalachian State University's Appalachian Atmospheric Interdisciplinary Research (AppalAIR) group, with support from NASA, have developed CAN-DOO: the Climate Action Network through Direct Observations and Outreach. CAN-DOO addresses climate science literacy by 1) Developing the infrastructure for sustaining and expanding public outreach through long-term climate measurements capable of complementing existing NASA measurements, 2) Enhancing public awareness of climate science and NASA's role in advancing our understanding of the Earth System, and 3) Introducing Science, Technology, Engineering, and Mathematics principles to homeschooled, public school, and Appalachian State University students through applied climate science activities. Project partners include the Grandfather Mountain Stewardship Foundation, Pisgah Astronomical Research Institute, and local elementary schools. In partnership with Grandfather Mountain, climate science awareness is promoted through citizen science activities, interactive public displays, and staff training. CAN-DOO engages students by involving them in the entire scientific investigative process as applied to climate science. We introduce local elementary and middle school students, homeschooled students throughout North Carolina, and undergraduate students in a new Global Climate Change course and select other courses at Appalachian State University to instrument assembly, measurement techniques, data collection, hypothesis testing, and drawing conclusions. Results are placed in the proper context via comparisons with other student data products, local research-grade measurements, and NASA measurements. Several educational modules have been developed that address specific topics in climate science. The modules are scalable and have been successfully implemented at levels ranging from 2nd grade through first-year graduate as well as with citizen science groups. They also can be applied in user-desired segments to a variety of Earth Science units. In this paper, we will introduce the project activities and present results from the first year of observations and outreach, with a special emphasis on two of the developed modules, the surface energy balance and aerosol optical depth module.

Taubman, B.; Sherman, J. P.; Perry, L. B.; Markham, J.; Kelly, G.

2011-12-01

260

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

SciTech Connect

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

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

2014-05-16

261

Direct observation of phase transitions: in situ diffraction measurements at the crystal scale  

NASA Astrophysics Data System (ADS)

Phase transitions often display determinate crystallographic orientation relationships between parent and symmetrically degenerate daughter domains. Preferred variant selection and orientation memory under the influence of deviatoric stress are the 'fingerprints' of the transformation mechanism, driving force, and microstructure. For the ?-? transition in iron - significant to the structure and anisotropy of the Earth's inner core - these have been studied primarily by texture analysis of polycrystalline powders; the convoluted nature of these data, however, render it essentially impossible to examine variant selection, and even precise orientation relationships themselves. Recently developed X-ray diffraction techniques have made it possible to answer these questions. Results from two measurements are presented. First, heterogeneous variant selection was observed and the specific ?/? orientation relationship was determined under quasi-static loading using High Energy Diffraction Microscopy at beamline 1-ID of APS-ANL. Second, the spatial heterogeneity and mutual exclusivity among ? variants was observed at the incipient transition using the Laue ?-diffraction technique at beamline 12.3.2. of ALS-LBNL. In both cases, a 60x25?m single crystal of iron was pressurized in a DAC and measured before and after the ?-? transition at 13GPa. In the HEDM experiment, spatial resolution is sacrificed for domain-averaged orientation and strain resoltuion, making it possible to quantify the magnitude of the applied deviatoric stress in situ. In the Laue ?-Diffraction technique, the local lattice orientations are mapped with 1?m resolution, displaying marked spatial variation. These pilot experiments open new possibilities for investigating high pressure/high temperature transformations in situ. By mapping both orientations and lattice strains, the nature of the mechanisms and driving forces can be illuminated. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Funding through the Laboratory Directed Research and Development program (10- ERD-053) is gratefully acknowledged.

Bernier, J. V.; Barton, N. R.; Farber, D.; Wenk, H.; Kunz, M.; Lienert, U.

2012-12-01

262

Direct observation of guanine radical cation deprotonation in G-quadruplex DNA.  

PubMed

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

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

2015-01-14

263

Far field observation and theoretical analyses of light directional imaging in metamaterial with stacked metal-dielectric films  

NASA Astrophysics Data System (ADS)

We report experimental observation of directional imaging of evanescent waves in layered metal-dielectric metamaterial. The investigation is performed with Ag/SiO2 multilayers combined with nano-object featured by a silicon mask slit. Evanescent waves of directional imaging are transferred to far field by roughening the top Ag layer and observed with a microscope objective. Experimental results agree well with numerical simulations. In addition, directional imaging behavior dependences on geometrical parameters are further presented and show great deviations with effective medium theory in some cases.

Wang, Changtao; Gao, Ping; Tao, Xing; Zhao, Zeyu; Pu, Mingbo; Chen, Po; Luo, Xiangang

2013-07-01

264

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

265

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

NASA Technical Reports Server (NTRS)

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

Lal, Ravindra

1994-01-01

266

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

267

Direct observation of domains in model stratum corneum lipid mixtures by Raman microspectroscopy.  

PubMed Central

Several studies on intact and model stratum corneum (SC), the top layer of the epidermis, have suggested the presence of crystalline domains. In the present work, we used micro-Raman mapping to detect lipid domains in model lipid mixtures formed by an equimolar mixture of ceramides, cholesterol, and palmitic acid, the three main lipid species of SC. We were able to determine the spatial distribution of the three compounds individually based on the systematic analysis of band areas. As a control, we studied freeze-dried lipid mixtures, and the Raman microspectroscopy reported faithfully the homogeneous distribution of the three compounds. Spectral mapping was then performed on hydrated equimolar mixtures carefully annealed. In this case, clear phase separations were observed. Domains enriched in cholesterol, ceramides, or palmitic acid with a size of a few tens of square microns were detected. These findings constitute the first direct evidence of the formation of heterogeneous domains in the SC lipid models in a bulk phase. Raman microspectroscopy is an innovative approach to characterize the conditions leading to the formation of domains and provides new insights into the understanding of the skin barrier. PMID:11566785

Percot, A; Lafleur, M

2001-01-01

268

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

269

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

270

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

271

Directly observing the motion of DNA molecules near solid-state nanopores.  

PubMed

We investigate the diffusion and the drift motion of ? DNA molecules near solid-state nanopores prior to their translocation through 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

2012-11-27

272

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

273

Testing a direction-dependent primordial power spectrum with observations of the Cosmic Microwave Background  

E-print Network

Statistical isotropy is often assumed in cosmology and should be tested rigorously against observational data. We construct simple quadratic estimators to reconstruct asymmetry in the primordial power spectrum from CMB temperature and polarization data and verify their accuracy using simulations with quadrupole power asymmetry. We show that the Planck mission, with its millions of signal-dominated modes of the temperature anisotropy, should be able to constrain the amplitude of any spherical multipole of a scale-invariant quadrupole asymmetry at the $0.01$ level ($2\\sigma$). Almost independent constraints can be obtained from polarization at the $0.03$ level after four full-sky surveys, providing an important consistency test. If the amplitude of the asymmetry is large enough, constraining its scale-dependence should become possible. In scale-free quadrupole models with $1\\%$ asymmetry, consistent with the current limits from WMAP temperature data (after correction for beam asymmetries), Planck should constrain the spectral index $q$ of power-law departures from asymmetry to $\\Delta q = 0.3$. Finally, we show how to constrain models with axisymmetry in the same framework. For scale-free quadrupole models, Planck should constrain the direction of the asymmetry to a $1\\sigma$ accuracy of about $2$ degrees using one year of temperature data.

Yin-Zhe Ma; George Efstathiou; Anthony Challinor

2014-05-15

274

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

275

The propagation of auroral hiss observed on the ground as deduced from direction-finding measurements  

NASA Astrophysics Data System (ADS)

Based on the direction-finding results of auroral VLF hiss at Syowa (geomag. lat. -70°), an extensive ray tracing analysis, and an estimation of transmission loss in the simulated auroral ionosphere, the propagation characteristics of ground-based auroral hiss in the magnetosphere and ionosphere are deduced ; incoherent transmission of impulsive hiss with a wide frequency range (? 100 kHz) from localized exit regions at the ionospheric level almost coincident with some localized regions of bright electron auroras; non-ducted propagation of continuous hiss with a narrow frequency range (?20 kHz) after emerging from a duct exit at higher altitudes (3000-5000 km); and coherent transmission from an exit region at the ionospheric level between Syowa and the location of a quiet auroral arc appearing poleward far from Syowa. Coupled with previous spacebased observations and model calculations of the auroral hiss power flux spectrum, we see that impulsive hiss emissions generated in a wide range of higher to low altitudes by the beam amplification are trapped in irregularities of decreased electron density outside the auroral arc at lower altitudes, propagate down to the ionosphere and are transmitted to the ground, and that after emerging from a duct exit at altitudes of 3000-5000 km, continuous hiss emissions are propagated in a non-ducted mode down to the ionosphere at different latitudes, corresponding to the initial wave normals at the duct exit, and are transmitted to the ground.

Yoshihito, Tanaka; Masanori, Nishino

1988-03-01

276

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

277

Direct observations of nitric oxide produced by energetic electron precipitation into the Antarctic middle atmosphere  

NASA Astrophysics Data System (ADS)

We report the first ground-based passive microwave observations made from Troll station, Antarctica, which show enhanced mesospheric nitric oxide (NO) volume mixing ratio reaching levels of 1.2 ppmv, or 2-3 orders of magnitude above background, at 70-80 km during small, relatively isolated geomagnetic storms in 2008. The mesospheric NO peaked 2 days after enhanced NO at higher altitudes (110-150 km) measured by the SABER satellite, and 2 days after peaks in the >30 keV and >300 keV electron flux measured by POES, although the 300 keV electron flux remained high. High time resolution data shows that mesospheric NO was enhanced at night and decayed during the day and built up to high levels over a period of 3-4 days. The altitude profile of mesospheric NO suggests direct production by ˜300 keV electron precipitation. Simulations using the Sodankylä Ion and Neutral Chemistry model show that the delay between thermospheric and mesospheric NO enhancements was primarily a result of the weaker production rate at lower altitudes by ˜300 keV electrons competing against strong day-time losses.

Newnham, David A.; Espy, Patrick J.; Clilverd, Mark A.; Rodger, Craig J.; Seppälä, Annika; Maxfield, David J.; Hartogh, Paul; Holmén, Kim; Horne, Richard B.

2011-10-01

278

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

279

Direct observation of radiation belt electrons precipitated by the controlled injection of VLF signals from a ground-based transmitter  

Microsoft Academic Search

Radiation belt electrons precipitated by controlled injection of VLF signals from a ground based transmitter have been directly observed for the first time. These observations were part of the SEEP (Stimulated Emission of Energetic Particles) experiment conducted during May - December 1982. Key elements of SEEP were the controlled modulation of VLF transmitters and a sensitive low altitude satellite payload

W. L. Imhof; J. B. Reagan; H. D. Voss; E. E. Gaines; D. W. Datlowe; J. Mobilia; R. A. Helliwell; J. Katsufrakis; R. G. Joiner

1983-01-01

280

The vulnerability of groundwater to pesticide contamination estimated directly from observations of presence or absence in wells  

Microsoft Academic Search

This study uses a Bayesian methodology to calculate the vulnerability of groundwater to pesticide contamination directly from monitoring data. This measure of vulnerability does not rely on expert opinion or the interpretation of pollutant transport models. The technique combines information from different sets of observations over periods of years, and can combine observations for a range of pesticide compounds yet

Fred Worrall; Tim Besien

2005-01-01

281

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

NASA Astrophysics Data System (ADS)

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

Chilcote, Jeffrey Kaplan

282

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

283

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

284

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

285

Allowance tracking workstation  

SciTech Connect

The Clean Air Act Amendments of 1990 and EPA`s Acid Rain Program unleashed an accountability monster on electric utilities. A software product was developed through establishment of a virtual corporation between ten (10) utilities and a software developer. The product has the ability to address different informational and transactional needs of the various departmental users within a utility, tracking and recording allowances, and producing various internal and external reports.

