Improving atomic displacement and replacement calculations with physically realistic damage models

DOE PAGES

Nordlund, Kai; Zinkle, Steven J.; Sand, Andrea E.; ...

2018-03-14

Atomic collision processes are fundamental to numerous advanced materials technologies such as electron microscopy, semiconductor processing and nuclear power generation. Extensive experimental and computer simulation studies over the past several decades provide the physical basis for understanding the atomic-scale processes occurring during primary displacement events. The current international standard for quantifying this energetic particle damage, the Norgett-Robinson-Torrens displacements per atom (NRT-dpa) model, has nowadays several well-known limitations. In particular, the number of radiation defects produced in energetic cascades in metals is only ~1/3 the NRT-dpa prediction, while the number of atoms involved in atomic mixing is about a factor ofmore » 30 larger than the dpa value. Here we propose two new complementary displacement production estimators (athermal recombination corrected dpa, arc-dpa) and atomic mixing (replacements per atom, rpa) functions that extend the NRT-dpa by providing more physically realistic descriptions of primary defect creation in materials and may become additional standard measures for radiation damage quantification.« less

Improving atomic displacement and replacement calculations with physically realistic damage models.

PubMed

Nordlund, Kai; Zinkle, Steven J; Sand, Andrea E; Granberg, Fredric; Averback, Robert S; Stoller, Roger; Suzudo, Tomoaki; Malerba, Lorenzo; Banhart, Florian; Weber, William J; Willaime, Francois; Dudarev, Sergei L; Simeone, David

2018-03-14

Atomic collision processes are fundamental to numerous advanced materials technologies such as electron microscopy, semiconductor processing and nuclear power generation. Extensive experimental and computer simulation studies over the past several decades provide the physical basis for understanding the atomic-scale processes occurring during primary displacement events. The current international standard for quantifying this energetic particle damage, the Norgett-Robinson-Torrens displacements per atom (NRT-dpa) model, has nowadays several well-known limitations. In particular, the number of radiation defects produced in energetic cascades in metals is only ~1/3 the NRT-dpa prediction, while the number of atoms involved in atomic mixing is about a factor of 30 larger than the dpa value. Here we propose two new complementary displacement production estimators (athermal recombination corrected dpa, arc-dpa) and atomic mixing (replacements per atom, rpa) functions that extend the NRT-dpa by providing more physically realistic descriptions of primary defect creation in materials and may become additional standard measures for radiation damage quantification.

Two-point motional Stark effect diagnostic for Madison Symmetric Torus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ko, J.; Den Hartog, D. J.; Caspary, K. J.

2010-10-15

A high-precision spectral motional Stark effect (MSE) diagnostic provides internal magnetic field measurements for Madison Symmetric Torus (MST) plasmas. Currently, MST uses two spatial views - on the magnetic axis and on the midminor (off-axis) radius, the latter added recently. A new analysis scheme has been developed to infer both the pitch angle and the magnitude of the magnetic field from MSE spectra. Systematic errors are reduced by using atomic data from atomic data and analysis structure in the fit. Reconstructed current density and safety factor profiles are more strongly and globally constrained with the addition of the off-axis radiusmore » measurement than with the on-axis one only.« less

Internal and external atomic steps in graphite exhibit dramatically different physical and chemical properties.

PubMed

Lee, Hyunsoo; Lee, Han-Bo-Ram; Kwon, Sangku; Salmeron, Miquel; Park, Jeong Young

2015-04-28

We report on the physical and chemical properties of atomic steps on the surface of highly oriented pyrolytic graphite (HOPG) investigated using atomic force microscopy. Two types of step edges are identified: internal (formed during crystal growth) and external (formed by mechanical cleavage of bulk HOPG). The external steps exhibit higher friction than the internal steps due to the broken bonds of the exposed edge C atoms, while carbon atoms in the internal steps are not exposed. The reactivity of the atomic steps is manifested in a variety of ways, including the preferential attachment of Pt nanoparticles deposited on HOPG when using atomic layer deposition and KOH clusters formed during drop casting from aqueous solutions. These phenomena imply that only external atomic steps can be used for selective electrodeposition for nanoscale electronic devices.

Atomic weights of the elements--Review 2000 (IUPAC Technical Report)

USGS Publications Warehouse

de Laeter, John R.; Böhlke, John Karl; De Bièvre, P.; Hidaka, H.; Peiser, H.S.; Rosman, K.J.R.; Taylor, P.D.P.

2003-01-01

A consistent set of internationally accepted atomic weights has long been an essential aim of the scientific community because of the relevance of these values to science and technology, as well as to trade and commerce subject to ethical, legal, and international standards. The standard atomic weights of the elements are regularly evaluated, recommended, and published in updated tables by the Commission on Atomic Weights and Isotopic Abundances (CAWIA) of the International Union of Pure and Applied Chemistry (IUPAC). These values are invariably associated with carefully evaluated uncertainties. Atomic weights were originally determined by mass ratio measurements coupled with an understanding of chemical stoichiometry, but are now based almost exclusively on knowledge of the isotopic composition (derived from isotope-abundance ratio measurements) and the atomic masses of the isotopes of the elements. Atomic weights and atomic masses are now scaled to a numerical value of exactly 12 for the mass of the carbon isotope of mass number 12. Technological advances in mass spectrometry and nuclear-reaction energies have enabled atomic masses to be determined with a relative uncertainty of better than 1 ×10−7 . Isotope abundances for an increasing number of elements can be measured to better than 1 ×10−3 . The excellent precision of such measurements led to the discovery that many elements, in different specimens, display significant variations in their isotope-abundance ratios, caused by a variety of natural and industrial physicochemical processes. While such variations increasingly place a constraint on the uncertainties with which some standard atomic weights can be stated, they provide numerous opportunities for investigating a range of important phenomena in physical, chemical, cosmological, biological, and industrial processes. This review reflects the current and increasing interest of science in the measured differences between source-specific and even sample-specific atomic weights. These relative comparisons can often be made with a smaller uncertainty than is achieved in the best calibrated “absolute ” (=SI-traceable) atomic-weight determinations. Accurate determinations of the atomic weights of certain elements also influence the values of fundamental constants such as the Avogadro, Faraday, and universal gas constants. This review is in two parts: the first summarizes the development of the science of atomic-weight determinations during the 20th century; the second summarizes the changes and variations that have been recognized in the values and uncertainties of atomic weights, on an element-by-element basis, in the latter part of the 20th century.

Resilience among Japanese atomic bomb survivors.

PubMed

Knowles, A

2011-03-01

The purpose of the study was to explore the experience of atomic bomb survivors from Hiroshima and Nagasaki. Never has the world experienced such extreme devastation as with the atomic bombings of Hiroshima and Nagasaki, Japan, in August 1945. Although significant quantitative research has been completed about the medical effects following radiation, the literature lacks qualitative exploration from a holistic health perspective. This was a qualitative descriptive study, using methods of narrative analysis, oral history and ethnography. The sample for this research included eight individuals who were exposed to the atomic bombings in Japan and currently reside in the United States. Findings provide insight to the resilience that the survivors exhibited immediately following the bomb, as well as throughout the 65 years following the event. From ethnographic data and interviews with survivors, a thematic structure was developed that depicts the essential elements of the atomic bomb experience. Two ways of being in the world followed the bombing: surviving and thriving, with resilience serving as a lever, allowing for fluid movement over time across the continuum. Individuals experiencing surviving exhibited anxiety about their personal and family members' health, expressed mistrust, and felt a stigma associated with being a survivor. For those who were thriving, peace activism, overcoming and forgiveness were typically displayed. Findings from this study add to the disaster nursing literature and highlight the role resilience plays in the atomic bomb survivors' life perspective. © 2011 The Author. International Nursing Review © 2011 International Council of Nurses.

Optical Frequency Standards Based on Neutral Atoms and Molecules

NASA Astrophysics Data System (ADS)

Riehle, Fritz; Helmcke, Juergen

The current status and prospects of optical frequency standards based on neutral atomic and molecular absorbers are reviewed. Special attention is given to an optical frequency standard based on cold Ca atoms which are interrogated with a pulsed excitation scheme leading to resolved line structures with a quality factor Q > 10^12. The optical frequency was measured by comparison with PTB's primary clock to be νCa = 455 986 240 494.13 kHz with a total relative uncertainty of 2.5 x10^-13. After a recent recommendation of the International Committee of Weights and Measures (CIPM), this frequency standard now represents one of the most accurate realizations of the length unit.

5 CFR 352.401 - Purpose.

Code of Federal Regulations, 2014 CFR

2014-01-01

... of Presidential Appointees and Elected Officers by the International Atomic Energy Agency § 352.401 Purpose. The purpose of this subpart is to implement section 6(b) of the International Atomic Energy... officers who leave their positions and within 90 days enter employment with the International Atomic Energy...

5 CFR 352.401 - Purpose.

Code of Federal Regulations, 2013 CFR

2013-01-01

... of Presidential Appointees and Elected Officers by the International Atomic Energy Agency § 352.401 Purpose. The purpose of this subpart is to implement section 6(b) of the International Atomic Energy... officers who leave their positions and within 90 days enter employment with the International Atomic Energy...

5 CFR 352.401 - Purpose.

Code of Federal Regulations, 2010 CFR

2010-01-01

... of Presidential Appointees and Elected Officers by the International Atomic Energy Agency § 352.401 Purpose. The purpose of this subpart is to implement section 6(b) of the International Atomic Energy... officers who leave their positions and within 90 days enter employment with the International Atomic Energy...

5 CFR 352.401 - Purpose.

Code of Federal Regulations, 2012 CFR

2012-01-01

... of Presidential Appointees and Elected Officers by the International Atomic Energy Agency § 352.401 Purpose. The purpose of this subpart is to implement section 6(b) of the International Atomic Energy... officers who leave their positions and within 90 days enter employment with the International Atomic Energy...

5 CFR 352.401 - Purpose.

Code of Federal Regulations, 2011 CFR

2011-01-01

... of Presidential Appointees and Elected Officers by the International Atomic Energy Agency § 352.401 Purpose. The purpose of this subpart is to implement section 6(b) of the International Atomic Energy... officers who leave their positions and within 90 days enter employment with the International Atomic Energy...

48 CFR 204.470 - U.S.-International Atomic Energy Agency Additional Protocol.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 48 Federal Acquisition Regulations System 3 2010-10-01 2010-10-01 false U.S.-International Atomic Energy Agency Additional Protocol. 204.470 Section 204.470 Federal Acquisition Regulations System DEFENSE... Information Within Industry 204.470 U.S.-International Atomic Energy Agency Additional Protocol. ...

48 CFR 204.470 - U.S.-International Atomic Energy Agency Additional Protocol.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 48 Federal Acquisition Regulations System 3 2011-10-01 2011-10-01 false U.S.-International Atomic Energy Agency Additional Protocol. 204.470 Section 204.470 Federal Acquisition Regulations System DEFENSE... Information Within Industry 204.470 U.S.-International Atomic Energy Agency Additional Protocol. ...

48 CFR 204.470 - U.S.-International Atomic Energy Agency Additional Protocol.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 48 Federal Acquisition Regulations System 3 2012-10-01 2012-10-01 false U.S.-International Atomic Energy Agency Additional Protocol. 204.470 Section 204.470 Federal Acquisition Regulations System DEFENSE... Information Within Industry 204.470 U.S.-International Atomic Energy Agency Additional Protocol. ...

48 CFR 204.470 - U.S.-International Atomic Energy Agency Additional Protocol.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 48 Federal Acquisition Regulations System 3 2014-10-01 2014-10-01 false U.S.-International Atomic Energy Agency Additional Protocol. 204.470 Section 204.470 Federal Acquisition Regulations System DEFENSE... Information Within Industry 204.470 U.S.-International Atomic Energy Agency Additional Protocol. ...

48 CFR 204.470 - U.S.-International Atomic Energy Agency Additional Protocol.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 48 Federal Acquisition Regulations System 3 2013-10-01 2013-10-01 false U.S.-International Atomic Energy Agency Additional Protocol. 204.470 Section 204.470 Federal Acquisition Regulations System DEFENSE... Information Within Industry 204.470 U.S.-International Atomic Energy Agency Additional Protocol. ...

IV INTERNATIONAL CONFERENCE ON ATOM AND MOLECULAR PULSED LASERS (AMPL'99): IV International Conference on Atomic and Molecular Pulsed Gas Lasers (AMPL'99)

NASA Astrophysics Data System (ADS)

Evtushenko, Gennadii S.; Kopylova, T. N.; Soldatov, A. N.; Tarasenko, Viktor F.; Yakovlenko, Sergei I.; Yancharina, A. M.

2000-06-01

A brief review of the most interesting papers presented at the IV International Conference on Atomic and Molecular Pulsed Gas Lasers (AMPL'99), which was held in Tomsk, September 13-17, 1999, is provided.

Runaway Geneeration In Disruptions Of Plasmas In TFTR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fredrickson, E. D.; Bell, M. G.; Taylor, G.

2014-03-31

Many disruptions in the Tokamak Fusion Test Reactor (TFTR) [D. Meade and the TFTR Group, in Proceedings of the International Conference on Plasma Physics and Controlled Nuclear Fusion, Washington, DC, 1990 (International Atomic Energy Agency, Vienna, 1991), Vol. 1, pp. 9-24] produced populations of runaway electrons which carried a significant fraction of the original plasma current. In this paper, we describe experiments where, following a disruption of a low-beta, reversed shear plasma, currents of up to 1 MA carried mainly by runaway electrons were controlled and then ramped down to near zero using the ohmic transformer. In the longer lastingmore » runaway plasmas, Parail-Pogutse instabilities were observed.« less

Laser and Optical Subsystem for NASA's Cold Atom Laboratory

NASA Astrophysics Data System (ADS)

Kohel, James; Kellogg, James; Elliott, Ethan; Krutzik, Markus; Aveline, David; Thompson, Robert

2016-05-01

We describe the design and validation of the laser and optics subsystem for NASA's Cold Atom Laboratory (CAL), a multi-user facility being developed at NASA's Jet Propulsion Laboratory for studies of ultra-cold quantum gases in the microgravity environment of the International Space Station. Ultra-cold atoms will be generated in CAL by employing a combination of laser cooling techniques and evaporative cooling in a microchip-based magnetic trap. Laser cooling and absorption imaging detection of bosonic mixtures of 87 Rb and 39 K or 41 K will be accomplished using a high-power (up to 500 mW ex-fiber), frequency-agile dual wavelength (767 nm and 780 nm) laser and optical subsystem. The CAL laser and optical subsystem also includes the capability to generate high-power multi-frequency optical pulses at 784.87 nm to realize a dual-species Bragg atom interferometer. Currently at Humboldt-Universität zu Berlin.

Developing a Nuclear Global Health Workforce Amid the Increasing Threat of a Nuclear Crisis.

PubMed

Burkle, Frederick M; Dallas, Cham E

2016-02-01

This study argues that any nuclear weapon exchange or major nuclear plant meltdown, in the categories of human systems failure and conflict-based crises, will immediately provoke an unprecedented public health emergency of international concern. Notwithstanding nuclear triage and management plans and technical monitoring standards within the International Atomic Energy Agency and the World Health Organization (WHO), the capacity to rapidly deploy a robust professional workforce with the internal coordination and collaboration capabilities required for large-scale nuclear crises is profoundly lacking. A similar dilemma, evident in the early stages of the Ebola epidemic, was eventually managed by using worldwide infectious disease experts from the Global Outbreak Alert and Response Network and multiple multidisciplinary WHO-supported foreign medical teams. This success has led the WHO to propose the development of a Global Health Workforce. A strategic format is proposed for nuclear preparedness and response that builds and expands on the current model for infectious disease outbreak currently under consideration. This study proposes the inclusion of a nuclear global health workforce under the technical expertise of the International Atomic Energy Agency and WHO's Radiation Emergency Medical Preparedness and Assistance Network leadership and supported by the International Health Regulations Treaty. Rationales are set forth for the development, structure, and function of a nuclear workforce based on health outcomes research that define the unique health, health systems, and public health challenges of a nuclear crisis. Recent research supports that life-saving opportunities are possible, but only if a rapidly deployed and robust multidisciplinary response component exists.

75 FR 7337 - Certifications Pursuant to Section 104 of the United States-India Nuclear Cooperation Approval...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-02-19

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2010-02-05

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Polarized internal target apparatus

DOEpatents

Holt, Roy J.

1986-01-01

A polarized internal target apparatus with a polarized gas target of improved polarization and density achieved by mixing target gas atoms with a small amount of alkali metal gas atoms, and passing a high intensity polarized light source into the mixture to cause the alkali metal gas atoms to become polarized which interact in spin exchange collisions with target gas atoms yielding polarized target gas atoms.

76 FR 41312 - Honeywell International Inc.; Establishment of Atomic Safety And Licensing Board

Federal Register 2010, 2011, 2012, 2013, 2014

2011-07-13

...] Honeywell International Inc.; Establishment of Atomic Safety And Licensing Board Pursuant to delegation by..., notice is hereby given that an Atomic Safety and Licensing Board (Board) is being established to preside... comprised of the following administrative judges: Paul S. Ryerson, Chair, Atomic Safety and Licensing Board...

Polarized internal target apparatus

DOEpatents

Holt, R.J.

1984-10-10

A polarized internal target apparatus with a polarized gas target of improved polarization and density (achieved by mixing target gas atoms with a small amount of alkali metal gas atoms, and passing a high intensity polarized light source into the mixture to cause the alkali metal gas atoms to become polarized which interact in spin exchange collisions with target gas atoms yielding polarized target gas atoms) is described.

Part Marking and Identification Materials on MISSE

NASA Technical Reports Server (NTRS)

Finckenor, Miria M.; Roxby, Donald L.

2008-01-01

Many different spacecraft materials were flown as part of the Materials on International Space Station Experiment (MISSE), including several materials used in part marking and identification. The experiment contained Data Matrix symbols applied using laser bonding, vacuum arc vapor deposition, gas assisted laser etch, chemical etch, mechanical dot peening, laser shot peening, and laser induced surface improvement. The effects of ultraviolet radiation on nickel acetate seal versus hot water seal on sulfuric acid anodized aluminum are discussed. These samples were exposed on the International Space Station to the low Earth orbital environment of atomic oxygen, ultraviolet radiation, thermal cycling, and hard vacuum, though atomic oxygen exposure was very limited for some samples. Results from the one-year exposure on MISSE-3 and MISSE-4 are compared to those from MISSE-1 and MISSE-2, which were exposed for four years. Part marking and identification materials on the current MISSE -6 experiment are also discussed.

When Do Commercial Reactors Permanently Shut Down?

EIA Publications

2011-01-01

For those wishing to obtain current data, the following resources are available: U.S. reactors, go to the Energy Information Administration's nuclear reactor shutdown list. (Note: As of April 30, 2010, the last U.S. reactor to permanently shut down was Big Rock Point in 1997.) Foreign Reactors, go to the Power Reactor Information System (PRIS) on the International Atomic Energy Agency's website.

Excitation and relaxation of metastable atomic states in an active medium of a repetitively pulsed copper vapour laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bokhan, P A; Zakrevskii, D E; Lavrukhin, M A

2016-02-28

The influence of a pre-pulse population of copper atom metastable states and their sub-population at a current pulse edge on the copper vapour laser pulse energy is studied under optimal temperature conditions. Experiments have been performed with active elements of a commercial laser having an internal diameter of a discharge channel of 14 and 20 mm. It is found that at a pulse repetition frequency of 12 – 14 kHz, corresponding to a maximal output power, the reduction of the energy due to a residual population of metastable states is by an order of magnitude less than due to theirmore » sub-population at a current pulse edge. The modelling based on the experimental results obtained has shown that in the case of an active element with an internal diameter of 14 mm, a decrease in the pulse leading edge from ∼25 ns to 0.6 ns does not reduce the laser pulse energy up to the repetition frequency of ∼50 kHz at an average output power of 70 W m{sup -1} and efficiency of ∼11%. (lasers)« less

Atomic Forces for Geometry-Dependent Point Multipole and Gaussian Multipole Models

PubMed Central

Elking, Dennis M.; Perera, Lalith; Duke, Robert; Darden, Thomas; Pedersen, Lee G.

2010-01-01

In standard treatments of atomic multipole models, interaction energies, total molecular forces, and total molecular torques are given for multipolar interactions between rigid molecules. However, if the molecules are assumed to be flexible, two additional multipolar atomic forces arise due to 1) the transfer of torque between neighboring atoms, and 2) the dependence of multipole moment on internal geometry (bond lengths, bond angles, etc.) for geometry-dependent multipole models. In the current study, atomic force expressions for geometry-dependent multipoles are presented for use in simulations of flexible molecules. The atomic forces are derived by first proposing a new general expression for Wigner function derivatives ∂Dlm′m/∂Ω. The force equations can be applied to electrostatic models based on atomic point multipoles or Gaussian multipole charge density. Hydrogen bonded dimers are used to test the inter-molecular electrostatic energies and atomic forces calculated by geometry-dependent multipoles fit to the ab initio electrostatic potential (ESP). The electrostatic energies and forces are compared to their reference ab initio values. It is shown that both static and geometry-dependent multipole models are able to reproduce total molecular forces and torques with respect to ab initio, while geometry-dependent multipoles are needed to reproduce ab initio atomic forces. The expressions for atomic force can be used in simulations of flexible molecules with atomic multipoles. In addition, the results presented in this work should lead to further development of next generation force fields composed of geometry-dependent multipole models. PMID:20839297

Efficient Multiphoton Generation in Waveguide Quantum Electrodynamics.

PubMed

González-Tudela, A; Paulisch, V; Kimble, H J; Cirac, J I

2017-05-26

Engineering quantum states of light is at the basis of many quantum technologies such as quantum cryptography, teleportation, or metrology among others. Though, single photons can be generated in many scenarios, the efficient and reliable generation of complex single-mode multiphoton states is still a long-standing goal in the field, as current methods either suffer from low fidelities or small probabilities. Here we discuss several protocols which harness the strong and long-range atomic interactions induced by waveguide QED to efficiently load excitations in a collection of atoms, which can then be triggered to produce the desired multiphoton state. In order to boost the success probability and fidelity of each excitation process, atoms are used to both generate the excitations in the rest, as well as to herald the successful generation. Furthermore, to overcome the exponential scaling of the probability of success with the number of excitations, we design a protocol to merge excitations that are present in different internal atomic levels with a polynomial scaling.

Damped-Dynamics Flexible Fitting

PubMed Central

Kovacs, Julio A.; Yeager, Mark; Abagyan, Ruben

2008-01-01

In fitting atomic structures into EM maps, it often happens that the map corresponds to a different conformation of the structure. We have developed a new methodology to handle these situations that preserves the covalent geometry of the structure and allows the modeling of large deformations. The first goal is achieved by working in generalized coordinates (positional and internal coordinates), and the second by avoiding harmonic potentials. Instead, we use dampers (shock absorbers) between every pair of atoms, combined with a force field that attracts the atomic structure toward incompletely occupied regions of the EM map. The trajectory obtained by integrating the resulting equations of motion converges to a conformation that, in our validation cases, was very close to the target atomic structure. Compared to current methods, our approach is more efficient and robust against wrong solutions and to overfitting, and does not require user intervention or subjective decisions. Applications to the computation of transition pathways between known conformers, homology and loop modeling, as well as protein docking, are also discussed. PMID:18586844

Damped-dynamics flexible fitting.

PubMed

Kovacs, Julio A; Yeager, Mark; Abagyan, Ruben

2008-10-01

In fitting atomic structures into EM maps, it often happens that the map corresponds to a different conformation of the structure. We have developed a new methodology to handle these situations that preserves the covalent geometry of the structure and allows the modeling of large deformations. The first goal is achieved by working in generalized coordinates (positional and internal coordinates), and the second by avoiding harmonic potentials. Instead, we use dampers (shock absorbers) between every pair of atoms, combined with a force field that attracts the atomic structure toward incompletely occupied regions of the EM map. The trajectory obtained by integrating the resulting equations of motion converges to a conformation that, in our validation cases, was very close to the target atomic structure. Compared to current methods, our approach is more efficient and robust against wrong solutions and to overfitting, and does not require user intervention or subjective decisions. Applications to the computation of transition pathways between known conformers, homology and loop modeling, as well as protein docking, are also discussed.

Conductive-probe atomic force microscopy characterization of silicon nanowire

PubMed Central

2011-01-01

The electrical conduction properties of lateral and vertical silicon nanowires (SiNWs) were investigated using a conductive-probe atomic force microscopy (AFM). Horizontal SiNWs, which were synthesized by the in-plane solid-liquid-solid technique, are randomly deployed into an undoped hydrogenated amorphous silicon layer. Local current mapping shows that the wires have internal microstructures. The local current-voltage measurements on these horizontal wires reveal a power law behavior indicating several transport regimes based on space-charge limited conduction which can be assisted by traps in the high-bias regime (> 1 V). Vertical phosphorus-doped SiNWs were grown by chemical vapor deposition using a gold catalyst-driving vapor-liquid-solid process on higly n-type silicon substrates. The effect of phosphorus doping on the local contact resistance between the AFM tip and the SiNW was put in evidence, and the SiNWs resistivity was estimated. PMID:21711623

Atomic Oxygen Fluence Monitor

NASA Technical Reports Server (NTRS)

Banks, Bruce A.

2011-01-01

This innovation enables a means for actively measuring atomic oxygen fluence (accumulated atoms of atomic oxygen per area) that has impinged upon spacecraft surfaces. Telemetered data from the device provides spacecraft designers, researchers, and mission managers with real-time measurement of atomic oxygen fluence, which is useful for prediction of the durability of spacecraft materials and components. The innovation is a compact fluence measuring device that allows in-space measurement and transmittance of measured atomic oxygen fluence as a function of time based on atomic oxygen erosion yields (the erosion yield of a material is the volume of material that is oxidized per incident oxygen atom) of materials that have been measured in low Earth orbit. It has a linear electrical response to atomic oxygen fluence, and is capable of measuring high atomic oxygen fluences (up to >10(exp 22) atoms/sq cm), which are representative of multi-year low-Earth orbital missions (such as the International Space Station). The durability or remaining structural lifetime of solar arrays that consist of polymer blankets on which the solar cells are attached can be predicted if one knows the atomic oxygen fluence that the solar array blanket has been exposed to. In addition, numerous organizations that launch space experiments into low-Earth orbit want to know the accumulated atomic oxygen fluence that their materials or components have been exposed to. The device is based on the erosion yield of pyrolytic graphite. It uses two 12deg inclined wedges of graphite that are over a grit-blasted fused silica window covering a photodiode. As the wedges erode, a greater area of solar illumination reaches the photodiode. A reference photodiode is also used that receives unobstructed solar illumination and is oriented in the same direction as the pyrolytic graphite covered photodiode. The short-circuit current from the photodiodes is measured and either sent to an onboard data logger, or transmitted to a receiving station on Earth. By comparison of the short-circuit currents from the fluence-measuring photodiode and the reference photodiode, one can compute the accumulated atomic oxygen fluence arriving in the direction that the fluence monitor is pointing. The device produces a signal that is linear with atomic oxygen fluence using a material whose atomic oxygen erosion yield has been measured over a period of several years in low-Earth orbit.

Falling Behind: International Scrutiny of the Peaceful Atom

DTIC Science & Technology

2008-02-01

confused with critical masses .5 Significant quantity values currently in use by the IAEA are given in Table 1. In a previous Natural Resources... actinides and fission products would not add significantly to the plutonium mass , the state could divert the spiked plutonium to a small clandestine...and manufacturing processes and should not be 152 confused with critical masses . Significant quantities are used in establishing the quantity

Thermodynamics of atomic and ionized hydrogen: analytical results versus equation-of-state tables and Monte Carlo data.

PubMed

Alastuey, A; Ballenegger, V

2012-12-01

We compute thermodynamical properties of a low-density hydrogen gas within the physical picture, in which the system is described as a quantum electron-proton plasma interacting via the Coulomb potential. Our calculations are done using the exact scaled low-temperature (SLT) expansion, which provides a rigorous extension of the well-known virial expansion-valid in the fully ionized phase-into the Saha regime where the system is partially or fully recombined into hydrogen atoms. After recalling the SLT expansion of the pressure [A. Alastuey et al., J. Stat. Phys. 130, 1119 (2008)], we obtain the SLT expansions of the chemical potential and of the internal energy, up to order exp(-|E_{H}|/kT) included (E_{H}≃-13.6 eV). Those truncated expansions describe the first five nonideal corrections to the ideal Saha law. They account exactly, up to the considered order, for all effects of interactions and thermal excitations, including the formation of bound states (atom H, ions H^{-} and H_{2}^{+}, molecule H_{2},⋯) and atom-charge and atom-atom interactions. Among the five leading corrections, three are easy to evaluate, while the remaining ones involve well-defined internal partition functions for the molecule H_{2} and ions H^{-} and H_{2}^{+}, for which no closed-form analytical formula exist currently. We provide accurate low-temperature approximations for those partition functions by using known values of rotational and vibrational energies. We compare then the predictions of the SLT expansion, for the pressure and the internal energy, with, on the one hand, the equation-of-state tables obtained within the opacity program at Livermore (OPAL) and, on the other hand, data of path integral quantum Monte Carlo (PIMC) simulations. In general, a good agreement is found. At low densities, the simple analytical SLT formulas reproduce the values of the OPAL tables up to the last digit in a large range of temperatures, while at higher densities (ρ∼10^{-2} g/cm^{3}), some discrepancies among the SLT, OPAL, and PIMC results are observed.

[Study on the method for the determination of trace boron, molybdenum, silver, tin and lead in geochemical samples by direct current arc full spectrum direct reading atomic emission spectroscopy (DC-Arc-AES)].

PubMed

Hao, Zhi-hong; Yao, Jian-zhen; Tang, Rui-ling; Zhang, Xue-mei; Li, Wen-ge; Zhang, Qin

2015-02-01

The method for the determmation of trace boron, molybdenum, silver, tin and lead in geochemical samples by direct current are full spectrum direct reading atomic emission spectroscopy (DC-Arc-AES) was established. Direct current are full spectrum direct reading atomic emission spectrometer with a large area of solid-state detectors has functions of full spectrum direct reading and real-time background correction. The new electrodes and new buffer recipe were proposed in this paper, and have applied for national patent. Suitable analytical line pairs, back ground correcting points of elements and the internal standard method were selected, and Ge was used as internal standard. Multistage currents were selected in the research on current program, and each current set different holding time to ensure that each element has a good signal to noise ratio. Continuous rising current mode selected can effectively eliminate the splash of the sample. Argon as shielding gas can eliminate CN band generating and reduce spectral background, also plays a role in stabilizing the are, and argon flow 3.5 L x min(-1) was selected. Evaporation curve of each element was made, and it was concluded that the evaporation behavior of each element is consistent, and combined with the effects of different spectrographic times on the intensity and background, the spectrographic time of 35s was selected. In this paper, national standards substances were selected as a standard series, and the standard series includes different nature and different content of standard substances which meet the determination of trace boron, molybdenum, silver, tin and lead in geochemical samples. In the optimum experimental conditions, the detection limits for B, Mo, Ag, Sn and Pb are 1.1, 0.09, 0.01, 0.41, and 0.56 microg x g(-1) respectively, and the precisions (RSD, n=12) for B, Mo, Ag, Sn and Pb are 4.57%-7.63%, 5.14%-7.75%, 5.48%-12.30%, 3.97%-10.46%, and 4.26%-9.21% respectively. The analytical accuracy was validated by national standards and the results are in agreement with certified values. The method is simple, rapid, is an advanced analytical method for the determination of trace amounts of geochemical samples' boron, molybdenum, silver, tin and lead, and has a certain practicality.

iMODFIT: efficient and robust flexible fitting based on vibrational analysis in internal coordinates.

PubMed

Lopéz-Blanco, José Ramón; Chacón, Pablo

2013-11-01

Here, we employed the collective motions extracted from Normal Mode Analysis (NMA) in internal coordinates (torsional space) for the flexible fitting of atomic-resolution structures into electron microscopy (EM) density maps. The proposed methodology was validated using a benchmark of simulated cases, highlighting its robustness over the full range of EM resolutions and even over coarse-grained representations. A systematic comparison with other methods further showcased the advantages of this proposed methodology, especially at medium to lower resolutions. Using this method, computational costs and potential overfitting problems are naturally reduced by constraining the search in low-frequency NMA space, where covalent geometry is implicitly maintained. This method also effectively captures the macromolecular changes of a representative set of experimental test cases. We believe that this novel approach will extend the currently available EM hybrid methods to the atomic-level interpretation of large conformational changes and their functional implications. Copyright © 2013 Elsevier Inc. All rights reserved.

5 CFR 352.403 - Definitions.

Code of Federal Regulations, 2012 CFR

2012-01-01

... of Presidential Appointees and Elected Officers by the International Atomic Energy Agency § 352.403 Definitions. In this subpart: (a) Agency means the International Atomic Energy Agency; (b) Officer means any...

5 CFR 352.403 - Definitions.

Code of Federal Regulations, 2011 CFR

2011-01-01

... of Presidential Appointees and Elected Officers by the International Atomic Energy Agency § 352.403 Definitions. In this subpart: (a) Agency means the International Atomic Energy Agency; (b) Officer means any...

5 CFR 352.403 - Definitions.

Code of Federal Regulations, 2013 CFR

2013-01-01

... of Presidential Appointees and Elected Officers by the International Atomic Energy Agency § 352.403 Definitions. In this subpart: (a) Agency means the International Atomic Energy Agency; (b) Officer means any...

5 CFR 352.403 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-01-01

... of Presidential Appointees and Elected Officers by the International Atomic Energy Agency § 352.403 Definitions. In this subpart: (a) Agency means the International Atomic Energy Agency; (b) Officer means any...

5 CFR 352.403 - Definitions.

Code of Federal Regulations, 2014 CFR

2014-01-01

... of Presidential Appointees and Elected Officers by the International Atomic Energy Agency § 352.403 Definitions. In this subpart: (a) Agency means the International Atomic Energy Agency; (b) Officer means any...

An atomic gravitational wave interferometric sensor in low earth orbit (AGIS-LEO)

NASA Astrophysics Data System (ADS)

Hogan, Jason M.; Johnson, David M. S.; Dickerson, Susannah; Kovachy, Tim; Sugarbaker, Alex; Chiow, Sheng-Wey; Graham, Peter W.; Kasevich, Mark A.; Saif, Babak; Rajendran, Surjeet; Bouyer, Philippe; Seery, Bernard D.; Feinberg, Lee; Keski-Kuha, Ritva

2011-07-01

We propose an atom interferometer gravitational wave detector in low Earth orbit (AGIS-LEO). Gravitational waves can be observed by comparing a pair of atom interferometers separated by a 30 km baseline. In the proposed configuration, one or three of these interferometer pairs are simultaneously operated through the use of two or three satellites in formation flight. The three satellite configuration allows for the increased suppression of multiple noise sources and for the detection of stochastic gravitational wave signals. The mission will offer a strain sensitivity of {<10^{-18}/sqrt{Hz}} in the 50mHz-10Hz frequency range, providing access to a rich scientific region with substantial discovery potential. This band is not currently addressed with the LIGO, VIRGO, or LISA instruments. We analyze systematic backgrounds that are relevant to the mission and discuss how they can be mitigated at the required levels. Some of these effects do not appear to have been considered previously in the context of atom interferometry, and we therefore expect that our analysis will be broadly relevant to atom interferometric precision measurements. Finally, we present a brief conceptual overview of shorter-baseline ({lesssim100 m}) atom interferometer configurations that could be deployed as proof-of-principle instruments on the International Space Station (AGIS-ISS) or an independent satellite.

Application of Temperature-Controlled Thermal Atomization for Printing Electronics in Space

NASA Technical Reports Server (NTRS)

Wu, Chih-Hao; Thompson, Furman V.

2017-01-01

Additive Manufacturing (AM) is a technology that builds three dimensional objects by adding material layer-upon-layer throughout the fabrication process. The Electrical, Electronic and Electromechanical (EEE) parts packaging group at Marshall Space Flight Center (MSFC) is investigating how various AM and 3D printing processes can be adapted to the microgravity environment of space to enable on demand manufacturing of electronics. The current state-of-the art processes for accomplishing the task of printing electronics through non-contact, direct-write means rely heavily on the process of atomization of liquid inks into fine aerosols to be delivered ultimately to a machine's print head and through its nozzle. As a result of cumulative International Space Station (ISS) research into the behaviors of fluids in zero-gravity, our experience leads us to conclude that the direct adaptation of conventional atomization processes will likely fall short and alternative approaches will need to be explored. In this report, we investigate the development of an alternative approach to atomizing electronic materials by way of thermal atomization, to be used in place of conventional aerosol generation and delivery processes for printing electronics in space.

Effect of the intra-layer potential distributions and spatial currents on the performance of graphene SymFETs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hasan, Mehdi; Sensale-Rodriguez, Berardi, E-mail: berardi.sensale@utah.edu

2015-09-15

In this paper, a two-dimensional (2-D) model for a graphene symmetric field effect transistor (SymFET), which considers (a) the intra-graphene layer potential distributions and (b) the internal current flows through the device, is presented and discussed. The local voltages along the graphene electrodes as well as the current-voltage characteristics of the device are numerically calculated based on a single-particle tunneling model. Our numerical results show that: (i) when the tunneling current is small, due to either a large tunneling thickness (≥ 2 atomic layers of BN) or a small coherence length, the voltage distributions along the graphene electrodes have almostmore » zero variations upon including these distributed effects, (ii) when the tunnel current is large, due to either a small tunneling thickness (∼ 1 atomic layer of BN) or due to a large coherence length, the local voltage distributions along the graphene electrodes become appreciable and the device behavior deviates from that predicted by a 1-D approximation. These effects, which are not captured in one-dimensional SymFET models, can provide a better understanding about the electron dynamics in the device and might indicate potential novel applications for this proposed device.« less

Test of time-reversal invariance at COSY (TRIC)

NASA Astrophysics Data System (ADS)

Eversheim, D.; Valdau, Yu.; Lorentz, B.

2013-03-01

At the Cooler Synchrotron COSY a novel (P-even, T-odd) null test of time-reversal invariance to an accuracy of 10 - 6 is planned as an internal target transmission experiment. The parity conserving time-reversal violating observable is the total cross-section asymmetry Ay,xz. This quantity is measured using a polarized proton beam with an energy of 135 MeV and an internal tensor polarized deuteron target from the PAX atomic beam source. The reaction rate will be measured by means of an integrating beam current transformer. Thus, in this experiment the cooler synchroton ring serves as ideal forward spectrometer, as a detector, and an accelerator.

Interplay between Switching Driven by the Tunneling Current and Atomic Force of a Bistable Four-Atom Si Quantum Dot.

PubMed

Yamazaki, Shiro; Maeda, Keisuke; Sugimoto, Yoshiaki; Abe, Masayuki; Zobač, Vladimír; Pou, Pablo; Rodrigo, Lucia; Mutombo, Pingo; Pérez, Ruben; Jelínek, Pavel; Morita, Seizo

2015-07-08

We assemble bistable silicon quantum dots consisting of four buckled atoms (Si4-QD) using atom manipulation. We demonstrate two competing atom switching mechanisms, downward switching induced by tunneling current of scanning tunneling microscopy (STM) and opposite upward switching induced by atomic force of atomic force microscopy (AFM). Simultaneous application of competing current and force allows us to tune switching direction continuously. Assembly of the few-atom Si-QDs and controlling their states using versatile combined AFM/STM will contribute to further miniaturization of nanodevices.

Improving Hall Thruster Plume Simulation through Refined Characterization of Near-field Plasma Properties

NASA Astrophysics Data System (ADS)

Huismann, Tyler D.

Due to the rapidly expanding role of electric propulsion (EP) devices, it is important to evaluate their integration with other spacecraft systems. Specifically, EP device plumes can play a major role in spacecraft integration, and as such, accurate characterization of plume structure bears on mission success. This dissertation addresses issues related to accurate prediction of plume structure in a particular type of EP device, a Hall thruster. This is done in two ways: first, by coupling current plume simulation models with current models that simulate a Hall thruster's internal plasma behavior; second, by improving plume simulation models and thereby increasing physical fidelity. These methods are assessed by comparing simulated results to experimental measurements. Assessment indicates the two methods improve plume modeling capabilities significantly: using far-field ion current density as a metric, these approaches used in conjunction improve agreement with measurements by a factor of 2.5, as compared to previous methods. Based on comparison to experimental measurements, recent computational work on discharge chamber modeling has been largely successful in predicting properties of internal thruster plasmas. This model can provide detailed information on plasma properties at a variety of locations. Frequently, experimental data is not available at many locations that are of interest regarding computational models. Excepting the presence of experimental data, there are limited alternatives for scientifically determining plasma properties that are necessary as inputs into plume simulations. Therefore, this dissertation focuses on coupling current models that simulate internal thruster plasma behavior with plume simulation models. Further, recent experimental work on atom-ion interactions has provided a better understanding of particle collisions within plasmas. This experimental work is used to update collision models in a current plume simulation code. Previous versions of the code assume an unknown dependence between particles' pre-collision velocities and post-collision scattering angles. This dissertation focuses on updating several of these types of collisions by assuming a curve fit based on the measurements of atom-ion interactions, such that previously unknown angular dependences are well-characterized.

Sixteenth International Conference on the physics of electronic and atomic collisions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dalgarno, A.; Freund, R.S.; Lubell, M.S.

1989-01-01

This report contains abstracts of papers on the following topics: photons, electron-atom collisions; electron-molecule collisions; electron-ion collisions; collisions involving exotic species; ion- atom collisions, ion-molecule or atom-molecule collisions; atom-atom collisions; ion-ion collisions; collisions involving rydberg atoms; field assisted collisions; collisions involving clusters and collisions involving condensed matter.

Development of the negative ion beams relevant to ITER and JT-60SA at Japan Atomic Energy Agency.

PubMed

Hanada, M; Kojima, A; Tobari, H; Nishikiori, R; Hiratsuka, J; Kashiwagi, M; Umeda, N; Yoshida, M; Ichikawa, M; Watanabe, K; Yamano, Y; Grisham, L R

2016-02-01

In order to realize negative ion sources and accelerators to be applicable to International Thermonuclear Experimental Reactor and JT-60 Super Advanced, a large cesium (Cs)-seeded negative ion source and a multi-aperture and multi-stage electric acceleration have been developed at Japan Atomic Energy Agency (JAEA). Long pulse production and acceleration of the negative ion beams have been independently carried out. The long pulse production of the high current beams has achieved 100 s at the beam current of 15 A by modifying the JT-60 negative ion source. The pulse duration time is increased three times longer than that before the modification. As for the acceleration, a pulse duration time has been also extended two orders of magnitudes from 0.4 s to 60 s. The developments of the negative ion source and acceleration at JAEA are well in progress towards the realization of the negative ion sources and accelerators for fusion applications.

Real-time sub-Ångstrom imaging of reversible and irreversible conformations in rhodium catalysts and graphene

NASA Astrophysics Data System (ADS)

Kisielowski, Christian; Wang, Lin-Wang; Specht, Petra; Calderon, Hector A.; Barton, Bastian; Jiang, Bin; Kang, Joo H.; Cieslinski, Robert

2013-07-01

The dynamic responses of a rhodium catalyst and a graphene sheet are investigated upon random excitation with 80 kV electrons. An extraordinary electron microscope stability and resolution allow studying temporary atom displacements from their equilibrium lattice sites into metastable sites across projected distances as short as 60 pm. In the rhodium catalyst, directed and reversible atom displacements emerge from excitations into metastable interstitial sites and surface states that can be explained by single atom trajectories. Calculated energy barriers of 0.13 eV and 1.05 eV allow capturing single atom trapping events at video rates that are stabilized by the Rh [110] surface corrugation. Molecular dynamics simulations reveal that randomly delivered electrons can also reversibly enhance the sp3 and the sp1 characters of the sp2-bonded carbon atoms in graphene. The underlying collective atom motion can dynamically stabilize characteristic atom displacements that are unpredictable by single atom trajectories. We detect three specific displacements and use two of them to propose a path for the irreversible phase transformation of a graphene nanoribbon into carbene. Collectively stabilized atom displacements greatly exceed the thermal vibration amplitudes described by Debye-Waller factors and their measured dose rate dependence is attributed to tunable phonon contributions to the internal energy of the systems. Our experiments suggest operating electron microscopes with beam currents as small as zepto-amperes/nm2 in a weak-excitation approach to improve on sample integrity and allow for time-resolved studies of conformational object changes that probe for functional behavior of catalytic surfaces or molecules.

The International Colloquium on Atomic Spectra and Oscillator Strengths for Astrophysical and Laboratory Plasmas

NASA Technical Reports Server (NTRS)

Sugar, J.; Leckrone, D.

1993-01-01

This was the fourth in a series of colloquia begun at the University of Lund, Sweden in 1983 and subsequently held in Toledo, Ohio and Amsterdam, The Netherlands. The purpose of these meetings is to provide an international forum for communication between major users of atomic spectroscopic data and the providers of these data. These data include atomic wavelengths, line shapes, energy levels, lifetimes, and oscillator strengths. Speakers were selected from a wide variety of disciplines including astrophysics, laboratory plasma research, spectrochemistry, and theoretical and experimental atomic physics.

Comparison of Y-jet and OIL effervescent atomizers based on internal and external two-phase flow characteristics

NASA Astrophysics Data System (ADS)

Mlkvik, Marek; Zaremba, Matous; Jedelsky, Jan; Jicha, Miroslav

2016-03-01

Presented paper focuses on spraying of two viscous liquids (μ = 60 and 143 mPa·s) by two types of twinfluid atomizers with internal mixing. We compared the well-known Y-jet atomizer with the less known, "outside in liquid" (OIL), configuration of the effervescent atomizer. The required liquid viscosity was achieved by using the water-maltodextrin solutions of different concentrations. Both the liquids were sprayed at two gas inlet pressures (Δp = 0.14 and 0.28 MPa) and various gas-to-liquid ratios (GLR = 2.5%, 5%, 10% and 20%). The comparison was focused on four characteristics: liquid flow-rate (for the same working regimes, defined by Δp and GLR), internal flow regimes, Weber numbers of a liquid breakup (We) and droplet sizes. A high-speed camera and Malvern Spraytec laser diffraction system were used to obtain necessary experimental data. Comparing the results of our experiments, we can state that for both the liquids the OIL atomizer reached higher liquid flow-rates at corresponding working regimes, it was typical by annular internal flow and higher We in the near-nozzle region at all the working regimes. As a result, it produced considerably smaller droplets than the second tested atomizing device, especially for GLR < 10%.

Single atoms in a MOT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meschede, Dieter; Ueberholz, Bernd; Gomer, Victor

1999-06-11

We are experimenting with individual neutral cesium atoms stored in a magneto-optical trap. The atoms are detected by their resonance fluorescence, and fluorescence fluctuations contain signatures of the atomic internal and external degrees of freedom. This noninvasive probe provides a rich source of information about atomic dynamics at all relevant time scales.

Technology development for laser-cooled clocks on the International Space Station

NASA Technical Reports Server (NTRS)

Klipstein, W. M.

2003-01-01

The PARCS experiment will use a laser-cooled cesium atomic clock operating in the microgravity environment aboard the International Space Station to provide both advanced tests of gravitational theory to demonstrate a new cold-atom clock technology for space.

Internal Spin Control, Squeezing and Decoherence in Ensembles of Alkali Atomic Spins

NASA Astrophysics Data System (ADS)

Norris, Leigh Morgan

Large atomic ensembles interacting with light are one of the most promising platforms for quantum information processing. In the past decade, novel applications for these systems have emerged in quantum communication, quantum computing, and metrology. Essential to all of these applications is the controllability of the atomic ensemble, which is facilitated by a strong coupling between the atoms and light. Non-classical spin squeezed states are a crucial step in attaining greater ensemble control. The degree of entanglement present in these states, furthermore, serves as a benchmark for the strength of the atom-light interaction. Outside the broader context of quantum information processing with atomic ensembles, spin squeezed states have applications in metrology, where their quantum correlations can be harnessed to improve the precision of magnetometers and atomic clocks. This dissertation focuses upon the production of spin squeezed states in large ensembles of cold trapped alkali atoms interacting with optical fields. While most treatments of spin squeezing consider only the case in which the ensemble is composed of two level systems or qubits, we utilize the entire ground manifold of an alkali atom with hyperfine spin f greater than or equal to 1/2, a qudit. Spin squeezing requires non-classical correlations between the constituent atomic spins, which are generated through the atoms' collective coupling to the light. Either through measurement or multiple interactions with the atoms, the light mediates an entangling interaction that produces quantum correlations. Because the spin squeezing treated in this dissertation ultimately originates from the coupling between the light and atoms, conventional approaches of improving this squeezing have focused on increasing the optical density of the ensemble. The greater number of internal degrees of freedom and the controllability of the spin-f ground hyperfine manifold enable novel methods of enhancing squeezing. In particular, we find that state preparation using control of the internal hyperfine spin increases the entangling power of squeezing protocols when f>1/2. Post-processing of the ensemble using additional internal spin control converts this entanglement into metrologically useful spin squeezing. By employing a variation of the Holstein-Primakoff approximation, in which the collective spin observables of the atomic ensemble are treated as quadratures of a bosonic mode, we model entanglement generation, spin squeezing and the effects of internal spin control. The Holstein-Primakoff formalism also enables us to take into account the decoherence of the ensemble due to optical pumping. While most works ignore or treat optical pumping phenomenologically, we employ a master equation derived from first principles. Our analysis shows that state preparation and the hyperfine spin size have a substantial impact upon both the generation of spin squeezing and the decoherence of the ensemble. Through a numerical search, we determine state preparations that enhance squeezing protocols while remaining robust to optical pumping. Finally, most work on spin squeezing in atomic ensembles has treated the light as a plane wave that couples identically to all atoms. In the final part of this dissertation, we go beyond the customary plane wave approximation on the light and employ focused paraxial beams, which are more efficiently mode matched to the radiation pattern of the atomic ensemble. The mathematical formalism and the internal spin control techniques that we applied in the plane wave case are generalized to accommodate the non-homogeneous paraxial probe. We find the optimal geometries of the atomic ensemble and the probe for mode matching and generation of spin squeezing.

Internal Spin Control, Squeezing and Decoherence in Ensembles of Alkali Atomic Spins

NASA Astrophysics Data System (ADS)

Norris, Leigh Morgan

Large atomic ensembles interacting with light are one of the most promising platforms for quantum information processing. In the past decade, novel applications for these systems have emerged in quantum communication, quantum computing, and metrology. Essential to all of these applications is the controllability of the atomic ensemble, which is facilitated by a strong coupling between the atoms and light. Non-classical spin squeezed states are a crucial step in attaining greater ensemble control. The degree of entanglement present in these states, furthermore, serves as a benchmark for the strength of the atom-light interaction. Outside the broader context of quantum information processing with atomic ensembles, spin squeezed states have applications in metrology, where their quantum correlations can be harnessed to improve the precision of magnetometers and atomic clocks. This dissertation focuses upon the production of spin squeezed states in large ensembles of cold trapped alkali atoms interacting with optical fields. While most treatments of spin squeezing consider only the case in which the ensemble is composed of two level systems or qubits, we utilize the entire ground manifold of an alkali atom with hyperfine spin f greater or equal to 1/2, a qudit. Spin squeezing requires non-classical correlations between the constituent atomic spins, which are generated through the atoms' collective coupling to the light. Either through measurement or multiple interactions with the atoms, the light mediates an entangling interaction that produces quantum correlations. Because the spin squeezing treated in this dissertation ultimately originates from the coupling between the light and atoms, conventional approaches of improving this squeezing have focused on increasing the optical density of the ensemble. The greater number of internal degrees of freedom and the controllability of the spin-f ground hyperfine manifold enable novel methods of enhancing squeezing. In particular, we find that state preparation using control of the internal hyperfine spin increases the entangling power of squeezing protocols when f >1/2. Post-processing of the ensemble using additional internal spin control converts this entanglement into metrologically useful spin squeezing. By employing a variation of the Holstein-Primakoff approximation, in which the collective spin observables of the atomic ensemble are treated as quadratures of a bosonic mode, we model entanglement generation, spin squeezing and the effects of internal spin control. The Holstein-Primakoff formalism also enables us to take into account the decoherence of the ensemble due to optical pumping. While most works ignore or treat optical pumping phenomenologically, we employ a master equation derived from first principles. Our analysis shows that state preparation and the hyperfine spin size have a substantial impact upon both the generation of spin squeezing and the decoherence of the ensemble. Through a numerical search, we determine state preparations that enhance squeezing protocols while remaining robust to optical pumping. Finally, most work on spin squeezing in atomic ensembles has treated the light as a plane wave that couples identically to all atoms. In the final part of this dissertation, we go beyond the customary plane wave approximation on the light and employ focused paraxial beams, which are more efficiently mode matched to the radiation pattern of the atomic ensemble. The mathematical formalism and the internal spin control techniques that we applied in the plane wave case are generalized to accommodate the non-homogeneous paraxial probe. We find the optimal geometries of the atomic ensemble and the probe for mode matching and generation of spin squeezing.

Experimental Preparation and Measurement of Quantum States of Motion of a Trapped Atom

DTIC Science & Technology

1997-01-01

trapped atom are quantum harmonic oscillators, their couplings to internal atomic levels (described by the Jaynes - Cummings model (JCM) [ l , 21) are... wave approximation in a frame rotating with WO, where hwo is the energy difference of the two internal levels, the interaction of the classical laser... Jaynes - Cummings model , the system is suited to realizing many proposals originally introduced in the realm of quantum optics and cavity quantum

PREFACE: NC-AFM 2003: Proceedings of the 6th International Conference on Non-contact Atomic Force Microscopy

NASA Astrophysics Data System (ADS)

Reichling, Michael

2004-02-01

Direct nanoscale and atomic resolution imaging is a key issue in nanoscience and nanotechnology. The invention of the dynamic force microscope in the early 1990s was an important step forward in this direction as this instrument provides a universal tool for measuring the topography and many other physical and chemical properties of surfaces at the nanoscale. Operation in the so-called non-contact mode now allows direct atomic resolution imaging of electrically insulating surfaces and nanostructures which has been an unsolved problem during the first decade of nanotechnology. Today, we face a most rapid development of the technique and an extension of its capabilities far beyond imaging; atomically resolved force spectroscopy provides information about local binding properties and researchers now develop sophisticated schemes of force controlled atomic manipulation with the tip of the force microscope. Progress in the field of non-contact force microscopy is discussed at the annually held NC-AFM conferences that are part of a series started in 1998 with a meeting in Osaka, Japan. The 6th International Conference on Non-contact Atomic Force Microscopy took place in Dingle, Ireland, from 31 August to 3 September 2003 and this special issue is a compilation of the original publications of work presented at this meeting. The papers published here well reflect recent achievements, current trends and some of the challenging new directions in non-contact force microscopy that have been discussed during the most stimulating conference days in Dingle. Fundamental aspects of forces and dissipation relevant in imaging and spectroscopy have been covered by experimental and theoretical contributions yielding a more detailed understanding of tip--surface interaction in force microscopy. Novel and improved imaging and spectroscopy techniques have been introduced that either improve the performance of force microscopy or pave the way towards new functionalities and applications. With regard to studies on the specific systems investigated, there was a strong emphasis on oxides and ionics, as well as on organic systems. Following previous pioneering work in uncovering the atomic structure of insulating oxides with force microscopy, it was shown in the meeting that this important class of materials is now accessible for a quantitative atomic scale surface characterization. Single organic molecules and ordered organic layers are building blocks for functional nanostructures currently developed in many laboratories for applications in molecular electronics and sensor technologies. The Dingle conference impressively demonstrated that dynamic force microscopy is ready for its application as an analytical tool for these promising future nanotechnologies. The meeting was a great success scientifically and participants enjoyed the beauty of the conference site. I would like to thank all members of the international steering committee, the programme committee and the co-chairs, J Pethica, A Shluger and G Thornton, for their efforts in preparing the meeting. The members of the local organising committee, J Ballentine-Armstrong, G Cross, S Dunne, S Jarvis and Ö Özer, kept the meeting running smoothly and created a very pleasant atmosphere. The generous financial support from Science Foundation Ireland (SFI), is greatly appreciated; SFI is dramatically raising the profile of Irish science. I would also like to express my sincere gratitude to N Couzin and the journal team from Institute of Physics Publishing for their editorial management and perfect co-operation in the preparation of this special issue.

Replacing critical rare earth materials in high energy density magnets

NASA Astrophysics Data System (ADS)

McCallum, R. William

2012-02-01

High energy density permanent magnets are crucial to the design of internal permanent magnet motors (IPM) for hybride and electric vehicles and direct drive wind generators. Current motor designs use rare earth permanent magnets which easily meet the performance goals, however, the rising concerns over cost and foreign control of the current supply of rare earth resources has motivated a search for non-rare earth based permanent magnets alloys with performance metrics which allow the design of permanent magnet motors and generators without rare earth magnets. This talk will discuss the state of non-rare-earth permanent magnets and efforts to both improve the current materials and find new materials. These efforts combine first principles calculations and meso-scale magnetic modeling with advance characterization and synthesis techniques in order to advance the state of the art in non rare earth permanent magnets. The use of genetic algorithms in first principle structural calculations, combinatorial synthesis in the experimental search for materials, atom probe microscopy to characterize grain boundaries on the atomic level, and other state of the art techniques will be discussed. In addition the possibility of replacing critical rare earth elements with the most abundant rare earth Ce will be discussed.

The EDDA experiment at COSY

NASA Astrophysics Data System (ADS)

Rohdjess, H.

1998-01-01

Polarized and unpolarized proton-proton elastic scattering is investigated with the EDDA-experiment at the Cooler Synchrotron COSY at Jülich to significantly improve the world data base in the beam energy range 500-2500 MeV. Measurements during beam acceleration with thin internal targets and a large acceptance detector produce excitation functions over a broad angular and energy range with unprecedented internal consistency. Data taking with an unpolarized CH2 fiber target and an unpolarized beam have been completed and the derived differential cross sections demonstrate the benefit of this technique. With a polarized atomic beam target recently installed in COSY and a polarized COSY beam—currently under development—the measurements will be extended to analyzing powers and spin correlation parameters.

Information exchange of the Atomic Energy Society of Japan with nuclear societies worldwide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hori, Masao; Tomita, Yasushi

2000-07-01

The Atomic Energy Society of Japan (AESJ) exchanges information with nuclear societies worldwide by intersocietal communication through international councils of nuclear societies and through bilateral agreements between foreign societies and by such media as international meetings, publications, and Internet applications.

76 FR 51357 - Notice of Availability: American Assured Fuel Supply

Federal Register 2010, 2011, 2012, 2013, 2014

2011-08-18

... nonproliferation objectives by supporting civil nuclear energy development while minimizing proliferation risks... to the Atomic Energy of 1954, as amended (Pub. L. 83-703), and the Nuclear Non-Proliferation Act of... the International Atomic Energy Agency's (IAEA) International Nuclear Fuel Bank (INFB) initiative...

Clarifying Atomic Weights: A 2016 Four-Figure Table of Standard and Conventional Atomic Weights

ERIC Educational Resources Information Center

Coplen, Tyler B.; Meyers, Fabienne; Holden, Norman E.

2017-01-01

To indicate that atomic weights of many elements are not constants of nature, in 2009 and 2011 the Commission on Isotopic Abundances and Atomic Weights (CIAAW) of the International Union of Pure and Applied Chemistry (IUPAC) replaced single-value standard atomic weight values with atomic weight intervals for 12 elements (hydrogen, lithium, boron,…

Top-down, decoupled control of constitutive parameters in electromagnetic metamaterials with dielectric resonators of internal anisotropy.

PubMed

Koo, Sukmo; Mason, Daniel R; Kim, Yunjung; Park, Namkyoo

2017-02-10

A meta-atom platform providing decoupled tuning for the constitutive wave parameters remains as a challenging problem, since the proposition of Pendry. Here we propose an electromagnetic meta-atom design of internal anisotropy (ε r  ≠ ε θ ), as a pathway for decoupling of the effective- permittivity ε eff and permeability μ eff . Deriving effective parameters for anisotropic meta-atom from the first principles, and then subsequent inverse-solving the obtained decoupled solution for a target set of ε eff and μ eff , we also achieve an analytic, top-down determination for the internal structure of a meta-atom. To realize the anisotropy from isotropic materials, a particle of spatial permittivity modulation in r or θ direction is proposed. As an application example, a matched zero index dielectric meta-atom is demonstrated, to enable the super-funneling of a 50λ-wide flux through a sub-λ slit; unharnessing the flux collection limit dictated by the λ-zone.

Top-down, decoupled control of constitutive parameters in electromagnetic metamaterials with dielectric resonators of internal anisotropy

NASA Astrophysics Data System (ADS)

Koo, Sukmo; Mason, Daniel R.; Kim, Yunjung; Park, Namkyoo

2017-02-01

A meta-atom platform providing decoupled tuning for the constitutive wave parameters remains as a challenging problem, since the proposition of Pendry. Here we propose an electromagnetic meta-atom design of internal anisotropy (εr ≠ εθ), as a pathway for decoupling of the effective- permittivity εeff and permeability μeff. Deriving effective parameters for anisotropic meta-atom from the first principles, and then subsequent inverse-solving the obtained decoupled solution for a target set of εeff and μeff, we also achieve an analytic, top-down determination for the internal structure of a meta-atom. To realize the anisotropy from isotropic materials, a particle of spatial permittivity modulation in r or θ direction is proposed. As an application example, a matched zero index dielectric meta-atom is demonstrated, to enable the super-funneling of a 50λ-wide flux through a sub-λ slit; unharnessing the flux collection limit dictated by the λ-zone.

77 FR 6094 - Submission for OMB Review; Comment Request

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-07

....-International Atomic Energy Agency Additional Protocol. Under the U.S.-International Atomic Energy Agency (IAEA...-related activities to the IAEA and potentially provide access to IAEA inspectors for verification purposes. The U.S.-IAEA Additional Protocol permits the United States unilaterally to declare exclusions from...

TIPTOPbase: the Iron Project and the Opacity Project Atomic Database

NASA Astrophysics Data System (ADS)

Mendoza, Claudio; Nahar, Sultana; Pradhan, Anil; Seaton, Micheal; Zeippen, Claude

2001-05-01

The Opacity Project, the IRON Project, and the RmaX Network (The Opacity Project Team, Vol.1,2), IOPP, Bristol (1995,1996); Hummer et al., Astron. Astrophys. 279, 298 (1993) are international computational efforts concerned with the production of high quality atomic data for astrophysical applications. Research groups from Canada, France, Germany, UK, USA and Venezuela are involved. Extensive data sets containing accurate energy levels, f-values, A-values, photoionisation cross sections, collision strengths, recombination rates, and opacitites have been computed for cosmically abundant elements using state-of-the-art atomic physics codes. Their volume, completeness and overall accuracy are presently unmatched in the field of laboratory astrophysics. Some of the data sets have been available since 1993 from a public on-line database service referred to as TOPbase (Cunto et al Astron. Astrophys. 275), L5 (1993), ( http://cdsweb.u-strasbg.fr/OP.html at CDS France, and http://heasarc.gsfc.nasa.gov/topbase, at NSAS USA). We are currently involved in a major effort to scale the existing database services to develop a robust platform for the high-profile dissemination of atomic data to the scientific community within the next 12 months. (Partial support from the NSF and NASA is acknowledged.)

Control of atomic transition rates via laser-light shaping

NASA Astrophysics Data System (ADS)

Jáuregui, R.

