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Sample records for atomic ag-o chains

  1. 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.

  2. Doping of Semiconducting Atomic Chains

    NASA Technical Reports Server (NTRS)

    Toshishige, Yamada; Kutler, Paul (Technical Monitor)

    1997-01-01

    Due to the rapid progress in atom manipulation technology, atomic chain electronics would not be a dream, where foreign atoms are placed on a substrate to form a chain, and its electronic properties are designed by controlling the lattice constant d. It has been shown theoretically that a Si atomic chain is metallic regardless of d and that a Mg atomic chain is semiconducting or insulating with a band gap modified with d. For electronic applications, it is essential to establish a method to dope a semiconducting chain, which is to control the Fermi energy position without altering the original band structure. If we replace some of the chain atoms with dopant atoms randomly, the electrons will see random potential along the chain and will be localized strongly in space (Anderson localization). However, if we replace periodically, although the electrons can spread over the chain, there will generally appear new bands and band gaps reflecting the new periodicity of dopant atoms. This will change the original band structure significantly. In order to overcome this dilemma, we may place a dopant atom beside the chain at every N lattice periods (N > 1). Because of the periodic arrangement of dopant atoms, we can avoid the unwanted Anderson localization. Moreover, since the dopant atoms do not constitute the chain, the overlap interaction between them is minimized, and the band structure modification can be made smallest. Some tight-binding results will be discussed to demonstrate the present idea.

  3. Doping Scheme of Semiconducting Atomic Chains

    NASA Technical Reports Server (NTRS)

    Toshishige, Yamada; Saini, Subhash (Technical Monitor)

    1998-01-01

    Atomic chains, precise structures of atomic scale created on an atomically regulated substrate surface, are candidates for future electronics. A doping scheme for intrinsic semiconducting Mg chains is considered. In order to suppress the unwanted Anderson localization and minimize the deformation of the original band shape, atomic modulation doping is considered, which is to place dopant atoms beside the chain periodically. Group I atoms are donors, and group VI or VII atoms are acceptors. As long as the lattice constant is long so that the s-p band crossing has not occurred, whether dopant atoms behave as donors or acceptors is closely related to the energy level alignment of isolated atomic levels. Band structures are calculated for Br-doped (p-type) and Cs-doped (n-type) Mg chains using the tight-binding theory with universal parameters, and it is shown that the band deformation is minimized and only the Fermi energy position is modified.

  4. Doping Scheme in Atomic Chain Electronics

    NASA Technical Reports Server (NTRS)

    Toshishige, Yamada

    1997-01-01

    Due to the dramatic reduction in MOS size, there appear many unwanted effects. In these small devices, the number of dopant atoms in the channel is not macroscopic and electrons may suffer significantly different scattering from device to device since the spatial distribution of dopant atoms is no longer regarded as continuous. This prohibits integration, while it is impossible to control such dopant positions within atomic scale. A fundamental solution is to create electronics with simple but atomically precise structures, which could be fabricated with recent atom manipulation technology. All the constituent atoms are placed as planned, and then the device characteristics are deviation-free, which is mandatory for integration. Atomic chain electronics belongs to this category. Foreign atom chains or arrays form devices, and they are placed on the atomically flat substrate surface. We can design the band structure and the resultant Fermi energy of these structures by manipulating the lattice constant. Using the tight-binding theory with universal parameters, it has been predicted that isolated Si chains and arrays are metallic, Mg chains are insulating, and Mg arrays have metallic and insulating phases [1]. The transport properties along a metallic chain have been studied, emphasizing the role of the contact to electrodes [2]. For electronic applications, it is essential to establish a method to dope a semiconducting chain, which is to control the Fermi energy position without altering the original band structure. If we replace some of the chain atoms with dopant atoms randomly, the electrons will see random potential along die chain and will be localized strongly in space (Anderson localization). However, if we replace periodically, although the electrons can spread over the chain, there will generally appear new bands and band gaps reflecting the new periodicity of dopant atoms. This will change the original band structure significantly. In order to overcome

  5. On Substrate for Atomic Chain Electronics

    NASA Technical Reports Server (NTRS)

    Yamada, Toshishige; Bauschlicher, Charles W., Jr.; Partridge, Harry; Saini, Subhash (Technical Monitor)

    1998-01-01

    A substrate for future atomic chain electronics, where adatoms are placed at designated positions and form atomically precise device components, is studied theoretically. The substrate has to serve as a two-dimensional template for adatom mounting with a reasonable confinement barrier and also provide electronic isolation, preventing unwanted coupling between independent adatom structures. However, the two requirements conflict. For excellent electronic isolation, we may seek adatom confinement via van der Waals interaction without chemical bonding to the substrate atoms, but the confinement turns out to be very weak and hence unsatisfactory. An alternative chemical bonding scheme with excellent structural strength is examined, but even fundamental adatom chain properties such as whether chains are semiconducting or metallic are strongly influenced by the nature of the chemical bonding, and electronic isolation is not always achieved. Conditions for obtaining semiconducting chains with well-localized surface-modes, leading to good isolation, are clarified and discussed.

  6. Substrate Effects for Atomic Chain Electronics

    NASA Technical Reports Server (NTRS)

    Yamada, Toshishige; Saini, Subhash (Technical Monitor)

    1998-01-01

    A substrate for future atomic chain electronics, where adatoms are placed at designated positions and form atomically precise device components, is studied theoretically. The substrate has to serve as a two-dimensional template for adatom mounting with a reasonable confinement barrier and also provide electronic isolation, preventing unwanted coupling between independent adatom structures. For excellent structural stability, we demand chemical bonding between the adatoms and substrate atoms, but then good electronic isolation may not be guaranteed. Conditions are clarified for good isolation. Because of the chemical bonding, fundamental adatom properties are strongly influenced: a chain with group IV adatoms having two chemical bonds, or a chain with group III adatoms having one chemical bond is semiconducting. Charge transfer from or to the substrate atoms brings about unintentional doping, and the electronic properties have to be considered for the entire combination of the adatom and substrate systems even if the adatom modes are well localized at the surface.

  7. Defect-induced conductance oscillations in short atomic chains

    NASA Astrophysics Data System (ADS)

    Wawrzyniak-Adamczewska, M.; Kostyrko, T.

    2012-05-01

    Electronic transport through a junction made of two gold electrodes connected with a gold chain containing a silver impurity is analyzed with a tight binding model and the density-functional theory. It is shown that the conductance depends in a simple way on the position of the impurity in the chain and the parity of the total number of atoms of the chain. For an odd chain the conductance takes on a higher value when the Ag impurity substitutes an even Au atom in the chain, and a lower one for an odd position of the Ag atom. In the case of an even chain the conductance hardly depends on the position of the Ag atom. This new kind of a defect-induced parity oscillation of the conductance is significantly more prominent than the well-known even-odd effect related to the dependence of the conductance on the parity of number of atoms in perfect chains.

  8. Carbon nanotube-clamped metal atomic chain

    PubMed Central

    Tang, Dai-Ming; Yin, Li-Chang; Li, Feng; Liu, Chang; Yu, Wan-Jing; Hou, Peng-Xiang; Wu, Bo; Lee, Young-Hee; Ma, Xiu-Liang; Cheng, Hui-Ming

    2010-01-01

    Metal atomic chain (MAC) is an ultimate one-dimensional structure with unique physical properties, such as quantized conductance, colossal magnetic anisotropy, and quantized magnetoresistance. Therefore, MACs show great potential as possible components of nanoscale electronic and spintronic devices. However, MACs are usually suspended between two macroscale metallic electrodes; hence obvious technical barriers exist in the interconnection and integration of MACs. Here we report a carbon nanotube (CNT)-clamped MAC, where CNTs play the roles of both nanoconnector and electrodes. This nanostructure is prepared by in situ machining a metal-filled CNT, including peeling off carbon shells by spatially and elementally selective electron beam irradiation and further elongating the exposed metal nanorod. The microstructure and formation process of this CNT-clamped MAC are explored by both transmission electron microscopy observations and theoretical simulations. First-principles calculations indicate that strong covalent bonds are formed between the CNT and MAC. The electrical transport property of the CNT-clamped MAC was experimentally measured, and quantized conductance was observed. PMID:20427743

  9. Ultrasonic atomization of liquids in drop-chain acoustic fountains

    PubMed Central

    Simon, Julianna C.; Sapozhnikov, Oleg A.; Khokhlova, Vera A.; Crum, Lawrence A.; Bailey, Michael R.

    2015-01-01

    When focused ultrasound waves of moderate intensity in liquid encounter an air interface, a chain of drops emerges from the liquid surface to form what is known as a drop-chain fountain. Atomization, or the emission of micro-droplets, occurs when the acoustic intensity exceeds a liquid-dependent threshold. While the cavitation-wave hypothesis, which states that atomization arises from a combination of capillary-wave instabilities and cavitation bubble oscillations, is currently the most accepted theory of atomization, more data on the roles of cavitation, capillary waves, and even heat deposition or boiling would be valuable. In this paper, we experimentally test whether bubbles are a significant mechanism of atomization in drop-chain fountains. High-speed photography was used to observe the formation and atomization of drop-chain fountains composed of water and other liquids. For a range of ultrasonic frequencies and liquid sound speeds, it was found that the drop diameters approximately equalled the ultrasonic wavelengths. When water was exchanged for other liquids, it was observed that the atomization threshold increased with shear viscosity. Upon heating water, it was found that the time to commence atomization decreased with increasing temperature. Finally, water was atomized in an overpressure chamber where it was found that atomization was significantly diminished when the static pressure was increased. These results indicate that bubbles, generated by either acoustic cavitation or boiling, contribute significantly to atomization in the drop-chain fountain. PMID:25977591

  10. Emerging magnetic order in platinum atomic contacts and chains

    PubMed Central

    Strigl, Florian; Espy, Christopher; Bückle, Maximilian; Scheer, Elke; Pietsch, Torsten

    2015-01-01

    The development of atomic-scale structures revealing novel transport phenomena is a major goal of nanotechnology. Examples include chains of atoms that form while stretching a transition metal contact or the predicted formation of magnetic order in these chains, the existence of which is still debated. Here we report an experimental study of the magneto-conductance (MC) and anisotropic MC with atomic-size contacts and mono-atomic chains of the nonmagnetic metal platinum. We find a pronounced and diverse MC behaviour, the amplitude and functional dependence change when stretching the contact by subatomic distances. These findings can be interpreted as a signature of local magnetic order in the chain, which may be of particular importance for the application of atomic-sized contacts in spintronic devices of the smallest possible size. PMID:25649440

  11. Substrate Effects on Electronic Properties of Atomic Chains

    NASA Technical Reports Server (NTRS)

    Yamada, Toshishige; Saini, Subhash (Technical Monitor)

    1998-01-01

    Atomic chains, precise structures of adatoms created on an atomically regulated surface, are candidates for constituent elements in future electronics. It was predicted that Si chains were metallic and Mg chains were semiconducting, and a doping method was also discussed. The substrate was assumed to work as a non-interacting template holding the adatoms. However, this scheme requires a low-temperature environment so that the adatoms will not displace from their ideal positions due to unwanted thermal agitation. For better structural stability, we may seek a scheme to allow the adatoms to form chemical bonding with the substrate atoms and secure their positions. The chemical bonding has two major effects on the chain electronic properties. First, only the remaining s and p orbitals in an adatom not used for the chemical bonding can decide chain band structures, rather than the full set of orbitals previously assumed. Second, because of a possible HOMO energy difference between adatom and substrate atom, semiconducting chains are unintentionally doped. These effects are studied with a self-consistent tight-binding method with universal parameters. With one adatom per unit cell, adatom chains are semiconducting: (1) if adatoms are of group III and form one chemical bond per adatom, or (2) if adatoms are of group IV and form two chemical bonds. 'Me previous result [I I of realizing semiconducting chains by group II adatoms without chemical bonds is consistent with this picture. When the HOMO energy in an adatom is shallower than that in a substrate atom, the entire chain is positively polarized, unintentionally achieving p-type doping. When deeper, the chain is negatively charged, achieving n-type doping.

  12. 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)). PMID:24849670

  13. Chains of carbon atoms: A vision or a new nanomaterial?

    PubMed

    Banhart, Florian

    2015-01-01

    Linear strings of sp(1)-hybridized carbon atoms are considered as a possible phase of carbon since decades. Whereas the debate about the stability of the corresponding bulk phase carbyne continues until today, the existence of isolated chains of carbon atoms has meanwhile been corroborated experimentally. Since graphene, as the two-dimensional sp(2)-bonded allotrope of carbon, has become a vast field, the question about the importance of one-dimensional carbon became of renewed interest. The present article gives an overview of the work that has been carried out on chains of carbon atoms in the past one or two decades. The review concentrates on isolated chains of carbon atoms and summarizes the experimental observations to date. While the experimental information is still very limited, many calculations of the physical and chemical properties have been published in the past years. Some of the most important theoretical studies and their importance in the present experimental situation are reviewed. PMID:25821697

  14. Chains of carbon atoms: A vision or a new nanomaterial?

    PubMed Central

    2015-01-01

    Summary Linear strings of sp1-hybridized carbon atoms are considered as a possible phase of carbon since decades. Whereas the debate about the stability of the corresponding bulk phase carbyne continues until today, the existence of isolated chains of carbon atoms has meanwhile been corroborated experimentally. Since graphene, as the two-dimensional sp2-bonded allotrope of carbon, has become a vast field, the question about the importance of one-dimensional carbon became of renewed interest. The present article gives an overview of the work that has been carried out on chains of carbon atoms in the past one or two decades. The review concentrates on isolated chains of carbon atoms and summarizes the experimental observations to date. While the experimental information is still very limited, many calculations of the physical and chemical properties have been published in the past years. Some of the most important theoretical studies and their importance in the present experimental situation are reviewed. PMID:25821697

  15. Electronic Conduction through Atomic Chains, Quantum Well and Quantum Wire

    NASA Astrophysics Data System (ADS)

    Sharma, A. C.

    2011-07-01

    Charge transport is dynamically and strongly linked with atomic structure, in nanostructures. We report our ab-initio calculations on electronic transport through atomic chains and the model calculations on electron-electron and electron-phonon scattering rates in presence of random impurity potential in a quantum well and in a quantum wire. We computed synthesis and ballistic transport through; (a) C and Si based atomic chains attached to metallic electrodes, (b) armchair (AC), zigzag (ZZ), mixed, rotated-AC and rotated-ZZ geometries of small molecules made of 2S, 6C & 4H atoms attaching to metallic electrodes, and (c) carbon atomic chain attached to graphene electrodes. Computed results show that synthesis of various atomic chains are practically possible and their transmission coefficients are nonzero for a wide energy range. The ab-initio calculations on electronic transport have been performed with the use of Landauer-type scattering formalism formulated in terms of Grben's functions in combination with ground-state DFT. The electron-electron and electron-phonon scattering rates have been calculated as function of excitation energy both at zero and finite temperatures for disordered 2D and 1D systems. Our model calculations suggest that electron scattering rates in a disordered system are mainly governed by effective dimensionality of a system, carrier concentration and dynamical screening effects.

  16. Encapsulating "armchair" carbon nanotubes with "zigzag" chains of Fe atoms

    NASA Astrophysics Data System (ADS)

    Boutko, V. G.; Gusev, A. A.; Shevtsova, T. N.; Pashkevich, Yu. G.

    2016-05-01

    Ab initio calculations of structural, electron, and magnetic properties of "armchair" carbon nanotubes (NT) encapsulated by a "zigzag" chain of Fe atoms Fe2@(n,n)m (m = 1, 2; n = 4, 5, 6, 7, 8, 9), are performed within the framework of the density functional theory. It is shown that optimizing the structure along the NT axis can significantly impact the binding energy of the NT and the Fe atom chain. It follows from the calculations that Fe2@(5,5) is the most stable of all the investigated encapsulated nanotubes. A two-fold decrease in the concentration of Fe in an encapsulated NT converts the system from exothermic to endothermic (Fe2@(5,5)m) and vice versa (Fe2@(6,6)m)). For large radii of an encapsulated NT (>4.13 Å) the binding energy of the NT and the Fe atom chain goes to zero, and the magnetic moments of the Fe atoms and the deviation of the Fe atoms from the NT axis go toward analogous values of the free "zigzag" Fe atom chain.

  17. Stability of conductance oscillations in carbon atomic chains

    NASA Astrophysics Data System (ADS)

    Yu, Jing-Xin; Hou, Zhi-Wei; Liu, Xiu-Ying

    2015-06-01

    The conductance stabilities of carbon atomic chains (CACs) with different lengths are investigated by performing theoretical calculations using the nonequilibrium Green’s function method combined with density functional theory. Regular even-odd conductance oscillation is observed as a function of the wire length. This oscillation is influenced delicately by changes in the end carbon or sulfur atoms as well as variations in coupling strength between the chain and leads. The lowest unoccupied molecular orbital in odd-numbered chains is the main transmission channel, whereas the conductance remains relatively small for even-numbered chains and a significant drift in the highest occupied molecular orbital resonance toward higher energies is observed as the number of carbon atoms increases. The amplitude of the conductance oscillation is predicted to be relatively stable based on a thiol joint between the chain and leads. Results show that the current-voltage evolution of CACs can be affected by the chain length. The differential and second derivatives of the conductance are also provided. Project supported by the National Natural Science Foundation of China (Grant Nos. 11304079, 11404094, and 51201059), the Priority Scientific and Technological Project of Henan Province, China (Grant No. 14A140027), the School Fund (Grant No. 2012BS055), and the Plan of Natural Science Fundamental Research of Henan University of Technology, China (Grant No. 2014JCYJ15).

  18. Substrate Effects on Electronic Properties of Atomic Chains

    NASA Technical Reports Server (NTRS)

    Yamada, Toshishige; Saini, Subhash (Technical Monitor)

    1998-01-01

    When the device size is reduced down to 0.07 micrometers, the number of dopant atoms in the channel will no longer be macroscopic, typically less than a hundred. A spatial distribution of these dopant atoms will fluctuate statistically from device to device even in identically designed devices, and this places a serious limitation for integration. It is, however, impractical to control dopant positions within atomic dimension. One fundamental solution to this problem is to create electronics with atomically precise, but preferably simple structures. Atomic chains, precise structures of adatoms created on an atomically regulated surface, are candidates for constituent components in future electronics. All the adatoms will be placed at designated positions on the substrate, and all the device structures will be precise, free from any deviations. It was predicted using the tight-binding calculation with universal parameters that silicon chains were metallic and magnesium chains were semiconducting regardless of the lattice spacing, and a possible doping method was also proposed. In these treatments, the substrate was assumed to serve as a non-interacting template holding the adatoms without a formation of chemical bonding with substrate atoms. However, this scheme may not be easy to implement experimentally. Adatoms will have to be fixed with a van der Waals force on the substrate, but the force is generally weak and an extremely low temperature environment has to be prepared to suppress their unwanted thermal displacement. It may be logical to seek a scheme to allow the adatoms to form chemical bonding with the substrate atoms and secure their positions. The substrate effects are studied in detail.

  19. First principles calculation of the structural, electronic, and magnetic properties of Au-Pd atomic chains

    SciTech Connect

    Dave, Mudra R.; Sharma, A. C.

    2015-06-24

    The structural, electronic and magnetic properties of free standing Au-Pd bimetallic atomic chain is studied using ab-initio method. It is found that electronic and magnetic properties of chains depend on position of atoms and number of atoms. Spin polarization factor for different atomic configuration of atomic chain is calculated predicting a half metallic behavior. It suggests a total spin polarised transport in these chains.

  20. Approaching the quantum limit for plasmonics: linear atomic chains

    NASA Astrophysics Data System (ADS)

    Bryant, Garnett W.

    2016-07-01

    Optical excitations in atomic-scale materials can be strongly mixed, with contributions from both single-particle transitions and collective response. This complicates the quantum description of these excitations, because there is no clear way to define their quantization. To develop a quantum theory for these optical excitations, they must first be characterized so that single-particle-like and collective excitations can be identified. Linear atomic chains, such as atom chains on surfaces, linear arrays of dopant atoms in semiconductors, or linear molecules, provide ideal testbeds for studying collective excitations in small atomic-scale systems. We use exact diagonalization to study the many-body excitations of finite (10 to 25) linear atomic chains described by a simplified model Hamiltonian. Exact diagonalization results can be very different from the density functional theory (DFT) results usually obtained. Highly correlated, multiexcitonic states, strongly dependent on the electron–electron interaction strength, dominate the exact spectral and optical response but are not present in DFT excitation spectra. The ubiquitous presence of excitonic many-body states in the spectra makes it hard to identify plasmonic excitations. A combination of criteria involving a many-body state’s transfer dipole moment, balance, transfer charge, dynamical response, and induced-charge distribution do strongly suggest which many-body states should be considered as plasmonic. This analysis can be used to reveal the few plasmonic many-body states hidden in the dense spectrum of low-energy single-particle-like states and many higher-energy excitonic-like states. These excitonic states are the predominant excitation because of the many possible ways to develop local correlations.

  1. Dynamical entanglement purification using chains of atoms and optical cavities

    SciTech Connect

    Gonta, Denis; Loock, Peter van

    2011-10-15

    In the framework of cavity QED, we propose a practical scheme to purify dynamically a bipartite entangled state using short chains of atoms coupled to high-finesse optical cavities. In contrast to conventional entanglement purification protocols, we avoid controlled-not gates, thus reducing complicated pulse sequences and superfluous qubit operations. Our interaction scheme works in a deterministic way and, together with entanglement distribution and swapping, opens a route toward efficient quantum repeaters for long-distance quantum communication.

  2. Stretching of Single Polymer Chains Using the Atomic Force Microscope

    NASA Astrophysics Data System (ADS)

    Ortiz, C.; van der Vegte, E. W.; van Swieten, E.; Robillard, G. T.; Hadziioannou, G.

    1998-03-01

    A variety of macroscopic phenomenon involve "nanoscale" polymer deformation including rubber elasticity, shear yielding, strain hardening, stress relaxation, fracture, and flow. With the advent of new and improved experimental techniques, such as the atomic force microscope (AFM), the probing of physical properties of polymers has reached finer and finer scales. The development of mixed self-assembling monolayer techniques and the chemical functionalization of AFM probe tips has allowed for mechanical experiments on single polymer chains of molecular dimensions. In our experiments, mixed monolayers are prepared in which end-functionalized, flexible polymer chains of thiol-terminated poly(methacrylic acid) are covalently bonded, isolated, and randomly distributed on gold substrates. The coils are then imaged, tethered to a gold-coated AFM tip, and stretched between the tip and the substrate in a conventional force / distance experiment. An increase in the attractive force due to entropic, elastic resistance to stretching, as well as fracture of the polymer chain is observed. The effect of chain stiffness, topological constraints, strain rate, mechanical hysteresis, and stress relaxation were investigated. Force modulation techniques were also employed in order to image the viscoelastic character of the polymer chains. Parallel work includes similar studies of biological systems such as wheat gluten proteins and polypeptides.

  3. Structure of Self-Assembled Mn Atom Chains on Si(001).

    PubMed

    Villarreal, R; Longobardi, M; Köster, S A; Kirkham, Ch J; Bowler, D; Renner, Ch

    2015-12-18

    Mn has been found to self-assemble into atomic chains running perpendicular to the surface dimer reconstruction on Si(001). They differ from other atomic chains by a striking asymmetric appearance in filled state scanning tunneling microscopy (STM) images. This has prompted complicated structural models involving up to three Mn atoms per chain unit. Combining STM, atomic force microscopy, and density functional theory we find that a simple necklacelike chain of single Mn atoms reproduces all their prominent features, including their asymmetry not captured by current models. The upshot is a remarkably simpler structure for modeling the electronic and magnetic properties of Mn atom chains on Si(001). PMID:26722930

  4. Atomic spin chains as testing ground for quantum magnetism

    NASA Astrophysics Data System (ADS)

    Otte, Sander

    2015-03-01

    The field of quantum magnetism aims to capture the rich emergent physics that arises when multiple spins interact, in terms of elementary models such as the spin 1/2 Heisenberg chain. Experimental platforms to verify these models are rare and generally do not provide the possibility to detect spin correlations locally. In my lab we use low-temperature scanning tunneling microscopy to design and build artificial spin lattices with atomic precision. Inelastic electron tunneling spectroscopy enables us to identify the ground state and probe spin excitations as a function of system size, location inside the lattice and coupling parameter values. Two types of collective excitations that play a role in many dynamic magnetic processes are spin waves (magnons) and spinons. Our experiments enable us to study both types of excitations. First, we have been able to map the standing spin wave modes of a ferromagnetic bit of six atoms, and to determine their role in the collective reversal process of the bit (Spinelli et al., Nature Materials 2014). More recently, we have crafted antiferromagnetic spin 1/2 XXZ chains, which allow us to observe spinon excitations, as well as the stepwise transition to a fully aligned phase beyond the critical magnetic field (Toskovic et al., in preparation). These findings create a promising experimental environment for putting quantum magnetic models to the test. Research funded by NWO and FOM.

  5. Mediator and label free estimation of stress biomarker using electrophoretically deposited Ag@AgO-polyaniline hybrid nanocomposite.

    PubMed

    Kaushik, Ajeet; Vasudev, Abhay; Arya, Sunil K; Bhansali, Shekhar

    2013-12-15

    Cortisol, a steroid hormone, is an important biomarker for psychological stress and its detection is gaining prominence for personalized health monitoring. In present work, electrophoretically deposited nanocomposite films of polyaniline (PANI) and core-shell Ag@AgO nanoparticles (NP~5 nm) have been explored as an electro-active nanostructured platform for Anti-cortisol antibody (Anti-Cab) immobilization for electrochemical immunosensing of cortisol. Covalent binding of Anti-Cab onto Ag@AgO-PANI nanocomposite was achieved using EDC/NHS chemistry, which results in the amide bond formation between amino groups of PANI and COOH groups of anti-Cab. Nonspecific binding sites on the immunosensing electrodes were blocked using bovine serum albumin (BSA). The uniform distribution of electro-active and surface charged Ag@AgO NP in PANI matrix results in a nanoporous granular morphology (roughness~10 nm) that provides a functionalized conductive microenvironment for Anti-Cab immobilization. The BSA/Anti-Cab/Ag@AgO-PANI/Au bioelectrodes have been characterized using electrochemical impedance technique (EIS), cyclic voltammetric (CV) technique and atomic force microscopic (AFM) technique, respectively. In CV studies nanocomposite exhibited characteristic response current peak corresponding to AgO NP (0.25 V) with large magnitude of current response and resulted in high electron transport at the electrode-electrolyte interface without a mediator. Electrochemical response studies via CV for the fabricated BSA/Anti-Cab/Ag@AgO-PANI/Au immunosensor as a function of cortisol concentration exhibited a wide linear detection range of 1 pM-1 µM, a detection limit of 0.64 pM mL(-1)(lower than ELISA), and high sensitivity 66 µA M(-1) with a regression coefficient of 0.998. The findings of present work may explore the application of Ag@AgO-PANI hybrid nanocomposite to detect cortisol and other biomarkers for point-of-care application. PMID:23831854

  6. Helical [110] gold nanowires make longer linear atomic chains

    NASA Astrophysics Data System (ADS)

    Amorim, Edgard; da Silva, Edison

    2009-03-01

    Experiments performed on nanowires (NWs) synthesized by electron beam irradiation technique have shown that gold NWs formed along the [110] direction become helical when the NWs are sufficiently thin [1]. Moreover, helical and other non-crystalline structures have been theoretically predicted to other few metals [2]. Our study using tight-binding molecular dynamics show that gold NWs formed along the [110] direction reconstruct upon stress to form helical NWs. We discuss this formation and our results seem to indicate that an intrinsic mechanism is responsible for the formation of the helical structure. These helical NWs evolve on stretching to form linear atomic chains (LACs) and because they do not form symmetrical tips, these NWs produce longer LACs than other NWs. We use ab initio calculations to study the NW obtained from the tigth-binding simulations at stages close to rupture and compare LAC distances obtained with both methods. Furthermore, we investigate the electronic structure of the NW close to rupture [3]. [1] Y. Kondo, and K. Takayanagi, Science 289, 606 (2000). [2] O. Gulseren, F. Ercolessi and E. Tosatti, Phys. Rev. Lett. 80, 3775 (1998). [3] E.P.M. Amorim and E.Z. da Silva, Phys. Rev. Lett. 101, 125502 (2008).

  7. Surface-enhanced Raman scattering from Ag nanoparticles formed by visible laser irradiation of thermally annealed AgO{sub x} thin films

    SciTech Connect

    Fujimaki, Makoto; Awazu, Koichi; Tominaga, Junji; Iwanabe, Yasuhiko

    2006-10-01

    Visible laser irradiation of AgO{sub x} thin films forms Ag nanoparticles, which then results in surface-enhanced Raman scattering (SERS). The efficiency of this Ag nanoparticle formation strongly depends on the properties of the AgO{sub x} thin films. Thermal annealing causes changes in physical properties such as deoxidization of the films and aggregation of Ag atoms in the films. In the present research, the effects of the changes induced by thermal annealing on SERS efficiency were examined. It was found that AgO{sub x} thin films annealed at 300 deg. C for 5 min in a N{sub 2} atmosphere were suitable for the formation of Ag nanoparticles effective for SERS, while films that were not annealed were not. From these results, it was deduced that the Ag aggregation resulting from thermal annealing in AgO{sub x} thin films promotes the Ag nanoparticle formation.

  8. The magnetism and spin-dependent electronic transport properties of boron nitride atomic chains.

    PubMed

    An, Yipeng; Zhang, Mengjun; Wu, Dapeng; Fu, Zhaoming; Wang, Tianxing; Jiao, Zhaoyong; Wang, Kun

    2016-07-28

    Very recently, boron nitride atomic chains were successively prepared and observed in experiments [O. Cretu et al., ACS Nano 8, 11950 (2015)]. Herein, using a first-principles technique, we study the magnetism and spin-dependent electronic transport properties of three types of BN atomic chains whose magnetic moment is 1 μB for BnNn-1, 2 μB for BnNn, and 3 μB for BnNn+1 type atomic chains, respectively. The spin-dependent electronic transport results demonstrate that the short BnNn+1 chain presents an obvious spin-filtering effect with high spin polarization ratio (>90%) under low bias voltages. Yet, this spin-filtering effect does not occur for long BnNn+1 chains under high bias voltages and other types of BN atomic chains (BnNn-1 and BnNn). The proposed short BnNn+1 chain is predicted to be an effective low-bias spin filters. Moreover, the length-conductance relationships of these BN atomic chains were also studied. PMID:27475355

  9. Strain-induced metal–semiconductor transition observed in atomic carbon chains

    PubMed Central

    La Torre, A.; Botello-Mendez, A.; Baaziz, W.; Charlier, J. -C.; Banhart, F.

    2015-01-01

    Carbyne, the sp1-hybridized phase of carbon, is still a missing link in the family of carbon allotropes. While the bulk phases of carbyne remain elusive, the elementary constituents, that is, linear chains of carbon atoms, have already been observed using the electron microscope. Isolated atomic chains are highly interesting one-dimensional conductors that have stimulated considerable theoretical work. Experimental information, however, is still very limited. Here we show electrical measurements and first-principles transport calculations on monoatomic carbon chains. When the 1D system is under strain, the chains are semiconducting corresponding to the polyyne structure with alternating bond lengths. Conversely, when the chain is unstrained, the ohmic behaviour of metallic cumulene with uniform bond lengths is observed. This confirms the recent prediction of a metal–insulator transition that is induced by strain. The key role of the contacting leads explains the rectifying behaviour measured in monoatomic carbon chains in a nonsymmetric contact configuration. PMID:25818506

  10. Area-efficient nonvolatile carry chain based on pass-transistor/atom-switch hybrid logic

    NASA Astrophysics Data System (ADS)

    Bai, Xu; Tsuji, Yukihide; Sakamoto, Toshitsugu; Morioka, Ayuka; Miyamura, Makoto; Tada, Munehiro; Banno, Naoki; Okamoto, Koichiro; Iguchi, Noriyuki; Hada, Hiromitsu

    2016-04-01

    For the first time, an area-efficient nonvolatile carry chain combining look-up tables and a pass-transistor-logic-based adder is newly developed using complementary atom switches without additional CMOS circuits. A proposed tristate switch composed of three pairs of complementary atom switches selects one of “0”, “1”, and the “carry_in” signal as the input of a common multiplexer for both a look-up table and an adder. The developed nonvolatile carry chain achieves the reductions of 20% area, 17% delay, and 17% power consumption, respectively, in comparison with a conventional nonvolatile carry chain using dedicated CMOS gates.

  11. Plasmon-induced dynamics of H{sub 2} splitting on a silver atomic chain

    SciTech Connect

    Yan, Lei; Ding, Zijing; Song, Peng; Wang, Fangwei; Meng, Sheng

    2015-08-24

    Localized surface plasmon resonances (LSPR) supported in metal nanostructures can be efficiently harnessed to drive photocatalytic reactions, whose atomic scale mechanism remains a challenge. Here, real-time dynamics of H{sub 2} photosplitting on a linear silver atomic chain, upon exposure to femtosecond laser pulses, has been investigated using time-dependent density functional theory. The wavelength dependent H{sub 2} splitting process is strongly coupled to LSPR excitation in silver chain. We identify that hot electrons produced in the silver chain by plasmon excitation are transferred to the antibonding state of the adsorbed H{sub 2} and trigger H{sub 2} dissociation, consistent with experimental observations. Increasing illumination intensity and the length of atomic chain promote H{sub 2} splitting, thanks to stronger LSPR. Dynamic electronic response can be quantitatively described within the present approach, providing insights towards a complete fundamental understanding on plasmon-induced chemical reactions at the microscopic scale.

  12. Study on nitrogen doped carbon atom chains with negative differential resistance effect

    NASA Astrophysics Data System (ADS)

    Shen, Ji-Mei; Liu, Jing; Min, Yi; Zhou, Li-Ping

    2016-05-01

    Recent calculations (Mahmoud and Lugli, 2013, [21]) of gold leads sandwiching carbon chains which are separated by diphenyl-dimethyl demonstrated that the negative differential resistance (NDR) effect appears only for "odd" numbers of carbon atoms. In this paper, according to a first-principles study based on non-equilibrium Green's function combining density functional theory, we find that the NDR effect appears both for "odd" and for "even" numbers of carbon atoms when the chains are doped by nitrogen atom. Our calculations remove the restriction of "odd/even" chains for the NDR effect, which may promise the potential applications of carbon chains in the nano-scale or molecular devices in the future.

  13. Observation of Aubry-type transition in finite atom chains via friction.

    PubMed

    Bylinskii, Alexei; Gangloff, Dorian; Counts, Ian; Vuletić, Vladan

    2016-07-01

    The highly nonlinear many-body physics of a chain of mutually interacting atoms in contact with a periodic substrate gives rise to complex static and dynamical phenomena, such as structural phase transitions and friction. In the limit of an infinite chain incommensurate with the substrate, Aubry predicted a transition with increasing substrate potential, from the chain's intrinsic arrangement free to slide on the substrate, to a pinned arrangement favouring the substrate pattern. So far, the Aubry transition has not been observed. Here, using spatially resolved position and friction measurements of cold trapped ions in an optical lattice, we observed a finite version of the Aubry transition and the onset of its hallmark fractal atomic arrangement. Notably, the observed critical lattice depth for few-ion chains agrees well with the infinite-chain prediction. Our results elucidate the connection between competing ordering patterns and superlubricity in nanocontacts-the elementary building blocks of friction. PMID:26998915

  14. One-dimensional Mn atom chains templated on a Si(001) surface

    NASA Astrophysics Data System (ADS)

    Köster, Sigrun A.; Owen, James H. G.; Bianco, François; Sena, Alex M. P.; Bowler, David R.; Renner, Christoph

    2011-03-01

    Single-atom chains on a wide gap substrate are a very attractive embodiment of a truly one-dimensional system to explore the remarkable physical properties emerging in such low dimensions. We present self-assembled single-atom Mn chains on a Si(001) surface with Bi nanolines, which serve to increase greatly the average length of the Mn chains. They grow perpendicular to the Si(001) dimer rows, at densities which can be adjusted by means of the growth parameter. High resolution scanning tunneling microscopy (STM) micrographs are in perfect agreement with density functional theory (DFT), providing detailed insight into the chain structure. We further discuss low temperature STM spectroscopy and spin dependent DFT modeling suggesting Mn-chains are indeed a suitable candidate to observe electronic and magnetic properties in one-dimension experimentally. This work was supported by the MaNEP research program via the swiss national science foundation (SNF).

  15. Antiferromagnetic Heisenberg Spin Chain of a Few Cold Atoms in a One-Dimensional Trap

    NASA Astrophysics Data System (ADS)

    Murmann, S.; Deuretzbacher, F.; Zürn, G.; Bjerlin, J.; Reimann, S. M.; Santos, L.; Lompe, T.; Jochim, S.

    2015-11-01

    We report on the deterministic preparation of antiferromagnetic Heisenberg spin chains consisting of up to four fermionic atoms in a one-dimensional trap. These chains are stabilized by strong repulsive interactions between the two spin components without the need for an external periodic potential. We independently characterize the spin configuration of the chains by measuring the spin orientation of the outermost particle in the trap and by projecting the spatial wave function of one spin component on single-particle trap levels. Our results are in good agreement with a spin-chain model for fermionized particles and with numerically exact diagonalizations of the full few-fermion system.

  16. Fractional Band Filling in an Atomic Chain Structure

    NASA Astrophysics Data System (ADS)

    Crain, J. N.; Kirakosian, A.; Altmann, K. N.; Bromberger, C.; Erwin, S. C.; McChesney, J. L.; Lin, J.-L.; Himpsel, F. J.

    2003-05-01

    A new chain structure of Au is found on stepped Si(111) which exhibits a 1/4-filled band and a pair of ≥1/2-filled bands with a combined filling of 4/3. Band dispersions and Fermi surfaces for Si(553)-Au are obtained by photoemission and compared to that of Si(557)-Au. The dimensionality of both systems is determined using a tight binding fit. The fractional band filling makes it possible to preserve metallicity in the presence of strong correlations.

  17. Wired up: interconnecting two-dimensional materials with one-dimensional atomic chains.

    PubMed

    Rong, Youmin; Warner, Jamie H

    2014-12-23

    Atomic wires are chains of atoms sequentially bonded together and epitomize the structural form of a one-dimensional (1D) material. In graphene, they form as interconnects between regions when the nanoconstriction eventually becomes so narrow that it is reduced to one atom thick. In this issue of ACS Nano, Cretu et al. extend the discovery of 1D atomic wire interconnects in two-dimensional (2D) materials to hexagonal boron nitride. We highlight recent progress in the area of 1D atomic wires within 2D materials, with a focus on their atomic-level structural analysis using aberration-corrected transmission electron microscopy. We extend this discussion to the formation of nanowires in transition metal dichalcogenides under similar electron-beam irradiation conditions. The future outlook for atomic wires is considered in the context of new 2D materials and hybrids of C, B, and N. PMID:25474120

  18. Single-photon transport through an atomic chain coupled to a one-dimensional nanophotonic waveguide

    NASA Astrophysics Data System (ADS)

    Liao, Zeyang; Zeng, Xiaodong; Zhu, Shi-Yao; Zubairy, M. Suhail

    2015-08-01

    We study the dynamics of a single-photon pulse traveling through a linear atomic chain coupled to a one-dimensional (1D) single mode photonic waveguide. We derive a time-dependent dynamical theory for this collective many-body system which allows us to study the real time evolution of the photon transport and the atomic excitations. Our analytical result is consistent with previous numerical calculations when there is only one atom. For an atomic chain, the collective interaction between the atoms mediated by the waveguide mode can significantly change the dynamics of the system. The reflectivity of a photon can be tuned by changing the ratio of coupling strength and the photon linewidth or by changing the number of atoms in the chain. The reflectivity of a single-photon pulse with finite bandwidth can even approach 100 % . The spectrum of the reflected and transmitted photon can also be significantly different from the single-atom case. Many interesting physical phenomena can occur in this system such as the photonic band-gap effects, quantum entanglement generation, Fano-like interference, and superradiant effects. For engineering, this system may serve as a single-photon frequency filter, single-photon modulation, and may find important applications in quantum information.

  19. Accelerated CO2 transport on surface of AgO nanoparticles in ionic liquid BMIMBF4

    PubMed Central

    Ji, Dahye; Kang, Yong Soo; Kang, Sang Wook

    2015-01-01

    The AgO nanoparticles were utilized for a CO2 separation membrane. The AgO nanoparticles were successfully generated in ionic liquid 1-butyl-3-methyl imidazolium tetrafluoroborate (BMIMBF4) by favorable interaction between the surface of particles and the counteranion of BMIMBF4. The generated AgO nanoparticles were confirmed by TEM, and the average size was 20 nm. Coordinative interactions of dissociated AgO particles with BMIM+BF4− were investigated by FT-Raman spectroscopy. When the ionic liquid BMIMBF4 containing AgO nanoparticles was utilized as a CO2 separation membrane, the separation performance was largely enhanced. PMID:26549605

  20. Quantum Spin Dimers from Chiral Dissipation in Cold-Atom Chains

    NASA Astrophysics Data System (ADS)

    Ramos, Tomás; Pichler, Hannes; Daley, Andrew J.; Zoller, Peter

    2014-12-01

    We consider the nonequilibrium dynamics of a driven dissipative spin chain with chiral coupling to a one-dimensional (1D) bosonic bath, and its atomic implementation with a two-species mixture of cold quantum gases. The reservoir is represented by a spin-orbit coupled 1D quasicondensate of atoms in a magnetized phase, while the spins are identified with motional states of a separate species of atoms in an optical lattice. The chirality of reservoir excitations allows the spins to couple differently to left- and right-moving modes, which in our atomic setup can be tuned from bidirectional to purely unidirectional. Remarkably, this leads to a pure steady state in which pairs of neighboring spins form dimers that decouple from the remainder of the chain. Our results also apply to current experiments with two-level emitters coupled to photonic waveguides.

  1. One-photon scattering by an atomic chain in a two-mode resonator: cyclic conditions

    PubMed Central

    2014-01-01

    In this work, a chain of N identical two-level atoms coupled with a quantized electromagnetic field, initially prepared via a single-photon Fock state, is investigated. The N-particle state amplitude of the system is calculated for several space configurations of the atoms in the Weisskopf-Wigner approximation. It was shown that the space configuration of an atomic chain, the total number of atoms, and even the available volume for the field modes define the behavior of the system state amplitude with time. Applying the condition of ‘cyclic bonds’, presented in this work, to the elaborated theory allows to describe the system time evolution, practically, for any space configuration. PMID:24860278

  2. One-photon scattering by an atomic chain in a two-mode resonator: cyclic conditions

    NASA Astrophysics Data System (ADS)

    Sizhuk, Andrii S.; Yezhov, Stanislav M.

    2014-05-01

    In this work, a chain of N identical two-level atoms coupled with a quantized electromagnetic field, initially prepared via a single-photon Fock state, is investigated. The N-particle state amplitude of the system is calculated for several space configurations of the atoms in the Weisskopf-Wigner approximation. It was shown that the space configuration of an atomic chain, the total number of atoms, and even the available volume for the field modes define the behavior of the system state amplitude with time. Applying the condition of `cyclic bonds', presented in this work, to the elaborated theory allows to describe the system time evolution, practically, for any space configuration.

  3. One-photon scattering by an atomic chain in a two-mode resonator: cyclic conditions.

    PubMed

    Sizhuk, Andrii S; Yezhov, Stanislav M

    2014-01-01

    In this work, a chain of N identical two-level atoms coupled with a quantized electromagnetic field, initially prepared via a single-photon Fock state, is investigated. The N-particle state amplitude of the system is calculated for several space configurations of the atoms in the Weisskopf-Wigner approximation. It was shown that the space configuration of an atomic chain, the total number of atoms, and even the available volume for the field modes define the behavior of the system state amplitude with time. Applying the condition of 'cyclic bonds', presented in this work, to the elaborated theory allows to describe the system time evolution, practically, for any space configuration. PMID:24860278

  4. Crystallization behavior of single isotactic poly(methyl methacrylate) chains visualized by atomic force microscopy.

    PubMed

    Anzai, Takahiro; Kawauchi, Mariko; Kawauchi, Takehiro; Kumaki, Jiro

    2015-01-01

    We have, for the first time, successfully visualized the crystallization behavior of a single isolated polymer chain at the molecular level by atomic force microscopy (AFM). Previously, we found that isotactic poly(methyl methacrylate) (it-PMMA) formed two-dimensional folded chain crystals composed of double-stranded helices upon compression of its Langmuir monolayer on a water surface, and the molecular images of the crystals deposited on mica were clearly visualized by AFM (Kumaki, J.; et al. J. Am. Chem. Soc. 2005, 127, 5788). In the present study, a high-molecular-weight it-PMMA was diluted in a monolayer of an it-PMMA oligomer which cannot crystallize at the experimental temperature due to its low molecular weight. At a low surface pressure, isolated amorphous chains of the high-molecular-weight it-PMMA solubilized in the oligomer monolayer were observed. On compression, the isolated chains converted to crystals composed of a single chain, typically some small crystallites linked by an amorphous chain like a necklace. Detailed AFM observations of the crystals indicated that the crystalline nuclei preferentially formed at the ends of the chains, and the size of the nuclei was almost independent of the molecular weight of it-PMMA over a wide range. At an extremely slow compression, crystallization was promoted, resulting in crystallization of the whole chain. The crystallization behavior of a single isolated chain provides new insights in understanding the polymer crystallization process. PMID:25496047

  5. Catalytic behavior of `Pt-atomic chain encapsulated gold nanotube': A density functional study

    NASA Astrophysics Data System (ADS)

    Nigam, Sandeep; Majumder, Chiranjib

    2016-05-01

    With an aim to design novel material and explore its catalytic performance towards CO oxidation, Pt atomic chain was introduced inside gold nanotube (Au-NT). Theoretical calculations at the level of first principles formalism was carried out to investigate the atomic and electronic properties of the composite. Geometrically Pt atoms prefer to align in zig-zag fashion. Significant electronic charge transfer from inside Pt atoms to the outer wall Au atoms is observed. Interaction of O2 with Au-NT wall follows by injection of additional electronic charge in the anti-bonding orbital of oxygen molecule leading to activation of the O-O bond. Further interaction of CO molecule with the activated oxygen molecule leads to spontaneous oxidation reaction and formation of CO2.

  6. Correlation between morphology, electron band structure, and resistivity of Pb atomic chains on the Si(5 5 3)-Au surface.

    PubMed

    Jałochowski, M; Kwapiński, T; Łukasik, P; Nita, P; Kopciuszyński, M

    2016-07-20

    Structural and electron transport properties of multiple Pb atomic chains fabricated on the Si(5 5 3)-Au surface are investigated using scanning tunneling spectroscopy, reflection high electron energy diffraction, angular resolved photoemission electron spectroscopy and in situ electrical resistance. The study shows that Pb atomic chains growth modulates the electron band structure of pristine Si(5 5 3)-Au surface and hence changes its sheet resistivity. Strong correlation between chains morphology, electron band structure and electron transport properties is found. To explain experimental findings a theoretical tight-binding model of multiple atomic chains interacting on effective substrate is proposed. PMID:27228462

  7. Correlation between morphology, electron band structure, and resistivity of Pb atomic chains on the Si(5 5 3)-Au surface

    NASA Astrophysics Data System (ADS)

    Jałochowski, M.; Kwapiński, T.; Łukasik, P.; Nita, P.; Kopciuszyński, M.

    2016-07-01

    Structural and electron transport properties of multiple Pb atomic chains fabricated on the Si(5 5 3)-Au surface are investigated using scanning tunneling spectroscopy, reflection high electron energy diffraction, angular resolved photoemission electron spectroscopy and in situ electrical resistance. The study shows that Pb atomic chains growth modulates the electron band structure of pristine Si(5 5 3)-Au surface and hence changes its sheet resistivity. Strong correlation between chains morphology, electron band structure and electron transport properties is found. To explain experimental findings a theoretical tight-binding model of multiple atomic chains interacting on effective substrate is proposed.

  8. Atomic structure and dynamic behaviour of truly one-dimensional ionic chains inside carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Senga, Ryosuke; Komsa, Hannu-Pekka; Liu, Zheng; Hirose-Takai, Kaori; Krasheninnikov, Arkady V.; Suenaga, Kazu

    2014-11-01

    Materials with reduced dimensionality have attracted much interest in various fields of fundamental and applied science. True one-dimensional (1D) crystals with single-atom thickness have been realized only for few elemental metals (Au, Ag) or carbon, all of which showed very short lifetimes under ambient conditions. We demonstrate here a successful synthesis of stable 1D ionic crystals in which two chemical elements, one being a cation and the other an anion, align alternately inside carbon nanotubes. Unusual dynamical behaviours for different atoms in the 1D lattice are experimentally corroborated and suggest substantial interactions of the atoms with the nanotube sheath. Our theoretical studies indicate that the 1D ionic crystals have optical properties distinct from those of their bulk counterparts and that the properties can be engineered by introducing atomic defects into the chains.

  9. Dissociation energies of Ag-RG (RG = Ar, Kr, Xe) and AgO molecules from velocity map imaging studies.

    PubMed

    Cooper, Graham A; Kartouzian, Aras; Gentleman, Alexander S; Iskra, Andreas; van Wijk, Robert; Mackenzie, Stuart R

    2015-09-28

    The near ultraviolet photodissociation dynamics of silver atom-rare gas dimers have been studied by velocity map imaging. Ag-RG (RG = Ar, Kr, Xe) species generated by laser ablation are excited in the region of the C ((2)Σ(+))←X ((2)Σ(+)) continuum leading to direct, near-threshold dissociation generating Ag* ((2)P3/2) + RG ((1)S0) products. Images recorded at excitation wavelengths throughout the C ((2)Σ(+))←X ((2)Σ(+)) continuum, coupled with known atomic energy levels, permit determination of the ground X ((2)Σ(+)) state dissociation energies of 85.9 ± 23.4 cm(-1) (Ag-Ar), 149.3 ± 22.4 cm(-1) (Ag-Kr), and 256.3 ± 16.0 cm(-1) (Ag-Xe). Three additional photolysis processes, each yielding Ag atom photoproducts, are observed in the same spectral region. Two of these are markedly enhanced in intensity upon seeding the molecular beam with nitrous oxide, and are assigned to photodissociation of AgO at the two-photon level. These features yield an improved ground state dissociation energy for AgO of 15 965 ± 81 cm(-1), which is in good agreement with high level calculations. The third process results in Ag atom fragments whose kinetic energy shows anomalously weak photon energy dependence and is assigned tentatively to dissociative ionization of the silver dimer Ag2. PMID:26429006

  10. Visualizing Majorana fermions in a chain of magnetic atoms on a superconductor

    NASA Astrophysics Data System (ADS)

    Yazdani, Ali

    2015-12-01

    A chain of magnetic atoms on the surface of a superconductor provides a versatile platform for realizing a one-dimensional topological superconductivity phase with edge-bounded Majorana fermions zero modes. This platform lends itself to spatial resolved measurements with scanning tunneling microscope (STM) that enables direct visualization of the presence of a localized Majorana zero mode. Experiments on self-assembled chains of Fe atoms on the surface of Pb show that such a system can be experimentally fabricated and studied using various high-resolution STM measurement techniques. Spatial and energy resolved STM experiments provide strong evidence for Majorana bound states that emerge due to the combination of Fe’s ferromagnetism and spin-orbit coupling of the superconducting Pb substrate. These studies provide a roadmap for optimizing topological superconductivity in this one-dimensional platform and its extension to realize chiral two-dimensional superconductors.

  11. Atomic spin-chain realization of a model for quantum criticality

    NASA Astrophysics Data System (ADS)

    Toskovic, R.; van den Berg, R.; Spinelli, A.; Eliens, I. S.; van den Toorn, B.; Bryant, B.; Caux, J.-S.; Otte, A. F.

    2016-07-01

    The ability to manipulate single atoms has opened up the door to constructing interesting and useful quantum structures from the ground up. On the one hand, nanoscale arrangements of magnetic atoms are at the heart of future quantum computing and spintronic devices; on the other hand, they can be used as fundamental building blocks for the realization of textbook many-body quantum models, illustrating key concepts such as quantum phase transitions, topological order or frustration as a function of system size. Here, we use low-temperature scanning tunnelling microscopy to construct arrays of magnetic atoms on a surface, designed to behave like spin-1/2 XXZ Heisenberg chains in a transverse field, for which a quantum phase transition from an antiferromagnetic to a paramagnetic phase is predicted in the thermodynamic limit. Site-resolved measurements on these finite-size realizations reveal a number of sudden ground state changes when the field approaches the critical value, each corresponding to a new domain wall entering the chains. We observe that these state crossings become closer for longer chains, suggesting the onset of critical behaviour. Our results present opportunities for further studies on quantum behaviour of many-body systems, as a function of their size and structural complexity.

  12. Electronic transport in large systems through a QUAMBO-NEGF approach: Application to atomic carbon chains

    NASA Astrophysics Data System (ADS)

    Fang, X. W.; Zhang, G. P.; Yao, Y. X.; Wang, C. Z.; Ding, Z. J.; Ho, K. M.

    2011-10-01

    The conductance of single-atom carbon chain (SACC) between two zigzag graphene nanoribbons (GNR) is studied by an efficient scheme utilizing tight-binding (TB) parameters generated via quasi-atomic minimal basis set orbitals (QUAMBOs) and non-equilibrium Green's function (NEGF). Large systems (SACC contains more than 50 atoms) are investigated and the electronic transport properties are found to correlate with SACC's parity. The SACCs provide a stable off or on state in broad energy region (0.1-1 eV) around Fermi energy. The off state is not sensitive to the length of SACC while the corresponding energy region decreases with the increase of the width of GNR.

  13. Atomic-Level Characterization of the Chain-Flipping Mechanism in Fatty-Acids Biosynthesis.

    PubMed

    Colizzi, Francesco; Masetti, Matteo; Recanatini, Maurizio; Cavalli, Andrea

    2016-08-01

    During fatty acids biosynthesis the elongating acyl chain is sequestered within the core of the highly conserved acyl carrier protein (ACP). At each catalytic step, the acyl intermediates are transiently delivered from ACP to the active site of the enzymatic counterparts and, at the same time, are protected from the solvent to prevent nonselective reactivity. Yet, the molecular determinants of such a universal transition-termed chain flipping-remain poorly understood. Here we capture the atomic-level details of the chain-flipping mechanism by using metadynamics simulations. We observe the fatty-acid chain gliding through the protein-protein interface with barely 30% of its surface exposed to water molecules. The small ACP's helix III acts as gatekeeper of the process, and we find its conformational plasticity critical for a successful substrate transfer. The results are in agreement with a wide range of experimental observations and provide unprecedented insight on the molecular determinants and driving forces of the chain-flipping process. PMID:27409360

  14. Observation of Majorana fermions in ferromagnetic atomic chains on a superconductor

    NASA Astrophysics Data System (ADS)

    Nadj-Perge, Stevan

    2015-03-01

    Majorana fermions are zero-energy excitations predicted to localize at the edge of a topological superconductor, a state of matter that can form when a ferromagnetic system is placed in proximity to a conventional superconductor with strong spin-orbit interaction. With the goal of realizing a one-dimensional topological superconductor, we have fabricated ferromagnetic iron atomic chains on the surface of superconducting lead. Using high-resolution spectroscopic imaging techniques, we show that the onset of superconductivity, which gaps the electronic density of states in the bulk of the chains, is accompanied by the appearance of zero-energy end-states. This spatially resolved signature provides strong evidence, corroborated by other observations and theoretical modeling, for the formation of a topological phase and edge-bound Majorana states in this system. Our results demonstrates that atomic chains are viable platform for future experiments to manipulate Majorana bound states and to realize other related 1D or 2D topological superconducting phases. This work has done in collaboration with Ilya K. Drozdov, Jian Li, Hua Chen, Sangjun Jeon, Jungpil Seo, Allan H. MacDonald, B. Andrei Bernevig and Ali Yazdani. We acknowledge ONR, NSF-MRSEC, ARO-MRUI, NSF-DMR and EU Marie Curie for support.

