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Sample records for polarization remains metastably

  1. Two-photon polarization Fourier spectroscopy of metastable atomic hydrogen

    International Nuclear Information System (INIS)

    Duncan, A.J.; Beyer, H.-J.; Kleinpoppen, H.; Sheikh, Z.A,; B-Z Univ., Multan

    1997-01-01

    A novel Fourier-transform spectroscopic method using two-photon polarization to determine the spectral distribution of the two photons emitted in the spontaneous decay of metastable atomic hydrogen is described. The method uses birefringent retardation plates and takes advantage of the subtle interplay between the spectral properties and the entangled polarization properties of the radiation emitted in the decay. Assuming the validity of the theoretical spectral distribution, it is shown that the experimental results agree well with theory. On the other hand, success in solving the inverse problem of determining the spectral distribution from the experimental results is limited by the small number of experimental points. However, making reasonable assumptions it is deduced that the observed spectrum is characterized by a broadband signal of width (0.43 ± 0.06) x 10 16 rad s -1 and centre angular frequency (0.77 ± 0.03) x 10 16 rad s -1 in good agreement with the predictions of 0.489 x 10 16 rad s -1 and 0.775 x 10 16 rad s -1 , respectively, obtained from the theoretical spectral distribution modified to take account of the absorption of the two-photon radiation in air. The values of 1.5 fs for the coherence time and 440 nm for the coherence length for single photons of the two-photon pair which are obtained from the measured bandwidth imply that, in the ideal case, these values are determined by the essentially zero lifetime of the virtual intermediate state of the decay process rather than the long lifetime of the metastable state which, it is suggested, determines the coherence time and coherence length appropriate to certain types of fourth-order interference experiments. (Author)

  2. Visualization and manipulation of meta-stable polarization variants in multiferroic materials

    Directory of Open Access Journals (Sweden)

    Moonkyu Park

    2013-04-01

    Full Text Available Here we demonstrate the role of meta-stable polarization variants in out-of-plane polarization switching behavior in epitaxially grown BiFeO3 thin films using angle-resolved piezoresponse force microscopy (AR-PFM. The out-of-plane polarization switching mainly occurred at the boundary between meta-stable and stable polarization domains, and was accompanied by a significant change in in-plane domain configuration from complicated structure with 12 polarization variants to simple stripe structure with 4 polarization variants. These results imply that the biased tip rearranges the delicately balanced domain configuration, which is determined by the competition between electrostatic and strain energies, into simple interweaving one that is more thermodynamically stable.

  3. Metastable hydrogen

    International Nuclear Information System (INIS)

    Dose, V.

    1982-01-01

    This paper deals with the basic physical properties of the metastable 2 2 sub(1/2) state of atomic hydrogen. Applications relying on its special properties, including measurement of the Lamb shift, production of spin-polarized protons and the measurement of molecular electric moments, are discussed. (author)

  4. Simple and efficient method of spin-polarizing a metastable helium beam by diode laser optical pumping

    International Nuclear Information System (INIS)

    Granitza, B.; Salvietti, M.; Torello, E.; Mattera, L.; Sasso, A.

    1995-01-01

    Diode laser optical pumping to produce a highly spin-polarized metastable He beam to be used in a spin-polarized metastable atom deexcitation spectroscopy experiment on magnetized surfaces is described. Efficient pumping of the beam is performed by means of an SDL-6702 distributed Bragg reflector diode laser which yields 50 mW of output power in a single longitudinal mode at 1083 nm, the resonance wavelength for the 2 3 S→2 3 P 0,1,2 (D 0 , D 1 , and D 2 ) transitions of He*. The light is circularly polarized by a quarter-wave plate, allowing easy change of the sense of atomic polarization. The laser frequency can be locked to the atomic transition for several hours by phase-sensitive detection of the saturated absorption signal in a He discharge cell. Any of the three transitions of the triplet system can be pumped with the laser but the maximum level of atomic polarization of 98.5% is found pumping the D 2 line. copyright 1995 American Institute of Physics

  5. Spin-polarized 3He nuclear targets and metastable 4He atoms by optical pumping with a tunable, Nd:YAP laser

    International Nuclear Information System (INIS)

    Bohler, C.L.; Schearer, L.D.; Leduc, M.; Nacher, P.J.; Zachorowski, L.; Milner, R.G.; McKeown, R.D.; Woodward, C.E.

    1988-01-01

    Several Nd:YAP lasers were constructed which could be broadly tuned in the 1083-nm region which includes the helium 2 3 S-2 3 P transition, using a Lyot filter and thin, uncoated etalons within the laser cavity. 1 W of power could be extracted at 1083 nm through a 1% transmitting output coupler. This laser beam was used to optically pump metastable 4 He and 3 He 2 3 S helium atoms in a weak discharge cell, spin polarizing the metastable ensemble. In a 3 He cell the polarization is transferred to the nuclear spin system. A 3 He target cell at 0.3 Torr was polarized to 52% in a few minutes. We describe the application of this system to the design of polarized targets for experiments in nuclear physics

  6. Spatial profiles of electron and metastable atom densities in positive polarity fast ionization waves sustained in helium

    International Nuclear Information System (INIS)

    Weatherford, Brandon R.; Barnat, E. V.; Xiong, Zhongmin; Kushner, Mark J.

    2014-01-01

    Fast ionization waves (FIWs), often generated with high voltage pulses over nanosecond timescales, are able to produce large volumes of ions and excited states at moderate pressures. The mechanisms of FIW propagation were experimentally and computationally investigated to provide insights into the manner in which these large volumes are excited. The two-dimensional structure of electron and metastable densities produced by short-pulse FIWs sustained in helium were measured using laser-induced fluorescence and laser collision-induced fluorescence diagnostics for times of 100–120 ns after the pulse, as the pressure was varied from 1 to 20 Torr. A trend of center-peaked to volume-filling to wall-peaked electron density profiles was observed as the pressure was increased. Instantaneous FIW velocities, obtained from plasma-induced emission, ranged from 0.1 to 3 × 10 9  cm s −1 , depending on distance from the high voltage electrode and pressure. Predictions from two-dimensional modeling of the propagation of a single FIW correlated well with the experimental trends in electron density profiles and wave velocity. Results from the model show that the maximum ionization rate occurs in the wavefront, and the discharge continues to propagate forward after the removal of high voltage from the powered electrode due to the potential energy stored in the space charge. As the pressure is varied, the radial distribution of the ionization rate is shaped by changes in the electron mean free path, and subsequent localized electric field enhancement at the walls or on the centerline of the discharge.

  7. Patterns of faunal extinction and paleoclimatic change from mid-Holocene mammoth and polar bear remains, Pribilof Islands, Alaska

    Science.gov (United States)

    Veltre, Douglas W.; Yesner, David R.; Crossen, Kristine J.; Graham, Russell W.; Coltrain, Joan B.

    2008-07-01

    Qagnaxˆ Cave, a lava tube cave on St. Paul Island in the Pribilofs, has recently produced a mid-Holocene vertebrate faunal assemblage including woolly mammoth, polar bear, caribou, and Arctic fox. Several dates on the mammoth remains converge on 5700 14C yr BP. These dates, ~ 2300 yr younger than mammoth dates previously published from the Pribilof Islands, make these the youngest remains of proboscideans, and of non-extinct Quaternary megafauna, recovered from North America. Persistence of mammoths on the Pribilofs is most parsimoniously explained by the isolation of the Pribilofs and the lack of human presence in pre-Russian contact times, but an additional factor may have been the local existence of high-quality forage in the form of grasses enriched by nutrients derived from local Holocene tephras. This interpretation is reinforced by stable carbon and nitrogen isotope values obtained from the mammoth remains. The endpoint of mammoth survival in the Pribilofs is unknown, but maybe coterminous with the arrival of polar bears whose remains in the cave date to the Neoglacial cold period of ~ 4500 to 3500 14C yr BP. The polar bear record corroborates a widespread cooling of the Bering Sea region at that time.

  8. Modeling the metastable dynamics of correlated structures

    Science.gov (United States)

    Shakirov, Alexey M.; Tsibulsky, Sergey V.; Antipov, Andrey E.; Shchadilova, Yulia E.; Rubtsov, Alexey N.

    2015-01-01

    Metastable quantum dynamics of an asymmetric triangular cluster that is coupled to a reservoir is investigated. The dynamics is governed by bath-mediated transitions, which in part require a thermal activation process. The decay rate is controlled by tuning the excitation spectrum of the frustrated cluster. We use the master equation approach and construct transition operators in terms of many-body states. We analyze dynamics of observables and reveal metastability of an excited state and of a magnetically polarized ground state.

  9. Electron spin polarization effects in low energy electron diffraction, ion neutralization and metastable atom deexcitation at solid surfaces. Progress report No. 4, 1 January-31 December 1984

    International Nuclear Information System (INIS)

    1984-01-01

    In the present contract year, a GaAs polarized electron source has been used to undertake a polarized LEED study of order-disorder transformations at Cu 3 Au (100) and (111) surfaces. A polarized LEED study of Cu (100) has also been initiated. A polarized MDS study of Ni(110) surface magnetism has been completed. Spin dependences in the Auger electron yield were observed that provide a measure of the surface magnetism and were used to probe the dependence of surface magnetism on temperature and adsorbate coverage. A similar study using a ferromagnetic glass is now underway. A Mott polarization analyzer, constructed to measure the ESP of the ejected electrons, is also being installed on the apparatus. Such measurements provide direct information concerning the dynamics of secondary electron ejection and the details of adsorbate-substrate bonding

  10. Metastable Phases in Ice Clouds

    Science.gov (United States)

    Weiss, Fabian; Baloh, Philipp; Kubel, Frank; Hoelzel, Markus; Parker, Stewart; Grothe, Hinrich

    2014-05-01

    Polar Stratospheric Clouds and Cirrus Clouds contain both, pure water ice and phases of nitric acid hydrates. Preferentially for the latter, the thermodynamically stable phases have intensively been investigated in the past (e.g. nitric acid trihydrate, beta-NAT). As shown by Peter et al. [1] the water activity inside clouds is higher than expected, which might be explained by the presence of metastable stable phases (e.g. cubic ice). However, also metastable nitric acid hydrates might be important due to the inherent non-equilibrium freezing conditions in the upper atmosphere. The delta ice theory of Gao et al. [2] presents a model approach to solve this problem by involving both metastable ice and NAT as well. So it is of high interest to investigate the metastable phase of NAT (i.e. alpha-NAT), the structure of which was unknown up to the presence. In our laboratory a production procedure for metastable alpha-NAT has been developed, which gives access to neutron diffraction and X-ray diffraction measurements, where sample quantities of several Gramm are required. The diffraction techniques were used to solve the unknown crystalline structure of metastable alpha-NAT, which in turn allows the calculation of the vibrational spectra, which have also been recorded by us in the past. Rerefences [1] Peter, T., C. Marcolli, P. Spichtinger, T. Corti, M. B. Baker, and T. Koop. When dry air is too humid. Science, 314:1399-1402, 2006. [2] Gao, R., P. Popp, D. Fahey, T. Marcy, R. L. Herman, E. Weinstock, D. Baumgardener, T. Garrett, K. Rosenlof, T. Thompson, T. P. Bui, B. Ridley, S. C. Wofsy, O. B. Toon, M. Tolbert, B. Kärcher, Th. Peter, P. K. Hudson, A. Weinheimer, and A. Heymsfield. Evidence That Nitric Acid Increases Relative Humidity in Low-Temperature Cirrus Clouds, Science, 303:516-520, 2004. [3] Tizek, H., E. Knözinger, and H. Grothe. Formation and phase distribution of nitric acid hydrates in the mole fraction range xHNO3<0.25: A combined XRD and IR study, PCCP, 6

  11. Metastable superconducting alloys

    International Nuclear Information System (INIS)

    Johnson, W.L.

    1978-07-01

    The study of metastable metals and alloys has become one of the principal activities of specialists working in the field of superconducting materials. Metastable crystalline superconductors such as the A15-type materials have been given much attention. Non-crystalline superconductors were first studied over twenty years ago by Buckel and Hilsch using the technique of thin film evaporation on a cryogenic substrate. More recently, melt-quenching, sputtering, and ion implantation techniques have been employed to produce a variety of amorphous superconductors. The present article presents a brief review of experimental results and a survey of current work on these materials. The systematics of superconductivity in non-crystalline metals and alloys are described along with an analysis of the microscopic parameters which underlie the observed trends. The unique properties of these superconductors which arise from the high degree of structural disorder in the amorphous state are emphasized

  12. Metastability of transient states

    Science.gov (United States)

    Rafailov, Michael K.

    2017-05-01

    High intensity ultrashort pulse causes dramatic perturbations in electronic structure of condensed matter. In the same time energy in high intensity single pulse may not be sufficient to disrupt sample thermal equilibrium. Interesting experimental results in ultrashort pulse photo-excited solids have been reported recently on transient athermal phenomena induced by ultrashort high intensity low energy pulse - phenomena related to both athermal phase transitions and athermal state changes. Athermal non-equilibrium of electronic system - and induced changes in magnetic and optical states, may exist only for a period of time comparable to excited carriers' relaxation time. That time is not sufficient for emerging application ranging from light induced superconductivity to infrared countermeasures. While single pulse interaction with condensed matter leading to transit state appearance is well observed, documented, and, to some extends, explained, one of the major problem is to maintain meta-stability of such transient states. Metastability of athermal non-equilibrium that could last well beyond electronic system relaxation time. The objective of this paper is to discuss some issues and approaches to meta-stability of transient states induced by ultrashort pulses in condensed matter.

  13. Topodynamics of metastable brains

    Science.gov (United States)

    Tozzi, Arturo; Peters, James F.; Fingelkurts, Andrew A.; Fingelkurts, Alexander A.; Marijuán, Pedro C.

    2017-07-01

    The brain displays both the anatomical features of a vast amount of interconnected topological mappings as well as the functional features of a nonlinear, metastable system at the edge of chaos, equipped with a phase space where mental random walks tend towards lower energetic basins. Nevertheless, with the exception of some advanced neuro-anatomic descriptions and present-day connectomic research, very few studies have been addressing the topological path of a brain embedded or embodied in its external and internal environment. Herein, by using new formal tools derived from algebraic topology, we provide an account of the metastable brain, based on the neuro-scientific model of Operational Architectonics of brain-mind functioning. We introduce a ;topodynamic; description that shows how the relationships among the countless intertwined spatio-temporal levels of brain functioning can be assessed in terms of projections and mappings that take place on abstract structures, equipped with different dimensions, curvatures and energetic constraints. Such a topodynamical approach, apart from providing a biologically plausible model of brain function that can be operationalized, is also able to tackle the issue of a long-standing dichotomy: it throws indeed a bridge between the subjective, immediate datum of the naïve complex of sensations and mentations and the objective, quantitative, data extracted from experimental neuro-scientific procedures. Importantly, it opens the door to a series of new predictions and future directions of advancement for neuroscientific research.

  14. Digital Synchronizer without Metastability

    Science.gov (United States)

    Simle, Robert M.; Cavazos, Jose A.

    2009-01-01

    A proposed design for a digital synchronizing circuit would eliminate metastability that plagues flip-flop circuits in digital input/output interfaces. This metastability is associated with sampling, by use of flip-flops, of an external signal that is asynchronous with a clock signal that drives the flip-flops: it is a temporary flip-flop failure that can occur when a rising or falling edge of an asynchronous signal occurs during the setup and/or hold time of a flip-flop. The proposed design calls for (1) use of a clock frequency greater than the frequency of the asynchronous signal, (2) use of flip-flop asynchronous preset or clear signals for the asynchronous input, (3) use of a clock asynchronous recovery delay with pulse width discriminator, and (4) tying the data inputs to constant logic levels to obtain (5) two half-rate synchronous partial signals - one for the falling and one for the rising edge. Inasmuch as the flip-flop data inputs would be permanently tied to constant logic levels, setup and hold times would not be violated. The half-rate partial signals would be recombined to construct a signal that would replicate the original asynchronous signal at its original rate but would be synchronous with the clock signal.

  15. Formation of Metastable Crystals from Supercooled, Supersaturated, and Supercompressed Liquids: Role of Crystal-Liquid Interfacial Free Energy

    Directory of Open Access Journals (Sweden)

    Geun Woo Lee

    2017-10-01

    Full Text Available The formation mechanism of metastable crystals from metastable liquids still remains elusive, although controlling the metastability of crystals and liquids already plays a crucial role in designing new materials in physics, chemistry, biology, and materials science. This review article describes how metastable phases can be obtained by controlling temperature, concentration, and pressure. In particular, I show the role of crystal-liquid interfacial free energy in the formation of metastable crystals from metastable liquids at a given driving force. In a microscopic viewpoint, local structure similarity between the metastable crystals and liquid determines the crystal-liquid interfacial free energy, and thus the nucleation barrier for the metastable crystals. The effect of the interfacial free energy on the formation of metastable crystals from supercooled, supersaturated, and supercompressed liquids will be demonstrated with metallic liquids, aqueous solutions, and water.

  16. Studying Thermodynamics of Metastable States

    OpenAIRE

    Kornyushin, Yuri

    2007-01-01

    Simple classical thermodynamic approach to the general description of metastable states is presented. It makes it possible to calculate the explicit dependence of the Gibbs free energy on temperature, to calculate the heat capacity, the thermodynamic barrier, dividing metastable and more stable states, and the thermal expansion coefficient. Thermodynamic stability under mechanical loading is considered. The influence of the heating (cooling) rate on the measured dynamic heat capacity is inves...

  17. Bitopic Ligands and Metastable Binding Sites

    DEFF Research Database (Denmark)

    Fronik, Philipp; Gaiser, Birgit I; Sejer Pedersen, Daniel

    2017-01-01

    of orthosteric binding sites. Bitopic ligands have been employed to address the selectivity problem by combining (linking) an orthosteric ligand with an allosteric modulator, theoretically leading to high-affinity subtype selective ligands. However, it remains a challenge to identify suitable allosteric binding...... that have been reported to date, this type of bitopic ligands would be composed of two identical pharmacophores. Herein, we outline the concept of bitopic ligands, review metastable binding sites, and discuss their potential as a new source of allosteric binding sites....

  18. Electron spin polarization effects in low-energy electron diffraction, ion neutralization, and metastable-atom deexcitation at solid surfaces. Progress report No. 3, January 1-December 31, 1983

    International Nuclear Information System (INIS)

    Walters, G.K.; Dunning, F.B.

    1983-01-01

    The importance of electron spin polarization (ESP) effects in the various spectroscopies used to study solid surfaces has become increasingly apparent in recent years. Recent low energy electron diffraction (LEED) investigations in this laboratory and elsewhere have shown that a great deal of new information contributing to the understanding of the geometrical arrangements of atoms at a surface can be obtained if the polarization of the various LEED beams is measured, or if the incident electron beam is polarized. Polarized LEED studies have shown large polarization features that are very sensitive to the presence of adsorbed layers, surface reconstruction, etc. In addition, theory suggests that polarization measurements can provide a more sensitive test of many of the parameters used in a surface model than can conventional LEED intensity measurements alone. Polarized LEED has also been applied to the study of surface magnetism. In the present contract year, polarized LEED has been used, together with Auger analysis and LEED intensity measurements, as a diagnostic to characterize Ni(001) surfaces produced by laser annealing

  19. Metastable supersymmetry breaking without scales

    Energy Technology Data Exchange (ETDEWEB)

    Bruemmer, Felix

    2010-11-15

    We construct new examples of models of metastable D=4 N=1 supersymmetry breaking in which all scales are generated dynamically. Our models rely on Seiberg duality and on the ISS mechanism of supersymmetry breaking in massive SQCD. Some of the electric quark superfields arise as composites of a strongly coupled gauge sector. This allows us to start with a simple cubic superpotential and an asymptotically free gauge group in the ultraviolet, and end up with an infrared effective theory which breaks supersymmetry dynamically in a metastable state. (orig.)

  20. Electron collisions with metastable helium

    International Nuclear Information System (INIS)

    Jacka, M.; Kelly, J.; Lohmann, B.; Buckman, S.

    1996-01-01

    Measurements and theoretical studies of electron scattering from the metastable 2 1,3 S excited states of helium are briefly reviewed. A high resolution hemispherical electron spectrometer with a position sensitive detector, developed for the study of low energy differential scattering from metastable excited states is discussed in detail. This assisted in the measurement of excitation processes characterised by extremely low count rates. The first results of angular distributions for electrons superelastically scattered from the 2 1,3 S states at incident energies of 5, 10 and 30 eV are presented. They have been normalised in magnitude to the convergent close coupling calculation. Cross sections from a 29-state R-matrix calculation and the first order many body theory calculation are also included for comparison. These measurements are in excellent agreement with the convergent close coupling calculations of Bray et al. (1994). 28 refs., 4 figs

  1. Instability of colliding metastable strings

    Energy Technology Data Exchange (ETDEWEB)

    Hiramatsu, Takashi [Kyoto Univ. (Japan). Yukawa Inst. for Theoretical Physics; Eto, Minoru [Yamagata Univ. (Japan). Dept. of Physics; Kamada, Kohei [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Kobayashi, Tatsuo [Kyoto Univ. (Japan). Dept. of Physics; Ookouchi, Yutaka [Kyoto Univ. (Japan). Dept. of Physics; Kyoto Univ. (Japan). The Hakubi Center for Advanced Research

    2013-04-15

    We investigate the collision dynamics of two metastable strings which can be viewed as tube-like domain walls with winding numbers interpolating a false vacuum and a true vacuum. We find that depending on the relative angle and speed of two strings, instability of strings increases and the false vacuum is filled out by rapid expansion of the strings or of a remnant of the collision.

  2. Metastable states in magnetic nanorings

    DEFF Research Database (Denmark)

    Castaño, F. J.; Ross, C. A.; Frandsen, Cathrine

    2003-01-01

    Magnetization states and hysteresis behavior of small ferromagnetic rings, of diameters 180-520 nm, have been investigated using magnetic force microscopy. In addition to the expected bi-domain ("onion") and flux-closed ("vortex") magnetization states, a metastable state has been found....... This "twisted" state contains a 360degrees domain wall which can exist over a wide range of applied fields. Four possible configurations of the twisted state are possible. Micromagnetic modeling shows that the twisted state is stabilised in small diameter, narrow rings. Additionally, more complex configurations...... such as double twisted states with two 360degrees walls have been observed....

  3. Vacuum metastability with black holes

    International Nuclear Information System (INIS)

    Burda, Philipp; Gregory, Ruth; Moss, Ian G. annd

    2015-01-01

    We consider the possibility that small black holes can act as nucleation seeds for the decay of a metastable vacuum, focussing particularly on the Higgs potential. Using a thin-wall bubble approximation for the nucleation process, which is possible when generic quantum gravity corrections are added to the Higgs potential, we show that primordial black holes can stimulate vacuum decay. We demonstrate that for suitable parameter ranges, the vacuum decay process dominates over the Hawking evaporation process. Finally, we comment on the application of these results to vacuum decay seeded by black holes produced in particle collisions.

  4. Geometrically induced metastability and holography

    Energy Technology Data Exchange (ETDEWEB)

    Aganagic, Mina; Aganagic, Mina; Beem, Christopher; Seo, Jihye; Vafa, Cumrun

    2006-10-23

    We construct metastable configurations of branes and anti-branes wrapping 2-spheres inside local Calabi-Yau manifolds and study their large N duals. These duals are Calabi-Yau manifolds in which the wrapped 2-spheres have been replaced by 3-spheres with flux through them, and supersymmetry is spontaneously broken. The geometry of the non-supersymmetric vacuum is exactly calculable to all orders of the't Hooft parameter, and to the leading order in 1/N. The computation utilizes the same matrix model techniques that were used in the supersymmetric context. This provides a novel mechanism for breaking supersymmetry in the context of flux compactifications.

  5. Spin dynamics in tunneling decay of a metastable state

    OpenAIRE

    Ban, Yue; Sherman, E. Ya.

    2012-01-01

    We analyze spin dynamics in the tunneling decay of a metastable localized state in the presence of spin-orbit coupling. We find that the spin polarization at short time scales is affected by the initial state while at long time scales both the probability- and the spin density exhibit diffraction-in-time phenomenon. We find that in addition to the tunneling time the tunneling in general can be characterized by a new parameter, the tunneling length. Although the tunneling length is independent...

  6. Cold and trapped metastable noble gases

    NARCIS (Netherlands)

    Vassen, W.; Cohen-Tannoudji, C.; Leduc, M.; Boiron, D.; Westbrook, C.I.; Truscott, A.; Baldwin, K.; Birkl, G.; Cancio, P.; Trippenbach, M.

    2012-01-01

    Experimental work on cold, trapped metastable noble gases is reviewed. The aspects which distinguish work with these atoms from the large body of work on cold, trapped atoms in general is emphasized. These aspects include detection techniques and collision processes unique to metastable atoms.

  7. Metastable state en route to traveling-wave synchronization state

    Science.gov (United States)

    Park, Jinha; Kahng, B.

    2018-02-01

    The Kuramoto model with mixed signs of couplings is known to produce a traveling-wave synchronized state. Here, we consider an abrupt synchronization transition from the incoherent state to the traveling-wave state through a long-lasting metastable state with large fluctuations. Our explanation of the metastability is that the dynamic flow remains within a limited region of phase space and circulates through a few active states bounded by saddle and stable fixed points. This complex flow generates a long-lasting critical behavior, a signature of a hybrid phase transition. We show that the long-lasting period can be controlled by varying the density of inhibitory/excitatory interactions. We discuss a potential application of this transition behavior to the recovery process of human consciousness.

  8. Metastable neural dynamics mediates expectation

    Science.gov (United States)

    Mazzucato, Luca; La Camera, Giancarlo; Fontanini, Alfredo

    Sensory stimuli are processed faster when their presentation is expected compared to when they come as a surprise. We previously showed that, in multiple single-unit recordings from alert rat gustatory cortex, taste stimuli can be decoded faster from neural activity if preceded by a stimulus-predicting cue. However, the specific computational process mediating this anticipatory neural activity is unknown. Here, we propose a biologically plausible model based on a recurrent network of spiking neurons with clustered architecture. In the absence of stimulation, the model neural activity unfolds through sequences of metastable states, each state being a population vector of firing rates. We modeled taste stimuli and cue (the same for all stimuli) as two inputs targeting subsets of excitatory neurons. As observed in experiment, stimuli evoked specific state sequences, characterized in terms of `coding states', i.e., states occurring significantly more often for a particular stimulus. When stimulus presentation is preceded by a cue, coding states show a faster and more reliable onset, and expected stimuli can be decoded more quickly than unexpected ones. This anticipatory effect is unrelated to changes of firing rates in stimulus-selective neurons and is absent in homogeneous balanced networks, suggesting that a clustered organization is necessary to mediate the expectation of relevant events. Our results demonstrate a novel mechanism for speeding up sensory coding in cortical circuits. NIDCD K25-DC013557 (LM); NIDCD R01-DC010389 (AF); NSF IIS-1161852 (GL).

  9. Consitutive modeling of metastable austenitic stainless steel

    NARCIS (Netherlands)

    Perdahcioglu, Emin Semih; Perdahcioglu, Emin Semih

    2008-01-01

    Metastable austenitic stainless steels combine high formability and high strength, which are generally opposing properties in materials. This property is a consequence of the martensitic phase transformation that takes place during deformation. This transformation is purely mechanically induced

  10. Metastability and Rydberg states of triatomic hydrogen

    International Nuclear Information System (INIS)

    Helm, H.

    1991-01-01

    The np,nd and nf Rydberg series of H 3 have been studied by one- or two-photon excitation from the lowest metastable state of H 3 :B2p 2 A 2 ''. The lifetime of the metastable state has been measured and the influence of an external electric field on the Rydberg states has been studied under both aspects of dynamics (field-ionization and field-induced predissociation) and structure (Strak effect)

  11. Control of switching between metastable superconducting states in δ-MoN nanowires.

    Science.gov (United States)

    Buh, Jože; Kabanov, Viktor; Baranov, Vladimir; Mrzel, Aleš; Kovič, Andrej; Mihailovic, Dragan

    2015-12-21

    The superconducting state in one-dimensional nanosystems is very delicate. While fluctuations of the phase of the superconducting wave function lead to the spontaneous decay of persistent supercurrents in thin superconducting wires and nanocircuits, discrete phase-slip fluctuations can also lead to more exotic phenomena, such as the appearance of metastable superconducting states in current-bearing wires. Here we show that switching between different metastable superconducting states in δ-MoN nanowires can be very effectively manipulated by introducing small amplitude electrical noise. Furthermore, we show that deterministic switching between metastable superconducting states with different numbers of phase-slip centres can be achieved in both directions with small electrical current pulse perturbations of appropriate polarity. The observed current-controlled bi-stability is in remarkable agreement with theoretically predicted trajectories of the system switching between different limit cycle solutions of a model one-dimensional superconductor.

  12. Optically polarized 3He

    Science.gov (United States)

    Gentile, T. R.; Nacher, P. J.; Saam, B.; Walker, T. G.

    2018-01-01

    This article reviews the physics and technology of producing large quantities of highly spin-polarized 3He nuclei using spin-exchange (SEOP) and metastability-exchange (MEOP) optical pumping. Both technical developments and deeper understanding of the physical processes involved have led to substantial improvements in the capabilities of both methods. For SEOP, the use of spectrally narrowed lasers and K-Rb mixtures has substantially increased the achievable polarization and polarizing rate. For MEOP nearly lossless compression allows for rapid production of polarized 3He and operation in high magnetic fields has likewise significantly increased the pressure at which this method can be performed, and revealed new phenomena. Both methods have benefitted from development of storage methods that allow for spin-relaxation times of hundreds of hours, and specialized precision methods for polarimetry. SEOP and MEOP are now widely applied for spin-polarized targets, neutron spin filters, magnetic resonance imaging, and precision measurements. PMID:29503479

  13. Optically polarized 3He

    Science.gov (United States)

    Gentile, T. R.; Nacher, P. J.; Saam, B.; Walker, T. G.

    2017-10-01

    This article reviews the physics and technology of producing large quantities of highly spin-polarized 3He nuclei using spin-exchange (SEOP) and metastability-exchange (MEOP) optical pumping. Both technical developments and deeper understanding of the physical processes involved have led to substantial improvements in the capabilities of both methods. For SEOP, the use of spectrally narrowed lasers and K-Rb mixtures has substantially increased the achievable polarization and polarizing rate. For MEOP nearly lossless compression allows for rapid production of polarized 3He and operation in high magnetic fields has likewise significantly increased the pressure at which this method can be performed, and revealed new phenomena. Both methods have benefitted from development of storage methods that allow for spin-relaxation times of hundreds of hours, and specialized precision methods for polarimetry. SEOP and MEOP are now widely applied for spin-polarized targets, neutron spin filters, magnetic resonance imaging, and precision measurements.

  14. Pathways for Metastable Carbonate Synthesis

    Science.gov (United States)

    Whittaker, Michael L.

    the formation of a nucleus changes the system composition. In systems chemically similar to ACC, amorphous strontium carbonate (ASC) is also observed in liposomes, but crystallizes rapidly, while amorphous barium carbonate (ABC) is not. We show that ACC can be made with over 50% barium, forming ACBC, but crystallizes at a dramatically faster rate with increasing barium. I demonstrate that this process dramatically departs from the classical description applied to ACC crystallization. It can be explained by the increasing short- and mid-range order in ACBC with increasing barium, which resembles that of crystalline Ca1-xBaxCO3 and selectively lowers the barrier to its formation relative to lower-energy structures. This Ca1-xBaxCO3 phase has been misidentified as calcite in the literature, but we solve the structure, assign the new spacegroup R3m, and call it balcite. Balcite is only thermodynamically stable above 525°C, and is over 30% harder than calcite. In the absence of calcium, I show that ABC is a highly transient precursor to a previously uncharacterized BaCO3·H2 O phase. This phase forms as very thin (10 nm) and extremely anisotropic platelets, which themselves recrystallize rapidly into witherite (BaCO 3). These examples demonstrate the power of amorphous precursors to enable metastable crystalline materials through thermodynamically downhill transformations, and the ability of confined volumes to reduce the rate of these transformations and enable their quantification.

  15. Entropy-driven metastable defects in silicon

    International Nuclear Information System (INIS)

    Hamilton, B.; Peaker, A.R.; Pantelides, S.T.

    1989-01-01

    The known metastable defects are usually describable by a configuration coordinate diagram in which two energy minima are separated by a barrier. This diagram does not change with temperature and each configuration is stable over some temperature range. Here we report the observation of a novel metastability: A configuration change occurs spontaneously and abruptly at a critical temperature, giving rise to a discontinuous DLTS (deep level transient spectroscopy) spectrum. We propose that this phenomenon is a manifestation of entropy variations in the configurational space. (author) 12 refs., 4 figs

  16. Metastable states of small rare gas crystallites

    Science.gov (United States)

    Etters, R. D.; Danilowicz, R.; Kaelberer, J.

    1977-01-01

    Metastable states of rare gas crystallites containing N atoms are investigated for N = 5,6,7, and 8. In particular, the stability, structures, structural transformation, and binding energy versus temperature are determined using a Monte Carlo method. The square pyramid isomer for N = 5 is found to be unstable at any finite temperature. The other metastable isomers are all found to make spontaneous transitions to the ground state if the temperature is greater than about one half that of meltings. Comparisons with previous work are also made

  17. Chalcogenides Metastability and Phase Change Phenomena

    CERN Document Server

    Kolobov, Alexander V

    2012-01-01

    A state-of-the-art description of metastability observed in chalcogenide alloys is presented with the accent on the underlying physics. A comparison is made between sulphur(selenium)-based chalcogenide glasses, where numerous photo-induced phenomena take place entirely within the amorphous phase, and tellurides where a reversible crystal-to-amorphous phase-change transformation is a major effect. Applications of metastability in devices¿optical memories and nonvolatile electronic phase-change random-access memories among others are discussed, including the latest trends. Background material essential for understanding current research in the field is also provided.

  18. Stabilization of metastable tetragonal zirconia nanocrystallites by surface modification

    DEFF Research Database (Denmark)

    Nielsen, Mette Skovgaard; Almdal, Kristoffer; Lelieveld, A. van

    2011-01-01

    Metastable tetragonal zirconia nanocrystallites were studied in humid air and in water at room temperature (RT). A stabilizing effect of different surfactants on the tetragonal phase was observed. Furthermore, the phase stability of silanized metastable tetragonal zirconia nanocrystallites...

  19. Modelling the material behaviour of metastable stainless

    NARCIS (Netherlands)

    Datta, K.; Geijselaers, Hubertus J.M.; Post, J.; Beyer, J.; Huetink, Han; Cesar de Sa, Jose M.A.; Santos, Abel D.

    2007-01-01

    Metastable austenitic stainless steels are designed to be thermodynamically unstable such that deformation even at room temperatures can bring about a change in the phase of face centred cubic austenite to either hexagonal close packed martensite and/or to body centred cubic martensite. This solid

  20. Metastable and bistable defects in silicon

    International Nuclear Information System (INIS)

    Mukashev, Bulat N; Abdullin, Kh A; Gorelkinskii, Yurii V

    2000-01-01

    Existing data on the properties and structure of metastable and bistable defects in silicon are analyzed. Primary radiation-induced defects (vacancies, self-interstitial atoms, and Frenkel pairs), complexes of oxygen, carbon, hydrogen, and other impurity atoms and defects with negative correlation energy are considered. (reviews of topical problems)

  1. Inelastic collision rates of trapped metastable hydrogen

    NARCIS (Netherlands)

    Landhuis, D; Matos, L; Moss, SC; Steinberger, JK; Vant, K; Willmann, L; Greytak, TJ; Kleppner, D

    We report the first detailed decay studies of trapped metastable (2S) hydrogen. By two-photon excitation of ultracold H samples, we have produced clouds of at least 5x10(7) magnetically trapped 2S atoms at densities greater than 4x10(10) cm(-3) and temperatures below 100 muK. At these densities and

  2. Polarization holography

    DEFF Research Database (Denmark)

    Nikolova, L.; Ramanujam, P.S.

    Current research into holography is concerned with applications in optically storing, retrieving, and processing information. Polarization holography has many unique properties compared to conventional holography. It gives results in high efficiency, achromaticity, and special polarization...... properties. This books reviews the research carried out in this field over the last 15 years. The authors provide basic concepts in polarization and the propagation of light through anisotropic materials, before presenting a sound theoretical basis for polarization holography. The fabrication...... and characterization of azobenzene based materials, which remain the most efficient for the purpose, is described in detail. This is followed by a description of other materials that are used in polarization holography. An in-depth description of various applications, including display holography and optical storage...

  3. Metastable states in amorphous chalcogenide semiconductors

    CERN Document Server

    Mikla, Victor I

    2009-01-01

    This book addresses an interesting and technologically important class of materials, the amorphous chalcogenide semiconductors. Experimental results on the structural and electronic metastable states in Se-rich chalcogenides are presented. Special attention is paid to the states in the mobility gap and their sensitivity to various factors such as irradiation, annealing and composition. Photoinduced changes of structure and physical properties are also considered and structural transformation at photocrystallization is studied in detail. Finally, the authors discuss potential applications of th

  4. Detonation of Meta-stable Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Kuhl, Allen; Kuhl, Allen L.; Fried, Laurence E.; Howard, W. Michael; Seizew, Michael R.; Bell, John B.; Beckner, Vincent; Grcar, Joseph F.

    2008-05-31

    We consider the energy accumulation in meta-stable clusters. This energy can be much larger than the typical chemical bond energy (~;;1 ev/atom). For example, polymeric nitrogen can accumulate 4 ev/atom in the N8 (fcc) structure, while helium can accumulate 9 ev/atom in the excited triplet state He2* . They release their energy by cluster fission: N8 -> 4N2 and He2* -> 2He. We study the locus of states in thermodynamic state space for the detonation of such meta-stable clusters. In particular, the equilibrium isentrope, starting at the Chapman-Jouguet state, and expanding down to 1 atmosphere was calculated with the Cheetah code. Large detonation pressures (3 and 16 Mbar), temperatures (12 and 34 kilo-K) and velocities (20 and 43 km/s) are a consequence of the large heats of detonation (6.6 and 50 kilo-cal/g) for nitrogen and helium clusters respectively. If such meta-stable clusters could be synthesized, they offer the potential for large increases in the energy density of materials.

  5. Radiation-sustained nanocluster metastability in oxide dispersion strengthened materials

    Energy Technology Data Exchange (ETDEWEB)

    Ribis, J., E-mail: joel.ribis@cea.fr [CEA, DEN, SRMA, F-91191 Gif sur Yvette (France); Bordas, E.; Trocellier, P.; Serruys, Y. [CEA, DEN, Service de Recherches de Métallurgie Physique, Laboratoire JANNUS, 91191 Gif sur Yvette (France); Carlan, Y. de [CEA, DEN, SRMA, F-91191 Gif sur Yvette (France); Legris, A. [UMET, CNRS/UMR 8207, Bât. C6, Univ. Lille 1, 59655 Villeneuve d’Ascq (France)

    2015-12-15

    ODS materials constitute a new promising class of structural materials for advanced fission and fusion energy application. These Fe–Cr based ferritic steels contain ultra-high density of dispersion-strengthening nanoclusters conferring excellent mechanical properties to the alloy. Hence, guarantee the nanocluster stability under irradiation remain a critical issue. Nanoclusters are non-equilibrium multicomponent compounds (YTiCrO) forming through a complex nucleation pathway during the elaboration process. In this paper, it is proposed to observe the response of these nanoclusters when the system is placed far from equilibrium by means of ion beam. The results indicate that the Y, Ti, O and Cr atoms self-organized so that nanoclusters coarsened but maintain their non-equilibrium chemical composition. It is discussed that the radiation-sustained nanocluster metastability emerges from cooperative effects: radiation-induced Ostwald ripening, permanent creation of vacancies in the clusters, and fast Cr diffusion mediated by interstitials.

  6. Interaction of rare gas metastable atoms

    International Nuclear Information System (INIS)

    Wang, A.Z.F.

    1977-11-01

    The physical and chemical properties of metastable rare gas atoms are discussed and summarized. This is followed by a detailed examination of the various possible pathways whereby the metastable's excess electronic energy can be dissipated. The phenomenon of chemi-ionization is given special emphasis, and a theoretical treatment based on the use of complex (optical) potential is presented. This is followed by a discussion on the unique advantages offered by elastic differential cross section measurements in the apprehension of the fundamental forces governing the ionization process. The methodology generally adopted to extract information about the interaction potential for scattering data is also systematically outlined. Two widely studied chemi-ionization systems are then closely examined in the light of accurate differential cross section measurements obtained in this work. The first system is He(2 3 S) + Ar for which one can obtain an interaction potential which is in good harmony with the experimental results of other investigators. The validity of using the first-order semiclassical approximation for the phase shifts calculation in the presence of significant opacities is also discussed. The second reaction studied is He*+D 2 for which measurements were made on both spin states of the metastable helium. A self-consistent interaction potential is obtained for the triplet system, and reasons are given for not being able to do likewise for the singlet system. The anomalous hump proposed by a number of laboratories is analyzed. Total elastic and ionization cross sections as well as rate constants are calculated for the triplet case. Good agreement with experimental data is found. Finally, the construction and operation of a high power repetitively pulsed nitrogen laser pumped dye laser system is described in great details. Details for the construction and operation of a flashlamp pumped dye laser are likewise given

  7. Transient cognitive dynamics, metastability, and decision making.

    Directory of Open Access Journals (Sweden)

    Mikhail I Rabinovich

    2008-05-01

    Full Text Available The idea that cognitive activity can be understood using nonlinear dynamics has been intensively discussed at length for the last 15 years. One of the popular points of view is that metastable states play a key role in the execution of cognitive functions. Experimental and modeling studies suggest that most of these functions are the result of transient activity of large-scale brain networks in the presence of noise. Such transients may consist of a sequential switching between different metastable cognitive states. The main problem faced when using dynamical theory to describe transient cognitive processes is the fundamental contradiction between reproducibility and flexibility of transient behavior. In this paper, we propose a theoretical description of transient cognitive dynamics based on the interaction of functionally dependent metastable cognitive states. The mathematical image of such transient activity is a stable heteroclinic channel, i.e., a set of trajectories in the vicinity of a heteroclinic skeleton that consists of saddles and unstable separatrices that connect their surroundings. We suggest a basic mathematical model, a strongly dissipative dynamical system, and formulate the conditions for the robustness and reproducibility of cognitive transients that satisfy the competing requirements for stability and flexibility. Based on this approach, we describe here an effective solution for the problem of sequential decision making, represented as a fixed time game: a player takes sequential actions in a changing noisy environment so as to maximize a cumulative reward. As we predict and verify in computer simulations, noise plays an important role in optimizing the gain.

  8. Levy flights: transitions and meta-stability

    International Nuclear Information System (INIS)

    Imkeller, Peter; Pavlyukevich, Ilya

    2006-01-01

    We consider Levy flights of stability index α element of (0, 2) in a potential landscape in the limit of a small noise parameter. We give a purely probabilistic description of the random dynamics on the basis of a special decomposition of the driving Levy processes into independent small jumps and compound Poisson parts. We prove that escape times from a potential well are exponentially distributed and their mean values increase as a power ε -α of the noise intensity ε. This allows us to obtain meta-stability results for a jump diffusion in a double-well potential. (letter to the editor)

  9. Metastable He deexcitation at semiconductor interfaces

    International Nuclear Information System (INIS)

    Pasquali, L.; Nannarone, S.

    2005-01-01

    A review is given of the application of metastable deexcitation spectroscopy (MDS) to the study of the interface formation between semiconductors and different materials. In particular we present an overview of the results obtained on nanostructured interfaces, where strain and reaction between the substrate and the overlayer atoms drive the growth mode and the morphology of the system. As prototypical examples we discuss the growth of CaF 2 on silicon and rare earths (Yb, Er) on silicon and gallium arsenide. The mechanisms and chemical reactions which bring to interface formation are examined on the basis of MDS results and their comparison with photoemission

  10. Collisional interaction between metastable neon atoms

    Energy Technology Data Exchange (ETDEWEB)

    Drunen, Wouter Johannes van

    2008-07-07

    In this thesis, the study of cold gases of neon atoms in different metastable states is described. It contains measurements of the collisional parameters for both the 3s[3/2]{sub 2} and the 3s'[1/2]{sub 0} metastable state and the dependence of the inelastic loss on external fields. Furthermore, the investigation of frequency dependent laser-induced collisions, and the possibility to excite photoassociation resonances is presented. For the measurements described here, neon atoms have been confined in a magnetooptical trap, in a magnetostatic trap, or in an optical dipole trap, respectively. By laser cooling inside the magnetic trap, atomic samples with more than 95 percent occupation of the magnetic substate m{sub J} = +2 could be prepared. They have a typical temperature of 0.5 mK, central densities up to 10{sup 11} cm{sup -3}, and a central phase-space density of up to 2.2.10{sup -7}. After loading the optical dipole trap from the magnetic trap, 2.5.10{sup 6} atoms with typical temperatures of 0.1 mK, and central densities up to 5.10{sup 10} cm{sup -3} were trapped. By evaporative cooling of the atoms in the magnetic trap we could increase the phase-space density by a factor of 200 to 5.10{sup -5}. Investigating the frequency dependence of laser-induced collisions did not reveal an experimental signature for the excitation of photoassociation resonances. For the {sup 3}D{sub 3} line a frequency dependence of laser enhanced Penning ionization was observed. Measurement of the two-body loss coefficient as function of the magnetic field showed a field dependence of the inelastic loss. These losses increase towards both small and large offset fields. The implementation of an optical dipole trap allowed us to trap the {sup 3}P{sub 0} metastable state. From the trap loss measurements we determined the two-body loss coefficient of the {sup 3}P{sub 0} metastable state for both bosonic isotopes {sup 20}Ne and {sup 22}Ne. For {sup 20}Ne we obtained {beta}=6{sup +5}{sub

  11. The glassy and supercooled state of elemental sulfur: Vibrational modes, structure metastability, and polymer content

    Science.gov (United States)

    Andrikopoulos, K. S.; Kalampounias, A. G.; Falagara, O.; Yannopoulos, S. N.

    2013-09-01

    We report a detailed investigation of vibrational modes, structure, and dynamics of elemental sulfur in the glassy and the supercooled state, using Raman scattering and ab initio calculations. Polarized Raman spectra are recorded - for sulfur quenched from 473 K - over a broad temperature range from 93 K to 273 K where the supercooled liquid crystallized. The temperature induced shifts of the majority of the vibrational modes are determined and compared with the corresponding ones of crystalline sulfur. Analysis of the reduced isotropic spectra showed that the structure of the quenched product is composed of eight member rings (S8) and polymeric chains (Sμ) with a relative fraction comparable to that of the parent liquid at 473 K. Low temperature spectra, where spectral line broadening due to thermal effects is limited, revealed that two different polymeric species are present in the glass with distinct vibrational frequencies. Their interpretation was assisted by ab initio calculations used to simulate the vibrational frequencies of polymeric chains S8k (k = 1, …, 7). Theoretical results exhibit an increasing breathing mode frequency for sulfur chains up to k = 2, although it remains constant beyond the above value. The polymeric content is metastable; heating the glass above its glass transition temperature, Tg, destabilizes the chains and drives them back to the more thermodynamically stable rings. This bond interchange mechanism provides the structural origin of a secondary relaxation process in supercooled sulfur reported long ago, which has been also considered as a complication in the correct fragility estimation of this material. Finally, the Boson peak of the glass was found to exhibit strong temperature dependence even at temperatures below Tg.

  12. Fish remains and humankind

    Directory of Open Access Journals (Sweden)

    Andrew K G Jones

    1997-08-01

    Full Text Available The four papers in this issue represent a trawl of the reports presented to the Fourth meeting of the International Council for Archaeozoology (ICAZ Fish Remains Working Group, which met at the University of York in 1987. The conference discussed material from many parts of the world - from Australasia to the north-west coast of America - and many eras, ranging in date from the early Pleistocene to the 1980s. It demonstrated both the variety of work being carried out and the growing interest in ancient fish remains. Internet Archaeology plans to publish other batches of papers from this conference. These reports will demonstrate the effort being made to distinguish between assemblages of fish remains which have been deposited by people and those which occur in ancient deposits as a result of the action of other agents. To investigate this area, experiments with modern material and observations of naturally occurring fish bone assemblages are supplemented with detailed analysis of ancient and modern fish remains. The papers published here illustrate the breadth of research into osteology, biogeography, documentary research, and the practicalities of recovering fish remains. Read, digest and enjoy them! Using the Internet for publishing research papers is not only ecologically sound (saving paper, etc. it disseminates scholarship to anyone anywhere on the planet with access to what is gradually becoming necessary technology in the late 20th century. Hopefully, future groups of papers will include video and audio material recorded at the conference, and so enable those who could not attend to gain further insights into the meeting and the scholarship underpinning this area of research.

  13. Metastable Layered Cobalt Chalcogenides from Topochemical Deintercalation.

    Science.gov (United States)

    Zhou, Xiuquan; Wilfong, Brandon; Vivanco, Hector; Paglione, Johnpierre; Brown, Craig M; Rodriguez, Efrain E

    2016-12-21

    We present a general strategy to synthesize metastable layered materials via topochemical deintercalation of thermodynamically stable phases. Through kinetic control of the deintercalation reaction, we have prepared two hypothesized metastable compounds, CoSe and CoS, with the anti-PbO type structure from the starting compounds KCo 2 Se 2 and KCo 2 S 2 , respectively. Thermal stability, crystal structure from X-ray and neutron diffraction, magnetic susceptibility, magnetization, and electrical resistivity are studied for these new layered chalcogenides; both CoSe and CoS are found to be weak itinerant ferromagnets with Curie temperatures close to 10 K. Due to the weak van der Waals forces between the layers, CoSe is found to be a suitable host for further intercalation of guest species such as Li-ethylenediamine. From first-principles calculations, we explain why the Co chalcogenides are ferromagnets instead of superconductors as in their iron analogues. Bonding analysis of the calculated electronic density of states both explains their phase stability and predicts the limits of our deintercalation technique. Our results have broad implications for the rational design of new two-dimensional building blocks for functional materials.

  14. Kinetics of optically pumped Ar metastables.

    Science.gov (United States)

    Han, Jiande; Heaven, Michael C

    2014-11-15

    Optically pumped lasers that use metastable excited states of Ar have been demonstrated using both pulsed and CW excitation. In terms of Paschen labeling of the states of Ar, the laser system uses excitation of the 2p9-1s5 transition, and lases on the 2p10-1s5 line. Collisional transfer of population from 2p9 to 2p10 is achieved using He as the buffer gas. For the purpose of modeling and developing this laser, rate constants for state-to-state transfer in Ar(2p(i))+Ar/He mixtures are needed. As the 2p10 level can radiate down to 1s4, this lower level also plays a significant role in the laser kinetics. Consequently, rate constants for the relaxation of 1s4 by Ar and He are also required. In the present study we have used pulsed laser excitation techniques to measure rate constants of relevance to the optically pumped metastable Ar laser.

  15. [PALEOPATHOLOGY OF HUMAN REMAINS].

    Science.gov (United States)

    Minozzi, Simona; Fornaciari, Gino

    2015-01-01

    Many diseases induce alterations in the human skeleton, leaving traces of their presence in ancient remains. Paleopathological examination of human remains not only allows the study of the history and evolution of the disease, but also the reconstruction of health conditions in the past populations. This paper describes the most interesting diseases observed in skeletal samples from the Roman Imperial Age necropoles found in urban and suburban areas of Rome during archaeological excavations in the last decades. The diseases observed were grouped into the following categories: articular diseases, traumas, infections, metabolic or nutritional diseases, congenital diseases and tumours, and some examples are reported for each group. Although extensive epidemiological investigation in ancient skeletal records is impossible, the palaeopathological study allowed to highlight the spread of numerous illnesses, many of which can be related to the life and health conditions of the Roman population.

  16. Tensorial analysis of the long-range interaction between metastable alkaline-earth-metal atoms

    International Nuclear Information System (INIS)

    Santra, Robin; Greene, Chris H.

    2003-01-01

    Alkaline-earth-metal atoms in their lowest (nsnp) 3 P 2 state are exceptionally long lived and can be trapped magnetically. The nonspherical atomic structure leads to anisotropic long-range interactions between two metastable alkaline-earth-metal atoms. The anisotropy affects the rotational motion of the diatomic system and couples states of different rotational quantum numbers. This paper develops a tensorial decomposition of the most important long-range interaction operators, and a systematic inclusion of molecular rotations, in the presence of an external magnetic field. This analysis illuminates the nature of the coupling between the various degrees of freedom. The consequences are illustrated by application to a system of practical interest: metastable 88 Sr. Using atomic parameters determined in a nearly ab initio calculation, we compute adiabatic potential-energy curves. The anisotropic interatomic interaction, in combination with the applied magnetic field, is demonstrated to induce the formation of a long-range molecular potential well. This curve correlates to two fully polarized, low-field seeking atoms in a rotational s-wave state. The coupling among molecular rotational states controls the existence of the potential well, and its properties vary as a function of magnetic-field strength, thus allowing the scattering length in this state to be tuned. The scattering length of metastable 88 Sr displays a resonance at a field of 339 G

  17. Centrifugal tensioned metastable fluid detectors for trace radiation sources: experimental verification and military employment

    OpenAIRE

    Chiaverotti, Dominic J.

    2016-01-01

    Approved for public release; distribution is unlimited Centrifugal tensioned metastable fluid detectors (CTMFDs) promise a compact, easy to use, highly sensitive, robust, discriminatory, mobile sensor platform that could detect the presence of special nuclear materials in real time. CTMFDs could help in the detection of fast neutrons or alpha particles that are telltale signs of nuclear material, while remaining blind to gamma radiation that could otherwise interfere with the desired measu...

  18. The liquid metastable miscibility gap in Cu-based systems

    DEFF Research Database (Denmark)

    Curiotto, S.; Greco, R.; Pryds, Nini

    2007-01-01

    . In order to predict the phase equilibria and the mechanisms of microstructure formation, a determination of the metastable monotectics in the phase diagrams is essential. This paper focuses on the up-to-date findings on the Cu–Co, Cu–Fe and Cu–Co–Fe metastable miscibility gap in the liquid phase...

  19. Non-resonant two and three-photon ionization of the singlet and triplet metastable helium atoms of an atomic jet

    International Nuclear Information System (INIS)

    Mathieu, Bernard.

    1978-01-01

    The three-photon ionization cross-section of the helium metastables He(2 1 S) and He(2 3 S) is determined by means of the linearly polarized radiation of a pulsed ruby laser with an emission wavelength equal to 6946.4 A at 19 0 C. Two-photon ionization, obtained by doubling the laser beam frequency, is also studied [fr

  20. Selective removal of either metastable species from a mixed 3P 0,2 rare-gas metastable beam

    Science.gov (United States)

    Dunning, F. B.; Cook, T. B.; West, W. P.; Stebbings, R. F.

    1975-01-01

    A tunable CW laser has been used to selectively remove either of the two metastable species, 3P 0,2, which are initially present in a neon metastable beam. The method is applicable to other rare gases and provides the opportunity for separate investigation of effects due to atoms in either the 3P 0 or 3P 2 state.

  1. Metastable electroweak vacuum. Implications for inflation

    Energy Technology Data Exchange (ETDEWEB)

    Lebedev, Oleg; Westphal, Alexander [DESY Theory Group, Hamburg (Germany)

    2012-10-15

    Within the Standard Model, the current Higgs and top quark data favor metastability of the electroweak vacuum, although the uncertainties are still significant. The true vacuum is many orders of magnitude deeper than ours and the barrier separating the two is tiny compared to the depth of the well. This raises a cosmological question: how did the Higgs field get trapped in the shallow minimum and why did it stay there during inflation? The Higgs initial conditions before inflation must be fine-tuned to about one part in 10{sup 8} in order for the Higgs field to end up in the right vacuum. In this note, we show that these problems can be resolved if there is a small positive coupling between the Higgs and the inflaton.

  2. The Lotus effect: superhydrophobicity and metastability.

    Science.gov (United States)

    Marmur, Abraham

    2004-04-27

    To learn how to mimic the Lotus effect, superhydrophobicity of a model system that resembles the Lotus leaf is theoretically discussed. Superhydrophobicity is defined by two criteria: a very high water contact angle and a very low roll-off angle. Since it is very difficult to calculate the latter for rough surfaces, it is proposed here to use the criterion of a very low wet (solid-liquid) contact area as a simple, approximate substitute for the roll-off angle criterion. It is concluded that nature employs metastable states in the heterogeneous wetting regime as the key to superhydrophobicity on Lotus leaves. This strategy results in two advantages: (a) it avoids the need for high steepness protrusions that may be sensitive to breakage and (b) it lowers the sensitivity of the superhydrophobic states to the protrusion distance.

  3. From materials control to astrophysics: metastable superconductors

    International Nuclear Information System (INIS)

    Waysand, G.

    1984-01-01

    The basic properties of metastable superconducting materials are reviewed: superheated domain, size of the granules, reading of the change of state. In the case of superheating, the phase transition can occur following two paths: a) increase of temperature (thermal nucleation) which allows an analysis of the calorimetric behavior for particle detection; b) increase of the applied magnetic field which allows the evaluation of surface defects promoting the nucleation of the normal state, and, more generally, the study of the superheated material as a disordered system. The thermal nucleation is useful for X-ray detection in non-destructive control as well as for the solar neutrino detection in real time. The magnetic nucleation is the basis for a proposal of detection of magnetic monopoles by induction [fr

  4. Photoassociative spectroscopy of ultracold metastable argon

    International Nuclear Information System (INIS)

    Shaffer, M. K.; Ranjit, G.; Sukenik, C. I.; Walhout, M.

    2011-01-01

    We present results of photoassociative spectroscopy performed on ultracold metastable argon atoms in a magneto-optical trap. Ion spectra are obtained with laser detuning up to a few gigahertz below the 4s[3/2] 2 →4p[5/2] 3 trapping transition at 811 nm and with intensities in a range of ∼(10 2 -10 5 )I Sat . We also compute dipole-dipole potentials for both singly and doubly excited diatomic molecules and use a Leroy-Bernstein analysis to determine the approximate vibrational spacings in the (s+p) and (p+p) manifolds. Based on this theoretical framework, we explain a broad background feature in our data and suggest that double-excitation mechanisms are likely responsible for sharp dips in the ion signal.

  5. Metastable memristive lines for signal transmission and information processing applications

    Science.gov (United States)

    Slipko, Valeriy A.; Pershin, Yuriy V.

    2017-04-01

    Traditional studies of memristive devices have mainly focused on their applications in nonvolatile information storage and information processing. Here, we demonstrate that the third fundamental component of information technologies—the transfer of information—can also be employed with memristive devices. For this purpose, we introduce a metastable memristive circuit. Combining metastable memristive circuits into a line, one obtains an architecture capable of transferring a signal edge from one space location to another. We emphasize that the suggested metastable memristive lines employ only resistive circuit components. Moreover, their networks (for example, Y-connected lines) have an information processing capability.

  6. Laser-induced metastable phases in liquids

    Science.gov (United States)

    Nath, Arpita; Sharma, Pooja; Khare, Alika

    2018-02-01

    Pulsed laser ablation at solid–liquid interfaces is gaining wide acceptance due to the production of functional nanomaterials having potential implications. The complex phenomena involved in the laser ablation process cause extreme pressure and temperature and a highly transient preferential growth of metastable phases is possible. Understanding of the nucleation phenomena of laser-produced nanoparticles in liquid is still limited and more orientated towards exploring the applicability of the nanoparticulates. The current work thus focuses on the nucleation dynamics of the high-pressure phase of TiO2 having an orthorhombic α-PbO2-like structure formed during pulsed laser ablation at the titanium–water interface. The nucleation time (10‑11 to 10‑8 s), growth velocity (maximum of ~100 nm ns‑1) and particle statistics are calculated and compared with experimentally derived particle statistics (3–180 nm). Pulsed laser ablation in liquid is also accompanied by mechanical phenomena known as cavitation bubbles. Insight into the possible role played by cavitation bubbles in the nucleation of nanoparticulates is outlined.

  7. Quantum mechanical metastability: When and why?

    International Nuclear Information System (INIS)

    Boyanovsky, D.; Willey, R.; Holman, R.

    1992-01-01

    We study quantum mechanical metastability with an eye towards false vacuum decay. We point out some technical and conceptual problems with the familiar bounce treatment of this process. We illustrate with simple quantum mechanical examples that the bounce formalism fails to account for the correct boundary conditions. It is also shown, that the bounce approach overestimates the time scales for tunneling of localized packets in typical (slightly) biased double well potentials. We present a thorough WKB analysis with particular attention to semiclassical trajectories corresponding to complex saddle points. We point out that the boundary conditions determine the proper choice of saddle points and the bounce approach fails to account for semiclassical trajectories in many physically relevant cases. We recognize that these saddle points account for the matching conditions of the WKB wave functions beyond the barriers and restore unitarity and reality of eigenvalues for self-adjoint boundary conditions. We provide a novel approach to the semiclassical analysis of out of equilibrium decay in real time in quantum statistical mechanics. (orig.)

  8. Metastable fragmentation of silver bromide clusters

    International Nuclear Information System (INIS)

    L'Hermite, J.M.; Rabilloud, F.; Marcou, L.; Labastie, P.

    2001-01-01

    The abundance spectra and the fragmentation channels of silver bromide clusters have been measured and analyzed. The most abundant species are Ag n Br n - 1 + and Ag n Br n + 1 - and Ag 14 Br 13 + is a magic number, revealing their ionic nature. However, some features depart from what is generally observed for alkali-halide ionic clusters. From a certain size, Ag n Br n - 1 + is no more the main series, and Ag n Br n - 2, 3 + series become almost as important. The fast fragmentation induced by a UV laser makes the cations lose more bromine than silver ions and lead to more silver-rich clusters. Negative ions mass spectra contain also species with more silver atoms than required by stoichiometry. We have investigated the metastable fragmentation of the cations using a new experimental method. The large majority of the cations release mainly a neutral Ag 3 Br 3 cluster. These decay channels are in full agreement with our recent ab initio DFT calculations, which show that Ag + -Ag + repulsion is reduced due to a globally attractive interaction of their d orbitals. This effect leads to a particularly stable trimer (AgBr) 3 and to quasi-planar cyclic structures of (AgBr) n clusters up to n = 6. We have shown that these two features may be extended to other silver halides, to silver hydroxides (AgOH) n , and to cuprous halide compounds. (orig.)

  9. Investigation of systematic errors of metastable "atomic pair" number

    CERN Document Server

    Yazkov, V

    2015-01-01

    Sources of systematic errors in analysis of data, collected in 2012, are analysed. Esti- mations of systematic errors in a number of “atomic pairs” fr om metastable π + π − atoms are presented.

  10. Influence of radiation on metastability-based TRNG

    Science.gov (United States)

    Wieczorek, Piotr Z.; Wieczorek, Zbigniew

    2017-08-01

    This paper presents a True Random Number Generator (TRNG) based on Flip-Flops with violated timing constraints. The proposed circuit has been implemented in a Xilinx Spartan 6 device. The TRNG circuit utilizes the metastability phenomenon as a source of randomness. Therefore, in the paper the influence of timing constraints on the flip-flop metastability proximity is discussed. The metastable range of operation enhances the noise influence on a Flip-Flop behavior. Therefore, the influence of an external stochastic source on the flip-flop operation is also investigated. For this purpose a radioactive source of radiation was used. According to the results shown in the paper the radiation increases the unpredictability of the metastable process of flip-flops operating as the randomness source in the TRNG. The statistical properties of TRNG operating in an increased radiation conditions were verified with the NIST battery of statistical tests.

  11. The Importance of Kinetic Metastability: Some Common Everyday Examples

    Science.gov (United States)

    Jensen, William B.

    2015-01-01

    The importance of kinetic metastability is illustrated in detail using several common household products and recommendations are made for how this important and widespread, but often neglected, phenomenon can be more effectively presented in the introductory chemistry textbook.

  12. Extension of equilibrium formation criteria to metastable microalloys

    International Nuclear Information System (INIS)

    Kaufmann, E.N.; Vianden, R.; Chelikowsky, J.R.; Phillips, J.C.

    1977-01-01

    Metastable microalloys of 25 metallic elements with beryllium have been prepared by ion implantation. The injected atoms have been found to occupy one of three sites available in the solvent lattice. A modified Laudau-Ginsburg expansion using bulk alloy variables proposed by Miedema is completely successful in predicting the observed metastable-site preferences and indicates a broader applicability of these variables than was heretofore anticipated

  13. Metastable enhancement of C+ and O+ capture reactions

    International Nuclear Information System (INIS)

    Thomas, E.W.