2015-04-01

A modular systematic analysis of the feasibility of modifying atomic transition rates by tailoring the electromagnetic field of an external coherent light source is presented. The formalism considers both the center of mass and internal degrees of freedom of the atom, and all properties of the field: frequency, angular spectrum, and polarization. General features of recoil effects for internal forbidden transitions are discussed. A comparative analysis of different structured light sources is explicitly worked out. It includes spherical waves, Gaussian beams, Laguerre-Gaussian beams, and propagation invariant beams with closed analytical expressions. It is shown that increments in the order of magnitude of the transition rates for Gaussian and Laguerre-Gaussian beams, with respect to those obtained in the paraxial limit, require waists of the order of the wavelength, while propagation invariant modes may considerably enhance transition rates under more favorable conditions. For transitions that can be naturally described as modifications of the atomic angular momentum, this enhancement is maximal (within propagation invariant beams) for Bessel modes, Mathieu modes can be used to entangle the internal and center-of-mass involved states, and Weber beams suppress this kind of transition unless they have a significant component of odd modes. However, if a recoil effect of the transition with an adequate symmetry is allowed, the global transition rate (center of mass and internal motion) can also be enhanced using Weber modes. The global analysis presented reinforces the idea that a better control of the transitions between internal atomic states requires both a proper control of the available states of the atomic center of mass, and shaping of the background electromagnetic field.

Overview of International Thermonuclear Experimental Reactor (ITER) engineering design activities*

NASA Astrophysics Data System (ADS)

Shimomura, Y.

1994-05-01

The International Thermonuclear Experimental Reactor (ITER) [International Thermonuclear Experimental Reactor (ITER) (International Atomic Energy Agency, Vienna, 1988), ITER Documentation Series, No. 1] project is a multiphased project, presently proceeding under the auspices of the International Atomic Energy Agency according to the terms of a four-party agreement among the European Atomic Energy Community (EC), the Government of Japan (JA), the Government of the Russian Federation (RF), and the Government of the United States (US), ``the Parties.'' The ITER project is based on the tokamak, a Russian invention, and has since been brought to a high level of development in all major fusion programs in the world. The objective of ITER is to demonstrate the scientific and technological feasibility of fusion energy for peaceful purposes. The ITER design is being developed, with support from the Parties' four Home Teams and is in progress by the Joint Central Team. An overview of ITER Design activities is presented.

Tissue banking in Asia Pacific region: past, present and future.

PubMed

Nather, Aziz; Mandy, Foong Shi Yun; Ning, Tan; Kaiying, Wang

2018-04-25

Tissue banking in the Asia Pacific regions is driven by two main forces-firstly the International Atomic Energy Agency (IAEA) via Regional Co-operative Agreement projects and secondly by the Asia Pacific Association of Surgical Tissue Banking (APASTB). This overview is written in three sections: (1) History of tissue banking in individual country in the region. (2) History of APASTB. (3) History of IAEA programme in Asia Pacific region. The current status and future of the tissue banking programme in the region will be discussed.

Market Research Survey of Commercial Off-The-Shelf (COTS) Portable MS Systems for IAEA Safeguards Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hart, Garret L.; Hager, George J.; Barinaga, Charles J.

2013-02-01

This report summarizes the results for the market research survey of mass spectrometers that are deemed pertinent to International Atomic Energy Agency (IAEA) needs and strategic objectives. The focus of the report is on MS instruments that represent currently available (or soon to be) commercial off-the shelf (COTS) technology and weigh less than 400 pounds. A compilation of all available MS instruments (36 COTS and 2 R&D) is presented, along with pertinent information regarding each instrument.

Scattered Atomic Oxygen Effects on Spacecraft Materials

NASA Technical Reports Server (NTRS)

Banks, Bruce A.; Miller, Sharon K. R.; deGroh, Kim K.; Demko, Rikako

2003-01-01

Low Earth orbital (LEO) atomic oxygen cannot only erode the external surfaces of polymers on spacecraft, but can cause degradation of surfaces internal to components on the spacecraft where openings to the space environment exist. Although atomic oxygen attack on internal or interior surfaces may not have direct exposure to the LEO atomic oxygen flux scattered impingement can have serious degradation effects where sensitive interior surfaces are present. The effects of atomic oxygen erosion of polymer interior to an aperture on a spacecraft is simulated using Monte Carlo computational techniques. A 2-dimensional model is used to provide quantitative indications of the attenuation of atomic oxygen flux as a function of distance into a parallel walled cavity. The degree of erosion re1ative is compared between the various interior locations and the external surface of a LEO spacecraft.

Atomic Oxygen Effects on Spacecraft Materials

NASA Technical Reports Server (NTRS)

Banks, Bruce A.; Miller, Sharon K. R.; deGroh, Kim K.; Demko, Rikako

2003-01-01

Low Earth orbital (LEO) atomic oxygen cannot only erode the external surfaces of polymers on spacecraft, but can cause degradation of surfaces internal to components on the spacecraft where openings to the space environment exist. Although atomic oxygen attack on internal or interior surfaces may not have direct exposure to the LEO atomic oxygen flux, scattered impingement can have can have serious degradation effects where sensitive interior surfaces are present. The effects of atomic oxygen erosion of polymers interior to an aperture on a spacecraft is simulated using Monte Carlo computational techniques. A 2-dimensional model is used to provide quantitative indications of the attenuation of atomic oxygen flux as a function of distance into a parallel walled cavity. The degree of erosion relative is compared between the various interior locations and the external surface of an LEO spacecraft.

Atomic memory access hardware implementations

DOEpatents

Ahn, Jung Ho; Erez, Mattan; Dally, William J

2015-02-17

Atomic memory access requests are handled using a variety of systems and methods. According to one example method, a data-processing circuit having an address-request generator that issues requests to a common memory implements a method of processing the requests using a memory-access intervention circuit coupled between the generator and the common memory. The method identifies a current atomic-memory access request from a plurality of memory access requests. A data set is stored that corresponds to the current atomic-memory access request in a data storage circuit within the intervention circuit. It is determined whether the current atomic-memory access request corresponds to at least one previously-stored atomic-memory access request. In response to determining correspondence, the current request is implemented by retrieving data from the common memory. The data is modified in response to the current request and at least one other access request in the memory-access intervention circuit.

76 FR 58049 - Atomic Safety and Licensing Board; Honeywell International, Inc.; Metropolis Works Uranium...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-19

... NUCLEAR REGULATORY COMMISSION [Docket No. 40-3392-MLA; ASLBP No. 11-910-01-MLA-BD01] Atomic Safety and Licensing Board; Honeywell International, Inc.; Metropolis Works Uranium Conversion Facility... assurance for its Metropolis Works uranium conversion facility in Metropolis, Illinois. \\1\\ LBP-11-19, 74...

Developing the World's Digital Collection on Peaceful Uses of Atomic Energy.

ERIC Educational Resources Information Center

Levine, Emil

1997-01-01

Discusses the developers/development, maintainers, and users of the digital collection on peaceful uses of nuclear energy, produced by the International Nuclear Information System (INIS) of the International Atomic Energy Agency (IAEA). Sensitive to users in both developing and highly developed countries, this system provides closer linkage…

A report from the 2013 international symposium: the evaluation of the effects of low-dose radiation exposure in the life span study of atomic bomb survivors and other similar studies.

PubMed

Grant, E J; Ozasa, K; Ban, N; de González, A Berrington; Cologne, J; Cullings, H M; Doi, K; Furukawa, K; Imaoka, T; Kodama, K; Nakamura, N; Niwa, O; Preston, D L; Rajaraman, P; Sadakane, A; Saigusa, S; Sakata, R; Sobue, T; Sugiyama, H; Ullrich, R; Wakeford, R; Yasumura, S; Milder, C M; Shore, R E

2015-05-01

The RERF International Low-Dose Symposium was held on 5-6 December 2013 at the RERF campus in Hiroshima, Japan, to discuss the issues facing the Life Span Study (LSS) and other low-dose studies. Topics included the current status of low-dose risk detection, strategies for low-dose epidemiological and statistical research, methods to improve communication between epidemiologists and biologists, and the current status of radiological studies and tools. Key points made by the participants included the necessity of pooling materials over multiple studies to gain greater insight where data from single studies are insufficient; generating models that reflect epidemiological, statistical, and biological principles simultaneously; understanding confounders and effect modifiers in the current data; and taking into consideration less studied factors such as the impact of dose rate. It is the hope of all participants that this symposium be used as a trigger for further studies, especially those using pooled data, in order to reach a greater understanding of the health effects of low-dose radiation.

Conductive atomic force microscopy study of the photoexcitation effect on resistive switching in ZrO2(Y) films with Au nanoparticles

NASA Astrophysics Data System (ADS)

Novikov, A. S.; Filatov, D. O.; Antonov, D. A.; Antonov, I. N.; Shenina, M. E.; Gorshkov, O. N.

2018-03-01

We report on the experimental observation of the effect of optical excitation on resistive switching in ultrathin ZrO2(Y) films with single-layered arrays of Au nanoparticles. The samples were prepared by depositing nanometer-thick Au films sandwiched between two ZrO2(Y) layers by magnetron sputtering followed by annealing. Resistive switching was studied by conductive atomic force microscopy by measuring cyclic current-voltage curves of a probe-to-sample contact. The contact area was illuminated by radiation of a semiconductor laser diode with the wavelength corresponding to the plasmon resonance in an Au nanoparticle array. The enhancement of the hysteresis in cyclic current-voltage curves due to bipolar resistive switching under illumination was observed. The effect was attributed to heating of Au nanoparticles due to plasmonic optical absorption and a plasmon resonance, which enhances internal photoemission of electrons from the Fermi level in Au nanoparticles into the conduction band of ZrO2(Y). Both factors promote resistive switching in a ZrO2(Y) matrix.

Internal flow characteristics in scaled pressure-swirl atomizer

NASA Astrophysics Data System (ADS)

Malý, Milan; Sapík, Marcel; Jedelský, Jan; Janáčková, Lada; Jícha, Miroslav; Sláma, Jaroslav; Wigley, Graham

2018-06-01

Pressure-swirl atomizers are used in a wide range of industrial applications, e.g.: combustion, cooling, painting, food processing etc. Their spray characteristics are closely linked to the internal flow which predetermines the parameters of the liquid sheet formed at the discharge orifice. To achieve a better understanding of the spray formation process, the internal flow was characterised using Laser Doppler Anemometry (LDA) and high-speed imaging in a transparent model made of cast PMMA (Poly(methyl methacrylate)). The design of the transparent atomizer was derived from a pressure-swirl atomizer as used in a small gas turbine. Due to the small dimensions, it was manufactured in a scale of 10:1. It has modular concept and consists of three parts which were ground, polished and bolted together. The original kerosene-type jet A-1 fuel had to be replaced due to the necessity of a refractive index match. The new working liquid should also be colourless, non-aggressive to the PMMA and have the appropriate viscosity to achieve the same Reynolds number as in the original atomizer. Several liquids were chosen and tested to satisfy these requirements. P-Cymene was chosen as the suitable working liquid. The internal flow characteristics were consequently examined by LDA and high-speed camera using p-Cymene and Kerosene-type jet A-1 in comparative manner.

New Concepts and Fermilab Facilities for Antimatter Research

NASA Astrophysics Data System (ADS)

Jackson, Gerald

2008-04-01

There has long been significant interest in continuing antimatter research at the Fermi National Accelerator Laboratory. Beam kinetic energies ranging from 10 GeV all the way down to the eV scale and below are of interest. There are three physics missions currently being developed: the continuation of charmonium physics utilizing an internal target; atomic physics with in-flight generated antihydrogen atoms; and deceleration to thermal energies and paasage of antiprotons through a grating system to determine their gravitation acceleration. Non-physics missions include the study of medical applications, tests of deep-space propulsion concepts, low-risk testing of nuclear fuel elements, and active interrogation for smuggled nuclear materials in support of homeland security. This paper reviews recent beam physics and accelerator technology innovations in the development of methods and new Fermilab facilities for the above missions.

Nuclear Power and the Environment.

ERIC Educational Resources Information Center

International Atomic Energy Agency, Vienna (Austria).

This booklet is a summary of an international symposium, held in August 1970 in New York City, on the environmental aspects of nuclear power stations. The symposium was convened under the sponsorship of the International Atomic Energy Agency (IAEA) and the U.S. Atomic Energy Commission (USAEC). The information is presented in a condensed and…

Test of Time-Reversal Invariance at COSY (TRIC)

NASA Astrophysics Data System (ADS)

Eversheim, D.; Valdau, Yu.; Lorentz, B.

2016-02-01

At the Cooler Synchrotron COSY a novel (P-even, T-odd) null test of time-reversal invariance to an accuracy of 10-6 is planned as an internal target transmission experiment. The parity conserving time-reversal violating observable is the total cross-section asymmetry Ay,xz. This quantity is measured using a polarized proton beam with an energy of 135 MeV and an internal tensor polarized deuteron target from the PAX atomic beam source. The reaction rate will be determined by the lifetime of the beam. Consequently, the accuracy of the current measurement of the circulating proton beam is crucial for this experiment. Thus, the cooler synchroton ring serves as an ideal forward spectrometer, as a detector, and an accelerator.

Summary of the XIII International Workshop on Polarized Sources, Targets and Polarimetry

NASA Astrophysics Data System (ADS)

Rathmann, F.

2011-01-01

The workshops on polarized sources, targets, and polarimetry are held every two years. The present meeting took place in Ferrara, Italy, and was organized by the University of Ferrara. Sessions on Polarized Proton and Deuterium Sources, Polarized Electron Sources, Polarimetry, Polarized Solid Targets, and Polarized Internal Targets, highlighted topics, recent developments, and progress in the field. A session decicated to Future Facilities provided an overview of a number of new activities in the spin-physics sector at facilities that are currently in the planning stage. Besides presenting a broad overview of polarized ion sources, electron sources, solid and gaseous targets, and their neighboring fields, the workshop also addressed the application of polarized atoms in applied sciences and medicine that is becoming increasingly important.

Proton-proton elastic scattering excitation functions at intermediate energies

NASA Astrophysics Data System (ADS)

Rohdjess, H.

1998-05-01

Polarized and unpolarized proton-proton elastic scattering is investigated with the EDDA-experiment at the Cooler Synchrotron COSY at Jülich to significantly improve the world data base in the beam energy range 500-2500 MeV. Measurements during beam acceleration with thin internal targets and a large acceptance detector provide excitation functions over a broad angular and energy range with unprecedented internal consistency. Data taking with an unpolarized CH2 fiber target and an unpolarized beam have been completed and the derived differential cross sections are presented and compared to a recent phase shift analysis. With a polarized atomic beam target newly installed in COSY and a polarized COSY beam—currently under development—the measurements will be extended to analyzing powers and spin correlation parameters.

The International Atomic Energy Agency's activities in radiation medicine and cancer: promoting global health through diplomacy.

PubMed

Deatsch-Kratochvil, Amanda N; Pascual, Thomas Neil; Kesner, Adam; Rosenblatt, Eduardo; Chhem, Rethy K

2013-02-01

Global health has been an issue of seemingly low political importance in comparison with issues that have direct bearing on countries' national security. Recently, health has experienced a "political revolution" or a rise in political importance. Today, we face substantial global health challenges, from the spread of infectious disease, gaps in basic maternal and child health care, to the globalization of cancer. A recent estimate states that the "overall lifetime risk of developing cancer (both sexes) is expected to rise from more than one in three to one in two by 2015." These issues pose significant threats to international health security. To successfully combat these grave challenges, the international community must embrace and engage in global health diplomacy, defined by scholars Thomas Novotny and Vicanne Adams as a political activity aimed at improving global health, while at the same time maintaining and strengthening international relations. The IAEA (International Atomic Energy Agency) is an international organization with a unique mandate to "accelerate and enlarge the contribution of atomic energy to peace, health, and prosperity throughout the world." This article discusses global health diplomacy, reviews the IAEA's program activities in human health by focusing on radiation medicine and cancer, and the peaceful applications of atomic energy within the context of global health diplomacy. Copyright © 2013 Canadian Association of Radiologists. Published by Elsevier Inc. All rights reserved.

PREFACE: 8th Asian International Seminar on Atomic and Molecular Physics (AISAMP)

NASA Astrophysics Data System (ADS)

Williams, Jim F.; Buckman, Steve; Bieske, Evan J.

2009-09-01

These proceedings arose from the 8th Asian International Seminar on Atomic and Molecular Physics (AISAMP) which was held at the University of Western Australia 24-28 November 2008. The history of AISAMP (Takayanagi and Matsuzawa 2002) recognizes its origin from the Japan-China meeting of 1985, and the first use of the name 'The First Asian International Seminar on Atomic and Molecular Physics (AISAMP)' in 1992. The initial attendees, Japan and China, were joined subsequently by scientists from Korea, Taiwan, India, Australia and recently by Malaysia, Thailand, Vietnam, Turkey Iran, UK and USA. The main purpose of the biennial AISAMP series is to create a wide forum for exchanging ideas and information among atomic and molecular scientists and to promote international collaboration. The scope of the AISAMP8 meeting included pure, strategic and applied research involving atomic and molecular structure and processes in all forms of matter and antimatter. For 2008 the AISAMP conference incorporated the Australian Atomic and Molecular Physics and Quantum Chemistry meeting. The topics for AISAMP8 embraced themes from earlier AISAMP meetings and reflected new interests, in atomic and molecular structures, spectroscopy and collisions; atomic and molecular physics with laser or synchrotron radiation; quantum information processing using atoms and molecules; atoms and molecules in surface physics, nanotechnology, biophysics, atmospheric physics and other interdisciplinary studies. The implementation of the AISAMP themes, as well as the international representation of research interests, is indicated both in the contents list of these published manuscripts as well as in the program for the meeting. Altogether, 184 presentations were made at the 8th AISAMP, including Invited Talks and Contributed Poster Presentations, of which 60 appear in the present Proceedings after review by expert referees in accordance with the usual practice of Journal of Physics: Conference Series of the Institute of Physics. The support from the IOPCS staff made this publication possible. The 8th AISAMP was sponsored primarily by the University of Western Australia and Curtin University of Technology, both in Perth, Western Australia, and by Journal of Physics: Conference Series. Support was also received from the International Council of Science, ICSU. Guidance and active participation from colleagues, particularly from the University of Western Australia, and Curtin University, and from the Australian National University and Melbourne University were sources of strength for the actual organization of the conference. Dr Elena Semidelova receives special thanks for her organizing abilities. We hope that this issue of Journal of Physics: Conference Series will be referenced widely and that it will strengthen ties between all scientists and their countries. Evan Bieske, Stephen Buckman and Jim F Williams Guest Editors

ACES MWL data analysis center at SYRTE

NASA Astrophysics Data System (ADS)

Meynadier, F.; Delva, P.; le Poncin-Lafitte, C.; Guerlin, C.; Laurent, P.; Wolf, P.

2017-12-01

The ACES-PHARAO mission aims at operating a cold-atom caesium clock on board the International Space Station, and performs two-way time transfer with ground terminals, in order to allow highly accurate and stable comparisons of its internal timescale with those found in various metrology institutes. Scientific goals in fundamental physics include tests of the gravitational redshift with unprecedented accuracy, and search for a violation of the Lorentz local invariance. As launch is coming closer we are getting ready to process the data expected to come from ACES Microwave Link (MWL) once on board the International Space Station. Several hurdles have been cleared in our software in the past months, as we managed to implement algorithms that reach target accuracy for ground/space desynchronisation measurement. I will present the current status of data analysis preparation, as well as the activities that will take place at SYRTE in order to set up its data processing center.

Stereotactic radiotherapy of primary lung cancer and other targets: results of consultant meeting of the International Atomic Energy Agency.

PubMed

Nagata, Yasushi; Wulf, Joern; Lax, Ingmar; Timmerman, Robert; Zimmermann, Frank; Stojkovski, Igor; Jeremic, Branislav

2011-03-01

To evaluate the current status of stereotactic body radiotherapy (SBRT) and identify both advantages and disadvantages of its use in developing countries, a meeting composed of consultants of the International Atomic Energy Agency was held in Vienna in November 2006. Owing to continuous developments in the field, the meeting was extended by subsequent discussions and correspondence (2007-2010), which led to the summary presented here. The advantages and disadvantages of SBRT expected to be encountered in developing countries were identified. The definitions, typical treatment courses, and clinical results were presented. Thereafter, minimal methodology/technology requirements for SBRT were evaluated. Finally, characteristics of SBRT for developing countries were recommended. Patients for SBRT should be carefully selected, because single high-dose radiotherapy may cause serious complications in some serial organs at risk. Clinical experiences have been reported in some populations of lung cancer, lung oligometastases, liver cancer, pancreas cancer, and kidney cancer. Despite the disadvantages expected to be experienced in developing countries, SBRT using fewer fractions may be useful in selected patients with various extracranial cancers with favorable outcome and low toxicity. Copyright © 2011 Elsevier Inc. All rights reserved.

The International Atomic Energy Agency

ERIC Educational Resources Information Center

Dufour, Joanne

2004-01-01

The dropping of atomic bombs on Hiroshima and Nagasaki in World War II inaugurated a new era in world history, the atomic age. After the war, the Soviet Union, eager to develop the same military capabilities as those demonstrated by the United States, soon rivaled the U.S. as an atomic and nuclear superpower. Faced by the possibility of…

Interpretation of ES, CS, and IOS approximations within a translational--internal coupling scheme. I. Atom--diatom collisions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Coombe, D.A.; Snider, R.F.

1979-12-01

Rotational invariance is applied to the description of atom--diatom collisions in a translational--internal coupling scheme, to obtain energy sudden (ES), centrifugal sudden (CS), and infinite order sudden (IOS) approximations to the reduced scattering S matrix S (j-barlambda-bar;L;jlambda). The method of presentation emphasizes that the translational--internal coupling scheme is actually the more natural description of collision processes in which one or more directions are assumed to be conserved.

IV INTERNATIONAL CONFERENCE ON ATOM AND MOLECULAR PULSED LASERS (AMPL'99): Efficient long-pulse XeCl laser with a prepulse formed by an inductive energy storage device

NASA Astrophysics Data System (ADS)

Baksht, E. Kh; Panchenko, Aleksei N.; Tarasenko, Viktor F.

2000-06-01

An efficient electric-discharge XeCl laser is developed, which is pumped by a self-sustained discharge with a prepulse formed by a generator with an inductive energy storage device and a semiconductor current interrupter on a basis of semiconductor opening switch (SOS) diodes. An output energy up to 800 mJ, a pulse length up to 450 ns, and a total laser efficiency of 2.2% were attained by using spark UV preionisation.

Atomic Oxygen Durability Testing of an International Space Station Solar Array Validation Coupon

NASA Technical Reports Server (NTRS)

Forkapa, Mark J.; Stidham, Curtis; Banks, Bruce A.; Rutledge, Sharon K.; Ma, David H.; Sechkar, Edward A.

1996-01-01

An International Space Station solar array validation coupon was exposed in a directed atomic oxygen beam for space environment durability testing at the NASA Lewis Research Center. Exposure to atomic oxygen and intermittent tensioning of the solar array were conducted to verify the solar array#s durability to low Earth orbital atomic oxygen and to the docking threat of plume loading both of which are anticipated over its expected mission life of fifteen years. The validation coupon was mounted on a specially designed rotisserie. The rotisserie mounting enabled the solar and anti-solar facing side of the array to be exposed to directed atomic oxygen in a sweeping arrival process replicating space exposure. The rotisserie mounting also enabled tensioning, in order to examine the durability of the array and its hinge to simulated plume loads. Flash testing to verify electrical performance of the solar array was performed with a solar simulator before and after the exposure to atomic oxygen and tensile loading. Results of the flash testing indicated little or no degradation in the solar array#s performance. Photographs were also taken of the array before and after the durability testing and are included along with comparisons and discussions in this report. The amount of atomic oxygen damage appeared minor with the exception of a very few isolated defects. There were also no indications that the simulated plume loadings had weakened or damaged the array, even though there was some erosion of Kapton due to atomic oxygen attack. Based on the results of this testing, it is apparent that the International Space Station#s solar arrays should survive the low Earth orbital atomic oxygen environment and docking threats which are anticipated over its expected mission life.

Data needs for X-ray astronomy satellites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kallman, T.

I review the current status of atomic data for X-ray astronomy satellites. This includes some of the astrophysical issues which can be addressed, current modeling and analysis techniques, computational tools, the limitations imposed by currently available atomic data, and the validity of standard assumptions. I also discuss the future: challenges associated with future missions and goals for atomic data collection.

Internal dynamics of F-actin and myosin subfragment-1 studied by quasielastic neutron scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matsuo, Tatsuhito; Arata, Toshiaki; Oda, Toshiro

2015-04-10

Various biological functions related to cell motility are driven by the interaction between the partner proteins, actin and myosin. To obtain insights into how this interaction occurs, the internal dynamics of F-actin and myosin subfragment-1 (S1) were characterized by the quasielastic neutron scattering measurements on the solution samples of F-actin and S1. Contributions of the internal motions of the proteins to the scattering spectra were separated from those of the global macromolecular diffusion. Analysis of the spectra arising from the internal dynamics showed that the correlation times of the atomic motions were about two times shorter for F-actin than formore » S1, suggesting that F-actin fluctuates more rapidly than S1. It was also shown that the fraction of the immobile atoms is larger for S1 than for F-actin. These results suggest that F-actin actively facilitates the binding of myosin by utilizing the more frequent conformational fluctuations than those of S1. - Highlights: • We studied the internal dynamics of F-actin and myosin S1 by neutron scattering. • The correlation times of the atomic motions were smaller for F-actin than for S1. • The fraction of the immobile atoms was also smaller for F-actin than for S1. • Our results suggest that mobility of atoms in F-actin is higher than that in S1. • We propose that high flexibility of F-actin facilitates the binding of myosin.« less

Sources of Information on Atomic Energy, International Series of Monographs in Library and Information Science, Volume 2.

ERIC Educational Resources Information Center

Anthony, L. J.

This book provides a comprehensive survey of the principal national and international organizations which are sources of information on atomic and nuclear energy and of the published literature in this field. Organizations in all the major nuclear countries such as the United States, Britain, the Soviet Union, France, and Japan are described, and…

Steady-State Solutions Originating from an Enhanced Nonlinear Feedback in a Hybrid Opto-mechanical System

NASA Astrophysics Data System (ADS)

Fan, Qiu-Bo; Wang, Yi-Ru; Chen, Jin; Pan, Yue-Wu; Han, Bai-Ping; Fu, Chang-Bao; Sun, Yan

2017-06-01

The steady-state properties of a hybrid system are investigated in this paper. Many cold atoms in the four-level tripod configuration are confined in an optical cavity with a movable end mirror. The confined cold atoms are driven with two external classical fields and an internal cavity field. The internal cavity field is excited by an external driving field and shows a radiation pressure upon the movable end mirror. The coupling of atom-light and opto-mechanical interactions is enhanced by embedding a four-level atomic system in a typical opto-mechanical cavity. And an enhanced nonlinear feedback mechanism is offered by the enhanced coupling, which permits the observation of five and three steady-state solutions for relevant variables near two-photon resonance. The enhanced nonlinear feedback mechanism also allows us to observe the obvious difference in the double-EIT phenomenon between the atom-assisted opto-mechanical system and usual atom-field system.

The hyperfine excitation of OH radicals by He

NASA Astrophysics Data System (ADS)

Marinakis, Sarantos; Kalugina, Yulia; Lique, François

2016-04-01

Hyperfine-resolved collisions between OH radicals and He atoms are investigated using quantum scattering calculations and the most recent ab initio potential energy surface, which explicitly takes into account the OH vibrational motion. Such collisions play an important role in astrophysics, in particular in the modelling of OH masers. The hyperfine-resolved collision cross sections are calculated for collision energies up to 2500 cm-1 from the nuclear spin free scattering S-matrices using a recoupling technique. The collisional hyperfine propensities observed are discussed. As expected, the results from our work suggest that there is a propensity for collisions with ΔF = Δj. The new OH-He hyperfine cross sections are expected to significantly help in the modelling of OH masers from current and future astronomical observations. Contribution to the Topical Issue "Atomic Cluster Collisions (7th International Symposium)", edited by Gerardo Delgado Barrio, Andrey Solov'Yov, Pablo Villarreal, Rita Prosmiti.

26 CFR 1.164-8 - Payments for municipal services in atomic energy communities.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 26 Internal Revenue 2 2013-04-01 2013-04-01 false Payments for municipal services in atomic energy... Corporations § 1.164-8 Payments for municipal services in atomic energy communities. (a) General. For taxable... any community (as defined in section 21b of the Atomic Energy Community Act of 1955 (42 U.S.C. 2304...

26 CFR 1.164-8 - Payments for municipal services in atomic energy communities.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 26 Internal Revenue 2 2010-04-01 2010-04-01 false Payments for municipal services in atomic energy... Corporations § 1.164-8 Payments for municipal services in atomic energy communities. (a) General. For taxable... any community (as defined in section 21b of the Atomic Energy Community Act of 1955 (42 U.S.C. 2304...

26 CFR 1.164-8 - Payments for municipal services in atomic energy communities.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 26 Internal Revenue 2 2011-04-01 2011-04-01 false Payments for municipal services in atomic energy... Corporations § 1.164-8 Payments for municipal services in atomic energy communities. (a) General. For taxable... any community (as defined in section 21b of the Atomic Energy Community Act of 1955 (42 U.S.C. 2304...

26 CFR 1.164-8 - Payments for municipal services in atomic energy communities.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 26 Internal Revenue 2 2012-04-01 2012-04-01 false Payments for municipal services in atomic energy... Corporations § 1.164-8 Payments for municipal services in atomic energy communities. (a) General. For taxable... any community (as defined in section 21b of the Atomic Energy Community Act of 1955 (42 U.S.C. 2304...

26 CFR 1.164-8 - Payments for municipal services in atomic energy communities.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 26 Internal Revenue 2 2014-04-01 2014-04-01 false Payments for municipal services in atomic energy... Corporations § 1.164-8 Payments for municipal services in atomic energy communities. (a) General. For taxable... any community (as defined in section 21b of the Atomic Energy Community Act of 1955 (42 U.S.C. 2304...

PST 2009: XIII International Workshop on Polarized Sources Targets and Polarimetry

NASA Astrophysics Data System (ADS)

Lenisa, Paolo

2011-05-01

The workshops on polarized sources, targets, and polarimetry are held every two years. In 2009 the meeting took place in Ferrara, Italy, and was organized by the University of Ferrara and INFN. Sessions on Polarized Proton and Deuterium Sources, Polarized Electron Sources, Polarimetry, Polarized Solid Targets, and Polarized Internal Targets, highlighted topics, recent developments, and progress in the field. A session dedicated to Future Facilities provided an overview of a number of new activities in the spin-physics sector at facilities that are currently in the planning stage. Besides presenting a broad overview of polarized ion sources, electron sources, solid and gaseous targets, and their neighbouring fields, the workshop also addressed the application of polarized atoms in applied sciences and medicine that is becoming increasingly important.

Time activities at the BIPM

NASA Technical Reports Server (NTRS)

Thomas, Claudine

1995-01-01

The generation and dissemination of International Atomic Time, TAI, and of Coordinated Universal Time, UTC, are explicitly mentioned in the list of the principal tasks of the BIPM, recalled in the Comptes Rendus of the 18th Conference Generale des Poids et Mesures, in 1987. These tasks are fulfilled by the BIPM Time Section, thanks to international cooperation with national timing centers, which maintain, under metrological conditions, the clocks used to generate TAI. Besides the current work of data collection and processing, research activities are carried out in order to adapt the computation of TAI to the most recent improvements occurring in the time and frequency domains. Studies concerning the application of general relativity and pulsar timing to time metrology are also actively pursued. This paper summarizes the work done in all these fields and outlines future projects.

FOREWORD: 4th International Colloquium on Atomic Spectra and Oscillator Strengths for Astrophysical and Laboratory Plasmas

NASA Astrophysics Data System (ADS)

Leckrone, David S.; Sugar, Jack

1993-01-01

In 1983 the Atomic Spectroscopy Group at the University of Lund organized a conference at Lund the purpose of which was to establish a dialogue between scientists whose research made use of basic atomic data, and scientists whose research produced such data. The data in question include complete descriptions of atomic and ionic spectra, accurate transition wavelengths and relative intensities, energy levels, lifetimes, oscillator strengths, line shapes, and nuclear effects (hyperfine structure and isotope shifts). The "consumers" in urgent need of new or improved atomic data included astrophysicsts, laboratory plasma physicists, and spectrochemists. The synergism between these specialists and the theoretical and experimental atomic physicists resulted in a highly successful meeting, attended by approximately 70 people. The rapid advances foreseen at that time in all of these areas of observational, experimental and theoretical science stimulated planning for a second conference on this subject in 1986 at the University of Toledo, and subsequently a third meeting was held at the Royal Netherlands Academy of Arts and Sciences in Amsterdam in 1989. Again attendance at the latter two meetings totaled approximately 70 researchers. The participants in Amsterdam agreed to re-convene at the National Institute of Standards and Technology (NIST) in Gaithersburg, Maryland, in 1992, maintaining the frequency of these conferences at one every three years. The present Topical Issue of Physica Scripta consists of 31 invited reviews given at the Gaithersburg meeting. Extended abstracts of 63 poster papers from the meeting are being published in NIST Special Publication SP850. Approximately 170 scientists attended the Gaithersburg conference, representing a substantial growth in the size of meetings in this series. One session of the conference was devoted to an informal workshop, at which any participant could give a brief oral statement about his or her most immediate data need or about work currently in progress. This resulted in a number of interesting exchanges, and served to facilitate the coordination of work to be done in the near term. Over the past 15 years we have witnessed the explosive growth of astrophysical spectroscopic observations in both the ultraviolet and infrared bands. Recently, with the launch of the Hubble Space Telescope, the precision and resolution of such data have reached remarkable levels, giving one the sense that the body of atomic data currently to be found in the literature lags far behind what is needed to adequately interpret the observations. Similarly, high temperature laboratory experiments in plasma physics, e.g. fusion energy and x-ray lasers, are demanding larger quantities of atomic data over a wide range of ionization states. Fortunately, the experimental and computational techniques of atomic physics have kept pace. One may cite, for example, the extraordinary precision inherent in recent laboratory work with laser-induced fluorescence spectroscopy and with Fourier transform spectrometers, and for data of highly-ionized atoms, with ion traps and tokamak plasmas. The major challenge is to nurture and support expanded activity in those sub-disciplines of atomic physics that apply such modern techniques to the production of extensive volumes of atomic data, and to reinvigorate such "old fashioned" subjects as the term analysis of new, more accurate laboratory spectra. This series of conferences has a very special character. It is not sponsored or supported by any particular institution, government organization or professional society. The meetings occur only because they serve the common scientific interests of a broad and diverse group of people from around the world. They have had the delightful effect of stimulating professional collaborations and friendships among astronomers, physicists, chemists, mathematicians, and others, who might not have initially realized that they shared so much in common. The series has also demonstrated that the dialogue between "users" and "providers" of atomic data is a two-way conversation, with atomic physicists beginning to view astrophysical and laboratory plasmas as unique sources of new information about the structure of complex atomic species. The fifth International Colloquium on Atomic Spectra and Oscillator Strengths for Astrophysical and Laboratory Plasmas is scheduled to take place in Meudon, France in 1995.

Observation of a superfluid Hall effect

PubMed Central

Jiménez-García, Karina; Williams, Ross A.; Beeler, Matthew C.; Perry, Abigail R.; Phillips, William D.; Spielman, Ian B.

2012-01-01

Measurement techniques based upon the Hall effect are invaluable tools in condensed-matter physics. When an electric current flows perpendicular to a magnetic field, a Hall voltage develops in the direction transverse to both the current and the field. In semiconductors, this behavior is routinely used to measure the density and charge of the current carriers (electrons in conduction bands or holes in valence bands)—internal properties of the system that are not accessible from measurements of the conventional resistance. For strongly interacting electron systems, whose behavior can be very different from the free electron gas, the Hall effect’s sensitivity to internal properties makes it a powerful tool; indeed, the quantum Hall effects are named after the tool by which they are most distinctly measured instead of the physics from which the phenomena originate. Here we report the first observation of a Hall effect in an ultracold gas of neutral atoms, revealed by measuring a Bose–Einstein condensate’s transport properties perpendicular to a synthetic magnetic field. Our observations in this vortex-free superfluid are in good agreement with hydrodynamic predictions, demonstrating that the system’s global irrotationality influences this superfluid Hall signal. PMID:22699494

Approaching the Limit in Atomic Spectrochemical Analysis.

ERIC Educational Resources Information Center

Hieftje, Gary M.

1982-01-01

To assess the ability of current analytical methods to approach the single-atom detection level, theoretical and experimentally determined detection levels are presented for several chemical elements. A comparison of these methods shows that the most sensitive atomic spectrochemical technique currently available is based on emission from…

International Low-Earth-Orbit Spacecraft Materials Test Program Initiated for Better Prediction of Durability and Performance

NASA Technical Reports Server (NTRS)

Rutledge, Sharon K.

1999-01-01

Spacecraft in low Earth orbit (LEO) are subjected to many components of the environment, which can cause them to degrade much more rapidly than intended and greatly shorten their functional life. The atomic oxygen, ultraviolet radiation, and cross contamination present in LEO can affect sensitive surfaces such as thermal control paints, multilayer insulation, solar array surfaces, and optical surfaces. The LEO Spacecraft Materials Test (LEO-SMT) program is being conducted to assess the effects of simulated LEO exposure on current spacecraft materials to increase understanding of LEO degradation processes as well as to enable the prediction of in-space performance and durability. Using ground-based simulation facilities to test the durability of materials currently flying in LEO will allow researchers to compare the degradation evidenced in the ground-based facilities with that evidenced on orbit. This will allow refinement of ground laboratory test systems and the development of algorithms to predict the durability and performance of new materials in LEO from ground test results. Accurate predictions based on ground tests could reduce development costs and increase reliability. The wide variety of national and international materials being tested represent materials being functionally used on spacecraft in LEO. The more varied the types of materials tested, the greater the probability that researchers will develop and validate predictive models for spacecraft long-term performance and durability. Organizations that are currently participating in the program are ITT Research Institute (USA), Lockheed Martin (USA), MAP (France), SOREQ Nuclear Research Center (Israel), TNO Institute of Applied Physics (The Netherlands), and UBE Industries, Ltd. (Japan). These represent some of the major suppliers of thermal control and sensor materials currently flying in LEO. The participants provide materials that are exposed to selected levels of atomic oxygen, vacuum ultraviolet radiation, contamination, or synergistic combined environments at the NASA Lewis Research Center. Changes in characteristics that could affect mission performance or lifetime are then measured. These characteristics include changes in mass, solar absorptance, and thermal emittance. The durability of spacecraft materials from U.S. suppliers is then compared with those of materials from other participating countries. Lewis will develop and validate performance and durability prediction models using this ground data and available space data. NASA welcomes the opportunity to consider additional international participants in this program, which should greatly aid future spacecraft designers as they select materials for LEO missions.

10 CFR 810.7 - Generally authorized activities.

Code of Federal Regulations, 2014 CFR

2014-01-01

... Energy DEPARTMENT OF ENERGY ASSISTANCE TO FOREIGN ATOMIC ENERGY ACTIVITIES § 810.7 Generally authorized activities. In accordance with section 57b(2) of the Atomic Energy Act, the Secretary of Energy has... United States of America and the International Atomic Energy Agency for the Application of Safeguards in...

10 CFR 810.7 - Generally authorized activities.

Code of Federal Regulations, 2013 CFR

2013-01-01

... Energy DEPARTMENT OF ENERGY ASSISTANCE TO FOREIGN ATOMIC ENERGY ACTIVITIES § 810.7 Generally authorized activities. In accordance with section 57b(2) of the Atomic Energy Act, the Secretary of Energy has... United States of America and the International Atomic Energy Agency for the Application of Safeguards in...

10 CFR 810.7 - Generally authorized activities.

Code of Federal Regulations, 2012 CFR

2012-01-01

... Energy DEPARTMENT OF ENERGY ASSISTANCE TO FOREIGN ATOMIC ENERGY ACTIVITIES § 810.7 Generally authorized activities. In accordance with section 57b(2) of the Atomic Energy Act, the Secretary of Energy has... United States of America and the International Atomic Energy Agency for the Application of Safeguards in...

Magneto-optical cooling of atoms.

PubMed

Raizen, Mark G; Budker, Dmitry; Rochester, Simon M; Narevicius, Julia; Narevicius, Edvardas

2014-08-01

We propose an alternative method to laser cooling. Our approach utilizes the extreme brightness of a supersonic atomic beam, and the adiabatic atomic coilgun to slow atoms in the beam or to bring them to rest. We show how internal-state optical pumping and stimulated optical transitions, combined with magnetic forces, can be used to cool the translational motion of atoms. This approach does not rely on momentum transfer from photons to atoms, as in laser cooling. We predict that our method can surpass laser cooling in terms of flux of ultracold atoms and phase-space density, with lower required laser power.

Electrodeposition of Isolated Platinum Atoms and Clusters on Bismuth-Characterization and Electrocatalysis.

PubMed

Zhou, Min; Dick, Jeffrey E; Bard, Allen J

2017-12-06

We describe a method for the electrodeposition of an isolated single Pt atom or small cluster, up to 9 atoms, on a bismuth ultramicroelectrode (UME). This deposition was immediately followed by electrochemical characterization via the hydrogen evolution reaction (HER) that occurs readily on the electrodeposited Pt but not on Bi. The observed voltammetric current plateau, even for a single atom, which behaves as an electrode, allows the estimation of deposit size. Pt was plated from solutions of femtomolar PtCl 6 2- , which allowed precise control of the arrival of ions and thus the plating rate on the Bi UME, to one ion every few seconds. This allowed the atom-by-atom fabrication of isolated platinum deposits, ranging from single atoms to 9-atom clusters. The limiting currents in voltammetry gave the size and number of atoms of the clusters. Given the stochasticity of the plating process, we show that the number of atoms plated over a given time (10 and 20 s) follows a Poisson distribution. Taking the potential at a certain current density as a measure of the relative rate of the HER, we found that the potential shifted positively as the size increased, with single atoms showing the largest overpotentials compared to bulk Pt.

A new approach to driving and controlling precision lasers for cold-atom science

NASA Astrophysics Data System (ADS)

Luey, Ben; Shugrue, Jeremy; Anderson, Mike

2014-05-01

Vescent's Integrated Control Electronics (ICE) Platform is a new approach to controlling and driving lasers and other electoral devices in complex atomic and optical experiments. By employing low-noise, high-bandwidth analog electronics with digital control, ICE combines the performance of analog design with the convenience of the digital world. Utilizing a simple USB COM port interface, ICE can easily be controlled via LabView, Python, or an FPGA. High-speed TTL inputs enable precise external timing or triggering. ICE is capable of generating complex timing internally, enabling ICE to drive an entire experiment or it can be directed by an external control program. The system is capable of controlling up to 8 unique ICE slave boards providing flexibility to tailor an assortment of electronics hardware to the needs of a specific experiment. Examples of ICE slave boards are: a current controller and peak-lock laser servo, a four channel temperature controller, a current controller and offset phase lock servo. A single ensemble can drive, stabilize, and frequency lock 3 lasers in addition to powering an optical amplifier, while still leaving 2 remaining slots for further control needs. Staff Scientist

Metathesis process for preparing an alpha, omega-functionalized olefin

DOEpatents

Burdett, Kenneth A.; Mokhtarzadeh, Morteza; Timmers, Francis J.

2010-10-12

A cross-metathesis process for preparing an .alpha.,.omega.-functionalized olefin, such as methyl 9-decenoate, and an .alpha.-olefin having three or more carbon atoms, such as 1-decene. The process involves contacting in a first reaction zone an .alpha.-functionalized internal olefin, such as methyl oleate, and an .alpha.-olefinic monomer having three or more carbon atoms, such as 1-decene, with a first metathesis catalyst to prepare an effluent stream containing the .alpha.,.omega.-functionalized olefin, such as methyl 9-decenoate, an unfunctionalized internal olefin, such as 9-octadecene, unconverted reactant olefins, and optionally, an .alpha.,.omega.-difunctionalized internal olefinic dimer, such as dimethyl 9-octadecen-1,18-dioate; separating said effluent streams; then contacting in a second reaction zone the unfunctionalized internal olefin with ethylene in the presence of a second metathesis catalyst to obtain a second product effluent containing the .alpha.-olefinic monomer having three or more carbon atoms; and cycling a portion of the .alpha.-olefinic monomer stream(s) to the first zone.

Measuring the internal energies of species emitted from hypervelocity nanoprojectile impacts on surfaces using recalibrated benzylpyridinium probe ions

NASA Astrophysics Data System (ADS)

DeBord, J. Daniel; Verkhoturov, Stanislav V.; Perez, Lisa M.; North, Simon W.; Hall, Michael B.; Schweikert, Emile A.

2013-06-01

We present herein a framework for measuring the internal energy distributions of vibrationally excited molecular ions emitted from hypervelocity nanoprojectile impacts on organic surfaces. The experimental portion of this framework is based on the measurement of lifetime distributions of "thermometer" benzylpyridinium ions dissociated within a time of flight mass spectrometer. The theoretical component comprises re-evaluation of the fragmentation energetics of benzylpyridinium ions at the coupled-cluster singles and doubles with perturbative triples level. Vibrational frequencies for the ground and transition states of select molecules are reported, allowing for a full description of vibrational excitations of these molecules via Rice-Ramsperger-Kassel-Marcus unimolecular fragmentation theory. Ultimately, this approach is used to evaluate the internal energy distributions from the measured lifetime distributions. The average internal energies of benzylpyridinium ions measured from 440 keV Au400+4 impacts are found to be relatively low (˜0.24 eV/atom) when compared with keV atomic bombardment of surfaces (1-2 eV/atom).

H. R. 3743: This Act may be cited as the Iran Nuclear Proliferation Prevention Act of 1998, Introduced in the House of Representatives, One Hundred Fifth Congress, Second Session, April 29, 1998

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1998-04-29

The purpose of this bill is to withhold voluntary proportional assistance for programs and projects of the International Atomic Energy Agency relating to the development and completion of the Bushehr nuclear power plant in Iran, and for other purposes. This bill is divided into the following sections: Section 1. Short Title; Section 2. Findings; Section 3. Withholding of voluntary contributions to the International Atomic Energy Agency for programs and projects in Iran. Section 4. Annual review by Secretary of State of programs and projects of the International Atomic Energy Agency; United States opposition to programs and projects of the Agencymore » in Iran; Section 5. Reporting Requirements; and Section 7. Sense of the Congress.« less

Evaluation of the United States Support Program’s Internship and Junior Professional Officer Programs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cruz J.; Patterson, J.; Pepper, S.

2012-07-15

The U.S. Support Program (USSP) to International Atomic Energy Agency (IAEA) Safeguards established a program of one-year paid internships for students and recent graduates. The program was in effect from 2002 until 2006 with a total of forty-one U.S. citizens and permanent residents placed in the IAEA. The USSP created a Junior Professional Officer (JPO) Program in 2005 that replaced the internship program at the IAEA. The JPO program creates opportunities for U.S. college graduates to become IAEA employees for a period of one to two years to help increase the effectiveness and efficiency of safeguards. The twenty three formermore » and current JPOs work in varying fields such as software development, information collection and analysis, non-destructive analysis systems, and unattended monitoring systems. This paper will look at the impacts of the USSP internship and JPO program on the interns and JPOs, the U.S. government, and the IAEA. Academic backgrounds, past involvement in nuclear fields, program assessment, and post-program positions were recorded and analyzed through two studies using questionnaires sent to former interns and former and current JPOs. This paper will discuss the effects of the programs on the careers of the interns and JPOs, present the evaluations of the internship and JPO Programs, and report the recommendations for changes.« less

Documentation and Analysis of IAEA (International Atomic Energy Agency) Safeguards Implementation at the Exxon Nuclear Fuel Fabrication Plant.

DTIC Science & Technology

1984-10-01

SAFEGUARDS AT SIMILAR FACILTTIES ASEA -ATOM LEU FUEL FABRICATION PLANT IN VASTERAS, SWEDEN..................B-1 APPENDIX C - EFFECTS OF NONMEASUREMENT ERRORS...second visit was to the ASEA -ATOM’s fuel fabrication plant in Vasteras, Sweden. The safeguards specialists for those plants were interviewed by R...Facilities, ASEA -ATOM LEU Fuel Fabrication Plant in Vasteras, Sweden, by V. Andersson of ASEA -ATOM, Vasteras, Sweden and R. Nilson of Exxon Nuclear

Modeling of Elastic Collisions between High Energy and Slow Neutral Atoms

DTIC Science & Technology

2015-07-01

cylindrical test cell, and the currents on the four different electrodes-Inner Cylinder , Exit Plate, Back Aperture, and Collector Plat~were measured...Inner Cylinder electrode. Nevertheless, the neutral atom current to the Inner Cylinder electrode predicted by the VHS model is comparable to the...Figure 9. Normalized curre nt at the Inner Cylinder e lectrode. the point of collision. T he discrepancy in the Exit Plate neutral atom current is due to

[Atomic/ionic fluorescence in microwave plasma torch discharge with excitation of high current and microsecond pulsed hollow cathode lamp: Ca atomic/ionic fluorescence spectrometry].

PubMed

Gong, Zhen-bin; Liang, Feng; Yang, Peng-yuan; Jin, Qin-han; Huang, Ben-li

2002-02-01

A system of atomic and ionic fluorescence spectrometry in microwave plasma torch (MPT) discharge excited by high current microsecond pulsed hollow cathode lamp (HCMP HCL) has been developed. The operation conditions for Ca atomic and ionic fluorescence spectrometry have been optimized. Compared with atomic fluorescence spectrometry (AFS) in argon microwave induced plasma (MIP) and MPT with the excitation of direct current and conventional pulsed HCL, the system with HCMP HCL excitation can improve AFS and ionic fluorescence spectrometry (IFS) detection limits in MPT atomizer and ionizer. Detection limits (3 sigma) with HCMP HCL-MPT-AFS/IFS are 10.1 ng.mL-1 for Ca I 422.7 nm, 14.6 ng.mL-1 for Ca II 393.4 nm, and 37.4 ng.mL-1 for Ca II 396.8 nm, respectively.

Development of the Science Data System for the International Space Station Cold Atom Lab

NASA Technical Reports Server (NTRS)

van Harmelen, Chris; Soriano, Melissa A.

2015-01-01

Cold Atom Laboratory (CAL) is a facility that will enable scientists to study ultra-cold quantum gases in a microgravity environment on the International Space Station (ISS) beginning in 2016. The primary science data for each experiment consists of two images taken in quick succession. The first image is of the trapped cold atoms and the second image is of the background. The two images are subtracted to obtain optical density. These raw Level 0 atom and background images are processed into the Level 1 optical density data product, and then into the Level 2 data products: atom number, Magneto-Optical Trap (MOT) lifetime, magnetic chip-trap atom lifetime, and condensate fraction. These products can also be used as diagnostics of the instrument health. With experiments being conducted for 8 hours every day, the amount of data being generated poses many technical challenges, such as downlinking and managing the required data volume. A parallel processing design is described, implemented, and benchmarked. In addition to optimizing the data pipeline, accuracy and speed in producing the Level 1 and 2 data products is key. Algorithms for feature recognition are explored, facilitating image cropping and accurate atom number calculations.

Enhanced Spin Squeezing in Atomic Ensembles via Control of the Internal Spin States

NASA Astrophysics Data System (ADS)

Shojaee, Ezad; Norris, Leigh; Baragiola, Ben; Montano, Enrique; Hemmer, Daniel; Jessen, Poul; Deutsch, Ivan

2015-05-01

Abstract: We study the process by which the collective spin squeezing of an ensemble of Cesium atoms is enhanced by control of the internal spin state of the atoms. By increasing the initial atomic projection noise, one can enhance the Faraday interaction that entangles the atoms with a probe. The light acts as a quantum bus for creating atom-atom entanglement via measurement backaction. Further control can be used to transfer this entanglement to metrologically useful squeezing. We numerically simulate this protocol by a stochastic master equation, including QND measurement and optical pumping, which accounts for decoherence and transfer of coherences between magnetic sub-levels. We study the tradeoff between the enhanced entangling interaction and increased rates of decoherence for different initial state preparations. Under realistic conditions, we find that we can achieve squeezing with a ``CAT-State'' superpostion |F = 4, Mz = 4> + |F, Mz = -4> of ~ 9.9 dB and for the spin coherent state |F = 4, Mx = 4> of ~ 7.5 dB. The increased entanglement enabled by the CAT state preparation is partially, but not completely reduced by the increased fragility to decoherence. National Science Foundation.

Regulatory cross-cutting topics for fuel cycle facilities.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Denman, Matthew R.; Brown, Jason; Goldmann, Andrew Scott

This report overviews crosscutting regulatory topics for nuclear fuel cycle facilities for use in the Fuel Cycle Research & Development Nuclear Fuel Cycle Evaluation and Screening study. In particular, the regulatory infrastructure and analysis capability is assessed for the following topical areas: Fire Regulations (i.e., how applicable are current Nuclear Regulatory Commission (NRC) and/or International Atomic Energy Agency (IAEA) fire regulations to advance fuel cycle facilities) Consequence Assessment (i.e., how applicable are current radionuclide transportation tools to support risk-informed regulations and Level 2 and/or 3 PRA) While not addressed in detail, the following regulatory topic is also discussed: Integrated Security,more » Safeguard and Safety Requirement (i.e., how applicable are current Nuclear Regulatory Commission (NRC) regulations to future fuel cycle facilities which will likely be required to balance the sometimes conflicting Material Accountability, Security, and Safety requirements.)« less

Some Aspects of Advanced Tokamak Modeling in DIII-D

NASA Astrophysics Data System (ADS)

St John, H. E.; Petty, C. C.; Murakami, M.; Kinsey, J. E.

2000-10-01

We extend previous work(M. Murakami, et al., General Atomics Report GA-A23310 (1999).) done on time dependent DIII-D advanced tokamak simulations by introducing theoretical confinement models rather than relying on power balance derived transport coefficients. We explore using NBCD and off axis ECCD together with a self-consistent aligned bootstrap current, driven by the internal transport barrier dynamics generated with the GLF23 confinement model, to shape the hollow current profile and to maintain MHD stable conditions. Our theoretical modeling approach uses measured DIII-D initial conditions to start off the simulations in a smooth consistent manner. This mitigates the troublesome long lived perturbations in the ohmic current profile that is normally caused by inconsistent initial data. To achieve this goal our simulation uses a sequence of time dependent eqdsks generated autonomously by the EFIT MHD equilibrium code in analyzing experimental data to supply the history for the simulation.

Boosting the Light: X-ray Physics in Confinement

ScienceCinema

Rhisberger, Ralf [HASYLAB/ DESY

2017-12-09

Remarkable effects are observed if light is confined to dimensions comparable to the wavelength of the light. The lifetime of atomic resonances excited by the radiation is strongly reduced in photonic traps, such as cavities or waveguides. Moreover, one observes an anomalous boost of the intensity scattered from the resonant atoms. These phenomena results from the strong enhancement of the photonic density of states in such geometries. Many of these effects are currently being explored in the regime of vsible light due to their relevance for optical information processing. It is thus appealing to study these phenomena also for much shorter wavelengths. This talk illuminates recent experiments where synchrotron x-rays were trapped in planar waveguides to resonantly excite atomos ([57]Fe nuclei_ embedded in them. In fact, one observes that the radiative decay of these excited atoms is strongly accelerated. The temporal acceleration of the decay goes along with a strong boost of the radiation coherently scattered from the confined atmos. This can be exploited to obtain a high signal-to-noise ratio from tiny quantities of material, leading to manifold applications in the investigation of nanostructured materials. One application is the use of ultrathin probe layers to image the internal structure of magnetic layer systems.

A Technology Demonstration Experiment for Laser Cooled Atomic Clocks in Space

NASA Technical Reports Server (NTRS)

Klipstein, W. M.; Kohel, J.; Seidel, D. J.; Thompson, R. J.; Maleki, L.; Gibble, K.

2000-01-01

We have been developing a laser-cooling apparatus for flight on the International Space Station (ISS), with the intention of demonstrating linewidths on the cesium clock transition narrower than can be realized on the ground. GLACE (the Glovebox Laser- cooled Atomic Clock Experiment) is scheduled for launch on Utilization Flight 3 (UF3) in 2002, and will be mounted in one of the ISS Glovebox platforms for an anticipated 2-3 week run. Separate flight definition projects funded at NIST and Yale by the Micro- gravity Research Division of NASA as a part of its Laser Cooling and Atomic Physics (LCAP) program will follow GLACE. Core technologies for these and other LCAP missions are being developed at JPL, with the current emphasis on developing components such as the laser and optics subsystem, and non-magnetic vacuum-compatible mechanical shutters. Significant technical challenges in developing a space qualifiable laser cooling apparatus include reducing the volume, mass, and power requirements, while increasing the ruggedness and reliability in order to both withstand typical launch conditions and achieve several months of unattended operation. This work was performed at the Jet Propulsion Laboratory under a contract with the National Aeronautics and Space Administration.

Laboratory Studies of Vibrational Relaxation: Important Insights for Mesospheric OH

NASA Astrophysics Data System (ADS)

Kalogerakis, K. S.; Matsiev, D.

2016-12-01

The hydroxyl radical has a key role in the chemistry and energetics of the Earth's middle atmosphere. A detailed knowledge of the rate constants and relevant pathways for OH(high v) vibrational relaxation by atomic and molecular oxygen and their temperature dependence is absolutely critical for understanding mesospheric OH and extracting reliable chemical heating rates from atmospheric observations. We have developed laser-based experimental approaches to study the complex collisional energy transfer processes involving the OH radical and other relevant atmospheric species. Previous work in our laboratory indicated that the total removal rate constant for OH(v = 9) + O at room temperature is more than one order of magnitude larger than that for removal by O2. Thus, O atoms are expected to significantly influence the intensity and vibrational distribution extracted from the Meinel OH(v) emissions. We will report our most recent laboratory experiments that corroborate the aforementioned result for fast OH(v = 9) + O and provide important new insights on the mechanistic pathways involved. We will also highlight relevant atmospheric implications, including warranted revisions of current mesospheric OH models. Research supported by SRI International Internal R&D and NSF Aeronomy grant AGS-1441896. Previously supported by NASA Geospace Science grant NNX12AD09G.

Properties of zirconium silicate and zirconium-silicon oxynitride high-k dielectric alloys for advanced microelectronic applications: Chemical and electrical characterizations

NASA Astrophysics Data System (ADS)

Ju, Byongsun

2005-11-01

As the microelectronic devices are aggressively scaled down to the 1999 International Technology Roadmap, the advanced complementary metal oxide semiconductor (CMOS) is required to increase packing density of ultra-large scale integrated circuits (ULSI). High-k alternative dielectrics can provide the required levels of EOT for device scaling at larger physical thickness, thereby providing a materials pathway for reducing the tunneling current. Zr silicates and its end members (SiO2 and ZrO2) and Zr-Si oxynitride films, (ZrO2)x(Si3N 4)y(SiO2)z, have been deposited using a remote plasma-enhanced chemical vapor deposition (RPECVD) system. After deposition of Zr silicate, the films were exposed to He/N2 plasma to incorporate nitrogen atoms into the surface of films. The amount of incorporated nitrogen atoms was measured by on-line Auger electron spectrometry (AES) as a function of silicate composition and showed its local minimum around the 30% silicate. The effect of nitrogen atoms on capacitance-voltage (C-V) and leakage-voltage (J-V) were also investigated by fabricating metal-oxide-semiconductor (MOS) capacitors. Results suggested that incorporating nitrogen into silicate decreased the leakage current in SiO2-rich silicate, whereas the leakage increased in the middle range of silicate. Zr-Si oxynitride was a pseudo-ternary alloy and no phase separation was detected by x-ray photoelectron spectroscopy (XPS) analysis up to 1100°C annealing. The leakage current of Zr-Si oxynitride films showed two different temperature dependent activation energies, 0.02 eV for low temperature and 0.3 eV for high temperature. Poole-Frenkel emission was the dominant leakage mechanism. Zr silicate alloys with no Si3N4 phase were chemically separated into the SiO2 and ZrO2 phase as annealed above 900°C. While chemical phase separation in Zr silicate films with Si 3N4 phase (Zr-Si oxynitride) were suppressed as increasing the amount of Si3N4 phase due to the narrow bonding network m Si3N4 phase. (3.4 bonds/atom for Si3 N4 network, 2.67 bonds/atom for SiO2 network).

1998 Conference on Precision Electromagnetic Measurements Digest. Proceedings.

NASA Astrophysics Data System (ADS)

Nelson, T. L.

The following topics were dealt with: fundamental constants; caesium standards; AC-DC transfer; impedance measurement; length measurement; units; statistics; cryogenic resonators; time transfer; QED; resistance scaling and bridges; mass measurement; atomic fountains and clocks; single electron transport; Newtonian constant of gravitation; stabilised lasers and frequency measurements; cryogenic current comparators; optical frequency standards; high voltage devices and systems; international compatibility; magnetic measurement; precision power measurement; high resolution spectroscopy; DC transport standards; waveform acquisition and analysis; ion trap standards; optical metrology; quantised Hall effect; Josephson array comparisons; signal generation and measurement; Avogadro constant; microwave networks; wideband power standards; antennas, fields and EMC; quantum-based standards.

Hydrodynamical instabilities induced by atomic diffusion in F and A stars : Impact on the opacity profile and asteroseimic age determination

NASA Astrophysics Data System (ADS)

Deal, M.; Richard, O.; Vauclair, S.

2017-12-01

Atomic diffusion, including the effect of radiative accelerations on individual elements, leads to important variations of the chemical composition inside the stars. The accumulation in specific layers of the elements, which are the main contributors of the local opacity, leads to hydrodynamical instabilities that modify the internal stellar structure and surface abundances. The modification of the initial chemical composition has important effects on the internal stellar mixing and leads to different surface and internal abundances of the elements. These processes also modify the age determination by asteroseismology.

UTC Dissemination to the Real-Time User

NASA Technical Reports Server (NTRS)

Levine, Judah

1996-01-01

The current definition of Coordinated Universal Time (UTC) dates from 1972. The duration of a UTC second is defined in terms of the frequency of a hyperfine transition in the ground state of cesium. This standard frequency is realized in a number of different laboratories using ensembles of commercial cesium clocks and a few primary frequency standards. The data from all of these devices are transmitted periodically to the Bureau International des Poids et Mesures (BIPM) in Sevres, France, where they are combined in a statistical procedure to produce International Atomic Time (TAI). The time of this scale is adjusted as needed ('coordinated') by adding or dropping integer seconds so as to keep it within plus or minus 0.9 s of UT1, a time scale based on the observation of the transit times of stars and corrected for the predicted seasonal variations in these observations. When the leap seconds are included into TAI, the result is called UTC. The difference between TAI and UTC is therefore an exact integer number of seconds. This difference is currently 29 s and will become 30 s at 0 UTC on 1 January 1996.

Nuclear and radiological emergencies: Building capacity in medical physics to support response.

PubMed

Berris, Theocharis; Nüsslin, Fridtjof; Meghzifene, Ahmed; Ansari, Armin; Herrera-Reyes, Eduardo; Dainiak, Nicholas; Akashi, Makoto; Gilley, Debbie; Ohtsuru, Akira

2017-10-01

Medical physicists represent a valuable asset at the disposal of a structured and planned response to nuclear or radiological emergencies (NREs), especially in the hospital environment. The recognition of this fact led the International Atomic Energy Agency (IAEA) and the International Organization for Medical Physics (IOMP) to start a fruitful collaboration aiming to improve education and training of medical physicists so that they may support response efforts in case of NREs. Existing shortcomings in specific technical areas were identified through international consultations supported by the IAEA and led to the development of a project aiming at preparing a specific and standardized training package for medical physicists in support to NREs. The Project was funded through extra-budgetary contribution from Japan within the IAEA Nuclear Safety Action Plan. This paper presents the work accomplished through that project and describes the current steps and future direction for enabling medical physicists to better support response to NREs. Copyright © 2017 Associazione Italiana di Fisica Medica. All rights reserved.

