Second-order Monte Carlo wave-function approach to the relaxation effects on ringing revivals in a molecular system interacting with a strongly squeezed coherent field

International Nuclear Information System (INIS)

Nakano, Masayoshi; Kishi, Ryohei; Nitta, Tomoshige; Yamaguchi, Kizashi

2004-01-01

We investigate the relaxation effects on the quantum dynamics in a two-state molecular system interacting with a single-mode strongly amplitude-squeezed coherent field using the second-order Monte Carlo wave-function method. The molecular population inversion (collapse-revival behavior of Rabi oscillations) is known to show the echoes after each revival, which are referred to as ringing revivals, in the case of strongly squeezed coherent fields with oscillatory photon-number distributions due to the phase-space interference effect. Two types of relaxation effects, i.e., cavity relaxation (the dissipation of an internal single mode to outer mode) and molecular coherent (phase) relaxation caused by nuclear vibrations on ringing revivals are investigated from the viewpoint of the quantum-phase dynamics using the quasiprobability (Q function) distribution of a single-mode field and the off-diagonal molecular density matrix ρ elec1,2 (t). It turns out that the molecular phase relaxation attenuates both the entire revival-collapse behavior and the increase in ρ elec1,2 (t) during the quiescent region, whereas a very slight cavity relaxation particularly suppresses the echoes in ringing revivals more significantly than the first revival but hardly changes a primary variation in envelope of ρ elec1,2 (t) in the nonrelaxation case

Enhancement of strong-field multiple ionization in the vicinity of the conical intersection in 1,3-cyclohexadiene ring opening

International Nuclear Information System (INIS)

Petrovic, Vladimir S.; Kim, Jaehee; Schorb, Sebastian; White, James; Cryan, James P.; Zipp, Lucas; Glownia, J. Michael; Broege, Douglas; Miyabe, Shungo; Tao, Hongli; Martinez, Todd; Bucksbaum, Philip H.

2013-01-01

Nonradiative energy dissipation in electronically excited polyatomic molecules proceeds through conical intersections, loci of degeneracy between electronic states. We observe a marked enhancement of laser-induced double ionization in the vicinity of a conical intersection during a non-radiative transition. We measured double ionization by detecting the kinetic energy of ions released by laser-induced strong-field fragmentation during the ring-opening transition between 1,3-cyclohexadiene and 1,3,5-hexatriene. The enhancement of the double ionization correlates with the conical intersection between the HOMO and LUMO orbitals

How does the blue-ringed octopus (Hapalochlaena lunulata) flash its blue rings?

Science.gov (United States)

Mäthger, Lydia M; Bell, George R R; Kuzirian, Alan M; Allen, Justine J; Hanlon, Roger T

2012-11-01

The blue-ringed octopus (Hapalochlaena lunulata), one of the world's most venomous animals, has long captivated and endangered a large audience: children playing at the beach, divers turning over rocks, and biologists researching neurotoxins. These small animals spend much of their time in hiding, showing effective camouflage patterns. When disturbed, the octopus will flash around 60 iridescent blue rings and, when strongly harassed, bite and deliver a neurotoxin that can kill a human. Here, we describe the flashing mechanism and optical properties of these rings. The rings contain physiologically inert multilayer reflectors, arranged to reflect blue-green light in a broad viewing direction. Dark pigmented chromatophores are found beneath and around each ring to enhance contrast. No chromatophores are above the ring; this is unusual for cephalopods, which typically use chromatophores to cover or spectrally modify iridescence. The fast flashes are achieved using muscles under direct neural control. The ring is hidden by contraction of muscles above the iridophores; relaxation of these muscles and contraction of muscles outside the ring expose the iridescence. This mechanism of producing iridescent signals has not previously been reported in cephalopods and we suggest that it is an exceptionally effective way to create a fast and conspicuous warning display.

Cottonwood Tree Rings and Climate in Western North America

Science.gov (United States)

Friedman, J. M.; Edmondson, J.; Griffin, E. R.; Meko, D. M.; Merigliano, M. F.; Scott, J. A.; Scott, M. L.; Touchan, R.

2012-12-01

In dry landscapes of interior western USA, cottonwood (Populus spp.) seedling establishment often occurs only close to river channels after floods. Where winter is sufficiently cold, cottonwoods also have distinct annual rings and can live up to 370 years, allowing us to reconstruct the long-term history of river flows and channel locations. We have analyzed the annual rate of cottonwood establishment along streams in Montana, Wyoming, Colorado, North Dakota and Idaho. Because the trees germinate next to the river, establishment rates are strongly correlated with the rate of channel migration driven by floods. Along large rivers dominated by snowmelt from the mountains, interannual variation in peak flows and cottonwood establishment is small, and century-scale variation driven by climate change is apparent. The upper Snake, Yellowstone and Green rivers all show a strong decrease in cottonwood establishment beginning in the late 1800s and continuing to the present, indicating a decrease in peak flows prior to flow regulation by large dams. This is consistent with published tree-ring studies of montane conifers showing decreases in snowpack at the same time scale. In contrast, beginning in the late 1800s cottonwood ring widths along the Little Missouri River, North Dakota show an increase in annual growth that continues into the present. Because annual growth is strongly correlated with April-July flows (r=0.69) the ring-width data suggest an increase in April-July flows at the same time tree establishment dates suggest a decrease in peak flows. These results may be reconciled by the hypothesis that increases in low temperatures have decreased snowpack while lengthening the growing season.

TREE-RING INDICES AND ISOTOPE SIGNATURES OF PINUS PONDEROSA RELATED TO HISTORIC OZONE CHANGES OUTSIDE LOS ANGELES

Science.gov (United States)

Ozone concentrations in the Los Angeles (LA) basin were at historic highs in the late 1970s. Since that time Clean Air regulations have helped lower ozone, but little is known of the long-term vegetation responses. Extensive research has used tree-ring indices together with the...

Structure and dynamics of ringed galaxies

International Nuclear Information System (INIS)

Buta, R.J.

1984-01-01

In many spiral and SO galaxies, single or multiple ring structures are visible in the disk. These inner rings (r), outer rings (R), and nuclear rings (nr) were investigated by means of morphology, photometry, and spectroscopy in order to provide basic data on a long neglected phenomenon. The metric properties of each ring are investigated and found to correlate with the structure of the parent galaxy. When properly calibrated, inner rings in barred (SB) systems can be used as geometric extragalactic distance indicators to distances in excess of 100 Mpc. Other statistics are presented that confirm previous indications that the rings have preferred shapes, relative sizes, and orientations with respect to bars. A survey is made of the less homogeneous non-barred (SA) ringed systems, and the causes of the inhomogeneity are isolated. It is shown that rings can be identified in multiple-ring SA systems that are exactly analogous to those in barred spirals

Resonance tuning due to Coulomb interaction in strong near-field coupled metamaterials

International Nuclear Information System (INIS)

Roy Chowdhury, Dibakar; Xu, Ningning; Zhang, Weili; Singh, Ranjan

2015-01-01

Coulomb's law is one of the most fundamental laws of physics that describes the electrostatic interaction between two like or unlike point charges. Here, we experimentally observe a strong effect of Coulomb interaction in tightly coupled terahertz metamaterials where the split-ring resonator dimers in a unit cell are coupled through their near fields across the capacitive split gaps. Using a simple analytical model, we evaluated the Coulomb parameter that switched its sign from negative to positive values indicating the transition in the nature of Coulomb force from being repulsive to attractive depending upon the near field coupling between the split ring resonators. Apart from showing interesting effects in the strong coupling regime between meta-atoms, Coulomb interaction also allows an additional degree of freedom to achieve frequency tunable dynamic metamaterials

Inferring biome-scale net primary productivity from tree-ring isotopes

Science.gov (United States)

Pederson, N.; Levesque, M.; Williams, A. P.; Hobi, M. L.; Smith, W. K.; Andreu-Hayles, L.

2017-12-01

Satellite estimates of vegetation growth (net primary productivity; NPP), tree-ring records, and forest inventories indicate that ongoing climate change and rising atmospheric CO2 concentration are altering productivity and carbon storage of forests worldwide. The impact of global change on the trends of NPP, however, remain unknown because of the lack of long-term high-resolution NPP data. For the first time, we tested if annually resolved carbon (δ13C) and oxygen (δ18O) stable isotopes from the cellulose of tree rings from trees in temperate regions could be used as a tool for inferring NPP across spatiotemporal scales. We compared satellite NPP estimates from the moderate-resolution imaging spectroradiometer sensor (MODIS, product MOD17A) and a newly developed global NPP dataset derived from the Global Inventory Modeling and Mapping Studies (GIMMS) dataset to annually resolved tree-ring width and δ13C and δ18O records from four sites along a hydroclimatic gradient in Eastern and Central United States. We found strong correlations across large geographical regions between satellite-derived NPP and tree-ring isotopes that ranged from -0.40 to -0.91. Notably, tree-ring derived δ18O had the strongest relation to climate. The results were consistent among the studied tree species (Quercus rubra and Liriodendron tulipifera) and along the hydroclimatic conditions of our network. Our study indicates that tree-ring isotopes can potentially be used to reconstruct NPP in time and space. As such, our findings represent an important breakthrough for estimating long-term changes in vegetation productivity at the biome scale.

Mechanical improvement of metal reinforcement rings for a finite ring-shaped superconducting bulk

Science.gov (United States)

Huang, Chen-Guang; Zhou, You-He

2018-03-01

As a key technique, reinforcement of type-II superconducting bulks with metal rings can efficiently improve their mechanical properties to enhance the maximum trapped field. In this paper, we study the magnetostrictive and fracture behaviors of a finite superconducting ring bulk reinforced by three typical reinforcing structures composed of metal rings during the magnetizing process by means of the minimization of magnetic energy and the finite element method. After a field-dependent critical current density is adopted, the magnetostriction, pinning-induced stress, and crack tip stress intensity factor are calculated considering the demagnetization effects. The results show that the mechanical properties of the ring bulk are strongly dependent on the reinforcing structure and the material and geometrical parameters of the metal rings. Introducing the metal ring can significantly reduce the hoop stress, and the reduction effect by internal reinforcement is much improved relative to external reinforcement. By comparison, bilateral reinforcement seems to be the best candidate structure. Only when the metal rings have particular Young's modulus and radial thickness will they contribute to improve the mechanical properties the most. In addition, if an edge crack is pre-existing in the ring bulk, the presence of metal rings can effectively avoid crack propagation since it reduces the crack tip stress intensity factor by nearly one order of magnitude.

Self-pumped passive ring mirror in crystals with strong fanning

Science.gov (United States)

Bogodaev, Nickolai V.; Ivleva, Ludmila I.; Korshunov, A. S.; Mamaev, A. V.; Polozkov, N. N.; Zozulya, Aleksei A.

1992-12-01

Most photorefractive crystals, suitable for the realization of self-pumped four-wave mixing phase conjugation and mutual conjugation geometries, are characterized by the high level of fanning. In some cases it may mean that the nonlinearity of these crystals is already too large to be good and a decrease in the value of a nonlinear coupling coefficient may result in an improved performance of these geometries. This point is illustrated using geometry of a self- pumped ring mirror.

On the evolution of vortex rings with swirl

International Nuclear Information System (INIS)

Naitoh, Takashi; Okura, Nobuyuki; Gotoh, Toshiyuki; Kato, Yusuke

2014-01-01

A laminar vortex ring with swirl, which has the meridional velocity component inside the vortex core, was experimentally generated by the brief fluid ejection from a rotating outlet. The evolution of the vortex ring was investigated with flow visualizations and particle image velocimetry measurements in order to find the influence of swirling flow in particular upon the transition to turbulence. Immediately after the formation of a vortex ring with swirl, a columnar strong vortex along the symmetric axis is observed in all cases of the present experiment. Then the characteristic fluid discharging from a vortex ring with swirl referred to as “peeling off” appears. The amount of discharging fluid due to the “peeling off” increases with the angular velocity of the rotating outlet. We conjectured that the mechanism generating the “peeling off” is related to the columnar strong vortex by close observations of the spatio-temporal development of the vorticity distribution and the cutting 3D images constructed from the successive cross sections of a vortex ring. While a laminar vortex ring without swirl may develop azimuthal waves around its circumference at some later time and the ring structure subsequently breaks, the swirling flow in a vortex ring core reduces the amplification rate of the azimuthal wavy deformation and preserved its ring structure. Then the traveling distance of a vortex ring can be extended using the swirl flow under certain conditions

On the evolution of vortex rings with swirl

Energy Technology Data Exchange (ETDEWEB)

Naitoh, Takashi, E-mail: naitoh.takashi@nitech.ac.jp [Department of Engineering Physics, Electronics and Mechanics, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Okura, Nobuyuki, E-mail: ohkura@meijo-u.ac.jp [Department of Vehicle and Mechanical Engineering, Meijo University, 1-501 Shiogamaguchi Tempaku-ku, Nagoya 468-8502 (Japan); Gotoh, Toshiyuki, E-mail: gotoh.toshiyuki@nitech.ac.jp [Department of Scientific and Engineering Simulation, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Kato, Yusuke [Controller Business Unit Engineering Division 1, Engineering Department 3, Denso Wave Incorporated, 1 Yoshiike Kusagi Agui-cho, Chita-gun Aichi 470-2297 (Japan)

2014-06-15

A laminar vortex ring with swirl, which has the meridional velocity component inside the vortex core, was experimentally generated by the brief fluid ejection from a rotating outlet. The evolution of the vortex ring was investigated with flow visualizations and particle image velocimetry measurements in order to find the influence of swirling flow in particular upon the transition to turbulence. Immediately after the formation of a vortex ring with swirl, a columnar strong vortex along the symmetric axis is observed in all cases of the present experiment. Then the characteristic fluid discharging from a vortex ring with swirl referred to as “peeling off” appears. The amount of discharging fluid due to the “peeling off” increases with the angular velocity of the rotating outlet. We conjectured that the mechanism generating the “peeling off” is related to the columnar strong vortex by close observations of the spatio-temporal development of the vorticity distribution and the cutting 3D images constructed from the successive cross sections of a vortex ring. While a laminar vortex ring without swirl may develop azimuthal waves around its circumference at some later time and the ring structure subsequently breaks, the swirling flow in a vortex ring core reduces the amplification rate of the azimuthal wavy deformation and preserved its ring structure. Then the traveling distance of a vortex ring can be extended using the swirl flow under certain conditions.

Quantum ring with the Rashba spin-orbit interaction in the regime of strong light-matter coupling

Science.gov (United States)

Kozin, V. K.; Iorsh, I. V.; Kibis, O. V.; Shelykh, I. A.

2018-04-01

We developed the theory of electronic properties of semiconductor quantum rings with the Rashba spin-orbit interaction irradiated by an off-resonant high-frequency electromagnetic field (dressing field). Within the Floquet theory of periodically driven quantum systems, it is demonstrated that the dressing field drastically modifies all electronic characteristics of the rings, including spin-orbit coupling, effective electron mass, and optical response. In particular, the present effect paves the way to controlling the spin polarization of electrons with light in prospective ring-shaped spintronic devices.

Sponge 'tree rings' : new indicators of ocean variability?

International Nuclear Information System (INIS)

Ellwood, M.; Kelly, M.

2003-01-01

Certain marine sponges offer a unique approach to the problem of recording environmental change. These sponges and their spicules grow by putting on concentric layers of silica material on a seasonal basis, rather like tree rings. The concentrations of certain chemicals in the surrounding water, and the growth rate of the sponge itself, are archived in the silica deposited. The information in each layer of silica can be used to deduce environmental conditions on a range of scales; years, decades and centuries. (author). 7 figs

Topological ring currents in the "empty" ring of benzo-annelated perylenes.

Science.gov (United States)

Dickens, Timothy K; Mallion, Roger B

2011-01-27

Cyclic conjugation in benzo-annelated perylenes is examined by means of the topological π-electron ring currents calculated for each of their constituent rings, in a study that is an exact analogy of a recent investigation by Gutman et al. based on energy-effect values for the corresponding rings in each of these structures. "Classical" approaches, such as Kekulé structures, Clar "sextet" formulas, and circuits of conjugation, predict that the central ring in perylene is "empty" and thus contributes negligibly to cyclic conjugation. However, conclusions from the present calculations of topological ring currents agree remarkably with those arising from the earlier study involving energy-effect values in that, contrary to what would be predicted from the classical approaches, rings annelated in an angular fashion relative to the central ring of these perylene structures materially increase the extent of that ring's involvement in cyclic conjugation. It is suggested that such close quantitative agreement between the predictions of these two superficially very different indices (energy effect and topological ring current) might be due to the fact that, ultimately, both depend, albeit in ostensibly quite different ways, only on an adjacency matrix that contains information about the carbon-carbon connectivity of the conjugated system in question.

Vertically coupled double quantum rings at zero magnetic field

OpenAIRE

Malet, Francesc; Barranco, Manuel; Lipparini, Enrico; Pi, Ricardo Mayol Martí; Climente, Juan Ignacio; Planelles, Josep

2006-01-01

Within local-spin-density functional theory, we have investigated the `dissociation' of few-electron circular vertical semiconductor double quantum ring artificial molecules at zero magnetic field as a function of inter-ring distance. In a first step, the molecules are constituted by two identical quantum rings. When the rings are quantum mechanically strongly coupled, the electronic states are substantially delocalized, and the addition energy spectra of the artificial molecule resemble thos...

Polarized particles in storage rings

International Nuclear Information System (INIS)

Derbenev, Ya.S.; Kondratenko, A.M.; Serednyakov, S.I.; Skrinskij, A.N.; Tumajkin, G.M.; Shatunov, Yu.M.

1977-01-01

Experiments with polarized beams on the VEPP-2M and SPEAK storage rings are described. Possible methods of producing polarized particle beams in storage rings as well as method of polarization monitoring are counted. Considered are the processes of radiation polarization of electrons and positrons. It is shown, that to preserve radiation polarization the introduction of regions with a strong sign-variable magnetic field is recommended. Methods of polarization measurement are counted. It is suggested for high energies to use dependence of synchrotron radiation power on transverse polarization of electrons and positrons. Examples of using polarizability of colliding beams in storage rings are presented

Radioactive gold ring dermatitis

International Nuclear Information System (INIS)

Miller, R.A.; Aldrich, J.E.

1990-01-01

A superficial squamous cell carcinoma developed in a woman who wore a radioactive gold ring for more than 30 years. Only part of the ring was radioactive. Radiation dose measurements indicated that the dose to basal skin layer was 2.4 Gy (240 rad) per week. If it is assumed that the woman continually wore her wedding ring for 37 years since purchase, she would have received a maximum dose of approximately 4600 Gy

Discovery Of B Ring Propellers In Cassini UVIS, And ISS

Science.gov (United States)

Sremcevic, Miodrag; Stewart, G. R.; Albers, N.; Esposito, L. W.

2012-10-01

We present evidence for the existence of propellers in Saturn's B ring by combining data from Cassini Ultraviolet Imaging Spectrograph (UVIS) and Imaging Science Subsystem (ISS) experiments. We identify two propeller populations: (1) tens of degrees wide propellers in the dense B ring core, and (2) smaller, more A ring like, propellers populating the inner B ring. The prototype of the first population is an object observed at 18 different epochs between 2005 and 2010. The ubiquitous propeller "S" shape is seen both in UVIS occultations as an optical depth depletion and in ISS as a 40 degrees wide bright stripe in unlit geometries and dark in lit geometries. Combining the available Cassini data we infer that the object is a partial gap embedded in the high optical depth region of the B ring. The gap moves at orbital speed consistent with its radial location. From the radial separation of the propeller wings we estimate that the embedded body, which causes the propeller structure, is about 1.5km in size located at a=112,921km. The UVIS occultations indicate an asymmetric propeller "S" shape. Since the object is located at an edge between high and relatively low optical depth, this asymmetry is most likely a consequence of the strong surface mass density gradient. We estimate that there are possibly dozen up to 100 other propeller objects in Saturn's B ring. The location of the discovered body, at an edge of a dense ringlet within the B ring, suggests a novel mechanism for the up to now illusive B ring irregular large-scale structure of alternating high and low optical depth ringlets. We propose that this B ring irregular structure may have its cause in the presence of many embedded bodies that shepherd the individual B ring ringlets.

Lamb shift of energy levels in quantum rings

International Nuclear Information System (INIS)

Kryuchkyan, G Yu; Kyriienko, O; Shelykh, I A

2015-01-01

We study the vacuum radiative corrections to energy levels of a confined electron in quantum rings. The calculations are provided for the Lamb shift of energy levels in a low-momentum region of virtual photons and for both one-dimensional and two-dimensional quantum rings. We show that contrary to the well known case of a hydrogen atom the value of the Lamb shift increases with the magnetic momentum quantum number m. We also investigate the dependence of the Lamb shift on magnetic flux piercing the ring and demonstrate a presence of magnetic-flux-dependent oscillations. For a one-dimensional ring the value of the shift strongly depends on the radius of the ring. It is small for semiconductor rings but can attain measurable quantities in natural organic ring-shape molecules, such as benzene, cycloalcanes and porphyrins. (paper)

Storage Rings

International Nuclear Information System (INIS)

Fischer, W.

2010-01-01

Storage rings are circular machines that store particle beams at a constant energy. Beams are stored in rings without acceleration for a number of reasons (Tab. 1). Storage rings are used in high-energy, nuclear, atomic, and molecular physics, as well as for experiments in chemistry, material and life sciences. Parameters for storage rings such as particle species, energy, beam intensity, beam size, and store time vary widely depending on the application. The beam must be injected into a storage ring but may not be extracted (Fig. 1). Accelerator rings such as synchrotrons are used as storage rings before and after acceleration. Particles stored in rings include electrons and positrons; muons; protons and anti-protons; neutrons; light and heavy, positive and negative, atomic ions of various charge states; molecular and cluster ions, and neutral polar molecules. Spin polarized beams of electrons, positrons, and protons were stored. The kinetic energy of the stored particles ranges from 10 -6 eV to 3.5 x 10 12 eV (LHC, 7 x 10 12 eV planned), the number of stored particles from one (ESR) to 1015 (ISR). To store beam in rings requires bending (dipoles) and transverse focusing (quadrupoles). Higher order multipoles are used to correct chromatic aberrations, to suppress instabilities, and to compensate for nonlinear field errors of dipoles and quadrupoles. Magnetic multipole functions can be combined in magnets. Beams are stored bunched with radio frequency systems, and unbunched. The magnetic lattice and radio frequency system are designed to ensure the stability of transverse and longitudinal motion. New technologies allow for better storage rings. With strong focusing the beam pipe dimensions became much smaller than previously possible. For a given circumference superconducting magnets make higher energies possible, and superconducting radio frequency systems allow for efficient replenishment of synchrotron radiation losses of large current electron or positron beams

A FODO racetrack ring for nuSTORM: design and optimization

Energy Technology Data Exchange (ETDEWEB)

Liu, A.; Bross, A.; Neuffer, D.

2017-07-01

The goal of nuSTORM is to provide well-defined neutrino beams for precise measurements of neutrino cross-sections and oscillations. The nuSTORM decay ring is a compact racetrack storage ring with a circumference of ~ 480 m that incorporates large aperture (60 cm diameter) magnets. There are many challenges in the design. In order to incorporate the Orbit Combination section (OCS), used for injecting the pion beam into the ring, a dispersion suppressor is needed adjacent to the OCS . Concurrently, in order to maximize the number of useful muon decays, strong bending dipoles are needed in the arcs to minimize the arc length. These dipoles create strong chromatic effects, which need to be corrected by nonlinear sextupole elements in the ring. In this paper, a FODO racetrack ring design and its optimization using sextupolar fields via both a Genetic Algorithm (GA) and a Simulated Annealing (SA) algorithm will be discussed.

Lifetime measurement of ATF damping ring

International Nuclear Information System (INIS)

Okugi, T.; Hayano, H.; Kubo, K.; Naito, T.; Terunuma, N.; Urakawa, J.; Zimmermann, F.

1998-06-01

The purpose of the ATF damping ring is the development of technologies for producing a low emittance beam required in future linear colliders such as JLC. The lifetime of the damping ring is very short (typically a few minutes). It is limited by elastic beam-gas scattering along with a small dynamic aperture, and by single intra-beam scattering (Touschek effect). The Touschek lifetime strongly depends upon the charge density of the beam, especially, the size of the vertical emittance. In this paper, the authors report the results of beam lifetime measurements in the ATF damping ring and the estimation of the vertical emittance from these measurements

The CERN intersecting storage rings and strong interactions at high energies

CERN Document Server

Cocconi, Giuseppe

1973-01-01

The coming into operation of the Intersecting Storage Rings (ISR) at the European Centre of Nuclear Research (CERN), near Geneva, has made it possible in the past two years to study the behaviour of matter at the highest densities ever obtained artificially, hundreds of times greater than the density of matter in nuclei and even in the densest stars. An account is given of some of the results obtained thus far; this is followed by a brief discussion of possible future developments. (17 refs).

Pollution and Climate Effects on Tree-Ring Nitrogen Isotopes

Science.gov (United States)

Savard, M. M.; Bégin, C.; Marion, J.; Smirnoff, A.

2009-04-01

BACKGROUND Monitoring of nitrous oxide concentration only started during the last 30 years in North America, but anthropogenic atmospheric nitrogen has been significantly emitted over the last 150 years. Can geochemical characteristics of tree rings be used to infer past changes in the nitrogen cycle of temperate regions? To address this question we use nitrogen stable isotopes in 125 years-long ring series from beech specimens (Fagus grandifolia) of the Georgian Bay Islands National Park (eastern Ontario), and pine (Pinus strobus) and beech trees of the Arboretum Morgan near Montreal (western Quebec). To evaluate the reliability of the N stable isotopes in wood treated for removal of soluble materials, we tested both tree species from the Montreal area. The reproducibility from tree to tree was excellent for both pine and beech trees, the isotopic trends were strongly concordant, and they were not influenced by the heartwood-sapwood transition zone. The coherence of changes of the isotopic series observed for the two species suggests that their tree-ring N isotopic values can serve as environmental indicator. RESULTS AND INTERPRETATION In Montreal and Georgian Bay, the N isotopes show strong and similar parallel agreement (Gleichlaufigkeit test) with the climatic parameters. So in fact, the short-term isotopic fluctuations correlate directly with summer precipitation and inversely with summer and spring temperature. A long-term decreasing isotope trend in Montreal indicates progressive changes in soil chemistry after 1951. A pedochemical change is also inferred for the Georgian Bay site on the basis of a positive N isotopic trend initiated after 1971. At both sites, the long-term ^15N series correlate with a proxy for NOx emissions (Pearson correlation), and carbon-isotope ring series suggest that the same trees have been impacted by phytotoxic pollutants (Savard et al., 2009a). We propose that the contrasted long-term nitrogen-isotope changes of Montreal and

Ring power balance observing plasma stability constraints

International Nuclear Information System (INIS)

Campbell, R.B.; Logan, B.G.

1982-01-01

Ring power balance is performed for an E-ring stabilized tandem mirror reactor, taking into account constraints imposed by plasma stability. The two most important criteria are the stability of the core interchange and hot electron interchange modes. The former determines the ring thickness, the latter determines the minimum hot electron temperature; both quantities are important for power balance. The combination of the hot electron interchange constraint and the fact that the barrier density is low places the operating point on the synchrotron dominated branch of power balance. The reference case considered here requires a reasonable 34 MW of heating power deposited in the rings. We also have examined the sensitivity of the required ring power on uncertainties in the numerical coefficients of the stability constraints. We have found that the heating power is strongly affected

Propellers in Saturn's rings

Science.gov (United States)

Sremcevic, M.; Stewart, G. R.; Albers, N.; Esposito, L. W.

2013-12-01

Theoretical studies and simulations have demonstrated the effects caused by objects embedded in planetary rings. Even if the objects are too small to be directly observed, each creates a much larger gravitational imprint on the surrounding ring material. These strongly depend on the mass of the object and range from "S" like propeller-shaped structures for about 100m-sized icy bodies to the opening of circumferential gaps as in the case of the embedded moons Pan and Daphnis and their corresponding Encke and Keeler Gaps. Since the beginning of the Cassini mission many of these smaller objects (~data from Cassini Ultraviolet Imaging Spectrograph (UVIS) and Imaging Science Subsystem (ISS) experiments. We show evidence that B ring seems to harbor two distinct populations of propellers: "big" propellers covering tens of degrees in azimuth situated in the densest part of B ring, and "small" propellers in less dense inner B ring that are similar in size and shape to known A ring propellers. The population of "big" propellers is exemplified with a single object which is observed for 5 years of Cassini data. The object is seen as a very elongated bright stripe (40 degrees wide) in unlit Cassini images, and dark stripe in lit geometries. In total we report observing the feature in images at 18 different epochs between 2005 and 2010. In UVIS occultations we observe this feature as an optical depth depletion in 14 out of 93 occultation cuts at corrotating longitudes compatible with imaging data. Combining the available Cassini data we infer that the object is a partial gap located at r=112,921km embedded in the high optical depth region of the B ring. The gap moves at Kepler speed appropriate for its radial location. Radial offsets of the gap locations in UVIS occultations are consistent with an asymmetric propeller shape. The asymmetry of the observed shape is most likely a consequence of the strong surface mass density gradient, as the feature is located at an edge between

Hybridization in the Ensatina Ring Species, Strong selection against hybrids at a hybrid zone in the ensatina ring species complex and its evolutionary implications

Energy Technology Data Exchange (ETDEWEB)

Alexandrino, Joao; Baird, Stuart J.E.; Lawson, Lucinda; Macey, J. Robert; Moritz, Craig; Wake, David B.

2005-04-22

The analysis of interactions between lineages at varying levels of genetic divergence can provide insights into the process of speciation through the accumulation of incompatible mutations. Ring species, and especially the Ensatina eschscholtzii system exemplify this approach. The plethodontid salamanders Ensatina eschscholtzii xanthoptica and Ensatina eschscholtzii platensis hybridize in the Central Sierran foothills of California. We compared the genetic structure across two transects (southern and northern Calaveras Co.), one of which was re-sampled over 20 years, and examined diagnostic molecular markers (eight allozyme loci and mitochondrial DNA) and a diagnostic quantitative trait (color pattern). Key results across all studies were: (i) cline centers for all markers were coincident and the zones were narrow, with width estimates of 730m to 2000m; (ii) cline centers at the northern Calaveras transect were coincident between 1981 and 2001, demonstrating repeatability over 5 generations; (iii) there are very few if any putative F1's, but a relatively high number of backcrossed individuals (57-86 percent) in the central portion of transects; (iv) we found substantial linkage disequilibrium in all three studies and strong heterozygote deficit both in northern Calaveras, in 2001, and southern Calaveras. Both linkage disequilibrium and heterozygote deficit show maximum values near the center of the zones (R and Fis, approx. equal to 0.5). Using estimates of cline width and dispersal, we infer strong selection against hybrids (s* approx. equal to 46-75 percent). This is sufficient to promote accumulation of differences at loci that are neutral or under divergent selection, but would still allow for introgression of adaptive alleles. The evidence for strong, but incomplete isolation across this centrally located contact is consistent with theory suggesting a gradual increase in postzygotic incompatibility between allopatric populations subject to divergent

The Centaur Chariklo and its rings system from stellar occultations in 2017

Science.gov (United States)

Leiva, Rodrigo; Sicardy, Bruno; Camargo, Julio; Ortiz, Jose Luis; Berard, Diane; Desmars, Josselin; Chariklo Occultations Team; Rio Group; Lucky Star Occultation Team; Granada Occultation Team

2017-10-01

A stellar occultation in June 3, 2013 revealed the presence of a dense ring system around the Centaur object (10199) Chariklo (Braga-Ribas et al., Nature 2014). Subsequent analysis of occultation data and long-term photometric variations indicate that Chariklo's body is elongated (Leiva et al. 2017, submitted) and that the main ring exhibits significant longitudinal variations of the radial width (Bérard et al. 2017, in press). We report three multi-chord high-quality stellar occultation by Chariklo on April 9, 2017 and June 22, 2017 from Namibia, and July 23 2017 from South America. The analysis of this new data set is underway, but preliminary results are consistent with triaxial ellipsoidal models. From this analysis we will:-present refined models for the size and shape of Chariklo's main body andevaluate the heights and slopes of its topographic features.-give constraints on the longitudinal width variations of Chariklo's rings andexplore the possibility to obtain the rings apsidal precession rate.Chariklo's shape and topography have strong consequences on the dynamics of the rings through Lindblad-type resonances between mean motion of the ring particles and the spin of the main body, while the rings precession rate gives constraints on the dynamical oblateness of the main body.**Part of the research leading to these results has received funding from the European Research Council under the European Community’s H2020 (2014-2020/ ERC Grant Agreement n 669416 ”LUCKY STAR”).

Spin transitions in semiconductor quantum rings

International Nuclear Information System (INIS)

Baxevanis, Benjamin; Pfannkuche, Daniela

2010-01-01

We adopt the path integral Monte Carlo method to accurately resolve the total spin of the ground state of electrons confined in a quantum ring with different geometries. Using this method, an evaluation of the ground state of three electrons in a ring shows a spin transition to the fully polarized state by increasing the radius and thereby enhancing the Coulomb interaction. The total spin of the ground state is determined by the mutual interplay of confinement and electron-electron interaction. An analysis of the four-electron ring demonstrates that in this case no spin transitions take place. Furthermore, the effect of geometric distortion of the ring on its ground state has been investigated. Elliptically deforming the ring breaks the symmetry of the system and leads to the removal of orbital degeneracy. For strong distortion the splitting between hybridized states is sufficient to overcome the exchange-energy saving associated with a higher spin state. We have found that this effect removes the polarization of three electrons. Even in a four-electron ring the ground state is forced by the distortion to be unpolarized and thus suppressing the Hund's rule ground state.

INJECTION EFFICIENCY IN COMPTON RING NESTOR

Directory of Open Access Journals (Sweden)

P. I. Gladkikh

2017-12-01

Full Text Available NESTOR is the hard X-ray source that is under commissioning at NSC KIPT. NESTOR based on the Compton scattering of laser photons on relativistic electrons. The structure of the facility can be represented as the following components: a linear accelerator, a transport channel, a storage ring, and a laser-optical system. Electrons are stored in the storage ring for energy of 40-200 MeV. Inevitable alignment errors of magnetic elements are strongly effect on the beam dynamics in the storage ring. These errors lead to a shift of the equilibrium orbit relative to the ideal one. Significant shift of the equilibrium orbit could lead to loss of the beam on physical apertures. Transverse sizes of electron and laser beams are only few tens of microns at the interaction point. The shift of electron beam at the interaction point could greatly complicate the operation adjustment of storage ring without sufficient beam position diagnostic system. This article presents the simulation results of the efficiency of electron beam accumulation in the NESTOR storage ring. Also, this article is devoted to electron beam dynamics due to alignment errors of magnetic element in the ring.

Systematic Search for Rings around Kepler Planet Candidates: Constraints on Ring Size and Occurrence Rate

Science.gov (United States)

Aizawa, Masataka; Masuda, Kento; Kawahara, Hajime; Suto, Yasushi

2018-05-01

We perform a systematic search for rings around 168 Kepler planet candidates with sufficient signal-to-noise ratios that are selected from all of the short-cadence data. We fit ringed and ringless models to their light curves and compare the fitting results to search for the signatures of planetary rings. First, we identify 29 tentative systems, for which the ringed models exhibit statistically significant improvement over the ringless models. The light curves of those systems are individually examined, but we are not able to identify any candidate that indicates evidence for rings. In turn, we find several mechanisms of false positives that would produce ringlike signals, and the null detection enables us to place upper limits on the size of the rings. Furthermore, assuming the tidal alignment between axes of the planetary rings and orbits, we conclude that the occurrence rate of rings larger than twice the planetary radius is less than 15%. Even though the majority of our targets are short-period planets, our null detection provides statistical and quantitative constraints on largely uncertain theoretical models of the origin, formation, and evolution of planetary rings.

Dark matter axions and caustic rings

International Nuclear Information System (INIS)

Sikivie, P.

1997-01-01

This report contains discussions on the following topics: the strong CP problem; dark matter axions; the cavity detector of galactic halo axions; and caustic rings in the density distribution of cold dark matter halos

Fano resonance and persistent current of a quantum ring

International Nuclear Information System (INIS)

Xiong Yongjian; Liang Xianting

2004-01-01

We investigate electron transport and persistent current of a quantum ring weakly attached to current leads. Assuming there is direct coupling (weakly or strongly) between two leads, electrons can transmit by the inter-lead coupling or tunneling through the quantum ring. The interference between the two paths yields asymmetric Fano line shape for conductance. In presence of interior magnetic flux, there is persistent current along the ring with narrow resonance peaks. The positions of the conductance resonances and the persistent current peaks correspond to the quasibound levels of the closed ring. This feature is helpful to determine the energy spectrum of the quantum ring. Our results show that the proposed setup provides a tunable Fano system

Radar imaging of Saturn's rings

Science.gov (United States)

Nicholson, Philip D.; French, Richard G.; Campbell, Donald B.; Margot, Jean-Luc; Nolan, Michael C.; Black, Gregory J.; Salo, Heikki J.

2005-09-01

We present delay-Doppler images of Saturn's rings based on radar observations made at Arecibo Observatory between 1999 and 2003, at a wavelength of 12.6 cm and at ring opening angles of 20.1°⩽|B|⩽26.7°. The average radar cross-section of the A ring is ˜77% relative to that of the B ring, while a stringent upper limit of 3% is placed on the cross-section of the C ring and 9% on that of the Cassini Division. These results are consistent with those obtained by Ostro et al. [1982, Icarus 49, 367-381] from radar observations at |B|=21.4°, but provide higher resolution maps of the rings' reflectivity profile. The average cross-section of the A and B rings, normalized by their projected unblocked area, is found to have decreased from 1.25±0.31 to 0.74±0.19 as the rings have opened up, while the circular polarization ratio has increased from 0.64±0.06 to 0.77±0.06. The steep decrease in cross-section is at variance with previous radar measurements [Ostro et al., 1980, Icarus 41, 381-388], and neither this nor the polarization variations are easily understood within the framework of either classical, many-particle-thick or monolayer ring models. One possible explanation involves vertical size segregation in the rings, whereby observations at larger elevation angles which see deeper into the rings preferentially see the larger particles concentrated near the rings' mid-plane. These larger particles may be less reflective and/or rougher and thus more depolarizing than the smaller ones. Images from all four years show a strong m=2 azimuthal asymmetry in the reflectivity of the A ring, with an amplitude of ±20% and minima at longitudes of 67±4° and 247±4° from the sub-Earth point. We attribute the asymmetry to the presence of gravitational wakes in the A ring as invoked by Colombo et al. [1976, Nature 264, 344-345] to explain the similar asymmetry long seen at optical wavelengths. A simple radiative transfer model suggests that the enhancement of the azimuthal

Tree ring imprints of long-term changes in climate in western ...

Indian Academy of Sciences (India)

Prakash

2009-10-26

Oct 26, 2009 ... tree-ring sampling sites poses difficulty in calibrating tree-ring data against climate data especially precipitation for its strong spatial .... drained soils are its primary ecological requirement. The .... rapid radiation loss at night.

Novel Fiber-Optic Ring Acoustic Emission Sensor.

Science.gov (United States)

Wei, Peng; Han, Xiaole; Xia, Dong; Liu, Taolin; Lang, Hao

2018-01-13

Acoustic emission technology has been applied to many fields for many years. However, the conventional piezoelectric acoustic emission sensors cannot be used in extreme environments, such as those with heavy electromagnetic interference, high pressure, or strong corrosion. In this paper, a novel fiber-optic ring acoustic emission sensor is proposed. The sensor exhibits high sensitivity, anti-electromagnetic interference, and corrosion resistance. First, the principle of a novel fiber-optic ring sensor is introduced. Different from piezoelectric and other fiber acoustic emission sensors, this novel sensor includes both a sensing skeleton and a sensing fiber. Second, a heterodyne interferometric demodulating method is presented. In addition, a fiber-optic ring sensor acoustic emission system is built based on this method. Finally, fiber-optic ring acoustic emission experiments are performed. The novel fiber-optic ring sensor is glued onto the surface of an aluminum plate. The 150 kHz standard continuous sinusoidal signals and broken lead signals are successfully detected by the novel fiber-optic ring acoustic emission sensor. In addition, comparison to the piezoelectric acoustic emission sensor is performed, which shows the availability and reliability of the novel fiber-optic ring acoustic emission sensor. In the future, this novel fiber-optic ring acoustic emission sensor will provide a new route to acoustic emission detection in harsh environments.

The influence of summertime fog and overcast clouds on the growth of a coastal Californian pine: a tree-ring study.

Science.gov (United States)

Williams, A Park; Still, Christopher J; Fischer, Douglas T; Leavitt, Steven W

2008-06-01

The coast of California is home to numerous rare, endemic conifers and other plants that are limited in distribution by drought sensitivity and the summer-dry climate that prevails across most of the state. Ecologists have long assumed that some coastal plant populations survived the early Pleistocene transition to a warmer and drier environment because they benefit from frequent fog and stratus clouds that provide water and shade during the rainless summer. One such population is that of Torrey pine (Pinus torreyana ssp. Insularis) on Santa Rosa Island in Channel Islands National Park. Here we report that the tree-ring width record from this population indicates strong growth sensitivities to summer fog drip and cloud shading. We quantified the effects of summer cloud cover by comparing ring-width indices to coastal airport cloud-frequency records (1944-2004). For the first time observed, summertime cloud frequency correlated positively with ring-width indices, regardless of whether the effect of rainfall was first removed from the ring-width record. The effect of ground-level fog was strongest in July early mornings (03:00 PST, R(2) = 0.262, P clouds high enough to provide shade but not fog water was also strongest in July, but climbed steadily throughout the day before becoming strongest in late afternoon (16:00-18:00 PST, R(2) = 0.148, P clouds is strongly affected by pre-summer rainfall. A change in the height and/or timing of coastal cloud formation with climate change would likely affect this and other populations of California's coastal vegetation.

<strong>Improved indicators and monitoring of pesticide usestrong>

DEFF Research Database (Denmark)

Sørensen, Peter Borgen; Kjær, Christian; Kudsk, Per

, and directly inside, the agricultural areas so this excludes the risk for contamination of groundwater and the human risk. Elements from existing indicators are combined in a way that can make optimal use of the available data, where the level of complexity is adjusted to fit the conditions of uncertainty......  The goal for the new improved indicator, PestNaB (Pesticiders NaturBelastning), was to develop a valid indicator reflecting the potential risk for nature due to application of pesticides and based on available data set for Danish conditions. The focus is on risk in relation the nature close to...... to predict one year as more/less risky as an other year or to predict one geographically area are more risky than another area. It is also possible to compare different means of risk reduction in order to find the most effective one, or to find the cheapest way to reduce risk....

The rings of Uranus

Science.gov (United States)

Elliot, J. L.; Dunham, E.; Mink, D.

1977-01-01

A description is given of the observation of five brief occultations of the star SAO 158687 which occurred both before and after its occultation by Uranus on March 10, 1977. The events were observed with a three-channel occultation photometer, attached to a 91-cm telescope. The observations indicate that at least five rings encircle the planet Uranus. Possible reasons for the narrowness of the Uranus rings are discussed.

Quantum correlations in a bipartite multiqubit spin ring system

International Nuclear Information System (INIS)

Doronin, S I; Fel’dman, E B; Kuznetsova, E I

2015-01-01

We consider a spin ring with an arbitrary number of spins on the ring and one spin in its center in a strong external magnetic field. The spins on the ring are connected by the secular dipole–dipole interactions and interact with the central spin through the Heisenberg zz-interaction. We show that the quantum discord, describing quantum correlations between the ring and the central spin, can be obtained analytically for an arbitrary number of the spins in the high-temperature approximation. We demonstrate the evolution of quantum correlations at different numbers of the spins. The contributions of longitudinal and transversal spin interactions to the quantum discord are discussed. (paper)

SXLS storage ring design

International Nuclear Information System (INIS)

Anon.

1991-01-01

X-ray lithography has emerged as a strong candidate to meet the demands of ever finer linewidths on integrated circuits, particularly for linewidths less than .25 microns. Proximity printing X-ray lithography makes use of soft X-rays to shadow print an image of a mask onto a semiconductor wafer to produce integrated circuits. To generate the required X-rays in sufficient quantities to make commercial production viable, electron storage rings have been proposed as the soft X-ray sources. Existing storage rings have been used to do the initial development work and the success of these efforts has led the lithographers to request that new rings be constructed that are dedicated to X-ray lithography. As a result of a series of workshops held at BNL [10.3] which were attended by both semiconductor and accelerator scientists, the following set of zeroth order specifications' on the light and electron beam of a storage ring for X-ray lithography were developed: critical wavelength of light: λ c = 6 to 10 angstroms, white light power: P = 0.25 to 2.5 watts/mrad, horizontal collection angle per port: θ = 10 to 50 mrad, electron beam sizes: σ x ∼ σ y y ' < 1 mrad

Compressible Vortex Ring

Science.gov (United States)

Elavarasan, Ramasamy; Arakeri, Jayawant; Krothapalli, Anjaneyulu

1999-11-01

The interaction of a high-speed vortex ring with a shock wave is one of the fundamental issues as it is a source of sound in supersonic jets. The complex flow field induced by the vortex alters the propagation of the shock wave greatly. In order to understand the process, a compressible vortex ring is studied in detail using Particle Image Velocimetry (PIV) and shadowgraphic techniques. The high-speed vortex ring is generated from a shock tube and the shock wave, which precedes the vortex, is reflected back by a plate and made to interact with the vortex. The shadowgraph images indicate that the reflected shock front is influenced by the non-uniform flow induced by the vortex and is decelerated while passing through the vortex. It appears that after the interaction the shock is "split" into two. The PIV measurements provided clear picture about the evolution of the vortex at different time interval. The centerline velocity traces show the maximum velocity to be around 350 m/s. The velocity field, unlike in incompressible rings, contains contributions from both the shock and the vortex ring. The velocity distribution across the vortex core, core diameter and circulation are also calculated from the PIV data.

Novel Fiber-Optic Ring Acoustic Emission Sensor

Directory of Open Access Journals (Sweden)

Peng Wei

2018-01-01

Full Text Available Acoustic emission technology has been applied to many fields for many years. However, the conventional piezoelectric acoustic emission sensors cannot be used in extreme environments, such as those with heavy electromagnetic interference, high pressure, or strong corrosion. In this paper, a novel fiber-optic ring acoustic emission sensor is proposed. The sensor exhibits high sensitivity, anti-electromagnetic interference, and corrosion resistance. First, the principle of a novel fiber-optic ring sensor is introduced. Different from piezoelectric and other fiber acoustic emission sensors, this novel sensor includes both a sensing skeleton and a sensing fiber. Second, a heterodyne interferometric demodulating method is presented. In addition, a fiber-optic ring sensor acoustic emission system is built based on this method. Finally, fiber-optic ring acoustic emission experiments are performed. The novel fiber-optic ring sensor is glued onto the surface of an aluminum plate. The 150 kHz standard continuous sinusoidal signals and broken lead signals are successfully detected by the novel fiber-optic ring acoustic emission sensor. In addition, comparison to the piezoelectric acoustic emission sensor is performed, which shows the availability and reliability of the novel fiber-optic ring acoustic emission sensor. In the future, this novel fiber-optic ring acoustic emission sensor will provide a new route to acoustic emission detection in harsh environments.

Energy spectra of quantum rings.

Science.gov (United States)

Fuhrer, A; Lüscher, S; Ihn, T; Heinzel, T; Ensslin, K; Wegscheider, W; Bichler, M

2001-10-25

Quantum mechanical experiments in ring geometries have long fascinated physicists. Open rings connected to leads, for example, allow the observation of the Aharonov-Bohm effect, one of the best examples of quantum mechanical phase coherence. The phase coherence of electrons travelling through a quantum dot embedded in one arm of an open ring has also been demonstrated. The energy spectra of closed rings have only recently been studied by optical spectroscopy. The prediction that they allow persistent current has been explored in various experiments. Here we report magnetotransport experiments on closed rings in the Coulomb blockade regime. Our experiments show that a microscopic understanding of energy levels, so far limited to few-electron quantum dots, can be extended to a many-electron system. A semiclassical interpretation of our results indicates that electron motion in the rings is governed by regular rather than chaotic motion, an unexplored regime in many-electron quantum dots. This opens a way to experiments where even more complex structures can be investigated at a quantum mechanical level.

Missing Rings in Pinus halepensis - The Missing Link to Relate the Tree-Ring Record to Extreme Climatic Events.

Science.gov (United States)

Novak, Klemen; de Luis, Martin; Saz, Miguel A; Longares, Luis A; Serrano-Notivoli, Roberto; Raventós, Josep; Čufar, Katarina; Gričar, Jožica; Di Filippo, Alfredo; Piovesan, Gianluca; Rathgeber, Cyrille B K; Papadopoulos, Andreas; Smith, Kevin T

2016-01-01

Climate predictions for the Mediterranean Basin include increased temperatures, decreased precipitation, and increased frequency of extreme climatic events (ECE). These conditions are associated with decreased tree growth and increased vulnerability to pests and diseases. The anatomy of tree rings responds to these environmental conditions. Quantitatively, the width of a tree ring is largely determined by the rate and duration of cell division by the vascular cambium. In the Mediterranean climate, this division may occur throughout almost the entire year. Alternatively, cell division may cease during relatively cool and dry winters, only to resume in the same calendar year with milder temperatures and increased availability of water. Under particularly adverse conditions, no xylem may be produced in parts of the stem, resulting in a missing ring (MR). A dendrochronological network of Pinus halepensis was used to determine the relationship of MR to ECE. The network consisted of 113 sites, 1,509 trees, 2,593 cores, and 225,428 tree rings throughout the distribution range of the species. A total of 4,150 MR were identified. Binomial logistic regression analysis determined that MR frequency increased with increased cambial age. Spatial analysis indicated that the geographic areas of south-eastern Spain and northern Algeria contained the greatest frequency of MR. Dendroclimatic regression analysis indicated a non-linear relationship of MR to total monthly precipitation and mean temperature. MR are strongly associated with the combination of monthly mean temperature from previous October till current February and total precipitation from previous September till current May. They are likely to occur with total precipitation lower than 50 mm and temperatures higher than 5°C. This conclusion is global and can be applied to every site across the distribution area. Rather than simply being a complication for dendrochronology, MR formation is a fundamental response of trees

Evidence for Break-Up of Clumps in Dynamically Stirred Regions of Saturn's Rings

Science.gov (United States)

Colwell, J. E.; Sega, D. N.; Jerousek, R. G.; Cooney, J. H.; Esposito, L. W.

2017-12-01

Stellar occultations of Saturn's rings observed by the Cassini Ultraviolet Imaging Spectrograph (UVIS) High Speed Photometer (HSP) record stellar brightness seen through the rings as photon counts that are described by Poisson counting statistics in the absence of intervening ring material. The variance in the data increases above counting statistics due to the discrete sizes of the ring particles, with larger particles leading to a larger variance at a given optical depth. We take advantage of the high spatial resolution and multiple viewing geometries of the UVIS occultations to study variations in particle size near and within strongly perturbed regions of Saturn's A ring, in particular the strong first order Lindblad resonances with Janus and the Mimas 5:3 Lindblad resonance and inner vertical resonance. The variance shows changes in the area-weighted particle size between peaks and troughs in the density waves as well as an overall decrease in particle size in the broad "halo" regions that bracket the strong Janus Lindblad resonances in the A ring. In addition we see a decrease in particle size at the location of the Mimas 5:3 bending wave wavetrain itself, and an increase in optical depth at the location of the wave when viewed from high elevation angles out of the ring plane. Taken together, these observations suggest that clumps of particles, perhaps the ubiquitous A ring self-gravity wakes, are disaggregated in the bending wave, even though standard bending wave theory does not predict enhanced collision velocities. We also examine the skewness, a higher order moment of the occultation data, that is diagnostic of asymmetries in the particle size distribution. We use Monte Carlo simulations of occultations to match the first three moments of the data (the signal mean, or equivalently the optical depth, the variance, and the skewness) to illustrate differences in ring particle size in these perturbed regions.

The Case for Massive and Ancient Rings of Saturn

Science.gov (United States)

Esposito, Larry W.

2016-04-01

Analysis of Voyager and Pioneer 11 results give a mass for Saturn's rings, M = 5 x 10-8 Msat. This is about the mass of Saturn's small moon Mimas. This has been interpreted as a lower limit to the ring mass (Esposito et al 1983), since the thickest parts of the rings were not penetrated by the stellar occultstion, and this calculation assumes an unvarying particle size throughout the rings. Because the rings are constantly bombarded by micrometeroids, their current composition of nearly pure water ice implies such low mass rings must have formed recently. The case is par-ticularly strong for Saturn's A ring, where the data are the best, implying the A ring is less than 10% of the age of the Saturn (Esposito 1986). Cassini results com-pound this problem. UVIS spectra are consistent with either young rings or rings about 10x as massive as the Voyager estimate (Elliott and Esposito (2011). CDA confirms the impacting mass flux is similar to that as-sumed for the pollution calculations (Kempf etal 2015). VIMS analysis of density wave signatures in the B ring gives a value of about 1/3 the Voyager value (Hedmann etal 2016). This VIMS result implies the rings are even younger! The problem is that young rings are very unlikely to be formed recently, meaning that we live in a very special epoch, following some unlikely recent origin… like disruption of a medium sized moon or capture of the fragments of a disrupted comet. This paradox (Charnoz etal 2009) is unre-solved. Alternative interpretations: To take the VIMS results at face value, Saturn's low mass rings must be very young. The optically thick B ring must be made of small, porous or fractal particles. This is hard to understand, since the particles are continually colliding every few hours and temporary aggregates will stir the collision velocities to higher values. An alternative is that we accept the higher mass interpretation of the Pioneer 11 results (Esposito etal 2008) using the granola bar model of Colwell

Injection, compression and stability of intense ion-rings

International Nuclear Information System (INIS)

Sudan, R.N.

1975-01-01

Recent advances in pulsed high power ion beam technology make possible the creation of intense ion-rings with strong self-magnetic fields by single pulse injection. Such ion rings have several uses in controlled fusion e.g., to produce a min parallel B parallel magnetic geometry with a mirror ratio much higher than is possible with external conductors. For even stronger ion rings a min parallel B parallel with closed lines of force (ASTRON type) can be created. For this purpose, since the ion energies required are much higher than are available from high power sources, magnetic compression can be utilized to increase the ion energy. The success of this scheme depends critically on the stability of the ion ring. The low frequency perturbations of the ring-plasma system is examined by means of a generalization of the energy principle which established sufficient conditions for stability. The high-frequency micro-instabilities and their nonlinear consequences are discussed in terms of conventional techniques

Ring Confidential Transactions

Directory of Open Access Journals (Sweden)

Shen Noether

2016-12-01

Full Text Available This article introduces a method of hiding transaction amounts in the strongly decentralized anonymous cryptocurrency Monero. Similar to Bitcoin, Monero is a cryptocurrency which is distributed through a proof-of-work “mining” process having no central party or trusted setup. The original Monero protocol was based on CryptoNote, which uses ring signatures and one-time keys to hide the destination and origin of transactions. Recently the technique of using a commitment scheme to hide the amount of a transaction has been discussed and implemented by Bitcoin Core developer Gregory Maxwell. In this article, a new type of ring signature, A Multilayered Linkable Spontaneous Anonymous Group signature is described which allows one to include a Pedersen Commitment in a ring signature. This construction results in a digital currency with hidden amounts, origins and destinations of transactions with reasonable efficiency and verifiable, trustless coin generation. The author would like to note that early drafts of this were publicized in the Monero Community and on the #bitcoin-wizards IRC channel. Blockchain hashed drafts are available showing that this work was started in Summer 2015, and completed in early October 2015. An eprint is also available at http://eprint.iacr.org/2015/1098.

Sphagnum moss disperses spores with vortex rings.

Science.gov (United States)

Whitaker, Dwight L; Edwards, Joan

2010-07-23

Sphagnum spores, which have low terminal velocities, are carried by turbulent wind currents to establish colonies many kilometers away. However, spores that are easily kept aloft are also rapidly decelerated in still air; thus, dispersal range depends strongly on release height. Vascular plants grow tall to lift spores into sufficient wind currents for dispersal, but nonvascular plants such as Sphagnum cannot grow sufficiently high. High-speed videos show that exploding capsules of Sphagnum generate vortex rings to efficiently carry spores high enough to be dispersed by turbulent air currents. Spores launched ballistically at similar speeds through still air would travel a few millimeters and not easily reach turbulent air. Vortex rings are used by animals; here, we report vortex rings generated by plants.

