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1

Psychometrics of Direct Observation  

Microsoft Academic Search

Abstract.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 ob- servation are presented, the contributions to assessment practice reviewed, and a specific proposal is offered for evaluating the psychometric merit of direct obser- vation in both practitioner developed and commercial\\/research

John M. Hintze

2

Direct observation detonator operation  

NASA Astrophysics Data System (ADS)

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

Hall, Charles R.

2001-11-01

3

Direct observation of time reversal violation  

NASA Astrophysics Data System (ADS)

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

Bernabéu, J.

2013-06-01

4

Interstellar Neutral Hydrogen - Direct Observation by IBEX-LO  

NASA Astrophysics Data System (ADS)

The Interstellar Boundary Explorer has now completed two "spring pass" observations which allow us to observe incoming interstellar neutral atoms directly. We report on the time of flight mass spectrum observed by the IBEX-LO instrument, which allows us to separate the most common element visible in the interstellar wind at 1AU (Helium), and determine the properties of the undisturbed bulk Hydrogen in the very local interstellar medium.

Saul, L. A.; Wurz, P.; Moebius, E.; McComas, D. J.; Fuselier, S. A.; Petersen, L.; Moreno, D. F.

2010-12-01

5

Observe how the monsoon changes direction  

NSDL National Science Digital Library

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

Education, Terc. C.; Littell, Mcdougal

2003-01-01

6

Direct Observation of Academic Learning Time.  

ERIC Educational Resources Information Center

|Classroom variables associated with academic learning time (ALT)--instructional time, on-task behavior, and student success rate--are positively related to student achievement. Guidelines and forms are provided for teachers and supervisors to gather objective and usable information on these ALT components through direct classroom observation…

Wilson, Rich

1987-01-01

7

Switchable reporter enzymes based on mutually exclusive domain interactions allow antibody detection directly in solution  

PubMed Central

Detection of antibodies is essential for the diagnosis of many diseases including infections, allergies and autoimmune diseases. Current heterogeneous immunoassays require multiple time-consuming binding and washing steps, which limits their application in point-of-care diagnostics and high-throughput screening. Here we report switchable reporter enzymes that allow simple colorimetric detection of antibodies directly in solution. Our approach is based on the antibody-induced disruption of an intramolecular interaction between TEM1-?-lactamase and its inhibitor protein BLIP. Using the HIV1-p17 antibody as an initial target, the interaction between enzyme and inhibitor was carefully tuned to yield a reporter enzyme whose activity increased 10-fold in the presence of pM antibody concentrations. Reporter enzymes for two other antibodies (HA-tag and Dengue virus type I) were obtained by simply replacing the epitope sequences. This new sensor design represents a modular and generic approach to construct antibody reporter enzymes without the cumbersome optimization required by previous engineering strategies.

Banala, Sambashiva; Aper, Stijn J.A.; Schalk, Werner; Merkx, Maarten

2013-01-01

8

Switchable reporter enzymes based on mutually exclusive domain interactions allow antibody detection directly in solution.  

PubMed

Detection of antibodies is essential for the diagnosis of many diseases including infections, allergies, and autoimmune diseases. Current heterogeneous immunoassays require multiple time-consuming binding and washing steps, which limits their application in point-of-care diagnostics and high-throughput screening. Here, we report switchable reporter enzymes that allow simple colorimetric detection of antibodies directly in solution. Our approach is based on the antibody-induced disruption of an intramolecular interaction between TEM1 ?-lactamase and its inhibitor protein BLIP. Using the HIV1-p17 antibody as an initial target, the interaction between enzyme and inhibitor was carefully tuned to yield a reporter enzyme whose activity increased 10-fold in the presence of pM antibody concentrations. Reporter enzymes for two other antibodies (HA-tag and Dengue virus type I) were obtained by simply replacing the epitope sequences. This new sensor design represents a modular and generic approach to construct antibody reporter enzymes without the cumbersome optimization required by previous engineering strategies. PMID:23941162

Banala, Sambashiva; Aper, Stijn J A; Schalk, Werner; Merkx, Maarten

2013-08-13

9

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

Code of Federal Regulations, 2013 CFR

...Costs of leasing, acquiring, installing, operating, repairing and maintaining communication systems, including radio, microwave facilities, and computer production controls for the NPSL operations are allowable. If communication facilities...

2013-07-01

10

Direct observation limits on antimatter gravitation  

SciTech Connect

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

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

2008-06-01

11

First Direct Observation of Muon Antineutrino Disappearance  

SciTech Connect

This Letter reports the first direct observation of muon antineutrino disappearance. The MINOS experiment has taken data with an accelerator beam optimized for {bar {nu}}{sub {mu}} production, accumulating an exposure of 1.71 x 10{sup 20} protons on target. In the Far Detector, 97 charged current {bar {nu}}{sub {mu}} events are observed. The no-oscillation hypothesis predicts 156 events and is excluded at 6.3{sigma}. The best fit to oscillation yields |{Delta}{bar m}{sup 2}| = [3.36{sub -0.40}{sup +0.46}(stat){+-}0.06(syst)] x 10{sup -3} eV{sup 2}, sin{sup 2}(2{bar {Theta}}) = 0.86{sub -0.12}{sup +0.11}(stat) {+-} 0.01(syst). The MINOS {nu}{sub {mu}} and {bar {nu}}{sub {mu}} measurements are consistent at the 2.0% confidence level, assuming identical underlying oscillation parameters.

Bishai, M.; Diwan, M.V.; Jaffe, D.E.; Ling, L.; Viren, B.; Whitehead, L.

2011-07-05

12

Direct observation of beamed Raman scattering.  

PubMed

Appropriately designed surface plasmon nanostructures enable the emission patterns of surface-enhanced Raman scattering to be modified to facilitate efficient collection, an effect sometimes termed "beamed Raman scattering". Here, we demonstrate the direct and unambiguous observation of this phenomenon by separating the Raman emission pattern from the luminescent background using energy momentum spectroscopy. We observe beamed Raman scattering from two types of optical antennas: the first are Yagi-Uda optical antennas, and the second are optical dimer antennas formed above a plasmonic substrate consisting of a gold film integrated with a one-dimensional array of gold stripes. For both antenna types, the emission patterns from different Raman lines are simultaneously measured. For the second antenna type, the emission patterns show signatures stemming from the bandstructure of the plasmonic substrate. PMID:23101429

Zhu, Wenqi; Wang, Dongxing; Crozier, Kenneth B

2012-11-13

13

First Direct Observation of Muon Antineutrino Disappearance  

NASA Astrophysics Data System (ADS)

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

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

2011-07-01

14

Diffuse x-rays: directly observing dark matter?  

SciTech Connect

Several independent observations of the galactic core suggest hitherto unexplained sources of energy. We suggest that dark matter in the form of dense antimatter nuggets could provide a natural site for electron and proton annihilation, providing 511 keV photons, gamma rays, and diffuse keV x-ray radiation. We show that identifying dark matter as antimatter nuggets is consistent with the observed emissions, and we make definite predictions about their spectrum and morphology. If correct, our proposal not only identifies dark matter and explains baryogenesis, but also allows x-ray observations to directly probe the matter distribution in our galaxy.

Forbes, Michael McNeil [Nuclear Theory Group, Department of Physics, University of Washington, Seattle, WA 98195-1560 (United States); Zhitnitsky, Ariel R, E-mail: mforbes@alum.mit.edu, E-mail: arz@physics.ubc.ca [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z1 (Canada)

2008-01-15

15

A channel that allows inwardly directed fluxes of anions in protoplasts derived from wheat roots  

Microsoft Academic Search

An anion channel that only allows outward current flow (anion influx) has been identified in protoplasts derived from wheat (Triticum aestivum L., Triticum turgidum L.) roots. The anion outward rectifier (anion OR) measured by patch-clamp of whole cells activated very quickly, usually reaching a steady-state level in less than 100 ms and was easily distinguished from the cation outward rectifier

M. Skerrett; S. D. Tyerman

1994-01-01

16

High resolution synteny maps allowing direct comparisons between the coffee and tomato genomes  

Microsoft Academic Search

Tomato (Solanum lycopersicum) and coffee (Coffea canephora) belong to the sister families Solanaceae and Rubiaceae, respectively. We report herein the mapping of a common set of 257\\u000a Conserved Ortholog Set II genes in the genomes of both species. The mapped markers are well distributed across both genomes\\u000a allowing the first syntenic comparison between species from these two families. The majority

Florent Lefebvre-Pautigny; Feinan Wu; Murielle Philippot; Michel Rigoreau; Priyono; Mohamed Zouine; Pierre Frasse; Mondher Bouzayen; Pierre Broun; Vincent Pétiard; Steven D. Tanksley; Dominique Crouzillat

2010-01-01

17

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

18

Direct observations of galactic cosmic rays  

NASA Astrophysics Data System (ADS)

The mysterious " radiation ... entering our atmosphere from above" discovered by Hess in 1912 is now known to be dominated by relativistic charged particles, mostly with energies in the GeV-range, but extending to energies higher by many orders of magnitude. As none of these particles can penetrate the earth's atmosphere without interaction, detailed studies of their composition and energy spectra require observations with high-altitude balloons or spacecraft. This became possible only towards the middle of the 20th century. The direct measurements have now revealed much detail about the Galactic cosmic rays below 1015eV, but do not yet provide much overlap with the air-shower region of energies. A historic overview of the measurements is given, beginning with the realization that the majority of the cosmic rays are protons. The discovery and astrophysical significance of the heavier nuclei, and of the ultra-heavy nuclei beyond iron and up to the actinides, are then described, and measurements of the isotopic composition are discussed. Observations of the individual energy spectra are reviewed, and finally, the detection of electrons, positrons, and anti-protons in the cosmic rays, and the searches for exotic or unusual phenomena are summarized. Emphasis is given to the fact that all of these discoveries have become possible through the evolution of increasingly sophisticated detection techniques, a process that is continuing through the present time. The precise knowledge of the abundance distributions of the elements in the cosmic rays and of their isotopic composition permits a comparison with the "universal abundance scale" and provides strong constraints on the origin of the cosmic-ray material in the interstellar medium. "Clock-isotopes" reveal the time history of the particles. The shapes of the energy spectra of the individual cosmic-ray components are related to evolving ideas about particle acceleration and propagation in the Galaxy. In conclusion, prospects for future work are briefly discussed.

Müller, Dietrich

2012-08-01

19

Retrograde bridging nail in periprosthetic femoral fracture treatment which allows direct weight bearing.  

PubMed

The bridging nail is a retrograde intramedullary femoral nail designed to stabilize periprosthetic femoral fractures. It offers a minimal invasive surgical approach in combination with early mobilization. The goal of this study was to evaluate the osteosynthesis under full weight-bearing conditions. Three groups of five composite fibreglass femora were prepared with a cemented hip stem. Group 1 underwent cyclic axial loading with 1500 N during 150 000 cycles. After completion, linear loading to failure was conducted. Groups 2 and 3 were submitted to linear increased torsional loading with and without an axial load respectively. Failure was defined as rotational movement of the connection (slippage). In the axial cyclic loading configuration, one specimen failed after 122 000 cycles. Four specimens passed 150 000 cycles and failed after linearly increasing the axial loading of 1940-2600 N (mean, 2408 N +/- 313 standard deviation (SD)). Slippage was first detected at a torque varying between 2.5 and 8.2 Nm (mean, 5.1 Nm +/- 2.1 SD) in group 2 and between 10.0 and 15.4 Nm (mean, 13.0 N m +/- 2.3 SD) in group 3. In conclusion the bridging nail offers a stable connection with the stem of a hip arthroplasty which can resist high repetitive loads, representative of direct full axial weight bearing. The biomechanical results support the clinical experience of a stable osteosynthesis enabling early post-operative mobilization. PMID:18756682

Zuurmond, R G; Pilot, P; Verburg, A D; van Os, J J; Verdonschot, N

2008-07-01

20

Comparative genome sequencing of Escherichia coli allows observation of bacterial evolution on a laboratory timescale  

Microsoft Academic Search

We applied whole-genome resequencing of Escherichia coli to monitor the acquisition and fixation of mutations that conveyed a selective growth advantage during adaptation to a glycerol-based growth medium. We identified 13 different de novo mutations in five different E. coli strains and monitored their fixation over a 44-d period of adaptation. We obtained proof that the observed spontaneous mutations were

Christopher D Herring; Anu Raghunathan; Christiane Honisch; Trina Patel; M Kenyon Applebee; Andrew R Joyce; Thomas J Albert; Frederick R Blattner; Dirk van den Boom; Charles R Cantor; Bernhard Ø Palsson

2006-01-01

21

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

22

Direct observation of microbubbles in directional solidification of salol  

SciTech Connect

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

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

1990-03-26

23

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

24

Direct observation of longitudinally polarised W ± bosons  

Microsoft Academic Search

The three different helicity states of W± bosons, produced in the reaction e+e??W+W????qq? are studied using leptonic and hadronic W decays at s=183 GeV and 189 GeV. The W polarisation is also measured as a function of the scattering angle between the W? and the direction of the e? beam. The analysis demonstrates that W bosons are produced with all

M. Acciarri; P. Achard; O. Adriani; M. Aguilar-Benitez; J. Alcaraz; G. Alemanni; J. Allaby; A. Aloisio; M. G. Alviggi; G. Ambrosi; H. Anderhub; V. P. Andreev; T. Angelescu; F. Anselmo; A. Arefiev; T. Azemoon; T. Aziz; P. Bagnaia; L. Baksay; A. Balandras; R. C. Ball; S. Banerjee; A. Barczyk; R. Barillère; L. Barone; P. Bartalini; M. Basile; R. Battiston; A. Bay; F. Becattini; U. Becker; F. Behner; L. Bellucci; J. Berdugo; P. Berges; B. Bertucci; B. L. Betev; S. Bhattacharya; M. Biasini; A. Biland; J. J. Blaising; S. C. Blyth; G. J. Bobbink; A. Böhm; L. Boldizsar; B. Borgia; D. Bourilkov; M. Bourquin; S. Braccini; J. G. Branson; V. Brigljevic; F. Brochu; A. Buffini; A. Buijs; J. D. Burger; W. J. Burger; A. Button; X. D. Cai; M. Campanelli; M. Capell; G. Cara Romeo; G. Carlino; A. M. Cartacci; J. Casaus; G. Castellini; F. Cavallari; N. Cavallo; C. Cecchi; M. Cerrada; F. Cesaroni; M. Chamizo; Y. H. Chang; U. K. Chaturvedi; M. Chemarin; A. Chen; G. Chen; H. F. Chen; H. S. Chen; G. Chiefari; L. Cifarelli; F. Cindolo; C. Civinini; I. Clare; R. Clare; G. Coignet; A. P. Colijn; N. Colino; S. Costantini; F. Cotorobai; B. Cozzoni; B. de la Cruz; A. Csilling; S. Cucciarelli; T. S. Dai; J. A. van Dalen; R. D'Alessandro; R. de Asmundis; P. Déglon; A. Degré; K. Deiters; D. della Volpe; P. Denes; F. DeNotaristefani; A. De Salvo; M. Diemoz; D. van Dierendonck; F. Di Lodovico; C. Dionisi; M. Dittmar; A. Dominguez; A. Doria; M. T. Dova; D. Duchesneau; D. Dufournaud; P. Duinker; I. Duran; H. El Mamouni; A. Engler; F. J. Eppling; F. C. Erné; P. Extermann; M. Fabre; R. Faccini; M. A. Falagan; S. Falciano; A. Favara; J. Fay; O. Fedin; M. Felcini; T. Ferguson; F. Ferroni; H. Fesefeldt; E. Fiandrini; J. H. Field; F. Filthaut; P. H. Fisher; I. Fisk; G. Forconi; L. Fredj; K. Freudenreich; C. Furetta; Yu. Galaktionov; S. N. Ganguli; P. Garcia-Abia; M. Gataullin; S. S. Gau; S. Gentile; N. Gheordanescu; S. Giagu; Z. F. Gong; G. Grenier; O. Grimm; M. W. Gruenewald; M. Guida; R. van Gulik; V. K. Gupta; A. Gurtu; L. J. Gutay; D. Haas; A. Hasan; D. Hatzifotiadou; T. Hebbeker; A. Hervé; P. Hidas; J. Hirschfelder; H. Hofer; G. Holzner; H. Hoorani; S. R. Hou; I. Iashvili; B. N. Jin; L. W. Jones; P. de Jong; I. Josa-Mutuberr??a; R. A. Khan; M. Kaur; M. N. Kienzle-Focacci; D. Kim; J. K. Kim; S. C. Kim; J. Kirkby; D. Kiss; W. Kittel; A. Klimentov; A. C. König; A. Kopp; V. Koutsenko; M. Kräber; R. W. Kraemer; W. Krenz; A. Krüger; A. Kunin; P. Ladron de Guevara; I. Laktineh; G. Landi; K. Lassila-Perini; M. Lebeau; A. Lebedev; P. Lebrun; P. Lecomte; P. Lecoq; P. Le Coultre; H. J. Lee; J. M. Le Goff; R. Leiste; E. Leonardi; P. Levtchenko; C. Li; S. Likhoded; C. H. Lin; W. T. Lin; F. L. Linde; L. Lista; Z. A. Liu; W. Lohmann; E. Longo; Y. S. Lu; K. Lübelsmeyer; C. Luci; D. Luckey; L. Lugnier; L. Luminari; W. Lustermann; W. G. Ma; M. Maity; L. Malgeri; A. Malinin; C. Maña; D. Mangeol; P. Marchesini; G. Marian; J. P. Martin; F. Marzano; G. G. G. Massaro; K. Mazumdar; R. R. McNeil; S. Mele; L. Merola; M. Meschini; W. J. Metzger; M. von der Mey; A. Mihul; H. Milcent; G. Mirabelli; J. Mnich; G. B. Mohanty; P. Molnar; B. Monteleoni; T. Moulik; G. S. Muanza; F. Muheim; A. J. M. Muijs; M. Musy; M. Napolitano; F. Nessi-Tedaldi; H. Newman; T. Niessen; A. Nisati; H. Nowak; Y. D. Oh; G. Organtini; A. Oulianov; C. Palomares; D. Pandoulas; S. Paoletti; P. Paolucci; R. Paramatti; H. K. Park; I. H. Park; G. Pascale; G. Passaleva; S. Patricelli; T. Paul; M. Pauluzzi; C. Paus; F. Pauss; M. Pedace; S. Pensotti; D. Perret-Gallix; B. Petersen; D. Piccolo; F. Pierella; M. Pieri; P. A. Piroué; E. Pistolesi; V. Plyaskin; M. Pohl; V. Pojidaev; H. Postema; J. Pothier; N. Produit; D. Prokofiev; J. Quartieri; G. Rahal-Callot; M. A. Rahaman; P. Raics; N. Raja; R. Ramelli; P. G. Rancoita; A. Raspereza; G. Raven; P. Razis; D. Ren; M. Rescigno; S. Reucroft; T. van Rhee; S. Riemann; K. Riles; A. Robohm; J. Rodin; B. P. Roe; L. Romero; A. Rosca; S. Rosier-Lees; J. A. Rubio; D. Ruschmeier; H. Rykaczewski; S. Saremi; S. Sarkar; J. Salicio; E. Sanchez; M. P. Sanders; M. E. Sarakinos; C. Schäfer; V. Schegelsky; S. Schmidt-Kaerst; D. Schmitz; H. Schopper; D. J. Schotanus; G. Schwering; C. Sciacca; D. Sciarrino; A. Seganti; L. Servoli; S. Shevchenko; N. Shivarov; V. Shoutko; E. Shumilov; A. Shvorob; T. Siedenburg; D. Son; B. Smith; P. Spillantini; M. Steuer; D. P. Stickland; A. Stone; H. Stone; B. Stoyanov; A. Straessner; K. Sudhakar; G. Sultanov; L. Z. Sun; H. Suter; J. D. Swain; Z. Szillasi; T. Sztaricskai; X. W. Tang; L. Tauscher; L. Taylor; C. Timmermans; Samuel C. C. Ting; S. M. Ting; S. C. Tonwar; J. Tóth; C. Tully; K. L. Tung; Y. Uchida; J. Ulbricht; E. Valente; G. Vesztergombi; I. Vetlitsky; D. Vicinanza; G. Viertel; S. Villa; M. Vivargent; S. Vlachos; I. Vodopianov; H. Vogel; H. Vogt; I. Vorobiev; A. A. Vorobyov; A. Vorvolakos

2000-01-01

25

Sensor calibration for multiple direction reflectance observations  

NASA Astrophysics Data System (ADS)

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

26

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

27

Direct observation of dissociated dislocations in garnet.  

PubMed

Dislocation core structures in garnet [grossularite (Ca(2.9)Fe(II)(0.1))(Al(1.9)Fe(III)(0.1)Si(3.0)O(12)] have been examined with near atomic resolution transmission electron microscopy. Dissociated dislocations have been observed as parallel a/4<111> partial dislocations that are separated by stacking faults. The partial dislocations have narrow cores ( approximately 3 burgers vectors), and the stacking fault zone between the narrow partial dislocations is apparently a low-energy configuration that results from the occupancy of previously unfilled dodecahedral and tetrahedral sites. Previous studies of garnet dislocations suggested that dissociation involves departures from garnet stoichiometry (that is, trace amounts of impurities), but evidence of detectable amounts of impurities has not been found even in the highest resolution images. These results have implications for mantle mineral rheology and transformations as well as for ceramics of material science interest. PMID:17737669

Allen, F M; Smith, B K; Buseck, P R

1987-12-18

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.

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

2012-01-01

29

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

30

29. WEST CONFEDERATE AVENUE, OBSERVATION TOWER, IRON BENCH AND DIRECTION ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

29. WEST CONFEDERATE AVENUE, OBSERVATION TOWER, IRON BENCH AND DIRECTION FINDER, VIEW ACROSS AGRICULTURAL LANDSCAPE TOWARDS THE "HIGHWATER MARK." VIEW NE. - Gettysburg National Military Park Tour Roads, Gettysburg, Adams County, PA

31

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

Microsoft Academic Search

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

O. Aulov; D. J. Lary

2010-01-01

32

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

PubMed

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

Jin, Dayong; Piper, James A

2011-02-23

33

Plasmon Surface Polariton Dispersion by Direct Optical Observation.  

ERIC Educational Resources Information Center

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

Swalen, J. D.; And Others

1980-01-01

34

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

35

The first direct observation of positronium hyperfine splitting  

NASA Astrophysics Data System (ADS)

The direct transition from ortho-positronium to para-positronium with high-power sub-THz radiation has been observed with 5.1 ? significance. The observed transition rate is consistent with the theoretical calculation. A sub-THz gyrotron is used as the light source, and a quasi-optical Fabry-Perot cavity is utilized to accumulate the radiation. This is the first observation of the positronium hyperfine splitting (Ps-HFS), which leads to the first direct measurement of Ps-HFS with a target accuracy of 100 ppm in several years.

Suehara, Taikan; Yamazaki, Takayuki; Miyazaki, Akira; Akimoto, Ginga; Ishida, Akira; Namba, Toshio; Asai, Shoji; Kobayashi, Tomio; Saito, Haruo; Idehara, Toshitaka; Ogawa, Isamu; Sabchevski, Svilen

2012-04-01

36

Direct observations of neutron irradiation damage in alpha-iron  

Microsoft Academic Search

Transmission electron microscopy is used to observe damage in alpha -Fe ; foils, following irradiation of the foils to total doses of 5 x 10¹⁷ to 1 x ; 10¹⁹ neutrons\\/cm² (neutron energy above 1 Mev). The irradiations are ; carried out at 60 deg C. The irradiation damage can be observed directly, in the ; form of fine black

B. L. Eyre

1962-01-01

37

The direct observation of cosmic ray composition from JACEE  

Microsoft Academic Search

The Japanese-American Cooperative Emulsion Experiment (JACEE) group has performed direct observation of cosmic ray composition (proton through iron) at energies 1012 to 1015eV in 10 balloon flights. 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

T. H. Burnett; S. Dake; J. H. Derrickson; W. F. Fountain; M. Fuki; J. C. Gregory; T. Hayashi; R. Holynski; J. Iwai; W. V. Jones; A. Jurak; J. J. Lord; O. Miyamura; H. Oda; T. Ogata; T. A. Parnell; F. E. Roberts; S. Strausz; T. Tabuki; Y. Takahashi; T. Tominaga; J. W. Watts; J. P. Wefel; B. Wilczynska; H. Wilczynski; R. J. Wilkes; W. Wolter; B. Wosiek

1991-01-01

38

Direct observations of resource sharing in coral reef fish  

Microsoft Academic Search

Extrait La complexité structurale des récifs coralliens rend difficile le recensement des poissons qui y vivent, alors que cependant ces rassemblements extrêmement complexes offrent une excellente occasion d'étudier les mécanismes aboutissant au développement et au maintien d'une communauté animale hautement diversifiée. Au cours des operations «Tektite» et «FLARE» les auteurs ont procédé à une observation directe de populations de poissons

C. L. Smith; J. C. Tyler

1973-01-01

39

Direct Observation of Safety Belt Use in Michigan, Fall 1994.  

National Technical Information Service (NTIS)

Results of a direct observation survey of safety belt use in Michigan for fall of 1994 are reported. Belt use was estimated separately for each vehicle type. Within each vehicle type, belt use by gender, age, road type, day of week, and time of day was es...

D. W. Eby F. M. Streff C. Christoff

1994-01-01

40

Direct Observation of Ultrafast Non-thermal Melting by Ultrafast X-ray Diffraction  

Microsoft Academic Search

Ultrafast nonthermal melting of femtosecond laser-irradiated germanium was observed directly for the first time using sub-picosecond, 1.54-angstrom x-ray diffraction. Such measurements allow the study of transient atomic motion fundamental to many processes in physics, chemistry, and biology.

C. W. Siders; T. Guo; K. R. Wilson

41

Construction of an Hpa I and Hin dII plasmid vector allowing direct selection of transformants harboring recombinant plasmids  

Microsoft Academic Search

The construction of the vector plasmid pKN80 is described, which can be used as HpaI or HindII cloning vehicle with direct selection on transformants harboring hybrid plasmids. pKN80 carries the EcoRI·C fragment of phage Mu DNA coding for a killing function which is efficiently expressed upon transformation of pKN80 into Mu-sensitive bacteria. Cloning of DNA fragments at the single HpaI

Wolfgang Schumann; Universitfit Konstanz

1979-01-01

42

Direct observation of confined single chain dynamics by neutron scattering.  

PubMed

Neutron spin echo has revealed the single chain dynamic structure factor of entangled polymer chains confined in cylindrical nanopores with chain dimensions either much larger or smaller than the lateral pore sizes. In both situations, a slowing down of the dynamics with respect to the bulk behavior is only observed at intermediate times. The results at long times provide a direct microscopic measurement of the entanglement distance under confinement. They constitute the first experimental microscopic evidence of the dilution of the total entanglement density in a polymer melt under strong confinement, a phenomenon that so far was hypothesized on the basis of various macroscopic observations. PMID:20866999

Martín, J; Krutyeva, M; Monkenbusch, M; Arbe, A; Allgaier, J; Radulescu, A; Falus, P; Maiz, J; Mijangos, C; Colmenero, J; Richter, D

2010-05-11

43

Direct observation of ion-irradiation-induced chemical mixing  

SciTech Connect

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

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

2011-01-01

44

Direct Observation of Ion-irradiation-induced Chemical Mixing  

SciTech Connect

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

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

2011-11-01

45

Micro cutting of tungsten carbides with sem direct observation method  

Microsoft Academic Search

This paper describes the micro cutting of wear resistant tungsten carbides using PCD (Poly-Crystalline Diamond) cutting tools\\u000a in performance with SEM (Scanning Electron Microscope) direct observation method. Turning experiments were also carried out\\u000a on this alloy (V50) using a PCD cutting tool. One of the purposes of this study is to describe clearly the cutting mechanism\\u000a of tungsten carbides and

Heo Sung-jung

2004-01-01

46

Questionnaires vs observational and direct measurements: a systematic review  

Microsoft Academic Search

Background: Physical work requirements can be estimated by several different methods, each with its own advantages and disadvantages. To reduce the occurrence of work-related musculoskeletal disorders, a quantitative assessment of work-related, physical risk factors is needed.Objective: To examine the validity of self-administered questionnaires (SAQ) in assessing work-related physical demands when compared to an expert's evaluation using observational and\\/or direct measurement.Methods:

Heriberto Barriera-Viruet; Tarek M. Sobeih; Nancy Daraiseh; Sam Salem

2006-01-01

47

Direct observation of exercise counseling in community family practice  

Microsoft Academic Search

Background: Although physical activity is important for the prevention and management of a variety of common chronic diseases, the prevalence and patient and visit characteristics associated with provision of physical activity advice by community family physicians is not well understood.Methods: In a cross-sectional multi-method study of 138 family physicians in northeast Ohio, exercise advice was measured by direct observation and

Tod R. Podl; Meredith A. Goodwin; George E. Kikano; Kurt C. Stange

1999-01-01

48

Direct Observation of the Strange b Baryon Xib-  

Microsoft Academic Search

We report the first direct observation of the strange b baryon Xib-(Xi¯b+). We reconstruct the decay Xib--->J\\/psiXi-, with J\\/psi-->mu+mu-, and Xi--->Lambdapi--->ppi-pi- in pp¯ collisions at s=1.96TeV. Using 1.3fb-1 of data collected by the D0 detector, we observe 15.2±4.4(stat)-0.4+1.9(syst) Xib- candidates at a mass of 5.774±0.011(stat)±0.015(syst)GeV. The significance of the observed signal is 5.5sigma, equivalent to a probability of 3.3×10-8 of

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

2007-01-01

49

Direct Observation of Microbial Inhibition of Calcite Dissolution  

PubMed Central

Vertical scanning interferometry (VSI) provides a method for quantification of surface topography at the angstrom to nanometer level. Time-dependent VSI measurements can be used to study the surface-normal retreat across crystal and other solid surfaces during dissolution or corrosion processes. Therefore, VSI can be used to directly and nondestructively measure mineral dissolution rates with high precision. We have used this method to compare the abiotic dissolution behavior of a representative calcite (CaCO3) cleavage face with that observed upon addition of an environmental microbe, Shewanella oneidensis MR-1, to the crystal surface. From our direct observations, we have concluded that the presence of the microbes results in a significant inhibition of the rate of calcite dissolution. This inhibition appears to be a 2nd-order effect that is related to the formation of etch pits. The opening of etch pits was greatly inhibited in the presence of added bacteria, suggesting that the bacterial cells exert their effect by inhibiting the formation of etch pits at high-energy sites at the crystal surface caused by lattice defects, e.g., screw or point dislocations. The experimental methodology thus provides a nondestructive, directly quantifiable, and easily visualized view of the interactions of microbes and minerals during weathering (or corrosion) processes or during mineral precipitation.

Luttge, Andreas; Conrad, Pamela G.

2004-01-01

50

Direct observation of correlated interdomain motion in alcohol dehydrogenase.  

PubMed

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. PMID:18851497

Biehl, Ralf; Hoffmann, Bernd; Monkenbusch, Michael; Falus, Peter; Préost, Sylvain; Merkel, Rudolf; Richter, Dieter

2008-09-26

51

Direct Observation of Correlated Interdomain Motion in Alcohol Dehydrogenase  

NASA Astrophysics Data System (ADS)

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; Hoffmann, Bernd; Monkenbusch, Michael; Falus, Peter; Préost, Sylvain; Merkel, Rudolf; Richter, Dieter

2008-09-01

52

Direct observation of thermal relaxation in artificial spin ice.  

PubMed

We study the thermal relaxation of artificial spin ice with photoemission electron microscopy, and are able to directly observe how such a system finds its way from an energetically excited state to the ground state. On plotting vertex-type populations as a function of time, we can characterize the relaxation, which occurs in two stages, namely a string and a domain regime. Kinetic Monte Carlo simulations agree well with the temporal evolution of the magnetic state when including disorder, and the experimental results can be explained by considering the effective interaction energy associated with the separation of pairs of vertex excitations. PMID:23952441

Farhan, A; Derlet, P M; Kleibert, A; Balan, A; Chopdekar, R V; Wyss, M; Perron, J; Scholl, A; Nolting, F; Heyderman, L J

2013-08-02

53

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

54

Direct observation of capacitor switching using planar electrodes  

SciTech Connect

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

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

2010-01-01

55

Direct observation of local atomic order in a metallic glass  

NASA Astrophysics Data System (ADS)

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

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

2011-01-01

56

Compassionate Allowances  

MedlinePLUS

... Allowances (CAL) are a way of quickly identifying diseases and other medical conditions that invariably qualify under the Listing of Impairments ... Security and Disability Determination Services communities, counsel of medical and ... on rare diseases, cancers, traumatic brain injury (TBI) and stroke, early- ...