Advances in positron and electron scattering*

NASA Astrophysics Data System (ADS)

Limão-Vieira, Paulo; García, Gustavo; Krishnakumar, E.; Petrović, Zoran; Sullivan, James; Tanuma, Hajime

2016-10-01

The topical issue on Advances in Positron and Electron Scattering" combines contributions from POSMOL 2015 together with others devoted to celebrate the unprecedented scientific careers of our loyal colleagues and trusted friends Steve Buckman (Australian National University, Australia) and Michael Allan (University of Fribourg, Switzerland) on the occasion of their retirements. POSMOL 2015, the XVIII International Workshop on Low-Energy Positron and Positronium Physics and the XIX International Symposium on Electron-Molecule Collisions and Swarms, was held at Universidade NOVA de Lisboa, Lisboa, Portugal, from 17-20 July 2015. The international workshop and symposium allowed to achieve a very privileged forum of sharing and developing our scientific expertise on current aspects of positron, positronium and antiproton interactions with electrons, atoms, molecules and solid surfaces, and related topics, as well as electron interactions with molecules in both gaseous and condensed phases. Particular topics include studies of electron interactions with biomolecules, electron induced surface chemistry and the study of plasma processes. Recent developments in the study of swarms are also fully addressed.

High performance current and spin diode of atomic carbon chain between transversely symmetric ribbon electrodes.

PubMed

Dong, Yao-Jun; Wang, Xue-Feng; Yang, Shuo-Wang; Wu, Xue-Mei

2014-08-21

We demonstrate that giant current and high spin rectification ratios can be achieved in atomic carbon chain devices connected between two symmetric ferromagnetic zigzag-graphene-nanoribbon electrodes. The spin dependent transport simulation is carried out by density functional theory combined with the non-equilibrium Green's function method. It is found that the transverse symmetries of the electronic wave functions in the nanoribbons and the carbon chain are critical to the spin transport modes. In the parallel magnetization configuration of two electrodes, pure spin current is observed in both linear and nonlinear regions. However, in the antiparallel configuration, the spin-up (down) current is prohibited under the positive (negative) voltage bias, which results in a spin rectification ratio of order 10(4). When edge carbon atoms are substituted with boron atoms to suppress the edge magnetization in one of the electrodes, we obtain a diode with current rectification ratio over 10(6).

High performance current and spin diode of atomic carbon chain between transversely symmetric ribbon electrodes

PubMed Central

Dong, Yao-Jun; Wang, Xue-Feng; Yang, Shuo-Wang; Wu, Xue-Mei

2014-01-01

We demonstrate that giant current and high spin rectification ratios can be achieved in atomic carbon chain devices connected between two symmetric ferromagnetic zigzag-graphene-nanoribbon electrodes. The spin dependent transport simulation is carried out by density functional theory combined with the non-equilibrium Green's function method. It is found that the transverse symmetries of the electronic wave functions in the nanoribbons and the carbon chain are critical to the spin transport modes. In the parallel magnetization configuration of two electrodes, pure spin current is observed in both linear and nonlinear regions. However, in the antiparallel configuration, the spin-up (down) current is prohibited under the positive (negative) voltage bias, which results in a spin rectification ratio of order 104. When edge carbon atoms are substituted with boron atoms to suppress the edge magnetization in one of the electrodes, we obtain a diode with current rectification ratio over 106. PMID:25142376

An international conference in honour of the centennial of the birth of Ya.B. Zeldovich, "Subatomic Particles, Nucleons, Atoms, the Universe: Processes and Structure"

NASA Astrophysics Data System (ADS)

Kilin, S. Ya.; Ruffini, R.; Vereshchagin, G.

2015-06-01

An international conference in honour of the centennial of the birth of Ya.B. Zeldovich, "Subatomic Particles, Nucleons, Atoms, the Universe: Processes and Structure" was held in Minsk, Belarus on March 10-14, 2014. Scientific papers based on plenary presentations made at this conference are being published in Volumes 6 and 7, 2015 of "Astronomy Reports."

Polarized deuterium internal target at AmPS (NIKHEF)

NASA Astrophysics Data System (ADS)

Ferro-Luzzi, M.; Zhou, Z.-L.; van den Brand, J. F. J.; Bulten, H. J.; Alarcon, R.; van Bakel, N.; Botto, T.; Bouwhuis, M.; van Buuren, L.; Comfort, J.; Doets, M.; Dolfini, S.; Ent, R.; Geurts, D.; Heimberg, P.; Higinbotham, D. W.; de Jager, C. W.; Lang, J.; de Lange, D. J.; Norum, B.; Passchier, I.; Poolman, H. R.; Six, E.; Steijger, J.; Szczerba, D.; Unal, O.; de Vries, H.

1998-01-01

We describe the polarized deuterium target internal to the NIKHEF medium-energy electron storage ring. Tensor polarized deuterium was produced in an atomic beam source and injected into a storage cell target. A Breit-Rabi polarimeter was used to monitor the injected atomic beam intensity and polarization. An electrostatic ion-extraction system and a Wien filter were utilized to measure on-line the atomic fraction of the target gas in the storage cell. This device was supplemented with a tensor polarization analyzer using the neutron anisotropy of the 3H(d,n)α reaction at 60 keV. This method allows determining the density-averaged nuclear polarization of the target gas, independent of spatial and temporal variations. We address issues important for polarized hydrogen/deuterium internal targets, such as the effects of spin-exchange collisions and resonant transitions induced by the RF fields of the charged particle beam.

Probing Membrane Order and Topography in Supported Lipid Bilayers by Combined Polarized Total Internal Reflection Fluorescence-Atomic Force Microscopy

PubMed Central

Oreopoulos, John; Yip, Christopher M.

2009-01-01

Determining the local structure, dynamics, and conformational requirements for protein-protein and protein-lipid interactions in membranes is critical to understanding biological processes ranging from signaling to the translocating and membranolytic action of antimicrobial peptides. We report here the application of a combined polarized total internal reflection fluorescence microscopy-in situ atomic force microscopy platform. This platform's ability to image membrane orientational order was demonstrated on DOPC/DSPC/cholesterol model membranes containing the fluorescent membrane probe, DiI-C20 or BODIPY-PC. Spatially resolved order parameters and fluorophore tilt angles extracted from the polarized total internal reflection fluorescence microscopy images were in good agreement with the topographical details resolved by in situ atomic force microscopy, portending use of this technique for high-resolution characterization of membrane domain structures and peptide-membrane interactions. PMID:19254557

Polarized deuterium internal target at AmPS (NIKHEF)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Norum, Blaine; De Jager, Cornelis; Geurts, D.

1997-08-01

We describe the polarized deuterium target internal to the NIKHEF medium-energy electron storage ring. Tensor polarized deuterium was produced in an atomic beam source and injected into a storage cell target. A Breit-Rabi polarimeter was used to monitor the injected atomic beam intensity and polarization. An electrostatic ion-extraction system and a Wien filter were utilized to measure on-line the atomic fraction of the target gas in the storage cell. This device was supplemented with a tensor polarization analyzer using the neutron anisotropy of the 3H(d,n)sigma reaction at 60 keV. This method allows determining the density-averaged nuclear polarization of the targetmore » gas, independent of spatial and temporal variations. We address issues important for polarized hydrogen/deuterium internal targets, such as the effects of spin-exchange collisions and resonant transitions induced by the RF fields of the charged particle beam.« less

Polarized deuterium internal target at AmPS (NIKHEF)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ferro-Luzzi, M.; NIKHEF, P.O. Box 41882, 1009 DB Amsterdam; Zhou, Z.-L.

1998-01-20

We describe the polarized deuterium target internal to the NIKHEF medium-energy electron storage ring. Tensor polarized deuterium was produced in an atomic beam source and injected into a storage cell target. A Breit-Rabi polarimeter was used to monitor the injected atomic beam intensity and polarization. An electrostatic ion-extraction system and a Wien filter were utilized to measure on-line the atomic fraction of the target gas in the storage cell. This device was supplemented with a tensor polarization analyzer using the neutron anisotropy of the {sup 3}H(d,n){alpha} reaction at 60 keV. This method allows determining the density-averaged nuclear polarization of themore » target gas, independent of spatial and temporal variations. We address issues important for polarized hydrogen/deuterium internal targets, such as the effects of spin-exchange collisions and resonant transitions induced by the RF fields of the charged particle beam.« less

Spectr-W3 Online Database On Atomic Properties Of Atoms And Ions

NASA Astrophysics Data System (ADS)

Faenov, A. Ya.; Magunov, A. I.; Pikuz, T. A.; Skobelev, I. Yu.; Loboda, P. A.; Bakshayev, N. N.; Gagarin, S. V.; Komosko, V. V.; Kuznetsov, K. S.; Markelenkov, S. A.

2002-10-01

Recent progress in the novel information technologies based on the World-Wide Web (WWW) gives a new possibility for a worldwide exchange of atomic spectral and collisional data. This facilitates joint efforts of the international scientific community in basic and applied research, promising technological developments, and university education programs. Special-purpose atomic databases (ADBs) are needed for an effective employment of large-scale datasets. The ADB SPECTR developed at MISDC of VNIIFTRI has been used during the last decade in several laboratories in the world, including RFNC-VNIITF. The DB SPECTR accumulates a considerable amount of atomic data (about 500,000 records). These data were extracted from publications on experimental and theoretical studies in atomic physics, astrophysics, and plasma spectroscopy during the last few decades. The information for atoms and ions comprises the ionization potentials, the energy levels, the wavelengths and transition probabilities, and, to a lesser extent, -- also the autoionization rates, and the electron-ion collision cross-sections and rates. The data are supplied with source references and comments elucidating the details of computations or measurements. Our goal is to create an interactive WWW information resource based on the extended and updated Web-oriented database version SPECTR-W3 and its further integration into the family of specialized atomic databases on the Internet. The version will incorporate novel experimental and theoretical data. An appropriate revision of the previously accumulated data will be performed from the viewpoint of their consistency to the current state-of-the-art. We are particularly interested in cooperation for storing the atomic collision data. Presently, a software shell with the up-to-date Web-interface is being developed to work with the SPECTR-W3 database. The shell would include the subsystems of information retrieval, input, update, and output in/from the database and present the users a handful of capabilities to formulate the queries with various modes of the search prescriptions, to present the information in tabular, graphic, and alphanumeric form using the formats of the text and HTML documents. The SPECTR-W3 Website is being arranged now and is supposed to be freely accessible round-the-clock on a dedicated Web server at RFNC VNIITF. The Website is being created with the employment of the advanced Internet technologies and database development techniques by using the up-to-date software of the world leading software manufacturers. The SPECTR-W3 ADB FrontPage would also include a feedback channel for the user comments and proposals as well as the hyperlinks to the Websites of the other ADBs and research centers in Europe, the USA, the Middle and Far East, running the investigations in atomic physics, plasma spectroscopy, astrophysics, and in adjacent areas. The effort is being supported by the International Science and Technology Center under the project sharp/mesh/hash1785-01.

Oak Ridge National Laboratory Office of International Nuclear Safeguards: Human Capital Development Activity in FY16

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gilligan, Kimberly V.; Gaudet, Rachel N.

In 2007, the U.S. Department of Energy National Nuclear Security Administration (DOE NNSA) Office of Nonproliferation and Arms Control (NPAC) completed a comprehensive review of the current and potential future challenges facing the international safeguards system. One of the report’s key recommendations was for DOE NNSA to launch a major new program to revitalize the international safeguards technology and human resource base. In 2007, at the International Atomic Energy Agency (IAEA) General Conference, then Secretary of Energy Samuel W. Bodman announced the newly created Next Generation Safeguards Initiative (NGSI). NGSI consists of five program elements: policy development and outreach, conceptsmore » and approaches, technology and analytical methodologies, human capital development (HCD), and infrastructure development. This report addresses the HCD component of NGSI. The goal of the HCD component as defined in the NNSA Program Plan is “to revitalize and expand the international safeguards human capital base by attracting and training a new generation of talent.” The major objectives listed in the HCD goal include education and training, outreach to universities and professional societies, postdoctoral appointments, and summer internships at national laboratories.« less

The metrology of time.

PubMed

Arias, Elisa Felicitas

2005-09-15

Measuring time is a continuous activity, an international and restless enterprise hidden in time laboratories spread all over the planet. The Bureau International des Poids et Mesures is charged with coordinating activities for international timekeeping and it makes use of the world's capacity to produce a remarkably stable and accurate reference time-scale. Commercial atomic clocks beating the second in national laboratories can reach a stability of one part in 10(14) over a 5 day averaging time, compelling us to research the most highly performing methods of remote clock comparison. The unit of the international time-scale is the second of the International System of Units, realized with an uncertainty of the order 10(-15) by caesium fountains. Physicists in a few time laboratories are making efforts to gain one order of magnitude in the uncertainty of the realization of the second, and more refined techniques of time and frequency transfer are in development to accompany this progress. Femtosecond comb technology will most probably contribute in the near future to enhance the definition of the second with the incorporation of optical clocks. We will explain the evolution of the measuring of time, current state-of-the-art measures and future challenges.

48 CFR 252.204-7010 - Requirement for Contractor To Notify DoD if the Contractor's Activities are Subject to Reporting...

Code of Federal Regulations, 2013 CFR

2013-10-01

... Atomic Energy Agency Additional Protocol. 252.204-7010 Section 252.204-7010 Federal Acquisition... Atomic Energy Agency Additional Protocol. As prescribed in 204.470-3, use the following clause....-International Atomic Energy Agency Additional Protocol (JAN 2009) (a) If the Contractor is required to report...

48 CFR 252.204-7010 - Requirement for Contractor To Notify DoD if the Contractor's Activities are Subject to Reporting...

Code of Federal Regulations, 2014 CFR

2014-10-01

... Atomic Energy Agency Additional Protocol. 252.204-7010 Section 252.204-7010 Federal Acquisition... Atomic Energy Agency Additional Protocol. As prescribed in 204.470-3, use the following clause....-International Atomic Energy Agency Additional Protocol (JAN 2009) (a) If the Contractor is required to report...

48 CFR 252.204-7010 - Requirement for Contractor to Notify DoD if the Contractor's Activities are Subject to Reporting...

Code of Federal Regulations, 2012 CFR

2012-10-01

... Atomic Energy Agency Additional Protocol. 252.204-7010 Section 252.204-7010 Federal Acquisition... Atomic Energy Agency Additional Protocol. As prescribed in 204.470-3, use the following clause....-International Atomic Energy Agency Additional Protocol (JAN 2009) (a) If the Contractor is required to report...

48 CFR 252.204-7010 - Requirement for Contractor to Notify DoD if the Contractor's Activities are Subject to Reporting...

Code of Federal Regulations, 2011 CFR

2011-10-01

... Atomic Energy Agency Additional Protocol. 252.204-7010 Section 252.204-7010 Federal Acquisition... Atomic Energy Agency Additional Protocol. As prescribed in 204.470-3, use the following clause....-International Atomic Energy Agency Additional Protocol (JAN 2009) (a) If the Contractor is required to report...

Genetic radiation risks: a neglected topic in the low dose debate

PubMed Central

2016-01-01

Objectives To investigate the accuracy and scientific validity of the current very low risk factor for hereditary diseases in humans following exposures to ionizing radiation adopted by the United Nations Scientific Committee on the Effects of Atomic Radiation and the International Commission on Radiological Protection. The value is based on experiments on mice due to reportedly absent effects in the Japanese atomic bomb (Abomb) survivors. Methods To review the published evidence for heritable effects after ionising radiation exposures particularly, but not restricted to, populations exposed to contamination from the Chernobyl accident and from atmospheric nuclear test fallout. To make a compilation of findings about early deaths, congenital malformations, Down’s syndrome, cancer and other genetic effects observed in humans after the exposure of the parents. To also examine more closely the evidence from the Japanese A-bomb epidemiology and discuss its scientific validity. Results Nearly all types of hereditary defects were found at doses as low as one to 10 mSv. We discuss the clash between the current risk model and these observations on the basis of biological mechanism and assumptions about linear relationships between dose and effect in neonatal and foetal epidemiology. The evidence supports a dose response relationship which is non-linear and is either biphasic or supralinear (hogs-back) and largely either saturates or falls above 10 mSv. Conclusions We conclude that the current risk model for heritable effects of radiation is unsafe. The dose response relationship is non-linear with the greatest effects at the lowest doses. Using Chernobyl data we derive an excess relative risk for all malformations of 1.0 per 10 mSv cumulative dose. The safety of the Japanese A-bomb epidemiology is argued to be both scientifically and philosophically questionable owing to errors in the choice of control groups, omission of internal exposure effects and assumptions about linear dose response. PMID:26791091

Defect-suppressed atomic crystals in an optical lattice.

PubMed

Rabl, P; Daley, A J; Fedichev, P O; Cirac, J I; Zoller, P

2003-09-12

We present a coherent filtering scheme which dramatically reduces the site occupation number defects for atoms in an optical lattice by transferring a chosen number of atoms to a different internal state via adiabatic passage. With the addition of superlattices it is possible to engineer states with a specific number of atoms per site (atomic crystals), which are required for quantum computation and the realization of models from condensed matter physics, including doping and spatial patterns. The same techniques can be used to measure two-body spatial correlation functions.

Quantum teleportation with atoms trapped in cavities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cho, Jaeyoon; Lee, Hai-Woong

2004-09-01

We propose a scheme to implement the quantum teleportation protocol with single atoms trapped in cavities. The scheme is based on the adiabatic passage and the polarization measurement. We show that it is possible to teleport the internal state of an atom trapped in a cavity to an atom trapped in another cavity with the success probability of 1/2 and the fidelity of 1. The scheme is resistant to a number of considerable imperfections such as the violation of the Lamb-Dicke condition, weak atom-cavity coupling, spontaneous emission, and detection inefficiency.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Numakura, H.

The structure and the formation mechanism of oxides during internal oxidation have attracted much attention, and extensive studies have been carried out on this subject. Recently, Jang et al. reported the results of atom-probe microanalysis of oxide particles, or solute-oxygen clusters, in an internally oxidized Cu-0.16 at.% Mg alloy. They found that the composition varies from particle to particle even in the same specimen, and reported that some clusters consist only of magnesium atoms. On the basis of the results, they suggested that the oxidation proceeds in this alloy as follows: (1) the solute atoms form clusters, (2) the clustersmore » absorb oxygen atoms to form both hypo- and hyperstoichiometric oxide particles, (3) the particles grow to form the stoichiometric oxide, MgO. They show the presence of Mg atom clusters with no oxygen association. By assuming that the analyzed area is in the unoxidized region, i.e., ahead of the oxidation front, they interpret this observation as evidence for clustering of the solute atoms prior to oxide formation. However, according to the phase diagram, such clustering is not expected in the absence of oxygen, since the solute concentration, 0.16 at.%, is far below the solubility limit at the oxidation temperature of 900[degree]C, about 3.5 at.%. In atom probe experiments, it sometimes happens that detection efficiencies for different ion species are considerably different because some experimental parameters are not chosen properly. It seems possible that the data resulted from an unusually low detection efficiency for O ions. Since their conclusion raises an important issue on the mechanism of internal oxidation, it is desirable to examine experimental conditions carefully, and to check the reproducibility of data.« less

Iodine-129 measurements in soil samples from Dolon village near the Semipalatinsk nuclear test site.

PubMed

Endo, Satoru; Tomita, Junpei; Tanaka, Kenichi; Yamamoto, Masayoshi; Fukutani, Satoshi; Imanaka, Tetsuji; Sakaguchi, Aya; Amano, Hikaru; Kawamura, Hidehisa; Kawamura, Hisao; Apsalikov, Kazbek N; Gusev, Boris I; Whitehead, Neil E; Shinkarev, Sergey; Hoshi, Masaharu

2008-07-01

Dolon village, located about 60 km from the border of the Semipalatinsk nuclear test site, is known to be heavily contaminated by the first USSR atomic bomb test in August 1949. Soil samples around Dolon were taken in October 2005 in an attempt to evaluate internal thyroid dose arising from incorporation of radioiodine isotopes (mainly (131)I). Iodine-129 in soil was measured by using the technique of accelerator mass spectrometry. The (129)I/(127)I atom ratios measured were in the range from 3.3 x 10(-9) to 3.3 x 10(-7). These values were within the range of the current background level ( approximately 10(-9) to 10(-7)) in the environment, including contributions from the global fallout of atmospheric nuclear tests and local fallout of nuclear facilities. The (129)I atom accumulated level in soil ranged from 1.28 x 10(13) to 1.59 x 10(14) atoms m(-2), the average (8.0 x 10(13)) of which was higher than the background level of (2-5) x 10(13). From the relationship between (129)I and( 137)Cs (corrected for background and decay from 1949 to 2005) accumulated levels, the background level of (129)I and the (129)I/(137)Cs ratio around Dolon were estimated to be (6.4 +/- 0.4) x 10(13) atoms m(-2) and 0.25 +/- 0.16, respectively. This (129)I/(137)Cs ratio is almost similar to the fission yield ratio for (239)Pu fast fission (0.24).

An ignition key for atomic-scale engines

NASA Astrophysics Data System (ADS)

Dundas, Daniel; Cunningham, Brian; Buchanan, Claire; Terasawa, Asako; Paxton, Anthony T.; Todorov, Tchavdar N.

2012-10-01

A current-carrying resonant nanoscale device, simulated by non-adiabatic molecular dynamics, exhibits sharp activation of non-conservative current-induced forces with bias. The result, above the critical bias, is generalized rotational atomic motion with a large gain in kinetic energy. The activation exploits sharp features in the electronic structure, and constitutes, in effect, an ignition key for atomic-scale motors. A controlling factor for the effect is the non-equilibrium dynamical response matrix for small-amplitude atomic motion under current. This matrix can be found from the steady-state electronic structure by a simpler static calculation, providing a way to detect the likely appearance, or otherwise, of non-conservative dynamics, in advance of real-time modelling.

Evidence for non-conservative current-induced forces in the breaking of Au and Pt atomic chains.

PubMed

Sabater, Carlos; Untiedt, Carlos; van Ruitenbeek, Jan M

2015-01-01

This experimental work aims at probing current-induced forces at the atomic scale. Specifically it addresses predictions in recent work regarding the appearance of run-away modes as a result of a combined effect of the non-conservative wind force and a 'Berry force'. The systems we consider here are atomic chains of Au and Pt atoms, for which we investigate the distribution of break down voltage values. We observe two distinct modes of breaking for Au atomic chains. The breaking at high voltage appears to behave as expected for regular break down by thermal excitation due to Joule heating. However, there is a low-voltage breaking mode that has characteristics expected for the mechanism of current-induced forces. Although a full comparison would require more detailed information on the individual atomic configurations, the systems we consider are very similar to those considered in recent model calculations and the comparison between experiment and theory is very encouraging for the interpretation we propose.

Evidence for non-conservative current-induced forces in the breaking of Au and Pt atomic chains

PubMed Central

Sabater, Carlos; Untiedt, Carlos

2015-01-01

Summary This experimental work aims at probing current-induced forces at the atomic scale. Specifically it addresses predictions in recent work regarding the appearance of run-away modes as a result of a combined effect of the non-conservative wind force and a ‘Berry force’. The systems we consider here are atomic chains of Au and Pt atoms, for which we investigate the distribution of break down voltage values. We observe two distinct modes of breaking for Au atomic chains. The breaking at high voltage appears to behave as expected for regular break down by thermal excitation due to Joule heating. However, there is a low-voltage breaking mode that has characteristics expected for the mechanism of current-induced forces. Although a full comparison would require more detailed information on the individual atomic configurations, the systems we consider are very similar to those considered in recent model calculations and the comparison between experiment and theory is very encouraging for the interpretation we propose. PMID:26734525

Elementary! A Nuclear Forensics Workshop Teaches Vital Skills to International Practitioners

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brim, Cornelia P.; Minnema, Lindsay T.

The article describes the Nuclear Forensics Workshop sponsored by the International Atomic Energy Agency (IAEA), the Office of Nonproliferation and International Security (NIS) and hosted by Pacific Northwest National Laboratory October 28-November 8, 2013 in Richland,Washington. Twenty-six participants from 10 countries attended the workshop. Experts from from Los Alamos, Lawrence Livermore, and Pacific Northwest national laboratories collaborated with an internationally recognized cadre of experts from the U.S. Department of Homeland Security and other U.S. agencies, IAEA, the Australian Nuclear Science and Technology Organisation, the United Kingdom Atomic Weapons Establishment (AWE), and the European Union Joint Research Center Institute for Transuraniummore » Elements, to train practitioners in basic methodologies of nuclear forensic examinations.« less

Coherent backscattering of light by an inhomogeneous cloud of cold atoms

NASA Astrophysics Data System (ADS)

Labeyrie, Guillaume; Delande, Dominique; Müller, Cord A.; Miniatura, Christian; Kaiser, Robin

2003-03-01

When a quasiresonant laser beam illuminates an optically thick cloud of laser-cooled rubidium atoms, the average diffuse intensity reflected off the sample is enhanced in a narrow angular range around the direction of exact backscattering. This phenomenon is known as coherent backscattering (CBS). By detuning the laser from resonance, we are able to modify the light scattering mean-free path inside the sample and we record accordingly the variations of the CBS cone shape. We then compare the experimental data with theoretical calculations and Monte Carlo simulations including the effect of the light polarization and of the internal structure of the atoms. We confirm that the internal structure strongly affects the enhancement factor of the cone and we show that the unusual shape of the atomic medium—approximately a spherically-symmetric, Gaussian density profile—strongly affects the width and shape of the cone.

Improved spin squeezing of an atomic ensemble through internal state control

NASA Astrophysics Data System (ADS)

Hemmer, Daniel; Montano, Enrique; Deutsch, Ivan; Jessen, Poul

2016-05-01

Squeezing of collective atomic spins is typically generated by quantum backaction from a QND measurement of the relevant spin component. In this scenario the degree of squeezing is determined by the measurement resolution relative to the quantum projection noise (QPN) of a spin coherent state (SCS). Greater squeezing can be achieved through optimization of the 3D geometry of probe and atom cloud, or by placing the atoms in an optical cavity. We explore here a complementary strategy that relies on quantum control of the large internal spin available in alkali atoms such as Cs. Using a combination of rf and uw magnetic fields, we coherently map the internal spins in our ensemble from the SCS (| f = 4, m = 4>) to a ``cat'' state which is an equal superposition of | f = 4, m = 4>and | f = 4, m = -4>. This increases QPN by a factor of 2 f = 8 relative to the SCS, and therefore the amount of backaction and spin-spin entanglement produced by our QND measurement. In a final step, squeezing generated in the cat state basis can be mapped back to the SCS basis, where it corresponds to increased squeezing of the physical spin. Our experiments suggest that up to 8dB of metrologically useful squeezing can be generated in this way, compared to ~ 3 dB in an otherwise identical experiment starting from a SCS.

Electric field imaging of single atoms

PubMed Central

Shibata, Naoya; Seki, Takehito; Sánchez-Santolino, Gabriel; Findlay, Scott D.; Kohno, Yuji; Matsumoto, Takao; Ishikawa, Ryo; Ikuhara, Yuichi

2017-01-01

In scanning transmission electron microscopy (STEM), single atoms can be imaged by detecting electrons scattered through high angles using post-specimen, annular-type detectors. Recently, it has been shown that the atomic-scale electric field of both the positive atomic nuclei and the surrounding negative electrons within crystalline materials can be probed by atomic-resolution differential phase contrast STEM. Here we demonstrate the real-space imaging of the (projected) atomic electric field distribution inside single Au atoms, using sub-Å spatial resolution STEM combined with a high-speed segmented detector. We directly visualize that the electric field distribution (blurred by the sub-Å size electron probe) drastically changes within the single Au atom in a shape that relates to the spatial variation of total charge density within the atom. Atomic-resolution electric field mapping with single-atom sensitivity enables us to examine their detailed internal and boundary structures. PMID:28555629

Atomic and Molecular Data and their Applications★

NASA Astrophysics Data System (ADS)

Drake, Gordon W. F.; Yoon, Jung-Sik; Kato, Daiji; Karwasz, Grzegorz

2018-03-01

This topical issue on Atomic and molecular data and their applications was motivated by the 10th International Conference on Atomic and Molecular Data (ICAMDATA 2016), which was held from September 26 to 29, 2016 in Gunsan, Republic of Korea. The topics of this issue reflect those of the conference program. The scientific papers in the topical issue cover the fields of atomic and molecular structure, radiative transitions, scattering processes, data base development, and the applications of atomic and molecular data to plasma modeling. Contribution to the Topical Issue "Atomic and Molecular Data and their Applications", edited by Gordon W.F. Drake, Jung-Sik Yoon, Daiji Kato, and Grzegorz Karwasz.

Rugged, Tunable Extended-Cavity Diode Laser

NASA Technical Reports Server (NTRS)

Moore, Donald; Brinza, David; Seidel, David; Klipstein, William; Choi, Dong Ho; Le, Lam; Zhang, Guangzhi; Iniguez, Roberto; Tang, Wade

2007-01-01

A rugged, tunable extended-cavity diode laser (ECDL) has been developed to satisfy stringent requirements for frequency stability, notably including low sensitivity to vibration. This laser is designed specifically for use in an atomic-clock experiment to be performed aboard the International Space Station (ISS). Lasers of similar design would be suitable for use in terrestrial laboratories engaged in atomic-clock and atomic-physics research.

O-regime dynamics and modeling in Tore Supra

NASA Astrophysics Data System (ADS)

Turco, F.; Giruzzi, G.; Imbeaux, F.; Udintsev, V. S.; Artaud, J. F.; Barana, O.; Dumont, R.; Mazon, D.; Ségui, J.-L.

2009-06-01

The regime of nonlinear temperature oscillations (O-regime), characteristic of noninductive discharges on Tore Supra [Équipe Tore Supra, Proceedings of the 12th International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Nice, France, 1988 (International Atomic Energy Agency, Vienna, 1989), Vol. 1, p. 9], is investigated in its triggering and suppressing mechanism. This regime can be described by two nonlinearly coupled equations for the current density j(r ) and the electron temperature Te(r) where the equation coefficients are functions of j and Te themselves. Both the integrated modeling code CRONOS [V. Basiuk et al., Nucl. Fusion 43, 822 (2003)] and a two-patch predator-prey system with diffusion and noise have been used and results have been compared to the experimental observations of the O-regime. A database of discharges is analyzed which features monotonic, flat, and reversed safety factor (q) profiles in order to characterize the action of external actuators on the regime dynamics with the widest generality. Electron cyclotron current drive and neutral beam injections have been used in order to induce localized perturbations in the total current profile j(r ) as well as to change the plasma confinement conditions in the central region. Magnetic shear perturbations and modifications of the heat transport turn out to be the central parameters governing the dynamics of the O-regime.

Tritium handling experience at Atomic Energy of Canada Limited

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suppiah, S.; McCrimmon, K.; Lalonde, S.

2015-03-15

Canada has been a leader in tritium handling technologies as a result of the successful CANDU reactor technology used for power production. Over the last 50 to 60 years, capabilities have been established in tritium handling and tritium management in CANDU stations, tritium removal processes for heavy and light water, tritium measurement and monitoring, and understanding the effects of tritium on the environment. This paper outlines details of tritium-related work currently being carried out at Atomic Energy of Canada Limited (AECL). It concerns the CECE (Combined Electrolysis and Catalytic Exchange) process for detritiation, tritium-compatible electrolysers, tritium permeation studies, and tritiummore » powered batteries. It is worth noting that AECL offers a Tritium Safe-Handling Course to national and international participants, the course is a mixture of classroom sessions and hands-on practical exercises. The expertise and facilities available at AECL is ready to address technological needs of nuclear fusion and next-generation nuclear fission reactors related to tritium handling and related issues.« less

Potential application of LIBS to NNSA next generation safeguards initiative (NGSI)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barefield Ii, James E; Clegg, Samuel M; Veirs, Douglas K

2009-01-01

In a climate in which states and nations have been and perhaps currently are involved in the prol iferation of nuclear materials and technologies, advanced methodologies and improvements in current measurement techniques are needed to combat new threats and increased levels of sophistication. The Department of Energy through the National Nuclear Security Administration (NNSA) has undertaken a broad review of International Safeguards. The conclusion from that review was that a comprehensive initiative to revitalize international safeguards technology and the human resource base was urgently needed to keep pace with demands and increasingly sophisticated emerging safeguards challenges. To address these challenges,more » NNSA launched the Next Generation Safeguards Initiative (NGSI) to develop policies, concepts, technologies, expertise, and infrastructure necessary to sustain the international safeguards system as its mission evolves for the next 25 years. NGSI is designed to revitalize and strengthen the U.S. safeguards technical base, recognizing that without a robust program the United States of America will not be in a position to exercise leadership or provide the necessary support to the IAEA (International Atomic Energy Agency). International safeguards as administrated by the IAEA are the primary vehicle for verifying compliance with the peaceful use and nonproliferation of nuclear materials and technologies. Laser Induced Breakdown Spectroscopy or LIBS has the potential to support the goals of NGSI as follows: by providing (1) automated analysis in complex nuclear processing or reprocessing facilities in real-time or near real-time without sample preparation or removal, (2) isotopic and important elemental ratio (Cm/Pu, Cm/U, ... etc) analysis, and (3) centralized remote control, process monitoring, and analysis of nuclear materials in nuclear facilities at multiple locations within the facility. Potential application of LIBS to international safeguards as outlined in the NGSI will be discussed.« less

High-power Al-free active region (λ= 852nm) DFB laser diodes for atomic clocks and interferometry applications

NASA Astrophysics Data System (ADS)

Ligeret, V.; Vermersch, F.-J.; Bansropun, S.; Lecomte, M.; Calligaro, M.; Parillaud, O.; Krakowski, M.

2017-11-01

Atomic clocks will be used in the future European positioning system Galileo. Among them, the optically pumped clocks provide a better alternative with comparable accuracy for a more compact system. For these systems, diode lasers emitting at 852nm are strategic components. The laser in a conventional bench for atomic clocks presents disadvantages for spatial applications. A better approach would be to realise a system based on a distributed-feedback laser (DFB). We have developed the technological foundations of such lasers operating at 852nm. These include an Al free active region, a single spatial mode ridge waveguide and a DFB structure. The device is a separate confinement heterostructure with a GaInP large optical cavity and a single compressive strained GaInAsP quantum well. The broad area laser diodes are characterised by low internal losses (<3cm -1 ), a high internal efficiency (94%) and a low transparency current density (100A/cm2). For an AR-HR coated ridge Fabry Perot laser, we obtain a power of 230mW with M2=1.3. An optical power of 150mW was obtained at 854nm wavelength, 20°C for AR-HR coated devices. We obtain a single spatial mode emission with M2=1.21 and a SMSR over 30dB, both at 150mW. DFB Lasers at 852.12nm, corresponding to the D2 caesium transition, were then realised with a power of 40mW, 37°C for uncoated devices. The SMSR is over 30dB and the M2=1.33 at 40mW. Furthermore, the preliminary results of the linewidth obtained with a Fabry Perot interferometer give a value of less than 2MHz.

History and Organizations for Radiological Protection.

PubMed

Kang, Keon Wook

2016-02-01

International Commission on Radiological Protection (ICRP), an independent international organization established in 1925, develops, maintains, and elaborates radiological protection standards, legislation, and guidelines. United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) provides scientific evidence. World Health Organization (WHO) and International Atomic Energy Agency (IAEA) utilise the ICRP recommendations to implement radiation protection in practice. Finally, radiation protection agencies in each country adopt the policies, and adapt them to each situation. In Korea, Nuclear Safety and Security Commission is the governmental body for nuclear safety regulation and Korea Institute of Nuclear Safety is a public organization for technical support and R&D in nuclear safety and radiation protection.

Internal Energy Transfer and Dissociation Model Development using Accelerated First-Principles Simulations of Hypersonic Flow Features

DTIC Science & Technology

2013-07-11

in Fig. 3) is simulated. Each atom interacts with its neighboring atoms through a potential energy surface (PES), such as the simple Lennard - Jones ... Lennard -­‐ Jones  (LJ)   potential  energy  surface  (PES)  dictating  atomic  interaction  forces. The main point of this section is to...the potential energy surface (PES) that governs individual atomic interaction forces. In contrast to existing rotational energy models, we found

How can we probe the atom mass currents induced by synthetic gauge fields?

NASA Astrophysics Data System (ADS)

Paramekanti, Arun; Killi, Matthew; Trotzky, Stefan

2013-05-01

Ultracold atomic fermions and bosons in an optical lattice can have quantum ground states which support equilibrium currents in the presence of synthetic magnetic fields or spin orbit coupling. As a tool to uncover these mass currents, we propose using an anisotropic quantum quench of the optical lattice which dynamically converts the current patterns into measurable density patterns. Using analytical calculations and numerical simulations, we show that this scheme can probe diverse equilibrium bulk current patterns in Bose superfluids and Fermi fluids induced by synthetic magnetic fields, as well as detect the chiral edge currents in topological states of atomic matter such as quantum Hall and quantum spin Hall insulators. This work is supported by NSERC of Canada and the Canadian Institute for Advanced Research.

Ultrafast terahertz control of extreme tunnel currents through single atoms on a silicon surface

NASA Astrophysics Data System (ADS)

Jelic, Vedran; Iwaszczuk, Krzysztof; Nguyen, Peter H.; Rathje, Christopher; Hornig, Graham J.; Sharum, Haille M.; Hoffman, James R.; Freeman, Mark R.; Hegmann, Frank A.

2017-06-01

Ultrafast control of current on the atomic scale is essential for future innovations in nanoelectronics. Extremely localized transient electric fields on the nanoscale can be achieved by coupling picosecond duration terahertz pulses to metallic nanostructures. Here, we demonstrate terahertz scanning tunnelling microscopy (THz-STM) in ultrahigh vacuum as a new platform for exploring ultrafast non-equilibrium tunnelling dynamics with atomic precision. Extreme terahertz-pulse-driven tunnel currents up to 107 times larger than steady-state currents in conventional STM are used to image individual atoms on a silicon surface with 0.3 nm spatial resolution. At terahertz frequencies, the metallic-like Si(111)-(7 × 7) surface is unable to screen the electric field from the bulk, resulting in a terahertz tunnel conductance that is fundamentally different than that of the steady state. Ultrafast terahertz-induced band bending and non-equilibrium charging of surface states opens new conduction pathways to the bulk, enabling extreme transient tunnel currents to flow between the tip and sample.

The internal structure of the planets Mercury, Venus, Mars and Jupiter according to the Savic-Kasanin theory

NASA Astrophysics Data System (ADS)

Savic, P.

The internal structure of Mercury, Venus, Mars, and Jupiter is considered in the framework of the Savic-Kasanin theory of the behavior of materials under high pressure. The main hypothesis underlying the theory is based on the deformation of the electron shells by the dislocation and ejection of electrons from atoms in a given material. This theory is discussed in relation to the spontaneous effect of gravitation and cooling on atoms in the material of a celestial body.

Atom-atom entanglement by single-photon detection.

PubMed

Slodička, L; Hétet, G; Röck, N; Schindler, P; Hennrich, M; Blatt, R

2013-02-22

A scheme for entangling distant atoms is realized, as proposed in the seminal paper by [C. Cabrillo et al., Phys. Rev. A 59, 1025 (1999)]. The protocol is based on quantum interference and detection of a single photon scattered from two effectively one meter distant laser cooled and trapped atomic ions. The detection of a single photon heralds entanglement of two internal states of the trapped ions with high rate and with a fidelity limited mostly by atomic motion. Control of the entangled state phase is demonstrated by changing the path length of the single-photon interferometer.

Spin-polarized currents generated by magnetic Fe atomic chains.

PubMed

Lin, Zheng-Zhe; Chen, Xi

2014-06-13

Fe-based devices are widely used in spintronics because of high spin-polarization and magnetism. In this work, freestanding Fe atomic chains, the thinnest wires, were used to generate spin-polarized currents due to the spin-polarized energy bands. By ab initio calculations, the zigzag structure was found to be more stable than the wide-angle zigzag structure and had a higher ratio of spin-up and spin-down currents. By our theoretical prediction, Fe atomic chains have a sufficiently long thermal lifetime only at T ≦̸ 150 K, while C atomic chains are very stable even at T = 1000 K. This means that the spintronic devices based on Fe chains could work only at low temperatures. A system constructed by a short Fe chain sandwiched between two graphene electrodes could be used as a spin-polarized current generator, while a C chain could not be used in this way. The present work may be instructive and meaningful to further practical applications based on recent technical developments on the preparation of metal atomic chains (Proc. Natl. Acad. Sci. USA 107 9055 (2010)).

Training Activities on Radioactive Waste Management at Moscow SIA -Radon-: Experience, Practice, Theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Batyukhnova, O.G.; Arustamov, A.E.; Dmitriev, S.A.

Management of radioactive waste relates to the category of hazardous activities. Hence the requirements to the professional level of managers and personnel working in this industry are very high. Education, training and examination of managers, operators and workers are important elements of assuring safe and efficient operation of radioactive waste management sites. The International Education Training Centre (IETC) at Moscow State Unitary Enterprise Scientific and Industrial Association 'Radon' (SIA 'Radon'), in co-operation with the International Atomic Energy Agency (IAEA), has developed expertise and provided training to waste management personnel for the last 10 years. The paper summarizes the current experiencemore » of the SIA 'Radon' in the organisation and implementation of the IAEA sponsored training and others events and outlines some of strategic educational elements, which IETC will continue to pursue in the coming years. (authors)« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ferrada, J.J.

This report compiles preliminary information that supports the premise that a repository is needed in Latin America and analyzes the nuclear situation (mainly in Argentina and Brazil) in terms of nuclear capabilities, inventories, and regional spent-fuel repositories. The report is based on several sources and summarizes (1) the nuclear capabilities in Latin America and establishes the framework for the need of a permanent repository, (2) the International Atomic Energy Agency (IAEA) approach for a regional spent-fuel repository and describes the support that international institutions are lending to this issue, (3) the current situation in Argentina in order to analyze themore » Argentinean willingness to find a location for a deep geological repository, and (4) the issues involved in selecting a location for the repository and identifies a potential location. This report then draws conclusions based on an analysis of this information. The focus of this report is mainly on spent fuel and does not elaborate on other radiological waste sources.« less

Proceedings ICASS 2017

NASA Astrophysics Data System (ADS)

Fu, Qiang; Schaaf, Peter

2018-07-01

This special issue of the high impact international peer reviewed journal Applied Surface Science represents the proceedings of the 2nd International Conference on Applied Surface Science ICASS held 12-16 June 2017 in Dalian China. The conference provided a forum for researchers in all areas of applied surface science to present their work. The main topics of the conference are in line with the most popular areas of research reported in Applied Surface Science. Thus, this issue includes current research on the role and use of surfaces in chemical and physical processes, related to catalysis, electrochemistry, surface engineering and functionalization, biointerfaces, semiconductors, 2D-layered materials, surface nanotechnology, energy, new/functional materials and nanotechnology. Also the various techniques and characterization methods will be discussed. Hence, scientific research on the atomic and molecular level of material properties investigated with specific surface analytical techniques and/or computational methods is essential for any further progress in these fields.

Molecular Origins of Internal Friction Effects on Protein Folding Rates

PubMed Central

Sirur, Anshul

2014-01-01

Recent experiments on protein folding dynamics have revealed strong evidence for internal friction effects. That is, observed relaxation times are not simply proportional to the solvent viscosity as might be expected if the solvent were the only source of friction. However, a molecular interpretation of this remarkable phenomenon is currently lacking. Here, we use all-atom simulations of peptide and protein folding in explicit solvent, to probe the origin of the unusual viscosity dependence. We find that an important contribution to this effect, explaining the viscosity dependence of helix formation and the folding of a helix-containing protein, is the insensitivity of torsion angle isomerization to solvent friction. The influence of this landscape roughness can, in turn, be quantitatively explained by a rate theory including memory friction. This insensitivity of local barrier crossing to solvent friction is expected to contribute to the viscosity dependence of folding rates in larger proteins. PMID:24986114

Molecular origins of internal friction effects on protein-folding rates.

PubMed

de Sancho, David; Sirur, Anshul; Best, Robert B

2014-07-02

Recent experiments on protein-folding dynamics have revealed strong evidence for internal friction effects. That is, observed relaxation times are not simply proportional to the solvent viscosity as might be expected if the solvent were the only source of friction. However, a molecular interpretation of this remarkable phenomenon is currently lacking. Here, we use all-atom simulations of peptide and protein folding in explicit solvent, to probe the origin of the unusual viscosity dependence. We find that an important contribution to this effect, explaining the viscosity dependence of helix formation and the folding of a helix-containing protein, is the insensitivity of torsion angle isomerization to solvent friction. The influence of this landscape roughness can, in turn, be quantitatively explained by a rate theory including memory friction. This insensitivity of local barrier crossing to solvent friction is expected to contribute to the viscosity dependence of folding rates in larger proteins.

Un projet d'horloge atomique spatiale utlilsant le refroidissement des atomes par faisceaux laser: PHARAO

NASA Astrophysics Data System (ADS)

Laurent, Ph.; Lemonde, P.; Simon, E.; Santarelli, G.; Petit, P.; Dimarcq, N.; Clairon, A.; Salomon, C.; Audoin, C.; Changeart, F. Jamin; Gonzalez, F.

2018-04-01

This paper, "Un projet d'horloge atomique spatiale utlilsant le refroidissement des atomes par faisceaux laser: PHARAO," was presented as part of International Conference on Space Optics—ICSO 1997, held in Toulouse, France.

Dispersion Forces and the Molecular Origin of Internal Friction in Protein.

PubMed

Sashi, Pulikallu; Ramakrishna, Dasari; Bhuyan, Abani K

2016-08-23

Internal friction in macromolecules is one of the curious phenomena that control conformational changes and reaction rates. It is held here that dispersion interactions and London-van der Waals forces between nonbonded atoms are major contributors to internal friction. To demonstrate this, the flipping motion of aromatic rings of F10 and Y97 amino acid residues of cytochrome c has been studied in glycerol/water mixtures by cross relaxation-suppressed exchange nuclear magnetic resonance spectroscopy. The ring-flip rate is highly overdamped by glycerol, but this is not due to the effect of protein-solvent interactions on the Brownian dynamics of the protein, because glycerol cannot penetrate into the protein to slow the internal collective motions. Sound velocity in the protein under matching solvent conditions shows that glycerol exerts its effect by rather smothering the protein interior to produce reduced molecular compressibility and root-mean-square volume fluctuation (δVRMS), implying an increased number of dispersion interactions of nonbonded atoms. Hence, δVRMS can be used as a proxy for internal friction. By using the ansatz that internal friction is related to nonbonded interactions by the equation f(n) = f0 + f1n + f2n(2) + ..., where the variable n is the extent of nonbonded interactions with fi coefficients, the barrier to aromatic ring rotation is found to be flat. Also interesting is the appearance of a turnover region in the δVRMS dependence of the ring-flip rate, suggesting anomalous internal diffusion. We conclude that cohesive forces among nonbonded atoms are major contributors to the molecular origin of internal friction.

Determining Nuclear Fingerprints: Glove Boxes, Radiation Protection, and the International Atomic Energy Agency.

PubMed

Rentetzi, Maria

2017-06-01

In a nuclear laboratory, a glove box is a windowed, sealed container equipped with two flexible gloves that allow the user to manipulate nuclear materials from the outside in an ostensibly safe environment. As a routine laboratory device, it invites neglect from historians and storytellers of science. Yet, since especially the Gulf War, glove boxes have put the interdependence of science, diplomacy, and politics into clear relief. Standing at the intersection of history of science and international history, technological materials and devices such as the glove box can provide penetrating insight into the role of international diplomatic organizations to the global circulation and control of scientific knowledge. The focus here is on the International Atomic Energy Agency. Copyright © 2017 The Author. Published by Elsevier Ltd.. All rights reserved.

Estimation of 99Mo production rates from natural molybdenum in research reactors.

PubMed

Blaauw, M; Ridikas, D; Baytelesov, S; Salas, P S Bedregal; Chakrova, Y; Eun-Ha, Cho; Dahalan, R; Fortunato, A H; Jacimovic, R; Kling, A; Muñoz, L; Mohamed, N M A; Párkányi, D; Singh, T; Van Dong Duong

2017-01-01

Molybdenum-99 is one of the most important radionuclides for medical diagnostics. In 2015, the International Atomic Energy Agency organized a round-robin exercise where the participants measured and calculated specific saturation activities achievable for the 98 Mo(n,γ) 99 Mo reaction. This reaction is of interest as a means to locally, and on a small scale, produce 99 Mo from natural molybdenum. The current paper summarises a set of experimental results and reviews the methodology for calculating the corresponding saturation activities. Activation by epithermal neutrons and also epithermal neutron self-shielding are found to be of high importance in this case.

A hybrid system of a membrane oscillator coupled to ultracold atoms

NASA Astrophysics Data System (ADS)

Kampschulte, Tobias

2015-05-01

The control over micro- and nanomechanical oscillators has recently made impressive progress. First experiments demonstrated ground-state cooling and single-phonon control of high-frequency oscillators using cryogenic cooling and techniques of cavity optomechanics. Coupling engineered mechanical structures to microscopic quantum system with good coherence properties offers new possibilities for quantum control of mechanical vibrations, precision sensing and quantum-level signal transduction. Ultracold atoms are an attractive choice for such hybrid systems: Mechanical can either be coupled to the motional state of trapped atoms, which can routinely be ground-state cooled, or to the internal states, for which a toolbox of coherent manipulation and detection exists. Furthermore, atomic collective states with non-classical properties can be exploited to infer the mechanical motion with reduced quantum noise. Here we use trapped ultracold atoms to sympathetically cool the fundamental vibrational mode of a Si3N4 membrane. The coupling of membrane and atomic motion is mediated by laser light over a macroscopic distance and enhanced by an optical cavity around the membrane. The observed cooling of the membrane from room temperature to 650 +/- 230 mK shows that our hybrid mechanical-atomic system operates at a large cooperativity. Our scheme could provide ground-state cooling and quantum control of low-frequency oscillators such as levitated nanoparticles, in a regime where purely optomechanical techniques cannot reach the ground state. Furthermore, we will present a scheme where an optomechanical system is coupled to internal states of ultracold atoms. The mechanical motion is translated into a polarization rotation which drives Raman transitions between atomic ground states. Compared to the motional-state coupling, the new scheme enables to couple atoms to high-frequency structures such as optomechanical crystals.

Evaluation of effervescent atomizer internal design on the spray unsteadiness using a phase/Doppler particle analyzer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Meng; Duan, YuFeng; Zhang, TieNan

2010-09-15

The purpose of this research was to investigate the dependence of effervescent spray unsteadiness on operational conditions and atomizer internal design by the ideal spray theory of Edwards and Marx. The convergent-divergent effervescent atomizer spraying water with air as atomizing medium in the ''outside-in'' gas injection was used in this study. Results demonstrated that droplet formation process at various air to liquid ratio (ALR) led to the spray unsteadiness and all droplet size classes exhibited unsteadiness behavior in spray. The spray unsteadiness reduced quickly at ALR of 3% and decreased moderately at ALR of other values as the axial distancemore » increased. When the axial distance was 200 mm, the spray unsteadiness reduced dramatically with the increase in radial distance, but lower spray unsteadiness at the center of spray and higher spray unsteadiness at the edge of spray were shown as the axial distance increased. The spray unsteadiness at the center region of spray increased with the injection pressure. Low spray unsteadiness and good atomization performance can be obtained when the diameter of incline aeration holes increased at ALR of 10%. Although short mixing chamber with large discharge orifice diameter for convergent-divergent effervescent atomizer produced good atomization, the center region of spay showed high spray unsteadiness and maybe formed the droplet clustering. (author)« less

Structural tuning of nanogaps using electromigration induced by field emission current with bipolar biasing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yagi, Mamiko; Ito, Mitsuki; Shirakashi, Jun-ichi, E-mail: shrakash@cc.tuat.ac.jp

We report a new method for fabrication of Ni nanogaps based on electromigration induced by a field emission current. This method is called “activation” and is demonstrated here using a current source with alternately reversing polarities. The activation procedure with alternating current bias, in which the current source polarity alternates between positive and negative bias conditions, is performed with planar Ni nanogaps defined on SiO{sub 2}/Si substrates at room temperature. During negative biasing, a Fowler-Nordheim field emission current flows from the source (cathode) to the drain (anode) electrode. The Ni atoms at the tip of the drain electrode are thusmore » activated and then migrate across the gap from the drain to the source electrode. In contrast, in the positive bias case, the field emission current moves the activated atoms from the source to the drain electrode. These two procedures are repeated until the tunnel resistance of the nanogaps is successively reduced from 100 TΩ to 48 kΩ. Scanning electron microscopy and atomic force microscopy studies showed that the gap separation narrowed from approximately 95 nm to less than 10 nm because of the Ni atoms that accumulated at the tips of both the source and drain electrodes. These results show that the alternately biased activation process, which is a newly proposed atom transfer technique, can successfully control the tunnel resistance of the Ni nanogaps and is a suitable method for formation of ultrasmall nanogap structures.« less

Study of quality assurance regulations for linear accelerators in Korea: A comparison study between the current status in Korea and the international guidelines

NASA Astrophysics Data System (ADS)

Lee, Hyunho; Jeong, Seonghoon; Jo, Yunhui; Yoon, Myonggeun

2015-07-01

Quality assurance (QA) for medical linear accelerators is indispensable for appropriate cancer treatment. Some international organizations and advanced Western countries have provided QA guidelines for linear accelerators. Currently, QA regulations for linear accelerators in Korean hospitals specify a system in which each hospital stipulates its independent hospital-based protocols for QA procedures (HP_QAPs) and conducts QA based on those HP_QAPs while regulatory authorities verify whether items under those HP_QAPs have been performed. However, because this regulatory method cannot guarantee the quality of universal treatment and QA items with tolerance criteria are different in many hospitals, the presentation of standardized QA items and tolerance criteria is essential. In this study, QA items in HP_QAPs from various hospitals and those presented by international organizations, such as the International Atomic Energy Agency, the European Union, and the American Association of Physicist in Medicine, and by advanced Western countries, such as the USA, the UK, and Canada, were compared. Concordance rates between QA items for linear accelerators that were presented by the aforementioned organizations and those currently being implemented in Korean hospitals were shown to exhibit a daily QA of 50%, a weekly QA of 22%, a monthly QA of 43%, and an annual QA of 65%, and the overall concordance rates of all QA items were approximately 48%. In the comparison between QA items being implemented in Korean hospitals and those being implemented in advanced Western countries, concordance rates were shown to exhibit a daily QA of 50%, a weekly QA of 33%, a monthly QA of 60%, and an annual QA of 67%, and the overall concordance rates of all QA items were approximately 57%. The results of this study indicate that the HP_QAPs currently implemented by Korean hospitals as QA standards for linear accelerators used in radiation therapy do not meet international standards. If this problem is to be solved, national standardized QA items and procedures for linear accelerators need to be developed.

Efficient Procedure for the Numerical Calculation of Harmonic Vibrational Frequencies Based on Internal Coordinates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miliordos, Evangelos; Xantheas, Sotiris S.

We propose a general procedure for the numerical calculation of the harmonic vibrational frequencies that is based on internal coordinates and Wilson’s GF methodology via double differentiation of the energy. The internal coordinates are defined as the geometrical parameters of a Z-matrix structure, thus avoiding issues related to their redundancy. Linear arrangements of atoms are described using a dummy atom of infinite mass. The procedure has been automated in FORTRAN90 and its main advantage lies in the nontrivial reduction of the number of single-point energy calculations needed for the construction of the Hessian matrix when compared to the corresponding numbermore » using double differentiation in Cartesian coordinates. For molecules of C 1 symmetry the computational savings in the energy calculations amount to 36N – 30, where N is the number of atoms, with additional savings when symmetry is present. Typical applications for small and medium size molecules in their minimum and transition state geometries as well as hydrogen bonded clusters (water dimer and trimer) are presented. Finally, in all cases the frequencies based on internal coordinates differ on average by <1 cm –1 from those obtained from Cartesian coordinates.« less

The Design, Fabrication and Characterization of a Transparent Atom Chip

PubMed Central

Chuang, Ho-Chiao; Huang, Chia-Shiuan; Chen, Hung-Pin; Huang, Chi-Sheng; Lin, Yu-Hsin

2014-01-01

This study describes the design and fabrication of transparent atom chips for atomic physics experiments. A fabrication process was developed to define the wire patterns on a transparent glass substrate to create the desired magnetic field for atom trapping experiments. An area on the chip was reserved for the optical access, so that the laser light can penetrate directly through the glass substrate for the laser cooling process. Furthermore, since the thermal conductivity of the glass substrate is poorer than other common materials for atom chip substrate, for example silicon, silicon carbide, aluminum nitride. Thus, heat dissipation copper blocks are designed on the front and back of the glass substrate to improve the electrical current conduction. The testing results showed that a maximum burnout current of 2 A was measured from the wire pattern (with a width of 100 μm and a height of 20 μm) without any heat dissipation design and it can increase to 2.5 A with a heat dissipation design on the front side of the atom chips. Therefore, heat dissipation copper blocks were designed and fabricated on the back of the glass substrate just under the wire patterns which increases the maximum burnout current to 4.5 A. Moreover, a maximum burnout current of 6 A was achieved when the entire backside glass substrate was recessed and a thicker copper block was electroplated, which meets most requirements of atomic physics experiments. PMID:24922456

The theoretical current-voltage dependence of a non-degenerate disordered organic material obtained with conductive atomic force microscopy

NASA Astrophysics Data System (ADS)

Woellner, Cristiano F.; Freire, José A.; Guide, Michele; Nguyen, Thuc-Quyen

2011-08-01

We develop a simple continuum model for the current voltage characteristics of a material as measured by the conducting atomic force microscopy, including space charge effects. We address the effect of the point contact on the magnitude of the current and on the transition voltages between the different current regimes by comparing these with the corresponding expressions obtained with planar electrodes.

Simulation of Quantum Phenomena in Nanowire Sensors

DTIC Science & Technology

2014-12-17

Ag and Pt atoms: search for nanocatalysts, Journal of Physics B: Atomic, Molecular and Optical Physics, (07 2011): 0. doi: 10.1088/0953- 4075/44...International Advisory Committee, African Laser Centre Annual Workshop 3-5 Nov. 2014, Moroccan Foundation for Advanced Science, Innovation & Research...atoms encapsulated inside C180 and C240 we found: 1) The Xe-C180 and Xe-C240 binding energies along some high symmetry directions showed the

Surface Modification Engineered Assembly of Novel Quantum Dot Architectures for Advanced Applications

DTIC Science & Technology

2008-02-09

Campbell, S. Ogata, and F. Shimojo, “ Multimillion atom simulations of nanosystems on parallel computers,” in Proceedings of the International...nanomesas: multimillion -atom molecular dynamics simulations on parallel computers,” J. Appl. Phys. 94, 6762 (2003). 21. P. Vashishta, R. K. Kalia...and A. Nakano, “ Multimillion atom molecular dynamics simulations of nanoparticles on parallel computers,” Journal of Nanoparticle Research 5, 119-135

Graph Theoretical Representation of Atomic Asymmetry and Molecular Chirality of Benzenoids in Two-Dimensional Space

PubMed Central

Zhao, Tanfeng; Zhang, Qingyou; Long, Hailin; Xu, Lu

2014-01-01

In order to explore atomic asymmetry and molecular chirality in 2D space, benzenoids composed of 3 to 11 hexagons in 2D space were enumerated in our laboratory. These benzenoids are regarded as planar connected polyhexes and have no internal holes; that is, their internal regions are filled with hexagons. The produced dataset was composed of 357,968 benzenoids, including more than 14 million atoms. Rather than simply labeling the huge number of atoms as being either symmetric or asymmetric, this investigation aims at exploring a quantitative graph theoretical descriptor of atomic asymmetry. Based on the particular characteristics in the 2D plane, we suggested the weighted atomic sum as the descriptor of atomic asymmetry. This descriptor is measured by circulating around the molecule going in opposite directions. The investigation demonstrates that the weighted atomic sums are superior to the previously reported quantitative descriptor, atomic sums. The investigation of quantitative descriptors also reveals that the most asymmetric atom is in a structure with a spiral ring with the convex shape going in clockwise direction and concave shape going in anticlockwise direction from the atom. Based on weighted atomic sums, a weighted F index is introduced to quantitatively represent molecular chirality in the plane, rather than merely regarding benzenoids as being either chiral or achiral. By validating with enumerated benzenoids, the results indicate that the weighted F indexes were in accordance with their chiral classification (achiral or chiral) over the whole benzenoids dataset. Furthermore, weighted F indexes were superior to previously available descriptors. Benzenoids possess a variety of shapes and can be extended to practically represent any shape in 2D space—our proposed descriptor has thus the potential to be a general method to represent 2D molecular chirality based on the difference between clockwise and anticlockwise sums around a molecule. PMID:25032832

Attenuation of Scattered Thermal Energy Atomic Oxygen

NASA Technical Reports Server (NTRS)

Banks, Bruce a.; Seroka, Katelyn T.; McPhate, Jason B.; Miller, Sharon K.

2011-01-01

The attenuation of scattered thermal energy atomic oxygen is relevant to the potential damage that can occur within a spacecraft which sweeps through atomic oxygen in low Earth orbit (LEO). Although there can be significant oxidation and resulting degradation of polymers and some metals on the external surfaces of spacecraft, there are often openings on a spacecraft such as telescope apertures, vents, and microwave cavities that can allow atomic oxygen to enter and scatter internally to the spacecraft. Atomic oxygen that enters a spacecraft can thermally accommodate and scatter to ultimately react or recombine on surfaces. The atomic oxygen that does enter a spacecraft can be scavenged by use of high erosion yield polymers to reduce its reaction on critical surfaces and materials. Polyoxymethylene and polyethylene can be used as effective atomic oxygen scavenging polymers.

Coherent wave packet dynamics in a double-well potential in cavity

NASA Astrophysics Data System (ADS)

Zheng, Li; Li, Gang; Ding, Ming-Song; Wang, Yong-Liang; Zhang, Yun-Cui

2018-02-01

We investigate the coherent wave packet dynamics of a two-level atom trapped in a symmetric double-well potential in a near-resonance cavity. Prepared on one side of the double-well potential, the atom wave packet oscillates between the left and right wells, while recoil induced by the emitted photon from the atom entangles the atomic internal and external degrees of freedom. The collapse and revival of the tunneling occurs. Adjusting the width of the wave packets, one can modify the tunneling frequency and suppress the tunneling.

Many particle spectroscopy of atoms, molecules, clusters and surfaces: international conference MPS-2016

NASA Astrophysics Data System (ADS)

Grum-Grzhimailo, Alexei N.; Popov, Yuri V.; Gryzlova, Elena V.; Solov'yov, Andrey V.

2017-07-01

The conference on Many Particle Spectroscopy of Atoms, Molecules, Clusters and Surfaces (MPS-2016) brought together near to a hundred scientists in the field of electronic, photonic, atomic and molecular collisions, and spectroscopy from around the world. We deliver an Editorial of a topical issue presenting original research results from some of the participants on both experimental and theoretical studies involving many particle spectroscopy of atoms, molecules, clusters and surfaces. Contribution to the Topical Issue "Many Particle Spectroscopy of Atoms, Molecules, Clusters and Surfaces", edited by A.N. Grum-Grzhimailo, E.V. Gryzlova, Yu.V. Popov, and A.V. Solov'yov.