    1992-01-01

    The project is devoted to the study of charge transfer neutralization of Carbon and oxygen ions in H and H 2 gases at energies from 10 to 500 eV. A major motivation was to provide cross section data to support analysis of edge plasmas in Tokamak Fusion devices. The first objective was to measure cross sections for metastable excited singly charged ions separately from the cross sections for ground state ions. Previously published values are confusing because the beams used included unknown fractions of metastables and these metastables have cross sections greatly different from the ground states. The program was fully accomplished, metastable cross sections were found to be over an order of magnitude greater than ones for the ground state and existing discrepancies in the literature were resolved. Considerable effort was devoted to the design and operation of ion source configurations were the metastable content of the ion beam was known. Subsequently study progressed to the neutralization of multiply charged C and 0 ions in the same targets. First there has been a need to develop ion sources which can produce useful beams of multiply charged species. This has now been accomplished. The intent is to use these sources for the measurement of cross sections with again an attempt to differentiate between the behavior of ground and metastably excited species

  14. In Situ Observations of Phase Transitions in Metastable Nickel (Carbide)/Carbon Nanocomposites

    Science.gov (United States)

    2016-01-01

    Nanocomposite thin films comprised of metastable metal carbides in a carbon matrix have a wide variety of applications ranging from hard coatings to magnetics and energy storage and conversion. While their deposition using nonequilibrium techniques is established, the understanding of the dynamic evolution of such metastable nanocomposites under thermal equilibrium conditions at elevated temperatures during processing and during device operation remains limited. Here, we investigate sputter-deposited nanocomposites of metastable nickel carbide (Ni3C) nanocrystals in an amorphous carbon (a-C) matrix during thermal postdeposition processing via complementary in situ X-ray diffractometry, in situ Raman spectroscopy, and in situ X-ray photoelectron spectroscopy. At low annealing temperatures (300 °C) we observe isothermal Ni3C decomposition into face-centered-cubic Ni and amorphous carbon, however, without changes to the initial finely structured nanocomposite morphology. Only for higher temperatures (400–800 °C) Ni-catalyzed isothermal graphitization of the amorphous carbon matrix sets in, which we link to bulk-diffusion-mediated phase separation of the nanocomposite into coarser Ni and graphite grains. Upon natural cooling, only minimal precipitation of additional carbon from the Ni is observed, showing that even for highly carbon saturated systems precipitation upon cooling can be kinetically quenched. Our findings demonstrate that phase transformations of the filler and morphology modifications of the nanocomposite can be decoupled, which is advantageous from a manufacturing perspective. Our in situ study also identifies the high carbon content of the Ni filler crystallites at all stages of processing as the key hallmark feature of such metal–carbon nanocomposites that governs their entire thermal evolution. In a wider context, we also discuss our findings with regard to the much debated potential role of metastable Ni3C as a catalyst phase in graphene and

  15. PREPARATION, CHARACTERIZATION, AND PHARMACEUTICAL APPLICATION OF LINEAR DEXTRINS .1. PREPARATION AND CHARACTERIZATION OF AMYLODEXTRIN, METASTABLE AMYLODEXTRINS, AND METASTABLE AMYLOSE

    NARCIS (Netherlands)

    WIERIK, GHPT; EISSENS, AC; BESEMER, AC; LERK, CF

    The linear dextrin amylodextrin was prepared by enzymatic hydrolysis from waxy maize. Four metastable amylodextrins were prepared by complexation with different volatile organic compounds. All products showed partial dissolution into water at room temperature, because of dissolution of molecules

  16. Polarization Optics

    OpenAIRE

    Fressengeas, Nicolas

    2010-01-01

    The physics of polarization optics *Polarized light propagation *Partially polarized light; DEA; After a brief introduction to polarization optics, this lecture reviews the basic formalisms for dealing with it: Jones Calculus for totally polarized light and Stokes parameters associated to Mueller Calculus for partially polarized light.

  17. Effect of nitrogen alloying on the semiconducting properties of passive films and metastable pitting susceptibility of 316L and 316LN stainless steels

    International Nuclear Information System (INIS)

    Lee, Jae-Bong; Yoon, Sang-In

    2010-01-01

    The beneficial effect of nitrogen alloying on the corrosion resistance of stainless steels has been attributed to the increase of the local pH within the active sites and the enhanced repassivation of the metastable pits. In order to better understand the effect of nitrogen alloying, in situ capacitance measurements and potentiostatic polarization were conducted for 316L and 316LN stainless steels with different nitrogen contents in deaerated 0.1 M Na 2 SO 4 and 0.1 M NaCl aqueous solutions. The Mott-Schottky plots obtained from the in situ capacitance measurements offered information on the donor concentration and the thickness of the space charge region within the passive film. The metastable pitting susceptibility was investigated by performing potentiostatic polarization tests. The results showed that nitrogen alloying decreased the donor densities and the number of metastable pits, while the absorption of chloride ions on the passive film had the opposite effect. Auger electron spectroscopy (AES) analysis demonstrated that nitrogen alloying enriched the chromium within the passive film. The relationship between the semiconducting properties of the passive film and the metastable pitting susceptibility was elucidated.

  18. Fusion with highly spin polarized HD and D2

    International Nuclear Information System (INIS)

    Honig, A.; Letzring, S.; Skupsky, S.

    1993-01-01

    The experimental efforts over the past 5 years have been aimed at carrying out ICF shots with spin-polarized D fuel. The authors successfully prepared polarized D in HD, and solved the problems of loading target shells with their carefully prepared isotopic mixtures, polarizing them so that the D polarization remains metastably frozen-in for about half a day, and carrying out the various cold transfer requirements at Syracuse, where the target is prepared, and at Rochester, where the cold target is inserted into the OMEGA fusion chamber. A principal concern during this past year was overcoming difficulties encountered in maintaining the integrity of the fragile cold target during the multitude of cold-transfers required for the experiment. These difficulties arose from insufficient rigidity of the cold transfer systems, which were constrained to be of small diameter by the narrow central access bore of the dilution refrigerator, and were exacerbated by the multitude of required target shell manipulations between different environments, each with different coupling geometry, including target shell permeation, polarization, storage, transport, retrieval and insertion into OMEGA. The authors did solve all of these problems, and were able to position a cold, high density but unpolarized target with required precision in OMEGA. Upon shooting the accurately positioned unpolarized high density cold target, no neutron yield was observed. Inspection inside the OMEGA tank after the shot indicated the absence of neutron yield was due to mal-timing or insufficient retraction rate of OMEGA's fast shroud mechanism, resulting in interception of at least 20 of the 24 laser beams by the faulty shroud. In spite of this, all elements of the complex experiment the authors originally undertook have been successfully demonstrated, and the cold retrieval concepts and methods they developed are being utilized on the ICF upgrades at Rochester and at Livermore

  19. From thermites to metastable interstitial composites (MIC); Des thermites classiques aux composites interstitiels metastables

    Energy Technology Data Exchange (ETDEWEB)

    Comet, M.; Spitzer, D. [Institut Franco-Allemand de Saint-Louis (ISL) (France)

    2006-07-15

    Thermites are non-nuclear materials with the highest bulk energetic potential (10-25 kJ.cm{sup -3}). Thermites mixtures are composed of a metal oxide and an oxo-phile metal used as a strong reducer. Contrary to explosive energetic compositions, thermites have a high density, a low kinetic of combustion. Moreover, they have a smaller sensitivity than explosive energetic compositions regarding thermal and mechanical stresses. Finally, they do not detonate and generate small quantities of gaseous products. Decomposition of thermites is an oxido-reduction reaction between two solid phases. The kinetic of combustion is governed by the mass transfer between the oxidant and the reducing phase. That is the reason why nano-structuration dramatically increases the speed of combustion of metastable interstitial composites (MIC) which can reach 895 m.s{sup -1}. This paper aims to describe the experimental methods currently used to elaborate MIC and to point out their limits. (authors)

  20. A metastable liquid melted from a crystalline solid under decompression

    Science.gov (United States)

    Lin, Chuanlong; Smith, Jesse S.; Sinogeikin, Stanislav V.; Kono, Yoshio; Park, Changyong; Kenney-Benson, Curtis; Shen, Guoyin

    2017-01-01

    A metastable liquid may exist under supercooling, sustaining the liquid below the melting point such as supercooled water and silicon. It may also exist as a transient state in solid-solid transitions, as demonstrated in recent studies of colloidal particles and glass-forming metallic systems. One important question is whether a crystalline solid may directly melt into a sustainable metastable liquid. By thermal heating, a crystalline solid will always melt into a liquid above the melting point. Here we report that a high-pressure crystalline phase of bismuth can melt into a metastable liquid below the melting line through a decompression process. The decompression-induced metastable liquid can be maintained for hours in static conditions, and transform to crystalline phases when external perturbations, such as heating and cooling, are applied. It occurs in the pressure-temperature region similar to where the supercooled liquid Bi is observed. Akin to supercooled liquid, the pressure-induced metastable liquid may be more ubiquitous than we thought.

  1. {332}〈113〉 Deformation Twinning in Metastable β-type Titanium Alloys

    Directory of Open Access Journals (Sweden)

    CHEN Bin

    2017-01-01

    Full Text Available {332} deformation twinning is a unique deformation mode which can have some special features and a strong influence on the mechanical properties for metastable β-type titanium alloys.{332} deformation twinning has already got more and more attention.The research situation and observed characteristics for the {332} deformation twinning are summarized in this paper.Some typical models for the {332} twinning are reviewed,and their assumptions and remaining problems are presented so as to provide useful information for understanding and revealing the deformation mechanism of {332} deformation twinning.

  2. Metastability and reliability of CdTe solar cells

    Science.gov (United States)

    Guo, Da; Brinkman, Daniel; Shaik, Abdul R.; Ringhofer, Christian; Vasileska, Dragica

    2018-04-01

    Thin-film modules of all technologies often suffer from performance degradation over time. Some of the performance changes are reversible and some are not, which makes deployment, testing, and energy-yield prediction more challenging. Manufacturers devote significant empirical efforts to study these phenomena and to improve semiconductor device stability. Still, understanding the underlying reasons of these instabilities remains clouded due to the lack of ability to characterize materials at atomistic levels and the lack of interpretation from the most fundamental material science. The most commonly alleged causes of metastability in CdTe devices, such as ‘migration of Cu’, have been investigated rigorously over the past fifteen years. Still, the discussion often ended prematurely with stating observed correlations between stress conditions and changes in atomic profiles of impurities or CV doping concentration. Multiple hypotheses suggesting degradation of CdTe solar cell devices due to interaction and evolution of point defects and complexes were proposed, and none of them received strong theoretical or experimental confirmation. It should be noted that atomic impurity profiles in CdTe provide very little intelligence on active doping concentrations. The same elements could form different energy states, which could be either donors or acceptors, depending on their position in crystalline lattice. Defects interact with other extrinsic and intrinsic defects; for example, changing the state of an impurity from an interstitial donor to a substitutional acceptor often is accompanied by generation of a compensating intrinsic interstitial donor defect. Moreover, all defects, intrinsic and extrinsic, interact with the electrical potential and free carriers so that charged defects may drift in the electric field and the local electrical potential affects the formation energy of the point defects. Such complexity of interactions in CdTe makes understanding of temporal

  3. Classification of knotted tori in 2-metastable dimension

    Energy Technology Data Exchange (ETDEWEB)

    Cencelj, Matija; Repovs, Dusan; Skopenkov, Mihail B

    2012-11-30

    This paper is devoted to the classical Knotting Problem: for a given manifold N and number m describe the set of isotopy classes of embeddings N{yields}S{sup m}. We study the specific case of knotted tori, that is, the embeddings S{sup p} Multiplication-Sign S{sup q}{yields}S{sup m}. The classification of knotted tori up to isotopy in the metastable dimension range m {>=} p + 3/2q + 2, p{<=}q, was given by Haefliger, Zeeman and A. Skopenkov. We consider the dimensions below the metastable range and give an explicit criterion for the finiteness of this set of isotopy classes in the 2-metastable dimension. Bibliography: 35 titles.

  4. Classification of knotted tori in 2-metastable dimension

    KAUST Repository

    Cencelj, Matija

    2012-11-30

    This paper is devoted to the classical Knotting Problem: for a given manifold N and number m describe the set of isotopy classes of embeddings N → Sm. We study the specific case of knotted tori, that is, the embeddings Sp × Sq → Sm. The classification of knotted tori up to isotopy in the metastable dimension range m > p + 3 2 q + 2, p 6 q, was given by Haefliger, Zeeman and A. Skopenkov. We consider the dimensions below the metastable range and give an explicit criterion for the finiteness of this set of isotopy classes in the 2-metastable dimension: Theorem. Assume that p+ 4 3 q +2 < mp+ 3 2 q +2 and m > 2p+q +2. Then the set of isotopy classes of smooth embeddings Sp × Sq → Sm is infinite if and only if either q + 1 or p + q + 1 is divisible by 4. © 2012 RAS(DoM) and LMS.

  5. Synthesis of a polar ordered oxynitride perovskite

    Science.gov (United States)

    Vadapoo, Rajasekarakumar; Ahart, Muhtar; Somayazulu, Maddury; Holtgrewe, Nicholas; Meng, Yue; Konopkova, Zuzana; Hemley, Russell J.; Cohen, R. E.

    2017-06-01

    For decades, numerous attempts have been made to produce polar oxynitride perovskites, where some of the oxygen is replaced by nitrogen, but a polar ordered oxynitride has never been demonstrated. Caracas and Cohen [Appl. Phys. Lett. 91, 092902 (2007), 10.1063/1.2776370] studied possible ordered polar oxynitrides within density-functional theory (DFT) and found a few candidates that were predicted to be insulating and at least metastable. YSi O2N stood out with huge predicted polarization and nonlinear optic coefficients. In this study, we demonstrate the synthesis of perovskite-structured YSi O2N by using a combination of a diamond-anvil cell and in situ laser-heating techniques. Subsequent in situ x-ray diffraction, second-harmonic generation, and Raman-scattering measurements confirm that it is polar and a strong nonlinear optical material, with structure and properties similar to those predicted by DFT.

  6. Synthesis of a polar ordered oxynitride perovskite

    Energy Technology Data Exchange (ETDEWEB)

    Vadapoo, Rajasekarakumar; Ahart, Muhtar; Somayazulu, Maddury; Holtgrewe, Nicholas; Meng, Yue; Konopkova, Zuzana; Hemley, Russell J.; Cohen, R. E.

    2017-06-01

    For decades, numerous attempts have been made to produce polar oxynitride perovskites, where some of the oxygen is replaced by nitrogen, but a polar ordered oxynitride has never been demonstrated. Caracas and Cohen [Appl. Phys. Lett. 91, 092902 (2007)] studied possible ordered polar oxynitrides within density-functional theory (DFT) and found a few candidates that were predicted to be insulating and at least metastable. YSi O 2 N stood out with huge predicted polarization and nonlinear optic coefficients. In this study, we demonstrate the synthesis of perovskite-structured YSi O 2 N by using a combination of a diamond-anvil cell and in situ laser-heating techniques. Subsequent in situ x-ray diffraction, second-harmonic generation, and Raman-scattering measurements confirm that it is polar and a strong nonlinear optical material, with structure and properties similar to those predicted by DFT.

  7. Metastable bcc phase formation in the Nb-Cr system

    Energy Technology Data Exchange (ETDEWEB)

    Thoma, D.J.; Schwarz, R.B. [Los Alamos National Lab., NM (United States); Perepezko, J.H. [Wisconsin Univ., Madison, WI (United States). Dept. of Materials Science and Engineering; Plantz, D.H. [Coast Guard Academy, New London, CT (United States). Dept. of Engineering

    1993-08-01

    Extended metastable bcc solid solutions of Nb-Xat.%Cr (X = 35, 50, 57, 77, 82, and 94) were synthesized by two-anvil splat-quenching. In addition, bcc (Nb-67at.%Cr) was prepared by mechanically alloying mixtures of niobium and chromium powders. The lattice parameters were measured by X-ray diffraction and the Young`s moduli were measured by low-load microindentation. The composition dependence of the lattice parameters and elastic moduli show a positive deviation with respect to a rule of mixtures. During continuous heating at 15C/min., the metastable precursor bcc phases decomposed at temperatures above 750C to uniformly refined microstructures.

  8. Metastable and scaling regimes of one-dimensional Kawasaki dynamics

    Science.gov (United States)

    Albarracín, F. A. Gómez; Rosales, H. D.; Grynberg, M. D.

    2016-04-01

    We investigate the large-time scaling regimes arising from a variety of metastable structures in a chain of Ising spins with both first- and second-neighbor couplings while subject to Kawasaki dynamics. Depending on the ratio and sign of these former, different dynamic exponents are suggested by finite-size scaling analyses of relaxation times. At low but nonzero temperatures these are calculated via exact diagonalizations of the evolution operator in finite chains under several activation barriers. In the absence of metastability the dynamics is always diffusive.

  9. Nanoprocessing of metastable nm-period multilayers

    Science.gov (United States)

    Gorbunov, A. A.; Richter, J.; Pompe, W.

    Nanometer-period nickel-carbon multilayers were used as a medium for the fabrication of nanostructures by gap voltage manipulations in a scanning tunneling microscope. The written metallic structures were stable over at least several weeks. No traces of tip material were found in the processed areas. Two well-distinguished hillock-like nanostructure types were observed depending on the tip-sample separation, polarity and interaction time. Relatively slow local annealing under positive sample potential without a direct tip-sample contact resulted in the formation of nanostructures about 20 nm wide and a few nm high. Rapid melting followed by metal melt extrusion was observed if the tip contacted the sample during the nanostructure formation. These metal-like structures were tens of nm high and had a good electronic contrast to the initial carbon-coated surface. The formation of nanostructures was strongly dependent on the tip condition. Possible mechanisms of nanostructure formation are discussed.

  10. Isomerization of metastable amine radical cations by dissociation-recombination

    DEFF Research Database (Denmark)

    Pedersen, Anders Holmen; Nielsen, Christian Benedikt; Bojesen, Gustav

    2015-01-01

    The metastable molecular ions of primary aliphatic amines branched at C2 can isomerize by cleavage-recombination, thereby facilitating fragmentation reactions that require less energy than simple cleavage of the initial molecular ion. This process complements the reactions described by Audier...

  11. Metastable defect response in CZTSSe from admittance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Koeper, Mark J.; Hages, Charles J.; Li, Jian V.; Levi, Dean; Agrawal, Rakesh

    2017-10-02

    Admittance spectroscopy is a useful tool used to study defects in semiconductor materials. However, metastable defect responses in non-ideal semiconductors can greatly impact the measurement and therefore the interpretation of results. Here, admittance spectroscopy was performed on Cu2ZnSn(S,Se)4 where metastable defect response is illustrated due to the trapping of injected carriers into a deep defect state. To investigate the metastable response, admittance measurements were performed under electrically and optically relaxed conditions in comparison to a device following a low level carrier-injection pretreatment. The relaxed measurement demonstrates a single capacitance signature while two capacitance signatures are observed for the device measured following carrier-injection. The deeper level signature, typically reported for kesterites, is activated by charge trapping following carrier injection. Both signatures are attributed to bulk level defects. The significant metastable response observed on kesterites due to charge trapping obscures accurate interpretation of defect levels from admittance spectroscopy and indicates that great care must be taken when performing and interpreting this measurement on non-ideal devices.

  12. Atmospheric instability as a loss of a metastable equilibrium

    OpenAIRE

    Kornyushin, Yuri

    2007-01-01

    General thermodynamic theory of metastable states is used in this short note to try to understand better atmospheric instabilities. It is shown that not only cooling of a cloud can lead to rain, but heating also, especially when there are charged water drops in a cloud (in this case we have rain with lightning). The influence of the global warming on weather is discussed.

  13. Metastability thresholds for anisotropic bootstrap percolation in three dimensions

    NARCIS (Netherlands)

    Van Enter, A.C.D.; Fey, A.

    2012-01-01

    In this paper we analyze several anisotropic bootstrap percolation models in three dimensions. We present the order of magnitude for the metastability thresholds for a fairly general class of models. In our proofs, we use an adaptation of the technique of dimensional reduction. We find that the

  14. Metastability Thresholds for Anisotropic Bootstrap Percolation in Three Dimensions

    NARCIS (Netherlands)

    Van Enter, A.C.D.; Fey, A.

    2012-01-01

    In this paper we analyze several anisotropic bootstrap percolation models in three dimensions. We present the order of magnitude for the metastability thresholds for a fairly general class of models. In our proofs, we use an adaptation of the technique of dimensional reduction. We find that the

  15. Metastability Thresholds for Anisotropic Bootstrap Percolation in Three Dimensions

    NARCIS (Netherlands)

    Enter, Aernout C.D. van; Fey, Anne

    In this paper we analyze several anisotropic bootstrap percolation models in three dimensions. We present the order of magnitude for the metastability thresholds for a fairly general class of models. In our proofs, we use an adaptation of the technique of dimensional reduction. We find that the

  16. Tumor ocular metastásico Metastatic ocular tumor

    Directory of Open Access Journals (Sweden)

    Martha G Domínguez Expósito

    2004-06-01

    Full Text Available El carcinoma metastásico del ojo es considerado la neoplasia maligna que más frecuente se encuentra de forma intraocular. Solo cerca del 10 % de las personas que tienen una o más lesiones metastásicas intraoculares son detectadas clínicamente antes de la muerte. A menudo, el carcinoma metastásico ocular es diagnosticado por el oftalmólogo ante la presencia de síntomas oculares. Las lesiones están localizadas con preferencia en coroides. Nos motivo a realizar la presentación de este caso la presencia de lesiones intraoculares múltiples tumorales metastásicos en un paciente cuyo síntoma de presentación fue la disminución de la agudeza visualThe eye metastatic carcinoma is considered the most frequently found intraocular malignant neoplasia. Only 10 % of the persons with one or more metastatic intraocular injuries are clinically detected before death. The metastatic ocular carcinoma is often diagnosed by the ophthalmologist in the presence of ocular symptoms. The injuries are preferably located in the choroid. The appearance of multiple metastatic intraaocular tumoral injuries in a patient whose chief complaint was the reduction of visual acuity motivated us to presente this case

  17. Colour chemistry - a study of metastable multiquark molecules

    International Nuclear Information System (INIS)

    Chan, H.-M.; Fukugita, M.; Hansson, T.H.; Hoffman, H.J.; Konishi, K.; Hoegaasen, H.; Tsou, S.T.

    1978-03-01

    A framework is proposed for treating metastable multiquark states in general, borrowing some of the chemist's concepts and terminology. Lists of 'ions' and 'bonds' are are compiled which allow one in principle to construct models of complex 'molecules' and to predict their masses and decays. (author)

  18. Metastable atom probe for measuring electron beam density profiles

    Science.gov (United States)

    Lockhart, J. M.; Zorn, J. C.

    1972-01-01

    Metastable atom probe was developed for measuring current density in electron beam as function of two arbitrary coordinates, with spatial resolution better than 0.5 mm. Probe shows effects of space charge, magnetic fields, and other factors which influence electron current density, but operates with such low beam densities that introduced perturbation is very small.

  19. 235U isotope enrichment in the metastable levels of UI

    International Nuclear Information System (INIS)

    Gagne, J.M.; Demers, Y.; Dreze, C.; Pianarosa, P.

    1983-01-01

    We have used optical pumping to produce a substantial 235 U enrichment in the metastable levels of UI in the discharge afterglow of a hollow-cathode vapor generator. The measured isotope-enrichment factor for the level at 3800 cm -1 is approximately 20

  20. Metastability in spin polarised Fermi gases and quasiparticle decays

    DEFF Research Database (Denmark)

    Sadeghzadeh, Kayvan; Bruun, Georg; Lobo, Carlos

    2011-01-01

    We investigate the metastability associated with the first order transition from normal to superfluid phases in the phase diagram of two-component polarised Fermi gases.We begin by detailing the dominant decay processes of single quasiparticles.Having determined the momentum thresholds of each pr...

  1. Tractable Quantification of Metastability for Robust Bipedal Locomotion

    Science.gov (United States)

    2015-06-01

    Mathematics GPA 4.0/4.0 2007-2011 Sabanci University, Istanbul B.S. in Mechatronics Engineering Minor in Mathematics GPA 3.88/4.0 Major GPA: 3.96/4.00...on Mechatronics (ICM), pages 997-1002, April 2011. viii Abstract Tractable Quantification of Metastability for Robust Bipedal Locomotion by Cenk Oguz

  2. Fusion with highly spin polarized HD and D2

    International Nuclear Information System (INIS)

    Honig, A.; Letzring, S.; Skupsky, S.

    1993-01-01

    Our experimental efforts over the past 5 years have been aimed at cazrying out ICF shots with spin-polarized 0 fuel. We successfully prepared polarized 0 in HD, and solved the problems of loading target shells with our carefully prepared isotopic -rnixt.l.l?-es, polarizing them so that the 0 polarization remains metastably frozen-in for about half a day, and carrying out the various cold transfer requirements at Syracuse, where the target is prepared, and at Rochester, where the cold target is inserted fusion chamber. Upon shooting the accurately positioned unpolarized high density cold target, no neutron yield was observed. Inspection inside the OMEGA tank after the shot indicated the absence of neutron yield was dus to mal-timing or insufficient retraction rate of OMEGA'S fast shroud mechanism, resulting in interception of at least 20 of the 24 laser beams by the faulty shroud. In spits of this, all alements of the complex experiment we originally undertook have been successfully demonstrated, and the cold retrieval concepts and methods we developed are being utilized on the ICF upgrades at Rochester and at Livermore. In addition to the solution of the interface problems, we obtained novel results on polymer shell characteristics at low temperatures, and continuation of these experiments is c = ently supported by KLUP. Extensive additional mappings were ca=ied out of nuclear spin relaxation rates of H and D in solid HD in the temperature-magnetic field rangs of 0.01 to 4.2K and 0 - 13 Tesla. New phenomena were discovered, such as association of impurity clustering with very low temperature motion, and inequality of the growth-rate and decay-rate of the magnetization

  3. A metastable helium trap for atomic collision physics

    International Nuclear Information System (INIS)

    Colla, M.; Gulley, R.; Uhlmann, L.; Hoogerland, M.D.; Baldwin, K.G.H.; Buckman, S.J.

    1999-01-01

    Full text: Metastable helium in the 2 3 S state is an important species for atom optics and atomic collision physics. Because of its large internal energy (20eV), long lifetime (∼8000s) and large collision cross section for a range of processes, metastable helium plays an important role in atmospheric physics, plasma discharges and gas laser physics. We have embarked on a program of studies on atom-atom and electron-atom collision processes involving cold metastable helium. We confine metastable helium atoms in a magneto-optic trap (MOT), which is loaded by a transversely collimated, slowed and 2-D focussed atomic beam. We employ diode laser tuned to the 1083 nm (2 3 S 1 - 2 3 P2 1 ) transition to generate laser cooling forces in both the loading beam and the trap. Approximately 10 million helium atoms are trapped at temperatures of ∼ 1mK. We use phase modulation spectroscopy to measure the trapped atomic density. The cold, trapped atoms can collide to produce either atomic He + or molecular He 2 + ions by Penning Ionisation (PI) or Associative Ionisation (AI). The rate of formation of these ions is dependant upon the detuning of the trapping laser from resonance. A further laser can be used to connect the 2 3 S 1 state to another higher lying excited state, and variation of the probe laser detuning used to measure interatomic collision potential. Electron-atom collision processes are studied using a monochromatic electron beam with a well defined spatial current distribution. The total trap loss due to electron collisions is measured as a function of electron energy. Results will be presented for these atomic collision physics measurements involving cold, trapped metastable helium atoms. Copyright (1999) Australian Optical Society

  4. Construction and characterization of a spin polarized helium ion beam for surface electronic structure studies

    International Nuclear Information System (INIS)

    Harrison, A.R.

    1982-01-01

    Ion neutralization and metastable de-excitation spectroscopy, INS and MDS, allow detailed analysis of the surface electronic configuration of metals. The orthodox application of these spectroscopies may be enhanced by electronic spin polarization of the probe beams. For this reason, a spin polarized helium ion beam has been constructed. The electronic spin of helium metastables created within an rf discharge may be spacially aligned by optically pumping the atoms. Subsequent collisions between metastables produce helium ions which retain the orientation of the electronic spin. Extracted ion polarization, although not directly measurable, may be estimated from extracted electron polarization, metastable polarization, pumping radiation absorption and current modulation measurements. Ions extracted from the optically pumped discharge exhibit an estimated polarization of about ten per cent at a beam current of a few tenths of a microampere. Extraction of helium ions from the discharge requires that the ions have a high kinetic energy. However, to avoid undesirable kinetic electron ejection from the target surface, the ions must be decelerated. Examination of various deceleration configurations, in paticular exponential and linear deceleration fields, and experimental observation indicate that a linear decelerating field produces the best low energy beam to the target surface

  5. Influence of nanoparticle formation on the time and the space resolved metastable density in argon-acetylene plasmas

    Science.gov (United States)

    Stefanović, I.; Sadeghi, N.; Winter, J.; Sikimić, B.

    2017-06-01

    Different diagnostic techniques are used to monitor the dynamics of electrons and Ar*(1s5) metastable atoms in the active plasma phase and in the afterglow of a capacitively coupled radio-frequency (RF) discharge operated in different gas mixtures and at different input powers. Diode laser absorption at 772.38 nm is used to measure the time resolved density of Ar*(1s5) atoms in either continuous-wave mode or pulsed RF discharges with 100 Hz pulsing frequency. Simultaneously, microwave interferometry recorded the time dependence of the electron density. Different plasma conditions, namely: (1) pure argon, (2) argon +5.9% acetylene before nanoparticle formation, (3) argon +5.9% acetylene after dust particles have been formed and (4) argon with dust particles remaining in the plasma volume but without acetylene are studied. The measured steady-state Ar*(1s5) density in the middle of the reactor is several times larger in the dusty argon plasma than in the pure argon discharge for the same discharge powers. At the same time, the electron density is several times less in the dusty plasma. These changes are caused by dust formation: the electric field in the bulk plasma is enhanced and thus consequently the electron temperature increases. Laser induced fluorescence (LIF) is used to measure the time and space resolved Ar*(1s5) axial distribution. In the pure argon discharge, the axial Ar*(1s5) metastable distribution has a characteristic saddle-like shape with maxima in the region of the sheaths. With dust particles inside, the axial distribution changes dramatically with the maximum at the discharge mid-plane, revealing an α-γ‧ transition. The spatial distribution and absolute density of metastable atoms are influenced by the formation of a void in the cloud of nanoparticles. Depending on the size of the void, the Ar*(1s5) density reduction inside the void is between 30% and 50%. The high Ar*(1s5) metastable density in the dusty plasma afterglow strongly influences

  6. Block Copolymer Metastability: Scientific Nightmare or Engineering Dream?

    Science.gov (United States)

    Bates, Frank S.

    1997-03-01

    Most experimental studies and almost all theories that deal with block copolymers, or mixtures of block copolymers and homopolymers, have been designed from an equilibrium perspective. Yet a myriad of factors conspire to retard approach to equilibrium in these systems, including: subtle features in the free energy surface that are controlled by ordered state symmetry; a coupling between microphase separation and entanglement dynamics; complex molecular architectures such as multiblock, starblock, and miktoarm. Even unentangled low molecular weight diblock copolymers, the simplest and dynamically least encumbered materials, exhibit long-lived metastable states that confound attempts to validate equilibrium theories. However, this apparent dilemma can be exploited through clever processing strategies. This lecture will address two opposing consequences of block copolymer metastability. The first is a potential nightmare: Can we ever establish universal block copolymer phase diagrams? The second is the stuff of dreams: Self-assembled thermoset nanocomposites.

  7. Accumulation of chromium metastable atoms into an optical trap

    Science.gov (United States)

    Chicireanu, R.; Beaufils, Q.; Pouderous, A.; Laburthe-Tolra, B.; Maréchal, É.; Vernac, L.; Keller, J.-C.; Gorceix, O.

    2007-11-01

    We report the fast accumulation of a large number of metastable 52Cr atoms in a mixed trap, formed by the superposition of a strongly confining optical trap and a quadrupolar magnetic trap. The steady state is reached after about 400 ms, providing a cloud of more than one million metastable atoms at a temperature of about 100 μK, with a peak density of 1018 atoms m-3. We have optimized the loading procedure, and measured the light shift of the ^5D4 state by analyzing how the trapped atoms respond to a parametric excitation. We compare this result to a theoretical evaluation based on the available spectroscopic data for chromium atoms.

  8. Planktic foraminifera form their shells via metastable carbonate phases.

    Science.gov (United States)

    Jacob, D E; Wirth, R; Agbaje, O B A; Branson, O; Eggins, S M

    2017-11-02

    The calcium carbonate shells of planktic foraminifera provide our most valuable geochemical archive of ocean surface conditions and climate spanning the last 100 million years, and play an important role in the ocean carbon cycle. These shells are preserved in marine sediments as calcite, the stable polymorph of calcium carbonate. Here, we show that shells of living planktic foraminifers Orbulina universa and Neogloboquadrina dutertrei originally form from the unstable calcium carbonate polymorph vaterite, implying a non-classical crystallisation pathway involving metastable phases that transform ultimately to calcite. The current understanding of how planktic foraminifer shells record climate, and how they will fare in a future high-CO 2 world is underpinned by analogy to the precipitation and dissolution of inorganic calcite. Our findings require a re-evaluation of this paradigm to consider the formation and transformation of metastable phases, which could exert an influence on the geochemistry and solubility of the biomineral calcite.

  9. Equilibrium and metastable nanoscale domains in ultrathin magnets

    Czech Academy of Sciences Publication Activity Database

    Kisielewski, M.; Maziewski, A.; Polyakova, T.; Zablotskyy, Vitaliy A.

    2006-01-01

    Roč. 3, č. 5 (2006), s. 1333-1338 ISSN 1610-1634. [International Conference on Nanoscale Magnetism ICNM-2005. Istanbul, 03.07.2005-07.07.2005] Grant - others:Polish State Committee for Sci. Research(PL) 4 T11B 006 24; Marie Curie Fondation(PL) NANOMAG-LAB, N 2004-003177 Institutional research plan: CEZ:AV0Z10100520 Keywords : ultrathin films * metastable domains * thermodynamics. Subject RIV: BM - Solid Matter Physics ; Magnetism

  10. Decadal variability and metastability in the Southern Hemisphere

    Science.gov (United States)

    O'Kane, Terence; Risbey, James; Franzke, Christian; Horenko, Illia; Monselesan, Didier

    2014-05-01

    An examination of systematic changes in the metastability of the southern hemisphere 500hPa circulation is performed using both cluster analysis techniques and split flow blocking indices. The cluster methodology is a purely data-driven approach for parametrisation whereby a multi-scale approximation to non-stationary dynamical processes is achieved through optimal sequences of locally stationary fast Vector Auto-Regressive Factor (VARX) processes and some slow (or persistent) hidden process switching between them. Comparison is made with blocking indices commonly used in weather forecasting and climate analysis to identify dynamically relevant metastable regimes in the 500hPa circulation in both reanalysis and AMIP model data sets. Our analysis characterises the metastable regime in both reanalysis and model data sets prior to 1978 as positive and negative phases of a hemispheric mid-latitude blocking state with the Southern Annular Mode (SAM) associated with a transition state. Post 1978, SAM emerges as a true metastable state replacing the negative phase of the hemispheric blocking pattern. The hidden state frequency of occurrences exhibits strong trends. The blocking pattern dominates in the early 1980s then gradually decreases. There is a corresponding increase in the SAM frequency of occurrence. This trend is largely evident in the reanalysis summer and spring but was not evident in the AMIP data set. Non-stationary cluster analysis was then further used to identify the Southern Oceans response to the systematic changes in the mid-latitude atmospheric circulation and identify dynamical regimes associated with subsurface thermocline anomalies which were found to teleconnect the Pacific and Atlantic regions of the Antarctic Circumpolar Current (ACC).

  11. Automatic acquisition and shape analysis of metastable peaks

    International Nuclear Information System (INIS)

    Maendli, H.; Robbiani, R.; Kuster, Th.; Seibl, J.

    1979-01-01

    A method for automatic acquisition and evaluation of metastable peaks due to transitions in the first field-free region of a double focussing mass spectrometer is presented. The data are acquired by computer-controlled repetitive scanning of the accelerating voltage and concomitant accumulation, the evaluation made by a mathematical derivatization of the resulting curve. Examples for application of the method are given. (Auth.)

  12. Investigations of Shock Wave Synthesis of Metastable Compounds.

    Science.gov (United States)

    1997-01-01

    Institute of Chemical Physics in Chernogolovka, Russian Academy of Science 8. 705 Chernogolovka, Moscow Region, 142432, Russia Phone: 7-096-5171930 Fax...materials etc. The development of metastable state physics and chemistry is intimately connected with the elaboration of special production methods...of Sci., Inorgan. mat., 19968, V. 22, No 6, p. 966 5. Nekrasov, B.V. Principles of General Chemestry , Moscow, "Khimiya", 1979, V. 2, p. 309 6. Dremin

  13. Radiation-induced metastable ordered phase in gallium nitride

    International Nuclear Information System (INIS)

    Ishimaru, Manabu

    2010-01-01

    Energetic particle irradiation is one of the useful ways for realizing metastable phases far from the equilibrium state. In the present study, we performed electron-beam-irradiation into gallium nitride (GaN) with a wurtzite structure and examined its structural changes using transmission electron microscopy. It was found that superlattice Bragg reflections appear in the electron diffraction patterns of the irradiated GaN. This suggests that the wurtzite GaN transforms to another crystalline structure with atomic ordering.

  14. Modeling of diode pumped metastable rare gas lasers.

    Science.gov (United States)

    Yang, Zining; Yu, Guangqi; Wang, Hongyan; Lu, Qisheng; Xu, Xiaojun

    2015-06-01

    As a new kind of optically pumped gaseous lasers, diode pumped metastable rare gas lasers (OPRGLs) show potential in high power operation. In this paper, a multi-level rate equation based model of OPRGL is established. A qualitative agreement between simulation and Rawlins et al.'s experimental result shows the validity of the model. The key parameters' influences and energy distribution characteristics are theoretically studied, which is useful for the optimized design of high efficient OPRGLs.

  15. Metastable states in NO2+ probed with Auger spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Püttner, R.; Sekushin, V.; Fukuzawa, H.; Uhlíková, T.; Špirko, Vladimír; Asahina, T.; Kuze, N.; Kato, H.; Hoshino, M.; Tanaka, H.; Thomas, T. D.; Kukk, E.; Tamenori, Y.; Kaindl, G.; Ueda, K.

    2011-01-01

    Roč. 13, č. 41 (2011), s. 18436-18446 ISSN 1463-9076 Grant - others:GA ČR(CZ) GP203/09/P306; GA AV ČR(CZ) IAA400400504; GA MŠk(CZ) LC06071 Program:IA; LC Institutional research plan: CEZ:AV0Z40550506 Keywords : NO2+metastable states * Auger spectroscopy * vibrational energies Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.573, year: 2011

  16. Trapping metastable chromium atoms in a crossed optical dipole trap

    Science.gov (United States)

    Beaufils, Q.; Chicireanu, R.; Pouderous, A.; Laburthe-Tolra, B.; Maréchal, E.; Vernac, L.; Keller, J.-C.; Gorceix, O.

    We report the fast accumulation of up to 1 million 52Cr metastable atoms in a mixed trap formed by the superposition of a quadrupolar magnetic trap and a strongly confining optical trap. The cloud is at a temperature of 100 μK with a peak density of 1018 atoms/m3, which is a promising starting point to reach quantum degeneracy by forced evaporation in an optical trap.

  17. An internal polarized 3He target for electron storage rings

    International Nuclear Information System (INIS)

    Kramer, L.H.; Massachusetts Inst. of Tech., Cambridge, MA; DeSchepper, D.; Massachusetts Inst. of Tech., Cambridge, MA; Milner, R.G.; Massachusetts Inst. of Tech., Cambridge, MA; Pate, S.F.; Massachusetts Inst. of Tech., Cambridge, MA; Shin, T.; Massachusetts Inst. of Tech., Cambridge, MA

    1995-01-01

    We describe an internal polarized 3 He target currently under construction which will be used in several electron storage ring experiments. The target is based on the technique of metastability exchange laser optical pumping, where the polarized atoms flow into a cryogenically-cooled storage cell. This novel technique allows for high precision measurements where the beam interacts with the pure atomic species. Both the HERMES experiment at DESY and the BLAST detector at the MIT Bates Laboratory will use the polarized 3 He target in their measurements. Details of the target system, including the provisions needed to incorporate the target into the electron storage ring, are presented. (orig.)

  18. Cross sections of electron excitation out of metastable helium levels with a fast metastable target product produced via charge exchange

    International Nuclear Information System (INIS)

    Lagus, M.E.; Boffard, J.B.; Anderson, L.W.; Lin, C.C.

    1996-01-01

    Absolute direct cross sections for electron excitation out of the 2 3 S level and into the 3 3 D, 4 3 D, and 3 3 S levels of the helium atom from threshold to 500 eV and into the 3 3 P level over a more limited energy range have been measured using a fast metastable atomic beam target. We produce the metastable atoms via near-resonant charge exchange between a 1.6-keV He + ion beam and Cs vapor. Because this reaction is highly nonresonant with the ground state of helium, the charge-transfer process yields a primarily metastable beam. We use a thermal detector which we calibrate with ions to measure absolutely the neutral beam flux. The atomic beam is crossed by an electron beam, and we collect the resulting fluorescence at right angles to both the electron and atomic beams. We obtain the cross sections for excitation out of the 2 3 S level into the various excited levels by monitoring the emission out of the excited level of interest. copyright 1996 The American Physical Society

  19. Polarization developments

    International Nuclear Information System (INIS)

    Prescott, C.Y.

    1993-07-01

    Recent developments in laser-driven photoemission sources of polarized electrons have made prospects for highly polarized electron beams in a future linear collider very promising. This talk discusses the experiences with the SLC polarized electron source, the recent progress with research into gallium arsenide and strained gallium arsenide as a photocathode material, and the suitability of these cathode materials for a future linear collider based on the parameters of the several linear collider designs that exist

  20. Atomic approaches in metastable antiprotonic helium atoms. REPLY to 'analysis of the lifetimes and fractions of antiprotons trapped in metastable antiprotonic-helium states' by I. Shimamura and M. Kimura

    International Nuclear Information System (INIS)

    Yamazaki, Toshimitsu; Ohtsuki, Kazumasa.

    1994-08-01

    In the present note the authors clarify the purpose of YO and complement its essential points, thus showing that the criticisms of SK are inappropriate. The paper YO [1] was aimed at discussing some new aspects related to the metastability of hadronic helium atoms which had been discovered when negative kaons [2], negative pions [3] and antiprotons [4] were stopped in liquid helium. The delayed fraction, time spectrum shape and lifetimes were the observables. Further experimental studies are in progress [5], and as of today there is no successful explanation for these interesting phenomena. So, YO tried to give brief and rather qualitative estimates for the observations in an intuitive way, considering only the leading terms. The following problems are discussed in as simple a manner as possible, starting from the exotic-atom viewpoints of Condo [6] and Russell [7]: i)the atomic core polarization effect, ii)the structure and radiative lifetimes, iii)the non-statistical distribution of the angular momentum and an estimate of the delayed fraction, and iv)the isotope effect, though the title represents only i). To respond to the comments of SK, it is important to consider the correspondence between the atomic approach and the molecular approach for the metastable antiprotonic helium atom of Condo-Russell. We therefore begin this note with a discussion of this aspect. (author)

  1. And the Dead Remain Behind

    Directory of Open Access Journals (Sweden)

    Peter Read

    2013-08-01

    Full Text Available In most cultures the dead and their living relatives are held in a dialogic relationship. The dead have made it clear, while living, what they expect from their descendants. The living, for their part, wish to honour the tombs of their ancestors; at the least, to keep the graves of the recent dead from disrepair. Despite the strictures, the living can fail their responsibilities, for example, by migration to foreign countries. The peripatetic Chinese are one of the few cultures able to overcome the dilemma of the wanderer or the exile. With the help of a priest, an Australian Chinese migrant may summon the soul of an ancestor from an Asian grave to a Melbourne temple, where the spirit, though removed from its earthly vessel, will rest and remain at peace. Amongst cultures in which such practices are not culturally appropriate, to fail to honour the family dead can be exquisitely painful. Violence is the cause of most failure.

  2. Metastable hydronium ions in UV-irradiated ice

    International Nuclear Information System (INIS)

    Moon, Eui-Seong; Kang, Heon

    2012-01-01

    We show that the irradiation of UV light (10−11 eV) onto an ice film produces metastable hydronium (H 3 O + ) ions in the ice at low temperatures (53–140 K). Evidence of the presence of metastable hydronium ions was obtained by experiments involving adsorption of methylamine onto UV-irradiated ice films and hydrogen-deuterium (H/D) isotopic exchange reaction. The methylamine adsorption experiments showed that photogenerated H 3 O + species transferred a proton to the methylamine arriving at the ice surface, thus producing the methyl ammonium ion, which was detected by low energy sputtering method. The H 3 O + species induced the H/D exchange of water, which was monitored through the detection of water isotopomers on the surface by using the Cs + reactive ion scattering method. Thermal and temporal stabilities of H 3 O + and its proton migration activity were examined. The lifetime of the hydronium ions in the amorphized ice was greater than 1 h at ∼53 K and decreased to ∼5 min at 140 K. Interestingly, a small portion of hydronium ions survived for an extraordinarily long time in the ice, even at 140 K. The average migration distance of protons released from H 3 O + in the ice was estimated to be about two water molecules at ∼54 K and about six molecules at 100 K. These results indicate that UV-generated hydronium ions can be efficiently stabilized in low-temperature ice. Such metastable hydronium ions may play a significant role in the acid-base chemistry of ice particles in interstellar clouds.

  3. Metastable Features of Economic Networks and Responses to Exogenous Shocks.

    Directory of Open Access Journals (Sweden)

    Ali Hosseiny

    Full Text Available It is well known that a network structure plays an important role in addressing a collective behavior. In this paper we study a network of firms and corporations for addressing metastable features in an Ising based model. In our model we observe that if in a recession the government imposes a demand shock to stimulate the network, metastable features shape its response. Actually we find that there exists a minimum bound where any demand shock with a size below it is unable to trigger the market out of recession. We then investigate the impact of network characteristics on this minimum bound. We surprisingly observe that in a Watts-Strogatz network, although the minimum bound depends on the average of the degrees, when translated into the language of economics, such a bound is independent of the average degrees. This bound is about 0.44ΔGDP, where ΔGDP is the gap of GDP between recession and expansion. We examine our suggestions for the cases of the United States and the European Union in the recent recession, and compare them with the imposed stimulations. While the stimulation in the US has been above our threshold, in the EU it has been far below our threshold. Beside providing a minimum bound for a successful stimulation, our study on the metastable features suggests that in the time of crisis there is a "golden time passage" in which the minimum bound for successful stimulation can be much lower. Hence, our study strongly suggests stimulations to arise within this time passage.

  4. Austenite stability in the high strength metastable stainless steels

    OpenAIRE

    S.J. Pawlak

    2007-01-01

    Purpose: The aim of the present paper was to study the peculiarities of the austenite to martensite phase transformation (A-M), which is an essential step in the production technology of the high strength metastable stainless steels.Design/methodology/approach: The desired control over A-M transformation have been achieved by proper design of the steel chemistry, cold working and heat treatment.Findings: For a range of steel compositions, it was shown that severe cold working leads to fully m...

  5. Simple model for the dynamics towards metastable states

    International Nuclear Information System (INIS)

    Meijer, P.H.E.; Keskin, M.; Bodegom, E.

    1986-01-01

    Circumstances under which a quenched system will freeze in a metastable state are studied in simple systems with long-range order. The model used is the time-dependent pair approximation, based on the most probable path (MPP) method. The time dependence of the solution is shown by means of flow diagrams. The fixed points and other features of the differential equations in time are independent of the choice of the rate constants. It is explained qualitatively how the system behaves under varying descending temperatures: the role of the initial conditions, the dependence on the quenching rate, and the response to precooling

  6. Investigating the Metastability of Clathrate Hydrates for Energy Storage

    Energy Technology Data Exchange (ETDEWEB)

    Koh, Carolyn Ann [Colorado School of Mines, Golden, CO (United States)

    2014-11-18

    Important breakthrough discoveries have been achieved from the DOE award on the key processes controlling the synthesis and structure-property relations of clathrate hydrates, which are critical to the development of clathrate hydrates as energy storage materials. Key achievements include: (i) the discovery of key clathrate hydrate building blocks (stable and metastable) leading to clathrate hydrate nucleation and growth; (ii) development of a rapid clathrate hydrate synthesis route via a seeding mechanism; (iii) synthesis-structure relations of H2 + CH4/CO2 binary hydrates to control thermodynamic requirements for energy storage and sequestration applications; (iv) discovery of a new metastable phase present during clathrate hydrate structural transitions. The success of our research to-date is demonstrated by the significant papers we have published in high impact journals, including Science, Angewandte Chemie, J. Am. Chem. Soc. Intellectual Merits of Project Accomplishments: The intellectual merits of the project accomplishments are significant and transformative, in which the fundamental coupled computational and experimental program has provided new and critical understanding on the key processes controlling the nucleation, growth, and thermodynamics of clathrate hydrates containing hydrogen, methane, carbon dioxide, and other guest molecules for energy storage. Key examples of the intellectual merits of the accomplishments include: the first discovery of the nucleation pathways and dominant stable and metastable structures leading to clathrate hydrate formation; the discovery and experimental confirmation of new metastable clathrate hydrate structures; the development of new synthesis methods for controlling clathrate hydrate formation and enclathration of molecular hydrogen. Broader Impacts of Project Accomplishments: The molecular investigations performed in this project on the synthesis (nucleation & growth)-structure-stability relations of clathrate

  7. Metastable carbon in two chondritic porous interplanetary dust particles

    International Nuclear Information System (INIS)

    Rietmeijer, F.J.M.; Mackinnon, I.D.R.

    1987-01-01

    An analytical electron microscope study is presented on carbonaceous material in two chondritic porous aggregates, W7029* A and W7010* A2, from the Johnson Space Center Cosmic Dust Collection. The finding of well-ordered carbon-2H (lonsdaleite) in the two aggregates suggests that a record of hydrocarbon carbonization may be preserved in these materials. This carbon is a metastable phase resulting from hydrous pyrolysis below 300-350 0 C and may be a precursor to poorly graphitized carbons in primitive extra terrestrial materials. (UK)

  8. Numerical transfer-matrix study of a model with competing metastable states

    DEFF Research Database (Denmark)

    Fiig, T.; Gorman, B.M.; Rikvold, P.A.

    1994-01-01

    The Blume-Capel model, a three-state lattice-gas model capable of displaying competing metastable states, is investigated in the limit of weak, long-range interactions. The methods used are scalar field theory, a numerical transfer-matrix method, and dynamical Monte Carlo simulations...... 'metastable free-energy density This transfer-matrix approach gives a free-energy cost of nucleation that supports the proportionality relation for the decay rate of the metastable phase T proportional to\\Imf alpha\\, even in cases where two metastable states compete. The picture that emerges from this study...

  9. Green business will remain green

    International Nuclear Information System (INIS)

    Marcan, P.

    2008-01-01

    It all started with two words. Climate change. The carbon dioxide trading scheme, which was the politicians' idea on solving the number one global problem, followed. Four years ago, when the project was begun, there was no data for project initiation. Quotas for polluters mainly from energy production and other energy demanding industries were distributed based on spreadsheets, maximum output and expected future development of economies. Slovak companies have had a chance to profit from these arrangements since 2005. Many of them took advantage of the situation and turned the excessive quotas into an extraordinary profit which often reached hundreds of million Sk. The fact that the price of free quotas offered for sale dropped basically to 0 in 2006 only proved that the initial distribution was too generous. And the market reacted to the first official measurements of emissions. Slovak companies also contributed to this development. However, when planning the maximum emission volumes for 2008-2012 period, in spite of the fact that actual data were available, their expectations were not realistic. A glance at the figures in the proposal of the Ministry of Environment is sufficient to realize that there will be no major change in the future. And so for many Slovak companies business with a green future will remain green for the next five years. The state decided to give to selected companies even more free space as far as emissions are concerned. The most privileged companies can expect quotas increased by tens of percent. (author)

  10. Polarization, political

    NARCIS (Netherlands)

    Wojcieszak, M.; Mazzoleni, G.; Barnhurst, K.G.; Ikeda, K.; Maia, R.C.M.; Wessler, H.

    2015-01-01

    Polarization has been studied in three different forms: on a social, group, and individual level. This entry first focuses on the undisputed phenomenon of elite polarization (i.e., increasing adherence of policy positions among the elites) and also outlines different approaches to assessing mass

  11. Silicon photonics: some remaining challenges

    Science.gov (United States)

    Reed, G. T.; Topley, R.; Khokhar, A. Z.; Thompson, D. J.; Stanković, S.; Reynolds, S.; Chen, X.; Soper, N.; Mitchell, C. J.; Hu, Y.; Shen, L.; Martinez-Jimenez, G.; Healy, N.; Mailis, S.; Peacock, A. C.; Nedeljkovic, M.; Gardes, F. Y.; Soler Penades, J.; Alonso-Ramos, C.; Ortega-Monux, A.; Wanguemert-Perez, G.; Molina-Fernandez, I.; Cheben, P.; Mashanovich, G. Z.

    2016-03-01

    This paper discusses some of the remaining challenges for silicon photonics, and how we at Southampton University have approached some of them. Despite phenomenal advances in the field of Silicon Photonics, there are a number of areas that still require development. For short to medium reach applications, there is a need to improve the power consumption of photonic circuits such that inter-chip, and perhaps intra-chip applications are viable. This means that yet smaller devices are required as well as thermally stable devices, and multiple wavelength channels. In turn this demands smaller, more efficient modulators, athermal circuits, and improved wavelength division multiplexers. The debate continues as to whether on-chip lasers are necessary for all applications, but an efficient low cost laser would benefit many applications. Multi-layer photonics offers the possibility of increasing the complexity and effectiveness of a given area of chip real estate, but it is a demanding challenge. Low cost packaging (in particular, passive alignment of fibre to waveguide), and effective wafer scale testing strategies, are also essential for mass market applications. Whilst solutions to these challenges would enhance most applications, a derivative technology is emerging, that of Mid Infra-Red (MIR) silicon photonics. This field will build on existing developments, but will require key enhancements to facilitate functionality at longer wavelengths. In common with mainstream silicon photonics, significant developments have been made, but there is still much left to do. Here we summarise some of our recent work towards wafer scale testing, passive alignment, multiplexing, and MIR silicon photonics technology.

  12. Isothermal α″ formation in β metastable titanium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Aeby-Gautier, E., E-mail: Elisabeth.Gautier@mines.inpl-nancy.fr [Institut Jean Lamour, UMR CNRS Nancy Université, UPVM 7198, Nancy (France); Settefrati, A. [Institut Jean Lamour, UMR CNRS Nancy Université, UPVM 7198, Nancy (France); Airbus Operations, Materials and Processes, Toulouse (France); Bruneseaux, F. [Institut Jean Lamour, UMR CNRS Nancy Université, UPVM 7198, Nancy (France); Appolaire, B. [Laboratoire d’Etudes des Microstructures ONERA – CNRS Chatillon (France); Denand, B.; Dehmas, M.; Geandier, G.; Boulet, P. [Institut Jean Lamour, UMR CNRS Nancy Université, UPVM 7198, Nancy (France)

    2013-11-15

    Highlights: ► Isothermal kinetics of orthorhombic α″ formation is characterized by HEXRD. ► Cell parameters of parent and product phases are obtained. ► Partitioning of solutes during the transformation and the ageing is discussed. -- Abstract: Thanks to time resolved high energy X-ray diffraction, isothermal decomposition of β metastable phase was studied, directly after solution treatment in the β temperature range, for temperatures ranging from 300 to 450 °C for two beta metastable alloys (Ti 17 and Ti 5553). The formation of an orthorhombic α″ phase is clearly identified at the beginning of the transformation whatever the alloy studied. If transformation occurs at the higher temperature an evolution of α″ is observed toward the hexagonal α phase. The phase amounts and the mean cell parameters of each phase were quantified by the Rietveld refinement method. The obtained cell parameters evolutions and the orthorhombicity of α″ are discussed. Moreover, the orthorhombicity of α″ compared to that obtained for stress induced martensite may indicate a slight partitioning of solutes in isothermal α″.

  13. Axonal Actin Transport Driven By Metastable Actin Filaments

    Science.gov (United States)

    Chakrabarty, Nilaj; Ganguly, Archan; Roy, Subhojit; Jung, Peter

    Actin is one of the key constituents of the neuronal cytoskeleton and is responsible for driving important cellular processes like axon elongation. Axonal actin is synthesized in the cell body and transported at rates of 0.25 - 3 mm/day, as shown by in-vivo pulse-chase radiolabelling studies. However, the underlying transport mechanisms are unknown. Recent experiments in cultured neurons have revealed a dynamic network of metastable actin filaments (actin trails). Actin trails seem to originate from focal actin hotspots which colocalize with stationary endosomes. Interestingly, the number of actin trails extending anterogradely is higher than the ones extending retrogradely. We hypothesize that the bulk axonal transport of actin originates from this directional asymmetry of the number of actin trails. To test this, we constructed a computational model of actin trail growth and simulated the pulse-chase experiment. In our model, local, metastable trails, which grow with their barbed ends anchored to the hotspots, drive the bulk anterograde transport. Our results indicate that the observed bias of the nucleation probabilities and the elongation rate of actin trails are sufficient to drive the bulk transport of actin at rates that agree with in-vivo pulse chase experiments.

  14. Fluxes, hierarchies, and metastable vacua in supersymmetric field theories

    International Nuclear Information System (INIS)

    Bruemmer, F.

    2008-01-01

    This thesis concerns topics both in low-energy effective field theories from type IIB superstring flux compactifications and in four-dimensional, rigidly supersymmetric gauge theories. We introduce flux compactifications with so-called ''warped throat'' regions, which lead to large hierarchies of scales in the effective four-dimensional theory. The correspondence between a particular such throat and a five-dimensional Randall-Sundrum-like model is established. We shown how certain string-theoretic features of the compactification, such as moduli stabilization by fluxes or the presence of an unstabilized Kaehler modulus, are incorporated in the five-dimensional picture. The KKLT construction for metastable de Sitter vacua is reviewed, as well as some possible modifications involving spontaneous F-term supersymmetry breaking. For KKLT-like models with their hidden sector localized inside a throat, the mediation of supersymmetry breaking to the visible sector is investigated. We review the mechanism of mixed modulus-anomaly mediation, and show that there can be additional equally important gravity-mediated contributions. We finally turn to the ISS model of metastable dynamical supersymmetry breaking in four dimensions, and present a renormalizable extension which generates a large hierarchy naturally. We also recapitulate how the ISS model may be obtained from a type IIB superstring model. (orig.)

  15. Negative pion trapping by metastable state in liquid helium

    International Nuclear Information System (INIS)

    Nakamura, S.N.; Iwasaki, M.; Outa, H.

    1991-11-01

    We found long-lived metastable states of stopped π - 's in liquid helium by measuring time spectra of two different delayed products: 1) protons emitted after π - absorption by 4 He nuclei and 2) 70-MeV electrons originating from free π - → e - (ν e )-bar decay. The lifetime and fraction of delayed π - absorption obtained by emitted protons are 7.26±0.12 nsec and 1.66±0.05%, respectively. The free-decay fraction was calculated to be 0.64±0.03% from this result, which is consistent with the observed free-decay fraction of π e2 decay. These results imply that 2.30±0.07% of stopped π - are trapped in metastable states which have an overall lifetime of 10.1±0.2 nsec. The same experiment and analysis were performed for stopped π - in liquid neon. No evidence for trapping was found in liquid neon. (author)

  16. Demonstration of a diode-pumped metastable Ar laser.

    Science.gov (United States)

    Han, Jiande; Glebov, Leonid; Venus, George; Heaven, Michael C

    2013-12-15

    Pulsed lasing from optically pumped rare gas metastable atoms (Ne, Ar, Kr, and Xe) has been demonstrated previously. The laser relies on a three-level scheme, which involves the (n+1)p[5/2](3) and (n+1)p[1/2](1) states from the np(5)(n+1)p electronic configuration and the metastable (n+1)s[3/2](2) level of the np(5)(n+1)s configuration (Racah notation). Population inversions were achieved using relaxation from ((n+1)p[5/2](3) to (n+1)p[1/2](1) induced by collisions with helium or argon at pressures near 1 atm. Pulsed lasing was easily achieved using the high instantaneous pump intensities provided by a pulsed optical parametric oscillator excitation laser. In the present study we examine the potential for the development of a continuous wave (CW) optically pumped Ar laser. We report lasing of the 4p[1/2](1)→4s[3/2](2) (912.547 nm) transition following CW diode laser excitation of the 4p[5/2](3)←4s[3/2](2) line (811.754 nm). A pulsed discharge was used to generate Ar 4s[3/2](2), and the time-resolved lasing kinetics provide insights concerning the radiative and collisional relaxation processes.

  17. Fluxes, hierarchies, and metastable vacua in supersymmetric field theories

    Energy Technology Data Exchange (ETDEWEB)

    Bruemmer, F.

    2008-02-06

    This thesis concerns topics both in low-energy effective field theories from type IIB superstring flux compactifications and in four-dimensional, rigidly supersymmetric gauge theories. We introduce flux compactifications with so-called ''warped throat'' regions, which lead to large hierarchies of scales in the effective four-dimensional theory. The correspondence between a particular such throat and a five-dimensional Randall-Sundrum-like model is established. We shown how certain string-theoretic features of the compactification, such as moduli stabilization by fluxes or the presence of an unstabilized Kaehler modulus, are incorporated in the five-dimensional picture. The KKLT construction for metastable de Sitter vacua is reviewed, as well as some possible modifications involving spontaneous F-term supersymmetry breaking. For KKLT-like models with their hidden sector localized inside a throat, the mediation of supersymmetry breaking to the visible sector is investigated. We review the mechanism of mixed modulus-anomaly mediation, and show that there can be additional equally important gravity-mediated contributions. We finally turn to the ISS model of metastable dynamical supersymmetry breaking in four dimensions, and present a renormalizable extension which generates a large hierarchy naturally. We also recapitulate how the ISS model may be obtained from a type IIB superstring model. (orig.)

  18. Polar Bears

    Science.gov (United States)

    Amstrup, Steven C.; Douglas, David C.; Reynolds, Patricia E.; Rhode, E.B.

    2002-01-01

    Polar bears (Ursus maritimus) are hunted throughout most of their range. In addition to hunting polar bears of the Beaufort Sea region are exposed to mineral and petroleum extraction and related human activities such as shipping road-building, and seismic testing (Stirling 1990).Little was known at the start of this project about how polar bears move about in their environment, and although it was understood that many bears travel across political borders, the boundaries of populations had not been delineated (Amstrup 1986, Amstrup et al. 1986, Amstrup and DeMaster 1988, Garner et al. 1994, Amstrup 1995, Amstrup et al. 1995, Amstrup 2000).As human populations increase and demands for polar bears and other arctic resources escalate, managers must know the sizes and distributions of the polar bear populations. Resource managers also need reliable estimates of breeding rates, reproductive intervals, litter sizes, and survival of young and adults.Our objectives for this research were 1) to determine the seasonal and annual movements of polar bears in the Beaufort Sea, 2) to define the boundaries of the population(s) using this region, 3) to determine the size and status of the Beaufort Sea polar bear population, and 4) to establish reproduction and survival rates (Amstrup 2000).

  19. LABORATORY FREQUENCY REDISTRIBUTION FUNCTION FOR THE POLARIZED Λ-TYPE THREE-TERM ATOM

    Energy Technology Data Exchange (ETDEWEB)

    Casini, R. [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307-3000 (United States); Manso Sainz, R. [Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany)

    2016-12-20

    We present the frequency redistribution function for a polarized three-term atom of the Λ-type in the collisionless regime, and we specialize it to the case where both the initial and final terms of the three-state transition are metastable (i.e., with infinitely sharp levels). This redistribution function represents a generalization of the well-known R {sub II} function to the case where the lower terms of the transition can be polarized and carry atomic coherence, and it can be applied to the investigation of polarized line formation in tenuous plasmas, where collisional rates may be low enough that anisotropy-induced atomic polarization survives even in the case of metastable levels.