Martin, J.L. [Indianapolis Power and Light Co., IN (United States)

1995-12-31

286

A comparison of modified directly observed therapy to standard care for chronic hepatitis C.  

PubMed

Hepatitis C virus (HCV) is the most common chronic blood-borne infection in the United States. Effective treatments are available, however adherence to treatment is challenging. Modified directly observed therapy (mDOT) with weekly administration of pegylated interferon might improve adherence and outcomes for patients infected with chronic HCV. The purpose of this study was to compare two treatment protocols and examine predictors of sustained virologic response (SVR). This retrospective review compares HCV treatment outcomes in two outpatient clinics at an urban academic medical center. Gastroenterology fellows provided standard treatment (SC) in one clinic; a nurse practitioner administered weekly pegylated interferon injections weekly in a primary care clinic. All patients received oral ribavirin. Data was extracted from the medical records of all treated patients over a 5-year period. 155 treatment-naïve, chronically infected HCV patients were treated. Ninety-seven patients received mDOT treatment and 58 received standard care. Mean age was 46 years. Genotype 1 represented 59 % of the sample. The mDOT patients were significantly more likely to be younger (44 vs. 50 years), have a history of injection drug use (93.1 vs. 50.0 %), and be HIV-infected (13.5 vs. 2 %) compared to SC patients. The overall SVR rate was 45.2 % and did not differ between the groups in unadjusted analyses (p = 0.95). Genotype was the only predictor of SVR. Patients treated by nurse practitioners trained in HCV care and seen weekly for interferon injections have comparable treatment outcomes to patients treated by specialists. PMID:23471655

Cioe, Patricia A; Stein, Michael D; Promrat, Kittichai; Friedmann, Peter D

2013-08-01

287

Polymerization of fibrin: Direct observation and quantification of individual B:b knob-hole interactions.  

PubMed

The polymerization of fibrin occurs primarily through interactions between N-terminal A- and B-knobs, which are exposed by the cleavage of fibrinopeptides A and B, respectively, and between corresponding a- and b-holes in the gamma- and beta-modules. Of the potential knob-hole interactions--A:a, B:b, A:b, and B:a--the first has been shown to be critical for fibrin formation, but the roles of the others have remained elusive. Using laser tweezers-based force spectroscopy, we observed and quantified individual B:b and A:b interactions. Both desA-fibrin with exposed A-knobs and desB-fibrin bearing B-knobs interacted with fragment D from the gammaD364H fibrinogen containing b-holes but no functional a-holes. The strength of single B:b interactions was found to be 15 to 20 pN, approximately 6-fold weaker than A:a interactions. B:b binding was abrogated by B-knob mimetic peptide, the (beta15-66)2 fragment containing 2 B-knobs, and a monoclonal antibody against the beta15-21 sequence. The interaction of desB-fibrin with fragment D containing a- and b-holes produced the same forces that were insensitive to A-knob mimetic peptide, suggesting that B:a interactions were absent. These results directly demonstrate for the first time B:b binding mediated by natural B-knobs exposed in a fibrin monomer. PMID:16940416

Litvinov, Rustem I; Gorkun, Oleg V; Galanakis, Dennis K; Yakovlev, Sergiy; Medved, Leonid; Shuman, Henry; Weisel, John W

2007-01-01

288

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

PubMed Central

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

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

2014-01-01

289

Direct Observation of Individual KCNQ1 Potassium Channels Reveals Their Distinctive Diffusive Behavior*  

PubMed Central

We have directly observed the trafficking and fusion of ion channel containing vesicles and monitored the release of individual ion channels at the plasma membrane of live mammalian cells using total internal reflection fluorescence microscopy. Proteins were fused in-frame with green or red fluorescent proteins and expressed at low level in HL-1 and HEK293 cells. Dual color imaging revealed that vesicle trafficking involved motorized movement along microtubules followed by stalling, fusion, and subsequent release of individual ion channels at the plasma membrane. We found that KCNQ1-KCNE1 complexes were released in batches of about 5 molecules per vesicle. To elucidate the properties of ion channel complexes at the cell membrane we tracked the movement of individual molecules and compared the diffusive behavior of two types of potassium channel complex (KCNQ1-KCNE1 and Kir6.2-SUR2A) to that of a G-protein coupled receptor, the A1 adenosine receptor. Plots of mean squared displacement against time intervals showed that mobility depended on channel type, cell type, and temperature. Analysis of the mobility of wild type KCNQ1-KCNE1 complexes showed the existence of a significant immobile subpopulation and also a significant number of molecules that demonstrated periodic stalling of diffusive movements. This behavior was enhanced in cells treated with jasplakinolide and was abrogated in a C-terminal truncated form (KCNQ1(R518X)-KCNE1) of the protein. This mutant has been identified in patients with the long QT syndrome. We propose that KCNQ1-KCNE1 complexes interact intermittently with the actin cytoskeleton via the C-terminal region and this interaction may have a functional role. PMID:19940153

Mashanov, Gregory I.; Nobles, Muriel; Harmer, Stephen C.; Molloy, Justin E.; Tinker, Andrew

2010-01-01

290

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

Code of Federal Regulations, 2012 CFR

...observed collection on the form. (e) The collector shall ensure that the observer is the same gender as the individual. A person of the opposite gender may not act as the observer under any conditions. The observer may be a different person...

2012-01-01

291

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

Code of Federal Regulations, 2010 CFR

...observed collection on the form. (e) The collector shall ensure that the observer is the same gender as the individual. A person of the opposite gender may not act as the observer under any conditions. The observer may be a different person...

2010-01-01

292

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

Code of Federal Regulations, 2014 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...

2014-10-01

293

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

294

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

Code of Federal Regulations, 2011 CFR

...observed collection on the form. (e) The collector shall ensure that the observer is the same gender as the individual. A person of the opposite gender may not act as the observer under any conditions. The observer may be a different person...

2011-01-01

295

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

296

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

Code of Federal Regulations, 2013 CFR

...observed collection on the form. (e) The collector shall ensure that the observer is the same gender as the individual. A person of the opposite gender may not act as the observer under any conditions. The observer may be a different person...

2013-01-01

297

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

298

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

299

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

2010-07-26

300

Isolating observer-based reference directions in human spatial memory: Head, body, and the self-to-array axis  

PubMed Central

Several lines of research have suggested the importance of egocentric reference systems for determining how the spatial properties of one’s environment are mentally organized. Yet relatively little is known about the bases for egocentric reference systems in human spatial memory. In three experiments, we examine the relative importance of observer-based reference directions in human memory by controlling the orientation of head and body during acquisition. Experiment 1 suggests that spatial memory is organized by a head-aligned reference direction; however, Experiment 2 shows that a body-aligned reference direction can be more influential than a head-aligned direction when the axis defined by the relative positions of the observer and the learned environment (the “self-to-array” axis) is properly controlled. A third experiment shows that the self-to-array axis is distinct from – and can dominate – retina, head, and body-based egocentric reference systems. PMID:17316594

Waller, David; Lippa, Yvonne; Richardson, Adam

2007-01-01

301

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

Microsoft Academic Search

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

ROBERT WEST; DAVINA FRENCH; RICHARD KEMP; JAMES ELANDER

1993-01-01

302

The Biasing Effects of Labels on Direct Observation by Preservice Teachers  

ERIC Educational Resources Information Center

Observational bias can significantly affect results attained through observation. This study focused on 122 preservice teacher educators who conducted a structured observation, using momentary time sampling procedures with 10-second intervals, to measure student on-task and off-task behaviors. The experimental variable altered was the…

Allday, R. Allan; Duhon, Gary J.; Blackburn-Ellis, Sarah; Van Dycke, Jamie L.

2011-01-01

303

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

304

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

PubMed

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

Midgley, Nick

2007-08-01

305

Numerical observation of preferred directionality in ion ejection from stretched rectilinear ion traps  

NASA Astrophysics Data System (ADS)

We report on numerical investigations of directionality of ion ejection in stretched rectilinear ion traps (RIT). Three 4-electrode trap geometries have been investigated. In all cases, one pair of electrodes has slits at their center and the other pair has no slits. The studied traps include the RIT-S, in which the mass analyzer electrodes are symmetrically positioned around the central axis; the RIT-X, in which the mass analyzer has a stretch in the direction of the electrodes which have slits (labeled as x-direction); and the RIT-Y, in which the mass analyzer has a stretch in the direction of the electrodes which have no slits (labeled as y-direction). Our analysis has been carried out on two-dimensional (2D) fields at the centre of an infinitely long mass analyzer. The boundary element method (BEM) has been used for field computations. The trajectory of ion motion has been generated using Runge Kutta fourth order integration. Three sets of simulations have been carried out on each of the RIT-S, the RIT-X and the RIT-Y to check for directionality of ion ejection. In the first, we numerically obtain the stability region on the potential (Udc- Vrf) axes. In the second we generate an escape velocity plot with UdcD0 for different values of Vrf. In the third, we simulate the mass selective boundary ejection experiment on a single ion. In the symmetric RIT-S, as expected, all three simulations show that there is an equal probability of ion reaching the trap boundary in either of the x- or y-directions. For the stretched traps, however, the results are dramatically different. For the RIT-X, all three simulations suggest that ion destabilization at the stability boundary occurs in the x-directionE Similarly, for the RIT-Y, ions preferentially get destabilized in the y-direction. That is, ions reaching the trap boundary overwhelmingly prefer the stretch direction.

Krishnaveni, A.; Kumar Verma, Neeraj; Menon, A. G.; Mohanty, Atanu K.

2008-08-01

306

DIRECT MICROSCOPIC OBSERVATION AND VISUALIZATION OF CAMPYLOBACTER JEJUNI VIABILITY ON CHICKEN SKIN  

Technology Transfer Automated Retrieval System (TEKTRAN)

The objective of this study was to develop a method to identify specific sites on chicken skin, which allow Campylobacter jejuni survival. This method employs confocal laser scanning microscopy (CSLM) visualization of Campylobacter jejuni transformed with Pcgfp plasmid (GFP-Campylobacter) exposed t...

307

Direct observation of glycogen synthesis in human muscle with sup 13 C NMR  

SciTech Connect

On the basis of previous indirect measurements, skeletal muscle has been implicated as the major site of glucose uptake and it has been suggested that muscle glycogen formation is the dominant pathway. However, direct measurements of the rates of glycogen synthesis have not been possible by previous techniques. The authors have developed {sup 13}C NMR methods to measure directly the rate of human muscle glycogen formation from infused, isotopically labeled (1-{sup 13}C)glucose. They show that under conditions of imposed hyperglycemia and hyperinsulinemia, a majority of the infused glucose was converted to muscle glycogen in a normal man. This directly shows that muscle is the major site of glucose disposal under these conditions, and provides quantitation of the glucose flux to muscle glycogen.

Jue, T.; Rothman, D.L.; Shulman, G.I.; Tavitian, B.A.; DeFronzo, R.A.; Shulman, R.G. (Yale Univ., New Haven, CT (USA))

1989-06-01

308

Direct observation of large quantum interference effect in anthraquinone solid-state junctions.  