Extreme Adiabatic Expansion in Micro-gravity: Modeling for the Cold Atomic Laboratory

NASA Astrophysics Data System (ADS)

Sackett, C. A.; Lam, T. C.; Stickney, J. C.; Burke, J. H.

2017-12-01

The upcoming Cold Atom Laboratory mission for the International Space Station will allow the investigation of ultracold gases in a microgravity environment. Cold atomic samples will be produced using evaporative cooling in a magnetic chip trap. We investigate here the possibility to release atoms from the trap via adiabatic expansion. We discuss both general considerations and a detailed model of the planned apparatus. We find that it should be possible to reduce the mean trap confinement frequency to about 0.2 Hz, which will correspond to a three-dimensional sample temperature of about 150 pK and a mean atom velocity of 0.1 mm/s.

Hyperfine state entanglement of spinor BEC and scattering atom

NASA Astrophysics Data System (ADS)

Li, Zhibing; Bao, Chengguang; Zheng, Wei

2018-05-01

Condensate of spin-1 atoms frozen in a unique spatial mode may possess large internal degrees of freedom. The scattering amplitudes of polarized cold atoms scattered by the condensate are obtained with the method of fractional parentage coefficients that treats the spin degrees of freedom rigorously. Channels with scattering cross sections enhanced by the square of the atom number of the condensate are found. Entanglement between the condensate and the propagating atom can be established by scattering. Entanglement entropy is analytically obtained for arbitrary initial states. Our results also give a hint for the establishment of quantum thermal ensembles in the hyperfine space of spin states.

Extreme Adiabatic Expansion in Micro-gravity: Modeling for the Cold Atomic Laboratory

NASA Astrophysics Data System (ADS)

Sackett, C. A.; Lam, T. C.; Stickney, J. C.; Burke, J. H.

2018-05-01

The upcoming Cold Atom Laboratory mission for the International Space Station will allow the investigation of ultracold gases in a microgravity environment. Cold atomic samples will be produced using evaporative cooling in a magnetic chip trap. We investigate here the possibility to release atoms from the trap via adiabatic expansion. We discuss both general considerations and a detailed model of the planned apparatus. We find that it should be possible to reduce the mean trap confinement frequency to about 0.2 Hz, which will correspond to a three-dimensional sample temperature of about 150 pK and a mean atom velocity of 0.1 mm/s.

Enhancement of Local Photovoltaic Current at Ferroelectric Domain Walls in BiFeO3

PubMed Central

Yang, Ming-Min; Bhatnagar, Akash; Luo, Zheng-Dong; Alexe, Marin

2017-01-01

Domain walls, which are intrinsically two dimensional nano-objects exhibiting nontrivial electronic and magnetic behaviours, have been proven to play a crucial role in photovoltaic properties of ferroelectrics. Despite this recognition, the electronic properties of domain walls under illumination until now have been accessible only to macroscopic studies and their effects upon the conduction of photovoltaic current still remain elusive. The lack of understanding hinders the developing of nanoscale devices based on ferroelectric domain walls. Here, we directly characterize the local photovoltaic and photoconductive properties of 71° domain walls on BiFeO3 thin films with a nanoscale resolution. Local photovoltaic current, proven to be driven by the bulk photovoltaic effect, has been probed over the whole illuminated surface by using a specially designed photoelectric atomic force microscopy and found to be significantly enhanced at domain walls. Additionally, spatially resolved photoconductive current distribution reveals a higher density of excited carriers at domain walls in comparison with domains. Our measurements demonstrate that domain wall enhanced photovoltaic current originates from its high conduction rather than the internal electric field. This photoconduction facilitated local photovoltaic current is likely to be a universal property of topological defects in ferroelectric semiconductors. PMID:28216672

Enhancement of Local Photovoltaic Current at Ferroelectric Domain Walls in BiFeO3.

PubMed

Yang, Ming-Min; Bhatnagar, Akash; Luo, Zheng-Dong; Alexe, Marin

2017-02-20

Domain walls, which are intrinsically two dimensional nano-objects exhibiting nontrivial electronic and magnetic behaviours, have been proven to play a crucial role in photovoltaic properties of ferroelectrics. Despite this recognition, the electronic properties of domain walls under illumination until now have been accessible only to macroscopic studies and their effects upon the conduction of photovoltaic current still remain elusive. The lack of understanding hinders the developing of nanoscale devices based on ferroelectric domain walls. Here, we directly characterize the local photovoltaic and photoconductive properties of 71° domain walls on BiFeO 3 thin films with a nanoscale resolution. Local photovoltaic current, proven to be driven by the bulk photovoltaic effect, has been probed over the whole illuminated surface by using a specially designed photoelectric atomic force microscopy and found to be significantly enhanced at domain walls. Additionally, spatially resolved photoconductive current distribution reveals a higher density of excited carriers at domain walls in comparison with domains. Our measurements demonstrate that domain wall enhanced photovoltaic current originates from its high conduction rather than the internal electric field. This photoconduction facilitated local photovoltaic current is likely to be a universal property of topological defects in ferroelectric semiconductors.

The Microstructural Basis of Damping in High Damping Alloys

DTIC Science & Technology

1989-09-01

This transformation is diffusionless and is characterized by the cooperative movement of atoms in a given section of crystal. Removal of the stress...martensites. The cooperative movement of atoms causes large internal friction and high damping. The temperature range in which this transformation can

Kinematic cooling of molecules in a magneto-optical trap

NASA Astrophysics Data System (ADS)

Takase, Ken; Chandler, David W.; Strecker, Kevin E.

2008-05-01

We will present our current progress on a new experimental technique aimed at slowing and cooling hot molecules using a single collision with magneto-optically trapped atoms. Kinematic cooling, unlike buffer gas and sympathetic cooling, relies only on a single collision between the molecule and atom to stop the molecule in the laboratory frame. This technique has recently been demonstrated in a crossed atomic and molecular beam machine to produce 35mK samples of nitric oxide via a single collision with argon [1]. In this technique we replace the atomic beam with a sample magneto-optically trapped atoms. We are currently designing and building a new apparatus to attempt these experiments. [1] Kevin E. Strecker and David W. Chandler (to be published)

The Role of Atomic Energy in the Promotion of International Collaboration

DOE R&D Accomplishments Database

Rabi, I. I.

1959-10-31

A brief survey is presented of the international cooperation which made a success of the First Geneva Conference and which has initiated many international scientific meetings since that time. The policy of the United States in this respect is discussed. (J.S.R.)

INF and IAEA: A comparative analysis of verification strategy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scheinman, L.; Kratzer, M.

1992-07-01

This is the final report of a study on the relevance and possible lessons of Intermediate Range Nuclear Force (INF) verification to the International Atomic Energy Agency (IAEA) international safeguards activities.

Interpretation of ES, CS, and IOS approximations within a translational-internal coupling scheme. II. Application to atom--diatom kinetic cross sections

DOE Office of Scientific and Technical Information (OSTI.GOV)

Coombe, D.A.; Snider, R.F.

1980-02-15

ES, CS, and IOS approximations to atom--diatom kinetic cross sections are derived. In doing so, reduced S-matrices in a translational-internal coupling scheme are stressed. This entails the insertion of recently obtained approximate reduced S-matrices in the translational-internal coupling scheme into previously derived general expressions for the kinetic cross sections. Of special interest is the structure (rotational j quantum number dependence) of the kinetic cross sections associated with the Senftleben Beenakker effects and of pure internal state relaxation phenomena. The viscomagnetic effect is used as an illustrative example. It is found in particular that there is a great similarity of structuremore » between the energy sudden (and IOS) approximation and the previously derived distorted wave Born results.« less

Microgravity

NASA Image and Video Library

2001-01-24

An artist's concept of the Primary Atomic Clock Reference System (PARCS) plarned to fly on the International Space Station (ISS). PARCS will make even more accurate atomic time available to everyone, from physicists testing Einstein's Theory of Relativity, to hikers using the Global Positioning System to find their way. In ground-based atomic clocks, lasers are used to cool and nearly stop atoms of cesium whose vibrations are used as the time base. The microgravity of space will allow the atoms to be suspended in the clock rather than circulated in an atomic fountain, as required on Earth. PARCS is being developed by the Jet Propulsion Laboratory with principal investigators at the National Institutes of Standards and Technology and the University of Colorado, Boulder. See also No. 0103191

Statistical analysis of dimer formation in supersaturated metal vapor based on molecular dynamics simulation

NASA Astrophysics Data System (ADS)

Korenchenko, Anna E.; Vorontsov, Alexander G.; Gelchinski, Boris R.; Sannikov, Grigorii P.

2018-04-01

We discuss the problem of dimer formation during the homogeneous nucleation of atomic metal vapor in an inert gas environment. We simulated nucleation with molecular dynamics and carried out the statistical analysis of double- and triple-atomic collisions as the two ways of long-lived diatomic complex formation. Close pair of atoms with lifetime greater than the mean time interval between atom-atom collisions is called a long-lived diatomic complex. We found that double- and triple-atomic collisions gave approximately the same probabilities of long-lived diatomic complex formation, but internal energy of the resulted state was essentially lower in the second case. Some diatomic complexes formed in three-particle collisions are stable enough to be a critical nucleus.

Effect of the cesium and potassium doping of multiwalled carbon nanotubes grown in an electrical arc on their emission characteristics

NASA Astrophysics Data System (ADS)

Izrael'yants, K. R.; Orlov, A. P.; Ormont, A. B.; Chirkova, E. G.

2017-04-01

The effect of cesium and potassium atoms deposited onto multiwalled carbon nanotubes grown in an electrical arc on their emission characteristics was studied. The current-voltage characteristics of the field electron emission of specimens with cesium or potassium doped multiwalled carbon nanotubes of this type were revealed to retain their linear character in the Fowler-Nordheim coordinates within several orders of magnitude of change in the emission current. The deposition of cesium and potassium atoms was shown to lead to a considerable increase in the emission current and a decrease in the work function φ of studied emitters with multiwalled nanotubes. The work function was established to decrease to φ 3.1 eV at an optimal thickness of coating with cesium atoms and to φ 2.9 eV in the case of doping with potassium atoms. Cesium and potassium deposition conditions optimal for the attainment of a maximum emission current were found.

Overview of the MISSE 7 Polymers and Zenith Polymers Experiments After 1.5 Years of Space Exposure

NASA Technical Reports Server (NTRS)

Yi, Grace T.; de Groh, Kim K.; Banks, Bruce A.; Haloua, Athena; Imka, Emily C.; Mitchell, Gianna G.

2013-01-01

As part of the Materials International Space Station Experiment 7 (MISSE 7), two experiments called the Polymers Experiment and the Zenith Polymers Experiment were flown on the exterior of the International Space Station (ISS) and exposed to the low Earth orbit (LEO) space environment for 1.5 years. The Polymers Experiment contained 47 samples, which were flown in a ram or wake flight orientation. The objectives of the Polymers Experiment were to determine the LEO atomic oxygen erosion yield (Ey, volume loss per incident oxygen atoms, given in cu cm/atom) of the polymers, and to determine if atomic oxygen erosion of high and low ash containing polymers is dependent on fluence. The Zenith Polymers Experiment was flown in a zenith flight orientation. The primary objective of the Zenith Polymers Experiment was to determine the effect of solar exposure on the erosion of fluoropolymers. Kapton H (DuPont, Wilmington, DE) was flown in each experiment for atomic oxygen fluence determination. This paper provides an introduction to both the MISSE 7 Polymers Experiment and the MISSE 7 Zenith Polymers Experiment, and provides initial erosion yield results.

Transfer of Orbital and Spin angular momentum from non-paraxial optical vortex to atomic BEC

NASA Astrophysics Data System (ADS)

Bhowmik, Anal; Mondal, Pradip Kumar; Majumder, Sonjoy; Deb, Bimalendu

2017-04-01

Allen and co-workers first brought up the realization that optical vortex can carry well defined orbital angular momentum (OAM) associated with its spatial mode. Spin angular momentum (SAM) of the light, associated with the polarization, interacts with the internal electronic motion of the atom. The exchange of orbital angular momentum (OAM) between optical vortex and the center-of-mass (CM) motion of an atom or molecule is well known in paraxial approximation. We show that, how the total angular momentum (TAM) of non-paraxial optical vortex is shared with atom, in terms of OAM and SAM. Both the angular momenta are now possible to be transferred to the internal electronic and external CM motion of atom. Here we have studied how the Rabi frequencies of the excitations of two-photon Raman transitions with respect to focusing angles. Also, we investigate the properties of the vortex superposed state for a Bose-Einstein condensate condensate by a single non-paraxial vortex beam. The density distribution of the vortex-antivortex superposed state has a petal structure which is determined by the quantum circulations and proportion of the vortex and antivortex.

Entangling two unequal atoms through a common bath

DOE Office of Scientific and Technical Information (OSTI.GOV)

Benatti, F.; Marzolino, U.; Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34014 Trieste

The evolution of two, noninteracting, two-level atoms immersed in a weakly coupled bath can be described by a refined, time-coarse-grained Markovian evolution, still preserving complete positivity. We find that this improved, reduced dynamics is able to entangle the two atoms even when their internal frequencies are unequal, an effect that appears impossible in the standard weak-coupling-limit approach. We study in detail this phenomenon for an environment made of quantum fields.

About vortex-like atomic motion in a loaded single crystal

NASA Astrophysics Data System (ADS)

Dmitriev, A. I.; Nikonov, A. Yu.

2017-12-01

The paper presents a molecular dynamics study of internal stress and atomic displacement redistributions in a preliminary loaded solid. The study demonstrates the possibility of self-organized vortices as dynamic defects of typical size 1-5 nm due to atomic motion in the elastic region at the stage of relaxation. The simulation results agree well with experimental data on strain localization in elastic distortion regions which gives rise to nanodipoles of partial disclinations.

Experimental nonlinear dynamical studies in cesium magneto-optical trap using time-series analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anwar, M., E-mail: mamalik2000@gmail.com; Islam, R.; Faisal, M.

2015-03-30

A magneto-optical trap of neutral atoms is essentially a dissipative quantum system. The fast thermal atoms continuously dissipate their energy to the environment via spontaneous emissions during the cooling. The atoms are, therefore, strongly coupled with the vacuum reservoir and the laser field. The vacuum fluctuations as well as the field fluctuations are imparted to the atoms as random photon recoils. Consequently, the external and internal dynamics of atoms becomes stochastic. In this paper, we have investigated the stochastic dynamics of the atoms in a magneto-optical trap during the loading process. The time series analysis of the fluorescence signal showsmore » that the dynamics of the atoms evolves, like all dissipative systems, from deterministic to the chaotic regime. The subsequent disappearance and revival of chaos was attributed to chaos synchronization between spatially different atoms in the magneto-optical trap.« less

Low-power embedded read-only memory using atom switch and silicon-on-thin-buried-oxide transistor

NASA Astrophysics Data System (ADS)

Sakamoto, Toshitsugu; Tada, Munehiro; Tsuji, Yukihide; Makiyama, Hideki; Hasegawa, Takumi; Yamamoto, Yoshiki; Okanishi, Shinobu; Banno, Naoki; Miyamura, Makoto; Okamoto, Koichiro; Iguchi, Noriyuki; Ogasahara, Yasuhiro; Oda, Hidekazu; Kamohara, Shiro; Yamagata, Yasushi; Sugii, Nobuyuki; Hada, Hiromitsu

2015-04-01

We developed an atom-switch read-only memory (ROM) fabricated on silicon-on-thin-buried-oxide (SOTB) for use in a low-power microcontroller for the first time. An atom switch with a low programming voltage and large ON/OFF conductance ratio is suitable for low-power nonvolatile memory. The atom-switch ROM using an SOTB transistor uses a 0.34-1.2 V operating voltage and 12 µA/MHz active current (or 4.5 µW/MHz active power). Furthermore, the sleep current is as low as 0.4 µA when a body bias voltage is applied to the SOTB.

INF and IAEA: A comparative analysis of verification strategy. [Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scheinman, L.; Kratzer, M.

1992-07-01

This is the final report of a study on the relevance and possible lessons of Intermediate Range Nuclear Force (INF) verification to the International Atomic Energy Agency (IAEA) international safeguards activities.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hanada, M., E-mail: hanada.masaya@jaea.go.jp; Kojima, A.; Tobari, H.

In order to realize negative ion sources and accelerators to be applicable to International Thermonuclear Experimental Reactor and JT-60 Super Advanced, a large cesium (Cs)-seeded negative ion source and a multi-aperture and multi-stage electric acceleration have been developed at Japan Atomic Energy Agency (JAEA). Long pulse production and acceleration of the negative ion beams have been independently carried out. The long pulse production of the high current beams has achieved 100 s at the beam current of 15 A by modifying the JT-60 negative ion source. The pulse duration time is increased three times longer than that before the modification.more » As for the acceleration, a pulse duration time has been also extended two orders of magnitudes from 0.4 s to 60 s. The developments of the negative ion source and acceleration at JAEA are well in progress towards the realization of the negative ion sources and accelerators for fusion applications.« less

The terrestrial ring current - From in situ measurements to global images using energetic neutral atoms

NASA Technical Reports Server (NTRS)

Roelof, Edmond C.; Williams, Donald J.

1988-01-01

Electrical currents flowing in the equatorial magnetosphere, first inferred from ground-based magnetic disturbances, are carried by trapped energetic ions. Spacecraft measurements have determined the spectrum and composition of those currents, and the newly developed technique of energetic-neutral-atom imaging allows the global dynamics of that entire ion population to be viewed from a single spacecraft.

10 CFR 810.3 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-01-01

... pursuant to section 142 of the Atomic Energy Act. Sensitive nuclear technology means any information... nuclear material (SNM) or which a U.S. provider of assistance knows or has reason to know will be used for... International Atomic Energy Agency. Non-nuclear-weapon state is a country not recognized as a nuclear-weapon...

Quantum decoherence in electronic current flowing through carbon nanotubes induced by thermal atomic vibrations

NASA Astrophysics Data System (ADS)

Ishizeki, Keisuke; Sasaoka, Kenji; Konabe, Satoru; Souma, Satofumi; Yamamoto, Takahiro

2018-06-01

We theoretically investigate quantum decoherence in electronic currents flowing through metallic carbon nanotubes caused by thermal atomic vibrations using the time-dependent Schrödinger equation for an open system. We reveal that the quantum coherence of conduction electrons decays exponentially with tube length at a fixed temperature, and that the decay rate increases with temperature. We also find that the phase relaxation length due to the thermal atomic vibrations is inversely proportional to temperature.

Updated atomic weights: Time to review our table

USGS Publications Warehouse

Coplen, Tyler B.; Meyers, Fabienne; Holden, Norman E.

2016-01-01

Despite common belief, atomic weights are not necessarily constants of nature. Scientists’ ability to measure these values is regularly improving, so one would expect that the accuracy of these values should be improving with time. It is the task of the IUPAC (International Union of Pure and Applied Chemistry) Commission on Isotopic Abundances and Atomic Weights (CIAAW) to regularly review atomic-weight determinations and release updated values.According to an evaluation published in Pure and Applied Chemistry [1], even the most simplified table abridged to four significant digits needs to be updated for the elements selenium and molybdenum. According to the most recent 2015 release of "Atomic Weights of the Elements" [2], another update is needed for ytterbium.

University of Maryland MRSEC - Research: IRG1

Science.gov Websites

structure based on fundamental interactions, to device preparation and characterization. Materials systems figure: Electrical current in nanoscale structure perturbed by scattering at atomic scale features on its surfaces. An electrical current in a nanoscale structure is perturbed by scattering at atomic scale

Air blast type coal slurry fuel injector

DOEpatents

Phatak, Ramkrishna G.

1986-01-01

A device to atomize and inject a coal slurry in the combustion chamber of an internal combustion engine, and which eliminates the use of a conventional fuel injection pump/nozzle. The injector involves the use of compressed air to atomize and inject the coal slurry and like fuels. In one embodiment, the breaking and atomization of the fuel is achieved with the help of perforated discs and compressed air. In another embodiment, a cone shaped aspirator is used to achieve the breaking and atomization of the fuel. The compressed air protects critical bearing areas of the injector.

Atomic and close-to-atomic scale manufacturing—A trend in manufacturing development

NASA Astrophysics Data System (ADS)

Fang, Fengzhou

2016-12-01

Manufacturing is the foundation of a nation's economy. It is the primary industry to promote economic and social development. To accelerate and upgrade China's manufacturing sector from "precision manufacturing" to "high-performance and high-quality manufacturing", a new breakthrough should be found in terms of achieving a "leap-frog development". Unlike conventional manufacturing, the fundamental theory of "Manufacturing 3.0" is beyond the scope of conventional theory; rather, it is based on new principles and theories at the atomic and/or closeto- atomic scale. Obtaining a dominant role at the international level is a strategic move for China's progress.

Air blast type coal slurry fuel injector

DOEpatents

Phatak, R.G.

1984-08-31

A device to atomize and inject a coal slurry in the combustion chamber of an internal combustion engine is disclosed which eliminates the use of a conventional fuel injection pump/nozzle. The injector involves the use of compressed air to atomize and inject the coal slurry and like fuels. In one embodiment, the breaking and atomization of the fuel is achieved with the help of perforated discs and compressed air. In another embodiment, a cone shaped aspirator is used to achieve the breaking and atomization of the fuel. The compressed air protects critical bearing areas of the injector.

Parallel Low-Loss Measurement of Multiple Atomic Qubits

NASA Astrophysics Data System (ADS)

Kwon, Minho; Ebert, Matthew F.; Walker, Thad G.; Saffman, M.

2017-11-01

We demonstrate low-loss measurement of the hyperfine ground state of rubidium atoms by state dependent fluorescence detection in a dipole trap array of five sites. The presence of atoms and their internal states are minimally altered by utilizing circularly polarized probe light and a strictly controlled quantization axis. We achieve mean state detection fidelity of 97% without correcting for imperfect state preparation or background losses, and 98.7% when corrected. After state detection and correction for background losses, the probability of atom loss due to the state measurement is <2 % and the initial hyperfine state is preserved with >98 % probability.

RERTR 2009 (Reduced Enrichment for Research and Test Reactors)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Totev, T.; Stevens, J.; Kim, Y. S.

2010-03-01

The U.S. Department of Energy/National Nuclear Security Administration's Office of Global Threat Reduction in cooperation with the China Atomic Energy Authority and International Atomic Energy Agency hosted the 'RERTR 2009 International Meeting on Reduced Enrichment for Research and Test Reactors.' The meeting was organized by Argonne National Laboratory, China Institute of Atomic Energy and Idaho National Laboratory and was held in Beijing, China from November 1-5, 2009. This was the 31st annual meeting in a series on the same general subject regarding the conversion of reactors within the Global Threat Reduction Initiative (GTRI). The Reduced Enrichment for Research and Testmore » Reactors (RERTR) Program develops technology necessary to enable the conversion of civilian facilities using high enriched uranium (HEU) to low enriched uranium (LEU) fuels and targets.« less

Atomic data and spectral analysis of carbon, nitrogen, oxygen and silicon ions observed with the International Ultraviolet Explorer

NASA Technical Reports Server (NTRS)

Pradhan, Anil K.

1992-01-01

According to the plan presented in the original proposal we have now completed most of the atomic calculations involving collision strengths and rate coefficients for electron impact excitation of C II, N III, and O IV ions. These have been reported in the first two publications appended with this report. We have now moved into the applications phase of the project with the new data being used to analyze the International Ultraviolet Explorer (IUE) observations of a variety of objects, as described in the third publication recently submitted (also appended). The analysis and interpretation of archival data will continue well into the next year with several collaborators that the PI and Co-PI are involved with. In addition, the atomic calculations on Si II have been started.

Is Current CMBR Temperature: The Scale Independent Quantum Gravitational Result of Black Hole Cosmology?

NASA Astrophysics Data System (ADS)

Seshavatharam, U. V. S.; Lakshminarayana, S.

If one is willing to consider the current cosmic microwave back ground temperature as a quantum gravitational effect of the evolving primordial cosmic black hole (universe that constitutes dynamic space-time and exhibits quantum behavior) automatically general theory of relativity and quantum mechanics can be combined into a `scale independent' true unified model of quantum gravity. By considering the `Planck mass' as the initial mass of the baby Hubble volume, past and current physical and thermal parameters of the cosmic black hole can be understood. Current rate of cosmic black hole expansion is being stopped by the microscopic quantum mechanical lengths. In this new direction authors observed 5 important quantum mechanical methods for understanding the current cosmic deceleration. To understand the ground reality of current cosmic rate of expansion, sensitivity and accuracy of current methods of estimating the magnitudes of current CMBR temperature and current Hubble constant must be improved and alternative methods must be developed. If it is true that galaxy constitutes so many stars, each star constitutes so many hydrogen atoms and light is coming from the excited electron of galactic hydrogen atom, then considering redshift as an index of `whole galaxy' receding may not be reasonable. During cosmic evolution, at any time in the past, in hydrogen atom emitted photon energy was always inversely proportional to the CMBR temperature. Thus past light emitted from older galaxy's excited hydrogen atom will show redshift with reference to the current laboratory data. As cosmic time passes, in future, the absolute rate of cosmic expansion can be understood by observing the rate of increase in the magnitude of photon energy emitted from laboratory hydrogen atom. Aged super novae dimming may be due to the effect of high cosmic back ground temperature. Need of new mathematical methods & techniques, computer simulations, advanced engineering skills seem to be essential in this direction.

NO.sub.x reduction method

DOEpatents

Sekar, Ramanujam R.; Hoppie, Lyle O.

1996-01-01

A method of reducing oxides of nitrogen (NO.sub.X) in the exhaust of an internal combustion engine includes producing oxygen enriched air and nitrogen enriched air by an oxygen enrichment device. The oxygen enriched air may be provided to the intake of the internal combustion engine for mixing with fuel. In order to reduce the amount of NO.sub.X in the exhaust of the internal combustion engine, the molecular nitrogen in the nitrogen enriched air produced by the oxygen enrichment device is subjected to a corona or arc discharge so as to create a plasma and as a result, atomic nitrogen. The resulting atomic nitrogen then is injected into the exhaust of the internal combustion engine causing the oxides of nitrogen in the exhaust to be reduced into nitrogen and oxygen. In one embodiment of the present invention, the oxygen enrichment device that produces both the oxygen and nitrogen enriched air can include a selectively permeable membrane.

Expansion and internal friction in unfolded protein chain.

PubMed

Yasin, U Mahammad; Sashi, Pulikallu; Bhuyan, Abani K

2013-10-10

Similarities in global properties of homopolymers and unfolded proteins provide approaches to mechanistic description of protein folding. Here, hydrodynamic properties and relaxation rates of the unfolded state of carbonmonoxide-liganded cytochrome c (cyt-CO) have been measured using nuclear magnetic resonance and laser photolysis methods. Hydrodynamic radius of the unfolded chain gradually increases as the solvent turns increasingly better, consistent with theory. Curiously, however, the rate of intrachain contact formation also increases with an increasing denaturant concentration, which, by Szabo, Schulten, and Schulten theory for the rate of intramolecular contact formation in a Gaussian polymer, indicates growing intramolecular diffusion. It is argued that diminishing nonbonded atom interactions with increasing denaturant reduces internal friction and, thus, increases the rate of polypeptide relaxation. Qualitative scaling of the extent of unfolding with nonbonded repulsions allows for description of internal friction by a phenomenological model. The degree of nonbonded atom interactions largely determines the extent of internal friction.

Effect of incorporation of nitrogen atoms in Al2O3 gate dielectric of wide-bandgap-semiconductor MOSFET on gate leakage current and negative fixed charge

NASA Astrophysics Data System (ADS)

Kojima, Eiji; Chokawa, Kenta; Shirakawa, Hiroki; Araidai, Masaaki; Hosoi, Takuji; Watanabe, Heiji; Shiraishi, Kenji

2018-06-01

We performed first-principle calculations to investigate the effect of incorporation of N atoms into Al2O3 gate dielectrics. Our calculations show that the defect levels generated by VO in Al2O3 are the origin of the stress-induced gate leakage current and that VOVAl complexes in Al2O3 cause negative fixed charge. We revealed that the incorporation of N atoms into Al2O3 eliminates the VO defect levels, reducing the stress-induced gate leakage current. Moreover, this suppresses the formation of negatively charged VOVAl complexes. Therefore, AlON can reduce both stress-induced gate leakage current and negative fixed charge in wide-bandgap-semiconductor MOSFETs.

Zirconium Hydride Space Power Reactor design.

NASA Technical Reports Server (NTRS)

Asquith, J. G.; Mason, D. G.; Stamp, S.

1972-01-01

The Zirconium Hydride Space Power Reactor being designed and fabricated at Atomics International is intended for a wide range of potential applications. Throughout the program a series of reactor designs have been evaluated to establish the unique requirements imposed by coupling with various power conversion systems and for specific applications. Current design and development emphasis is upon a 100 kilowatt thermal reactor for application in a 5 kwe thermoelectric space power generating system, which is scheduled to be fabricated and ground tested in the mid 70s. The reactor design considerations reviewed in this paper will be discussed in the context of this 100 kwt reactor and a 300 kwt reactor previously designed for larger power demand applications.

Microwave-assisted deuterium exchange: the convenient preparation of isotopically labelled analogues for stable isotope dilution analysis of volatile wine phenols.

PubMed

Crump, Anna M; Sefton, Mark A; Wilkinson, Kerry L

2014-11-01

This study reports the convenient, low cost, one-step synthesis of labelled analogues of six volatile phenols, guaiacol, 4-methylguaiacol, 4-ethylguaiacol, 4-ethylphenol, eugenol and vanillin, using microwave-assisted deuterium exchange, for use as internal standards for stable isotope dilution analysis. The current method improves on previous strategies in that it enables incorporation of deuterium atoms on the aromatic ring, thereby ensuring retention of the isotope label during mass spectrometry fragmentation. When used as standards for SIDA, these labelled volatile phenols will improve the accuracy and reproducibility of quantitative food and beverage analysis. Copyright © 2014 Elsevier Ltd. All rights reserved.

Current-induced changes of migration energy barriers in graphene and carbon nanotubes

NASA Astrophysics Data System (ADS)

Obodo, J. T.; Rungger, I.; Sanvito, S.; Schwingenschlögl, U.

2016-05-01

An electron current can move atoms in a nanoscale device with important consequences for the device operation and breakdown. We perform first principles calculations aimed at evaluating the possibility of changing the energy barriers for atom migration in carbon-based systems. In particular, we consider the migration of adatoms and defects in graphene and carbon nanotubes. Although the current-induced forces are large for both the systems, in graphene the force component along the migration path is small and therefore the barrier height is little affected by the current flow. In contrast, the same barrier is significantly reduced in carbon nanotubes as the current increases. Our work also provides a real-system numerical demonstration that current-induced forces within density functional theory are non-conservative.An electron current can move atoms in a nanoscale device with important consequences for the device operation and breakdown. We perform first principles calculations aimed at evaluating the possibility of changing the energy barriers for atom migration in carbon-based systems. In particular, we consider the migration of adatoms and defects in graphene and carbon nanotubes. Although the current-induced forces are large for both the systems, in graphene the force component along the migration path is small and therefore the barrier height is little affected by the current flow. In contrast, the same barrier is significantly reduced in carbon nanotubes as the current increases. Our work also provides a real-system numerical demonstration that current-induced forces within density functional theory are non-conservative. Electronic supplementary information (ESI) available. See DOI: 10.1039/C6NR00534A

Feedback control of persistent-current oscillation based on the atomic-clock technique

NASA Astrophysics Data System (ADS)

Yu, Deshui; Dumke, Rainer

2018-05-01

We propose a scheme of stabilizing the persistent-current Rabi oscillation based on the flux qubit-resonator-atom hybrid structure. The low-Q L C resonator weakly interacts with the flux qubit and maps the persistent-current Rabi oscillation of the flux qubit onto the intraresonator electric field. This oscillating electric field is further coupled to a Rydberg-Rydberg transition of the 87Rb atoms. The Rabi-frequency fluctuation of the flux qubit is deduced from measuring the atomic population via the fluorescence detection and stabilized by feedback controlling the external flux bias. Our numerical simulation indicates that the feedback-control method can efficiently suppress the background fluctuations in the flux qubit, especially in the low-frequency limit. This technique may be extensively applicable to different types of superconducting circuits, paving a way to long-term-coherence superconducting quantum information processing.

Engineering quantum hyperentangled states in atomic systems

NASA Astrophysics Data System (ADS)

Nawaz, Mehwish; -Islam, Rameez-ul; Abbas, Tasawar; Ikram, Manzoor

2017-11-01

Hyperentangled states have boosted many quantum informatics tasks tremendously due to their high information content per quantum entity. Until now, however, the engineering and manipulation of such states were limited to photonic systems only. In present article, we propose generating atomic hyperentanglement involving atomic internal states as well as atomic external momenta states. Hypersuperposition, hyperentangled cluster, Bell and Greenberger-Horne-Zeilinger states are engineered deterministically through resonant and off-resonant Bragg diffraction of neutral two-level atoms. Based on the characteristic parameters of the atomic Bragg diffraction, such as comparatively large interaction times and spatially well-separated outputs, such decoherence resistant states are expected to exhibit good overall fidelities and offer the evident benefits of full controllability, along with extremely high detection efficiency, over the counterpart photonic states comprised entirely of flying qubits.

Direct Determination of Nonmetals in Solution with Atomic Spectrometry.

ERIC Educational Resources Information Center

McGregor, David A.; And Others

1988-01-01

Addresses solution nonmetal determinations on a fundamental level. Characterizes research in this area of chemical instrumentation. Discusses the fundamental limitations of nonmetal atomic spectrometry, the status of nonmetals and atomic spectroscopic techniques, and current directions in solution nonmetal determinations. (CW)

International Atomic Energy Agency specialists meeting on experience in ageing, maintenance, and modernization of instrumentation and control systems for improving nuclear power plant availability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1993-10-01

This report presents the proceedings of the Specialist`s Meeting on Experience in Aging, Maintenance and Modernization of Instrumentation and Control Systems for Improving Nuclear Power Plant Availability that was held at the Ramada Inn in Rockville, Maryland on May 5--7, 1993. The Meeting was presented in cooperation with the Electric Power Research Institute, Oak Ridge National Laboratory and the International Atomic Energy Agency. There were approximately 65 participants from 13 countries at the Meeting. Individual reports have been cataloged separately.

Task Force Report: Assessment of Nuclear Monitoring and Verification Technologies

DTIC Science & Technology

2014-01-01

environment in which implemented  Project demands on, and assess capabilities of, International Atomic Energy Agency in next 15-20 years with expected...the Department of  Energy   (DOE) and  the  Intelligence  Community  (IC)  to  support  future  monitoring  and  verification  of  nuclear...could be  enabled by  expansion of  the  role of  the  International Atomic  Energy   Agency  (IAEA)  for  assuming  responsibility  for  the

Anomalous I-V curve for mono-atomic carbon chains

NASA Astrophysics Data System (ADS)

Song, Bo; Sanvito, Stefano; Fang, Haiping

2010-10-01

The electronic transport properties of mono-atomic carbon chains were studied theoretically using a combination of density functional theory and the non-equilibrium Green's functions method. The I-V curves for the chains composed of an even number of atoms and attached to gold electrodes through sulfur exhibit two plateaus where the current becomes bias independent. In contrast, when the number of carbon atoms in the chain is odd, the electric current simply increases monotonically with bias. This peculiar behavior is attributed to dimerization of the chains, directly resulting from their one-dimensional nature. The finding is expected to be helpful in designing molecular devices, such as carbon-chain-based transistors and sensors, for nanoscale and biological applications.

Publicity as an Instrument of Reform.

ERIC Educational Resources Information Center

Caudill, Susan

Albert Einstein and the Emergency Committee of Atomic Scientists (ECAS) conducted a reform-based public communication campaign for the international control of atomic energy after the Second World War. The Committee raised funds and sought publicity for its proposed solution to the problem of war and the management of peace. Its solution was the…

Development of Low Cost Gas Atomization of Precursor Powders for Simplified ODS Alloy Production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, Iver

2014-08-05

A novel gas atomization reaction synthesis (GARS) method was developed in this project to enable production (at our partner’s facility) a precursor Ni-Cr-Y-Ti powder with a surface oxide and an internal rare earth (RE) containing intermetallic compound (IMC) phase. Consolidation and heat-treatment experiments were performed at Ames Lab to promote the exchange of oxygen from the surface oxide to the RE intermetallic to form nano-metric oxide dispersoids. Alloy selection was aided by an internal oxidation and serial grinding experiments at Ames Lab and found that Hf-containing alloys may form more stable dispersoids than Ti-containing alloy, i.e., the Hf-containing system exhibitedmore » five different oxide phases and two different intermetallics compared to the two oxide phases and one intermetallic in the Ti-containing alloys. Since the simpler Ti-containing system was less complex to characterize, and make observations on the effects of processing parameters, the Ti-containing system was selected by Ames Lab for experimental atomization trials at our partner. An internal oxidation model was developed at Ames Lab and used to predict the heat treatment times necessary for dispersoid formation as a function of powder size and temperature. A new high-pressure gas atomization (HPGA) nozzle was developed at Ames Lab with the aim of promoting fine powder production at scales similar to that of the high gas-flow and melt-flow of industrial atomizers. The atomization nozzle was characterized using schlieren imaging and aspiration pressure testing at Ames Lab to determine the optimum melt delivery tip geometry and atomization pressure to promote enhanced secondary atomization mechanisms. Six atomization trials were performed at our partner to investigate the effects of: gas atomization pressure and reactive gas concentration on the particle size distribution (PSD) and the oxygen content of the resulting powder. Also, the effect on the rapidly solidified microstructure (as a function of powder size) was investigated at Ames Lab as a function of reactive gas composition and bulk alloy composition. The results indicated that the pulsatile gas atomization mechanism and a significantly enhanced yield of fine powders reported in the literature for this type of process were not observed. Also it was determined that reactive gas may marginally improve the fine powder yield but further experiments are required. The oxygen content in the gas also did not have any detrimental effect on the microstructure (i.e. did not significantly reduce undercooling). On the contrary, the oxygen addition to the atomization gas may have mitigated some potent catalytic nucleation sites, but not enough to significantly alter the microstructure vs. particle size relationship. Overall the downstream injection of oxygen was not found to significantly affect either the particle size distribution or undercooling (as inferred from microstructure and XRD observations) but injection further upstream, including in the gas atomization nozzle, remains to be investigated in later work.« less

Laser Cooling the Diatomic Molecule CaH

NASA Astrophysics Data System (ADS)

Velasquez, Joe, III; Di Rosa, Michael

2014-06-01

To laser-cool a species, a closed (or nearly closed) cycle is required to dissipate translational energy through many directed laser-photon absorption and subsequent randomly-directed spontaneous emission events. Many atoms lend themselves to such a closed-loop cooling cycle. Attaining laser-cooled molecular species is challenging because of their inherently complex internal structure, yet laser-cooling molecules could lead to studies in interesting chemical dynamics among other applications. Typically, laser-cooled atoms are assembled into molecules through photoassociation or Feschbach resonance. CaH is one of a few molecules whose internal structure is quite atom-like, allowing a nearly closed cycle without the need for many repumping lasers. We will also present our work-to-date on laser cooling this molecule. We employ traditional pulsed atomic/molecular beam techniques with a laser vaporization source to generate species with well-defined translational energies over a narrow range of velocity. In this way, we can apply laser-cooling to most species in the beam along a single dimension (the beam's axis). This project is funded by the LDRD program of the Los Alamos National Laboratory.

Bismuth as a general internal standard for lead in atomic absorption spectrometry.

PubMed

Bechlin, Marcos A; Fortunato, Felipe M; Ferreira, Edilene C; Gomes Neto, José A; Nóbrega, Joaquim A; Donati, George L; Jones, Bradley T

2014-06-11

Bismuth was evaluated as internal standard for Pb determination by line source flame atomic absorption spectrometry (LS FAAS), high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS) and line source graphite furnace atomic absorption spectrometry (LS GFAAS). Analysis of samples containing different matrices indicated close relationship between Pb and Bi absorbances. Correlation coefficients of calibration curves built up by plotting A(Pb)/A(Bi)versus Pb concentration were higher than 0.9953 (FAAS) and higher than 0.9993 (GFAAS). Recoveries of Pb improved from 52-118% (without IS) to 97-109% (IS, LS FAAS); 74-231% (without IS) to 96-109% (IS, HR-CS FAAS); and 36-125% (without IS) to 96-110% (IS, LS GFAAS). The relative standard deviations (n=12) were reduced from 0.6-9.2% (without IS) to 0.3-4.3% (IS, LS FAAS); 0.7-7.7% (without IS) to 0.1-4.0% (IS, HR-CS FAAS); and 2.1-13% (without IS) to 0.4-5.9% (IS, LS GFAAS). Copyright © 2014 Elsevier B.V. All rights reserved.

FOREWORD: Modern Applications of Timescales Modern Applications of Timescales

NASA Astrophysics Data System (ADS)

Arias, E. F.; Lewandowski, W.

2011-08-01

The development of the first atomic frequency standard by Louis Essen in the 1950s is at the origin of the adoption of the atomic definition of the SI second by the 13th General Conference on Weights and Measures in 1967 and the consequent adoption of the atomic timescale. After the short reign of ephemeris time as the world's reference timescale from 1954 until 1967, Coordinated Universal Time (UTC), synchronized to universal time UT1, appeared as the best compromise for satisfying the requests of all users. At the moment of the discussion on the adoption of an atomic timescale to replace ephemeris time, the possibility of having both an astronomical time and an atomic time to serve different purposes was discussed. In the words of Essen [1], this 'would cause endless confusion as well as involving duplication of equipment'. Forty years after the adoption of the definition of Coordinated Universal Time at the International Telecommunication Union (ITU), we are close to the moment of making a decision on whether or not to decouple UTC from its tight link to the rotation of the Earth embodied in UT1. It has been a ten-year process of discussion, mainly at the ITU with the input of the International Astronomical Union, the BIPM, the Consultative Committee for Time and Frequency and other organizations. The majority opinion supported the change based on developers and users of systems that need time synchronization to a stable and continuous reference timescale; others insist on the necessity of keeping the leap-second strategy for serving some applications or just for tradition. It is our hope that, as happened in the seventies, the most appropriate definition to serve all modern applications will be adopted with the consensus of the different sectors. The redirection of international timekeeping from astronomy to metrology can be considered the benchmark that started the era of modern timescales, all based on atomic properties. The aim of this special issue of Metrologia is to review timescales in use today, either the internationally recognized references or those adapted to some specific applications, to discuss new and future developments and to present the sometimes complex procedures for making international recommendations. We are grateful to our colleagues who, without exception, accepted our invitation to contribute to this special issue. Reference Henderson D 2005 Metrologia 42 S4-29 The pdf file contains an appendix: "Glossary of acronyms related to timescales used in this issue".

Interaction-induced conducting-non-conducting transition of ultra-cold atoms in one-dimensional optical lattices

NASA Astrophysics Data System (ADS)

Chien, Chih-Chun; Gruss, Daniel; Di Ventra, Massimiliano; Zwolak, Michael

2013-06-01

The study of time-dependent, many-body transport phenomena is increasingly within reach of ultra-cold atom experiments. We show that the introduction of spatially inhomogeneous interactions, e.g., generated by optically controlled collisions, induce negative differential conductance in the transport of atoms in one-dimensional optical lattices. Specifically, we simulate the dynamics of interacting fermionic atoms via a micro-canonical transport formalism within both a mean-field and a higher-order approximation, as well as with a time-dependent density-matrix renormalization group (DMRG). For weakly repulsive interactions, a quasi-steady-state atomic current develops that is similar to the situation occurring for electronic systems subject to an external voltage bias. At the mean-field level, we find that this atomic current is robust against the details of how the interaction is switched on. Further, a conducting-non-conducting transition exists when the interaction imbalance exceeds some threshold from both our approximate and time-dependent DMRG simulations. This transition is preceded by the atomic equivalent of negative differential conductivity observed in transport across solid-state structures.

Rotational spectrum of 1,1-difluoroethane-argon: influence of the interaction with the Ar atom on the V 3 barrier to internal rotation of the methyl group

NASA Astrophysics Data System (ADS)

Velino, Biagio; Melandri, Sonia; Favero, Paolo G.; Dell'Erba, Adele; Caminati, Walther

2000-01-01

The free-jet millimeter-wave absorption spectrum of 1,1-difluoroethane-Ar is reported. Most of the measured lines are split due to internal rotation of the methyl group and the tunnelling motion of Ar connecting two equivalent potential energy minima. The Ar atom, close to the CHF 2 group, eclipses one of the methylic hydrogens in the symmetryless geometry of the complex, reducing in this way the barrier to the internal rotation of the methyl group with respect to isolated 1,1-difluoroethane. For high J levels the distance of Ar from the molecule increases, however, due to the centrifugal distortion, and the barrier increases towards the value for 1,1-difluoroethane.

SHORT COMMUNICATION: Comparison between two mobile absolute gravimeters: optical versus atomic interferometers

NASA Astrophysics Data System (ADS)

Merlet, S.; Bodart, Q.; Malossi, N.; Landragin, A.; Pereira Dos Santos, F.; Gitlein, O.; Timmen, L.

2010-08-01

We report a comparison between two absolute gravimeters: the LNE-SYRTE cold atom gravimeter and FG5#220 of Leibniz Universität of Hannover. They rely on different principles of operation: atomic and optical interferometry. Both are movable which enabled them to participate in the last International Comparison of Absolute Gravimeters (ICAG'09) at BIPM. Immediately after, their bilateral comparison took place in the LNE watt balance laboratory and showed an agreement of (4.3 ± 6.4) µGal.

Atomic cluster collisions

NASA Astrophysics Data System (ADS)

Korol, Andrey V.; Solov'yov, Andrey

2013-01-01

Atomic cluster collisions are a field of rapidly emerging research interest by both experimentalists and theorists. The international symposium on atomic cluster collisions (ISSAC) is the premier forum to present cutting-edge research in this field. It was established in 2003 and the most recent conference was held in Berlin, Germany in July of 2011. This Topical Issue presents original research results from some of the participants, who attended this conference. This issues specifically focuses on two research areas, namely Clusters and Fullerenes in External Fields and Nanoscale Insights in Radiation Biodamage.

Light-pulse atom interferometric device

DOEpatents

Biedermann, Grant; McGuinness, Hayden James Evans; Rakholia, Akash; Jau, Yuan-Yu; Schwindt, Peter; Wheeler, David R.

2016-03-22

An atomic interferometric device useful, e.g., for measuring acceleration or rotation is provided. The device comprises at least one vapor cell containing a Raman-active chemical species, an optical system, and at least one detector. The optical system is conformed to implement a Raman pulse interferometer in which Raman transitions are stimulated in a warm vapor of the Raman-active chemical species. The detector is conformed to detect changes in the populations of different internal states of atoms that have been irradiated by the optical system.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Domengie, F., E-mail: florian.domengie@st.com; Morin, P.; Bauza, D.

We propose a model for dark current induced by metallic contamination in a CMOS image sensor. Based on Shockley-Read-Hall kinetics, the expression of dark current proposed accounts for the electric field enhanced emission factor due to the Poole-Frenkel barrier lowering and phonon-assisted tunneling mechanisms. To that aim, we considered the distribution of the electric field magnitude and metal atoms in the depth of the pixel. Poisson statistics were used to estimate the random distribution of metal atoms in each pixel for a given contamination dose. Then, we performed a Monte-Carlo-based simulation for each pixel to set the number of metalmore » atoms the pixel contained and the enhancement factor each atom underwent, and obtained a histogram of the number of pixels versus dark current for the full sensor. Excellent agreement with the dark current histogram measured on an ion-implanted gold-contaminated imager has been achieved, in particular, for the description of the distribution tails due to the pixel regions in which the contaminant atoms undergo a large electric field. The agreement remains very good when increasing the temperature by 15 °C. We demonstrated that the amplification of the dark current generated for the typical electric fields encountered in the CMOS image sensors, which depends on the nature of the metal contaminant, may become very large at high electric field. The electron and hole emissions and the resulting enhancement factor are described as a function of the trap characteristics, electric field, and temperature.« less

Reduction of surface leakage current by surface passivation of CdZn Te and other materials using hyperthermal oxygen atoms

DOEpatents

Hoffbauer, Mark A.; Prettyman, Thomas H.

2001-01-01

Reduction of surface leakage current by surface passivation of Cd.sub.1-x Zn.sub.x Te and other materials using hyperthermal oxygen atoms. Surface effects are important in the performance of CdZnTe room-temperature radiation detectors used as spectrometers since the dark current is often dominated by surface leakage. A process using high-kinetic-energy, neutral oxygen atoms (.about.3 eV) to treat the surface of CdZnTe detectors at or near ambient temperatures is described. Improvements in detector performance include significantly reduced leakage current which results in lower detector noise and greater energy resolution for radiation measurements of gamma- and X-rays, thereby increasing the accuracy and sensitivity of measurements of radionuclides having complex gamma-ray spectra, including special nuclear materials.

Health consequences of Chernobyl: the New York Academy of Sciences publishes an antidote to the nuclear establishment's pseudo-science.

PubMed

Katz, Alison Rosamund

2010-01-01

In February 2010, the New York Academy of Sciences published the most complete and up-to-date collection of evidence, from independent, scientific sources all over the world, on the health and environmental consequences of the Chernobyl accident. For 24 years, through a high-level, internationally coordinated cover-up of the world's most serious industrial accident, the nuclear lobby has deprived the world of a unique and critically important source of scientific information. The International Atomic Energy Agency (IAEA), mouthpiece of the nuclear establishment, has coordinated the cover-up through the dissemination and imposition of crude pseudo-science. Regrettably, the World Health Organization, a U.N. agency on which the world's people rely for guidance, is subordinate to the IAEA in matters of radiation and health, has participated in the cover-up, and stands accused of non-assistance to populations in danger. The new book on Chernobyl makes available huge amounts of evidence from independent studies undertaken in the affected countries, unique and valuable data that have been ignored by the international health establishment. This comprehensive account of the full dimensions of the catastrophe reveals the shameful inadequacy of current international assistance to the affected populations. It also demonstrates, once more, that future energy options cannot include nuclear power.

Advanced gas atomization production of oxide dispersion strengthened (ODS) Ni-base superalloys through process and solidification control

NASA Astrophysics Data System (ADS)

Meyer, John Louis Lamb

A novel gas atomization reaction synthesis (GARS) method was utilized to produce precursor Ni-Cr-Y-Ti powder with a surface oxide and an internal rare earth (RE)-containing intermetallic. Although Al is necessary for industrial superalloy production, the Ni-Cr base alloy system was selected as a simplified system more amenable to characterization. This was done in an effort to better study the effects of processing parameters. Consolidation and heat-treatment were performed to promote the exchange of oxygen from the surface oxide to the RE intermetallic to form nanometric oxide dispersoids. Alloy selection was aided by an internal oxidation and serial grinding experiment that found that Hf-containing alloys may form more stable dispersoids than Ti-containing alloys, but the Hf-containing system exhibited five different oxide phases and two different intermetallics compared to the two oxide phases and one intermetallic in the Ti-containing alloys. Since the simpler Ti-containing system was easier to characterize, and make observations on the effects of processing parameters, the Ti-containing system was used for experimental atomization trials. An internal oxidation model was used to predict the heat treatment times necessary for dispersoid formation as a function of powder size and temperature. A new high-pressure gas atomization (HPGA) nozzle was developed with the aim of promoting fine powder production at scales similar to that of the high gas-flow and melt-flow of industrial atomizers. The atomization nozzle was characterized using schlieren imaging and aspiration pressure testing to determine the optimum melt delivery tip geometry and atomization pressure to promote enhanced secondary atomization mechanisms. Six atomization trials were performed to investigate the effects of gas atomization pressure and reactive-gas concentration on the particle size distribution (PSD). Also, the effect on the rapidly solidified microstructure (as a function of powder size) was investigated as a function of reactive-gas composition and bulk alloy composition. The results indicate that the pulsation mechanism and optimum PSDs reported in the literature were not observed. Also, it was determined that reactive gas may marginally improve the PSD, but further experiments are required. The oxygen content in the gas was also not found to be detrimental to the microstructure (i.e., did not catalyze nucleation), but may have removed potent catalytic nucleation sites, although not enough to significantly alter the microstructure. Overall, the downstream injection of oxygen was not found to significantly affect either the PSD or undercooling (as inferred from microstructure and XRD observations), but injection further upstream, including in the gas atomization nozzle, remains to be investigated.

Red Aurora as Seen From the International Space Station (ISS)

NASA Technical Reports Server (NTRS)

2001-01-01

Auroras are caused when high-energy electrons pour down from the Earth's magnetosphere and collide with atoms. Red aurora, as captured here by a still digital camera aboard the International Space Station (ISS), occurs from 200 km to as high as 500 km altitude and is caused by the emission of 6300 Angstrom wavelength light from oxygen atoms. The light is emitted when the atoms return to their original unexcited state. The white spot in the image is from a light on inside of the ISS that is reflected off the inside of the window. The pale blue arch on the left side of the frame is sunlight reflecting off the atmospheric limb of the Earth. At times of peaks in solar activity, there are more geomagnetic storms and this increases the auroral activity viewed on Earth and by astronauts from orbit.

Topography and Mechanical Property Mapping of International Simple Glass Surfaces with Atomic Force Microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pierce, Eric M

2014-01-01

Quantitative Nanomechanical Peak Force (PF-QNM) TappingModeTM atomic force microscopy measurements are presented for the first time on polished glass surfaces. The PF-QNM technique allows for topography and mechanical property information to be measured simultaneously at each pixel. Results for the international simple glass which represents a simplified version of SON68 glass suggests an average Young s modulus of 78.8 15.1 GPa is within the experimental error of the modulus measured for SON68 glass (83.6 2 GPa) with conventional approaches. Application of the PF-QNM technique will be extended to in situ glass corrosion experiments with the goal of gaining atomic-scale insightsmore » into altered layer development by exploiting the mechanical property differences that exist between silica gel (e.g., altered layer) and pristine glass surface.« less

Roles of dynamical symmetry breaking in driving oblate-prolate transitions of atomic clusters

NASA Astrophysics Data System (ADS)

Oka, Yurie; Yanao, Tomohiro; Koon, Wang Sang

2015-04-01

This paper explores the driving mechanisms for structural transitions of atomic clusters between oblate and prolate isomers. We employ the hyperspherical coordinates to investigate structural dynamics of a seven-atom cluster at a coarse-grained level in terms of the dynamics of three gyration radii and three principal axes, which characterize overall mass distributions of the cluster. Dynamics of gyration radii is governed by two kinds of forces. One is the potential force originating from the interactions between atoms. The other is the dynamical forces called the internal centrifugal forces, which originate from twisting and shearing motions of the system. The internal centrifugal force arising from twisting motions has an effect of breaking the symmetry between two gyration radii. As a result, in an oblate isomer, activation of the internal centrifugal force that has the effect of breaking the symmetry between the two largest gyration radii is crucial in triggering structural transitions into prolate isomers. In a prolate isomer, on the other hand, activation of the internal centrifugal force that has the effect of breaking the symmetry between the two smallest gyration radii is crucial in triggering structural transitions into oblate isomers. Activation of a twisting motion that switches the movement patterns of three principal axes is also important for the onset of structural transitions between oblate and prolate isomers. Based on these trigger mechanisms, we finally show that selective activations of specific gyration radii and twisting motions, depending on the isomer of the cluster, can effectively induce structural transitions of the cluster. The results presented here could provide further insights into the control of molecular reactions.

Safety assessment guidance in the International Atomic Energy Agency RADWASS Program

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vovk, I.F.; Seitz, R.R.

1995-12-31

The IAEA RADWASS programme is aimed at establishing a coherent and comprehensive set of principles and standards for the safe management of waste and formulating the guidelines necessary for their application. A large portion of this programme has been devoted to safety assessments for various waste management activities. Five Safety Guides are planned to be developed to provide general guidance to enable operators and regulators to develop necessary framework for safety assessment process in accordance with international recommendations. They cover predisposal, near surface disposal, geological disposal, uranium/thorium mining and milling waste, and decommissioning and environmental restoration. The Guide on safetymore » assessment for near surface disposal is at the most advanced stage of preparation. This draft Safety Guide contains guidance on description of the disposal system, development of a conceptual model, identification and description of relevant scenarios and pathways, consequence analysis, presentation of results and confidence building. The set of RADWASS publications is currently undergoing in-depth review to ensure a harmonized approach throughout the Safety Series.« less

EDITORIAL: Cold Quantum GasesEditorial: Cold Quantum Gases

NASA Astrophysics Data System (ADS)

Vassen, W.; Hemmerich, A.; Arimondo, E.

2003-04-01

This Special Issue of Journal of Optics B: Quantum and Semiclassical Optics brings together the contributions of various researchers working on theoretical and experimental aspects of cold quantum gases. Different aspects of atom optics, matter wave interferometry, laser manipulation of atoms and molecules, and production of very cold and degenerate gases are presented. The variety of subjects demonstrates the steadily expanding role associated with this research area. The topics discussed in this issue, extending from basic physics to applications of atom optics and of cold atomic samples, include: bulletBose--Einstein condensation bulletFermi degenerate gases bulletCharacterization and manipulation of quantum gases bulletCoherent and nonlinear cold matter wave optics bulletNew schemes for laser cooling bulletCoherent cold molecular gases bulletUltra-precise atomic clocks bulletApplications of cold quantum gases to metrology and spectroscopy bulletApplications of cold quantum gases to quantum computing bulletNanoprobes and nanolithography. This special issue is published in connection with the 7th International Workshop on Atom Optics and Interferometry, held in Lunteren, The Netherlands, from 28 September to 2 October 2002. This was the last in a series of Workshops organized with the support of the European Community that have greatly contributed to progress in this area. The scientific part of the Workshop was managed by A Hemmerich, W Hogervorst, W Vassen and J T M Walraven, with input from members of the International Programme Committee who are listed below. The practical aspects of the organization were ably handled by Petra de Gijsel from the Vrije Universiteit in Amsterdam. The Workshop was funded by the European Science Foundation (programme BEC2000+), the European Networks 'Cold Quantum Gases (CQG)', coordinated by E Arimondo, and 'Cold Atoms and Ultraprecise Atomic Clocks (CAUAC)', coordinated by J Henningsen, by the German Physical Society (DFG), by the Dutch Foundation for Fundamental Research on Matter (FOM) and by the Dutch Gelderland province. We thank all these sponsors and the members of the International Programme Committee for making the Workshop such a success. At this point we take the opportunity to express our gratitude to both authors and reviewers, for their efforts in preparing and ensuring the high quality of the papers in this special issue. Wim Vassen Vrije Universiteit, Amsterdam Andreas Hemmerich Universität Hamburg Ennio Arimondo Università di Pisa Guest Editors International Programme Committee A Aspect Orsay, France E Cornell Boulder, USA W Ertmer Hannover, Germany T W Haensch Munich, Germany A Hemmerich Hamburg, Germany W Hogervorst Amsterdam, The Netherlands D Kleppner Cambridge, USA C Salomon Paris, France G V Shlyapnikov Amsterdam, Paris, Moscow S Stringari Trento, Italy W Vassen Amsterdam, The Netherlands J T M Walraven Amsterdam, The Netherlands

Absolute Gravity Datum in the Age of Cold Atom Gravimeters

NASA Astrophysics Data System (ADS)

Childers, V. A.; Eckl, M. C.

2014-12-01

The international gravity datum is defined today by the International Gravity Standardization Net of 1971 (IGSN-71). The data supporting this network was measured in the 1950s and 60s using pendulum and spring-based gravimeter ties (plus some new ballistic absolute meters) to replace the prior protocol of referencing all gravity values to the earlier Potsdam value. Since this time, gravimeter technology has advanced significantly with the development and refinement of the FG-5 (the current standard of the industry) and again with the soon-to-be-available cold atom interferometric absolute gravimeters. This latest development is anticipated to provide improvement in the range of two orders of magnitude as compared to the measurement accuracy of technology utilized to develop ISGN-71. In this presentation, we will explore how the IGSN-71 might best be "modernized" given today's requirements and available instruments and resources. The National Geodetic Survey (NGS), along with other relevant US Government agencies, is concerned about establishing gravity control to establish and maintain high order geodetic networks as part of the nation's essential infrastructure. The need to modernize the nation's geodetic infrastructure was highlighted in "Precise Geodetic Infrastructure, National Requirements for a Shared Resource" National Academy of Science, 2010. The NGS mission, as dictated by Congress, is to establish and maintain the National Spatial Reference System, which includes gravity measurements. Absolute gravimeters measure the total gravity field directly and do not involve ties to other measurements. Periodic "intercomparisons" of multiple absolute gravimeters at reference gravity sites are used to constrain the behavior of the instruments to ensure that each would yield reasonably similar measurements of the same location (i.e. yield a sufficiently consistent datum when measured in disparate locales). New atomic interferometric gravimeters promise a significant increase in accuracy. Our presentation will also explore the impact of such an instrument on our theory of how to constrain the gravity datum and on how to ensure stability, repeatability, and reproducibility across different absolute gravimeter systems.

Regular and Chaotic Spatial Distribution of Bose-Einstein Condensed Atoms in a Ratchet Potential

NASA Astrophysics Data System (ADS)

Li, Fei; Xu, Lan; Li, Wenwu

2018-02-01

We study the regular and chaotic spatial distribution of Bose-Einstein condensed atoms with a space-dependent nonlinear interaction in a ratchet potential. There exists in the system a space-dependent atomic current that can be tuned via Feshbach resonance technique. In the presence of the space-dependent atomic current and a weak ratchet potential, the Smale-horseshoe chaos is studied and the Melnikov chaotic criterion is obtained. Numerical simulations show that the ratio between the intensities of optical potentials forming the ratchet potential, the wave vector of the laser producing the ratchet potential or the wave vector of the modulating laser can be chosen as the controlling parameters to result in or avoid chaotic spatial distributional states.

Internal exposure to neutron-activated 56Mn dioxide powder in Wistar rats: part 1: dosimetry.

PubMed

Stepanenko, Valeriy; Rakhypbekov, Tolebay; Otani, Keiko; Endo, Satoru; Satoh, Kenichi; Kawano, Noriyuki; Shichijo, Kazuko; Nakashima, Masahiro; Takatsuji, Toshihiro; Sakaguchi, Aya; Kato, Hiroaki; Onda, Yuichi; Fujimoto, Nariaki; Toyoda, Shin; Sato, Hitoshi; Dyussupov, Altay; Chaizhunusova, Nailya; Sayakenov, Nurlan; Uzbekov, Darkhan; Saimova, Aisulu; Shabdarbaeva, Dariya; Skakov, Mazhin; Vurim, Alexandr; Gnyrya, Vyacheslav; Azimkhanov, Almas; Kolbayenkov, Alexander; Zhumadilov, Kasym; Kairikhanova, Yankar; Kaprin, Andrey; Galkin, Vsevolod; Ivanov, Sergey; Kolyzhenkov, Timofey; Petukhov, Aleksey; Yaskova, Elena; Belukha, Irina; Khailov, Artem; Skvortsov, Valeriy; Ivannikov, Alexander; Akhmedova, Umukusum; Bogacheva, Viktoria; Hoshi, Masaharu

2017-03-01

There were two sources of ionizing irradiation after the atomic bombings of Hiroshima and Nagasaki: (1) initial gamma-neutron irradiation at the moment of detonation and (2) residual radioactivity. Residual radioactivity consisted of two components: radioactive fallout containing fission products, including radioactive fissile materials from nuclear device, and neutron-activated radioisotopes from materials on the ground. The dosimetry systems DS86 and DS02 were mainly devoted to the assessment of initial radiation exposure to neutrons and gamma rays, while only brief considerations were given for the estimation of doses caused by residual radiation exposure. Currently, estimation of internal exposure of atomic bomb survivors due to dispersed radioactivity and neutron-activated radioisotopes from materials on the ground is a matter of some interest, in Japan. The main neutron-activated radionuclides in soil dust were 24 Na, 28 Al, 31 Si, 32 P, 38 Cl, 42 K, 45 Ca, 46 Sc, 56 Mn, 59 Fe, 60 Co, and 134 Cs. The radionuclide 56 Mn (T 1/2 = 2.58 h) is known as one of the dominant beta- and gamma emitters during the first few hours after neutron irradiation of soil and other materials on ground, dispersed in the form of dust after a nuclear explosion in the atmosphere. To investigate the peculiarities of biological effects of internal exposure to 56 Mn in comparison with external gamma irradiation, a dedicated experiment with Wistar rats exposed to neutron-activated 56 Mn dioxide powder was performed recently by Shichijo and coworkers. The dosimetry required for this experiment is described here. Assessment of internal radiation doses was performed on the basis of measured 56 Mn activity in the organs and tissues of the rats and of absorbed fractions of internal exposure to photons and electrons calculated with the MCNP-4C Monte Carlo using a mathematical rat phantom. The first results of this international multicenter study show that the internal irradiation due to incorporated 56 Mn powder is highly inhomogeneous, and that the most irradiated organs of the experimental animals are: large intestine, small intestine, stomach, and lungs. Accumulated absorbed organ doses were 1.65, 1.33, 0.24, 0.10 Gy for large intestine, small intestine, stomach, and lungs, respectively. Other organs were irradiated at lower dose levels. These results will be useful for interpretation of the biological effects of internal exposure of experimental rats to powdered 56 Mn as observed by Shichijo and coworkers.