57

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

58

Direct observations of ultra-high energy cosmic rays  

NASA Astrophysics Data System (ADS)

Balloon-borne emulsion chambers are being used for direct observations of primary cosmic rays at energies up to about 10 to the 14th eV. So far, energy spectra measurements for individual species are available only for protons and helium, which apparently agree with single power law extrapolation of lower energy data, although the possibility of a bend in the proton spectrum has been revived recently. The composition of heavy nuclei around 10 to the 14th eV seems to be consistent with an E exp -1.7 power law extrapolation from 100 GeV/nucleon data. Some anomalous interactions provide evidence that high energy nucleus-nucleus collisions cannot be explained by simple superpositions of nucleon-nucleon collisions. Within about a decade, long exposures in space using the Space Transportation System and/or the Space Station/Space Platform could provide the opportunity for direct cosmic ray observations to energies as high as 10 to the 16th eV.

Jones, W. V.

59

Direct Observation of Vortex Dynamics in Superconducting Films with Regular Arrays of Defects  

PubMed

The microscopic mechanism of the matching effect in a superconductor, which manifested itself as the production of peaks or cusps in the critical current at specific values of the applied magnetic field, was investigated with Lorentz microscopy to allow direct observation of the behavior of vortices in a niobium thin film having a regular array of artificial defects. Vortices were observed to form regular and consequently rigid lattices at the matching magnetic field, at its multiples, and at its fractions. The dynamic observation furthermore revealed that vortices were most difficult to move at the matching field, whereas excess vortices moved easily. PMID:8895460

Harada; Kamimura; Kasai; Matsuda; Tonomura; Moshchalkov

1996-11-15

60

Direct observation of hierarchical folding in single riboswitch aptamers.  

PubMed

Riboswitches regulate genes through structural changes in ligand-binding RNA aptamers. With the use of an optical-trapping assay based on in situ transcription by a molecule of RNA polymerase, single nascent RNAs containing pbuE adenine riboswitch aptamers were unfolded and refolded. Multiple folding states were characterized by means of both force-extension curves and folding trajectories under constant force by measuring the molecular contour length, kinetics, and energetics with and without adenine. Distinct folding steps correlated with the formation of key secondary or tertiary structures and with ligand binding. Adenine-induced stabilization of the weakest helix in the aptamer, the mechanical switch underlying regulatory action, was observed directly. These results provide an integrated view of hierarchical folding in an aptamer, demonstrating how complex folding can be resolved into constituent parts, and supply further insights into tertiary structure formation. PMID:18174398

Greenleaf, William J; Frieda, Kirsten L; Foster, Daniel A N; Woodside, Michael T; Block, Steven M

2008-01-03

61

Direct Observation of Cotranscriptional Folding in an Adenine Riboswitch  

PubMed Central

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

Frieda, Kirsten L.; Block, Steven M.

2012-01-01

62

Direct observation of smectic layers in thermotropic liquid crystals.  

PubMed

We demonstrate subnanometer resolution cryo-TEM imaging of smectic layers in the smectic and nematic phases of two bent-core liquid crystals. Our results show perfect periodicity over several hundred layers in the smectic phase and also provide the first direct evidence of smectic clusters on length scales of 30-50 nm in a nematic liquid crystal. The results are corroborated with small angle x-ray scattering measurements. The observation of smectic clusters in the nematic phase is of special interest in bent-core liquid crystals, where the smectic clusters are stable over wide temperature ranges, in contrast to the well-known pretransitional "cybotactic" clusters that appear only in the vicinity of a bulk smectic phase. The means to characterize and manipulate this nanoscale molecular order could open up completely new liquid crystal-based technologies. PMID:23005329

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

2012-09-07

63

Direct Observation of Smectic Layers in Thermotropic Liquid Crystals  

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

64

Direct observation of cotranscriptional folding in an adenine riboswitch.  

PubMed

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

Frieda, Kirsten L; Block, Steven M

2012-10-19

65

Direct observation of electron dynamics in the attosecond domain  

NASA Astrophysics Data System (ADS)

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

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

2005-07-01

66

Dental injury after conventional direct laryngoscopy: a prospective observational study.  

PubMed

This observational study assessed the frequency and risk factors of dental damage after classic direct laryngoscopy for tracheal intubation in 536 adult patients. The patients' sex, age, height, weight, dental condition, dental mobility, Mallampati class, interincisor gap, thyromental distance, neck circumference, and head and neck extension were recorded. From anaesthesia records, the difficulty of intubation, the number of attempts, type of neuromuscular blocking agent used and duration of anaesthesia were recorded. After anaesthesia, examination revealed that 134 patients (25.0%) had dental damage affecting 162 teeth (147 maxillary; 15 mandibular). Enamel fracture was the commonest injury. In tooth number 21, the interincisor gap (OR 2.5 (95% CI 1.0-5.9)) and in tooth number 22, the number of intubation attempts (OR 5.3 (95% CI 1.3-22.0)) were considered a risk factor for dental injury. Conventional direct laryngoscopy is associated with a strikingly high incidence of dental damage, although specific risk factors remain unclear. PMID:24047290

Mourão, J; Neto, J; Luís, C; Moreno, C; Barbosa, J; Carvalho, J; Tavares, J

2013-10-01

67

Direct Observation of Prompt Solar Flare Perturbation to Stratospheric Electrodynamics  

NASA Astrophysics Data System (ADS)

Several solar flare events were observed during the MINIS balloon experiment from SANAE station Antarctica, January 2005. The balloon payloads carried a large number of particle and field instruments which clearly identified several direct one-to-one perturbations between energetic particle flux enhancements, and the stratospheric electric field. Previous stratospheric electric field experiments have also detected one to one correlations with solar flares of both enormous size (August 1972) and quite small (February 1984). The flares during the MINIS flights produced a surprising influence on both the vertical electric field (as in the previous experiments) as well as on the horizontal electric field. The dramatic vertical electric field reductions, seen by MINIS as well as the earlier flights, may be directly related to the global circuit return currents and the influence of changing electrical conductivity. However, during the MINIS flight, we will show that the horizontal electric field also dropped to near zero. This could be caused by an abrupt cessation in large scale convection (at least locally), or by a rapid reconfiguration of the magnetosphere, perturbing the mapping of electric fields from the magnetosphere to the latitude of the balloon.

Holzworth, R. H.; Bering, E. A.; Kokorowski, M.; Reddell, B. D.; McCarthy, M. P.; Bale, S.; Blake, J. B.; Collier, A. B.; Hughes, A. R.; Lay, E.; Lin, R. P.; Millan, R. M.; Moraal, H.; O'Brien, T. P.; Parks, G. K.; Pulupa, M.; Sample, J. G.; Smith, D. M.; Stoker, P.; Woodger, L.

2005-12-01

68

Direct observation of solidification microstructures around absolute stability  

SciTech Connect

This paper presents, for the first time, experimental evidence for absolute stability in a transparent alloy. The succinonitrile-argon system was used to investigate the morphological transition from a cellular to a planar solid-liquid interface at high solidification velocities. Directional solidification of the organic contained in thin capillary tubes was observed in situ with an optical microscope. At the maximum interface velocity of 1.5 mm/s, a reduction of the solute content of the alloy resulted in a morphological transition from a cellular to a planar growth front. This transition developed in three stages: (1) transition from deep cylindrical cells to mixed patterns of cylindrical and elongated cells; (ii) transition from cylindrical and elongated cells to low amplitude cells; (iii) transition from low amplitude cells to plane front. Within the limits of uncertainties with respect to the material properties and the thermal gradient, correspondence between the experimental results on plane front transition and linear stability theory exists. It is shown that the transitions observed are located in the region near the limit point of the neutral stability curve on the branch for absolute morphological stability.

Ludwig, A.; Kurz, W. [Swiss Federal Inst. of Tech., Lausanne (Switzerland). Dept. of Materials

1996-09-01

69

SPICA coronagraph for direct observation of exo-planets  

NASA Astrophysics Data System (ADS)

Space Infrared telescope for Cosmology and Astrophysics(SPICA) is a next generation infrared space-borne telescope mission led by Japan Aerospace Exploration Agency(JAXA). The SPICA satellite will have a telescope with 3.5m diameter monolithic primary mirror, and the whole telescope is cooled to 4.5 K. The satellite is planed to be launched in 2017 by an H-IIA rocket of JAXA and execute infrared observations in mainly 5-200 micron wavelengths. We are developing the mid-infrared coronagraph as one of the focal plane instruments of SPICA. The primary target is direct observations of Jovian exo-planets. We consider coronagraph by the binary shaped pupil mask is the baseline method for the SPICA coronagraph, because of its simplicity and robustness. In a laboratory experiment of a binary shaped pupil mask, checkerboard mask with optical laser, raw contrast of 7x10-8 was achieved. On the other hand, we are evaluating Phase Induced Amplitude Apodization(PIAA) to get higher performance solution. Development of cryogenic optics is important for the SPICA coroangraph. To reduce wave front error for coronagraph, cryogenic deformable mirror is needed if we will decide to adopt AO for SPICA coroangraph. To reduce pointing vibration by cryocooler and other component on the satellite, development of cryogenic tip-tilt mirror is also undergoing.

Enya, Keigo

70

Direct observation of magnetic cycles in Sun-like stars  

NASA Astrophysics Data System (ADS)

A sample of 19 solar-type stars, probing masses between 0.6 and 1.4 solar masses and rotation periods between 3.4 and 43 days, was regularly observed using the NARVAL spectropolarimeter at Telescope Bernard Lyot (Pic du Midi, France) between 2007 and 2011. The Zeeman-Doppler Imaging technique is employed to reconstruct the large-scale photospheric magnetic field structure of the targets and investigate its long-term temporal evolution. We present here the first results of this project with the observation of short magnetic cycles in several stars, showing up a succession of polarity reversals over the timespan of our monitoring. Preliminary trends suggest that short cycles are more frequent for stellar periods below a dozen days and for stellar masses above about one solar mass. The cycles lengths unveiled by the direct tracking of polarity switches are significantly shorter than those derived from previous studies based on chromospheric activity monitoring, suggesting the coexistence of several magnetic timescales in a same star.

Morgenthaler, A.; Petit, P.; Morin, J.; Aurière, M.; Dintrans, B.; Konstantinova-Antova, R.; Marsden, S.

2011-12-01

71

The cosmic microwave background: observing directly the early universe  

NASA Astrophysics Data System (ADS)

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

de Bernardis, Paolo; Masi, Silvia

2012-09-01

72

Direct observation of the dynamic process underlying allosteric signal transmission.  

PubMed

Allosteric regulation is an effective mechanism of control in biological processes. In allosteric proteins a signal originating at one site in the molecule is communicated through the protein structure to trigger a specific response at a remote site. Using NMR relaxation dispersion techniques we directly observe the dynamic process through which the KIX domain of CREB binding protein communicates allosteric information between binding sites. KIX mediates cooperativity between pairs of transcription factors through binding to two distinct interaction surfaces in an allosteric manner. We show that binding the activation domain of the mixed lineage leukemia (MLL) transcription factor to KIX induces a redistribution of the relative populations of KIX conformations toward a high-energy state in which the allosterically activated second binding site is already preformed, consistent with the Monod-Wyman-Changeux (WMC) model of allostery. The structural rearrangement process that links the two conformers and by which allosteric information is communicated occurs with a time constant of 3 ms at 27 degrees C. Our dynamic NMR data reveal that an evolutionarily conserved network of hydrophobic amino acids constitutes the pathway through which information is transmitted. PMID:19203263

Brüschweiler, Sven; Schanda, Paul; Kloiber, Karin; Brutscher, Bernhard; Kontaxis, Georg; Konrat, Robert; Tollinger, Martin

2009-03-01

73

Directly observed treatment, short course in tuberculous meningitis: Indian perspective  

PubMed Central

Background: Effectiveness of intermittent short course chemotherapy for tuberculous meningitis (TBM) has not been well studied. There are scarce reported studies on this issue in the world literature. Neurologists all over India are reluctant to accept Directly Observed Treatment Short course (DOTS) for TBM since its introduction in India. Aim: We did a prospective study to assess effectiveness of Revised National TB Control Program (RNTCP-DOTS) regimes among TBM patients. Materials and Methods: In this study we include the TBM patients admitted from September 2008 to March 2011. All were referred to RNTCP for treatment. Diagnostic Algorithm as per RNTCP guidelines was strictly followed and treatment outcome and follow-up status were recorded. We exclude HIV and pediatric age group. Results: A total of 42 cases registered for DOTS regimen were included in the study, of which 35 completed the treatment (83%). All the patients were started with DOTS but finally 78% received actual DOTS. All patients were given 9 months intermitted regimen as per RNTCP guidelines. Seven patients died during the treatment (16%). Conclusion: We found intermitted short course chemotherapy was effective in TBM.

Sharma, Shri Ram; Lynrah, Kyrshang G.; Sharma, Nalini; Lyngdoh, Monaliza

2013-01-01

74

Direct observation of hematopoietic progenitor chimerism in fetal freemartin cattle  

PubMed Central

Background Cattle twins are well known as blood chimeras. However, chimerism in the actual hematopoietic progenitor compartment has not been directly investigated. Here, we analyzed fetal liver of chimeric freemartin cattle by combining a new anti-bovine CD34 antibody and Y-chromosome specific in situ hybridization. Results Bull-derived CD34+ cells were detected in the liver of the female sibling (freemartin) at 60 days gestation. The level of bull-derived CD34+ cells was lower in the freemartin than in its male siblings. Bull (Y+) and cow hematopoietic cells often occurred in separate clusters. Around clusters of Y+CD34+ cells, Y+CD34- cells were typically observed. The thymi were also strongly chimeric at 60 days of gestation. Conclusion The fetal freemartin liver contains clusters of bull-derived hematopoietic progenitors, suggesting clonal expansion and differentiation. Even the roots of the hematopoietic system in cattle twins are thus strongly chimeric from the early stages of fetal development. However, the hematopoietic seeding of fetal liver apparently started already before the onset of functional vascular anastomosis.

Niku, Mikael; Pessa-Morikawa, Tiina; Taponen, Juhani; Iivanainen, Antti

2007-01-01

75

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

76

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

Code of Federal Regulations, 2013 CFR

...Energy NUCLEAR REGULATORY COMMISSION FITNESS FOR DUTY PROGRAMS Collecting Specimens...collector shall explain to the donor the reason for direct observation of the collection...that the collection was observed and the reason(s) for the directly observed...

2013-01-01

77

Direct Observation of Small Cluster Mobility and Ripening.  

National Technical Information Service (NTIS)

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 deposit...

K. Heinemann H. Poppa

1975-01-01

78

Practice of directly observed treatment (DOT) for tuberculosis in southern Thailand: comparison between different types of DOT observers  

Microsoft Academic Search

SETTING: A government health system in southern Thailand where the directly observed treatment, short- course (DOTS) strategy has been implemented. OBJECTIVE: To compare the practice of actual directly observed treatment (DOT) and the observer sustainabil- ity for different types of observer. METHODS: During 1999-2000, 411 patients with new smear-positive pulmonary tuberculosis were followed up. The patients and\\/or their observers were

P. Pungrassami; S. P. Johnsen; V. Chongsuvivatwong; J. Olsen; H. T. Sørensen

79

Direct observation of non-fully-symmetric coherent optical phonons by femtosecond x-ray diffraction  

NASA Astrophysics Data System (ADS)

We directly measure by femtosecond time-resolved x-ray diffraction the Eg symmetry coherent phonon excited in bismuth by a strong optical pulse. The magnitude of the Eg mode observed is 0.2 pm peak-to-peak, compared against the 2.7-pm initial displacement of the fully symmetric A1g mode. The much smaller motion of the Eg mode is a consequence of the short lifetime of the electronic states that drive the atomic motion. The experimentally measured magnitude of the Eg motion allows us to rule out a previously suggested scenario for explaining the dynamics in bismuth that relies on strong coupling between these modes.

Johnson, S. L.; Beaud, P.; Möhr-Vorobeva, E.; Caviezel, A.; Ingold, G.; Milne, C. J.

2013-02-01

80

Direct Observation of the Controlled Magnetization Reversal Processes in Py/Al/Py Assymmetric Ring Stacks  

SciTech Connect

Electron holographic experiments were performed to study the magnetization reversal process of patterned Py/Al/Py (20nm/20nm/10nm) asymmetric ring stacks. By changing the in-plane field applied perpendicular to the ring's symmetric axis, we directly observed the vortex-based magnetization reversal process through controlled domain wall motion and annihilation. The two magnetic layers were found to switch at different critical fields, leading to the existence of various distinct domain state combinations. Quantitative agreement was obtained between measured phase shifts and those derived from micromagnetic calculations, which allows us to resolve the layer-by-layer magnetic behavior as a function of applied external field.

Huang, L.; Schofield, M.A.; Zhu, Y.

2009-07-27

81

Direct observation of ferromagnetic exchange by magnetic force microscopy  

Microsoft Academic Search

In this study, the exchange coupling at the interface of two different magnetic materials remains is investigated by using an original local technique combining lithography with scanning probe microscopy. A home-made magnetic force microscopy device that allows measurements in perpendicular magnetic field up to 1.8 T, operating in noncontact mode is used. The sample used is a bilayer of thin

A. Vanhaverbeke; M. Viret; O. Klein

2005-01-01

82

Direct Observation of Magnetic Vortices in Superconductors Using Electron Waves  

Microsoft Academic Search

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

Akira Tonomura

1998-01-01

83

Direct observation of capacitor switching using planar electrodes  

Microsoft Academic Search

Ferroelectric polarization switching in epitaxial (110) BiFeO films is studied using piezoresponse force microscopy of a model in-plane capacitor structure. The electrode orientation is chosen such that only two active domain variants exist. Studies of the kinetics of domain evolution allows clear visualization of nucleation sites, as well as forward and lateral growth stages of domain formation. It is found

Nina Balke; Martin Gajek; Alexander K. Tagantsev; Ying-Hao Chu; Ramamoorthy Ramesh; Sergei V. Kalinin

2010-01-01

84

DIRECT OBSERVATIONS OF THERMOSPHERIC WINDS DURING GEOMAGNETIC STORMS  

Microsoft Academic Search

Direct measurements of thermospheric winds were made during two geomagnetic storms. Winds were detected (a) in the stable auroral red arc of October 31 to November 1, 1968, and (b) during the aurora .of May 14-15, 1969. In both storms the measured winds were from the north and persisted throughout the night with a velocity between 250 and 400 m

P. B. Hays; R. G. Roble

1971-01-01

85

Direct Observation of IBW Induced Poloidal Flow in TFTR  

SciTech Connect

Shearing of the plasma poloidal rotation velocity was observed during application of ion Bernstein wave IBW) power in the Tokamak Fusion Test Reactor (TFTR) tokamak. The first evidence of corroboration between measured poloidal velocity shearing and actively induced Reynolds stress effects is presented. A model reproduces salient experimental features: The observed sheared flow occurs near the tritium fifth harmonic cyclotron resonance layer and depends strongly on the tritium density, in agreement with the model. Furthermore, the model reproduces the observed insensitivity of the induced rotation to the tritium density in the region between the third deuterium harmonic layer and the fifth tritium harmonic layer.

Bell, R.E.; Bernabei, S.; Hosca, J.C.; LeBlanc, B.P.; Majeski, R.; et al.

1998-11-01

86

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

PubMed Central

We have examined the structure of S-layers isolated from Sulfolobus acidocaldarius using atomic force microscopy (AFM) and transmission electron microscopy (TEM). From the AFM images, we were able to directly observe individual dimers of the crystal, defects in the crystal structure, and twin boundaries. We have identified two types of boundaries, one defined by a mirror plane and the other by a glide plane. This work shows that twin boundaries are highly structured regions that are directly related to the organization of units within each crystal domain. Projection maps from TEM images have shown that there are significant differences in the final average maps has allowed us to relate high magnification views obtained by AFM to the relatively high resolution information obtained by electron microscopy and image processing. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 6

Devaud, G; Furcinitti, P S; Fleming, J C; Lyon, M K; Douglas, K

1992-01-01

87

Direct Uv Observations of the Circumstellar Envelope of alpha Orionis,  

National Technical Information Service (NTIS)

Observations were made in the IUE LWP camera, low dispersion mode, with alpha Ori being offset various distances from the center of the Long Wavelength Large Aperture along its major axis. Signal was acquired at all offset positions and is comprised of un...

R. E. Stencel K. G. Carpenter J. E. Pesce S. Skinner A. Brown

1988-01-01

88

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

89

Direct observation of ion-irradiation-induced chemical mixing  

Microsoft Academic Search

Irradiation-induced dissolution of particles and mixing at heterogeneous interfaces in materials is of importance for ion beam processing and radiation materials sciences. Modeling has predicted dissolution of particles and homogenization at sharp chemical interfaces; imaging and depth profiling techniques have also been used to observe damage and mixing resulting from ion or neutron bombardment. Analytical scanning transmission electron microscopy has

C. M. Parish; P. D. Edmondson; Y. Zhang; Michael K. Miller

2011-01-01

90

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

91

Direct observation of disulfide isomerization in a single protein  

PubMed Central

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

Alegre-Cebollada, Jorge; Kosuri, Pallav; Rivas-Pardo, Jaime Andres; Fernandez, Julio M.

2011-01-01

92

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

93

Future directions in X-ray\\/gamma-ray observations  

Microsoft Academic Search

Facilities available for X ray and gamma ray astronomical observations in the late 1980s are described, with an emphasis on NASA programs. Current European programs for launching Rosat and Exosat will provide coverage in the 0.4-60 keV energy range. The proposed NASA advanced X ray astrophysics facility is intended to cover the 0.1-8 keV range with higher than 0.5 arcsec

D. A. Kniffen

1982-01-01

94

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

PubMed

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

Peak, Derek; Regier, Tom

2012-03-09

95

Drug administration errors in paediatric wards: a direct observation approach.  

PubMed

Paediatric patients are more vulnerable to drug administration errors due to a lack of appropriate drug dosages and strengths for use in this group of patients. Therefore, the aim of the present study was to determine the extent and types of drug administration errors in two paediatric wards and to identify measures to reduce such errors. A researcher was stationed in two paediatric wards of a teaching hospital to observe all drugs administered to paediatric inpatients in each of the ward, for 1 day in a week over ten consecutive weeks. All data were recorded in a data collection form and then compared with the actual drugs and dosages prescribed for the patients. Of the 857 drug administrations observed, 100 doses had errors, and this gave an error rate of 11.7% [95% confidence interval (CI) 9.5-13.9%]. If wrong time administration errors were excluded, the error rate reduced to 7.8% (95% CI 6.0-9.6%). The most common types of drug administration errors were incorrect time of administration (28.8%), followed by incorrect drug preparation (26%), omission errors (16.3%) and incorrect dose (11.5%). None of the errors observed were considered as potentially life threatening, although 40.4% could possibly cause patient harm. Drug administration errors are as common in paediatric wards in Malaysia as in other countries. Double-checking should be conducted, as this could reduce drug administration errors by about 20%, but collaborative efforts between all healthcare professionals are essential. PMID:19823870

Chua, Siew Siang; Chua, Hui Ming; Omar, Asma

2009-10-14

96

Direct observation of muon pair production by cosmic ray muons  

NASA Astrophysics Data System (ADS)

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 theoretical calculations of the cross section but is about 7 times lower than the prediction obtained with the cross section formula widely used earlier for various estimations.

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

97

Direct observation of hexokinase translocation in stimulated macrophages.  

PubMed Central

1. Fluorescence imaging of antibodies was used to show that phorbol 12-myristate 13-acetate (PMA) induces a 4-fold increase in the amount of hexokinase relative to the control in the cortical shell of rat peritoneal macrophage cytosol adjacent to the plasma membrane, and a corresponding depletion in the amount of hexokinase in the central core of the cytosol. However, there was no significant PMA-dependent change in the distribution of glucose-6-phosphate dehydrogenase. 2. Cytochalasin D, an inhibitor of actin microfilament polymerization, prevented the PMA-induced hexokinase translocation and also reduced the PMA-dependent increases in 2-deoxy-D-glucose transport and glucose-dependent PMA-stimulated superoxide production. 3. PMA caused a contraction of the width of the cortical F-actin zone. Cytochalasin D caused some dispersal of F-actin within the cell, increasing the density of F-actin within the central cytosolic core and causing aggregation of the F-actin within the cortex. These data are consistent with the view that PMA induces attachment of hexokinase to microfilaments within the cortical zone adjacent to the cell membrane of macrophages, and cytochalasin D prevents this attachment. This is the first direct demonstration of the translocation of hexokinase to the plasma membrane in activated cells, and supports the view that enhanced hexokinase activity in the cortical region of the cytosol is an important early component of the macrophage activation process. Images Figure 1 Figure 2 Figure 4 Figure 9

Pedley, K C; Jones, G E; Magnani, M; Rist, R J; Naftalin, R J

1993-01-01

98

Direction and orientation of CME/ICME events observed by STEREO  

NASA Astrophysics Data System (ADS)

The two NASA STEREO spacecraft are now approaching a quadrature configuration with respect to the Earth. In conjunction with the rising solar activity this represents a great opportunity to study coronal mass ejections (CMEs) during their journey from the Sun to 1 AU. We are in particular concerned with those events which were observed by the STEREO/SECCHI imaging instrument in the inner heliosphere and which were also detected in situ at 1 AU with STEREO (IMPACT/PLASTIC) or WIND (SWE/MFI). This allows for example to check (1) if the direction of propagation given by various direction-finding techniques is indeed correlated with the signatures which are later observed in situ and (2) if the orientation of the magnetic flux rope inside the ICME, which we model using the Grad-Shafranov technique, is reflected in properties of the CME. Also, the classic three-part structure of CMEs can be related to the in situ data. The results are discussed regarding the possibility to forecast ICME properties from observations closer to the Sun.

Moestl, Christian; Rollett, Tanja; Temmer, Manuela; Farrugia, Charles; Veronig, Astrid; Galvin, Antoinette; Biernat, Helfried K.

99

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

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 the oceanic CO2 increase revisited  

PubMed Central

We show, from recent data obtained at specimen North Pacific stations, that the fossil fuel CO2 signal is strongly present in the upper 400 m, and that we may consider areal extrapolations from geochemical surveys to determine the magnitude of ocean fossil fuel CO2 uptake. The debate surrounding this topic is illustrated by contrasting reports which suggest, based upon atmospheric observations and models, that the oceanic CO2 sink is small at these latitudes; or that the oceanic CO2 sink, based upon oceanic data and models, is large. The difference between these two estimates is at least a factor of two. There are contradictions arising from estimates based on surface partial pressures of CO2 alone, where the signal sought is small compared with regional and seasonal variability; and estimates of the accumulated subsurface burden, which correlates well other oceanic tracers. Ocean surface waters today contain about 45 ?mol?kg?1 excess CO2 compared with those of the preindustrial era, and the signal is rising rapidly. What limits should we place on such calculations? The answer lies in the scientific questions to be asked. Recovery of the fossil fuel CO2 contamination signal from analysis of ocean water masses is robust enough to permit reasonable budget estimates. However, because we do not have sufficient data from the preindustrial ocean, the estimation of the required Redfield oxidation ratio in the upper several hundred meters is already blurred by the very fossil fuel CO2 signal we seek to resolve.

Brewer, Peter G.; Goyet, Catherine; Friederich, Gernot

1997-01-01

102

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

103

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

104

Bistatic-Radar Techniques for Observing Long-Wavelength Directional Ocean-Wave Spectra  

Microsoft Academic Search

Bistatic-radar Bragg scattering of medium-to long-wavelength radio waves by ocean waves can be used as a means for observing directional ocean-wave spectra. Only moderate antenna directivity is required; areal and directional resolution are provided by high-resolution delay-Doppler processing of the radar echoes. Directional characteristics of long-wavelength (80-200 m) ocean waves have been observed using LORAN A transmission (1.85 MHz) and

Calvin Teague

1971-01-01

105

Direct Imaging of an Emerging Flux Rope and a Resulting Chromospheric Jet Observed by Hinode  

NASA Astrophysics Data System (ADS)

Magnetic flux emergence has been traditionally observed on the disk by identifying changes in magnetograms. Observations near the limb offer an alternative perspective and allow direct imaging of emerging flux ropes. We present Hinode/SOT Ca II H observations of such an event in an equatorial coronal hole on 2007 February 9. The precursor of the event was a bundle of fine material threads that extended at an oblique angle above the chromosphere and appeared to rotate about a common axis. This bundle first slowly and then rapidly swung up, accompanied by a loop that appeared at the base of the bundle and expanded at comparable rates. During the first (slow rise) stage, the apex of the loop ascended at 16 km/s, a velocity similar to that of H-alpha arch filaments (e.g., Chou & Zirin) and of emerging flux ropes expanding into the corona as found in MHD simulations (e.g., Fan & Gibson; Martinez-Sykora). The second stage started at the onset of a GOES A5 flare and the loop expansion accelerated, reaching a velocity of 130 km/s when the loop appeared to rupture near the peak of the flare. The material bundle then swung back in a whiplike manner and developed into a collimated jet, exhibiting oscillatory transverse motions across its axis, as expected from unwinding twists. Some jet material fell back along smooth streamlines, which bypass an unseen dome and presumably a null point in the low corona, depicting an inverted-Y shape. Some of these observations resemble the model (e.g., Uchida & Shibata) of the emergence of a twisted flux rope into an open field region that leads to reconnection and formation of a jet. Some observations are, however, not predicted in previous models and we will discuss their implications.

Liu, Wei; Berger, T.; Title, A. M.; Tarbell, T. D.; DeRosa, M.

2010-05-01

106

Directional surface plasmon coupled luminescence for analytical sensing applications: which metal, what wavelength, what observation angle?  

PubMed

The ability of luminescent species in the near-field to both induce and couple to surface plasmons has been known for many years, with highly directional emission from films (Surface Plasmon Coupled Luminescence, SPCL) facilitating the development of sensitive near-field assay sensing platforms, to name but just one application. Because of the near-field nature of the effect, only luminescent species (fluorescence, chemiluminescence and phosphorescence) within a few hundred nanometers from the surface play a role in coupling, which in terms of biosensing, provides for limited penetration into optically dense media, such as in whole blood. Another attractive feature is the highly polarized and angular dependent emission which allows both fixed angle and wavelength dependent emission angles to be realized at high polarization ratios. In this paper, a generic procedure based on theoretical Fresnel calculations, which outlines the step-by-step selection of an appropriate metal for SPCL applications is presented. It is also shown that 11 different metals have differing properties in different spectral regions and offer either fixed angle or wavelength-dependent angular shifts in emission. In addition, it is shown that both chemiluminescence and phosphorescence can also be observed in a highly directional manner similar to coupled fluorescence. PMID:19601619

Aslan, Kadir; Geddes, Chris D

2009-08-15

107

Heliospheric Observations of STEREO-Directed Coronal Mass Ejections in 2008 - 2010: Lessons for Future Observations of Earth-Directed CMEs  

NASA Astrophysics Data System (ADS)

We present a study of coronal mass ejections (CMEs) which impacted one of the STEREO spacecraft between January 2008 and early 2010. We focus our study on 20 CMEs which were observed remotely by the Heliospheric Imagers (HIs) onboard the other STEREO spacecraft up to large heliocentric distances. We compare the predictions of the Fixed-? and Harmonic Mean (HM) fitting methods, which only differ by the assumed geometry of the CME. It is possible to use these techniques to determine from remote-sensing observations the CME direction of propagation, arrival time and final speed which are compared to in-situ measurements. We find evidence that for large viewing angles, the HM fitting method predicts the CME direction better. However, this may be due to the fact that only wide CMEs can be successfully observed when the CME propagates more than 100? from the observing spacecraft. Overall eight CMEs, originating from behind the limb as seen by one of the STEREO spacecraft can be tracked and their arrival time at the other STEREO spacecraft can be successfully predicted. This includes CMEs, such as the events on 4 December 2009 and 9 April 2010, which were viewed 130? away from their direction of propagation. Therefore, we predict that some Earth-directed CMEs will be observed by the HIs until early 2013, when the separation between Earth and one of the STEREO spacecraft will be similar to the separation of the two STEREO spacecraft in 2009 - 2010.

