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Sample records for rotating cyclic structures

  1. Finite element forced vibration analysis of rotating cyclic structures

    NASA Technical Reports Server (NTRS)

    Elchuri, V.; Smith, G. C. C.

    1981-01-01

    A capability was added to the general purpose finite element program NASTRAN Level 17.7 to conduct forced vibration analysis of tuned cyclic structures rotating about their axes of symmetry. The effects of Coriolis and centripetal accelerations together with those due to linear acceleration of the axis of rotation were included. The theoretical development of this capability is presented.

  2. Forced vibration analysis of rotating cyclic structures in NASTRAN

    NASA Technical Reports Server (NTRS)

    Elchuri, V.; Gallo, A. M.; Skalski, S. C.

    1981-01-01

    A new capability was added to the general purpose finite element program NASTRAN Level 17.7 to conduct forced vibration analysis of tuned cyclic structures rotating about their axis of symmetry. The effects of Coriolis and centripetal accelerations together with those due to linear acceleration of the axis of rotation were included. The theoretical, user's, programmer's and demonstration manuals for this new capability are presented.

  3. 3D imaging of particle-scale rotational motion in cyclically driven granular flows

    NASA Astrophysics Data System (ADS)

    Harrington, Matt; Powers, Dylan; Cooper, Eric; Losert, Wolfgang

    Recent experimental advances have enabled three-dimensional (3D) imaging of motion, structure, and failure within granular systems. 3D imaging allows researchers to directly characterize bulk behaviors that arise from particle- and meso-scale features. For instance, segregation of a bidisperse system of spheres under cyclic shear can originate from microscopic irreversibilities and the development of convective secondary flows. Rotational motion and frictional rotational coupling, meanwhile, have been less explored in such experimental 3D systems, especially under cyclic forcing. In particular, relative amounts of sliding and/or rolling between pairs of contacting grains could influence the reversibility of both trajectories, in terms of both position and orientation. In this work, we apply the Refractive Index Matched Scanning technique to a granular system that is cyclically driven and measure both translational and rotational motion of individual grains. We relate measured rotational motion to resulting shear bands and convective flows, further indicating the degree to which pairs and neighborhoods of grains collectively rotate.

  4. The structures of cyclic dihydronium cations.

    PubMed

    Wallace, Sonjae; Huang, Lulu; Massa, Lou; Mukhopadhyay, Uday; Bernal, Ivan; Karle, Jerome

    2007-10-23

    Recent experimental discoveries have revealed the existence of hitherto unexpected cyclic hydronium di-cations trapped within crystal structures. The molecular formulas are (H(14)O(6))(2+), present as two isomers, four- and six-member cyclic structures, and (H(18)O(8))(2+), an eight-member cyclic structure. As these unprecedented hydronium species are stabilized by the crystal structures in which they are captured, the question arises whether they could be stable as independent species as, for example, in solution or gas phase. Quantum mechanical density functional theory calculations are used to investigate this question. We find these doubly charged cyclic hydronium structures to be energetically stable and, as between the four- and six-member structures, the former has more binding energy than the latter. We also determine the theoretically optimized structures for all three ions and give their calculated atomic charges for both their crystal and optimized geometries.

  5. ROTATIONAL AND CYCLICAL VARIABILITY IN {gamma} CASSIOPEIAE. II. FIFTEEN SEASONS

    SciTech Connect

    Henry, Gregory W.; Smith, Myron A. E-mail: msmith@stsci.edu

    2012-11-20

    The B0.5 IVe star {gamma} Cas is of great interest because it is the prototype of a small group of classical Be stars having hard X-ray emission of unknown origin. We discuss results from ongoing B and V observations of the {gamma} Cas star-disk system acquired with an Automated Photometric Telescope during the observing seasons 1997-2011. In an earlier study, Smith, Henry, and Vishniac showed that light variations in {gamma} Cas are dominated by a series of comparatively prominent cycles with amplitudes of 0.02-0.03 mag and lengths of 2-3 months, superimposed on a 1.21 day periodic signal some five times smaller, which they attributed to rotation. The cycle lengths clustered around 70 days, with a total range of 50-91 days. Changes in both cycle length and amplitude were observed from year to year. These authors also found the V-band cycles to be 30%-40% larger than the B-band cycles. In the present study, we find continued evidence for these variability patterns and for the bimodal distribution of the {Delta}B/{Delta}V amplitude ratios in the long cycles. During the 2010 observing season, {gamma} Cas underwent a mass-loss event ({sup o}utburst{sup )}, as evidenced by the brightening and reddening seen in our new photometry. This episode coincided with a waning of the amplitude in the ongoing cycle. The Be outburst ended the following year, and the light-curve amplitude returned to pre-outburst levels. This behavior reinforces the interpretation that cycles arise from a global disk instability. We have determined a more precise value of the rotation period, 1.215811 {+-} 0.000030 days, using the longer 15-season data set and combining solutions from the V and B light curves. Remarkably, we also find that both the amplitude and the asymmetry of the rotational waveform changed over the years. We review arguments for this modulation arising from transits of a surface magnetic disturbance. Finally, to a limit of 5 mmag, we find no evidence for any photometric

  6. Controlled Reduction with Unactuated Cyclic Variables: Application to 3D Bipedal Walking with Passive Yaw Rotation

    PubMed Central

    Righetti, Ludovic

    2014-01-01

    This paper shows that viscous damping can shape momentum conservation laws in a manner that stabilizes yaw rotation and enables steering for underactuated 3D walking. We first show that unactuated cyclic variables can be controlled by passively shaped conservation laws given a stabilizing controller in the actuated coordinates. We then exploit this result to realize controlled geometric reduction with multiple unactuated cyclic variables. We apply this underactuated control strategy to a five-link 3D biped to produce exponentially stable straight-ahead walking and steering in the presence of passive yawing. PMID:25554709

  7. Discovery of a large time scale cyclic evolution of radio pulsars rotational frequency.

    NASA Astrophysics Data System (ADS)

    Beskin, G.; Biryukov, A.; Karpov, S.

    2006-08-01

    The recent massive measurements of pulsar frequency second derivatives have shown that they are 100-1000 times larger than expected for standard pulsar slowdown low. Moreover, the second derivatives as well as braking indices are even negative for about half of pulsars. We explain these paradoxical results on the basis of the statistical analysis of the rotational parameters (frequency, its first and second derivatives) of the subset of 295 pulsars taken mostly from the ATNF database. We have found strong correlation of second and first frequency derivatives either for positive (correlation coefficient r~0.9) and negative (r~0.85) values of second derivative, and of the frequency and and its first derivative (r~0.7). We interpret these dependencies as evolutionary ones due to the first frequency derivative being nearly proportional to the characteristic age. The derived statistical relations as well as "anomalous" values of the second frequency derivative are well explained in the framework of the simple model of cyclic evolution of the rotational frequency of the pulsars. It combines the secular change of the rotational parameters according to the power law with braking index n~5 and harmonic oscillations of 100--1000 years period with an amplitude from 10^-3 Hz for young pulsars to 10^-10 Hz for elder ones. The physical nature of these cyclic variations of the rotational frequency may be similar to the well-known red timing noise, however, with much larger characteristic time scale.

  8. A computer program for cyclic plasticity and structural fatigue analysis

    NASA Technical Reports Server (NTRS)

    Kalev, I.

    1980-01-01

    A computerized tool for the analysis of time independent cyclic plasticity structural response, life to crack initiation prediction, and crack growth rate prediction for metallic materials is described. Three analytical items are combined: the finite element method with its associated numerical techniques for idealization of the structural component, cyclic plasticity models for idealization of the material behavior, and damage accumulation criteria for the fatigue failure.

  9. Facet-rotated echelle grating for cyclic wavelength router with uniform loss and flat passband.

    PubMed

    Mu, Ge; Huang, Pingli; Wu, Lin; He, Jian-Jun

    2015-09-01

    A novel method for designing a cyclic echelle grating wavelength router with uniform loss and flat passband is proposed and experimentally demonstrated. A 4×4 cyclic wavelength router with a channel spacing of 400 GHz at 1550 nm wavelength band is designed and fabricated in InP. Measurement results show that the loss of 16 input-output combinations varies from 9 to 19.3 dB in a conventional design, with a nonuniformity of 10.3 dB, while the 1-dB spectral bandwidth is only 0.3 nm. By rotating angles of grating facets according to an appropriately designed distribution function, the loss nonuniformity is reduced to 1.5 dB, and a flat-top spectral response with 1 dB bandwidth of 1.0 nm is achieved simultaneously.

  10. Structure modulation driven by cyclic deformation in nanocrystalline NiFe

    SciTech Connect

    Cheng, Sheng; Wang, Xun-Li; Zhao, Yh; Wang, Yinmin; Liaw, Peter K; Lavernia, Ej

    2010-01-01

    Theoretical modeling suggests that the grain size remains unchanged during fatigue crack growth in nanocrystalline metals. Here we demonstrate that a modulated structure is generated in a nanocrystalline Ni-Fe alloy under cyclic deformation. Substantial grain coarsening and loss of growth twins are observed in the path of fatigue cracks, while the grains away from the cracks remain largely unaffected. Statistical analyses suggest that the grain coarsening is realized through the grain lattice rotation and coalescence and the loss of growth twins may be related to the detwinning process near crack tip.

  11. Rotation and Structure in the Universe

    NASA Astrophysics Data System (ADS)

    Praton, Elizabeth A.

    1993-01-01

    Rotation and structure in the universe are studied in two investigations. The first investigation is a theoretical exploration of structure formation in the young universe, when localized angular momentum is present. The second investigation is an exploration of the "signature" localized large scale rotation or transverse motion might leave in observational "redshift maps" of structure in the universe. In the first investigation, analytic approximations to the virial equations of equilibrium for rotating, self -gravitating gaseous bodies are studied in the multi-equilibrium regime. Such bodies may collapse via a "phase transition" before reaching dynamical instability. The phase transition mass is calculated for a simple cosmological scenario and found to be the size of a small galaxy. The dynamical collapse mass, by contrast, is much larger and grows rapidly as the universe expands. In the second investigation, a redshift space artifact is studied which results from an "infall" field surrounding a rich galaxy cluster. In a simulation, a redshift map of an infall region shows an artificial "ring" of galaxies encircling the "finger of god" artifact produced by the simulated cluster core. When the observer has transverse motion or the infall region has rotation, the ring tilts on the finger. Redshift maps of two nearby clusters, Virgo and Fornax, are compared against the simulation. Redshift space structure surrounding Virgo shows a strong resemblence to the simulation's ring, although structure surrounding Fornax is less similar. Both Virgo's and Fornax's "rings" tilt. Taken together, the tilt directions are not consistent with a uniform translation of the rest frame. The directions are consistent with either a steep tidal shear produced by a "Great Attractor" or with rotation about each cluster.

  12. Ballistic and Cyclic Rig Testing of Braided Composite Fan Case Structures

    NASA Technical Reports Server (NTRS)

    Watson, William R.; Roberts, Gary D.; Pereira, J. Michael; Braley, Michael S.

    2015-01-01

    FAA fan blade-out certification testing on turbofan engines occurs very late in an engine's development program and is very costly. It is of utmost importance to approach the FAA Certification engine test with a high degree of confidence that the containment structure will not only contain the high-energy debris, but that it will also withstand the cyclic loads that occur with engine spooldown and continued rotation as the non-running engine maintains a low rotor RPM due to forced airflow as the engine-out aircraft returns to an airport. Accurate rig testing is needed for predicting and understanding material behavior of the fan case structure during all phases of this fan blade-out event.

  13. Semiclassical shell structure in rotating Fermi systems

    SciTech Connect

    Magner, A. G.; Sitdikov, A. S.; Khamzin, A. A.; Bartel, J.

    2010-06-15

    The collective moment of inertia is derived analytically within the cranking model for any rotational frequency of the harmonic-oscillator potential well and at a finite temperature. Semiclassical shell-structure components of the collective moment of inertia are obtained for any potential by using the periodic-orbit theory. We found semiclassically their relation to the free-energy shell corrections through the shell-structure components of the rigid-body moment of inertia of the statistically equilibrium rotation in terms of short periodic orbits. The shell effects in the moment of inertia exponentially disappear with increasing temperature. For the case of the harmonic-oscillator potential, one observes a perfect agreement of the semiclassical and quantum shell-structure components of the free energy and the moment of inertia for several critical bifurcation deformations and several temperatures.

  14. Linear-cyclic polymer structural transformation and its reversible control using a rational rotaxane strategy.

    PubMed

    Ogawa, Takahiro; Usuki, Naoya; Nakazono, Kazuko; Koyama, Yasuhito; Takata, Toshikazu

    2015-04-01

    Linear-cyclic polymer structural transformation and its reversibility are demonstrated by a simple but rational strategy using the structural characteristics of crown ether-based rotaxanes. The structure of a polymer containing a [1]rotaxane unit at one end was controlled by conventional protection-deprotection reactions, giving rise to a reversible linear-cyclic polymer structural transformation. PMID:25531061

  15. Linear-cyclic polymer structural transformation and its reversible control using a rational rotaxane strategy.

    PubMed

    Ogawa, Takahiro; Usuki, Naoya; Nakazono, Kazuko; Koyama, Yasuhito; Takata, Toshikazu

    2015-04-01

    Linear-cyclic polymer structural transformation and its reversibility are demonstrated by a simple but rational strategy using the structural characteristics of crown ether-based rotaxanes. The structure of a polymer containing a [1]rotaxane unit at one end was controlled by conventional protection-deprotection reactions, giving rise to a reversible linear-cyclic polymer structural transformation.

  16. Structures and Surface Properties of "Cyclic" Polyoxyethylene Alkyl Ethers: Unusual Behavior of Cyclic Surfactants in Water.

    PubMed

    Hirose, Yuki; Taira, Toshiaki; Sakai, Kenichi; Sakai, Hideki; Endo, Akira; Imura, Tomohiro

    2016-08-23

    The cyclization of amphiphiles has emerged as an attractive strategy for inducing remarkable properties in these materials without changing their chemical composition. In this study, we successfully synthesized three cyclic polyoxyethylene dodecyl ethers (c-POEC12's) with different ring sizes and explored the effects of their topology on their surface and self-assembly properties related to their function, comparing them with those of their linear counterparts (l-POEC12's). The surface activity of the c-POEC12's remained almost constant despite the change in their hydrophobic and hydrophilic balance (HLB) value, while that of the l-POEC12's decreased with an increase in the HLB value as general surfactants. In contrast to the normal micelles seen in the case of the l-POEC12's (3.4-9.7 nm), the cyclization of the POEC12's resulted in the formation of large spherical structures 72.8-256.8 nm in size. It also led to a dramatic decrease of 28 °C in the cloud point temperature. Furthermore, the cyclization of the POEC12's markedly suppressed the rate of protease hydrolysis caused by the surfactants. The initial rate of reduction of a detergent enzyme from Bacillus licheniformis was increased by more than 40% in the case of c-POE600C12 and c-POE1000C12, even though they exhibited surface activities almost equal to or higher than those of their linear counterparts. These results suggest that cyclization induces unusual aqueous behaviors in POEC12, making the surfactant milder with respect to detergent enzymes while ensuring it exhibits increased surface activity. PMID:27462805

  17. Fatigue Testing of TBC on Structural Steel by Cyclic Bending

    NASA Astrophysics Data System (ADS)

    Musalek, Radek; Kovarik, Ondrej; Medricky, Jan; Curry, Nicholas; Bjorklund, Stefan; Nylen, Per

    2015-01-01

    For applications with variable loading, fatigue performance of coated parts is of utmost importance. In this study, fatigue performance of conventional structural steel coated with thermal barrier coating (TBC) was evaluated in cyclic bending mode by "SF-Test" device. Testing was carried out at each stage of the TBC preparation process, i.e., for as-received and grit-blasted substrates, as well as for samples with Ni-based bond-coat and complete TBC: bond-coat with YSZ-based top-coat. Comparison of results obtained for different loading amplitudes supplemented by fractographic analysis enabled identification of dominating failure mechanisms and demonstrated applicability of the high-frequency resonant bending test for evaluation of fatigue resistance alteration at each stage of the TBC deposition process.

  18. Structural Interactions within Lithium Salt Solvates: Cyclic Carbonates and Esters

    SciTech Connect

    Seo, D. M.; Afroz, Taliman; Allen, Joshua L.; Boyle, Paul D.; Trulove, Paul C.; De Long, Hugh C.; Henderson, Wesley A.

    2014-11-13

    Only limited information is available regarding the manner in which cyclic carbonate and ester solvents coordinate Li+ cations in electrolyte solutions for lithium batteries. One approach to gleaning significant insight into these interactions is to examine crystalline solvate structures. To this end, eight new solvate structures are reported with ethylene carbonate, γ-butyrolactone and γ-valerolactone: (EC)3:LiClO4, (EC)2:LiClO4, (EC)2:LiBF4, (GBL)4:LiPF6, (GBL)1:LiClO4, (GVL)1:LiClO4, (GBL)1:LiBF4 and (GBL)1:LiCF3SO3. The crystal structure of (EC)1:LiCF3SO3 is also re-reported for comparison. These structures enable the factors which govern the manner in which the ions are coordinated and the ion/solvent packing—in the solid-state—to be scrutinized in detail.

  19. Mercury's Interior Structure, Rotation, and Tides

    NASA Astrophysics Data System (ADS)

    van Hoolst, Tim; Sohl, Frank; Holin, Igor; Verhoeven, Olivier; Dehant, Véronique; Spohn, Tilman

    2007-10-01

    This review addresses the deep interior structure of Mercury. Mercury is thought to consist of similar chemical reservoirs (core, mantle, crust) as the other terrestrial planets, but with a relatively much larger core. Constraints on Mercury’s composition and internal structure are reviewed, and possible interior models are described. Large advances in our knowledge of Mercury’s interior are not only expected from imaging of characteristic surface features but particularly from geodetic observations of the gravity field, the rotation, and the tides of Mercury. The low-degree gravity field of Mercury gives information on the differences of the principal moments of inertia, which are a measure of the mass concentration toward the center of the planet. Mercury’s unique rotation presents several clues to the deep interior. From observations of the mean obliquity of Mercury and the low-degree gravity data, the moments of inertia can be obtained, and deviations from the mean rotation speed (librations) offer an exciting possibility to determine the moment of inertia of the mantle. Due to its proximity to the Sun, Mercury has the largest tides of the Solar System planets. Since tides are sensitive to the existence and location of liquid layers, tidal observations are ideally suited to study the physical state and size of the core of Mercury.

  20. Mercury's Interior Structure, Rotation, and Tides

    NASA Astrophysics Data System (ADS)

    van Hoolst, Tim; Sohl, Frank; Holin, Igor; Verhoeven, Olivier; Dehant, Véronique; Spohn, Tilman

    This review addresses the deep interior structure of Mercury. Mercury is thought to consist of similar chemical reservoirs (core, mantle, crust) as the other terrestrial planets, but with a relatively much larger core. Constraints on Mercury's composition and internal structure are reviewed, and possible interior models are described. Large advances in our knowledge of Mercury's interior are not only expected from imaging of characteristic surface features but particularly from geodetic observations of the gravity field, the rotation, and the tides of Mercury. The low-degree gravity field of Mercury gives information on the differences of the principal moments of inertia, which are a measure of the mass concentration toward the center of the planet. Mercury's unique rotation presents several clues to the deep interior. From observations of the mean obliquity of Mercury and the low-degree gravity data, the moments of inertia can be obtained, and deviations from the mean rotation speed (librations) offer an exciting possibility to determine the moment of inertia of the mantle. Due to its proximity to the Sun, Mercury has the largest tides of the Solar System planets. Since tides are sensitive to the existence and location of liquid layers, tidal observations are ideally suited to study the physical state and size of the core of Mercury.

  1. Vibrations of structures with cyclic symmetry: Application to the case of turbine engines

    NASA Astrophysics Data System (ADS)

    Meziere, Ludovic

    1994-03-01

    A great number of gas turbine components gives cyclic symmetry properties which may be useful to analyze such parts. The resonance occurrences are numerous because of the different harmonics of the rotational speed. Shift phase characteristics between each periodic sector can be easily used to represent the complex system forces made of air flow distortions for instance. The aerodynamical forces are transmitted to the structure mainly by the blades. From this point, we note under some stationary pressure deviations, fixed in the space reference, that the airfoil undergoes pressure fluctuations during its revolution cycle. This stationary phenomena is periodic in the blade reference. It shows a forward or backward wave propagation whose frequency is determined within each frame. A couple of eigen modes, except under some particular conditions, can be found using cyclic symmetry conditions at exactly the same eigen value. The linear combination of both modes are used to analyze the wave propagation. Resonance conditions are shown in this paper and an assessment of an excitability factor has been introduced to reckon the potentially dangerous modes. This method is applied on a modal analysis of an impeller of a gas turbine engine designed by TURBOMECA. This step is pre-requisite to a complete simulation of dynamic responses incorporating dissipative functions and the aeroelastic coupling which mainly governs such a vibration phenomena.

  2. Magnetospheric structure of rotation powered pulsars

    SciTech Connect

    Arons, J. California Univ., Livermore, CA . Inst. of Geophysics and Planetary Physics)

    1991-01-07

    I survey recent theoretical work on the structure of the magnetospheres of rotation powered pulsars, within the observational constraints set by their observed spindown, their ability to power synchrotron nebulae and their ability to produce beamed collective radio emission, while putting only a small fraction of their energy into incoherent X- and gamma radiation. I find no single theory has yet given a consistent description of the magnetosphere, but I conclude that models based on a dense outflow of pairs from the polar caps, permeated by a lower density flow of heavy ions, are the most promising avenue for future research. 106 refs., 4 figs., 2 tabs.

  3. Structure of fenchone by broadband rotational spectroscopy.

    PubMed

    Loru, Donatella; Bermúdez, Miguel A; Sanz, M Eugenia

    2016-08-21

    The bicyclic terpenoid fenchone (C10H16O, 1,3,3-trimethylbicyclo[2.2.1]heptan-2-one) has been investigated by chirped pulse Fourier transform microwave spectroscopy in the 2-8 GHz frequency region. The parent species and all heavy atom isotopologues have been observed in their natural abundance. The experimental rotational constants of all isotopic species observed have been determined and used to obtain the substitution (rs) and effective (r0) structures of fenchone. Calculations at the B3LYP, M06-2X, and MP2 levels of theory with different basis sets were carried out to check their performance against experimental results. The structure of fenchone has been compared with those of norbornane (bicyclo[2.2.1]heptane) and the norbornane derivatives camphor (1,7,7-trimethylbicyclo[2.2.1]heptan-2-one) and camphene (3,3-dimethyl-2-methylenebicyclo[2.2.1]heptane), both with substituents at C2. The structure of fenchone is remarkably similar to those of camphor and camphene. Comparison with camphor allows identification of changes in ∠CCC angles due to the different position of the methyl groups. All norbornane derivatives display similar structural changes with respect to norbornane. These changes mainly affect the bond lengths and angles of the six-membered rings, indicating that the substituent at C2 drives structural adjustments to minimise ring strain after its introduction. PMID:27544109

  4. Structure of fenchone by broadband rotational spectroscopy

    NASA Astrophysics Data System (ADS)

    Loru, Donatella; Bermúdez, Miguel A.; Sanz, M. Eugenia

    2016-08-01

    The bicyclic terpenoid fenchone (C10H16O, 1,3,3-trimethylbicyclo[2.2.1]heptan-2-one) has been investigated by chirped pulse Fourier transform microwave spectroscopy in the 2-8 GHz frequency region. The parent species and all heavy atom isotopologues have been observed in their natural abundance. The experimental rotational constants of all isotopic species observed have been determined and used to obtain the substitution (rs) and effective (r0) structures of fenchone. Calculations at the B3LYP, M06-2X, and MP2 levels of theory with different basis sets were carried out to check their performance against experimental results. The structure of fenchone has been compared with those of norbornane (bicyclo[2.2.1]heptane) and the norbornane derivatives camphor (1,7,7-trimethylbicyclo[2.2.1]heptan-2-one) and camphene (3,3-dimethyl-2-methylenebicyclo[2.2.1]heptane), both with substituents at C2. The structure of fenchone is remarkably similar to those of camphor and camphene. Comparison with camphor allows identification of changes in ∠CCC angles due to the different position of the methyl groups. All norbornane derivatives display similar structural changes with respect to norbornane. These changes mainly affect the bond lengths and angles of the six-membered rings, indicating that the substituent at C2 drives structural adjustments to minimise ring strain after its introduction.