Trends of perfluorochemicals in Greenland ringed seals and polar bears: indications of shifts to decreasing trends.

Science.gov (United States)

Rigét, Frank; Bossi, Rossana; Sonne, Christian; Vorkamp, Katrin; Dietz, Rune

2013-11-01

Time-series of perfluorinated alkylated substances (PFASs) in East Greenland polar bears and East and West Greenland ringed seals were updated in order to deduce whether a response to the major reduction in perfluoroalkyl production in the early 2000s had occurred. Previous studies had documented an exponential increase of perfluorooctane sulphonate (PFOS) in liver tissue from both species. In the present study, PFOS was still the far most dominant compound constituting 92% (West Greenland ringed seals), 88% (East Greenland ringed seals) and 85% (East Greenland polar bears). The PFOS concentrations increased up to 2006 with doubling times of approximately 6 years for the ringed seal populations and 14 years in case of polar bears. Since then a rapid decrease has occurred with clearing half-lives of approximately 1, 2 and 4 years, respectively. In polar bears perfluorohexane sulphonate (PFHxS) and perfluorooctane sulphonamide (PFOSA) also showed decreasing trends in recent years as do perfluorodecanoic acid (PFDA) and perfluoroundecanoic acid (PFUnA). For the West Greenland ringed seal population perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), PFDA and PFUnA peaked in the mid 2000s, whereas PFNA, PFDA and PFUnA in the East Greenland population have been stable or increasing in recent years. The peak of PFASs in Greenland ringed seals and polar bears occurred at a later time than in Canadian seals and polar bears and considerably later than observed in seal species from more southern latitudes. We suggest that this could be explained by the distance to emission hot-spots and differences in long-range transport to the Arctic. Copyright © 2013 Elsevier Ltd. All rights reserved.

Transverse Periodic Beam Loading Effects in a Storage Ring

International Nuclear Information System (INIS)

Thompson, J.R.; Byrd, J.M.

2009-01-01

Uneven beam fill patterns in storage rings, such as gaps in the fill patterns, leads to periodic, or transient loading of the modes of the RF cavities. We show that an analogous effect can occur in the loading of a dipole cavity mode when the beam passes off the electrical center of the cavity mode. Although this effect is small, it results in a variation of the transverse offset of the beam along the bunch train. For ultralow emittance beams, such as optimized third generation light sources and damping rings, this effect results in a larger projected emittance of the beam compared with the single bunch emittance. The effect is particularly strong for the case when a strong dipole mode has been purposely added to the ring, such as a deflecting, or 'crab' cavity. We derive an approximate analytic solution for the variation of the beam-induced deflecting voltage along the bunch train.

Ring Theory

CERN Document Server

Jara, Pascual; Torrecillas, Blas

1988-01-01

The papers in this proceedings volume are selected research papers in different areas of ring theory, including graded rings, differential operator rings, K-theory of noetherian rings, torsion theory, regular rings, cohomology of algebras, local cohomology of noncommutative rings. The book will be important for mathematicians active in research in ring theory.

GaSb quantum rings in GaAs/Al{sub x}Ga{sub 1−x}As quantum wells

Energy Technology Data Exchange (ETDEWEB)

Hodgson, P. D., E-mail: pdhodgson@hotmail.co.uk; Hayne, M.; Robson, A. J.; Zhuang, Q. D. [Department of Physics, Lancaster University, Lancaster LA1 4YB (United Kingdom); Danos, L. [Department of Chemistry, Lancaster University, Lancaster LA1 4YB (United Kingdom)

2016-01-28

We report the results of continuous and time-resolved photoluminescence measurements on type-II GaSb quantum rings embedded within GaAs/Al{sub x}Ga{sub 1−x}As quantum wells. A range of samples were grown with different well widths, compensation-doping concentrations within the wells, and number of quantum-ring layers. We find that each of these variants have no discernible effect on the radiative recombination, except for the very narrowest (5 nm) quantum well. In contrast, single-particle numerical simulations of the sample predict changes in photoluminescence energy of up to 200 meV. This remarkable difference is explained by the strong Coulomb binding of electrons to rings that are multiply charged with holes. The resilience of the emission to compensation doping indicates that multiple hole occupancy of the quantum rings is required for efficient carrier recombination, regardless of whether these holes come from doping or excitation.

Evidence of Accretion in Saturn's F Ring (Invited)

Science.gov (United States)

Agnor, C. B.; Buerle, K.; Murray, C. D.; Evans, M. W.; Cooper, N. J.; Williams, G. W.

2010-12-01

Lying slightly outside the classical Roche radius and being strongly perturbed by the adjacent moons Prometheus and Pandora, Saturn's F ring represents a unique astrophysical laboratory for examining the processes of mass accretion and moonlet formation. Recent images from the Cassini spacecraft reveal optically thick clumps, capable of casting shadows, and associated structures in regions of the F ring following close passage by Prometheus. Here we examine the accretion environment of the F ring and Prometheus' role in moonlet formation and evolution. Using the observed structures adjacent to these clumps and dynamical arguments we estimate the masses of these clumps and find them comparable to that of ~10-20-km contiguous moonlets. Further, we show that Prometheus' perturbations on the F ring create regions of enhanced density and low relative velocity that may accelerate the accretion of clumps and moonlets.

Trichomonas vaginalis clinical isolates: cytoadherence and adherence to polystyrene, intrauterine device, and vaginal ring.

Science.gov (United States)

Dos Santos, Odelta; Rigo, Graziela Vargas; Macedo, Alexandre José; Tasca, Tiana

2017-12-01

The parasitism by Trichomonas vaginalis is complex and in part is mediated by cytoadherence accomplished via five surface proteins named adhesins and a glycoconjugate called lipophosphoglycan (TvLPG). In this study, we evaluated the ability of T. vaginalis isolates to adhere to cells, plastic (polystyrene microplates), intrauterine device (IUD), and vaginal ring. Of 32 T. vaginalis isolates, 4 (12.5%) were strong adherent. The T. vaginalis isolates TV-LACM6 and TV-LACM14 (strong polystyrene-adherent) were also able to adhere to IUD and vaginal ring. Following chemical treatments, results demonstrated that the T. vaginalis components, lipophosphoglycan, cytoskeletal proteins, and surface molecules, were involved in both adherence to polystyrene and cytoadherence. The gene expression level from four adhesion proteins was highest in trophozoites adhered to cells than trophozoites adhered to the abiotic surface (polystyrene microplate). Our data indicate the major involvement of TvLPG in adherence to polystyrene, and that adhesins are important for cytoadherence. Furthermore, to our knowledge, this is the first report showing the T. vaginalis adherence to contraceptive devices, reaffirming its importance as pathogen among women in reproductive age.

Missing Rings in Pinus halepensis – The Missing Link to Relate the Tree-Ring Record to Extreme Climatic Events

Science.gov (United States)

Novak, Klemen; de Luis, Martin; Saz, Miguel A.; Longares, Luis A.; Serrano-Notivoli, Roberto; Raventós, Josep; Čufar, Katarina; Gričar, Jožica; Di Filippo, Alfredo; Piovesan, Gianluca; Rathgeber, Cyrille B. K.; Papadopoulos, Andreas; Smith, Kevin T.

2016-01-01

Climate predictions for the Mediterranean Basin include increased temperatures, decreased precipitation, and increased frequency of extreme climatic events (ECE). These conditions are associated with decreased tree growth and increased vulnerability to pests and diseases. The anatomy of tree rings responds to these environmental conditions. Quantitatively, the width of a tree ring is largely determined by the rate and duration of cell division by the vascular cambium. In the Mediterranean climate, this division may occur throughout almost the entire year. Alternatively, cell division may cease during relatively cool and dry winters, only to resume in the same calendar year with milder temperatures and increased availability of water. Under particularly adverse conditions, no xylem may be produced in parts of the stem, resulting in a missing ring (MR). A dendrochronological network of Pinus halepensis was used to determine the relationship of MR to ECE. The network consisted of 113 sites, 1,509 trees, 2,593 cores, and 225,428 tree rings throughout the distribution range of the species. A total of 4,150 MR were identified. Binomial logistic regression analysis determined that MR frequency increased with increased cambial age. Spatial analysis indicated that the geographic areas of south-eastern Spain and northern Algeria contained the greatest frequency of MR. Dendroclimatic regression analysis indicated a non-linear relationship of MR to total monthly precipitation and mean temperature. MR are strongly associated with the combination of monthly mean temperature from previous October till current February and total precipitation from previous September till current May. They are likely to occur with total precipitation lower than 50 mm and temperatures higher than 5°C. This conclusion is global and can be applied to every site across the distribution area. Rather than simply being a complication for dendrochronology, MR formation is a fundamental response of trees

Missing rings in Pinus halepensis – the missing link to relate the tree-ring record to extreme climatic events

Directory of Open Access Journals (Sweden)

Klemen eNovak

2016-05-01

Full Text Available Climate predictions for the Mediterranean Basin include increased temperatures, decreased precipitation, and increased frequency of extreme climatic events (ECE. These conditions are associated with decreased growth of trees and their increased vulnerability to pests and diseases. The anatomy of tree rings is responsive to these environmental conditions. Quantitatively, the width of a tree ring is largely determined by the rate and duration of cell division by the vascular cambium. In the Mediterranean climate, cambial cell division may occur throughout almost the entire year. Alternatively, cell division may stop during relatively cool and dry winters, only to resume in the same year with milder temperatures and increased availability of water. Under particularly adverse conditions, no xylem may be produced in parts of the stem, resulting in a missing ring (MR, which can link tree-ring anatomy to the occurrence of extreme events. A dendrochronological network of Pinus halepensis, a widespread tree species in the Mediterranean basin, was used to determine the relationship of MR to ECE. The network consisted of 113 sites throughout its distribution range. Binomial logistic regression analysis of 2595 MR series determined that MR increased in frequency with increased cambial age. Spatial analysis indicated that the geographic areas of southeastern Spain and northern Algeria contained the greatest frequency of MR. Further regression analysis indicated that the relationship of MR to total monthly precipitation and mean temperature was non-linear. In this first determination of climatic influences on MR, the formation of MR was most strongly associated with the combination of monthly mean temperature above 10°C from previous October till current February and total precipitation below 50 mm from previous September till current May. This conclusion is global and can be applied to every site across the distribution area. Rather than simply being a

Impact of imitation processes on the effectiveness of ring vaccination.

Science.gov (United States)

Wells, Chad R; Tchuenche, Jean M; Meyers, Lauren Ancel; Galvani, Alison P; Bauch, Chris T

2011-11-01

Ring vaccination can be a highly effective control strategy for an emerging disease or in the final phase of disease eradication, as witnessed in the eradication of smallpox. However, the impact of behavioural dynamics on the effectiveness of ring vaccination has not been explored in mathematical models. Here, we analyze a series of stochastic models of voluntary ring vaccination. Contacts of an index case base vaccinating decisions on their own individual payoffs to vaccinate or not vaccinate, and they can also imitate the behaviour of other contacts of the index case. We find that including imitation changes the probability of containment through ring vaccination considerably. Imitation can cause a strong majority of contacts to choose vaccination in some cases, or to choose non-vaccination in other cases-even when the equivalent solution under perfectly rational (non-imitative) behaviour yields mixed choices. Moreover, imitation processes can result in very different outcomes in different stochastic realizations sampled from the same parameter distributions, by magnifying moderate tendencies toward one behaviour or the other: in some realizations, imitation causes a strong majority of contacts not to vaccinate, while in others, imitation promotes vaccination and reduces the number of secondary infections. Hence, the effectiveness of ring vaccination can depend significantly and unpredictably on imitation processes. Therefore, our results suggest that risk communication efforts should be initiated early in an outbreak when ring vaccination is to be applied, especially among subpopulations that are heavily influenced by peer opinions.

Successful betatron acceleration of kiloampere electron rings in RECE-Christa

International Nuclear Information System (INIS)

Taggart, D.P.; Parker, M.R.; Hopman, H.J.; Jayakumar, R.; Fleischmann, H.H.

1984-01-01

This paper reports on betatron acceleration experiments using the space-charge-neutralized electron rings in the RECE-Christa device. Magnetic probe and x-ray-absorption measurements indicate that electron ring currents of up to 2 kA were accelerated to 3.3 +- 0.3 MeV without indication of instabilities. A similar neutralization and acceleration method also appears applicable to electron rings generated in B/sub theta/-free configurations

Injection envelope matching in storage rings

International Nuclear Information System (INIS)

Minty, M.G.; Spence, W.L.

1995-05-01

The shape and size of the transverse phase space injected into a storage ring can be deduced from turn-by-turn measurements of the transient behavior of the beam envelope in the ring. Envelope oscillations at 2 x the β-tron frequency indicate the presence of a β-mismatch, while envelope oscillations at the β-tron frequency are the signature of a dispersion function mismatch. Experiments in injection optimization using synchrotron radiation imaging of the beam and a fast-gated camera at the SLC damping rings are reported

Bacterial biomass in warm-core Gulf Stream ring 82-B: mesoscale distributions, temporal changes and production

Science.gov (United States)

Ducklow, Hugh

1986-11-01

The distribution of bacterioplankton biomass and productivity in warm-core Gulf Stream ring 82-B generally corresponded to the physical and dynamical structure of the ring. Mean cell volumes were uniform for 4 months, but were larger by a factor of 2-3 in the high velocity (frontal) region (HVR) near the ring edge. As a result of this gradient and higher abundances, water column biomass and production were highest in the front, which appeared to be a local maximum in those properties. In this regard bacterioplankton contrasted strongly to phytoplankton, which exhibited strong local maxima at the center of the ring in June. In April when the water column inside the ring was isothermal to 450 m, bacterial biomass and production were low and uniform to 250 and 50 m, respectively. Bacterioplankton responded dramatically to the vernal restratification of the ring. In June when the surface layer was characterized by a strong pycnocline at 10-40 m, bacterial biomass and production often had strong subsurface maxima, and were 3 and 5 times greater than in April, respectively. Abundance exceeded 1.5 × 10 9 cells l -1 at ring center and exceeded 3 × 10 9 l -1 in the HVR. Turnover rates for the euphotic zone bacterioplankton as a whole were 0.24 d -1 in April, 0.56 d -1 in June, and 0.27 d -1 in August at ring center. Bacterial production averaged 12% of hourly primary production (range 1-32%), suggesting that bacteria control a significant and sometimes large portion of the carbon cycling in the euphotic zone. These data suggest that warm-core rings are sites of enhanced variability of bacterioplankton properties in the open sea. Furthermore, the data strongly support recent work showing that frontal zones are sites of locally enhanced bacterial biomass and production. In the ring system as a whole, the euphotic zone bacterioplankton biomass and production were comparable to and occasionally greater than the biomass and production of the >64 μm zooplankton, especially in

Experience with a high-brightness storage ring: the NSLS 750 MeV vuv ring

International Nuclear Information System (INIS)

Galayda, J.

1984-01-01

The NSLS vuv ring is the first implementation of the proposals of R. Chasman and G.K. Green for a synchrotron radiation source with enhanced brightness: its lattice is a series of achromatic bends with two zero-gradient dipoles each, giving small damped emittance; and these bends are connected by straight sections with zero dispersion to accommodate wigglers and undulators without degrading the radiation damping properties of the ring. The virtues of the Chasman-Green lattice, its small betatron and synchrotron emittances, may be understood with some generality; e.g. the electron γm 0 c 2 energy and the number of achromatic bends M sets a lower limit on the betatron emittance of e/sub x/ > 7.7 x 10 -13 γ 2 /M meter-radians. There is strong interest in extrapolation of this type of lattice to 6 GeV and to 32 achromatic bends. The subject of this report is the progress toward achieving performance in the vuv ring limited by the radiation damping parameters optimized in its design. 14 refs., 4 figs., 1 tab

Detecting long-term growth trends using tree rings: a critical evaluation of methods.

Science.gov (United States)

Peters, Richard L; Groenendijk, Peter; Vlam, Mart; Zuidema, Pieter A

2015-05-01

Tree-ring analysis is often used to assess long-term trends in tree growth. A variety of growth-trend detection methods (GDMs) exist to disentangle age/size trends in growth from long-term growth changes. However, these detrending methods strongly differ in approach, with possible implications for their output. Here, we critically evaluate the consistency, sensitivity, reliability and accuracy of four most widely used GDMs: conservative detrending (CD) applies mathematical functions to correct for decreasing ring widths with age; basal area correction (BAC) transforms diameter into basal area growth; regional curve standardization (RCS) detrends individual tree-ring series using average age/size trends; and size class isolation (SCI) calculates growth trends within separate size classes. First, we evaluated whether these GDMs produce consistent results applied to an empirical tree-ring data set of Melia azedarach, a tropical tree species from Thailand. Three GDMs yielded similar results - a growth decline over time - but the widely used CD method did not detect any change. Second, we assessed the sensitivity (probability of correct growth-trend detection), reliability (100% minus probability of detecting false trends) and accuracy (whether the strength of imposed trends is correctly detected) of these GDMs, by applying them to simulated growth trajectories with different imposed trends: no trend, strong trends (-6% and +6% change per decade) and weak trends (-2%, +2%). All methods except CD, showed high sensitivity, reliability and accuracy to detect strong imposed trends. However, these were considerably lower in the weak or no-trend scenarios. BAC showed good sensitivity and accuracy, but low reliability, indicating uncertainty of trend detection using this method. Our study reveals that the choice of GDM influences results of growth-trend studies. We recommend applying multiple methods when analysing trends and encourage performing sensitivity and reliability

Small slot waveguide rings for on-chip quantum optical circuits.

Science.gov (United States)

Rotenberg, Nir; Türschmann, Pierre; Haakh, Harald R; Martin-Cano, Diego; Götzinger, Stephan; Sandoghdar, Vahid

2017-03-06

Nanophotonic interfaces between single emitters and light promise to enable new quantum optical technologies. Here, we use a combination of finite element simulations and analytic quantum theory to investigate the interaction of various quantum emitters with slot-waveguide rings. We predict that for rings with radii as small as 1.44 μm, with a Q-factor of 27,900, near-unity emitter-waveguide coupling efficiencies and emission enhancements on the order of 1300 can be achieved. By tuning the ring geometry or introducing losses, we show that realistic emitter-ring systems can be made to be either weakly or strongly coupled, so that we can observe Rabi oscillations in the decay dynamics even for micron-sized rings. Moreover, we demonstrate that slot waveguide rings can be used to directionally couple emission, again with near-unity efficiency. Our results pave the way for integrated solid-state quantum circuits involving various emitters.

OBSERVATION OF STRONG - STRONG AND OTHER BEAM - BEAM EFFECTS IN RHIC

International Nuclear Information System (INIS)

FISCHER, W.; BLASKIEWICZ, M.; BRENNAN, J.M.; CAMERON, P.; CONNOLLY, R.; MONTAG, C.; PEGGS, S.; PILAT, F.; PTITSYN, V.; TEPIKIAN, S.; TRBOJEVIC, D.; VAN ZEIJTS, J.

2003-01-01

RHIC is currently the only hadron collider in which strong-strong beam-beam effects can be seen. For the first time, coherent beam-beam modes were observed in a bunched beam hadron collider. Other beam-beam effects in RHIC were observed in operation and in dedicated experiments with gold ions, deuterons and protons. Observations include measurements of beam-beam induced tune shifts, lifetime and emittance growth measurements with and without beam-beam interaction, and background rates as a function of tunes. During ramps unequal radio frequencies in the two rings cause the crossing points to move longitudinally. Thus bunches experience beam-beam interactions only in intervals and the tunes are modulated. In this article we summarize the most important beam-beam observations made so far

Report of the eRHIC Ring-Ring Working Group

Energy Technology Data Exchange (ETDEWEB)

Aschenauer, E. C. [Brookhaven National Lab. (BNL), Upton, NY (United States); Berg, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Blaskiewicz, M. [Brookhaven National Lab. (BNL), Upton, NY (United States); Brennan, M. [Brookhaven National Lab. (BNL), Upton, NY (United States); Fedotov, A. [Brookhaven National Lab. (BNL), Upton, NY (United States); Fischer, W. [Brookhaven National Lab. (BNL), Upton, NY (United States); Litvinenko, V. [Brookhaven National Lab. (BNL), Upton, NY (United States); Montag, C. [Brookhaven National Lab. (BNL), Upton, NY (United States); Palmer, R. [Brookhaven National Lab. (BNL), Upton, NY (United States); Parker, B. [Brookhaven National Lab. (BNL), Upton, NY (United States); Peggs, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Ptitsyn, V. [Brookhaven National Lab. (BNL), Upton, NY (United States); Ranjbar, V. [Brookhaven National Lab. (BNL), Upton, NY (United States); Tepikian, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Trbojevic, D. [Brookhaven National Lab. (BNL), Upton, NY (United States); Willeke, F. [Brookhaven National Lab. (BNL), Upton, NY (United States)

2015-10-13

This report evaluates the ring-ring option for eRHIC as a lower risk alternative to the linac-ring option. The reduced risk goes along with a reduced initial luminosity performance. However, a luminosity upgrade path is kept open. This upgrade path consists of two branches, with the ultimate upgrade being either a ring-ring or a linac-ring scheme. The linac-ring upgrade could be almost identical to the proposed linac-ring scheme, which is based on an ERL in the RHIC tunnel. This linac-ring version has been studied in great detail over the past ten years, and its significant risks are known. On the other hand, no detailed work on an ultimate performance ring-ring scenario has been performed yet, other than the development of a consistent parameter set. Pursuing the ring-ring upgrade path introduces high risks and requires significant design work that is beyond the scope of this report.

"Ring" in the solo child singing voice.

Science.gov (United States)

Howard, David M; Williams, Jenevora; Herbst, Christian T

2014-03-01

Listeners often describe the voices of solo child singers as being "pure" or "clear"; these terms would suggest that the voice is not only pleasant but also clearly audible. The audibility or clarity could be attributed to the presence of high-frequency partials in the sound: a "brightness" or "ring." This article aims to investigate spectrally the acoustic nature of this ring phenomenon in children's solo voices, and in particular, relating it to their "nonring" production. Additionally, this is set in the context of establishing to what extent, if any, the spectral characteristics of ring are shared with those of the singer's formant cluster associated with professional adult opera singers in the 2.5-3.5kHz region. A group of child solo singers, acknowledged as outstanding by a singing teacher who specializes in teaching professional child singers, were recorded in a major UK concert hall performing Come unto him, all ye that labour, from the aria He shall feed his flock from The Messiah by GF Handel. Their singing was accompanied by a recording of a piano played through in-ear headphones. Sound pressure recordings were made from well within the critical distance in the hall. The singers were observed to produce notes with and without ring, and these recordings were analyzed in the frequency domain to investigate their spectra. The results indicate that there is evidence to suggest that ring in child solo singers is carried in two areas of the output spectrum: first in the singer's formant cluster region, centered around 4kHz, which is more than 1000Hz higher than what is observed in adults; and second in the region around 7.5-11kHz where a significant strengthening of harmonic presence is observed. A perceptual test has been carried out demonstrating that 94% of 62 listeners label a synthesized version of the calculated overall average ring spectrum for all subjects as having ring when compared with a synthesized version of the calculated overall average nonring

AN N-BODY INTEGRATOR FOR GRAVITATING PLANETARY RINGS, AND THE OUTER EDGE OF SATURN'S B RING

International Nuclear Information System (INIS)

Hahn, Joseph M.; Spitale, Joseph N.

2013-01-01

A new symplectic N-body integrator is introduced, one designed to calculate the global 360° evolution of a self-gravitating planetary ring that is in orbit about an oblate planet. This freely available code is called epi i nt, and it is distinct from other such codes in its use of streamlines to calculate the effects of ring self-gravity. The great advantage of this approach is that the perturbing forces arise from smooth wires of ring matter rather than discreet particles, so there is very little gravitational scattering and so only a modest number of particles are needed to simulate, say, the scalloped edge of a resonantly confined ring or the propagation of spiral density waves. The code is applied to the outer edge of Saturn's B ring, and a comparison of Cassini measurements of the ring's forced response to simulations of Mimas's resonant perturbations reveals that the B ring's surface density at its outer edge is σ 0 = 195 ± 60 g cm –2 , which, if the same everywhere across the ring, would mean that the B ring's mass is about 90% of Mimas's mass. Cassini observations show that the B ring-edge has several free normal modes, which are long-lived disturbances of the ring-edge that are not driven by any known satellite resonances. Although the mechanism that excites or sustains these normal modes is unknown, we can plant such a disturbance at a simulated ring's edge and find that these modes persist without any damping for more than ∼10 5 orbits or ∼100 yr despite the simulated ring's viscosity ν s = 100 cm 2 s –1 . These simulations also indicate that impulsive disturbances at a ring can excite long-lived normal modes, which suggests that an impact in the recent past by perhaps a cloud of cometary debris might have excited these disturbances, which are quite common to many of Saturn's sharp-edged rings

Moving ring reactor 'Karin-1'

International Nuclear Information System (INIS)

1983-12-01

The conceptual design of a moving ring reactor ''Karin-1'' has been carried out to advance fusion system design, to clarify the research and development problems, and to decide their priority. In order to attain these objectives, a D-T reactor with tritium breeding blanket is designed, a commercial reactor with net power output of 500 MWe is designed, the compatibility of plasma physics with fusion engineering is demonstrated, and some other guideline is indicated. A moving ring reactor is composed mainly of three parts. In the first formation section, a plasma ring is formed and heated up to ignition temperature. The plasma ring of compact torus is transported from the formation section through the next burning section to generate fusion power. Then the plasma ring moves into the last recovery section, and the energy and particles of the plasma ring are recovered. The outline of a moving ring reactor ''Karin-1'' is described. As a candidate material for the first wall, SiC was adopted to reduce the MHD effect and to minimize the interaction with neutrons and charged particles. The thin metal lining was applied to the SiC surface to solve the problem of the compatibility with lithium blanket. Plasma physics, the engineering aspect and the items of research and development are described. (Kako, I.)

The opposition effect in Saturn's main rings as seen by Cassini ISS: 4. Correlations of the surge morphology with surface albedos and VIMS spectral properties

Science.gov (United States)

Déau, Estelle; Dones, Luke; Mishchenko, Michael I.; West, Robert A.; Helfenstein, Paul; Hedman, Matt M.; Porco, Carolyn C.

2018-05-01

In this paper, we continue our analysis of the saturnian ring opposition effect seen by Cassini ISS. The ring opposition effect is a peak in the rings' reflectivity caused as the directions from a spot on the rings to the observer and to the light source, respectively, converge toward zero degrees. So far, the exact origin of the ring's opposition effect is still a matter of debate. In our previous work (Déau, et al., 2013, Icarus, 226, 591-603), we compared the opposition effect morphology with the rings' optical depth and found that only the slope of the linear part of the rings' phase curves was strongly correlated with the optical depth. We interpreted this as an indication of the predominant role of interparticle shadowing at moderate phase angles (α ∼ 10-40o). More recently (Déau, 2015, Icarus, 253, 311-345), we showed that interparticle shadowing cannot explain the behavior at low phase angles (α Journal Letters, 711, L71-L74). We find that the opposition surge morphology is strongly correlated with the water ice band depth and the regolith albedo. We interpret this finding as an indication that coherent backscattering plays a role in affecting both the water ice band depths and the opposition surge at low phase angles (α < 1o). As the regolith albedo and spectral properties are related to the grain size, porosity, roughness, and composition, we try to assess which of these regolith properties are preponderant in coherent backscattering. Our study is able to narrow down the parameter space of these properties, whose values allow a good match between the angular width predicted by models of coherent backscattering and the width of the observed peak.

Seco-B-Ring Steroidal Dienynes with Aromatic D Ring: Design, Synthesis and Biological Evaluation

Directory of Open Access Journals (Sweden)

Marcin Szybinski

2017-10-01

Full Text Available Continuing our structure-activity studies on the vitamin D analogs with the altered intercyclic seco-B-ring fragment, we designed compounds possessing dienyne system conjugated with the benzene D ring. Analysis of the literature data and the docking experiments seemed to indicate that the target compounds could mimic the ligands with a good affinity to the vitamin D receptor (VDR. Multi-step synthesis of the C/D-ring building block of the tetralone structure was achieved and its enol triflate was coupled with the known A-ring fragments, possessing conjugated enyne moiety, using Sonogashira protocol. The structures of the final products were confirmed by NMR, UV and mass spectroscopy. Their binding affinities for the full-length human VDR were determined and it was established that compound substituted at C-2 with exomethylene group showed significant binding to the receptor. This analog was also able to induce monocytic differentiation of HL-60 cells.

From the Icy Satellites to Small Moons and Rings: Spectral Indicators by Cassini-VIMS Unveil Compositional Trends in the Saturnian System

Science.gov (United States)

Filacchione, G.; Capaccioni, F.; Ciarniello, M.; Nicholson, P. D.; Clark, R. N.; Cuzzi, J. N.; Buratti, B. B.; Cruikshank, D. P.; Brown, R. H.

2017-01-01

Despite water ice being the most abundant species on Saturn satellites' surfaces and ring particles, remarkable spectral differences in the 0.35-5.0 μm range are observed among these objects. Here we report about the results of a comprehensive analysis of more than 3000 disk-integrated observations of regular satellites and small moons acquired by VIMS aboard Cassini mission between 2004 and 2016. These observations, taken from very different illumination and viewing geometries, allow us to classify satellites' and rings' compositions by means of spectral indicators, e.g. 350-550 nm - 550-950 nm spectral slopes and water ice band parameters [1,2,3]. Spectral classification is further supported by indirect retrieval of temperature by means of the 3.6 μm I/F peak wavelength [4,5]. The comparison with syntethic spectra modeled by means of Hapke's theory point to different compositional classes where water ice, amorphous carbon, tholins and CO2 ice in different quantities and mixing modalities are the principal endmembers [3, 6]. When compared to satellites, rings appear much more red at visible wavelengths and show more intense 1.5-2.0 μm band depths [7]. Our analysis shows that spectral classes are detected among the principal satellites with Enceladus and Tethys the ones with stronger water ice band depths and more neutral spectral slopes while Rhea evidences less intense band depths and more red visible spectra. Even more intense reddening in the 0.55-0.95 μm range is observed on Iapetus leading hemisphere [8] and on Hyperion [9]. With an intermediate reddening, the minor moons seems to be the spectral link between the principal satellites and main rings [10]: Prometheus and Pandora appear similar to Cassini Division ring particles. Epimetheus shows more intense water ice bands than Janus. Epimetheus' visible colors are similar to water ice rich moons while Janus is more similar to C ring particles. Finally, Dione and Tethys lagrangian satellites show a very

Chemical Sensors Based on Optical Ring Resonators

Science.gov (United States)

Homer, Margie; Manfreda, Allison; Mansour, Kamjou; Lin, Ying; Ksendzov, Alexander

2005-01-01

Chemical sensors based on optical ring resonators are undergoing development. A ring resonator according to this concept is a closed-circuit dielectric optical waveguide. The outermost layer of this waveguide, analogous to the optical cladding layer on an optical fiber, is a made of a polymer that (1) has an index of refraction lower than that of the waveguide core and (2) absorbs chemicals from the surrounding air. The index of refraction of the polymer changes with the concentration of absorbed chemical( s). The resonator is designed to operate with relatively strong evanescent-wave coupling between the outer polymer layer and the electromagnetic field propagating along the waveguide core. By virtue of this coupling, the chemically induced change in index of refraction of the polymer causes a measurable shift in the resonance peaks of the ring. In a prototype that has been used to demonstrate the feasibility of this sensor concept, the ring resonator is a dielectric optical waveguide laid out along a closed path resembling a racetrack (see Figure 1). The prototype was fabricated on a silicon substrate by use of standard techniques of thermal oxidation, chemical vapor deposition, photolithography, etching, and spin coating. The prototype resonator waveguide features an inner cladding of SiO2, a core of SixNy, and a chemical-sensing outer cladding of ethyl cellulose. In addition to the ring Chemical sensors based on optical ring resonators are undergoing development. A ring resonator according to this concept is a closed-circuit dielectric optical waveguide. The outermost layer of this waveguide, analogous to the optical cladding layer on an optical fiber, is a made of a polymer that (1) has an index of refraction lower than that of the waveguide core and (2) absorbs chemicals from the surrounding air. The index of refraction of the polymer changes with the concentration of absorbed chemical( s). The resonator is designed to operate with relatively strong

A dusty road connecting Saturn and its rings - preliminary results from Cassini Cosmic Dust Analyser during the Grand Finale Mission

Science.gov (United States)

Hsu, S.; Burton, M. E.; Horanyi, M.; Kempf, S.; Khawaja, N.; Moragas-Klostermeyer, G.; Postberg, F.; Schirdenwahn, D.; Seiss, M.; Schmidt, J.; Spahn, F.; Srama, R.

2017-12-01

The Cosmic Dust Analyzer observations during the Cassini Grand Finale Orbits were designed for the in situ characterization of Saturn's ring composition and to study their interaction with the host planet. It is found that the gap between the inner most D ring and Saturn is almost free of larger, micron-sized dust grains but rich in nanodust particles (radius smaller than 100 nm) that only become detectable by CDA because of the high spacecraft speed of 30 km/s through this region. Regarding the grain composition, while the majority of CDA mass spectra recorded during this phase are too faint to be individually calibrated, two types of mass spectra have been identified - water ice and silicates. These two types of grains were detected at different locations with respect to the ring plane, indicating that there are compositional differences across the rings. As for the dynamics, the observations confirm the transport of charged nanodust from the main rings along magnetic field lines to the planet, as previously proposed. The agreement between the simulated density profile and the observation strongly suggests nanodust as a pathway of ring-planet interaction associated with both exogenous (e.g., impactor ejecta) and endogenous (ionospheric plasma charging) processes. CDA measurements do not indicate significant temporal variation during the the Grand Finale orbits. The measured flux corresponds to a mass transport of < 0.1 kg/sec from the main rings to Saturn in the form of nanodust, with most of the deposition occurring near the equator.

A retrospective study of the indications and outcomes of capsular tension ring insertion during cataract surgery at a tertiary teaching hospital

Directory of Open Access Journals (Sweden)

Wang BZ

2013-03-01

Full Text Available Bob Z Wang, Elsie Chan, Rasik B Vajpayee The Royal Victorian Eye and Ear Hospital, East Melbourne, Victoria, Australia; Centre for Eye Research Australia, University of Melbourne, East Melbourne, Victoria, Australia Background: The purpose was to determine preoperative indications, intraoperative procedures, and outcomes of capsular tension ring (CTR insertion during cataract surgery. Methods: A review of all patients undergoing cataract surgery with insertion of a CTR between July 2000 and June 2010 was conducted at The Royal Victorian Eye and Ear Hospital, a large tertiary teaching hospital in Victoria, Australia. Information relating to each patient's demographic details, preoperative assessment, surgical procedure, and postoperative assessment were obtained. Results: Eighty-four eyes of 82 patients were included in this study. The main indications for CTR insertion were previous trauma, pseudoexfoliation syndrome, and mature cataracts. Twenty-one eyes (25.0% did not have any obvious preoperative indication. A posterior capsule tear was the most common intraoperative complication (3.6%. An intraocular lens was successfully implanted in the bag in 72 eyes (85.7%. Postoperatively, the most common complications were a decentered intraocular lens (8.3% and persistent corneal edema (6.0%. Overall, 61 eyes (72.6% had better postoperative visual acuity compared with preoperative acuity, with 67 patients (79.8% achieving vision of 20/40 or better. Conclusion: For the majority of cases, CTR use in complex cataract surgeries is associated with improved postoperative outcomes. CTR implantation is most commonly required in patients with known risk factors for zonular instability. Keywords: capsular tension ring, cataract extraction, indications, outcomes

A silicone elastomer vaginal ring for HIV prevention containing two microbicides with different mechanisms of action.

Science.gov (United States)

Fetherston, Susan M; Boyd, Peter; McCoy, Clare F; McBride, Marcella C; Edwards, Karen-Leigh; Ampofo, Stephen; Malcolm, R Karl

2013-02-14

Vaginal rings are currently being developed for the long-term (at least 30 days) continuous delivery of microbicides against human immunodeficiency virus (HIV). Research to date has mostly focused on devices containing a single antiretroviral compound, exemplified by the 25mg dapivirine ring currently being evaluated in a Phase III clinical study. However, there is a strong clinical rationale for combining antiretrovirals with different mechanisms of action in a bid to increase breadth of protection and limit the emergence of resistant strains. Here we report the development of a combination antiretroviral silicone elastomer matrix-type vaginal ring for simultaneous controlled release of dapivirine, a non-nucleoside reverse transcriptase inhibitor, and maraviroc, a CCR5-targeted HIV-1 entry inhibitor. Vaginal rings loaded with 25mg dapivirine and various quantities of maraviroc (50-400mg) were manufactured and in vitro release assessed. The 25mg dapivirine and 100mg maraviroc formulation was selected for further study. A 24-month pharmaceutical stability evaluation was conducted, indicating good product stability in terms of in vitro release, content assay, mechanical properties and related substances. This combination ring product has now progressed to Phase I clinical testing. Copyright © 2012 Elsevier B.V. All rights reserved.

ASSOCIATIVE RINGS SOLVED AS LIE RINGS

Directory of Open Access Journals (Sweden)

M. B. Smirnov

2011-01-01

Full Text Available The paper has proved that an associative ring which is solvable of a n- class as a Lie ring has a nilpotent ideal of the nilpotent class not more than 3×10n–2  and a corresponding quotient ring satisfies an identity [[x1, x2, [x3, x4

Possible origin of Saturn's newly discovered outer ring

International Nuclear Information System (INIS)

Moehlmann, D.

1986-01-01

Within a planetogonic model the self-gravitationally caused formation of pre-planetary and pre-satellite rings from an earlier thin disk is reported. The theoretically derived orbital radii of these rings are compared with the orbital levels in the planetary system and the satellite systems of Jupiter, Saturn and Uranus. From this comparison it is concluded that at the radial position of Saturn's newly discovered outer ring an early pre-satellite ring of more or less evolved satellites could have existed. These satellites should have been disturbed in their evolution by the gravitation of the neighbouring massive satellite Titan. The comparison also may indicate similarities between the asteroidal belt and the newly discovered outer ring of Saturn

Relating tree growth to rainfall in Bolivian rain forests: a test for six species using tree ring analysis.

Science.gov (United States)

Brienen, Roel J W; Zuidema, Pieter A

2005-11-01

Many tropical regions show one distinct dry season. Often, this seasonality induces cambial dormancy of trees, particularly if these belong to deciduous species. This will often lead to the formation of annual rings. The aim of this study was to determine whether tree species in the Bolivian Amazon region form annual rings and to study the influence of the total amount and seasonal distribution of rainfall on diameter growth. Ring widths were measured on stem discs of a total of 154 trees belonging to six rain forest species. By correlating ring width and monthly rainfall data we proved the annual character of the tree rings for four of our study species. For two other species the annual character was proved by counting rings on trees of known age and by radiocarbon dating. The results of the climate-growth analysis show a positive relationship between tree growth and rainfall in certain periods of the year, indicating that rainfall plays a major role in tree growth. Three species showed a strong relationship with rainfall at the beginning of the rainy season, while one species is most sensitive to the rainfall at the end of the previous growing season. These results clearly demonstrate that tree ring analysis can be successfully applied in the tropics and that it is a promising method for various research disciplines.

The impact of exospheric neutral dynamics on ring current decay

Science.gov (United States)

Ilie, R.; Liemohn, M. W.; Skoug, R. M.; Funsten, H. O.; Gruntman, M.; Bailey, J. J.; Toth, G.

2015-12-01

The geocorona plays an important role in the energy budget of the Earth's inner magnetosphere since charge exchange of energetic ions with exospheric neutrals makes the exosphere act as an energy sink for ring current particles. Long-term ring current decay following a magnetic storm is mainly due to these electron transfer reactions, leading to the formation energetic neutral atoms (ENAs) that leave the ring current system on ballistic trajectories. The number of ENAs emitted from a given region of space depends on several factors, such as the energy and species of the energetic ion population in that region and the density of the neutral gas with which the ions undergo charge exchange. However, the density and structure of the exosphere are strongly dependent on changes in atmospheric temperature and density as well as charge exchange with the ions of plasmaspheric origin, which depletes the geocorona (by having a neutral removed from the system). Moreover, the radiation pressure exerted by solar far-ultraviolet photons pushes the geocoronal hydrogen away from the Earth in an anti-sunward direction to form a tail of neutral hydrogen. TWINS ENA images provide a direct measurement of these ENA losses and therefore insight into the dynamics of the ring current decay through interactions with the geocorona. We assess the influence of geocoronal neutrals on ring current formation and decay by analysis of the predicted ENA emissions using 6 different geocoronal models and simulations from the HEIDI ring current model during storm time. Comparison with TWINS ENA images shows that the location of the peak ENA enhancements is highly dependent on the distribution of geocoronal hydrogen density. We show that the neutral dynamics has a strong influence on the time evolution of the ring current populations as well as on the formation of energetic neutral atoms.

RING STAR FORMATION RATES IN BARRED AND NONBARRED GALAXIES

International Nuclear Information System (INIS)

Grouchy, R. D.; Buta, R. J.; Salo, H.; Laurikainen, E.

2010-01-01

Nonbarred ringed galaxies are relatively normal galaxies showing bright rings of star formation in spite of lacking a strong bar. This morphology is interesting because it is generally accepted that a typical galactic disk ring forms when material collects near a resonance, set up by the pattern speed of a bar or bar-like perturbation. Our goal in this paper is to examine whether the star formation properties of rings are related to the strength of a bar or, in the absence of a bar, to the non-axisymmetric gravity potential in general. For this purpose, we obtained Hα emission line images and calculated the line fluxes and star formation rates (SFRs) for 16 nonbarred SA galaxies and four weakly barred SAB galaxies with rings. For comparison, we combine our new observations with a re-analysis of previously published data on five SA, seven SAB, and 15 SB galaxies with rings, three of which are duplicates from our sample. With these data, we examine what role a bar may play in the star formation process in rings. Compared to barred ringed galaxies, we find that the inner ring SFRs and Hα+[N II] equivalent widths in nonbarred ringed galaxies show a similar range and trend with absolute blue magnitude, revised Hubble type, and other parameters. On the whole, the star formation properties of inner rings, excluding the distribution of H II regions, are independent of the ring shapes and the bar strength in our small samples. We confirm that the deprojected axis ratios of inner rings correlate with maximum relative gravitational force Q g ; however, if we consider all rings, a better correlation is found when a local bar forcing at the radius of the ring, Q r , is used. Individual cases are described and other correlations are discussed. By studying the physical properties of these galaxies, we hope to gain a better understanding of their placement in the scheme of the Hubble sequence and how they formed rings without the driving force of a bar.

Mapping Ring Particle Cooling across Saturn's Rings with Cassini CIRS

Science.gov (United States)

Brooks, Shawn M.; Spilker, L. J.; Edgington, S. G.; Pilorz, S. H.; Deau, E.

2010-10-01

Previous studies have shown that the rings' thermal inertia, a measure of their response to changes in the thermal environment, varies from ring to ring. Thermal inertia can provide insight into the physical structure of Saturn's ring particles and their regoliths. Low thermal inertia and quick temperature responses are suggestive of ring particles that have more porous or fluffy regoliths or that are riddled with cracks. Solid, coherent particles can be expected to have higher thermal inertias (Ferrari et al. 2005). Cassini's Composite Infrared Spectrometer has recorded millions of spectra of Saturn's rings since its arrival at Saturn in 2004 (personal communication, M. Segura). CIRS records far infrared radiation between 10 and 600 cm-1 (16.7 and 1000 µm) at focal plane 1 (FP1), which has a field of view of 3.9 mrad. Thermal emission from Saturn's rings peaks in this wavelength range. FP1 spectra can be used to infer ring temperatures. By tracking how ring temperatures vary, we can determine the thermal inertia of the rings. In this work we focus on CIRS observations of the shadowed portion of Saturn's rings. The thermal budget of the rings is dominated by the solar radiation absorbed by its constituent particles. When ring particles enter Saturn's shadow this source of energy is abruptly cut off. As a result, ring particles cool as they traverse Saturn's shadow. From these shadow observations we can create cooling curves at specific locations across the rings. We will show that the rings' cooling curves and thus their thermal inertia vary not only from ring to ring, but by location within the individual rings. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. Copyright 2010 California Institute of Technology. Government sponsorship acknowledged.

Breakaway frictions of dynamic O-rings in mechanical seals

Science.gov (United States)

Lai, Tom; Kay, Peter

1993-05-01

Breakaway friction of a dynamic O-ring affects the mechanical seal's response to large axial shaft movement and face wear. However, little data exist to help designers. Therefore, a test rig was developed to measure breakaway friction. The research quantitatively shows the effects of lubrication with silicone grease and a change of surface finish. By using the Taguchi statistical experimental design method, the significance of test parameters was evaluated with a minimum number of tests. It was found that fluid pressure, dwell time, and O-ring percentage squeeze affect O-ring breakaway friction more than the O-ring cross sectional diameter and axial sliding speed within the range of values tested. The authors showed that breakaway friction increased linearly with pressure. However, O-rings made of different materials had significantly different increase rates, even if they had nominally the same durometer hardness. Breakaway friction also increased with logarithm of dwell time. Again, the increase rate depended strongly on the specific O-ring material tested. These observations led the authors to believe that the typical approach of generalizing data based on generic polymer type and durometer was inappropriate.

Localized persistent spin currents in defect-free quasiperiodic rings with Aharonov–Casher effect

International Nuclear Information System (INIS)

Qiu, R.Z.; Chen, C.H.; Cheng, Y.H.; Hsueh, W.J.

2015-01-01

We propose strongly localized persistent spin current in one-dimensional defect-free quasiperiodic Thue–Morse rings with Aharonov–Casher effect. The results show that the characteristics of these localized persistent currents depend not only on the radius filling factor, but also on the strength of the spin–orbit interaction. The maximum persistent spin currents in systems always appear in the ring near the middle position of the system array whether or not the Thue–Morse rings array is symmetrical. The magnitude of the persistent currents is proportional to the sharpness of the resonance peak, which is dependent on the bandwidth of the allowed band in the band structure. The maximum persistent spin currents also increase exponentially as the generation order of the system increases. - Highlights: • Strongly localized persistent spin current in quasiperiodic AC rings is proposed. • Localized persistent spin currents are much larger than those produced by traditional mesoscopic rings. • Characteristics of the localized persistent currents depend on the radius filling factor and SOI strength. • The maximum persistent current increases exponentially with the system order. • The magnitude of the persistent currents is related to the sharpness of the resonance

Size filtering effect in vertical stacks of In(Ga)As/GaAs self-assembled quantum rings

International Nuclear Information System (INIS)

Ouerghui, W.; Melliti, A.; Maaref, M.A.; Martinez-Pastor, J.; Gomis, J.; Granados, D.; Garcia, J.M.

2006-01-01

We present a systematic study of closely In(Ga)As/InAs quantum rings (QRs) grown by molecular beam epitaxy (MBE). Photoluminescence (PL) experiments show a strong filtering effect in the ring being stacked and simultaneous linewidth narrowing for the appropriate layer thickness (thinner thickness). If the spacer thickness is further reduced, a strong coupling between the nanostructures is produced and the signal shifts to low energy

Dynamics of rings around elongated bodies

Science.gov (United States)

Sicardy, Bruno; Leiva, Rodrigo; Ortiz, Jose Luis; Santos Sanz, Pablo; Renner, Stefan; El Moutamid, Maryame; Berard, Diane; Desmars, Josselin; Meza, Erick; Rossi, Gustavo; Braga-Ribas, Felipe; Camargo, Julio; Vieira-Martins, Roberto; Morales, Nicolas; Duffard, Rene; Colas, Francois; Maquet, Lucie; Bouley, Sylvain; Bath, Karl-Ludwig; Beisker, Wolfgang; Dauverge, Jean-Luc; Kretlow, Mike; Chariklo Occultations Team; Haumea Occultation Team

2017-10-01

Dense and narrow rings are encountered around small bodies like the Centaur object Chariklo, and possibly Chiron. The rings and central bodies can be studied in great details thanks to stellar occultations, which accuracies at the km-level. Here we present new results from three high-quality occultations by Chariklo observed in 2017. They provide new insights on the ring geometry and Chariklo's shape. Data are currently being analyzed, but preliminary results are consistent with a triaxial model for Chariklo, with semi-axes a>b>c, where (a-b) may reach values as large as 10-15 km, depending on the model.Such large values induce a strong coupling between the body and an initial collisional debris disk from which the rings emerged. This coupling stems from Lindblad resonances between the ring particle mean motion and Chariklo's spin rate. We find that the resonances clear the corotation zone (estimated to lie at about 215 km from Chariklo's center) in very short time scales (centuries) and pushes the material well beyond the 3/2 resonance - that lies at an estimated radius of 280 km, thus consistent with the radius of Chariklo's main ring C1R, 390 km.Other cases will be examined in view of multi-chord stellar occultations by Trans-Neptunian Objects successfully observed in 2017, as they provide constraints for the presence of material around these bodies. Results and dynamical implications will be presented.Part of this work has received funding from the European Research Council under the European Community's H2020 2014-2020 ERC grant Agreement n°669416 "Lucky Star"

Formation Number Of Laminar Vortex Rings. Numerical Simulations

International Nuclear Information System (INIS)

Rosenfeld, M.; Rambod, E.; Gharib, M.

1998-01-01

The formation time scale of axisymmetric vortex rings is studied numerically for relatively long discharge times. Experimental findings on the existence and universality of a formation time scale, referred to as the formation number, are confirmed. The formation number is indicative of the time a vortex ring acquires its maximal circulation. For vortex rings generated by impulsive motion of a piston, the formation number was found experimentally to be approximately 4. Numerical extension of the experimental study to thick shear layers indicates that the scaled circulation of the pinched-off vortex is relatively insensitive of the details of the formation process, such as the velocity program, velocity profile or vortex generator geometry. In contrast, the formation number does depend on the velocity profile

Ion effects in the SLC electron damping ring under exceptionally poor vacuum conditions

International Nuclear Information System (INIS)

Zimmermann, F.; Krejcik, P.; Minty, M.; Pritzkau, D.; Raubenheimer, T.; Ross, M.; Woodley, M.

1997-10-01

In 1996, due to a catastrophic kicker chamber failure in the SLC electron damping ring, the ring vacuum system was contamianted for several months. During this time, the vertical emittance of the beam extracted from the ring was increased by a large factor (4--20). The emittance slowly decreased as the vacuum pressure gradually improved. At the same time, an intermittent vertical instability was observed. Both the emittance blow-up and the instability behavior depended strongly on beam current, ring pressure, number of bunches in the ring (1 or 2), duty cycle, store time and betatron tunes. In this report, the authors describe the observations, and compare them with predictions from classical ion-trapping and ion-instability theories

Tritium concentrations in tree ring cellulose

International Nuclear Information System (INIS)

Kaji, Toshio; Momoshima, Noriyuki; Takashima, Yoshimasa.

1989-01-01

Measurements of tritium (tissue bound tritium; TBT) concentration in tree rings are presented and discussed. Such measurement is expected to provide a useful means of estimating the tritium level in the environment in the past. The concentration of tritium bound in the tissue (TBT) in a tree ring considered to reflect the environmental tritium level in the area at the time of the formation of the ring, while the concentration of tritium in the free water in the tissue represents the current environmental tritium level. First, tritium concentration in tree ring cellulose sampled from a cedar tree grown in a typical environment in Fukuoka Prefecture is compared with the tritium concentration in precipitation in Tokyo. Results show that the year-to-year variations in the tritium concentration in the tree rings agree well with those in precipitation. The maximum concentration, which occurred in 1963, is attibuted to atmospheric nuclear testing which was performed frequently during the 1961 - 1963 period. Measurement is also made of the tritium concentration in tree ring cellulose sampled from a pine tree grown near the Isotope Center of Kyushu University (Fukuoka). Results indicate that the background level is higher probably due to the release of tritium from the facilities around the pine tree. Thus, measurement of tritium in tree ring cellulose clearly shows the year-to-year variation in the tritium concentration in the atmosphere. (N.K.)

Parameter scan for the CLIC Damping rings under the infleunce of intrabeam scattering

OpenAIRE

Antoniou, F; Martini, M; Papaphilippou, Y; Vivoli, A

2010-01-01

Due to the high bunch density, the output emittances of the CLIC Damping Rings (DR) are strongly dominated by the effect of Intrabeam Scattering (IBS). In an attempt to optimize the ring design, the bench-marking of the multiparticle tracking code SIRE with the classical IBS formalisms and approximations is first considered. The scaling of the steady state emittances and IBS growth rates is also studied, with respect to several ring parameters including energy, bunch charge and wiggler charac...

Parameter scan for the CLIC Damping rings under the infleunce of intrabeam scattering

CERN Document Server

Antoniou, F; Papaphilippou, Y; Vivoli, A

2010-01-01

Due to the high bunch density, the output emittances of the CLIC Damping Rings (DR) are strongly dominated by the effect of Intrabeam Scattering (IBS). In an attempt to optimize the ring design, the bench-marking of the multiparticle tracking code SIRE with the classical IBS formalisms and approximations is first considered. The scaling of the steady state emittances and IBS growth rates is also studied, with respect to several ring parameters including energy, bunch charge and wiggler characteristics.

Dependency of the regio- and stereoselectivity of intramolecular, ring-closing glycosylations upon the ring size

Directory of Open Access Journals (Sweden)

Patrick Claude

2011-12-01

Full Text Available Phenyl 3,4,6-tri-O-benzyl-2-O-(3-carboxypropionyl-1-thio-β-D-galactopyranoside (1 was condensed via its pentafluorophenyl ester 2 with 5-aminopentyl (4a, 4-aminobutyl (4b, 3-aminopropyl (4c and 2-aminoethyl 4,6-O-benzylidene-β-D-glucopyranoside (4d, prepared from the corresponding N-Cbz protected glucosides 3a–d, to give the corresponding 2-[3-(alkylcarbamoylpropionyl] tethered saccharides 5a–d. Intramolecular, ring closing glycosylation of the saccharides with NIS and TMSOTf afforded the tethered β(1→3 linked disaccharides 6a–c, the α(1→3 linked disaccharides 7a–d and the α(1→2 linked disaccharide 8d in ratios depending upon the ring size formed during glycosylation. No β(1→2 linked disaccharides were formed. Molecular modeling of saccharides 6–8 revealed that a strong aromatic stacking interaction between the aromatic parts of the benzyl and benzylidene protecting groups in the galactosyl and glucosyl moieties was mainly responsible for the observed regioselectivity and anomeric selectivity of the ring-closing glycosylation step.

Annual rings in a native Hawaiian tree, Sophora chrysophylla, on Maunakea, Hawai‘i

Science.gov (United States)

Kainana S. Francisco; Patrick J. Hart; Jinbao Li; Edward R. Cook; Patrick J. Baker

2015-01-01

Annual rings are not commonly produced in tropical trees because they grow in a relatively aseasonal environment. However, in the subalpine zones of Hawai‘i's highest volcanoes, there is often strong seasonal variability in temperature and rainfall. Using classical dendrochronological methods, annual growth rings were shown to occur in Sophora...

Terfenol-D/Pb(Zr,Ti)O{sub 3} disk-ring multiferroic heterostructures coupled through normal stresses

Energy Technology Data Exchange (ETDEWEB)

Li, Lei; Chen, Xiang Ming [Zhejiang University, Laboratory of Dielectric Materials, Department of Materials Science and Engineering, Hangzhou (China)

2010-03-15

Disk-ring multiferroic heterostructures composed of Terfenol-D and Pb(Zr,Ti)O{sub 3} (PZT) were prepared and characterized, for which the ferromagnetic and ferroelectric phases were coupled through normal stresses instead of the shear stresses that acted in most of the previous multiferroic heterostructures. High low-frequency magnetoelectric coefficients of 0.10-0.75 V cm{sup -1} Oe{sup -1} were attained for the disk-ring heterostructures, which indicated the strong magnetoelectric coupling. Moreover, a symmetrical resonant peak was observed for dE{sub 3}/dH{sub 3} in the frequency range of 1-200 kHz, while another weak peak with asymmetrical shape also existed at a lower frequency for dE{sub 3}/dH{sub 1}, which was due to the combination of two vibration modes. (orig.)