Lugaz, N.; Kintner, P.; Möstl, C.; Jian, L. K.; Davis, C. J.; Farrugia, C. J.

2012-08-01

108

Direct Observation of Rates of Preventive Service Delivery in Community Family Practice  

Microsoft Academic Search

Background. Data on preventive service delivery in primary care practice have been limited by indirect methods of measurement. This study describes directly observed rates of preventive service delivery during outpatient visits to community family physicians.Methods. In a multimethod cross-sectional study, research nurses directly observed consecutive patient visits in the offices of 138 family physicians in Northeast Ohio. Patient eligibility for

Kurt C. Stange; Susan A. Flocke; Meredith A. Goodwin; Robert B. Kelly; Stephen J. Zyzanski

2000-01-01

109

A direct observation instrument for assessment of nurses’ patient transfer technique (DINO)  

Microsoft Academic Search

The aim of this project was to develop a direct observation instrument to assess the work technique of nursing personnel during patient transfers and to test the validity and reliability of the instrument. An expert group developed this instrument, called DINO (DIrect Nurse Observation instrument for assessment of work technique during patient transfers), which contains 16 items divided into three

Christina Johnsson; Katarina Kjellberg; Anders Kjellberg; Monica Lagerström

2004-01-01

110

Direct Observations of Clouds on Brown Dwarfs: A Spitzer Study of Extreme Cases  

NASA Astrophysics Data System (ADS)

Clouds play a fundamental role in the emergent spectral energy distributions and observed variability of very low mass stars and brown dwarfs, yet hey have only been studied indirectly thus far. Recent indications of a broad silicate grain absorption feature in the 8-11 micron spectra of mid-type L dwarfs, and evidence that the strength of this absorption varies according to broad-band near-infrared color, may finally allow the first direct studies of clouds and condensate grain properties in brown dwarf atmospheres. We propose to observe a sample of 18 ``extreme'' L dwarfs - objects with unusually blue and red near-infrared colors - with IRAC and IRS to study the 8-11 micron feature in detail (including grain size distributions and bulk compositions), and to constrain advanced condensate cloud atmosphere models currently in development. Our program provides a unique examination of the general processes of cloud formation by focusing on the relatively warm photospheres of late-type brown dwarfs.

Burgasser, Adam; Cruz, Kelle; Cushing, Michael; Kirkpatrick, J. Davy; Looper, Dagny; Lowrance, Patrick; Marley, Mark; Saumon, Didier

2008-03-01

111

Speed-sensorless direct torque control of induction motors using an adaptive flux observer  

Microsoft Academic Search

This paper presents a new sensorless induction motor drive. The drive uses an adaptive flux observer for speed estimation and the discrete-time direct torque control technique for torque and stator flux control. The adaptive flux observer uses a mechanical model to improve the behavior during speed transients. The estimated stator flux of the adaptive observer is used in the discrete-time

Jehudi Maes; Jan A. Melkebeek

2000-01-01

112

Assimilation of wind speed and direction observations: A new formulation and results from idealized experiments  

NASA Astrophysics Data System (ADS)

We present a new methodology for assimilating wind observations in their observed form of speed and direction, while taking into account both speed and direction error. It ensures the analyzed speed and direction will be consistent with their background and observed values. The new formulation is implemented in WRFDA, and idealized experiments are used to demonstrate the potential benefit. The results suggest that analyses from the new formulation are more reasonable when compared to the conventional methodology. The forecasts generated in these idealized experiments also demonstrate the value of this new formulation.

Huang, Xiang-Yu; Gao, Feng; Jacobs, Neil; Wang, Hongli

2013-04-01

113

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

PubMed

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

Lavender; Davis; Owens

2000-09-01

114

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

115

Stimulation and Mineback Experiment Project. The Direct Observation of Hydraulic and Explosive Fracturing Tests.  

National Technical Information Service (NTIS)

Hydraulic and explosive fracturing experiments have been conducted adjacent to an existing tunnel complex at DOE's Nevada Test Site and have been directly observed by subsequent mineback through the experimental area. A proppant distribution fracture expe...

D. A. Northrop N. R. Warpinski R. A. Schmidt C. W. Smith

1978-01-01

116

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…

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

2010-01-01

117

Direct observation of blocked nanoscale surface evaporation on SiO2 nanodroplets  

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

118

Simultaneous Measurements of direct, semi-direct and indirect aerosol forcing with Stacked Autonomous UAVs: A New Observing Platform  

NASA Astrophysics Data System (ADS)

We report here first time demonstration with three autonomously flying Unmanned Aerial Vehicles (UAVs) of cloudy sky albedo, transmission atmospheric solar absorption, aerosol and cloud droplet concentrations and number densities. From these direct measurements we derive the direct, semi-direct and the first indirect aerosol forcing. The observing system consisted of 3 light weight UAVs, instrumented with miniaturized instruments (Roberts et al, 2006; Ramana et al, 2006; Corrigan et al 2006) for measuring aerosol concentrations and size distribution, cloud microphysical properties, black carbon concentration and broad band and narrow band solar fluxes. The airborne measurements were validated and augmented by the Atmospheric Brown Clouds Maldives Climate Observatory (ABC_MCO) in the island of Hanimaadhoo in the N. Indian Ocean (Corrigan et al, 2006; Ramana and Ramanathan 2006). The campaign was conducted during March and early April of 2006 when this region is subject to long range transport of pollution from S. Asia. In the stacked 3_UAV configuration, one flew in the boundary layer below clouds to characterize the aerosols feeding the clouds and the transmission of solar radiation by the absorbing aerosol layer and clouds above; the second inside the trade cumulus clouds to directly observe the fully nucleated cloud drop size and concentrations and total liquid water content; and the third above the cloud to determine the incoming solar and the reflected solar radiation. The 3-UAVs were programmed to sample the same region(or clouds) within seconds of each other, thus providing unique insights into how aerosols and boundary layer dynamics modulate the cloud microphysics and thus the albedo and solar absorption of cloudy skies in the planet. The period of observations also included a major dust-soot event which revealed a large increase in atmospheric solar absorption. We will present results on how 3- dimensional clouds with absorbing aerosols modulate atmospheric solar absorption, cloud microphysical properties, cloudy sky surface and TOA forcing and surface solar forcing. asia.ucsd.edu/MAC/secure/Index.htm

Ramanathan, V.; Roberts, G.; Ramana, M. V.; Corrigan, C.; Nguyen, H.

2006-12-01

119

Observer-based direct field orientation: analysis and comparison of alternative methods  

Microsoft Academic Search

This paper focuses on methods of achieving direct field orientation (DFO) of induction machines based on closed-loop, stator, and rotor flux observers which are well suited to both zero and very high-speed operation. Both observer topologies are dominated by a current model at zero and low speeds, and a voltage model at high speeds. Application of such rotor and stator

Patrick L. Jansen; Robert D. Lorenz; Donald W. Novotny

1994-01-01

120

Direct observation of particle deposition on the membrane surface during crossflow microfiltration  

Microsoft Academic Search

In the crossflow microfiltration of particles, a deposit cake layer tends to form on the membrane and this usually controls the performance of the filtration process. This paper presents observations of particle deposition on membrane surfaces using a non-invasive, in situ, continuous direct observation through the membrane (DOTM) technique. The particles used in the experiments were typical of microfiltration processes,

H. Li; A. G. Fane; H. G. L. Coster; S. Vigneswaran

1998-01-01

121

Easy flat embedding of oriented samples in hydrophilic resin (LR White) under controlled atmosphere: application allowing both nucleic acid hybridizations (CARD-FISH) and ultrastructural observations.  

PubMed

Hydrophilic resins present the advantage of making possible both hybridization experiments involving either antibodies or oligonucleotide probes and ultrastructural observations. Whereas various embedding protocols are available, only very few concern flat-embedded preparations. In this study we describe an easy protocol for flat embedding of small-oriented biological samples in hydrophilic resins (LR White). The most important constraints are (i) to polymerize the samples under argon-saturated atmosphere (avoiding oxygen which is an inhibitor of LR White polymerization) and (ii) to use transparent flat embedding molds. Two kinds of samples were analyzed: small pieces of large tissue that need to be accurately oriented for a valuable analysis and very small organisms such as free-living nematodes, which are very hard to investigate with conventional paraffin wax embedding techniques. Semi-thin sections strongly reinforce the quality of the observations from oligonucleotidic in situ hybridization experiments by reducing the background usually encountered in oligonucleotide probe hybridization experiments from sections. Such protocols could also permit a cheap alternative to the use of laser scanning confocal microscopes for oligonucleotidic in situ hybridization as in FISH and CARD-FISH experiments from histological sections. The interest of this embedding protocol is reinforced by the fact that molecular in situ hybridization experiments and ultrastructural observations from thin sections can be carried out from a single-small individual (<1mm in length) sample. PMID:18187186

Gros, Olivier; Maurin, Leslie C

2008-01-09

122

High-resolution direct infusion-based mass spectrometry in combination with whole 13C metabolome isotope labeling allows unambiguous assignment of chemical sum formulas.  

PubMed

A new strategy for direct infusion-based metabolite analysis employing a combination of high-resolution mass spectrometry and (13)C-isotope labeling of entire metabolomes is described. Differentially isotope labeled metabolite extracts from otherwise identically grown reference plants were prepared and infused into a Fourier transform ion cyclotron resonance mass spectrometer. The derived accurate mass lists from each extract were searched, using an in-house-developed database search tool, against a number of comprehensive metabolite databases. Comparison of the retrieved chemical formulas from both, the (12)C and (13)C samples, leads to two major advantages compared to nonisotope-based metabolite fingerprinting: first, removal of background contaminations from the result list, due to the (12)C/(13)C peak pairing principle and therefore positive identification of compounds of true biological origin; second, elimination of ambiguity in chemical formula assignment due to the same principle, leading to the clear association of one measured mass to only one chemical formula. Applying this combination of strategies to metabolite extracts of the model plant Arabidopsis thaliana therefore resulted in the reproducible identification of more than 1000 unambiguous chemical sum formulas of biological origin of which more than 80% have not been associated to Arabidopsis before. PMID:19072260

Giavalisco, Patrick; Hummel, Jan; Lisec, Jan; Inostroza, Alvaro Cuadros; Catchpole, Gareth; Willmitzer, Lothar

2008-12-15

123

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

NASA Astrophysics Data System (ADS)

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.

Viswanath, B.; Ramanathan, Shriram

2013-07-01

124

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

NASA Astrophysics Data System (ADS)

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

Aulov, O.; Lary, D. J.

2010-12-01

125

Direct Observation of Markovian Behavior of the Mechanical Unfolding of Individual Proteins  

PubMed Central

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 ?-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.

Cao, Yi; Kuske, Rachel; Li, Hongbin

2008-01-01

126

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

PubMed

The pyrolyses of phenol and d(5)-phenol (C(6)H(5)OH and C(6)D(5)OH) have been studied using a high temperature, microtubular (?tubular) SiC reactor. Product detection is via both photon ionization (10.487 eV) time-of-flight mass spectrometry and matrix isolation infrared spectroscopy. Gas exiting the heated reactor (375 K-1575 K) is subject to a free expansion after a residence time in the ?tubular reactor of approximately 50-100 ?s. The expansion from the reactor into vacuum rapidly cools the gas mixture and allows the detection of radicals and other highly reactive intermediates. We find that the initial decomposition steps at the onset of phenol pyrolysis are enol/keto tautomerization to form cyclohexadienone followed by decarbonylation to produce cyclopentadiene; C(6)H(5)OH ? c-C(6)H(6) = O ? c-C(5)H(6) + CO. The cyclopentadiene loses a H atom to generate the cyclopentadienyl radical which further decomposes to acetylene and propargyl radical; c-C(5)H(6) ? c-C(5)H(5) + H ? HC?CH + HCCCH(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(6)H(5)O-H ? C(6)H(5)O + H ? c-C(5)H(5) + CO. The direct decarbonylation reaction remains an important channel in the thermal decomposition mechanisms of the dihydroxybenzenes. Both catechol (o-HO-C(6)H(4)-OH) and hydroquinone (p-HO-C(6)H(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. PMID:22299873

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

2012-01-28

127

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

NASA Astrophysics Data System (ADS)

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

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

2012-01-01

128

Direct TEM observation of the welding of asperities between two single crystal gold films  

Microsoft Academic Search

The information of grain boundaries between two gold films in contact was directly observed on a hot stage in a transmission electron microscope at a temperature that was less than 0.4 of the gold melting point. This is believed to be the first direct evidence of metal-to-metal welding by the formation of grain boundaries at touching asperities. These welds can

Chan Siu-Wai

1988-01-01

129

IBEX Direct Observations of the Very Local Interstellar Medium -The Second Spring Viewing  

NASA Astrophysics Data System (ADS)

NASA's IBEX mission has enabled direct measurement of neutral atoms which enter our helio-sphere from local interstellar space. The IBEX spacecraft is now passing a second observation period in which the geometry is favorable to directly measure neutral atoms from outside the solar system: the "spring passage". We report here the constraints on the VLISM Helium parameters from these passages, as well as implications for the rest of the IBEX mission based on comparing these two time periods.

Saul, Lukas; Wurz, Peter; McComas, David; Möbius, Eberhard; Bzowski, Maciej; Fuselier, Stephen

130

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

SciTech Connect

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

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

2006-01-25

131

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

SciTech Connect

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

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

2012-10-22

132

High resolution observations of compact radio sources in the directions of supernova remnants  

Microsoft Academic Search

VLBI observations of five compact radio sources located in the directions of supernova remnants (SNRs) are reported which were performed at a wavelength of 2.8 or 3.7 cm with resolutions of the order of 1 milliarcsec. The sources observed (and the SNRs near them) include CL4 (the Cygnus Loop), G127.11 plus 0.54 (G127.1 plus 0.5), G74.84 plus 1.22 (G74.9 plus

B. J. Geldzahler

1978-01-01

133

An assessment of depolarisation models of crossflow microfiltration by direct observation through the membrane  

Microsoft Academic Search

Direct observation through the membrane (DOTM) has been applied to monitor the deposition of supermicron particles (3–12?m) on microfiltration membranes and to identify the critical fluxes for cake formation as a function of crossflow. The observed critical fluxes are compared with predictions from various models. It is found that the shear-induced diffusivity model predicts acceptable critical flux for latex particles

H Li; A. G Fane; H. G. L Coster; S Vigneswaran

2000-01-01

134

Recent Results from IBEX ENA and Direct Interstellar Neutral Observations and Implications for the Outer Heliosphere  

NASA Astrophysics Data System (ADS)

The Interstellar Boundary Explorer (IBEX) is the first mission to directly observe the global interaction of our heliosphere with the local interstellar medium. IBEX measures Energetic Neutral Atoms (ENAs) from ~0.1-6 keV, produced through charge exchange in the outer heliosphere. These observations led to the discovery of the IBEX ribbon of enhanced emissions, ordered by the external, interstellar magnetic field, which is superposed on a more smoothly varying globally distributed ENA flux. The first three years of IBEX observations have been recently culled and corrected for various backgrounds to produce a quantitative data set with significantly reduced statistical uncertainties. These observations show that from 2009-2011, both the ribbon and globally distributed ENA fluxes have been decreasing for all regions except the heliotail. The energy and spatial distributions of the ENAs indicate a quite direct recycling of solar wind ions into returned ribbon ENAs. In addition to ENAs from the outer heliosphere, IBEX also directly measures the interstellar neutral atoms entering from the interstellar medium; these observations include the first direct measurements of interstellar neutral H, O, and Ne. IBEX observations of interstellar He show that the heliosphere is moving more slowly with respect to the LISM than thought from previous Ulysses observations. The combination of this slower speed, IBEX and Voyager observations indicating a relatively strong interstellar magnetic field, and several independent models indicate that there is currently no Bow Shock ahead of the heliosphere. This paper summarizes these and other recent IBEX results and discusses the implications for our understanding of the outer heliosphere.

McComas, David

2013-04-01

135

Directly observed therapy for the treatment of tuberculosis—evidence based dosage guidelines  

Microsoft Academic Search

Tuberculosis is a communicable disease with public health implications and effective treatment is essential for control of the disease and prevention of the emergence of drug resistant strains. Drug therapy for this disease is well established and discussion now surrounds frequency of administration, duration of treatment and methods of improving compliance. Directly observed intermittent therapy of tuberculosis is supported by

R. Bednall; G. Dean; N. Bateman

1999-01-01

136

The direct observation of magnetic images in electromagnet vibrating sample magnetometers  

Microsoft Academic Search

The authors report incontrovertible evidence of the first direct observation of ferromagnetic images in iron-core electromagnet vibrating sample magnetometers (VSMs) and determine their magnitude. They demonstrate experimentally that the ferromagnetic image strength at low field approaches that of the magnetic sample source moment and find image contributions of up to 25% in one typical VSM system studied. Quadrature image formation

S. R. Hoon; S. N. M. Willcock

1988-01-01

137

Direct observation of the defect structure of polycrystalline diamond by scanning electron microscopy  

Microsoft Academic Search

A method has been demonstrated to directly observe the surface crystallography and defect structures in diamond films by scanning electron microscopy. Individual diamond crystals in the polycrystalline films are polished to a rms smoothness of less than 2 nm using iron metal at temperatures in excess of 725 °C. In the absence of topography, the detailed microstructure of the films

A. B. Harker; J. F. DeNatale; J. F. Flintoff; J. J. Breen

1993-01-01

138

Direct observation of the infinite percolation cluster in thin films: Evidence for a double percolation process  

NASA Astrophysics Data System (ADS)

Direct observation of the infinite percolation cluster at the percolation threshold is shown. We use crystallization propagation in an amorphous thin film. The morphological analysis of the infinite cluster shows good agreement with that predicted by percolation theory. The crystallization process can be described using an invasion percolation model in a fractal network. At the macroscopic scale, crystallization induces a double percolation.

Jensen, Pablo; Melinon, Patrice; Treilleux, Michel; Hu, Jian Xiong; Dumas, Jean; Hoareau, Alain; Cabaud, Bernard

1993-03-01

139

Direct observation of the infinite percolation cluster in thin films: Evidence for a double percolation process  

Microsoft Academic Search

Direct observation of the infinite percolation cluster at the percolation threshold is shown. We use crystallization propagation in an amorphous thin film. The morphological analysis of the infinite cluster shows good agreement with that predicted by percolation theory. The crystallization process can be described using an invasion percolation model in a fractal network. At the macroscopic scale, crystallization induces a

Pablo Jensen; Patrice Melinon; Michel Treilleux; Jian Xiong Hu; Jean Dumas; Alain Hoareau; Bernard Cabaud

1993-01-01

140

Direct observation of Coulomb crystals and liquids in strongly coupled rf dusty plasmas  

Microsoft Academic Search

The strongly coupled dusty plasmas are formed by suspending negatively charged SiO2 fine particles with 10 mum diameter in weakly ionized rf Ar discharges. The Coulomb crystals and liquids are directly observed for the first time using an optical microscope. By properly controlling the system parameters, hexagonal, fcc and bcc crystal structures and solids with coexisting different crystal structures can

J. H. Chu; Lin I

1994-01-01

141

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.

2013-01-01

142

Global anthropogenic aerosol direct forcing derived from satellite and ground-based observations  

Microsoft Academic Search

A global estimate of the direct effects of anthropogenic aerosols on solar radiation in cloudy skies is obtained by integrating satellite and ground-based observations with models of aerosol chemistry, transport, and radiative transfer. The models adopt global distribution of aerosol optical depths (from MODIS), clouds, water vapor, ozone, and surface albedo from various satellite climatology. Gaps and errors in satellite

Chul Eddy Chung; V. Ramanathan; Dohyeong Kim; I. A. Podgorny

2005-01-01

143

Direct Observations of Along-Isopycnal Upwelling and Diapycnal Velocity at a Shelfbreak Front  

Microsoft Academic Search

By mapping the three-dimensional density field while simultaneously tracking a subsurface, isopycnal float, direct observations of upwelling along a shelfbreak front were made on the southern flank of Georges Bank. The thermohaline and bio-optical fields were mapped using a towed undulating vehicle, and horizontal velocity was measured with a shipboard acoustic Doppler current profiler. A subsurface isopycnal float capable of

John A. Barth; Dave Hebert; Andrew C. Dale; David S. Ullman

2004-01-01

144

A hybrid signal injection and sliding mode observer for direct torque and flux controlled IPMSM drive  

Microsoft Academic Search

This paper proposes a new speed sensorless direct torque and flux controlled interior permanent magnet synchronous motor (IPMSM) drive. Closed-loop control of both the torque and stator flux linkage are achieved by using two proportional-integral (PI) controllers. The reference voltage vectors are generated by a SVM unit. The drive uses an adaptive sliding mode observer for joint stator flux and

Gilbert Foo; M. F. Rahman

2009-01-01

145

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

146

Direct observations of the mechanisms of interference between Daphnia and Keratella cochlearis  

Microsoft Academic Search

Direct observation was used to describe and quantify four types of interaction between Daphnia (D. pulex, D. rosea, D. galeata mendotae, D. ambigua, and D. magna) and the rotifer, Keratella cochlearis f. tecta. The types of encounter differed primarily in duration, in the appendage move- ments elicited in Daphnia, and in the damage lo Keratella. Egg-carrying rotifers were just as

CAROLYN W. BURNS; JOHN J. GILBERT

1986-01-01

147

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

148

Assessment of welfare on 24 commercial UK dairy goat farms based on direct observations  

Microsoft Academic Search

The preliminary findings from an investigation into the health and welfare of goats on commercial dairy goat farms in the UK are described. An assessment protocol involving direct observations of the goats was developed in order to assess their welfare. Twenty-four dairy goat farms in England and Wales were visited and assessed during the period autumn 2004 to summer 2005.

K. Anzuino; N. J. Bell; K. J. Bazeley; C. J. Nicol

2010-01-01

149

A direct construction of nonlinear discrete-time observer with linearizable error dynamics  

Microsoft Academic Search

We provide a direct method for the construction of a change of coordinates for the design of nonlinear discrete-time observers. An explicit expression of a change of coordinates is given. Some simulations for chaotic systems, such as Lozi system and Henon system, are provided to illustrate the method. The proposed approach can be applied to continuous-time systems once the corresponding

MingQing Xiao

2005-01-01

150

A direct method for the construction of nonlinear discrete-time observer with linearizable error dynamics  

Microsoft Academic Search

We provide a direct method for the design of nonlinear discrete-time observers by a construction of a change of variables. An explicit expression of the change of variables is given. Some simulations for chaotic systems, such as Lozi system and He´non system, are provided to illustrate the proposed method.

MingQing Xiao

2006-01-01

151

The Directly Observed Therapy Short-Course (DOTS) strategy in Samara Oblast, Russian Federation  

Microsoft Academic Search

BACKGROUND: The World Health Organisation (WHO) defines Russia as one of the 22 highest-burden countries for tuberculosis (TB). The WHO Directly Observed Treatment Short Course (DOTS) strategy employing a standardised treatment for 6 months produces the highest cure rates for drug sensitive TB. The Russian TB service traditionally employed individualised treatment. The purpose of this study was to implement a

Y Balabanova; F Drobniewski; I Fedorin; S Zakharova; V Nikolayevskyy; R Atun; R Coker

2006-01-01

152

Direct Observation of Dynamical Bifurcation between Two Driven Oscillation States of a Josephson Junction  

Microsoft Academic Search

We performed a novel phase-sensitive microwave reflection experiment which directly probes the dynamics of the Josephson plasma resonance in both the linear and the nonlinear regime. When the junction was driven below the plasma frequency into the nonlinear regime, we observed for the first time the transition between two different dynamical states predicted for nonlinear systems. In our experiment, this

I. Siddiqi; R. Vijay; F. Pierre; C. M. Wilson; L. Frunzio; M. Metcalfe; C. Rigetti; R. J. Schoelkopf; M. H. Devoret; D. Vion; D. Esteve

2005-01-01

153

Using Surface Observations to Constrain the Direction and Magnitude of Mantle Flow Beneath Western North America  

Microsoft Academic Search

While the motions of the surface tectonic plates are well determined, the accompanying horizontal mantle flow is not. Observations of surface deformation (GPS velocities and Quaternary fault slip rates) and upper mantle seismic anisotropy are combined for the first time, to provide a direct estimate of this flow field. We apply our investigation to western North America where seismic tomography

W. E. Holt; P. G. Silver

2001-01-01

154

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

PubMed

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

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

2013-05-01

155

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

156

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

157

Direct simulation of a directional solidification experiment observed in situ and real-time using X-ray imaging  

NASA Astrophysics Data System (ADS)

It has been shown in the last decade that in situ and real-time observation of metallic alloy solidification is possible by using X-ray monitoring conducted at third generation synchrotron sources. A detailed analysis of a Bridgman experiment carried out at ESRF with an Al - 3.5 wt% Ni alloy was presented earlier [1]. This article proposes a direct simulation of the solidification of the entire sample for this experiment, in which all the dendritic grains are individually represented as they nucleate and grow in the experiment. This is possible by extracting from the radiographs a list of all the nucleated grains, including the positions and orientations of their main trunks. Simulation is performed using a two-dimensional (2D) Cellular Automaton (CA) - Finite Element (FE) model. As a result of the coupling between the CA and FE methods, consequences of the macroscopic transport of heat, liquid momentum and solute mass on the development of the dendritic grain structure are accounted for, and vice versa. The macroscopic deformation of the columnar front observed during the experiment is reproduced, as well as the columnar-to-equiaxed transition. The influence of flow patterns on macrosegregation is also discussed.

Reinhart, G.; Gandin, Ch-A.; Mangelinck-Noël, N.; Nguyen-Thi, H.; Billia, B.; Baruchel, J.

2012-07-01

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 Observation of the Dynamics of Semiflexible Polymers in Shear Flow  

NASA Astrophysics Data System (ADS)

The flow behavior of polymeric liquids can be traced back to the complex conformational dynamics of polymer molecules in shear flow, which poses a major challenge to theory and experiment alike due to the inherently large number of degrees of freedom. Here we directly determine the configurational dynamics of individual actin filaments with varying lengths in a well defined shear geometry by combining microscopy, microfluidics, and a semiautomated moving stage. This allows the identification of the microscopic mechanisms and the derivation of an analytical model for the dynamics of individual filaments based on the balance of drag, bending, and stochastic forces.

Harasim, Markus; Wunderlich, Bernhard; Peleg, Orit; Kröger, Martin; Bausch, Andreas R.

2013-03-01

160

Direct observation of NH2* reactions with oxygen, amino acids, and melanins.  

PubMed

We report the direct observation of the quenching of the weakly absorbing transient due to the amino radical by oxygen and, hence determine, by a totally direct method, the corresponding rate constant (k = (1.1 +/- 0.1) x 10(9) dm3 mol(-1) s(-1)). We also report the rate constants for the reactions of the amino radical with several amino acids and models of black eumelanin and blond/red phaeomelanin. These reactions lead to a mechanism, based on free radicals, that can explain why ammonia is useful in commercial hair (melanin) bleaching, avoiding excessive amino acid (hair protein) damage. PMID:18215026

Clarke, K; Edge, R; Johnson, V; Land, E J; Navaratnam, S; Truscott, T G

2008-01-24

161

Direct observation of charge ordering in magnetite using resonant multiwave x-ray diffraction.  

PubMed

Charge disproportion at octahedral Fe sites in magnetite was observed at low temperature using two inversion-symmetry related three-wave resonant x-ray diffraction, 022-311 and 002-?3?1, near the iron K edge. Both of the three-wave cases involve the (002) forbidden-weak reflection. The self-normalized three-wave to two-wave (002) diffraction intensity ratio automatically cancels the self-absorption effect and leads to direct determination of charge disproportion for magnetite below 120 K. This approach provides a more direct and effective way for extracting charge-ordering information. PMID:22540813

Weng, Shih-Chang; Lee, Yen-Ru; Chen, Cheng-Gang; Chu, Chia-Hung; Soo, Yun-Liang; Chang, Shih-Lin

2012-04-05

162

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

SciTech Connect

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

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

2007-07-01

163

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

SciTech Connect

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

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

2007-10-22

164

Direct observation of quantum phonon fluctuations in a one-dimensional Bose gas.  

PubMed

We report the first direct observation of collective quantum fluctuations in a continuous field. Shot-to-shot atom number fluctuations in small subvolumes of a weakly interacting, ultracold atomic 1D cloud are studied using in situ absorption imaging and statistical analysis of the density profiles. In the cloud centers, well in the quantum quasicondensate regime, the ratio of chemical potential to thermal energy is ?/k(B)T?4, and, owing to high resolution, up to 20% of the microscopically observed fluctuations are quantum phonons. Within a nonlocal analysis at variable observation length, we observe a clear deviation from a classical field prediction, which reveals the emergence of dominant quantum fluctuations at short length scales, as the thermodynamic limit breaks down. PMID:23003615

Armijo, Julien

2012-06-01

165

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

PubMed Central

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

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

2010-01-01

166

First direct observation of the Van Hove singularity in the tunnelling spectra of cuprates  

PubMed Central

In two-dimensional (2D) lattices, the electronic levels are unevenly spaced, and the density of states (DOS) displays a logarithmic divergence known as the Van Hove singularity (VHS). This is the case in particular for the layered cuprate superconductors. The scanning tunnelling microscope (STM) probes the DOS, and is therefore the ideal tool to observe the VHS. No STM study of cuprate superconductors has reported such an observation so far giving rise to a debate about the possibility of observing directly the normal state DOS in the tunnelling spectra. In this study, we show for the first time that the VHS is unambiguously observed in STM measurements performed on the cuprate Bi2Sr2CuO6+? (Bi-2201). Beside closing the debate, our analysis proves the presence of the pseudogap in the overdoped side of the phase diagram of Bi-2201 and discredits the scenario of the pseudogap phase crossing the superconducting dome.

Piriou, A.; Jenkins, N.; Berthod, C.; Maggio-Aprile, I.; Fischer, ?.

2011-01-01

167

Direct observation of mass oscillations due to ablative Richtmyer-Meshkov instability in plastic targets.  

PubMed

We report the first direct experimental observation of the ablative Richtmyer-Meshkov instability. It manifests itself in oscillations of areal mass that occur during the shock transit time, which are caused by the "rocket effect" or dynamic overpressure characteristic of interaction between the laser absorption zone and the ablation front. With the 4-ns-long Nike KrF laser pulse and our novel diagnostic technique (monochromatic x-ray imaging coupled to a streak camera) we were able to register a peak and a valley of the areal-mass variation before the observed onset of the Rayleigh-Taylor growth. PMID:11800835

Aglitskiy, Y; Velikovich, A L; Karasik, M; Serlin, V; Pawley, C J; Schmitt, A J; Obenschain, S P; Mostovych, A N; Gardner, J H; Metzler, N

2001-12-06

168

Direct observation of a nodeless superconducting energy gap in the optical conductivity of iron-pnictides  

Microsoft Academic Search

The temperature-dependent optical reflectivity and complex transmissivity of an epitaxially grown Ba(Fe$_{0.9}$Co$_{0.1}$)$_2$As$_2$ thin film were measured and the optical conductivity and permittivity evaluated over a wide frequency range. The opening of the superconducting gap $2\\\\Delta_0 = 3.7$ meV below $T_c\\\\approx 20$ K is {\\\\em directly} observed by a completely vanishing optical conductivity. The temperature and frequency dependent electrodynamic properties of

B. Gorshunov; D. Wu; A. A. Voronkov; P. Kallina; K. Iida; S. Haindl; F. Kurth; L. Schultz; B. Holzapfel; M. Dressel

2009-01-01

169

Direct observation of charge inversion by multivalent ions as a universal electrostatic phenomenon.  