  5. Enhanced biological denitrification in the cyclic rotating bed reactor with catechol as carbon source.

    PubMed

    Moussavi, Gholamreza; Jafari, Seyed Javad; Yaghmaeian, Kamyar

    2015-08-01

    The performance of CRBR in denitrification with catechol carbon source is presented. The influence of inlet nitrate concentration, hydraulic retention time (HRT), media filling ratio and rotational speed of media on the performance of CRBR was investigated. The bioreactor could denitrify over 95% of the nitrate at an inlet concentration up to 1000 mg NO3(-)/L and a short HRT as low as 18 h. The optimum media filling ratio at which the maximum denitrification was achieved in the CRBR was 30% and the contribution of media at this condition was around 36%. The optimum ratio of media filling at which the maximum denitrification was 20 rpm and the contribution of rotational speed under this condition was around 17%. According to the findings, the CRBR is a high rate bioreactor and thus serves as an appropriate technology for denitrification of wastewaters containing a high concentration of nitrate and toxic organic compounds. PMID:25898088

  6. Analysis of structures with rotating, flexible substructures

    NASA Technical Reports Server (NTRS)

    Hopkins, A. Stewart; Likins, Peter

    1987-01-01

    A new methodology has been developed for the dynamic analysis of flexible structures, parts of which may be experiencing discrete motion relative to other parts. This methodology provides the capability of representing the continuum deformations typically treated using finite element methods. In addition, it provides the capability of representing the discrete motion at joints traditionally available with multibody methods. After decomposing the structure into substructures and associating a frame of reference with each substructure, the equations of motion for each substructure can be written explicitly including contributions due to the frame of reference generalized coordinates. By expanding the set of constraints to include constraints that eliminate the redundancy introduced by the frame generalized coordinates, the equations of motion become amenable to solution. The first digital computer program using this methodology, the General Rotorcraft Aeromechanical Stability Program (GRASP), was introduced in 1986. Although GRASP is limited to applications involving steady-state rotation, extension to arbitrary motions (including spin-up) can be accomplished by the selective retention of nonlinear terms in this formulation.

  7. Recent developments in reassessment of jacket structures under extreme storm cyclic loading. Part 2: Cyclic capacity of tubular members

    SciTech Connect

    Amdahl, J.; Skallerud, B.H.; Eide, O.I.; Johansen, A.

    1995-12-31

    Tubular members with D/t ratio 35, 45, 60 and 80 were tested under controlled axial displacement described by an amplitude and a mean level. The material was structural steel to St. 52-3N, with minimum yield stress 345 MPa. The slenderness ratio of the specimens were in the range 50--70. During testing, the specimens were instrumented for measurements of longitudinal and transversal deflections, ovalization, and extreme fiber strains. Number of cycles to local buckling and through thickness cracking was recorded. Selected tests were simulated by use of the nonlinear beam-column FE program USFOS and the shell FE program ABAQUS. Comparisons were made to the corresponding test results. Monotonic and cyclic capacity criteria of tubular members are discussed on the basis of the results obtained.

  8. Structural tailoring of counter rotation propfans

    NASA Technical Reports Server (NTRS)

    Brown, Kenneth W.; Hopkins, D. A.

    1989-01-01

    The STAT program was designed for the optimization of single rotation, tractor propfan designs. New propfan designs, however, generally consist of two counter rotating propfan rotors. STAT is constructed to contain two levels of analysis. An interior loop, consisting of accurate, efficient approximate analyses, is used to perform the primary propfan optimization. Once an optimum design has been obtained, a series of refined analyses are conducted. These analyses, while too computer time expensive for the optimization loop, are of sufficient accuracy to validate the optimized design. Should the design prove to be unacceptable, provisions are made for recalibration of the approximate analyses, for subsequent reoptimization.

  9. Structural basis for cyclic terpene biosynthesis by tobacco 5-epi-aristolochene synthase

    SciTech Connect

    Starks, C.M.; Noel, J.P. |; Back, K.; Chappell, J.

    1997-09-19

    Terpene cyclases catalyze the synthesis of cyclic terpenes with 10-, 15-, and 20-carbon acyclic isoprenoid diphosphates as substrates. Plants have been a source of there natural products by providing a homologous set of terpene synthases. The crystal structures of 5-epi-aristolochene synthase, a sesquiterpene cyclase from tobacco, alone and complexed separately with two farnesyl diposphate analogs were analyzed. These structures reveal an unexpected enzymatic mechanism for the synthesis of the bicyclic product, 5-epi-aristolochene, and provide a basis for understanding the stereochemical selectivity displayed by other cyclases in the biosynthesis of pharmacologically important cyclic terpenes. As such, these structures provide templates for the engineering of novel terpene cyclases.

  10. Discriminating the structure of rotated three-dimensional figures.

    PubMed

    Barfield, W; Salvendy, G

    1987-10-01

    Visualizing the structure of transformed (by rotation) three-dimensional (3-D) figures is an important aspect of information processing for computer-graphics tasks. However, little research exists to establish the speed and accuracy in which subjects perform discrimination tasks for transformed images and the effects of rotation variables on perceiving transformed images. This research tests the effects of figural complexity, angles and axes of rotation on the speed and accuracy in which subjects discriminate the structure of rotated 3-D wireframe images. Results show that response times are affected more by angles than axes of rotation, the specific form of the image affects error rates, and the number of 90 degrees bends which determine the structure of an image may be an inadequate measure of form complexity for the task described here.

  11. Automated shell theory for rotating structures (ASTROS)

    NASA Technical Reports Server (NTRS)

    Foster, B. J.; Thomas, J. M.

    1971-01-01

    A computer program for analyzing axisymmetric shells with inertial forces caused by rotation about the shell axis is developed by revising the STARS II shell program. The basic capabilities of the STARS II shell program, such as the treatment of the branched shells, stiffened wall construction, and thermal gradients, are retained.

  12. Turbulent rotating plane Couette flow: Reynolds and rotation number dependency of flow structure and momentum transport

    NASA Astrophysics Data System (ADS)

    Kawata, Takuya; Alfredsson, P. Henrik

    2016-07-01

    Plane Couette flow under spanwise, anticyclonic system rotation [rotating plane Couette flow (RPCF)] is studied experimentally using stereoscopic particle image velocimetry for different Reynolds and rotation numbers in the fully turbulent regime. Similar to the laminar regime, the turbulent flow in RPCF is characterized by roll cells, however both instantaneous snapshots of the velocity field and space correlations show that the roll cell structure varies with the rotation number. All three velocity components are measured and both the mean flow and all four nonzero Reynolds stresses are obtained across the central parts of the channel. This also allows us to determine the wall shear stress from the viscous stress and the Reynolds stress in the center of the channel, and for low rotation rates the wall shear stress increases with increasing rotation rate as expected. The results show that zero absolute vorticity is established in the central parts of the channel of turbulent RPCF for high enough rotation rates, but also that the mean velocity profile for certain parameter ranges shows an S shape giving rise to a negative velocity gradient in the center of the channel. We find that from an analysis of the Reynolds stress transport equation using the present data there is a transport of the Reynolds shear stress towards the center of the channel, which may then result in a negative mean velocity gradient there.

  13. Recent developments in reassessment of jacket structures under extreme storm cyclic loading. Part 1: Overview

    SciTech Connect

    Eide, O.I.; Skallerud, B.H.; Johansen, A.; Amdahl, J.

    1995-12-31

    An attractive approach to integrity assessment of jacket structures subjected to extreme storm cyclic loading is based on considerations of system strength rather than component strength. The system strength is determined by nonlinear pushover analyses. Nonlinear cyclic analyses are undertaken to determine if the system strength will be degraded due to repeated action of extreme waves. In the present series of papers, conditions for application and extension of such a procedure are addressed. Tubular members with D/t ratio in the range 35--80 were tested under extreme cyclic loading to investigate criteria for onset of local buckling and number of cycles to through thickness cracking. Tubular T-joints were tested under extreme cyclic loading to investigate degradation of cyclic capacity imposed by low cycle fatigue cracking. In part 1 of this series of papers, an overview of the developed methodology for integrity assessment of jacket structures is given. Conditions for application are addressed and illustrated by way of an example study.

  14. Three dimensional dynamics of rotating structures under mixed boundary conditions

    NASA Astrophysics Data System (ADS)

    Bediz, Bekir; Romero, L. A.; Ozdoganlar, O. Burak

    2015-12-01

    This paper presents the spectral-Tchebychev (ST) technique for solution of three dimensional (3D) dynamics of rotating structures. In particular, structures that exhibit coupled dynamic response require a 3D modeling approach to capture their dynamic behavior. Rotational motions further complicate this behavior, inducing coriolis, centrifugal softening, and (nonlinear) stress-stiffening effects. Therefore, a 3D solution approach is needed to accurately capture the rotational dynamics. The presented 3D-ST technique provides a fast-converging and precise solution approach for rotational dynamics of structures with complex geometries and mixed boundary conditions. Specifically, unlike finite elements techniques, the presented technique uses a series expansion approach considering distributed-parameter system equations: The integral boundary value problem for rotating structures is discretized using the spectral-Tchebychev approach. To simplify the domain of the structures, cross-sectional and rotational transformations are applied to problems with curved cross-section and pretwisted geometry. The nonlinear terms included in the integral boundary value problem are linearized around an equilibrium solution using the quasi-static method. As a result, mass, damping, and stiffness matrices, as well as a forcing vector, are obtained for a given rotating structure. Several case studies are then performed to demonstrate the application and effectiveness of the 3D-ST solution. For each problem, the natural frequencies and modes shapes from the 3D-ST solution are compared to those from the literature (when available) and to those from a commercial finite elements software. The case studies include rotating/spinning parallelepipeds under free and mixed boundary conditions, and a cantilevered pretwisted beam (i.e., rotating blade) with an airfoil geometry rotating on a hub. It is seen that the natural frequencies and mode shapes from the 3D-ST technique differ from those from the

  15. Rotational order–disorder structure of fluorescent protein FP480

    SciTech Connect

    Pletnev, Sergei; Morozova, Kateryna S.; Verkhusha, Vladislav V.; Dauter, Zbigniew

    2009-09-01

    An analysis of the rotational order–disorder structure of fluorescent protein FP480 is presented. In the last decade, advances in instrumentation and software development have made crystallography a powerful tool in structural biology. Using this method, structural information can now be acquired from pathological crystals that would have been abandoned in earlier times. In this paper, the order–disorder (OD) structure of fluorescent protein FP480 is discussed. The structure is composed of tetramers with 222 symmetry incorporated into the lattice in two different ways, namely rotated 90° with respect to each other around the crystal c axis, with tetramer axes coincident with crystallographic twofold axes. The random distribution of alternatively oriented tetramers in the crystal creates a rotational OD structure with statistically averaged I422 symmetry, although the presence of very weak and diffuse additional reflections suggests that the randomness is only approximate.

  16. Vector Majorization Technique for Rotation to a Specified Simple Structure.

    ERIC Educational Resources Information Center

    Trendafilov, Nickolay T.

    In the technique developed by K. G. Joreskog to solve the problem for oblique rotation to a specified simple structure, the basic concept is that the simple structure solution itself is determined only by the zero coefficients of the reference-structure matrix and not by the coefficients of non-zero magnitude. Following this, prior information…

  17. Multilevel Modeling of Two Cyclical Processes: Extending Differential Structural Equation Modeling to Nonlinear Coupled Systems

    ERIC Educational Resources Information Center

    Butner, Jonathan; Amazeen, Polemnia G.; Mulvey, Genna M.

    2005-01-01

    The authors present a dynamical multilevel model that captures changes over time in the bidirectional, potentially asymmetric influence of 2 cyclical processes. S. M. Boker and J. Graham's (1998) differential structural equation modeling approach was expanded to the case of a nonlinear coupled oscillator that is common in bimanual coordination…

  18. Estimation of Cyclic Interstory Drift Capacity of Steel Framed Structures and Future Applications for Seismic Design

    PubMed Central

    Bojórquez, Edén; Reyes-Salazar, Alfredo; Ruiz, Sonia E.; Terán-Gilmore, Amador

    2014-01-01

    Several studies have been devoted to calibrate damage indices for steel and reinforced concrete members with the purpose of overcoming some of the shortcomings of the parameters currently used during seismic design. Nevertheless, there is a challenge to study and calibrate the use of such indices for the practical structural evaluation of complex structures. In this paper, an energy-based damage model for multidegree-of-freedom (MDOF) steel framed structures that accounts explicitly for the effects of cumulative plastic deformation demands is used to estimate the cyclic drift capacity of steel structures. To achieve this, seismic hazard curves are used to discuss the limitations of the maximum interstory drift demand as a performance parameter to achieve adequate damage control. Then the concept of cyclic drift capacity, which incorporates information of the influence of cumulative plastic deformation demands, is introduced as an alternative for future applications of seismic design of structures subjected to long duration ground motions. PMID:25089288

  19. Estimation of cyclic interstory drift capacity of steel framed structures and future applications for seismic design.

    PubMed

    Bojórquez, Edén; Reyes-Salazar, Alfredo; Ruiz, Sonia E; Terán-Gilmore, Amador

    2014-01-01

    Several studies have been devoted to calibrate damage indices for steel and reinforced concrete members with the purpose of overcoming some of the shortcomings of the parameters currently used during seismic design. Nevertheless, there is a challenge to study and calibrate the use of such indices for the practical structural evaluation of complex structures. In this paper, an energy-based damage model for multidegree-of-freedom (MDOF) steel framed structures that accounts explicitly for the effects of cumulative plastic deformation demands is used to estimate the cyclic drift capacity of steel structures. To achieve this, seismic hazard curves are used to discuss the limitations of the maximum interstory drift demand as a performance parameter to achieve adequate damage control. Then the concept of cyclic drift capacity, which incorporates information of the influence of cumulative plastic deformation demands, is introduced as an alternative for future applications of seismic design of structures subjected to long duration ground motions.

  20. Mechanical features of the shuttle rotating service structure

    NASA Technical Reports Server (NTRS)

    Crump, J. M.

    1985-01-01

    With the development of the space shuttle launching facilities, it became mandatory to develop a shuttle rotating service structure to provide for the insertion and/or removal of payloads at the launch pads. The rotating service structure is a welded tubular steel space frame 189 feet high, 65 feet wide, and weighing 2100 tons. At the pivot column the structure is supported on a 30 inch diameter hemispherical bearing. At the opposite terminus the structure is supported on two truck assemblies each having eight 36 inch diameter double flanged wheels. The following features of the rotating service structure are discussed: (1) thermal expansion and contraction; (2) hurricane tie downs; (3) payload changeout room; (4) payload ground handling mechanism; (5) payload and orbiter access platforms; and (6) orbiter cargo bay access.

  1. Edge Plasma Structure with Rotating Resonant Magnetic Perturbations at TEXTOR

    NASA Astrophysics Data System (ADS)

    Stoschus, H.; Schmitz, O.; Frerichs, H.; Lehnen, M.; Reiser, D.; Unterberg, B.; Samm, U.; Textor Research Team

    2011-10-01

    Rotating Resonant Magnetic Perturbations impose a characteristic modulation to the electron density and temperature in the TEXTOR plasma edge (r / a > 0 . 9). The modulation matches the position of the magnetic topology modeled in vacuum approximation for low relative rotation of frel = - 0 . 2 kHz between RMP field and toroidal plasma rotation. With increasing relative rotation (frel = 1 . 8 kHz), the plasma structure at the outermost rational flux surface is shifted by π / 2 in counter-Bt direction due to internal plasma response. The shift is correlated to a smaller displacement of the plasma structure in front of the RMP coils of 0 . 1 π . This indicates a competition between the near-field of the RMP coils and the net magnetic field at the rational flux surface. Work supported in part by US DOE under DE-AC05-06OR23100.

  2. Development of a simplified procedure for cyclic structural analysis

    NASA Technical Reports Server (NTRS)

    Kaufman, A.

    1984-01-01

    Development was extended of a simplified inelastic analysis computer program (ANSYMP) for predicting the stress-strain history at the critical location of a thermomechanically cycled structure from an elastic solution. The program uses an iterative and incremental procedure to estimate the plastic strains from the material stress-strain properties and a plasticity hardening model. Creep effects can be calculated on the basis of stress relaxation at constant strain, creep at constant stress, or a combination of stress relaxation and creep accumulation. The simplified method was exercised on a number of problems involving uniaxial and multiaxial loading, isothermal and nonisothermal conditions, dwell times at various points in the cycles, different materials, and kinematic hardening. Good agreement was found between these analytical results and nonlinear finite-element solutions for these problems. The simplified analysis program used less than 1 percent of the CPU time required for a nonlinear finite-element analysis.

  3. Nuclear structure in the dinuclear model with rotating clusters

    SciTech Connect

    Adamian, G. G.; Antonenko, N. V.; Jolos, R. V.; Palchikov, Yu. V.; Shneidman, T. M.; Scheid, W.

    2007-08-15

    The dinuclear-system model can be applied to nuclear structure. Here, we study deformed clusters which rotate with respect to the internuclear distance and exchange nucleons. The model can be used to explain the band structure of nuclear spectra, especially the parity splitting observed in actinides, e.g., in {sup 238}U.

  4. Structure of STING bound to cyclic di-GMP reveals the mechanism of cyclic dinucleotide recognition by the immune system.

    PubMed

    Shu, Chang; Yi, Guanghui; Watts, Tylan; Kao, C Cheng; Li, Pingwei

    2012-06-24

    STING (stimulator of interferon genes) is an innate immune sensor of cyclic dinucleotides that regulates the induction of type I interferons. STING's C-terminal domain forms a V-shaped dimer and binds a cyclic diguanylate monophosphate (c-di-GMP) at the dimer interface by both direct and solvent-mediated hydrogen bonds. Guanines of c-di-GMP stack against the phenolic rings of a conserved tyrosine, and mutations at the c-di-GMP binding surface reduce nucleotide binding and affect signaling.

  5. Multilayer cyclic C{sub 6} structures intercalated with metal atoms

    SciTech Connect

    Kuzmin, Stanislav; Duley, Walter W.

    2011-02-15

    A new type of tubular inorganic metal-carbon sandwich molecule based on cyclic C{sub 6} is proposed. These consist of multiple layers of cyclic C{sub 6} with intercalated metal atoms. Structures and electronic properties of these molecules have been calculated using first-principles density functional techniques. We have evaluated all metals in the first six periods of the periodic table, except for the lanthanides, as possible components of such molecules. Our calculations show high bond energy and small energy gaps in many of these structures. We suggest that the high structural stability and high conductivity in these sandwich compounds make them very promising for use in nanoelectronic applications.

  6. Structural effects of three-dimensional angle-interlock woven composite undergoing bending cyclic loading

    NASA Astrophysics Data System (ADS)

    Jin, LiMin; Yao, Yao; Yu, YiMin; Rotich, Gideon; Sun, BaoZhong; Gu, BoHong

    2014-03-01

    This paper reports the structural effects of three-dimensional (3-D) angle-interlock woven composite (3DAWC) undergoing three-point bending cyclic loading from experimental and finite element analysis (FEA) approaches. In experiment, the fatigue tests were conducted to measure the bending deflection and to observe the damage morphologies. By the FEA approach, a micro-structural unit-cell model of the 3DAWC was established at the yarn level to simulate the fatigue damage. The stress degradation at the loading condition of constant deformation amplitude was calculated to show the degradation of mechanical properties. In addition, the stress distribution, fatigue damage evolution and critical damage regions were also obtained to qualitatively reveal the structural effects and damage mechanisms of the 3DAWC subjected to three-point bending cyclic loading.

  7. Complex eigenvalue analysis of rotating structures

    NASA Technical Reports Server (NTRS)

    Patel, J. S.; Seltzer, S. M.

    1972-01-01

    A FORTRAN subroutine to NASTRAN which constructs coriolis and centripetal acceleration matrices, and a centrifugal load vector due to spin about a selected point or about the mass center of the structure is discussed. The rigid translational degrees of freedom can be removed by using a transformation matrix T and its explicitly given inverse. These matrices are generated in the subroutine and their explicit expressions are given.

  8. 18-Membered cyclic esters derived from glycolide and lactide: preparations, structures and coordination to sodium ions

    SciTech Connect

    Chisholm, Malcolm H.; Gallucci, Judith C.; Yin, Hongfeng

    2008-06-30

    From reactions between glycolide or lactide (4 equiv.) with 4-dimethylaminopyridine, DMAP (1 equiv.) and NaBPh4 (1 equiv.) in benzene at 70 C the cyclic ester adducts (CH{sub 2}C(O)O){sub 6}NaBPh{sub 4} and (CHMeC(O)O){sub 6}NaBPh{sub 4} are formed respectively. The structures of the salts Na[(S,R,S,R,S,R)-(CH{sub 3}CHC(O)O){sub 6}]{sub 2}BPh{sub 4} {center_dot} CH{sub 3}CN and (CH{sub 2}C(O)O){sub 6}NaBPh{sub 4} {center_dot} (CH{sub 3}CN){sub 2} are reported. The cyclic esters were separated by chromatography and the structures of (CH{sub 2}C(O)O){sub 6}, (S,R,R,R,R,R)-(CHMeC(O)O){sub 6} and (S,S,R,R,R,R)-(CHMeC(O)O){sub 6} were determined. The {sup 1}H and {sup 13}C NMR data are reported for one of each of the six enantiomers of (CHMeC(O)O){sub 6} and the two meso isomers. The mechanism for the formation of these 18-membered rings is discussed in terms of an initial reaction between DMAP and NaBPh{sub 4} in hot benzene that produces NaPh and DMAP:BPh{sub 3} in the presence of the monomer lactide. The cyclic esters (CHMeC(O)O){sub 6} can also be obtained from the reaction between polylactide, PLA, in the presence of DMAP and NaBPh{sub 4}. The cyclic esters 3-methyl-1,4-dioxane-2,5-dione and 3,6,6-trimethyl-1,4-dioxane-2,5-dione undergo similar ring enlarging reactions to give cyclic 18-membered ring esters as determined by ESI-MS.

  9. Estimating ankle rotational constraints from anatomic structure

    NASA Astrophysics Data System (ADS)

    Baker, H. H.; Bruckner, Janice S.; Langdon, John H.

    1992-09-01

    Three-dimensional biomedical data obtained through tomography provide exceptional views of biological anatomy. While visualization is one of the primary purposes for obtaining these data, other more quantitative and analytic uses are possible. These include modeling of tissue properties and interrelationships, simulation of physical processes, interactive surgical investigation, and analysis of kinematics and dynamics. As an application of our research in modeling tissue structure and function, we have been working to develop interactive and automated tools for studying joint geometry and kinematics. We focus here on discrimination of morphological variations in the foot and determining the implications of these on both hominid bipedal evolution and physical therapy treatment for foot disorders.

  10. Rotation and internal structure of Population III protostars

    NASA Astrophysics Data System (ADS)

    Stacy, Athena; Greif, Thomas H.; Klessen, Ralf S.; Bromm, Volker; Loeb, Abraham

    2013-05-01

    We analyse the cosmological simulations performed in the recent work of Greif et al., which followed the early growth and merger history of Population III (Pop III) stars while resolving scales as small as 0.05 R⊙. This is the first set of cosmological simulations to self-consistently resolve the rotation and internal structure of Pop III protostars. We find that Pop III stars form under significant rotational support which is maintained for the duration of the simulations. The protostellar surfaces spin from ˜50 per cent to nearly 100 per cent of Keplerian rotational velocity. These rotation rates persist after experiencing multiple stellar merger events. In the brief time period simulated (˜10 yr), the protostars show little indication of convective instability, and their properties furthermore show little correlation with the properties of their host minihaloes. If Pop III protostars within this range of environments generally form with high degrees of rotational support, and if this rotational support is maintained for a sufficient amount of time, this has a number of crucial implications for Pop III evolution and nucleosynthesis, as well as the possibility for Pop III pair-instability supernovae, and the question of whether the first stars produced gamma-ray bursts.

  11. Complete action for open superstring field theory with cyclic A ∞ structure

    NASA Astrophysics Data System (ADS)

    Erler, Theodore; Okawa, Yuji; Takezaki, Tomoyuki

    2016-08-01

    We construct a gauge invariant action for the Neveu-Schwarz and Ramond sectors of open superstring field theory realizing a cyclic A ∞ structure, providing the first complete and fully explicit solution to the classical Batalin-Vilkovisky master equation in superstring field theory. We also demonstrate the equivalence of our action to the Wess-Zumino-Witten-based construction of Kunitomo and one of the authors.