  20. Experiments on state selection and Penning ionisation with fast metastable rare gas atoms

    International Nuclear Information System (INIS)

    Kroon, J.P.C.

    1985-01-01

    This thesis describes experiments with metastable He/Ne atoms. The experiments are performed in a crossed beam machine. Two different sources are used for the production of metastable atoms: a source for the production of metastable atoms in the thermal energy range and a hollow cathode arc for the production of metastable atoms in the superthermal energy range (1-7 eV). The progress made in the use of the hollow cathode arc is described as well as the experimental set-up. The rare gas energy-level diagram is characterized by two metastable levels. By optical pumping it is possible to select a single metastable level, both for He and Ne. For the case of He this is done by a recently built He quenchlamp which selectively quenches the metastable 2 1 S level population. In the thermal energy range the quenching is complete; in the superthermal energy range the 2 1 S level population is only partly quenched. For the optical pumping of Ne* atoms a cw dye laser is used. New experiments have been started on the measurement, in a crossed beam machine, of the fluorescence caused by inelastic collisions where metastable atoms are involved. The He* + Ne system is used as a pilot study for these experiments. The He-Ne laser is based on this collision system. (Auth.)

  1. Gas–liquid nucleation at large metastability: unusual features and a new formalism

    International Nuclear Information System (INIS)

    Santra, Mantu; Singh, Rakesh S; Bagchi, Biman

    2011-01-01

    Nucleation at large metastability is still largely an unsolved problem, even though it is a problem of tremendous current interest, with wide-ranging practical value, from atmospheric research to materials science. It is now well accepted that the classical nucleation theory (CNT) fails to provide a qualitative picture and gives incorrect quantitative values for such quantities as activation-free energy barrier and supersaturation dependence of nucleation rate, especially at large metastability. In this paper, we present an alternative formalism to treat nucleation at large supersaturation by introducing an extended set of order parameters in terms of the kth largest liquid-like clusters, where k = 1 is the largest cluster in the system, k = 2 is the second largest cluster and so on. At low supersaturation, the size of the largest liquid-like cluster acts as a suitable order parameter. At large supersaturation, the free energy barrier for the largest liquid-like cluster disappears. We identify this supersaturation as the one at the onset of kinetic spinodal. The kinetic spinodal is system-size-dependent. Beyond kinetic spinodal many clusters grow simultaneously and competitively and hence the nucleation and growth become collective. In order to describe collective growth, we need to consider the full set of order parameters. We derive an analytic expression for the free energy of formation of the kth largest cluster. The expression predicts that, at large metastability (beyond kinetic spinodal), the barrier of growth for several largest liquid-like clusters disappears, and all these clusters grow simultaneously. The approach to the critical size occurs by barrierless diffusion in the cluster size space. The expression for the rate of barrier crossing predicts weaker supersaturation dependence than what is predicted by CNT at large metastability. Such a crossover behavior has indeed been observed in recent experiments (but eluded an explanation till now). In order

  2. Metastable modular metastructures for on-demand reconfiguration of band structures and nonreciprocal wave propagation

    Science.gov (United States)

    Wu, Z.; Zheng, Y.; Wang, K. W.

    2018-02-01

    We present an approach to achieve adaptable band structures and nonreciprocal wave propagation by exploring and exploiting the concept of metastable modular metastructures. Through studying the dynamics of wave propagation in a chain composed of finite metastable modules, we provide experimental and analytical results on nonreciprocal wave propagation and unveil the underlying mechanisms that facilitate such unidirectional energy transmission. In addition, we demonstrate that via transitioning among the numerous metastable states, the proposed metastructure is endowed with a large number of bandgap reconfiguration possibilities. As a result, we illustrate that unprecedented adaptable nonreciprocal wave propagation can be realized using the metastable modular metastructure. Overall, this research elucidates the rich dynamics attainable through the combinations of periodicity, nonlinearity, spatial asymmetry, and metastability and creates a class of adaptive structural and material systems capable of realizing tunable bandgaps and nonreciprocal wave transmissions.

  3. Excitation into 3p55p levels from the metastable levels of Ar

    International Nuclear Information System (INIS)

    Jung, R. O.; Boffard, John B.; Anderson, L. W.; Lin, Chun C.

    2007-01-01

    Measurements of cross sections for electron-impact excitation out of the J=0 and J=2 3p 5 4s metastable levels of argon into nine of the ten levels of the 3p 5 5p manifold are presented in the energy range from threshold to 10 eV. A mixed target of atoms in both metastable levels was created by a hollow cathode discharge. Laser quenching was used to depopulate either one of the metastable levels, allowing separate measurements of the cross sections from each of the two metastable levels. Unlike the metastable excitation cross sections into 3p 5 4p levels, the cross sections into the 3p 5 5p levels are not found to be proportional to optical oscillator strengths

  4. Spin exchange in polarized deuterium

    International Nuclear Information System (INIS)

    Przewoski, B. von; Meyer, H.O.; Balewski, J.; Doskow, J.; Ibald, R.; Pollock, R.E.; Rinckel, T.; Wellinghausen, A.; Whitaker, T.J.; Daehnick, W.W.; Haeberli, W.; Schwartz, B.; Wise, T.; Lorentz, B.; Rathmann, F.; Pancella, P.V.; Saha, Swapan K.; Thoerngren-Engblom, P.

    2003-01-01

    We have measured the vector and tensor polarization of an atomic deuterium target as a function of the target density. The polarized deuterium was produced in an atomic beam source and injected into a storage cell. For this experiment, the atomic beam source was operated without rf transitions, in order to avoid complications from the unknown efficiency of these transitions. In this mode, the atomic beam is vector and tensor polarized and both polarizations can be measured simultaneously. We used a 1.2-cm-diam and 27-cm-long storage cell, which yielded an average target density between 3 and 9x10 11 at/cm 3 . We find that the tensor polarization decreases with increasing target density while the vector polarization remains constant. The data are in quantitative agreement with the calculated effect of spin exchange between deuterium atoms at low field

  5. Metastability and thermophysical properties of metallic bulk glass forming alloys

    International Nuclear Information System (INIS)

    Wunderlich, R.K.; Fecht, H.J.

    1998-01-01

    The absence of crystallization over a wide time/temperature window can be used to produce bulk metallic glass by relatively slow cooling of the melt. For a number of alloys, including several multicomponent Zr-based alloys, the relevant thermodynamic and thermomechanical properties of the metastable glassy and undercooled liquid states have been measured below and above the glass transition temperature. These measurements include specific heat, viscosity, volume, and elastic properties as a function of temperature. As a result, it becomes obvious that the maximum undercooling for these alloys is given by an isentropic condition before an enthalpic or isochoric instability is reached. Alternatively, these glasses can also be produced by mechanical alloying, thus replacing the thermal disorder by static disorder and resulting in the same thermodynamic glass state. During heating through the undercooled liquid, a nanoscale phase separation occurs for most glasses as a precursor of crystallization

  6. Light activated phase transformation of metastable tetragonal nanocrystalline zirconia

    DEFF Research Database (Denmark)

    Nielsen, Mette Skovgaard; Almdal, Kristoffer; van Lelieveld, A

    2012-01-01

    This study searches for small molecules, which can be generated by photoacid generators (PAGs) capable of inducing the tetragonal-to-monoclinic transformation in zirconia nanocrystals. Metastable tetragonal zirconia nanocrystals were exposed in alcohol suspension. X-ray diffraction analysis showed...... that water, HCl, HF, and NH3, all initiate phase transformation of tetragonal zirconia at room temperature, whereas NBu4Cl and NBu4OH do not. 2-(4-Methoxystyryl)-4,6-bis(trichloromethyl)-1,3,5-triazine) was the most efficient (monoclinic volume fraction reached 0.57) out of the four tested PAGs....... For dispersion in a dimethacrylate matrix together with zirconia crystals, a monoclinic volume fraction of 0.19 was observed after 2 min of exposure to light, increasing to 0.6 after 30 min....

  7. Fundamentals of metastability exchange optical pumping in helium

    International Nuclear Information System (INIS)

    Batz, M; Nacher, P-J; Tastevin, G

    2011-01-01

    Advances in metastability exchange optical pumping (MEOP) at high laser powers, but also at high gas pressures and high magnetic field strengths, has provided strong motivation for revisiting the understanding of the limitations of this powerful technique. A comprehensive model has been developed for improved description of the combined effects of OP, ME, and relaxation, and of detailed MEOP features observed over the broad range of operating conditions. A brief description is provided, with illustrative comparisons of computed and experimental results. This improved tool is used to explain the excellent photon efficiency of OP obtained at all field strengths. It is combined with an angular momentum budget approach to quantitatively investigate the newly discovered strong OP-enhanced polarisation losses that currently limits MEOP performance.

  8. Fundamentals of metastability exchange optical pumping in helium

    Science.gov (United States)

    Batz, M.; Nacher, P.-J.; Tastevin, G.

    2011-06-01

    Advances in metastability exchange optical pumping (MEOP) at high laser powers, but also at high gas pressures and high magnetic field strengths, has provided strong motivation for revisiting the understanding of the limitations of this powerful technique. A comprehensive model has been developed for improved description of the combined effects of OP, ME, and relaxation, and of detailed MEOP features observed over the broad range of operating conditions. A brief description is provided, with illustrative comparisons of computed and experimental results. This improved tool is used to explain the excellent photon efficiency of OP obtained at all field strengths. It is combined with an angular momentum budget approach to quantitatively investigate the newly discovered strong OP-enhanced polarisation losses that currently limits MEOP performance.

  9. Metastable Helium Molecules as Tracers in Superfluid 4He

    International Nuclear Information System (INIS)

    Guo, W.; Wright, J. D.; Cahn, S. B.; Nikkel, J. A.; McKinsey, D. N.

    2009-01-01

    Metastable helium molecules generated in a discharge near a sharp tungsten tip immersed in superfluid 4 He are imaged using a laser-induced-fluorescence technique. By pulsing the tip, a small cloud of He 2 * molecules is produced. We can determine the normal-fluid velocity in a heat-induced counterflow by tracing the position of a single molecule cloud. As we run the tip in continuous field-emission mode, a normal-fluid jet from the tip is generated and molecules are entrained in the jet. A focused 910 nm pump laser pulse is used to drive a small group of molecules to the first excited vibrational level of the triplet ground state. Subsequent imaging of the tagged molecules with an expanded 925 nm probe laser pulse allows us to measure the flow velocity of the jet. The techniques we developed provide new tools in quantitatively studying the normal fluid flow in superfluid helium.

  10. Metastable decay of photoionized niobium clusters: Evaporation vs fission fragmentation

    International Nuclear Information System (INIS)

    Cole, S.K.; Liu, K.; Riley, S.J.

    1986-01-01

    The metastable decay of photoionized niobium clusters (Nb/sub n/ + ) has been observed in a newly constructed cluster beam machine. The decay manifests itself in the time-of-flight (TOF) mass spectrum as an asymmetric broadening of daughter ion peaks. Pulsed ion extraction has been used to measure the decay rate constants and to establish the mechanism of the fragmentation, evaporation and/or fission of the photoionized clusters. It is found that within the experimental time window evaporation dominates for the smaller clusters (n 6 sec -1 . The average kinetic energy release is also determined and is found to be on the order of 5 MeV. 8 refs., 3 figs., 1 tab

  11. Fast neutron spectroscopy with tensioned metastable fluid detectors

    Energy Technology Data Exchange (ETDEWEB)

    Grimes, T.F.; Taleyarkhan, R.P., E-mail: rusi@purdue.edu

    2016-09-11

    This paper describes research into development of a rapid-turnaround, neutron-spectroscopy capable (gamma-beta blind), high intrinsic efficiency sensor system utilizing the tensioned metastable fluid detector (TMFD) architecture. The inability of prevailing theoretical models (developed successfully for the classical bubble chamber) to adequately predict detection thresholds for tensioned metastable fluid conditions is described. Techniques are presented to overcome these inherent shortcomings, leading thereafter, to allow successful neutron spectroscopy using TMFDs – via the newly developed Single Atom Spectroscopy (SAS) approach. SAS also allows for a unique means for rapidly determining neutron energy thresholds with TMFDs. This is accomplished by simplifying the problem of determining Cavitation Detection Events (CDEs) arising from neutron interactions with one in which several recoiling atom species contribute to CDEs, to one in which only one dominant recoil atom need be considered. The chosen fluid is Heptane (C{sub 7}H{sub 16}) for which only recoiling C atoms contribute to CDEs. Using the SAS approach, the threshold curve for Heptane was derived using isotope neutron source data, and then validated against experiments with mono-energetic (2.45/14 MeV) neutrons from D-D and D-T accelerators. Thereafter the threshold curves were used to produce the response matrix for various geometries. The response matrices were in turn combined with experimental data to recover the continuous spectra of fission (Cf-252) and (α,n) Pu–Be isotopic neutron sources via an unfolding algorithm. A generalized algorithm is also presented for performing neutron spectroscopy using any other TMFD fluid that meets the SAS approach assumptions.

  12. Fast neutron spectroscopy with tensioned metastable fluid detectors

    Science.gov (United States)

    Grimes, T. F.; Taleyarkhan, R. P.

    2016-09-01

    This paper describes research into development of a rapid-turnaround, neutron-spectroscopy capable (gamma-beta blind), high intrinsic efficiency sensor system utilizing the tensioned metastable fluid detector (TMFD) architecture. The inability of prevailing theoretical models (developed successfully for the classical bubble chamber) to adequately predict detection thresholds for tensioned metastable fluid conditions is described. Techniques are presented to overcome these inherent shortcomings, leading thereafter, to allow successful neutron spectroscopy using TMFDs - via the newly developed Single Atom Spectroscopy (SAS) approach. SAS also allows for a unique means for rapidly determining neutron energy thresholds with TMFDs. This is accomplished by simplifying the problem of determining Cavitation Detection Events (CDEs) arising from neutron interactions with one in which several recoiling atom species contribute to CDEs, to one in which only one dominant recoil atom need be considered. The chosen fluid is Heptane (C7H16) for which only recoiling C atoms contribute to CDEs. Using the SAS approach, the threshold curve for Heptane was derived using isotope neutron source data, and then validated against experiments with mono-energetic (2.45/14 MeV) neutrons from D-D and D-T accelerators. Thereafter the threshold curves were used to produce the response matrix for various geometries. The response matrices were in turn combined with experimental data to recover the continuous spectra of fission (Cf-252) and (α,n) Pu-Be isotopic neutron sources via an unfolding algorithm. A generalized algorithm is also presented for performing neutron spectroscopy using any other TMFD fluid that meets the SAS approach assumptions.

  13. Collisional interactions in isotope and spin mixtures of laser-cooled metastable neon atoms

    International Nuclear Information System (INIS)

    Schuetz, Jan

    2013-01-01

    Laser-cooled metastable neon atoms (Ne * ) present a fascinating atomic system: The extremely low kinetic energy of the cold atoms stands in strong contrast to the large internal energy of the metastable state 3 P 2 and leads to unique collisional interaction properties that are dominated by ionizing collisions. In this work, experimental investigations of the collisional interactions of Ne * are presented. In particular, collisional interactions in isotope mixtures and in mixtures of different Zeeman sublevels (vertical stroke m J right angle) are studied. With a lifetime of 14.7s, the metastable state 3 P 2 serves as an effective ground state for the laser manipulation. The Ne * atoms are cooled down to a temperature of several 100μK using laser cooling techniques and stored in a magneto optical or magnetic trap. The cold, trapped atoms can then be used for experiments. In order to cool and trap isotope mixtures, the isotope shift of the atomic transition 3 P 2 3 D 3 that is used for laser manipulation has to be known with high precision. In this work, the shift of the transition between the isotopes 20 Ne, 21 Ne, and 22 Ne has been measured and, using the advantages of laser-cooled atoms, the accuracy of the measurement was improved by one order of magnitude compared to previous measurements. For 21 Ne also the hyperfine interaction constants of the state 3 D 3 for magnetic dipole and electric quadrupole interaction have been measured. The collisional interactions of spin-polarized Ne * in all two-isotope mixtures of 20 Ne, 21 Ne, and 22 Ne have been investigated. The investigations are focused on the question whether the heteronuclear collisional interactions are favorable for sympathetic cooling. Rate coefficients for heteronuclear ionizing collisions and upper bounds for heteronuclear thermal relaxation cross sections have been measured. In all cases, the measured ratio of elastic to inelastic collisions is not favorable for heteronuclear sympathetic cooling

  14. Political polarization

    OpenAIRE

    Dixit, Avinash K.; Weibull, Jörgen W.

    2007-01-01

    Failures of government policies often provoke opposite reactions from citizens; some call for a reversal of the policy, whereas others favor its continuation in stronger form. We offer an explanation of such polarization, based on a natural bimodality of preferences in political and economic contexts and consistent with Bayesian rationality.

  15. Political polarization.

    Science.gov (United States)

    Dixit, Avinash K; Weibull, Jörgen W

    2007-05-01

    Failures of government policies often provoke opposite reactions from citizens; some call for a reversal of the policy, whereas others favor its continuation in stronger form. We offer an explanation of such polarization, based on a natural bimodality of preferences in political and economic contexts and consistent with Bayesian rationality.

  16. Carcinoma hepatocelular metastático em Jaguatirica (Leopardus pardalis

    Directory of Open Access Journals (Sweden)

    Dayane F.H. Miranda

    2015-11-01

    Full Text Available RESUMO: O carcinoma hepatocelular (CHC é uma neoplasia rara nos animais domésticos e em espécies selvagens foi relatado somente em antílopes, veado, cães da pradaria e furões, mas não existem relatos em Leopardus pardalis (jaguatirica. Este trabalho descreve um caso de carcinoma hepatocelular metastático em uma fêmea felina de aproximadamente 18 anos de idade, da espécie Leopardus pardalis, proveniente do Parque Zoobotânico de Teresina-PI, com histórico de anorexia, apatia e evolução ao óbito que foi encaminhada ao Setor de Patologia Animal da Universidade Federal do Piauí para exame anatomopatológico. À necropsia foram observadas duas nodulações de aproximadamente 8,0cm de diâmetro no fígado, de coloração variando da brancacenta ao vermelhado claro, amarelada a vermelho escuro, subdivididas em lóbulos por tecido conjuntivo. No pâncreas foram observadas múltiplas nodulações de aproximadamente 1,0 cm de diâmetro, com superfície lisa, consistência firme, coloração vermelho-amarelada. A superfície de corte dos rins também apresentava várias nodulações milimétricas de distribuição multifocal, na região córtico-medular, consistência firme, coloração branco-acinzentada ou amarelada, sugerindo metástase. Os fragmentos das lesões de fígado foram coletados e no exame microscópico observaram-se proliferação de hepatócitos em cordões bem diferenciados, formando trabéculas com espessura de três ou mais células. Os hepatócitos apresentavam-se volumosos, pleomórficos, com citoplasma eosinofílico. Na coloração com PAS constataram-se, regularmente, acúmulo de glicogênio nos hepatócitos neoplásicos. A confirmação foi feita pela técnica de imunoistoquímica, utilizando-se anticorpo monoclonal (Hepatocyte Specific Antigen. Os achados anatomohistopatológicos, e o auxilio da imunoistoquímica permitiram concluir pelo diagnóstico de hepatocarcinoma trabecular metastático em Leopardus pardalis

  17. PAMELA, DAMA, INTEGRAL and signatures of metastable excited WIMPs

    Energy Technology Data Exchange (ETDEWEB)

    Finkbeiner, Douglas P. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Slatyer, Tracy R. [Physics Department, Harvard University, Cambridge, MA 02138 (United States); Weiner, Neal [Center for Cosmology and Particle Physics, Department of Physics, New York University, New York, NY 10003 (United States); Yavin, Itay, E-mail: dfinkbeiner@cfa.harvard.edu, E-mail: tslatyer@fas.harvard.edu, E-mail: neal.weiner@nyu.edu, E-mail: iyavin@princeton.edu [Department of Physics, Princeton University, Princeton, NJ 08544 (United States)

    2009-09-01

    Models of dark matter with ∼ GeV scale force mediators provide attractive explanations of many high energy anomalies, including PAMELA, ATIC, and the WMAP haze. At the same time, by exploiting the ∼ MeV scale excited states that are automatically present in such theories, these models naturally explain the DAMA/LIBRA and INTEGRAL signals through the inelastic dark matter (iDM) and exciting dark matter (XDM) scenarios, respectively. Interestingly, with only weak kinetic mixing to hypercharge to mediate decays, the lifetime of excited states with δ < 2m{sub electron} is longer than the age of the universe. The fractional relic abundance of these excited states depends on the temperature of kinetic decoupling, but can be appreciable. There could easily be other mechanisms for rapid decay, but the consequences of such long-lived states are intriguing. We find that CDMS constrains the fractional relic population of ∼ 100 keV states to be ∼< 10{sup −2}, for a 1 TeV WIMP with σ{sub n} = 10{sup −40} cm{sup 2}. Upcoming searches at CDMS, as well as xenon, silicon, and argon targets, can push this limit significantly lower. We also consider the possibility that the DAMA excitation occurs from a metastable state into the XDM state, which decays via e{sup +}e{sup −} emission, which allows lighter states to explain the INTEGRAL signal due to the small kinetic energies required. Such models yield dramatic signals from down-scattering, with spectra peaking at high energies, sometimes as high as ∼ 1 MeV, well outside the usual search windows. Such signals would be visible at future Ar and Si experiments, and may be visible at Ge and Xe experiments, although γ-rays associated with nuclear excitations would complicate the signal for these heavier targets. We also consider other XDM models involving ∼ 500 keV metastable states, and find they can allow lighter WIMPs to explain INTEGRAL as well.

  18. Metastable State Diamond Growth and its Applications to Electronic Devices.

    Science.gov (United States)

    Jeng, David Guang-Kai

    Diamond which consists of a dense array of carbon atoms joined by strong covalent bonds and formed into a tetrahedral crystal structure has remarkable mechanical, thermal, optical and electrical properties suitable for many industrial applications. With a proper type of doping, diamond is also an ideal semiconductor for high performance electronic devices. Unfortunately, natural diamond is rare and limited by its size and cost, it is not surprising that people continuously look for a synthetic replacement. It was believed for long time that graphite, another form of carbon, may be converted into diamond under high pressure and temperature. However, the exact condition of conversion was not clear. In 1939, O. I. Leipunsky developed an equilibrium phase diagram between graphite and diamond based on thermodynamic considerations. In the phase diagram, there is a low temperature (below 1000^ circC) and low pressure (below 1 atm) region in which diamond is metastable and graphite is stable, therefore establishes the conditions for the coexistence of the two species. Leipunsky's pioneer work opened the door for diamond synthesis. In 1955, the General Electric company (GE) was able to produce artificial diamond at 55k atm pressure and a temperature of 2000^ circC. Contrary to GE, B. Derjaguin and B. V. Spitzyn in Soviet Union, developed a method of growing diamonds at 1000^circC and at a much lower pressure in 1956. Since then, researchers, particularly in Soviet Union, are continuously looking for methods to grow diamond and diamond film at lower temperatures and pressures with slow but steady progress. It was only in the early 80's that the importance of growing diamond films had attracted the attentions of researchers in the Western world and in Japan. Recent progress in plasma physics and chemical vapor deposition techniques in integrated electronics technology have pushed the diamond growth in its metastable states into a new era. In this research, a microwave plasma

  19. Analysis of conductive target influence in plasma jet experiments through helium metastable and electric field measurements

    Science.gov (United States)

    Darny, T.; Pouvesle, J.-M.; Puech, V.; Douat, C.; Dozias, S.; Robert, Eric

    2017-04-01

    The use of cold atmospheric pressure plasma jets for in vivo treatments implies most of the time plasma interaction with conductive targets. The effect of conductive target contact on the discharge behavior is studied here for a grounded metallic target and compared to the free jet configuration. In this work, realized with a plasma gun, we measured helium metastable HeM (23S1) concentration (by laser absorption spectroscopy) and electric field (EF) longitudinal and radial components (by electro-optic probe). Both diagnostics were temporally and spatially resolved. Mechanisms after ionization front impact on the target surface have been identified. The remnant conductive ionized channel behind the ionization front electrically transiently connects the inner high voltage electrode to the target. Due to impedance mismatching between the ionized channel and the target, a secondary ionization front is initiated and rapidly propagates from the target surface to the inner electrode through this ionized channel. This leads to a greatly enhanced HeM production inside the plasma plume and the capillary. Forward and reverse dynamics occur with further multi reflections of more or less damped ionization fronts between the inner electrode and the target as long as the ionized channel is persisting. This phenomenon is very sensitive to parameters such as target distance and ionized channel conductivity affecting electrical coupling between these two and evidenced using positive or negative voltage polarity and nitrogen admixture. In typical operating conditions for the plasma gun used in this work, it has been found that after the secondary ionization front propagation, when the ionized channel is conductive enough, a glow like discharge occurs with strong conduction current. HeM production and all species excitation, especially reactive ones, are then driven by high voltage pulse evolution. The control of forward and reverse dynamics, impacting on the production of the glow

  20. Integrins and epithelial cell polarity.

    Science.gov (United States)

    Lee, Jessica L; Streuli, Charles H

    2014-08-01

    Cell polarity is characterised by differences in structure, composition and function between at least two poles of a cell. In epithelial cells, these spatial differences allow for the formation of defined apical and basal membranes. It has been increasingly recognised that cell-matrix interactions and integrins play an essential role in creating epithelial cell polarity, although key gaps in our knowledge remain. This Commentary will discuss the mounting evidence for the role of integrins in polarising epithelial cells. We build a model in which both inside-out signals to polarise basement membrane assembly at the basal surface, and outside-in signals to control microtubule apical-basal orientation and vesicular trafficking are required for establishing and maintaining the orientation of epithelial cell polarity. Finally, we discuss the relevance of the basal integrin polarity axis to cancer. This article is part of a Minifocus on Establishing polarity. © 2014. Published by The Company of Biologists Ltd.

  1. Fast metastable hydrogen atoms from H2 molecules: twin atoms

    Directory of Open Access Journals (Sweden)

    Trimèche A.

    2015-01-01

    Full Text Available It is a difficult task to obtain “twin atoms”, i.e. pairs of massive particles such that one can perform experiments in the same fashion that is routinely done with “twin photons”. One possible route to obtain such pairs is by dissociating homonuclear diatomic molecules. We address this possibility by investigating the production of metastable H(2s atoms coming from the dissociation of cold H2 molecules produced in a Campargue nozzle beam crossing an electron beam from a high intensity pulsed electron gun. Dissociation by electron impact was chosen to avoid limitations of target molecular excited states due to selection rules. Detectors placed several centimeters away from the collision center, and aligned with respect to possible common molecular dissociation channel, analyze the neutral fragments as a function of their time-of-flight (TOF through Lyman-α detection. Evidence for the first time observed coincidence of pairs of H(2s atoms obtained this way is presented.

  2. Finding metastabilities in reversible Markov chains based on incomplete sampling

    Directory of Open Access Journals (Sweden)

    Fackeldey Konstantin

    2017-01-01

    Full Text Available In order to fully characterize the state-transition behaviour of finite Markov chains one needs to provide the corresponding transition matrix P. In many applications such as molecular simulation and drug design, the entries of the transition matrix P are estimated by generating realizations of the Markov chain and determining the one-step conditional probability Pij for a transition from one state i to state j. This sampling can be computational very demanding. Therefore, it is a good idea to reduce the sampling effort. The main purpose of this paper is to design a sampling strategy, which provides a partial sampling of only a subset of the rows of such a matrix P. Our proposed approach fits very well to stochastic processes stemming from simulation of molecular systems or random walks on graphs and it is different from the matrix completion approaches which try to approximate the transition matrix by using a low-rank-assumption. It will be shown how Markov chains can be analyzed on the basis of a partial sampling. More precisely. First, we will estimate the stationary distribution from a partially given matrix P. Second, we will estimate the infinitesimal generator Q of P on the basis of this stationary distribution. Third, from the generator we will compute the leading invariant subspace, which should be identical to the leading invariant subspace of P. Forth, we will apply Robust Perron Cluster Analysis (PCCA+ in order to identify metastabilities using this subspace.

  3. Effect of shot peening on metastable austenitic stainless steels

    International Nuclear Information System (INIS)

    Fargas, G.; Roa, J.J.; Mateo, A.

    2015-01-01

    In this work, shot peening was performed in a metastable austenitic stainless steel EN 1.4318 (AISI 301LN) in order to evaluate its effect on austenite to martensite phase transformation and also the influence on the fatigue limit. Two different steel conditions were considered: annealed, i.e., with a fully austenitic microstructure, and cold rolled, consisting of a mixture of austenite and martensite. X-ray diffraction, electron back-scattered diffraction and focus ion beam, as well as nanoindentation techniques, were used to elucidate deformation mechanisms activated during shot peening and correlate with fatigue response. Results pointed out that extensive plastic deformation and phase transformation developed in annealed specimens as a consequence of shot peening. However, the increase of roughness and the generation of microcracks led to a limited fatigue limit improvement. In contrast, shot peened cold rolled specimens exhibited enhanced fatigue limit. In the latter case, the main factor that determined the influence on the fatigue response was the distance from the injector, followed successively by the exit speed of the shots and the coverage factor

  4. Cosmic strings in a braneworld theory with metastable gravitons

    International Nuclear Information System (INIS)

    Lue, Arthur

    2002-01-01

    If the graviton possesses an arbitrarily small (but nonvanishing) mass, perturbation theory implies that cosmic strings have a nonzero Newtonian potential. Nevertheless in Einstein gravity, where the graviton is strictly massless, the Newtonian potential of a cosmic string vanishes. This discrepancy is an example of the van Dam-Veltman-Zakharov (VDVZ) discontinuity. We present a solution for the metric around a cosmic string in a braneworld theory with a graviton metastable on the brane. This theory possesses those features that yield a VDVZ discontinuity in massive gravity, but nevertheless is generally covariant and classically self-consistent. Although the cosmic string in this theory supports a nontrivial Newtonian potential far from the source, one can recover the Einstein solution in a region near the cosmic string. That latter region grows as the graviton's effective linewidth vanishes (analogous to a vanishing graviton mass), suggesting the lack of a VDVZ discontinuity in this theory. Moreover, the presence of scale dependent structure in the metric may have consequences for the search for cosmic strings through gravitational lensing techniques

  5. Defect-related electronic metastabilities in chalcopyrite compounds

    Energy Technology Data Exchange (ETDEWEB)

    Hammer, Maria S., E-mail: maria.hammer@uni-oldenburg.de [Energy and Semiconductor Research Laboratory, Department of Physics, University of Oldenburg, 26111 Oldenburg (Germany); Neugebohrn, Nils; Riediger, Julia; Neerken, Janet; Ohland, Jörg; Riedel, Ingo [Energy and Semiconductor Research Laboratory, Department of Physics, University of Oldenburg, 26111 Oldenburg (Germany); Kiowski, Oliver; Wischmann, Wiltraud [Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg (ZSW), Industriestr. 6, 70565 Stuttgart (Germany)

    2014-04-15

    So far, in Cu(In,Ga)Se{sub 2} solar cells the metastable behavior of the key parameters, i.e. open circuit voltage, short circuit current and fill factor, and the corresponding defect physics were typically investigated independently. In order to contribute to this issue, we systematically varied between annealed and light soaked state and investigated the influence of these processes on the solar cell parameters as well as on the defect physics. In this work, we attempt to correlate the key parameters of the solar cells and the defect physics by discussing experimental results obtained from temperature dependent current–voltage measurements (IVT) as well as from capacitance voltage (CV), admittance (AS) and deep-level transient spectroscopy (DLTS). A commonly observed defect contribution in Cu(In,Ga)Se{sub 2} solar cells is the so-called N1 signature. The activation energy of this signature was found to increase upon air-annealing in the dark which goes along with a decrease in the open circuit voltage and the effective doping density. In this paper we will discuss the correlation between annealing-induced shifting of defect energies and the variation of the key parameters.

  6. Phase Transformation of Metastable Austenite in Steel during Nano indentation

    International Nuclear Information System (INIS)

    Ahn, Taehong; Lee, Sung Bo; Han, Heung Nam; Park, Kyungtae

    2013-01-01

    These can produce geometrical softening accompanied by a sudden displacement excursion during load-controlled nanoindentation, which referred to in the literature as a pop-in. In this study, phase transformation of metastable austenite to stress-induced ε martensite which causes pop-ins during nanoindentation of steel will be reported and discussed. This study investigated the relationship between pop-in behavior of austenite in the early stage of nanoindentation and formation of ε martensite based on microstructural analyses. The load-displacement curve obtained from nanoindentation revealed stepwise pop-ins in the early stage of plastic deformation. From analyses of high resolution TEM images, a cluster of banded structure under the indent turned out a juxtaposition of (111) planes of γ austenite and (0001) planes of ε martensite. The calculation of displacement along indentation axis for (111) slip system by formation of ε martensite showed that geometrical softening can also occur by ε martensite formation when considering that the stress-induced ε martensite transformation is the predominant deformation mode in the early stage of plastic deformation and its monopartial nature as well. These microstructural investigations strongly suggest that the pop-in behavior in the early stage of plastic deformation of austenite is closely related to the formation of ε martensite

  7. Phase Transformation of Metastable Austenite in Steel during Nano indentation

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, Taehong [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Lee, Sung Bo; Han, Heung Nam [Seoul National Univ., Seoul (Korea, Republic of); Park, Kyungtae [Hanbat National Univ., Daejeon (Korea, Republic of)

    2013-05-15

    These can produce geometrical softening accompanied by a sudden displacement excursion during load-controlled nanoindentation, which referred to in the literature as a pop-in. In this study, phase transformation of metastable austenite to stress-induced ε martensite which causes pop-ins during nanoindentation of steel will be reported and discussed. This study investigated the relationship between pop-in behavior of austenite in the early stage of nanoindentation and formation of ε martensite based on microstructural analyses. The load-displacement curve obtained from nanoindentation revealed stepwise pop-ins in the early stage of plastic deformation. From analyses of high resolution TEM images, a cluster of banded structure under the indent turned out a juxtaposition of (111) planes of γ austenite and (0001) planes of ε martensite. The calculation of displacement along indentation axis for (111) slip system by formation of ε martensite showed that geometrical softening can also occur by ε martensite formation when considering that the stress-induced ε martensite transformation is the predominant deformation mode in the early stage of plastic deformation and its monopartial nature as well. These microstructural investigations strongly suggest that the pop-in behavior in the early stage of plastic deformation of austenite is closely related to the formation of ε martensite.

  8. Metastability in plyometric training on unstable surfaces: a pilot study

    Science.gov (United States)

    2014-01-01

    Background In the past, plyometric training (PT) has been predominantly performed on stable surfaces. The purpose of this pilot study was to examine effects of a 7-week lower body PT on stable vs. unstable surfaces. This type of exercise condition may be denoted as metastable equilibrium. Methods Thirty-three physically active male sport science students (age: 24.1 ± 3.8 years) were randomly assigned to a PT group (n = 13) exercising on stable (STAB) and a PT group (n = 20) on unstable surfaces (INST). Both groups trained countermovement jumps, drop jumps, and practiced a hurdle jump course. In addition, high bar squats were performed. Physical fitness tests on stable surfaces (hexagonal obstacle test, countermovement jump, hurdle drop jump, left-right hop, dynamic and static balance tests, and leg extension strength) were used to examine the training effects. Results Significant main effects of time (ANOVA) were found for the countermovement jump, hurdle drop jump, hexagonal test, dynamic balance, and leg extension strength. A significant interaction of time and training mode was detected for the countermovement jump in favor of the INST group. No significant improvements were evident for either group in the left-right hop and in the static balance test. Conclusions These results show that lower body PT on unstable surfaces is a safe and efficient way to improve physical performance on stable surfaces. PMID:25089202

  9. FPGA Implementation of Metastability-Based True Random Number Generator

    Science.gov (United States)

    Hata, Hisashi; Ichikawa, Shuichi

    True random number generators (TRNGs) are important as a basis for computer security. Though there are some TRNGs composed of analog circuit, the use of digital circuits is desired for the application of TRNGs to logic LSIs. Some of the digital TRNGs utilize jitter in free-running ring oscillators as a source of entropy, which consume large power. Another type of TRNG exploits the metastability of a latch to generate entropy. Although this kind of TRNG has been mostly implemented with full-custom LSI technology, this study presents an implementation based on common FPGA technology. Our TRNG is comprised of logic gates only, and can be integrated in any kind of logic LSI. The RS latch in our TRNG is implemented as a hard-macro to guarantee the quality of randomness by minimizing the signal skew and load imbalance of internal nodes. To improve the quality and throughput, the output of 64-256 latches are XOR'ed. The derived design was verified on a Xilinx Virtex-4 FPGA (XC4VFX20), and passed NIST statistical test suite without post-processing. Our TRNG with 256 latches occupies 580 slices, while achieving 12.5Mbps throughput.

  10. Maternal nutrition at conception modulates DNA methylation of human metastable epialleles

    Science.gov (United States)

    In experimental animals, maternal diet during the periconceptional period influences the establishment of DNA methylation at metastable epialleles in the offspring, with permanent phenotypic consequences. Pronounced naturally occurring seasonal differences in the diet of rural Gambian women allowed ...

  11. Localization of metastable atom beams with optical standing waves: nanolithography at the heisenberg limit

    Science.gov (United States)

    Johnson; Thywissen; Dekker; Berggren; Chu; Younkin; Prentiss

    1998-06-05

    The spatially dependent de-excitation of a beam of metastable argon atoms, traveling through an optical standing wave, produced a periodic array of localized metastable atoms with position and momentum spreads approaching the limit stated by the Heisenberg uncertainty principle. Silicon and silicon dioxide substrates placed in the path of the atom beam were patterned by the metastable atoms. The de-excitation of metastable atoms upon collision with the surface promoted the deposition of a carbonaceous film from a vapor-phase hydrocarbon precursor. The resulting patterns were imaged both directly and after chemical etching. Thus, quantum-mechanical steady-state atom distributions can be used for sub-0.1-micrometer lithography.

  12. Behavior of 23S metastable state He atoms in low-temperature recombining plasmas

    Science.gov (United States)

    Kajita, Shin; Tsujihara, Tadashi; Aramaki, Mitsutoshi; van der Meiden, Hennie; Oshima, Hiroshi; Ohno, Noriyasu; Tanaka, Hirohiko; Yasuhara, Ryo; Akiyama, Tsuyoshi; Fujii, Keisuke; Shikama, Taiichi

    2017-07-01

    We measured the electron density and temperature using laser Thomson scattering and metastable state (23S) of He atoms by laser absorption spectroscopy in the detached recombining plasmas in the divertor simulator NAGDIS-II. Using the measured electron density and temperature combined with the particle trajectory trace simulation, we discussed the behavior of the metastable state He atoms based on comparisons with the experimental results. It is shown that the metastable state atoms are mainly produced in the peripheral region of the plasma column, where the temperature is lower than the central part, and diffused in the vacuum vessel. It was shown that the 0D model is not valid and the transport of the metastable states is to be taken into account for the population distribution of He atoms in the detached plasmas.

  13. Experimental determination of the constitutive behaviour of a metastable austenitic stainless steel

    NARCIS (Netherlands)

    Post, J.; Nolles, H.; Datta, K.; Datta, K.; Geijselaers, Hubertus J.M.

    2008-01-01

    This article presents measurements to describe the constitutive behaviour of a semi-austenitic precipitation hardenable stainless steel called Sandvik Nanoflex™, during metal forming and hardening. The material is metastable, which causes strain-induced transformation during forming. Depending on

  14. Polar low monitoring

    Science.gov (United States)

    Bobylev, Leonid; Zabolotskikh, Elizaveta; Mitnik, Leonid

    2010-05-01

    Polar lows are intense mesoscale atmospheric low pressure weather systems, developing poleward of the main baroclinic zone and associated with high surface wind speeds. Small size and short lifetime, sparse in-situ observations in the regions of their development complicate polar low study. Our knowledge of polar lows and mesocyclones has come almost entirely during the period of satellite remote sensing since, by virtue of their small horizontal scale, it was rarely possible to analyse these lows on conventional weather charts using only the data from the synoptic observing network. However, the effects of intense polar lows have been felt by coastal communities and seafarers since the earliest times. These weather systems are thought to be responsible for the loss of many small vessels over the centuries, although the nature of the storms was not understood and their arrival could not be predicted. The actuality of the polar low research is stipulated by their high destructive power: they are a threat to such businesses as oil and gas exploration, fisheries and shipping. They could worsen because of global warming: a shrinking of sea ice around the North Pole, which thawed to its record minimum in the summer of 2007, is likely to give rise to more powerful storms that form only over open water and can cause hurricane-strength winds. Therefore, study of polar lows, their timely detection, tracking and forecasting represents a challenge for today meteorology. Satellite passive microwave data, starting from Special Sensor Microwave Imager (SSM/I) onboard Defense Meteorological Satellite Program (DMSP) satellite, remain invaluable source of regularly available remotely sensed data to study polar lows. The sounding in this spectral range has several advantages in comparison with observations in visible and infrared ranges and Synthetic Aperture Radar (SAR) data: independence on day time and clouds, regularity and high temporal resolution in Polar Regions. Satellite

  15. Development of a novel direction-position sensing fast neutron detector using tensioned metastable fluids

    Science.gov (United States)

    Archambault, Brian C.; Webster, Jeffrey A.; Lapinskas, Joseph R.; Grimes, Thomas F.; Taleyarkhan, Rusi

    2012-05-01

    A directional-position sensing fast neutron sensor utilizing the acoustic tensioned metastable fluid detector (ATMFD) is described. This ATMFD system enables the determination of directionality of incoming neutron radiation with a single detector, and is developed based on a combination of experimentation and theoretical assessments. Benchmarking and qualifications studies conducted with a 1 Ci Pu-Be neutron source produced encouraging results. These results indicated that the ATMFD is not only comparable in technical performance with competing directional fast neutron detector-bank technologies under development worldwide, but it promised to do so with a single detector and at a significant reduction in both cost and size while remaining completely blind to nonneutron background radiation. Applications to neutron source spatial imaging and standoff detection with the ATMFD system are also presented. The ATMFD was found to successfully locate a hidden neutron source in a blind test. Assessments for practically relevant situations were conducted and it was revealed that an ATMFD system (with a 6 cm×10 cm cross-sectional area) could offer directionality on incoming neutron radiation from a 8 kg Pu source at 25 m standoff, with a resolution of 11.2°, with 68% confidence within 60 s. Position and neutron source image sensing capability were also demonstrated using two ATMFDs.

  16. Metastable honeycomb SrTiO3/SrIrO3 heterostructures

    International Nuclear Information System (INIS)

    Anderson, T. J.; Ryu, S.; Podkaminer, J. P.; Ma, Y.; Eom, C. B.; Zhou, H.; Xie, L.; Irwin, J.; Rzchowski, M. S.; Pan, X. Q.

    2016-01-01

    Recent theory predictions of exotic band topologies in (111) honeycomb perovskite SrIrO 3 layers sandwiched between SrTiO 3 have garnered much attention in the condensed matter physics and materials communities. However, perovskite SrIrO 3 film growth in the (111) direction remains unreported, as efforts to synthesize pure SrIrO 3 on (111) perovskite substrates have yielded films with monoclinic symmetry rather than the perovskite structure required by theory predictions. In this study, we report the synthesis of ultra-thin metastable perovskite SrIrO 3 films capped with SrTiO 3 grown on (111) SrTiO 3 substrates by pulsed laser deposition. The atomic structure of the ultra-thin films was examined with scanning transmission electron microscopy (STEM), which suggests a perovskite layering distinct from the bulk SrIrO 3 monoclinic phase. In-plane 3-fold symmetry for the entire heterostructure was confirmed using synchrotron surface X-ray diffraction to measure symmetry equivalent crystal truncation rods. Our findings demonstrate the ability to stabilize (111) honeycomb perovskite SrIrO 3 , which provides an experimental avenue to probe the phenomena predicted for this material system.

  17. Primary populations of metastable antiprotonic $^{4}He$ and $^{3}He$ atoms

    CERN Document Server

    Hori, Masaki; Hayano, R S; Ishikawa, T; Sakuguchi, J; Tasaki, T; Widmann, E; Yamaguchi, H; Torii, H A; Juhász, B; Horváth, D; Yamazaki, T

    2002-01-01

    Initial population distributions of metastable antiprotonic **4He and **3He atoms over principal and angular momentum quantum numbers were investigated using laser spectroscopy. The total fractions of antiprotons captured into the metastable states of the atoms were deduced. Cascade calculations were performed using the measure populations to reproduce the delayed annihilation time spectrum. Results showed agreement between the simulated and measured spectra. (Edited abstract) 30 Refs.

  18. Mathematical model to analyze the dissolution behavior of metastable crystals or amorphous drug accompanied with a solid-liquid interface reaction.

    Science.gov (United States)

    Hirai, Daiki; Iwao, Yasunori; Kimura, Shin-Ichiro; Noguchi, Shuji; Itai, Shigeru

    2017-04-30

    Metastable crystals and the amorphous state of poorly water-soluble drugs in solid dispersions (SDs), are subject to a solid-liquid interface reaction upon exposure to a solvent. The dissolution behavior during the solid-liquid interface reaction often shows that the concentration of drugs is supersaturated, with a high initial drug concentration compared with the solubility of stable crystals but finally approaching the latter solubility with time. However, a method for measuring the precipitation rate of stable crystals and/or the potential solubility of metastable crystals or amorphous drugs has not been established. In this study, a novel mathematical model that can represent the dissolution behavior of the solid-liquid interface reaction for metastable crystals or amorphous drug was developed and its validity was evaluated. The theory for this model was based on the Noyes-Whitney equation and assumes that the precipitation of stable crystals at the solid-liquid interface occurs through a first-order reaction. Moreover, two models were developed, one assuming that the surface area of the drug remains constant because of the presence of excess drug in the bulk and the other that the surface area changes in time-dependency because of agglomeration of the drug. SDs of Ibuprofen (IB)/polyvinylpyrrolidone (PVP) were prepared and their dissolution behaviors under non-sink conditions were fitted by the models to evaluate improvements in solubility. The model assuming time-dependent surface area showed good agreement with experimental values. Furthermore, by applying the model to the dissolution profile, parameters such as the precipitation rate and the potential solubility of the amorphous drug were successfully calculated. In addition, it was shown that the improvement in solubility with supersaturation was able to be evaluated quantitatively using this model. Therefore, this mathematical model would be a useful tool to quantitatively determine the supersaturation

  19. Magnetic Evidence for Metastable Ferrihydrite Particles in a Vertisol

    Science.gov (United States)

    Gehring, A. U.; Schill, E.; Weidler, P. G.; Luster, J.

    2004-12-01

    Poorly crystalline iron oxides in soils are of ecological importance since their chemical properties (e.g. solubility, surface area and reactivity) affect the bioavailability of iron and promote processes such as adsorption and transport of metals, pesticides, and organic nutrients. In natural environments these highly reactive phases are difficult to detect because they form generally a minor component with a nano-sized nature. Ferrihydrite is the best known phase among these materials with ambiguous identity. For the magnetic and soil-chemical investigation a Vertisol in southern Mali was chosen. Southern Mali has a subtropical climate with a wet and a dry season, an annual rainfall of 1300mm, and an average temperature of 27° C. The Vertisol mainly consists of montmorillonite and quartz, and no iron oxides were detected by X-ray diffractometry. It has a relatively high amount of oxalate extractable Fe and reveals a strong increase of IRM acquisition at 77K compared to room temperature. In order to characterize the low temperature magnetic phase, AC susceptibility frequency experiments on bulk samples were conducted between 2 and 300K with 10 and 1000Hz. The in-phase susceptibility exhibited an increase at 120K followed by two peaks at 65 and 35K and a steep increase at 25K. In the temperature range of the peaks a clear frequency dependency was observed. The out-of-phase component revealed a similar behavior with a more pronounced frequency dependency below 65K. The beginning of magnetic ordering in the out-of-phase component at about 120K and the two peaks are assigned to two ferrihydrites with different magnetic properties. After oven-drying the bulk samples at 60° C, the two peaks had vanished. This behavior suggests that ferrihydrites are metastable and convert into a thermodynamically more stable phase.

  20. Population dynamics of metastable growth-rate phenotypes.

    Directory of Open Access Journals (Sweden)

    Lindsay S Moore

    Full Text Available Neo-Darwinian evolution has presented a paradigm for population dynamics built on random mutations and selection with a clear separation of time-scales between single-cell mutation rates and the rate of reproduction. Laboratory experiments on evolving populations until now have concentrated on the fixation of beneficial mutations. Following the Darwinian paradigm, these experiments probed populations at low temporal resolution dictated by the rate of rare mutations, ignoring the intermediate evolving phenotypes. Selection however, works on phenotypes rather than genotypes. Research in recent years has uncovered the complexity of genotype-to-phenotype transformation and a wealth of intracellular processes including epigenetic inheritance, which operate on a wide range of time-scales. Here, by studying the adaptation dynamics of genetically rewired yeast cells, we show a novel type of population dynamics in which the intracellular processes intervene in shaping the population structure. Under constant environmental conditions, we measure a wide distribution of growth rates that coexist in the population for very long durations (>100 generations. Remarkably, the fastest growing cells do not take over the population on the time-scale dictated by the width of the growth-rate distributions and simple selection. Additionally, we measure significant fluctuations in the population distribution of various phenotypes: the fraction of exponentially-growing cells, the distributions of single-cell growth-rates and protein content. The observed fluctuations relax on time-scales of many generations and thus do not reflect noisy processes. Rather, our data show that the phenotypic state of the cells, including the growth-rate, for large populations in a constant environment is metastable and varies on time-scales that reflect the importance of long-term intracellular processes in shaping the population structure. This lack of time-scale separation between the

  1. Metastable structures and size effects in small group dynamics

    Directory of Open Access Journals (Sweden)

    Rosapia eLauro Grotto

    2014-07-01

    Full Text Available In his seminal works on group dynamics Bion defined a specific therapeutic setting allowing psychoanalytic observations on group phenomena. In describing the setting he proposed that the group was where his voice arrived. This physical limit was later made operative by assuming that the natural dimension of a therapeutic group is around 12 people. Bion introduced a theory of the group aspects of the mind in which proto-mental individual states spontaneously evolve into shared psychological states that are characterized by a series of features: 1 they emerge as a consequence of the natural tendency of (both conscious and unconscious emotions to combine into structured group patterns; 2 they have a certain degree of stability in time; 3 they tend to alternate so that the dissolution of one is rapidly followed by the emergence of another; 4 they can be described in qualitative terms according to the nature of the emotional mix that dominates the state, in structural terms by a kind of typical 'leadership’ pattern, and in 'cognitive’ terms by a set of implicit expectations that are helpful in explaining the group behavior (i.e. the group behaves 'as if’ it was assuming that…. Here we adopt a formal approach derived from Socio-physics in order to explore some of the structural and dynamic properties of this small group dynamics. We will described data from an analytic DS model simulating small group interactions of agents endowed with a very simplified emotional and cognitive dynamic in order to assess the following main points: 1 are metastable collective states allowed to emerge in the model and if so, under which conditions in the parameter space? 3 can these states be differentiated in structural terms? 3 to what extent are the emergent dynamic features of the systems dependent of the system size? We will finally discuss possible future applications of the quantitative descriptions of the interaction structure in the small group clinical

  2. Metastable structures and size effects in small group dynamics.

    Science.gov (United States)

    Lauro Grotto, Rosapia; Guazzini, Andrea; Bagnoli, Franco

    2014-01-01

    In his seminal works on group dynamics Bion defined a specific therapeutic setting allowing psychoanalytic observations on group phenomena. In describing the setting he proposed that the group was where his voice arrived. This physical limit was later made operative by assuming that the natural dimension of a therapeutic group is around 12 people. Bion introduced a theory of the group aspects of the mind in which proto-mental individual states spontaneously evolve into shared psychological states that are characterized by a series of features: (1) they emerge as a consequence of the natural tendency of (both conscious and unconscious) emotions to combine into structured group patterns; (2) they have a certain degree of stability in time; (3) they tend to alternate so that the dissolution of one is rapidly followed by the emergence of another; (4) they can be described in qualitative terms according to the nature of the emotional mix that dominates the state, in structural terms by a kind of typical "leadership" pattern, and in "cognitive" terms by a set of implicit expectations that are helpful in explaining the group behavior (i.e., the group behaves "as if" it was assuming that). Here we adopt a formal approach derived from Socio-physics in order to explore some of the structural and dynamic properties of this small group dynamics. We will described data from an analytic DS model simulating small group interactions of agents endowed with a very simplified emotional and cognitive dynamic in order to assess the following main points: (1) are metastable collective states allowed to emerge in the model and if so, under which conditions in the parameter space? (2) can these states be differentiated in structural terms? (3) to what extent are the emergent dynamic features of the systems dependent of the system size? We will finally discuss possible future applications of the quantitative descriptions of the interaction structure in the small group clinical setting.

  3. Metastable states and energy flow pathway in square graphene resonators

    Science.gov (United States)

    Wang, Yisen; Zhu, Zhigang; Zhang, Yong; Huang, Liang

    2018-01-01

    Nonlinear interaction between flexural modes is critical to heat conductivity and mechanical vibration of two-dimensional materials such as graphene. Much effort has been devoted to understand the underlying mechanism. In this paper, we examine solely the out-of-plane flexural modes and identify their energy flow pathway during thermalization process. The key is the development of a universal scheme that numerically characterizes the strength of nonlinear interactions between normal modes. In particular, for our square graphene system, the modes are grouped into four classes by their distinct symmetries. The couplings are significantly larger within a class than between classes. As a result, the equations for the normal modes in the same class as the initially excited one can be approximated by driven harmonic oscillators, therefore, they get energy almost instantaneously. Because of the hierarchical organization of the mode coupling, the energy distribution among the modes will arrive at a stable profile, where most of the energy is localized on a few modes, leading to the formation of "natural package" and metastable states. The dynamics for modes in other symmetry classes follows a Mathieu type of equation, thus, interclass energy flow, when the initial excitation energy is small, starts typically when there is a mode that lies in the unstable region in the parameter space of Mathieu equation. Due to strong coupling of the modes inside the class, the whole class will get energy and be lifted up by the unstable mode. This characterizes the energy flow pathway of the system. These results bring fundamental understandings to the Fermi-Pasta-Ulam problem in two-dimensional systems with complex potentials, and reveal clearly the physical picture of dynamical interactions between the flexural modes, which will be crucial to the understanding of their abnormal contribution to heat conduction and nonlinear mechanical vibrations.

  4. Production of H(2s) fast metastable atoms (0.25-3 keV) on a Cs target. Detection of the α Lyman radiation induced by Stark effect: polarisation. Destruction of H(2s) atoms on an IH target

    International Nuclear Information System (INIS)

    Valance, Antoine.

    1974-01-01

    The production, detection and destruction of the 2S1/2 metastable state of the hydrogen atom were studied. The quasi-resonant charge exchange processes between fast protons and cesium target, in the total cross sections for production of metastable H(2s) atoms and radiative H(2p) atoms showed structures hitherto unobserved. The theoretical study is based on calculation of the adiabatic molecular potential terms of the ionic quasi-molecule (CsH) + , taking a Helmann type pseudopotential to describe the electron with respect to the core of the cesium ion. The probabilities of transition towards the output channels are calculated using a stationary state perturbation method. From the data obtained the interferece phenomena of excited quasi-molecular states can be interpreted coherently in slow collision. The probability of transition along the inelastic output channels displays characteristics of a harmonic oscillatory function inversely proportional to the speed of approach of the particles. The frequency of these oscillations depends very slightly on the impact parameter. The theory proposed involves three Σ states. During detection of the metastable ions the Lyman-α radiation induced in the de-excitation electric field by Stark effect present anisotropic features. The degree of polarization measured as a function of the field strength oscillates around a slow decay toward a limit-1 at strong electric field. A theory not accounting for the hyperfine structure of states mixed by Stark effect showed a double oscillatory structure containing the two frequencies correlated to the 2P1/2 and 2P3/2 states from the 2S1/2 state. Finally the results on the electron detachment reaction between fast metastable atoms and hydroiodic acid target have contributed towards research on polarized proton sources [fr

  5. Strategic Polarization.

    Science.gov (United States)

    Kalai, Adam; Kalai, Ehud

    2001-08-01

    In joint decision making, similarly minded people may take opposite positions. Consider the example of a marriage in which one spouse gives generously to charity while the other donates nothing. Such "polarization" may misrepresent what is, in actuality, a small discrepancy in preferences. It may be that the donating spouse would like to see 10% of their combined income go to charity each year, while the apparently frugal spouse would like to see 8% donated. A simple game-theoretic analysis suggests that the spouses will end up donating 10% and 0%, respectively. By generalizing this argument to a larger class of games, we provide strategic justification for polarization in many situations such as debates, shared living accommodations, and disciplining children. In some of these examples, an arbitrarily small disagreement in preferences leads to an arbitrarily large loss in utility for all participants. Such small disagreements may also destabilize what, from game-theoretic point of view, is a very stable equilibrium. Copyright 2001 Academic Press.

  6. Accelerating and storing polarized hadron beams

    International Nuclear Information System (INIS)

    Teng, L.C.

    1990-10-01

    Polarization hadron experiments at high energies continue to generate surprises. Many questions remain unanswered or unanswerable within the frame work of QCD. These include such basic questions as to why at high energies the polarization analyzing power in pp elastic scattering remains high, why hyperons are produced with high polarizations etc. It is, therefore, interesting to investigate the possibilities of accelerating and storing polarized beams in high energy colliders. On the technical side the recent understanding and confirmation of the actions of partial and multiple Siberian snakes made it possible to contemplate accelerating and storing polarized hadron beams to multi-TeV energies. In this paper, we will examine the equipment, the operation and the procedure required to obtain colliding beams of polarized protons at TeV energies

  7. Formation of Kinetically Trapped Nanoscopic Unilamellar Vesicles from Metastable Nanodiscs

    Energy Technology Data Exchange (ETDEWEB)

    Nieh, Mu-Ping [Univ. of Connecticut, Storrs, CT (United States). Inst. of Materials Science, Dept. of Chemical, Materials & Biomolecular Engineering; Dolinar, Paul [Univ. of Ottawa, ON (Canada); Kucerka, Norbert [National Research Council, Chalk River, ON (Canada). Chalk River Lab., Canadian Neutron Beam Centre; Comenius Univ., Bratislava (Slovakia). Dept. of Physical Chemistry of Drugs; Kline, Steven R. [National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States); Debeer-Schmitt, Lisa M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Neutron Scattering Science Division; Littrell, Kenneth C. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Neutron Scattering Science Division; Katsaras, John [National Research Council, Chalk River, ON (Canada). Chalk River Lab., Canadian Neutron Beam Centre; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Neutron Scattering Science Division; Brock Univ., St. Catharines, ON (Canada). Dept. of Physics; Univ. of Guelph, ON (Canada). Guelph-Waterloo Physics Inst.

    2011-09-27

    Zwitterionic long-chain lipids (e.g., dimyristoyl phosphatidylcholine, DMPC) spontaneously form onion-like, thermodynamically stable structures in aqueous solutions (commonly known as multilamellar vesicles, or MLVs). It has also been reported that the addition of zwitterionic short-chain (i.e., dihexanoyl phosphatidylcholine, DHPC) and charged long-chain (i.e., dimyristoyl phosphatidylglycerol, DMPG) lipids to zwitterionic long-chain lipid solutions results in the formation of unilamellar vesicles (ULVs). Here, we report a kinetic study on lipid mixtures composed of DMPC, DHPC, and DMPG. Two membrane charge densities (i.e., [DMPG]/[DMPC] = 0.01 and 0.001) and two solution salinities (i.e., [NaCl] = 0 and 0.2 M) are investigated. Upon dilution of the high-concentration samples at 50 °C, thermodynamically stable MLVs are formed, in the case of both weakly charged and high salinity solution mixtures, implying that the electrostatic interactions between bilayers are insufficient to cause MLVs to unbind. Importantly, in the case of these samples small angle neutron scattering (SANS) data show that, initially, nanodiscs (also known as bicelles) or bilayered ribbons form at low temperatures (i.e., 10 °C), but transform into uniform size, nanoscopic ULVs after incubation at 10 °C for 20 h, indicating that the nanodisc is a metastable structure. The instability of nanodiscs may be attributed to low membrane rigidity due to a reduced charge density and high salinity. Moreover, the uniform-sized ULVs persist even after being heated to 50 °C, where thermodynamically stable MLVs are observed. This result clearly demonstrates that these ULVs are kinetically trapped, and that the mechanical properties (e.g., bending rigidity) of 10 C nanodiscs favor the formation of nanoscopic ULVs over that of MLVs. From a practical point of view, this method of forming uniform-sized ULVs may lend itself to their mass production, thus making them economically feasible for medical

  8. DISCOVERY OF POLARIZATION REVERBERATION IN NGC 4151

    Energy Technology Data Exchange (ETDEWEB)

    Gaskell, C. Martin; Shoji, Masatoshi [Department of Physics and Astronomy, University of Nebraska, Lincoln, NE 68588-0111 (United States); Goosmann, Rene W. [Observatoire astronomique de Strasbourg, 11 rue de l' Universite, F-67000 Strasbourg (France); Merkulova, Nelly I.; Shakhovskoy, Nikolay M., E-mail: martin.gaskell@uv.cl, E-mail: mshoji@astro.as.utexas.edu, E-mail: rene.goosmann@astro.unistra.fr [Crimean Astrophysical Observatory, Nauchny, Crimea 98409 (Ukraine)

    2012-04-20

    Observations of the optical polarization of NGC 4151 in 1997-2003 show variations of an order of magnitude in the polarized flux while the polarization position angle remains constant. The amplitude of variability of the polarized flux is comparable to the amplitude of variability of the total U-band flux, except that the polarized flux follows the total flux with a lag of 8 {+-} 3 days. The time lag and the constancy of the position angle strongly favor a scattering origin for the variable polarization rather than a non-thermal synchrotron origin. The orientation of the position angle of the polarized flux (parallel to the radio axis) and the size of the lag imply that the polarization arises from electron scattering in a flattened region within the low-ionization component of the broad-line region. Polarization from dust scattering in the equatorial torus is ruled out as the source of the lag in polarized flux because it would produce a larger lag and, unless the half-opening angle of the torus is >53 Degree-Sign , the polarization would be perpendicular to the radio axis. We note a long-term change in the percentage of polarization at similar total flux levels, and this could be due either to changing non-axisymmetry in the optical continuum emission or a change in the number of scatterers on a timescale of years.

  9. Calculation of the relative metastabilities of proteins using the CHNOSZ software package

    Directory of Open Access Journals (Sweden)

    Dick Jeffrey M

    2008-10-01

    Full Text Available Abstract Background Proteins of various compositions are required by organisms inhabiting different environments. The energetic demands for protein formation are a function of the compositions of proteins as well as geochemical variables including temperature, pressure, oxygen fugacity and pH. The purpose of this study was to explore the dependence of metastable equilibrium states of protein systems on changes in the geochemical variables. Results A software package called CHNOSZ implementing the revised Helgeson-Kirkham-Flowers (HKF equations of state and group additivity for ionized unfolded aqueous proteins was developed. The program can be used to calculate standard molal Gibbs energies and other thermodynamic properties of reactions and to make chemical speciation and predominance diagrams that represent the metastable equilibrium distributions of proteins. The approach takes account of the chemical affinities of reactions in open systems characterized by the chemical potentials of basis species. The thermodynamic database included with the package permits application of the software to mineral and other inorganic systems as well as systems of proteins or other biomolecules. Conclusion Metastable equilibrium activity diagrams were generated for model cell-surface proteins from archaea and bacteria adapted to growth in environments that differ in temperature and chemical conditions. The predicted metastable equilibrium distributions of the proteins can be compared with the optimal growth temperatures of the organisms and with geochemical variables. The results suggest that a thermodynamic assessment of protein metastability may be useful for integrating bio- and geochemical observations.

  10. An electrostatic elliptical mirror for neutral polar molecules.

    Science.gov (United States)

    González Flórez, A Isabel; Meek, Samuel A; Haak, Henrik; Conrad, Horst; Santambrogio, Gabriele; Meijer, Gerard

    2011-11-14

    Focusing optics for neutral molecules finds application in shaping and steering molecular beams. Here we present an electrostatic elliptical mirror for polar molecules consisting of an array of microstructured gold electrodes deposited on a glass substrate. Alternating positive and negative voltages applied to the electrodes create a repulsive potential for molecules in low-field-seeking states. The equipotential lines are parallel to the substrate surface, which is bent in an elliptical shape. The mirror is characterized by focusing a beam of metastable CO molecules and the results are compared to the outcome of trajectory simulations.