PubMed

We have directly observed reversal of the polarity of charged surfaces in water upon the addition of trivalent and quadrivalent ions using atomic force microscopy. The bulk concentration of multivalent ions at which charge inversion reversibly occurs depends only very weakly on the chemical composition, surface structure, size, and lipophilicity of the ions, but is very sensitive to their valence. These results support the theoretical proposal that spatial correlations between ions are the driving mechanism behind charge inversion. PMID:15525062

Besteman, K; Zevenbergen, M A G; Heering, H A; Lemay, S G

2004-10-20

170

The assessment of maladaptive parent-child interaction by direct observation: An analysis of methods  

Microsoft Academic Search

Six direct observation technologies for assessing parent-child interactions are examined: Descriptive-narrative, event recording, three types of interval sampling, and sequential event recording. Selected articles in the clinical literature are reviewed to illustrate use of each technology. Furthermore, the yield of each procedure in terms of four assessment criteria was evaluated: precise description of the parent-child interaction, target selection, identification of

Mark W. Roberts; Rex Forehand

1978-01-01

171

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

Microsoft Academic Search

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

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

2003-01-01

172

Direct Observation of Sinusoidal Ultrasonically Induced Birefringence in Liquid Crystal in the Isotropic Phase  

Microsoft Academic Search

Direct observation of sinusoidal ultrasonically induced birefringence was successfully carried out in 4-cyano-4'-pentylbiphenyl in the isotropic phase. The temperature dependence of the birefringence per unit intensity was compared with the estimated value using the theoretical expression for ultrasonically induced birefringence based on the de Gennes' phenomenological theory for translational-reorientational coupling. The agreement of the experimental results with those from the

Tatsuro Matsuoka; Yoshitaka Mizutani; Shinobu Koda

2005-01-01

173

Direct Observation of Sinusoidal Ultrasonically Induced Birefringence in Liquid Crystal in the Isotropic Phase  

NASA Astrophysics Data System (ADS)

Direct observation of sinusoidal ultrasonically induced birefringence was successfully carried out in 4-cyano-4'-pentylbiphenyl in the isotropic phase. The temperature dependence of the birefringence per unit intensity was compared with the estimated value using the theoretical expression for ultrasonically induced birefringence based on the de Gennes' phenomenological theory for translational-reorientational coupling. The agreement of the experimental results with those from the estimation validates the theoretical treatment.

Matsuoka, Tatsuro; Mizutani, Yoshitaka; Koda, Shinobu

2005-06-01

174

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

Microsoft Academic Search

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

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

2007-01-01

175

Direct observation of a concealed glass transition in a Mg-Ni-Nd metallic glass  

Microsoft Academic Search

Glass transition and crystallization behavior of Mg75Ni10Nd15 metallic glass has been studied by a temperature-modulated differential scanning calorimeter (TMDSC) and a normal differential scanning calorimeter (DSC). The truly vitreous state of the as-spun Mg75Ni10Nd15 alloy was confirmed by the direct observation of the glass transition through TMDSC measurements, which was not perceptible in the normal DSC heating scans. It was

Z. P. Lu; C. T. Liu; C. H. Kam; Y. Li

2003-01-01

176

Direct observation of a concealed glass transition in a Mg–Ni–Nd metallic glass  

Microsoft Academic Search

Glass transition and crystallization behavior of Mg75Ni10Nd15 metallic glass has been studied by a temperature-modulated differential scanning calorimeter (TMDSC) and a normal differential scanning calorimeter (DSC). The truly vitreous state of the as-spun Mg75Ni10Nd15 alloy was confirmed by the direct observation of the glass transition through TMDSC measurements, which was not perceptible in the normal DSC heating scans. It was

Z. P. Lu; C. T. Liu; C. H. Kam; Y. Li

2003-01-01

177

Direct time-domain observation of laser pulse filaments in transparent media  

SciTech Connect

The interplay among self-focusing, energy depletion, and plasma formation is fundamental to the understanding of laser-matter interaction. In this article, we present the first direct time-resolved observations of the propagation of intense femtosecond laser pulses experiencing conical emission, self-focusing, self-guiding, beam filamentation, plasma defocusing, and continuum generation in wide-band-gap dielectrics. We demonstrate that continuum generation involves different mechanisms as a function of deposited energy.

Dachraoui, H.; Oberer, C.; Michelswirth,; Heinzmann, U. [Molecular and Surface Physics, Faculty of Physics, Bielefeld University, D-33615 Bielefeld (Germany)

2010-10-15

178

Observation of Direct Ionization of He by Highly Charged Ions at Low Velocity  

Microsoft Academic Search

We have observed direct target ionization of He at low velocity (0.2 to 1.7 a.u.) by highly charged ions of C6+, N7+, O8+, Ar16+, and Xe30+. The measured single ionization cross sections increase rapidly with increasing velocity. The cross sections, divided by the charge of the incident projectile, are found to lie on a universal curve when plotted versus the

W. Wu; C. L. Cocke; J. P. Giese; F. Melchert; M. L. A. Raphaelian; M. Stoeckli

1995-01-01

179

Direct observation of oscillatory-shear-induced order in colloidal suspensions  

NASA Astrophysics Data System (ADS)

We use optical microscopy to directly study ordering in concentrated colloidal suspensions of model hard spheres subjected to oscillatory shear in a parallel plate geometry. At high strain amplitude the particles order quickly into hexagonal planes in the plane of shear, oriented so that a close-packed direction is parallel to the velocity axis, corresponding to previous scattering observations in other geometries. At low strain a polycrystalline structure forms, consisting of hexagonally ordered regions now with a distribution of different orientations, peaked around an orientation where a close-packed direction is now perpendicular to the velocity axis. Such polycrystallinity explains the evidence of disorder previously noted in scattering patterns. The ordered regions grow until ``grains'' fill the sample. Various examples of local disorder are observed in the shear-ordered structures, including vacancies, dislocations, and stacking faults. The observed motion of the planes during the cycle is complicated, but there is some evidence of a ``zigzag'' motion of planes at high strain, as has been proposed in previous studies.

Haw, M. D.; Poon, W. C. K.; Pusey, P. N.

1998-06-01

180

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

181

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

PubMed

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

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

2012-10-01

182

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.

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

2012-01-01

183

Rationale, design, and sample characteristics of a randomized controlled trial of directly observed antiretroviral therapy delivered in methadone clinics  

PubMed Central

Background Directly observed therapy (DOT) programs for HIV treatment have demonstrated feasibility, acceptability, and improved viral suppression, but few have been rigorously tested. We describe a randomized controlled trial testing the efficacy of an antiretroviral DOT program in methadone maintenance clinics. Our objective was to determine if DOT is more efficacious than self-administered antiretroviral therapy for reducing HIV viral load, improving adherence, and reducing drug resistance among opioid dependent drug users receiving methadone treatment. Methods Participants were randomized to treatment as usual (TAU) or antiretroviral DOT for the 24-week intervention. TAU participants received standard adherence counseling, and DOT participants received standard adherence counseling plus directly observed antiretroviral therapy, which was delivered at the same time as they received daily methadone. Assessments occurred at baseline, weekly for 8 weeks, and then monthly for 4 months. Our primary outcomes were between group changes from baseline to the end of the intervention in: HIV viral load, antiretroviral adherence, and number of viral mutations. Results Between June 2004 and August 2007, we screened 3,231 methadone maintained patients and enrolled 77; 39 participants were randomized to DOT and 38 to TAU. 65 completed the 24-week intervention. Conclusions Our trial will allow rigorous evaluation of the efficacy of directly observed antiretroviral therapy delivered in methadone clinics for improving adherence and clinical 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 HIV-infected drug users receiving methadone for opioid dependence.

Berg, Karina M.; Mouriz, Jennifer; Li, Xuan; Duggan, Elise; Goldberg, Uri; Arnsten, Julia H.

2009-01-01

184

Direct Observation of Charge Carrier Diffusion and Localization in an InGaN Multi Quantum Well  

NASA Astrophysics Data System (ADS)

The temperature dependence of the diffusion constant of an InGaN/GaN multi quantum well (MQW) emitting at 465 nm is studied by time of flight measurements. Utilizing a confocal microscopy setup and scanning the pinhole across the image plane allows us to observe charge carrier diffusion in real space with submicron resolution and to determine the diffusion constant by fitting the time delays of the spatially dependent photoluminescence signal using a simple diffusion model. We see direct evidence for a strong decrease of charge carrier mobility below 110 K and for localization of charge carriers at 10 K. The diffusion constant increases continuously with temperature up to about 0.27 cm2 s-1 at 293 K.

Solowan, Hans-Michael; Danhof, Julia; Schwarz, Ulrich T.

2013-08-01

185

Real-time direct observation of Li in LiCoO2 cathode material  

NASA Astrophysics Data System (ADS)

The direct observation of light elements such as Li is a challenge even for state-of-the-art electron microscopy techniques because such elements scatter electrons only weakly. Using the annular bright field scanning transmission electron microscopy imaging technique, we have simultaneously visualized columns of Li, O, and Co ions in the lithium-ion battery cathode material LiCoO2, which is one of the most important cathode materials for industrial applications. The annular bright field image exhibits a good signal-to-noise ratio and the image contrast is not reversed as the specimen thickness changes. The direct visualization of light elements in real time with this method represents an important breakthrough in characterizing the active materials in solid-state electrochemical devices.

Huang, Rong; Hitosugi, Taro; Findlay, Scott D.; Fisher, Craig A. J.; Ikuhara, Yumi H.; Moriwake, Hiroki; Oki, Hideki; Ikuhara, Yuichi

2011-01-01

186

Direct observation of a propagating spin wave induced by spin-transfer torque.  

PubMed

Spin torque oscillators with nanoscale electrical contacts are able to produce coherent spin waves in extended magnetic films, and offer an attractive combination of electrical and magnetic field control, broadband operation, fast spin-wave frequency modulation, and the possibility of synchronizing multiple spin-wave injection sites. However, many potential applications rely on propagating (as opposed to localized) spin waves, and direct evidence for propagation has been lacking. Here, we directly observe a propagating spin wave launched from a spin torque oscillator with a nanoscale electrical contact into an extended Permalloy (nickel iron) film through the spin transfer torque effect. The data, obtained by wave-vector-resolved micro-focused Brillouin light scattering, show that spin waves with tunable frequencies can propagate for several micrometres. Micromagnetic simulations provide the theoretical support to quantitatively reproduce the results. PMID:21873993

Madami, M; Bonetti, S; Consolo, G; Tacchi, S; Carlotti, G; Gubbiotti, G; Mancoff, F B; Yar, M A; Akerman, J

2011-08-28

187

Direct atomic force microscopy observation of DNA tile crystal growth at the single-molecule level.  

PubMed

While the theoretical implications of models of DNA tile self-assembly have been extensively researched and such models have been used to design DNA tile systems for use in experiments, there has been little research testing the fundamental assumptions of those models. In this paper, we use direct observation of individual tile attachments and detachments of two DNA tile systems on a mica surface imaged with an atomic force microscope (AFM) to compile statistics of tile attachments and detachments. We show that these statistics fit the widely used kinetic Tile Assembly Model and demonstrate AFM movies as a viable technique for directly investigating DNA tile systems during growth rather than after assembly. PMID:22694312

Evans, Constantine G; Hariadi, Rizal F; Winfree, Erik

2012-06-13

188

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

PubMed Central

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

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

2013-01-01

189

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

PubMed

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

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

2013-01-01

190

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

NASA Astrophysics Data System (ADS)

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

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

2011-06-01

191

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

192

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

NASA Astrophysics Data System (ADS)

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

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

193

Direct observations of ecosystem light use efficiency from MAIAC/MODIS  

NASA Astrophysics Data System (ADS)

The fraction of photosynthetically active radiation (FPAR) incident upon and absorbed by vegetated ecosystems is a standard MODIS product. From this and satellite observations of incident PAR flux, ecosystem photosynthetic capacity can be measured remotely, but not ecosystem photosynthetic rate. The missing link is remotely sensed observations of ecosystem light-use efficiency (LUE) (the efficiency with which ecosystems convert absorbed PAR into carbon), which is modulated by plant physiology in response to rapidly changing extant environmental conditions. LUE is currently estimated from models that attempt to relate plant physiological response to their environment (soil moisture, fertility etc); however accuracies are limited by the uncertainty of the required inputs at landscape scales - primarily precipitation and soil hydrological characteristics. To rectify this situation, a number of recent studies were directed at measuring ecosystem LUE directly from MODIS using a photochemical reflectance index (PRI) - based on the reflectance measurements from MODIS bands 11 and 12 (~531 and ~550 nm). Results however have shown that quantifying the relationship between MODIS PRI and ecosystem LUE remains challenging. In addition, atmospherically induced aerosol variability confounds the subtle PRI signal. Here, we introduce and evaluate a new approach (MAIAC) that minimizes cloud interference, and aerosol and surface bidirectional reflectance effects on PRI. Using tower measured LUE, we evaluate our approach and demonstrate a strong relationship (r2=0.74, p<0.01) between tower based observations of both PRI and LUE and those from atmospherically corrected MODIS data; these correlations remained robust throughout the vegetation period of 2006. Swath observations yielded better results than gridded data (r2=0.58, p<0.01) both of which included forward and backscatter observations. As expected from theoretical considerations, MODIS PRI values were strongly related to canopy shadow fraction viewed by MODIS.

Hall, F. G.; Hilker, T.; Lyapustin, A.; Wang, Y.; Coops, N.; Drolet, G.

2009-12-01

194

Direct observation of the uptake of outer membrane proteins by the periplasmic chaperone Skp.  

PubMed

The transportation of membrane proteins through the aqueous subcellular space is an important and challenging process. Its molecular mechanism and the associated structural change are poorly understood. Periplasmic chaperones, such as Skp in Escherichia coli, play key roles in the transportation and protection of outer membrane proteins (OMPs) in Gram-negative bacteria. The molecular mechanism through which Skp interacts with and protects OMPs remains mysterious. Here, a combined experimental and molecular dynamics simulation study was performed to gain the structural and dynamical information in the process of OMPs and Skp binding. Stopped-flow experiments on site specific mutated and labeled Skp and several OMPs, namely OmpC, the transmembrane domain of OmpA, and OmpF, allowed us to obtain the mechanism of OMP entering the Skp cavity, and molecular dynamics simulations yielded detailed molecular interactions responsible for this process. Both experiment and simulation show that the entrance of OMP into Skp is a highly directional process, which is initiated by the interaction between the N-terminus of OMP and the bottom "tentacle" domain of Skp. The opening of the more flexible tentacle of Skp, the non-specific electrostatic interactions between OMP and Skp, and the constant formation and breaking of salt bridges between Skp and its substrate together allow OMP to enter Skp and gradually "climb" into the Skp cavity in the absence of an external energy supply. PMID:23049938

Lyu, Zhi-Xin; Shao, Qiang; Gao, Yi Qin; Zhao, Xin Sheng

2012-09-26

195

Direct Observation of the Uptake of Outer Membrane Proteins by the Periplasmic Chaperone Skp  

PubMed Central

The transportation of membrane proteins through the aqueous subcellular space is an important and challenging process. Its molecular mechanism and the associated structural change are poorly understood. Periplasmic chaperones, such as Skp in Escherichia coli, play key roles in the transportation and protection of outer membrane proteins (OMPs) in Gram-negative bacteria. The molecular mechanism through which Skp interacts with and protects OMPs remains mysterious. Here, a combined experimental and molecular dynamics simulation study was performed to gain the structural and dynamical information in the process of OMPs and Skp binding. Stopped-flow experiments on site specific mutated and labeled Skp and several OMPs, namely OmpC, the transmembrane domain of OmpA, and OmpF, allowed us to obtain the mechanism of OMP entering the Skp cavity, and molecular dynamics simulations yielded detailed molecular interactions responsible for this process. Both experiment and simulation show that the entrance of OMP into Skp is a highly directional process, which is initiated by the interaction between the N-terminus of OMP and the bottom “tentacle” domain of Skp. The opening of the more flexible tentacle of Skp, the non-specific electrostatic interactions between OMP and Skp, and the constant formation and breaking of salt bridges between Skp and its substrate together allow OMP to enter Skp and gradually “climb” into the Skp cavity in the absence of an external energy supply.

Lyu, Zhi-Xin; Shao, Qiang; Gao, Yi Qin; Zhao, Xin Sheng

2012-01-01

196

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

197

Direct Observation of Protein Microcrystals in Crystallization Buffer by Atmospheric Scanning Electron Microscopy  

PubMed Central

X-ray crystallography requires high quality crystals above a given size. This requirement not only limits the proteins to be analyzed, but also reduces the speed of the structure determination. Indeed, the tertiary structures of many physiologically important proteins remain elusive because of the so-called “crystallization bottleneck”. Once microcrystals have been obtained, crystallization conditions can be optimized to produce bigger and better crystals. However, the identification of microcrystals can be difficult due to the resolution limit of optical microscopy. Electron microscopy has sometimes been utilized instead, with the disadvantage that the microcrystals usually must be observed in vacuum, which precludes the usage for crystal screening. The atmospheric scanning electron microscope (ASEM) allows samples to be observed in solution. Here, we report the use of this instrument in combination with a special thin-membrane dish with a crystallization well. It was possible to observe protein crystals of lysozyme, lipase B and a histone chaperone TAF-I? in crystallization buffers, without the use of staining procedures. The smallest crystals observed with ASEM were a few ?m in width, and ASEM can be used with non-transparent solutions. Furthermore, the growth of salt crystals could be monitored in the ASEM, and the difference in contrast between salt and protein crystals made it easy to distinguish between these two types of microcrystals. These results indicate that the ASEM could be an important new tool for the screening of protein microcrystals.

Maruyama, Yuusuke; Ebihara, Tatsuhiko; Nishiyama, Hidetoshi; Konyuba, Yuji; Senda, Miki; Numaga-Tomita, Takuro; Senda, Toshiya; Suga, Mitsuo; Sato, Chikara

2012-01-01

198

Direct Observation of Counseling on Colorectal Cancer in Rural Primary Care Practices  

PubMed Central

To better understand colorectal cancer (CRC) screening practices in primary care, medical students directly observed physician-patient encounters in 38 physician offices. CRC was discussed with 14% of patients ?50 years of age; 87% of discussions were initiated by the physician. The rate of discussions varied among the practices from 0% to 41% of office visits. Discussions were more common for new patient visits, with younger patients, and in the 24% of offices that utilized flow sheets. The frequency of CRC discussions in physician offices varies widely. More widespread implementation of simple office systems, such as flow sheets, is needed to improve CRC screening rates.

Ellerbeck, Edward F; Engelman, Kimberly K; Gladden, Joe; Mosier, Michael C; Raju, G S; Ahluwalia, Jasjit S

2001-01-01

199

Direct observation of interband spin-orbit coupling in a two-dimensional electron system.  

PubMed

We report the direct observation of interband spin-orbit (SO) coupling in a two-dimensional (2D) surface electron system, in addition to the anticipated Rashba spin splitting. Using angle-resolved photoemission experiments and first-principles calculations on Bi-Ag-Au heterostructures, we show that the effect strongly modifies the dispersion as well as the orbital and spin character of the 2D electronic states, thus giving rise to considerable deviations from the Rashba model. The strength of the interband SO coupling is tuned by the thickness of the thin film structures. PMID:23003070

Bentmann, Hendrik; Abdelouahed, Samir; Mulazzi, Mattia; Henk, Jürgen; Reinert, Friedrich

2012-05-07

200

Observation of intermediate template directed SiC nanowire growth in Si-C-N systems.  

PubMed

SiC nanowires (NWs) are commonly prepared in a Si-C-N system, but its formation mechanism is not fully understood. High resolution transmission electron microscopy and electron energy loss spectroscopy observation recorded the growth process of how Si(3)N(4) NWs were transformed into SiC NWs, and demonstrated the validity of an intermediate template directed SiC NW growth via carbothermal reduction of intermediate Si(3)N(4) NWs in a Si-C-N system. Based on this discovery, an intermediate-template growth mechanism of SiC NWs was proposed. PMID:23018814

Xia, Min; Yang, Shize; Guo, Hongyan; Hao, Wei; Yan, Qingzhi; Ge, Changchun

2012-09-27

201

Direct observation of feedout-related mass oscillations in plastic targets.  

PubMed

"Feedout" means the transfer of mass perturbations from the rear to the front surface of a driven target. When a planar shock wave breaks out at a rippled rear surface of the target, a lateral pressure gradient drives sonic waves in a rippled rarefaction wave propagating back to the front surface. This process redistributes mass in the volume of the target, forming the feedout-generated seed for ablative Rayleigh-Taylor (RT) instability. We report the first direct experimental observation of areal-mass oscillation associated with feedout, followed by the onset of exponential RT growth. PMID:11800836

Aglitskiy, Y; Velikovich, A L; Karasik, M; Serlin, V; Pawley, C J; Schmitt, A J; Obenschain, S P; Mostovych, A N; Gardner, J H; Metzler, N

2001-12-06

202

History dependence of directly observed magnetocaloric effects in (Mn, Fe)As  

NASA Astrophysics Data System (ADS)

We use a calorimetric technique operating in sweeping magnetic field to study the thermomagnetic history-dependence of the magnetocaloric effect (MCE) in Mn0.985Fe0.015As. We study the magnetization history for which a ``colossal'' MCE has been reported when inferred indirectly via a Maxwell relation. We observe no colossal effect in the direct calorimetric measurement. We further examine the impact of mixed-phase state on the MCE and show that the first order contribution scales linearly with the phase fraction. This validates various phase-fraction based methods developed to remove the colossal peak anomaly from Maxwell-based estimates.

Bratko, Milan; Morrison, Kelly; de Campos, Ariana; Gama, Sergio; Cohen, Lesley F.; Sandeman, Karl G.

2012-06-01

203

Direct Observation of Interband Spin-Orbit Coupling in a Two-Dimensional Electron System  

NASA Astrophysics Data System (ADS)

We report the direct observation of interband spin-orbit (SO) coupling in a two-dimensional (2D) surface electron system, in addition to the anticipated Rashba spin splitting. Using angle-resolved photoemission experiments and first-principles calculations on Bi-Ag-Au heterostructures, we show that the effect strongly modifies the dispersion as well as the orbital and spin character of the 2D electronic states, thus giving rise to considerable deviations from the Rashba model. The strength of the interband SO coupling is tuned by the thickness of the thin film structures.

Bentmann, Hendrik; Abdelouahed, Samir; Mulazzi, Mattia; Henk, Jürgen; Reinert, Friedrich

2012-05-01

204

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

205

Rationale and design of a randomized controlled trial of directly observed hepatitis C treatment delivered in methadone clinics  

PubMed Central

Background Most methadone-maintained injection drug users (IDUs) have been infected with hepatitis C virus (HCV), but few initiate HCV treatment. Physicians may be reluctant to treat HCV in IDUs because of concerns about treatment adherence, psychiatric comorbidity, or ongoing drug use. Optimal HCV management approaches for IDUs remain unknown. We are conducting a randomized controlled trial in a network of nine methadone clinics with onsite HCV care to determine whether modified directly observed therapy (mDOT), compared to treatment as usual (TAU), improves adherence and virologic outcomes among opioid users. Methods/Design We plan to enroll 80 HCV-infected adults initiating care with pegylated interferon alfa-2a (IFN) plus ribavirin, and randomize them to mDOT (directly observed daily ribavirin plus provider-administered weekly IFN) or TAU (self-administered ribavirin plus provider-administered weekly IFN). Our outcome measures are: 1) self-reported and pill count adherence, and 2) end of treatment response (ETR) or sustained viral response (SVR). We will use mixed effects linear models to assess differences in pill count adherence between treatment arms (mDOT v. TAU), and we will assess differences between treatment arms in the proportion of subjects with ETR or SVR with chi square tests. Of the first 40 subjects enrolled: 21 have been randomized to mDOT and 19 to TAU. To date, the sample is 77% Latino, 60% HCV genotype-1, 38% active drug users, and 27% HIV-infected. Our overall retention rate at 24 weeks is 92%, 93% in the mDOT arm and 92% in the TAU arm. Discussion This paper describes the design and rationale of a randomized clinical trial comparing modified directly observed HCV therapy delivered in a methadone program to on-site treatment as usual. Our trial will allow rigorous evaluation of the efficacy of directly observed HCV therapy (both pegylated interferon and ribavirin) for improving adherence and clinical outcomes. This detailed description of trial methodology can serve as a template for the development of future DOT programs, and can also guide protocols for studies among HCV-infected drug users receiving methadone for opiate dependence. Trial Registration ClinicalTrials.gov: NCT01442311

2011-01-01

206

Direct Observation of a Gas Molecule (H2, Ar) Swallowed by C60  

SciTech Connect

Various types of endohedral fullerene complexes are known to date. The well known metallofullerenes are generally produced by arc-discharge method, but the use of such extremely drastic conditions is apparently not suitable for encapsulation of unstable molecules or gases. We recently succeeded in incorporation of a H2 molecule or an Ar atom in 100% into a C60. In order to observe the endohedral gas molecule directly, the X-ray diffraction analysis using synchrotron radiation were carried out. We observed a gas molecule encapsulated in each fullerene cage using structure analysis and the maximum entropy method. These gas molecules are floating inside of the hollow cavities and are completely isolated from the outside.

Sawa, H. [Photon Factory, KEK, Tsukuba 305-0801 (Japan); Department of Materials Structure Science, Graduate Univ. for Advanced Studies, Tsukuba 305-0801 (Japan); Kakiuchi, T. [Department of Materials Structure Science, Graduate Univ. for Advanced Studies, Tsukuba 305-0801 (Japan); Wakabayashi, Y. [Photon Factory, KEK, Tsukuba 305-0801 (Japan); Murata, Y.; Murata, M.; Komatsu, K. [ICR, Kyoto University, Uji, Kyoto 611-0011 (Japan); Yakigaya, K. [AMS, Univ. of Tokyo, Kashiwa 277-8561 (Japan); Takagi, H. [AMS, Univ. of Tokyo, Kashiwa 277-8561 (Japan); RIKEN, Institute of Physical and Chemical Research, Wako, 351-0198 (Japan); Dragoe, N. [LEMHE, Univ. Paris XI - ICMMO, 410 --91405 Orsay Cedex (France)

2007-01-19

207

Direct observation of stochastic domain-wall depinning in magnetic nanowires.  

PubMed

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 Ni80Fe20 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. PMID:19392479

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

2009-04-10

208

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

SciTech Connect

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

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

2011-01-15

209

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

210

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

211

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

212

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

SciTech Connect

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

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

2011-09-02

213

Hydrogen atoms under magnification: direct observation of the nodal structure of Stark states.  

PubMed

To describe the microscopic properties of matter, quantum mechanics uses wave functions, whose structure and time dependence is governed by the Schrödinger equation. In atoms the charge distributions described by the wave function are rarely observed. The hydrogen atom is unique, since it only has one electron and, in a dc electric field, the Stark Hamiltonian is exactly separable in terms of parabolic coordinates (?, ?, ?). As a result, the microscopic wave function along the ? coordinate that exists in the vicinity of the atom, and the projection of the continuum wave function measured at a macroscopic distance, share the same nodal structure. In this Letter, we report photoionization microscopy experiments where this nodal structure is directly observed. The experiments provide a validation of theoretical predictions that have been made over the last three decades. PMID:23745864

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

2013-05-20

214

Direct observation of DNA rotation during transcription by Escherichia coli RNA polymerase  

NASA Astrophysics Data System (ADS)

Helical filaments driven by linear molecular motors are anticipated to rotate around their axis, but rotation consistent with the helical pitch has not been observed. 14S dynein and non-claret disjunctional protein (ncd) rotated a microtubule more efficiently than expected for its helical pitch, and myosin rotated an actin filament only poorly. For DNA-based motors such as RNA polymerase, transcription-induced supercoiling of DNA supports the general picture of tracking along the DNA helix. Here we report direct and real-time optical microscopy measurements of rotation rate that are consistent with high-fidelity tracking. Single RNA polymerase molecules attached to a glass surface rotated DNA for >100 revolutions around the right-handed screw axis of the double helix with a rotary torque of >5pNnm. This real-time observation of rotation opens the possibility of resolving individual transcription steps.

Harada, Yoshie; Ohara, Osamu; Takatsuki, Akira; Itoh, Hiroyasu; Shimamoto, Nobuo; Kinosita, Kazuhiko

2001-01-01

215

Are health personnel the best choice for directly observed treatment in southern Thailand? A comparison of treatment outcomes among different types of observers  

Microsoft Academic Search

A prospective study was conducted in 24 districts in southern Thailand in 1999 with directly observed treatment, short-course strategy (DOTS) implemented to determine treatment outcomes in relation to the practical observer among 455 enrolled patients with tuberculosis. Health personnel (HP), community members (CM), family members (FM) and self-administration (SA) were initially assigned to be DOT observers in 43%, 5%, 44%

Petchawan Pungrassami; Virasakdi Chongsuvivatwong

2002-01-01

216

Mobile technology for the facilitation of direct observation and assessment of student performance.  

PubMed

Background: We developed, implemented, and assessed a web-based clinical evaluation application (i.e., CEX app) for Internet-enabled mobile devices, including mobile phones. The app displays problem-specific checklists that correspond to training problems created by the Clerkship Directors in Internal Medicine. Purpose: We hypothesized that use of the CEX app for directly observing students' clinical skills would be feasible and acceptable, and would demonstrate adequate reliability and validity. Methods: Between July 2010 and February 2012, 266 third-year medical students completed 5 to 10 formative CEXs during their internal medicine clerkship. The observers (attendings and residents), who performed the CEX, used the app to guide and document their observations, record their time observing and giving feedback to the students, and their overall satisfaction with the CEX app. Interrater reliability and validity were assessed with 17 observers who viewed 6 videotaped student-patient encounters, and by measuring the correlation between student CEX scores and their scores on subsequent standardized-patient Objective Structured Clinical Examination (OSCE) exams. Results: A total of 2,523 CEXs were completed by 411 observers. The average number of evaluations per student was 9.8 (± 1.8 SD), and the average number of CEXs completed per observer was 6 (± 11.8 SD). Observers spent less than 10 min on 45.3% of the CEXs and 68.6% of the feedback sessions. An overwhelming majority of observers (90.6%) reported satisfaction with the CEX. Interrater reliability was measured at 0.69 among the observers viewing the videotapes, and their ratings discriminated between competent and noncompetent performances. Student CEX grades, however, did not correlate with their end of 3rd-year OSCE scores. Conclusions: The use of this CEX app is feasible and it captures students' clinical performance data with a high rate of user satisfaction. Our embedded checklists had adequate interrater reliability and concurrent validity. The grades measured on this app, however, were not predictive of subsequent student performance. PMID:24112197

Ferenchick, Gary S; Solomon, David; Foreback, Jami; Towfiq, Basim; Kavanaugh, Kevin; Warbasse, Larry; Addison, James; Chames, Frances; Dandan, Alvin; Mohmand, Asad

2013-01-01

217

Magnetospheric ULF waves directly driven by solar wind oscillations: An observational assessment  

NASA Astrophysics Data System (ADS)

The Ultra-low-frequency (ULF) waves in the magnetosphere play an important role in energizing the radiation belt particles. Understanding how the solar wind directly and indirectly generates ULF waves in the magnetosphere can help build an empirical model of ULF spectrum that is based solely on the solar wind data. It is well understood that various macro-scale solar wind conditions can favor the excitation of ULF waves. The Kelvin- Helmholtz instability during high-speed solar wind and the dayside and nightside reconnections during southward IMF are two examples for the indirect association between the solar wind and magnetospheric ULF waves. In recent years, an increasing amount of attention is paid to the direct driving of magnetospheric ULF waves by solar wind oscillations. These ultra-low-frequency oscillations in the solar wind may originate in part from the normal-mode oscillations of the Sun. In this study we assess the importance of the solar wind oscillations in directly driving the magnetospheric ULF waves by examining the correlation between the solar wind and magnetospheric observations. The data include the high-cadence interplanetary field records collected by the ACE spacecraft, the magnetic field data from Polar and GOES satellites, and the ground magnetometer data from the Mid-continent Magnetoseismic Chain (McMAC).

Cruz-Abeyro, J. A.; Chi, P. J.

2007-12-01

218

Suzaku Observations of the Merging Cluster Abell 85: Temperature Map and Impact Direction  

NASA Astrophysics Data System (ADS)

To investigate the present situation of the merging in the southern outer region of Abell 85, we carried out long-time (˜100 ks) observations with Suzaku, and produced an X-ray hardness ratio map. We found a high hardness ratio peak on the east side of a subcluster located south of the cluster; an X-ray spectrum of the region including this peak indicates a high temperature of ˜8.5 keV. This hot spot has not been reported so far. We consider that this hot spot is a postshock region produced by the infall of the subcluster from the southwest. By using the Rankine-Hugoniot jump conditions for shocks, the Mach number and the infall velocity of the subcluster were obtained as 1.5±0.2 and 1950+290-280km s-1, respectively, in the case of merging with the subcluster from the southwest direction. By using the difference in redshift between A 85 and the subcluster obtained from optical observations, the angle between the line of sight and the direction of the motion of the subcluster is estimated to be 75°+7°-8°. We estimate the kinetic energy of the subcluster and the energy used for the intracluster medium (ICM) heating to be ˜1063 and lsim 8 × 1060erg, respectively. This shows that the deceleration of the subcluster by the ICM heating has been negligibly small.