  12. Rotational order–disorder structure of fluorescent protein FP480

    PubMed Central

    Pletnev, Sergei; Morozova, Kateryna S.; Verkhusha, Vladislav V.; Dauter, Zbigniew

    2009-01-01

    In the last decade, advances in instrumentation and software development have made crystallography a powerful tool in structural biology. Using this method, structural information can now be acquired from pathological crystals that would have been abandoned in earlier times. In this paper, the order–disorder (OD) structure of fluorescent protein FP480 is discussed. The structure is composed of tetramers with 222 symmetry incorporated into the lattice in two different ways, namely rotated 90° with respect to each other around the crystal c axis, with tetramer axes coincident with crystallo­graphic twofold axes. The random distribution of alternatively oriented tetramers in the crystal creates a rotational OD structure with statistically averaged I422 symmetry, although the presence of very weak and diffuse additional reflections suggests that the randomness is only approximate. PMID:19690368

  13. Structural Flexibility and Conformation Features of Cyclic Dinucleotides in Aqueous Solutions.

    PubMed

    Che, Xing; Zhang, Jun; Zhu, Yanyu; Yang, Lijiang; Quan, Hui; Gao, Yi Qin

    2016-03-17

    Cyclic dinucleotides are able to trigger the innate immune system by activating STING. It was found that the binding affinity of asymmetric 2'3'-cGAMP to symmetric dimer of STING is 3 orders of magnitude higher than that of the symmetric 3'3'-cyclic dinucleotides. Such a phenomenon has not been understood yet. Here we show that the subtle changes in phosphodiester linkage of CDNs lead to their distinct structural properties which correspond to the varied binding affinities. 2'-5' and/or 3'-5' linked CDNs adopt specific while different types of ribose puckers and backbone conformations. That ribose conformations and base types have different propensities for anti or syn glycosidic conformations further affects the overall flexibility of CDNs. The counterbalance between backbone ring tension and electrostatic repulsion, both affected by the ring size, also contributes to the different flexibility of CDNs. Our calculations reveal that the free energy cost for 2'3'-cGAMP to adopt the STING-bound structure is smaller than that for 3'3'-cGAMP and cyclic-di-GMP. These findings may serve as a reference for design of CDN-analogues as vaccine adjuvants. Moreover, the cyclization pattern of CDNs closely related to their physiological roles suggests the importance of understanding structural properties in the study of protein-ligand interactions.

  14. Formation and evolution of tweed structures on high-purity aluminum polycrystalline foils under cyclic tension

    NASA Astrophysics Data System (ADS)

    Kuznetsov, P. V.; Vlasov, I. V.; Sklyarova, E. A.; Smekalina, T. V.

    2015-10-01

    Peculiarities of formation and evolution of tweed structures on the surface of high-purity aluminum polycrystalline foils under cyclic tension were studied using an atom force microscope and a white light interferometer. Tweed structures of micron and submicron sizes were found on the foils at different number of cycles. In the range of 42,000 < N < 95,000 cycles destruction of tweed patterns is observed, which leads to their disappearance from the surface of the foils. Formation of tweed structures of various scales is discussed in terms of the Grinfeld instability.

  15. Formation and evolution of tweed structures on high-purity aluminum polycrystalline foils under cyclic tension

    SciTech Connect

    Kuznetsov, P. V.; Vlasov, I. V.; Sklyarova, E. A.; Smekalina, T. V.

    2015-10-27

    Peculiarities of formation and evolution of tweed structures on the surface of high-purity aluminum polycrystalline foils under cyclic tension were studied using an atom force microscope and a white light interferometer. Tweed structures of micron and submicron sizes were found on the foils at different number of cycles. In the range of 42,000 < N < 95,000 cycles destruction of tweed patterns is observed, which leads to their disappearance from the surface of the foils. Formation of tweed structures of various scales is discussed in terms of the Grinfeld instability.

  16. Spectral structure of Earth rotation parameter series (SHA).

    NASA Astrophysics Data System (ADS)

    Zhu, Yuanlan; Zhu, Wenyao

    Using the Marple algorithm of AR spectrum, the authors have analysed the spectral structure of ERP(SHA) series. Some main periodical terms of both polar motion and Earth rotation have been derived well from this series. This shows that the ERP(SHA) series can be reliably applied to astronomical and geophysical researches.

  17. Structure and mechanism of E. coli RNA 2',3'-cyclic phosphodiesterase.

    PubMed

    Remus, Barbara S; Jacewicz, Agata; Shuman, Stewart

    2014-11-01

    2H (two-histidine) phosphoesterase enzymes are distributed widely in all domains of life and are implicated in diverse RNA and nucleotide transactions, including the transesterification and hydrolysis of cyclic phosphates. Here we report a biochemical and structural characterization of the Escherichia coli 2H protein YapD YadP [corrected], which was identified originally as a reversible transesterifying "nuclease/ligase" at RNA 2',5'-phosphodiesters. We find that YapD YadP [corrected] is an "end healing" cyclic phosphodiesterase (CPDase) enzyme that hydrolyzes an HORNA>p substrate with a 2',3'-cyclic phosphodiester to a HORNAp product with a 2'-phosphomonoester terminus, without concomitant end joining. Thus we rename this enzyme ThpR (two-histidine 2',3'-cyclic phosphodiesterase acting on RNA). The 2.0 Å crystal structure of ThpR in a product complex with 2'-AMP highlights the roles of extended histidine-containing motifs (43)HxTxxF(48) and (125)HxTxxR(130) in the CPDase reaction. His43-Nε makes a hydrogen bond with the ribose O3' leaving group, thereby implicating His43 as a general acid catalyst. His125-Nε coordinates the O1P oxygen of the AMP 2'-phosphate (inferred from geometry to derive from the attacking water nucleophile), pointing to His125 as a general base catalyst. Arg130 makes bidentate contact with the AMP 2'-phosphate, suggesting a role in transition-state stabilization. Consistent with these inferences, changing His43, His125, or Arg130 to alanine effaced the CPDase activity of ThpR. Phe48 makes a π-π stack on the adenine nucleobase. Mutating Phe28 to alanine slowed the CPDase by an order of magnitude. The tertiary structure and extended active site motifs of ThpR are conserved in a subfamily of bacterial and archaeal 2H enzymes. PMID:25239919

  18. Structure elucidation of Sch 20562, a glucosidic cyclic dehydropeptide lactone--the major component of W-10 antifungal antibiotic.

    PubMed

    Afonso, A; Hon, F; Brambilla, R

    1999-04-01

    A novel bacterium designated as Aeromonas sp. W-10 produces the antibiotic W-10 complex which comprises of two major and several minor components. The two major components from this complex, Sch 20562 (1) and Sch 20561 (1a), are of biological interest in view of their potent antifungal activity. The chemical degradation studies utilized for the assignment of structure 1 for Sch 20562 are described here. Some of the noteworthy diversity of structural features in this glucosidic cyclic dehydrononapeptide lactone 1 are: an N-terminal (D)-beta-hydroxymyristyl unit, three D-amino acid units, two (E)-alpha-aminocrotonyl units, and an O-alpha-D-glucosyl-N-methyl-L-allo-threonine unit. The structure determination of 1 utilized the selective cleavage of the dehydropeptide units by ozonolysis to form fragments that were sequenced by mass spectrometry. The stereochemistry of the amino acid units were assigned by isolation of the free amino acids from the hydrolysates of the fragments. The stereochemistry of the alpha-aminocrotonyl units and the glucosidic linkage were assigned by nmr spectroscopy and molecular rotation data.

  19. Structural and energetic analysis of activation by a cyclic nucleotide binding domain

    PubMed Central

    Altieri, Stephen L.; Clayton, Gina M.; Silverman, William R.; Olivares, Adrian O.; De La Cruz, Enrique M.; Thomas, Lise R.; Morais-Cabral, João H.

    2008-01-01

    Summary MlotiK1 is a prokaryotic homolog of cyclic nucleotide-dependent ion channels which contains an intracellular C-terminal cyclic nucleotide binding domain (CNB domain). X-ray structures have been solved of the CNB domain in the absence of ligand and bound to cAMP. Both the full-length channel and CNB domain fragment are easily expressed and purified, making MlotiK1 a useful model system for dissecting activation by ligand binding. We have used X-ray crystallography to determine three new MlotiK1 CNB domain structures: a second apo configuration, a cGMP-bound structure, and a second cAMP-bound structure. In combination, the five MlotiK1 CNB domain structures provide a unique opportunity for analyzing, within a single protein, the structural differences between the apo and bound states and the structural variability within each state. With this analysis as a guide, we have probed the nucleotide selectivity and importance of specific residue side chains in ligand binding and channel activation. These data help to identify ligand-protein interactions that are important for ligand-dependence in MlotiK1 and more globally in the class of nucleotide-dependent proteins. PMID:18619611

  20. Hardware efficient implementation of DFT using an improved first-order moments based cyclic convolution structure

    NASA Astrophysics Data System (ADS)

    Xiong, Jun; Liu, J. G.; Cao, Li

    2015-12-01

    This paper presents hardware efficient designs for implementing the one-dimensional (1D) discrete Fourier transform (DFT). Once DFT is formulated as the cyclic convolution form, the improved first-order moments-based cyclic convolution structure can be used as the basic computing unit for the DFT computation, which only contains a control module, a barrel shifter and (N-1)/2 accumulation units. After decomposing and reordering the twiddle factors, all that remains to do is shifting the input data sequence and accumulating them under the control of the statistical results on the twiddle factors. The whole calculation process only contains shift operations and additions with no need for multipliers and large memory. Compared with the previous first-order moments-based structure for DFT, the proposed designs have the advantages of less hardware consumption, lower power consumption and the flexibility to achieve better performance in certain cases. A series of experiments have proven the high performance of the proposed designs in terms of the area time product and power consumption. Similar efficient designs can be obtained for other computations, such as DCT/IDCT, DST/IDST, digital filter and correlation by transforming them into the forms of the first-order moments based cyclic convolution.

  1. The Rotational Spectrum and Conformational Structures of Methyl Valerate

    NASA Astrophysics Data System (ADS)

    Nguyen, Ha Vinh Lam; Stahl, Wolfgang

    2015-06-01

    Methyl valerate, C4H9COOCH3, belongs to the class of fruit esters, which play an important role in nature as odorants of different fruits, flowers, and wines. A sufficient explanation for the structure-odor relation of is not available. It is known that predicting the odor of a substance is not possible by knowing only its chemical formula. A typical example is the blueberry- or pine apple-like odor of ethyl isovalerate while its isomers ethyl valerate and isoamyl acetate smell like green apple and banana, respectively. Obviously, not only the composition but also the molecular structures are not negligible by determining the odor of a substance. Gas phase structures of fruit esters are thus important for a first step towards the determination of structure-odor relation since the sense of smell starts from gas phase molecules. For this purpose, a combination of microwave spectroscopy and quantum chemical calculations (QCCs) is an excellent tool. Small esters often have sufficient vapor pressure to be transferred easily in the gas phase for a rotational study but already contain a large number of atoms which makes them too big for classical structure determination by isotopic substitution and requires nowadays a comparison with the structures optimized by QCCs. On the other hand, the results from QCCs have to be validated by the experimental values. About the internal dynamics, the methoxy methyl group -COOCH3 of methyl acetate shows internal rotation with a barrier of 424.581(56) wn. A similar barrier height of 429.324(23) wn was found in methyl propionate, where the acetyl group is extended to the propionyl group. The investigation on methyl valerate fits well in this series of methyl alkynoates. In this talk, the structure of the most energetic favorable conformer as well as the internal rotation shown by the methoxy methyl group will be reported. It could be confirmed that the internal rotation barrier of the methoxy methyl group remains by longer alkyl chain.

  2. The rotational spectrum and structure of the HOOO radical.

    PubMed

    Suma, Kohsuke; Sumiyoshi, Yoshihiro; Endo, Yasuki

    2005-06-24

    The adduct of the hydroxyl radical with oxygen has been studied theoretically, in connection with atmospheric reactions, but its stability and structure remained an open question. Pure rotational spectra of the HOOO and DOOO radicals have now been observed in a supersonic jet by using a Fourier-transform microwave spectrometer with a pulsed discharge nozzle. The molecular constants extracted from 12 rotational transitions with fine and hyperfine splittings support a trans planar molecular structure, in contrast to the cis planar structure predicted by most ab initio calculations. The bond linking the HO and O2 moieties is fairly long (1.688 angstroms) and comparable to the F-O bond in the isoelectronic FOO radical.

  3. Flow Structure on a Rotating Wing: Effect of Rossby Number

    NASA Astrophysics Data System (ADS)

    Wolfinger, Maxwell; Rockwell, Donald

    2013-11-01

    The flow structure on a rotating wing is determined via stereoscopic particle image velocimetry. Sectional and three-dimensional, volumetric reconstructions define the flow patterns as a function of Rossby number Ro. An aspect ratio AR = 1 rectangular, flat plate is rotated at a geometric angle of attack α = 45°. The flow structure is determined at various angles of rotation, in order to characterize both the initial development and the fully evolved state of the flow structure. The Rossby number Ro =rg / C is varied via alteration of the radius of gyration rg of the wing, to give values from Ro = 1.2 to Ro = 5.1. Large changes of the flow structure are represented by images of of spanwise vorticity, Q-criterion; spanwise velocity; and downwash velocity. At the lowest Rossby number Ro = 1.2, a vortex is attached to the leading edge of the wing; it is present along most of the span. At higher Rossby numbers Ro = 2.1 and Ro = 5.1, this leading-edge vortex becomes less organized and deflects away from the surface of the wing. At a Rossby number Ro = 5.1 the structure of the flow in the vicinity of the leading edge resembles a separated shear layer. The nature of other elements of the three-dimensional flow, such as the root and tip vortices and the downwash velocity, are closely related to the degree of coherence of the leading-edge vortex.

  4. Structural and evolutionary divergence of cyclic nucleotide binding domains in eukaryotic pathogens: Implications for drug design☆

    PubMed Central

    Mohanty, Smita; Kennedy, Eileen J.; Herberg, Friedrich W.; Hui, Raymond; Taylor, Susan S.; Langsley, Gordon; Kannan, Natarajan

    2015-01-01

    Many cellular functions in eukaryotic pathogens are mediated by the cyclic nucleotide binding (CNB) domain, which senses second messengers such as cyclic AMP and cyclic GMP. Although CNB domain-containing proteins have been identified in many pathogenic organisms, an incomplete understanding of how CNB domains in pathogens differ from other eukaryotic hosts has hindered the development of selective inhibitors for CNB domains associated with infectious diseases. Here, we identify and classify CNB domain-containing proteins in eukaryotic genomes to understand the evolutionary basis for CNB domain functional divergence in pathogens. We identify 359 CNB domain-containing proteins in 31 pathogenic organisms and classify them into distinct subfamilies based on sequence similarity within the CNB domain as well as functional domains associated with the CNB domain. Our study reveals novel subfamilies with pathogen-specific variations in the phosphate-binding cassette. Analyzing these variations in light of existing structural and functional data provides new insights into ligand specificity and promiscuity and clues for drug design. This article is part of a Special Issue entitled: Inhibitors of Protein Kinases. PMID:25847873

  5. Crystal structure of human insulin-regulated aminopeptidase with specificity for cyclic peptides.

    PubMed

    Hermans, Stefan J; Ascher, David B; Hancock, Nancy C; Holien, Jessica K; Michell, Belinda J; Chai, Siew Yeen; Morton, Craig J; Parker, Michael W

    2015-02-01

    Insulin-regulated aminopeptidase (IRAP or oxytocinase) is a membrane-bound zinc-metallopeptidase that cleaves neuroactive peptides in the brain and produces memory enhancing effects when inhibited. We have determined the crystal structure of human IRAP revealing a closed, four domain arrangement with a large, mostly buried cavity abutting the active site. The structure reveals that the GAMEN exopeptidase loop adopts a very different conformation from other aminopeptidases, thus explaining IRAP's unique specificity for cyclic peptides such as oxytocin and vasopressin. Computational docking of a series of IRAP-specific cognitive enhancers into the crystal structure provides a molecular basis for their structure-activity relationships and demonstrates that the structure will be a powerful tool in the development of new classes of cognitive enhancers for treating a variety of memory disorders such as Alzheimer's disease.

  6. Rotating structures and vortices in low temperature plasmas

    NASA Astrophysics Data System (ADS)

    Boeuf, Jean-Pierre

    2014-10-01

    Rotating structures are present in a number of low temperature EXB devices such as Hall thrusters, magnetrons, Penning discharges etc...Some aspects of the physics of these rotating instabilities are specific to low temperature plasmas because of the relatively large collisionality, the role of ionization, and the fact that ions are often non-magnetized. On the basis of fully kinetic simulations (Particle-In-Cell Monte Carlo Collisions) we describe the formation of a rotating instability associated with an ionization front (``rotating spoke'') and driven by a cross-field current in a self-sustained cylindrical magnetron discharge at gas pressure on the order of 1 Pa. The rotating spoke is a strong double layer (electrostatic sheath) moving towards the higher potential region at a velocity close to the critical ionization velocity, a concept proposed by Alfvén in the context of the formation of the solar system. The mechanisms of cross-field electron transport induced by this instability are analyzed. At lower pressure (<0.01 Pa) the plasma of a magnetron discharge is non-neutral and the simulations predict the formation of electron vortices rotating in the azimuthal direction and resulting from the diocotron instability. The properties of these vortices are specific since they form in a self-sustained discharge where ionization (and losses at the ends of the plasma column) play an essential role in contrast with the electron vortices in pure electron plasmas. We discuss and analyze the mechanisms leading to the generation, dynamics and merging of these self-sustained electron vortices, and to the periodic ejection of fast electrons at the column ends (consistent with previous experimental observations).

  7. Effects of molecular structure on oxidation reactivity of cyclic hydrocarbons: Experimental observations and conformational analysis

    SciTech Connect

    Yang, Yi; Boehman, Andre L.; Simmie, John M.

    2010-12-15

    This work concerns the pre-ignition reactivity of cyclic hydrocarbons and its dependence on cyclic structures. In the first part, global reactivity of five cyclic hydrocarbons, methylcyclopentane (MCP), cyclohexane (CH), methylcyclohexane (MCH), decahydronaphthalene (decalin), and 1,2,3,4-tetrahydronaphthalene (tetralin), whose detailed product analyses were recently reported [Y. Yang, A.L. Boehman, Proc. Combust. Inst. 32(1) (2009) 419-426; Y. Yang, A.L. Boehman, Combust. Flame 157(3) (2010) 495-505], were compared over a range of compression ratio and intake temperature in a motored engine. Molecular structure exerts a profound effect on low temperature oxidation reactivity. Decalin is the most reactive compound whose extent of oxidation increases monotonically with increasing temperature and pressure. MCH shows higher low temperature reactivity than CH, and both show distinct negative temperature coefficient behavior. MCP and tetralin exhibit little low temperature reaction before critical conditions are reached for autoignition. In the second part, conformational analysis is conducted to understand how molecular structures affect the low temperature oxidative reactivity, in particular the (1,5) H-shift of fuel peroxy radicals (ROO{yields}{sup (1,5)}QOOH), the key step in low temperature chain branching. In comparison with open-chain structures, cyclic structures significantly reduce the total number of hydrogens that can be abstracted in the (1,5) H-shift. This is because the (1,5) H-shift of a cyclohexylperoxy radical requires both the peroxy group and the to-be-abstracted hydrogen locate at an axial position on the cyclohexane ring. The total number of available hydrogens in decalin, MCH, CH, and tetralin is 14, 11, 6, and 4, respectively. Also important is the number of hydrogens available for the (1,5) isomerization of a given peroxy group, i.e., the degeneracy of the (1,5) H-shift. Degeneracy in (1,5) H-shift for decalin, MCH, CH, and tetralin is

  8. Structural Optimization Methodology for Rotating Disks of Aircraft Engines

    NASA Technical Reports Server (NTRS)

    Armand, Sasan C.

    1995-01-01

    In support of the preliminary evaluation of various engine technologies, a methodology has been developed for structurally designing the rotating disks of an aircraft engine. The structural design methodology, along with a previously derived methodology for predicting low-cycle fatigue life, was implemented in a computer program. An interface computer program was also developed that gathers the required data from a flowpath analysis program (WATE) being used at NASA Lewis. The computer program developed for this study requires minimum interaction with the user, thus allowing engineers with varying backgrounds in aeropropulsion to successfully execute it. The stress analysis portion of the methodology and the computer program were verified by employing the finite element analysis method. The 10th- stage, high-pressure-compressor disk of the Energy Efficient Engine Program (E3) engine was used to verify the stress analysis; the differences between the stresses and displacements obtained from the computer program developed for this study and from the finite element analysis were all below 3 percent for the problem solved. The computer program developed for this study was employed to structurally optimize the rotating disks of the E3 high-pressure compressor. The rotating disks designed by the computer program in this study were approximately 26 percent lighter than calculated from the E3 drawings. The methodology is presented herein.

  9. Crystal structure of cyclic nucleotide-binding-like protein from Brucella abortus.

    PubMed

    He, Zheng; Gao, Yuan; Dong, Jing; Ke, Yuehua; Li, Xuemei; Chen, Zeliang; Zhang, Xuejun C

    2015-12-25

    The cyclic nucleotide-binding (CNB)-like protein (CNB-L) from Brucella abortus shares sequence homology with CNB domain-containing proteins. We determined the crystal structure of CNB-L at 2.0 Å resolution in the absence of its C-terminal helix and nucleotide. The 3D structure of CNB-L is in a two-fold symmetric form. Each protomer shows high structure similarity to that of cGMP-binding domain-containing proteins, and likely mimics their nucleotide-free conformation. A key residue, Glu17, mediates the dimerization and prevents binding of cNMP to the canonical ligand-pocket. The structurally observed dimer of CNB-L is stable in solution, and thus is likely to be biologically relevant.

  10. Crystal structure of cyclic nucleotide-binding-like protein from Brucella abortus.

    PubMed

    He, Zheng; Gao, Yuan; Dong, Jing; Ke, Yuehua; Li, Xuemei; Chen, Zeliang; Zhang, Xuejun C

    2015-12-25

    The cyclic nucleotide-binding (CNB)-like protein (CNB-L) from Brucella abortus shares sequence homology with CNB domain-containing proteins. We determined the crystal structure of CNB-L at 2.0 Å resolution in the absence of its C-terminal helix and nucleotide. The 3D structure of CNB-L is in a two-fold symmetric form. Each protomer shows high structure similarity to that of cGMP-binding domain-containing proteins, and likely mimics their nucleotide-free conformation. A key residue, Glu17, mediates the dimerization and prevents binding of cNMP to the canonical ligand-pocket. The structurally observed dimer of CNB-L is stable in solution, and thus is likely to be biologically relevant. PMID:26549229

  11. Neutron structure of the cyclic glucose-bound xylose isomerase E186Q mutant.

    PubMed

    Munshi, Parthapratim; Snell, Edward H; van der Woerd, Mark J; Judge, Russell A; Myles, Dean A A; Ren, Zhong; Meilleur, Flora

    2014-02-01

    Ketol-isomerases catalyze the reversible isomerization between aldoses and ketoses. D-Xylose isomerase carries out the first reaction in the catabolism of D-xylose, but is also able to convert D-glucose to D-fructose. The first step of the reaction is an enzyme-catalyzed ring opening of the cyclic substrate. The active-site amino-acid acid/base pair involved in ring opening has long been investigated and several models have been proposed. Here, the structure of the xylose isomerase E186Q mutant with cyclic glucose bound at the active site, refined against joint X-ray and neutron diffraction data, is reported. Detailed analysis of the hydrogen-bond networks at the active site of the enzyme suggests that His54, which is doubly protonated, is poised to protonate the glucose O5 position, while Lys289, which is neutral, promotes deprotonation of the glucose O1H hydroxyl group via an activated water molecule. The structure also reveals an extended hydrogen-bonding network that connects the conserved residues Lys289 and Lys183 through three structurally conserved water molecules and residue 186, which is a glutamic acid to glutamine mutation.