Achieving Translationally Invariant Trapped Ion Rings

Science.gov (United States)

Urban, Erik; Li, Hao-Kun; Noel, Crystal; Hemmerling, Boerge; Zhang, Xiang; Haeffner, Hartmut

2017-04-01

We present the design and implementation of a novel surface ion trap design in a ring configuration. By eliminating the need for wire bonds through the use of electrical vias and using a rotationally invariant electrode configuration, we have realized a trap that is able to trap up to 20 ions in a ring geometry 45um in diameter, 400um above the trap surface. This large trapping height to ring diameter ratio allows for global addressing of the ring with both lasers and electric fields in the chamber, thereby increasing our ability to control the ring as a whole. Applying compensating electric fields, we measure very low tangential trap frequencies (less than 20kHz) corresponding to rotational barriers down to 4mK. This measurement is currently limited by the temperature of the ions but extrapolation indicates the barrier can be reduced much further with more advanced cooling techniques. Finally, we show that we are able to reduce this energy barrier sufficiently such that the ions are able to overcome it either through thermal motion or rotational motion and delocalize over the full extent of the ring. This work was funded by the Keck Foundation and the NSF.

Properties of tree rings in LSST sensors

International Nuclear Information System (INIS)

Park, H.Y.; Tsybychev, D.; Nomerotski, A.

2017-01-01

Images of uniformly illuminated sensors for the Large Synoptic Survey Telescope have circular periodic patterns with an appearance similar to tree rings. These patterns are caused by circularly symmetric variations of the dopant concentration in the monocrystal silicon boule induced by the manufacturing process. Non-uniform charge density results in the parasitic electric field inside the silicon sensor, which may distort shapes of astronomical sources. In this study we analyzed data from fifteen LSST sensors produced by ITL to determine the main parameters of the tree rings: amplitude and period, and also variability across the sensors tested at Brookhaven National Laboratory. Tree ring pattern has a weak dependence on the wavelength. However the ring amplitude gets smaller as wavelength gets longer, since longer wavelengths penetrate deeper into the silicon. Tree ring amplitude gets larger as it gets closer to the outer part of the wafer, from 0.1 to 1.0%, indicating that the resistivity variation is larger for larger radii.

Imprint of the Atlantic multidecadal oscillation on tree-ring widths in northeastern Asia since 1568.

Directory of Open Access Journals (Sweden)

Xiaochun Wang

Full Text Available We present a new tree-ring reconstruction of the Atlantic Multidecadal Oscillation (AMO spanning 1568-2007 CE from northeast Asia. Comparison of the instrumental AMO index, an existing tree-ring based AMO reconstruction, and this new record show strongly similar annual to multidecadal patterns of variation over the last 440 years. Warm phases of the AMO are related to increases in growth of Scots pine trees and moisture availability in northeast China and central eastern Siberia. Multi-tape method (MTM and cross-wavelet analyses indicate that robust multidecadal (∼64-128 years variability is present throughout the new proxy record. Our results have important implications concerning the influence of North Atlantic sea surface temperatures on East Asian climate, and provide support for the possibility of an AMO signature on global multidecadal climate variability.

Connections between Star Cluster Populations and Their Host Galaxy Nuclear Rings

Science.gov (United States)

Ma, Chao; de Grijs, Richard; Ho, Luis C.

2018-04-01

Nuclear rings are excellent laboratories for probing diverse phenomena such as the formation and evolution of young massive star clusters and nuclear starbursts, as well as the secular evolution and dynamics of their host galaxies. We have compiled a sample of 17 galaxies with nuclear rings, which are well resolved by high-resolution Hubble and Spitzer Space Telescope imaging. For each nuclear ring, we identified the ring star cluster population, along with their physical properties (ages, masses, and extinction values). We also determined the integrated ring properties, including the average age, total stellar mass, and current star formation rate (SFR). We find that Sb-type galaxies tend to have the highest ring stellar mass fraction with respect to the host galaxy, and this parameter is correlated with the ring’s SFR surface density. The ring SFRs are correlated with their stellar masses, which is reminiscent of the main sequence of star-forming galaxies. There are striking correlations between star-forming properties (i.e., SFR and SFR surface density) and nonaxisymmetric bar parameters, appearing to confirm previous inferences that strongly barred galaxies tend to have lower ring SFRs, although the ring star formation histories turn out to be significantly more complicated. Nuclear rings with higher stellar masses tend to be associated with lower cluster mass fractions, but there is no such relation for the ages of the rings. The two youngest nuclear rings in our sample, NGC 1512 and NGC 4314, which have the most extreme physical properties, represent the young extremity of the nuclear ring age distribution.

Three dimensional atom probe imaging of GaAsSb quantum rings

International Nuclear Information System (INIS)

Beltran, A.M.; Marquis, E.A.; Taboada, A.G.; Ripalda, J.M.; Garcia, J.M.; Molina, S.I.

2011-01-01

Unambiguous evidence of ring-shaped self-assembled GaSb nanostructures grown by molecular beam epitaxy is presented on the basis of atom-probe tomography reconstructions and dark field transmission electron microscopy imaging. The GaAs capping process causes a strong segregation of Sb out of the center of GaSb quantum dots, leading to the self-assembled GaAs x Sb 1-x quantum rings of 20-30 nm in diameter with x∼0.33. -- Highlights: → Atom-probe tomography resolves QR morphology of GaSb self-assembled GaSb buried nanostructures. → From atom-probe tomography compositional distribution has been obtained. → Strong segregation and morphological changes are observed with respect to uncapped QR.

Black rings

International Nuclear Information System (INIS)

Emparan, Roberto; Reall, Harvey S

2006-01-01

A black ring is a five-dimensional black hole with an event horizon of topology S 1 x S 2 . We provide an introduction to the description of black rings in general relativity and string theory. Novel aspects of the presentation include a new approach to constructing black ring coordinates and a critical review of black ring microscopics. (topical review)

Electron transmission through coupled quantum dots in an Aharonov-Bohm ring

International Nuclear Information System (INIS)

Joe, Y. S.; Kim, Y. D.

2006-01-01

Stimulated by recent intriguing experiments with a quantum dot in an Aharonov-Bohm (AB) ring, we investigate novel resonant phenomena by studying the total transmission probability of nanoscale AB ring with embedded double quantum dots in one arm and a magnetic flux passing through the rings' center. In this system, we show an overlapping and merging of Fano resonances as the interaction parameter between the dots changes. In the strong overlapping region of Fano resonances, the transmission zeros leave the real-energy axis and move away in opposite directions in the complex-energy plane. The behavior of the Fano zero-pole resonances in the complex-energy plane as a function of the external magnetic flux is also investigated for various coupling integrals between the quantum dots in the ring.

Cell culture arrays using micron-sized ferromagnetic ring-shaped thin films

Energy Technology Data Exchange (ETDEWEB)

Huang, Chen-Yu; Wei, Zung-Hang, E-mail: wei@pme.nthu.edu.tw [Department of Power Mechanical Engineering, National Tsing Hua University, Hsinchu City 300, Taiwan (China); Lai, Mei-Feng; Ger, Tzong-Rong [Institute of NanoEngineering and MicroSystems, National Tsing Hua University, Hsinchu City 300, Taiwan (China)

2015-05-07

Cell patterning has become an important technology for tissue engineering. In this research, domain walls are formed at the two ends of a ferromagnetic ring thin film after applying a strong external magnetic field, which can effectively attract magnetically labeled cells and control the position for biological cell. Magnetophoresis experiment was conducted to quantify the magnetic nanoparticle inside the cells. A ring-shaped magnetic thin films array was fabricated through photolithography. It is observed that magnetically labeled cells can be successfully attracted to the two ends of the ring-shaped magnetic thin film structure and more cells were attracted and further attached to the structures. The cells are co-cultured with the structure and kept proliferating; therefore, such ring thin film can be an important candidate for in-vitro biomedical chips or tissue engineering.

Cell culture arrays using micron-sized ferromagnetic ring-shaped thin films

International Nuclear Information System (INIS)

Huang, Chen-Yu; Wei, Zung-Hang; Lai, Mei-Feng; Ger, Tzong-Rong

2015-01-01

Cell patterning has become an important technology for tissue engineering. In this research, domain walls are formed at the two ends of a ferromagnetic ring thin film after applying a strong external magnetic field, which can effectively attract magnetically labeled cells and control the position for biological cell. Magnetophoresis experiment was conducted to quantify the magnetic nanoparticle inside the cells. A ring-shaped magnetic thin films array was fabricated through photolithography. It is observed that magnetically labeled cells can be successfully attracted to the two ends of the ring-shaped magnetic thin film structure and more cells were attracted and further attached to the structures. The cells are co-cultured with the structure and kept proliferating; therefore, such ring thin film can be an important candidate for in-vitro biomedical chips or tissue engineering

Variations in Ring Particle Cooling across Saturn's Rings with Cassini CIRS

Science.gov (United States)

Brooks, S. M.; Spilker, L. J.; Pilorz, S.; Edgington, S. G.; Déau, E.; Altobelli, N.

2010-12-01

Cassini's Composite Infrared Spectrometer has recorded over two million of spectra of Saturn's rings in the far infrared since arriving at Saturn in 2004. CIRS records far infrared radiation between 10 and 600 cm-1 ( 16.7 and 1000 μ {m} ) at focal plane 1 (FP1), which has a field of view of 3.9 mrad. Thermal emission from Saturn’s rings peaks in this wavelength range. Ring temperatures can be inferred from FP1 data. By tracking how ring temperatures vary, we can determine the thermal inertia of the rings. Previous studies have shown that the rings' thermal inertia, a measure of their response to changes in the thermal environment, varies from ring to ring. Thermal inertia can provide insight into the physical structure of Saturn's ring particles and their regoliths. Low thermal inertia and rapidly changing temperatures are suggestive of ring particles that have more porous or fluffy regoliths or that are riddled with cracks. Solid particles can be expected to have higher thermal inertias. Ferrari et al. (2005) fit thermal inertia values of 5218 {Jm)-2 {K}-1 {s}-1/2 to their B ring data and 6412 {Jm)-2 {K}-1 {s}-1/2 to their C ring data. In this work we focus on CIRS observations of the shadowed portion of Saturn's rings. The rings’ thermal budget is dominated by its absorption of solar radiation. As a result, ring particles abruptly cool as they traverse Saturn's shadow. From these shadow observations we can create cooling curves at specific locations across the rings. We will show that the rings' cooling curves and thus their thermal inertia vary not only from ring to ring, but by location within the individual rings. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. Copyright 2010 California Institute of Technology. Government sponsorship acknowledged.

Ring current proton decay by charge exchange

Science.gov (United States)

Smith, P. H.; Hoffman, R. A.; Fritz, T.

1975-01-01

Explorer 45 measurements during the recovery phase of a moderate magnetic storm have confirmed that the charge exchange decay mechanism can account for the decay of the storm-time proton ring current. Data from the moderate magnetic storm of 24 February 1972 was selected for study since a symmetrical ring current had developed and effects due to asymmetric ring current losses could be eliminated. It was found that after the initial rapid decay of the proton flux, the equatorially mirroring protons in the energy range 5 to 30 keV decayed throughout the L-value range of 3.5 to 5.0 at the charge exchange decay rate calculated by Liemohn. After several days of decay, the proton fluxes reached a lower limit where an apparent equilibrium was maintained, between weak particle source mechanisms and the loss mechanisms, until fresh protons were injected into the ring current region during substorms. While other proton loss mechanisms may also be operating, the results indicate that charge exchange can entirely account for the storm-time proton ring current decay, and that this mechanism must be considered in all studies involving the loss of proton ring current particles.

MUSE-INGS ON AM1354-250: COLLISIONS, SHOCKS, AND RINGS

Energy Technology Data Exchange (ETDEWEB)

Conn, Blair C. [Gemini Observatory, Recinto AURA, Colina El Pino, Casilla 603, La Serena (Chile); Fogarty, L. M. R. [Sydney Institute for Astronomy, School of Physics, The University of Sydney, A28, Sydney, 2006 (Australia); Smith, Rory [Yonsei University, Graduate School of Earth System Sciences-Astronomy-Atmospheric Sciences, Yonsei-ro 50, Seoul 120-749 (Korea, Republic of); Candlish, Graeme N., E-mail: bconn@gemini.edu [Departamento de Astronomía, Universidad de Concepción, Casilla 160-C, Concepción (Chile)

2016-03-10

We present Multi Unit Spectroscopic Explorer observations of AM1354-250, confirming its status as a collisional ring galaxy that has recently undergone an interaction, creating its distinctive shape. We analyze the stellar and gaseous emission throughout the galaxy finding direct evidence that the gaseous ring is expanding with a velocity of ∼70 km s{sup −1} and that star formation is occurring primarily in H ii regions associated with the ring. This star formation activity is likely triggered by this interaction. We find evidence for several excitation mechanisms in the gas, including emission consistent with shocked gas in the expanding ring and a region of LINER-like emission in the central core of the galaxy. Evidence of kinematic disturbance in both the stars and gas, possibly also triggered by the interaction, can be seen in all of the velocity maps. The ring galaxy retains a weak spiral structure, strongly suggesting the progenitor galaxy was a massive spiral prior to the collision with its companion an estimated 140 ± 12 Myr ago.

Alternative loop rings

CERN Document Server

Goodaire, EG; Polcino Milies, C

1996-01-01

For the past ten years, alternative loop rings have intrigued mathematicians from a wide cross-section of modern algebra. As a consequence, the theory of alternative loop rings has grown tremendously. One of the main developments is the complete characterization of loops which have an alternative but not associative, loop ring. Furthermore, there is a very close relationship between the algebraic structures of loop rings and of group rings over 2-groups. Another major topic of research is the study of the unit loop of the integral loop ring. Here the interaction between loop rings and group ri

Primitivity and weak distributivity in near rings and matrix near rings

International Nuclear Information System (INIS)

Abbasi, S.J.

1993-08-01

This paper shows the structure of matrix near ring constructed over a weakly distributive and primative near ring. It is proved that a weakly distributive primitive near ring is a ring and the matrix near rings constructed over it is also a bag. (author). 14 refs

A neutron diffraction study of residual stress and plastic strain in welded beryllium rings

Energy Technology Data Exchange (ETDEWEB)

Brown, D.W.; Varma, R.; Bourke, M.A.M.; Holden, T.M. [Los Alamos National Lab., Los Alamos, NM (United States); Ely, T.; Spooner, S. [Oak Ridge National Lab., Oak Ridge, TN (United States)

2002-07-01

We present a study of residual stresses associated with the welding of beryllium rings. Using novel analysis techniques, information about residual stresses and plastic deformation of the base metal were obtained. In the post-welded state, the rings have a strong tensile circumferential residual stress and show evidence of significant plastic deformation. (orig.)

Vortex-ring-induced large bubble entrainment during drop impact

KAUST Repository

Thoraval, Marie-Jean; Li, Yangfan; Thoroddsen, Sigurdur T

2016-01-01

, produced in the neck between the drop and the pool, controls the crater deformations and pinchoff. However, it is not the strongest vortex rings that are responsible for the large bubbles, as they interact too strongly with the pool surface and self

The Lord of Rings - the mysterious case of the stolen rings: a critical analysis

Science.gov (United States)

Sandrelli, S.

water, represented by simple objects like apples, spinning tops and so on) to re-build the rings. The kids can buy the ingredients from different planets: every planet has ingredients in quantities which are proportionate to the real physical properties of that celestial object. After collecting the ingredients, they must carry them to the "The Red Giant" and indicate their best recipe to Mr Schioppanelli. Depending on the recipe, rings can be too strict or too luminous or too fast rotating and so on. The winning group is the one which prepares the best recipe to cook the rings in the smallest amount of time. After presentig this specific (and mysterious) case, we analyse the advantage- disadvantage ratio of such an activity, beeing as funny as dispersive.

On the propagation and decay of North Brazil Current rings

Science.gov (United States)

Jochumsen, Kerstin; Rhein, Monika; Hüttl-Kabus, Sabine; BöNing, Claus W.

2010-10-01

Near the western boundary of the tropical North Atlantic, where the North Brazil Current (NBC) retroflects into the North Equatorial Countercurrent, large anticyclonic rings are shed. After separating from the retroflection region, the so-called NBC rings travel northwestward along the Brazilian coast, until they reach the island chain of the Lesser Antilles and disintegrate. These rings contribute substantially to the upper limb return flow of the Atlantic Meridional Overturning Circulation by carrying South Atlantic Water into the northern subtropical gyre. Their relevance for the northward transport of South Atlantic Water depends on the frequency of their generation as well as on their horizontal and vertical structure. The ring shedding and propagation and the complex interaction of the rings with the Lesser Antilles are investigated in the ? Family of Linked Atlantic Model Experiments (FLAME) model. The ring properties simulated in FLAME reach the upper limit of the observed rings in diameter and agree with recent observations on seasonal variability, which indicates a maximum shedding during the first half of the year. When the rings reach the shallow topography of the Lesser Antilles, they are trapped by the island triangle of St. Lucia, Barbados and Tobago and interact with the island chain. The model provides a resolution that is capable of resolving the complex topographic conditions at the islands and illuminates various possible fates for the water contained in the rings. It also reproduces laboratory experiments that indicate that both cyclones and anticyclones are formed after a ring passes through a topographic gap. Trajectories of artificial floats, which were inserted into the modeled velocity field, are used to investigate the pathways of the ring cores and their fate after they encounter the Lesser Antilles. The majority of the floats entered the Caribbean, while the northward Atlantic pathway was found to be of minor importance. No prominent

Magnetoconductance fluctuations in a strongly correlated disordered ring system at low temperatures

International Nuclear Information System (INIS)

Chen, H.; Ishihara, M.; Li, Z.; Kawazoe, Y.

1996-01-01

Using a recursive real-space Green close-quote s-function technique in the tight-binding model, we study the influence of the electron-electron Hubbard interaction on the magnetoconductance fluctuations in a disordered ring at low temperatures. Our numerical results improve the previous theoretical predictions for the magnetoconductance fluctuations as a function of magnetic flux compared with experiments. Meanwhile, we find several anomalous phenomena at low temperatures, which do not survive at high temperatures. For the Fermi level E f =0.1t (t is the hopping integral) the envelope of magnetoconductance fluctuations drops to a lower value at some magnetic flux, while the Hubbard interaction causes the drop to occur at larger flux. The magnetoconductance fluctuations vary with the Hubbard interaction for magnetic flux around 20Φ 0 (Φ 0 =hc/e) mainly in the range of small U. The Hubbard interaction narrows the widths of the main peaks in the Fourier spectrum, but it does not change their positions. copyright 1996 The American Physical Society

Ring Chromosome 17 Not Involving the Miller-Dieker Region: A Case with Drug-Resistant Epilepsy.

Science.gov (United States)

Coppola, Antonietta; Morrogh, Deborah; Farrell, Fiona; Balestrini, Simona; Hernandez-Hernandez, Laura; Krithika, S; Sander, Josemir W; Waters, Jonathan J; Sisodiya, Sanjay M

2017-12-01

Chromosomal abnormalities are often identified in people with neurodevelopmental disorders including intellectual disability, autism, and epilepsy. Ring chromosomes, which usually involve gene copy number loss, are formed by fusion of subtelomeric or telomeric chromosomal regions. Some ring chromosomes, including ring 14, 17, and 20, are strongly associated with seizure disorders. We report an individual with a ring chromosome 17, r(17)(p13.3q25.3), with a terminal 17q25.3 deletion and no short arm copy number loss, and with a phenotype characterized by intellectual disability and drug-resistant epilepsy, including a propensity for nonconvulsive status epilepticus.

Rings in drugs.

Science.gov (United States)

Taylor, Richard D; MacCoss, Malcolm; Lawson, Alastair D G

2014-07-24

We have analyzed the rings, ring systems, and frameworks in drugs listed in the FDA Orange Book to understand the frequency, timelines, molecular property space, and the application of these rings in different therapeutic areas and target classes. This analysis shows that there are only 351 ring systems and 1197 frameworks in drugs that came onto the market before 2013. Furthermore, on average six new ring systems enter drug space each year and approximately 28% of new drugs contain a new ring system. Moreover, it is very unusual for a drug to contain more than one new ring system and the majority of the most frequently used ring systems (83%) were first used in drugs developed prior to 1983. These observations give insight into the chemical novelty of drugs and potentially efficient ways to assess compound libraries and develop compounds from hit identification to lead optimization and beyond.

Self-organized formation of GaSb/GaAs quantum rings.

Science.gov (United States)

Timm, R; Eisele, H; Lenz, A; Ivanova, L; Balakrishnan, G; Huffaker, D L; Dähne, M

2008-12-19

Ring-shaped GaSb/GaAs quantum dots, grown by molecular beam epitaxy, were studied using cross-sectional scanning tunneling microscopy. These quantum rings have an outer shape of a truncated pyramid with baselengths around 15 nm and heights of about 2 nm but are characterized by a clear central opening extending over about 40% of the outer baselength. They form spontaneously during the growth and subsequent continuous capping of GaSb/GaAs quantum dots due to the large strain and substantial As-for-Sb exchange reactions leading to strong Sb segregation.

Lit and unlit side temperatures of the Main Rings of Saturn.

Science.gov (United States)

Flandes, A.; Garcia, A.; Deau, E.; Spilker, L. J.

2017-12-01

The differences in the temperatures of both the lit and unlit sides of the main rings of Saturn can reveal important information about their structure. In general, the temperature of the main rings strongly depends upon the distribution and the general structure of the ensembles of particles that compose them, mainly due to shadowing effects that modulate how much energy reaches the individual particles -granted that the direct solar energy is the main driver of the rings' temperature-. In order to reproduce the temperatures of both sides of the rings, we use a semi-analytical energy balance model (considering solar direct and Saturn reflected energy, Saturn thermal energy and particles' thermal energies), where the shadowed fractional areas of the rings are removed through a shadowing function. We obtain this function (dependent on the solar elevation angle) for 13 different regions (for the A, CD, B and C rings) along the radial direction that are simulated using arrays of lambertian spherical particles based on the average properties of the structure of these regions derived from the Cassini UVIS observations. The obtained synthetic temperatures are compared to the Cassini CIRS measured temperatures (from -22º to equinox) with good agreement.

Development and evaluation of accelerated drug release testing methods for a matrix-type intravaginal ring.

Science.gov (United States)

Externbrink, Anna; Eggenreich, Karin; Eder, Simone; Mohr, Stefan; Nickisch, Klaus; Klein, Sandra

2017-01-01

Accelerated drug release testing is a valuable quality control tool for long-acting non-oral extended release formulations. Currently, several intravaginal ring candidates designed for the long-term delivery of steroids or anti-infective drugs are being in the developing pipeline. The present article addresses the demand for accelerated drug release methods for these formulations. We describe the development and evaluation of accelerated release methods for a steroid releasing matrix-type intravaginal ring. The drug release properties of the formulation were evaluated under real-time and accelerated test conditions. Under real-time test conditions drug release from the intravaginal ring was strongly affected by the steroid solubility in the release medium. Under sufficient sink conditions that were provided in release media containing surfactants drug release was Fickian diffusion driven. Both temperature and hydro-organic dissolution media were successfully employed to accelerate drug release from the formulation. Drug release could be further increased by combining the temperature effect with the application of a hydro-organic release medium. The formulation continued to exhibit a diffusion controlled release kinetic under the investigated accelerated conditions. Moreover, the accelerated methods were able to differentiate between different prototypes of the intravaginal ring that exhibited different release profiles under real-time test conditions. Overall, the results of the present study indicate that both temperature and hydro-organic release media are valid parameters for accelerating drug release from the intravaginal ring. Variation of either a single or both parameters yielded release profiles that correlated well with real-time release. Copyright © 2016 Elsevier B.V. All rights reserved.

Quantized levitation states of superconducting multiple-ring systems

International Nuclear Information System (INIS)

Haley, S.B.; Fink, H.J.

1996-01-01

The quantized levitation, trapped, and suspension states of a magnetic microsphere held in equilibrium by two fixed superconducting (SC) microrings are calculated by minimizing the free energy of the system. Each state is a discrete function of two independent fluxoid quantum numbers of the rings. When the radii of the SC rings are of the same order as the Ginzburg-Landau coherence length ξ(T), the system exhibits a small set of gravity and temperature-dependent levels. The levels of a weakly magnetized particle are sensitive functions of the gravitational field, indicating potential application as an accelerometer, and for trapping small magnetic particles in outer space or on Earth. The equilibrium states of a SC ring levitated by another SC ring are also calculated. copyright 1996 The American Physical Society

Catch history of ringed seals (Phoca hispida in Canada

Directory of Open Access Journals (Sweden)

Randall R Reeves

1998-06-01

Full Text Available The ringed seal (Phoca hispida has always been a staple in the diet and household economy of Inuit in Canada. The present paper was prepared at the request of the NAMMCO Scientific Committee to support their assessment of ringed seal stocks in the North Atlantic Basin and adjacent arctic and subarctic waters. Specifically, our objective was to evaluate recent and current levels of use of ringed seals by Canadian Inuit. Annual removals probably were highest (possibly greater than 100,000 in the 1960s and 1970s, a period when sealskin prices were particularly strong. Catches declined substantially in the 1980s following a collapse in sealskin prices, presumably related to the European trade ban on skins from newborn harp and hooded seals (Phoca groenlandica and Cystophora cristata, respectively. Recent catch levels throughout Canada (1980s and early 1990s are believed to be in the order of 50,000 to 65,000 ringed seals, with a total average annual kill (including hunting loss in the high tens of thousands. No reliable system is in place to monitor catches of ringed seals, so any estimate must be derived from a heterogeneous array of sources.

Non-Linear Dynamics of Saturn's Rings

Science.gov (United States)

Esposito, L. W.

2016-12-01

Non-linear processes can explain why Saturn's rings are so active and dynamic. Ring systems differ from simple linear systems in two significant ways: 1. They are systems of granular material: where particle-to-particle collisions dominate; thus a kinetic, not a fluid description needed. Stresses are strikingly inhomogeneous and fluctuations are large compared to equilibrium. 2. They are strongly forced by resonances: which drive a non-linear response, that push the system across thresholds that lead to persistent states. Some of this non-linearity is captured in a simple Predator-Prey Model: Periodic forcing from the moon causes streamline crowding; This damps the relative velocity. About a quarter phase later, the aggregates stir the system to higher relative velocity and the limit cycle repeats each orbit, with relative velocity ranging from nearly zero to a multiple of the orbit average. Summary of Halo Results: A predator-prey model for ring dynamics produces transient structures like `straw' that can explain the halo morphology and spectroscopy: Cyclic velocity changes cause perturbed regions to reach higher collision speeds at some orbital phases, which preferentially removes small regolith particles; surrounding particles diffuse back too slowly to erase the effect: this gives the halo morphology; this requires energetic collisions (v ≈ 10m/sec, with throw distances about 200km, implying objects of scale R ≈ 20km).Transform to Duffing Eqn : With the coordinate transformation, z = M2/3, the Predator-Prey equations can be combined to form a single second-order differential equation with harmonic resonance forcing.Ring dynamics and history implications: Moon-triggered clumping explains both small and large particles at resonances. We calculate the stationary size distribution using a cell-to-cell mapping procedure that converts the phase-plane trajectories to a Markov chain. Approximating it as an asymmetric random walk with reflecting boundaries

Ring cavity surface emitting semiconductor lasers

International Nuclear Information System (INIS)

Mujagic, E.

2010-01-01

�m. Characterizations indicate a high temperature operation of MIR ring-CSELs along with a reduction in threshold current density of MIR devices by 35% as compared to Fabry-Perot devices. The lower operating currents in ring-CSELs became noticeable in continuous wave (CW) operation with a 50K higher maximum temperature than in FP lasers. A two-fold enhancement in radiation efficiency was obtained in MIR and THz ring-CSELs as compared to FP emitters. The DFB grating on top of the resonator gives rise to a single-mode operation of ring-CSELs for all operation currents. Linear wavelength tuning is achieved by fabricating different gratings periods as well as by a variation in temperature. The slope efficiency and the threshold current density does not seem to significantly depend on the grating period, which is attributed to the absence of mirrors. The incorporated circular waveguide geometry along with the surface emitting character gives rise to symmetric and low divergence azimuthally polarized optical beams. The recorded far-fields indicate a ring shaped interference patterns with lobe separations of 1.34 o and 14.14 o for MIR and THz ring-CSELs, respectively. Fabrication of detuned gratings led to a grating period induced as well as to a tunable wavelength induced beam shaping, with beam patterns ranging from spot to wide ring cross sections. (author) [de

Parameters and design optimization of the ring piezoelectric ceramic transformer

Directory of Open Access Journals (Sweden)

Jiří Erhart

2015-09-01

Full Text Available Main aim of the presented paper is the theoretical analysis and experimental verification of the transformation parameters for the new type of nonhomogeneously poled ring transformer. The input part is poled in the thickness direction and output part in the radial direction. Two transformer geometries are studied — the input part is at inner ring segment, or it is at the outer ring segment. The optimum electrode size aspect ratios have been found experimentally as d1∕D≈0.60−0.65 for the ring with aspect ratio d∕D=0.2. The fundamental as well as higher overtone resonances were studied for the transformation ratio, the optimum resistive load, efficiency and no-load transformation ratio. Higher overtones have better transformation parameters compared to the fundamental resonance. The new type ring transformer exhibits very high transformation ratios up to 200 under no-load and up to 13.4 under a high efficiency of 97% at the optimum load conditions of 10 kΩ. Strong electric field gradient at the output circuit is applicable for the electrical discharge generation.

Six centuries of May-July precipitation in Cyprus from tree rings

Science.gov (United States)

Touchan, Ramzi; Christou, Andreas K.; Meko, David M.

2014-12-01

A May-July precipitation nested reconstruction for the period AD 1415-2010 was developed from multi-century tree-ring records of Pinus nigra, Pinus brutia, and Cedrus brevifolia for Cyprus. Calibration and verification statistics for the period 1917-2010 show a good level of skill, and split-sample validation over 1917-2010 supports temporal stability of the tree-ring signal for precipitation. Smoothed annual time series of reconstructed precipitation and a tally of drought events in a moving time window indicate that the calibration period is not representative of the full range of drought variability. While convective precipitation in the warm season may be driven strongly by local factors, composite maps of geopotential height anomaly for dry years and wet years support large-scale atmospheric-flow influence related to height anomalies over the broader region of northeast Africa and the eastern Mediterranean. Emerging positive trend in reconstruction residuals may be an early sign of exacerbation of drought stress on trees by recent warming in May-July. Future warming expected from increases in greenhouse gases poses a threat to forest resources in Cyprus and elsewhere in the Mediterranean.

The influence of climate variability on polar bear (Ursus maritimus) and ringed seal (Pusa hispida) population dynamics

DEFF Research Database (Denmark)

Rosing-Asvid, A.

2006-01-01

Unusually high polar bear (Ursus maritimus Phipps, 1774) predation on ringed seal (Pusa hispida (Schreber, 1775)) pups and increased survival of polar bear cubs during mild springs is documented in published articles. Strong predation on newborn ringed seal pups in early spring, however, is likely...... to lower the overall energy intake of polar bears if ringed seal pups are their main food, because the energetic value of ringed seal pups increases 7-8 times during the 6 week lactation period. So although hunting success in early spring increases cub survival during the period after den emergence......,when they are most vulnerable, it is likely to increase the number of starving bears later in the season. This negative-feedback effect of strong spring predation will not occur in areas where other seal species are abundant during summer, and polar bears in such areas are likely to exhibit population growth during...

Oxygen isotopes in tree rings are a good proxy for Amazon precipitation and El Niño-Southern Oscillation variability

Science.gov (United States)

Brienen, Roel J. W.; Helle, Gerd; Pons, Thijs L.; Guyot, Jean-Loup; Gloor, Manuel

2012-10-01

We present a unique proxy for the reconstruction of variation in precipitation over the Amazon: oxygen isotope ratios in annual rings in tropical cedar (Cedrela odorata). A century-long record from northern Bolivia shows that tree rings preserve the signal of oxygen isotopes in precipitation during the wet season, with weaker influences of temperature and vapor pressure. Tree ring δ18O correlates strongly with δ18O in precipitation from distant stations in the center and west of the basin, and with Andean ice core δ18O showing that the signal is coherent over large areas. The signal correlates most strongly with basin-wide precipitation and Amazon river discharge. We attribute the strength of this (negative) correlation mainly to the cumulative rainout processes of oxygen isotopes (Rayleigh distillation) in air parcels during westward transport across the basin. We further find a clear signature of the El Niño-Southern Oscillation (ENSO) in the record, with strong ENSO influences over recent decades, but weaker influence from 1925 to 1975 indicating decadal scale variation in the controls on the hydrological cycle. The record exhibits a significant increase in δ18O over the 20th century consistent with increases in Andean δ18O ice core and lake records, which we tentatively attribute to increased water vapor transport into the basin. Taking these data together, our record reveals a fresh path to diagnose and improve our understanding of variation and trends of the hydrological cycle of the world's largest river catchment.

The Ring Current Response to Solar and Interplanetary Storm Drivers

Science.gov (United States)

Mouikis, C.; Kistler, L. M.; Bingham, S.; Kronberg, E. A.; Gkioulidou, M.; Huang, C. L.; Farrugia, C. J.

2014-12-01

The ring current responds differently to the different solar and interplanetary storm drivers such as coronal mass injections, (CME's), corotating interaction regions (CIR's), high-speed streamers and other structures. The resulting changes in the ring current particle pressure, in turn, change the global magnetic field, controlling the transport of the radiation belts. To quantitatively determine the field changes during a storm throughout the magnetosphere, it is necessary to understand the transport, sources and losses of the particles that contribute to the ring current. Because the measured ring current energy spectra depend not only on local processes, but also on the history of the ions along their entire drift path, measurements of ring current energy spectra at two or more locations can be used to strongly constrain the time dependent magnetic and electric fields. In this study we use data predominantly from the Cluster and the Van Allen Probes, covering more than a full solar cycle (from 2001 to 2014). For the period 2001-2012, the Cluster CODIF and RAPID measurements of the inner magnetosphere are the primary data set used to monitor the storm time ring current variability. After 2012, the Cluster data set complements the data from the Van Allen Probes HOPE and RBSPICE instruments, providing additional measurements from different MLT and L shells. Selected storms from this periods, allow us to study the ring current dynamics and pressure changes, as a function of L shell, magnetic local time, and the type of interplanetary disturbances.

Non-Linear Dynamics of Saturn’s Rings

Science.gov (United States)

Esposito, Larry W.

2015-11-01

Non-linear processes can explain why Saturn’s rings are so active and dynamic. Ring systems differ from simple linear systems in two significant ways: 1. They are systems of granular material: where particle-to-particle collisions dominate; thus a kinetic, not a fluid description needed. We find that stresses are strikingly inhomogeneous and fluctuations are large compared to equilibrium. 2. They are strongly forced by resonances: which drive a non-linear response, pushing the system across thresholds that lead to persistent states.Some of this non-linearity is captured in a simple Predator-Prey Model: Periodic forcing from the moon causes streamline crowding; This damps the relative velocity, and allows aggregates to grow. About a quarter phase later, the aggregates stir the system to higher relative velocity and the limit cycle repeats each orbit.Summary of Halo Results: A predator-prey model for ring dynamics produces transient structures like ‘straw’ that can explain the halo structure and spectroscopy: This requires energetic collisions (v ≈ 10m/sec, with throw distances about 200km, implying objects of scale R ≈ 20km).Transform to Duffing Eqn : With the coordinate transformation, z = M2/3, the Predator-Prey equations can be combined to form a single second-order differential equation with harmonic resonance forcing.Ring dynamics and history implications: Moon-triggered clumping at perturbed regions in Saturn’s rings creates both high velocity dispersion and large aggregates at these distances, explaining both small and large particles observed there. We calculate the stationary size distribution using a cell-to-cell mapping procedure that converts the phase-plane trajectories to a Markov chain. Approximating the Markov chain as an asymmetric random walk with reflecting boundaries allows us to determine the power law index from results of numerical simulations in the tidal environment surrounding Saturn. Aggregates can explain many dynamic aspects

White Ring; White ring

Energy Technology Data Exchange (ETDEWEB)

Aoki, H.; Yuzawa, H. [Nikken Sekkei Ltd., Osaka (Japan)

1998-01-05

White Ring is a citizen`s gymnasium used for figure skating and short track speed skating games of 18th Winter Olympic Games in 1998. White Ring is composed of a main-arena and a sub-arena. For the main-arena with an area 41mtimes66m, an ice link can be made by disengaging the potable floor and by flowing brine in the bridged polystyrene pipes embedded in the concrete floor. Due to the fortunate groundwater in this site, well water is used for the outside air treatment energy in 63% during heating and in 35% during cooling. Ammonia is used as a cooling medium for refrigerating facility. For the heating of audience area in the large space, heat load from the outside is reduced by enhancing the heat insulation performance of the roof of arena. The audience seats are locally heated using heaters. For the White Ring, high quality environment is realized for games through various functions of the large-scale roof of the large space. Success of the big event was expected. 15 figs., 4 tabs.

Token Ring Project

Directory of Open Access Journals (Sweden)

Adela Ionescu

2007-01-01

Full Text Available Ring topology is a simple configuration used to connect processes that communicate among themselves. A number of network standards such as token ring, token bus, and FDDI are based on the ring connectivity. This article will develop an implementation of a ring of processes that communicate among themselves via pipe links. The processes are nodes in the ring. Each process reads from its standard input and writes in its standard output. N-1 process redirects the its standard output to a standard input of the process through a pipe. When the ring-structure is designed, the project can be extended to simulate networks or to implement algorithms for mutual exclusion

Spin dynamics and quantum tunneling in Fe8 nanomagnet and in AFM rings by NMR

Science.gov (United States)

Baek, Seung-Ho

In this thesis, our main interest has been to investigate the spin dynamics and quantum tunneling in single molecule magnets (SMMs). For this we have selected two different classes of SMMs: a ferromagnetic total high spin S = 10 cluster Fe8 and antiferromagnetic (AFM) ring-type clusters. For Fe8, our efforts have been devoted to the investigation of the quantum tunneling of magnetization in the very low temperature region. The most remarkable experimental finding in Fe8 is that the nuclear spin-lattice relaxation rate (1/T1) at low temperatures takes place via strong collision mechanism, and thus it allows to measure directly the tunneling rate vs. T and H for the first time. For AFM rings, we have shown that 1/T1 probes the thermal fluctuations of the magnetization in the intermediate temperature range. We find that the fluctuations are dominated by a single characteristic frequency which has a power-law T-dependence indicative of fluctuations due to electron-acoustic phonon interactions.

Spin Dynamics and Quantum Tunneling in Fe8 Nanomagnet and in AFM Rings by NMR

International Nuclear Information System (INIS)

Seung-Ho-Baek

2004-01-01

In this thesis, our main interest has been to investigate the spin dynamics and quantum tunneling in single molecule magnets (SMMs), For this we have selected two different classes of SMMs: a ferrimagnetic total high spin S = 10 cluster Fe8 and antiferromagnetic (AFM) ring-type clusters. For Fe8, our efforts have been devoted to the investigation of the quantum tunneling of magnetization in the very low temperature region. The most remarkable experimental finding in Fe8 is that the nuclear spin-lattice relaxation rate (1/T l ) at low temperatures takes place via strong collision mechanism, and thus it allows to measure directly the tunneling rate vs T and H for the first time. For AFM rings, we have shown that 1/T l probes the thermal fluctuations of the magnetization in the intermediate temperature range. We find that the fluctuations are dominated by a single characteristic frequency which has a power law T-dependence indicative of fluctuations due to electron-acoustic phonon interactions

Three dimensional atom probe imaging of GaAsSb quantum rings.

Science.gov (United States)

Beltrán, A M; Marquis, E A; Taboada, A G; Ripalda, J M; García, J M; Molina, S I

2011-07-01

Unambiguous evidence of ring-shaped self-assembled GaSb nanostructures grown by molecular beam epitaxy is presented on the basis of atom-probe tomography reconstructions and dark field transmission electron microscopy imaging. The GaAs capping process causes a strong segregation of Sb out of the center of GaSb quantum dots, leading to the self-assembled GaAs(x)Sb(1-x) quantum rings of 20-30 nm in diameter with x ∼ 0.33. Copyright © 2011 Elsevier B.V. All rights reserved.

Semi-algebraic function rings and reflectors of partially ordered rings

CERN Document Server

Schwartz, Niels

1999-01-01

The book lays algebraic foundations for real geometry through a systematic investigation of partially ordered rings of semi-algebraic functions. Real spectra serve as primary geometric objects, the maps between them are determined by rings of functions associated with the spectra. The many different possible choices for these rings of functions are studied via reflections of partially ordered rings. Readers should feel comfortable using basic algebraic and categorical concepts. As motivational background some familiarity with real geometry will be helpful. The book aims at researchers and graduate students with an interest in real algebra and geometry, ordered algebraic structures, topology and rings of continuous functions.

Rotating ring-ring electrode theory and experiment

NARCIS (Netherlands)

Kuiken, H.K.; Bakkers, E.P.A.M.; Ligthart, H.; Kellyb, J.J.

2000-01-01

A model is presented for the rotating ring-ring electrode. Although the electrode is defined by four characteristic lengths, it is shown that the collection efficiency depends on only two dimensionless parameters. A simple relationship between these and the corresponding parameters for the rotating

75 FR 77475 - Endangered and Threatened Species; Proposed Threatened Status for Subspecies of the Ringed Seal

Science.gov (United States)

2010-12-10

... underwent independent peer review by five scientists with expertise in ringed seal biology, Arctic sea ice... in the lee of ice hummocks. The seasonality of ice cover strongly influences ringed seal movements... sufficient for lair formation only where pressure ridges or ice hummocks cause the snow to form drifts at...

Propagation and collision of soliton rings in quantum semiconductor plasmas

International Nuclear Information System (INIS)

El-Shamy, E.F.; Gohman, F.S.

2014-01-01

The intrinsic localization of electrostatic wave energies in quantum semiconductor plasmas can be described by solitary pulses. The collision properties of these pulses are investigated. In the present study, the fundamental model includes the quantum term, degenerate pressure of the plasma species, and the electron/hole exchange–correlation effects. In cylindrical geometry, using the extended Poincaré–Lighthill–Kuo (PLK) method, the Korteweg–de Vries (KdV) equations and the analytical phase shifts after the collision of two soliton rings are derived. Typical values for GaSb and GaN semiconductors are used to estimate the basic features of soliton rings. It is found that the pulses of GaSb semiconductor carry more energies than the pulses of GaN semiconductor. In addition, the degenerate pressure terms of electrons and holes have strong impact on the phase shift. The present theory may be useful to analyze the collision of localized coherent electrostatic waves in quantum semiconductor plasmas. - Highlights: • The propagation and the collision of pulses in quantum semiconductor plasmas are studied. • Numerical calculations reveal that pulses may exist only in dark soliton rings for electron–hole quantum plasmas. • Typical values for GaSb and GaN semiconductors are used to estimate the basic features of soliton rings. • It is found that the pulses of GaSb semiconductor carry more energies than the pulses of GaN semiconductor. • The degenerate pressure terms of electrons and holes have strong impact on the phase shift

Structure–Activity Relationship of Oligomeric Flavan-3-ols: Importance of the Upper-Unit B-ring Hydroxyl Groups in the Dimeric Structure for Strong Activities

Directory of Open Access Journals (Sweden)

Yoshitomo Hamada

2015-10-01

Full Text Available Proanthocyanidins, which are composed of oligomeric flavan-3-ol units, are contained in various foodstuffs (e.g., fruits, vegetables, and drinks and are strongly biologically active compounds. We investigated which element of the proanthocyanidin structure is primarily responsible for this functionality. In this study, we elucidate the importance of the upper-unit of 4–8 condensed dimeric flavan-3-ols for antimicrobial activity against Saccharomyces cerevisiae (S. cerevisiae and cervical epithelioid carcinoma cell line HeLa S3 proliferation inhibitory activity. To clarify the important constituent unit of proanthocyanidin, we synthesized four dimeric compounds, (−-epigallocatechin-[4,8]-(+-catechin, (−-epigallocatechin-[4,8]-(−-epigallocatechin, (−-epigallocatechin-[4,8]-(−-epigallocatechin-3-O-gallate, and (+-catechin-[4,8]-(−-epigallocatechin and performed structure–activity relationship (SAR studies. In addition to antimicrobial activity against S. cerevisiae and proliferation inhibitory activity on HeLa S3 cells, the correlation of 2,2-diphenyl-l-picrylhydrazyl radical scavenging activity with the number of phenolic hydroxyl groups was low. On the basis of the results of our SAR studies, we concluded that B-ring hydroxyl groups of the upper-unit of the dimer are crucially important for strong and effective activity.

Accretion in Saturn's F Ring

Science.gov (United States)

Meinke, B. K.; Esposito, L. W.; Stewart, G.

2012-12-01

Saturn's F ring is the solar system's principal natural laboratory for direct observation of accretion and disruption processes. The ring resides in the Roche zone, where tidal disruption competes with self-gravity, which allows us to observe the lifecycle of moonlets. Just as nearby moons create structure at the B ring edge (Esposito et al. 2012) and the Keeler gap (Murray 2007), the F ring "shepherding" moons Prometheus and Pandora stir up ring material and create observably changing structures on timescales of days to decades. In fact, Beurle et al (2010) show that Prometheus makes it possible for "distended, yet gravitationally coherent clumps" to form in the F ring, and Barbara and Esposito (2002) predicted a population of ~1 km bodies in the ring. In addition to the observations over the last three decades, the Cassini Ultraviolet Imaging Spectrograph (UVIS) has detected 27 statistically significant features in 101 occultations by Saturn's F ring since July 2004. Seventeen of those 27 features are associated with clumps of ring material. Two features are opaque in occultation, which makes them candidates for solid objects, which we refer to as Moonlets. The 15 other features partially block stellar signal for 22 m to just over 3.7 km along the radial expanse of the occultation. Upon visual inspection of the occultation profile, these features resemble Icicles, thus we will refer to them as such here. The density enhancements responsible for such signal attenuations are likely due to transient clumping of material, evidence that aggregations of material are ubiquitous in the F ring. Our lengthy observing campaign reveals that Icicles are likely transient clumps, while Moonlets are possible solid objects. Optical depth is an indicator of clumping because more-densely aggregated material blocks more light; therefore, it is natural to imagine moonlets as later evolutionary stage of icicle, when looser clumps of material compact to form a feature that appears

Influences of magma chamber ellipticity on ring fracturing and eruption at collapse calderas

International Nuclear Information System (INIS)

Holohan, Eoghan P; Walsh, John J; Vries, Benjamin van Wyk de; Troll, Valentin R; Walter, Thomas R

2008-01-01

Plan-view ellipticity of a pre-caldera magma reservoir, and its influence on the development of caldera ring fracturing and eruptive behaviour, have not previously been subjected to dedicated evaluation. We experimentally simulated caldera collapse into elliptical magma chambers and found that collapse into highly-elliptical chambers produced a characteristic pattern of ring-fault localization and lateral propagation. Although results are preliminary, the general deformation pattern for elliptical resurgence shows strong similarities to elliptical collapse. Ring faults accommodating uplift again initiate around the chamberos short axis and are reverse, but dip inward. Field and geophysical observations at several elliptical calderas of varying scale (e.g. Long Valley, Katmai, and Rabaul calderas) are consistent with a control from elliptical magma chamber geometry on ring fracturing and eruption, as predicted from our experiments.

Influences of magma chamber ellipticity on ring fracturing and eruption at collapse calderas

Energy Technology Data Exchange (ETDEWEB)

Holohan, Eoghan P; Walsh, John J [Fault Analysis Group, School of Geological Sciences, University College Dublin, Belfield, Dublin 4 (Ireland); Vries, Benjamin van Wyk de [Laboratoire Magmas et Volcans, 5 rue Kessler, 63038 Clermont-Ferrand (France); Troll, Valentin R [Department of Earth Sciences, Uppsala University, SE-752 36, Uppsala (Sweden); Walter, Thomas R [GFZ Potsdam, Telegrafenberg, Potsdam, D-14473 (Germany)], E-mail: Eoghan.Holohan@ucd.ie

2008-10-01

Plan-view ellipticity of a pre-caldera magma reservoir, and its influence on the development of caldera ring fracturing and eruptive behaviour, have not previously been subjected to dedicated evaluation. We experimentally simulated caldera collapse into elliptical magma chambers and found that collapse into highly-elliptical chambers produced a characteristic pattern of ring-fault localization and lateral propagation. Although results are preliminary, the general deformation pattern for elliptical resurgence shows strong similarities to elliptical collapse. Ring faults accommodating uplift again initiate around the chamberos short axis and are reverse, but dip inward. Field and geophysical observations at several elliptical calderas of varying scale (e.g. Long Valley, Katmai, and Rabaul calderas) are consistent with a control from elliptical magma chamber geometry on ring fracturing and eruption, as predicted from our experiments.

INMS measures an influx of molecules from Saturn's rings

Science.gov (United States)

Perry, M. E.

2017-12-01

In 1984, Connerney and Waite proposed water influx from Saturn's rings to explain the low electron densities measured during Pioneer and Voyager radio occultation experiments. Charge exchange with this minor species depleted the H+ ions and provided a faster path to electron recombination. With ice the primary constituent of the rings, water was the most likely in-falling molecule. During the Grand Finale orbits, Cassini's Ion and Neutral Mass Spectrometer (INMS) detected and quantified an influx from the rings. Unexpectedly, the primary influx molecules are CH4 and a heavier carbon-bearing species. Water was detected, but quantities were factors of ten lower than these other species. Distribution in both altitude and latitude are consistent with a ring influx. The concentration of the minor species in Saturn's atmosphere shows that they enter Saturn's atmosphere from the top. Both molecules have their highest concentrations at the highest altitudes, with concentrations >0.4% at 3,500 km altitude and only 0.02% at 2,700 km. Molecules from the rings deorbit to Saturn's atmosphere at altitudes near 4,000 km, consistent with the INMS measurements. The latitudinal dependence of the minor species indicates that their source is near the equatorial plane. At high altitudes, the minor species were observed primarily at zero latitude, where the 28u species was six times more concentrated than at 5° latitude. At lower altitudes, the peaking ratio was 1, indicating that the species had diffused and was fully mixed into Saturn's H2 atmosphere. The lighter molecule, CH4, diffuses more rapidly than the 28u species. INMS also detected both of these species during the earlier F-ring passes, finding that the neutrals were centered at the ring plane and extended 3,000 km (half width, half max) north and south.

Kayser-Fleischer Rings

Science.gov (United States)

... Support Contacts Lab Tracker/Copper Calculator Stories Programs & Research ... About Everything you need to know about Wilson Disease Kayser-Fleischer Rings Definition Kayser-Fleischer Ring: Clinical sign. Brownish-yellow ring visible around the corneo- ...

Planetary Rings

Science.gov (United States)

Nicholson, P. D.

2001-11-01

A revolution in the studies in planetary rings studies occurred in the period 1977--1981, with the serendipitous discovery of the narrow, dark rings of Uranus, the first Voyager images of the tenuous jovian ring system, and the many spectacular images returned during the twin Voyager flybys of Saturn. In subsequent years, ground-based stellar occultations, HST observations, and the Voyager flybys of Uranus (1986) and Neptune (1989), as well as a handful of Galileo images, provided much additional information. Along with the completely unsuspected wealth of detail these observations revealed came an unwelcome problem: are the rings ancient or are we privileged to live at a special time in history? The answer to this still-vexing question may lie in the complex gravitational interactions recent studies have revealed between the rings and their retinues of attendant satellites. Among the four known ring systems, we see elegant examples of Lindblad and corotation resonances (first invoked in the context of galactic disks), electromagnetic resonances, spiral density waves and bending waves, narrow ringlets which exhibit internal modes due to collective instabilities, sharp-edged gaps maintained via tidal torques from embedded moonlets, and tenuous dust belts created by meteoroid impact onto parent bodies. Perhaps most puzzling is Saturn's multi-stranded, clumpy F ring, which continues to defy a simple explanation 20 years after it was first glimpsed in grainy images taken by Pioneer 11. Voyager and HST images reveal a complex, probably chaotic, dynamical interaction between unseen parent bodies within this ring and its two shepherd satellites, Pandora and Prometheus. The work described here reflects contributions by Joe Burns, Jeff Cuzzi, Luke Dones, Dick French, Peter Goldreich, Colleen McGhee, Carolyn Porco, Mark Showalter, and Bruno Sicardy, as well as those of the author. This research has been supported by NASA's Planetary Geology and Geophysics program and the

Beam-beam force and storage ring parameters

International Nuclear Information System (INIS)

Herrera, J.C.

1979-01-01

The fundamental aspects of the beam--beam force as it occurs in Intersecting Storage Rings are reported. The way in which the effect of the beam--particle electromagnetic force (weak--strong interaction) is different in the case of unbunched proton beams which cross each other at an angle (as in the ISR and in ISABELLE) is shown, as compared to the case of electron--positron beams where bunches collide head-on

Relating ring width of Mediterranean evergreen species to seasonal and annual variations of precipitation and temperature

Science.gov (United States)

Nijland, W.; Jansma, E.; Addink, E. A.; Domínguez Delmás, M.; de Jong, S. M.

2011-05-01

Plant growth in Mediterranean landscapes is limited by the typical summer-dry climate. Forests in these areas are only marginally productive and may be quite susceptible to modern climate change. To improve our understanding of forest sensitivity to annual and seasonal climatic variability, we use tree-ring measurements of two Mediterranean evergreen tree species: Quercus ilex L. and Arbutus unedo L. We sampled 34 stems of these species on three different types of substrates in the Peyne study area in southern France. The resulting chronologies were analysed in combination with 38 yr of monthly precipitation and temperature data to reconstruct the response of stem growth to climatic variability. Results indicate a strong positive response to May and June precipitation, as well as a significant positive influence of early-spring temperatures and a negative growth response to summer heat. Comparison of the data with more detailed productivity measurements in two contrasting years confirms these observations and shows a strong productivity limiting effect of low early-summer precipitation. The results show that tree-ring data from Q.ilex and A.unedo can provide valuable information about the response of these tree species to climate variability, improving our ability to predict the effects of climate change in Mediterranean ecosystems.

Development and status of superconducting SR-ring

International Nuclear Information System (INIS)

Toyota, Eijiro; Tomimasu, Takio.

1991-01-01

Recently, attention has been paid to synchrotron radiation as a powerful tool for material science research, and for the most advanced research, stronger beam is sought for, therefore, large scale synchrotron radiation source facilities are going to be constructed. In contrast with the move toward large scale like this, effort is exerted to reduce the size by using superconductivity and to utilize for industries. Especially Japan precedes most in this field, and has already succeeded in the beam generation. This move to reduce size and pursue economic efficiency is noteworthy as that of supplementing the trend to large scale on the other hand, and its outline is explained. Synchrotron radiation means the strong beam emitted in tangential direction when the electrons or positrons moving at the velocity close to the velocity of light are bent in a magnetic field. The device which stably generates synchrotron radiation is an electron storage ring. The features of synchrotron radiation are explained. The history of synchrotron radiation research, the trend of development of superconducting synchrotron radiation ring, the actual examples of superconducting SR rings and their problems are described. (K.I.)

Morphological survey of bar, lens, and ring components in galaxies: Secular evolution in galaxy structure

International Nuclear Information System (INIS)

Kormendy, J.