  11. Core-level photoabsorption study of defects and metastable bonding configurations in boron nitride

    Energy Technology Data Exchange (ETDEWEB)

    Jimenez, I.; Jankowski, A.F.; Terminello, L.J. [Lawrence Berkeley National Lab., CA (United States)] [and others

    1997-04-01

    Boron nitride is an interesting material for technological applications and for fundamental solid state physics investigations. It is a compound isoelectronic with carbon and, like carbon can possess sp{sup 2} and sp{sup 3} bonded phases resembling graphite and diamond. BN crystallizes in the sp{sup 2}-bonded hexagonal (h-BN), rhombohedral (r-BN) and turbostratic phases, and in the sp{sup 3}-bonded cubic (c-BN) and wurtzite (w-BN) phases. A new family of materials is obtained when replacing C-C pairs in graphite with isoelectronic B-N pairs, resulting in C{sub 2}BN compounds. Regarding other boron compounds, BN is exceptional in the sense that it has standard two-center bonds with conventional coordination numbers, while other boron compounds (e.g. B{sub 4}C) are based on the boron icosahedron unit with three-center bonds and high coordination numbers. The existence of several allotropic forms and fullerene-like structures for BN suggests a rich variety of local bonding and poses the questions of how this affects the local electronic structure and how the material accommodates the stress induced in the transition regions between different phases. One would expect point defects to play a crucial role in stress accommodation, but these must also have a strong influence in the electronic structure, since the B-N bond is polar and a point defect will thus be a charged structure. The study of point defects in relationship to the electronic structure is of fundamental interest in these materials. Recently, the authors have shown that Near-Edge X-ray Absorption Fine Structure (NEXAFS) is sensitive to point defects in h-BN, and to the formation of metastable phases even in amorphous materials. This is significant since other phase identification techniques like vibrational spectroscopies or x-ray diffraction yield ambiguous results for nanocrystalline and amorphous samples. Serendipitously, NEXAFS also combines chemical selectivity with point defect sensitivity.

  12. Precessing deuteron polarization

    International Nuclear Information System (INIS)

    Sitnik, I.M.; Volkov, V.I.; Kirillov, D.A.; Piskunov, N.M.; Plis, Yu.A.

    2002-01-01

    The feasibility of the acceleration in the Nuclotron of deuterons polarized in the horizontal plane is considered. This horizontal polarization is named precessing polarization. The effects of the main magnetic field and synchrotron oscillations are included. The precessing polarization is supposed to be used in studying the polarization parameters of the elastic dp back-scattering and other experiments

  13. Extraction of DNA from Skeletal Remains.

    Science.gov (United States)

    Edson, Suni M; McMahon, Timothy P

    2016-01-01

    Acquisition of DNA from skeletal remains can be a delicate process. With the advent of improved extraction buffers that provide complete demineralization of the osseous materials, extraction of total genomic DNA from nearly any skeletal element is possible. This chapter describes both traditional organic and more newly developed inorganic extraction methods for fresh and dried skeletal remains.

  14. EDITORIAL MALARIA DIAGNOSIS Malaria remains the most ...

    African Journals Online (AJOL)

    hi-tech

    2005-03-02

    Mar 2, 2005 ... Malaria remains the most significant parasitic disease affecting man. Prompt and accurate diagnosis of malaria is the key to cost effective management (1). Since the identification of Plasmodium parasites in human blood in 1880, the diagnosis of malaria has remained a hot bed of scientific discussion.

  15. Metastable decay of argon clusters after photoionisation at high excess energies

    International Nuclear Information System (INIS)

    Steger, H.; Vries, J. de; Kamke, W.; Hertel, I.V.

    1991-01-01

    Recently Maerk and collaborators reported the metastable emission of large fractions from argon and neon cluster ions after electron impact ionisation at high excess energies. The decay was interpreted as the result of an intra-cluster excitation of a metastable state by one of the electrons involved in the ionisation process. Here we report the first direct observation of such a correlated two electron process during photoionisation of argon clusters using synchrotron radiation and the TPEPICO technique. We observe at least two distinct maxima of the metastable TPEPICO spectrum at around 27 eV and 28.5 eV, the former being consistent with the previously reported energetic threshold for electron impact ionisation. (orig.)

  16. A mathematical model for metastable condition determination in highly flashing liquid flows through expansion devices

    International Nuclear Information System (INIS)

    Angelo, E.; Angelo, G.; Andrade, D.A.

    2012-01-01

    Highlights: ► A mathematical model to determine the metastable flow degree in expansions. ► This model is based on the evaporation wave theory and a pressure jump discontinuity condition. ► The proposed model is not appropriate in cases where is present a low intensity evaporation wave. - Abstract: The determination of the metastability condition in fluid flows through singularities (expansion devices) when flashing occurs is the key to determine the mass flow rate going through devices when there is a great pressure difference between upstream and downstream. An application of the evaporation waves considered together with a maximizing condition for the pressure jump through the wave to determine the metastable state is presented. The model results are compared to several outflows reported in the literature indicating values within engineering standards for those flows in which fluids are highly superheated (highly expanded flashing liquid jets).

  17. High-scale validity of a two-Higgs-doublet scenario: metastability included

    Energy Technology Data Exchange (ETDEWEB)

    Chakrabarty, Nabarun; Mukhopadhyaya, Biswarup [Harish-Chandra Research Institute, Regional Centre for Accelerator-based Particle Physics, Allahabad (India)

    2017-03-15

    We identify regions in a Type-II two-Higgs-doublet model which correspond to a metastable electroweak vacuum with lifetime larger than the age of the universe. We analyse scenarios which retain perturbative unitarity up to grand unification and Planck scales. Each point in the parameter space is restricted using data from the Large Hadron Collider (LHC) as well as flavour and precision electroweak constraints. We find that substantial regions of the parameter space are thus identified as corresponding to metastability, which complement the allowed regions for absolute stability, for top quark mass at the high as well as low end of its currently allowed range. Thus, a two-Higgs-doublet scenario with the electroweak vacuum, either stable or metastable, can sail through all the way up to the Planck scale without facing any contradiction. (orig.)

  18. Stern Gerlach interferometry with metastable argon atoms: an immaterial mask modulating the profile of a supersonic beam

    CERN Document Server

    Viaris De Lesegno, B; Perales, F; Mainos, C; Reinhardt, J; Baudon, J; Grancharova, D; Durt, T; Robert, J; Boustimi, M; Bocvarski, V; Dos Santos, F P; Durt, T; Haberland, H

    2003-01-01

    A new Stern Gerlach interferometer operating with a nozzle beam of metastable argon atoms Ar* (3p sup 5 4s, sup 3 P sub 2) is described. The selection of incoming (polarisation) and outgoing (analysis) Zeeman sublevels is achieved by use of laser induced transitions at two wavelengths, 811.5 nm (closed J 2 -> J = 3 transition) and 801.5 nm (open J = 2 -> J = 2 transition). Linear superpositions of Zeeman sublevels, just beyond the polarizer and just before the analyser, are prepared by means of two zones where Majorana transitions take place. In between, a controlled magnetic field configuration (the phase object) is produced within a triple mu-metal shielding. Standard interference patterns are obtained by scanning the field and detecting the atoms by secondary electron emission from a Faraday cup. When a static radial magnetic gradient is used, the beam profile is modulated by interference. The transverse pattern. which can be translated at will by adding a homogeneous field, is observed for the first time ...

  19. Geomagnetic polarity transitions

    Science.gov (United States)

    Merrill, Ronald T.; McFadden, Phillip L.

    1999-05-01

    reasonable to draw the following conclusions with varying degrees of confidence. There appears to be a substantial decrease in the mean intensity of the dipole field during a transition to ˜25% of its usual value. The duration of an average geomagnetic polarity transition is not well known but probably lies between 1000 and 8000 years. Values outside these bounds have been reported, but we give reasons as to why such outliers are likely to be artifacts. The reversal process is probably longer than the manifestation of the reversal at Earth's surface as recorded in paleomagnetic directional data. Convection hiatus during a geomagnetic polarity transition seems unlikely, and free-decay models for reversals appear to be generally incompatible with the data. This implies that certain theorems in dynamo theory, such as Cowling's theorem, should not be invoked to explain the origin of reversals. Unfortunately, the detailed description of directional changes during transitions remains controversial. Contrary to common belief, certain low-degree nondipole fields can produce significant longitudinal confinement of virtual geomagnetic poles (VGP) during a transition. The data are currently inadequate to refute or verify claims of longitudinal dipole confinement, VGP clustering, or other systematics during polarity transitions.

  20. Molecular Dynamics Simulations and Classical Multidimensional Scaling Unveil New Metastable States in the Conformational Landscape of CDK2.

    Directory of Open Access Journals (Sweden)

    Pasquale Pisani

    Full Text Available Protein kinases are key regulatory nodes in cellular networks and their function has been shown to be intimately coupled with their structural flexibility. However, understanding the key structural mechanisms of large conformational transitions remains a difficult task. CDK2 is a crucial regulator of cell cycle. Its activity is finely tuned by Cyclin E/A and the catalytic segment phosphorylation, whereas its deregulation occurs in many types of cancer. ATP competitive inhibitors have failed to be approved for clinical use due to toxicity issues raised by a lack of selectivity. However, in the last few years type III allosteric inhibitors have emerged as an alternative strategy to selectively modulate CDK2 activity. In this study we have investigated the conformational variability of CDK2. A low dimensional conformational landscape of CDK2 was modeled using classical multidimensional scaling on a set of 255 crystal structures. Microsecond-scale plain and accelerated MD simulations were used to populate this landscape by using an out-of-sample extension of multidimensional scaling. CDK2 was simulated in the apo-form and in complex with the allosteric inhibitor 8-anilino-1-napthalenesulfonic acid (ANS. The apo-CDK2 landscape analysis showed a conformational equilibrium between an Src-like inactive conformation and an active-like form. These two states are separated by different metastable states that share hybrid structural features with both forms of the kinase. In contrast, the CDK2/ANS complex landscape is compatible with a conformational selection picture where the binding of ANS in proximity of the αC helix causes a population shift toward the inactive conformation. Interestingly, the new metastable states could enlarge the pool of candidate structures for the development of selective allosteric CDK2 inhibitors. The method here presented should not be limited to the CDK2 case but could be used to systematically unmask similar mechanisms

  1. Understanding metastable phase transformation during crystallization of RDX, HMX and CL-20: experimental and DFT studies.

    Science.gov (United States)

    Ghosh, Mrinal; Banerjee, Shaibal; Shafeeuulla Khan, Md Abdul; Sikder, Nirmala; Sikder, Arun Kanti

    2016-09-14

    Multiphase growth during crystallization severely affects deliverable output of explosive materials. Appearance and incomplete transformation of metastable phases are a major source of polymorphic impurities. This article presents a methodical and molecular level understanding of the metastable phase transformation mechanism during crystallization of cyclic nitramine explosives, viz. RDX, HMX and CL-20. Instantaneous reverse precipitation yielded metastable γ-HMX and β-CL-20 which undergo solution mediated transformation to the respective thermodynamic forms, β-HMX and ε-CL-20, following 'Ostwald's rule of stages'. However, no metastable phase, anticipated as β-RDX, was evidenced during precipitation of RDX, which rather directly yielded the thermodynamically stable α-phase. The γ→β-HMX and β→ε-CL-20 transformations took 20 and 60 minutes respectively, whereas formation of α-RDX was instantaneous. Density functional calculations were employed to identify the possible transition state conformations and to obtain activation barriers for transformations at wB97XD/6-311++G(d,p)(IEFPCM)//B3LYP/6-311G(d,p) level of theory. The computed activation barriers and lattice energies responsible for transformation of RDX, HMX and CL-20 metastable phases to thermodynamic ones conspicuously supported the experimentally observed order of phase stability. This precise result facilitated an understanding of the occurrence of a relatively more sensitive and less dense β-CL-20 phase in TNT based melt-cast explosive compositions, a persistent and critical problem unanswered in the literature. The crystalline material recovered from such compositions revealed a mixture of β- and ε-CL-20. However, similar compositions of RDX and HMX never showed any metastable phase. The relatively long stability with the highest activation barrier is believed to restrict complete β→ε-CL-20 transformation during processing. Therefore a method is suggested to overcome this issue.

  2. Polare maskuliniteter

    Directory of Open Access Journals (Sweden)

    Marit Anne Hauan

    2012-05-01

    Full Text Available In this paper my aim is to read and understand the journal of Gerrit de Veer from the last journey of William Barents to the Arctic Regions in 1596 and the journal of captain Junge on his hunting trip from Tromsø to Svalbard in 1834.It is nearly 240 years between this to voyages. The first journal is known as the earliest report from the arctic era. Gerrit de Veer adds instructive copper engravings to his text and give us insight in the crews meeting with this new land. Captain Junges journal is found together with his dead crew in a house in a fjord nearby Ny-Ålesund and has no drawings, but word. Both of these journals may be read as sources of the knowledge and understanding of the polar region. They might also unveil the ideas of how to deal with and survive under the challenges that is given. In addition one can ask if the sources can tell us more about how men describe their challenges. Can the way they expressed themselves in the journals give us an understanding of masculinity? And not least help us to create good questions of the change in the ideas of masculinities which is said to follow the change in understanding of the wilderness.

  3. Accelerated Recombination in Cold Dense Plasmas with Metastable Ions due to Resonant Deexcitation

    International Nuclear Information System (INIS)

    Ralchenko, Yu.V.; Maron, M.

    2001-01-01

    In a recombining plasma the metastable states are known to accumulate population thereby slowing down the recombination process. We show that a proper account of the doubly-excited autoionizing states, populated through collisional 3-body recombination of metastable ions, results in a significant acceleration of recombination. 3-body recombination followed by collisional (de)excitations and autoionization effectively produces deexcitation via the following chain of elementary events: A fully time-dependent collisional-radiative (CR) modeling for stripped ions of carbon recombining in a cold dense plasma demonstrates an order of magnitude faster recombination of He-like ions. The CR model used in calculations is discussed in details

  4. Field Induced Magnetic Moments in a Metastable Iron-Mercury Alloy

    DEFF Research Database (Denmark)

    Pedersen, M.S.; Mørup, Steen; Linderoth, Søren

    1996-01-01

    The magnetic properties of a metastable iron-mercury alloy have been investigated in the temperature range from 5 to 200 K by Mossbauer spectroscopy and magnetization measurements. At low temperature the magnetic moment per iron atom is larger than af alpha-Fe. The effective spontaneous magnetic ....... It was found that the field-induced increase of the magnetic moment in the metastable iron-mecury alloy was about 0.06 Bohr magnetons per iron atom in the temperature range from 5 to 200 K for a field change from 6 to 12 T....

  5. Formation of metastable tetragonal zirconia nanoparticles: Competitive influence of the dopants and surface state

    Energy Technology Data Exchange (ETDEWEB)

    Gorban, Oksana, E-mail: matscidep@aim.com [Donetsk Institute for Physics and Engineering named after A.A. Galkin of the NAS of Ukraine, Nauki av. 46, Kyiv 03680 (Ukraine); Synyakina, Susanna; Volkova, Galina; Gorban, Sergey; Konstantiova, Tetyana [Donetsk Institute for Physics and Engineering named after A.A. Galkin of the NAS of Ukraine, Nauki av. 46, Kyiv 03680 (Ukraine); Lyubchik, Svetlana, E-mail: s_lyubchik@yahoo.com [REQUIMTE, Universida de Nova de Lisboa, 2829-516 Caparica (Portugal)

    2015-12-15

    The effect of the surface modification of the nanoparticles of amorphous and crystalline partially stabilized zirconia by fluoride ions on stability of the metastable tetragonal phase was investigated. Based on the DSC, titrimetry and FTIR spectroscopy data it was proven that surface modification of the xerogel resulted from an exchange of the fluoride ions with the basic OH groups. The effect of the powder pre-calcination temperature before modification on the formation of metastable tetragonal phase in partially stabilized zirconia was investigated. It was shown that the main factor of tetragonal zirconia stabilization is the state of nanoparticles surface at pre-crystallization temperatures.

  6. Hydrogen-assisted laser-induced resonant transitions between metastable states of antiprotonic helium atoms

    International Nuclear Information System (INIS)

    Ketzer, B.; Hartmann, F.J.; Egidy, T. von

    1996-11-01

    Laser resonance transitions between normally metastable states of antiprotonic helium atoms were observed making use of state dependent quenching effects caused by small admixtures of H 2 molecules. By selectively shortening the lifetimes of states with higher principal quantum number n as compared to those of lower n, this method for the first time provides access to all initially populated metastable states of p-bar He + atoms. This was demonstrated by observing the transitions (n,l) = (38,l) → (39,l+1), l 35, 36, 37 and (n,l) = (37,l) → (38,l+1), l = 34, 35, 36. (author)

  7. Beam experiments with state selected Ne (3P0, 3P2) metastable atoms

    International Nuclear Information System (INIS)

    Verheijen, M.J.

    1984-01-01

    Metastable rare gas atoms play an important role in all types of plasmas and gas discharges, e.g. in fluorescent lamps and in laser discharges (helium-neon laser or excimer lasers). In this thesis, the metastable states of NeI are studied. First, the theory of excited neon atoms and diatomic molecules is introduced, as well as Penning ionisation. Next, some experimental facilities are described (e.g. the dye laser system). With these instruments, natural lifetime measurements of the 2p fine structure states of NeI are carried out. Results are reported. Finally, total Penning ionisation cross sections are calculated using the optical potential model. (Auth.)

  8. Hydrogen-assisted laser-induced resonant transitions between metastable states of antiprotonic helium atoms

    CERN Document Server

    Ketzer, B; Von Egidy, T; Maierl, C; Pohl, R; Eades, John; Widmann, E; Yamazaki, T; Kumakura, M; Morita, N; Hayano, R S; Hori, Masaki; Ishikawa, T; Torii, H A; Sugai, I; Horváth, D

    1997-01-01

    Laser resonance transitions between normally metastable states of antiprotonic helium atoms were observed making use of state dependent quenching effects caused by small admixtures of \\htwo\\ molecules. By selectively shortening the lifetimes of states with higher principal quantum number $n$ as compared to those of lower $n$, this method for the first time provides access to all initially populated metastable states of \\pbar\\hep\\ atoms. This was demonstrated by observing the transitions $(n,l)=(38,l)\\rightarrow (39,l+1),\\ l=35,36,37$ and $(n,l)=(37,l)\\rightarrow (38,l+1),\\ l=34,35,36$.

  9. Averaging out magnetic forces with fast rf sweeps in an optical trap for metastable chromium atoms

    Science.gov (United States)

    Beaufils, Q.; Chicireanu, R.; Pouderous, A.; de Souza Melo, W.; Laburthe-Tolra, B.; Maréchal, E.; Vernac, L.; Keller, J. C.; Gorceix, O.

    2008-05-01

    We introduce a time-averaged trap in which the internal state of the atoms is rapidly modulated to modify the magnetic trapping potential. In our experiment, fast radio-frequency linear sweeps flip the spins of atoms at a fast rate, which averages out the magnetic forces. We use this procedure to optimize the accumulation of metastable chromium atoms in an optical dipole trap from a magneto-optical trap. The potential experienced by the metastable atoms is identical to the bare optical dipole potential, so that this procedure allows for trapping all magnetic sublevels, hence increasing by up to 80% the final number of accumulated atoms.

  10. Electron-impact excitation out of the metastable levels of Krypton

    International Nuclear Information System (INIS)

    Jung, R.O.; Stone, Tom E.; Boffard, John B.; Anderson, L.W.; Lin, Chun C.

    2005-01-01

    We have measured the electron-impact excitation cross sections out of the two metastable levels of Kr into the ten levels of the 4p 5 5p configuration. For a common 4p 5 5p final level, the peak excitation cross sections out of the two individual 4p 5 5s metastable levels are found to differ by 1 to 2 orders of magnitude. This is explained by the special features of the electronic structure of the two configurations involved. The peak cross sections are 10 to 1600 times larger than the corresponding peak cross sections out of the ground state

  11. BECN2 interacts with ATG14 through a metastable coiled-coil to mediate autophagy: BECN2 CCD Structure and Interaction with ATG14

    Energy Technology Data Exchange (ETDEWEB)

    Su, Minfei; Li, Yue; Wyborny, Shane; Neau, David; Chakravarthy, Srinivas; Levine, Beth; Colbert, Christopher L.; Sinha, Sangita C. (NDSU); (IIT); (Cornell); (UTSMC)

    2017-03-12

    ATG14 binding to BECN/Beclin homologs is essential for autophagy, a critical catabolic homeostasis pathway. Here, we show that the α-helical, coiled-coil domain (CCD) of BECN2, a recently identified mammalian BECN1 paralog, forms an antiparallel, curved homodimer with seven pairs of nonideal packing interactions, while the BECN2 CCD and ATG14 CCD form a parallel, curved heterodimer stabilized by multiple, conserved polar interactions. Compared to BECN1, the BECN2 CCD forms a weaker homodimer, but binds more tightly to the ATG14 CCD. Mutation of nonideal BECN2 interface residues to more ideal pairs improves homodimer self-association and thermal stability. Unlike BECN1, all BECN2 CCD mutants bind ATG14, although more weakly than wild type. Thus, polar BECN2 CCD interface residues result in a metastable homodimer, facilitating dissociation, but enable better interactions with polar ATG14 residues stabilizing the BECN2:ATG14 heterodimer. These structure-based mechanistic differences in BECN1 and BECN2 homodimerization and heterodimerization likely dictate competitive ATG14 recruitment.

  12. Studies on optical pumping cells (OPC) to polarize 3He

    International Nuclear Information System (INIS)

    Hutanu, V.; Rupp, A.

    2004-01-01

    The technique applied at HMI to obtain nuclear-spin-polarized 3 He, used in neutron spin filters (NSFs), is metastability-exchange optical pumping. To prepare efficient NSF, one must highly polarize 3 He nuclei in the optical pumping volume (OPV) and reduce the polarization losses during the compression phase. Great progress has been achieved in reducing of depolarization due to the recent development of both, large polarization preserving piston compressors and long relaxation time filter cells. It is even more important to significantly enhance the 3 He polarization rate during optical pumping in order to increase NSF efficiency. Different cells materials were tested, such as Duran and quartz glass. In order to use the laser light more efficiently and to decrease the risk of 3 He depolarization due to unfavorable reflections, antireflection (AR) coatings were used on cell windows made of quartz glass. They were compared with the ones without coating, made of quartz, Duran and BK7 glass. The comparison of various techniques to mount the windows such as blowing, gluing or molecular diffusion was also conducted. It indicated that the molecular diffusion is the most suitable technique because of a better purity of the gas in the cell and the preservation of the optical flatness of the windows. Cells, for practical reasons each entirely made from the same material (Duran, Quartz glass) with windows mounted using this method, showed the best polarization performance

  13. Persistence of metastable vortex lattice domains in MgB2 in the presence of vortex motion.

    Science.gov (United States)

    Rastovski, C; Schlesinger, K J; Gannon, W J; Dewhurst, C D; DeBeer-Schmitt, L; Zhigadlo, N D; Karpinski, J; Eskildsen, M R

    2013-09-06

    Recently, extensive vortex lattice metastability was reported in MgB2 in connection with a second-order rotational phase transition. However, the mechanism responsible for these well-ordered metastable vortex lattice phases is not well understood. Using small-angle neutron scattering, we studied the vortex lattice in MgB2 as it was driven from a metastable to the ground state through a series of small changes in the applied magnetic field. Our results show that metastable vortex lattice domains persist in the presence of substantial vortex motion and directly demonstrate that the metastability is not due to vortex pinning. Instead, we propose that it is due to the jamming of counterrotated vortex lattice domains which prevents a rotation to the ground state orientation.

  14. A Statistical Study on the Effect of Hydrostatic Pressure on Metastable Pitting Corrosion of X70 Pipeline Steel

    Directory of Open Access Journals (Sweden)

    Zixuan Yang

    2017-11-01

    Full Text Available Hydrostatic pressure effects on pitting initiation and propagation in X70 steel are investigated by evaluating metastable pitting probability using electrochemical methods and immersion corrosion tests in containing chlorine ion solution. Potentiodynamic tests indicated that hydrostatic pressure can decrease the breakdown potential and lead to a reduced transpassivity region. Metastable test results revealed that hydrostatic pressure can increase metastable pitting formation frequency and promote stabilization of metastable pitting growth. Electrochemical impedance spectroscopy (EIS results indicate that Hydrostatic pressure decreases the charge transfer resistance and increases the dissolution rate within the cavities. Corrosion test results also indicated that pitting initiation and propagation are accelerated by hydrostatic pressure. Result validity was verified by evaluating metastable pitting to predict pitting corrosion resistance.

  15. Polarization Observations of the Fermi blazars

    Science.gov (United States)

    Rani, Bindu; S. Jorstad, A. P. Marscher (BU, USA), K. Sokolovsky (IAASARS, Greece), I. Agudo (CSIC, Spain)

    2018-01-01

    Ever since the revolutionary discovery by the Fermi mission that active galactic nuclei (AGN) produce copious amounts of high-energy emission, its origin has remained elusive. Using high-frequency radio interferometry (VLBI) polarization imaging, we could probe the magnetic field topology of the compact high-energy emission regions in blazars. A case study for blazar 3C 279 reveals presence of multiple gamma-ray emission regions. The observed anti-correlation between gamma-ray flux and percentage polarization at optical bands challenges the current high-energy emission models. In addition to the turbulent component responsible for gamma-ray flares, our analysis suggests the presence of a steady polarized component having with its polarization direction aligned along the jet axis. The steady polarized component could possibly be the toroidal component of the helical magnetic field. To better understand the acceleration processes in jets, high-energy polarization missions are of great importance.

  16. Decay of Metastable State with Account of Agglomeration and Relaxation Processes

    Directory of Open Access Journals (Sweden)

    Victor Kurasov

    2016-01-01

    Full Text Available Theoretical description of the metastable phase decay kinetics in the presence of specific connections between the embryos of small sizes has been given. The theory of the decay kinetics in the presence of relaxation processes is constructed in analytical manner. The m-mers nucleation is investigated and the global kinetics of decay is also constructed in this case analytically.

  17. Thermal decay rate of a metastable state with two degrees of ...

    Indian Academy of Sciences (India)

    I I Gontchar

    2017-06-01

    Jun 1, 2017 ... Abstract. Accuracy of the Kramers approximate formula for the thermal decay rate of the metastable state is studied for the two-dimensional potential pocket. This is done by comparing with the quasistationary rate resulting from the dynamical modelling. It is shown that the Kramers rate is in agreement with ...

  18. Quantum mechanical look at the radioactive-like decay of metastable dark energy

    Energy Technology Data Exchange (ETDEWEB)

    Szydlowski, Marek [Jagiellonian University, Astronomical Observatory, Krakow (Poland); Jagiellonian University, Mark Kac Complex Systems Research Centre, Krakow (Poland); Stachowski, Aleksander [Jagiellonian University, Astronomical Observatory, Krakow (Poland); Urbanowski, Krzysztof [University of Zielona Gora, Institute of Physics, Zielona Gora (Poland)

    2017-12-15

    We derive the Shafieloo, Hazra, Sahni and Starobinsky (SHSS) phenomenological formula for the radioactive-like decay of metastable dark energy directly from the principles of quantum mechanics. To this aim we use the Fock-Krylov theory of quantum unstable states. We obtain deeper insight on the decay process as having three basic phases: the phase of radioactive decay, the next phase of damping oscillations, and finally the phase of power-law decay. We consider the cosmological model with matter and dark energy in the form of decaying metastable dark energy and study its dynamics in the framework of non-conservative cosmology with an interacting term determined by the running cosmological parameter. We study the cosmological implications of metastable dark energy and estimate the characteristic time of ending of the radioactive-like decay epoch to be 2.2 x 10{sup 4} of the present age of the Universe. We also confront the model with astronomical data which show that the model is in good agreement with the observations. Our general conclusion is that we are living in the epoch of the radioactive-like decay of metastable dark energy which is a relict of the quantum age of the Universe. (orig.)

  19. Probing metastable Sm2+ and optically stimulated tunnelling emission in YPO4: Ce, Sm

    DEFF Research Database (Denmark)

    Prasad, Amit Kumar; Kook, Myung Ho; Jain, Mayank

    2017-01-01

    optical stimulation. The work presented here adds further details to the energy levels of the metastable Sm2+ defect and the electron transfer processes by undertaking measurements of a) Sm2+ excitation spectrum through the internal 5D0 → 7F2 emission at 7 K, b) relaxation lifetime of Sm2+ (5D0 state...

  20. Metastable states in antiprotonic helium atoms an island stability in a sea of continuum

    CERN Document Server

    Korobov, V I

    2002-01-01

    In this contribution we consider a phenomenon of metastable states in antiprotonic helium atoms, precise spectroscopy of these states and a present-day study of the electromagnetic properties of antiprotons. Calculation of nonrelativistic energies, relativistic and QED corrections as well as the fine and hyperfine structure and the magnetic moment of an antiproton are the main parts of this study. Refs. 22 (nevyjel)

  1. Correction for Metastability in the Quantification of PID in Thin-film Module Testing

    DEFF Research Database (Denmark)

    Hacke, Peter; Spataru, Sergiu; Johnston, Steve

    2017-01-01

    A fundamental change in the analysis for the accelerated stress testing of thin-film modules is proposed, whereby power changes due to metastability and other effects that may occur due to the thermal history are removed from the power measurement that we obtain as a function of the applied stres...

  2. Triple differential cross-sections for the ionization of metastable 2P ...

    Indian Academy of Sciences (India)

    2016-10-06

    Oct 6, 2016 ... Abstract. In this paper, triple differential cross-sections for the ionization of metastable 2P-state hydrogen atoms by 250 eV electron energy with exchange effects for various kinematic conditions are calculated. Multiple scattering theory proposed by Das and Seal in Phys. Rev. A 47, 2978 (1993) is utilized ...

  3. Effect of pinning and driving force on the metastability effects in ...

    Indian Academy of Sciences (India)

    electromagnetic response determine the metastability effects seen in the first and the third harmonic response of the AC susceptibility across the temperature ..... matter, which is different from its obvious role in measuring the shielding response from the macroscopic screening currents induced by its imposition on the ...

  4. Fish remains and humankind: part two

    Directory of Open Access Journals (Sweden)

    Andrew K G Jones

    1998-07-01

    Full Text Available The significance of aquatic resources to past human groups is not adequately reflected in the published literature - a deficiency which is gradually being acknowledged by the archaeological community world-wide. The publication of the following three papers goes some way to redress this problem. Originally presented at an International Council of Archaeozoology (ICAZ Fish Remains Working Group meeting in York, U.K. in 1987, these papers offer clear evidence of the range of interest in ancient fish remains across the world. Further papers from the York meeting were published in Internet Archaeology 3 in 1997.

  5. Theoretical investigation of existence of meta-stability in iron and cobalt clusters

    Science.gov (United States)

    Berry, Habte Dulla; Zhang, Qinfang; Wang, Baolin

    2018-03-01

    Nowadays considerable attention has been given for researches on magnetic properties of transition metal clusters (specifically FeN and CoN). This is because these clusters offer big hopes for the possibility of presenting significant magnetic anisotropy energy which is critical for technological applications. This study intends to find out the causes for the existence of the two states (ground and meta-stable) in Iron and Cobalt clusters. The study also explains the role of valence electrons for the existence of magnetism in the two states by using the concept of ionization potential, electron dipole polarizabilities, chemical hardness and softness of the clusters. Assuming that, when all itinerant electrons are at s-level and also at the d-level (ns = n andns → 0.) the ground state and meta-stable state energies with distinct energy minima are (Egs = l / 2 n +εc n - 2μB hn andEms =εd n - gμB hn) respectively. The findings also showed that polarizability of small cluster of the specified elements are increased compared with the bulk value, which means that there is an effective increase in the cluster radius due to the spilling out of the electronic charge. Furthermore, it is obvious that 4s electrons are more delocalized than the 3d electrons so that they spill out more than the 3d electrons. This leads to the conclusion that 4s electrons are primarily responsible for the enhanced polarizabilities and for shell structure effects. This indicates that polarizability at the meta-stable state is less than that of the ground state i.e. the meta-stable state loses its s electron. Therefore the two minima represent a ground state of configuration 3 d↑5 3 d↓ 2 + δ 4s 2 - δ with energy Egs and meta-stable state of configuration 3 d↑5 3 d↓ 3 + δ 4s 1 - δ with energy Ems for Co clusters and a ground state configuration 3 d↑5 3 d↓ 1 + δ 4s 2 - δ with energy Egs an meta-stable state of configuration 3 d↑5 3 d↓ 2 + δ 4s 1 - δ with energy Ems for

  6. Kadav Moun PSA (:60) (Human Remains)

    Centers for Disease Control (CDC) Podcasts

    2010-02-18

    This is an important public health announcement about safety precautions for those handling human remains. Language: Haitian Creole.  Created: 2/18/2010 by Centers for Disease Control and Prevention (CDC).   Date Released: 2/18/2010.

  7. Essential Qualities of Math Teaching Remain Unknown

    Science.gov (United States)

    Cavanagh, Sean

    2008-01-01

    According to a new federal report, the qualities of an effective mathematics teacher remain frustratingly elusive. The report of the National Mathematics Advisory Panel does not show what college math content and coursework are most essential for teachers. While the report offered numerous conclusions about math curriculum, cognition, and…

  8. Remaining Life Expectancy With and Without Polypharmacy

    DEFF Research Database (Denmark)

    Wastesson, Jonas W; Canudas-Romo, Vladimir; Lindahl-Jacobsen, Rune

    2016-01-01

    OBJECTIVES: To investigate the remaining life expectancy with and without polypharmacy for Swedish women and men aged 65 years and older. DESIGN: Age-specific prevalence of polypharmacy from the nationwide Swedish Prescribed Drug Register (SPDR) combined with life tables from Statistics Sweden...

  9. Juveniles' Motivations for Remaining in Prostitution

    Science.gov (United States)

    Hwang, Shu-Ling; Bedford, Olwen

    2004-01-01

    Qualitative data from in-depth interviews were collected in 1990-1991, 1992, and 2000 with 49 prostituted juveniles remanded to two rehabilitation centers in Taiwan. These data are analyzed to explore Taiwanese prostituted juveniles' feelings about themselves and their work, their motivations for remaining in prostitution, and their difficulties…

  10. Lifetime of the metastable 23S1 state in stored Li+ ions

    International Nuclear Information System (INIS)

    Knight, R.D.

    1979-04-01

    A laser-induced fluorescence technique combined with the observation of spontaneous magnetic dipole photons from the highly metastable 2 3 S 1 state of Li + was used to measure the radiative lifetime of this state. The ions are created by electron impact on a lithium atomic beam and are subsequently stored for periods of many seconds in an RF-quadrupole ion trap. A tunable dye laser excites the 2 3 S--2 3 P, transition at 5485A, and the intercombination electric dipole transition 2 3 P 1 --1 1 S 0 at 202A is observed. This process depletes the metastable population in a time tau/sub d/ 3 S 1 / and provides a measure of the total number of metastables. Comparison with the rate of 210A spontaneously emitted photons yields a measured value for the 2 3 S 1 radiative lifetime of tau/sub rad/ = 58.6 +- 12.9 sec, where the quoted error represents 95% confidence levels. The theoretical lifetime is tau/sub theory/ = 49.0 sec. The measured value includes data taken with both 6 Li + and 7 Li + isotopes and was corrected for the slightly different detector efficiencies at 202A and 210A. A careful study of nonradiative quenching of the metastable state was necessary to understand observed differences between tau/sub rad/ and tau/sub 3 S 1 /, the total metastable lifetime. Spatial density profiles of the ions within the trap, useful for determining the ion temperature, were obtained by scanning the laser beam horizontally across the ion trap while storing 2 3 P 1 -- 1 S 0 photon counts as a function of the laser beam's position. Agreement with a simple equilibrium model, including space charge effects, is satisfactory. A study of the optical pumping process is necessary to understand the laser-ion interaction, and observational and theoretical data are presented. 47 references

  11. Polarized electron sources

    Energy Technology Data Exchange (ETDEWEB)

    Prepost, R. [Univ. of Wisconsin, Madison, WI (United States)

    1994-12-01

    The fundamentals of polarized electron sources are described with particular application to the Stanford Linear Accelerator Center. The SLAC polarized electron source is based on the principle of polarized photoemission from Gallium Arsenide. Recent developments using epitaxially grown, strained Gallium Arsenide cathodes have made it possible to obtain electron polarization significantly in excess of the conventional 50% polarization limit. The basic principles for Gallium and Arsenide polarized photoemitters are reviewed, and the extension of the basic technique to strained cathode structures is described. Results from laboratory measurements of strained photocathodes as well as operational results from the SLAC polarized source are presented.

  12. Forensic dentistry: 1. Identification of human remains.

    Science.gov (United States)

    Pretty, Iain A

    2007-12-01

    For many forensic dentists the identification of found human remains will comprise the majority of their case work. However, there is rarely a typical dental identification. The resilience of teeth and their supporting tissues to peri- and post-mortem assaults provides a wealth of information for those interested in the identity of the deceased. Chemical attack, burning, burial, submersion, and even severe head and neck trauma are all withstood by the dentition to an extent where identification is possible. The lack of a tentative identification or failure to locate dental or similar ante-mortem records is a more common reason for an odontological investigation to fail. The purpose of this review is to describe the techniques employed by forensic dentists to identify human remains and also to provide details of some of the novel developments within this area.

  13. Becoming and remaining homeless: a qualitative investigation.

    Science.gov (United States)

    Morrell-Bellai, T; Goering, P N; Boydell, K M

    2000-09-01

    This article reports the qualitative findings of a multimethod study of the homeless population in Toronto, Canada. The qualitative component sought to identify how people become homeless and why some individuals remain homeless for an extended period of time or cycle in and out of homelessness (the chronically homeless). In-depth, semistructured interviews were conducted with 29 homeless adults. The findings suggest that people both become and remain homeless due to a combination of macro level factors (poverty, lack of employment, low welfare wages, lack of affordable housing) and personal vulnerability (childhood abuse or neglect, mental health symptoms, impoverished support networks, substance abuse). Chronically homeless individuals often reported experiences of severe childhood trauma and tended to attribute their continued homelessness to a substance abuse problem. It is concluded that both macro and individual level factors must be considered in planning programs and services to address the issue of homelessness in Canada.

  14. Explosives remain preferred methods for platform abandonment

    International Nuclear Information System (INIS)

    Pulsipher, A.; Daniel, W. IV; Kiesler, J.E.; Mackey, V. III

    1996-01-01

    Economics and safety concerns indicate that methods involving explosives remain the most practical and cost-effective means for abandoning oil and gas structures in the Gulf of Mexico. A decade has passed since 51 dead sea turtles, many endangered Kemp's Ridleys, washed ashore on the Texas coast shortly after explosives helped remove several offshore platforms. Although no relationship between the explosions and the dead turtles was ever established, in response to widespread public concern, the US Minerals Management Service (MMS) and National Marine Fisheries Service (NMFS) implemented regulations limiting the size and timing of explosive charges. Also, more importantly, they required that operators pay for observers to survey waters surrounding platforms scheduled for removal for 48 hr before any detonations. If observers spot sea turtles or marine mammals within the danger zone, the platform abandonment is delayed until the turtles leave or are removed. However, concern about the effects of explosives on marine life remains

  15. Unified Numerical Solver for Device Metastabilities in CdTe Thin-Film PV

    Energy Technology Data Exchange (ETDEWEB)

    Vasileska, Dragica [Arizona State Univ., Tempe, AZ (United States)

    2017-08-17

    Thin-film modules of all technologies often suffer from performance degradation over time. Some of the performance changes are reversible and some are not, which makes deployment, testing, and energy-yield prediction more challenging. Manufacturers de-vote significant empirical efforts to study these phenomena and to improve semiconduc-tor device stability. Still, understanding the underlying reasons of these instabilities re-mains clouded due to the lack of ability to characterize materials at atomistic levels and the lack of interpretation from the most fundamental material science. The most com-monly alleged causes of metastability in CdTe device, such as “migration of Cu,” have been investigated rigorously over the past fifteen years. Still, the discussion often ended prematurely with stating observed correlations between stress conditions and changes in atomic profiles of impurities or CV doping concentration. Multiple hypotheses sug-gesting degradation of CdTe solar cell devices due to interaction and evolution of point defects and complexes were proposed, and none of them received strong theoretical or experimental confirmation. It should be noted that atomic impurity profiles in CdTe pro-vide very little intelligence on active doping concentrations. The same elements could form different energy states, which could be either donors or acceptors, depending on their position in crystalline lattice. Defects interact with other extrinsic and intrinsic de-fects; for example, changing the state of an impurity from an interstitial donor to a sub-stitutional acceptor often is accompanied by generation of a compensating intrinsic in-terstitial donor defect. Moreover, all defects, intrinsic and extrinsic, interact with the elec-trical potential and free carriers so that charged defects may drift in the electric field and the local electrical potential affects the formation energy of the point defects. Such complexity of interactions in CdTe makes understanding of

  16. Distribution of albatross remains in the Far East regions during the Holocene, based on zooarchaeological remains.

    Science.gov (United States)

    Eda, Masaki; Higuchi, Hiroyoshi

    2004-07-01

    Many albatross remains have been found in the Japanese Islands and the surrounding areas, such as Sakhalin and South Korea. These remains are interesting for two reasons: numerous sites from which albatross remains have been found are located in coastal regions of the Far East where no albatrosses have been distributed recently, and there are some sites in which albatross remains represent a large portion of avian remains, although albatrosses are not easily preyed upon by human beings. We collected data on albatross remains from archaeological sites in the Far East regions during the Holocene and arranged the remains geographically, temporally and in terms of quantity. Based on these results, we showed that coastal areas along the Seas of Okhotsk and Japan have rarely been used by albatrosses in Modern times, though formerly there were many albatrosses. We proposed two explanations for the shrinkage of their distributional range: excessive hunting in the breeding areas, and distributional changes of prey for albatrosses.

  17. Charge transport in non-polar and semi-polar III-V nitride heterostructures

    International Nuclear Information System (INIS)

    Konar, Aniruddha; Verma, Amit; Fang, Tian; Zhao, Pei; Jana, Raj; Jena, Debdeep

    2012-01-01

    Compared to the intense research focus on the optical properties, the transport properties in non-polar and semi-polar III-nitride semiconductors remain relatively unexplored to date. The purpose of this paper is to discuss charge-transport properties in non-polar and semi-polar orientations of GaN in a comparative fashion to what is known for transport in polar orientations. A comprehensive approach is adopted, starting from an investigation of the differences in the electronic bandstructure along different polar orientations of GaN. The polarization fields along various orientations are then discussed, followed by the low-field electron and hole mobilities. A number of scattering mechanisms that are specific to non-polar and semi-polar GaN heterostructures are identified, and their effects are evaluated. Many of these scattering mechanisms originate due to the coupling of polarization with disorder and defects in various incarnations depending on the crystal orientation. The effect of polarization orientation on carrier injection into quantum-well light-emitting diodes is discussed. This paper ends with a discussion of orientation-dependent high-field charge-transport properties including velocity saturation, instabilities and tunneling transport. Possible open problems and opportunities are also discussed. (paper)

  18. X-ray laser implementation by means of a strong source of high-spin metastable atoms

    International Nuclear Information System (INIS)

    Helman, J.S.; Rau, C.; Bunge, C.F.

    1983-01-01

    High-spin metastable atomic beams of high density and extremely small divergence can be produced by electron capture during grazing-angle scattering of ion beams at ferromagnetic surfaces. This can be used to generate a long-lived reservoir of Li 1s2s2p 4 P/sub 5/2//sup ts0/ with enough density of metastables so that after laser-induced transfer to Li 1s2p/sup ts2/P strong lasing at 207 A should occur. This novel technique can also be used to produce a variety of other metastables known as potential candidates for lasing at shorter wavelengths

  19. Shotgun microbial profiling of fossil remains

    DEFF Research Database (Denmark)

    Der Sarkissian, Clio; Ermini, Luca; Jónsson, Hákon

    2014-01-01

    Millions to billions of DNA sequences can now be generated from ancient skeletal remains thanks to the massive throughput of next-generation sequencing platforms. Except in cases of exceptional endogenous DNA preservation, most of the sequences isolated from fossil material do not originate from...... community profiling of the seven specimens revealed site-specific environmental signatures. These microbial communities appear to comprise mainly organisms that colonized the fossils recently. Our approach significantly extends the amount of useful data that can be recovered from ancient specimens using...

  20. Shotgun microbial profiling of fossil remains.

    Science.gov (United States)

    Der Sarkissian, C; Ermini, L; Jónsson, H; Alekseev, A N; Crubezy, E; Shapiro, B; Orlando, L

    2014-04-01

    Millions to billions of DNA sequences can now be generated from ancient skeletal remains thanks to the massive throughput of next-generation sequencing platforms. Except in cases of exceptional endogenous DNA preservation, most of the sequences isolated from fossil material do not originate from the specimen of interest, but instead reflect environmental organisms that colonized the specimen after death. Here, we characterize the microbial diversity recovered from seven c. 200- to 13 000-year-old horse bones collected from northern Siberia. We use a robust, taxonomy-based assignment approach to identify the microorganisms present in ancient DNA extracts and quantify their relative abundance. Our results suggest that molecular preservation niches exist within ancient samples that can potentially be used to characterize the environments from which the remains are recovered. In addition, microbial community profiling of the seven specimens revealed site-specific environmental signatures. These microbial communities appear to comprise mainly organisms that colonized the fossils recently. Our approach significantly extends the amount of useful data that can be recovered from ancient specimens using a shotgun sequencing approach. In future, it may be possible to correlate, for example, the accumulation of postmortem DNA damage with the presence and/or abundance of particular microbes. © 2014 John Wiley & Sons Ltd.

  1. Geographical Income Polarization

    DEFF Research Database (Denmark)

    Azhar, Hussain; Jonassen, Anders Bruun

    inter municipal income inequality. Counter factual simulations show that rising property prices to a large part explain the rise in polarization. One side-effect of polarization is tendencies towards a parallel polarization of residence location patterns, where low skilled individuals tend to live......In this paper we estimate the degree, composition and development of geographical income polarization based on data at the individual and municipal level in Denmark from 1984 to 2002. Rising income polarization is reconfirmed when applying new polarization measures, the driving force being greater...

  2. Some remaining problems in HCDA analysis

    International Nuclear Information System (INIS)

    Chang, Y.W.

    1981-01-01

    The safety assessment and licensing of liquid-metal fast breeder reactors (LMFBRs) requires an analysis on the capability of the reactor primary system to sustain the consequences of a hypothetical core-disruptive accident (HCDA). Although computational methods and computer programs developed for HCDA analyses can predict reasonably well the response of the primary containment system, and follow up the phenomena of HCDA from the start of excursion to the time of dynamic equilibrium in the system, there remain areas in the HCDA analysis that merit further analytical and experimental studies. These are the analysis of fluid impact on reactor cover, three-dimensional analysis, the treatment of the perforated plates, material properties under high strain rates and under high temperatures, the treatment of multifield flows, and the treatment of prestressed concrete reactor vessels. The purpose of this paper is to discuss the structural mechanics of HCDA analysis in these areas where improvements are needed

  3. Political, energy events will remain interwoven

    International Nuclear Information System (INIS)

    Jones, D.P.

    1991-01-01

    This paper reports that it is possible to discuss the significance of political and energy events separately, but, in truth, they are intricately interwoven. Furthermore, there are those who will argue that since the two are inseparable, the future is not predictable; so why bother in the endeavor. It is possible that the central point of the exercise may have been missed-yes, the future is unpredictable exclamation point However, the objective of prediction is secondary. The objective of understanding the dynamic forces of change is primary exclamation point With this view of recent history, it is perhaps appropriate to pause and think about the future of the petroleum industry. The future as shaped by political, energy, economic, environmental and technological forces will direct our lives and markets during this decade. Most importantly, what will be the direction that successful businesses take to remain competitive in a global environment? These are interesting issues worthy of provocative thoughts and innovative ideas

  4. Nuclear remains an economic and ecologic asset

    International Nuclear Information System (INIS)

    Le Ngoc, Boris

    2015-01-01

    The author herein outlines the several benefits of nuclear energy and nuclear industry for France. He first outlines that France possesses 97 per cent of de-carbonated electricity thanks to nuclear energy (77 pc) and renewable energies (20 pc, mainly hydraulic), and that renewable energies must be developed in the building and transport sectors to be able to get rid of the environmentally and financially costly fossil energies. He outlines that reactor maintenance and the nuclear fuel cycle industry are fields of technological leadership for the French nuclear industry which is, after motor industry and aircraft industry, the third industrial sector in France. He indicates that nuclear electricity is to remain the most competitive one, and that nuclear energy and renewable energies must not be opposed to it but considered as complementary in the struggle against climate change, i.e. to reduce greenhouse gas emissions and to get rid of the prevalence of fossil energies

  5. Does hypertension remain after kidney transplantation?

    Directory of Open Access Journals (Sweden)

    Gholamreza Pourmand

    2015-05-01

    Full Text Available Hypertension is a common complication of kidney transplantation with the prevalence of 80%. Studies in adults have shown a high prevalence of hypertension (HTN in the first three months of transplantation while this rate is reduced to 50- 60% at the end of the first year. HTN remains as a major risk factor for cardiovascular diseases, lower graft survival rates and poor function of transplanted kidney in adults and children. In this retrospective study, medical records of 400 kidney transplantation patients of Sina Hospital were evaluated. Patients were followed monthly for the 1st year, every two months in the 2nd year and every three months after that. In this study 244 (61% patients were male. Mean ± SD age of recipients was 39.3 ± 13.8 years. In most patients (40.8% the cause of end-stage renal disease (ESRD was unknown followed by HTN (26.3%. A total of 166 (41.5% patients had been hypertensive before transplantation and 234 (58.5% had normal blood pressure. Among these 234 individuals, 94 (40.2% developed post-transplantation HTN. On the other hand, among 166 pre-transplant hypertensive patients, 86 patients (56.8% remained hypertensive after transplantation. Totally 180 (45% patients had post-transplantation HTN and 220 patients (55% didn't develop HTN. Based on the findings, the incidence of post-transplantation hypertension is high, and kidney transplantation does not lead to remission of hypertension. On the other hand, hypertension is one of the main causes of ESRD. Thus, early screening of hypertension can prevent kidney damage and reduce further problems in renal transplant recipients.

  6. Effect of the subgap conductance on the metastable states in a Josephson tunnel junction

    International Nuclear Information System (INIS)

    Cristiano, R.; Pagano, S.; Silvestrini, P.; Gray, K.E.; Liengme, O.

    1987-09-01

    An investigation of the decay rate of metastable states in Josephson tunnel junctions in presence of thermal noise is presented. We have observed that, in the extremely underdamped regime, there is an exponential temperature dependence of the best fit value for the shunt conductance. Such a dependence shows a close relation with the temperature dependence of the subgap conductance, suggesting that the effective conductance for the escape from the metastable states obeys to a quasi-particle thermal activation mechanism. The introduction of this effective conductance into the lifetime expression for the zero-voltage states leads to significant changes in the width of the switching current distributions. A comparisons of the experimental data with the proposed model is reported. 7 refs., 2 figs

  7. Improving of wear resistance of alloys with metastable austenite structure in abrasion wearing

    International Nuclear Information System (INIS)

    Popov, V.S.; Brykov, N.N.; Pugachev, G.A.

    1979-01-01

    The effect of grain composition of abrasive masses upon the wear resistance of alloys having a metastable austenitic structure is studied. The investigations have been carried out on Kh12F1 steel, using diffraction and hardness measurements and the metallographic analysis. Experimental data indicate that the specific wear of the stable alloys increases substantially with the size of abrasive particles. As regards the metastable alloys, the increase in the size of the abrasive grains has little effect upon the specific wear, as the increasing abradability of the grains is compensated for by the strengthening of the rubbing surfaces, this resulting from the ability of the metal surface layer to underao structure transformations in the course of wear

  8. Bixbyite-type V2O3--a metastable polymorph of vanadium sesquioxide.

    Science.gov (United States)

    Weber, D; Stork, A; Nakhal, S; Wessel, C; Reimann, C; Hermes, W; Müller, A; Ressler, T; Pöttgen, R; Bredow, T; Dronskowski, R; Lerch, M

    2011-07-18

    A metastable polymorph of vanadium sesquioxide was prepared by the reaction of vanadium trifluoride with a water-saturated gaseous mixture of 10 vol % hydrogen in argon. The new polymorph crystallizes in the bixbyite-type structure. At temperatures around 823 K a transformation to the well-known corundum-type phase is observed. Quantum-chemical calculations show that the bixbyite-type structure is about 9 kJ/mol less stable than the known corundum-based one. This result, in combination with the absence of imaginary modes in the phonon density of states, supports the classification of the bixbyite-type phase as a metastable V(2)O(3) polymorph. At ~50 K a paramagnetic to canted antiferromagnetic transition is detected.

  9. Model reduction for slow-fast stochastic systems with metastable behaviour.

    Science.gov (United States)

    Bruna, Maria; Chapman, S Jonathan; Smith, Matthew J

    2014-05-07

    The quasi-steady-state approximation (or stochastic averaging principle) is a useful tool in the study of multiscale stochastic systems, giving a practical method by which to reduce the number of degrees of freedom in a model. The method is extended here to slow-fast systems in which the fast variables exhibit metastable behaviour. The key parameter that determines the form of the reduced model is the ratio of the timescale for the switching of the fast variables between metastable states to the timescale for the evolution of the slow variables. The method is illustrated with two examples: one from biochemistry (a fast-species-mediated chemical switch coupled to a slower varying species), and one from ecology (a predator-prey system). Numerical simulations of each model reduction are compared with those of the full system.

  10. Photo-crystallography: from the structure towards the electron density of metastable states

    Energy Technology Data Exchange (ETDEWEB)

    Legrand, V [Laboratoire de Cristallographie et de Modelisation des Materiaux Mineraux et Biologiques, CNRS UMR 7036, UHP Nancy 1, Faculte des sciences, Boulevard des Aiguillettes, BP 239, 54506 Vandoeuvre-les-Nancy Cedex (France); Carbonera, C [Institut de Chimie de la Matiere Condensee de Bordeaux, UPR CNRS 9048, Universite de Bordeaux 1, Groupe de Sciences Moleculaires, 87 Avenue du Docteur Schweitzer, 33608 Pessac cedex (France); Pillet, S [Laboratoire de Cristallographie et de Modelisation des Materiaux Mineraux et Biologiques, CNRS UMR 7036, UHP Nancy 1, Faculte des sciences, Boulevard des Aiguillettes, BP 239, 54506 Vandoeuvre-les-Nancy Cedex (France); Souhassou, M [Laboratoire de Cristallographie et de Modelisation des Materiaux Mineraux et Biologiques, CNRS UMR 7036, UHP Nancy 1, Faculte des sciences, Boulevard des Aiguillettes, BP 239, 54506 Vandoeuvre-les-Nancy Cedex (France); Letard, J F [Institut de Chimie de la Matiere Condensee de Bordeaux, UPR CNRS 9048, Universite de Bordeaux 1, Groupe de Sciences Moleculaires, 87 Avenue du Docteur Schweitzer, 33608 Pessac cedex (France); Guionneau, P [Institut de Chimie de la Matiere Condensee de Bordeaux, UPR CNRS 9048, Universite de Bordeaux 1, Groupe de Sciences Moleculaires, 87 Avenue du Docteur Schweitzer, 33608 Pessac cedex (France); Lecomte, C [Laboratoire de Cristallographie et de Modelisation des Materiaux Mineraux et Biologiques, CNRS UMR 7036, UHP Nancy 1, Faculte des sciences, Boulevard des Aiguillettes, BP 239, 54506 Vandoeuvre-les-Nancy Cedex (France)

    2005-01-01

    A photo-crystallographic study of Fe(btr){sub 2}(NCS){sub 2}{center_dot}H{sub 2}O was performed in order to describe the modification of structures and charge densities on going from the ground low spin (LS) state to the metastable high spin (HS) state during the LIESST phenomenon at 15 K. Related photo-magnetic and spectroscopic measurements are also described. We show that at 15 K, the thermally quenched and photo-induced structures of the metastable HS state are identical. For comparison, we also derived the structure of the HS and LS states at 130 K in the hysteresis loop; the thermal spin transition and the LIESST spin transition exhibit similar structural behaviours.

  11. A novel series of isoreticular metal organic frameworks: Realizing metastable structures by liquid phase epitaxy

    KAUST Repository

    Liu, Jinxuan

    2012-12-04

    A novel class of metal organic frameworks (MOFs) has been synthesized from Cu-acetate and dicarboxylic acids using liquid phase epitaxy. The SURMOF-2 isoreticular series exhibits P4 symmetry, for the longest linker a channel-size of 3 3 nm2 is obtained, one of the largest values reported for any MOF so far. High quality, ab-initio electronic structure calculations confirm the stability of a regular packing of (Cu++) 2-carboxylate paddle-wheel planes with P4 symmetry and reveal, that the SURMOF-2 structures are in fact metastable, with a fairly large activation barrier for the transition to the bulk MOF-2 structures exhibiting a lower, twofold (P2 or C2) symmetry. The theoretical calculations also allow identifying the mechanism for the low-temperature epitaxial growth process and to explain, why a synthesis of this highly interesting, new class of high-symmetry, metastable MOFs is not possible using the conventional solvothermal process.

  12. High-frequency magneto-impedance in metastable metallic materials: An overview

    International Nuclear Information System (INIS)

    Vinai, F.; Coisson, M.; Tiberto, P.

    2006-01-01

    The giant magneto-impedance effect (GMI) is a common feature of a wide class of metastable ferromagnetic alloys. This effect can be enhanced by submitting the as-prepared materials to suitable thermal treatments. Recently, a remarkably high magneto-impedance response has been observed in the GHz region for several systems. The increase in miniaturization of telecommunication devices dramatically increases the working frequencies; as a consequence, the interest in studying magneto-impedance effect leads to microwave region. In this paper, analogies and differences among the magneto-transport effect observed in ferromagnetic metastable alloys will be highlighted and discussed from the experimental point of view in a wide range of frequencies

  13. Rare quantum metastable states in the strongly dispersive Jaynes-Cummings oscillator

    OpenAIRE

    Mavrogordatos, Th; Barratt, F; Asari, U; Szafulski, P; Ginossar, Eran; Szymanska, M

    2018-01-01

    We present evidence of metastable rare quantum- uctuation switching for the driven dissipative Jaynes-Cummings (JC) oscillator coupled to a zero-temperature bath in the strongly dispersive regime. We show that single-atom complex amplitude bistability is accompanied by the appearance of a low-amplitude long-lived transient state, hereinafter called `dark state', having a distribution with quasi-Poissonian statistics both for the coupled qubit and cavity mode. We find that the ...

  14. Texture evolution in thin-sheets on AISI 301 metastable stainless steel under dynamic loading

    Energy Technology Data Exchange (ETDEWEB)

    Kim, K.Y. [Posco Steels, Pohan, South Korea (Korea, Republic of); Kozaczek, K. [Oak Ridge National Lab., TN (United States); Kulkarni, S.M. [TRW Vehicle Safety Systems, Mesa, AZ (United States); Bastias, P.C.; Hahn, G.T. [Vanderbilt Univ., Nashville, TN (United States)

    1995-05-08

    The evolution of texture in thin sheets of metastable austenitic stainless steel AISI 301 is affected by external conditions such as loading rate and temperature, by inhomogeneous deformation phenomena such as twinning and shear band formation, and by the concurent strain induced phase transformation of the retained austenitc ({gamma}) into martensite ({alpha}). The present paper describes texture measurements on different gauges of AISI 301 prior and after uniaxial stretching under different conditions.

  15. Current status of free radicals and electronically excited metastable species as high energy propellants

    Science.gov (United States)

    Rosen, G.

    1973-01-01

    A survey is presented of free radicals and electronically excited metastable species as high energy propellants for rocket engines. Nascent or atomic forms of diatomic gases are considered free radicals as well as the highly reactive diatomic triatomic molecules that posess unpaired electrons. Manufacturing and storage problems are described, and a review of current experimental work related to the manufacture of atomic hydrogen propellants is presented.

  16. Formation and metastable decomposition of unprotonated ammonia cluster ions upon femtosecond ionization

    International Nuclear Information System (INIS)

    Buzza, S.A.; Wei, S.; Purnell, J.; Castleman, A.W. Jr.

    1995-01-01

    The formation and metastable dissociation mechanism of unprotonated ammonia cluster ions, (NH 3 ) + n , produced by multiphoton ionization (MPI) at 624 nm and a nominal pulse width of 350 fs, are investigated through a reflectron time-of-flight (TOF) mass spectrometric technique. Detection of the unprotonated ions after femtosecond and nanosecond multiphoton ionization under various intensity conditions is explained. The role of the energy of the ionizing photons, and the observation of these ions after femtosecond MPI is examined. The formation of the unprotonated series is found to be a function of intensity in the case of ionization on the nanosecond time scale, but not so for the femtosecond time domain. The results can be explained in terms of ionization mechanisms and ionizing pulse durations. The findings of the present study suggest that the unprotonated ions are trapped behind the barrier to intracluster proton transfer and/or concomitant NH 2 loss. The studies of metastable decomposition also reveal that the unprotonated ammonia cluster ions dissociate in the field-free region of the TOF by losing an NH 2 radical rather than via the evaporative loss of NH 3 as occurs for protonated clusters. Additionally, isotopic investigations of the unimolecular decay reveal a strong dependence on the conditions of cluster formation. The cluster formation condition dependence of the unimolecular decay is further investigated by altering formation temperatures and observing the consequences reflected by changes in the spontaneous metastable decay rate constant. This is a unique example of a cluster system whose metastable dissociation does not obey an evaporative ensemble model

  17. A metastable equilibrium model for the relative abundances of microbial phyla in a hot spring.

    Directory of Open Access Journals (Sweden)

    Jeffrey M Dick

    Full Text Available Many studies link the compositions of microbial communities to their environments, but the energetics of organism-specific biomass synthesis as a function of geochemical variables have rarely been assessed. We describe a thermodynamic model that integrates geochemical and metagenomic data for biofilms sampled at five sites along a thermal and chemical gradient in the outflow channel of the hot spring known as "Bison Pool" in Yellowstone National Park. The relative abundances of major phyla in individual communities sampled along the outflow channel are modeled by computing metastable equilibrium among model proteins with amino acid compositions derived from metagenomic sequences. Geochemical conditions are represented by temperature and activities of basis species, including pH and oxidation-reduction potential quantified as the activity of dissolved hydrogen. By adjusting the activity of hydrogen, the model can be tuned to closely approximate the relative abundances of the phyla observed in the community profiles generated from BLAST assignments. The findings reveal an inverse relationship between the energy demand to form the proteins at equal thermodynamic activities and the abundance of phyla in the community. The distance from metastable equilibrium of the communities, assessed using an equation derived from energetic considerations that is also consistent with the information-theoretic entropy change, decreases along the outflow channel. Specific divergences from metastable equilibrium, such as an underprediction of the relative abundances of phototrophic organisms at lower temperatures, can be explained by considering additional sources of energy and/or differences in growth efficiency. Although the metabolisms used by many members of these communities are driven by chemical disequilibria, the results support the possibility that higher-level patterns of chemotrophic microbial ecosystems are shaped by metastable equilibrium states that

  18. Production of Ar and Xe metastables in rare gas mixtures in a dielectric barrier discharge

    Science.gov (United States)

    Mikheyev, Pavel A.; Han, Jiande; Clark, Amanda; Sanderson, Carl; Heaven, Michael C.