  15. A New One-dimensional Quantum Material - Ta2Pd3Se8 Atomic Chain

    NASA Astrophysics Data System (ADS)

    Liu, Xue; Liu, Jinyu; Hu, Jin; Yue, Chunlei; Mao, Zhiqiang; Wei, Jiang; Antipina, Liubov; Sorokin, Pavel; Sanchez, Ana

    Since the discovery of carbon nanotube, there has been a persistent effort to search for other one dimensional (1D) quantum systems. However, only a few examples have been found. We report a new 1D example - semiconducting Ta2Pd3Se8. We demonstrate that the Ta2Pd3Se8 nanowire as thin as 1.3nm can be easily obtained by applying simple mechanical exfoliation from its bulk counterpart. High resolution TEM shows an intrinsic 1D chain-like crystalline morphology on these nano wires, indicating weak bonding between these atomic chains. Theoretical calculation shows a direct bandgap structure, which evolves from 0.53eV in the bulk to 1.04eV in single atomic chain. The field effect transistor based on Ta2Pd3Se8 nanowire achieved a promising performance with 104On/Off ratio and 80 cm2V-1s-1 mobility. Low temperature transport study reflects two different mechanisms, variable range hopping and thermal activation, which dominate the transport properties at different temperature regimes. Ta2Pd3Se8 nanowire provides an intrinsic 1D material system for the study low dimensional condensed matter physics.

  16. Ferromagnetic ground state for a hypothetical iron-based extended metal atom chain.

    PubMed

    Szarek, Paweł; Wegner, Wojciech; Grochala, Wojciech

    2016-03-01

    Theoretical calculations for the first tri-iron-based extended metal atom chain (EMAC) molecule are reported. The studied triple-high-spin (S = 6) complex exhibits ferromagnetic ordering (according to Ising and spin-projection approximations), which renders it unique among all previously prepared and theoretically calculated EMAC compounds. This ordering originates from the prevailing ferromagnetic nearest-neighbor interactions, while the magnetic superexchange between terminal Fe(2+) sites is weaker and antiferromagnetic. Calculations indicate that this linear chain system based on a tri-iron core shows potential for the development of spin-frustrated behavior, which could be achieved through rational modification of the equatorial and axial ligands. PMID:26910724

  17. Tunable self-assembled spin chains of strongly interacting cold atoms for demonstration of reliable quantum state transfer

    NASA Astrophysics Data System (ADS)

    Loft, N. J. S.; Marchukov, O. V.; Petrosyan, D.; Zinner, N. T.

    2016-04-01

    We have developed an efficient computational method to treat long, one-dimensional systems of strongly interacting atoms forming self-assembled spin chains. Such systems can be used to realize many spin chain model Hamiltonians tunable by the external confining potential. As a concrete demonstration, we consider quantum state transfer in a Heisenberg spin chain and we show how to determine the confining potential in order to obtain nearly perfect state transfer.

  18. An Ab Initio Study of the Low-Lying Doublet States of AgO and AgS

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Partridge, Harry; Langhoff, Stephen R.

    1990-01-01

    Spectroscopic constants (D(sub o), r(sub e), mu(sub e), T(sub e)) are determined for the doublet states of AgO and AgS below approx. = 30000/cm. Large valence basis sets are employed in conjunction with relativistic effective core potentials (RECPs). Electron correlation is included using the modified coupled-pair functional (MCPF) and multireference configuration interaction (MRCI) methods. The A(sup 2)Sigma(sup +) - X(sup 2)Pi band system is found to occur in the near infrared (approx. = 9000/cm) and to be relatively weak with a radiative lifetime of 900 microns for A(sup 2)Sigma(sup +) (upsilon = 0). The weakly bound C(sup 2)Pi state (our notation), the upper state of the blue system, is found to require high levels of theoretical treatment to determine a quantitatively accurate potential. The red system is assigned as a transition from the C(sup 2)Pi state to the previously unobserved A(sup 2)Sigma(sup +) state. Several additional transitions are identified that should be detectable experimentally. A more limited study is performed for the vertical excitation spectrum of AgS. In addition, a detailed all-electron study of the X(sup 2)Pi and A(sup 2)Sigma(sup +) states of AgO is carried out using large atomic natural orbital (ANO) basis sets. Our best calculated D(sub o) value for AgO is significantly less than the experimental value, which suggests that there may be some systematic error in the experimental determination.

  19. Harnack Inequalities and Discrete—Continuous Error Estimates for a Chain of Atoms with Two—Body Interactions

    NASA Astrophysics Data System (ADS)

    Benguria, R.; Dolbeault, J.; Monneau, R.

    2009-01-01

    We consider deformations in ℝ3 of an infinite linear chain of atoms where each atom interacts with all others through a two-body potential. We compute the effect of an external force applied to the chain. At equilibrium, the positions of the particles satisfy an Euler-Lagrange equation. For large classes of potentials, we prove that every solution is well approximated by the solution of a continuous model when applied forces and displacements of the atoms are small. We establish an error estimate between the discrete and the continuous solution based on a Harnack lemma of independent interest. Finally we apply our results to some Lennard-Jones potentials.

  20. Average-atom model combined with the hypernetted chain approximation applied to warm dense matter.

    PubMed

    Hou, Yong; Bredow, Richard; Yuan, Jianmin; Redmer, Ronald

    2015-03-01

    We have combined the average-atom model with the hypernetted chain approximation (AAHNC) to describe the electronic and ionic structure in the warm dense matter regime. On the basis of the electronic and ionic structures, the x-ray Thomson scattering (XRTS) spectrum is calculated using the random-phase approximation. While the electronic structure is described within the average-atom model, the effects of other ions on the electronic structure are considered using an integral equation method of the theory of liquids, namely the hypernetted chain approximation. The ion-ion pair potential is calculated using the modified Gordon-Kim model based on the electronic density distribution. Finally, the electronic and ionic structures are determined self-consistently. The XRTS spectrum is calculated according to the Chihara formula, where the scattering contributions are divided into three components: elastic, bound-free, and free-free. Comparison of the present AAHNC results with other theoretical models and experimental data shows very good agreement. Thus the AAHNC model can give a reasonable description of the electronic and ionic structure in warm dense matter. PMID:25871231

  1. Spin-polarised edge states in atomic Mn chains supported on Cu2N/Cu (100).

    PubMed

    Choi, Deung-Jang; Robles, Roberto; Gauyacq, Jean-Pierre; Rubio-Verdú, Carmen; Lorente, Nicolás; Ignacio Pascual, José

    2016-06-15

    Scanning tunnelling microscopy and density functional theory studies of manganese chains adsorbed on Cu2N/Cu (100) reveal an unsuspected electronic edge state at [Formula: see text] eV above the Fermi energy. This Tamm-like state is strongly localised to the terminal Mn atoms of the chain and fully spin polarised. However, no equivalence is found for occupied states, and the electronic structure at [Formula: see text]  -1 eV is mainly spin unpolarised due to the extended p-states of the N atoms that mediate the coupling between the Mn atoms in the chain. The spin polarisation of the edge state is affected by the antiferromagnetic ordering of the chains leading to non-trivial consequences. PMID:27158116

  2. Spin-polarised edge states in atomic Mn chains supported on Cu2N/Cu (100)

    NASA Astrophysics Data System (ADS)

    Choi, Deung-Jang; Robles, Roberto; Gauyacq, Jean-Pierre; Rubio-Verdú, Carmen; Lorente, Nicolás; Pascual, José Ignacio

    2016-06-01

    Scanning tunnelling microscopy and density functional theory studies of manganese chains adsorbed on Cu2N/Cu (100) reveal an unsuspected electronic edge state at ∼ 1 eV above the Fermi energy. This Tamm-like state is strongly localised to the terminal Mn atoms of the chain and fully spin polarised. However, no equivalence is found for occupied states, and the electronic structure at ∼   ‑1 eV is mainly spin unpolarised due to the extended p-states of the N atoms that mediate the coupling between the Mn atoms in the chain. The spin polarisation of the edge state is affected by the antiferromagnetic ordering of the chains leading to non-trivial consequences.

  3. Fast equilibration protocol for million atom systems of highly entangled linear polyethylene chains

    NASA Astrophysics Data System (ADS)

    Sliozberg, Yelena R.; Kröger, Martin; Chantawansri, Tanya L.

    2016-04-01

    Equilibrated systems of entangled polymer melts cannot be produced using direct brute force equilibration due to the slow reptation dynamics exhibited by high molecular weight chains. Instead, these dense systems are produced using computational techniques such as Monte Carlo-Molecular Dynamics hybrid algorithms, though the use of soft potentials has also shown promise mainly for coarse-grained polymeric systems. Through the use of soft-potentials, the melt can be equilibrated via molecular dynamics at intermediate and long length scales prior to switching to a Lennard-Jones potential. We will outline two different equilibration protocols, which use various degrees of information to produce the starting configurations. In one protocol, we use only the equilibrium bond angle, bond length, and target density during the construction of the simulation cell, where the information is obtained from available experimental data and extracted from the force field without performing any prior simulation. In the second protocol, we moreover utilize the equilibrium radial distribution function and dihedral angle distribution. This information can be obtained from experimental data or from a simulation of short unentangled chains. Both methods can be used to prepare equilibrated and highly entangled systems, but the second protocol is much more computationally efficient. These systems can be strictly monodisperse or optionally polydisperse depending on the starting chain distribution. Our protocols, which utilize a soft-core harmonic potential, will be applied for the first time to equilibrate a million particle system of polyethylene chains consisting of 1000 united atoms at various temperatures. Calculations of structural and entanglement properties demonstrate that this method can be used as an alternative towards the generation of entangled equilibrium structures.

  4. Conductance and spin-filter effects of oxygen-incorporated Au, Cu, and Fe single-atom chains

    NASA Astrophysics Data System (ADS)

    Zheng, Xiaolong; Xie, Yi-Qun; Ye, Xiang; Ke, San-Huang

    2015-01-01

    We studied the spin-polarized electron transport in oxygen-incorporated Au, Cu, and Fe single-atom chains (SACs) by first-principles calculations. We first investigated the mechanism responsible for the low conductance (<1G0) of the Au and Cu SACs in an oxygen environment reported in recent experiments. We found that for the Au SACs, the low conductance plateau around 0.6G0 can be attributed to a distorted chain doped with a single oxygen atom, while the 0.1G0 conductance comes from a linear chain incorporated with an oxygen molecule and is caused by an antibonding state formed by oxygen's occupied frontier orbital with dz orbitals of adjacent Au atoms. For the Cu SACs, the conductance about 0.3G0 is ascribed to a special configuration that contains Cu and O atoms in an alternating sequence. This exhibits an even-odd conductance oscillation with an amplitude of ˜0.1G0. In contrast, for the alternating Fe-O SACs, conductance overall decreases with an increase in O atoms and it approaches nearly zero for the chain with more than four O atoms. While the Cu-O SACs behave as perfect spin filters for one spin channel due to the half metallic nature, the Fe-O SACs can serve as perfect spin filters for two spin channels depending on the polarity of the applied gate voltage.

  5. Carbyne from first principles: chain of C atoms, a nanorod or a nanorope.

    PubMed

    Liu, Mingjie; Artyukhov, Vasilii I; Lee, Hoonkyung; Xu, Fangbo; Yakobson, Boris I

    2013-11-26

    We report an extensive study of the properties of carbyne using first-principles calculations. We investigate carbyne's mechanical response to tension, bending, and torsion deformations. Under tension, carbyne is about twice as stiff as the stiffest known materials and has an unrivaled specific strength of up to 7.5 × 10(7) N·m/kg, requiring a force of ∼10 nN to break a single atomic chain. Carbyne has a fairly large room-temperature persistence length of about 14 nm. Surprisingly, the torsional stiffness of carbyne can be zero but can be "switched on" by appropriate functional groups at the ends. Further, under appropriate termination, carbyne can be switched into a magnetic semiconductor state by mechanical twisting. We reconstruct the equivalent continuum elasticity representation, providing the full set of elastic moduli for carbyne, showing its extreme mechanical performance (e.g., a nominal Young's modulus of 32.7 TPa with an effective mechanical thickness of 0.772 Å). We also find an interesting coupling between strain and band gap of carbyne, which is strongly increased under tension, from 2.6 to 4.7 eV under a 10% strain. Finally, we study the performance of carbyne as a nanoscale electrical cable and estimate its chemical stability against self-aggregation, finding an activation barrier of 0.6 eV for the carbyne-carbyne cross-linking reaction and an equilibrium cross-link density for two parallel carbyne chains of 1 cross-link per 17 C atoms (2.2 nm). PMID:24093753

  6. Numerical experiments on the modulation theory for the nonlinear atomic chain

    NASA Astrophysics Data System (ADS)

    Dreyer, W.; Herrmann, M.

    2008-02-01

    Modulation theory with periodic travelling waves is a powerful, but not rigorous tool to derive a thermodynamic description for atomic chains with nearest neighbour interactions (FPU chains). This theory is sufficiently complex to deal with strong oscillations on the microscopic scale, and therefore it is capable to describe the creation of temperature and the transport of heat on a macroscopic scale. In this paper we investigate the validity of modulation theory by means of several numerical experiments. We start with a survey on the foundations of modulation theory. In particular, we discuss the hyperbolic scaling, the notion of cold data, microscopic oscillations and Young measures, periodic and modulated travelling waves, and, finally, the resulting macroscopic conservation laws. Afterwards we discuss how the validity of a macroscopic theory may be tested within numerical simulations of the microscopic dynamics. To this end we describe an approach to thermodynamic data exploration which is motivated by the theory of Young measures, and relies on mesoscopic windows in space and time. The last part is devoted to several numerical experiments including examples with periodic boundary conditions and smooth initial data, and macroscopic Riemann problems. We interpret the outcome of these experiments in the framework of thermodynamics, and end up with two conclusions. (1) There are many examples for which modulation theory provides in fact the right thermodynamic description because it can predict both the structure of the microscopic oscillations and their macroscopic evolution correctly. (2) Modulation theory will fail if the oscillations exhibit a more complicate structure.

  7. Quantifying the atomic-level mechanics of single long physisorbed molecular chains

    PubMed Central

    Kawai, Shigeki; Koch, Matthias; Gnecco, Enrico; Sadeghi, Ali; Pawlak, Rémy; Glatzel, Thilo; Schwarz, Jutta; Goedecker, Stefan; Hecht, Stefan; Baratoff, Alexis; Grill, Leonhard; Meyer, Ernst

    2014-01-01

    Individual in situ polymerized fluorene chains 10–100 nm long linked by C–C bonds are pulled vertically from an Au(111) substrate by the tip of a low-temperature atomic force microscope. The conformation of the selected chains is imaged before and after manipulation using scanning tunneling microscopy. The measured force gradient shows strong and periodic variations that correspond to the step-by-step detachment of individual fluorene repeat units. These variations persist at constant intensity until the entire polymer is completely removed from the surface. Calculations based on an extended Frenkel–Kontorova model reproduce the periodicity and magnitude of these features and allow us to relate them to the detachment force and desorption energy of the repeat units. The adsorbed part of the polymer slides easily along the surface during the pulling process, leading to only small oscillations as a result of the high stiffness of the fluorenes and of their length mismatch with respect to the substrate surface structure. A significant lateral force also is caused by the sequential detachment of individual units. The gained insight into the molecule–surface interactions during sliding and pulling should aid the design of mechanoresponsive nanosystems and devices. PMID:24591611

  8. Electronic torsional sound in linear atomic chains: Chemical energy transport at 1000 km/s.

    PubMed

    Kurnosov, Arkady A; Rubtsov, Igor V; Maksymov, Andrii O; Burin, Alexander L

    2016-07-21

    We investigate entirely electronic torsional vibrational modes in linear cumulene chains. The carbon nuclei of a cumulene are positioned along the primary axis so that they can participate only in the transverse and longitudinal motions. However, the interatomic electronic clouds behave as a torsion spring with remarkable torsional stiffness. The collective dynamics of these clouds can be described in terms of electronic vibrational quanta, which we name torsitons. It is shown that the group velocity of the wavepacket of torsitons is much higher than the typical speed of sound, because of the small mass of participating electrons compared to the atomic mass. For the same reason, the maximum energy of the torsitons in cumulenes is as high as a few electronvolts, while the minimum possible energy is evaluated as a few hundred wavenumbers and this minimum is associated with asymmetry of zero point atomic vibrations. Theory predictions are consistent with the time-dependent density functional theory calculations. Molecular systems for experimental evaluation of the predictions are proposed. PMID:27448902

  9. Electronic torsional sound in linear atomic chains: Chemical energy transport at 1000 km/s

    NASA Astrophysics Data System (ADS)

    Kurnosov, Arkady A.; Rubtsov, Igor V.; Maksymov, Andrii O.; Burin, Alexander L.

    2016-07-01

    We investigate entirely electronic torsional vibrational modes in linear cumulene chains. The carbon nuclei of a cumulene are positioned along the primary axis so that they can participate only in the transverse and longitudinal motions. However, the interatomic electronic clouds behave as a torsion spring with remarkable torsional stiffness. The collective dynamics of these clouds can be described in terms of electronic vibrational quanta, which we name torsitons. It is shown that the group velocity of the wavepacket of torsitons is much higher than the typical speed of sound, because of the small mass of participating electrons compared to the atomic mass. For the same reason, the maximum energy of the torsitons in cumulenes is as high as a few electronvolts, while the minimum possible energy is evaluated as a few hundred wavenumbers and this minimum is associated with asymmetry of zero point atomic vibrations. Theory predictions are consistent with the time-dependent density functional theory calculations. Molecular systems for experimental evaluation of the predictions are proposed.

  10. Dissociation energies of Ag–RG (RG = Ar, Kr, Xe) and AgO molecules from velocity map imaging studies

    SciTech Connect

    Cooper, Graham A.; Gentleman, Alexander S.; Iskra, Andreas; Wijk, Robert van; Mackenzie, Stuart R.; Kartouzian, Aras

    2015-09-28

    The near ultraviolet photodissociation dynamics of silver atom—rare gas dimers have been studied by velocity map imaging. Ag–RG (RG = Ar, Kr, Xe) species generated by laser ablation are excited in the region of the C ({sup 2}Σ{sup +})←X ({sup 2}Σ{sup +}) continuum leading to direct, near-threshold dissociation generating Ag* ({sup 2}P{sub 3/2}) + RG ({sup 1}S{sub 0}) products. Images recorded at excitation wavelengths throughout the C ({sup 2}Σ{sup +})←X ({sup 2}Σ{sup +}) continuum, coupled with known atomic energy levels, permit determination of the ground X ({sup 2}Σ{sup +}) state dissociation energies of 85.9 ± 23.4 cm{sup −1} (Ag–Ar), 149.3 ± 22.4 cm{sup −1} (Ag–Kr), and 256.3 ± 16.0 cm{sup −1} (Ag–Xe). Three additional photolysis processes, each yielding Ag atom photoproducts, are observed in the same spectral region. Two of these are markedly enhanced in intensity upon seeding the molecular beam with nitrous oxide, and are assigned to photodissociation of AgO at the two-photon level. These features yield an improved ground state dissociation energy for AgO of 15 965 ± 81 cm{sup −1}, which is in good agreement with high level calculations. The third process results in Ag atom fragments whose kinetic energy shows anomalously weak photon energy dependence and is assigned tentatively to dissociative ionization of the silver dimer Ag{sub 2}.

  11. Implementation of Outstanding Electronic Transport in Polar Covalent Boron Nitride Atomic Chains: another Extraordinary Odd-Even Behaviour

    PubMed Central

    Xu, Xiaodong; Li, Weiqi; Liu, Linhua; Feng, Jikang; Jiang, Yongyuan; Tian, Wei Quan

    2016-01-01

    A theoretical investigation of the unique electronic transport properties of the junctions composed of boron nitride atomic chains bridging symmetric graphene electrodes with point-contacts is executed through non-equilibrium Green’s function technique in combination with density functional theory. Compared with carbon atomic chains, the boron nitride atomic chains have an alternative arrangement of polar covalent B-N bonds and different contacts coupling electrodes, showing some unusual properties in functional atomic electronic devices. Remarkably, they have an extraordinary odd-even behavior of conductivity with the length increase. The rectification character and negative differential resistance of nonlinear current-voltage characteristics can be achieved by manipulating the type of contacts between boron nitride atomic chains bridges and electrodes. The junctions with asymmetric contacts have an intrinsic rectification, caused by stronger coupling in the C-N contact than the C-B contact. On the other hand, for symmetric contact junctions, it is confirmed that the transport properties of the junctions primarily depend on the nature of contacts. The junctions with symmetric C-N contacts have higher conductivity than their C-B contacts counterparts. Furthermore, the negative differential resistances of the junctions with only C-N contacts is very conspicuous and can be achieved at lower bias. PMID:27211110

  12. Implementation of Outstanding Electronic Transport in Polar Covalent Boron Nitride Atomic Chains: another Extraordinary Odd-Even Behaviour.

    PubMed

    Xu, Xiaodong; Li, Weiqi; Liu, Linhua; Feng, Jikang; Jiang, Yongyuan; Tian, Wei Quan

    2016-01-01

    A theoretical investigation of the unique electronic transport properties of the junctions composed of boron nitride atomic chains bridging symmetric graphene electrodes with point-contacts is executed through non-equilibrium Green's function technique in combination with density functional theory. Compared with carbon atomic chains, the boron nitride atomic chains have an alternative arrangement of polar covalent B-N bonds and different contacts coupling electrodes, showing some unusual properties in functional atomic electronic devices. Remarkably, they have an extraordinary odd-even behavior of conductivity with the length increase. The rectification character and negative differential resistance of nonlinear current-voltage characteristics can be achieved by manipulating the type of contacts between boron nitride atomic chains bridges and electrodes. The junctions with asymmetric contacts have an intrinsic rectification, caused by stronger coupling in the C-N contact than the C-B contact. On the other hand, for symmetric contact junctions, it is confirmed that the transport properties of the junctions primarily depend on the nature of contacts. The junctions with symmetric C-N contacts have higher conductivity than their C-B contacts counterparts. Furthermore, the negative differential resistances of the junctions with only C-N contacts is very conspicuous and can be achieved at lower bias. PMID:27211110

  13. Implementation of Outstanding Electronic Transport in Polar Covalent Boron Nitride Atomic Chains: another Extraordinary Odd-Even Behaviour

    NASA Astrophysics Data System (ADS)

    Xu, Xiaodong; Li, Weiqi; Liu, Linhua; Feng, Jikang; Jiang, Yongyuan; Tian, Wei Quan

    2016-05-01

    A theoretical investigation of the unique electronic transport properties of the junctions composed of boron nitride atomic chains bridging symmetric graphene electrodes with point-contacts is executed through non-equilibrium Green’s function technique in combination with density functional theory. Compared with carbon atomic chains, the boron nitride atomic chains have an alternative arrangement of polar covalent B-N bonds and different contacts coupling electrodes, showing some unusual properties in functional atomic electronic devices. Remarkably, they have an extraordinary odd-even behavior of conductivity with the length increase. The rectification character and negative differential resistance of nonlinear current-voltage characteristics can be achieved by manipulating the type of contacts between boron nitride atomic chains bridges and electrodes. The junctions with asymmetric contacts have an intrinsic rectification, caused by stronger coupling in the C-N contact than the C-B contact. On the other hand, for symmetric contact junctions, it is confirmed that the transport properties of the junctions primarily depend on the nature of contacts. The junctions with symmetric C-N contacts have higher conductivity than their C-B contacts counterparts. Furthermore, the negative differential resistances of the junctions with only C-N contacts is very conspicuous and can be achieved at lower bias.

  14. Fourier Transform Spectroscopy of theA2Σ+-X2ΠiTransition of AgO

    NASA Astrophysics Data System (ADS)

    O'Brien, L. C.; Wall, S. J.; Sieber, M. K.

    1997-05-01

    TheA2Σ+-X2Πinear-infrared electronic transition of AgO was observed for the first time. The spectrum was recorded with the high resolution Fourier transform spectrometer associated with the McMath-Pierce Solar Telescope at Kitt Peak. The excited AgO molecules were produced in a low pressure silver hollow cathode sputter source. Constants for theA2Σ+state of107AgO and109AgO and improvedX2Πiconstants for107AgO and109AgO are presented. These two states are not a unique perturber pair and they do not follow the pure precession model.

  15. Conductance and spin-filter effects of oxygen-incorporated Au, Cu, and Fe single-atom chains

    SciTech Connect

    Zheng, Xiaolong; Xie, Yi-Qun Ye, Xiang; Ke, San-Huang

    2015-01-28

    We studied the spin-polarized electron transport in oxygen-incorporated Au, Cu, and Fe single-atom chains (SACs) by first-principles calculations. We first investigated the mechanism responsible for the low conductance (<1G{sub 0}) of the Au and Cu SACs in an oxygen environment reported in recent experiments. We found that for the Au SACs, the low conductance plateau around 0.6G{sub 0} can be attributed to a distorted chain doped with a single oxygen atom, while the 0.1G{sub 0} conductance comes from a linear chain incorporated with an oxygen molecule and is caused by an antibonding state formed by oxygen's occupied frontier orbital with d{sub z} orbitals of adjacent Au atoms. For the Cu SACs, the conductance about 0.3G{sub 0} is ascribed to a special configuration that contains Cu and O atoms in an alternating sequence. This exhibits an even-odd conductance oscillation with an amplitude of ∼0.1G{sub 0}. In contrast, for the alternating Fe-O SACs, conductance overall decreases with an increase in O atoms and it approaches nearly zero for the chain with more than four O atoms. While the Cu-O SACs behave as perfect spin filters for one spin channel due to the half metallic nature, the Fe-O SACs can serve as perfect spin filters for two spin channels depending on the polarity of the applied gate voltage.

  16. Evaluation of the end-to-end distance of chains solubilized in a polymer Langmuir monolayer by atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Kumaki, Jiro

    Polymer chain packing in two-dimensional (2D) condense state is still not well understood. Direct observation of the chain packing in a monolayer should be the best way to understand this, however, it is still difficult even using atomic force microscopy (AFM) except for extraordinarily thick polymers. In this study, we successfully evaluate the end-to-end distance of the chains in a Langmuir-Blodgett monolayer composed of a conventional polymer by AFM. We successfully solubilized a small amount of a polystyrene-b-poly(methyl methacrylate)-b-polystyrene (PS-b-PMMA-b-PS) triblock copolymer in a PMMA Langmuir monolayer with the PS blocks being condensed as single-PS-block particles which could be used as a probe of the position of the chain ends. The evaluated end-to-end distance was 2.5 times longer than that of the 2D ideal chain, indicating the chains in the 2D monolayer are not strongly segregated but interpenetrates into other chains.

  17. One-dimensionality in atomic nuclei: A candidate for linear-chain α clustering in 14C

    NASA Astrophysics Data System (ADS)

    Fritsch, A.; Beceiro-Novo, S.; Suzuki, D.; Mittig, W.; Kolata, J. J.; Ahn, T.; Bazin, D.; Becchetti, F. D.; Bucher, B.; Chajecki, Z.; Fang, X.; Febbraro, M.; Howard, A. M.; Kanada-En'yo, Y.; Lynch, W. G.; Mitchell, A. J.; Ojaruega, M.; Rogers, A. M.; Shore, A.; Suhara, T.; Tang, X. D.; Torres-Isea, R.; Wang, H.

    2016-01-01

    The clustering of α particles in atomic nuclei results in the self-organization of various geometrical arrangements at the femtometer scale. The one-dimensional alignment of multiple α particles is known as linear-chain structure, evidence of which has been highly elusive. We show via resonant elastic and inelastic α scattering of a radioactive 10Be beam that excited states in the neutron-rich nucleus 14C agree with recent predictions of linear-chain structure based on an antisymmetrized molecular dynamics model.

  18. Anion-radical oxygen centers in small (AgO)n clusters: Density functional theory predictions

    NASA Astrophysics Data System (ADS)

    Trushin, Egor V.; Zilberberg, Igor L.

    2013-02-01

    Anion-radical form of the oxygen centers O- is predicted at the DFT level for small silver oxide particles having the AgO stoichiometry. Model clusters (AgO)n appear to be ferromagnetic with appreciable spin density at the oxygen centers. In contrast to these clusters, the Ag2O model cluster have no unpaired electrons in the ground state. The increased O/Ag ratio in the oxide particles is proved to be responsible for the spin density at oxygen centers.

  19. 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

  20. Alternative types of molecule-decorated atomic chains in Au-CO-Au single-molecule junctions.

    PubMed

    Balogh, Zoltán; Makk, Péter; Halbritter, András

    2015-01-01

    We investigate the formation and evolution of Au-CO single-molecule break junctions. The conductance histogram exhibits two distinct molecular configurations, which are further investigated by a combined statistical analysis. According to conditional histogram and correlation analysis these molecular configurations show strong anticorrelations with each other and with pure Au monoatomic junctions and atomic chains. We identify molecular precursor configurations with somewhat higher conductance, which are formed prior to single-molecule junctions. According to detailed length analysis two distinct types of molecule-affected chain-formation processes are observed, and we compare these results to former theoretical calculations considering bridge- and atop-type molecular configurations where the latter has reduced conductance due to destructive Fano interference. PMID:26199840

  1. Alternative types of molecule-decorated atomic chains in Au–CO–Au single-molecule junctions

    PubMed Central

    Balogh, Zoltán; Makk, Péter

    2015-01-01

    Summary We investigate the formation and evolution of Au–CO single-molecule break junctions. The conductance histogram exhibits two distinct molecular configurations, which are further investigated by a combined statistical analysis. According to conditional histogram and correlation analysis these molecular configurations show strong anticorrelations with each other and with pure Au monoatomic junctions and atomic chains. We identify molecular precursor configurations with somewhat higher conductance, which are formed prior to single-molecule junctions. According to detailed length analysis two distinct types of molecule-affected chain-formation processes are observed, and we compare these results to former theoretical calculations considering bridge- and atop-type molecular configurations where the latter has reduced conductance due to destructive Fano interference. PMID:26199840

  2. Producing high-accuracy lattice models from protein atomic coordinates including side chains.

    PubMed

    Mann, Martin; Saunders, Rhodri; Smith, Cameron; Backofen, Rolf; Deane, Charlotte M

    2012-01-01

    Lattice models are a common abstraction used in the study of protein structure, folding, and refinement. They are advantageous because the discretisation of space can make extensive protein evaluations computationally feasible. Various approaches to the protein chain lattice fitting problem have been suggested but only a single backbone-only tool is available currently. We introduce LatFit, a new tool to produce high-accuracy lattice protein models. It generates both backbone-only and backbone-side-chain models in any user defined lattice. LatFit implements a new distance RMSD-optimisation fitting procedure in addition to the known coordinate RMSD method. We tested LatFit's accuracy and speed using a large nonredundant set of high resolution proteins (SCOP database) on three commonly used lattices: 3D cubic, face-centred cubic, and knight's walk. Fitting speed compared favourably to other methods and both backbone-only and backbone-side-chain models show low deviation from the original data (~1.5 Å RMSD in the FCC lattice). To our knowledge this represents the first comprehensive study of lattice quality for on-lattice protein models including side chains while LatFit is the only available tool for such models. PMID:22934109

  3. Producing High-Accuracy Lattice Models from Protein Atomic Coordinates Including Side Chains

    PubMed Central

    Mann, Martin; Saunders, Rhodri; Smith, Cameron; Backofen, Rolf; Deane, Charlotte M.

    2012-01-01

    Lattice models are a common abstraction used in the study of protein structure, folding, and refinement. They are advantageous because the discretisation of space can make extensive protein evaluations computationally feasible. Various approaches to the protein chain lattice fitting problem have been suggested but only a single backbone-only tool is available currently. We introduce LatFit, a new tool to produce high-accuracy lattice protein models. It generates both backbone-only and backbone-side-chain models in any user defined lattice. LatFit implements a new distance RMSD-optimisation fitting procedure in addition to the known coordinate RMSD method. We tested LatFit's accuracy and speed using a large nonredundant set of high resolution proteins (SCOP database) on three commonly used lattices: 3D cubic, face-centred cubic, and knight's walk. Fitting speed compared favourably to other methods and both backbone-only and backbone-side-chain models show low deviation from the original data (~1.5 Å RMSD in the FCC lattice). To our knowledge this represents the first comprehensive study of lattice quality for on-lattice protein models including side chains while LatFit is the only available tool for such models. PMID:22934109

  4. Generation and Control of Chains of Entangled Atom-Ion Pairs with Quantum Light

    SciTech Connect

    Shapiro, Moshe; Brumer, Paul

    2011-04-15

    Coherent control using quantum light incident upon molecules in an optical lattice is shown to give rise to a direct way of writing arbitrary sequences of entangled atom-ion pairs. There is no evident limitation on the length of the word (i.e., the number of qbits) that can be formed.

  5. DFT modelling of the [M-Pd-M] 6+ metal atom chains (M = Ni, Pd): Structural, electronic and magnetic issues

    NASA Astrophysics Data System (ADS)

    López, Xavier; Rohmer, Marie-Madeleine; Bénard, Marc

    2008-11-01

    Following the recent findings on heterometallic string complexes, we extend the recently published work on NiPdNi(dpa) 4Cl 2 to discuss the Ni-Pd-Ni and Pd 3 chains with equatorial ligands (L) being dipyridylamide (dpa), 2,6-bis(phenylamido)pyridine (BPAP) and N, N'-bis-( p-toluenesulfonyl)-pyridyldiamide (Lpts), using the DFT formalism. The analysis of such a hypothetical series of linear trimetallics anticipates that, for NiPdNi(dpa) 4Cl 2, the extended valence shell of palladium strengthens the antiferromagnetic coupling between high-spin terminal nickel atoms. For L = BPAP the system, as expected, becomes diamagnetic, and antiferromagnetism reappears for L = Lpts. The theoretical modelling of the coupling following the Heisenberg Hamiltonian applied to two magnetic centres (H^=-2JS·S) gives -2 J = 320 and 497 cm -1 for L = dpa and Lpts, respectively. Pd 3 chains display an enhanced tendency to be diamagnetic with various ligands. More specifically with dpa, Pd 3(dpa) 4Cl 2—should it be synthesized—could be magnetically inactive since the strongly antiferromagnetic state generated by the coupling of two terminal, high-spin Pd atoms (-2 J = 1393 cm -1) is computed to be in close competition with the diamagnetic, closed-shell state. For L = Lpts as for BPAP, the hypothetic [Pd 3] 6+ chain is predicted to be diamagnetic, resulting from the high energy of the antibonding d(Pd)-p(N) orbital. The shift toward diamagnetism induced by the replacement of Ni by Pd in terminal position is therefore assigned to a stronger N → M donation interaction with M = Pd.

  6. The Luttinger liquid in superlattice structures: atomic gases, quantum dots and the classical Ising chain

    NASA Astrophysics Data System (ADS)

    Bhattacherjee, Aranya B.; Jha, Pradip; Kumar, Tarun; Mohan, Man

    2011-01-01

    We study the physical properties of a Luttinger liquid in a superlattice that is characterized by alternating two tunneling parameters. Using the bosonization approach, we describe the corresponding Hubbard model by the equivalent Tomonaga-Luttinger model. We analyze the spin-charge separation and transport properties of the superlattice system. We suggest that cold Fermi gases trapped in a bichromatic optical lattice and coupled quantum dots offer the opportunity to measure these effects in a convenient manner. We also study the classical Ising chain with two tunneling parameters. We find that the classical two-point correlator decreases as the difference between the two tunneling parameters increases.

  7. Average atom model based on Quantum Hyper-Netted Chain method

    NASA Astrophysics Data System (ADS)

    Chihara, Junzo

    2016-06-01

    The study shows how to define, without any ad hoc assumption, the average ion charge ZI in the electron-ion model for plasmas and liquid metals: this definition comes out of the condition that a plasma consisting of electrons and nuclei can be described as an electron-ion mixture. Based on this definition of the average ion charge, the Quantum Hyper-Netted Chain (QHNC) method takes account of the thermal ionization and the resonant-state contribution to the bound electrons forming an ion. On the other hand, Blenski and Cichocki (2007) have derived a formula to determine the uniform electron density in a plasma as an electron-ion mixture by using the variational method with the help of the local density approximation. Without use of any approximation, we derived the formula determining the electron density in an extended form on the basis of the density functional theory. This formula is shown to be valid also for the QHNC method.

  8. Fractional Quantum Hall Effects for Bosonic Atoms in a Chain of Rotating Traps

    NASA Astrophysics Data System (ADS)

    Zhao, Jianshi; Jacome, Louis; Gemelke, Nathan

    2015-05-01

    Fractional quantum Hall (FQH) physics familiar from two-dimensional electron systems has also been predicted to appear in a gas of interacting bosons that are confined to a rapidly rotating trap. Due to the emergent gauge physics, such states exhibit novel properties, including excitations with fractionalized mass and statistics. In this talk, we consider an experimental strategy of creating many FQH samples along a chain of lattice sites, coupled together via tunneling. We calculate a mean-field phase diagram and derive an effective field theory to describe this system and find that it supports novel insulator and superfluid states with localized FQH behavior. The coarse structure of the phase diagram and transport properties near phase transitions reveal novel properties of excitations in the parent FQH states, and exhibit new observable relations between thermodynamic quantities such as compressibility and moment of inertia attributable to topological constraints. We describe experimental pathways to create such states and extract new smoking gun signatures of FQH physics. Supported by NSF Grant No. PHY-1068570.

  9. Helical order in one-dimensional magnetic atom chains and possible emergence of Majorana bound states

    NASA Astrophysics Data System (ADS)

    Kim, Younghyun; Cheng, Meng; Bauer, Bela; Lutchyn, Roman M.; Das Sarma, S.

    2014-08-01

    We theoretically obtain the phase diagram of localized magnetic impurity spins arranged in a one-dimensional chain on top of a one- or two-dimensional electron gas. The interactions between the spins are mediated by the Ruderman-Kittel-Kasuya-Yosida mechanism through the electron gas. Recent work predicts that such a system may intrinsically support topological superconductivity without spin-orbit coupling when a helical spin-density wave is spontaneously formed in the spins, and superconductivity is induced in the electron gas. We analyze, using both analytical and numerical techniques, the conditions under which such a helical spin state is stable in a realistic situation in the presence of disorder. We show that (i) it appears only when the spins are coupled to a (quasi-) one-dimensional electron gas, and (ii) it becomes unstable towards the formation of (anti)ferromagnetic domains if the disorder in the impurity spin positions δR becomes comparable with the Fermi wavelength. We also examine the stability of the helical state against Gaussian potential disorder in the electronic system using a diagrammatic approach. Our results suggest that in order to stabilize the helical spin state and thus the emergent topological superconductivity under realistic experimental conditions, a sufficiently strong Rashba spin-orbit coupling, giving rise to Dzyaloshinskii-Moriya interactions, is required.

  10. Analytic study of the chain dark decomposition reaction of iodides - atomic iodine donors - in the active medium of a pulsed chemical oxygen-iodine laser: 2. Limiting parameters of the branching chain dark decomposition reaction of iodides

    SciTech Connect

    Andreeva, Tamara L; Kuznetsova, S V; Maslov, Aleksandr I; Sorokin, Vadim N

    2009-08-31

    The final stages in the development of a branching chain decomposition reaction of iodide in the active medium of a pulsed chemical oxygen-iodine laser (COIL) are analysed. Approximate expressions are derived to calculate the limiting parameters of the chain reaction: the final degree of iodide decomposition, the maximum concentration of excited iodine atoms, the time of its achievement, and concentrations of singlet oxygen and iodide at that moment. The limiting parameters, calculated by using these expressions for a typical composition of the active medium of a pulsed COIL, well coincide with the results of numerical calculations. (active media)

  11. AgH, Ag/sub 2/, and AgO revisited: Basis set extensions

    SciTech Connect

    Martin, R.L.

    1987-05-01

    An extended basis set has been developed for Ag which significantly improves the agreement between theoretical and experimental spectroscopic parameters for AgH, AgO, and Ag/sub 2/. The major improvement comes about as a result of the improved treatment of electron correlation in the Ag d shell upon the introduction of f functions. Their inclusion produces very slight differences at the SCF level, but significant reductions in r/sub e/ and increases in ..omega../sub e/ and D/sub e/ in the Mo-dash-barller--Plesset perturbation theory expansion. At the MP4(SDTQ) level, typical results are 0.02 A too long for r/sub e/, 4% too low for ..omega../sub e/, and 10 kcal too small for D/sub e/. From a pragmatic standpoint, MP2 give results very similar to this at a much reduced level of effort.

  12. Surface effects on the mechanical elongation of AuCu nanowires: De-alloying and the formation of mixed suspended atomic chains

    SciTech Connect

    Lagos, M. J.; Autreto, P. A. S.; Galvao, D. S. Ugarte, D.; Bettini, J.; Sato, F.; Dantas, S. O.

    2015-03-07

    We report here an atomistic study of the mechanical deformation of Au{sub x}Cu{sub (1−x)} atomic-size wires (nanowires (NWs)) by means of high resolution transmission electron microscopy experiments. Molecular dynamics simulations were also carried out in order to obtain deeper insights on the dynamical properties of stretched NWs. The mechanical properties are significantly dependent on the chemical composition that evolves in time at the junction; some structures exhibit a remarkable de-alloying behavior. Also, our results represent the first experimental realization of mixed linear atomic chains (LACs) among transition and noble metals; in particular, surface energies induce chemical gradients on NW surfaces that can be exploited to control the relative LAC compositions (different number of gold and copper atoms). The implications of these results for nanocatalysis and spin transport of one-atom-thick metal wires are addressed.

  13. Ultracold few fermionic atoms in needle-shaped double wells: spin chains and resonating spin clusters from microscopic Hamiltonians emulated via antiferromagnetic Heisenberg and t–J models

    NASA Astrophysics Data System (ADS)

    Yannouleas, Constantine; Brandt, Benedikt B.; Landman, Uzi

    2016-07-01

    Advances with trapped ultracold atoms intensified interest in simulating complex physical phenomena, including quantum magnetism and transitions from itinerant to non-itinerant behavior. Here we show formation of antiferromagnetic ground states of few ultracold fermionic atoms in single and double well (DW) traps, through microscopic Hamiltonian exact diagonalization for two DW arrangements: (i) two linearly oriented one-dimensional, 1D, wells, and (ii) two coupled parallel wells, forming a trap of two-dimensional, 2D, nature. The spectra and spin-resolved conditional probabilities reveal for both cases, under strong repulsion, atomic spatial localization at extemporaneously created sites, forming quantum molecular magnetic structures with non-itinerant character. These findings usher future theoretical and experimental explorations into the highly correlated behavior of ultracold strongly repelling fermionic atoms in higher dimensions, beyond the fermionization physics that is strictly applicable only in the 1D case. The results for four atoms are well described with finite Heisenberg spin-chain and cluster models. The numerical simulations of three fermionic atoms in symmetric DWs reveal the emergent appearance of coupled resonating 2D Heisenberg clusters, whose emulation requires the use of a t–J-like model, akin to that used in investigations of high T c superconductivity. The highly entangled states discovered in the microscopic and model calculations of controllably detuned, asymmetric, DWs suggest three-cold-atom DW quantum computing qubits.

  14. Main-Chain and Side-Chain Sequence-Regulated Vinyl Copolymers by Iterative Atom Transfer Radical Additions and 1:1 or 2:1 Alternating Radical Copolymerization.

    PubMed

    Soejima, Takamasa; Satoh, Kotaro; Kamigaito, Masami

    2016-01-27

    Main- and side-chain sequence-regulated vinyl copolymers were prepared by a combination of iterative atom transfer radical additions (ATRAs) of vinyl monomers for side-chain control and 1:1 or 2:1 alternating radical copolymerization of the obtained side-chain sequenced "oligomonomers" and vinyl comonomers for main-chain control. A complete set of sequence-regulated trimeric vinyl oligomers of styrene (S) and/or methyl acrylate (A) were first synthesized via iterative ATRAs of these monomers to a halide of monomeric S or A unit (X-S or X-A) under optimized conditions with appropriate ruthenium or copper catalysts, which were selected depending on the monomers and halides. The obtained halogen-capped oligomers were then converted into a series of maleimide (M)-ended oligomonomers with different monomer compositions and sequences (M-SSS, M-ASS, M-SAS, M-AAS, M-SSA, M-ASA, M-SAA, M-AAA) by a substitution reaction of the halide with furan-protected maleimide anion followed by deprotection of the furan units. These maleimide-ended oligomonomers were then radically copolymerized with styrene or limonene to enable the 1:1 or 2:1 monomer-sequence regulation in the main chain and finally result in the main- and side-chain sequence-regulated vinyl copolymers with high molecular weights in high yield. The properties of the sequence-regulated vinyl copolymers depended on not only the monomer compositions but also the monomer sequences. The solubility was highly affected by the outer monomer units in the side chains whereas the glass transition temperatures were primarily affected by the two successive monomer sequences. PMID:26761148

  15. Solvothermal Preparation of ZnO Nanorods as Anode Material for Improved Cycle Life Zn/AgO Batteries

    PubMed Central

    Ullah, Shafiq; Ahmed, Fiaz; Badshah, Amin; Ali Altaf, Ataf; Raza, Ramsha; Lal, Bhajan; Hussain, Rizwan

    2013-01-01

    Nano materials with high surface area increase the kinetics and extent of the redox reactions, thus resulting in high power and energy densities. In this study high surface area zinc oxide nanorods have been synthesized by surfactant free ethylene glycol assisted solvothermal method. The nanorods thus prepared have diameters in the submicron range (300∼500 nm) with high aspect ratio. They have uniform geometry and well aligned direction. These nanorods are characterized by XRD, SEM, Specific Surface Area Analysis, solubility in alkaline medium, EDX analysis and galvanostatic charge/discharge studies in Zn/AgO batteries. The prepared zinc oxide nanorods have low solubility in alkaline medium with higher structural stability, which imparts the improved cycle life stability to Zn/AgO cells. PMID:24146807

  16. Interrelationship between long-wave current sensitivity and thermionic current of Ag-O-Cs photocathode and problems of its tolerable physical model

    NASA Astrophysics Data System (ADS)

    Rabinovich, A. I.; Pakhomov, M. T.

    1993-01-01

    Interrelation between current sensitivity at (lambda) >= 1.06 micrometers and thermoemission current (calculate data and their correlation with experimental results) is used as an indicator of choice between the donor and acceptor models of Ag-O-Cs-photocathode.

  17. Fast atoms and negative chain-cluster fragments from laser-induced Coulomb explosions in a super-fluid film of ultra-dense deuterium D(-1)

    NASA Astrophysics Data System (ADS)

    Andersson, Patrik U.; Holmlid, Leif

    2012-10-01

    Fragments from laser-induced Coulomb explosions (CE) in a thin super-fluid film of ultra-dense deuterium D(-1) on a vertical surface are now observed by both negative and positive time-of-flight mass spectrometry. The so-called normal phase of the super-fluid is probably associated with D4 clusters and gives only neutral atomic fragments with a kinetic energy from the CE of 945 eV. The super-fluid phase is associated with long chain clusters D2N with N deuteron pairs and gives cluster fragments by CE mainly with a kinetic energy of 315 eV from the central cleavage in a neutral, positive or negative form. This indicates that the chain clusters are standing perpendicularly to the surface. The fragment charge state is influenced by the external field, which indicates efficient charge transfer processes.

  18. Diffusion across the modified polyethylene separator GX in the heat-sterilizable AgO-Zn battery

    NASA Technical Reports Server (NTRS)

    Lutwack, R.

    1973-01-01

    Models of diffusion across an inert membrane have been studied using the computer program CINDA. The models were constructed to simulate various conditions obtained in the consideration of the diffusion of Ag (OH)2 ions in the AgO-Zn battery. The effects on concentrations across the membrane at the steady state and on the fluxout as a function of time were used to examine the consequences of stepwise reducing the number of sources of ions, of stepwise blocking the source and sink surfaces, of varying the magnitude of the diffusion coefficient for a uniform membrane, of varying the diffusion coefficient across the membrane, and of excluding volumes to diffusion.

  19. The Unique Gas-Phase Chemistry of the [AuO](+) /CH4 Couple: Selective Oxygen-Atom Transfer to, Rather than Hydrogen-Atom Abstraction from, Methane.

    PubMed

    Zhou, Shaodong; Li, Jilai; Schlangen, Maria; Schwarz, Helmut

    2016-08-26

    The thermal reaction of [AuO](+) with methane has been explored using FT-ICR mass spectrometry complemented by high-level quantum chemical calculations. In contrast to the previously studied congener [CuO](+) , and to [AgO](+) , [AuO](+) reacts with CH4 exclusively via oxygen-atom transfer to form CH3 OH, and a novel mechanistic scenario for this selective oxidation process has been revealed. Also, the origin of the inertness of the [AgO](+) /CH4 couple has been addressed computationally. PMID:27390885

  20. Controllable magnetic solitons excitations in an atomic chain of spinor Bose-Einstein condensates confined in an optical lattice

    NASA Astrophysics Data System (ADS)

    Zhao, Xing-Dong; Geng, Z.; Zhao, Xu; Qian, J.; Zhou, Lu; Li, Y.; Zhang, Weiping

    2014-06-01

    We propose an experimental scheme to show that the nonlinear magnetic solitary excitations can be achieved in an atomic spinor Bose-Einstein condensate confined in a blue-detuned optical lattice. Through exact theoretical calculations, we find that the magnetic solitons can be generated by the static magnetic dipole-dipole interaction (MDDI), of which the interaction range can be well controlled. We derive the existence conditions of the magnetic solitons under the nearest-neighboring, the next-nearest-neighboring approximations as well as the long-range consideration. It is shown that the long-range feature of the MDDI plays an important role in determining the existence of magnetic solitons in this system. In addition, to facilitate the experimental observation, we apply an external laser field to drive the lattice, and the existence regions for the magnetic soliton induced by the anisotropic light-induced dipole-dipole interaction are also investigated.

  1. Development and testing of a high cycle life 30 A-h sealed AgO-Zn battery

    NASA Technical Reports Server (NTRS)

    Bogner, R. S.

    1972-01-01

    A two-phase program was initiated to investigate design parameters and technology to develop an improved AgO-Zn battery. The basic performance goal was 100 charge/discharge cycles (22 h/2 h) at 50 percent depth of discharge following a six-month period of charged stand at room temperature. Phase 1, cell evaluation, involved testing 70 cells in five-cell groups. The major design variables were active material ratios, electrolyte concentrations, separator systems, and negative plate shape. Phase 1 testing showed that cycle life could be improved 10 percent to 20 percent by using greater ratios of zinc to silver oxide and higher electrolyte concentrations. Wedge-shaped negatives increased cycle life by nearly 100 percent. Phase 2 battery evaluation, which was initiated before the Phase 1 results were known completely, involved evaluation of six designs as 19-cell batteries. Only one battery exceeded 100 cycles following nine months charged stand.

  2. Electrospun regenerated cellulose nanofibrous membranes surface-grafted with polymer chains/brushes via the atom transfer radical polymerization method for catalase immobilization.

    PubMed

    Feng, Quan; Hou, Dayin; Zhao, Yong; Xu, Tao; Menkhaus, Todd J; Fong, Hao

    2014-12-10

    In this study, an electrospun regenerated cellulose (RC) nanofibrous membrane with fiber diameters of ∼200-400 nm was prepared first; subsequently, 2-hydroxyethyl methacrylate (HEMA), 2-dimethylaminoethyl methacrylate (DMAEMA), and acrylic acid (AA) were selected as the monomers for surface grafting of polymer chains/brushes via the atom transfer radical polymerization (ATRP) method. Thereafter, four nanofibrous membranes (i.e., RC, RC-poly(HEMA), RC-poly(DMAEMA), and RC-poly(AA)) were explored as innovative supports for immobilization of an enzyme of bovine liver catalase (CAT). The amount/capacity, activity, stability, and reusability of immobilized catalase were evaluated, and the kinetic parameters (Vmax and Km) for immobilized and free catalase were determined. The results indicated that the respective amounts/capacities of immobilized catalase on RC-poly(HEMA) and RC-poly(DMAEMA) nanofibrous membranes reached 78 ± 3.5 and 67 ± 2.7 mg g(-1), which were considerably higher than the previously reported values. Meanwhile, compared to that of free CAT (i.e., 18 days), the half-life periods of RC-CAT, RC-poly(HEMA)-CAT, RC-poly(DMAEMA)-CAT, and RC-poly(AA)-CAT were 49, 58, 56, and 60 days, respectively, indicating that the storage stability of immobilized catalase was also significantly improved. Furthermore, the immobilized catalase exhibited substantially higher resistance to temperature variation (tested from 5 to 70 °C) and lower degree of sensitivity to pH value (tested from 4.0 and 10.0) than the free catalase. In particular, according to the kinetic parameters of Vmax and Km, the nanofibrous membranes of RC-poly(HEMA) (i.e., 5102 μmol mg(-1) min(-1) and 44.89 mM) and RC-poly(DMAEMA) (i.e., 4651 μmol mg(-1) min(-1) and 46.98 mM) had the most satisfactory biocompatibility with immobilized catalase. It was therefore concluded that the electrospun RC nanofibrous membranes surface-grafted with 3-dimensional nanolayers of polymer chains/brushes would be

  3. Inulin crystal initiation via a glucose-fructose cross-link of adjacent polymer chains: atomic force microscopy and static molecular modelling.

    PubMed

    Cooper, Peter D; Rajapaksha, K Harinda; Barclay, Thomas G; Ginic-Markovic, Milena; Gerson, Andrea R; Petrovsky, Nikolai

    2015-03-01

    Semi-crystalline microparticles of inulin (MPI) have clinical utility as potent human vaccine adjuvants but their relevant surface structure and crystal assembly remain undefined. We show inulin crystal surfaces to resemble multi-layered, discoid radial spherulites resulting from very rapid formation of complex tertiary structures, implying directed crystal initiation. Physical and in silico molecular modelling of unit cells confirm steric feasibility of initiation by hydrogen-bonded cross-linking of terminal glucose to a fructose of another chain, mimicking bonding in sucrose crystals. A strong, chelate-like dual H-bond is proposed to compel the known antiparallel alignment of inulin chains. Such cross-linking would require one extra fructose per chain in the native inulin crystal, as observed. Completion of five H-bonded internal ring-domains would 'lock in' each new 6-fructose structural unit of each antiparallel helix pair to create a new isoform. All known properties of inulin isoforms follow readily from these concepts. PMID:25498723

  4. Characterization of the molecular species of glycerophospholipids from rabbit kidney: an alternative approach to the determination of the fatty acyl chain position by negative ion fast atom bombardment combined with mass-analysed ion kinetic energy analysis.

    PubMed

    Chen, S; Curcuruto, O; Catinella, S; Traldi, P; Menon, G

    1992-12-01

    An alternative approach to identifying fatty acid chain position in the molecular species of glycerophospholipids has been studied and developed. The fatty acyl groups esterified to the glycerol backbone in isomeric glycerophosphatidyl-choline, -serine and -ethanolamine as well as glycerophosphatidic acid can be detected by the presence of a pair of anions derived from phosphatidic acid parent ions (M minus the polar head groups in glycerophospholipids), designed to be [M--polar head--R2COOH]- and [M--polar head--R2CO--H]-, produced by negative ion fast atom bombardment combined with mass-analysed ion kinetic energy analysis. Because of the significant abundance of [M--polar head--R2COOH]- anion, fatty acid chains differing by 2 Da can be distinguished by accurate measurements of the electrostatic voltage related to this ion. Three-volt differences can be evidenced. Using this approach, the molecular species of glycerophosphatidyl-choline, -serine, -ethanolamine and -inositol from rabbit kidney were characterized after the separation of both class and species by normal and reversed-phase high-performance liquid chromatography, respectively. We identified 11 arachidonoyl-containing molecular species of glycerophospholipids and the other 17 lipid molecules in this biological material. A couple of 1- alkenyl-2-arachidonoyl-sn-glycerol-3-phosphoethanolamine species, identified as plasmalogen GPE 16:0-20:4 and plasmalogen GPE 18:0-20:4, were found for the first time in rabbit kidney. PMID:1477110

  5. Combined dynamic scanning tunneling microscopy and frequency modulation atomic force microscopy investigations on polythiophene chains on graphite with a tuning fork sensor

    NASA Astrophysics Data System (ADS)

    Polesel-Maris, Jérôme; Lubin, Christophe; Thoyer, François; Cousty, Jacques

    2011-04-01

    Polythiophene molecules adsorbed on a highly oriented pyrolytic graphite surface were studied by combined dynamic scanning tunneling microscopy (STM) and frequency modulation atomic force microscopy (FM-AFM) with a quartz tuning fork sensor operating in Qplus mode and equipped with a Pt/Ir tip. Upon completing a careful sub-angström oscillation amplitude calibration of the probe, experiments were conducted in an ultra high vacuum at room temperature. By selecting the tip/surface distance regulation parameter, one can select the type of simultaneous information obtained in an area. For distance regulation based on the mean tunneling current, dynamic STM images together with maps of tip/surface force gradient were obtained. FM-AFM images with maps of the tunneling current were also acquired when the distance regulation was based on the frequency shift. Comparison between these images reveals interesting features. For example the tip which operates in STM mode with ultra low current (<10 pA) generates different interaction forces above molecules or graphite. Changes in energy dissipation processes as small as tens of millielectronvolts per cycle were recorded when the tip oscillates above the polymer or on the graphite surface. Hence data demonstrates that a stiff piezoelectric tuning fork of several kilonewtons/meters working as an AFM/STM probe with sub-angström amplitude can characterize weakly adsorbed molecules.