1979-01-01

A morphological survey of barred galaxies is made to investigate the frequency of occurrence, nature, and size distributions of bars, lenses, inner and outer rings, and global spiral structure. The 121 brightest available barred galaxies are examined on Sky Survey copy plates, and on deeper and larger-scale plates, with the following main results.1. Lenses and inner rings are components of major importance in barred galaxies, occurring, respectively, in 54% of SBO--SBa, and 76% of SBab--SBc galaxies. Few early-type galaxies have rings; almost no late-type ones have lenses.2. There is an intimate connection between bars and lenses: in 17 of 20 galaxies with both components, the bar exactly fills the lens in one dimension.3. We suggest that lenses originate as bars, through an unknown process which makes some bars evolve away to a nearly axisymmetric state. Several properties of the proposed process are deduced. We emphasize the possible importance of internal processes of secular evolution in galaxy structure.4. Several galaxies, notably NGC 3945, seem to have strongly triaxial bulge components.5. Inner rings are round. Lenses tend to be slightly triaxial, flattened ellipsoids, with a preferred equatorial axis ratio of approx.0.9 +- 0.05. Most outer rings are prolate, the shortest dimension being the one filled by the bar.6. The sizes of bars, rings, and lenses are well correlated with the absolute magnitude of the galaxy, such that the mean surface brightness is constant for each morphological type. The form of the correlation M/sub B/+5 log D= constant is such that these diameters cannot be used as distance indicators. We show that the galaxy mass determines the bar size uniquely.7. Spiral structure in SB galaxies is distorted to resemble inner and outer rings, showing that the arms feel the potential of the bar. Also, of 61 survey galaxies with spiral structure, 55 have global patterns usually interpreted as density waves

A Computer Vision Approach to Identify Einstein Rings and Arcs

Science.gov (United States)

Lee, Chien-Hsiu

2017-03-01

Einstein rings are rare gems of strong lensing phenomena; the ring images can be used to probe the underlying lens gravitational potential at every position angles, tightly constraining the lens mass profile. In addition, the magnified images also enable us to probe high-z galaxies with enhanced resolution and signal-to-noise ratios. However, only a handful of Einstein rings have been reported, either from serendipitous discoveries or or visual inspections of hundred thousands of massive galaxies or galaxy clusters. In the era of large sky surveys, an automated approach to identify ring pattern in the big data to come is in high demand. Here, we present an Einstein ring recognition approach based on computer vision techniques. The workhorse is the circle Hough transform that recognise circular patterns or arcs in the images. We propose a two-tier approach by first pre-selecting massive galaxies associated with multiple blue objects as possible lens, than use Hough transform to identify circular pattern. As a proof-of-concept, we apply our approach to SDSS, with a high completeness, albeit with low purity. We also apply our approach to other lenses in DES, HSC-SSP, and UltraVISTA survey, illustrating the versatility of our approach.

Preparation for electron ring - plasma ring merging experiments in RECE-MERGE

International Nuclear Information System (INIS)

Taggart, D.; Sekiguchi, A.; Fleischmann, H.H.

1986-01-01

The formation of a mixed-CT using relativistic electron rings and gun-produced plasma rings by MERGE-ing them axially is simulated. This process is similar to the axial stacking of relativistic electron rings in RECE-Christa. The results of their first plasm production experiment are reported here. After study of the gun-produced plasma's properties is completed, the gun will be mounted at the downstream end of the vacuum tank and the source of relativistic electron rings will be at the upstream end. The two rings, formed at opposite ends of the tank, will be translated axially and merged

Exploring the Strengths and Limits of Strong and Weak Sustainability Indicators: A Case Study of the Assessment of China’s Megacities with EF and GPI

Directory of Open Access Journals (Sweden)

Lu Huang

2018-01-01

Full Text Available The perspective of strong/weak sustainability has a great impact on sustainability assessment. In this study, two most widely used indices, Ecological Footprint (EF and Genuine Progress Indicator (GPI for strong and weak sustainability assessment, were employed to evaluate the sustainability of China’s ten megacities between 1978 and 2015. The results showed that the ecological footprint had been enlarged in the past twenty years; while the genuine economic welfare started to increase since 2005. The cities of Xi’an, Chengdu, Chongqing, and Shanghai met the threshold of below 2.5 global hectares for EF/capita, and over 3000 dollars/capita (in 2010 US$ for GPI/capita. By analyzing and comparing the characteristics, the processes and results, and the complementary features of evaluation methods of EF and GPI, the research suggested that: (1 Strong and weak sustainability indicators, with their own pros/cons in sustainability assessment, should be used carefully; (2 Weak sustainability indicators could be analyzed from the perspective of strong sustainability; (3 Strong sustainability indicators need to be developed urgently. The results in this study could guide the selection of sustainability indicators, and help interpret the results of sustainability assessment.

Vibration of Elastic Functionally Graded Thick Rings

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Guang-Hui Xu

2017-01-01

Full Text Available The free vibration behaviors of functionally graded rings were investigated theoretically. The material graded in the thickness direction according to the power law rule and the rings were assumed to be in plane stress and plane strain states. Based on the first-order shear deformation theory and the kinetic relation of von Kárman type, the frequency equation for free vibration of functionally graded ring was derived. The derived results were verified by those in literatures which reveals that the present theory can be appropriate to predict the free vibration characteristics for quite thick rings with the radius-to-thickness ratio from 60 down to 2.09. Comparison between the plane stress case and the plane strain case indicates a slight difference. Meanwhile, the effects of the structural dimensional parameters and the material inhomogeneous parameter are examined. It is interesting that the value of the logarithmic form of vibration frequency is inversely proportional to the logarithmic form of the radius-to-thickness ratio or the mean radius.

Health effects associated with exposure to radioactively contaminated gold rings

International Nuclear Information System (INIS)

Baptiste, M.S.; Rothenberg, R.; Nasca, P.C.; Janerich, D.T.; Stutzman, C.D.; Rimawi, K.; O'Brien, W.; Matuszek, J.

1984-01-01

This study was designed to assess the health risks associated with exposure to radioactively contaminated gold rings. A group of 135 exposed individuals, who were identified through a statewide jewelry screening program, were studied to determine the frequency of carcinoma and other skin problems on the ring finger. Severity of skin problems increased with increasing length of wear. Forty-one of the exposures were associated with mild to severe skin problems. Nine of the individuals studied were diagnosed as having histologically confirmed squamous cell carcinomas at the site of exposure. The incidence of skin cancer on the ring finger was eleven times that expected for men and forty-five times that expected for women. These data indicate that physicians who have patients with skin lesions of the ring finger should be aware of the possibility of exposure to a radioactive gold ring

Rings Research in the Next Decade

Science.gov (United States)

Burns, J. A.; Tiscareno, M. S.

2009-12-01

The study of planetary ring systems forms a key component of planetary science for several reasons: 1) The evolution and current states of planets and their satellites are affected in many ways by rings, while 2) conversely, properties of planets and moons and other solar system populations are revealed by their effects on rings; 3) highly structured and apparently delicate ring systems may be bellwethers, constraining various theories of the origin and evolution of their entire planetary system; and finally, 4) planetary rings provide an easily observable analogue to other astrophysical disk systems, enabling real “ground truth” results applicable to disks much more remote in space and/or time, including proto-planetary disks, circum-stellar disks, and even galaxies. Significant advances have been made in rings science in the past decade. The highest-priority rings research recommendations of the last Planetary Science Decadal Survey were to operate and extend the Cassini orbiter mission at Saturn; this has been done with tremendous success, accounting for much of the progress made on key science questions, as we will describe. Important progress in understanding the rings of Saturn and other planets has also come from Earth-based observational and theoretical work, again as prioritized by the last Decadal Survey. However, much important work remains to be done. At Saturn, the Cassini Solstice Mission must be brought to a successful completion. Priority should also be placed on sending spacecraft to Neptune and/or Uranus, now unvisited for more than 20 years. At Jupiter and Pluto, opportunities afforded by visiting spacecraft capable of studying rings should be exploited. On Earth, the need for continued research and analysis remains strong, including in-depth analysis of rings data already obtained, numerical and theoretical modeling work, laboratory analysis of materials and processes analogous to those found in the outer solar system, and continued Earth

Molecular spectrum of laterally coupled quantum rings under intense terahertz radiation.

Science.gov (United States)

Baghramyan, Henrikh M; Barseghyan, Manuk G; Laroze, David

2017-09-05

We study the influence of intense THz laser radiation and electric field on molecular states of laterally coupled quantum rings. Laser radiation shows the capability to dissociate quantum ring molecule and add 2-fold degeneracy to the molecular states at the fixed value of the overlapping size between rings. It is shown that coupled to decoupled molecular states phase transition points form almost a straight line with a slope equal to two. In addition, the electric field direction dependent energy spectrum shows unexpected oscillations, demonstrating strong coupling between molecular states. Besides, intraband absorption is considered, showing both blue and redshifts in its spectrum. The obtained results can be useful for the controlling of degeneracy of the discrete energy spectrum of nanoscale structures and in the tunneling effects therein.

Comparing Sources of Storm-Time Ring Current O+

Science.gov (United States)

Kistler, L. M.

2015-12-01

The first observations of the storm-time ring current composition using AMPTE/CCE data showed that the O+ contribution to the ring current increases significantly during storms. The ring current is predominantly formed from inward transport of the near-earth plasma sheet. Thus the increase of O+ in the ring current implies that the ionospheric contribution to the plasma sheet has increased. The ionospheric plasma that reaches the plasma sheet can come from both the cusp and the nightside aurora. The cusp outflow moves through the lobe and enters the plasma sheet through reconnection at the near-earth neutral line. The nightside auroral outflow has direct access to nightside plasma sheet. Using data from Cluster and the Van Allen Probes spacecraft, we compare the development of storms in cases where there is a clear input of nightside auroral outflow, and in cases where there is a significant cusp input. We find that the cusp input, which enters the tail at ~15-20 Re becomes isotropized when it crosses the neutral sheet, and becomes part of the hot (>1 keV) plasma sheet population as it convects inward. The auroral outflow, which enters the plasma sheet closer to the earth, where the radius of curvature of the field line is larger, does not isotropize or become significantly energized, but remains a predominantly field aligned low energy population in the inner magnetosphere. It is the hot plasma sheet population that gets accelerated to high enough energies in the inner magnetosphere to contribute strongly to the ring current pressure. Thus it appears that O+ that enters the plasma sheet further down the tail has a greater impact on the storm-time ring current than ions that enter closer to the earth.

Ballistic Transport: After the Cassini Grand Finale, is there a Final Consensus on Ring Origin and Age?

Science.gov (United States)

Estrada, P. R.; Durisen, R. H.; Cuzzi, J. N.

2017-12-01

As the Cassini mission comes to its much anticipated end, somewhat befittingly to be immortalized and enshrined for all time within the gaseous confines of a planet named for the Greek god of time (Kronos), we find the time appropriate to return to the subject of ring age and origin. During Cassini's remarkable tenure, important measurements have been obtained that can help to elucidate and perhaps settle the debate once and for all on whether the rings are young or old. At the forefront lie the results of the Cassini Dust Analyzer (CDA) experiment which indicate that the range of the micrometeoroid flux at infinity for Saturn are comparable to the nominal value of the meteoroid flux value currently adopted for use in ballistic transport (BT) applications and models (Estrada et al., 2015, 2017). Moreover, the source of the micrometeoroid flux has been localized to the Edgeworth-Kuiper Belt (EKB) and is not cometary in origin as previously assumed (Altobelli et al., 2015). A major consequence of these measurements is that the EKB flux is much more gravitationally focused increasing the impact flux on the rings by a factor of ˜25 relative to cometary. This implies that the process of micrometeoroid bombardment and BT is likely even more influential in the rings' structural and compositional evolution over time. This measurement taken together with recent analysis of the bulk mass fraction of non-icy constituents (Zhang et al., 2017a,b) using Cassini radiometry data argue strongly for young rings. Another observation that will help to provide a constraint (though not absolute) is the pending measurement of the (B) ring mass. A high mass estimate as argued by some does not necessarily mean old rings, whereas a low mass ring would certainly imply as much. There are several factors that can offer insight on to the age of the rings from BT modeling, such as saturation of the ramp(s), color differences across the B-C (A-CD) boundaries, color differences across plateaus

Cassini UVIS solar occultations by Saturn's F ring and the detection of collision-produced micron-sized dust

Science.gov (United States)

Becker, Tracy M.; Colwell, Joshua E.; Esposito, Larry W.; Attree, Nicholas O.; Murray, Carl D.

2018-05-01

We present an analysis of eleven solar occultations by Saturn's F ring observed by the Ultraviolet Imaging Spectrograph (UVIS) on the Cassini spacecraft. In four of the solar occultations we detect an unambiguous signal from diffracted sunlight that adds to the direct solar signal just before or after the occultations occur. The strongest detection was a 10% increase over the direct signal that was enabled by the accidental misalignment of the instrument's pointing. We compare the UVIS data with images of the F ring obtained by the Cassini Imaging Science Subsystem (ISS) and find that in each instance of an unambiguous diffraction signature in the UVIS data, the ISS data shows that there was a recent disturbance in that region of the F ring. Similarly, the ISS images show a quiescent region of the F ring for all solar occultations in which no diffraction signature was detected. We therefore conclude that collisions in the F ring produce a population of small ring particles that can produce a detectable diffraction signal immediately interior or exterior to the F ring. The clearest example of this connection comes from the strong detection of diffracted light in the 2007 solar occultation, when the portion of the F ring that occulted the Sun had suffered a large collisional event, likely with S/2004 S 6, several months prior. This collision was observed in a series of ISS images (Murray et al., 2008). Our spectral analysis of the data shows no significant spectral features in the F ring, indicating that the particles must be at least 0.2 μm in radius. We apply a forward model of the solar occultations, accounting for the effects of diffracted light and the attenuated direct solar signal, to model the observed solar occultation light curves. These models constrain the optical depth, radial width, and particle size distribution of the F ring. We find that when the diffraction signature is present, we can best reproduce the occultation data using a particle population

Groups, rings, modules

CERN Document Server

Auslander, Maurice

2014-01-01

This classic monograph is geared toward advanced undergraduates and graduate students. The treatment presupposes some familiarity with sets, groups, rings, and vector spaces. The four-part approach begins with examinations of sets and maps, monoids and groups, categories, and rings. The second part explores unique factorization domains, general module theory, semisimple rings and modules, and Artinian rings. Part three's topics include localization and tensor products, principal ideal domains, and applications of fundamental theorem. The fourth and final part covers algebraic field extensions

Saturn's Rings Edge-on

Science.gov (United States)

1995-01-01

In one of nature's most dramatic examples of 'now-you see-them, now-you-don't', NASA's Hubble Space Telescope captured Saturn on May 22, 1995 as the planet's magnificent ring system turned edge-on. This ring-plane crossing occurs approximately every 15 years when the Earth passes through Saturn's ring plane.For comparison, the top picture was taken by Hubble on December 1, 1994 and shows the rings in a more familiar configuration for Earth observers.The bottom picture was taken shortly before the ring plane crossing. The rings do not disappear completely because the edge of the rings reflects sunlight. The dark band across the middle of Saturn is the shadow of the rings cast on the planet (the Sun is almost 3 degrees above the ring plane.) The bright stripe directly above the ring shadow is caused by sunlight reflected off the rings onto Saturn's atmosphere. Two of Saturn's icy moons are visible as tiny starlike objects in or near the ring plane. They are, from left to right, Tethys (slightly above the ring plane) and Dione.This observation will be used to determine the time of ring-plane crossing and the thickness of the main rings and to search for as yet undiscovered satellites. Knowledge of the exact time of ring-plane crossing will lead to an improved determination of the rate at which Saturn 'wobbles' about its axis (polar precession).Both pictures were taken with Hubble's Wide Field Planetary Camera 2. The top image was taken in visible light. Saturn's disk appears different in the bottom image because a narrowband filter (which only lets through light that is not absorbed by methane gas in Saturn's atmosphere) was used to reduce the bright glare of the planet. Though Saturn is approximately 900 million miles away, Hubble can see details as small as 450 miles across.The Wide Field/Planetary Camera 2 was developed by the Jet Propulsion Laboratory and managed by the Goddard Spaced Flight Center for NASA's Office of Space Science.This image and other images and

The Rotating Ring-Ring Electrode. Theory and Experiment

NARCIS (Netherlands)

Kuiken, H.K.; Bakkers, E.P.A.M.; Ligthart, H.; Kelly, J.J.

2000-01-01

A model is presented for the rotating ring-ring electrode. Although the electrode is defined by four characteristic lengths, it is shown that the collection efficiency depends on only two dimensionless parameters. A simple relationship between these and the corresponding parameters for the rotating

Wear Analysis of Top Piston Ring to Reduce Top Ring Reversal Bore Wear

Directory of Open Access Journals (Sweden)

P. Ilanthirayan

2017-12-01

Full Text Available The piston rings are the most important part in engine which controls the lubricating oil consumption and blowby of the gases. The lubricating film of oil is provided to seal of gases towards crankcase and also to give smooth friction free translatory motion between rings and liner. Of the three rings present top ring is more crucial as it does the main work of restricting gases downwards the crankcase. Boundary lubrication is present at the Top dead centre (TDC and Bottom dead centre (BDC of the liner surface. In addition to this, top ring is exposed to high temperature gases which makes the oil present near the top ring to get evaporated and decreasing its viscosity, making metal-metal contact most of the time. Due to this at TDC, excess wear happens on the liner which is termed as Top ring reversal bore wear. The wear rate depends upon many parameters such as lubrication condition, viscosity index, contact type, normal forces acting on ring, geometry of ring face, surface roughness, material property. The present work explores the wear depth for different geometries of barrel ring using Finite Element model with the help of Archard wear law and the same is validated through experimentation. The study reveals that Asymmetric barrel rings have less contact pressure which in turn reduces the wear at Top dead centre.

Drop impact entrapment of bubble rings

KAUST Repository

Thoraval, M.-J.

2013-04-29

We use ultra-high-speed video imaging to look at the initial contact of a drop impacting on a liquid layer. We observe experimentally the vortex street and the bubble-ring entrapments predicted numerically, for high impact velocities, by Thoraval et al. (Phys. Rev. Lett., vol. 108, 2012, article 264506). These dynamics mainly occur within 50 -s after the first contact, requiring imaging at 1 million f.p.s. For a water drop impacting on a thin layer of water, the entrapment of isolated bubbles starts through azimuthal instability, which forms at low impact velocities, in the neck connecting the drop and pool. For Reynolds number Re above -12 000, up to 10 partial bubble rings have been observed at the base of the ejecta, starting when the contact is -20% of the drop size. More regular bubble rings are observed for a pool of ethanol or methanol. The video imaging shows rotation around some of these air cylinders, which can temporarily delay their breakup into micro-bubbles. The different refractive index in the pool liquid reveals the destabilization of the vortices and the formation of streamwise vortices and intricate vortex tangles. Fine-scale axisymmetry is thereby destroyed. We show also that the shape of the drop has a strong influence on these dynamics. 2013 Cambridge University Press.

PREFACE: Special section on vortex rings Special section on vortex rings

Science.gov (United States)

Fukumoto, Yasuhide

2009-10-01

This special section of Fluid Dynamics Research includes five articles on vortex rings in both classical and quantum fluids. The leading scientists of the field describe the trends in and the state-of-the-art development of experiments, theories and numerical simulations of vortex rings. The year 2008 was the 150th anniversary of 'vortex motion' since Hermann von Helmholtz opened up this field. In 1858, Helmholtz published a paper in Crelle's Journal which put forward the concept of 'vorticity' and made the first analysis of vortex motion. Fluid mechanics before that was limited to irrotational motion. In the absence of vorticity, the motion of an incompressible homogeneous fluid is virtually equivalent to a rigid-body motion in the sense that the fluid motion is determined once the boundary configuration is specified. Helmholtz proved, among other things, that, without viscosity, a vortex line is frozen into the fluid. This Helmholtz's law immediately implies the preservation of knots and links of vortex lines and its implication is enormous. One of the major trends of fluid mechanics since the latter half of the 20th century is to clarify the topological meaning of Helmholtz's law and to exploit it to develop theoretical and numerical methods to find the solutions of the Euler equations and to develop experimental techniques to gain an insight into fluid motion. Vortex rings are prominent coherent structures in a variety of fluid motions from the microscopic scale, through human and mesoscale to astrophysical scales, and have attracted people's interest. The late professor Philip G Saffman (1981) emphasized the significance of studies on vortex rings. One particular motion exemplifies the whole range of problems of vortex motion and is also a commonly known phenomenon, namely the vortex ring or smoke ring. Vortex rings are easily produced by dropping drops of one liquid into another, or by puffing fluid out of a hole, or by exhaling smoke if one has the skill

Vortex rings

CERN Document Server

Akhmetov, D G

2009-01-01

This text on vortex rings covers their theoretical foundation, systematic investigations, and practical applications such as the extinction of fires at gushing oil wells. It pays special attention to the formation and motion of turbulent vortex rings.

Superconducting analogs of quantum optical phenomena: Macroscopic quantum superpositions and squeezing in a superconducting quantum-interference device ring

International Nuclear Information System (INIS)

Everitt, M.J.; Clark, T.D.; Stiffell, P.B.; Prance, R.J.; Prance, H.; Vourdas, A.; Ralph, J.F.

2004-01-01

In this paper we explore the quantum behavior of a superconducting quantum-interference device (SQUID) ring which has a significant Josephson coupling energy. We show that the eigenfunctions of the Hamiltonian for the ring can be used to create macroscopic quantum superposition states of the ring. We also show that the ring potential may be utilized to squeeze coherent states. With the SQUID ring as a strong contender as a device for manipulating quantum information, such properties may be of great utility in the future. However, as with all candidate systems for quantum technologies, decoherence is a fundamental problem. In this paper we apply an open systems approach to model the effect of coupling a quantum-mechanical SQUID ring to a thermal bath. We use this model to demonstrate the manner in which decoherence affects the quantum states of the ring

Vertex ring-indexed Lie algebras

International Nuclear Information System (INIS)

Fairlie, David; Zachos, Cosmas

2005-01-01

Infinite-dimensional Lie algebras are introduced, which are only partially graded, and are specified by indices lying on cyclotomic rings. They may be thought of as generalizations of the Onsager algebra, but unlike it, or its sl(n) generalizations, they are not subalgebras of the loop algebras associated with sl(n). In a particular interesting case associated with sl(3), their indices lie on the Eisenstein integer triangular lattice, and these algebras are expected to underlie vertex operator combinations in CFT, brane physics, and graphite monolayers

Design parameters for a small storage ring optimized as an x-ray lithography source

International Nuclear Information System (INIS)

Grobman, W.D.

1983-01-01

This paper examines the design parameters for a ''compact storage ring'' which is matched well to x-ray lithographic requirements, but is as small as possible. This calculation uses a model of a lithographic system which obtains its input parameters from a technology of mask, resist and beam line based on the IBM program at the Brookhaven National Laboratory vacuum ultraviolet electron storage ring. Based on this lithographic system, we model exposure throughput as a function of storage ring parameters to understand which storage ring designs provide adequate but not excessive soft x-ray flux in the lithographically important region. Our scan of storage ring sources will cover a wide range of energies and magnetic fields, to permit consideration of superconducting as well as more standard strong- or weak-focusing designs. Furthermore, we will show that the results of the calculations presented here can be scaled in a simple way to cover a wide range of x-ray lithography system assumptions

A Feeding Strategy in Inner L-Shape Ring Hot Rolling Process

Directory of Open Access Journals (Sweden)

Wen Meng

2017-01-01

Full Text Available In order to make the inner L-shape ring polling process with a closed die structure (ILRRCDS on the top and bottom of the driven roll stable, at first, this paper established the mathematical model for ILRRCDS. Then, the plastic penetration and biting-in conditions for ILRRCDS were deduced based on plain ring rolling theory. Moreover, a feeding strategy that can realize a constant growth of the ring’s outer radius was proposed and the reasonable value ranges of the feed rate of the mandrel were determined. The numerical simulation model for ILRRCDS is established based on ABAQUS software. Finally, the equivalent plastic strain (PEEQ and temperature distributions of rolled ring were obtained. The results indicated that the proposed feeding strategy can realize a stable ILRRCDS. At the end of ILRRCDS, the PEEQ at the inner radius surface of the ring is maximum, the PEEQ at the outer radius surface of the ring takes the second place, and the PEEQ at the middle part of ring is minimum. With the increase of rolling time, the higher temperature zone of the rolled ring gradually moves from the center part of the ring to the “inner corner zone” of the ring.

Optimization of the geometrical stability in square ring laser gyroscopes

International Nuclear Information System (INIS)

Santagata, R; Beghi, A; Cuccato, D; Belfi, J; Beverini, N; Virgilio, A Di; Ortolan, A; Porzio, A; Solimeno, S

2015-01-01

Ultra-sensitive ring laser gyroscopes are regarded as potential detectors of the general relativistic frame-dragging effect due to the rotation of the Earth. Our project for this goal is called GINGER (gyroscopes in general relativity), and consists of a ground-based triaxial array of ring lasers aimed at measuring the rotation rate of the Earth with an accuracy of 10 −14 rad s −1 . Such an ambitious goal is now within reach, as large-area ring lasers are very close to the required sensitivity and stability. However, demanding constraints on the geometrical stability of the optical path of the laser inside the ring cavity are required. Thus, we have begun a detailed study of the geometry of an optical cavity in order to find a control strategy for its geometry that could meet the specifications of the GINGER project. As the cavity perimeter has a stationary point for the square configuration, we identify a set of transformations on the mirror positions that allows us to adjust the laser beam steering to the shape of a square. We show that the geometrical stability of a square cavity strongly increases by implementing a suitable system to measure the mirror distances, and that the geometry stabilization can be achieved by measuring the absolute lengths of the two diagonals and the perimeter of the ring. (paper)

The physics interests of a 10 TeV proton synchrotron, 400 x 400 GeV2 proton storage rings, and electron-proton storage rings

International Nuclear Information System (INIS)

Camilleri, L.

1976-01-01

This report consists of a collection of documents produced by two Study Groups, one on a multi-TeV Proton Synchrotron and the other on 400 x 400 GeV 2 Proton Storage Rings. In both studies the reactions of interest in the weak, electromagnetic and strong interactions are discussed. The technical feasibility of the relevant experiments is investigated by attempting. in each case, the design of an experimental set-up. Event rates are estimated using currently p revailing theoretical models and by extrapolation of results at present accelerators. In addition to the work of the two Study Groups, a section on the physics interests and technical problems of ep Storage Rings is included. (author)

Numerical simulation of injection and resistive trapping of ion rings

International Nuclear Information System (INIS)

Mankofsky, A.; Friedman, A.; Sudan, R.N.

1981-01-01

Numerical studies of the injection and resistive trapping efficiency of ion rings, using an improved algorithm are presented. Trapping efficiency is found to be strongly dependent upon the number of particles injected and upon mirror ratios in the system. Wall resistivity and beam divergence affect the process to a lesser extent. (author)

Geometry of deformed black holes. II. Schwarzschild hole surrounded by a Bach-Weyl ring

Science.gov (United States)

Basovník, M.; Semerák, O.

2016-08-01

We continue to study the response of black-hole space-times on the presence of additional strong sources of gravity. Restricting ourselves to static and axially symmetric (electro)vacuum exact solutions of Einstein's equations, we first considered the Majumdar-Papapetrou solution for a binary of extreme black holes in a previous paper, while here we deal with a Schwarzschild black hole surrounded by a concentric thin ring described by the Bach-Weyl solution. The geometry is again revealed on the simplest invariants determined by the metric (lapse function) and its gradient (gravitational acceleration), and by curvature (Kretschmann scalar). Extending the metric inside the black hole along null geodesics tangent to the horizon, we mainly focus on the black-hole interior (specifically, on its sections at constant Killing time) where the quantities behave in a way indicating a surprisingly strong influence of the external source. Being already distinct on the level of potential and acceleration, this is still more pronounced on the level of curvature: for a sufficiently massive and/or nearby (small) ring, the Kretschmann scalar even becomes negative in certain toroidal regions mostly touching the horizon from inside. Such regions have been interpreted as those where magnetic-type curvature dominates, but here we deal with space-times which do not involve rotation and the negative value is achieved due to the electric-type components of the Riemann/Weyl tensor. The Kretschmann scalar also shapes rather nontrivial landscapes outside the horizon.

The plasmasheet H+ and O+ contribution on the storm time ring current

Science.gov (United States)

Mouikis, C.; Bingham, S.; Kistler, L. M.; Spence, H. E.; Gkioulidou, M.; Claudepierre, S. G.; Farrugia, C. J.

2015-12-01

The source population of the storm time ring current is the night side plasma sheet. We use Van Allen Probes and Cluster observations to determine the contribution of the convecting plasma sheet H+ and O+ particles in the storm time development of the ring current. Using the Volland-Stern model with a dipole magnetic field together with the identification of the observed energy cutoffs in the particle spectra, we specify the pressure contributed by H+ and O+ populations that are on open drift paths vs. the pressure contributed by the trapped populations, for different local times. We find that during the storm main phase most of the ring current pressure in the pre-midnight inner magnetosphere is contributed by particles on open drift paths that cause the development of a strong partial ring current that causes most of the main phase Dst drop. These particles can reach as deep as L~2 and their pressure compares to the local magnetic field pressure as deep as L~3. During the recovery phase, if these particles are not lost at the magnetopause, will become trapped and will contribute to the symmetric ring current.

Spin Dynamics and Quantum Tunneling in Fe8 Nanomagnet and in AFM Rings by NMR

Energy Technology Data Exchange (ETDEWEB)

Ho-Baek, Seung [Iowa State Univ., Ames, IA (United States)

2004-01-01

In this thesis, our main interest has been to investigate the spin dynamics and quantum tunneling in single molecule magnets (SMMs), For this we have selected two different classes of SMMs: a ferrimagnetic total high spin S = 10 cluster Fe8 and antiferromagnetic (AFM) ring-type clusters. For Fe8, our efforts have been devoted to the investigation of the quantum tunneling of magnetization in the very low temperature region. The most remarkable experimental finding in Fe8 is that the nuclear spin-lattice relaxation rate (1/T{sub l}) at low temperatures takes place via strong collision mechanism, and thus it allows to measure directly the tunneling rate vs T and H for the first time. For AFM rings, we have shown that 1/T{sub l} probes the thermal fluctuations of the magnetization in the intermediate temperature range. We find that the fluctuations are dominated by a single characteristic frequency which has a power law T-dependence indicative of fluctuations due to electron-acoustic phonon interactions.

RINGED ACCRETION DISKS: EQUILIBRIUM CONFIGURATIONS

Energy Technology Data Exchange (ETDEWEB)

Pugliese, D.; Stuchlík, Z., E-mail: d.pugliese.physics@gmail.com, E-mail: zdenek.stuchlik@physics.cz [Institute of Physics and Research Centre of Theoretical Physics and Astrophysics, Faculty of Philosophy and Science, Silesian University in Opava, Bezručovo náměstí 13, CZ-74601 Opava (Czech Republic)

2015-12-15

We investigate a model of a ringed accretion disk, made up by several rings rotating around a supermassive Kerr black hole attractor. Each toroid of the ringed disk is governed by the general relativity hydrodynamic Boyer condition of equilibrium configurations of rotating perfect fluids. Properties of the tori can then be determined by an appropriately defined effective potential reflecting the background Kerr geometry and the centrifugal effects. The ringed disks could be created in various regimes during the evolution of matter configurations around supermassive black holes. Therefore, both corotating and counterrotating rings have to be considered as being a constituent of the ringed disk. We provide constraints on the model parameters for the existence and stability of various ringed configurations and discuss occurrence of accretion onto the Kerr black hole and possible launching of jets from the ringed disk. We demonstrate that various ringed disks can be characterized by a maximum number of rings. We present also a perturbation analysis based on evolution of the oscillating components of the ringed disk. The dynamics of the unstable phases of the ringed disk evolution seems to be promising in relation to high-energy phenomena demonstrated in active galactic nuclei.

Stirling engine piston ring

Science.gov (United States)

Howarth, Roy B.

1983-01-01

A piston ring design for a Stirling engine wherein the contact pressure between the piston and the cylinder is maintained at a uniform level, independent of engine conditions through a balancing of the pressure exerted upon the ring's surface and thereby allowing the contact pressure on the ring to be predetermined through the use of a preloaded expander ring.

Physics of quantum rings

International Nuclear Information System (INIS)

Fomin, Vladimir M.

2014-01-01

Presents the new class of materials of quantum rings. Provides an elemental basis for low-cost high-performance devices promising for electronics, optoelectronics, spintronics and quantum information processing. Explains the physical properties of quantum rings to cover a gap in scientific literature. Presents the application of most advanced nanoengineering and nanocharacterization techniques. This book deals with a new class of materials, quantum rings. Innovative recent advances in experimental and theoretical physics of quantum rings are based on the most advanced state-of-the-art fabrication and characterization techniques as well as theoretical methods. The experimental efforts allow to obtain a new class of semiconductor quantum rings formed by capping self-organized quantum dots grown by molecular beam epitaxy. Novel optical and magnetic properties of quantum rings are associated with non-trivial topologies at the nanoscale. An adequate characterization of quantum rings is possible on the basis of modern characterization methods of nanostructures, such as Scanning Tunneling Microscopy. A high level of complexity is demonstrated to be needed for a dedicated theoretical model to adequately represent the specific features of quantum rings. The findings presented in this book contribute to develop low-cost high-performance electronic, spintronic, optoelectronic and information processing devices based on quantum rings.

Response of APS storage ring basemat to ambient vibration

International Nuclear Information System (INIS)

Jendrzejczyk, J.A.; Wambsganss, M.W.; Smith, R.K.

1992-08-01

The storage ring of the Advanced Photon Source (APS) facility at Argonne is very sensitive to vibration. Large vibration amplitudes would result in degraded machine performance. Because the storage ring assembly is supported on the storage ring basemat, the dynamics of the basemat are critical to successful operation. Before construction began, a survey of site ground vibration indicated that the site was acceptable from a vibration standpoint. When construction of the linear accelerator (Linac) floor slab and shielding walls was completed, dynamic-response measurements were conducted. The slab/wall system showed attenuation of soilborne vibrations in the horizontal directions, but an amplification (approximately a factor of 1.5) of vertical vibration at a frequency of 7.7 Hz. Vibration response of the slab/wall system at all other frequencies showed attenuation of soilborne vibrations. Dynamic-response measurements were also conducted on an incomplete section of the storage ring basemat. Although this section was not prototypical, results were similar to those of the Linac floor in the horizontal direction, showing large damping and attenuation of horizontal soilborne vibrations. While the basemat followed the soil vibration in the vertical direction, no large amplification was observed. However, measured vertical amplitudes on the basemat were a function of location, indicating a modal response. A series of vibration response measurements was conducted on a completed section of the storage ring basemat/tunnel adjacent and to the west of the Early Assembly Area (EAA) on May 21, 1992, and is the subject of this report

Sierra San Pedro Mártir, Baja California, cool-season precipitation reconstructed from earlywood width of Abies concolor tree rings

Science.gov (United States)

Meko, D. M.; Touchan, R.; Díaz, J. Villanueva; Griffin, D.; Woodhouse, C. A.; Castro, C. L.; Carillo, C.; Leavitt, S. W.

2013-12-01

Tree ring data are analyzed for a multicentury record of drought history in the Sierra San Pedro Mártir (SSPM) of Baja California, Mexico. Climatic variation in the study area is of particular interest because the SSPM is a rich biotic environment at the southern limit of the California floristic province and the southern limit of the planetary jet stream. Future shifts in the jet stream would be expected to have amplified effect on this marginal environment. The study applies linear regression to tree ring indices of earlywood-width of Abies concolor to estimate a 353 year (1658-2010 C.E.) record of cool-season (October-April) precipitation, P, in SSPM. Time-nested regression models account for more than half the variance of grid point P in calibration periods of length 50-65 years. Cross-spectral analysis indicates strong tracking of observed P by the reconstruction over a broad range of frequencies. Robustness of the reconstruction is supported by synchrony of reconstructed P with tree ring variations in other tree species from SSPM. The reconstruction emphasizes the severity of the 1950s drought in a long-term context and the single-year intensity of droughts in the last decade: 2007 stands out as the driest reconstructed year, with a high percentage of missing rings in A. concolor. The reconstruction identifies the early twentieth century pluvial as the wettest epoch in the last 353 years in the SSPM. High-elevation tree species in SSPM may be especially well-suited to sensing snowpack-related moisture variations associated with a southerly branched jet stream and the types of weather systems active in the pluvial.

α-Skew π-McCoy Rings

Directory of Open Access Journals (Sweden)

Areej M. Abduldaim

2013-01-01

Full Text Available As a generalization of α-skew McCoy rings, we introduce the concept of α-skew π-McCoy rings, and we study the relationships with another two new generalizations, α-skew π1-McCoy rings and α-skew π2-McCoy rings, observing the relations with α-skew McCoy rings, π-McCoy rings, α-skew Armendariz rings, π-regular rings, and other kinds of rings. Also, we investigate conditions such that α-skew π1-McCoy rings imply α-skew π-McCoy rings and α-skew π2-McCoy rings. We show that in the case where R is a nonreduced ring, if R is 2-primal, then R is an α-skew π-McCoy ring. And, let R be a weak (α,δ-compatible ring; if R is an α-skew π1-McCoy ring, then R is α-skew π2-McCoy.

Stable carbon isotopic composition of tree rings from a pine tree from Augustów Wilderness, Poland, as a temperature and local environment conditions indicator.

Science.gov (United States)

Pawelczyk, Slawomira; Pazdur, Anna; Halas, Stanislaw

2004-06-01

Tree rings can be used as archives of climatic and environmental data with annual resolution. Tree rings widths, maximum late wood density and other parameters as stable composition in tree rings can be used for the reconstruction of past climatic and environmental changes. Stable carbon isotope ratios in tree rings may provide valuable information on past climatic conditions. 13C/12C ratios of plant organic matter can reflect corresponding 13C/12C ratio of atmospheric CO2 during formation of the rings. Investigations of isotopic carbon composition in tree rings from in the ecologically clean the Augustów Wilderness region in the north-eastern part of Poland (22 degrees 58'E, 53 degrees 51'N) (nowadays a sanctuary) were undertaken. Series of delta13C in alpha-cellulose and in wholewood were acquired. Those measurements constituted a part of more complex investigations of carbon isotope composition in tree rings including the measurements of radiocarbon concentration and tree ring widths. This article presents preliminary results. It is argued that contrary to the tree ring widths and delta13C in wholewood that do not reveal significant correlation with temperature, the variation of delta13C in the latewood alpha-cellulose is correlated with combined July and August temperatures. Copyright 2004 Taylor and Francis Ltd.

Relating ring width of Mediterranean evergreen species to seasonal and annual variations of precipitation and temperature

Directory of Open Access Journals (Sweden)

W. Nijland

2011-05-01

Full Text Available Plant growth in Mediterranean landscapes is limited by the typical summer-dry climate. Forests in these areas are only marginally productive and may be quite susceptible to modern climate change. To improve our understanding of forest sensitivity to annual and seasonal climatic variability, we use tree-ring measurements of two Mediterranean evergreen tree species: Quercus ilex L. and Arbutus unedo L. We sampled 34 stems of these species on three different types of substrates in the Peyne study area in southern France. The resulting chronologies were analysed in combination with 38 yr of monthly precipitation and temperature data to reconstruct the response of stem growth to climatic variability. Results indicate a strong positive response to May and June precipitation, as well as a significant positive influence of early-spring temperatures and a negative growth response to summer heat. Comparison of the data with more detailed productivity measurements in two contrasting years confirms these observations and shows a strong productivity limiting effect of low early-summer precipitation. The results show that tree-ring data from Q.ilex and A.unedo can provide valuable information about the response of these tree species to climate variability, improving our ability to predict the effects of climate change in Mediterranean ecosystems.

VUV optical ring resonator for Duke storage ring free electron laser

Energy Technology Data Exchange (ETDEWEB)

Park, S.H.; Litvinenko, V.N.; Madey, J.M.J. [Duke Univ., Durham, NC (United States)] [and others

1995-12-31

The conceptual design of the multifaceted-mirror ring resonator for Duke storage ring VUV FEL is presented. The expected performance of the OK-4 FEL with ring resonator is described. We discuss in this paper our plans to study reflectivity of VUV mirrors and their resistivity to soft X-ray spontaneous radiation from OK-4 undulator.

Nanophysics in graphene: neutrino physics in quantum rings and superlattices.

Science.gov (United States)

Fertig, H A; Brey, Luis

2010-12-13

Electrons in graphene at low energy obey a two-dimensional Dirac equation, closely analogous to that of neutrinos. As a result, quantum mechanical effects when the system is confined or subjected to potentials at the nanoscale may be quite different from what happens in conventional electronic systems. In this article, we review recent progress on two systems where this is indeed the case: quantum rings and graphene electrons in a superlattice potential. In the former case, we demonstrate that the spectrum reveals signatures of 'effective time-reversal symmetry breaking', in which the spectra are most naturally interpreted in terms of effective magnetic flux contained in the ring, even when no real flux is present. A one-dimensional superlattice potential is shown to induce strong band-structure changes, allowing the number of Dirac points at zero energy to be manipulated by the strength and/or period of the potential. The emergence of new Dirac points is shown to be accompanied by strong signatures in the conduction properties of the system.

Stable CSR in storage rings: A model

International Nuclear Information System (INIS)

Sannibale, Fernando; Byrd, John M.; Loftsdottir, Agusta; Venturini, Marco; Abo-Bakr, Michael; Feikes, Jorge; Holldack, Karsten; Kuske, Peter; Wustefeld, Godehart; Hubers, Heinz-Willerm; Warnock, Robert

2005-01-01

A comprehensive historical view of the work done on coherent synchrotron radiation (CSR) in storage rings is given in reference [1]. Here we want just to point out that even if the issue of CSR in storage rings was already discussed over 50 years ago, it is only recently that a considerable number of observations have been reported. In fact, intense bursts of coherent synchrotron radiation with a stochastic character were measured in the terahertz frequency range, at several synchrotron light source storage rings [2-8]. It has been shown [8-11], that this bursting emission of CSR is associated with a single bunch instability, usually referred as microbunching instability (MBI), driven by the fields of the synchrotron radiation emitted by the bunch itself. Of remarkably different characteristics was the CSR emission observed at BESSY II in Berlin, when the storage ring was tuned into a special low momentum compaction mode [12, 13]. In fact, the emitted radiation was not the quasi-random bursting observed in the other machines, but a powerful and stable flux of broadband CSR in the terahertz range. This was an important result, because it experimentally demonstrated the concrete possibility of constructing a stable broadband source with extremely high power in the terahertz region. Since the publication of the first successful experiment using the ring as a CSR source [14], BESSY II has regular scheduled user s shifts dedicated to CSR experiments. At the present time, several other laboratories are investigating the possibility of a CSR mode of operation [15-17] and a design for a new ring optimized for CSR is at an advanced stage [18]. In what follows, we describe a model that first accounts for the BESSY II observations and then indicates that the special case of BESSY II is actually quite general and typical when relativistic electron storage rings are tuned for short bunches. The model provides a scheme for predicting and optimizing the performance of ring

Stable CSR in Storage Rings: A Model

International Nuclear Information System (INIS)

Sannibale, F.

2005-01-01

A comprehensive historical view of the work done on coherent synchrotron radiation (CSR) in storage rings is given in reference [1]. Here we want just to point out that even if the issue of CSR in storage rings was already discussed over 50 years ago, it is only recently that a considerable number of observations have been reported. In fact, intense bursts of coherent synchrotron radiation with a stochastic character were measured in the terahertz frequency range, at several synchrotron light source storage rings [2-8]. It has been shown [8-11], that this bursting emission of CSR is associated with a single bunch instability, usually referred as microbunching instability (MBI), driven by the fields of the synchrotron radiation emitted by the bunch itself. Of remarkably different characteristics was the CSR emission observed at BESSY II in Berlin, when the storage ring was tuned into a special low momentum compaction mode [12, 13]. In fact, the emitted radiation was not the quasi-random bursting observed in the other machines, but a powerful and stable flux of broadband CSR in the terahertz range. This was an important result, because it experimentally demonstrated the concrete possibility of constructing a stable broadband source with extremely high power in the terahertz region. Since the publication of the first successful experiment using the ring as a CSR source [14], BESSY II has regular scheduled user's shifts dedicated to CSR experiments. At the present time, several other laboratories are investigating the possibility of a CSR mode of operation [15-17] and a design for a new ring optimized for CSR is at an advanced stage [18]. In what follows, we describe a model that first accounts for the BESSY II observations and then indicates that the special case of BESSY II is actually quite general and typical when relativistic electron storage rings are tuned for short bunches. The model provides a scheme for predicting and optimizing the performance of ring

Interaction Region Design for a Ring-Ring LHeC

CERN Document Server

Thompson, L N S; Bernard, N R; Fitterer, M; Holzer, B; Klein, M; Kostka, P

2011-01-01

tively low energy and moderately high intensity provides high luminosity TeV-scale e-p collisions at one of the LHC interaction points, running simultaneously with existing experiments. Two designs are studied; an electron ring situated in the LHC tunnel, and an electron linac. The focus of this paper is on the ring design. Designing an e-p machine presents interesting accelerator physics and design challenges, particularly when considering the interaction region. These include coupled optics, beam separation and unconventional mini-beta focusing schemes. Designs are constrained by an array of interdependent factors, including beam-beam interaction, detector dimensions and acceptance, luminosity and synchrotron radiation. Methods of addressing these complex issues are discussed. The current designs for the LHeC Ring-Ring interaction region and long straight section are presented and discussed, in the context of the project goals and design challenges encountered. Future developments and work are also discusse...

The calculated longitudinal impedance of the SLC [Stanford Linear Collider] damping rings

International Nuclear Information System (INIS)

Bane, K.L.F.

1988-05-01

A high level of current dependent bunch lengthening has been observed in the north damping ring of the Stanford Linear Collider (SLC), indicating that the ring's impedance is very inductive. This level of bunch lengthening will limit the performance of the SLC. In order to study the problem of bunch lengthening in the damping ring and the possibility of reducing their inductance we compute, in this report, the longitudinal impedance of the damping ring vacuum chamber. More specifically we find the response function of the ring to a short gaussian bunch. This function will later be used as a driving term in the longitudinal equation of motion. We also identify the important inductive elements of the vacuum chamber and estimate their contribution to the total ring inductance. This information will be useful in assessing the effect of vacuum chamber modifications. 7 refs. , 8 figs., 1 tab

Stress analysis of HLW containers. Preliminary ring test exercise Compas project

International Nuclear Information System (INIS)

1989-01-01

This document describes the series of experiments and associated calculations performed as the Compas preliminary ring test exercise. A number of mild steel rings, representative of sections through HLW containers, some notched and pre-cracked, were tested in compression right up to and beyond their ultimate load. The Compas project partners independently modelled the behaviour of these rings using their finite element codes. Four different ring types were tested, and each test was repeated three times. For three of the ring types, the three test repetitions gave identical results. The fourth ring, which was not modelled by the partners, had a 4 mm thick layer of weld metal deposited on its surface. The three tests on this ring did not give identical results and suggested that the effect of welding methods should be addressed at a later stage of the project. Fracture was not found to be a significant cause of ring failure. The results of the ring tests were compared with the partners predictions, and additionally some time was spent assessing where the use of the codes could be improved. This exercise showed that the partners codes have the ability to produce results within acceptable limits. Most codes were unable to model stable crack growth. There were indications that some codes would not be able to cope with a significantly more complex three-dimensional analysis

Ring and jet-like structures and two-dimensional intermittency in nucleus-nucleus collisions at 200 AGeV/c

International Nuclear Information System (INIS)

Ghosh, M.K.; Haldar, P.K.; Manna, S.K.; Mukhopadhyay, A.; Singh, G.

2011-01-01

We have investigated the presence of ring and/or jet-like structures in the angular emission of secondary charged mesons (shower tracks) coming out of 16 O-Ag/Br and 32 S-Ag/Br interactions, each at an incident momentum of 200 AGeV/c. Nuclear photographic emulsion technique has been used to collect the experimental data. The experimental results have been compared with the results simulated by Monte Carlo method. The analysis indicates presence of ring and jet-like structures in the experimental data beyond statistical noise. This kind of jet structure is expected to give rise to a strong two-dimensional (2d) intermittency. The self-affine behaviour of 2d scaled factorial moments (SFM) has therefore been investigated and the strength of 2d intermittency has been determined. For each set of data the 2d results have been compared with the respective one-dimensional (1d) intermittency results.

The use of twin-ring Ilizarov external fixator constructs: application and biomechanical proof-of principle with possible clinical indications

Directory of Open Access Journals (Sweden)

Magnissalis Evangelos A

2011-08-01

Full Text Available Abstract Background In peri- or intra-articular fractures of the tibia or femur, the presence of short metaphyseal bone fragments may make the application of an Ilizarov external fixator (IEF challenging. In such cases, it may be necessary to bridge the adjacent joint in order to ensure stable fixation. The twin-ring (TR module of circular external fixation is proposed as an alternative method that avoids joint bridging, without compromising stability of fixation. The aim of this study is to present the experimental tests performed to compare the biomechanical characteristics of the single- and TR IEF modules. The clinical application of the TR module in select patients is also presented and the merits of this technique are discussed. Methods In this experimental study, the passive stiffness and stability of the single-ring (SR and twin-ring (TR IEF modules were tested under axial and shear loading conditions. In each module, two perpendicular wires on the upper surface and another two wires on the lower surface of the rings were used for fixation of the rings on plastic acetal cylinders simulating long bones. Results In axial loading, the main outcome measure was stiffness and the SR module proved stiffer than the TR. In shear loading, the main outcome measure was stability, the TR module proving more stable than the SR. Discussion The TR configuration, being stiffer in shear loading, may make joint bridging unnecessary when an IEF is applied. If it is still required, TR frames allow for an earlier discontinuation of bridging; either case is in favour of a successful final outcome. Conclusion The application of the TR module has led to satisfactory clinical outcomes and should be considered as an alternative in select trauma patients treated with an IEF. Biomechanically, the TR module possesses features which enhance fracture healing and at the same time obviate the need for bridging adjacent joints, thereby significantly reducing patient

Externally controlled local magnetic field in a conducting mesoscopic ring coupled to a quantum wire

International Nuclear Information System (INIS)

Maiti, Santanu K.

2015-01-01

In the present work, the possibility of regulating local magnetic field in a quantum ring is investigated theoretically. The ring is coupled to a quantum wire and subjected to an in-plane electric field. Under a finite bias voltage across the wire a net circulating current is established in the ring which produces a strong magnetic field at its centre. This magnetic field can be tuned externally in a wide range by regulating the in-plane electric field, and thus, our present system can be utilized to control magnetic field at a specific region. The feasibility of this quantum system in designing spin-based quantum devices is also analyzed

Influence of ring growth rate on damage development in hot ring rolling

NARCIS (Netherlands)

Wang, C.; Geijselaers, H. J.M.; Omerspahic, E.; Recina, V.; van den Boogaard, A. H.

2015-01-01

As an incremental forming process of bulk metal, ring rolling provides a cost effective process route to manufacture seamless rings. In the production of hot rolled rings, defects such as porosity can sometimes be found in high alloyed steel, manufactured from ingots having macro-segregation. For

New results on strong-interaction effects in antiprotonic hydrogen

International Nuclear Information System (INIS)

Anagnostopoulos, D. F.; Augsburger, M.; Borchert, G.; Castelli, C.; Chatellard, D.; El-Khoury, P.; Egger, J.-P.; Gorke, H.; Gotta, D.; Hauser, P.; Indelicato, P.; Kirch, K.; Lenz, S.; Nelms, N.; Rashid, K.; Schult, O. W. B.; Siems, Th.; Simons, L. M.

1999-01-01

Lyman and Balmer transitions of antiprotonic hydrogen and deuterium have been measured at the Low-Energy Antiproton Ring LEAR at CERN in order to determine the strong interaction effects. The X-rays were detected using Charge-Coupled Devices (CCDs) and a reflection type crystal spectrometer. The results of the measurements support the meson-exchange models describing the medium and long range part of the nucleon-antinucleon interaction

Ring rotational speed trend analysis by FEM approach in a Ring Rolling process

Science.gov (United States)

Allegri, G.; Giorleo, L.; Ceretti, E.

2018-05-01

Ring Rolling is an advanced local incremental forming technology to fabricate directly precise seamless ring-shape parts with various dimensions and materials. In this process two different deformations occur in order to reduce the width and the height of a preform hollow ring; as results a diameter expansion is obtained. In order to guarantee a uniform deformation, the preform is forced toward the Driver Roll whose aim is to transmit the rotation to the ring. The ring rotational speed selection is fundamental because the higher is the speed the higher will be the axial symmetry of the deformation process. However, it is important to underline that the rotational speed will affect not only the final ring geometry but also the loads and energy needed to produce it. Despite this importance in industrial environment, usually, a constant value for the Driver Roll angular velocity is set so to result in a decreasing trend law for the ring rotational speed. The main risk due to this approach is not fulfilling the axial symmetric constrain (due to the diameter expansion) and to generate a high localized ring section deformation. In order to improve the knowledge about this topic in the present paper three different ring rotational speed trends (constant, linearly increasing and linearly decreasing) were investigated by FEM approach. Results were compared in terms of geometrical and dimensional analysis, loads and energies required.

Ring correlations in random networks.

Science.gov (United States)

Sadjadi, Mahdi; Thorpe, M F

2016-12-01

We examine the correlations between rings in random network glasses in two dimensions as a function of their separation. Initially, we use the topological separation (measured by the number of intervening rings), but this leads to pseudo-long-range correlations due to a lack of topological charge neutrality in the shells surrounding a central ring. This effect is associated with the noncircular nature of the shells. It is, therefore, necessary to use the geometrical distance between ring centers. Hence we find a generalization of the Aboav-Weaire law out to larger distances, with the correlations between rings decaying away when two rings are more than about three rings apart.

New edge magnetoplasmon for a two-dimensional electron gas in a ring geometry

International Nuclear Information System (INIS)

Proetto, C.R.

1992-09-01

The dynamical response of a classical two-dimensional electron gas confined in a ring geometry under a perpendicular magnetic field is analysed. Within the hydrodynamical approach and in the strong magnetic field limit, a new set of antidot edge magnetoplasmons is obtained, corresponding to density oscillations circulating along the inner boundary of the ring and whose frequency increases with magnetic field. The associated self-induced distribution of densities and currents are presented, together with an analysis of the size dependence of these perimeter waves. (author). 15 refs, 4 figs

Alpha - Skew Pi - Armendariz Rings

Directory of Open Access Journals (Sweden)

Areej M Abduldaim

2018-03-01

Full Text Available In this article we introduce a new concept called Alpha-skew Pi-Armendariz rings (Alpha - S Pi - ARas a generalization of the notion of Alpha-skew Armendariz rings.Another important goal behind studying this class of rings is to employ it in order to design a modern algorithm of an identification scheme according to the evolution of using modern algebra in the applications of the field of cryptography.We investigate general properties of this concept and give examples for illustration. Furthermore, this paperstudy the relationship between this concept and some previous notions related to Alpha-skew Armendariz rings. It clearly presents that every weak Alpha-skew Armendariz ring is Alpha-skew Pi-Armendariz (Alpha-S Pi-AR. Also, thisarticle showsthat the concepts of Alpha-skew Armendariz rings and Alpha-skew Pi- Armendariz rings are equivalent in case R is 2-primal and semiprime ring.Moreover, this paper proves for a semicommutative Alpha-compatible ringR that if R[x;Alpha] is nil-Armendariz, thenR is an Alpha-S Pi-AR. In addition, if R is an Alpha - S Pi -AR, 2-primal and semiprime ring, then N(R[x;Alpha]=N(R[x;Alpha]. Finally, we look forwardthat Alpha-skew Pi-Armendariz rings (Alpha-S Pi-ARbe more effect (due to their properties in the field of cryptography than Pi-Armendariz rings, weak Armendariz rings and others.For these properties and characterizations of the introduced concept Alpha-S Pi-AR, we aspire to design a novel algorithm of an identification scheme.

The Cornell field-reversed ion ring experiment FIREX: experimental design and first results

International Nuclear Information System (INIS)

Podulka, W.J.; Greenly, J.B.; Anderson, D.E.; Glidden, S.C.; Hammer, D.A.; Omelchenko, Yu.A.; Sudan, R.N.

1996-01-01

The goal of FIREX (Field-reversed Ion Ring EXperiment) is to produce a fully field-reversed ring with 1 MeV protons. Such a ring requires about (2-3) x 10 17 protons, or 30-50 mC of charge. This charge is to be injected as an annular proton beam through a suitable magnetic cusp configuration to produce a compact ring. The critical design issues for the ion beam accelerator are described. First experimental results of ion diode operation indicate that the design is capable of producing the required beam parameters. (author). 4 figs., 4 refs

The Cornell field-reversed ion ring experiment FIREX: experimental design and first results

Energy Technology Data Exchange (ETDEWEB)

Podulka, W J; Greenly, J B; Anderson, D E; Glidden, S C; Hammer, D A; Omelchenko, Yu A; Sudan, R N [Cornell Univ., Ithaca, NY (United States). Laboratory of Plasma Studies

1997-12-31

The goal of FIREX (Field-reversed Ion Ring EXperiment) is to produce a fully field-reversed ring with 1 MeV protons. Such a ring requires about (2-3) x 10{sup 17} protons, or 30-50 mC of charge. This charge is to be injected as an annular proton beam through a suitable magnetic cusp configuration to produce a compact ring. The critical design issues for the ion beam accelerator are described. First experimental results of ion diode operation indicate that the design is capable of producing the required beam parameters. (author). 4 figs., 4 refs.