Tanaka, Nobuhiro; Furuzawa, Akihiro; Miyoshi, Shigeru J.; Tamura, Takayuki; Takata, Tadafumi

2010-06-01

219

Direct observation of the superfluid phase transition in ultracold Fermi gases.  

PubMed

Phase transitions are dramatic phenomena: water freezes into ice, atomic spins spontaneously align in a magnet, and liquid helium becomes superfluid. Sometimes, such a drastic change in behaviour is accompanied by a visible change in appearance. The hallmark of Bose-Einstein condensation and superfluidity in trapped, weakly interacting Bose gases is the sudden formation of a dense central core inside a thermal cloud. However, in strongly interacting gases--such as the recently observed fermionic superfluids--there is no longer a clear separation between the superfluid and the normal parts of the cloud. The detection of fermion pair condensates has required magnetic field sweeps into the weakly interacting regime, and the quantitative description of these sweeps presents a major theoretical challenge. Here we report the direct observation of the superfluid phase transition in a strongly interacting gas of 6Li fermions, through sudden changes in the shape of the clouds--in complete analogy to the case of weakly interacting Bose gases. By preparing unequal mixtures of the two spin components involved in the pairing, we greatly enhance the contrast between the superfluid core and the normal component. Furthermore, the distribution of non-interacting excess atoms serves as a direct and reliable thermometer. Even in the normal state, strong interactions significantly deform the density profile of the majority spin component. We show that it is these interactions that drive the normal-to-superfluid transition at the critical population imbalance of 70 +/- 5 per cent (ref. 12). PMID:16823447

Zwierlein, Martin W; Schunck, Christian H; Schirotzek, André; Ketterle, Wolfgang

2006-07-01

220

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

PubMed Central

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

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

2012-01-01

221

Direct observation of one-dimensional diffusion and transcription by Escherichia coli RNA polymerase.  

PubMed

The dynamics of nonspecific and specific Escherichia coli RNA polymerase (RNAP)-DNA complexes have been directly observed using scanning force microscopy operating in buffer. To this end, imaging conditions had to be found in which DNA molecules were adsorbed onto mica strongly enough to be imaged, but loosely enough to be able to diffuse on the surface. In sequential images of nonspecific complexes, RNAP was seen to slide along DNA, performing a one-dimensional random walk. Heparin, a substance known to disrupt nonspecific RNAP-DNA interactions, prevented sliding. These observations suggest that diffusion of RNAP along DNA constitutes a mechanism for accelerated promoter location. Sequential images of single, transcribing RNAP molecules were also investigated. Upon addition of 5 microM nucleoside triphosphates to stalled elongation complexes in the liquid chamber, RNAP molecules were seen to processively thread their template at rates of 1.5 nucleotide/s in a direction consistent with the promoter orientation. Transcription assays, performed with radiolabeled, mica-bound transcription complexes, confirmed this rate, which was about three times smaller than the rate of complexes in solution. This assay also showed that the pattern of pause sites and the termination site were affected by the surface. By using the Einstein-Sutherland friction-diffusion relation the loading force experienced by RNAP due to DNA-surface friction is estimated and discussed. PMID:10512846

Guthold, M; Zhu, X; Rivetti, C; Yang, G; Thomson, N H; Kasas, S; Hansma, H G; Smith, B; Hansma, P K; Bustamante, C

1999-10-01

222

Direct observation of one-dimensional diffusion and transcription by Escherichia coli RNA polymerase.  

PubMed Central

The dynamics of nonspecific and specific Escherichia coli RNA polymerase (RNAP)-DNA complexes have been directly observed using scanning force microscopy operating in buffer. To this end, imaging conditions had to be found in which DNA molecules were adsorbed onto mica strongly enough to be imaged, but loosely enough to be able to diffuse on the surface. In sequential images of nonspecific complexes, RNAP was seen to slide along DNA, performing a one-dimensional random walk. Heparin, a substance known to disrupt nonspecific RNAP-DNA interactions, prevented sliding. These observations suggest that diffusion of RNAP along DNA constitutes a mechanism for accelerated promoter location. Sequential images of single, transcribing RNAP molecules were also investigated. Upon addition of 5 microM nucleoside triphosphates to stalled elongation complexes in the liquid chamber, RNAP molecules were seen to processively thread their template at rates of 1.5 nucleotide/s in a direction consistent with the promoter orientation. Transcription assays, performed with radiolabeled, mica-bound transcription complexes, confirmed this rate, which was about three times smaller than the rate of complexes in solution. This assay also showed that the pattern of pause sites and the termination site were affected by the surface. By using the Einstein-Sutherland friction-diffusion relation the loading force experienced by RNAP due to DNA-surface friction is estimated and discussed.

Guthold, M; Zhu, X; Rivetti, C; Yang, G; Thomson, N H; Kasas, S; Hansma, H G; Smith, B; Hansma, P K; Bustamante, C

1999-01-01

223

Direct and real-time observation of rotary movement of a DNA nanomechanical device.  

PubMed

Analogous to the biologically abundant protein-based linear molecular machines that translocate along their target surface, we have recently constructed the DNA-based synthetic molecular motors that effect linear movement or navigate a network of tracks on a DNA origami substrate. However, a DNA-based molecular machine with rotary function, analogous to rotary proteins, is still unexplored. Here, we report the construction of a rotary motor based on the B-Z conformational transition of DNA and the direct and real-time observation of its function within a frame-shaped DNA origami. The motor can be switched off by introducing conditions that stabilize B-DNA, while it can be fueled by adding Z-DNA-promoting high-saline buffer. When MgCl(2) was used as external stimulus, 70% of the motors rotated, while 76% of the stators/controls exhibited no rotation. Such a motor system could be successfully applied to perform multiple actions aimed for our benefit. Moreover, for the first time we have directly observed the B-Z conformational transition of DNA in real-time, which shed light on the fundamental understanding of DNA conformations. PMID:23311576

Rajendran, Arivazhagan; Endo, Masayuki; Hidaka, Kumi; Sugiyama, Hiroshi

2013-01-11

224

Direct observation of a local thermal vibration anomaly in a quasicrystal  

NASA Astrophysics Data System (ADS)

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

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

2003-01-01

225

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

PubMed

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

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

2003-01-23

226

Polarization and direction of arrival of Jovian quasiperiodic bursts observed by Cassini  

NASA Astrophysics Data System (ADS)

Jovian quasiperiodic (QP) radio bursts are suspected to be associated with relativistic particle accelerations occurring with a quasiperiodicity between a few minutes and a few tens of minutes in Jupiter's polar magnetosphere. Understanding the excitation and propagation of QP bursts could help us to better understand this periodic energization process. A first necessary step is to measure the wave mode, source location, and directivity of QP bursts. For that purpose, we performed a statistical analysis of goniopolarimetric measurements of QP bursts made with the Radio and Plasma Wave Science investigation (RPWS) onboard Cassini spacecraft during the Jupiter flyby of 2000-2001. We studied two groups of QP bursts on 22 and 23 December 2000, and we found consistent source directions about 50 RJ north of Jupiter with an error bar ?20 RJ. Statistics of the Stokes parameters indicate that QP bursts are partially left-handed polarized (V > 0, Q, U < 0). Together with the direction finding results, these polarization statistics imply that QP bursts observed from low latitudes are L-O mode waves which have been excited in the northern polar source, have propagated toward high latitudes, and then got refracted equatorward in the magnetosheath. Dependence of the Stokes parameters on the longitude indicates that QP bursts are excited within a particular phase range of the planetary rotation, when the system III longitude of the sub-solar point is between 260° and 480°. This implies that QP radio bursts and associated particle accelerations always occur within the same rotational sector, suggesting the existence of a recurrent magnetospheric disturbance at the planetary rotation period. Finally, we propose a possible scenario for the generation and propagation of QP bursts by combining the results of the present study with those of other recent observational and theoretical studies.

Kimura, T.; Cecconi, B.; Zarka, P.; Kasaba, Y.; Tsuchiya, F.; Misawa, H.; Morioka, A.

2012-11-01

227

Direct Observation of Enzymes Replicating DNA Using a Single-molecule DNA Stretching Assay  

PubMed Central

We describe a method for observing real time replication of individual DNA molecules mediated by proteins of the bacteriophage replication system. Linearized ? DNA is modified to have a biotin on the end of one strand, and a digoxigenin moiety on the other end of the same strand. The biotinylated end is attached to a functionalized glass coverslip and the digoxigeninated end to a small bead. The assembly of these DNA-bead tethers on the surface of a flow cell allows a laminar flow to be applied to exert a drag force on the bead. As a result, the DNA is stretched close to and parallel to the surface of the coverslip at a force that is determined by the flow rate (Figure 1). The length of the DNA is measured by monitoring the position of the bead. Length differences between single- and double-stranded DNA are utilized to obtain real-time information on the activity of the replication proteins at the fork. Measuring the position of the bead allows precise determination of the rates and processivities of DNA unwinding and polymerization (Figure 2).

Kulczyk, Arkadiusz W.; Tanner, Nathan A.; Loparo, Joseph J.; Richardson, Charles C.; van Oijen, Antoine M.

2010-01-01

228

Shallow vent architecture of Puyehue Cordón-Caulle, as revealed by direct observation of explosive activity  

NASA Astrophysics Data System (ADS)

On June 4, 2011, an explosive eruption of rhyodacitic magma began at the Puyehue Cordón-Caulle volcanic complex (PCCVC), southern Chile. Initial Plinian phases of the eruption produced tephra plumes reaching > 14 km high, the ash from which quickly circumnavigated the globe to cause widespread disruption to air traffic in the Southern Hemisphere. Within two weeks, the continuing explosive eruption was joined by synchronous effusion of lava. We present observations of complex vent activity made 7 months after the eruption onset, on January 4th and 10th, 2012, when explosive activity from PCCVC continued at a lower level of intensity. Fortuitous climatic conditions permitted direct, ground-based observation and video recording of transient vent dynamics within the asymmetrical tephra cone around the main eruptive vent complex and site of lava effusion, as well as real-time collection of juvenile ash as it rained out directly from the active plume. On Jan. 4, explosive activity was semi-continuous ash jetting punctuated by Vulcanian-like blasts. In the ~50m-diameter sub-circular base of the ~400 m-wide, asymmetrical tephra cone, near-continuous ash jetting was observed from two primary point sources. The northerly source was clearly visible, with time-averaged diameter of ~10 m, and the apparently larger southerly source was mostly obscured from view by the ash plume. Activity was at all times somewhat erratic, but followed a rough cyclicity on 30-45 s timescales, consisting of: (1) restriction of the point source into a focused ash jet up to ~50 m high, producing coarse ash dominated by tube pumice (with minor free pyroxene crystals); followed by (2) Vulcanian-like failure of the region around the point source, producing incandescent ballistic bombs thrown up to 100-200 m from the vent. Jetting from the two main point sources combined in the crater to produce a low gas-thrust region and sustained buoyant plume. Directed ash plumes that climbed and breached the inner wall of the tephra cone were entrained upward into the main vertical portion of the plume. On Jan. 10, explosive activity was manifested as semi-continuous ash jetting from multiple point sources, as accommodated by a 10-20 m high incipient dome that had formed in the tephra cone. At any given time, up to 10 discrete point and linear sources of gas and ash discharge could be seen. These had variable directionality and produced plumes with spatially and temporally variable ash contents. Cycles of overpressure buildup and vent failure were still observed, but rarely produced significant bombs. Instead, failure was characterized by the simultaneous or staggered opening of many additional point discharge sources, often defining a dish-like structure around - but not disturbing - the incipient dome. During this lower-intensity activity, no defined gas-thrust region was maintained and the plume would often collapse to fill the tephra cone. Directed plumes that breached the cone continued to descend its outer slopes. Ongoing analysis of juvenile pyroclasts and video footage permits an assessment of overpressure buildup and release in the shallow conduit of the PCCVC, and an assessment of the complex shallow vent architecture. We address the ideas: (1) that to describe explosive ash jetting from a single "vent" is a gross oversimplification of what is actually a highly transient, multiple point-source vent complex subject to variations in permeability and rate/type of discharge; and (2) that gas and ash jetting and Vulcanian blasts play an important if not necessary role in generating degassed magma that erupts effusively (see Castro et al., this session).

Schipper, C. I.; Tuffen, H.; Castro, J. M.

2012-04-01

229

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

230

Direct observations of Venus upper mesospheric temperatures from ground based spectroscopy of CO2  

NASA Astrophysics Data System (ADS)

We report direct observations of temperatures in the Venus upper mesosphere around 110 km altitude (0.15 Pa). Information about temperatures at these altitude regions are sparse especially for the dayside of Venus. Data was acquired during three observing campaigns between March and June 2009 at the McMath-Pierce Solar Telescope of the National Solar Observatory on Kitt Peak, Arizona, using the Cologne Tuneable Heterodyne Infrared Spectrometer (THIS). The linewidths of fully resolved non-thermal emission lines in the 10.6 ?m band of CO2 were used to derive temperatures on the Venus dayside. Temperatures were measured with high spatial resolution at 115 positions on the Venus dayside between 67°N and 90°S and various offsets from the apparent discs central meridian longitude (CML) providing the first extensive dataset for the dayside mesosphere. The retrieved temperatures show a strong local time and latitude dependence. Values of 160 K are observed close to the terminator and at the South pole while temperaturs reach 250 K at the sub solar point. These high values are in disagreement with the predictions of the Venus International Reference Atmosphere model but are consistent with earlier measurements from 2007.

Sonnabend, G.; Kroetz, P.; Sornig, M.; Stupar, D.

2010-06-01

231

Direct observation of feedout-related areal mass oscillations in planar plastic targets.  

NASA Astrophysics Data System (ADS)

"Feedout" means the transfer of mass perturbations from the rear to the front surface of a driven target. The oscillations are expected if the perturbation wavelength ? is not large compared to 2? L_s, where Ls is the shock-compressed target thickness. We report the first direct experimental observation of areal mass oscillation associated with feedout, followed by the onset of exponential RT growth. Our experiments were performed with the Nike KrF laser at irradiation 50 TW/cm^2. The mass redistribution in the target was observed with the aid of monochromatic x-ray imaging coupled to a streak camera. We used 40 to 60 ?m thick CH targets rippled on the rear side with wavelengths of either 30 or 45 ?m, the ratio 2? L_s/? thus being close to 2. Two phase reversals of mass variation predicted by the theory and simulations were consistently observed both on the original images and on the time histories of Fourier amplitudes.

Aglitskiy, Y.; Metzler, N.; Velikovich, A. L.; Karasik, M.; Serlin, V.; Pawley, C.; Mostovych, A. N.; Schmitt, A. J.; Obenschain, S. P.; Gardner, J. H.

2001-10-01

232

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

PubMed

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

Lan, Fei; Li, Guangyong

2013-04-18

233

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.

2013-10-01

234

Direct observation of vortices in an array of holes at low temperature: temperature dependance and first visualization of localized superconductivity  

Microsoft Academic Search

A scanning micro superconducting quantum interference device (microSQUID) microscope is used to directly image vortices in a superconducting Al thin film. We observe the temperature dependence of the vortex distribution in a regular defect (hole) array patterned into the Al film. The first direct observation of the localized superconducting state around the holes is shown as well as the effect

Cecile Veauvy; Klaus Hasselbach; Dominique Mailly

2004-01-01

235

recommended dietary allowances (RDA)  

Microsoft Academic Search

\\u000a values for vitamins and minerals, determined by the Food and Nutrition Board of the National Research Council (US); intake\\u000a of the RDA will provide adequate nutrition in most healthy persons under usual environ mental stresses; they are not minimum\\u000a requirements; ? see recommended daily allowances.

Gerhard Nahler

236

Taxing sulfur dioxide emission allowances  

SciTech Connect

The acid rain control program authorized by Title IV of the Clean Air Act Amendments of 1990 (CAAA) was designed to reduce the adverse effects of acid rain by limiting emissions of sulfur dioxide (SO[sub 2]) into the atmosphere. The program is a complex scheme involving the issuance, consumption, holding, and trading of emission allowances for SO[sub 2]. Not surprisingly, electric utilities will face federal income tax issues in connection with the program. Under the emission allowance program, the U.S. Environmental Protection Agency (EPA) will issue emission allowance to owners or operators of certain utility power plants at no cost to the recipients. An emission allowance is an authorization to emit one ton of SO[sub 2] during or after the calendar year for which it is issued. If a utility power plant subject to the program emits SO[sub 2] in excess of its allowances, the owner or operator will be subject to a penalty of $2,000 a ton, and must offset the excess emissions with allowances in the subsequent year. Allowances may be bought and sold. Phase I of the program begins January 1, 1995, and will apply to 110 utility generating units. Phase II takes effect January 1, 2000, and will include most electric utility generating units. EPA will withhold a specified number of allowances for direct sale and auction. The resulting proceeds will be paid to the utilities from which the allowances were withheld. The Internal Revenue Service (IRS) has provided somewhat limited guidance on several tax issues raised by the program. Significant tax issues and the positions articulated by the IRS (if any) are discussed in this article.

Nelson, G.L. (Reid Priest, Washington, DC (United States))

1993-09-15

237

Direct observation of mean-field induced phase collapse and retrieval in soft bosonic lattices  

NASA Astrophysics Data System (ADS)

We study the response of BEC+optical lattice system to sudden frustration of Josephson tunneling between adjacent lattice sites in the large filling factor (soft) regime[1]. We introduce a new experimental method which effectively discriminates between homogeneous (on-site) phase diffusion[2] and inhomogeneous (site-to-site) dephasing mechanisms. With this method, we observe quantitative agreement between the predicted and measured phase diffusion times. In particular, we demonstrate that the phase diffusion time can be increased by reducing the number fluctuations associated with the initial lattice states. This work extends the work of Greiner, et al.[3] to the large filling factor regime. Finally, we describe and demonstrate a technique for retrieval of long range phase coherence from this system. Surprisingly, coherence can be suddenly regained by abruptly allowing Josephson tunneling. We discuss the implications of these observations for envisioned superfluid de Broglie wave interferometers and in the study of non-adiabatic effects in superfluid/Mott-insulating systems. [1] Orzel, C., Tuchman, A. K., Fenselau, M. L., Yasuda, M. & Kasevich, M. A. Science 291, 2386-2389 (2001). [2] A. Imamoglu, M. Lewenstein & L. You. Phys. Rev. Lett. 78, 2511(1997). [3] M. Greiner, O. Mandel, T. Esslinger, T. W. H"ansch & I. Bloch. Nature 415, 39 (2002)

Li, Wei; Tuchman, Ari; Chien, Hui-Chun; Kasevich, Mark

2006-05-01

238

Direct observation of the double Auger decay of a K hole  

NASA Astrophysics Data System (ADS)

The double Auger (DA) decay of a K hole has been observed directly by detecting the two emitted electrons in coincidence. The hole was created in 37Cl following the electron-capture decay of 37Ar. The probability of DA decay, per Auger decay, with the two electrons both having an energy greater than 250 eV was found to be 3.7+/-0.2%. The DA probability was found to decrease exponentially as the energy partitioning between the two electrons changed from the asymmetric case (E1>>E2) to the symmetric case (E1~=E2). The DA probability accounts for the bulk of the intensity of high charge states previously measured in 37Cl.

Hindi, M. M.; Zhu, Lin; Avci, Recep; Mio?inovi?, P. M.; Kozub, R. L.; Lapeyre, G. J.

1996-06-01

239

Direct observation and dynamics of spontaneous skyrmion-like magnetic domains in a ferromagnet.  

PubMed

The structure and dynamics of submicrometre magnetic domains are the main factors determining the physical properties of magnetic materials. Here, we report the first observation of skyrmion-like magnetic nanodomains in a ferromagnetic manganite, La0.5Ba0.5MnO3, using Lorentz transmission electron microscopy (LTEM). The skyrmion-like magnetic domains appear as clusters above the Curie temperature. We found that the repeated reversal of magnetic chirality is caused by thermal fluctuation. The closely spaced clusters exhibit dynamic coupling, and the repeated magnetization reversal becomes fully synchronized with the same chirality. Quantitative analysis of such dynamics was performed by LTEM to directly determine the barrier energy for the magnetization reversal of skyrmion-like nanometre domains. This study is expected to pave the way for further investigation of the unresolved nature and dynamics of magnetic vortex-like nanodomains. PMID:23624696

Nagao, Masahiro; So, Yeong-Gi; Yoshida, Hiroyuki; Isobe, Masaaki; Hara, Toru; Ishizuka, Kazuo; Kimoto, Koji

2013-04-28

240

Direct observation of superconducting gaps in iron-based superconductors by laser ARPES  

NASA Astrophysics Data System (ADS)

We have developed a new apparatus for carrying out ultra-high energy resolution laser-excited angle-resolved photoemission spectroscopy (laser ARPES). The achieved energy resolution is ~ 70 ?eV at a sample temperature ~ 1.5 K. As a test case, we have measured the superconducting gap of elemental metal Sn (Tc = 3.7 K). We have used this laser-ARPES apparatus, to directly observe the superconducting gap of various iron-based superconductors. The spectra of FeTe0.6Se0.4 below Tc show a very clear temperature dependent superconducting coherence peak. Preliminary momentum-dependent results indicate an anisotropic superconducting gap in FeTe0.6Se0.4.

Okazaki, Kozo

2013-07-01

241

Direct observation of nodes and twofold symmetry in FeSe superconductor.  

PubMed

We investigated the electron-pairing mechanism in an iron-based superconductor, iron selenide (FeSe), using scanning tunneling microscopy and spectroscopy. Tunneling conductance spectra of stoichiometric FeSe crystalline films in their superconducting state revealed evidence for a gap function with nodal lines. Electron pairing with twofold symmetry was demonstrated by direct imaging of quasiparticle excitations in the vicinity of magnetic vortex cores, Fe adatoms, and Se vacancies. The twofold pairing symmetry was further supported by the observation of striped electronic nanostructures in the slightly Se-doped samples. The anisotropy can be explained in terms of the orbital-dependent reconstruction of electronic structure in FeSe. PMID:21680839

Song, Can-Li; Wang, Yi-Lin; Cheng, Peng; Jiang, Ye-Ping; Li, Wei; Zhang, Tong; Li, Zhi; He, Ke; Wang, Lili; Jia, Jin-Feng; Hung, Hsiang-Hsuan; Wu, Congjun; Ma, Xucun; Chen, Xi; Xue, Qi-Kun

2011-06-17

242

Direct Observation of Site Specific Molecular Chemisorption of O2 on TiO2 (110)  

SciTech Connect

Molecularly chemisorbed O2 species were directly imaged on reduced TiO2(110) at 50 K with high-resolution scanning tunneling microscopy (STM). Two different O2 adsorption channels, one at bridging oxygen vacancies (VO) and another at five-fold coordinated terminal titanium atoms (Ti5c), have been identified. While O2 species at Ti5c site appears as a single protrusion centered on the Ti5c row, the O2 at VO manifests itself by a disappearance of the VO feature. It is found that STM tip can easily dissociate O2 species, unless extremely low magnitudes of the tunneling parameters are used. The O2 molecules chemisorbed at low temperatures at these two distinct sites are the most likely precursors for the two previously established O2 dissociation channels, observed at temperatures above 150 and 230 K at the VO and Ti5c sites, respectively.

Wang, Zhitao; Du, Yingge; Dohnalek, Zdenek; Lyubinetsky, Igor

2010-12-16

243

Direct observation and dynamics of spontaneous skyrmion-like magnetic domains in a ferromagnet  

NASA Astrophysics Data System (ADS)

The structure and dynamics of submicrometre magnetic domains are the main factors determining the physical properties of magnetic materials. Here, we report the first observation of skyrmion-like magnetic nanodomains in a ferromagnetic manganite, La0.5Ba0.5MnO3, using Lorentz transmission electron microscopy (LTEM). The skyrmion-like magnetic domains appear as clusters above the Curie temperature. We found that the repeated reversal of magnetic chirality is caused by thermal fluctuation. The closely spaced clusters exhibit dynamic coupling, and the repeated magnetization reversal becomes fully synchronized with the same chirality. Quantitative analysis of such dynamics was performed by LTEM to directly determine the barrier energy for the magnetization reversal of skyrmion-like nanometre domains. This study is expected to pave the way for further investigation of the unresolved nature and dynamics of magnetic vortex-like nanodomains.

Nagao, Masahiro; So, Yeong-Gi; Yoshida, Hiroyuki; Isobe, Masaaki; Hara, Toru; Ishizuka, Kazuo; Kimoto, Koji

2013-05-01

244

Direct observation of a concealed glass transition in a Mg-Ni-Nd metallic glass  

NASA Astrophysics Data System (ADS)

Glass transition and crystallization behavior of Mg75Ni10Nd15 metallic glass has been studied by a temperature-modulated differential scanning calorimeter (TMDSC) and a normal differential scanning calorimeter (DSC). The truly vitreous state of the as-spun Mg75Ni10Nd15 alloy was confirmed by the direct observation of the glass transition through TMDSC measurements, which was not perceptible in the normal DSC heating scans. It was concluded that the glass transition signal was concealed by the relatively strong concurrent signal of the primary crystallization. This was further confirmed by the fact that the glass transition was revealed by both TMDSC and DSC for the samples with negligible heat release from the primary crystallization.

Lu, Z. P.; Liu, C. T.; Kam, C. H.; Li, Y.

2003-02-01

245

Dynamic structure of the translocon SecYEG in membrane: direct single molecule observations.  

PubMed

Purified SecYEG was reconstituted into liposomes and studied in near-native conditions using atomic force microscopy. These SecYEG proteoliposomes were active in translocation assays. Changes in the structure of SecYEG as a function of time were directly visualized. The dynamics observed were significant in magnitude (?1-10 ?) and were attributed to the two large loops of SecY linking transmembrane helices 6-7 and 8-9. In addition, we identified a distribution between monomers and dimers of SecYEG as well as a smaller population of higher order oligomers. This work provides a new vista of the flexible and dynamic structure of SecYEG, an intricate and vital membrane protein. PMID:23609442

Sanganna Gari, Raghavendar Reddy; Frey, Nathan C; Mao, Chunfeng; Randall, Linda L; King, Gavin M

2013-04-22

246

Direct observation of superconducting gaps in iron-based superconductors by laser ARPES  

NASA Astrophysics Data System (ADS)

We have developed a new apparatus for carrying out ultra-high energy resolution laser-based angle-resolved photoemission spectroscopy (laser ARPES). From the spectra of the evaporated gold and superconducting (SC) gap of Sn (Tc = 3.7 K) sample, we conclude that the best energy resolution is ˜70 ?eV and the lowest sample temperature is ˜1.0 K. We have used this laser-ARPES apparatus, to directly observe the SC gap of various iron-based superconductors. The spectra of FeTe0.6Se0.4 below Tc show a very clear temperature-dependent superconducting coherence peak, and the SC-gap nodes of KFe2As2 are found in the middle Fermi surface (FS) around the FS angle ? = ±5.0°.

Okazaki, Kozo

2013-11-01

247

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

NASA Astrophysics Data System (ADS)

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

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

2008-02-01

248

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

NASA Astrophysics Data System (ADS)

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

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

2004-05-01

249

Direct Observation of the Femtosecond Excited-State cis-trans Isomerization in Bacteriorhodopsin  

NASA Astrophysics Data System (ADS)

Femtosecond optical measurement techniques have been used to study the primary photoprocesses in the light-driven transmembrane proton pump bacteriorhodopsin. Light-adapted bacteriorhodopsin was excited with a 60-femtosecond pump pulse at 618 nanometers, and the transient absorption spectra from 560 to 710 nanometers were recorded from -50 to 1000 femtoseconds by means of 6-femtosecond probe pulses. By 60 femtoseconds, a broad transient hole appeared in the absorption spectrum whose amplitude remained constant for about 200 femtoseconds. Stimulated emission in the 660- to 710-nanometer region and excited-state absorption in the 560- to 580-nanometer region appeared promptly and then shifted and decayed from 0 to ~ 150 femtoseconds. These spectral features provide a direct observation of the 13-trans to 13-cis torsional isomerization of the retinal chromophore on the excited-state potential surface. Absorption due to the primary ground-state photoproduct J appears with a time constant of ~ 500 femtoseconds.

Mathies, Richard A.; Brito Cruz, C. H.; Pollard, Walter T.; Shank, Charles V.

1988-05-01

250

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

PubMed

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

2013-05-06

251

Magnetospheric ULF waves directly driven by solar wind oscillations: An observational assessment  

NASA Astrophysics Data System (ADS)

The Ultra-low-frequency (ULF) waves in the magnetosphere play an important role in energizing the radiation belt particles. It is well understood that various macro-scale solar wind conditions can favor the excitation of ULF waves. The Kelvin-Helmholtz instability during high-speed solar wind and the dayside and nightside reconnections during southward IMF are two examples for the indirect association between the solar wind and magnetospheric ULF waves. In recent years, an increasing amount of attention is paid to the direct driving of magnetospheric ULF waves by solar wind oscillations. These ULF oscillations in the solar wind may originate in part from the normal-mode oscillations of the Sun. In this study we assess the importance of the solar wind oscillations in directly driving the magnetospheric ULF waves by examining the correlation between the solar wind and magnetospheric observations. The data include the high-cadence interplanetary field records collected by the Geotail spacecraft, the magnetic field data from the Polar satellite, and the ground magnetometer data from the Mid-continent Magnetoseismic Chain (McMAC). We find that the solar wind oscillations in general do resemble the magnetospheric ULF waves in the spectral content. For many events we have examined, the coherence for wave periods longer than 5 min is less than 0.4, contradicting the notion that the low-frequency ULF waves in the solar wind can directly drive the magnetospheric oscillations at the same frequency. Our results also imply that the physical processes internal to the magnetosphere, such as field line resonance, may be more important in defining the ULF spectrum in the magnetosphere.

Lopez Cruz-Abeyro, Jose Antonio

252

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

NASA Astrophysics Data System (ADS)

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

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

2010-11-01

253

Direct observation of Landau levels of massless and massive Dirac fermions.  

NASA Astrophysics Data System (ADS)

The low energy quasiparticles in graphene resemble massless relativistic particles (Dirac fermions): they have a linear energy-momentum spectrum and possess internal degrees of freedom arising from the crystal symmetry of the honeycomb lattice, leading to particle anti-particle pairs. When two layers of graphene are coupled together, the quasiparticles acquire a band-mass and are transformed into chiral massive fermions. Both types of quasiparticles develop unusual Landau levels in a magnetic field which profoundly alter the magneto-transport properties. We will report the direct observation of the Landau levels associated with these quasiparticles using a low temperature STM in fields up to 12 Tesla. The experiments reveal two independent sequences of Landau levels that provide evidence for the coexistence of massless and massive Dirac fermions. The energy levels of the former exhibit a square-root dependence on both field and Landau-level index n, while the latter are linear in field with a Landau-level index dependence of [n(n+1)]^1/2. Both sequences exhibit a zero energy Landau level which is a unique and direct consequence of the quantum-relativistic nature of these quasiparticles.

Li, Guohong; Andrei, Eva Y.

2007-03-01

254

Circulating mechanism of the "pure" venous flap: direct observation of microcirculation.  

PubMed

The circulating mechanism of the "pure" venous flap was studied via venography and direct observation of the microcirculation through transparent ear chambers and ear edges in a rabbit model. The flap, without arterial inflow, survived with normal hair growth and wound healing. Renewed blood circulation occurred 3 to 5 hr after transfer There were two typical flow patterns in the venules: one was a shaking movement with high frequency and short range; the other was a pendulum-like movement with low frequency and long range. The former was related to heart rate, while the later was not. The pendulum-like movement was the main flow responsible for perfusion of capillaries. Blood flow in the capillaries occurred 1 to 2 hr later than that in the venules. The pendulum-like flow perfused the capillaries in two ways: one was in the direction of venules to capillaries and then back to venules along the same route; the other was from venules to arterioles through arteriovenous shunts and then to capillaries. The first type of perfusion was gradually replaced by the second 2 days after transfer. There were extensive venous plexus flows in the flap, which lasted more than 4 weeks after transfer. Revascularized vessels ultimately supplied blood to the flap. The dynamic energy for the movement of blood at an early post-transfer stage was probably due to spontaneous venomotion. PMID:9590608

Yuan, R; Shan, Y; Zhu, S

1998-04-01

255

Direct observation of female mating frequency using time-lapse photography.  