PubMed

Quantum interference in cross-conjugated molecules embedded in solid-state devices was investigated by direct current-voltage and differential conductance transport measurements of anthraquinone (AQ)-based large area planar junctions. A thin film of AQ was grafted covalently on the junction base electrode by diazonium electroreduction, while the counter electrode was directly evaporated on top of the molecular layer. Our technique provides direct evidence of a large quantum interference effect in multiple CMOS compatible planar junctions. The quantum interference is manifested by a pronounced dip in the differential conductance close to zero voltage bias. The experimental signature is well developed at low temperature (4 K), showing a large amplitude dip with a minimum >2 orders of magnitude lower than the conductance at higher bias and is still clearly evident at room temperature. A temperature analysis of the conductance curves revealed that electron-phonon coupling is the principal decoherence mechanism causing large conductance oscillations at low temperature. PMID:23805821

Rabache, Vincent; Chaste, Julien; Petit, Philippe; Della Rocca, Maria Luisa; Martin, Pascal; Lacroix, Jean-Christophe; McCreery, Richard L; Lafarge, Philippe

2013-07-17

309

A fishery-independent assessment of an overfished rockfish stock, cowcod ( Sebastes levis ), using direct observations from an occupied submersible  

Microsoft Academic Search

A meaningful assessment of cowcod (Sebastes levis) has been conducted using visual, nonextractive, habitat- specific methods. Following the precipitous decline of rockfish (Sebastes spp.) stocks along the Pacific coast, it was evident that more effective methods were needed to assess several species in untrawlable habitats. Cowcod were surveyed within large Cowcod Conservation Areas (CCAs) off southern California using direct observations

Mary M. Yoklavich; Milton S. Love; Karin A. Forney

2007-01-01

310

Nevirapine ( NVP ) and Protease Inhibitor ( PI ) Based Regimens in a Directly Observed Therapy ( DOT ) Program for Intravenous Drug Users ( IDUs )  

Microsoft Academic Search

Background of study: The treatment of HIV-infected IDUs presents unique challenges, including co-infection with agents such as HCV, interaction with drugs such as methadone, and the use of strategies used to enhance adherence with often complex highly active antiretroviral therapy (HAART) regimens. Within the context of a methadone maintenance program for heroin users, we have established a directly observed therapy

Brian Conway; Jennie Prasad; Nadine Smith; Stanley de Vlaming

311

Direct observation of band-gap closure for a semiconducting carbon nanotube in a large parallel magnetic field.  

PubMed

We have investigated the magnetoconductance of semiconducting carbon nanotubes (CNTs) in pulsed, parallel magnetic fields up to 60 T, and report the direct observation of the predicted band-gap closure and the reopening of the gap under variation of the applied magnetic field. We also highlight the important influence of mechanical strain on the magnetoconductance of the CNTs. PMID:21405643

Jhang, S H; Marga?ska, M; Skourski, Y; Preusche, D; Grifoni, M; Wosnitza, J; Strunk, C

2011-03-01

312

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

E-print Network

for solid/solid systems, very few attempts have been made to experimentally characterize dispersionPHYSICAL REVIEW B 88, 144307 (2013) Direct observation of the phonon dispersion of a three-dimensional solid/solid hypersonic colloidal crystal Gaohua Zhu,1,* Nichlas Z. Swinteck,2 Songtao Wu,1 Jin S. Zhang

Deymier, Pierre

313

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.

314

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

NASA Technical Reports Server (NTRS)

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

Ivory, K.; Schwenn, R.

1995-01-01

315

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

ERIC Educational Resources Information Center

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

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

2006-01-01

316

Direct Observation of Charge Transfer at a MgO(111) Surface A. Subramanian,1,* L. D. Marks,1  

E-print Network

Direct Observation of Charge Transfer at a MgO(111) Surface A. Subramanian,1,* L. D. Marks,1 O on the polar (111) surface of MgO and refine the valence charge distribution. The surface is nonstoichiometric. The partial charges that we obtain for the surface atoms are in reasonable agreement with empirical bond

Marks, Laurence D.

317

Direct Observation of Polymer Sheathing in Carbon Nanotube-Polycarbonate Composites  

Microsoft Academic Search

A series of observations of polymer sheathing in multiwalled carbon nanotube (MWCNT)-polycarbonate composites are presented. This sheathing was observed in images of the composite fracture surface and is consistent with diameter distributions of the as-received and embedded MWCNTs. A novel nanomanipulation experiment, where the sheathing balls up when contacted by an AFM tip, confirms this phenomenon. This sheathing layer is

W. Ding; A. Eitan; F. T. Fisher; X. Chen; D. A. Dikin; R. Andrews; L. C. Brinson; L. S. Schadler; R. S. Ruoff

2003-01-01

318

HF Radar Observation of Wave Directional Spectra in a Strong Current Regime  

Microsoft Academic Search

Dual Wellen HF Radar (WERA) systems have been observing near-surface currents and wave parameters over the Southeast Florida shelf since June 2004 as a part of the Southeast Atlantic Coastal Ocean Observing System (SEACOOS). The region of coverage includes the Florida Straits and the Florida Current (FC) which typically has maximum surface velocities approaching 2 ms\\

Brian K. Haus; Mei Wang; L. K. Shay; L. R. Wyatt

2007-01-01

319

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

320

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

321

Simultaneous imaging and spectroscopic observation of high temperature cusp loops and bi-directional inflow in the solar flare  

NASA Astrophysics Data System (ADS)

We succeeded in the simultaneous observation of high temperature cusp loops and bi-directional inflow of a solar flare. Solar flares are huge explosion in the solar corona. The standard model of solar flares based on the magnetic reconnection includes bi-directional inflow toward the reconnection point. Corresponding to the bi-directional inflow, high temperature loops like a cusp shape are formed due to the the magnetic reconnection. SOD/AIA is an EUV imaging telescope and has a great spatial and temporal resolution. On the other hand, it is difficult to know the temperature from the imaging data only because it includes emission from different lines. Therefore simultaneous spectroscopic observation is important. Hinode/EIS is an EUV spectrometer and useful for the spectroscopy of the plasma. We analyzed imaging data with SDO/AIA and spectroscopic data with Hinode/EIS of a C-class flare that occurred in 2012 beyond the solar limb. As a result, bi-directional inflow are observed with the images of 171A filter (around 1MK). At the same time, cusp loops are observed with the raster scans of FeXXIV emission line (over 10 MK) at the region surrounded by the bi-directional inflow. Cusp loops are also observed with high temperature filter 131A (over 10 MK). 131A filter also includes cool temperature emissions (logT ~ 5.6), however the results of the simultaneous spectroscopic observation of FeXXIV supports that these cusp loops have high temperature over 10MK. This is clear evidence that 1MK loops are heated over 10MK by the magnetic reconnection. Additionally, a strong blueshift over 300km/s is observed with FeXXIV as a Doppler shift at the region of the current sheet. This speed might reach Alfv'en speed considering the angle of the loop, which also supports the magnetic reconnection. These results indeed support the standard model and this is the first simultaneous observation of bi-directional inflow with imaging and cusp loops with spectroscopy as long as we know.

Matsui, Y.; Yokoyama, T.

2013-12-01

322

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

323

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

324

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

325

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

Microsoft Academic Search

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

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

1977-01-01

326

DIRECT OBSERVATION OF COMPOSITIONALLY HOMOGENEOUS ACH BAND-GAP-MODULATED SUPERLATTICES  

Microsoft Academic Search

It is shown that amorphous hydrogenated carbon (a-C:H) band-gap-modulated superlattices can be observed by transmission electron microscopy. The layering proves to be well defined and it is demonstrated that changes in the band gap from 1.5 to 2.8 eV cannot be associated with ordered graphitic regions, in that crystalline regions larger than 0.5 nm are not observed. Differences in the

CA DAVIS; SRP SILVA; RE DUNINBORKOWSKI; GAJ AMARATUNGA; KM KNOWLES; WM STOBBS

1995-01-01

327

Direct observation and analysis of indentation cracking on glasses and ceramics  

Microsoft Academic Search

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

Robert F. Cook; George M. Pharr

1990-01-01

328

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

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

329

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

330

Direct Observation of Inward Electron Flux being Blocked in the Large Helical Device  

NASA Astrophysics Data System (ADS)

We present a particle transport phenomenon caused by a hydrogen ice pellet injection (PI) into the Large Helical Device. The electron density (ne) profile evolution after a PI was measured by using a 200-channel Thomson scattering diagnostic. The highly hollow ne-profile caused by a PI faded out as time elapsed with a very slight increase in the ne at the core region, giving a direct evidence for the inward electron flux being almost completely blocked in the core region.

Narihara, Kazumichi; Sakamoto, Ryuichi; Yamada, Ichihiro; Funaba, Hisamichi; Shoji, Mamoru; Yokoyama, Masayuki; Hayashi, Hiroshi; LHD Experimental Group

331

DIRECT OBSERVATION OF THE ALPHA-EPSILON TRANSITION IN SHOCKED SINGLE CRYSTAL IRON  

SciTech Connect

In-situ x-ray diffraction was used to study the response of single crystal iron under shock conditions. Measurements of the response of [001] iron showed a uniaxial compression of the initially bcc lattice along the shock direction by up to 6% at 13 GPa. Above this pressure, the lattice responded with a further collapse of the lattice by 15-18% and a transformation to a hcp structure. The in-situ measurements are discussed and results summarized.

Kalantar, D H; Collins, G W; Colvin, J D; Davies, H M; Eggert, J H; Hawreliak, J; Lorenzana, H E; Meyers, M A; Rosolankova, K; Schneider, M S; Sheppard, J; Stolken, J S; Wark, J S

2005-08-23

332

Direct Observation of the {alpha}-{epsilon} Transition in Shocked Single Crystal Iron  

SciTech Connect

In-situ x-ray diffraction was used to study the response of single crystal iron under shock conditions. Measurements of the response of [001] iron showed a uniaxial compression of the initially bcc lattice along the shock direction by up to 6% at 13 GPa. Above this pressure, the lattice responded with a further collapse of the lattice by 15-18% and a transformation to the hcp structure. The in-situ measurements are discussed and results summarized.

Kalantar, D. H.; Collins, G. W.; Colvin, J. D.; Eggert, J. H.; Hawreliak, J.; Lorenzana, H. E.; Stoelken, J. S. [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States); Davies, H. M. [AWE Aldermaston, Reading, RG7 4PR (United Kingdom); Meyers, M. A.; Schneider, M. S. [University of California at San Diego, La Jolla, CA 92093 (United States); Rosolankova, K.; Sheppard, J.; Wark, J. S. [Department of Physics, Clarendon Laboratory, University of Oxford, Oxford, OX1 3PU (United Kingdom)

2006-07-28

333

Direct Constraints on Minimal Supersymmetry from Fermi-LAT Observations of the Dwarf Galaxy Segue 1  

E-print Network

The dwarf galaxy Segue 1 is one of the most promising targets for the indirect detection of dark matter. Here we examine what constraints 9 months of Fermi-LAT gamma-ray observations of Segue 1 place upon the Constrained Minimal Supersymmetric Standard Model (CMSSM), with the lightest neutralino as the dark matter particle. We use nested sampling to explore the CMSSM parameter space, simultaneously fitting other relevant constraints from accelerator bounds, the relic density, electroweak precision observables, the anomalous magnetic moment of the muon and B-physics. We include spectral and spatial fits to the Fermi observations, a full treatment of the instrumental response and its related uncertainty, and detailed background models. We also perform an extrapolation to 5 years of observations, assuming no signal is observed from Segue 1 in that time. Results marginally disfavour models with low neutralino masses and high annihilation cross-sections. Virtually all of these models are however already disfavoured by existing experimental or relic density constraints.

