Science.gov

Sample records for allowing direct observation

  1. Dipole-allowed direct band gap silicon superlattices

    NASA Astrophysics Data System (ADS)

    Oh, Young Jun; Lee, In-Ho; Kim, Sunghyun; Lee, Jooyoung; Chang, Kee Joo

    2015-12-01

    Silicon is the most popular material used in electronic devices. However, its poor optical properties owing to its indirect band gap nature limit its usage in optoelectronic devices. Here we present the discovery of super-stable pure-silicon superlattice structures that can serve as promising materials for solar cell applications and can lead to the realization of pure Si-based optoelectronic devices. The structures are almost identical to that of bulk Si except that defective layers are intercalated in the diamond lattice. The superlattices exhibit dipole-allowed direct band gaps as well as indirect band gaps, providing ideal conditions for the investigation of a direct-to-indirect band gap transition. The fact that almost all structural portions of the superlattices originate from bulk Si warrants their stability and good lattice matching with bulk Si. Through first-principles molecular dynamics simulations, we confirmed their thermal stability and propose a possible method to synthesize the defective layer through wafer bonding.

  2. Dipole-allowed direct band gap silicon superlattices.

    PubMed

    Oh, Young Jun; Lee, In-Ho; Kim, Sunghyun; Lee, Jooyoung; Chang, Kee Joo

    2015-01-01

    Silicon is the most popular material used in electronic devices. However, its poor optical properties owing to its indirect band gap nature limit its usage in optoelectronic devices. Here we present the discovery of super-stable pure-silicon superlattice structures that can serve as promising materials for solar cell applications and can lead to the realization of pure Si-based optoelectronic devices. The structures are almost identical to that of bulk Si except that defective layers are intercalated in the diamond lattice. The superlattices exhibit dipole-allowed direct band gaps as well as indirect band gaps, providing ideal conditions for the investigation of a direct-to-indirect band gap transition. The fact that almost all structural portions of the superlattices originate from bulk Si warrants their stability and good lattice matching with bulk Si. Through first-principles molecular dynamics simulations, we confirmed their thermal stability and propose a possible method to synthesize the defective layer through wafer bonding. PMID:26656482

  3. Dipole-allowed direct band gap silicon superlattices

    PubMed Central

    Oh, Young Jun; Lee, In-Ho; Kim, Sunghyun; Lee, Jooyoung; Chang, Kee Joo

    2015-01-01

    Silicon is the most popular material used in electronic devices. However, its poor optical properties owing to its indirect band gap nature limit its usage in optoelectronic devices. Here we present the discovery of super-stable pure-silicon superlattice structures that can serve as promising materials for solar cell applications and can lead to the realization of pure Si-based optoelectronic devices. The structures are almost identical to that of bulk Si except that defective layers are intercalated in the diamond lattice. The superlattices exhibit dipole-allowed direct band gaps as well as indirect band gaps, providing ideal conditions for the investigation of a direct-to-indirect band gap transition. The fact that almost all structural portions of the superlattices originate from bulk Si warrants their stability and good lattice matching with bulk Si. Through first-principles molecular dynamics simulations, we confirmed their thermal stability and propose a possible method to synthesize the defective layer through wafer bonding. PMID:26656482

  4. Direct observation of time reversal violation

    SciTech Connect

    Bernabeu, J.

    2013-06-12

    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.

  5. Direct observation of time reversal violation

    NASA Astrophysics Data System (ADS)

    Bernabu, J.

    2013-06-01

    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.

  6. 30 CFR 220.011 - Schedule of allowable direct and allocable joint costs and credits.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... event of oil spills or other environmental damage are allowable. The costs of actual control and cleanup of oil spills and resulting responsibilities required by applicable laws and regulations are... PAYMENT FOR OUTER CONTINENTAL SHELF OIL AND GAS LEASES § 220.011 Schedule of allowable direct...

  7. 30 CFR 1220.011 - Schedule of allowable direct and allocable joint costs and credits.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... event of oil spills or other environmental damage are allowable. The costs of actual control and cleanup of oil spills and resulting responsibilities required by applicable laws and regulations are... PAYMENT FOR OUTER CONTINENTAL SHELF OIL AND GAS LEASES § 1220.011 Schedule of allowable direct...

  8. 30 CFR 1220.011 - Schedule of allowable direct and allocable joint costs and credits.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... event of oil spills or other environmental damage are allowable. The costs of actual control and cleanup of oil spills and resulting responsibilities required by applicable laws and regulations are... PAYMENT FOR OUTER CONTINENTAL SHELF OIL AND GAS LEASES § 1220.011 Schedule of allowable direct...

  9. 30 CFR 1220.011 - Schedule of allowable direct and allocable joint costs and credits.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... event of oil spills or other environmental damage are allowable. The costs of actual control and cleanup of oil spills and resulting responsibilities required by applicable laws and regulations are... PAYMENT FOR OUTER CONTINENTAL SHELF OIL AND GAS LEASES § 1220.011 Schedule of allowable direct...

  10. Direct observation limits on antimatter gravitation

    SciTech Connect

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

    2008-06-01

    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.

  11. Directly observed therapy for treating tuberculosis

    PubMed Central

    Karumbi, Jamlick; Garner, Paul

    2015-01-01

    Background Tuberculosis (TB) requires at least six months of treatment. If treatment is incomplete, patients may not be cured and drug resistance may develop. Directly Observed Therapy (DOT) is a specific strategy, endorsed by the World Health Organization, to improve adherence by requiring health workers, community volunteers or family members to observe and record patients taking each dose. Objectives To evaluate DOT compared to self-administered therapy in people on treatment for active TB or on prophylaxis to prevent active disease. We also compared the effects of different forms of DOT. Search methods We searched the following databases up to 13 January 2015: the Cochrane Infectious Diseases Group Specialized Register; the Cochrane Central Register of Controlled Trials (CENTRAL), published in the Cochrane Library; MEDLINE; EMBASE; LILACS and mRCT. We also checked article reference lists and contacted relevant researchers and organizations. Selection criteria Randomized controlled trials (RCTs) and quasi-RCTs comparing DOT with routine self-administration of treatment or prophylaxis at home. Data collection and analysis Two review authors independently assessed risk of bias of each included trial and extracted data. We compared interventions using risk ratios (RR) with 95% confidence intervals (CI). We used a random-effects model if meta-analysis was appropriate but heterogeneity present (I2 statistic = 50%). We assessed the quality of the evidence using the GRADE approach. Main results Eleven trials including 5662 participants met the inclusion criteria. DOT was performed by a range of people (nurses, community health workers, family members or former TB patients) in a variety of settings (clinic, the patient's home or the home of a community volunteer). DOT versus self-administered Six trials from South Africa, Thailand, Taiwan, Pakistan and Australia compared DOT with self-administered therapy for treatment. Trials included DOT at home by family members, community health workers (who were usually supervised); DOT at home by health staff; and DOT at health facilities. TB cure was low with self-administration across all studies (range 41% to 67%), and direct observation did not substantially improve this (RR 1.08, 95% CI 0.91 to 1.27; five trials, 1645 participants, moderate quality evidence). In a subgroup analysis stratified by the frequency of contact between health services in the self-treatment arm, daily DOT may improve TB cure when compared to self-administered treatment where patients in the self-administered group only visited the clinic every month (RR 1.15, 95% CI 1.06 to 1.25; two trials, 900 participants); but with contact in the control becoming more frequent, this small effect was not apparent (every two weeks: RR 0.96, 95% CI 0.83 to 1.12; one trial, 497 participants; every week: RR 0.90, 95% CI 0.68 to 1.21; two trials, 248 participants). Treatment completion showed a similar pattern, ranging from 59% to 78% in the self-treatment groups, and direct observation did not improve this (RR 1.07, 95% CI 0.96 to 1.19; six trials, 1839 participants, moderate quality evidence). DOT at home versus DOT at health facility In four trials that compared DOT at home by family members, or community health workers, with DOT by health workers at a health facility there was little or no difference in cure or treatment completion (cure: RR 1.02, 95% CI 0.88 to 1.18, four trials, 1556 participants, moderate quality evidence; treatment completion: RR 1.04, 95% CI 0.91 to 1.17, three trials, 1029 participants, moderate quality evidence). DOT by family member versus DOT by community health worker Two trials compared DOT at home by family members with DOT at home by community health workers. There was also little or no difference in cure or treatment completion (cure: RR 1.02, 95% CI 0.86 to 1.21; two trials, 1493 participants, moderate quality evidence; completion: RR 1.05, 95% CI 0.90 to 1.22; two trials, 1493 participants, low quality evidence). Specific patient categories A trial of 300 intravenous drug users in the USA evaluated direct observation with no observation in TB prophylaxis to prevent active disease and showed little difference in treatment completion (RR 1.00, 95% CI 0.88 to 1.13; one trial, 300 participants, low quality evidence). Authors' conclusions From the existing trials, DOT did not provide a solution to poor adherence in TB treatment. Given the large resource and cost implications of DOT, policy makers might want to reconsider strategies that depend on direct observation. Other options might take into account financial and logistical barriers to care; approaches that motivate patients and staff; and defaulter follow-up. PLAIN LANGUAGE SUMMARY Directly observing people with TB take their drugs to help them complete their treatment This Cochrane Review summarises trials evaluating the effects of directly observed therapy (DOT) for treating people with tuberculosis (TB) or people on prophylaxis to prevent active disease compared to self-administered treatment. After searching for relevant trials up to 13 January 2015, we included 11 randomized controlled trials, enrolling 5662 people with TB, and conducted between 1995 and 2008. What is DOT and how might it improve treatment outcomes for people with TB DOT is one strategy to ensure that patients with TB take all their medication. An 'observer' acceptable to the patient and the health system observes the patient taking every dose of their medication, and records this for the health system to monitor. The World Health Organization currently recommends that people with TB are treated for at least six months to achieve cure. These long durations of treatment can be difficult for patients to complete, especially once they are well and need to return to work. Failure to complete treatment can lead to relapse and even death in individuals, and also has important public health consequences, such as increased TB transmission and the development of drug resistance. What the research says Overall, cure and treatment completion in both self-treatment and DOT groups was low, and DOT did not substantially improve this. Small effects were seen in a subgroup of studies where the self-treatment group were monitored less frequently than the DOT group. There is probably no difference in TB cure or treatment completion when the direct observation was conducted at home or at the clinic (moderate quality evidence). There is probably little or no difference in TB cure direct observation is conducted by a community health worker or family member (moderate quality evidence) and there may be little or no difference in treatment completion either (low quality evidence). Direct observation may have little or no effect on treatment completion in injection drug users (low quality evidence). The authors conclude that DOT on its own may not offer the solution to poor adherence in people taking TB medication. PMID:26022367

  12. First direct observation of muon antineutrino disappearance

    DOE PAGESBeta

    Adamson, P.

    2011-07-05

    This letter reports the first direct observation of muon antineutrino disappearance. The MINOS experiment has taken data with an accelerator beam optimized for ν̄μ production, accumulating an exposure of 1.71 x 1020 protons on target. In the Far Detector, 97 charged current ν̄μ events are observed. The no-oscillation hypothesis predicts 156 events and is excluded at 6.3σ. The best fit to oscillation yields |Δm̄2| = (3.36-0.40 +0.46(stat.) ± 0.06(syst.)) x 10-3 eV2, sin2(2 θ̄) = 0.86-0.12+0.11 (stat.) ± 0.01(syst.). The MINOS νμ and ν̄μ measurements are consistent at the 2.0% confidence level, assuming identical underlying oscillation parameters.

  13. Direct observation of laser guided corona discharges.

    PubMed

    Wang, Tie-Jun; Wei, Yingxia; Liu, Yaoxiang; Chen, Na; Liu, Yonghong; Ju, Jingjing; Sun, Haiyi; Wang, Cheng; Lu, Haihe; Liu, Jiansheng; Chin, See Leang; Li, Ruxin; Xu, Zhizhan

    2015-01-01

    Laser based lightning control holds a promising way to solve the problem of the long standing disaster of lightning strikes. But it is a challenging project due to insufficient understanding of the interaction between laser plasma channel and high voltage electric filed. In this work, a direct observation of laser guided corona discharge is reported. Laser filament guided streamer and leader types of corona discharges were observed. An enhanced ionization took place in the leader (filament) through the interaction with the high voltage discharging field. The fluorescence lifetime of laser filament guided corona discharge was measured to be several microseconds, which is 3 orders of magnitude longer than the fluorescence lifetime of laser filaments. This work could be advantageous towards a better understanding of laser assisted leader development in the atmosphere. PMID:26679271

  14. Direct observation of laser guided corona discharges

    NASA Astrophysics Data System (ADS)

    Wang, Tie-Jun; Wei, Yingxia; Liu, Yaoxiang; Chen, Na; Liu, Yonghong; Ju, Jingjing; Sun, Haiyi; Wang, Cheng; Lu, Haihe; Liu, Jiansheng; Chin, See Leang; Li, Ruxin; Xu, Zhizhan

    2015-12-01

    Laser based lightning control holds a promising way to solve the problem of the long standing disaster of lightning strikes. But it is a challenging project due to insufficient understanding of the interaction between laser plasma channel and high voltage electric filed. In this work, a direct observation of laser guided corona discharge is reported. Laser filament guided streamer and leader types of corona discharges were observed. An enhanced ionization took place in the leader (filament) through the interaction with the high voltage discharging field. The fluorescence lifetime of laser filament guided corona discharge was measured to be several microseconds, which is 3 orders of magnitude longer than the fluorescence lifetime of laser filaments. This work could be advantageous towards a better understanding of laser assisted leader development in the atmosphere.

  15. Direct observation of laser guided corona discharges

    PubMed Central

    Wang, Tie-Jun; Wei, Yingxia; Liu, Yaoxiang; Chen, Na; Liu, Yonghong; Ju, Jingjing; Sun, Haiyi; Wang, Cheng; Lu, Haihe; Liu, Jiansheng; Chin, See Leang; Li, Ruxin; Xu, Zhizhan

    2015-01-01

    Laser based lightning control holds a promising way to solve the problem of the long standing disaster of lightning strikes. But it is a challenging project due to insufficient understanding of the interaction between laser plasma channel and high voltage electric filed. In this work, a direct observation of laser guided corona discharge is reported. Laser filament guided streamer and leader types of corona discharges were observed. An enhanced ionization took place in the leader (filament) through the interaction with the high voltage discharging field. The fluorescence lifetime of laser filament guided corona discharge was measured to be several microseconds, which is 3 orders of magnitude longer than the fluorescence lifetime of laser filaments. This work could be advantageous towards a better understanding of laser assisted leader development in the atmosphere. PMID:26679271

  16. Transgenic, Fluorescent Leishmania mexicana Allow Direct Analysis of the Proteome of Intracellular Amastigotes*S?

    PubMed Central

    Paape, Daniel; Lippuner, Christoph; Schmid, Monika; Ackermann, Renate; Barrios-Llerena, Martin E.; Zimny-Arndt, Ursula; Brinkmann, Volker; Arndt, Benjamin; Pleissner, Klaus Peter; Jungblut, Peter R.; Aebischer, Toni

    2008-01-01

    Investigating the proteome of intracellular pathogens is often hampered by inadequate methodologies to purify the pathogen free of host cell material. This has also precluded direct proteome analysis of the intracellular, amastigote form of Leishmania spp., protozoan parasites that cause a spectrum of diseases that affect some 12 million patients worldwide. Here a method is presented that combines classic, isopycnic density centrifugation with fluorescent particle sorting for purification by exploiting transgenic, fluorescent parasites to allow direct proteome analysis of the purified organisms. By this approach the proteome of intracellular Leishmania mexicana amastigotes was compared with that of extracellular promastigotes that are transmitted by insect vectors. In total, 509 different proteins were identified by mass spectrometry and database search. This number corresponds to ?6% of gene products predicted from the reference genome of Leishmania major. Intracellular amastigotes synthesized significantly more proteins with basic pI and showed a greater abundance of enzymes of fatty acid catabolism, which may reflect their living in acidic habitats and metabolic adaptation to nutrient availability, respectively. Bioinformatics analyses of the genes corresponding to the protein data sets produced clear evidence for skewed codon usage and translational bias in these organisms. Moreover analysis of the subset of genes whose products were more abundant in amastigotes revealed characteristic sequence motifs in 3?-untranslated regions that have been linked to translational control elements. This suggests that proteome data sets may be used to identify regulatory elements in mRNAs. Last but not least, at 6% coverage the proteome identified all vaccine antigens tested to date. Thus, the present data set provides a valuable resource for selection of candidate vaccine antigens. PMID:18474515

  17. Diffuse x-rays: directly observing dark matter?

    SciTech Connect

    Forbes, Michael McNeil; Zhitnitsky, Ariel R E-mail: arz@physics.ubc.ca

    2008-01-15

    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.

  18. Direct observation of a magnetic Bose glass

    SciTech Connect

    Hong, Tao; Zheludev, Andrey I; Manaka, H.; Regnault, L.-P.

    2010-01-01

    A Bose glass is a novel state of matter that emerges in systems of interacting bosons in the presence of quenched disorder. At sufficiently low temperatures, disorder-free bosons are subject to so-called Bose-Einstein condensation (BEC). BEC can involve atoms in liquid 4He, laser-cooled ions in magnetic traps,2 Cooper pairs in superconductors, or magnons in magnetic systems. Due to peculiarities of Bose statistics, particles lose their individuality and occupy a unique quantum-mechanical state. The wave function of this condensate establishes long-range quantum phase coherence across a macroscopic sample. This, in turn, spawns unique quantum phenomena such as superfluity,5 Josephson effect6 and vortex matter. For repulsive bosons, quenched disorder disrupts the condensate and interferes with phase coherence. The result is a peculiar glassy state with only short-range phase correlations. While some experimental evidence of this was found in ultracold atoms,9 novel high-temperature superconductors,10 and quantum magnets,11, 12 none of the studies were direct. The key characteristic, namely the wave function of the condensate disrupted by disorder on the microscopic scale, remained inaccessible. Hereby we report a direct neutron diffraction observation of short range correlations of the BEC order parameter in a magnetic Bose glass. This phase is realized in the quantum spin ladder compound IPA-Cu(Cl0.96Br0.04)3, where disorder is induced by random chemical substitution.

  19. First direct observation of muon antineutrino disappearance

    SciTech Connect

    Adamson, P.

    2011-07-05

    This letter reports the first direct observation of muon antineutrino disappearance. The MINOS experiment has taken data with an accelerator beam optimized for ν̄μ production, accumulating an exposure of 1.71 x 1020 protons on target. In the Far Detector, 97 charged current ν̄μ events are observed. The no-oscillation hypothesis predicts 156 events and is excluded at 6.3σ. The best fit to oscillation yields |Δm̄2| = (3.36-0.40 +0.46(stat.) ± 0.06(syst.)) x 10-3 eV2, sin2(2 θ̄) = 0.86-0.12+0.11 (stat.) ± 0.01(syst.). The MINOS νμ and ν̄μ measurements are consistent at the 2.0% confidence level, assuming identical underlying oscillation parameters.

  20. Direct observation of Josephson vortex cores

    NASA Astrophysics Data System (ADS)

    Roditchev, Dimitri; Brun, Christophe; Serrier-Garcia, Lise; Cuevas, Juan Carlos; Bessa, Vagner Henrique Loiola; Miloevi?, Milorad Vlado; Debontridder, Franois; Stolyarov, Vasily; Cren, Tristan

    2015-04-01

    Superconducting correlations may propagate between two superconductors separated by a tiny insulating or metallic barrier, allowing a dissipationless electric current to flow. In the presence of a magnetic field, the maximum supercurrent oscillates and each oscillation corresponding to the entry of one Josephson vortex into the barrier. Josephson vortices are conceptual blocks of advanced quantum devices such as coherent terahertz generators or qubits for quantum computing, in which on-demand generation and control is crucial. Here, we map superconducting correlations inside proximity Josephson junctions using scanning tunnelling microscopy. Unexpectedly, we find that such Josephson vortices have real cores, in which the proximity gap is locally suppressed and the normal state recovered. By following the Josephson vortex formation and evolution we demonstrate that they originate from quantum interference of Andreev quasiparticles, and that the phase portraits of the two superconducting quantum condensates at edges of the junction decide their generation, shape, spatial extent and arrangement. Our observation opens a pathway towards the generation and control of Josephson vortices by applying supercurrents through the superconducting leads of the junctions, that is, by purely electrical means without any need for a magnetic field, which is a crucial step towards high-density on-chip integration of superconducting quantum devices.

  1. Direct observation of fast protein conformational switching

    PubMed Central

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

    2008-01-01

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

  2. 30 CFR 1220.011 - Schedule of allowable direct and allocable joint costs and credits.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... event of oil spills or other environmental damage are allowable. The costs of actual control and cleanup of oil spills and resulting responsibilities required by applicable laws and regulations are... DETERMINING NET PROFIT SHARE PAYMENT FOR OUTER CONTINENTAL SHELF OIL AND GAS LEASES § 1220.011 Schedule...

  3. Direct observation of microbubbles in directional solidification of salol

    SciTech Connect

    Williams, L.M.; Srinivasan, M.R.; Cummins, H.Z. )

    1990-03-26

    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.

  4. Demonstration of a new technology which allows direct sensor integration on flexible substrates

    NASA Astrophysics Data System (ADS)

    Petropoulos, A.; Goustouridis, D.; Speliotes, T.; Kaltsas, G.

    2009-04-01

    In this work we present a fabrication method for developing thermal sensors on flexible organic substrates. The constructed devices consist of Pt resistors which are directly integrated to the copper tracks of a flexible copper-clad laminate. They reside on top of a 12 ? m thick SU-8 planarization layer, while a sacrificial layer utilized by the negative photoresist ma-N was used in order to define the resistor pattern. The resistors can act as both heating and temperature sensing elements, while due to small thickness and the low thermal conductivity of the Kapton substrate, a very effective thermal isolation is achieved. The minimum radius of curvature of the fabricated devices was found to be 5 mm. As the device is in direct communication to the macrowolrd, the need for wire bonding is eliminated, while the final surface of the produced sensor is relatively planar. The overall process is simple and cost-effective with minimal requirements in fabrication time. The potential application field of the presented devices is considered quite extensive as they can be directly expanded into flexible sensors able to measure quantities such as fluid flow rate, displacement or vacuum.

  5. Observation of front propagation in directional solidification

    NASA Astrophysics Data System (ADS)

    Gleeson, J. T.; Finn, P. L.; Cladis, P. E.

    1992-06-01

    We describe how spatial variation in the critical pulling speed for directional solidification is induced by breaking the symmetry about the pulling direction. This spatial variation results in localized nucleation of the Mullins-Sekerka instability. After nucleation, the instability spreads via front propagation. The front propagation is studied as a function of pulling speed, leading to a powerful test of the nature of the bifurcation from the planar to the cellular state. Furthermore, growth in the leading edge of the front is studied in detail, as is the resulting cellular array after the front's passage. We find that front propagation enhances the wavelength selection dramatically compared to the case where the cellular array nucleates everywhere simultaneously.

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

    PubMed Central

    2010-01-01

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

  7. Bacterial RTX Toxins Allow Acute ATP Release from Human Erythrocytes Directly through the Toxin Pore*

    PubMed Central

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

    2014-01-01

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

  8. Direct Observation of Hierarchical Contact Line Depinning

    NASA Astrophysics Data System (ADS)

    Paxson, Adam; Varanasi, Kripa

    2011-11-01

    We report a technique for observing the dynamic behavior of a liquid contact line at high magnification using environmental scanning electron microscopy. We find that on a superhydrophobic surface consisting of an array micropillars, the receding contact line exhibits discrete hierarchical de-pinning events. As the macroscopic contact line recedes across the pillars, a capillary bridge is formed and displays a local microscopic contact angle that is equivalent to the macroscale contact angle observed on a flat surface of the same composition. By considering the line density of the microscale features and the pinning strength of each of those features, we relate the macroscopic contact angle and adhesion to the multiscale hierarchical roughness. This mechanism helps to explain the necessity for multiple length scales exhibited by lotus leaves and other superhydrophobic surfaces.

  9. Direct Observation of Paramagnons in Palladium

    SciTech Connect

    Doubble, R.; Hayden, S M.; Dai, Pengcheng; Mook Jr, Herbert A; Thompson, James R; Frost, C.

    2010-01-01

    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.

  10. Relaxed Observance of Traditional Marriage Rules Allows Social Connectivity without Loss of Genetic Diversity

    PubMed Central

    Guillot, Elsa G.; Hazelton, Martin L.; Karafet, Tatiana M.; Lansing, J. Stephen; Sudoyo, Herawati; Cox, Murray P.

    2015-01-01

    Marriage rules, the community prescriptions that dictate who an individual can or cannot marry, are extremely diverse and universally present in traditional societies. A major focus of research in the early decades of modern anthropology, marriage rules impose social and economic forces that help structure societies and forge connections between them. However, in those early anthropological studies, the biological benefits or disadvantages of marriage rules could not be determined. We revisit this question by applying a novel simulation framework and genome-wide data to explore the effects of Asymmetric Prescriptive Alliance, an elaborate set of marriage rules that has been a focus of research for many anthropologists. Simulations show that strict adherence to these marriage rules reduces genetic diversity on the autosomes, X chromosome and mitochondrial DNA, but relaxed compliance produces genetic diversity similar to random mating. Genome-wide data from the Indonesian community of Rindi, one of the early study populations for Asymmetric Prescriptive Alliance, are more consistent with relaxed compliance than strict adherence. We therefore suggest that, in practice, marriage rules are treated with sufficient flexibility to allow social connectivity without significant degradation of biological diversity. PMID:25968961

  11. Relaxed Observance of Traditional Marriage Rules Allows Social Connectivity without Loss of Genetic Diversity.

    PubMed

    Guillot, Elsa G; Hazelton, Martin L; Karafet, Tatiana M; Lansing, J Stephen; Sudoyo, Herawati; Cox, Murray P

    2015-09-01

    Marriage rules, the community prescriptions that dictate who an individual can or cannot marry, are extremely diverse and universally present in traditional societies. A major focus of research in the early decades of modern anthropology, marriage rules impose social and economic forces that help structure societies and forge connections between them. However, in those early anthropological studies, the biological benefits or disadvantages of marriage rules could not be determined. We revisit this question by applying a novel simulation framework and genome-wide data to explore the effects of Asymmetric Prescriptive Alliance, an elaborate set of marriage rules that has been a focus of research for many anthropologists. Simulations show that strict adherence to these marriage rules reduces genetic diversity on the autosomes, X chromosome and mitochondrial DNA, but relaxed compliance produces genetic diversity similar to random mating. Genome-wide data from the Indonesian community of Rindi, one of the early study populations for Asymmetric Prescriptive Alliance, are more consistent with relaxed compliance than strict adherence. We therefore suggest that, in practice, marriage rules are treated with sufficient flexibility to allow social connectivity without significant degradation of biological diversity. PMID:25968961

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

    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 m2. 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 m 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.

  13. 46 CFR 148.03-3 - Direction and observation.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 5 2010-10-01 2010-10-01 false Direction and observation. 148.03-3 Section 148.03-3 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) DANGEROUS CARGOES CARRIAGE OF SOLID HAZARDOUS MATERIALS IN BULK Minimum Transportation Requirements § 148.03-3 Direction and observation. Loading or off-loading of a solid...

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

    PubMed Central

    Escobar, Gina M.; Maffei, Arianna; Miller, Paul

    2014-01-01

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

  15. Direct observations of field-induced assemblies in magnetite ferrofluids

    PubMed Central

    Mousavi, N. S. Susan

    2015-01-01

    Evolution of microstructures in magnetite-based ferrofluids with weak dipolar moments (particle size ≤ 10 nm) is studied with an emphasis on examining the effects of particle concentration (ϕ) and magnetic field strength (H) on the structures. Nanoparticles are dispersed in water at three different concentrations, ϕ = 0.15%, 0.48%, and 0.59% (w/v) [g/ml%] and exposed to uniform magnetic fields in the range of H = 0.05–0.42 T. Cryogenic transmission electron microscopy is employed to provide in-situ observations of the field-induced assemblies in such systems. As the magnetic field increases, the Brownian colloids are observed to form randomly distributed chains aligned in the field direction, followed by head-to-tail chain aggregation and then lateral aggregation of chains termed as zippering. By increasing the field in low concentration samples, the number of chains increases, though their length does not change dramatically. Increasing concentration increases the length of the linear particle assemblies in the presence of a fixed external magnetic field. Thickening of the chains due to zippering is observed at relatively high fields. Through a systematic variation of concentration and magnetic field strength, this study shows that both magnetic field strength and change in concentration can strongly influence formation of microstructures even in weak dipolar systems. Additionally, the results of two commonly used support films on electron microscopy grids, continuous carbon and holey carbon films, are compared. Holey carbon film allows us to create local regions of high concentrations that further assist the development of field-induced assemblies. The experimental observations provide a validation of the zippering effect and can be utilized in the development of models for thermophysical properties such as thermal conductivity. PMID:25829566

  16. Direct observations of field-induced assemblies in magnetite ferrofluids

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  17. Direct observations of field-induced assemblies in magnetite ferrofluids

    SciTech Connect

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

    2015-03-14

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

  18. Direct Observation of Two Proton Radioactivity Using Digital Photography

    SciTech Connect

    Rykaczewski, Krzysztof Piotr; Pfutzner, M.; Dominik, Wojciech; Janas, Z.; Miernik, K.; Bingham, C. R.; Czyrkowski, Henryk; Cwiok, Mikolaj; Darby, Iain; Dabrowski, Ryszard; Ginter, T. N.; Grzywacz, Robert Kazimierz; Karny, M.; Korgul, A.; Kusmierz, Waldemar; Liddick, Sean; Rajabali, Mustafa; Stolz, A.

    2007-01-01

    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.

  19. Plasmon Surface Polariton Dispersion by Direct Optical Observation.

    ERIC Educational Resources Information Center

    Swalen, J. D.; And Others

    1980-01-01

    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)

  20. Retinex Image Processing: Improved Fidelity To Direct Visual Observation

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

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

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

    PubMed Central

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

    2012-01-01

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

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

    PubMed Central

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

    1978-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Yu, Hongbin; Zhang, Zhibo

    2013-01-01

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

  4. Direct observation of the structural isomerization of a cationic group 4 Ziegler-Natta insertion product.

    PubMed

    Keaton, Richard J; Sita, Lawrence R

    2002-08-01

    An experimental model that allows for direct observation of a structural isomerization that is relevant to the group 4 metal-mediated Ziegler-Natta polymerization of alpha-olefins is presented. More specifically, several features of this system are consistent with current theories presented for chain epimerization that occurs during propene polymerization. PMID:12149009

  5. Direct observation of condensate and vortex confinement in nanostructured superconductors

    NASA Astrophysics Data System (ADS)

    Timmermans, M.; Serrier-Garcia, L.; Perini, M.; Van de Vondel, J.; Moshchalkov, V. V.

    2016-02-01

    In this work we report a scanning tunneling microscopy investigation of lithographically defined superconducting nanosquares. The obtained spectroscopic maps reveal the spatial evolution of both the superconducting condensate and the screening currents as a function of the applied magnetic field. The symmetry of the nanostructure is imposed on the condensate and it controls the distribution of the vortices inside the nanosquare. Our local study allows exploring the impact of small structural defects, omnipresent in these kind of structures, on both the supercurrent and vortex distribution. As a result, direct experimental evidence of vortex pinning and current crowding at the nanoscale has been obtained.

  6. Covalent attachment of lipid vesicles to a fluid supported bilayer allows observation of DNA-mediated vesicle interactions

    PubMed Central

    van Lengerich, Bettina; Rawle, Robert J.; Boxer, Steven G.

    2010-01-01

    Specific membrane interactions such as lipid vesicle docking and fusion can be mediated by synthetic DNA-lipid conjugates as a model for the protein-driven processes that are ubiquitous in biological systems. Here we present a method of tethering vesicles to a supported lipid bilayer that allows simultaneous deposition of cognate vesicle partners displaying complementary DNA, resulting in well-mixed populations of tethered vesicles that are laterally mobile. Vesicles are covalently attached to a supporting lipid bilayer using a DNA-templated click reaction; then DNA-mediated interactions between tethered vesicles are triggered by spiking the salt concentration. These interactions, such as docking and fusion, can then be observed for individual vesicles as they collide on the surface. The architecture of this new system also permits control over the number of lipid anchors that tether the vesicle to the supporting bilayer. The diffusion coefficient of tethered vesicles anchored by two lipids is approximately 1.6-fold slower than that of vesicles anchored only with a single lipid, consistent with a simple physical model. PMID:20180548

  7. Covalent attachment of lipid vesicles to a fluid-supported bilayer allows observation of DNA-mediated vesicle interactions.

    PubMed

    van Lengerich, Bettina; Rawle, Robert J; Boxer, Steven G

    2010-06-01

    Specific membrane interactions such as lipid vesicle docking and fusion can be mediated by synthetic DNA-lipid conjugates as a model for the protein-driven processes that are ubiquitous in biological systems. Here we present a method of tethering vesicles to a supported lipid bilayer that allows the simultaneous deposition of cognate vesicle partners displaying complementary DNA, resulting in well-mixed populations of tethered vesicles that are laterally mobile. Vesicles are covalently attached to a supporting lipid bilayer using a DNA-templated click reaction; then DNA-mediated interactions between tethered vesicles are triggered by spiking the salt concentration. These interactions, such as docking and fusion, can then be observed for individual vesicles as they collide on the surface. The architecture of this new system also permits control over the number of lipid anchors that tether the vesicle to the supporting bilayer. The diffusion coefficient of tethered vesicles anchored by two lipids is approximately 1.6-fold slower than that of vesicles anchored only with a single lipid, consistent with a simple physical model. PMID:20180548

  8. Microcrack closure in rocks under stress - Direct observation

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

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

  9. Multiangle Observations of Directional Reflectances of Snow Fields

    NASA Technical Reports Server (NTRS)

    Chang, A.T.C.; Hall, D. K.; Foster, J. L.

    1997-01-01

    Accurate measurements of snow areas and surface albedo are crucial to advancing our understanding of the global climate system. This is because of the highly reflective nature of snow combined with its large surface coverage (snow can cover up to 40 % of the Earth's land surface during the Northern Hemisphere winter). The reflectance of snow varies with both solar incidence angle and the viewing angle. Visible sensors with different spatial resolutions have been used to infer the snow parameters. Currently, only nadir-viewing directional reflectance data are available from satellite observations. Observations at multiple angles are needed to infer the hemispheric reflectance albedo of snow fields. We propose to study the directional reflectance of snow fields using POLDER data, which contains information from different viewing angles and polarization. POLDER was successfully launched an the ADEOS-1 satellite in August, 1996, however, because POLDER data are not yet available, data from ASAS, a pointable, airborne spectroradiometer, were used in this study. Data collected over Glacier National Park of Montana show strong angular dependence. Preliminary results confirm the anisotropic nature of the snow reflectance. Knowledge of the bi-directional reflectance function(BDRF) of snow -covered surfaces is the key to developing a true albedo model in the future.

  10. Direct observation of negative-index microwave surface waves

    NASA Astrophysics Data System (ADS)

    Dockrey, J. A.; Horsley, S. A. R.; Hooper, I. R.; Sambles, J. R.; Hibbins, A. P.

    2016-02-01

    Waves propagating in a negative-index material have wave-front propagation (wavevector, k) opposite in direction to that of energy flow (Poynting vector, S). Here we present an experimental realisation at microwave frequencies of an analogous surface wave phenomenon whereby a metasurface supports a surface mode that has two possible wavevector eigenstates within a narrow band of frequencies: one that supports surface waves with positive mode index, and another that supports surface waves with negative mode index. Phase sensitive measurements of the near-field of surface waves across the metasurface show the contrasting spatial evolution of the two eigenstates, providing a unique opportunity to directly observe the negative-index phenomenon.

  11. Direct observation of negative-index microwave surface waves

    PubMed Central

    Dockrey, J. A.; Horsley, S. A. R.; Hooper, I. R.; Sambles, J. R.; Hibbins, A. P.

    2016-01-01

    Waves propagating in a negative-index material have wave-front propagation (wavevector, k) opposite in direction to that of energy flow (Poynting vector, S). Here we present an experimental realisation at microwave frequencies of an analogous surface wave phenomenon whereby a metasurface supports a surface mode that has two possible wavevector eigenstates within a narrow band of frequencies: one that supports surface waves with positive mode index, and another that supports surface waves with negative mode index. Phase sensitive measurements of the near-field of surface waves across the metasurface show the contrasting spatial evolution of the two eigenstates, providing a unique opportunity to directly observe the negative-index phenomenon. PMID:26903284

  12. Direct observation of negative-index microwave surface waves.

    PubMed

    Dockrey, J A; Horsley, S A R; Hooper, I R; Sambles, J R; Hibbins, A P

    2016-01-01

    Waves propagating in a negative-index material have wave-front propagation (wavevector, k) opposite in direction to that of energy flow (Poynting vector, S). Here we present an experimental realisation at microwave frequencies of an analogous surface wave phenomenon whereby a metasurface supports a surface mode that has two possible wavevector eigenstates within a narrow band of frequencies: one that supports surface waves with positive mode index, and another that supports surface waves with negative mode index. Phase sensitive measurements of the near-field of surface waves across the metasurface show the contrasting spatial evolution of the two eigenstates, providing a unique opportunity to directly observe the negative-index phenomenon. PMID:26903284

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

    ERIC Educational Resources Information Center

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

    2014-01-01

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

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

    ERIC Educational Resources Information Center

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

    2014-01-01

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

  15. Direct observation of Kelvin waves excited by quantized vortex reconnection

    PubMed Central

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

    2014-01-01

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

  16. Direct Observations of PMC Local Time Variations by Aura OMI

    NASA Technical Reports Server (NTRS)

    DeLand, Matthew T.; Shettle, Eric P.; Thomas, Gary E.; Olivero, John J.

    2010-01-01

    The Ozone Monitoring Instrument (OMI) on the Aura satellite obtains unique measurements for polar mesospheric cloud (PMC) analysis. Its wide cross-track viewing swath and high along-track spatial resolution makes it possible to directly evaluate PMC occurrence frequency and brightness variations between 6S" and 8S' latitude as a function of local time over a 12-14 h continuous period. OMI PMC local time variations are closely coupled to concurrent variations in measurement scattering angle, so that ice phase function effects must be considered when interpreting the observations. Two different phase functions corresponding to bright and faint clouds are examined in this analysis. OMI observations show maximum frequency and albedo values at 8-10 h local time in the Northern Hemisphere, with decreasing amplitude at higher latitudes. Southern Hemisphere values reach a minimum at 18-20 h LT. Larger variations are seen in Northern Hemisphere data. No statistically significant longitudinal dependence was seen.

  17. Direct observation of small cluster mobility and ripening

    NASA Technical Reports Server (NTRS)

    Heinemann, K.; Poppa, H.

    1976-01-01

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

  18. Direct observations of the evolution of polar cap ionization patches.

    PubMed

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

    2013-03-29

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

  19. Evidence of Arctic sea ice thinning from direct observations

    NASA Astrophysics Data System (ADS)

    Renner, Angelika H. H.; Gerland, Sebastian; Haas, Christian; Spreen, Gunnar; Beckers, Justin F.; Hansen, Edmond; Nicolaus, Marcel; Goodwin, Harvey

    2014-07-01

    The Arctic sea ice cover is rapidly shrinking, but a direct, longer-term assessment of the ice thinning remains challenging. A new time series constructed from in situ measurements of sea ice thickness at the end of the melt season in Fram Strait shows a thinning by over 50% during 2003-2012. The modal and mean ice thickness along 79N decreased at a rate of 0.3 and 0.2 m yr-1, respectively, with long-term averages of 2.5 and 3 m. Airborne observations reveal an east-west thickness gradient across the strait in spring but not in summer due to advection from more different source regions. There is no clear relationship between interannual ice thickness variability and the source regions of the ice. The observed thinning is therefore likely a result of Arctic-wide reduction in ice thickness with a potential shift in exported ice types playing a minor role.