Double Rashba Quantum Dots Ring as a Spin Filter

Directory of Open Access Journals (Sweden)

Chi Feng

2008-01-01

Full Text Available AbstractWe theoretically propose a double quantum dots (QDs ring to filter the electron spin that works due to the Rashba spin–orbit interaction (RSOI existing inside the QDs, the spin-dependent inter-dot tunneling coupling and the magnetic flux penetrating through the ring. By varying the RSOI-induced phase factor, the magnetic flux and the strength of the spin-dependent inter-dot tunneling coupling, which arises from a constant magnetic field applied on the tunneling junction between the QDs, a 100% spin-polarized conductance can be obtained. We show that both the spin orientations and the magnitude of it can be controlled by adjusting the above-mentioned parameters. The spin filtering effect is robust even in the presence of strong intra-dot Coulomb interactions and arbitrary dot-lead coupling configurations.

A Bell inequality for a class of multilocal ring networks

Science.gov (United States)

Frey, Michael

2017-11-01

Quantum networks with independent sources of entanglement (hidden variables) and nodes that execute joint quantum measurements can create strong quantum correlations spanning the breadth of the network. Understanding of these correlations has to the present been limited to standard Bell experiments with one source of shared randomness, bilocal arrangements having two local sources of shared randomness, and multilocal networks with tree topologies. We introduce here a class of quantum networks with ring topologies comprised of subsystems each with its own internally shared source of randomness. We prove a Bell inequality for these networks, and to demonstrate violations of this inequality, we focus on ring networks with three-qubit subsystems. Three qubits are capable of two non-equivalent types of entanglement, GHZ and W-type. For rings of any number N of three-qubit subsystems, our inequality is violated when the subsystems are each internally GHZ-entangled. This violation is consistently stronger when N is even. This quantitative even-odd difference for GHZ entanglement becomes extreme in the case of W-type entanglement. When the ring size N is even, the presence of W-type entanglement is successfully detected; when N is odd, the inequality consistently fails to detect its presence.

Plasma-ring, fast-opening switch

International Nuclear Information System (INIS)

Hartman, C.W.; Eddleman, J.; Hammer, J.H.

1986-01-01

The authors discuss a fast-opening switch concept based on magnetically confined plasma rings, PROS (for Plasma Ring Opening Switch). In PROS, the plasma ring, confined by Bθ /sub and B/poloidal /sub fields of a compact torus, provide a low mass, localized conduction path between coaxial electrodes. To operate the switch, driver current is passed across the electrodes through the ring, storing inductive energy in external inductance and between the electrodes on the driver side of the ring. The ring is accelerated away from the driver by the field of the driver current and passes over a load gap transferring the current to the load. The authors distinguish two configurations in PROS, straight PROS where the electrodes are coaxial cylinders, and cone PROS with conical electrodes. In straight PROS ring acceleration takes place during the inductive store period as in foil switches, but with the localized ring providing the current path. Increased performance is predicted for the cone PROS (see figure) which employs compression of the ring in the cone during the inductive store period. Here, the B/θ /sub field of the driver forces the ring towards the apex of the cone but the force is in near balance with the opposing component of the radial equilibrium force of the ring along the cone. As a result, the ring undergoes a slow, quasistatic compression limited only by resistive decay of the ring field. Slow compression allows inductive storage with low-power drivers (homopoloar, magneto cumulative generators, high C-low V capacitor banks, etc.). Near the apex of the cone, near peak compression, the ring is allowed to enter a straight coaxial section where, because of low-mass, it rapidly accelerates to high velocity and crosses the load gap

Quasi-one-dimensional density of states in a single quantum ring.

Science.gov (United States)

Kim, Heedae; Lee, Woojin; Park, Seongho; Kyhm, Kwangseuk; Je, Koochul; Taylor, Robert A; Nogues, Gilles; Dang, Le Si; Song, Jin Dong

2017-01-05

Generally confinement size is considered to determine the dimensionality of nanostructures. While the exciton Bohr radius is used as a criterion to define either weak or strong confinement in optical experiments, the binding energy of confined excitons is difficult to measure experimentally. One alternative is to use the temperature dependence of the radiative recombination time, which has been employed previously in quantum wells and quantum wires. A one-dimensional loop structure is often assumed to model quantum rings, but this approximation ceases to be valid when the rim width becomes comparable to the ring radius. We have evaluated the density of states in a single quantum ring by measuring the temperature dependence of the radiative recombination of excitons, where the photoluminescence decay time as a function of temperature was calibrated by using the low temperature integrated intensity and linewidth. We conclude that the quasi-continuous finely-spaced levels arising from the rotation energy give rise to a quasi-one-dimensional density of states, as long as the confined exciton is allowed to rotate around the opening of the anisotropic ring structure, which has a finite rim width.

Radio and optical observations of 0218+357 - The smallest Einstein ring?

Science.gov (United States)

O'Dea, Christopher P.; Baum, Stefi A.; Stanghellini, Carlo; Dey, Arjun; Van Breugel, Wil; Deustua, Susana; Smith, Eric P.

1992-01-01

VLA radio observations and optical imaging and spectroscopy of the Einstein radio ring 0218+357 are presented. The ring is detected at 22.4 GHz and shows a basically similar structure at 5, 15, and 22.4 GHz. The B component has varied and was about 15 percent brighter in the 8.4 GHz data than in the data of Patnaik et al. (1992). The ring is highly polarized. A weak jetlike feature extending out roughly 2 arcsec to the southeast of component A is detected at 6 cm. The source has amorphous radio structure extending out to about 11 arcsec from the core. For an adopted redshift of 0.68, the extended radio emission is very powerful. The optical spectrum is rather red and shows no strong features. A redshift of about 0.68 is obtained. The identification is a faint compact m(r) about 20 galaxy which extends to about 4.5 arcsec (about 27 kpc). As much as 50 percent of the total light may be due to a central AGN. The observed double core and ring may be produced by an off-center radio core with extended radio structure.

Fusion Rings for Quantum Groups

DEFF Research Database (Denmark)

Andersen, Henning Haahr; Stroppel, Catharina

2014-01-01

We study the fusion rings of tilting modules for a quantum group at a root of unity modulo the tensor ideal of negligible tilting modules. We identify them in type A with the combinatorial rings from Korff, C., Stroppel, C.: The sl(ˆn)k-WZNW fusion ring: a combinato-rial construction...... and a realisation as quotient of quantum cohomology. Adv. Math. 225(1), 200–268, (2010) and give a similar description of the sp2n-fusion ring in terms of non-commutative symmetric functions. Moreover we give a presentation of all fusion rings in classical types as quotients of polynomial rings. Finally we also...... compute the fusion rings for type G2....

The LSU Electron Storage Ring, the first commercially-built storage ring

International Nuclear Information System (INIS)

Sah, R.

1990-01-01

The Brobeck Division of Maxwell Laboratories, Inc., is building the first industrially-produced storage ring. It will be located at Louisiana State University (LSU) at the Center for Advanced Microstructures and Devices (CAMD) in Baton Rouge. The purpose of this electron storage ring is to provide intense beams of x-rays to advance the state-of-the-art in lithography and to permit research in a broad area. This facility consists of a 1.2 GeV, 400 mA electron storage ring with a 200 MeV linac injector. The magnet lattice is a Chasman-Green design (double-bend achromat), and the ring circumference is 55.2 meters. There are four 3.0 meter, dispersion-free straight sections, one for injection, one for the 500 MHz RF cavity, and two for possible future insertion devices. The storge ring construction project is in the detailed-design stage, and many systems are in the initial stages of fabrication. 4 figs., 1 tab

Trends of 13C/12C ratios in pinyon tree rings of the American Southwest and the global carbon cycle

International Nuclear Information System (INIS)

Leavitt, S.W.; Long, A.

1986-01-01

An accurate atmospheric 13 C/ 12 C chronology can provide important constraints to models of the global carbon cycle. Trees accumulate carbon from atmospheric CO 2 into growth rings and offer potential for 13 C/ 12 C reconstructions, but results have not been reproducible. This paper presents δ 13 C curves from 5 sites, representing 20 pinyon (Pinus edulis) trees, where cores of 4 trees from each site have been pooled into a composite sample. Isotopic analysis of cellulose in 5-yr ring groups produces curves with a general trend of decreasing δ 13 C after 1800, but with pronounced short-term fluctuations superimposed upon the trend. Evidence indicates the fluctuations are strongly related to moisture availability (drought). A mean curve of the 5 δ 13 C chronologies from which the fossil-fuel component is subtracted suggests a substantial biospheric CO 2 contribution to the atmosphere since 1800

Fusion rings and fusion ideals

DEFF Research Database (Denmark)

Andersen, Troels Bak

by the so-called fusion ideals. The fusion rings of Wess-Zumino-Witten models have been widely studied and are well understood in terms of precise combinatorial descriptions and explicit generating sets of the fusion ideals. They also appear in another, more general, setting via tilting modules for quantum......This dissertation investigates fusion rings, which are Grothendieck groups of rigid, monoidal, semisimple, abelian categories. Special interest is in rational fusion rings, i.e., fusion rings which admit a finite basis, for as commutative rings they may be presented as quotients of polynomial rings...

Molecular dynamics simulation study of nonconcatenated ring polymers in a melt. I. Statics

Science.gov (United States)

Halverson, Jonathan D.; Lee, Won Bo; Grest, Gary S.; Grosberg, Alexander Y.; Kremer, Kurt

2011-05-01

Molecular dynamics simulations were conducted to investigate the structural properties of melts of nonconcatenated ring polymers and compared to melts of linear polymers. The longest rings were composed of N = 1600 monomers per chain which corresponds to roughly 57 entanglement lengths for comparable linear polymers. For the rings, the radius of gyration squared, , was found to scale as N4/5 for an intermediate regime and N2/3 for the larger rings indicating an overall conformation of a crumpled globule. However, almost all beads of the rings are "surface beads" interacting with beads of other rings, a result also in agreement with a primitive path analysis performed in the next paper [J. D. Halverson, W. Lee, G. S. Grest, A. Y. Grosberg, and K. Kremer, J. Chem. Phys. 134, 204905 (2011)], 10.1063/1.3587138. Details of the internal conformational properties of the ring and linear polymers as well as their packing are analyzed and compared to current theoretical models.

Effective tuning of electron charge and spin distribution in a dot-ring nanostructure at the ZnO interface

Science.gov (United States)

Chakraborty, Tapash; Manaselyan, Aram; Barseghyan, Manuk

2018-05-01

Electronic states and the Aharonov-Bohm effect in ZnO quantum dot-ring nanostructures containing few interacting electrons reveal several unique features. We have shown here that in contrast to the dot-rings made of conventional semiconductors, such as InAs or GaAs, the dot-rings in ZnO heterojunctions demonstrate several unique characteristics due to the unusual properties of quantum dots and rings in ZnO. In particular the energy spectra of the ZnO dot-ring and the Aharnov-Bohm oscillations are strongly dependant on the electron number in the dot or in the ring. Therefore even small changes of the confinement potential, sizes of the dot-ring or the magnetic field can drastically change the energy spectra and the behavior of Aharonov-Bohm oscillations in the system. Due to this interesting phenomena it is possible to effectively control with high accuracy the electron charge and spin distribution inside the dot-ring structure. This controlling can be achieved either by changing the magnetic field or the confinement potentials.

Instrumental neutron activation analysis of tree rings for dendrochemical studies

International Nuclear Information System (INIS)

Schaumloffel, J.C.; Filby, R.H.

1996-01-01

Instrumental neutron activation analysis (INAA) was employed to determine zinc, cadmium and potassium concentrations in the growth rings of ponderosa pine (Pinus ponderosa Dougl.) trees growing along the shores of Lake Roosevelt in Washington State, U.S.A. where mineral processing activities have resulted in high burdens of zinc and cadmium in the lake sediments. The tree growing along the contaminated waterway display elevated concentrations of zinc in its growth rings relative to a tree growing along an uncontaminated tributary of Lake Roosevelt. Cadmium concentrations in the growth rings from both sites are similar from 1988 to 1993. Water quality data indicate an increased concentration of cadmium in the lake from 1984 to 1988. The increased concentrations of cadmium in the lake water were reflected in apparent increases in concentrations of cadmium in individual rings of the tree sampled at the contaminated site. This suggests that translocation of cadmium in the sapwood of heartwood-forming species does not occur in the short term, and thus may not be a limiting factor in using trees as environmental monitors for cadmium. In addition, five-year tree ring segments were analyzed and subsequently reanalyzed as individual single-year ring segments. The analytical data obtained for the pooled individual rings are essentially the same as for the five-year segments, demonstrating the utility of NAA for dendrochemical studies. (author). 24 refs., 5 figs., 2 tabs

Evaluation of ring impedance of the Photon Factory storage ring

International Nuclear Information System (INIS)

Kiuchi, T.; Izawa, M.; Tokumoto, S.; Hori, Y.; Sakanaka, S.; Kobayashi, M.; Kobayakawa, H.

1992-05-01

The loss parameters of the ducts in the Photon Factory (PF) storage ring were evaluated using the wire method and the code TBCI. Both the measurement and the calculation were done for a different bunch length (σ) ranging from 23 to 80 ps. The PF ring impedance was estimated to be |Z/n|=3.2 Ω using the broadband impedance model. The major contribution to the impedance comes from the bellows and the gate valve sections. Improvements of these components will lower the ring impedance by half. (author)

From rotating atomic rings to quantum Hall states.

Science.gov (United States)

Roncaglia, M; Rizzi, M; Dalibard, J

2011-01-01

Considerable efforts are currently devoted to the preparation of ultracold neutral atoms in the strongly correlated quantum Hall regime. However, the necessary angular momentum is very large and in experiments with rotating traps this means spinning frequencies extremely near to the deconfinement limit; consequently, the required control on parameters turns out to be too stringent. Here we propose instead to follow a dynamic path starting from the gas initially confined in a rotating ring. The large moment of inertia of the ring-shaped fluid facilitates the access to large angular momenta, corresponding to giant vortex states. The trapping potential is then adiabatically transformed into a harmonic confinement, which brings the interacting atomic gas in the desired quantum-Hall regime. We provide numerical evidence that for a broad range of initial angular frequencies, the giant-vortex state is adiabatically connected to the bosonic ν = 1/2 Laughlin state.

Waves in Saturn's rings probed by radio occultation

International Nuclear Information System (INIS)

Rosen, P.A.

1989-01-01

Thirty wave features, observed in 3.6 and 13 cm-wavelength optical depth profiles of Saturn's rings obtained by Voyager 1 radio occultation, are analyzed individually and comparatively. Many are the signature of spiral density waves and bending waves excited by gravitational resonances with Saturn's satellites. A new technique for locating waveform extrema, which fits a sinusoid to each half cycle of wave data, quantifies the wavelength variation across a feature. Fitting dispersion models to the derived wavelengths provides new estimates of ambient surface mass density σ in each wave region. For fourteen weak density waves in Ring A, modelling of the waveform near resonance with linear density wave theory gives independent estimates of σ, as well as reliable estimates of resonance location. Measurements of wave amplitude damping give an upper bound for ring thickness 2H, where H is the ring scale height. In the wave regions studied, Rings A, B, and C have 30 approx-lt σ approx-lt 70, σ approx-gt 65, and σ ∼ 1 g/cm 2 , respectively. Mass loading estimates from waveform modelling are 20 to 40% larger than dispersion-derived values, suggesting accumulation of mass in the wave regions. The average offset of derived wave location from theoretical resonance is about 1 km. Model waveforms of overlapping waves excited by the satellites Janus and Epimethenus agree well with observed morphologies in the linear region near resonance. In Ring C, dispersion analysis indicates that the most prominent wave feature, previously unidentified, is a one-armed spiral wave

Tree Rings: Timekeepers of the Past.

Science.gov (United States)

Phipps, R. L.; McGowan, J.

One of a series of general interest publications on science issues, this booklet describes the uses of tree rings in historical and biological recordkeeping. Separate sections cover the following topics: dating of tree rings, dating with tree rings, tree ring formation, tree ring identification, sample collections, tree ring cross dating, tree…

New results on strong-interaction effects in antiprotonic hydrogen

CERN Document Server

Gotta, D; Augsburger, M A; Borchert, G L; Castelli, C M; Chatellard, D; El-Khoury, P; Egger, J P; Gorke, H; Hauser, P R; Indelicato, P J; Kirch, K; Lenz, S; Nelms, N; Rashid, K; Schult, O W B; Siems, T; Simons, L M

1999-01-01

Lyman and Balmer transitions of antiprotonic hydrogen and deuterium have been measured at the low-energy antiproton ring LEAR at CERN in order to determine the strong interaction effects. The X-rays were detected using charge-coupled devices (CCDs) and a reflection type crystal spectrometer. The results of the measurements support the meson-exchange models describing the medium and long range part of the nucleon-antinucleon interaction. (33 refs).

Electronic states of on- and off-center donors in quantum rings of finite width

International Nuclear Information System (INIS)

Lima, R.P.A.; Amado, M.

2008-01-01

The electronic states of a hydrogenic donor in two-dimensional quantum rings are calculated by taking into account the finite width of the potential well in the ring. In addition, a strong magnetic field is applied perpendicular to the quantum ring. Using the effective-mass approximation at the Γ valley, the radial Hamiltonian for the envelope-function is exactly diagonalized in the case of on-center donors. The corresponding energy levels for different angular momenta are studied as a function of the applied magnetic field. In the case of off-center donors, a perturbation approach is considered and its limitations are discussed. Finally, we calculate the absorption spectra and oscillator strength for different intraband transitions, specifically for on-center donors

The effect of geometric scattering on the oscillatory magnetoconductance in multiply connected disordered mesoscopic rings

International Nuclear Information System (INIS)

Basu, C.; Gu Benyuan.

1994-12-01

We present the quantum mechanical calculations on the conductance of a quantum waveguide consisting of multiply connected mesoscopic rings with disordered ring-circumferences and ballistic lead connections between the rings with the transfer matrix approach. The profiles of the conductance as functions of the magnetic flux and the Fermi wave number of electrons depend on the number of rings as also on the geometric configuration of the system. The conductance spectrum of this system for disordered ring circumferences, disordered ring intervals and disordered magnetic flux is examined in detail. Studying the effect of geometric scattering and the two different length scales involved in the network, namely, the ring circumference and the ballistic lead connections on the conductance profile, we find that there exist two kinds of mini-bands, one originating from the bound states of the rings, i.e. the intrinsic mini-bands, and the other associated with the connecting leads between the adjacent rings, which are the extra mini-bands. These two kinds of mini-bands respond differently to external perturbations in parameters. Unlike the system of potential scatterers, this system of geometric scatterers show complete band formations at all energies even for finite systems and there is a preferential decay of the energy states depending upon the type of disorder introduced. The conductance band structures strongly depend on the geometric configuration of the network and so by controlling the geometric parameters, the conductance band structures can be artificially tailored. (author). 18 refs, 6 figs

Group graded associated ideals with flat base change of rings and ...

Indian Academy of Sciences (India)

developed in [12] for G-associated ideals, that is, the behaviour of G-associated ideals. (AssG) with short exact sequences. Second, in §4 we consider the generalized notions of. G-associated prime ideals for not necessarily Noetherian rings and introduce strong Krull. G-associated ideals (AssSG) with flat base change of ...

Vortex-ring-induced large bubble entrainment during drop impact

KAUST Repository

Thoraval, Marie-Jean

2016-03-29

For a limited set of impact conditions, a drop impacting onto a pool can entrap an air bubble as large as its own size. The subsequent rise and rupture of this large bubble plays an important role in aerosol formation and gas transport at the air-sea interface. The large bubble is formed when the impact crater closes up near the pool surface and is known to occur only for drops that are prolate at impact. Herein we use experiments and numerical simulations to show that a concentrated vortex ring, produced in the neck between the drop and the pool, controls the crater deformations and pinchoff. However, it is not the strongest vortex rings that are responsible for the large bubbles, as they interact too strongly with the pool surface and self-destruct. Rather, it is somewhat weaker vortices that can deform the deeper craters, which manage to pinch off the large bubbles. These observations also explain why the strongest and most penetrating vortex rings emerging from drop impacts are not produced by oblate drops but by more prolate drop shapes, as had been observed in previous experiments.

Blowing smoke rings in superfluid helium

International Nuclear Information System (INIS)

Allum, D.R.; McClintock, P.V.E.

1977-01-01

Among experiments designed to investigate the properties of superfluids, measurements are discussed which aim at determining the variation in the speed of an ion with the size of the electric field propelling it through liquid helium. The experimental set up using helium ions is described. The velocity-field characteristic shows an initial rise but at a higher electric field the ions exhibit the curious behaviour of slowing down before again increasing speed with force. The reason for this region of slowing down is here explained as being due to the fact that the charge is no longer carried by a free ion but, rather, by a charged vortex ring. As the ion speeds thorugh the liquid it suddenly creates a vortex ring and as one of the fundamental characteristics of a vortex ring is that its velocity is inversely proportional to its radius the speed reduction is explained. The subsequent rise in the characteristic indicates that the charge carriers are no longer straightforward charged vortex rings. This behaviour is attributed to ions 'falling off' their rings soon after creating them. It would appear that the force exerted by the electric field is so large that it overcomes the hydrodynamic force which binds the ion to the slowly moving vortex, enabling the ion to escape and accelerate away. In a final levelling off part of the characteristic curve it is considered that the ions are travelling faster than the critical velocity for roton creation, but are moving far below that for phonon creation. One may therefore conclude that the ion, as it travels through the liquid, transforms energy extracted from the electric field into rotons, which fan out forming a sort of wake behind it. (U.K.)

Magnetic forces and localized resonances in electron transfer through quantum rings.

Science.gov (United States)

Poniedziałek, M R; Szafran, B

2010-11-24

We study the current flow through semiconductor quantum rings. In high magnetic fields the current is usually injected into the arm of the ring preferred by classical magnetic forces. However, for narrow magnetic field intervals that appear periodically on the magnetic field scale the current is injected into the other arm of the ring. We indicate that the appearance of the anomalous-non-classical-current circulation results from Fano interference involving localized resonant states. The identification of the Fano interference is based on the comparison of the solution of the scattering problem with the results of the stabilization method. The latter employs the bound-state type calculations and allows us to extract both the energy of metastable states localized within the ring and the width of resonances by analysis of the energy spectrum of a finite size system as a function of its length. The Fano resonances involving states of anomalous current circulation become extremely narrow on both the magnetic field and energy scales. This is consistent with the orientation of the Lorentz force that tends to keep the electron within the ring and thus increases the lifetime of the electron localization within the ring. Absence of periodic Fano resonances in electron transfer probability through a quantum ring containing an elastic scatterer is also explained.

Some Aspects of Ring Theory

CERN Document Server

Herstein, IN

2011-01-01

S. Amitsur: Associative rings with identities.- I.N. Herstein: Topics in ring theory.- N. Jacobson: Representation theory of Jordan algebras.- I. Kaplansky: The theory of homological dimension.- D. Buchsbaum: Complexes in local ring theory.- P.H. Cohn: Two topics in ring theory.- A.W. Goldie: Non-commutative localisation.

Improving the Accuracy of Laplacian Estimation with Novel Variable Inter-Ring Distances Concentric Ring Electrodes

Directory of Open Access Journals (Sweden)

Oleksandr Makeyev

2016-06-01

Full Text Available Noninvasive concentric ring electrodes are a promising alternative to conventional disc electrodes. Currently, the superiority of tripolar concentric ring electrodes over disc electrodes, in particular, in accuracy of Laplacian estimation, has been demonstrated in a range of applications. In our recent work, we have shown that accuracy of Laplacian estimation can be improved with multipolar concentric ring electrodes using a general approach to estimation of the Laplacian for an (n + 1-polar electrode with n rings using the (4n + 1-point method for n ≥ 2. This paper takes the next step toward further improving the Laplacian estimate by proposing novel variable inter-ring distances concentric ring electrodes. Derived using a modified (4n + 1-point method, linearly increasing and decreasing inter-ring distances tripolar (n = 2 and quadripolar (n = 3 electrode configurations are compared to their constant inter-ring distances counterparts. Finite element method modeling and analytic results are consistent and suggest that increasing inter-ring distances electrode configurations may decrease the truncation error resulting in more accurate Laplacian estimates compared to respective constant inter-ring distances configurations. For currently used tripolar electrode configuration, the truncation error may be decreased more than two-fold, while for the quadripolar configuration more than a six-fold decrease is expected.

Improving the Accuracy of Laplacian Estimation with Novel Variable Inter-Ring Distances Concentric Ring Electrodes

Science.gov (United States)

Makeyev, Oleksandr; Besio, Walter G.

2016-01-01

Noninvasive concentric ring electrodes are a promising alternative to conventional disc electrodes. Currently, the superiority of tripolar concentric ring electrodes over disc electrodes, in particular, in accuracy of Laplacian estimation, has been demonstrated in a range of applications. In our recent work, we have shown that accuracy of Laplacian estimation can be improved with multipolar concentric ring electrodes using a general approach to estimation of the Laplacian for an (n + 1)-polar electrode with n rings using the (4n + 1)-point method for n ≥ 2. This paper takes the next step toward further improving the Laplacian estimate by proposing novel variable inter-ring distances concentric ring electrodes. Derived using a modified (4n + 1)-point method, linearly increasing and decreasing inter-ring distances tripolar (n = 2) and quadripolar (n = 3) electrode configurations are compared to their constant inter-ring distances counterparts. Finite element method modeling and analytic results are consistent and suggest that increasing inter-ring distances electrode configurations may decrease the truncation error resulting in more accurate Laplacian estimates compared to respective constant inter-ring distances configurations. For currently used tripolar electrode configuration, the truncation error may be decreased more than two-fold, while for the quadripolar configuration more than a six-fold decrease is expected. PMID:27294933

an extended octagonal ring dynamometer for measurement of forces

African Journals Online (AJOL)

NIJOTECH

The analysis, design, construction, evaluation and use of an extended octagonal ring dynamometer for ... For tillage applications, it has been used ..... confirmed that the dynamometer and the measurement system were capable of indicating.

Digestion of chrysanthemum stunt viroid by leaf extracts of Capsicum chinense indicates strong RNA-digesting activity.

Science.gov (United States)

Iraklis, Boubourakas; Kanda, Hiroko; Nabeshima, Tomoyuki; Onda, Mayu; Ota, Nao; Koeda, Sota; Hosokawa, Munetaka

2016-08-01

CSVd could not infect Nicotiana benthamiana when the plants were pretreated with crude leaf extract of Capsicum chinense 'Sy-2'. C. chinense leaves were revealed to contain strong RNA-digesting activity. Several studies have identified active antiviral and antiviroid agents in plants. Capsicum plants are known to contain antiviral agents, but the mechanism of their activity has not been determined. We aimed to elucidate the mechanism of Capsicum extract's antiviroid activity. Chrysanthemum stunt viroid (CSVd) was inoculated into Nicotiana benthamiana plants before or after treating the plants with a leaf extract of Capsicum chinense 'Sy-2'. CSVd infection was determined using quantitative reverse transcription-polymerase chain reaction (qRT-PCR) 3 weeks after inoculation. When Capsicum extract was sprayed or painted onto N. benthamiana before inoculation, it was effective in preventing infection by CSVd. To evaluate CSVd digestion activity in leaf extracts, CSVd was mixed with leaf extracts of Mirabilis, Phytolacca, Pelargonium and Capsicum. CSVd-digesting activities were examined by quantifying undigested CSVd using qRT-PCR, and RNA gel blotting permitted visualization of the digested CSVd. Only Capsicum leaf extract digested CSVd, and in the Capsicum treatment, small digested CSVd products were detected by RNA gel blot analysis. When the digesting experiment was performed for various cultivars and species of Capsicum, only cultivars of C. chinense showed strong CSVd-digesting activity. Our observations indicated that Capsicum extract contains strong RNA-digesting activity, leading to the conclusion that this activity is the main mechanism for protection from infection by CSVd through spraying or painting before inoculation. To our knowledge, this is the first report of a strong RNA-digesting activity by a plant extract.

Tree-ring growth patterns and climatic signals along a vertical transect of larch sites in the Simplon and Rhône Valleys (Switzerland)

Science.gov (United States)

Riechelmann, Dana F. C.; Esper, Jan

2017-04-01

State-of-the-art millennial long temperature reconstructions from the European Alps integrate wood samples of Larix decidua Mill. from the Lötschental and Simplon regions in Switzerland (Büntgen et al., 2005; 2006). Some of the oldest samples that enable the extension of the time-series back into the first millennium AD are obtained from old buildings in Simplon Village, through the precise location of these samples and the elevation of sampling sites remain unknown. We here evaluate the growth characteristics of larch tree-ring width data along a vertical transect in the Simplon and Rhône valleys. 330 trees from nine sites in 985, 1100, 1400, 1575, 1710, 1712, 1900, 2020, and 2150 m asl have been sampled and analysed for their climate signals. The results indicate a stronger temperature signal in the tree-ring width with increasing elevation. The lower the sites the more a drought signal is imprinted in the ring width data. The intermediate site at 1400 m asl does not show any pronounced climate signal. A comparison of growth patterns of living-tree sites with samples from the historical buildings in Simplon Village (Riechelmann et al., 2013) indicates the construction timber to origin from intermediate to higher elevations. We therefore do not expect strong temperature signal from these timbers. References: Büntgen, U., Esper, J., Frank, D.C., Nicolussi, K., Schmidhalter, M., 2005. A 1052-year tree-ring proxy for Alpine summer temperatures. Climate Dynamics 25: 141-153. Büntgen, U., Frank, D.C., Nievergelt, D., Esper J., 2006. Summer temperature variations in the European Alps, A.D. 755-2004. Journal of Climate 19: 5606-5623. Riechelmann, D.F.C., Schmidhalter, M., Büntgen, U., Esper, J., 2013. Extending a high-elevation larch ring width chronology from the Simplon region in the Swiss Alps over the past millenium. TRACE 11:103-108.

Study of improvement in 1st ring`s gas-seal; Top ring no gas seal seino kojo no kento

Energy Technology Data Exchange (ETDEWEB)

Ando, H; Tateishi, Y; Fujimura, K; Hitosugi, H [Nippon Piston Ring Co. Ltd., Tokyo (Japan)

1997-10-01

The authors studied the effect of an angle of 1st ring twist on the amount of blow-by concerning higher speed/higher output engines for motorcycles. As a result, the authors found the twist made the ring restrained in a ring groove of piston , and confirmed its suitable range for blow-by. By means of the developed optimization method, the authors have achieved significant reduction in blow-by at high engine speed. 1 ref., 9 figs., 2 tabs.

Optimizing ring-based CSR sources

International Nuclear Information System (INIS)

Byrd, J.M.; De Santis, S.; Hao, Z.; Martin, M.C.; Munson, D.V.; Li, D.; Nishimura, H.; Robin, D.S.; Sannibale, F.; Schlueter, R.D.; Schoenlein, R.; Jung, J.Y.; Venturini, M.; Wan, W.; Zholents, A.A.; Zolotorev, M.

2004-01-01

Coherent synchrotron radiation (CSR) is a fascinating phenomenon recently observed in electron storage rings and shows tremendous promise as a high power source of radiation at terahertz frequencies. However, because of the properties of the radiation and the electron beams needed to produce it, there are a number of interesting features of the storage ring that can be optimized for CSR. Furthermore, CSR has been observed in three distinct forms: as steady pulses from short bunches, bursts from growth of spontaneous modulations in high current bunches, and from micro modulations imposed on a bunch from laser slicing. These processes have their relative merits as sources and can be improved via the ring design. The terahertz (THz) and sub-THz region of the electromagnetic spectrum lies between the infrared and the microwave . This boundary region is beyond the normal reach of optical and electronic measurement techniques and sources associated with these better-known neighbors. Recent research has demonstrated a relatively high power source of THz radiation from electron storage rings: coherent synchrotron radiation (CSR). Besides offering high power, CSR enables broadband optical techniques to be extended to nearly the microwave region, and has inherently sub-picosecond pulses. As a result, new opportunities for scientific research and applications are enabled across a diverse array of disciplines: condensed matter physics, medicine, manufacturing, and space and defense industries. CSR will have a strong impact on THz imaging, spectroscopy, femtosecond dynamics, and driving novel non-linear processes. CSR is emitted by bunches of accelerated charged particles when the bunch length is shorter than the wavelength being emitted. When this criterion is met, all the particles emit in phase, and a single-cycle electromagnetic pulse results with an intensity proportional to the square of the number of particles in the bunch. It is this quadratic dependence that can

Optical properties of an elliptic quantum ring: Eccentricity and electric field effects

Science.gov (United States)

Bejan, Doina; Stan, Cristina; Niculescu, Ecaterina C.

2018-04-01

We have theoretically studied the electronic and optical properties of a GaAs/AlGaAs elliptic quantum ring under in-plane electric field. The effects of an eccentric internal barrier -placed along the electric field direction, chosen as x-axis- and incident light polarization are particularly taken into account. The one-electron energy spectrum and wave functions are found using the adiabatic approximation and the finite element method within the effective-mass model. We show that it is possible to repair the structural distortion by applying an appropriate in-plane electric field, and the compensation is almost complete for all electronic states under study. For both concentric and eccentric quantum ring the intraband optical properties are very sensitive to the electric field and probe laser polarization. As expected, in the systems with eccentricity distortions the energy spectrum, as well as the optical response, strongly depends on the direction of the externally applied electric field, an effect that can be used as a signature of ring eccentricity. We demonstrated the possibility of generating second harmonic response at double resonance condition for incident light polarized along the x-axis if the electric field or/and eccentric barrier break the inversion symmetry. Also, strong third harmonic signal can be generated at triple resonance condition for a specific interval of electric field values when using y-polarized light.

Viscosity of ring polymer melts

KAUST Repository

Pasquino, Rossana

2013-10-15

We have measured the linear rheology of critically purified ring polyisoprenes, polystyrenes, and polyethyleneoxides of different molar masses. The ratio of the zero-shear viscosities of linear polymer melts η0,linear to their ring counterparts η0,ring at isofrictional conditions is discussed as a function of the number of entanglements Z. In the unentangled regime η0,linear/η 0,ring is virtually constant, consistent with the earlier data, atomistic simulations, and the theoretical expectation η0,linear/ η0,ring = 2. In the entanglement regime, the Z-dependence of ring viscosity is much weaker than that of linear polymers, in qualitative agreement with predictions from scaling theory and simulations. The power-law extracted from the available experimental data in the rather limited range 1 < Z < 20, η0,linear/η0,ring ∼ Z 1.2±0.3, is weaker than the scaling prediction (η0,linear/η0,ring ∼ Z 1.6±0.3) and the simulations (η0,linear/ η0,ring ∼ Z2.0±0.3). Nevertheless, the present collection of state-of-the-art experimental data unambiguously demonstrates that rings exhibit a universal trend clearly departing from that of their linear counterparts, and hence it represents a major step toward resolving a 30-year-old problem. © 2013 American Chemical Society.

Viscosity of ring polymer melts

KAUST Repository

Pasquino, Rossana; Vasilakopoulos, Thodoris C.; Jeong, Youncheol; Lee, Hyojoon; Rogers, Simon A.; Sakellariou, Georgios; Allgaier, Jü rgen B.; Takano, Atsushi; Brá s, Ana Rita E; Chang, Taihyun; Gooß en, Sebastian; Pyckhout-Hintzen, Wim; Wischnewski, Andreas; Hadjichristidis, Nikolaos; Richter, Dieter R.; Rubinstein, Michael H.; Vlassopoulos, Dimitris

2013-01-01

We have measured the linear rheology of critically purified ring polyisoprenes, polystyrenes, and polyethyleneoxides of different molar masses. The ratio of the zero-shear viscosities of linear polymer melts η0,linear to their ring counterparts η0,ring at isofrictional conditions is discussed as a function of the number of entanglements Z. In the unentangled regime η0,linear/η 0,ring is virtually constant, consistent with the earlier data, atomistic simulations, and the theoretical expectation η0,linear/ η0,ring = 2. In the entanglement regime, the Z-dependence of ring viscosity is much weaker than that of linear polymers, in qualitative agreement with predictions from scaling theory and simulations. The power-law extracted from the available experimental data in the rather limited range 1 < Z < 20, η0,linear/η0,ring ∼ Z 1.2±0.3, is weaker than the scaling prediction (η0,linear/η0,ring ∼ Z 1.6±0.3) and the simulations (η0,linear/ η0,ring ∼ Z2.0±0.3). Nevertheless, the present collection of state-of-the-art experimental data unambiguously demonstrates that rings exhibit a universal trend clearly departing from that of their linear counterparts, and hence it represents a major step toward resolving a 30-year-old problem. © 2013 American Chemical Society.

A study of Solar-Enso correlation with southern Brazil tree ring index (1955- 1991)

Science.gov (United States)

Rigozo, N.; Nordemann, D.; Vieira, L.; Echer, E.

The effects of solar activity and El Niño-Southern Oscillation on tree growth in Southern Brazil were studied by correlation analysis. Trees for this study were native Araucaria (Araucaria Angustifolia)from four locations in Rio Grande do Sul State, in Southern Brazil: Canela (29o18`S, 50o51`W, 790 m asl), Nova Petropolis (29o2`S, 51o10`W, 579 m asl), Sao Francisco de Paula (29o25`S, 50o24`W, 930 m asl) and Sao Martinho da Serra (29o30`S, 53o53`W, 484 m asl). From these four sites, an average tree ring Index for this region was derived, for the period 1955-1991. Linear correlations were made on annual and 10 year running averages of this tree ring Index, of sunspot number Rz and SOI. For annual averages, the correlation coefficients were low, and the multiple regression between tree ring and SOI and Rz indicates that 20% of the variance in tree rings was explained by solar activity and ENSO variability. However, when the 10 year running averages correlations were made, the coefficient correlations were much higher. A clear anticorrelation is observed between SOI and Index (r=-0.81) whereas Rz and Index show a positive correlation (r=0.67). The multiple regression of 10 year running averages indicates that 76% of the variance in tree ring INdex was explained by solar activity and ENSO. These results indicate that the effects of solar activity and ENSO on tree rings are better seen on long timescales.

Læring og refleksion

DEFF Research Database (Denmark)

Wahlgren, B.; Rattleff, Pernille; Høyrup, S.

State of the art inden for forskning om læring på arbejdspladsen samt gennemgang af læringsteori og refleksionsbegrebet hos Dewey, Dreyfus, Schön, Argyris, Kolb, Jarvis, Mezirow og Brookfield. Afsluttes med diskussion af syntetiseret model for læring på arbejdspladsen.......State of the art inden for forskning om læring på arbejdspladsen samt gennemgang af læringsteori og refleksionsbegrebet hos Dewey, Dreyfus, Schön, Argyris, Kolb, Jarvis, Mezirow og Brookfield. Afsluttes med diskussion af syntetiseret model for læring på arbejdspladsen....

Birth Control Ring

Science.gov (United States)

... Health Food & Fitness Diseases & Conditions Infections Drugs & Alcohol School & Jobs Sports Expert Answers (Q&A) Staying Safe Videos for Educators Search English Español Birth Control Ring KidsHealth / For Teens / Birth Control Ring What's ...

A correlation for safety valve blowdown and ring settings

International Nuclear Information System (INIS)

Singh, A.; Shak, D.

1982-01-01

The blowdown of a spring loaded safety valve is defined as the difference between the pressure at which the valve opens and the pressure at which the valve fully closes under certain fluid flow conditions. Generally, the blowdown is expressed in terms of percentage of the opening pressure. An extensive series of tests carried out in the EPRI/PWR Utilities Valve Test Program has shown that the blowdown of safety valves can in general be strongly dependent upon the valve geometry and other parameters such as ring adjustments, spring stiffness, backpressure etc. In the present study, correlations have been developed using the EPRI safety valve test data to predict the expected blowdown as a function of adjustment ring settings for geometrically similar valves under steam discharge conditions. The correlation is validated against two different size Dresser valves

From coffee ring to spherulites ring of poly(ethylene oxide) film from drying droplet

Science.gov (United States)

Hu, Yinchun; Zhang, Xuerong; Qiu, Maibo; Wei, Yan; Zhou, Qiong; Huang, Di

2018-03-01

We discuss how the "spherulites ring" morphology and "coffee ring" profile of PEO film formed by the drying droplet at glass substrate with different heating rate. Upon increasing the heating rate of substrate, it is found that deposited PEO film from drying droplet shows the unusually observed "coffee ring" profile and "spherulites ring" morphology. The main mechanism for this phenomenon is proposed to be an enhanced Marangoni convection which is induced by the increased solute concentration gradient and reduced viscous force above 70 °C. A simple formation mechanism of the unusually observed "coffee ring" profile and "spherulites ring" morphology is proposed. These findings can be exploited to trace the center of Marangoni convection, with potential applications in designing the spherulite patterns of crystalline polymer films in ink-jet printing and self-assembly fields.

Tree-ring chronologies and stable carbon isotopic composition reveal impacts of hydro-climate change on bottomland hardwood forests of South-Central Texas

Science.gov (United States)

Deshpande, A. G.; Lafon, C. W.; Hyodo, A.; Boutton, T. W.; Moore, G. W.

2017-12-01

Over the last three decades, South-Central Texas has experienced an increase in frequency and intensity of hydro-climatic anomalies such as extreme droughts and floods. These extreme events can have negative impacts on forest health and can strongly alter a wide range of ecosystem processes. Tree increment growth in bottomland hardwood forests is influenced by droughts and floods, which affects the carbon isotope values (δ13C) in tree-ring cellulose. This study aims to assess the impacts of hydro-climate change on the growth and physiological response of bottomland hardwood forests by investigating variations in radial growth and tree-ring carbon isotopic composition. Annual ring-width chronologies for 41 years (1975-2016) were developed from 24 water oak (Quercus nigra) trees at 4 sites along a 25 km transect located in the San Bernard River watershed. The δ13C values in cellulose were measured from 4-year ring composites including years with anomalously high and low precipitation. Dendroclimatology analysis involved correlating ring-width index with precipitation records and Palmer Drought Sensitivity Index (PDSI). Radial growth was more closely associated with spring-summer (Feb-Aug) precipitation (R2 = 0.42, pstress, as indicated by narrower growth rings and increased cellulose δ13C. However, the inter-site variation in δ13C indicated large hydro-climatic variation between sites (2.79-4.24‰ for wet years and 0.53-1.50‰ for drought years). δ13C values showed an increase of 0.78‰ and 2.40‰ from the wettest (1991-1994) to the driest period (2008-2011) at two of our sites, possibly due to drought-induced moisture-deficit-stress. However, at the other two sites, the δ13C values of tree rings from the same periods decreased by 0.65‰ and 1.19‰, possibly emanating from flooding-induced stress caused by waterlogging. This study provides insights on how hydro-climatic variations affect riparian forest health in the region and acts as a baseline for

Femtosecond laser-induced concentric ring microstructures on Zr-based metallic glass

International Nuclear Information System (INIS)

Ma Fengxu; Yang Jianjun; Xiaonong Zhu; Liang Chunyong; Wang Hongshui

2010-01-01

Surface morphological evolution of Zr-based metallic glass ablated by femtosecond lasers is investigated in atmosphere condition. Three types of permanent ring structures with micro-level spacing are observed for different laser shots and fluences. In the case of low laser fluences, the generation of annular patterns with nonthermal features is observed on the rippled structure with the subwavelength scale, and the ring spacing shows a decrease tendency from the center to the margin. While in the case of high laser fluences, the concentric rings formation within the laser spot is found to have evident molten traces and display the increasing ring spacing along the radial direction. Moreover, when the laser shots accumulation becomes large, the above two types of ring microstructures begin to develop into the common ablation craters. Analysis and discussion suggests that the stress-induced condensation of ablation vapors and the frozen thermocapillary waves on the molten surfaces should be responsible for the formation of two different types of concentric ring structures, respectively. Eventually, a processing window for each resulting surface microstructure type is obtained experimentally and indicates the possibility to control the morphological transitions among different types.

Phosphazene-promoted metal-free ring-opening polymerization of ethylene oxide initiated by carboxylic acid

KAUST Repository

Zhao, Junpeng; Pahovnik, David; Gnanou, Yves; Hadjichristidis, Nikolaos

2014-01-01

The effectiveness of carboxylic acid as initiator for the anionic ring-opening polymerization of ethylene oxide was investigated with a strong phosphazene base (t-BuP4) used as promoter. Kinetic study showed an induction period, i.e., transformation

New chromaticity compensation approach and dynamic aperture increase in the SSRF storage ring

International Nuclear Information System (INIS)

Tian Shunqiang; Hou Jie; Chen Guangling; Chinese Academy of Sciences, Beijing; Liu Guimin

2008-01-01

Strong chromatic sextupoles used to compensate natural chromaticities in the third generation light source storage ring usually reduce dynamic aperture drastically. Many optimization methods can be used to find solutions that provide large dynamic apertures. This paper discusses a new optimization approach of sextupole strengths with step-by-step procedure, which is applied in the SSRF storage ring, and a better solution is obtained. Investigating driving terms generated by the sextupoles in every step can analyze their convergences and guide the weight setting among different terms in object function of the single resonance approach based on the perturbation theory. (authors)

The suitability of annual tree growth rings as environmental archives: Evidence from Sr, Nd, Pb and Ca isotopes in spruce growth rings from the Strengbach watershed

Science.gov (United States)

Stille, Peter; Schmitt, Anne-Désirée; Labolle, François; Pierret, Marie-Claire; Gangloff, Sophie; Cobert, Florian; Lucot, Eric; Guéguen, Florence; Brioschi, Laure; Steinmann, Marc; Chabaux, François

2012-05-01

The combination of the Sr, Nd and Pb isotope systems, recognized as tracers of sources, with the Ca isotope system, known to reveal biology-related fractionations, allowed us to test the reliability of spruce (Picea abies) growth rings as environmental archives through time (from 1916 to 1983) in a forest ecosystem affected by acid atmospheric deposition. Sr and Pb isotopes have already been applied in former tree-ring studies, whereas the suitability of Nd and Ca isotope systems is checked in the present article. Our Sr and Nd isotope data indicate an evolution in the cation origin with a geogenic origin for the oldest rings and an atmospheric origin for the youngest rings. Ca isotopes show, for their part, an isotopic homogeneity which could be linked to the very low weathering flux of Ca. Since this flux is weak the spruces' root systems have pumped the Ca mainly from the organic matter-rich top-soil over the past century. In contrast, the annual growth rings studied are not reliable and suitable archives of past Pb pollution.

THE RING IN THE FOLK STORIES-HALK ANLATILARINDA YÜZÜK

Directory of Open Access Journals (Sweden)

Yaprak Pelin Uluışık

2017-04-01

Full Text Available A ring is not just a piece of jewelry that indicates commitment, endless unity and loyalty; it is a symbol that has a chain of common meanings intertwined with similar features in different geographies. It is seen that rings in myths, epics, legends, fairy tales and folk stories provide features such as power, control, wisdom, youth, earthly and spiritual prosperity, good fortune, invisibility, shape changing, talking with plants and animals. Heroes wearing these rings that protect the human soul from the evil will not suffer in any way. In the stories of the west, it is often mentioned about cursed rings that effects its owner in a bad manner and brings only bad luck. These rings, located in places that can be associated with the underground such as the ground, the hole, the cave and the water bed, are given to the heroes by supernatural beings or wise men. Supernatural beings, such as demons or giants, are trapped in these rings, many of which are magical, as slaves of the rings at an unknown time. When the hero rubs his ring, reverses it, puts it in his mouth; when he hits the ring or whistles to it, the slave of the ring comes out and asks the hero for his wish. This wish is carried out by the slave right after the hero tells the slave what he wishes. In this article, many examples from the Chinese myths to the Arabic tales, from the Babylonian Talmud to the descriptions of Scandinavian, Celtic, Welsh, French and Spanish culture have been examined in order to determine the characteristics of the rings mentioned in folkloric tales. In addition, many examples of Turkish folk literature from Dede Korkut to Anatolian tales were also discussed.

Revisit the modeling of the Saturnian ring atmosphere and ionosphere from the "Cassini Grand Finale" results

Science.gov (United States)

Tseng, W. L.; Johnson, R. E.; Tucker, O. J.; Perry, M. E.; Ip, W. H.

2017-12-01

During the Cassini Grand Finale mission, this spacecraft, for the first time, has done the in-situ measurements of Saturn's upper atmosphere and its rings and provides critical information for understanding the coupling dynamics between the main rings and the Saturnian system. The ring atmosphere is the source of neutrals (i.e., O2, H2, H; Tseng et al., 2010; 2013a), which is primarily generated by photolytic decomposition of water ice (Johnson et al., 2006), and plasma (i.e., O2+ and H2+; Tseng et al., 2011) in the Saturnian magnetosphere. In addition, the main rings have strong interaction with Saturn's atmosphere and ionosphere (i.e., a source of oxygen into Saturn's upper atmosphere and/or the "ring rain" in O'Donoghue et al., 2013). Furthermore, the near-ring plasma environment is complicated by the neutrals from both the seasonally dependent ring atmosphere and Enceladus torus (Tseng et al., 2013b), and, possibly, from small grains from the main and tenuous F and G rings (Johnson et al.2017). The data now coming from Cassini Grand Finale mission already shed light on the dominant physics and chemistry in this region of Saturn's magnetosphere, for example, the presence of carbonaceous material from meteorite impacts in the main rings and each gas species have similar distribution in the ring atmosphere. We will revisit the details in our ring atmosphere/ionosphere model to study, such as the source mechanism for the organic material and the neutral-grain-plasma interaction processes.

Sizes of the Smallest Particles at Saturn Ring Edges from Diffraction in UVIS Stellar Occultations

Science.gov (United States)

Eckert, S.; Colwell, J. E.; Becker, T. M.; Esposito, L. W.

2017-12-01

Cassini's Ultraviolet Imaging Spectrograph (UVIS) has observed more than 150 ring stellar occultations since its arrival at Saturn in 2004. We use stellar occultation data from the UVIS High Speed Photometer (HSP) to identify diffraction signals at ring edges caused by small particles diffracting light into the detector and consequently increasing the signal above that of the unocculted star. The shape of a diffraction signal is indicative of the particle size distribution at the ring edge, which may be a dynamically perturbed region. Becker et al. (2015 Icarus doi:10.1016/j.icarus.2015.11.001) analyzed diffraction signals at the outer edge of the A Ring and the edges of the Encke Gap. We apply the Becker et al. (2015) model to the outer edge of the B Ring as well as the edges of ringlets within the C Ring and Cassini Division. In addition, we analyze diffraction signatures at the A Ring outer edge in 2 new occultations. The best-fit model signals to these occultations are consistent with the findings of Becker et al. (2015) who found an average minimum particle size amin =4.5 mm and average power law slope q=3.2. At the B Ring outer edge, we detect a diffraction signal in 10 of 28 occultations in which the diffraction signal would be observable according to our criteria for star brightness and observation geometry. We find a mean amin =11 mm and a mean q=3.0. At both edges of the so-called "Strange" ringlet (R6) we find a mean amin = 20 mm and mean q values of 3.0 and 2.8 at the inner and outer edges, respectively. In contrast, we do not observe any clear diffraction signals at either edge of the wider Huygens ringlet. This could imply an absence of cm-scale or smaller particles and indicates that collisions here may be less vigorous than at the other ring edges analyzed in this study. We detect diffraction in a small fraction ( 10%) of occultations at 3 ringlets within the Cassini Division: the Herschel ringlet, the Laplace ringlet, and the Barnard ringlet. We

Superconducting wiggler magnets for beam-emittance damping rings

CERN Document Server

Schoerling, Daniel

2012-01-01

Ultra-low emittance beams with a high bunch charge are necessary for the luminosity performance of linear electron-positron colliders, such as the Compact Linear Collider (CLIC). An effective way to create ultra-low emittance beams with a high bunch charge is to use damping rings, or storage rings equipped with strong damping wiggler magnets. The remanent field of the permanent magnet materials and the ohmic losses in normal conductors limit the economically achievable pole field in accelerator magnets operated at around room temperature to below the magnetic saturation induction, which is 2.15 T for iron. In wiggler magnets, the pole field in the center of the gap is reduced further like the hyperbolic cosine of the ratio of the gap size and the period length multiplied by pi. Moreover, damping wiggler magnets require relatively large gaps because they have to accept the un-damped beam and to generate, at a small period length, a large magnetic flux density amplitude to effectively damp the beam emittance....

Field-reversing electron and ion rings for the confinement and heating of plasmas. Annual progress report, October 1, 1985-September 30, 1986

International Nuclear Information System (INIS)

Fleischmann, H.H.

1986-10-01

During the present, second period of our contract, the effort of our RECE-group was focussed mainly in four areas: (1) the design and construction of our new main experimental device, the megavolt ion coil experiment (MICE, aimed at generating 1-MeV ion rings) was continued. The device construction was completed and injection experiments recently have started using a half-cusp arrangement. (2) Using our smaller MERGE device (500 keV electrons, cusp injection), we investigated as expected the precessional stabilization of strong electron rings by a resistive wall. As expected, the experiments are completed. The results show excellent agreement with the basic theoretical expectations of our earlier analytic calculations and also with a more detailed computer code recently compiled. (3) Also, our MERGE device was completed as expected; experiments showed successful generation of electron and plasma rings; first experiments on the merging of these rings show a rapid attraction between the rings, which is to be properly slowed down by the introduction of a resistive wall. (4) Our pilot model calculations on mixed-CT configurations were nearly completed; including a survey of relevant plasma ring equilibria with a strong large-orbit particle components. Rough stability limits were obtained by studying the magnetic interaction between the two components

The Mechanics of a Chain or Ring of Spherical Magnets

KAUST Repository

Hall, Cameron L.; Vella, Dominic; Goriely, Alain

2013-01-01

Strong magnets, such as neodymium-iron-boron magnets, are increasingly being manufactured as spheres. Because of their dipolar characters, these spheres can easily be arranged into long chains that exhibit mechanical properties reminiscent of elastic strings or rods. While simple formulations exist for the energy of a deformed elastic rod, it is not clear whether or not they are also appropriate for a chain of spherical magnets. In this paper, we use discrete-to-continuum asymptotic analysis to derive a continuum model for the energy of a deformed chain of magnets based on the magnetostatic interactions between individual spheres. We find that the mechanical properties of a chain of magnets differ significantly from those of an elastic rod: while both magnetic chains and elastic rods support bending by change of local curvature, nonlocal interaction terms also appear in the energy formulation for a magnetic chain. This continuum model for the energy of a chain of magnets is used to analyze small deformations of a circular ring of magnets and hence obtain theoretical predictions for the vibrational modes of a circular ring of magnets. Surprisingly, despite the contribution of nonlocal energy terms, we find that the vibrations of a circular ring of magnets are governed by the same equation that governs the vibrations of a circular elastic ring. Copyright © by SIAM.

Multiplicative Structure and Hecke Rings of Generator Matrices for Codes over Quotient Rings of Euclidean Domains

Directory of Open Access Journals (Sweden)

Hajime Matsui

2017-12-01

Full Text Available In this study, we consider codes over Euclidean domains modulo their ideals. In the first half of the study, we deal with arbitrary Euclidean domains. We show that the product of generator matrices of codes over the rings mod a and mod b produces generator matrices of all codes over the ring mod a b , i.e., this correspondence is onto. Moreover, we show that if a and b are coprime, then this correspondence is one-to-one, i.e., there exist unique codes over the rings mod a and mod b that produce any given code over the ring mod a b through the product of their generator matrices. In the second half of the study, we focus on the typical Euclidean domains such as the rational integer ring, one-variable polynomial rings, rings of Gaussian and Eisenstein integers, p-adic integer rings and rings of one-variable formal power series. We define the reduced generator matrices of codes over Euclidean domains modulo their ideals and show their uniqueness. Finally, we apply our theory of reduced generator matrices to the Hecke rings of matrices over these Euclidean domains.