Pat Scott; Jan Conrad; Joakim Edsjö; Lars Bergström; Christian Farnier; Yashar Akrami

2009-12-15

334

Direct Observations of Sigma Phase Growth and Dissolution in 2205 Duplex Stainless Steel  

SciTech Connect

The formation and growth of sigma ({sigma}) phase in a 2205 duplex stainless steel is monitored during an 850 C isothermal heat treatment using an in situ synchrotron x-ray diffraction technique. At this temperature, {sigma} phase is first observed within approximately 40 seconds of the start of the isothermal heat treatment and grows rapidly over the course of the 3600 second heat treatment to a volume fraction of approximately 13%. A simultaneous increase in the austenite ({gamma}) volume fraction and a decrease in the ferrite ({delta}) volume fraction are observed. The {sigma} phase formed at this temperature is rapidly dissolved within approximately 200 seconds when the temperature is increased to 1000 C. Accompanying this rapid dissolution of the {sigma} phase, the {delta} and {gamma} volume fractions both approach the balanced (50/50) level observed in the as-received material.

Palmer, T; Elmer, J; Babu, S; Specht, E

2005-06-14

335

Direct observations of sigma phase growth and dissolution in 2205 duplex stainless steel  

SciTech Connect

The formation and growth of sigma ({sigma}) phase in a 2205 duplex stainless steel is monitored during an 850 C isothermal heat treatment using an in situ synchrotron x-ray diffraction technique. At this temperature, {sigma} phase is first observed within approximately 40 seconds of the start of the isothermal heat treatment and grows rapidly over the course of the 3600 second heat treatment to a volume fraction of approximately 13%. A simultaneous increase in the austenite ({gamma}) volume fraction and a decrease in the ferrite ({delta}) volume fraction are observed. The {sigma} phase formed at this temperature is rapidly dissolved within approximately 200 seconds when the temperature is increased to 1000 C. Accompanying this rapid dissolution of the {sigma} phase, the {delta} and {gamma} volume fractions both approach the balanced (50/50) level observed in the as-received material.

Palmer, T.A.; Elmer, J.W.; Babu, S.S.; Specht, E.D. (LLNL); (ORNL)

2007-10-10

336

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

PubMed

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

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

2014-12-19

337

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

338

Direct constraint on the distance of ?2 Velorum from AMBER/VLTI observations  

NASA Astrophysics Data System (ADS)

Context: Interferometry can provide spatially resolved observations of massive star binary systems and their colliding winds, which thus far have been studied mostly with spatially unresolved observations. Aims: We present the first AMBER/VLTI observations, taken at orbital phase 0.32, of the Wolf-Rayet and O (WR+O) star binary system ?2 Velorum and use the interferometric observables to constrain its properties. Methods: The AMBER/VLTI instrument was used with the telescopes UT2, UT3, and UT4 on baselines ranging from 46 m to 85 m. It delivered spectrally dispersed visibilities, as well as differential and closure phases, with a resolution R=1500 in the spectral band 1.95-2.17 ?m. We interpret these data in the context of a binary system with unresolved components, neglecting in a first approximation the wind-wind collision zone flux contribution. Results: Using WR- and O-star synthetic spectra, we show that the AMBER/VLTI observables result primarily from the contribution of the individual components of the WR+O binary system. We discuss several interpretations of the residuals, and speculate on the detection of an additional continuum component, originating from the free-free emission associated with the wind-wind collision zone (WWCZ), and contributing at most to the observed K-band flux at the 5% level. Based on the accurate spectroscopic orbit and the Hipparcos distance, the expected absolute separation and position angle at the time of observations were 5.1±0.9 mas and 66±15°, respectively. However, using theoretical estimates for the spatial extent of both continuum and line emission from each component, we infer a separation of 3.62+0.11-0.30 mas and a position angle of 73+9-11°, compatible with the expected one. Our analysis thus implies that the binary system lies at a distance of 368+38-13 pc, in agreement with recent spectrophotometric estimates, but significantly larger than the Hipparcos value of 258+41-31 pc. Based on observations collected at the European Southern Observatory, Paranal, Chile, within the guaranteed time programme 074.A-9025(A).

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

2007-03-01

339

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

340

Direct Observation of Double-Core-Hole Shake-Up States in Photoemission  

NASA Astrophysics Data System (ADS)

Direct measurements of Ar+ 1 s-12 p-1n l double-core-hole shake-up states are reported using conventional single-channel photoemission, offering a new and relatively easy means to study such species. The high-quality results yield accurate energies and lifetimes of the double-core-hole states. Their photoemission spectrum also can be likened to 1 s absorption of an exotic argon ion with a 2 p core vacancy, providing new information about the spectroscopy of both this unusual ionic state as well as the neutral atom.

Püttner, Ralph; Goldsztejn, Gildas; Céolin, Denis; Rueff, Jean-Pascal; Moreno, Thierry; Kushawaha, Rajesh K.; Marchenko, Tatiana; Guillemin, Renaud; Journel, Loïc; Lindle, Dennis W.; Piancastelli, Maria Novella; Simon, Marc

2015-03-01

341

Direct observation of sp{sup 3} bonding in tetrahedral amorphous carbon using ultraviolet Raman spectroscopy  

SciTech Connect

The vibrational modes of the sp{sup 3} sites in tetrahedral amorphous carbon ({ital ta}-C) thin films are revealed directly using ultraviolet Raman spectroscopy at 244 nm excitation and are shown to produce a Raman peak centered around 1100 cm{sup {minus}1}. In addition, the main Raman peak associated with sp{sup 2} vibrational modes is shifted upward in frequency by 100 cm{sup {minus}1} relative to its position in spectra excited at 514 nm. The spectra are interpreted in terms of the bonding in {ital ta}-C. {copyright} {ital 1997 American Institute of Physics.}

Gilkes, K.W. [School of Physics, University of East Anglia, Norwich NR47TJ (United Kingdom)] [School of Physics, University of East Anglia, Norwich NR47TJ (United Kingdom); Sands, H.S.; Batchelder, D.N. [Department of Physics and Astronomy, University of Leeds, Leeds LS29JT (United Kingdom)] [Department of Physics and Astronomy, University of Leeds, Leeds LS29JT (United Kingdom); Robertson, J.; Milne, W.I. [Engineering Department, Cambridge CB21PZ (United Kingdom)] [Engineering Department, Cambridge CB21PZ (United Kingdom)

1997-04-01

342

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

NASA Astrophysics Data System (ADS)

Toward the design of large-scale electronic circuits that are entirely spintronics-driven, organic semiconductors have been identified as a promising medium to transport information using the electron spin. This requires a ferromagnetic metal-organic interface that is highly spin-polarized at and beyond room temperature, but this key building block is still lacking. We show how the interface between Co and phthalocyanine molecules constitutes a promising candidate. In fact, spin-polarized direct and inverse photoemission experiments reveal a high degree of spin polarization at room temperature at this interface.

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.

2014-08-01

343

Direct velocity observations of volume flux between Iceland and the Shetland Islands  

NASA Astrophysics Data System (ADS)

Atlantic Waters flowing northward into the Nordic Seas are important for their role as an early indicator of changes to deepwater formation. As such, this requires a fundamental understanding of the pathways and volume fluxes through the primary passageways from the Atlantic into the Nordic Seas. A mean annual volume transport of 6.1 ± 0.3 Sv was observed flowing in above the ?t = 27.8 isopycnal (a proxy for the lower limit of Atlantic Water depth), through the Faroe Shetland Channel (FSC) and over the Iceland Faroes Ridge (IFR) from March 2008 to June 2012, using repeat velocity sections obtained from a vessel mounted Acoustic Doppler Current Profiler (ADCP). A new vessel route has expanded the spatial coverage of FSC observations and reveals a difference in average inflow transport, which most likely results from an interannual variation in the total transport through the FSC, which in turn is tied to a weakening of the southerly flow over the western slope of the channel. This interannual variability has increased the mean transport through the FSC from 0.9 Sv observed over the first 2 years of this program by Rossby and Flagg (2012) to a 4.5 year mean of 1.7 ± 0.2 Sv, which emphasizes the importance of knowing the flow along the Faroese shelf. Interannual fluctuations in transport observed over the IFR are related to the width of the inflow over the Faroese half of the ridge.

Childers, Katelin H.; Flagg, Charles N.; Rossby, Thomas

2014-09-01

344

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

E-print Network

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

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

2015-01-01

345

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

346

Using Numerical Modeling and Direct Observation to Investigate Hypoxia in a Shallow Wind-Driven Bay  

Microsoft Academic Search

Corpus Christi (CC) Bay, Texas, USA is a shallow (average depth around 3 m) wind-driven bay that is subjected to diurnal wind variation. However, our observations suggests that this bay becomes stratified during the summer time and hypoxic (< 2 mg\\/l dissolved oxygen [DO]) condition develops in the southeast part of it, near the Laguna Madre and at the mouth

Mohammad Shahidul Islam; James S. Bonner

2006-01-01

347

Direct Observation of a Transition of a Surface Plasmon Resonance from a Photonic Crystal Effect  

E-print Network

and switching of SPs. Recently, SP-enhanced terahertz transmission in highly doped semiconductor gratings terahertz transmission. The resonance profiles of the SP modes are well described by the Fano model is observed in a semiconductor array of subwavelength holes by optical pump-terahertz probe measurements

348

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

Microsoft Academic Search

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

C. J. Chapman; A. L. Rice

1971-01-01

349

Assessing Parenting Practices through Parent-Report and Direct Observation during Parent-Training  

ERIC Educational Resources Information Center

The specific parenting domains measured by the Alabama Parenting Questionnaire (APQ) make it particularly relevant to interventions concerned with the modification of parenting practices. This study assessed the validity and clinical utility of parent reports on the APQ using observational data of parents and children (N=56, aged 4-8 years)…

Hawes, David J.; Dadds, Mark R.

2006-01-01

350

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

Microsoft Academic Search

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

Worapan Kusakunniran; Hongdong Li; Jian Zhang

2009-01-01

351

Sporadic-E observations during LoVHF transionospheric direction finder measurements  

NASA Astrophysics Data System (ADS)

A year long experimental program was conducted to measure refractive bending or how much the signal deviates from true line of sight, at low VHF (LoVHF) frequencies (29.5 MHz), and to determine whether this deviation or error could be predicted using large-scale ionospheric models such as the Ionospheric Conductivity and Electron Density (ICED) program. An experiment to directly measure the angle of arrival of a 29.5 MHz signal from an orbiting satellite was successfully completed. The satellite was in a circular orbit at an altitude of 1000 km. It was shown that refractive errors can be directly related to the electron density along the measurement slant range. The introduction of irregular patches of electron density occurring during sporadic-E events produced both horizontal and vertical gradients introducing large errors in both azimuth and elevation measurements. Nineteen test periods in May, June, July, and Aug. 1989 were affected by mid-latitude sporadic-E with the daytime E-region critical frequencies (foE's) reaching 13 MHz in one case. This paper will present examples of these effects.

Rose, Robert B.

352

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

NASA Astrophysics Data System (ADS)

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

Lusted, Roderick M.

1994-05-01

353

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

354

Absorption Measure Distribution of the Outflow in IRAS 13349+2438: Direct Observation of Thermal Instability?  

E-print Network

We analyze the Chandra X-ray spectrum obtained with the HETGS grating spectrometer of IRAS 13349+2438, which has one of the richest absorption spectra of a quasar outflow. Absorption from almost all charge states of Fe is detected. This allows for a detailed reconstruction of the absorption measure distribution (AMD), which we define as the continuous distribution of column density as a function of ionization parameter. We find a double peaked AMD for IRAS 13349+2438 with a total (ionized) column density of N_H = (1.2 +- 0.3)* 10^{22} cm^-2} assuming solar iron abundance. For comparison, we perform a similar analysis on the well studied HETGS spectrum of NGC 3783. Both sources feature a deep minimum in column density consistent with no absorption from gas at temperatures of 4.5 thermal instability in this temperature regime.

Holczer, T; Kaspi, S; Holczer, Tomer; Behar, Ehud; Kaspi, Shai

2007-01-01

355

Absorption Measure Distribution of the Outflow in IRAS 13349+2438: Direct Observation of Thermal Instability?  