  20. Direct observation of thitherto unobservable quantum phenomena by using electrons

    PubMed Central

    Tonomura, Akira

    2005-01-01

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

  1. Directly observable optical properties of sprites in Central Europe

    NASA Astrophysics Data System (ADS)

    Br, Jzsef

    2013-04-01

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

  2. Direct observation of photoinduced bent nitrosyl excited-state complexes

    SciTech Connect

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

    2008-06-28

    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.

  3. Fostering directly observed treatment in tuberculosis: a program manager's perspective.

    PubMed

    Shrivastava, Saurabh Rambiharilal; Shrivastava, Prateek Saurabh; Ramasamy, Jegadeesh

    2014-01-01

    Global Tuberculosis (TB) report (2013) has revealed that an estimated 8.6 million people developed TB of which, India accounts for almost 26% of the cases. These estimates clearly suggest that the country's efforts to achieve Millennium Development Goal 6 by 2015 have not delivered the desired output. In India, the TB prevention and control activities are supervised and implemented under the Revised National TB Control Program (RNTCP), which recognizes that implementation of a good quality Directly Observed Treatment with Short course chemotherapy (DOTS) is the first priority for TB control. Directly Observed Treatment (DOT) is the key element in DOTS strategy, in which a DOT provider insures and supports the patients in consuming their drugs throughout the course of treatment. In order to meet the country's vision to achieve universal access of TB care, the RNTCP has launched a "treatment adherence scheme" (public-private partnership scheme). Further, an evidence-based integrated strategy should be formulated for addressing the identified barriers which advocates universal administration of DOT. To conclude, DOT in RNTCP insures long-term adherence to the treatment, with right drugs in right doses, at right intervals and thus plays an indispensable role in improving the outcome indicators of the program and the quality of life in patients. PMID:24596899

  4. Direct Observation Assessment of Milestones: Problems with Reliability

    PubMed Central

    Schott, Meghan; Kedia, Raashee; Promes, Susan B.; Swoboda, Thomas; ORourke, Kevin; Green, Walter; Liu, Rachel; Stansfield, Brent; Santen, Sally A.

    2015-01-01

    Introduction Emergency medicine (EM) milestones are used to assess residents progress. While some milestone validity evidence exists, there is a lack of standardized tools available to reliably assess residents. Inherent to this is a concern that we may not be truly measuring what we intend to assess. The purpose of this study was to design a direct observation milestone assessment instrument supported by validity and reliability evidence. In addition, such a tool would further lend validity evidence to the EM milestones by demonstrating their accurate measurement. Methods This was a multi-center, prospective, observational validity study conducted at eight institutions. The Critical Care Direct Observation Tool (CDOT) was created to assess EM residents during resuscitations. This tool was designed using a modified Delphi method focused on content, response process, and internal structure validity. Paying special attention to content validity, the CDOT was developed by an expert panel, maintaining the use of the EM milestone wording. We built response process and internal consistency by piloting and revising the instrument. Raters were faculty who routinely assess residents on the milestones. A brief training video on utilization of the instrument was completed by all. Raters used the CDOT to assess simulated videos of three residents at different stages of training in a critical care scenario. We measured reliability using Fleiss kappa and interclass correlations. Results Two versions of the CDOT were used: one used the milestone levels as global rating scales with anchors, and the second reflected a current trend of a checklist response system. Although the raters who used the CDOT routinely rate residents in their practice, they did not score the residents performances in the videos comparably, which led to poor reliability. The Fleiss kappa of each of the items measured on both versions of the CDOT was near zero. Conclusion The validity and reliability of the current EM milestone assessment tools have yet to be determined. This study is a rigorous attempt to collect validity evidence in the development of a direct observation assessment instrument. However, despite strict attention to validity evidence, inter-rater reliability was low. The potential sources of reducible variance include rater- and instrument-based error. Based on this study, there may be concerns for the reliability of other EM milestone assessment tools that are currently in use. PMID:26594281

  5. Direct observation of the strange b baryon Xib-.

    PubMed

    Abazov, V M; Abbott, B; Abolins, M; Acharya, B S; Adams, M; Adams, T; Aguilo, E; Ahn, S H; Ahsan, M; Alexeev, G D; Alkhazov, G; Alton, A; Alverson, G; Alves, G A; Anastasoaie, M; Ancu, L S; Andeen, T; Anderson, S; Andrieu, B; Anzelc, M S; Arnoud, Y; Arov, M; Arthaud, M; Askew, A; Asman, B; Assis Jesus, A C S; Atramentov, O; Autermann, C; Avila, C; Ay, C; Badaud, F; Baden, A; Bagby, L; Baldin, B; Bandurin, D V; Banerjee, S; Banerjee, P; Barberis, E; Barfuss, A-F; Bargassa, P; Baringer, P; Barreto, J; Bartlett, J F; Bassler, U; Bauer, D; Beale, S; Bean, A; Begalli, M; Begel, M; Belanger-Champagne, C; Bellantoni, L; Bellavance, A; Benitez, J A; Beri, S B; Bernardi, G; Bernhard, R; Berntzon, L; Bertram, I; Besançon, M; Beuselinck, R; Bezzubov, V A; Bhat, P C; Bhatnagar, V; Biscarat, C; Blazey, G; Blekman, F; Blessing, S; Bloch, D; Bloom, K; Boehnlein, A; Boline, D; Bolton, T A; Borissov, G; Bos, K; Bose, T; Brandt, A; Brock, R; Brooijmans, G; Bross, A; Brown, D; Buchanan, N J; Buchholz, D; Buehler, M; Buescher, V; Burdin, S; Burke, S; Burnett, T H; Buszello, C P; Butler, J M; Calfayan, P; Calvet, S; Cammin, J; Caron, S; Carvalho, W; Casey, B C K; Cason, N M; Castilla-Valdez, H; Chakrabarti, S; Chakraborty, D; Chan, K M; Chan, K; Chandra, A; Charles, F; Cheu, E; Chevallier, F; Cho, D K; Choi, S; Choudhary, B; Christofek, L; Christoudias, T; Cihangir, S; Claes, D; Clément, C; Clément, B; Coadou, Y; Cooke, M; Cooper, W E; Corcoran, M; Couderc, F; Cousinou, M-C; Crépé-Renaudin, S; Cutts, D; Cwiok, M; da Motta, H; Das, A; Davies, G; De, K; de Jong, S J; de Jong, P; De La Cruz-Burelo, E; De Oliveira Martins, C; Degenhardt, J D; Déliot, F; Demarteau, M; Demina, R; Denisov, D; Denisov, S P; Desai, S; Diehl, H T; Diesburg, M; Dominguez, A; Dong, H; Dudko, L V; Duflot, L; Dugad, S R; Duggan, D; Duperrin, A; Dyer, J; Dyshkant, A; Eads, M; Edmunds, D; Ellison, J; Elvira, V D; Enari, Y; Eno, S; Ermolov, P; Evans, H; Evdokimov, A; Evdokimov, V N; Ferapontov, A V; Ferbel, T; Fiedler, F; Filthaut, F; Fisher, W; Fisk, H E; Ford, M; Fortner, M; Fox, H; Fu, S; Fuess, S; Gadfort, T; Galea, C F; Gallas, E; Galyaev, E; Garcia, C; Garcia-Bellido, A; Gavrilov, V; Gay, P; Geist, W; Gelé, D; Gerber, C E; Gershtein, Y; Gillberg, D; Ginther, G; Gollub, N; Gómez, B; Goussiou, A; Grannis, P D; Greenlee, H; Greenwood, Z D; Gregores, E M; Grenier, G; Gris, Ph; Grivaz, J-F; Grohsjean, A; Grünendahl, S; Grünewald, M W; Guo, J; Guo, F; Gutierrez, P; Gutierrez, G; Haas, A; Hadley, N J; Haefner, P; Hagopian, S; Haley, J; Hall, I; Hall, R E; Han, L; Hanagaki, K; Hansson, P; Harder, K; Harel, A; Harrington, R; Hauptman, J M; Hauser, R; Hays, J; Hebbeker, T; Hedin, D; Hegeman, J G; Heinmiller, J M; Heinson, A P; Heintz, U; Hensel, C; Herner, K; Hesketh, G; Hildreth, M D; Hirosky, R; Hobbs, J D; Hoeneisen, B; Hoeth, H; Hohlfeld, M; Hong, S J; Hooper, R; Hossain, S; Houben, P; Hu, Y; Hubacek, Z; Hynek, V; Iashvili, I; Illingworth, R; Ito, A S; Jabeen, S; Jaffré, M; Jain, S; Jakobs, K; Jarvis, C; Jesik, R; Johns, K; Johnson, C; Johnson, M; Jonckheere, A; Jonsson, P; Juste, A; Käfer, D; Kahn, S; Kajfasz, E; Kalinin, A M; Kalk, J R; Kalk, J M; Kappler, S; Karmanov, D; Kasper, J; Kasper, P; Katsanos, I; Kau, D; Kaur, R; Kaushik, V; Kehoe, R; Kermiche, S; Khalatyan, N; Khanov, A; Kharchilava, A; Kharzheev, Y M; Khatidze, D; Kim, H; Kim, T J; Kirby, M H; Kirsch, M; Klima, B; Kohli, J M; Konrath, J-P; Kopal, M; Korablev, V M; Kothari, B; Kozelov, A V; Krop, D; Kryemadhi, A; Kuhl, T; Kumar, A; Kunori, S; Kupco, A; Kurca, T; Kvita, J; Lacroix, F; Lam, D; Lammers, S; Landsberg, G; Lazoflores, J; Lebrun, P; Lee, W M; Leflat, A; Lehner, F; Lellouch, J; Lesne, V; Leveque, J; Lewis, P; Li, J; Li, Q Z; Li, L; Lietti, S M; Lima, J G R; Lincoln, D; Linnemann, J; Lipaev, V V; Lipton, R; Liu, Y; Liu, Z; Lobo, L; Lobodenko, A; Lokajicek, M; Lounis, A; Love, P; Lubatti, H J; Lyon, A L; Maciel, A K A; Mackin, D; Madaras, R J; Mättig, P; Magass, C; Magerkurth, A; Makovec, N; Mal, P K; Malbouisson, H B; Malik, S; Malyshev, V L; Mao, H S; Maravin, Y; Martin, B; McCarthy, R; Melnitchouk, A; Mendes, A; Mendoza, L; Mercadante, P G; Merekov, Y P; Merkin, M; Merritt, K W; Meyer, J; Meyer, A; Michaut, M; Millet, T; Mitrevski, J; Molina, J; Mommsen, R K; Mondal, N K; Moore, R W; Moulik, T; Muanza, G S; Mulders, M; Mulhearn, M; Mundal, O; Mundim, L; Nagy, E; Naimuddin, M; Narain, M; Naumann, N A; Neal, H A; Negret, J P; Neustroev, P; Nilsen, H; Nomerotski, A; Novaes, S F; Nunnemann, T; O'Dell, V; O'Neil, D C; Obrant, G; Ochando, C; Onoprienko, D; Oshima, N; Osta, J; Otec, R; Otero y Garzón, G J; Owen, M; Padley, P; Pangilinan, M; Panov, G; Parashar, N; Park, S-J; Park, S K; Parsons, J; Partridge, R; Parua, N; Patwa, A; Pawloski, G; Penning, B; Perea, P M; Peters, K; Peters, Y; Pétroff, P; Petteni, M; Piegaia, R; Piper, J; Pleier, M-A; Podesta-Lerma, P L M; Podstavkov, V M; Pogorelov, Y; Pol, M-E; Polozov, P; Pompos, A; Pope, B G; Popov, A V; Potter, C; Prado da Silva, W L; Prosper, H B; Protopopescu, S; Qian, J; Quadt, A; Quinn, B; Rakitine, A; Rangel, M S; Rani, K J; Ranjan, K; Ratoff, P N; Renkel, P; Reucroft, S; Rich, P; Rijssenbeek, M; Ripp-Baudot, I; Rizatdinova, F; Robinson, S; Rodrigues, R F; Royon, C; Rozhdestvenski, A; Rubinov, P; Ruchti, R; Safronov, G; Sajot, G; Sánchez-Hernández, A; Sanders, M P; Santoro, A; Savage, G; Sawyer, L; Scanlon, T; Schaile, D; Schamberger, R D; Scheglov, Y; Schellman, H; Schieferdecker, P; Schliephake, T; Schmitt, C; Schwanenberger, C; Schwartzman, A; Schwienhorst, R; Sekaric, J; Sengupta, S; Severini, H; Shabalina, E; Shamim, M; Shary, V; Shchukin, A A; Shivpuri, R K; Shpakov, D; Siccardi, V; Simak, V; Sirotenko, V; Skubic, P; Slattery, P; Smirnov, D; Smith, R P; Snow, J; Snow, G R; Snyder, S; Söldner-Rembold, S; Sonnenschein, L; Sopczak, A; Sosebee, M; Soustruznik, K; Souza, M; Spurlock, B; Stark, J; Steele, J; Stolin, V; Stone, A; Stoyanova, D A; Strandberg, J; Strandberg, S; Strang, M A; Strauss, M; Strauss, E; Ströhmer, R; Strom, D; Strovink, M; Stutte, L; Sumowidagdo, S; Svoisky, P; Sznajder, A; Talby, M; Tamburello, P; Tanasijczuk, A; Taylor, W; Telford, P; Temple, J; Tiller, B; Tissandier, F; Titov, M; Tokmenin, V V; Tomoto, M; Toole, T; Torchiani, I; Trefzger, T; Tsybychev, D; Tuchming, B; Tully, C; Tuts, P M; Unalan, R; Uvarov, S; Uvarov, L; Uzunyan, S; Vachon, B; van den Berg, P J; van Eijk, B; Van Kooten, R; van Leeuwen, W M; Varelas, N; Varnes, E W; Vartapetian, A; Vasilyev, I A; Vaupel, M; Verdier, P; Vertogradov, L S; Vertogradova, Y; Verzocchi, M; Villeneuve-Seguier, F; Vint, P; Vokac, P; Von Toerne, E; Voutilainen, M; Vreeswijk, M; Wagner, R; Wahl, H D; Wang, L; Wang, M H L S; Warchol, J; Watts, G; Wayne, M; Weber, M; Weber, G; Weerts, H; Wenger, A; Wermes, N; Wetstein, M; White, A; Wicke, D; Wilson, G W; Wimpenny, S J; Wobisch, M; Wood, D R; Wyatt, T R; Xie, Y; Yacoob, S; Yamada, R; Yan, M; Yasuda, T; Yatsunenko, Y A; Yip, K; Yoo, H D; Youn, S W; Yu, J; Yu, C; Yurkewicz, A; Zatserklyaniy, A; Zeitnitz, C; Zhang, D; Zhao, T; Zhou, B; Zhu, J; Zielinski, M; Zieminska, D; Zieminski, A; Zivkovic, L; Zutshi, V; Zverev, E G

    2007-08-01

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

  6. [A new thermodynamic function, which allows easy determination of the direction of a reaction and its energetic characteristics].

    PubMed

    Bobrovnik, S A

    2005-01-01

    A new thermodynamic function, namely a universal variable Q, is suggested for the description of reversible chemical reactions. According to the definition, if the reaction is represented by the equation aA + bB = gG + hH, and K is the equilibrium constant, the universal variable Q is: Q = aG(g)aH(h)/(aA(a)aB(b)K). Then, Q is a dimensionless variable, which has the following properties: Q = 1 for the state of equilibrium, Q < 1 for spontaneous reactions, and Q > 1 for the reverse reaction. Knowledge of Q allows determination of the Gibbs energy and standard Gibbs energy by the same formula deltaG = RTlnQ. PMID:16335278

  7. Direct Observation of Acoustic Oscillations in InAs Nanowires

    SciTech Connect

    Mariager, Simon O.; Khakhulin, Dmitry; Lemke, Henrik T.; Kjr, Kasper S.; Guerin, Laurent; Nuccio, Laura; Srensen, Claus B.; Nielsen, Martin M.; Feidenhans?l, Robert

    2010-09-02

    Time-resolved X-ray diffraction and optical reflectivity are used to directly measure three different acoustic oscillations of InAs nanowires. The oscillations are excited by a femtosecond laser pulse and evolve at three different time scales. We measure the absolute scale of the initial radial expansion of the fundamental breathing eigenmode and determine the frequency by transient optical reflectivity. For the extensional eigenmode we measure the oscillations of the average radial and axial lattice constants and determine the amplitude of oscillations and the average extension. Finally we observe a bending motion of the nanowires. The frequencies of the eigenmodes are in good agreements with predictions made by continuum elasticity theory and we find no difference in the speed of sound between the wurtzite nanowires and cubic bulk crystals, but the measured strain is influenced by the interaction between different modes. The wurtzite crystal structure of the nanowires however has an anisotropic thermal expansion.

  8. Direct observation of ordered configurations of hydrogen adatoms on graphene

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    Ordered configurations of hydrogen adatoms on graphene have received great attention because they are closely tied to tuning of graphene properties including large band gap opening and formation of specific magnetic orders, both of which are highly desirable in potential applications. Many ordered structures of hydrogenated graphene have been proposed, including double sided and single sided ones, with the calculated band gap width depending on the respective H coverage. However, none of these ordered structures has been observed directly. Here we report direct imaging of several ordered configurations of H adatoms on graphene by scanning tunneling microscopy. The H atoms in the configurations exhibit apparent sublattice selectivity and tiny deviations from the exact atop-of-carbon positions. Scanning tunneling spectroscopy measurements of the configurations showed a larger than 0.6 eV gap in the local density of states. These findings can be well explained by our density functional theory simulations based on models of double sided H configurations. Z. H. thanks the NBRP of China (Grant 2012CB921300) and the Chinese Ministry of Education for financial supports. E. W., X. Z. L. and Z. H. thank the National Natural Science Foundation of China (Grant 11074005, 91021007 and 11275008) for financial supports.

  9. Enabling direct nanoscale observations of biological reactions with dynamic TEM

    PubMed Central

    Evans, James E.; Browning, Nigel D.

    2013-01-01

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

  10. Direct observation of episodic growth in an abyssal xenophyophore (Protista)

    NASA Astrophysics Data System (ADS)

    Gooday, A. J.; Bett, B. J.; Pratt, D. N.

    1993-11-01

    Three specimens of the xenophyophore Reticulammina labyrinthica were photographed on the Madeira Abyssal Plain (316.1'N, 2110.9'W; 4944 m) using the Bathysnap time-lapse camera system. During the 8 month observation period, the specimens underwent an estimated 3-10 fold increase in volume. Growth occurred episodically in several distinct phases, each lasting 2-3 days, during which sediment was collected and incorporated into the test. These phases were separated by fairly regular periods of about 2 months when the organisms showed little obvious activity. The growth phases were approximately synchronous between specimens. However, it is not clear whether the periodicity and apparent synchronization of these events resulted from an external (environmental) cue or whether growth is internally controlled and the synchronization arose by chance. These unique observations, which represent the first direct measurement of growth in any abyssal organism living outside a hydrothermal vent field, suggest that xenophyophores combine test growth with deposit feeding. The tests appear to grow more quickly, and to be more active, dynamic structures, than previously believed.

  11. Direct observation of solidification microstructures around absolute stability

    SciTech Connect

    Ludwig, A.; Kurz, W.

    1996-09-01

    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.

  12. Direct observation, study and control of molecular super rotors

    NASA Astrophysics Data System (ADS)

    Korobenko, Aleksey; Milner, Alexander; Hepburn, John; Milner, Valery

    2014-05-01

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

  13. Femtosecond direct observation of charge transfer between bases in DNA

    PubMed Central

    Wan, Chaozhi; Fiebig, Torsten; Schiemann, Olav; Barton, Jacqueline K.; Zewail, Ahmed H.

    2000-01-01

    Charge transfer in supramolecular assemblies of DNA is unique because of the notion that the ?-stacked bases within the duplex may mediate the transport, possibly leading to damage and/or repair. The phenomenon of transport through ?-stacked arrays over a long distance has an analogy to conduction in molecular electronics, but the mechanism still needs to be determined. To decipher the elementary steps and the mechanism, one has to directly measure the dynamics in real time and in suitably designed, structurally well characterized DNA assemblies. Here, we report our first observation of the femtosecond dynamics of charge transport processes occurring between bases within duplex DNA. By monitoring the population of an initially excited 2-aminopurine, an isomer of adenine, we can follow the charge transfer process and measure its rate. We then study the effect of different bases next to the donor (acceptor), the base sequence, and the distance dependence between the donor and acceptor. We find that the charge injection to a nearest neighbor base is crucial and the time scale is vastly different: 10 ps for guanine and up to 512 ps for inosine. Depending on the base sequence the transfer can be slowed down or inhibited, and the distance dependence is dramatic over the range of 14 ?. These observations provide the time scale, and the range and efficiency of the transfer. The results suggest the invalidity of an efficient wire-type behavior and indicate that long-range transport is a slow process of a different mechanism. PMID:11106376

  14. The observation of a coronal transient directed at earth

    NASA Technical Reports Server (NTRS)

    Howard, R. A.; Michels, D. J.; Sheeley, N. R., Jr.; Koomen, M. J.

    1982-01-01

    The paper reports the observation of a large coronal transient that can only be interpreted as a three-dimensional structure. Its form is one which has not been observed before: a gradually expanding, sun-centered disk of excess brightness, whose projected radius increased from 4 to 8 solar radii during 0832-0958 UT on November 27, 1979. This earth-directed transient was the source of an interplanetary shock wave that reached ISEE 3 at 0649 UT, November 30, and earth at 0738 UT, November 30. Fitting the shock speed at ISEE 3 and the average transit speed from the sun to ISEE 3 to a power law of the form V = (V sub 0)(r exp -n), it is found that V sub 0 = 1980 km/s and n = 0.294, in good agreement with shock wave models. The shock speed predicted by the power law at 10 solar radii is 1000 km/s, in good agreement with the estimated frontal speed of the transient.

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

    SciTech Connect

    Critchfield, L.R.

    1997-12-31

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

  16. Direct observation of lipoprotein cholesterol ester degradation in lysosomes.

    PubMed Central

    Lusa, S; Tanhuanpää, K; Ezra, T; Somerharju, P

    1998-01-01

    We have investigated whether pyrene-labelled cholesterol esters (PyrnCEs) (n indicates the number of aliphatic carbons in the pyrene-chain) can be used to observe the degradation of low-density lipoprotein (LDL)-derived cholesterol esters (CEs) in the lysosomes of living cells. To select the optimal substrates, hydrolysis of the PyrnCE species by lysosomal acid lipase (LAL) in detergent/phospholipid micelles was compared. The rate of hydrolysis varied markedly depending on the length of the pyrenyl chain. Pyr10CE was clearly the best substrate, while Pyr4CE was practically unhydrolysed. Pyr10CE and [3H]cholesteryl linoleate, the major CE species in LDL, were hydrolysed equally by LAL when incorporated together into reconstituted LDL (rLDL) particles, thus indicating that Pyr10CE is a reliable reporter of the lysosomal degradation of native CEs. When rLDL particles containing Pyr4CE or Pyr10CE were incubated with fibroblasts, the accumulation of bright intracellular vesicular fluorescence was observed with the former fluorescent derivative, but not with the latter. However, when the cells were treated with chloroquine, an inhibitor of lysosomal hydrolysis, or when cells with defective LAL were employed, Pyr10CE also accumulated in vesicular structures. HPLC analysis of cellular lipid extracts fully supported these imaging results. It is concluded that PyrnCEs can be used to observe degradation of CEs directly in living cells. This should be particularly useful when exploring the mechanisms responsible for the accumulation of lipoprotein-derived CEs in complex systems such as the arterial intima. PMID:9601074

  17. Observations of wind stress direction during Typhoon Chaba (2010)

    NASA Astrophysics Data System (ADS)

    Potter, Henry; Collins, Clarence O.; Drennan, William M.; Graber, Hans C.

    2015-11-01

    Direct flux measurements of stress direction taken at the ocean surface during Typhoon Chaba (2010) over 3 days are examined for wind speeds between 12 and 26.5 m s-1. Results show stress deviated up to 35° from the wind direction and resided predominantly between the wind and peak wave directions in both bimodal and unimodal seas. Off-wind stress angle was most pronounced in Chaba's wake where wind sea and swell created an apparent unimodal system with narrow directional spread. These conditions lasted 2 days during which the stress direction was midway between the wind and wave directions. The implications for tropical cyclone forecasting are discussed.

  18. Microcrack closure in rocks under stress: direct observation

    SciTech Connect

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

    1980-12-10

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

  19. Direct observation of interface instability during crystal growth

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

  20. Method for observing phase objects without halos and directional shadows

    NASA Astrophysics Data System (ADS)

    Suzuki, Yoshimasa; Kajitani, Kazuo; Ohde, Hisashi

    2015-03-01

    A new microscopy method for observing phase objects without halos and directional shadows is proposed. The key optical element is an annular aperture at the front focal plane of a condenser with a larger diameter than those used in standard phase contrast microscopy. The light flux passing through the annular aperture is changed by the specimen's surface profile and then passes through an objective and contributes to image formation. This paper presents essential conditions for realizing the method. In this paper, images of colonies formed by induced pluripotent stem (iPS) cells using this method are compared with the conventional phase contrast method and the bright-field method when the NA of the illumination is small to identify differences among these techniques. The outlines of the iPS cells are clearly visible with this method, whereas they are not clearly visible due to halos when using the phase contrast method or due to weak contrast when using the bright-field method. Other images using this method are also presented to demonstrate a capacity of this method: a mouse ovum and superimposition of several different images of mouse iPS cells.

  1. Direct observation of symmetry-specific precession in a ferrimagnet

    NASA Astrophysics Data System (ADS)

    Warnicke, P.; Stavitski, E.; Lee, J.-S.; Yang, A.; Chen, Z.; Zuo, X.; Zohar, S.; Bailey, W. E.; Harris, V. G.; Arena, D. A.

    2015-09-01

    Here we demonstrate an experimental observation of GHz-scale spin dynamics resolved to sublattice octahedral (Oh) tetrahedral (Td) sites in a spinel ferrimagnet, in this case a Mn-ferrite thin film. X-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) are used, in combination with multiplet calculations, to uniquely identify the spectral signature from Mn2 + and Fe2 +,3 + on Oh and Td lattice sites. With the sample under rf excitation, the spin alignment of the sublattices is tracked with time-resolved XMCD (TR-XMCD). The spin alignment of the sublattices is mostly antiferromagnetic. The phase difference between the Oh Fe2 + [Oh Fe3 +] and Td Mn2 + sites is 181.2 3 .8? [183 .3?3 .7? ] at 150 K and 186.6 2 .2? [182 .0?2 .2? ] at 300 K. Such direct measurement of the dynamic coupling, exchange stiffness, and damping enabled by TR-XMCD across sublattices will be essential for optimizing the development of future-generation microwave devices.

  2. Direct observation of critical adsorption on colloidal particles.

    PubMed

    Bertrand, C E; Godfrin, P D; Liu, Y

    2015-08-28

    Despite the fundamental role adsorbed solvent layers play in generating critical Casimir forces between colloidal particles, the structure of these layers has yet to be directly determined. Using small-angle neutron scattering, we have measured critical adsorption on the surface of small spherical silica particles suspended in a binary mixture of lutidine and water. The surface concentration profile and excess adsorption ? were studied as functions of temperature at the critical concentration and three off-critical concentrations. We are able to differentiate three distinct contributions to the excess adsorption including the intrinsic shape of the concentration profile. The adsorption associated with the profile shape is found to increase monotonically with increasing 2,6-lutidine concentration and to decrease with increasing temperature, this later observation is consistent with expectations for curvature induced corrections to planar adsorption and leads to ??(T-Tc)/Tc (-0.52), where Tc is the critical temperature. This scaling relation corresponds to a stronger divergence than found in the planar case, but a substantially weaker divergence than found previously. PMID:26328864

  3. Degassing-induced crystallization in basalts: direct experimental observations

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  4. Direct Observations Of Microbial Activity At Extreme Pressures

    NASA Astrophysics Data System (ADS)

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

    2002-12-01

    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.

  5. Compassionate Allowances

    MedlinePLUS

    ... Institutions Government Services Online Self-employed Small Business Software Developers Our Agency General Information About Us Ask for a Speaker Awards Careers with Social Security Compassionate Allowances Death Master File (Death Index) ...

  6. A direct way to observe absolute molecular handedness

    NASA Astrophysics Data System (ADS)

    Vager, Zeev

    2014-07-01

    We claim that the polarization of electrons tunneling through the molecular electric dipole direction uniquely determines the handedness of chiral centers. Unique labeling of chiral stereo-centers must include their handedness. The conventional method is formally known as the R, S nomenclature or the Ingold-Prelog priority (CIP) rules. It requires knowledge of the spatial absolute configuration of that center. Traditionally, experimental methods of extracting handedness go through the absolute configuration and only then would the CIP convention be applied. Here we show that a direct experimental method of determination of the natural molecular handedness by the polarization of tunneling electrons is almost always compatible with the CIP convention. By the sole use of symmetry arguments we show that the chiral molecular symmetry eliminates the need of fine structure splitting. As a consequence, the polarization of electrons tunneling through the molecular electric dipole direction uniquely determines their handedness.

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

    SciTech Connect

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

    2009-07-27

    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.

  8. Direct Observation that Bainite can Grow Below MS

    NASA Astrophysics Data System (ADS)

    Kolmskog, Peter; Borgenstam, Annika; Hillert, Mats; Hedstrm, Peter; Babu, Sudarsanam Suresh; Terasaki, Hidenori; Komizo, Yu-Ichi

    2012-12-01

    In situ simultaneous synchrotron X-ray diffraction and laser scanning confocal microscopy have confirmed that bainite in steels can grow below the martensite start temperature. This observation suggests that the formation curves for bainite in time-temperature-transformation diagrams should be extended below the martensite start temperature. Furthermore, the implication of this observation on the growth mechanism of bainitic ferrite is discussed.

  9. A Study of Student Teaching Using Direct Observation.

    ERIC Educational Resources Information Center

    Coker, Joan G.; Coker, Homer

    Thirty-three student teachers were observed in elementary school classrooms to determine if they manifested 16 interactive behaviors identified as desirable by college of education faculty. Teaching assistants used the Georgia Assessment of Teaching Effectiveness (GATE), an instrument which requires the observers to objectively record, but not

  10. Tracking individual membrane proteins and their biochemistry: The power of direct observation.

    PubMed

    Barden, Adam O; Goler, Adam S; Humphreys, Sara C; Tabatabaei, Samaneh; Lochner, Martin; Ruepp, Marc-David; Jack, Thomas; Simonin, Jonathan; Thompson, Andrew J; Jones, Jeffrey P; Brozik, James A

    2015-11-01

    The advent of single molecule fluorescence microscopy has allowed experimental molecular biophysics and biochemistry to transcend traditional ensemble measurements, where the behavior of individual proteins could not be precisely sampled. The recent explosion in popularity of new super-resolution and super-localization techniques coupled with technical advances in optical designs and fast highly sensitive cameras with single photon sensitivity and millisecond time resolution have made it possible to track key motions, reactions, and interactions of individual proteins with high temporal resolution and spatial resolution well beyond the diffraction limit. Within the purview of membrane proteins and ligand gated ion channels (LGICs), these outstanding advances in single molecule microscopy allow for the direct observation of discrete biochemical states and their fluctuation dynamics. Such observations are fundamentally important for understanding molecular-level mechanisms governing these systems. Examples reviewed here include the effects of allostery on the stoichiometry of ligand binding in the presence of fluorescent ligands; the observation of subdomain partitioning of membrane proteins due to microenvironment effects; and the use of single particle tracking experiments to elucidate characteristics of membrane protein diffusion and the direct measurement of thermodynamic properties, which govern the free energy landscape of protein dimerization. The review of such characteristic topics represents a snapshot of efforts to push the boundaries of fluorescence microscopy of membrane proteins to the absolute limit. This article is part of the Special Issue entitled 'Fluorescent Tools in Neuropharmacology'. PMID:25998277

  11. Direct UV observations of the circumstellar envelope of alpha Orionis

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

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

  12. Photometric and CCD direct image observation of comet Encke

    NASA Technical Reports Server (NTRS)

    Mccrosky, R. E.

    1981-01-01

    Attempted detection of periodic variations in brightness of the comet Encke is described. Viewing problems due to the position, faintness, and rate of motion of the comet are discussed. The failure of attempts to perform photoelectric photometry and CCD imaging is described. Photometric observations of the prototype Earth crosser, (1862) Apollo, are described and a photoelectric light curve of observations made during a four-hour period is presented.

  13. Direct observation of t2g orbital ordering in magnetite.

    PubMed

    Schlappa, J; Schssler-Langeheine, C; Chang, C F; Ott, H; Tanaka, A; Hu, Z; Haverkort, M W; Schierle, E; Weschke, E; Kaindl, G; Tjeng, L H

    2008-01-18

    Using soft-x-ray diffraction at the site-specific resonances in the Fe L2,3 edge, we find clear evidence for orbital and charge ordering in magnetite below the Verwey transition. The spectra show directly that the (001/2) diffraction peak (in cubic notation) is caused by t2g orbital ordering at octahedral Fe2+ sites and the (001) by a spatial modulation of the t2g occupation. PMID:18232896

  14. The First Direct Observation of Double-Beta Decay

    NASA Astrophysics Data System (ADS)

    Moe, Michael

    2014-10-01

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

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

    SciTech Connect

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

    2012-01-13

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

  16. Direct observation shows superposition and large scale flexibility within cytoplasmic dynein motors moving along microtubules.

    PubMed

    Imai, Hiroshi; Shima, Tomohiro; Sutoh, Kazuo; Walker, Matthew L; Knight, Peter J; Kon, Takahide; Burgess, Stan A

    2015-01-01

    Cytoplasmic dynein is a dimeric AAA(+) motor protein that performs critical roles in eukaryotic cells by moving along microtubules using ATP. Here using cryo-electron microscopy we directly observe the structure of Dictyostelium discoideum dynein dimers on microtubules at near-physiological ATP concentrations. They display remarkable flexibility at a hinge close to the microtubule binding domain (the stalkhead) producing a wide range of head positions. About half the molecules have the two heads separated from one another, with both leading and trailing motors attached to the microtubule. The other half have the two heads and stalks closely superposed in a front-to-back arrangement of the AAA(+) rings, suggesting specific contact between the heads. All stalks point towards the microtubule minus end. Mean stalk angles depend on the separation between their stalkheads, which allows estimation of inter-head tension. These findings provide a structural framework for understanding dynein's directionality and unusual stepping behaviour. PMID:26365535

  17. Direct observation of multistep energy transfer in LHCII with fifth-order 3D electronic spectroscopy

    PubMed Central

    Zhang, Zhengyang; Lambrev, Petar H.; Wells, Kym L.; Garab, Gy?z?; Tan, Howe-Siang

    2015-01-01

    During photosynthesis, sunlight is efficiently captured by light-harvesting complexes, and the excitation energy is then funneled towards the reaction centre. These photosynthetic excitation energy transfer (EET) pathways are complex and proceed in a multistep fashion. Ultrafast two-dimensional electronic spectroscopy (2DES) is an important tool to study EET processes in photosynthetic complexes. However, the multistep EET processes can only be indirectly inferred by correlating different cross peaks from a series of 2DES spectra. Here we directly observe multistep EET processes in LHCII using ultrafast fifth-order three-dimensional electronic spectroscopy (3DES). We measure cross peaks in 3DES spectra of LHCII that directly indicate energy transfer from excitons in the chlorophyll b (Chl b) manifold to the low-energy level chlorophyll a (Chl a) via mid-level Chl a energy states. This new spectroscopic technique allows scientists to move a step towards mapping the complete complex EET processes in photosynthetic systems. PMID:26228055

  18. Direct observation shows superposition and large scale flexibility within cytoplasmic dynein motors moving along microtubules

    PubMed Central

    Imai, Hiroshi; Shima, Tomohiro; Sutoh, Kazuo; Walker, Matthew L.; Knight, Peter J.; Kon, Takahide; Burgess, Stan A.

    2015-01-01

    Cytoplasmic dynein is a dimeric AAA+ motor protein that performs critical roles in eukaryotic cells by moving along microtubules using ATP. Here using cryo-electron microscopy we directly observe the structure of Dictyostelium discoideum dynein dimers on microtubules at near-physiological ATP concentrations. They display remarkable flexibility at a hinge close to the microtubule binding domain (the stalkhead) producing a wide range of head positions. About half the molecules have the two heads separated from one another, with both leading and trailing motors attached to the microtubule. The other half have the two heads and stalks closely superposed in a front-to-back arrangement of the AAA+ rings, suggesting specific contact between the heads. All stalks point towards the microtubule minus end. Mean stalk angles depend on the separation between their stalkheads, which allows estimation of inter-head tension. These findings provide a structural framework for understanding dynein's directionality and unusual stepping behaviour. PMID:26365535

  19. Direct observation shows superposition and large scale flexibility within cytoplasmic dynein motors moving along microtubules

    NASA Astrophysics Data System (ADS)

    Imai, Hiroshi; Shima, Tomohiro; Sutoh, Kazuo; Walker, Matthew L.; Knight, Peter J.; Kon, Takahide; Burgess, Stan A.

    2015-09-01

    Cytoplasmic dynein is a dimeric AAA+ motor protein that performs critical roles in eukaryotic cells by moving along microtubules using ATP. Here using cryo-electron microscopy we directly observe the structure of Dictyostelium discoideum dynein dimers on microtubules at near-physiological ATP concentrations. They display remarkable flexibility at a hinge close to the microtubule binding domain (the stalkhead) producing a wide range of head positions. About half the molecules have the two heads separated from one another, with both leading and trailing motors attached to the microtubule. The other half have the two heads and stalks closely superposed in a front-to-back arrangement of the AAA+ rings, suggesting specific contact between the heads. All stalks point towards the microtubule minus end. Mean stalk angles depend on the separation between their stalkheads, which allows estimation of inter-head tension. These findings provide a structural framework for understanding dynein's directionality and unusual stepping behaviour.

  20. Direct observation of multistep energy transfer in LHCII with fifth-order 3D electronic spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Zhengyang; Lambrev, Petar H.; Wells, Kym L.; Garab, Gy?z?; Tan, Howe-Siang

    2015-07-01

    During photosynthesis, sunlight is efficiently captured by light-harvesting complexes, and the excitation energy is then funneled towards the reaction centre. These photosynthetic excitation energy transfer (EET) pathways are complex and proceed in a multistep fashion. Ultrafast two-dimensional electronic spectroscopy (2DES) is an important tool to study EET processes in photosynthetic complexes. However, the multistep EET processes can only be indirectly inferred by correlating different cross peaks from a series of 2DES spectra. Here we directly observe multistep EET processes in LHCII using ultrafast fifth-order three-dimensional electronic spectroscopy (3DES). We measure cross peaks in 3DES spectra of LHCII that directly indicate energy transfer from excitons in the chlorophyll b (Chl b) manifold to the low-energy level chlorophyll a (Chl a) via mid-level Chl a energy states. This new spectroscopic technique allows scientists to move a step towards mapping the complete complex EET processes in photosynthetic systems.

  1. Direct observation of multistep energy transfer in LHCII with fifth-order 3D electronic spectroscopy.

    PubMed

    Zhang, Zhengyang; Lambrev, Petar H; Wells, Kym L; Garab, Gy?z?; Tan, Howe-Siang

    2015-01-01

    During photosynthesis, sunlight is efficiently captured by light-harvesting complexes, and the excitation energy is then funneled towards the reaction centre. These photosynthetic excitation energy transfer (EET) pathways are complex and proceed in a multistep fashion. Ultrafast two-dimensional electronic spectroscopy (2DES) is an important tool to study EET processes in photosynthetic complexes. However, the multistep EET processes can only be indirectly inferred by correlating different cross peaks from a series of 2DES spectra. Here we directly observe multistep EET processes in LHCII using ultrafast fifth-order three-dimensional electronic spectroscopy (3DES). We measure cross peaks in 3DES spectra of LHCII that directly indicate energy transfer from excitons in the chlorophyll b (Chl b) manifold to the low-energy level chlorophyll a (Chl a) via mid-level Chl a energy states. This new spectroscopic technique allows scientists to move a step towards mapping the complete complex EET processes in photosynthetic systems. PMID:26228055

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

    ERIC Educational Resources Information Center

    International Montessori Society (NJ3), 2011

    2011-01-01

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

  3. Direct observation of disulfide isomerization in a single protein

    PubMed Central

    Alegre-Cebollada, Jorge; Kosuri, Pallav; Rivas-Pardo, Jaime Andrs; Fernndez, Julio M.