    2017-12-01

    Optically pumped all-rare-gas lasers (OPRGL) utilize metastable atoms of the heavier rare gases as lasing species. The required number density of metastables for efficient laser operation is 1012–1013 cm‑3 in He buffer gas at pressures in the 400–1000 Torr range. Such metastable densities are easily produced in a nanosecond pulsed discharge, even at pressures larger than atmospheric, but problems appear when one is trying to achieve continuous production. The reason for low production efficiency in many types of continuous discharge at atmospheric pressure is the low value of the E/N parameter (<5–6 Td). In the present work, we have examined the possibility of using a dielectric barrier discharge (DBD) to provide near continuous, high densities of Ar and Xe metastables. Experiments were performed using a 20 kHz DBD in binary Ar and Xe mixtures with He, and in ternary Ar:Xe:He mixtures at pressures up to 1 atmosphere. Concentrations were measured by means of tunable diode laser absorption spectroscopy. Time-averaged [Ar(1s5)] and [Xe(1s5)] number densities on the order of 1012 cm‑3 were readily achieved. The temporal behavior of [Xe(1s5)] throughout the DBD cycle was observed. The results demonstrate the feasibility of using DBDs for OPRGL development. Spectral scans over the absorption lines were also used to examine the pressure broadening coefficients for the 912.3 nm Ar line in He and the Xe 904.5 nm line in Ne and He.

  19. Characterization of strain-induced martensitic transformation in a metastable austenitic stainless steel

    International Nuclear Information System (INIS)

    Hausild, P.; Davydov, V.; Drahokoupil, J.; Landa, M.; Pilvin, P.

    2010-01-01

    Kinetics of deformation-induced martensitic transformation in metastable austenitic steel AISI 301 was characterized by several techniques including classical light metallography, scanning electron microscopy, X-ray diffraction, neutron diffraction and electron back scattered diffraction. In situ monitoring of magnetic properties, acoustic emission and temperature increase during tensile tests at different strain rates was also performed. Results obtained by different methods are compared and discussed.

  20. Accelerated Metastable Solid-liquid Interdiffusion Bonding with High Thermal Stability and Power Handling

    Science.gov (United States)

    Huang, Ting-Chia; Smet, Vanessa; Kawamoto, Satomi; Pulugurtha, Markondeya R.; Tummala, Rao R.

    2018-01-01

    Emerging high-performance systems are driving the need for advanced packaging solutions such as 3-D integrated circuits (ICs) and 2.5-D system integration with increasing performance and reliability requirements for off-chip interconnections. Solid-liquid interdiffusion (SLID) bonding resulting in all-intermetallic joints has been proposed to extend the applicability of solders, but faces fundamental and manufacturing challenges hindering its wide adoption. This paper introduces a Cu-Sn SLID interconnection technology, aiming at stabilization of the microstructure in the Cu6Sn5 metastable phase rather than the usual stable Cu3Sn phase. This enables formation of a void-free interface yielding higher mechanical strength than standard SLID bonding, as well as significantly reducing the transition time. The metastable SLID technology retains the benefits of standard SLID with superior I/O pitch scalability, thermal stability and current handling capability, while advancing assembly manufacturability. In the proposed concept, the interfacial reaction is controlled by introducing Ni(P) diffusion barrier layers, designed to effectively isolate the metastable Cu6Sn5 phase preventing any further transformation. Theoretical diffusion and kinetic models were applied to design the Ni-Cu-Sn interconnection stack to achieve the targeted joint composition. A daisy chain test vehicle was used to demonstrate this technology as a first proof of concept. Full transition to Cu6Sn5 was successfully achieved within a minute at 260°C as confirmed by scanning electron microscope (SEM) and x-ray energy dispersive spectroscopy (XEDS) analysis. The joint composition was stable through 10× reflow, with outstanding bond strength averaging 90 MPa. The metastable SLID interconnections also showed excellent electromigration performance, surviving 500 h of current stressing at 105 A/cm2 at 150°C.

  1. Melting in Two-Dimensional Lennard-Jones Systems: Observation of a Metastable Hexatic Phase

    International Nuclear Information System (INIS)

    Chen, K.; Kaplan, T.; Mostoller, M.

    1995-01-01

    Large scale molecular dynamics simulations of two-dimensional melting have been carried out using a recently revised Parrinello-Rahman scheme on massively parallel supercomputers. A metastable state is observed between the solid and liquid phases in Lennard-Jones systems of 36 864 and 102 400 atoms. This intermediate state shows the characteristics of the hexatic phase predicted by the theory of Kosterlitz, Thouless, Halperin, Nelson, and Young

  2. Properties of the triplet metastable states of the alkaline-earth-metal atoms

    International Nuclear Information System (INIS)

    Mitroy, J.; Bromley, M.W.J.

    2004-01-01

    The static and dynamic properties of the alkaline-earth-metal atoms in their metastable state are computed in a configuration interaction approach with a semiempirical model potential for the core. Among the properties determined are the scalar and tensor polarizabilities, the quadrupole moment, some of the oscillator strengths, and the dispersion coefficients of the van der Waals interaction. A simple method for including the effect of the core on the dispersion parameters is described

  3. A Metastable Equilibrium Model for the Relative Abundances of Microbial Phyla in a Hot Spring

    Science.gov (United States)

    Dick, Jeffrey M.; Shock, Everett L.

    2013-01-01

    Many studies link the compositions of microbial communities to their environments, but the energetics of organism-specific biomass synthesis as a function of geochemical variables have rarely been assessed. We describe a thermodynamic model that integrates geochemical and metagenomic data for biofilms sampled at five sites along a thermal and chemical gradient in the outflow channel of the hot spring known as “Bison Pool” in Yellowstone National Park. The relative abundances of major phyla in individual communities sampled along the outflow channel are modeled by computing metastable equilibrium among model proteins with amino acid compositions derived from metagenomic sequences. Geochemical conditions are represented by temperature and activities of basis species, including pH and oxidation-reduction potential quantified as the activity of dissolved hydrogen. By adjusting the activity of hydrogen, the model can be tuned to closely approximate the relative abundances of the phyla observed in the community profiles generated from BLAST assignments. The findings reveal an inverse relationship between the energy demand to form the proteins at equal thermodynamic activities and the abundance of phyla in the community. The distance from metastable equilibrium of the communities, assessed using an equation derived from energetic considerations that is also consistent with the information-theoretic entropy change, decreases along the outflow channel. Specific divergences from metastable equilibrium, such as an underprediction of the relative abundances of phototrophic organisms at lower temperatures, can be explained by considering additional sources of energy and/or differences in growth efficiency. Although the metabolisms used by many members of these communities are driven by chemical disequilibria, the results support the possibility that higher-level patterns of chemotrophic microbial ecosystems are shaped by metastable equilibrium states that depend on both the

  4. Photoinduced metastability and degradation of poly[methyl(phenyl)silylene] as seen by thermoluminescence

    Czech Academy of Sciences Publication Activity Database

    Kadashchuk, A.; Nešpůrek, Stanislav; Ostapenko, N.; Skryshevskii, Yu.; Zaika, V.

    2001-01-01

    Roč. 35, special issue (2001), s. 413-428 ISSN 1058-725X R&D Projects: GA AV ČR IAA1050901; GA MŠk OC 518.10; GA AV ČR KSK4050111 Institutional research plan: CEZ:AV0Z4050913 Keywords : metastability * degradation * poly[methyl(phenyl)silylene] Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 0.457, year: 2001

  5. Crystallographic Stability of Metastable Phase Formed by Containerless Processing in REFeO3 (RE: Rare-Earth Element)

    Science.gov (United States)

    Kuribayashi, Kazuhiko; Kumar, M. S. Vijaya

    2012-01-01

    Undercooling a melt often facilitates a metastable phase to nucleate preferentially. Although the classical nucleation theory shows that the most critical factor for forming a metastable phase is the interface free energy, the crystallographic stability is also indispensable for the phase to be frozen at ambient temperature. In compound materials such as oxides, authors have suggested that the decisive factors for forming a critical nucleus are not only the free energy difference but also the difference of the entropy of fusion between stable and metastable phases. In the present study, using REFeO3 (RE: rare-earth element) as a model material, we investigate the formation of a metastable phase from undercooled melts with respect to the competitive nucleation and crystallographical stabilities of both phases.

  6. Polarized Light Corridor Demonstrations.

    Science.gov (United States)

    Davies, G. R.

    1990-01-01

    Eleven demonstrations of light polarization are presented. Each includes a brief description of the apparatus and the effect demonstrated. Illustrated are strain patterns, reflection, scattering, the Faraday Effect, interference, double refraction, the polarizing microscope, and optical activity. (CW)

  7. Off-shell M5 brane, perturbed Seiberg-Witten theory, and metastable vacua

    International Nuclear Information System (INIS)

    Marsano, Joseph; Papadodimas, Kyriakos; Shigemori, Masaki

    2008-01-01

    We demonstrate that, in an appropriate limit, the off-shell M5-brane worldvolume action effectively captures the scalar potential of Seiberg-Witten theory perturbed by a small superpotential and, consequently, any nonsupersymmetric vacua that it describes. This happens in a similar manner to the emergence from M5's of the scalar potential describing certain type IIB flux configurations [J. Marsano, K. Papadodimas, M. Shigemori, Nonsupersymmetric brane/antibrane configurations in type IIA and M theory, Nucl. Phys. B 789 (2008) 294, (arXiv: 0705.0983 [hep-th])]. We then construct exact nonholomorphic M5 configurations in the special case of SU(2) Seiberg-Witten theory deformed by a degree six superpotential which correspond to the recently discovered metastable vacua of Ooguri, Ookouchi, Park [H. Ooguri, Y. Ookouchi, C.S. Park, Metastable vacua in perturbed Seiberg-Witten theories, (arXiv: 0704.3613 [hep-th])], and Pastras [G. Pastras, Non-supersymmetric metastable vacua in N=2 SYM softly broken to N=1, (arXiv: 0705.0505 [hep-th])]. These solutions take the approximate form of a holomorphic Seiberg-Witten geometry with harmonic embedding along a transverse direction and allow us to obtain geometric intuition for local stability of the gauge theory vacua. As usual, dynamical processes in the gauge theory, such as the decay of nonsupersymmetric vacua, take on a different character in the M5 description which, due to issues of boundary conditions, typically involves runaway behavior in MQCD

  8. An automatic method for the determination of saturation curve and metastable zone width of lysine monohydrochloride

    Science.gov (United States)

    Rabesiaka, Mihasina; Porte, Catherine; Bonnin-Paris, Johanne; Havet, Jean-Louis

    2011-10-01

    An essential tool in the study of crystallization is the saturation curve and metastable zone width, since the shape of the solubility curve defines the crystallization mode and the supersaturation conditions, which are the driving force of crystallization. The purpose of this work was to determine saturation and supersaturation curves of lysine monohydrochloride by an automatic method based on the turbidity of the crystallization medium. As lysine solution is colored, the interest of turbidimetry is demonstrated. An automated installation and the procedure to determine several points on the saturation curve and metastable zone width were set up in the laboratory. On-line follow-up of the solution turbidity and temperature enabled the dissolution and nucleation temperatures of the crystals to be determined by measuring attenuation of the light beam by suspended particles. The thermal regulation system was programmed so that the heating rate took into account the system inertia, i.e. duration related to the dissolution rate of the compound. Using this automatic method, the saturation curve and the metastable zone width of lysine monohydrochloride were plotted.

  9. Mass spectrometry of solid samples in open air using combined laser ionization and ambient metastable ionization

    International Nuclear Information System (INIS)

    He, X.N.; Xie, Z.Q.; Gao, Y.; Hu, W.; Guo, L.B.; Jiang, L.; Lu, Y.F.

    2012-01-01

    Mass spectrometry of solid samples in open air was carried out using combined laser ionization and metastable ionization time-of-flight mass spectrometry (LI-MI-TOFMS) in ambient environment for qualitative and semiquantitative (relative analyte information, not absolute information) analysis. Ambient metastable ionization using a direct analysis in realtime (DART) ion source was combined with laser ionization time-of-flight mass spectrometry (LI-TOFMS) to study the effects of combining metastable and laser ionization. A series of metallic samples from the National Institute of Standards and Technology (NIST 494, 495, 498, 499, and 500) and a pure carbon target were characterized using LI-TOFMS in open air. LI-MI-TOFMS was found to be superior to laser-induced breakdown spectroscopy (LIBS). Laser pulse energies between 10 and 200 mJ at the second harmonic (532 nm) of an Nd:YAG laser were applied in the experiment to obtain a high degree of ionization in plasmas. Higher laser pulse energy improves signal intensities of trace elements (such as Fe, Cr, Mn, Ni, Ca, Al, and Ag). Data were analyzed by numerically calculating relative sensitivity coefficients (RSCs) and limit of detections (LODs) from mass spectrometry (MS) and LIBS spectra. Different parameters, such as boiling point, ionization potential, RSC, LOD, and atomic weight, were shown to analyze the ionization and MS detection processes in open air.

  10. A comparison of binding energy and metastable zone width for adipic acid with various additives

    Science.gov (United States)

    Myerson, Allan S.; Jang, Shyh M.

    1995-12-01

    The binding energy of nine alkanoic acids to the major crystal faces of adipic acid were calculated employing molecular modelling techniques. The results indicate that the alkanoic acids bind strongly to the surface when compared to solvents and to adipic acid itself indicating that the alkanoic acids could be potential growth and nucleation inhibitors. The binding energies were found to increase with increasing carbon number to C 14 to decrease from C 14 to C 16 and then to increase again. The effect of the alkanoic acids on the metastable zone width of adipic acid in ethanol solution were measured employing a differential scanning calorimeter. The results showed that each of the nine alkanoic acids increased the metastable zone width. The metastable zone widths were found to increase with increasing carbon number to C 14 to decrease from C 14 to C 16 and to then increase again thus correlating well with the results obtained from binding energies. These results indicate that binding energy calculations appear to provide a valid method to screen impurities as potential nucleation inhibitors.

  11. Shear response of grain boundaries with metastable structures by molecular dynamics simulations

    Science.gov (United States)

    Zhang, Liang; Lu, Cheng; Shibuta, Yasushi

    2018-04-01

    Grain boundaries (GBs) can play a role as the favored locations to annihilate point defects, such as interstitial atoms and vacancies. It is thus highly probable that different boundary structures can be simultaneously present in equilibrium with each other in the same GB, and thus the GB achieves a metastable state. However, the structural transition and deformation mechanism of such GBs are currently not well understood. In this work, molecular dynamics simulations were carried out to study the multiple structures of a Σ5(310)/[001] GB in bicrystal Al and to investigate the effect of structural multiplicity on the mechanical and kinetic properties of such a GB. Different GB structures were obtained by changing the starting atomic configuration of the bicrystal model, and the GB structures had significantly different atomic density. For the Σ5(310) GB with metastable structures, GB sliding was the dominant mechanism at a low temperature (T = 10 K) under shear stress. The sliding mechanism resulted from the uncoordinated transformation of the inhomogeneous structural units. The nucleation of voids was observed during GB sliding at the low temperature, and the voids subsequently evolved to a nanocrack at the boundary plane. Increasing the temperature can induce the structural transition of local GB structures and can change their overall kinetic properties. GB migration with occasional GB sliding dominated the deformation mechanism at elevated temperatures (T = 300 and 600 K), and the migration process of the metastable GB structures is closely related to the thermally assisted diffusion mechanism.

  12. Phase transformation of metastable cubic γ-phase in U-Mo alloys

    International Nuclear Information System (INIS)

    Sinha, V.P.; Hegde, P.V.; Prasad, G.J.; Dey, G.K.; Kamath, H.S.

    2010-01-01

    Over the past decade considerable efforts have been put by many fuel designers to develop low enriched uranium (LEU 235 ) base U-Mo alloy as a potential fuel for core conversion of existing research and test reactors which are running on high enriched uranium (HEU > 85%U 235 ) fuel and also for the upcoming new reactors. U-Mo alloy with minimum 8 wt% molybdenum shows excellent metastability with cubic γ-phase in cast condition. However, it is important to characterize the decomposition behaviour of metastable cubic γ-uranium in its equilibrium products for in reactor fuel performance point of view. The present paper describes the phase transformation behaviour of cubic γ-uranium phase in U-Mo alloys with three different molybdenum compositions (i.e. 8 wt%, 9 wt% and 10 wt%). U-Mo alloys were prepared in an induction melting furnace and characterized by X-ray diffraction (XRD) method for phase determination. Microstructures were developed for samples in as cast condition. The alloys were hot rolled in cubic γ-phase to break the cast structure and then they were aged at 500 o C for 68 h and 240 h, so that metastable cubic γ-uranium will undergo eutectoid decomposition to form equilibrium phases of orthorhombic α-uranium and body centered tetragonal U 2 Mo intermetallic compound. U-Mo alloy samples with different ageing history were then characterized by XRD for phase and development of microstructure.

  13. Lifetimes of metastable levels of singly ionized titanium: theory and experiment

    International Nuclear Information System (INIS)

    Palmeri, P; Quinet, P; Biemont, E; Gurell, J; Lundin, P; Royen, P; Mannervik, S; Norlin, L-O; Blagoev, K

    2008-01-01

    This paper presents new theoretical lifetimes of metastable levels in singly ionized titanium, Ti II. Along with the lifetimes, transition probabilities for several decay channels from these metastable levels are presented. The calculations are supported by experimental lifetime determinations of the 3d 3 b 2 D 5/2 and 3d 2 ( 3 P)4s b 2 P 3/2 levels along with revised values of the previously published lifetimes of the 3d 2 ( 3 P)4s b 4 P 5/2 and 3d 2 ( 3 P)4s b 2 P 1/2 levels originating partly from a reanalysis utilizing a recently developed method applied on the previously recorded data and partly from new measurements. The presented theoretical investigation of lifetimes of metastable levels in Ti II shows that the HFR calculations are in general compatible with measurements performed using the ion storage ring CRYRING of Stockholm University. The transition probabilities of forbidden lines derived from the new lifetime values will be useful for the diagnostics of low density laboratory or astrophysical plasmas, particularly those encountered in the strontium filament found in the ejecta of η Carinae

  14. SMART POINT CLOUD: DEFINITION AND REMAINING CHALLENGES

    Directory of Open Access Journals (Sweden)

    F. Poux

    2016-10-01

    Full Text Available Dealing with coloured point cloud acquired from terrestrial laser scanner, this paper identifies remaining challenges for a new data structure: the smart point cloud. This concept arises with the statement that massive and discretized spatial information from active remote sensing technology is often underused due to data mining limitations. The generalisation of point cloud data associated with the heterogeneity and temporality of such datasets is the main issue regarding structure, segmentation, classification, and interaction for an immediate understanding. We propose to use both point cloud properties and human knowledge through machine learning to rapidly extract pertinent information, using user-centered information (smart data rather than raw data. A review of feature detection, machine learning frameworks and database systems indexed both for mining queries and data visualisation is studied. Based on existing approaches, we propose a new 3-block flexible framework around device expertise, analytic expertise and domain base reflexion. This contribution serves as the first step for the realisation of a comprehensive smart point cloud data structure.

  15. Smart Point Cloud: Definition and Remaining Challenges

    Science.gov (United States)

    Poux, F.; Hallot, P.; Neuville, R.; Billen, R.

    2016-10-01

    Dealing with coloured point cloud acquired from terrestrial laser scanner, this paper identifies remaining challenges for a new data structure: the smart point cloud. This concept arises with the statement that massive and discretized spatial information from active remote sensing technology is often underused due to data mining limitations. The generalisation of point cloud data associated with the heterogeneity and temporality of such datasets is the main issue regarding structure, segmentation, classification, and interaction for an immediate understanding. We propose to use both point cloud properties and human knowledge through machine learning to rapidly extract pertinent information, using user-centered information (smart data) rather than raw data. A review of feature detection, machine learning frameworks and database systems indexed both for mining queries and data visualisation is studied. Based on existing approaches, we propose a new 3-block flexible framework around device expertise, analytic expertise and domain base reflexion. This contribution serves as the first step for the realisation of a comprehensive smart point cloud data structure.

  16. The Human Remains from HMS Pandora

    Directory of Open Access Journals (Sweden)

    D.P. Steptoe

    2002-04-01

    Full Text Available In 1977 the wreck of HMS Pandora (the ship that was sent to re-capture the Bounty mutineers was discovered off the north coast of Queensland. Since 1983, the Queensland Museum Maritime Archaeology section has carried out systematic excavation of the wreck. During the years 1986 and 1995-1998, more than 200 human bone and bone fragments were recovered. Osteological investigation revealed that this material represented three males. Their ages were estimated at approximately 17 +/-2 years, 22 +/-3 years and 28 +/-4 years, with statures of 168 +/-4cm, 167 +/-4cm, and 166cm +/-3cm respectively. All three individuals were probably Caucasian, although precise determination of ethnicity was not possible. In addition to poor dental hygiene, signs of chronic diseases suggestive of rickets and syphilis were observed. Evidence of spina bifida was seen on one of the skeletons, as were other skeletal anomalies. Various taphonomic processes affecting the remains were also observed and described. Compact bone was observed under the scanning electron microscope and found to be structurally coherent. Profiles of the three skeletons were compared with historical information about the 35 men lost with the ship, but no precise identification could be made. The investigation did not reveal the cause of death. Further research, such as DNA analysis, is being carried out at the time of publication.

  17. Polarized Moessbauer transitions

    International Nuclear Information System (INIS)

    Barb, D.

    1975-01-01

    Theoretical aspects of the emission, absorption and scattering of polarized gamma rays are reviewed for a general case of combined magnetic and electric hyperfine interactions; various possibilities of obtaining polarized gamma sources are described and examples are given of the applications of Moessbauer spectroscopy with polarized gamma rays in solving problems of solid state physics. (A.K.)

  18. What remains of the Arrow oil?

    International Nuclear Information System (INIS)

    Sergy, G.; Owens, E.

    1993-01-01

    In February 1970, the tanker Arrow became grounded 6.5 km off the north shore of Chedabucto Bay, Nova Scotia, and nearly 72,000 bbl of Bunker C fuel oil were released from the vessel during its subsequent breakup and sinking. The oil was washed ashore in various degrees over an estimated 305 km of the bay's 604-km shoreline, of which only 48 km were cleaned. In addition, the tanker Kurdistan broke in two in pack ice in March 1979 in the Cabot Strait area, spilling ca 54,000 bbl of Bunker C, some of which was later found at 16 locations along the northeast and east shorelines of Chedabucto Bay. In summer 1992, a systematic ground survey of the bay's shorelines was conducted using Environment Canada Shoreline Cleanup Assessment Team (SCAT) procedures. Standard observations were made of oil distribution and width, thickness, and character of the oil residues in 419 coastal segments. Results from the survey are summarized. Oil was found to be present on 13.3 km of the shoreline, with heavy oiling restricted to 1.3 km primarily in the areas of Black Duck Cove and Lennox Passage. Some of this residual oil was identified as coming from the Arrow. Natural weathering processes account for removal of most of the spilled oil from the bay. Oil remaining on the shore was found in areas outside of the zone of physical wave action, in areas of nearshore mixing where fine sediments are not present to weather the oil through biophysical processes, or in crusts formed by oil weathered on the surface. The systematic description of oiled shorelines using the SCAT methodology proved very successful, even for such an old spill. 6 refs

  19. Ghost Remains After Black Hole Eruption

    Science.gov (United States)

    2009-05-01

    NASA's Chandra X-ray Observatory has found a cosmic "ghost" lurking around a distant supermassive black hole. This is the first detection of such a high-energy apparition, and scientists think it is evidence of a huge eruption produced by the black hole. This discovery presents astronomers with a valuable opportunity to observe phenomena that occurred when the Universe was very young. The X-ray ghost, so-called because a diffuse X-ray source has remained after other radiation from the outburst has died away, is in the Chandra Deep Field-North, one of the deepest X-ray images ever taken. The source, a.k.a. HDF 130, is over 10 billion light years away and existed at a time 3 billion years after the Big Bang, when galaxies and black holes were forming at a high rate. "We'd seen this fuzzy object a few years ago, but didn't realize until now that we were seeing a ghost", said Andy Fabian of the Cambridge University in the United Kingdom. "It's not out there to haunt us, rather it's telling us something - in this case what was happening in this galaxy billions of year ago." Fabian and colleagues think the X-ray glow from HDF 130 is evidence for a powerful outburst from its central black hole in the form of jets of energetic particles traveling at almost the speed of light. When the eruption was ongoing, it produced prodigious amounts of radio and X-radiation, but after several million years, the radio signal faded from view as the electrons radiated away their energy. HDF 130 Chandra X-ray Image of HDF 130 However, less energetic electrons can still produce X-rays by interacting with the pervasive sea of photons remaining from the Big Bang - the cosmic background radiation. Collisions between these electrons and the background photons can impart enough energy to the photons to boost them into the X-ray energy band. This process produces an extended X-ray source that lasts for another 30 million years or so. "This ghost tells us about the black hole's eruption long after

  20. The Physics of Polarization

    Science.gov (United States)

    Landi Degl'Innocenti, Egidio

    2015-10-01

    The introductory lecture that has been delivered at this Symposium is a condensed version of an extended course held by the author at the XII Canary Island Winter School from November 13 to November 21, 2000. The full series of lectures can be found in Landi Degl'Innocenti (2002). The original reference is organized in 20 Sections that are here itemized: 1. Introduction, 2. Description of polarized radiation, 3. Polarization and optical devices: Jones calculus and Muller matrices, 4. The Fresnel equations, 5. Dichroism and anomalous dispersion, 6. Polarization in everyday life, 7. Polarization due to radiating charges, 8. The linear antenna, 9. Thomson scattering, 10. Rayleigh scattering, 11. A digression on Mie scattering, 12. Bremsstrahlung radiation, 13. Cyclotron radiation, 14. Synchrotron radiation, 15. Polarization in spectral lines, 16. Density matrix and atomic polarization, 17. Radiative transfer and statistical equilibrium equations, 18. The amplification condition in polarized radiative transfer, and 19. Coupling radiative transfer and statistical equilibrium equations.

  1. Self-organization in the localised failure regime: metastable attractors and their implications on force chain functionality

    Science.gov (United States)

    Pucilowski, Sebastian; Tordesillas, Antoinette; Froyland, Gary

    2017-06-01

    In transitive metastable chaotic dynamical systems, there are no invariant neighbourhoods in the phase space. The best that one can do is look for metastable or almost-invariant (AI) regions as a means to decompose the system into its basic self-organising building blocks. Here we study the metastable dynamics of a dense granular material embodying strain localization in 3D from the perspective of its conformational landscape: the state space of all observed conformations as defined by the local topology of individual grains relative to their first ring of contacting neighbors. We determine the metastable AI sets that divide this conformational landscape, such that grain rearrangements from one conformation to another conformation in the same AI set occurs with high probability: by contrast, grain rearrangements involving conformational transitions between AI sets are unlikely. The great majority of conformational transitions are identity transitions: grains rearrange and exchange contacts to preserve those topological properties with the greatest influence on cluster stability, namely, the number of contacts and 3-cycles. Force chains show a clear preference for that AI set with the most number of accessible and highly connected conformations. Here force chains continually explore the conformational landscape, wandering from one rarely inhabited conformation to another. As force chains become overloaded and buckle, the energy released enables member grains to overcome the high dynamical barriers that separate metastable regions and subsequently escape one region to enter another in the conformational landscape. Thus, compared to grains locked in stable force chains, those in buckling force chains, confined to the shear band, show a greater propensity for not only non-identity transitions within each metastable region but also inter-transitions between metastable regions.

  2. Coherent and non coherent atom optics experiment with an ultra-narrow beam of metastable rare gas atoms; Experiences d'optique atomique coherente ou non avec un jet superfin d'atomes metastables de gaz rares

    Energy Technology Data Exchange (ETDEWEB)

    Grucker, J

    2007-12-15

    In this thesis, we present a new type of atomic source: an ultra-narrow beam of metastable atoms produced by resonant metastability exchange inside a supersonic beam of rare gas atoms. We used the coherence properties of this beam to observe the diffraction of metastable helium, argon and neon atoms by a nano-transmission grating and by micro-reflection-gratings. Then, we evidenced transitions between Zeeman sublevels of neon metastable {sup 3}P{sub 2} state due to the quadrupolar part of Van der Waals potential. After we showed experimental proofs of the observation of this phenomenon, we calculated the transition probabilities in the Landau - Zener model. We discussed the interest of Van der Waals - Zeeman transitions for atom interferometry. Last, we described the Zeeman cooling of the supersonic metastable argon beam ({sup 3}P{sub 2}). We have succeeded in slowing down atoms to speeds below 100 m/s. We gave experimental details and showed the first time-of-flight measurements of slowed atoms.

  3. [Review] Polarization and Polarimetry

    Science.gov (United States)

    Trippe, Sascha

    2014-02-01

    Polarization is a basic property of light and is fundamentally linked to the internal geometry of a source of radiation. Polarimetry complements photometric, spectroscopic, and imaging analyses of sources of radiation and has made possible multiple astrophysical discoveries. In this article I review (i) the physical basics of polarization: electromagnetic waves, photons, and parameterizations; (ii) astrophysical sources of polarization: scattering, synchrotron radiation, active media, and the Zeeman, Goldreich-Kylafis, and Hanle effects, as well as interactions between polarization and matter (like birefringence, Faraday rotation, or the Chandrasekhar-Fermi effect); (iii) observational methodology: on-sky geometry, influence of atmosphere and instrumental polarization, polarization statistics, and observational techniques for radio, optical, and X/γ wavelengths; and (iv) science cases for astronomical polarimetry: solar and stellar physics, planetary system bodies, interstellar matter, astrobiology, astronomical masers, pulsars, galactic magnetic fields, gamma-ray bursts, active galactic nuclei, and cosmic microwave background radiation.

  4. Glassy and Metastable Crystalline BaTi2O5 by Containerless Processing

    Science.gov (United States)

    Yoda, Shinichi; Kentei Yu, Yu; Kumar, Vijaya; Kameko, Masashi

    Many efforts have been devoted to forming bulk glass from the melt of ferroelectric crystalline materials without adding any network-forming oxides such as SiO2 due to the potential for producing transparent glass ceramics with high dielectric constant and enhanced piezoelectric, pyroelectric and electro-optic use. The containerless processing is an attractive synthesis tech-nique as it can prevent melt contamination, minimize heterogeneous nucleation, and allow melt to achieve deep undercooling for forming metastable and glassy materials. We have fabricated a new ferroelectric materiel BaTi2 O5 [1] as bulk glass from melt by us-ing containerless processing and studied the phase relationship between microstructure and ferroelectric properties of BaTi2 O5 [2]. The structures of glassy and metastable crystalline BaTi2 O5 fabricated by the containerless pro-cessing were comprehensively investigated by combined X-ray and neutron diffractions, XANES analyses and computer simulations [3]. The 3-dimensional atomic structure of glassy BaTi2 O5 (g-BaTi2 O5 ), simulated by Reverse Monte Carlo (RMC) modelling on diffraction data, shows that extremely distorted TiO5 polyhedra interconnected with both corner-and edge-shared oxy-gen, formed a higher packing density structure than that of conventional silicate glass linked with only corner-sharing of SiO4 polyhedra. In addition, XANES measurement reveales that five-coordinated TiO5 polyhedra were formable in the crystallized metastable a-and b-BaTi2 O5 phases. The structure of metastable b-BaTi2 O5 was solved by ab initio calculation, and refined by Rietveld refinement as group Pnma with unit lattices a = 10.23784 ˚, b = 3.92715 ˚, c A A = 10.92757 A ˚. Our results show that the glass-forming ability enhanced by containerless pro-cessing, not by `strong glass former', fabricated new bulk oxide glasses with peculiar structures and properties. The intermediate-range structure of g-BaTi2 O5 and the crystalline structure of

  5. Polarization feedback laser stabilization

    Science.gov (United States)

    Esherick, P.; Owyoung, A.

    1987-09-28

    A system for locking two Nd:YAG laser oscillators includes an optical path for feeding the output of one laser into the other with different polarizations. Elliptical polarization is incorporated into the optical path so that the change in polarization that occurs when the frequencies coincide may be detected to provide a feedback signal to control one laser relative to the other. 4 figs.

  6. Polarization in Sagittarius A*

    OpenAIRE

    Bower, Geoffrey C.

    2000-01-01

    We summarize the current state of polarization observations of Sagittarius A*, the compact radio source and supermassive black hole candidate in the Galactic Center. These observations are providing new tools for understanding accretion disks, jets and their environments. Linear polarization observations have shown that Sgr A* is unpolarized at frequencies as high as 86 GHz. However, recent single-dish observations indicate that Sgr A* may have strong linear polarization at frequencies higher...

  7. Recombination and detachment in oxygen discharges: the role of metastable oxygen molecules

    International Nuclear Information System (INIS)

    Gudmundsson, J T

    2004-01-01

    A global (volume averaged) model of oxygen discharges is used to study the transition from a recombination dominated discharge to a detachment dominated discharge. The model includes the metastable oxygen molecules O 2 (a 1 Δ g ) and O 2 (b 1 Σ g + ) and the three Herzberg states O 2 (A 3 Σ u + , A' 3 Δ u , c 1 Σ u - ). Dissociative attachment of the oxygen molecule in the ground state O 2 ( 3 Σ g - ) and the metastable oxygen molecule O 2 (a 1 Δ g ) are the dominating channels for creation of the negative oxygen ion O - . At high pressures, dissociative attachment of the Herzberg states contributes significantly to the creation of the negative oxygen ion, O - . The detachment by a collision of the metastable oxygen molecule O 2 (b 1 Σ g + ) with the oxygen ion, O - , is a significant loss process for the O - at pressures above 10 mTorr. Its contribution to the loss is more significant at a lower applied power, but at the higher pressures it is always significant. Detachment by collision with O( 3 P) is also an important loss mechanism for O - . We find that ion-ion recombination is the dominating loss process for negative ions in oxygen discharges at low pressures and calculate the critical pressure where the contributions of recombination reactions and detachment reactions are equal. This critical pressure depends on the applied power, increases with applied power and is in the range 5-14 mTorr in the pressure and power range investigated

  8. Metastable high-entropy dual-phase alloys overcome the strength-ductility trade-off.

    Science.gov (United States)

    Li, Zhiming; Pradeep, Konda Gokuldoss; Deng, Yun; Raabe, Dierk; Tasan, Cemal Cem

    2016-06-09

    Metals have been mankind's most essential materials for thousands of years; however, their use is affected by ecological and economical concerns. Alloys with higher strength and ductility could alleviate some of these concerns by reducing weight and improving energy efficiency. However, most metallurgical mechanisms for increasing strength lead to ductility loss, an effect referred to as the strength-ductility trade-off. Here we present a metastability-engineering strategy in which we design nanostructured, bulk high-entropy alloys with multiple compositionally equivalent high-entropy phases. High-entropy alloys were originally proposed to benefit from phase stabilization through entropy maximization. Yet here, motivated by recent work that relaxes the strict restrictions on high-entropy alloy compositions by demonstrating the weakness of this connection, the concept is overturned. We decrease phase stability to achieve two key benefits: interface hardening due to a dual-phase microstructure (resulting from reduced thermal stability of the high-temperature phase); and transformation-induced hardening (resulting from the reduced mechanical stability of the room-temperature phase). This combines the best of two worlds: extensive hardening due to the decreased phase stability known from advanced steels and massive solid-solution strengthening of high-entropy alloys. In our transformation-induced plasticity-assisted, dual-phase high-entropy alloy (TRIP-DP-HEA), these two contributions lead respectively to enhanced trans-grain and inter-grain slip resistance, and hence, increased strength. Moreover, the increased strain hardening capacity that is enabled by dislocation hardening of the stable phase and transformation-induced hardening of the metastable phase produces increased ductility. This combined increase in strength and ductility distinguishes the TRIP-DP-HEA alloy from other recently developed structural materials. This metastability-engineering strategy should

  9. Airborne Laser Polarization Sensor

    Science.gov (United States)

    Kalshoven, James, Jr.; Dabney, Philip

    1991-01-01

    Instrument measures polarization characteristics of Earth at three wavelengths. Airborne Laser Polarization Sensor (ALPS) measures optical polarization characteristics of land surface. Designed to be flown at altitudes of approximately 300 m to minimize any polarizing or depolarizing effects of intervening atmosphere and to look along nadir to minimize any effects depending on look angle. Data from measurements used in conjunction with data from ground surveys and aircraft-mounted video recorders to refine mathematical models used in interpretation of higher-altitude polarimetric measurements of reflected sunlight.

  10. Polarization at SLC

    International Nuclear Information System (INIS)

    Swartz, M.L.

    1988-07-01

    The SLAC Linear Collider has been designed to readily accommodate polarized electron beams. Considerable effort has been made to implement a polarized source, a spin rotation system, and a system to monitor the beam polarization. Nearly all major components have been fabricated. At the current time, several source and polarimeter components have been installed. The installation and commissioning of the entire system will take place during available machine shutdown periods as the commissioning of SLC progresses. It is expected that a beam polarization of 45% will be achieved with no loss in luminosity. 13 refs., 15 figs

  11. Metastable liquids

    CERN Document Server

    Balibar, S

    2003-01-01

    How far can one supercool a liquid before it crystallizes? How much can one stretch it before cavitation occurs? In order to answer such questions, we have studied liquid helium, a model system. In this review, we show the limitations of the elementary 'standard nucleation theory'. We then show that the existence of 'spinodal' limits needs to be considered in the framework of 'density functional' methods. We also briefly consider the possibility of nucleation by quantum tunnelling. The main emphasis is on cavitation and crystallization in liquid helium, but we also mention several connections with more classical systems, in particular water.

  12. Investigation into the production of metastable Nb3Ge powder via the rotating electrode process

    International Nuclear Information System (INIS)

    McCormick, J.P.

    1977-12-01

    The production of metastable Nb 3 Ge powder via the rotating electrode process (REP) employing ''splat cooling'' was investigated. An electrode capable of withstanding the thermal shock of the electric arc used in REP was produced through powder metallurgy techniques. The effect of various parameters involved in the rotating electrode process was studied in correlation with process control and crystal structure, microstructure and compositional analyses of the powder produced. Superconducting transition temperature measurements were made on the powder both as-produced and after annealing experiments

  13. The effect of metastability in the process of fatigue of an austenitic stainless steel

    International Nuclear Information System (INIS)

    Pacheco, D.J.

    1977-01-01

    The influence of martensitic phase transformation on the process of pulsating tensile stress is studied in a metastable type AISI 316 stainless steel in the temperature range from 25 to -196 0 C. Annealed as well as previously deformed specimens are tested for the typical microstructural characteristics. It is concluded that the fatigue limit as well as the crack mechanisms depend upon the nature of the slip of crystalographic planes. The martensitic transformation previously induced by plastic deformation shows an undesirable fatigue character, in the annealed state and tested at 25 0 C, the type 316 steel will need a plastic deformation equal to or slightly above 9% for pulsating tension fracture [pt

  14. Metastable Magnesium fluorescence spectroscopy using a frequency-stabilized 517 nm laser

    DEFF Research Database (Denmark)

    He, Ming; Jensen, Brian B; Therkildsen, Kasper T

    2009-01-01

    We present a laser operating at 517 nm for our Magnesium laser-cooling and atomic clock project. A two-stage Yb-doped fiber amplifier (YDFA) system generates more than 1.5 W of 1034 nm light when seeded with a 15 mW diode laser. Using a periodically poled lithium niobate (PPLN) waveguide, we...... obtained more than 40 mW of 517 nm output power by single pass frequency doubling. In addition, fluorescence spectroscopy of metastable magnesium atoms could be used to stabilize the 517 nm laser to an absolute frequency within 1 MHz....

  15. Metastable decoherence-free subspaces and electromagnetically induced transparency in interacting many-body systems

    DEFF Research Database (Denmark)

    Macieszczak, Katarzyna; Zhou, Yanli; Hofferberth, Sebastian

    2017-01-01

    We investigate the dynamics of a generic interacting many-body system under conditions of electromagnetically induced transparency (EIT). This problem is of current relevance due to its connection to nonlinear optical media realized by Rydberg atoms. In an interacting system the structure...... of the dynamics and the approach to the stationary state becomes far more complex than in the case of conventional EIT. In particular, we discuss the emergence of a metastable decoherence-free subspace, whose dimension for a single Rydberg excitation grows linearly in the number of atoms. On approach...

  16. Investigation of strain-induced martensitic transformation in metastable austenite using nanoindentation

    International Nuclear Information System (INIS)

    Ahn, T.-H.; Oh, C.-S.; Kim, D.H.; Oh, K.H.; Bei, H.; George, E.P.; Han, H.N.

    2010-01-01

    Strain-induced martensitic transformation of metastable austenite was investigated by nanoindentation of individual austenite grains in multi-phase steel. A cross-section prepared through one of these indented regions using focused ion beam milling was examined by transmission electron microscopy. The presence of martensite underneath the indent indicates that the pop-ins observed on the load-displacement curve during nanoindentation correspond to the onset of strain-induced martensitic transformation. The pop-ins can be understood as resulting from the selection of a favorable martensite variant during nanoindentation.

  17. Investigation of Strain-Induced Martensitic Transformation in Metastable Austenite using Nanoindentation

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, T.-H. [Seoul National University; Oh, C.-S. [Korean Institute of Materials Science; Kim, D. H. [Seoul National University; Oh, K. H. [Seoul National University; Bei, Hongbin [ORNL; George, Easo P [ORNL; Han, H. N. [Seoul National University

    2010-01-01

    Strain-induced martensitic transformation of metastable austenite was investigated by nanoindentation of individual austenite grains in multi-phase steel. A cross-section prepared through one of these indented regions using focused ion beam milling was examined by transmission electron microscopy. The presence of martensite underneath the indent indicates that the pop-ins observed on the load-displacement curve during nanoindentation correspond to the onset of strain-induced martensitic transformation. The pop-ins can be understood as resulting from the selection of a favorable martensite variant during nanoindentation.

  18. Improvement of metastable crystal of acetaminophen via control of crystal growth rate

    Science.gov (United States)

    Nii, Kosuke; Maruyama, Mihoko; Okada, Shino; Adachi, Hiroaki; Takano, Kazufumi; Murakami, Satoshi; Yoshikawa, Hiroshi Y.; Matsumura, Hiroyoshi; Inoue, Tsuyoshi; Imanishi, Masayuki; Tsukamoto, Katsuo; Yoshimura, Masashi; Mori, Yusuke

    2018-03-01

    We showed a relationship among the growth rate, defect generation process, and stability of the metastable phase form II crystal of acetaminophen. Appropriate control of the form II crystal growth rate via slow cooling and nanosize crystal seeding not only suppressed the defect formation but improved the crystallinity of form II. The boundary condition between the interfacial control and transport control was determined based on the relationship between the crystal growth rate and supersaturation. The nanosize crystal seeds met the conditions of interfacial control; thus, the serious defects were suppressed. Finally, better temporal stability of the form II crystal was achieved.

  19. Self-diffusion coefficients of the metastable Lennard-Jones vapor

    Energy Technology Data Exchange (ETDEWEB)

    Nie Chu; Zhou Youhua [School of Physics and Information Engineering, Jianghan University, Wuhan 430056 (China); Marlow, W H; Hassan, Y A [Department of Nuclear Engineering, Texas A and M University, College Station, TX 77843 (United States)], E-mail: yhzhou@jhun.edu.cn

    2008-10-15

    Self-diffusion coefficients of a metastable Lennard-Jones vapor were obtained using the memory function formalism and the frequency moments of the velocity autocorrelation function at reduced temperatures from 0.75 to 1.0. The radial density distribution functions used to evaluate the second, fourth and sixth frequency moments of the velocity autocorrelation function were obtained from the restricted canonical ensemble Monte Carlo simulation (Corti and Debenedetti 1994 Chem. Eng. Sci. 49 2717). The self-diffusion coefficients at reduced temperature 0.75 do not vary monotonically as the density increases, and for the other three temperatures the self-diffusion coefficients vary normally.

  20. Quenching of metastable antiprotonic helium atoms in collisions with deuterium molecules

    CERN Document Server

    Juhász, B; Hayano, R S; Hori, Masaki; Horváth, D; Ishikawa, T; Sakaguchi, J; Torii, H A; Widmann, E; Yamaguchi, H; Yamazaki, T

    2002-01-01

    Quenching of metastable antiprotonic helium atoms in collisions with deuterium molecules has been studied using laser spectroscopy at CERN's new Antiproton Decelerator facility. The quenching cross- sections of the states (n, l)=(39, 36), (39, 37), and (39, 38) were determined from the decay rates of the states which were observed using the "deuterium-assisted inverse resonance" (DAIR) method. The results. revealed a similar (n, l)-dependence of the quenching cross- sections as in the case of hydrogen but the values were smaller by a factor of ~1.5. (27 refs).

  1. Structure and properties of the metastable bacteriocin Lcn972 from Lactococcus lactis

    Science.gov (United States)

    Turner, David L.; Lamosa, Pedro; Rodríguez, Ana; Martínez, Beatriz

    2013-01-01

    Lactococcus lactis subsp. lactis IPLA 972 produces a polypeptide bacteriocin of 7.5 kDa which has a bactericidal effect on sensitive lactococci, inhibiting septum formation in dividing cells. The active form is a monomer that is metastable under normal conditions but is stabilised by glycerol. The NMR structure of Lcn972 shows a β-sandwich comprising two three-stranded antiparallel β-sheets. Detaching the final strand could allow the sandwich to open, and the irreversible unfolding leads to a loss of antibacterial activity. Covalent linkage of the final strand should increase the stability of Lcn972 and facilitate the study of its interaction with lipid II.

  2. Solid-state characterization of paracetamol metastable polymorphs formed in binary mixtures with hydroxypropylmethylcellulose

    Energy Technology Data Exchange (ETDEWEB)

    Rossi, Alessandra; Savioli, Alessandra; Bini, Marcella; Capsoni, Doretta; Massarotti, Vincenzo; Bettini, Ruggero; Gazzaniga, Andrea; Sangalli, Maria Edvige; Giordano, Ferdinando

    2003-11-28

    Two metastable polymorphs of paracetamol (forms II and III) were prepared by appropriate thermal methods from binary mixtures containing 10% (w/w) of hydroxypropylmethylcellulose. By controlling the reheating step, it was possible to address the recrystallization of the drug either into form II or III. Moreover, it was observed that form III transforms either into form II or I depending on the preparation method. The physical characterization of the polymorphs was performed by means of micro-Fourier transform infrared spectroscopy (MFTIR) and powder X-ray diffractometry (PXRD), both temperature controlled.

  3. Stable and metastable equilibrium states of the Zr-O system

    International Nuclear Information System (INIS)

    Versaci, R.A.; Abriata, J.P.; Garces, J.; Comision Nacional de Energia Atomica, San Carlos de Bariloche

    1987-01-01

    The precise knowledge of the phase diagrams is of fundamental importance for the comprehension of processes like soldering and thermal treatment. The Zr-O diagram has been widely studied, mainly in the zone corresponding to ZrO 2 . A critical analysis of the existing information about this diagram is presented. Furthermore, a lot of information about the phase equilibrium, metastable phase, crystal structure, thermodynamic properties and a possible diagram for pressures higher than one atmosphere is presented. (M.E.L.) [es

  4. Influence of relaxation processes on the evaluation of the metastable defect density in Cu(In,Ga)Se{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Maciaszek, M.; Zabierowski, P. [Faculty of Physics, Warsaw University of Technology, Koszykowa 75, Warszawa 00 662 (Poland)

    2016-06-07

    In this contribution, we investigated by means of numerical simulations the influence of relaxation processes related to metastable defects on electrical characteristics of Cu(In,Ga)Se{sub 2}. In particular, we analyzed the relaxation of a metastable state induced by illumination at a fixed temperature as well as the dependence of the hole concentration on the temperature during cooling. The knowledge of these two relaxation processes is crucial in the evaluation of the hole concentration in the relaxed state and after light soaking. We have shown that the distribution of the metastable defects can be considered frozen below 200 K. The hole capture cross section was estimated as ∼3 × 10{sup −15} cm{sup 2}. It was shown that the usually used cooling rates may lead to relevant changes of the hole concentration. We calculated the lower limit of the hole concentration after cooling, and we presented how it depends on densities of shallow acceptors and metastable defects. Moreover, we proposed a method which allows for the evaluation of shallow acceptor and metastable defect densities from two capacitance-voltage profiles measured in the relaxed and light soaking states. Finally, we indicated experimental conditions in which the influence of relaxation processes on the accuracy of this method is the smallest.

  5. Coherent and non coherent atom optics experiment with an ultra-narrow beam of metastable rare gas atoms

    International Nuclear Information System (INIS)

    Grucker, J.

    2007-12-01

    In this thesis, we present a new type of atomic source: an ultra-narrow beam of metastable atoms produced by resonant metastability exchange inside a supersonic beam of rare gas atoms. We used the coherence properties of this beam to observe the diffraction of metastable helium, argon and neon atoms by a nano-transmission grating and by micro-reflection-gratings. Then, we evidenced transitions between Zeeman sublevels of neon metastable 3 P 2 state due to the quadrupolar part of Van der Waals potential. After we showed experimental proofs of the observation of this phenomenon, we calculated the transition probabilities in the Landau - Zener model. We discussed the interest of Van der Waals - Zeeman transitions for atom interferometry. Last, we described the Zeeman cooling of the supersonic metastable argon beam ( 3 P 2 ). We have succeeded in slowing down atoms to speeds below 100 m/s. We gave experimental details and showed the first time-of-flight measurements of slowed atoms

  6. RHIC Polarized proton operation

    International Nuclear Information System (INIS)

    Huang, H.; Ahrens, L.; Alekseev, I.G.; Aschenauer, E.; Atoian, G.; Bai, M.; Bazilevsky, A.; Blaskiewicz, M.; Brennan, J.M.; Brown, K.A.; Bruno, D.; Connolly, R.; Dion, A.; D'Ottavio, T.; Drees, K.A.; Fischer, W.; Gardner, C.; Glenn, J.W.; Gu, X.; Harvey, M.; Hayes, T.; Hoff, L.; Hulsart, R.L.; Laster, J.; Liu, C.; Luo, Y.; MacKay, W.W.; Makdisi, Y.; Marr, G.J.; Marusic, A.; Meot, F.; Mernick, K.; Michnoff, R.; Minty, M.; Montag, C.; Morris, J.; Nemesure, S.; Poblaguev, A.; Ptitsyn, V.; Ranjibar, V.; Robert-Demolaize, G.; Roser, T.; Schmidke, B.; Schoefer, V.; Severino, F.; Smirnov, D.; Smith, K.; Steski, D.; Svirida, D.; Tepikian, S.; Trbojevic, D.; Tsoupas, N.; Tuozzolo, J.E.; Wang, G.; Wilinski, M.; Yip, K.; Zaltsman, A.; Zelenski, A.; Zeno, K.; Zhang, S.Y.

    2011-01-01

    The Relativistic Heavy Ion Collider (RHIC) operation as the polarized proton collider presents unique challenges since both luminosity(L) and spin polarization(P) are important. With longitudinally polarized beams at the experiments, the figure of merit is LP 4 . A lot of upgrades and modifications have been made since last polarized proton operation. A 9 MHz rf system is installed to improve longitudinal match at injection and to increase luminosity. The beam dump was upgraded to increase bunch intensity. A vertical survey of RHIC was performed before the run to get better magnet alignment. The orbit control is also improved this year. Additional efforts are put in to improve source polarization and AGS polarization transfer efficiency. To preserve polarization on the ramp, a new working point is chosen such that the vertical tune is near a third order resonance. The overview of the changes and the operation results are presented in this paper. Siberian snakes are essential tools to preserve polarization when accelerating polarized beams to higher energy. At the same time, the higher order resonances still can cause polarization loss. As seen in RHIC, the betatron tune has to be carefully set and maintained on the ramp and during the store to avoid polarization loss. In addition, the orbit control is also critical to preserve polarization. The higher polarization during this run comes from several improvements over last run. First we have a much better orbit on the ramp. The orbit feedback brings down the vertical rms orbit error to 0.1mm, much better than the 0.5mm last run. With correct BPM offset and vertical realignment, this rms orbit error is indeed small. Second, the jump quads in the AGS improved input polarization for RHIC. Third, the vertical tune was pushed further away from 7/10 snake resonance. The tune feedback maintained the tune at the desired value through the ramp. To calibrate the analyzing power of RHIC polarimeters at any energy above

  7. RHIC Polarized proton operation

    Energy Technology Data Exchange (ETDEWEB)

    Huang, H.; Ahrens, L.; Alekseev, I.G.; Aschenauer, E.; Atoian, G.; Bai, M.; Bazilevsky, A.; Blaskiewicz, M.; Brennan, J.M.; Brown, K.A.; Bruno, D.; Connolly, R.; Dion, A.; D' Ottavio, T.; Drees, K.A.; Fischer, W.; Gardner, C.; Glenn, J.W.; Gu, X.; Harvey, M.; Hayes, T.; Hoff, L.; Hulsart, R.L.; Laster, J.; Liu, C.; Luo, Y.; MacKay, W.W.; Makdisi, Y.; Marr, G.J.; Marusic, A.; Meot, F.; Mernick, K.; Michnoff, R,; Minty, M.; Montag, C.; Morris, J.; Nemesure, S.; Poblaguev, A.; Ptitsyn, V.; Ranjibar, V.; Robert-Demolaize, G.; Roser, T.; J.; Severino, F.; Schmidke, B.; Schoefer, V.; Severino, F.; Smirnov, D.; Smith, K.; Steski, D.; Svirida, D.; Tepikian, S.; Trbojevic, D.; Tsoupas, N.; Tuozzolo, J. Wang, G.; Wilinski, M.; Yip, K.; Zaltsman, A.; Zelenski, A.; Zeno, K.; Zhang, S.Y.

    2011-03-28

    The Relativistic Heavy Ion Collider (RHIC) operation as the polarized proton collider presents unique challenges since both luminosity(L) and spin polarization(P) are important. With longitudinally polarized beams at the experiments, the figure of merit is LP{sup 4}. A lot of upgrades and modifications have been made since last polarized proton operation. A 9 MHz rf system is installed to improve longitudinal match at injection and to increase luminosity. The beam dump was upgraded to increase bunch intensity. A vertical survey of RHIC was performed before the run to get better magnet alignment. The orbit control is also improved this year. Additional efforts are put in to improve source polarization and AGS polarization transfer efficiency. To preserve polarization on the ramp, a new working point is chosen such that the vertical tune is near a third order resonance. The overview of the changes and the operation results are presented in this paper. Siberian snakes are essential tools to preserve polarization when accelerating polarized beams to higher energy. At the same time, the higher order resonances still can cause polarization loss. As seen in RHIC, the betatron tune has to be carefully set and maintained on the ramp and during the store to avoid polarization loss. In addition, the orbit control is also critical to preserve polarization. The higher polarization during this run comes from several improvements over last run. First we have a much better orbit on the ramp. The orbit feedback brings down the vertical rms orbit error to 0.1mm, much better than the 0.5mm last run. With correct BPM offset and vertical realignment, this rms orbit error is indeed small. Second, the jump quads in the AGS improved input polarization for RHIC. Third, the vertical tune was pushed further away from 7/10 snake resonance. The tune feedback maintained the tune at the desired value through the ramp. To calibrate the analyzing power of RHIC polarimeters at any energy above

  8. Our Polar Past

    Science.gov (United States)

    Clary, Renee; Wandersee, James

    2009-01-01

    The study of polar exploration is fascinating and offers students insights into the history, culture, and politics that affect the developing sciences at the farthest ends of Earth. Therefore, the authors think there is value in incorporating polar exploration accounts within modern science classrooms, and so they conducted research to test their…

  9. Terahertz polarization imaging

    NARCIS (Netherlands)

    Van der Valk, N.C.J.; Van der Marel, W.A.M.; Planken, P.C.M.

    2005-01-01

    We present a new method to measure the polarization state of a terahertz pulse by using a modified electrooptic sampling setup. To illustrate the power of this method, we show two examples in which the knowledge of the polarization of the terahertz pulse is essential for interpreting the results:

  10. Polarized proton beams

    International Nuclear Information System (INIS)

    Roser, T.

    1995-01-01

    The acceleration of polarized proton beams in circular accelerators is complicated by the presence of numerous depolarizing spin resonances. Careful and tedious minimization of polarization loss at each of these resonances allowed acceleration of polarized proton beams up to 22 GeV. It has been the hope that Siberian Snakes, which are local spin rotators inserted into ring accelerators, would eliminate these resonances and allow acceleration of polarized beams with the same ease and efficiency that is now routine for unpolarized beams. First tests at IUCF with a full Siberian Snake showed that the spin dynamics with a Snake can be understood in detail. The author now has results of the first tests of a partial Siberian Snake at the AGS, accelerating polarized protons to an energy of about 25 GeV. These successful tests of storage and acceleration of polarized proton beams open up new possibilities such as stored polarized beams for internal target experiments and high energy polarized proton colliders

  11. Polar Science Is Cool!

    Science.gov (United States)

    Weeks, Sophie

    2012-01-01

    Children are fascinated by the fact that polar scientists do research in extremely cold and dangerous places. In the Arctic they might be viewed as lunch by a polar bear. In the Antarctic, they could lose toes and fingers to frostbite and the wind is so fast it can rip skin off. They camp on ice in continuous daylight, weeks from any form of…

  12. Single-electron capture collisions of ground and metastable Ne2+ ions with molecular gases

    Science.gov (United States)

    Hasan, A.; Abu-Haija, O.; Harris, J.; Elkafrawy, T.; Kayani, A.; Kamber, E. Y.

    2013-09-01

    Using the translational energy-gain spectroscopy technique, we have measured the energy-gain spectra and absolute total cross sections for single-electron capture in collisions of Ne2+ with N2, CO2 and H2O at laboratory impact energies between 50 and 400 eV and 0° scattering angles. In all the collision systems studied here, reaction channels have been observed which indicate the presence of the long-lived metastable states of (2s2 2p4 1D and 1S) in the Ne2+ incident beam. These measurements also indicate that capture from the metastable states into excited states of the projectile product ions is the most important inelastic process. Contributions from capture accompanied by the excitation and ionization of the target product are also detected. In addition, the energy dependence of the total single-electron capture cross sections is studied and found to slowly increase with increasing impact energy. The present data are compared with the theoretical calculations of the classical over the barrier, extended classical over the barrier and Landau-Zener models.

  13. Co thin film with metastable bcc structure formed on GaAs(111 substrate

    Directory of Open Access Journals (Sweden)

    Minakawa Shigeyuki

    2014-07-01

    Full Text Available Co thin films are prepared on GaAs(111 substrates at temperatures ranging from room temperature to 600 ºC by radio-frequency magnetron sputtering. The growth behavior and the detailed resulting film structure are investigated by in-situ reflection high-energy electron diffraction and X-ray diffraction. In early stages of film growth at temperatures lower than 200 ºC, Co crystals with metastable A2 (bcc structure are formed, where the crystal structure is stabilized through hetero-epitaxial growth. With increasing the film thickness beyond 2 nm, the metastable structure starts to transform into more stable A1 (fcc structure through atomic displacements parallel to the A2{110} close-packed planes. The crystallographic orientation relationship between the A2 and the transformed A1 crystals is A1{111} || A2{110}. When the substrate temperature is higher than 400 ºC, Ga atoms of substrate diffuse into the Co films and a Co-Ga alloy with bcc-based ordered structure of B2 is formed.

  14. Metastable garnet in oceanic crust at the top of the lower mantle.

    Science.gov (United States)

    Kubo, Tomoaki; Ohtani, Eiji; Kondo, Tadashi; Kato, Takumi; Toma, Motomasa; Hosoya, Tomofumi; Sano, Asami; Kikegawa, Takumi; Nagase, Toshiro

    As oceanic tectonic plates descend into the Earth's lower mantle, garnet (in the basaltic crust) and silicate spinel (in the underlying peridotite layer) each decompose to form silicate perovskite-the 'post-garnet' and 'post-spinel' transformations, respectively. Recent phase equilibrium studies have shown that the post-garnet transformation occurs in the shallow lower mantle in a cold slab, rather than at approximately 800 km depth as earlier studies indicated, with the implication that the subducted basaltic crust is unlikely to become buoyant enough to delaminate as it enters the lower mantle. But here we report results of a kinetic study of the post-garnet transformation, obtained from in situ X-ray observations using sintered diamond anvils, which show that the kinetics of the post-garnet transformation are significantly slower than for the post-spinel transformation. Although metastable spinel quickly breaks down at a temperature of 1,000 K, we estimate that metastable garnet should survive of the order of 10 Myr even at 1,600 K. Accordingly, the expectation of where the subducted oceanic crust would be buoyant spans a much wider depth range at the top of the lower mantle, when transformation kinetics are taken into account.

  15. Polymer escape from a metastable Kramers potential: path integral hyperdynamics study.

    Science.gov (United States)

    Shin, Jaeoh; Ikonen, Timo; Khandkar, Mahendra D; Ala-Nissila, Tapio; Sung, Wokyung

    2010-11-14

    We study the dynamics of flexible, semiflexible, and self-avoiding polymer chains moving under a Kramers metastable potential. Due to thermal noise, the polymers, initially placed in the metastable well, can cross the potential barrier, but these events are extremely rare if the barrier is much larger than thermal energy. To speed up the slow rate processes in computer simulations, we extend the recently proposed path integral hyperdynamics method to the cases of polymers. We consider the cases where the polymers' radii of gyration are comparable to the distance between the well bottom and the barrier top. We find that, for a flexible polymers, the crossing rate (R) monotonically decreases with chain contour length (L), but with the magnitude much larger than the Kramers rate in the globular limit. For a semiflexible polymer, the crossing rate decreases with L but becomes nearly constant for large L. For a fixed L, the crossing rate becomes maximum at an intermediate bending stiffness. For the self-avoiding chain, the rate is a nonmonotonic function of L, first decreasing with L, and then, above a certain length, increasing with L. These findings can be instrumental for efficient separation of biopolymers.

  16. Tuning the morphology of metastable MnS films by simple chemical bath deposition technique

    Science.gov (United States)

    Dhandayuthapani, T.; Girish, M.; Sivakumar, R.; Sanjeeviraja, C.; Gopalakrishnan, R.

    2015-10-01

    In the present investigation, we have prepared the spherical particles, almond-like, and cauliflower-like morphological structures of metastable MnS films on glass substrate by chemical bath deposition technique at low temperature without using any complexing or chelating agent. The morphological change of MnS films with molar ratio may be due to the oriented aggregation of adjacent particles. The compositional purity of deposited film was confirmed by the EDAX study. X-ray diffraction and micro-Raman studies confirm the sulfur source concentration induced enhancement in the crystallization of films with metastable MnS phase (zinc-blende β-MnS, and wurtzite γ-MnS). The shift in PL emission peak with molar ratio may be due to the change in optical energy band gap of the MnS, which was further confirmed by the optical absorbance study. The paramagnetic behavior of the sample was confirmed by the M-H plot.

  17. Tuning the morphology of metastable MnS films by simple chemical bath deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Dhandayuthapani, T. [Directorate of Distance Education, Alagappa University, Karaikudi 630004 (India); Girish, M. [Department of Physics, Alagappa University, Karaikudi 630004 (India); Sivakumar, R., E-mail: krsivakumar1979@yahoo.com [Directorate of Distance Education, Alagappa University, Karaikudi 630004 (India); Sanjeeviraja, C. [Department of Physics, Alagappa Chettiar College of Engineering and Technology, Karaikudi 630004 (India); Gopalakrishnan, R. [Department of Physics, Anna University, Chennai 600025 (India)

    2015-10-30

    Graphical abstract: - Highlights: • MnS films with diverse morphological features were prepared without any complexing agent. • The change in morphology of MnS films may be due to the “oriented aggregation”. • The dual role (as sulfur source and structure directing agent) of thiourea was observed. • Sulfur source concentration induced enhancement in the crystallization of films. - Abstract: In the present investigation, we have prepared the spherical particles, almond-like, and cauliflower-like morphological structures of metastable MnS films on glass substrate by chemical bath deposition technique at low temperature without using any complexing or chelating agent. The morphological change of MnS films with molar ratio may be due to the oriented aggregation of adjacent particles. The compositional purity of deposited film was confirmed by the EDAX study. X-ray diffraction and micro-Raman studies confirm the sulfur source concentration induced enhancement in the crystallization of films with metastable MnS phase (zinc-blende β-MnS, and wurtzite γ-MnS). The shift in PL emission peak with molar ratio may be due to the change in optical energy band gap of the MnS, which was further confirmed by the optical absorbance study. The paramagnetic behavior of the sample was confirmed by the M–H plot.