E-print Network

We analyze the Chandra X-ray spectrum obtained with the HETGS grating spectrometer of IRAS 13349+2438, which has one of the richest absorption spectra of a quasar outflow. Absorption from almost all charge states of Fe is detected. This allows for a detailed reconstruction of the absorption measure distribution (AMD), which we define as the continuous distribution of column density as a function of ionization parameter. We find a double peaked AMD for IRAS 13349+2438 with a total (ionized) column density of N_H = (1.2 +- 0.3)* 10^{22} cm^-2} assuming solar iron abundance. For comparison, we perform a similar analysis on the well studied HETGS spectrum of NGC 3783. Both sources feature a deep minimum in column density consistent with no absorption from gas at temperatures of 4.5 thermal instability in this temperature regime.

Tomer Holczer; Ehud Behar; Shai Kaspi

2007-03-14

356

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. Zoë; Langan, Paul; Kovalevsky, Andrey Y.

2012-01-01

357

Observation of directly interacting coherent two-level systems in an amorphous material  

NASA Astrophysics Data System (ADS)

Parasitic two-level tunnelling systems originating from structural material defects affect the functionality of various microfabricated devices by acting as a source of noise. In particular, superconducting quantum bits may be sensitive to even single defects when these reside in the tunnel barrier of the qubit’s Josephson junctions, and this can be exploited to observe and manipulate the quantum states of individual tunnelling systems. Here, we detect and fully characterize a system of two strongly interacting defects using a novel technique for high-resolution spectroscopy. Mutual defect coupling has been conjectured to explain various anomalies of glasses, and was recently suggested as the origin of low-frequency noise in superconducting devices. Our study provides conclusive evidence of defect interactions with full access to the individual constituents, demonstrating the potential of superconducting qubits for studying material defects. All our observations are consistent with the assumption that defects are generated by atomic tunnelling.

Lisenfeld, Jürgen; Grabovskij, Grigorij J.; Müller, Clemens; Cole, Jared H.; Weiss, Georg; Ustinov, Alexey V.

2015-02-01

358

Observation of dust torus with poloidal rotation in direct current glow discharge plasma  

NASA Astrophysics Data System (ADS)

Observation of dust cloud rotation in parallel-plate DC glow discharge plasma is reported here. The experiments are carried out at high pressures (˜130 Pa) with a metallic ring placed on the lower electrode (cathode). The dust cloud rotates poloidally in the vertical plane near the cathode surface. This structure is continuous toroidally. Absence of magnetic field rules out the possibility of E × B induced ion flow as the cause of dust rotation. The dust rotational structures exist even with water cooled cathode. Therefore, temperature gradient driven mechanisms, such as thermophoretic force, thermal creep flow, and free convection cannot be causing the observed dust rotation. Langmuir probe measurement reveals the existence of a sharp density gradient near the location of the rotating dust cloud. The gradient in the density, giving rise to a gradient in the ion drag force, has been identified as the principal cause behind the rotation of dust particles.

Kaur, Manjit; Bose, Sayak; Chattopadhyay, P. K.; Sharma, Devendra; Ghosh, J.; Saxena, Y. C.

2015-03-01

359

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

PubMed Central

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

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

2014-01-01

360

Direct observation of thermionic emission pattern of hemispherical single-crystal LaB6  

NASA Astrophysics Data System (ADS)

Thermionic emission pattern from a hemispherical LaB6 cathode of <110> orientation was made using an experimental setup similar to Martin's experiment. The emission pattern from a clean surface has clearly indicated that the bright region consists of (100) spot surrounded by four (210) spots. This suggests that the bright spots (except for the center spot in the cross-over images observed for <100>, <110>, and <111> LaB6 cathodes correspond to (210) spots as deduced by Oshima et al. Emission patterns at different vacuum conditions are also observed to find that a specific emission pattern appears with good reproducibility corresponding to the change of vacuum condition, leading to existence of enhanced thermionic emission.

Shimizu, R.; Onoda, H.; Hagiwara, H.; Ishii, S.

1981-10-01

361

Observation of directly interacting coherent two-level systems in an amorphous material  

PubMed Central

Parasitic two-level tunnelling systems originating from structural material defects affect the functionality of various microfabricated devices by acting as a source of noise. In particular, superconducting quantum bits may be sensitive to even single defects when these reside in the tunnel barrier of the qubit’s Josephson junctions, and this can be exploited to observe and manipulate the quantum states of individual tunnelling systems. Here, we detect and fully characterize a system of two strongly interacting defects using a novel technique for high-resolution spectroscopy. Mutual defect coupling has been conjectured to explain various anomalies of glasses, and was recently suggested as the origin of low-frequency noise in superconducting devices. Our study provides conclusive evidence of defect interactions with full access to the individual constituents, demonstrating the potential of superconducting qubits for studying material defects. All our observations are consistent with the assumption that defects are generated by atomic tunnelling. PMID:25652611

Lisenfeld, Jürgen; Grabovskij, Grigorij J.; Müller, Clemens; Cole, Jared H.; Weiss, Georg; Ustinov, Alexey V.

2015-01-01

362

Representativeness of direct observations selected using a work-sampling equation.  

PubMed

Deciding on appropriate sampling to obtain representative samples of behavior is important but not straightforward, because the relative duration of the target behavior may affect its observation in a given sampling interval. Work-sampling methods, which offer a way to adjust the frequency of sampling according to a priori or ongoing estimates of the behavior to achieve a preselected level of representativeness, may provide a solution. Full-week observations of 7 behaviors were conducted for 3 students with autism spectrum disorder and intellectual disabilities. Work-sampling methods were used to select momentary time samples from the full time-of-interest, which produced representative samples. However, work sampling required impractically high numbers of time samples to obtain representative samples. More practical momentary time samples produced less representative samples, particularly for low-duration behaviors. The utility and limits of work-sampling methods for applied behavior analysis are discussed. PMID:25754895

Sharp, Rebecca A; Mudford, Oliver C; Elliffe, Douglas

2015-03-01

363

Direct Observation of Stretched-Exponential Relaxation in Low-Temperature Lennard-Jones Systems Using the Cage Correlation Function  

NASA Astrophysics Data System (ADS)

We report on the direct observation of stretched exponential relaxation in low-temperature monatomic Lennard-Jones systems which were cooled slowly from the liquid phase to form crystals with a large number of defects. We use the cage correlation function [E. Rabani, J. D. Gezelter, and B. J. Berne, J. Chem. Phys. 107, 6867 (1997)] which measures changes in atomic surroundings to observe the stretched exponential relaxations. We obtain a distribution of hopping rates assuming that the origin of the Kohlrausch-Williams-Watts law is from static disorder in the distribution of barrier heights.

Rabani, Eran; Gezelter, J. Daniel; Berne, B. J.

1999-05-01

364

Direct observation of copper-induced metalation of 5,15-diphenylporphyrin on Au(111) by scanning tunneling microscopy  

NASA Astrophysics Data System (ADS)

In-situ metalation process of porphyrin molecules has been investigated by introducing guest copper atoms into porphyrins on the gold substrate in various ways. Scanning tunneling microscopy observations unambiguously demonstrate that the copper atoms aggregate to form islands directly on the gold surface at room temperature regardless of whether this gold surface is covered by the molecular layer or not. Under thermal activation of 363 K, these introduced copper atoms at the gold surface can be incorporated into the macrocycles of the molecules. Based on such experimental observations, a pathway for copper induced metalation is proposed: a copper atom prefers to enter the porphyrin macrocycles from the bottom of the molecule.

Xiang, Feifei; Li, Chao; Wang, Zhongping; Liu, Xiaoqing; Jiang, Danfeng; Leng, Xinli; Ling, Jie; Wang, Li

2015-03-01

365

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

366

Direct observation of individual RecA filaments assembling on single DNA molecules  

E-print Network

is performed using the fluorescent DNA-binding dye YOYO-1. The trapped bead­ YOYO-1­DNA complex is then moved (panels 1 and 2) shows a l DNA molecule in the observation channel before and after dissociation of YOYO-1.9 Optical trap Biotinylated DNA Streptavidin-coated polystyrene bead YOYO-1 321 d No NaCl No NaCl 66 mM Na

Kowalczykowski, Stephen C.

367

Direct observation of the birth of a nanocrystalline nucleus in an amorphous matrix  

SciTech Connect

Nucleation of crystals within an amorphous phase can be induced using electron beam irradiation in an electron microscope. In contrast to generally believed two-step phase transformation involving nucleation and growth, we observe a three-step transformation: a two-step nucleation stage followed by the growth process. The two steps in the nucleation stage are: the formation of a basic crystalline skeleton followed by the diffusion of excess defects to the periphery of the crystalline skeleton.

Rauf, Ijaz A. [Eminent Tech Corporation, 46 Casabel Drive, Maple, Ontario L6A 3L7 (Canada)

2008-10-06

368

Direct Observation to Chemokine Receptor 5 on T-lymphocyte Cell Surface Using Fluorescent Metal Nanoprobes  

PubMed Central

Chemokine receptor 5 (CCR5) is a cell surface protein required for HIV-1 infection. It is important to detect the amount and observe the spatial distribution of the CCR5 receptors on the cell surfaces. In this report, we describes the metal nanoparticles which were specially designed as molecular fluorescent probes for imaging of CCR5 receptors on the T-lymphocytic PM1 cell surfaces. These CCR5 monoclonal antibodies (mAbs) metal complexes were prepared by labeling mAbs with Alexa Fluor 680 followed by covalent binding the labeled mAbs on the 20 nm silver nanoparticles. Compared with the labeled mAbs without metal, the mAb-metal complexes were found to display enhanced emission intensity and shortened lifetime due to interactions between fluorophores and metal. The mAb-metal complexes were incubated with the PM1 cell lines. The confocal fluorescent intensity and lifetime cell images were recorded on single cells. It was observed that the mAb-metal complexes could be clearly distinguished from the cellular autofluorescence. By analyzing a pool of cell images, we observed that most CCR5 receptors appeared as clusters on the cell surfaces. The fluorophore-metal complexes developed in this report are generally useful for detection of cell surface receptors and provide a new class of probe to study the interaction between the CCR5 receptors with viral gp120 during HIV infections. PMID:20705055

Zhang, Jian; Fu, Yi; Li, Ge; Nowaczyk, Kazimierz; Zhao, Richard Y.; Lakowicz, Joseph R.

2010-01-01

369

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

370

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

SciTech Connect

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

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

2006-09-15

371

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

372

Galactic HI on the 50-AU scale in the direction of three extra-galactic sources observed with MERLIN  

E-print Network

We present MERLIN observations of Galactic 21-cm HI absorption at an angular resolution of c. 0.1-0.2 arcsec and a velocity resolution of 0.5 km/s, in the direction of three moderately low latitude (-8< b <-12 deg) extragalactic radio sources, 3C111, 3C123 and 3C161, all of which are heavily reddened. HI absorption is observed against resolved background emission sources up to c. 2 arcsec in extent and we distinguish details of the opacity distribution within 1-1.5 arcsec regions towards 3C~123 and 3C~161. This study is the second MERLIN investigation of small scale structure in interstellar HI (earlier work probed Galactic HI in the directions of the compact sources 3C138 and 3C147). The 0.1-arcsec scale is intermediate between HI absorption studies made with other fixed element interferometers with resolution of 1 to 10 arcsec and VLBI studies with resolutions of 10-20 milli-arcsec. At a scale of 1 arcsec (about 500 AU), prominent changes in Galactic HI opacity in excess of 1-1.5 are determined in the direction of 3C161 with a signal-to-noise ratio of at least 10 sigma. Possible fluctuations in the HI opacity at the level of about 1 are detected at the 2.5-3 sigma level in the direction of 3C123.