Simulation of magnetization and levitation properties of arrays of ring-shaped type-II superconductors

Energy Technology Data Exchange (ETDEWEB)

Liu, Jun, E-mail: linxj8686@163.com; Huang, Chenguang; Yong, Huadong; Zhou, Youhe, E-mail: zhouyh@lzu.edu.cn

2017-03-15

Highlights: • A strong magnetic coupling appears if the gap between the superconducting rings is small. • The saturation magnetization of superconducting rings is related to the radial gap but independent of the vertical gap. • The array of rings in a non-uniform field experiences a levitation force, which increases with increasing height or thickness of the rings. - Abstract: This paper presents an analysis of the magnetic and mechanical properties of arrays of superconducting rings arranged in axial, radial, and matrix configurations under different magnetic fields. In terms of the Bean's critical state model and the minimum magnetic energy method, the dependences of the magnetization and levitation behaviors on the geometry, number, and gap of the superconducting rings are obtained. The results show that when the applied field is spatially uniform, the magnetic property of the superconducting array is associated with the gaps between the rings. For the case of small gaps, the entire array becomes not easy to be fully penetrated by the induced currents, and the magnetic field profiles of which are almost the same as ones in a single large ring. If the superconducting array is fully penetrated, its saturation magnetization value is affected by the radial interval and, however, is almost independent of the vertical separation. When the applied field produced by a cylindrical permanent magnet is nonuniform, the superconducting array will be subjected to a levitation force. The levitation force increases monotonically and finally reaches a saturation value with increasing height or thickness of the rings, and such saturation value is closely related to the inner radius of the array.

Binomial Rings: Axiomatisation, Transfer and Classification

OpenAIRE

Xantcha, Qimh Richey

2011-01-01

Hall's binomial rings, rings with binomial coefficients, are given an axiomatisation and proved identical to the numerical rings studied by Ekedahl. The Binomial Transfer Principle is established, enabling combinatorial proofs of algebraical identities. The finitely generated binomial rings are completely classified. An application to modules over binomial rings is given.

Years of annual ring formation of trees and elements of minute amount

International Nuclear Information System (INIS)

Katayama, Yukio

1988-01-01

The structure of the trunks of trees is briefly explained, and the effect of environmental factors such as light, rain, soil, temperature and so on and the effect of environmental pollution are conceivable. The examples of the research on the quantitative determination of the elements of minute amount contained in the annual rings of trees and their use as the living things for environmental pollution index are shown, and the problems are considered. The concentration of manganese contained in annual rings may be used as environmental pollution index. It was pointed out that cadmium accumulated in annual rings had a strong correlation with the decrease of annual ring width. K-40 once taken in annual rings moved radially in connection with physical and physiological actions. The authors have examined the distribution of the elements of minute amount in the trunks, using Japanese cedar, white fir and oak as the specimens. For the quantitative analysis of the elements of minute amount, thermal neutron radioactivation analysis was used, which can analyze many elements simultaneously by nondestructive method. The elements of minute amount in the trunks of Japanese cedar, the difference of the distribution according to the kinds of trees, and the movement of elements within trunks are reported. The application of PIXE method to this analysis is considered. (Kako, I.)

Galactic rings revisited - I. CVRHS classifications of 3962 ringed galaxies from the Galaxy Zoo 2 Database

Science.gov (United States)

Buta, Ronald J.

2017-11-01

Rings are important and characteristic features of disc-shaped galaxies. This paper is the first in a series that re-visits galactic rings with the goals of further understanding the nature of the features and for examining their role in the secular evolution of galaxy structure. The series begins with a new sample of 3962 galaxies drawn from the Galaxy Zoo 2 citizen science data base, selected because zoo volunteers recognized a ring-shaped pattern in the morphology as seen in Sloan Digital Sky Survey colour images. The galaxies are classified within the framework of the Comprehensive de Vaucouleurs revised Hubble-Sandage system. It is found that zoo volunteers cued on the same kinds of ring-like features that were recognized in the 1995 Catalogue of Southern Ringed Galaxies. This paper presents the full catalogue of morphological classifications, comparisons with other sources of classifications and some histograms designed mainly to highlight the content of the catalogue. The advantages of the sample are its large size and the generally good quality of the images; the main disadvantage is the low physical resolution that limits the detectability of linearly small rings such as nuclear rings. The catalogue includes mainly inner and outer disc rings and lenses. Cataclysmic (`encounter-driven') rings (such as ring and polar ring galaxies) are recognized in less than 1 per cent of the sample.

Quantum Fourier Transform Over Galois Rings

OpenAIRE

Zhang, Yong

2009-01-01

Galois rings are regarded as "building blocks" of a finite commutative ring with identity. There have been many papers on classical error correction codes over Galois rings published. As an important warm-up before exploring quantum algorithms and quantum error correction codes over Galois rings, we study the quantum Fourier transform (QFT) over Galois rings and prove it can be efficiently preformed on a quantum computer. The properties of the QFT over Galois rings lead to the quantum algorit...

Coupling thermal atomic vapor to an integrated ring resonator

International Nuclear Information System (INIS)

Ritter, R; Kübler, H; Pfau, T; Löw, R; Gruhler, N; Pernice, W H P

2016-01-01

Strongly interacting atom–cavity systems within a network with many nodes constitute a possible realization for a quantum internet which allows for quantum communication and computation on the same platform. To implement such large-scale quantum networks, nanophotonic resonators are promising candidates because they can be scalably fabricated and interconnected with waveguides and optical fibers. By integrating arrays of ring resonators into a vapor cell we show that thermal rubidium atoms above room temperature can be coupled to photonic cavities as building blocks for chip-scale hybrid circuits. Although strong coupling is not yet achieved in this first realization, our approach provides a key step towards miniaturization and scalability of atom–cavity systems. (paper)

In vivo structure of the E. coli FtsZ-ring revealed by photoactivated localization microscopy (PALM).

Science.gov (United States)

Fu, Guo; Huang, Tao; Buss, Jackson; Coltharp, Carla; Hensel, Zach; Xiao, Jie

2010-09-13

The FtsZ protein, a tubulin-like GTPase, plays a pivotal role in prokaryotic cell division. In vivo it localizes to the midcell and assembles into a ring-like structure-the Z-ring. The Z-ring serves as an essential scaffold to recruit all other division proteins and generates contractile force for cytokinesis, but its supramolecular structure remains unknown. Electron microscopy (EM) has been unsuccessful in detecting the Z-ring due to the dense cytoplasm of bacterial cells, and conventional fluorescence light microscopy (FLM) has only provided images with limited spatial resolution (200-300 nm) due to the diffraction of light. Hence, given the small sizes of bacteria cells, identifying the in vivo structure of the Z-ring presents a substantial challenge. Here, we used photoactivated localization microscopy (PALM), a single molecule-based super-resolution imaging technique, to characterize the in vivo structure of the Z-ring in E. coli. We achieved a spatial resolution of ∼35 nm and discovered that in addition to the expected ring-like conformation, the Z-ring of E. coli adopts a novel compressed helical conformation with variable helical length and pitch. We measured the thickness of the Z-ring to be ∼110 nm and the packing density of FtsZ molecules inside the Z-ring to be greater than what is expected for a single-layered flat ribbon configuration. Our results strongly suggest that the Z-ring is composed of a loose bundle of FtsZ protofilaments that randomly overlap with each other in both longitudinal and radial directions of the cell. Our results provide significant insight into the spatial organization of the Z-ring and open the door for further investigations of structure-function relationships and cell cycle-dependent regulation of the Z-ring.

In vivo structure of the E. coli FtsZ-ring revealed by photoactivated localization microscopy (PALM.

Directory of Open Access Journals (Sweden)

Guo Fu

2010-09-01

Full Text Available The FtsZ protein, a tubulin-like GTPase, plays a pivotal role in prokaryotic cell division. In vivo it localizes to the midcell and assembles into a ring-like structure-the Z-ring. The Z-ring serves as an essential scaffold to recruit all other division proteins and generates contractile force for cytokinesis, but its supramolecular structure remains unknown. Electron microscopy (EM has been unsuccessful in detecting the Z-ring due to the dense cytoplasm of bacterial cells, and conventional fluorescence light microscopy (FLM has only provided images with limited spatial resolution (200-300 nm due to the diffraction of light. Hence, given the small sizes of bacteria cells, identifying the in vivo structure of the Z-ring presents a substantial challenge. Here, we used photoactivated localization microscopy (PALM, a single molecule-based super-resolution imaging technique, to characterize the in vivo structure of the Z-ring in E. coli. We achieved a spatial resolution of ∼35 nm and discovered that in addition to the expected ring-like conformation, the Z-ring of E. coli adopts a novel compressed helical conformation with variable helical length and pitch. We measured the thickness of the Z-ring to be ∼110 nm and the packing density of FtsZ molecules inside the Z-ring to be greater than what is expected for a single-layered flat ribbon configuration. Our results strongly suggest that the Z-ring is composed of a loose bundle of FtsZ protofilaments that randomly overlap with each other in both longitudinal and radial directions of the cell. Our results provide significant insight into the spatial organization of the Z-ring and open the door for further investigations of structure-function relationships and cell cycle-dependent regulation of the Z-ring.

Novel manifestations of the Aharonov-Bohm effect in quantum rings and Moebius rings

International Nuclear Information System (INIS)

Fomin, Vladimir M.

2013-01-01

- An overview is given on the recent experimental and theoretical advancements in studies of novel manifestations of the Aharonov-Bohm quantum-interference effect for excitons confined to self assembled quantum rings and other semiconductor nanostructures with ring-like states of charge carriers as well as for electrons in Moebius rings at the micro- and nanoscale. The exciton Aharonov-Bohm effect can be effectively controlled by an out-of-plane magnetic field, a vertical electric field, a spin disorder. A 'delocalization-to-localization' transition for the electron ground state occurs in a Moebius ring as it is made more inhomogeneous. (authors)

Ring closure in actin polymers

Energy Technology Data Exchange (ETDEWEB)

Sinha, Supurna, E-mail: supurna@rri.res.in [Raman Research Institute, Bangalore 560080 (India); Chattopadhyay, Sebanti [Doon University, Dehradun 248001 (India)

2017-03-18

We present an analysis for the ring closure probability of semiflexible polymers within the pure bend Worm Like Chain (WLC) model. The ring closure probability predicted from our analysis can be tested against fluorescent actin cyclization experiments. We also discuss the effect of ring closure on bend angle fluctuations in actin polymers. - Highlights: • Ring closure of biopolymers. • Worm like chain model. • Predictions for experiments.

On P-coherent endomorphism rings

Indian Academy of Sciences (India)

A ring is called right -coherent if every principal right ideal is finitely presented. Let M R be a right -module. We study the -coherence of the endomorphism ring of M R . It is shown that is a right -coherent ring if and only if every endomorphism of M R has a pseudokernel in add M R ; S is a left -coherent ring if and ...

Structure and assembly of the essential RNA ring component of a viral DNA packaging motor.

Science.gov (United States)

Ding, Fang; Lu, Changrui; Zhao, Wei; Rajashankar, Kanagalaghatta R; Anderson, Dwight L; Jardine, Paul J; Grimes, Shelley; Ke, Ailong

2011-05-03

Prohead RNA (pRNA) is an essential component in the assembly and operation of the powerful bacteriophage 29 DNA packaging motor. The pRNA forms a multimeric ring via intermolecular base-pairing interactions between protomers that serves to guide the assembly of the ring ATPase that drives DNA packaging. Here we report the quaternary structure of this rare multimeric RNA at 3.5 Å resolution, crystallized as tetrameric rings. Strong quaternary interactions and the inherent flexibility helped rationalize how free pRNA is able to adopt multiple oligomerization states in solution. These characteristics also allowed excellent fitting of the crystallographic pRNA protomers into previous prohead/pRNA cryo-EM reconstructions, supporting the presence of a pentameric, but not hexameric, pRNA ring in the context of the DNA packaging motor. The pentameric pRNA ring anchors itself directly to the phage prohead by interacting specifically with the fivefold symmetric capsid structures that surround the head-tail connector portal. From these contacts, five RNA superhelices project from the pRNA ring, where they serve as scaffolds for binding and assembly of the ring ATPase, and possibly mediate communication between motor components. Construction of structure-based designer pRNAs with little sequence similarity to the wild-type pRNA were shown to fully support the packaging of 29 DNA.

Coherent Synchrotron Radiation in Storage Rings

International Nuclear Information System (INIS)

Venturini, Marco

2002-01-01

We take a detour from the main theme of this volume and present a discussion of coherent synchrotron radiation (CSR) in the context of storage rings rather than single-pass systems. Interest in this topic has been revived by a series of measurements carried out at several light source facilities. There is strong evidence that the observed coherent signal is accompanied by a beam instability, possibly driven by CSR itself. In this paper we review a ''self-consistent'' model of longitudinal beam dynamics in which CSR is the only agent of collective forces. The model yields numerical solutions that appear to reproduce the main features of the observations

Nonannual tree rings in a climate-sensitive Prioria copaifera chronology in the Atrato River, Colombia.

Science.gov (United States)

Herrera-Ramirez, David; Andreu-Hayles, Laia; Del Valle, Jorge I; Santos, Guaciara M; Gonzalez, Paula L M

2017-08-01

In temperate climates, tree growth dormancy usually ensures the annual nature of tree rings, but in tropical environments, determination of annual periodicity can be more complex. The purposes of the work are as follows: (1) to generate a reliable tree-ring width chronology for Prioria copaifera Griseb. (Leguminoceae), a tropical tree species dwelling in the Atrato River floodplains, Colombia; (2) to assess the climate signal recorded by the tree-ring records; and (3) to validate the annual periodicity of the tree rings using independent methods. We used standard dendrochronological procedures to generate the P. copaifera tree-ring chronology. We used Pearson correlations to evaluate the relationship of the chronology with the meteorological records, climate regional indices, and gridded precipitation/sea surface temperature products. We also evaluated 24 high-precision 14 C measurements spread over a range of preselected tree rings, with assigned calendar years by dendrochronological techniques, before and after the bomb spike in order to validate the annual nature of the tree rings. The tree-ring width chronology was statistically reliable, and it correlated significantly with local records of annual and October-December (OND) streamflow and precipitation across the upper river watershed (positive), and OND temperature (negative). It was also significantly related to the Oceanic Niño Index, Pacific Decadal Oscillation, and the Southern Oscillation Index, as well as sea surface temperatures over the Caribbean and the Pacific region. However, 14 C high-precision measurements over the tree rings demonstrated offsets of up to 40 years that indicate that P. copaifera can produce more than one ring in certain years. Results derived from the strongest climate-growth relationship during the most recent years of the record suggest that the climatic signal reported may be due to the presence of annual rings in some of those trees in recent years. Our study alerts about

Faithfully quadratic rings

CERN Document Server

Dickmann, M

2015-01-01

In this monograph the authors extend the classical algebraic theory of quadratic forms over fields to diagonal quadratic forms with invertible entries over broad classes of commutative, unitary rings where -1 is not a sum of squares and 2 is invertible. They accomplish this by: (1) Extending the classical notion of matrix isometry of forms to a suitable notion of T-isometry, where T is a preorder of the given ring, A, or T = A^2. (2) Introducing in this context three axioms expressing simple properties of (value) representation of elements of the ring by quadratic forms, well-known to hold in

Physiological Responses during Cycling With Oval Chainrings (Q-Ring and Circular Chainrings

Directory of Open Access Journals (Sweden)

Alfredo Cordova

2014-06-01

Full Text Available The aim of this study was to compare the physiological responses of cyclists using round (C-ring or oval (Q-ring chainrings during an incremental test until exhaustion. Following a randomized design, fourteen male elite cyclists [age (mean ± SD: 21.1 ± 2.1 yr; VO2max: 78.5 ± 5.3 mL·kg-1min-1] performed two incremental maximal tests separated by 48 h (one with C-rings, the other with Q-rings. Starting at 100 W, the workload was increased by 25 W every 3 min until volitional exhaustion. Maximal heart rate, power output and oxygen consumption were compared. Blood lactate was monitored throughout the test. After the incremental test, 4 intermittent 20-s maximal sprints with a 60-s recovery period in between were performed. Maximal isometric voluntary contractions were performed at rest and immediately after each 20-s maximal sprint, and the force and EMG RMS amplitude were recorded from the vastus medialis and vastus lateralis muscles. For the incremental exercise test, no significant differences were found in the maximal power output (P=0.12, oxygen consumption (P=0.39, and heart rate (P=0.32 between Q-rings and C-rings. Throughout the incremental test, lactate levels were comparable when using both the C-rings and Q-rings (P=0.47. During the short sprints, power output was 2.5–6.5% greater for Q-rings than for C-rings (P=0.22. The decline in EMG RMS amplitude observed during the incremental tests was comparable for Q-rings and C-rings (0.42. These findings indicate that the oval chainring design, presented here as “Q-rings”, did not significantly influence the physiological response to an incremental exercise test as compared to a conventional chainring.

BERKELEY: ALS ring

Energy Technology Data Exchange (ETDEWEB)

Anon.

1993-06-15

Everybody at Lawrence Berkeley Laboratory's Center for Beam Physics is pleased with the rapid progress in commissioning LBL's Advanced Light Source (ALS) electron storage ring, the foundation for this third-generation synchrotron radiation facility. Designed for a maximum current of 400 mA, the ALS storage ring reached 407 mA just 24 days after storing the first beam on 16 March. ALS construction as a US Department of Energy (DOE) national user facility to provide high-brightness vacuum ultra-violet and soft x-ray radiation began in October 1987. One technical requirement marking project completion was to accumulate a 50-mA current in the storage ring. The ALS passed this milestone on 24 March, a week ahead of the official deadline. Once injected, the electron beam decays quasi-exponentially primarily because of interactions with residual gas molecules in the storage-ring vacuum chamber. Eventually, when the pressure in the vacuum chamber with beam decreases toward the expected operating level of 1 nano Torr, it will only be necessary to refill the storage ring at intervals of four to eight hours. At present the vacuum is improving rapidly as surfaces are irradiated (scrubbed) by the synchrotron radiation itself. At 100 mA, beam lifetime was about one hour (9 April)

BERKELEY: ALS ring

International Nuclear Information System (INIS)

Anon.

1993-01-01

Everybody at Lawrence Berkeley Laboratory's Center for Beam Physics is pleased with the rapid progress in commissioning LBL's Advanced Light Source (ALS) electron storage ring, the foundation for this third-generation synchrotron radiation facility. Designed for a maximum current of 400 mA, the ALS storage ring reached 407 mA just 24 days after storing the first beam on 16 March. ALS construction as a US Department of Energy (DOE) national user facility to provide high-brightness vacuum ultra-violet and soft x-ray radiation began in October 1987. One technical requirement marking project completion was to accumulate a 50-mA current in the storage ring. The ALS passed this milestone on 24 March, a week ahead of the official deadline. Once injected, the electron beam decays quasi-exponentially primarily because of interactions with residual gas molecules in the storage-ring vacuum chamber. Eventually, when the pressure in the vacuum chamber with beam decreases toward the expected operating level of 1 nano Torr, it will only be necessary to refill the storage ring at intervals of four to eight hours. At present the vacuum is improving rapidly as surfaces are irradiated (scrubbed) by the synchrotron radiation itself. At 100 mA, beam lifetime was about one hour (9 April)

Accidental ingestion of BiTine ring and a note on inefficient ring separation forceps

Directory of Open Access Journals (Sweden)

Baghele ON

2011-05-01

Full Text Available Om Nemichand Baghele1, Mangala Om Baghele21Department of Periodontology, SMBT Dental College and Hospital, Sangamner, Ahmednagar, Maharashtra, India; 2Private General Dental Practice, Mumbai, IndiaBackground: Accidental ingestion of medium-to-large instruments is relatively uncommon during dental treatment but can be potentially dangerous. A case of BiTine ring ingestion is presented with a note on inefficient ring separation forceps.Case description: A 28-year-old male patient accidentally ingested the BiTine ring (2 cm diameter, 0.5 cm outward projections while it was being applied to a distoproximal cavity in tooth # 19. The ring placement forceps were excessively flexible; bending of the beaks towards the ring combined with a poor no-slippage mechanism led to sudden disengagement of the ring and accelerated movement towards the pharynx. We followed the patient with bulk forming agents and radiographs. Fortunately the ring passed out without any complications.Clinical implications: Checking equipment and methods is as important as taking precautions against any preventable medical emergency. It is the responsibility of the clinician to check, verify and then use any instrument/equipment.Keywords: foreign bodies/radiography, foreign bodies/complications, equipment failure, dental instrument, accidental ingestion

On the Laurent polynomial rings

International Nuclear Information System (INIS)

Stefanescu, D.

1985-02-01

We describe some properties of the Laurent polynomial rings in a finite number of indeterminates over a commutative unitary ring. We study some subrings of the Laurent polynomial rings. We finally obtain two cancellation properties. (author)

The Hi-Ring DCN Architecture

DEFF Research Database (Denmark)

Galili, Michael; Kamchevska, Valerija; Ding, Yunhong

2016-01-01

We will review recent work on the proposed hierarchical ring-based architecture (HiRing) proposed for data center networks. We will discuss the architecture and initial demonstrations of optical switching performance and time-domain synchronization......We will review recent work on the proposed hierarchical ring-based architecture (HiRing) proposed for data center networks. We will discuss the architecture and initial demonstrations of optical switching performance and time-domain synchronization...

EBT ring physics

International Nuclear Information System (INIS)

Uckan, N.A.

1980-04-01

This workshop attempted to evaluate the status of the current experimental and theoretical understanding of hot electron ring properties. The dominant physical processes that influence ring formation, scaling, and their optimal behavior are also studied. Separate abstracts were prepared for each of the 27 included papers

SPARC experiments at the high-energy storage ring

International Nuclear Information System (INIS)

Stöhlker, Thomas; Litvinov, Yuri A; Bagnoud, Vincent; Dimopoulou, Christina; Dolinskii, Alexei; Geppert, Christopher; Hagmann, Siegbert; Katayama, Takeshi; Kühl, Thomas; Nörtershäuser, Wilfried; Steck, Markus; Bechstedt, Ulf; Maier, Rudolf; Prasuhn, Dieter; Stockhorst, Hans; Schuch, Reinhold

2013-01-01

The physics program of the SPARC collaboration at the Facility for Antiproton and Ion Research (FAIR) focuses on the study of collision phenomena in strong and even extreme electromagnetic fields and on the fundamental interactions between electrons and heavy nuclei up to bare uranium. Here we give a short overview on the challenging physics opportunities of the high-energy storage ring at FAIR for future experiments with heavy-ion beams at relativistic energies with particular emphasis on the basic beam properties to be expected. (paper)

Ground Movement in SSRL Ring

International Nuclear Information System (INIS)

Sunikumar, Nikita

2011-01-01

Users of the Stanford Synchrotron Radiation Lightsource (SSRL) are being affected by diurnal motion of the synchrotron's storage ring, which undergoes structural changes due to outdoor temperature fluctuations. In order to minimize the effects of diurnal temperature fluctuations, especially on the vertical motion of the ring floor, scientists at SSRL tried three approaches: painting the storage ring white, covering the asphalt in the middle of the ring with highly reflective Mylar and installing Mylar on a portion of the ring roof and walls. Vertical motion in the storage ring is measured by a Hydrostatic Leveling System (HLS), which calculates the relative height of water in a pipe that extends around the ring. The 24-hr amplitude of the floor motion was determined using spectral analysis of HLS data, and the ratio of this amplitude before and after each experiment was used to quantitatively determine the efficacy of each approach. The results of this analysis showed that the Mylar did not have any significant effect on floor motion, although the whitewash project did yield a reduction in overall HLS variation of 15 percent. However, further analysis showed that the reduction can largely be attributed to a few local changes rather than an overall reduction in floor motion around the ring. Future work will consist of identifying and selectively insulating these local regions in order to find the driving force behind diurnal floor motion in the storage ring.

Robust mesoscopic superposition of strongly correlated ultracold atoms

International Nuclear Information System (INIS)

Hallwood, David W.; Ernst, Thomas; Brand, Joachim

2010-01-01

We propose a scheme to create coherent superpositions of annular flow of strongly interacting bosonic atoms in a one-dimensional ring trap. The nonrotating ground state is coupled to a vortex state with mesoscopic angular momentum by means of a narrow potential barrier and an applied phase that originates from either rotation or a synthetic magnetic field. We show that superposition states in the Tonks-Girardeau regime are robust against single-particle loss due to the effects of strong correlations. The coupling between the mesoscopically distinct states scales much more favorably with particle number than in schemes relying on weak interactions, thus making particle numbers of hundreds or thousands feasible. Coherent oscillations induced by time variation of parameters may serve as a 'smoking gun' signature for detecting superposition states.

Correction of vertical dispersion and betatron coupling for the CLIC damping ring

CERN Document Server

Korostelev, M S

2006-01-01

The sensitivity of the CLIC damping ring to various kinds of alignment errors has been studied. Without any correction, fairly small vertical misalignments of the quadrupoles and, in particular, the sextupoles, introduce unacceptable distortions of the closed orbit as well as intolerable spurious vertical dispersion and coupling due to the strong focusing optics of the damping ring. A sophisticated beam-based correction scheme has been developed to bring the design target emittances and the dynamic aperture back to the ideal value. The correction using dipolar correctors and several skew quadrupole correctors allows a minimization of the closed-orbit distortion, the cross-talk between vertical and horizontal closed orbits, the residual vertical dispersion and the betatron coupling.

How does climate influence xylem morphogenesis over the growing season? Insights from long-term intra-ring anatomy in Picea abies.

Science.gov (United States)

Castagneri, Daniele; Fonti, Patrick; von Arx, Georg; Carrer, Marco

2017-04-01

During the growing season, the cambium of conifer trees produces successive rows of xylem cells, the tracheids, that sequentially pass through the phases of enlargement and secondary wall thickening before dying and becoming functional. Climate variability can strongly influence the kinetics of morphogenetic processes, eventually affecting tracheid shape and size. This study investigates xylem anatomical structure in the stem of Picea abies to retrospectively infer how, in the long term, climate affects the processes of cell enlargement and wall thickening. Tracheid anatomical traits related to the phases of enlargement (diameter) and wall thickening (wall thickness) were innovatively inspected at the intra-ring level on 87-year-long tree-ring series in Picea abies trees along a 900 m elevation gradient in the Italian Alps. Anatomical traits in ten successive tree-ring sectors were related to daily temperature and precipitation data using running correlations. Close to the altitudinal tree limit, low early-summer temperature negatively affected cell enlargement. At lower elevation, water availability in early summer was positively related to cell diameter. The timing of these relationships shifted forward by about 20 (high elevation) to 40 (low elevation) d from the first to the last tracheids in the ring. Cell wall thickening was affected by climate in a different period in the season. In particular, wall thickness of late-formed tracheids was strongly positively related to August-September temperature at high elevation. Morphogenesis of tracheids sequentially formed in the growing season is influenced by climate conditions in successive periods. The distinct climate impacts on cell enlargement and wall thickening indicate that different morphogenetic mechanisms are responsible for different tracheid traits. Our approach of long-term and high-resolution analysis of xylem anatomy can support and extend short-term xylogenesis observations, and increase our

Physiological Responses during Cycling With Oval Chainrings (Q-Ring) and Circular Chainrings.

Science.gov (United States)

Cordova, Alfredo; Latasa, Iban; Seco, Jesus; Villa, Gerardo; Rodriguez-Falces, Javier

2014-05-01

The aim of this study was to compare the physiological responses of cyclists using round (C-ring) or oval (Q-ring) chainrings during an incremental test until exhaustion. Following a randomized design, twelve male elite cyclists [age (mean ± SD): 21.1 ± 2.1 yr; VO2max: 78.1 ± 5.3 mL·kg(-1)min(-1)] performed two incremental maximal tests separated by 48 h (one with C-rings, the other with Q-rings). Starting at 100 W, the workload was increased by 25 W every 3 min until volitional exhaustion. Maximal heart rate, power output and oxygen consumption were compared. Blood lactate was monitored throughout the test. After the incremental test, 4 intermittent 20-s maximal sprints with a 60-s recovery period in between were performed. Maximal isometric voluntary contractions were performed at rest and immediately after each 20-s maximal sprint, and the force and EMG RMS amplitude were recorded from the vastus medialis and vastus lateralis muscles. For the incremental exercise test, no significant differences were found in the maximal power output (P=0.12), oxygen consumption (P=0.39), and heart rate (P=0.32) between Q-rings and C-rings. Throughout the incremental test, lactate levels were comparable when using both the C-rings and Q-rings (P=0.47). During the short sprints, power output was 2.5-6.5% greater for Q-rings than for C-rings (P=0.22). The decline in EMG RMS amplitude observed during the incremental tests was comparable for Q-rings and C-rings (0.42). These findings indicate that the oval chainring design, presented here as "Q-rings", did not significantly influence the physiological response to an incremental exercise test as compared to a conventional chainring. Key pointsDuring the incremental exercise test, no significant differences were found in power output, oxygen consumption or heart rate between oval "Q-rings" and conventional chainrings.Over the course of the incremental test, blood lactate levels were comparable for the oval "Q-rings" and

Token ring technology report

CERN Document Server

2013-01-01

Please note this is a Short Discount publication. This report provides an overview of the IBM Token-Ring technology and products built by IBM and compatible vendors. It consists of two sections: 1. A summary of the design trade-offs for the IBM Token-Ring. 2. A summary of the products of the major token-ring compatible vendors broken down by adapters and components, wiring systems, testing, and new chip technology.

Structure and catalytic activation of the TRIM23 RING E3 ubiquitin ligase: DAWIDZIAK et al.

Energy Technology Data Exchange (ETDEWEB)

Dawidziak, Daria M. [Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville Virginia; Sanchez, Jacint G. [Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville Virginia; Wagner, Jonathan M. [Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville Virginia; Ganser-Pornillos, Barbie K. [Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville Virginia; Pornillos, Owen [Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville Virginia

2017-07-24

Tripartite motif (TRIM) proteins comprise a large family of RING-type ubiquitin E3 ligases that regulate important biological processes. An emerging general model is that TRIMs form elongated antiparallel coiled-coil dimers that prevent interaction of the two attendant RING domains. The RING domains themselves bind E2 conjugating enzymes as dimers, implying that an active TRIM ligase requires higher-order oligomerization of the basal coiled-coil dimers. Here, we report crystal structures of the TRIM23 RING domain in isolation and in complex with an E2–ubiquitin conjugate. Our results indicate that TRIM23 enzymatic activity requires RING dimerization, consistent with the general model of TRIM activation.

Optical absorptions of an exciton in a quantum ring: Effect of the repulsive core

International Nuclear Information System (INIS)

Xie, Wenfang

2013-01-01

We study the optical absorptions of an exciton in a quantum ring. The quantum ring is described as a circular quantum dot with a repulsive core. The advantage of our methodology is that one can investigate the influence of the repulsive core by varying two parameters in the confinement potential. The linear, third-order nonlinear and total optical absorption coefficients have been examined with the change of the confinement potential. The results show that the optical absorptions are strongly affected by the repulsive core. Moreover, the repulsive core can influence the oscillation in the resonant peak of the absorption coefficients.

Cooperative ring exchange and quantum melting of vortex lattices in atomic Bose-Einstein condensates

International Nuclear Information System (INIS)

Ghosh, Tarun Kanti; Baskaran, G.

2004-01-01

Cooperative ring exchange is suggested as a mechanism of quantum melting of vortex lattices in a rapidly rotating quasi-two-dimensional atomic Bose-Einstein condensate (BEC). Using an approach pioneered by Kivelson et al. [Phys. Rev. Lett. 56, 873 (1986)] for the fractional quantized Hall effect, we calculate the condition for quantum melting instability by considering large-correlated ring exchanges in a two-dimensional Wigner crystal of vortices in a strong 'pseudomagnetic field' generated by the background superfluid Bose particles. BEC may be profitably used to address issues of quantum melting of a pristine Wigner solid devoid of complications of real solids

Prototype moving-ring reactor

International Nuclear Information System (INIS)

Smith, A.C. Jr.; Ashworth, C.P.; Abreu, K.E.

1982-01-01

We have completed a design of the Prototype Moving-Ring Reactor. The fusion fuel is confined in current-carrying rings of magnetically-field-reversed plasma (Compact Toroids). The plasma rings, formed by a coaxial plasma gun, undergo adiabatic magnetic compression to ignition temperature while they are being injected into the reactor's burner section. The cylindrical burner chamber is divided into three burn stations. Separator coils and a slight axial guide field gradient are used to shuttle the ignited toroids rapidly from one burn station to the next, pausing for 1/3 of the total burn time at each station. D-T- 3 He ice pellets refuel the rings at a rate which maintains constant radiated power

Toward Detection of Exoplanetary Rings via Transit Photometry: Methodology and a Possible Candidate

Energy Technology Data Exchange (ETDEWEB)

Aizawa, Masataka; Masuda, Kento; Suto, Yasushi [Department of Physics, The University of Tokyo, Tokyo, 113-0033 (Japan); Uehara, Sho [Department of Physics, Tokyo Metropolitan University, Tokyo 192-4397 (Japan); Kawahara, Hajime, E-mail: aizawa@utap.phys.s.u-tokyo.ac.jp [Department of Earth and Planetary Science, The University of Tokyo, Tokyo 113-0033 (Japan)

2017-04-01

The detection of a planetary ring of exoplanets remains one of the most attractive, but challenging, goals in the field of exoplanetary science. We present a methodology that implements a systematic search for exoplanetary rings via transit photometry of long-period planets. This methodology relies on a precise integration scheme that we develop to compute a transit light curve of a ringed planet. We apply the methodology to 89 long-period planet candidates from the Kepler data so as to estimate, and/or set upper limits on, the parameters of possible rings. While the majority of our samples do not have sufficient signal-to-noise ratios (S/Ns) to place meaningful constraints on ring parameters, we find that six systems with higher S/Ns are inconsistent with the presence of a ring larger than 1.5 times the planetary radius, assuming a grazing orbit and a tilted ring. Furthermore, we identify five preliminary candidate systems whose light curves exhibit ring-like features. After removing four false positives due to the contamination from nearby stars, we identify KIC 10403228 as a reasonable candidate for a ringed planet. A systematic parameter fit of its light curve with a ringed planet model indicates two possible solutions corresponding to a Saturn-like planet with a tilted ring. There also remain two other possible scenarios accounting for the data; a circumstellar disk and a hierarchical triple. Due to large uncertain factors, we cannot choose one specific model among the three.

Polycomb Group Proteins RING1A and RING1B Regulate the Vegetative Phase Transition in Arabidopsis

Directory of Open Access Journals (Sweden)

Jian Li

2017-05-01

Full Text Available Polycomb group (PcG protein-mediated gene silencing is a major regulatory mechanism in higher eukaryotes that affects gene expression at the transcriptional level. Here, we report that two conserved homologous PcG proteins, RING1A and RING1B (RING1A/B, are required for global H2A monoubiquitination (H2Aub in Arabidopsis. The mutation of RING1A/B increased the expression of members of the SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL gene family and caused an early vegetative phase transition. The early vegetative phase transition observed in ring1a ring1b double mutant plants was dependent on an SPL family gene, and the H2Aub status of the chromatin at SPL locus was dependent on RING1A/B. Moreover, mutation in RING1A/B affected the miRNA156a-mediated vegetative phase transition, and RING1A/B and the AGO7-miR390-TAS3 pathway were found to additively regulate this transition in Arabidopsis. Together, our results demonstrate that RING1A/B regulates the vegetative phase transition in Arabidopsis through the repression of SPL family genes.

Researches on the Piston Ring

Science.gov (United States)

Ehihara, Keikiti

1944-01-01

In internal combustion engines, steam engines, air compressors, and so forth, the piston ring plays an important role. Especially, the recent development of Diesel engines which require a high compression pressure for their working, makes, nowadays, the packing action of the piston ring far more important than ever. Though a number of papers have been published in regard to researches on the problem of the piston ring, none has yet dealt with an exact measurement of pressure exerted on the cylinder wall at any given point of the ring. The only paper that can be traced on this subject so far is Mr. Nakagawa's report on the determination of the relative distribution of pressure on the cylinder wall, but the measuring method adopted therein appears to need further consideration. No exact idea has yet been obtained as to how the obturation of gas between the piston and cylinder, the frictional resistance of the piston, and the wear of the cylinder wall are affected by the intensity and the distribution of the radial pressure of the piston ring. Consequently, the author has endeavored, by employing an apparatus of his own invention, to get an exact determination of the pressure distribution of the piston ring. By means of a newly devised ring tester, to which piezoelectricity of quartz was applied, the distribution of the radial pressure of many sample rings on the market was accurately determined. Since many famous piston rings show very irregular pressure distribution, the author investigated and achieved a manufacturing process of the piston ring which will exert uniform pressure on the cylinder wall. Temperature effects on the configuration and on the mean spring power have also been studied. Further, the tests were performed to ascertain how the gas tightness of the piston ring may be affected by the number or spring power. The researches as to the frictional resistance between the piston ring and the cylinder wall were carried out, too. The procedure of study, and

A possible link between the rotation of Saturn and its ring structure

International Nuclear Information System (INIS)

Franklin, F.A.; Colombo, G.; Cook, A.F.

1982-01-01

Evidence is presented which indicates that two previously unidentified, yet conspicuous gaps in Saturn's rings lie at distances corresponding to 2/3 and 4/3 of the planet's rotation period. It is argued that gaps such as these can be produced in a ring of large bodies or small uncharged particles only by a non-axisymmetric gravitational field a fact that is relevant to models of planetary interiors. (U.K.)

Tetrel Bonding as a Vehicle for Strong and Selective Anion Binding

Directory of Open Access Journals (Sweden)

Steve Scheiner

2018-05-01

Full Text Available Tetrel atoms T (T = Si, Ge, Sn, and Pb can engage in very strong noncovalent interactions with nucleophiles, which are commonly referred to as tetrel bonds. The ability of such bonds to bind various anions is assessed with a goal of designing an optimal receptor. The Sn atom seems to form the strongest bonds within the tetrel family. It is most effective in the context of a -SnF3 group and a further enhancement is observed when a positive charge is placed on the receptor. Connection of the -SnF3 group to either an imidazolium or triazolium provides a strong halide receptor, which can be improved if its point of attachment is changed from the C to an N atom of either ring. Aromaticity of the ring offers no advantage nor is a cyclic system superior to a simple alkyl amine of any chain length. Placing a pair of -SnF3 groups on a single molecule to form a bipodal dicationic receptor with two tetrel bonds enhances the binding, but falls short of a simple doubling. These two tetrel groups can be placed on opposite ends of an alkyl diamine chain of any length although SnF3+NH2(CH2nNH2SnF3+ with n between 2 and 4 seems to offer the strongest halide binding. Of the various anions tested, OH− binds most strongly: OH− > F− > Cl− > Br− > I−. The binding energy of the larger NO3− and HCO3− anions is more dependent upon the charge of the receptor. This pattern translates into very strong selectivity of binding one anion over another. The tetrel-bonding receptors bind far more strongly to each anion than an equivalent number of K+ counterions, which leads to equilibrium ratios in favor of the former of many orders of magnitude.

Magnetization of two coupled rings

International Nuclear Information System (INIS)

Avishai, Y; Luck, J M

2009-01-01

We investigate the persistent currents and magnetization of a mesoscopic system consisting of two clean metallic rings sharing a single contact point in a magnetic field. Many novel features with respect to the single-ring geometry are underlined, including the explicit dependence of wavefunctions on the Aharonov-Bohm fluxes, the complex pattern of two-fold and three-fold degeneracies, the key role of length and flux commensurability, and in the case of commensurate ring lengths the occurrence of idle levels which do not carry any current. Spin-orbit interactions, induced by the electric fields of charged wires threading the rings, give rise to a peculiar version of the Aharonov-Casher effect where, unlike for a single ring, spin is not conserved. Remarkably enough, this can only be realized when the Aharonov-Bohm fluxes in both rings are neither integer nor half-integer multiples of the flux quantum

Compartmental transport model of microbicide delivery by an intravaginal ring

Science.gov (United States)

Geonnotti, Anthony R.; Katz, David F.

2010-01-01

Topical antimicrobials, or microbicides, are being developed to prevent HIV transmission through local, mucosal delivery of antiviral compounds. While hydrogel vehicles deliver the majority of current microbicide products, intravaginal rings (IVRs) are an alternative microbicide modality in preclinical development. IVRs provide a long-term dosing alternative to hydrogel use, and might provide improved user adherence. IVR efficacy requires sustained delivery of antiviral compounds to the entire vaginal compartment. A two-dimensional, compartmental vaginal drug transport model was created to evaluate the delivery of drugs from an intravaginal ring. The model utilized MRI-derived ring geometry and location, experimentally defined ring fluxes and vaginal fluid velocities, and biophysically relevant transport theory. Model outputs indicated the presence of potentially inhibitory concentrations of antiviral compounds along the entire vaginal canal within 24 hours following IVR insertion. Distributions of inhibitory concentrations of antiviral compounds were substantially influenced by vaginal fluid flow and production, while showing little change due to changes in diffusion coefficients or ring fluxes. Additionally, model results were predictive of in vivo concentrations obtained in clinical trials. Overall, this analysis initiates a mechanistic computational framework, heretofore missing, to understand and evaluate the potential of IVRs for effective delivery of antiviral compounds. PMID:20222027

Ring ductility of irradiated Inconel 706 and Nimonic PE16

International Nuclear Information System (INIS)

Huang, F.H.; Fish, R.L.

1984-01-01

The tensile ductility of fast neutron-irradiated, precipitation-hardened alloys Inconel 706 and Nimonic PE16 has been observed to be very low for certain test conditions. Explanations for the low ductility behavior have been sought by examination of broken tensile specimens with microscopy and other similar techniques. A ring compression test provides a method of evaluating the ductility of irradiated cladding specimens. Unlike the conventional uniaxial tensile testing in which the tensile specimen is deformed uniformly, the ring specimen is subjected to localized bending where the crack is initiated. The ductility can be estimated through an analysis of the bending of a ring in terms of strain hardening. Ring sections from irradiated, solution-treated Inconel 706 and Nimonic PE16 were compressed in the diametral direction to provide load-deflection records over a wide range of irradiation and test temperatures. Results showed that ductility in both alloys decreased with increasing test temperatures. The poorest ductility was exhibited at different irradiation temperatures in the two alloys - near 550 0 C for PE16 and 460 to 520 0 C for Inconel 706. The ring ductility data indicate that the grain boundary strength is a major factor in controlling the ductility of the PE16 alloy

Tree-rings and climate: Implications for Great Basin paleoenvironmental studies

International Nuclear Information System (INIS)

Graybill, D.A.; Rose, M.R.; Nials, F.L.

1994-01-01

The Quaternary Sciences Center of the Desert Research Institute is currently conducting a multi-phased study of floral, faunal, and geomorphic response to long- and short-term climate change and extremes in assessing Yucca Mountain's suitability as a high-level nuclear waste repository. Preliminary results of these studies indicate synchronous responses in late Holocene tree-ring, palynology and geomorphic records. A tree-ring chronology for paleoclimatic reconstruction is developed by collection of multiple cores from 20-60 living trees and a similar number of dead trees in a climate-sensitive location. Samples are cross-dated and every growth layer in each specimen is measured to the nearest .001 mm. The measured ring width series potentially contain a variety of climatic, biological, and anthropogenic signals. Each ring width series is subjected to a numerical standarization procedure that removes an age-related biological growth trend, reduces endogeneous and exogenous stand disturbance factors, and maximizes any climatic signal that is present. Each of these empirically defined components can be graphically portrayed and subjected to further analyses. The geophysical signal analysis techniques involved in the standarized protocol are well-documented and established. The final result is a tree-ring chronology that represents regional paleoclimatic variability over the time represented by the sample population

The role of substorms in the formation of the ring current

International Nuclear Information System (INIS)

Rostoker, G.

1996-01-01

It has long been recognized that the formation of the terrestrial ring current is accompanied by strong substorm expansive phase activity in the auroral oval. While large amplitude substorm activity seems to be a prerequisite for ring current formation to take place, it has long been puzzling as to why some large amplitude substorm activity in the auroral oval is not associated with significant ring current development. In this paper I shall outline the basis for the renovated boundary layer dynamics model of magnetospheric substorms showing how the onset of the substorm expansive phase can be associated with a sudden decrease in shielding space charge in the region of the near-Earth plasma sheet threaded by Region 2 field-aligned currents. I shall suggest that an episode of sufficiently large southward IMF lasting over a sufficiently lengthy period of time can lead to a sequence of substorm expansive phases, each one being initiated closer to the Earth than the previous one. Each expansive phase is attributed to a sudden decrease in radially localized cross-tail current (viz. a decrease in shielding space charge) and with each onset the inner edge of the plasma sheet moves inward. The inductive electric field associated with each crosstail current decrease is responsible for the acceleration of already energetic particles to energies of significance for ring current formation. Only when the inner edge of the crosstail current is sufficiently close to the Earth do the acceleration processes associated with substorm onset produce a long lived ring current. copyright 1996 American Institute of Physics

Analytical model for double split ring resonators with arbitrary ring width

DEFF Research Database (Denmark)

Zhurbenko, Vitaliy; Jensen, Thomas; Krozer, Viktor

2008-01-01

For the first time, the analytical model for a double split ring resonator with unequal width rings is developed. The proposed models for the resonators with equal and unequal widths are based on an impedance matrix representation and provide the prediction of performance in a wide frequency range...

Pure subrings of the rings Zχ

International Nuclear Information System (INIS)

Tsarev, Andrei V

2009-01-01

Pure subrings of finite rank in the Z-adic completion of the ring of integers and in its homomorphic images are considered. Certain properties of these rings are studied (existence of an identity element, decomposability into a direct sum of essentially indecomposable ideals, condition for embeddability into a csp-ring, etc.). Additive groups of these rings and conditions under which these rings are subrings of algebraic number fields are described. Bibliography: 12 titles.

Characteristics of Chongan ring structure and its controlling role on uranium mineralization

International Nuclear Information System (INIS)

Liu Linqing

2001-01-01

A large ring structure has been discovered in Chong'an region on the basis of geological interpretation of remote sensing images. The data acquired from analysis of regional geology and in-situ investigation indicate that the ring structure is initiated during caledonian and activated for several times afterwards; It displays the highest activity during Yanshanian. Under the effect of this structure, Gulou-Masha lenticular geological body was firmed, controlling the regional distribution of uranium mineralization and anomalies occur in forms of central and bilateral symmetry. The data indicate that it is prospective to prospect uranium deposit in this region; therefore, more work should be placed on the deep levels

Ring accelerators

International Nuclear Information System (INIS)

Gisler, G.; Faehl, R.

1983-01-01

We present two-dimensional simulations in (r-z) and r-theta) cylinderical geometries of imploding-liner-driven accelerators of rings of charged particles. We address issues of azimuthal and longitudinal stability of the rings. We discuss self-trapping designs in which beam injection and extraction is aided by means of external cusp fields. Our simulations are done with the 2-1/2-D particle-in-cell plasma simulation code CLINER, which combines collisionless, electromagnetic PIC capabilities with a quasi-MHD finite element package

Testing reachability and stabilizability of systems over polynomial rings using Gröbner bases

NARCIS (Netherlands)

Habets, L.C.G.J.M.

1993-01-01

Conditions for the reachability and stabilizability of systems over polynomial rings are well-known in the literature. For a system $ \\Sigma = (A,B)$ they can be expressed as right-invertibility cconditions on the matrix $(zI - A \\mid B)$. Therefore there is quite a strong algebraic relationship

Manipulation of vortex rings for flow control

International Nuclear Information System (INIS)

Toyoda, Kuniaki; Hiramoto, Riho

2009-01-01

This paper reviews the dynamics of vortex rings and the control of flow by the manipulation of vortex rings. Vortex rings play key roles in many flows; hence, the understanding of the dynamics of vortex rings is crucial for scientists and engineers dealing with flow phenomena. We describe the structures and motions of vortex rings in circular and noncircular jets, which are typical examples of flows evolving into vortex rings. For circular jets the mechanism of evolving, merging and breakdown of vortex rings is described, and for noncircular jets the dynamics of three-dimensional deformation and interaction of noncircular vortex rings under the effect of self- and mutual induction is discussed. The application of vortex-ring manipulation to the control of various flows is reviewed with successful examples, based on the relationship between the vortex ring dynamics and the flow properties. (invited paper)

The Rings of Saturn

Science.gov (United States)

Cuzzi, J. N.; Filacchione, G.; Marouf, E. A.

2018-03-01

One could become an expert on Saturn's iconic rings pretty easily in the early 1970s, as very little was known about them beyond the distinction between the A, B, and C rings, and the Cassini Division or "gap" between rings A and B (Alexander, 1962; Bobrov, 1970). Water ice was discovered spectroscopically on the ring particle surfaces, and radar and microwave emission observations proved that the particles must be centimeters to meters in size, consisting primarily, not just superficially, of water ice (Pollack, 1975). While a 2:1 orbital resonance with Mimas had long been suspected of having something to do with the Cassini Division, computers of the time were unable to model the subtle dynamical effects that we now know to dominate ring structure. This innocent state of affairs was exploded by the Voyager 1 and 2 encounters in 1980 and 1981. Spectacular images revealed filigree structure and odd regional color variations, and exquisitely detailed radial profiles of fluctuating particle abundance were obtained from the first stellar and radio occultations, having resolution almost at the scale of single particles. Voyager-era understanding was reviewed by Cuzzi et al. (1984) and Esposito et al. (1984). While the Voyager data kept ring scientists busy for decades, planning which led to the monumentally successful NASA-ESA-ASI Cassini mission, which arrived in 2004, had been under way even before Voyager got to Saturn. A review of pre-Cassini knowledge of Saturn's Rings can be found in Orton et al. (2009). This chapter will build on recent topical and process-specific reviews that treat the gamut of ring phenomena and its underlying physics in considerable detail (Colwell et al., 2009; Cuzzi et al., 2009; Horányi et al., 2009; Schmidt et al., 2009; Esposito, 2010; Tiscareno, 2013b; Esposito, 2014). We will follow and extend the general organization of Cuzzi et al. (2010), the most recent general discussion of Saturn's rings. For brevity and the benefit of the

A numerical study of viscous vortex rings using a spectral method

Science.gov (United States)

Stanaway, S. K.; Cantwell, B. J.; Spalart, Philippe R.

1988-01-01

Viscous, axisymmetric vortex rings are investigated numerically by solving the incompressible Navier-Stokes equations using a spectral method designed for this type of flow. The results presented are axisymmetric, but the method is developed to be naturally extended to three dimensions. The spectral method relies on divergence-free basis functions. The basis functions are formed in spherical coordinates using Vector Spherical Harmonics in the angular directions, and Jacobi polynomials together with a mapping in the radial direction. Simulations are performed of a single ring over a wide range of Reynolds numbers (Re approximately equal gamma/nu), 0.001 less than or equal to 1000, and of two interacting rings. At large times, regardless of the early history of the vortex ring, it is observed that the flow approaches a Stokes solution that depends only on the total hydrodynamic impulse, which is conserved for all time. At small times, from an infinitely thin ring, the propagation speeds of vortex rings of varying Re are computed and comparisons are made with the asymptotic theory by Saffman. The results are in agreement with the theory; furthermore, the error is found to be smaller than Saffman's own estimate by a factor square root ((nu x t)/R squared) (at least for Re=0). The error also decreases with increasing Re at fixed core-to-ring radius ratio, and appears to be independent of Re as Re approaches infinity). Following a single ring, with Re=500, the vorticity contours indicate shedding of vorticity into the wake and a settling of an initially circular core to a more elliptical shape, similar to Norbury's steady inviscid vortices. Finally, we consider the case of leapfrogging vortex rings with Re=1000. The results show severe straining of the inner vortex core in the first pass and merging of the two cores during the second pass.

Carbon isotope variation in shrub willow (Salix spp.) ring-wood as an indicator of long-term water status, growth and survival

International Nuclear Information System (INIS)

Schifman, Laura A.; Stella, John C.; Volk, Timothy A.; Teece, Mark A.

2012-01-01

Quantifying interannual change in water status of woody plants using stable carbon isotopes provides insight on long-term plant ecophysiology and potential success in variable environments, including under-utilized agricultural land for biomass production and highly disturbed sites for phytoremediation applications. We analyzed δ 13 C values in annual ring-wood of four shrub willow varieties used for biomass production and phytoremediation at three sites in central New York State (U.S.A). We tested a cost-effective sampling method for estimating whole-shrub water status by comparing δ 13 C values of the plant’s largest stem against a composite sample of all stems. The largest stem showed 0.3‰ 13 C enrichment (range −0.7–1.1‰) compared to the whole-plant, making it a more sensitive indicator of water status than the composite sample. Growing season precipitation exerted a strong negative influence on wood tissue chemistry, with an average 0.26‰ 13 C depletion per 100 mm increase in precipitation. An average annual 0.28‰ 13 C enrichment was also observed with increased plant age; this pattern was consistent among all four willow varieties and across sites. Finally, increased 13 C enrichment in wood tissue was positively associated with plant size at the individual plant level, and associated negatively and more variably survival at the plot scale. These results have important implications for the design and management of biomass production and phytoremediation systems. Increased sensitivity of older plants suggests that longer rotations may experience growth limitations and/or lower survival in low-precipitation years, resulting in reduced yields of biomass crops and loss of effectiveness in phytoremediation applications. -- Highlights: ► A 0.26‰ 13 C depletion in wood tissue occurred per 100 mm increase in precipitation. ► There was an average 13 C enrichment with plant age and size for all varieties. ► Greater 13 C enrichment often lead to

Design of a quasi-isochronous storage ring for THz light source

International Nuclear Information System (INIS)

Zhu Jiapeng; Xu Hongliang; Feng Guangyao; Lan Jieqin

2012-01-01

A quasi-isochronous storage ring is designed by manipulating lattice parameters to introduce a negative dispersion function to the dispersion section. This quasi-isochronous storage ring is designed for a THz synchrotron radiation source. The simulation of the optics function and beam emittance shows its feasibility, and the tracing result of particles indicates that the designed ring has a good particle dynamic aperture. In addition, a three-dimensional model of the vacuum chamber used for photon radiation in the quasi-isochronous mode is also designed. The eigenmodes of the chamber are simulated, and characteristic parameters such as quality factor, power loss and characteristic impedance are also calculated. The result shows that the vacuum chamber has little effect on the circulating beam. (authors)

Helium/solid powder O-ring leakage correlation experiments using a radiotracer

International Nuclear Information System (INIS)

Bild, R.W.; Leisher, W.B.; Weissman, S.H.; Seya, M.

1984-01-01

UO 2 definitely leaked past the O-ring in three of the tests confirming the major results of the previous work. Continuous leakage at these levels may require additional precautions under present regulatory policies. The mechanism and the time and particle size dependence for the leakage are not known, but there is some indication leakage is more likely at low temperatures. It is possible leakage is due to movement of the O-ring during temperature or pressure cycling at the beginning or end of a test. The radiotracer method involves less labor and is much less susceptible to contamination than the previous method. Future work will investigate leakage past lubricated O-rings and time dependence of leakage. 1 reference, 1 table

Non-Markovian response of ultrafast coherent electronic ring currents in chiral aromatic molecules in a condensed phase

International Nuclear Information System (INIS)

Mineo, H.; Lin, S. H.; Fujimura, Y.; Xu, J.; Xu, R. X.; Yan, Y. J.

2013-01-01

Results of a theoretical study on non-Markov response for femtosecond laser-driven coherent ring currents in chiral aromatic molecules embedded in a condensed phase are presented. Coherent ring currents are generated by coherent excitation of a pair of quasi-degenerated π-electronic excited states. The coherent electronic dynamical behaviors are strongly influenced by interactions between the electronic system and phonon bath in a condensed phase. Here, the bath correlation time is not instantaneous but should be taken to be a finite time in ultrashort time-resolved experiments. In such a case, Markov approximation breaks down. A hierarchical master equation approach for an improved semiclassical Drude dissipation model was adopted to examine the non-Markov effects on ultrafast coherent electronic ring currents of (P)-2,2 ′ -biphenol in a condensed phase. Time evolution of the coherent ring current derived in the hierarchical master equation approach was calculated and compared with those in the Drude model in the Markov approximation and in the static limit. The results show how non-Markovian behaviors in quantum beat signals of ring currents depend on the Drude bath damping constant. Effects of temperatures on ultrafast coherent electronic ring currents are also clarified

Examination techniques for non-magnetic rings

International Nuclear Information System (INIS)

Metala, M.J.; Kilpatrick, N.L.; Frank, W.W.