  6. Electron transfer and multi-atom abstraction reactions between atomic metal anions and NO, NO2 and SO2

    NASA Astrophysics Data System (ADS)

    Butson, J. M.; Curtis, S.; Mayer, P. M.

    2016-05-01

    The atomic metal anions Fe-, Cs-, Cu- and Ag- were reacted with NO, NO2 and SO2 to form intact NO-, NO2- and SO2- with no fragmentation. Yields for the molecular anions ranged from 4 to 97% and were found to correlate to the exothermicity of the electron transfer process. Sequential oxygen atom extraction was found to take place between the metal anions and NO and NO2. Reactions between NO2 and Fe- resulted in FeO-, FeO2- and FeO3- while reactions of Cu- with NO2 resulted in CuO- and CuO2-. Reactions of Cu- and Ag- with NO resulted in CuO- and AgO- respectively.

  7. Lattice Vibrations in a Linear Triatomic Chain

    ERIC Educational Resources Information Center

    Kesavasamy, K.; Krishnamurthy, N.

    1978-01-01

    Discusses the vibrations of a linear triatomic chain and shows that the addition of the third atom gives rise to an extra optical branch. The nature of the normal modes in ionic crystals and molecular crystals is also discussed. (GA)

  8. Smallest Nanoelectronics with Adatom Chains

    NASA Technical Reports Server (NTRS)

    Yamada, Toshishige; Saini, Subhash (Technical Monitor)

    1998-01-01

    This viewgraph presentation is focused on the general aspect of atomic chain electronics that I have been studying. Results have been published before, but are being rederived here using a new physical/mathematical picture/model, which deepens the physical understanding. Precise adatom structures can be used as a template on a regulated surface with no uncertainty.

  9. Precise Nanoelectronics with Adatom Chains

    NASA Technical Reports Server (NTRS)

    Yamada, Toshishige

    1999-01-01

    Adatom chains on an atomically regulated substrate will be building components in future precise nanoelectronics. Adatoms need to be secured with chemical bonding, but then electronic isolation between the adatom and substrate systems is not guaranteed. A one-dimensional model shows that good isolation with existence of surface states is expected on an s-p crossing substrate such as Si, Ge, or GaAs, reflecting the bulk nature of the substrate. Isolation is better if adatoms are electronically similar to the substrate atoms, and can be manipulated by hydrogenation. Chain structures with group IV adatoms with two chemical bonds, or group III adatoms with one chemical bond, are semiconducting, reflecting the surface nature of the substrate. These structures are unintentionally doped due to the charge transfer across the chemical bonds. Physical properties of adatom chains have to be determined for the unified adatom-substrate system.

  10. Modeling of polypeptide chains as C alpha chains, C alpha chains with C beta, and C alpha chains with ellipsoidal lateral chains.

    PubMed

    Fogolari, F; Esposito, G; Viglino, P; Cattarinussi, S

    1996-03-01

    In an effort to reduce the number of degrees of freedom necessary to describe a polypeptide chain we analyze the statistical behavior of polypeptide chains when represented as C alpha chains, C alpha chains with C beta atoms attached, and C alpha chains with rotational ellipsoids as models of side chains. A statistical analysis on a restricted data set of 75 unrelated protein structures is performed. The comparison of the database distributions with those obtained by model calculation on very short polypeptide stretches allows the dissection of local versus nonlocal features of the distributions. The database distribution of the bend angles of polypeptide chains of pseudo bonded C alpha atoms spans a restricted range of values and shows a bimodal structure. On the other hand, the torsion angles of the C alpha chain may assume almost all possible values. The distribution is bimodal, but with a much broader probability distribution than for bend angles. The C alpha - C beta vectors may be taken as representative of the orientation of the lateral chain, as the direction of the bond is close to the direction of the vector joining C alpha to the ad hoc defined center of the "steric mass" of the side chain. Interestingly, both the bend angle defined by C alpha i-C alpha i+1-C beta i+1 and the torsional angle offset of the pseudo-dihedral C alpha i-C alpha i+1-C alpha i+2-C beta i+2 with respect to C alpha i-C alpha i+1-C alpha i+2-C alpha i+3 span a limited range of values. The latter results show that it is possible to give a more realistic representation of polypeptide chains without introducing additional degrees of freedom, i.e., by just adding to the C alpha chain a C beta with given side-chain properties. However, a more realistic description of side chains may be attained by modeling side chains as rotational ellipsoids that have roughly the same orientation and steric hindrance. To this end, we define the steric mass of an atom as proportional to its van der

  11. Structure and Stability of Monatomic Metallic Chains

    NASA Astrophysics Data System (ADS)

    Batra, Inder P.; Sen, Prasenjit; Ciraci, S.

    2001-03-01

    We have investigated atomic and electronic structure of Au and Al monatomic chains by using first-principle plane wave method within density-functional theory. Despite their different valencies, Au and Al form planar zigzag chains with each atom having four nearest neighbors. The zigzag structure is stable against linearization and non-planar deformations. We performed an extensive charge density analysis and finite temperature calculations to reveal the origin of the unusual atomic structure in these one dimensional metallic systems. The implications of the zigzag structure on the electronic properties and the balistic electron conduction have been examined.

  12. Liquid atomization

    NASA Astrophysics Data System (ADS)

    Bayvel, L.; Orzechowski, Z.

    The present text defines the physical processes of liquid atomization, the primary types of atomizers and their design, and ways of measuring spray characteristics; it also presents experimental investigation results on atomizers and illustrative applications for them. Attention is given to the macrostructural and microstructural parameters of atomized liquids; swirl, pneumatic, and rotary atomizers; and optical drop sizing methods, with emphasis on nonintrusive optical methods.

  13. Anisotropic Transport of Electrons in a Novel FET Channel with Chains of InGaAs Nano-Islands Embedded along Quasi-Periodic Multi-Atomic Steps on Vicinal (111)B GaAs

    SciTech Connect

    Akiyama, Y.; Kawazu, T.; Noda, T.; Sakaki, H.

    2010-01-04

    We have studied electron transport in n-AlGaAs/GaAs heterojunction FET channels, in which chains of InGaAs nano-islands are embedded along quasi-periodic steps. By using two samples, conductance G{sub para}(V{sub g}) parallel to the steps and G{sub perp}(V{sub g}) perpendicular to them were measured at 80 K as functions of gate voltage V{sub g}. At sufficiently high V{sub g}, G{sub para} at 80 K is several times as high as G{sub perp}, which manifests the anisotropic two-dimensional transport of electrons. When V{sub g} is reduced to -0.7 V, G{sub perp} almost vanishes, while {sub Gpara} stays sizable unless V{sub g} is set below -0.8 V. These results indicate that 'inter-chain' barriers play stronger roles than 'intra-chain' barriers.

  14. Crater Chains

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    The large crater at the top of this THEMIS visible image has several other craters inside of it. Most noticeable are the craters that form a 'chain' on the southern wall of the large crater. These craters are a wonderful example of secondary impacts. They were formed when large blocks of ejecta from an impact crashed back down onto the surface of Mars. Secondaries often form radial patterns around the impact crater that generated them, allowing researchers to trace them back to their origin.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

    Image information: VIS instrument. Latitude 19.3, Longitude 347.5 East (12.5 West). 19 meter/pixel resolution.

  15. Atomic polarizabilities

    SciTech Connect

    Safronova, M. S.; Mitroy, J.; Clark, Charles W.; Kozlov, M. G.

    2015-01-22

    The atomic dipole polarizability governs the first-order response of an atom to an applied electric field. Atomic polarization phenomena impinge upon a number of areas and processes in physics and have been the subject of considerable interest and heightened importance in recent years. In this paper, we will summarize some of the recent applications of atomic polarizability studies. A summary of results for polarizabilities of noble gases, monovalent, and divalent atoms is given. The development of the CI+all-order method that combines configuration interaction and linearized coupled-cluster approaches is discussed.

  16. An innovative method for joining materials at low temperature using silver (nano)particles derived from [AgO2C(CH2OCH2)3H

    NASA Astrophysics Data System (ADS)

    Oestreicher, Annerose; Röhrich, Tobias; Wilden, Johannes; Lerch, Martin; Jakob, Alexander; Lang, Heinrich

    2013-01-01

    A novel method for the manufacture of compact sintered silver layers as joining materials at low temperatures without applying pressure is described. The metal-organic silver complex [AgO2C(CH2OCH2)3H] (3) is used, which generates silver nanoparticles with heat treatment below 200 °C. Complex (3) provides the features for the formation of a molten metal-like silver phase in which silver particles in the nanometer and submicron size range, respectively, are completely miscible. Within this study, copper specimens were bonded, and the joints were evaluated by cross-sectional scanning electron microscope (SEM) images. Moreover, this approach enables the incorporation of copper. An example is given with an average amount of 20 at.% copper content in the silver layer.

  17. Dangling chain elastomers as repeatable fibrillar adhesives.

    PubMed

    Sitti, Metin; Cusick, Brian; Aksak, Burak; Nese, Alper; Lee, Hyung-il; Dong, Hongchen; Kowalewski, Tomasz; Matyjaszewski, Krzysztof

    2009-10-01

    This work reports on repeatable adhesive materials prepared by controlled grafting of dangling hetero chains from polymer elastomers. The dangling chain elastomer system was prepared by grafting poly(n-butyl acrylate) (PBA) chains from prefunctionalized polydimethylsiloxane (PDMS) elastomer networks using atom transfer radical polymerization. To study the effects of chain growth and network strain as they relate to network adhesion mechanics, various lengths of PBA chains with degree of polymerizations (DP) of 65, 281, 508, and 1200 were incorporated into the PDMS matrix. PBA chains with a DP value of 281 grafted from a flat PDMS substrate showed the highest (approximately 3.5-fold) enhancement of nano- and macroscale adhesion relative to a flat raw (ungrafted and not prefunctionalized) PDMS substrate. Moreover, to study the effect of PBA dangling chains on adhesion in fibrillar elastomer structures inspired by gecko foot hairs, a dip-transfer fabrication method was used to graft PBA chains with a DP value of 296 from the tip endings of mushroom-shaped PDMS micropillars. A PBA chain covered micropillar array showed macroscale adhesion enhancement up to approximately 7 times relative to the flat ungrafted prefunctionalized PDMS control substrate, showing additional nonoptimized approximately 2-fold adhesion enhancement due to fibrillar structuring and mushroom-shaped tip ending. These dangling hetero chains on elastomer micro-/nanofibrillar structures may provide a novel fabrication platform for multilength scale, repeatable, and high-strength fibrillar adhesives inspired by gecko foot hairs. PMID:20355863

  18. Dissipative Quantum Control of a Spin Chain

    NASA Astrophysics Data System (ADS)

    Morigi, Giovanna; Eschner, Jürgen; Cormick, Cecilia; Lin, Yiheng; Leibfried, Dietrich; Wineland, David J.

    2015-11-01

    A protocol is discussed for preparing a spin chain in a generic many-body state in the asymptotic limit of tailored nonunitary dynamics. The dynamics require the spectral resolution of the target state, optimized coherent pulses, engineered dissipation, and feedback. As an example, we discuss the preparation of an entangled antiferromagnetic state, and argue that the procedure can be applied to chains of trapped ions or Rydberg atoms.

  19. Realization of a Strained Atomic Wire Superlattice.

    PubMed

    Song, Inkyung; Goh, Jung Suk; Lee, Sung-Hoon; Jung, Sung Won; Shin, Jin Sung; Yamane, Hiroyuki; Kosugi, Nobuhiro; Yeom, Han Woong

    2015-11-24

    A superlattice of strained Au-Si atomic wires is successfully fabricated on a Si surface. Au atoms are known to incorporate into the stepped Si(111) surface to form a Au-Si atomic wire array with both one-dimensional (1D) metallic and antiferromagnetic atomic chains. At a reduced density of Au, we find a regular array of Au-Si wires in alternation with pristine Si nanoterraces. Pristine Si nanoterraces impose a strain on the neighboring Au-Si wires, which modifies both the band structure of metallic chains and the magnetic property of spin chains. This is an ultimate 1D version of a strained-layer superlattice of semiconductors, defining a direction toward the fine engineering of self-assembled atomic-scale wires. PMID:26446292

  20. Health supply chain management.

    PubMed

    Zimmerman, Rolf; Gallagher, Pat

    2010-01-01

    This chapter gives an educational overview of: * The actual application of supply chain practice and disciplines required for service delivery improvement within the current health environment. * A rationale for the application of Supply Chain Management (SCM) approaches to the Health sector. * The tools and methods available for supply chain analysis and benchmarking. * Key supply chain success factors. PMID:20407173

  1. Adjusting the Chain Gear

    NASA Astrophysics Data System (ADS)

    Koloc, Z.; Korf, J.; Kavan, P.

    The adjustment (modification) deals with gear chains intermediating (transmitting) motion transfer between the sprocket wheels on parallel shafts. The purpose of the adjustments of chain gear is to remove the unwanted effects by using the chain guide on the links (sliding guide rail) ensuring a smooth fit of the chain rollers into the wheel tooth gap.

  2. Atomic supersymmetry

    NASA Technical Reports Server (NTRS)

    Kostelecky, V. Alan

    1993-01-01

    Atomic supersymmetry is a quantum-mechanical supersymmetry connecting the properties of different atoms and ions. A short description of some established results in the subject are provided and a few recent developments are discussed including the extension to parabolic coordinates and the calculation of Stark maps using supersymmetry-based models.

  3. Atomic Calligraphy

    NASA Astrophysics Data System (ADS)

    Imboden, Matthias; Pardo, Flavio; Bolle, Cristian; Han, Han; Tareen, Ammar; Chang, Jackson; Christopher, Jason; Corman, Benjamin; Bishop, David

    2013-03-01

    Here we present a MEMS based method to fabricate devices with a small number of atoms. In standard semiconductor fabrication, a large amount of material is deposited, after which etching removes what is not wanted. This technique breaks down for structures that approach the single atom limit, as it is inconceivable to etch away all but one atom. What is needed is a bottom up method with single or near single atom precision. We demonstrate a MEMS device that enables nanometer position controlled deposition of gold atoms. A digitally driven plate is swept as a flux of gold atoms passes through an aperture. Appling voltages on four comb capacitors connected to the central plate by tethers enable nanometer lateral precision in the xy plane over 15x15 sq. microns. Typical MEMS structures have manufacturing resolutions on the order of a micron. Using a FIB it is possible to mill apertures as small as 10 nm in diameter. Assuming a low incident atomic flux, as well as an integrated MEMS based shutter with microsecond response time, it becomes possible to deposit single atoms. Due to their small size and low power consumption, such nano-printers can be mounted directly in a cryogenic system at ultrahigh vacuum to deposit clean quench condensed metallic structures.

  4. Liquid atomization

    SciTech Connect

    Walzel, P. )

    1993-01-01

    A systematic review of different liquid atomizers is presented, accompanied by a discussion of various mechanisms of droplet formation in a gas atmosphere as a function of the liquid flow-regime and the geometry of the atomizer. Equations are presented for the calculation of the mean droplet-diameter. In many applications, details of the droplet size distribution are, also, important, e.g., approximate values of the breadth of the droplet formation are given. The efficiency of utilization of mechanical energy in droplet formation is indicated for the different types of atomizers. Atomization is used, in particular, for the following purposes: (1) atomization of fuels; (2) making granular products; (3) carrying out mass-transfer operations; and (4) coating of surfaces.

  5. Nuclear structure notes on element 115 decay chains

    SciTech Connect

    Rudolph, D. Sarmiento, L. G.; Forsberg, U.

    2015-10-15

    Hitherto collected data on more than hundred α-decay chains stemming from element 115 are combined to probe some aspects of the underlying nuclear structure of the heaviest atomic nuclei yet created in the laboratory.

  6. Reactivity and Catalytic Activity of Hydrogen Atom Chemisorbed Silver Clusters.

    PubMed

    Manzoor, Dar; Pal, Sourav

    2015-06-18

    Metal clusters of silver have attracted recent interest of researchers as a result of their potential in different catalytic applications and low cost. However, due to the completely filled d orbital and very high first ionization potential of the silver atom, the silver-based catalysts interact very weakly with the reacting molecules. In the current work, density functional theory calculations were carried out to investigate the effect of hydrogen atom chemisorption on the reactivity and catalytic properties of inert silver clusters. Our results affirm that the hydrogen atom chemisorption leads to enhancement in the binding energy of the adsorbed O2 molecule on the inert silver clusters. The increase in the binding energy is also characterized by the decrease in the Ag-O and increase in the O-O bond lengths in the case of the AgnH silver clusters. Pertinent to the increase in the O-O bond length, a significant red shift in the O-O stretching frequency is also noted in the case of the AgnH silver clusters. Moreover, the hydrogen atom chemisorbed silver clusters show low reaction barriers and high heat of formation of the final products for the environmentally important CO oxidation reaction as compared to the parent catalytically inactive clusters. The obtained results were compared with those of the corresponding gold and hydrogen atom chemisorbed gold clusters obtained at the same level of theory. It is expected the current computational study will provide key insights for future advances in the design of efficient nanosilver-based catalysts through the adsorption of a small atom or a ligand. PMID:25988294

  7. Increased frequency of CD4{sup -}8{sup -}T cells bearing T-cell receptor {alpha}{beta} chains in peripheral blood of atomic bomb survivors exposed to high doses

    SciTech Connect

    Yoichiro Kusunoki; Seishi Kyoizumi; Yuko Hirai; Shoichiro Fujita; Mitoshi Akiyama

    1994-07-01

    A rare T-cell subpopulation, CD4{sup -z}8{sup -}{alpha}{beta} cells, may be differentiated through a pathway (or pathways) different from the pathway(s) of conventional CD4+ or CD8+ cells. In the present study, the frequencies of CD4{sup -}8{sup -} T cells in peripheral-blood {alpha}{beta} T cells in 409 atomic bomb survivors were determined to investigate late effects of radiation on the composition of human T-cell subpopulations. The frequency of CD4{sup -}8{sup -}{alpha}{beta} T-cell decreased significantly with the subject`s age and was higher in females than males. A significant increase in the frequency was found in the survivors exposed to more than 1.5Gy, suggesting that the previous radiation exposure altered differentiation and development of T cells. 25 refs., 4 figs., 3 tabs.

  8. Laser amplifier chain

    DOEpatents

    Hackel, R.P.

    1992-10-20

    A laser amplifier chain has a plurality of laser amplifiers arranged in a chain to sequentially amplify a low-power signal beam to produce a significantly higher-power output beam. Overall efficiency of such a chain is improved if high-gain, low efficiency amplifiers are placed on the upstream side of the chain where only a very small fraction of the total pumped power is received by the chain and low-gain, high-efficiency amplifiers are placed on the downstream side where a majority of pumping energy is received by the chain. 6 figs.

  9. Laser amplifier chain

    DOEpatents

    Hackel, Richard P.

    1992-01-01

    A laser amplifier chain has a plurality of laser amplifiers arranged in a chain to sequentially amplify a low-power signal beam to produce a significantly higher-power output beam. Overall efficiency of such a chain is improved if high-gain, low efficiency amplifiers are placed on the upstream side of the chain where only a very small fraction of the total pumped power is received by the chain and low-gain, high-efficiency amplifiers are placed on the downstream side where a majority of pumping energy is received by the chain.

  10. Acting Atoms.

    ERIC Educational Resources Information Center

    Farin, Susan Archie

    1997-01-01

    Describes a fun game in which students act as electrons, protons, and neutrons. This activity is designed to help students develop a concrete understanding of the abstract concept of atomic structure. (DKM)

  11. Kinetic Atom.

    ERIC Educational Resources Information Center

    Wilson, David B.

    1981-01-01

    Surveys the research of scientists like Joule, Kelvin, Maxwell, Clausius, and Boltzmann as it comments on the basic conceptual issues involved in the development of a more precise kinetic theory and the idea of a kinetic atom. (Author/SK)

  12. Newton's Atom

    NASA Astrophysics Data System (ADS)

    Chaney, Andrea; Espinosa, James; Espinosa, James

    2006-10-01

    At the turn of the twentieth century, physicists and chemists were developing atomic models. Some of the phenomena that they had to explain were the periodic table, the stability of the atom, and the emission spectra. Niels Bohr is known as making the first modern picture that accounted for these. Unknown to much of the physics community is the work of Walter Ritz. His model explained more emission spectra and predates Bohr's work. We will fit several spectra using Ritz's magnetic model for the atom. The problems of stability and chemical periodicity will be shown to be challenges that this model has difficulty solving, but we will present some potentially useful adaptations to the Ritzian atom that can account for them.

  13. Cold Atoms

    NASA Astrophysics Data System (ADS)

    Bellac, Michel Le

    2014-11-01

    This chapter and the following one address collective effects of quantum particles, that is, the effects which are observed when we put together a large number of identical particles, for example, electrons, helium-4 or rubidium-85 atoms. We shall see that quantum particles can be classified into two categories, bosons and fermions, whose collective behavior is radically different. Bosons have a tendency to pile up in the same quantum state, while fermions have a tendency to avoid each other. We say that bosons and fermions obey two different quantum statistics, the Bose-Einstein and the Fermi-Dirac statistics, respectively. Temperature is a collective effect, and in Section 5.1 we shall explain the concept of absolute temperature and its relation to the average kinetic energy of molecules. We shall describe in Section 5.2 how we can cool atoms down thanks to the Doppler effect, and explain how cold atoms can be used to improve the accuracy of atomic clocks by a factor of about 100. The effects of quantum statistics are prominent at low temperatures, and atom cooling will be used to obtain Bose-Einstein condensates at low enough temperatures, when the atoms are bosons.

  14. Fibonacci chain polynomials: Identities from self-similarity

    NASA Technical Reports Server (NTRS)

    Lang, Wolfdieter

    1995-01-01

    Fibonacci chains are special diatomic, harmonic chains with uniform nearest neighbor interaction and two kinds of atoms (mass-ratio r) arranged according to the self-similar binary Fibonacci sequence ABAABABA..., which is obtained by repeated substitution of A yields AB and B yields A. The implications of the self-similarity of this sequence for the associated orthogonal polynomial systems which govern these Fibonacci chains with fixed mass-ratio r are studied.

  15. Superheavy-element spectroscopy: Correlations along element 115 decay chains

    NASA Astrophysics Data System (ADS)

    Rudolph, D.; Forsberg, U.; Sarmiento, L. G.; Golubev, P.; Fahlander, C.

    2016-05-01

    Following a brief summary of the region of the heaviest atomic nuclei yet created in the laboratory, data on more than hundred α-decay chains associated with the production of element 115 are combined to investigate time and energy correlations along the observed decay chains. Several of these are analysed using a new method for statistical assessments of lifetimes in sets of decay chains.

  16. Relations in Chains

    ERIC Educational Resources Information Center

    Mineur, B. W.

    1973-01-01

    The criticisms made against chain indexing are reviewed, and PRECIS briefly considered as a possible (but improbable) general substitute for indexing. The failures of chain indexing arise mainly from an overemphasis on generic relationships. The use of symbols to represent relations between terms is suggested for the chain index. (80 references)…

  17. Atomic research

    NASA Technical Reports Server (NTRS)

    Hadaway, James B.; Connatser, Robert; Cothren, Bobby; Johnson, R. B.

    1993-01-01

    Work performed by the University of Alabama in Huntsville's (UAH) Center for Applied Optics (CAO) entitled Atomic Research is documented. Atomic oxygen (AO) effects on materials have long been a critical concern in designing spacecraft to withstand exposure to the Low Earth Orbit (LEO) environment. The objective of this research effort was to provide technical expertise in the design of instrumentation and experimental techniques for analyzing materials exposed to atomic oxygen in accelerated testing at NASA/MSFC. Such testing was required to answer fundamental questions concerning Space Station Freedom (SSF) candidate materials and materials exposed to atomic oxygen aboard the Long-Duration Exposure Facility (LDEF). The primary UAH task was to provide technical design, review, and analysis to MSFC in the development of a state-of-the-art 5eV atomic oxygen beam facility required to simulate the RAM-induced low earth orbit (LEO) AO environment. This development was to be accomplished primarily at NASA/MSFC. In support of this task, contamination effects and ultraviolet (UV) simulation testing was also to be carried out using NASA/MSFC facilities. Any materials analysis of LDEF samples was to be accomplished at UAH.

  18. Actuated atomizer

    NASA Technical Reports Server (NTRS)

    Tilton, Charles (Inventor); Weiler, Jeff (Inventor); Palmer, Randall (Inventor); Appel, Philip (Inventor)

    2008-01-01

    An actuated atomizer is adapted for spray cooling or other applications wherein a well-developed, homogeneous and generally conical spray mist is required. The actuated atomizer includes an outer shell formed by an inner ring; an outer ring; an actuator insert and a cap. A nozzle framework is positioned within the actuator insert. A base of the nozzle framework defines swirl inlets, a swirl chamber and a swirl chamber. A nozzle insert defines a center inlet and feed ports. A spool is positioned within the coil housing, and carries the coil windings having a number of turns calculated to result in a magnetic field of sufficient strength to overcome the bias of the spring. A plunger moves in response to the magnetic field of the windings. A stop prevents the pintle from being withdrawn excessively. A pintle, positioned by the plunger, moves between first and second positions. In the first position, the head of the pintle blocks the discharge passage of the nozzle framework, thereby preventing the atomizer from discharging fluid. In the second position, the pintle is withdrawn from the swirl chamber, allowing the atomizer to release atomized fluid. A spring biases the pintle to block the discharge passage. The strength of the spring is overcome, however, by the magnetic field created by the windings positioned on the spool, which withdraws the plunger into the spool and further compresses the spring.

  19. Atom Interferometry

    SciTech Connect

    Kasevich, Mark

    2008-05-08

    Atom de Broglie wave interferometry has emerged as a tool capable of addressing a diverse set of questions in gravitational and condensed matter physics, and as an enabling technology for advanced sensors in geodesy and navigation. This talk will review basic principles, then discuss recent applications and future directions. Scientific applications to be discussed include measurement of G (Newton's constant), tests of the Equivalence Principle and post-Newtonian gravity, and study of the Kosterlitz-Thouless phase transition in layered superfluids. Technology applications include development of precision gyroscopes and gravity gradiometers. The talk will conclude with speculative remarks looking to the future: Can atom interference methods be used to detect gravity waves? Can non-classical (entangled/squeezed state) atom sources lead to meaningful sensor performance improvements?

  20. Atom Interferometry

    SciTech Connect

    Mark Kasevich

    2008-05-07

    Atom de Broglie wave interferometry has emerged as a tool capable of addressing a diverse set of questions in gravitational and condensed matter physics, and as an enabling technology for advanced sensors in geodesy and navigation. This talk will review basic principles, then discuss recent applications and future directions. Scientific applications to be discussed include measurement of G (Newton’s constant), tests of the Equivalence Principle and post-Newtonian gravity, and study of the Kosterlitz-Thouless phase transition in layered superfluids. Technology applications include development of precision gryoscopes and gravity gradiometers. The talk will conclude with speculative remarks looking to the future: Can atom interference methods be sued to detect gravity waves? Can non-classical (entangled/squeezed state) atom sources lead to meaningful sensor performance improvements?

  1. Atom Interferometry

    ScienceCinema

    Mark Kasevich

    2010-01-08

    Atom de Broglie wave interferometry has emerged as a tool capable of addressing a diverse set of questions in gravitational and condensed matter physics, and as an enabling technology for advanced sensors in geodesy and navigation. This talk will review basic principles, then discuss recent applications and future directions. Scientific applications to be discussed include measurement of G (Newton?s constant), tests of the Equivalence Principle and post-Newtonian gravity, and study of the Kosterlitz-Thouless phase transition in layered superfluids. Technology applications include development of precision gryoscopes and gravity gradiometers. The talk will conclude with speculative remarks looking to the future: Can atom interference methods be sued to detect gravity waves? Can non-classical (entangled/squeezed state) atom sources lead to meaningful sensor performance improvements?

  2. Structural, morphological and optical properties of Ag-AgO thin films with the effect of increasing film thickness and annealing temperature

    NASA Astrophysics Data System (ADS)

    Pal, Anil Kumar; Bharathi Mohan, D.

    2015-10-01

    Ag films of thickness ranging from 5 to 60 nm were deposited by thermal evaporation technique followed by air annealing process with temperature varying from 50 to 250 °C. Morphological properties such as particle size, shape, surface roughness and number particles density were studied by atomic force microscope (AFM). The structural transition from quasi-amorphous to nanocrystalline to crystalline upon increasing film thickness and annealing temperature were studied. Ag films with smallest particle size and surface roughness were achieved up to film thickness of 7 nm. The possibility of surface oxidation of Ag on both as deposited and annealed films was studied through Raman mapping by using confocal Raman spectroscopy. Ag film was X-ray amorphous even after annealing process up to the film thickness of 7 nm and above which the crystallinity reached maximum at 250 °C. The surface plasmon resonance (SPR) with a symmetric line shape due to dipole-dipole interactions was found to be very strong for film thickness of 5 nm at 100 °C, attributed to the formation of smaller Ag NPs size of ∼22 nm with least size distribution and higher particles number density of ∼1625 μm-2 in a self-organized fashion. With an increase of film thickness and annealing temperature, an asymmetric broad absorption arose due to increase in damping of collective electron oscillation on bulky NPs. Theoretical absorption spectra were simulated using extended Maxwell garnet method showing a decent agreement with experimental data. The real and imaginary parts of dielectric constants were determined and plotted for different film thicknesses of as deposited Ag films. Even though the film is oxidized at the surface level, it still can be used for plasmonic sensor applications however the film thickness should be approximately 7 nm for the enhanced result.

  3. Structure of Human Ferritin L Chain

    SciTech Connect

    Wang,Z.; Li, C.; Ellenburg, M.; Soistman, E.; Ruble, J.; Wright, B.; Ho, J.; Carter, D.

    2006-01-01

    Ferritin is the major iron-storage protein present in all cells. It generally contains 24 subunits, with different ratios of heavy chain (H) to light chain (L), in the shape of a hollow sphere hosting up to 4500 ferric Fe atoms inside. H-rich ferritins catalyze the oxidation of iron(II), while L-rich ferritins promote the nucleation and storage of iron(III). Several X-ray structures have been determined, including those of L-chain ferritins from horse spleen (HoSF), recombinant L-chain ferritins from horse (HoLF), mouse (MoLF) and bullfrog (BfLF) as well as recombinant human H-chain ferritin (HuHF). Here, structures have been determined of two crystal forms of recombinant human L-chain ferritin (HuLF) obtained from native and perdeuterated proteins. The structures show a cluster of acidic residues at the ferrihydrite nucleation site and at the iron channel along the threefold axis. An ordered Cd{sup 2+} structure is observed within the iron channel, offering further insight into the route and mechanism of iron transport into the capsid. The loop between helices D and E, which is disordered in many other L-chain structures, is clearly visible in these two structures. The crystals generated from perdeuterated HuLF will be used for neutron diffraction studies.

  4. Gushing metal chain

    NASA Astrophysics Data System (ADS)

    Belyaev, Alexander; Sukhanov, Alexander; Tsvetkov, Alexander

    2016-03-01

    This article addresses the problem in which a chain falls from a glass from some height. This phenomenon demonstrates a paradoxical rise of the chain over the glass. To explain this effect, an initial hypothesis and an appropriate theory are proposed for calculating the steady fall parameters of the chain. For this purpose, the modified Cayley's problem of falling chain given its rise due to the centrifugal force of upward inertia is solved. Results show that the lift caused by an increase in linear density at the part of chain where it is being bent (the upper part) is due to the convergence of the chain balls to one another. The experiments confirm the obtained estimates of the lifting chain.

  5. Crater chains on Mercury

    NASA Astrophysics Data System (ADS)

    Shevchenko, V.; Skobeleva, T.

    After discovery of disruption comet Shoemaker-Levy 9 into fragment train before it's collision with Jupiter there was proposed that linear crater chains on the large satellites of Jupiter and on the Moon are impact scars of past tidally disrupted comets.It's known that radar images have revealed the possible presence of water ice deposits in polar regions of Mercury. Impacts by a few large comets seem to provide the best explanation for both the amount and cleanliness of the ice deposits on Mercury because they have a larger volatile content that others external sources, for example, asteroid. A number of crater chains on the surface of Mercury are most likely the impact tracks of "fragment trains" of comets tidally disrupted by Sun or by Mercury and are not secondary craters. Mariner 10 image set (the three Mariner 10 flybys in 1974-1975) was used to recognize the crater chains these did not associate with secondary crater ejecta from observed impact structures. As example, it can be shown such crater chain located near crater Imhotep and crater Ibsen (The Kuiper Quadrangle of Mercury). Resolution of the Mariner 10 image is about 0.54 km/pixel. The crater chain is about 50 km long. It was found a similar crater chain inside large crater Sophocles (The Tolstoj Quadrangle of Mercury). The image resolution is about 1.46 km/pixel. The chain about 50 km long is located in northen part of the crater. Image resolution limits possibility to examine the form of craters strongly. It seems the craters in chains have roughly flat floor and smooth form. Most chain craters are approximately circular. It was examined many images from the Mariner 10 set and there were identified a total 15 crater chains and were unable to link any of these directly to any specific large crater associated with ejecta deposits. Chain craters are remarkably aligned. All distinguished crater chains are superposed on preexisting formations. A total of 127 craters were identified in the 15 recognized

  6. Atomic rivals

    SciTech Connect

    Goldschmidt, B.

    1990-01-01

    This book is a memoir of rivalries among the Allies over the bomb, by a participant and observer. Nuclear proliferation began in the uneasy wartime collaboration of the United States, England, Canada, and Free France to produce the atom bomb. Through the changes of history, a young French chemist had a role in almost every act of this international drama. This memoir is based on Goldschmidt's own recollections, interviews with other leading figures, and 3,000 pages of newly declassified documents in Allied archives. From his own start as Marie Curie's lab assistant, Goldschmidt's career was closely intertwined with Frances complicated rise to membership in the nuclear club. As a refugee from the Nazis, he became part of the wartime nuclear energy project in Canada and found himself the only French scientist to work (although briefly) on the American atom bomb project.

  7. Atomic arias

    NASA Astrophysics Data System (ADS)

    Crease, Robert P.

    2009-01-01

    The American composer John Adams uses opera to dramatize controversial current events. His 1987 work Nixon in China was about the landmark meeting in 1972 between US President Richard Nixon and Chairman Mao Zedong of China; The Death of Klinghoffer (1991) was a musical re-enactment of an incident in 1985 when Palestinian terrorists kidnapped and murdered a wheelchair-bound Jewish tourist on a cruise ship. Adams's latest opera, Doctor Atomic, is also tied to a controversial event: the first atomic-bomb test in Alamogordo, New Mexico, on 16 June 1945. The opera premièred in San Francisco in 2005, had a highly publicized debut at the Metropolitan Opera in New York in 2008, and will have another debut on 25 February - with essentially the same cast - at the English National Opera in London.

  8. Chain entanglements. I. Theory

    NASA Astrophysics Data System (ADS)

    Fixman, Marshall

    1988-09-01

    A model of concentrated polymer solution dynamics is described. The forces in a linear generalized Langevin equation for the motion of a probe chain are derived on the assumption that all relaxation of the forces is due to motion of the surrounding matrix. Vicinal chain displacements are classified as viscoelastic deformation, reptation, and minor residual fluctuations. The latter provide a torsional relaxation of the primitive path that minimizes the significance of transverse forces on the probe chain. All displacements of vicinal segments are assumed proportional to the forces that they exert on the probe chain. In response to an external force, the displacement of the probe chain relative to a laboratory frame is increased by viscoelastic deformation of the matrix, but reptative diffusion relative to the deforming matrix is slowed down. The net effect on translational diffusion is negligible if the probe and vicinal chains have the same chain length N, but the friction constant for reptative motion is increased by a factor N1-xs. xs=1/2 if Gaussian conformational statistics applies during the disengagement process, while xs =0.6 if excluded volume statistics applies. The translational friction constant is βp ˜N2, as in reptation theory, but the viscosity is η˜N4-xs . The persistence of entanglements during the translational diffusion of the probe chain across many radii of gyration is rationalized pictorially in terms of correlated reptative motion of the probe and vicinal chains.

  9. Atomic physics

    SciTech Connect

    Livingston, A.E.; Kukla, K.; Cheng, S.

    1995-08-01

    In a collaboration with the Atomic Physics group at Argonne and the University of Toledo, the Atomic Physics group at the University of Notre Dame is measuring the fine structure transition energies in highly-charged lithium-like and helium-like ions using beam-foil spectroscopy. Precise measurements of 2s-2p transition energies in simple (few-electron) atomic systems provide stringent tests of several classes of current atomic- structure calculations. Analyses of measurements in helium-like Ar{sup 16+} have been completed, and the results submitted for publication. A current goal is to measure the 1s2s{sup 3}S{sub 1} - 1s2p{sup 3}P{sub 0} transition wavelength in helium-like Ni{sup 26+}. Measurements of the 1s2s{sup 2}S{sub 1/2} - 1s2p{sup 2}P{sub 1/2,3/2} transition wavelengths in lithium-like Kr{sup 33+} is planned. Wavelength and lifetime measurements in copper-like U{sup 63+} are also expected to be initiated. The group is also participating in measurements of forbidden transitions in helium-like ions. A measurement of the lifetime of the 1s2s{sup 3}S{sub 1} state in Kr{sup 34+} was published recently. In a collaboration including P. Mokler of GSI, Darmstadt, measurements have been made of the spectral distribution of the 2E1 decay continuum in helium-like Kr{sup 34+}. Initial results have been reported and further measurements are planned.

  10. Chain Reaction Polymerization.

    ERIC Educational Resources Information Center

    McGrath, James E.

    1981-01-01

    The salient features and importance of chain-reaction polymerization are discussed, including such topics as the thermodynamics of polymerization, free-radical polymerization kinetics, radical polymerization processes, copolymers, and free-radical chain, anionic, cationic, coordination, and ring-opening polymerizations. (JN)

  11. Critical Chain Exercises

    ERIC Educational Resources Information Center

    Doyle, John Kevin

    2010-01-01

    Critical Chains project management focuses on holding buffers at the project level vs. task level, and managing buffers as a project resource. A number of studies have shown that Critical Chain project management can significantly improve organizational schedule fidelity (i.e., improve the proportion of projects delivered on time) and reduce…

  12. Single-Chain Semiconducting Polymer Dots

    PubMed Central

    2015-01-01

    This work describes the preparation and validation of single-chain semiconducting polymer dots (sPdots), which were generated using a method based on surface immobilization, washing, and cleavage. The sPdots have an ultrasmall size of ∼3.0 nm as determined by atomic force microscopy, a size that is consistent with the anticipated diameter calculated from the molecular weight of the single-chain semiconducting polymer. sPdots should find use in biology and medicine as a new class of fluorescent probes. The FRET assay this work presents is a simple and rapid test to ensure methods developed for preparing sPdot indeed produced single-chain Pdots as designed. PMID:25521606

  13. Predicting the chemical stability of monatomic chains

    NASA Astrophysics Data System (ADS)

    Lin, Zheng-Zhe; Chen, Xi

    2013-02-01

    A simple model for evaluating the thermal atomic transfer rates in nanosystems (Lin Z.-Z. et al., EPL, 94 (2011) 40002) was developed to predict the chemical reaction rates of nanosystems with small gas molecules. The accuracy of the model was verified by MD simulations for molecular adsorption and desorption on a monatomic chain. By the prediction, a monatomic carbon chain should survive for 1.2 × 102 years in the ambient of 1 atm O2 at room temperature, and it is very invulnerable to N2, H2O, NO2, CO and CO2, while a monatomic gold chain quickly ruptures in vacuum. It is worth noting that since the model can be easily applied via common ab initio calculations, it could be widely used in the prediction of chemical stability of nanosystems.

  14. Cooperative spin decoherence in finite spin chains

    NASA Astrophysics Data System (ADS)

    Delgado, Fernando; Fernandez-Rossier, Joaquin

    2014-03-01

    Overcoming the problem of relaxation and decoherence of magnetic nanostructures is one of the mayor goals in magnetic data storage. Although spin chains with as few as 12 magnetic atoms have revealed stability in cryogenic conditions, understanding the mechanism leading to these effects is essential for the engineered of stable structures. Here we consider the problem of spin decoherence and relaxation of finite size quantum spin chains due to elastic and spin conserving interactions with an electron gas. Specifically, we consider how the decoherence (T2) and relaxation (T1) times between the two degenerate ground states of a chain of N coupled spins compares with the one of an isolated spin in the same environment. We find that the spin decoherence time of Ising chains can be either enhanced or suppressed depending on the matching between the Fermi wavelength 2 π /kF and the inter-spin distance a. In particular, we find that depending on the values of kF a , it can show, for certain values that depends on the dimensionality of the electron gas, a cooperative enhancement proportional to N2 of the decoherence, analogous to super radiance decay of atom ensembles, or a suppression.

  15. Atomic Clocks

    NASA Astrophysics Data System (ADS)

    Wynands, Robert

    Time is a strange thing. On the one hand it is arguably the most inaccessible physical phenomenon of all: both in that it is impossible to manipulate or modify—for all we know—and in that even after thousands of years mankind's philosophers still have not found a fully satisfying way to understand it. On the other hand, no other quantity can be measured with greater precision. Today's atomic clocks allow us to reproduce the length of the second as the SI unit of time with an uncertainty of a few parts in 1016—orders of magnitude better than any other quantity. In a sense, one can say [1

  16. Majorana states in helical Shiba chains and ladders

    NASA Astrophysics Data System (ADS)

    Ojanen, Teemu; Poyhonen, Kim; Westsrom, Alex; Rontynen, Joel; Nanotheory Team

    2014-03-01

    Motivated by recent proposals to realize Majorana bound states in chains and arrays of magnetic atoms deposited on top of a superconductor, we study the topological properties of various chain structures, ladders and two-dimensional arrangements exhibiting magnetic helices. We show that magnetic domain walls where the chirality of a magnetic helix is inverted support two protected Majorana states giving rise to a tunneling conductance peak twice the height of a single Majorana state. Multiple overlapping Majorana states are protected by chiral symmetry which is present in systems exhibiting planar magnetic textures. Thus the topological properties of coupled chains exhibit nontrivial behaviour as a function of the number of chains beyond the even-odd dichotomy expected from Z2 classification. In addition, it is possible that a ladder of two or more coupled chains exhibit Majorana edge states even when decoupled chains are trivial. The authors acknowledge the Academy of Finland for support.

  17. SUMO chains: polymeric signals.

    PubMed

    Vertegaal, Alfred C O

    2010-02-01

    Ubiquitin and ubiquitin-like proteins are conjugated to a wide variety of target proteins that play roles in all biological processes. Target proteins are conjugated to ubiquitin monomers or to ubiquitin polymers that form via all seven internal lysine residues of ubiquitin. The fate of these target proteins is controlled in a chain architecture-dependent manner. SUMO (small ubiquitin-related modifier) shares the ability of ubiquitin to form chains via internal SUMOylation sites. Interestingly, a SUMO-binding site in Ubc9 is important for SUMO chain synthesis. Similar to ubiquitin-polymer cleavage by USPs (ubiquitin-specific proteases), SUMO chain formation is reversible. SUMO polymers are cleaved by the SUMO proteases SENP6 [SUMO/sentrin/SMT3 (suppressor of mif two 3)-specific peptidase 6], SENP7 and Ulp2 (ubiquitin-like protease 2). SUMO chain-binding proteins including ZIP1, SLX5/8 (synthetic lethal of unknown function 5/8), RNF4 (RING finger protein 4) and CENP-E (centromere-associated protein E) have been identified that interact non-covalently with SUMO chains, thereby regulating target proteins that are conjugated to SUMO multimers. SUMO chains play roles in replication, in the turnover of SUMO targets by the proteasome and during mitosis and meiosis. Thus signalling via polymers is an exciting feature of the SUMO family. PMID:20074033

  18. Atom Skimmers and Atom Lasers Utilizing Them

    NASA Technical Reports Server (NTRS)

    Hulet, Randall; Tollett, Jeff; Franke, Kurt; Moss, Steve; Sackett, Charles; Gerton, Jordan; Ghaffari, Bita; McAlexander, W.; Strecker, K.; Homan, D.

    2005-01-01

    Atom skimmers are devices that act as low-pass velocity filters for atoms in thermal atomic beams. An atom skimmer operating in conjunction with a suitable thermal atomic-beam source (e.g., an oven in which cesium is heated) can serve as a source of slow atoms for a magneto-optical trap or other apparatus in an atomic-physics experiment. Phenomena that are studied in such apparatuses include Bose-Einstein condensation of atomic gases, spectra of trapped atoms, and collisions of slowly moving atoms. An atom skimmer includes a curved, low-thermal-conduction tube that leads from the outlet of a thermal atomic-beam source to the inlet of a magneto-optical trap or other device in which the selected low-velocity atoms are to be used. Permanent rare-earth magnets are placed around the tube in a yoke of high-magnetic-permeability material to establish a quadrupole or octupole magnetic field leading from the source to the trap. The atoms are attracted to the locus of minimum magnetic-field intensity in the middle of the tube, and the gradient of the magnetic field provides centripetal force that guides the atoms around the curve along the axis of the tube. The threshold velocity for guiding is dictated by the gradient of the magnetic field and the radius of curvature of the tube. Atoms moving at lesser velocities are successfully guided; faster atoms strike the tube wall and are lost from the beam.

  19. Translocation of reptating chains

    NASA Astrophysics Data System (ADS)

    Żurek, S.; Drzewiński, A.; van Leeuwen, J. M. J.

    2011-05-01

    Voltage-driven translocation is modeled with the Rubinstein-Duke rules for hopping reptons in one- and two-dimensional lattices. The chain is driven through the pore by a bias potential promoting the transition of stored length in one direction. Coupling states give a semi-periodicity of the process that enables us to relate the properties to the stationary state of the master equation. The exact solution for short chains and Monte Carlo simulations for longer chains are used to calculate displacements, velocities and the translocation time.

  20. Viewing minerals, atom by atom

    NASA Astrophysics Data System (ADS)

    Maggs, William Ward

    With state-of-the-art technology supported by scissors and bungy cords, Earth scientists are beginning to look at mineral surfaces and mineral-fluid interactions on an atomic scale.The instrument that can provide such a detailed view is the scanning tunneling microscope (STM), which made a great theoretical and practical splash when it was introduced in 1981 by Gerd Binnig and Heinrich Rohrer, physicists at IBM's laboratory in Zurich. They won a Nobel Prize in Physics for their work 5 years later.

  1. EIT in resonator chains: similarities and differences with atomic media

    NASA Technical Reports Server (NTRS)

    Matsko, A. B.; Maleki, L.; Savchenkov, A. A.; Ilchenko, V. S.

    2004-01-01

    We theoretically study a parallel configuration of two interacting whispering gallery mode optical resonators and show a narrow-band modal structure as a basis for a widely tunable delay line. For the optimum coupling configuration the system can possess an unusually narrow spectral feature with a much narrower bandwidth than the loaded bandwidth of each individual resonator.

  2. Atomic magnetometer

    DOEpatents

    Schwindt, Peter; Johnson, Cort N.

    2012-07-03

    An atomic magnetometer is disclosed which uses a pump light beam at a D1 or D2 transition of an alkali metal vapor to magnetically polarize the vapor in a heated cell, and a probe light beam at a different D2 or D1 transition to sense the magnetic field via a polarization rotation of the probe light beam. The pump and probe light beams are both directed along substantially the same optical path through an optical waveplate and through the heated cell to an optical filter which blocks the pump light beam while transmitting the probe light beam to one or more photodetectors which generate electrical signals to sense the magnetic field. The optical waveplate functions as a quarter waveplate to circularly polarize the pump light beam, and as a half waveplate to maintain the probe light beam linearly polarized.

  3. Tailoring the Electronic Structure of Gold Chains on Vicinal Silicon

    NASA Astrophysics Data System (ADS)

    Crain, Jason; Altmann, Kyle; Bromberger, Christian; Erwin, Steven; Kirakosian, Armen; McChesney, Jessica; Lin, Jia-Ling; Himpsel, Franz

    2003-03-01

    Surface states on silicon provide a unique opportunity to study one-dimensional electron systems. By growing chains of gold atoms on vicinal silicon surfaces we demonstrate the capability of engineering one-dimensional metallic states with varying inter-chain spacing and electron count. Using high-resolution angle-resolved photoemission we map the band structures and Fermi surfaces for these atomic chains. The resulting metallic bands exhibit novel properties including the formation of two half-filled metallic bands in place of a single semiconducting band and the formation of a fractionally filled band. From the Fermi surfaces we calculate the one-dimensional versus two-dimensional coupling strengths and demonstrate that their ratio can be tuned from 12:1 to >70:1 by increasing the chain spacing via the miscut angle. [1] [1] J. N. Crain et al., submitted.

  4. Factorialsum Number Chains.

    ERIC Educational Resources Information Center

    Lamb, John, Jr.

    1989-01-01

    Describes several phenomena in which interesting properties of numbers are demonstrated. Includes discussions of amicable, perfect, and sociable numbers. Presents computer programs for conducting a number chain search. (RT)

  5. Respiratory chain supercomplexes.

    PubMed

    Schägger, H

    2001-01-01

    Respiratory chain supercomplexes have been isolated from mammalian and yeast mitochondria, and bacterial membranes. Functional roles of respiratory chain supercomplexes are catalytic enhancement, substrate channelling, and stabilization of complex I by complex III in mammalian cells. Bacterial supercomplexes are characterized by their relatively high detergent-stability compared to yeast or mammalian supercomplexes that are stable to sonication. The mobility of substrate cytochrome c increases in the order bacterial, yeast, and mammalian respiratory chain. In bacterial supercomplexes, the electron transfer between complexes III and IV involves movement of the mobile head of a tightly bound cytochrome c, whereas the yeast S. cerevisiae seems to use substrate channelling of a mobile cytochrome c, and mammalian respiratory chains have been described to use a cytochrome c pool. Dimeric ATP synthase seems to be specific for mitochondrial OXPHOS systems. Monomeric complex V was found in Acetobacterium woodii and Paracoccus denitrificans. PMID:11798023

  6. Light chain nephropathy.

    PubMed

    Darouich, Sihem; Bettaieb, Ilhem; Aouadia, Raja; Hedri, Hafedh; Abderrahim, Ezzeddine; Goucha, Rym; Khedher, Adel

    2015-01-01

    Light chain deposition disease (LCDD) is characterized by the tissue deposition of monotypic immunoglobulin light chains of either kappa or lambda isotype. It is the archetypal systemic disease that is most frequently diagnosed on a kidney biopsy, although the deposits may involve several other organs. This brief review focuses on the clinicopathological features of LCDD-associated nephropathy with an emphasis on the diagnostic and therapeutic difficulties related to this elusive condition. PMID:26022011

  7. A method to configure protein side-chains from the main-chain trace in homology modelling.

    PubMed

    Eisenmenger, F; Argos, P; Abagyan, R

    1993-06-01

    Protein homology modelling typically involves the prediction of side-chain conformations in the modelled protein while assuming a main-chain trace taken from a known tertiary structure of a protein with homologous sequence. It is generally believed that the need to examine all possible combinations of side-chain conformations poses the major obstacle to accurate homology modelling. Methods proposed heretofore use only discrete or limited searches of the side-chain torsion angle space to mitigate the combinatorial problem and also rely on simplified energy functions for calculational speed. The configurational constraints are typically based upon use of frequently observed torsion angles, fixed steps in torsion angles, or oligopeptide segments taken from tertiary structural databanks that are similar in sequence and conformation with the target structure. In the present work, a more fundamental approach is explored for several protein structures and it is demonstrated that the combinatorial barrier in side-chain placement hardly exists. Each side-group can be configured individually in the environment of only the backbone atoms using a systematic search procedure combined with extensive local energy minimization. Tests, using the main-chain or both the main-chain and remaining side-chain atoms to calculate low energy geometries for each residue, established the dominance of the main-chain contribution. The final structure is achieved by combining the individually placed side-chains followed by a full energy refinement of the structure. The prediction accuracy of the present homology modelling technique was assessed relative to other automated procedures and was found to yield improved predictions relative to the known side-chain conformations determined by X-ray crystallography. PMID:8515455

  8. Observation of Individual Fluorine Atom from Highly Oriented Poly (tetrafluoroethylene) Films by Atomic Force Microscopy

    NASA Technical Reports Server (NTRS)

    Lee, Jonathan A.,; Paley, Mark S.

    1999-01-01

    Direct observation of the film thickness, molecular structure and individual fluorine atoms from highly oriented poly(tetrafluoroethylene) (PTFE) films were achieved using atomic force microscopy (AFM). A thin PTFE film is mechanically deposited onto a smooth glass substrate at specific temperatures by a friction transfer technique. Atomic resolution images of these films show that the chain-like helical structures of the PTFE macromolecules are aligned parallel to each other with an intermolecular spacing of 5.72 A, and individual fluorine atoms are clearly observed along these twisted molecular chains with an interatomic spacing of 2.75 A. Furthermore, the first direct AFM measurements for the radius of the fluorine-helix, and of the carbon-helix in sub-angstrom scale are reported as 1.70 A and 0.54 A respectively.

  9. Observation of Individual Fluorine Atoms from Highly Oriented Poly(Tetrafluoroethylene) Films by Atomic Force Microscopy

    NASA Technical Reports Server (NTRS)

    Lee, J. A.

    2000-01-01

    Direct observation of the film thickness, molecular structure, and individual fluorine atoms from highly oriented poly(tetrafluoroethylene) (PTFE) films were achieved using atomic force microscopy (AFM). A thin PTFE film is mechanically deposited onto a smooth glass substrate at specific temperatures by a friction-transfer technique. Atomic resolution images of these films show that the chain-like helical structures of the PTFE macromolecules are aligned parallel to each other with an intermolecular spacing of 5.72 A, and individual fluorine atoms are clearly observed along these twisted molecular chains with an interatomic spacing of 2.75 A. Furthermore, the first direct AFM measurements for the radius of the fluorine-helix, and of the carbon-helix in sub-angstrom scale are reported as 1.7 and 0.54 A respectively.

  10. Topological Superconductivity with Magnetic Atoms

    NASA Astrophysics Data System (ADS)

    Glazman, Leonid

    2015-03-01

    Chains of magnetic impurities embedded in a conventional s-wave superconductor may induce the formation of a topologically non-trivial superconducting phase. If such a phase is formed along a chain, then its ends carry Majorana fermions. We investigate this possibility theoretically by developing a tight-binding Bogoliubov-de Gennes description, starting from the Shiba bound states induced by the individual magnetic impurities. While the resulting Hamiltonian has similarities with the Kitaev model for one-dimensional spinless p-wave superconductors, there are also important differences, most notably the long-range (power-law) nature of hopping and pairing as well as the complex hopping amplitudes. We develop an analytical theory, complemented by numerical approaches, which accounts for the electron long-range pairing and hopping along the chain, inhomogeneous magnetic order in the chain of embedded impurities or spin-orbit coupling in the host superconductor, and the possibility of direct electron hopping between the impurity atoms. This allows us to elucidate the domain of parameters favoring the formation of a topological phase and to find the spatial structure of Majorana states appearing in that phase. This talk is based on joint work with F. von Oppen, Falko Pientka, and Yang Peng.