    2011-01-01

    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. PMID:22024885

  4. Dynamic control of directional asymmetry observed in ultrafast laser direct writing

    NASA Astrophysics Data System (ADS)

    Salter, P. S.; Booth, M. J.

    2012-10-01

    A liquid crystal spatial light modulator (SLM) is used to control the focal symmetry and the associated directional "quill" effect encountered when using a femtosecond laser for direct laser writing of fused silica. Applying a blazed grating to the SLM effectively introduces pulse front tilt to the fabrication beam and a spatiotemporal asymmetry at the focus. As a result different fabricated features are generated when moving the substrate in opposite directions relative to the tilt. It is additionally shown that inhomogeneous pupil illumination can cause similar directionality in the fabrication via a spatial asymmetry in the focus.

  5. Direct observation of warping in the plasma sheet of Saturn

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

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

  6. Direct observation of bubble-assisted electroluminescence in liquid xenon

    NASA Astrophysics Data System (ADS)

    Erdal, E.; Arazi, L.; Chepel, V.; Rappaport, M. L.; Vartsky, D.; Breskin, A.

    2015-11-01

    Bubble formation in liquid xenon underneath a Thick Gaseous Electron Multiplier (THGEM) electrode immersed in liquid xenon was observed with a CCD camera. With voltage across the THGEM, the appearance of bubbles was correlated with that of electroluminescence signals induced by ionization electrons from alpha-particle tracks. This confirms recent indirect evidence that the observed photons are due to electroluminescence within a xenon vapor layer trapped under the electrode. The bubbles seem to emerge spontaneously due to heat flow from 300 K into the liquid, or in a controlled manner by locally boiling the liquid with resistive wires. Controlled bubble formation resulted in energy resolution of σ/E ≈ 7.5% for ~ 6000 ionization electrons. The phenomenon could pave ways towards the conception of large-volume `local dual-phase' noble-liquid TPCs.

  7. 10 CFR 26.115 - Collecting a urine specimen under direct observation.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 1 2012-01-01 2012-01-01 false Collecting a urine specimen under direct observation. 26... for Testing § 26.115 Collecting a urine specimen under direct observation. (a) Procedures for... specimen under direct observation, the collector shall obtain the agreement of the FFD program manager...

  8. 10 CFR 26.115 - Collecting a urine specimen under direct observation.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 1 2010-01-01 2010-01-01 false Collecting a urine specimen under direct observation. 26... for Testing § 26.115 Collecting a urine specimen under direct observation. (a) Procedures for... specimen under direct observation, the collector shall obtain the agreement of the FFD program manager...

  9. 10 CFR 26.115 - Collecting a urine specimen under direct observation.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 1 2011-01-01 2011-01-01 false Collecting a urine specimen under direct observation. 26... for Testing § 26.115 Collecting a urine specimen under direct observation. (a) Procedures for... specimen under direct observation, the collector shall obtain the agreement of the FFD program manager...

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

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 1 2014-01-01 2014-01-01 false Collecting a urine specimen under direct observation. 26... for Testing § 26.115 Collecting a urine specimen under direct observation. (a) Procedures for... specimen under direct observation, the collector shall obtain the agreement of the FFD program manager...

  11. 10 CFR 26.115 - Collecting a urine specimen under direct observation.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 1 2013-01-01 2013-01-01 false Collecting a urine specimen under direct observation. 26... for Testing § 26.115 Collecting a urine specimen under direct observation. (a) Procedures for... specimen under direct observation, the collector shall obtain the agreement of the FFD program manager...

  12. The direct observation of irradiation damage in zirconium and its alloys

    NASA Astrophysics Data System (ADS)

    Buckley, S. N.; Bullough, R.; Hayns, M. R.

    1980-04-01

    Direct observations of the dislocation climb rate in electron-irradiated zirconium and dilute zirconium alloys are reported. These observations allow a detailed physical model to be constructed which provides a consistent view of irradiation growth in these materials, under electron irradiation. We are inevitably led to postulate that the vacancy is more mobile (0.65 eV) than previously thought (1.2 eV) and that the tin present in Zircaloy acts as an atom-sized vacancy trap with a binding energy of 0.3 eV. The dependence of the results obtained on the foil geometry and the probable surface contamination during irradiation are discussed with reference to extensions to neutron-irradiated bulk material.

  13. Direct observation of reverse transcriptases by scanning tunneling microscopy.

    PubMed

    Lewerenz, H J; Jungblut, H; Campbell, S A; Giersig, M; Mller, D J

    1992-09-01

    First images on a nanometer scale of reverse transcriptases (RT) of the human immunodeficiency virus (HIV-1) and of the Moloney murine leukemia virus (MuLV) obtained by scanning tunneling microscopy (STM) are reported. The common feature of the observed molecules is a ring-type or horseshoe shape with hole diameters of approximately 30 A. The STM images are compared with high resolution transmission electron microscopy (TEM) and existing structure predictions. The similarities of the structural data obtained by STM and TEM and their agreement with the structure prediction for the RT of HIV-1 shows the principal possibility to image such biomolecules by STM. PMID:1280957

  14. Internal waves in the Aral Sea: the first direct observations

    NASA Astrophysics Data System (ADS)

    Khymchenko, Ielizaveta; Serebryany, Andrey; Zavialov, Peter

    2014-05-01

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

  15. Direct observation of hexokinase translocation in stimulated macrophages.

    PubMed Central

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

    1993-01-01

    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 PMID:8484732

  16. The direct flexoelectric effect observed in polyvinylidene fluoride films

    NASA Astrophysics Data System (ADS)

    Ramachandran, Narayanan

    Piezoelectricity in Polyvinylidene Fluoride (PVDF) was observed long back and significant development has been made since its discovery. The theory on this property has predominantly revolved about the polymorphism and unique structure of PVDF. Of the four structures PVDF can be fabricated namely alpha, beta, gamma and delta, apart from the alpha phase the other 3 have piezoelectricity property in them. This thesis concentrates on the beta phase PVDF as they have the highest piezoelectric effect present due to non cancellation of dipoles. In the past, research in the beta phase PVDF was conducted in stretched films. This thesis concentrates on the film properties in the unstretched condition. Flexoelectricty is a property which was first observed in 1969 in crystalline dielectric materials. The extension of this phenomenon in PVDF films is discussed in the thesis. Flexoelectricity is more dominant in the micro and nano scale and it depends on the strain gradients induced in a material thus generating a polarization. Hence this property is present in all dielectric materials when subjected to strain gradients unlike piezoelectricity which corresponds to only a particular class of materials. The films are fabricated by solution polymerization and phase characterization is confirmed by x-ray diffraction. The experimental verification of flexoelectricty and piezoelectricity, and the calculation of coefficients are discussed in unstretched condition of films. The Young's Modulus for these films is also calculated experimentally. This value is necessary to compute the piezoelectric coefficient. Analyzing the result we notice that the negative value of the flexoelectric coefficient corresponds to the trend seen in paraelectric BST crystals. The hypothesis is that the randomness in the molecular arrangement in unstretched films is synonymous to paraelectric BST crystals. Based on the coefficients computed the flexoelectric coefficient seems to be more dominant in the films. This result seems interesting and encouraging and thus giving us an opportunity to utilize the shape dependent characteristics in sensor applications.

  17. Directly observing continuum emission from self-gravitating spiral waves

    NASA Astrophysics Data System (ADS)

    Hall, Cassandra; Forgan, Duncan; Rice, Ken; Harries, Tim J.; Klaassen, Pamela D.; Biller, Beth

    2016-02-01

    We use a simple, self-consistent, self-gravitating semi-analytic disc model to conduct an examination of the parameter space in which self-gravitating discs may exist. We then use Monte-Carlo radiative transfer to generate synthetic ALMA images of these self-gravitating discs to determine the subset of this parameter space in which they generate non-axisymmetric structure that is potentially detectable by ALMA. Recently, several transition discs have been observed to have non-axisymmetric structure that extends out to large radii. It has been suggested that one possible origin of these asymmetries could be spiral density waves induced by disc self-gravity. We use our simple model to see if these discs exist in the region of parameter space where self-gravity could feasibly explain these spiral features. We find that for self-gravity to play a role in these systems typically requires a disc mass around an order of magnitude higher than the observed disc masses for the systems. The spiral amplitudes produced by self-gravity in the local approximation are relatively weak when compared to amplitudes produced by tidal interactions, or spirals launched at Lindblad resonances due to embedded planets in the disc. As such, we ultimately caution against diagnosing spiral features as being due to self-gravity, unless the disc exists in the very narrow region of parameter space where the spiral wave amplitudes are large enough to produce detectable features, but not so large as to cause the disc to fragment.

  18. Direct observation of the oceanic CO2 increase?revisited

    PubMed Central

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

    1997-01-01

    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. PMID:11607738

  19. Direct Observation of Completely Processed Calcium Carbonate Dust Particles

    SciTech Connect

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

    2005-05-27

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

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

    ERIC Educational Resources Information Center

    Hites, Lacey S.; Lundervold, Duane A.

    2013-01-01

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

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  2. On the Merits of Direct Observation of Periodical Usage: An Empirical Study.

    ERIC Educational Resources Information Center

    Bustion, Marifran; And Others

    1992-01-01

    An auxiliary study of the direct observation method for counting periodical usage in Evans Library at Texas A&M University found that student observations contain substantial error and that aggregation problems and cost issues are fundamental constraints to this method. Concludes direct observation may be useful in calibrating the results of other

  3. Direct Observation of Dimerization between Different CREB1 Isoforms in a Living Cell

    PubMed Central

    Sadamoto, Hisayo; Saito, Kenta; Muto, Hideki; Kinjo, Masataka; Ito, Etsuro

    2011-01-01

    Cyclic AMP-responsive element binding protein 1 (CREB1) plays multiple functions as a transcription factor in gene regulation. CREB1 proteins are also known to be expressed in several spliced isoforms that act as transcriptional activators or repressors. The activator isoforms, possessing the functional domains for kinase induction and for interaction with other transcriptional regulators, act as transcriptional activators. On the other hand, some isoforms, lacking those functional domains, are reported to be repressors that make heterodimers with activator isoforms. The complex and ingenious function for CREB1 arises in part from the variation in their spliced isoforms, which allows them to interact with each other. To date, however, the dimerization between the activator and repressor isoforms has not yet been proved directly in living cells. In this study, we applied fluorescence cross-correlation spectroscopy (FCCS) to demonstrate direct observation of dimerization between CREB1 activator and repressor. The FCCS is a well established spectroscopic method to determine the interaction between the different fluorescent molecules in the aqueous condition. Using differently labeled CREB1 isoforms, we successfully observed the interaction of CREB1 activator and repressor via dimerization in the nuclei of cultured cells. As a result, we confirmed the formation of heterodimer between CREB1 activator and repressor isoforms in living cells. PMID:21673803

  4. Observation of uniaxial anisotropy along the [100] direction in crystalline Fe film

    PubMed Central

    Bac, Seul-Ki; Lee, Hakjoon; Lee, Sangyoep; Choi, Seonghoon; Yoo, Taehee; Lee, Sanghoon; Liu, X.; Furdyna, J. K.

    2015-01-01

    We report an observation of uniaxial magnetic anisotropy along the [100] crystallographic direction in crystalline Fe film grown on Ge buffers deposited on a (001) GaAs substrate. As expected, planar Hall resistance (PHR) measurements reveal the presence of four in-plane magnetic easy axes, indicating the dominance of the cubic anisotropy in the film. However, systematic mapping of the PHR hysteresis loops observed during magnetization reversal at different field orientations shows that the easy axes along the and are not equivalent. Such breaking of the cubic symmetry can only be ascribed to the presence of uniaxial anisotropy along the direction of the Fe film. Analysis of the PHR data measured as a function of orientation of the applied magnetic field allowed us to quantify the magnitude of this uniaxial anisotropy field as Oe. Although this value is only 1.5% of cubic anisotropy field, its presence significantly changes the process of magnetization reversal, revealing the important role of the uniaxial anisotropy in Fe films. Breaking of the cubic symmetry in the Fe film deposited on a Ge buffer is surprising, and we discuss possible reason for this unexpected behavior. PMID:26635278

  5. Direct Observation of a Semi-Bare Electron Coulomb Field Recover

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

    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.

  6. 49 CFR 40.67 - When and how is a directly observed collection conducted?

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... the observer's name in the “Remarks” line of the CCF (Step 2). (m) As the employee, if you decline to... refusal to test. (n) As the collector, when you learn that a directly observed collection should have...

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

    PubMed

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

    2015-01-01

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

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

    PubMed Central

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

    2015-01-01

    Observation and tracking of fluorescently labeled molecules and particles in living cells reveals detailed information about intracellular processes on the molecular level. Whereas light microscopic particle observation is usually limited to two-dimensional projections of short trajectory segments, we report here image-based real-time three-dimensional single particle tracking in an active feedback loop with single molecule sensitivity. We tracked particles carrying only 13 fluorophores deep inside living tissue with high spatio-temporal resolution. Using this approach, we succeeded to acquire trajectories containing several hundred localizations. We present statistical methods to find significant deviations from random Brownian motion in such trajectories. The analysis allowed us to directly observe transitions in the mobility of ribosomal (r)RNA and Balbiani ring (BR) messenger (m)RNA particles in living Chironomus tentans salivary gland cell nuclei. We found that BR mRNA particles displayed phases of reduced mobility, while rRNA particles showed distinct binding events in and near nucleoli. PMID:25414330

  9. DIRECT OBSERVATION OF THE COOLING OF THE CASSIOPEIA A NEUTRON STAR

    SciTech Connect

    Heinke, Craig O.; Ho, Wynn C. G. E-mail: wynnho@slac.stanford.ed

    2010-08-20

    The cooling rate of young neutron stars (NSs) gives direct insight into their internal makeup. Although the temperatures of several young NSs have been measured, until now a young NS has never been observed to decrease in temperature over time. We fit nine years of archival Chandra ACIS spectra of the likely NS in the {approx}330 yr old Cassiopeia A supernova remnant with our non-magnetic carbon atmosphere model. Our fits show a relative decline in the surface temperature by 4% (5.4{sigma}, from (2.12 {+-} 0.01) x 10{sup 6} K in 2000 to (2.04 {+-} 0.01) x 10{sup 6} K in 2009) and the observed flux by 21%. Using a simple model for NS cooling, we show that this temperature decline could indicate that the NS became isothermal sometime between 1965 and 1980, and constrains some combinations of neutrino emission mechanisms and envelope compositions. However, the NS is likely to have become isothermal soon after formation, in which case the temperature history suggests episodes of additional heating or more rapid cooling. Observations over the next few years will allow us to test possible explanations for the temperature evolution.

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

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

    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.

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

    PubMed

    Oshima, Yusuke; Furihata, Chie; Sato, Hidetoshi

    2009-10-01

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

  12. Direct Observation of Virtual Electrode Formation Through a Novel Electrolyte-to-Electrode Transition

    NASA Astrophysics Data System (ADS)

    Siegel, David; El Gabaly, Farid; Bartelt, Norman; McCarty, Kevin

    2014-03-01

    Novel electrochemical solutions to problems in energy storage and transportation can drive renewable energy to become an economically viable alternative to fossil fuels. In many electrochemical systems, the behavior of a device can be fundamentally limited by the surface area of a triple phase boundary, the boundary region where a gas-phase species, electrode, and electrolyte coincide. When the electrode is an ionic insulator the triple phase boundary is typically a one-dimensional boundary with nanometer-scale thickness: ions cannot transport through the electrode, while electrons cannot be transported through the electrolyte. Here we present direct experimental measurements of a novel electrolyte-to-electrode transition with photoemission electron microscopy, and observe that the surface of an ionically conductive, electronically insulative solid oxide electrolyte undergoes a transition into a mixed electron-ion conductor in the vicinity of a metal electrode. Our direct experimental measurements allow us to characterize this system and address the mechanisms of ionic reactions and transport through comparisons with theoretical modeling to provide us with a physical picture of the processes involved. Our results provide insight into one of the mechanisms of ion transport in an electrochemical cell that may be generalizable to other systems.

  13. Direct Observation of Active Protein Folding Using Lock-in Force Spectroscopy

    PubMed Central

    Schlierf, Michael; Berkemeier, Felix; Rief, Matthias

    2007-01-01

    Direct observation of the folding of a single polypeptide chain can provide important information about the thermodynamic states populated along its folding pathway. In this study, we present a lock-in force-spectroscopy technique that improves resolution of atomic-force microscopy force spectroscopy to 400 fN. Using this technique we show that immunoglobulin domain 4 from Dictyostelium discoideum filamin (ddFLN4) refolds against forces of ?4 pN. Our data show folding of this domain proceeds directly from an extended state and no thermodynamically distinct collapsed state of the polypeptide before folding is populated. Folding of ddFLN4 under load proceeds via an intermediate state. Three-state folding allows ddFLN4 to fold against significantly larger forces than would be possible for a mere two-state folder. We present a general model for protein folding kinetics under load that can predict refolding forces based on chain-length and zero force refolding rate. PMID:17704164

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

    NASA Astrophysics Data System (ADS)

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

    2008-03-01

    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.

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

    PubMed Central

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

    1986-01-01

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

  16. Wide-field direct CCD observations supporting the Astro-1 Space Shuttle mission's Ultraviolet Imaging Telescope

    NASA Technical Reports Server (NTRS)

    Hintzen, Paul; Angione, Ron; Talbert, Freddie; Cheng, K.-P.; Smith, Eric; Stecher, Theodore P.

    1993-01-01

    Wide field direct CCD observations are being obtained to support and complement the vacuum-ultraviolet (VUV) images provided by Astro's Ultraviolet Imaging Telescope (UIT) during a Space Shuttle flight in December 1990. Because of the wide variety of projects addressed by UIT, the fields observed include (1) galactic supernova remnants such as the Cygnus Loop and globular clusters such as Omega Cen and M79; (2) the Magellanic Clouds, M33, M81, and other galaxies in the Local Group; and (3) rich clusters of galaxies, principally the Perseus cluster and Abell 1367. Ground-based observations have been obtained for virtually all of the Astro-1 UIT fields. The optical images allow identification of individual UV sources in each field and provide the long baseline in wavelength necessary for accurate analysis of UV-bright sources. To facilitate use of our optical images for analysis of UIT data and other projects, we plan to archive them, with the UIT images, at the National Space Science Data Center (NSSDC), where they will be universally accessible via anonymous FTP. The UIT, one of three telescopes comprising the Astro spacecraft, is a 38-cm f/9 Ritchey-Chretien telescope on which high quantum efficiency, solar-blind image tubes are used to record VUV images on photographic film. Five filters with passbands centered between 1250A and 2500A provide both VUV colors and a measurement of extinction via the 2200A dust feature. The resulting calibrated VUV pictures are 40 arcminutes in diameter at 2.5 arcseconds resolution. The capabilities of UIT, therefore, complement HST's WFPC: the latter has 40 times greater collecting area, while UIT's usable field has 170 times WFPC's field area.

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

    PubMed

    Lavender; Davis; Owens

    2000-09-01

    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

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

    NASA Technical Reports Server (NTRS)

    Liu, W. T.; Tang, W.

    2000-01-01

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

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

    ERIC Educational Resources Information Center

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

    2010-01-01

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

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

    SciTech Connect

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

    2010-01-21

    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.

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

    PubMed

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

    2015-01-15

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

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

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2006-12-01

    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

  4. Observations of nonlinear interactions in directionally spread shoaling surface gravity waves

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  5. Direct observation of single molecule conformational change of tight-turn paperclip DNA triplex in solution.

    PubMed

    Liu, Ching-Ping; Wey, Ming-Tsai; Chang, Chia-Ching; Kan, Lou-Sing

    2009-10-01

    DNA triplex modulates gene expression by forming stable conformation in physiological condition. However, it is not feasible to observe this unique molecular structure of large molecule with 54 oligodeoxynucleotides directly by conventional nuclear magnetic approach. In this study, we observed directly single molecular images of paperclip DNA triplexes formation in a buffer solution of pH 6.0 by atomic force microscopy (AFM). Meanwhile, a diffuse "tail" of unwound DNA was observed in pH 8.0 solution. This designable approach in visualizing the overall structures and shapes of oligo-DNAs at the single molecular level, by AFM, is applicable to other biopolymers as well. PMID:18931945

  6. Anodal transcranial direct current stimulation over premotor cortex facilitates observational learning of a motor sequence.

    PubMed

    Wade, Stephanie; Hammond, Geoff

    2015-06-01

    Motor skills, including complex movement sequences, can be acquired by observing a model without physical practice of the skill, a phenomenon known as observational learning. Observational learning of motor skills engages the same memory substrate as physical practice, and is thought to be mediated by the action observation network, a bilateral fronto-parietal circuit with mirror-like properties. We examined the effects of anodal transcranial direct current stimulation (tDCS) over premotor cortex, a key node of the action observation network, on observational learning of a serial response time task. Results showed that anodal tDCS during observation of the to-be-learned sequence facilitated reaction times in the subsequent behavioral test. The study provides evidence that increasing excitability of the action observation network during observation can facilitate later motor skill acquisition. PMID:25865458

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

    NASA Astrophysics Data System (ADS)

    Boylan, Patrick Joseph

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

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

    NASA Astrophysics Data System (ADS)

    Aulov, O.; Lary, D. J.

    2010-12-01

    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.

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

    PubMed Central

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

    2014-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-01-01

    The pyrolyses of phenol and d5-phenol (C6H5OH and C6D5OH) have been studied using a high temperature, microtubular (μtubular) 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 μtubular reactor of approximately 50-100 μs. 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.

  11. Observations of the relationship between directionality and decay rate of radon in a confined experiment

    NASA Astrophysics Data System (ADS)

    Steinitz, G.; Kotlarsky, P.; Piatibratova, O.

    2015-05-01

    Radon (222Rn) is a radioactive inert gas with an accepted half life of 3.8235 days. Its unique, systematic and complex variation in the geological environment and in simulation experiments combined with lack of understanding of the underlying drivers lead us to conduct tests of its apparent half life. A primary test took into account experimental observations indicating anisotropy of the gamma radiation from radon in air, which is related to global orientation. Using a goniometric configuration radon diffuses into two identical cylinders oriented along Earth axis of rotation and in a vertical and perpendicular direction to the latter. Detectors placed on cylinder ends measure gamma radiation sub parallel to these directions. At steady state and confined conditions different patterns of daily signals are observed in the two directions. Isolating the cylinders from the source leads to an exponential decrease on which similar daily signals are superimposed, having amplitudes proportional to the level of the remaining radon. The indicated apparent half-lives are in significant difference from the accepted value: 0.861 0.003 days in the pole direction and 2.308 0.008 days in the vertical direction. The outcome is in conformity with observations on radon signals in confined conditions and their different manifestation at different directions.

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

    SciTech Connect

    Lee, J.-G.; Hong, S.-H.; Ahner, J.; Zhao, X.; Chen, L.; Johnson, J.K.; Yates, J.T., Jr.

    2006-01-25

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

    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.

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

    PubMed

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

    2012-10-22

    Phase transformation of amorphous-silicon during millisecond annealing using micro-thermal-plasma-jet irradiation was directly observed using a high-speed camera with microsecond time resolution. An oval-shaped molten-silicon region adjacent to the solid phase crystallization region was clearly observed, followed by lateral large grain growth perpendicular to a liquid-solid interface. Furthermore, leading wave crystallization (LWC), which showed intermittent explosive crystallization, was discovered in front of the moving molten region. The growth mechanism of LWC has been investigated on the basis of numerical simulation implementing explosive movement of a thin liquid layer driven by released latent heat diffusion in a lateral direction. PMID:23185095

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

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

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

  16. Direct Observation of Excitonic Lasing from Single ZnO Nanobelts at Room Temperature

    NASA Astrophysics Data System (ADS)

    Bando, Kazuki; Sawabe, Taiki; Asaka, Koji; Masumoto, Yasuaki

    2005-06-01

    Excitonic lasing from single ZnO nanobelts was observed at room temperature, which was due to the exciton-exciton scattering processes appearing under intense light excitation. Morphologies of the nanobelts are rectangular shapes, so that crystalline facets of the nanobelts acted as the lasing cavity mirrors. We demonstrated that mode spacings correspond to cavity lengths of the respective nanobelts, and directly observed the lasing from single ZnO nanobelts by mapping of the luminescence intensity.

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

    PubMed Central

    2013-01-01

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

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

    ERIC Educational Resources Information Center

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

    2007-01-01

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

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

    ERIC Educational Resources Information Center

    Oner, Pinar; Oner, Ozgur; Munir, Kerim

    2014-01-01

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

  20. Considering Systematic Direct Observation after a Century of Research--Commentary on the Special Issue

    ERIC Educational Resources Information Center

    Stichter, Janine P.; Riley-Tillman, T. Chris

    2014-01-01

    Systematic Direct Observation (SDO) has played a pivotal role in the field of Emotional and/or Behavioral Disorders (EBD) since its inception as a key part of understanding more about the behaviors, contexts that impact them, and the effective supports necessary for this population. This methodology is an ongoing charge for everyone. The authors

  1. Standardizing the Pre-Licensure Supervision Process: A Commentary on Advocating for Direct Observation of Skills

    ERIC Educational Resources Information Center

    Gray, Neal D.; Erickson, Paul

    2013-01-01

    The present paper advocates for standardized regulations and laws for supervision of pre-licensed counselors in the United States, particularly for direct observation of clinical skills. A review of regulations by the American Counseling Association (ACA) Office of Professional Affairs (2012) reveals that only two states (Arizona and North

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

    ERIC Educational Resources Information Center

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

    2011-01-01

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

  3. Directly observed relations in complete galaxy samples and the predictions of redshift-distance power laws

    PubMed Central

    Segal, I. E.

    1986-01-01

    Directly observed relations in complete galaxy samples (apparent magnitude or diameter vs. redshift) are compared with the predictions of redshift-distance power laws. The predictions are obtained by an objective, nonparametric, statistically uniform, and fully reproducible procedure. In all cases the linear law fits even more poorly than a cubic law, and the optimal law is approximately quadratic. Even a 1.2 power law is conspicuously better-fitting than a linear law. The results of the present study in terms of directly measured quantities are consistent with and confirm earlier studies in terms of theoretical quantities such as absolute magnitudes and diameters. They show that there is no positive evidence for the Hubble law in manifestly fair galaxy samples and that the law can be reconciled with the data in complete samples only, if at all, by the adjunction of a tissue of ancillary hypotheses, none of which is capable of direct observational substantiation. PMID:16593765

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

    NASA Astrophysics Data System (ADS)

    Herique, A.; Kofman, W. W.

    2013-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-07-01

    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.

  6. Evaluating worker vibration exposures using self-reported and direct observation estimates of exposure duration.

    PubMed

    McCallig, Margaret; Paddan, Gurmail; Van Lente, Eric; Moore, Ken; Coggins, Marie

    2010-12-01

    The objective of this study was to compare objective and subjective methods of collecting exposure time data for hand arm vibration (HAV) and whole-body vibration (WBV), and to evaluate the impact of inaccurate exposure times' on the calculation of the average vibration exposure over an 8 h working day A(8). The study was carried out in the engineering services and maintenance departments of a construction and property management company. Worker exposure time data was collected using three methods, questionnaire surveys, daily worker interviews and 8 h direct workplace observations. Vibration magnitudes (m/s(2)) were measured for a range of hand tools and vehicles, and daily vibration exposure estimates A(8) were calculated using exposure times observed, reported in interview and self reported in the questionnaire. Results from the study showed that self-reported exposure time estimates from the questionnaire survey were a factor of 9.0 (median value) times greater for HAV and a factor of 6.0 (median value) times greater for WBV when compared with direct observation estimates. Exposure times reported in interview were higher, than those observed, but more reliable than those self reported in the questionnaire; a factor of 2.1 (median value) times greater for HAV and a factor of 1.4 (median value) times greater for WBV. A(8) values calculated using questionnaire exposure times were up to 66% and 75% greater for sources of HAV and WBV respectively when compared to A(8) values calculated using observed exposure times. For the purposes of carrying out a reliable risk assessment, results from this study indicate that direct measurements of worker exposure time are not recommended over questionnaires especially where work is highly variable for example in construction and property management. Worker interviews or direct workplace observation methods were found to be reliable alternative methods for collecting exposure time. PMID:20462567

  7. Expression of fluorescent proteins within the repeat long region of the Marek's disease virus genome allows direct identification of infected cells while retaining full pathogenicity.

    PubMed

    Jarosinski, Keith W; Donovan, Kathleen M; Du, Guixin

    2015-04-01

    Marek's disease virus (MDV) is a lymphotropic alphaherpesvirus and causes Marek's disease (MD) in chickens. RLORF4 is an MDV-specific gene located in the repeat long (RL) regions of the genome and is directly involved in attenuation. In this report, we generated recombinant (r)MDVs in which eGFP or mRFP was inserted in-frame of the 3' end of the RLORF4 gene. In vitro growth was unaffected and infected cells could be identified by using fluorescent microscopy. Interestingly, though inserted in-frame with RLORF4, eGFP and mRFP were expressed alone, confirming mRNA expression and splicing within the RL of MDV is complex. In vivo, rMDVs expressing mRFP or eGFP caused tumors similar to wild-type MDV. Fluorescent protein expression could be seen in spleen, tumor, and feather follicle epithelial cells. These results show that expression of fluorescent proteins within the RL region results in fluorescent rMDVs that still maintains full pathogenicity in the chicken. PMID:25725150

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

    ERIC Educational Resources Information Center

    Adamson, Reesha M.; Wachsmuth, Sean T.

    2014-01-01

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

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

    ERIC Educational Resources Information Center

    Adamson, Reesha M.; Wachsmuth, Sean T.

    2014-01-01

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

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

    SciTech Connect

    Muto, Takayuki

    2011-09-20

    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.

  11. A Novel 7-Single Nucleotide Polymorphism-Based Clonotyping Test Allows Rapid Prediction of Antimicrobial Susceptibility of Extraintestinal Escherichia coli Directly From Urine Specimens

    PubMed Central

    Tchesnokova, Veronika; Avagyan, Hovhannes; Billig, Mariya; Chattopadhyay, Sujay; Aprikian, Pavel; Chan, Diana; Pseunova, Julietta; Rechkina, Elena; Riddell, Kim; Scholes, Delia; Fang, Ferric C.; Johnson, James R.; Sokurenko, Evgeni V.

    2016-01-01

    Background. Escherichia coli is a highly clonal pathogen. Extraintestinal isolates belong to a limited number of genetically related groups, which often exhibit characteristic antimicrobial resistance profiles. Methods. We developed a rapid clonotyping method for extraintestinal E coli based on detection of the presence or absence of 7 single nucleotide polymorphisms (SNPs) within 2 genes (fumC and fimH). A reference set of 2559 E coli isolates, primarily of urinary origin, was used to predict the resolving power of the 7-SNP-based typing method, and 582 representative strains from this set were used to evaluate test robustness. Results. Fifty-four unique SNP combinations (“septatypes”) were identified in the reference strains. These septatypes yielded a clonal group resolution power on par with that of traditional multilocus sequence typing. In 72% of isolates, septatype identity predicted sequence type identity with at least 90% (mean, 97%) accuracy. Most septatypes exhibited highly distinctive antimicrobial susceptibility profiles. The 7-SNP-based test could be performed with high specificity and sensitivity using single or multiplex conventional polymerase chain reaction (PCR) and quantitative PCR. In the latter format, E coli presence and septatype identity were determined directly in urine specimens within 45 minutes with bacterial loads as low as 102 colony-forming units/mL and, at clinically significant bacterial loads, with 100% sensitivity and specificity. Conclusions. 7-SNP-based typing of E coli can be used for both epidemiological studies and clinical diagnostics, which could greatly improve the empirical selection of antimicrobial therapy. PMID:26925427

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

    SciTech Connect

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

    2012-01-28

    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.

  13. Directly observed therapy for tuberculosis given twice weekly in the workplace in urban South Africa.

    PubMed

    Bechan, S; Connolly, C; Short, G M; Standing, E; Wilkinson, D

    1997-01-01

    Effective models of delivery of directly observed therapy (DOT) for tuberculosis in resource-poor settings are needed. Intermittent chemotherapy may be an important component of DOT delivered in the community as it means fewer visits to supervisors. There is no published evidence on the efficacy of twice weekly therapy given from the start of treatment without an intensive daily phase. We analysed data from 3 large cohort studies in a migrant, urban workforce in South Africa between 1975 and 1983. All patients received 4 drugs (isoniazid, rifampicin, pyrazinamide and streptomycin) twice weekly under direct observation by a nurse in the workplace. Of 444 patients, 378 (85.1%) completed treatment. Cure could be assessed in 362, and 348 (96.1%, 95% confidence interval 93.7-97.8%) were bacteriologically cured. Sputum status was assessed at 2-3 months in 343 patients and 309 (90.1%) were sputum negative. Eighteen patients relapsed (5.7%; 2.9/100 patient-years of observation). DOT can be effectively delivered to a migrant, urban workforce, and 4-drug therapy given twice weekly under direct observation is efficacious. PMID:9509184

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

    SciTech Connect

    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

    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.

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

    SciTech Connect

    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

    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.

  16. Gravity Waves Generated by Convection: A New Idealized Model Tool and Direct Validation with Satellite Observations

    NASA Astrophysics Data System (ADS)

    Alexander, M. Joan; Stephan, Claudia

    2015-04-01

    In climate models, gravity waves remain too poorly resolved to be directly modelled. Instead, simplified parameterizations are used to include gravity wave effects on model winds. A few climate models link some of the parameterized waves to convective sources, providing a mechanism for feedback between changes in convection and gravity wave-driven changes in circulation in the tropics and above high-latitude storms. These convective wave parameterizations are based on limited case studies with cloud-resolving models, but they are poorly constrained by observational validation, and tuning parameters have large uncertainties. Our new work distills results from complex, full-physics cloud-resolving model studies to essential variables for gravity wave generation. We use the Weather Research Forecast (WRF) model to study relationships between precipitation, latent heating/cooling and other cloud properties to the spectrum of gravity wave momentum flux above midlatitude storm systems. Results show the gravity wave spectrum is surprisingly insensitive to the representation of microphysics in WRF. This is good news for use of these models for gravity wave parameterization development since microphysical properties are a key uncertainty. We further use the full-physics cloud-resolving model as a tool to directly link observed precipitation variability to gravity wave generation. We show that waves in an idealized model forced with radar-observed precipitation can quantitatively reproduce instantaneous satellite-observed features of the gravity wave field above storms, which is a powerful validation of our understanding of waves generated by convection. The idealized model directly links observations of surface precipitation to observed waves in the stratosphere, and the simplicity of the model permits deep/large-area domains for studies of wave-mean flow interactions. This unique validated model tool permits quantitative studies of gravity wave driving of regional circulation and provides a new method for future development of realistic convective gravity wave parameterizations.

  17. Validation of simulated flow direction and hydraulic gradients with hydraulic head observations using open source GIS

    NASA Astrophysics Data System (ADS)

    Vandersteen, Katrijn; Rogiers, Bart; Gedeon, Matej

    2015-04-01

    It is recommended to check hydraulic gradients and flow directions predicted by a groundwater flow model that is calibrated solely with hydraulic head observations. It has been demonstrated in literature that substantial errors can be made when the model is not calibrated on these state variables. Therefore, in this work, we perform a validation of a steady-state groundwater flow model, representing part of the Neogene aquifer (60 km2) in Belgium. This model was developed and calibrated solely on groundwater head measurements, in the framework of the environmental impact assessment of the near surface repository for low- and intermediate-level short-lived waste, realized by ONDRAF/NIRAS at Dessel, Belgium. Horizontal flow directions, horizontal and vertical gradients for the entire area of the groundwater model were estimated from measurements at shallow monitoring wells within the groundwater flow model domain, and compared to the flow directions and vertical gradients predicted by the model. For obtaining horizontal flow directions and gradients, triangulation of groundwater levels was performed for combinations of three neighboring hydraulic head observations in the same hydrogeological layer within the model. The simulated equivalents at the same monitoring wells were used to repeat the same methodology, and calculate flow direction components. This analysis was performed in SAGA GIS and was visualized through QGIS. Comparison of the flow directions and flow gradients obtained from measurements and simulations gives an indication on the model performance. The calculations were performed for three sandy hydrogeological units used in the model. A similar procedure was performed for the vertical hydraulic head gradients, where any combination of two hydraulic head observations at the same location but at different levels within the aquifer were used to validate the vertical gradients predicted by the model. Besides model validation on average hydraulic heads, the variability of flow direction and hydraulic gradients in time was checked, by using the actually measured monthly time series, to verify the applicability of the steady-state modelling approach. This basic assessment of flow directions and gradients using open source GIS can be used to identify potential areas of interest, were more detailed investigations would be recommended.

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

    NASA Technical Reports Server (NTRS)

    Spinhime, James

    1993-01-01

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

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

    PubMed

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

    2014-10-10

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

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

    PubMed

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

    2014-09-26

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

  1. Direct observations of a flare related coronal and solar wind disturbance

    NASA Technical Reports Server (NTRS)

    Gosling, J. T.; Hildner, E.; Macqueen, R. M.; Munro, R. H.; Poland, A. I.; Ross, C. L.

    1975-01-01

    Numerous mass ejections from the sun have been detected with orbiting coronagraphs. Here for the first time we document and discuss the direct association of a coronagraph observed mass ejection, which followed a 2B flare, with a large interplanetary shock wave disturbance observed at 1 AU. Estimates of the mass and energy content of the coronal disturbance are in reasonably good agreement with estimates of the mass and energy content of the solar wind disturbance at 1 AU. The energy estimates as well as the transit time of the disturbance are also in good agreement with numerical models of shock wave propagation in the solar wind.

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

    NASA Technical Reports Server (NTRS)

    Crisp, David; Komar, George (Technical Monitor)

    2001-01-01

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

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

    SciTech Connect

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

    2015-02-09

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

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

    PubMed

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

    2014-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

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

    PubMed

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

    2013-11-13

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

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

    PubMed

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

    2010-11-13

    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. The main welfare issues identified were lameness and claw overgrowth, udder and teat lesions, skin lesions and pruritus. PMID:21262609

  8. Warming experiments elucidate the drivers of observed directional changes in tundra vegetation.

    PubMed

    Hollister, Robert D; May, Jeremy L; Kremers, Kelseyann S; Tweedie, Craig E; Oberbauer, Steven F; Liebig, Jennifer A; Botting, Timothy F; Barrett, Robert T; Gregory, Jessica L

    2015-05-01

    Few studies have clearly linked long-term monitoring with insitu experiments to clarify potential drivers of observed change at a given site. This is especially necessary when findings from a site are applied to a much broader geographic area. Here, we document vegetation change at Barrow and Atqasuk, Alaska, occurring naturally and due to experimental warming over nearly two decades. An examination of plant cover, canopy height, and community indices showed more significant differences between years than due to experimental warming. However, changes with warming were more consistent than changes between years and were cumulative in many cases. Most cases of directional change observed in the control plots over time corresponded with a directional change in response to experimental warming. These included increases in canopy height and decreases in lichen cover. Experimental warming resulted in additional increases in evergreen shrub cover and decreases in diversity and bryophyte cover. This study suggests that the directional changes occurring at the sites are primarily due to warming and indicates that further changes are likely in the next two decades if the regional warming trend continues. These findings provide an example of the utility of coupling insitu experiments with long-term monitoring to accurately document vegetation change in response to global change and to identify the underlying mechanisms driving observed changes. PMID:26140204

  9. Warming experiments elucidate the drivers of observed directional changes in tundra vegetation

    PubMed Central

    Hollister, Robert D; May, Jeremy L; Kremers, Kelseyann S; Tweedie, Craig E; Oberbauer, Steven F; Liebig, Jennifer A; Botting, Timothy F; Barrett, Robert T; Gregory, Jessica L

    2015-01-01

    Few studies have clearly linked long-term monitoring with in situ experiments to clarify potential drivers of observed change at a given site. This is especially necessary when findings from a site are applied to a much broader geographic area. Here, we document vegetation change at Barrow and Atqasuk, Alaska, occurring naturally and due to experimental warming over nearly two decades. An examination of plant cover, canopy height, and community indices showed more significant differences between years than due to experimental warming. However, changes with warming were more consistent than changes between years and were cumulative in many cases. Most cases of directional change observed in the control plots over time corresponded with a directional change in response to experimental warming. These included increases in canopy height and decreases in lichen cover. Experimental warming resulted in additional increases in evergreen shrub cover and decreases in diversity and bryophyte cover. This study suggests that the directional changes occurring at the sites are primarily due to warming and indicates that further changes are likely in the next two decades if the regional warming trend continues. These findings provide an example of the utility of coupling in situ experiments with long-term monitoring to accurately document vegetation change in response to global change and to identify the underlying mechanisms driving observed changes. PMID:26140204

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

    SciTech Connect

    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

    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.