  18. Evidence of existence of metastable SrFe{sub 12}O{sub 19} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Martinez Garcia, R., E-mail: rmartinez@fi.uba.ar [Laboratorio de Solidos Amorfos, INTECIN, Facultad de Ingenieria, Universidad de Buenos Aires, Paseo Colon 850, C1063ACV, Buenos Aires (Argentina); Bilovol, V.; Socolovsky, L.M. [Laboratorio de Solidos Amorfos, INTECIN, Facultad de Ingenieria, Universidad de Buenos Aires, Paseo Colon 850, C1063ACV, Buenos Aires (Argentina); Pirota, K. [Laboratorio de Materiais e Baixas Temperaturas, Instituto de Fisica ' Gleb Wataghin' , UNICAMP, 13083-970 Campinas, SP (Brazil)

    2011-12-15

    The existence of metastable hexaferrite is reported. Synthesis of strontium hexaferrite, SrFe{sub 12}O{sub 19}, at 400 deg. C was realized under controlled oxygen atmosphere. Such technique allows obtaining of SrFe{sub 12}O{sub 19} at lower temperatures than those by traditional methods (above 800 deg. C). Phase transformation occurred during a measurement of magnetization vs. temperature (heating up to 625 deg. C). The heat treatment induces a change from SrFe{sub 12}O{sub 19} to {gamma}-Fe{sub 2}O{sub 3} (as the main phase), and SrFeO{sub 2.74} to Sr{sub 2}Fe{sub 2}O{sub 5}. Together with these phase transformations, an increment in the amount of SrCO{sub 3} is detected. Magnetic study of the samples, before and after the heating, supports the structural analysis conclusions. - Highlights: > SrFe{sub 12}O{sub 19}, as the majority phase, is obtained by heat treatment at 400 deg. C under oxygen flux. > Hexaferrite nanoparticles have crystalline imperfections that make it an unstable phase. > Together with these phase transformations, an increment in the amount of SrCO{sub 3} is detected. > To our knowledge, this is the first report of the existence of metastable SrFe{sub 12}O{sub 19}.

  19. Supramolecular stabilization of metastable tautomers in solution and the solid state.

    Science.gov (United States)

    Juribašić, Marina; Bregović, Nikola; Stilinović, Vladimir; Tomišić, Vladislav; Cindrić, Marina; Sket, Primož; Plavec, Janez; Rubčić, Mirta; Užarević, Krunoslav

    2014-12-22

    This work presents a successful application of a recently reported supramolecular strategy for stabilization of metastable tautomers in cocrystals to monocomponent, non-heterocyclic, tautomeric solids. Quantum-chemical computations and solution studies show that the investigated Schiff base molecule, derived from 3-methoxysalicylaldehyde and 2-amino-3-hydroxypyridine (ap), is far more stable as the enol tautomer. In the solid state, however, in all three obtained polymorphic forms it exists solely as the keto tautomer, in each case stabilized by an unexpected hydrogen-bonding pattern. Computations have shown that hydrogen bonding of the investigated Schiff base with suitable molecules shifts the tautomeric equilibrium to the less stable keto form. The extremes to which supramolecular stabilization can lead are demonstrated by the two polymorphs of molecular complexes of the Schiff base with ap. The molecules of both constituents of molecular complexes are present as metastable tautomers (keto anion and protonated pyridine, respectively), which stabilize each other through a very strong hydrogen bond. All the obtained solid forms proved stable in various solid-state and solvent-mediated methods used to establish their relative thermodynamic stabilities and possible interconversion conditions. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. A Metastate HMM with Application to Gene Structure Identification in Eukaryotes

    Directory of Open Access Journals (Sweden)

    Winters-Hilt Stephen

    2010-01-01

    Full Text Available We introduce a generalized-clique hidden Markov model (HMM and apply it to gene finding in eukaryotes (C. elegans. We demonstrate a HMM structure identification platform that is novel and robustly-performing in a number of ways. The generalized clique HMM begins by enlarging the primitive hidden states associated with the individual base labels (as exon, intron, or junk to substrings of primitive hidden states, or footprint states, having a minimal length greater than the footprint state length. The emissions are likewise expanded to higher order in the fundamental joint probability that is the basis of the generalized-clique, or "metastate", HMM. We then consider application to eukaryotic gene finding and show how such a metastate HMM improves the strength of coding/noncoding-transition contributions to gene-structure identification. We will describe situations where the coding/noncoding-transition modeling can effectively recapture the exon and intron heavy tail distribution modeling capability as well as manage the exon-start needle-in-the-haystack problem. In analysis of the C. elegans genome we show that the sensitivity and specificity (SN,SP results for both the individual-state and full-exon predictions are greatly enhanced over the standard HMM when using the generalized-clique HMM.

  1. Influences of depletion potential on vapor-liquid critical point metastability

    Directory of Open Access Journals (Sweden)

    S. Zhou

    2016-04-01

    Full Text Available Phase behavior of a neutral colloid dispersion is investigated based on an improved Asakura-Oosawa (AO model. Several observations are made: (i an increase of solvent fugacity can enlarge the fluid-solid (FS coexistence region, and this makes fugacity become a powerful factor in tuning a vapor-liquid transition (VLT critical point metastability. (ii A reducing of size ratio of the solvent versus colloid particle can enlarge the FS coexistence region as well as lower the VLT critical temperature, and a combination of the two effects makes the size ratio an extremely powerful factor adjusting the VLT critical point metastability. (iii Existence of a long-range attraction term in the effective colloid potential is not a necessary condition for occurrence of a vapor-solid transition (VST, and short-ranged oscillatory depletion potential also can induce the VST over an even broader temperature range. (iv Sensitivity of the freezing line on the size ratio is disclosed, and one can make use of the sensitivity to prepare mono-disperse colloid of well-controlled diameter by following a fractionated crystallization scheme; moreover, broadening of the FST coexistence region by raising the solvent fugacity and/or lowering the size ratio has important implication for crystallization process.

  2. Polymorphism in Elemental Silicon: Probabilistic Interpretation of the Realizability of Metastable Structures

    Energy Technology Data Exchange (ETDEWEB)

    Stevanovic, Vladan [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Jones, Eric [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2017-11-03

    With few systems of technological interest having been studied as extensively as elemental silicon, there currently exists a wide disparity between the number of predicted low-energy silicon polymorphs and those that have been experimentally realized as metastable at ambient conditions. We put forward an explanation for this disparity wherein the likelihood of formation of a given polymorph under near-equilibrium conditions can be estimated on the basis of mean-field isothermal-isobaric (N,p,T) ensemble statistics. The probability that a polymorph will be experimentally realized is shown to depend upon both the hypervolume of that structure's potential energy basin of attraction and a Boltzmann factor weight containing the polymorph's potential enthalpy per particle. Both attributes are calculated using density functional theory relaxations of randomly generated initial structures. We find that the metastable polymorphism displayed by silicon can be accounted for using this framework to the exclusion of a very large number of other low-energy structures.

  3. Metastable phase formation in ion-irradiated nickel-aluminum alloys

    International Nuclear Information System (INIS)

    Eridon, J.M.

    1986-01-01

    Phase transformations induced by ion beam mixing of nickel-aluminum alloys with 500-keV krypton ions were investigated over a range of temperatures (80 K to 300K), composition (NiAl 3 , NiAl, Ni 1 Al), initial structures (both nickel-aluminum layers and ordered intermetallic compounds), and doses (ranging from 2 x 10 14 cm -2 to 5 x 10 16 cm -2 ). Samples were formed by alternate evaporation of layers of nickel and aluminum in high vacuum onto copper grids. These samples were check for purity with energy dispersive-x-ray spectroscopy, electron energy-loss spectroscopy, and Rutherford backscattering spectrometry. A portion of these samples was annealed to form the intermetallic compounds appropriate to the given composition. Irradiations were performed at both room temperature (300 K) and 80 K using the 2-MV ion accelerator at Argonne National Laboratory. Phase transformations were observed during both in-situ irradiations in the High Voltage Electron Microscopy at Argonne and also in subsequent electron-diffraction analysis of an array of samples irradiated in a target chamber. Metastable phases formed include disordered crystalline structures at composition s of 25% and 50% aluminum, an amorphous structure at 75% aluminum, and a hexagonal closed-packed structure formed at 25% aluminum. These metastable states were all converted to the stable intermetallic compounds through annealing treatments

  4. The metastable state of nucleocapsids of enveloped viruses as probed by high hydrostatic pressure.

    Science.gov (United States)

    Gaspar, L P; Terezan, A F; Pinheiro, A S; Foguel, D; Rebello, M A; Silva, J L

    2001-03-09

    Enveloped viruses fuse their membranes with cellular membranes to transfer their genomes into cells at the beginning of infection. What is not clear, however, is the role of the envelope (lipid bilayer and glycoproteins) in the stability of the viral particle. To address this question, we compared the stability between enveloped and nucleocapsid particles of the alphavirus Mayaro using hydrostatic pressure and urea. The effects were monitored by intrinsic fluorescence, light scattering, and binding of fluorescent dyes, including bis(8-anilinonaphthalene-1-sulfonate) and ethidium bromide. Pressure caused a drastic dissociation of the nucleocapsids as determined by tryptophan fluorescence, light scattering, and gel filtration chromatography. Pressure-induced dissociation of the nucleocapsids was poorly reversible. In contrast, when the envelope was present, pressure effects were much less marked and were highly reversible. Binding of ethidium bromide occurred when nucleocapsids were dissociated under pressure, indicating exposure of the nucleic acid, whereas enveloped particles underwent no changes. Overall, our results demonstrate that removal of the envelope with the glycoproteins leads the particle to a metastable state and, during infection, may serve as the trigger for disassembly and delivery of the genome. The envelope acts as a "Trojan horse," gaining entry into the host cell to allow release of a metastable nucleocapsid prone to disassembly.

  5. Detecting metastable olivine wedge beneath Japan Sea with deep earthquake coda wave interferometry

    Science.gov (United States)

    Shen, Z.; Zhan, Z.

    2017-12-01

    It has been hypothesized for decades that the lower-pressure olivine phase would kinetically persist in the interior of slab into the transition zone, forming a low-velocity "Metastable Olivine Wedge" (MOW). MOW, if exists, would play a critical role in generating deep earthquakes and parachuting subducted slabs with its buoyancy. However, seismic evidences for MOW are still controversial, and it is suggested that MOW can only be detected using broadband waveforms given the wavefront healing effects for travel times. On the other hand, broadband waveforms are often complicated by shallow heterogeneities. Here we propose a new method using the source-side interferometry of deep earthquake coda to detect MOW. In this method, deep earthquakes are turned into virtual sensors with the reciprocity theorem, and the transient strain from one earthquake to the other is estimated by cross-correlating the coda from the deep earthquake pair at the same stations. This approach effectively isolates near-source structure from complicated shallow structures, hence provide finer resolution to deep slab structures. We apply this method to Japan subduction zone with Hi-Net data, and our preliminary result does not support a large MOW model (100km thick at 410km) as suggested by several previous studies. Metastable olivine at small scales or distributed in an incoherent manner in deep slabs may still be possible.

  6. A novel metastable state magnetic phase of monolayer FeSe.

    Science.gov (United States)

    Meng, Lijun; Yu, Jun; Peng, Haiyan; Li, Yanru; Zhong, Jianxin

    2018-03-05

    We found a novel metastable magnetic phase by systematically calculating total energy of monolayer FeSe in various antiferromagnetic (AFM) orders using first-principles method. The new metastable magnetic phase named as QAFM is a magnetic state with short-range magnetic structure which can be regarded as a transitional state between checkerboard-like antiferromagnetic state and collinear antiferromagnetic state. Both magnetic moments with important fluctuation and charge density difference with a 24 reconstruction of orbitals breaks C4 symmetry and maybe commonly corresponds to the nematic phase in recent transmission electron microscopy (TEM) and neutron scattering experiment observations. Its electronic band displays a Dirac-like band structure along -X in the folding Brillouin zone of supercell. The QAFM phase of FeSe holds metallic feature with dxz, dyz and dz2 band crossing Fermi level even including spin-orbit coupling. Additionally, the weight of 3d orbitals varies as the applied expansion strain which maybe directly correlated with the emerging nematic phase and superconducting state of strained monolayer FeSe. The finding of novel magnetic order maybe provide important clues to elucidate the relationship of antiferromagnetism and superconductivity for unconventional Fe-based superconductor. © 2018 IOP Publishing Ltd.

  7. Experimental and theoretical investigations on the polymorphism and metastability of BiPO4.

    Science.gov (United States)

    Achary, S N; Errandonea, D; Muñoz, A; Rodríguez-Hernández, P; Manjón, F J; Krishna, P S R; Patwe, S J; Grover, V; Tyagi, A K

    2013-11-14

    In this work we report the metastability and the energetics of the phase transitions of three different polymorphs of BiPO4, namely trigonal (Phase-I, space group P3(1)21), monoclinic monazite-type (Phase-II, space group P2(1)/n) and SbPO4-type monoclinic (Phase-III, space group P2(1)/m) from ambient and non-ambient temperature powder XRD and neutron diffraction studies as well as ab initio density functional theory (DFT) calculations. The symmetry ambiguity between P2(1) and P2(1)/m of the high temperature polymorph of BiPO4 has been resolved by a neutron diffraction study. The structure and vibrational properties of these polymorphs of the three polymorphs have also been reported in detail. Total energy calculations have been used to understand the experimentally observed metastable behavior of trigonal and monazite-type BiPO4. Interestingly, all of the three phases were found to coexist after heating a single phasic trigonal BiPO4 to 773 K. The irreversible nature of these phase transitions has been explained by the concepts of the interplay of the structural distortion, molar volume and total energy.

  8. High-Strength Stereolithographic 3D Printed Nanocomposites: Graphene Oxide Metastability.

    Science.gov (United States)

    Manapat, Jill Z; Mangadlao, Joey Dacula; Tiu, Brylee David Buada; Tritchler, Grace C; Advincula, Rigoberto C

    2017-03-22

    The weak thermomechanical properties of commercial 3D printing plastics have limited the technology's application mainly to rapid prototyping. In this report, we demonstrate a simple approach that takes advantage of the metastable, temperature-dependent structure of graphene oxide (GO) to enhance the mechanical properties of conventional 3D-printed resins produced by stereolithography (SLA). A commercially available SLA resin was reinforced with minimal amounts of GO nanofillers and thermally annealed at 50 and 100 °C for 12 h. Tensile tests revealed increasing strength and modulus at an annealing temperature of 100 °C, with the highest tensile strength increase recorded at 673.6% (for 1 wt % GO). Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) also showed increasing thermal stability with increasing annealing temperature. The drastic enhancement in mechanical properties, which is seen to this degree in 3D-printed samples reported in literature, is attributed to the metastable structure of GO, polymer-nanofiller cross-linking via acid-catalyzed esterification, and removal of intercalated water, thus improving filler-matrix interaction as evidenced by spectroscopy and microscopy analyses.

  9. Kinetic crystallization separation process of the inositol isomers by controlling metastable zones

    Science.gov (United States)

    Konuki, Kaname; Hirasawa, Izumi

    2013-06-01

    D-chiro-inositol (DCI) is prepared by the immobilized enzyme reaction which uses myo-inositol (MI) as the substrate and the conversion rate is about 13%. The aim of this study was to develop a separation method for high purity DCI crystals from a reaction solution including low purity DCI only by the crystallization process. We succeeded in separating DCI crystals of 96% purity by water cooling crystallization, but it was presumed that scale-up was difficult. Although we tried anti-solvent crystallization similar to water cooling crystallization, high purity DCI crystals were not obtained. Therefore, we proposed the crystallization separation process by controlling metastable zones. The purity of a desired compound is controlled by this process, because solid-liquid separation is achieved before crystallization of compound in metastable zone. By the crystallization using this method, the DCI crystals of 97% purity were obtained. Although the yield per batch is about 50%, the actual yield is improved as the last mother liquor returns into the process of the following batch. When this process was repeated, the purity and the yield of DCI were reproduced and the robustness of this process was proved. It is expected that scale-up of this process will be successful, and this purification method could be applicable to similar systems such as separation of isomers and analogs.

  10. Meta-stable Solidification Created by the Detonation Method of Coating Formation

    Directory of Open Access Journals (Sweden)

    W. Wołczyński

    2012-04-01

    Full Text Available Particles of the Fe-Al type (less than 50m in diameter were sprayed onto the 045 steel substrate by means of the detonation method. The TEM, SAED and EDX analyses revealed that the Fe-Al particles have been partially melted in the experiment of coating formation. Particle undergone melting even within about 80% of its volume. Therefore, solidification of the melted part of particles was expected. Solidification differed significantly due to a large range of chemical composition of applied particles (from 15 at.% Al up to 63 at.% Al. A single particle containing 63 at.% Al was subjected to the detailed analysis, only. The TEM / SAED techniques revealed in the solidified part of particle three sub-layers: an amorphous phase,, periodically situated FeAl + Fe2Al5 phases, and a non-equilibrium phase,.A hypothesis dealing with the inter-metallic phases formation in such a single particle of the nominal composition N0 0.63 is presented. At first, the solid / liquid system is treated as an interconnection: substrate/liquid/nonmelted particle part. Therefore, it issuggested that the solidification occurs simultaneously in two directions: towards a substrate and towards a non-melted part of particle. The solidification mechanism is referred to the Fe-Al meta-stable phase diagram. It is shown that the melted part of particle solidifies rapidly according to the phase diagram of meta-stable equilibrium and at a significant deviation from the thermodynamic equilibrium.

  11. Precision Polarization of Neutrons

    Science.gov (United States)

    Martin, Elise; Barron-Palos, Libertad; Couture, Aaron; Crawford, Christopher; Chupp, Tim; Danagoulian, Areg; Estes, Mary; Hona, Binita; Jones, Gordon; Klein, Andi; Penttila, Seppo; Sharma, Monisha; Wilburn, Scott

    2009-05-01

    Determining polarization of a cold neutron beam to high precision is required for the next generation neutron decay correlation experiments at the SNS, such as the proposed abBA and PANDA experiments. Precision polarimetry measurements were conducted at Los Alamos National Laboratory with the goal of determining the beam polarization to the level of 10-3 or better. The cold neutrons from FP12 were polarized using optically polarized ^3He gas as a spin filter, which has a highly spin-dependent absorption cross section. A second ^ 3He spin filter was used to analyze the neutron polarization after passing through a resonant RF spin rotator. A discussion of the experiment and results will be given.

  12. Parallel Polarization State Generation.

    Science.gov (United States)

    She, Alan; Capasso, Federico

    2016-05-17

    The control of polarization, an essential property of light, is of wide scientific and technological interest. The general problem of generating arbitrary time-varying states of polarization (SOP) has always been mathematically formulated by a series of linear transformations, i.e. a product of matrices, imposing a serial architecture. Here we show a parallel architecture described by a sum of matrices. The theory is experimentally demonstrated by modulating spatially-separated polarization components of a laser using a digital micromirror device that are subsequently beam combined. This method greatly expands the parameter space for engineering devices that control polarization. Consequently, performance characteristics, such as speed, stability, and spectral range, are entirely dictated by the technologies of optical intensity modulation, including absorption, reflection, emission, and scattering. This opens up important prospects for polarization state generation (PSG) with unique performance characteristics with applications in spectroscopic ellipsometry, spectropolarimetry, communications, imaging, and security.

  13. Polarization at the SLC

    Energy Technology Data Exchange (ETDEWEB)

    Moffeit, K.C.

    1988-10-01

    The Stanford Linear collider was designed to accommodate polarized electron beams. Longitudinally polarized electrons colliding with unpolarized positrons at a center of mass energy near the Z/sup 0/ mass can be used as novel and sensitive probes of the electroweak process. A gallium arsenide based photon emission source will provide a beam of longitudinally polarized electrons of about 45 percent polarization. A system of bend magnets and a superconducting solenoid will be used to rotate the spins so that the polarization is preserved while the 1.21 GeV electrons are stored in the damping ring. Another set of bend magnets and two superconducting solenoids orient the spin vectors so that longitudinal polarization of the electrons is achieved at the collision point with the unpolarized positrons. A system to monitor the polarization based on Moller and Compton scattering will be used. Nearly all major components have been fabricated and tested. Subsystems of the source and polarimeters have been installed, and studies are in progress. The installation and commissioning of the entire system will take place during available machine shutdown periods as the commissioning of SLC progresses. 8 refs., 16 figs., 1 tab.

  14. Small-angle X-ray scattering studies of metastable intermediates of beta-lactoglobulin isolated after heat-induced aggregation

    DEFF Research Database (Denmark)

    Carrotta, R.; Arleth, L.; Pedersen, J.S.

    2003-01-01

    Small-angle x-ray scattering was used for studying intermediate species, isolated after heat-induced aggregation of the A variant of bovine P-lactoglobulin. The intermediates were separated in two fractions, the heated metastable dimer and heated metastable oligomers larger than the dimer. The pa...

  15. Polarized atomic beams for targets

    International Nuclear Information System (INIS)

    Grueebler, W.

    1984-01-01

    The basic principle of the production of polarized atomic hydrogen and deuterium beams are reviewed. The status of the present available polarization, density and intensity are presented. The improvement of atomic beam density by cooling the hydrogen atoms to low velocity is discussed. The possible use of polarized atomic beams as targets in storage rings is shown. It is proposed that polarized atomic beams can be used to produce polarized gas targets with high polarization and greatly improved density

  16. Polarized scintillator targets

    Science.gov (United States)

    van den Brandt, B.; Bunyatova, E. I.; Hautle, P.; Konter, J. A.; Mango, S.

    2000-05-01

    The hydrogen nuclei in an organic scintillator have been polarized to more than 80% and the deuterons in its fully deuterated version to 24%. The scintillator, doped with TEMPO, has been polarized dynamically in a field of 2.5 T in a vertical dilution refrigerator in which a plastic lightguide transports the scintillation light from the sample in the mixing chamber to a photomultiplier outside the cryostat. Sizeable solid samples with acceptable optical properties and light output have been prepared and successfully operated as "live" polarized targets in nuclear physics experiments.

  17. Polarized scintillator targets

    Energy Technology Data Exchange (ETDEWEB)

    Brandt, B. van den E-mail: vandenbrandt@psi.ch; Bunyatova, E.I.; Hautle, P.; Konter, J.A.; Mango, S

    2000-05-21

    The hydrogen nuclei in an organic scintillator have been polarized to more than 80% and the deuterons in its fully deuterated version to 24%. The scintillator, doped with TEMPO, has been polarized dynamically in a field of 2.5 T in a vertical dilution refrigerator in which a plastic lightguide transports the scintillation light from the sample in the mixing chamber to a photomultiplier outside the cryostat. Sizeable solid samples with acceptable optical properties and light output have been prepared and successfully operated as 'live' polarized targets in nuclear physics experiments.

  18. Heidelberg polarized alkali source

    International Nuclear Information System (INIS)

    Kraemer, D.; Steffens, E.; Jaensch, H.; Philipps Universitaet, Marburg, Germany)

    1984-01-01

    A new atomic beam type polarized alkali ion source has been installed at Heidelberg. In order to improve the beam polarization considerably optical pumping is applied in combination with an adiabatic medium field transition which results in beams in single hyperfine sublevels. The m state population is determined by laser-induced fluorescence spectroscopy. Highly polarized beams (P/sub s/ > 0.9, s = z, zz) with intensities of 30 to 130 μA can be extracted for Li + and Na + , respectively

  19. Polarization measurement in the COMPASS polarized target

    CERN Document Server

    Kondo, K; Baum, G; Berglund, P; Doshita, N; Gautheron, F; Görtz, S; Hasegawa, T; Horikawa, N; Ishimoto, S; Iwata, T; Kisselev, Yu V; Koivuniemi, J H; Le Goff, J M; Magnon, A; Meyer, W; Reicherz, G; Matsuda, T

    2004-01-01

    Continuous wave nuclear magnetic resonance (NMR) is used to determine the target polarization in the COMPASS experiment. The system is made of the so-called Liverpool Q-meters, Yale-cards, and VME modules for data taking and system controlling. In 2001 the NMR coils were embedded in the target material, while in 2002 and 2003 the coils were mounted on the outer surface of the target cells to increase the packing factor of the material. Though the error of the measurement became larger with the outer coils than with the inner coils, we have performed stable measurements throughout the COMPASS run time for 3 years. The maximum polarization was +57% and -53% as the average in the target cells.

  20. Networking for proteins : A yeast two-hybrid and RNAi profiling approach to uncover C. elegans cell polarity regulators

    NARCIS (Netherlands)

    Koorman, T.

    2016-01-01

    Cell polarity is a near universal trait of life and guides many aspects of animal development. Although a number of key polarity proteins have been identified, many interactions with proteins acting downstream likely remain to be elucidated. Mutations in polarity proteins or deregulation of polarity

  1. Collisional effects on metastable atom population in vapour generated by electron beam heating

    International Nuclear Information System (INIS)

    Dikshit, B; Majumder, A; Bhatia, M S; Mago, V K

    2008-01-01

    The metastable atom population distribution in a free expanding uranium vapour generated by electron beam (e-beam) heating is expected to depart from its original value near the source due to atom-atom collisions and interaction with electrons of the e-beam generated plasma co-expanding with the vapour. To investigate the dynamics of the electron-atom and atom-atom interactions at different e-beam powers (or source temperatures), probing of the atomic population in ground (0 cm -1 ) and 620 cm -1 metastable states of uranium was carried out by the absorption technique using a hollow cathode discharge lamp. The excitation temperature of vapour at a distance ∼30 cm from the source was calculated on the basis of the measured ratio of populations in 620 to 0 cm -1 states and it was found to be much lower than both the source temperature and estimated translational temperature of the vapour that is cooled by adiabatic free expansion. This indicated relaxation of the metastable atoms by collisions with low energy plasma electrons was so significant that it brings the excitation temperature below the translational temperature of the vapour. So, with increase in e-beam power and hence atom density, frequent atom-atom collisions are expected to establish equilibrium between the excitation and translational temperatures, resulting in an increase in the excitation temperature (i.e. heating of vapour). This has been confirmed by analysing the experimentally observed growth pattern of the curve for excitation temperature with e-beam power. From the observed excitation temperature at low e-beam power when atom-atom collisions can be neglected, the total de-excitation cross section for relaxation of the 620 cm -1 state by interaction with low energy electrons was estimated and was found to be ∼10 -14 cm 2 . Finally using this value of cross section, the extent of excitational cooling and heating by electron-atom and atom-atom collisions are described at higher e-beam powers

  2. Metastable phases freezing from melts of reciprocal systems PbX + CdI2=CdX + PbI2 (X=S, Se, Te)

    International Nuclear Information System (INIS)

    Odin, I.N.; Chukichev, M.V.

    2001-01-01

    The transformations in the mutual PbX + CdI 2 =CdX + PbI 2 (X=S, Se, Te) systems leading to the crystallization of metastable polytypical modifications of lead iodide in metastable ternary compounds are studied for the first time. Microstructural and X-ray diffraction analyses were conducted. Their phase diagrams were constructed. The luminescence properties of the stable and metastable modifications of the lead iodide and the metastable compound Pb 4 SeI 6 were investigated. The lines 504 and 512 nm are noted in the 2H-PbI 2 cathodoluminescence spectra. The close lines - 508 and 516 nm provide for the 6R-PbI 2 modification. The metastable compound Pb 4 SeI 6 is characterized by the 769 and 868 nm lines [ru

  3. Dynamic nuclear spin polarization

    Energy Technology Data Exchange (ETDEWEB)

    Stuhrmann, H.B. [GKSS-Forschungszentrum Geesthacht GmbH (Germany)

    1996-11-01

    Polarized neutron scattering from dynamic polarized targets has been applied to various hydrogenous materials at different laboratories. In situ structures of macromolecular components have been determined by nuclear spin contrast variation with an unprecedented precision. The experiments of selective nuclear spin depolarisation not only opened a new dimension to structural studies but also revealed phenomena related to propagation of nuclear spin polarization and the interplay of nuclear polarisation with the electronic spin system. The observation of electron spin label dependent nuclear spin polarisation domains by NMR and polarized neutron scattering opens a way to generalize the method of nuclear spin contrast variation and most importantly it avoids precontrasting by specific deuteration. It also likely might tell us more about the mechanism of dynamic nuclear spin polarisation. (author) 4 figs., refs.

  4. Time Domain Induced Polarization

    DEFF Research Database (Denmark)

    Fiandaca, Gianluca; Auken, Esben; Christiansen, Anders Vest

    2012-01-01

    Time-domain-induced polarization has significantly broadened its field of reference during the last decade, from mineral exploration to environmental geophysics, e.g., for clay and peat identification and landfill characterization. Though, insufficient modeling tools have hitherto limited the use...... of time-domaininduced polarization for wider purposes. For these reasons, a new forward code and inversion algorithm have been developed using the full-time decay of the induced polarization response, together with an accurate description of the transmitter waveform and of the receiver transfer function......%. Furthermore, the presence of low-pass filters in time-domain-induced polarization instruments affects the early times of the acquired decays (typically up to 100 ms) and has to be modeled in the forward response to avoid significant loss of resolution. The developed forward code has been implemented in a 1D...

  5. Polarized proton colliders

    International Nuclear Information System (INIS)

    Roser, T.

    1995-01-01

    High energy polarized beam collisions will open up the unique physics opportunities of studying spin effects in hard processes. This will allow the study of the spin structure of the proton and also the verification of the many well documented expectations of spin effects in perturbative QCD and parity violation in W and Z production. Proposals for polarized proton acceleration for several high energy colliders have been developed. A partial Siberian Snake in the AGS has recently been successfully tested and full Siberian Snakes, spin rotators, and polarimeters for RHIC are being developed to make the acceleration of polarized beams to 250 GeV possible. This allows for the unique possibility of colliding two 250 GeV polarized proton beams at luminosities of up to 2 x 10 32 cm -2 s -1

  6. Polarized electron sources for linear colliders

    International Nuclear Information System (INIS)

    Clendenin, J.E.; Ecklund, S.D.; Miller, R.H.; Schultz, D.C.; Sheppard, J.C.

    1992-07-01

    Linear colliders require high peak current beams with low duty factors. Several methods to produce polarized e - beams for accelerators have been developed. The SLC, the first linear collider, utilizes a photocathode gun with a GaAs cathode. Although photocathode sources are probably the only practical alternative for the next generation of linear colliders, several problems remain to be solved, including high voltage breakdown which poisons the cathode, charge limitations that are associated with the condition of the semiconductor cathode, and a relatively low polarization of ≤5O%. Methods to solve or at least greatly reduce the impact of each of these problems are at hand

  7. Plasma polarization spectroscopy

    International Nuclear Information System (INIS)

    Iwamae, Atsushi; Horimoto, Yasuhiro; Fujimoto, Takashi; Hasegawa, Noboru; Sukegawa, Kouta; Kawachi, Tetsuya

    2005-01-01

    The electron velocity distribution function (EVDF) in plasma can be anisotropic in laser-produced plasmas. We have developed a new technique to evaluate the polarization degree of the emission lines in the extreme vacuum ultra violet wavelength region. The polarization of the emission lines and the continuums from the lithium-like nitrogen and from helium- and hydrogen-like carbon in recombining plasma is evaluated. Particle simulation in the velocity space gives the time scale for relaxation of anisotropic EVDFs. (author)

  8. Ultracold Polar Molecules

    Science.gov (United States)

    2016-04-01

    AFRL-AFOSR-UK-TR-2016-0005 Ultracold Polar Molecules Jeremy Hutson UNIVERSITY OF DURHAM Final Report 04/01/2016 DISTRIBUTION A: Distribution approved...DATES COVERED (From - To) 15-Jan-2010 to 14-Jul-2015 4. TITLE AND SUBTITLE Final Report on Grant FA8655-10-1-3033 on Ultracold Polar Molecules 5a...formation of ultracold 87RbCs molecules in their rovibrational ground state by magnetoassociation followed by STIRAP, resulting in 14 papers acknowledging

  9. Hsp Polarization Verification

    Science.gov (United States)

    Bless, Robert

    1991-07-01

    This proposal defines the procedure for determining the instrumental polarization of the polarimetric IDT (IDT#1, POL) on the HSP. 1 of 2 unpolarized standard stars wil be observed using various filter-polarizer combinations. These observations will permit the instrumental polarization to be calibrated. The instrumental polarization must be determined to a high precision in order to vectoriallly remove it from HSP polarization observations to determine the actual astronomical polarization. Final run of proposal will look at one of 2 possible stars previously observed to get another look at the throughput. Revision History: Mark H. Slovak 8/30/88 Translated to V2 proposal instructions (RPSS V6.2) S. Laurent 1/20/89 Updated: Sally Laurent 2/24/89, 3/20/89, 4/13/89, 5/12/89 Modified: P. Stanley 1/15/90 - change to use CTA selected targets only; Fixes for aberration problem - SALM 7/30/90; Based on SV/HSP 1386. New submission changed targets and revised scheduling strategy. Revised: 26 Aug 92 J. Dolan, L. Walter, P. Reppert want to re-run the proposal (3985) one last time to bring down errors.

  10. Correlation Between Microstructure and Mechanical Properties Before and After Reversion of Metastable Austenitic Stainless Steels

    Science.gov (United States)

    Fargas, Gemma; Zapata, Ana; Roa, Joan Josep; Sapezanskaia, Ina; Mateo, Antonio

    2015-12-01

    Reversion treatments are a way to improve the mechanical response of metastable austenitic stainless steels by means of grain refinement. To effectively apply those treatments, the steel must be previously deformed to induce a significant amount of martensitic transformation. In this work, the effect of reversion treatments was studied on a commercial AISI 301LN grade subjected to an industrial cold rolling process, with thickness reductions not higher than 40 pct. Microstructural changes and evolution of both monotonic and cyclic mechanical properties were investigated after cold rolling and upon reversion treatments. Results revealed that the finer austenitic microstructure obtained after reversion leads to an interesting combination of properties, with strong increments in hardness and yield strength, and also fatigue limit improvement, as compared to the initial annealed condition.

  11. Effects of Voltage-Bias Annealing on Metastable Defect Populations in CIGS and CZTSe Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Harvey, Steven P.; Johnston, Steve; Teeter, Glenn

    2016-11-21

    We report on voltage-bias annealing (VBA) experiments performed on CIGS and CZTSe solar cells. In these experiments, completed devices were annealed at moderate temperatures and subsequently quenched with continuously applied voltage bias. These treatments resulted in substantial reversible changes in device characteristics. Photovoltaic (PV) conversion efficiency of the CIGS device varied from below 3% to above 15%, with corresponding changes in CIGS hole density from ~1014 cm-3 to ~1017 cm-3. In the CZTSe device, open-circuit voltage varied from 289 meV to 446 meV, caused by an approximately factor of fifty change in the CZTSe hole density. We interpret these findings in terms of reversible changes to the metastable point-defect populations that control key properties in these materials. Implications for optimization of PV materials and connections to long-term stability of PV devices are discussed.

  12. Correction for Metastability in the Quantification of PID in Thin-film Module Testing: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Hacke, Peter L [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Johnston, Steven [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Spataru, Sergiu [Aalborg University

    2017-10-01

    A fundamental change in the analysis for the accelerated stress testing of thin-film modules is proposed, whereby power changes due to metastability and other effects that may occur due to the thermal history are removed from the power measurement that we obtain as a function of the applied stress factor. The power of reference modules normalized to an initial state - undergoing the same thermal and light- exposure history but without the applied stress factor such as humidity or voltage bias - is subtracted from that of the stressed modules. For better understanding and appropriate application in standardized tests, the method is demonstrated and discussed for potential-induced degradation testing in view of the parallel-occurring but unrelated physical mechanisms that can lead to confounding power changes in the module.

  13. Monte Carlo approach to the decay rate of a metastable system with an arbitrarily shaped barrier

    International Nuclear Information System (INIS)

    Bao, Jing-Dong; Bi, Lei; Jia, Ying

    2007-01-01

    A path integral Monte Carlo method based on the fast-Fourier transform technique combined with the important sampling method is proposed to calculate the decay rate of a metastable quantum system with an arbitrary shape of a potential barrier. The contribution of all fluctuation actions is included which can be used to check the accuracy of the usual steepest-descent approximation, namely, the perturbation expansion of potential. The analytical approximation is found to produce the decay rate of a particle in a cubic potential being about 20% larger than the Monte Carlo data at the crossover temperature. This disagreement increases with increasing complexity of the potential shape. We also demonstrate via Langevin simulation that the postsaddle potential influences strongly upon the classical escape rate

  14. Three-body abrasive wear behaviour of metastable spheroidal carbide cast irons with different chromium contents

    International Nuclear Information System (INIS)

    Efremenko, Vasily; Pastukhova, Tatiana; Chabak, Yuliia; Efremenko, Alexey; Shimizu, Kazumichi; Kusumoto, Kenta; Brykov, Michail

    2018-01-01

    The effect of heat treatment and chromium contents (up to 9.1 wt.%) on the wear resistance of spheroidal carbide cast iron (9.5 wt.% V) was studied using optical and scanning electron microscopy, X-ray diffractometry, dilatometry and three-body abrasive testing. It was found that quenching from 760 C and 920 C improved the alloys' wear resistance compared to the as-cast state due to the formation of metastable austenite transforming into martensite under abrasion. The wear characteristics of alloys studied are 1.6 - 2.3 times higher than that of reference cast iron (12 wt.% V) having stable austenitic matrix. Chromium addition decreases surface damage due to the formation of M_7C_3 carbides, while it reduces wear resistance owing to austenite stabilization to abrasion-induced martensite transformation. The superposition of these factors results in decreasing the alloys' wear behaviour with chromium content increase.

  15. Metastable Cadmium (53P1) production in the Cd+-Na charge-exchange collision

    International Nuclear Information System (INIS)

    Coelho, L.F.

    1987-01-01

    The 326.1 nm emission cross section for the collision process Cd + +Na -> Cd(5 3 P 1 ) + Na + was measured in the energy range 1.5-4.9 KeV. It decreases monotonically from 5 to 2x10 -15 cm 2 . Due to a near degeneracy in energy, this channel presents a much larges cross section than all others (except 5 3 P 0 and 5 3 P 2 , which are highly metastable). This justifies the neglect of the cascade mechanism for populating the 5 3 P 1 , state and, consequently, allows the identification of the 326.1 nm emission cross section with the 5 3 P 1 charge-exchanger excitation cross section. The measured values agree well with theoretical estimates obtained with Olson's model for near-resonant charge exchange. (author) [pt

  16. NATO Advanced Research Workshop on Metastable Systems under Pressure: Platform for New Technologies and Environmental Applications

    CERN Document Server

    Rzoska, Sylwester; Mazur, Victor

    2010-01-01

    The fundamental insight and the technological & environmental relevance of metastable systems have given a strong impetus from the last decade development of extreme pressures experimental techniques, from the GPa region to the challenging negative pressures domain. The ultimate verification of theoretical models and reliable equations for portraying basic properties for such systems seems to be possible only when including temperature and pressure paths. This volume presents a set of papers related to novel findings on the glass transition phenomenon, phase transitions in liquid crystals, critical mixtures, bioliquids, geophysical system which can reveal surprising "secret" features only when using extreme pressures. This can be illustrated by the link between colloidal and molecular glassformers, the universal onset of the non-trivial dynamics in glasses, demistification of the secondary relaxation or novel findings associated with liquid - liquid near critical transitions in critical mixture, liquid cr...

  17. Metastable Magnesium fluorescence spectroscopy using a frequency-stabilized 517 nm laser

    DEFF Research Database (Denmark)

    He, Ming; Jensen, Brian B; Therkildsen, Kasper T

    2009-01-01

    We present a laser operating at 517 nm for our Magnesium laser-cooling and atomic clock project. A two-stage Yb-doped fiber amplifier (YDFA) system generates more than 1.5 W of 1034 nm light when seeded with a 15 mW diode laser. Using a periodically poled lithium niobate (PPLN) waveguide, we obta...... obtained more than 40 mW of 517 nm output power by single pass frequency doubling. In addition, fluorescence spectroscopy of metastable magnesium atoms could be used to stabilize the 517 nm laser to an absolute frequency within 1 MHz.......We present a laser operating at 517 nm for our Magnesium laser-cooling and atomic clock project. A two-stage Yb-doped fiber amplifier (YDFA) system generates more than 1.5 W of 1034 nm light when seeded with a 15 mW diode laser. Using a periodically poled lithium niobate (PPLN) waveguide, we...

  18. Formation of Metastable Water Chains on Anatase TiO 2 (101)

    Energy Technology Data Exchange (ETDEWEB)

    Dahal, Arjun P.; Dohnalek, Zdenek

    2017-09-11

    Anatase TiO2 is indispensable material for energy-harvesting applications and catalysis. In this study, we employ scanning tunneling microscopy (STM) and study water adsorption on most stable TiO2(101) surface of anatase. We demonstrate that at very low temperatures (80 K), water has the transient mobility that allows it to move on the surface and form extended chains. In contrast with many other oxides, these water chains are only metastable in nature. Adsorption at higher temperatures, where sustained diffusion is observed (190 K) leads to isolated water monomers in accord with prior literature. We speculate that the observed low-temperature mobility is a result of adsorption in a long-lived precursor state with a low diffusion barrier.

  19. Time-of-flight spectroscopy of metastable photodissociation fragments in vacuum-UV

    International Nuclear Information System (INIS)

    Fisher, C.H.; Welge, K.H.

    1974-01-01

    Photofragment time-of-flight experiments carried out at photon energies > approximately 11.8eV (1050A) is reported. Processes of the kind AB+hν→A*+B have been investigated where A* is an electronically excited species in a metastable state that can be detected by Auger electron emission from metal surfaces. The present work has been concerned with the identification of dissociation processes from N 2 O, CO 2 , and OCS, measurement of recoil energies and, for the first time, also angular dependent experiments. One objective of the work was to further explore the potential of such studies in the vacuum uv. Their feasibility was demonstrated previously in preliminary experiments

  20. Metastable primordial germ cell-like state induced from mouse embryonic stem cells by Akt activation

    Energy Technology Data Exchange (ETDEWEB)

    Yamano, Noriko [Graduate School of Frontier Biosciences, Osaka University, 2-2 Yamada-oka, Suita, Osaka 565-0871 (Japan); Kimura, Tohru, E-mail: tkimura@patho.med.osaka-u.ac.jp [Department of Pathology, Medical School, Osaka University, 2-2 Yamada-oka, Suita, Osaka 565-0871 (Japan); Watanabe-Kushima, Shoko [Graduate School of Frontier Biosciences, Osaka University, 2-2 Yamada-oka, Suita, Osaka 565-0871 (Japan); Shinohara, Takashi [Department of Molecular Genetics, Graduate School of Medicine, Kyoto University, Kyoto 606-8501 (Japan); Nakano, Toru, E-mail: tnakano@patho.med.osaka-u.ac.jp [Graduate School of Frontier Biosciences, Osaka University, 2-2 Yamada-oka, Suita, Osaka 565-0871 (Japan); Department of Pathology, Medical School, Osaka University, 2-2 Yamada-oka, Suita, Osaka 565-0871 (Japan)

    2010-02-12

    Specification to primordial germ cells (PGCs) is mediated by mesoderm-induction signals during gastrulation. We found that Akt activation during in vitro mesodermal differentiation of embryonic stem cells (ESCs) generated self-renewing spheres with differentiation states between those of ESCs and PGCs. Essential regulators for PGC specification and their downstream germ cell-specific genes were expressed in the spheres, indicating that the sphere cells had commenced differentiation to the germ lineage. However, the spheres did not proceed to spermatogenesis after transplantation into testes. Sphere cell transfer to the original feeder-free ESC cultures resulted in chaotic differentiation. In contrast, when the spheres were cultured on mouse embryonic fibroblasts or in the presence of ERK-cascade and GSK3 inhibitors, reversion to the ESC-like state was observed. These results indicate that Akt signaling promotes a novel metastable and pluripotent state that is intermediate to those of ESCs and PGCs.

  1. Mass spectrometric probes of metal cluster distributions and metastable ion decay

    International Nuclear Information System (INIS)

    Parks, E.K.; Liu, K.; Cole, S.K.; Riley, S.J.

    1988-01-01

    The study of metal clusters has provided both an opportunity and a challenge to the application of mass spectrometry. These days the most often-used technique for cluster generation - laser vaporization - leads to extensive distributions of cluster sizes, from one to perhaps thousands of atoms, and most studies reported to date use excimer laser ionization and time-of-flight mass spectrometry for cluster detection. Our apparatus is a simple one-stage TOF design employing Wiley-McLauren spatial focusing and a one-meter drift tube. In a second apparatus employing a pulsed valve in the cluster source, we see asymmetric broadening of niobium cluster mass peaks under multiphoton ionization conditions, indicating metastable decay of parent cluster ions. Other studies of niobium clusters have shown no such asymmetric peaks. 2 figs

  2. Metastable Phase Separation and Concomitant Solute Redistribution of Liquid Fe-Cu-Sn Ternary Alloy

    International Nuclear Information System (INIS)

    Xiao-Mei, Zhang; Wei-Li, Wang; Ying, Ruan; Bing-Bo, Wei

    2010-01-01

    Liquid Fe-Cu-Sn ternary alloys with lower Sn contents are usually assumed to display a peritectic-type solidification process under equilibrium condition. Here we show that liquid Fe 47.5 Cu 47.5 Sn 5 ternary alloy exhibits a metastable immiscibility gap in the undercooling range of 51–329 K (0.19T L ). Macroscopic phase separation occurs once undercooling exceeds 196 K and causes the formation of a floating Fe-rich zone and a descending Cu-rich zone. Solute redistribution induces the depletion of Sn concentration in the Fe-rich zone and its enrichment in the Cu-rich zone. The primary Fe phase grows dendritically and its growth velocity increases with undercooling until the appearance of notable macrosegregation, but will decrease if undercooling further increases beyond 236 K. The microsegregation degrees of both solutes in Fe and Cu phases vary only slightly with undercooling. (condensed matter: structure, mechanical and thermal properties)

  3. Microstructural investigations and monitoring of low-cycle fatigue degradation in meta-stable austenitic steel

    International Nuclear Information System (INIS)

    Grosse, M.; Kalkhof, D.; Niffenegger, M.

    2000-01-01

    The microstructural changes in the pre-crack stage of low-cycle fatigue (LCF) damage in austenitic pipework steels have been characterised by neutron and X-ray diffraction. The LCF damage evolution in the meta-stable austenitic steel causes a deformation-induced phase transformation from austenite to martensite. Thresholds exist for the formation of martensite as a function of both the load amplitude and the number of LCF cycles. Magnetic stray field and eddy-current measurements were chosen to transfer the results of material characterisation to an on-line monitoring non destructive testing (NDT) method. The density and distribution of martensite obtained from neutron diffraction experiments were used for the calibration of these methods. Both techniques were able to detect the very low amount of martensite in the different-aged specimens (0.5 - 3.1 vol % martensite, usage factors from 0 to 1). (authors)

  4. Population of Metastable States in Stable Hafnium and Ytterbium Nuclei via Beam Break-up

    International Nuclear Information System (INIS)

    Malwela, T.; Ntshangase, S.S.; Shirinda, O.; Bark, R.A.; Gueorguieva, E.; Lawrie, J.J.; Mullins, S.M.; Murray, S.H.T.; Sharpey-Schafer, J.F.; Gal, J.; Kalinka, G.; Krasznahorkay, A.; Molnar, J.; Nyako, B.M.; Timar, J.; Zolnai, L.; Hlatshwayo, T.; Juhasz, K.; Komati, F.S.; Scheurer, J.N.

    2005-01-01

    The ''Chessboard'' section of the DIAMANT charged-particle array has been coupled with the AFRODITE γ-ray spectrometer at the iThemba Laboratory for Accelerator Based Sciences. Charged-particle-γ-ray coincidence data were recorded during the bombardment of a 176Yb target with a 13C beam at an energy of 90 MeV. The purpose of the investigation was to study the population of metastable states in hafium nuclei via incomplete fusion reactions in which the beam breaks up due to its α-cluster character. Of note was the observation of the band based on the Kπ = 16+, T1/2 = 31 year isomer in 178Hf to its 19+ member. Also, decays from the high-K isomeric states in 174Yb and 176Yb. which were populated via 3αxn channels, indicative of complete break-up of the 13C beam

  5. Low-temperature thermal expansion of metastable intermetallic Fe-Cr phases

    International Nuclear Information System (INIS)

    Gorbunoff, A.; Levin, A.A.; Meyer, D.C.

    2009-01-01

    The thermal expansion coefficients (TEC) of metastable disordered intermetallic Fe-Cr phases formed in thin Fe-Cr alloy films prepared by an extremely non-equilibrium method of the pulsed laser deposition are studied. The lattice parameters of the alloys calculated from the low-temperature wide-angle X-ray diffraction (WAXRD) patterns show linear temperature dependencies in the temperature range 143-293 K and a deviation from the linearity at lower temperatures. The linear thermal expansion coefficients determined from the slopes of the linear portions of the temperature-lattice parameter dependencies differ significantly from phase to phase and from the values expected for the body-centered cubic (b.c.c.) Fe 1-x Cr x solid solutions. Strain-crystallite size analysis of the samples is performed. Predictions about the Debye temperature and the mechanical properties of the alloys are made.

  6. Photorecharging of rare-earth ions in a glass and the metastable valence form of the activator

    Energy Technology Data Exchange (ETDEWEB)

    Arbuzov, V.I.; Tolstoi, M.N.; Elerts, M.A.; Trokshs, Ya.S.

    1988-05-01

    The aim of this study was to compare the spectra of absorption and luminescence of europium and cerium in the stable or metastable state in model sodium silicate glasses. The spectra of the optical transitions of electrons between the 4f states and the charge-transfer states at photorecharged (metastable) (Ce/sup 3 +/) ions are shifted approximately 0.6 eV toward lower energies by comparison with the spectra of stable Ce/sup 4 +/ ions. The spectra of the f-d absorption of the photorecharged (Ce/sup 4 +/)/sup /minus// and (Eu/sup 3 +/)/sup /minus// are shifted (0.01-0.15) eV toward lower energies relative to the spectra of the stable analogs Ce/sup 3 +/ and Eu/sup +/. Metastable (Ce/sup 4 +/)/sup /minus// and (Eu/sup 3 +/)/sup /minus//, unlike the analogs, do not luminesce on excitation. Trivalent europium has f-f luminescence characteristics in both stable (Eu/sup 2 +/) and metastable (Eu/sup 2 +/)/sup +/ states. In this case the luminescence spectra of the Eu/sup 3 +/ and the (Eu/sup 2 +/)/sup +/ ions are the same.

  7. Metastable enhancement of C+ and O+ capture reactions: Annual report, July 1, 1988--June 30,1989

    International Nuclear Information System (INIS)

    Thomas, E.W.; Moran, T.F.

    1989-01-01

    The project seeks to study the charge capture reactions of C + and O + in various gases (principally H 2 and He) to determine the difference between cross sections for the ground and metastable excited states of the projectile species. Emphasis is on very low energy collisions close to threshold and data in practice extends over collision energies from 10 to 500 eV; comparison can be made with data from other sources at higher energies. In general terms cross sections for the metastable species are higher by a factor of ten than for the ground state at low energies (10 eV), are surprisingly invariant with energy, are approached by the ground state cross sections at about 10 5 eV, after which both cross sections fall. We have shown also that the metastable content of C + and O + fluxes produced by dissociative ionization of various carbon containing molecules is 15 to 30%. We conclude that in the consideration of a situation involving neutralization of C + and O + (as for example in the edge of a fusion plasma) the metastable content may be high and will influence the net cross section significantly. Present data are not always in agreement with previously published results

  8. From phase transitions to the topological renaissance. Comment on "Topodynamics of metastable brains" by Arturo Tozzi et al.

    Science.gov (United States)

    Somogyvári, Zoltán; Érdi, Péter

    2017-07-01

    The neural topodynamics theory of Tozzi et al. [13] has two main foci: metastable brain dynamics and the topological approach based on the Borsuk-Ulam theorem (BUT). Briefly, metastable brain dynamics theory hypothesizes that temporary stable synchronization and desynchronization of large number of individual dynamical systems, formed by local neural circuits, are responsible for coding of complex concepts in the brain and sudden changes of these synchronization patterns correspond to operational steps. But what dynamical network could form the substrate for this metastable dynamics, capable of entering into a combinatorially high number of metastable synchronization patterns and exhibit rapid transient changes between them? The general problem is related to the discrimination between ;Black Swans; and ;Dragon Kings;. While BSs are related to the theory of self-organized criticality, and suggests that high-impact extreme events are unpredictable, Dragon-kings are associated with the occurrence of a phase transition, whose emergent organization is based on intermittent criticality [9]. Widening the limits of predictability is one of the big open problems in the theory and practice of complex systems (Sect. 9.3 of Érdi [2]).

  9. Dynamic functional connectivity and brain metastability during altered states of consciousness.

    Science.gov (United States)

    Cavanna, Federico; Vilas, Martina G; Palmucci, Matías; Tagliazucchi, Enzo

    2017-10-03

    The scientific study of human consciousness has greatly benefited from the development of non-invasive brain imaging methods. The quest to identify the neural correlates of consciousness combined psychophysical experimentation with neuroimaging tools such as functional magnetic resonance imaging (fMRI) to map the changes in neural activity associated with conscious vs. unconscious percepts. Different neuroimaging methods have also been applied to characterize spontaneous brain activity fluctuations during altered states of consciousness, and to develop quantitative metrics for the level of consciousness. Most of these studies, however, have not explored the dynamic nature of the whole-brain imaging data provided by fMRI. A series of empirical and computational studies strongly suggests that the temporal fluctuations observed in this data present a non-trivial structure, and that this structure is compatible with the exploration of a discrete repertoire of states. In this review we focus on how dynamic neuroimaging can be used to address theoretical accounts of consciousness based on the hypothesis of a dynamic core, i.e. a constantly evolving and transiently stable set of coordinated neurons that constitute an integrated and differentiated physical substrate for each conscious experience. We review work exploring the possibility that metastability in brain dynamics leads to a repertoire of dynamic core states, and discuss how it might be modified during altered states of consciousness. This discussion prompts us to review neuroimaging studies aimed to map the dynamic exploration of the repertoire of states as a function of consciousness. Complementary studies of the dynamic core hypothesis using perturbative methods are also discussed. Finally, we propose that a link between metastability in brain dynamics and the level of consciousness could pave the way towards a mechanistic understanding of altered states of consciousness using tools from dynamical systems

  10. Metastability and avalanche dynamics in strongly correlated gases with long-range interactions

    Science.gov (United States)

    Hruby, Lorenz; Dogra, Nishant; Landini, Manuele; Donner, Tobias; Esslinger, Tilman

    2018-03-01

    We experimentally study the stability of a bosonic Mott insulator against the formation of a density wave induced by long-range interactions and characterize the intrinsic dynamics between these two states. The Mott insulator is created in a quantum degenerate gas of 87-Rubidium atoms, trapped in a 3D optical lattice. The gas is located inside and globally coupled to an optical cavity. This causes interactions of global range, mediated by photons dispersively scattered between a transverse lattice and the cavity. The scattering comes with an atomic density modulation, which is measured by the photon flux leaking from the cavity. We initialize the system in a Mott-insulating state and then rapidly increase the global coupling strength. We observe that the system falls into either of two distinct final states. One is characterized by a low photon flux, signaling a Mott insulator, and the other is characterized by a high photon flux, which we associate with a density wave. Ramping the global coupling slowly, we observe a hysteresis loop between the two states—a further signature of metastability. A comparison with a theoretical model confirms that the metastability originates in the competition between short- and global-range interactions. From the increasing photon flux monitored during the switching process, we find that several thousand atoms tunnel to a neighboring site on the timescale of the single-particle dynamics. We argue that a density modulation, initially forming in the compressible surface of the trapped gas, triggers an avalanche tunneling process in the Mott-insulating region.

  11. Kinetic analysis of rare gas metastable production and optically pumped Xe lasers

    Science.gov (United States)

    Demyanov, A. V.; Kochetov, I. V.; Mikheyev, P. A.; Azyazov, V. N.; Heaven, M. C.

    2018-01-01

    Optically pumped all-rare-gas lasers use metastable rare gas atoms as the lasing species in mixtures with He or Ar buffer gas. The metastables are generated in a glow discharge, and we report model calculations for the optimal production of Ne*, Ar*, Kr* and Xe*. Discharge efficiency was estimated by solving the Boltzmann equation. Laser efficiency, gain and output power of the CW optically pumped Xe laser were assessed as functions of heavier rare gas content, pressure, optical pump intensity and the optical path length. It was found that, for efficient operation the heavier rare gas content has to be of the order of one percent or less, and the total pressure—in the range 0.3–1.5 atm. Output power and specific discharge power increase approximately linearly with pump intensity over the output range from 300–500 W cm‑2. Ternary mixtures Xe:Ar:He were found to be the most promising. Total laser efficiency was found to be nearly the same for pumping the 2p8 or 2p9 state, reaching 61%–70% for a pump intensity of ~720 W cm‑2 when the Xe fraction was in the range 0.001 ÷ 0.01 and Ar fraction—0.1 ÷ 0.5. However, when the 2p8 state was pumped, the maximum total efficiency occurred at larger pressures than for pumping of the 2p9 state. The discharge power density required to sustain a sufficient Xe* number density was in the range of tens of watts per cubic centimeter for 50% Ar in the mixture.

  12. The Controller Synthesis of Metastable Oxides Utilizing Epitaxy and Epitaxial Stabilization

    Energy Technology Data Exchange (ETDEWEB)

    Schlom, Darrell

    2003-12-02

    Molecular beam epitaxy (MBE) has achieved unparalleled control in the integration of semiconductors at the nanometer. These advances were made through the use of epitaxy, epitaxial stabilization, and a combination of composition-control techniques including adsorption-controlled growth and RHEED-based composition control that we have developed, understood, and utilized for the growth of oxides. Also key was extensive characterization (utilizing RHEED, four-circle x-ray diffraction, AFM, TEM, and electrical characterization techniques) in order to study growth modes, optimize growth conditions, and probe the structural, dielectric, and ferroelectric properties of the materials grown. The materials that we have successfully engineered include titanates (PbTiO3, Bi4Ti3O12), tantalates (SrBi2Ta2O9), and niobates (SrBi2Nb2O9); layered combinations of these perovskite-related materials (Bi4Ti3O12-SrTiO3 and Bi4Ti3O12-PbTiO3 Aurivillius phases and metastable PbTiO3/SrTiO3 and BaTiO3/SrTiO3 superlattices), and new metastable phases (Srn+1TinO3n+1 Ruddlesden-Popper phases). The films were grown by reactive MBE and pulsed laser deposition (PLD). Many of these materials are either new or have been synthesized with the highest perfection ever reported. The controlled synthesis of such layered oxide heterostructures offers great potential for tailoring the superconducting, ferroelectric, and dielectric properties of these materials. These properties are important for energy technologies.

  13. Structural Properties and Thermodynamic Stability of Metastable Phases in the Zr-Nb and Ti-V Systems

    International Nuclear Information System (INIS)

    Aurelio, Gabriela

    2003-01-01

    The structural properties and relative stability of metastable phases have been studied in the Zr-Nb and Ti-V systems.The first part of this Thesis is connected to a previous work performed in our Group (G. Grad, PhD Thesis, Instituto Balseiro, Argentina, 1999).It presents a phenomenological analysis of the systematics of interatomic distances in the omega (Ω ) and bcc (β) phases of the transition metals, which concerns a parameter entering into Pauling's resonating-valence- bond-theory and the structural and bonding properties of the Ω and β phases.Neutron diffraction experiments in Zr-Nb and Ti-V alloys are reported, aimed at studying possible atomic ordering in the Ω phase and the composition dependence of its interatomic distances.An extensive neutron diffraction study was performed on a series of Zr-Nb and Ti-V alloys quenched from high temperatures, where β is the stable phase.Upon quenching, three metastable structures are formed, viz., the hcp (∝ q ) phase, the Ω q phase, and the untransformed β q phase.The structural properties of these metastable phases were determined as a function of the Nb and V contents to generate a reliable experimental database.With such data, a series of issues are discussed related to the structure, relative stability, and phase relations in the alloys and its constitutive elements.The effect of composition upon the lattice parameters of the metastable β q and Ω q phases was combined in a consistent way with a critical analysis of structural and thermophysical data on the metastable phases of Ti and Zr.The relative stability of the metastable ∝ q , Ω q and β q phases in Zr-Nb alloys, and its evolution towards thermodynamic equilibrium, were studied combining neutron thermodiffraction and analytical electron microscopy techniques.During isothermal heat treatments performed at high temperature, the structural properties of the alloys were determined as a function of temperature, time and composition.A method of

  14. Polarized Light Microscopy

    Science.gov (United States)

    Frandsen, Athela F.

    2016-01-01

    Polarized light microscopy (PLM) is a technique which employs the use of polarizing filters to obtain substantial optical property information about the material which is being observed. This information can be combined with other microscopy techniques to confirm or elucidate the identity of an unknown material, determine whether a particular contaminant is present (as with asbestos analysis), or to provide important information that can be used to refine a manufacturing or chemical process. PLM was the major microscopy technique in use for identification of materials for nearly a century since its introduction in 1834 by William Fox Talbot, as other techniques such as SEM (Scanning Electron Microscopy), FTIR (Fourier Transform Infrared spectroscopy), XPD (X-ray Powder Diffraction), and TEM (Transmission Electron Microscopy) had not yet been developed. Today, it is still the only technique approved by the Environmental Protection Agency (EPA) for asbestos analysis, and is often the technique first applied for identification of unknown materials. PLM uses different configurations in order to determine different material properties. With each configuration additional clues can be gathered, leading to a conclusion of material identity. With no polarizing filter, the microscope can be used just as a stereo optical microscope, and view qualities such as morphology, size, and number of phases. With a single polarizing filter (single polars), additional properties can be established, such as pleochroism, individual refractive indices, and dispersion staining. With two polarizing filters (crossed polars), even more can be deduced: isotropy vs. anisotropy, extinction angle, birefringence/degree of birefringence, sign of elongation, and anomalous polarization colors, among others. With the use of PLM many of these properties can be determined in a matter of seconds, even for those who are not highly trained. McCrone, a leader in the field of polarized light microscopy, often

  15. The evolution of tensor polarization

    International Nuclear Information System (INIS)

    Huang, H.; Lee, S.Y.; Ratner, L.

    1993-01-01

    By using the equation of motion for the vector polarization, the spin transfer matrix for spin tensor polarization, the spin transfer matrix for spin tensor polarization is derived. The evolution equation for the tensor polarization is studied in the presence of an isolate spin resonance and in the presence of a spin rotor, or snake

  16. Polarized Electrons at Jefferson Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Sinclair, C.K.

    1997-12-31

    The CEBAF accelerator at Jefferson laboratory can deliver CW electron beams to three experimental halls simultaneously. A large fraction of the approved scientific program at the lab requires polarized electron beams. Many of these experiments, both polarized and unpolarized, require high average beam current as well. Since all electrons delivered to the experimental halls originate from the same cathode, delivery of polarized beam to a single hall requires using the polarized source to deliver beam to all experiments in simultaneous operation. The polarized source effort at Jefferson Lab is directed at obtaining very long polarized source operational lifetimes at high average current and beam polarization; at developing the capability to deliver all electrons leaving the polarized source to the experimental halls; and at delivering polarized beam to multiple experimental halls simultaneously.initial operational experience with the polarized source will be presented.

  17. Polarized electrons at Jefferson laboratory

    International Nuclear Information System (INIS)

    The CEBAF accelerator at Jefferson laboratory can deliver CW electron beams to three experimental halls simultaneously. A large fraction of the approved scientific program at the lab requires polarized electron beams. Many of these experiments, both polarized and unpolarized, require high average beam current as well. Since all electrons delivered to the experimental halls originate from the same cathode, delivery of polarized beam to a single hall requires using the polarized source to deliver beam to all experiments in simultaneous operation. The polarized source effort at Jefferson Lab is directed at obtaining very long polarized source operational lifetimes at high average current and beam polarization; at developing the capability to deliver all electrons leaving the polarized source to the experimental halls; and at delivering polarized beam to multiple experimental halls simultaneously. Initial operational experience with the polarized source will be presented

  18. Polarized protons at RHIC

    International Nuclear Information System (INIS)

    Tannenbaum, M.J.

    1990-12-01

    The Physics case is presented for the use of polarized protons at RHIC for one or two months each year. This would provide a facility with polarizations of approx-gt 50% high luminosity ∼2.0 x 10 32 cm -2 s -1 , the possibility of both longitudinal and transverse polarization at the interaction regions, and frequent polarization reversal for control of systematic errors. The annual integrated luminosity for such running (∼10 6 sec per year) would be ∫ Ldt = 2 x 10 38 cm -2 -- roughly 20 times the total luminosity integrated in ∼ 10 years of operation of the CERN Collider (∼10 inverse picobarns, 10 37 cm -2 ). This facility would be unique in the ability to perform parity-violating measurements and polarization test of QCD. Also, the existence of p-p collisions in a new energy range would permit the study of ''classical'' reactions like the total cross section and elastic scattering, etc., and serve as a complement to measurements from p-bar p colliders. 11 refs

  19. The Bochum Polarized Target

    International Nuclear Information System (INIS)

    Reicherz, G.; Goertz, S.; Harmsen, J.; Heckmann, J.; Meier, A.; Meyer, W.; Radtke, E.