  12. Structural integrity and failure mechanisms of a smart piezoelectric actuator under a cyclic bending mode

    NASA Astrophysics Data System (ADS)

    Woo, Sung-Choong; Goo, Nam Seo

    2008-08-01

    Information on the onset and evolution of damage within materials is essential for guaranteeing the integrity of actuator systems. The authors have evaluated the structural integrity and the failure mechanisms of smart composite actuators with a PZT ceramic plate under electric cyclic loading. For this, two kinds of actuators, actuator 1 and actuator 2, were manufactured. Prior to the main testing, performance testing was performed on the actuators to determine their resonant frequencies. Electric cyclic tests were conducted up to twenty million cycles. An acoustic emission technique was used for monitoring the damage evolution in real time. We observed the extent of the damage after testing using scanning electron microscopy and reflected optical microscopy to support characteristics in the acoustic emission behavior that corresponded to specific types of damage mechanisms. It was shown that the initial damage mechanism of the smart composite actuator under electric cyclic loading originated from the transgranular micro-fatigue damage in the PZT ceramic layer. With increasing cycles, a local intergranular crack initiated and developed onto the surface of the PZT ceramic layer or propagated into the internal layer. Finally, short-circuiting led to the electric breakdown of the actuator. These results were different depending on the drive frequencies and the configuration of the actuators. Moreover, we differentiated between the aforementioned damage mechanisms via AE signal pattern analyses based on the primary frequency and the waveform. From our results, we conclude that the drive frequency and the existence of a protecting layer are dominant factors in the structural integrity of the smart composite actuator.

  13. Large Molecule Structures by Broadband Fourier Transform Molecular Rotational Spectroscopy

    NASA Astrophysics Data System (ADS)

    Evangelisti, Luca; Seifert, Nathan A.; Spada, Lorenzo; Pate, Brooks

    2016-06-01

    Fourier transform molecular rotational resonance spectroscopy (FT-MRR) using pulsed jet molecular beam sources is a high-resolution spectroscopy technique that can be used for chiral analysis of molecules with multiple chiral centers. The sensitivity of the molecular rotational spectrum pattern to small changes in the three dimensional structure makes it possible to identify diastereomers without prior chemical separation. For larger molecules, there is the additional challenge that different conformations of each diastereomer may be present and these need to be differentiated from the diastereomers in the spectral analysis. Broadband rotational spectra of several larger molecules have been measured using a chirped-pulse FT-MRR spectrometer. Measurements of nootkatone (C15H22O), cedrol (C15H26O), ambroxide (C16H28O) and sclareolide (C16H26O2) are presented. These spectra are measured with high sensitivity (signal-to-noise ratio near 1,000:1) and permit structure determination of the most populated isomers using isotopic analysis of the 13C and 18O isotopologues in natural abundance. The accuracy of quantum chemistry calculations to identify diastereomers and conformers and to predict the dipole moment properties needed for three wave mixing measurements is examined.

  14. Coherent structures in rotating non-neutral plasma

    NASA Astrophysics Data System (ADS)

    Lund, Steven M.; Ramos, Jesus J.; Davidson, Ronald C.

    1993-01-01

    Nonaxisymmetric (∂/∂θ≠0) rotating equilibria are investigated theoretically for strongly magnetized, low-density (ωpe2/ωce2≪1) pure electron plasmas confined in cylindrical geometry. These two-dimensional equilibria are also called rotating coherent structures, and are stationary (time independent) in a frame of reference rotating with angular velocity ωr=const about the cylinder axis (r=0). Radial confinement of the pure electron plasma is provided by a uniform axial magnetic field B0ez, and a grounded, perfectly conducting, cylindrical wall is located at radius r=rw. The analysis is based on a nonrelativistic, guiding-center model in the cold-fluid limit (the continuity and Poisson equations) that treats the electrons as a massless fluid (me→0) with E×B flow velocity Ve=-(c/B0)∇φ×ez. Within this model, general rotating equilibria with electron density ne≡nR(r,θ-ωrt) and electrostatic potential φ≡φR(r,θ-ωrt) have the property that the electron density is functionally related to the streamfunction ψR=-eφR+ωr(eB0/2c)r2 by nR=nR(ψR). The streamfunction ψR satisfies the nonlinear equilibrium equation ∇2ψR=-4πe2nR(ψR)+2ωreB0/c with ψR=ωr(eB0/2c)rw2≡ψw=const on the cylindrical wall at r=rw. Following a general discussion of rotating equilibria, an integral equation formulation of the nonlinear equilibrium equation is developed to investigate equilibria with ``waterbag'' (step-function) density profiles. In this investigation, a numerical method is formulated that can be used to construct diverse classes of highly nonlinear waterbag equilibria. This method is employed to investigate two classes of nonaxisymmetric equilibria that are nonlinear extrapolations of well-known small-amplitude equilibria. These two classes of rotating equilibria bear strong similarities to coherent structures observed experimentally by Driscoll and Fine [Phys. Fluids B 2, 1359 (1990)].

  15. Validation of structural analysis methods using burner liner cyclic rig test data

    NASA Technical Reports Server (NTRS)

    Thompson, R.

    1983-01-01

    The objectives of the hot section technology (HOST) burner liner cyclic rig test program are basically threefold: (1) to assist in developing predictive tools needed to improve design analyses and procedures for the efficient and accurate prediction of burner liner structural response; (2) to calibrate, evaluate and validate these predictive tools by comparing the predicted results with the experimental data generated in the tests; and (3) to evaluate existing as well as advanced temperature and strain measurement instrumentation, both contact and noncontact, in a simulated engine cycle environment. The data generated will include measurements of the thermal environment (metal surface temperatures) as well as structural (strain) and life (fatigue) responses of simulated burner liners and specimens under controlled boundary and operating conditions. These data will be used to calibrate, compare and validate analytical theories, methodologies and design procedures, as well as improvements in them, for predicting liner temperatures, stress-strain responses and cycles to failure. Comparison of predicted results with experimental data will be used to show where the predictive theories, etc. need improvements. In addition, as the predictive tools, as well as the tests, test methods, and data acquisition and reduction techniques, are developed and validated, a proven, integrated analysis/experiment method will be developed to determine the cyclic life of a simulated burner liner.

  16. MAGNETIC STRUCTURE OF RAPIDLY ROTATING FK COMAE-TYPE CORONAE

    SciTech Connect

    Cohen, O.; Drake, J. J.; Kashyap, V. L.; Korhonen, H.; Elstner, D.; Gombosi, T. I.

    2010-08-10

    We present a three-dimensional simulation of the corona of an FK Com-type rapidly rotating G giant using a magnetohydrodynamic model that was originally developed for the solar corona in order to capture the more realistic, non-potential coronal structure. We drive the simulation with surface maps for the radial magnetic field obtained from a stellar dynamo model of the FK Com system. This enables us to obtain the coronal structure for different field topologies representing different periods of time. We find that the corona of such an FK Com-like star, including the large-scale coronal loops, is dominated by a strong toroidal component of the magnetic field. This is a result of part of the field being dragged by the radial outflow, while the other part remains attached to the rapidly rotating stellar surface. This tangling of the magnetic field, in addition to a reduction in the radial flow component, leads to a flattening of the gas density profile with distance in the inner part of the corona. The three-dimensional simulation provides a global view of the coronal structure. Some aspects of the results, such as the toroidal wrapping of the magnetic field, should also be applicable to coronae on fast rotators in general, which our study shows can be considerably different from the well-studied and well-observed solar corona. Studying the global structure of such coronae should also lead to a better understanding of their related stellar processes, such as flares and coronal mass ejections, and in particular should lead to an improved understanding of mass and angular momentum loss from such systems.

  17. POMM: design of rotating mechanism and hexapod structure

    NASA Astrophysics Data System (ADS)

    Côté, Patrice; Leclerc, Mélanie; Demers, Mathieu; Bastien, Pierre; Hernandez, Olivier

    2014-08-01

    The new high precision polarimeter for the "Observatoire du Mont Mégantic" (POMM) is an instrument designed to observe exoplanets and other targets in the visible and near infrared wavebands. The requirements to achieve these observation goals are posing unusual challenges to structural and mechanical designers. In this paper, the detailed design, analysis and laboratory results of the key mechanical structure and sub-systems are presented. First, to study extremely low polarization, the birefringence effect due to stresses in the optical elements must be kept to the lowest possible values. The double-wedge Wollaston custom prism assembly that splits the incoming optical beam is made of bonded α-BBO to N-BK-7 glass lenses. Because of the large mismatch of coefficients of thermal expansion and temperatures as low as -40°C that can be encountered at Mont-Mégantic observatory, a finite element analysis (FEA) model is developed to find the best adhesive system to minimize stresses. Another critical aspect discussed in details is the implementation of the cascaded rotating elements and the twin rotating stages. Special attention is given to the drive mechanism and encoding technology. The objective was to reach high absolute positional accuracy in rotation without any mechanical backlash. As for many other instruments, mass, size and dimensional stability are important critera for the supporting structure. For a cantilevered device, such as POMM, a static hexapod is an attractive solution because of the high stiffness to weight ratio. However, the mechanical analysis revealed that the specific geometry of the dual channel optical layout also added an off-axis counterbalancing problem. To reach an X-Y displacement error on the detector smaller than 35μm for 0-45° zenith angle, further structural optimization was done using FEA. An imaging camera was placed at the detector plane during assembly to measure the actual optical beam shift under varying gravitational

  18. The relationship between cyclic variations in spark-ignition engines and the small structure of turbulence

    SciTech Connect

    Hill, P.G.; Kapil, A. . Dept. of Mechanical Engineering)

    1989-11-01

    The hypothesis that cyclic variations in combustion in spark-ignition engines originate in the small-scale structure of turbulence is further examined in the light of experimental data from a single-cylinder research engine. The data cover a wide range of engine speed and equivalence ratio. The effects of spark electrode geometry, spark gap, chamber geometry, and throttling are examined. The general conclusion is that the standard deviation in burning time, deduced for the smallest size flame kernels, is estimated within experimental uncertainty by a parameter {lambda}4{mu}/sub l/, in which {lambda} is the Taylor microscale and {mu}/sub l/ is the laminar burning velocity of the unburned mixture. The experimental results are thus consistent with the interaction of an effectively point-source ignition with the turbulence structure model of Tennekes, and with the idea that rapid burning takes place in the vortex tube regions of high dissipation.

  19. Structure of the singularity inside a realistic rotating black hole

    NASA Astrophysics Data System (ADS)

    Ori, Amos

    1992-04-01

    The structure and results of an analysis of the asymptotic behavior of nonlinear, asymmetric, metric perturbations near the Cauchy horizon inside a Kerr black hole are presented. This analysis suggests that metric perturbations, to all orders in the perturbation expansion, are finite and small at the Cauchy horizon, even though their gradients (and the curvature) diverge there. Accordingly, objects which fall into a realistic rotating blackhole a longtime after the collapse will not be crushed by a tidal gravitational deformations as they approach the curvature singularity.

  20. Femtosecond-laser fabrication of cyclic structures in the bulk of transparent dielectrics

    NASA Astrophysics Data System (ADS)

    Vartapetov, S. K.; Ganin, D. V.; Lapshin, K. E.; Obidin, A. Z.

    2015-08-01

    We report the results of the experiments on developing precision micromachining technology, obtained under the conditions of focusing the pulses of a femtosecond (FS) laser into the volume of a transparent material, which is important, particularly, in the processing of biomaterials in ophthalmology. The implementation conditions and some characteristic features of the special regime of micromachining are determined, when at a definite relation between the sample scanning velocity and the repetition rate of FS pulses the region, destroyed by the laser radiation, is shifted along the optical axis towards the objective and back, forming cyclic patterns inside the sample. It is supposed that the main causes of the damage region shift are the induced modification of the refractive index and the reduction of the damage threshold due to the change in the material density and structure in the microscopic domain, adjacent to the boundary of the cavity produced by the previous pulse. The results of the performed study with the above regime taken into account were used in the technology of precision cutting of crystals, glasses and polymers. The best quality of the cut surface is achieved under the conditions, eliminating the appearance of the cyclic regime. In the samples of polycarbonate, polymethyl methacrylate and fused silica the cylindrical cavities were obtained with the aspect ratio higher than 200, directed along the laser beam, and microcapillaries with the diameter 1 - 2 μm in the direction, perpendicular to this beam.

  1. Sequence-specific 1H assignment and secondary structure of the bacteriocin AS-48 cyclic peptide.

    PubMed

    Langdon, G M; Bruix, M; Gálvez, A; Valdivia, E; Maqueda, M; Rico, M

    1998-07-01

    The bacteriocin AS-48 is a cationic peptide (7149 Da) having a broad antimicrobial spectrum, encoded by the 68 kb conjugative plasmid pMB2 from Enterococcus faecalis S-48. It is a unique peptide since it has a cyclic structure, which is achieved by the formation of a tail-head peptide bond after ribosomal synthesis (Gálvez et al., 1989; Martínez-Bueno et al., 1994; Samyn et al., 1994). Preliminary CD and calorimetric studies (data not shown) pointed towards a highly helical and very stable three dimensional structure. All the information gathered until now indicates that the target of AS-48 is the cytoplasmic membrane in which it opens channels or pores, leading to dissipation of the proton motive force and cell death, which in some cases is also followed by bacterial lysis (Gálvez et al., 1991). This peptide is a suitable tool for studying protein-membrane interactions, and it also offers promising perspectives for biotechnological applications. Knowledge of the 3D structure of AS-48 is a first step in the conduct of further structure-function studies. Here we report the complete 1H NMR assignment of its proton resonances together with the resulting secondary structure pattern as prerequisites for the determination of a high-resolution 3D solution structure.

  2. Correlation of electronic structures of three cyclic dipeptides with their photoemission spectra

    NASA Astrophysics Data System (ADS)

    Arachchilage, Anoja P. Wickrama; Wang, Feng; Feyer, Vitaliy; Plekan, Oksana; Prince, Kevin C.

    2010-11-01

    We have investigated the electronic structure of three cyclic dipeptides: cyclo(Glycyl-Glycyl) (cGG), cyclo(Leucyl-Prolyl) (cLP), and cyclo(Phenylalanyl-Prolyl) (cPP). These compounds are biologically active and cLP and cPP are derived from cGG (also known as diketopiperazine), by the addition of the respective functional groups of the amino acids, namely, phenyl, alkyl or a fused pyrrolidine ring (proline). Experimental valence and core level spectra have been interpreted in the light of theoretical calculations to identify the basic chemical properties associated with the central ring, and with the additional functional groups in cLP and cPP. The theoretically simulated spectra of all three cyclic dipeptides in both valence and core spaces agreed reasonably well with the experimental spectra. The three molecules displayed similarities in their core spectra, suggesting that the diketopiperazine structure plays an important role in determining the inner shell spectrum. The experimental C 1s spectra of cLP and cPP are analogous but differ from cGG due to the side chains attached to the diketopiperazine structure. Single spectral peaks in the N 1s (and O 1s) spectra of the dipeptides indicate that the chemical environment of the nitrogen atoms (and oxygen atoms) are very similar, although they show a small splitting in the simulated spectra of cPL and cPP, due to the reduction of their point group symmetry. Valence band spectra of the three dipeptides in the frontier orbital region of 9-11 eV exhibit similarities; however theoretical analysis shows that significant changes occur due to the involvement of the side chain in the frontier orbitals of cPP, while lesser changes are found for cLP.

  3. Synthesis, crystal structure and NMR investigation of a new type of cyclic steroidal dimer based on brassinosteroids

    NASA Astrophysics Data System (ADS)

    Khripach, Vladimir A.; Zhabinskii, Vladimir N.; Konstantinova, Olga V.; Tsavlovskii, Dmitrii V.; Baranovsky, Alexander V.; Lyakhov, Alexander S.; Drašar, Pavel

    2013-01-01

    A new type of cyclic steroidal dimer based on brassinosteroids has been synthesized via the reaction of 24-epibrassinolide with 1,4-phenylenediboronic acid and structurally characterized by single-crystal X-ray diffraction and 2D NMR analysis. The crystal structure of the dimer was found to contain rather large solvent accessible voids.

  4. Rotational Spectrum and Carbon Atom Structure of Dihydroartemisinic Acid

    NASA Astrophysics Data System (ADS)

    Evangelisti, Luca; Seifert, Nathan A.; Spada, Lorenzo; Pate, Brooks

    2016-06-01

    Dihydroartemisinic acid (DHAA, C15H24O2, five chiral centers) is a precursor in proposed low-cost synthetic routes to the antimalarial drug artemisinin. In one reaction process being considered in pharmaceutical production, DHAA is formed from an enantiopure sample of artemisinic acid through hydrogenation of the alkene. This reaction needs to properly set the stereochemistry of the asymmetric carbon for the synthesis to produce artemisinin. A recrystallization process can purify the diastereomer mixture of the hydrogenation reaction if the unwanted epimer is produced in less than 10% abundance. There is a need in the process analytical chemistry to rapidly (less than 1 min) measure the diastereomer excess and current solutions, such a HPLC, lack the needed measurement speed. The rotational spectrum of DHAA has been measured at 300:1 signal-to-noise ratio in a chirped-pulsed Fourier transform microwave spectrometer operating from 2-8 GHz using simple heating of the compound. The 13C isotope analysis provides a carbon atom structure that confirms the diastereomer. This structure is in excellent agreement with quantum chemistry calculations at the B2PLYPD3/ 6-311++G** level of theory. The DHAA spectrum is expected to be fully resolved from the unwanted diastereomer raising the potential for fast diastereomer excess measurement by rotational spectroscopy in the pharmaceutical production process.

  5. Structural and Functional Analysis of DDX41: a bispecific immune receptor for DNA and cyclic dinucleotide

    PubMed Central

    Omura, Hiroki; Oikawa, Daisuke; Nakane, Takanori; Kato, Megumi; Ishii, Ryohei; Ishitani, Ryuichiro; Tokunaga, Fuminori; Nureki, Osamu

    2016-01-01

    In the innate immune system, pattern recognition receptors (PRRs) specifically recognize ligands derived from bacteria or viruses, to trigger the responsible downstream pathways. DEAD box protein 41 (DDX41) is an intracellular PRR that triggers the downstream pathway involving the adapter STING, the kinase TBK1, and the transcription factor IRF3, to activate the type I interferon response. DDX41 is unique in that it recognizes two different ligands; i.e., double-stranded DNA (dsDNA) and cyclic dinucleotides (CDN), via its DEAD domain. However, the structural basis for the ligand recognition by the DDX41 DEAD domain has remained elusive. Here, we report two crystal structures of the DDX41 DEAD domain in apo forms, at 1.5 and 2.2 Å resolutions. A comparison of the two crystal structures revealed the flexibility in the ATP binding site, suggesting its formation upon ATP binding. Structure-guided functional analyses in vitro and in vivo demonstrated the overlapped binding surface for dsDNA and CDN, which is distinct from the ATP-binding site. We propose that the structural rearrangement of the ATP binding site is crucial for the release of ADP, enabling the fast turnover of DDX41 for the dsDNA/CDN-induced STING activation pathway. PMID:27721487

  6. Degradation and COD removal of catechol in wastewater using the catalytic ozonation process combined with the cyclic rotating-bed biological reactor.

    PubMed

    Aghapour, Ali Ahmad; Moussavi, Gholamreza; Yaghmaeian, Kamyar

    2015-07-01

    The effect of ozonation catalyzed with MgO/granular activated carbon (MgO/GAC) composite as a pretreatment process on the performance of cyclic rotating-bed biological reactor (CRBR) for the catechol removal from wastewater has been investigated. CRBR with acclimated biomasses could efficiently remove catechol and its related COD from wastewater at organic loading rate (OLR) of 7.82 kg COD/m(3).d (HRT of 9 h). Then, OLR increased to 15.64 kg COD/m(3).d (HRT of 4.5 h) and CRBR failed. Catalytic ozonation process (COP) used as a pre-treatment and could improve the performance of the failed CRBR. The overall removal efficiency of the combined process attained respective steady states of 91% and 79% for degradation and COD removal of catechol. Therefore, the combined process is more effective in degradation and COD removal of catechol; it is also a viable alternative for upgrading industrial wastewater treatment plant.

  7. Carbon dioxide in an ionic liquid: Structural and rotational dynamics.

    PubMed

    Giammanco, Chiara H; Kramer, Patrick L; Yamada, Steven A; Nishida, Jun; Tamimi, Amr; Fayer, Michael D

    2016-03-14

    Ionic liquids (ILs), which have widely tunable structural motifs and intermolecular interactions with solutes, have been proposed as possible carbon capture media. To inform the choice of an optimal ionic liquid system, it can be useful to understand the details of dynamics and interactions on fundamental time scales (femtoseconds to picoseconds) of dissolved gases, particularly carbon dioxide (CO2), within the complex solvation structures present in these uniquely organized materials. The rotational and local structural fluctuation dynamics of CO2 in the room temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EmimNTf2) were investigated by using ultrafast infrared spectroscopy to interrogate the CO2 asymmetric stretch. Polarization-selective pump probe measurements yielded the orientational correlation function of the CO2 vibrational transition dipole. It was found that reorientation of the carbon dioxide occurs on 3 time scales: 0.91 ± 0.03, 8.3 ± 0.1, 54 ± 1 ps. The initial two are attributed to restricted wobbling motions originating from a gating of CO2 motions by the IL cations and anions. The final (slowest) decay corresponds to complete orientational randomization. Two-dimensional infrared vibrational echo (2D IR) spectroscopy provided information on structural rearrangements, which cause spectral diffusion, through the time dependence of the 2D line shape. Analysis of the time-dependent 2D IR spectra yields the frequency-frequency correlation function (FFCF). Polarization-selective 2D IR experiments conducted on the CO2 asymmetric stretch in the parallel- and perpendicular-pumped geometries yield significantly different FFCFs due to a phenomenon known as reorientation-induced spectral diffusion (RISD), revealing strong vector interactions with the liquid structures that evolve slowly on the (independently measured) rotation time scales. To separate the RISD contribution to the FFCF from the structural spectral

  8. Carbon dioxide in an ionic liquid: Structural and rotational dynamics

    NASA Astrophysics Data System (ADS)

    Giammanco, Chiara H.; Kramer, Patrick L.; Yamada, Steven A.; Nishida, Jun; Tamimi, Amr; Fayer, Michael D.

    2016-03-01

    Ionic liquids (ILs), which have widely tunable structural motifs and intermolecular interactions with solutes, have been proposed as possible carbon capture media. To inform the choice of an optimal ionic liquid system, it can be useful to understand the details of dynamics and interactions on fundamental time scales (femtoseconds to picoseconds) of dissolved gases, particularly carbon dioxide (CO2), within the complex solvation structures present in these uniquely organized materials. The rotational and local structural fluctuation dynamics of CO2 in the room temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EmimNTf2) were investigated by using ultrafast infrared spectroscopy to interrogate the CO2 asymmetric stretch. Polarization-selective pump probe measurements yielded the orientational correlation function of the CO2 vibrational transition dipole. It was found that reorientation of the carbon dioxide occurs on 3 time scales: 0.91 ± 0.03, 8.3 ± 0.1, 54 ± 1 ps. The initial two are attributed to restricted wobbling motions originating from a gating of CO2 motions by the IL cations and anions. The final (slowest) decay corresponds to complete orientational randomization. Two-dimensional infrared vibrational echo (2D IR) spectroscopy provided information on structural rearrangements, which cause spectral diffusion, through the time dependence of the 2D line shape. Analysis of the time-dependent 2D IR spectra yields the frequency-frequency correlation function (FFCF). Polarization-selective 2D IR experiments conducted on the CO2 asymmetric stretch in the parallel- and perpendicular-pumped geometries yield significantly different FFCFs due to a phenomenon known as reorientation-induced spectral diffusion (RISD), revealing strong vector interactions with the liquid structures that evolve slowly on the (independently measured) rotation time scales. To separate the RISD contribution to the FFCF from the structural spectral

  9. Structure of merger remnants. II - Progenitors with rotating bulges

    NASA Technical Reports Server (NTRS)

    Hernquist, Lars

    1993-01-01

    Mergers of identical galaxies consisting of self-gravitating disks, bulges, and halos are examined in the context of the suggestion that such events may form elliptical galaxies. Unlike earlier studies, the simulations reported here include effects arising from intrinsic spin of bulges. It is found that the disks and bulges are able to redistribute their angular momentum so that the luminous remnants rotate slowly near their centers. In addition, if the bulges are sufficiently concentrated, the core radii of the remnants are significantly reduced relative to those of end-states formed in mergers between pure stellar disks to the extent that the remnants share structural properties with observed elliptical galaxies. Nevertheless, it does appear that stellar-dynamical mergers between spiral progenitors will represent a viable mechanism for the production of massive elliptical galaxies only if sufficient mass resides already in dense, spheroidal components. These results suggest that any ellipticals formed in this manner having featureless light profiles were victims of a 'disk-bulge conspiracy' analogous to the disk-halo conspiracy thought to give rise to smooth rotation curves in spiral galaxies. Possible observational signatures of mergers are discussed, along with implications of the findings for our understanding of galaxy formation and evolution.