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

    PubMed Central

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

    2012-01-01

    Optimal foraging models predict that large predators should concentrate on large prey in order to maximize their net gain of energy intake. Here, we show that the largest species of sea turtle, Dermochelys coriacea, does not strictly adhere to this general pattern. Field observations combined with a theoretical model suggest that a 300 kg leatherback turtle would meet its energetic requirements by feeding for 34 h a day on 4 g jellyfish, but only if prey were aggregated in high-density patches. Therefore, prey abundance rather than prey size may, in some cases, be the overriding parameter for foraging leatherbacks. This is a classic example where the presence of small prey in the diet of a large marine predator may reflect profitable foraging decisions if the relatively low energy intake per small individual prey is offset by high encounter rates and minimal capture and handling costs. This study provides, to our knowledge, the first quantitative estimates of intake rate for this species. PMID:22090203

  12. Global observations of the spectrally resolved direct effect of aerosols over clouds

    NASA Astrophysics Data System (ADS)

    de Graaf, M.; Tilstra, G.; Stammes, P.

    2011-12-01

    The direct radiative effect of absorbing aerosols in cloudy scenes is currently not well constrained. The simultaneous observation of both clouds and aerosols is seriously limited due to their heterogeneous distribution in both space and time. Space-based observations have the potential of monitoring cloud and aerosol distributions on a daily basis, but most current satellite aerosol retrieval algorithms rely on cloud screening before retrieving aerosol information. Furthermore, results often depend strongly on aerosol micro-physical property assumptions. With the space-borne spectrometer ENVISAT/SCIAMACHY, that measures 92% of the solar energy spectrum incident on the Earth's atmosphere, the aerosol direct effect can be quantified directly, avoiding most of these limitations. The absorption of radiation by small, absorbing aerosols is large in the ultraviolet (UV), and can be detected using UV-reflectance measurements, even in the presence of clouds. The aerosol absorption decreases quickly with increasing wavelength and cloud optical thickness and cloud droplet size can be retrieved in the near-infrared, where aerosol effects are sufficiently small. These retrieved cloud parameters can be used to find a modelled unpolluted cloud reflectance spectrum for the scene (with the aerosols removed), using pre-computed data bases from a radiative transfer model. In this way, cloud and aerosol effects can be separated for the polluted cloud scene. The spectrally resolved direct effect can be determined by comparison of the measured polluted scene reflectance spectrum and the modelled clean cloud reflectance spectrum. Aerosol micro-physical property assumptions are avoided through the modelling of pure cloud spectra only. Although the global coverage of SCIAMACHY is only once every six days, over 8 years of global reflectance spectra and direct effect of aerosols over clouds data are available from this method, which will be presented here.

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

    PubMed Central

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

    2012-01-01

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

  14. General analysis of direct dark matter detection: From microphysics to observational signatures

    NASA Astrophysics Data System (ADS)

    Dent, James B.; Krauss, Lawrence M.; Newstead, Jayden L.; Sabharwal, Subir

    2015-09-01

    Beginning with a set of simplified models for spin-0, spin-1/2 , and spin-1 dark matter candidates, we derive the full set of nonrelativistic operators and nuclear matrix elements relevant for direct detection of dark matter and use these to calculate rates and recoil spectra for scattering on various target nuclei. This allows us to explore what high energy physics constraints might be obtainable from direct detection experiments, what degeneracies exist, which operators are ubiquitous, and which are unlikely or subdominant. We find that there are operators which are common to all spins as well operators which are unique to spin-1/2 and spin-1 and elucidate two new operators which have not been previously considered. In addition we demonstrate how recoil energy spectra can distinguish fundamental microphysics if multiple target nuclei are used. Our work provides a complete road map for taking generic fundamental dark matter theories and calculating rates in direct detection experiments. This provides a useful guide for experimentalists designing experiments and theorists developing new dark matter models.

  15. Observations of black carbon induced semi direct effect over Northeast India

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  16. Effectiveness of home-based directly observed treatment for tuberculosis in Kweneng West subdistrict, Botswana

    PubMed Central

    Kabongo, Diulu

    2010-01-01

    ABSTRACT Background Tuberculosis (TB) and HIV are major public health problems in Botswana. In the face of growing TB notification rates, a low cure rate, human resource constraints and poor accessibility to health facilities, Botswana Ministry of Health decided to offer home-based directly observed treatment (DOT) using community volunteers. Objectives The aim of this study was to assess the outcomes of home-based directly observed treatment (HB-DOT) versus facility-based, directly observed treatment (FB-DOT) in the Kweneng West subdistrict in Botswana and to explore the acceptability of HB-DOT among TB patients, community volunteers and health workers. Method A quantitative, observational study using routinely collected TB data from 405 TB patients was conducted and combined with 20 qualitative in-depth interviews. Results The overall cure rate for smear-positive pulmonary TB patients was 78.5%. Treatment outcomes were not statistically different between FB-DOT and HB-DOT. Contact tracing was significantly better in FB-DOT patients. Interviews revealed advantages and disadvantages for both FB and HB options and that flexibility in the choice or mix of options was important. A number of suggestions were made by the interviewees to improve the HB-DOT programme. Conclusion HB-DOT is at least as good as FB-DOT in terms of the treatment outcomes, but attention must be given to contact tracing. HB-DOT offers some patients the flexibility they need to adhere to TB treatment and community volunteers may be strengthened by ongoing training and support from health workers, financial incentives and provision of basic equipment.

  17. Direct observation of electric double layers at solution surfaces by means of electron spectroscopy

    NASA Astrophysics Data System (ADS)

    Moberg, R.; Bkman, F.; Bohman, O.; Siegbahn, H. O. G.

    1991-04-01

    Solutions of fatty acid potassium salts in formamide have been investigated using electron spectroscopy in the angular resolved mode. The variable surface sensitivity thus achieved allows details of the electric double layers formed at the solution surfaces to be investigated. The cation distribution is found to vary as a function of solution concentration. The simple diffuse layer theory based on the Poisson-Boltzmann equations is found inadequate in describing the observed features. The data suggest that structural changes occur at the higher concentrations forming closer bound cation states at the surface. These findings qualitatively confirm recent theoretical model predictions by other workers.

  18. Investigating common clinical presentations in first opinion small animal consultations using direct observation

    PubMed Central

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

    2015-01-01

    Understanding more about the clinical presentations encountered in veterinary practice is vital in directing research towards areas relevant to practitioners. The aim of this study was to describe all problems discussed during a convenience sample of consultations using a direct observation method. A data collection tool was used to gather data by direct observation during small animal consultations at eight sentinel practices. Data were recorded for all presenting and non-presenting specific health problems discussed. A total of 1901 patients were presented with 3206 specific health problems discussed. Clinical presentation varied widely between species and between presenting and non-presenting problems. Skin lump, vomiting and inappetence were the most common clinical signs reported by the owner while overweight/obese, dental tartar and skin lump were the most common clinical examination findings. Skin was the most frequently affected body system overall followed by non-specific problems then the gastrointestinal system. Consultations are complex, with a diverse range of different clinical presentations seen. Considering the presenting problem only may give an inaccurate view of the veterinary caseload, as some common problems are rarely the reason for presentation. Understanding the common diagnoses made is the next step and will help to further focus questions for future research. PMID:25564472

  19. An accuracy measurement method for star trackers based on direct astronomic observation.

    PubMed

    Sun, Ting; Xing, Fei; Wang, Xiaochu; You, Zheng; Chu, Daping

    2016-01-01

    Star tracker is one of the most promising optical attitude measurement devices and it is widely used in spacecraft for its high accuracy. However, how to realize and verify such an accuracy remains a crucial but unsolved issue until now. The authenticity of the accuracy measurement method of a star tracker will eventually determine the satellite performance. A new and robust accuracy measurement method for a star tracker based on the direct astronomical observation is proposed here. In comparison with the conventional method with simulated stars, this method utilizes real navigation stars as observation targets which makes the measurement results more authoritative and authentic. Transformations between different coordinate systems are conducted on the account of the precision movements of the Earth, and the error curves of directional vectors are obtained along the three axes. Based on error analysis and accuracy definitions, a three-axis accuracy evaluation criterion has been proposed in this paper, which could determine pointing and rolling accuracy of a star tracker directly. Experimental measurements confirm that this method is effective and convenient to implement. Such a measurement environment is close to the in-orbit conditions and it can satisfy the stringent requirement for high-accuracy star trackers. PMID:26948412

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

    PubMed

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

    2015-01-10

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

  1. Investigating common clinical presentations in first opinion small animal consultations using direct observation.

    PubMed

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

    2015-05-01

    Understanding more about the clinical presentations encountered in veterinary practice is vital in directing research towards areas relevant to practitioners. The aim of this study was to describe all problems discussed during a convenience sample of consultations using a direct observation method. A data collection tool was used to gather data by direct observation during small animal consultations at eight sentinel practices. Data were recorded for all presenting and non-presenting specific health problems discussed. A total of 1901 patients were presented with 3206 specific health problems discussed. Clinical presentation varied widely between species and between presenting and non-presenting problems. Skin lump, vomiting and inappetence were the most common clinical signs reported by the owner while overweight/obese, dental tartar and skin lump were the most common clinical examination findings. Skin was the most frequently affected body system overall followed by non-specific problems then the gastrointestinal system. Consultations are complex, with a diverse range of different clinical presentations seen. Considering the presenting problem only may give an inaccurate view of the veterinary caseload, as some common problems are rarely the reason for presentation. Understanding the common diagnoses made is the next step and will help to further focus questions for future research. PMID:25564472

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

    PubMed Central

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

    2015-01-01

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

  3. Apparatus for Direct Optical Fiber Through-Lens Illumination of Microscopy or Observational Objects

    NASA Technical Reports Server (NTRS)

    Kadogawa, Hiroshi (Inventor)

    2001-01-01

    In one embodiment of the invention, a microscope or other observational apparatus, comprises a hollow tube, a lens mounted to the tube, a light source and at least one flexible optical fiber having an input end and an output end. The input end is positioned to receive light from the light source, and the output end is positioned within the tube so as to directly project light along a straight path to the lens to illuminate an object to be viewed. The path of projected light is uninterrupted and free of light deflecting elements. By passing the light through the lens, the light can be diffused or otherwise defocused to provide more uniform illumination across the surface of the object, increasing the quality of the image of the object seen by the viewer. The direct undeflected and uninterrupted projection of light, without change of direction, eliminates the need for light-deflecting elements, such as beam-splitters, mirrors, prisms, or the like, to direct the projected light towards the object.

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

    ERIC Educational Resources Information Center

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

    2014-01-01

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

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

    ERIC Educational Resources Information Center

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

    2014-01-01

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

  6. Freud's views on early female sexuality in the light of direct child observation.

    PubMed

    Kleeman, J A

    1976-01-01

    Freud's writings on early female sexuality are reviewed in order to demonstrate which of his central assumptions are supported and which have been corrected by the direct observation of young children. The study of the emergence of core gender identity in little girls is a key to the modification of Freud's statements on the onset of and crucial factors in the development of femininity. Cognitive functions, learning experiences, and language are believed to be more important than Freud stressed, and penis envy and feelings of inferiority are relegated to a less universal and less necessary place in the onset of femininity. The role of the father is given different emphasis. Direct observation clarifies many aspects of masturbation or early genital self-stimulation in the young female: its onset; its feminine rather than masculine character; its early vicissitudes; its importance relative to other behavior; the impact of the discovery of anatomical difference; one special way it is affected by parental attitude; and how it contrasts with comparable behavior in the young male. Observation refutes Freud's often quoted statement that masturbation is further removed from the nature of women than of men. PMID:803149

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

    SciTech Connect

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

    2014-01-08

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

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

    PubMed

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

    2014-01-01

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

  9. Direct Observation of Chiral Topological Solitons in 1D Charge-Density Waves

    NASA Astrophysics Data System (ADS)

    Kim, Tae-Hwan; Cheon, Sangmo; Lee, Sung-Hoon; Yeom, Han Woong

    2015-03-01

    Macroscopic and classical solitons are easily and ubiquitously found, from tsunami to blood pressure pulses, but those in microscopic scale are hard to observe. While the existence of such topological solitons were predicted theoretically and evidenced indirectly by the transport and infrared spectroscopy measurements, the direct observation has been hampered by their high mobility and small dimension. In this talk, we show direct observation of topological solitons in the quasi-1D charge-density wave (CDW) ground state of indium atomic wires, which are consisting of interacting double Peierls chains. Such solitons exhibit a characteristic spatial variation of the CDW amplitudes as expected from the electronic structure. Furthermore, these solitons have an exotic hidden topology originated by topologically different 4-fold degenerate CDW ground states. Their exotic topology leads to the chirality of 1D topological solitons through interaction between two solitons in the double Peierls chains. Detailed scanning tunneling microscopy and spectroscopy reveal their chiral nature at the atomic scale. This work paves the avenue toward the microscopic exploitation of the peculiar properties of nanoscale chiral solitons.

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

    PubMed Central

    Djeghloul, F.; Ibrahim, F.; Cantoni, M.; Bowen, M.; Joly, L.; Boukari, S.; Ohresser, P.; Bertran, F.; Le Fvre, 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

    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

  11. Photoacoustics of single laser-trapped nanodroplets for the direct observation of nanofocusing in aerosol photokinetics.

    PubMed

    Cremer, Johannes W; Thaler, Klemens M; Haisch, Christoph; Signorell, Ruth

    2016-01-01

    Photochemistry taking place in atmospheric aerosol droplets has a significant impact on the Earth's climate. Nanofocusing of electromagnetic radiation inside aerosols plays a crucial role in their absorption behaviour, since the radiation flux inside the droplet strongly affects the activation rate of photochemically active species. However, size-dependent nanofocusing effects in the photokinetics of small aerosols have escaped direct observation due to the inability to measure absorption signatures from single droplets. Here we show that photoacoustic measurements on optically trapped single nanodroplets provide a direct, broadly applicable method to measure absorption with attolitre sensitivity. We demonstrate for a model aerosol that the photolysis is accelerated by an order of magnitude in the sub-micron to micron size range, compared with larger droplets. The versatility of our technique promises broad applicability to absorption studies of aerosol particles, such as atmospheric aerosols where quantitative photokinetic data are critical for climate predictions. PMID:26979973

  12. Direct assessment of groundwater vulnerability from single observations of multiple contaminants

    USGS Publications Warehouse

    Worrall, F.; Kolpin, D.W.

    2003-01-01

    Groundwater vulnerability is a central concept in pollution risk assessment, yet its estimation has been largely a matter of expert judgment. This work applies a method for the direct calculation of vulnerability from monitoring well observations of pesticide concentrations. The method has two major advantages: it is independent of the compounds being examined, and it has a direct probabilistic interpretation making it ideal for risk assessment. The methodology was applied to data from a groundwater monitoring program in the midwestern United States. The distribution of the vulnerabilities was skewed toward zero. Spatial distribution of the vulnerabilities shows them to be controlled by both regional and local factors. Methods are presented for estimating the necessary sample sizes for vulnerability studies. The further application of the approach developed in this study to understanding groundwater pollution is discussed.

  13. Photoacoustics of single laser-trapped nanodroplets for the direct observation of nanofocusing in aerosol photokinetics

    PubMed Central

    Cremer, Johannes W.; Thaler, Klemens M.; Haisch, Christoph; Signorell, Ruth

    2016-01-01

    Photochemistry taking place in atmospheric aerosol droplets has a significant impact on the Earth's climate. Nanofocusing of electromagnetic radiation inside aerosols plays a crucial role in their absorption behaviour, since the radiation flux inside the droplet strongly affects the activation rate of photochemically active species. However, size-dependent nanofocusing effects in the photokinetics of small aerosols have escaped direct observation due to the inability to measure absorption signatures from single droplets. Here we show that photoacoustic measurements on optically trapped single nanodroplets provide a direct, broadly applicable method to measure absorption with attolitre sensitivity. We demonstrate for a model aerosol that the photolysis is accelerated by an order of magnitude in the sub-micron to micron size range, compared with larger droplets. The versatility of our technique promises broad applicability to absorption studies of aerosol particles, such as atmospheric aerosols where quantitative photokinetic data are critical for climate predictions. PMID:26979973

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

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

    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-unique relationships between saturation and velocity in sandstones dependent on texture and fluid displacement history: fuller understanding of these phenomena is needed for accurate assessment of time lapse seismic measurements, be they for oil and gas recovery or for CO2 disposal purposes. Gassmann, F., 1951, Elastic waves through a packing of spheres. Geophysics 16, 673-685; Mavko, G., T. Mukerji, and J. Dvorkin, 1998, The Rock Physics Handbook: Tools for seismic analysis in porous media: Cambridge University Press. Wood, A. W., 1955, A Textbook of Sound, The MacMillan Co., New York, 360 pp. Hill, R., 1963, Elastic properties of reinforced solids: some theoretical principles. J. Mech. Phys. Solids, 11, 357-372. Hill, R., 1952, The elastic behavior of crystalline aggregates. Proc. Physical Soc., London, A65, 349-354. J. Toms, T.M. Mueller, B. Gurevich, 2007 Seismic attenuation in porous rocks with random patchy saturation. Geophysical Prospecting, 55, 671-678.

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

    PubMed Central

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

    2014-01-01

    The distribution of ions and charge at solid-water interfaces plays an essential role in a wide range of processes in biology, geology and technology. While theoretical models of the solid-electrolyte interface date back to the early 20th century, a detailed picture of the structure of the electric double layer has remained elusive, largely because of experimental techniques have not allowed direct observation of the behaviour of ions, i.e. with subnanometer resolution. We have made use of recent advances in high-resolution Atomic Force Microscopy to reveal, with atomic level precision, the ordered adsorption of the mono- and divalent ions that are common in natural environments to heterogeneous gibbsite/silica surfaces in contact with aqueous electrolytes. Complemented by density functional theory, our experiments produce a detailed picture of the formation of surface phases by templated adsorption of cations, anions and water, stabilized by hydrogen bonding. PMID:24850566

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

    NASA Astrophysics Data System (ADS)

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

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

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

    PubMed Central

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

    2014-01-01

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

  18. Direct Observation of Coherent Oscillations in Solution due to Microheterogeneous Environment

    PubMed Central

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

    2014-01-01

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

  19. Direct experimental observation of periodic intensity modulation along a straight hollow-core optical waveguide

    SciTech Connect

    Pfeifer, T.; Downer, M. C.

    2007-05-15

    We report the direct observation of periodic intensity modulation of a laser pulse propagating in a hollow-core waveguide. A series of equally spaced plasma sparks along the gas-filled capillary is produced. This effect can be explained by the beating of different fiber modes, which are excited by controlling the size of the focal spot at the capillary entrance. As compared with an artificial modulated waveguide structure, our presented approach represents an easier and more flexible quasi-phase-matching scheme for nonlinear-optical frequency conversion.

  20. Validity, reliability, feasibility, acceptability and educational impact of direct observation of procedural skills (DOPS).

    PubMed

    Naeem, Naghma

    2013-01-01

    Direct observation of procedural skills (DOPS) is a new workplace assessment tool. The aim of this narrative review of literature is to summarize the available evidence about the validity, reliability, feasibility, acceptability and educational impact of DOPS. A PubMed database and Google search of the literature on DOPS published from January 2000 to January 2012 was conducted which yielded 30 articles. Thirteen articles were selected for full text reading and review. In the reviewed literature, DOPS was found to be a useful tool for assessment of procedural skills, but further research is required to prove its utility as a workplace based assessment instrument. PMID:23286629

  1. First direct observation of reactive carbenes in the cavities of cation-exchanged Y zeolites.

    PubMed

    Moya-Barrios, Reinaldo; Cozens, Frances L

    2004-03-18

    [reaction: see text] Herein we report the first direct observation of reactive carbenes within the cavities of cation-exchanged Y zeolites. Chloro(phenyl)- and bromo(phenyl)carbenes were generated upon laser photolysis of 3-halo-3-phenyldiazirines incorporated within dry zeolites and the absolute reactivity of the carbenes was investigated as a function of counterbalancing cation and coincorporated quenchers in order to elucidate the behavior of these intermediates within zeolites. Product analysis performed upon thermolysis of the diazirine in Y zeolites yielded products that were identified as those derived from the carbene. PMID:15012055

  2. The 'semitorrid' gas observed in the direction of Gamma-2 Velorum and the Gum nebula

    NASA Technical Reports Server (NTRS)

    Bruhweiler, F. C.; Kondo, J.; Mccluskey, G. E., Jr.

    1979-01-01

    On the basis of recent IUE observations in the far-ultraviolet, the authors report the detection of a 'semitorrid' region of the interstellar medium in the direction of Gamma-2 Velorum and the Gum nebula. The characteristic temperature of this gas is in the 40,000 K range, between the warm (around 1000 K) and hot (roughly 100,000-1,000,000 K) regions reported by various investigators. This temperature is compatible with the theoretical temperature ascribed to the 'fossil Stromgren sphere' by Brandt et al. and Alexander et al.

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

    PubMed

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

    2012-12-28

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

  4. Direct Observation of a Localized Magnetic Soliton in a Spin-Transfer Nanocontact.

    PubMed

    Backes, D; Maci, F; Bonetti, S; Kukreja, R; Ohldag, H; Kent, A D

    2015-09-18

    We report the direct observation of a localized magnetic soliton in a spin-transfer nanocontact using scanning transmission x-ray microscopy. Experiments are conducted on a lithographically defined 150 nm diameter nanocontact to an ultrathin ferromagnetic multilayer with perpendicular magnetic anisotropy. Element-resolved x-ray magnetic circular dichroism images show an abrupt onset of a magnetic soliton excitation localized beneath the nanocontact at a threshold current. However, the amplitude of the excitation ?25 at the contact center is far less than that predicted (?180), showing that the spin dynamics is not described by existing models. PMID:26431016

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

    SciTech Connect

    Elmer, J. W.; Specht, Eliot D

    2010-01-01

    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

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

    PubMed Central

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

    2012-01-01

    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

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

    SciTech Connect

    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.; Borcea, C.; Companis, I.; Brown, B. A.; Oliveira Santos, F. de; Perrot, L.; Thomas, J.-C.

    2011-09-02

    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.

  8. Direct observation of TALE protein dynamics reveals a two-state search mechanism

    NASA Astrophysics Data System (ADS)

    Cuculis, Luke; Abil, Zhanar; Zhao, Huimin; Schroeder, Charles M.

    2015-06-01

    Transcription activator-like effector (TALE) proteins are a class of programmable DNA-binding proteins for which the fundamental mechanisms governing the search process are not fully understood. Here we use single-molecule techniques to directly observe TALE search dynamics along DNA templates. We find that TALE proteins are capable of rapid diffusion along DNA using a combination of sliding and hopping behaviour, which suggests that the TALE search process is governed in part by facilitated diffusion. We also observe that TALE proteins exhibit two distinct modes of action during the search process--a search state and a recognition state--facilitated by different subdomains in monomeric TALE proteins. Using TALE truncation mutants, we further demonstrate that the N-terminal region of TALEs is required for the initial non-specific binding and subsequent rapid search along DNA, whereas the central repeat domain is required for transitioning into the site-specific recognition state.

  9. Direct observation of liquid nucleus growth in homogeneous melting of colloidal crystals

    NASA Astrophysics Data System (ADS)

    Wang, Ziren; Wang, Feng; Peng, Yi; Han, Yilong

    2015-04-01

    The growth behaviour of liquid nucleus is crucial for crystal melting, but its kinetics is difficult to predict and remains challenging in experiment. Here we directly observed the growth of individual liquid nuclei in homogeneous melting of three-dimensional superheated colloidal crystals with single-particle dynamics by video microscopy. The growth rate of nucleus at weak superheating is well fitted by generalizing the Wilson-Frenkel law of crystallization to melting and including the surface tension effects and non-spherical-shape effects. As the degree of superheating increases, the growth rate is enhanced by nucleus shape fluctuation, nuclei coalescence and multimer attachment. The results provide new guidance for the refinement of nucleation theory, especially for the poorly understood strong-superheating regime. The universal Lindemann parameter observed at the superheat limit and solid-liquid interfaces indicates a connection between homogeneous and heterogeneous melting.

  10. Direct observation of liquid nucleus growth in homogeneous melting of colloidal crystals.

    PubMed

    Wang, Ziren; Wang, Feng; Peng, Yi; Han, Yilong

    2015-01-01

    The growth behaviour of liquid nucleus is crucial for crystal melting, but its kinetics is difficult to predict and remains challenging in experiment. Here we directly observed the growth of individual liquid nuclei in homogeneous melting of three-dimensional superheated colloidal crystals with single-particle dynamics by video microscopy. The growth rate of nucleus at weak superheating is well fitted by generalizing the Wilson-Frenkel law of crystallization to melting and including the surface tension effects and non-spherical-shape effects. As the degree of superheating increases, the growth rate is enhanced by nucleus shape fluctuation, nuclei coalescence and multimer attachment. The results provide new guidance for the refinement of nucleation theory, especially for the poorly understood strong-superheating regime. The universal Lindemann parameter observed at the superheat limit and solid-liquid interfaces indicates a connection between homogeneous and heterogeneous melting. PMID:25897801

  11. Direct observation of an abrupt insulator-to-metal transition in dense liquid deuterium

    NASA Astrophysics Data System (ADS)

    Knudson, M. D.; Desjarlais, M. P.; Becker, A.; Lemke, R. W.; Cochrane, K. R.; Savage, M. E.; Bliss, D. E.; Mattsson, T. R.; Redmer, R.

    2015-06-01

    Eighty years ago, it was proposed that solid hydrogen would become metallic at sufficiently high density. Despite numerous investigations, this transition has not yet been experimentally observed. More recently, there has been much interest in the analog of this predicted metallic transition in the dense liquid, due to its relevance to planetary science. Here, we show direct observation of an abrupt insulator-to-metal transition in dense liquid deuterium. Experimental determination of the location of this transition provides a much-needed benchmark for theory and may constrain the region of hydrogen-helium immiscibility and the boundary-layer pressure in standard models of the internal structure of gas-giant planets.

  12. Direct observation and imaging of a spin-wave soliton with p-like symmetry

    NASA Astrophysics Data System (ADS)

    Bonetti, S.; Kukreja, R.; Chen, Z.; Maci, F.; Hernndez, J. M.; Eklund, A.; Backes, D.; Frisch, J.; Katine, J.; Malm, G.; Urazhdin, S.; Kent, A. D.; Sthr, J.; Ohldag, H.; Drr, H. A.

    2015-11-01

    Spin waves, the collective excitations of spins, can emerge as nonlinear solitons at the nanoscale when excited by an electrical current from a nanocontact. These solitons are expected to have essentially cylindrical symmetry (that is, s-like), but no direct experimental observation exists to confirm this picture. Using a high-sensitivity time-resolved magnetic X-ray microscopy with 50 ps temporal resolution and 35 nm spatial resolution, we are able to create a real-space spin-wave movie and observe the emergence of a localized soliton with a nodal line, that is, with p-like symmetry. Micromagnetic simulations explain the measurements and reveal that the symmetry of the soliton can be controlled by magnetic fields. Our results broaden the understanding of spin-wave dynamics at the nanoscale, with implications for the design of magnetic nanodevices.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  14. Direct observation of liquid nucleus growth in homogeneous melting of colloidal crystals

    PubMed Central

    Wang, Ziren; Wang, Feng; Peng, Yi; Han, Yilong

    2015-01-01

    The growth behaviour of liquid nucleus is crucial for crystal melting, but its kinetics is difficult to predict and remains challenging in experiment. Here we directly observed the growth of individual liquid nuclei in homogeneous melting of three-dimensional superheated colloidal crystals with single-particle dynamics by video microscopy. The growth rate of nucleus at weak superheating is well fitted by generalizing the Wilson–Frenkel law of crystallization to melting and including the surface tension effects and non-spherical-shape effects. As the degree of superheating increases, the growth rate is enhanced by nucleus shape fluctuation, nuclei coalescence and multimer attachment. The results provide new guidance for the refinement of nucleation theory, especially for the poorly understood strong-superheating regime. The universal Lindemann parameter observed at the superheat limit and solid–liquid interfaces indicates a connection between homogeneous and heterogeneous melting. PMID:25897801

  15. Direct observation and imaging of a spin-wave soliton with p-like symmetry.

    PubMed

    Bonetti, S; Kukreja, R; Chen, Z; Maci, F; Hernndez, J M; Eklund, A; Backes, D; Frisch, J; Katine, J; Malm, G; Urazhdin, S; Kent, A D; Sthr, J; Ohldag, H; Drr, H A

    2015-01-01

    Spin waves, the collective excitations of spins, can emerge as nonlinear solitons at the nanoscale when excited by an electrical current from a nanocontact. These solitons are expected to have essentially cylindrical symmetry (that is, s-like), but no direct experimental observation exists to confirm this picture. Using a high-sensitivity time-resolved magnetic X-ray microscopy with 50?ps temporal resolution and 35?nm spatial resolution, we are able to create a real-space spin-wave movie and observe the emergence of a localized soliton with a nodal line, that is, with p-like symmetry. Micromagnetic simulations explain the measurements and reveal that the symmetry of the soliton can be controlled by magnetic fields. Our results broaden the understanding of spin-wave dynamics at the nanoscale, with implications for the design of magnetic nanodevices. PMID:26567699

  16. Direct observation and imaging of a spin-wave soliton with p-like symmetry

    DOE PAGESBeta

    Bonetti, S.; Kukreja, R.; Chen, Z.; Macià, F.; Hernàndez, J. M.; Eklund, A.; Backes, D.; Frisch, J.; Katine, J.; Malm, G.; et al

    2015-11-16

    Spin waves, the collective excitations of spins, can emerge as nonlinear solitons at the nanoscale when excited by an electrical current from a nanocontact. These solitons are expected to have essentially cylindrical symmetry (that is, s-like), but no direct experimental observation exists to confirm this picture. Using a high-sensitivity time-resolved magnetic X-ray microscopy with 50 ps temporal resolution and 35 nm spatial resolution, we are able to create a real-space spin-wave movie and observe the emergence of a localized soliton with a nodal line, that is, with p-like symmetry. Moreover, micromagnetic simulations explain the measurements and reveal that the symmetrymore » of the soliton can be controlled by magnetic fields. Our results broaden the understanding of spin-wave dynamics at the nanoscale, with implications for the design of magnetic nanodevices.« less

  17. Direct observation and imaging of a spin-wave soliton with p-like symmetry

    SciTech Connect

    Bonetti, S.; Kukreja, R.; Chen, Z.; Macià, F.; Hernàndez, J. M.; Eklund, A.; Backes, D.; Frisch, J.; Katine, J.; Malm, G.; Urazhdin, S.; Kent, A. D.; Stöhr, J.; Ohldag, H.; Dürr, H. A.

    2015-11-16

    Spin waves, the collective excitations of spins, can emerge as nonlinear solitons at the nanoscale when excited by an electrical current from a nanocontact. These solitons are expected to have essentially cylindrical symmetry (that is, s-like), but no direct experimental observation exists to confirm this picture. Using a high-sensitivity time-resolved magnetic X-ray microscopy with 50 ps temporal resolution and 35 nm spatial resolution, we are able to create a real-space spin-wave movie and observe the emergence of a localized soliton with a nodal line, that is, with p-like symmetry. Moreover, micromagnetic simulations explain the measurements and reveal that the symmetry of the soliton can be controlled by magnetic fields. Our results broaden the understanding of spin-wave dynamics at the nanoscale, with implications for the design of magnetic nanodevices.

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

    SciTech Connect

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

    2012-04-24

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

  19. Interactions between C and Cu atoms in single-layer graphene: direct observation and modelling.

    PubMed

    Kano, Emi; Hashimoto, Ayako; Kaneko, Tomoaki; Tajima, Nobuo; Ohno, Takahisa; Takeguchi, Masaki

    2015-12-17

    Metal doping into the graphene lattice has been studied recently to develop novel nanoelectronic devices and to gain an understanding of the catalytic activities of metals in nanocarbon structures. Here we report the direct observation of interactions between Cu atoms and single-layer graphene by transmission electron microscopy. We document stable configurations of Cu atoms in the graphene sheet and unique transformations of graphene promoted by Cu atoms. First-principles calculations based on density functional theory reveal a reduction of energy barrier that caused rotation of C-C bonds near Cu atoms. We discuss two driving forces, electron irradiation and in situ heating, and conclude that the observed transformations were mainly promoted by electron irradiation. Our results suggest that individual Cu atoms can promote reconstruction of single-layer graphene. PMID:26645468

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

    SciTech Connect

    Uhlir, V.; Pizzini, S.; Rougemaille, N.; Ranno, L.; Fruchart, O.; Wagner, E.; Vogel, J.; Cros, V.; Jimenez, E.; Camarero, J.; Urbanek, M.; Gaudin, G.; Sirotti, F.

    2011-01-15

    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.

  1. Direct observation of TALE protein dynamics reveals a two-state search mechanism

    PubMed Central

    Cuculis, Luke; Abil, Zhanar; Zhao, Huimin; Schroeder, Charles M.

    2015-01-01

    Transcription activator-like effector (TALE) proteins are a class of programmable DNA-binding proteins for which the fundamental mechanisms governing the search process are not fully understood. Here we use single-molecule techniques to directly observe TALE search dynamics along DNA templates. We find that TALE proteins are capable of rapid diffusion along DNA using a combination of sliding and hopping behaviour, which suggests that the TALE search process is governed in part by facilitated diffusion. We also observe that TALE proteins exhibit two distinct modes of action during the search process—a search state and a recognition state—facilitated by different subdomains in monomeric TALE proteins. Using TALE truncation mutants, we further demonstrate that the N-terminal region of TALEs is required for the initial non-specific binding and subsequent rapid search along DNA, whereas the central repeat domain is required for transitioning into the site-specific recognition state. PMID:26027871

  2. Direct observation and imaging of a spin-wave soliton with p-like symmetry

    PubMed Central

    Bonetti, S.; Kukreja, R.; Chen, Z.; Macià, F.; Hernàndez, J. M.; Eklund, A.; Backes, D.; Frisch, J.; Katine, J.; Malm, G.; Urazhdin, S.; Kent, A. D.; Stöhr, J.; Ohldag, H.; Dürr, H. A.

    2015-01-01

    Spin waves, the collective excitations of spins, can emerge as nonlinear solitons at the nanoscale when excited by an electrical current from a nanocontact. These solitons are expected to have essentially cylindrical symmetry (that is, s-like), but no direct experimental observation exists to confirm this picture. Using a high-sensitivity time-resolved magnetic X-ray microscopy with 50 ps temporal resolution and 35 nm spatial resolution, we are able to create a real-space spin-wave movie and observe the emergence of a localized soliton with a nodal line, that is, with p-like symmetry. Micromagnetic simulations explain the measurements and reveal that the symmetry of the soliton can be controlled by magnetic fields. Our results broaden the understanding of spin-wave dynamics at the nanoscale, with implications for the design of magnetic nanodevices. PMID:26567699

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

    USGS Publications Warehouse

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

    1994-01-01

    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.

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

    SciTech Connect

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

    2008-11-01

    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.

  5. Direct observation of the translocation mechanism of transcription termination factor Rho.

    PubMed

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

    2015-02-27

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

  6. Interactions between C and Cu atoms in single-layer graphene: direct observation and modelling

    NASA Astrophysics Data System (ADS)

    Kano, Emi; Hashimoto, Ayako; Kaneko, Tomoaki; Tajima, Nobuo; Ohno, Takahisa; Takeguchi, Masaki

    2015-12-01

    Metal doping into the graphene lattice has been studied recently to develop novel nanoelectronic devices and to gain an understanding of the catalytic activities of metals in nanocarbon structures. Here we report the direct observation of interactions between Cu atoms and single-layer graphene by transmission electron microscopy. We document stable configurations of Cu atoms in the graphene sheet and unique transformations of graphene promoted by Cu atoms. First-principles calculations based on density functional theory reveal a reduction of energy barrier that caused rotation of C-C bonds near Cu atoms. We discuss two driving forces, electron irradiation and in situ heating, and conclude that the observed transformations were mainly promoted by electron irradiation. Our results suggest that individual Cu atoms can promote reconstruction of single-layer graphene.Metal doping into the graphene lattice has been studied recently to develop novel nanoelectronic devices and to gain an understanding of the catalytic activities of metals in nanocarbon structures. Here we report the direct observation of interactions between Cu atoms and single-layer graphene by transmission electron microscopy. We document stable configurations of Cu atoms in the graphene sheet and unique transformations of graphene promoted by Cu atoms. First-principles calculations based on density functional theory reveal a reduction of energy barrier that caused rotation of C-C bonds near Cu atoms. We discuss two driving forces, electron irradiation and in situ heating, and conclude that the observed transformations were mainly promoted by electron irradiation. Our results suggest that individual Cu atoms can promote reconstruction of single-layer graphene. Electronic supplementary information (ESI) available: Three TEM movies, additional TEM data corresponding to movies, calculated models, and lifetime results. See DOI: 10.1039/c5nr05913e

  7. Performing Gram stain directly on catheter tips: assessment of the quality of the observation process.

    PubMed

    Guembe, M; Pérez-Granda, M J; Rivera, M L; Martín-Rabadán, P; Bouza, E

    2015-06-01

    A previous study performed in our institution showed that catheter tip (CT) staining by combining acridine orange and Gram stain (GS) before culture anticipated catheter colonization with exhaustive and careful observation by a highly trained technician. Our objective was to assess the validity values of GS without acridine orange on an external smear of CT for predicting catheter colonization and catheter-related bloodstream infection (C-RBSI). We compared different periods of observation and the results of two technicians with different levels of professional experience. Over a 5-month period, the roll-plate technique was preceded by direct GS of all CTs sent to the microbiology laboratory. The reading was taken at ×100 by two observers with different skill levels. Each observer performed a routine examination (3 min along three longitudinal lines) and an exhaustive examination (5 min along five longitudinal lines). The presence of at least one cell was considered positive. All slides were read before culture results were known. We included a total of 271 CTs from 209 patients. The prevalence of catheter colonization and C-RBSI was 16.2 % and 5.1 %, respectively. Routine and exhaustive examinations revealed only 29.5 % and 40.9 % of colonized catheters, respectively (p < 0.001). In contrast, they revealed high negative predictive values for C-RBSI (96.5 % and 96.3 %, respectively). Our study shows that the yield of GS performed directly on CTs is greater when staining is performed exhaustively. However, the decision to implement this approach in daily routine will depend on the prevalence rate of catheter colonization at each institution. PMID:25633826

  8. Direct observation of ballistic and drift carrier transport regimes in InAs nanowires

    NASA Astrophysics Data System (ADS)

    Zhou, X.; Dayeh, S. A.; Aplin, D.; Wang, D.; Yu, E. T.

    2006-07-01

    Conductive atomic force microscopy has been used to characterize distance-dependent electron transport behavior in InAs nanowires grown by metal-organic chemical vapor deposition. Using a conducting diamond-coated tip as a local electrical probe in an atomic force microscope, the resistance of the InAs nanowire has been measured as a function of electron transport distance within the nanowire. Two regimes of transport behavior are observed: for distances of 200nm or less, resistance independent of electron transport distance, indicative of ballistic electron transport, is observed; for greater distances, the resistance is observed to increase linearly with distance, as expected for conventional drift transport. These observations are in very good qualitative accord with the Landauer formalism for mesoscopic carrier transport, and the resistance values derived from these measurements are in good quantitative agreement with carrier concentrations and mobilities determined in separate experiments. These results provide direct information concerning distances over which ballistic transport occurs in InAs nanowires as well as demonstrating the ability of the scanning probe techniques employed to characterize nanoscale transport characteristics in semiconductor nanowire structures.