ORNL Named as Part of IAES Research Reactor Hub

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

The International Atomic Energy Agency (IAEA) has named ORNL and Idaho National Laboratory part of an International Centre based on Research Reactors. The designation makes the United States one of only three countries identified for unique capabilities and excellence in nuclear research.

Direct measurements of safety factor profiles with motional Stark effect for KSTAR tokamak discharges with internal transport barriers

NASA Astrophysics Data System (ADS)

Ko, J.; Chung, J.

2017-06-01

The safety factor profile evolutions have been measured from the plasma discharges with the external current drive mechanism such as the multi-ion-source neutral beam injection for the Korea Superconducting Tokamak Advanced Research (KSTAR) for the first time. This measurement has been possible by the newly installed motional Stark effect (MSE) diagnostic system that utilizes the polarized Balmer-alpha emission from the energetic neutral deuterium atoms induced by the Stark effect under the Lorentz electric field. The 25-channel KSTAR MSE diagnostic is based on the conventional photoelastic modulator approach with the spatial and temporal resolutions less than 2 cm (for the most of the channels except 2 to 3 channels inside the magnetic axis) and about 10 ms, respectively. The strong Faraday rotation imposed on the optical elements in the diagnostic system is calibrated out from a separate and well-designed polarization measurement procedure using an in-vessel reference polarizer during the toroidal-field ramp-up phase before the plasma experiment starts. The combination of the non-inductive current drive during the ramp-up and shape control enables the formation of the internal transport barrier where the pitch angle profiles indicate flat or slightly hollow profiles in the safety factor.

15 CFR 781.1 - Definitions of terms used in the Additional Protocol Regulations (APR).

Code of Federal Regulations, 2010 CFR

2010-01-01

... United States of America and the International Atomic Energy Agency for the Application of Safeguards in... Additional Protocol. Agreement State. Any State of the United States with which the U.S. Nuclear Regulatory Commission (NRC) has entered into an effective agreement under Subsection 274b of the Atomic Energy Act of...

15 CFR 781.1 - Definitions of terms used in the Additional Protocol Regulations (APR).

Code of Federal Regulations, 2011 CFR

2011-01-01

... United States of America and the International Atomic Energy Agency for the Application of Safeguards in... Additional Protocol. Agreement State. Any State of the United States with which the U.S. Nuclear Regulatory Commission (NRC) has entered into an effective agreement under Subsection 274b of the Atomic Energy Act of...

15 CFR 781.1 - Definitions of terms used in the Additional Protocol Regulations (APR).

Code of Federal Regulations, 2014 CFR

2014-01-01

... United States of America and the International Atomic Energy Agency for the Application of Safeguards in... Additional Protocol. Agreement State. Any State of the United States with which the U.S. Nuclear Regulatory Commission (NRC) has entered into an effective agreement under Subsection 274b of the Atomic Energy Act of...

15 CFR 781.1 - Definitions of terms used in the Additional Protocol Regulations (APR).

Code of Federal Regulations, 2012 CFR

2012-01-01

... United States of America and the International Atomic Energy Agency for the Application of Safeguards in... Additional Protocol. Agreement State. Any State of the United States with which the U.S. Nuclear Regulatory Commission (NRC) has entered into an effective agreement under Subsection 274b of the Atomic Energy Act of...

15 CFR 781.1 - Definitions of terms used in the Additional Protocol Regulations (APR).

Code of Federal Regulations, 2013 CFR

2013-01-01

... United States of America and the International Atomic Energy Agency for the Application of Safeguards in... Additional Protocol. Agreement State. Any State of the United States with which the U.S. Nuclear Regulatory Commission (NRC) has entered into an effective agreement under Subsection 274b of the Atomic Energy Act of...

[Microsecond Pulsed Hollow Cathode Lamp as Enhanced Excitation Source of Hydride Generation Atomic Fluorescence Spectrometry].

PubMed

Zhang, Shuo

2015-09-01

The spectral, electrical and atomic fluorescence characteristics of As, Se, Sb and Pb hollow cathode lamps (HCLs) powered by a laboratory-built high current microsecond pulse (HCMP) power supply were studied, and the feasibility of using HCMP-HCLs as the excitation source of hydride generation atomic fluorescence spectrometry (HG-AFS) was evaluated. Under the HCMP power supply mode, the As, Se, Sb, Pb HCLs can maintain stable glow discharge at frequency of 100~1000 Hz, pulse width of 4.0~20 μs and pulse current up to 4.0 A. Relationship between the intensity of characteristic emission lines and HCMP power supply parameters, such as pulse current, power supply voltage, pulse width and frequency, was studied in detail. Compared with the conventional pulsed (CP) HCLs used in commercial AFS instruments, HCMP-HCLs have a narrower pulse width and much stronger pulse current. Under the optimized HCMP power supply parameters, the intensity of atomic emission lines of As, Se, Sb HCLs had sharp enhancement and that indicated their capacity of being a novel HG-AFS excitation source. However, the attenuation of atomic lines and enhancement of ionic lines negated such feasibility of HCMP-Pb HCL. Then the HG-AFS analytical capability of using the HCMP-As/Se/Sb HCLs excitation source was established and results showed that the HCMP-HCL is a promising excitation source for HG-AFS.

International Atomic Energy Agency Safeguards: Challenge and response

NASA Astrophysics Data System (ADS)

Spector, Leonard S.

2017-11-01

This article provides a critical review of the nuclear accounting and inspection system of the International Atomic Energy Agency (IAEA), known as "IAEA safeguards." The article focuses on the multiple challenges the Agency confronts in verifying that all nuclear activities in the countries under its safeguards system are being pursued for exclusively peaceful purposes. The principal challenges noted are those posed by: undeclared facilities, the development of enrichment and reprocessing capabilities, illicit procurement activities, denial of inspector access, difficulties in verifying absence of weaponization activities, and difficulties in establishing that all nuclear-relevant activities in a state are peaceful. The article is in the form of annotated PowerPoint briefing slides.

Performance of Loran-C chains relative to UTC

NASA Technical Reports Server (NTRS)

Chi, A. R.

1974-01-01

The long term performance of the eight Loran-C chains in terms of the Coordinated Universal Time (UTC) of the U.S. Naval Observatory (USNO) and the use of the Loran-C navigation system to maintain the user's clock to a UTC scale, are examined. The atomic time (AT) scale and the UTC of several national laboratories and observatories relative to the international atomic time (TAI) are presented. In addition, typical performance of several NASA tracking station clocks, relative to the USNO master clock, is also presented. Recent revision of the Coordinated Universal Time (UTC) by the International Radio Consultative Committee (CCIR) is given in an appendix.

Non-equilibrium effects in high temperature chemical reactions

NASA Technical Reports Server (NTRS)

Johnson, Richard E.

1987-01-01

Reaction rate data were collected for chemical reactions occurring at high temperatures during reentry of space vehicles. The principle of detailed balancing is used in modeling kinetics of chemical reactions at high temperatures. Although this principle does not hold for certain transient or incubation times in the initial phase of the reaction, it does seem to be valid for the rates of internal energy transitions that occur within molecules and atoms. That is, for every rate of transition within the internal energy states of atoms or molecules, there is an inverse rate that is related through an equilibrium expression involving the energy difference of the transition.

Four Years of Practical Arrangements between IAEA and Moscow SIA 'Radon': Preliminary Results - 13061

DOE Office of Scientific and Technical Information (OSTI.GOV)

Batyukhnova, O.G.; Karlina, O.K.; Neveikin, P.P.

The International Education Training Centre (IETC) at Moscow State Unitary Enterprise Scientific and Industrial Association 'Radon' (SIA 'Radon'), in co-operation with the International Atomic Energy Agency (IAEA), has developed expertise and provided training to waste management personnel for the last 15 years. Since 1997, the educational system of the enterprise with the support of the IAEA has acquired an international character: more than 470 experts from 35 countries- IAEA Member States completed the professional development. Training is conducted at various thematic courses or fellowships for individual programs and seminars on IAEA technical projects. In June 2008 a direct agreement (Practicalmore » Arrangements) was signed between SIA 'Radon' and the IAEA on cooperation in the field of development of new technologies, expert's advice to IAEA Member States, and, in particular, the training of personnel in the field of radioactive waste management (RWM), which opens up new perspectives for fruitful cooperation of industry professionals. The paper summarizes the current experience of the SIA 'Radon' in the organization and implementation of the IAEA sponsored training and others events and outlines some of strategic educational elements, which IETC will continue to pursue in the coming years. (authors)« less

Current issues and actions in radiation protection of patients.

PubMed

Holmberg, Ola; Malone, Jim; Rehani, Madan; McLean, Donald; Czarwinski, Renate

2010-10-01

Medical application of ionizing radiation is a massive and increasing activity globally. While the use of ionizing radiation in medicine brings tremendous benefits to the global population, the associated risks due to stochastic and deterministic effects make it necessary to protect patients from potential harm. Current issues in radiation protection of patients include not only the rapidly increasing collective dose to the global population from medical exposure, but also that a substantial percentage of diagnostic imaging examinations are unnecessary, and the cumulative dose to individuals from medical exposure is growing. In addition to this, continued reports on deterministic injuries from safety related events in the medical use of ionizing radiation are raising awareness on the necessity for accident prevention measures. The International Atomic Energy Agency is engaged in several activities to reverse the negative trends of these current issues, including improvement of the justification process, the tracking of radiation history of individual patients, shared learning of safety significant events, and the use of comprehensive quality audits in the clinical environment. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

NASA Goddard Thermal Technology Overview 2018

NASA Technical Reports Server (NTRS)

Butler, Dan; Swanson, Ted

2018-01-01

This presentation summarizes the current plans and efforts at NASA/Goddard to develop new thermal control technology for anticipated future missions. It will also address some of the programmatic developments currently underway at NASA, especially with respect to the NASA Technology Development Program. The effects of the recently submitted NASA budget will also be addressed. While funding for basic technology development is still tight, significant efforts are being made in direct support of flight programs. Thermal technology Implementation on current flight programs will be reviewed, and the recent push for Cube-sat mission development will also be addressed. Many of these technologies also have broad applicability to DOD, DOE, and commercial programs. Partnerships have been developed with the Air Force, Navy, and various universities to promote technology development. In addition, technology development activities supported by internal research and development (IRAD) program and the Small Business Innovative Research (SBIR) program are reviewed in this presentation. Specific technologies addressed include; two-phase systems applications and issues on NASA missions, latest developments of thermal control coatings, Atomic Layer Deposition (ALD), Micro-scale Heat Transfer, and various other research activities.

Investigation of tunneling current and local contact potential difference on the TiO2(110) surface by AFM/KPFM at 78 K.

PubMed

Wen, Huan Fei; Li, Yan Jun; Arima, Eiji; Naitoh, Yoshitaka; Sugawara, Yasuhiro; Xu, Rui; Cheng, Zhi Hai

2017-03-10

We propose a new multi-image method for obtaining the frequency shift, tunneling current and local contact potential difference (LCPD) on a TiO 2 (110) surface with atomic resolution. The tunneling current image reveals rarely observed surface oxygen atoms contrary to the conventional results. We analyze how the surface and subsurface defects affect the distribution of the LCPD. In addition, the subsurface defects are observed clearly in the tunneling current image, in contrast to a topographic image. To clarify the origin of the atomic contrast, we perform site-dependent spectroscopy as a function of the tip-sample distance. The multi-image method is expected to be widely used to investigate the charge transfer phenomena between the nanoparticles and surface sites, and it is useful for elucidating the mechanisms of catalytic reactions.

A quantum network of clocks

NASA Astrophysics Data System (ADS)

Kómár, P.; Kessler, E. M.; Bishof, M.; Jiang, L.; Sørensen, A. S.; Ye, J.; Lukin, M. D.

2014-08-01

The development of precise atomic clocks plays an increasingly important role in modern society. Shared timing information constitutes a key resource for navigation with a direct correspondence between timing accuracy and precision in applications such as the Global Positioning System. By combining precision metrology and quantum networks, we propose a quantum, cooperative protocol for operating a network of geographically remote optical atomic clocks. Using nonlocal entangled states, we demonstrate an optimal utilization of global resources, and show that such a network can be operated near the fundamental precision limit set by quantum theory. Furthermore, the internal structure of the network, combined with quantum communication techniques, guarantees security both from internal and external threats. Realization of such a global quantum network of clocks may allow construction of a real-time single international time scale (world clock) with unprecedented stability and accuracy.

PREFACE: Atomic Spectra and Oscillator Strengths (ASOS9) Atomic Spectra and Oscillator Strengths (ASOS9)

NASA Astrophysics Data System (ADS)

Wahlgren, Glenn M.; Wiese, Wolfgang L.; Beiersdorfer, Peter

2009-05-01

For the first time since its inaugural meeting in Lund in 1983, the triennial international conference on Atomic Spectroscopy and Oscillator Strengths for Astrophysical and Laboratory Plasmas (ASOS) returned to Lund, Sweden. Lund has been a home to atomic spectroscopy since the time of Janne Rydberg, and included the pioneering work in laboratory and solar spectroscopy by Bengt Edlén, who presented the initial ASOS talk in 1983. The ninth ASOS was hosted by the Lund Observatory and Physics Department of Lund University, 7-10 August 2007, and was attended by 99 registrants. An encouraging sign for the field was the number of young researchers in attendance. This volume of Physica Scripta contains contributions from the invited presentations of the conference. For the first time, papers from the ASOS9 poster presentations have been made feely available online in a complementary volume of Journal of Physics: Conference Series. With these two volumes the character of ASOS9 is more evident, and together they serve as a review of the state of atomic spectroscopy for spectrum analysis and the determination of oscillator strengths and their applications. The goal of ASOS is to be a forum for atomic spectroscopy, where both the providers and the users of atomic data, which includes wavelengths, energy levels, lifetimes, oscillator strengths and line shape parameters, can meet to discuss recent advances in experimental and theoretical techniques and their application to understanding the physical processes that are responsible for producing observed spectra. The applications mainly originate from the fields of astrophysics and plasma physics, which includes fusion energy and lighting research. The oral presentations, all but one of which are presented in this volume, provided an extensive synopsis of techniques currently in use and those that are being planned. New to ASOS9 was the extent to which techniques such as cold, trapped atoms and molecules and frequency combs are being used to determine fundamental quantities. Atomic data for programs in astronomical infrared spectroscopy were highlighted by both oral and poster contributions as being an important area in the near future. As part of ASOS9 we were honored to celebrate the retirement of Professor Sveneric Johansson. At a special session on the spectroscopy of iron, which was conducted in his honor, he presented his insights into the Fe II term system and his most recent work with astrophysical applications. Professor Johansson was also honored with heart-felt acknowledgments at the conference dinner on an unusually warm Lund summer evening. Prior to the publication of these proceedings, we were extremely saddened to learn of Sveneric's passing on 10 October 2008. Sveneric Johansson, a founding father of the ASOS conference series, was widely known for his pioneering work on the atomic structure of heavy elements as a well as for his leadership of the international FERRUM Project, which successfully determined a definitive set of spectroscopic data for Fe II. His knowledge of spectroscopy, his leadership qualities and his friendship will be sadly missed. Acknowledgments The spirit of ASOS has been maintained by the dedication of the organizing committees that have kept a tight focus on the nature of the conference yet allowed for the incorporation of new areas of research in the field. The International Program Committee for ASOS9 are to be commended for their efforts in providing an interesting program. They have also served as the primary source of manuscript referees, who along with other referees have performed a valuable service. Many thanks must be given to the local organizing committee, who made the return of ASOS to Lund a memorable experience, both through the many opportunities for social gatherings during the conference and a post-conference outing through Skåne. We would also like to express our appreciation to the Royal Swedish Academy of Sciences, the Royal Physiographic Society in Lund, the Wenner-Gren Foundation and the Lund Laser Centre and Department of Physics for their generous support in making ASOS9 possible. Sveneric Johansson 1942-2008. Professor Sveneric Johansson 1942-2008.

Science Goals of the Primary Atomic Reference Clock in Space (PARCS) Experiment

NASA Technical Reports Server (NTRS)

Ashby, N.

2003-01-01

The PARCS (Primary Atomic Reference Clock in Space) experiment will use a laser-cooled Cesium atomic clock operating in the microgravity environment aboard the International Space Station (ISS) to provide both advanced tests of gravitational theory and to demonstrate a new cold-atom clock technology for space. PARCS is a joint project of the National Institute of Standards and Technology (NIST), NASA's Jet Propulsion Laboratory (JPL), and the University of Colorado (CU). This paper concentrates on the scientific goals of the PARCS mission. The microgravity space environment allows laser-cooled Cs atoms to have Ramsey times in excess of those feasible on Earth, resulting in improved clock performance. Clock stabilities of 5x10(exp -14) at one second, and accuracies better than 10(exp -16) are projected.

Joint CPT and N resonance in compact atomic time standards

NASA Astrophysics Data System (ADS)

Crescimanno, Michael; Hohensee, Michael; Xiao, Yanhong; Phillips, David; Walsworth, Ron

2008-05-01

Currently development efforts towards small, low power atomic time standards use current-modulated VCSELs to generate phase-coherent optical sidebands that interrogate the hyperfine structure of alkali atoms such as rubidium. We describe and use a modified four-level quantum optics model to study the optimal operating regime of the joint CPT- and N-resonance clock. Resonant and non-resonant light shifts as well as modulation comb detuning effects play a key role in determining the optimal operating point of such clocks. We further show that our model is in good agreement with experimental tests performed using Rb-87 vapor cells.

Isotope reference materials

USGS Publications Warehouse

Coplen, Tyler B.

2010-01-01

Measurement of the same isotopically homogeneous sample by any laboratory worldwide should yield the same isotopic composition within analytical uncertainty. International distribution of light element isotopic reference materials by the International Atomic Energy Agency and the U.S. National Institute of Standards and Technology enable laboratories to achieve this goal.

Nitrogen spark denoxer

DOEpatents

Ng, Henry K.; Novick, Vincent J.; Sekar, Ramanujam R.

1997-01-01

A NO.sub.X control system for an internal combustion engine includes an oxygen enrichment device that produces oxygen and nitrogen enriched air. The nitrogen enriched air contains molecular nitrogen that is provided to a spark plug that is mounted in an exhaust outlet of an internal combustion engine. As the nitrogen enriched air is expelled at the spark gap of the spark plug, the nitrogen enriched air is exposed to a pulsating spark that is generated across the spark gap of the spark plug. The spark gap is elongated so that a sufficient amount of atomic nitrogen is produced and is injected into the exhaust of the internal combustion engine. The injection of the atomic nitrogen into the exhaust of the internal combustion engine causes the oxides of nitrogen to be reduced into nitrogen and oxygen such that the emissions from the engine will have acceptable levels of NO.sub.X. The oxygen enrichment device that produces both the oxygen and nitrogen enriched air can include a selectively permeable membrane.

Guidelines and recommended terms for expression of stable-isotope-ratio and gas-ratio measurement results

USGS Publications Warehouse

Coplen, Tyler B.

2011-01-01

To minimize confusion in the expression of measurement results of stable isotope and gas-ratio measurements, recommendations based on publications of the Commission on Isotopic Abundances and Atomic Weights of the International Union of Pure and Applied Chemistry (IUPAC) are presented. Whenever feasible, entries are consistent with the Système International d'Unités, the SI (known in English as the International System of Units), and the third edition of the International Vocabulary of Basic and General Terms in Metrology (VIM, 3rd edition). The recommendations presented herein are approved by the Commission on Isotopic Abundances and Atomic Weights and are designed to clarify expression of quantities related to measurement of isotope and gas ratios to ensure that quantity equations instead of numerical value equations are used for quantity definitions. Examples of column headings consistent with quantity calculus (also called the algebra of quantities) and examples of various deprecated usages connected with the terms recommended are presented.

Mesoscopic coherence in light scattering from cold, optically dense and disordered atomic systems

NASA Astrophysics Data System (ADS)

Kupriyanov, D. V.; Sokolov, I. M.; Havey, M. D.

2017-02-01

Coherent effects manifested in light scattering from cold, optically dense and disordered atomic systems are reviewed from a primarily theoretical point of view. Development of the basic theoretical tools is then elaborated through several physical atomic physics based processes which have been at least partly explored experimentally. These include illustrations drawn from the coherent backscattering effect, random lasing in atomic gases, quantum memories and light-atoms interface assisted by the light trapping mechanism. Current understanding and challenges associated with the transition to high atomic densities and cooperativity in the scattering process are also discussed in some detail.

Atom chip microscopy: A novel probe for strongly correlated materials

NASA Astrophysics Data System (ADS)

Kasch, Brian; Naides, Matthew; Turner, Richard; Ray, Ushnish; Lev, Benjamin

2010-03-01

Atom chip technology---substrates supporting micron-sized current-carrying wires that create magnetic microtraps near surfaces for thermal or degenerate gases of neutral atoms---will enable single-shot, large area detection of magnetic flux below the 10-7 flux quantum level. By harnessing the extreme sensitivity of Bose-Einstein condensates (BECs) to external perturbations, cryogenic atom chips could provide a magnetic flux detection capability that surpasses all other techniques by a factor of 10^2--10^3. We describe the merits of atom chip microscopy, our Rb BEC and atom chip apparatus, and prospects for imaging strongly correlated condensed matter materials.

Detection prospects of the cosmic neutrino background

NASA Astrophysics Data System (ADS)

Li, Yu-Feng

2015-04-01

The existence of the cosmic neutrino background (CνB) is a fundamental prediction of the standard Big Bang cosmology. Although current cosmological probes provide indirect observational evidence, the direct detection of the CνB in a laboratory experiment is a great challenge to the present experimental techniques. We discuss the future prospects for the direct detection of the CνB, with the emphasis on the method of captures on beta-decaying nuclei and the PTOLEMY project. Other possibilities using the electron-capture (EC) decaying nuclei, the annihilation of extremely high-energy cosmic neutrinos (EHECνs) at the Z-resonance, and the atomic de-excitation method are also discussed in this review (talk given at the International Conference on Massive Neutrinos, Singapore, 9-13 February 2015).

Electrodynamic Dust Shield Technology for Thermal Radiators Used in Lunar Exploration

NASA Technical Reports Server (NTRS)

Calle, Carlos I.; Hogue, Michael D.; Snyder, Sarah J.; Clements, Sidney J.; Johansen, Michael R.; Chen, Albert

2011-01-01

Two general types of thermal radiators are being considered for lunar missions: coated metallic surfaces and Second Surface Mirrors. Metallic surfaces are coated with a specially formulated white paint that withstands the space environment and adheres well to aluminium, the most common metal used in space hardware. AZ-93 White Thermal Control Paint, developed for the space program, is an electrically conductive inorganic coating that offers thermal control for spacecraft. It is currently in use on satellite surfaces (Fig 1). This paint withstands exposure to atomic oxygen, charged particle radiation, and vacuum ultraviolet radiation form 118 nm to 170 nm while reflecting 84 to 85% of the incident solar radiation and emitting 89-93% of the internal heat generated inside the spacecraft.

Laser frequency-offset locking based on the frequency modulation spectroscopy with higher harmonic detection

NASA Astrophysics Data System (ADS)

Wang, Anqi; Meng, Zhixin; Feng, Yanying

2017-10-01

We design a fiber electro-optic modulator (FEOM)-based laser frequency-offset locking system using frequency modulation spectroscopy (FMS) with the 3F modulation. The modulation signal and the frequency-offset control signal are simultaneously loaded on the FEOM by a mixer in order to suppress the frequency and power jitter caused by internal modulation on the current or piezoelectric ceramic transducer (PZT). It is expected to accomplish a fast locking, a widely tunable frequency-offset, a sensitive and rapid detection of narrow spectral features with the 3F modulation. The laser frequency fluctuation is limited to +/-1MHz and its overlapping Allan deviation is around 10-12 in twenty minutes, which successfully meets the requirements of the cold atom interferometer.

Inner Magnetosphere Imager (IMI) instrument heritage

NASA Technical Reports Server (NTRS)

Wilson, G. R.

1993-01-01

This report documents the heritage of instrument concepts under consideration for the Inner Magnetosphere Imager (IMI) mission. The proposed IMI will obtain the first simultaneous images of the component regions of the inner magnetosphere and will enable scientists to relate these global images to internal and external influences as well as local observations. To obtain simultaneous images of component regions of the inner magnetosphere, measurements will be made of: (1) the ring current and inner plasma sheet using energetic neutral atoms; (2) the plasmasphere using extreme ultraviolet; (3) the electron and proton auroras using far ultraviolet and x rays; and (4) the geocorona using FUV. Instrument concepts that show heritage and traceability to those that will be required to meet the IMI measurement objectives are described.

High-precision two-dimensional atom localization from four-wave mixing in a double-Λ four-level atomic system

NASA Astrophysics Data System (ADS)

Shui, Tao; Yang, Wen-Xing; Chen, Ai-Xi; Liu, Shaopeng; Li, Ling; Zhu, Zhonghu

2018-03-01

We propose a scheme for high-precision two-dimensional (2D) atom localization via the four-wave mixing (FWM) in a four-level double-Λ atomic system. Due to the position-dependent atom-field interaction, the 2D position information of the atoms can be directly determined by the measurement of the normalized light intensity of output FWM-generated field. We further show that, when the position-dependent generated FWM field has become sufficiently intense, efficient back-coupling to the FWM generating state becomes important. This back-coupling pathway leads to competitive multiphoton destructive interference of the FWM generating state by three supplied and one internally generated fields. We find that the precision of 2D atom localization can be improved significantly by the multiphoton destructive interference and depends sensitively on the frequency detunings and the pump field intensity. Interestingly enough, we show that adjusting the frequency detunings and the pump field intensity can modify significantly the FWM efficiency, and consequently lead to a redistribution of the atoms. As a result, the atom can be localized in one of four quadrants with holding the precision of atom localization.

Atomic-scale simulation of dust grain collisions: Surface chemistry and dissipation beyond existing theory

NASA Astrophysics Data System (ADS)

Quadery, Abrar H.; Doan, Baochi D.; Tucker, William C.; Dove, Adrienne R.; Schelling, Patrick K.

2017-10-01

The early stages of planet formation involve steps where submicron-sized dust particles collide to form aggregates. However, the mechanism through which millimeter-sized particles aggregate to kilometer-sized planetesimals is still not understood. Dust grain collision experiments carried out in the environment of the Earth lead to the prediction of a 'bouncing barrier' at millimeter-sizes. Theoretical models, e.g., Johnson-Kendall-Roberts and Derjaguin-Muller-Toporov theories, lack two key features, namely the chemistry of dust grain surfaces, and a mechanism for atomic-scale dissipation of energy. Moreover, interaction strengths in these models are parameterized based on experiments done in the Earth's environment. To address these issues, we performed atomic-scale simulations of collisions between nonhydroxylated and hydroxylated amorphous silica nanoparticles. We used the ReaxFF approach which enables modeling chemical reactions using an empirical potential. We found that nonhydroxylated nanograins tend to adhere with much higher probability than suggested by existing theories. By contrast, hydroxylated nanograins exhibit a strong tendency to bounce. Also, the interaction between dust grains has the characteristics of a strong chemical force instead of weak van der Waals forces. This suggests that the formation of strong chemical bonds and dissipation via internal atomic vibration may result in aggregation beyond what is expected based on our current understanding. Our results also indicate that experiments should more carefully consider surface conditions to mimic the space environment. We also report results of simulations with molten silica nanoparticles. It is found that molten particles are more likely to adhere due to viscous dissipation, which supports theories that suggest aggregation to kilometer scales might require grains to be in a molten state.

Determination of Vanadium, Tin and Mercury in Atmospheric Particulate Matter and Cement Dust Samples by Direct Current Plasma Atomic Emission Spectrometry.

ERIC Educational Resources Information Center

Hindy, Kamal T.; And Others

1992-01-01

An atmospheric pollution study applies direct current plasma atomic emission spectrometry (DCP-AES) to samples of total suspended particulate matter collected in two industrial areas and one residential area, and cement dust collected near major cement factories. These samples were analyzed for vanadium, tin, and mercury. The results indicate the…

[Current approach to zoning atomic shipbuilding plants].

PubMed

Blekher, A Ia

2005-01-01

The paper discusses the currently introduced radiation-and-hygienic system for zoning atomic shipbuilding plants, in accordance with which three radiation-and-hygienic zones (a strict regime zone, a controlled approach zone, and a free regime zone) are established at the plant site and two zones (a sanitary-and-protective zone and a follow-up zone) are also established outside the plant site.

Atomically Thin Femtojoule Memristive Device

DOE PAGES

Zhao, Huan; Dong, Zhipeng; Tian, He; ...

2017-10-25

The morphology and dimension of the conductive filament formed in a memristive device are strongly influenced by the thickness of its switching medium layer. Aggressive scaling of this active layer thickness is critical toward reducing the operating current, voltage, and energy consumption in filamentary-type memristors. Previously, the thickness of this filament layer has been limited to above a few nanometers due to processing constraints, making it challenging to further suppress the on-state current and the switching voltage. In this paper, the formation of conductive filaments in a material medium with sub-nanometer thickness formed through the oxidation of atomically thin two-dimensionalmore » boron nitride is studied. The resulting memristive device exhibits sub-nanometer filamentary switching with sub-pA operation current and femtojoule per bit energy consumption. Furthermore, by confining the filament to the atomic scale, current switching characteristics are observed that are distinct from that in thicker medium due to the profoundly different atomic kinetics. The filament morphology in such an aggressively scaled memristive device is also theoretically explored. Finally, these ultralow energy devices are promising for realizing femtojoule and sub-femtojoule electronic computation, which can be attractive for applications in a wide range of electronics systems that desire ultralow power operation.« less

Sub-atomic resolution X-ray crystallography and neutron crystallography: promise, challenges and potential.

PubMed

Blakeley, Matthew P; Hasnain, Samar S; Antonyuk, Svetlana V

2015-07-01

The International Year of Crystallography saw the number of macromolecular structures deposited in the Protein Data Bank cross the 100000 mark, with more than 90000 of these provided by X-ray crystallography. The number of X-ray structures determined to sub-atomic resolution (i.e. ≤1 Å) has passed 600 and this is likely to continue to grow rapidly with diffraction-limited synchrotron radiation sources such as MAX-IV (Sweden) and Sirius (Brazil) under construction. A dozen X-ray structures have been deposited to ultra-high resolution (i.e. ≤0.7 Å), for which precise electron density can be exploited to obtain charge density and provide information on the bonding character of catalytic or electron transfer sites. Although the development of neutron macromolecular crystallography over the years has been far less pronounced, and its application much less widespread, the availability of new and improved instrumentation, combined with dedicated deuteration facilities, are beginning to transform the field. Of the 83 macromolecular structures deposited with neutron diffraction data, more than half (49/83, 59%) were released since 2010. Sub-mm(3) crystals are now regularly being used for data collection, structures have been determined to atomic resolution for a few small proteins, and much larger unit-cell systems (cell edges >100 Å) are being successfully studied. While some details relating to H-atom positions are tractable with X-ray crystallography at sub-atomic resolution, the mobility of certain H atoms precludes them from being located. In addition, highly polarized H atoms and protons (H(+)) remain invisible with X-rays. Moreover, the majority of X-ray structures are determined from cryo-cooled crystals at 100 K, and, although radiation damage can be strongly controlled, especially since the advent of shutterless fast detectors, and by using limited doses and crystal translation at micro-focus beams, radiation damage can still take place. Neutron crystallography therefore remains the only approach where diffraction data can be collected at room temperature without radiation damage issues and the only approach to locate mobile or highly polarized H atoms and protons. Here a review of the current status of sub-atomic X-ray and neutron macromolecular crystallography is given and future prospects for combined approaches are outlined. New results from two metalloproteins, copper nitrite reductase and cytochrome c', are also included, which illustrate the type of information that can be obtained from sub-atomic-resolution (∼0.8 Å) X-ray structures, while also highlighting the need for complementary neutron studies that can provide details of H atoms not provided by X-ray crystallography.

Enhanced squeezing of a collective spin via control of its qudit subsystems.

PubMed

Norris, Leigh M; Trail, Collin M; Jessen, Poul S; Deutsch, Ivan H

2012-10-26

Unitary control of qudits can improve the collective spin squeezing of an atomic ensemble. Preparing the atoms in a state with large quantum fluctuations in magnetization strengthens the entangling Faraday interaction. The resulting increase in interatomic entanglement can be converted into metrologically useful spin squeezing. Further control can squeeze the internal atomic spin without compromising entanglement, providing an overall multiplicative factor in the collective squeezing. We model the effects of optical pumping and study the tradeoffs between enhanced entanglement and decoherence. For realistic parameters we see improvements of ~10 dB.

Modeling of Photoionized Plasmas

NASA Technical Reports Server (NTRS)

Kallman, Timothy R.

2010-01-01

In this paper I review the motivation and current status of modeling of plasmas exposed to strong radiation fields, as it applies to the study of cosmic X-ray sources. This includes some of the astrophysical issues which can be addressed, the ingredients for the models, the current computational tools, the limitations imposed by currently available atomic data, and the validity of some of the standard assumptions. I will also discuss ideas for the future: challenges associated with future missions, opportunities presented by improved computers, and goals for atomic data collection.

Ground-Laboratory to In-Space Atomic Oxygen Correlation for the PEACE Polymers

NASA Astrophysics Data System (ADS)

Stambler, Arielle H.; Inoshita, Karen E.; Roberts, Lily M.; Barbagallo, Claire E.; de Groh, Kim K.; Banks, Bruce A.

2009-01-01

The Materials International Space Station Experiment 2 (MISSE 2) Polymer Erosion and Contamination Experiment (PEACE) polymers were exposed to the environment of low Earth orbit (LEO) for 3.95 years from 2001 to 2005. There were forty-one different PEACE polymers, which were flown on the exterior of the International Space Station (ISS) in order to determine their atomic oxygen erosion yields. In LEO, atomic oxygen is an environmental durability threat, particularly for long duration mission exposures. Although space flight experiments, such as the MISSE 2 PEACE experiment, are ideal for determining LEO environmental durability of spacecraft materials, ground-laboratory testing is often relied upon for durability evaluation and prediction. Unfortunately, significant differences exist between LEO atomic oxygen exposure and atomic oxygen exposure in ground-laboratory facilities. These differences include variations in species, energies, thermal exposures and radiation exposures, all of which may result in different reactions and erosion rates. In an effort to improve the accuracy of ground-based durability testing, ground-laboratory to in-space atomic oxygen correlation experiments have been conducted. In these tests, the atomic oxygen erosion yields of the PEACE polymers were determined relative to Kapton H using a radio-frequency (RF) plasma asher (operated on air). The asher erosion yields were compared to the MISSE 2 PEACE erosion yields to determine the correlation between erosion rates in the two environments. This paper provides a summary of the MISSE 2 PEACE experiment; it reviews the specific polymers tested as well as the techniques used to determine erosion yield in the asher, and it provides a correlation between the space and ground-laboratory erosion yield values. Using the PEACE polymers' asher to in-space erosion yield ratios will allow more accurate in-space materials performance predictions to be made based on plasma asher durability evaluation.

Length and Dimensional Measurements at NIST

PubMed Central

Swyt, Dennis A.

2001-01-01

This paper discusses the past, present, and future of length and dimensional measurements at NIST. It covers the evolution of the SI unit of length through its three definitions and the evolution of NBS-NIST dimensional measurement from early linescales and gage blocks to a future of atom-based dimensional standards. Current capabilities include dimensional measurements over a range of fourteen orders of magnitude. Uncertainties of measurements on different types of material artifacts range down to 7×10−8 m at 1 m and 8 picometers (pm) at 300 pm. Current work deals with a broad range of areas of dimensional metrology. These include: large-scale coordinate systems; complex form; microform; surface finish; two-dimensional grids; optical, scanning-electron, atomic-force, and scanning-tunneling microscopies; atomic-scale displacement; and atom-based artifacts. PMID:27500015

The polarized atomic-beam target for the EDDA experiment and the time-reversal invariance test at COSY

NASA Astrophysics Data System (ADS)

Eversheim, P. D.; Altmeier, M.; Felden, O.

1997-02-01

For the the EDDA experiment, which was set up to measure the p¯-p¯ excitation function during the acceleration ramp of the cooler synchrotron COSY at Jülich, a polarized atomic-beam target was designed regarding the restrictions imposed by the geometry of the EDDA detector. Later, when the time-reversal invariance experiment is to be performed, the EDDA detector will serve as efficient internal polarimeter and the source has to deliver tensor polarized deuterons. The modular design of this polarized atomic-beam target that allows to meet these conditions will be discussed in comparison to other existing polarized atomic-beam targets.

Teleportation of atomic and photonic states in low-Q cavity QED

NASA Astrophysics Data System (ADS)

Peng, Zhao-Hui; Zou, Jian; Liu, Xiao-Juan; Kuang, Le-Man

2012-11-01

We propose two alternative teleportation protocols in low-Q cavity QED. Through the input-output process of photons, we can generate atom-photon entangled states as the quantum channel. Then we propose to teleport single-atom (two-atom entangled) state using coherent photonic states, and to teleport single photonic state with the assistance of three-level atom. The distinct feature of our protocols is that we can teleport both atomic and photonic states via the input-output process of photons in the low-Q cavity. Furthermore, as our protocols work in low-Q cavities and only involve virtual excitation of atoms, they are insensitive to both cavity decay and atomic spontaneous emission, and may be feasible with current technology.

SCALAR MULTI-PASS ATOMIC MAGNETOMETER

DTIC Science & Technology

2017-08-01

primarily by atomic shot noise. Furthermore, the spectrum of quantum spin noise provides information on the time correlation between the spins and...the resulting light to be shot -noise-limited both with and without the polarizer in place. Newer Vixar VCSELs with internal gratings on output...described on inside pages STINFO COPY AIR FORCE RESEARCH LABORATORY SENSORS DIRECTORATE WRIGHT-PATTERSON AIR FORCE BASE, OH 45433-7320

Evaluation of Low-Earth-Orbit Environmental Effects on International Space Station Thermal Control Materials

NASA Technical Reports Server (NTRS)

Dever, Joyce A.

1998-01-01

Many spacecraft thermal control coatings in low Earth orbit (LEO) can be affected by solar ultraviolet radiation and atomic oxygen. Ultraviolet radiation can darken some polymers and oxides commonly used in thermal control materials. Atomic oxygen can erode polymer materials, but it may reverse the ultraviolet-darkening effect on oxides. Maintaining the desired solar absorptance for thermal control coatings is important to assure the proper operating temperature of the spacecraft. Thermal control coatings to be used on the International Space Station (ISS) were evaluated for their performance after exposure in the NASA Lewis Research Center's Atomic Oxygen-Vacuum Ultraviolet Exposure (AO-VUV) facility. This facility simulated the LEO environments of solar vacuum ultraviolet (VUV) radiation (wavelength range, 115 to 200 nanometers (nm)) and VUV combined with atomic oxygen. Solar absorptance was measured in vacuo to eliminate the "bleaching" effects of ambient oxygen on VUV-induced degradation. The objective of these experiments was to determine solar absorptance increases of various thermal control materials due to exposure to simulated LEO conditions similar to those expected for ISS. Work was done in support of ISS efforts at the requests of Boeing Space and Defense Systems and Lockheed Martin Vought Systems.

Evaluation of Self-Propelled High-Energy Ultrasonic Atomizer on Azoxystrobin and Tebuconazole Application in Sunlit Greenhouse Tomatoes.

PubMed

Li, Yan-Jie; Li, Yi-Fan; Chen, Rong-Hua; Li, Xue-Sheng; Pan, Can-Ping; Song, Jian-Li

2018-05-28

In this study, a self-propelled high-energy ultrasonic atomizer was evaluated in terms of deposition on the canopy, the loss to the ground, and fungicide residues in cherry tomato and tomato. Artificial collectors fixed to the upper side and underside of the leaves at different depths and heights were used to collect the depositions. A reliable analytical method for determination of azoxystrobin and tebuconazole in artificial collectors and residue samples was developed by using liquid chromatography triple-quadrupole mass spectrometry. The results showed that the atomizer distributed the droplets evenly throughout the greenhouse with good uniformity (CVs below 39%). The ratio of depositions on the internal and external sides was 66⁻83%, and the ratio of depositions on the underside and upper side was 39⁻50%. There were no significant differences in depositions between two different height crops. The residues of azoxystrobin and tebuconazole in tomato and cherry tomato fruits were far below the maximum residue limits at harvest time. In general, self-propelled high-energy ultrasonic atomizer used in a greenhouse could increase the depositions, especially on the underside and internal side of the canopies, and lead to a reduction of operator exposure risk.

New Active Optical Technique Developed for Measuring Low-Earth-Orbit Atomic Oxygen Erosion of Polymers

NASA Technical Reports Server (NTRS)

Banks, Bruce A.; deGroh, Kim K.; Demko, Rikako

2003-01-01

Polymers such as polyimide Kapton (DuPont) and Teflon FEP (DuPont, fluorinated ethylene propylene) are commonly used spacecraft materials because of desirable properties such as flexibility, low density, and in the case of FEP, a low solar absorptance and high thermal emittance. Polymers on the exterior of spacecraft in the low-Earth-orbit (LEO) environment are exposed to energetic atomic oxygen. Atomic oxygen reaction with polymers causes erosion, which is a threat to spacecraft performance and durability. It is, therefore, important to understand the atomic oxygen erosion yield E (the volume loss per incident oxygen atom) of polymers being considered in spacecraft design. The most common technique for determining E is a passive technique based on mass-loss measurements of samples exposed to LEO atomic oxygen during a space flight experiment. There are certain disadvantages to this technique. First, because it is passive, data are not obtained until after the flight is completed. Also, obtaining the preflight and postflight mass measurements is complicated by the fact that many polymers absorb water and, therefore, the mass change due to water absorption can affect the E data. This is particularly true for experiments that receive low atomic oxygen exposures or for samples that have a very low E. An active atomic oxygen erosion technique based on optical measurements has been developed that has certain advantages over the mass-loss technique. This in situ technique can simultaneously provide the erosion yield data on orbit and the atomic oxygen exposure fluence, which is needed for erosion yield determination. In the optical technique, either sunlight or artificial light can be used to measure the erosion of semitransparent or opaque polymers as a result of atomic oxygen attack. The technique is simple and adaptable to a rather wide range of polymers, providing that they have a sufficiently high optical absorption coefficient. If one covers a photodiode with a uniformly thick sheet of semitransparent polymer such as Kapton H polyimide, then as atomic oxygen erodes the polymer, the short-circuit current from the photodiode will increase in an exponential manner with fluence. This nonlinear response with fluence results in a lack of sensitivity for measuring low atomic oxygen fluences. However, if one uses a variable-thickness polymer or carbon sample, which is configured as shown in the preceding figure, then a linear response can be achieved for opaque materials using a parabolic well for a circular geometry detector or a V-shaped well for a rectangular-geometry detector. Variable-thickness samples can be fabricated using many thin polymer layers. For semitransparent polymers such as Kapton H polyimide, there is an initial short-circuit current that is greater than zero. This current has a slightly nonlinear dependence on atomic oxygen fluence in comparison to opaque materials such as black Kapton as shown in the graph. For this graph figure, the total thickness of Kapton H was assumed to be 0.03 cm. The photodiode short-circuit current shown in the graph was generated on the basis of preliminary measurements-a total reflectance rho of 0.0424 and an optical absorption coefficient a of 146.5 cm(sup -1). In addition to obtaining on-orbit data, the advantage of this active erosion and erosion yield measurement technique is its simplicity and reliance upon well-characterized fluence witness materials as well as a nearly linear photodiode short-circuit current dependence upon atomic oxygen fluence. The optical technique is useful for measuring either atomic oxygen fluence or erosion, depending on the information desired. To measure the atomic oxygen erosion yield of a test material, one would need to have two photodiode sensors, one for the test material and one that uses a known erosion yield material (such as Kapton) to measure the atomic oxygen fluence.

Preparation of Greenberger-Horne-Zeilinger Entangled States in the Atom-Cavity Systems

NASA Astrophysics Data System (ADS)

Xu, Nan

2018-02-01

We present a new simple scheme for the preparation of Greenberger-Horne-Zeilinger maximally entangled states of two two-level atoms. The distinct feature of the effective Hamiltonian is that there is no energy exchange between the atoms and the cavity.. Thus the scheme is insensitive to the effect of cavity field and the atom radiation.This protocol may be realizable in the realm of current physical experiment.

The influence of current collector corrosion on the performance of electrochemical capacitors

NASA Astrophysics Data System (ADS)

Wojciechowski, Jarosław; Kolanowski, Łukasz; Bund, Andreas; Lota, Grzegorz

2017-11-01

This paper discusses the effect of current collector (stainless steel 316L) corrosion on the performance of electrochemical capacitors operated in aqueous electrolytes. This topic seems to be often neglected in scientific research. The studied electrolytes were 1 M H2SO4, 1 M KI, 1 M Na2SO4, 1 M KOH and 6 M KOH. The corrosion process was investigated by means of selected direct and alternating current techniques. The surface of the current collectors as well as the corrosion products were characterised using scanning electron microscopy, energy-dispersive X-ray spectroscopy, Raman spectroscopy and atomic force microscopy. Stainless steel 316L in alkaline solutions is characterised by the lowest values of corrosion potentials whereas the potentials in acidic media become the most noble. Our studies show that corrosion potentials increase with decreasing pH value. This phenomenon can be explained with the formation of passive oxide films on the stainless steel current collectors. The passive oxide films are usually thicker and more porous in alkaline solutions than that in the other electrolytes. The processes occurring at the electrode/electrolyte interfaces strongly influence the working parameters of electrochemical capacitors such as voltage, working potentials of single electrodes, self-discharge as well as the internal resistance and cycling stability.

The earth's ring current - Present situation and future thrusts

NASA Technical Reports Server (NTRS)

Williams, D. J.

1987-01-01

Particle distributions, currents, and the ring current situation prior to the August 1984 launch of the AMPTE Charge Composition Explorer (CCE) are discussed. CCE results which demonstrate the capability of these new measurements to pursue questions of ring current sources, energization, and transport are presented. Consideration is given to various ring current generation mechanisms which have been discussed in the literature, and a two-step generation process which to a certain extent unifies the previous mechanisms is presented. The first in-situ global observations of ring current decay as obtained through the detection of energetic neutral atoms generated by charge exchange interactions between the ring current and hydrogen geocorona are discussed, as well as the possibility of using the detection of energetic neutral atoms to obtain global images of the earth's ring current.

QED theory of multiphoton transitions in atoms and ions

NASA Astrophysics Data System (ADS)

Zalialiutdinov, Timur A.; Solovyev, Dmitry A.; Labzowsky, Leonti N.; Plunien, Günter

2018-03-01

This review surveys the quantum theory of electromagnetic radiation for atomic systems. In particular, a review of current theoretical studies of multiphoton processes in one and two-electron atoms and highly charged ions is provided. Grounded on the quantum electrodynamics description the multiphoton transitions in presence of cascades, spin-statistic behaviour of equivalent photons and influence of external electric fields on multiphoton in atoms and anti-atoms are discussed. Finally, the nonresonant corrections which define the validity of the concept of the excited state energy levels are introduced.

Direct solid analysis of powdered tungsten carbide hardmetal precursors by laser-induced argon spark ablation with inductively coupled plasma atomic emission spectrometry.

PubMed

Holá, Markéta; Kanický, Viktor; Mermet, Jean-Michel; Otruba, Vítezslav

2003-12-01

The potential of the laser-induced argon spark atomizer (LINA-Spark atomizer) coupled with ICP-AES as a convenient device for direct analysis of WC/Co powdered precursors of sintered hardmetals was studied. The samples were presented for the ablation as pressed pellets prepared by mixing with powdered silver binder containing GeO2 as internal standard. The pellets were ablated with the aid of a Q-switched Nd:YAG laser (1064 nm) focused 16 mm behind the target surface with a resulting estimated power density of 5 GW cm(-2). Laser ablation ICP-AES signals were studied as a function of ablation time, and the duration of time prior to measurement (pre-ablation time) which was necessary to obtain reliable results was about 40 s. Linear calibration plots were obtained up to 10% (m/m) Ti, 9% Ta and 3.5% Nb both without internal standardization and by using germanium as an added internal standard or tungsten as a contained internal standard. The relative uncertainty at the centroid of the calibration line was in the range from +/- 6% to +/- 11% for Nb, Ta and Ti both with and without internal standardisation by Ge. A higher spread of points about the regression was observed for cobalt for which the relative uncertainty at the centroid was in the range from +/- 9% to +/- 14%. Repeatability of results was improved by the use of both Ge and W internal standards. The lowest determinable quantities calculated for calibration plots were 0.060% Co, 0.010% Nb, 0.16% Ta and 0.030% Ti with internal standardization by Ge. The LA-ICP-AES analyses of real samples led to good agreement with the results obtained by solution-based ICP determination with a relative bias not exceeding 10%. The elimination of the dissolution procedure of powdered tungsten (Nb, Ta, Ti) carbide is the principal advantage of the developed LA-ICP-AES method.

PREFACE: 7th Asian International Seminar on Atomic and Molecular Physics

NASA Astrophysics Data System (ADS)

Deshmukh, Pranawa C.; Chakraborty, Purushottam; Williams, Jim F.

2007-09-01

These proceedings arose from the 7th Asian International Seminar on Atomic and Molecular Physics (AISAMP) which was held at the Indian Institute of Technology, Madras from 4-7 December 2006. The history of the AISAMP has been reviewed by Takayanagi http://www.physics.iitm.ac.in/~aisamp7/history.html. This international seminar/conference series grew out of the Japan-China meetings which were launched in 1985, the fourth of which was held in 1992 and carried a second title: The First Asian International Seminar on Atomic and Molecular Physics (AISAMP), thus providing a formal medium for scientists in this part of the world to report periodically and exchange their scientific thoughts. The founding nations of Japan and China were joined subsequently by Korea, Taiwan, India and Australia. The aims of the symposia included bringing together leading experts and students of atomic and molecular physics, the discussion of important problems, learning and sharing modern techniques and expanding the horizons of modern atomic and molecular physics. The fields of interest ranged from atomic and molecular structure and dynamics to photon, electron and positron scattering, to quantum information processing, the effects of symmetry and many body interactions, laser cooling, cold traps, electric and magnetic fields and to atomic and molecular physics with synchrotron radiation. Particular interest was evident in new techniques and the changes of the physical properties from atomic to condensed matter. Details of the 7th AISAMP, including the topics for the special sessions and the full programme, are available online at the conference website http://www.physics.iitm.ac.in/~aisamp7/. In total, 95 presentations were made at the 7th AISAMP, these included the Invited Talks and Contributed Poster Presentations, of which 52 appear in the present Proceedings after review by expert referees, refereed to the usual standard of the Institute of Physics journal: Journal of Physics B: Atomic, Molecular and Optical Physics. We received extensive support from the Journal of Physics: Conference Series staff; Graham Douglas, in particular, has been of tremendous help. The 7th AISAMP was very well attended and was sponsored primarily by the host Indian Institute of Technology, Madras (Chennai), the Board of Research in Nuclear Sciences, (Department of Atomic Energy, Government of India), the Department of Science and Technology, (Government of India), and the Asian Office of Aerospace Research and Development (AOARD) of the US Air Force. There was support from various quarters—each was invaluable and added to the success of the 7th AISAMP. We are very grateful to all the sponsors. It is superfluous to add that guidance and active participation from several colleagues within the host Institute was the primary source of strength for the actual organization of the conference and the multitude of arrangements for the organization came from the young graduate students at the IIT-Madras. We hope that this volume of Journal of Physics: Conference Series will be referenced widely and that it will strengthen ties between various countries in the region in and around Asia, and also of course to all scientists in this field the world over. Pranawa C Deshmukh, Purushottam Chakraborty and Jim F Williams Editors Conference photograph

An Assessment of the Potential Use of BNNTs for Boron Neutron Capture Therapy.

PubMed

Ferreira, Tiago H; Miranda, Marcelo C; Rocha, Zildete; Leal, Alexandre S; Gomes, Dawidson A; Sousa, Edesia M B

2017-04-12

Currently, nanostructured compounds have been standing out for their optical, mechanical, and chemical features and for the possibilities of manipulation and regulation of complex biological processes. One of these compounds is boron nitride nanotubes (BNNTs), which are a nanostructured material analog to carbon nanotubes, but formed of nitrogen and boron atoms. BNNTs present high thermal stability along with high chemical inertia. Among biological applications, its biocompatibility, cellular uptake, and functionalization potential can be highlighted, in addition to its eased utilization due to its nanometric size and tumor cell internalization. When it comes to new forms of therapy, we can draw attention to boron neutron capture therapy (BNCT), an experimental radiotherapy characterized by a boron-10 isotope carrier inside the target and a thermal neutron beam focused on it. The activation of the boron-10 atom by a neutron generates a lithium atom, a gamma ray, and an alpha particle, which can be used to destroy tumor tissues. The aim of this work was to use BNNTs as a boron-10 carrier for BNCT and to demonstrate its potential. The nanomaterial was characterized through XRD, FTIR, and SEM. The WST-8 assay was performed to confirm the cell viability of BNNTs. The cells treated with BNNTs were irradiated with the neutron beam of a Triga reactor, and the apoptosis caused by the activation of the BNNTs was measured with a calcein AM/propidium iodide test. The results demonstrate that this nanomaterial is a promising candidate for cancer therapy through BNCT.

Towards the distribution network of time and frequency

NASA Astrophysics Data System (ADS)

Lipiński, M.; Krehlik, P.; Śliwczyński, Ł.; Buczek, Ł.; Kołodziej, J.; Nawrocki, J.; Nogaś, P.; Dunst, P.; Lemański, D.; Czubla, A.; Pieczerak, J.; Adamowicz, W.; Pawszak, T.; Igalson, J.; Binczewski, A.; Bogacki, W.; Ostapowicz, P.; Stroiński, M.; Turza, K.

2014-05-01

In the paper the genesis, current stage and perspectives of the OPTIME project are described. The main goal of the project is to demonstrate that the newdeveloped at AGH technology of fiber optic transfer of the atomic clocks reference signals is ready to be used in building the domestic Time and Frequency distribution network. In the first part we summarize the two-year continuous operation of 420 kmlong link connecting the Laboratory of Time and Frequency at Central Office of Measures GUM in Warsaw and Time Service Laboratory at Astrogeodynamic Obserwatory AOS in Borowiec near Poznan. For the first time, we are reporting the two year comparison of UTC(PL) and UTC(AOS) atomic timescales with this link, and we refer it to the results of comparisons performed by GPS-based methods. We also address some practical aspects of maintaining time and frequency dissemination over fiber optical network. In the second part of the paper the concept of the general architecture of the distribution network with two Reference Time and Frequency Laboratories and local repositories is proposed. Moreover the brief project of the second branch connecting repositories in Poznan Polish Supercomputing and Networking Center and Torun Nicolaus Copernicus University with the first end-users in Torun such as National Laboratory of Atomic, Molecular and Optical Physics and Nicolaus Copernicus Astronomical Center is described. In the final part the perspective of developing the network both in the domestic range as far as extention with the international connections possibilities are presented.

Qubit-loss-free fusion of atomic W states via photonic detection

NASA Astrophysics Data System (ADS)

Ding, Cheng-Yun; Kong, Fan-Zhen; Yang, Qing; Yang, Ming; Cao, Zhuo-Liang

2018-06-01

In this paper, we propose two new qubit-loss-free (QLF) fusion schemes for W states in cavity QED system. Resonant interactions between atoms and single cavity mode constitute the main fusion mechanism, with which atomic |W_{n+m}> and |W_{n+m+q}> states can be generated, respectively, from a |Wn> and a |Wm>; and from a |Wn>, a |Wm> and a |Wq>, by detecting the cavity mode. The QLF property of the schemes makes them more efficient and simpler than the currently existing ones, and fewer intermediate steps and memory resources are required for generating a target large-scale W state. Furthermore, the fusion of atomic states can be realized via the detection on cavity mode rather than the much complicated atomic detection, which makes our schemes feasible. In addition, the analyses of the optimal resource cost and the experimental feasibility indicate that the present schemes are simple and efficient, and maybe implementable within the current experimental techniques.

Solar and Geothermal Energy: New Competition for the Atom

ERIC Educational Resources Information Center

Carter, Luther J.

1974-01-01

Describes new emphasis on research into solar and geothermal energy resources by governmental action and recent legislation and the decreased emphasis on atomic power in supplementing current energy shortages. (BR)

Internal force corrections with machine learning for quantum mechanics/molecular mechanics simulations.

PubMed

Wu, Jingheng; Shen, Lin; Yang, Weitao

2017-10-28

Ab initio quantum mechanics/molecular mechanics (QM/MM) molecular dynamics simulation is a useful tool to calculate thermodynamic properties such as potential of mean force for chemical reactions but intensely time consuming. In this paper, we developed a new method using the internal force correction for low-level semiempirical QM/MM molecular dynamics samplings with a predefined reaction coordinate. As a correction term, the internal force was predicted with a machine learning scheme, which provides a sophisticated force field, and added to the atomic forces on the reaction coordinate related atoms at each integration step. We applied this method to two reactions in aqueous solution and reproduced potentials of mean force at the ab initio QM/MM level. The saving in computational cost is about 2 orders of magnitude. The present work reveals great potentials for machine learning in QM/MM simulations to study complex chemical processes.

Intermediate-Size Inducer Pump design report. [LMFBR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boardman, T.J.

1979-06-15

This report summarizes the mechanical, structural, and hydrodynamic design of the Intermediate-Size Inducer Pump (ISIP). The design was performed under Atomics International's DOE Base Technology Program by the Atomics International and Rocketdyne Divisions of Rockwell International. The pump was designed to utilize the FFTF prototype pump frame as a test vehicle to test the inducer, impeller, and diffuser plus necessary adapter hardware under simulated Large Scale Liquid Metal Fast Breeder Reactor service conditions. The report describes the design requirements including the purpose and objectives, and discusses those design efforts and considerations made to meet the requirements. Included in the reportmore » are appendices showing calculative methods and results. Also included are overall assembly and layout drawings plus some details used as illustrations for discussion of the design results and the results of water tests performed on a model of the inducer.« less

Atomic-order thermal nitridation of group IV semiconductors for ultra-large-scale integration

NASA Astrophysics Data System (ADS)

Murota, Junichi; Le Thanh, Vinh

2015-03-01

One of the main requirements for ultra-large-scale integration (ULSI) is atomic-order control of process technology. Our concept of atomically controlled processing for group IV semiconductors is based on atomic-order surface reaction control in Si-based CVD epitaxial growth. On the atomic-order surface nitridation of a few nm-thick Ge/about 4 nm-thick Si0.5Ge0.5/Si(100) by NH3, it is found that N atoms diffuse through nm-order thick Ge layer into Si0.5Ge0.5/Si(100) substrate and form Si nitride, even at 500 °C. By subsequent H2 heat treatment, although N atomic amount in Ge layer is reduced drastically, the reduction of the Si nitride is slight. It is suggested that N diffusion in Ge layer is suppressed by the formation of Si nitride and that Ge/atomic-order N layer/Si1-xGex/Si (100) heterostructure is formed. These results demonstrate the capability of CVD technology for atomically controlled nitridation of group IV semiconductors for ultra-large-scale integration. Invited talk at the 7th International Workshop on Advanced Materials Science and Nanotechnology IWAMSN2014, 2-6 November, 2014, Ha Long, Vietnam.

Magnetic conveyor belt for transporting and merging trapped atom clouds.

PubMed

Hänsel, W; Reichel, J; Hommelhoff, P; Hänsch, T W

2001-01-22

We demonstrate an integrated magnetic device which transports cold atoms near a surface with very high positioning accuracy. Time-dependent currents in a lithographic conductor pattern create a moving chain of potential wells; atoms are transported in these wells while remaining confined in all three dimensions. We achieve mean fluxes up to 10(6) s(-1) with a negligible heating rate. An extension of this device allows merging of atom clouds by unification of two Ioffe-Pritchard potentials. The unification, which we demonstrate experimentally, can be performed without loss of phase space density. This novel, all-magnetic atom manipulation offers exciting perspectives, such as trapped-atom interferometry.

Absolute frequency measurement of the ? optical clock transition in ? with an uncertainty of ? using a frequency link to international atomic time

NASA Astrophysics Data System (ADS)

Baynham, Charles F. A.; Godun, Rachel M.; Jones, Jonathan M.; King, Steven A.; Nisbet-Jones, Peter B. R.; Baynes, Fred; Rolland, Antoine; Baird, Patrick E. G.; Bongs, Kai; Gill, Patrick; Margolis, Helen S.

2018-03-01

The highly forbidden ? electric octupole transition in ? is a potential candidate for a redefinition of the SI second. We present a measurement of the absolute frequency of this optical transition, performed using a frequency link to International Atomic Time to provide traceability to the SI second. The ? optical frequency standard was operated for 76% of a 25-day period, with the absolute frequency measured to be 642 121 496 772 645.14(26) Hz. The fractional uncertainty of ? is comparable to that of the best previously reported measurement, which was made by a direct comparison to local caesium primary frequency standards.

Melting of isolated tin nanoparticles

PubMed

Bachels; Guntherodt; Schafer

2000-08-07

The melting of isolated neutral tin cluster distributions with mean sizes of about 500 atoms has been investigated in a molecular beam experiment by calorimetrically measuring the clusters' formation energies as a function of their internal temperature. For this purpose the possibility to adjust the temperature of the clusters' internal degrees of freedom by means of the temperature of the cluster source's nozzle was exploited. The melting point of the investigated tin clusters was found to be lowered by 125 K and the latent heat of fusion per atom is reduced by 35% compared to bulk tin. The melting behavior of the isolated tin clusters is discussed with respect to the occurrence of surface premelting.

Chernobyl: an unbelievable failure to help.

PubMed

Bertell, Rosalie

2008-01-01

The disaster at the Chernobyl power reactor near Kiev, which began on April 26, 1986, was one of the world's worst industrial accidents. Yet the global community, usually most generous in its aid to a stricken community, has been slow to understand the scope of the disaster and reach out to the most devastated people of Ukraine, Belarus, and Russia. This article probes the causes of this confusion of perception and failure of response; clearly the problem is one of communication. Has the International Atomic Energy Agency betrayed the victims of the Chernobyl disaster because of its plans to promote the "peaceful atom" nuclear program in the developing world? Has the World Health Organization failed to provide clear, reliable information on the health effects resulting from the disaster? Are other historical problems or actors interfering with reasonable handling of the late effects of a nuclear disaster? Most importantly, what can be done to remedy this situation, to assist those most hurt by the late effects of Chernobyl and prevent such injustice in future? With the current promotion of nuclear energy as a "solution" to global climate change, we need to take a sober second look at the nuclear energy experiment and management of its hazards.