  10. Tetrasulfur, S4: rotational spectrum, interchange tunneling, and geometrical structure.

    PubMed

    McCarthy, M C; Thorwirth, S; Gottlieb, C A; Thaddeus, P

    2004-07-01

    The rotational spectrum of S4 has been observed for the first time in an electrical discharge through sulfur vapor. Two techniques have been used: Fourier transform microwave spectroscopy and long-path millimeter-wave absorption spectroscopy. Small, but systematic shifts of the measured transition frequencies of the normal isotopic species indicate that S4 has C2v symmetry but with a low-lying transition state of D2h symmetry, yielding interchange tunneling at 14.1(2) kHz in its ground vibrational state. From the rotational constants of the normal and the single 34S isotopic species, an experimental (r0) structure has been derived: S4 is a singlet planar trapezoid with a terminal bond length of 1.899(7) A, a central bond of 2.173(32) A, and an S-S-S angle of 103.9(8) degrees. Like thiozone (S3), S4 is a candidate for detection in the atmosphere of the Jovian moon Io and in other astronomical sources. PMID:15260588

  11. Anisotropic Structure of Rotating Homogeneous Turbulence at High Reynolds Numbers

    NASA Technical Reports Server (NTRS)

    Cambon, Claude; Mansour, Nagi N.; Squires, Kyle D.; Rai, Man Mohan (Technical Monitor)

    1995-01-01

    Large eddy simulation is used to investigate the development of anisotropies and the evolution towards a quasi two-dimensional state in rotating homogeneous turbulence at high Reynolds number. The present study demonstrates the existence of two transitions in the development of anisotropy. The first transition marks the onset of anisotropy and occurs when a macro-Rossby number (based on a longitudinal integral lengthscale) has decreased to near unity while the second transition occurs when a micro-Rossby number (defined in this work as the ratio of the rms fluctuating vorticity to background vorticity) has decreased to unity. The anisotropy marked by the first transition corresponds to a reduction in dimensionality while the second transition corresponds to a polarization of the flow, i.e., relative dominance of the velocity components in the plane normal to the rotation axis. Polarization is reflected by emergence of anisotropy measures based on the two-dimensional component of the turbulence. Investigation of the vorticity structure shows that the second transition is also characterized by an increasing tendency for alignment between the fluctuating vorticity vector and the background angular velocity vector with a preference for corrotative vorticity.

  12. Anisotropic structure of homogeneous turbulence subjected to uniform rotation

    NASA Technical Reports Server (NTRS)

    Cambon, C.; Mansour, N. N.; Squires, K. D.

    1994-01-01

    Large-eddy simulation results are used to investigate the development of anisotropies and the possible transition towards a quasi two-dimensional state in rotating turbulence at high Reynolds number. The present study demonstrates the existence of two transitions that are identified by two Rossby numbers. The first transition marks the onset of anisotropic effects and corresponds to a macro Rossby number Ro(sup L) (based on a longitudinal integral length scale) near unity. A second transition can be defined in terms of a lower bound of micro-Rossby number Ro(sup w) also near unity (defined in this work as the ratio of the rms fluctuating vorticity to background vorticity) and corresponds to a continued development of anisotropy but with an increasing emergence of those indicators based on the pure two-dimensional component of the flow, e.g., integral length scales measured along the rotation axis. Investigation of the vorticity structure shows that the second transition is also characterized by an increasing tendency for alignment between the fluctuating vorticity vector and the basic angular velocity vector with a preference for corotative vorticity.

  13. Exciton Localization in Extended π-Electron Systems: Comparison of Linear and Cyclic Structures.

    PubMed

    Thiessen, Alexander; Würsch, Dominik; Jester, Stefan-S; Aggarwal, A Vikas; Idelson, Alissa; Bange, Sebastian; Vogelsang, Jan; Höger, Sigurd; Lupton, John M

    2015-07-30

    We employ five π-conjugated model materials of different molecular shape-oligomers and cyclic structures-to investigate the extent of exciton self-trapping and torsional motion of the molecular framework following optical excitation. Our studies combine steady state and transient fluorescence spectroscopy in the ensemble with measurements of polarization anisotropy on single molecules, supported by Monte Carlo simulations. The dimer exhibits a significant spectral red shift within ∼100 ps after photoexcitation which is attributed to torsional relaxation. This relaxation mechanism is inhibited in the structurally rigid macrocyclic analogue. However, both systems show a high degree of exciton localization but with very different consequences: while, in the macrocycle, the exciton localizes randomly on different parts of the ring, scrambling polarization memory, in the dimer, localization leads to a deterministic exciton position with luminescence characteristics of a dipole. Monte Carlo simulations allow us to quantify the structural difference between the emitting and absorbing units of the π-conjugated system in terms of disorder parameters.

  14. Bacteriocin AS-48, a microbial cyclic polypeptide structurally and functionally related to mammalian NK-lysin.

    PubMed

    González, C; Langdon, G M; Bruix, M; Gálvez, A; Valdivia, E; Maqueda, M; Rico, M

    2000-10-10

    The solution structure of bacteriocin AS-48, a 70-residue cyclic polypeptide from Enterococcus faecalis, consists of a globular arrangement of five alpha-helices enclosing a compact hydrophobic core. The head-to-tail union lies in the middle of helix 5, a fact that is shown to have a pronounced effect on the stability of the three-dimensional structure. Positive charges in the side chains of residues in helix 4 and in the turn linking helix 4 to helix 5 form a cluster that most probably determine its antibacterial activity by promoting pore formation in cell membranes. A similar five-helix structural motif has been found in the antimicrobial NK-lysin, an effector polypeptide of T and natural killer (NK) cells. Bacteriocin AS-48 lacks the three disulfide bridges characteristic of the saposin fold present in NK-lysin, and has no sequence homology with it. Nevertheless, the similar molecular architecture and high positive charge strongly suggest a common mechanism of antibacterial action.

  15. Bacteriocin AS-48, a microbial cyclic polypeptide structurally and functionally related to mammalian NK-lysin

    PubMed Central

    González, Carlos; Langdon, Grant M.; Bruix, Marta; Gálvez, Antonio; Valdivia, Eva; Maqueda, Mercedes; Rico, Manuel

    2000-01-01

    The solution structure of bacteriocin AS-48, a 70-residue cyclic polypeptide from Enterococcus faecalis, consists of a globular arrangement of five α-helices enclosing a compact hydrophobic core. The head-to-tail union lies in the middle of helix 5, a fact that is shown to have a pronounced effect on the stability of the three-dimensional structure. Positive charges in the side chains of residues in helix 4 and in the turn linking helix 4 to helix 5 form a cluster that most probably determine its antibacterial activity by promoting pore formation in cell membranes. A similar five-helix structural motif has been found in the antimicrobial NK-lysin, an effector polypeptide of T and natural killer (NK) cells. Bacteriocin AS-48 lacks the three disulfide bridges characteristic of the saposin fold present in NK-lysin, and has no sequence homology with it. Nevertheless, the similar molecular architecture and high positive charge strongly suggest a common mechanism of antibacterial action. PMID:11005847

  16. Rgg protein structure-function and inhibition by cyclic peptide compounds.

    PubMed

    Parashar, Vijay; Aggarwal, Chaitanya; Federle, Michael J; Neiditch, Matthew B

    2015-04-21

    Peptide pheromone cell-cell signaling (quorum sensing) regulates the expression of diverse developmental phenotypes (including virulence) in Firmicutes, which includes common human pathogens, e.g., Streptococcus pyogenes and Streptococcus pneumoniae. Cytoplasmic transcription factors known as "Rgg proteins" are peptide pheromone receptors ubiquitous in Firmicutes. Here we present X-ray crystal structures of a Streptococcus Rgg protein alone and in complex with a tight-binding signaling antagonist, the cyclic undecapeptide cyclosporin A. To our knowledge, these represent the first Rgg protein X-ray crystal structures. Based on the results of extensive structure-function analysis, we reveal the peptide pheromone-binding site and the mechanism by which cyclosporin A inhibits activation of the peptide pheromone receptor. Guided by the Rgg-cyclosporin A complex structure, we predicted that the nonimmunosuppressive cyclosporin A analog valspodar would inhibit Rgg activation. Indeed, we found that, like cyclosporin A, valspodar inhibits peptide pheromone activation of conserved Rgg proteins in medically relevant Streptococcus species. Finally, the crystal structures presented here revealed that the Rgg protein DNA-binding domains are covalently linked across their dimerization interface by a disulfide bond formed by a highly conserved cysteine. The DNA-binding domain dimerization interface observed in our structures is essentially identical to the interfaces previously described for other members of the XRE DNA-binding domain family, but the presence of an intermolecular disulfide bond buried in this interface appears to be unique. We hypothesize that this disulfide bond may, under the right conditions, affect Rgg monomer-dimer equilibrium, stabilize Rgg conformation, or serve as a redox-sensitive switch.

  17. Engineering Skills Formation in Britain: Cyclical and Structural Issues. Towards a National Skills Agenda. Skills Task Force Research Paper 7.

    ERIC Educational Resources Information Center

    Mason, Geoff

    Cyclical and structural issues in engineering skills formation in Great Britain were studied through a review of recent employment patterns, income patterns, employment projections, recent trends in education and training, and recent developments in technology and work organization. The review focused on the following issues: (1) the extent and…

  18. Cyclic and Linear Monoterpenes in Phospholipid Membranes: Phase Behavior, Bilayer Structure, and Molecular Dynamics.

    PubMed

    Pham, Quoc Dat; Topgaard, Daniel; Sparr, Emma

    2015-10-13

    Monoterpenes are abundant in essential oils extracted from plants. These relatively small and hydrophobic molecules have shown important biological functions, including antimicrobial activity and membrane penetration enhancement. The interaction between the monoterpenes and lipid bilayers is considered important to the understanding of the biological functions of monoterpenes. In this study, we investigated the effect of cyclic and linear monoterpenes on the structure and dynamics of lipids in model membranes. We have studied the ternary system 1,2-dimyristoyl-sn-glycero-3-phosphocholine-monoterpene-water as a model with a focus on dehydrated conditions. By combining complementary techniques, including differential scanning calorimetry, solid-state nuclear magnetic resonance, and small- and wide-angle X-ray scattering, bilayer structure, phase transitions, and lipid molecular dynamics were investigated at different water contents. Monoterpenes cause pronounced melting point depression and phase segregation in lipid bilayers, and the extent of these effects depends on the hydration conditions. The addition of a small amount of thymol to the fluid bilayer (volume fraction of 0.03 in the bilayer) leads to an increased order in the acyl chain close to the bilayer interface. The findings are discussed in relation to biological systems and lipid formulations. PMID:26375869

  19. Structural, nanomechanical, and computational characterization of D,L-cyclic peptide assemblies.

    PubMed

    Rubin, Daniel J; Amini, Shahrouz; Zhou, Feng; Su, Haibin; Miserez, Ali; Joshi, Neel S

    2015-03-24

    The rigid geometry and tunable chemistry of D,L-cyclic peptides makes them an intriguing building-block for the rational design of nano- and microscale hierarchically structured materials. Herein, we utilize a combination of electron microscopy, nanomechanical characterization including depth sensing-based bending experiments, and molecular modeling methods to obtain the structural and mechanical characteristics of cyclo-[(Gln-D-Leu)4] (QL4) assemblies. QL4 monomers assemble to form large, rod-like structures with diameters up to 2 μm and lengths of tens to hundreds of micrometers. Image analysis suggests that large assemblies are hierarchically organized from individual tubes that undergo bundling to form larger structures. With an elastic modulus of 11.3 ± 3.3 GPa, hardness of 387 ± 136 MPa and strength (bending) of 98 ± 19 MPa the peptide crystals are among the most robust known proteinaceous micro- and nanofibers. The measured bending modulus of micron-scale fibrils (10.5 ± 0.9 GPa) is in the same range as the Young's modulus measured by nanoindentation indicating that the robust nanoscale network from which the assembly derives its properties is preserved at larger length-scales. Materials selection charts are used to demonstrate the particularly robust properties of QL4 including its specific flexural modulus in which it outperforms a number of biological proteinaceous and nonproteinaceous materials including collagen and enamel. The facile synthesis, high modulus, and low density of QL4 fibers indicate that they may find utility as a filler material in a variety of high efficiency, biocompatible composite materials.

  20. Structural, nanomechanical, and computational characterization of D,L-cyclic peptide assemblies.

    PubMed

    Rubin, Daniel J; Amini, Shahrouz; Zhou, Feng; Su, Haibin; Miserez, Ali; Joshi, Neel S

    2015-03-24

    The rigid geometry and tunable chemistry of D,L-cyclic peptides makes them an intriguing building-block for the rational design of nano- and microscale hierarchically structured materials. Herein, we utilize a combination of electron microscopy, nanomechanical characterization including depth sensing-based bending experiments, and molecular modeling methods to obtain the structural and mechanical characteristics of cyclo-[(Gln-D-Leu)4] (QL4) assemblies. QL4 monomers assemble to form large, rod-like structures with diameters up to 2 μm and lengths of tens to hundreds of micrometers. Image analysis suggests that large assemblies are hierarchically organized from individual tubes that undergo bundling to form larger structures. With an elastic modulus of 11.3 ± 3.3 GPa, hardness of 387 ± 136 MPa and strength (bending) of 98 ± 19 MPa the peptide crystals are among the most robust known proteinaceous micro- and nanofibers. The measured bending modulus of micron-scale fibrils (10.5 ± 0.9 GPa) is in the same range as the Young's modulus measured by nanoindentation indicating that the robust nanoscale network from which the assembly derives its properties is preserved at larger length-scales. Materials selection charts are used to demonstrate the particularly robust properties of QL4 including its specific flexural modulus in which it outperforms a number of biological proteinaceous and nonproteinaceous materials including collagen and enamel. The facile synthesis, high modulus, and low density of QL4 fibers indicate that they may find utility as a filler material in a variety of high efficiency, biocompatible composite materials. PMID:25757883

  1. Structure and Energetics of Allosteric Regulation of HCN2 Ion Channels by Cyclic Nucleotides.

    PubMed

    DeBerg, Hannah A; Brzovic, Peter S; Flynn, Galen E; Zagotta, William N; Stoll, Stefan

    2016-01-01

    Hyperpolarization-activated cyclic nucleotide-gated (HCN) ion channels play an important role in regulating electrical activity in the heart and brain. They are gated by the binding of cyclic nucleotides to a conserved, intracellular cyclic nucleotide-binding domain (CNBD), which is connected to the channel pore by a C-linker region. Binding of cyclic nucleotides increases the rate and extent of channel activation and shifts it to less hyperpolarized voltages. We probed the allosteric mechanism of different cyclic nucleotides on the CNBD and on channel gating. Electrophysiology experiments showed that cAMP, cGMP, and cCMP were effective agonists of the channel and produced similar increases in the extent of channel activation. In contrast, electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) on the isolated CNBD indicated that the induced conformational changes and the degrees of stabilization of the active conformation differed for the three cyclic nucleotides. We explain these results with a model where different allosteric mechanisms in the CNBD all converge to have the same effect on the C-linker and render all three cyclic nucleotides similarly potent activators of the channel. PMID:26559974

  2. Structure and Energetics of Allosteric Regulation of HCN2 Ion Channels by Cyclic Nucleotides*

    PubMed Central

    DeBerg, Hannah A.; Brzovic, Peter S.; Flynn, Galen E.; Zagotta, William N.; Stoll, Stefan

    2016-01-01

    Hyperpolarization-activated cyclic nucleotide-gated (HCN) ion channels play an important role in regulating electrical activity in the heart and brain. They are gated by the binding of cyclic nucleotides to a conserved, intracellular cyclic nucleotide-binding domain (CNBD), which is connected to the channel pore by a C-linker region. Binding of cyclic nucleotides increases the rate and extent of channel activation and shifts it to less hyperpolarized voltages. We probed the allosteric mechanism of different cyclic nucleotides on the CNBD and on channel gating. Electrophysiology experiments showed that cAMP, cGMP, and cCMP were effective agonists of the channel and produced similar increases in the extent of channel activation. In contrast, electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) on the isolated CNBD indicated that the induced conformational changes and the degrees of stabilization of the active conformation differed for the three cyclic nucleotides. We explain these results with a model where different allosteric mechanisms in the CNBD all converge to have the same effect on the C-linker and render all three cyclic nucleotides similarly potent activators of the channel. PMID:26559974

  3. About parallel computing on spatial rotations in spin mesomorphic structures

    NASA Astrophysics Data System (ADS)

    Nesterov, Michal M.; Tarkhanov, Victor I.

    2004-05-01

    An approach to coherent parallel computing on finite spatial rotations is considered. It is shown that such rotations are elements of 4-dimensional (4D) space and to design any algorithms with them we need to change Boole logic to more complicated rotational one. The latter is provided by formalism of Cayley-Klein parameters, which is compatible with geometric Clifford algebra and all its elements of pure and mixed grades: vectors, scalars, paravectors, quaternions, spinors, etc.

  4. Molecular structure and mechanisms of action of cyclic and linear ion transport antibiotics.

    PubMed

    Duax, W L; Griffin, J F; Langs, D A; Smith, G D; Grochulski, P; Pletnev, V; Ivanov, V

    1996-01-01

    Ionophores are antibiotics that induce ion transport across natural and artificial membranes. The specific function of a given ionophore depends upon its selectivity and the kinetics of ion capture, transport, and release. Systematic studies of complexed and uncomplexed forms of linear and cyclic ionophores provide insight into molecular mechanisms of ion capture and release and the basis for ion selectivity. The cyclic dodecadepsipeptide valinomycin, cyclo[(-L-Val-D-Hyi-D-Val-L-Lac)3-], transports potassium ions across cellular membrane bilayers selectively. The x-ray crystallographic and nmr spectroscopic data concerning the structures of Na+, K+, and Ba+2 complexes are consistent and provide a rationale for the K+ selectivity of valinomycin. Three significantly different conformations of valinomycin are observed in anhydrous crystals, in hydrated crystals grown from dimethylsulfoxide, and in crystals grown from dioxane. Each of these conformations suggests a different mechanism of ion capture. One of the observed conformations has an elliptical structure stabilized by four 4<--1 intramolecular hydrogen bonds and two 5<--1 hydrogen bonds. Ion capture could be readily achieved by disruption of the 5<--1 hydrogen bonds to permit coordination to a potassium ion entering the cavity. The conformation found in crystals obtained from dimethyl sulfoxide is an open flower shape having three petals and three 4<--1 hydrogen bonds. Complexation could proceed by a closing up of the three petals of the flower around the desolvating ion. In the third form, water molecules reside in the central cavity of a bracelet structure having six 4<--1 hydrogen bonds. Two of these bracelets stack over one another with their valine-rich faces surrounding a dioxane molecule. The stacked molecules form a channel approximately 20 A in length, suggesting that under certain circumstances valinomycin might function as a channel. A series of analogues of valinomycin differing in ring composition

  5. Resonance assisted hydrogen bonds in open-chain and cyclic structures of malonaldehyde enol: A theoretical study

    NASA Astrophysics Data System (ADS)

    Trujillo, Cristina; Sánchez-Sanz, Goar; Alkorta, Ibon; Elguero, José; Mó, Otilia; Yáñez, Manuel

    2013-09-01

    In 1989 Gilli, Bellucci, Ferretti and Bertolasi introduced the notion of Resonance Assisted Hydrogen Bonding (RAHB) one of the most fruitful concepts in structural chemistry. After reviewing our previous contributions to this topic, the present work analyzes theoretically this concept especially in non-cyclic structures. Geometries, electron densities and Laplacian at the bond critical points, cooperativity through many body interaction energies, deformation energies as well as NMR properties (chemical shifts and 2hJOO coupling constants) are used for the discussion.

  6. Genome-based discovery, structure prediction and functional analysis of cyclic lipopeptide antibiotics in Pseudomonas species.

    PubMed

    de Bruijn, Irene; de Kock, Maarten J D; Yang, Meng; de Waard, Pieter; van Beek, Teris A; Raaijmakers, Jos M

    2007-01-01

    Analysis of microbial genome sequences have revealed numerous genes involved in antibiotic biosynthesis. In Pseudomonads, several gene clusters encoding non-ribosomal peptide synthetases (NRPSs) were predicted to be involved in the synthesis of cyclic lipopeptide (CLP) antibiotics. Most of these predictions, however, are untested and the association between genome sequence and biological function of the predicted metabolite is lacking. Here we report the genome-based identification of previously unknown CLP gene clusters in plant pathogenic Pseudomonas syringae strains B728a and DC3000 and in plant beneficial Pseudomonas fluorescens Pf0-1 and SBW25. For P. fluorescens SBW25, a model strain in studying bacterial evolution and adaptation, the structure of the CLP with a predicted 9-amino acid peptide moiety was confirmed by chemical analyses. Mutagenesis confirmed that the three identified NRPS genes are essential for CLP synthesis in strain SBW25. CLP production was shown to play a key role in motility, biofilm formation and in activity of SBW25 against zoospores of Phytophthora infestans. This is the first time that an antimicrobial metabolite is identified from strain SBW25. The results indicate that genome mining may enable the discovery of unknown gene clusters and traits that are highly relevant in the lifestyle of plant beneficial and plant pathogenic bacteria.

  7. The Structural Basis of Cyclic Diguanylate Signal Transduction by PilZ Domains

    SciTech Connect

    Benach,J.; Swaminathan, S.; Tamayo, R.; Handelman, S.; Folta-Stogniew, E.; Ramos, J.; Forouhar, F.; Neely, H.; Seetharaman, J.; et al

    2007-01-01

    The second messenger cyclic diguanylate (c-di-GMP) controls the transition between motile and sessile growth in eubacteria, but little is known about the proteins that sense its concentration. Bioinformatics analyses suggested that PilZ domains bind c-di-GMP and allosterically modulate effector pathways. We have determined a 1.9 Angstroms crystal structure of c-di-GMP bound to VCA0042/PlzD, a PilZ domain-containing protein from Vibrio cholerae. Either this protein or another specific PilZ domain-containing protein is required for V. cholerae to efficiently infect mice. VCA0042/PlzD comprises a C-terminal PilZ domain plus an N-terminal domain with a similar beta-barrel fold. C-di-GMP contacts seven of the nine strongly conserved residues in the PilZ domain, including three in a seven-residue long N-terminal loop that undergoes a conformational switch as it wraps around c-di-GMP. This switch brings the PilZ domain into close apposition with the N-terminal domain, forming a new allosteric interaction surface that spans these domains and the c-di-GMP at their interface. The very small size of the N-terminal conformational switch is likely to explain the facile evolutionary diversification of the PilZ domain.

  8. Discovery and structural characterization of a phospholamban-binding cyclic peptide and design of novel inhibitors of phospholamban.

    PubMed

    Tilgmann, Carola; Pollesello, Piero; Ovaska, Martti; Kaivola, Juha; Pystynen, Jarmo; Tiainen, Eija; Yliperttula, Marjo; Annila, Arto; Levijoki, Jouko

    2013-04-01

    The interplay between cardiac sarcoplasmic Ca(2+)ATPase and phospholamban is a key regulating factor of contraction and relaxation in the cardiac muscle. In heart failure, aberrations in the inhibition of sarcoplasmic Ca(2+)ATPase by phospholamban are associated with anomalies in cardiac functions. In experimental heart failure models, modulation of the interaction between these two proteins has been shown to be a potential therapeutic approach. The aim of our research was to find molecules able to interfere with the inhibitory activity of phospholamban on sarcoplasmic Ca(2+)ATPase. For this purpose, a portion of phospholamban was synthesized and used as target for a phage-display peptide library screening. The cyclic peptide C-Y-W-E-L-E-W-L-P-C-A was found to bind to phospholamban (1-36) with high specificity. Its functional activity was tested in Ca(2+)uptake assays utilizing preparations from cardiac sarcoplasmic reticulum. By synthesizing and testing a series of alanine point-mutated cyclic peptides, we identified which amino acid was important for the inhibition of the phospholamban function. The structures of active and inactive alanine-mutated cyclic peptides, and of phospholamban (1-36), were determined by NMR. This structure-activity analysis allowed building a model of phospholamban -cyclic peptide complex. Thereafter, a simple pharmacophore was defined and used for the design of small molecules. Finally, examples of such molecules were synthesized and characterized as phospholamban inhibitors.