W. M. Goss; A. M. S. Richards; T. W. B. Muxlow; P. Thomasson

2008-04-05

373

Direct observation of nanoparticle superlattice formation by using liquid cell transmission electron microscopy.  

PubMed

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. PMID:22360715

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

2012-03-27

374

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

375

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

SciTech Connect

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

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

2014-04-07

376

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

377

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

378

High-temperature corrosion observed in austenitic coils and tubes in a direct reduction process  

SciTech Connect

The subject of this study is related to the performance of austenitic steel coils and tubes, in a range of temperatures between 425 and 870 C for the transport of reducing gas, in an installation involving the direct reduction of iron-ore by reforming natural gas. Evidence is presented that metal dusting is not the only unique high-temperature corrosion mechanism that caused catastrophic failures of austenitic 304 (UNS S30400) coils and HK-40 (UNS J94204) tubes. Sensitization as well as stress corrosion cracking occurred in 304 stainless steel coils and metal dusting took place in HK-40 tubes, a high resistance alloy. The role of continuous injection of H{sub 2}S into the process is suggested to avoid the high resistance metal dusting corrosion mechanism found in this kind of installation.

Campillo, B.; Gonzalez, C.; Hernandez-Duque, G.; Juarez-Islas, J.A.

2000-02-01

379

Direct Observation of Multiferroic Vortex Domains in YMnO3  

PubMed Central

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

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

2013-01-01

380

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

PubMed Central

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

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

2006-01-01

381

The propagation of auroral hiss observed on the ground as deduced from direction-finding measurements  

NASA Astrophysics Data System (ADS)

The propagation characteristics of ground-based auroral hiss in the magnetosphere and ionosphere are studied based on direction-finding results of auroral VLF hiss at Syowa, an extensive ray tracing analysis, and an estimation of transmission loss in the simulated auroral ionosphere. The results indicate that impulsive hiss emissions generated in a wide range of high to low altitudes by the beam amplification are trapped in irregularities of decreased electron density outside the auroral arc at lower altitudes. After emerging from a duct exit at altitudes of 3000-5000 km, continuous hiss emissions are propagated in a nonducted mode down to the ionosphere at different latitudes and are transmitted to the ground.

Tanaka, Yoshihito; Nishino, Masanori

1988-03-01

382

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

SciTech Connect

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

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

2014-06-30

383

First direct observation of FEL (free-electron laser) lasing from. lambda. = 20 to 45. mu. m  

SciTech Connect

In recent experiments at Los Alamos, we directly observed for the first time free-electron laser (FEL) fundamental wavelengths from 20 to 45{mu}m. Our 1988 facility's demonstrated wavelength span now extends from 9 to 45{mu}m. Upgrades are in progress to increase this span. This wavelength region uniquely complements existing FEL applications facilities. 5 refs., 6 figs., 1 tab.

Lumpkin, A.H.; Feldman, D.W.; Sollid, J.E.; Warren, R.W.; Stein, W.E.; Johnson, W.J.; Watson, J.M.; Newnam, B.E.; Goldstein, J.C.

1989-01-01

384

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

E-print Network

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

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

2011-01-12

385

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

386

Direct observation of depth profile of magnetic moment by magnetic circular dichroism  

NASA Astrophysics Data System (ADS)

The magnetic properties at the interface between Fe and Cr wedge layers are investigated with a new depth-resolved soft x-ray photoemission spectroscopy (SXPS)[1], combined with magnetic circular dichroism (MCD). The layers of Fe (10 A)/ Cr (50 A wedge- shaped) are grown on a periodic multilayer (B 4 C(22.5A)/W(17.1 A)) _40, which provides the strong standing wave effects of 40 The unique angular dependence of photoelectron intensity of Fe and Cr has been observed at each different Cr wedge thickness and show excellent agreement with the theoretical calculation. To maximize the enhancement and contrast of standing wave effect inside of sample, the sample position is tuned to the Bragg angle position, at which the MCD measurement with SXPS along the different thickness of Cr wedge layer provides the depth profile of the magnetic moment of Fe and Cr. A strong antiparallel coupling across the interface of Cr magnetic moment is clearly resolved while the apparent reduction of Fe magnetic moment is observed near the interface. This observation is consistent with the other works on the same system [2] and even describes how the magnetic moment behaves inside of the sample from the top surface to the interface in one single sample preparation. In this experiment, a new depth-resolved SXPS has been successfully implemented to magnetic multilayer system and prove to be powerful technique to study the buried interface of magnetic system, as proposed by our former work [1]. [1] S.-H. Yang, B. S. Mun, A.W. Kay, S.-K. Kim, J. B. Kortright , J.H. Underwood, Z. Hussain, C. S. Fadley, Surf. Sci. 461 L557-L564 (2000) [2] G. Panaccione, F. Sirotti, E. Narducci, and G. Rossi, Phys. Rev. B 55, 389 (1997)

Mun, Bongjin Simon; Yang, See-Hun; Mannella, Norman; Kay, Alex W.; Kim, Sang-Koog; Kortright, Jeffrey B.; Underwood, Jim H.; Hussain, Zahid; Fadley, Charles S.

2001-03-01

387

Direct observation of field-free alignment of asymmetric molecules in excited states  

NASA Astrophysics Data System (ADS)

The excited state dynamics of o-dichlorobenzene has been studied by femtosecond time-resolved photoelectron imaging. The lifetime of the first excited state S1 of o-dichlorobenzene was determined to be 482 ± 10 ps. Field-free nonadiabatic alignment of the o-dichlorobenzene on the first excited state S1 (with an asymmetry parameter k = 0.153) by a femtosecond laser pulse was observed via time-resolved photoelectron angular distributions. Rotational wave packet revivals on the S1 state of the typical asymmetric molecule o-dichlorobenzene at 296 ps has been measured.

Qin, Chaochao; Liu, Yuzhu; Zhang, Song; Wang, Yanmei; Tang, Ying; Zhang, Bing

2011-03-01

388

Direct observation of localized high current densities in GaN films  

NASA Astrophysics Data System (ADS)

Local high current densities in areas around dislocations with a screw component might be responsible for the observed high leakage currents in GaN-based electronic devices. Using ballistic electron emission microscopy, threading dislocations with a screw component are found to be accompanied by high current densities and low effective Schottky barrier heights. The electronic states responsible for this extremely nonuniform behavior of GaN films are metastable trap states. The experimental results show that acceptor- and donor-like charge traps coexist in the vicinity of dislocations with a screw component.

Brazel, E. G.; Chin, M. A.; Narayanamurti, V.

1999-04-01

389

Artemisinin combination therapy can result in clinical failure if oral therapy is not directly observed  

PubMed Central

Intravenous artesunate therapy is the first-line therapy for severe malaria, and is highly efficacious when used in combination with an oral partner drug such as doxycycline or atovaquone-proguanil. However, treatment failure occurs routinely with artesunate monotherapy due to the very short half-life of this drug. In North America, experience with artesunate is limited. With the pressure to discharge patients early, administration of the essential oral partner drug is often left to the discretion of the patient. Thus, treatment failure may be commonplace if nonadherence is a factor, as was observed in the case described in the present report. PMID:24489564

Chan, Wilson W; Virmani, Divya; Pillai, Dylan R

2013-01-01

390

Direct observation of tiers in the energy landscape of a chromoprotein: A single-molecule study  

PubMed Central

Single-molecule spectroscopic techniques were applied to individual pigments embedded in a chromoprotein. A sensitive tool to monitor structural fluctuations of the protein backbone in the local environment of the chromophore is provided by recording the changes of the spectral positions of the pigment absorptions as a function of time. The data provide information about the organization of the energy landscape of the protein in tiers that can be characterized by an average barrier height. Additionally, a correlation between the average barrier height within a distinct tier and the time scale of the structural fluctuations is observed. PMID:14671325

Hofmann, Clemens; Aartsma, Thijs J.; Michel, Hartmut; Köhler, Jürgen

2003-01-01

391

How to directly observe Landau levels in driven-dissipative strained honeycomb lattices  

E-print Network

We study the driven-dissipative steady-state of a coherently-driven Bose field in a honeycomb lattice geometry. In the presence of a suitable spatial modulation of the hopping amplitudes, a valley-dependent artificial magnetic field appears and the low-energy eigenmodes have the form of relativistic Landau levels. We show how the main properties of the Landau levels can be extracted by observing the peaks in the absorption spectrum of the system and the corresponding spatial intensity distribution. Finally, quantitative predictions for realistic lattices based on photonic or microwave technologies are discussed.

Salerno, Grazia; Price, Hannah M; Carusotto, Iacopo

2015-01-01

392

Direct observation of fine-scale energy banding in echo-enabled harmonic generation  

NASA Astrophysics Data System (ADS)

We describe the experimental observation of highly nonlinear energy striations generated by two lasers in a relativistic electron beam in an echo-enabled harmonic generation (EEHG) setup. The rich energy banding structure results from strong dispersion of the sinusoidally modulated beam, and measurements of the banding spectrum enable benchmarking, optimization, and characterization of the concomitant EEHG process. Results are found to be in good agreement with theory, and suggest that the presented technique can facilitate the practical implementation of EEHG to generate intense, fully coherent light in future advanced accelerator-based light sources.

Hemsing, E.; Xiang, D.; Dunning, M.; Weathersby, S.; Hast, C.; Raubenheimer, T.

2014-01-01

393

Singlet fission in rubrene single crystal: direct observation by femtosecond pump-probe spectroscopy.  

PubMed

The excited state dynamics of rubrene in solution and in the single crystal were studied by femtosecond pump-probe spectroscopy under various excitation conditions. Singlet fission was demonstrated to play a predominant role in the excited state relaxation of the rubrene crystal in contrast to rubrene in solution. Upon 500 nm excitation, triplet excitons form on the picosecond time scale via fission from the lowest excited singlet state. Upon 250 nm excitation, fission from upper excited singlet states is observed within 200 fs. PMID:22510785

Ma, Lin; Zhang, Keke; Kloc, Christian; Sun, Handong; Michel-Beyerle, Maria E; Gurzadyan, Gagik G

2012-06-21

394

Direct observation of tiers in the energy landscape of a chromoprotein: a single-molecule study.  

PubMed

Single-molecule spectroscopic techniques were applied to individual pigments embedded in a chromoprotein. A sensitive tool to monitor structural fluctuations of the protein backbone in the local environment of the chromophore is provided by recording the changes of the spectral positions of the pigment absorptions as a function of time. The data provide information about the organization of the energy landscape of the protein in tiers that can be characterized by an average barrier height. Additionally, a correlation between the average barrier height within a distinct tier and the time scale of the structural fluctuations is observed. PMID:14671325

Hofmann, Clemens; Aartsma, Thijs J; Michel, Hartmut; Köhler, Jürgen

2003-12-23

395

Direct observation of ion transfer in contact charging between a metal and a polymer  

NASA Astrophysics Data System (ADS)

Triboelectric charging between metals and insulators is usually thought to involve electron transfer. Doping some polymers with a small amount of salt can significantly change their charging properties, even reversing the sign to which they charge upon contact with a given metal. We show by means of secondary-ion mass spectrometry that ions of the salt are transferred across the interface in contacts between a doped polymer and a metal. Specifically, we observe a transfer of bromine ions when polystyrene doped with a small amount of the salt cetylpyridinium bromide is contacted to an indium surface.

Mizes, H. A.; Conwell, E. M.; Salamida, D. P.