    2001-01-01

    The Bochum 'Polarized Target' group develops the target material 6 LiD for the COMPASS experiment at CERN. Several different materials like alcohols, alcanes and ammonia are under investigation. Solid State Targets are polarized in magnetic fields higher than B=2.5T and at temperatures below T=1K. For the Dynamic Nuclear Polarization process, paramagnetic centers are induced chemically or by irradiation with ionizing beams. The radical density is a critical factor for optimization of polarization and relaxation times at adequate magnetic fields and temperatures. In a high sensitive EPR--apparatus, an evaporator and a dilution cryostat with a continuous wave NMR--system, the materials are investigated and optimized. To improve the polarization measurement, the Liverpool NMR-box is modified by exchanging the fixed capacitor for a varicap diode which not only makes the tuning very easy but also provides a continuously tuned circuit. The dependence of the signal area upon the circuit current is measured and it is shown that it follows a linear function

  20. Polarity-Dependent Isomerization of an Unsymmetrical Overcrowded Ethylene Promoted by Zwitterionic Contribution in the Twisted Isomer.

    Science.gov (United States)

    Hirao, Yasukazu; Nagamachi, Nobuhiro; Hosoi, Katsuma; Kubo, Takashi

    2018-03-02

    The twisted form of bianthrone is known as a metastable state provided by a photo-induced or thermal-induced isomerization of the folded form, and thus prevents the isolation and the detailed analysis of its electronic structure. In this study, an unsymmetrical bianthrone (2), consisting of the electron-withdrawing anthrone and electron-donating acridane, have been synthesized and shown to exhibit a solvent-polarity-dependent isomerization reaction between the folded and twisted isomers. With increasing the polarity of the solvent, 2 showed an isomerization reaction from the folded form to the twisted form. The stabilization of the twisted isomer in polar solvents can be interpreted as proof of its relatively large zwitterionic character. The DMF solution of 2 displayed paramagnetically-broadened NMR signals from the thermally populated triplet state resulting from rotation of the weakened ethylenic double bond of the twisted isomer. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. In-line Fiber Polarizer

    OpenAIRE

    Perumalsamy, Priya

    1998-01-01

    Polarizers and polarization devices are important components in fiber optic communication and sensor systems. There is a growing need for efficient low loss components that are compatible with optical fibers. An all fiber in-line polarizer is a more desirable alternative that could be placed at appropriate intervals along communication links. An in-line fiber polarizer was fabricated and tested. The in-line fiber polarizer operates by coupling optical energy propagatin...

  2. Political Competition and Polarization

    DEFF Research Database (Denmark)

    Schultz, Christian

    This paper considers political competition and the consequences of political polarization when parties are better informed about how the economy functions than voters are. Specifically, parties know the cost producing a public good, voters do not. An incumbent's choice of policy acts like a signa...... for costs before an upcoming election. It is shown that the more polarized the political parties the more distorted the incumbent's policy choice.......This paper considers political competition and the consequences of political polarization when parties are better informed about how the economy functions than voters are. Specifically, parties know the cost producing a public good, voters do not. An incumbent's choice of policy acts like a signal...

  3. Physics of polarized targets

    CERN Document Server

    Niinikoski, Tapio

    2014-01-01

    For developing, building and operating solid polarized targets we need to understand several fields of physics that have seen sub stantial advances during the last 50 years. W e shall briefly review a selection of those that are important today. These are: 1) quantum statistical methods to describe saturation and relaxation in magnetic resonance; 2) equal spin temperature model for dy namic nuclear polarization; 3 ) weak saturation during NMR polarization measurement; 4 ) refrigeration using the quantum fluid properties of helium isotopes. These, combined with superconducting magnet technologies, permit today to reach nearly complete pola rization of almost any nuclear spins. Targets can be operated in frozen spin mode in rather low and inhomogeneous field of any orientation, and in DNP mode in beams of high intensity. Beyond such experiments of nuclear and particle physics, applications a re also emerging in macromolecular chemistry and in magnetic resonance imaging. This talk is a tribute to Michel Borghini...

  4. No More Polarization, Please!

    DEFF Research Database (Denmark)

    Hansen, Mia Reinholt

    The organizational science literature on motivation has for long been polarized into two main positions; the organizational economic position focusing on extrinsic motivation and the organizational behavior position emphasizing intrinsic motivation. With the rise of the knowledge economy...... and the increasing levels of complexities it entails, such polarization is not fruitful in the attempt to explain motivation of organizational members. This paper claims that a more nuanced perspective on motivation, acknowledging the co-existence of intrinsic and extrinsic motivation, the possible interaction...... between the two as well as different types of motivations filling in the gap between the two polar types, is urgently needed in the organizational science literature. By drawing on the research on intrinsic and extrinsic motivation conducted in social psychology and combining this with contributions from...

  5. Polarized source upgrading

    International Nuclear Information System (INIS)

    Clegg, T.B.; Rummel, R.L.; Carter, E.P.; Westerfeldt, C.R.; Lovette, A.W.; Edwards, S.E.

    1985-01-01

    The decision was made this past year to move the Lamb-shift polarized ion source which was first installed in the laboratory in 1970. The motivation was the need to improve the flexibility of spin-axis orientation by installing the ion source with a new Wien-filter spin precessor which is capable of rotating physically about the beam axis. The move of the polarized source was accomplished in approximately two months, with the accelerator being turned off for experiments during approximately four weeks of this time. The occasion of the move provided the opportunity to rewire completely the entire polarized ion source frame and to rebuild approximately half of the electronic chassis on the source. The result is an ion source which is now logically wired and carefully documented. Beams obtained from the source are much more stable than those previously available

  6. A lunar polar expedition

    Science.gov (United States)

    Dowling, Richard; Staehle, Robert L.; Svitek, Tomas

    1992-09-01

    Advanced exploration and development in harsh environments require mastery of basic human survival skill. Expeditions into the lethal climates of Earth's polar regions offer useful lessons for tommorrow's lunar pioneers. In Arctic and Antarctic exploration, 'wintering over' was a crucial milestone. The ability to establish a supply base and survive months of polar cold and darkness made extensive travel and exploration possible. Because of the possibility of near-constant solar illumination, the lunar polar regions, unlike Earth's may offer the most hospitable site for habitation. The World Space Foundation is examining a scenario for establishing a five-person expeditionary team on the lunar north pole for one year. This paper is a status report on a point design addressing site selection, transportation, power, and life support requirements.

  7. POLARIZED NEUTRONS IN RHIC

    Energy Technology Data Exchange (ETDEWEB)

    COURANT,E.D.

    1998-04-27

    There does not appear to be any obvious way to accelerate neutrons, polarized or otherwise, to high energies by themselves. To investigate the behavior of polarized neutrons the authors therefore have to obtain them by accelerating them as components of heavier nuclei, and then sorting out the contribution of the neutrons in the analysis of the reactions produced by the heavy ion beams. The best neutron carriers for this purpose are probably {sup 3}He nuclei and deuterons. A polarized deuteron is primarily a combination of a proton and a neutron with their spins pointing in the same direction; in the {sup 3}He nucleus the spins of the two protons are opposite and the net spin (and magnetic moment) is almost the same as that of a free neutron. Polarized ions other than protons may be accelerated, stored and collided in a ring such as RHIC provided the techniques proposed for polarized proton operation can be adapted (or replaced by other strategies) for these ions. To accelerate polarized particles in a ring, one must make provisions for overcoming the depolarizing resonances that occur at certain energies. These resonances arise when the spin tune (ratio of spin precession frequency to orbit frequency) resonates with a component present in the horizontal field. The horizontal field oscillates with the vertical motion of the particles (due to vertical focusing); its frequency spectrum is dominated by the vertical oscillation frequency and its modulation by the periodic structure of the accelerator ring. In addition, the magnet imperfections that distort the closed orbit vertically contain all integral Fourier harmonics of the orbit frequency.

  8. Dark Polar Dunes

    Science.gov (United States)

    2005-01-01

    20 January 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image, acquired during northern summer in December 2004, shows dark, windblown sand dunes in the north polar region of Mars. A vast sea of sand dunes nearly surrounds the north polar cap. These landforms are located near 80.3oN, 144.1oW. Light-toned features in the image are exposures of the substrate that underlies the dune field. The image covers an area about 3 km (1.9 mi) wide and is illuminated by sunlight from the lower left.

  9. Imaging with Polarized Neutrons

    Directory of Open Access Journals (Sweden)

    Nikolay Kardjilov

    2018-01-01

    Full Text Available Owing to their zero charge, neutrons are able to pass through thick layers of matter (typically several centimeters while being sensitive to magnetic fields due to their intrinsic magnetic moment. Therefore, in addition to the conventional attenuation contrast image, the magnetic field inside and around a sample can be visualized by detecting changes of polarization in a transmitted beam. The method is based on the spatially resolved measurement of the cumulative precession angles of a collimated, polarized, monochromatic neutron beam that traverses a magnetic field or sample.

  10. The polar mesosphere

    International Nuclear Information System (INIS)

    Morris, Ray; Murphy, Damian

    2008-01-01

    The mesosphere region, which lies at the edge of space, contains the coldest layer of the Earth's atmosphere, with summer temperatures as low as minus 130 °C. In this extreme environment ice aerosol layers have appeared since the dawn of industrialization—whose existence may arguably be linked to human influence—on yet another layer of the Earth's fragile atmosphere. Ground-based and space-based experiments conducted in the Arctic and Antarctic during the International Polar Year (IPY) aim to address limitations in our knowledge and to advance our understanding of thermal and dynamical processes at play in the polar mesosphere

  11. Internal polarized targets

    Energy Technology Data Exchange (ETDEWEB)

    Kinney, E.R.; Coulter, K.; Gilman, R.; Holt, R.J.; Kowalczyk, R.S.; Napolitano, J.; Potterveld, D.H.; Young, L. (Argonne National Lab., IL (USA)); Mishnev, S.I.; Nikolenko, D.M.; Popov, S.G.; Rachek, I.A.; Temnykh, A.B.; Toporkov, D.K.; Tsentalovich, E.P.; Wojtsekhowski, B.B. (AN SSSR, Novosibirsk (USSR). Inst. Yadernoj Fiziki)

    1989-01-01

    Internal polarized targets offer a number of advantages over external targets. After a brief review of the basic motivation and principles behind internal polarized targets, the technical aspects of the atomic storage cell will be discussed in particular. Sources of depolarization and the means by which their effects can be ameliorated will be described, especially depolarization by the intense magnetic fields arising from the circulating particle beam. The experience of the Argonne Novosibirsk collaboration with the use of a storage cell in a 2 GeV electron storage ring will be the focus of this technical discussion. 17 refs., 11 figs.

  12. AGS polarized H- source

    International Nuclear Information System (INIS)

    Kponou, A.; Alessi, J.G.; Sluyters, T.

    1985-01-01

    The AGS polarized H - source is now operational. During a month-long experimental physics run in July 1984, pulses equivalent to 15 μA x 300 μs (approx. 3 x 10 10 protons) were injected into the RFQ preaccelerator. Beam polarization, measured at 200 MeV, was approx. 75%. After the run, a program to increase the H - yield of the source was begun and significant progress has been made. The H - current is now frequently 20 to 30 μA. A description of the source and some details of our operating experience are given. We also briefly describe the improvement program

  13. The physics of polarization

    Science.gov (United States)

    Landi Degl'Innocenti, Egidio

    This course is intended to give a description of the basic physical concepts which underlie the study and the interpretation of polarization phenomena. Apart from a brief historical introduction (Sect. 1), the course is organized in three parts. A first part (Sects. 2 - 6) covers the most relevant facts about the polarization phenomena that are typically encountered in laboratory applications and in everyday life. In Sect. 2, the modern description of polarization in terms of the Stokes parameters is recalled, whereas Sect. 3 is devoted to introduce the basic tools of laboratory polarimetry, such as the Jones calculus and the Mueller matrices. The polarization phenomena which are met in the reflection and refraction of a beam of radiation at the separation surface between two dielectrics, or between a dielectric and a metal, are recalled in Sect. 4. Finally, Sect. 5 gives an introduction to the phenomena of dichroism and of anomalous dispersion and Sect. 6 summarizes the polarization phenomena that are commonly encountered in everyday life. The second part of this course (Sects. 7-14) deals with the description, within the formalism of classical physics, of the spectro-polarimetric properties of the radiation emitted by accelerated charges. Such properties are derived by taking as starting point the Liénard and Wiechert equations that are recalled and discussed in Sect. 7 both in the general case and in the non-relativistic approximation. The results are developed to find the percentage polarization, the radiation diagram, the cross-section and the spectral characteristics of the radiation emitted in different phenomena particularly relevant from the astrophysical point of view. The emission of a linear antenna is derived in Sect. 8. The other Sections are devoted to Thomson scattering (Sect. 9), Rayleigh scattering (Sect. 10), Mie scattering (Sect. 11), bremsstrahlung radiation (Sect. 12), cyclotron radiation (Sect. 13), and synchrotron radiation (Sect. 14

  14. Polarized Proton Collisions at RHIC

    CERN Document Server

    Bai, Mei; Alekseev, Igor G; Alessi, James; Beebe-Wang, Joanne; Blaskiewicz, Michael; Bravar, Alessandro; Brennan, Joseph M; Bruno, Donald; Bunce, Gerry; Butler, John J; Cameron, Peter; Connolly, Roger; De Long, Joseph; Drees, Angelika; Fischer, Wolfram; Ganetis, George; Gardner, Chris J; Glenn, Joseph; Hayes, Thomas; Hseuh Hsiao Chaun; Huang, Haixin; Ingrassia, Peter; Iriso, Ubaldo; Laster, Jonathan S; Lee, Roger C; Luccio, Alfredo U; Luo, Yun; MacKay, William W; Makdisi, Yousef; Marr, Gregory J; Marusic, Al; McIntyre, Gary; Michnoff, Robert; Montag, Christoph; Morris, John; Nicoletti, Tony; Oddo, Peter; Oerter, Brian; Osamu, Jinnouchi; Pilat, Fulvia Caterina; Ptitsyn, Vadim; Roser, Thomas; Satogata, Todd; Smith, Kevin T; Svirida, Dima; Tepikian, Steven; Tomas, Rogelio; Trbojevic, Dejan; Tsoupas, Nicholaos; Tuozzolo, Joseph; Vetter, Kurt; Wilinski, Michelle; Zaltsman, Alex; Zelenski, Anatoli; Zeno, Keith; Zhang, S Y

    2005-01-01

    The Relativistic Heavy Ion Collider~(RHIC) provides not only collisions of ions but also collisions of polarized protons. In a circular accelerator, the polarization of polarized proton beam can be partially or fully lost when a spin depolarizing resonance is encountered. To preserve the beam polarization during acceleration, two full Siberian snakes were employed in RHIC to avoid depolarizing resonances. In 2003, polarized proton beams were accelerated to 100~GeV and collided in RHIC. Beams were brought into collisions with longitudinal polarization at the experiments STAR and PHENIX by using spin rotators. RHIC polarized proton run experience demonstrates that optimizing polarization transmission efficiency and improving luminosity performance are significant challenges. Currently, the luminosity lifetime in RHIC is limited by the beam-beam effect. The current state of RHIC polarized proton program, including its dedicated physics run in 2005 and efforts to optimize luminosity production in beam-beam limite...

  15. 7 CFR 160.29 - Containers to remain intact.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Containers to remain intact. 160.29 Section 160.29... STANDARDS FOR NAVAL STORES Analysis, Inspection, and Grading on Request § 160.29 Containers to remain intact... the containers holding such naval stores remain intact as sampled until the analysis, classification...

  16. On the hardenability of Nb-modified metastable beta Ti-5553 alloy

    Energy Technology Data Exchange (ETDEWEB)

    Campo, K.N.; Andrade, D.R.; Opini, V.C.; Mello, M.G.; Lopes, E.S.N.; Caram, R., E-mail: caram@fem.unicamp.br

    2016-05-15

    Among the commercially available titanium alloys, the metastable β Ti-5553 alloy (Ti–5Al–5V–5Mo–3Cr–0.5Fe wt.%) is an object of great interest because it is employed in aerospace structural applications, primarily in the replacement of steel components. One of the primary advantages of this alloy is its high hardenability, which allows it to retain the β phase at room temperature, even at low cooling rates, thereby allowing the thermoprocessing of thick parts. The aim of this investigation was to evaluate the effect of the replacement of V with Nb on the hardenability of Ti-5553. Based on the molybdenum equivalent criterion, the Nb-modified Ti-5553 alloy was designed to present 12 wt.% of Nb instead of 5 wt.% of V. Samples of both alloys were prepared by melting them in an arc furnace under an inert atmosphere, heat-treated at high temperatures for 12 h and plastic deformed using swage forging. Finally, these samples were solution heat-treated at temperatures above the β-transus followed by cooling at different rates using water quenching, furnace cooling and a modified Jominy end quench test. Characterization was performed by measuring Vickers hardness, X-ray diffraction, and light optical, scanning electron and transmission electron microscopy. The results obtained indicate that metastable β phase can be retained when the cooling rate is higher than 21 °C/s for both alloys. At lower cooling rates, α phase precipitation was observed, but it appeared to be less evident in the Nb-modified Ti-5553, suggesting that the replacement of V with Nb increased the hardenability of the alloy. - Highlights: • Hardenability of Ti alloys are assessed using a modified Jominy end quench test. • Ti-5553 and Nb-modified Ti-5553 are subjected to continuous cooling experiments. • β phase decomposition kinetics is reduced by replacing V with Nb in Ti-5553. • Nb-modified Ti-5553 features improved hardenability. • Replacement of V with Nb causes the

  17. A metastable HCP intermetallic phase in Cu-Al bilayer films

    Energy Technology Data Exchange (ETDEWEB)

    Cha, Limei

    2006-07-01

    obtain the temperature range in which the HCP metastable phase will be stable. According to the XRD measurements, it is found that the metastable HCP phase exists below 120 C. (orig.)

  18. Material Characterization of Fatigue Specimens made from Meta-stable Austenitic Stainless Steel

    Energy Technology Data Exchange (ETDEWEB)

    Niffenegger, M.; Grosse, M.; Kalkhof, D.; Leber, H. [Paul Scherrer Institut Villigen (Switzerland); Vincent, A.; Pasco, L.; Morin, M. [Insa de Lyon (France)

    2003-07-01

    The main objective of the EU-project CRETE (Contract No.: FIS5-1999-00280) was to assess the capability and the reliability of innovative NDT-inspection techniques for the detection of material degradation, induced by thermal fatigue and neutron irradiation, of metastable austenitic and ferritic low-alloy steel. Several project partners tested aged or irradiated samples, using various techniques (acoustic, magnetic and thermoelectric). However, these indirect methods require a careful interpretation of the measured signal in terms of micro-structural evolutions due to ageing of the material. Therefore the material had to be characterized in its undamaged, as well as in its damaged state. The present report summarises only the material characterization of the fatigue specimens. It is issued simultaneously as an PSI Bericht and the CRETE work package 3 (WP3) report. Each partner according to their own specifications purchased three materials under investigation, namely AISI 347, AISI 321 and AISI 304L. After sending the material to PSI, all fatigue specimens were manufactured by the same Swiss company. Each partner was responsible for his fatigue tests which are documented in the report WP1, written by FANP. In order to characterize the material in its unfatigued as well as in its fatigued state and to consider microstructural changes related to fatigue damage the methods listed below were employed either by PSI or by INSA de Lyon: (1) Inductive Coupled Plasma Emission Photometry (ICP-OES) was applied to determine the chemical composition, (2) Scanning electron microscopy (SEM) for observing cracks, slip bands between grain and twin boundaries, - Ferromaster for measuring the magnetic permeability, (3) Physical Properties Measuring System (PPMS) for measuring magnetization characteristics, (4) Neutron- and advanced X-ray diffraction methods for the quantitative determination of martensite, - Transmission electron microscopy (TEM) for the observation of crystalline

  19. Lobbying and political polarization

    OpenAIRE

    Ursprung, Heinrich W.

    2002-01-01

    Standard spatial models of political competition give rise to equilibria in which the competing political parties or candidates converge to a common position. In this paper I show how political polarization can be generated in models that focus on the nexus between pre-election interest group lobbying and electoral competition.

  20. Fluorescence confocal polarizing microscopy

    Indian Academy of Sciences (India)

    Much of the modern understanding of orientational order in liquid crystals (LCs) is based on polarizing microscopy (PM). A PM image bears only two-dimensional (2D) information, integrating the 3D pattern of optical birefringence over the path of light. Recently, we proposed a technique to image 3D director patterns by ...

  1. Polarization of Bremsstrahlung

    International Nuclear Information System (INIS)

    Miller, J.

    1957-01-01

    The numerical results for the polarization of Bremsstrahlung are presented. The multiple scattering of electrons in the target is taken into account. The angular-and photon energy dependences are seen on the curves for an incident 25 MeV electron energy. (Author) [fr

  2. DESY: HERA polarization

    International Nuclear Information System (INIS)

    Anon.

    1992-01-01

    The new HERA electron-proton collider at DESY in Hamburg achieved the first luminosity for electron-proton collisions on 19 October last year. Only one month later, on 20 November, HERA passed another important milestone with the observation of transverse electron polarization

  3. Titan Polar Landscape Evolution

    Science.gov (United States)

    Moore, Jeffrey M.

    2016-01-01

    With the ongoing Cassini-era observations and studies of Titan it is clear that the intensity and distribution of surface processes (particularly fluvial erosion by methane and Aeolian transport) has changed through time. Currently however, alternate hypotheses substantially differ among specific scenarios with respect to the effects of atmospheric evolution, seasonal changes, and endogenic processes. We have studied the evolution of Titan's polar region through a combination of analysis of imaging, elevation data, and geomorphic mapping, spatially explicit simulations of landform evolution, and quantitative comparison of the simulated landscapes with corresponding Titan morphology. We have quantitatively evaluated alternate scenarios for the landform evolution of Titan's polar terrain. The investigations have been guided by recent geomorphic mapping and topographic characterization of the polar regions that are used to frame hypotheses of process interactions, which have been evaluated using simulation modeling. Topographic information about Titan's polar region is be based on SAR-Topography and altimetry archived on PDS, SAR-based stereo radar-grammetry, radar-sounding lake depth measurements, and superposition relationships between geomorphologic map units, which we will use to create a generalized topographic map.

  4. Graphics of polar figure

    International Nuclear Information System (INIS)

    Macias B, L.R.

    1991-11-01

    The objective of this work, is that starting from a data file coming from a spectra that has been softened, and of the one that have been generated its coordinates to project it in stereographic form, to create the corresponding polar figure making use of the Cyber computer of the ININ by means of the GRAPHOS package. This work only requires a Beta, Fi and Intensity (I) enter data file. It starts of the existence of a softened spectra of which have been generated already with these data, making use of some language that in this case was FORTRAN for the Cyber computer, a program is generated supported in the Graphos package that allows starting of a reading of the Beta, Fi, I file, to generate the points in a stereographic projection and that it culminates with the graph of the corresponding polar figure. The program will request the pertinent information that is wanted to capture in the polar figure just as: date, name of the enter file, indexes of the polar figure, number of levels, radio of the stereographic projection (cms.), crystalline system to which belongs the sample, name the neuter graph file by create and to add the own general data. (Author)

  5. Characteristics of volume polarization holography with linear polarization light

    Science.gov (United States)

    Zang, Jinliang; Wu, An'an; Liu, Ying; Wang, Jue; Lin, Xiao; Tan, Xiaodi; Shimura, Tsutomu; Kuroda, Kazuo

    2015-10-01

    Volume polarization holographic recording in phenanthrenequinone-doped poly(methyl methacrylate) (PQ-PMMA) photopolymer with linear polarized light is obtained. The characteristics of the volume polarization hologram are experimentally investigated. It is found that beyond the paraxial approximation the polarization states of the holographic reconstruction light are generally different from the signal light. Based on vector wave theoretical analyses and material properties, the special exposure condition for correctly holographic reconstruction is obtained and experimentally demonstrated.

  6. Study of the metastable singlet of molecular nitrogen and of oxygen atoms in discharges and post-discharges

    International Nuclear Information System (INIS)

    Magne, Lionel

    1991-01-01

    Whereas discharges in nitrogen, in oxygen and in their mixtures are used in many different industrial processes (surface treatment, nitridation, oxidation, and so on), in order to get a better knowledge on nitrogen electronic states, this research thesis reports the study of the metastable singlet state of molecular nitrogen, and of oxygen atoms in their fundamental state. The molecular metastable has been observed by far-UV optical emission spectroscopy, in the positive column of a continuous discharge and in time post-discharge. As far as continuous discharge is concerned, the author measured the vibrational distribution of this state. A kinetic model has been developed, and calculated vibrational distributions are in good agreement with measurements. The density of oxygen atoms in fundamental state in time post-discharge has been measured by far-UV absorption optical spectroscopy. The probability of atom re-association of glass walls is deduced from the obtained results [fr

  7. Dimensional effects and scalability of Meta-Stable Dip (MSD) memory effect for 1T-DRAM SOI MOSFETs

    Science.gov (United States)

    Hubert, A.; Bawedin, M.; Cristoloveanu, S.; Ernst, T.

    2009-12-01

    The difficult scaling of bulk Dynamic Random Access Memories (DRAMs) has led to various concepts of capacitor-less single-transistor (1T) architectures based on SOI transistor floating-body effects. Amongst them, the Meta-Stable Dip RAM (MSDRAM), which is a double-gate Fully Depleted SOI transistor, exhibits attractive performances. The Meta-Stable Dip effect results from the reduced junction leakage current and the long carrier generation lifetime in thin silicon film transistors. In this study, various devices with different gate lengths, widths and silicon film thicknesses have been systematically explored, revealing the impact of transistor dimensions on the MSD effect. These experimental results are discussed and validated by two-dimensional numerical simulations. It is found that MSD is maintained for small dimensions even in standard SOI MOSFETs, although specific optimizations are expected to enhance MSDRAM performances.

  8. Stable and metastable equilibria in PbSe + SnI2=SnSe + PbI2

    International Nuclear Information System (INIS)

    Odin, I.N.; Grin'ko, V.V.; Kozlovskij, V.F.; Demidova, E.D.

    2003-01-01

    T-x-y phase diagrams of the PbSe + SnI 2 =SnSe + PbI 2 mutual system (stable states) are plotted for the first time. It is shown that melt, solid solutions on the base of components of the mutual system and phase on the base of Sn 2 SeI 4 take part in phase equilibria. Transformations in the PbSe + SnI 2 =SnSe + PbI 2 mutual system leading to crystallization of metastable polytype modifications of lead iodides and metastable ternary compound forming in PbSe-PbI 2 system are investigated for the first time [ru

  9. Demonstration of a CW diode-pumped Ar metastable laser operating at 4  W.

    Science.gov (United States)

    Han, J; Heaven, M C; Moran, P J; Pitz, G A; Guild, E M; Sanderson, C R; Hokr, B

    2017-11-15

    Optically pumped rare gas lasers are being investigated as potential high-energy, high beam quality systems. The lasing medium consists of rare gas atoms (Rg=Ne, Ar, Kr, or Xe) that have been electric discharge excited to the metastable np 5 (n+1)s P3 2 state. Following optical excitation, helium (He) at pressures of 200-1000 Torr is used as the energy transfer agent to create a population inversion. The primary technical difficulty for this scheme is the discharge production of sufficient Rg* metastables in the presence of >200  Torr of He. In this Letter, we describe a pulsed discharge that yields >10 13   cm -3 Ar* in the presence of He at total pressures up to 750 Torr. Using this discharge, a diode-pumped Ar* laser providing 4.1 W has been demonstrated.

  10. Experiments with Fermilab polarized proton and polarized antiproton beams

    International Nuclear Information System (INIS)

    Yokosawa, A.

    1990-01-01

    We summarize activities concerning the Fermilab polarized beams. They include a brief description of the polarized-beam facility, measurements of beam polarization by polarimeters, asymmetry measurements in the π degree production at high p perpendicular and in the Λ (Σ degree), π ± , π degree production at large x F , and Δσ L (pp, bar pp) measurements. 18 refs

  11. NUCLEON POLARIZATION IN 3-BODY MODELS OF POLARIZED LI-6

    NARCIS (Netherlands)

    SCHELLINGERHOUT, NW; KOK, LP; COON, SA; ADAM, RM

    1993-01-01

    Just as He-3 --> can be approximately characterized as a polarized neutron target, polarized Li-6D has been advocated as a good isoscalar nuclear target for the extraction of the polarized gluon content of the nucleon. The original argument rests upon a presumed ''alpha + deuteron'' picture of Li-6,

  12. Determination of metastable zone width of potassium sulfate in aqueous solution by ultrasonic sensor and FBRM

    Science.gov (United States)

    Luo, Mengjie; Liu, Chenglin; Xue, Jin; Li, Ping; Yu, Jianguo

    2017-07-01

    The metastable zone width (MSZW) and nucleation kinetics of potassium sulfate in the aqueous solution were investigated. MSZW was measured using both the ultrasonic velocity sensor and the focused beam reflectance measurement (FBRM) at different cooling rate, stirring rate and impurities concentration (aluminum ions and silicon ions), and the effects of these conditions on MSZW were discussed in details. In addition, the accuracy and sensitivity of detectors to measure the nucleation temperature of potassium sulfate in the aqueous solution were compared between the ultrasonic velocity sensor and FBRM over a wider range of operating conditions. Although two detectors measured MSZW with an acceptable accuracy, the ultrasonic velocity sensor had a higher sensitivity to the phase transition of potassium sulfate in solution since it directly detected the concentration change of potassium sulfate in solution. Furthermore, both self-consistent Nývlt-like equation method and classical 3D nucleation theory approach were applied to estimate MSZW of potassium sulfate in aqueous solution. According to these classical theories, the nucleation kinetics parameters were calculated based on the measured MSZW data for potassium sulfate aqueous solution with 40 °C, 50 °C and 60 °C saturation temperature, respectively. It was found two approaches could describe MSZW of potassium sulfate aqueous system very well.

  13. Crystal nucleation and dendrite growth of metastable phases in undercooled melts

    International Nuclear Information System (INIS)

    Herlach, Dieter

    2011-01-01

    Research highlights: → Homogenous nucleation. → Effects of convection on dendrite growth kinetics. → Description of disorder trapping validated by experiment. - Abstract: An undercooled melt possesses an enhanced free enthalpy that opens up the possibility to crystallize metastable crystalline solids in competition with their stable counterparts. Crystal nucleation selects the crystallographic phase whereas the growth dynamics controls microstructure evolution. We apply containerless processing techniques such as electromagnetic and electrostatic levitation to containerlesss undercool and solidify metallic melts. Owing to the complete avoidance of heterogeneous nucleation on container-walls a large undercooling range becomes accessible with the extra benefit that the freely suspended drop is direct accessible for in situ observation of crystallization far away from equilibrium. Results of investigations of maximum undercoolability on pure zirconium are presented showing the limit of maximum undercoolability set by the onset of homogeneous nucleation. Rapid dendrite growth is measured as a function of undercooling by a high-speed camera and analysed within extended theories of non-equilibrium solidification. In such both supersaturated solid solutions and disordered superlattice structure of intermetallics are formed at high growth velocities. A sharp interface theory of dendrite growth is capable to describe the non-equilibrium solidification phenomena during rapid crystallization of deeply undercooled melts. Eventually, anomalous growth behaviour of Al-rich Al-Ni alloys is presented, which may be caused by forced convection.

  14. Plasma effects on the metastable H0(2s) atom

    International Nuclear Information System (INIS)

    Benage, J.F. Jr.

    1986-01-01

    Atomic radiative processes that occur in plasmas have long been of interest of plasma physicists. The process investigated here is atomic dipole transitions, specifically transitions from the metastable 2s to the 2p in hydrogen, which are induced by processes that occur in the plasma. An experiment was done to measure the rate of transitions from 2s to 2p in hydrogen. This experiment was divided into two sections. The first was to measure the transition rate in a near equilibrium plasma. The second section measured the transition rate when RF oscillations were imposed on the plasma. Results of the first part show that microscopic fluctuating electric fields produced by the motions of the charged particles induce transitions from 2s to 2p in hydrogen. The magnitude of this effect is compared to predicted transition rates due to collisions with electrons and ions and to rates predicted for an equilibrium plasma. In the second part, the plasma was shown to act as a filter, preventing transitions from being caused by the RF unless the RF was in the range where plasma waves could be launched. The interpretation given for this effect is that, when the oscillations are inducing transitions, it is because plasma waves are being launched in the plasma and it is these waves that are inducing the transitions

  15. Theoretical and experimental study of carburisation and decarburisation of a meta-stable austenitic steel

    Directory of Open Access Journals (Sweden)

    Charles West

    2005-12-01

    Full Text Available Metastable austenitic stainless steels are known to undergo a partial transformation of austenite to martensite as a consequence of plastic deformation. In the case of cyclic loading, a certain level of plastic strain must be exceeded, and phase formation takes place after an incubation period, during which the necessary amount of plastic deformation is accumulated. The susceptibility of the austenitic phase to deformation-induced martensite formation is strongly affected by the temperature of loading and the stability of austenite, which itself depends on the chemical composition. A key element in this regard is carbon which stabilizes the austenitic phase. It is shown in this study that the carbon concentration can be analysed systematically and reproducible by means of annealing treatments, if the parameters of these treatments are carefully defined on the basis of advanced theoretical thermodynamic and kinetic considerations. First results on the effect of carbon concentration and temperature of fatigue testing on the austenite/martensite transformation are presented, in order to illustrate the significance of these parameters on the martensite formation rate.

  16. Adsorption on metal oxides Studies with the metastable impact electron spectroscopy

    CERN Document Server

    Krischok, S; Kempter, V

    2002-01-01

    An overview is given on the application of metastable impact electron spectroscopy, in combination with UPS, to the study of clean magnesia and titania surfaces and their interaction with metal atoms and small molecules. The mechanisms for metal adsorption on reducible (titania) and non-reducible (magnesia) substrates are different: while on titania the metal atom often bonds by electron transfer to Ti3d states, it is hybridization of the adsorbate and anion wavefunctions which accounts for the bonding on MgO. In the case of H sub 2 O, molecular adsorption takes place both on MgO and TiO sub 2; on the other hand, water-alkali coadsorption leads to hydroxide formation. In the case of CO sub 2 , chemisorption takes place in form of carbonate (CO sub 3) species. These originate from the CO sub 2 interaction with O sup 2 sup - surface anions. While for CaO chemisorption takes place at regular oxygen sites, for MgO this occurs at low-coordinated oxygen ions only; for TiO sub 2 chemisorption requires alkali coadsor...

  17. Nuclear dynamics in the metastable phase of the solid acid caesium hydrogen sulfate.

    Science.gov (United States)

    Krzystyniak, Maciej; Drużbicki, Kacper; Fernandez-Alonso, Felix

    2015-12-14

    High-resolution spectroscopic measurements using thermal and epithermal neutrons and first-principles calculations within the framework of density-functional theory are used to investigate the nuclear dynamics of light and heavy species in the metastable phase of caesium hydrogen sulfate. Within the generalised-gradient approximation, extensive calculations show that both 'standard' and 'hard' formulations of the Perdew-Burke-Ernzerhof functional supplemented by Tkatchenko-Scheffler dispersion corrections provide an excellent description of the known structure, underlying vibrational density of states, and nuclear momentum distributions measured at 10 and 300 K. Encouraged by the agreement between experiment and computational predictions, we provide a quantitative appraisal of the quantum contributions to nuclear motions in this solid acid. From this analysis, we find that only the heavier caesium atoms reach the classical limit at room temperature. Contrary to naïve expectation, sulfur exhibits a more pronounced quantum character relative to classical predictions than the lighter oxygen atom. We interpret this hitherto unexplored nuclear quantum effect as arising from the tighter binding environment of this species in this technologically relevant material.

  18. Metastability, spectrum, and eigencurrents of the Lennard-Jones-38 network

    International Nuclear Information System (INIS)

    Cameron, Maria K.

    2014-01-01

    We develop computational tools for spectral analysis of stochastic networks representing energy landscapes of atomic and molecular clusters. Physical meaning and some properties of eigenvalues, left and right eigenvectors, and eigencurrents are discussed. We propose an approach to compute a collection of eigenpairs and corresponding eigencurrents describing the most important relaxation processes taking place in the system on its way to the equilibrium. It is suitable for large and complex stochastic networks where pairwise transition rates, given by the Arrhenius law, vary by orders of magnitude. The proposed methodology is applied to the network representing the Lennard-Jones-38 cluster created by Wales's group. Its energy landscape has a double funnel structure with a deep and narrow face-centered cubic funnel and a shallower and wider icosahedral funnel. However, the complete spectrum of the generator matrix of the Lennard-Jones-38 network has no appreciable spectral gap separating the eigenvalue corresponding to the escape from the icosahedral funnel. We provide a detailed description of the escape process from the icosahedral funnel using the eigencurrent and demonstrate a superexponential growth of the corresponding eigenvalue. The proposed spectral approach is compared to the methodology of the Transition Path Theory. Finally, we discuss whether the Lennard-Jones-38 cluster is metastable from the points of view of a mathematician and a chemical physicist, and make a connection with experimental works

  19. Metastable states and quasicycles in a stochastic Wilson-Cowan model of neuronal population dynamics

    KAUST Repository

    Bressloff, Paul C.

    2010-11-03

    We analyze a stochastic model of neuronal population dynamics with intrinsic noise. In the thermodynamic limit N→∞, where N determines the size of each population, the dynamics is described by deterministic Wilson-Cowan equations. On the other hand, for finite N the dynamics is described by a master equation that determines the probability of spiking activity within each population. We first consider a single excitatory population that exhibits bistability in the deterministic limit. The steady-state probability distribution of the stochastic network has maxima at points corresponding to the stable fixed points of the deterministic network; the relative weighting of the two maxima depends on the system size. For large but finite N, we calculate the exponentially small rate of noise-induced transitions between the resulting metastable states using a Wentzel-Kramers- Brillouin (WKB) approximation and matched asymptotic expansions. We then consider a two-population excitatory or inhibitory network that supports limit cycle oscillations. Using a diffusion approximation, we reduce the dynamics to a neural Langevin equation, and show how the intrinsic noise amplifies subthreshold oscillations (quasicycles). © 2010 The American Physical Society.

  20. Nucleation kinetics of polymorphic transition from phase II to phase III of hexachloroethane: Metastability/unstability

    Science.gov (United States)

    Koga, Yoshikata

    1987-10-01

    The conversions of the transition from phase II to III of C 2Cl 6 were measured for the range between 38.81 and 41.15°C (the transition point: 43.64°C). A simple model was devised appropriate to the present mononucleus transition. Using this, the induction periods, that are inversely proportional to the nucleation rates, were extracted from the observed curves. The resulting induction periods varied from 0.07 to 1500 h. In terms of the classical nucleation theory, though its applicability for such a wide variation is questionable, it was shown that there are two temperature regions bounded at about 40.8°C in which nucleation behaviours are different. As shown in the previous papers, the growth rates of the same transition were too fast to measure below a certain threshold temperature which was lower than 41.9°C. These threshold behaviours in nucleation and growth were tentatively attributed to the change-over from metastability to unstability.

  1. Characterization of the metastable Cu-Fe nanoparticles prepared by the mechanical alloying route

    Directory of Open Access Journals (Sweden)

    Mahsa Barzegar Vishlaghi

    2014-12-01

    Full Text Available Although Cu and Fe are immiscible under equilibrium conditions, they can form supersaturated solid solutions by mechanical alloying. In this paper, nano-structured of the metastable Cu-Fe phase containing 10, 15, 20 and 25% wt Fe were synthesized by intensive ball milling for 15h, in order to achieve a solid solution of Fe in Cu. The phase composition, dissolution of the Fe atoms into the Cu matrix, and the morphology of the milling products were studied by X-ray Diffraction (XRD, Energy Dispersive Spectrometer (EDS, and Field Emission Scanning Electron Microscope (FESEM techniques, respectively. The mean crystallite size of the milled samples was determined by XRD peak broadening using the Williamson-Hall approximation. The XRD analysis results showed that the solid solubility of the Fe in the Cu was extended to 20%wt after milling for 15 h, and a homogeneous solid solution of Cu80Fe20 with a mean crystallite size of 19nm was obtained. The mean crystallite size decreased with increasing milling time and it was more evident in the initial stage of the milling. The Cu lattice parameter increased by dissolving the Fe into the Cu matrix probably due to the magneto-volume effect in the Cu-Fe alloys. The FESEM observations showed that the milling products were agglomerates consisting of uniform particles. The Vibrating Sample Magnetometer (VSM results showed that the Cu80Fe20 powder has soft magnetic properties.

  2. Design of an experimental apparatus for measurement of the surface tension of metastable fluids

    Science.gov (United States)

    Vinš, V.; Hrubý, J.; Hykl, J.; Blaha, J.; Šmíd, B.

    2013-04-01

    A unique experimental apparatus for measurement of the surface tension of aqueous mixtures has been designed, manufactured, and tested in our laboratory. The novelty of the setup is that it allows measurement of surface tension by two different methods: a modified capillary elevation method in a long vertical capillary tube and a method inspired by the approach of Hacker (National Advisory Committee for Aeronautics, Technical Note 2510, 1-20, 1951), i.e. in a short horizontal capillary tube. Functionality of all main components of the apparatus, e.g., glass chamber with the capillary tube, temperature control unit consisting of two thermostatic baths with special valves for rapid temperature jumps, helium distribution setup allowing pressure variation above the liquid meniscus inside the capillary tube, has been successfully tested. Preliminary results for the surface tension of the stable and metastable supercooled water measured by the capillary elevation method at atmospheric pressure are provided. The surface tension of water measured at temperatures between +26 °C and -11 °C is in good agreement with the extrapolated IAPWS correlation (IAPWS Release on Surface Tension of Ordinary Water Substance, September 1994); however it disagrees with data by Hacker.

  3. Defects and metastable structures of MgAl{sub 2}O{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Chen, S.P.; Yan, M. [Los Alamos National Lab., NM (United States); Grimes, R.W.; Vyas, S. [The Royal Institution of Great Britain, London (United Kingdom); Gale, J.D. [Imperial Coll., London (United Kindgom). Dept. of Chemistry

    1995-07-01

    This paper presents calculated properties of normal and inverse spinel structures of MgAl{sub 2}O{sub 4} and of point defects in the spinel structure. These results provide information for further study of possible metastable states. Calculated properties of ``amorphous`` structure are also presented. Atomistic simulations show that in MgAl{sub 2}O{sub 4} spinel structure, the exchange of an Mg{sup 2+} ion with an Al{sup 3+} ion has the lowest energy increase, 0. 92eV/atom. The Schottky defect increases the energy by 3.71 eV/atom. Frenkel defects are difficult to form, increasing the energy at least 4.59eV/atom for the Mg{sup 2+} Frenkel defect. Proposed rock salt structure of MgAl{sub 2}O{sub 4} has smaller volume and larger Young modulus, and the amorphosu state has larger volume and smaller Young modulus than the MgAl{sub 2}O{sub 4} spinel.

  4. Adsorption on metal oxides: Studies with the metastable impact electron spectroscopy

    International Nuclear Information System (INIS)

    Krischok, S.; Hoefft, O.; Kempter, V.

    2002-01-01

    An overview is given on the application of metastable impact electron spectroscopy, in combination with UPS, to the study of clean magnesia and titania surfaces and their interaction with metal atoms and small molecules. The mechanisms for metal adsorption on reducible (titania) and non-reducible (magnesia) substrates are different: while on titania the metal atom often bonds by electron transfer to Ti3d states, it is hybridization of the adsorbate and anion wavefunctions which accounts for the bonding on MgO. In the case of H 2 O, molecular adsorption takes place both on MgO and TiO 2 ; on the other hand, water-alkali coadsorption leads to hydroxide formation. In the case of CO 2 , chemisorption takes place in form of carbonate (CO 3 ) species. These originate from the CO 2 interaction with O 2- surface anions. While for CaO chemisorption takes place at regular oxygen sites, for MgO this occurs at low-coordinated oxygen ions only; for TiO 2 chemisorption requires alkali coadsorption

  5. Current reversals and metastable states in the infinite Bose-Hubbard chain with local particle loss

    Science.gov (United States)

    Kiefer-Emmanouilidis, M.; Sirker, J.

    2017-12-01

    We present an algorithm which combines the quantum trajectory approach to open quantum systems with a density-matrix renormalization-group scheme for infinite one-dimensional lattice systems. We apply this method to investigate the long-time dynamics in the Bose-Hubbard model with local particle loss starting from a Mott-insulating initial state with one boson per site. While the short-time dynamics can be described even quantitatively by an equation of motion (EOM) approach at the mean-field level, many-body interactions lead to unexpected effects at intermediate and long times: local particle currents far away from the dissipative site start to reverse direction ultimately leading to a metastable state with a total particle current pointing away from the lossy site. An alternative EOM approach based on an effective fermion model shows that the reversal of currents can be understood qualitatively by the creation of holon-doublon pairs at the edge of the region of reduced particle density. The doublons are then able to escape while the holes move towards the dissipative site, a process reminiscent—in a loose sense—of Hawking radiation.

  6. Design amphiphilic dipolar π-systems for stimuli-responsive luminescent materials using metastable states.

    Science.gov (United States)

    Yagai, Shiki; Okamura, Satoru; Nakano, Yujiro; Yamauchi, Mitsuaki; Kishikawa, Keiki; Karatsu, Takashi; Kitamura, Akihide; Ueno, Akira; Kuzuhara, Daiki; Yamada, Hiroko; Seki, Tomohiro; Ito, Hajime

    2014-06-05

    π-Conjugated compounds that exhibit tunable luminescence in the solid state under external mechanical stimuli have potential applications in sensors and imaging devices. However, no rational designs have been proposed that impart these mechano-responsive luminescent properties to π-conjugated compounds. Here we demonstrate a strategy for mechano-responsive luminescent materials by imparting amphiphilic and dipolar characteristics to a luminescent π-conjugated system. The oligo(p-phenylenevinylene) luminophore with a didodecylamino group at one end and a tri(ethylene glycol) ester group at the other end yields segregated solid structures by separately aggregating its hydrophobic and hydrophilic moieties. The segregated structures force the molecules to align in the same direction, thereby generating a conflict between the side-chain aggregation and dipolar stabilization of the π-system. Consequently, these metastable solid structures can be transformed through mechanical stimulation to a more stable structure, from a π-π stacked aggregate to a liquid crystal and further to a crystalline phase with variable luminescence.

  7. Energy barriers between metastable states in first-order quantum phase transitions

    Science.gov (United States)

    Wald, Sascha; Timpanaro, André M.; Cormick, Cecilia; Landi, Gabriel T.

    2018-02-01

    A system of neutral atoms trapped in an optical lattice and dispersively coupled to the field of an optical cavity can realize a variation of the Bose-Hubbard model with infinite-range interactions. This model exhibits a first-order quantum phase transition between a Mott insulator and a charge density wave, with spontaneous symmetry breaking between even and odd sites, as was recently observed experimentally [Landig et al., Nature (London) 532, 476 (2016), 10.1038/nature17409]. In the present paper, we approach the analysis of this transition using a variational model which allows us to establish the notion of an energy barrier separating the two phases. Using a discrete WKB method, we then show that the local tunneling of atoms between adjacent sites lowers this energy barrier and hence facilitates the transition. Within our simplified description, we are thus able to augment the phase diagram of the model with information concerning the height of the barrier separating the metastable minima from the global minimum in each phase, which is an essential aspect for the understanding of the reconfiguration dynamics induced by a quench across a quantum critical point.

  8. Energetics and metastability of the adenine dication observed in proton-adenine collisions

    Science.gov (United States)

    Moretto-Capelle, Patrick; Le Padellec, Arnaud; Brière, Guillaume; Massou, Sophie; Franceries, Frédéric

    2007-12-01

    We present here a study that deals with the correlated fragmentation of a doubly charged adenine molecular target induced by a 100keV proton beam. We have elucidated part of the dissociation dynamics for several channels and have obtained the corresponding kinetic energy released values. We have extracted activation energies by combining our experimental data with computations using the ab initio GAMESS code. We have observed metastability patterns against fragmentation, for which we have extracted the temporal mechanism (one or two steps). Subsequently, we have obtained lifetimes in the 100-200ns range. In the simplest case of two-body fragmentation with the emission of mass 28, the determination of transition states and reaction paths has showed that emission of the H-C-N-H fragment is preferred to that of C -N-H2. From the calculated activation barriers and lifetimes, we have deduced an equivalent temperature of the dication that we have compared with the existing models.

  9. Hyperbolic periodic orbits in nongradient systems and small-noise-induced metastable transitions

    Science.gov (United States)

    Tao, Molei

    2018-01-01

    Small noise can induce rare transitions between metastable states, which can be characterized by Maximum Likelihood Paths (MLPs). Nongradient systems contrast gradient systems in that MLP does not have to cross the separatrix at a saddle point, but instead possibly at a point on a hyperbolic periodic orbit. A numerical approach for identifying such unstable periodic orbits is proposed based on String method. In a special class of nongradient systems ('orthogonal-type'), there are provably local MLPs that cross such saddle point or hyperbolic periodic orbit, and the separatrix crossing location determines the associated local maximum of transition rate. In general cases, however, the separatrix crossing may not determine a unique local maximum of the rate, as we numerically observed a counter-example in a sheared 2D-space Allen-Cahn SPDE. It is a reasonable conjecture that there are always local MLPs associated with each attractor on the separatrix, such as saddle point or hyperbolic periodic orbit; our numerical experiments did not disprove so.

  10. Thermal stability and phase transformation of metastable phases in Zr-Nb

    International Nuclear Information System (INIS)

    Aurelio, G.; Fernandez Guillermet, Armando

    2003-01-01

    The lattice parameters of the bcc (β) and (Ω) phases occurring metastability in a series of Zr-rich Zr-Nb alloys have been determined at and above room temperature (TR) using neutron diffraction techniques. In the first place, the effect of temperature changes upon the lattice parameters of the β and Ω phases in alloys with 10 and 18 at. % Nb was monitored using neutron thermo-diffraction. A method of analysis is applied to the data, which involve a confrontation between the observed structural properties and an idealized -or 'reference'- behavior (RB) which admits a simple mathematical description. A generalized form of the law of Vegard is adopted as RB for the β phase, whereas a specific RB is proposed for the Ω structure. The experimental data are well accounted for by this interpretation scheme, leading to a picture of the isothermal reactions occurring at high temperature, which involves the transfer of Nb from the Ω to the β phase. Finally, the neutron diffraction data on the Ω phase is combined with an electron microscopy study for the alloy with 10 at. % Nb aged at 773 K, which provides information on the composition of this phase and its evolution towards thermodynamic equilibrium. (author)

  11. Monte Carlo simulation of induction time and metastable zone width; stochastic or deterministic?

    Science.gov (United States)

    Kubota, Noriaki

    2018-03-01

    The induction time and metastable zone width (MSZW) measured for small samples (say 1 mL or less) both scatter widely. Thus, these two are observed as stochastic quantities. Whereas, for large samples (say 1000 mL or more), the induction time and MSZW are observed as deterministic quantities. The reason for such experimental differences is investigated with Monte Carlo simulation. In the simulation, the time (under isothermal condition) and supercooling (under polythermal condition) at which a first single crystal is detected are defined as the induction time t and the MSZW ΔT for small samples, respectively. The number of crystals just at the moment of t and ΔT is unity. A first crystal emerges at random due to the intrinsic nature of nucleation, accordingly t and ΔT become stochastic. For large samples, the time and supercooling at which the number density of crystals N/V reaches a detector sensitivity (N/V)det are defined as t and ΔT for isothermal and polythermal conditions, respectively. The points of t and ΔT are those of which a large number of crystals have accumulated. Consequently, t and ΔT become deterministic according to the law of large numbers. Whether t and ΔT may stochastic or deterministic in actual experiments should not be attributed to change in nucleation mechanisms in molecular level. It could be just a problem caused by differences in the experimental definition of t and ΔT.

  12. Structure and magnetic properties of metastable Co-Cu solid solution nanowire arrays fabricated by electrodeposition

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Tao; Li, Fashen; Wang, Ying; Song, Lijing [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou Univesity, Lanzhou 730000 (China)

    2006-08-15

    Nanowire arrays of the metastable Co{sub x}Cu{sub 1-x} (0.20{<=}x{<=}0.85) solid solution system which can not be obtained by equilibrium methods, were prepared by electrodeposition in pores of anodic aluminum oxide (AAO) template, and subsequently annealed at different temperatures. The as-deposited samples all show single phase of fcc structure, and lattice parameters decrease with the increase of Co content and fundamentally accord with Vegard's law. The phase transition with heat treatment was investigated by X-ray diffraction and differential thermal analysis (DTA) which further confirmed the formation of solid solution. With Co content increasing, the coercivity along nanowire axis for as-deposited samples increases, but it decreases for the annealed samples at 700 C. This phenomenon was explained considering the interaction of Co particles through Cu in nanowires after phase separation. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  13. Stable, metastable and unstable solutions of a spin-1 Ising system based on the free energy surfaces

    Science.gov (United States)

    Keskİin, Mustafa; Özgan, Şükrü

    1990-04-01

    Stable, metastable and unstable solutions of a spin-1 Ising model with bilinear and biquadratic interactions are found by using the free energy surfaces. The free energy expression is obtained in the lowest approximation of the cluster variation method. All these solutions are shown in the two-dimensional phase space, especially the unstable solutions which in some cases are difficult to illustrate in the two-dimensional phase space, found by Keskin et al. recently.

  14. Using ion production to monitor the birth and death of a metastable helium Bose-Einstein condensate

    International Nuclear Information System (INIS)

    Seidelin, S; Sirjean, O; Gomes, J Viana; Boiron, D; Westbrook, C I; Aspect, A

    2003-01-01

    We discuss observations of the ion flux from a cloud of trapped 2 3 S 1 metastable helium atoms. Both Bose-Einstein condensates (BEC) and thermal clouds were investigated. The ion flux is compared with time-of-flight observations of the expanded cloud. We show data concerning BEC formation and decay, as well as measurements of two-and three-body ionization rate constants. We also discuss possible improvements and extensions of our results

  15. Formation of N2(A3Σ+u , v = 0–3)metastable species in decaying nitrogen streamer

    Czech Academy of Sciences Publication Activity Database

    Šimek, Milan; Ambrico, P. F.; Prukner, Václav

    2013-01-01

    Roč. 46, č. 48 (2013), s. 485205-485205 ISSN 0022-3727 R&D Projects: GA ČR(CZ) GAP205/12/1709 Institutional support: RVO:61389021 Keywords : nitrogen metastable * streamer * optical diagnostics * laser-induced fluorescence * LIF Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.521, year: 2013 http://iopscience.iop.org/0022-3727/46/48/485205/pdf/0022-3727_46_48_485205.pdf

  16. State-selective electron capture in collisions of ground and metastable O2+ ions with H(1s)

    International Nuclear Information System (INIS)

    Cabello, C N; Errea, L F; Fernandez, L; Mendez, L; Macias, A; Rabadan, I; Riera, A

    2003-01-01

    An ab initio calculation of the electron capture cross sections for collisions of ground and metastable states of O 2+ with H(1s) is presented. For impact energies between 0.125 and 3.4 keV amu -1 , we find good agreement between the cross sections from the ground state ion with the mixed beam experimental data of Phaneuf et al (Phaneuf A, Alvarez I, Meyer F W and Crandall D H 1982 Phys. Rev. A 26 1892)

  17. Results on the role of metastable Ar atoms in a 9-MHz high-power atmospheric ICP by using emission/absorption spectrometry

    International Nuclear Information System (INIS)

    Gunter, W.; Zeeman, P.B.; Visser, K.

    1984-01-01

    An investigation into the role of overpopulations of metastable argon levels as agents for causing non-local thermal equilibrium (LTE) in an inductively coupled plasma source (ICP), was carried out. Four argon transitions in the near infrared region were monitored through absorption measurements at two different observation heights in a 9-MHz high-power ICP. The lower states of the four transitions consist of two metastable (11.55 and 11.72 eV) and two radiating (11.62 and 11.83 eV) levels. Comparison of measured metastable level to radiating level absorbance ratios with calculated population ratios gave an indication whether overpopulations of certain levels existed. Results indicate no overpopulation of metastable states with respect to radiating states, arguing against their role as non-LTE mechanism agents. This conclusion is, however, preliminary, since the calculation of absolute population densities from absorbance measurements must still be carried out

  18. Influence of additive L-phenylalanine on stabilization of metastable α-form of L-glutamic acid in cooling crystallization

    Science.gov (United States)

    Quang, Khuu Chau; Nhan, Le Thi Hong; Huyen, Trinh Thi Thanh; Tuan, Nguyen Anh

    2017-09-01

    The influence of additive amino acid L-phenylalanine on stabilization of metastable α-form of L-glutamic acid was investigated in cooling crystallization. The present study found that the additive L-phenylalanine could be used to stabilize the pure metastable α-form in L-glutamic acid crystallization, where the additive concentration of 0.05-0.1 (g/L) was sufficient to stabilize the 100% wt metastable α-form in solid product at L-glutamic acid concentration of 30-45 (g/L). Additionally, the present results indicated that the adsorption of additive L-phenylalanine on the (001) surface of α-form was more favorable than that of the β-form molecular, so the nucleation sites of stable β-form was occupied by additive molecular, which resulted in inhibition of nucleation and growth of β-form, allowing stabilization of metastable α-form.

  19. Path lumping: An efficient algorithm to identify metastable path channels for conformational dynamics of multi-body systems

    Science.gov (United States)

    Meng, Luming; Sheong, Fu Kit; Zeng, Xiangze; Zhu, Lizhe; Huang, Xuhui

    2017-07-01

    Constructing Markov state models from large-scale molecular dynamics simulation trajectories is a promising approach to dissect the kinetic mechanisms of complex chemical and biological processes. Combined with transition path theory, Markov state models can be applied to identify all pathways connecting any conformational states of interest. However, the identified pathways can be too complex to comprehend, especially for multi-body processes where numerous parallel pathways with comparable flux probability often coexist. Here, we have developed a path lumping method to group these parallel pathways into metastable path channels for analysis. We define the similarity between two pathways as the intercrossing flux between them and then apply the spectral clustering algorithm to lump these pathways into groups. We demonstrate the power of our method by applying it to two systems: a 2D-potential consisting of four metastable energy channels and the hydrophobic collapse process of two hydrophobic molecules. In both cases, our algorithm successfully reveals the metastable path channels. We expect this path lumping algorithm to be a promising tool for revealing unprecedented insights into the kinetic mechanisms of complex multi-body processes.

  20. Characterization of Cr-rich Cr-Sb multilayer films: Syntheses of a new metastable phase using modulated elemental reactants

    International Nuclear Information System (INIS)

    Regus, Matthias; Mankovsky, Sergiy; Polesya, Svitlana; Kuhn, Gerhard; Ditto, Jeffrey; Schürmann, Ulrich; Jacquot, Alexandre; Bartholomé, Kilian; Näther, Christian; Winkler, Markus; König, Jan D.; Böttner, Harald; Kienle, Lorenz; Johnson, David C.; Ebert, Hubert; Bensch, Wolfgang

    2015-01-01

    The new metastable compound Cr 1+x Sb with x up to 0.6 has been prepared via a thin film approach using modulated elemental reactants and investigated by in-situ X-ray reflectivity, X-ray diffraction, differential scanning calorimetry, energy dispersive X-ray analysis as well as transmission electron microscopy and atomic force microscopy. The new Cr-rich antimonide crystallizes in a structure related to the Ni 2 In-type structure, where the crystallographic position (1/3, 2/3, 3/4) is partially occupied by excess Cr. The elemental layers of the pristine material interdiffused significantly before Cr 1+x Sb crystallized. A change in the activation energy was observed for the diffusion process when crystal growth starts. First-principles electronic structure calculations provide insight into the structural stability, magnetic properties and resistivity of Cr 1+x Sb. - Graphical abstract: 1 amorphous multilayered film 2 interdiffused amorphous film 3 metastable crystalline phase 4 thermodynamic stable phase (and by-product). - Highlights: • Interdiffusion of amorphous Cr and Sb occurs before crystallization. • Crystallization of a new metastable phase Cr 1.6 Sb in Ni 2 In-type structure. • The new Cr-rich phase shows half-metallic behavior

  1. Two new Np-Ga phases: α-NpGa2 and metastable m-NpGa2

    International Nuclear Information System (INIS)

    Giessen, B.C.; Elliott, R.O.

    1976-01-01

    Following an earlier study of metastable Np-rich Np-Ga alloys, rapidly quenched Np-Ga alloys with 63-80 at.% Ga were prepared and studied. Two new NpGa 2 phases, both with an AlB 2 type structure, were found: α-NpGa 2 , with a=4.246A, c=4.060A, c/a=0.956 and m-NpGa 2 , with a=4.412A, c=3.642A, c/a=0.825. While m-NpGa 2 was observed only in very fast quenched (splat cooled) samples and appears to be metastable, α-NpGa 2 is probably an equilibrium phase. In a splat cooled alloy with 75 at.% Ga, another, unidentified, metastable phase was observed. Crystal chemical discussions of atomic volumes, interatomic distances and axial ratios are given; the volume difference between the two forms of NpGa 2 is correlated with a valence change of Np. (Auth.)

  2. Metastable state in a tensile-strained Cu Σ 5 grain boundary: A first-principles study

    Science.gov (United States)

    Meng, Fan-Shun; Liu, Yong-Li; Zhang, Hui; Li, Jiu-Hui; Zhao, Xing; Qi, Yang

    2018-02-01

    The Cu Σ 5 grain boundary (GB) fracture process has been simulated by the first-principles computational tensile test. An additional metastable state has been discovered during tensile tests. The energy of ideal mirror-symmetric GBs continuously changes with tensile strains. However, at high strains, more stable structures with lower energy are found when some atoms on GBs are artificially relocated. Thus the structures obtained on ideal GBs are not stable and will not occur under actual tensile experiments, which is the exact reason for the occurrence of these unstable structures, which may be considered as additional metastable states. Finally, a large amount of calculations have also been performed to search underlying, more stable GB structures and arrived at almost identical previous results. These results indicate that structures of symmetric GBs under tensile tests should be very carefully optimized by introducing small perturbations even if the energy of the system increases smoothly with increasing tensile strain. In addition, the exclusion of metastable states usually plays a major role in investigating the mechanical properties under tensile test.

  3. Exploration of the phase diagram of liquid water in the low-temperature metastable region using synthetic fluid inclusions

    DEFF Research Database (Denmark)

    Qiu, Chen; Krüger, Yves; Wilke, Max

    2016-01-01

    We present new experimental data of the low-temperature metastable region of liquid water derived from high-density synthetic fluid inclusions (996−916 kg/m3) in quartz. Microthermometric measurements include: i) Prograde (upon heating) and retrograde (upon cooling) liquid-vapour homogenisation. ...... a maximum of the bubble nucleation curve in the ϱ–T plane at around 40 °C. The new experimental data represent valuable benchmarks to evaluate and further improve theoretical models describing the p–V–T properties of metastable water in the low-temperature region......We present new experimental data of the low-temperature metastable region of liquid water derived from high-density synthetic fluid inclusions (996−916 kg/m3) in quartz. Microthermometric measurements include: i) Prograde (upon heating) and retrograde (upon cooling) liquid-vapour homogenisation. We...... used single ultrashort laser pulses to stimulate vapour bubble nucleation in initially monophase liquid inclusions. Water densities were calculated based on prograde homogenisation temperatures using the IAPWS-95 formulation. We found retrograde liquid-vapour homogenisation temperatures in excellent...

  4. Polarized electron beams at SLAC

    International Nuclear Information System (INIS)

    Moffeit, K.C.