PubMed

One basic condition of postmating sexual selection is that females mate more than once before fertilizing their ova. Knowledge of the frequency and extent of multiple mating in a given population or species is therefore important in order to fully understand the potential for sexual selection, in the form of sperm competition, sexual conflict and cryptic female choice. Surprisingly, there are only a handful of studies that have attempted to estimate the frequency of multiple mating in insects (including Drosophila) and none have made direct observations over extended periods of time. Here we use time-lapse photography to directly score matings in isolated pairs of D. melanogaster and show that multiple mating in the laboratory occurs at a high frequency but at comparable rates with wild caught females. We also find that the interval to remating rises approximately additively with each mating, indicating either an increase in female resistance or male reluctance to remate. These results suggest that the opportunity for postmating sexual selection in laboratory and natural environments are not dramatically different and that there may be a causal link between the rise in female mating resistance and the concomitant rise in the cost of mating. The method is easily executed and could be adapted to other insect models. PMID:19242110

Kuijper, Bram; Morrow, Edward H

2009-05-01

256

Direct GRB fireball Lorentz factor measurements through REM early afterglow observations  

NASA Astrophysics Data System (ADS)

The huge energies involved in gamma-ray bursts (GRBs) coupled with the short emission time scales unavoidably imply that the emitting source is moving relativistically, with a speed close to that of light. Here we present the REM telescope observations of the early-time near-infrared light curves of the GRB 060418 and GRB 060607A afterglows. The detection of the afterglow peak provides for the first time a direct measurement of the initial Lorentz factor ?0 of the radiating material. We find that the emitting region was indeed highly relativistic in the first seconds after the explosions, with ?0˜400. Comparison with the Lorentz factor as determined at later epochs provides direct evidence that the emitting shell is decelerating and confirms that the afterglow emission is powered by the dissipation of bulk kinetic energy. The deceleration radius was inferred to be R dec?1017 cm. This is much larger than the internal shocks radius (believed to power the prompt emission), thus providing further evidence for a different origin of the prompt and afterglow stages of the GRB.

Vergani, Susanna D.

2007-10-01

257

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

PubMed Central

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

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

1999-01-01

258

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

PubMed Central

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

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

2012-01-01

259

Directional spreading function of the sea wave spectrum at short scale, inferred from multifrequency radar observations  

NASA Astrophysics Data System (ADS)

Several models of the directional spreading function of the sea wave spectrum have been proposed in the literature for low wavenumbers. In this paper we propose a high-wavenumber extrapolation of those models, obtained by fitting a correcting term which vanishes at large scales (low wavenumbers). At short scales (high wavenumbers) the correcting term is constrained by multifrequency microwave observations of the normalized radar cross section ?° from P band (frequency = 0.43 GHz) up to Ka band (frequency = 34.43 GHz), together with optical observations of the sea surface slope variance. Two formulations are given, one providing a high-wavenumber extrapolation to Apel's [1994] formulation and the other providing a high-wavenumber extrapolation to Donelan et al.'s [1985] and Banner's [1990] formulation. The correcting term ?, expressed as a function of wavenumber k and wind speed U by means of six least squares fitted parameters, is found to vary strongly with k and slightly with U. Another simpler expression for ?, involving only the dependence with k by means of three fitted parameters, is therefore also proposed. According to our fitted model of the spreading function, there is a spectral region in the short gravity range where the sea spectrum shows only a weak dependence on the direction, in accordance with the previous models. However, unlike them, our model gives an increase of the anisotropy of the spreading function at higher wavenumbers, in such a way that the ratio between the cross-wind and along-wind spectral densities of the folded spectrum is reduced to no more than 35% at high wavenumbers (k ? 1000 rad/m). This increase of anisotropy at high frequency is in accordance with conclusions drawn by previous authors from radar backscatter data, which were, however, limited to narrow spectral bands since their analyses involved only single-frequency radar data.

Caudal, G.; Hauser, D.

1996-07-01

260

Gossip as an alternative for direct observation in games of indirect reciprocity.  

PubMed

Communication about social topics is abundant in human societies, and many functions have been attributed to such gossiping. One of these proposed functions is the management of reputations. Reputation by itself has been shown to have a strong influence on cooperation dynamics in games of indirect reciprocity, and this notion helps to explain the observed high level of cooperation in humans. Here we designed a game to test a widespread assumption that gossip functions as a vector for the transmission of social information. This empirical study (with 14 groups of nine students each) focuses on the composition of gossip, information transfer by gossip, and the behavior based on gossip information. We show that gossip has a strong influence on the resulting behavior even when participants have access to the original information (i.e., direct observation) as well as gossip about the same information. Thus, it is evident that gossip has a strong manipulative potential. Furthermore, gossip about cooperative individuals is more positive than gossip about uncooperative individuals, gossip comments transmit social information successfully, and cooperation levels are higher when people encounter positive compared with negative gossip. PMID:17947384

Sommerfeld, Ralf D; Krambeck, Hans-Jürgen; Semmann, Dirk; Milinski, Manfred

2007-10-18

261

Direct dark matter search by observing electrons produced in neutralino nucleus collisions  

NASA Astrophysics Data System (ADS)

Exotic dark matter and dark energy together seem to dominate in the Universe. Supersymmetry naturally provides a candidate for the dark matter constituents via the lightest supersymmetric particle (LSP). The most important process for directly detecting dark matter is the LSP nucleus elastic scattering by measuring the energy of the recoiling nucleus. In the present work we explore a novel process, which has definite experimental advantages, that is the detection of the dark matter constituents by observing the low energy ionization electrons. These electrons, which are produced during the LSP nucleus collision, may be observed separately or in coincidence with the recoiling nuclei. We develop the formalism and apply it in calculating the ratio of the ionization rate to the nuclear recoil rate in a variety of atoms including 20Ne, 40Ar, 76Ge, 78Kr and 132Xe, employing realistic Hartree Fock electron wave functions. The obtained ratios are essentially independent of all parameters of supersymmetry except the neutralino mass, but they crucially depend on the electron energy cutoff. These ratios per electron tend to increase with the atomic number and can be as high as 10%. Based on our results it is both interesting and realistic to detect the LSP by measuring the ionization electrons following the LSP nuclear collisions.

Moustakidis, Ch. C.; Vergados, J. D.; Ejiri, H.

2005-10-01

262

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

NASA Astrophysics Data System (ADS)

Global ocean acidification is a prominent, inexorable change associated with rising levels of atmospheric CO2. Here we present the first basin-wide direct observations of recently declining pH, along with estimates of anthropogenic and non-anthropogenic contributions to that signal. Along 152°W in the North Pacific Ocean (22-56°N), pH changes between 1991 and 2006 were essentially zero below about 800 m depth. However, in the upper 500 m, significant pH changes, as large as -0.06, were observed. Anthropogenic and non-anthropogenic contributions over the upper 800 m are estimated to be of similar magnitude. In the surface mixed layer (depths to ˜100 m), the extent of pH change is consistent with that expected under conditions of seawater/atmosphere equilibration, with an average rate of change of -0.0017/yr. Future mixed layer changes can be expected to closely mirror changes in atmospheric CO2, with surface seawater pH continuing to fall as atmospheric CO2 rises.

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

2010-01-01

263

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

264

Direct observations of colloid retention in granular media in the presence of energy barriers, and implications for inferred mechanisms from indirect observations.  

PubMed

In this paper we present direct observations of retention of colloids in granular porous media over a large size range (0.21-9.0 microm) and generalize the significance of attachment in grain to grain contacts and attachment on the open surface as a function of colloid:collector ratio. We examine reversibility of attachment via these mechanisms with respect to ionic strength reduction and fluid velocity increase. We relate these direct observations to existing literature, and in some cases offer alternative interpretations of mechanisms of retention drawn from indirect observations (e.g. via column effluent and retained concentrations). PMID:20132959

Johnson, William P; Pazmino, Eddy; Ma, Huilian

2009-12-21

265

Directly Observed Antiretroviral Therapy Eliminates Adverse Effects of Active Drug Use on Adherence  

PubMed Central

BACKGROUND The impact of adherence enhancing interventions on the relationship between active drug use and adherence is largely unknown. METHODS We conducted a 24-week randomized controlled trial of antiretroviral directly observed therapy (DOT) versus treatment as usual (TAU) among HIV-infected methadone patients. Our outcome measure was pill count antiretroviral adherence, and our major independent variables were treatment arm (DOT v. TAU) and active drug use (opiates, cocaine, or both opiates and cocaine). We defined any drug use as ? one positive urine toxicology result, and frequent drug use as ?50% tested urines positive. We used mixed-effects linear models to evaluate associations between adherence and drug use, and included a treatment arm-by-drug use interaction term to evaluate whether DOT moderates associations between drug use and adherence. RESULTS 39 participants were randomized to DOT and 38 to TAU. We observed significant associations between adherence and active drug use, but these were limited to TAU participants. Adherence was worse in TAU participants with any opiate use than in TAU participants without (63% v 75%, p < 0.01); and worse among those with any polysubstance (both opiate and cocaine) use than without (60% v 73%, p=0.01). We also observed significant decreases in adherence among TAU participants with frequent opiate or frequent polysubstance use, compared to no drug use. Among DOT participants, active drug use was not associated with worse adherence. CONCLUSIONS Active opiate or polysubstance use decreases antiretroviral adherence, but the negative impact of drug use on adherence is eliminated by antiretroviral DOT.

Nahvi, Shadi; Litwin, Alain H.; Heo, Moonseong; Berg, Karina M.; Li, Xuan; Arnsten, Julia H.

2011-01-01

266

Phase-field modeling and experimental observation of the irregular interface morphology during directional solidification  

NASA Astrophysics Data System (ADS)

Evolution of the complex solid-liquid interface morphology during a solidification process is an important issue in solidification theory since the morphology eventually dictates the final microstructure of the solidified material and therefore the material properties. Significant progress have been made in recent years in the study of the formation and development of regular dendritic growth, while only limited understanding is achieved for the irregular interface patterns observed in many industry processes. This dissertation focuses on the physical mechanisms of the development and transition of various irregular interface patterns, including the tilted dendritic, the seaweed, and the degenerate patterns. Both experimental observations and numerical simulation using the phase field modeling are performed. A special effort is devoted on the effects of the capillary anisotropy and the kinetic anisotropy in the evolution of the interface morphology during solidification. Experimentally, a directional solidification system is constructed to observe in situ the interface morphology by using the transparent organic material succinonitrile. With such a system, both the regular interface patterns (cellular and dendritic) and the irregular interface patterns (seaweed, degenerate and tilted dendritic) are observed. The effects of the temperature gradient and the interface velocity on the development and transition of the irregular interface patterns are investigated. It is found that the interface morphology transits from the seaweed to the tilted dendritic pattern as the interface velocity increases, while the tilted dendritic pattern may transit to the degenerate seaweed pattern as the temperature gradient increases. Under certain conditions, dendrites and seaweed coexist within the same grain. The dynamic transitions among various patterns and the effect of the solidification conditions are examined in detail. Numerically, a 2-D phase field model is developed to simulate the formation of the irregular interface patterns. Both the capillary anisotropy and the kinetic anisotropy are incorporated into the model. For the first time, the effect of the kinetic anisotropy on the formation of the irregular interface patterns is investigated in the case of a small capillary anisotropy. It has been found that the kinetic anisotropy has a profound influence on the development of the irregular interface patterns. The simulation finds that the interface morphology transits from the cellular into the seaweed and then into the tilted dendritic pattern as the kinetic anisotropy increases. The large angle tilted dendrites are also successfully reproduced. The simulation results agree well with our experimental observations.

Guo, Taiming

267

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

PubMed Central

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 into mainstream health care practices for tic disorders (e.g., psychiatry and neurology), the use of direct observation as a primary assessment tool has been neglected in favor of less objective methods. Hesitation to use direct observation appears to stem largely from concerns about the generalizability of clinic observations to other settings (e.g., home) and a lack of consensus regarding the most appropriate and feasible techniques for conducting and scoring direct observation. The purpose of the current study was to evaluate and establish a reliable, valid, and feasible direct-observation protocol capable of being transported to research and clinical settings. A total of 43 children with tic disorders, collected from two outpatient specialty clinics, were assessed using direct (videotape samples) and indirect (Yale Global Tic Severity Scale; YGTSS) methods. Videotaped observation samples were collected across 3 consecutive weeks and two different settings (clinic and home), were scored using both exact frequency counts and partial-interval coding, and were compared to data from a common indirect measure of tic severity (the YGTSS). In addition, various lengths of videotaped segments were scored to determine the optimal observation length. Results show that (a) clinic-based observations correspond well to home-based observations, (b) brief direct-observation segments scored with time-sampling methods reliably quantified tics, and (c) indirect methods did not consistently correspond with the direct methods.

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

2006-01-01

268

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

269

The influence of program acceptability on the effectiveness of public health policy: a study of directly observed therapy for tuberculosis.  

PubMed Central

OBJECTIVES: This study examined how patient acceptability influences the effectiveness of directly observed therapy for tuberculosis. METHODS: Decision and sensitivity analyses were used in assessing influences. RESULTS: If mandatory directly observed therapy discourages 6% of initial tuberculosis patients (range: 4% to 10%) from seeking care, then such therapy will be less effective than self-administered therapy. Directly observed therapy is more effective than repeated self-administered therapy for patients failing to complete initial treatment unless 32% (range: 27% to 38%) of patients avoid seeking care. CONCLUSIONS: Patient acceptability must be taken into consideration before selecting public health strategies.

Heymann, S J; Sell, R; Brewer, T F

1998-01-01

270

Direct observations of formation and propagation of subpolar eddies into the Subtropical North Atlantic  

NASA Astrophysics Data System (ADS)

Subsurface float and moored observations are presented to show for the first time the formation and propagation of anticyclonic submesoscale coherent vortices that transport relatively cold, fresh subpolar water to the interior subtropical North Atlantic. Acoustically tracked RAFOS floats released in the southward-flowing Western Boundary Current at the exit of the Labrador Sea reveal the formation of three of these eddies at the southern tip of the Grand Banks (42°N, 50°W). Using a recently developed method to detect eddies in float trajectories and estimate their kinematic properties, it was found that the eddies had average rotation periods of 5-7 day at radii of 10-25 km, with mean rotation speeds of up to 0.3 m s-1. One especially long-lived (5.1 months) eddy crossed under the Gulf Stream path and translated southwestward in the subtropical recirculation to at least 35°N, where it hit one of the Corner Rise Seamounts. Velocity, temperature and salinity measurements from a nine-month deployment of two moorings south of the Gulf Stream at 38°N, 50°W reveal the passage of at least two eddies with similar hydrographic and kinematic properties. The core temperature and salinity properties of the eddies imply their formation at intermediate levels of the Labrador Current south of the Tail of the Grand Banks. These observations confirm earlier speculation that eddies form in this region and transport anomalously cold, low-salinity water directly into the subtropical interior. Possible formation mechanisms and potential importance of these eddies to interior ventilation and the equatorward spreading of Labrador Sea Water are discussed.

Bower, Amy S.; Hendry, Ross M.; Amrhein, Daniel E.; Lilly, Jonathan M.

2013-01-01

271

Determination of miscibility pressure by direct observation method. Quarterly report, January 1-March 31, 1982  

SciTech Connect

The objective of the project is to conduct laboratory tests to: (1) develop a method for determining MMP through direct observation using a high pressure cell; (2) determine feasibility of in-situ foam generation by visual observation and microphotographic technique. The project is presently organized and carried out in three major fronts: (1) MMP test; (2) high pressure sampling and chemical analysis; and (3) foam study and displacement test. The technical progress in each of these areas is discussed. The effects of temperature on MMP and appearance of CO/sub 2/-rich phase for four crude oils tested are plotted. The MMP is the pressure at which the CO/sub 2/-rich phase becomes miscible with CO/sub 2/ vapor. The results of gas chromatographic analysis for the four crude oils tested are presented. As previously stated the richness of C/sub 5/ to C/sub 20/ components is the key factor for determining the quality and stability of the miscible transition zone. The surfactant/CO/sub 2/ ratio relative to foam quality and foam quantity are presented in a table and also plotted. The plotted figures show: (1) the foam qualities increased as the surfactant rates are decreased; (2) at 75/sup 0/F, the foam quality increases as the pressure is decreased whereas the reverse is true for temperature at 120/sup 0/F; (3) foam generating rate increased with increasing surfactant/CO/sub 2/ ratio; (4) high temperatures tend to lower the rate and high pressures tend to increase the rate at 120/sup 0/F but to decrease at 75/sup 0/F; (5) foam quality was found to be affected more by surfactant/CO/sub 2/ ratio, and to a lesser degree by pressure and temperature. (ATT)

Wang, G. C.

1982-01-01

272

Direct observation of the electroadsorptive effect on ultrathin films for microsensor and catalytic-surface control.  

PubMed

Microchemical sensors and catalytic reactors make use of gases during adsorption in specific ways on selected materials. Fine-tuning is normally achieved by morphological control and material doping. The latter relates surface properties to the electronic structure of the bulk, and this suggests the possibility of electronic control. Although unusual for catalytic surfaces, such phenomena are sometimes reported for microsensors, but with little understanding of the underlying mechanisms. Herein, direct observation of the electroadsorptive effect by a combination of X-ray photoelectron spectroscopy and conductivity analysis on nanometre-thick semiconductor films on buried control electrodes is reported. For the SnO2/NO2 model system, NO3 surface species, which normally decay at the latest within minutes, can be kept stable for 1.5 h with a high coverage of 15% under appropriate electric fields. This includes uncharged states, too, and implies that nanoelectronic structures provide control over the predominant adsorbate conformation on exterior surfaces and thus opens the field for chemically reactive interfaces with in situ tunability. PMID:23687010

Doll, Theodor; Velasco-Velez, Juan J; Rosenthal, Dirk; Avila, Jonathan; Fuenzalida, Victor

2013-05-17

273

Build a better mouse: directly-observed issues in computer use for adults with SMI.  

PubMed

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

2013-03-01

274

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

275

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

2012-10-12

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

2012-05-07

277

Direct observation of steps in rotation of the bacterial flagellar motor.  

PubMed

The bacterial flagellar motor is a rotary molecular machine that rotates the helical filaments that propel many species of swimming bacteria. The rotor is a set of rings up to 45 nm in diameter in the cytoplasmic membrane; the stator contains about ten torque-generating units anchored to the cell wall at the perimeter of the rotor. The free-energy source for the motor is an inward-directed electrochemical gradient of ions across the cytoplasmic membrane, the protonmotive force or sodium-motive force for H+-driven and Na+-driven motors, respectively. Here we demonstrate a stepping motion of a Na+-driven chimaeric flagellar motor in Escherichia coli at low sodium-motive force and with controlled expression of a small number of torque-generating units. We observe 26 steps per revolution, which is consistent with the periodicity of the ring of FliG protein, the proposed site of torque generation on the rotor. Backwards steps despite the absence of the flagellar switching protein CheY indicate a small change in free energy per step, similar to that of a single ion transit. PMID:16208378

Sowa, Yoshiyuki; Rowe, Alexander D; Leake, Mark C; Yakushi, Toshiharu; Homma, Michio; Ishijima, Akihiko; Berry, Richard M

2005-10-01

278

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

PubMed Central

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

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

2012-01-01

279

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

280

Direct observation of the gene organization of the complement C4 and 21- hydroxylase loci by pulsed field gel electrophoresis  

PubMed Central

Pulsed field gel electrophoresis and enzymes that cut genomic DNA infrequently have been used to define large RFLPs at the human C4 loci. With the enzymes BssH II or Sac II, and C4 or 21-hydroxylase DNA probes, it has been possible to observe directly the number of C4 genes present on a haplotype, and also whether the C4 genes are long (6-7-kb intron present) or short (6-7-kb intron absent). Haplotypes that have either two long C4 genes or one long and one short C4 gene generate BssH II fragments of approximately 115 or approximately 105 kb, respectively. Haplotypes that have either a single long or a single short C4 gene generate BssH II fragments of approximately 80 or approximately 70 kb, respectively. This technique has been used to analyze the DNA isolated from PBMC and allows the complete definition of the C4 gene organization of an individual without the need for family studies.

1989-01-01

281

Direct observation of a sulfonyl azide excited state and its decay processes by ultrafast time-resolved IR spectroscopy.  

PubMed

The photochemistry of 2-naphthylsulfonyl azide (2-NpSO(2)N(3)) was studied by femtosecond time-resolved infrared (TR-IR) spectroscopy and with quantum chemical calculations. Photolysis of 2-NpSO(2)N(3) with 330 nm light promotes 2-NpSO(2)N(3) to its S(1) state. The S(1) excited state has a prominent azide vibrational band. This is the first direct observation of the S(1) state of a sulfonyl azide, and this vibrational feature allows a mechanistic study of its decay processes. The S(1) state decays to produce the singlet nitrene. Evidence for the formation of the pseudo-Curtius rearrangement product (2-NpNSO(2)) was inconclusive. The singlet sulfonylnitrene (1)(2-NpSO(2)N) is a short-lived species (? ? 700 ± 300 ps in CCl(4)) that decays to the lower-energy and longer-lived triplet nitrene (3)(2-NpSO(2)N). Internal conversion of the S(1) excited state to the ground state S(0) is an efficient deactivation process. Intersystem crossing of the S(1) excited state to the azide triplet state contributes only modestly to deactivation of the S(1) state of 2-NpSO(2)N(3). PMID:22462556

Kubicki, Jacek; Luk, Hoi Ling; Zhang, Yunlong; Vyas, Shubham; Peng, Huo-Lei; Hadad, Christopher M; Platz, Matthew S

2012-04-13

282

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

283

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

2012-03-08

284

Direct observation of the properties of cholesterol in membranes by deuterium NMR.  

PubMed

The properties of cholesterol in bilayers of egg phosphatidylcholine (PC) were investigated directly by means of 2H-NMR of specifically-deuterated species (C3, C7, C26, C27). Quadrupole splittings were a measure of molecular ordering, and relaxation times T1 and T2e were indicators of rates of motion. The importance of the use of echoes for spectral acquisition is emphasised, particularly to obtain accurate values of the quadrupole splitting. In the case of overlapping powder patterns from two labelled positions, the use of the absolute value mode of spectral presentation is shown to yield reasonable estimates of the individual quadrupole splittings. Spectral properties were monitored as a function of cholesterol concentration and temperature. Increasing cholesterol concentration led to a high degree of ordering for the rigid ring system of cholesterol, approaching a molecular order parameter of 0.8 at 50 mol% cholesterol. The isopropyl methyl groups were in all cases less ordered and more mobile than the ring system, but responded in a similar fashion to variable cholesterol concentration and temperature. The observation of a minimum in the temperature dependence of T1 for cholesterol-7,7-d2 led to a direct estimate of its correlation time for molecular motion, 3.5 X 10(-9) S rad-1. This indicates that the overall rate of motion of cholesterol is considerably slower than that of the lipids in which it is located. The short T2e values suggest that the motional spectrum of cholesterol is rich in low frequencies. The parallel temperature and cholesterol dependences of quadrupole splittings for different positions on the rigid ring system of cholesterol indicate that the position of the axis of motional averaging of the molecule is not changing, and is the same as that determined in an earlier study. It is emphasised that the steep temperature dependence and small quadrupole splittings for the chain isopropyl methyl groups of cholesterol do not necessarily indicate a high degree of disorder, but may be due to their axes of motional averaging lying at angles close to 54 degrees with respect to the director of the ordered lipids. PMID:7160030

Taylor, M G; Akiyama, T; Saitô, H; Smith, I C

1982-12-01

285

24 CFR 17.43 - Allowable claims.  

Code of Federal Regulations, 2013 CFR

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

2013-04-01

286

Directly Observed Therapy (DOT) for Nonadherent HIV-Infected Youth: Lessons Learned, Challenges Ahead  

PubMed Central

Abstract Adherence to medications is critical to optimizing HIV care and is a major challenge in youth. The utility of directly observed therapy (DOT) to improve adherence in youth with HIV remains undefined and prompted this pilot study. Four U.S. sites were selected for this 24-week cooperative group study to assess feasibility and to identify the logistics of providing DOT to HIV-infected youth with demonstrated adherence problems. Once-a-day DOT was provided by DOT facilitators at the participant's choice of a community-based location and DOT tapered over 12 weeks to self-administered therapy based on ongoing adherence assessments. Twenty participants, median age 21 years and median CD4 227?cells/?l, were enrolled. Participants chose their homes for 82% of DOT visits. Compliance with recommended DOT visits was (median) 91%, 91%, and 83% at weeks 4, 8, and 12, respectively. Six participants completed >90% of the study-specified DOT visits and successfully progressed to self-administered therapy (DOT success); only half sustained >90% medication adherence 12 weeks after discontinuing DOT. Participants considered DOT successes were more likely to have higher baseline depression scores (p?=?0.046). Via exit surveys participants reported that meeting with the facilitator was easy, DOT increased their motivation to take medications, they felt sad when DOT ended, and 100% would recommend DOT to a friend. In conclusion, this study shows that while community-based DOT is safe, feasible, and as per participant feedback, acceptable to youth, DOT is not for all and the benefits appear short-lived. Depressed youth appear to be one subgroup that would benefit from this intervention. Study findings should help inform the design of larger community-based DOT intervention studies in youth.

Belzer, Marvin; Britto, Paula; Garvie, Patricia A.; Hu, Chengcheng; Graham, Bobbie; Neely, Michael; McSherry, George; Spector, Stephen A.; Flynn, Patricia M.

2010-01-01

287

Rates of ingestion and their variability between individual calanoid copepods: Direct observations  

SciTech Connect

The goals of this study were to determine rates of ingestion and fecal pellet release, and their variability, for individual planktonic copepods over extended periods of time (>20 min). Ingestions and rejections of individual cells of the diatom Thalassiosira eccentrica by a adult females of the calanoid Paracalanus aculeatus were directly quantified by observing individual copepods continuously at cell concentrations ranging from 0.1 to 1.2 mm{sup 3} l{sup {minus}1}. Average ingestion rates increased with increasing food concentration, but were not significantly different between 0.3 and 1.0 mm{sup 3} l{sup {minus}1} (9.8 and 32.7 {mu}g Cl{sup {minus}1}) of T.eccentrica. Rates of cell rejections were low and similar at 0.1 and 0.3. but were significantly higher at 1.0 mm{sup 3} l{sup {minus}1}. The coefficients of variation for average ingestion rates of individual copepods hardly differed between food concentrations, ranging from 17 to 22%, and were close to those for average fecal pellet release intervals which ranged from 15 to 21%. A comparison between individuals at each food concentration found no significant differences at 1.0; at 0.1 and 0.3 mm{sup 3} l{sup {minus}1}, respectively, ingestion rates of four out of five females did not differ significantly from each other. Average intervals between fecal pellet releases were similar at 0.3 and 1.0 mm{sup 3} l{sup {minus}1}. Fecal pellet release intervals between individuals were significantly different at each food concentration; these significant differences were attributed to rather narrow ranges of pellet release intervals of each individual female. Potential sources/causes of variability in the sizes and rates of copepods in the ocean are evaluated.

Paffenhoefer, G.A.; Lewis, K.D. [Skidaway Inst. of Oceanography, Savannah, GA (United States); Bundy, M.H. [Skidaway Inst. of Oceanography, Savannah, GA (United States)]|[Alfred-Wegener-Institut fuer Polar- und Meeresforschung, Bremerhaven (Germany). Inst. fuer Fernerkundung (IFE); Metz, C. [Alfred-Wegener-Institut fuer Polar- und Meeresforschung, Bremerhaven (Germany). Inst. fuer Fernerkundung (IFE)

1995-12-01

288

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

NASA Astrophysics Data System (ADS)

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

Cash, Webster C.; New Worlds Study Team

2009-01-01

289

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

NASA Astrophysics Data System (ADS)

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

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

2009-01-01

290

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

291

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

Microsoft Academic Search

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

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

2011-01-01

292

Direct observation of the alpha-epsilon phase transformation in shocked single crystal iron  

Microsoft Academic Search

The technique of in-situ wide angle diffraction provides direct access to study the dynamic deformation of a material during the shock process. This technique has been used to study the shock response of single crystal Fe on a ns time-scale. Single crystals of Fe (001) were shock compressed by direct laser irradiation using the OMEGA, Janus, and Vulcan lasers. The

Daniel H. Kalantar; J. Hawreliak; M. Schneider

2005-01-01

293

Flight direction in some rocky mountain mayflies (Ephemeroptera), with observations of parasitism  

Microsoft Academic Search

Adult mayflies (Ephemeroptera) were sampled using sticky traps at several locations along a Rocky Mountain stream. Eight genera were collected, of which imagos oiBaetis spp and Rhilhrogena hageni were most common. Baetis was represented almost exclusively by females and flight direction was significantly in the upstream direction. In R. hageni both males and females were included. Females appeared to fly

Alexander S. Flecker; J. David Allan

1988-01-01

294

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

Microsoft Academic Search

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

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

2003-01-01

295

Direct and in vitro observation of growth hormone receptor molecules in A549 human lung epithelial cells by nanodiamond labeling  

NASA Astrophysics Data System (ADS)

This letter presents direct observation of growth hormone receptor in one single cancer cell using nanodiamond-growth hormone complex as a specific probe. The interaction of surface growth hormone receptor of A549 human lung epithelial cells with growth hormone was observed using nanodiamond's unique spectroscopic signal via confocal Raman mapping. The growth hormone molecules were covalent conjugated to 100 nm diameter carboxylated nanodiamonds, which can be recognized specifically by the growth hormone receptors of A549 cell. The Raman spectroscopic signal of diamond provides direct and in vitro observation of growth hormone receptors in physiology condition in a single cell level.

Cheng, C.-Y.; Perevedentseva, E.; Tu, J.-S.; Chung, P.-H.; Cheng, C.-L.; Liu, K.-K.; Chao, J.-I.; Chen, P.-H.; Chang, C.-C.

2007-04-01

296

Direct observation of microtubule-f-actin interaction in cell free lysates.  