  9. Study on the spatial structure of brachystemin C, a new cyclic peptide from Brachystemma calycinum

    NASA Astrophysics Data System (ADS)

    Wang, Cheng; Zhang, Li-Li; Lu, Yang; Zheng, Qi-Tai; Cheng, Yong-Xian; Zhou, Jun; Tan, Ning-Hua

    2004-01-01

    A new cyclic octapeptide, brachstemin C (the molecular formula: C 38H 56N 8O 9), was isolated from the root of Brachystemma calycinum. The types and sequence of the amino acids of the title compound were confirmed by spectral analyses and X-ray diffraction. The stereochemistry of the title cyclic octapeptide was clarified by X-ray crystallographic study. The cyclic octapeptide backbone contains three β-turns. Two of them are type I β-turns and one is type III β-turn (right-handed 3 10 helix). There are intermolecular hydrogen bonds between the cyclic peptide and the solvent molecules which maintained the steady spatial arrangement in crystal.

  10. Chemical modification and structure-activity relationships of pyripyropenes. 2. 1,11-Cyclic analogs.

    PubMed

    Obata, R; Sunazuka, T; Kato, Y; Tomoda, H; Harigaya, Y; Omura, S

    1996-11-01

    A series of 1,11-cyclic analogs of pyripyropene A were prepared. Replacement of the 1,11-acyl groups of pyripyropenes with 1,11-cyclic acetals effectively improved in vitro acyl CoA:cholesterol acyltransferase (ACAT) inhibitory activity. Especially noteworthy is benzylidene acetal analog 35, the most potent inhibitor (IC50 = 5.6 nM) among the derivatives prepared so far, which showed 16 times more potent inhibitory activity than pyripyropene A. PMID:8982344

  11. A statistical study of magnetopause structures: Tangential versus rotational discontinuities

    NASA Astrophysics Data System (ADS)

    Chou, Y.-C.; Hau, L.-N.

    2012-08-01

    A statistical study of the structure of Earth's magnetopause is carried out by analyzing two-year AMPTE/IRM plasma and magnetic field data. The analyses are based on the minimum variance analysis (MVA), the deHoffmann-Teller (HT) frame analysis and the Walén relation. A total of 328 magnetopause crossings are identified and error estimates associated with MVA and HT frame analyses are performed for each case. In 142 out of 328 events both MVA and HT frame analyses yield high quality results which are classified as either tangential-discontinuity (TD) or rotational-discontinuity (RD) structures based only on the Walén relation: Events withSWA ≤ 0.4 (SWA ≥ 0.5) are classified as TD (RD), and rest (with 0.4 < SWA < 0.5) is classified as "uncertain," where SWA refers to the Walén slope. With this criterion, 84% of 142 events are TDs, 12% are RDs, and 4% are uncertain events. There are a large portion of TD events which exhibit a finite normal magnetic field component Bnbut have insignificant flow as compared to the Alfvén velocity in the HT frame. Two-dimensional Grad-Shafranov reconstruction of forty selected TD and RD events show that single or multiple X-line accompanied with magnetic islands are common feature of magnetopause current. A survey plot of the HT velocity associated with TD structures projected onto the magnetopause shows that the flow is diverted at the subsolar point and accelerated toward the dawn and dusk flanks.

  12. Structural strength of cancellous specimens from bovine femur under cyclic compression

    PubMed Central

    Endo, Kaori; Yamada, Satoshi; Todoh, Masahiro; Takahata, Masahiko; Iwasaki, Norimasa

    2016-01-01

    The incidence of osteoporotic fractures was estimated as nine million worldwide in 2000, with particular occurrence at the proximity of joints rich in cancellous bone. Although most of these fractures spontaneously heal, some fractures progressively collapse during the early post-fracture period. Prediction of bone fragility during progressive collapse following initial fracture is clinically important. However, the mechanism of collapse, especially the gradual loss of the height in the cancellous bone region, is not clearly proved. The strength of cancellous bone after yield stress is difficult to predict since structural and mechanical strength cannot be determined a priori. The purpose of this study was to identify whether the baseline structure and volume of cancellous bone contributed to the change in cancellous bone strength under cyclic loading. A total of fifteen cubic cancellous bone specimens were obtained from two 2-year-old bovines and divided into three groups by collection regions: femoral head, neck, and proximal metaphysis. Structural indices of each 5-mm cubic specimen were determined using micro-computed tomography. Specimens were then subjected to five cycles of uniaxial compressive loading at 0.05 mm/min with initial 20 N loading, 0.3 mm displacement, and then unloading to 0.2 mm with 0.1 mm displacement for five successive cycles. Elastic modulus and yield stress of cancellous bone decreased exponentially during five loading cycles. The decrease ratio of yield stress from baseline to fifth cycle was strongly correlated with bone volume fraction (BV/TV, r = 0.96, p < 0.01) and structural model index (SMI, r = − 0.81, p < 0.01). The decrease ratio of elastic modulus from baseline to fifth cycle was also correlated with BV/TV (r = 0.80, p < 0.01) and SMI (r = − 0.78, p < 0.01). These data indicate that structural deterioration of cancellous bone is associated with bone strength after yield stress. This study suggests that baseline cancellous

  13. Structure elucidation of Sch 20561, a cyclic dehydropeptide lactone--a major component of W-10 antifungal antibiotic.

    PubMed

    Afonso, A; Hon, F; Brambilla, R; Puar, M S

    1999-04-01

    Antibiotic W-10 is a fermentation complex produced by the bacterium Aeromonas sp. W-10. The cyclic dehydropeptide lactones Sch 20562 (1) and Sch 20561 (2) are the major components of this fermentation complex and are of biological interest in view of their unique structural features and potent antifungal activity. The chemical degradation studies that were utilized in the assignment of structure 2 for Sch 20561 are described here. The structure determination of 2 made use of the ozonolytic cleavage of the dehydropeptide units to form fragments that were sequenced by mass spectrometry. The cyclic dehydropeptide lactone Sch 20561 (2) was found to be the aglycone of Sch 20562 (1) and these two natural products were correlated by a chemical transformation involving the deglucosidation of 1 to form 2.

  14. Hierarchical spatial structure of genetically variable nucleopolyhedroviruses infecting cyclic populations of western tent caterpillars.

    PubMed

    Cooper, Dawn; Cory, Jenny S; Myers, Judith H

    2003-04-01

    The cyclic population dynamics of western tent caterpillars, Malacosoma californicum pluviale, are associated with epizootics of a nucleopolyhedrovirus, McplNPV. Given the dynamic fluctuations in host abundance and levels of viral infection, host resistance and virus virulence might be expected to change during different phases of the cycle. As a first step in determining if McplNPV virulence and population structure change with host density, we used restriction fragment length polymorphism (RFLP) analysis to examine the genetic diversity of McplNPV infecting western tent caterpillar populations at different spatial scales. Thirteen dominant genetic variants were identified in 39 virus isolates (individual larvae) collected from field populations during one year of low host density, and another distinct variant was discovered among nine additional isolates in two subsequent years of declining host density. The distribution of these genetic variants was not random and indicated that the McplNPV population was structured at several spatial levels. A high proportion of the variation could be explained by family grouping, which suggested that isolates collected within a family were more likely to be the same than isolates compared among populations. Additionally, virus variants from within populations (sites) were more likely to be the same than isolates collected from tent caterpillar populations on different islands. This may indicate that there is limited mixing of virus among tent caterpillar families and populations when host population density is low. Thus there is potential for the virus to become locally adapted to western tent caterpillar populations in different sites. However, no dominant genotype was observed at any site. Whether and how selection acts on the genetically diverse nucleopolyhedrovirus populations as host density changes will be investigated over the next cycle of tent caterpillar populations.

  15. Strong intermolecular vibrational coupling through cyclic hydrogen-bonded structures revealed by ultrafast continuum mid-IR spectroscopy.

    PubMed

    Stingel, Ashley M; Calabrese, Carmella; Petersen, Poul B

    2013-12-12

    Cyclic hydrogen-bonded structures are common motifs in biological systems, providing structural stability and mediating proton transfer for redox reactions. The mechanism of proton transfer across hydrogen-bonded interfaces depends on the strength of the intermolecular coupling between bridging OH/NH vibrational modes. Here we present a novel ultrafast continuum mid-IR spectroscopy experiment to study the vibrational dynamics of the 7-azaindole-acetic acid (7AI-Ac) heterodimer as a model system for asymmetric cyclic hydrogen-bonded structures. In addition to spreading of the excitation across the whole OH band within the time resolution of the experiment, excitation of a 300 cm(-1) region of the ∼1000 cm(-1) broad OH stretching mode of the acetic acid monomer leads to a frequency shift in the NH stretching mode of the 7AI monomer. This indicates that the NH and OH stretching modes located on the two monomers are strongly coupled despite being separated by 750 cm(-1). The strong coupling further causes the OH and NH bands to decay with a common decay time of ∼2.5 ps. This intermolecular coupling is mediated through the hydrogen-bonded structure of the 7AI-Ac heterodimer and is likely a general property of cyclic hydrogen-bonded structures. Characterizing the vibrational dynamics of and the coupling between the high-frequency OH/NH modes will be important for understanding proton transfer across such molecular interfaces.

  16. Magnetic field structure evolution in rotating magnetic field plasmas

    SciTech Connect

    Petrov, Yuri; Yang Xiaokang; Huang, T.-S.

    2008-07-15

    A study of magnetic field structure evolution during 40-ms plasma discharge has been performed in a new device with 80 cm long/40 cm diameter cylindrical chamber, in which a plasma current I{sub p}{approx_equal}2 kA was driven and sustained by a rotating magnetic field. The main focus of the experiments is on how the changes in externally applied magnetic field affect the current profile and magnetic field in plasma. During plasma discharge, a pulse current was briefly fed to a magnetic coil located at the midplane (middle coil). The magnetic field in cross section of plasma was scanned with pickup probes. Two regimes were studied: without and with an external toroidal field (TF) produced by axial I{sub z} current. With a relatively small current (I{sub m} {<=} 600 A) in the middle coil, the plasma current is boosted up to 5 kA. The magnetic flux surfaces become extended along the axial Z direction, sometimes with the formation of doublet shape plasma. The regime without TF appears to be less stable, presumably due to the reversal of plasma current in central area of plasma column.

  17. Structural response of a rotating bladed disk to rotor whirl

    NASA Technical Reports Server (NTRS)

    Crawley, E. F.

    1985-01-01

    A set of high speed rotating whirl experiments were performed in the vacuum of the MIT Blowdown Compressor Facility on the MIT Aeroelastic Rotor, which is structurally typical of a modern high bypass ratio turbofan stage. These tests identified the natural frequencies of whirl of the rotor system by forcing its response using an electromagnetic shaker whirl excitation system. The excitation was slowly swept in frequency at constant amplitude for several constant rotor speeds in both a forward and backward whirl direction. The natural frequencies of whirl determined by these experiments were compared to those predicted by an analytical 6 DOF model of a flexible blade-rigid disk-flexible shaft rotor. The model is also presented in terms of nondimensional parameters in order to assess the importance of the interation between the bladed disk dynamics and the shaft-disk dynamics. The correlation between the experimental and predicted natural frequencies is reasonable, given the uncertainty involved in determining the stiffness parameters of the system.

  18. Rotational spectrum and structure of the Ne-HCN dimer

    NASA Astrophysics Data System (ADS)

    Gutowsky, H. S.; Keen, J. D.; Germann, T. C.; Emilsson, T.; Augspurger, J. D.; Dykstra, C. E.

    1993-05-01

    Microwave rotational transitions have been observed at low J (0-3) for several isotopic species of the Ne-HCN dimer using the Balle/Flygare Mark II Fourier transform spectrometer with a pulsed nozzle as the source. For 20Ne-HC 14N, the main K=0 transitions give rotational constants B¯, DJ, and HJ of 2772.816 and 1.280 MHz and 1.173 kHz. The 14N nuclear quadrupole constant increases linearly with J(J+1) at a slope Dχ of -12.7 kHz from a value for χa(14N) of -0.957 MHz at J=0. The pseudodiatomic approximation for B¯ and χa(14N) leads to a value of 3.89 Å for the Ne to HC 14N center-of-mass (c.m.) distance R, and to 46.8° for the ``average'' bend angle θ of HC 14N. Some of the K=0, J=1→2, and J=2→3 transitions exhibit one or two weak satellites ˜30 MHz away, usually below, but also both above and below. The J=1→2 low frequency satellites for 20Ne-HC 14N and 20Ne-HC 15N, nominally 111→212, are symmetrical doublets with splittings of 305 and 439 kHz, respectively. The 14N hyperfine structure (hfs) is identical for the two 20Ne-HC 14N components as is the Stark effect for 20Ne-HC 15N. The molecular mechanics for clusters (MMC) model was used to calculate potential energy surfaces for Rg-HCN dimers, giving stabilities of 21, 37, 85, and 108 cm-1 with He, Ne, Ar, and Kr as the rare gas. A qualitative comparison of the experimental properties for the dimers with Ne, Ar, and Kr as the rare gas is based on the surfaces. The extremely mobile internal dynamics of Ne-HCN are attributed to its potential surface, which is both very shallow and isotropic.

  19. Ligand-induced structural changes in the cyclic nucleotide-modulated potassium channel MloK1

    PubMed Central

    Kowal, Julia; Chami, Mohamed; Baumgartner, Paul; Arheit, Marcel; Chiu, Po-Lin; Rangl, Martina; Scheuring, Simon; Schröder, Gunnar F.; Nimigean, Crina M.; Stahlberg, Henning

    2014-01-01

    Cyclic nucleotide-modulated ion channels are important for signal transduction and pacemaking in eukaryotes. The molecular determinants of ligand gating in these channels are still unknown, mainly because of a lack of direct structural information. Here we report ligand-induced conformational changes in full-length MloK1, a cyclic nucleotide-modulated potassium channel from the bacterium Mesorhizobium loti, analysed by electron crystallography and atomic force microscopy. Upon cAMP binding, the cyclic nucleotide-binding domains move vertically towards the membrane, and directly contact the S1–S4 voltage sensor domains. This is accompanied by a significant shift and tilt of the voltage sensor domain helices. In both states, the inner pore-lining helices are in an ‘open’ conformation. We propose a mechanism in which ligand binding can favour pore opening via a direct interaction between the cyclic nucleotide-binding domains and voltage sensors. This offers a simple mechanistic hypothesis for the coupling between ligand gating and voltage sensing in eukaryotic HCN channels. PMID:24469021

  20. Heat-Driven Rotation in Cholesteric Droplets with a Double Twisted Structure

    NASA Astrophysics Data System (ADS)

    Ito, Fumiya; Yoshioka, Jun; Tabe, Yuka

    2016-11-01

    In an isotropic-cholesteric coexistence system, a single-helix structure is formed in the cholesteric droplets, and when a temperature gradient is applied, unidirectional rotations are induced in these droplets. However, in a previous work, we showed that a double twisted structure was also formed in the droplets by changing droplet size or chirality. In this paper, we find that unidirectional rotations are also induced by applying a temperature gradient to droplets with a double twisted structure. Here, however, the rotational behavior is strongly dependent on the relationship between the direction of the helical axis and the temperature gradient. Unidirectional rotation is induced when one of the helical axes is parallel to the gradient, whereas no rotation is found when all of the axes are perpendicular to the temperature gradient. These results suggest that the macroscopic helix plays a significant role in the heat-driven rotational dynamics of cholesteric droplets.

  1. Isolation and structure determination of obyanamide, a novel cytotoxic cyclic depsipeptide from the marine cyanobacterium Lyngbya confervoides.

    PubMed

    Williams, Philip G; Yoshida, Wesley Y; Moore, Richard E; Paul, Valerie J

    2002-01-01

    Obyanamide (1) was isolated from a variety of the marine cyanobacterium Lyngbya confervoides collected in Saipan, Commonwealth of the Northern Mariana Islands. Gross structure elucidation of this novel cyclic depsipeptide relied on extensive application of 2D NMR techniques. The absolute stereochemistry was deduced by chiral chromatography of the hydrolysis products and comparison with authentic and synthetic standards. Obyanamide (1) was cytotoxic against KB cells with an IC(50) of 0.58 microg/mL.

  2. Stellar structures and the enigma of pulsars rotation frequency decay

    NASA Astrophysics Data System (ADS)

    de Oliveira, H. O.; Marinho, R. M., Jr.; Maglhaes, N. S.

    2015-07-01

    Pulsars are astrophysical objects normally modelled as compact neutron stars that originated from the collapse of another star. This model, that we name canonical, assumes that pulsars are described by spherical magnetized dipoles that rotate, usually with the magnetic axis misaligned to the rotation axis. This misalignment would be responsible for the observation of radiation emitted in well-defined time intervals in a certain direction (lighthouse effect), the typical observational characteristic of this kind of star. It has been noticed that the rotation frequency of pulsars is slowly decaying with time (spin down), implying a gradual decrease of the rotational angular velocity (Ω). Such decay can be quantified by a dimensionless parameter called “braking index” (“n”), given by n = ΩΩ/(Ω)2, where a dot indicates a time derivative. The canonical model predicts that this index has one only value for all pulsars, equal to three. However, observational data indicate that actual braking indices are less than three, representing an enigma. The main goal of this research is the exploration of a more precise model for pulsars’ rotation frequency decay.

  3. Experimental study on active structural acoustic control of rotating machinery using rotating piezo-based inertial actuators

    NASA Astrophysics Data System (ADS)

    Zhao, G.; Alujević, N.; Depraetere, B.; Pinte, G.; Swevers, J.; Sas, P.

    2015-07-01

    In this paper, two Piezo-Based Rotating Inertial Actuators (PBRIAs) are considered for the suppression of the structure-borne noise radiated from rotating machinery. As add-on devices, they can be directly mounted on a rotational shaft, in order to intervene as early as possible in the transfer path between disturbance and the noise radiating surfaces. A MIMO (Multi-Input-Multi-Output) form of the FxLMS control algorithm is employed to generate the appropriate actuation signals, relying on a linear interpolation scheme to approximate time varying secondary plants. The proposed active vibration control approach is tested on an experimental test bed comprising a rotating shaft mounted in a frame to which a noise-radiating plate is attached. The disturbance force is introduced by an electro-dynamic shaker. The experimental results show that when the shaft spins below 180 rpm, more than a 7 dB reduction can be achieved in terms of plate vibrations, along with a reduction in the same order of magnitude in terms of noise radiation.

  4. Effect of substrate rotation on domain structure and magnetic relaxation in magnetic antidot lattice arrays

    SciTech Connect

    Mallick, Sougata; Mallik, Srijani; Bedanta, Subhankar

    2015-08-28

    Microdimensional triangular magnetic antidot lattice arrays were prepared by varying the speed of substrate rotation. The pre-deposition patterning has been performed using photolithography technique followed by a post-deposition lift-off. Surface morphology taken by atomic force microscopy depicted that the growth mechanism of the grains changes from chain like formation to island structures due to the substrate rotation. Study of magnetization reversal via magneto optic Kerr effect based microscopy revealed reduction of uniaxial anisotropy and increase in domain size with substrate rotation. The relaxation measured under constant magnetic field becomes faster with rotation of the substrate during deposition. The nature of relaxation for the non-rotating sample can be described by a double exponential decay. However, the relaxation for the sample with substrate rotation is well described either by a double exponential or a Fatuzzo-Labrune like single exponential decay, which increases in applied field.

  5. Structure elucidation at the nanomole scale. 1. Trisoxazole macrolides and thiazole-containing cyclic peptides from the nudibranch Hexabranchus sanguineus.

    PubMed

    Dalisay, Doralyn S; Rogers, Evan W; Edison, Arthur S; Molinski, Tadeusz F

    2009-04-01

    A single specimen of Hexabranchus sanguineus, a nudibranch from the Indo-Pacific that is known to sequester kabiramides B and C and other trisoxazole macrolides, yielded new kabiramide analogues, 9-desmethylkbiramide B and 33-methyltetrahydrohalichondramide, and two new unexpected thiazole-containing cyclic peptides in submicromolar amounts. The structures of these cyclic peptides were determined by analyses of 1D and 2D NMR spectra recorded with a state-of-the-art 1 mm (1)H NMR high-temperature superconducting microcryoprobe, together with mass spectra. In addition to two proline residues, each peptide contains a thiazole- or oxazole-modified amino acid residue, together with conventional amino acid residues. All of the amino acid residues were l, as determined by Marfey's analysis of the acid hydrolysates of the peptides. This is the first report of cyclic thiazole peptides from H. sanguineus. Since thiazole-oxazole-modified peptides are typically associated with cyanobacteria and tunicates, the finding may imply a dietary component of the H. sanguineus that was previously overlooked. PMID:19254038

  6. Structure parameters in rotating Couette-Poiseuille channel flow

    NASA Technical Reports Server (NTRS)

    Knightly, George H.; Sather, D.

    1986-01-01

    It is well-known that a number of steady state problems in fluid mechanics involving systems of nonlinear partial differential equations can be reduced to the problem of solving a single operator equation of the form: v + lambda Av + lambda B(v) = 0, v is the summation of H, lambda is the summation of one-dimensional Euclid space, where H is an appropriate (real or complex) Hilbert space. Here lambda is a typical load parameter, e.g., the Reynolds number, A is a linear operator, and B is a quadratic operator generated by a bilinear form. In this setting many bifurcation and stability results for problems were obtained. A rotating Couette-Poiseuille channel flow was studied, and it showed that, in general, the superposition of a Poiseuille flow on a rotating Couette channel flow is destabilizing.

  7. Structure parameters in rotating Couette-Poiseuille channel flow

    NASA Astrophysics Data System (ADS)

    Knightly, George H.; Sather, D.

    It is well-known that a number of steady state problems in fluid mechanics involving systems of nonlinear partial differential equations can be reduced to the problem of solving a single operator equation of the form: v + lambda Av + lambda B(v) = 0, v is the summation of H, lambda is the summation of one-dimensional Euclid space, where H is an appropriate (real or complex) Hilbert space. Here lambda is a typical load parameter, e.g., the Reynolds number, A is a linear operator, and B is a quadratic operator generated by a bilinear form. In this setting many bifurcation and stability results for problems were obtained. A rotating Couette-Poiseuille channel flow was studied, and it showed that, in general, the superposition of a Poiseuille flow on a rotating Couette channel flow is destabilizing.

  8. Theoretical characterisation of the SSO, cyclic SOS and SOS isomers

    NASA Astrophysics Data System (ADS)

    Denis, Pablo A.

    2010-01-01

    The SSO, cyclic SOS and open SOS isomers have been investigated, employing the CCSD(T) methodology and the cc-pV(X + d)Z X = 3, 4, 5, 6 basis sets. The anharmonic force fields have been calculated to predict the fundamental vibrational frequencies, rotational constants, vibration-rotation corrections, anharmonic corrections to zero-point energies, and structural parameters. At the CCSD(T)/CBS limit and including corrections for scalar relativistic effects, complete quadruple excitations, spin-orbit and core-valence correlation effects, the estimated enthalpies of formation are -13.9 ± 1, 32.1 ± 1, and -51.2 ± 1 kcal/mol, for SSO, cyclic-SOS and open-SOS, respectively. Finally, it was found that the asymmetric SO stretch of the open and cyclic SOS isomers are located in a nearly identical position and it is likely that SOS also maybe present in the surface of Io.

  9. Structures of the PelD Cyclic Diguanylate Effector Involved in Pellicle Formation in Pseudomonas aeruginosa PAO1

    PubMed Central

    Li, Zhi; Chen, Jui-Hui; Hao, Yue; Nair, Satish K.