    1992-11-01

    SLAC has successfully accelerated high energy polarized electrons for the Stanford Linear Collider and fixed polarized nuclear target experiments. The polarized electron beams at SLAC use a gallium arsenide (GaAlAs for E-142) photon emission source to provide the beam of polarized electrons with polarization of approximately 28% (41% for E-142). While the beam emittance is reduced in the damping ring for SLC operation a system of bend magnets and superconducting solenoids preserve and orient the spin direction for maximum longitudinal polarization at the collision point. The electron polarization is monitored with a Compton scattering polarimeter, and was typically 22% at the e+e- collision point for the 1992 run. Improvements are discussed to increase the source polarization and to reduce the depolarization effects between the source and the collision point

  5. Analytical polarization calculations beyond SLIM

    International Nuclear Information System (INIS)

    Barber, D.P.

    1989-01-01

    A comparison is made between the theories of Bell and Leinaas and of Derbenev and Kondratenko for the spin polarization in electron storage rings. A calculation of polarization in HERA using the program SMILE of Mane is presented

  6. Fragmented metastable states exist in an attractive bose-einstein condensate for atom numbers well above the critical number of the Gross-Pitaevskii theory.

    Science.gov (United States)

    Cederbaum, Lorenz S; Streltsov, Alexej I; Alon, Ofir E

    2008-02-01

    It is well known that attractive condensates do not posses a stable ground state in three dimensions. The widely used Gross-Pitaevskii theory predicts the existence of metastable states up to some critical number N(cr)(GP) of atoms. It is demonstrated here that fragmented metastable states exist for atom numbers well above N(cr)(GP). The fragments are strongly overlapping in space. The results are obtained and analyzed analytically as well as numerically. The implications are discussed.

  7. Metastable He2- ions formed by two-electron attachment to the excited He2+ Σg+ (1σg22σg1) core

    International Nuclear Information System (INIS)

    Adamowicz, L.; Pluta, T.

    1991-01-01

    Four metastable states (1 4 Π u , 2 4 Π u , 4 Φ u , and 4 I u ), resulting from two-electron attachments to the excited He 2 + core ( 2 Σ g + ), are characterized using the numerical Hartree-Fock method. It is determined that such metastable states are formed when both valence electrons are placed into equally diffused orbitals, which have bonding charter, and whose angular momentum quantum numbers do not differ by more than 1

  8. Optical properties of metastable shallow acceptors in Mg-doped GaN layers grown by metal-organic vapor phase epitaxy

    OpenAIRE

    Pozina, Galia; Hemmingsson, Carl; Bergman, Peder; Kawashima, T.; Amano, H.; Akasaki, I.; Usui, A.; Monemar, Bo

    2010-01-01

    GaN layers doped by Mg show a metastable behavior of the near-band-gap luminescence caused by electron irradiation or UV excitation. At low temperatures < 30 K the changes in luminescence are permanent. Heating to room temperature recovers the initial low temperature spectrum shape completely. Two acceptors are involved in the recombination process as confirmed by transient PL. In as-grown samples a possible candidate for the metastable acceptor is C-N, while after annealing a second m...

  9. Characterization Method for the Relaxation Process of Metastable Defect States in Cu(In,Ga)Se2 Thin Films with Photoisothermal Capacitance Transient Spectroscopy

    Science.gov (United States)

    Okada, Hiroshi; Minemoto, Takashi

    2011-02-01

    A simple, spectroscopic method is proposed for the characterization of metastable defects in semiconductors using modified photoisothermal capacitance transient spectroscopy (photo-ICTS). A photo-ICTS method using a weighting function is formularized for the conversion process between two defect states. The potential energy barrier separating two configurations of the metastable defect in Cu(In,Ga)Se2 thin films has been successfully analyzed along with a tentatively determined defect concentration.

  10. On Determinants of Political Polarization

    OpenAIRE

    Grechyna, Daryna

    2015-01-01

    Political polarization has been shown to significantly influence a country's economic performance. However, little is known about the drivers of political polarization. In this article, we aim to identify the main determinants of political polarization using Bayesian Model Averaging to overcome the problem of model uncertainty. We find that the level of trust within a country and the degree of income inequality are the most robust determinants of political polarization.

  11. Polarized electrogowdy spacetimes censored

    Energy Technology Data Exchange (ETDEWEB)

    Nungesser, Ernesto, E-mail: ernesto.nungesser@aei.mpg.d [Max-Planck-Institut fuer Gravitationsphysik, Albert-Einstein-Institut, Am Muehlenberg 1, 14476 Potsdam (Germany)

    2010-05-01

    A sketch of the proof of strong cosmic censorship is presented for a class of solutions of the Einstein-Maxwell equations, those with polarized Gowdy symmetry. A key element of the argument is the observation that by means of a suitable choice of variables the central equations in this problem can be written in a form where they are identical to the central equations for general (i.e. non-polarized) vacuum Gowdy spacetimes. Using this it is seen that the results of Ringstroem on strong cosmic censorship in the vacuum case have implications for the Einstein-Maxwell case. Working out the geometrical meaning of these analytical results leads to the main conclusion.

  12. Self-Sustaining Dynamical Nuclear Polarization Oscillations in Quantum Dots

    DEFF Research Database (Denmark)

    Rudner, Mark Spencer; Levitov, Leonid

    2013-01-01

    Early experiments on spin-blockaded double quantum dots revealed robust, large-amplitude current oscillations in the presence of a static (dc) source-drain bias. Despite experimental evidence implicating dynamical nuclear polarization, the mechanism has remained a mystery. Here we introduce......) and nuclear spin diffusion, which governs dynamics of the spatial profile of nuclear polarization. The proposed framework naturally explains the differences in phenomenology between vertical and lateral quantum dot structures as well as the extremely long oscillation periods....

  13. Elimination of polarization degeneracy in circularly symmetric bianisotropic waveguides: a decoupled case.

    Science.gov (United States)

    Xu, Jing; Wu, Bingbing; Chen, Yuntian

    2015-05-04

    Mode properties of circularly symmetric waveguides with one special type of bianisotropy are studied using finite element approach. We find that the polarization degeneracy in circularly symmetric waveguides can be eliminated, by introducing intrinsic crossing coupling between electric and magnetic moments in the constituent units of the waveguide media. Breaking the polarization degeneracy in high order mode groups is also confirmed numerically. With the bianisotropic parameters chosen in this work, the x and y-polarized modes remain decoupled. Typically, the y-polarized modes remain completely unchanged, while the x-polarized modes are turned into leaky modes that are lossy along propagation direction. A perturbation model from coupled mode theory is developed to explain the results and shows excellent agreement. Such asymmetric behavior between different polarizations might be feasible and useful for developing compact polarizers in terahertz or mid-infrared regime.

  14. PEPPo: Using a Polarized Electron Beam to Produce Polarized Positrons

    Energy Technology Data Exchange (ETDEWEB)

    Adeyemi, Adeleke H. [Hampton Univ., Hampton, VA (United States); et al.

    2015-09-01

    Polarized positron beams have been identified as either an essential or a significant ingredient for the experimental program of both the present and next generation of lepton accelerators (JLab, Super KEK B, ILC, CLIC). An experiment demonstrating a new method for producing polarized positrons has been performed at the Continuous Electron Beam Accelerator Facility at Jefferson Lab. The PEPPo (Polarized Electrons for Polarized Positrons) concept relies on the production of polarized e⁻/e⁺ pairs from the bremsstrahlung radiation of a longitudinally polarized electron beam interacting within a high-Z conversion target. PEPPo demonstrated the effective transfer of spin-polarization of an 8.2 MeV/c polarized (P~85%) electron beam to positrons produced in varying thickness tungsten production targets, and collected and measured in the range of 3.1 to 6.2 MeV/c. In comparison to other methods this technique reveals a new pathway for producing either high-energy or thermal polarized positron beams using a relatively low polarized electron beam energy (~10MeV) .This presentation will describe the PEPPo concept, the motivations of the experiment and high positron polarization achieved.

  15. Polarization induced doped transistor

    Science.gov (United States)

    Xing, Huili; Jena, Debdeep; Nomoto, Kazuki; Song, Bo; Zhu, Mingda; Hu, Zongyang

    2016-06-07

    A nitride-based field effect transistor (FET) comprises a compositionally graded and polarization induced doped p-layer underlying at least one gate contact and a compositionally graded and doped n-channel underlying a source contact. The n-channel is converted from the p-layer to the n-channel by ion implantation, a buffer underlies the doped p-layer and the n-channel, and a drain underlies the buffer.

  16. Polar bears, Ursus maritimus

    Science.gov (United States)

    Rode, Karyn D.; Stirling, Ian

    2017-01-01

    Polar bears are the largest of the eight species of bears found worldwide and are covered in a pigment-free fur giving them the appearance of being white. They are the most carnivorous of bear species consuming a high-fat diet, primarily of ice-associated seals and other marine mammals. They range throughout the circumpolar Arctic to the southernmost extent of seasonal pack ice.

  17. Polarized advanced fuel reactors

    International Nuclear Information System (INIS)

    Kulsrud, R.M.

    1987-07-01

    The d- 3 He reaction has the same spin dependence as the d-t reaction. It produces no neutrons, so that if the d-d reactivity could be reduced, it would lead to a neutron-lean reactor. The current understanding of the possible suppression of the d-d reactivity by spin polarization is discussed. The question as to whether a suppression is possible is still unresolved. Other advanced fuel reactions are briefly discussed. 11 refs

  18. On polarization in biomembranes

    DEFF Research Database (Denmark)

    Zecchi, Karis Amata

    close to physiological conditions, making these effects biologically relevant. In this work, we consider the case of asymmetric membranes which can display spontaneous polarization in the absence of a field. Close to the phase transition, we find that the membrane displays piezoelectric, flexoelectric...... on different geometries point in the direction of a flexoelectric mechanism behind current rectification in lipid bilayers. Finally, we suggest that our updated equivalent circuit should be included in the interpretation of elctrophysiological data....

  19. Multifrequency Behaviour of Polars

    Directory of Open Access Journals (Sweden)

    K. Reinsch

    2015-02-01

    Full Text Available Cataclysmic variables emit over a wide range of the electromagnetic spectrum. In this paper I will review observations of polars in relevant passbands obtained during the last decade and will discuss their diagnostical potential to access the physics of the main components within the binary systems. This will include a discussion of intrinsic source variability and the quest for simultaneous multi-frequency observations.

  20. Polar Business Design

    Directory of Open Access Journals (Sweden)

    Sébastien Caisse

    2014-02-01

    Full Text Available Polar business design aims to enable entrepreneurs, managers, consultants, researchers, and business students to better tackle model-based analysis, creation, and transformation of businesses, ventures, and, more generically, collective endeavors of any size and purpose. It is based on a systems-thinking approach that builds on a few interrelated core concepts to create holistic visual frameworks. These core concepts act as poles linked by meaningful dyads, flows, and faces arranged in geometric shapes. The article presents two such polar frameworks as key findings in an ongoing analytic autoethnography: the three-pole Value−Activity−Stakeholder (VAS triquetra and the four-pole Offer−Creation−Character−Stakeholder (OCCS tetrahedron. The VAS triquetra is a more aggregated model of collective endeavors. The OCCS tetrahedron makes a trade-off between a steeper learning curve and deeper, richer representation potential. This article discusses how to use these two frameworks as well as their limits, and explores the potential that polar business design offers for future research.

  1. Metastable configurations of a finite-size chain of classical spins within the one-dimensional chiral XY-model

    Energy Technology Data Exchange (ETDEWEB)

    Popov, Alexander P., E-mail: APPopov@mephi.ru [Department of Molecular Physics, National Research Nuclear University MEPhI, Kashirskoe shosse 31, 115409 Moscow (Russian Federation); Gloria Pini, Maria, E-mail: mariagloria.pini@isc.cnr.it [Istituto dei Sistemi Complessi del CNR (CNR-ISC), Unità di Firenze, Via Madonna del Piano 10, I-50019 Sesto Fiorentino (Italy); Rettori, Angelo [Dipartimento di Fisica ed Astronomia, Università di Firenze, Via G. Sansone 1, I-50019 Sesto Fiorentino (Italy)

    2016-03-15

    The metastable states of a finite-size chain of N classical spins described by the chiral XY-model on a discrete one-dimensional lattice are calculated by means of a general theoretical method recently developed by one of us. This method allows one to determine all the possible equilibrium magnetic states in an accurate and systematic way. The ground state of a chain consisting of N classical XY spins is calculated in the presence of (i) a symmetric ferromagnetic exchange interaction, favoring parallel alignment of nearest neighbor spins, (ii) a uniaxial anisotropy, favoring a given direction in the film plane, and (iii) an antisymmetric Dzyaloshinskii–Moriya interaction (DMI), favoring perpendicular alignment of nearest neighbor spins. In addition to the ground state with a non-uniform helical spin arrangement, which originates from the energy competition in the finite-size chain with open boundary conditions, we have found a considerable number of higher-energy equilibrium states. In the investigated case of a chain with N=10 spins and a DMI much smaller than the in-plane uniaxial anisotropy, it turns out that a metastable (unstable) state of the finite chain is characterized by a configuration where none (at least one) of the inner spins is nearly parallel to the hard axis. The role of the DMI is to establish a unique rotational sense for the helical ground state. Moreover, the number of both metastable and unstable equilibrium states is doubled with respect to the case of zero DMI. This produces modifications in the Peierls–Nabarro potential encountered by a domain wall during its displacement along the discrete spin chain. - Highlights: • A finite-size chain of N classical spins within the XY-chiral model is investigated. • Using a systematic theoretical method, all equilibrium states are calculated for N=10. • The ground state has a non-uniform helical order with unique rotational sense. • Metastable states contain a domain wall whose energy

  2. Theoretical and experimental study of metastable solid solutions and phase stability within the immiscible Ag-Mo binary system

    Science.gov (United States)

    Sarakinos, K.; Greczynski, G.; Elofsson, V.; Magnfält, D.; Högberg, H.; Alling, B.

    2016-03-01

    Metastable solid solutions are phases that are synthesized far from thermodynamic equilibrium and offer a versatile route to design materials with tailor-made functionalities. One of the most investigated classes of metastable solid solutions with widespread technological implications is vapor deposited ternary transition metal ceramic thin films (i.e., nitrides, carbides, and borides). The vapor-based synthesis of these ceramic phases involves complex and difficult to control chemical interactions of the vapor species with the growing film surface, which often makes the fundamental understanding of the composition-properties relations a challenging task. Hence, in the present study, we investigate the phase stability within an immiscible binary thin film system that offers a simpler synthesis chemistry, i.e., the Ag-Mo system. We employ magnetron co-sputtering to grow Ag1-xMox thin films over the entire composition range along with x-ray probes to investigate the films structure and bonding properties. Concurrently, we use density functional theory calculations to predict phase stability and determine the effect of chemical composition on the lattice volume and the electronic properties of Ag-Mo solid solutions. Our combined theoretical and experimental data show that Mo-rich films (x ≥ ˜0.54) form bcc Mo-Ag metastable solid solutions. Furthermore, for Ag-rich compositions (x ≤ ˜0.21), our data can be interpreted as Mo not being dissolved in the Ag fcc lattice. All in all, our data show an asymmetry with regards to the mutual solubility of Ag and Mo in the two crystal structures, i.e., Ag has a larger propensity for dissolving in the bcc-Mo lattice as compared to Mo in the fcc-Ag lattice. We explain these findings in light of isostructural short-range clustering that induces energy difference between the two (fcc and bcc) metastable phases. We also suggest that the phase stability can be explained by the larger atomic mobility of Ag atoms as compared to that

  3. Bird remains from the Maastrichtian type area (Late Cretaceous)

    NARCIS (Netherlands)

    Dyke, Gareth J.; Schulp, A. S.; Jagt, J. W M

    2008-01-01

    Remains of Late Cretaceous birds are rare, which is especially true for Europe and the type area of the Maastrichtian Stage (southeast Netherlands, northeast Belgium) in particular. In the present paper, we record new remains (isolated tarsometatarsus and radius) that document the presence of both

  4. Building AN International Polar Data Coordination Network

    Science.gov (United States)

    Pulsifer, P. L.; Yarmey, L.; Manley, W. F.; Gaylord, A. G.; Tweedie, C. E.

    2013-12-01

    discuss remaining challenges. Lastly, to establish a sustainable Arctic Data Coordination Network (ADCN) as part of a broader polar Network will require adequate continued resources. We conclude by outlining proposed business models for the emerging Arctic Data Coordination Network and a broader polar Network.

  5. Coupled Lattice Polarization and Ferromagnetism in Multiferroic NiTiO 3 Thin Films

    Energy Technology Data Exchange (ETDEWEB)

    Varga, Tamas; Droubay, Timothy C.; Kovarik, Libor; Nandasiri, Manjula I. [Imaging; Shutthanandan, Vaithiyalingam; Hu, Dehong; Kim, Bumsoo [Materials; Department; Jeon, Seokwoo [Department; Hong, Seungbum [Materials; Department; Li, Yulan; Chambers, Scott A.

    2017-06-22

    Polarization-induced weak ferromagnetism (WFM) was demonstrated a few years back in LiNbO3-type compounds, MTiO3 (M = Fe, Mn, Ni). Although the coexistence of ferroelectric polarization and ferromagnetism has been demonstrated in this rare multiferroic family before, first in bulk FeTiO3, then in thin-film NiTiO3, the coupling of the two order parameters has not been confirmed Here, we report the stabilization of polar, ferromagnetic NiTiO3 by oxide epitaxy on a LiNbO3 substrate utilizing tensile strain and demonstrate the theoretically predicted coupling between its polarization and ferromagnetism by X-ray magnetic circular dichroism under applied fields. The experimentally observed direction of ferroic ordering in the film is supported by simulations using the phase-field approach. Our work validates symmetry-based criteria and first-principles calculations of the coexistence of ferroelectricity and WFM in MTiO3 transition metal titanates crystallizing in the LiNbO3 structure. It also demonstrates the applicability of epitaxial strain as a viable alternative to high-pressure crystal growth to stabilize metastable materials and a valuable tuning parameter to simultaneously control two ferroic order parameters to create a multiferroic. Multiferroic NiTiO3 has potential applications in spintronics where ferroic switching is used, such as new four-stage memories and electromagnetic switches.

  6. Coupled Lattice Polarization and Ferromagnetism in Multiferroic NiTiO 3 Thin Films

    Energy Technology Data Exchange (ETDEWEB)

    Varga, Tamas; Droubay, Timothy C.; Kovarik, Libor; Nandasiri, Manjula I.; Shutthanandan, Vaithiyalingam; Hu, Dehong; Kim, Bumsoo; Jeon, Seokwoo; Hong, Seungbum; Li, Yulan; Chambers, Scott A.

    2017-06-22

    Polarization-induced weak ferromagnetism has been predicted recently in LiNbO3-type MTiO3 (M = Fe, Mn, Ni). While coexisting ferroelectric polarization and ferromagnetism have been demonstrated in this family before, first in bulk FeTiO3, then in thin-film NiTiO3, the coupling of the two order parameters has not been confirmed. Here we report the stabilization of polar, ferromagnetic NiTiO3 by oxide epitaxy on LiNbO3 substrate utilizing tensile strain, and demonstrate the theory-predicted coupling between its polarization and ferromagnetism by x-ray magnetic circular dichroism under applied fields. The experimentally observed direction of ferroic ordering in the film is supported by simulation using phase-field approach. Our work validates symmetry-based criteria and first-principles calculations of the coexistence of ferroelectricity and weak ferromagnetism in MTiO3 transition metal titanates crystallizing in the LiNbO3 structure. It also demonstrates the applicability of epitaxial strain as a viable alternative to high-pressure crystal growth to stabilize metastable materials, and a valuable tuning parameter to simultaneously control two ferroic order parameters to create a multiferroic.

  7. Metastable liquid-liquid transition in a molecular model of water.

    Science.gov (United States)

    Palmer, Jeremy C; Martelli, Fausto; Liu, Yang; Car, Roberto; Panagiotopoulos, Athanassios Z; Debenedetti, Pablo G

    2014-06-19

    Liquid water's isothermal compressibility and isobaric heat capacity, and the magnitude of its thermal expansion coefficient, increase sharply on cooling below the equilibrium freezing point. Many experimental, theoretical and computational studies have sought to understand the molecular origin and implications of this anomalous behaviour. Of the different theoretical scenarios put forward, one posits the existence of a first-order phase transition that involves two forms of liquid water and terminates at a critical point located at deeply supercooled conditions. Some experimental evidence is consistent with this hypothesis, but no definitive proof of a liquid-liquid transition in water has been obtained to date: rapid ice crystallization has so far prevented decisive measurements on deeply supercooled water, although this challenge has been overcome recently. Computer simulations are therefore crucial for exploring water's structure and behaviour in this regime, and have shown that some water models exhibit liquid-liquid transitions and others do not. However, recent work has argued that the liquid-liquid transition has been mistakenly interpreted, and is in fact a liquid-crystal transition in all atomistic models of water. Here we show, by studying the liquid-liquid transition in the ST2 model of water with the use of six advanced sampling methods to compute the free-energy surface, that two metastable liquid phases and a stable crystal phase exist at the same deeply supercooled thermodynamic condition, and that the transition between the two liquids satisfies the thermodynamic criteria of a first-order transition. We follow the rearrangement of water's coordination shell and topological ring structure along a thermodynamically reversible path from the low-density liquid to cubic ice. We also show that the system fluctuates freely between the two liquid phases rather than crystallizing. These findings provide unambiguous evidence for a liquid-liquid transition in

  8. AHaH computing-from metastable switches to attractors to machine learning.

    Directory of Open Access Journals (Sweden)

    Michael Alexander Nugent

    Full Text Available Modern computing architecture based on the separation of memory and processing leads to a well known problem called the von Neumann bottleneck, a restrictive limit on the data bandwidth between CPU and RAM. This paper introduces a new approach to computing we call AHaH computing where memory and processing are combined. The idea is based on the attractor dynamics of volatile dissipative electronics inspired by biological systems, presenting an attractive alternative architecture that is able to adapt, self-repair, and learn from interactions with the environment. We envision that both von Neumann and AHaH computing architectures will operate together on the same machine, but that the AHaH computing processor may reduce the power consumption and processing time for certain adaptive learning tasks by orders of magnitude. The paper begins by drawing a connection between the properties of volatility, thermodynamics, and Anti-Hebbian and Hebbian (AHaH plasticity. We show how AHaH synaptic plasticity leads to attractor states that extract the independent components of applied data streams and how they form a computationally complete set of logic functions. After introducing a general memristive device model based on collections of metastable switches, we show how adaptive synaptic weights can be formed from differential pairs of incremental memristors. We also disclose how arrays of synaptic weights can be used to build a neural node circuit operating AHaH plasticity. By configuring the attractor states of the AHaH node in different ways, high level machine learning functions are demonstrated. This includes unsupervised clustering, supervised and unsupervised classification, complex signal prediction, unsupervised robotic actuation and combinatorial optimization of procedures-all key capabilities of biological nervous systems and modern machine learning algorithms with real world application.

  9. Preparation of meta-stable phases of barium titanate by Sol-hydrothermal method

    Directory of Open Access Journals (Sweden)

    Mahalakshmi Selvaraj

    2015-11-01

    Full Text Available Two low-cost chemical methods of sol–gel and the hydrothermal process have been strategically combined to fabricate barium titanate (BaTiO3 nanopowders. This method was tested for various synthesis temperatures (100 °C to 250 °C employing barium dichloride (BaCl2 and titanium tetrachloride (TiCl4 as precursors and sodium hydroxide (NaOH as mineralizer for synthesis of BaTiO3 nanopowders. The as-prepared BaTiO3 powders were investigated for structural characteristics using x-ray diffraction (XRD, scanning electron microscopy (SEM and transmission electron microscopy (TEM. The overall analysis indicates that the hydrothermal conditions create a gentle environment to promote the formation of crystalline phase directly from amorphous phase at the very low processing temperatures investigated. XRD analysis showed phase transitions from cubic - tetragonal - orthorhombic - rhombohedral with increasing synthesis temperature and calculated grain sizes were 34 – 38 nm (using the Scherrer formula. SEM and TEM analysis verified that the BaTiO3 nanopowders synthesized by this method were spherical in shape and about 114 - 170 nm in size. The particle distribution in both SEM and TEM shows that as the reaction temperature increases from 100 °C to 250 °C, the particles agglomerate. Selective area electron diffraction (SAED shows that the particles are crystalline in nature. The study shows that choosing suitable precursor and optimizing pressure and temperature; different meta-stable (ferroelectric phases of undoped BaTiO3 nanopowders can be stabilized by the sol-hydrothermal method.

  10. Coriocarcinoma metastásico a yeyuno. Reporte de tres casos

    Directory of Open Access Journals (Sweden)

    J.L. Martínez-Ordaz

    2012-07-01

    Full Text Available El 5,0% de los pacientes con coriocarcinoma desarrollan metástasis a intestino delgado. Los tumores de intestino delgado son raros, y generalmente las metástasis son de carcinomas de pulmón, mama o melanoma. La sintomatología es vaga y la mayoría son hallazgos de autopsia. Los síntomas principales están relacionados con la presencia de tumor abdominal o hemorragia, oclusión o perforación intestinal. Presentamos los casos de 3 pacientes con metástasis de coriocarcinoma a intestino delgado. Una mujer de 24 años con oclusión intestinal secundaria a intususcepción originada en un pólipo de coriocarcinoma metastásico, y dos hombres de 18 y 24 años con historia de tumor testicular, que presentaron 2 y 10 meses posterior a orquiectomía, hemorragia de tubo digestivo por metástasis de coriocarcinoma a intestino delgado. El manejo fue endoscópico en un caso y quirúrgico en los restantes. Dos pacientes fallecieron en el postoperatorio mediato y el restante durante el primer año de seguimiento. Las metástasis de coriocarcinoma son muy raras. Las manifestaciones clínicas principales son hemorragia u oclusión intestinal. El manejo puede ser médico o quirúrgico para su resolución. La mayoría de los pacientes con coriocarcinoma responden a quimioterapia, pero el pronóstico es peor para aquellos con metástasis a intestino delgado.

  11. Electronic structure and switching behavior of the metastable silicene domain boundary

    Science.gov (United States)

    Oh, Youngtek; Cho, Yeonchoo; Kwon, Hyeokshin; Lee, Junsu; Jeon, Insu; Ko, Wonhee; Kim, Hyo Won; Ku, JiYeon; Kim, Gunn; Suh, Hwansoo; Hwang, Sung Woo

    2017-06-01

    Silicene, a silicon allotrope with a buckled honeycomb lattice, has been extensively studied in the search for materials with graphene-like properties. Here, we study the domain boundaries of a silicene 4 × 4 superstructure on an Ag(111) surface at the atomic resolution using scanning tunneling microscopy (STM) and spectroscopy (STS) along with density functional theory calculations. The silicene domain boundaries (β-phases) are formed at the interface between misaligned domains (α-phases) and show a bias dependence, forming protrusions or depressions as the sample bias changes. In particular, the STM topographs of the silicene-substrate system at a bias of ˜2.0 V show brightly protruding domain boundaries, which can be explained by an energy state originating from the Si 3s and 3pz orbitals. In addition, the topographs depicting the vicinity of the domain boundaries show that the structure does not follow the buckled geometry of the atomic ball-and-stick model. Inside the domain, STS data showed a step-up at ˜0.4 V, which originated from the Si 3p orbitals. We found this step-up to have shifted, which may be attributed to the strain effect at the interface regions between silver and silicene and between the domain and its boundary upon performing spatially resolved STS measurements. The metastable characteristic of the domain boundary (β-phase) causes changes, such as creation or annihilation, in the buckling structures (switching behavior). The observed low activation energy for the buckling change between distinct states may find applications in the electronic control of properties related to domain boundary structures in silicene.

  12. Metastable equilibrium solubility behavior of carbonated apatite in the presence of solution strontium.

    Science.gov (United States)

    Heslop, D D; Bi, Y; Baig, A A; Higuchi, W I

    2004-01-01

    The purpose of this study was to use the concept of metastable equilibrium solubility (MES) to describe the anomalous solubility behavior of carbonated apatite (CAP) in the presence of solution strontium. A CAP sample (4.8 wt% CO(3), synthesized at 70 degrees C) was prepared by precipitation. Baseline MES distributions were determined in a series of 0.1 M acetate buffers containing only calcium and phosphate (no strontium) over a broad range of solution conditions. In order to assess the influence of strontium, MES profiles were then determined in a similar fashion with 20, 30, 40, 50, 60, 70, and 80% of the solution calcium being replaced on an equal molar basis by solution strontium. From the compositions of the equilibrating buffer solutions, ion activity products (IAPs) of the form Ca(10-n)Sr(n)(PO(4))(6)(OH)(2) (n = 0-10) were calculated in an attempt to determine the correct function governing the dissolution of the CAP preparation. The results demonstrate the following important findings: (a) at high solution strontium/calcium ratios (i.e., when 60% or more of the solution calcium was replaced by strontium), the MES profiles in all the experiments were found to be essentially superimposable when the solution IAPs were calculated using the stoichiometry of Ca(6)Sr(4)(PO(4))(6)(OH)(2), and (b), at low solution strontium/calcium ratios (i.e., when 40% or less of the solution calcium was replaced by strontium), the stoichiometry yielding MES data superpositioning was found to be that of hydroxyapatite. When other stoichiometries were assumed, good superpositioning of the data was not possible.

  13. A polarity-induced defect mechanism for conductivity and magnetism at polar-nonpolar oxide interfaces.

    Science.gov (United States)

    Yu, Liping; Zunger, Alex

    2014-10-13

    The discovery of conductivity and magnetism at the polar-nonpolar interfaces of insulating nonmagnetic oxides such as LaAlO3 and SrTiO3 has raised prospects for attaining interfacial functionalities absent in the component materials. Yet, the microscopic origin of such emergent phenomena remains unclear, posing obstacles to design of improved functionalities. Here we present first principles calculations of electronic and defect properties of LaAlO3/SrTiO3 interfaces and reveal a unifying mechanism for the origins of both conductivity and magnetism. We demonstrate that the polar discontinuity across the interface triggers thermodynamically the spontaneous formation of certain defects that in turn cancel the polar field induced by the polar discontinuity. The ionization of the spontaneously formed surface oxygen vacancy defects leads to interface conductivity, whereas the unionized Ti-on-Al antisite defects lead to interface magnetism. The proposed mechanism suggests practical design principles for inducing and controlling both conductivity and magnetism at general polar-nonpolar interfaces.

  14. A Bayesian Framework for Remaining Useful Life Estimation

    Data.gov (United States)

    National Aeronautics and Space Administration — The estimation of remaining useful life (RUL) of a faulty component is at the center of system prognostics and health management. It gives operators a potent tool in...

  15. Micro-distribution and mechanical characteristics analysis of remaining oil

    Directory of Open Access Journals (Sweden)

    Hongxia Sun

    2017-12-01

    Full Text Available As the water drive reservoir enters extra high water cut stage (greater than 80%, remaining oil distribution becomes increasingly dispersed. Research on micro residual oil in pore appears particularly important for reservoir development at extra high water cut stage. Oil occurrence characteristics recognition helps to understand the distribution of remaining oil and the mechanical characteristics of oil is the guide for tapping the remaining oil. On the basis of pore scale oil–water two phase flow experiments, micro distribution of remaining oil is divided into four occurrence states in accordance with oil features at different stage of water flooding, the flake of remaining oil, oil column, oil droplet and oil film. A quantitative characterization method of remaining oil occurrence states is established. By using micro numerical simulation method, change rules of four occurrence states of remaining oil during the process of water displacement and the mechanical characteristics of different occurrence state of remaining oil are analyzed. Results show that the continuous oil phase gradually transforms to discontinuous phase and even to dispersed phases during the water flooding process. At extra high water cut stage, most of remaining oil are dispersed oil columns, oil droplets and oil films, which are the main target of remaining oil to be tapped. By changing water flow direction or increasing the displacement pressure gradient, the surface adsorption force acting on oil columns are overcome, and then the oil columns begin to move and finally to be produced out. Oil droplets in pore-throat center are scoured and carried out by water as the increase of the injection volume, while the oil droplets in blind ends and the oil films are extracted out by adding chemicals to reduce the interfacial tension, so as to enhance oil recovery. For water flooding reservoir, the corresponding tapping measures for four types of oil occurrence states brought

  16. Method for recovering elemental silicon from cutting remains.

    OpenAIRE

    Ulset, Torgeir; Julrud, Stein; Cassayre, Laurent; Chamelot, Pierre; Massot, Laurent; Taxil, Pierre

    2008-01-01

    This invention relates to a method for recovering elemental silicon cutting remains containing silicon particles, wherein the method comprises manufacturing solid anodes from the cutting remains, arranging one or more manufactured anode (s) in an electrolytic cell with a molten salt electrolyte and one or more cathode (s), and applying a potential difference between the one or more anode (s) and cathode (s) to obtain an oxidation of metallic silicon in the one or more anode (s), tran...

  17. Polar ring galaxies in the Galaxy Zoo

    Science.gov (United States)

    Finkelman, Ido; Funes, José G.; Brosch, Noah

    2012-05-01

    We report observations of 16 candidate polar-ring galaxies (PRGs) identified by the Galaxy Zoo project in the Sloan Digital Sky Survey (SDSS) data base. Deep images of five galaxies are available in the SDSS Stripe82 data base, while to reach similar depth we observed the remaining galaxies with the 1.8-m Vatican Advanced Technology Telescope. We derive integrated magnitudes and u-r colours for the host and ring components and show continuum-subtracted Hα+[N II] images for seven objects. We present a basic morphological and environmental analysis of the galaxies and discuss their properties in comparison with other types of early-type galaxies. Follow-up photometric and spectroscopic observations will allow a kinematic confirmation of the nature of these systems and a more detailed analysis of their stellar populations.

  18. Circularly polarized antennas

    CERN Document Server

    Gao, Steven; Zhu, Fuguo

    2013-01-01

    This book presents a comprehensive insight into the design techniques for different types of CP antenna elements and arrays In this book, the authors address a broad range of topics on circularly polarized (CP) antennas. Firstly, it introduces to the reader basic principles, design techniques and characteristics of various types of CP antennas, such as CP patch antennas, CP helix antennas, quadrifilar helix antennas (QHA), printed quadrifilar helix antennas (PQHA), spiral antenna, CP slot antennas, CP dielectric resonator antennas, loop antennas, crossed dipoles, monopoles and CP horns. Adva

  19. Plasma polarization spectroscopy

    CERN Document Server

    Iwamae, Atsushi

    2008-01-01

    Plasma Polarization Spectroscopy (PPS) is now becoming a standard diagnostic technique for working with laboratory plasmas. This new area needs a comprehensive framework, both experimental and theoretical. This book reviews the historical development of PPS, develops a general theoretical formulation to deal with this phenomenon, along with an overview of relevant cross sections, and reports on laboratory experiments so far performed. It also includes various facets that are interesting from this standpoint, e.g. X-ray lasers and effects of microwave irradiation. It also offers a timely discussion of instrumentation that is quite important in a practical PPS experiment.

  20. System for measuring the proton polarization in a polarized target

    International Nuclear Information System (INIS)

    Karnaukhov, I.M.; Lukhanin, A.A.; Telegin, Yu.N.; Trotsenko, V.I.; Chechetenko, V.F.

    1984-01-01

    The system for measuring the proton polarization in a polarized target representing the high-sensitivity nuclear magnetic resonance (NMR) is described Q-meter with series connection and a circuit for measuring system resonance characteristic is used for NMR-absorption signal recording. Measuring coil is produced of a strip conductor in order to obtain uniform system sensitivity to polarization state in all target volume and improve signal-to-noise ratio. Polarization measuring system operates ion-line with the M-6000 computer. The total measuring error for the value of free proton polarization in target taking into account the error caused by local depolarization of working substance under irradiation by high-intense photon beam is <= 6%. Long-term application of the described system for measuring the proton polarization in the LUEh-20000 accelerator target used in the pion photoproduction experiments has demonstrated its high reliability

  1. Polar drive on OMEGA

    Directory of Open Access Journals (Sweden)

    Radha P.B.

    2013-11-01

    Full Text Available High-convergence polar-drive experiments are being conducted on OMEGA [T. R. Boehly et al., Opt. Commum. 133, 495 (1997] using triple-picket laser pulses. The goal of OMEGA experiments is to validate modeling of oblique laser deposition, heat conduction in the presence of nonradial thermal gradients in the corona, and implosion energetics in the presence of laser–plasma interactions such as crossed-beam energy transfer. Simulated shock velocities near the equator, where the beams are obliquely incident, are within 5% of experimentally inferred values in warm plastic shells, well within the required accuracy for ignition. High, near-one-dimensional areal density is obtained in warm-plastic-shell implosions. Simulated backlit images of the compressing core are in good agreement with measured images. Outstanding questions that will be addressed in the future relate to the role of cross-beam transfer in polar drive irradiation and increasing the energy coupled into the target by decreasing beam obliquity.

  2. Metastability of a-SiO{sub x}:H thin films for c-Si surface passivation

    Energy Technology Data Exchange (ETDEWEB)

    Serenelli, L., E-mail: luca.serenelli@enea.it [ENEA Research centre “Casaccia”, via Anguillarese 301, 00123 Rome (Italy); DIET University of Rome “Sapienza”, via Eudossiana 18, 00184 Rome (Italy); Martini, L. [DIET University of Rome “Sapienza”, via Eudossiana 18, 00184 Rome (Italy); Imbimbo, L. [ENEA Research centre “Casaccia”, via Anguillarese 301, 00123 Rome (Italy); DIET University of Rome “Sapienza”, via Eudossiana 18, 00184 Rome (Italy); Asquini, R. [DIET University of Rome “Sapienza”, via Eudossiana 18, 00184 Rome (Italy); Menchini, F.; Izzi, M.; Tucci, M. [ENEA Research centre “Casaccia”, via Anguillarese 301, 00123 Rome (Italy)

    2017-01-15

    Highlights: • a-SiO{sub x}:H film deposition by RF-PECVD is optimized from SiH{sub 4}, CO{sub 2} and H{sub 2} gas mixture. • Metastability of a-SiO{sub x}:H/c-Si passivation is investigated under thermal annealing and UV exposure. • A correlation between passivation metastability and Si−H bonds is found by FTIR spectra. • A metastability model is proposed. - Abstract: The adoption of a-SiO{sub x}:H films obtained by PECVD in heterojunction solar cells is a key to further increase their efficiency, because of its transparency in the UV with respect to the commonly used a-Si:H. At the same time this layer must guarantee high surface passivation of the c-Si to be suitable in high efficiency solar cell manufacturing. On the other hand the application of amorphous materials like a-Si:H and SiN{sub x} on the cell frontside expose them to the mostly energetic part of the sun spectrum, leading to a metastability of their passivation properties. Moreover as for amorphous silicon, thermal annealing procedures are considered as valuable steps to enhance and stabilize thin film properties, when performed at opportune temperature. In this work we explored the reliability of a-SiO{sub x}:H thin film layers surface passivation on c-Si substrates under UV exposition, in combination with thermal annealing steps. Both p- and n-type doped c-Si substrates were considered. To understand the effect of UV light soaking we monitored the minority carriers lifetime and Si−H and Si−O bonding, by FTIR spectra, after different exposure times to light coming from a deuterium lamp, filtered to UV-A region, and focused on the sample to obtain a power density of 50 μW/cm{sup 2}. We found a certain lifetime decrease after UV light soaking in both p- and n-type c-Si passivated wafers according to a a-SiO{sub x}:H/c-Si/a-SiO{sub x}:H structure. The role of a thermal annealing, which usually enhances the as-deposited SiO{sub x} passivation properties, was furthermore considered. In

  3. Forensic considerations when dealing with incinerated human dental remains.

    Science.gov (United States)

    Reesu, Gowri Vijay; Augustine, Jeyaseelan; Urs, Aadithya B

    2015-01-01

    Establishing the human dental identification process relies upon sufficient post-mortem data being recovered to allow for a meaningful comparison with ante-mortem records of the deceased person. Teeth are the most indestructible components of the human body and are structurally unique in their composition. They possess the highest resistance to most environmental effects like fire, desiccation, decomposition and prolonged immersion. In most natural as well as man-made disasters, teeth may provide the only means of positive identification of an otherwise unrecognizable body. It is imperative that dental evidence should not be destroyed through erroneous handling until appropriate radiographs, photographs, or impressions can be fabricated. Proper methods of physical stabilization of incinerated human dental remains should be followed. The maintenance of integrity of extremely fragile structures is crucial to the successful confirmation of identity. In such situations, the forensic dentist must stabilise these teeth before the fragile remains are transported to the mortuary to ensure preservation of possibly vital identification evidence. Thus, while dealing with any incinerated dental remains, a systematic approach must be followed through each stage of evaluation of incinerated dental remains to prevent the loss of potential dental evidence. This paper presents a composite review of various studies on incinerated human dental remains and discusses their impact on the process of human identification and suggests a step by step approach. Copyright © 2014 Elsevier Ltd and Faculty of Forensic and Legal Medicine. All rights reserved.

  4. Triviality of the ground-state metastate in long-range Ising spin glasses in one dimension

    Science.gov (United States)

    Read, N.

    2018-01-01

    We consider the one-dimensional model of a spin glass with independent Gaussian-distributed random interactions, which have mean zero and variance 1/|i -j | 2 σ, between the spins at sites i and j for all i ≠j . It is known that, for σ >1 , there is no phase transition at any nonzero temperature in this model. We prove rigorously that, for σ >3 /2 , any translation-covariant Newman-Stein metastate for the ground states (i.e., the frequencies with which distinct ground states are observed in finite-size samples in the limit of infinite size, for given disorder) is trivial and unique. In other words, for given disorder and asymptotically at large sizes, the same ground state, or its global spin flip, is obtained (almost) always. The proof consists of two parts: One is a theorem (based on one by Newman and Stein for short-range two-dimensional models), valid for all σ >1 , that establishes triviality under a convergence hypothesis on something similar to the energies of domain walls and the other (based on older results for the one-dimensional model) establishes that the hypothesis is true for σ >3 /2 . In addition, we derive heuristic scaling arguments and rigorous exponent inequalities which tend to support the validity of the hypothesis under broader conditions. The constructions of various metastates are extended to all values σ >1 /2 . Triviality of the metastate in bond-diluted power-law models for σ >1 is proved directly.

  5. Nucleation and growth kinetics of co-deposited copper and selenium precursors to form metastable copper selenides

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, John O.; Anderson, Michael D.; Ngai, Tim; Allen, Thomas [Materials Science Institute and Department of Chemistry, University of Oregon, Eugene, OR 97403 (United States); Johnson, David C., E-mail: davej@uoregon.edu [Materials Science Institute and Department of Chemistry, University of Oregon, Eugene, OR 97403 (United States)

    2011-10-06

    Highlights: > Nucleation and growth of compounds from co-deposited Cu and Se films investigated. > {alpha}-CuSe forms on deposit of films with less than 60% Se. > Metastable cubic CuSe{sub 2} nucleates for Se rich films. > Slow heating rates favor nucleation of metastable cubic CuSe{sub 2} over {gamma}-CuSe. - Abstract: The nucleation and growth kinetics of binary copper-selenium compounds from co-deposited copper and selenium films as a function of annealing temperature and time was investigated. The thermally driven evolution of crystalline phases was followed using differential scanning calorimetry and X-ray diffraction. Below 60% selenium, hexagonal {alpha}-CuSe formed during the deposition and a reversible endothermic transition at {approx}130 deg. C was observed for the phase transition into hexagonal {gamma}-CuSe. Above 60% selenium the samples are amorphous as deposited and there is competition between the formation of {gamma}-CuSe and cubic CuSe{sub 2} as annealing temperature is increased. Slow rates of temperature increase favor the formation of CuSe{sub 2} over {gamma}-CuSe and near 66% selenium only cubic CuSe{sub 2} forms during an exothermic event between 100 deg. C and 110 deg. C. It is surprising that the metastable cubic CuSe{sub 2} initially nucleates and grows rather than the thermodynamically stable orthorhombic CuSe{sub 2} polymorph. Kissinger analysis yields an activation energy for nucleation of 1.6 eV for cubic CuSe{sub 2}. CuSe nucleates throughout the composition region investigated. Hexagonal {alpha}-CuSe reacts with selenium to form the thermodynamically stable orthorhombic polymorph of CuSe{sub 2} as the temperature approaches the melting point of selenium.

  6. Synthesis and characterization of metastable, 20 nm-sized Pna21-LiCoPO4 nanospheres

    International Nuclear Information System (INIS)

    Ludwig, Jennifer; Nordlund, Dennis; Doeff, Marca M.; Nilges, Tom

    2017-01-01

    The majority of research activities on LiCoPO 4 are focused on the phospho-olivine (space group Pnma), which is a promising high-voltage cathode material for Li-ion batteries. In contrast, comparably little is known about its metastable Pna2 1 modification. Herein, we present a comprehensive study on the structure–property relationships of 15–20 nm Pna2 1 -LiCoPO 4 nanospheres prepared by a simple microwave-assisted solvothermal process. Unlike previous reports, the results indicate that the compound is non-stoichiometric and shows cation-mixing with Co ions on the Li sites, which provides an explanation for the poor electrochemical performance. Co L 2,3 -edge X-ray absorption spectroscopic data confirm the local tetrahedral symmetry of Co 2+ . Comprehensive studies on the thermal stability using thermogravimetric analysis, differential scanning calorimetry, and in situ powder X-ray diffraction show an exothermic phase transition to olivine Pnma-LiCoPO 4 at 527 °C. The influence of the atmosphere and the particle size on the thermal stability is also investigated. - Graphical abstract: Blue nano-sized Pna2 1 -LiCoPO 4, featuring tetrahedrally-coordinated Co 2+ , was synthesized in a rapid one-step microwave-assisted solvothermal process. The phase relation between this metastable and the stable polymorph was analyzed and electrochemical properties are discussed. - Highlights: • Preparation of uniform 15–20 nm nanospheres of metastable Pna2 1 -LiCoPO 4 polymorph. • Structure redetermination shows cation-mixing (Co blocking Li sites). • In situ investigation of phase transformation to olivine Pnma-LiCoPO 4 at 527 °C. • Pna2 1 -LiCoPO 4 reemerges as a stable high-temperature phase above 800 °C. • X-ray absorption spectroscopy confirms local tetrahedral symmetry (T d Co 2+ ).

  7. Polarized proton collider at RHIC

    Energy Technology Data Exchange (ETDEWEB)

    Alekseev, I.; Allgower, C.; Bai, M.; Batygin, Y.; Bozano, L.; Brown, K.; Bunce, G.; Cameron, P.; Courant, E.; Erin, S.; Escallier, J.; Fischer, W.; Gupta, R.; Hatanaka, K.; Huang, H.; Imai, K.; Ishihara, M.; Jain, A.; Lehrach, A.; Kanavets, V.; Katayama, T.; Kawaguchi, T.; Kelly, E.; Kurita, K.; Lee, S.Y.; Luccio, A.; MacKay, W.W. E-mail: mackay@bnl.govhttp://www.rhichome.bnl.gov/People/waldowaldo@bnl.gov; Mahler, G.; Makdisi, Y.; Mariam, F.; McGahern, W.; Morgan, G.; Muratore, J.; Okamura, M.; Peggs, S.; Pilat, F.; Ptitsin, V.; Ratner, L.; Roser, T.; Saito, N.; Satoh, H.; Shatunov, Y.; Spinka, H.; Syphers, M.; Tepikian, S.; Tominaka, T.; Tsoupas, N.; Underwood, D.; Vasiliev, A.; Wanderer, P.; Willen, E.; Wu, H.; Yokosawa, A.; Zelenski, A.N

    2003-03-01

    In addition to heavy ion collisions (RHIC Design Manual, Brookhaven National Laboratory), RHIC will also collide intense beams of polarized protons (I. Alekseev, et al., Design Manual Polarized Proton Collider at RHIC, Brookhaven National Laboratory, 1998, reaching transverse energies where the protons scatter as beams of polarized quarks and gluons. The study of high energy polarized protons beams has been a long term part of the program at BNL with the development of polarized beams in the Booster and AGS rings for fixed target experiments. We have extended this capability to the RHIC machine. In this paper we describe the design and methods for achieving collisions of both longitudinal and transverse polarized protons in RHIC at energies up to {radical}s=500 GeV.

  8. Cutmarked human remains bearing Neandertal features and modern human remains associated with the Aurignacian at Les Rois.

    Science.gov (United States)

    Ramirez Rozzi, Fernando V; d'Errico, Francesco; Vanhaeren, Marian; Grootes, Pieter M; Kerautret, Bertrand; Dujardin, Véronique

    2009-01-01

    The view that Aurignacian technologies and their associated symbolic manifestations represent the archaeologicalproxy for the spread of Anatomically Modern Humans into Europe, is supported by few diagnostic human remains, including those from the Aurignacian site of Les Rois in south-western France. Here we reassess the taxonomic attribution of the human remains, their cultural affiliation, and provide five new radiocarbon dates for the site. Patterns of tooth growth along with the morphological and morphometric analysis of the human remains indicate that a juvenile mandible showing cutmarks presents some Neandertal features, whereas another mandible is attributed to Anatomically Modern Humans. Reappraisal of the archaeological sequence demonstrates that human remains derive from two layers dated to 28-30 kyr BP attributed to the Aurignacian, the only cultural tradition detected at the site. Three possible explanations may account for this unexpected evidence. The first one is that the Aurignacian was exclusively produced by AMH and that the child mandible from unit A2 represents evidence for consumption or, more likely, symbolic use of a Neandertal child by Aurignacian AMH The second possible explanation is that Aurignacian technologies were produced at Les Rois by human groups bearing both AMH and Neandertal features. Human remains from Les Rois would be in this case the first evidence of a biological contact between the two human groups. The third possibility is that all human remains from Les Rois represent an AMH population with conserved plesiomorphic characters suggesting a larger variation in modern humans from the Upper Palaeolithic.

  9. Numerical study on the time evolutions of the electric field in helium plasma jets with positive and negative polarities

    Science.gov (United States)

    Viegas, Pedro; Péchereau, François; Bourdon, Anne

    2018-02-01

    This paper presents 2D simulations of atmospheric pressure discharges in helium with N2 and O2 admixtures, propagating in a dielectric tube between a point electrode and a grounded metallic target. For both positive and negative polarities, the propagation of the first ionization front is shown to correspond to a peak of the absolute value of the axial electric field inside the tube, but also outside the tube. After the impact on the metallic target, a rebound front is shown to propagate from the target to the point electrode. This rebound front is 2-3 times faster than the first ionization front. Close to the high voltage point, this rebound front corresponds to a second peak of the absolute value of the axial electric field. Close to the target, as the first ionization and rebound fronts are close in time, only one peak is observed. The dynamics of the absolute value of the radial component of electric field outside the tube is shown to present an increase during the first ionization front propagation and a fast decrease corresponding to the propagation of the rebound front. These time evolutions of the electric field components are in agreement with experiments. Finally, we have shown that the density of metastable He* in 99% He—1% N2 and 99% He—1% O2 atmospheric pressure discharges are very close. Close to the grounded target, the peak density of reactive species is significantly increased due to the synergy between the first ionization and rebound fronts, as observed in experiments. Similar results are obtained for both voltage polarities, but the peak density of metastable He* close to the target is shown to be two times less in negative polarity than in positive polarity.

  10. Linear polarization of BY Draconis

    International Nuclear Information System (INIS)

    Koch, R.H.; Pfeiffer, R.J.

    1976-01-01

    Linear polarization measurements are reported in four bandpasses for the flare star BY Dra. The red polarization is intrinsically variable at a confidence level greater than 99 percent. On a time scale of many months, the variability is not phase-locked to either a rotational or a Keplerian ephemeris. The observations of the three other bandpasses are useful principally to indicate a polarization spectrum rising toward shorter wavelengths

  11. Polarity in Mammalian Epithelial Morphogenesis

    OpenAIRE

    Roignot, Julie; Peng, Xiao; Mostov, Keith

    2013-01-01

    Cell polarity is fundamental for the architecture and function of epithelial tissues. Epithelial polarization requires the intervention of several fundamental cell processes, whose integration in space and time is only starting to be elucidated. To understand what governs the building of epithelial tissues during development, it is essential to consider the polarization process in the context of the whole tissue. To this end, the development of three-dimensional organotypic cell culture model...

  12. Preparation, properties, and application characteristics of metastable layers of the Ti-Si-C-N system

    International Nuclear Information System (INIS)

    Fella, R.

    1992-10-01

    In the Ti-Si-C and Ti-Si-C-N systems, metastable layers were precipitated by means of non-reactive magnetron sputtering of hot-pressed two-phase TiC/SiC and TiN/SiC targets with 20 mole% and 50 mole% SiC. The preparation parameters were varied as follows: ion bombardment during precipitation (bias sputtering), substrate temperature, and annealing times when annealing amorphous 50%:50% TiC/SiC and 50%:50% TiN/SiC layers. Sputtering of targets containing 20% SiC was found to result in monophase fcc layers (NaCl structure). This was documented on the basis of X-ray and electron diffraction patterns. Direct precipitation of targets with 50 mole% SiC resulted in amorphous layers. Increasing the ion bombardment during accretion, raising the substrate temperature, and annealing amorphous 50%:50% TiC/SiC and 50%:50% TiN/SiC (layers precipitated directly) resulted in the crystallization of TiC and TiN nanocrystallites, respectively, imbedded in an amorphous SiC matrix. These crystallites were detected both by X-ray and by electron diffractions and by XPS studies. The XPS measurements of crystalline TiC and amorphous SiC reference layers demonstrated the existence of new kinds of carbon interface phases ('pseudocarbide layers') around TiC and amorphous SiC regions, respectively, which have a positive impact on the mechanical properties of the layers. The hardness of the layers can be correlated with the degrees of crystallization and texture. Adhesion and toughness are worse in SiC-bearing layers than PVD TiC and TiN layers, respectively. The application characteristics of the layers were determined by model wear tests relative to 100Cr6 by means of a pin/disk tribometer. N-bearing layers were found to have clearly higher friction coefficients and greater wear than layers without N. (orig.)

  13. Ion beam synthesis and characterization of metastable group-IV alloy semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Kobayashi, Naoto; Hasegawa, Masataka; Hayashi, Nobuyuki; Makita, Yunosuke; Shibata, Hajime [Electrotechnical Lab., Tsukuba, Ibaraki (Japan); Katsumata, Hiroshi; Uekusa, Shin-ichiro

    1997-03-01

    New Group-IV metastable alloy semiconductors and their heterostructures based on combinations of C-Si-Ge-Sn are recently attracting interest because of feasible new electronic and optoelectronic application in Si-technology and here research works on synthesis and characterization of the epitaxial heterostructures of Si-C, Si-Sn on Si fabricated by ion implantation together either with ion-beam-induced epitaxial crystallization (IBIEC) or solid phase epitaxial growth (SPEG) have been investigated. Formations of layers of Si{sub 1-y}C{sub y} (y=0.014 at peak concentration) on Si(100) have been performed by high-dose implantation of 17 keV C ions and successive IBIEC with 400 keV Ar or Ge ion bombardments at 300-400degC or SPEG up to 750degC. Crystalline growth by IBIEC has shown a lower growth rate in Si{sub 1-y}C{sub y}/Si than in intrinsic Si due mainly to the strain existence, which was observed by the X-ray diffraction (XRD) measurements. Photoluminescence(PL) measurements have revealed I{sub 1} or G line emissions that are relevant to small vacancy clusters or C pair formation, respectively. The crystalline growth of Si{sub 1-z}Sn{sub z} layers by 110 keV {sup 120}Sn ion implantation (z=0.029 and z=0.058 at peak concentration) into Si(100) followed either by IBIEC or by SPEG has been also investigated. PL emission from both IBIEC-grown and SPEG-grown samples with the lower Sn concentration has shown similar peaks to those by ion-implanted and annealed Si samples with intense I{sub 1} or I{sub 1}-related (Ar) peaks. Present results suggest that IBIEC has a feature for the non-thermal equilibrium fabrication of Si-C and Si-Sn alloy semiconductors. (J.P.N.)

  14. Development of nano/sub-micron grain structures in metastable austenitic stainless steels

    Science.gov (United States)

    Rajasekhara, Shreyas

    2007-12-01

    This dissertation is a part of a collaborative work between the University of Texas, Austin-Texas, the University of Oulu, Oulu-Finland, and Outokumpu Stainless Oy, Tornio-Finland, to develop commercial austenitic stainless steels with high strength and ductility. The idea behind this work involves cold-rolling a commercial metastable austenitic stainless steel - AISI 301LN stainless steel to produce strain-induced martensite, followed by an annealing treatment to generate nano/sub-micron grained austenite. AISI 301LN stainless steel sheets are cold-rolled to 63% reduction and subsequently annealed at 600°C, 700°C, 800°C, 900°C and 1000°C for 1, 10 and 100 seconds. The samples are analyzed by X-Ray diffraction, SQUID, transmission electron microscopy, and tensile testing to fundamentally understand the microstructural evolution, the mechanism for the martensite → austenite reversion, the formation of nano/sub-micron austenite grains, and the relationship between the microstructure and the strength obtained in this stainless steel. The results show that cold-rolled AISI 301LN stainless steel consist of dislocation-cell martensite, heavily deformed lath-martensite and austenite shear bands. Subsequent annealing at 600°C for short durations of 1 and 10 seconds leads to negligible martensite to austenite reversion. These 600°C samples exhibit a similar microstructure to the cold-rolled sample. However, for samples annealed at 600°C for 100 seconds and those annealed at higher temperatures (700°C, 800°C, 900°C and 1000°C) exhibit equiaxed austenitic grains of sizes 0.2mum-10mum and secondary phase precipitates. The microstructural analysis also reveals that the martensite → austenite reversion occurs via a diffusion-type reversion mechanism. In this regard, a generalized form of Avrami's equation is used to model the kinetics of martensite → austenite phase reversion. The results from the model agree reasonably well with the experiments. Furthermore

  15. Metastable Cu(I)-niobate semiconductor with a low-temperature, nanoparticle-mediated synthesis.

    Science.gov (United States)

    Choi, Jonglak; King, Nacole; Maggard, Paul A

    2013-02-26

    A nanoparticle synthetic strategy for the preparation of a new metastable Cu(I)-niobate is described, and that involves multipored Li₃NbO₄ nanoparticles as a precursor. A hydrothermal reaction of HNbO₃ and LiOH·H₂O in PEG200 and water at ∼180 °C yields ∼15-40 nm Li₃NbO₄ particles. These particles are subsequently used in a solvothermal copper(I)-exchange reaction with excess CuCl at 150 °C. Heating these products within the used CuCl flux (mp = 430 °C) to 450 °C for 30 min yields ∼4-12 nm Cu₂Nb₈O₂₁ crystalline nanoparticles, and for a heating time of 24 h yields μm-sized, rod-shaped crystals. The new structure was characterized by single-crystal X-ray diffraction to have a condensed network consisting of NbO₇ polyhedra and chains of elongated CuO₄ tetrahedra. The compound thermally decomposes starting at ∼250 °C and higher temperatures, depending on the particle sizes, owing to the loss of the weakly coordinated Cu(I) cations from the structure and a concurrent disproportionation reaction at its surfaces. Thus, conventional solid-state reactions involving higher temperatures and bulk reagents have proven unsatisfactory for its synthesis. The measured bandgap size is ∼1.43-1.65 eV (indirect) and shows a dependence on the particle sizes. Electronic structure calculations based on density functional theory show that the bandgap transition results from the excitation of electrons at the band edges between filled Cu(I) 3d¹⁰-orbitals and empty Nb(V) 4d⁰-orbitals, respectively. The p-type nature of the Cu₂Nb₈O₂₁ particles was confirmed in photoelectrochemical measurements on polycrystalline films that show a strong photocathodic current under visible-light irradiation in aqueous solutions. These results demonstrate the general utility of reactive nanoscale precursors in the synthetic discovery of new Cu(I)-based semiconducting oxides and which also show promise for use in solar energy conversion applications.

  16. Metastable Equilibrium Solubility Distribution of Carbonated Apatite as a Function of Solution Composition.

    Science.gov (United States)

    Chhettry; Wang; Hsu; Fox; Baig; Barry; Zhuang; Otsuka; Higuchi

    1999-10-01

    Previous studies have shown that carbonated apatites (CAPs) exhibit the phenomenon of metastable equilibrium solubility (MES) in weak acid media. The purpose of the present investigation was to examine two questions: first, whether the MES concept is applicable to a broader range of solution conditions and, second, whether a driving force function associated with a surface complex having a constant stoichiometry governs the dissolution of CAP and, if so, what is this stoichiometry. CAP preparations with carbonate contents of 1.8-5.7 wt% (synthesized by hydrolysis of dicalcium phosphate anhydrate in solutions of varying bicarbonate levels or by direct precipitation from supersaturated calcium/phosphate/carbonate solutions) were studied as follows. MES distributions for each of the CAP preparations were determined by equilibrating the CAP under stirred conditions in a series of acetate buffers (0.10 M) containing various levels of calcium and phosphate in the pH range 4.5-6.5 and a solution calcium/phosphate ratio in the range 0.1-10. The amount dissolved in each instance was regarded as the fraction of the CAP possessing an MES value greater than that corresponding to the ion activity product (IAP) of the equilibrating solution. The solution IAPs were calculated from the solution compositions using plausible calcium phosphate stoichiometries, viz., dicalcium phosphate dihydrate, octacalcium phosphate, tricalcium phosphate, hydroxyapatite, carbonated apatite (based on the bulk composition of the particular CAP involved in the experiment), and tetracalcium phosphate. The fraction of CAP dissolved was plotted against the solution IAPs for each experimental set using each of the six assumed stoichiometries for the surface complex. The results demonstrated that the MES concept was applicable to all of the CAP preparations in media of various solution compositions and different pH levels. The most important new outcome of this study was that MES profiles for each of the

  17. Effects of severe plastic deformation on grain refinement and martensitic transformation in a metastable β Ti alloy

    International Nuclear Information System (INIS)

    Zafari, A; Wei, X S; Xu, W; Xia, K

    2015-01-01

    A Ti-5553 metastable β alloy was subjected to high pressure torsion (HPT) to obtain a nano β grain structure. The β grains were dramatically refined from an initial size of ∼1 mm to < 50 nm during HPT. The stress induced martensitic α' plates divided β grains into smaller domains and enabled subgrains to form even in very fine grains. The reverse α' to β transformation occurred when the thickness of the α' laths reached < ∼10 nm, leading to pure β nano-grains. Further deformation to an equivalent strain of 242 resulted in grain growth and the formation of well defined grain boundaries. (paper)

  18. The influence of the martensitic transformation on the fatigue of an AISI type 316 metastable stainless steel

    International Nuclear Information System (INIS)

    Pacheco, D.J; Sousa e Silva, A.S. de; Monteiro, S.N.

    The influence of the martensitic transformation on the process of pulse tension fatigue of a AISI type 316 metastable stainless steel was studied at 25 0 and 196 0 c. The fatigue tests were performed on annealed and cold worked specimens in order to separate the effects of static transformation, dynamic transformation and work hardening. The fatigue limits obtained from the corresponding Wohler curves were compared for the different test conditions. The results showed that the fatigue is not affected by the dynamically induced martensite. On the other hand the static martensite, previously induced, appears to decrease the resistance to fatigue. The reasons for these effects are discussed. (Author) [pt

  19. Holocene insect remains from south-western Greenland

    DEFF Research Database (Denmark)

    Bøcher, Jens Jensenius; Bennike, Ole; Wagner, Bernd

    2012-01-01

    Remains of plants and invertebrates from Holocene deposits in south-western Greenland include a number of insect fragments from Heteroptera and Coleoptera. Some of the finds extend the known temporal range of the species considerably back in time, and one of the taxa has not previously been found...... in Greenland either fossil or extant. The fossil fauna includes the weevil Rutidosoma globulus which is at present extremely rare in Greenland. Its rarity might indicate that it is a recent immigrant, but the fossil finds provide a minimum date for its arrival at around 5840 cal. years B. P. Other remains...

  20. A polarized alkali ion source

    International Nuclear Information System (INIS)

    Boettger, R.; Tungate, G.; Bauer, B.; Egelhof, P.; Moebius, K.H.; Steffens, E.

    1978-01-01

    The beam foil technique has been applied to detect nuclear vector polarization of a 10 keV 23 Na + beam. The result was about 70% of the atomic beam polarization thus limiting the depolarization by the surface ionizer to at most 30%. In a Coulomb excitation experiment with a tensor polarized 42 MeV 23 Na 7+ beam an effect of 0.011 +- 0.003 was measured yielding a value of t 20 approx. 0.04 for the beam polarization. The depolarization during the acceleration process can be estimated to be about 0.8. (orig.) [de