PubMed

Coordinated interplay of the microtubule and actin cytoskeletons has long been known to be crucial for many cellular processes including cell migration and cytokinesis. However, interactions between these two systems have been difficult to document by conventional approaches, for a variety of technical reasons. Here the distribution of f-actin and microtubules were analyzed in the absence of fixation using Xenopus egg extracts as an in vitro source of microtubules and f-actin, demembranated Xenopus sperm to nucleate microtubule asters, fluorescent phalloidin as a probe for f-actin, and fluorescent tubulin as a probe for microtubules. F-actin consistently colocalized in a lengthwise manner with microtubules of asters subjected to extensive washing in flow chambers. F-actin-microtubule association was heterogenous within a given aster, such that f-actin is most abundant toward the distal (plus) ends of microtubules, and microtubules heavily labeled with f-actin are found in close proximity to microtubules devoid of f-actin. However, this distribution changed over time, in that 5 minute asters had more f-actin in their interiors than did 15 minute asters. Microtubule association with f-actin was correlated with microtubule bending and kinking, while elimination of f-actin resulted in straighter microtubules, indicating that the in vitro interaction between f-actin and microtubules is functionally significant. F-actin was also found to associate in a lengthwise fashion with microtubules in asters centrifuged through 30% sucrose, and microtubules alone (i.e. microtubules not seeded from demembranated sperm) centrifuged through sucrose, indicating that the association cannot be explained by flow-induced trapping and alignment of f-actin by aster microtubules. Further, cosedimentation analysis revealed that microtubule-f-actin association could be reconstituted from microtubules assembled from purified brain tubulin and f-actin assembled from purified muscle actin in the presence, but not the absence, of Xenopus oocyte microtubule binding proteins. The results provide direct evidence for an association between microtubules and f-actin in vitro, indicate that this interaction is mediated by one or more microtubule binding proteins, and suggest that this interaction may be responsible for the mutual regulation of the microtubule and actomyosin cytoskeletons observed in vivo. PMID:10341213

Sider, J R; Mandato, C A; Weber, K L; Zandy, A J; Beach, D; Finst, R J; Skoble, J; Bement, W M

1999-06-01

297

Direct observation of subtropical mode water circulation in the western North Atlantic Ocean  

NASA Astrophysics Data System (ADS)

Eighteen Degree Water (EDW) is the dominant subtropical mode water of the North Atlantic subtropical gyre and is hypothesized as an interannual reservoir of anomalous heat, nutrients and CO2. Although isolated beneath the stratified upper-ocean at the end of each winter, EDW may re-emerge in subsequent years to influence mixed layer properties and consequently air-sea interaction and primary productivity. Here we report on recent quasi-Lagrangian measurements of EDW circulation and stratification in the western subtropical gyre using an array of acoustically-tracked, isotherm-following, bobbing profiling floats programmed to track and intensively sample the vertically homogenized EDW layer and directly measure velocity on the 18.5 °C isothermal surface. The majority of the CLIVAR Mode Water Dynamics Experiment (CLIMODE) bobbers drifted within the subtropical gyre for 2.5-3.5 years, many exhibiting complex looping patterns indicative of an energetic eddy field. Bobber-derived Lagrangian integral time and length scales (3 days, 68 km) associated with motion on 18.5 °C were consistent with previous measurements in the Gulf Stream extension region and fall between previous estimates at the ocean surface and thermocline depth. Several bobbers provided evidence of long-lived submesoscale coherent vortices associated with substantial EDW thickness. While the relative importance of such vortices remains to be determined, our observations indicate that these features can have a profound effect on EDW distribution. EDW thickness (defined using a vertical temperature gradient criterion) exhibits seasonal changes in opposition to a layer bounded by the 17 °C and 19 °C isotherms. In particular, EDW thickness is generally greatest in winter (as a result of buoyancy-forced convection), while the 17°-19 °C layer is thickest in summer consistent with seasonal Ekman pumping. Contrary to previous hypotheses, the bobber data suggest that a substantial fraction of subducted EDW is isolated from the atmosphere for periods of less than 24 months. Seasonal-to-biennial re-emergence (principally within the recirculation region south of the Gulf Stream) appears to be a common scenario which should be considered when assessing the climatic and biogeochemical consequences of EDW.

Fratantoni, David M.; Kwon, Young-Oh; Hodges, Benjamin A.

2013-07-01

298

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

299

Calculating the propagation direction of coronal mass ejections by connecting in situ observations with heliospheric images  

NASA Astrophysics Data System (ADS)

We determined the propagation direction of two coronal mass ejections by using data provided by the Heliospheric Imagers (HI) and the PLASTIC and IMPACT instruments onboard the two STEREO satellites. To facilitate the tracking of the CME's leading edge we made time-elongation plots (J-plots) for the investigated events and tracked the apparent leading edge therein several times in order to estimate the measurement error. For converting elongation to distance we compared several methods (Point-P, Fixed-Phi and their harmonic mean). To determine the direction of the CME's propagation in the ecliptic we connected the CME-track derived from HI J-plots with the measured in situ arrival time by modifying the propagation direction within the used model equations. The resulting directions and their errors are discussed with respect to the different assumptions used for each technique.

Rollett, Tanja; Möstl, Christian; Temmer, Manuela; Veronig, Astrid; Biernat, Helfried K.

2010-05-01

300

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

Microsoft Academic Search

Thermospheric neutral winds at Arecibo show a long-term trend over timeThe vector magnitude of the wind increased slightly and its direction rotated CCWDecreases in neutral density\\/temperature and ion coupling help explain trends

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

2011-01-01

301

Direct Observation of Oil Consumption Mechanisms in a Production Spark Ignition Engine Using Fluorescence Techniques.  

National Technical Information Service (NTIS)

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-in...

R. M. Lusted

1994-01-01

302

Direct observation of magnetization switching in focused-ion-beam-fabricated magnetic nanotubes  

NASA Astrophysics Data System (ADS)

In this letter, a direct measurement of "easy" magnetization switching indicating zero-magnetization remanence in a magnetic probe with a cross section as narrow as 60 x60 nm2, and as tall as 750 nm, is presented. Magnetic force microscopy was utilized to test focused-ion-beam-fabricated nanomagnetic probes. The data directly indicate that unlike a regular solid probe, a probe with a tubelike ending (nanotube) provides substantially "easier" switching.

Khizroev, Sakhrat; Kryder, Mark H.; Litvinov, Dmitri; Thompson, David A.

2002-09-01

303

Direct observation of strain relaxation in iron layers on W(110) by time-resolved STM  

Microsoft Academic Search

Time-resolved,in-situ-applied STM has been used to study the epitaxial growth of iron on W(110) at room temperature. By this way, sequences of STM images show directly the atomistics of the growth process on the surface. The first layer of iron on W(110) grows pseudomorphically without a preferred growth direction. Beginning with the second layer, the islands grow anisotropically with preferred

C. Jensen; K. Reshöft; U. Köhler

1996-01-01

304

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

305

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

Microsoft Academic Search

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

Tomer Holczer; Ehud Behar; Shai Kaspi

2007-01-01

306

Direct Spectroscopic Observation of the Structural Origin of Peroxide Generation from Co-Based Pyrolyzed Porphyrins for ORR Applications  

SciTech Connect

Pyrolyzed transition metal based porphyrins present an attractive alternative to state of the art Pt-based electrocatalysts for fuel cell applications based on their comparatively low cost. Unfortunately, the large array of precursors and synthetic strategies has led to considerable ambiguity regarding the specific structure/property relationships that give rise to their activity for oxygen reduction. Specifically, considerable debate exists in actual chemical structure of the pyrolyzed reaction centers, and their relationship to membrane-damaging peroxide yield. In this manuscript a comprehensive electrochemical and spectroscopic study of pyrolyzed CoTMPP produced via a self-templating process is presented. The resulting electrocatalysts are not carbon-supported, but are highly porous self-supported pyropolymers. Rotating ring disk electrode measurements showed that the materials pyrolyzed at 700 C exhibited the highest performance, whereas pyrolysis at 800 C resulted in a significant increase in the peroxide yield. X-ray photoelectron spectroscopy and Co L and K edge extended X-ray absorption fine structure (EXAFS) studies confirm that the majority of the Co-N4 active site has broken down to Co-N2 at 800 C. Application of ?{mu} analysis (an X-ray absorption near-edge structure difference technique) to the in situ Co K edge EXAFS data allowed for direct spectroscopic observation of the geometry of Oads on the pyropolymer active sites. The specific geometrical adsorption of molecular oxygen with respect to the plane of the Co-Nx moieties highly influences the oxygen reduction reaction pathway. The application of the ?{mu} technique to other transition metal based macrocycle electrocatalyst systems is expected to provide similarly detailed information.

Ziegelbauer,J.; Olson, T.; Pylypenko, S.; Alamgir, F.; Jaye, C.; Atanassov, P.; Mukerjee, S.

2008-01-01

307

Direct observation of fault zone structure and mechanics in three-dimensions: A study of the SEMP fault system, Austria  

NASA Astrophysics Data System (ADS)

Outcrops of the Salzach-Ennstal-Mariazell-Puchberg (SEMP) fault system exhumed from depths of ˜4--17 km allow for the direct observation of fault zone structures throughout the crust, and provide insights into the way this fault, and perhaps others, distributes strain in three dimensions. At Gstatterboden, exhumed from ˜4--8 km, grain size distributions and small fault data reveal the presence of a 10-m-wide high-strain core towards which strain localized during fault evolution. Brittle fracture was accommodated via constrained comminution, which only occurs in strain-weakening rheologies and favors localization. Exposures of the SEMP at Lichtensteinklamm and Kitzlochklamm, exhumed from ˜12 km depth, bracket the brittle ductile transition. At these outcrops, the SEMP is characterized by a ˜70-m-wide, cataclastic fault core that has been altered to clays that transitions downward into a wide, ductile shear zone that has accommodated only minor amounts of strain, placing the majority of displacement on the razor-sharp fault contact. Deformation mechanisms transition from cataclasis and minor amounts of dislocation creep in calcite, to dislocation creep in quartz and calcite occurring against a background of fault-normal solution mass transfer. The ductile/ductile-brittle Rinderkarsee shear zone, exhumed from ˜17 km, marks the SEMP's continuation into the Tauern Window and is composed of three distinct shear zones. The southern, 100-m-wide shear zone has accommodated the most strain, and shows evidence for creep-accommodated grain boundary sliding in feldspar and quartz, while incipient shear zones contain ductile quartz and brittle-feldspars that undergo dislocation creep as fluids alter Kspar to muscovite, which localizes strain along felspar grain boundaries, encouraging ductility. These findings are compared to results from other faults exhumed from similar depth ranges, highlighting fundamental fault zone structures and characteristics.

Frost, Erik Karl

308

Direct observation of proteolytic cleavage at the S2 site upon forced unfolding of the Notch negative regulatory region.  

PubMed

The conserved Notch signaling pathway plays crucial roles in developing and self-renewing tissues. Notch is activated upon ligand-induced conformation change of the Notch negative regulatory region (NRR) unmasking a key proteolytic site (S2) and facilitating downstream events. Thus far, the molecular mechanism of this signal activation is not defined. However, strong indirect evidence favors a model whereby transendocytosis of the Notch extracellular domain, in tight association with ligand into the ligand-bearing cell, exerts a force on the NRR to drive the required structure change. Here, we demonstrate that force applied to the human Notch2 NRR can indeed expose the S2 site and, crucially, allow cleavage by the metalloprotease TACE (TNF-alpha-converting enzyme). Molecular insight into this process is achieved using atomic force microscopy and molecular dynamics simulations on the human Notch2 NRR. The data show near-sequential unfolding of its constituent LNR (Lin12-Notch repeat) and HD (heterodimerization) domains, at forces similar to those observed for other protein domains with a load-bearing role. Exposure of the S2 site is the first force "barrier" on the unfolding pathway, occurring prior to unfolding of any domain, and achieved via removal of the LNRAB linker region from the HD domain. Metal ions increase the resistance of the Notch2 NRR to forced unfolding, their removal clearly facilitating unfolding at lower forces. The results provide direct demonstration of force-mediated exposure and cleavage of the Notch S2 site and thus firmly establish the feasibility of a mechanotransduction mechanism for ligand-induced Notch activation. PMID:23011796

Stephenson, Natalie L; Avis, Johanna M

2012-09-24

309

Observations of Surface Wave Azimuthal Anisotropy in Southern California by Direct Application of the Beamforming Method  

NASA Astrophysics Data System (ADS)

We use the Southern California Seismic Network as an array and apply a beamforming method for 190 teleseismic events to determine their Rayleigh surface wave phase velocities and their arrival directions. Our results indicate that the array aperture has excellent resolution for periods 16-100 seconds but above 100 seconds phase velocities begin to show large error bars because of its spatial size. We recover the ubiquitous pattern of azimuthal phase velocity variation of Rayleigh waves for periods 16-50 seconds; the amplitude variations are about 1-1.5%, consistent with an assumption of a weakly anisotropic medium. Our results also confirm an assumption in most studies, of negligible dependence on the 4-theta component. Though these results apply only in Southern California, direct confirmation of small 4-theta variations seems to be rare. Our analysis shows that anisotropy is present in the period range 15-50 seconds which correspond approximately to 50-200 km wavelengths, and suggests anisotropy extends to the upper mantle with an prevalent anisotropic fast axis that is oriented along the direction SE-NW (110/290 degrees clockwise from North). This direction is interesting in that it is sub-parallel with the Mohave section of the San Andreas Fault. It is this section of the fault that is misaligned with the general direction of the North America-Pacific Plate boundary. Thus we speculate that the fast axis alignment may be associated with shear and compression of the Transverse Ranges.

Alvizuri, C. R.; Tanimoto, T.

2010-12-01

310

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

2013-07-09

311

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

312

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

SciTech Connect

We report a precise, direct spectroscopic measurement of simultaneous bi-directional outflows from a reconnection event in a laboratory plasma. Outflow speeds are as Alfvenic and Abel analysis shows that the outflows are generated in the plasma core. A Sweet-Parker like analysis of outflow speed coupled with external measurements of reconnection electric field and assumption of Spitzer resistivity predict an aspect ratio of the reconnection layer and reconnection rate that are close to that measured in the experiment and in simulations. However, this analysis underestimates the absolute scale of the layer, indicating other than 2D resistive physics is at play.

Brown, M. R.; Cothran, C. D.; Gray, T. [Department of Physics and Astronomy, Center for Magnetic Self Organization, Swarthmore College, Swarthmore, Pennsylvania 19081-1397 (United States); Myers, C. E.; Belova, E. V. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

2012-08-15

313

The Development of a Direct Observation Code for Use in Preschool Settings.  

ERIC Educational Resources Information Center

Reports development of observation system, Preschool Observation Code (POC), for use across phases of preschool intervention design and evaluation. Describes purpose of code, procedures used for code, procedures used for code construction, and two related studies of interrater and criterion-referenced agreement. Discusses practical issues related…

Bramlett, Ronald K.; Barnett, David W.

1993-01-01

314

Direct observation of electron-transfer-induced conformational transformation (molecular actuation) in a bichromophoric electron donor.  

PubMed

With the aid of laser-flash photolysis, the one-electron oxidation of conformationally mobile tetramethoxydibenzobicyclo[4.4.1]undecane (1), using photoexcited chloranil as an oxidant, allows us to show that extended 1(+•) undergoes a conformational transformation to ?-stacked folded 1(+•) on a microsecond time scale (? ? 1 ?s), which is at least six times longer than that found for the conformationally locked model compound. PMID:20491456

Shukla, Ruchi; Thakur, Khushabu; Chebny, Vincent J; Reid, Scott A; Rathore, Rajendra

2010-05-21

315

Direct Observation of the Alpha-Epsilon Transition in Shocked Single Crystal Iron.  

National Technical Information Service (NTIS)

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. ...

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

2005-01-01

316

Direct observation of a propagating spin wave induced by spin-transfer torque  

Microsoft Academic Search

Spin torque oscillators with nanoscale electrical contacts are able to produce coherent spin waves in extended magnetic films, and offer an attractive combination of electrical and magnetic field control, broadband operation, fast spin-wave frequency modulation, and the possibility of synchronizing multiple spin-wave injection sites. However, many potential applications rely on propagating (as opposed to localized) spin waves, and direct evidence

M. Madami; S. Bonetti; G. Consolo; S. Tacchi; G. Carlotti; G. Gubbiotti; F. B. Mancoff; M. A. Yar; J. Åkerman

2011-01-01

317

Modeling of Observability During In-Drilling Alignment for Horizontal Directional Drilling  

Microsoft Academic Search

Navigation performance is an important factor in horizontal directional drilling. In-drilling alignment (IDA) was previously suggested to improve downhole navigation performance when utilizing an inertial navigation system (INS). It was shown that the IDA process enhances the ability to estimate INS bias and drift errors and, particularly, their azimuth-related components. It was suggested that this improvement was related to a

Efraim Pecht; Martin P. Mintchev

2007-01-01

318

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

319

Four-Month-Olds' Discrimination of Optic Flow Patterns Depicting Different Directions of Observer Motion  

Microsoft Academic Search

One of the most powerful sources of information about spatial relationships avail- able to mobile organisms is the pattern of visual motion called optic flow. Despite its importance for spatial perception and for guiding locomotion, very little is known about how the ability to perceive one's direction of motion, or heading, from optic flow develops early in life. In this

Rick O. Gilmore; Heather J. Rettke

2003-01-01

320

Direct Observations of the Mechanical Behaviors of the Cytoskeleton in Living Fibroblasts  

Microsoft Academic Search

Cytoskeletal proteins tagged with green fluo- rescent protein were used to directly visualize the me- chanical role of the cytoskeleton in determining cell shape. Rat embryo (REF 52) fibroblasts were deformed using glass needles either uncoated for purely physical manipulations, or coated with laminin to induce attach- ment to the cell surface. Cells responded to uncoated probes in accordance with

Steven R. Heidemann; Stefanie Kaech; Robert E. Buxbaum; Andrew Matus

1999-01-01

321

Observation of Turbulent Mixing in Lean-Direct-Injection Combustion at Elevated Pressure.  

National Technical Information Service (NTIS)

We report the first quantitative single-shot multiscalar data obtained from a realistic air-fed lean-direct-injection burner operating on gaseous methane (CH4) fuel at elevated pressure (5 atm) using single-shot spontaneous Raman spectroscopy. From a stat...

J. Kojima Q. V. Nguyen

2008-01-01

322

Direct observation of interfacial C60 cluster formation in polystyrene-C60 nanocomposite films  

NASA Astrophysics Data System (ADS)

Large interfacial C60 clusters were directly imaged at the supporting film-substrate interface in physically detached polystyrene-C60 nanocomposite films by atomic force microscopy, confirming the stabilizing mechanism previously hypothesized for thin polymer films. Additionally, we found that the C60 additive influences basic thermodynamic film properties such as the interfacial energy and the film thermal expansion coefficient.

Tark Han, Joong; Lee, Geon-Woong; Kim, Sangcheol; Lee, Hae-Jeong; Douglas, Jack F.; Karim, Alamgir

2009-03-01

323

Direct observation of the alignment of ferromagnetic spins by antiferromagnetic spins  

Microsoft Academic Search

The arrangement of spins at interfaces in a layered magnetic material often has an important effect on the properties of the material. One example of this is the directional coupling between the spins in an antiferromagnet and those in an adjacent ferromagnet, an effect first discovered in 1956 and referred to as exchange bias. Because of its technological importance for

F. Nolting; A. Scholl; J. Stöhr; J. W. Seo; J. Fompeyrine; H. Siegwart; J.-P. Locquet; S. Anders; J. Lüning; E. E. Fullerton; M. F. Toney; M. R. Scheinfein; H. A. Padmore

2000-01-01

324

Direct TEM observation of the welding of asperities between two single-crystal gold films  

Microsoft Academic Search

To understand the microscopic interaction between two metal surfaces, a direct transmission electron microscopic (TEM) examination of metal-to-metal contacts was performed. Gold was chosen for this study to eliminate complications due to surface oxides and to gain insight into the anomalously high coefficient of friction between two nonlubricated gold surfaces. The formation of grain boundaries between two gold films in

SIU-WAI CHAN

1989-01-01

325

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

PubMed Central

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

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

2010-01-01

326

DIRECT OBSERVATIONAL EVIDENCE OF FILAMENT MATERIAL WITHIN INTERPLANETARY CORONAL MASS EJECTIONS  

SciTech Connect

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

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

2010-11-01

327

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

328

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

329

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

SciTech Connect

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

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

2010-05-01

330

Direct observation of flux behavior in high-Tc oxide superconductors using the Faraday effect of iron garnet films  

Microsoft Academic Search

A new direct observation method for the dynamical magnetic flux behavior in superconductors was developed by using the Faraday effect of an iron garnet film with perpendicular magnetization and stripe domains. The domain structure observed optically in the iron garnet film in contact with an YBa2Cu3O(x) sample reveals the magnetic field distribution of the latter. It was found that the

Satoshi Gotoh; Naoki Koshizuka; Masashi Yoshida; Masato Murakami; Shoji Tanaka

1990-01-01

331

ENCODER-LESS OPERATION OF A DIRECT TORQUE CONTROLLED IPM MOTOR DRIVE WITH A NOVEL SLIDING MODE OBSERVER  

Microsoft Academic Search

This paper reports an improvement of encoder-less operation performance of direct torque controlled (DTC) interior permanent magnet (IPM) synchronous motor drives. A completely encoder-less IPM motor drive with DTC, which uses a new sliding mode observer for speed estimation, is presented. The experimental results show that the proposed observer is able to deliver more accurate estimation than open-loop speed estimator

Z. Xu; M. F. Rahman

2004-01-01

332

Liquid Crystal Formation in Suspensions of Hard Rodlike Colloidal Particles: Direct Observation of Particle Arrangement and Self-Ordering Behavior  

Microsoft Academic Search

We successfully prepared monodisperse, hard rodlike colloidal particles with a wide range of length-to-width ratios (L\\/W). In their suspensions liquid crystals, or nematic (N) and smectic (Sm) phases, spontaneously appeared. The size of the particles made it possible to directly observe their arrangement and dynamics with an optical microscope. The phase behavior observed exhibited an I (isotropic)-Sm transition for L\\/W=3.5

Hideatsu Maeda; Yoshiko Maeda

2003-01-01

333

Kinetic modeling of phase transformations occurring in the HAZ of C-Mn steel welds based on direct observations  

Microsoft Academic Search

In situ Spatially Resolved X-Ray Diffraction (SRXRD) experiments were performed in the heat-affected zone (HAZ) of gas tungsten arc (GTA) welds of AISI 1005 C-Mn steel to directly observe welding induced phase transformations. These real-time observations were semi-quantified using diffraction peak profile analysis to construct a phase transformation map revealing ferrite (?) and austenite (?) phase concentration gradients in the

J. W. Elmer; T. A. Palmer; W. Zhang; B. Wood; T. DebRoy

2003-01-01

334

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

335

Direct Observation of Magnetic Flux Behavior in High-Tc Oxide Superconductors  

Microsoft Academic Search

The magnetic flux behavior in YBa2Cu3Ox specimens under various applied fields was observed at 10K and 77K using the Faraday effect of an iron garnet film with stripe magnetic domains. The magnetic flux distribution was determined by optical observation of the domain structure in the iron garnet film placed on the sample. The magnetic flux gradients in a crystal fabricated

S. Gotoh; N. Koshizuka; M. Yoshida; H. Fujimoto; M. Murakami; H. Izumi; K. Ohata

1992-01-01

336

Direct Observation of the Turbulent emf and Transport of Magnetic Field in a Liquid Sodium Experiment  

NASA Astrophysics Data System (ADS)

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.; Zane Taylor, Nicholas; Forest, Cary B.; Jenko, Frank; Limone, Angelo; Pinton, Jean-François; Plihon, Nicolas; Verhille, Gautier

2012-11-01

337

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

SciTech Connect

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

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

2009-01-22

338

Barkhausen noise measurements give direct observation of magnetocrystalline anisotropy energy in ferromagnetic polycrystals  

NASA Astrophysics Data System (ADS)

This paper presents experimental evidence of the capability of Barkhausen noise measurements to estimate the angular dependence of the average magnetocrystalline energy in soft magnetic polycrystalline materials. Three different API 5L steel samples, all obtained from out-of-service pipelines, were investigated using crystallographic texture and Barkhausen noise measurements. The angular dependence of the rms voltage of the Barkhausen signal was determined in each sample for the time band corresponding to the saturation-to-remanence part of the hysteresis loop where irreversible domain rotation occurs. For each angular position, the rms voltage of the Barkhausen noise signal in this time band was interpreted as a direct measure of the magnetocrystalline anisotropy energy of the polycrystal in the corresponding direction. A strong correlation between the angular dependence of both the rms voltage of the Barkhausen signal in the time band of interest and the average magnetocrystalline energy obtained from crystallographic texture measurements was found experimentally.

Espina-Hernández, J. H.; Pérez-Benítez, J. A.; Caleyo, F.; Baudin, T.; Helbert, A. L.; Hallen, J. M.

2013-10-01

339

Observation of Direct CP Violation in KS,L --> pipi Decays  

Microsoft Academic Search

We have compared the decay rates of KL and KS to pi+pi- and pi0pi0 final states using a subset of the data from the KTeV experiment (E832) at Fermilab. We find that the direct-CP-violation parameter Re\\\\(?'\\/?\\\\) is equal to [28.0+\\/-3.0\\\\(stat\\\\)+\\/-2.8\\\\(syst\\\\)]×10-4. This result definitively establishes the existence of CP violation in a decay process.

A. Alavi-Harati; I. F. Albuquerque; T. Alexopoulos; M. Arenton; K. Arisaka; S. Averitte; A. R. Barker; L. Bellantoni; A. Bellavance; J. Belz; R. Ben-David; D. R. Bergman; E. Blucher; G. J. Bock; C. Bown; S. Bright; E. Cheu; S. Childress; R. Coleman; M. D. Corcoran; G. Corti; B. Cox; M. B. Crisler; A. R. Erwin; R. Ford; A. Glazov; A. Golossanov; G. Graham; J. Graham; K. Hagan; E. Halkiadakis; K. Hanagaki; S. Hidaka; Y. B. Hsiung; V. Jejer; J. Jennings; D. A. Jensen; R. Kessler; H. G. Kobrak; J. Ladue; A. Lath; A. Ledovskoy; P. L. McBride; A. P. McManus; P. Mikelsons; E. Monnier; T. Nakaya; U. Nauenberg; K. S. Nelson; H. Nguyen; V. O'dell; M. Pang; R. Pordes; V. Prasad; C. Qiao; B. Quinn; E. J. Ramberg; R. E. Ray; A. Roodman; M. Sadamoto; S. Schnetzer; K. Senyo; P. Shanahan; P. S. Shawhan; W. Slater; N. Solomey; S. V. Somalwar; R. L. Stone; I. Suzuki; E. C. Swallow; R. A. Swanson; S. A. Taegar; R. J. Tesarek; G. B. Thomson; P. A. Toale; A. Tripathi; R. Tschirhart; Y. W. Wah; J. Wang; H. B. White; J. Whitmore; B. Winstein; R. Winston; J.-Y. Wu; T. Yamanaka; E. D. Zimmerman

1999-01-01

340

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

341

Direct Observation of the alpha-? Transition in Shocked Single Crystal Iron  

Microsoft Academic Search

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

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

2006-01-01

342

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

343

Direct Observation of Nodes and Twofold Symmetry in FeSe Superconductor  

Microsoft Academic Search

We investigated the electron-pairing mechanism in an iron-based superconductor, iron selenide (FeSe), using scanning tunneling microscopy and spectroscopy. Tunneling conductance spectra of stoichiometric FeSe crystalline films in their superconducting state revealed evidence for a gap function with nodal lines. Electron pairing with twofold symmetry was demonstrated by direct imaging of quasiparticle excitations in the vicinity of magnetic vortex cores, Fe

Can-Li Song; Yi-Lin Wang; Peng Cheng; Ye-Ping Jiang; Wei Li; Tong Zhang; Zhi Li; Ke He; Lili Wang; Jin-Feng Jia; Hsiang-Hsuan Hung; Congjun Wu; Xucun Ma; Xi Chen; Qi-Kun Xue

2011-01-01

344

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

Microsoft Academic Search

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

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

2005-01-01

345

Direct Observation of Multiple Pathways of DNA Stacking Using Single-Molecule AFM  

Microsoft Academic Search

During DNA interactions, single-stranded DNA (ssDNA) is often stretched and stabilized by coupling with ssDNA binding proteins to serve as an intermediate state. The conformational and energetic changes of stretched DNA are of great interest because of their relevance in biological functions. Direct manipulation of DNA has yielded much of the information about the mechanical properties of DNA without the

Ching-Hwa Kiang; Wei-Hung Chen

2009-01-01

346

Direct Observation of the Momentun-Density Profile of Excited and Oriented Sodium Atoms  

Microsoft Academic Search

The noncoplanar symmetric (e,2e> cross section is obtained for sodium atoms pumped by sigma+ laser light tuned to the 3S21\\/2(F=2)3P23\\/2(F'=3) transition. The excited pumped atoms are in themF'=3 state, or in terms of orbital momentum in the ml=+1 state. The coordinate frame is chosen so that the momentum density of the excited state is probed in the kx direction with

Y. Zheng; I. E. McCarthy; E. Weigold; D. Zhang

1990-01-01

347

Direct Observation of the Resistive Wall Mode in a Tokamak and Its Interaction with Plasma Rotation  

SciTech Connect

Using newly developed techniques and improved diagnostics, rotating wall-stabilized discharges have been maintained in the DIII-D tokamak for 30 characteristic resistive wall decay times{emdash}significantly longer than was previously achieved. The terminating resistive wall mode has been directly identified using internal fluctuation diagnostics, and its correlation with the slowdown in the plasma rotation is established. {copyright} {ital 1999} {ital The American Physical Society}

Garofalo, A.M.; Bialek, J.; Navratil, G.A.; Sabbagh, S.A. [Columbia University, New York, New York 10027 (United States); Turnbull, A.D.; Chu, M.S.; Groebner, R.J.; La Haye, R.J.; Lao, L.L.; Osborne, T.H.; Scoville, J.T.; Strait, E.J.; Taylor, T.S. [General Atomics, San Diego, California 92186-5608 (United States); Austin, M.E. [The University of Texas at Austin, Austin, Texas 78712 (United States); Comer, K.J. [University of Wisconsin, Madison, Wisconsin 53706-1687 (United States); Fredrickson, E.D. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Lazarus, E.A. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Rice, B.W. [Lawrence Livermore National Laboratory, Livermore, California 94551-9900 (United States)

1999-05-01

348

Polymer tensiometers with ceramic cones: direct observations of matric pressures in drying soils  

Microsoft Academic Search

Measuring soil water potentials is crucial to characterize vadose zone processes. Conventional tensiometers only measure until approximately -0.09 MPa, and indirect methods may suffer from the non-uniqueness in the relationship between matric potential and measured properties. Recently developed polymer tensiometers (POTs) are able to directly measure soil matric potentials until the theoretical wilting point (-1.6 MPa). By minimizing the volume

M. J. van der Ploeg; H. P. A. Gooren; G. Bakker; C. W. Hoogendam; C. Huiskes; L. K. Koopal; H. Kruidhof; G. H. de Rooij

2010-01-01

349

Direct Observation of the Segregated Microstructures within Co-Cr Film Grains  

NASA Astrophysics Data System (ADS)

The existence of a segregated microstructure within sputtered 4.1 ?m-thick Co-22 at%Cr film grains is proved directly by high-spatial-resolution X-ray microanalysis. The results indicate the existence of grains comprising a Cr-rich core surrounded by a Co-rich ring, and an indication of Cr-enriched grain boundaries. This microstructure coincides well with the latent microstructure revealed by selective wet-etching with dilute aqua regia.

Maeda, Yasushi; Takahashi, Masaya

1989-02-01

350

Direct Observation of Massless Domain Wall Dynamics in Nanostripes with Perpendicular Magnetic Anisotropy  

NASA Astrophysics Data System (ADS)

Domain wall motion induced by nanosecond current pulses in nanostripes with perpendicular magnetic anisotropy (Pt/Co/AlOx) is shown to exhibit negligible inertia. Time-resolved magnetic microscopy during current pulses reveals that the domain walls start moving, with a constant speed, as soon as the current reaches a constant amplitude, and no or little motion takes place after the end of the pulse. The very low “mass” of these domain walls is attributed to the combination of their narrow width and high damping parameter ?. Such a small inertia should allow accurate control of domain wall motion by tuning the duration and amplitude of the current pulses.

Vogel, J.; Bonfim, M.; Rougemaille, N.; Boulle, O.; Miron, I. M.; Auffret, S.; Rodmacq, B.; Gaudin, G.; Cezar, J. C.; Sirotti, F.; Pizzini, S.

2012-06-01

351

Direct torque and flux controlled IPM synchronous motor drive using a hybrid signal injection and adaptive sliding mode observer  

Microsoft Academic Search

This paper proposes a new speed sensorless direct torque and flux controlled interior permanent magnet synchronous motor (IPMSM) drive. Closed-loop control of both the torque and stator flux linkage are achieved by using two proportional-integral (PI) controllers. The reference voltage vectors are generated by a space vector modulation (SVM) unit. The drive uses an adaptive sliding mode observer for joint

Gilbert Foo; M. F. Rahman

2009-01-01

352

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

353

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

354

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

355

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

PubMed

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

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

2011-04-21

356

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); 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); West, R.N.; Badrzadeh, S. [Department of Physics, University of Texas at Arlington, P.O.Box 19059, Arlington, Texas 76019 (United States)

1997-08-01

357

ARTEX - in-situ observation of directional solidification of Al-Si alloys on TEXUS 39  

NASA Astrophysics Data System (ADS)

The goal of the experiment in the ARTEX furnace facility (Aerogel technology for microgravity solidification on TEXUS) during the sounding rocket flight TEXUS 39 in May 2001 was twofold, consisting primarily in the technology demonstration of the furnace equipped with the fragile aerogels as a was submitted to directional solidification in order to determine the influence of diffusive versus convective material transport conditions on the microstructure evolution. The scientific objective was defined by the ESA-MAP MICAST project studying the influence of controlled convection on the microstructure evolution.

Ahrweiler, Sonja; Ratke, Lorenz; Masslow, Hans Dieter

2003-08-01

358

Molecular machines directly observed by high-speed atomic force microscopy.  