1990-01-01

Until the introduction of 18Mn18Cr rings a few years ago, most non-magnetic steel rings for generator rotors were made from 18Mn5Cr alloy steel, which is highly susceptible to stress corrosion cracking in the presence of water. This, the latest in a series of papers on the subject of non-magnetic rings by the authors' company, provides a discussion of nondestructive examination of 18Mn5Cr rings for stress corrosion distress. With rings on the rotor, fluorescent penetrant, ultrasonic and special visual techniques are applied. With rings off the rotor, the fluorescent penetrant technique is used, with and without stress enhancement

Ionization cooling ring for muons

Directory of Open Access Journals (Sweden)

R. Palmer

2005-06-01

Full Text Available Practical ionization cooling rings could lead to lower cost or improved performance in neutrino factory or muon collider designs. The ring modeled here uses realistic three-dimensional fields. The performance of the ring compares favorably with the linear cooling channel used in the second U.S. Neutrino Factory Study. The normalized 6D emittance of an ideal ring is decreased by a factor of approximately 240, compared with a factor of only 15 for the linear channel. We also examine such real-world effects as windows on the absorbers and rf cavities and leaving empty lattice cells for injection and extraction. For realistic conditions the ring decreases the normalized 6D emittance by a factor of 49.

Cryogenic Concept for the Low-energy Electrostatic Cryogenic Storage Ring (CSR) at MPI-K in Heidelberg

International Nuclear Information System (INIS)

Hahn, R. von; Andrianarijaona, V.; Crespo Lopez-Urrutia, J. R.; Fadil, H.; Grieser, M.; Mallinger, V.; Orlov, D. A.; Schroeter, C. D.; Schwalm, D.; Ullrich, J.; Weber, T.; Wolf, A.; Haberstroh, Ch.; Quack, H.; Rappaport, M.; Zajfman, D.

2006-01-01

At the Max-Planck-Institut fuer Kernphysik in Heidelberg a next generation electrostatic storage ring for cryogenic temperatures is under development. The main focus of this unique machine is the research on ions, molecules and clusters up to bio molecules in the energy range of 20-300 keV at low temperatures down to 2 Kelvin. The achievement of this low temperature for all material walls seen by the ions in the storage ring will allow novel experiments to be performed, such as rotational and vibrational state control of molecular ions and their interaction with ultra-low energy electrons and laser radiation. The low temperature of the storage ring not only causes a strong reduction of black body radiation incident onto the stored particles, but also acts as a large cryopump, expected to lead to a vacuum in the 10-15 mbar range. In this paper the cryogenic concept of the storage ring and the related vacuum design will be presented

Long-term effects of drought on tree-ring growth and carbon isotope variability in Scots pine in a dry environment.

Science.gov (United States)

Timofeeva, Galina; Treydte, Kerstin; Bugmann, Harald; Rigling, Andreas; Schaub, Marcus; Siegwolf, Rolf; Saurer, Matthias

2017-08-01

Drought frequency is increasing in many parts of the world and may enhance tree decline and mortality. The underlying physiological mechanisms are poorly understood, however, particularly regarding chronic effects of long-term drought and the response to increasing temperature and vapor pressure deficit (VPD). We combined analyses of radial growth and stable carbon isotope ratios (δ13C) in tree rings in a mature Scots pine (Pinus sylvestris L.) forest over the 20th century to elucidate causes of tree mortality in one of the driest parts of the European Alps (Pfynwald, Switzerland). We further compared trees that have recently died with living trees in a 10-year irrigation experiment, where annual precipitation was doubled. We found a sustained growth increase and immediate depletion of δ13C values for irrigated trees, indicating higher stomatal conductance and thus indeed demonstrating that water is a key limiting factor for growth. Growth of the now-dead trees started declining in the mid-1980s, when both mean temperature and VPD increased strongly. But growth of these trees was reduced to some extent already several decades earlier, while intrinsic water-use efficiency derived from δ13C values was higher. This indicates a more conservative water-use strategy compared with surviving trees, possibly at the cost of low carbon uptake and long-term reduction of the needle mass. We observed reduced climatic sensitivity of raw tree-ring δ13C for the now-dead in contrast to surviving trees, indicating impaired stomatal regulation, although this difference between the tree groups was smaller after detrending the data. Higher autocorrelation and a lower inter-annual δ13C variability of the now-dead trees further indicates a strong dependence on (low) carbon reserves. We conclude that the recent increase in atmospheric moisture demand in combination with insufficient soil water supply was the main trigger for mortality of those trees that were weakened by long

Diclofenac removal in urine using strong-base anion exchange polymer resins.

Science.gov (United States)

Landry, Kelly A; Boyer, Treavor H

2013-11-01

One of the major sources of pharmaceuticals in the environment is wastewater effluent of which human urine contributes the majority of pharmaceuticals. Urine source separation has the potential to isolate pharmaceuticals at a higher concentration for efficient removal as well as produce a nutrient byproduct. This research investigated the efficacy of using strong-base anion exchange polymer resins to remove the widely detected and abundant pharmaceutical, diclofenac, from synthetic human urine under fresh and ureolyzed conditions. The majority of experiments were conducted using a strong-base, macroporous, polystyrene resin (Purolite A520E). Ion-exchange followed a two-step removal rate with rapid removal in 1 h and equilibrium removal in 24 h. Diclofenac removal was >90% at a resin dose of 8 mL/L in both fresh and ureolyzed urine. Sorption of diclofenac onto A520E resin was concurrent with desorption of an equivalent amount of chloride, which indicates the ion-exchange mechanism is occurring. The presence of competing ions such as phosphate and citrate did not significantly impact diclofenac removal. Comparisons of three polystyrene resins (A520E, Dowex 22, Dowex Marathon 11) as well as one polyacrylic resin (IRA958) were conducted to determine the major interactions between anion exchange resin and diclofenac. The results showed that polystyrene resins provide the highest level of diclofenac removal due to electrostatic interactions between quaternary ammonium functional groups of resin and carboxylic acid of diclofenac and non-electrostatic interactions between resin matrix and benzene rings of diclofenac. Diclofenac was effectively desorbed from A520E resin using a regeneration solution that contained 4.5% (m/m) NaCl in an equal-volume mixture of methanol and water. The greater regeneration efficiency of the NaCl/methanol-water mixture over the aqueous NaCl solution supports the importance of non-electrostatic interactions between resin matrix and benzene rings

Self-gravitation in Saturn's rings

International Nuclear Information System (INIS)

Salo, H.; Lukkari, J.

1982-01-01

In a ring-shaped collisional system self-gravitation reduces the equilibrium values of the geometric and optical thickness. In Saturn's rings both effects are appreciable. The previously found discrepancy between the calculated profile and the observed profile of the rings is chiefly caused by the omission of self-gravitation. (Auth.)

Saturn’s ring temperatures at equinox

Science.gov (United States)

Spilker, Linda J.; Ferrari, C.; Morishima, R.

2013-10-01

Modeling the thermal emission of Saturn's rings is challenging due to the numerous heating sources as well as the structural properties of the disk and of the particles that are closely related. At equinox, however, the main rings are externally heated by Saturn alone and the problem is somewhat simplified. We test the abilities of our current models to reproduce the temperatures observed with the Cassini CIRS instrument around equinox in August 2009. A simple semi-analytic model which includes mutual shadowing effects can mostly explain the radial profile of the equinox ring temperatures, except the model predicts lower temperatures than those observed for the A ring. The temperature variation at a given saturnocentric radius is primarily caused by observational geometry variations relative to Saturn. The observed temperature increases with decreasing Saturn-ring-observer angle. In addition, we found evidence that the leading hemispheres of particles are warmer than the trailing hemispheres at least for the C ring and probably for the A and B rings as well. This is explained if some fraction of particles has spin rates lower than the synchronous rotation rate as predicted by N-body simulations. The spin model for a monolayer ring (Ferrari, C., Leyrat, C., 2006, Astron. Astrophys. 447, 745-760) can fit the temperature variations with spacecraft longitude observed in the C ring with currently known thermal properties and a mixing of slow and fast rotators. The multilayer model (Morishima, R., Salo, H., Ohtsuki, K., 2009, Icarus 201, 634-654) can reproduce the temperatures of the B and C rings but gives A ring temperatures that are significantly lower than those observed as does the simple semi-analytic model. More advanced models which take into account self-gravity wakes may explain the A ring temperature behavior.

Split ring containment attachment device

International Nuclear Information System (INIS)

Sammel, A.G.

1996-01-01

A containment attachment device is described for operatively connecting a glovebag to plastic sheeting covering hazardous material. The device includes an inner split ring member connected on one end to a middle ring member wherein the free end of the split ring member is inserted through a slit in the plastic sheeting to captively engage a generally circular portion of the plastic sheeting. A collar potion having an outer ring portion is provided with fastening means for securing the device together wherein the glovebag is operatively connected to the collar portion. 5 figs

Critical contribution of aromatic rings to specific recognition of polyether rings. The case of ciguatoxin CTX3C-ABC and its specific antibody 1C49.

Science.gov (United States)

Tsumoto, Kouhei; Yokota, Akiko; Tanaka, Yoshikazu; Ui, Mihoko; Tsumuraya, Takeshi; Fujii, Ikuo; Kumagai, Izumi; Nagumo, Yoko; Oguri, Hiroki; Inoue, Masayuki; Hirama, Masahiro

2008-05-02

To address how proteins recognize polyether toxin compounds, we focused on the interaction between the ABC ring compound of ciguatoxin 3C and its specific antibody, 1C49. Surface plasmon resonance analyses indicated that Escherichia coli-expressed variable domain fragments (Fv) of 1C49 had the high affinity constants and slow dissociation constants typical of antigen-antibody interactions. Linear van't Hoff analyses suggested that the interaction is enthalpy-driven. We resolved the crystal structure of 1C49 Fv bound to ABC ring compound of ciguatoxin 3C at a resolution of 1.7A. The binding pocket of the antibody had many aromatic rings and bound the antigen by shape complementarity typical of hapten-antibody interactions. Three hydrogen bonds and many van der Waals interactions were present. We mutated several residues of the antibody to Ala, and we used surface plasmon resonance to analyze the interactions between the mutated antibodies and the antigen. This analysis identified Tyr-91 and Trp-96 in the light chain as hot spots for the interaction, and other residues made incremental contributions by conferring enthalpic advantages and reducing the dissociation rate constant. Systematic mutation of Tyr-91 indicated that CH-pi and pi-pi interactions between the aromatic ring at this site and the antigen made substantial contributions to the association, and van der Waals interactions inhibited dissociation, suggesting that aromaticity and bulkiness are critical for the specific recognition of polyether compounds by proteins.

An N-body Integrator for Planetary Rings

Science.gov (United States)

Hahn, Joseph M.

2011-04-01

A planetary ring that is disturbed by a satellite's resonant perturbation can respond in an organized way. When the resonance lies in the ring's interior, the ring responds via an m-armed spiral wave, while a ring whose edge is confined by the resonance exhibits an m-lobed scalloping along the ring-edge. The amplitude of these disturbances are sensitive to ring surface density and viscosity, so modelling these phenomena can provide estimates of the ring's properties. However a brute force attempt to simulate a ring's full azimuthal extent with an N-body code will likely fail because of the large number of particles needed to resolve the ring's behavior. Another impediment is the gravitational stirring that occurs among the simulated particles, which can wash out the ring's organized response. However it is possible to adapt an N-body integrator so that it can simulate a ring's collective response to resonant perturbations. The code developed here uses a few thousand massless particles to trace streamlines within the ring. Particles are close in a radial sense to these streamlines, which allows streamlines to be treated as straight wires of constant linear density. Consequently, gravity due to these streamline is a simple function of the particle's radial distance to all streamlines. And because particles are responding to smooth gravitating streamlines, rather than discrete particles, this method eliminates the stirring that ordinarily occurs in brute force N-body calculations. Note also that ring surface density is now a simple function of streamline separations, so effects due to ring pressure and viscosity are easily accounted for, too. A poster will describe this N-body method in greater detail. Simulations of spiral density waves and scalloped ring-edges are executed in typically ten minutes on a desktop PC, and results for Saturn's A and B rings will be presented at conference time.

Minimal Gromov-Witten rings

International Nuclear Information System (INIS)

Przyjalkowski, V V

2008-01-01

We construct an abstract theory of Gromov-Witten invariants of genus 0 for quantum minimal Fano varieties (a minimal class of varieties which is natural from the quantum cohomological viewpoint). Namely, we consider the minimal Gromov-Witten ring: a commutative algebra whose generators and relations are of the form used in the Gromov-Witten theory of Fano varieties (of unspecified dimension). The Gromov-Witten theory of any quantum minimal variety is a homomorphism from this ring to C. We prove an abstract reconstruction theorem which says that this ring is isomorphic to the free commutative ring generated by 'prime two-pointed invariants'. We also find solutions of the differential equation of type DN for a Fano variety of dimension N in terms of the generating series of one-pointed Gromov-Witten invariants

Coherent Instabilities of ILC Damping Ring

Energy Technology Data Exchange (ETDEWEB)

Heifets, S.; Stupakov, G.; Bane, K.; /SLAC

2006-09-27

The paper presents the first attempt to estimates the ILC damping ring impedance and compare thresholds of the classical instabilities for several designs initially proposed for the DR. The work was carried out in the spring of 2006. Since then the choice of the DR is narrowed. Nevertheless, the analysis described may be useful for the next iterations of the beam stability. Overall, the conventional instabilities will have little impact on the ring performance provided the careful design of the ring minimizes the impedance below acceptable level indicated above. The only exception is the transverse CB instability. The longitudinal CB is less demanding. However, even the transverse CB instability would have threshold current above nominal provided the aperture in the wigglers is increased from 8 mm to 16 mm. The microwave instability needs more studies. Nevertheless, we should remember that the ILC DR is different from existing high-current machines at least in two respects: absence of the beam-beam tune spread stabilizing beams in colliders, and unusual strict requirements for low emittance. That may cause new problems such as bunch emittance dilution due to high-frequency wakes (BPMs, grooves), etc. Even if such a possibility exists, it probably universal for all machines and ought be addressed in the design of vacuum components rather than have effect on the choice of the machine design.

Electro-optical hybrid slip ring

Science.gov (United States)

Hong, En

2005-11-01

The slip ring is a rotary electrical interface, collector, swivel or rotary joint. It is a physical system that can perform continuous data transfer and data exchange between a stationary and a rotating structure. A slip ring is generally used to transfer data or power from an unrestrained, continuously rotating electro-mechanical system in real-time, thereby simplifying operations and eliminating damage-prone wires dangling from moving joints. Slip rings are widely used for testing, evaluating, developing and improving various technical equipment and facilities with rotating parts. They are widely used in industry, especially in manufacturing industries employing turbo machinery, as in aviation, shipbuilding, aerospace, defense, and in precise facilities having rotating parts such as medical Computerized Tomography (CT) and MRI scanners and so forth. Therefore, any improvement in slip ring technology can impact large markets. Research and development in this field will have broad prospects long into the future. The goal in developing the current slip ring technology is to improve and increase the reliability, stability, anti-interference, and high data fidelity between rotating and stationary structures. Up to now, there have been numerous approaches used for signal and data transfer utilizing a slip ring such as metal contacts, wires, radio transmission, and even liquid media. However, all suffer from drawbacks such as data transfer speed limitations, reliability, stability, electro-magnetic interference and durability. The purpose of the current research is to break through these basic limitations using an optical solution, thereby improving performance in current slip ring applications. This dissertation introduces a novel Electro-Optical Hybrid Slip Ring technology, which makes "through the air" digital-optical communication between stationary and rotating systems a reality with high data transfer speed, better reliability and low interference susceptibility

Injector Design for a Model Electron Ring at the University of Maryland

Science.gov (United States)

Godlove, T.; Bernal, S.; Deng, J. J.; Li, Y.; Reiser, M.; Wang, J. G.; Zou, Y.

1997-05-01

A model electron recirculator is being developed at the University of Maryland. It employs a 10-keV, space-charge-dominated beam injected into a 1.8-m radius ring equipped with a strong-focusing lattice based on printed-circuit quadrupoles and dipoles. The motivation and general features are described in separate papers. Here we describe the design for injecting a single-turn bunch into the ring. The system includes a low-emittance e-gun, matching section, pulsed dipole and Panofsky quadrupole. The dipole at the injection point must deflect the beam -10^circ during entry and +10^circ after entry, with about 25 ns transition time. The Panofsky quadrupole must be off during entry and on for subsequent laps, with a similar rise time.

Double acting stirling engine piston ring

Science.gov (United States)

Howarth, Roy B.

1986-01-01

A piston ring design for a Stirling engine wherein the contact pressure between the piston and the cylinder is maintained at a uniform level, independent of engine conditions through a balancing of the pressure exerted upon the ring's surface and thereby allowing the contact pressure on the ring to be predetermined through the use of a preloaded expander ring.

Ring current and auroral electrojets in connection with interplanetary medium parameters during magnetic storm

Directory of Open Access Journals (Sweden)

Y. I. Feldstein

1994-06-01

Full Text Available The relationship between the auroral electrojet indices (AE and the ring current magnetic field (DR was investigated by observations obtained during the magnetic storm on 1-3 April 1973. During the storm main phase the DR development is accompanied by a shift of the auroral electrojets toward the equator. As a result, the standard AE indices calculated on the basis of data from auroral observatories was substantially lower than the real values (AE'. To determine AE' during the course of a storm main phase data from subauroral magnetic observatories should be used. It is shown that the intensity of the indices (AE' which take into account the shift of the electrojets is increased substantially relative to the standard indices during the storm main phase. AE' values are closely correlated with geoeffective solar wind parameters. A high correlation was obtained between AE' and the energy flux into the ring current during the storm main phase. Analysis of magnetic field variations during intervals with intense southward IMF components demonstrates a decrease of the saturation effect of auroral electrojet currents if subauroral stations magnetic field variations are taken into account. This applies both to case studies and statistical data. The dynamics of the electrojets in connection with the development of the ring current and of magnetospheric substorms can be described by the presence (absence of saturation for minimum (maximum AE index values during a 1-h interval. The ring current magnetic field asymmetry (ASY was calculated as the difference between the maximum and minimum field values along a parallel of latitude at low latitudes. The ASY value is closely correlated with geoeffective solar wind parameters and simultaneously is a more sensitive indicator of IMF Bz variations than the symmetric ring current. ASY increases (decreases faster during the main phase (the recovery phase than DR. The magnetic field decay at low latitudes in the

Fusion Rings for Quantum Groups

DEFF Research Database (Denmark)

Andersen, Henning Haahr; Stroppel, Catharina

2012-01-01

We study the fusion rings of tilting modules for a quantum group at a root of unity modulo the tensor ideal of negligible tilting modules. We identify them in type A with the combinatorial rings from [12] and give a similar description of the sp2n-fusion ring in terms of noncommutative symmetric...

Topological rings

CERN Document Server

Warner, S

1993-01-01

This text brings the reader to the frontiers of current research in topological rings. The exercises illustrate many results and theorems while a comprehensive bibliography is also included. The book is aimed at those readers acquainted with some very basic point-set topology and algebra, as normally presented in semester courses at the beginning graduate level or even at the advanced undergraduate level. Familiarity with Hausdorff, metric, compact and locally compact spaces and basic properties of continuous functions, also with groups, rings, fields, vector spaces and modules, and with Zorn''s Lemma, is also expected.

Forandringslæring med autismediagnoser?

DEFF Research Database (Denmark)

Gustafson, Kari Ingrid; Mørck, Line Lerche

2013-01-01

Artiklen drøfter en række aktuelle spørgsmål omkring læring hos børn og unge med autisme-spektrum-forstyrrelses diagnoser. Der introduceres til en social praksisteoretisk forståelse af forandringslæring, der diskuterer forandring ikke kun i relation til en persons identitet, men også aktuelle og...... potentielle forandringer, når det gælder overskridelse af binær logik i autisme versus normalitet, samt i relation til at overskride individualiserede og dualistiske problem-forståelser af fejl og mangler ved det autistiske barn. Det illustreres, hvordan disse former for dualistisk tænkning er forankret i et...... Rasmus’ ændringer i læring, selvforståelse og tilhørsforhold perspektiveres med andre ASF-diagnostiseredes læring udforsket bl.a. gennem gruppeinterviews i regi af Asperger-foreningen. Artiklen byder således på et alternativ i form af at forstå forandringslæring som overskridende læring, med langt større...

Magmatic development of the outer Vøring Margin

Science.gov (United States)

Breivik, Asbjorn; Faleide, Jan Inge; Mjelde, Rolf; Flueh, Ernst; Murai, Yoshio

2013-04-01

The Vøring Plateau off mid-Norway is a volcanic passive margin, located north of the East Jan Mayen Fracture Zone (EJMFZ). Large volumes of magmatic rocks were emplaced during Early Eocene margin formation. In 2003, an ocean bottom seismometer survey was acquired on the Vøring and Lofoten margins. One profile crosses from the Vøring Plateau to the Vøring Spur, an oceanic plateau north of the EJMFZ. The P-wave data were modeled by ray-tracing in a 2D velocity model of the crust. The process behind the excess magmatism can be estimated by comparing seismic velocity (VP) with igneous thickness (H). This profile and two other profiles farther north show a positive H-VP correlation, consistent with a hot mantle reservoir of finite extent under the margin at breakup. However, during the first two million years, magma production appears to be augmented by a secondary process. By 51-51.5 Ma melting may be caused by elevated mantle temperature alone. Seismic stratigraphy around the Vøring Spur shows at least two inversion events, with the main episode tentatively in the Upper Miocene, apparently through igneous growth to create the up to 15 km crustal thickness. The H-VP correlation of the spur is low, indicating constant and moderate-degree mantle melting not tied to the breakup magmatism. The admittance function between bathymetry and free-air gravity shows that the high is near local isostatic equilibrium, discounting that compressional flexure at the EJMFZ shaped the high. We also find no evidence for the proposed Early Eocene triple junction in the area.

Central regions of LIRGs: rings, hidden starbursts, Supernovae and star clusters

International Nuclear Information System (INIS)

Väisänen, Petri; Randriamanakoto, Zara; Escala, Andres; Kankare, Erkki; Mattila, Seppo; Reunanen, Juha; Kotilainen, Jari; Rajpaul, Vinesh; Ryder, Stuart; Zijlstra, Albert

2012-01-01

We study star formation (SF) in very active environments, in luminous IR galaxies, which are often interacting. A variety of phenomena are detected, such as central starbursts, circumnuclear SF, obscured SNe tracing the history of recent SF, massive super star clusters, and sites of strong off-nuclear SF. All of these can be ultimately used to define the sequence of triggering and propagation of star-formation and interplay with nuclear activity in the lives of gas rich galaxy interactions and mergers. In this paper we present analysis of high-spatial resolution integral field spectroscopy of central regions of two interacting LIRGs. We detect a nuclear 3.3 μm PAH ring around the core of NGC 1614 with thermal-IR IFU observations. The ring's characteristics and relation to the strong star-forming ring detected in recombination lines are presented, as well as a scenario of an outward expanding starburst likely initiated with a (minor) companion detected within a tidal feature. We then present NIR IFU observations of IRAS 19115-2124, aka the Bird, which is an intriguing triple encounter. The third component is a minor one, but, nevertheless, is the source of 3/4 of the SFR of the whole system. Gas inflows and outflows are detected in their nuclei locations. Finally, we briefly report on our on-going NIR adaptive optics imaging survey of several dozen LIRGs. We have detected highly obscured core-collapse SNe in the central kpc, and discuss the statistics of 'missing SNe' due to dust extinction. We are also determining the characteristics of hundreds of super star clusters in and around the core regions of LIRGs, as a function of host-galaxy properties.

Catalytic ring opening of cyclic hydrocarbons in diesel fuels

Energy Technology Data Exchange (ETDEWEB)

Calemma, V.; Ferrari, M. [Eni S.p.A., San Donato Milanese (Italy). R and M Div.; Rabl, S.; Haas, A.; Santi, D.; Weitkamp, J. [Stuttgart Univ. (Germany). Inst. of Chemical Technology

2013-11-01

An approach for high-aromatic streams upgrading, allowing to meet future diesel quality standards, is saturation of the aromatic structures followed by the selective breaking of endocyclic C-C bonds of naphthenic structures so formed to produce alkanes with the same number of carbon atoms as the starting molecule ('selective ring opening, SRO'). Although theoretically, SRO is a promising route for upgrading low-value feeds to high-quality products, in practice, it continues to be a challenge owing to its complex chemistry. Product characteristics, do not only depend on the composition of the feed, but also on the operating conditions and the nature of the catalyst. Very recently, novel catalysts ('HIgh-PErformance Ring Opening Catalysts, HIPEROCs') were developed which allow a very selective ring opening of the model compound decalin to paraffins without degradation of the carbon number. The hydroconversion of dearomatized Light Cycle Oil (DeAr-LCO) over the abovementioned catalysts resulted in a remarkable change of the chemical structure of the feed with a strong decrease of naphthenic structures with two or more condensed rings and a concomitant increase of alkyl-substituted cyclohexanes and open-chain alkanes. The changes occurring in the chemical structures of feedstock during hydroconversion resulted in a remarkable increase of the Cetane Index of the products up to 11 units. In the present contribution, we examine the main factors affecting activity and selectivity of SRO catalysts in the light of the recent literature dealing with the subject and we report on the recent advances in hydroconversion of refinery cuts such as DeAr- LCO over HIPEROCs. (orig.)

Vortex rings in classical and quantum systems

International Nuclear Information System (INIS)

Barenghi, C F; Donnelly, R J

2009-01-01

The study of vortex rings has been pursued for decades and is a particularly difficult subject. However, the discovery of quantized vortex rings in superfluid helium has greatly increased interest in vortex rings with very thin cores. While rapid progress has been made in the simulation of quantized vortex rings, there has not been comparable progress in laboratory studies of vortex rings in a viscous fluid such as water. This article overviews the history and current frontiers of classical and quantum vortex rings. After introducing the classical results, this review discusses thin-cored vortex rings in superfluid helium in section 2, and recent progress in understanding vortex rings of very thin cores propagating in water in section 3. (invited paper)

Occurrence of annual growth rings in Rhizophora mangle in a region with low climate seasonality

Directory of Open Access Journals (Sweden)

BRUNNA T. SOUZA

2016-01-01

Full Text Available ABSTRACT The formation of annual growth rings has been confirmed for several mangrove species in the last decade, among which is the Rhizophora mangle. However, the record of annual rings for this species was made in a region with high hydric seasonality, a widely recognized induction factor of annual rings in tropical species. In this sense, the present study aimed to verify the occurrence of annual growth rings in R. mangle in the mangroves of Guaratiba (Rio de Janeiro, Southeastern Brazil, a region with low hydric seasonality. For this purpose, the crossdating technique was applied in ten trees collected with known age (seven years. The growth rings are characterized by alternating layers of low vessel density (earlywood and high vessel density (latewood. Multiple regression analysis indicated that growth rings width variation is driven by precipitation, water surplus, water deficit and water storage. Crossdating analysis confirmed the existence of annual growth rings in the R. mangle in Guaratiba. This discovery in a region with low hydric seasonality increases the dendrocronological potential of this species and suggests the importance of biological factors (eg. phenological behavior as complementary inductors for the formation of growth rings in this species.

Laparoscopic appendicectomy using endo-ring applicator and fallope rings

International Nuclear Information System (INIS)

Ali, Iyoob V; Maliekkal, Joji I

2009-01-01

Wider adoption of laparoscopic appendicectomy (LA) is limited by problems in securing the appendiceal base as well as the cost and the duration compared with the open procedure. The objective of this study was to assess the feasibility and efficacy of a new method for securing the appendiceal base in LA, so as to make the entire procedure simpler and cheaper, and hence, more popular. Twenty-five patients who were candidates for appendicectomy (emergency as well as elective) and willing for the laparoscopic procedure were selected for this study. Ports used were 10 mm at the umbilicus, 5 mm at the lower right iliac fossa, and 10 mm at the left iliac fossa. Extremely friable, ruptured, or turgid organs of diameters larger than 8 mm were excluded from the study. The mesoappendix was divided close to the appendix by diathermy. Fallope rings were applied to the appendiceal base using a special ring applicator, and the appendix was divided and extracted through the lumen of the applicator. The procedure was successful in 23 (92%) cases, and the mean duration of the procedure was 20 minutes (15-32 minutes). There were no procedural complications seen during a median follow-up of two weeks. The equipment and rings were cheaper when compared with that of the standard methods of securing the base of the appendix. LA using fallope rings is a safe, simple, easy-to-learn, and economically viable method. (author)

Spectrophotometric study of Saturn's main rings by means of Monte Carlo ray-tracing and Hapke's theory

Science.gov (United States)

Ciarniello, Mauro; Filacchione, Gianrico; D'Aversa, Emiliano; Cuzzi, Jeffrey N.; Capaccioni, Fabrizio; Hedman, Matthew M.; Dalle Ore, Cristina M.; Nicholson, Philip D.; Clark, Roger Nelson; Brown, Robert H.; Cerroni, Priscilla; Spilker, Linda

2017-10-01

This work is devoted to the investigation of the spectrophotometric properties of Saturn's rings from Cassini-VIMS (Visible and Infrared Mapping Spectrometer) observations. The dataset used for this analysis is represented by ten radial spectrograms of the rings which have been derived in Filacchione et al. (2014) by radial mosaics produced by VIMS. Spectrograms report the measured radiance factor of the main Saturn's rings as a function of both radial distance (from 73.500 to 141.375 km) and wavelength (0.35-5.1 µm) for different observation geometries (phase angle ranging in the 1.9°-132.2° interval). We take advantage of a Monte Carlo ray-tracing routine to characterize the photometric behavior of the rings at each wavelength and derive the spectral Bond albedo of rings particles. This quantity is used to infer the composition of the regolith covering rings particles by applying Hapke's theory. Four different regions, characterized by different optical depths, and respectively located in the C ring, inner B ring, mid B ring and A ring, have been investigated. Results from spectral modeling indicate that rings spectrum can be described by water ice with minimal inclusion of organic materials (tholin, exogenous material, which is more effective in the less dense regions of the rings because of their lower content of pure water ice.

SMARANDACHE NON-ASSOCIATIVE RINGS

OpenAIRE

Vasantha, Kandasamy

2002-01-01

An associative ring is just realized or built using reals or complex; finite or infinite by defining two binary operations on it. But on the contrary when we want to define or study or even introduce a non-associative ring we need two separate algebraic structures say a commutative ring with 1 (or a field) together with a loop or a groupoid or a vector space or a linear algebra. The two non-associative well-known algebras viz. Lie algebras and Jordan algebras are mainly built using a vecto...

Heavy ion storage rings

International Nuclear Information System (INIS)

Schuch, R.

1987-01-01

A brief overview of synchrotron storage rings for heavy ions, which are presently under construction in different accelerator laboratories is given. Ions ranging from protons up to uranium ions at MeV/nucleon energies will be injected into these rings using multiturn injection from the accelerators available or being built in these laboratories. After injection, it is planned to cool the phase space distribution of the ions by merging them with cold electron beams or laser beams, or by using stochastic cooling. Some atomic physics experiments planned for these rings are presented. 35 refs

Dynamics of pollutant indicators during flood events in a small river under strong anthropogenic pressures

Science.gov (United States)

Brion, Natacha; Carbonnel, Vincent; Elskens, Marc; Claeys, Philippe; Verbanck, Michel A.

2017-04-01

In densely populated regions, human activities profoundly modify natural water circulation as well as water quality, with increased hydrological risks (floods, droughts,…) and chemical hazards (untreated sewage releases, industrial pollution,…) as consequence. In order to assess water and pollutants dynamics and their mass-balance in strongly modified river system, it is important to take into account high flow events as a significant fraction of water and pollutants loads may occur during these short events which are generally underrepresented in classical mass balance studies. A good example of strongly modified river systems is the Zenne river in and around the city of Brussels (Belgium).The Zenne River (Belgium) is a rather small but dynamic rain fed river (about 10 m3/s in average) that is under the influence of strong contrasting anthropogenic pressures along its stretch. While the upstream part of its basin is rather characterized by agricultural land-use, urban and industrial areas dominate the downstream part. In particular, the city of Brussels (1.1M inhabitants) discharges in the Zenne River amounts of wastewater that are large compared to the natural riverine flow. In order to assess water and pollutants dynamics and their mass-balance in the Zenne hydrographic network, we followed water flows and concentrations of several water quality tracers during several flood episodes with an hourly frequency and at different locations along the stretch of the River. These parameters were chosen as indicators of a whole range of pollutions and anthropogenic activities. Knowledge of the high-frequency pollutants dynamics during floods is required for establishing accurate mass-balances of these elements. We thus report here the dynamics of selected parameters during entire flood events, from the baseline to the decreasing phase and at hourly frequency. Dynamics at contrasting locations, in agricultural or urban environments are compared. In particular, the

Electron gas interacting in a metal, submitted to a strong magnetic field

International Nuclear Information System (INIS)

Alcaraz, Francisco Castilho

1977-01-01

Using the propagator's technique in the grand ensemble developed by Montroll and Ward we investigate the magnetic properties of an interacting electron gas in a strong magnetic field. The free propagator properly constructed shows that the spin paramagnetism does not have a term with strong temperature dependence, contrary to the result of Isihara. Considering the electron density to be constant, the dHVA oscillations in the magnetic susceptibility and sound velocity, considering the effects of first exchange interactions, show only one phase in agreement with experimental result, while Ichimura and Isihara obtained two phases differing by π/2. The effects of first order exchange interactions in the dHVA oscillations of the magnetic susceptibility and sound velocity give rise to an exponential factor in the amplitudes of oscillator (Dingle factor), being the Dingle temperature linearly dependent of the Fermi velocity. The calculations of the ring diagram contribution to the grand partition function, show that the approximation used by Isihara for this calculations is not good and the dHVA oscillations of the contributions from the ring diagrams for the grand partition function have a phase differing by π/2 from that obtained by Isihara. (author)

Tinkering at the main-ring lattice

Energy Technology Data Exchange (ETDEWEB)

Ohnuma, S.

1982-08-23

To improve production of usable antiprotons using the proton beam from the main ring and the lossless injection of cooled antiprotons into the main ring, modifications of the main ring lattice are recommended.

The ring plus project: safety and acceptability of vaginal rings that protect women from unintended pregnancy

OpenAIRE

Schurmans, C?line; De Baetselier, Irith; Kestelyn, Evelyne; Jespers, Vicky; Delvaux, Th?r?se; Agaba, Stephen K; van Loen, Harry; Menten, Joris; van de Wijgert, Janneke; Crucitti, Tania

2015-01-01

Background Research is ongoing to develop multipurpose vaginal rings to be used continuously for contraception and to prevent Human Immunodeficiency Virus (HIV) infection. Contraceptive vaginal rings (CVRs) are available in a number of countries and are most of the time used intermittently i.e. three weeks out of a 4-week cycle. Efficacy trials with a dapivirine-containing vaginal ring for HIV prevention are ongoing and plans to develop multi-purpose vaginal rings for prevention of both HIV a...

Aging and lifetime prediction of O-ring seals

International Nuclear Information System (INIS)

Koemmling, Anja

2017-01-01

In some applications, elastomer seals have to remain leak tight over extended time periods (up to several decades) as an exchange of the seals is not practical. Therefore, it is necessary to be able to predict the lifetime of such seals reliably. For this reason, ageing experiments with O-rings and sheets based on hydrogenated acrylonitrile butadiene rubber (HNBR), ethylene propylene diene rubber (EPDM) and fluorocarbon rubber (FKM) were performed over up to two years at different temperatures. For investigating the changes of material properties during ageing, measurements of i.a. hardness and tensile behaviour as well as dynamic-mechanical and thermogravimetric analyses were conducted. For assessing the relaxation and recovery behaviour of the ageing seals, compression stress relaxation and compression set experiments were performed. Furthermore, leakage rate was measured to detect seal failure. By examining the aged samples, both the property changes and the responsible degradation mechanisms were characterised. Additionally, the most suitable approach for lifetime predictions should be determined using the large database of results from different test methods performed at several ageing times and temperatures. This included identifying an end-of-lifetime criterion that correlates with leakage and thus seal failure. Regarding the property changes and degradation mechanisms of HNBR, a pronounced embrittlement was observed due to dominant crosslinking reactions during ageing. These also resulted in a decrease of oxygen permeability, leading to a reduction of the oxygen transport into the interior sample (mainly of the thicker O-rings). This resulted in diffusion-limited oxidation effects (DLO effects), meaning that the interior of the sample aged less strongly than regions close to the surface. During ageing of EPDM, both chain scission and crosslinking occurred, which became noticeable in deteriorated tensile properties and decreased compression force as well as

Pyrimidine-pyridine ring interconversion

NARCIS (Netherlands)

Plas, van der H.C.

2003-01-01

This chapter discusses the pyrimidine-to-pyridine ring transformation and pyridine-to-pyrimidine ring transformation. In nucleophile-induced pyrimidine-to-pyridine rearrangements, two types of reactions can be distinguished depending on the structure of the nucleophile: (1) reactions in which the

Electron beam cooling at a magnetic storage ring, TARN II, and an electrostatic storage ring

International Nuclear Information System (INIS)

Tanabe, Tetsumi

2006-01-01

At the High Energy Accelerator Research Organization (KEK), a magnetic storage ring, TARN II, with an electron cooler was operated from 1989 to 1999, while an electrostatic storage ring with a small electron cooler has been operational since 2000. In this paper, the electron cooling at TARN II and the electrostatic storage ring is described. (author)

Leapfrogging of multiple coaxial viscous vortex rings

International Nuclear Information System (INIS)

Cheng, M.; Lou, J.; Lim, T. T.

2015-01-01

A recent theoretical study [Borisov, Kilin, and Mamaev, “The dynamics of vortex rings: Leapfrogging, choreographies and the stability problem,” Regular Chaotic Dyn. 18, 33 (2013); Borisov et al., “The dynamics of vortex rings: Leapfrogging in an ideal and viscous fluid,” Fluid Dyn. Res. 46, 031415 (2014)] shows that when three coaxial vortex rings travel in the same direction in an incompressible ideal fluid, each of the vortex rings alternately slips through (or leapfrogs) the other two ahead. Here, we use a lattice Boltzmann method to simulate viscous vortex rings with an identical initial circulation, radius, and separation distance with the aim of studying how viscous effect influences the outcomes of the leapfrogging process. For the case of two identical vortex rings, our computation shows that leapfrogging can be achieved only under certain favorable conditions, which depend on Reynolds number, vortex core size, and initial separation distance between the two rings. For the case of three coaxial vortex rings, the result differs from the inviscid model and shows that the second vortex ring always slips through the leading ring first, followed by the third ring slipping through the other two ahead. A simple physical model is proposed to explain the observed behavior

THE DESTRUCTION OF THE CIRCUMSTELLAR RING OF SN 1987A

International Nuclear Information System (INIS)

Fransson, Claes; Migotto, Katia; Lundqvist, Peter; Taddia, Francesco; Sollerman, Jesper; Larsson, Josefin; Pesce, Dominic; Chevalier, Roger A.; Challis, Peter; Kirshner, Robert P.; France, Kevin; Leibundgut, Bruno; Spyromilio, Jason; McCray, Richard; Jerkstrand, Anders; Mattila, Seppo; Smith, Nathan; Wheeler, J. Craig; Crotts, Arlin; Garnavich, Peter

2015-01-01

We present imaging and spectroscopic observations with Hubble Space Telescope and Very Large Telescope of the ring of SN 1987A from 1994 to 2014. After an almost exponential increase of the shocked emission from the hotspots up to day ∼8000 (∼2009), both this and the unshocked emission are now fading. From the radial positions of the hotspots we see an acceleration of these up to 500–1000 km s −1 , consistent with the highest spectroscopic shock velocities from the radiative shocks. In the most recent observations (2013 and 2014), we find several new hotspots outside the inner ring, excited by either X-rays from the shocks or by direct shock interaction. All of these observations indicate that the interaction with the supernova ejecta is now gradually dissolving the hotspots. We predict, based on the observed decay, that the inner ring will be destroyed by ∼2025

Characteristics of hot electron ring in a simple magnetic mirror field

International Nuclear Information System (INIS)

Hosokawa, M.; Ikegami, H.

1980-12-01

Characteristics of hot electron ring are studied in a simple magnetic mirror machine (mirror ratio 2 : 1) with a diameter of 30 cm at the midplane and with the distance of 80 cm between the mirrors. Maximum microwave input power is 5 kW at 6.4 GHz with the corresponding power density of approximately 0.3 W/cm 3 . With a background cold plasma of 4 x 10 11 cm -3 , hot electron rings are most effectively generated in two cases when the magnetic field on the axis of the midplane is set near the fundamental or the second harmonic electron cyclotron resonance to the applied microwave frequency. Density profile of the hot electrons is observed to take a so-called ring shape with a radius controllable by the magnetic field intensity and with an axial length of approximately 10 cm. The radial cut view of the ring, however, indicates an M shape density profile, and the density of the hot electrons on the axis is about one half of the density at the ring. Approximately 30 msec is needed before generating the hot electron ring at the density of 10 10 cm -3 with an average kinetic energy of 100 keV. The ultimate energy distribution function is observed to have a stepwise cut in the high energy tail and no energetic components above 1 MeV are detected. The hot electron ring is susceptible to a few instabilities which can be artificially triggered. One of the instabilities is observed to associate with a loss of lower energetic electrons and microwave bursts. At the instability, the ring shape is observed to transform into a filled cylinder in a few microseconds and disappear. (author)

Long-Term Leak Tightness Of O-Ring Seals In The 9975 Shipping Package

International Nuclear Information System (INIS)

Hoffman, E.; Skidmore, E.; Daugherty, W.

2010-01-01

O-ring seals in the 9975 shipping package containment vessels are fabricated from a Viton GLT or GLT-S compound. Long-term testing of these O-rings has been performed to support service life predictions for packages used for long-term storage. Since the only criterion for O-ring performance is to maintain a leak-tight seal, leak testing is the primary indicator of service life. Fixtures have been aging at elevated temperatures to provide data for service life predictions. Limited leak test failures have been observed at the higher temperatures. This provides the opportunity for comparison to trends based on other O-ring properties, such as compression stress relaxation. Initial data suggest that the CSR data have some predictive value for a leak-tight service life, but other factors can complicate efforts to draw definitive conclusions.

HYDROCARBON EMISSION RINGS IN PROTOPLANETARY DISKS INDUCED BY DUST EVOLUTION

Energy Technology Data Exchange (ETDEWEB)

Bergin, Edwin A.; Du, Fujun; Schwarz, K.; Zhang, K. [Department of Astronomy, University of Michigan, 311 West Hall, 1085 S. University Ave, Ann Arbor, MI 48109 (United States); Cleeves, L. Ilsedore [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Blake, G. A. [Division of Geological and Planetary Sciences, MC 150-21, California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125 (United States); Visser, R. [European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748, Garching (Germany)

2016-11-01

We report observations of resolved C{sub 2}H emission rings within the gas-rich protoplanetary disks of TW Hya and DM Tau using the Atacama Large Millimeter Array. In each case the emission ring is found to arise at the edge of the observable disk of millimeter-sized grains (pebbles) traced by submillimeter-wave continuum emission. In addition, we detect a C{sub 3}H{sub 2} emission ring with an identical spatial distribution to C{sub 2}H in the TW Hya disk. This suggests that these are hydrocarbon rings (i.e., not limited to C{sub 2}H). Using a detailed thermo-chemical model we show that reproducing the emission from C{sub 2}H requires a strong UV field and C/O > 1 in the upper disk atmosphere and outer disk, beyond the edge of the pebble disk. This naturally arises in a disk where the ice-coated dust mass is spatially stratified due to the combined effects of coagulation, gravitational settling and drift. This stratification causes the disk surface and outer disk to have a greater permeability to UV photons. Furthermore the concentration of ices that transport key volatile carriers of oxygen and carbon in the midplane, along with photochemical erosion of CO, leads to an elemental C/O ratio that exceeds unity in the UV-dominated disk. Thus the motions of the grains, and not the gas, lead to a rich hydrocarbon chemistry in disk surface layers and in the outer disk midplane.

Redox shuttles having an aromatic ring fused to a 1,1,4,4-tetrasubstituted cyclohexane ring

Science.gov (United States)

Weng, Wei; Zhang, Zhengcheng; Amine, Khalil

2015-12-01

An electrolyte includes an alkali metal salt; an aprotic solvent; and a redox shuttle additive including an aromatic compound having at least one aromatic ring fused with at least one non-aromatic ring, the aromatic ring having two or more oxygen or phosphorus-containing substituents.

Ring current shifts in {sup 19}F-NMR of membrane proteins

Energy Technology Data Exchange (ETDEWEB)

Liu, Dongsheng, E-mail: liudsh@shanghaitech.edu.cn; Wüthrich, Kurt, E-mail: kwuthrich@shanghaitech.edu.cn [ShanghaiTech University, iHuman Institute (China)

2016-05-15

Fluorine-19 NMR markers are attractive reporter groups for use in studies of complex biomacromolecular systems, in particular also for studies of function-related conformational equilibria and rate processes in membrane proteins. Advantages of {sup 19}F-NMR probes include high sensitivity of the {sup 19}F chemical shifts to variations in the non-covalent environment. Nonetheless, in studies of G protein-coupled receptors (GPCR) we encountered situations where {sup 19}F chemical shifts were not responsive to conformational changes that had been implicated by other methods. This prompted us to examine possible effects of aromatic ring current fields on the chemical shifts of {sup 19}F-NMR probes used in GPCRs. Analysis of previously reported {sup 19}F-NMR data on the β{sub 2}-adrenergic receptor and mammalian rhodopsin showed that all {sup 19}F-labeling sites which manifested conformational changes are located near aromatic residues. Although ring current effects are small when compared to other known non-covalent effects on {sup 19}F chemical shifts, there is thus an indication that their contributions are significant when studying activation processes in GPCRs, since the observed activation-related {sup 19}F-NMR chemical shifts are comparable in size to the calculated ring current shifts. Considering the impact of ring current shifts may thus be helpful in identifying promising indigenous or engineered labeling sites for future {sup 19}F-NMR studies of GPCR activation, and novel information may be obtained on the nature of conformational rearrangements near the {sup 19}F-labels. It will then also be interesting to see if the presently indicated role of ring current shifts in membrane protein studies with {sup 19}F-NMR markers can be substantiated by a more extensive data base resulting from future studies.

Numerical investigation of a vortex ring impinging on a coaxial aperture

Science.gov (United States)

Hu, Jiacheng; Peterson, Sean D.

2017-11-01

Recent advancements in smart materials have sparked an interest in the development of small scale fluidic energy harvesters for powering distributed applications in aquatic environments, where coherent vortex structures are prevalent. Thus, it is crucial to investigate the interaction of viscous vortices in the proximity of a thin plate (a common harvester configuration). Hence, the present study systematically examines the interaction of a vortex ring impinging on an infinitesimally thin wall with a coaxially aligned annular aperture. The rigid aperture serves as an axisymmetric counterpart of the thin plate, and the vortex ring represents a typical coherent vortex structure. The results indicate that the vortex dynamics can be categorized into two regimes based on the aperture to ring radius ratio (Rr). The rebound regime (Rr = 0.9 , and an increase in the vortex ring impulse is observed for 1.0 energy harvesting strategy in vortex impact configurations. This work was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant (RGPIN-05778) and Alexander Graham Bell Canada Graduate Scholarship (CGS-D).

Free electron laser and microwave instability interplay in a storage ring

Directory of Open Access Journals (Sweden)

G. L. Orlandi

2004-06-01

Full Text Available Collective effects, such as the microwave instability, influence the longitudinal dynamics of an electron beam in a storage ring. In a storage ring free electron laser (FEL they can compete with the induced beam heating and thus be treated as a further concomitant perturbing source of the beam dynamics. Bunch length and energy spread measurements, carried out at the Super-ACO storage ring, can be correctly interpreted according to a broad-band impedance model. Quantitative estimations of the relative role that is played by the microwave instability and the laser heating in shaping the beam longitudinal dynamics have been obtained by the analysis of the equilibrium laser power. It has been performed in terms of either a theoretical limit, implemented with the measured beam longitudinal characteristics, or the numerical results obtained by a macroparticle tracking code, which includes the laser pulse propagation. Such an analysis, carried out for different operating points of the Super-ACO storage ring FEL, indicates that the laser heating counteracts the microwave instability.

Interaction of Vortex Ring with Cutting Plate

Science.gov (United States)

Musta, Mustafa

2015-11-01

The interaction of a vortex ring impinging on a thin cutting plate was made experimentally using Volumetric 3-component Velocitmetry (v3v) technique. The vortex rings were generated with piston-cylinder vortex ring generator using piston stroke-to-diameter ratios and Re at 2-3 and 1500 - 3000, respectively. The cutting of vortex rings below center line leads to the formation of secondary vortices on each side of the plate which is look like two vortex rings, and a third vortex ring propagates further downstream in the direction of the initial vortex ring, which is previously showed by flow visualization study of Weigand (1993) and called ``trifurcation''. Trifurcation is very sensitive to the initial Reynolds number and the position of the plate with respect to the vortex ring generator pipe. The present work seeks more detailed investigation on the trifurcation using V3V technique. Conditions for the formation of trifurcation is analyzed and compared with Weigand (1993). The formed secondary vortex rings and the propagation of initial vortex ring in the downstream of the plate are analyzed by calculating their circulation, energy and trajectories.

Magnetic ring for stripping enhancement

International Nuclear Information System (INIS)

Selph, F.

1992-10-01

A ring designed to recycle ions through a stripping medium offers the possibility for increasing output of the desired charge state by up to 4x. This could be a very important component of a Radioactive Nuclear Beam Facility. In order for such a ring to work effectively it must satisfy certain design conditions. These include achromaticity at the stripper, a dispersed region for an extraction magnet, and a number of first and higher order optics constraints which are necessary to insure that the beam emittance is not degraded unduly by the ring. An example is given of a candidate design of a stripping ring

Acceleration of magnetized plasma rings

International Nuclear Information System (INIS)

Hartman, D.; Eddleman, J.; Hammer, J.H.

1982-01-01

One scheme is considered, acceleration of a ring between coaxial electrodes by a B/sub theta/ field as in a coaxial rail-gun. If the electrodes are conical, a ring accelerated towards the apex of the cone undergoes self-similar compression (focussing) during acceleration. Because the allowable acceleration force F/sub a/ = kappa U/sub m//R (kappa - 2 , the accelerating distance for conical electrodes is considerably shortened over that required for coaxial electrodes. In either case however, since the accelerating flux can expand as the ring moves, most of the accelerating field energy can be converted into kinetic energy of the ring leading to high efficiency

Effect of five-membered ring and heteroatom substitution on charge transport properties of perylene discotic derivatives: A theoretical approach

Energy Technology Data Exchange (ETDEWEB)

Navarro, Amparo, E-mail: anavarro@ujaen.es; Fernández-Liencres, M. Paz; Peña-Ruiz, Tomás; Granadino-Roldán, José M.; Fernández-Gómez, Manuel [Departamento de Química Física y Analítica, Universidad de Jaén, Campus Las Lagunillas, E23071 Jaén (Spain); García, Gregorio [Instituto de Energía Solar and Departamento TFB, E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid, Ciudad Universitaria, Madrid 28040 (Spain)

2016-08-07

Density functional theory calculations were carried out to investigate the evolvement of charge transport properties of a set of new discotic systems as a function of ring and heteroatom (B, Si, S, and Se) substitution on the basic structure of perylene. The replacement of six-membered rings by five-membered rings in the reference compound has shown a prominent effect on the electron reorganization energy that decreases ∼0.2 eV from perylene to the new carbon five-membered ring derivative. Heteroatom substitution with boron also revealed to lower the LUMO energy level and increase the electron affinity, therefore lowering the electron injection barrier compared to perylene. Since the rate of the charge transfer between two molecules in columnar discotic systems is strongly dependent on the orientation of the stacked cores, the total energy and transfer integral of a dimer as a disc is rotated with respect to the other along the stacking axis have been predicted. Aimed at obtaining a more realistic approach to the bulk structure, the molecular geometry of clusters made up of five discs was fully optimized, and charge transfer rate and mobilities were estimated for charge transport along a one dimensional pathway. Heteroatom substitution with selenium yields electron transfer integral values ∼0.3 eV with a relative disc orientation of 25°, which is the preferred angle according to the dimer energy profile. All the results indicate that the tetraselenium-substituted derivative, not synthetized so far, could be a promising candidate among those studied in this work for the fabrication of n-type semiconductors based on columnar discotic liquid crystals materials.

Activity of 3-Ketosteroid 9α-Hydroxylase (KshAB) Indicates Cholesterol Side Chain and Ring Degradation Occur Simultaneously in Mycobacterium tuberculosis*

Science.gov (United States)

Capyk, Jenna K.; Casabon, Israël; Gruninger, Robert; Strynadka, Natalie C.; Eltis, Lindsay D.

2011-01-01

Mycobacterium tuberculosis (Mtb), a significant global pathogen, contains a cholesterol catabolic pathway. Although the precise role of cholesterol catabolism in Mtb remains unclear, the Rieske monooxygenase in this pathway, 3-ketosteroid 9α-hydroxylase (KshAB), has been identified as a virulence factor. To investigate the physiological substrate of KshAB, a rhodococcal acyl-CoA synthetase was used to produce the coenzyme A thioesters of two cholesterol derivatives: 3-oxo-23,24-bisnorchol-4-en-22-oic acid (forming 4-BNC-CoA) and 3-oxo-23,24-bisnorchola-1,4-dien-22-oic acid (forming 1,4-BNC-CoA). The apparent specificity constant (kcat/Km) of KshAB for the CoA thioester substrates was 20–30 times that for the corresponding 17-keto compounds previously proposed as physiological substrates. The apparent KmO2 was 90 ± 10 μm in the presence of 1,4-BNC-CoA, consistent with the value for two other cholesterol catabolic oxygenases. The Δ1 ketosteroid dehydrogenase KstD acted with KshAB to cleave steroid ring B with a specific activity eight times greater for a CoA thioester than the corresponding ketone. Finally, modeling 1,4-BNC-CoA into the KshA crystal structure suggested that the CoA moiety binds in a pocket at the mouth of the active site channel and could contribute to substrate specificity. These results indicate that the physiological substrates of KshAB are CoA thioester intermediates of cholesterol side chain degradation and that side chain and ring degradation occur concurrently in Mtb. This finding has implications for steroid metabolites potentially released by the pathogen during infection and for the design of inhibitors for cholesterol-degrading enzymes. The methodologies and rhodococcal enzymes used to generate thioesters will facilitate the further study of cholesterol catabolism. PMID:21987574

Activity of 3-ketosteroid 9α-hydroxylase (KshAB) indicates cholesterol side chain and ring degradation occur simultaneously in Mycobacterium tuberculosis.

Science.gov (United States)

Capyk, Jenna K; Casabon, Israël; Gruninger, Robert; Strynadka, Natalie C; Eltis, Lindsay D

2011-11-25

Mycobacterium tuberculosis (Mtb), a significant global pathogen, contains a cholesterol catabolic pathway. Although the precise role of cholesterol catabolism in Mtb remains unclear, the Rieske monooxygenase in this pathway, 3-ketosteroid 9α-hydroxylase (KshAB), has been identified as a virulence factor. To investigate the physiological substrate of KshAB, a rhodococcal acyl-CoA synthetase was used to produce the coenzyme A thioesters of two cholesterol derivatives: 3-oxo-23,24-bisnorchol-4-en-22-oic acid (forming 4-BNC-CoA) and 3-oxo-23,24-bisnorchola-1,4-dien-22-oic acid (forming 1,4-BNC-CoA). The apparent specificity constant (k(cat)/K(m)) of KshAB for the CoA thioester substrates was 20-30 times that for the corresponding 17-keto compounds previously proposed as physiological substrates. The apparent K(m)(O(2)) was 90 ± 10 μM in the presence of 1,4-BNC-CoA, consistent with the value for two other cholesterol catabolic oxygenases. The Δ(1) ketosteroid dehydrogenase KstD acted with KshAB to cleave steroid ring B with a specific activity eight times greater for a CoA thioester than the corresponding ketone. Finally, modeling 1,4-BNC-CoA into the KshA crystal structure suggested that the CoA moiety binds in a pocket at the mouth of the active site channel and could contribute to substrate specificity. These results indicate that the physiological substrates of KshAB are CoA thioester intermediates of cholesterol side chain degradation and that side chain and ring degradation occur concurrently in Mtb. This finding has implications for steroid metabolites potentially released by the pathogen during infection and for the design of inhibitors for cholesterol-degrading enzymes. The methodologies and rhodococcal enzymes used to generate thioesters will facilitate the further study of cholesterol catabolism.