1990-04-01

396

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

397

Observation of the exotic nucleus {sup 145}Tm via its direct proton decay  

SciTech Connect

Proton emission from {sup 145}Tm was observed for the first time via the {sup 92}Mo({sup 58}Ni,p4n) reaction, using the Holifield Radioactive Ion Beam Facility Recoil Mass Spectrometer in conjunction with a double-sided Si strip detector at the focal plane. The measured energy of the emitted proton is 1.728(10) MeV and its half-life is 3.5(10) {mu}s, the shortest ever observed for ground-state proton radioactivity. When compared to the calculated WKB half-life for an l=5 transfer, the spectroscopic factor is 0.51(16), which is consistent with the value of 0.64 calculated via the BCS approximation for a spherical nucleus. Also, the half-life of {sup 113}Cs was determined with a greater precision than previously available to be 16.7(7) {mu}sec. {copyright} {ital 1998} {ital The American Physical Society}

Batchelder, J.C. [UNIRIB, Oak Ridge Associated Universities, Oak Ridge, Tennessee 37831 (United States)] [UNIRIB, Oak Ridge Associated Universities, Oak Ridge, Tennessee 37831 (United States); Bingham, C.R.; Rykaczewski, K.; Toth, K.S.; Gross, C.J.; McConnell, J.W.; Baktash, C.; Mas, J.F.; Milner, W.T.; Paul, S.D.; Shapira, D.; Yu, C.H. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)] [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Bingham, C.R.; Xu, X.J. [University of Tennessee, Knoxville, Tennessee 37996 (United States)] [University of Tennessee, Knoxville, Tennessee 37996 (United States); Rykaczewski, K. [Warsaw University, 00681 Warsaw, Hoza69 (Poland)] [Warsaw University, 00681 Warsaw, Hoza69 (Poland); Davinson, T.; McKenzie, J.A.; Woods, P.J. [University of Edinburgh, EdinburghEH9 3JZ (United Kingdom)] [University of Edinburgh, EdinburghEH9 3JZ (United Kingdom); Ginter, T.N.; Hamilton, J.H. [Vanderbilt University, Nashville, Tennessee 37235 (United States)] [Vanderbilt University, Nashville, Tennessee 37235 (United States); Gross, C.J. [Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee 37831 (United States)] [Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee 37831 (United States); Zganjar, E.F. [Louisiana State University, Baton Rouge, Louisiana 70803 (United States)] [Louisiana State University, Baton Rouge, Louisiana 70803 (United States); Walters, W.B. [University of Maryland, College Park, Maryland 20742 (United States)] [University of Maryland, College Park, Maryland 20742 (United States); Greene, J. [Argonne National Laboratory, Argonne, Illinois 60439 (United States)] [Argonne National Laboratory, Argonne, Illinois 60439 (United States); Xu, X.J. [Institute of Modern Physics, Lanzhou, 730000 (China)] [Institute of Modern Physics, Lanzhou, 730000 (China); Xu, X.J. [Joint Institute for Heavy Ion Research, Oak Ridge, Tennessee 37831 (United States)] [Joint Institute for Heavy Ion Research, Oak Ridge, Tennessee 37831 (United States)

1998-03-01

398

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

399

Direct observation of a borane-silane complex involved in frustrated Lewis-pair-mediated hydrosilylations.  

PubMed

Perfluorarylborane Lewis acids catalyse the addition of silicon-hydrogen bonds across C=C, C=N and C=O double bonds. This 'metal-free' hydrosilylation has been proposed to occur via borane activation of the silane Si-H bond, rather than through classical Lewis acid/base adducts with the substrate. However, the key borane/silane adduct had not been observed experimentally. Here it is shown that the strongly Lewis acidic, antiaromatic 1,2,3-tris(pentafluorophenyl)-4,5,6,7-tetrafluoro-1-boraindene forms an observable, isolable adduct with triethylsilane. The equilibrium for adduct formation was studied quantitatively through variable-temperature NMR spectroscopic investigations. The interaction of the silane with the borane occurs through the Si-H bond, as evidenced by trends in the Si-H coupling constant and the infrared stretching frequency of the Si-H bond, as well as by X-ray crystallography and theoretical calculations. The adduct's reactivity with nucleophiles demonstrates conclusively the role of this species in metal-free 'frustrated-Lewis-pair' hydrosilylation reactions. PMID:25343603

Houghton, Adrian Y; Hurmalainen, Juha; Mansikkamäki, Akseli; Piers, Warren E; Tuononen, Heikki M

2014-11-01

400

The direct observation of alkali vapor species in biomass combustion and gasification  

SciTech Connect

This report summarizes new data from screening various feedstocks for alkali vapor release under combustion conditions. The successful development of a laboratory flow reactor and molecular beam, mass spectrometer interface is detailed. Its application to several herbaceous and woody feedstocks, as well as a fast-pyrolysis oil, under 800 and 1,100{degrees}C batch combustion, is documented. Chlorine seems to play a large role in the facile mobilization of potassium. Included in the report is a discussion of relevant literature on the alkali problem in combustors and turbines. Highlighted are the phenomena identified in studies on coal and methods that have been applied to alkali speciation. The nature of binding of alkali in coal versus biomass is discussed, together with the implications for the ease of release. Herbaceous species and many agricultural residues appear to pose significant problems in release of alkali species to the vapor at typical combustor temperatures. These problems could be especially acute in direct combustion fired turbines, but may be ameliorated in integrated gasification combined cycles.

French, R.J.; Dayton, D.C.; Milne, T.A.

1994-01-01

401

Direct observation of multimer stabilization in the mechanical unfolding pathway of a protein undergoing oligomerization.  

PubMed

Understanding how protein oligomerization affects the stability of monomers in self-assembled structures is crucial to the development of new protein-based nanomaterials and protein cages for drug delivery. Here, we use single-molecule force spectroscopy (AFM-SMFS), protein engineering, and computer simulations to evaluate how dimerization and tetramerization affects the stability of the monomer of Streptavidin, a model homotetrameric protein. The unfolding force directly relates to the folding stability, and we find that monomer of Streptavidin is mechanically stabilized by 40% upon dimerization, and that it is stabilized an additional 24% upon tetramerization. We also find that biotin binding increases stability by another 50% as compared to the apo-tetrameric form. We used the distribution of unfolding forces to extract properties of the underlying energy landscape and found that the distance to the transition state is decreased and the barrier height is increased upon multimerization. Finally, we investigated the origin of the strengthening by ligand binding. We found that, rather than being strengthened through intramolecular contacts, it is strengthened due to the contacts provided by the biotin-binding loop that crosses the interface between the dimers. PMID:25639698

Scholl, Zackary N; Yang, Weitao; Marszalek, Piotr E

2015-02-24

402

Direct observation of cytosine flipping and covalent catalysis in a DNA methyltransferase  

PubMed Central

Methylation of the five position of cytosine in DNA plays important roles in epigenetic regulation in diverse organisms including humans. The transfer of methyl groups from the cofactor S-adenosyl-l-methionine is carried out by methyltransferase enzymes. Using the paradigm bacterial methyltransferase M.HhaI we demonstrate, in a chemically unperturbed system, the first direct real-time analysis of the key mechanistic events—the flipping of the target cytosine base and its covalent activation; these changes were followed by monitoring the hyperchromicity in the DNA and the loss of the cytosine chromophore in the target nucleotide, respectively. Combined with studies of M.HhaI variants containing redesigned tryptophan fluorophores, we find that the target base flipping and the closure of the mobile catalytic loop occur simultaneously, and the rate of this concerted motion inversely correlates with the stability of the target base pair. Subsequently, the covalent activation of the target cytosine is closely followed by but is not coincident with the methyl group transfer from the bound cofactor. These findings provide new insights into the temporal mechanism of this physiologically important reaction and pave the way to in-depth studies of other base-flipping systems. PMID:21245034

Gerasimait?, R?ta; Merkien?, Egl?; Klimašauskas, Saulius

2011-01-01

403

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

404

Direct observation of enhanced emission sites in nitrogen implanted hybrid structured ultrananocrystalline diamond films  

SciTech Connect

A hybrid-structured ultrananocrystalline diamond (h-UNCD) film, synthesized on Si-substrates by a two-step microwave plasma enhanced chemical vapour deposition (MPECVD) process, contains duplex structure with large diamond aggregates evenly dispersed in a matrix of ultra-small grains ({approx}5 nm). The two-step plasma synthesized h-UNCD films exhibit superior electron field emission (EFE) properties than the one-step MPECVD deposited UNCD films. Nitrogen-ion implantation/post-annealing processes further improve the EFE properties of these films. Current imaging tunnelling spectroscopy in scanning tunnelling spectroscopy mode directly shows increased density of emission sites in N implanted/post-annealed h-UNCD films than as-prepared one. X-ray photoelectron spectroscopy measurements show increased sp{sup 2} phase content and C-N bonding fraction in N ion implanted/post-annealed films. Transmission electron microscopic analysis reveals that the N implantation/post-annealing processes induce the formation of defects in the diamond grains, which decreases the band gap and increases the density of states within the band gap of diamond. Moreover, the formation of nanographitic phase surrounding the small diamond grains enhanced the conductivity at the diamond grain boundaries. Both of the phenomena enhance the EFE properties.

Panda, Kalpataru; Sundaravel, B.; Panigrahi, B. K. [Materials Physics Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Chen, Huang-Chin; Lin, I.-Nan [Department of Physics, Tamkang University, New-Taipei 251, Taiwan (China)

2013-02-07

405

What is the probability that direct detection experiments have observed dark matter?  

NASA Astrophysics Data System (ADS)

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.

Bozorgnia, Nassim; Schwetz, Thomas

2014-12-01

406

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

407

Direct observation of individual particle armored bubble interaction, stability, and coalescence dynamics.  

PubMed

The interactions between two individual particle-stabilized bubbles were investigated, in the absence of surfactant, using a combination of coalescence rig and high-speed video camera. This combination allows the visualization of bubble coalescence dynamics which provide information on bubble stability. Experimental data suggested that bubble stability is enhanced by both the adsorption of particles at the interface as indicated by the long induction time and the increase in damping coefficient at high surface coverage. The interaction between an armored bubble and a bare bubble (asymmetric interaction) can be destabilized through the addition of a small amount of salt, which suggested that electrostatic interactions play a significant role in bubble stability. Interestingly, the DLVO theory cannot be used to describe the bubble stability in the case of a symmetric interaction as coalescence was inhibited at 0.1 M KCl in both the absence and presence of particles at the interfaces. Furthermore, bubbles can also be destabilized by increasing the particle hydrophobicity. This behavior is due to thinner liquid films between bubbles and an increase in film drainage rate. The fraction of particles detached from the bubble surface after film rupture was found to be very similar within the range of solution ionic strength, surface coverage, and particle hydrophobicity studied. This lack of dependence implies that the kinetic energy generated by the coalescing bubbles is larger than the attachment energy of the particles and dominates the detachment process. This study illuminates the stability behavior of individual particle-stabilized bubbles and has potential impact on processes which involve their interaction. PMID:23796213

Tan, Sin-Ying; Ata, Seher; Wanless, Erica J

2013-07-18

408

Structure of the Antarctic Circumpolar Current in Drake Passage From Direct Velocity Observations  

NASA Astrophysics Data System (ADS)

The structure of the Antarctic Circumpolar Current (ACC) in the upper 1000~m of Drake Passage is examined using nearly three years of shipboard Acoustic Doppler Current Profiler (SADCP) velocity data from a 38~kHz Ocean Surveyor mounted in the hull of the Antarctic supply vessel ARSV Laurence M. Gould. The principal fronts of the ACC are clearly visible, with the Subantarctic Front (SAF) and Polar Front (PF) jets having widths of about 100~km and 150~km, respectively. Depth-mean current speeds in the SAF and PF jets are ~40~cm~s-1, while the eddy kinetic energy (EKE) has a maximum of ~700~cm2s-2 between the PF and the SAF. Horizontal-wavenumber velocity spectra peak at ~350~km. These numbers are similar to surface-layer values found by Lenn et al. (J. Mar. Res., 2007). The transport estimated from the mean section between the surface and 1030~m is ~100~Sv, or about 70% of the canonical total transport. The extended depth range available from the 38~kHz instrument allows us to investigate the depth structure of the current. The mean current is largely barotropic, while EKE and shear variance exhibit strong depth dependence. In cross-sectional averages current shear is small and nearly constant to 600~m, below which depth the current speed drops off more quickly; mean jet speeds are around 50~cm~s-1 at 46~m (the first depth bin) and 20~cm~s-1 at 1030~m. Various possibilities for a vertical structure function are explored. EKE is intensified above 600~m between the SAF and PF. Shear variance is strongest in the surface layer. Vertical-wavenumber spectra of currents and current shear reveal negligible rotation. Through-passage currents have more energy at the lowest vertical wavenumbers (wavelengths of ~1000~m), while at scales smaller than ~100~m, energy in across-passage currents is greater.