Concept for Inclusion of Analytical and Computational Capability in Optical Plume Anomaly Detection (OPAD) for Measurement of Neutron Flux

NASA Technical Reports Server (NTRS)

Patrick, M. Clinton; Cooper, Anita E.; Powers, W. T.

2004-01-01

Researchers are working on many konts to make possible high speed, automated classification and quantification of constituent materials in numerous environments. NASA's Marshall Space Flight Center has implemented a system for rocket engine flow fields/plumes; the Optical Plume Anomaly Detection (OPAD) system was designed to utilize emission and absorption spectroscopy for monitoring molecular and atomic particulates in gas plasma. An accompanying suite of tools and analytical package designed to utilize information collected by OPAD is known as the Engine Diagnostic Filtering System (EDIFIS). The current combination of these systems identifies atomic and molecular species and quantifies mass loss rates in H2/O2 rocket plumes. Additionally, efforts are being advanced to hardware encode components of the EDIFIS in order to address real-time operational requirements for health monitoring and management. This paper addresses the OPAD with its tool suite, and discusses what is considered a natural progression: a concept for migrating OPAD towards detection of high energy particles, including neutrons and gamma rays. The integration of these tools and capabilities will provide NASA with a systematic approach to monitor space vehicle internal and external environment.

NOVA SCIENCE UNIT 15, FUNDAMENTAL PARTICLES 4.

ERIC Educational Resources Information Center

1964

THE PRINCIPLES OF ATOMIC STRUCTURE WHICH ARE STRESSED ARE THAT ATOMS ARE MADE UP OF A NUCLEUS WITH A POSITIVE CHARGE, SURROUNDED BY ELECTRONS WITH A NEGATIVE CHARGE, AND THAT THERE IS NO CHANGE IN THE ATOM WHEN THE POSITIVE AND NEGATIVE CHARGES ARE EQUAL. EXPERIMENTS ILLUSTRATE THAT CURRENT ELECTRICITY IS ACTUALLY ELECTRONS IN MOTION, THAT THERE…

Trapped atoms along nanophotonic resonators

NASA Astrophysics Data System (ADS)

Fields, Brian; Kim, May; Chang, Tzu-Han; Hung, Chen-Lung

2017-04-01

Many-body systems subject to long-range interactions have remained a very challenging topic experimentally. Ultracold atoms trapped in extreme proximity to the surface of nanophotonic structures provides a dynamic system combining the strong atom-atom interactions mediated by guided mode photons with the exquisite control implemented with trapped atom systems. The hybrid system promises pair-wise tunability of long-range interactions between atomic pseudo spins, allowing studies of quantum magnetism extending far beyond nearest neighbor interactions. In this talk, we will discuss our current status developing high quality nanophotonic ring resonators, engineered on CMOS compatible optical chips with integrated nanostructures that, in combination with a side illuminating beam, can realize stable atom traps approximately 100nm above the surface. We will report on our progress towards loading arrays of cold atoms near the surface of these structures and studying atom-atom interaction mediated by photons with high cooperativity.

INTRODUCTION: The 8th International Conference on Vacuum Ultraviolet Radiation Physics

NASA Astrophysics Data System (ADS)

Nilsson, Per Olof; Hedin, Lars

1987-01-01

The VUV conferences series The international conferences on vacuum ultraviolet radiation physics started in 1962, and are now being held every third year. VUV-8 took place at Lund University, August 4-8, 1986. VUV-9 will be arranged at the University of Hawaii, USA, August 14-18, 1989, with Prof. C S Fadley as conference chairman. Chairman of the international advisory board for the period 1986-89 is Prof. L Hedin. The theme of the series can be summarized as experimental and theoretical progress in research fields utilizing the interaction of VUV radiation with matter. The topics cover broad areas within atomic and molecular physics, solid state physics and VUV instrumentation. The conferences emphasize interdisciplinary aspects. To these belong common experimental techniques as, e.g., synchrotron radiation instrumentation, and common theoretical foundations for the description of photon interactions with matter. The VUV-8 conference The VUV-8 conference in Lund was attended by 300 participants from 26 countries. An address list of the participants is given at the end of this volume. There were 33 invited papers given as plenary or key-note talks. As many as 229 posters were presented; 49 of them were also given orally. These numbers are typical for the VUV conferences, except for the number of posters, which was unusually large. In the conference planning the poster sessions were stressed, and particular care was taken to provide a good atmosphere at these sessions. Thus the posters were kept up during the whole conference, coffee was served in the hail with the posters and there were convenient places to sit down close to the posters. Considering the wide scope of the conference it was necessary to emphasize a limited number of topics of high current interest and importance. Thus besides traditional topics, several rapidly expanding fields were discussed in special sessions. At VUV-8 there were the following sessions. Theory of atoms and molecules photoabsorption and -ionization of atoms and molecules and related phenomena multiphoton and other dynamical processes plasma physics VUV lasers time resolved spectroscopy instrumentation for VUV radiation synchrotron radiation centres solid state spectroscopy dynamical processes involving localized levels fundamental aspects of photoemission spin-polarized photoemission inverse photoemission semiconductors organic materials adsorbates Proceedings of VUV-8 The present volume contains most of the invited papers (28 out of 33). Regarding the contributed papers, over 50 are now being published in regular issues of PHYSICA SCRIPTA. These papers will also appear in a reprint volume, PHYSICA SCRIPTA RS4, which soon will be available. Abstracts of invited and contributed papers appeared in three conference volumes as follows: Volume I: Atomic and molecular physics. Instrumentation. Volume II: Solid state physics. Volume III: Post deadline papers. These books have been registered in an international data base and can thus be cited as published documents. Copies may be received from the conference secretary.* Acknowledgements We would like to thank our sponsors, which are listed on the following page, the members of the international program committee, and all others who helped in the planning of the program. Above all we like to thank those who worked with the local organization. Due to their dedicated efforts the conference ran very smoothly with a pleasant atmosphere.

Spin-dependent electronic transport properties of transition metal atoms doped α-armchair graphyne nanoribbons

NASA Astrophysics Data System (ADS)

Fotoohi, Somayeh; Haji-Nasiri, Saeed

2018-04-01

Spin-dependent electronic transport properties of single 3d transition metal (TM) atoms doped α-armchair graphyne nanoribbons (α-AGyNR) are investigated by non-equilibrium Green's function (NEGF) method combined with density functional theory (DFT). It is found that all of the impurity atoms considered in this study (Fe, Co, Ni) prefer to occupy the sp-hybridized C atom site in α-AGyNR, and the obtained structures remain planar. The results show that highly localized impurity states are appeared around the Fermi level which correspond to the 3d orbitals of TM atoms, as can be derived from the projected density of states (PDOS). Moreover, Fe, Co, and Ni doped α-AGyNRs exhibit magnetic properties due to the strong spin splitting property of the energy levels. Also for each case, the calculated current-voltage characteristic per super-cell shows that the spin degeneracy in the system is obviously broken and the current becomes strongly spin dependent. Furthermore, a high spin-filtering effect around 90% is found under the certain bias voltages in Ni doped α-AGyNR. Additionally, the structure with Ni impurity reveals transfer characteristic that is suitable for designing a spin current switch. Our findings provide a high possibility to design the next generation spin nanodevices with novel functionalities.

Magnesium-based methods, systems, and devices

DOEpatents

Zhao, Yufeng; Ban, Chunmei; Ruddy, Daniel; Parilla, Philip A.; Son, Seoung-Bum

2017-12-12

An aspect of the present invention is an electrical device, where the device includes a current collector and a porous active layer electrically connected to the current collector to form an electrode. The porous active layer includes MgB.sub.x particles, where x.gtoreq.1, mixed with a conductive additive and a binder additive to form empty interstitial spaces between the MgB.sub.x particles, the conductive additive, and the binder additive. The MgB.sub.x particles include a plurality of boron sheets of boron atoms covalently bound together, with a plurality of magnesium atoms reversibly intercalated between the boron sheets and ionically bound to the boron atoms.

Scanning ion-conductance and atomic force microscope with specialized sphere-shaped nanopippettes

NASA Astrophysics Data System (ADS)

Zhukov, M. V.; Sapozhnikov, I. D.; Golubok, A. O.; Chubinskiy-Nadezhdin, V. I.; Komissarenko, F. E.; Lukashenko, S. Y.

2017-11-01

A scanning ion-conductance microscope was designed on the basis of scanning probe microscope NanoTutor. The optimal parameters of nanopipettes fabrication were found according to scanning electron microscopy diagnostics, current-distance I (Z) and current-voltage characteristics. A comparison of images of test objects, including biological samples, was carried out in the modes of optical microscopy, atomic force microscopy and scanning ion-conductance microscopy. Sphere-shaped nanopippettes probes were developed and tested to increase the stability of pipettes, reduce invasiveness and improve image quality of atomic force microscopy in tapping mode. The efficiency of sphere-shaped nanopippettes is shown.

Time-dependent density-functional theory simulation of local currents in pristine and single-defect zigzag graphene nanoribbons

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, Shenglai, E-mail: shenglai.he@vanderbilt.edu; Russakoff, Arthur; Li, Yonghui

2016-07-21

The spatial current distribution in H-terminated zigzag graphene nanoribbons (ZGNRs) under electrical bias is investigated using time-dependent density-functional theory solved on a real-space grid. A projected complex absorbing potential is used to minimize the effect of reflection at simulation cell boundary. The calculations show that the current flows mainly along the edge atoms in the hydrogen terminated pristine ZGNRs. When a vacancy is introduced to the ZGNRs, loop currents emerge at the ribbon edge due to electrons hopping between carbon atoms of the same sublattice. The loop currents hinder the flow of the edge current, explaining the poor electric conductancemore » observed in recent experiments.« less

Effect of the seed layer on the Y0.5Gd0.5Ba2Cu3O7-σ film fabricated by PLD

NASA Astrophysics Data System (ADS)

Yao, Yanjie; Wang, Wei; Liu, Linfei; Lu, Saidan; Wu, Xiang; Zheng, Tong; Liu, Shunfan; Li, Yijie

2018-06-01

The surface morphology and internal residual stress have influence on the critical current density (Jc) of REBa2Cu3O7-σ (REBCO) coated conductor. In order to modulate them, a series of Y0.5Gd0.5Ba2Cu3O7-σ (YGBCO) films were prepared by pulsed laser deposition (PLD) through introducing a seed layer in this paper. The thicknesses of seed layer changes from about 2 nm to 30 nm. For comparison, a standard sample without seed layer was fabricated at the same deposition condition. The surface morphology was illustrated by Scanning electron microscopy (SEM). The surface roughness was scanned by Atomic force microscopy (AFM). The microstructure and internal strain were measured by X-ray Diffraction (XRD). DC four-probe method was used to measure the critical current of the samples at 77 K and self-field. As a result, all samples have high Jc of about 4 MA/cm2, while the self-field Jc of the YGBCO films can be promoted by the seed layer. The results of our research work are as follows. First of all, seed layer makes the deposition of the YGBCO layer much easier to control. By this way, we can decrease the surface roughness of the samples. Furthermore, the internal residual stress of the YGBCO films with seed layer decrease. Finally, the best thickness of the seed layer was found by summarizing and analyzing the conditions of seed layer.

Understanding Chemistry: Current and Possible

ERIC Educational Resources Information Center

Sanderson, R. T.

1976-01-01

Describes an instructional approach for teaching the cause-and-effect relationship between the qualities of atoms and the properties of their chemical compositions. Discusses atomic structure, ionization energies, homonuclear and heteronuclear bonding, and bond dissociation. (MLH)

Atom chips in the real world: the effects of wire corrugation

NASA Astrophysics Data System (ADS)

Schumm, T.; Estève, J.; Figl, C.; Trebbia, J.-B.; Aussibal, C.; Nguyen, H.; Mailly, D.; Bouchoule, I.; Westbrook, C. I.; Aspect, A.

2005-02-01

We present a detailed model describing the effects of wire corrugation on the trapping potential experienced by a cloud of atoms above a current carrying micro wire. We calculate the distortion of the current distribution due to corrugation and then derive the corresponding roughness in the magnetic field above the wire. Scaling laws are derived for the roughness as a function of height above a ribbon shaped wire. We also present experimental data on micro wire traps using cold atoms which complement some previously published measurements [CITE] and which demonstrate that wire corrugation can satisfactorily explain our observations of atom cloud fragmentation above electroplated gold wires. Finally, we present measurements of the corrugation of new wires fabricated by electron beam lithography and evaporation of gold. These wires appear to be substantially smoother than electroplated wires.

Proceedings of the International Workshop on Condensed Matter Theories (8th) Held in San Juan, Puerto Rico on 1-5 June 1992

DTIC Science & Technology

1993-01-15

Canosa, R. Rossignoli and A. Plastino 10. Time-dependent N-Level Systems J. Aliaga , J.L Gruver and A. N. Proto 7 4 Atoms and Molecules 1. Atoms in...Interfacial Phase Transitions Underlying Amphiphile Micellar Self-Assembly A. Robledo and C. Varea 3. Hot-solid Properties From Liquid Structure Within

Classification of ligand molecules in PDB with graph match-based structural superposition.

PubMed

Shionyu-Mitsuyama, Clara; Hijikata, Atsushi; Tsuji, Toshiyuki; Shirai, Tsuyoshi

2016-12-01

The fast heuristic graph match algorithm for small molecules, COMPLIG, was improved by adding a structural superposition process to verify the atom-atom matching. The modified method was used to classify the small molecule ligands in the Protein Data Bank (PDB) by their three-dimensional structures, and 16,660 types of ligands in the PDB were classified into 7561 clusters. In contrast, a classification by a previous method (without structure superposition) generated 3371 clusters from the same ligand set. The characteristic feature in the current classification system is the increased number of singleton clusters, which contained only one ligand molecule in a cluster. Inspections of the singletons in the current classification system but not in the previous one implied that the major factors for the isolation were differences in chirality, cyclic conformations, separation of substructures, and bond length. Comparisons between current and previous classification systems revealed that the superposition-based classification was effective in clustering functionally related ligands, such as drugs targeted to specific biological processes, owing to the strictness of the atom-atom matching.

Multipolar electrostatics based on the Kriging machine learning method: an application to serine.

PubMed

Yuan, Yongna; Mills, Matthew J L; Popelier, Paul L A

2014-04-01

A multipolar, polarizable electrostatic method for future use in a novel force field is described. Quantum Chemical Topology (QCT) is used to partition the electron density of a chemical system into atoms, then the machine learning method Kriging is used to build models that relate the multipole moments of the atoms to the positions of their surrounding nuclei. The pilot system serine is used to study both the influence of the level of theory and the set of data generator methods used. The latter consists of: (i) sampling of protein structures deposited in the Protein Data Bank (PDB), or (ii) normal mode distortion along either (a) Cartesian coordinates, or (b) redundant internal coordinates. Wavefunctions for the sampled geometries were obtained at the HF/6-31G(d,p), B3LYP/apc-1, and MP2/cc-pVDZ levels of theory, prior to calculation of the atomic multipole moments by volume integration. The average absolute error (over an independent test set of conformations) in the total atom-atom electrostatic interaction energy of serine, using Kriging models built with the three data generator methods is 11.3 kJ mol⁻¹ (PDB), 8.2 kJ mol⁻¹ (Cartesian distortion), and 10.1 kJ mol⁻¹ (redundant internal distortion) at the HF/6-31G(d,p) level. At the B3LYP/apc-1 level, the respective errors are 7.7 kJ mol⁻¹, 6.7 kJ mol⁻¹, and 4.9 kJ mol⁻¹, while at the MP2/cc-pVDZ level they are 6.5 kJ mol⁻¹, 5.3 kJ mol⁻¹, and 4.0 kJ mol⁻¹. The ranges of geometries generated by the redundant internal coordinate distortion and by extraction from the PDB are much wider than the range generated by Cartesian distortion. The atomic multipole moment and electrostatic interaction energy predictions for the B3LYP/apc-1 and MP2/cc-pVDZ levels are similar, and both are better than the corresponding predictions at the HF/6-31G(d,p) level.

Neutral atom analyzers for diagnosing hot plasmas: A review of research at the ioffe physicotechnical institute

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kislyakov, A. I.; Petrov, M. P.

2009-07-15

Research on neutral particle diagnostics of thermonuclear plasmas that has been carried out in recent years at the Ioffe Physicotechnical Institute of the Russian Academy of Sciences (St. Petersburg, Russia) is reviewed. Work on the creation and improvement of neutral atom analyzers was done in two directions: for potential applications (in particular, on the International Thermonuclear Experimental Reactor, which is now under construction at Cadarache in France) and for investigation of the ion plasma component in various devices (in particular, in the largest tokamaks, such as JET, TFTR, and JT-60). Neutral atom analyzers are the main tool for studying themore » behavior of hydrogen ions and isotopes in magnetic confinement systems. They make it possible to determine energy spectra, to perform the isotope analysis of atom fluxes from the plasma, to measure the absolute intensity of the fluxes, and to record how these parameters vary with time. A comparative description of the analyzers developed in recent years at the Ioffe Institute is given. These are ACORD-12/24 analyzers for recording 0.2-100-keV hydrogen and deuterium atoms with a tunable range of simultaneously measured energies, CNPA compact analyzers for a fixed energy gain in the ranges 80-1000 eV and 0.8-100 keV, an ISEP analyzer for simultaneously recording the atoms of all the three hydrogen isotopes (H, D, and T) in the energy range 5-700 keV, and GEMMA analyzers for recording atom fluxes of hydrogen and helium isotopes in the range 0.1-4 MeV. The scintillating detectors of the ISEP and GEMMA analyzers have a lowered sensitivity to neutrons and thus can operate without additional shielding in neutron fields of up to 10{sup 9} n/(cm{sup 2} s). These two types of analyzers, intended to operate under deuterium-tritium plasma conditions, are prototypes of atom analyzers created at the Ioffe Institute for use in the International Thermonuclear Experimental Reactor. With these analyzers, a number of new results have been obtained in recent years in various devices. Some results are presented from investigation of ions in the Globus-M spherical tokamak, the W7-AS stellarator, and the JET tokamak by means of the analyzers developed at the Ioffe Institute. Challenges and opportunities for applying these diagnostics in the International Thermonuclear Experimental Reactor project are discussed.« less

Towards a rational approach for heavy-atom derivative screening in protein crystallography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agniswamy, Johnson; Joyce, M. Gordon; Hammer, Carl H.

2008-04-01

Heavy-atom derivatization is routinely used in protein structure determination and is thus of critical importance in structural biology. In order to replace the current trial-and-error heavy-atom derivative screening with a knowledge-based rational derivative-selection method, the reactivity of more than 40 heavy-atom compounds over a wide range of buffer and pH values was systematically examined using peptides which contained a single reactive amino-acid residue. Heavy-atom derivatization is routinely used in protein structure determination and is thus of critical importance in structural biology. In order to replace the current trial-and-error heavy-atom derivative screening with a knowledge-based rational derivative-selection method, the reactivity ofmore » more than 40 heavy-atom compounds over a wide range of buffer and pH values was systematically examined using peptides which contained a single reactive amino-acid residue. Met-, Cys- and His-containing peptides were derivatized against Hg, Au and Pt compounds, while Tyr-, Glu-, Asp-, Asn- and Gln-containing peptides were assessed against Pb compounds. A total of 1668 reactive conditions were examined using mass spectrometry and were compiled into heavy-atom reactivity tables. The results showed that heavy-atom derivatization reactions are highly linked to buffer and pH, with the most accommodating buffer being MES at pH 6. A group of 21 compounds were identified as most successful irrespective of ligand or buffer/pH conditions. To assess the applicability of the peptide heavy-atom reactivity to proteins, lysozyme crystals were derivatized with a list of peptide-reactive compounds that included both known and new compounds for lysozyme derivatization. The results showed highly consistent heavy-atom reactivities between the peptides and lysozyme.« less

Stimulated transitions in resonant atom Majorana mixing

NASA Astrophysics Data System (ADS)

Bernabéu, José; Segarra, Alejandro

2018-02-01

Massive neutrinos demand to ask whether they are Dirac or Majorana particles. Majorana neutrinos are an irrefutable proof of physics beyond the Standard Model. Neutrinoless double electron capture is not a process but a virtual Δ L = 2 mixing between a parent A Z atom and a daughter A ( Z - 2) excited atom with two electron holes. As a mixing between two neutral atoms and the observable signal in terms of emitted two-hole X-rays, the strategy, experimental signature and background are different from neutrinoless double beta decay. The mixing is resonantly enhanced for almost degeneracy and, under these conditions, there is no irreducible background from the standard two-neutrino channel. We reconstruct the natural time history of a nominally stable parent atom since its production either by nature or in the laboratory. After the time periods of atom oscillations and the decay of the short-lived daughter atom, at observable times the relevant "stationary" states are the mixed metastable long-lived state and the non-orthogonal short-lived excited state, as well as the ground state of the daughter atom. We find that they have a natural population inversion which is most appropriate for exploiting the bosonic nature of the observed atomic transitions radiation. Among different observables of the atom Majorana mixing, we include the enhanced rate of stimulated X-ray emission from the long-lived metastable state by a high-intensity X-ray beam: a gain factor of 100 can be envisaged at current XFEL facilities. On the other hand, the historical population of the daughter atom ground state can be probed by exciting it with a current pulsed optical laser, showing the characteristic absorption lines: the whole population can be excited in a shorter time than typical pulse duration.

Current global and Korean issues in radiation safety of nuclear medicine procedures.

PubMed

Song, H C

2016-06-01

In recent years, the management of patient doses in medical imaging has evolved as concern about radiation exposure has increased. Efforts and techniques to reduce radiation doses are focussed not only on the basis of patient safety, but also on the fundamentals of justification and optimisation in cooperation with international organisations such as the International Commission on Radiological Protection, the International Atomic Energy Agency, and the World Health Organization. The Image Gently campaign in children and Image Wisely campaign in adults to lower radiation doses have been initiated in the USA. The European Association of Nuclear Medicine paediatric dosage card, North American consensus guidelines, and Nuclear Medicine Global Initiative have recommended the activities of radiopharmaceuticals that should be administered in children. Diagnostic reference levels (DRLs), developed predominantly in Europe, may be an important tool to manage patient doses. In Korea, overexposure to radiation, even from the use of medical imaging, has become a public issue, particularly since the accident at the Fukushima nuclear power plant. As a result, the Korean Nuclear Safety and Security Commission revised the technical standards for radiation safety management in medical fields. In parallel, DRLs for nuclear medicine procedures have been collected on a nationwide scale. Notice of total effective dose from positron emission tomography-computed tomography for cancer screening has been mandatory since mid-November 2014. © The International Society for Prosthetics and Orthotics.

Quasi-Solid-State Single-Atom Transistors.

PubMed

Xie, Fangqing; Peukert, Andreas; Bender, Thorsten; Obermair, Christian; Wertz, Florian; Schmieder, Philipp; Schimmel, Thomas

2018-06-21

The single-atom transistor represents a quantum electronic device at room temperature, allowing the switching of an electric current by the controlled and reversible relocation of one single atom within a metallic quantum point contact. So far, the device operates by applying a small voltage to a control electrode or "gate" within the aqueous electrolyte. Here, the operation of the atomic device in the quasi-solid state is demonstrated. Gelation of pyrogenic silica transforms the electrolyte into the quasi-solid state, exhibiting the cohesive properties of a solid and the diffusive properties of a liquid, preventing the leakage problem and avoiding the handling of a liquid system. The electrolyte is characterized by cyclic voltammetry, conductivity measurements, and rotation viscometry. Thus, a first demonstration of the single-atom transistor operating in the quasi-solid-state is given. The silver single-atom and atomic-scale transistors in the quasi-solid-state allow bistable switching between zero and quantized conductance levels, which are integer multiples of the conductance quantum G 0  = 2e 2 /h. Source-drain currents ranging from 1 to 8 µA are applied in these experiments. Any obvious influence of the gelation of the aqueous electrolyte on the electron transport within the quantum point contact is not observed. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Polarized negative ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haeberli, W.

1981-04-01

This paper presents a survey of methods, commonly in use or under development, to produce beams of polarized negative ions for injection into accelerators. A short summary recalls how the hyperfine interaction is used to obtain nuclear polarization in beams of atoms. Atomic-beam sources for light ions are discussed. If the best presently known techniques are incorporated in all stages of the source, polarized H/sup -/ and D/sup -/ beams in excess of 10 ..mu..A can probably be achieved. Production of polarized ions from fast (keV) beams of polarized atoms is treated separately for atoms in the H(25) excited statemore » (Lamb-Shift source) and atoms in the H(1S) ground state. The negative ion beam from Lamb-Shift sources has reached a plateau just above 1 ..mu..A, but this beam current is adequate for many applications and the somewhat lower beam current is compensated by other desirable characteristics. Sources using fast polarized ground state atoms are in a stage of intense development. The next sections summarize production of polarized heavy ions by the atomic beam method, which is well established, and by optical pumping, which has recently been demonstrated to yield very large nuclear polarization. A short discussion of proposed ion sources for polarized /sup 3/He/sup -/ ions is followed by some concluding remarks.« less

A computer model for liquid jet atomization in rocket thrust chambers

NASA Astrophysics Data System (ADS)

Giridharan, M. G.; Lee, J. G.; Krishnan, A.; Yang, H. Q.; Ibrahim, E.; Chuech, S.; Przekwas, A. J.

1991-12-01

The process of atomization has been used as an efficient means of burning liquid fuels in rocket engines, gas turbine engines, internal combustion engines, and industrial furnaces. Despite its widespread application, this complex hydrodynamic phenomenon has not been well understood, and predictive models for this process are still in their infancy. The difficulty in simulating the atomization process arises from the relatively large number of parameters that influence it, including the details of the injector geometry, liquid and gas turbulence, and the operating conditions. In this study, numerical models are developed from first principles, to quantify factors influencing atomization. For example, the surface wave dynamics theory is used for modeling the primary atomization and the droplet energy conservation principle is applied for modeling the secondary atomization. The use of empirical correlations has been minimized by shifting the analyses to fundamental levels. During applications of these models, parametric studies are performed to understand and correlate the influence of relevant parameters on the atomization process. The predictions of these models are compared with existing experimental data. The main tasks of this study were the following: development of a primary atomization model; development of a secondary atomization model; development of a model for impinging jets; development of a model for swirling jets; and coupling of the primary atomization model with a CFD code.

A report on the implementation aspects of the International Atomic Energy Agency's first doctoral coordinated research project, "Management of liver cancer using radionuclide methods with special emphasis on trans-arterial radio-conjugate therapy and internal dosimetry".

PubMed

Padhy, Ajit Kumar; Dondi, Maurizio

2008-03-01

Liver cancer is one of the most dreaded cancers, and it is highly prevalent in the developing countries, where the resources are extremely scarce to deal with this disease using the current commercially available and expensive therapeutic radiopharmaceuticals. The International Atomic Energy Agency (IAEA), in pursuit of its mandate to promote the application of nuclear technology in the health care in its Member States, has developed and clinically evaluated a new and cost-effective therapeutic radio-conjugate, rhenium-188 ((188)Re)-lipiodol for the treatment of hepatocellular carcinoma through its first Doctoral Coordinated Research Project. The ready availability of no-carrier-added (188)Re from the tungsten-188/(188)Re generator represents a potentially important source of a therapeutic radioisotope for a broad range of therapeutic applications in nuclear medicine. The alumina-based tungsten-188/(188)Re generator system comes with reasonable cost and exhibits attractive therapeutic properties, excellent performance and very long useful shelf-life. Because of the long shelf-life of several months, the use of this generator offers a unique opportunity for the cost-effective and routine availability of a versatile therapeutic radioisotope on an on-demand basis. Further, using its extensive global network and outreach, the IAEA has also transferred the technology of the in-house preparation and use of (188)Re-labeled lipiodol to many institutions around the world, which can now prepare (188)Re-labeled lipiodol in their own radiopharmacy laboratories and treat patients. This effort of the IAEA in trying to address some of the challenges of liver cancer therapy in developing countries has been and truly a global venture with involvement and contributions from several organizations, institutions and numerous individuals. This article discusses some of the implementation aspects of this very important activity of the Agency.

Ethyl 2-[(carbamothioyl-amino)-imino]-propano-ate.

PubMed

Corrêa, Charlane C; Graúdo, José Eugênio J C; de Oliveira, Luiz Fernando C; de Almeida, Mauro V; Diniz, Renata

2011-08-01

The title compound, C(6)H(11)N(3)O(2)S, consists of a roughly planar mol-ecule (r.m.s deviation from planarity = 0.077 Å for the non-H atoms) and has the S atom in an anti position to the imine N atom. This N atom is the acceptor of a strongly bent inter-nal N-H⋯N hydrogen bond donated by the amino group. In the crystal, mol-ecules are arranged in undulating layers parallel to (010). The mol-ecules are linked via inter-molecular amino-carboxyl N-H⋯O hydrogen bonds, forming chains parallel to [001]. The chains are cross-linked by N(carbazone)-H⋯S and C-H⋯S inter-actions, forming infinite sheets.

Conductive atomic force microscopy studies on the transformation of GeSi quantum dots to quantum rings.

PubMed

Zhang, S L; Xue, F; Wu, R; Cui, J; Jiang, Z M; Yang, X J

2009-04-01

Conductive atomic force microscopy has been employed to study the topography and conductance distribution of individual GeSi quantum dots (QDs) and quantum rings (QRs) during the transformation from QDs to QRs by depositing an Si capping layer on QDs. The current distribution changes significantly with the topographic transformation during the Si capping process. Without the capping layer, the QDs are dome-shaped and the conductance is higher at the ring region between the center and boundary than that at the center. After capping with 0.32 nm Si, the shape of the QDs changes to pyramidal and the current is higher at both the center and the arris. When the Si capping layer increases to 2 nm, QRs are formed and the current of individual QRs is higher at the rim than that at the central hole. By comparing the composition distributions obtained by scanning Auger microscopy and atomic force microscopy combined with selective chemical etching, the origin of the current distribution change is discussed.

Report on the activities of the Danish Atomic Energy Commission up to 31 March 1957

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

1958-01-15

Activities of the Danish Atomic Energy Commission from its establishment in 1955 through March, 1957, are reported. The technical and administrative organization of the Commission are outlined. Contracts were signed for the purchase of two reactors. The site for a reactor research establishment was acquired on the Risoe Peninsula near Roskilde. Land for agricultural experiments was acquired nearby. Buildings and facilities were nearing completion by 1957. Training programs for personnel were held. Areas of international cooperation in the peaceful use of atomic energy are outlined. A statement of expenditures is included. (C.H.)

Assessing the engagement, learning, and overall experience of students operating an atomic absorption spectrophotometer with remote access technology.

PubMed

Erasmus, Daniel J; Brewer, Sharon E; Cinel, Bruno

2015-01-01

The use of internet-based technologies in the teaching of laboratories has emerged as a promising education tool. This study evaluated the effectiveness of using remote access technology to operate an atomic absorption spectrophotometer in analyzing the iron content in a crude myoglobin extract. Sixty-two students were surveyed on their level of engagement, learning, and overall experience. Feedback from students suggests that the use of remote access technology is effective in teaching students the principles of chemical analysis by atomic absorption spectroscopy. © 2014 The International Union of Biochemistry and Molecular Biology.

Structural transitions in electron beam deposited Co-carbonyl suspended nanowires at high electrical current densities.

PubMed

Gazzadi, Gian Carlo; Frabboni, Stefano

2015-01-01

Suspended nanowires (SNWs) have been deposited from Co-carbonyl precursor (Co2(CO)8) by focused electron beam induced deposition (FEBID). The SNWs dimensions are about 30-50 nm in diameter and 600-850 nm in length. The as-deposited material has a nanogranular structure of mixed face-centered cubic (FCC) and hexagonal close-packed (HCP) Co phases, and a composition of 80 atom % Co, 15 atom % O and 5 atom % C, as revealed by transmission electron microscopy (TEM) analysis and by energy-dispersive X-ray (EDX) spectroscopy, respectively. Current (I)-voltage (V) measurements with current densities up to 10(7) A/cm(2) determine different structural transitions in the SNWs, depending on the I-V history. A single measurement with a sudden current burst leads to a polycrystalline FCC Co structure extended over the whole wire. Repeated measurements at increasing currents produce wires with a split structure: one half is polycrystalline FCC Co and the other half is graphitized C. The breakdown current density is found at 2.1 × 10(7) A/cm(2). The role played by resistive heating and electromigration in these transitions is discussed.

Clarifying atomic weights: A 2016 four-figure table of standard and conventional atomic weights

USGS Publications Warehouse

Coplen, Tyler B.; Meyers, Fabienne; Holden, Norman E.

2017-01-01

To indicate that atomic weights of many elements are not constants of nature, in 2009 and 2011 the Commission on Isotopic Abundances and Atomic Weights (CIAAW) of the International Union of Pure and Applied Chemistry (IUPAC) replaced single-value standard atomic weight values with atomic weight intervals for 12 elements (hydrogen, lithium, boron, carbon, nitrogen, oxygen, magnesium, silicon, sulfur, chlorine, bromine, and thallium); for example, the standard atomic weight of nitrogen became the interval [14.00643, 14.00728]. CIAAW recognized that some users of atomic weight data only need representative values for these 12 elements, such as for trade and commerce. For this purpose, CIAAW provided conventional atomic weight values, such as 14.007 for nitrogen, and these values can serve in education when a single representative value is needed, such as for molecular weight calculations. Because atomic weight values abridged to four figures are preferred by many educational users and are no longer provided by CIAAW as of 2015, we provide a table containing both standard atomic weight values and conventional atomic weight values abridged to four figures for the chemical elements. A retrospective review of changes in four-digit atomic weights since 1961 indicates that changes in these values are due to more accurate measurements over time or to the recognition of the impact of natural isotopic fractionation in normal terrestrial materials upon atomic weight values of many elements. Use of the unit “u” (unified atomic mass unit on the carbon mass scale) with atomic weight is incorrect because the quantity atomic weight is dimensionless, and the unit “amu” (atomic mass unit on the oxygen scale) is an obsolete term: Both should be avoided.

Adsorption of O_{2} on Ag(111): Evidence of Local Oxide Formation.

PubMed

Andryushechkin, B V; Shevlyuga, V M; Pavlova, T V; Zhidomirov, G M; Eltsov, K N

2016-07-29

The atomic structure of the disordered phase formed by oxygen on Ag(111) at low coverage is determined by a combination of low-temperature scanning tunneling microscopy and density functional theory. We demonstrate that the previous assignment of the dark objects in STM to chemisorbed oxygen atoms is incorrect and incompatible with trefoil-like structures observed in atomic-resolution images in current work. In our model, each object is an oxidelike ring formed by six oxygen atoms around the vacancy in Ag(111).

Theory of ionizing neutrino-atom collisions: The role of atomic recoil

NASA Astrophysics Data System (ADS)

Kouzakov, Konstantin A.; Studenikin, Alexander I.

2016-04-01

We consider theoretically ionization of an atom by neutrino impact taking into account electromagnetic interactions predicted for massive neutrinos by theories beyond the Standard Model. The effects of atomic recoil in this process are estimated using the one-electron and semiclassical approximations and are found to be unimportant unless the energy transfer is very close to the ionization threshold. We show that the energy scale where these effects become important is insignificant for current experiments searching for magnetic moments of reactor antineutrinos.

Metal atomization spray nozzle

DOEpatents

Huxford, Theodore J.

1993-01-01

A spray nozzle for a magnetohydrodynamic atomization apparatus has a feed passage for molten metal and a pair of spray electrodes mounted in the feed passage. The electrodes, diverging surfaces which define a nozzle throat and diverge at an acute angle from the throat. Current passes through molten metal when fed through the throat which creates the Lorentz force necessary to provide atomization of the molten metal.

The influence of atomic alignment on absorption and emission spectroscopy

NASA Astrophysics Data System (ADS)

Zhang, Heshou; Yan, Huirong; Richter, Philipp

2018-06-01

Spectroscopic observations play essential roles in astrophysics. They are crucial for determining physical parameters in the universe, providing information about the chemistry of various astronomical environments. The proper execution of the spectroscopic analysis requires accounting for all the physical effects that are compatible to the signal-to-noise ratio. We find in this paper the influence on spectroscopy from the atomic/ground state alignment owing to anisotropic radiation and modulated by interstellar magnetic field, has significant impact on the study of interstellar gas. In different observational scenarios, we comprehensively demonstrate how atomic alignment influences the spectral analysis and provide the expressions for correcting the effect. The variations are even more pronounced for multiplets and line ratios. We show the variation of the deduced physical parameters caused by the atomic alignment effect, including alpha-to-iron ratio ([X/Fe]) and ionisation fraction. Synthetic observations are performed to illustrate the visibility of such effect with current facilities. A study of PDRs in ρ Ophiuchi cloud is presented to demonstrate how to account for atomic alignment in practice. Our work has shown that due to its potential impact, atomic alignment has to be included in an accurate spectroscopic analysis of the interstellar gas with current observational capability.

Atomically Thin Al2O3 Films for Tunnel Junctions

NASA Astrophysics Data System (ADS)

Wilt, Jamie; Gong, Youpin; Gong, Ming; Su, Feifan; Xu, Huikai; Sakidja, Ridwan; Elliot, Alan; Lu, Rongtao; Zhao, Shiping; Han, Siyuan; Wu, Judy Z.

2017-06-01

Metal-insulator-metal tunnel junctions are common throughout the microelectronics industry. The industry standard AlOx tunnel barrier, formed through oxygen diffusion into an Al wetting layer, is plagued by internal defects and pinholes which prevent the realization of atomically thin barriers demanded for enhanced quantum coherence. In this work, we employ in situ scanning tunneling spectroscopy along with molecular-dynamics simulations to understand and control the growth of atomically thin Al2O3 tunnel barriers using atomic-layer deposition. We find that a carefully tuned initial H2O pulse hydroxylated the Al surface and enabled the creation of an atomically thin Al2O3 tunnel barrier with a high-quality M -I interface and a significantly enhanced barrier height compared to thermal AlOx . These properties, corroborated by fabricated Josephson junctions, show that atomic-layer deposition Al2O3 is a dense, leak-free tunnel barrier with a low defect density which can be a key component for the next generation of metal-insulator-metal tunnel junctions.

Isomerization and fragmentation reactions of gaseous phenylarsane radical cations and phenylarsanyl cations. A study by tandem mass spectrometry and theoretical calculations.

PubMed

Letzel, Matthias; Kirchhoff, Dirk; Grützmacher, Hans-Friedrich; Stein, Daniel; Grützmacher, Hansjörg

2006-04-28

The unimolecular reactions of radical cations and cations derived from phenylarsane, C6H5AsH2 (1) and dideutero phenylarsane, C6H5AsD2 (1-d2), were investigated by methods of tandem mass spectrometry and theoretical calculations. The mass spectrometric experiments reveal that the molecular ion of phenylarsane, 1*+, exhibits different reactivity at low and high internal excess energy. Only at low internal energy the observed fragmentations are as expected, that is the molecular ion 1*+ decomposes almost exclusively by loss of an H atom. The deuterated derivative 1-d2 with an AsD2 group eliminates selectively a D atom under these conditions. The resulting phenylarsenium ion [C6H5AsH]+, 2+, decomposes rather easily by loss of the As atom to give the benzene radical cation [C6H6]*+ and is therefore of low abundance in the 70 eV EI mass spectrum. At high internal excess energy, the ion 1*+ decomposes very differently either by elimination of an H2 molecule, or by release of the As atom, or by loss of an AsH fragment. Final products of these reactions are either the benzoarsenium ion 4*+, or the benzonium ion [C6H7]+, or the benzene radical cation, [C6H6]*+. As key-steps, these fragmentations contain reductive eliminations from the central As atom under H-H or C-H bond formation. Labeling experiments show that H/D exchange reactions precede these fragmentations and, specifically, that complete positional exchange of the H atoms in 1*+ occurs. Computations at the UMP2/6-311+G(d)//UHF/6-311+G(d) level agree best with the experimental results and suggest: (i) 1*+ rearranges (activation enthalpy of 93 kJ mol(-1)) to a distinctly more stable (DeltaH(r)(298) = -64 kJ mol(-1)) isomer 1 sigma*+ with a structure best represented as a distonic radical cation sigma complex between AsH and benzene. (ii) The six H atoms of the benzene moiety of 1 sigma*+ become equivalent by a fast ring walk of the AsH group. (iii) A reversible isomerization 1+<==>1 sigma*+ scrambles eventually all H atoms over all positions in 1*+. The distonic radical cation 1*+ is predisposed for the elimination of an As atom or an AsH fragment. The calculations are in accordance with the experimentally preferred reactions when the As atom and the AsH fragment are generated in the quartet and triplet state, respectively. Alternatively, 1*(+) undergoes a reductive elimination of H2 from the AsH2 group via a remarkably stable complex of the phenylarsandiyl radical cation, [C6H5As]*+ and an H2 molecule.

Roothaan's approach to solve the Hartree-Fock equations for atoms confined by soft walls: Basis set with correct asymptotic behavior.

PubMed

Rodriguez-Bautista, Mariano; Díaz-García, Cecilia; Navarrete-López, Alejandra M; Vargas, Rubicelia; Garza, Jorge

2015-07-21

In this report, we use a new basis set for Hartree-Fock calculations related to many-electron atoms confined by soft walls. One- and two-electron integrals were programmed in a code based in parallel programming techniques. The results obtained with this proposal for hydrogen and helium atoms were contrasted with other proposals to study just one and two electron confined atoms, where we have reproduced or improved the results previously reported. Usually, an atom enclosed by hard walls has been used as a model to study confinement effects on orbital energies, the main conclusion reached by this model is that orbital energies always go up when the confinement radius is reduced. However, such an observation is not necessarily valid for atoms confined by penetrable walls. The main reason behind this result is that for atoms with large polarizability, like beryllium or potassium, external orbitals are delocalized when the confinement is imposed and consequently, the internal orbitals behave as if they were in an ionized atom. Naturally, the shell structure of these atoms is modified drastically when they are confined. The delocalization was an argument proposed for atoms confined by hard walls, but it was never verified. In this work, the confinement imposed by soft walls allows to analyze the delocalization concept in many-electron atoms.

Roothaan’s approach to solve the Hartree-Fock equations for atoms confined by soft walls: Basis set with correct asymptotic behavior

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rodriguez-Bautista, Mariano; Díaz-García, Cecilia; Navarrete-López, Alejandra M.

2015-07-21

In this report, we use a new basis set for Hartree-Fock calculations related to many-electron atoms confined by soft walls. One- and two-electron integrals were programmed in a code based in parallel programming techniques. The results obtained with this proposal for hydrogen and helium atoms were contrasted with other proposals to study just one and two electron confined atoms, where we have reproduced or improved the results previously reported. Usually, an atom enclosed by hard walls has been used as a model to study confinement effects on orbital energies, the main conclusion reached by this model is that orbital energiesmore » always go up when the confinement radius is reduced. However, such an observation is not necessarily valid for atoms confined by penetrable walls. The main reason behind this result is that for atoms with large polarizability, like beryllium or potassium, external orbitals are delocalized when the confinement is imposed and consequently, the internal orbitals behave as if they were in an ionized atom. Naturally, the shell structure of these atoms is modified drastically when they are confined. The delocalization was an argument proposed for atoms confined by hard walls, but it was never verified. In this work, the confinement imposed by soft walls allows to analyze the delocalization concept in many-electron atoms.« less

Atomic and molecular data for space astronomy - Needs, analysis, and availability; 21st IAU General Assembly, Buenos Aires, Argentina, July 23-Aug. 1, 1991, Selected Papers

NASA Technical Reports Server (NTRS)

Smith, Peter L. (Editor); Wiese, Wolfgang L. (Editor)

1992-01-01

The present volume on atomic and molecular spectroscopic data for space astrophysics discusses scientific problems and laboratory data needs associated with the Hubble Space Telescope, atomic data needed for far ultraviolet astronomy with HUT and FUSE and for analysis of EUV and X-ray spectra, and data for observations of interstellar medium with the Hubble Space Telescope. Attention is also given to atomic and molecular data for analysis of IR spectra from ISO and SIRTF, atomic data from the opacity project, sources of atomic spectroscopic data for astrophysics, and summary of current molecular data bases.

Simultaneous measurement of the surface temperature and the release of atomic sodium from a burning black liquor droplet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saw, Woei L.; Nathan, Graham J.; School of Mechanical Engineering, The University of Adelaide

2010-04-15

Simultaneous measurement of the concentration of released atomic sodium, swelling, surface and internal temperature of a burning black liquor droplet under a fuel lean and rich condition has been demonstrated. Two-dimensional two-colour optical pyrometry was employed to determine the distribution of surface temperature and swelling of a burning black liquor droplet while planar laser-induced fluorescence (PLIF) was used to assess the temporal release of atomic sodium. The key findings of these studies are: (i) the concentration of atomic sodium released during the drying and devolatilisation stages was found to be correlated with the external surface area; and (ii) the insignificantmore » presence of atomic sodium during the char consumption stage shows that sodium release is suppressed by the lower temperature and by the high CO{sub 2} content in and around the particle. (author)« less

Master equation with quantized atomic motion including dipole-dipole interactions

NASA Astrophysics Data System (ADS)

Damanet, François; Braun, Daniel; Martin, John

2016-05-01

We derive a markovian master equation for the internal dynamics of an ensemble of two-level atoms including all effects related to the quantization of their motion. Our equation provides a unifying picture of the consequences of recoil and indistinguishability of atoms beyond the Lamb-Dicke regime on both their dissipative and conservative dynamics, and is relevant for experiments with ultracold trapped atoms. We give general expressions for the decay rates and the dipole-dipole shifts for any motional states, and we find analytical formulas for a number of relevant states (Gaussian states, Fock states and thermal states). In particular, we show that the dipole-dipole interactions and cooperative photon emission can be modulated through the external state of motion. The effects predicted should be experimentally observable with Rydberg atoms. FD would like to thank the F.R.S.-FNRS for financial support. FD is a FRIA Grant holder of the Fonds de la Recherche Scientifique-FNRS.

Fundamental Interactions for Atom Interferometry with Ultracold Quantum Gases in a Microgravity Environment

NASA Astrophysics Data System (ADS)

D'Incao, Jose P.; Willians, Jason R.

2015-05-01

Precision atom interferometers (AI) in space are a key element for several applications of interest to NASA. Our proposal for participating in the Cold Atom Laboratory (CAL) onboard the International Space Station is dedicated to mitigating the leading-order systematics expected to corrupt future high-precision AI-based measurements of fundamental physics in microgravity. One important focus of our proposal is to enhance initial state preparation for dual-species AIs. Our proposed filtering scheme uses Feshbach molecular states to create highly correlated mixtures of heteronuclear atomic gases in both their position and momentum distributions. We will detail our filtering scheme along with the main factors that determine its efficiency. We also show that the atomic and molecular heating and loss rates can be mitigated at the unique temperature and density regimes accessible on CAL. This research is supported by the National Aeronautics and Space Administration.

Nuclear Regulatory Commission Issuances. Opinions and decisions of the Nuclear Regulatory Commission with selected orders: July 1, 1992--December 31, 1992, Volume 36, Pages 1--396

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1992-12-31

This is the thirty-sixth volume of issuances (1-396) of the Nuclear Regulatory Commission and its Atomic Safety and Licensing Boards, Administrative Law Judges, and Office Directors. It covers the period from July 1, 1992-December 31, 1992. Atomic Safety and Licensing Boards are authorized by Section 191 of the Atomic Energy Act of 1954. These Boards, comprised of three members conduct adjudicatory hearings on applications to construct and operate nuclear power plants and related facilities and issue initial decisions which, subject to internal review and appellate procedures, become the final Commission action with respect to those applications. Boards are drawn frommore » the Atomic Safety and Licensing Board Panel, comprised of lawyers, nuclear physicists and engineers, environmentalists, chemists, and economists. The Atomic Energy Commission first established Licensing Boards in 1962 and the Panel in 1967.« less

Quantum spin dynamics with pairwise-tunable, long-range interactions

PubMed Central

Hung, C.-L.; González-Tudela, Alejandro; Cirac, J. Ignacio; Kimble, H. J.

2016-01-01

We present a platform for the simulation of quantum magnetism with full control of interactions between pairs of spins at arbitrary distances in 1D and 2D lattices. In our scheme, two internal atomic states represent a pseudospin for atoms trapped within a photonic crystal waveguide (PCW). With the atomic transition frequency aligned inside a band gap of the PCW, virtual photons mediate coherent spin–spin interactions between lattice sites. To obtain full control of interaction coefficients at arbitrary atom–atom separations, ground-state energy shifts are introduced as a function of distance across the PCW. In conjunction with auxiliary pump fields, spin-exchange versus atom–atom separation can be engineered with arbitrary magnitude and phase, and arranged to introduce nontrivial Berry phases in the spin lattice, thus opening new avenues for realizing topological spin models. We illustrate the broad applicability of our scheme by explicit construction for several well-known spin models. PMID:27496329

MISSE PEACE Polymers Atomic Oxygen Erosion Results

NASA Technical Reports Server (NTRS)

deGroh, Kim, K.; Banks, Bruce A.; McCarthy, Catherine E.; Rucker, Rochelle N.; Roberts, Lily M.; Berger, Lauren A.

2006-01-01

Forty-one different polymer samples, collectively called the Polymer Erosion and Contamination Experiment (PEACE) Polymers, have been exposed to the low Earth orbit (LEO) environment on the exterior of the International Space Station (ISS) for nearly 4 years as part of Materials International Space Station Experiment 2 (MISSE 2). The objective of the PEACE Polymers experiment was to determine the atomic oxygen erosion yield of a wide variety of polymeric materials after long term exposure to the space environment. The polymers range from those commonly used for spacecraft applications, such as Teflon (DuPont) FEP, to more recently developed polymers, such as high temperature polyimide PMR (polymerization of monomer reactants). Additional polymers were included to explore erosion yield dependence upon chemical composition. The MISSE PEACE Polymers experiment was flown in MISSE Passive Experiment Carrier 2 (PEC 2), tray 1, on the exterior of the ISS Quest Airlock and was exposed to atomic oxygen along with solar and charged particle radiation. MISSE 2 was successfully retrieved during a space walk on July 30, 2005, during Discovery s STS-114 Return to Flight mission. Details on the specific polymers flown, flight sample fabrication, pre-flight and post-flight characterization techniques, and atomic oxygen fluence calculations are discussed along with a summary of the atomic oxygen erosion yield results. The MISSE 2 PEACE Polymers experiment is unique because it has the widest variety of polymers flown in LEO for a long duration and provides extremely valuable erosion yield data for spacecraft design purposes.

Nonequilibrium forces between atoms and dielectrics mediated by a quantum field

NASA Astrophysics Data System (ADS)

Behunin, Ryan O.; Hu, Bei-Lok

2011-07-01

In this paper we give a first principles microphysics derivation of the nonequilibrium forces between an atom, treated as a three-dimensional harmonic oscillator, and a bulk dielectric medium modeled as a continuous lattice of oscillators coupled to a reservoir. We assume no direct interaction between the atom and the medium but there exist mutual influences transmitted via a common electromagnetic field. By employing concepts and techniques of open quantum systems we introduce coarse-graining to the physical variables—the medium, the quantum field, and the atom’s internal degrees of freedom, in that order—to extract their averaged effects from the lowest tier progressively to the top tier. The first tier of coarse-graining provides the averaged effect of the medium upon the field, quantified by a complex permittivity (in the frequency domain) describing the response of the dielectric to the field in addition to its back action on the field through a stochastic forcing term. The last tier of coarse-graining over the atom’s internal degrees of freedom results in an equation of motion for the atom’s center of mass from which we can derive the force on the atom. Our nonequilibrium formulation provides a fully dynamical description of the atom’s motion including back-action effects from all other relevant variables concerned. In the long-time limit we recover the known results for the atom-dielectric force when the combined system is in equilibrium or in a nonequilibrium stationary state.

Summary report on transportation of nuclear fuel materials in Japan : transportation infrastructure, threats identified in open literature, and physical protection regulations.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cochran, John Russell; Ouchi, Yuichiro; Furaus, James Phillip

2008-03-01

This report summarizes the results of three detailed studies of the physical protection systems for the protection of nuclear materials transport in Japan, with an emphasis on the transportation of mixed oxide fuel materials1. The Japanese infrastructure for transporting nuclear fuel materials is addressed in the first section. The second section of this report presents a summary of baseline data from the open literature on the threats of sabotage and theft during the transport of nuclear fuel materials in Japan. The third section summarizes a review of current International Atomic Energy Agency, Japanese and United States guidelines and regulations concerningmore » the physical protection for the transportation of nuclear fuel materials.« less

Source of polarized ions for the JINR accelerator complex

NASA Astrophysics Data System (ADS)

Belov, A. S.; Donets, D. E.; Fimushkin, V. V.; Kovalenko, A. D.; Kutuzova, L. V.; Prokofichev, Yu V.; Shutov, V. B.; Turbabin, A. V.; Zubets, V. N.

2017-12-01

The JINR atomic beam type polarized ion source is described. Results of tests of the plasma ionizer with a storage cell and of tuning of high frequency transition units are presented. The source was installed in a linac injector hall of NUCLOTRON in May 2016. The source has been commissioned and used in the NUCLOTRON runs in 2016 and February - March 2017. Polarized and unpolarized deuteron beams were produced as well as polarized protons for acceleration in the NUCLOTRON. Polarized deuteron beam with pulsed current up to 2 mA has been produced. Deuteron beam polarization of 0.6-0.9 of theoretical values for different modes of high frequency transition units operation has been measured with the NUCLOTRON ring internal polarimeter for the accelerated deuteron and proton beams.

Current-induced changes of migration energy barriers in graphene and carbon nanotubes.

PubMed

Obodo, J T; Rungger, I; Sanvito, S; Schwingenschlögl, U

2016-05-21

An electron current can move atoms in a nanoscale device with important consequences for the device operation and breakdown. We perform first principles calculations aimed at evaluating the possibility of changing the energy barriers for atom migration in carbon-based systems. In particular, we consider the migration of adatoms and defects in graphene and carbon nanotubes. Although the current-induced forces are large for both the systems, in graphene the force component along the migration path is small and therefore the barrier height is little affected by the current flow. In contrast, the same barrier is significantly reduced in carbon nanotubes as the current increases. Our work also provides a real-system numerical demonstration that current-induced forces within density functional theory are non-conservative.

Atomically dispersed Ni(i) as the active site for electrochemical CO2 reduction

NASA Astrophysics Data System (ADS)

Yang, Hong Bin; Hung, Sung-Fu; Liu, Song; Yuan, Kaidi; Miao, Shu; Zhang, Liping; Huang, Xiang; Wang, Hsin-Yi; Cai, Weizheng; Chen, Rong; Gao, Jiajian; Yang, Xiaofeng; Chen, Wei; Huang, Yanqiang; Chen, Hao Ming; Li, Chang Ming; Zhang, Tao; Liu, Bin

2018-02-01

Electrochemical reduction of CO2 to chemical fuel offers a promising strategy for managing the global carbon balance, but presents challenges for chemistry due to the lack of effective electrocatalyst. Here we report atomically dispersed nickel on nitrogenated graphene as an efficient and durable electrocatalyst for CO2 reduction. Based on operando X-ray absorption and photoelectron spectroscopy measurements, the monovalent Ni(i) atomic center with a d9 electronic configuration was identified as the catalytically active site. The single-Ni-atom catalyst exhibits high intrinsic CO2 reduction activity, reaching a specific current of 350 A gcatalyst-1 and turnover frequency of 14,800 h-1 at a mild overpotential of 0.61 V for CO conversion with 97% Faradaic efficiency. The catalyst maintained 98% of its initial activity after 100 h of continuous reaction at CO formation current densities as high as 22 mA cm-2.

Reinventing solid state electronics: Harnessing quantum confinement in bismuth thin films

NASA Astrophysics Data System (ADS)

Gity, Farzan; Ansari, Lida; Lanius, Martin; Schüffelgen, Peter; Mussler, Gregor; Grützmacher, Detlev; Greer, J. C.

2017-02-01

Solid state electronics relies on the intentional introduction of impurity atoms or dopants into a semiconductor crystal and/or the formation of junctions between different materials (heterojunctions) to create rectifiers, potential barriers, and conducting pathways. With these building blocks, switching and amplification of electrical currents and voltages are achieved. As miniaturisation continues to ultra-scaled transistors with critical dimensions on the order of ten atomic lengths, the concept of doping to form junctions fails and forming heterojunctions becomes extremely difficult. Here, it is shown that it is not needed to introduce dopant atoms nor is a heterojunction required to achieve the fundamental electronic function of current rectification. Ideal diode behavior or rectification is achieved solely by manipulation of quantum confinement using approximately 2 nm thick films consisting of a single atomic element, the semimetal bismuth. Crucially for nanoelectronics, this approach enables room temperature operation.

Development of Safety Assessment Code for Decommissioning of Nuclear Facilities

NASA Astrophysics Data System (ADS)

Shimada, Taro; Ohshima, Soichiro; Sukegawa, Takenori

A safety assessment code, DecDose, for decommissioning of nuclear facilities has been developed, based on the experiences of the decommissioning project of Japan Power Demonstration Reactor (JPDR) at Japan Atomic Energy Research Institute (currently JAEA). DecDose evaluates the annual exposure dose of the public and workers according to the progress of decommissioning, and also evaluates the public dose at accidental situations including fire and explosion. As for the public, both the internal and the external doses are calculated by considering inhalation, ingestion, direct radiation from radioactive aerosols and radioactive depositions, and skyshine radiation from waste containers. For external dose for workers, the dose rate from contaminated components and structures to be dismantled is calculated. Internal dose for workers is calculated by considering dismantling conditions, e.g. cutting speed, cutting length of the components and exhaust velocity. Estimation models for dose rate and staying time were verified by comparison with the actual external dose of workers which were acquired during JPDR decommissioning project. DecDose code is expected to contribute the safety assessment for decommissioning of nuclear facilities.

A generic biokinetic model for noble gases with application to radon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leggett, Richard Wayne; Marsh, James; Gregoratto, Demetrio

The International Commission for Radiological Protection (ICRP) currently uses a dose conversion coefficient to calculate effective dose per unit exposure to radon and its progeny. The coefficient is derived by dividing the detriment associated with unit exposure to radon, as estimated from epidemiological studies, by the detriment per unit effective dose, as estimated mainly from atomic bomb survivor data and animal studies. In a recent statement the ICRP indicated that future guidance on exposure to radon and its progeny will be developed in the same way as guidance for any other radionuclide. That is, intake of radon and progeny willmore » be limited on the basis of effective dose coefficients derived from biokinetic and dosimetric models. This paper proposes a biokinetic model for systemic (absorbed) radon for use in the calculation of dose coefficients for inhaled or ingested radon. The model is based largely on physical laws governing transfer of a non-reactive and soluble gas between materials. Model predictions are shown to be consistent with results of controlled studies of the fate of internally deposited radon in human subjects.« less

Development of New Transportation/Storage Cask System for Use by DOE Russian Research Reactor Fuel Return Program

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michael Tyacke; Frantisek Svitak; Jiri Rychecky

2010-04-01

The United States, the Russian Federation, and the International Atomic Energy Agency (IAEA) have been working together on a program called the Russian Research Reactor Fuel Return (RRRFR) Program. The purpose of this program is to return Soviet or Russian supplied high-enriched uranium (HEU) fuel currently stored at Russian-designed research reactors throughout the world to Russia. To accommodate transport of the HEU spent nuclear fuel (SNF), a new large-capacity transport/storage cask system was specially designed for handling and operations under the unique conditions for these research reactor facilities. This new cask system is named the ŠKODA VPVR/M cask. The design,more » licensing, testing, and delivery of this new cask system are the results of a significant international cooperative effort by several countries and involved numerous private and governmental organizations. This paper contains the following sections: (1) Introduction/Background; (2) VPVR/M Cask Description; (3) Ancillary Equipment, (4) Cask Licensing; (5) Cask Demonstration and Operations; (6) IAEA Procurement, Quality Assurance Inspections, Fabrication, and Delivery; and, (7) Summary and Conclusions.« less

Development of a New Transportation/Storage Cask System for Use by the DOE Russian Research Reactor Fuel Return Program

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michael J. Tyacke; Frantisek Svitak; Jiri Rychecky

2007-10-01

The United States, the Russian Federation, and the International Atomic Energy Agency (IAEA) have been working together on a program called the Russian Research Reactor Fuel Return (RRRFR) Program. The purpose of this program is to return Soviet or Russian-supplied high-enriched uranium (HEU) fuel, currently stored at Russian-designed research reactors throughout the world, to Russia. To accommodate transport of the HEU spent nuclear fuel (SNF), a new large-capacity transport/storage cask system was specially designed for handling and operations under the unique conditions at these research reactor facilities. This new cask system is named the ŠKODA VPVR/M cask. The design, licensing,more » testing, and delivery of this new cask system result from a significant international cooperative effort by several countries and involved numerous private and governmental organizations. This paper contains the following sections: 1) Introduction; 2) VPVR/M Cask Description; 3) Ancillary Equipment, 4) Cask Licensing; 5) Cask Demonstration and Operations; 6) IAEA Procurement, Quality Assurance Inspections, Fabrication, and Delivery; and, 7) Conclusions.« less

Simulating Chiral Magnetic and Separation Effects with Spin-Orbit Coupled Atomic Gases

PubMed Central

Huang, Xu-Guang

2016-01-01

The chiral magnetic and chiral separation effects—quantum-anomaly-induced electric current and chiral current along an external magnetic field in parity-odd quark-gluon plasma—have received intense studies in the community of heavy-ion collision physics. We show that analogous effects occur in rotating trapped Fermi gases with Weyl-Zeeman spin-orbit coupling where the rotation plays the role of an external magnetic field. These effects can induce a mass quadrupole in the atomic cloud along the rotation axis which may be tested in future experiments. Our results suggest that the spin-orbit coupled atomic gases are potential simulators of the chiral magnetic and separation effects. PMID:26868084

Employing Si solar cell technology to increase efficiency of ultra-thin Cu(In,Ga)Se2 solar cells.

PubMed

Vermang, Bart; Wätjen, Jörn Timo; Fjällström, Viktor; Rostvall, Fredrik; Edoff, Marika; Kotipalli, Ratan; Henry, Frederic; Flandre, Denis

2014-10-01

Reducing absorber layer thickness below 500 nm in regular Cu(In,Ga)Se 2 (CIGS) solar cells decreases cell efficiency considerably, as both short-circuit current and open-circuit voltage are reduced because of incomplete absorption and high Mo/CIGS rear interface recombination. In this work, an innovative rear cell design is developed to avoid both effects: a highly reflective rear surface passivation layer with nano-sized local point contact openings is employed to enhance rear internal reflection and decrease the rear surface recombination velocity significantly, as compared with a standard Mo/CIGS rear interface. The formation of nano-sphere shaped precipitates in chemical bath deposition of CdS is used to generate nano-sized point contact openings. Evaporation of MgF 2 coated with a thin atomic layer deposited Al 2 O 3 layer, or direct current magnetron sputtering of Al 2 O 3 are used as rear surface passivation layers. Rear internal reflection is enhanced substantially by the increased thickness of the passivation layer, and also the rear surface recombination velocity is reduced at the Al 2 O 3 /CIGS rear interface. (MgF 2 /)Al 2 O 3 rear surface passivated ultra-thin CIGS solar cells are fabricated, showing an increase in short circuit current and open circuit voltage compared to unpassivated reference cells with equivalent CIGS thickness. Accordingly, average solar cell efficiencies of 13.5% are realized for 385 nm thick CIGS absorber layers, compared with 9.1% efficiency for the corresponding unpassivated reference cells.