  11. Selected spectroscopic results on element 115 decay chains

    DOE PAGESBeta

    Rudolph, D.; Forsberg, U.; Golubev, P.; Sarmiento, L. G.; Yakushev, A.; Andersson, L. -L.; Di Nitto, A.; Düllmann, Ch. E.; Gates, J. M.; Gregorich, K. E.; et al

    2014-08-24

    We observed thirty correlated α-decay chains in an experiment studying the fusion-evaporation reaction 48Ca + 243Am at the GSI Helmholtzzentrum fur Schwerionenforschung. The decay characteristics of the majority of these 30 chains are consistent with previous observations and interpretations of such chains to originate from isotopes of element Z = 115. High-resolution α-photon coincidence spectroscopy in conjunction with comprehensive Monte-Carlo simulations allow to propose excitation schemes of atomic nuclei of the heaviest elements, thereby probing nuclear structure models near the 'Island of Stability' with unprecedented experimental precision.

  12. Selected spectroscopic results on element 115 decay chains

    SciTech Connect

    Rudolph, D.; Forsberg, U.; Golubev, P.; Sarmiento, L. G.; Yakushev, A.; Andersson, L. -L.; Di Nitto, A.; Düllmann, Ch. E.; Gates, J. M.; Gregorich, K. E.; Gross, C. J.; Herzberg, R. -D.; Heßberger, F. P.; Khuyagbaatar, J.; Kratz, J. V.; Rykaczewski, K.; Schädel, M.; Åberg, S.; Ackermann, D.; Block, M.; Brand, H.; Carlsson, B. G.; Cox, D.; Derkx, X.; Eberhardt, K.; Even, J.; Fahlander, C.; Gerl, J.; Jäger, E.; Kindler, B.; Krier, J.; Kojouharov, I.; Kurz, N.; Lommel, B.; Mistry, A.; Mokry, C.; Nitsche, H.; Omtvedt, J. P.; Papadakis, P.; Ragnarsson, I.; Runke, J.; Schaffner, H.; Schausten, B.; Thörle-Pospiech, P.; Torres, T.; Traut, T.; Trautmann, N.; Türler, A.; Ward, A.; Ward, D. E.; Wiehl, N.

    2014-08-24

    We observed thirty correlated α-decay chains in an experiment studying the fusion-evaporation reaction 48Ca + 243Am at the GSI Helmholtzzentrum fur Schwerionenforschung. The decay characteristics of the majority of these 30 chains are consistent with previous observations and interpretations of such chains to originate from isotopes of element Z = 115. High-resolution α-photon coincidence spectroscopy in conjunction with comprehensive Monte-Carlo simulations allow to propose excitation schemes of atomic nuclei of the heaviest elements, thereby probing nuclear structure models near the 'Island of Stability' with unprecedented experimental precision.

  13. Phasic Triplet Markov Chains.

    PubMed

    El Yazid Boudaren, Mohamed; Monfrini, Emmanuel; Pieczynski, Wojciech; Aïssani, Amar

    2014-11-01

    Hidden Markov chains have been shown to be inadequate for data modeling under some complex conditions. In this work, we address the problem of statistical modeling of phenomena involving two heterogeneous system states. Such phenomena may arise in biology or communications, among other fields. Namely, we consider that a sequence of meaningful words is to be searched within a whole observation that also contains arbitrary one-by-one symbols. Moreover, a word may be interrupted at some site to be carried on later. Applying plain hidden Markov chains to such data, while ignoring their specificity, yields unsatisfactory results. The Phasic triplet Markov chain, proposed in this paper, overcomes this difficulty by means of an auxiliary underlying process in accordance with the triplet Markov chains theory. Related Bayesian restoration techniques and parameters estimation procedures according to the new model are then described. Finally, to assess the performance of the proposed model against the conventional hidden Markov chain model, experiments are conducted on synthetic and real data. PMID:26353069

  14. Chain formation and chain dynamics in a dilute magnetorheological fluid.

    PubMed

    Hagenbüchle, M; Liu, J

    1997-10-20

    Magnetorheological fluids are suspensions of magnetizable particles that reversibly change from liquid to solid when subjected to a magnetic field. A field-induced structure of dipolar chains is responsible for these changes. Our work aimed at understanding chain dynamics and the kinetics of chain formation by using dynamic light scattering. Chain length is determined by measurement of the diffusion coefficient. Chain-length growth shows a Smoluchowski behavior. PMID:18264283

  15. Spatial Data Supply Chains

    NASA Astrophysics Data System (ADS)

    Varadharajulu, P.; Azeem Saqiq, M.; Yu, F.; McMeekin, D. A.; West, G.; Arnold, L.; Moncrieff, S.

    2015-06-01

    This paper describes current research into the supply of spatial data to the end user in as close to real time as possible via the World Wide Web. The Spatial Data Infrastructure paradigm has been discussed since the early 1990s. The concept has evolved significantly since then but has almost always examined data from the perspective of the supplier. It has been a supplier driven focus rather than a user driven focus. The current research being conducted is making a paradigm shift and looking at the supply of spatial data as a supply chain, similar to a manufacturing supply chain in which users play a significant part. A comprehensive consultation process took place within Australia and New Zealand incorporating a large number of stakeholders. Three research projects that have arisen from this consultation process are examining Spatial Data Supply Chains within Australia and New Zealand and are discussed within this paper.

  16. "Bohr's Atomic Model."

    ERIC Educational Resources Information Center

    Willden, Jeff

    2001-01-01

    "Bohr's Atomic Model" is a small interactive multimedia program that introduces the viewer to a simplified model of the atom. This interactive simulation lets students build an atom using an atomic construction set. The underlying design methodology for "Bohr's Atomic Model" is model-centered instruction, which means the central model of the…

  17. Supply-Chain Optimization Template

    NASA Technical Reports Server (NTRS)

    Quiett, William F.; Sealing, Scott L.

    2009-01-01

    The Supply-Chain Optimization Template (SCOT) is an instructional guide for identifying, evaluating, and optimizing (including re-engineering) aerospace- oriented supply chains. The SCOT was derived from the Supply Chain Council s Supply-Chain Operations Reference (SCC SCOR) Model, which is more generic and more oriented toward achieving a competitive advantage in business.

  18. Solitons in Granular Chains

    SciTech Connect

    Manciu, M.; Sen, S.; Hurd, A.J.

    1999-04-12

    The authors consider a chain of elastic (Hertzian) grains that repel upon contact according to the potential V = a{delta}{sup u}, u > 2, where {delta} is the overlap between the grains. They present numerical and analytical results to show that an impulse initiated at an end of a chain of Hertzian grains in contact eventually propagates as a soliton for all n > 2 and that no solitons are possible for n {le} 2. Unlike continuous, they find that colliding solitons in discrete media initiative multiple weak solitons at the point of crossing.

  19. Hybrid ion chains inside an optical cavity

    NASA Astrophysics Data System (ADS)

    Zhou, Zichao; Siverns, James; Quraishi, Qudsia

    2016-05-01

    Trapped ions remain a leading candidate for the implementation of large-scale quantum networks. These networks require nodes that can store and process quantum information as well as communicate with each other though photonic flying qubits. We propose to use hybrid ion chains of barium, for communication, and ytterbium, for quantum information processing. We report on progress in setting up a hybrid ion chain in a versatile four-blade trap using high numerical aperture collection optics. Although the visible photons produced from barium ions are more favorable as they are not suitable for long distance fiber communication. With this in mind, we intend to implement frequency conversion to overcome this issue. Also, with the view toward increasing the flying-qubit production rate, we propose a cavity-based system to enhance interactions between the ions and photons. The cavity axis is to be placed along the axial direction of the trap allowing a chain of multiple ions to interact with the cavity at the same time. With this configuration the atom-photon coupling strength can be improved by sqrt(N), where N is the number of ions. Experiments will focus on exploring the dynamics of hybrid ion chain, dual species quantum information processing, two-colour entanglement and phase gates assisted by the ion-cavity coupling are to be explored.

  20. Atomic Energy Basics, Understanding the Atom Series.

    ERIC Educational Resources Information Center

    Atomic Energy Commission, Oak Ridge, TN. Div. of Technical Information.

    This booklet is part of the "Understanding the Atom Series," though it is a later edition and not included in the original set of 51 booklets. A basic survey of the principles of nuclear energy and most important applications are provided. These major topics are examined: matter has molecules and atoms, the atom has electrons, the nucleus,…

  1. Anomalous Energy Transport in FPU- Chain

    NASA Astrophysics Data System (ADS)

    Mellet, Antoine; Merino-Aceituno, Sara

    2015-08-01

    This paper is devoted to the derivation of a macroscopic fractional diffusion equation describing heat transport in an anharmonic chain. More precisely, we study here the so-called FPU- chain, which is a very simple model for a one-dimensional crystal in which atoms are coupled to their nearest neighbors by a harmonic potential, weakly perturbed by a quartic potential. The starting point of our mathematical analysis is a kinetic equation: Lattice vibrations, responsible for heat transport, are modeled by an interacting gas of phonons whose evolution is described by the Boltzmann phonon equation. Our main result is the rigorous derivation of an anomalous diffusion equation starting from the linearized Boltzmann phonon equation.

  2. Solitary waves in nonlinear coupled incommensurate chains

    NASA Astrophysics Data System (ADS)

    Dikandé, A. M.; Kofané, T. C.

    1994-01-01

    We present dynamical theory of soliton excitations in nonlinear coupled incommensurate chains which consists of two deformable chains of different atomic species, each with its own chemical potential, on the same substrate. In the continuum approximation, the motion equations are a set of coupled Sine-Gordon equations. The soliton solutions of these coupled equations are studied in detail. It has been shown that the frequency of the internal oscillations depends on the coupling parameter. The interaction energy between the two weakly coupled Sine-Gordon systems has been found. Results of the dynamical theory have been related to the transport properties in organic conductors such as TTF-TCNQ, KCP and others. Indeed, we have calculated some meaningful physical parameters of these compounds within the soliton limit, and discussed different types of behaviors shown at the transition with respect to variations of the physical parameters.

  3. INTERACTING QUANTUM SPIN CHAINS

    SciTech Connect

    ZHELUDEV,A.

    2001-09-09

    A brief review of recent advances in neutron scattering studies of low-dimensional quantum magnets is followed by a particular example. The separation of single-particle and continuum states in the weakly-coupled S = l/2 chains system BaCu{sub 2}Si{sub 2}O{sub 7} is described in some detail.

  4. Exploration Supply Chain Simulation

    NASA Technical Reports Server (NTRS)

    2008-01-01

    The Exploration Supply Chain Simulation project was chartered by the NASA Exploration Systems Mission Directorate to develop a software tool, with proper data, to quantitatively analyze supply chains for future program planning. This tool is a discrete-event simulation that uses the basic supply chain concepts of planning, sourcing, making, delivering, and returning. This supply chain perspective is combined with other discrete or continuous simulation factors. Discrete resource events (such as launch or delivery reviews) are represented as organizational functional units. Continuous resources (such as civil service or contractor program functions) are defined as enabling functional units. Concepts of fixed and variable costs are included in the model to allow the discrete events to interact with cost calculations. The definition file is intrinsic to the model, but a blank start can be initiated at any time. The current definition file is an Orion Ares I crew launch vehicle. Parameters stretch from Kennedy Space Center across and into other program entities (Michaud Assembly Facility, Aliant Techsystems, Stennis Space Center, Johnson Space Center, etc.) though these will only gain detail as the file continues to evolve. The Orion Ares I file definition in the tool continues to evolve, and analysis from this tool is expected in 2008. This is the first application of such business-driven modeling to a NASA/government-- aerospace contractor endeavor.

  5. Heavy Chain Diseases

    MedlinePlus

    ... cells often prevents proper absorption of nutrients from food (malabsorption), resulting in severe diarrhea and weight loss. A rare form that affects the respiratory tract also exists. Blood tests are done when alpha heavy chain disease is suspected. Serum protein electrophoresis, measurement of ...

  6. Polymerase chain reaction system

    DOEpatents

    Benett, William J.; Richards, James B.; Stratton, Paul L.; Hadley, Dean R.; Milanovich, Fred P.; Belgrader, Phil; Meyer, Peter L.

    2004-03-02

    A portable polymerase chain reaction DNA amplification and detection system includes one or more chamber modules. Each module supports a duplex assay of a biological sample. Each module has two parallel interrogation ports with a linear optical system. The system is capable of being handheld.

  7. Atwood's Heavy Chain

    ERIC Educational Resources Information Center

    Beeken, Paul

    2011-01-01

    While perusing various websites in search of a more challenging lab for my students, I came across a number of ideas where replacing the string in an Atwood's machine with a simple ball chain like the kind found in lamp pulls created an interesting system to investigate. The replacement of the string produced a nice nonuniform acceleration, but…

  8. Breaking the Chains

    ERIC Educational Resources Information Center

    Stanistreet, Paul

    2007-01-01

    In 1792 more than 350,000 people in Britain signed a petition calling for an end to the slave trade. It was, writes historian Adam Hochschild in his book "Bury the Chains," "the first time in history that a large number of people became outraged, and stayed outraged for many years, over someone else's rights". In 1807--after 15 years of…

  9. Freezing distributed entanglement in spin chains

    SciTech Connect

    D'Amico, Irene; Lovett, Brendon W.; Spiller, Timothy P.

    2007-09-15

    We show how to freeze distributed entanglement that has been created from the natural dynamics of spin chain systems. The technique that we propose simply requires single-qubit operations and isolates the entanglement in specific qubits at the ends of branches. Such frozen entanglement provides a useful resource, for example for teleportation or distributed quantum processing. The scheme can be applied to a wide range of systems--including actual spin systems and alternative qubit embodiments in strings of quantum dots, molecules, or atoms.

  10. Enumeration of Ring–Chain Tautomers Based on SMIRKS Rules

    PubMed Central

    2015-01-01

    A compound exhibits (prototropic) tautomerism if it can be represented by two or more structures that are related by a formal intramolecular movement of a hydrogen atom from one heavy atom position to another. When the movement of the proton is accompanied by the opening or closing of a ring it is called ring–chain tautomerism. This type of tautomerism is well observed in carbohydrates, but it also occurs in other molecules such as warfarin. In this work, we present an approach that allows for the generation of all ring–chain tautomers of a given chemical structure. Based on Baldwin’s Rules estimating the likelihood of ring closure reactions to occur, we have defined a set of transform rules covering the majority of ring–chain tautomerism cases. The rules automatically detect substructures in a given compound that can undergo a ring–chain tautomeric transformation. Each transformation is encoded in SMIRKS line notation. All work was implemented in the chemoinformatics toolkit CACTVS. We report on the application of our ring–chain tautomerism rules to a large database of commercially available screening samples in order to identify ring–chain tautomers. PMID:25158156

  11. Cross-contact chain

    NASA Technical Reports Server (NTRS)

    Lieneweg, Udo (Inventor)

    1988-01-01

    A system is provided for use with wafers that include multiple integrated circuits that include two conductive layers in contact at multiple interfaces. Contact chains are formed beside the integrated circuits, each contact chain formed of the same two layers as the circuits, in the form of conductive segments alternating between the upper and lower layers and with the ends of the segments connected in series through interfaces. A current source passes a current through the series-connected segments, by way of a pair of current tabs connected to opposite ends of the series of segments. While the current flows, voltage measurements are taken between each of a plurality of pairs of voltage tabs, the two tabs of each pair connected to opposite ends of an interface that lies along the series-connected segments. A plot of interface conductances on a normal probability chart, enables prediction of the yield of good integrated circuits from the wafer.

  12. Cross-contact chain

    NASA Technical Reports Server (NTRS)

    Lieneweg, U. (Inventor)

    1986-01-01

    A system is provided for use with wafers that include multiple integrated circuits that include two conductive layers in contact at multiple interfaces. Contact chains are formed beside the integrated circuits, each contact chain formed of the same two layers as the circuits, in the form of conductive segments alternating between the upper and lower layers and with the ends of the segments connected in series through interfaces. A current source passes a current through the series-connected segments, by way of a pair of current tabs connected to opposite ends of the series of segments. While the current flows, voltage measurements are taken between each of a plurality of pairs of voltage tabs, the two tabs of each pair connected to opposite ends of an interface that lies along the series-connected segments. A plot of interface conductances on normal probability chart enables prediction of the yield of good integrated circuits from the wafer.

  13. Streamlining the supply chain.

    PubMed

    Neumann, Lydon

    2003-07-01

    Effective management of the supply chain requires attention to: Product management--formulary development and maintenance, compliance, clinical involvement, standardization, and demand-matching. Sourcing and contracting--vendor consolidation, GPO portfolio management, price leveling, content management, and direct contracting Purchasing and payment-cycle--automatic placement, web enablement, centralization, evaluated receipts settlement, and invoice matching Inventory and distribution management--"unofficial" and "official" locations, vendor-managed inventory, automatic replenishment, and freight management. PMID:12866156

  14. Callisto Crater Chain Mosaic

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This mosaic of three images shows an area within the Valhalla region on Jupiter's moon, Callisto. North is to the top of the mosaic and the Sun illuminates the surface from the left. The smallest details that can be discerned in this picture are knobs and small impact craters about 160 meters (175 yards) across. The mosaic covers an area approximately 45 kilometers (28 miles) across. It shows part of a prominent crater chain located on the northern part of the Valhalla ring structure.

    Crater chains can form from the impact of material ejected from large impacts (forming secondary chains) or by the impact of a fragmented projectile, perhaps similar to the Shoemaker-Levy 9 cometary impacts into Jupiter in July 1994. It is believed this crater chain was formed by the impact of a fragmented projectile. The images which form this mosaic were obtained by the solid state imaging system aboard NASA's Galileo spacecraft on Nov. 4, 1996 (Universal Time).

    Launched in October 1989, Galileo entered orbit around Jupiter on December 7, 1995. The spacecraft's mission is to conduct detailed studies of the giant planet, its largest moons and the Jovian magnetic environment. The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

    This image and other images and data received from Galileo are posted on the World Wide Web Galileo mission home page at http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at http:// www.jpl.nasa.gov/galileo/sepo.

  15. The innovation value chain.

    PubMed

    Hansen, Morten T; Birkinshaw, Julian

    2007-06-01

    The challenges of coming up with fresh ideas and realizing profits from them are different for every company. One firm may excel at finding good ideas but may have weak systems for bringing them to market. Another organization may have a terrific process for funding and rolling out new products and services but a shortage of concepts to develop. In this article, Hansen and Birkinshaw caution executives against using the latest and greatest innovation approaches and tools without understanding the unique deficiencies in their companies' innovation systems. They offer a framework for evaluating innovation performance: the innovation value chain. It comprises the three main phases of innovation (idea generation, conversion, and diffusion) as well as the critical activities performed during those phases (looking for ideas inside your unit; looking for them in other units; looking for them externally; selecting ideas; funding them; and promoting and spreading ideas companywide). Using this framework, managers get an end-to-end view of their innovation efforts. They can pinpoint their weakest links and tailor innovation best practices appropriately to strengthen those links. Companies typically succumb to one of three broad "weakest-link" scenarios. They are idea poor, conversion poor, or diffusion poor. The article looks at the ways smart companies - including Intuit, P&G, Sara Lee, Shell, and Siemens- modify the best innovation practices and apply them to address those organizations' individual needs and flaws. The authors warn that adopting the chain-based view of innovation requires new measures of what can be delivered by each link in the chain. The approach also entails new roles for employees "external scouts" and "internal evangelists," for example. Indeed, in their search for new hires, companies should seek out those candidates who can help address particular weaknesses in the innovation value chain. PMID:17580654

  16. Visualizing Redox Dynamics of a Single Ag/AgCl Heterogeneous Nanocatalyst at Atomic Resolution.

    PubMed

    Wu, Yimin A; Li, Liang; Li, Zheng; Kinaci, Alper; Chan, Maria K Y; Sun, Yugang; Guest, Jeffrey R; McNulty, Ian; Rajh, Tijana; Liu, Yuzi

    2016-03-22

    Operando characterization of gas-solid reactions at the atomic scale is of great importance for determining the mechanism of catalysis. This is especially true in the study of heterostructures because of structural correlation between the different parts. However, such experiments are challenging and have rarely been accomplished. In this work, atomic scale redox dynamics of Ag/AgCl heterostructures have been studied using in situ environmental transmission electron microscopy (ETEM) in combination with density function theory (DFT) calculations. The reduction of Ag/AgCl to Ag is likely a result of the formation of Cl vacancies while Ag(+) ions accept electrons. The oxidation process of Ag/AgCl has been observed: rather than direct replacement of Cl by O, the Ag/AgCl nanocatalyst was first reduced to Ag, and then Ag was oxidized to different phases of silver oxide under different O2 partial pressures. Ag2O formed at low O2 partial pressure, whereas AgO formed at atmospheric pressure. By combining in situ ETEM observation and DFT calculations, this structural evolution is characterized in a distinct nanoscale environment. PMID:26937679

  17. Ultracold-Atom Accelerometers

    NASA Technical Reports Server (NTRS)

    Noever, David A.

    1995-01-01

    Proposed class of accelerometers and related motion sensors based on use of ultracold atoms as inertial components of motion transducers. Ultracold atoms supplant spring-and-mass components of older accelerometers. As used here, "ultracold atoms" means atoms with kinetic energies equivalent to temperatures equal to or less than 20 mK. Acclerometers essentially frictionless. Primary advantage high sensitivity.

  18. Neutral atom traps.

    SciTech Connect

    Pack, Michael Vern

    2008-12-01

    This report describes progress in designing a neutral atom trap capable of trapping sub millikelvin atom in a magnetic trap and shuttling the atoms across the atom chip from a collection area to an optical cavity. The numerical simulation and atom chip design are discussed. Also, discussed are preliminary calculations of quantum noise sources in Kerr nonlinear optics measurements based on electromagnetically induced transparency. These types of measurements may be important for quantum nondemolition measurements at the few photon limit.

  19. Requirements of supply chain management in differentiating European pork chains.

    PubMed

    Trienekens, Jacques; Wognum, Nel

    2013-11-01

    This paper summarizes results obtained by research into pork chain management in the EU Integrated Project Q-Porkchains. Changing demands for intrinsic and extrinsic quality attributes of pork products impact the way supply chain management should be organized from the farmer down to the consumer. The paper shows the importance of Quality Management Systems for integrating supply chains and enhancing consumer confidence. The paper also presents innovations in information system integration for aligning information exchange in the supply chain and logistics concepts based on innovative measurement technologies at the slaughterhouse stage. In the final section research challenges towards sustainable pork supply chains satisfying current consumer demands are presented. PMID:23611335

  20. Confined linear carbon chains as a route to bulk carbyne

    NASA Astrophysics Data System (ADS)

    Shi, Lei; Rohringer, Philip; Suenaga, Kazu; Niimi, Yoshiko; Kotakoski, Jani; Meyer, Jannik C.; Peterlik, Herwig; Wanko, Marius; Cahangirov, Seymur; Rubio, Angel; Lapin, Zachary J.; Novotny, Lukas; Ayala, Paola; Pichler, Thomas

    2016-06-01

    Strong chemical activity and extreme instability in ambient conditions characterize carbyne, an infinite sp1 hybridized carbon chain. As a result, much less has been explored about carbyne as compared to other carbon allotropes such as fullerenes, nanotubes and graphene. Although end-capping groups can be used to stabilize carbon chains, length limitations are still a barrier for production, and even more so for application. We report a method for the bulk production of long acetylenic linear carbon chains protected by thin double-walled carbon nanotubes. The synthesis of very long arrangements is confirmed by a combination of transmission electron microscopy, X-ray diffraction and (near-field) resonance Raman spectroscopy. Our results establish a route for the bulk production of exceptionally long and stable chains composed of more than 6,000 carbon atoms, representing an elegant forerunner towards the final goal of carbyne’s bulk production.

  1. Smallest Nanoelectronic with Atomic Devices with Precise Structures

    NASA Technical Reports Server (NTRS)

    Yamada, Toshishige

    2000-01-01

    Since its invention in 1948, the transistor has revolutionized our everyday life - transistor radios and TV's appeared in the early 1960s, personal computers came into widespread use in the mid-1980s, and cellular phones, laptops, and palm-sized organizers dominated the 1990s. The electronics revolution is based upon transistor miniaturization; smaller transistors are faster, and denser circuitry has more functionality. Transistors in current generation chips are 0.25 micron or 250 nanometers in size, and the electronics industry has completed development of 0.18 micron transistors which will enter production within the next few years. Industry researchers are now working to reduce transistor size down to 0.13 micron - a thousandth of the width of a human hair. However, studies indicate that the miniaturization of silicon transistors will soon reach its limit. For further progress in microelectronics, scientists have turned to nanotechnology to advance the science. Rather than continuing to miniaturize transistors to a point where they become unreliable, nanotechnology offers the new approach of building devices on the atomic scale [see sidebar]. One vision for the next generation of miniature electronics is atomic chain electronics, where devices are composed of atoms aligned on top of a substrate surface in a regular pattern. The Atomic Chain Electronics Project (ACEP) - part of the Semiconductor Device Modeling and Nanotechnology group, Integrated Product Team at the NAS Facility has been developing the theory of understanding atomic chain devices, and the author's patent for atomic chain electronics is now pending.

  2. Syntheses of protoporphyrin-IX derivatives bearing extended propionate side-chains.

    PubMed

    Holmes, Robert T; Lu, Jianming; Mwakwari, Celinah; Smith, Kevin M

    2009-05-29

    In order to investigate the relationship between depth within membranes of singlet oxygen generation and effectiveness of photodynamic therapy of tumors, analogs of protoporphyrin-IX 1 bearing five 4 and seven 5 carbon atoms (in place of the 3-carbon atom chain in 1) were synthesized from monopyrrole precursors. PMID:20161404

  3. Theory of Topological Superconductivity in Ferromagnetic Metal Chains on Superconducting Substrates

    NASA Astrophysics Data System (ADS)

    Chen, Hua

    2015-03-01

    Recent experiments have provided evidence that one-dimensional (1D) topological superconductivity based on transition metal atom chains formed on a superconducting substrate can be realized experimentally when the chain behaves like a ferromagnetic macrospin. In this talk I will address the structural and bonding considerations which determine whether or not a particular atom chain will have magnetic and electronic properties favorable for topological superconductivity. By using a Slater-Koster tight-binding model to account for important features of transition metal electronic structure, I conclude that topological states are common for ferromagnetic chains on superconductors and that they are nearly universal when ferromagnetic transition metal chains form straight lines on superconducting substrates. The proximity induced superconducting gap on the chain is ~ ΔEso / J where Δ is the s-wave pair-potential on the chain, Eso is the spin-orbit splitting energy induced in the normal chain state bands by hybridization with the superconducting substrate, and J is the exchange-splitting of the ferromagnetic chain d-bands. Because of the topological character of the 1D superconducting state, Majorana end modes appear within the gaps of finite length chains. I will specifically discuss the spatial decay length of the Majorana end modes which can be much shorter than the coherence length from the induced p-wave gap on the chain due to its strong coupling to the three-dimensional superconducting substrate, in agreement with experimental results. Pb is a particularly favorable substrate material for ferromagnetic chain topological superconductivity because it provides both strong s - wave pairing and strong Rashba spin-orbit coupling, but there seems to be considerable scope to optimize the 1D topological superconductivity by varying the atomic composition and structure of the chain. The authors acknowledge support from the Office of Naval Research under Grant ONR-N00014-14-1-0330.

  4. Radiology's value chain.

    PubMed

    Enzmann, Dieter R

    2012-04-01

    A diagnostic radiology value chain is constructed to define its main components, all of which are vulnerable to change, because digitization has caused disaggregation of the chain. Some components afford opportunities to improve productivity, some add value, while some face outsourcing to lower labor cost and to information technology substitutes, raising commoditization risks. Digital image information, because it can be competitive at smaller economies of scale, allows faster, differential rates of technological innovation of components, initiating a centralization-to-decentralization technology trend. Digitization, having triggered disaggregation of radiology's professional service model, may soon usher in an information business model. This means moving from a mind-set of "reading images" to an orientation of creating and organizing information for greater accuracy, faster speed, and lower cost in medical decision making. Information businesses view value chain investments differently than do small professional services. In the former model, producing a better business product will extend image interpretation beyond a radiologist's personal fund of knowledge to encompass expanding external imaging databases. A follow-on expansion with integration of image and molecular information into a report will offer new value in medical decision making. Improved interpretation plus new integration will enrich and diversify radiology's key service products, the report and consultation. A more robust, information-rich report derived from a "systems" and "computational" radiology approach will be facilitated by a transition from a professional service to an information business. Under health care reform, radiology will transition its emphasis from volume to greater value. Radiology's future brightens with the adoption of a philosophy of offering information rather than "reads" for decision making. Staunchly defending the status quo via turf wars is unlikely to constitute a

  5. Musical Markov Chains

    NASA Astrophysics Data System (ADS)

    Volchenkov, Dima; Dawin, Jean René

    A system for using dice to compose music randomly is known as the musical dice game. The discrete time MIDI models of 804 pieces of classical music written by 29 composers have been encoded into the transition matrices and studied by Markov chains. Contrary to human languages, entropy dominates over redundancy, in the musical dice games based on the compositions of classical music. The maximum complexity is achieved on the blocks consisting of just a few notes (8 notes, for the musical dice games generated over Bach's compositions). First passage times to notes can be used to resolve tonality and feature a composer.

  6. Monte Carlo without chains

    SciTech Connect

    Chorin, Alexandre J.

    2007-12-12

    A sampling method for spin systems is presented. The spin lattice is written as the union of a nested sequence of sublattices, all but the last with conditionally independent spins, which are sampled in succession using their marginals. The marginals are computed concurrently by a fast algorithm; errors in the evaluation of the marginals are offset by weights. There are no Markov chains and each sample is independent of the previous ones; the cost of a sample is proportional to the number of spins (but the number of samples needed for good statistics may grow with array size). The examples include the Edwards-Anderson spin glass in three dimensions.

  7. Atomic Fuel, Understanding the Atom Series. Revised.

    ERIC Educational Resources Information Center

    Hogerton, John F.

    This publication is part of the "Understanding the Atom" series. Complete sets of the series are available free to teachers, schools, and public librarians who can make them available for reference or use by groups. Among the topics discussed are: What Atomic Fuel Is; The Odyssey of Uranium; Production of Uranium; Fabrication of Reactor Fuel…

  8. Atomic Fisher information versus atomic number

    NASA Astrophysics Data System (ADS)

    Nagy, Á.; Sen, K. D.

    2006-12-01

    It is shown that the Thomas Fermi Fisher information is negative. A slightly more sophisticated model proposed by Gáspár provides a qualitatively correct expression for the Fisher information: Gáspár's Fisher information is proportional to the two-third power of the atomic number. Accurate numerical calculations show an almost linear dependence on the atomic number.

  9. Atomic Particle Detection, Understanding the Atom Series.

    ERIC Educational Resources Information Center

    Hellman, Hal

    This booklet is one of the booklets in the "Understanding the Atom Series" published by the U. S. Atomic Energy Commission for high school science teachers and their students. The instruments used to detect both particles and electromagnetic radiation that emerge from the nucleus are described. The counters reviewed include ionization chambers,…

  10. Extremely long-lived magnetic excitations in supported Fe chains

    NASA Astrophysics Data System (ADS)

    Gauyacq, J. P.; Lorente, N.

    2016-07-01

    We report on a theoretical study of the lifetime of the first excited state of spin chains made of an odd number of Fe atoms on C u2N /Cu (100 ) . Yan, Choi, Burgess, Rolf-Pissarczyk, and Loth [Nat. Nanotech. 10, 40 (2015), 10.1038/nnano.2014.281] recently observed very long lifetimes in the case of F e3 chains. We consider the decay of the first excited state induced by electron-hole pair creation in the substrate. For a finite magnetic field, the two lowest-lying states in the chain have a quasi-Néel state structure. Decay from one state to the other strongly depends on the degree of entanglement of the local spins in the chain. The weak entanglement in the chain accounts for the long lifetimes that increase exponentially with chain length. Despite their apparently very different properties, the behavior of odd and even chains is governed by the same kind of phenomena, in particular entanglement effects. The present results account quite well for the lifetimes recently measured by Yan et al. on F e3 .

  11. Nanoscience of single polymer chains revealed by nanofishing.

    PubMed

    Nakajima, Ken; Nishi, Toshio

    2006-01-01

    The invention of atomic force microscopy (AFM) enabled us to study the statistical properties of single polymer chains by a method called "nanofishing," which stretches a single polymer chain adsorbed on a substrate with its one end by picking it at the other end. A force-extension curve obtained for a single polystyrene chain in a Theta solvent (cyclohexane) shows good agreement with a worm-like chain model and, therefore, gives microscopic information about entropic elasticity. Furthermore, the nanofishing technique can be used for dynamic viscoelastic measurement of single polymer chains. An AFM cantilever is mechanically oscillated at its resonant frequency during the stretching process. This technique enables the estimation of quantitative and simultaneous elongation-dependent changes of stiffness and viscosity of a single chain with the use of a phenomenological model. In this study, the effect of solvent on viscosity in low extension regions reveals that the viscosity is attributed to monomer-solvent friction. Thus, static and dynamic nanofishing techniques are shown to give powerful experimental proofs for several basic questions in polymer physics. The techniques are expected to reveal hidden properties of polymer chains or polymer solutions by any types of macroscopic measurements in the future. PMID:17099889

  12. Imaging of spin waves in atomically designed nanomagnets

    NASA Astrophysics Data System (ADS)

    Spinelli, Anna; Bryant, Benjamin; Delgado, Fernando; Fernández-Rossier, Joaquín; Otte, Alexander F.

    2015-03-01

    Exploring the transition from individual quantum spins to classical magnetism is crucial for the development of nanoscale magnetic memory storage solutions. Our aim is to search for signs of collective spin behavior in magnetic lattices built on a surface. Using the tip of a low temperature scanning tunneling microscope (STM), we position Fe atoms on a Cu2N/Cu(100) network with atomic precision, to build ferromagnetically coupled spin chains up to 6 atoms that exhibit bistable behavior. Using a combination of inelastic electron tunnelling spectroscopy and spin polarized STM, we are able to probe the spin dynamics during the magnetization reversal of the whole chain, after a local excitation. Our experiments allow us to observe the nodal structure of the standing spin waves confined inside the chain, and, through combination with theoretical calculations, we can understand their role in making the system switch from one metastable magnetic state to the other.

  13. [Trophic chains in soil].

    PubMed

    2013-01-01

    Trophic links of soil animals are extensively diverse but also flexible. Moreover, feeding activity of large soil saprotrophs often cascades into a range of ecosystem-level consequences via the ecological engineering. Better knowledge on the main sources of energy utilized by soil animals is needed for understanding functional structure of soil animal communities and their participation in the global carbon cycling. Using published and original data, we consider the relative importance of dead organic matter and saprotrophic microorganisms as a basal energy source in the detritus-based food chains, the feeding of endogeic macrofauna on the stabilized soil organic matter, and the role of recent photosynthate in the energy budget of soil communities. Soil food webs are spatially and functionally compartmentalized, though the separation of food chains into bacteria- and fungi-based channels seems to be an over-simplification. The regulation of the litter decomposition rates via top-down trophic interactions across more than one trophic level is only partly supported by experimental data, but mobile litter-dwelling predators play a crucial role in integrating local food webs within and across neighboring ecosystems. PMID:25508107

  14. [Trophic chains in soil].

    PubMed

    Goncharov, A A; Tiunov, A V

    2013-01-01

    Trophic links of soil animals are extensively diverse but also flexible. Moreover, feeding activity of large soil saprotrophs often cascades into a range of ecosystem-level consequences via the ecological engineering. Better knowledge on the main sources of energy utilized by soil animals is needed for understanding functional structure of soil animal communities and their participation in the global carbon cycling. Using published and original data, we consider the relative importance of dead organic matter and saprotrophic microorganisms as a basal energy source in the detritus-based food chains, the feeding of endogeic macrofauna on the stabilized soil organic matter, and the role of recent photosynthate in the energy budget of soil communities. Soil food webs are spatially and functionally compartmentalized, though the separation of food chains into bacteria- and fungi-based channels seems to be an over-simplification. The regulation of the litter decomposition rates via top-down trophic interactions across more than one trophic level is only partly supported by experimental data, but mobile litter-dwelling predators play a crucial role in integrating local food webs within and across neighboring ecosystems. PMID:25438576

  15. Titanium-capped carbon chains as promising new hydrogen storage media

    NASA Astrophysics Data System (ADS)

    Liu, Chun-Sheng; An, Hui; Zeng, Zhi

    The capacity of Ti-capped sp carbon atomic chains for use as hydrogen storage media is studied using first-principles density functional theory. The Ti atom is strongly attached at one end of the carbon chains via d-p hybridization, forming stable TiCn complexes. We demonstrate that the number of adsorbed H2 on Ti through Kubas interaction depends upon the chain types. For polyyne (n even) or cumulene (n odd) structures, each Ti atom can hold up to five or six H2 molecules, respectively. Furthermore, the TiC5 chain effectively terminated on a C20 fullerene can store hydrogen with optimal binding of 0.52 eV/H2. Our results reveal a possible way to explore high-capacity hydrogen storage materials in truly one-dimensional carbon structures.

  16. Titanium-capped carbon chains as promising new hydrogen storage media.

    PubMed

    Liu, Chun-Sheng; An, Hui; Zeng, Zhi

    2011-02-14

    The capacity of Ti-capped sp carbon atomic chains for use as hydrogen storage media is studied using first-principles density functional theory. The Ti atom is strongly attached at one end of the carbon chains via d-p hybridization, forming stable TiC(n) complexes. We demonstrate that the number of adsorbed H(2) molecules on Ti through Kubas interactions depends upon the chain types. For polyyne (n even) or cumulene (n odd) structures, each Ti atom can hold up to five or six H(2) molecules, respectively. Furthermore, the TiC(5) chain effectively terminated on a C(20) fullerene can store hydrogen with an optimal binding energy of 0.52 eV per H(2) molecule. Our results reveal a possible way to explore high-capacity hydrogen storage materials in truly one-dimensional carbon structures. PMID:21135955

  17. Transport properties for carbon chain sandwiched between heteroatom-doped carbon nanotubes with different doping sites

    NASA Astrophysics Data System (ADS)

    Liu, Wenjiang; Deng, Xiaoqing; Cai, Shaohong

    2016-07-01

    The First-principles calculation is used to investigate the transport properties of a carbon chain connected with N-and/or B-doped caped carbon nanotube acting as electrodes. The I-V curves of the carbon chain are affected by the N/B doping sites, and rectifying behavior can be obtained distinctly when the carbon chain is just connected onto two doping atom sites (N- chain-B), and a weak rectification occurs when N (B) doping at other sites. Interestingly, the spin-filtering effects exist in the junction when it is doped at other sites, undoped system, or N-terminal carbon chains. However, no this behavior is found in N-chain-B and B-chain-B systems. The analysis on the transmission spectra, PDOS, LDOS, spin density, and the electron transmission pathways give an insight into the observed results for the system.

  18. Dual chain synthetic heparin-binding growth factor analogs

    DOEpatents

    Zamora, Paul O.; Pena, Louis A.; Lin, Xinhua

    2012-04-24

    The invention provides synthetic heparin-binding growth factor analogs having two peptide chains each branched from a branch moiety, such as trifunctional amino acid residues, the branch moieties separated by a first linker of from 3 to about 20 backbone atoms, which peptide chains bind a heparin-binding growth factor receptor and are covalently bound to a non-signaling peptide that includes a heparin-binding domain, preferably by a second linker, which may be a hydrophobic second linker. The synthetic heparin-binding growth factor analogs are useful as pharmaceutical agents, soluble biologics or as surface coatings for medical devices.

  19. Dual chain synthetic heparin-binding growth factor analogs

    DOEpatents

    Zamora, Paul O.; Pena, Louis A.; Lin, Xinhua

    2009-10-06

    The invention provides synthetic heparin-binding growth factor analogs having two peptide chains each branched from a branch moiety, such as trifunctional amino acid residues, the branch moieties separated by a first linker of from 3 to about 20 backbone atoms, which peptide chains bind a heparin-binding growth factor receptor and are covalently bound to a non-signaling peptide that includes a heparin-binding domain, preferably by a second linker, which may be a hydrophobic second linker. The synthetic heparin-binding growth factor analogs are useful as pharmaceutical agents, soluble biologics or as surface coatings for medical devices.

  20. Robustness of discrete semifluxons in closed Bose–Hubbard chains

    NASA Astrophysics Data System (ADS)

    Gallemí, A.; Guilleumas, M.; Martorell, J.; Mayol, R.; Polls, A.; Juliá-Díaz, B.

    2016-07-01

    We present the properties of the ground state and low-energy excitations of Bose–Hubbard chains with a geometry that varies from open to closed and with a tunable twisted link. In the vicinity of the symmetric π-flux case the system behaves as an interacting gas of discrete semifluxons for finite chains and interactions in the Josephson regime. The energy spectrum of the system is studied by direct diagonalization and by solving the corresponding Bogoliubov–de Gennes equations. The atom–atom interactions are found to enhance the presence of strongly correlated macroscopic superpositions of semifluxons.

  1. Presenting the Bohr Atom.

    ERIC Educational Resources Information Center

    Haendler, Blanca L.

    1982-01-01

    Discusses the importance of teaching the Bohr atom at both freshman and advanced levels. Focuses on the development of Bohr's ideas, derivation of the energies of the stationary states, and the Bohr atom in the chemistry curriculum. (SK)

  2. The atomic strain tensor

    SciTech Connect

    Mott, P.H.; Argon, A.S. ); Suter, U.W. Massachusetts Institute of Technology, Cambridge, MA )

    1992-07-01

    A definition of the local atomic strain increments in three dimensions and an algorithm for computing them is presented. An arbitrary arrangement of atoms is tessellated in to Delaunay tetrahedra, identifying interstices, and Voronoi polyhedra, identifying atomic domains. The deformation gradient increment tensor for interstitial space is obtained from the displacement increments of the corner atoms of Delaunay tetrahedra. The atomic site strain increment tensor is then obtained by finding the intersection of the Delaunay tetrahedra with the Voronoi polyhedra, accumulating the individual deformation gradient contributions of the intersected Delaunay tetrahedra into the Voronoi polyhedra. An example application is discussed, showing how the atomic strain clarifies the relative local atomic movement for a polymeric glass treated at the atomic level. 6 refs. 10 figs.

  3. Myosin light-chain phosphatase.

    PubMed Central

    Morgan, M; Perry, S V; Ottaway, J

    1976-01-01

    1. A method for the isolation of a new enzyme, myosin light-chain phosphatase, from rabbit white skeletal muscle by using a Sepharose-phosphorylated myosin light-chain affinity column is described. 2. The enzyme migrated as a single component on electrophoresis in sodium dodecyl sulphate/polyacrylamide gel at pH7.0, with apparent mol.wt. 70000. 3. The enzyme was highly specific for the phosphorylated P-light chain of myosin, had pH optima at 6.5 and 8.0 and was not inhibited by NaF. 4. A Ca2+-sensitive 'ATPase' (adenosine triphosphatase) system consisting of myosin light-chain kinase, myosin light-chain phosphatase and the P-light chain is described. 5. Evidence is presented for a phosphoryl exchange between Pi, phosphorylated P-light chain and myosin light-chain phosphatase. 6. Heavy meromyosin prepared by chymotryptic digestion can be phosphorylated by myosin light-chain kinase. 7. The ATPase activities of myosin and heavy meromyosin, in the presence and absence of F-actin, were not significantly changed (+/- 10%) by phosphorylation of the P-light chain. Images PLATE 1 PMID:186030

  4. Potential enhancement of antibacterial activity of graphene oxide-silver nanocomposite by introducing C2 carbon chain linkage

    NASA Astrophysics Data System (ADS)

    Yun, Hyosuk; Ahmed, Mohammad Shamsuddin; Lee, Kyungmi; Jeon, Seungwon; Lee, Chul Won

    2016-01-01

    Various carbon chain linkages were introduced during the process of synthesizing silver-nanoparticles (AgNPs)-decorated graphene nanocomposites [referred to as GO-Cx-Ag where, HS-(CH2)x-SH = Cx and x = 0, 2, or 4] to evaluate antibacterial properties. The nano-structures of GO-Cx-Ag were characterized using TEM and XPS, revealing that GO-C2-Ag comprises well-dispersed and smaller AgNPs anchored onto the surface of graphene sheets than the GO-C0-Ag and GO-C4-Ag. The antibacterial activities of those nanocomposites were assessed using paper-disk diffusion and minimal inhibitory concentration (MIC) methods against Gram-negative and Gram-positive bacteria. The results showed that carbon chain linkers enhanced the antibacterial activity against Gram-negative Salmonella typhimurium and Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus. In particular, GO-C2-Ag showed higher antibacterial activity than GO-C0-Ag and GO-C4-Ag due to nearly eight times higher reactive oxygen species (ROS) formation which determined by fluorescence-based ROS detection experiment. Also, LC-inductively coupled plasma mass spectrometer (LC-ICP-MS) demonstrated that the Ag release from GO-Cx-Ag was insignificant (0.03%). However, the higher ROS formation from GO-C2-Ag was facilitated by higher dispersion, smaller size, and well attachment of AgNPs with AgO species onto graphene sheets. These results suggest that the medium length carbon chain linkers in between Ag and GO can be utilized to improve antibacterial activity.

  5. Atoms in Action

    SciTech Connect

    2009-01-01

    This movie produced with Berkeley Lab's TEAM 0.5 microscope shows the growth of a hole and the atomic edge reconstruction in a graphene sheet. An electron beam focused to a spot on the sheet blows out the exposed carbon atoms to make the hole. The carbon atoms then reposition themselves to find a stable configuration. http://newscenter.lbl.gov/press-releases/2009/03/26/atoms-in-action/

  6. Atomizing nozzle and process

    DOEpatents

    Anderson, Iver E.; Figliola, Richard S.; Molnar, Holly M.

    1993-07-20

    High pressure atomizing nozzle includes a high pressure gas manifold having a divergent expansion chamber between a gas inlet and arcuate manifold segment to minimize standing shock wave patterns in the manifold and thereby improve filling of the manifold with high pressure gas for improved melt atomization. The atomizing nozzle is especially useful in atomizing rare earth-transition metal alloys to form fine powder particles wherein a majority of the powder particles exhibit particle sizes having near-optimum magnetic properties.

  7. Atomizing nozzle and process

    DOEpatents

    Anderson, Iver E.; Figliola, Richard S.; Molnar, Holly M.

    1992-06-30

    High pressure atomizing nozzle includes a high pressure gas manifold having a divergent expansion chamber between a gas inlet and arcuate manifold segment to minimize standing shock wave patterns in the manifold and thereby improve filling of the manifold with high pressure gas for improved melt atomization. The atomizing nozzle is especially useful in atomizing rare earth-transition metal alloys to form fine powder particles wherein a majority of the powder particles exhibit particle sizes having near-optimum magnetic properties.

  8. Adaptive atom-optics in atom interferometry

    NASA Astrophysics Data System (ADS)

    Marable, M. L.; Savard, T. A.; Thomas, J. E.

    1997-02-01

    We suggest a general technique for creating virtual atom-optical elements which are adaptive. The shape and position of these elements is determined by the frequency distribution for optical fields which induce transitions in a high gradient potential. This adaptive method is demonstrated in an all-optical atom interferometer, by creating either a variable optical slit or a variable optical grating which is scanned across the atomic spatial patterns to measure the fringes. This method renders mechanical motion of the interferometer elements unnecessary.

  9. NNSA TRITIUM SUPPLY CHAIN

    SciTech Connect

    Wyrick, Steven; Cordaro, Joseph; Founds, Nanette; Chambellan, Curtis

    2013-08-21

    Savannah River Site plays a critical role in the Tritium Production Supply Chain for the National Nuclear Security Administration (NNSA). The entire process includes: • Production of Tritium Producing Burnable Absorber Rods (TPBARs) at the Westinghouse WesDyne Nuclear Fuels Plant in Columbia, South Carolina • Production of unobligated Low Enriched Uranium (LEU) at the United States Enrichment Corporation (USEC) in Portsmouth, Ohio • Irradiation of TPBARs with the LEU at the Tennessee Valley Authority (TVA) Watts Bar Reactor • Extraction of tritium from the irradiated TPBARs at the Tritium Extraction Facility (TEF) at Savannah River Site • Processing the tritium at the Savannah River Site, which includes removal of nonhydrogen species and separation of the hydrogen isotopes of protium, deuterium and tritium.

  10. The glassy wormlike chain

    NASA Astrophysics Data System (ADS)

    Kroy, Klaus; Glaser, Jens

    2007-11-01

    We introduce a new model for the dynamics of a wormlike chain (WLC) in an environment that gives rise to a rough free energy landscape, which we name the glassy WLC. It is obtained from the common WLC by an exponential stretching of the relaxation spectrum of its long-wavelength eigenmodes, controlled by a single parameter \\boldsymbol{\\cal E} . Predictions for pertinent observables such as the dynamic structure factor and the microrheological susceptibility exhibit the characteristics of soft glassy rheology and compare favourably with experimental data for reconstituted cytoskeletal networks and live cells. We speculate about the possible microscopic origin of the stretching, implications for the nonlinear rheology, and the potential physiological significance of our results.

  11. Polymerase chain displacement reaction.

    PubMed

    Harris, Claire L; Sanchez-Vargas, Irma J; Olson, Ken E; Alphey, Luke; Fu, Guoliang

    2013-02-01

    Quantitative PCR assays are now the standard method for viral diagnostics. These assays must be specific, as well as sensitive, to detect the potentially low starting copy number of viral genomic material. We describe a new technique, polymerase chain displacement reaction (PCDR), which uses multiple nested primers in a rapid, capped, one-tube reaction that increases the sensitivity of normal quantitative PCR (qPCR) assays. Sensitivity was increased by approximately 10-fold in a proof-of-principle test on dengue virus sequence. In PCDR, when extension occurs from the outer primer, it displaces the extension strand produced from the inner primer by utilizing a polymerase that has strand displacement activity. This allows a greater than 2-fold increase of amplification product for each amplification cycle and therefore increased sensitivity and speed over conventional PCR. Increased sensitivity in PCDR would be useful in nucleic acid detection for viral diagnostics. PMID:23384180

  12. Atomic Spectra Database (ASD)

    National Institute of Standards and Technology Data Gateway

    SRD 78 NIST Atomic Spectra Database (ASD) (Web, free access)   This database provides access and search capability for NIST critically evaluated data on atomic energy levels, wavelengths, and transition probabilities that are reasonably up-to-date. The NIST Atomic Spectroscopy Data Center has carried out these critical compilations.

  13. Images of Atoms.

    ERIC Educational Resources Information Center

    Wright, Tony

    2003-01-01

    Recommends using a simple image, such as the fuzzy atom ball to help students develop a useful understanding of the molecular world. Explains that the image helps students easily grasp ideas about atoms and molecules and leads naturally to more advanced ideas of atomic structure, chemical bonding, and quantum physics. (Author/NB)

  14. The Nature of Atoms.

    ERIC Educational Resources Information Center

    Holden, Alan

    This monograph was written for the purpose of presenting physics to college students who are not preparing for careers in physics. It deals with the nature of atoms, and treats the following topics: (1) the atomic hypothesis, (2) the chemical elements, (3) models of an atom, (4) a particle in a one-dimensional well, (5) a particle in a central…

  15. Protein-ligand docking with multiple flexible side chains.

    PubMed

    Zhao, Yong; Sanner, Michel F

    2008-09-01

    In this work, we validate and analyze the results of previously published cross docking experiments and classify failed dockings based on the conformational changes observed in the receptors. We show that a majority of failed experiments (i.e. 25 out of 33, involving four different receptors: cAPK, CDK2, Ricin and HIVp) are due to conformational changes in side chains near the active site. For these cases, we identify the side chains to be made flexible during docking calculation by superimposing receptors and analyzing steric overlap between various ligands and receptor side chains. We demonstrate that allowing these side chains to assume rotameric conformations enables the successful cross docking of 19 complexes (ligand all atom RMSD < 2.0 A) using our docking software FLIPDock. The number of side receptor side chains interacting with a ligand can vary according to the ligand's size and shape. Hence, when starting from a complex with a particular ligand one might have to extend the region of potential interacting side chains beyond the ones interacting with the known ligand. We discuss distance-based methods for selecting additional side chains in the neighborhood of the known active site. We show that while using the molecular surface to grow the neighborhood is more efficient than Euclidian-distance selection, the number of side chains selected by these methods often remains too large and additional methods for reducing their count are needed. Despite these difficulties, using geometric constraints obtained from the network of bonded and non-bonded interactions to rank residues and allowing the top ranked side chains to be flexible during docking makes 22 out of 25 complexes successful. PMID:18034309

  16. Platinum atomic wire encapsulated in gold nanotubes: A first principle study

    SciTech Connect

    Nigam, Sandeep Majumder, Chiranjib; Sahoo, Suman K.; Sarkar, Pranab

    2014-04-24

    The nanotubes of gold incorporated with platinum atomic wire have been investigated by means of firstprinciples density functional theory with plane wave pseudopotential approximation. The structure with zig-zag chain of Pt atoms in side gold is found to be 0.73 eV lower in energy in comparison to straight chain of platinum atoms. The Fermi level of the composite tube was consisting of d-orbitals of Pt atoms. Further interaction of oxygen with these tubes reveals that while tube with zig-zag Pt prefers dissociative adsorption of oxygen molecule, the gold tube with linear Pt wire favors molecular adsorption.

  17. Platinum atomic wire encapsulated in gold nanotubes: A first principle study

    NASA Astrophysics Data System (ADS)

    Nigam, Sandeep; Sahoo, Suman K.; Sarkar, Pranab; Majumder, Chiranjib

    2014-04-01

    The nanotubes of gold incorporated with platinum atomic wire have been investigated by means of firstprinciples density functional theory with plane wave pseudopotential approximation. The structure with zig-zag chain of Pt atoms in side gold is found to be 0.73 eV lower in energy in comparison to straight chain of platinum atoms. The Fermi level of the composite tube was consisting of d-orbitals of Pt atoms. Further interaction of oxygen with these tubes reveals that while tube with zig-zag Pt prefers dissociative adsorption of oxygen molecule, the gold tube with linear Pt wire favors molecular adsorption.

  18. 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.

  19. Chains, bombs, potrzebies and slugs

    NASA Astrophysics Data System (ADS)

    Jewess, Mike; McDowell, Alex; Maxfield, Stephen; Hunt, A. G.; Hicks, Bruce

    2010-03-01

    I read with pleasure Robert Crease's article on unusual units (February pp17-19). However, the article stated that an acre is 10×10 chains, when it is in fact 10×1 chains. Incidentally, a distance of 10 chains (220 yards) is known as a furlong, a word that suggests the length of a ploughed furrow and that is still used in horse-racing.

  20. Single atom electrochemical and atomic analytics

    NASA Astrophysics Data System (ADS)

    Vasudevan, Rama

    In the past decade, advances in electron and scanning-probe based microscopies have led to a wealth of imaging and spectroscopic data with atomic resolution, yielding substantial insight into local physics and chemistry in a diverse range of systems such as oxide catalysts, multiferroics, manganites, and 2D materials. However, typical analysis of atomically resolved images is limited, despite the fact that image intensities and distortions of the atoms from their idealized positions contain unique information on the physical and chemical properties inherent to the system. Here, we present approaches to data mine atomically resolved images in oxides, specifically in the hole-doped manganite La5/8Ca3/8MnO3, on epitaxial films studied by in-situ scanning tunnelling microscopy (STM). Through application of bias to the STM tip, atomic-scale electrochemistry is demonstrated on the manganite surface. STM images are then further analyzed through a suite of algorithms including 2D autocorrelations, sliding window Fourier transforms, and others, and can be combined with basic thermodynamic modelling to reveal relevant physical and chemical descriptors including segregation energies, existence and strength of atomic-scale diffusion barriers, surface energies and sub-surface chemical species identification. These approaches promise to provide tremendous insights from atomically resolved functional imaging, can provide relevant thermodynamic parameters, and auger well for use with first-principles calculations to yield quantitative atomic-level chemical identification and structure-property relations. This research was sponsored by the Division of Materials Sciences and Engineering, BES, DOE. Research was conducted at the Center for Nanophase Materials Sciences, which also provided support and is a DOE Office of Science User Facility.