Firing, Y. L.; Chereskin, T. K.

2008-12-01

409

Direct Observation of Differences of Carotenoid Polyene Chain cis/trans Isomers Resulting from Structural Topology  

PubMed Central

In the present paper, trapped ion mobility spectrometry (TIMS) and theoretical calculations have been used to study carotenoid geometrical motifs generated by photoisomerization from the all-trans geometry. Multiple geometric isomers of the carotenoids lutein and zeaxanthin were separated using TIMS (R > 110) for [M]+, [M + H]+, and [M – 18]+ molecular species. Comparison of observed cross sections with those obtained from molecular dynamics calculations showed that the number of cis double bonds and s-cis single bonds in the polyene chain determine the topology space of the carotenoid. The intensities of IMS signals are correlated with the relative stability of these geometric isomers.1,2 The most stable isomer is the all-trans geometry regardless of the ionization state ([M – 18]+, [M]+, and [M + H]+), and structural stability decreases with the increasing number of cis and/or s-cis bonds in the polyene chain. PMID:24428664

2015-01-01

410

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

411

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

412

Direct observation of ON and OFF pathways in the Drosophila visual system.  

PubMed

Visual motion perception is critical to many animal behaviors, and flies have emerged as a powerful model system for exploring this fundamental neural computation. Although numerous studies have suggested that fly motion vision is governed by a simple neural circuit [1-3], the implementation of this circuit has remained mysterious for decades. Connectomics and neurogenetics have produced a surge in recent progress, and several studies have shown selectivity for light increments (ON) or decrements (OFF) in key elements associated with this circuit [4-7]. However, related studies have reached disparate conclusions about where this selectivity emerges and whether it plays a major role in motion vision [8-13]. To address these questions, we examined activity in the neuropil thought to be responsible for visual motion detection, the medulla, of Drosophila melanogaster in response to a range of visual stimuli using two-photon calcium imaging. We confirmed that the input neurons of the medulla, the LMCs, are not responsible for light-on and light-off selectivity. We then examined the pan-neural response of medulla neurons and found prominent selectivity for light-on and light-off in layers of the medulla associated with two anatomically derived pathways (L1/L2 associated) [14, 15]. We next examined the activity of prominent interneurons within each pathway (Mi1 and Tm1) and found that these neurons have corresponding selectivity for light-on or light-off. These results provide direct evidence that motion is computed in parallel light-on and light-off pathways, demonstrate that this selectivity emerges in neurons immediately downstream of the LMCs, and specify where crucial elements of motion computation occur. PMID:24704075

Strother, James A; Nern, Aljoscha; Reiser, Michael B

2014-05-01

413

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

414

Direct observation of grafting interlayer phosphate in Mg/Al layered double hydroxides  

SciTech Connect

The grafting of interlayer phosphate in synthetic Mg/Al layered double hydroxides with interlayer hydrogen phosphate (LDH-HPO{sub 4}) has been studied by XRD, TG/DTA, FT-IR, XPS and XANES. The basal spacing of crystalline LDH-HPO{sub 4} decreases in two stages with increasing temperature, from 1.06 nm to 0.82 nm at 333 K in the first transition, and to 0.722 nm at 453 K in the second. The first stage occurs due to the loss of interlayer water and rearrangement of the interlayer HPO{sub 4}{sup 2-}. In the second transition, the interlayer phosphate is grafted to the layer by the formation of direct bonding to metal cations in the layer, accompanied by a change in polytype of the crystalline structure. The grafted phosphate becomes immobilized and cannot be removed by anion-exchange with 1-octanesulfonate. The LDH is amorphous at 743 K but decomposes to Mg{sub 3}(PO{sub 4}){sub 2}, AlPO{sub 4}, MgO and MgAl{sub 2}O{sub 4} after heated to 1273 K. - Graphical abstract: The cross section of the synthetic Mg, Al layered double hydroxides in Phase 1, with interlayer hydrogen phosphate Phase 2, and with grafted phosphate, Phase 3. Highlights: Black-Right-Pointing-Pointer The grafting of hydrogen phosphate intercalated Mg/Al-LDH has been studied. Black-Right-Pointing-Pointer The basal spacing of crystalline LDH-HPO{sub 4} decreases in two stages with increasing temperature. Black-Right-Pointing-Pointer The first decrease is due to loss of interlayer water, the second is attributed to phosphate grafting. Black-Right-Pointing-Pointer The grafted interlayer phosphate becomes immobilized and cannot be removed by anion-exchange.

Shimamura, Akihiro [School of Chemical Sciences, University of Auckland 23 Symonds St, 1142 Auckland (New Zealand); MacDiarmid Institute for Advanced Materials and Nanotechnology (New Zealand); Kanezaki, Eiji, E-mail: kanezaki@chem.tokushima-u.ac.jp [Department of Chemical Science and Technology, Graduate School of Advanced Technology and Science, University of Tokushima, 2-1 Minamijosanjima, Tokushima 770-8506 (Japan); Jones, Mark I. [Department of Chemical and Material Engineering, University of Auckland, 20 Symonds St, 1142 Auckland (New Zealand); Metson, James B. [School of Chemical Sciences, University of Auckland 23 Symonds St, 1142 Auckland (New Zealand); MacDiarmid Institute for Advanced Materials and Nanotechnology (New Zealand)

2012-02-15

415

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

416

Direct nanoscale observations of the coupled dissolution of calcite and dolomite and the precipitation of gypsum  

PubMed Central

Summary In-situ atomic force microscopy (AFM) experiments were performed to study the overall process of dissolution of common carbonate minerals (calcite and dolomite) and precipitation of gypsum in Na2SO4 and CaSO4 solutions with pH values ranging from 2 to 6 at room temperature (23 ± 1 °C). The dissolution of the carbonate minerals took place at the (104) cleavage surfaces in sulfate-rich solutions undersaturated with respect to gypsum, by the formation of characteristic rhombohedral-shaped etch pits. Rounding of the etch pit corners was observed as solutions approached close-to-equilibrium conditions with respect to calcite. The calculated dissolution rates of calcite at pH 4.8 and 5.6 agreed with the values reported in the literature. When using solutions previously equilibrated with respect to gypsum, gypsum precipitation coupled with calcite dissolution showed short gypsum nucleation induction times. The gypsum precipitate quickly coated the calcite surface, forming arrow-like forms parallel to the crystallographic orientations of the calcite etch pits. Gypsum precipitation coupled with dolomite dissolution was slower than that of calcite, indicating the dissolution rate to be the rate-controlling step. The resulting gypsum coating partially covered the surface during the experimental duration of a few hours. PMID:25161860

Cama, Jordi; Soler, Josep Maria; Putnis, Christine V

2014-01-01

417

Some Structural Observations of Self-Assembling, Fibrillar Gels Composed of Two-Directional Bolaform Arborols  

SciTech Connect

Arborols are dumbbell shaped molecules (bolaform amphiphiles) in which a hydrophobic spacer separates two hydrophilic end groups. They are a valuable model for naturally occurring fibers, such as actin or amyloid. Applications to materials science can be envisioned. On cooling from warm aqueous or methanolic solutions, arborols spontaneously assemble into long fibers. When the solutions are above a certain concentration that depends on the hydrophilic/hydrophobic balance, this leads to thermally reversible gels stabilized by a mechanism that is poorly understood. With the help of wide angle X-ray scattering, details of the arborol fiber and gel structure were obtained on wet gels. The characteristic dimensions of the fibers vary in a sensible fashion with the molecular specifics. Solvent character appears to affect the average domain length of arborols stacked into fibers. Fluorescently labeled arborols were prepared. The label does not prevent incorporation into the fibrillar structure, rendering fibril bundles visible in wet gels. Bundles are visible in concentrated gels, but not in less concentrated sols. These results are consistent with observations of dried arborols using atomic force microscopy and with previously published freeze-fracture electron microscopy and small angle X-ray scattering experiments on dried gels.

Sun, J.

2005-01-12

418

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

419

Direct observation of ultrafast-electron-transfer reactions unravels high effectiveness of reductive DNA damage  

PubMed Central

Both water and electron-transfer reactions play important roles in chemistry, physics, biology, and the environment. Oxidative DNA damage is a well-known mechanism, whereas the relative role of reductive DNA damage is unknown. The prehydrated electron (), a novel species of electrons in water, is a fascinating species due to its fundamental importance in chemistry, biology, and the environment. is an ideal agent to observe reductive DNA damage. Here, we report both the first in situ femtosecond time-resolved laser spectroscopy measurements of ultrafast-electron-transfer (UET) reactions of with various scavengers (KNO3, isopropanol, and dimethyl sulfoxide) and the first gel electrophoresis measurements of DNA strand breaks induced by and OH• radicals co-produced by two-UV-photon photolysis of water. We strikingly found that the yield of reductive DNA strand breaks induced by each is twice the yield of oxidative DNA strand breaks induced by each OH• radical. Our results not only unravel the long-standing mystery about the relative role of radicals in inducing DNA damage under ionizing radiation, but also challenge the conventional notion that oxidative damage is the main pathway for DNA damage. The results also show the potential of femtomedicine as a new transdisciplinary frontier and the broad significance of UET reactions of in many processes in chemistry, physics, biology, and the environment. PMID:21730183

Nguyen, Jenny; Ma, Yuhan; Luo, Ting; Bristow, Robert G.; Jaffray, David A.; Lu, Qing-Bin

2011-01-01

420

Direct observations of the Antarctic circumpolar current transport on the northern flank of the Kerguelen Plateau  

NASA Astrophysics Data System (ADS)

standing meander in the Antarctic Circumpolar Current (ACC) found on the northern flank of the Kerguelen Plateau was investigated during the Southern Ocean Finestructure cruise in November-December 2008. An 18 year time series of surface geostrophic currents from satellite altimetry shows that the meander as observed during this survey is typical of the region. Hydrographic stations were occupied between 65-75°E and 43-48°S on the shelf (~200 m depth) and slope into the deep ocean to the north of Kerguelen (~4700 m), providing the most detailed survey of this region to date. Geostrophic shears are referenced to lowered acoustic Doppler current profiler velocities to give the first estimate of the total volume transport in this region, and the transport budget is closed around the survey box. The Subtropical Front, Subantarctic Front, and a northern branch of the Polar Front together have an associated transport of 174 ± 22 Sv eastward. While 174 Sv is large compared with typical Drake Passage transports, it is reconciled with other estimates of the total transport with the additional 15 Sv of the Indonesian Throughflow. Baroclinic transport referenced to the deepest common level between station pairs is 119 Sv, consistent with other estimates of the baroclinic transport in this area. At this longitude, the fronts of the ACC are exceptionally close together. We discuss the exchange of properties across the fronts.

Damerell, G. M.; Heywood, K. J.; Stevens, D. P.

2013-03-01