    2012-01-01

    The second messenger bis-(3′–5′)-cyclic dimeric guanosine monophosphate (c-di-GMP) plays a vital role in the global regulation in bacteria. Here, we describe structural and biochemical characterization of a novel c-di-GMP effector PelD that is critical to the formation of pellicles by Pseudomonas aeruginosa. We present high-resolution structures of a cytosolic fragment of PelD in apo form and its complex with c-di-GMP. The structure contains a bi-domain architecture composed of a GAF domain (commonly found in cyclic nucleotide receptors) and a GGDEF domain (found in c-di-GMP synthesizing enzymes), with the latter binding to one molecule of c-di-GMP. The GGDEF domain has a degenerate active site but a conserved allosteric site (I-site), which we show binds c-di-GMP with a Kd of 0.5 μm. We identified a series of residues that are crucial for c-di-GMP binding, and confirmed the roles of these residues through biochemical characterization of site-specific variants. The structures of PelD represent a novel class of c-di-GMP effector and expand the knowledge of scaffolds that mediate c-di-GMP recognition. PMID:22810222

  10. Solution structure of the squash trypsin inhibitor MCoTI-II. A new family for cyclic knottins.

    PubMed

    Heitz, A; Hernandez, J F; Gagnon, J; Hong, T T; Pham, T T; Nguyen, T M; Le-Nguyen, D; Chiche, L

    2001-07-10

    The "knottin" fold is a stable cysteine-rich scaffold, in which one disulfide crosses the macrocycle made by two other disulfides and the connecting backbone segments. This scaffold is found in several protein families with no evolutionary relationships. In the past few years, several homologous peptides from the Rubiaceae and Violaceae families were shown to define a new structural family based on macrocyclic knottin fold. We recently isolated from Momordica cochinchinensis seeds the first known macrocyclic squash trypsin inhibitors. These compounds are the first members of a new family of cyclic knottins. In this paper, we present NMR structural studies of one of them, MCoTI-II, and of a beta-Asp rearranged form, MCoTI-IIb. Both compounds display similar and well-defined conformations. These cyclic squash inhibitors share a similar conformation with noncyclic squash inhibitors such as CPTI-II, and it is postulated that the main effect of the cyclization is a reduced sensitivity to exo-proteases. On the contrary, clear differences were detected with the three-dimensional structures of other known cyclic knottins, i.e., kalata B1 or circulin A. The two-disulfide cystine-stabilized beta-sheet motif [Heitz et al. (1999) Biochemistry 38, 10615-10625] is conserved in the two families, whereas in the C-to-N linker, one disulfide bridge and one loop are differently located. The molecular surface of MCoTI-II is almost entirely charged in contrast to circulin A that displays a well-marked amphiphilic character. These differences might explain why the isolated macrocyclic squash inhibitors from M. cochinchinensis display no significant antibacterial activity, whereas circulins and kalata B1 do. PMID:11434766

  11. Solution structure of the squash trypsin inhibitor MCoTI-II. A new family for cyclic knottins.

    PubMed

    Heitz, A; Hernandez, J F; Gagnon, J; Hong, T T; Pham, T T; Nguyen, T M; Le-Nguyen, D; Chiche, L

    2001-07-10

    The "knottin" fold is a stable cysteine-rich scaffold, in which one disulfide crosses the macrocycle made by two other disulfides and the connecting backbone segments. This scaffold is found in several protein families with no evolutionary relationships. In the past few years, several homologous peptides from the Rubiaceae and Violaceae families were shown to define a new structural family based on macrocyclic knottin fold. We recently isolated from Momordica cochinchinensis seeds the first known macrocyclic squash trypsin inhibitors. These compounds are the first members of a new family of cyclic knottins. In this paper, we present NMR structural studies of one of them, MCoTI-II, and of a beta-Asp rearranged form, MCoTI-IIb. Both compounds display similar and well-defined conformations. These cyclic squash inhibitors share a similar conformation with noncyclic squash inhibitors such as CPTI-II, and it is postulated that the main effect of the cyclization is a reduced sensitivity to exo-proteases. On the contrary, clear differences were detected with the three-dimensional structures of other known cyclic knottins, i.e., kalata B1 or circulin A. The two-disulfide cystine-stabilized beta-sheet motif [Heitz et al. (1999) Biochemistry 38, 10615-10625] is conserved in the two families, whereas in the C-to-N linker, one disulfide bridge and one loop are differently located. The molecular surface of MCoTI-II is almost entirely charged in contrast to circulin A that displays a well-marked amphiphilic character. These differences might explain why the isolated macrocyclic squash inhibitors from M. cochinchinensis display no significant antibacterial activity, whereas circulins and kalata B1 do.

  12. ROTATION OF COMET 103P/HARTLEY 2 FROM STRUCTURES IN THE COMA

    SciTech Connect

    Samarasinha, Nalin H.; Mueller, Beatrice E. A.; A'Hearn, Michael F.; Farnham, Tony L.; Gersch, Alan

    2011-06-10

    The CN coma structure of the NASA EPOXI mission target, comet 103P/Hartley 2, was observed during 20 nights from 2010 September to December. These CN images probe the rotational state of the comet's nucleus and provide a ground-based observational context to complement the EPOXI observations. A dynamically excited cometary nucleus with a changing rotational rate is observed, a characteristic not seen in any comet in the past. The lack of rotational damping during the four-month observing interval places constraints on the interior structure of the nucleus.

  13. The Rotating Spiral Structure of the Vela Pulsar Jet

    NASA Astrophysics Data System (ADS)

    Kargaltsev, Oleg; Durant, M.; Pavlov, G. G.; Bykov, A. M.; Kropotina, J.; Levenfish, K.

    2013-01-01

    Eleven 40-ks Chandra ACIS observations of the Vela pulsar wind nebula were taken between July 2009 and September 2010. Our analysis of the images of the variable Vela pulsar jet have revealed a remarkable periodic pattern. The observed variations are consistent with those of expected for a steadily rotating helical jet projected on the sky. Such behavior can be a manifestation of neutron star precession, possibly amplified by MHD instabilities. This work is supported by NASA through CXO grant G09-0084B and by the Ministry of Education and Science of the Russian Federation (Contract No. 11.G34.31.0001).

  14. PEP-FOLD: an updated de novo structure prediction server for both linear and disulfide bonded cyclic peptides.

    PubMed

    Thévenet, Pierre; Shen, Yimin; Maupetit, Julien; Guyon, Frédéric; Derreumaux, Philippe; Tufféry, Pierre

    2012-07-01

    In the context of the renewed interest of peptides as therapeutics, it is important to have an on-line resource for 3D structure prediction of peptides with well-defined structures in aqueous solution. We present an updated version of PEP-FOLD allowing the treatment of both linear and disulphide bonded cyclic peptides with 9-36 amino acids. The server makes possible to define disulphide bonds and any residue-residue proximity under the guidance of the biologists. Using a benchmark of 34 cyclic peptides with one, two and three disulphide bonds, the best PEP-FOLD models deviate by an average RMS of 2.75 Å from the full NMR structures. Using a benchmark of 37 linear peptides, PEP-FOLD locates lowest-energy conformations deviating by 3 Å RMS from the NMR rigid cores. The evolution of PEP-FOLD comes as a new on-line service to supersede the previous server. The server is available at: http://bioserv.rpbs.univ-paris-diderot.fr/PEP-FOLD.

  15. Rotational spectroscopy of antipyretics: conformation, structure, and internal dynamics of phenazone.

    PubMed

    Écija, Patricia; Cocinero, Emilio J; Lesarri, Alberto; Fernández, José A; Caminati, Walther; Castaño, Fernando

    2013-03-21

    The conformational and structural preferences of phenazone (antipyrine), the prototype of non-opioid pyrazolone antipyretics, have been probed in a supersonic jet expansion using rotational spectroscopy. The conformational landscape of the two-ring assembly was first explored computationally, but only a single conformer was predicted, with the N-phenyl and N-methyl groups on opposite sides of the pyrazolone ring. Consistently, the microwave spectrum evidenced a rotational signature arising from a single molecular structure. The spectrum exhibited very complicated fine and hyperfine patterns (not resolvable with any other spectroscopic technique) originated by the simultaneous coupling of the methyl group internal rotation and the spins of the two (14)N nuclei with the overall rotation. The internal rotation tunnelling was ascribed to the C-CH3 group and the barrier height established experimentally (7.13(10) kJ mol(-1)). The internal rotation of the N-CH3 group has a lower limit of 9.4 kJ mol(-1). The structure of the molecule was determined from the rotational parameters, with the phenyl group elevated ca. 25° with respect to the average plane of the pyrazolic moiety and a phenyl torsion of ca. 52°. The origin of the conformational preferences is discussed in terms of the competition between intramolecular C-H···N and C-H···O weak hydrogen bonds.

  16. Flow Structure on a Wing Due to Unsteady Pitch-Up and Rotation Maneuvers

    NASA Astrophysics Data System (ADS)

    Bross, Matthew; Yilmaz, Turgut; Rockwell, Donald

    2013-11-01

    The flow structure along a rectangular (low aspect ratio) wing undergoing pure pitch-up, pitch-up with rotation, and pure rotation is characterized as a function of dimensionless convective time τ during each maneuver. Quantitative imaging via angular displacement stereo particle image velocimetry was used to determine the three-dimensional velocity field, thereby allowing analysis of the effects of different wing kinematics via representations of Q-criterion, vorticity flux, and velocity and vorticity contours. Despite the difference in wing kinematics, interactions between leading-edge and tip vortices persist across all values of τ. The three-dimensional flow structure involves a symmetric pattern along the wing during pure pitch-up and transforms to a conical leading-edge vortex in conjunction with a tip vortex that extends into the wake for both pitch-up with rotation and pure rotation. This observation suggests that rotational motion has a greater influence than pitching motion in establishing the form and scale of the leading-edge vortex. Finally, sectional images of the flow structure arising from combined pitch-up and rotation were acquired at three different pitch rates relative to a given rate of pure rotation at fixed angle of attack.

  17. Rotational spectroscopy of antipyretics: Conformation, structure, and internal dynamics of phenazone

    NASA Astrophysics Data System (ADS)

    Écija, Patricia; Cocinero, Emilio J.; Lesarri, Alberto; Fernández, José A.; Caminati, Walther; Castaño, Fernando

    2013-03-01

    The conformational and structural preferences of phenazone (antipyrine), the prototype of non-opioid pyrazolone antipyretics, have been probed in a supersonic jet expansion using rotational spectroscopy. The conformational landscape of the two-ring assembly was first explored computationally, but only a single conformer was predicted, with the N-phenyl and N-methyl groups on opposite sides of the pyrazolone ring. Consistently, the microwave spectrum evidenced a rotational signature arising from a single molecular structure. The spectrum exhibited very complicated fine and hyperfine patterns (not resolvable with any other spectroscopic technique) originated by the simultaneous coupling of the methyl group internal rotation and the spins of the two 14N nuclei with the overall rotation. The internal rotation tunnelling was ascribed to the C-CH3 group and the barrier height established experimentally (7.13(10) kJ mol-1). The internal rotation of the N-CH3 group has a lower limit of 9.4 kJ mol-1. The structure of the molecule was determined from the rotational parameters, with the phenyl group elevated ca. 25° with respect to the average plane of the pyrazolic moiety and a phenyl torsion of ca. 52°. The origin of the conformational preferences is discussed in terms of the competition between intramolecular C-H⋯N and C-H⋯O weak hydrogen bonds.

  18. On the detection of natural frequencies and mode shapes of submerged rotating disk-like structures from the casing

    NASA Astrophysics Data System (ADS)

    Presas, Alexandre; Valentin, David; Egusquiza, Eduard; Valero, Carme; Seidel, Ulrich

    2015-08-01

    To avoid resonance problems in rotating turbomachinery components such as impellers, it is of paramount importance to determine the natural frequencies of these parts when they are under operation. Nevertheless, most of these rotating structures are inaccessible and in some cases submerged and confined. To measure the natural frequencies of submerged impellers from the rotating frame is complicated, because sensors have to be well fixed, withstand with large pressure and centrifugal forces. Furthermore, the signals have to be transmitted to the stationary frame. For this reason it may be advantageous to measure the natural frequencies with sensors placed on the casing. In this paper, the analysis of rotating disk-like structures submerged and confined has been performed from the stationary frame. Previously, an analytical model to determine the natural frequencies and mode shapes of the disk from the rotating frame is presented. Once natural frequencies and mode shapes are obtained in the rotating frame, the transmission to the stationary frame has been deduced. A rotating disk test rig has been used for the experimental study. It consist of a rotating disk that has been excited from the rotating frame with a piezoelectric patch and it response has been measured from both rotating and stationary frame. Results shows that for rotating submerged structures in heavy fluids such as water, not only the structural modes of the rotating part are different than for rotating structures in air, but also the transmission from the rotating to the stationary frame.

  19. Identification and Structural Characterization of Naturally-Occurring Broad-Spectrum Cyclic Antibiotics Isolated from Paenibacillus

    NASA Astrophysics Data System (ADS)

    Knolhoff, Ann M.; Zheng, Jie; McFarland, Melinda A.; Luo, Yan; Callahan, John H.; Brown, Eric W.; Croley, Timothy R.

    2015-08-01

    The rise of antimicrobial resistance necessitates the discovery and/or production of novel antibiotics. Isolated strains of Paenibacillus alvei were previously shown to exhibit antimicrobial activity against a number of pathogens, such as E. coli, Salmonella, and methicillin-resistant Staphylococcus aureus (MRSA). The responsible antimicrobial compounds were isolated from these Paenibacillus strains and a combination of low and high resolution mass spectrometry with multiple-stage tandem mass spectrometry was used for identification. A group of closely related cyclic lipopeptides was identified, differing primarily by fatty acid chain length and one of two possible amino acid substitutions. Variation in the fatty acid length resulted in mass differences of 14 Da and yielded groups of related MSn spectra. Despite the inherent complexity of MS/MS spectra of cyclic compounds, straightforward analysis of these spectra was accomplished by determining differences in complementary product ion series between compounds that differ in molecular weight by 14 Da. The primary peptide sequence assignment was confirmed through genome mining; the combination of these analytical tools represents a workflow that can be used for the identification of complex antibiotics. The compounds also share amino acid sequence similarity to a previously identified broad-spectrum antibiotic isolated from Paenibacillus. The presence of such a wide distribution of related compounds produced by the same organism represents a novel class of broad-spectrum antibiotic compounds.

  20. Structure and dynamics of a rotating superfluid Bose-Fermi mixture

    NASA Astrophysics Data System (ADS)

    Wen, Linghua; Li, Jinghong

    2014-11-01

    We investigate the structure and dynamics of a rotating superfluid Bose-Fermi mixture (SBFM) made of superfluid bosons and two-component (spin-up and -down) superfluid fermions. A ground-state phase diagram for the nonrotating case of a SBFM with specific parameters is given, where the ground-state configuration of a nonrotating SBFM is mainly determined by the boson-fermion interaction. For the rotating case of a SBFM with a sufficiently large rotation frequency, we show that the system supports a mixed phase and three typical layer-separated phases. In particular, the visible vortex formation in the fermionic superfluid exhibits a remarkable hysteresis effect during the dynamical evolution of a rotating SBFM, which is evidently different from the case of rotating two-component Bose-Einstein condensates.

  1. Installation of rotating-machinery skids on offshore structures interface and structural aspects

    SciTech Connect

    Canacci, M.; Giusti, S.; Zucchi, O.

    1995-12-31

    One of the most important aspects, to be considered, in the offshore installation of turbomachinery and reciprocating compressors is the interface between the machine skid and the main structure. The whole structural design is to be such that under the most severe static and dynamic loads the machine alignment and the vibrations are maintained to acceptable levels either if the rotating machinery is installed in a module or directly on the platform deck. There are two structural solutions to achieve the above conditions and they are: the multipoint skid, typically used when the structure stiffness allows it, and the three point supported skid that is used whenever the main structure displacements are too high for the conventional baseplates. Both multipoint and three point skids have been studied to accommodate different types of driver and driven machines. To assure the suitability of the baseplates against the several operating conditions its design is carried out by applying a finite element analysis either in static or dynamic conditions considering the simulation of the machine effects and the stiffness characteristics of the main structure. The purpose of this paper is to illustrate the Nuovo Pignone criteria and experiences of designing machine skids suitable for the most severe operating conditions, maintaining reliability, available and operability of the units.

  2. Thermodynamics of the hydrogen bonding of nitrogen-containing cyclic and aromatic compounds with proton donors: The structure-property relationship

    NASA Astrophysics Data System (ADS)

    Rakipov, I. T.; Varfolomeev, M. A.; Kirgizov, A. Yu.; Solomonov, B. N.

    2014-12-01

    Enthalpies of dissolution are measured at infinite dilution of nitrogen-containing cyclic (pyrrolidine, piperidine) and aromatic compounds (aniline, N-methylaniline, N,N-dimethylaniline, N-methylimidazole, pyridine, 2-, 3-, 4-methylpyridine, pyrrole, N-methylpyrrole) in chloroform and dichloromethane, and vice versa ( T = 298.15 K). The enthalpies of hydrogen bonds in the above systems are calculated. Relationships between resulting thermochemical data and the structure of nitrogen-containing cyclic and aromatic compounds are explored.

  3. Cyclic pentapeptide analogs based on endomorphin-2 structure: cyclization studies using liquid chromatography combined with on-line mass spectrometry and tandem mass spectrometry.

    PubMed

    Piekielna, Justyna; Kluczyk, Alicja; Perlikowska, Renata; Janecka, Anna

    2014-05-01

    The cyclization of linear analogs based on endomorphin-2 structure, Tyr/Dmt-d-Lys-Phe-Phe-Asp-NH2 and Tyr/Dmt-d-Cys-Phe-Phe-Cys-NH2 (where Dmt=2',6'-dimethyltyrosine), resulting in obtaining lactam or disulfide derivatives, was studied using liquid chromatography combined with on-line mass spectrometry (LC-MS) and tandem mass spectrometry (LC-MS/MS). In case of cyclization via an amide bond, the formation of the cyclic monomers, cyclic but not linear dimers and even traces of cyclic trimers was observed. Disulfide bridge containing peptides was obtained by the solid-phase synthesis of the linear sequences, followed by either in-solution or on-resin cyclization. In case of the in-solution cyclization, the expected cyclic monomers were the only products. When oxidation of the cysteine residues was performed when the peptides were still on the resin, cyclic monomer and two cyclodimers, parallel and antiparallel, were found. Digestion of the isolated cyclodimers with α-chymotrypsin allowed for their unambiguous identification. The comparison of the cyclic monomer/dimer ratios for analogs with Tyr versus Dmt in position 1 revealed that the presence of the exocyclic Dmt favored formation of the cyclic monomer, most likely due to the increased steric bulk of this amino acid side-chain as compared with Tyr.

  4. Rotational structures and the wobbling mode in {sup 167}Ta

    SciTech Connect

    Hartley, D. J.; Ludington, A.; Pifer, R.; Seyfried, E. P.; Vanhoy, J. R.; Janssens, R. V. F.; Carpenter, M. P.; Lauritsen, T.; McCutchan, E. A.; Zhu, S.; Riedinger, L. L.; Darby, I. G.; Riley, M. A.; Wang, X.; Aguilar, A.; Chiara, C. J.; Chowdhury, P.; Lakshmi, S.; Shirwadkar, U.; Tandel, S. K.

    2011-06-15

    Excited states in the neutron-deficient nucleus {sup 167}Ta were studied through the {sup 120}Sn({sup 51}V,4n) reaction. Twelve rotational bands have been observed and the relative excitation energy of each sequence is now known owing to the multiple interband connections. Several quasineutron alignments were observed that aided in the quasiparticle assignments of these bands. The resulting interpretation is in line with observations in neighboring nuclei. Trends in the wobbling phonon energy seen in {sup 161,163,165,167}Lu and {sup 167}Ta are also discussed and particle-rotor model calculations (assuming constant moments of inertia) are found to be inconsistent with the experimental data.

  5. Structural and spectral characteristics of the cross-linked dimer derived from electrooxidation of cyclic 1,N2-propanoguanosine.

    PubMed

    Murakami, Hiroya; Esaka, Yukihiro; Uno, Bunji

    2011-01-01

    The acetaldehyde-derived cyclic propano adduct of 2'-deoxyguanosine was easily oxidized electrochemically into the cross-linked dimer as an oxidative product. The structural and spectroscopic characteristics of the dimer were investigated by MS, (1)H and (13)C-NMR, UV, and DFT calculations. The dimer formation was inferred from a molecular ionic peak of m/z 705 ([(2M-2H)+H](+), M being the molecular weight of the monomer) on the ESI-MS spectra and the chemical formula as C(28)H(36)N(10)O(12) provided by the high-resolution ESI-MS results. The C2-N5 linkage between the two monomers in the dimer was deduced from the (1)H- and (13)C-NMR spectral results. In addition, the correlations in the 2-dimensional NMR spectra (DQF-COSY and HMBC) were consistently explained by the structure of the C2-N5 cross-linked dimer. UV spectral measurements also support the C2-N5 linking in the dimer formation. The formation of the cross-link dimer as an oxidative lesion of the acetaldehyde-derived cyclic propano adduct of guanosine is expected to interfere with DNA replication and to contribute to acetaldehyde-mediated genotoxicity.

  6. Controlling the anisotropy and domain structure with oblique deposition and substrate rotation

    SciTech Connect

    Chowdhury, N.; Bedanta, S.

    2014-02-15

    Effect of substrate rotation on anisotropy and domain structure for a thin ferromagnetic film has been investigated in this work. For this purpose Co films with 10 nm thickness have been prepared by sputtering with oblique angle of incidence for various substrate rotations. This method of preparation induces a uniaxial anisotropy due to shadow deposition effect. The magnetization reversal is studied by magneto-optic Kerr effect (MOKE) based microscope in the longitudinal geometry. The Co films prepared by rotating the substrate with 10 and 20 rpm weakens the anisotropy but does not completely give isotropic films. But this leads to high dispersion in local grain anisotropy resulting in ripple and labyrinth domains. It is observed that the substrate rotation has moderate effect on uniaxial anisotropy but has significant effect on the magnetization reversal process and the domain structure.

  7. Large rotation FE transient analysis of piezolaminated thin-walled smart structures

    NASA Astrophysics Data System (ADS)

    Zhang, S. Q.; Schmidt, R.

    2013-10-01

    A geometrically nonlinear large rotation shell theory is proposed for dynamic finite element (FE) analysis of piezoelectric integrated thin-walled smart structures. The large rotation theory, which has six independent kinematic parameters but expressed by five nodal degrees of freedom (DOFs), is based on first-order shear deformation (FOSD) hypothesis. The two-dimensional (2D) FE model is constructed using eight-node quadrilateral shell elements with five mechanical DOFs per node and one electrical DOF per piezoelectric material layer with linear constitutive equations. The linear and nonlinear dynamic responses are determined by the central difference algorithm (CDA) and the Newmark method. The results are compared with those obtained by simplified nonlinear theories, as well as those reported in the literature. It is shown that the present large rotation theory yields considerable improvement if the structures undergo large displacements and rotations.

  8. Controlling the anisotropy and domain structure with oblique deposition and substrate rotation

    NASA Astrophysics Data System (ADS)

    Chowdhury, N.; Bedanta, S.

    2014-02-01

    Effect of substrate rotation on anisotropy and domain structure for a thin ferromagnetic film has been investigated in this work. For this purpose Co films with 10 nm thickness have been prepared by sputtering with oblique angle of incidence for various substrate rotations. This method of preparation induces a uniaxial anisotropy due to shadow deposition effect. The magnetization reversal is studied by magneto-optic Kerr effect (MOKE) based microscope in the longitudinal geometry. The Co films prepared by rotating the substrate with 10 and 20 rpm weakens the anisotropy but does not completely give isotropic films. But this leads to high dispersion in local grain anisotropy resulting in ripple and labyrinth domains. It is observed that the substrate rotation has moderate effect on uniaxial anisotropy but has significant effect on the magnetization reversal process and the domain structure.

  9. Structure and stoichiometry of an accessory subunit TRIP8b interaction with hyperpolarization-activated cyclic nucleotide-gated channels

    PubMed Central

    Bankston, John R.; Camp, Stacey S.; DiMaio, Frank; Lewis, Alan S.; Chetkovich, Dane M.; Zagotta, William N.