Employing Si solar cell technology to increase efficiency of ultra-thin Cu(In,Ga)Se2 solar cells

PubMed Central

Vermang, Bart; Wätjen, Jörn Timo; Fjällström, Viktor; Rostvall, Fredrik; Edoff, Marika; Kotipalli, Ratan; Henry, Frederic; Flandre, Denis

2014-01-01

Reducing absorber layer thickness below 500 nm in regular Cu(In,Ga)Se2 (CIGS) solar cells decreases cell efficiency considerably, as both short-circuit current and open-circuit voltage are reduced because of incomplete absorption and high Mo/CIGS rear interface recombination. In this work, an innovative rear cell design is developed to avoid both effects: a highly reflective rear surface passivation layer with nano-sized local point contact openings is employed to enhance rear internal reflection and decrease the rear surface recombination velocity significantly, as compared with a standard Mo/CIGS rear interface. The formation of nano-sphere shaped precipitates in chemical bath deposition of CdS is used to generate nano-sized point contact openings. Evaporation of MgF2 coated with a thin atomic layer deposited Al2O3 layer, or direct current magnetron sputtering of Al2O3 are used as rear surface passivation layers. Rear internal reflection is enhanced substantially by the increased thickness of the passivation layer, and also the rear surface recombination velocity is reduced at the Al2O3/CIGS rear interface. (MgF2/)Al2O3 rear surface passivated ultra-thin CIGS solar cells are fabricated, showing an increase in short circuit current and open circuit voltage compared to unpassivated reference cells with equivalent CIGS thickness. Accordingly, average solar cell efficiencies of 13.5% are realized for 385 nm thick CIGS absorber layers, compared with 9.1% efficiency for the corresponding unpassivated reference cells. PMID:26300619

Current status of free radicals and electronically excited metastable species as high energy propellants

NASA Technical Reports Server (NTRS)

Rosen, G.

1973-01-01

A survey is presented of free radicals and electronically excited metastable species as high energy propellants for rocket engines. Nascent or atomic forms of diatomic gases are considered free radicals as well as the highly reactive diatomic triatomic molecules that posess unpaired electrons. Manufacturing and storage problems are described, and a review of current experimental work related to the manufacture of atomic hydrogen propellants is presented.

Snoek Relaxation in Fe-Cr Alloys and Interstitial-Substitutional Interaction

NASA Astrophysics Data System (ADS)

Golovin, I. S.; Blanter, M. S.; Schaller, R.

1997-03-01

The internal friction (IF) spectra of -Fe, Fe-Cr ferritic alloys and Cr have been investigated in a frequency range of 0.01 to 10 Hz. A Snoek-type relaxation was found in all the investigated C doped Fe-Cr alloys, starting from pure Fe and finishing with pure Cr. The temperature location of the Snoek peak (Tmax) in -Fe was found to be 315 K (1 Hz). The activation energy deduced from the T - f shift was 0.81 eV. Tmax in Cr was 433 K with an activation energy of 1.11 eV. The Snoek-type peaks in Fe-Cr alloys are much wider than in pure Fe or pure Cr. The temperature location of the peak versus chromium content curve exhibits a maximum in the vicinity of 35 wt% Cr (Tmax was 573 to 578 K, f 1.2 Hz and the activation energy was about 1.45 eV). It is important that Cr atoms in α-Fe have a more pronounced influence on the temperature location of the peak than Fe atoms have in chromium. A new model based on the atomic interactions is proposed to explain the influence of composition on Snoek peak location. The internal friction has been simulated by a Monte Carlo method, using C-C and C-substitutional atom (s) interaction energies. A model of long-range strain-induced (elastic) interaction supplemented by the chemical interaction in the two nearest coordination shells around an immobile substitutional atom was used for the C-s interaction. The interatomic interaction was supposed to affect IF by changing both the carbon atom arrangement (short-range order) and the energy of C atoms in octahedral interstices, and therefore the activation energy of IF. The peak temperatue calculated coincides well with the experimental ones if the value for the chemical interaction in the first coordination shell (Hchem) for C-Cr in Fe is - 0.15 eV and for C-Fe in Cr +0.15 eV. The difference in the influence of Cr in α-Fe and Fe in Cr is accounted for by a difference in the elastic and chemical interaction both between the carbon atoms and the substitutional atoms. The relaxation process in chromium Fe-based alloys is due to the carbon atom diffusion under stress between octahedral interstices of first and second coordination shells around the Cr atoms, and in Cr-based alloys, between second and third shells around the Fe atoms.

Papers arising from IAEA Coordinated Research Project "Utilization of ion accelerators for studying and modelling of radiation induced defects in semiconductors and insulators" (F11016)

NASA Astrophysics Data System (ADS)

Vittone, Ettore; Breese, Mark; Simon, Aliz

2016-04-01

Within the International Atomic Energy Agency (IAEA) Department of Nuclear Sciences and Applications, activities are carried out to assist and advise IAEA Member States in assessing their needs for capacity building, research and development in nuclear sciences. Support is also provided to Member States' activities geared towards deriving benefits in fields such as (i) advanced materials for nuclear applications, (ii) application of accelerators and associated instrumentation, and (iii) nuclear, atomic and molecular data. One of the means that the IAEA uses to deliver its programme is Coordinated Research Projects (CRPs) which are very effective in stimulating international research and scientific interaction among the Member States.

Lego bricks and the octet rule: Molecular models for biochemical pathways with plastic, interlocking toy bricks.

PubMed

Lin, Henry J; Lehoang, Jennifer; Kwan, Isabel; Baghaee, Anita; Prasad, Priya; Ha-Chen, Stephanie J; Moss, Tanesha; Woods, Jeremy D

2018-01-01

The 8 studs on a 2 × 4 Lego brick conveniently represent the outer shell of electrons for carbon, nitrogen, and oxygen atoms. We used Lego bricks to model these atoms, which are then joined together to form molecules by following the Lewis octet rule. A variety of small biological molecules can be modeled in this way, such as most amino acids, fatty acids, glucose, and various intermediate metabolites. Model building with these familiar toys can be a helpful, hands-on exercise for learning-or re-learning-biochemical pathways. © 2017 by The International Union of Biochemistry and Molecular Biology, 46(1):54-57, 2018. © 2017 The International Union of Biochemistry and Molecular Biology.

Comparison of High-Performance Fiber Materials Properties in Simulated and Actual Space Environments

NASA Technical Reports Server (NTRS)

Finckernor, M. M.

2017-01-01

A variety of high-performance fibers, including Kevlar, Nomex, Vectran, and Spectra, have been tested for durability in the space environment, mostly the low Earth orbital environment. These materials have been tested in yarn, tether/cable, and fabric forms. Some material samples were tested in a simulated space environment, such as the Atomic Oxygen Beam Facility and solar simulators in the laboratory. Other samples were flown on the International Space Station as part of the Materials on International Space Station Experiment. Mass loss due to atomic oxygen erosion and optical property changes due to ultraviolet radiation degradation are given. Tensile test results are also presented, including where moisture loss in a vacuum had an impact on tensile strength.

Challenges of sulfur SAD phasing as a routine method in macromolecular crystallography.

PubMed

Doutch, James; Hough, Michael A; Hasnain, S Samar; Strange, Richard W

2012-01-01

The sulfur SAD phasing method allows the determination of protein structures de novo without reference to derivatives such as Se-methionine. The feasibility for routine automated sulfur SAD phasing using a number of current protein crystallography beamlines at several synchrotrons was examined using crystals of trimeric Achromobacter cycloclastes nitrite reductase (AcNiR), which contains a near average proportion of sulfur-containing residues and two Cu atoms per subunit. Experiments using X-ray wavelengths in the range 1.9-2.4 Å show that we are not yet at the level where sulfur SAD is routinely successful for automated structure solution and model building using existing beamlines and current software tools. On the other hand, experiments using the shortest X-ray wavelengths available on existing beamlines could be routinely exploited to solve and produce unbiased structural models using the similarly weak anomalous scattering signals from the intrinsic metal atoms in proteins. The comparison of long-wavelength phasing (the Bijvoet ratio for nine S atoms and two Cu atoms is ~1.25% at ~2 Å) and copper phasing (the Bijvoet ratio for two Cu atoms is 0.81% at ~0.75 Å) for AcNiR suggests that lower data multiplicity than is currently required for success should in general be possible for sulfur phasing if appropriate improvements to beamlines and data collection strategies can be implemented.

Metal atomization spray nozzle

DOEpatents

Huxford, T.J.

1993-11-16

A spray nozzle for a magnetohydrodynamic atomization apparatus has a feed passage for molten metal and a pair of spray electrodes mounted in the feed passage. The electrodes, diverging surfaces which define a nozzle throat and diverge at an acute angle from the throat. Current passes through molten metal when fed through the throat which creates the Lorentz force necessary to provide atomization of the molten metal. 6 figures.

Gas atomized precursor alloy powder for oxide dispersion strengthened ferritic stainless steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rieken, Joel

Gas atomization reaction synthesis (GARS) was employed as a simplified method for producing precursor powders for oxide dispersion strengthened (ODS) ferritic stainless steels (e.g., Fe-Cr-Y-(Ti,Hf)-O), departing from the conventional mechanical alloying (MA) process. During GARS processing a reactive atomization gas (i.e., Ar-O 2) was used to oxidize the powder surfaces during primary break-up and rapid solidification of the molten alloy. This resulted in envelopment of the powders by an ultra-thin (t < 150 nm) metastable Cr-enriched oxide layer that was used as a vehicle for solid-state transport of O into the consolidated microstructure. In an attempt to better understand themore » kinetics of this GARS reaction, theoretical cooling curves for the atomized droplets were calculated and used to establish an oxidation model for this process. Subsequent elevated temperature heat treatments, which were derived from Rhines pack measurements using an internal oxidation model, were used to promote thermodynamically driven O exchange reactions between trapped films of the initial Cr-enriched surface oxide and internal Y-enriched intermetallic precipitates. This novel microstructural evolution process resulted in the successful formation of nano-metric Y-enriched dispersoids, as confirmed using high energy X-ray diffraction and transmission electron microscopy (TEM), equivalent to conventional ODS alloys from MA powders. The thermal stability of these Y-enriched dispersoids was evaluated using high temperature (1200°C) annealing treatments ranging from 2.5 to 1,000 hrs of exposure. In a further departure from current ODS practice, replacing Ti with additions of Hf appeared to improve the Y-enriched dispersoid thermal stability by means of crystal structure modification. Additionally, the spatial distribution of the dispersoids was found to depend strongly on the original rapidly solidified microstructure. To exploit this, ODS microstructures were engineered from different powder particle size ranges, illustrating microstructural control as a function of particle solidification rate. The consolidation of ultra-fine powders (dia. ≤ 5μm) resulted in a significant reduction in dispersoid size and spacing, consistent with initial scanning electron microscopy studies on as-atomized cross-sectioned particles that suggested that these powders solidified above the threshold velocity to effectively solute trap Y within the α-(Fe,Cr) matrix. Interestingly, when the solidification velocity as a function of particle size was extracted from the aforementioned theoretical particle cooling curves, it could be offered as supporting evidence for these microstructure observations. Thermal-mechanical treatments also were used to create and evaluate the stability of a dislocation substructure within these alloys, using microhardness and TEM analysis of the alloy sub-grain and grain structure. Moreover, elevated temperature tensile tests up to 800°C were used to assess the initial mechanical strength of the ODS microstructure.« less

NASA Goddard Thermal Technology Overview 2017

NASA Technical Reports Server (NTRS)

Butler, Dan; Swanson, Ted

2017-01-01

This presentation summarizes the current plans and efforts at NASA Goddard to develop new thermal control technology for anticipated future missions. It will also address some of the programmatic developments currently underway at NASA, especially with respect to the NASA Technology Development Program. The effects of the recently enacted FY 17 NASA budget, which includes a sizeable increase, will also be addressed. While funding for basic technology development is still tight, significant efforts are being made in direct support of flight programs. Thermal technology Implementation on current flight programs will be reviewed, and the recent push for CubeSat mission development will also be addressed. Many of these technologies also have broad applicability to DOD (Dept. of Defense), DOE (Dept. of the Environment), and commercial programs. Partnerships have been developed with the Air Force, Navy, and various universities to promote technology development. In addition, technology development activities supported by internal research and development (IRAD) program and the Small Business Innovative Research (SBIR) program are reviewed in this presentation. Specific technologies addressed include; two-phase systems applications and issues on NASA missions, latest developments of electro-hydrodynamically pumped systems, Atomic Layer Deposition (ALD), Micro-scale Heat Transfer, and various other research activities.

NASA Goddard Thermal Technology Overview 2016

NASA Technical Reports Server (NTRS)

Butler, Dan; Swanson, Ted

2016-01-01

This presentation summarizes the current plans and efforts at NASA Goddard to develop new thermal control technology for anticipated future missions. It will also address some of the programmatic developments currently underway at NASA, especially with respect to the NASA Technology Development Program. The effects of the recently enacted FY 16 NASA budget, which includes a sizeable increase, will also be addressed. While funding for basic technology development is still tight, significant efforts are being made in direct support of flight programs. Thermal technology implementation on current flight programs will be reviewed, and the recent push for Cube-sat mission development will also be addressed. Many of these technologies also have broad applicability to DOD, DOE, and commercial programs. Partnerships have been developed with the Air Force, Navy, and various universities to promote technology development. In addition, technology development activities supported by internal research and development (IRAD) program and the Small Business Innovative Research (SBIR) program are reviewed in this presentation. Specific technologies addressed include; two-phase systems applications and issues on NASA missions, latest developments of electro-hydrodynamically pumped systems, Atomic Layer Deposition (ALD), Micro-scale Heat Transfer, and various other research activities.

Phantom force induced by tunneling current: a characterization on Si(111).

PubMed

Weymouth, A J; Wutscher, T; Welker, J; Hofmann, T; Giessibl, F J

2011-06-03

Simultaneous measurements of tunneling current and atomic forces provide complementary atomic-scale data of the electronic and structural properties of surfaces and adsorbates. With these data, we characterize a strong impact of the tunneling current on the measured force on samples with limited conductivity. The effect is a lowering of the effective gap voltage through sample resistance which in turn lowers the electrostatic attraction, resulting in an apparently repulsive force. This effect is expected to occur on other low-conductance samples, such as adsorbed molecules, and to strongly affect Kelvin probe measurements when tunneling occurs.

Photon Counting as a Probe of Superfluidity in a Two-Band Bose-Hubbard System Coupled to a Cavity Field

NASA Astrophysics Data System (ADS)

Rajaram, Sara; Trivedi, Nandini

2013-12-01

We show that photon number measurement can be used to detect superfluidity for a two-band Bose-Hubbard model coupled to a cavity field. The atom-photon coupling induces transitions between the two internal atomic levels and results in entangled polaritonic states. In the presence of a cavity field, we find different photon numbers in the Mott-insulating versus superfluid phases, providing a method of distinguishing the atomic phases by photon counting. Furthermore, we examine the dynamics of the photon field after a rapid quench to zero atomic hopping by increasing the well depth. We find a robust correlation between the field’s quench dynamics and the initial superfluid order parameter, thereby providing a novel and accurate method of determining the order parameter.

Annual Report to Congress of the Atomic Energy Commission for 1969

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seaborg, Glenn T.

1970-01-31

The document represents the 1969 Annual Report of the Atomic Energy Commission (AEC) to Congress. The report opens with ''An Introduction to the Atomic Energy Programs during 1969'' followed by 17 Chapters, 8 appendices and an index. Chapters are as follows: (1) Source, Special, and Byproduct Nuclear Materials; (2) Nuclear Materials Safeguards; (3) The Nuclear Defense Effort; (4) Naval Propulsion Reactors; (5) Reactor Development and Technology; (6) Licensing and Regulating the Atom; (7) Operational and Public Safety; (8) Space Nuclear Propulsion; (9) Specialized Nuclear Power; (10) Isotopic Radiation Applications; (11) Peaceful Nuclear Explosives; (12) International Affairs and Cooperation; (13) Informationalmore » and Related Activities; (14) Nuclear Education and Training; (15) Biomedical and Physical Research; (16) Industrial Participation Aspects; and, (17) Administrative and Management Matters.« less

Annual Report to Congress of the Atomic Energy Commission for 1968

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seaborg, Glenn T.

1969-01-31

The document represents the 1968 Annual Report of the Atomic Energy Commission (AEC) to Congress. The report opens with ''An Introduction to the Atomic Energy Programs during 1968'' followed by 17 Chapters, 8 appendices and an index. Chapters are as follows: (1) Source, Special, and Nuclear Byproduct Materials; (2) Nuclear Materials Safeguards; (3) The Nuclear Defense Effort; (4) Naval Propulsion Reactors; (5) Reactor Development and Technology; (6) Licensing and Regulating the Atom; (7) Operational and Public Safety; (8) Nuclear Rocket Propulsion; (9) Specialized Nuclear Power; (10) Isotopic Radiation Applications; (11) Peaceful Nuclear Explosives; (12) International Affairs and Cooperation; (13) Informationalmore » and Related Activities; (14) Nuclear Education and Training; (15) Biomedical and Physical Research; (16) Industrial Participation Aspects; and, (17) Administrative and Management Matters.« less

Quantum optical circulator controlled by a single chirally coupled atom

NASA Astrophysics Data System (ADS)

Scheucher, Michael; Hilico, Adèle; Will, Elisa; Volz, Jürgen; Rauschenbeutel, Arno

2016-12-01

Integrated nonreciprocal optical components, which have an inherent asymmetry between their forward and backward propagation direction, are key for routing signals in photonic circuits. Here, we demonstrate a fiber-integrated quantum optical circulator operated by a single atom. Its nonreciprocal behavior arises from the chiral interaction between the atom and the transversally confined light. We demonstrate that the internal quantum state of the atom controls the operation direction of the circulator and that it features a strongly nonlinear response at the single-photon level. This enables, for example, photon number-dependent routing and novel quantum simulation protocols. Furthermore, such a circulator can in principle be prepared in a coherent superposition of its operational states and may become a key element for quantum information processing in scalable integrated optical circuits.

A single-mode external cavity diode laser using an intra-cavity atomic Faraday filter with short-term linewidth <400 kHz and long-term stability of <1 MHz.

PubMed

Keaveney, James; Hamlyn, William J; Adams, Charles S; Hughes, Ifan G

2016-09-01

We report on the development of a diode laser system - the "Faraday laser" - using an atomic Faraday filter as the frequency-selective element. In contrast to typical external-cavity diode laser systems which offer tunable output frequency but require additional control systems in order to achieve a stable output frequency, our system only lases at a single frequency, set by the peak transmission frequency of the internal atomic Faraday filter. Our system has both short-term and long-term stability of less than 1 MHz, which is less than the natural linewidth of alkali-atomic D-lines, making similar systems suitable for use as a "turn-key" solution for laser-cooling experiments.

Ground-Laboratory to In-Space Atomic Oxygen Correlation for the Polymer Erosion and Contamination Experiment (PEACE) Polymers

NASA Technical Reports Server (NTRS)

Stambler, Arielle H.; Inoshita, Karen E.; Roberts, Lily M.; Barbagallo, Claire E.; deGroh, Kim K.; Banks, Bruce A.

2011-01-01

The Materials International Space Station Experiment 2 (MISSE 2) Polymer Erosion and Contamination Experiment (PEACE) polymers were exposed to the environment of low Earth orbit (LEO) for 3.95 years from 2001 to 2005. There were 41 different PEACE polymers, which were flown on the exterior of the International Space Station (ISS) in order to determine their atomic oxygen erosion yields. In LEO, atomic oxygen is an environmental durability threat, particularly for long duration mission exposures. Although spaceflight experiments, such as the MISSE 2 PEACE experiment, are ideal for determining LEO environmental durability of spacecraft materials, ground-laboratory testing is often relied upon for durability evaluation and prediction. Unfortunately, significant differences exist between LEO atomic oxygen exposure and atomic oxygen exposure in ground-laboratory facilities. These differences include variations in species, energies, thermal exposures and radiation exposures, all of which may result in different reactions and erosion rates. In an effort to improve the accuracy of ground-based durability testing, ground-laboratory to in-space atomic oxygen correlation experiments have been conducted. In these tests, the atomic oxygen erosion yields of the PEACE polymers were determined relative to Kapton H using a radio-frequency (RF) plasma asher (operated on air). The asher erosion yields were compared to the MISSE 2 PEACE erosion yields to determine the correlation between erosion rates in the two environments. This paper provides a summary of the MISSE 2 PEACE experiment; it reviews the specific polymers tested as well as the techniques used to determine erosion yield in the asher, and it provides a correlation between the space and ground laboratory erosion yield values. Using the PEACE polymers asher to in-space erosion yield ratios will allow more accurate in-space materials performance predictions to be made based on plasma asher durability evaluation.

Energetic ion, atom, and molecule reactions and excitation in low-current H2 discharges: H(alpha) Doppler profiles.

PubMed

Petrović, Z Lj; Phelps, A V

2009-12-01

Absolute spectral emissivities for Doppler broadened H(alpha) profiles are measured and compared with predictions of energetic hydrogen ion, atom, and molecule behavior in low-current electrical discharges in H2 at very high electric field E to gas density N ratios E/N and low values of Nd , where d is the parallel-plate electrode separation. These observations reflect the energy and angular distributions for the excited atoms and quantitatively test features of multiple-scattering kinetic models in weakly ionized hydrogen in the presence of an electric field that are not tested by the spatial distributions of H(alpha) emission. Absolute spectral intensities agree well with predictions. Asymmetries in Doppler profiles observed parallel to the electric field at 4

Roles of dynamical symmetry breaking in driving oblate-prolate transitions of atomic clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oka, Yurie, E-mail: ok-yu@fuji.waseda.jp; Yanao, Tomohiro, E-mail: yanao@waseda.jp; Koon, Wang Sang, E-mail: koon@cds.caltech.edu

2015-04-07

This paper explores the driving mechanisms for structural transitions of atomic clusters between oblate and prolate isomers. We employ the hyperspherical coordinates to investigate structural dynamics of a seven-atom cluster at a coarse-grained level in terms of the dynamics of three gyration radii and three principal axes, which characterize overall mass distributions of the cluster. Dynamics of gyration radii is governed by two kinds of forces. One is the potential force originating from the interactions between atoms. The other is the dynamical forces called the internal centrifugal forces, which originate from twisting and shearing motions of the system. The internalmore » centrifugal force arising from twisting motions has an effect of breaking the symmetry between two gyration radii. As a result, in an oblate isomer, activation of the internal centrifugal force that has the effect of breaking the symmetry between the two largest gyration radii is crucial in triggering structural transitions into prolate isomers. In a prolate isomer, on the other hand, activation of the internal centrifugal force that has the effect of breaking the symmetry between the two smallest gyration radii is crucial in triggering structural transitions into oblate isomers. Activation of a twisting motion that switches the movement patterns of three principal axes is also important for the onset of structural transitions between oblate and prolate isomers. Based on these trigger mechanisms, we finally show that selective activations of specific gyration radii and twisting motions, depending on the isomer of the cluster, can effectively induce structural transitions of the cluster. The results presented here could provide further insights into the control of molecular reactions.« less

EDITORIAL: Special issue on time scale algorithms

NASA Astrophysics Data System (ADS)

Matsakis, Demetrios; Tavella, Patrizia

2008-12-01

This special issue of Metrologia presents selected papers from the Fifth International Time Scale Algorithm Symposium (VITSAS), including some of the tutorials presented on the first day. The symposium was attended by 76 persons, from every continent except Antarctica, by students as well as senior scientists, and hosted by the Real Instituto y Observatorio de la Armada (ROA) in San Fernando, Spain, whose staff further enhanced their nation's high reputation for hospitality. Although a timescale can be simply defined as a weighted average of clocks, whose purpose is to measure time better than any individual clock, timescale theory has long been and continues to be a vibrant field of research that has both followed and helped to create advances in the art of timekeeping. There is no perfect timescale algorithm, because every one embodies a compromise involving user needs. Some users wish to generate a constant frequency, perhaps not necessarily one that is well-defined with respect to the definition of a second. Other users might want a clock which is as close to UTC or a particular reference clock as possible, or perhaps wish to minimize the maximum variation from that standard. In contrast to the steered timescales that would be required by those users, other users may need free-running timescales, which are independent of external information. While no algorithm can meet all these needs, every algorithm can benefit from some form of tuning. The optimal tuning, and even the optimal algorithm, can depend on the noise characteristics of the frequency standards, or of their comparison systems, the most precise and accurate of which are currently Two Way Satellite Time and Frequency Transfer (TWSTFT) and GPS carrier phase time transfer. The interest in time scale algorithms and its associated statistical methodology began around 40 years ago when the Allan variance appeared and when the metrological institutions started realizing ensemble atomic time using more than one single atomic clock. An international symposium dedicated to these topics was initiated in 1972 as the first International Symposium on Atomic Time Scale Algorithms and it was the beginning of a series: 1st Symposium: organized at the NIST (NBS at that epoch) in 1972, 2nd Symposium: again at the NIST in 1982, 3rd Symposium: in Italy at the INRIM (IEN at that epoch) in 1988, 4th Symposium: in Paris at the BIPM in 2002 (see Metrologia 40 (3), 2003) 5th Symposium: in San Fernando, Spain at the ROA in 2008. The early symposia were concerned with establishing the basics of how to estimate and characterize the behavior of an atomic frequency standard in an unambiguous and clearly identifiable way, and how to combine the reading of different clocks to form an optimal time scale within a laboratory. Later, as atomic frequency standards began to be used as components in larger systems, interest grew in understanding the impact of a clock in a more complex environment. For example, use of clocks in telecommunication networks in a Synchronous Digital Hierarchy created a need to measure the maximum time error spanned by a clock in a certain interval. Timekeeping metrologists became interested in estimating time deviations and time stability, so they had to find ways to convert their common frequency characteristics to time characteristics. Tests of fundamental physics provided a motivation for launching atomic frequency standards into space in long-lasting missions, whose high-precision measurements might be available for only a few hours a day, yielding a series of clock data with many gaps and outliers for which a suitable statistical analysis was necessary to extract as much information as possible from the data. In the 21st century, the field has been transformed by the advent of atomic-clock-based Global Navigation Satellite Systems (GNSS), the steady increase in precision brought about by rapidly improving clocks and measurement systems, and the growing number of relatively inexpensive small clock ensembles. Although technological transformations have raised the intensity and changed the details of the debates, the VITSAS conference showed that even the issues raised by the early symposia are still current. This selection of papers encompasses the full breadth of the VITSAS, including tutorials, laboratory-specific innovations and practices, GNSS applications, UTC generation, TWSTFT applications, GPS applications, small-ensemble applications, robust algorithms, and statistical measures that are either robust themselves or which reflect nonstationarity and robustness characteristics of the clocks. The Editors of this special issue of Metrologia would like to express their thanks to the referees of the papers published here for all their hard work, to Drs Juan Palacio and Javier Galindo and the people of the ROA, and to all the attendees for the excellent symposium they have created.

Defect States in InP/InGaAs/InP Heterostructures by Current-Voltage Characteristics and Deep Level Transient Spectroscopy.

PubMed

Vu, Thi Kim Oanh; Lee, Kyoung Su; Lee, Sang Jun; Kim, Eun Kyu

2018-09-01

We studied defect states in In0.53Ga0.47As/InP heterojunctions with interface control by group V atoms during metalorganic chemical vapor (MOCVD) deposition. From deep level transient spectroscopy (DLTS) measurements, two defects with activation energies of 0.28 eV (E1) and 0.15 eV (E2) below the conduction band edge, were observed. The defect density of E1 for In0.53Ga0.47As/InP heterojunctions with an addition of As and P atoms was about 1.5 times higher than that of the heterojunction added P atom only. From the temperature dependence of current- voltage characteristics, the thermal activation energies of In0.53Ga0.47As/InP of heterojunctions were estimated to be 0.27 and 0.25 eV, respectively. It appeared that the reverse light current for In0.53Ga0.47As/InP heterojunction added P atom increased only by illumination of a 940 nm-LED light source. These results imply that only the P addition at the interface can enhance the quality of InGaAs/InP heterojunction.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hznnera, K.; Hetzler, F.; Hyden, L.

From international nuclear industries fair; Basel, Switzerland (16 Oct 1972). Some features of ASEA-ATOM's BWR fuel design and fabrication processes are given. The in pile fuel performance experience to date is reviewed. (auth)

Theoretical atomic physics code development I: CATS: Cowan Atomic Structure Code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abdallah, J. Jr.; Clark, R.E.H.; Cowan, R.D.

An adaptation of R.D. Cowan's Atomic Structure program, CATS, has been developed as part of the Theoretical Atomic Physics (TAPS) code development effort at Los Alamos. CATS has been designed to be easy to run and to produce data files that can interface with other programs easily. The CATS produced data files currently include wave functions, energy levels, oscillator strengths, plane-wave-Born electron-ion collision strengths, photoionization cross sections, and a variety of other quantities. This paper describes the use of CATS. 10 refs.

Annihilation in Gases and Galaxies

NASA Technical Reports Server (NTRS)

Drachman, Richard J. (Editor)

1990-01-01

This publication contains most of the papers, both invited and contributed, that were presented at the Workshop of Annihilation in Gases and Galaxies. This was the fifth in a biennial series associated with the International Conference on the Physics of Electronic and Atomic Collisions. Subjects covered included the scattering and annihilation of positrons and positronium atoms in various media, including those of astrophysical interest. In addition, the topics of antimatter and dark matter were covered.

Estimated Environmental Exposures for MISSE-7B

NASA Technical Reports Server (NTRS)

Finckenor, Miria M.; Moore, Chip; Norwood, Joseph K.; Henrie, Ben; DeGroh, Kim

2012-01-01

This paper details the 18-month environmental exposure for Materials International Space Station Experiment 7B (MISSE-7B) ram and wake sides. This includes atomic oxygen, ultraviolet radiation, particulate radiation, thermal cycling, meteoroid/space debris impacts, and observed contamination. Atomic oxygen fluence was determined by measured mass and thickness loss of polymers of known reactivity. Diodes sensitive to ultraviolet light actively measured solar radiation incident on the experiment. Comparisons to earlier MISSE flights are discussed.

Naval Reactors Prime Contractor Team (NRPCT) Experiences and Considerations With Irradiation Test Performance in an International Environment

DOE Office of Scientific and Technical Information (OSTI.GOV)

MH Lane

2006-02-15

This letter forwards a compilation of knowledge gained regarding international interactions and issues associated with Project Prometheus. The following topics are discussed herein: (1) Assessment of international fast reactor capability and availability; (2) Japanese fast reactor (JOYO) contracting strategy; (3) NRPCT/Program Office international contract follow; (4) Completion of the Japan Atomic Energy Agency (JAEA)/Pacific Northwest National Laboratory (PNNL) contract for manufacture of reactor test components; (5) US/Japanese Departmental interactions and required Treaties and Agreements; and (6) Non-technical details--interactions and considerations.

Internal Energy Distribution in Sympathetically Cooled Molecular Ions

NASA Astrophysics Data System (ADS)

Thompson, Robert I.; Fisher, Amy; Harmon, Thomas; Winslade, Clayton; Ahmadi, Nasser

2002-05-01

Over the past year a research program at the University of Calgary has begun looking at the distribution of energy in the internal degrees of freedom (vibrational and rotational) of trapped and sympathetically cooled molecular ions. Ion traps are capable of holding mixed samples of charged atoms and molecules simultaneously. Atomic ions in the trapped cloud can be laser cooled by traditional techniques. The molecular ions are not directly laser cooled, but all of the trapped particles are charged so they interact strongly through Coulomb forces. It has been experimentally demonstrated that the external or translational degrees of freedom of the non-laser-cooled species are significantly lowered through this interaction (e.g. [1]). However, there is little known about the energy distribution in the in the internal degrees of freedom. This poster will outline the results of our theoretical work, as well as the technical design, construction, and initial work in the laboratory. [1] T. Baba and I. Waki, Jpn. J. Appl. Phys. 35, L1134 (1996).

Photochemistry of nucleic acid bases and their thio- and aza-analogues in solution.

PubMed

Pollum, Marvin; Martínez-Fernández, Lara; Crespo-Hernández, Carlos E

2015-01-01

The steady-state and time-resolved photochemistry of the natural nucleic acid bases and their sulfur- and nitrogen-substituted analogues in solution is reviewed. Emphasis is given to the experimental studies performed over the last 3-5 years that showcase topical areas of scientific inquiry and those that require further scrutiny. Significant progress has been made toward mapping the radiative and nonradiative decay pathways of nucleic acid bases. There is a consensus that ultrafast internal conversion to the ground state is the primary relaxation pathway in the nucleic acid bases, whereas the mechanism of this relaxation and the level of participation of the (1)πσ*, (1) nπ*, and (3)ππ* states are still matters of debate. Although impressive research has been performed in recent years, the microscopic mechanism(s) by which the nucleic acid bases dissipate excess vibrational energy to their environment, and the role of the N-glycosidic group in this and in other nonradiative decay pathways, are still poorly understood. The simple replacement of a single atom in a nucleobase with a sulfur or nitrogen atom severely restricts access to the conical intersections responsible for the intrinsic internal conversion pathways to the ground state in the nucleic acid bases. It also enhances access to ultrafast and efficient inter-system crossing pathways that populate the triplet manifold in yields close to unity. Determining the coupled nuclear and electronic pathways responsible for the significantly different photochemistry in these nucleic acid base analogues serves as a convenient platform to examine the current state of knowledge regarding the photodynamic properties of the DNA and RNA bases from both experimental and computational perspectives. Further investigations should also aid in forecasting the prospective use of sulfur- and nitrogen-substituted base analogues in photochemotherapeutic applications.

GenLocDip: A Generalized Program to Calculate and Visualize Local Electric Dipole Moments.

PubMed

Groß, Lynn; Herrmann, Carmen

2016-09-30

Local dipole moments (i.e., dipole moments of atomic or molecular subsystems) are essential for understanding various phenomena in nanoscience, such as solvent effects on the conductance of single molecules in break junctions or the interaction between the tip and the adsorbate in atomic force microscopy. We introduce GenLocDip, a program for calculating and visualizing local dipole moments of molecular subsystems. GenLocDip currently uses the Atoms-In-Molecules (AIM) partitioning scheme and is interfaced to various AIM programs. This enables postprocessing of a variety of electronic structure output formats including cube and wavefunction files, and, in general, output from any other code capable of writing the electron density on a three-dimensional grid. It uses a modified version of Bader's and Laidig's approach for achieving origin-independence of local dipoles by referring to internal reference points which can (but do not need to be) bond critical points (BCPs). Furthermore, the code allows the export of critical points and local dipole moments into a POVray readable input format. It is particularly designed for fragments of large systems, for which no BCPs have been calculated for computational efficiency reasons, because large interfragment distances prevent their identification, or because a local partitioning scheme different from AIM was used. The program requires only minimal user input and is written in the Fortran90 programming language. To demonstrate the capabilities of the program, examples are given for covalently and non-covalently bound systems, in particular molecular adsorbates. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Removing Beam Current Artifacts in Helium Ion Microscopy: A Comparison of Image Processing Techniques.

PubMed

Barlow, Anders J; Portoles, Jose F; Sano, Naoko; Cumpson, Peter J

2016-10-01

The development of the helium ion microscope (HIM) enables the imaging of both hard, inorganic materials and soft, organic or biological materials. Advantages include outstanding topographical contrast, superior resolution down to <0.5 nm at high magnification, high depth of field, and no need for conductive coatings. The instrument relies on helium atom adsorption and ionization at a cryogenically cooled tip that is atomically sharp. Under ideal conditions this arrangement provides a beam of ions that is stable for days to weeks, with beam currents in the order of picoamperes. Over time, however, this stability is lost as gaseous contamination builds up in the source region, leading to adsorbed atoms of species other than helium, which ultimately results in beam current fluctuations. This manifests itself as horizontal stripe artifacts in HIM images. We investigate post-processing methods to remove these artifacts from HIM images, such as median filtering, Gaussian blurring, fast Fourier transforms, and principal component analysis. We arrive at a simple method for completely removing beam current fluctuation effects from HIM images while maintaining the full integrity of the information within the image.

Quantum optical tests of complementarity: Quantum eraser and the decoherence time of a local measurement process

NASA Astrophysics Data System (ADS)

Abranyos, Yonatan

1999-10-01

Quantum optical tests of the fundamental principles of quantum mechanics, in particular, complementarity, entanglement and non-locality, are the central themes of this dissertation. A which-path experiment is implemented based on a recent experiment by Eichmann et al. [1] involving two four-level atoms. In the version considered here a continuous Broad Band Excitation field drives the two trapped atoms and, depending on the type of scattering, information about which atom scattered the light is stored in the internal degrees of the atoms. Entanglement of the atoms-photon system is intimately connected to the availability of ``which way'' information. The quantum eraser disentangles the atoms-photon system and consequently ``which way'' information is lost leading to interference. Two different experimental schemes based on the Eichmann et al. experiment are proposed for the implementation of the quantum eraser. The quantum eraser schemes erase the ``which way'' information and interference is observed in the second order correlation function. With a slight modification of the experiment, a scheme that allows to verify recently derived inequalities by Englert [2] in connection with distinguishability and visibility in a two-way interferometer is proposed. These inequalities, in some sense, can be regarded as quantifying the notion of wave-particle duality. The visibility of interference depends on the detected polarization direction of the scattered light, and a reading out of the internal atomic states of one of the two atoms provides for partial ``which way'' information or distinguishability of the two different paths. Finally, the quantum eraser is used to measure the decoherence time of a local measurement process. The experiment proposed is similar to the quantum eraser setup and contains the complete measurement process of system-meter-environment interaction. The decoherence time is quantitatively expressed in the amount of reduction of the visibility in the second order correlation function. In addition, it explores how we can cast the question of quantum coherence of mesoscopic or macroscopic systems with a quantum eraser or in general interference experiments.

Atomic data and spectral modeling constraints from high-resolution X-ray observations of the Perseus cluster with Hitomi

NASA Astrophysics Data System (ADS)

Hitomi Collaboration; Aharonian, Felix; Akamatsu, Hiroki; Akimoto, Fumie; Allen, Steven W.; Angelini, Lorella; Audard, Marc; Awaki, Hisamitsu; Axelsson, Magnus; Bamba, Aya; Bautz, Marshall W.; Blandford, Roger; Brenneman, Laura W.; Brown, Gregory V.; Bulbul, Esra; Cackett, Edward M.; Chernyakova, Maria; Chiao, Meng P.; Coppi, Paolo S.; Costantini, Elisa; de Plaa, Jelle; de Vries, Cor P.; den Herder, Jan-Willem; Done, Chris; Dotani, Tadayasu; Ebisawa, Ken; Eckart, Megan E.; Enoto, Teruaki; Ezoe, Yuichiro; Fabian, Andrew C.; Ferrigno, Carlo; Foster, Adam R.; Fujimoto, Ryuichi; Fukazawa, Yasushi; Furuzawa, Akihiro; Galeazzi, Massimiliano; Gallo, Luigi C.; Gandhi, Poshak; Giustini, Margherita; Goldwurm, Andrea; Gu, Liyi; Guainazzi, Matteo; Haba, Yoshito; Hagino, Kouichi; Hamaguchi, Kenji; Harrus, Ilana M.; Hatsukade, Isamu; Hayashi, Katsuhiro; Hayashi, Takayuki; Hayashida, Kiyoshi; Hell, Natalie; Hiraga, Junko S.; Hornschemeier, Ann; Hoshino, Akio; Hughes, John P.; Ichinohe, Yuto; Iizuka, Ryo; Inoue, Hajime; Inoue, Yoshiyuki; Ishida, Manabu; Ishikawa, Kumi; Ishisaki, Yoshitaka; Iwai, Masachika; Kaastra, Jelle; Kallman, Tim; Kamae, Tsuneyoshi; Kataoka, Jun; Katsuda, Satoru; Kawai, Nobuyuki; Kelley, Richard L.; Kilbourne, Caroline A.; Kitaguchi, Takao; Kitamoto, Shunji; Kitayama, Tetsu; Kohmura, Takayoshi; Kokubun, Motohide; Koyama, Katsuji; Koyama, Shu; Kretschmar, Peter; Krimm, Hans A.; Kubota, Aya; Kunieda, Hideyo; Laurent, Philippe; Lee, Shiu-Hang; Leutenegger, Maurice A.; Limousin, Olivier; Loewenstein, Michael; Long, Knox S.; Lumb, David; Madejski, Greg; Maeda, Yoshitomo; Maier, Daniel; Makishima, Kazuo; Markevitch, Maxim; Matsumoto, Hironori; Matsushita, Kyoko; McCammon, Dan; McNamara, Brian R.; Mehdipour, Missagh; Miller, Eric D.; Miller, Jon M.; Mineshige, Shin; Mitsuda, Kazuhisa; Mitsuishi, Ikuyuki; Miyazawa, Takuya; Mizuno, Tsunefumi; Mori, Hideyuki; Mori, Koji; Mukai, Koji; Murakami, Hiroshi; Mushotzky, Richard F.; Nakagawa, Takao; Nakajima, Hiroshi; Nakamori, Takeshi; Nakashima, Shinya; Nakazawa, Kazuhiro; Nobukawa, Kumiko K.; Nobukawa, Masayoshi; Noda, Hirofumi; Odaka, Hirokazu; Ohashi, Takaya; Ohno, Masanori; Okajima, Takashi; Ota, Naomi; Ozaki, Masanobu; Paerels, Frits; Paltani, Stéphane; Petre, Robert; Pinto, Ciro; Porter, Frederick S.; Pottschmidt, Katja; Reynolds, Christopher S.; Safi-Harb, Samar; Saito, Shinya; Sakai, Kazuhiro; Sasaki, Toru; Sato, Goro; Sato, Kosuke; Sato, Rie; Sawada, Makoto; Schartel, Norbert; Serlemtsos, Peter J.; Seta, Hiromi; Shidatsu, Megumi; Simionescu, Aurora; Smith, Randall K.; Soong, Yang; Stawarz, Łukasz; Sugawara, Yasuharu; Sugita, Satoshi; Szymkowiak, Andrew; Tajima, Hiroyasu; Takahashi, Hiromitsu; Takahashi, Tadayuki; Takeda, Shin'ichiro; Takei, Yoh; Tamagawa, Toru; Tamura, Takayuki; Tanaka, Takaaki; Tanaka, Yasuo; Tanaka, Yasuyuki T.; Tashiro, Makoto S.; Tawara, Yuzuru; Terada, Yukikatsu; Terashima, Yuichi; Tombesi, Francesco; Tomida, Hiroshi; Tsuboi, Yohko; Tsujimoto, Masahiro; Tsunemi, Hiroshi; Tsuru, Takeshi Go; Uchida, Hiroyuki; Uchiyama, Hideki; Uchiyama, Yasunobu; Ueda, Shutaro; Ueda, Yoshihiro; Uno, Shin'ichiro; Urry, C. Megan; Ursino, Eugenio; Watanabe, Shin; Werner, Norbert; Wilkins, Dan R.; Williams, Brian J.; Yamada, Shinya; Yamaguchi, Hiroya; Yamaoka, Kazutaka; Yamasaki, Noriko Y.; Yamauchi, Makoto; Yamauchi, Shigeo; Yaqoob, Tahir; Yatsu, Yoichi; Yonetoku, Daisuke; Zhuravleva, Irina; Zoghbi, Abderahmen; Raassen, A. J. J.

2018-03-01

The Hitomi Soft X-ray Spectrometer spectrum of the Perseus cluster, with ˜5 eV resolution in the 2-9 keV band, offers an unprecedented benchmark of the atomic modeling and database for hot collisional plasmas. It reveals both successes and challenges of the current atomic data and models. The latest versions of AtomDB/APEC (3.0.8), SPEX (3.03.00), and CHIANTI (8.0) all provide reasonable fits to the broad-band spectrum, and are in close agreement on best-fit temperature, emission measure, and abundances of a few elements such as Ni. For the Fe abundance, the APEC and SPEX measurements differ by 16%, which is 17 times higher than the statistical uncertainty. This is mostly attributed to the differences in adopted collisional excitation and dielectronic recombination rates of the strongest emission lines. We further investigate and compare the sensitivity of the derived physical parameters to the astrophysical source modeling and instrumental effects. The Hitomi results show that accurate atomic data and models are as important as the astrophysical modeling and instrumental calibration aspects. Substantial updates of atomic databases and targeted laboratory measurements are needed to get the current data and models ready for the data from the next Hitomi-level mission.

Formation and disruption of current paths of anodic porous alumina films by conducting atomic force microscopy

NASA Astrophysics Data System (ADS)

Oyoshi, K.; Nigo, S.; Inoue, J.; Sakai, O.; Kitazawa, H.; Kido, G.

2010-11-01

Anodic porous alumina (APA) films have a honeycomb cell structure of pores and a voltage-induced bi-stable switching effect. We have applied conducting atomic force microscopy (CAFM) as a method to form and to disrupt current paths in the APA films. A bi-polar switching operation was confirmed. We have firstly observed terminals of current paths as spots or areas typically on the center of the triangle formed by three pores. In addition, though a part of the current path showed repetitive switching, most of them were not observed again at the same position after one cycle of switching operations in the present experiments. This suggests that a part of alumina structure and/or composition along the current paths is modified during the switching operations.

The influence of molecular symmetry and topological factors on the internal heavy atom effect in aromatic and heteroaromatic compounds

NASA Astrophysics Data System (ADS)

Nijegorodov, N.; Mabbs, R.

2001-06-01

The absorption and fluorescence properties of 26 specially selected aromatic and heteroaromatic compounds, from different classes, are studied quantum chemically and experimentally at room temperature (293 K). Seven of these compounds have not been studied before. The compounds are arranged in seven groups, which illustrate different cases of the internal heavy atom effect. The quantum yield of fluorescence, γ and fluorescence decay time, τf of deaerated and non-deaerated cyclohexane or ethanol solutions are measured. The oscillator strength, fe, fluorescence rate constant, kf, natural lifetime, τ0t, and intersystem crossing rate constant, kST, were calculated for each compound. The orbital nature of the lowest excited singlet state and direction of polarization of the S0→ S1 transitions are determined using the PPP-CI method for each molecule. The investigation shows that substitution of a heavy atom(s) (Cl, S, Br, I etc.) into an aromatic or heteroaromatic molecule may produce different changes in all the fluorescence parameters (sometimes dramatically) and not necessarily lead to the quenching of fluorescence. Substitution of a heavy atom(s) may increase the value of the spin-orbit operator, \\Hcirc SO, if the S0→ S1 excitation is localized to some extent on a carbon atom bonded to a heavy atom(s) or on the heavy atom itself (Ö or S). Such substitution may change the symmetry of a molecule and hence the values of the ΨS 1\\HcircsoΨT i' matrix elements would change (in molecules of higher symmetry groups not all Ti states are able to mix with the perturbing S1 state). Such substitution may change the arrangement of Ti states below the S1, state and hence, the Franck-Condon factors would change. Such substitution may also change the value of the ΨS 0M jΨS 1 matrix element and, consequently, the oscillator strength of the S0→ S1 transition would change. A combination of all these possible changes determines the value of kf and kST and, consequently, determines the value of γ and τf. It is observed that in many cases, the value of the spin-orbit operator is related to the dipole moment operator, e.g. if the introduction of a heavy atom increases kST then, as a rule, it decreases fe( 1A→ 1La).

76 FR 65634 - Assistance to Foreign Atomic Energy Activities

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-24

... Nuclear Nonproliferation (NA-20), Office of Nonproliferation and International Security (NA-24), 1000... Administrator for Defense Nuclear Nonproliferation, National Nuclear Security Administration, U.S. Department of...

Use of the ICRP system for the protection of marine ecosystems.

PubMed

Telleria, D; Cabianca, T; Proehl, G; Kliaus, V; Brown, J; Bossio, C; Van der Wolf, J; Bonchuk, I; Nilsen, M

2015-06-01

The International Commission on Radiological Protection (ICRP) recently reinforced the international system of radiological protection, initially focused on humans, by identifying principles of environmental protection and proposing a framework for assessing impacts of ionising radiation on non-human species, based on a reference flora and fauna approach. For this purpose, ICRP developed dosimetric models for a set of Reference Animals and Plants, which are representative of flora and fauna in different environments (terrestrial, freshwater, marine), and produced criteria based on information on radiation effects, with the aim of evaluating the level of potential or actual radiological impacts, and as an input for decision making. The approach developed by ICRP for flora and fauna is consistent with the approach used to protect humans. The International Atomic Energy Agency (IAEA) includes considerations on the protection of the environment in its safety standards, and is currently developing guidelines to assess radiological impacts based on the aforementioned ICRP approach. This paper presents the method developed by IAEA, in a series of meetings with international experts, to enable assessment of the radiological impact to the marine environment in connection with the Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter 1972 (London Convention 1972). This method is based on IAEA's safety standards and ICRP's recommendations, and was presented in 2013 for consideration by representatives of the contracting parties of the London Convention 1972; it was approved for inclusion in its procedures, and is in the process of being incorporated into guidelines. © The International Society for Prosthetics and Orthotics Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

A full quantum analysis of the Stern-Gerlach experiment using the evolution operator method: analyzing current issues in teaching quantum mechanics

NASA Astrophysics Data System (ADS)

Benítez Rodríguez, E.; Arévalo Aguilar, L. M.; Piceno Martínez, E.

2017-03-01

To the quantum mechanics specialists community it is a well-known fact that the famous original Stern-Gerlach experiment (SGE) produces entanglement between the external degrees of freedom (position) and the internal degree of freedom (spin) of silver atoms. Despite this fact, almost all textbooks on quantum mechanics explain this experiment using a semiclassical approach, where the external degrees of freedom are considered classical variables, the internal degree is treated as a quantum variable, and Newton's second law is used to describe the dynamics. In the literature there are some works that analyze this experiment in its full quantum mechanical form. However, astonishingly, to the best of our knowledge the original experiment, where the initial states of the spin degree of freedom are randomly oriented coming from the oven, has not been analyzed yet in the available textbooks using the Schrödinger equation (to the best of our knowledge there is only one paper that treats this case: Hsu et al (2011 Phys. Rev. A 83 012109)). Therefore, in this contribution we use the time-evolution operator to give a full quantum mechanics analysis of the SGE when the initial state of the internal degree of freedom is completely random, i.e. when it is a statistical mixture. Additionally, as the SGE and the development of quantum mechanics are heavily intermingled, we analyze some features and drawbacks in the current teaching of quantum mechanics. We focus on textbooks that use the SGE as a starting point, based on the fact that most physicist do not use results from physics education research, and comment on traditional pedagogical attitudes in the physics community.

The fabrication of a double-layer atom chip with through silicon vias for an ultra-high-vacuum cell

NASA Astrophysics Data System (ADS)

Chuang, Ho-Chiao; Lin, Yun-Siang; Lin, Yu-Hsin; Huang, Chi-Sheng

2014-04-01

This study presents a double-layer atom chip that provides users with increased diversity in the design of the wire patterns and flexibility in the design of the magnetic field. It is more convenient for use in atomic physics experiments. A negative photoresist, SU-8, was used as the insulating layer between the upper and bottom copper wires. The electrical measurement results show that the upper and bottom wires with a width of 100 µm can sustain a 6 A current without burnout. Another focus of this study is the double-layer atom chips integrated with the through silicon via (TSV) technique, and anodically bonded to a Pyrex glass cell, which makes it a desired vacuum chamber for atomic physics experiments. Thus, the bonded glass cell not only significantly reduces the overall size of the ultra-high-vacuum (UHV) chamber but also conducts the high current from the backside to the front side of the atom chip via the TSV under UHV (9.5 × 10-10 Torr). The TSVs with a diameter of 70 µm were etched through by the inductively coupled plasma ion etching and filled by the bottom-up copper electroplating method. During the anodic bonding process, the electroplated copper wires and TSVs on atom chips also need to pass the examination of the required bonding temperature of 250 °C, under an applied voltage of 1000 V. Finally, the UHV test of the double-layer atom chips with TSVs at room temperature can be reached at 9.5 × 10-10 Torr, thus satisfying the requirements of atomic physics experiments under an UHV environment.

High-temperature site preference and atomic short-range ordering characteristics of ternary alloying elements in γ'-Ni3Al intermetallics

NASA Astrophysics Data System (ADS)

Eriş, Rasim; Mekhrabov, Amdulla O.; Akdeniz, M. Vedat

2017-10-01

Remarkable high-temperature mechanical properties of nickel-based superalloys are correlated with the arrangement of ternary alloying elements in L12-type-ordered γ‧-Ni3Al intermetallics. In the current study, therefore, high-temperature site occupancy preference and energetic-structural characteristics of atomic short-range ordering (SRO) of ternary alloying X elements (X = Mo, W, Ta, Hf, Re, Ru, Pt or Co) in Ni75Al21.875X3.125 alloy systems have been studied by combining the statistico-thermodynamical theory of ordering and electronic theory of alloys in the pseudopotential approximation. Temperature dependence of site occupancy tendencies of alloying X element atoms has been predicted by calculating partial ordering energies and SRO parameters of Ni-Al, Ni-X and Al-X atomic pairs. It is shown that, all ternary alloying element atoms (except Pt) tend to occupy Al, whereas Pt atoms prefer to substitute for Ni sub-lattice sites of Ni3Al intermetallics. However, in contrast to other X elements, sub-lattice site occupancy characteristics of Re atoms appear to be both temperature- and composition-dependent. Theoretical calculations reveal that site occupancy preference of Re atoms switches from Al to both Ni and Al sites at critical temperatures, Tc, for Re > 2.35 at%. Distribution of Re atoms at both Ni and Al sub-lattice sites above Tc may lead to localised supersaturation of the parent Ni3Al phase and makes possible the formation of topologically close-packed (TCP) phases. The results of the current theoretical and simulation study are consistent with other theoretical and experimental investigations published in the literature.

Atomic clocks for geodesy.

PubMed

Mehlstäubler, Tanja E; Grosche, Gesine; Lisdat, Christian; Schmidt, Piet O; Denker, Heiner

2018-06-01

We review experimental progress on optical atomic clocks and frequency transfer, and consider the prospects of using these technologies for geodetic measurements. Today, optical atomic frequency standards have reached relative frequency inaccuracies below 10 -17 , opening new fields of fundamental and applied research. The dependence of atomic frequencies on the gravitational potential makes atomic clocks ideal candidates for the search for deviations in the predictions of Einstein's general relativity, tests of modern unifying theories and the development of new gravity field sensors. In this review, we introduce the concepts of optical atomic clocks and present the status of international clock development and comparison. Besides further improvement in stability and accuracy of today's best clocks, a large effort is put into increasing the reliability and technological readiness for applications outside of specialized laboratories with compact, portable devices. With relative frequency uncertainties of 10 -18 , comparisons of optical frequency standards are foreseen to contribute together with satellite and terrestrial data to the precise determination of fundamental height reference systems in geodesy with a resolution at the cm-level. The long-term stability of atomic standards will deliver excellent long-term height references for geodetic measurements and for the modelling and understanding of our Earth.

Atomic clocks for geodesy

NASA Astrophysics Data System (ADS)

Mehlstäubler, Tanja E.; Grosche, Gesine; Lisdat, Christian; Schmidt, Piet O.; Denker, Heiner

2018-06-01

We review experimental progress on optical atomic clocks and frequency transfer, and consider the prospects of using these technologies for geodetic measurements. Today, optical atomic frequency standards have reached relative frequency inaccuracies below 10‑17, opening new fields of fundamental and applied research. The dependence of atomic frequencies on the gravitational potential makes atomic clocks ideal candidates for the search for deviations in the predictions of Einstein’s general relativity, tests of modern unifying theories and the development of new gravity field sensors. In this review, we introduce the concepts of optical atomic clocks and present the status of international clock development and comparison. Besides further improvement in stability and accuracy of today’s best clocks, a large effort is put into increasing the reliability and technological readiness for applications outside of specialized laboratories with compact, portable devices. With relative frequency uncertainties of 10‑18, comparisons of optical frequency standards are foreseen to contribute together with satellite and terrestrial data to the precise determination of fundamental height reference systems in geodesy with a resolution at the cm-level. The long-term stability of atomic standards will deliver excellent long-term height references for geodetic measurements and for the modelling and understanding of our Earth.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burrow, O.; Carroll, A.; Chattopadhyay, S.

A cold atom interferometer is being developed using 85Rb atoms towards a search for the dark contents of the vacuum, and as a test stand for inertial sensing applications. Here we outline the current status of the experiment and report the observation of Ramsey interference fringes in the apparatus.

Translocation Thermodynamics of Linear and Cyclic Nonaarginine into Model DPPC Bilayer via Coarse-Grained Molecular Dynamics Simulation: Implications of Pore Formation and Nonadditivity

PubMed Central

2015-01-01

Structural mechanisms and underlying thermodynamic determinants of efficient internalization of charged cationic peptides (cell-penetrating peptides, CPPs) such as TAT, polyarginine, and their variants, into cells, cellular constructs, and model membrane/lipid bilayers (large and giant unilamellar or multilamelar vesicles) continue to garner significant attention. Two widely held views on the translocation mechanism center on endocytotic and nonendocytotic (diffusive) processes. Espousing the view of a purely diffusive internalization process (supported by recent experimental evidence, [Säälik, P.; et al. J. Controlled Release2011, 153, 117–125]), we consider the underlying free energetics of the translocation of a nonaarginine peptide (Arg9) into a model DPPC bilayer. In the case of the Arg9 cationic peptide, recent experiments indicate a higher internalization efficiency of the cyclic structure (cyclic Arg9) relative to the linear conformer. Furthermore, recent all-atom resolution molecular dynamics simulations of cyclic Arg9 [Huang, K.; et al. Biophys. J., 2013, 104, 412–420] suggested a critical stabilizing role of water- and lipid-constituted pores that form within the bilayer as the charged Arg9 translocates deep into the bilayer center. Herein, we use umbrella sampling molecular dynamics simulations with coarse-grained Martini lipids, polarizable coarse-grained water, and peptide to explore the dependence of translocation free energetics on peptide structure and conformation via calculation of potentials of mean force along preselected reaction paths allowing and preventing membrane deformations that lead to pore formation. Within the context of the coarse-grained force fields we employ, we observe significant barriers for Arg9 translocation from bulk aqueous solution to bilayer center. Moreover, we do not find free-energy minima in the headgroup–water interfacial region, as observed in simulations using all-atom force fields. The pore-forming paths systematically predict lower free-energy barriers (ca. 90 kJ/mol lower) than the non pore-forming paths, again consistent with all-atom force field simulations. The current force field suggests no preference for the more compact or covalently cyclic structures upon entering the bilayer. Decomposition of the PMF into the system’s components indicates that the dominant stabilizing contribution along the pore-forming path originates from the membrane as both layers of it deformed due to the formation of pore. Furthermore, our analysis revealed that although there is significant entropic stabilization arising from the enhanced configurational entropy exposing more states as the peptide moves through the bilayer, the enthalpic loss (as predicted by the interactions of this coarse-grained model) far outweighs any former stabilization, thus leading to significant barrier to translocation. Finally, we observe reduction in the translocation free-energy barrier for a second Arg9 entering the bilayer in the presence of an initial peptide restrained at the center, again, in qualitative agreement with all-atom force fields. PMID:24506488

Atomization methods for forming magnet powders

DOEpatents

Sellers, Charles H.; Branagan, Daniel J.; Hyde, Timothy A.

2000-01-01

The invention encompasses methods of utilizing atomization, methods for forming magnet powders, methods for forming magnets, and methods for forming bonded magnets. The invention further encompasses methods for simulating atomization conditions. In one aspect, the invention includes an atomization method for forming a magnet powder comprising: a) forming a melt comprising R.sub.2.1 Q.sub.13.9 B.sub.1, Z and X, wherein R is a rare earth element; X is an element selected from the group consisting of carbon, nitrogen, oxygen and mixtures thereof; Q is an element selected from the group consisting of Fe, Co and mixtures thereof; and Z is an element selected from the group consisting of Ti, Zr, Hf and mixtures thereof; b) atomizing the melt to form generally spherical alloy powder granules having an internal structure comprising at least one of a substantially amorphous phase or a substantially nanocrystalline phase; and c) heat treating the alloy powder to increase an energy product of the alloy powder; after the heat treatment, the alloy powder comprising an energy product of at least 10 MGOe. In another aspect, the invention includes a magnet comprising R, Q, B, Z and X, wherein R is a rare earth element; X is an element selected from the group consisting of carbon, nitrogen, oxygen and mixtures thereof; Q is an element selected from the group consisting of Fe, Co and mixtures thereof; and Z is an element selected from the group consisting of Ti, Zr, Hf and mixtures thereof; the magnet comprising an internal structure comprising R.sub.2.1 Q.sub.13.9 B.sub.1.

PREFACE Preface

NASA Astrophysics Data System (ADS)

Bachor, Hans; Drummond, Peter; Hannaford, Peter

2011-01-01

The 22nd International Conference on Atomic Physics (ICAP 2010) was held from 25 to 30 July, 2010 in Cairns, Tropical North Queensland, Australia. This conference followed on from the series of highly successful biennial ICAP conferences held in Storrs, Innsbruck, Rio, Cambridge MA, Florence, Windsor, Amsterdam, Boulder, Munich, Ann Arbor, Paris, Tokyo, Seattle, Göteborg, Cambridge MA, Riga, Berkeley, Heidelberg, Boulder, Oxford and New York. ICAP 2010 was attended by 630 participants from 37 countries. The conference presented an outstanding program of papers covering the most recent advances in atomic physics, including atomic tests of fundamental physics and basic symmetries; precision measurements, including atomic clocks, atom interferometers and fundamental constants; ultracold gases and Bose-Einstein condensates; ultracold Fermi gases; ultracold molecules; quantum simulators with atoms and ions; few-body systems; ultrafast phenomena and free electron lasers; quantum information with atoms and ions; quantum optics and cavity QED with atoms; and hybrid and optomechanical systems. The papers in this Proceedings represent a collection of the invited talks. The conference program consisted of 48 invited talks presented in plenary sessions, including 10 'hot topic' talks highlighting the most recent advances in the field, and about 490 poster papers presented in three afternoon sessions. The program included talks by Nobel Laureates Claude Cohen-Tannoudji, Wolfgang Ketterle and Bill Phillips, a memorium talk commemorating the scientific life of Vladilen Letokhov, and an evening lecture by Alain Aspect on 'Wave particle duality for a single photon: quantum weirdness brought to light'. The conference was preceded by a two-day workshop in Cairns on Variation of Fundamental Constants and Violation of Fundamental Symmetries P, T(EDM), CPT, Lorentz Invariance, organised by the University of New South Wales; and three-day Student Workshop at Cape Tribulation, organized by the Australian Research Council Centre of Excellence for Quantum-Atom Optics (ACQAO). A website with full details of the conference program, abstracts and other information can be found at: http://www.swin.edu.au/icap2010. We would like to thank the participants, especially those who contributed talks, posters and manuscripts, for making ICAP2010 such an exciting and memorable conference. We thank the Program Committee for putting together an outstanding program and the ICAP International Advisory Committee for their expert advice and suggestions. We gratefully acknowledge the financial support of our sponsors: the Australian National University, the Australian Research Council Centre of Excellence for Quantum-Atom Optics, Griffith University, the Ian Potter Foundation, the International Union of Pure and Applied Physics, the National Institute of Standards and Technology, Swinburne University of Technology, and contributors to the trade exhibition: Coherent, Coherent Scientific, the Institute of Physics Publishing, Lastek, NewSpec, Nufern, Oxford University Press, Spectra-Physics, Springer, Toptica Photonics and Warsash Scientific. Finally, we thank our Conference Secretariat, Maria Lamari, and the Local Organising Committee for their tireless and expert efforts in the organisation of ICAP2010, and the staff of the Cairns Convention Centre, whose friendly and efficient service contributed much to the success of the conference. The next ICAP conference is planned to be held in Palaiseau, France from 23 to 27 July 2012 (http://www.ifraf.org/icap2012). Hans BachorPeter DrummondPeter HannafordEditors

Chip-Scale Atomic Magnetometers

NASA Astrophysics Data System (ADS)

Knappe, Svenja

2010-03-01

Atomic magnetometers have reached sensitivities rivaling those of superconducting quantum interference devices (SQUIDs) in some frequency ranges [1]. A major advancement in atomic magnetometry was made possible by implementing interrogation schemes that suppress spin-exchange collisions between the alkali atoms [2]. Good signal-to-noise can be achieved by operation at very high alkali densities. At the same time, it introduces the challenge to create uniform spin-polarization and monitor the atomic precession about the magnetic field in atomic vapors with large optical densities. Off-resonant detection of the polarization rotation rather than the absorption is essential to operate in this regime. By use of microfabrication methods, we are miniaturizing such atomic magnetometers. They consist of miniature vapor cells with volumes of a few cubic millimeters integrated with micro-optical components. We present the advancement in sensitivities of such devices over nearly four orders of magnitude [3]. This allows for small low-power room-temperature devices with sensitivities that get close to those of SQUIDs in the frequency range around 100 Hz. We outline the current performance of chip-scale atomic magnetometers and the major challenges. Apart from efficient pumping and probing at high optical densities, these include magnetic noise caused by several sensor components and environmental factors, noise on the light fields, as well as magnetic fields from current-carrying parts, such as heaters, lasers, and photodetectors.[4pt] [1] Allred et al., Phys. Rev. Lett. 89, 130801 (2002) [0pt] [2] Happer and Tam, Phys. Rev. A 16, 1877 (1977) [0pt] [3] Griffith et al., Appl. Phys. Lett 94, 023502 (2009)

The shadow map: a general contact definition for capturing the dynamics of biomolecular folding and function.