  9. Cortical kinematic processing of executed and observed goal-directed hand actions.

    PubMed

    Marty, Brice; Bourguignon, Mathieu; Jousmäki, Veikko; Wens, Vincent; Op de Beeck, Marc; Van Bogaert, Patrick; Goldman, Serge; Hari, Riitta; De Tiège, Xavier

    2015-10-01

    Motor information conveyed by viewing the kinematics of an agent's action helps to predict how the action will unfold. Still, how observed movement kinematics is processed in the brain remains to be clarified. Here, we used magnetoencephalography (MEG) to determine at which frequency and where in the brain, the neural activity is coupled with the kinematics of executed and observed motor actions. Whole-scalp MEG signals were recorded from 11 right-handed healthy adults while they were executing (Self) or observing (Other) similar goal-directed hand actions performed by an actor placed in front of them. Actions consisted of pinching with the right hand green foam-made pieces mixed in a heap with pieces of other colors placed on a table, and put them in a plastic pot on the right side of the heap. Subjects' and actor's forefinger movements were monitored with an accelerometer. The coherence between movement acceleration and MEG signals was computed at the sensor level. Then, cortical sources coherent with movement acceleration were identified with Dynamic Imaging of Coherent Sources. Statistically significant sensor-level coherence peaked at the movement frequency (F0) and its first harmonic (F1) in both movement conditions. Apart from visual cortices, statistically significant local maxima of coherence were observed in the right posterior superior temporal gyrus (F0), bilateral superior parietal lobule (F0 or F1) and primary sensorimotor cortex (F0 or F1) in both movement conditions. These results suggest that observing others' actions engages the viewer's brain in a similar kinematic-related manner as during own action execution. These findings bring new insights into how human brain activity covaries with essential features of observed movements of others. PMID:26123380

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

    NASA Astrophysics Data System (ADS)

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

    2010-03-01

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

  11. Direct Observation of Solar Coronal Magnetic Fields by Vector Tomography of the Coronal Emission Line Polarizations

    NASA Astrophysics Data System (ADS)

    Kramar, M.; Lin, H.; Tomczyk, S.

    2016-03-01

    We present the first direct “observation” of the global-scale, 3D coronal magnetic fields of Carrington Rotation (CR) Cycle 2112 using vector tomographic inversion techniques. The vector tomographic inversion uses measurements of the Fe xiii 10747 Å Hanle effect polarization signals by the Coronal Multichannel Polarimeter (CoMP) and 3D coronal density and temperature derived from scalar tomographic inversion of Solar Terrestrial Relations Observatory (STEREO)/Extreme Ultraviolet Imager (EUVI) coronal emission lines (CELs) intensity images as inputs to derive a coronal magnetic field model that best reproduces the observed polarization signals. While independent verifications of the vector tomography results cannot be performed, we compared the tomography inverted coronal magnetic fields with those constructed by magnetohydrodynamic (MHD) simulations based on observed photospheric magnetic fields of CR 2112 and 2113. We found that the MHD model for CR 2112 is qualitatively consistent with the tomography inverted result for most of the reconstruction domain except for several regions. Particularly, for one of the most noticeable regions, we found that the MHD simulation for CR 2113 predicted a model that more closely resembles the vector tomography inverted magnetic fields. In another case, our tomographic reconstruction predicted an open magnetic field at a region where a coronal hole can be seen directly from a STEREO-B/EUVI image. We discuss the utilities and limitations of the tomographic inversion technique, and present ideas for future developments.

  12. The Exozodiacal Dust Problem for Direct Observations of ExoEarths

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  13. Direct Observation of Photoinduced Charge Separation in Ruthenium Complex/Ni(OH)2 Nanoparticle Hybrid.

    PubMed

    Tang, Yu; Pattengale, Brian; Ludwig, John; Atifi, Abderrahman; Zinovev, Alexander V; Dong, Bin; Kong, Qingyu; Zuo, Xiaobing; Zhang, Xiaoyi; Huang, Jier

    2015-01-01

    Ni(OH)2 have emerged as important functional materials for solar fuel conversion because of their potential as cost-effective bifunctional catalysts for both hydrogen and oxygen evolution reactions. However, their roles as photocatalysts in the photoinduced charge separation (CS) reactions remain unexplored. In this paper, we investigate the CS dynamics of a newly designed hybrid catalyst by integrating a Ru complex with Ni(OH)2 nanoparticles (NPs). Using time resolved X-ray absorption spectroscopy (XTA), we directly observed the formation of the reduced Ni metal site (~60?ps), unambiguously demonstrating CS process in the hybrid through ultrafast electron transfer from Ru complex to Ni(OH)2 NPs. Compared to the ultrafast CS process, the charge recombination in the hybrid is ultraslow (?50?ns). These results not only suggest the possibility of developing Ni(OH)2 as solar fuel catalysts, but also represent the first time direct observation of efficient CS in a hybrid catalyst using XTA. PMID:26673578

  14. Direct Observation of Photoinduced Charge Separation in Ruthenium Complex/Ni(OH)2 Nanoparticle Hybrid

    PubMed Central

    Tang, Yu; Pattengale, Brian; Ludwig, John; Atifi, Abderrahman; Zinovev, Alexander V.; Dong, Bin; Kong, Qingyu; Zuo, Xiaobing; Zhang, Xiaoyi; Huang, Jier

    2015-01-01

    Ni(OH)2 have emerged as important functional materials for solar fuel conversion because of their potential as cost-effective bifunctional catalysts for both hydrogen and oxygen evolution reactions. However, their roles as photocatalysts in the photoinduced charge separation (CS) reactions remain unexplored. In this paper, we investigate the CS dynamics of a newly designed hybrid catalyst by integrating a Ru complex with Ni(OH)2 nanoparticles (NPs). Using time resolved X-ray absorption spectroscopy (XTA), we directly observed the formation of the reduced Ni metal site (~60 ps), unambiguously demonstrating CS process in the hybrid through ultrafast electron transfer from Ru complex to Ni(OH)2 NPs. Compared to the ultrafast CS process, the charge recombination in the hybrid is ultraslow (≫50 ns). These results not only suggest the possibility of developing Ni(OH)2 as solar fuel catalysts, but also represent the first time direct observation of efficient CS in a hybrid catalyst using XTA. PMID:26673578

  15. Direct Observation of Photoinduced Charge Separation in Ruthenium Complex/Ni(OH)2 Nanoparticle Hybrid

    NASA Astrophysics Data System (ADS)

    Tang, Yu; Pattengale, Brian; Ludwig, John; Atifi, Abderrahman; Zinovev, Alexander V.; Dong, Bin; Kong, Qingyu; Zuo, Xiaobing; Zhang, Xiaoyi; Huang, Jier

    2015-12-01

    Ni(OH)2 have emerged as important functional materials for solar fuel conversion because of their potential as cost-effective bifunctional catalysts for both hydrogen and oxygen evolution reactions. However, their roles as photocatalysts in the photoinduced charge separation (CS) reactions remain unexplored. In this paper, we investigate the CS dynamics of a newly designed hybrid catalyst by integrating a Ru complex with Ni(OH)2 nanoparticles (NPs). Using time resolved X-ray absorption spectroscopy (XTA), we directly observed the formation of the reduced Ni metal site (~60 ps), unambiguously demonstrating CS process in the hybrid through ultrafast electron transfer from Ru complex to Ni(OH)2 NPs. Compared to the ultrafast CS process, the charge recombination in the hybrid is ultraslow (≫50 ns). These results not only suggest the possibility of developing Ni(OH)2 as solar fuel catalysts, but also represent the first time direct observation of efficient CS in a hybrid catalyst using XTA.

  16. Direct observation and control of hydrogen-bond dynamics using low-temperature scanning tunneling microscopy

    NASA Astrophysics Data System (ADS)

    Kumagai, Takashi

    2015-08-01

    Hydrogen(H)-bond dynamics are involved in many elementary processes in chemistry and biology. Because of its fundamental importance, a variety of experimental and theoretical approaches have been employed to study the dynamics in gas, liquid, solid phases, and their interfaces. This review describes the recent progress of direct observation and control of H-bond dynamics in several model systems on a metal surface by using low-temperature scanning tunneling microscopy (STM). General aspects of H-bond dynamics and the experimental methods are briefly described in chapter 1 and 2. In the subsequent four chapters, I present direct observation of an H-bond exchange reaction within a single water dimer (chapter 3), a symmetric H bond (chapter 4) and H-atom relay reactions (chapter 5) within water-hydroxyl complexes, and an intramolecular H-atom transfer reaction (tautomerization) within a single porphycene molecule (chapter 6). These results provide novel microscopic insights into H-bond dynamics at the single-molecule level, and highlight significant impact on the process from quantum effects, namely tunneling and zero-point vibration, resulting from the small mass of H atom. Additionally, local environmental effect on H-bond dynamics is also examined by using atom/molecule manipulation with the STM.

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

    SciTech Connect

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

    2010-12-01

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

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

    SciTech Connect

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

    2014-01-17

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

  19. Not seeing or feeling is still believing: conscious and non-conscious pain modulation after direct and observational learning

    PubMed Central

    Egorova, Natalia; Park, Joel; Orr, Scott P.; Kirsch, Irving; Gollub, Randy L.; Kong, Jian

    2015-01-01

    Our experience with the world is shaped not only directly through personal exposure but also indirectly through observing others and learning from their experiences. Using a conditioning paradigm, we investigated how directly and observationally learned information can affect pain perception, both consciously and non-consciously. Differences between direct and observed cues were manifest in higher pain ratings and larger skin conductance responses to directly experienced cues. However, the pain modulation effects produced by conditioning were of comparable magnitude for direct and observational learning. These results suggest that social observation can induce positive and negative pain modulation. Importantly, the fact that cues learned by observation and activated non-consciously still produced a robust conditioning effect that withstood extinction highlights the role of indirect exposure in placebo and nocebo effects. PMID:26578164

  20. Toward the Direct Measurement of Coronal Magnetic Fields: An Airborne Infrared Spectrometer for Eclipse Observations

    NASA Astrophysics Data System (ADS)

    Samra, J.; DeLuca, E. E.; Golub, L.; Cheimets, P.

    2014-12-01

    The solar magnetic field enables the heating of the corona and provides its underlying structure. Energy stored in coronal magnetic fields is released in flares and coronal mass ejections (CME) and provides the ultimate source of energy for space weather. Therefore, direct measurements of the coronal magnetic field have significant potential to enhance understanding of coronal dynamics and improve solar forecasting models. Of particular interest are observations of coronal field lines in the transitional region between closed and open flux systems, providing important information on the origin of the slow solar wind. While current instruments routinely observe only the photospheric and chromospheric magnetic fields, a proposed airborne spectrometer will take a step toward the direct observation of coronal fields by measuring plasma emission in the infrared at high spatial and spectral resolution. The targeted lines are four forbidden magnetic dipole transitions between 2 and 4 ?m. The airborne system will consist of a telescope, grating spectrometer, and pointing/stabilization system to be flown on the NSF/NCAR High-performance Instrumented Airborne Platform for Environmental Research (HIAPER) during the August 2017 total solar eclipse. The project incorporates several optical engineering challenges, centered around maintaining adequate spectral and spatial resolution in a compact and inexpensive package and on a moving platform. Design studies are currently underway to examine the tradeoffs between various optical geometries and control strategies for the pointing/stabilization system. The results will be presented and interpreted in terms of the consequences for the scientific questions. In addition, results from a laboratory prototype and simulations of the final system will be presented.

  1. Direct observations of a mini-magnetosphere in the lunar plasma wake

    NASA Astrophysics Data System (ADS)

    Ma, Yonghui; Wong, Hon-Cheng; Xu, Xiaojun

    2015-04-01

    In this report, we present direct observations of a mini-magnetosphere when ARTEMIS P2 is passing through the lunar wake, where the lunar surface and crustal fields are shielded from the solar wind flows. We find the magnetic field amplification simultaneously with the dropout of plasma density and particle energy fluxes when the orbit of P2 is just over the margin of Imbrium antipode anomaly which is centered at 162o E, 33o S. The observational interval of these characteristic features is merely 95 seconds (from 1413:15 UT to 1414:50 UT on December 9th 2012) and the orbit altitude of P2 is ~226 km. The strength of magnetic field at P2 orbit altitude (~226 km) can reach ~9 nT over the anomaly region compared to the relatively small value of ~6 nT in the neighboring regions. In addition to these, we also detect the moderate ion and electron temperature increase inside the mini-magnetosphere as well as the rotation in the magnetic field direction near the boundary of mini-magnetosphere. These field and plasma parameters demonstrate that the vertical size of the mini-magnetosphere near lunar surface can at least extend to ~230 km in the near-vacuum lunar wake without the interaction with the solar wind. We also try to explain the detailed plasma dynamics performed within this mini-magnetosphere by dipole model or non-dipolar model. This study may open up a new view of studying lunar mini-magnetosphere by spacecraft observations in the lunar wake where magnetic anomaly fields are almost undisturbed.

  2. Shallow vent architecture of Puyehue Cordn-Caulle, as revealed by direct observation of explosive activity

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    On June 4, 2011, an explosive eruption of rhyodacitic magma began at the Puyehue Cordn-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).

  3. In situ stress estimates from hydraulic fracturing and direct observation of crack orientation

    NASA Astrophysics Data System (ADS)

    Warren, William E.; Smith, Carl W.

    1985-07-01

    Estimates of in situ stress in G Tunnel, Rainier Mesa, Nevada Test Site, have been obtained with hydraulic fracturing techniques. This work represents a nontraditional use of hydraulic fracturing in that it was performed primarily in horizontal boreholes drilled into the formation from access drifts tunneled into the mesa rather than the usual operation performed at depth in vertical boreholes drilled from the surface. Several operations were performed in essentially orthogonal triads of boreholes located at a point. A significant feature of this work is the mineback operation in which the borehole is mined out to reveal the actual fracture. During the hydraulic fracturing operation, colored dye was added to the fracturing fluid which left an easily detectable stain on the fracture surface. Direct observation of the fracture orientation away from the borehole establishes the direction of the minimum compressive in situ stress and the plane of the other two principal stresses. In one borehole, which was not aligned along a principal stress direction, a modified mineback operation revealed a fracture plane that twisted as it grew away from the borehole, aligning itself finally in a plane determined by the in situ stresses. This twisting is consistent with theoretical predictions of borehole stresses under these conditions. This same mineback also showed that fracture of the formation initiated at or under one of the packers, indicating that the packers may have an effet on in situ stress estimates. General observations of over 100 tests performed in G Tunnel show that under the sloping portion of the mesa, fracture planes are not vertical but dip in a direction tending to parallel the mesa slope. Deep into the tunnel and well under the flat part of the mesa, fractures are essentially vertical with strikes approximately N45°E, which substantiates the usual vertical fracture assumption in traditional fracture operations performed at depth in vertical boreholes. Advantages, limitations, and problem areas associated with extracting in situ stress fields from hydraulic fracture pressure records are discussed in detail.

  4. Direct observation by using Brewster angle microscopy of the diacetylene polimerization in mixed Langmuir film.

    PubMed

    Ariza-Carmona, Luisa; Martn-Romero, Mara T; Giner-Casares, Juan J; Camacho, Luis

    2015-12-01

    Mixed Langmuir monolayers of 10,12-Pentacosadiynoic acid (DA) and amphiphilic hemicyanine (HSP) have been fabricated at the air-water interface. The mixed monolayer has been proved to be completely homogeneous. The DA molecules are arranged in a single monolayer within the mixed Langmuir monolayer, as opposed to the typical trilayer architecture for the pure DA film. Brewster angle microscopy has been used to reveal the mesoscopic structure of the mixed Langmuir monolayer. Flower shape domains with internal anisotropy due the ordered alignment of hemicyanine groups have been observed. Given the absorption features of the hemicyanine groups at the wavelength used in the BAM experiments, the enhancement of reflection provoked by the absorption process leads to the observed anisotropy. The ordering of such groups is promoted by their strong self-aggregation tendency. Under UV irradiation at the air-water interface, polydiacetylene (PDA) has been fabricated. In spite a significant increase in the domains reflectivity has been observed owing to the modification in the mentioned enhanced reflection, the texture of the domains remains equal. The PDA polymer chain therefore grows in the same direction in which the HSP molecules are aligned. This study is expected to enrich the understanding and design of fabrication of PDA at interfaces. PMID:26263495

  5. Direct Observation of a Majorana Quasiparticle Heat Capacity in 3He

    NASA Astrophysics Data System (ADS)

    Bunkov, Y. M.

    2014-04-01

    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).

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

    NASA Astrophysics Data System (ADS)

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

    2010-06-01

    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 μm 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.

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

    PubMed

    Lan, Fei; Li, Guangyong

    2013-05-01

    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

  8. Direct observation of the two-plasmon-decay common plasma wave using ultraviolet Thomson scattering

    NASA Astrophysics Data System (ADS)

    Follett, R. K.; Edgell, D. H.; Henchen, R. J.; Hu, S. X.; Katz, J.; Michel, D. T.; Myatt, J. F.; Shaw, J.; Froula, D. H.

    2015-03-01

    A 263-nm Thomson-scattering beam was used to directly probe two-plasmon-decay (TPD) excited electron plasma waves (EPWs) driven by between two and five 351-nm beams on the OMEGA Laser System. The amplitude of these waves was nearly independent of the number of drive beams at constant overlapped intensity, showing that the observed EPWs are common to the multiple beams. In an experimental configuration where the Thomson-scattering diagnostic was not wave matched to the common TPD EPWs, a broad spectrum of TPD-driven EPWs was observed, indicative of nonlinear effects associated with TPD saturation. Electron plasma waves corresponding to Langmuir decay of TPD EPWs were observed in both Thomson-scattering spectra, suggesting the Langmuir decay instability as a TPD saturation mechanism. Simulated Thomson-scattering spectra from three-dimensional numerical solutions of the extended Zakharov equations of TPD are in excellent agreement with the experimental spectra and verify the presence of the Langmuir decay instability.

  9. Deformation Twinning in Zirconium: Direct Experimental Observations and Polycrystal Plasticity Predictions

    NASA Astrophysics Data System (ADS)

    Singh, Jaiveer; Mahesh, Sivasambu; Kumar, Gulshan; Pant, Prita; Srivastava, D.; Dey, G. K.; Saibaba, N.; Samajdar, I.

    2015-11-01

    Deformation twinning was directly observed in three commercial zirconium alloy samples during split channel die plane-strain compression. One pair of samples had similar starting texture but different grain size distributions, while another pair had similar grain size distribution but different starting textures. Extension twinning was found to be more sensitive to the starting texture than to the grain size distribution. Also, regions of intense deformation near grain boundaries were observed. A hierarchical binary tree-based polycrystal plasticity model, implementing the Chin-Hosford-Mendorf twinning criterion, captured the experimentally observed twinning grains' lattice orientation distribution, and the twin volume fraction evolution, provided the critical resolved shear stress for extension twinning, τ0 , was assumed much larger than any of the values reported in the literature, based on the viscoplastic self-consistent model. A comparison of the models suggests that τ0 obtained using the present model and the viscoplastic self-consistent models physically correspond to the critical stress required for twin nucleation, and twin growth, respectively.

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

    NASA Astrophysics Data System (ADS)

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

    2006-08-01

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

  11. Direct observation of the two-plasmon-decay common plasma wave using ultraviolet Thomson scattering.

    PubMed

    Follett, R K; Edgell, D H; Henchen, R J; Hu, S X; Katz, J; Michel, D T; Myatt, J F; Shaw, J; Froula, D H

    2015-03-01

    A 263-nm Thomson-scattering beam was used to directly probe two-plasmon-decay (TPD) excited electron plasma waves (EPWs) driven by between two and five 351-nm beams on the OMEGA Laser System. The amplitude of these waves was nearly independent of the number of drive beams at constant overlapped intensity, showing that the observed EPWs are common to the multiple beams. In an experimental configuration where the Thomson-scattering diagnostic was not wave matched to the common TPD EPWs, a broad spectrum of TPD-driven EPWs was observed, indicative of nonlinear effects associated with TPD saturation. Electron plasma waves corresponding to Langmuir decay of TPD EPWs were observed in both Thomson-scattering spectra, suggesting the Langmuir decay instability as a TPD saturation mechanism. Simulated Thomson-scattering spectra from three-dimensional numerical solutions of the extended Zakharov equations of TPD are in excellent agreement with the experimental spectra and verify the presence of the Langmuir decay instability. PMID:25871046

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

    NASA Astrophysics Data System (ADS)

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

    2009-11-01

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

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

    NASA Astrophysics Data System (ADS)

    Zhao, Liang; Xue, Mei

    2015-04-01

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

  14. Direct observation of finite size effects in chains of antiferromagnetically coupled spins

    PubMed Central

    Guidi, T.; Gillon, B.; Mason, S. A.; Garlatti, E.; Carretta, S.; Santini, P.; Stunault, A.; Caciuffo, R.; van Slageren, J.; Klemke, B.; Cousson, A.; Timco, G. A.; Winpenny, R. E. P.

    2015-01-01

    Finite spin chains made of few magnetic ions are the ultimate-size structures that can be engineered to perform spin manipulations for quantum information devices. Their spin structure is expected to show finite size effects and its knowledge is of great importance both for fundamental physics and applications. Until now a direct and quantitative measurement of the spatial distribution of the magnetization of such small structures has not been achieved even with the most advanced microscopic techniques. Here we present measurements of the spin density distribution of a finite chain of eight spin-3/2 ions using polarized neutron diffraction. The data reveal edge effects that are a consequence of the finite size and of the parity of the chain and indicate a noncollinear spin arrangement. This is in contrast with the uniform spin distribution observed in the parent closed chain and the collinear arrangement in odd-open chains. PMID:25952539

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

    PubMed Central

    Jourdan, M.; Minr, J.; Braun, J.; Kronenberg, A.; Chadov, S.; Balke, B.; Gloskovskii, A.; Kolbe, M.; Elmers, H.J.; Schnhense, G.; Ebert, H.; Felser, C.; Klui, M.

    2014-01-01

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

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

    PubMed

    Jourdan, M; Minr, J; Braun, J; Kronenberg, A; Chadov, S; Balke, B; Gloskovskii, A; Kolbe, M; Elmers, H J; Schnhense, G; Ebert, H; Felser, C; Klui, M

    2014-01-01

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

  17. Direct observation of Kramers-Kronig self-phasing in coherently combined fiber lasers.

    PubMed

    Chiang, Hung-Sheng; Leger, James R; Nilsson, Johan; Sahu, Jayanta

    2013-10-15

    A highly stable coherent beam-combining system has been designed to measure self-phasing in fiber lasers due to nonlinear effects. Whereas self-phasing in previous coherent combination experiments has been principally attributed to wavelength shifting, these wavelength effects have been efficiently suppressed in our experiment by using a dual-core fiber with closely balanced optical path lengths. The self-phasing from nonlinear effects could then be measured independently and directly by common-path interferometry with a probe laser. The Kramers-Kronig effect in the fiber gain media was observed to induce a phase shift that effectively canceled the applied path length errors, resulting in efficient lasing under all phase conditions. This process was demonstrated to result in robust lasing over a large range of pump conditions. PMID:24321934

  18. Direct observations of American eels migrating across the continental shelf to the Sargasso Sea.

    PubMed

    Bguer-Pon, Mlanie; Castonguay, Martin; Shan, Shiliang; Benchetrit, Jos; Dodson, Julian J

    2015-01-01

    Since inferring spawning areas from larval distributions in the Sargasso Sea a century ago, the oceanic migration of adult American eels has remained a mystery. No adult eel has ever been observed migrating in the open ocean or in the spawning area. Here, we track movements of maturing eels equipped with pop-up satellite archival tags from the Scotian Shelf (Canada) into the open ocean, with one individual migrating 2,400 km to the northern limit of the spawning site in the Sargasso Sea. The reconstructed routes suggest a migration in two phases: one over the continental shelf and along its edge in shallow waters; the second in deeper waters straight south towards the spawning area. This study is the first direct evidence of adult Anguilla migrating to the Sargasso Sea and represents an important step forward in the understanding of routes and migratory cues. PMID:26505325

  19. Direct Observation of a Gate Tunable Band Gap in Electrical Transport in ABC-Trilayer Graphene

    NASA Astrophysics Data System (ADS)

    Khodkov, Tymofiy; Khrapach, Ivan; Craciun, Monica Felicia; Russo, Saverio

    2015-07-01

    Few layer graphene systems such as Bernal stacked bilayer and rhombohedral (ABC-) stacked trilayer offer the unique possibility to open an electric field tunable energy gap. To date, this energy gap has been experimentally confirmed in optical spectroscopy. Here we report the first direct observation of the electric field tunable energy gap in electronic transport experiments on doubly gated suspended ABC-trilayer graphene. From a systematic study of the non-linearities in current \\textit{versus} voltage characteristics and the temperature dependence of the conductivity we demonstrate that thermally activated transport over the energy-gap dominates the electrical response of these transistors. The estimated values for energy gap from the temperature dependence and from the current voltage characteristics follow the theoretically expected electric field dependence with critical exponent $3/2$. These experiments indicate that high quality few-layer graphene are suitable candidates for exploring novel tunable THz light sources and detectors.

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

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  1. Copernicus observations of interstellar matter in the direction of HR 1099

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

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

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

    PubMed

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

    2013-05-01

    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

  4. Direct Observation of Sulfur Radicals as Reaction Media in Lithium Sulfur Batteries

    SciTech Connect

    Wang, Qiang; Zheng, Jianming; Walter, Eric; Pan, Huilin; Lv, Dongping; Zuo, Pengjian; Chen, Honghao; Deng, Z. D.; Liaw, Bor Y.; Yu, Xiqian; Yang, Xiao-Qing; Zhang, Ji-Guang; Liu, Jun; Xiao, Jie

    2015-01-09

    Lithium sulfur (Li-S) battery has been regaining tremendous interest in recent years because of its attractive attributes such as high gravimetric energy, low cost and environmental benignity. However, it is still not conclusively known how polysulfide ring/chain participates in the whole cycling and whether the discharge and charge processes follow the same pathway. Herein, we demonstrate the direct observation of sulfur radicals by using in situ electron paramagnetic resonance (EPR) technique. Based on the concentration changes of sulfur radicals at different potentials and the electrochemical characteristics of the cell, it is revealed that the chemical and electrochemical reactions in Li-S cell are driving each other to proceed through sulfur radicals, leading to two completely different reaction pathways during discharge and charge. The proposed radical mechanism may provide new perspectives to investigate the interactions between sulfur species and the electrolyte, inspiring novel strategies to develop Li-S battery technology.

  5. Direct observation of collective modes coupled to molecular orbitaldriven charge transfer

    NASA Astrophysics Data System (ADS)

    Ishikawa, Tadahiko; Hayes, Stuart A.; Keskin, Sercan; Corthey, Gastn; Hada, Masaki; Pichugin, Kostyantyn; Marx, Alexander; Hirscht, Julian; Shionuma, Kenta; Onda, Ken; Okimoto, Yoichi; Koshihara, Shin-ya; Yamamoto, Takashi; Cui, Hengbo; Nomura, Mitsushiro; Oshima, Yugo; Abdel-Jawad, Majed; Kato, Reizo; Miller, R. J. Dwayne

    2015-12-01

    Correlated electron systems can undergo ultrafast photoinduced phase transitions involving concerted transformations of electronic and lattice structure. Understanding these phenomena requires identifying the key structural modes that couple to the electronic states. We report the ultrafast photoresponse of the molecular crystal Me4P[Pt(dmit)2]2, which exhibits a photoinduced charge transfer similar to transitions between thermally accessible states, and demonstrate how femtosecond electron diffraction can be applied to directly observe the associated molecular motions. Even for such a complex system, the key large-amplitude modes can be identified by eye and involve a dimer expansion and a librational mode. The dynamics are consistent with the time-resolved optical study, revealing how the electronic, molecular, and lattice structures together facilitate ultrafast switching of the state.

  6. Direct observation of DNA distortion by the RSC chromatin remodelling complex

    PubMed Central

    Lia, Giuseppe; Praly, Elise; Ferreira, Helder; Stockdale, Chris; Tse-Dinh, Yuk Ching; Dunlap, David; Croquette, Vincent; Bensimon, David; Owen-Hughes, Tom

    2012-01-01

    The Snf2 family represents a functionally diverse class of ATPase sharing the ability to modify DNA structure. Here we use a magnetic trap and an Atomic Force Microscope to monitor the activity of a member of this class: the RSC complex. This enzyme causes transient shortenings in DNA length involving translocation of typically 400 bp within 2 seconds resulting in the formation of a loop whose size depends on both the force applied to the DNA and the ATP concentration. The majority of loops decrease in size within a time similar to that with which they are formed suggesting that the motor has the ability to translocate in different directions. Loop formation is also associated with the generation of negative DNA supercoiling. These observations support the idea that the ATPase motors of the Snf2 family proteins act as DNA translocases specialised to generate transient distortions in DNA structure. PMID:16455496

  7. Direct Observation of Morphological Tranformation from Twisted Ribbons into Helical Ribbons

    SciTech Connect

    Pashuck, E.Thomas; Stupp, Samuel I.

    2010-07-01

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

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

    PubMed Central

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

    2001-01-01

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

  9. Direct observation of the hyperfine transition of ground-state positronium.

    PubMed

    Yamazaki, T; Miyazaki, A; Suehara, T; Namba, T; Asai, S; Kobayashi, T; Saito, H; Ogawa, I; Idehara, T; Sabchevski, S

    2012-06-22

    We report the first direct measurement of the hyperfine transition of the ground state positronium. The hyperfine structure between ortho-positronium and para-positronium is about 203 GHz. We develop a new optical system to accumulate about 10 kW power using a gyrotron, a mode converter, and a Fabry-Prot cavity. The hyperfine transition has been observed with a significance of 5.4 standard deviations. The transition probability is measured to be A = 3.1(-1.2)(+1.6) 10(-8) s(-1) for the first time, which is in good agreement with the theoretical value of 3.37 10(-8) s(-1). PMID:23004598

  10. Direct observation of collective modes coupled to molecular orbital-driven charge transfer.

    PubMed

    Ishikawa, Tadahiko; Hayes, Stuart A; Keskin, Sercan; Corthey, Gastn; Hada, Masaki; Pichugin, Kostyantyn; Marx, Alexander; Hirscht, Julian; Shionuma, Kenta; Onda, Ken; Okimoto, Yoichi; Koshihara, Shin-ya; Yamamoto, Takashi; Cui, Hengbo; Nomura, Mitsushiro; Oshima, Yugo; Abdel-Jawad, Majed; Kato, Reizo; Miller, R J Dwayne

    2015-12-18

    Correlated electron systems can undergo ultrafast photoinduced phase transitions involving concerted transformations of electronic and lattice structure. Understanding these phenomena requires identifying the key structural modes that couple to the electronic states. We report the ultrafast photoresponse of the molecular crystal Me4P[Pt(dmit)2]2, which exhibits a photoinduced charge transfer similar to transitions between thermally accessible states, and demonstrate how femtosecond electron diffraction can be applied to directly observe the associated molecular motions. Even for such a complex system, the key large-amplitude modes can be identified by eye and involve a dimer expansion and a librational mode. The dynamics are consistent with the time-resolved optical study, revealing how the electronic, molecular, and lattice structures together facilitate ultrafast switching of the state. PMID:26680192

  11. Direct Observation of Sulfur Radicals as Reaction Media in lithium Sulfur Batteries

    SciTech Connect

    Wang, Qiang; Zheng, Jianming; Walter, Eric D.; Pan, Huilin; Lu, Dongping; Zuo, Pengjian; Chen, Honghao; Deng, Zhiqun; Liaw, Bor Yann; Yu, Xiqian; Yang, Xiaoning; Zhang, Jiguang; Liu, Jun; Xiao, Jie

    2014-12-09

    Lithium sulfur (Li-S) battery has been regaining tremendous interest in recent years because of its attractive attributes such as high gravimetric energy, low cost and environmental benignity. However, it is still not conclusively known how polysulfide ring/chain participates in the whole cycling and whether the discharge and charge process follow the same pathway. Herein, we demonstrate the direct observation of sulfur radicals by using in situ electron paramagnetic resonance (EPR) technique. Based on the concentration changes of sulfur radicals at different potentials, it is revealed that the chemical and electrochemical reactions in Li-S cell are driven each other to proceed through sulfur radicals, leading to two completely different reaction pathways during discharge and charge. The proposed radical mechanism may provide new insights to investigate the interactions between sulfur species and the electrolyte, inspiring novel strategies to develop Li-S battery technology.

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

    PubMed

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

    2014-02-21

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

  13. Direct Observation of Sulfur Radicals as Reaction Media in Lithium Sulfur Batteries

    DOE PAGESBeta

    Wang, Qiang; Zheng, Jianming; Walter, Eric; Pan, Huilin; Lv, Dongping; Zuo, Pengjian; Chen, Honghao; Deng, Z. D.; Liaw, Bor Y.; Yu, Xiqian; et al

    2015-01-09

    Lithium sulfur (Li-S) battery has been regaining tremendous interest in recent years because of its attractive attributes such as high gravimetric energy, low cost and environmental benignity. However, it is still not conclusively known how polysulfide ring/chain participates in the whole cycling and whether the discharge and charge processes follow the same pathway. Herein, we demonstrate the direct observation of sulfur radicals by using in situ electron paramagnetic resonance (EPR) technique. Based on the concentration changes of sulfur radicals at different potentials and the electrochemical characteristics of the cell, it is revealed that the chemical and electrochemical reactions in Li-Smore » cell are driving each other to proceed through sulfur radicals, leading to two completely different reaction pathways during discharge and charge. The proposed radical mechanism may provide new perspectives to investigate the interactions between sulfur species and the electrolyte, inspiring novel strategies to develop Li-S battery technology.« less

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

    PubMed

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

    2015-02-24

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

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

    PubMed

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

    2014-10-01

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

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

    SciTech Connect

    Jayaram, R.; Miller, M.K.

    1995-07-01

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

  19. Direct observation of intermediate states during the stepping motion of kinesin-1.

    PubMed

    Isojima, Hiroshi; Iino, Ryota; Niitani, Yamato; Noji, Hiroyuki; Tomishige, Michio

    2016-04-01

    The dimeric motor protein kinesin-1 walks along microtubules by alternatingly hydrolyzing ATP and moving two motor domains ('heads'). Nanometer-precision single-molecule studies demonstrated that kinesin takes regular 8-nm steps upon hydrolysis of each ATP; however, the intermediate states between steps have not been directly visualized. Here, we employed high-temporal resolution dark-field microscopy to directly visualize the binding and unbinding of kinesin heads to or from microtubules during processive movement. Our observations revealed that upon unbinding from microtubules, the labeled heads were displaced rightward and underwent tethered diffusive movement. Structural and kinetic analyses of wild-type and mutant kinesins with altered neck linker lengths provided evidence that rebinding of the unbound head to the rear-binding site is prohibited by a tension increase in the neck linker and that ATP hydrolysis by the leading head is suppressed when both heads are bound to the microtubule, thereby explaining how the two heads coordinate to move in a hand-over-hand manner. PMID:26928936

  20. Cluster and RBSP observations of propagation directions of whistler-mode chorus

    NASA Astrophysics Data System (ADS)

    Santolik, O.; Macusova, E.; Kolmasova, I.; Kurth, W. S.; Hospodarsky, G. B.; Kletzing, C.; Cornilleau-Wehrlin, N.; Pickett, J. S.; Gurnett, D. A.; Wygant, J. R.; Bonnell, J. W.

    2012-12-01

    Electromagnetic emissions of whistler-mode chorus have been identified as a source of energy for the relativistic electrons in the outer Van Allen radiation belt. Being generated by anisotropic electron populations in the source region around the equatorial minimum of the geomagnetic field, chorus is believed to transfer energy between different parts of the electron phase space distribution. It has been shown that chorus, on average, carries enough power to account for the observed changes in the radiation belt fluxes at time scales on the order of one day. However, propagation directions of these emissions control their ability to efficiently interact with electrons. We investigate 10 years of measurements of the Cluster mission in order to determine the probability density functions of propagation directions of chorus as a function of geomagnetic latitude, magnetic local time, L* parameter, and frequency. These results give context to new measurements of whistler-mode chorus by the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) Waves instrument onboard the Radiation Belt Storm Probes (RBSP) spacecraft.

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

    PubMed Central

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

    2014-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-11-01

    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.

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

    PubMed Central

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

    1999-01-01

    Cytoskeletal proteins tagged with green fluorescent protein were used to directly visualize the mechanical 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 attachment to the cell surface. Cells responded to uncoated probes in accordance with a three-layer model in which a highly elastic nucleus is surrounded by cytoplasmic microtubules that behave as a jelly-like viscoelastic fluid. The third, outermost cortical layer is an elastic shell under sustained tension. Adhesive, laminin-coated needles caused focal recruitment of actin filaments to the contacted surface region and increased the cortical layer stiffness. This direct visualization of actin recruitment confirms a widely postulated model for mechanical connections between extracellular matrix proteins and the actin cytoskeleton. Cells tethered to laminin-treated needles strongly resisted elongation by actively contracting. Whether using uncoated probes to apply simple deformations or laminin-coated probes to induce surface-to-cytoskeleton interaction we observed that experimentally applied forces produced exclusively local responses by both the actin and microtubule cytoskeleton. This local accomodation and dissipation of force is inconsistent with the proposal that cellular tensegrity determines cell shape. PMID:10189372

  4. Dislocation structures in nanoindented ductile metals—a transmission electron microscopy direct observation

    NASA Astrophysics Data System (ADS)

    Graça, S.; Carvalho, P. A.; Colaço, R.

    2011-08-01

    Several attempts have been made over recent years to understand indentation size effect (ISE). The theoretical models, based essentially on strain gradient plasticity theories, such as the Nix-Gao model, predict that ISE is caused by an increase in the density of dislocations as the indentation size decreases. Molecular dynamics simulation results tend to confirm this fact, but the truth is that very few experimental studies exist on the direct observation of how dislocations are generated and accommodated in the vicinity of nanoindentations. In this study, using a Ni transmission electron microscopy thin foil as model material, we show that when the material is submitted to atomic force microscopy-based nanoindentation a high dislocation density zone is generated at the centre of the indented region, and that prismatic loop and helical dislocations are emitted sidewards from the central region of the nanoindentation along the lang1 1 0rang directions. Moreover, we show that the dislocation array formed during the nanoindentation process is far from the ideal model proposed by Nix and Gao, based on load axi-centred dislocation loops. With this study we aim at contributing to a better comprehension of ISE mechanisms in ductile metals.

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

    NASA Astrophysics Data System (ADS)

    Li, Guohong; Andrei, Eva Y.

    2007-03-01

    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.

  6. Direct radiative feedback due to biogenic secondary organic aerosol estimated from boreal forest site observations

    NASA Astrophysics Data System (ADS)

    Lihavainen, Heikki; Asmi, Eija; Aaltonen, Veijo; Makkonen, Ulla; Kerminen, Veli-Matti

    2015-10-01

    We used more than five years of continuous aerosol measurements to estimate the direct radiative feedback parameter associated with the formation of biogenic secondary organic aerosol (BSOA) at a remote continental site at the edge of the boreal forest zone in Northern Finland. Our upper-limit estimate for this feedback parameter during the summer period (ambient temperatures above 10 °C) was -97 ± 66 mW m-2 K-1 (mean ± STD) when using measurements of the aerosol optical depth (fAOD) and -63 ± 40 mW m-2 K-1 when using measurements of the ‘dry’ aerosol scattering coefficient at the ground level (fσ). Here STD represents the variability in f caused by the observed variability in the quantities used to derive the value of f. Compared with our measurement site, the magnitude of the direct radiative feedback associated with BSOA is expected to be larger in warmer continental regions with more abundant biogenic emissions, and even larger in regions where biogenic emissions are mixed with anthropogenic pollution.