  1. Supply Chain Coordination in Hospitals

    NASA Astrophysics Data System (ADS)

    Rego, Nazaré; de Sousa, Jorge Pinho

    This paper presents an innovative approach to support the definition of strategies for the design of alternative configurations of hospital supply chains. This approach was developed around a hybrid Tabu Search / Variable Neighbourhood Search metaheuristic, that uses several neighbourhood structures. The flexibility of the procedure allows its application to supply chains with different topologies and atypical cost characteristics. A preliminary computational experience shows the approach potential in solving large scale supply chain configuration problems. The future incorporation of this approach in a broader Decision Support System (DSS) will provide a tool that can significantly contribute to an increase of healthcare supply chains efficiency and encourage the establishment of collaborative partnerships between their members.

  2. Dynamical Aspects of Inextensible Chains

    NASA Astrophysics Data System (ADS)

    Ferrari, Franco; Pyrka, Maciej

    In the present work, a method to impose the inextensibility constraints on the dynamics of a chain fluctuating in a thermal bath at fixed temperature is investigated. The final goal is to construct the probability function of the chain and the generating functional of the correlation functions of the relevant degrees of freedom of the system. First, we study the dynamics of a freely hinged chain composed by massive beads connected together by massless segments of fixed length. It is shown that a system of this kind may be described by a set of Langevin equations in which the noise is characterized by a non-gaussian probability distribution. Starting from these Langevin equations, the generating functional of the freely hinged chain is derived in path integral form. A connection with a stochastic process governed by a Fokker-Planck equation is established. Next, a chain composed by one-dimensional bars with constant mass distribution is considered. A path integral expression of the generating functional for a chain of this type is derived. Finally, it is verified that in the limit in which the chain becomes continuous, both generating functionals of the freely hinged chain and of the freely jointed bar chain converge to the same result as expected.

  3. Human laminin B2 chain

    SciTech Connect

    Pikkarainen, T.; Kallunki, T.; Tryggvason, K.

    1988-05-15

    The complete amino acid sequence of the human laminin B2 chains has been determined by sequencing of cDNA clones. The six overlapping clones studied cover approximately 7.5 kilobases of which 5312 nucleotides were sequenced from the 5' end. The open reading frame codes for a 33-residue signal peptide and a 1576-residue B2 chain proper, which is 189 residues less than in the highly homologous B1 chain. Computer analysis revealed that the B2 chain consists of distinct domains that contain helical structures, cysteine-rich repeats, and globular regions, as does the B1 chain. However, domain ..cap alpha.. and domain ..beta.. of the B1 chain have no counterpart in B2, and the number of cysteine-rich repeats is 12, or 1 less than in the B1 chain. The degree of homology between the two chains is highest in the cysteine repeat-containing domains III and V where 40% of the residues match. However, in helical domains I/II only 16% of residues match. The results demonstrate that the B1 and B2 chains of laminin are highly homologous proteins that are probably the products of related genes.

  4. Multilevel Atomic Coherent States and Atomic Holomorphic Representation

    NASA Technical Reports Server (NTRS)

    Cao, Chang-Qi; Haake, Fritz

    1996-01-01

    The notion of atomic coherent states is extended to the case of multilevel atom collective. Based on atomic coherent states, a holomorphic representation for atom collective states and operators is defined. An example is given to illustrate its application.

  5. Chiral solitons in a coupled double Peierls chain

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

    Chiral edge states are the hallmark of two- and three-dimensional topological materials, but their one-dimensional (1D) analog has not yet been found. We report that the 1D topological edge states, solitons, of the charge density wave system of indium atomic wires self-assembled on a silicon surface have chirality. The system is described by a coupled double Peierls-dimerized atomic chain, where the interchain coupling induces dynamical sublattice symmetry breaking. This changes its topological symmetry from Z2×Z2 to Z4 and endows solitons with a chiral degree of freedom. Chiral solitons can produce quantized charge transport across the chain that is topologically protected and controllable by the soliton’s chirality. Individual right- and left-chiral solitons in indium wires are directly identified by scanning tunneling microscopy.

  6. Chiral solitons in a coupled double Peierls chain.

    PubMed

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

    2015-10-01

    Chiral edge states are the hallmark of two- and three-dimensional topological materials, but their one-dimensional (1D) analog has not yet been found. We report that the 1D topological edge states, solitons, of the charge density wave system of indium atomic wires self-assembled on a silicon surface have chirality. The system is described by a coupled double Peierls-dimerized atomic chain, where the interchain coupling induces dynamical sublattice symmetry breaking. This changes its topological symmetry from Z₂× Z₂to Z₄ and endows solitons with a chiral degree of freedom. Chiral solitons can produce quantized charge transport across the chain that is topologically protected and controllable by the soliton's chirality. Individual right- and left-chiral solitons in indium wires are directly identified by scanning tunneling microscopy. PMID:26450206

  7. Carbon chain abundance in the diffuse interstellar medium

    NASA Technical Reports Server (NTRS)

    Allamandola, L. J.; Hudgins, D. M.; Bauschlicher, C. W. Jr; Langhoff, S. R.

    1999-01-01

    Thanks to the mid-IR sensitivities of the ISO and IRTS orbiting spectrometers it is now possible to search the diffuse interstellar medium for heretofore inaccessible molecular emission. In view of the recent strong case for the presence of C(7-) (Kirkwood et al. 1998, Tulej et al. 1998),and the fact that carbon chains possess prominent infrared active modes in a very clean portion of the interstellar spectrum, we have analyzed the IRTS spectrum of the diffuse interstellar medium for the infrared signatures of these species. Theoretical and experimental infrared band frequencies and absolute intensities of many different carbon chain species are presented. These include cyanopolyynes, neutral and anionic linear carbon molecules, and neutral and ionized, even-numbered, hydrogenated carbon chains. We show that--as a family--these species have abundances in the diffuse ISM on the order of 10(-10) with respect to hydrogen, values consistent with their abundances in dense molecular clouds. Assuming an average length of 10 C atoms per C-chain implies that roughly a millionth of the cosmically available carbon is in the form of carbon chains and that carbon chains can account for a few percent of the visible to near-IR diffuse interstellar band (DIB) total equivalent width (not DIB number).

  8. Chain Dynamics in Magnetorheological Suspensions

    NASA Technical Reports Server (NTRS)

    Gast, A. P.; Furst, E. M.

    1999-01-01

    Magnetorheological (MR) suspensions are composed of colloidal particles which acquire dipole moments when subjected to an external magnetic field. At sufficient field strengths and concentrations, the dipolar particles rapidly aggregate to form long chains. Subsequent lateral cross-linking of the dipolar chains is responsible for a rapid liquid-to-solid-like rheological transition. The unique, magnetically-activated rheological properties of MR suspensions make them ideal for interfacing mechanical systems to electronic controls. Additionally, the ability to experimentally probe colloidal suspensions interacting through tunable anisotropic potentials is of fundamental interest. Our current experimental work has focused on understanding the fluctuations of dipolar chains. It has been proposed by Halsey and Toor (HT) that the strong Landau-Peierls thermal fluctuations of dipolar chains could be responsible for long-range attractions between chains. Such interactions will govern the long-time relaxation of MR suspensions. We have synthesized monodisperse neutrally buoyant MR suspensions by density matching stabilized ferrofluid emulsion droplets with D2O. This allows us to probe the dynamics of the dipolar chains using light scattering without gravitational, interfacial, and polydispersity effects to resolve the short-wavelength dynamics of the dipolar chains. We used diffusing wave spectroscopy to measure these dynamics. The particle displacements at short times that show an independence to the field strength, but at long times exhibit a constrained, sub-diffusive motion that slows as the dipole strength is increased. The experiments are in good qualitative agreement with Brownian dynamics simulations of dipolar chains. Although there have been several important and detailed studies of the structure and interactions in MR suspensions, there has not been conclusive evidence that supports or contradicts the HT model prediction that long-range interactions exist between

  9. Exploring membrane respiratory chains.

    PubMed

    Marreiros, Bruno C; Calisto, Filipa; Castro, Paulo J; Duarte, Afonso M; Sena, Filipa V; Silva, Andreia F; Sousa, Filipe M; Teixeira, Miguel; Refojo, Patrícia N; Pereira, Manuela M

    2016-08-01

    Acquisition of energy is central to life. In addition to the synthesis of ATP, organisms need energy for the establishment and maintenance of a transmembrane difference in electrochemical potential, in order to import and export metabolites or to their motility. The membrane potential is established by a variety of membrane bound respiratory complexes. In this work we explored the diversity of membrane respiratory chains and the presence of the different enzyme complexes in the several phyla of life. We performed taxonomic profiles of the several membrane bound respiratory proteins and complexes evaluating the presence of their respective coding genes in all species deposited in KEGG database. We evaluated 26 quinone reductases, 5 quinol:electron carriers oxidoreductases and 18 terminal electron acceptor reductases. We further included in the analyses enzymes performing redox or decarboxylation driven ion translocation, ATP synthase and transhydrogenase and we also investigated the electron carriers that perform functional connection between the membrane complexes, quinones or soluble proteins. Our results bring a novel, broad and integrated perspective of membrane bound respiratory complexes and thus of the several energetic metabolisms of living systems. This article is part of a Special Issue entitled 'EBEC 2016: 19th European Bioenergetics Conference, Riva del Garda, Italy, July 2-6, 2016', edited by Prof. Paolo Bernardi. PMID:27044012

  10. Verifying the Hanging Chain Model

    ERIC Educational Resources Information Center

    Karls, Michael A.

    2013-01-01

    The wave equation with variable tension is a classic partial differential equation that can be used to describe the horizontal displacements of a vertical hanging chain with one end fixed and the other end free to move. Using a web camera and TRACKER software to record displacement data from a vibrating hanging chain, we verify a modified version…

  11. Chain Transfer of Vegetable Oil Macromonomers in Acrylic Solution Copolymerization

    SciTech Connect

    Black, Micah; Messman, Jamie M; Rawlins, James

    2011-01-01

    Use of vegetable oil macromonomers (VOMMs) as comonomers in emulsion polymerization enables good film coalescence without the addition of solvents that constitute volatile organic compounds (VOCs). VOMMs are derived from renewable resources and offer the potential of post-application crosslinking via auto-oxidation. However, chain transfer reactions of VOMMs with initiator and/or polymer radicals during emulsion polymerization reduce the amount of allylic hydrogen atoms available for primary auto-oxidation during drying. Vegetable oils and derivatives were reacted in combination with butyl acrylate and methyl methacrylate via solution polymerization. The copolymerization was monitored using in situ infrared spectroscopy to determine the extent of chain transfer. 1H NMR spectroscopy was used to determine the loci of chain transfer and the molecular weight characteristics of the polymers were characterized by SEC. Solution polymerization was utilized to minimize temperature fluctuations and maintain polymer solubility during the initial characterization.

  12. Dynamics of DNA Chains on Flat and Patterned Surfaces

    NASA Astrophysics Data System (ADS)

    Li, Bingquan; Xiaohua, Fang; Seo, Young-Soo; Samuilov, Vladimir; Rafailovich, Miriam; Sokolov, Jonathan

    2003-03-01

    The electrophoresis of DNA chains on flat silicon and patterned surfaces was studied by Confocal Fluorescence Microscopy and Atomic Force Microscopy. Solutions of lambda DNA of 48,502 bp and Schizosaccharomyces pombe (S. pombe) of 3 6 Mb were deposited on different surfaces. The surfaces were chemically modified to be hydrophilic or SAM-covered and the patterns were produced over length scales from nano to micro size in the form of gratings or square arrays. The interaction with the surface and mobility of DNA chains depended on the surface chemistry, topography and ion concentration of buffer. The motion of individual chains in the electric field was analyzed both in terms of the dimensions and orientation of the pattern structure. Supported by NSF-MRSEC program (DMR-9632525)

  13. Developing sustainable food supply chains.

    PubMed

    Smith, B Gail

    2008-02-27

    This paper reviews the opportunities available for food businesses to encourage consumers to eat healthier and more nutritious diets, to invest in more sustainable manufacturing and distribution systems and to develop procurement systems based on more sustainable forms of agriculture. The important factors in developing more sustainable supply chains are identified as the type of supply chain involved and the individual business attitude to extending responsibility for product quality into social and environmental performance within their own supply chains. Interpersonal trust and working to standards are both important to build more sustainable local and many conserved food supply chains, but inadequate to transform mainstream agriculture and raw material supplies to the manufactured and commodity food markets. Cooperation among food manufacturers, retailers, NGOs, governmental and farmers' organizations is vital in order to raise standards for some supply chains and to enable farmers to adopt more sustainable agricultural practices. PMID:17766237

  14. Equilibrium distribution of the wave energy in a carbyne chain

    NASA Astrophysics Data System (ADS)

    Kovriguine, D. A.; Nikitenkova, S. P.

    2016-03-01

    The steady-state energy distribution of thermal vibrations at a given ambient temperature has been investigated based on a simple mathematical model that takes into account central and noncentral interactions between carbon atoms in a one-dimensional carbyne chain. The investigation has been performed using standard asymptotic methods of nonlinear dynamics in terms of the classical mechanics. In the first-order nonlinear approximation, there have been revealed resonant wave triads that are formed at a typical nonlinearity of the system under phase matching conditions. Each resonant triad consists of one longitudinal and two transverse vibration modes. In the general case, the chain is characterized by a superposition of similar resonant triplets of different spectral scales. It has been found that the energy equipartition of nonlinear stationary waves in the carbyne chain at a given temperature completely obeys the standard Rayleigh-Jeans law due to the proportional amplitude dispersion. The possibility of spontaneous formation of three-frequency envelope solitons in carbyne has been demonstrated. Heat in the form of such solitons can propagate in a chain of carbon atoms without diffusion, like localized waves.

  15. Graphite filter atomizer in atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Katskov, Dmitri A.

    2007-09-01

    Graphite filter atomizers (GFA) for electrothermal atomic absorption spectrometry (ETAAS) show substantial advantages over commonly employed electrothermal vaporizers and atomizers, tube and platform furnaces, for direct determination of high and medium volatility elements in matrices associated with strong spectral and chemical interferences. Two factors provide lower limits of detection and shorter determination cycles with the GFA: the vaporization area in the GFA is separated from the absorption volume by a porous graphite partition; the sample is distributed over a large surface of a collector in the vaporization area. These factors convert the GFA into an efficient chemical reactor. The research concerning the GFA concept, technique and analytical methodology, carried out mainly in the author's laboratory in Russia and South Africa, is reviewed. Examples of analytical applications of the GFA in AAS for analysis of organic liquids and slurries, bio-samples and food products are given. Future prospects for the GFA are discussed in connection with analyses by fast multi-element AAS.

  16. Advances in atomic physics

    PubMed Central

    El-Sherbini, Tharwat M.

    2013-01-01

    In this review article, important developments in the field of atomic physics are highlighted and linked to research works the author was involved in himself as a leader of the Cairo University – Atomic Physics Group. Starting from the late 1960s – when the author first engaged in research – an overview is provided of the milestones in the fascinating landscape of atomic physics. PMID:26425356

  17. Atomic Oxygen Effects

    NASA Technical Reports Server (NTRS)

    Miller, Sharon K. R.

    2014-01-01

    Atomic oxygen, which is the most predominant species in low Earth orbit, is highly reactive and can break chemical bonds on the surface of a wide variety of materials leading to volatilization or surface oxidation which can result in failure of spacecraft materials and components. This presentation will give an overview of how atomic oxygen reacts with spacecraft materials, results of space exposure testing of a variety of materials, and examples of failures caused by atomic oxygen.

  18. Metal atom oxidation laser

    DOEpatents

    Jensen, R.J.; Rice, W.W.; Beattie, W.H.

    1975-10-28

    A chemical laser which operates by formation of metal or carbon atoms and reaction of such atoms with a gaseous oxidizer in an optical resonant cavity is described. The lasing species are diatomic or polyatomic in nature and are readily produced by exchange or other abstraction reactions between the metal or carbon atoms and the oxidizer. The lasing molecules may be metal or carbon monohalides or monoxides.

  19. Metal atom oxidation laser

    DOEpatents

    Jensen, R.J.; Rice, W.W.; Beattie, W.H.

    1975-10-28

    A chemical laser which operates by formation of metal or carbon atoms and reaction of such atoms with a gaseous oxidizer in an optical resonant cavity is described. The lasing species are diatomic or polyatomic in nature and are readily produced by exchange or other abstraction reactions between the metal or carbon atoms and the oxidizer. The lasing molecules may be metal or carbon monohalides or monoxides. (auth)

  20. Solar Spectroscopy: Atomic Processes

    NASA Astrophysics Data System (ADS)

    Mason, H.; Murdin, P.

    2000-11-01

    A Greek philosopher called DEMOCRITUS (c. 460-370 BC) first introduced the concept of atoms (which means indivisible). His atoms do not precisely correspond to our atoms of today, which are not indivisible, but made up of a nucleus (protons with positive charge and neutrons which have no charge) and orbiting electrons (with negative charge). Indeed, in the solar atmosphere, the temperature is suc...

  1. Visualization of atom's orbits.

    PubMed

    Kim, Byungwhan

    2014-02-01

    High-resolution imaging techniques have been used to obtain views of internal shapes of single atoms or columns of atoms. This review article focuses on the visualization of internal atomic structures such as the configurations of electron orbits confined to atoms. This is accomplished by applying visualization techniques to the reported images of atoms or molecules as well as static and dynamic ions in a plasma. It was found that the photon and electron energies provide macroscopic and microscopic views of the orbit structures of atoms, respectively. The laser-imaged atoms showed a rugged orbit structure, containing alternating dark and bright orbits believed to be the pathways for an externally supplied laser energy and internally excited electron energy, respectively. By contrast, the atoms taken by the electron microscopy provided a structure of fine electron orbits, systematically formed in increasing order of grayscale representing the energy state of an orbit. This structure was identical to those of the plasma ions. The visualized electronic structures played a critical role in clarifying vague postulates made in the Bohr model. Main features proposed in the atomic model are the dynamic orbits absorbing an externally supplied electromagnetic energy, electron emission from them while accompanying light radiation, and frequency of electron waves not light. The light-accompanying electrons and ionic speckles induced by laser light signify that light is composed of electrons and ions. PMID:24749452

  2. Improved graphite furnace atomizer

    DOEpatents

    Siemer, D.D.

    1983-05-18

    A graphite furnace atomizer for use in graphite furnace atomic absorption spectroscopy is described wherein the heating elements are affixed near the optical path and away from the point of sample deposition, so that when the sample is volatilized the spectroscopic temperature at the optical path is at least that of the volatilization temperature, whereby analyteconcomitant complex formation is advantageously reduced. The atomizer may be elongated along its axis to increase the distance between the optical path and the sample deposition point. Also, the atomizer may be elongated along the axis of the optical path, whereby its analytical sensitivity is greatly increased.

  3. Electrochemical preparation of carbon chains and nanoparticles

    NASA Astrophysics Data System (ADS)

    Kavan, Ladislav

    1999-09-01

    The composite of carbon with alkali metal fluoride, C-MF(M=Li, Na) was prepared by cathodic defluorination of perfluorinated hydrocarbons at room temperature. Raman spectra of C-MF from PTFE indicate carbon chains (oligoynes, 1974-2024 cm-1) in addition to graphite-like carbon (1300-1500 cm-1). The oligoyne-containing carbon is partly selforganized by cross linking towards graphene. Highly-organized carbons were prepared from friction-deposited PTFE films. AFM confirms perfect ordering of the precursor molecules (up to atomic resolution), but the corresponding carbonization product is rapidly reconstructed upon contact to air. Raman spectra of oriented carbons display high conjugation lengths (up to 18 sp-bonded carbon atoms). Cyclic perfluorinated precursors are also smoothly defluorinated to elemental carbon. TEM indicates that these carbons contain about 1% of carbonaceous nanoparticles, i.e. nanotubes and onions. Also small quantity of fullerene C60(≈0.01%) was detected in the toluene extract.

  4. The CHAIN program: forging evolutionary links to underlying mechanisms.

    PubMed

    Neuwald, Andrew F

    2007-11-01

    Proteins evolve new functions by modifying and extending the molecular machinery of an ancestral protein. Such changes show up as divergent sequence patterns, which are conserved in descendent proteins that maintain the divergent function. After multiply-aligning a set of input sequences, the CHAIN program partitions the sequences into two functionally divergent groups and then outputs an alignment that is annotated to reveal the selective pressures imposed on divergent residue positions. If atomic coordinates are also provided, hydrogen bonds and other atomic interactions associated with various categories of divergent residues are graphically displayed. Such analyses establish links between protein evolutionary divergence and functionally crucial atomic features and, as a result, can suggest plausible molecular mechanisms for experimental testing. This is illustrated here by its application to bacterial clamp-loader ATPases. PMID:17962021

  5. 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

  6. Evanescent Wave Atomic Mirror

    NASA Astrophysics Data System (ADS)

    Ghezali, S.; Taleb, A.

    2008-09-01

    A research project at the "Laboratoire d'électronique quantique" consists in a theoretical study of the reflection and diffraction phenomena via an atomic mirror. This poster presents the principle of an atomic mirror. Many groups in the world have constructed this type of atom optics experiments such as in Paris-Orsay-Villetaneuse (France), Stanford-Gaithersburg (USA), Munich-Heidelberg (Germany), etc. A laser beam goes into a prism with an incidence bigger than the critical incidence. It undergoes a total reflection on the plane face of the prism and then exits. The transmitted resulting wave out of the prism is evanescent and repulsive as the frequency detuning of the laser beam compared to the atomic transition δ = ωL-ω0 is positive. The cold atomic sample interacts with this evanescent wave and undergoes one or more elastic bounces by passing into backward points in its trajectory because the atoms' kinetic energy (of the order of the μeV) is less than the maximum of the dipolar potential barrier ℏΩ2/Δ where Ω is the Rabi frequency [1]. In fact, the atoms are cooled and captured in a magneto-optical trap placed at a distance of the order of the cm above the prism surface. The dipolar potential with which interact the slow atoms is obtained for a two level atom in a case of a dipolar electric transition (D2 Rubidium transition at a wavelength of 780nm delivered by a Titane-Saphir laser between a fundamental state Jf = l/2 and an excited state Je = 3/2). This potential is corrected by an attractive Van der Waals term which varies as 1/z3 in the Lennard-Jones approximation (typical atomic distance of the order of λ0/2π where λ0 is the laser wavelength) and in 1/z4 if the distance between the atom and its image in the dielectric is big in front of λ0/2π. This last case is obtained in a quantum electrodynamic calculation by taking into account an orthornormal base [2]. We'll examine the role of spontaneous emission for which the rate is inversely

  7. Food Chain Security and Vulnerability

    NASA Astrophysics Data System (ADS)

    Brunet, Sébastien; Delvenne, Pierre; Claisse, Frédéric

    In our contemporary societies, the food chain could be defined as a macro-technical system, which depends on a wide variety of actors and risks analysis methods. In this contribution, risks related to the food chain are defined in terms of "modern risks" (Beck 1992). The whole national economic sector of food production/distribution is vulnerable to a local accident, which can affect the functioning of food chain, the export programs and even the political system. Such a complex socio-technical environment is undoubtedly vulnerable to intentional act such as terrorism.

  8. Proteoglycans and their heterogeneous glycosaminoglycans at the atomic scale

    PubMed Central

    Sattelle, Benedict M.; Shakeri, Javad; Cliff, Matthew J.; Almond, Andrew

    2015-01-01

    Proteoglycan spatiotemporal organization underpins extracellular matrix biology but atomic scale glimpses of this microarchitecture are obscured by glycosaminoglycan size and complexity. To overcome this, multi-microsecond aqueous simulations of chondroitin and dermatan sulfates were abstracted into a prior coarse-grained model, which was extended to heterogeneous glycosaminoglycans and small leucine-rich proteoglycans. Exploration of relationships between sequence and shape led to hypotheses that proteoglycan size is dependent on glycosaminoglycan unit composition but independent of sequence permutation. Uronic acid conformational equilibria were modulated by adjacent hexosamine sulfonation and iduronic acid increased glycosaminoglycan chain volume and rigidity, while glucuronic acid imparted chain plasticity. Consequently, block copolymeric glycosaminoglycans contained microarchitectures capable of multivalent binding to growth factors and collagen, with potential for interactional synergy at greater chain number. The described atomic scale views of proteoglycans and heterogeneous glycosaminoglycans provide structural routes to understanding their fundamental signaling and mechanical biological roles and development of new biomaterials. PMID:25645947

  9. Odd-even chain packing, molecular and thermal models for some long chain sodium(I) n-alkanoates

    NASA Astrophysics Data System (ADS)

    Nelson, Peter N.; Ellis, Henry A.

    2014-10-01

    A homologous series of sodium(I) n-alkanoates, NaCnH2n-1O2, with chain lengths n = 8-18, inclusive, have been synthesized and their structural and thermal properties investigated via Fourier Transform Infrared and Solid State 13C NMR spectroscopies, X-ray powder diffraction, Thermogravimetry, Differential Scanning Calorimetry, Polarizing light microscopy and variable temperature Infrared spectroscopy. The measurements show that metal-carboxylate coordination is via asymmetric chelating bidentate bonding with extensive carboxyl group inter-molecular interactions in which four oxygen atoms are bonded tetrahedrally to a sodium atom. Furthermore, the compounds crystallize in a monoclinic crystal system with the hydrocarbon chains in the fully extended all-trans conformation, advancing along the c-axis. Moreover, the chains are packed as tilted (θ ∼ 63°), non-overlapping, tail-to-tail lamellar bilayers that are not in the same plane, within a lamellar. Though these compounds are nearly isostructural, there are subtle differences in the packing of the hydrocarbon chains in the crystal lattice, resulting in odd-even alternation in the terminal methyl group asymmetric stretching vibration and chemical shift. These differences arise from the relative vertical distances between hydrocarbon planes within the lamellar; such that, for odd-chain compounds, larger inter-planar distances result in less efficient packing in the crystal lattice and hence, lower inter-planar van der Waals interactions between hydrocarbon chains. Thermal traces, for all compounds, show several partially reversible solid-solid pre-melting transitions associated with different degrees of gauche conformers in the alkyl chains. The reversible gauche-trans isomerism, of the methylene groups, is kinetically controlled; hence, super-cooling of the melt and other transitions, are observed for all compounds. The kinetics of chain reversion follow the exponential law of nucleation, though complicated by

  10. Modified Embedded Atom Method

    Energy Science and Technology Software Center (ESTSC)

    2012-08-01

    Interatomic force and energy calculation subroutine to be used with the molecular dynamics simulation code LAMMPS (Ref a.). The code evaluated the total energy and atomic forces (energy gradient) according to a cubic spline-based variant (Ref b.) of the Modified Embedded Atom Method (MEAM) with a additional Stillinger-Weber (SW) contribution.

  11. Atomic Scale Plasmonic Switch.

    PubMed

    Emboras, Alexandros; Niegemann, Jens; Ma, Ping; Haffner, Christian; Pedersen, Andreas; Luisier, Mathieu; Hafner, Christian; Schimmel, Thomas; Leuthold, Juerg

    2016-01-13

    The atom sets an ultimate scaling limit to Moore's law in the electronics industry. While electronics research already explores atomic scales devices, photonics research still deals with devices at the micrometer scale. Here we demonstrate that photonic scaling, similar to electronics, is only limited by the atom. More precisely, we introduce an electrically controlled plasmonic switch operating at the atomic scale. The switch allows for fast and reproducible switching by means of the relocation of an individual or, at most, a few atoms in a plasmonic cavity. Depending on the location of the atom either of two distinct plasmonic cavity resonance states are supported. Experimental results show reversible digital optical switching with an extinction ratio of 9.2 dB and operation at room temperature up to MHz with femtojoule (fJ) power consumption for a single switch operation. This demonstration of an integrated quantum device allowing to control photons at the atomic level opens intriguing perspectives for a fully integrated and highly scalable chip platform, a platform where optics, electronics, and memory may be controlled at the single-atom level. PMID:26670551

  12. Greek Atomic Theory.

    ERIC Educational Resources Information Center

    Roller, Duane H. D.

    1981-01-01

    Focusing on history of physics, which began about 600 B.C. with the Ionian Greeks and reaching full development within three centuries, suggests that the creation of the concept of the atom is understandable within the context of Greek physical theory; so is the rejection of the atomic theory by the Greek physicists. (Author/SK)

  13. Atomic and Molecular Physics

    NASA Technical Reports Server (NTRS)

    Bhatia, Anand K.

    2005-01-01

    A symposium on atomic and molecular physics was held on November 18, 2005 at Goddard Space Flight Center. There were a number of talks through the day on various topics such as threshold law of ionization, scattering of electrons from atoms and molecules, muonic physics, positron physics, Rydberg states etc. The conference was attended by a number of physicists from all over the world.

  14. When Atoms Want

    ERIC Educational Resources Information Center

    Talanquer, Vicente

    2013-01-01

    Chemistry students and teachers often explain the chemical reactivity of atoms, molecules, and chemical substances in terms of purposes or needs (e.g., atoms want or need to gain, lose, or share electrons in order to become more stable). These teleological explanations seem to have pedagogical value as they help students understand and use…

  15. Neutrino-atom collisions

    NASA Astrophysics Data System (ADS)

    Kouzakov, Konstantin A.; Studenikin, Alexander I.

    2016-05-01

    Neutrino-atom scattering provides a sensitive tool for probing nonstandard interactions of massive neutrinos in laboratory measurements. The ionization channel of this collision process plays an important role in experiments searching for neutrino magnetic moments. We discuss some theoretical aspects of atomic ionization by massive neutrinos. We also outline possible manifestations of neutrino electromagnetic properties in coherent elastic neutrino-nucleus scattering.

  16. Greek atomic theory

    NASA Astrophysics Data System (ADS)

    Roller, Duane H. D.

    1981-03-01

    Physics began about 600 B.C. with the Ionian Greeks and reached full development within three centuries. The creation of the concept of the atom is understandable within the context of Greek physical theory; so is the rejection of the atomic theory by the Greek physicists.

  17. Atomic Power Safety.

    ERIC Educational Resources Information Center

    Hogerton, John F.

    This publication is one of a series of information booklets for the general public published by The United States Atomic Energy Commission. Among the topics discussed are: What is Atomic Power?; What Does Safety Depend On?; Control of Radioactive Material During Operation; Accident Prevention; Containment in the Event of an Accident; Licensing and…

  18. Chain conformational and physicochemical properties of fucoidans from sea cucumber.

    PubMed

    Xu, Xiaoqi; Xue, Changhu; Chang, Yaoguang; Wang, Jun; Jiang, Kunhao

    2016-11-01

    Although fucoidans from sea cucumber (SC-FUCs) have been proven as potential bioactive polysaccharides and functional food ingridents, their chain conformation and physicochemical properties were still poorly understood. This study investigated the chain conformation of fucoidans from sea cucumber Acaudina molpadioides (Am-FUC), Isostichopus badionotus (Ib-FUC) and Apostichopus japonicus (Aj-FUC), of which primary structure has been recently clarified. Chain conformation parameters demonstrated that studied SC-FUCs adopted random coil conformation in 150mM NaCl solution (pH 7.4). Based on the worm-like cylinder model and atomic force microscopy, the chain stiffness of SC-FUCs was further evaluated as Am-FUC≈Ib-FUC>Aj-FUC. It was suggested that the existence of branch structure increased the chain flexibility, while sulfated pattern exerted limited influence. SC-FUCs demonstrated shear-thinning rheological behavior and negative charge. Am-FUC possessed a higher thermostability than Ib-FUC and Aj-FUC. These results have important implications for understanding the molecular characteristics of SC-FUCs, which could facilitate their further application. PMID:27516290

  19. Laser-Atomic Oscillator

    NASA Astrophysics Data System (ADS)

    Jau, Yuan-Yu; Happer, William

    2008-05-01

    We report a newly developed technique, laser-atomic oscillator, for simultaneously generating stable optical and electrical modulations with a very few components. It requires only a semiconductor laser, a vapor cell, and a few optical components. No photodetector and electronic feedback are needed. In this new system, the ground-state hyperfine coherence of alkali-metal atoms is spontaneously generated. The modulated laser light with a spectrum of a small optical comb is automatically produced, and the spacing between the comb peaks is photonically locked to the hyperfine frequency. The charge carriers in the semiconductor laser are also modulated at the hyperfine frequency. Laser-atomic oscillator is purely optical. Its simple structure allows the system to be very compact. We believe this new technique will bring some advantages in the applications of atomic chronometry, atomic magnetometry, and generation of multi-coherent light.

  20. Moving Single Atoms

    NASA Astrophysics Data System (ADS)

    Stuart, Dustin

    2016-05-01

    Single neutral atoms are promising candidates for qubits, the fundamental unit of quantum information. We have built a set of optical tweezers for trapping and moving single Rubidium atoms. The tweezers are based on a far off-resonant dipole trapping laser focussed to a 1 μm spot with a single aspheric lens. We use a digital micromirror device (DMD) to generate dynamic holograms of the desired arrangement of traps. The DMD has a frame rate of 20 kHz which, when combined with fast algorithms, allows for rapid reconfiguration of the traps. We demonstrate trapping of up to 20 atoms in arbitrary arrangements, and the transport of a single-atom over a distance of 14 μm with continuous laser cooling, and 5 μm without. In the meantime, we are developing high-finesse fibre-tip cavities, which we plan to use to couple pairs of single atoms to form a quantum network.

  1. Coaxial airblast atomizers

    NASA Technical Reports Server (NTRS)

    Hardalupas, Y.; Whitelaw, J. H.

    1993-01-01

    An experimental investigation was performed to quantify the characteristics of the sprays of coaxial injectors with particular emphasis on those aspects relevant to the performance of rocket engines. Measurements for coaxial air blast atomizers were obtained using air to represent the gaseous stream and water to represent the liquid stream. A wide range of flow conditions were examined for sprays with and without swirl for gaseous streams. The parameters varied include Weber number, gas flow rate, liquid flow rate, swirl, and nozzle geometry. Measurements were made with a phase Doppler velocimeter. Major conclusions of the study focused upon droplet size as a function of Weber number, effect of gas flow rate on atomization and spray spread, effect of nozzle geometry on atomization and spread, effect of swirl on atomization, spread, jet recirculation and breakup, and secondary atomization.

  2. Atomic Oxygen Textured Polymers

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A.; Rutledge, Sharon K.; Hunt, Jason D.; Drobotij, Erin; Cales, Michael R.; Cantrell, Gidget

    1995-01-01

    Atomic oxygen can be used to microscopically alter the surface morphology of polymeric materials in space or in ground laboratory facilities. For polymeric materials whose sole oxidation products are volatile species, directed atomic oxygen reactions produce surfaces of microscopic cones. However, isotropic atomic oxygen exposure results in polymer surfaces covered with lower aspect ratio sharp-edged craters. Isotropic atomic oxygen plasma exposure of polymers typically causes a significant decrease in water contact angle as well as altered coefficient of static friction. Such surface alterations may be of benefit for industrial and biomedical applications. The results of atomic oxygen plasma exposure of thirty-three (33) different polymers are presented, including typical morphology changes, effects on water contact angle, and coefficient of static friction.

  3. Bibliometric Application of Markov Chains.

    ERIC Educational Resources Information Center

    Pao, Miranda Lee; McCreery, Laurie

    1986-01-01

    A rudimentary description of Markov Chains is presented in order to introduce its use to describe and to predict authors' movements among subareas of the discipline of ethnomusicology. Other possible applications are suggested. (Author)

  4. Crystal-to-crystal transformation from a chain compound to a layered coordination polymer.

    PubMed

    Shi, Jinbiao; Zhang, Yan; Zhang, Bin; Zhu, Daoben

    2016-01-01

    A crystal-to-crystal transformation was observed from a green chain compound CuBr2(1,4-dioxane)2(H2O)2 (1) to a brown layered compound (CuBr2)3(1,4-dioxane)2 (2). The hydrogen bond connecting chains in were replaced by a μ-Br bridge in and the antiferromagnetic interaction between the metal atoms in became stronger than in 1. PMID:26600206

  5. Reinforcement learning in supply chains.

    PubMed

    Valluri, Annapurna; North, Michael J; Macal, Charles M

    2009-10-01

    Effective management of supply chains creates value and can strategically position companies. In practice, human beings have been found to be both surprisingly successful and disappointingly inept at managing supply chains. The related fields of cognitive psychology and artificial intelligence have postulated a variety of potential mechanisms to explain this behavior. One of the leading candidates is reinforcement learning. This paper applies agent-based modeling to investigate the comparative behavioral consequences of three simple reinforcement learning algorithms in a multi-stage supply chain. For the first time, our findings show that the specific algorithm that is employed can have dramatic effects on the results obtained. Reinforcement learning is found to be valuable in multi-stage supply chains with several learning agents, as independent agents can learn to coordinate their behavior. However, learning in multi-stage supply chains using these postulated approaches from cognitive psychology and artificial intelligence take extremely long time periods to achieve stability which raises questions about their ability to explain behavior in real supply chains. The fact that it takes thousands of periods for agents to learn in this simple multi-agent setting provides new evidence that real world decision makers are unlikely to be using strict reinforcement learning in practice. PMID:19885962

  6. Elastic properties of magnetosome chains

    NASA Astrophysics Data System (ADS)

    Kiani, Bahareh; Faivre, Damien; Klumpp, Stefan

    2015-04-01

    Magnetotactic bacteria swim and orient in the direction of a magnetic field thanks to the magnetosome chain, a cellular ‘compass needle’ that consists of a string of vesicle-enclosed magnetic nanoparticles aligned on a cytoskeletal filament. Here we investigate the mechanical properties of such a chain, in particular the bending stiffness. We determine the contribution of magnetic interactions to the bending stiffness and the persistence length of the chain. This contribution is comparable to, but typically smaller than the contribution of the semiflexible filament. For a chain of magnetic nanoparticles without a semiflexible filament, the linear configuration is typically metastable and the lowest energy structures are closed chains (flux closure rings) without a net magnetic moment that are thus not functional as a cellular compass. Our calculations show that the presence of the cytoskeletal filament stabilizes the chain against ring closure, either thermodynamically or kinetically, depending on the stiffness of the filament, confirming that such stabilization is one of the roles of this structure in these bacterial cells.

  7. Preparation of atomic oxygen resistant polymeric materials

    NASA Technical Reports Server (NTRS)

    Tortorelli, Victor J.; Hergenrother, P. M.; Connell, J. W.

    1991-01-01

    Polyphenyl quinoxalines (PPQs) are an important family of high performance polymers that offer good chemical and thermal stability coupled with excellent mechanical properties. These aromatic heterocyclic polymers are potentially useful as films, coatings, adhesives, and composite materials that demand stability in harsh environments. Our approach was to prepare PPQs with pendent siloxane groups using the appropriate chemistry and then evaluate these polymers before and after exposure to simulated atomic oxygen. Either monomer, the bis(o-diamine)s or the bis(alpha-diketone)s can be synthesized with a hydroxy group to which the siloxane chain will be attached. Several novel materials were prepared.

  8. VCSELs for atomic clocks

    NASA Astrophysics Data System (ADS)

    Serkland, Darwin K.; Peake, Gregory M.; Geib, Kent M.; Lutwak, Robert; Garvey, R. Michael; Varghese, Mathew; Mescher, Mark

    2006-02-01

    The spectroscopic technique of coherent population trapping (CPT) enables an all-optical interrogation of the groundstate hyperfine splitting of cesium (or rubidium), compared to the optical-microwave double resonance technique conventionally employed in atomic frequency standards. All-optical interrogation enables the reduction of the size and power consumption of an atomic clock by two orders of magnitude, and vertical-cavity surface-emitting lasers (VCSELs) are preferred optical sources due to their low power consumption and circular output beam. Several research teams are currently using VCSELs for DARPA's chip-scale atomic clock (CSAC) program with the goal of producing an atomic clock having a volume < 1 cm^3, a power consumption < 30 mW, and an instability (Allan deviation) < 1x10^-11 during a 1-hour averaging interval. This paper describes the VCSEL requirements for CPT-based atomic clocks, which include single mode operation, single polarization operation, modulation bandwidth > 4 GHz, low power consumption (for the CSAC), narrow linewidth, and low relative intensity noise (RIN). A significant manufacturing challenge is to reproducibly obtain the required wavelength at the specified VCSEL operating temperature and drive current. Data are presented that show the advantage of operating at the D1 (rather than D2) resonance of the alkali atoms. Measurements of VCSEL linewidth will be discussed in particular, since atomic clock performance is especially sensitive to this parameter.

  9. Linear chains and chain-like fractals from electrostatic heteroaggregation.

    PubMed

    Kim, Anthony Y; Hauch, Kip D; Berg, John C; Martin, James E; Anderson, Robert A

    2003-04-01

    The internal structure of materials prepared by aggregation of oppositely charged polystyrene spheres (electrostatic heteroaggregation) is investigated by static light scattering, optical microscopy, and Brownian dynamics simulation. Light scattering indicates ultralow mass fractal dimensions, as low as 1.2. Such low fractal dimensions, approaching the theoretical limit of a linear object, imply a chaining mechanism. Optical micrographs reveal linear chains with the particle charge alternating down the chains. Brownian dynamics simulation gives additional support for a chaining mechanism. For the polystyrene system (120-nm primary particle diameters), the fractal dimension is found to increase from 1.2 to 1.7 as the background electrolyte is increased. In terms of electrostatic screening, the results match those reported recently for larger polystyrene spheres. The low fractal dimensions appear to represent a crossover from linear chains to a structure of diffusion-limited aggregates; however, experiments under density-neutral conditions imply that sedimentation plays an important role in the formation of ultralow fractal dimensions. The practical implication is that microcomposites with a locally uniform distribution of starting materials and almost any degree of branching can be prepared from oppositely charged particles. PMID:12742045

  10. Atom trap trace analysis

    SciTech Connect

    Lu, Z.-T.; Bailey, K.; Chen, C.-Y.; Du, X.; Li, Y.-M.; O'Connor, T. P.; Young, L.

    2000-05-25

    A new method of ultrasensitive trace-isotope analysis has been developed based upon the technique of laser manipulation of neutral atoms. It has been used to count individual {sup 85}Kr and {sup 81}Kr atoms present in a natural krypton sample with isotopic abundances in the range of 10{sup {minus}11} and 10{sup {minus}13}, respectively. The atom counts are free of contamination from other isotopes, elements,or molecules. The method is applicable to other trace-isotopes that can be efficiently captured with a magneto-optical trap, and has a broad range of potential applications.

  11. Atomic and molecular supernovae

    SciTech Connect

    Liu, W.

    1997-12-01

    Atomic and molecular physics of supernovae is discussed with an emphasis on the importance of detailed treatments of the critical atomic and molecular processes with the best available atomic and molecular data. The observations of molecules in SN 1987A are interpreted through a combination of spectral and chemical modelings, leading to strong constraints on the mixing and nucleosynthesis of the supernova. The non-equilibrium chemistry is used to argue that carbon dust can form in the oxygen-rich clumps where the efficient molecular cooling makes the nucleation of dust grains possible. For Type Ia supernovae, the analyses of their nebular spectra lead to strong constraints on the supernova explosion models.

  12. Atomic and molecular supernovae

    NASA Technical Reports Server (NTRS)

    Liu, Weihong

    1997-01-01

    Atomic and molecular physics of supernovae is discussed with an emphasis on the importance of detailed treatments of the critical atomic and molecular processes with the best available atomic and molecular data. The observations of molecules in SN 1987A are interpreted through a combination of spectral and chemical modelings, leading to strong constraints on the mixing and nucleosynthesis of the supernova. The non-equilibrium chemistry is used to argue that carbon dust can form in the oxygen-rich clumps where the efficient molecular cooling makes the nucleation of dust grains possible. For Type Ia supernovae, the analyses of their nebular spectra lead to strong constraints on the supernova explosion models.

  13. Atomic mass evaluation

    SciTech Connect

    Wang, M.; Audi, G.; Kondev, F. G.; Xu, X.; Pfeiffer, B.

    2012-11-12

    The atomic masses are important input parameters for nuclear astrophysics calculations. The Atomic Mass Evaluation (AME) is the most reliable source for comprehensive information related to atomic masses. The latest AME was published in 2003. A new version, which will include the impact of a wealth of new, high-precision experimental data, will be published in December 2012. In this paper we will give the current status of AME2012. The mass surface has been changed significantly compared to AME2003, and the impact on astrophysics calculations is discussed.

  14. Trapping deuterium atoms

    SciTech Connect

    Wiederkehr, A. W.; Hogan, S. D.; Lambillotte, B.; Andrist, M.; Schmutz, H.; Agner, J.; Salathe, Y.; Merkt, F.

    2010-02-15

    Cold deuterium atoms in a supersonic beam have been decelerated from an initial velocity of 475 m/s to zero velocity in the laboratory frame using a 24-stage Zeeman decelerator. The atoms have been loaded in a magnetic quadrupole trap at a temperature of {approx}100 mK and an initial density of {approx}10{sup 6} cm{sup -3}. Efficient deceleration was achieved by pulsing the magnetic fields in the decelerator solenoids using irregular sequences of phase angles. Trap loading was optimized by monitoring and suppressing the observed reflection of the atoms by the field gradient of the back solenoid of the trap.

  15. Atom Transfer Radical Polymerization of Methacrylic Acid: A Won Challenge.

    PubMed

    Fantin, Marco; Isse, Abdirisak A; Venzo, Alfonso; Gennaro, Armando; Matyjaszewski, Krzysztof

    2016-06-15

    Polymerization of acidic monomers is one of the biggest challenges for atom transfer radical polymerization (ATRP). An intramolecular cyclization reaction leading to the loss of the C-X chain-end functionality was found to be the main reason for the partial termination of the growing polymer chains. Three approaches were used to overcome this problem: using Cl as the chain-end halogen, lowering the pH (to 0.9), and increasing polymerization rate. Methacrylic acid (MAA) was polymerized by both electrochemically mediated ATRP and supplemental activator and reducing agent ATRP up to high conversion (>90%), in t ≤ 4 h at 25 °C, using inexpensive and nontoxic reagents (NaCl, diluted HCl, water). Control over molecular weight (MW) dispersity was satisfactory, and MWs were in agreement with theoretical values. The "livingness" of the process was confirmed by an electrochemical switch, used to repeatedly and periodically deactivate/reactivate growing chains. PMID:27244091

  16. Precisely detecting atomic position of atomic intensity images.

    PubMed

    Wang, Zhijun; Guo, Yaolin; Tang, Sai; Li, Junjie; Wang, Jincheng; Zhou, Yaohe

    2015-03-01

    We proposed a quantitative method to detect atomic position in atomic intensity images from experiments such as high-resolution transmission electron microscopy, atomic force microscopy, and simulation such as phase field crystal modeling. The evaluation of detection accuracy proves the excellent performance of the method. This method provides a chance to precisely determine atomic interactions based on the detected atomic positions from the atomic intensity image, and hence to investigate the related physical, chemical and electrical properties. PMID:25544105

  17. Conceptual atomism rethought.

    PubMed

    Schneider, Susan

    2010-06-01

    Focusing on Machery's claim that concepts play entirely different roles in philosophy and psychology, I explain how one well-known philosophical theory of concepts, Conceptual Atomism (CA), when properly understood, takes into account both kinds of roles. PMID:20584416

  18. Atomic branching in molecules

    NASA Astrophysics Data System (ADS)

    Estrada, Ernesto; Rodríguez-Velázquez, Juan A.; Randić, Milan

    A graph theoretic measure of extended atomic branching is defined that accounts for the effects of all atoms in the molecule, giving higher weight to the nearest neighbors. It is based on the counting of all substructures in which an atom takes part in a molecule. We prove a theorem that permits the exact calculation of this measure based on the eigenvalues and eigenvectors of the adjacency matrix of the graph representing a molecule. The definition of this measure within the context of the Hückel molecular orbital (HMO) and its calculation for benzenoid hydrocarbons are also studied. We show that the extended atomic branching can be defined using any real symmetric matrix, as well as any Hermitian (self-adjoint) matrix, which permits its calculation in topological, geometrical, and quantum chemical contexts.

  19. Anti-atoms: Gotcha!

    NASA Astrophysics Data System (ADS)

    Surko, Clifford M.

    2011-07-01

    Refined techniques to mix cold antiprotons and positrons in a magnetic bottle show that antihydrogen atoms can be trapped for 15 minutes -- an improvement of four orders of magnitude over previous experiments.

  20. Atomic Bomb Health Benefits

    PubMed Central

    Luckey, T. D.

    2008-01-01

    Media reports of deaths and devastation produced by atomic bombs convinced people around the world that all ionizing radiation is harmful. This concentrated attention on fear of miniscule doses of radiation. Soon the linear no threshold (LNT) paradigm was converted into laws. Scientifically valid information about the health benefits from low dose irradiation was ignored. Here are studies which show increased health in Japanese survivors of atomic bombs. Parameters include decreased mutation, leukemia and solid tissue cancer mortality rates, and increased average lifespan. Each study exhibits a threshold that repudiates the LNT dogma. The average threshold for acute exposures to atomic bombs is about 100 cSv. Conclusions from these studies of atomic bomb survivors are: One burst of low dose irradiation elicits a lifetime of improved health.Improved health from low dose irradiation negates the LNT paradigm.Effective triage should include radiation hormesis for survivor treatment. PMID:19088902

  1. The Atomic Dating Game.

    ERIC Educational Resources Information Center

    Cummo, Evelyn; Matthews, Catherine E.

    2002-01-01

    Presents an activity designed to provide students with opportunities to practice drawing atomic models and discover the logical pairings of whole families on the periodic table. Follows the format of a television game show. (DDR)

  2. The CHIANTI atomic database

    NASA Astrophysics Data System (ADS)

    Young, P. R.; Dere, K. P.; Landi, E.; Del Zanna, G.; Mason, H. E.

    2016-04-01

    The freely available CHIANTI atomic database was first released in 1996 and has had a huge impact on the analysis and modeling of emissions from astrophysical plasmas. It contains data and software for modeling optically thin atom and positive ion emission from low density (≲1013 cm-3) plasmas from x-ray to infrared wavelengths. A key feature is that the data are assessed and regularly updated, with version 8 released in 2015. Atomic data for modeling the emissivities of 246 ions and neutrals are contained in CHIANTI, together with data for deriving the ionization fractions of all elements up to zinc. The different types of atomic data are summarized here and their formats discussed. Statistics on the impact of CHIANTI to the astrophysical community are given and examples of the diverse range of applications are presented.

  3. Atomic & Molecular Interactions

    SciTech Connect

    2002-07-12

    The Gordon Research Conference (GRC) on Atomic & Molecular Interactions was held at Roger Williams University, Bristol, RI. Emphasis was placed on current unpublished research and discussion of the future target areas in this field.

  4. Atom chip gravimeter

    NASA Astrophysics Data System (ADS)

    Schubert, Christian; Abend, Sven; Gebbe, Martina; Gersemann, Matthias; Ahlers, Holger; Müntinga, Hauke; Matthias, Jonas; Sahelgozin, Maral; Herr, Waldemar; Lämmerzahl, Claus; Ertmer, Wolfgang; Rasel, Ernst

    2016-04-01

    Atom interferometry has developed into a tool for measuring rotations [1], accelerations [2], and testing fundamental physics [3]. Gravimeters based on laser cooled atoms demonstrated residual uncertainties of few microgal [2,4] and were simplified for field applications [5]. Atomic gravimeters rely on the interference of matter waves which are coherently manipulated by laser light fields. The latter can be interpreted as rulers to which the position of the atoms is compared. At three points in time separated by a free evolution, the light fields are pulsed onto the atoms. First, a coherent superposition of two momentum states is produced, then the momentum is inverted, and finally the two trajectories are recombined. Depending on the acceleration the atoms experienced, the number of atoms detected in the output ports will change. Consequently, the acceleration can be determined from the output signal. The laser cooled atoms with microkelvin temperatures used in state-of-the-art gravimeters impose limits on the accuracy [4]. Therefore, ultra-cold atoms generated by Bose-Einstein condensation and delta-kick collimation [6,7] are expected to be the key for further improvements. These sources suffered from a low flux implying an incompatible noise floor, but a competitive performance was demonstrated recently with atom chips [8]. In the compact and robust setup constructed for operation in the drop tower [6] we demonstrated all steps necessary for an atom chip gravimeter with Bose-Einstein condensates in a ground based operation. We will discuss the principle of operation, the current performance, and the perspectives to supersede the state of the art. The authors thank the QUANTUS cooperation for contributions to the drop tower project in the earlier stages. This work is supported by the German Space Agency (DLR) with funds provided by the Federal Ministry for Economic Affairs and Energy (BMWi) due to an enactment of the German Bundestag under grant numbers DLR 50WM

  5. Improved Atomizer Resists Clogging

    NASA Technical Reports Server (NTRS)

    Dea, J. Y.

    1983-01-01

    Improved constant-output atomizer has conical orifice that permits air to sweep out all liquid thoroughly and prevent any buildup of liquid or dissolved solids. Capillary groove guides liquid to gas jet. Simple new design eliminates clogging.

  6. Disentangling of two intertwined chains

    NASA Astrophysics Data System (ADS)

    Baumgärtner, A.; Muthukumar, M.

    1986-01-01

    The nonequilibrium process of disentangling of two self-avoiding polymer chains is investigated using Monte Carlo methods. The initial configuration of the two chains corresponds to a double helix of M turns. Chains consisting of N=8M+1 segments with M=2, 4, and 8 have been simulated. The disentangling process is found to take place in two distinct stages. The first step is the softening of the original double helix configuration to form interpenetrating chains with their centers of mass not far away from each other. This process takes a typical time of the order of N3.0 ± 0.2 . During the first stage, the center of mass of the either strand obeys the diffusion law, with the diffusion coefficient D˜N-(1.6±0.2) . The second stage involves the actual unraveling of the interpenetrating chains to form the isolated coils. The time taken for this step is found to scale as N3.3±0.2 . After the disentangling is complete, we recover the Rouse behavior, D˜N-1 for the center of mass diffusion of each coil.

  7. Data-driven backward chaining

    NASA Technical Reports Server (NTRS)

    Haley, Paul

    1991-01-01

    The C Language Integrated Production System (CLIPS) cannot effectively perform sound and complete logical inference in most real-world contexts. The problem facing CLIPS is its lack of goal generation. Without automatic goal generation and maintenance, forward chaining can only deduce all instances of a relationship. Backward chaining, which requires goal generation, allows deduction of only that subset of what is logically true which is also relevant to ongoing problem solving. Goal generation can be mimicked in simple cases using forward chaining. However, such mimicry requires manual coding of additional rules which can assert an inadequate goal representation for every condition in every rule that can have corresponding facts derived by backward chaining. In general, for N rules with an average of M conditions per rule the number of goal generation rules required is on the order of N*M. This is clearly intractable from a program maintenance perspective. We describe the support in Eclipse for backward chaining which it automatically asserts as it checks rule conditions. Important characteristics of this extension are that it does not assert goals which cannot match any rule conditions, that 2 equivalent goals are never asserted, and that goals persist as long as, but no longer than, they remain relevant.

  8. 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.

  9. Optical atomic magnetometer

    DOEpatents

    Budker, Dmitry; Higbie, James; Corsini, Eric P

    2013-11-19

    An optical atomic magnetometers is provided operating on the principles of nonlinear magneto-optical rotation. An atomic vapor is optically pumped using linearly polarized modulated light. The vapor is then probed using a non-modulated linearly polarized light beam. The resulting modulation in polarization angle of the probe light is detected and used in a feedback loop to induce self-oscillation at the resonant frequency.

  10. Atomizing nozzle and method

    SciTech Connect

    Ting, Jason; Anderson, Iver E.; Terpstra, Robert L.

    2000-03-16

    A high pressure close-coupled gas atomizing nozzle includes multiple discrete gas jet discharge orifices having aerodynamically designed convergent-divergent geometry with an first converging section communicated to a gas supply manifold and to a diverging section by a constricted throat section to increase atomizing gas velocity. The gas jet orifices are oriented at gas jet apex angle selected relative to the melt supply tip apex angle to establish a melt aspiration condition at the melt supply tip.

  11. 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.