PubMed

Noel, Jeffrey K; Whitford, Paul C; Onuchic, José N

2012-07-26

Structure-based models (SBMs) are simplified models of the biomolecular dynamics that arise from funneled energy landscapes. We recently introduced an all-atom SBM that explicitly represents the atomic geometry of a biomolecule. While this initial study showed the robustness of the all-atom SBM Hamiltonian to changes in many of the energetic parameters, an important aspect, which has not been explored previously, is the definition of native interactions. In this study, we propose a general definition for generating atomically grained contact maps called "Shadow". The Shadow algorithm initially considers all atoms within a cutoff distance and then, controlled by a screening parameter, discards the occluded contacts. We show that this choice of contact map is not only well behaved for protein folding, since it produces consistently cooperative folding behavior in SBMs but also desirable for exploring the dynamics of macromolecular assemblies since, it distributes energy similarly between RNAs and proteins despite their disparate internal packing. All-atom structure-based models employing Shadow contact maps provide a general framework for exploring the geometrical features of biomolecules, especially the connections between folding and function.

Atom Interferometer Technologies in Space for Gravity Mapping and Gravity Science

NASA Astrophysics Data System (ADS)

Williams, Jason; Chiow, Sheng-Wey; Kellogg, James; Kohel, James; Yu, Nan

2015-05-01

Atom interferometers utilize the wave-nature of atomic gases for precision measurements of inertial forces, with potential applications ranging from gravity mapping for planetary science to unprecedented tests of fundamental physics with quantum gases. The high stability and sensitivity intrinsic to these devices already place them among the best terrestrial sensors available for measurements of gravitational accelerations, rotations, and gravity gradients, with the promise of several orders of magnitude improvement in their detection sensitivity in microgravity. Consequently, multiple precision atom-interferometer-based projects are under development at the Jet Propulsion Laboratory, including a dual-atomic-species interferometer that is to be integrated into the Cold Atom Laboratory onboard the International Space Station and a highly stable gravity gradiometer in a transportable design relevant for earth science measurements. We will present JPL's activities in the use of precision atom interferometry for gravity mapping and gravitational wave detection in space. Our recent progresses bringing the transportable JPL atom interferometer instrument to be competitive with the state of the art and simulations of the expected capabilities of a proposed flight project will also be discussed. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

Resonant quantum transitions in trapped antihydrogen atoms.

PubMed

Amole, C; Ashkezari, M D; Baquero-Ruiz, M; Bertsche, W; Bowe, P D; Butler, E; Capra, A; Cesar, C L; Charlton, M; Deller, A; Donnan, P H; Eriksson, S; Fajans, J; Friesen, T; Fujiwara, M C; Gill, D R; Gutierrez, A; Hangst, J S; Hardy, W N; Hayden, M E; Humphries, A J; Isaac, C A; Jonsell, S; Kurchaninov, L; Little, A; Madsen, N; McKenna, J T K; Menary, S; Napoli, S C; Nolan, P; Olchanski, K; Olin, A; Pusa, P; Rasmussen, C Ø; Robicheaux, F; Sarid, E; Shields, C R; Silveira, D M; Stracka, S; So, C; Thompson, R I; van der Werf, D P; Wurtele, J S

2012-03-07

The hydrogen atom is one of the most important and influential model systems in modern physics. Attempts to understand its spectrum are inextricably linked to the early history and development of quantum mechanics. The hydrogen atom's stature lies in its simplicity and in the accuracy with which its spectrum can be measured and compared to theory. Today its spectrum remains a valuable tool for determining the values of fundamental constants and for challenging the limits of modern physics, including the validity of quantum electrodynamics and--by comparison with measurements on its antimatter counterpart, antihydrogen--the validity of CPT (charge conjugation, parity and time reversal) symmetry. Here we report spectroscopy of a pure antimatter atom, demonstrating resonant quantum transitions in antihydrogen. We have manipulated the internal spin state of antihydrogen atoms so as to induce magnetic resonance transitions between hyperfine levels of the positronic ground state. We used resonant microwave radiation to flip the spin of the positron in antihydrogen atoms that were magnetically trapped in the ALPHA apparatus. The spin flip causes trapped anti-atoms to be ejected from the trap. We look for evidence of resonant interaction by comparing the survival rate of trapped atoms irradiated with microwaves on-resonance to that of atoms subjected to microwaves that are off-resonance. In one variant of the experiment, we detect 23 atoms that survive in 110 trapping attempts with microwaves off-resonance (0.21 per attempt), and only two atoms that survive in 103 attempts with microwaves on-resonance (0.02 per attempt). We also describe the direct detection of the annihilation of antihydrogen atoms ejected by the microwaves.

Rapid development of tissue bank achieved by International Atomic Energy Agency (IAEA) Tissue Banking Programme in China.

PubMed

Zhang, Yu-Min; Wang, Jian-Ru; Zhang, Nai-Li; Liu, Xiao-Ming; Zhou, Mo; Ma, Shao-Ying; Yang, Ting; Li, Bao-Xing

2014-09-01

Before 1986, the development of tissue banking in China has been slow and relatively uncoordinated. Under the support of International Atomic Energy Agency (IAEA), Tissue Banking in China experienced rapid development. In this period, China Institute for Radiation Protection tissue bank mastered systematic and modern tissue banking technique by IAEA training course and gradually developed the first regional tissue bank (Shanxi Provincial Tissue Bank, SPTB) to provide tissue allograft. Benefit from training course, SPTB promoted the development of tissue transplantation by ways of training, brochure, advertisement and meeting. Tissue allograft transplantation acquired recognition from clinic and supervision and administration from government. Quality system gradually is developing and perfecting. Tissue allograft transplantation and tissue bank are developing rapidly and healthy.

PREFACE: XXVIII International Conference on Photonic, Electronic and Atomic Collisions (ICPEAC 2013)

NASA Astrophysics Data System (ADS)

Xiao, Guoqing; Cai, Xiaohong; Ding, Dajun; Ma, Xinwen; Zhao, Yongtao

2014-04-01

The 28th International Conference on Photonic, Electronic and Atomic Collisions (XXVIII ICPEAC) was held by the Institute of Modern Physics, Chinese Academy of Sciences (IMP) on 24-30 July, 2013 in Lanzhou, China. The 444 conference participants came from 37 countries and/or regions. Five plenary lectures, more than 80 progress reports and special reports had been arranged according to the decision of the ICPEAC International General Committee. Meanwhile, more than 650 abstracts were selected as poster presentations. Before the conference, three highly distinguished scientists, Professor Joachim Burgdöorfer, Professor Hossein Sadeghpour and Professor Yasunori Yamazaki, presented tutorial lectures with the support of the IMP Branch of Youth Innovation Promotion Association, CAS (IMP-YIPA). During the conference, Professor Jianwei Pan from University of Sciences and Technology in China presented an enlightening public lecture on quantum communication. Furthermore, 2013 IUPAP Young Scientist Prize was awarded to Dr T Jahnke from Johann Wolfgang Goethe University of Germany. The Sheldon Datz Prize for an Outstanding Young Scientist Attending ICPEAC was awarded to Dr Diogo Almeida from University of Fribourg of Switzerland. As a biannual academic conference, ICPEAC is one of the most important international conferences on atomic and molecular physics. The topic of the conference covers the recent progresses in photonic, electronic, atomic, ionic, molecular, cluster collisions with matter. With a history back to 1958, ICPEAC came to China for the very first time. IMP has been preparing the conference six years before, ever since the ICPEAC International General Committee made the decision to hold the XXVIII ICPEAC in Lanzhou. This proceedings includes the papers of the two plenary lectures, 40 progress reports, 17 special reports and 337 posters, which were reviewed and revised according to the comments of the referees. The Local Organizing Committee would like to express its great appreciation to National Natural Science Foundation of China (NSFC), Chinese Academy of Sciences (CAS), International Union of Pure and Applied Physics (IUPAP), IMP, and IMP-YIPA for financial support, to Fangfang Ruan, Qiang Liang, Dacheng Zhang, Shukai Tian, Yuyu Wang, Wenping Zhu, Wei Liang, Mingwu Zhang, Haibo Yuan, Shan Sha, Jieru Ren, Jie Yang and Zhenhai Chen for their contributions to the organization, and to the volunteer group from Lanzhou University, the High School Attached Northwest Normal University and IMP for their excellent volunteer work. The Local Organizing Committee would like to thank all of the participants and the authors of the proceedings for their supports and contributions to the conference. Guoqing Xiao Director of Institute of Modern Physics, Chinese Academy of Sciences

Atomic-Layer-Deposited Transparent Electrodes for Silicon Heterojunction Solar Cells

DOE PAGES

Demaurex, Benedicte; Seif, Johannes P.; Smit, Sjoerd; ...

2014-11-01

We examine damage-free transparent-electrode deposition to fabricate high-efficiency amorphous silicon/crystalline silicon heterojunction solar cells. Such solar cells usually feature sputtered transparent electrodes, the deposition of which may damage the layers underneath. Using atomic layer deposition, we insert thin protective films between the amorphous silicon layers and sputtered contacts and investigate their effect on device operation. We find that a 20-nm-thick protective layer suffices to preserve, unchanged, the amorphous silicon layers beneath. Insertion of such protective atomic-layer-deposited layers yields slightly higher internal voltages at low carrier injection levels. However, we identify the presence of a silicon oxide layer, formed during processing,more » between the amorphous silicon and the atomic-layer-deposited transparent electrode that acts as a barrier, impeding hole and electron collection.« less

Atomic Chain Electronics

NASA Technical Reports Server (NTRS)

Yamada, Toshishige; Saini, Subhash (Technical Monitor)

1998-01-01

Adatom chains, precise structures artificially created on an atomically regulated surface, are the smallest possible candidates for future nanoelectronics. Since all the devices are created by combining adatom chains precisely prepared with atomic precision, device characteristics are predictable, and free from deviations due to accidental structural defects. In this atomic dimension, however, an analogy to the current semiconductor devices may not work. For example, Si structures are not always semiconducting. Adatom states do not always localize at the substrate surface when adatoms form chemical bonds to the substrate atoms. Transport properties are often determined for the entire system of the chain and electrodes, and not for chains only. These fundamental issues are discussed, which will be useful for future device considerations.

Exposure to an atomic bomb explosion is a risk factor for in-hospital death after esophagectomy to treat esophageal cancer.

PubMed

Nakashima, Y; Takeishi, K; Guntani, A; Tsujita, E; Yoshinaga, K; Matsuyama, A; Hamatake, M; Maeda, T; Tsutsui, S; Matsuda, H; Ishida, T

2015-01-01

Esophagectomy, one of the most invasive of all gastrointestinal operations, is associated with a high frequency of postoperative complications and in-hospital mortality. The purpose of the present study was to determine whether exposure to the atomic bomb explosion at Hiroshima in 1945 might be a preoperative risk factor for in-hospital mortality after esophagectomy in esophageal cancer patients. We thus reviewed the outcomes of esophagectomy in 31 atomic bomb survivors with esophageal cancer and 96 controls (also with cancer but without atomic bomb exposure). We compared the incidences of postoperative complications and in-hospital mortality. Of the clinicopathological features studied, mean patient age was significantly higher in atomic bomb survivors than in controls. Of the postoperative complications noted, atomic bomb survivors experienced a longer mean period of endotracheal intubation and higher incidences of severe pulmonary complications, severe anastomotic leakage, and surgical site infection. The factors associated with in-hospital mortality were exposure to the atomic bomb explosion, pulmonary comorbidities, and electrocardiographic abnormalities. Multivariate analysis revealed that exposure to the atomic bomb explosion was an independent significant preoperative risk factor for in-hospital mortality. Exposure to the atomic bomb explosion is thus a preoperative risk factor for in-hospital death after esophagectomy to treat esophageal cancer. © 2013 Wiley Periodicals, Inc. and the International Society for Diseases of the Esophagus.

About the atomic structures of icosahedral quasicrystals

NASA Astrophysics Data System (ADS)

Quiquandon, Marianne; Gratias, Denis

2014-01-01

This paper is a survey of the crystallographic methods that have been developed these last twenty five years to decipher the atomic structures of the icosahedral stable quasicrystals since their discovery in 1982 by D. Shechtman. After a brief recall of the notion of quasiperiodicity and the natural description of Z-modules in 3-dim as projection of regular lattices in N>3-dim spaces, we give the basic geometrical ingredients useful to describe icosahedral quasicrystals as irrational 3-dim cuts of ordinary crystals in 6-dim space. Atoms are described by atomic surfaces (ASs) that are bounded volumes in the internal (or perpendicular) 3-dim space and the intersections of which with the physical space are the actual atomic positions. The main part of the paper is devoted to finding the major properties of quasicrystalline icosahedral structures. As experimentally demonstrated, they can be described with a surprisingly few high symmetry ASs located at high symmetry special points in 6-dim space. The atomic structures are best described by aggregations and intersections of high symmetry compact interpenetrating atomic clusters. We show here that the experimentally relevant clusters are derived from one generic cluster made of two concentric triacontahedra scaled by τ and an external icosidodecahedron. Depending on which ones of the orbits of this cluster are eventually occupied by atoms, the actual atomic clusters are of type Bergman, Mackay, Tsai and others….

Application of Internal Standard Method for Several 3d-Transition Metallic Elements in Flame Atomic Absorption Spectrometry Using a Multi-wavelength High-resolution Spectrometer.

PubMed

Toya, Yusuke; Itagaki, Toshiko; Wagatsuma, Kazuaki

2017-01-01

We investigated a simultaneous internal standard method in flame atomic absorption spectrometry (FAAS), in order to better the analytical precision of 3d-transition metals contained in steel materials. For this purpose, a new spectrometer system for FAAS, comprising a bright xenon lamp as the primary radiation source and a high-resolution Echelle monochromator, was employed to measure several absorption lines at a wavelength width of ca. 0.3 nm at the same time, which enables the absorbances of an analytical line and also an internal standard line to be estimated. In considering several criteria for selecting an internal standard element and the absorption line, it could be suggested that platinum-group elements: ruthenium, rhodium, or palladium, were suitable for an internal standard element to determine the 3d-transition metal elements, such as titanium, iron, and nickel, by measuring an appropriate pair of these absorption lines simultaneously. Several variances of the absorption signal, such as a variation in aspirated amounts of sample solution and a short-period drift of the primary light source, would be corrected and thus reduced, when the absorbance ratio of the analytical line to the internal standard line was measured. In Ti-Pd, Ni-Rh, and Fe-Ru systems chosen as typical test samples, the repeatability of the signal respnses was investigated with/without the internal standard method, resulting in better precision when the internal standard method was applied in the FAAS with a nitrous oxide-acetylene flame rather than an air-acetylene flame.

Scanning tunneling microscopy current from localized basis orbital density functional theory

NASA Astrophysics Data System (ADS)

Gustafsson, Alexander; Paulsson, Magnus

2016-03-01

We present a method capable of calculating elastic scanning tunneling microscopy (STM) currents from localized atomic orbital density functional theory (DFT). To overcome the poor accuracy of the localized orbital description of the wave functions far away from the atoms, we propagate the wave functions, using the total DFT potential. From the propagated wave functions, the Bardeen's perturbative approach provides the tunneling current. To illustrate the method we investigate carbon monoxide adsorbed on a Cu(111) surface and recover the depression/protrusion observed experimentally with normal/CO-functionalized STM tips. The theory furthermore allows us to discuss the significance of s - and p -wave tips.

NMR Studies of Dynamic Biomolecular Conformational Ensembles

PubMed Central

Torchia, Dennis A.

2015-01-01

Multidimensional heteronuclear NMR approaches can provide nearly complete sequential signal assignments of isotopically enriched biomolecules. The availability of assignments together with measurements of spin relaxation rates, residual spin interactions, J-couplings and chemical shifts provides information at atomic resolution about internal dynamics on timescales ranging from ps to ms, both in solution and in the solid state. However, due to the complexity of biomolecules, it is not possible to extract a unique atomic-resolution description of biomolecular motions even from extensive NMR data when many conformations are sampled on multiple timescales. For this reason, powerful computational approaches are increasingly applied to large NMR data sets to elucidate conformational ensembles sampled by biomolecules. In the past decade, considerable attention has been directed at an important class of biomolecules that function by binding to a wide variety of target molecules. Questions of current interest are: “Does the free biomolecule sample a conformational ensemble that encompasses the conformations found when it binds to various targets; and if so, on what time scale is the ensemble sampled?” This article reviews recent efforts to answer these questions, with a focus on comparing ensembles obtained for the same biomolecules by different investigators. A detailed comparison of results obtained is provided for three biomolecules: ubiquitin, calmodulin and the HIV-1 trans-activation response RNA. PMID:25669739

Science Goals for the PARCS mission on the International Space Station

NASA Astrophysics Data System (ADS)

Ashby, Neil; Hollberg, Leo; Jefferts, Steven; Klipstein, William; Seidel, David; Sullivan, Donald

2003-05-01

The PARCS (Primary Atomic Reference Clock in Space) experiment will use a laser-cooled cesium atomic clock operating in the microgravity environment aboard the International Space Station (ISS) to provide both advanced tests of gravitational theory and to demonstrate a new cold-atom clock technology for space. This presentation concentrates on the scientific goals of the PARCS mission. The microgravity space environment allows laser-cooled Cs atoms to have Ramsey times in excess of those feasible on Earth, resulting in improved clock performance. Clock stabilities of 5×10-14 at one second, and uncertainties below 10-16 are projected. The relativistic frequency shift should be measurable at least 40 times better than the previous best measurement made by Gravity Probe A. Significant improvements in testing fundamental assumptions of relativity theory, such as local position invariance (LPI), are expected. PARCS is scheduled for launch in 2007 and may very well fly with the Stanford superconducting microwave oscillator (SUMO) which will allow a Kennedy-Thorndike-type experiment with an improvement of better than three orders of magnitude compared to previous best results. PARCS will also provide a much-improved realization of the second, and a stable time reference in space. PARCS is a joint project by the National Institue of Standards and Technology (NIST), the University of Colorado (CU) and NASA's Jet Propulsion Laboratory (JPL).

Molecular dynamics simulation of temperature effects on deposition of Cu film on Si by magnetron sputtering

NASA Astrophysics Data System (ADS)

Zhu, Guo; Sun, Jiangping; Zhang, Libin; Gan, Zhiyin

2018-06-01

The temperature effects on the growth of Cu thin film on Si (0 0 1) in the context of magnetron sputtering deposition were systematically studied using molecular dynamics (MD) method. To improve the comparability of simulation results at varying temperatures, the initial status data of incident Cu atoms used in all simulations were read from an identical file via LAMMPS-Python interface. In particular, crystalline microstructure, interface mixing and internal stress of Cu thin film deposited at different temperatures were investigated in detail. With raising the substrate temperature, the interspecies mixed volume and the proportion of face-centered cubic (fcc) structure in the deposited film both increased, while the internal compressive stress decreased. It was found that the fcc structure in the deposited Cu thin films was 〈1 1 1〉 oriented, which was reasonably explained by surface energy minimization and the selectivity of bombardment energy to the crystalline planes. The quantified analysis of interface mixing revealed that the diffusion of Cu atoms dominated the interface mixing, and the injection of incident Cu atoms resulted in the densification of phase near the film-substrate interface. More important, the distribution of atomic stress indicated that the compressive stress was mainly originated from the film-substrate interface, which might be attributed to the densification of interfacial phase at the initial stage of film deposition.

Relation between the Z-1 type expansion of the total energy of isoelectronic atoms and the many-electron theory on the electron correlation by Sinanoǧlu

NASA Astrophysics Data System (ADS)

Anno, Tosinobu; Teruya, Hirohide

1987-07-01

By applying the economical formula for the total energies of isoelectronic atoms presented by the present authors [J. Chem. Phys. 84, 6895 (1986)] to both the nonrelativistic exact energy and the Hartree-Fock energy, an expression of the Z-1 expansion type for the correlation energy is obtained for isoelectronic series involving the first-row atoms. Based upon the expression obtained, the following conclusions are derived on the relation between the Z-1 type expansion theory and Sinanoǧlu's many-electron theory (MET): (i) the Z2 term has nothing to do with the electron correlation; (ii) the term proportional to Z represents the internal correlation energy Eint in MET, at least when Z is large in comparison with the number of electrons N; (iii) the constant term in the Z-1 type expansion is the limiting value of the sum of the semi-internal and the all-external correlation energy (EF+Eu) when Z→∞ and its values for the ground-state atoms show a systematic trend when plotted against N; (iv) the sum of the Z-1 and the higher order terms in Z-1 represents the Z dependence of EF+Eu, although its small amount is attributable to a part of Eint when Z-N≲1.

44 CFR 402.2 - Restricted commodities.

Code of Federal Regulations, 2011 CFR

2011-10-01

... Office of International Trade, Department of Commerce, (b) articles on the list of arms, ammunition and..., including fissionable materials, controlled for export under the Atomic Energy Act of 1946. The restrictions...

44 CFR 402.2 - Restricted commodities.

Code of Federal Regulations, 2010 CFR

2010-10-01

... Office of International Trade, Department of Commerce, (b) articles on the list of arms, ammunition and..., including fissionable materials, controlled for export under the Atomic Energy Act of 1946. The restrictions...

The polarised internal target for the PAX experiment

NASA Astrophysics Data System (ADS)

Ciullo, G.; Barion, L.; Barschel, C.; Grigoriev, K.; Lenisa, P.; Nass, A.; Sarkadi, J.; Statera, M.; Steffens, E.; Tagliente, G.

2011-05-01

The PAX (Polarized Antiproton eXperiment) collaboration aims to polarise antiproton beams stored in ring by means of spin-filtering. The experimental setup is based on a polarised internal gas target, surrounded by a detection system for the measurement of spin observables. In this report, we present results from the commission of the PAX target (atomic beam source, openable cell, and polarimeter).

Reduced enrichment for research and test reactors: Proceedings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1993-07-01

The 15th annual Reduced Enrichment for Research and Test Reactors (RERTR) international meeting was organized by Ris{o} National Laboratory in cooperation with the International Atomic Energy Agency and Argonne National Laboratory. The topics of the meeting were the following: National Programs, Fuel Fabrication, Licensing Aspects, States of Conversion, Fuel Testing, and Fuel Cycle. Individual papers have been cataloged separately.

Monte Carlo Technique Used to Model the Degradation of Internal Spacecraft Surfaces by Atomic Oxygen

NASA Technical Reports Server (NTRS)

Banks, Bruce A.; Miller, Sharon K.

2004-01-01

Atomic oxygen is one of the predominant constituents of Earth's upper atmosphere. It is created by the photodissociation of molecular oxygen (O2) into single O atoms by ultraviolet radiation. It is chemically very reactive because a single O atom readily combines with another O atom or with other atoms or molecules that can form a stable oxide. The effects of atomic oxygen on the external surfaces of spacecraft in low Earth orbit can have dire consequences for spacecraft life, and this is a well-known and much studied problem. Much less information is known about the effects of atomic oxygen on the internal surfaces of spacecraft. This degradation can occur when openings in components of the spacecraft exterior exist that allow the entry of atomic oxygen into regions that may not have direct atomic oxygen attack but rather scattered attack. Openings can exist because of spacecraft venting, microwave cavities, and apertures for Earth viewing, Sun sensors, or star trackers. The effects of atomic oxygen erosion of polymers interior to an aperture on a spacecraft were simulated at the NASA Glenn Research Center by using Monte Carlo computational techniques. A two-dimensional model was used to provide quantitative indications of the attenuation of atomic oxygen flux as a function of the distance into a parallel-walled cavity. The model allows the atomic oxygen arrival direction, the Maxwell Boltzman temperature, and the ram energy to be varied along with the interaction parameters of the degree of recombination upon impact with polymer or nonreactive surfaces, the initial reaction probability, the reaction probability dependence upon energy and angle of attack, degree of specularity of scattering of reactive and nonreactive surfaces, and the degree of thermal accommodation upon impact with reactive and non-reactive surfaces to be varied to allow the model to produce atomic oxygen erosion geometries that replicate actual experimental results from space. The degree of erosion of various interior locations was compared with the erosion that would occur external to the spacecraft. Results of one cavity model indicate that, at depths into a two-dimensional cavity that are equal to 10 cavity widths, the erosion on the walls of the cavity is less than that on the top surface by over 2 orders of magnitude. Wall erosion near the surface of a cavity depends on which wall is receiving direct atomic oxygen attack. However, deep in the cavity little difference is present. Testing of various cavity models such as these gives spacecraft designers an indication of the level of threat to sensitive interior surfaces for different geometries. Even though the Monte Carlo model is two-dimensional, it can be used to provide qualitative information about spacecraft openings that are three-dimensional by offering reasonable insight as to the nature of the attenuation of damage that occurs within a spacecraft in low Earth orbit. As shown, there is more erosion on the side seeing direct atomic oxygen attack until a depth of approximately 5 times the width of the opening, where the erosion is the same on both sides.

Influence of atomic tip structure on the intensity of inelastic tunneling spectroscopy data analyzed by combined scanning tunneling spectroscopy, force microscopy, and density functional theory

NASA Astrophysics Data System (ADS)

Okabayashi, Norio; Gustafsson, Alexander; Peronio, Angelo; Paulsson, Magnus; Arai, Toyoko; Giessibl, Franz J.

2016-04-01

Achieving a high intensity in inelastic scanning tunneling spectroscopy (IETS) is important for precise measurements. The intensity of the IETS signal can vary by up to a factor of 3 for various tips without an apparent reason accessible by scanning tunneling microscopy (STM) alone. Here, we show that combining STM and IETS with atomic force microscopy enables carbon monoxide front-atom identification, revealing that high IETS intensities for CO/Cu(111) are obtained for single-atom tips, while the intensity drops sharply for multiatom tips. Adsorption of the CO molecule on a Cu adatom [CO/Cu/Cu(111)] such that the molecule is elevated over the substrate strongly diminishes the tip dependence of IETS intensity, showing that an elevated position channels most of the tunneling current through the CO molecule even for multiatom tips, while a large fraction of the tunneling current bypasses the CO molecule in the case of CO/Cu(111).

Detection of gas molecules on single Mn adatom adsorbed graphyne: a DFT-D study

NASA Astrophysics Data System (ADS)

Lu, Zhansheng; Lv, Peng; Ma, Dongwei; Yang, Xinwei; Li, Shuo; Yang, Zongxian

2018-02-01

As one of the prominent applications in intelligent systems, gas sensing technology has attracted great interest in both industry and academia. In the current study, the pristine graphyne (GY) without and with a single Mn atom is investigated to detect the gas molecules (CO, CH4, CO2, NH3, NO and O2). The pristine GY is promising to detect O2 molecules because of its chemical adsorption on GY with large electron transfer. The great stability of the Mn/GY is found, and the Mn atom prefers to anchor at the alkyne ring as a single atom. Upon single Mn atom anchoring, the sensitivity and selectivity of GY based gas sensors is significantly improved for various molecules, except CH4. The recovery time of the Mn/GY after detecting the gas molecules may help to appraise the detection efficiency for the Mn/GY. The current study will help to understand the mechanism of detecting the gas molecules, and extend the potentially fascinating applications of GY-based materials.

A computational study on tuning the field emission and electronic properties of BN nanocones by impurity atom doping

NASA Astrophysics Data System (ADS)

Ahmadi, S.; Delir Kheirollahi Nezhad, P.; Hosseinian, A.; Vessally, E.

2018-06-01

We have inspected the effect of substituting a boron or nitrogen atom of a BN nanocone (BNNC) by two impurity atoms with lower and higher atomic numbers based on the density functional theory calculations. Our results explain the experimental observations in a molecular level. Orbital and partial density of states analyses show that the doping processes increase the electrical conductivity by creating new states within the gap of BNNC as follows: BeB > ON > CB > CN. The electron emission current from the surface of BNNC is improved after the CB and BeB dopings, and it is decreased by CN and ON dopings. The BeB and CN dopings make the BNNC a p-type semiconductor and the CB and ON dopings make it an n-type one in good agreement with the experimental results. The ON and BeB doping processes are suggested for the field emission current, and electrical conductivity enhancement, respectively.

An atomic model of brome mosaic virus using direct electron detection and real-space optimization.

PubMed

Wang, Zhao; Hryc, Corey F; Bammes, Benjamin; Afonine, Pavel V; Jakana, Joanita; Chen, Dong-Hua; Liu, Xiangan; Baker, Matthew L; Kao, Cheng; Ludtke, Steven J; Schmid, Michael F; Adams, Paul D; Chiu, Wah

2014-09-04

Advances in electron cryo-microscopy have enabled structure determination of macromolecules at near-atomic resolution. However, structure determination, even using de novo methods, remains susceptible to model bias and overfitting. Here we describe a complete workflow for data acquisition, image processing, all-atom modelling and validation of brome mosaic virus, an RNA virus. Data were collected with a direct electron detector in integrating mode and an exposure beyond the traditional radiation damage limit. The final density map has a resolution of 3.8 Å as assessed by two independent data sets and maps. We used the map to derive an all-atom model with a newly implemented real-space optimization protocol. The validity of the model was verified by its match with the density map and a previous model from X-ray crystallography, as well as the internal consistency of models from independent maps. This study demonstrates a practical approach to obtain a rigorously validated atomic resolution electron cryo-microscopy structure.

Impact of Nagasaki atomic bomb exposure on myelodysplastic syndrome patients who are treated with azacitidine.

PubMed

Jo, Tatsuro; Horio, Kensuke; Shigematsu, Kazuto

2015-05-01

High-dose radiation exposure greatly increases the risk of myelodysplastic syndromes (MDS), however the clinical characteristics of MDS among atomic bomb survivors have not been thoroughly investigated to date. We designed this study to identify these characteristics. We retrospectively evaluated data from 13 atomic bomb survivors with MDS and 15 elderly patients with de novo MDS who were diagnosed between April 2011 and April 2013 at the Nagasaki Genbaku Hospital. All patients were treated with azacitidine (AZA; a hypomethylating agent) and overall survival rates were estimated. No clear difference was observed in the clinical response to AZA between the two groups. However, atomic bomb survivors had a survival disadvantage, independent of their karyotype. Minute genetic alterations caused by exposure to atomic radiation can adversely affect the response to AZA, even 66 years after the exposure. Further studies are required to clarify the mechanisms underlying this phenomenon. Copyright© 2015 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.

Droplet Breakup Mechanisms in Air-blast Atomizers

NASA Astrophysics Data System (ADS)

Aliabadi, Amir Abbas; Taghavi, Seyed Mohammad; Lim, Kelly

2011-11-01

Atomization processes are encountered in many natural and man-made phenomena. Examples are pollen release by plants, human cough or sneeze, engine fuel injectors, spray paint and many more. The physics governing the atomization of liquids is important in understanding and utilizing atomization processes in both natural and industrial processes. We have observed the governing physics of droplet breakup in an air-blast water atomizer using a high magnification, high speed, and high resolution LASER imaging technique. The droplet breakup mechanisms are investigated in three major categories. First, the liquid drops are flattened to form an oblate ellipsoid (lenticular deformation). Subsequent deformation depends on the magnitude of the internal forces relative to external forces. The ellipsoid is converted into a torus that becomes stretched and disintegrates into smaller drops. Second, the drops become elongated to form a long cylindrical thread or ligament that break up into smaller drops (Cigar-shaped deformation). Third, local deformation on the drop surface creates bulges and protuberances that eventually detach themselves from the parent drop to form smaller drops.

Nanophotonic Optical Isolator Controlled by the Internal State of Cold Atoms

NASA Astrophysics Data System (ADS)

Sayrin, Clément; Junge, Christian; Mitsch, Rudolf; Albrecht, Bernhard; O'Shea, Danny; Schneeweiss, Philipp; Volz, Jürgen; Rauschenbeutel, Arno

2015-10-01

The realization of nanophotonic optical isolators with high optical isolation even at ultralow light levels and low optical losses is an open problem. Here, we employ the link between the local polarization of strongly confined light and its direction of propagation to realize low-loss nonreciprocal transmission through a silica nanofiber at the single-photon level. The direction of the resulting optical isolator is controlled by the spin state of cold atoms. We perform our experiment in two qualitatively different regimes, i.e., with an ensemble of cold atoms where each atom is weakly coupled to the waveguide and with a single atom strongly coupled to the waveguide mode. In both cases, we observe simultaneously high isolation and high forward transmission. The isolator concept constitutes a nanoscale quantum optical analog of microwave ferrite resonance isolators, can be implemented with all kinds of optical waveguides and emitters, and might enable novel integrated optical devices for fiber-based classical and quantum networks.

Quantum test of the equivalence principle for atoms in coherent superposition of internal energy states

PubMed Central

Rosi, G.; D'Amico, G.; Cacciapuoti, L.; Sorrentino, F.; Prevedelli, M.; Zych, M.; Brukner, Č.; Tino, G. M.

2017-01-01

The Einstein equivalence principle (EEP) has a central role in the understanding of gravity and space–time. In its weak form, or weak equivalence principle (WEP), it directly implies equivalence between inertial and gravitational mass. Verifying this principle in a regime where the relevant properties of the test body must be described by quantum theory has profound implications. Here we report on a novel WEP test for atoms: a Bragg atom interferometer in a gravity gradiometer configuration compares the free fall of rubidium atoms prepared in two hyperfine states and in their coherent superposition. The use of the superposition state allows testing genuine quantum aspects of EEP with no classical analogue, which have remained completely unexplored so far. In addition, we measure the Eötvös ratio of atoms in two hyperfine levels with relative uncertainty in the low 10−9, improving previous results by almost two orders of magnitude. PMID:28569742

Controlling interactions between highly magnetic atoms with Feshbach resonances.

PubMed

Kotochigova, Svetlana

2014-09-01

This paper reviews current experimental and theoretical progress in the study of dipolar quantum gases of ground and meta-stable atoms with a large magnetic moment. We emphasize the anisotropic nature of Feshbach resonances due to coupling to fast-rotating resonant molecular states in ultracold s-wave collisions between magnetic atoms in external magnetic fields. The dramatic differences in the distribution of resonances of magnetic (7)S3 chromium and magnetic lanthanide atoms with a submerged 4f shell and non-zero electron angular momentum is analyzed. We focus on dysprosium and erbium as important experimental advances have been recently made to cool and create quantum-degenerate gases for these atoms. Finally, we describe progress in locating resonances in collisions of meta-stable magnetic atoms in electronic P-states with ground-state atoms, where an interplay between collisional anisotropies and spin-orbit coupling exists.

Inductively guided circuits for ultracold dressed atoms

PubMed Central

Sinuco-León, German A.; Burrows, Kathryn A.; Arnold, Aidan S.; Garraway, Barry M.

2014-01-01

Recent progress in optics, atomic physics and material science has paved the way to study quantum effects in ultracold atomic alkali gases confined to non-trivial geometries. Multiply connected traps for cold atoms can be prepared by combining inhomogeneous distributions of DC and radio-frequency electromagnetic fields with optical fields that require complex systems for frequency control and stabilization. Here we propose a flexible and robust scheme that creates closed quasi-one-dimensional guides for ultracold atoms through the ‘dressing’ of hyperfine sublevels of the atomic ground state, where the dressing field is spatially modulated by inductive effects over a micro-engineered conducting loop. Remarkably, for commonly used atomic species (for example, 7Li and 87Rb), the guide operation relies entirely on controlling static and low-frequency fields in the regimes of radio-frequency and microwave frequencies. This novel trapping scheme can be implemented with current technology for micro-fabrication and electronic control. PMID:25348163

Emergence of Huge Negative Spin-Transfer Torque in Atomically Thin Co layers

NASA Astrophysics Data System (ADS)

Je, Soong-Geun; Yoo, Sang-Cheol; Kim, Joo-Sung; Park, Yong-Keun; Park, Min-Ho; Moon, Joon; Min, Byoung-Chul; Choe, Sug-Bong

2017-04-01

Current-induced domain wall motion has drawn great attention in recent decades as the key operational principle of emerging magnetic memory devices. As the major driving force of the motion, the spin-orbit torque on chiral domain walls has been proposed and is currently extensively studied. However, we demonstrate here that there exists another driving force, which is larger than the spin-orbit torque in atomically thin Co films. Moreover, the direction of the present force is found to be the opposite of the prediction of the standard spin-transfer torque, resulting in the domain wall motion along the current direction. The symmetry of the force and its peculiar dependence on the domain wall structure suggest that the present force is, most likely, attributed to considerable enhancement of a negative nonadiabatic spin-transfer torque in ultranarrow domain walls. Careful measurements of the giant magnetoresistance manifest a negative spin polarization in the atomically thin Co films which might be responsible for the negative spin-transfer torque.

First principles calculation of current-induced forces in atomic gold contacts

NASA Astrophysics Data System (ADS)

Brandbyge, Mads; Stokbro, Kurt; Taylor, Jeremy; Mozos, Jose-Luis; Ordejon, Pablo

2002-03-01

We have recently developed an first principles method [1] for calculating the electronic structure, electronic transport, and forces acting on the atoms, for atomic scale systems connected to semi-infinite electrodes and with an applied voltage bias. Our method is based on the density functional theory (DFT) as implemented in the well tested SIESTA program [2]. We fully deal with the atomistic structure of the whole system, treating both the contact and the electrodes on the same footing. The effect of the finite bias (including selfconsistency and the solution of the electrostatic problem) is taken into account using nonequilibrium Green's functions. In this talk we show results for the forces acting on the contact atoms due to the nonequilibrium situation in the electronic subsystem, i.e. in the presence of an electronic current. We concentrate on one atom wide gold contacts/wires connected to bulk gold electrodes. References [1] Our implementation is called TranSIESTA and is described in M. Brandbyge, J. Taylor, K. Stokbro, J-L. Mozos, and P. Ordejon, cond-mat/0110650 [2] D. Sanchez-Portal, P. Ordejon, E. Artacho and J. Soler, Int. J. Quantum Chem. 65, 453 (1997).

Glass-wool study of laser-induced spin currents en route to hyperpolarized Cs salt

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ishikawa, Kiyoshi

2011-07-15

The nuclear spin polarization of optically pumped Cs atoms flows to the surface of Cs hydride in a vapor cell. A fine glass wool lightly coated with the salt helps greatly increase the surface area in contact with the pumped atoms and enhance the spin polarization of the salt nuclei. Even though the glass wool randomly scatters the pump light, the atomic vapor can be polarized with unpolarized light in a magnetic field. The measured enhancement in the salt enables study of the polarizations of light and atomic nuclei very near the salt surface.

Wideband digital frequency detector with subtraction-based phase comparator for frequency modulation atomic force microscopy.

PubMed

Mitani, Yuji; Kubo, Mamoru; Muramoto, Ken-ichiro; Fukuma, Takeshi

2009-08-01

We have developed a wideband digital frequency detector for high-speed frequency modulation atomic force microscopy (FM-AFM). We used a subtraction-based phase comparator (PC) in a phase-locked loop circuit instead of a commonly used multiplication-based PC, which has enhanced the detection bandwidth to 100 kHz. The quantitative analysis of the noise performance revealed that the internal noise from the developed detector is small enough to provide the theoretically limited noise performance in FM-AFM experiments in liquid. FM-AFM imaging of mica in liquid was performed with the developed detector, showing its stability and applicability to true atomic-resolution imaging in liquid.

Rashba spin-orbit coupling for neutral atoms

NASA Astrophysics Data System (ADS)

Campbell, Daniel; Juzeliūnas, Gediminas; Spielman, Ian

2011-05-01

We theoretically describe a new class of atom-laser coupling schemes which lead to effective spin-orbit coupled Hamiltonians for ultra-cold neutral atoms. By properly setting the optical phases, a pair of degenerate spin states emerge as the lowest energy states in the spectrum, and are thus immune to collisionally induced decay. These schemes use N cyclically coupled ground or metastable internal states but we will specialize to the four-level case for this talk. Time permitting, we will describe a possible implementation of this scheme for 87Rb that adds a controllable Dresselhaus component to the effective Hamiltonian in a natural way. NSF through PFC at JQI, ARO with funds from Atomtronics MURI and DARPA OLE, STREP NAMEQUAM.

Interaction of excited He and Ne rare gas metastable atoms with the CHF2Cl molecule

NASA Astrophysics Data System (ADS)

Chérid, M.; Ben Arfa, M.; Driss Khodja, M.

2005-06-01

We studied the Penning ionization of the CHF2Cl molecule with He and Ne metastable atoms (He* and Ne*). We measured the electron kinetic energy and the time-of-flight mass spectra; we also determined the branching ratio for the parent ion and charged CHF+2, CHFCl+, HCF+/CF+ and Cl+ fragments. These data led us to discuss the dissociation channels for all the energetically-accessible electronic states of the ionized molecule. We evidenced a marked contrast in the fragment ion proportions for Ne*-CHF2Cl and He*-CHF2Cl systems, and related it to the difference in polarizability and internal energy of the He* and Ne* atoms.

Enhancing the Area of a Raman Atom Interferometer Using a Versatile Double-Diffraction Technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leveque, T.; Gauguet, A.; Michaud, F.

2009-08-21

In this Letter, we demonstrate a new scheme for Raman transitions which realize a symmetric momentum-space splitting of 4(Planck constant/2pi)k, deflecting the atomic wave packets into the same internal state. Combining the advantages of Raman and Bragg diffraction, we achieve a three pulse state labeled an interferometer, intrinsically insensitive to the main systematics and applicable to all kinds of atomic sources. This splitting scheme can be extended to 4N(Planck constant/2pi)k momentum transfer by a multipulse sequence and is implemented on a 8(Planck constant/2pi)k interferometer. We demonstrate the area enhancement by measuring inertial forces.

Recent trends in precision measurements of atomic and nuclear properties with lasers and ion traps

NASA Astrophysics Data System (ADS)

Block, Michael

2017-11-01

The X. international workshop on "Application of Lasers and Storage Devices in Atomic Nuclei Research" took place in Poznan in May 2016. It addressed the latest experimental and theoretical achievements in laser and ion trap-based investigations of radionuclides, highly charged ions and antiprotons. The precise determination of atomic and nuclear properties provides a stringent benchmark for theoretical models and eventually leads to a better understanding of the underlying fundamental interactions and symmetries. This article addresses some general trends in this field and highlights select recent achievements presented at the workshop. Many of these are covered in more detail within the individual contributions to this special issue of Hyperfine Interactions.

PREFACE: International Conference on Many Particle Spectroscopy of Atoms, Molecules, Clusters and Surfaces (MPS2014)

NASA Astrophysics Data System (ADS)

Ancarani, Lorenzo Ugo

2015-04-01

This volume contains a collection of contributions from the invited speakers at the 2014 edition of the International Conference on Many Particle Spectroscopy of Atoms, Molecules, Clusters and Surfaces held in Metz, France, from 15th to 18th July 2014. This biennial conference alternates with the ICPEAC satellite International Symposium on (e,2e), Double Photoionization and Related Topics, and is concerned with experimental and theoretical studies of radiation interactions with matter. These include many-body and electron-electron correlation effects in excitation, and in single and multiple ionization of atoms, molecules, clusters and surfaces with various projectiles: electrons, photons and ions. More than 80 scientists, from 19 different countries around the world, came together to discuss the most recent progress on these topics. The scientific programme included 28 invited talks and a poster session extending over the three days of the meeting. Amongst the 51 posters, 11 have been selected and were advertised through short talks. Besides, Professor Nora Berrah gave a talk in memory of Professor Uwe Becker who sadly passed away shortly after co-chairing the previous edition of this conference. Financial support from the Institut Jean Barriol, Laboratoire SRSMC, Groupement de Recherche THEMS (CNRS), Ville de Metz, Metz Métropole, Conseil Général de la Moselle and Région Lorraine is gratefully acknowledged. Finally, I would like to thank the members of the local committee and the staff of the Université de Lorraine for making the conference run smoothly, the International Advisory Board for building up the scientific programme, the sessions chairpersons, those who gave their valuable time in carefully refereeing the articles of this volume and last, but not least, all participants for contributing to lively and fruitful discussions throughout the meeting.

Phonon interference control of atomic-scale metamirrors, meta-absorbers, and heat transfer through crystal interfaces

NASA Astrophysics Data System (ADS)

Kosevich, Yu. A.; Potyomina, L. G.; Darinskii, A. N.; Strelnikov, I. A.

2018-03-01

The paper theoretically studies the possibility of using the effects of phonon interference between paths through different interatomic bonds for the control of phonon heat transfer through internal crystal interfaces and for the design of phonon metamirrors and meta-absorbers. These metamirrors and meta-absorbers are considered to be defect nanolayers of atomic-scale thicknesses embedded in a crystal. Several analytically solvable three-dimensional lattice-dynamics models of the phonon metamirrors and meta-absorbers at the internal crystal planes are described. It is shown that due to destructive interference in the two or more phonon paths, the internal crystal planes, fully or partially filled with weakly bound or heavy-isotope defect atoms, can completely reflect or completely absorb phonons at the transmission antiresonances, whose wavelengths are larger than the effective thickness of the metamirror or meta-absorber. Due to cooperative superradiant effect, the spectral widths of the two-path interference antiresonances for the plane waves are given by the square of partial filling fraction in the defect crystal plane. Our analysis reveals that the presence of two or more phonon paths plays the dominant role in the emergence of the transmission antiresonances in phonon scattering at the defect crystal planes and in reduction of the thermal interface conductance in comparison with the Fano-resonance concept. We study analytically phonon transmission through internal crystal plane in a model cubic lattice of Si-like atoms, partially filled with Ge-like defect atoms. Such a plane can serve as interference phonon metamirror with the transmission antiresonances in the vicinities of eigenmode frequencies of Ge-like defect atoms in the terahertz frequency range. We predict the extraordinary phonon transmission induced by the two-path constructive interference of the lattice waves in resonance with the vibrations of rare host atoms, periodically distributed in the crystal plane almost completely filled with heavy-isotope defects. We show that the phonon-interference-induced transparency can be produced by the defect nanolayer with the non-nearest-neighbor interactions, filled with two types of isotopes with relatively small difference in masses or binding force constants. In this case, relatively broad transmission antiresonance is accompanied by the narrow transmission peak close to the antiresonance frequency. We describe the softening of the flexural surface acoustic wave, localized at the embedded defect nanolayer, caused by negative surface stress in the layer. The surface wave softening results in spatially periodic static bending deformation of the embedded nanolayer with the definite wave number. The latter effect is estimated for graphene monolayer embedded in a strained matrix of polyethylene. We analyze the effect of nonlinearity in the dynamics of defect atoms on the one- and two-path phonon interference and show that the interference transmission resonances and antiresonances are shifted in frequencies but not completely suppressed by rather strong anharmonicity of interatomic bonds. The reduction of the Kapitza thermal interface conductance caused by the destructive phonon interference in a defect monolayer is described. We show that the additional relatively weak non-nearest-neighbor interactions through the defect crystal plane filled with heavy isotopes substantially reduces the interface thermal conductance, and this effect is stronger in the three-dimensional system than in the quasi-one-dimensional systems studied previously.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kirk, Bernadette Lugue; Eipeldauer, Mary D; Whitaker, J Michael

In 2007, the Department of Energy's National Nuclear Security Administration (DOE/NNSA) Office of Nonproliferation and International Security (NA-24) completed a comprehensive review of the current and potential future challenges facing the international safeguards system. The review examined trends and events impacting the mission of international safeguards and the implications of expanding and evolving mission requirements on the legal authorities and institutions that serve as the foundation of the international safeguards system, as well as the technological, financial, and human resources required for effective safeguards implementation. The review's findings and recommendations were summarized in the report, 'International Safeguards: Challenges and Opportunitiesmore » for the 21st Century (October 2007)'. One of the report's key recommendations was for DOE/NNSA to launch a major new program to revitalize the international safeguards technology and human resource base. In 2007, at the International Atomic Energy Agency's General Conference, then Secretary of Energy Samuel W. Bodman announced the newly created Next Generation Safeguards Initiative (NGSI). NGSI consists of five program elements: (1) Policy development and outreach; (2) Concepts and approaches; (3) Technology and analytical methodologies; (4) Human resource development; and (5) Infrastructure development. The ensuing report addresses the 'Human Resource Development (HRD)' component of NGSI. The goal of the HRD as defined in the NNSA Program Plan (November 2008) is 'to revitalize and expand the international safeguards human capital base by attracting and training a new generation of talent.' One of the major objectives listed in the HRD goal includes education and training, outreach to universities, professional societies, postdoctoral appointments, and summer internships at national laboratories. ORNL is a participant in the NGSI program, together with several DOE laboratories such as Pacific Northwest National Laboratory (PNNL), Lawrence Livermore National Laboratory (LLNL), Brookhaven National Laboratory (BNL), and Los Alamos National Laboratory (LANL). In particular, ORNL's participation encompasses student internships, postdoctoral appointments, collaboration with universities in safeguards curriculum development, workshops, and outreach to professional societies through career fairs.« less

Optimized coupling of cold atoms into a fiber using a blue-detuned hollow-beam funnel

NASA Astrophysics Data System (ADS)

Poulin, Jerome; Light, Philip S.; Kashyap, Raman; Luiten, Andre N.

2011-11-01

We theoretically investigate the process of coupling cold atoms into the core of a hollow-core photonic-crystal optical fiber using a blue-detuned Laguerre-Gaussian beam. In contrast to the use of a red-detuned Gaussian beam to couple the atoms, the blue-detuned hollow beam can confine cold atoms to the darkest regions of the beam, thereby minimizing shifts in the internal states and making the guide highly robust to heating effects. This single optical beam is used as both a funnel and a guide to maximize the number of atoms into the fiber. In the proposed experiment, Rb atoms are loaded into a magneto-optical trap (MOT) above a vertically oriented optical fiber. We observe a gravito-optical trapping effect for atoms with high orbital momentum around the trap axis, which prevents atoms from coupling to the fiber: these atoms lack the kinetic energy to escape the potential and are thus trapped in the laser funnel indefinitely. We find that by reducing the dipolar force to the point at which the trapping effect just vanishes, it is possible to optimize the coupling of atoms into the fiber. Our simulations predict that by using a low-power (2.5 mW) and far-detuned (300 GHz) Laguerre-Gaussian beam with a 20-μm-radius core hollow fiber, it is possible to couple 11% of the atoms from a MOT 9 mm away from the fiber. When the MOT is positioned farther away, coupling efficiencies over 50% can be achieved with larger core fibers.

Effect of Intermetallic on Electromigration and Atomic Diffusion in Cu/SnAg3.0Cu0.5/Cu Joints: Experimental and First-Principles Study

NASA Astrophysics Data System (ADS)

Zhou, Wei; Liu, Lijuan; Li, Baoling; Wu, Ping

2009-06-01

Electromigration phenomena in a one-dimensional Cu/SnAg3.0Cu0.5/Cu joint were investigated with current stressing. The special effect of intermetallic compound (IMC) layers on the formation of serious electromigration damage induced by nonuniform current density distribution was discussed based on experimental results. Meanwhile, hillocks were observed both at the anode and near the cathode of the joint, and they were described as the result of diffusion of atoms and compressive stress released along grain boundaries to the relatively free surface. Moreover, the diffusion behavior of Cu at the cathode was analyzed with the electromigration equation, and the stability of Ag atoms in the solder during electromigration was evaluated with a first-principles method.

[Atomic/ionic fluorescence in microwave plasma torch discharge excited by high current microsecond pulsed hollow cathode lamp-europium atomic/ionic fluorescence spectrometry].

PubMed

Gong, Z; Liang, F; Yang, P; Jin, Q; Huang, B

1999-06-01

Eu atomic and ionic fluorescence spectrometry in microwave plasma torch discharge excited by high current microsecond pulsed hollow cathode lamp (HCMP HCL-MPT AFS/IFS) was studied. Operating conditions were optimized. The best detection limits for AFS and IFS obtained with a desolvated ultrasonic nebulization system were 42.0 ng/mL for Eu I 462.7 nm and 21.8 ng/mL for Eu II 381.97 nm, respectively, both were better than those given by the instruction manual of a Baird ICP AFS-2000 spectrometer using pneumatic concentric nebulizer with desolvation for AFS, but were significantly higher than those obtained by using the Baird spectrometer with a mini-monochromator and a ultrasonic nebulzer system.

The Tunneling Microscope: A New Look at the Atomic World.

ERIC Educational Resources Information Center

Golovchenko, J. A.

1986-01-01

A new instrument called the tunneling microscope has recently been developed that is capable of generating real-space images of surfaces showing atomic structure. Discusses current capabilities, limitations, and the physics involved in the technique. Includes results from a study of silicon crystal surfaces. (JN)

Atomic Absorption Spectroscopy. The Present and the Future.

ERIC Educational Resources Information Center

Slavin, Walter

1982-01-01

The status of current techniques and methods of atomic absorption (AA) spectroscopy (flame, hybrid, and furnace AA) is discussed, including limitations. Technological opportunities and how they may be used in AA are also discussed, focusing on automation, microprocessors, continuum AA, hybrid analyses, and others. (Author/JN)

Strain amplitude-dependent anelasticity in Cu-Ni solid solution due to thermally activated and athermal dislocation-point obstacle interactions

NASA Astrophysics Data System (ADS)

Kustov, S.; Gremaud, G.; Benoit, W.; Golyandin, S.; Sapozhnikov, K.; Nishino, Y.; Asano, S.

1999-02-01

Experimental investigations of the internal friction and the Young's modulus defect in single crystals of Cu-(1.3-7.6) at. % Ni have been performed for 7-300 K over a wide range of oscillatory strain amplitudes. Extensive data have been obtained at a frequency of vibrations around 100 kHz and compared with the results obtained for the same crystals at a frequency of ˜1 kHz. The strain amplitude dependence of the anelastic strain amplitude and the average friction stress acting on a dislocation due to solute atoms are also analyzed. Several stages in the strain amplitude dependence of the internal friction and the Young's modulus defect are revealed for all of the alloy compositions, at different temperatures and in different frequency ranges. For the 100 kHz frequency, low temperatures and low strain amplitudes (˜10-7-10-5), the amplitude-dependent internal friction and the Young's modulus defect are essentially temperature independent, and are ascribed to a purely hysteretic internal friction component. At higher strain amplitudes, a transition stage and a steep strain amplitude dependence of the internal friction and the Young's modulus defect are observed, followed by saturation at the highest strain amplitudes employed. These stages are temperature and frequency dependent and are assumed to be due to thermally activated motion of dislocations. We suggest that the observed regularities in the entire strain amplitude, temperature and frequency ranges correspond to a motion of dislocations in a two-component system of obstacles: weak but long-range ones, due to the elastic interaction of dislocations with solute atoms distributed in the bulk of the crystal; and strong short-range ones, due to the interaction of dislocations with solute atoms distributed close to dislocation glide planes. Based on these assumptions, a qualitative explanation is given for the variety of experimental observations.

Investigation of an alternating current plasma as an element selective atomic emission detector for high-resolution capillary gas chromatography and as a source for atomic absorption and atomic emission spectrometry

NASA Astrophysics Data System (ADS)

Ombaba, Jackson M.

This thesis deals with the construction and evaluation of an alternating current plasma (ACP) as an element-selective detector for high resolution capillary gas chromatography (GC) and as an excitation source for atomic absorption spectrometry (AAS) and atomic emission spectrometry (AES). The plasma, constrained in a quartz discharge tube at atmospheric pressure, is generated between two copper electrodes and utilizes helium as the plasma supporting gas. The alternating current plasma power source consists of a step-up transformer with a secondary output voltage of 14,000 V at a current of 23 mA. The device exhibits a stable signal because the plasma is self-seeding and reignites itself every half cycle. A tesla coil is not required to commence generation of the plasma if the ac voltage applied is greater than the breakdown voltage of the plasma-supporting gas. The chromatographic applications studied included the following: (1) the separation and selective detection of the organotin species, tributyltin chloride (TBT) and tetrabutyltin (TEBT), in environmental matrices including mussels (Mvutilus edullus) and sediment from Boston Harbor, industrial waste water and industrial sludge, and (2) the detection of methylcyclopentadienyl manganesetricarbonyl (MMT) and similar compounds used as gasoline additives. An ultrasonic nebulizer (common room humidifier) was utilized as a sample introduction device for aqueous solutions when the ACP was employed as an atomization source for atomic absorption spectrometry and as an excitation source for atomic emission spectrometry. Plasma diagnostic parameters studied include spatial electron number density across the discharge tube, electronic, excitation and ionization temperatures. Interference studies both in absorption and emission modes were also considered. Figures of merits of selected elements both in absorption and emission modes are reported. The evaluation of a computer-aided optimization program, Drylab GC, using spearmint oil and Environmental Protection Agency (EPA) standard mixture as probes is also discussed. The program supplied by LC Resources (Lafayette, CA) is used for separation optimization and prediction of gas chromatographic parameters. Column dead-time and average plate number were used as input data in conjunction with the retention times and peak areas of solutes at two different temperature programming rates. Once input data are entered into an IBM or IBM compatible personal computer, the program produces a 'relative resolution map' (RRM) which guides the analyst in selecting the most favorable temperature programming rate for the separation.

Interface modulated currents in periodically proton exchanged Mg doped lithium niobate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neumayer, Sabine M.; Rodriguez, Brian J., E-mail: brian.rodriguez@ucd.ie, E-mail: gallo@kth.se; Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4

2016-03-21

Conductivity in Mg doped lithium niobate (Mg:LN) plays a key role in the reduction of photorefraction and is therefore widely exploited in optical devices. However, charge transport through Mg:LN and across interfaces such as electrodes also yields potential electronic applications in devices with switchable conductivity states. Furthermore, the introduction of proton exchanged (PE) phases in Mg:LN enhances ionic conductivity, thus providing tailorability of conduction mechanisms and functionality dependent on sample composition. To facilitate the construction and design of such multifunctional electronic devices based on periodically PE Mg:LN or similar ferroelectric semiconductors, fundamental understanding of charge transport in these materials, asmore » well as the impact of internal and external interfaces, is essential. In order to gain insight into polarization and interface dependent conductivity due to band bending, UV illumination, and chemical reactivity, wedge shaped samples consisting of polar oriented Mg:LN and PE phases were investigated using conductive atomic force microscopy. In Mg:LN, three conductivity states (on/off/transient) were observed under UV illumination, controllable by the polarity of the sample and the externally applied electric field. Measurements of currents originating from electrochemical reactions at the metal electrode–PE phase interfaces demonstrate a memresistive and rectifying capability of the PE phase. Furthermore, internal interfaces such as domain walls and Mg:LN–PE phase boundaries were found to play a major role in the accumulation of charge carriers due to polarization gradients, which can lead to increased currents. The insight gained from these findings yield the potential for multifunctional applications such as switchable UV sensitive micro- and nanoelectronic devices and bistable memristors.« less

Effects of structural modification on reliability of nanoscale nitride HEMTs

NASA Astrophysics Data System (ADS)

Gaddipati, Vamsi Mohan

AlGaN based nanoscale high-electron-mobility transistors (HEMTs) are the next generation of transistor technology that features the unique combination of higher power, wider bandwidth, low noise, higher efficiency, and temperature/radiation hardness than conventional AlGaAs and Si based technologies. However, as evidenced by recent stress tests, reliability of these devices (characterized by a gradual decrease in the output current/power leading to failure of the device in just tens of hours of operation) remains a major concern. Although, in these tests, physical damages were clearly visible in the device, the root cause and nature of these damages have not yet been fully assessed experimentally. Therefore, a comprehensive theoretical study of the physical mechanisms responsible for degradation of AlGaN HEMTs is essential before these devices are deployed in targeted applications. The main objective of the proposed research is to computationally investigate how degradation of state-of-the-art nanoscale AlGaN HEMTs is governed by an intricate and dynamical coupling of thermo-electromechanical processes at different length (atoms-to-transistor) and time (femtosecondto- hours) scales while operating in high voltage, large mechanical, and high temperature/radiation stresses. This work centers around a novel hypotheses as follows: High voltage applied to AlGaN HEMT causes excessive internal heat dissipation, which triggers gate metal diffusion into the semiconducting barrier layer and structural modifications (defect ii formation) leading to diminished polarization induced charge density and output current. Since the dynamical system to be studied is complex, chaotic (where the evolution rule is guided by atomicity of the underlying material), and involve coupled physical processes, an in-house multiscale simulator (QuADS 3-D) has been employed and augmented, where material parameters are obtained atomistically using firstprinciples, structural relaxation and defect formations will be modeled by integrating molecular dynamics, and the influence of atomistic processes on charge and phonon transport and current degradation will be simulated using a coupled drift-diffusionthermodynamic framework.

Atomic-scale diffractive imaging of sub-cycle electron dynamics in condensed matter

PubMed Central

Yakovlev, Vladislav S.; Stockman, Mark I.; Krausz, Ferenc; Baum, Peter

2015-01-01

For interaction of light with condensed-matter systems, we show with simulations that ultrafast electron and X-ray diffraction can provide a time-dependent record of charge-density maps with sub-cycle and atomic-scale resolutions. Using graphene as an example material, we predict that diffraction can reveal localised atomic-scale origins of optical and electronic phenomena. In particular, we point out nontrivial relations between microscopic electric current and density in undoped graphene. PMID:26412407

Spectroscopic data for an astronomy database

NASA Technical Reports Server (NTRS)

Parkinson, W. H.; Smith, Peter L.

1995-01-01

Very few of the atomic and molecular data used in analyses of astronomical spectra are currently available in World Wide Web (WWW) databases that are searchable with hypertext browsers. We have begun to rectify this situation by making extensive atomic data files available with simple search procedures. We have also established links to other on-line atomic and molecular databases. All can be accessed from our database homepage with URL: http:// cfa-www.harvard.edu/ amp/ data/ amdata.html.