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

    PubMed Central

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

    1999-01-01

    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 carboniodine, CI, 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 CI bond. The elimination of two iodine atoms was shown to be nonconcerted, with reaction time of the second CI bond breakage being 17 2 ps. The structure of the short-lived C2F4I radical is more favorable to the classical radical structure than to the bridged radical structure. This leap in our ability to record structural changes on the ps and shorter time scales bodes well for many future applications in complex molecular systems. PMID:9892634

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

    Martensitic transformation usually creates hierarchical internal structures beyond mere change of the atomic crystal structure. Multi-stage nucleation is thus required, where nucleation (level-1) of the underlying atomic crystal lattice does not have to be immediately followed by the nucleation of higher-order superstructures (level-2 and above), such as polysynthetic laths. Using in situ transmission electron microscopy (TEM), we directly observe the nucleation of the level-2 superstructure in a Cu-Al-Ni single crystal under compression, with critical super-nuclei size L2c around 500 nm. When the sample size D decreases below L2c, the superelasticity behavior changes from a flat stress plateau to a continuously rising stress-strain curve. Such size dependence definitely would impact the application of shape memory alloys in miniaturized MEMS/NEMS devices.Martensitic transformation usually creates hierarchical internal structures beyond mere change of the atomic crystal structure. Multi-stage nucleation is thus required, where nucleation (level-1) of the underlying atomic crystal lattice does not have to be immediately followed by the nucleation of higher-order superstructures (level-2 and above), such as polysynthetic laths. Using in situ transmission electron microscopy (TEM), we directly observe the nucleation of the level-2 superstructure in a Cu-Al-Ni single crystal under compression, with critical super-nuclei size L2c around 500 nm. When the sample size D decreases below L2c, the superelasticity behavior changes from a flat stress plateau to a continuously rising stress-strain curve. Such size dependence definitely would impact the application of shape memory alloys in miniaturized MEMS/NEMS devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr05258c

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

    PubMed Central

    Blank, Melissa D.; Disharoon, Steven

    2009-01-01

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

  10. Direct observation of ultraslow hyperbolic polariton propagation with negative phase velocity

    NASA Astrophysics Data System (ADS)

    Yoxall, Edward; Schnell, Martin; Nikitin, Alexey Y.; Txoperena, Oihana; Woessner, Achim; Lundeberg, Mark B.; Casanova, Flix; Hueso, Luis E.; Koppens, Frank H. L.; Hillenbrand, Rainer

    2015-10-01

    Polaritons with hyperbolic dispersion are key to many emerging photonic technologies, including subdiffraction imaging, sensing and spontaneous emission engineering. Fundamental to their effective application are the lifetimes of the polaritons, as well as their phase and group velocities. Here, we combine time-domain interferometry and scattering-type near-field microscopy to visualize the propagation of hyperbolic polaritons in space and time, allowing the first direct measurement of all these quantities. In particular, we study infrared phonon polaritons in a thin hexagonal boron nitride waveguide exhibiting hyperbolic dispersion and deep subwavelength-scale field confinement. Our results revealin a natural materialnegative phase velocity paired with a remarkably slow group velocity of 0.002c and lifetimes in the picosecond range. While these findings show the polariton's potential for mediating strong light-matter interactions and negative refraction, our imaging technique paves the way to explicit nanoimaging of polariton propagation characteristics in other two-dimensional materials, metamaterials and waveguides.

  11. In-Situ Observation of Directional Solidifications of Al-Cu Alloys During Parabolic Flight Campaigns

    NASA Astrophysics Data System (ADS)

    Abou-Khalil, L.; Salloum-Abou-Jaoude, G.; Reinhart, G.; Pickmann, C.; Zimmermann, G.; Houltz, Y.; Li, J.; Janson, O.; Nguyen-Thi, H.

    2015-09-01

    It is well known that the final properties of materials are strongly related to the microstructures formed during growth and to the accompanying segregation, both being very sensitive to the natural hydrodynamic movements in the melt induced by gravity. Therefore, a deeper understanding of gravity effects on the solidification microstructure is of great importance for industrial applications. In the framework of the ESA-MAP project entitled XRMON (in-situ X-Ray MONitoring of advanced metallurgical processes under microgravity and terrestrial conditions), directional solidification experiments with in situ X-ray radiography were carried out during the 60th and 61st ESA — PF campaigns onboard the Airbus A300 operated by Novespace. Parabolic flights offer several successions of periods with normal gravity between two parabolas, and hyper gravity and microgravity during each parabola, which allows the impact of gravity level variations on the solidification microstructures to be investigated. For this purpose, a dedicated apparatus was designed and developed in collaboration with SSC (Swedish Space Corporation). XRMON-PFF (Parabolic Flight Facility) includes a Bridgman furnace dedicated to the solidification of Al-based alloys with an X-ray device that enables in situ characterization. Columnar and/or equiaxed growth of refined and non-refined Al2Owt.%Cu alloys were investigated and X-ray radiography was successfully used to assess the effect of periodic variations of the gravity level on the solidification microstructure formation. Preliminary results confirmed the strong influence of gravity on the solidification microstructure development.

  12. Direct real-time observation of actin filament branching mediated by Arp2/3 complex using total internal reflection fluorescence microscopy

    PubMed Central

    Amann, Kurt J.; Pollard, Thomas D.

    2001-01-01

    Existing methods for studying actin filament dynamics have allowed analysis only of bulk samples or individual filaments after treatment with the drug phalloidin, which perturbs filament dynamics. Total internal reflection fluorescence microscopy with rhodamine-labeled actin allowed us to observe polymerization in real time, without phalloidin. Direct measurements of filament growth confirmed the rate constants measured by electron microscopy and established that rhodamine actin is a kinetically inactive tracer for imaging. In the presence of activated Arp2/3 complex, growing actin filaments form branches at random sites along their sides, rather than preferentially from their barbed ends. PMID:11742068

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

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

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

    PubMed

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

    2014-10-01

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

  15. Direct observation of atomic-level nucleation and growth processes from an ultrathin metallic glass films

    NASA Astrophysics Data System (ADS)

    Huang, K. Q.; Cao, C. R.; Sun, Y. T.; Li, J.; Bai, H. Y.; Gu, L.; Zheng, D. N.; Wang, W. H.

    2016-01-01

    Till date, there have been no direct atomic-level experimental observations of the earliest stages of the nucleation and growth processes of nanocrystals formed by thermally induced crystallization in ultrathin metallic glasses (MGs). Here, we present a study of the crystallization process in atomically thin and highly stable MG films using double spherical aberration-corrected scanning transmission electron microscopy (Cs-TEM). Taking advantage of the stability of MG films with a slow crystallization process and the atomic-level high resolution of Cs-TEM, we observe the formation of the nucleus precursor of nanocrystals formed by atom aggregation followed by concomitant coalescence and stepwise evolution of the shape of the nanocrystals with a monodispersed and separated bimodal size distribution. Molecular dynamics simulation of the atomic motion in the glass film on a rigid amorphous substrate confirms the stepwise evolution processes of atom aggregation, cluster formation, cluster movement on the substrate, and cluster coalescence into larger crystalline particles. Our results might provide a better fundamental understanding of the nucleation and growth processes of nanocrystals in thin MG films.

  16. Direct Observations of Evolving Subglacial Drainage Beneath the Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

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

    2014-01-01

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

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

    PubMed Central

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

    1989-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Heinemann, K.; Poppa, H.

    1975-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

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

  20. Direct Attribution of the Anthropogenic climate signal to PHENological observations - DATAPHEN

    NASA Astrophysics Data System (ADS)

    Scheifinger, H.; Schnganer, T.; Zuvela-Aloise, M.; Matulla, C.

    2012-04-01

    Warming of the climate system has been widely observed during the last decades. Attribution analyses suggest that the global pattern of warming during the past half century is very likely caused by human-induced greenhouse gas forcing. Although up to present a considerable number of detection and attribution studies have been published dealing with the problem over a range of atmospheric parameters and over a large spatial range, there is still a dearth on direct attribution studies, which quantitatively link the human influence on the climate system with observed impacts for instance on the biosphere. This work intends to apply the direct attribution method via an end-to-end modelling system to quantitatively link anthropogenic forcing with the observed shift of phenological entry dates. From the PEP725 (Pan European Phenology data base, www.pep725.eu) 36 phenological phases have been select with a sufficient spatial coverage over Central Europe. In order to deduce the parameters for the Temperature Sum Model (TSM), daily mean temperatures from the ECA&D station network have been prepared. While working on the project a sufficient number of CMIP5 runs have become available, so that we could compile 7 models with an ensemble of 27 runs for the historicalNat case (20th century runs with natural forcing only) and 6 models with altogether 35 runs for the historical case (20th century runs with all forcings). Additionally there is one observational data set (ECA&D 0.25 resolution grid over Europe, http://eca.knmi.nl), two reanalysis runs (ERA40 and NCAR-NCEP) one 1000 year piControl (preindustrial control run), adding up to 66 data sets. The daily mean temperature data of the 66 above mentioned data sets are interpolated to all ECA&D stations, where the TSM parameters have been deduced. After the phenological entry dates have been modelled for 66 cases at the ECA&D stations, a mean Central European phenological time series is calculated. The subsequent statistical analysis includes a validation of the TSM and some consistency considerations. As a first step the monthly mean temperature time series from 1850 - 2000 of the GCM ensemble of different forcings (historical versus historicalNat) have been compared. Before applying the TSM it was checked, if above selected GCM temperature data sets already indicate any significant differences between the two forcing scenarios considered. In the global case a systematic difference in trend of about 0.5C can be observed from 1970 - 2005. In case of the Central European area (0E - 25E, 45N - 55N), which is the area, where most of the phenological observations come from, the difference of the two forcing scenarios are much less pronounced, but still clearly visible in case of yearly means and in all individual seasons.

  1. Direct Observation of Photoinduced Tautomerization in Single Molecules at a Metal Surface.

    PubMed

    Böckmann, H; Liu, S; Mielke, J; Gawinkowski, S; Waluk, J; Grill, L; Wolf, M; Kumagai, T

    2016-02-10

    Molecular switches are of fundamental importance in nature, and light is an important stimulus to selectively drive the switching process. However, the local dynamics of a conformational change in these molecules remain far from being completely understood at the single-molecule level. Here, we report the direct observation of photoinduced tautomerization in single porphycene molecules on a Cu(111) surface by using a combination of low-temperature scanning tunneling microscopy and laser excitation in the near-infrared to ultraviolet regime. It is found that the thermodynamically stable trans configuration of porphycene can be converted to the metastable cis configuration in a unidirectional fashion by photoirradiation. The wavelength dependence of the tautomerization cross section exhibits a steep increase around 2 eV and demonstrates that excitation of the Cu d-band electrons and the resulting hot carriers play a dominant role in the photochemical process. Additionally, a pronounced isotope effect in the cross section (∼100) is observed when the transferred hydrogen atoms are substituted with deuterium, indicating a significant contribution of zero-point energy in the reaction. Combined with the study of inelastic tunneling electron-induced tautomerization with the STM, we propose that tautomerization occurs via excitation of molecular vibrations after photoexcitation. Interestingly, the observed cross section of ∼10(-19) cm(2) in the visible-ultraviolet region is much higher than that of previously studied molecular switches on a metal surface, for example, azobenzene derivatives (10(-23)-10(-22) cm(2)). Furthermore, we examined a local environmental impact on the photoinduced tautomerization by varying molecular density on the surface and find substantial changes in the cross section and quenching of the process due to the intermolecular interaction at high density. PMID:26796945

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

    PubMed Central

    Cowsik, R.

    2007-01-01

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

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

    PubMed

    Cowsik, R

    2007-04-24

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

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

    ERIC Educational Resources Information Center

    SYKES, RONALD E.

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

  5. Direct video and hydrophone observations of submarine explosive eruptions at NW Rota-1 volcano, Mariana arc

    NASA Astrophysics Data System (ADS)

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

    2008-08-01

    Extraordinary video and hydrophone observations of a submarine explosive eruption were made with a remotely operated vehicle in April 2006 at a depth of 550-560 m on NW Rota-1 volcano in the Mariana arc. The observed eruption evolved from effusive to explosive, while the eruption rate increased from near zero to 10-100 m3/h. During the peak in activity, cyclic explosive bursts 2-6 min long were separated by shorter non-eruptive pauses lasting 10-100 s. The size of the ejecta increased with the vigor of the explosions. A portable hydrophone deployed near the vent recorded sounds correlated with the explosive bursts; the highest amplitudes were 50 dB higher than ambient noise at frequencies between 10 and 50 Hz. The acoustic data allow us to quantify the durations, amplitudes, and evolution of the eruptive events over time. The low eruption rate, high gas/lava ratio, and rhythmic eruptive behavior at NW Rota-1 are most consistent with a Strombolian eruptive style. We interpret that the eruption was primarily driven by the venting of magmatic gases, which was also the primary source of the sound recorded during the explosive bursts. The rhythmic nature of the bursts can be explained by partial gas segregation in the conduit and upward migration in a transitional regime between bubbly flow and fully developed slug flow. The strongest explosive bursts were accompanied by flashes of red glow and oscillating eruption plumes in the vent, apparently caused by magma-seawater interaction and rapid steam formation and condensation. This is the first time submarine explosive eruptions have been witnessed with simultaneous near-field acoustic recordings.

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

    NASA Astrophysics Data System (ADS)

    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

    The 33S(p,γ)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,γ)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,γ)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,γ)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,γ)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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

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

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

    PubMed Central

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

    2008-01-01

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

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

    PubMed

    Blanc, Frdric; Berthoud, Romain; Copret, Christophe; Lesage, Anne; Emsley, Lyndon; Singh, Rojendra; Kreickmann, Thorsten; Schrock, Richard R

    2008-08-26

    Grafting of [W([triple bond]NAr)(=CHtBu)(2,5-Me(2)NC(4)H(2))(2)] on a silica partially dehydroxylated at 700 degrees C (SiO(2- (700))) generates the corresponding monosiloxy complex [([triple bond]SiO)W([triple bond]NAr)(=CHtBu)(2,5-Me(2)NC(4)H(2))] as the major species (approximately 90%) along with [([triple bond]SiO)W([triple bond]NAr)(CH(2)tBu)(2,5-Me(2)NC(4)H(2))(2)], according to mass balance analysis, IR, and NMR studies. This heterogeneous catalyst displays good activity and stability in the metathesis of propene. Very importantly, solid state NMR spectroscopy allows observation of the propagating alkylidene as well as stable metallacyclobutane intermediates. These species have the same reactivity as the initial surface complex [([triple bond]SiO)W([triple bond]NAr)(=CHtBu)(2,5-Me(2)NC(4)H(2))], which shows that they are the key intermediates of alkene metathesis. PMID:18723685

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

    PubMed

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

    2014-12-01

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

  11. Direct Observation (DO) for Drug-Resistant Tuberculosis: Do We Really DO?

    PubMed Central

    Benbaba, Stella; Isaakidis, Petros; Das, Mrinalini; Jadhav, Sonakshi; Reid, Tony; Furin, Jennifer

    2015-01-01

    Introduction Directly-observed therapy (DOT) is recommended for drug-resistant tuberculosis (DR-TB) patients during their entire treatment duration. However, there is limited published evidence on implementation of direct observation (DO) in the field. This study aims to detail whether DO was followed with DR-TB patients in a Médecins Sans Frontières (MSF) tuberculosis program in Mumbai, India. Methods This was a cross-sectional, mixed-methods study. Existing qualitative data from a purposively-selected subset of 12 patients, 5 DOT-providers and 5 family members, were assessed in order to determine how DO was implemented. A questionnaire-based survey of DR-TB patients, their DOT-providers and MSF staff was completed between June and August 2014. Patients were defined as”following Strict DO” and “following DO” if a DOT-provider had seen the patient swallow his/her medications “every day” or “most of the days” respectively. If DO was not followed, reasons were also recorded. The qualitative data were analysed for theme and content and used to supplement the questionnaire-based data. Results A total of 70 DR-TB patients, 65 DOT-providers and 21 MSF health staff were included. Fifty-five per cent of the patients were HIV-co-infected and 41% had multidrug-resistant-TB plus additional resistance to a fluoroquinolone. Among all patients, only 14% (10/70) and 20% (14/70) self-reported “following Strict DO” and “following DO” respectively. Among DOT-providers, 46% (30/65) reported that their patients “followed DO”. MSF health staff reported none of the patients “followed DO”. Reasons for not implementing DO included the unavailability of DOT-provider, time spent, stigma and treatment adverse events. The qualitative data also revealed that “Strict DO” was rarely followed and noted the same reasons for lack of implementation. Conclusion This mixed-methods study has found that a majority of patients with DR-TB in Mumbai did not follow DO, and this was reported by patients and care-providers. These data likely reflect the reality of DO implementation in many high-burden settings, since this relatively small cohort was supported and closely monitored by a skilled team with access to multiple resources. The findings raise important concerns about the necessity of DO as a “pillar” of DR-TB treatment which need further validation in other settings. They also suggest that patient-centred adherence strategies might be better approaches for supporting patients on treatment. PMID:26713873

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

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

    PubMed Central

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

    1998-01-01

    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. PMID:9518978

  14. Implications of directly observed therapy in tuberculosis control measures among IDUs.

    PubMed Central

    Curtis, R; Friedman, S R; Neaigus, A; Jose, B; Goldstein, M; Des Jarlais, D C

    1994-01-01

    Tuberculosis (TB) is a rapidly growing problem among injecting drug users (IDU), especially those infected with human immunodeficiency virus. The authors review IDUs' responses to current TB control strategies and discuss the implications of their findings for the proposed implementation of directly observed therapy (DOT), a method for ensuring that patients take prescribed medication. Field workers carried out 210 ethnographic interviews with 68 IDUs in a Brooklyn, NY, community during 1990-93. Case studies suggested that many IDUs are uninformed about TB and often misinformed about their personal TB status. Ethnographic interviews and observations indicated that the threat of TB-related involuntary detainment may lead IDUs to avoid TB diagnostic procedures, treatment for TB, or drug abuse treatment, and to avoid AIDS outreach workers and other health-related services. IDUs who tested positive for the purified protein derivative (PPD) of TB sometimes have left hospitals before definitive diagnoses were made, because of a perceived lack of respectful treatment, fear of detention, or lack of adequate methadone therapy to relieve the symptoms of withdrawal from drugs. Current TB diagnosis and treatment systems are, at best, inadequate. The threat of TB-related detention discourages some IDUs from seeking any type of health care. There is an urgent need to educate IDUs about TB and to educate and sensitize health care providers about the lifestyles of IDUs. DOT may help in servicing this difficult-to-serve population, particularly if techniques are incorporated that have been developed for other successful public health interventions for IDUs. PMID:8190855

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

    PubMed Central

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

    2014-01-01

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

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

    PubMed

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

    2014-09-10

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

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

    SciTech Connect

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

    2011-08-15

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

  18. Long-term Observations of Electric Field, Temperature, Pressure, Humidity, Wind Speed, Wind Direction, Rainfall Rate and Solar Insolation at a Remote Meteorological Observing Station

    NASA Astrophysics Data System (ADS)

    Gallagher, F. W.; Beasley, W. H.; Bansemer, A. R.; Grimsley, D. L.; Byerley, L. G.

    2001-12-01

    For nearly two years we observed the electric field at the surface continually and simultaneously with observations of temperature, pressure, humidity, wind speed and direction, rainfall rate and solar insolation at a remote automated meteorological observing station in Norman, OK. The electric-field observations were made with electric-field mills that were cycled on every few minutes for a period of about 20 seconds, 24 hours a day, seven days a week for the entire period of time. We observed a number of interesting patterns in the observations, some familiar and some not. For example, monthly averages of the observations often yield Carnegie curves, but not always. We noted what appears to be a sunrise effect on some days. We present a representative sample of the observations.

  19. Direct Observation of Intermediates Involved in the Interruption of the Bischler-Napieralski Reaction.

    PubMed

    White, Kolby L; Mewald, Marius; Movassaghi, Mohammad

    2015-08-01

    The first mechanistic investigation of electrophilic amide activation of ?,?-disubstituted tertiary lactams and the direct observation of key intermediates by in situ FTIR, (1)H, (13)C, and (19)F NMR in our interrupted Bischler-Napieralski-based synthetic strategy to the aspidosperma alkaloids, including a complex tetracyclic diiminium ion, is discussed. The reactivity of a wide range of pyridines with trifluoromethanesulfonic anhydride was systematically examined, and characteristic IR absorption bands for the corresponding N-trifluoromethanesulfonylated pyridinium trifluoromethanesulfonates were assigned. The reversible formation of diiminium ether intermediates was studied, providing insight into divergent mechanistic pathways as a function of the steric environment of the amide substrate and stoichiometry of reagents. Importantly, when considering base additives during electrophilic amide activation, more hindered ?-quaternary tertiary lactams require the use of non-nucleophilic pyridine additives in order to avoid deactivation via a competing desulfonylation reaction. The isolation and full characterization of a tetracyclic iminium trifluoromethanesulfonate provided additional correlation between in situ characterization of sensitive intermediates and isolable compounds involved in this synthetic transformation. PMID:26166404

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

    NASA Astrophysics Data System (ADS)

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

    2011-10-01

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

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

    PubMed Central

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

    2000-01-01

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

  2. Direct Observation of an Oxepin from a Bacterial Cytochrome P450-Catalyzed Oxidation.

    PubMed

    Stok, Jeanette E; Chow, Sharon; Krenske, Elizabeth H; Farfan Soto, Clementina; Matyas, Csongor; Poirier, Raymond A; Williams, Craig M; De Voss, James J

    2016-03-18

    The cytochromes P450 are hemoproteins that catalyze a range of oxidative C-H functionalization reactions, including aliphatic and aromatic hydroxylation. These transformations are important in a range of biological contexts, including biosynthesis and xenobiotic biodegradation. Much work has been carried out on the mechanism of aliphatic hydroxylation, implicating hydrogen atom abstraction, but aromatic hydroxylation is postulated to proceed differently. One mechanism invokes as the key intermediate an arene oxide (and/or its oxepin tautomer). Conclusive isolation of this intermediate has remained elusive and, currently, direct formation of phenols from a Meisenheimer intermediate is believed to be favored. We report here the identification of a P450 [P450cam (CYP101A1) and P450cin (CYP176A1)]-generated arene oxide as a product of in vitro oxidation of tert-butylbenzene. Computations (CBS-QB3) predict that the arene oxide and oxepin have similar stabilities to other arene oxides/oxepins implicated (but not detected) in P450-mediated transformations, suggesting that arene oxides can be unstable terminal products of P450-catalyzed aromatic oxidation that can explain the origin of some observed metabolites. PMID:26811874

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  4. Direct observation of solid-state reversed transformation from crystals to quasicrystals in a Mg alloy.

    PubMed

    Liu, Jian-Fang; Yang, Zhi-Qing; Ye, Heng-Qiang

    2015-01-01

    Phase transformation of quasicrystals is of interest in various fields of science and technology. Interestingly, we directly observed unexpected solid-state epitaxial nucleation and growth of Zn6Mg3Y icosahedral quasicrystals in a Mg alloy at about 573?K which is about 300?K below the melting point of Zn6Mg3Y, in contrast to formation of quasicrystals through solidification that was usually found in many alloys. Maximizing local packing density of atoms associated with segregation of Y and Zn in Mg adjacent to Mg/Zn3MgY interfaces triggered atomic rearrangement in Mg to form icosahedra coupled epitaxially with surface distorted icosahedra of Zn3MgY, which plays a critical role in the nucleation of icosahedral clusters. A local Zn:Mg:Y ratio close to 6:3:1, corresponding to a valence electron concentration of about 2.15, should have been reached to trigger the formation of quasicrystals at Mg/Zn3MgY interfaces. The solid-state icosahedral ordering in crystals opens a new window for growing quasicrystals and understanding their atomic origin mechanisms. Epitaxial growth of quasicrystals onto crystals can modify the surface/interface structures and properties of crystalline materials. PMID:26066096

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

    PubMed Central

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

    2014-01-01

    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

  6. Direct Observation of a Carbon Filament in Water-Resistant Organic Memory.

    PubMed

    Lee, Byung-Hyun; Bae, Hagyoul; Seong, Hyejeong; Lee, Dong-Il; Park, Hongkeun; Choi, Young Joo; Im, Sung-Gap; Kim, Sang Ouk; Choi, Yang-Kyu

    2015-07-28

    The memory for the Internet of Things (IoT) requires versatile characteristics such as flexibility, wearability, and stability in outdoor environments. Resistive random access memory (RRAM) to harness a simple structure and organic material with good flexibility can be an attractive candidate for IoT memory. However, its solution-oriented process and unclear switching mechanism are critical problems. Here we demonstrate iCVD polymer-intercalated RRAM (i-RRAM). i-RRAM exhibits robust flexibility and versatile wearability on any substrate. Stable operation of i-RRAM, even in water, is demonstrated, which is the first experimental presentation of water-resistant organic memory without any waterproof protection package. Moreover, the direct observation of a carbon filament is also reported for the first time using transmission electron microscopy, which puts an end to the controversy surrounding the switching mechanism. Therefore, reproducibility is feasible through comprehensive modeling. Furthermore, a carbon filament is superior to a metal filament in terms of the design window and selection of the electrode material. These results suggest an alternative to solve the critical issues of organic RRAM and an optimized memory type suitable for the IoT era. PMID:26056735

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

    PubMed

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

    2012-05-22

    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

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

    PubMed Central

    Percot, A; Lafleur, M

    2001-01-01

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

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

    PubMed Central

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

    2012-01-01

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

  10. Direct observation of solid-state reversed transformation from crystals to quasicrystals in a Mg alloy

    NASA Astrophysics Data System (ADS)

    Liu, Jian-Fang; Yang, Zhi-Qing; Ye, Heng-Qiang

    2015-06-01

    Phase transformation of quasicrystals is of interest in various fields of science and technology. Interestingly, we directly observed unexpected solid-state epitaxial nucleation and growth of Zn6Mg3Y icosahedral quasicrystals in a Mg alloy at about 573?K which is about 300?K below the melting point of Zn6Mg3Y, in contrast to formation of quasicrystals through solidification that was usually found in many alloys. Maximizing local packing density of atoms associated with segregation of Y and Zn in Mg adjacent to Mg/Zn3MgY interfaces triggered atomic rearrangement in Mg to form icosahedra coupled epitaxially with surface distorted icosahedra of Zn3MgY, which plays a critical role in the nucleation of icosahedral clusters. A local Zn:Mg:Y ratio close to 6:3:1, corresponding to a valence electron concentration of about 2.15, should have been reached to trigger the formation of quasicrystals at Mg/Zn3MgY interfaces. The solid-state icosahedral ordering in crystals opens a new window for growing quasicrystals and understanding their atomic origin mechanisms. Epitaxial growth of quasicrystals onto crystals can modify the surface/interface structures and properties of crystalline materials.

  11. Direct observation of epitaxial organic film growth: temperature-dependent growth mechanisms and metastability.

    PubMed

    Marchetto, Helder; Schmidt, Thomas; Groh, Ullrich; Maier, Florian C; Lévesque, Pierre L; Fink, Rainer H; Freund, Hans-Joachim; Umbach, Eberhard

    2015-11-21

    The growth of the first ten layers of organic thin films on a smooth metallic substrate has been investigated in real-time using the model system PTCDA on Ag(111). The complex behaviour is comprehensively studied by electron microscopy, spectroscopy and diffraction in a combined PEEM/LEEM instrument revealing several new phenomena and yielding a consistent picture of this layer growth. PTCDA grows above room temperature in a Stranski-Krastanov mode, forming three-dimensional islands on a stable bi-layer, in competition with metastable 3rd and 4th layers. Around room temperature this growth mode changes into a quasi layer-by-layer growth, while at temperatures below about 250 K a Vollmer-Weber-like behaviour is observed. By means of laterally resolved soft X-ray absorption spectroscopy the orientation of all adsorbed molecules is found to be homogeneously flat lying on the surface, even during the growth process. The films grow epitaxially, showing long-range order with rotational domains. For the monolayer these domains could be directly analysed, showing an average size of several micrometers extending over substrate steps. PMID:26462749

  12. A Far-infrared Observational Test of the Directional Dependence in Radiative Grain Alignment

    NASA Astrophysics Data System (ADS)

    Vaillancourt, John E.; Andersson, B.-G.

    2015-10-01

    The alignment of interstellar dust grains with magnetic fields provides a key method for measuring the strength and morphology of the fields. In turn, this provides a means to study the role of magnetic fields from diffuse gas to dense star-forming regions. The physical mechanism for aligning the grains has been a long-term subject of study and debate. The theory of radiative torques, in which an anisotropic radiation field imparts sufficient torques to align the grains while simultaneously spinning them to high rotational velocities, has passed a number of observational tests. Here we use archival polarization data in dense regions of the Orion molecular cloud (OMC-1) at 100, 350, and 850 ?m to test the prediction that the alignment efficiency is dependent upon the relative orientations of the magnetic field and radiation anisotropy. We find that the expected polarization signal, with a 180-degree period, exists at all wavelengths out to radii of 1.5 arcmin centered on the Becklin-Neugebauer Kleinmann-Low (BNKL) object in OMC-1. The probabilities that these signals would occur due to random noise are low (?1%), and are lowest toward BNKL compared to the rest of the cloud. Additionally, the relative magnetic field to radiation anisotropy directions accord with theoretical predictions in that they agree to better than 15 at 100 ?m and 4 at 350 ?m.

  13. Patients Experience of Tuberculosis Treatment Using Directly Observed Treatment, Short-Course (DOTS): A Qualitative Study

    PubMed Central

    Behzadifar, Masoud; Mirzaei, Masoud; Behzadifar, Meysam; Keshavarzi, Abouzar; Behzadifar, Maryam; Saran, Maryam

    2015-01-01

    Background: Despite effective diagnosis and treatment, prevalence of tuberculosis (TB) is still growing. The directly observed treatment, short-course (DOTS) strategy to treat TB was introduced by the World Health Organization more than a decade ago. Little is known about patients experience of TB treatment, according to DOTS, in Iran. Objectives: This study aimed to understand the patients experience of tuberculosis treatment according to DOTS in Iran. Patients and Methods: This study is a qualitative study, using content analysis to examine patients experience of TB treatment and to understand their compliance during DOTS. In this study, a semi-structured interview with open questions was answered by 40 patients, who had a diagnosis of pulmonary and extrapulmonary tuberculosis, and improved during the course of their treatment. The method of sampling was purposive sample and the interview process lasted until data saturation. Results: Data analysis resulted in the extraction of six themes, which reflect the experiences of the study participants. The themes are: 1) individual factors; 2) change of the attitudes and beliefs of patients on TB treatment; 3) support terms of patients with tuberculosis; 4) the role of health care professionals; 5) social factors and 6) the financial burden. Conclusions: Successful completion of TB treatment requires an effective partnership between the patient and health care professionals, and a harmony between the cultural context, attitude of the patient, family support and health literacy. Future health policies should address these issues to improve patients adherence to DOTS. PMID:26023334

  14. Direct observation of solid-state reversed transformation from crystals to quasicrystals in a Mg alloy

    PubMed Central

    Liu, Jian-Fang; Yang, Zhi-Qing; Ye, Heng-Qiang

    2015-01-01

    Phase transformation of quasicrystals is of interest in various fields of science and technology. Interestingly, we directly observed unexpected solid-state epitaxial nucleation and growth of Zn 6 Mg 3 Y icosahedral quasicrystals in a Mg alloy at about 573 K which is about 300 K below the melting point of Zn 6 Mg 3 Y, in contrast to formation of quasicrystals through solidification that was usually found in many alloys. Maximizing local packing density of atoms associated with segregation of Y and Zn in Mg adjacent to Mg/Zn 3 MgY interfaces triggered atomic rearrangement in Mg to form icosahedra coupled epitaxially with surface distorted icosahedra of Zn 3 MgY, which plays a critical role in the nucleation of icosahedral clusters. A local Zn:Mg:Y ratio close to 6:3:1, corresponding to a valence electron concentration of about 2.15, should have been reached to trigger the formation of quasicrystals at Mg/Zn 3 MgY interfaces. The solid-state icosahedral ordering in crystals opens a new window for growing quasicrystals and understanding their atomic origin mechanisms. Epitaxial growth of quasicrystals onto crystals can modify the surface/interface structures and properties of crystalline materials. PMID:26066096

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

    NASA Technical Reports Server (NTRS)

    Lal, Ravindra

    1994-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-11-01

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

  17. Direct Observation of Reversible Electronic Energy Transfer Involving an Iridium Center

    PubMed Central

    2014-01-01

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

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

    SciTech Connect

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

    2007-06-01

    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.

  19. 49 CFR 40.67 - When and how is a directly observed collection conducted?

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... other specimen. (g) As the collector, you must ensure that the observer is the same gender as the employee. You must never permit an opposite gender person to act as the observer. The observer can be a... else is to observe the collection (e.g., in order to ensure a same gender observer), you must...

  20. Direct observation of infrared free induction decay of liquid water molecules with a femtosecond OPO at 3 micron

    SciTech Connect

    Crowell, R.A.; Holtom, G.R.; Xie, S.X.

    1994-05-01

    The infrared vibrational quantum beats of solution phase water molecules are directly observed at room temperature by up-coverting the free induction decay generated with a femtosecond optical parametric oscilator.

  1. Direct observations of seasonal exchange through the Bab el Mandab Strait

    NASA Astrophysics Data System (ADS)

    Murray, Stephen P.; Johns, William

    The exchange flow between the Red Sea and the Gulf of Aden-Indian Ocean through the Bab el Mandab Strait was measured continuously for 10 months, June 1995-March 1996. ADCP and temperature-salinity chain moorings allow an unprecedented look at the magnitude and seasonal evolution of the inflow layer from the Gulf of Aden, and the high salinity outflow layer from the Red Sea. The timing, structure, and evolution of the summer season mid-depth intrusion of cold, low salinity water into the Red Sea from the Gulf of Aden is measured for the complete intrusion cycle of 1995. We unexpectedly find the deep outflow still strong in June 1995, with speeds of 0.6 m/sec and transport of 0.4 Sv (1 Sv = 106 m/sec). From July to mid-September, the deep outflow persists but is attenuated to speeds of 0.2 m/sec and transport of 0.05 Sv. The dominant summer feature, the cold low salinity intermediate layer intrusion, persists for 3 months, occupies 70% of the water column in the Strait and carries approximately 1.7 1012 m of cold nutrient-rich water into the Red Sea. The winter regime begins in mid-September, is fully developed by early November, and continues to the end of our first observation interval in March 1996. Speeds in the lower layer are 0.8-1.0 m/sec and 0.4-0.6 m/sec in the upper layer. At maximum exchange in mid-February, outflow transport reaches 0.7 Sv. Ubiquitous oscillations in current and salinity at synoptic and intraseasonal periods appear closely related to fluctuations in the along-channel wind forcing and perhaps to coastally-trapped waves.

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

    SciTech Connect

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

    2014-02-11

    The prevalent approach to developing new nanomaterials is a trial and error process of iteratively altering synthesis procedures and then characterizing the resulting nanostructures. This is fundamentally limited in that the growth processes that occur during synthesis can only be inferred from the final synthetic structure. Directly observing real-time nanomaterial growth provides unprecedented insight into the relationship between synthesis conditions and product evolution, and facilitates a mechanistic approach to nanomaterial development. Here we use in situ liquid stage scanning transmission electron microscopy to observe the growth of mesoporous palladium in a solvated block copolymer (BCP) template under various synthesis conditions, and ultimately determine a refined synthesis procedure that yields ordered pores. We find that at low organic solvent (tetrahydrofuran, THF) content, the BCP assembles into a rigid, cylindrical micelle array with a high degree of short-range order, but poor long-range order. Upon slowing the THF evaporation rate using a solvent-vapor anneal step, the long-range order is greatly improved. The electron beam induces nucleation of small particles in the aqueous phase around the micelles. The small particles then flocculate and grow into denser structures that surround the micelles, forming an ordered mesoporous structure. The microscope observations revealed that template disorder can be addressed prior to reaction, and is not invariably induced by the growth process itself, allowing us to more quickly optimize the synthetic method. This work was conducted in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. The Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy under contract DE-AC05-76RL01830. This research was funded in part by: the Presidential Early Career Award for Scientist and Engineers for I.A., the University of California Academic Senate and the University of California Laboratory fee research grant, the Laboratory-Directed Research and Development program at Sandia National Laboratories, and the Chemical Imaging Initiative at Pacific Northwest National Laboratory. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    Mineralization of CO2 is regarded as the safest and most permanent option for carbon sequestration (e.g., O'Connor et al. 2005). So far, research has been concentrated on the carbonation of silicates such as olivine ((Mg,Fe)2SiO4) and serpentine (Mg3Si2O5(OH)4). However, also the less common hydroxide mineral brucite (Mg(OH)2) has recently become a focus of interest, owing to its much higher reactivity relative to silicate minerals at low temperature and P CO2 conditions(e.g., Zhao et al. 2010; Schaef et al. 2011). Utilization of brucite for carbon sequestration requires an in-depth understanding of the associated reaction mechanisms from the macro- to the nano-scale. Therefore, we have conducted a series of in-situ and ex-situ Atomic Force Microscopy (AFM) experiments enabling direct nano-scale observations of dissolution and precipitation features on brucite (001) cleavage surfaces. In particular, we tested the effects of pH (2-12), aqueous NaHCO3 concentration (1?M - 1M) and P CO2 (0-1 bar) on brucite dissolution and carbonation. Brucite dissolution proceeded by the formation and spreading of etch pits with equilateral triangular shapes. Measured etch pit spreading rates increased with decreasing pH (from 0.0300.008 nm/s at pH 9 to 0.700.07 nm/s at pH 2) and increasing NaHCO3 concentration (from 0.0380.004 nm/s in 1?M to 0.380.07 nm/s in 1M solution). In pure NaHCO3 solutions (pH 7.2-9.3) secondary phase precipitation was relatively minor. Enhanced precipitation was observed in slightly acidified NaHCO3 solutions (pH 5) as well as in solutions that were equilibrated with 1 bar CO2 (pH 4). Nucleation predominantly occurred in areas of high dissolution such as larger step edges. Initially, nucleating particles were only 1-2 nm and weakly attached to the brucite surface as they could be easily pushed away by the scanning tip during in-situ AFM experiments. Growth of the particles was observed after ex-situ AFM experiments lasting for several hours. The size of individual particles increased to about 100 nm within 16 h. Lateral spreading of the particles was rather limited. Instead, we observed the formation of particle clusters reaching total heights of up to 1 ?m after 32 h. SEM-EDX investigations confirmed that the precipitate is an Mg-rich carbonate phase (probably hydromagnesite). Our results contribute to an improved understanding of the mechanism of aqueous brucite carbonation at low temperature and P CO2 conditions and to a further understanding of carbonation reactions in general.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  6. Gulf Stream Power Characteristics near Cape Hatteras; Regional Model vs. Direct Current Observations

    NASA Astrophysics Data System (ADS)

    Lowcher, C.; Bane, J.; Gong, Y.; He, R.; Muglia, M.

    2014-12-01

    The Gulf Stream has current velocities reaching approximately 2 meters per second, which distinguish it as a potential source of marine hydrokinetic (MHK) energy. The upper continental slope off Cape Hatteras is a desirable area for development of offshore renewable energy because of the closeness of the Gulf Stream to the shelf edge and its minimal meanderings there. Using data from a moored 150-kHz ADCP and from the Mid-Atlantic Bight and South Atlantic Bight (MABSAB) ocean circulation model, MHK power characteristics have been computed for this area. These calculations quantify the Gulf Stream power resource and its temporal and spatial variations. During August 2013 - April 2014 at the moored ADCP site 30 meters below the surface and within the Stream's cyclonic shear zone, a comparison of the ADCP and MABSAB model reveals that the average current speeds from the two sources are nearly identical and have a magnitude of 1.15 m/s. A comparison for the same time period was made for Betz power, which yielded an observed average of 0.8 kW/m2 and a model average of 0.7 kW/m2, a difference of about 13%. The model has shown to be more conservative than the ADCP in its computation of current speed and Betz power, and it shows somewhat less variability than the ADCP in directionality of the Stream. Additionally, model data have been used to calculate annual average vector velocities and yearly Betz power averages for a number of years, and at various locations over the NC continental slope. These results depict the variation of the Stream's position along the NC coastline over the most recent years, and show that yearly averaged Betz power at a given location has significant inter-annual variations, with average power during one year being nearly four times greater than in another year.