  12. Correctly Expressing Atomic Weights

    NASA Astrophysics Data System (ADS)

    Paolini, Moreno; Cercignani, Giovanni; Bauer, Carlo

    2000-11-01

    Very often, atomic or molecular weights are expressed as dimensionless quantities, but although the historical importance of their definition as "pure numbers" is acknowledged, it is inconsistent with experimental formulas and with the theory of measure in general. Here, we propose on the basis of clear-cut formulas that, contrary to customary statements, atomic and molecular weights should be expressed as dimensional quantities (masses) in which the Dalton (= 1.663 x 10-24 g) is taken as the unit.

  13. Sharing the atom bomb

    SciTech Connect

    Chace, J.

    1996-01-01

    Shaken by the devastation of Hiroshima and Nagasaki and fearful that the American atomic monopoly would spark an arms race, Dean Acheson led a push in 1946 to place the bomb-indeed, all atomic energy-under international control. But as the memories of wartime collaboration faded, relations between the superpowers grew increasingly tense, and the confrontational atmosphere undid his proposal. Had Acheson succeeded, the Cold War might not have been. 2 figs.

  14. Spin currents and filtering behavior in zigzag graphene nanoribbons with adsorbed molybdenum chains

    NASA Astrophysics Data System (ADS)

    García-Fuente, A.; Gallego, L. J.; Vega, A.

    2015-04-01

    By means of density-functional-theoretic calculations, we investigated the structural, electronic and transport properties of hydrogen-passivated zigzag graphene nanoribbons (ZGNRs) on which a one-atom-thick Mo chain was adsorbed (with or without one or two missing atoms), or in which the passivating hydrogen atoms were replaced by Mo atoms. Mo-passivated ZGNRs proved to be nonmagnetic. ZGNRs with an adsorbed defect-free Mo chain were most stable with the Mo atoms forming dimers above edge bay sites, which suppressed the magnetic moments of the C atoms in that half of the ribbon; around the Fermi level of these systems, each spin component had a transmission channel via the Mo spz band and one had an additional channel created by polarization of the ZGNR π* band, leading to a net spin current. The absence of an Mo dimer from an Mo chain adsorbed at the ZGNR edge made the system a perfect spin filter at low voltage bias by suppressing the Mo spz band channels. Thus this last kind of hybrid system is a potential spin valve.

  15. Atomic mass compilation 2012

    SciTech Connect

    Pfeiffer, B.; Venkataramaniah, K.; Czok, U.; Scheidenberger, C.

    2014-03-15

    Atomic mass reflects the total binding energy of all nucleons in an atomic nucleus. Compilations and evaluations of atomic masses and derived quantities, such as neutron or proton separation energies, are indispensable tools for research and applications. In the last decade, the field has evolved rapidly after the advent of new production and measuring techniques for stable and unstable nuclei resulting in substantial ameliorations concerning the body of data and their precision. Here, we present a compilation of atomic masses comprising the data from the evaluation of 2003 as well as the results of new measurements performed. The relevant literature in refereed journals and reports as far as available, was scanned for the period beginning 2003 up to and including April 2012. Overall, 5750 new data points have been collected. Recommended values for the relative atomic masses have been derived and a comparison with the 2003 Atomic Mass Evaluation has been performed. This work has been carried out in collaboration with and as a contribution to the European Nuclear Structure and Decay Data Network of Evaluations.

  16. To Slip or Snap: Finite Length Chains and Yield Mechanisms in Polyethylene Fibers

    NASA Astrophysics Data System (ADS)

    O'Connor, Thomas; Robbins, Mark

    2015-03-01

    Understanding the microscopic mechanisms of yield in oriented polymer fibers is a long -standing problem. Advances in polymer processing have produced highly ordered polyethylene (PE) fibers with tensile strengths between 4-7 GPa, but these values are far less than the theoretical limiting strength of 25 Gpa due to C-C bond scission. This reduction in strength is caused by the presence of defects within the fiber. The simplest type of defect is chain ends which reflect the finite length of polymer chains. The presence of chain ends allows a polymer fiber to yield by chain slip without scission of covalent bonds. Here we present extensive united atom (UA) and all atom (AA) molecular dynamics simulations of crystalline PE fibers subjected to uniaxial tension. The fibers are fully aligned crystals constructed from chains of finite length N, with N spanning 3 orders of magnitude (101 -104 monomers). We explore the yield behavior of these systems and relate it to the dynamics of the underlying chain end defects. UA tensile strengths are systematically smaller than AA by a factor of about 3. Both show a saturation in tensile strength as N rises above 500 monomers. This reflects a saturation in the stress for chain ends to slip and implies a maximum tensile strength of 6 Gpa. Financial Support from: NSF IGERT-0801471; US Army Research Laboratory W911NF-12-2-0022.

  17. An all-atom structure-based potential for proteins: bridging minimal models with all-atom empirical forcefields.

    PubMed

    Whitford, Paul C; Noel, Jeffrey K; Gosavi, Shachi; Schug, Alexander; Sanbonmatsu, Kevin Y; Onuchic, José N

    2009-05-01

    Protein dynamics take place on many time and length scales. Coarse-grained structure-based (Go) models utilize the funneled energy landscape theory of protein folding to provide an understanding of both long time and long length scale dynamics. All-atom empirical forcefields with explicit solvent can elucidate our understanding of short time dynamics with high energetic and structural resolution. Thus, structure-based models with atomic details included can be used to bridge our understanding between these two approaches. We report on the robustness of folding mechanisms in one such all-atom model. Results for the B domain of Protein A, the SH3 domain of C-Src Kinase, and Chymotrypsin Inhibitor 2 are reported. The interplay between side chain packing and backbone folding is explored. We also compare this model to a C(alpha) structure-based model and an all-atom empirical forcefield. Key findings include: (1) backbone collapse is accompanied by partial side chain packing in a cooperative transition and residual side chain packing occurs gradually with decreasing temperature, (2) folding mechanisms are robust to variations of the energetic parameters, (3) protein folding free-energy barriers can be manipulated through parametric modifications, (4) the global folding mechanisms in a C(alpha) model and the all-atom model agree, although differences can be attributed to energetic heterogeneity in the all-atom model, and (5) proline residues have significant effects on folding mechanisms, independent of isomerization effects. Because this structure-based model has atomic resolution, this work lays the foundation for future studies to probe the contributions of specific energetic factors on protein folding and function. PMID:18837035

  18. Electronic properties of Fibonacci and random Si-Ge chains.

    PubMed

    Vasconcelos, M S; Azevedo, David L; Hadad, A; Galvão, D S

    2011-10-12

    In this paper we address a theoretical calculation of the electronic spectra of an Si-Ge atomic chain that is arranged in a Fibonacci quasi-periodic sequence, by using a semi-empirical quantum method based on the Hückel extended model. We apply the Fibonacci substitutional sequences in the atomic building blocks A(Si) and B(Ge) through the inflation rule or a recursion relation. In our ab initio calculations we use only a single point, which is sufficient for considering all the orbitals and charge distribution across the entire system. Although the calculations presented here are more complete than the models adopted in the literature which take into account the electronic interaction only up to the second and third neighbors, an interesting property remains in their electronic spectra: the fractality (which is the main signature of this kind of system). We discuss this fractality of the spectra and we compare them with the random arrangement of the Si-Ge atomic chain, and with previous results based on the tight-binding approximation of the Schrödinger equation considering up to the nearest neighbor. PMID:21937784

  19. Chain Length and Grafting Density Dependent Enhancement in the Hydrolysis of Ester-Linked Polymer Brushes.

    PubMed

    Melzak, Kathryn A; Yu, Kai; Bo, Deng; Kizhakkedathu, Jayachandran N; Toca-Herrera, José L

    2015-06-16

    Poly(N,N-dimethylacrylamide) (PDMA) brushes with different grafting density and chain length were grown from an ester group-containing initiator using surface-initiated polymerization. Hydrolysis of the PDMA chains from the surface was monitored by measuring thickness of the polymer layer by ellipsometry and extension length by atomic force microscopy. It was found that the initial rate of cleavage of one end-tethered PDMA chains was dependent on the grafting density and chain length; the hydrolysis rate was faster for high grafting density brushes and brushes with higher molecular weights. Additionally, the rate of cleavage of polymer chains during a given experiment changed by up to 1 order of magnitude as the reaction progressed, with a distinct transition to a lower rate as the grafting density decreased. Also, polymer chains undergo selective cleavage, with longer chains in a polydisperse brush being preferentially cleaved at one stage of the hydrolysis reaction. We suggest that the enhanced initial hydrolysis rates seen at high grafting densities and high chain lengths are due to mechanical activation of the ester bond connecting the polymer chains to the surface in association with high lateral pressure within the brush. These results have implications for the preparation of polymers brushes, their stability under harsh conditions, and the analysis of polymer brushes from partial hydrolysates. PMID:26010390

  20. Ligand chain length conveys thermochromism.

    PubMed

    Ganguly, Mainak; Panigrahi, Sudipa; Chandrakumar, K R S; Sasmal, Anup Kumar; Pal, Anjali; Pal, Tarasankar

    2014-08-14

    Thermochromic properties of a series of non-ionic copper compounds have been reported. Herein, we demonstrate that Cu(II) ion with straight-chain primary amine (A) and alpha-linolenic (fatty acid, AL) co-jointly exhibit thermochromic properties. In the current case, we determined that thermochromism becomes ligand chain length-dependent and at least one of the ligands (A or AL) must be long chain. Thermochromism is attributed to a balanced competition between the fatty acids and amines for the copper(II) centre. The structure-property relationship of the non-ionic copper compounds Cu(AL)2(A)2 has been substantiated by various physical measurements along with detailed theoretical studies based on time-dependent density functional theory. It is presumed from our results that the compound would be a useful material for temperature-sensor applications. PMID:24943491

  1. Chain reconfiguration in active noise

    NASA Astrophysics Data System (ADS)

    Samanta, Nairhita; Chakrabarti, Rajarshi

    2016-05-01

    In a typical single molecule experiment, the dynamics of an unfolded protein is studied by determining the reconfiguration time using long-range Förster resonance energy transfer, where the reconfiguration time is the characteristic decay time of the position correlation between two residues of the protein. In this paper we theoretically calculate the reconfiguration time for a single flexible polymer in the presence of active noise. The study suggests that though the mean square displacement grows faster, the chain reconfiguration is always slower in the presence of long-lived active noise with exponential temporal correlation. Similar behavior is observed for a worm-like semi-flexible chain and a Zimm chain. However it is primarily the characteristic correlation time of the active noise and not the strength that controls the increase in the reconfiguration time. In brief, such active noise makes the polymer move faster but the correlation loss between the monomers becomes slow.

  2. Quantum information processing with trapped ion chains

    NASA Astrophysics Data System (ADS)

    Manning, Timothy Andrew

    Trapped atomic ion systems are currently the most advanced platform for quantum information processing. Their long coherence times, pristine state initialization and detection, and precisely controllable and versatile interactions make them excellent quantum systems for experiments in quantum computation and quantum simulation. One of the more promising schemes for quantum computing consists of performing single and multi-qubit quantum gates on qubits in a linear ion crystal. Some of the key challenges of scaling such a system are the individual addressing of arbitrary subsets of ions and controlling the growing complexity of motional mode interactions as the number of qubits increases or when the gates are performed faster. Traditional entangling quantum gates between ion qubits use laser pulses to couple the qubit states to the collective motion of the crystal, thereby generating a spin-spin interaction that can produce entanglement between selected qubits. The intrinsic limitations on the performance of gates using this method can be alleviated by applying optimally shaped pulses instead of pulses with constant amplitude. This thesis explains the theory behind this pulse shaping scheme and how it is implemented on a chain of Yb ions held in a linear radiofrequency 'Paul' trap. Several experiments demonstrate the technique in chains of two, three, and five ions using various types of pulse shapes. A tightly focused individual addressing beam allows us to apply the entangling gates to a target pair of ions, and technical issues related to such tight focusing are discussed. Other advantages to the pulse shaping scheme include a robustness against detuning errors and the possibility of suppressing undesirable coupling due to optical spillover on neighboring ions. Combined with ion shuttling, we harness these features to perform sequential gates to different qubit pairs in order to create genuine tripartite entangled states and demonstrate the programmable quantum

  3. Leading a supply chain turnaround.

    PubMed

    Slone, Reuben E

    2004-10-01

    Just five years ago, salespeople at Whirlpool were in the habit of referring to their supply chain organization as the "sales disablers." Now the company excels at getting products to the right place at the right time--while managing to keep inventories low. How did that happen? In this first-person account, Reuben Slone, Whirlpool's vice president of Global Supply Chain, describes how he and his colleagues devised the right supply chain strategy, sold it internally, and implemented it. Slone insisted that the right focal point for the strategy was the satisfaction of consumers at the end of the supply chain. Most supply chain initiatives do the opposite: They start with the realities of a company's manufacturing base and proceed from there. Through a series of interviews with trade customers large and small, his team identified 27 different capabilities that drove industry perceptions of Whirlpool's performance. Knowing it was infeasible to aim for world-class performance across all of them, Slone weighed the costs of excelling at each and found the combination of initiatives that would provide overall competitive advantage. A highly disciplined project management office and broad training in project management were key to keeping work on budget and on benefit. Slone set an intense pace--three "releases" of new capabilities every month--that the group maintains to this day. Lest this seem like a technology story, however, Slone insists it is just as much a "talent renaissance." People are proud today to be part of Whirlpool's supply chain organization, and its new generation of talent will give the company a competitive advantage for years to come. PMID:15559580

  4. Peierls distortion of endohedral atoms in clathrate I

    NASA Astrophysics Data System (ADS)

    Tomono, Hidekazu; Tsumuraya, Kazuo

    2008-03-01

    The guest atom displacements in type II clathrates have been reported on experimental and theoretical points of view. The displacements are reported to be 0.6 å from the cage center of the Si28 cage to the hexagonal in the hydrogen terminated double caged Si28 cluster [1]. The distortion can be expected to occur in the type I clathrate which forms with bamboo structures in the x, y, and z directions. The guest atoms show Peiels distortion when we calculate the equilibrium distances between the two Na atoms which locate at the neighboring Si24 cages in the bamboo structure using periodic density functional calculation. The binding energy between the guest atoms is -0.10 eV/Na2. We also confirm the tendency of the Peierls distotion from the force directions of guest atoms in the double unit cells that contain four Na atoms in one dimension; We will propose the cohesion mechanism of the clathrates that the clathrates are precipitated states of the connecting endohedral atoms in the 14 group atoms. So are the hydroclathrates in which the guest molecules bind each other with chains. [1] H. Takenaka and K. Tsumuraya, Mater. Trans. 47, 63 (2006).

  5. Differential evolution Markov chain with snooker updater and fewer chains

    SciTech Connect

    Vrugt, Jasper A; Ter Braak, Cajo J F

    2008-01-01

    Differential Evolution Markov Chain (DE-MC) is an adaptive MCMC algorithm, in which multiple chains are run in parallel. Standard DE-MC requires at least N=2d chains to be run in parallel, where d is the dimensionality of the posterior. This paper extends DE-MC with a snooker updater and shows by simulation and real examples that DE-MC can work for d up to 50--100 with fewer parallel chains (e.g. N=3) by exploiting information from their past by generating jumps from differences of pairs of past states. This approach extends the practical applicability of DE-MC and is shown to be about 5--26 times more efficient than the optimal Normal random walk Metropolis sampler for the 97.5% point of a variable from a 25--50 dimensional Student T{sub 3} distribution. In a nonlinear mixed effects model example the approach outperformed a block-updater geared to the specific features of the model.

  6. First-principles simulations for excitation of currents in linear carbon chains under femtosecond laser pulse irradiation

    NASA Astrophysics Data System (ADS)

    Su, Gaoshi; Jiang, Lan; Wang, Feng; Qu, Liangti; Lu, Yongfeng

    2016-07-01

    We discuss the response of linear carbon chains to a femtosecond laser pulse. The influence of the chain structure on the excited currents was taken into account. The simulation results showed that excited currents were reversible when laser intensity was relatively weak. An unexpected decrease of current amplitude was found for a laser pulse with a wavelength of 200 nm, which may indicate the transient break of pi bonds in linear carbon chains. For chains with more than 10 atoms, the excited current oscillated with increasing amplitude during simulation time, which was due to the formation of plasma-like resonance.

  7. Tuning coercivity via iron chains in phthalocyanine thin films

    NASA Astrophysics Data System (ADS)

    Werber, Mathew Stephen

    We investigated the properties of magnetic hysteresis loops of Iron Phthalocyanine (FePc) thin films using a Vibrating Sample Magnetometer (VSM). The FePc thin films were deposited onto heated silicon substrates. During deposition the FePc molecules self-assemble into small crystallites ranging in size from 30 to 300 nm on average. Due to the planar shape of the molecule, chains of iron atoms are formed. The magnetic interaction within a chain is much stronger than between chains, making these thin films quasi-one-dimensional magnetic systems. The average length of the major axis of the grains increases with the temperature of the substrate (deposition temperature). Essentially the thin films are made up of many randomly oriented iron chains of variable length, which are parallel to the substrate surface. We show that the coercivity of hysteresis loops measured at 2 K increases linearly with the average major axis grain length. From interpolation, the minimum average grain length for hysteresis to occur is 8 nm, and every additional nano-meter in length increases the coercivity by 72 Oe. By measuring hysteresis loops of many thin films of varying thickness we found that the saturation magnetization is 31 emu/cm3. This corresponds to 2.0 +/- 0.6 micro B per iron ion, as compared to 2.22 microB for iron in a 3D lattice at 0 K. The choice of substrate also affects the hysteresis properties. Samples deposited on silicon substrates that had first been coated in gold with a rms roughness of approximately 1 nm will show much lower coercivity than corresponding silicon substrate samples. The planar gold surface allows for a different growth pattern in which the chains form vertically, perpendicular to the substrate. This lower coercivity suggests that the chains are shorter when vertically oriented.

  8. Phase diagram and entanglement of two interacting topological Kitaev chains

    NASA Astrophysics Data System (ADS)

    Herviou, Loïc; Mora, Christophe; Le Hur, Karyn

    2016-04-01

    A superconducting wire described by a p -wave pairing and a Kitaev Hamiltonian exhibits Majorana fermions at its edges and is topologically protected by symmetry. We consider two Kitaev wires (chains) coupled by a Coulomb-type interaction and study the complete phase diagram using analytical and numerical techniques. A topological superconducting phase with four Majorana fermions occurs until moderate interactions between chains. For large interactions, both repulsive and attractive, by analogy with the Hubbard model, we identify Mott phases with Ising-type magnetic order. For repulsive interactions, the Ising antiferromagnetic order favors the occurrence of orbital currents spontaneously breaking time-reversal symmetry. By strongly varying the chemical potentials of the two chains, quantum phase transitions towards fully polarized (empty or full) fermionic chains occur. In the Kitaev model, the quantum critical point separating the topological superconducting phase and the polarized phase belongs to the universality class of the critical Ising model in two dimensions. When increasing the Coulomb interaction between chains, then we identify an additional phase corresponding to two critical Ising theories (or two chains of Majorana fermions). We confirm the existence of such a phase from exact mappings and from the concept of bipartite fluctuations. We show the existence of negative logarithmic corrections in the bipartite fluctuations, as a reminiscence of the quantum critical point in the Kitaev model. Other entanglement probes such as bipartite entropy and entanglement spectrum are also used to characterize the phase diagram. The limit of large interactions can be reached in an equivalent setup of ultracold atoms and Josephson junctions.

  9. Atom-atom inelastic collisions and three-body atomic recombination in weakly ionized argon plasmas

    NASA Technical Reports Server (NTRS)

    Braun, C. G.; Kunc, J. A.

    1989-01-01

    A stationary collisional-radiative model including both inelastic electron-atom and atom-atom collisions is used to examine nonequilibrium weakly ionized argon plasmas with atomic densities 10 to the 16th to 10 to the 20th/cu cm, temperatures below 6000 K, and with different degrees of radiation trapping. It is shown that three-body atomic recombination becomes important at high particle densities. Comparison is made between the present approach and Thomson's theory for atomic recombination.

  10. Atomic spectrometry update - atomic mass spectrometry.

    SciTech Connect

    Bacon, J.; Crain, J. S.; McMahon, A. W.; Williams, J. G.; Analytical Chemistry Laboratory; The Macaulay Land Use Research Inst.; Manchester Metropolitan Univ.; Imperial Coll.

    1996-10-01

    The MS and XRF updates have been published together since their introduction in 1988. In the last few years, however, the two sections have been prepared independently of each other and it therefore seemed appropriate to publish the two sections separately. With effect from this issue, the MS Update will appear in the October issue of JAAS and the XRF Update in the November issue. The format used for the MS section is broadly similar to that used last year, with some additional sub-headings. This Update is intended to cover all atomic and stable isotopic MS techniques, but not those used in studies of fundamental nuclear physics and exotic nuclei far from stability. Also excluded are those reports in which MS is used as a tool in the study of molecular processes and of gaseous components. the review is based on critical selection of developments in instrumentation and methodology, notable for their innovation, originality or achievement of significant advances, and is not intended to be comprehensive in its coverage. Conference papers are only included if they contain enough information to show they meet these criteria, and our policy in general remains one of waiting for a development to appear in a full paper before inclusion in the review. a similar policy applies to foreign language papers unlikely to reach a wide audience. Routine applications of atomic MS are not included in this Update and the reader is referred to the Updates on Industrial Analysis: Metals, Chemicals and Advanced Materials (96/416), Environmental Analysis (96/1444) and Clinical and Biological Materials, Food and Beverages (96/2479). Also excluded are those applications, even if not routine, which use atomic spectroscopy as a tool for the study of a non-atomic property, for example, the use of stable isotope labeling of carbon or nitrogen in biomolecules in metabolic studies. There have been few general reviews on atomic MS of note in the period covered by this update. That of Colodner et al

  11. Atomic resolution holography.

    PubMed

    Hayashi, Kouichi

    2014-11-01

    Atomic resolution holography, such as X-ray fluorescence holography (XFH)[1] and photoelectron holography (PH), has the attention of researcher as an informative local structure analysis, because it provides three dimensional atomic images around specific elements within a range of a few nanometers. It can determine atomic arrangements around a specific element without any prior knowledge of structures. It is considered that the atomic resolution holographic is a third method of structural analysis at the atomic level after X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS). As known by many researchers, XRD and XAFS are established methods that are widespread use in various fields. XRD and XAFS provide information on long-range translational periodicities and very local environments, respectively, whereas the atomic resolution holography gives 3D information on the local order and can visualize surrounding atoms with a large range of coordination shells. We call this feature "3D medium-range local structure observation".In addition to this feature, the atomic resolution holography is very sensitive to the displacement of atoms from their ideal positions, and one can obtain quantitative information about local lattice distortions by analyzing reconstructed atomic images[2] When dopants with different atomic radii from the matrix elements are present, the lattices around the dopants are distorted. However, using the conventional methods of structural analysis, one cannot determine the extent to which the local lattice distortions are preserved from the dopants. XFH is a good tool for solving this problem.Figure 1 shows a recent achievement on a relaxor ferroelectric of Pb(Mg1/3Nb2/3)O3 (PMN) using XFH. The structural studies of relaxor ferroelectrics have been carried out by X-ray or neutron diffractions, which suggested rhombohedral distortions of their lattices. However, their true pictures have not been obtained, yet. The Nb Kα holograms showed

  12. Renormalization-group methods for the spectra of disordered chains

    NASA Astrophysics Data System (ADS)

    Robbins, Mark O.; Koiller, Belita

    1983-06-01

    A family of real-space renormalization techniques for calculating the Green's functions of disordered chains is developed and explored. The techniques are based on a recently proposed renormalization method which is rederived here and shown to be equivalent to a virtual-crystal approximation on a renormalized Hamiltonian. The derivation suggests how other conventional alloy methods can be coupled to the renormalization concept. Various examples are discussed. Short-range order in the occupation of alloy sites and very general disorder in the Hamiltonian-diagonal, off-diagonal, and environmental-are readily incorporated. The techniques are exact in the limits of high and low concentration and of complete short-range order and for the Lloyd model. All states are found to be localized, in agreement with exact treatments. Results for the alloy density of states are presented for various cases and compared to numerical simulations on long chains (105 atoms).

  13. Yeast phenylalanine transfer RNA: atomic coordinates and torsion angles.

    PubMed Central

    Quigley, G J; Seeman, N C; Wang, A H; Suddath, F L; Rich, A

    1975-01-01

    The atomic coordinates of yeast phenylalanine transfer RNA (tRNA) as well as the torsion angles of the polynucleotide chain are presented as derived from an x-ray diffraction analysis of orthorhombic crystals. A comparison is made between the coordinates obtained from analysis of monoclinic crystals of the same material. It is concluded that the molecule has substantially the same form in the orthorhombic and the monoclinic lattices, except for differences found between residues at the 3' end of the polynucleotides chain. A number of observations are made concerning hydrogen bonding interactions which may account for many of the residues conserved in all tRNA sequences. PMID:802512

  14. Novette chain design and performance

    SciTech Connect

    Hunt, J.T.; Speck, D.R.

    1980-12-11

    The design and performance of the Novette laser system, which is a two-beam, two-wavelength (1.05 ..mu.. and 0.53 ..mu..) target irradiation facility using phosphate glass laser chains, are discussed with information on the glass properties, controlling factors in the design selection, and projected performance with varying operating conditions. (LCL)

  15. Categorization Using Chains of Examples.

    ERIC Educational Resources Information Center

    Heit, Evan

    1992-01-01

    Presents a mathematical-categorization model using multiple-step chains of reasoning (CORs) and memory for examples. In 5 experiments, 144 undergraduates memorized descriptions of fictional people, then made predictions from incomplete descriptions using 1-, 2-, or 3-step CORs. The multiple-step context model with one- and two-step inference…

  16. Origin of the smaller conductances of Rh, Pb, and Co atomic junctions in hydrogen environment

    SciTech Connect

    Li, Xue; Chen, Mingyan; Ye, Xiang; Xie, Yi-qun; Ke, San-huang

    2015-02-14

    We study theoretically the structural and electronic origins of the smaller conductances (one conductance quantum, G{sub 0}, and smaller) of Rh, Pb, and Co metal atomic junctions (MAJs) in a hydrogen environment, as were measured in recent experiments. For the Rh MAJs, the 1G{sub 0} conductance is attributed to a stable contact bridged by a single hydrogen molecule whose antibonding state provides a single transport channel. For the Pb and Co MAJs the 1G{sub 0} conductance is, however, ascribed to a linear atomic chain adsorbing two dissociated H atoms, which largely reduces the density of states at the Fermi energy with respect to the pure ones. On the other hand, the small conductances of 0.3G{sub 0} (Rh) and 0.2G{sub 0} (Co) are due to H-decorated atomic chains connected to electrodes by a H atom.

  17. Supply chain challenges. building relationships.

    PubMed

    Beth, Scott; Burt, David N; Copacino, William; Gopal, Chris; Lee, Hau L; Lynch, Robert Porter; Morris, Sandra

    2003-07-01

    Supply chain management is all about software and systems, right? Put in the best technology, sit back, and watch as your processes run smoothly and the savings roll in? Apparently not. When HBR convened a panel of leading thinkers in the field of supply chain management, technology was not top of mind. People and relationships were the dominant issues of the day. The opportunities and problems created by globalization, for example, are requiring companies to establish relationships with new types of suppliers. The ever-present pressure for speed and cost containment is making it even more important to break down stubbornly high internal barriers and establish more effective cross-functional relationships. The costs of failure have never been higher. The leading supply chain performers are applying new technology, new innovations, and process thinking to far greater advantage than the laggards, reaping tremendous gains in all the variables that affect shareholder value: cost, customer service, asset productivity, and revenue generation. And the gap between the leaders and the losers is growing in almost every industry. This roundtable gathered many of the leading thinkers and doers in the field of supply chain management, including practitioners Scott Beth of Intuit, Sandra Morris of Intel, and Chris Gopal of Unisys. David Burt of the University of San Diego and Stanford's Hau Lee bring the latest research from academia. Accenture's William Copacino and the Warren Company's Robert Porter Lynch offer the consultant's perspectives. Together, they take a wide-ranging view of such topics as developing talent, the role of the chief executive, and the latest technologies, exploring both the tactical and the strategic in the current state of supply chain management. PMID:12858712

  18. A new assessment of the alleged link between element 115 and element 117 decay chains

    NASA Astrophysics Data System (ADS)

    Forsberg, U.; Rudolph, D.; Fahlander, C.; Golubev, P.; Sarmiento, L. G.; Åberg, S.; Block, M.; Düllmann, Ch. E.; Heßberger, F. P.; Kratz, J. V.; Yakushev, A.

    2016-09-01

    A novel rigorous statistical treatment is applied to available data (May 9, 2016) from search and spectroscopy experiments on the elements with atomic numbers Z = 115 and Z = 117. The present analysis implies that the hitherto proposed cross-reaction link between α-decay chains associated with the isotopes 293117 and 289115 is highly improbable.

  19. SPRITE and ASSAM: web servers for side chain 3D-motif searching in protein structures

    PubMed Central

    Nadzirin, Nurul; Gardiner, Eleanor J.; Willett, Peter; Artymiuk, Peter J.; Firdaus-Raih, Mohd

    2012-01-01

    Similarities in the 3D patterns of amino acid side chains can provide insights into their function despite the absence of any detectable sequence or fold similarities. Search for protein sites (SPRITE) and amino acid pattern search for substructures and motifs (ASSAM) are graph theoretical programs that can search for 3D amino side chain matches in protein structures, by representing the amino acid side chains as pseudo-atoms. The geometric relationship of the pseudo-atoms to each other as a pattern can be represented as a labeled graph where the pseudo-atoms are the graph's nodes while the edges are the inter-pseudo-atomic distances. Both programs require the input file to be in the PDB format. The objective of using SPRITE is to identify matches of side chains in a query structure to patterns with characterized function. In contrast, a 3D pattern of interest can be searched for existing occurrences in available PDB structures using ASSAM. Both programs are freely accessible without any login requirement. SPRITE is available at http://mfrlab.org/grafss/sprite/ while ASSAM can be accessed at http://mfrlab.org/grafss/assam/. PMID:22573174

  20. Cold Atom Magnetometers

    NASA Astrophysics Data System (ADS)

    Eto, Yujiro; Sadrove, Mark; Hirano, Takuya

    Detection of weak magnetic fields with high spatial resolution is an important technology for various applications such as biological imaging, detection of MRI signals and fundamental physics. Cold atom magnetometry enables 10-11 T/ Hz sqrt{text{Hz}} sensitivities at the micron scale, that is, at the scale of a typical biological cell size. This magnetometry takes advantage of unique properties of atomic gaseous Bose-Einstein condensates with internal spin degrees of freedom. In this chapter, we first overview various state-of-the-art magnetometers, addressing their sensitivities and spatial resolutions. Then we describe properties of spinor condensates, ultracold atom magnetometers, and the latest research developments achieved in the FIRST project, especially for the detection of alternate current magnetic fields using a spin-echo-based magnetometer. We also discuss future prospects of the magnetometers.

  1. Self-Organized Growth, Structure, and Magnetism of Monatomic Transition-Metal Oxide Chains

    NASA Astrophysics Data System (ADS)

    Ferstl, Pascal; Hammer, Lutz; Sobel, Christopher; Gubo, Matthias; Heinz, Klaus; Schneider, M. Alexander; Mittendorfer, Florian; Redinger, Josef

    2016-07-01

    We report on the self-organized growth of monatomic transition-metal oxide chains of (3 ×1 ) periodicity and unusual M O2 stoichiometry (M =Ni , Co, Fe, Mn) on Ir(100). We analyze their structural and magnetic properties by means of quantitative LEED, STM, and density functional theory (DFT) calculations. LEED analyses reveal a fascinating common atomic structure in which the transition-metal atoms sit above a missing-row structure of the surface and are coupled to the substrate only via oxygen atoms. This structure is confirmed by DFT calculations with structural parameters deviating by less than 1.7 pm. The DFT calculations predict that the NiO2 chains are nonmagnetic, CoO2 chains are ferromagnetic, while FeO2 and MnO2 are antiferromagnetic. All structures show only weak magnetic interchain coupling. Further, we demonstrate the growth of oxide chains of binary alloys of Co and Ni or Fe on Ir(100), which allows us to produce well-controlled ensembles of ferromagnetic chains of different lengths separated by nonmagnetic or antiferromagnetic segments.

  2. Self-Organized Growth, Structure, and Magnetism of Monatomic Transition-Metal Oxide Chains.

    PubMed

    Ferstl, Pascal; Hammer, Lutz; Sobel, Christopher; Gubo, Matthias; Heinz, Klaus; Schneider, M Alexander; Mittendorfer, Florian; Redinger, Josef

    2016-07-22

    We report on the self-organized growth of monatomic transition-metal oxide chains of (3×1) periodicity and unusual MO_{2} stoichiometry (M=Ni, Co, Fe, Mn) on Ir(100). We analyze their structural and magnetic properties by means of quantitative LEED, STM, and density functional theory (DFT) calculations. LEED analyses reveal a fascinating common atomic structure in which the transition-metal atoms sit above a missing-row structure of the surface and are coupled to the substrate only via oxygen atoms. This structure is confirmed by DFT calculations with structural parameters deviating by less than 1.7 pm. The DFT calculations predict that the NiO_{2} chains are nonmagnetic, CoO_{2} chains are ferromagnetic, while FeO_{2} and MnO_{2} are antiferromagnetic. All structures show only weak magnetic interchain coupling. Further, we demonstrate the growth of oxide chains of binary alloys of Co and Ni or Fe on Ir(100), which allows us to produce well-controlled ensembles of ferromagnetic chains of different lengths separated by nonmagnetic or antiferromagnetic segments. PMID:27494483

  3. Single atoms in a MOT

    SciTech Connect

    Meschede, Dieter; Ueberholz, Bernd; Gomer, Victor; Knappe, Svenja; Reiter, Uwe; Schadwinkel, Harald; Strauch, Frank

    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.

  4. Generation and manipulation of super-resolution spherical magnetization chains.

    PubMed

    Gong, Liping; Wang, Lu; Zhu, Zhuqing; Wang, Xiaolei; Zhao, Hua; Gu, Bing

    2016-07-20

    Based on the inverse Faraday effect, the light-induced magnetization field distributions are investigated for a 4π tight focusing configuration with azimuthally polarized beams. It is found that a superlong (16λ) magnetization chain, composed of 19 subwavelength (0.44λ) spherical spots with longitudinal magnetization field, can be achieved in the focal volume of the objective. Moreover, the magnetic force on a magnetic particle or particle trains produced by tightly focused azimuthally polarized beams are calculated and exploited for the stable trapping of magnetic particles. These unique focal field distributions may find potential applications in confocal microscopy, atom control, and magneto-optical data storage. PMID:27463938

  5. Structural and magnetic properties of FeMnx chains (x =1 -6 ) supported on Cu2N /Cu (100)

    NASA Astrophysics Data System (ADS)

    Choi, Deung-Jang; Robles, Roberto; Gauyacq, Jean-Pierre; Ternes, Markus; Loth, Sebastian; Lorente, Nicolás

    2016-08-01

    Heterogeneous atomic magnetic chains are built by atom manipulation on a Cu2N /Cu (100) substrate. Their magnetic properties are studied and rationalized by a combined scanning tunneling microscopy (STM) and density functional theory (DFT) work completed by model Hamiltonian studies. The chains are built using Fe and Mn atoms ontop of the Cu atoms along the N rows of the Cu2N surface. Here, we present results for FeMnx chains (x =1 -6 ) emphasizing the evolution of the geometrical, electronic, and magnetic properties with chain size. By fitting our results to a Heisenberg Hamiltonian we have studied the exchange-coupling matrix elements J for different chains. For the shorter chains, x ≤2 , we have included spin-orbit effects in the DFT calculations, extracting the magnetic anisotropy energy. Our results are also fitted to a simple anisotropic spin Hamiltonian and we have extracted values for the longitudinal-anisotropy D and transversal-anisotropy E constants. These parameters together with the values for J allow us to compute the magnetic excitation energies of the system and to compare them with the experimental data.

  6. Atomization and Mixing Study

    NASA Technical Reports Server (NTRS)

    Ferrenberg, A.; Hunt, K.; Duesberg, J.

    1985-01-01

    The primary objective was the obtainment of atomization and mixing performance data for a variety of typical liquid oxygen/hydrocarbon injector element designs. Such data are required to establish injector design criteria and to provide critical inputs to liquid rocket engine combustor performance and stability analysis, and computational codes and methods. Deficiencies and problems with the atomization test equipment were identified, and action initiated to resolve them. Test results of the gas/liquid mixing tests indicated that an assessment of test methods was required. A series of 71 liquid/liquid tests were performed.

  7. Computer Modeling Of Atomization

    NASA Technical Reports Server (NTRS)

    Giridharan, M.; Ibrahim, E.; Przekwas, A.; Cheuch, S.; Krishnan, A.; Yang, H.; Lee, J.

    1994-01-01

    Improved mathematical models based on fundamental principles of conservation of mass, energy, and momentum developed for use in computer simulation of atomization of jets of liquid fuel in rocket engines. Models also used to study atomization in terrestrial applications; prove especially useful in designing improved industrial sprays - humidifier water sprays, chemical process sprays, and sprays of molten metal. Because present improved mathematical models based on first principles, they are minimally dependent on empirical correlations and better able to represent hot-flow conditions that prevail in rocket engines and are too severe to be accessible for detailed experimentation.

  8. Atomic Force Microscope

    SciTech Connect

    Day, R.D.; Russell, P.E.

    1988-12-01

    The Atomic Force Microscope (AFM) is a recently developed instrument that has achieved atomic resolution imaging of both conducting and non- conducting surfaces. Because the AFM is in the early stages of development, and because of the difficulty of building the instrument, it is currently in use in fewer than ten laboratories worldwide. It promises to be a valuable tool for obtaining information about engineering surfaces and aiding the .study of precision fabrication processes. This paper gives an overview of AFM technology and presents plans to build an instrument designed to look at engineering surfaces.

  9. Hirshfeld atom refinement

    PubMed Central

    Capelli, Silvia C.; Bürgi, Hans-Beat; Dittrich, Birger; Grabowsky, Simon; Jayatilaka, Dylan

    2014-01-01

    Hirshfeld atom refinement (HAR) is a method which determines structural parameters from single-crystal X-ray diffraction data by using an aspherical atom partitioning of tailor-made ab initio quantum mechanical molecular electron densities without any further approximation. Here the original HAR method is extended by implementing an iterative procedure of successive cycles of electron density calculations, Hirshfeld atom scattering factor calculations and structural least-squares refinements, repeated until convergence. The importance of this iterative procedure is illustrated via the example of crystalline ammonia. The new HAR method is then applied to X-ray diffraction data of the dipeptide Gly–l-Ala measured at 12, 50, 100, 150, 220 and 295 K, using Hartree–Fock and BLYP density functional theory electron densities and three different basis sets. All positions and anisotropic displacement parameters (ADPs) are freely refined without constraints or restraints – even those for hydrogen atoms. The results are systematically compared with those from neutron diffraction experiments at the temperatures 12, 50, 150 and 295 K. Although non-hydrogen-atom ADPs differ by up to three combined standard uncertainties (csu’s), all other structural parameters agree within less than 2 csu’s. Using our best calculations (BLYP/cc-pVTZ, recommended for organic molecules), the accuracy of determining bond lengths involving hydrogen atoms from HAR is better than 0.009 Å for temperatures of 150 K or below; for hydrogen-atom ADPs it is better than 0.006 Å2 as judged from the mean absolute X-ray minus neutron differences. These results are among the best ever obtained. Remarkably, the precision of determining bond lengths and ADPs for the hydrogen atoms from the HAR procedure is comparable with that from the neutron measurements – an outcome which is obtained with a routinely achievable resolution of the X-ray data of 0.65 Å. PMID:25295177

  10. Pulsed atomic soliton laser

    SciTech Connect

    Carr, L.D.; Brand, J.

    2004-09-01

    It is shown that simultaneously changing the scattering length of an elongated, harmonically trapped Bose-Einstein condensate from positive to negative and inverting the axial portion of the trap, so that it becomes expulsive, results in a train of self-coherent solitonic pulses. Each pulse is itself a nondispersive attractive Bose-Einstein condensate that rapidly self-cools. The axial trap functions as a waveguide. The solitons can be made robustly stable with the right choice of trap geometry, number of atoms, and interaction strength. Theoretical and numerical evidence suggests that such a pulsed atomic soliton laser can be made in present experiments.

  11. Warm Vapor Atom Interferometer

    NASA Astrophysics Data System (ADS)

    Biedermann, Grant; Wheeler, David; Jau, Yuan-Yu; McGuinness, Hayden

    2014-05-01

    We present a light pulse atom interferometer using room temperature rubidium vapor. Doppler sensitive stimulated Raman transitions forming the atom optical elements inherently select a cold velocity group for the interferometer. The interferometer is configured to be sensitive to accelerations. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  12. Atom Tunneling in Chemistry.

    PubMed

    Meisner, Jan; Kästner, Johannes

    2016-04-25

    Quantum mechanical tunneling of atoms is increasingly found to play an important role in many chemical transformations. Experimentally, atom tunneling can be indirectly detected by temperature-independent rate constants at low temperature or by enhanced kinetic isotope effects. In contrast, the influence of tunneling on the reaction rates can be monitored directly through computational investigations. The tunnel effect, for example, changes reaction paths and branching ratios, enables chemical reactions in an astrochemical environment that would be impossible by thermal transition, and influences biochemical processes. PMID:26990917

  13. Iowa Powder Atomization Technologies

    SciTech Connect

    2012-01-01

    The same atomization effect seen in a fuel injector is being applied to titanium metal resulting in fine titanium powders that are less than half the width of a human hair. Titanium melts above 3,000°F and is highly corrosive therefore requiring specialized containers. The liquid titanium is poured through an Ames Laboratory - USDOE patented tube which is intended to increase the energy efficiency of the atomization process, which has the ability to dramatically decrease the cost of fine titanium powders. This novel process could open markets for green manufacturing of titanium components from jet engines to biomedical implants.

  14. Iowa Powder Atomization Technologies

    ScienceCinema

    None

    2013-03-01

    The same atomization effect seen in a fuel injector is being applied to titanium metal resulting in fine titanium powders that are less than half the width of a human hair. Titanium melts above 3,000°F and is highly corrosive therefore requiring specialized containers. The liquid titanium is poured through an Ames Laboratory - USDOE patented tube which is intended to increase the energy efficiency of the atomization process, which has the ability to dramatically decrease the cost of fine titanium powders. This novel process could open markets for green manufacturing of titanium components from jet engines to biomedical implants.

  15. Korean atomic bomb victims.

    PubMed

    Sasamoto, Yukuo

    2009-01-01

    After colonizing Korea, Japan invaded China, and subsequently initiated the Pacific War against the United States, Britain, and their allies. Towards the end of the war, U.S. warplanes dropped atomic bombs on Hiroshima and Nagasaki, which resulted in a large number of Koreans who lived in Hiroshima and Nagasaki suffering from the effects of the bombs. The objective of this paper is to examine the history of Korea atomic bomb victims who were caught in between the U.S., Japan, the Republic of Korea (South Korea) and the Democratic People's Republic of Korea (North Korea). PMID:20521424

  16. Radioecological studies in Korea atomic energy research institute, KAERI.

    PubMed

    Choi, Yong-Ho; Lim, Kwang-Muk; Jun, In; Keum, Dong-Kwon; Han, Moon-Hee

    2011-07-01

    Regarding the assessment of the terrestrial food chain dose to man, radioecology may be the field that is focused on the transfer of radionuclides from environmental media to food crops. In Korea, the environmental transfer of radionuclides to staple food crops have been investigated at Korea Atomic Energy Research Institute (KAERI) for the last 25 y mainly through radiotracer experiments in greenhouses. As a result, several hundreds of parameter values for the prediction of the radionuclide transfer have been produced. Many of them appear in two recent publications of International Atomic Energy Agency. This paper outlines the KAERI's past radioecological work and introduces the ongoing research and future plans. PMID:21525043

  17. Chain networking revealed by molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Zheng, Yexin; Tsige, Mesfin; Wang, Shi-Qing

    Based on Kremer-Grest model for entangled polymer melts, we demonstrate how the response of a polymer glass depends critically on the chain length. After quenching two melts of very different chain lengths (350 beads per chain and 30 beads per chain) into deeply glassy states, we subject them to uniaxial extension. Our MD simulations show that the glass of long chains undergoes stable necking after yielding whereas the system of short chains is unable to neck and breaks up after strain localization. During ductile extension of the polymer glass made of long chain significant chain tension builds up in the load-bearing strands (LBSs). Further analysis is expected to reveal evidence of activation of the primary structure during post-yield extension. These results lend support to the recent molecular model 1 and are the simulations to demonstrate the role of chain networking. This work is supported, in part, by a NSF Grant (DMR-EAGER-1444859)

  18. Chain Release Behavior of Gellan Gels

    NASA Astrophysics Data System (ADS)

    Hossain, Khandker S.; Nishinari, Katsuyoshi

    The chain release behavior from gellan gels was studied by immersing the gel into water and monitoring the mass loss as a function of time. Concentration of released gellan in the external solution was determined for gels of different sizes using phenol-sulfuric acid method. The chain release process became faster with increasing total surface area and volume. However the concentration of released chain normalized by surface area and volume suggests that the chain release itself is governed not only by the ionic effect and the amount of unassociated chains in gel but other factors such as osmotic pressure may play an important role on the chain release from the gels. The diffusion coefficient was estimated from the chain release process which is in the same order of magnitude reported for an isolated gellan chain by light scattering. Rheological measurements also suggest that the unassociated gellan chains are released out when immersed in pure water while unassociated chains are restricted to release out when immersed in salt solution due to the intrusion of cations which is responsible for further association of the unassociated gellan chains being in agreement with the previously published results. The elastic modulus of gels was increased by immersion of gels in water and in salt solutions, which can be attributed as the stiffening of network chains due to gel swelling and the conversion from free and unassociated chains into network chains, respectively, leading to an increase in elastic modulus with time.

  19. Polymer Chain Reinforcement across Narrow Interfaces: Entanglements Versus Chain Friction

    NASA Astrophysics Data System (ADS)

    Benkoski, Jason J.; Fredrickson, Glenn H.; Kramer, Edward J.

    2002-03-01

    It is widely believed that entangled chains that bridge a glassy polymer/polymer interface solely determine its fracture energy (G_c). However, experiments show that while Gc increases with interfacial width (w), Gc vs. w/d_t, where dt is the tube diameter of the melt, is not universal. For some polymer pairs Gc increases dramatically even when w << d_t, while for others Gc does not increase until w >= d_t. We demonstrate that the friction stress for polymer loop pull-out from the interface is given by f_monoρ_merw/2 where f_mono is the static friction coefficient per mer and ρ_mer is the mer number density. Unlike interfaces with short block copolymers, where the friction stress for block pull-out is limited by a maximum areal density of block copolymer, the polymer/polymer friction stress grows linearly with w. For interfaces as narrow as 3 nm, it can be large enough to induce crazing. A model that includes both loop pull-out and chain entanglement shows that modest changes in f_mono can account for the fact that Gc versus w/dt is non-universal. A high areal density of bridging, entangled chains is therefore sufficient, but not necessary, to reinforce polymer interfaces.

  20. Magnetic Control of Atomic Motion

    NASA Astrophysics Data System (ADS)

    Mazur, Tom; Bannerman, Travis; Chavez, Isaac; Clark, Rob; Libson, Adam; Raizen, Mark

    2010-03-01

    Using a sequence of pulsed electromagnetic coils, known as the atomic coilgun, we slowed supersonic beams of atomic neon and molecular oxygen. We report our progress toward adapting the atomic coilgun for magnetically trapping hydrogen isotopes. This work has motivated us to investigate other methods for magnetic control of atomic motion. We describe these techniques, and present calculations suggesting their utility in controlling atomic motion. We then outline our plans for using these methods in certain applications.

  1. Spatially resolved photoionization of ultracold atoms on an atom chip

    SciTech Connect

    Kraft, S.; Guenther, A.; Fortagh, J.; Zimmermann, C.

    2007-06-15

    We report on photoionization of ultracold magnetically trapped Rb atoms on an atom chip. The atoms are trapped at 5 {mu}K in a strongly anisotropic trap. Through a hole in the chip with a diameter of 150 {mu}m, two laser beams are focused onto a fraction of the atomic cloud. A first laser beam with a wavelength of 778 nm excites the atoms via a two-photon transition to the 5D level. With a fiber laser at 1080 nm the excited atoms are photoionized. Ionization leads to depletion of the atomic density distribution observed by absorption imaging. The resonant ionization spectrum is reported. The setup used in this experiment is suitable not only to investigate mixtures of Bose-Einstein condensates and ions but also for single-atom detection on an atom chip.

  2. Trapped Atoms in One-Dimensional Photonic Crystals

    NASA Astrophysics Data System (ADS)

    Kimble, H.

    2013-05-01

    I describe one-dimensional photonic crystals that support a guided mode suitable for atom trapping within a unit cell, as well as a second probe mode with strong atom-photon interactions. A new hybrid trap is analyzed that combines optical and Casimir-Polder forces to form stable traps for neutral atoms in dielectric nanostructures. By suitable design of the band structure, the atomic spontaneous emission rate into the probe mode can exceed the rate into all other modes by more than tenfold. The unprecedented single-atom reflectivity r0 ~= 0 . 9 for the guided probe field could create new scientific opportunities, including quantum many-body physics for 1 D atom chains with photon-mediated interactions and high-precision studies of vacuum forces. Towards these goals, my colleagues and I are pursuing numerical simulation, device fabrication, and cold-atom experiments with nanoscopic structures. Funding is provided by by the IQIM, an NSF PFC with support of the Moore Foundation, by the AFOSR QuMPASS MURI, by the DoD NSSEFF program (HJK), and by NSF Grant PHY0652914 (HJK). DEC acknowledges funding from Fundacio Privada Cellex Barcelona.

  3. Chiral atomically thin films

    NASA Astrophysics Data System (ADS)

    Kim, Cheol-Joo; Sánchez-Castillo, A.; Ziegler, Zack; Ogawa, Yui; Noguez, Cecilia; Park, Jiwoong

    2016-06-01

    Chiral materials possess left- and right-handed counterparts linked by mirror symmetry. These materials are useful for advanced applications in polarization optics, stereochemistry and spintronics. In particular, the realization of spatially uniform chiral films with atomic-scale control of their handedness could provide a powerful means for developing nanodevices with novel chiral properties. However, previous approaches based on natural or grown films, or arrays of fabricated building blocks, could not offer a direct means to program intrinsic chiral properties of the film on the atomic scale. Here, we report a chiral stacking approach, where two-dimensional materials are positioned layer-by-layer with precise control of the interlayer rotation (θ) and polarity, resulting in tunable chiral properties of the final stack. Using this method, we produce left- and right-handed bilayer graphene, that is, a two-atom-thick chiral film. The film displays one of the highest intrinsic ellipticity values (6.5 deg μm–1) ever reported, and a remarkably strong circular dichroism (CD) with the peak energy and sign tuned by θ and polarity. We show that these chiral properties originate from the large in-plane magnetic moment associated with the interlayer optical transition. Furthermore, we show that we can program the chiral properties of atomically thin films layer-by-layer by producing three-layer graphene films with structurally controlled CD spectra.

  4. Rutherford-Bohr atom

    NASA Astrophysics Data System (ADS)

    Heilbron, J. L.

    1981-03-01

    Bohr used to introduce his attempts to explain clearly the principles of the quantum theory of the atom with an historical sketch, beginning invariably with the nuclear model proposed by Rutherford. That was sound pedagogy but bad history. The Rutherford-Bohr atom stands in the middle of a line of work initiated by J.J. Thomson and concluded by the invention of quantum mechanics. Thompson's program derived its inspiration from the peculiar emphasis on models characteristic of British physics of the 19th century. Rutherford's atom was a late product of the goals and conceptions of Victorian science. Bohr's modifications, although ultimately fatal to Thomson's program, initially gave further impetus to it. In the early 1920s the most promising approach to an adequate theory of the atom appeared to be the literal and detailed elaboration of the classical mechanics of multiply periodic orbits. The approach succeeded, demonstrating in an unexpected way the force of an argument often advanced by Thomson: because a mechanical model is richer in implications than the considerations for which it was advanced, it can suggest new directions of research that may lead to important discoveries.

  5. Atomism, Pragmatism, Holism.

    ERIC Educational Resources Information Center

    Miller, John P.

    1986-01-01

    Examines three world views influencing curriculum development--atomism (underpinning competency-based education), pragmatism (promoting inquiry-based approaches), amd holism (associated with confluent or Waldorf education). Holism embodies the perennial philosophy and attempts to integrate cognitive, affective, and transpersonal dimensions,…

  6. INL Laboratory Scale Atomizer

    SciTech Connect

    C.R. Clark; G.C. Knighton; R.S. Fielding; N.P. Hallinan

    2010-01-01

    A laboratory scale atomizer has been built at the Idaho National Laboratory. This has proven useful for laboratory scale tests and has been used to fabricate fuel used in the RERTR miniplate experiments. This instrument evolved over time with various improvements being made ‘on the fly’ in a trial and error process.

  7. Atomic collisions, inelastic indeed

    NASA Astrophysics Data System (ADS)

    Bercegol, Herve; Ferrando, Gwenael; Lehoucq, Roland

    At the turn of the twentieth century, a hot controversy raged about the ability of Boltzmann's framework to take care of irreversibility. The so-called Loschmidt's paradox progressively faded with time during the last hundred years, due to the predictive efficiency of statistical mechanics. However, one detail at the origin of the controversy - the elasticity of atomic collisions - was not completely challenged. A semi-classical treatment of two atoms interacting with the vacuum zero-point field permits to predict a friction force acting against the rotation of the pair of atoms. By its form and its level, the calculated torque is a candidate as a physical cause for diffusion of energy and angular momentum, and consequently for entropy growth. It opens the way to a revision of the standard vision of irreversibility. This presentation will focus on two points. First we will discuss the recent result in a broader context of electromagnetic interactions during microscopic collisions. The predicted friction phenomenon can be compared to and distinguished from Collision-Induced Emission and other types of inelastic collisions. Second we will investigate the consequences of the friction torque on calculated trajectories of colliding atoms, quantifying the generation of dimers linked by dispersion forces.

  8. Bonds Between Atoms.

    ERIC Educational Resources Information Center

    Holden, Alan

    The field of inquiry into how atoms are bonded together to form molecules and solids crosses the borderlines between physics and chemistry encompassing methods characteristic of both sciences. At one extreme, the inquiry is pursued with care and rigor into the simplest cases; at the other extreme, suggestions derived from the more careful inquiry…

  9. Observational Evidence for Atoms.

    ERIC Educational Resources Information Center

    Jones, Edwin R., Jr.; Childers, Richard L.

    1984-01-01

    Discusses the development of the concept of atomicity and some of the many which can be used to establish its validity. Chemical evidence, evidence from crystals, Faraday's law of electrolysis, and Avogadro's number are among the areas which show how the concept originally developed from a purely philosophical idea. (JN)

  10. Atomically Traceable Nanostructure Fabrication.

    PubMed

    Ballard, Josh B; Dick, Don D; McDonnell, Stephen J; Bischof, Maia; Fu, Joseph; Owen, James H G; Owen, William R; Alexander, Justin D; Jaeger, David L; Namboodiri, Pradeep; Fuchs, Ehud; Chabal, Yves J; Wallace, Robert M; Reidy, Richard; Silver, Richard M; Randall, John N; Von Ehr, James

    2015-01-01

    Reducing the scale of etched nanostructures below the 10 nm range eventually will require an atomic scale understanding of the entire fabrication process being used in order to maintain exquisite control over both feature size and feature density. Here, we demonstrate a method for tracking atomically resolved and controlled structures from initial template definition through final nanostructure metrology, opening up a pathway for top-down atomic control over nanofabrication. Hydrogen depassivation lithography is the first step of the nanoscale fabrication process followed by selective atomic layer deposition of up to 2.8 nm of titania to make a nanoscale etch mask. Contrast with the background is shown, indicating different mechanisms for growth on the desired patterns and on the H passivated background. The patterns are then transferred into the bulk using reactive ion etching to form 20 nm tall nanostructures with linewidths down to ~6 nm. To illustrate the limitations of this process, arrays of holes and lines are fabricated. The various nanofabrication process steps are performed at disparate locations, so process integration is discussed. Related issues are discussed including using fiducial marks for finding nanostructures on a macroscopic sample and protecting the chemically reactive patterned Si(100)-H surface against degradation due to atmospheric exposure. PMID:26274555

  11. Diffraction by cold atoms

    NASA Astrophysics Data System (ADS)

    Strauch, F.; Gomer, V.; Schadwinkel, H.; Ueberholz, B.; Haubrich, D.; Meschede, D.