Δg: The new aromaticity index based on g-factor calculation applied for polycyclic benzene rings

Science.gov (United States)

Ucun, Fatih; Tokatlı, Ahmet

2015-02-01

In this work, the aromaticity of polycyclic benzene rings was evaluated by the calculation of g-factor for a hydrogen placed perpendicularly at geometrical center of related ring plane at a distance of 1.2 Å. The results have compared with the other commonly used aromatic indices, such as HOMA, NICSs, PDI, FLU, MCI, CTED and, generally been found to be in agreement with them. So, it was proposed that the calculation of the average g-factor as Δg could be applied to study the aromaticity of polycyclic benzene rings without any restriction in the number of benzene rings as a new magnetic-based aromaticity index.

A first course in noncommutative rings

CERN Document Server

Lam, T Y

2001-01-01

A First Course in Noncommutative Rings, an outgrowth of the author's lectures at the University of California at Berkeley, is intended as a textbook for a one-semester course in basic ring theory. The material covered includes the Wedderburn-Artin theory of semisimple rings, Jacobson's theory of the radical, representation theory of groups and algebras, prime and semiprime rings, local and semilocal rings, perfect and semiperfect rings, etc. By aiming the level of writing at the novice rather than the connoisseur and by stressing th the role of examples and motivation, the author has produced a text that is suitable not only for use in a graduate course, but also for self- study in the subject by interested graduate students. More than 400 exercises testing the understanding of the general theory in the text are included in this new edition.

Effects of Surface Irregularities on Piston Ring-Cylinder Tribo Pair of a Two Stroke Motor Engine in Hydrodynamic Lubrication

Directory of Open Access Journals (Sweden)

A. Zavos

2015-03-01

Full Text Available Tribological parameters such as friction, lubrication and wear influence strongly the engine component's life. In this study, a piston ring-cylinder system simulated taking into account the surface modifications under fully flooded lubrication and normal engine conditions. The hydrodynamic pressure field solved based on the Navier Stokes equations by Fluid Structure Interaction analysis. A real experimental data of piston ring-cylinder was used from a two stroke motor engine 50 cc. The surface irregularities are measured by 3D coordinate measurement machine while the engine has been worked about 4000 hours. The friction force, the hydrodynamic pressure, the oil film and the mechanical stresses were predicted for different engine conditions. Results show that the worn profile ring reduces the friction as well as the mechanical stresses increased. Surface condition of worn top ring was observed after a metallurgical profile analysis.

Design of Piston Ring Friction Tester Apparatus

DEFF Research Database (Denmark)

Klit, Peder

2006-01-01

One of the major prerequisites for calculating piston ring friction is a good description of the tribological situation. Piston rings operate in three different lubrication regimes and the theoretical models should be capable to describe this. A very important condition for describing the frictio......One of the major prerequisites for calculating piston ring friction is a good description of the tribological situation. Piston rings operate in three different lubrication regimes and the theoretical models should be capable to describe this. A very important condition for describing...... the frictional behavior of a piston ring correctly is knowledge about the amount of lubricant present. For piston rings the external load may be established by measuring the pressure distribution, i.e. the pressure drop in the piston ring package. Speed and temperature may also be established. The amount...... available is reflected in the friction absorbed in the bearing. The following properties will be measured: Oil fillm thickness - along liner (axial variation), oil film thickness - along piston ring (circumferential variation), piston tilt, temperature of piston rings and liner, pressure at piston lands...

Scalability analysis of the synchronizability for ring or chain networks with dense clusters

International Nuclear Information System (INIS)

Lu, Jun-An; Zhang, Yong; Chen, Juan; Lü, Jinhu

2014-01-01

It is well known that most real-world complex networks, such as the Internet and the World Wide Web, are evolving networks. An interesting fundamental question is: how do some important functions or dynamical behaviors of complex networks evolve with increasing network scale? This paper aims at investigating the scalability of the synchronizability for ring or chain networks with dense clusters as the network size increases. We discover some interesting phenomena as follows: (i) the synchronizability of ring or chain networks with clusters decreases with increasing network scale regardless of the inner structures of all communities; (ii) for the same network scale, the network synchronizability decreases more quickly with increasing number of cluster blocks than with increasing number of nodes within the cluster block; (iii) the number of rings or chains has a much more significant influence on the network synchronizability than the size of the rings or chains. Our results indicate that network synchronizability can be maintained with increasing network scale by avoiding ring and chain structures. (paper)

Study for ILC Damping Ring at KEKB

Energy Technology Data Exchange (ETDEWEB)

Flanagan, J.W.; Fukuma, H.; Kanazawa, K.I.; Koiso, H.; Masuzawa, M.; Ohmi, Kazuhito; Ohnishi, Y.; Oide, Katsunobu; Suetsugu, Y.; Tobiyama, M.; /KEK, Tsukuba; Pivi, M.; /SLAC

2011-11-04

ILC damping ring consists of very low emittance electron and positron storage rings. It is necessary for ILC damping ring to study electron cloud effects in such low emittance positron ring. We propose a low emittance operation of KEKB to study the effects.

Inhomogeneous molecular ring around the B[e] supergiant LHA 120-S 73

Science.gov (United States)

Kraus, M.; Cidale, L. S.; Arias, M. L.; Maravelias, G.; Nickeler, D. H.; Torres, A. F.; Borges Fernandes, M.; Aret, A.; Curé, M.; Vallverdú, R.; Barbá, R. H.

2016-10-01

Context. B[e] supergiants are evolved massive stars, enshrouded in a dense wind and surrounded by a molecular and dusty disk. The mechanisms that drive phases of enhanced mass loss and mass ejections, responsible for the shaping of the circumstellar material of these objects, are still unclear. Aims: We aim to improve our knowledge on the structure and dynamics of the circumstellar disk of the Large Magellanic Cloud B[e] supergiant LHA 120-S 73. Methods: High-resolution optical and near-infrared spectroscopic data were obtained over a period of 16 and 7 yr, respectively. The spectra cover the diagnostic emission lines from [Ca II] and [O I], as well as the CO bands. These features trace the disk at different distances from the star. We analyzed the kinematics of the individual emission regions by modeling their emission profiles. A low-resolution mid-infrared spectrum was obtained as well, which provides information on the composition of the dusty disk. Results: All diagnostic emission features display double-peaked line profiles, which we interpret as due to Keplerian rotation. We find that the profile of each forbidden line contains contributions from two spatially clearly distinct rings. In total, we find that LHA 120-S 73 is surrounded by at least four individual rings of material with alternating densities (or by a disk with strongly non-monotonic radial density distribution). Moreover, we find that the molecular ring must have gaps or at least strong density inhomogeneities, or in other words, a clumpy structure. The optical spectra additionally display a broad emission feature at 6160-6180 Å, which we interpret as molecular emission from TiO. The mid-infrared spectrum displays features of oxygen- and carbon-rich grain species, which indicates a long-lived, stable dusty disk. We cannot confirm the previously reported high value for the stellar rotation velocity. He I λ 5876 is the only clearly detectable pure atmospheric absorption line in our data. Its

Planetary ring systems properties, structures, and evolution

CERN Document Server

Murray, Carl D

2018-01-01

Planetary rings are among the most intriguing structures of our solar system and have fascinated generations of astronomers. Collating emerging knowledge in the field, this volume reviews our current understanding of ring systems with reference to the rings of Saturn, Uranus, Neptune, and more. Written by leading experts, the history of ring research and the basics of ring–particle orbits is followed by a review of the known planetary ring systems. All aspects of ring system science are described in detail, including specific dynamical processes, types of structures, thermal properties and their origins, and investigations using computer simulations and laboratory experiments. The concluding chapters discuss the prospects of future missions to planetary rings, the ways in which ring science informs and is informed by the study of other astrophysical disks, and a perspective on the field's future. Researchers of all levels will benefit from this thorough and engaging presentation.

Establishment of a tolerance budget for the advanced photon source storage ring

International Nuclear Information System (INIS)

Bizek, H.; Crosbie, E.; Lessner, E.; Teng, L.

1993-01-01

The limitations on the dynamic aperture of the Advanced Photon Source storage ring due to magnet misalignments and fabrication errors are presented. The reduction of the dynamic aperture is analyzed first for each error considered individually, and then for combined error multipole fields in dipole, quadrupole, and sextupole magnets, excluding and including magnet misalignments. Since misalignments of the strong quadrupoles in the ring induce large orbit distortions, the effects on the dynamic aperture are investigated before and after orbit correction. Effects of off-momentum particles and the tune dependence with momentum are also presented. This extensive analysis leads to the establishment of a tolerance budget. With all the errors set at the tolerance level, and with the orbit distortions corrected, the dynamic aperture reduction is no greater than 50% of that of the ideal machine

Establishment of a tolerance budget for the Advanced Photon Source storage ring

International Nuclear Information System (INIS)

Bizek, H.; Crosbie, E.; Lessner, E.; Teng, L.

1993-01-01

The limitations on the dynamic aperture of the Advanced Photon Source storage ring due to magnet misalignments and fabrication errors are presented. The reduction of the dynamic aperture is analyzed first for each error considered individually, and then for combined error multipole fields in dipole, quadrupole, and sextupole magnets, excluding and including magnet misalignments. Since misalignments of the strong quadrupoles in the ring induce large orbit distortions, the effects on the dynamic aperture are investigated before and after orbit correction. Effects of off-momentum particles and the tune dependence with momentum are also presented. This extensive analysis leads to the establishment of a tolerance budget. With all the errors set at the tolerance level and with the orbit distortions corrected, the dynamic aperture reduction is no greater than 50% of that of the ideal machine

Longitudinal beam instability due to the ring impedance at KEK's accelerator test facility damping ring

International Nuclear Information System (INIS)

Kim, Eun-San

2003-01-01

This paper shows the results of a numerical study of the impedance in the Accelerator Test Facility damping ring. The longitudinal impedance in the damping ring is shown to be inductive. It is shown that the total impedance |Z || /n| is 0.23 Ω and the inductance is L = 14 nH. In the extremely low emittance beam of the damping ring, bunch lengthening is caused by both the effects of potential-well distortion and intra-beam scattering. In this paper, the bunch-lengthening due to the ring impedance is numerically investigated, and the result shows qualitative agreement with the result of an analysis performed using the bunch-length measurement. With the calculated longitudinal impedance, the instability threshold in the damping ring is estimated to be a bunch population of 3.3 x 10 10 by using both a Vlasov equation approach and a multi-particle tracking method.

Intra-ring haptotropic rearrangements of Mn(CO3 in fluorenyl ligands

Directory of Open Access Journals (Sweden)

Souhila Laib

2017-02-01

Full Text Available Geometric parameters, and intra-ring haptotropic rearrangements π–π (intra-ring-HRs ŋ5⇌ŋ3 of the manganesetricarbonyl complexes (ŋ5-9-R-C13H8Mn(CO3, R = But and Ph in 18e zero-valence are carried out using density functional theory DFT at PBE/TZP level. The calculated activation barriers to ŋ5⇌ŋ3 intra-ring HR in (ŋ5-9-R-C13H8Mn(CO3, R = But and Ph are (28.5 and 69.5 kcal.mol−1 respectively. The compute of HOMA and FLU indexes indicates the reduction of aromaticity when going from free to coordinated complex. The energy decomposition analysis reveals the dominant ionic character in manganese–Cp bond in the presence of covalent contribution.

Interaction of scandium and titanium atoms with a carbon surface containing five- and seven-membered rings

International Nuclear Information System (INIS)

Krasnov, P. O.; Eliseeva, N. S.; Kuzubov, A. A.

2012-01-01

The use of carbon nanotubes coated by atoms of transition metals to store molecular hydrogen is associated with the problem of the aggregation of these atoms, which leads to the formation of metal clusters. The quantum-chemical simulation of cluster models of the carbon surface of a graphene type with scandium and titanium atoms has been performed. It has been shown that the presence of five- and seven-membered rings, in addition to six-membered rings, in these structures makes it possible to strongly suppress the processes of the migration of metal atoms over the surface, preventing their clustering.

Nonlinear analysis of ring oscillator circuits

KAUST Repository

Ge, Xiaoqing

2010-06-01

Using nonlinear systems techniques, we analyze the stability properties and synchronization conditions for ring oscillator circuits, which are essential building blocks in digital systems. By making use of its cyclic structure, we investigate local and global stability properties of an n-stage ring oscillator. We present a sufficient condition for global asymptotic stability of the origin and obtain necessity if the ring oscillator consists of identical inverter elements. We then give a synchronization condition for identical interconnected ring oscillators.

Nonlinear analysis of ring oscillator circuits

KAUST Repository

Ge, Xiaoqing; Arcak, Murat; Salama, Khaled N.

2010-01-01

Using nonlinear systems techniques, we analyze the stability properties and synchronization conditions for ring oscillator circuits, which are essential building blocks in digital systems. By making use of its cyclic structure, we investigate local and global stability properties of an n-stage ring oscillator. We present a sufficient condition for global asymptotic stability of the origin and obtain necessity if the ring oscillator consists of identical inverter elements. We then give a synchronization condition for identical interconnected ring oscillators.

Quality Assurance Project Plan for Verification of Sediment Ecotoxicity Assessment Ring(SEA Ring)

Science.gov (United States)

The objective of the verification is to test the efficacy and ability of the Sediment Ecotoxicity Assessment Ring (SEA Ring) to evaluate the toxicity of contaminants in the sediment, at the sediment-water interface, and WC to organisms that live in those respective environments.

Dynamical Evolution of Ring-Satellite Systems

Science.gov (United States)

Ohtsuki, Keiji

2005-01-01

The goal of this research was to understand dynamical processes related to the evolution of size distribution of particles in planetary rings and application of theoretical results to explain features in the present rings of giant planets. We studied velocity evolution and accretion rates of ring particles in the Roche zone. We developed a new numerical code for the evolution of ring particle size distribution, which takes into account the above results for particle velocity evolution and accretion rates. We also studied radial diffusion rate of ring particles due to inelastic collisions and gravitational encounters. Many of these results can be also applied to dynamical evolution of a planetesimal disk. Finally, we studied rotation rates of moonlets and particles in planetary rings, which would influence the accretional evolution of these bodies. We describe our key accomplishments during the past three years in more detail in the following.

Cosmic rings from colliding galaxies

Energy Technology Data Exchange (ETDEWEB)

Mitton, S

1976-11-18

Research on two ring galaxies has led to the proposal of an interaction model to account for the rings. It is envisaged that this class of galaxy is created when a compact galaxy crashes through the disc of a spiral galaxy. The results of a spectroscopic investigation of the galaxy known as the Cartwheel and of another ring galaxy 11 NZ 4 are discussed. The general picture of ring galaxies which emerges from these studies of a massive starry nucleus with a necklace of emitting gas and some spokes and along the spin axis of the wheel a small companion galaxy that is devoid of interstellar gas. An explanation of these properties is considered.

Comparison of water-use efficiency estimates based on tree-ring carbon isotopes with simulations of a dynamic vegetation model

Science.gov (United States)

Saurer, Matthias; Renato, Spahni; Fortunat, Joos; David, Frank; Kerstin, Treydte; Rolf, Siegwolf

2015-04-01

Tree-ring d13C-based estimates of intrinsic water-use efficiency (iWUE, reflecting the ratio of assimilation A to stomatal conductance gs) generally show a strong increase during the industrial period, likely associated with the increase in atmospheric CO2. However, it is not clear, first, if tree-ring d13C-derived iWUE-values indeed reflect actual plant and ecosystem-scale variability in fluxes and, second, what physiological changes were the drivers of the observed iWUE increase, changes in A or gs or both. To address these questions, we used a complex dynamic vegetation model (LPX) that combines process-based vegetation dynamics with land-atmosphere carbon and water exchange. The analysis was conducted for three functional types, representing conifers, oaks, larch, and various sites in Europe, where tree-ring isotope data are available. The increase in iWUE over the 20th century was comparable in LPX-simulations as in tree-ring-estimates, strengthening confidence in these results. Furthermore, the results from the LPX model suggest that the cause of the iWUE increase was reduced stomatal conductance during recent decades rather than increased assimilation. High-frequency variation reflects the influence of climate, like for example the 1976 summer drought, resulting in strongly reduced A and g in the model, particularly for oak.

Damping the e-p instability in the SNS accumulator ring

Science.gov (United States)

Evans, N. J.; Deibele, C.; Aleksandrov, A.; Xie, Z.

2018-03-01

A broadband, digital damper system for both transverse planes developed for the SNS accumulator ring has recently damped the first indications of the broadband 50-150 MHz e-p instability in a 1.2 MW neutron production beam. This paper presents details of the design and operation of the SNS damper system as well as results of active damping of the e-p instability in the SNS ring showing a reduction in power of betatron oscillation over the 10-300 MHz band of up to 70%. The spectral content of the beam during operation, with and without the damper system is presented and performance of the damper system is evaluated.

Fengycin produced by Bacillus subtilis 9407 plays a major role in the biocontrol of apple ring rot disease.

Science.gov (United States)

Fan, Haiyan; Ru, Jinjiang; Zhang, Yuanyuan; Wang, Qi; Li, Yan

2017-06-01

Apple ring rot, caused by Botryosphaeria dothidea, is a serious apple disease in China. Bacillus subtilis 9407 was isolated from healthy apples and showed strong antifungal activity against B. dothidea. To identify the primary antifungal compound of B. subtilis 9407 and determine its role in controlling apple ring rot, a transposon mutant library was constructed using TnYLB-1, and a mutant completely defective in antifungal activity was obtained. The gene inactivated in the antifungal activity mutant had 98.5% similarity to ppsB in B. subtilis subsp. subtilis str. 168, which encodes one of the five synthetases responsible for synthesizing fengycin. A markerless ppsB deletion mutant was constructed. Compared with the wild-type strain, lipopeptide crude extracts from ΔppsB showed almost no inhibition of B. dothidea mycelial growth. Furthermore, fengycin-like lipopeptides (retention factor 0.1-0.2) that exhibited antifungal activity against B. dothidea were observed in the wild-type strain by thin-layer chromatography (TLC)-bioautography analysis, but not in ΔppsB. Semipreparative reverse-phase high performance liquid chromatography (RP-HPLC) detection revealed that ΔppsB lost the ability to synthesize fengycin. These results suggest that ppsB is responsible for synthesizing fengycin and that fengycin is the major antifungal compound produced by B. subtilis 9407 against B. dothidea. Moreover, a biocontrol assay showed that the control efficacy of ΔppsB was reduced by half compared with the wild-type strain, indicating that fengycin plays a major role in controlling apple ring rot disease. This is the first report on the use of a B. subtilis strain as a potential biological control agent to control apple ring rot disease by the production of fengycin. Copyright © 2017 Elsevier GmbH. All rights reserved.

Thon rings from amorphous ice and implications of beam-induced Brownian motion in single particle electron cryo-microscopy

Energy Technology Data Exchange (ETDEWEB)

McMullan, G., E-mail: gm2@mrc-lmb.cam.ac.uk; Vinothkumar, K.R.; Henderson, R.

2015-11-15

We have recorded dose-fractionated electron cryo-microscope images of thin films of pure flash-frozen amorphous ice and pre-irradiated amorphous carbon on a Falcon II direct electron detector using 300 keV electrons. We observe Thon rings [1] in both the power spectrum of the summed frames and the sum of power spectra from the individual frames. The Thon rings from amorphous carbon images are always more visible in the power spectrum of the summed frames whereas those of amorphous ice are more visible in the sum of power spectra from the individual frames. This difference indicates that while pre-irradiated carbon behaves like a solid during the exposure, amorphous ice behaves like a fluid with the individual water molecules undergoing beam-induced motion. Using the measured variation in the power spectra amplitude with number of electrons per image we deduce that water molecules are randomly displaced by a mean squared distance of ∼1.1 Å{sup 2} for every incident 300 keV e{sup −}/Å{sup 2}. The induced motion leads to an optimal exposure with 300 keV electrons of 4.0 e{sup −}/Å{sup 2} per image with which to observe Thon rings centred around the strong 3.7 Å scattering peak from amorphous ice. The beam-induced movement of the water molecules generates pseudo-Brownian motion of embedded macromolecules. The resulting blurring of single particle images contributes an additional term, on top of that from radiation damage, to the minimum achievable B-factor for macromolecular structure determination. - Highlights: • Thon rings can be seen from amorphous ice. • Radiation damage to amorphous ice randomly displaces water molecules. • Each incident 300 keV e{sup −}/Å{sup 2} displaces water molecules on average by ∼1 Å. • Macromolecules embedded in amorphous ice undergo beam induced Brownian motion.

Extracellular cell wall β(1,3)glucan is required to couple septation to actomyosin ring contraction

Science.gov (United States)

Muñoz, Javier; Cortés, Juan Carlos G.; Sipiczki, Matthias; Ramos, Mariona; Clemente-Ramos, José Angel; Moreno, M. Belén; Martins, Ivone M.; Pérez, Pilar

2013-01-01

Cytokinesis has been extensively studied in different models, but the role of the extracellular cell wall is less understood. Here we studied this process in fission yeast. The essential protein Bgs4 synthesizes the main cell wall β(1,3)glucan. We show that Bgs4-derived β(1,3)glucan is required for correct and stable actomyosin ring positioning in the cell middle, before the start of septum formation and anchorage to the cell wall. Consequently, β(1,3)glucan loss generated ring sliding, oblique positioned rings and septa, misdirected septum synthesis indicative of relaxed rings, and uncoupling between a fast ring and membrane ingression and slow septum synthesis, suggesting that cytokinesis can progress with defective septum pushing and/or ring pulling forces. Moreover, Bgs4-derived β(1,3)glucan is essential for secondary septum formation and correct primary septum completion. Therefore, our results show that extracellular β(1,3)glucan is required for cytokinesis to connect the cell wall with the plasma membrane and for contractile ring function, as proposed for the equivalent extracellular matrix in animal cells. PMID:24165938

On Semiprime Noetherian PI-Rings

OpenAIRE

Chiba, Katsuo

2000-01-01

Let R be a semiprime Noetherian PI-ring and Q(R) the semisimple Artinian ring of fractions of R. We shall prove the following conditions are equivalent: (1) the Krull dimention of R is at most one, (2) Any ring between R and Q(R) is again right Noetherian, (3) Let a, b be central regular elements of Q(R). Then the subring R + aR[b] of Q(R) is right Noetherian.

Einstein Ring in Distant Universe

Science.gov (United States)

2005-06-01

on the newly discovered Einstein ring. The image quality ("seeing") of the R-band image is exceptional (0.5") and the image reveals the lensing system in stunning details. The central dot is the lens, a quiescent massive galaxy that distort the light emitted by background sources. The large arc surrounding the central lens is a part of the Einstein-ring created by a background source finely aligned with the lens. The reddish colour indicates that the redshift of the system is very large. FORS2 spectroscopy of the lensing system yield a redshift close to 1 for the lens (we see the lens as it was when the universe was half its present size), and a record-breaking redshift z=3.8 for a background source of such brightness, hence we see the object (a star forming galaxy) as it was when the universe was only 12% of its present age. The lensing model indicates that the light of the source is magnified at least 13 times. The right panel shows the reconstructed image based on the model of the lens and the source, showing the ring to extend over 3/4 of a circle. "There are only a very few optical rings or arcs known, and even less so in which the lens and the source are at large distance, i.e. more than about 7,000 million light-years away (or half the present age of the Universe)", says Rémi Cabanac, former ESO Fellow and now working at the Canada-France-Hawaii Telescope. "Moreover, very few are nearly complete", he adds. But in the case of this newly found cosmic ring, the images show it to extend to almost 3/4 of a circle. The lensing galaxy is located at a distance of about 8,000 million light-years from us, while the source galaxy whose light is distorted, is much farther away, at 12,000 million light-years. Thus, we see this galaxy as it was when the universe was only 12% of its present age. The lens magnifies the source almost 13 times. The observations reveal the galaxy acting as a lens to be a rather quiet galaxy, 40,000 light-years wide, with an old stellar

On zero divisor graph of unique product monoid rings over Noetherian reversible ring

Directory of Open Access Journals (Sweden)

Ebrahim Hashemi

2016-02-01

Full Text Available Let $R$ be an associative ring with identity and $Z^*(R$ be its set of non-zero zero divisors.  The zero-divisor graph of $R$, denoted by $Gamma(R$, is the graph whose vertices are the non-zero  zero-divisors of  $R$, and two distinct vertices $r$ and $s$ are adjacent if and only if $rs=0$ or $sr=0$.  In this paper, we bring some results about undirected zero-divisor graph of a monoid ring over reversible right (or left Noetherian ring $R$. We essentially classify the diameter-structure of this graph and show that $0leq mbox{diam}(Gamma(Rleq mbox{diam}(Gamma(R[M]leq 3$. Moreover, we give a characterization for the possible diam$(Gamma(R$ and diam$(Gamma(R[M]$, when $R$ is a reversible Noetherian ring and $M$ is a u.p.-monoid. Also, we study relations between the girth of $Gamma(R$ and that of $Gamma(R[M]$.

Imidazolopiperazines (IPZ) kill both rings and dormant rings in wild type and K13 artemisinin resistant Plasmodium falciparum in vitro.

Science.gov (United States)

Dembele, Laurent; Gupta, Devendra Kumar; Lim, Michelle Yi-Xiu; Ang, Xiaoman; Selva, Jeremy J; Chotivanich, Kesinee; Nguon, Chea; Dondorp, Arjen M; Bonamy, Ghislain M C; Diagana, Thierry T; Bifani, Pablo

2018-03-12

Artemisinin (ART) resistance has spread through Southeast Asia, posing serious threat to the control and elimination of malaria. ART resistance has been associated with mutations in the Plasmodium falciparum kelch-13 ( Pfk13 ) propeller domain. Phenotypically, ART resistance is defined as delayed parasite clearance in patients' due to the reduced susceptibility of early ring-stage parasites to the active metabolite of ART dihydroartemisinin (DHA). Early rings can enter a state of quiescence upon DHA exposure and resume growth in its absence. These quiescent rings are referred to as dormant rings or DHA-pretreated rings (called here dormant rings). The imidazolopiperazine (IPZ) is a novel class of antimalarial drugs, which has demonstrated efficacy in early clinical trials. Here, we characterized the stage of action of IPZ GNF179 and evaluated its activity against rings and dormant rings in wild type and ART resistant parasites. Unlike DHA, GNF179 does not induce dormancy. We show that GNF179 is more rapidly cidal against schizonts than ring and trophozoite stages. However, with 12 hours exposure, the compound effectively kills rings and dormant rings of both susceptible and ART resistant parasites within 72 hours. We further demonstrate that in combination with ART, GNF179 effectively prevent recrudescence of dormant rings including those bearing pfk13 propeller mutations. Copyright © 2018 Dembele et al.

Flood-Ring Formation and Root Development in Response to Experimental Flooding of Young Quercus robur Trees

Science.gov (United States)

Copini, Paul; den Ouden, Jan; Robert, Elisabeth M. R.; Tardif, Jacques C.; Loesberg, Walter A.; Goudzwaard, Leo; Sass-Klaassen, Ute

2016-01-01

Spring flooding in riparian forests can cause significant reductions in earlywood-vessel size in submerged stem parts of ring-porous tree species, leading to the presence of ‘flood rings’ that can be used as a proxy to reconstruct past flooding events, potentially over millennia. The mechanism of flood-ring formation and the relation with timing and duration of flooding are still to be elucidated. In this study, we experimentally flooded 4-year-old Quercus robur trees at three spring phenophases (late bud dormancy, budswell, and internode expansion) and over different flooding durations (2, 4, and 6 weeks) to a stem height of 50 cm. The effect of flooding on root and vessel development was assessed immediately after the flooding treatment and at the end of the growing season. Ring width and earlywood-vessel size and density were measured at 25- and 75-cm stem height and collapsed vessels were recorded. Stem flooding inhibited earlywood-vessel development in flooded stem parts. In addition, flooding upon budswell and internode expansion led to collapsed earlywood vessels below the water level. At the end of the growing season, mean earlywood-vessel size in the flooded stem parts (upon budswell and internode expansion) was always reduced by approximately 50% compared to non-flooded stem parts and 55% compared to control trees. This reduction was already present 2 weeks after flooding and occurred independent of flooding duration. Stem and root flooding were associated with significant root dieback after 4 and 6 weeks and mean radial growth was always reduced with increasing flooding duration. By comparing stem and root flooding, we conclude that flood rings only occur after stem flooding. As earlywood-vessel development was hampered during flooding, a considerable number of narrow earlywood vessels present later in the season, must have been formed after the actual flooding events. Our study indicates that root dieback, together with strongly reduced hydraulic

Complete snake and rotator schemes for spin polarization in proton rings and large electron rings

International Nuclear Information System (INIS)

Steffen, K.

1983-11-01

In order to maintain spin polarization in proton rings and large electron rings, some generalized Siberian Snake scheme may be required to make the spin tune almost independent of energy and thus avoid depolarizing resonances. The practical problem of finding such schemes that, at reasonable technical effort, can be made to work over large energy ranges has been addressed before and is here revisited in a broadened view and with added new suggestions. As a result, possibly optimum schemes for electron rings (LEP) and proton rings are described. In the proposed LEP scheme, spin rotation is devised such that, at the interaction points, the spin direction is longitudinal as required for experiments. (orig.)

Ring current and auroral electrojets in connection with interplanetary medium parameters during magnetic storm

Directory of Open Access Journals (Sweden)

Y. I. Feldstein

Full Text Available The relationship between the auroral electrojet indices (AE and the ring current magnetic field (DR was investigated by observations obtained during the magnetic storm on 1-3 April 1973. During the storm main phase the DR development is accompanied by a shift of the auroral electrojets toward the equator. As a result, the standard AE indices calculated on the basis of data from auroral observatories was substantially lower than the real values (AE'. To determine AE' during the course of a storm main phase data from subauroral magnetic observatories should be used. It is shown that the intensity of the indices (AE' which take into account the shift of the electrojets is increased substantially relative to the standard indices during the storm main phase. AE' values are closely correlated with geoeffective solar wind parameters. A high correlation was obtained between AE' and the energy flux into the ring current during the storm main phase. Analysis of magnetic field variations during intervals with intense southward IMF components demonstrates a decrease of the saturation effect of auroral electrojet currents if subauroral stations magnetic field variations are taken into account. This applies both to case studies and statistical data. The dynamics of the electrojets in connection with the development of the ring current and of magnetospheric substorms can be described by the presence (absence of saturation for minimum (maximum AE index values during a 1-h interval. The ring current magnetic field asymmetry (ASY was calculated as the difference between the maximum and minimum field values along a parallel of latitude at low latitudes. The ASY value is closely correlated with geoeffective solar wind parameters and simultaneously is a more sensitive indicator of IMF B_z variations than the symmetric ring current.

C-shaped diastereomers containing cofacial thiophene-substituted quinoxaline rings: synthesis, photophysical properties, and X-ray crystallography.

Science.gov (United States)

DeBlase, Catherine R; Finke, Ryan T; Porras, Jonathan A; Tanski, Joseph M; Nadeau, Jocelyn M

2014-05-16

Synthesis and characterization of two diastereomeric C-shaped molecules containing cofacial thiophene-substituted quinoxaline rings are described. A previously known bis-α-diketone was condensed with an excess of 4-bromo-1,2-diaminobenzene in the presence of zinc acetate to give a mixture of two C-shaped diastereomers with cofacial bromine-substituted quinoxaline rings. After chromatographic separation, thiophene rings were installed by a microwave-assisted Suzuki coupling reaction, resulting in highly emissive diastereomeric compounds that were studied by UV-vis, fluorescence, and NMR spectroscopy, as well as X-ray crystallography. The unique symmetry of each diastereomer was confirmed by NMR spectroscopy. NMR data indicated that the syn isomer has restricted rotation about the bond connecting the thiophene and quinoxaline rings, which was also observed in the solid state. The spectroscopic properties of the C-shaped diastereomers were compared to a model compound containing only a single thiophene-substituted quinoxaline ring. Ground state intramolecular π-π interactions in solution were detected by NMR and UV-vis spectroscopy. Red-shifted emission bands, band broadening, and large Stokes shifts were observed, which collectively suggest excited state π-π interactions that produce excimer-like emissions, as well as a remarkable positive emission solvatochromism, indicating charge-transfer character in the excited state.

Koffka's Ring Effect Depends on Thickness, Not Continuity

OpenAIRE

Abigail E. Huang; Alice J. Hon; Eric L. Altschuler

2007-01-01

More than 70 years ago Gestalt psychologist Kurt Koffka described a fascinating effect1,2: When a contiguous grey ring is placed on a background half of one shade of grey (different from the ring) and half of another shade of grey, the ring appears to be a homogenous. However, if the ring is slightly divided, now the two halves of the ring appear different shades of grey with the half of the ring on the darker background appearing lighter than the half of the ring on the darker background. Th...

Modelling of Resonantly Forced Density Waves in Dense Planetary Rings

Science.gov (United States)

Lehmann, M.; Schmidt, J.; Salo, H.

2014-04-01

Density wave theory, originally proposed to explain the spiral structure of galactic disks, has been applied to explain parts of the complex sub-structure in Saturn's rings, such as the wavetrains excited at the inner Lindblad resonances (ILR) of various satellites. The linear theory for the excitation and damping of density waves in Saturn's rings is fairly well developed (e.g. Goldreich & Tremaine [1979]; Shu [1984]). However, it fails to describe certain aspects of the observed waves. The non-applicability of the linear theory is already indicated by the "cusplike" shape of many of the observed wave profiles. This is a typical nonlinear feature which is also present in overstability wavetrains (Schmidt & Salo [2003]; Latter & Ogilvie [2010]). In particular, it turns out that the detailed damping mechanism, as well as the role of different nonlinear effects on the propagation of density waves remain intransparent. First attemps are being made to investigate the excitation and propagation of nonlinear density waves within a hydrodynamical formalism, which is also the natural formalism for describing linear density waves. A simple weakly nonlinear model, derived from a multiple-scale expansion of the hydrodynamic equations, is presented. This model describes the damping of "free" spiral density waves in a vertically integrated fluid disk with density dependent transport coefficients, where the effects of the hydrodynamic nonlinearities are included. The model predicts that density waves are linearly unstable in a ring region where the conditions for viscous overstability are met, which translates to a steep dependence of the shear viscosity with respect to the disk's surface density. The possibility that this dependence could lead to a growth of density waves with increasing distance from the resonance, was already mentioned in Goldreich & Tremaine [1978]. Sufficiently far away from the ILR, the surface density perturbation caused by the wave, is predicted to

Almost ring theory

CERN Document Server

2003-01-01

This book develops thorough and complete foundations for the method of almost etale extensions, which is at the basis of Faltings' approach to p-adic Hodge theory. The central notion is that of an "almost ring". Almost rings are the commutative unitary monoids in a tensor category obtained as a quotient V-Mod/S of the category V-Mod of modules over a fixed ring V; the subcategory S consists of all modules annihilated by a fixed ideal m of V, satisfying certain natural conditions. The reader is assumed to be familiar with general categorical notions, some basic commutative algebra and some advanced homological algebra (derived categories, simplicial methods). Apart from these general prerequisites, the text is as self-contained as possible. One novel feature of the book - compared with Faltings' earlier treatment - is the systematic exploitation of the cotangent complex, especially for the study of deformations of almost algebras.

IAG ring test animal proteins 2014

NARCIS (Netherlands)

Raamsdonk, van L.W.D.; Pinckaers, V.G.Z.; Scholtens-Toma, I.M.J.; Prins, T.W.; Voet, van der H.; Vliege, J.J.M.

2014-01-01

A ring test was organized for the detection of animal proteins in animal feed by microscopy in the framework of the annual ring tests of the IAG – International Association for Feeding stuff Analysis, Section Feeding stuff Microscopy. The aim of the ring study was to provide the participants

IAG ring test animal proteins 2015

NARCIS (Netherlands)

Raamsdonk, van L.W.D.; Rhee, van de N.E.; Scholtens-Toma, I.M.J.; Prins, T.W.; Vliege, J.J.M.; Pinckaers, V.G.Z.

2015-01-01

A ring test was organized for the detection of animal proteins in animal feed by microscopy in the framework of the annual ring tests of the IAG - International Association for Feeding stuff Analysis, Section Feeding stuff Microscopy. The organizer of the ring test was RIKILT - Wageningen UR, The

IAG ring test animal proteins 2013

NARCIS (Netherlands)

Raamsdonk, van L.W.D.; Pinckaers, V.G.Z.; Scholtens-Toma, I.M.J.; Prins, T.W.; Vliege, J.J.M.

2013-01-01

A ring test was organized for the detection of animal proteins in animal feed by microscopy in the framework of the annual ring tests of the IAG - International Association for Feeding stuff Analysis, Section Feeding stuff Microscopy. The organizer of the the ring study was to provide the

Cooling rings for TeV colliders

International Nuclear Information System (INIS)

Palmer, R.B.

1985-02-01

Consideration is given to quantum fluctuations, intra beam scattering, cooling rates, and ring acceptance in order to see if one can obtain a normalized emittance of 10 -8 in any plausible cooling ring. It is concluded that only a small gain is obtained by varying the partition functions, but a very significant gain is made by using higher bending fields. The ring is found to get bigger if the magnet apertures are increased. The ring diameter is found to increase if the momentum spread of the beam is reduced. It is shown that the power can be reduced by allowing a high beamstrahlung energy loss resulting in higher current in the cooling ring. Parameters are also given for a 10 -7 m radian emittance case

FY2017 status report: Model 9975 O-ring fixture long-term leak performance

Energy Technology Data Exchange (ETDEWEB)

Daugherty, W. L. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

2017-07-27

. However, uncertainty still exists in extrapolating these elevated temperature results to the lower temperatures of interest for normal storage in KAC. Measurement of compression set in O-rings removed from failed fixtures, compared to that from KAC surveillance O-rings, indicates margin remains for O-rings still in service. Aging and periodic leak testing will continue for the remaining PCV fixtures.

Vasorelaxant Effect of Osterici Radix Ethanol Extract on Rat Aortic Rings

Directory of Open Access Journals (Sweden)

Kyungjin Lee

2013-01-01

Full Text Available The root of Ostericum koreanum Maximowicz has been used as a traditional medicine called “Kanghwal” in Korea (or “Qianghuo” in China. The purpose of this study was to investigate the vasorelaxant activity and mechanism of action of an ethanol extract of the O. koreanum root (EOK. We used isolated rat aortic rings to assess the effects of EOK on various vasorelaxant or vasoconstriction factors. EOK induced vasorelaxation in phenylephrine hydrochloride (PE or KCl precontracted aortic rings in a concentration-dependent manner. However, the vasorelaxant effects of EOK on endothelium-intact aortic rings were reduced by pretreatment with L-NAME or methylene blue. In Ca2+-free Krebs-Henseleit solution, pretreatment with EOK (0.3 mg/mL completely inhibited PE-induced constriction. In addition, EOK (0.3 mg/mL also completely inhibited vasoconstriction induced by supplemental Ca2+ in aortic rings that were precontracted with PE or KCl. Furthermore, the EOK-induced vasorelaxation in PE-contracted aortic rings was inhibited by preincubation with nifedipine. These results indicate that the vasorelaxant effects of EOK are responsible for the induction of NO formation from L-Arg and NO-cGMP pathways, blockage of the extracellular Ca2+ entry via the receptor-operative Ca2+ channel and voltage-dependent calcium channel, and blockage of sarcoplasmic reticulum Ca2+ release via the inositol triphosphate pathway.

Magmatic development of the outer Vøring margin from seismic data

Science.gov (United States)

Breivik, Asbjørn; Faleide, Jan Inge; Mjelde, Rolf; Flueh, Ernst; Murai, Yoshio

2014-09-01

The Vøring Plateau off mid-Norway is a volcanic passive margin, located north of the East Jan Mayen Fracture Zone (EJMFZ). Large volumes of magmatic rocks were emplaced during Early Eocene margin formation. In 2003, an ocean bottom seismometer survey was acquired over the margin. One profile crosses from the Vøring Plateau to the Vøring Spur, a bathymetric high north of the EJMFZ. The P wave data were ray traced into a 2-D crustal velocity model. The velocity structure of the Vøring Spur indicates up to 15 km igneous crustal thickness. Magmatic processes can be estimated by comparing seismic velocity (VP) with igneous thickness (H). This and two other profiles show a positive H-VP correlation at the Vøring Plateau, consistent with elevated mantle temperature at breakup. However, during the first 2 Ma magma production was augmented by a secondary process, possibly small-scale convection. From ˜51.5 Ma excess melting may be caused by elevated mantle temperature alone. Seismic stratigraphy around the Vøring Spur shows that it was created by at least two uplift events, with the main episode close to the Miocene/Pliocene boundary. Low H-VP correlation of the spur is consistent with renewed igneous growth by constant, moderate-degree mantle melting, not related to the breakup magmatism. The admittance function between bathymetry and free-air gravity shows that the high is near local isostatic equilibrium, precluding that compressional flexure at the EJMFZ uplifted the high. We find a proposed Eocene triple junction model for the margin to be inconsistent with observations.

Dipole Magnets for the LHeC Ring-Ring Option

CERN Document Server

Tommasini, D; Chritin, R

2012-01-01

The Ring-Ring option of a Large Hadron electron Collider (LHeC) requires 3080 bending magnets, 5.35-meter-long each providing a magnetic field ranging from 0.0127 T at 10 GeV to 0.0763 T at 60 GeV. Main issues in the design of these magnets are the very low injection field, constituting a challenge in achieving a satisfactory field reproducibility from cycle to cycle, and the required compactness to fit in the existing LHC tunnel. This paper describes and discusses a design meeting these requirements, together with its experimental validation by the manufacture and measurement of a 400-mm-long magnet model.

The multi-bend achromat storage rings

Energy Technology Data Exchange (ETDEWEB)

Eriksson, Mikael [MAX IV Laboratory Ole Römers v. 1 22100 Lund Sweden (Sweden)

2016-07-27

Not very long ago, the 3{sup rd} generation storage ring technology was judged as mature. Most of the 3{sup rd} generation storage rings used the Double-Bend Achromat (DBA) or Triple-Bend Achromat (TBA) concepts. It was however a well-known fact that increasing the number of magnet cells in the rings is a powerful way of decreasing the electron beam emittance and thus the source brilliance, but at the penalty of increasing the size and cost of the rings. Preserving the Dynamic Aperture (DA) in the rings became also an issue when increasing the number of magnet cells. The Multi-Bend Achromat (MBA) concept, including a miniaturization of the ring elements, has now drastically changed the picture. The MBA rings, now in construction or being planned, offer orders of magnitudes higher brilliance than rings of conventional designs. Several light sources around the world are now implementing or planning to implement this MBA concept. This article touches on the science drivers for higher brilliance. We will then describe the MBA concept with its advantages as well as its challenges. A short survey of the MBA activity around the world will also be presented. The author apologies for focusing on the MAX IV project regarding technical solutions. This is motivated by that MAX IV is the facility he knows best and it might be regarded as a fore-runner for the MBA concept.

The multi-bend achromat storage rings

International Nuclear Information System (INIS)

Eriksson, Mikael

2016-01-01

Not very long ago, the 3"r"d generation storage ring technology was judged as mature. Most of the 3"r"d generation storage rings used the Double-Bend Achromat (DBA) or Triple-Bend Achromat (TBA) concepts. It was however a well-known fact that increasing the number of magnet cells in the rings is a powerful way of decreasing the electron beam emittance and thus the source brilliance, but at the penalty of increasing the size and cost of the rings. Preserving the Dynamic Aperture (DA) in the rings became also an issue when increasing the number of magnet cells. The Multi-Bend Achromat (MBA) concept, including a miniaturization of the ring elements, has now drastically changed the picture. The MBA rings, now in construction or being planned, offer orders of magnitudes higher brilliance than rings of conventional designs. Several light sources around the world are now implementing or planning to implement this MBA concept. This article touches on the science drivers for higher brilliance. We will then describe the MBA concept with its advantages as well as its challenges. A short survey of the MBA activity around the world will also be presented. The author apologies for focusing on the MAX IV project regarding technical solutions. This is motivated by that MAX IV is the facility he knows best and it might be regarded as a fore-runner for the MBA concept.

Ring wormholes via duality rotations

Directory of Open Access Journals (Sweden)

Gary W. Gibbons

2016-09-01

Full Text Available We apply duality rotations and complex transformations to the Schwarzschild metric to obtain wormhole geometries with two asymptotically flat regions connected by a throat. In the simplest case these are the well-known wormholes supported by phantom scalar field. Further duality rotations remove the scalar field to yield less well known vacuum metrics of the oblate Zipoy–Voorhees–Weyl class, which describe ring wormholes. The ring encircles the wormhole throat and can have any radius, whereas its tension is always negative and should be less than −c4/4G. If the tension reaches the maximal value, the geometry becomes exactly flat, but the topology remains non-trivial and corresponds to two copies of Minkowski space glued together along the disk encircled by the ring. The geodesics are straight lines, and those which traverse the ring get to the other universe. The ring therefore literally produces a hole in space. Such wormholes could perhaps be created by negative energies concentrated in toroidal volumes, for example by vacuum fluctuations.

Evidence for Quantisation in Planetary Ring Systems

OpenAIRE

WAYTE, RICHARD

2017-01-01

Absolute radial positions of the main features in Saturn's ring system have been calculated by adapting the quantum theory of atomic spectra. Fine rings superimposed upon broad rings are found to be covered by a harmonic series of the form N α A(r)1/2, where N and A are integers. Fourier analysis of the ring system shows that the spectral amplitude fits a response profile which is characteristic of a resonant system. Rings of Jupiter, Uranus and Neptune also obey the same rules. Involvement o...

States of an on-axis two-hydrogenic-impurity complex in concentric double quantum rings

International Nuclear Information System (INIS)

R-Fulla, M.; Marín, J.H.; Suaza, Y.A.; Duque, C.A.; Mora-Ramos, M.E.

2014-01-01

The energy structure of an on-axis two-donor system (D 2 0 ) confined in GaAs concentric double quantum rings under the presence of magnetic field and hydrostatic pressure was analyzed. Based on structural data for the double quantum ring morphology, a rigorous adiabatic procedure was implemented to separate the electrons' rapid in-plane motions from the slow rotational ones. A one-dimensional equation with an effective angular-dependent potential, which describes the two-electron rotations around the common symmetry axis of quantum rings was obtained. It was shown that D 2 0 complex characteristic features are strongly dependent on the quantum ring geometrical parameters. Besides, by changing the hydrostatic pressure and magnetic field strengths, it is possible to tune the D 2 0 energy structure. Our results are comparable to those previously reported for a single and negative ionized donor in a spherical quantum dot after a selective setting of the geometrical parameters of the structure. - Highlights: • We report the eigenenergies of a D 2 0 complex in concentric double quantum rings. • Our model is versatile enough to analyze the dissociation process D 2 0 →D 0 +D + +e − . • We compare the D 0 eigenenergies in horn toroidal and spherical shaped quantum dots. • We show the effects of hydrostatic pressure and magnetic field on the D 2 0 spectrum. • The use of hydrostatic pressure provides higher thermal stability to the D 2 0 complex

Ring shear characteristics of clays in fractured-zone-landslide. Hasaitai chisuberichi no nenseido no ring sendan tokusei

Energy Technology Data Exchange (ETDEWEB)

Yatabe, R; Yagi, N; Enoki, M [Ehime Univ., Ehime (Japan). Faculty of Engineering

1991-09-20

The importance of study on the residual strength, in addition to the peak strength, has been pointed out for the study of landslides. The residual strength characteristics, effects of shearing rate, and grain size of clays, as well as the residual strength characteristics of clay minerals of a fractured zone landslide were examined by ring shear tests. The residual friction angles {phi}{sub r} of the tested clays of the fractured zone landslide were from 10 to 31{degree}, and were smaller than those of shearing resistance angles {phi}{prime} obtained by triaxial tests by 5 to 15{degree}. Contrary to the pointing out made hitherto, no correlation between clay content CF and plastic index was recognized for {phi}{sub r} of clays of a fractured zone landslide. As regards CF, the relation with CF was far below the lowest limit indicated by now. Ring shear characteristics of principal structural clay minerals, vermiculite, mica, illite, chlorite, and kaolinite were investigated. {phi}{sub r} of these clay minerals were in the range from 10 to 25{degree}. 20 refs., 14 figs., 2 tabs.

Multiplication modules over non-commutative rings

International Nuclear Information System (INIS)

Tuganbaev, A A

2003-01-01

It is proved that each submodule of a multiplication module over a regular ring is a multiplicative module. If A is a ring with commutative multiplication of right ideals, then each projective right ideal is a multiplicative module, and a finitely generated A-module M is a multiplicative module if and only if all its localizations with respect to maximal right ideals of A are cyclic modules over the corresponding localizations of A. In addition, several known results on multiplication modules over commutative rings are extended to modules over not necessarily commutative rings

Status of the SLC damping rings

International Nuclear Information System (INIS)

Hutton, A.M.; Davies-White, W.A.; Delahaye, J.P.

1985-06-01

Electron beams of full design energy 1.21 GeV and nearly full design intensity 4 x 10 10 particles/pulse (design 5 x 10 10 ) have been extracted from the Stanford Linac and successfully stored in the electron damping ring. Beams of less intensity have been extracted from the ring and reinjected into the Linac. The present intensity limits are not thought to be fundamental. The operating experience with the electron ring and the status of the construction of the positron ring will be discussed. 11 refs., 1 fig., 2 tabs

The Ring of Five follows the traces

International Nuclear Information System (INIS)

Anon.

2015-01-01

The Ring of Five is an informal network of European experts in radioactivity detection belonging to public bodies such as the IRSN. After having evoked different cases of detection (detection of unusual traces of iodine 131 in the region of Stockholm in 2015, detection of high levels of traces of caesium 137 in Switzerland in 1968) which leaded to the identification of the origin of these traces, this article briefly recalls the history of the creation of this network which extended with the occurrence of the Chernobyl accident, describes how the information is transmitted, the use of modelling tools, and outlines that the detection of some species can be associated either to a nuclear accident or to an atmospheric nuclear bomb test, and indicates how new sensors, not sensitive to humidity, have been developed after a lack of detection of iodine 131. In a brief interview, the future of the Ring of Five, topics to be studied and current projects are briefly evoked

Damping of Resonantly Forced Density Waves in Dense Planetary Rings

Science.gov (United States)

Lehmann, Marius; Schmidt, Jürgen; Salo, Heikki

2016-10-01

We address the stability of resonantly forced density waves in dense planetary rings.Already by Goldreich and Tremaine (1978) it has been argued that density waves might be unstable, depending on the relationship between the ring's viscosity and the surface mass density. In the recent paper (Schmidt et al. 2016) we have pointed out that when - within a fluid description of the ring dynamics - the criterion for viscous overstability is satisfied, forced spiral density waves become unstable as well. In this case, linear theory fails to describe the damping.We apply the multiple scale formalism to derive a weakly nonlinear damping relation from a hydrodynamical model.This relation describes the resonant excitation and nonlinear viscous damping of spiral density waves in a vertically integrated fluid disk with density dependent transport coefficients. The model consistently predicts linear instability of density waves in a ring region where the conditions for viscous overstability are met. In this case, sufficiently far away from the Lindblad resonance, the surface mass density perturbation is predicted to saturate to a constant value due to nonlinear viscous damping. In general the model wave damping lengths depend on a set of input parameters, such as the distance to the threshold for viscous overstability and the ground state surface mass density.Our new model compares reasonably well with the streamline model for nonlinear density waves of Borderies et al. 1986.Deviations become substantial in the highly nonlinear regime, corresponding to strong satellite forcing.Nevertheless, we generally observe good or at least qualitative agreement between the wave amplitude profiles of both models. The streamline approach is superior at matching the total wave profile of waves observed in Saturn's rings, while our new damping relation is a comparably handy tool to gain insight in the evolution of the wave amplitude with distance from resonance, and the different regimes of

Characterization of heterocyclic rings through quantum chemical topology.

Science.gov (United States)

Griffiths, Mark Z; Popelier, Paul L A

2013-07-22

Five-membered rings are found in a myriad of molecules important in a wide range of areas such as catalysis, nutrition, and drug and agrochemical design. Systematic insight into their largely unexplored chemical space benefits from first principle calculations presented here. This study comprehensively investigates a grand total of 764 different rings, all geometry optimized at the B3LYP/6-311+G(2d,p) level, from the perspective of Quantum Chemical Topology (QCT). For the first time, a 3D space of local topological properties was introduced, in order to characterize rings compactly. This space is called RCP space, after the so-called ring critical point. This space is analogous to BCP space, named after the bond critical point, which compactly and successfully characterizes a chemical bond. The relative positions of the rings in RCP space are determined by the nature of the ring scaffold, such as the heteroatoms within the ring or the number of π-bonds. The summed atomic QCT charges of the five ring atoms revealed five features (number and type of heteroatom, number of π-bonds, substituent and substitution site) that dictate a ring's net charge. Each feature independently contributes toward a ring's net charge. Each substituent has its own distinct and systematic effect on the ring's net charge, irrespective of the ring scaffold. Therefore, this work proves the possibility of designing a ring with specific properties by fine-tuning it through manipulation of these five features.

Single photon emission and quantum ring-cavity coupling in InAs/GaAs quantum rings

International Nuclear Information System (INIS)

Gallardo, E; Nowak, A K; Sanvitto, D; Meulen, H P van der; Calleja, J M; MartInez, L J; Prieto, I; Alija, A R; Granados, D; Taboada, A G; GarcIa, J M; Postigo, P A; Sarkar, D

2010-01-01

Different InAs/GaAs quantum rings embedded in a photonic crystal microcavity are studied by quantum correlation measurements. Single photon emission, with g (2) (0) values around 0.3, is demonstrated for a quantum ring not coupled to the microcavity. Characteristic rise-times are found to be longer for excitons than for biexcitons, resulting in the time asymmetry of the exciton-biexciton cross-correlation. No antibunching is observed in another quantum ring weakly coupled to the microcavity.

Sap Flux Scaled Transpiration in Ring-porous Tree Species: Assumptions, Pitfalls and Calibration

Science.gov (United States)

Bush, S. E.; Hultine, K. R.; Ehleringer, J. R.

2008-12-01

Thermal dissipation probes for measuring sap flow (Granier-type) at the whole tree and stand level are routinely used in forest ecology and site water balance studies. While the original empirical relationship used to calculate sap flow was reported as independent of wood anatomy (ring-porous, diffuse-porous, tracheid), it has been suggested that potentially large errors in sap flow calculations may occur when using the original calibration for ring-porous species, due to large radial trends in sap velocity and/or shallow sapwood depth. Despite these concerns, sap flux measurements have rarely been calibrated in ring-porous taxa. We used a simple technique to calibrate thermal dissipation sap flux measurements on ring-porous trees in the lab. Calibration measurements were conducted on five ring-porous species in the Salt Lake City, USA metropolitan area including Quercus gambelii (Gambel oak), Gleditsia triacanthos (Honey locust), Elaeagnus angustifolia (Russian olive), Sophora japonica (Japanese pagoda), and Celtis occidentalis (Common hackberry). Six stems per species of approximately 1 m in length were instrumented with heat dissipation probes to measure sap flux concurrently with gravimetric measurements of water flow through each stem. Safranin dye was pulled through the stems following flow rate measurements to determine sapwood area. As expected, nearly all the conducting sapwood area was limited to regions within the current year growth rings. Consequently, we found that the original Granier equation underestimated sap flux density for all species considered. Our results indicate that the use of thermal dissipation probes for measuring sap flow in ring-porous species should be independently calibrated, particularly when species- specific calibration data are not available. Ring-porous taxa are widely distributed and represent an important component of the regional water budgets of many temperate regions. Our results are important for evaluating plant water

Powder metallurgy ferrous synchronizer ring with brass-based friction layer; Tetsu-do niso shoketsu synchronize ring no kaihatsu

Energy Technology Data Exchange (ETDEWEB)

Okajima, H; Yoshikawa, K; Miyajima, K; Sugiyama, M [Toyota Motor Corp., Aichi (Japan); Nakamura, M; Ito, M [Japan Powder Metallurgy Co. Ltd., Tokyo (Japan)

1997-10-01