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

    SciTech Connect

    Paffenhoefer, G.A.; Lewis, K.D.; Bundy, M.H. |; Metz, C.

    1995-12-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

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

  9. Video Allows Young Scientists New Ways to Be Seen

    ERIC Educational Resources Information Center

    Park, John C.

    2009-01-01

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

  10. Direct Observation of Secondary Organic Aerosol Formation during Cloud Condensation-Evaporation Cycles (SOAaq) in Simulation Chamber Experiments

    NASA Astrophysics Data System (ADS)

    Doussin, J. F.; Bregonzio-Rozier, L.; Giorio, C.; Siekmann, F.; Gratien, A.; Temime-Roussel, B.; Ravier, S.; Pangui, E.; Tapparo, A.; Kalberer, M.; Monod, A.

    2014-12-01

    Biogenic volatile organic compounds (BVOCs) undergo many reactions in the atmosphere and form a wide range of oxidised and water-soluble compounds. These compounds can partition into atmospheric water droplets, and react within the aqueous phase producing higher molecular weight and/or less volatile compounds which can remain in the particle phase after water evaporation and thus increase the organic aerosol mass (Ervens et al., 2011; Altieri et al., 2008; Couvidat et al., 2013). While this hypothesis is frequently discussed in the literature, so far, almost no direct observations of such a process have been provided.The aim of the present work is to study SOA formation from isoprene photooxidation during cloud condensation-evaporation cycles.The experiments were performed during the CUMULUS project (CloUd MULtiphase chemistry of organic compoUndS in the troposphere), in the CESAM simulation chamber located at LISA. CESAM is a 4.2 m3 stainless steel chamber equipped with realistic irradiation sources and temperature and relative humidity (RH) controls (Wang et al., 2011). In each experiment, isoprene was allowed to oxidize during several hours in the presence on nitrogen oxides under dry conditions. Gas phase compounds were analyzed on-line by a Proton Transfer Reaction Time of Flight Mass Spectrometer (PTR-ToF-MS), a Fourier Transform Infrared Spectrometer (FTIR), NOx and O3 analyzers. SOA formation was monitored on-line with a Scanning Mobility Particle Sizer (SMPS) and an Aerodyne High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS). The experimental protocol was optimised to generate cloud events in the simulation chamber, which allowed us to generate clouds lasting for ca. 10 minutes in the presence of light.In all experiments, we observed that during cloud formation, water-soluble gas-phase oxidation products (e.g., methylglyoxal, hydroxyacetone, acetaldehyde, formic acid, acetic acid and glycolaldehyde) readily partitioned into cloud droplets and new SOA mass was promptly produced which partly persisted after cloud evaporation. Chemical composition, elemental ratios and density of SOA, measured with the HR-ToF-AMS, were compared before, during cloud formation and after cloud evaporation.

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

    NASA Astrophysics Data System (ADS)

    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

    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 100nm 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.

  12. The Biasing Effects of Labels on Direct Observation by Preservice Teachers

    ERIC Educational Resources Information Center

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

    2011-01-01

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

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  14. Allowables for Structural Composites

    NASA Technical Reports Server (NTRS)

    Netles, Alan T.

    2004-01-01

    In order to obtain the most benefit from building a structure with composite laminates, the strength of the laminate must be known. Based on the "weakest link" theory, the lower strength numbers obtained from testing are the ones to be used for design and analysis. The strength value to be used is determined by a statistical analysis of the test data, and is known as an allowable. MIL-HDBK- 17 outlines procedures to follow for determining these allowables. There are two types of statistically determined allowables, A- Basis and B-Basis. A-Basis is defined as a strength value at which only 1 in 100 specimens will fail with a 95% confidence level. B-Basis is a strength value at which only 10 in 100 specimens will fail with a 95% confidence level. As more specimens are tested a higher value of strength can be used as a valid allowable. Composites are highly process dependent and show much strength variation with environment, so it is critical to test materials and environments that are representative of hardware. Either using data obtained from a previous test series, or extrapolation to a certain temperature is highly discouraged.

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

    NASA Astrophysics Data System (ADS)

    Kumar, Sugam; Aswal, V. K.

    2010-12-01

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

  16. Direct Observations of Children at Risk for Academic Failure: Benefits of an Intergenerational Visiting Program

    ERIC Educational Resources Information Center

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

    2004-01-01

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

  17. Direct observation and partial-width measurement of ?? decay of charmonium states

    NASA Astrophysics Data System (ADS)

    Baglin, C.; Baird, S.; Bassompierre, G.; Borreani, G.; Brient, J.-C.; Broll, C.; Brom, J.-M.; Bugge, L.; Buran, T.; Burq, J.-P.; Bussire, A.; Buzzo, A.; Cester, R.; Chemarin, M.; Chevallier, M.; Escoubes, B.; Fay, J.; Ferroni, S.; Gracco, V.; Guillaud, J.-P.; Khan-Aronsen, E.; Ille, B.; Kirsebom, K.; Lambert, M.; Leistam, L.; Lundby, A.; Macri, M.; Marchetto, F.; Menichetti, E.; Mrch, Ch.; Mouellic, B.; Pastrone, N.; Petrillo, L.; Pia, M. G.; Poole, J.; Poulet, M.; Rinaudo, G.; Santroni, A.; Severi, M.; Skjevling, G.; Stugu, B.

    1987-03-01

    As part of the charmonium formation experiment at the CERN Intersecting Storage Rings, we studied the reaction pp-->cc-->?? in an antiproton momentum scan through the ?c, ?1, and ?2 regions. We report events observed in the ?c and ?2 regions, whilst no event was observed in the ?1 region, as expected for a spin-1 state.

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

    ERIC Educational Resources Information Center

    Rork, Kristine E.; Morris, Tracy L.

    2009-01-01

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

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

    SciTech Connect

    Forsyth, R.J.; Balogh, A.; Smith, E.J.; Murphy, N.; McComas, D.J.

    1996-07-01

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

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

    ERIC Educational Resources Information Center

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

    2010-01-01

    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

  1. Observation of a time modulated muon flux in the direction of Cygnus X-3

    NASA Astrophysics Data System (ADS)

    Battistoni, G.; Bellotti, E.; Bloise, C.; Bologna, G.; Campana, P.; Castagnoli, C.; Castellina, A.; Chiarella, V.; Ciocio, A.; Cundy, D.; D'Ettorre-Piazzoli, B.; Fiorini, E.; Galeotti, P.; Iarocci, E.; Liguori, C.; Mannocchi, G.; Murtas, G.; Negri, P.; Nicoletti, G.; Picchi, P.; Price, M.; Pullia, A.; Ragazzi, S.; Rollier, M.; Saavedra, O.; Satta, L.; Serri, P.; Vernetto, S.; Zanotti, L.

    1985-06-01

    The analysis of angular and phase distribution is reported for high energy muons recorded in the NUSEX nucleon decay detector, located in the Mont Blanc tunnel at a depth of about 5000 hg of standard rock. Evidence is found for a signal correlated to the direction and time modulation of Cygnus X-3.

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

    NASA Astrophysics Data System (ADS)

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

    2008-02-01

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

  3. Observation of direct hadronic pairs in nucleus-nucleus collisions in JACEE emulsion chambers

    NASA Technical Reports Server (NTRS)

    Burnett, T. H.; Dake, S.; Fuki, M.; Gregory, J. C.; Hayashi, T.; Hayashi, T.; Holynski, R.; Iwai, J.; Jones, W. V.; Jurak, A.

    1985-01-01

    In a number of high energy ( or = 1 TeV/amu) nucleus-nucleus collisions observed in Japanese-American Cooperative Emulsion Experiment (JACEE) emulsion chambers, nonrandom spatial association of produced charged particles, mostly hadronic pairs, are observed. Similar narrow pairs are observed in about 100 events at much low energy (20 to 60 GeV/amu). Analysis shows that 30 to 50% of Pair abundances are understood by the Hambury-Brown-Twiss effect, and the remainder seems to require other explanations.

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

    SciTech Connect

    Yoshida, t.

    2010-05-03

    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.

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

    SciTech Connect

    Savani, N. P.; Owens, M. J.; Forsyth, R. J.; Rouillard, A. P.; Davies, J. A.

    2010-05-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

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

  7. Direct Observation of an Anomalous Spinel-to-Layered Phase Transition Mediated by Crystal Water Intercalation.

    PubMed

    Kim, Sangryun; Nam, Kwan Woo; Lee, Soyeon; Cho, Woosuk; Kim, Joo-Seong; Kim, Byung Gon; Oshima, Yoshifumi; Kim, Ju-Sik; Doo, Seok-Gwang; Chang, Hyuk; Aurbach, Doron; Choi, Jang Wook

    2015-12-01

    The phase transition of layered manganese oxides to spinel phases is a well-known phenomenon in rechargeable batteries and is the main origin of the capacity fading in these materials. This spontaneous phase transition is associated with the intrinsic properties of manganese, such as its size, preferred crystal positions, and reaction characteristics, and it is therefore very difficult to avoid. The introduction of crystal water by an electrochemical process enables the inverse phase transition from spinel to a layered Birnessite structure. Scanning transmission electron microscopy can be used to directly visualize the rearrangement of lattice atoms, the simultaneous insertion of crystal water, the formation of a transient structure at the phase boundary, and layer-by-layer progression of the phase transition from the edge. This research indicates that crystal water intercalation can reverse phase transformation with thermodynamically favored directionality. PMID:26474337

  8. Direct experimental observation of weakly-bound character of the attached electron in europium anion

    PubMed Central

    Cheng, Shi-Bo; Castleman, A. W.

    2015-01-01

    Direct experimental determination of precise electron affinities (EAs) of lanthanides is a longstanding challenge to experimentalists. Considerable debate exists in previous experiment and theory, hindering the complete understanding about the properties of the atomic anions. Herein, we report the first precise photoelectron imaging spectroscopy of europium (Eu), with the aim of eliminating prior contradictions. The measured EA (0.116??0.013?eV) of Eu is in excellent agreement with recently reported theoretical predictions, providing direct spectroscopic evidence that the additional electron is weakly attached. Additionally, a new experimental strategy is proposed that can significantly increase the yield of the lanthanide anions, opening up the best opportunity to complete the periodic table of the atomic anions. The present findings not only serve to resolve previous discrepancy but also will help in improving the depth and accuracy of our understanding about the fundamental properties of the atomic anions. PMID:26198741

  9. Direct experimental observation of weakly-bound character of the attached electron in europium anion.

    PubMed

    Cheng, Shi-Bo; Castleman, A W

    2015-01-01

    Direct experimental determination of precise electron affinities (EAs) of lanthanides is a longstanding challenge to experimentalists. Considerable debate exists in previous experiment and theory, hindering the complete understanding about the properties of the atomic anions. Herein, we report the first precise photoelectron imaging spectroscopy of europium (Eu), with the aim of eliminating prior contradictions. The measured EA (0.116 ± 0.013 eV) of Eu is in excellent agreement with recently reported theoretical predictions, providing direct spectroscopic evidence that the additional electron is weakly attached. Additionally, a new experimental strategy is proposed that can significantly increase the yield of the lanthanide anions, opening up the best opportunity to complete the periodic table of the atomic anions. The present findings not only serve to resolve previous discrepancy but also will help in improving the depth and accuracy of our understanding about the fundamental properties of the atomic anions. PMID:26198741

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

    SciTech Connect

    Rahbarnia, Kian; Brown, Benjamin P.; Clark, Mike M.; Kaplan, Elliot J.; Nornberg, Mark D.; Rasmus, Alex M.; Taylor, Nicholas Zane; Forest, Cary B.; Jenko, Frank; Limone, Angelo; Pinton, Jean-Francois; Plihon, Nicolas; Verhille, Gautier

    2012-11-10

    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.

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

    SciTech Connect

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

    2009-01-22

    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.

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

    SciTech Connect

    Garofalo, A.M.; Bialek, J.; Navratil, G.A.; Sabbagh, S.A.; 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.; Austin, M.E.; Comer, K.J.; Fredrickson, E.D.; Lazarus, E.A.; Rice, B.W.

    1999-05-01

    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}

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

    SciTech Connect

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

    2009-01-22

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

  14. Direct ECC Bypass Phenomena During LBLOCA Reflood Phase Observed in the MIDAS Test: Facility

    SciTech Connect

    Yun, B.J.; Kwon, T.S.; Euh, D.J.; Chu, I.C.; Song, C.H.; Park, J.K.

    2002-07-01

    One of the advanced design features of the APR-1400, direct vessel injection (DVI) system is being considered instead of conventional cold leg injection (CLI) system. It is known that the DVI system greatly enhances the reliability of the emergency core cooling (ECC) system. However, there is still a dispute on its performance in terms of water delivery to the reactor core during the reflood phase of a large-break loss-of-coolant accident (LOCA). Thus, experimental validation is in progress. In this paper, test results of a direct ECC bypass performed in the steam-water test facility called MIDAS (Multi-dimensional Investigation in Downcomer Annulus Simulation) is presented. The test condition is determined, based on the preliminary analysis of TRAC code, by applying the 'modified linear scaling method' with the 1/4.93 length scale. From the tests, ECC direct bypass fraction, steam condensation rate and information on the flow distribution in the upper annulus downcomer region is obtained. (authors)

  15. Direct observations of plasma upflows and condensation in a catastrophically cooling solar transition region loop

    SciTech Connect

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

    2013-12-01

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

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

    PubMed

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

    2014-12-19

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

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

    SciTech Connect

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

    2005-06-14

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

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

    SciTech Connect

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

    2007-10-10

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    USGS Publications Warehouse

    U.S. Geological Survey

    1892-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Wendt, Verena; Wst, Sabine; Bittner, Michael

    2013-04-01

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

  2. Observations of wind direction by automated analysis of images from Mars and the MSL rover

    NASA Astrophysics Data System (ADS)

    Francis, Raymond; Moores, John; McIsaac, Kenneth; Choi, David; Osinski, Gordon

    2014-02-01

    Past missions to Mars have revealed the presence of clouds in the atmosphere, visible both from the surface and from orbit. Where atmospheric sounding instrumentation is not available, the motion of such clouds can be used as a proxy for wind observations. Such observations aid in the study of the Martian climate, as well as of mass and moisture transport in the atmosphere. An understanding of the water cycle on Mars has important implications for models of the transport, distribution, and preservation of any biomarkers which might exist from past or present life on the planet.

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

    NASA Technical Reports Server (NTRS)

    Ivory, K.; Schwenn, R.

    1995-01-01

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

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

    ERIC Educational Resources Information Center

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

    2006-01-01

    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…

  5. Azimuthal instability of the interface in a shear banded flow by direct visual observation.

    PubMed

    Decruppe, J P; Bcu, L; Greffier, O; Fazel, N

    2010-12-17

    The stability of the shear banded flow of a Maxwellian fluid is studied from an experimental point of view using rheology and flow visualization with polarized light. We show that the one-layer homogeneous flow cannot sustain shear rates corresponding to the end of the stress plateau. The high shear rate branch is not found and the shear stress oscillates at the end of the plateau. An azimuthal instability appears: the shear induced band becomes unstable and the interface between the two bands undulates in time and space with a period ?, a wavelength ? and a wave vector k parallel to the direction of the tangential velocity. PMID:21231629

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

    SciTech Connect

    Vorobyev, A.Y.; Guo Chunlei

    2005-01-03

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

  7. Direct Observation of Electrostatically Driven Band Gap Renormalization in a Degenerate Perovskite Transparent Conducting Oxide.

    PubMed

    Lebens-Higgins, Z; Scanlon, D O; Paik, H; Sallis, S; Nie, Y; Uchida, M; Quackenbush, N F; Wahila, M J; Sterbinsky, G E; Arena, Dario A; Woicik, J C; Schlom, D G; Piper, L F J

    2016-01-15

    We have directly measured the band gap renormalization associated with the Moss-Burstein shift in the perovskite transparent conducting oxide (TCO), La-doped BaSnO_{3}, using hard x-ray photoelectron spectroscopy. We determine that the band gap renormalization is almost entirely associated with the evolution of the conduction band. Our experimental results are supported by hybrid density functional theory supercell calculations. We determine that unlike conventional TCOs where interactions with the dopant orbitals are important, the band gap renormalization in La-BaSnO_{3} is driven purely by electrostatic interactions. PMID:26824566

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

    NASA Astrophysics Data System (ADS)

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

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

  9. Observation and interpretation of energy efficient, diffuse direct current glow discharge at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Tang, Jie; Jiang, Weiman; Li, Jing; Wang, Yishan; Zhao, Wei; Duan, Yixiang

    2015-08-01

    A diffuse direct-current glow discharge was realized with low energy consumption and high energy utilization efficiency at atmospheric pressure. The formation of diffuse discharge was demonstrated by examining and comparing the electrical properties and optical emissions of plasmas. In combination with theoretical derivation and calculation, we draw guidelines that appearance of nitrogen ions at low electron density is crucial to enhance the ambipolar diffusion for the expansion of discharge channel and the increasing ambipolar diffusion near the cathode plays a key role in the onset of diffuse discharge. An individual-discharge-channel expansion model is proposed to explain the diffuse discharge formation.

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  11. DIRECT OBSERVATION OF A SHARP TRANSITION TO COHERENCE IN DENSE CORES

    SciTech Connect

    Pineda, Jaime E.; Goodman, Alyssa A.; Foster, Jonathan B.; Myers, Philip C.; Arce, Hector G.; Caselli, Paola; Rosolowsky, Erik W.

    2010-03-20

    We present NH{sub 3} observations of the B5 region in Perseus obtained with the Green Bank Telescope. The map covers a region large enough ({approx}11'x14') that it contains the entire dense core observed in previous dust continuum surveys. The dense gas traced by NH{sub 3}(1,1) covers a much larger area than the dust continuum features found in bolometer observations. The velocity dispersion in the central region of the core is small, presenting subsonic non-thermal motions which are independent of scale. However, it is because of the coverage and high sensitivity of the observations that we present the detection, for the first time, of the transition between the coherent core and the dense but more turbulent gas surrounding it. This transition is sharp, increasing the velocity dispersion by a factor of 2 in less than 0.04 pc (the 31'' beam size at the distance of Perseus, {approx}250 pc). The change in velocity dispersion at the transition is {approx}3 km s{sup -1} pc{sup -1}. The existence of the transition provides a natural definition of dense core: the region with nearly constant subsonic non-thermal velocity dispersion. From the analysis presented here, we can neither confirm nor rule out a corresponding sharp density transition.

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

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

    ERIC Educational Resources Information Center

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

    2014-01-01

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

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

    ERIC Educational Resources Information Center

    Soini, Anne; Villberg, Jari; Skslahti, Arja; Gubbels, Jessica; Mehtl, Anette; Kettunen, Tarja; Poskiparta, Marita

    2014-01-01

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

  15. Direct observation of titanium-centered octahedra in titanium–antimony–tellurium phase-change material

    PubMed Central

    Rao, Feng; Song, Zhitang; Cheng, Yan; Liu, Xiaosong; Xia, Mengjiao; Li, Wei; Ding, Keyuan; Feng, Xuefei; Zhu, Min; Feng, Songlin

    2015-01-01

    Phase-change memory based on Ti0.4Sb2Te3 material has one order of magnitude faster Set speed and as low as one-fifth of the Reset energy compared with the conventional Ge2Sb2Te5 based device. However, the phase-transition mechanism of the Ti0.4Sb2Te3 material remains inconclusive due to the lack of direct experimental evidence. Here we report a direct atom-by-atom chemical identification of titanium-centered octahedra in crystalline Ti0.4Sb2Te3 material with a state-of-the-art atomic mapping technology. Further, by using soft X-ray absorption spectroscopy and density function theory simulations, we identify in amorphous Ti0.4Sb2Te3 the titanium atoms preferably maintain the octahedral configuration. Our work may pave the way to more thorough understanding and tailoring of the nature of the Ti–Sb–Te material, for promoting the development of dynamic random access memory-like phase-change memory as an emerging storage-class memory to reform current memory hierarchy. PMID:26610374

  16. Direct observation of titanium-centered octahedra in titanium-antimony-tellurium phase-change material.

    PubMed

    Rao, Feng; Song, Zhitang; Cheng, Yan; Liu, Xiaosong; Xia, Mengjiao; Li, Wei; Ding, Keyuan; Feng, Xuefei; Zhu, Min; Feng, Songlin

    2015-01-01

    Phase-change memory based on Ti0.4Sb2Te3 material has one order of magnitude faster Set speed and as low as one-fifth of the Reset energy compared with the conventional Ge2Sb2Te5 based device. However, the phase-transition mechanism of the Ti0.4Sb2Te3 material remains inconclusive due to the lack of direct experimental evidence. Here we report a direct atom-by-atom chemical identification of titanium-centered octahedra in crystalline Ti0.4Sb2Te3 material with a state-of-the-art atomic mapping technology. Further, by using soft X-ray absorption spectroscopy and density function theory simulations, we identify in amorphous Ti0.4Sb2Te3 the titanium atoms preferably maintain the octahedral configuration. Our work may pave the way to more thorough understanding and tailoring of the nature of the Ti-Sb-Te material, for promoting the development of dynamic random access memory-like phase-change memory as an emerging storage-class memory to reform current memory hierarchy. PMID:26610374

  17. Direct observation of titanium-centered octahedra in titanium-antimony-tellurium phase-change material

    NASA Astrophysics Data System (ADS)

    Rao, Feng; Song, Zhitang; Cheng, Yan; Liu, Xiaosong; Xia, Mengjiao; Li, Wei; Ding, Keyuan; Feng, Xuefei; Zhu, Min; Feng, Songlin

    2015-11-01

    Phase-change memory based on Ti0.4Sb2Te3 material has one order of magnitude faster Set speed and as low as one-fifth of the Reset energy compared with the conventional Ge2Sb2Te5 based device. However, the phase-transition mechanism of the Ti0.4Sb2Te3 material remains inconclusive due to the lack of direct experimental evidence. Here we report a direct atom-by-atom chemical identification of titanium-centered octahedra in crystalline Ti0.4Sb2Te3 material with a state-of-the-art atomic mapping technology. Further, by using soft X-ray absorption spectroscopy and density function theory simulations, we identify in amorphous Ti0.4Sb2Te3 the titanium atoms preferably maintain the octahedral configuration. Our work may pave the way to more thorough understanding and tailoring of the nature of the Ti-Sb-Te material, for promoting the development of dynamic random access memory-like phase-change memory as an emerging storage-class memory to reform current memory hierarchy.

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

    PubMed

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

    2012-09-18

    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?HO hydrogen bonds. Hydrogen bonding networks that are ambiguous in the 0.85 ? ultrahigh resolution X-ray structure can be resolved by accurate orientation of water molecules. Furthermore, the high resolution of the reported structure has allowed for the anisotropic description of 36 deuterium atoms in the protein. The visibility of hydrogen and deuterium atoms in the nuclear density maps is discussed in relation to the resolution of the neutron data. PMID:22949690

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

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

    SciTech Connect

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

    2014-10-27

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

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

    PubMed

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

    2013-08-26

    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

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

    PubMed Central

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

    2014-01-01

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

  3. Evidence of L10 chemical order in CoPt nanoclusters: Direct observation and magnetic signature

    NASA Astrophysics Data System (ADS)

    Tournus, Florent; Tamion, Alexandre; Blanc, Nils; Hannour, Abdelkrim; Bardotti, Laurent; Prvel, Brigitte; Ohresser, Philippe; Bonet, Edgar; Epicier, Thierry; Dupuis, Vronique

    2008-04-01

    We report the synthesis and characterization of well-defined CoPt clusters with a mean diameter of 3 nm, produced in ultrahigh vacuum conditions following a physical route. Samples made of diluted layers of CoPt clusters embedded in amorphous carbon have been studied by transmission electron microscopy. High-resolution observations have revealed the appearance of L10 chemical order upon annealing, even for clusters with a 2 nm diameter, without cluster coalescence. The magnetic properties of both chemically disordered and ordered CoPt clusters embedded in amorphous carbon have then been measured by x-ray magnetic circular dichroism and superconducting quantum interference device magnetometry. Despite a striking change of the Co magnetic moment, the magnetic anisotropy of chemically ordered nanoparticles increases, with respect to the chemically disordered A1 phase, in much lower proportions than what is observed for the bulk.

  4. Direct in situ observations of single Fe atom catalytic processes and anomalous diffusion at graphene edges.

    PubMed

    Zhao, Jiong; Deng, Qingming; Avdoshenko, Stanislav M; Fu, Lei; Eckert, Jrgen; Rmmeli, Mark H

    2014-11-01

    Single-atom catalysts are of great interest because of their high efficiency. In the case of chemically deposited sp(2) carbon, the implementation of a single transition metal atom for growth can provide crucial insight into the formation mechanisms of graphene and carbon nanotubes. This knowledge is particularly important if we are to overcome fabrication difficulties in these materials and fully take advantage of their distinct band structures and physical properties. In this work, we present atomically resolved transmission EM in situ investigations of single Fe atoms at graphene edges. Our in situ observations show individual iron atoms diffusing along an edge either removing or adding carbon atoms (viz., catalytic action). The experimental observations of the catalytic behavior of a single Fe atom are in excellent agreement with supporting theoretical studies. In addition, the kinetics of Fe atoms at graphene edges are shown to exhibit anomalous diffusion, which again, is in agreement with our theoretical investigations. PMID:25331874

  5. Direct in situ observations of single Fe atom catalytic processes and anomalous diffusion at graphene edges

    PubMed Central

    Zhao, Jiong; Deng, Qingming; Avdoshenko, Stanislav M.; Fu, Lei; Eckert, Jrgen; Rmmeli, Mark H.

    2014-01-01

    Single-atom catalysts are of great interest because of their high efficiency. In the case of chemically deposited sp2 carbon, the implementation of a single transition metal atom for growth can provide crucial insight into the formation mechanisms of graphene and carbon nanotubes. This knowledge is particularly important if we are to overcome fabrication difficulties in these materials and fully take advantage of their distinct band structures and physical properties. In this work, we present atomically resolved transmission EM in situ investigations of single Fe atoms at graphene edges. Our in situ observations show individual iron atoms diffusing along an edge either removing or adding carbon atoms (viz., catalytic action). The experimental observations of the catalytic behavior of a single Fe atom are in excellent agreement with supporting theoretical studies. In addition, the kinetics of Fe atoms at graphene edges are shown to exhibit anomalous diffusion, which again, is in agreement with our theoretical investigations. PMID:25331874

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  7. Direct observation of an attosecond electron wave packet in a nitrogen molecule.

    PubMed

    Okino, Tomoya; Furukawa, Yusuke; Nabekawa, Yasuo; Miyabe, Shungo; Amani Eilanlou, A; Takahashi, Eiji J; Yamanouchi, Kaoru; Midorikawa, Katsumi

    2015-09-01

    Capturing electron motion in a molecule is the basis of understanding or steering chemical reactions. Nonlinear Fourier transform spectroscopy using an attosecond-pump/attosecond-probe technique is used to observe an attosecond electron wave packet in a nitrogen molecule in real time. The 500-as electronic motion between two bound electronic states in a nitrogen molecule is captured by measuring the fragment ions with the same kinetic energy generated in sequential two-photon dissociative ionization processes. The temporal evolution of electronic coherence originating from various electronic states is visualized via the fragment ions appearing after irradiation of the probe pulse. This observation of an attosecond molecular electron wave packet is a critical step in understanding coupled nuclear and electron motion in polyatomic and biological molecules to explore attochemistry. PMID:26601262

  8. Direct observation of an attosecond electron wave packet in a nitrogen molecule

    PubMed Central

    Okino, Tomoya; Furukawa, Yusuke; Nabekawa, Yasuo; Miyabe, Shungo; Amani Eilanlou, A.; Takahashi, Eiji J.; Yamanouchi, Kaoru; Midorikawa, Katsumi

    2015-01-01

    Capturing electron motion in a molecule is the basis of understanding or steering chemical reactions. Nonlinear Fourier transform spectroscopy using an attosecond-pump/attosecond-probe technique is used to observe an attosecond electron wave packet in a nitrogen molecule in real time. The 500-as electronic motion between two bound electronic states in a nitrogen molecule is captured by measuring the fragment ions with the same kinetic energy generated in sequential two-photon dissociative ionization processes. The temporal evolution of electronic coherence originating from various electronic states is visualized via the fragment ions appearing after irradiation of the probe pulse. This observation of an attosecond molecular electron wave packet is a critical step in understanding coupled nuclear and electron motion in polyatomic and biological molecules to explore attochemistry. PMID:26601262

  9. Direct observation of rapid impulsive electron heating during a beam plasma interaction

    NASA Astrophysics Data System (ADS)

    Boswell, R. W.; Hamberger, S. M.; Morey, I.; Porteous, R. K.; Kellogg, P. J.

    1984-04-01

    A beam of electrons injected into low-density gas may excite instabilities in the ambient plasma which is produced by collisional ionization. A rapid increase in the ionization rate can result under certain conditions because of a heating of the plasma electrons. The resulting process is usually called 'beam-plasma-discharge' (BPD). The present investigation is concerned with some observations which show that the breakdown occurs as a result of the acceleration of a significant fraction of the background plasma electrons. The acceleration ('heating') is caused by the large amplitude fields of short bursts of electrostatic electron waves which have a small spatial extent. Boswell and Kellogg (1983) have identified the considered type of BPD as BPD1. Attention is given to some detailed observations of BPD1 caused by bursts of monochromatic wave fields.

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

    PubMed

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

    2015-01-01

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

  11. Ultrafast imaging of electronic relaxation in n-propylbenzene: Direct observation of intermediate state.

    PubMed

    Liu, Yuzhu; Gerber, Thomas; Radi, Peter; Knopp, Gregor

    2015-10-01

    The ultrafast dynamics of the second singlet electronically excited state (S2) in n-propylbenzene has been investigated by femtosecond time-resolved photoelectron imaging coupled with photofragmentation spectroscopy. The intermediate state for the deactivation of the S2 state is observed by transient photoelectron kinetic energy distributions and photoelectron angular distributions. An ultrafast electronic relaxation process on timescale of the fitted ?50 fs was observed in the S2 state by time-resolved photoelectron imaging and it is attributed to the S1?S2 internal conversion (IC). The time constant of 1.23 (0.2) ps is determined for the further deactivation of the intermediate S1 state. PMID:25942085

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

    SciTech Connect

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

    2015-03-15

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

  13. Direct observations of the decay of beauty particles into charm particles

    NASA Astrophysics Data System (ADS)

    Albanese, J. P.; Alpe, V.; Aoki, S.; Arnold, R.; Baroni, G.; Barth, M.; Bartley, J. H.; Bertrand, D.; Bertrand-Coremans, G.; Bisi, V.; Breslin, A. C.; Carboni, G.; Chesi, E.; Chiba, K.; Cook, G. S.; Coupland, M.; Crosetti, G.; Davis, D. H.; Dell'Uomo, S.; Di Liberto, S.; Bonnelly, W.; Duff, B. G.; Esten, M. J.; Gamba, D.; Gerke, C.; Hazama, M.; Heymann, F. F.; Hoshino, K.; Imrie, D. C.; Isokane, Y.; Kazuno, M.; Kodama, Y.; Lush, G. J.; Maeda, Y.; Marzari-Chiesa, A.; Mazzoni, M. A.; Meddi, F.; Miyanishi, M.; Montwill, A.; Muciaccia, M. T.; Musset, P.; Nakamura, M.; Nakazawa, K.; Natali, S.; Niu, K.; Niwa, K.; Nuzzo, S.; Ohashi, M.; Piuz, F.; Poulard, G.; Ramello, L.; Riccati, L.; Romano, G.; Roosen, R.; Rosa, G.; Ruggieri, F.; Sato, Y.; Sasaki, H.; Sgarbi, C.; Shibuya, H.; Simone, S.; Sletten, H.; Tasaka, S.; Tesuka, I.; Tomita, Y.; Tovee, D. N.; Trent, P.; Tsuneoka, Y.; Ushida, N.; Yamakawa, O.; Yanagisawa, Y.

    1985-08-01

    The associated production of a pair of beauty particles B - and overlineB0 by a 350 GeV ? - interaction has been observed in an emulsion target inserted in an array of silicon microstrip detectors. Both beauty particles decay into charm particles, both of which are also observed to decay in the emulsion. Two negative muons were identified and their momenta measured in a large muon spectrometer. One muon has a pT of 1.9 GeV/ c and is associated with a beauty particle decay. The other, with a pT of 0.45 GeV/ c is associated with a charm particle decay. The flight times of the two beauty particles are respectively (0.8 0.1) 10 -13 s and (5 +2-1) 10 -13 s. Alternative interpretations of this event have negligible probability.

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

    SciTech Connect

    Rauf, Ijaz A.

    2008-10-06

    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.

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

    SciTech Connect

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

    2008-10-01

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

  16. Direct observation of molecular images of lanthanide phthalocyanines: III. Structural defects.

    PubMed

    Zhang, W P; Kuo, K H; Dorset, D L; Hou, Y F; Ni, J Z

    1989-04-01

    The crystal imperfections in thin films of lanthanide phthalocyanines (LnPc2H, Ln = Nd, Tb, Er, Tm, Yb, and Lu) grown expitaxially on KCl have been observed by molecular imaging. Grain and twin boundaries, stacking faults, point defects, vacancies, mosaic structures, and sometimes even some amorphous islands exist in the well-crystallized specimens. Combined with the results reported earlier, the packing characteristics of planar LnPc2H molecules can be well understood. PMID:2723815

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

    PubMed

    Doveil, Fabrice; Macor, Alessandro; Elskens, Yves

    2006-09-01

    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

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

    SciTech Connect

    Doveil, Fabrice; Macor, Alessandro; Elskens, Yves

    2006-09-15

    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.

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

    SciTech Connect

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

    2000-02-01

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

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

    PubMed

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

    2012-03-27

    Direct imaging of nanoparticle solutions by liquid phase transmission electron microscopy has enabled unique in situ studies of nanoparticle motion and growth. In the present work, we report on real-time formation of two-dimensional nanoparticle arrays in the very low diffusive limit, where nanoparticles are mainly driven by capillary forces and solvent fluctuations. We find that superlattice formation appears to be segregated into multiple regimes. Initially, the solvent front drags the nanoparticles, condensing them into an amorphous agglomerate. Subsequently, the nanoparticle crystallization into an array is driven by local fluctuations. Following the crystallization event, superlattice growth can also occur via the addition of individual nanoparticles drawn from outlying regions by different solvent fronts. The dragging mechanism is consistent with simulations based on a coarse-grained lattice gas model at the same limit. PMID:22360715

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

    SciTech Connect

    Zheng, He; Wu, Shujing; Sheng, Huaping; Liu, Chun; Liu, Yu; Cao, Fan; Zhou, Zhichao; Zhao, Dongshan E-mail: dszhao@whu.edu.cn; Wang, Jianbo E-mail: dszhao@whu.edu.cn; Zhao, Xingzhong

    2014-04-07

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

  2. Direct observation of two-step crystallization in nanoparticle superlattice formation

    SciTech Connect

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

    2011-10-06

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

  3. Feshbach enhanced s-wave scattering of fermions: direct observation with optimized absorption imaging

    NASA Astrophysics Data System (ADS)

    Genkina, D.; Aycock, L. M.; Stuhl, B. K.; Lu, H.-I.; Williams, R. A.; Spielman, I. B.

    2016-01-01

    We directly measured the normalized s-wave scattering cross-section of ultracold 40K atoms across a magnetic-field Feshbach resonance by colliding pairs of degenerate Fermi gases (DFGs) and imaging the scattered atoms. We extracted the scattered fraction for a range of bias magnetic fields, and measured the resonance location to be B 0 = 20.206(15) mT with width ? = 1.0(5) mT. To optimize the signal-to-noise ratio (SNR) of atom number in scattering images, we developed techniques to interpret absorption images in a regime where recoil induced detuning corrections are significant. These imaging techniques are generally applicable to experiments with lighter alkalis that would benefit from maximizing SNR on atom number counting at the expense of spatial imaging resolution.

  4. Direct observation of charge re-distribution in a MgB2 superconductor

    NASA Astrophysics Data System (ADS)

    Wu, Sheng Yun; Shih, Po-Hsun; Ji, Jhong-Yi; Chan, Ting-Shan; Yang, Chun Chuen

    2016-04-01

    To study the origin of negative thermal expansion effects near the superconducting transition temperature TC in MgB2, low-temperature high-energy synchrotron radiation x-ray diffraction was used to probe the charge redistribution near the boron atoms. Our results reveal that the in-plane hole-distribution of B‑ hops through the direct orbital overlap of Mg2+ along the c-axis at 50 K and is re-distributed out-of-plane. This study shows that the out-of-plane π-hole distribution plays a dominant role in the possible origin of superconductivity and negative thermal effects in MgB2.

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  6. Direct observation of the interaction of single fluorescent nucleotide analogue molecules with DNA polymerase I

    NASA Astrophysics Data System (ADS)

    Ye, Jing Yong; Yamane, Yuji; Yamauchi, Masayo; Nakatsuka, Hiroki; Ishikawa, Mitsuru

    2000-04-01

    The interaction of a fluorescent nucleotide analogue, 2'- (or-3')- O-(2,4,6-trinitrophenyl) adenosine 5'-triphosphate (TNP-ATP), with the Klenow fragment of DNA polymerase I (Pol I) was visualized at a single-molecule level. Upon excitation, individual enzyme-TNP-ATP complexes resulted in bright fluorescent spots owing to the increase of the fluorescence quantum yield of TNP-ATP when it bound to the enzyme molecule, whereas unbound TNP-ATP molecules were not visible in the single molecule detection. Thus, we directly investigated the individual interactions of TNP-ATP with the enzyme using single-molecule fluorescence imaging and time-resolved spectroscopy of single enzyme-TNP-ATP complexes without prior separation of the unbound probe molecules.

  7. Direct Observation of Triplet-State Population Dynamics in the RNA Uracil Derivative 1-Cyclohexyluracil.

    PubMed

    Brister, Matthew M; Crespo-Hernández, Carlos E

    2015-11-01

    Investigation of the excited-state dynamics in nucleic acid monomers is an area of active research due to the crucial role these early events play in DNA and RNA photodamage. The dynamics and rate at which the triplet state is populated are key mechanistic pathways yet to be fully elucidated. Direct spectroscopic evidence is presented in this contribution for intersystem crossing dynamics in a uracil derivative, 1-cyclohexyluracil. It is shown that intersystem crossing to the triplet manifold occurs in one picosecond or less in acetonitrile solution-at least an order of magnitude faster than previously estimated experimentally. Broadband transient absorption measurements also reveal the primary electronic relaxation pathways of the uracil chromophore, including the absorption spectra of the (1)ππ*, (1)nπ*, and (3)ππ* states and the rates of vibrational cooling in the ground and (3)ππ* states. The experimental results are supported by density functional calculations. PMID:26538051

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

    SciTech Connect

    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

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2006-12-01

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

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

    NASA Astrophysics Data System (ADS)

    Antn, M.; Romn, R.; Valenzuela, A.; Olmo, F. J.; Alados-Arboledas, L.

    2012-11-01

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

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

    NASA Astrophysics Data System (ADS)

    Antn, M.; Romn, R.; Valenzuela, A.; Olmo, F. J.; Alados-Arboledas, L.

    2013-03-01

    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.

  12. Microsatellite evolutionary rate and pattern in Schistocerca gregaria inferred from direct observation of germline mutations.