    1998-01-01

    We have observed diffraction of a laser probe beam by a trapped sample of cold atoms. The effect is only visible in the vicinity of a resonance line. The observed diffraction pattern arises from interference of the incident and scattered light wave, allowing reconstruction of geometric properties of the trapped sample from the holographic record.

  12. Atoms in Astronomy.

    ERIC Educational Resources Information Center

    Blanchard, Paul A.

    This booklet is part of an American Astronomical Society curriculum project designed to provide teaching materials to teachers of secondary school chemistry, physics, and earth science. A Basic Topics section discusses atomic structure, emphasizing states of matter at high temperature and spectroscopic analysis of light from the stars. A section…

  13. Chiral atomically thin films.

    PubMed

    Kim, Cheol-Joo; Sánchez-Castillo, A; Ziegler, Zack; Ogawa, Yui; Noguez, Cecilia; Park, Jiwoong

    2016-06-01

    Chiral materials possess left- and right-handed counterparts linked by mirror symmetry. These materials are useful for advanced applications in polarization optics, stereochemistry and spintronics. In particular, the realization of spatially uniform chiral films with atomic-scale control of their handedness could provide a powerful means for developing nanodevices with novel chiral properties. However, previous approaches based on natural or grown films, or arrays of fabricated building blocks, could not offer a direct means to program intrinsic chiral properties of the film on the atomic scale. Here, we report a chiral stacking approach, where two-dimensional materials are positioned layer-by-layer with precise control of the interlayer rotation (θ) and polarity, resulting in tunable chiral properties of the final stack. Using this method, we produce left- and right-handed bilayer graphene, that is, a two-atom-thick chiral film. The film displays one of the highest intrinsic ellipticity values (6.5 deg μm(-1)) ever reported, and a remarkably strong circular dichroism (CD) with the peak energy and sign tuned by θ and polarity. We show that these chiral properties originate from the large in-plane magnetic moment associated with the interlayer optical transition. Furthermore, we show that we can program the chiral properties of atomically thin films layer-by-layer by producing three-layer graphene films with structurally controlled CD spectra. PMID:26900756

  14. Atomic Oxygen Task

    NASA Technical Reports Server (NTRS)

    Hadaway, James B.

    1997-01-01

    This report details work performed by the Center for Applied Optics (CAO) at the University of Alabama in Huntsville (UAH) on the contract entitled 'Atomic Oxygen Task' for NASA's Marshall Space Flight Center (contract NAS8-38609, Delivery Order 109, modification number 1). Atomic oxygen effects on exposed materials remain a critical concern in designing spacecraft to withstand exposure in the Low Earth Orbit (LEO) environment. The basic objective of atomic oxygen research in NASA's Materials & Processes (M&P) Laboratory is to provide the solutions to material problems facing present and future space missions. The objective of this work was to provide the necessary research for the design of specialized experimental test configurations and development of techniques for evaluating in-situ space environmental effects, including the effects of atomic oxygen and electromagnetic radiation on candidate materials. Specific tasks were performed to address materials issues concerning accelerated environmental testing as well as specifically addressing materials issues of particular concern for LDEF analysis and Space Station materials selection.

  15. Energy from the Atom.

    ERIC Educational Resources Information Center

    Smith, Patricia L.

    This curriculum guide was written to supplement fifth and sixth grade science units on matter and energy. It was designed to provide more in-depth material on the atom. The first part, "Teacher Guide," contains background information, biographical sketches of persons in the history of nuclear energy, vocabulary, answer sheets, management sheets…

  16. One-dimensional topological chains with Majorana fermions in two-dimensional nontopological optical lattices

    NASA Astrophysics Data System (ADS)

    Jiang, Lei; Qu, Chunlei; Zhang, Chuanwei

    2016-06-01

    The recent experimental realization of one-dimensional (1D) equal Rashba-Dresselhaus spin-orbit coupling (ERD-SOC) for cold atoms provides a disorder-free and highly controllable platform for the implementation and observation of Majorana fermions (MFs), analogous to the broadly studied solid-state nanowire-superconductor heterostructures. However, the corresponding 1D chains of cold atoms possess strong quantum fluctuation, which may destroy the superfluids and MFs. In this paper, we show that such 1D topological chains with MFs may be on demand generated in a two- or three-dimensional nontopological optical lattice with 1D ERD-SOC by modifying local potentials on target locations using experimentally already implemented atomic gas microscopes or patterned (e.g., double- or triple-well) optical lattices. All ingredients in our scheme have been experimentally realized, and the combination of them may pave the way for the experimental observation of MFs in a clean system.

  17. EDITORIAL: Atomic layer deposition Atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Godlewski, Marek

    2012-07-01

    The growth method of atomic layer deposition (ALD) was introduced in Finland by Suntola under the name of atomic layer epitaxy (ALE). The method was originally used for deposition of thin films of sulphides (ZnS, CaS, SrS) activated with manganese or rare-earth ions. Such films were grown for applications in thin-film electroluminescence (TFEL) displays. The ALE mode of growth was also tested in the case of molecular beam epitaxy. Films grown by ALD are commonly polycrystalline or even amorphous. Thus, the name ALE has been replaced by ALD. In the 80s ALD was developed mostly in Finland and neighboring Baltic countries. Deposition of a range of different materials was demonstrated at that time, including II-VI semiconductors (e.g. CdTe, CdS) and III-V (e.g. GaAs, GaN), with possible applications in e.g. photovoltaics. The number of publications on ALD was slowly increasing, approaching about 100 each year. A real boom in interest came with the development of deposition methods of thin films of high-k dielectrics. This research was motivated by a high leakage current in field-effect transistors with SiO2-based gate dielectrics. In 2007 Intel introduced a new generation of integrated circuits (ICs) with thin films of HfO2 used as gate isolating layers. In these and subsequent ICs, films of HfO2 are deposited by the ALD method. This is due to their unique properties. The introduction of ALD to the electronics industry led to a booming interest in the ALD growth method, with the number of publications increasing rapidly to well above 1000 each year. A number of new applications were proposed, as reflected in this special issue of Semiconductor Science and Technology. The included articles cover a wide range of possible applications—in microelectronics, transparent electronics, optoelectronics, photovoltaics and spintronics. Research papers and reviews on the basics of ALD growth are also included, reflecting a growing interest in precursor chemistry and growth

  18. Towards biotracing in food chains.

    PubMed

    Hoorfar, Jeffrey; Wagner, Martin; Jordan, Kieran; Bouquin, Solveig Lind; Skiby, Jeffrey

    2011-03-01

    Biotracing is tracing (backward)/tracking (forward) biological contamination in the food/feed chain. Advances in detection technologies, improvements in molecular marker identification, clearer understanding of pathogenicity markers, improved modelling methodologies and, more importantly, the integration of these disciplines will lead to better capability in full-chain tracing and tracking biological contaminations (biotracing). The advantages of improved biotraceability are faster intervention, limited recalls and more targeted remedial action. The project is not dealing with risk assessments but developing tools that can be used in "second-generation" risk assessments involving quantitative microbiology. This concept is the core activity of BIOTRACER, which is an Integrated Project (2007-2011) funded by the EU 6th Framework Programme. The research in biotracing is organised into five Research Areas, and 21 cross-disciplinary work packages that cover tracing and tracking of contamination in feed, meat and dairy chains, in addition to accidental and deliberate contamination of bottled water. The BIOTRACER Consortium consists of 46 partners, including Europe's largest food/feed industries, several SMEs, and relevant International Cooperation (INCO) countries. The Consortium includes experts in predictive microbiology, database developers, software companies, risk assessors, risk managers, system biologists, food and molecular microbiologists, legislative officers, standardization and validation members and food retailers. The outcomes will ensure a more reliable and rapid response to a microbial contamination event. PMID:20627434

  19. Immunodiagnosis of alpha chain disease.

    PubMed Central

    Doe, W F; Danon, F; Seligmann, M

    1979-01-01

    Since the early diagnosis of alpha chain disease (alphaCD)) is essential to successful treatment and to epidemiological studies, the available immunodiagnostic techniques were compared for their sensitivity, specificity and ease of performance on a panel of sixteen sera, comprising ten alphaCD sera and six control sera containing either IgA myeloma protein or high levels of polyclonal IgA. Immunoselection by immunoelectrophoresis into gel containing a specially developed anti-Fabalpha antiserum provided the most sensitive and specific detection system for alphaCD protein. The same technique using anti-light chain antiserum for immunoselection was also highly sensitive, but proved less specific, being prone to false positives with difficult IgA myeloma proteins. Somewhat less sensitive, but specific and simple to perform, was immunoelectrophoresis using an antiserum recognizing the conformational specificities of Fabalpha as well as those of the constant region of alpha chains. Immunoselection using the Ouchterlony or rocket techniques proved to be less sensitive and prone to false positives when some IgA myeloma sera were tested. Images FIG. 1 FIG. 2 FIG. 3 FIG. 4 FIG. 5 FIG. 6 FIG. 7 PMID:113152

  20. Probing starch-iodine interaction by atomic force microscopy.

    PubMed

    Du, Xiongwei; An, Hongjie; Liu, Zhongdong; Yang, Hongshun; Wei, Lijuan

    2014-01-01

    We explored the interaction of iodine with three crystalline type starches, corn, potato, and sweet potato starches using atomic force microscopy. Results revealed that starch molecules aggregated through interaction with iodine solution as well as iodine vapor. Detailed fine structures such as networks, chains, and super-helical structures were found in iodide solution tests. The nanostructures formed due to iodine adsorption could help to understand the formation and properties of the starch-iodine complex. PMID:24338992

  1. Synthesis of a new element with atomic number Z=117

    SciTech Connect

    Oganessian, Yuri Ts.; Abdullin, F. Sh.; Bailey, P. D.; Benker, D. E.; Bennett, M. E.; Dmitriev, S.; Ezold, Julie G.; Hamilton, J. H.; Henderson, R.; Itkis, M. G.; Lobanov, Yu. V.; Mezentsev, A. N.; Moody, K.; Nelson, S. L.; Polyakov, A. N.; Porter, C. E.; Ramayya, A. V.; Riley, F. D.; Roberto, James B; Ryabinin, M. A.; Rykaczewski, Krzysztof Piotr; Sagaidak, R. N.; Shaughnessy, D.; Shirokovsky, I. V.; Stoyer, M.; Subbotin, V. G.; Sudowe, R.; Sukhov, A. M.; Tsyganov, Yu. S.; Utyonkov, V.; Voinov, A. A.; Vostokin, G. K.; Wilk, P. A.

    2010-01-01

    The discovery of a new chemical element with atomic number Z=117 is reported. The isotopes 293117 and 294117 were produced in fusion reactions between 48Ca and 249Bk. Decay chains involving eleven new nuclei were identified by means of the Dubna Gas Filled Recoil Separator. The measured decay properties show a strong rise of stability for heavier isotopes with Z111, validating the concept of the long sought island of enhanced stability for super-heavy nuclei.

  2. HPAM: Hirshfeld Partitioned Atomic Multipoles

    PubMed Central

    Elking, Dennis M.; Perera, Lalith; Pedersen, Lee G.

    2011-01-01

    An implementation of the Hirshfeld (HD) and Hirshfeld-Iterated (HD-I) atomic charge density partitioning schemes is described. Atomic charges and atomic multipoles are calculated from the HD and HD-I atomic charge densities for arbitrary atomic multipole rank lmax on molecules of arbitrary shape and size. The HD and HD-I atomic charges/multipoles are tested by comparing molecular multipole moments and the electrostatic potential (ESP) surrounding a molecule with their reference ab initio values. In general, the HD-I atomic charges/multipoles are found to better reproduce ab initio electrostatic properties over HD atomic charges/multipoles. A systematic increase in precision for reproducing ab initio electrostatic properties is demonstrated by increasing the atomic multipole rank from lmax = 0 (atomic charges) to lmax = 4 (atomic hexadecapoles). Both HD and HD-I atomic multipoles up to rank lmax are shown to exactly reproduce ab initio molecular multipole moments of rank L for L ≤ lmax. In addition, molecular dipole moments calculated by HD, HD-I, and ChelpG atomic charges only (lmax = 0) are compared with reference ab initio values. Significant errors in reproducing ab initio molecular dipole moments are found if only HD or HD-I atomic charges used. PMID:22140274

  3. Comparisons of Modified Backward Chaining: Backward Chaining with Leap-Aheads and Reverse Chaining with Leap-Aheads.

    ERIC Educational Resources Information Center

    Spooner, Fred; And Others

    1986-01-01

    Variations of backward chaining--backward chaining with leap-aheads (BCLA) and reverse chaining with leap-aheads (RCLA)-- were compared with four severely retarded learners (17-32 years) who were trained on two complex vocational tasks. Learning rate for the BCLA procedure was superior to the RCLA procedure. Time to criterion differences were…

  4. Relation chain based clustering analysis

    NASA Astrophysics Data System (ADS)

    Zhang, Cheng-ning; Zhao, Ming-yang; Luo, Hai-bo

    2011-08-01

    Clustering analysis is currently one of well-developed branches in data mining technology which is supposed to find the hidden structures in the multidimensional space called feature or pattern space. A datum in the space usually possesses a vector form and the elements in the vector represent several specifically selected features. These features are often of efficiency to the problem oriented. Generally, clustering analysis goes into two divisions: one is based on the agglomerative clustering method, and the other one is based on divisive clustering method. The former refers to a bottom-up process which regards each datum as a singleton cluster while the latter refers to a top-down process which regards entire data as a cluster. As the collected literatures, it is noted that the divisive clustering is currently overwhelming both in application and research. Although some famous divisive clustering methods are designed and well developed, clustering problems are still far from being solved. The k - means algorithm is the original divisive clustering method which initially assigns some important index values, such as the clustering number and the initial clustering prototype positions, and that could not be reasonable in some certain occasions. More than the initial problem, the k - means algorithm may also falls into local optimum, clusters in a rigid way and is not available for non-Gaussian distribution. One can see that seeking for a good or natural clustering result, in fact, originates from the one's understanding of the concept of clustering. Thus, the confusion or misunderstanding of the definition of clustering always derives some unsatisfied clustering results. One should consider the definition deeply and seriously. This paper demonstrates the nature of clustering, gives the way of understanding clustering, discusses the methodology of designing a clustering algorithm, and proposes a new clustering method based on relation chains among 2D patterns. In

  5. Information flow in the pharmaceutical supply chain.

    PubMed

    Yousefi, Nazila; Alibabaei, Ahmad

    2015-01-01

    Managing the supply chain plays an important role in creating competitive advantages for companies. Adequate information flow in supply chain is one of the most important issues in SCM. Therefore, using certain Information Systems can have a significant role in managing and integrating data and information within the supply chain. Pharmaceutical supply chain is more complex than many other supply chains, in the sense that it can affect social and political perspectives. On the other hand, managing the pharmaceutical supply chain is difficult because of its complexity and also government regulations in this field. Although, Iran has progressed a lot in pharmaceutical manufacturing, still there are many unsolved issues in managing the information flow in the pharmaceutical supply chain. In this study, we reviewed the benefits of using different levels of an integrated information system in the supply chain and the possible challenges ahead. PMID:26664401

  6. Information flow in the pharmaceutical supply chain

    PubMed Central

    Yousefi, Nazila; Alibabaei, Ahmad

    2015-01-01

    Managing the supply chain plays an important role in creating competitive advantages for companies. Adequate information flow in supply chain is one of the most important issues in SCM. Therefore, using certain Information Systems can have a significant role in managing and integrating data and information within the supply chain. Pharmaceutical supply chain is more complex than many other supply chains, in the sense that it can affect social and political perspectives. On the other hand, managing the pharmaceutical supply chain is difficult because of its complexity and also government regulations in this field. Although, Iran has progressed a lot in pharmaceutical manufacturing, still there are many unsolved issues in managing the information flow in the pharmaceutical supply chain. In this study, we reviewed the benefits of using different levels of an integrated information system in the supply chain and the possible challenges ahead. PMID:26664401

  7. Polymerization as a Model Chain Reaction

    ERIC Educational Resources Information Center

    Morton, Maurice

    1973-01-01

    Describes the features of the free radical, anionic, and cationic mechanisms of chain addition polymerization. Indicates that the nature of chain reactions can be best taught through the study of macromolecules. (CC)

  8. Atom inlays performed at room temperature using atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Sugimoto, Yoshiaki; Abe, Masayuki; Hirayama, Shinji; Oyabu, Noriaki; Custance, Óscar; Morita, Seizo

    2005-02-01

    The ability to manipulate single atoms and molecules laterally for creating artificial structures on surfaces is driving us closer to the ultimate limit of two-dimensional nanoengineering. However, experiments involving this level of manipulation have been performed only at cryogenic temperatures. Scanning tunnelling microscopy has proved, so far, to be a unique tool with all the necessary capabilities for laterally pushing, pulling or sliding single atoms and molecules, and arranging them on a surface at will. Here we demonstrate, for the first time, that it is possible to perform well-controlled lateral manipulations of single atoms using near-contact atomic force microscopy even at room temperature. We report the creation of 'atom inlays', that is, artificial atomic patterns formed from a few embedded atoms in the plane of a surface. At room temperature, such atomic structures remain stable on the surface for relatively long periods of time.

  9. Model protocells from single-chain lipids.

    PubMed

    Mansy, Sheref S

    2009-03-01

    Significant progress has been made in the construction of laboratory models of protocells. Most frequently the developed vesicle systems utilize single-chain lipids rather than the double-chain lipids typically found in biological membranes. Although single-chain lipids yield less robust vesicles, their dynamic characteristics are highly exploitable for protocellular functions. Herein the advantages of using single-chain lipids in the construction of protocells are discussed. PMID:19399223

  10. Model Protocells from Single-Chain Lipids

    PubMed Central

    Mansy, Sheref S.

    2009-01-01

    Significant progress has been made in the construction of laboratory models of protocells. Most frequently the developed vesicle systems utilize single-chain lipids rather than the double-chain lipids typically found in biological membranes. Although single-chain lipids yield less robust vesicles, their dynamic characteristics are highly exploitable for protocellular functions. Herein the advantages of using single-chain lipids in the construction of protocells are discussed. PMID:19399223

  11. Confined linear carbon chains as a route to bulk carbyne.

    PubMed

    Shi, Lei; Rohringer, Philip; Suenaga, Kazu; Niimi, Yoshiko; Kotakoski, Jani; Meyer, Jannik C; Peterlik, Herwig; Wanko, Marius; Cahangirov, Seymur; Rubio, Angel; Lapin, Zachary J; Novotny, Lukas; Ayala, Paola; Pichler, Thomas

    2016-06-01

    Strong chemical activity and extreme instability in ambient conditions characterize carbyne, an infinite sp(1) hybridized carbon chain. As a result, much less has been explored about carbyne as compared to other carbon allotropes such as fullerenes, nanotubes and graphene. Although end-capping groups can be used to stabilize carbon chains, length limitations are still a barrier for production, and even more so for application. We report a method for the bulk production of long acetylenic linear carbon chains protected by thin double-walled carbon nanotubes. The synthesis of very long arrangements is confirmed by a combination of transmission electron microscopy, X-ray diffraction and (near-field) resonance Raman spectroscopy. Our results establish a route for the bulk production of exceptionally long and stable chains composed of more than 6,000 carbon atoms, representing an elegant forerunner towards the final goal of carbyne's bulk production. PMID:27043782

  12. Interaction between DNA and Trimethyl-Ammonium Bromides with Different Alkyl Chain Lengths

    PubMed Central

    Cheng, Chao; Ran, Shi-Yong

    2014-01-01

    The interaction between λ—DNA and cationic surfactants with varying alkyl chain lengths was investigated. By dynamic light scattering method, the trimethyl-ammonium bromides-DNA complex formation was shown to be dependent on the length of the surfactant's alkyl chain. For surfactants with sufficient long alkyl chain (CTAB, TTAB, DTAB), the compacted particles exist with a size of ~60–110 nm at low surfactant concentrations. In contrast, high concentration of surfactants leads to aggregates with increased sizes. Atomic force microscope scanning also supports the above observation. Zeta potential measurements show that the potential of the particles decreases with the increase of surfactant concentration (CTAB, TTAB, DTAB), which contributes much to the coagulation of the particles. For OTAB, the surfactant with the shortest chain in this study, it cannot fully neutralize the charges of DNA molecules; consequently, the complex is looser than other surfactant-DNA structures. PMID:24574926

  13. Spin Chains and Electron Transfer at Stepped Silicon Surfaces.

    PubMed

    Aulbach, J; Erwin, S C; Claessen, R; Schäfer, J

    2016-04-13

    High-index surfaces of silicon with adsorbed gold can reconstruct to form highly ordered linear step arrays. These steps take the form of a narrow strip of graphitic silicon. In some cases--specifically, for Si(553)-Au and Si(557)-Au--a large fraction of the silicon atoms at the exposed edge of this strip are known to be spin-polarized and charge-ordered along the edge. The periodicity of this charge ordering is always commensurate with the structural periodicity along the step edge and hence leads to highly ordered arrays of local magnetic moments that can be regarded as "spin chains." Here, we demonstrate theoretically as well as experimentally that the closely related Si(775)-Au surface has--despite its very similar overall structure--zero spin polarization at its step edge. Using a combination of density-functional theory and scanning tunneling microscopy, we propose an electron-counting model that accounts for these differences. The model also predicts that unintentional defects and intentional dopants can create local spin moments at Si(hhk)-Au step edges. We analyze in detail one of these predictions and verify it experimentally. This finding opens the door to using techniques of surface chemistry and atom manipulation to create and control silicon spin chains. PMID:26974012

  14. Ionic interactions in platinum chloride linear-chain compounds

    SciTech Connect

    Batistic, I. ); Huang, X.Z.; Bishop, A.R.; Saxena, A. )

    1993-09-01

    Halogen-bridged transition-metal chain compounds have recently emerged as an important class of low-dimensional electronic materials with strong electron-lattice and electron-electron interactions. We introduce a many-body model for such materials which is quantitatively successful for highly valence-localized (strong charge-density-wave) members of the class, e.g., PtCl with various ligand structures. The model introduces nearest-neighbor Coulomb attraction [ital and] metal ion-ion electrostatic repulsion directly rather than through a linear Peierls-Hubbard Hamiltonian. These interactions have the effects of (i) modifying the on-site orbital energies, (ii) generating an effective [ital anharmonic] [ital intra]site electron-lattice coupling (leading to the formation of a charge-density wave even if the intersite electron-lattice coupling is weak), and (iii) acting as an effective [ital anharmonic] elastic force between neighboring metal and halogen atoms. The stoichiometric ground state and various defect states (polaron, bipolaron, kink, exciton) are studied within this framework by computing their optical absorption, Raman, and infrared spectra: The results agree well with available experimental data. Buckling of Cl atoms out of the chain axis in certain PtCl compounds is predicted to be important in order to obtain the observed Raman frequencies for [ital electron] polarons and bipolarons. Finally, a strong template'' effect is discussed by comparing two PtCl materials with different ligands and counterions.

  15. Extending the "Knowledge Advantage": Creating Learning Chains

    ERIC Educational Resources Information Center

    Maqsood, Tayyab; Walker, Derek; Finegan, Andrew

    2007-01-01

    Purpose: The purpose of this paper is to develop a synergy between the approaches of knowledge management in a learning organisation and supply chain management so that learning chains can be created in order to unleash innovation and creativity by managing knowledge in supply chains. Design/methodology/approach: Through extensive literature…

  16. Visualisation for System Learning in Supply Chains

    ERIC Educational Resources Information Center

    Lindskog, Magnus; Abrahamsson, Mats; Aronsson, Hakan

    2007-01-01

    Contemporary supply chains are vastly complex, and decisions made by actors have system-wide consequences that these might not be able to foresee. There are gaps between "best practice"-founded theory and actual practice in supply chains. To remedy this, we argue, the supply chain actors need to enhance systems knowledge. There is a need to…

  17. Learning to Integrate: Supply Chains Reconceptualised

    ERIC Educational Resources Information Center

    Sense, Andrew J.; Clements, Michael D. J.

    2007-01-01

    This paper introduces and explains a conception of supply chains from a situated learning perspective. This non-conventional supply chain perspective invites the reader to consider supply chain scenarios as "situated learning opportunities involving multiple communities of practice" interacting and participating together. It is argued that by…

  18. 1D ferrimagnetism in homometallic chains

    NASA Astrophysics Data System (ADS)

    Coronado, E.; Gómez-García, C. J.; Borrás-Almenar, J. J.

    1990-05-01

    The magnetic properties of the cobalt zigzag chain Co(bpy)(NCS)2 (bpy=2,2'-bipyridine) are discussed on the basis of an Ising-chain model that takes into account alternating Landé factors. It is emphasized, for the first time, that a homometallic chain containing only one type of site can give rise to a 1D ferrimagneticlike behavior.

  19. On a Result for Finite Markov Chains

    ERIC Educational Resources Information Center

    Kulathinal, Sangita; Ghosh, Lagnojita

    2006-01-01

    In an undergraduate course on stochastic processes, Markov chains are discussed in great detail. Textbooks on stochastic processes provide interesting properties of finite Markov chains. This note discusses one such property regarding the number of steps in which a state is reachable or accessible from another state in a finite Markov chain with M…

  20. Chains versus Independents: Newspaper and Market Characteristics.

    ERIC Educational Resources Information Center

    Hale, F. Dennis

    A study examined the marketing differences between large chain newspapers and small chain and independent newspapers by analyzing differences in characteristics of the newspapers, patterns of circulation, economic and social conditions of the market, and competition from other print media. The 200 newspapers studied--113 large chain and 87 small…

  1. The Advancement Value Chain: An Exploratory Model

    ERIC Educational Resources Information Center

    Leonard, Edward F., III

    2005-01-01

    Since the introduction of the value chain concept in 1985, several varying, yet virtually similar, value chains have been developed for the business enterprise. Shifting to higher education, can a value chain be found that links together the various activities of advancement so that an institution's leaders can actually look at the philanthropic…

  2. Tunnel current across linear homocatenated germanium chains

    SciTech Connect

    Matsuura, Yukihito

    2014-01-28

    The electronic transport properties of germanium oligomers catenating into linear chains (linear Ge chains) have been theoretically studied using first principle methods. The conduction mechanism of a Ge chain sandwiched between gold electrodes was analyzed based on the density of states and the eigenstates of the molecule in a two-probe environment. Like that of silicon chains (Si chains), the highest occupied molecular orbital of Ge chains contains the extended σ-conjugation of Ge 4p orbitals at energy levels close to the Fermi level; this is in contrast to the electronic properties of linear carbon chains. Furthermore, the conductance of a Ge chain is expected to decrease exponentially with molecular length L. The decay constant β, which is defined as e{sup −βL}, of a Ge chain is similar to that of a Si chain, whereas the conductance of the Ge chains is higher than that of Si chains even though the Ge–Ge bond length is longer than the Si–Si bond length.

  3. A Saturnian atom.

    PubMed

    Lee, E; Farrelly, D; Uzer, T

    1997-09-29

    In Bohr's original planetary model of the atom the electron moves along orbits of special geometric simplicity. While wave mechanics precludes the idea that a physical path could be ascribed to the electron, a classical or planetary atom can still be envisaged in which the electronic wavepacket neither spreads nor disperses as its center moves along the Kepler orbit, and this orbit is conned to a single plane in space. We show theoretically how an electronic wavepacket may be localized in this fashion in a similar way to ion confinement in a Penning trap. Because external fields are needed to keep the packet confined, a more fitting analogy than a planetary orbit is the motion of a charged dust grain in one of the rings of a giant planet such as Saturn. PMID:19373405

  4. Optical atomic clocks

    NASA Astrophysics Data System (ADS)

    Poli, N.; Oates, C. W.; Gill, P.; Tino, G. M.

    2013-12-01

    In the last ten years extraordinary results in time and frequency metrology have been demonstrated. Frequency-stabilization techniques for continuous-wave lasers and femtosecond optical frequency combs have enabled a rapid development of frequency standards based on optical transitions in ultra-cold neutral atoms and trapped ions. As a result, today's best performing atomic clocks tick at an optical rate and allow scientists to perform high-resolution measurements with a precision approaching a few parts in 1018. This paper reviews the history and the state of the art in optical-clock research and addresses the implementation of optical clocks in a possible future redefinition of the SI second as well as in tests of fundamental physics.

  5. Atomic Disorder in Tetrahedrite

    NASA Astrophysics Data System (ADS)

    Salasin, John Robert; Chakoumakos, Bryan; Rawn, Claudia; May, Andrew; Lara-Curzio, Edgar; McGuire, Michael; Cao, Huibo

    2015-03-01

    Thermoelectrics (TE) are materials which turn heat energy into electrical energy with applications spanning multiple disciplines including space exploration, Peltier cooling, and engine efficiency. Tetrahedrite is a copper sulfosalt with the general formula Cu12-xMx(Sb,As)4S13. Where M denotes a Cu2+ site frequently replaced in natural tetrahedrite with Zn, Fe, Hg, or Mn. It has a cubic structure with an I-43m symmetry, a = 10.4 Å, and only a handful of adjustable parameters. This structural study corroborates theoretical calculations on atomic disorder. Positional disorder of the trigonally coordinated Cu(2) site is suggested from the temperature dependence of the atomic displacement parameters determine from single-crystal x-ray and neutron diffraction. The displacements are extremely anisotropic for Cu(2) with a maximum rms static displacement of ~ 0.25 Å.

  6. Cavity enhanced atomic magnetometry

    PubMed Central

    Crepaz, Herbert; Ley, Li Yuan; Dumke, Rainer

    2015-01-01

    Atom sensing based on Faraday rotation is an indispensable method for precision measurements, universally suitable for both hot and cold atomic systems. Here we demonstrate an all-optical magnetometer where the optical cell for Faraday rotation spectroscopy is augmented with a low finesse cavity. Unlike in previous experiments, where specifically designed multipass cells had been employed, our scheme allows to use conventional, spherical vapour cells. Spherical shaped cells have the advantage that they can be effectively coated inside with a spin relaxation suppressing layer providing long spin coherence times without addition of a buffer gas. Cavity enhancement shows in an increase in optical polarization rotation and sensitivity compared to single-pass configurations. PMID:26481853

  7. D- mesic atoms

    NASA Astrophysics Data System (ADS)

    García-Recio, C.; Nieves, J.; Salcedo, L. L.; Tolos, L.

    2012-02-01

    The anti-D meson self-energy is evaluated self-consistently, using unitarized coupled-channel theory, by computing the in-medium meson-baryon T matrix in the C=-1,S=0 sector. The heavy pseudo-scalar and heavy vector mesons, D¯ and D¯*, are treated on equal footing as required by heavy-quark spin symmetry. Results for energy levels and widths of D- mesic atoms in 12C, 40Ca, 118Sn, and 208Pb are presented. The spectrum contains states of atomic and of nuclear types for all nuclei. D¯0-nucleus bound states are also obtained. We find that, after electromagnetic and nuclear cascade, these systems end up with the D¯ bound in the nucleus, either as a meson or as part of an exotic D¯N (pentaquark) loosely bound state.

  8. Cavity enhanced atomic magnetometry.

    PubMed

    Crepaz, Herbert; Ley, Li Yuan; Dumke, Rainer

    2015-01-01

    Atom sensing based on Faraday rotation is an indispensable method for precision measurements, universally suitable for both hot and cold atomic systems. Here we demonstrate an all-optical magnetometer where the optical cell for Faraday rotation spectroscopy is augmented with a low finesse cavity. Unlike in previous experiments, where specifically designed multipass cells had been employed, our scheme allows to use conventional, spherical vapour cells. Spherical shaped cells have the advantage that they can be effectively coated inside with a spin relaxation suppressing layer providing long spin coherence times without addition of a buffer gas. Cavity enhancement shows in an increase in optical polarization rotation and sensitivity compared to single-pass configurations. PMID:26481853

  9. Cavity enhanced atomic magnetometry

    NASA Astrophysics Data System (ADS)

    Crepaz, Herbert; Ley, Li Yuan; Dumke, Rainer

    2015-10-01

    Atom sensing based on Faraday rotation is an indispensable method for precision measurements, universally suitable for both hot and cold atomic systems. Here we demonstrate an all-optical magnetometer where the optical cell for Faraday rotation spectroscopy is augmented with a low finesse cavity. Unlike in previous experiments, where specifically designed multipass cells had been employed, our scheme allows to use conventional, spherical vapour cells. Spherical shaped cells have the advantage that they can be effectively coated inside with a spin relaxation suppressing layer providing long spin coherence times without addition of a buffer gas. Cavity enhancement shows in an increase in optical polarization rotation and sensitivity compared to single-pass configurations.

  10. Interfacing ultracold atoms and mechanical oscillators on an atom chip

    NASA Astrophysics Data System (ADS)

    Treutlein, Philipp

    2010-03-01

    Ultracold atoms can be trapped and coherently manipulated close to a chip surface using atom chip technology. This opens the exciting possibility of studying interactions between atoms and on-chip solid-state systems such as micro- and nanostructured mechanical oscillators. One goal is to form hybrid quantum systems, in which atoms are used to read out, cool, and coherently manipulate the oscillators' state. In our work, we investigate different coupling mechanisms between ultracold atoms and mechanical oscillators. In a first experiment, we use atom-surface forces to couple the vibrations of a mechanical cantilever to the motion of a Bose-Einstein condensate in a magnetic microtrap on an atom chip. The atoms are trapped at about one micrometer distance from the cantilever surface. We make use of the coupling to read out the cantilever vibrations with the atoms and observe resonant coupling to several well-resolved mechanical modes of the condensate. In a second experiment, we investigate coupling via a 1D optical lattice that is formed by a laser beam retroreflected from a SiN membrane oscillator. The optical lattice serves as a `transfer rod' that couples vibrations of the membrane to the atoms and vice versa. We point out that the strong coupling regime can be reached in coupled atom-oscillator systems by placing both the atoms and the oscillator in a high-finesse optical cavity.

  11. Effect of liquid film on atomizing performance in airblast atomizers

    NASA Astrophysics Data System (ADS)

    Zhao, Qishou; Gan, Xiaohua

    1991-08-01

    Results are presented from a comprehensive consideration of the relationship between experimental data obtained in the course of several years on atomization characteristics and both (1) liquid film thickness and (2) airblast atomizer dynamic characteristics. It is noted that no liquid accumulation arises at the atomizer's edges.

  12. Atomic Absorption, Atomic Fluorescence, and Flame Emission Spectrometry.

    ERIC Educational Resources Information Center

    Horlick, Gary

    1984-01-01

    This review is presented in six sections. Sections focus on literature related to: (1) developments in instrumentation, measurement techniques, and procedures; (2) performance studies of flames and electrothermal atomizers; (3) applications of atomic absorption spectrometry; (4) analytical comparisons; (5) atomic fluorescence spectrometry; and (6)…

  13. Atomic lighthouse effect.

    PubMed

    Máximo, C E; Kaiser, R; Courteille, Ph W; Bachelard, R

    2014-11-01

    We investigate the deflection of light by a cold atomic cloud when the light-matter interaction is locally tuned via the Zeeman effect using magnetic field gradients. This "lighthouse" effect is strongest in the single-scattering regime, where deviation of the incident field is largest. For optically dense samples, the deviation is reduced by collective effects, as the increase in linewidth leads to a decrease in magnetic field efficiency. PMID:25401364

  14. Semiclassical model for atoms

    PubMed Central

    Pearson, Ralph G.

    1981-01-01

    The energies of several two- and three-electron atoms, in both ground states and excited states, are calculated by a very simple semiclassical model. The only change from Bohr's original method is to replace definite orbits by probability distribution functions based on classical dynamics. The energies are better than Hartree-Fock values. There is still a need for an exchange-energy correction. Images PMID:16593047

  15. Atomic lighthouse effect

    NASA Astrophysics Data System (ADS)

    Máximo, C. E.; Kaiser, R.; Courteille, Ph. W.; Bachelard, R.

    2014-11-01

    We investigate the deflection of light by a cold atomic cloud when the light-matter interaction is locally tuned via the Zeeman effect using magnetic field gradients. This "lighthouse" effect is strongest in the single-scattering regime, where deviation of the incident field is largest. For optically dense samples, the deviation is reduced by collective effects, as the increase in linewidth leads to a decrease of the magnetic field efficiency.

  16. Wild atom: Nuclear terrorism

    SciTech Connect

    1998-12-31

    Nuclear explosives are no longer beyond the reach of terrorists. The wild Atom simulation demonstrated that, because interdiction is difficult, governments must combat illicit possession of nuclear weapons, improve working relationships among domestic agencies, and curb rivalries among national and international counterproliferation and counterterrorism officials. If a nuclear incident occurs, officials must be trained for consequence management; the national security community and the national disaster medical community should be well practiced in working together and with experts in other countries.

  17. Seeing single atoms.

    PubMed

    Isaacson, Michael S

    2012-12-01

    New discoveries and ideas often occur at the confluence of events and technologies that allow them to happen. So it was with the first electron microscopic observations of individual atoms at the University of Chicago laboratory of Albert Crewe forty years ago. This paper will describe the technologies developed then, present some of the historical instrumental details and describe the rationale for the designs that came about in that laboratory over a period of about a decade. PMID:22871487

  18. Atomic emission spectroscopy

    NASA Technical Reports Server (NTRS)

    Andrew, K. H.

    1975-01-01

    The relationship between the Slater-Condon theory and the conditions within the atom as revealed by experimental data was investigated. The first spectrum of Si, Rb, Cl, Br, I, Ne, Ar, and Xe-136 and the second spectrum of As, Cu, and P were determined. Methods for assessing the phase stability of fringe counting interferometers and the design of an autoranging scanning system for digitizing the output of an infrared spectrometer and recording it on magnetic tape are described.

  19. Atomic properties of Lu+

    NASA Astrophysics Data System (ADS)

    Paez, Eduardo; Arnold, K. J.; Hajiyev, Elnur; Porsev, S. G.; Dzuba, V. A.; Safronova, U. I.; Safronova, M. S.; Barrett, M. D.

    2016-04-01

    Singly ionized lutetium has recently been suggested as a potential clock candidate. Here we report a joint experimental and theoretical investigation of Lu+. Measurements relevant to practical clock operation are made and compared to atomic structure calculations. Calculations of scalar and tensor polarizabilities for clock states over a range of wavelengths are also given. These results will be useful for future work with this clock candidate.

  20. Crystallization of Polymer Chains Chemically Attached on a Surface: Lamellar Orientation from Flat-on to Edge-on.

    PubMed

    Chen, Yihuang; Gan, Tiansheng; Ma, Chunfeng; Wang, Linge; Zhang, Guangzhao

    2016-05-26

    Crystallization of polymer chains confined on a surface greatly influences surface properties. We have grafted comb-like copolymer, consisting of poly(2-hydroxyethyl methacrylate) (PHEMA) backbone and semicrystalline poly(ε-caprolactone) (PCL) side chains, on silicon surface and investigated the crystallization of such confined PCL chains upon solvent evaporation by using atomic force microscopy (AFM), grazing incidence wide-angle X-ray scattering (GI-WAXS), and polarized optical microscope (POM). Our studies reveal that the PCL chains align and form "flat-on" lamellae at a low PCL chain density. As the chain density increases, the comb-like polymer (PHEMA-g-PCL) chains undergo pancake-to-mushroom-to-brush transition, and the lamellae turn from "flat-on" to "edge-on" in orientation. Further increasing PCL chain density leads the "edge-on" lamellae to change from a quasi-two-dimensional (quasi-2D) to quasi-three-dimensional (quasi-3D). Because of the confinements of polymer chains, we can observe the evolution of spherulites at different stages during the mushroom-to-brush transition of PHEMA-g-PCL chains. The confinements also result in knobbly substructures in the edge-on lamellae. PMID:27149242

  1. Atomic Weights and Isotopic Compositions

    National Institute of Standards and Technology Data Gateway

    SRD 144 Atomic Weights and Isotopic Compositions (Web, free access)   The atomic weights are available for elements 1 through 111, and isotopic compositions or abundances are given when appropriate.

  2. Atom-Light Hybrid Interferometer.

    PubMed

    Chen, Bing; Qiu, Cheng; Chen, Shuying; Guo, Jinxian; Chen, L Q; Ou, Z Y; Zhang, Weiping

    2015-07-24

    A new type of hybrid atom-light interferometer is demonstrated with atomic Raman amplification processes replacing the beam splitting elements in a traditional interferometer. This nonconventional interferometer involves correlated optical and atomic waves in the two arms. The correlation between atoms and light developed with the Raman process makes this interferometer different from conventional interferometers with linear beam splitters. It is observed that the high-contrast interference fringes are sensitive to the optical phase via a path change as well as the atomic phase via a magnetic field change. This new atom-light correlated hybrid interferometer is a sensitive probe of the atomic internal state and should find wide applications in precision measurement and quantum control with atoms and photons. PMID:26252684

  3. Real and Hybrid Atomic Orbitals.

    ERIC Educational Resources Information Center

    Cook, D. B.; Fowler, P. W.

    1981-01-01

    Demonstrates that the Schrodinger equation for the hydrogenlike atom separates in both spheroconal and prolate spheroidal coordinates and that these separations provide a sound theoretical basis for the real and hybrid atomic orbitals. (Author/SK)

  4. Atomic phenomena in dense plasmas

    SciTech Connect

    Weisheit, J.C.

    1981-03-01

    The following chapters are included: (1) the plasma environment, (2) perturbations of atomic structure, (3) perturbations of atomic collisions, (4) formation of spectral lines, and (5) dielectronic recombination. (MOW)

  5. Simultaneous multielement atomic absorption spectrometry with graphite furnace atomization

    NASA Astrophysics Data System (ADS)

    Harnly, James M.; Miller-Ihli, Nancy J.; O'Haver, Thomas C.

    The extended analytical range capability of a simultaneous multielement atomic absorption continuum source spectrometer (SIMAAC) was tested for furnace atomization with respect to the signal measurement mode (peak height and area), the atomization mode (from the wall or from a platform), and the temperature program mode (stepped or ramped atomization). These parameters were evaluated with respect to the shapes of the analytical curves, the detection limits, carry-over contamination and accuracy. Peak area measurements gave more linear calibration curves. Methods for slowing the atomization step heating rate, the use of a ramped temperature program or a platform, produced similar calibration curves and longer linear ranges than atomization with a stepped temperature program. Peak height detection limits were best using stepped atomization from the wall. Peak area detection limits for all atomization modes were similar. Carry-over contamination was worse for peak area than peak height, worse for ramped atomization than stepped atomization, and worse for atomization from a platform than from the wall. Accurate determinations (100 ± 12% for Ca, Cu, Fe, Mn, and Zn in National Bureau of Standards' Standard Reference Materials Bovine Liver 1577 and Rice Flour 1568 were obtained using peak area measurements with ramped atomization from the wall and stepped atomization from a platform. Only stepped atomization from a platform gave accurate recoveries for K. Accurate recoveries, 100 ± 10%, with precisions ranging from 1 to 36 % (standard deviation), were obtained for the determination of Al, Co, Cr, Fe, Mn, Mo, Ni. Pb, V and Zn in Acidified Waters (NBS SRM 1643 and 1643a) using stepped atomization from a platform.

  6. Chemical Synthesis of Ubiquitin Chains.

    PubMed

    Hemantha, Hosahalli P; Bondalapati, Somasekhar; Singh, Sumeet K; Brik, Ashraf

    2015-01-01

    Chemical synthesis of complex biomolecules such as proteins is a challenging adventure, yet rewarding in driving various biochemical and biophysical research activities. Over the years, the refinement of peptide synthesis and invention of ligation methodologies have led to the successful synthesis of several complex protein targets. Ubiquitin bioconjugates, which are being studied intensively by many groups due to their involvement in numerous biological processes, represent a fine example where chemistry is greatly aiding these studies. In this article, we describe the synthetic routes and strategies to prepare different ubiquitin analogs with desired modifications, as well as di-ubiquitin chains. PMID:26629614

  7. Rapid prototyping of versatile atom chips for atom interferometry applications.

    NASA Astrophysics Data System (ADS)

    Kasch, Brian; Squires, Matthew; Olson, Spencer; Kroese, Bethany; Imhof, Eric; Kohn, Rudolph; Stuhl, Benjamin; Schramm, Stacy; Stickney, James

    2016-05-01

    We present recent advances in the manipulation of ultracold atoms with ex-vacuo atom chips (i.e. atom chips that are not inside to the UHV chamber). Details will be presented of an experimental system that allows direct bonded copper (DBC) atom chips to be removed and replaced in minutes, requiring minimal re-optimization of parameters. This system has been used to create Bose-Einstein condensates, as well as magnetic waveguides with precisely tunable axial parameters, allowing double wells, pure harmonic confinement, and modified harmonic traps. We investigate the effects of higher order magnetic field contributions to the waveguide, and the implications for confined atom interferometry.

  8. Indirect Determinations of Atomic Radii

    ERIC Educational Resources Information Center

    Walker, Noojin

    1976-01-01

    Describes laboratory activities which relate the mass, volume, density, and radii of atoms through the assumption that the smallest unit of matter is a cubic box containing one atom. From calculations based on macroscopic materials, the author feels that the concept of an atom may be better developed. (CP)

  9. Atomizer with liquid spray quenching

    DOEpatents

    Anderson, Iver E.; Osborne, Matthew G.; Terpstra, Robert L.

    1998-04-14

    Method and apparatus for making metallic powder particles wherein a metallic melt is atomized by a rotating disk or other atomizer at an atomizing location in a manner to form molten droplets moving in a direction away from said atomizing location. The atomized droplets pass through a series of thin liquid quenching sheets disposed in succession about the atomizing location with each successive quenching sheet being at an increasing distance from the atomizing location. The atomized droplets are incrementally cooled and optionally passivated as they pass through the series of liquid quenching sheets without distorting the atomized droplets from their generally spherical shape. The atomized, cooled droplets can be received in a chamber having a collection wall disposed outwardly of the series of liquid quenching sheets. A liquid quenchant can be flowed proximate the chamber wall to carry the cooled atomized droplets to a collection chamber where atomized powder particles and the liquid quenchant are separated such that the liquid quenchant can be recycled.

  10. Atomizer with liquid spray quenching

    DOEpatents

    Anderson, I.E.; Osborne, M.G.; Terpstra, R.L.

    1998-04-14

    Method and apparatus are disclosed for making metallic powder particles wherein a metallic melt is atomized by a rotating disk or other atomizer at an atomizing location in a manner to form molten droplets moving in a direction away from said atomizing location. The atomized droplets pass through a series of thin liquid quenching sheets disposed in succession about the atomizing location with each successive quenching sheet being at an increasing distance from the atomizing location. The atomized droplets are incrementally cooled and optionally passivated as they pass through the series of liquid quenching sheets without distorting the atomized droplets from their generally spherical shape. The atomized, cooled droplets can be received in a chamber having a collection wall disposed outwardly of the series of liquid quenching sheets. A liquid quenchant can be flowed proximate the chamber wall to carry the cooled atomized droplets to a collection chamber where atomized powder particles and the liquid quenchant are separated such that the liquid quenchant can be recycled. 6 figs.

  11. Lasers, Understanding the Atom Series.

    ERIC Educational Resources Information Center

    Hellman, Hal

    This booklet is one of the booklets in the "Understanding the Atom Series" published by the U. S. Atomic Energy Commission for high school science teachers and their students. Basic information for understanding the laser is provided including discussion of the electromagnetic spectrum, radio waves, light and the atom, coherent light, controlled…

  12. 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…

  13. Current Trends in Atomic Spectroscopy.

    ERIC Educational Resources Information Center

    Wynne, James J.

    1983-01-01

    Atomic spectroscopy is the study of atoms/ions through their interaction with electromagnetic radiation, in particular, interactions in which radiation is absorbed or emitted with an internal rearrangement of the atom's electrons. Discusses nature of this field, its status and future, and how it is applied to other areas of physics. (JN)

  14. Molecular dynamics simulations of silica nanoparticles grafted with poly(ethylene oxide) oligomer chains.

    PubMed

    Hong, Bingbing; Panagiotopoulos, Athanassios Z

    2012-03-01

    A molecular model of silica nanoparticles grafted with poly(ethylene oxide) oligomers has been developed for predicting the transport properties of nanoparticle organic-hybrid materials (NOHMs). Ungrafted silica nanoparticles in a medium of poly(ethylene oxide) oligomers were also simulated to clarify the effect of grafting on the dynamics of nanoparticles and chains. The model approximates nanoparticles as solid spheres and uses a united-atom representation for chains, including torsional and bond-bending interactions. The calculated viscosities from Green-Kubo relationships and temperature extrapolation are of the same order of magnitude as experimental data but show a smaller activation energy relative to real NOHMs systems. Grafted systems have higher viscosities, smaller diffusion coefficients, and slower chain dynamics than the ungrafted ones at high temperatures. At lower temperatures, grafted systems exhibit faster dynamics for both nanoparticles and chains relative to ungrafted systems, because of lower aggregation of particles and enhanced correlations between nanoparticles and chains. This agrees with the experimental observation that NOHMs have liquidlike behavior in the absence of a solvent. For both grafted and ungrafted systems at low temperatures, increasing chain length reduces the volume fraction of nanoparticles and accelerates the dynamics. However, at high temperatures, longer chains slow down nanoparticle diffusion. From the Stokes-Einstein relationship, it was determined that the coarse-grained treatment of nanoparticles leads to slip on the nanoparticle surfaces. Grafted systems obey the Stokes-Einstein relationship over the temperature range simulated, but ungrafted systems display deviations from it. PMID:22243140

  15. Acyl Chain Disorder and Azelaoyl Orientation in Lipid Membranes Containing Oxidized Lipids.

    PubMed

    Mendes Ferreira, Tiago; Sood, Rohit; Bärenwald, Ruth; Carlström, Göran; Topgaard, Daniel; Saalwächter, Kay; Kinnunen, Paavo K J; Ollila, O H Samuli

    2016-06-28

    Oxidized phospholipids occur naturally in conditions of oxidative stress and have been suggested to play an important role in a number of pathological conditions due to their effects on a lipid membrane acyl chain orientation, ordering, and permeability. Here we investigate the effect of the oxidized phospholipid 1-palmitoyl-2-azelaoyl-sn-glycero-3-phosphocholine (PazePC) on a model membrane of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) using a combination of (13)C-(1)H dipolar-recoupling nuclear magnetic resonance (NMR) experiments and united-atom molecular dynamics (MD) simulations. The obtained experimental order parameter SCH profiles show that the presence of 30 mol % PazePC in the bilayer significantly increases the gauche content of the POPC acyl chains, therefore decreasing the thickness of the bilayer, although with no stable bilayer pore formation. The MD simulations reproduce the disordering effect and indicate that the orientation of the azelaoyl chain is highly dependent on its protonation state with acyl chain reversal for fully deprotonated states and a parallel orientation along the interfacial plane for fully protonated states, deprotonated and protonated azelaoyl chains having negative and positive SCH profiles, respectively. Only fully or nearly fully protonated azelaoyl chain are observed in the (13)C-(1)H dipolar-recoupling NMR experiments. The experiments show positive SCH values for the azelaoyl segments confirming for the first time that oxidized chains with polar termini adopt a parallel orientation to the bilayer plane as predicted in MD simulations. PMID:27260273

  16. Biosynthesis and Elongation of Short- and Medium-Chain-Length Fatty Acids

    PubMed Central

    van der Hoeven, Rutger S.; Steffens, John C.

    2000-01-01

    Short- and medium-chain-length fatty acids (FAs) are important constituents of a wide array of natural products. Branched and straight short-chain-length FAs originate from branched chain amino acid metabolism, and serve as primers for elongation in FA synthase-like reactions. However, a recent model proposes that the one-carbon extension reactions that utilize 2-oxo-3-methylbutyric acid in leucine biosynthesis also catalyze a repetitive one-carbon elongation of short-chain primers to medium-chain-length FAs. The existence of such a mechanism would require a novel form of regulation to control carbon flux between amino acid and FA biosynthesis. A critical re-analysis of the data used to support this pathway fails to support the hypothesis for FA elongation by one-carbon extension cycles of α-ketoacids. Therefore, we tested the hypothesis experimentally using criteria that distinguish between one- and two-carbon elongation mechanisms: (a) isotopomer patterns in terminal carbon atom pairs of branched and straight FAs resulting from differential labeling with [13C]acetate; (b) [13C]threonine labeling patterns in odd- and even chain length FAs; and (c) differential sensitivity of elongation reactions to inhibition by cerulenin. All three criteria indicated that biosynthesis of medium-chain length FAs is mediated primarily by FA synthase-like reactions. PMID:10631271

  17. Conformational Optimization with Natural Degrees of Freedom: A Novel Stochastic Chain Closure Algorithm

    PubMed Central

    Levitt, Michael

    2010-01-01

    Abstract The present article introduces a set of novel methods that facilitate the use of “natural moves” or arbitrary degrees of freedom that can give rise to collective rearrangements in the structure of biological macromolecules. While such “natural moves” may spoil the stereochemistry and even break the bonded chain at multiple locations, our new method restores the correct chain geometry by adjusting bond and torsion angles in an arbitrary defined molten zone. This is done by successive stages of partial closure that propagate the location of the chain break backwards along the chain. At the end of these stages, the size of the chain break is generally reduced so much that it can be repaired by adjusting the position of a single atom. Our chain closure method is efficient with a computational complexity of O(Nd), where Nd is the number of degrees of freedom used to repair the chain break. The new method facilitates the use of arbitrary degrees of freedom including the “natural” degrees of freedom inferred from analyzing experimental (X-ray crystallography and nuclear magnetic resonance [NMR]) structures of nucleic acids and proteins. In terms of its ability to generate large conformational moves and its effectiveness in locating low energy states, the new method is robust and computationally efficient. PMID:20726792

  18. An overview of heavy-atom derivatization of protein crystals

    PubMed Central

    Pike, Ashley C. W.; Garman, Elspeth F.; Krojer, Tobias; von Delft, Frank; Carpenter, Elisabeth P.

    2016-01-01

    Heavy-atom derivatization is one of the oldest techniques for obtaining phase information for protein crystals and, although it is no longer the first choice, it remains a useful technique for obtaining phases for unknown structures and for low-resolution data sets. It is also valuable for confirming the chain trace in low-resolution electron-density maps. This overview provides a summary of the technique and is aimed at first-time users of the method. It includes guidelines on when to use it, which heavy atoms are most likely to work, how to prepare heavy-atom solutions, how to derivatize crystals and how to determine whether a crystal is in fact a derivative. PMID:26960118

  19. Atomic structure and electronic properties of the two-dimensional (Au ,Al )/Si (111 )2 ×2 compound

    NASA Astrophysics Data System (ADS)

    Gruznev, D. V.; Bondarenko, L. V.; Matetskiy, A. V.; Tupchaya, A. Y.; Chukurov, E. N.; Hsing, C. R.; Wei, C. M.; Eremeev, S. V.; Zotov, A. V.; Saranin, A. A.

    2015-12-01

    A combination of scanning tunneling microscopy, angle-resolved photoelectron spectroscopy, ab initio random structure searching, and density functional theory electronic structure calculations was applied to elucidate the atomic arrangement and electron band structure of the (Au ,Al )/Si (111 )2 ×2 two-dimensional compound formed upon Al deposition onto the mixed 5 ×2 /√{3 }×√{3 } Au/Si(111) surface. It was found that the most stable 2 ×2 -(Au, Al) compound incorporates four Au atoms, three Al atoms, and two Si atoms per 2 ×2 unit cell. Its atomic arrangement can be visualized as an array of meandering Au atomic chains with two-thirds of the Al atoms incorporated into the chains and one-third of the Al atoms interconnecting the chains. The compound is metallic and its electronic properties can be controlled by appropriate Al dosing since energetic location of the bands varies by ˜0.5 eV during increasing of Al contents. The 2 ×2 -(Au, Al) structure appears to be lacking the C3 v symmetry typical for the hexagonal lattices. The consequence of the peculiar atomic structure of the two-dimensional alloy is spin splitting of the metallic states, which should lead to anisotropy of the current-induced in-plane spin polarization.