PubMed

Molecular machines made of proteins are highly dynamic and carry out sophisticated biological functions. The direct and dynamic high-resolution visualization of molecular machines in action is considered to be the most straightforward approach to understanding how they function but this has long been infeasible until recently. High-speed atomic force microscopy has recently been realized, making such visualization possible. The captured images of myosin V, F1-ATPase, and bacteriorhodopsin have enabled their dynamic processes and structure dynamics to be revealed in great detail, giving unique and deep insights into their functional mechanisms. PMID:23318713

Ando, Toshio

2013-01-11

359

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

Microsoft Academic Search

The formation and growth of sigma (Ï) 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, Ï 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

T. A. Palmer; J. W. Elmer; S. S. Babu; E. D. Specht

2007-01-01

360

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

Microsoft Academic Search

The formation and growth of sigma (Ï) 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, Ï 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

T Palmer; J Elmer; S Babu; E Specht

2005-01-01

361

Direct Observations of Ligand Dynamics in Hemoglobin by Subpicosecond Infrared Spectroscopy  

Microsoft Academic Search

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

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

1989-01-01

362

Direct observations of heteroepitaxial diamond on silicon (110) substrate by microwave plasma chemical vapor deposition  

SciTech Connect

Heteroepitaxial diamond has been successfully deposited on Si (110) substrate by microwave plasma chemical vapor deposition method. The pretreatment consisted of carburization and bias-enhanced nucleation steps. Cross-sectional transmission electron microscopy reveals that diamond can be in the cube-on-cube epitaxial relationship with the Si substrate. Various orientation relationships between diamond and Si substrates have also been observed, depending on the location where the plasma applied. Near the center of the plasma, twins were rarely observed in cube-on-cube epitaxial regions. Away from the center of the plasma ball, {Sigma}3 twins are seen first, and then additional {Sigma}9 and {Sigma}27 twins occur near the edge of the plasma. In general, defect density in the epitaxial films is less than that observed in polycrystalline ones. No interlayer could be observed between diamond and silicon. In addition, 2H-type hexagonal diamond has also been found, and is in epitaxy with the Si substrate. {copyright} {ital 1996 Materials Research Society.}

Chen, C.J. [Materials Science Center, Tsin Hua University, Hsinchu, Taiwan 300, Republic of (China); Chang, L. [Division of Engineering and Applied Science, National Science Council, Taipei, Taiwan 10636, Republic of (China); Lin, T.S. [Materials Research Laboratories, Industrial Technology Research Institute, Hsinchu, Taiwan 31015, Republic of (China); Chen, F.R. [Materials Science Center, Tsin Hua University, Hsinchu, Taiwan 300, Republic of (China)

1996-04-01

363

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

Microsoft Academic Search

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

S. Amelinckx

1956-01-01

364

Global anthropogenic aerosol direct forcing derived from satellite and ground-based observations  

Microsoft Academic Search

surface. The uncertainty of about 10-20% in the surface and atmosphere forcing translates into a six fold uncertainty in the TOA forcing because the TOA forcing is a small sum of two large terms (surface and atmosphere) of opposing signs. Given the current state of observations and modeling, it is very difficult to further reduce the uncertainty in the estimated

Chul Eddy Chung; V. Ramanathan; Dohyeong Kim; I. A. Podgorny

2005-01-01

365

Direct observation of Frank-Read sources in stoichiometric bismuth telluride crystals  

Microsoft Academic Search

Stoichiometric crystals of bismuth telluride have been grown from the melt by the horizontal zone levelling technique. The multiplication of dislocations and dislocation density was studied by using chemical etching. Dislocation spirals and loops due to Frank-Read sources have been observed on the basal plane.

A. G. Kunjomana; E. Mathai

1991-01-01

366

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

Microsoft Academic Search

Deep penetration laser welding is associated with violent plasma generation which consists of metal vapour, ionized ions and electrons. The plasma resides both outside and inside the keyhole, known as the plasma plume and keyhole plasma, respectively. Plasma plumes have been studied extensively due to the convenience of observing them. However, very little work has been carried out on the

Xiangzhong Jin; Licheng Zeng; Yuanyong Cheng

2012-01-01

367

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

Microsoft Academic Search

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

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

1989-01-01

368

Parent Information and Direct Observation in the Diagnosis of Pervasive and Specific Developmental Disorders.  

ERIC Educational Resources Information Center

|An Autism Diagnostic Interview (ADI-R) was conducted with parents of 11 children with early infantile autism and 16 with a language disorder, along with a standardized Autism Diagnostic Observation Schedule (ADOS-G). Ten children with autism were correctly classified on both measures. One child with a language disorder was falsely classified on…

Noterdaeme, Michele; Mildenberger, Katrin; Sitter, Stefan; Amorosa, Hedwig

2002-01-01

369

Direct observation of decay of radioactive nuclei with spatial and time coincidence technique  

NASA Astrophysics Data System (ADS)

The position, energy and time sensitivity of the Timepix detector can be exploited for detection and spectroscopy of radioactive ions and their decay. The USB readout interface used for detector control and data acquisition can be adapted to receive an external clock and trigger from other detecting devices such as ionization chambers, scintillation and semiconductor detectors. Timepix can be thus used to (i) selectively detect chosen ions from a multiple-component ion beam, and (ii) record their subsequent decay. The high granularity of the pixel detector allows to apply not only temporal, but also spatial coincidence technique for background suppression. This is particularly important for scarcely populated nuclei. Results are demonstrated by the measurement of 8He and 6He ions decay products and decay half-lives. Experiments were done on short-lived nuclei using radioactive ion beams of the Lohengrin fission fragment mass separator at the ILL Grenoble.

Jakubek, J.; Platkevic, Michal; Granja, C.; Köster, U.; Pospisil, S.

2011-05-01

370

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.

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

2012-01-01

371

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

NASA Astrophysics Data System (ADS)

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

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

2005-03-01

372

Analytic Bounds on Causal Risk Differences in Directed Acyclic Graphs Involving Three Observed Binary Variables  

PubMed Central

We apply a linear programming approach which uses the causal risk difference (RDC) as the objective function and provides minimum and maximum values that RDC can achieve under any set of linear constraints on the potential response type distribution. We consider two scenarios involving binary exposure X, covariate Z and outcome Y. In the first, Z is not affected by X, and is a potential confounder of the causal effect of X on Y. In the second, Z is affected by X and intermediate in the causal pathway between X and Y. For each scenario we consider various linear constraints corresponding to the presence or absence of arcs in the associated directed acyclic graph (DAG), monotonicity assumptions, and presence or absence of additive-scale interactions. We also estimate Z-stratum-specific bounds when Z is a potential effect measure modifier and bounds for both controlled and natural direct effects when Z is affected by X. In the absence of any additional constraints deriving from background knowledge, the well-known bounds on RDc are duplicated: ?Pr(Y?X) ? RDC ? Pr(Y=X). These bounds have unit width, but can be narrowed by background knowledge-based assumptions. We provide and compare bounds and bound widths for various combinations of assumptions in the two scenarios and apply these bounds to real data from two studies.

Kaufman, Sol; Kaufman, Jay S.; MacLehose, Richard F.

2009-01-01

373

Experimental observation of the improvement in MTF from backthinning a CMOS direct electron detector.  

PubMed

The advantages of backthinning monolithic active pixel sensors (MAPS) based on complementary metal oxide semiconductor (CMOS) direct electron detectors for electron microscopy have been discussed previously; they include better spatial resolution (modulation transfer function or MTF) and efficiency at all spatial frequencies (detective quantum efficiency or DQE). It was suggested that a 'thin' CMOS detector would have the most outstanding properties [1-3] because of a reduction in the proportion of backscattered electrons. In this paper we show, theoretically (using Monte Carlo simulations of electron trajectories) and experimentally that this is indeed the case. The modulation transfer functions of prototype backthinned CMOS direct electron detectors have been measured at 300keV. At zero spatial frequency, in non-backthinned 700-mum-thick detectors, the backscattered component makes up over 40% of the total signal but, by backthinning to 100, 50 or 35mum, this can be reduced to 25%, 15% and 10%, respectively. For the 35mum backthinned detector, this reduction in backscatter increases the MTF by 40% for spatial frequencies between 0.1 and 1.0 Nyquist. As discussed in the main text, reducing backscattering in backthinned detectors should also improve DQE. PMID:19541421

McMullan, G; Faruqi, A R; Henderson, R; Guerrini, N; Turchetta, R; Jacobs, A; van Hoften, G

2009-05-18

374

Experimental observation of the improvement in MTF from backthinning a CMOS direct electron detector  

PubMed Central

The advantages of backthinning monolithic active pixel sensors (MAPS) based on complementary metal oxide semiconductor (CMOS) direct electron detectors for electron microscopy have been discussed previously; they include better spatial resolution (modulation transfer function or MTF) and efficiency at all spatial frequencies (detective quantum efficiency or DQE). It was suggested that a ‘thin’ CMOS detector would have the most outstanding properties [1–3] because of a reduction in the proportion of backscattered electrons. In this paper we show, theoretically (using Monte Carlo simulations of electron trajectories) and experimentally that this is indeed the case. The modulation transfer functions of prototype backthinned CMOS direct electron detectors have been measured at 300 keV. At zero spatial frequency, in non-backthinned 700-?m-thick detectors, the backscattered component makes up over 40% of the total signal but, by backthinning to 100, 50 or 35 ?m, this can be reduced to 25%, 15% and 10%, respectively. For the 35 ?m backthinned detector, this reduction in backscatter increases the MTF by 40% for spatial frequencies between 0.1 and 1.0 Nyquist. As discussed in the main text, reducing backscattering in backthinned detectors should also improve DQE.

McMullan, G.; Faruqi, A.R.; Henderson, R.; Guerrini, N.; Turchetta, R.; Jacobs, A.; van Hoften, G.

2009-01-01

375

Direct atomic force microscopy observations of monovalent ion induced binding of DNA to mica.  

PubMed

Multivalent ions in solution are known to mediate attraction between two like-charged molecules. Such attraction has proved useful in atomic force microscopy (AFM) where DNA may be immobilized to a mica surface facilitating direct imaging in liquid. Theories of DNA immobilization suggest that either 'salt bridging' or fluctuation in the positions of counter ions about both the mica surface and DNA backbone secure DNA to the mica substrate. Whilst both theoretical and experimental evidence suggest that immobilization is possible in the presence of divalent ions, very few studies identify that such immobilization is possible with monovalent ions. Here we present direct AFM evidence of DNA immobilized to mica in the presence of only monovalent ions. Our data depict E. coli plasmid pBR322 adsorbed onto the negatively charged mica both after short (10 min) and long (24 h) incubation periods. These data suggest the need to re-explore current theories of like-charge attraction to include the possibility of monovalent interactions. We suggest that this DNA immobilization strategy may offer the potential to image natural processes with limited immobilization forces and hence enable maximum conformational freedom of the immobilized biomolecule. PMID:15312194

Ellis, J S; Abdelhady, H G; Allen, S; Davies, M C; Roberts, C J; Tendler, S J B; Williams, P M

2004-09-01

376

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

377

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

PubMed

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

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

2013-08-26

378

Direct observations of thermally induced structural changes in amorphous silicon carbide  

SciTech Connect

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

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

2008-08-01

379

Direct observation of lateral current spreading in actively-driven ridge-waveguide lasers  

Microsoft Academic Search

We report results of two-dimensional local voltage measurement of the transverse cross-section of operating multi-quantum-well ridge-waveguide lasers. We observe lateral non- uniformity of local voltage in the n-cladding layers of the laser and attribute the voltage variation to two-dimensional carrier transport effect within the lasers. 02002 Optical Society of America OCIS codes: (140.2020) Diode lasers, (180.5810) Scanning microscopy

D. Ban; S. Kuntze; E. B. Sargent; St. J. Dixon-Warren; K. Hinzer; A. J. SpringThorpe; J. K. White

2003-01-01

380

Direct observation of lateral current spreading in ridge waveguide lasers using scanning voltage microscopy  

Microsoft Academic Search

We report results of two-dimensional (2D) local voltage measurement of the transverse cross section of operating multiquantum-well ridge-waveguide (RWG) lasers. We observe lateral nonuniformity of local voltage in the n-cladding layers of the laser and attribute the voltage variation to 2D carrier transport effect within the RWG lasers. The quantitative evaluation of this effect indicates the local vertical current density

D. Ban; E. H. Sargent; K. Hinzer; St. J. Dixon-Warren; A. J. Springthorpe; J. K. White

2003-01-01

381

Handheld Computers for Direct Observation of the Social and Physical Environment  

Microsoft Academic Search

This article evaluates the use of handheld computers for systematic observation of the social and physical environments. Handheld computers, also known as personal digital assistants (PDAs), make the advantages of computer-assisted data collection (CADC) more accessible to field-based researchers. In particular, CADC with handheld computers may improve data quality, reduce turnaround time, and enhance research capacity for community-academic partnerships. Here,

Clarence C. Gravlee; Shannon N. Zenk; Sachiko Woods; Zachary Rowe; Amy J. Schulz

2006-01-01

382

Direct observation of lipid hydroperoxides in phospholipid vesicles by electrospray mass spectrometry  

Microsoft Academic Search

Positive ion electrospray ionization mass spectrometry was used to obtain a lipid profile of vesicles prepared from egg yolk lethicin and enriched with arachidonylstearoyl phosphatidylcholine and dipalmitoyl phosphatidylcholine. The vesicles were oxidized by treatment with tert-butylhydroperoxide and iron (II) sulfate, and the formation of hydroperoxides of the polyunsaturated lipid arachidonylstearoyl phosphatidylcholine was observed. The native lipid signal at 832 a.m.u.

Corinne M. Spickett; Andrew R. Pitt; Amanda J. Brown

1998-01-01

383

Direct observation of liquid-phase sintering in the system iron-copper  

Microsoft Academic Search

The hot-stage of a scanning electron microscope has been used to observe liquid-phase sintering in the system iron-copper. The densification behaviour of compacts of Fe and Cu particles were determined. The influence of particle size of both components and the amount of liquid phase developed were investigated. In samples with about 20 vol % liquid phase, the densification kinetics as

Leonhard Froschauer; Richard M. Fulrath

1975-01-01

384

Direct Observations of Lateral Variation at the Core-Mantle Boundary  

Microsoft Academic Search

Recent deep events beneath the Philippines have been recorded by USArray providing evidence for multi-scale features on the Core-Mantle Boundary (CMB). While isolated seismograms of event-station pairs have been explained by abrupt edges, these dense array observations reveal multi-scale features ranging from 10 to 500 km. With the dense USArray records, we can measure the differential time (DeltaLR) between SPdKS

D. Sun; D. V. Helmberger; J. M. Jackson

2010-01-01

385

Direct Observation of Twin Formation in Iron4.4% Silicon Crystals  

Microsoft Academic Search

Single crystals of iron-4.4% silicon and of iron were subjected to impact compression at room temperature. High-speed cine-microscopic pictures were taken at a framing rate of 4--6× 105 sec-1 for observation of twin formation in the specimens. The twin formation lasted for a period of an order of 10 musec, resulting in a fairly uniform distribution of twins with a

Hirokatsu Masuda; Shin-ichi Hyodo; Ryukichi Honda

1967-01-01

386

Direct Observation of Double Bragg Reflections in X-Ray Diffraction Patterns of Pyrolytic Graphites  

Microsoft Academic Search

Several spurious peaks observed in the x-ray diffraction patterns of bulk specimens of pyrolytic graphites (PG) have been identified as double Bragg peaks. Their angular position is described by 2?hkl+2?h?k?l?, where ?hkl and ?h?k?l? are the Bragg angles of the participating single reflections. The intensity dependence of the peaks on the specimen shape and the specimen orientation is distinctly different

O. J. Guentert

1964-01-01

387

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

NASA Astrophysics Data System (ADS)

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.

2008-10-01

388

Direct measurements of stacking-fault energies from observations of dislocation nodes  

Microsoft Academic Search

From measurements of the radius of curvature of extended dislocation nodes observed by transmission electron microscopy, stacking-fault energies have been determined for a number of copper and silver base aluminium and zinc solid solution alloys and also for a number of nickel-cobalt alloys. Rough estimates of about 40, 25 and 150 erg cm respectively can be made of the stacking-fault

A. Howie; P. R. Swann

1961-01-01

389

Very high-resolution observations of compact radio sources in the directions of supernova remnants  

Microsoft Academic Search

Compact radio sources whose positions lie within the outlines of supernova remnants may be the stellar remnants of supernova explosions and, if they are related to the supernova remnants, may be used to explore the nature of any morphological connection between the Galactic and extragalactic radio sources. Three such compact sources, G 127.11+0.54, CL 4, and 2051+433, have been observed

B. J. Geldzahler; D. B. Shaffer

1981-01-01

390

Direct observation of the superfluid phase transition in ultracold Fermi gases  

Microsoft Academic Search

Water freezes into ice, atomic spins spontaneously align in a magnet, liquid\\u000ahelium becomes superfluid: Phase transitions are dramatic phenomena. However,\\u000adespite the drastic change in the system's behaviour, observing the transition\\u000acan sometimes be subtle. The hallmark of Bose-Einstein condensation (BEC) and\\u000asuperfluidity in trapped, weakly interacting Bose gases is the sudden\\u000aappearance of a dense central core inside

Christian H. Schunck; André Schirotzek; Wolfgang Ketterle; Martin W. Zwierlein

2006-01-01

391

Direct Observation of Species Liberated from GaAs Native Oxides during Atomic Hydrogen Cleaning  

Microsoft Academic Search

A real-time mass spectroscopic observation of liberated species was carried out to investigate the mechanism of atomic-hydrogen-( H•)-induced deoxidation of GaAs native oxides. Atomic hydrogen treatment at 410°C caused, initially, the liberation of molecular arsenic ( As2\\/As4), resulting in the removal of As oxides, which was then followed by the liberation of Ga2O, leading to complete deoxidation. These results indicate

Masamichi Yamada; Yuichi Ide

1994-01-01

392

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

Microsoft Academic Search

In this work, we present the first AMBER observations, of the Wolf-Rayet and\\u000aO (WR+O) star binary system y2 Velorum. The AMBER instrument was used with the\\u000atelescopes UT2, UT3, and UT4 on baselines ranging from 46m to 85m. It delivered\\u000aspectrally dispersed visibilities, as well as differential and closure phases,\\u000awith a resolution R = 1500 in the spectral

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

2006-01-01

393

Direct Observation of Abortive Initiation and Promoter Escape within Single Immobilized Transcription Complexes  

PubMed Central

Using total-internal-reflection fluorescence microscopy equipped with alternating-laser excitation, we were able to detect abortive initiation and promoter escape within single immobilized transcription complexes. Our approach uses fluorescence resonance energy transfer to monitor distances between a fluorescent probe incorporated in RNA polymerase (RNAP) and a fluorescent probe incorporated in DNA. We observe small, but reproducible and abortive-product-length-dependent, decreases in distance between the RNAP leading edge and DNA downstream of RNAP upon abortive initiation, and we observe large decreases in distance upon promoter escape. Inspection of population distributions and single-molecule time traces for abortive initiation indicates that, at a consensus promoter, at saturating ribonucleoside triphosphate concentrations, abortive-product release is rate-limiting (i.e., abortive-product synthesis and RNAP-active-center forward translocation are fast, whereas abortive-product dissociation and RNAP-active-center reverse translocation are slow). The results obtained using this new methodology confirm and extend those obtained from diffusing single molecules, and pave the way for real-time, single-molecule observations of the transitions between various states of the transcription complex throughout transcription.

Margeat, Emmanuel; Kapanidis, Achillefs N.; Tinnefeld, Philip; Wang, You; Mukhopadhyay, Jayanta; Ebright, Richard H.; Weiss, Shimon

2006-01-01

394

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

PubMed Central

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

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

1985-01-01

395

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

NASA Astrophysics Data System (ADS)

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

2006-09-01

396

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

397

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

398

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.

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

2013-01-01

399

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

400

Direct Observation of Multiferroic Vortex Domains in YMnO3.  

PubMed

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

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

2013-09-24

401

Magnetic coupling in Fe/Cr/Fe sandwich structures directly observed by polarised neutron reflection  

NASA Astrophysics Data System (ADS)

We have used polarised neutron reflection to directly determine the vector orientation of the individual Fe layer average magnetisations in an antiferromagnetically coupled 50 ÅFe/15 ÅCr/50 ÅFe sandwich structure prepared by sputtering. The spin dependent neutron wave in the multilayer structure is represented by a two component spinor and the resulting reflected intensity is found to be highly sensitive to variations in the orientations of the layer-dependent magnetisation vectors, permitting the preferred orientation of the average magnetisation in each Fe layer to be studied. The saturated state is found to correspond to a uniform ferromagnetic alignment of the Fe layer magnetisations. At low field, we are able to assess the degree to which the magnetic alignment is fully antiparallel, and conclude that our results are consistent with the development of a multidomain structure.

Bland, J. A. C.; Bateson, R. D.; Johnson, N. F.; Blundell, S. J.; Speriosu, V. S.; Metin, S.; Gurney, B. A.; Penfold, J.

1993-05-01

402

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

403

Direct observation of stepped proteolipid ring rotation in E. coli FoF1-ATP synthase  

PubMed Central

Although single-molecule experiments have provided mechanistic insight for several molecular motors, these approaches have proved difficult for membrane bound molecular motors like the FoF1-ATP synthase, in which proton transport across a membrane is used to synthesize ATP. Resolution of smaller steps in Fo has been particularly hampered by signal-to-noise and time resolution. Here, we show the presence of a transient dwell between Fo subunits a and c by improving the time resolution to 10 ?s at unprecedented S/N, and by using Escherichia coli FoF1 embedded in lipid bilayer nanodiscs. The transient dwell interaction requires 163 ?s to form and 175 ?s to dissociate, is independent of proton transport residues aR210 and cD61, and behaves as a leash that allows rotary motion of the c-ring to a limit of ?36° while engaged. This leash behaviour satisfies a requirement of a Brownian ratchet mechanism for the Fo motor where c-ring rotational diffusion is limited to 36°.

Ishmukhametov, Robert; Hornung, Tassilo; Spetzler, David; Frasch, Wayne D

2010-01-01

404

Direct Observation of Charge-Carrier Heating at WZ-ZB InP Nanowire Heterojunctions.  

PubMed

We have investigated the dynamics of hot charge carriers in InP nanowire ensembles containing a range of densities of zinc-blende inclusions along the otherwise wurtzite nanowires. From time-dependent photoluminescence spectra, we extract the temperature of the charge carriers as a function of time after nonresonant excitation. We find that charge-carrier temperature initially decreases rapidly with time in accordance with efficient heat transfer to lattice vibrations. However, cooling rates are subsequently slowed and are significantly lower for nanowires containing a higher density of stacking faults. We conclude that the transfer of charges across the type II interface is followed by release of additional energy to the lattice, which raises the phonon bath temperature above equilibrium and impedes the carrier cooling occurring through interaction with such phonons. These results demonstrate that type II heterointerfaces in semiconductor nanowires can sustain a hot charge-carrier distribution over an extended time period. In photovoltaic applications, such heterointerfaces may hence both reduce recombination rates and limit energy losses by allowing hot-carrier harvesting. PMID:23919626

Yong, Chaw Keong; Wong-Leung, Jennifer; Joyce, Hannah J; Lloyd-Hughes, James; Gao, Qiang; Tan, H Hoe; Jagadish, Chennupati; Johnston, Michael B; Herz, Laura M

2013-08-12

405

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

NASA Astrophysics Data System (ADS)

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

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

2010-03-01

406

Direct observation of a bent carbonyl ligand in a 19-electron transition metal complex.  

PubMed

The photochemistry of [CpRu(CO)2]2 in P(OMe)3/CH2Cl2 solution has been studied using picosecond time-resolved infrared (TRIR) spectroscopy. Photolysis at 400 nm leads to the formation of 17-electron CpRu(CO)2(•) radicals, which react on the picosecond time scale to form 19-electron CpRu(CO)2P(OMe)3(•) adducts. The TRIR spectra of this adduct display an unusually low CO stretching frequency for the antisymmetric CO stretching mode, suggesting that one carbonyl ligand adopts a bent configuration to avoid a 19-electron count at the metal center. This spectral assignment is supported by analogous experiments on [CpFe(CO)2]2 in the same solvent, combined with DFT studies on the structures of the 19-electron adducts. The DFT results predict a bent CO ligand in CpRu(CO)2P(OMe)3(•), whereas approximately linear Fe-C-O bond angles are predicted for CpFe(CO)2P(OMe)3(•). The observation of a bent CO ligand in the 19-electron ruthenium adduct is a surprising result, and it provides new insight into the solution-phase behavior of 19-electron complexes. TRIR spectra were also collected for [CpRu(CO)2]2 in neat CH2Cl2, and it is interesting to note that no singly bridged [CpRu(CO)]2(?-CO) photoproduct was observed to form following 400- or 267-nm excitation, despite previous observations of this species on longer time scales. PMID:23448247

Lomont, Justin P; Nguyen, Son C; Harris, Charles B

2013-03-12

407

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

PubMed Central

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

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

2013-01-01

408

Bistatic-radar observation of long-period, directional ocean-wave spectra with loran a.  

PubMed

Bistatic-radar scattering from medium- to long-wavelength (80 to 200 meters) ocean waves has been observed with the use of loran A (1.85 megahertz) transmissions and a receiver located 280 kilometers away. The received echoes have been converted into a time-delay, Doppler-frequency map in which the effects of anisotropies in the ocean-wave spectra are clearly shown. The distribution of the echoes in delay-Doppler space is consistent with Bragg scattering from trains of dispersed ocean waves. PMID:17833495

Peterson, A M; Teague, C C; Tyler, G L

1970-10-01

409

Hydrogen porosity in directional solidified aluminum-copper alloys: In situ observation  

SciTech Connect

Using a temperature gradient stage and real time micro-focus radiography the formation of porosity was observed in situ during the solidification of aluminum-copper alloys. Pore morphology was characterized both in the final structure and as a function of temperature during solidification, providing a qualitative insight into the relative importance of the competing physical processes. The effect of solidification velocity, thermal gradient and alloy composition on both the growth kinetics and final structure of the porosity was quantified. Statistical analysis was used to compare the trends in these results to both diffusion controlled and shrinkage driven pore growth.

Lee, P.D.; Hunt, J.D. [Univ. of Oxford (United Kingdom). Dept. of Materials

1997-10-01

410

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

411

Direct observation of nanocrystallite buckling in carbon fibers under bending load.  

PubMed

Single carbon fibers are deformed in bending by forming loops with varying radius. Position-resolved x-ray diffraction patterns from the bent fibers are collected from the tension to the compression region with a synchrotron radiation nanobeam of 100 nm size from a waveguide structure. A strain redistribution with a shift of the neutral axis is observed. A significant increase of the misorientation of the graphene sheets in the compression region shows that intense buckling of the nanosized carbon crystallites is the physical origin of different tensile and compressive properties. PMID:16384230

Loidl, D; Paris, O; Burghammer, M; Riekel, C; Peterlik, H

2005-11-21

412

Direct Observation of Nanocrystallite Buckling in Carbon Fibers under Bending Load  

SciTech Connect

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

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

2005-11-25

413

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

SciTech Connect

The excited state dynamics of o-dichlorobenzene has been studied by femtosecond time-resolved photoelectron imaging. The lifetime of the first excited state S{sub 1} of o-dichlorobenzene was determined to be 482 {+-} 10 ps. Field-free nonadiabatic alignment of the o-dichlorobenzene on the first excited state S{sub 1} (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 S{sub 1} 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 [State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, Hubei 430071 (China) and Graduate School of the Chinese Academy of Sciences, Beijing 100049 (China)

2011-03-15

414

A microfluidic imaging chamber for the direct observation of chemotactic transmigration  

PubMed Central

To study the roles of nonmuscle myosin II (NM-II) during invasive cell migration, microfluidic migration chambers have been designed and fabricated using photo- and soft-lithography microfabrication techniques. The chamber consists of two channels separated by a vertical barrier with multiple bays of pores with widths varying from 6 µm to 16 µm, and lengths varying from 25µm to 50µm. The cells are plated in the channel on one side of the barrier while a chemoattractant is flowed through the channel on the other side of the barrier. In these chambers, cells can be observed with transmitted light or fluorescence optics while they chemotax through various sized pores that impose differential mechanical resistance to transmigration. As an initial test of this device, we compared breast-cancer cell chemotactic transmigration through different pore sizes with and without inhibition of NM-II. Two distinct rates were observed as cells attempted to pull their nucleus through the smaller pores, and the faster nuclear transit mode was critically dependent on NM-II motor activity. The ability to monitor cells as they chemotax through pores of different dimensions within a single experimental system provides novel information on how pore size affects cell morphology and migration rate, providing a dramatic improvement of imaging potential relative to other in vitro transmigration systems such as Boyden chambers.

Breckenridge, Mark T.; Egelhoff, Thomas T.; Baskaran, Harihara

2010-01-01

415

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

PubMed

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

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

2012-11-15

416

Direct Observations of Heterogeneous Dust Processing in the Troposphere: Ambient Measurements, Source Compositions and Laboratory Studies  

NASA Astrophysics Data System (ADS)

The size and chemical composition of single dust particles in both background marine air and during dust events was determined using Aerosol Time-of-Flight Mass Spectrometry (ATOFMS) throughout the Indian and Pacific Oceans and Pacific coast during three major field campaigns: INDOEX, ACE-Asia and CIFEX. In general the chemical associations within individual particle spectra for the major dust particle types were very similar in all sampling locations. The dust mass spectra were dominated by various combinations of potassium, calcium, iron, and aluminum, with contributions from silicates, sodium, chloride and titanium oxides. The relative ion intensities often differed suggesting that the dust is a complex, externally mixed aggregate of varying mineral origins. Evidence of heterogeneous processing of the dust particles was also observed with ATOFMS using markers for nitrate, sulphate, and organic species. Aging of dust particles can dramatically alter their radiative and cloud-forming properties, changing the effects that dust will have on global climate. The dust spectra were also compared with those measured from collected dust, sand and soil samples in Asia and the United States. In general the mass spectra of the ambient and source dust particles were very similar, except that for the most part the source samples lacked evidence of atmospheric aging. Preliminary lab studies examining heterogeneous processing of dust in a flow tube will be presented. These studies investigate the relative reactivity of the different types of dust observed in the atmosphere and the competitive heterogeneous chemistry of dust and sea salt particles.

Sullivan, R. C.; Guazzotti, S.; Sodeman, D.; Coffee, K.; Holecek, J.; Spencer, M.; Prather, K. A.

2004-12-01

417

Direct observation of phase transition of GeSbTe thin films by Atomic Force Microscope  

NASA Astrophysics Data System (ADS)

GeSbTe (GST) thin films were deposited on quartz substrates using electron beam evaporation system and then annealed in nitrogen atmosphere at different temperatures, ranging from 20 °C to 300 °C. X-ray diffraction (XRD) and Atomic Force microscope (AFM) measurements were used to characterize the as-deposited and post-annealed thin films. Annealing treatment was found to induce changes on microstructure, surface roughness and grain size, indicating that with the increase of annealing temperature, the amorphous GST films first changed to face-centered-cubic (fcc) phase and then the stable hexagonal (hex) phase. Meanwhile, conductive-AFM (C-AFM) was used to produce crystallized GST dots on thin films. I-V spectroscopy results show that GST films can switch from amorphous state to crystalline state at threshold voltage. After switching, I-V curve exhibits ohmic characteristic, which is usually observed in crystallized GST films. By applying repeated I-V spectroscopies on the thin films, crystallized nuclei were observed. As the times of I-V spectroscopies increases, the area of written dots increases, and the center of the mark begin to ablate. The AFM images show that the shape of marks is an ablated center with a raised ring surrounding it.

Yang, Fei; Xu, Ling; Zhang, Rui; Geng, Lei; Tong, Liang; Xu, Jun; Su, Weining; Yu, Yao; Ma, Zhongyuan; Chen, Kunji

2012-10-01

418

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

419

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

2013-07-03

420

Direct observation of protein unfolded state compaction in the presence of macromolecular crowding.  

PubMed

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

Mikaelsson, Therese; Adén, Jörgen; Johansson, Lennart B-Å; Wittung-Stafshede, Pernilla

2013-02-01

421

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

PubMed

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

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

2009-06-01

422

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

PubMed

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