    PubMed

    Chapuis, M-P; Plantamp, C; Streiff, R; Blondin, L; Piou, C

    2015-12-01

    Unravelling variation among taxonomic orders regarding the rate of evolution in microsatellites is crucial for evolutionary biology and population genetics research. The mean mutation rate of microsatellites tends to be lower in arthropods than in vertebrates, but data are scarce and mostly concern accumulation of mutations in model species. Based on parent-offspring segregations and a hierarchical Bayesian model, the mean rate of mutation in the orthopteran insect Schistocerca gregaria was estimated at 2.1e(-4) per generation per untranscribed dinucleotide locus. This is close to vertebrate estimates and one order of magnitude higher than estimates from species of other arthropod orders, such as Drosophila melanogaster and Daphnia pulex. We also found evidence of a directional bias towards expansions even for long alleles and exceptionally large ranges of allele sizes. Finally, at transcribed microsatellites, the mean rate of mutation was half the rate found at untranscribed loci and the mutational model deviated from that usually considered, with most mutations involving multistep changes that avoid disrupting the reading frame. Our direct estimates of mutation rate were discussed in the light of peculiar biological and genomic features of S.gregaria, including specificities in mismatch repair and the dependence of its activity to allele length. Shedding new light on the mutational dynamics of grasshopper microsatellites is of critical importance for a number of research fields. As an illustration, we showed how our findings improve microsatellite application in population genetics, by obtaining a more precise estimation of S.gregaria effective population size from a published data set based on the same microsatellites. PMID:26562076

  13. Propagation directions of the mesospheric monochromatic inertial gravity waves observed with a lidar at Starfire Optical Range, New Mexico

    NASA Astrophysics Data System (ADS)

    Hu, Xiong; Gardner, Chester S.; Liu, Alan Z.; Swenson, Gary R.

    2003-03-01

    The University of Illinois Na wind/temperature lidar data collected at the Starfire Optical Range (SOR: 35N, 106.5W), NM, can be used to extract the dominant monochromatic inertial gravity waves and to characterize their features. By using simultaneously measured horizontal wind and temperature profiles the vertical wavelengths, intrinsic periods, and propagation directions can be determined using the hodograph method. A total of 700 waves were analyzed from about 300 h of observations. Waves with vertical wavelengths between 2 and 20 km and intrinsic periods between 1 and 20 h were fully characterized. 84.4% of the waves were propagating upwards. There was a prevailing direction towards the northeast in upward waves horizontal propagations over the year. This prevailing direction existed also in spring, summer and autumn. In winter, most waves propagated to the south and west. The filter theory of gravity waves propagating through the middle atmosphere can be used to give an explanation on the observations. Propagation directions of downward waves showed no prevailing directions over the year. A discussion was given on their different features for different seasons.

  14. Direct observation of stepped proteolipid ring rotation in E. coli FoF1-ATP synthase

    PubMed Central

    Ishmukhametov, Robert; Hornung, Tassilo; Spetzler, David; Frasch, Wayne D

    2010-01-01

    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. PMID:21037553

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

    PubMed

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

    2014-07-01

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

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

    PubMed Central

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

    2014-01-01

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

  17. Direct observation of conductive filament formation in Alq3 based organic resistive memories

    NASA Astrophysics Data System (ADS)

    Busby, Y.; Nau, S.; Sax, S.; List-Kratochvil, E. J. W.; Novak, J.; Banerjee, R.; Schreiber, F.; Pireaux, J.-J.

    2015-08-01

    This work explores resistive switching mechanisms in non-volatile organic memory devices based on tris(8-hydroxyquinolie)aluminum (Alq3). Advanced characterization tools are applied to investigate metal diffusion in ITO/Alq3/Ag memory device stacks leading to conductive filament formation. The morphology of Alq3/Ag layers as a function of the metal evaporation conditions is studied by X-ray reflectivity, while depth profile analysis with X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry is applied to characterize operational memory elements displaying reliable bistable current-voltage characteristics. 3D images of the distribution of silver inside the organic layer clearly point towards the existence of conductive filaments and allow for the identification of the initial filament formation and inactivation mechanisms during switching of the device. Initial filament formation is suggested to be driven by field assisted diffusion of silver from abundant structures formed during the top electrode evaporation, whereas thermochemical effects lead to local filament inactivation.

  18. Direct observation of an abrupt insulator-to-metal transition in dense liquid deuterium

    NASA Astrophysics Data System (ADS)

    Knudson, Marcus; Desjarlais, Michael; Becker, Andeas; Lemke, Raymond; Cochrane, Kyle; Savage, Mark; Bliss, David; Mattsson, Thomas; Redmer, Ronald

    2015-06-01

    Recently a so-called shock-ramp platform has been developed on the Sandia Z Accelerator to access off-Hugoniot states in liquids. The accelerator delivers a two-step current pulse; the first accelerates the electrode to a reasonably constant velocity, which upon impact with the sample cell creates a well-defined shock, the subsequent current rise produces ramp compression from the initially shocked state. This technique generates relatively cool (~1-2 kK), high pressure (>300 GPa), high compression (~10-15 fold compression) states, allowing experimental access to the region of phase space where hydrogen is predicted to undergo a first-order phase transition from an insulating molecular-like liquid to a conducting atomic-like liquid. In this talk we will discuss the experimental platform, survey the various theoretical predictions for the liquid-liquid, insulator-to-metal transition in hydrogen, and present the results of experiments that clearly show an abrupt transition to a metallic state. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  19. Direct observation and simulations of atomically resolved low loss images in graphene

    NASA Astrophysics Data System (ADS)

    Kapetanakis, Myron; Oxley, Mark; Idrobo, Juan-Carlos; Zhou, Wu; Pennycook, Stephen; Pantelides, Sokrates

    2014-03-01

    Aberration-corrected scanning transmission electron microscopy (STEM) at low voltages provides atomic-resolution imaging of many two-dimensional materials, such as pristine graphene, using core-loss and low-loss spectra. Traditionally, EELS-STEM imaging and density functional theory (DFT) simulations were carried out by two different communities with minimal overlap. One community includes diffraction but ignores solid-state effects in the spectra, while the other includes solid-state effects but leaves out diffraction and interference. Recent work has combined DFT calculations and dynamical scattering to allow the simulation of probe position dependent core-loss spectra. In this talk we describe extension of this work to calculations of STEM images based on low-loss spectroscopy. It is usually assumed that such signals are highly delocalized, since plasmons represent a collective excitation. Considering that not all low-loss excitations are plasmonic in nature, we examine the role of interband transitions in the formation of atomic resolution low-loss images. We compare experimental results that show atomic resolution lattice images of graphene based on low-loss signals with simulations of images based on low-loss scattering potentials.

  20. Direct Observation of Phase Transition Dynamics in Suspensions of Soft Colloidal Hydrogel Particles

    NASA Astrophysics Data System (ADS)

    Cho, Jae Kyu; Meng, Zhiyong; Lyon, L. Andrew; Breedveld, Victor

    2008-07-01

    Due to the tunability of their softness and volume as a function of temperature, poly(N-isopropylacrylamide) (pNIPAm) hydrogel particles have emerged as a model system for soft colloidal spheres. By introducing AAc as comonomer, one can also tune the particle volume via pH. We report on the phase behavior of these stimuli-responsive colloids as measured with a microdialysis cell. This device, which integrates microfluidics with Particle Tracking Video-microscopy allows for simple and quick investigation of the phase behavior of suspensions the soft colloidal hydrogel as a function of pH as well as its packing density. In particular, we demonstrate the existence of an unusually broad liquid/crystal coexistence region as a function of effective particle volume fraction. Additionally, we reveal that nonequilibrium jammed states can be created in the coexistence region upon sudden large changes of pH. The phase diagram is indicative of complex interparticle interactions with weakly attractive components.

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

    PubMed Central

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

    2012-01-01

    The 1.1 Å, 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…π 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 Å ultrahigh resolution X-ray structure can be resolved by accurate orientation of water molecules. Furthermore, the high resolution of the reported structure has allowed for the anisotropic description of 36 deuterium atoms in the protein. The visibility of hydrogen and deuterium atoms in the nuclear density maps is discussed in relation to the resolution of the neutron data. PMID:22949690

  2. Direct and instantaneous observation of intravenously injected substances using intravital confocal micro-videography

    PubMed Central

    Matsumoto, Yu; Nomoto, Takahiro; Cabral, Horacio; Matsumoto, Yoko; Watanabe, Sumiyo; Christie, R. James; Miyata, Kanjiro; Oba, Makoto; Ogura, Tadayoshi; Yamasaki, Yuichi; Nishiyama, Nobuhiro; Yamasoba, Tatsuya; Kataoka, Kazunori

    2010-01-01

    We describe the development and application of intravital confocal micro-videography to visualize entrance, distribution, and clearance of drugs within various tissues and organs. We use a Nikon A1R confocal laser scanning microscope system attached to an upright ECLIPSE FN1. The Nikon A1R allows simultaneous four channel acquisition and speed of 30 frames per second while maintaining high resolution of 512 512 scanned points. The key techniques of our intravital imaging are (1) to present a flat and perpendicular surface to the objective lens, and (2) to expose the subject with little or no bleeding to facilitate optical access to multiple tissues and organs, and (3) to isolate the subject from the body movement without compressing the blood vessels, and (4) to insert a tail vein catheter for timed injection without moving the subject. Ear lobe dermis tissue was accessible without surgery. Liver, kidney, and subcutaneous tumor were accessed following exteriorization through skin incision. In order to image initial extravasations of compounds into tissue following intravenous injection, movie acquisition was initialized prior to drug administration. Our technique can serve as a powerful tool for investigating biological mechanisms and functions of intravenously injected drugs, with both spatial and temporal resolution. PMID:21258542

  3. DIRECT OBSERVATIONS OF MAGNETIC FLUX ROPE FORMATION DURING A SOLAR CORONAL MASS EJECTION

    SciTech Connect

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

    2014-09-10

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

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

    NASA Astrophysics Data System (ADS)

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

    1990-04-01

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

  5. Direct Observation of Nanocrystallite Buckling in Carbon Fibers under Bending Load

    SciTech Connect

    Loidl, D.; Peterlik, H.; Paris, O.; Burghammer, M.; Riekel, C.

    2005-11-25

    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.

  6. Direct Observation of the Coherent Nuclear Response after the Absorption of a Photon

    NASA Astrophysics Data System (ADS)

    Liebel, M.; Schnedermann, C.; Bassolino, G.; Taylor, G.; Watts, A.; Kukura, P.

    2014-06-01

    How molecules convert light energy to perform a specific transformation is a fundamental question in photophysics. Ultrafast spectroscopy reveals the kinetics associated with electronic energy flow, but little is known about how absorbed photon energy drives nuclear motion. Here we used ultrabroadband transient absorption spectroscopy to monitor coherent vibrational energy flow after photoexcitation of the retinal chromophore. In the proton pump bacteriorhodopsin, we observed coherent activation of hydrogen-out-of-plane wagging and backbone torsional modes that were replaced by unreactive coordinates in the solution environment, concomitant with a deactivation of the reactive relaxation pathway.

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

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

  8. Extreme ultraviolet spectroscopy of G191-B2B - Direct observation of ionization edges

    NASA Technical Reports Server (NTRS)

    Wilkinson, Erik; Green, James C.; Cash, Webster

    1992-01-01

    We present the first spectrum of the hot, DA white dwarf G191-B2B (wd 0501 + 527) between 200 and 330 A. The spectrum, which has about 2 A resolution, was obtained with a sounding rocket-borne, grazing incidence spectrograph. The spectrum shows no evidence of He II, the expected primary opacity source in this wavelength region. Three ionization edges and one absorption feature were observed and are suggestive of O III existing in the photosphere of G191-B2B. Also noted is a broad spectral depression that may result from Fe VI in the photosphere.

  9. Direct mapping rather than motor prediction subserves modulation of corticospinal excitability during observation of actions in real time.

    PubMed

    Gueugneau, Nicolas; Mc Cabe, Sofia I; Villalta, Jorge I; Grafton, Scott T; Della-Maggiore, Valeria

    2015-06-01

    Motor facilitation refers to the specific increment in corticospinal excitability (CSE) elicited by the observation of actions performed by others. To date, the precise nature of the mechanism at the basis of this phenomenon is unknown. One possibility is that motor facilitation is driven by a predictive process reminiscent of the role of forward models in motor control. Alternatively, motor facilitation may result from a model-free mechanism by which the basic elements of the observed action are directly mapped onto their cortical representations. Our study was designed to discern these alternatives. To this aim, we recorded the time course of CSE for the first dorsal interosseous (FDI) and the abductor digiti minimi (ADM) during observation of three grasping actions in real time, two of which strongly diverged in kinematics from their natural (invariant) form. Although artificially slow movements used in most action observation studies might enhance the observer's discrimination performance, the use of videos in real time is crucial to maintain the time course of CSE within the physiological range of daily actions. CSE was measured at 4 time points within a 240-ms window that best captured the kinematic divergence from the invariant form. Our results show that CSE of the FDI, not the ADM, closely follows the functional role of the muscle despite the mismatch between the natural and the divergent kinematics. We propose that motor facilitation during observation of actions performed in real time reflects the model-free coding of perceived movement following a direct mapping mechanism. PMID:25810483

  10. Direct observation of optical near field in nanophotonics devices at the nanoscale using Scanning Thermal Microscopy.

    PubMed

    Grajower, Meir; Desiatov, Boris; Goykhman, Ilya; Stern, Liron; Mazurski, Noa; Levy, Uriel

    2015-10-19

    In recent years, following the miniaturization and integration of passive and active nanophotonic devices, thermal characterization of such devices at the nanoscale is becoming a task of crucial importance. The Scanning Thermal Microscopy (SThM) is a natural candidate for performing this task. However, it turns out that the SThM capability to precisely map the temperature of a photonic sample in the presence of light interacting with the sample is limited. This is because of the significant absorption of light by the SThM probe. As a result, the temperature of the SThM probe increases and a significant electrical signal which is directly proportional to the light intensity is obtained. As such, instead of measuring the temperature of the sample, one may directly measure the light intensity profile. While this is certainly a limitation in the context of thermal characterization of nanophotonic devices, this very property provides a new opportunity for optical near field characterization. In this paper we demonstrate numerically and experimentally the optical near field measurements of nanophotonic devices using a SThM probe. The system is characterized using several sets of samples with different properties and various wavelengths of operation. Our measurements indicate that the light absorption by the probe can be even larger than the light induced heat generation in the sample. The frequency response of the SThM system is characterized and the 3 dB frequency response was found to be ~1.5 kHz. The simplicity of the SThM system which eliminates the need for complex optical measurement setups together with its broadband wavelength of operation makes this approach an attractive alternative to the more conventional aperture and apertureless NSOM approaches. Finally, referring to its original role in characterizing thermal effects at the nanoscale, we propose an approach for characterizing the temperature profile of nanophotonic devices which are heated by light absorption within the device. This is achieved by spatially separating between the optical near field distribution and the SThM probe, taking advantage of the broader temperature profile as compared to the more localized light profile. PMID:26480438

  11. Direct observation of the latitudinal extent of a high-speed stream in the solar wind

    NASA Technical Reports Server (NTRS)

    Schwenn, R.; Montgomery, M. D.; Rosenbauer, H.; Miggenrieder, H.; Muehlhaeuser, K. H.; Bame, S. J.; Feldman, W. C.; Hansen, R. T.

    1978-01-01

    The latitudinal boundaries of stationary fast solar wind streams emerging from equatorward extensions of the sun's polar coronal holes are studied. Simultaneous data from the Helios 1 and Imp spacecraft at different heliographic latitudes are compared. The measured latitudinal speed gradient of 30 km/s/deg shows that large angular speed gradients occur at the leading edges of fast streams and also with respect to latitude. The data indicate that longitudinal speed gradients are steeper near 0.3 AU than at 1.0 AU. Generally, regions with large angular speed gradients are observed to separate fast streams from the surrounding slower plasma. This suggests the existence of mechanisms which diminish longitudinal speed gradients as the plasma travels toward 1.0 AU. It also seems that the distribution of solar wind speeds on a near-sun spherical surface has large mesalike high-speed regions. Comparisons of Helios 1 and Imp data with corona observations supports the hypothesis that high-speed solar wind streams emerge from coronal holes.

  12. Direct observation of asymmetric band structure of bilayer graphene through quantum capacitance measurements

    NASA Astrophysics Data System (ADS)

    Kanayama, Kaoru; Nagashio, Kosuke; Nishimura, Tomonori; Toriumi, Akira

    2014-03-01

    Although upper conduction and valence sub-bands in bilayer graphene are known to be asymmetric, a detailed analysis based on the electrical measurements is very limited due to the infirm quality of gate insulator. In this study, the electrical quality of the top-gate Y2O3 insulator is drastically improved by the high-pressure O2 post-deposition annealing at 100 atm and the carrier density of ~8*1013 cm-2 is achieved. In quantum capacitance measurements, the drastic increase of the density of states is observed in addition to the van Hove singularity, suggesting that the Fermi energy reaches upper sub-band. At the same carrier density, the sudden reduction of the conductivity is observed, indicating that the inter-band scattering occurs. The estimated carrier density required to fill the upper sub-bands is different between electron and hole sides, i.e., asymmetric band structure between upper conduction and valence bands is revealed by the electrical measurements.

  13. Direct observation of hygiene in a Peruvian shantytown: not enough handwashing and too little water

    PubMed Central

    Oswald, William E.; Hunter, Gabrielle C.; Lescano, Andres G.; Cabrera, Lilia; Leontsini, Elli; Pan, William K.; Soldan, Valerie Paz; Gilman, Robert H.

    2014-01-01

    Summary OBJECTIVE To document frequency of hygiene practices of mothers and children in a shantytown in Lima, Peru. METHODS Continuous monitoring over three 12-h sessions in households without in-house water connections to measure: (i) water and soap use of 32 mothers; (ii) frequency of interrupting faecal-hand contamination by washing; and (iii) the time until faecal-hand contamination became a possible transmission event. RESULTS During 1008 h of observation, 55% (65/119) of mothers’ and 69% (37/54) of children's faecal-hand contamination events were not followed within 15 min by handwashing or bathing. Nearly 40% (67/173) of faecal-hand contamination events became possible faecal-oral transmission events. There was no difference in the time-until-transmission between mothers and children (P = 0.43). Potential transmission of faecal material to food or mouth occurred in 64% of cases within 1 h of hand contamination. Mean water usage (6.5 l) was low compared to international disaster relief standards. CONCLUSIONS We observed low volumes of water usage, inadequate handwashing, and frequent opportunities for faecal contamination and possible transmission in this water-scarce community. PMID:19055623

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

    PubMed Central

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

    2013-01-01

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

  15. How fast can a baseball spin before an observer can't tell the direction of rotation?

    PubMed

    Shapiro, Arthur; Newport, Jonathan; DeVries, Bree

    2015-01-01

    In baseball, a pitcher throws a 3" ball toward a batter positioned 60.5 feet away. Shapiro et al (2009, 2011) hypothesized that a batter's perception of a pitch could be influenced by changes in the ball's retinal location (i.e., whether the batter views the ball centrally or peripherally). One question concerns whether a curveball spins too fast for a batter to discern the direction of spin. To address this question, we constructed a device in which a microcontroller spins a motor at rates up to 3000 rpm. A baseball rested on a driveshaft extending from the motor; an LCD shutter controlled the presentation duration (set at .6 sec); steady LED lights illuminated the ball. The observer viewed the ball from a distance of 140 cm (ball subtended 3.2 deg) and pressed one of two buttons to indicate the direction of perceived spin. Experiment 1: The ball was presented at rotation rates between 500 and 2500 rpm (40 trials in random order; half the trial were clockwise, half counter clockwise). Experiment 2: Similar set up, but on different sets of trials the observers viewed the ball either centrally or 10 deg in the periphery. Experiment 3: On different sets of trials the ball was positioned on the motor in a "2-seam" or a "4-seam" configuration. For all conditions, at rates up 1200 rpm, observers were typically correct 100% of the time, but near 2000 rpm, observers were typically at chance. Peripheral viewing and spin configuration had little effect on observer's ability to identify spin direction. Since an MLB curveball spins between 1400 and 1800 rpm, these pitches approach the limit of our perceptual resolution. The minor effect of peripheral viewing and spin configuration suggest, surprisingly, that our ability to perceive spin direction may be mediated by low spatial frequency channels. Meeting abstract presented at VSS 2015. PMID:26325974

  16. Direct observation of many-body charge density oscillations in a two-dimensional electron gas

    NASA Astrophysics Data System (ADS)

    Sessi, Paolo; Silkin, Vyacheslav M.; Nechaev, Ilya A.; Bathon, Thomas; El-Kareh, Lydia; Chulkov, Evgueni V.; Echenique, Pedro M.; Bode, Matthias

    2015-10-01

    Quantum interference is a striking manifestation of one of the basic concepts of quantum mechanics: the particle-wave duality. A spectacular visualization of this effect is the standing wave pattern produced by elastic scattering of surface electrons around defects, which corresponds to a modulation of the electronic local density of states and can be imaged using a scanning tunnelling microscope. To date, quantum-interference measurements were mainly interpreted in terms of interfering electrons or holes of the underlying band-structure description. Here, by imaging energy-dependent standing-wave patterns at noble metal surfaces, we reveal, in addition to the conventional surface-state band, the existence of an `anomalous' energy band with a well-defined dispersion. Its origin is explained by the presence of a satellite in the structure of the many-body spectral function, which is related to the acoustic surface plasmon. Visualizing the corresponding charge oscillations provides thus direct access to many-body interactions at the atomic scale.

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

    NASA Astrophysics Data System (ADS)

    Bozorgnia, Nassim; Schwetz, Thomas

    2014-12-01

    In Dark Matter direct detection we are facing the situation of some experiments reporting positive signals which are in conflict with limits from other experiments. Such conclusions are subject to large uncertainties introduced by the poorly known local Dark Matter distribution. We present a method to calculate an upper bound on the joint probability of obtaining the outcome of two potentially conflicting experiments under the assumption that the Dark Matter hypothesis is correct, but completely independent of assumptions about the Dark Matter distribution. In this way we can quantify the compatibility of two experiments in an astrophysics independent way. We illustrate our method by testing the compatibility of the hints reported by DAMA and CDMS-Si with the limits from the LUX and SuperCDMS experiments. The method does not require Monte Carlo simulations but is mostly based on using Poisson statistics. In order to deal with signals of few events we introduce the so-called ``signal length'' to take into account energy information. The signal length method provides a simple way to calculate the probability to obtain a given experimental outcome under a specified Dark Matter and background hypothesis.

  18. Direct observation of Σ7 domain boundary core structure in magnetic skyrmion lattice

    PubMed Central

    Matsumoto, Takao; So, Yeong-Gi; Kohno, Yuji; Sawada, Hidetaka; Ikuhara, Yuichi; Shibata, Naoya

    2016-01-01

    Skyrmions are topologically protected nanoscale magnetic spin entities in helical magnets. They behave like particles and tend to form hexagonal close-packed lattices, like atoms, as their stable structure. Domain boundaries in skyrmion lattices are considered to be important as they affect the dynamic properties of magnetic skyrmions. However, little is known about the fine structure of such skyrmion domain boundaries. We use differential phase contrast scanning transmission electron microscopy to directly visualize skyrmion domain boundaries in FeGe1−xSix induced by the influence of an “edge” of a crystal grain. Similar to hexagonal close-packed atomic lattices, we find the formation of skyrmion “Σ7” domain boundary, whose orientation relationship is predicted by the coincidence site lattice theory to be geometrically stable. On the contrary, the skyrmion domain boundary core structure shows a very different structure relaxation mode. Individual skyrmions can flexibly change their size and shape to accommodate local coordination changes and free volumes formed at the domain boundary cores. Although atomic rearrangement is a common structural relaxation mode in crystalline grain boundaries, skyrmions show very unique and thus different responses to such local lattice disorders. PMID:26933690

  19. Direct observation of many-body charge density oscillations in a two-dimensional electron gas.

    PubMed

    Sessi, Paolo; Silkin, Vyacheslav M; Nechaev, Ilya A; Bathon, Thomas; El-Kareh, Lydia; Chulkov, Evgueni V; Echenique, Pedro M; Bode, Matthias

    2015-01-01

    Quantum interference is a striking manifestation of one of the basic concepts of quantum mechanics: the particle-wave duality. A spectacular visualization of this effect is the standing wave pattern produced by elastic scattering of surface electrons around defects, which corresponds to a modulation of the electronic local density of states and can be imaged using a scanning tunnelling microscope. To date, quantum-interference measurements were mainly interpreted in terms of interfering electrons or holes of the underlying band-structure description. Here, by imaging energy-dependent standing-wave patterns at noble metal surfaces, we reveal, in addition to the conventional surface-state band, the existence of an 'anomalous' energy band with a well-defined dispersion. Its origin is explained by the presence of a satellite in the structure of the many-body spectral function, which is related to the acoustic surface plasmon. Visualizing the corresponding charge oscillations provides thus direct access to many-body interactions at the atomic scale. PMID:26498368

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

    SciTech Connect

    Panda, Kalpataru; Sundaravel, B.; Panigrahi, B. K.; Chen, Huang-Chin; Lin, I.-Nan

    2013-02-07

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

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

    PubMed

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

    2009-06-01

    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

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

    SciTech Connect

    Bozorgnia, Nassim; Schwetz, Thomas E-mail: schwetz@fysik.su.se

    2014-12-01

    In Dark Matter direct detection we are facing the situation of some experiments reporting positive signals which are in conflict with limits from other experiments. Such conclusions are subject to large uncertainties introduced by the poorly known local Dark Matter distribution. We present a method to calculate an upper bound on the joint probability of obtaining the outcome of two potentially conflicting experiments under the assumption that the Dark Matter hypothesis is correct, but completely independent of assumptions about the Dark Matter distribution. In this way we can quantify the compatibility of two experiments in an astrophysics independent way. We illustrate our method by testing the compatibility of the hints reported by DAMA and CDMS-Si with the limits from the LUX and SuperCDMS experiments. The method does not require Monte Carlo simulations but is mostly based on using Poisson statistics. In order to deal with signals of few events we introduce the so-called ''signal length'' to take into account energy information. The signal length method provides a simple way to calculate the probability to obtain a given experimental outcome under a specified Dark Matter and background hypothesis.

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

    NASA Astrophysics Data System (ADS)

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

    1994-01-01

    This report summarizes new data from screening various feedstocks for alkali vapor release under combustion conditions. The successful development of a laboratory flow reactor and molecular beam, mass spectrometer interface is detailed. Its application to several herbaceous and woody feedstocks, as well as a fast-pyrolysis oil, under 800 and 1100 C batch combustion, is documented. Chlorine seems to play a large role in the facile mobilization of potassium. Included in the report is a discussion of relevant literature on the alkali problem in combustors and turbines. Highlighted are the phenomena identified in studies on coal and methods that have been applied to alkali speciation. The nature of binding of alkali in coal versus biomass is discussed, together with the implications for the ease of release. Herbaceous species and many agricultural residues appear to pose significant problems in release of alkali species to the vapor at typical combustor temperatures. These problems could be especially acute in direct combustion fired turbines, but may be ameliorated in integrated gasification combined cycles.

  4. Direct Observation of Conformation of a Polymeric Coating with Implications in Microarray Applications

    PubMed Central

    Yalin, Aya; Damin, Francesco; zkumur, Emre; di Carlo, Gabriele; Goldberg, Bennett B.; Chiari, Marcella; nl, M. Selim

    2009-01-01

    Conformation of a three-dimensional polymeric coating (copoly(DMA-NAS-MAPS)), and immobilization and hybridization of DNA strands on the polymer coated surface are investigated. A conformational change, specifically the swelling of the surface adsorbed polymer upon hydration, is quantified in conjunction with the application of these polymer coatings for DNA microarray applications. Fluorescently labeled short DNA strands (23mer) covalently linked to the functional groups on the adsorbed polymer are used as probes to measure the swelling of the polymer. A fluorescence microscopy technique, Spectral Self-Interference Fluorescence Microscopy (SSFM), is utilized to directly measure the change in axial position of fluorophores due to swelling with sub-nanometer accuracy. Additionally, immobilization characteristics of single stranded DNA (ssDNA) and double stranded DNA (dsDNA) probes, as well as hybridization of ssDNA with target strands have been studied. The results show that ssDNA further away from the surface is hybridized more efficiently, which strengthens the earlier analysis of this polymeric coating as a simple but highly-efficient and robust DNA microarray surface chemistry. PMID:19061409

  5. Direct observation of Σ7 domain boundary core structure in magnetic skyrmion lattice.

    PubMed

    Matsumoto, Takao; So, Yeong-Gi; Kohno, Yuji; Sawada, Hidetaka; Ikuhara, Yuichi; Shibata, Naoya

    2016-02-01

    Skyrmions are topologically protected nanoscale magnetic spin entities in helical magnets. They behave like particles and tend to form hexagonal close-packed lattices, like atoms, as their stable structure. Domain boundaries in skyrmion lattices are considered to be important as they affect the dynamic properties of magnetic skyrmions. However, little is known about the fine structure of such skyrmion domain boundaries. We use differential phase contrast scanning transmission electron microscopy to directly visualize skyrmion domain boundaries in FeGe1-x Si x induced by the influence of an "edge" of a crystal grain. Similar to hexagonal close-packed atomic lattices, we find the formation of skyrmion "Σ7" domain boundary, whose orientation relationship is predicted by the coincidence site lattice theory to be geometrically stable. On the contrary, the skyrmion domain boundary core structure shows a very different structure relaxation mode. Individual skyrmions can flexibly change their size and shape to accommodate local coordination changes and free volumes formed at the domain boundary cores. Although atomic rearrangement is a common structural relaxation mode in crystalline grain boundaries, skyrmions show very unique and thus different responses to such local lattice disorders. PMID:26933690

  6. Direct observation of key photoinduced dynamics in a potential nano-delivery vehicle of cancer drugs.

    PubMed

    Sardar, Samim; Chaudhuri, Siddhi; Kar, Prasenjit; Sarkar, Soumik; Lemmens, Peter; Pal, Samir Kumar

    2015-01-01

    In recent times, significant achievements in the use of zinc oxide (ZnO) nanoparticles (NPs) as delivery vehicles of cancer drugs have been made. The present study is an attempt to explore the key photoinduced dynamics in ZnO NPs upon complexation with a model cancer drug protoporphyrin IX (PP). The nanohybrid has been characterized by FTIR, Raman scattering and UV-Vis absorption spectroscopy. Picosecond-resolved Frster resonance energy transfer (FRET) from the defect mediated emission of ZnO NPs to PP has been used to study the formation of the nanohybrid at the molecular level. Picosecond-resolved fluorescence studies of PP-ZnO nanohybrids reveal efficient electron migration from photoexcited PP to ZnO, eventually enhancing the ROS activity. The dichlorofluorescin (DCFH) oxidation and no oxidation of luminol in PP/PP-ZnO nanohybrids upon green light illumination unravel that the nature of ROS is essentially singlet oxygen rather than superoxide anions. Surface mediated photocatalysis of methylene blue (MB) in an aqueous solution of the nanohybrid has also been investigated. Direct evidence of the role of electron transfer as a key player in enhanced ROS generation from the nanohybrid is also clear from the photocurrent measurement studies. We have also used the nanohybrid in a model photodynamic therapy application in a light sensitized bacteriological culture experiment. PMID:25372615

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

    SciTech Connect

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

    1994-01-01

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

  8. 44 CFR 206.228 - Allowable costs.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Allowable costs. General policies for determining allowable costs are established in 44 CFR 13.22. Exceptions to those policies as allowed in 44 CFR 13.4 and 13.6 are explained below. (a) Eligible direct... accordance with 44 CFR part 207. (b)...

  9. Direct Observation of Short-Range Structural Coherence During a Charge Transfer Induced Spin Transition in a CoFe Prussian Blue Analogue by Transmission Electron Microscopy.

    PubMed

    Itoi, Miho; Jike, Toyoharu; Nishio-Hamane, Daisuke; Udagawa, Seiichi; Tsuda, Tetsuya; Kuwabata, Susumu; Boukheddaden, Kamel; Andrus, Matthew J; Talham, Daniel R

    2015-11-25

    The local structure within the Co-Fe atomic array of the photoswitchable coordination polymer magnet, K0.3Co[Fe(CN)6]0.77nH2O, is directly observed during charge transfer induced spin transition (CTIST), a solid-solid phase change, using high-resolution transmission electron microscopy (HRTEM). Along with the low-spin (LS) or thermally quenched high-spin (HS) states normally observed in CTIST solids at low temperature, slow cooling of K0.3Co[Fe(CN)6]0.77nH2O results in an intermediate phase containing both HS and LS domains with short coherence length. By mapping individual metal-metal distances, the nanometer-scale HS domains are directly visualized within the LS array. Temperature-dependent analyses allow monitoring of HS domain coarsening along the warming branch of the CTIST, providing direct visualization of the elastic process and insight into the mechanism of phase propagation. Normally sensitive to electron beam damage, the low-temperature TEM measurements of the porous coordination polymer are enabled by using appropriate ionic liquids instead of usual conductive thin-film coatings, an approach that should find general utility in related classes of materials. PMID:26510096

  10. S -shaped flow curves of shear thickening suspensions: Direct observation of frictional rheology

    NASA Astrophysics Data System (ADS)

    Pan, Zhongcheng; de Cagny, Henri; Weber, Bart; Bonn, Daniel

    2015-09-01

    We study the rheological behavior of concentrated granular suspensions of simple spherical particles. Under controlled stress, the system exhibits an S -shaped flow curve (stress vs shear rate) with a negative slope in between the low-viscosity Newtonian regime and the shear thickened regime. Under controlled shear rate, a discontinuous transition between the two states is observed. Stress visualization experiments with a fluorescent probe suggest that friction is at the origin of shear thickening. Stress visualization shows that the stress in the system remains homogeneous (no shear banding) if a stress is imposed that is intermediate between the high- and low-stress branches. The S -shaped shear thickening is then due to the discontinuous formation of a frictional force network between particles upon increasing the stress.

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

    PubMed Central

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

    2013-01-01

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

  12. Direct in situ observation of dynamic transport for electrolyte components by NMR combined with electrochemical measurements.

    PubMed

    Hayamizu, Kikuko; Seki, Shiro; Miyashiro, Hajime; Kobayashi, Yo

    2006-11-16

    Electrochemical studies provide broad, but not cation- or anion-specific information on the migration of charged ions. However, individual ion diffusion (as a weighted average of charged and neutral ions) can be measured using pulsed-gradient spin-echo (PGSE) NMR. In this paper, the lithium transport in an electrolyte including a lithium salt was measured using electrophoretic NMR (ENMR) with non-blocking electrodes. A propylene carbonate (PC) solution doped with LiN(SO(2)CF(3))(2) (LiTFSI) was inserted in a homemade NMR cell equipped with Li/Li electrodes. The drift migrations of lithium cation ((7)Li), anion ((19)F), and solvent ((1)H) were measured independently under potentials of up to 3.0 V. Greatly enhanced dynamic lithium transport was observed for the first time in the bulk electrolyte under an electric field closely related to real conditions in a rechargeable lithium battery. PMID:17091966

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

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Hiroyasu; Kubota, Kei; Harada, Akira

    2000-04-01

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

  14. Direct observation of intermediates in a thermodynamically controlled solid-state dynamic covalent reaction.

    PubMed

    Belenguer, Ana M; Lampronti, Giulio I; Wales, David J; Sanders, Jeremy K M

    2014-11-19

    We present the first polymorph interconversion study that uses solid-state dynamic covalent chemistry (DCC). This system exhibits unexpected and rich behavior, including the observation that under appropriate conditions the polymorph interconversion of a heterodimer proceeds through reversible covalent chemistry intermediates, and this route is facilitated by one of the two disulfide homodimers involved in the reaction. Furthermore, we demonstrate experimentally that in all cases a dynamic equilibrium is reached, meaning that changing the milling conditions affects the free energy difference between the two polymorphs and thus their relative stability. We suggest that this effect is due to the surface solvation energy combined with the high surface to volume ratio of the nanocrystalline powder. PMID:25314624

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

    SciTech Connect

    Venkatesan, Sriram; Scheu, Christina; Madsen, Morten H.; Krogstrup, Peter; Johnson, Erik; Schmid, Herbert

    2013-08-05

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

  16. S-shaped flow curves of shear thickening suspensions: direct observation of frictional rheology.

    PubMed

    Pan, Zhongcheng; de Cagny, Henri; Weber, Bart; Bonn, Daniel

    2015-09-01

    We study the rheological behavior of concentrated granular suspensions of simple spherical particles. Under controlled stress, the system exhibits an S-shaped flow curve (stress vs shear rate) with a negative slope in between the low-viscosity Newtonian regime and the shear thickened regime. Under controlled shear rate, a discontinuous transition between the two states is observed. Stress visualization experiments with a fluorescent probe suggest that friction is at the origin of shear thickening. Stress visualization shows that the stress in the system remains homogeneous (no shear banding) if a stress is imposed that is intermediate between the high- and low-stress branches. The S-shaped shear thickening is then due to the discontinuous formation of a frictional force network between particles upon increasing the stress. PMID:26465464

  17. Direct observation of electron emission and recombination processes by time domain measurements of charge pumping current

    NASA Astrophysics Data System (ADS)

    Hori, Masahiro; Watanabe, Tokinobu; Tsuchiya, Toshiaki; Ono, Yukinori

    2015-01-01

    To analyze the charge pumping (CP) sequence in detail, the source/drain electron current and the substrate hole current under the CP mode of transistors are simultaneously monitored in the time domain. Peaks are observed in both the electron and hole currents, which are, respectively, attributed to the electron emission from the interface defects and to the recombination with holes. The peak caused by the electron emission is found to consist of two components, strongly suggesting that the present time-domain measurement can enable us to resolve different kinds of interface defects. Investigating the correlation between the number of emitted and recombined electrons reveals that only one of the two components contributes to the CP current for the gate-pulse fall time from 6.25 10-4 to 1.25 10-2 s.

  18. Direct observation of electron emission and recombination processes by time domain measurements of charge pumping current

    SciTech Connect

    Hori, Masahiro Watanabe, Tokinobu; Ono, Yukinori; Tsuchiya, Toshiaki

    2015-01-26

    To analyze the charge pumping (CP) sequence in detail, the source/drain electron current and the substrate hole current under the CP mode of transistors are simultaneously monitored in the time domain. Peaks are observed in both the electron and hole currents, which are, respectively, attributed to the electron emission from the interface defects and to the recombination with holes. The peak caused by the electron emission is found to consist of two components, strongly suggesting that the present time-domain measurement can enable us to resolve different kinds of interface defects. Investigating the correlation between the number of emitted and recombined electrons reveals that only one of the two components contributes to the CP current for the gate-pulse fall time from 6.25 × 10{sup −4} to 1.25 × 10{sup −2} s.

  19. Laser beam directed at the lunar retro-reflector array: observations of the first returns.

    PubMed

    Faller, J; Winer, I; Carrion, W; Johnson, T S; Spadin, P; Robinson, L; Wampler, E J; Wieber, D

    1969-10-01

    On 1 August between 10:15 and 12:50 Universal Time, with the Lick Observatory 120-inch (304-cm) telescope and a laser operating at 6943 angstroms, return signals from an optical retro-reflector array placed on the moon by the Apollo 11 astronauts were successfully detected. After the return signal was first detected it continued to appear with the expected time delay for the remainder of the night. The observed range is in excellent agreement with the predicted ephemeris. Transmitting between 7 and 8 joules per pulse, we found that each return signal averaged more than one photoelectron. This is in good agreement with calculations of the expected signal strength. PMID:17769756

  20. Direct observation and temperature control of the surface Dirac gap in a topological crystalline insulator.

    PubMed

    Wojek, B M; Berntsen, M H; Jonsson, V; Szczerbakow, A; Dziawa, P; Kowalski, B J; Story, T; Tjernberg, O

    2015-01-01

    Since the advent of topological insulators hosting Dirac surface states, efforts have been made to gap these states in a controllable way. A new route to accomplish this was opened up by the discovery of topological crystalline insulators where the topological states are protected by crystal symmetries and thus prone to gap formation by structural changes of the lattice. Here we show a temperature-driven gap opening in Dirac surface states within the topological crystalline insulator phase in (Pb,Sn)Se. By using angle-resolved photoelectron spectroscopy, the gap formation and mass acquisition is studied as a function of composition and temperature. The resulting observations lead to the addition of a temperature- and composition-dependent boundary between massless and massive Dirac states in the topological phase diagram for (Pb,Sn)Se (001). Overall, our results experimentally establish the possibility to tune between massless and massive topological states on the surface of a topological system. PMID:26458506