  20. Two Cases of Heavy Chain MGUS.

    PubMed

    Van Keer, Jan; Meijers, Björn; Delforge, Michel; Verhoef, Gregor; Poesen, Koen

    2016-01-01

    Heavy chain diseases are rare variants of B-cell lymphomas that produce one of three classes of immunoglobulin heavy chains, without corresponding light chains. We describe two patients with asymptomatic heavy chain monoclonal gammopathy. The first patient is a 51-year-old woman with alpha paraprotein on serum immunofixation. The second case is a 46-year-old woman with gamma paraprotein on urine immunofixation. Neither patient had corresponding monoclonal light chains. Workup for multiple myeloma and lymphoma was negative in both patients. These two cases illustrate that heavy chain monoclonal gammopathy can exist in the absence of clinically apparent malignancy. Only a few reports of "heavy chain MGUS" have been described before. In the absence of specialized guidelines, we suggest a similar follow-up as for MGUS, while taking into account the higher probability of progression to lymphoma than to myeloma. PMID:27213064

  1. Two Cases of Heavy Chain MGUS

    PubMed Central

    Meijers, Björn; Delforge, Michel; Verhoef, Gregor; Poesen, Koen

    2016-01-01

    Heavy chain diseases are rare variants of B-cell lymphomas that produce one of three classes of immunoglobulin heavy chains, without corresponding light chains. We describe two patients with asymptomatic heavy chain monoclonal gammopathy. The first patient is a 51-year-old woman with alpha paraprotein on serum immunofixation. The second case is a 46-year-old woman with gamma paraprotein on urine immunofixation. Neither patient had corresponding monoclonal light chains. Workup for multiple myeloma and lymphoma was negative in both patients. These two cases illustrate that heavy chain monoclonal gammopathy can exist in the absence of clinically apparent malignancy. Only a few reports of “heavy chain MGUS” have been described before. In the absence of specialized guidelines, we suggest a similar follow-up as for MGUS, while taking into account the higher probability of progression to lymphoma than to myeloma. PMID:27213064

  2. Origin of membrane dipole potential: contribution of the phospholipid fatty acid chains.

    PubMed

    Peterson, Uwe; Mannock, David A; Lewis, Ruthven N A H; Pohl, Peter; McElhaney, Ronald N; Pohl, Elena E

    2002-08-01

    The large intrinsic membrane dipole potential, phi(d), is important for protein insertion and functioning as well as for ion transport across natural and model membranes. However, the origin of phi(d) is controversial. From experiments carried out with lipid monolayers, a significant dependence on the fatty acid chain length is suggested, whereas in experiments with lipid bilayers, the contribution of additional -CH(2)-groups seems negligibly small compared with that of the phospholipid carbonyl groups and lipid-bound water molecules. To compare the impact of the -CH(2)-groups of dipalmitoylphosphatidylcholine (DPPC) near and far from the glycerol backbone, we have varied the structure of DPPC by incorporation of sulfur atoms in place of methylene groups in different positions of the fatty acid chain. The phi(d) of symmetric lipid bilayers containing one heteroatom was obtained from the charge relaxation of oppositely charged hydrophobic ions. We have found that the substitution for a S-atom of a -CH(2)-group decreases phi(d). The effect (deltaphi(d) = -22.6 mV) is most pronounced for S-atoms near the lipid head group while a S-atom substitution in the C(13)- or C(14)-position of the hydrocarbon chain does not effect the bilayer dipole potential. Most probably deltaphi(d) does not originate from an altered dipole potential of the acyl chain containing an heteroatom but is mediated by the disruption of chain packing, leading to a decreased density of lipid dipoles in the membrane. PMID:12191841

  3. Nova chain design and performance

    SciTech Connect

    Simmons, W.W.; Glaze, J.A.; Trenholme, J.B.; Hagen, W.F.

    1980-09-04

    During the past year design of the Nova laser has undergone significant change as a result of developments in our laser glass and optical coating evaluation programs. Two notable aspects of the glass development program deserve emphasis. First, vendor qualification for production of fluorophosphate laser glass is progressing satisfactorily. There is a reasonable expectation that vendors can meet fluorophosphate glass specifications within Nova schedule constraints. Secondly, recent gain saturation measurements have shown that the saturation fluence of the fluorophosphate glass is larger than previously supposed (approx. 5.5 J/cm/sup 2/) and in fact is somewhat larger than Shiva silicate glasses. Hence, performance of Nova for pulses in the 3 ns and longer range should be satisfactory. For pulses in the 1 ns regime, of course, the fluorophosphate chain will have superior performance to that of silicate because of its low nonlinear index of refraction (approx. 30% that of silicate). These and other considerations have led us to choose a chain design based upon the use of fluorophosphate glass in our amplifiers.

  4. From isotropic to anisotropic side chain representations: comparison of three models for residue contact estimation.

    PubMed

    Sun, Weitao; He, Jing

    2011-01-01

    The criterion to determine residue contact is a fundamental problem in deriving knowledge-based mean-force potential energy calculations for protein structures. A frequently used criterion is to require the side chain center-to-center distance or the -to- atom distance to be within a pre-determined cutoff distance. However, the spatially anisotropic nature of the side chain determines that it is challenging to identify the contact pairs. This study compares three side chain contact models: the Atom Distance criteria (ADC) model, the Isotropic Sphere Side chain (ISS) model and the Anisotropic Ellipsoid Side chain (AES) model using 424 high resolution protein structures in the Protein Data Bank. The results indicate that the ADC model is the most accurate and ISS is the worst. The AES model eliminates about 95% of the incorrectly counted contact-pairs in the ISS model. Algorithm analysis shows that AES model is the most computational intensive while ADC model has moderate computational cost. We derived a dataset of the mis-estimated contact pairs by AES model. The most misjudged pairs are Arg-Glu, Arg-Asp and Arg-Tyr. Such a dataset can be useful for developing the improved AES model by incorporating the pair-specific information for the cutoff distance. PMID:21552527

  5. Transport of atom packets in a train of Ioffe-Pritchard traps

    SciTech Connect

    Lahaye, T.; Reinaudi, G.; Wang, Z.; Couvert, A.; Guery-Odelin, D.

    2006-09-15

    We demonstrate transport and evaporative cooling of several atomic clouds in a chain of magnetic Ioffe-Pritchard traps moving at a low speed (<1 m/s). The trapping scheme relies on the use of a magnetic guide for transverse confinement and of magnets fixed on a conveyor belt for longitudinal trapping. This experiment introduces a different approach for parallelizing the production of Bose-Einstein condensates as well as for the realization of a continuous atom laser.

  6. Quantum transport in ultracold atoms

    NASA Astrophysics Data System (ADS)

    Chien, Chih-Chun; Peotta, Sebastiano; di Ventra, Massimiliano

    2015-12-01

    Ultracold atoms confined by engineered magnetic or optical potentials are ideal to study phenomena otherwise difficult to realize or probe in the solid state, thanks to the ability to control the atomic interaction strength, number of species, density and geometry. Here, we review quantum transport phenomena in atomic gases that mirror and can either better elucidate or show fundamental differences with respect to those observed in mesoscopic and nanoscopic systems. We discuss the significant progress in transport experiments in atomic gases, the similarities and differences between transport in cold atoms and in condensed matter systems, and survey theoretical predictions that are difficult to verify in conventional set-ups.

  7. Atomization and mixing study

    NASA Technical Reports Server (NTRS)

    Ferrenberg, A.; Jaqua, V. W.

    1983-01-01

    The state of the art in atomization and mixing for triplet, pentad, and coaxial injectors is described. Injectors that are applicable for LOX/hydrocarbon propellants and main chamber and fuel rich preburner/gas generator mixture ratios are of special interest. Various applicable correlating equations and parameters as well as test data found in the literature are presented. The validity, utility, and important aspects of these data and correlations are discussed and the measurement techniques used are evaluated. Propellant mixing tests performed are described and summarized, results are reported, and tentative conclusions are included.

  8. Atomic transport of oxygen

    SciTech Connect

    Routbort, J.L.; Tomlins, G.W.

    1994-06-15

    Atomic transport of oxygen in nonstoichiometric oxides is an extremely important topic which overlaps science and technology. In many cases the diffusion of oxygen controls sintering, grain growth, and creep. High oxygen diffusivity is critical for efficient operation of many fuel cells. Additionally, oxygen diffusivities are an essential ingredient in any point defect model. Secondary Ion Mass Spectrometry (SIMS) is the most accurate modern technique to measure oxygen tracer diffusion. This paper briefly reviews the principles and applications of SIMS for the measurement of oxygen transport. Case studies are taken from recent work on ZnO and some high-temperature superconductors.

  9. Ultraviolet atomic emission detector

    NASA Technical Reports Server (NTRS)

    Braun, W.; Peterson, N. C.; Bass, A. M.; Kurylo, M. J., III (Inventor)

    1972-01-01

    A device and method are provided for performing qualitative and quantitative elemental analysis through the utilization of a vacuum UV chromatographic detector. The method involves the use of a carrier gas at low pressure. The gas carries a sample to a gas chromatograph column; the column output is directed to a microwave cavity. In this cavity, a low pressure microwave discharge produces fragmentation of the compounds present and generates intense atomic emissions in the vacuum ultraviolet. These emissions are isolated by a monochromator and measured by photometer to establish absolute concentration for the elements.

  10. Atomic data for fusion

    SciTech Connect

    Hunter, H.T.; Kirkpatrick, M.I.; Alvarez, I.; Cisneros, C.; Phaneuf, R.A.; Barnett, C.F.

    1990-07-01

    This report provides a handbook of recommended cross-section and rate-coefficient data for inelastic collisions between hydrogen, helium and lithium atoms, molecules and ions, and encompasses more than 400 different reactions of primary interest in fusion research. Published experimental and theoretical data have been collected and evaluated, and the recommended data are presented in tabular, graphical and parametrized form. Processes include excitation and spectral line emission, charge exchange, ionization, stripping, dissociation and particle interchange reactions. The range of collision energies is appropriate to applications in fusion-energy research.

  11. The coupled atom transistor.

    PubMed

    Jehl, X; Voisin, B; Roche, B; Dupont-Ferrier, E; De Franceschi, S; Sanquer, M; Cobian, M; Niquet, Y-M; Sklénard, B; Cueto, O; Wacquez, R; Vinet, M

    2015-04-22

    We describe the first implementation of a coupled atom transistor where two shallow donors (P or As) are implanted in a nanoscale silicon nanowire and their electronic levels are controlled with three gate voltages. Transport spectroscopy through these donors placed in series is performed both at zero and microwave frequencies. The coherence of the charge transfer between the two donors is probed by Landau-Zener-Stückelberg interferometry. Single-charge transfer at zero bias (electron pumping) has been performed and the crossover between the adiabatic and non-adiabatic regimes is studied. PMID:25783566

  12. The coupled atom transistor

    NASA Astrophysics Data System (ADS)

    Jehl, X.; Voisin, B.; Roche, B.; Dupont-Ferrier, E.; De Franceschi, S.; Sanquer, M.; Cobian, M.; Niquet, Y.-M.; Sklénard, B.; Cueto, O.; Wacquez, R.; Vinet, M.

    2015-04-01

    We describe the first implementation of a coupled atom transistor where two shallow donors (P or As) are implanted in a nanoscale silicon nanowire and their electronic levels are controlled with three gate voltages. Transport spectroscopy through these donors placed in series is performed both at zero and microwave frequencies. The coherence of the charge transfer between the two donors is probed by Landau-Zener-Stückelberg interferometry. Single-charge transfer at zero bias (electron pumping) has been performed and the crossover between the adiabatic and non-adiabatic regimes is studied.

  13. Hydrogen molecules and chains in a superstrong magnetic field

    NASA Technical Reports Server (NTRS)

    Lai, Dong; Salpeter, Edwin E.; Shapiro, Stuart L.

    1992-01-01

    The electronic structures of hydrogen polymolecules H(n) (n = 2,3,4,...) is studied in a superstrong magnetic field (B greater than about 10 exp 12 G) typically found on the surface of a neutron star. Simple analytical scaling relations for several limiting cases (e.g., large n, high B field) are derived. The binding energies of H(n) molecules are numerically calculated for various magnetic-field strengths. For a given magnetic-field strength, the binding energy per atom in the H(n) molecules is found to approach a constant value as n increases. For typical field strengths of interest, energy saturation is essentially achieved once n exceeds 3 to 4. Also considered is the structure of negative H ions in a high magnetic field. For B about 10 exp 12 G, the dissociation energy of an atom in a hydrogen chain and the ionization potential of H(-) are smaller than the ionization potential of neutral atomic hydrogen.

  14. Atomically resolved force microscopy at room temperature

    SciTech Connect

    Morita, Seizo

    2014-04-24

    Atomic force microscopy (AFM) can now not only image individual atoms but also construct atom letters using atom manipulation method even at room temperature (RT). Therefore, the AFM is the second generation atomic tool following the scanning tunneling microscopy (STM). However the AFM can image even insulating atoms, and also directly measure/map the atomic force and potential at the atomic scale. Noting these advantages, we have been developing a bottom-up nanostructuring system at RT based on the AFM. It can identify chemical species of individual atoms and then manipulate selected atom species to the predesigned site one-by-one to assemble complex nanostructures consisted of multi atom species at RT. Here we introduce our results toward atom-by-atom assembly of composite nanostructures based on the AFM at RT including the latest result on atom gating of nano-space for atom-by-atom creation of atom clusters at RT for semiconductor surfaces.

  15. Cancer in atomic bomb survivors

    SciTech Connect

    Shigematsu, I.; Kagan, A.

    1986-01-01

    This book presents information on the following topics: sampling of atomic bomb survivors and method of cancer detection in Hiroshima and Nagasaki; atomic bomb dosimetry for epidemiological studies of survivors in Hiroshima and Nagasaki; tumor and tissue registries in Hiroshima and Nagasaki; the cancer registry in Nagasaki, with atomic bomb survivor data, 1973-1977; cancer mortality; methods for study of delayed health effects of a-bomb radiation; experimental radiation carcinogenesis in rodents; leukemia, multiple myeloma, and malignant lymphoma; cancer of the thyroid and salivary glands; malignant tumors in atomic bomb survivors with special reference to the pathology of stomach and lung cancer; colorectal cancer among atomic bomb survivors; breast cancer in atomic bomb survivors; and ovarian neoplasms in atomic bomb survirors.

  16. Current-driven atomic waterwheels

    NASA Astrophysics Data System (ADS)

    Dundas, Daniel; McEniry, Eunan J.; Todorov, Tchavdar N.

    2009-02-01

    A current induces forces on atoms inside the conductor that carries it. It is now possible to compute these forces from scratch, and to perform dynamical simulations of the atomic motion under current. One reason for this interest is that current can be a destructive force-it can cause atoms to migrate, resulting in damage and in the eventual failure of the conductor. But one can also ask, can current be made to do useful work on atoms? In particular, can an atomic-scale motor be driven by electrical current, as it can be by other mechanisms? For this to be possible, the current-induced forces on a suitable rotor must be non-conservative, so that net work can be done per revolution. Here we show that current-induced forces in atomic wires are not conservative and that they can be used, in principle, to drive an atomic-scale waterwheel.

  17. Current-driven atomic waterwheels.

    PubMed

    Dundas, Daniel; McEniry, Eunan J; Todorov, Tchavdar N

    2009-02-01

    A current induces forces on atoms inside the conductor that carries it. It is now possible to compute these forces from scratch, and to perform dynamical simulations of the atomic motion under current. One reason for this interest is that current can be a destructive force--it can cause atoms to migrate, resulting in damage and in the eventual failure of the conductor. But one can also ask, can current be made to do useful work on atoms? In particular, can an atomic-scale motor be driven by electrical current, as it can be by other mechanisms? For this to be possible, the current-induced forces on a suitable rotor must be non-conservative, so that net work can be done per revolution. Here we show that current-induced forces in atomic wires are not conservative and that they can be used, in principle, to drive an atomic-scale waterwheel. PMID:19197311

  18. BetaSCPWeb: side-chain prediction for protein structures using Voronoi diagrams and geometry prioritization.

    PubMed

    Ryu, Joonghyun; Lee, Mokwon; Cha, Jehyun; Laskowski, Roman A; Ryu, Seong Eon; Kim, Deok-Soo

    2016-07-01

    Many applications, such as protein design, homology modeling, flexible docking, etc. require the prediction of a protein's optimal side-chain conformations from just its amino acid sequence and backbone structure. Side-chain prediction (SCP) is an NP-hard energy minimization problem. Here, we present BetaSCPWeb which efficiently computes a conformation close to optimal using a geometry-prioritization method based on the Voronoi diagram of spherical atoms. Its outputs are visual, textual and PDB file format. The web server is free and open to all users at http://voronoi.hanyang.ac.kr/betascpweb with no login requirement. PMID:27151195

  19. BetaSCPWeb: side-chain prediction for protein structures using Voronoi diagrams and geometry prioritization

    PubMed Central

    Ryu, Joonghyun; Lee, Mokwon; Cha, Jehyun; Laskowski, Roman A.; Ryu, Seong Eon; Kim, Deok-Soo

    2016-01-01

    Many applications, such as protein design, homology modeling, flexible docking, etc. require the prediction of a protein's optimal side-chain conformations from just its amino acid sequence and backbone structure. Side-chain prediction (SCP) is an NP-hard energy minimization problem. Here, we present BetaSCPWeb which efficiently computes a conformation close to optimal using a geometry-prioritization method based on the Voronoi diagram of spherical atoms. Its outputs are visual, textual and PDB file format. The web server is free and open to all users at http://voronoi.hanyang.ac.kr/betascpweb with no login requirement. PMID:27151195

  20. Continuous chain bit with downhole cycling capability

    DOEpatents

    Ritter, Don F.; St. Clair, Jack A.; Togami, Henry K.

    1983-01-01

    A continuous chain bit for hard rock drilling is capable of downhole cycling. A drill head assembly moves axially relative to a support body while the chain on the head assembly is held in position so that the bodily movement of the chain cycles the chain to present new composite links for drilling. A pair of spring fingers on opposite sides of the chain hold the chain against movement. The chain is held in tension by a spring-biased tensioning bar. A head at the working end of the chain supports the working links. The chain is centered by a reversing pawl and piston actuated by the pressure of the drilling mud. Detent pins lock the head assembly with respect to the support body and are also operated by the drilling mud pressure. A restricted nozzle with a divergent outlet sprays drilling mud into the cavity to remove debris. Indication of the centered position of the chain is provided by noting a low pressure reading indicating proper alignment of drilling mud slots on the links with the corresponding feed branches.

  1. Experiments in cold atom optics towards precision atom interferometry

    NASA Astrophysics Data System (ADS)

    Aveline, David C.

    Atom optics has been a highly active field of research with many scientific breakthroughs over the past two decades, largely due to successful advances in laser technology, microfabrication techniques, and the development of laser cooling and trapping of neutral atoms. This dissertation details several atom optics experiments with the motivation to develop tools and techniques for precision atom wave interferometry. It provides background information about atom optics and the fundamentals behind laser cooling and trapping, including basic techniques for cold gas thermometry and absorptive detection of atoms. A brief overview of magnetic trapping and guiding in tight wire-based traps is also provided before the experimental details are presented. We developed a novel laser source of 780 nm light using frequency-doubled 1560 nm fiber amplifier. This laser system provided up to a Watt of tunable frequency stabilized light for two Rb laser cooling and trapping experiments. One system generates Bose-Einstein condensates in an optical trap while the second is based on atom chip magnetic traps. The atom chip system, detailed in this thesis, was designed and built to develop the tools necessary for transport and loading large numbers of cold atoms and explore the potential for guided atom interferometry. Techniques and results from this experiment are presented, including an efficient magnetic transport and loading method to deliver cold atom to atom chip traps. We also developed a modeling tool for the magnetic fields formed by coiled wire geometries, as well as planar wire patterns. These models helped us design traps and determine adiabatic transportation of cold atoms between macro-scale traps and micro-traps formed on atom chips. Having achieved near unity transfer efficiency, we demonstrated that this approach promises to be a consistent method for loading large numbers of atoms into micro-traps. Furthermore, we discuss an in situ imaging technique to investigate

  2. Neuromorphic Atomic Switch Networks

    PubMed Central

    Martin-Olmos, Cristina; Shieh, Hsien Hang; Aono, Masakazu; Stieg, Adam Z.; Gimzewski, James K.

    2012-01-01

    Efforts to emulate the formidable information processing capabilities of the brain through neuromorphic engineering have been bolstered by recent progress in the fabrication of nonlinear, nanoscale circuit elements that exhibit synapse-like operational characteristics. However, conventional fabrication techniques are unable to efficiently generate structures with the highly complex interconnectivity found in biological neuronal networks. Here we demonstrate the physical realization of a self-assembled neuromorphic device which implements basic concepts of systems neuroscience through a hardware-based platform comprised of over a billion interconnected atomic-switch inorganic synapses embedded in a complex network of silver nanowires. Observations of network activation and passive harmonic generation demonstrate a collective response to input stimulus in agreement with recent theoretical predictions. Further, emergent behaviors unique to the complex network of atomic switches and akin to brain function are observed, namely spatially distributed memory, recurrent dynamics and the activation of feedforward subnetworks. These devices display the functional characteristics required for implementing unconventional, biologically and neurally inspired computational methodologies in a synthetic experimental system. PMID:22880101

  3. ATOMIC POWER PLANT

    DOEpatents

    Daniels, F.

    1957-11-01

    This patent relates to neutronic reactor power plants and discloses a design of a reactor utilizing a mixture of discrete units of a fissionable material, such as uranium carbide, a neutron moderator material, such as graphite, to carry out the chain reaction. A liquid metal, such as bismuth, is used as the coolant and is placed in the reactor chamber with the fissionable and moderator material so that it is boiled by the heat of the reaction, the boiling liquid and vapors passing up through the interstices between the discrete units. The vapor and flue gases coming off the top of the chamber are passed through heat exchangers, to produce steam, for example, and thence through condensers, the condensed coolant being returned to the chamber by gravity and the non- condensible gases being carried off through a stack at the top of the structure.

  4. Cl atom initiated oxidation of 1-alkenes under atmospheric conditions

    NASA Astrophysics Data System (ADS)

    Walavalkar, M.; Sharma, A.; Alwe, H. D.; Pushpa, K. K.; Dhanya, S.; Naik, P. D.; Bajaj, P. N.

    2013-03-01

    In view of the importance of the oxidation pathways of alkenes in the troposphere, and the significance of Cl atom as an oxidant in marine boundary layer (MBL) and polluted industrial atmosphere, the reactions of four 1-alkenes (C6-C9) with Cl atoms are investigated. The rate coefficients at 298 K are measured to be (4.0 ± 0.5), (4.4 ± 0.7), (5.5 ± 0.9) and (5.9 ± 1.7) × 10-10 cm3 molecule-1 s-1 for 1-hexene, 1-heptene, 1-octene and 1-nonene, respectively. The quoted errors include the experimental 2σ, along with the error in the reference rate coefficients. From the systematic increase in the rate coefficients with the number of carbon atoms, an approximate value for the average rate coefficient for hydrogen abstraction per CH2 group in alkenes is estimated to be (4.9 ± 0.3) × 10-11 cm3 molecule-1 s-1. Based on these rate coefficients, the contribution of Cl atom reactions towards the degradation of these molecules is found to be comparable to that of OH radical reactions, under MBL conditions. The products identified in gas phase indicate that Cl atom addition occurs mainly at the terminal carbon, leading to the formation of 1-chloro-2-ketones and 1-chloro-2-ols. The major gas phase products from the alkenyl radicals (formed by H atom abstraction) are different positional isomers of long chain enols and enones. A preference for dissociation leading to an allyl radical, resulting in aldehydes, lower by three carbon atoms, is indicated. The observed relative yields suggest that in general, the increased contribution of the reactions of Cl atoms towards degradation of 1-alkenes in NOx free air does not result in an increase in the generation of small aldehydes (carbon number < 4), including chloroethanal, as compared to that in the reaction of 1-butene.

  5. Pentagon chain in external fields

    NASA Astrophysics Data System (ADS)

    Kovács, György; Gulácsi, Zsolt

    2015-11-01

    We consider a pentagon chain described by a Hubbard type of model considered under periodic boundary conditions. The system (i) is placed in an external magnetic field perpendicular to the plane of the cells, and (ii) is in a site-selective manner under the action of an external electric potential. In these conditions, we show in an exact manner that the physical properties of the system can be qualitatively changed. The changes cause first strong modifications of the band structure of the system created by the one-particle part of the Hamiltonian, and second, produce marked changes of the phase diagram. We exemplify this by deducing ferromagnetic ground states in the presence of external fields in two different domains of the parameter space.

  6. Mapping Out Atom-Wall Interaction with Atomic Clocks

    SciTech Connect

    Derevianko, A.; Obreshkov, B.; Dzuba, V. A.

    2009-09-25

    We explore the feasibility of probing atom-wall interaction with atomic clocks based on atoms trapped in engineered optical lattices. Optical lattice is normal to the wall. By monitoring the wall-induced clock shift at individual wells of the lattice, one would measure the dependence of the atom-wall interaction on the atom-wall separation. We find that the induced clock shifts are large and observable at already experimentally demonstrated levels of accuracy. We show that this scheme may uniquely probe the long-range atom-wall interaction in all three qualitatively distinct regimes of the interaction: van der Waals (image-charge interaction), Casimir-Polder (QED vacuum fluctuations), and Lifshitz (thermal-bath fluctuations) regimes.

  7. Atomization Performance of an Atomizer with Internal Impingement

    NASA Astrophysics Data System (ADS)

    Wang, Muh-Rong; Lin, Tien-Chu; Lai, Teng-San; Tseng, Ing-Ren

    This paper describes the atomization performance of a newly designed atomizer with internal impinging mechanisms inside the atomizer. The spray drop size distribution was measured by a Malvern RT-Sizer. Results show that the Sauter mean diameter below 10µm has been achieved with GLR of 0.14. The minimum mean drop size can be lowered to 4.0µm under a test condition of the liquid pressure and gas pressure of 2.5bar and 3.5bar, respectively. This test suggests that extra fine atomization on the liquid phase can be achieved under low pressure conditions using this particular atomizer. Such performance cannot be easily achieved with the conventional nozzle design. Results also show that better atomization performance can be achieved by increasing the internal impinging angle and the orifice diameter. An empirical formula of SMD, in terms of operating conditions and nozzle length scale is also presented in this paper.

  8. Control of atom-atom entanglement by cavity detuning

    NASA Astrophysics Data System (ADS)

    Calderón, O.; Joya, M. R.; Fonseca Romero, K. M.

    2016-02-01

    Using the atomic levels previously employed to demonstrate a two-photon maser, we show that the atom-atom entanglement produced by the successive passage of two three-level Rydberg atoms across a single-mode lossless cavity can be enhanced using the Stark shift. The atoms are assumed to be prepared in their excited states and to interact with the field during the same amount of time. Employing a physically motivated perturbation-theory approach, we obtain an effective two-level Hamiltonian. We show that, within the limits of validity of the approximation, atomic entanglement can be controlled by changing the frequency of the cavity field, and can be enhanced up to a maximum where the squared concurrence attains the value 16/27.

  9. Free fatty acids chain length distribution affects the permeability of skin lipid model membranes.

    PubMed

    Uchiyama, Masayuki; Oguri, Masashi; Mojumdar, Enamul H; Gooris, Gert S; Bouwstra, Joke A

    2016-09-01

    The lipid matrix in the stratum corneum (SC) plays an important role in the barrier function of the skin. The main lipid classes in this lipid matrix are ceramides (CERs), cholesterol (CHOL) and free fatty acids (FFAs). The aim of this study was to determine whether a variation in CER subclass composition and chain length distribution of FFAs affect the permeability of this matrix. To examine this, we make use of lipid model membranes, referred to as stratum corneum substitute (SCS). We prepared SCS containing i) single CER subclass with either a single FFA or a mixture of FFAs and CHOL, or ii) a mixture of various CER subclasses with either a single FFA or a mixture of FFAs and CHOL. In vitro permeation studies were performed using ethyl-p-aminobenzoic acid (E-PABA) as a model drug. The flux of E-PABA across the SCS containing the mixture of FFAs was higher than that across the SCS containing a single FA with a chain length of 24 C atoms (FA C24), while the E-PABA flux was not effected by the CER composition. To select the underlying factors for the changes in permeability, the SCSs were examined by Fourier transform infrared spectroscopy (FTIR) and Small angle X-ray scattering (SAXS). All lipid models demonstrated a similar phase behavior. However, when focusing on the conformational ordering of the individual FFA chains, the shorter chain FFA (with a chain length of 16, 18 or 20 C atoms forming only 11m/m% of the total FFA level) had a higher conformational disordering, while the conformational ordering of the chains of the CER and FA C24 and FA C22 hardly did not change irrespective of the composition of the SCS. In conclusion, the conformational mobility of the short chain FFAs present only at low levels in the model SC lipid membranes has a great impact on the permeability of E-PABA. PMID:27287726

  10. Chemically Realistic Tetrahedral Lattice Models for Polymer Chains: Application to Polyethylene Oxide.

    PubMed

    Dietschreit, Johannes C B; Diestler, Dennis J; Knapp, Ernst W

    2016-05-10

    To speed up the generation of an ensemble of poly(ethylene oxide) (PEO) polymer chains in solution, a tetrahedral lattice model possessing the appropriate bond angles is used. The distance between noncovalently bonded atoms is maintained at realistic values by generating chains with an enhanced degree of self-avoidance by a very efficient Monte Carlo (MC) algorithm. Potential energy parameters characterizing this lattice model are adjusted so as to mimic realistic PEO polymer chains in water simulated by molecular dynamics (MD), which serves as a benchmark. The MD data show that PEO chains have a fractal dimension of about two, in contrast to self-avoiding walk lattice models, which exhibit the fractal dimension of 1.7. The potential energy accounts for a mild hydrophobic effect (HYEF) of PEO and for a proper setting of the distribution between trans and gauche conformers. The potential energy parameters are determined by matching the Flory radius, the radius of gyration, and the fraction of trans torsion angles in the chain. A gratifying result is the excellent agreement of the pair distribution function and the angular correlation for the lattice model with the benchmark distribution. The lattice model allows for the precise computation of the torsional entropy of the chain. The generation of polymer conformations of the adjusted lattice model is at least 2 orders of magnitude more efficient than MD simulations of the PEO chain in explicit water. This method of generating chain conformations on a tetrahedral lattice can also be applied to other types of polymers with appropriate adjustment of the potential energy function. The efficient MC algorithm for generating chain conformations on a tetrahedral lattice is available for download at https://github.com/Roulattice/Roulattice . PMID:27045228

  11. Kinetic Chain Rehabilitation: A Theoretical Framework

    PubMed Central

    Sciascia, Aaron; Cromwell, Robin

    2012-01-01

    Sequenced physiologic muscle activations in the upper and lower extremity result in an integrated biomechanical task. This sequencing is known as the kinetic chain, and, in upper extremity dominant tasks, the energy development and output follows a proximal to distal sequencing. Impairment of one or more kinetic chain links can create dysfunctional biomechanical output leading to pain and/or injury. When deficits exist in the preceding links, they can negatively affect the shoulder. Rehabilitation of shoulder injuries should involve evaluation for and restoration of all kinetic chain deficits that may hinder kinetic chain function. Rehabilitation programs focused on eliminating kinetic chain deficits, and soreness should follow a proximal to distal rationale where lower extremity impairments are addressed in addition to the upper extremity impairments. A logical progression focusing on flexibility, strength, proprioception, and endurance with kinetic chain influence is recommended. PMID:22666599

  12. Electron correlation energies in atoms

    NASA Astrophysics Data System (ADS)

    McCarthy, Shane Patrick

    This dissertation is a study of electron correlation energies Ec in atoms. (1) Accurate values of E c are computed for isoelectronic sequences of "Coulomb-Hooke" atoms with varying mixtures of Coulombic and Hooke character. (2) Coupled-cluster calculations in carefully designed basis sets are combined with fully converged second-order Moller-Plesset perturbation theory (MP2) computations to obtain fairly accurate, non-relativistic Ec values for the 12 closed-shell atoms from Ar to Rn. The complete basis-set (CBS) limits of MP2 energies are obtained for open-shell atoms by computations in very large basis sets combined with a knowledge of the MP2/CBS limit for the next larger closed-shell atom with the same valence shell structure. Then higher-order correlation corrections are found by coupled-cluster calculations using basis sets that are not quite as large. The method is validated for the open-shell atoms from Al to Cl and then applied to get E c values, probably accurate to 3%, for the 4th-period open-shell atoms: K, Sc-Cu, and Ga-Br. (3) The results show that, contrary to quantum chemical folklore, MP2 overestimates |Ec| for atoms beyond Fe. Spin-component scaling arguments are used to provide a simple explanation for this overestimation. (4) Eleven non-relativistic density functionals, including some of the most widely-used ones, are tested on their ability to predict non-relativistic, electron correlation energies for atoms and their cations. They all lead to relatively poor predictions for the heavier atoms. Several novel, few-parameter, density functionals for the correlation energy are developed heuristically. Four new functionals lead to improved predictions for the 4th-period atoms without unreasonably compromising accuracy for the lighter atoms. (5) Simple models describing the variation of E c with atomic number are developed.

  13. Efficient atomic clocks operated with several atomic ensembles.

    PubMed

    Borregaard, J; Sørensen, A S

    2013-08-30

    Atomic clocks are typically operated by locking a local oscillator (LO) to a single atomic ensemble. In this Letter, we propose a scheme where the LO is locked to several atomic ensembles instead of one. This results in an exponential improvement compared to the conventional method and provides a stability of the clock scaling as (αN)(-m/2) with N being the number of atoms in each of the m ensembles and α a constant depending on the protocol being used to lock the LO. PMID:24033017

  14. Cooperative scattering of light and atoms in ultracold atomic gases

    NASA Astrophysics Data System (ADS)

    Uys, H.; Meystre, P.

    2008-07-01

    Superradiance and coherent atomic recoil lasing are two closely related phenomena, both resulting from the cooperative scattering of light by atoms. In ultracold atomic gases below the critical temperature for Bose-Einstein condensation these processes take place with the simultaneous amplification of the atomic matter waves. We explore these phenomena by surveying some of the experimental and theoretical developments that have emerged in this field of study since the first observation of superradiant scattering from a Bose-Einstein condensate in 1999 [1].

  15. Evidence for chain molecules enriched in carbon, hydrogen, and oxygen in comet Halley

    NASA Technical Reports Server (NTRS)

    Mitchell, D. L.; Lin, R. P.; Anderson, K. A.; Carlson, C. W.; Curtis, D. W.

    1987-01-01

    In situ measurements of the composition and spatial distribution of heavy thermal positive ions in the coma of comet Halley were made with the heavy-ion analyzer RPA2-PICCA aboard the Giotto spacecraft. Above 50 atomic mass units an ordered series of mass peaks centered at 61, 75, 91, and 105 atomic mass units were observed. Each peak appears to be composed of three or more closely spaced masses. The abundances decrease and the dissociation rates increase smoothly with increasing mass. These observations suggest the presence of chain molecules that are enriched in carbon, oxygen, and hydrogen, such as polyoxymethylene (polymerized formaldehyde), in comet Halley.

  16. Optically controlled periodical chain of quantum rings

    NASA Astrophysics Data System (ADS)

    Hasan, M.; Iorsh, I. V.; Kibis, O. V.; Shelykh, I. A.

    2016-03-01

    We demonstrated theoretically that a circularly polarized electromagnetic field substantially modifies electronic properties of a periodical chain of quantum rings. Particularly, the field opens band gaps in the electron energy spectrum of the chain, generates edge electron currents, and induces the Fano-like features in the electron transport through the finite chain. These effects create physical prerequisites for the development of optically controlled nanodevices based on a set of coupled quantum rings.

  17. Atoms in astronomy

    NASA Technical Reports Server (NTRS)

    Blanchard, P. A.

    1976-01-01

    Aspects of electromagnetic radiation and atomic physics needed for an understanding of astronomical applications are explored. Although intended primarily for teachers, this brochure is written so that it can be distributed to students if desired. The first section, Basic Topics, is suitable for a ninth-grade general science class; the style is simple and repetitive, and no mathematics or physics background is required. The second section, Intermediate and Advanced Topics, requires a knowledge of the material in the first section and assumes a generally higher level of achievement and motivation on the part of the student. These latter topics might fit well into junior-level physics, chemistry, or earth-science courses. Also included are a glossary, a list of references and teaching aids, class exercises, and a question and answer section.

  18. Atomization in Sparkling Fireworks

    NASA Astrophysics Data System (ADS)

    Inoue, Chihiro; Koshi, Mitsuo; Terashima, Hiroshi; Himeno, Takehiro; Watanabe, Toshinori; Sparkling Fireworks Team

    2013-11-01

    The physics behind the beauty of sparkling fireworks has not been clarified yet due to a lack of coherent visualization results. In the present study, atomization process in sparkling fireworks is elucidated by using a high-speed video camera. In the first-half sequence of the fireworks, the fireball repeatedly expands, bursts, and shrinks due to the high pressure gas inside the fireball. In contrast, in the last-half sequence, the bubbly fireball slightly deforms, and small bubbles burst on the fireball. A scenario of droplets generation is as follows: a liquid thread extends from the bottom of the bursting fireball, and fragments into droplets. Thus the droplets originate from inside the fireball rather than from its surface.

  19. Photoionization of Atomic Sc

    NASA Astrophysics Data System (ADS)

    Sossah, A. M.; Zhou, H.-L.; Manson, S. T.; Hibbert, A.

    2009-05-01

    Photoionization cross sections are calculated for the ground ([Mg] 3p^63d4s^2 ^2D^e) state of atomic Sc for photon energies from threshold to 40.0 eV. The discrete Sc^+ orbitals are generated using both the AUTOSTRUCTURE and CIV3 codes, and R-matrix is used to carry out the cross section calculations. The results are compared with each other, then with previous calculations and available experimental data for final-ionic states representing the 3d and 4s main lines and associated satellites (ionization with excitation) in the region of the 3p -> 3d giant resonances [1]. Reasonably good agreement between our non-relativistic results and experiment is obtained. This work is supported by US DOE and NSF [4pt] [1] S. B. Whitfield, K. Kehoe, R. Wehlitz, M. O. Krause, and C. D. Caldwell ->hys. Rev. A 64, 022701 (2001).

  20. Atomic and gravitational clocks

    NASA Technical Reports Server (NTRS)

    Canuto, V. M.; Goldman, I.

    1982-01-01

    Atomic and gravitational clocks are governed by the laws of electrodynamics and gravity, respectively. While the strong equivalence principle (SEP) assumes that the two clocks have been synchronous at all times, recent planetary data seem to suggest a possible violation of the SEP. Past analysis of the implications of an SEP violation on different physical phenomena revealed no disagreement. However, these studies assumed that the two different clocks can be consistently constructed within the framework. The concept of scale invariance, and the physical meaning of different systems of units, are now reviewed and the construction of two clocks that do not remain synchronous - whose rates are related by a non-constant function beta sub a - is demonstrated. The cosmological character of beta sub a is also discussed.

  1. Forming particle chains in inertial microfluidic devices

    NASA Astrophysics Data System (ADS)

    Hood, Kaitlyn; Liu, Lawrence; Roper, Marcus

    2015-11-01

    Particles in microfluidic devices at finite Reynolds number self-assemble into evenly-spaced chains, which can be exploited in inertial microfluidic devices for flow cytometry, high speed imaging, and entrapment. While the location and number of chains can be manipulated by changing the channel geometry, the particle interactions are not understood well enough to manipulate the spacing between particles. We present a mathematical model of particle interactions and the formation of particle chains. We will address the following questions: Is there a preferred particle spacing? What are the conditions needed for chain formation?

  2. Effects of tethered chains on adhesion

    NASA Astrophysics Data System (ADS)

    Sides, Scott; Grest, Gary; Stevens, Mark

    2001-03-01

    We study adhesion between a polymer melt and substrate due to chemically attached polymer chains on the substrate surface. We have performed extensive molecular dynamics simulations to study the effect of temperature, crosslink density, tethered chain density (Σ), tethered chain length (N_t), tensile pull velocity (v) and chain stiffness on the adhesive failure mechanisms of pullout and/or scission of the tethered chains. We observe a crossover from pure chain pullout to chain scission as Nt and v are increased. The value of Nt at which this crossover occurs is comparable to the chain entanglement length for the coarse-grained model used. Experiments and simulations have shown that the energy required to separate a polymer melt from a substrate increases considerably if the formation of large voids, or crazing can be initiated in the melt. The onset of crazing depends on the temperature and the interaction strength of the substrate with the melt. We also present data illustrating the additional effects of tethered chains on crazing mechanisms.

  3. Magnetization dynamics in isolated Ising chains

    SciTech Connect

    Kudasov, A. N.

    2010-02-15

    The Glauber dynamics of an Ising chain or ring is shown to be determined by two characteristic times: {tau}{sub 1} for relaxation of the average magnetization per spin and {tau}{sub 2} for dynamical spontaneous symmetry breaking. An analytical solution for magnetization dynamics in a finite chain with fixed spins at both ends is found by the method of images. This solution is then used to calculate the spin-spin correlation functions for rings and chains. At low temperatures, since {tau}{sub 1} >> {tau}{sub 2}, there must exist a range of times when the chain is in one of two ordered states.

  4. Magnetic trap for thulium atoms

    SciTech Connect

    Sukachev, D D; Sokolov, A V; Chebakov, K A; Akimov, A V; Kolachevskii, N N; Sorokin, Vadim N

    2011-08-31

    For the first time ultra-cold thulium atoms were trapped in a magnetic quadrupole trap with a small field gradient (20 Gs cm{sup -1}). The atoms were loaded from a cloud containing 4x10{sup 5} atoms that were preliminarily cooled in a magneto-optical trap to the sub-Doppler temperature of 80 {mu}K. As many as 4x10{sup 4} atoms were trapped in the magnetic trap at the temperature of 40 {mu}K. By the character of trap population decay the lifetime of atoms was determined (0.5 s) and an upper estimate was obtained for the rate constant of inelastic binary collisions for spin-polarised thulium atoms in the ground state (g{sub in} < 10{sup -11}cm{sup 3} s{sup -1}). (magnetic traps)

  5. Entanglement of remote atomic qubits.

    PubMed

    Matsukevich, D N; Chanelière, T; Jenkins, S D; Lan, S-Y; Kennedy, T A B; Kuzmich, A

    2006-01-27

    We report observations of entanglement of two remote atomic qubits, achieved by generating an entangled state of an atomic qubit and a single photon at site , transmitting the photon to site in an adjacent laboratory through an optical fiber, and converting the photon into an atomic qubit. Entanglement of the two remote atomic qubits is inferred by performing, locally, quantum state transfer of each of the atomic qubits onto a photonic qubit and subsequent measurement of polarization correlations in violation of the Bell inequality [EQUATION: SEE TEXT]. We experimentally determine [EQUATION: SEE TEXT]. Entanglement of two remote atomic qubits, each qubit consisting of two independent spin wave excitations, and reversible, coherent transfer of entanglement between matter and light represent important advances in quantum information science. PMID:16486672

  6. Primary Atomic Clock Reference System

    NASA Technical Reports Server (NTRS)

    2001-01-01

    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

  7. Primary Atomic Clock Reference System

    NASA Technical Reports Server (NTRS)

    2001-01-01

    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. 0100120.

  8. Manipulation of ultracold atoms using double-loop microtraps

    NASA Astrophysics Data System (ADS)

    van Wijngaarden, W. A.; Jian, B.; Mouraviev, A.

    2016-05-01

    Ultracold atoms created using microtraps are being used in an increasing number of diverse applications. This paper reviews the double-loop microtrap which consists of two concentric circular wire loops carrying oppositely oriented currents. This generates a magnetic field configuration that traps a magnetic dipole in three-dimensions. The position of the trapped atoms relative to the atom chip surface containing the microwire loops, can be precisely controlled by applying different currents in the two loops or alternatively using a so called bias magnetic field oriented perpendicular to the chip surface. Double-loop microtraps can be daisy chained in series to create a one- or two-dimensional microtrap array. Experiments that have demonstrated a double-loop microtrap array are discussed. Future possibilities are presented as to how atoms can be transferred between adjacent microtraps as well as the use of an additional micro sized Ioffe coil to create a trap having a nonzero magnetic field minimum to reduce atom loss by suppressing Majorana transitions.

  9. Manipulation of Ultracold Atoms using Double-Loop Microtraps

    NASA Astrophysics Data System (ADS)

    van Wijngaarden, William; Jian, Bin; Mouraviev, Andrei

    2016-05-01

    Ultracold atoms created using microtraps are being used in an increasing number of diverse applications. This talk discusses exciting work demonstrating a double-loop microtrap which consists of two concentric circular wire loops carrying oppositely oriented currents. This generates a magnetic field configuration that traps a magnetic dipole in three dimensions. The position of the trapped atoms relative to the atom chip surface containing the microwire loops, can be precisely controlled by applying different currents in the two lops or alternatively using a so called bias magnetic field oriented perpendicular to the chip surface. An important advantage of the double-loop microtrap is that it can be daisy chained in series to create a one or two dimensional microtrap array. Future possibilities are presented as to how atoms can be transferred between adjacent microtraps as well as the use of an additional micro sized Ioffe coil to create a trap having a nonzero magnetic field minimum to reduce atom loss by suppressing Majorana transitions.

  10. Cold Atoms and Maxwell's Demon

    NASA Astrophysics Data System (ADS)

    Steck, Daniel A.

    2013-12-01

    Recent experiments have focused on realizing and studying asymmetric potential barriers for ultracold atoms. Practically speaking, asymmetric barriers, or "atomtronic diodes", open up newmethods for controlling cold atoms, and possibly methods for laser cooling atoms and molecules that are not amenable to present laser-cooling techniques. More fundamentally, asymmetric barriers are interesting as realizations of the textbook statistical-mechanics scenario of Maxwell's demon. This chapter reviews experimental progress in this area, as well as some related practical and theoretical issues.

  11. Real and hybrid atomic orbitals

    NASA Astrophysics Data System (ADS)

    Cook, D. B.; Fowler, P. W.

    1981-09-01

    It is shown that the Schrödinger equation for the hydrogenlike atom separates in both spheroconal and prolate spheroidal coordinates and that these separations provide a sound theoretical basis for the real and hybrid atomic orbitals. Thus the real and hybrid atomic orbitals have as sound a pedigree as the more familiar complex orbitals based on the separation of the Schrödinger equation in spherical polar coordinates.

  12. Phase shift due to atom-atom interactions in a light-pulse atom interferometer

    NASA Astrophysics Data System (ADS)

    Jannin, Raphaël; Cladé, Pierre; Guellati-Khélifa, Saïda

    2015-07-01

    We present a theoretical model allowing precise calculation of the phase shift induced by atom-atom interactions in a light-pulse atom interferometer based on two-photon Raman atom optics. This model is in good agreement with numerical simulations based on solving the Gross-Pitaevskii equation. The atom interferometer exhibits an atom-atom-interaction-induced phase shift when there is asymmetry between the two arms of the interferometer. In the case of a Ramsey-Bordé atom interferometer ({π /2 -π /2 }-{π /2 -π /2 } pulse configuration), the asymmetry comes from the fact that the number of atoms in each arm of the interferometer is not constant. In the case of a Mach-Zehnder ({π /2 -π -π /2 } pulse sequence), if the pulses are perfect, the number of atoms is constant in the interferometer. We study the effect due to imperfections of the light pulses as well as the effect due to the expansion of the cloud. Our model leads to precise and simple formulas of the mean-field phase shift as a function of the experimental parameters.

  13. Alpha-helical stabilization by side chain shielding of backbone hydrogen bonds.

    PubMed

    García, Angel E; Sanbonmatsu, Kevin Y

    2002-03-01

    We study atomic models of the thermodynamics of the structural transition of peptides that form alpha-helices. The effect of sequence variation on alpha-helix formation for alanine-rich peptides, Ac-Ala21-methyl amide (A21) and Ac-A5 (AAARA)3A-methyl amide (Fs peptide), is investigated by atomic simulation studies of the thermodynamics of the helix-coil transition in explicit water. The simulations show that the guanidinium group in the Arg side chains in the Fs peptide interacts with the carbonyl group four amino acids upstream in the chain and desolvates backbone hydrogen bonds. This desolvation can be directly correlated with a higher probability of hydrogen bond formation. We find that Fs has higher helical content than A21 at all temperatures. A small modification in the amber force field reproduces the experimental helical content and helix-coil transition temperatures for the Fs peptide. PMID:11867710

  14. Landau-Zener sweeps and sudden quenches in coupled Bose-Hubbard chains.

    PubMed

    Kasztelan, C; Trotzky, S; Chen, Y-A; Bloch, I; McCulloch, I P; Schollwöck, U; Orso, G

    2011-04-15

    We simulate numerically the dynamics of strongly correlated bosons in a two-leg ladder subject to a time-dependent energy bias between the two chains. When all atoms are initially in the leg with higher energy, we find a drastic reduction of the interchain particle transfer for slow linear sweeps, in quantitative agreement with recent experiments. This effect is preceded by a rapid broadening of the quasimomentum distribution of atoms, signaling the presence of a bath of low-energy excitations in the chains. We further investigate the scenario of quantum quenches to fixed values of the energy bias. We find that for a large enough density the momentum distribution relaxes to that of an equilibrium thermal state with the same energy. PMID:21568570

  15. Association Equilibrium for Cross-Associating Chains in a Good Solvent: Crowding and Other Nonideality Effects.

    PubMed

    Gotlib, Igor Yu; Malov, Ivan K; Victorov, Alexey I; Voznesenskiy, Mikhail A

    2016-07-28

    Association equilibrium has been studied by molecular dynamics (MD) for mixtures of cross-associating molecules (n-decamer+p-dimer and n-decamer+p-decamer) in a good solvent. Each monomer of n-decamers carries an associative site (n-sticker); each molecule of the second component contains two terminal associative sites (p-stickers). To model the univalent association between the n-sticker and the p-sticker, a technique based on introduction of dummy atoms has been used. We report MD data on the effects of temperature, chain flexibility, and location of the sticker within the chain on the association equilibrium. We find that the presence of nonassociating monomer units of p-chain has a substantial effect on the association equilibrium. This effect is similar to "crowding" in reactive mixtures known to be caused by the presence of inert molecules. Widely used mean field theories of associating chains (e.g., SAFT or Semenov-Rubinstein theory) do not account for the effect of crowding caused by the inert fragments of reactive chains. We introduce simple empirical corrections for crowding that describe association equilibrium in the presence of nonassociating fragment in a chain-like molecule. PMID:27359300

  16. Supramolecular Nanoparticles via Single-Chain Folding Driven by Ferrous Ions.

    PubMed

    Wang, Fei; Pu, Hongting; Jin, Ming; Wan, Decheng

    2016-02-01

    Single-chain nanoparticles can be obtained via single-chain folding assisted by intramolecular crosslinking reversibly or irreversibly. Single-chain folding is also an efficient route to simulate biomacromolecules. In present study, poly(N-hydroxyethylacrylamide-co-4'-(propoxy urethane ethyl acrylate)-2,2':6',2''-terpyridine) (P(HEAm-co-EMA-Tpy)) is synthesized via reversible addition fragmentation chain transfer polymerization. Single-chain folding and intramolecular crosslinking of P(HEAm-co-EMA-Tpy) are achieved via metal coordination chemistry. The intramolecular interaction is characterized on ultraviolet/visible spectrophotometer (UV-vis spectroscopy), proton nuclear magnetic resonance ((1)H NMR), and differential scanning calorimetry (DSC). The supramolecular crosslinking mediated by Fe(2+) plays an important role in the intramolecular collapsing of the single-chain and the formation of the nanoparticles. The size and morphology of the nanoparticles can be controlled reversibly via metal coordination chemistry, which can be characterized by dynamic light scattering (DLS), transmission electron microscope (TEM), and atomic force microscope (AFM). PMID:26748641

  17. Self-assembled aliphatic chain extended polyurethane nanobiohybrids: emerging hemocompatible biomaterials for sustained drug delivery.

    PubMed

    Mishra, Abhinay; Singh, Sunil K; Dash, Debabrata; Aswal, Vinod K; Maiti, Biswajit; Misra, Manjusri; Maiti, Pralay

    2014-05-01

    Novel polyurethanes (PUs) have been synthesized using an aliphatic diisocyanate and aliphatic chain extenders with varying chain length. Nanocomposites of PUs have been prepared by dispersing 2-D nanoclay in poly-ol followed by prepolymerization and subsequent chain extension using various chain extenders. Systematic improvement in toughness and adequate enhancement in stiffness in the presence of nanoclay has been observed for PUs with longer chain extenders, and these new classes of nanocomposites exhibit no toughness-stiffness trade-off. Bottom-up self-assembly starting from the molecular level to micron-scale crystallite has been revealed through electronic structure calculation, X-ray diffraction, small-angle neutron scattering, atomic force microscopy and optical images. The role of hydrogen bonding has been revealed for this type of supramolecular assembly, and in the presence of organically modified nanoclay hydrogen bonding contributes to the formation of bigger clusters of nanocomposites. Controlled biodegradation of PU and its nanocomposites has been investigated in enzymatic media. Biocompatibility of these novel nanocomposites has been extensively verified through platelet adhesion, aggregation and hemolysis assay. Sustained drug delivery by biocompatible pristine PU and its nanocomposites has been demonstrated either by controlling the crystallite size of the polyurethane through alteration of the aliphatic chain length of the extender or by incorporating disc-like nanoclay, creating a tortuous path that results in delayed diffusion. Hence, the developed nanohybrids are potential biomaterials for tissue engineering and drug delivery. PMID:24374322

  18. Optical atomic clocks and metrology

    NASA Astrophysics Data System (ADS)

    Ludlow, Andrew

    2014-05-01

    The atomic clock has long demonstrated the capability to measure time or frequency with very high precision. Consequently, these clocks are used extensively in technological applications such as advanced synchronization or communication and navigation networks. Optical atomic clocks are next- generation timekeepers which reference narrowband optical transitions between suitable atomic states. Many optical time/frequency standards utilize state-of-the-art quantum control and precision measurement. Combined with the ultrahigh quality factors of the atomic resonances at their heart, optical atomic clocks have promised new levels of timekeeping precision, orders of magnitude higher than conventional atomic clocks based on microwave transitions. Such measurement capability enables and/or enhances many of the most exciting applications of these clocks, including the study of fundamental laws of physics through the measurement of time evolution. Here, I will highlight optical atomic clocks and their utility, as well as review recent advances in their development and performance. In particular, I will describe in detail the optical lattice clock and the realization of frequency measurement at the level of one part in 1018. To push the performance of these atomic timekeepers to such a level and beyond, several key advances are being explored worldwide. These will be discussed generally, with particular emphasis on our recent efforts at NIST in developing the optical lattice clock based on atomic ytterbium.

  19. Energy partitioning for ``fuzzy'' atoms

    NASA Astrophysics Data System (ADS)

    Salvador, P.; Mayer, I.

    2004-03-01

    The total energy of a molecule is presented as a sum of one- and two-atomic energy components in terms of "fuzzy" atoms, i.e., such divisions of the three-dimensional physical space into atomic regions in which the regions assigned to the individual atoms have no sharp boundaries but exhibit a continuous transition from one to another. By proper definitions the energy components are on the chemical energy scale. The method is realized by using Becke's integration scheme and weight function permitting very effective numerical integrations.

  20. Versatile cold atom target apparatus

    SciTech Connect

    Goetz, Simone; Hoeltkemeier, Bastian; Hofmann, Christoph S.; Litsch, Dominic; DePaola, Brett D.; Weidemueller, Matthias

    2012-07-15

    We report on a compact and transportable apparatus that consists of a cold atomic target at the center of a high resolution recoil ion momentum spectrometer. Cold rubidium atoms serve as a target which can be operated in three different modes: in continuous mode, consisting of a cold atom beam generated by a two-dimensional magneto-optical trap, in normal mode in which the atoms from the beam are trapped in a three-dimensional magneto-optical trap (3D MOT), and in high density mode in which the 3D MOT is operated in dark spontaneous optical trap configuration. The targets are characterized using photoionization.