    2012-01-01

    Ion channels operate in intact tissues as part of large macromolecular complexes that can include cytoskeletal proteins, scaffolding proteins, signaling molecules, and a litany of other molecules. The proteins that make up these complexes can influence the trafficking, localization, and biophysical properties of the channel. TRIP8b (tetratricopetide repeat-containing Rab8b-interacting protein) is a recently discovered accessory subunit of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels that contributes to the substantial dendritic localization of HCN channels in many types of neurons. TRIP8b interacts with the carboxyl-terminal region of HCN channels and regulates their cell-surface expression level and cyclic nucleotide dependence. Here we examine the molecular determinants of TRIP8b binding to HCN2 channels. Using a single-molecule fluorescence bleaching method, we found that TRIP8b and HCN2 form an obligate 4:4 complex in intact channels. Fluorescence-detection size-exclusion chromatography and fluorescence anisotropy allowed us to confirm that two different domains in the carboxyl-terminal portion of TRIP8b—the tetratricopepide repeat region and the TRIP8b conserved region—interact with two different regions of the HCN carboxyl-terminal region: the carboxyl-terminal three amino acids (SNL) and the cyclic nucleotide-binding domain, respectively. And finally, using X-ray crystallography, we determined the atomic structure of the tetratricopepide region of TRIP8b in complex with a peptide of the carboxy-terminus of HCN2. Together, these experiments begin to uncover the mechanism for TRIP8b binding and regulation of HCN channels. PMID:22550182

  10. Uniform rotating field network structure to efficiently package a magnetic bubble domain memory

    NASA Technical Reports Server (NTRS)

    Wolfshagen, Ronald G. (Inventor); Ypma, John E. (Inventor); Murray, Glen W. (Inventor); Chen, Thomas T. (Inventor)

    1978-01-01

    A unique and compact open coil rotating magnetic field network structure to efficiently package an array of bubble domain devices is disclosed. The field network has a configuration which effectively enables selected bubble domain devices from the array to be driven in a vertical magnetic field and in an independent and uniform horizontal rotating magnetic field. The field network is suitably adapted to minimize undesirable inductance effects, improve capabilities of heat dissipation, and facilitate repair or replacement of a bubble device.

  11. Evaluation of flawed composite structural components under static and cyclic loading. [fatigue life of graphite-epoxy composite materials

    NASA Technical Reports Server (NTRS)

    Porter, T. R.

    1979-01-01

    The effects of initial defects on the fatigue and fracture response of graphite-epoxy composite laminates are presented. The structural laminates investigated were a typical angle ply laminate, a polar/hoop wound pressure vessel laminate, and a typical engine fan blade laminate. Defects investigated were full and half penetration circular holes, full and half penetration slits, and countersink holes. The effects of the defect size and type on the static fracture strength, fatigue performance, and residual static strength are shown as well as the results of loadings on damage propagation in composite laminates. The data obtained were used to define proof test levels as a qualification procedure in composite structure subjected to cyclic loading.

  12. Structure of the SthK Carboxy-Terminal Region Reveals a Gating Mechanism for Cyclic Nucleotide-Modulated Ion Channels

    PubMed Central

    Kesters, Divya; Brams, Marijke; Nys, Mieke; Wijckmans, Eveline; Spurny, Radovan; Voets, Thomas; Tytgat, Jan; Kusch, Jana; Ulens, Chris

    2015-01-01

    Cyclic nucleotide-sensitive ion channels are molecular pores that open in response to cAMP or cGMP, which are universal second messengers. Binding of a cyclic nucleotide to the carboxyterminal cyclic nucleotide binding domain (CNBD) of these channels is thought to cause a conformational change that promotes channel opening. The C-linker domain, which connects the channel pore to this CNBD, plays an important role in coupling ligand binding to channel opening. Current structural insight into this mechanism mainly derives from X-ray crystal structures of the C-linker/CNBD from hyperpolarization-activated cyclic nucleotide-modulated (HCN) channels. However, these structures reveal little to no conformational changes upon comparison of the ligand-bound and unbound form. In this study, we take advantage of a recently identified prokaryote ion channel, SthK, which has functional properties that strongly resemble cyclic nucleotide-gated (CNG) channels and is activated by cAMP, but not by cGMP. We determined X-ray crystal structures of the C-linker/CNBD of SthK in the presence of cAMP or cGMP. We observe that the structure in complex with cGMP, which is an antagonist, is similar to previously determined HCN channel structures. In contrast, the structure in complex with cAMP, which is an agonist, is in a more open conformation. We observe that the CNBD makes an outward swinging movement, which is accompanied by an opening of the C-linker. This conformation mirrors the open gate structures of the Kv1.2 channel or MthK channel, which suggests that the cAMP-bound C-linker/CNBD from SthK represents an activated conformation. These results provide a structural framework for better understanding cyclic nucleotide modulation of ion channels, including HCN and CNG channels. PMID:25625648

  13. Rotation and structure of FoF1-ATP synthase.

    PubMed

    Okuno, Daichi; Iino, Ryota; Noji, Hiroyuki

    2011-06-01

    F(o)F(1)-ATP synthase is one of the most ubiquitous enzymes; it is found widely in the biological world, including the plasma membrane of bacteria, inner membrane of mitochondria and thylakoid membrane of chloroplasts. However, this enzyme has a unique mechanism of action: it is composed of two mechanical rotary motors, each driven by ATP hydrolysis or proton flux down the membrane potential of protons. The two molecular motors interconvert the chemical energy of ATP hydrolysis and proton electrochemical potential via the mechanical rotation of the rotary shaft. This unique energy transmission mechanism is not found in other biological systems. Although there are other similar man-made systems like hydroelectric generators, F(o)F(1)-ATP synthase operates on the nanometre scale and works with extremely high efficiency. Therefore, this enzyme has attracted significant attention in a wide variety of fields from bioenergetics and biophysics to chemistry, physics and nanoscience. This review summarizes the latest findings about the two motors of F(o)F(1)-ATP synthase as well as a brief historical background.

  14. Hydrogen bond rotations as a uniform structural tool for analyzing protein architecture.

    PubMed

    Penner, Robert C; Andersen, Ebbe S; Jensen, Jens L; Kantcheva, Adriana K; Bublitz, Maike; Nissen, Poul; Rasmussen, Anton M H; Svane, Katrine L; Hammer, Bjørk; Rezazadegan, Reza; Nielsen, Niels Chr; Nielsen, Jakob T; Andersen, Jørgen E

    2014-12-17

    Proteins fold into three-dimensional structures, which determine their diverse functions. The conformation of the backbone of each structure is locally at each C(α) effectively described by conformational angles resulting in Ramachandran plots. These, however, do not describe the conformations around hydrogen bonds, which can be non-local along the backbone and are of major importance for protein structure. Here, we introduce the spatial rotation between hydrogen bonded peptide planes as a new descriptor for protein structure locally around a hydrogen bond. Strikingly, this rotational descriptor sampled over high-quality structures from the protein data base (PDB) concentrates into 30 localized clusters, some of which correlate to the common secondary structures and others to more special motifs, yet generally providing a unifying systematic classification of local structure around protein hydrogen bonds. It further provides a uniform vocabulary for comparison of protein structure near hydrogen bonds even between bonds in different proteins without alignment.

  15. Flow structure on a rotating wing: Effect of steady incident flow

    NASA Astrophysics Data System (ADS)

    Bross, M.; Ozen, C. A.; Rockwell, D.

    2013-08-01

    The flow structure along a rotating wing in steady incident flow is compared to the structure on a rotating wing in quiescent fluid, in order to clarify the effect of advance ratio J (ratio of free-stream velocity to tip velocity of wing). Stereoscopic particle image velocimetry leads to patterns of vorticity, velocity, and Q-criterion (constant values of the second invariant of the velocity gradient tensor), as well as streamlines, which allow identification of critical points of the flow. The effective angle of attack is held constant over the range of J, and the wing rotates from rest to a large angle that corresponds to attainment of the asymptotic state of the flow structure. Prior to the onset of motion, the wing is at high angle of attack and the steady incident flow yields a fully stalled state along the wing. After the onset of rotation, the stalled region quickly gives rise to a stable leading edge vortex. Throughout the rotation maneuver, the development of the flow structure in the leading edge region is relatively insensitive to the value of J. In the trailing-edge region, however, the structure of the shed vorticity layer is strongly dependent on the value of J. Further insight into the effects of J is provided by three-dimensional patterns of spanwise-oriented vorticity, spanwise velocity, and Q-criterion.

  16. Photoelectron spectra and structures of three cyclic dipeptides: PhePhe, TyrPro, and HisGly

    NASA Astrophysics Data System (ADS)

    Wickrama Arachchilage, Anoja P.; Wang, Feng; Feyer, Vitaliy; Plekan, Oksana; Prince, Kevin C.

    2012-03-01

    We have investigated the electronic structure of three cyclic dipeptides: cyclo(Histidyl-Glycyl) (cHisGly), cyclo(Tyrosyl-Prolyl) (cTyrPro), and cyclo(Phenylalanyl-Phenylalanyl) (cPhePhe) in the vapor phase, by means of photoemission spectroscopy and theoretical modeling. The last compound was evaporated from the solid linear dipeptide, but cyclised, losing water to form cPhePhe in the gas phase. The results are compared with our previous studies of three other cyclopeptides. Experimental valence and core level spectra have been interpreted in the light of calculations to identify the basic chemical properties associated with the central diketopiperazine ring, and with the additional functional groups. The valence spectra are generally characterized by a restricted set of outer valence orbitals separated by a gap from most other valence orbitals. The theoretically simulated core and valence spectra of all three cyclic dipeptides agree reasonably well with the experimental spectra. The central ring and the side chains act as independent chromophores whose spectra do not influence one another, except for prolyl dipeptides, where the pyrrole ring is fused with the central ring. In this case, significant changes in the valence and core level spectra were observed, and explained by stronger hybridization of the valence orbitals.

  17. Hyperfine Structure in Rotational Spectra of Deuterated Molecules: the Hds and ND_3 Case Studies

    NASA Astrophysics Data System (ADS)

    Cazzoli, Gabriele; Puzzarini, Cristina

    2016-06-01

    The determination of hyperfine parameters (quadrupole-coupling, spin-spin coupling, and spin-rotation constants) is one of the aims of high-resolution rotational spectroscopy. These parameters are relevant not only from a spectroscopic point of view, but also from a physical and/or chemical viewpoint, as they might provide detailed information on the chemical bond, structure, etc. In addition, the hyperfine structure of rotational spectra is so characteristic that its analysis may help in assigning the spectra of unknown species. In astronomical observations, hyperfine structures of rotational spectra would allow us to gain information on column densities and kinematics, and the omission of taking them into account can lead to a misinterpretation of the line width of the molecular emission lines. Nevertheless, the experimental determination of hyperfine constants can be a challenge not only for actual problems in resolving hyperfine structures themselves, but also due to the lack of reliable estimates or the complexity of the hyperfine structure itself. It is thus important to be able to rely on good predictions for such parameters, which can nowadays be provided by quantum-chemical calculations. In fact, the fruitful interplay of experiment and theory will be demonstrated by means of two study cases: the hypefine structure of the rotational spectra of HDS and ND_3. From an experimental point of view, the Lamb-dip technique has been employed to improve the resolving power in themillimeter- and submillimeterwave frequency range by at least one order of magnitude, thus making it possible to perform sub-Doppler measurements as well as to resolve narrow hyperfine structures. Concerning theory, it will be demonstrated that high-level calculations can provide quantitative estimates for hyperfine parameters (quadrupole coupling constants, spin-rotation tensors, spin-spin couplings, etc.) and shown how theoretical predictions are often essential for a detailed analysis of

  18. An Event-Related Potentials Study of Mental Rotation in Identifying Chemical Structural Formulas

    ERIC Educational Resources Information Center

    Huang, Chin-Fei; Liu, Chia-Ju

    2012-01-01

    The purpose of this study was to investigate how mental rotation strategies affect the identification of chemical structural formulas. This study conducted event-related potentials (ERPs) experiments. In addition to the data collected in the ERPs, a Chemical Structure Conceptual Questionnaire and interviews were also admin-istered for data…

  19. Structural Insights into the Role of the Cyclic Backbone in a Squash Trypsin Inhibitor*

    PubMed Central

    Daly, Norelle L.; Thorstholm, Louise; Greenwood, Kathryn P.; King, Gordon J.; Rosengren, K. Johan; Heras, Begoña; Martin, Jennifer L.; Craik, David J.

    2013-01-01

    MCoTI-II is a head-to-tail cyclic peptide with potent trypsin inhibitory activity and, on the basis of its exceptional proteolytic stability, is a valuable template for the design of novel drug leads. Insights into inhibitor dynamics and interactions with biological targets are critical for drug design studies, particularly for protease targets. Here, we show that the cyclization and active site loops of MCoTI-II are flexible in solution, but when bound to trypsin, the active site loop converges to a single well defined conformation. This finding of reduced flexibility on binding is in contrast to a recent study on the homologous peptide MCoTI-I, which suggested that regions of the peptide are more flexible upon binding to trypsin. We provide a possible explanation for this discrepancy based on degradation of the complex over time. Our study also unexpectedly shows that the cyclization loop, not present in acyclic homologues, facilitates potent trypsin inhibitory activity by engaging in direct binding interactions with trypsin. PMID:24169696

  20. A vision-based dynamic rotational angle measurement system for large civil structures.

    PubMed

    Lee, Jong-Jae; Ho, Hoai-Nam; Lee, Jong-Han

    2012-01-01

    In this paper, we propose a vision-based rotational angle measurement system for large-scale civil structures. Despite the fact that during the last decade several rotation angle measurement systems were introduced, they however often required complex and expensive equipment. Therefore, alternative effective solutions with high resolution are in great demand. The proposed system consists of commercial PCs, commercial camcorders, low-cost frame grabbers, and a wireless LAN router. The calculation of rotation angle is obtained by using image processing techniques with pre-measured calibration parameters. Several laboratory tests were conducted to verify the performance of the proposed system. Compared with the commercial rotation angle measurement, the results of the system showed very good agreement with an error of less than 1.0% in all test cases. Furthermore, several tests were conducted on the five-story modal testing tower with a hybrid mass damper to experimentally verify the feasibility of the proposed system.

  1. A vision-based dynamic rotational angle measurement system for large civil structures.

    PubMed

    Lee, Jong-Jae; Ho, Hoai-Nam; Lee, Jong-Han

    2012-01-01

    In this paper, we propose a vision-based rotational angle measurement system for large-scale civil structures. Despite the fact that during the last decade several rotation angle measurement systems were introduced, they however often required complex and expensive equipment. Therefore, alternative effective solutions with high resolution are in great demand. The proposed system consists of commercial PCs, commercial camcorders, low-cost frame grabbers, and a wireless LAN router. The calculation of rotation angle is obtained by using image processing techniques with pre-measured calibration parameters. Several laboratory tests were conducted to verify the performance of the proposed system. Compared with the commercial rotation angle measurement, the results of the system showed very good agreement with an error of less than 1.0% in all test cases. Furthermore, several tests were conducted on the five-story modal testing tower with a hybrid mass damper to experimentally verify the feasibility of the proposed system. PMID:22969348

  2. The Determination of Molecular Structure from Rotational Spectra

    DOE R&D Accomplishments Database

    Laurie, V. W.; Herschbach, D. R.

    1962-07-01

    An analysis is presented concerning the average molecular configuration variations and their effects on molecular structure determinations. It is noted that the isotopic dependence of the zero-point is often primarily governed by the isotopic variation of the average molecular configuration. (J.R.D.)

  3. Cyclization Phenomena in the Sol-Gel Polymerization of a,w-Bis(triethoxysilyl)alkanes and Incorporation of the Cyclic Structures into Network Silsesquioxane Polymers

    SciTech Connect

    Alam, T.M.; Carpenter, J.P.; Dorhout, P.K.; Greaves, J.; Loy, D.A.; Shaltout, R.; Shea, K.J.; Small, J.H.

    1999-01-04

    Intramolecular cyclizations during acid-catalyzed, sol-gel polymerizations of ct,co- bis(tietioxysilyl)aWmes substintidly lengtien gelties formonomers witietiylene- (l), propylene- (2), and butylene-(3)-bridging groups. These cyclizations reactions were found, using mass spectrometry and %i NMR spectroscopy, to lead preferentially to monomeric and dimeric products based on six and seven membered disilsesquioxane rings. 1,2- Bis(triethoxysilyl)ethane (1) reacts under acidic conditions to give a bicyclic drier (5) that is composed of two annelated seven membered rings. Under the same conditions, 1,3- bis(triethoxysilyl)propane (2), 1,4-bis(triethoxysilyl)butane (3), and z-1,4- bis(triethoxysilyl)but-2-ene (10) undergo an intramolecular condensation reaction to give the six membemd and seven membered cyclic disilsesquioxanes 6, 7, and 11. Subsequently, these cyclic monomers slowly react to form the tricyclic dirners 8,9 and 12. With NaOH as polymerization catalyst these cyclic silsesquioxanes readily ~aeted to afford gels that were shown by CP MAS z%i NMR and infr=d spectroscopes to retain some cyclic structures. Comparison of the porosity and microstructwe of xerogels prepared from the cyclic monomers 6 and 7 with gels prepared directly from their acyclic precursors 2 and 3, indicate that the final pore structure of the xerogels is markedly dependent on the nature of the precursor. In addition, despite the fact that the monomeric cyclic disilsesquioxane species can not be isolated from 1-3 under basic conditions due to their rapid rate of gelation, spectroscopic techniques also detected the presence of the cyclic structures in the resulting polymeric gels.

  4. Structure of Trichamide, a Cyclic Peptide from the Bloom-Forming Cyanobacterium Trichodesmium erythraeum, Predicted from the Genome Sequence†

    PubMed Central

    Sudek, Sebastian; Haygood, Margo G.; Youssef, Diaa T. A.; Schmidt, Eric W.

    2006-01-01

    A gene cluster for the biosynthesis of a new small cyclic peptide, dubbed trichamide, was discovered in the genome of the global, bloom-forming marine cyanobacterium Trichodesmium erythraeum ISM101 because of striking similarities to the previously characterized patellamide biosynthesis cluster. The tri cluster consists of a precursor peptide gene containing the amino acid sequence for mature trichamide, a putative heterocyclization gene, an oxidase, two proteases, and hypothetical genes. Based upon detailed sequence analysis, a structure was predicted for trichamide and confirmed by Fourier transform mass spectrometry. Trichamide consists of 11 amino acids, including two cysteine-derived thiazole groups, and is cyclized by an N—C terminal amide bond. As the first natural product reported from T. erythraeum, trichamide shows the power of genome mining in the prediction and discovery of new natural products. PMID:16751554

  5. Syntheses and Structural Characterizations of Iron(II) Complexes Containing Cyclic Diphosphine Ligands with Positioned Pendant Nitrogen Bases

    SciTech Connect

    Jacobsen, George M.; Shoemaker, R. K.; McNevin, Michael J.; Rakowski DuBois, Mary; DuBois, Daniel L.

    2007-09-24

    A series of new iron(II) complexes that contain cyclic diphosphine ligands with pendant amine bases, P2RN2R’, have been synthesized and characterized (where P2RN2R’ are substituted 1,5-diaza-3,7-diphosphacyclooctanes). These compounds include [Fe(P2PhN2Ph)(CH3CN)4](BF4)2 (1), cis-[Fe(CH3CN)2(P2PhN2Ph)2](BF4)2 (2a), cis-[Fe(CH3CN)2(P2CyN2Bz)2](BF4)2 (2b), cis-Fe(CH3CN)2(P2PhN2Bz)2](BF4)2 (2c), cis-Fe (P2PhN2Ph)2(Cl)2 (3), and trans-[HFe(CH3CN)(P2PhN2Ph)2](BF4), (4). The molecular structures of 1, 2b, and 4 have been confirmed by X-ray diffraction studies. For all complexes the cyclic diphosphine ligands contain one six-membered ring in a chair conformation and one six-membered ring in a boat conformation. For complex 4, the two rings that are in boat conformations result in N--H distances between the pendant amine nitrogens and the hydride ligand of 2.6 to 2.7 Å. Protonation of the pendant bases in complex 4 have been found to form several products. A structural assignment for a dominant protonated isomer has been assigned on the basis of 1H, 31P and 15N spectroscopic techniques. This work was supported by Grant CHE-0240106 from the National Science Foundation. D. L. D. acknowledges the support of the Office of Basic Energy Sciences of the Department of Energy, Chemical Sciences program. The Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

  6. Turbulent Compressible Convection with Rotation. Part 1; Flow Structure and Evolution

    NASA Technical Reports Server (NTRS)

    Brummell, Nicholas H.; Hurlburt, Neal E.; Toomre, Juri

    1996-01-01

    The effects of Coriolis forces on compressible convection are studied using three-dimensional numerical simulations carried out within a local modified f-plane model. The physics is simplified by considering a perfect gas occupying a rectilinear domain placed tangentially to a rotating sphere at various latitudes, through which a destabilizing heat flux is driven. The resulting convection is considered for a range of Rayleigh, Taylor, and Prandtl (and thus Rossby) numbers, evaluating conditions where the influence of rotation is both weak and strong. Given the computational demands of these high-resolution simulations, the parameter space is explored sparsely to ascertain the differences between laminar and turbulent rotating convection. The first paper in this series examines the effects of rotation on the flow structure within the convection, its evolution, and some consequences for mixing. Subsequent papers consider the large-scale mean shear flows that are generated by the convection, and the effects of rotation on the convective energetics and transport properties. It is found here that the structure of rotating turbulent convection is similar to earlier nonrotating studies, with a laminar, cellular surface network disguising a fully turbulent interior punctuated by vertically coherent structures. However, the temporal signature of the surface flows is modified by inertial motions to yield new cellular evolution patterns and an overall increase in the mobility of the network. The turbulent convection contains vortex tubes of many scales, including large-scale coherent structures spanning the full vertical extent of the domain involving multiple density scale heights. Remarkably, such structures align with the rotation vector via the influence of Coriolis forces on turbulent motions, in contrast with the zonal tilting of streamlines found in laminar flows. Such novel turbulent mechanisms alter the correlations which drive mean shearing flows and affect the

  7. Interface structure of co-rotating interaction regions

    NASA Technical Reports Server (NTRS)

    Ogilvie, K. W.; Roelof, E. C.; Forsyth, R. J.

    1997-01-01

    Plasma and particle observations on Ulysses during its passes through the southern and northern heliosphere have revealed that, inside the streamer belt, the large-scale structure of the quiet global heliosphere is dominated by corotating interaction regions (CIRs). Therefore, considerable attention is now being given to the internal plasma structure of CIRs, and in particular, to the manifestations of the stream interfaces that should mark their origins as interactions between low speed solar wind (in the low-latitude streamer belt) and high speed solar wind (from the equatorial extensions of the high latitude polar coronal holes). The SWICS and HI-SCALE experiments on Ulysses combine plasma and energetic particle measurements that are of considerable utility for such studies because, between them, they cover the proton energy range from 10 eV to 5 MeV. These measurements are used, together with magnetic field data, to study the remarkable series of CIRs that occurred during the period beginning July 1992 and the end of 1993 as Ulysses rose from the ecliptic to a southern heliographic latitude of 48 deg. The structure of the regions between the forward and reverse shocks were previously analyzed in terms of the proton specific entropy argument log that should exhibit a discontinuous jump at the stream interface. It was claimed that the stream interface, defined with respect to specific entropy, is also associated with a discontinuity in energetic proton intensities. The energetic particle data (greater than 60 keV) and how they were ordered with respect to interfaces and with respect to the magnetic field were examined.

  8. Unravelling the Conformational Landscape of Nicotinoids: the Structure of Cotinine by Broadband Rotational Spectroscopy

    NASA Astrophysics Data System (ADS)

    Uriarte, Iciar; Ecija, Patricia; Cocinero, Emilio J.; Perez, Cristobal; Caballero-Mancebo, Elena; Lesarri, Alberto

    2015-06-01

    Alkaloids such as nicotine, cotinine or anabasine share a common floppy structural motif consisting of a two-ring assembly with a 3-pyridil methylamine skeleton. In order to investigate the structure-activity relationship of these biomolecules, structural studies with rotational resolution have been carried out for nicotine and anabasine in the gas phase, where these molecules can be probed in an "interaction-free" environment (no solvent or crystal-packing interactions). We hereby present a structural investigation of cotinine in a jet expansion using the chirped-pulse Fourier-transform microwave (CP-FTMW) spectrometer recently built at the University of the Basque Country (UPV-EHU). The rotational spectrum (6-18 GHz) reveals the presence of two different conformations. The conformational preferences of cotinine originate from the internal rotation of the two ring moieties, the detected species differing in a near 180° rotation of pyridine. The final structure is modulated by steric effects. J.-U. Grabow, S. Mata, J. L. Alonso, I. Peña, S. Blanco, J. C. López, C. Cabezas, Phys. Chem. Chem. Phys. 2011, 13, 21063. A. Lesarri, E. J. Cocinero, L. Evangelisti, R. D. Suenram, W. Caminati, J.-U. Grabow, Chem. Eur. J. 2010, 16, 10214.

  9. Effect of paddy-upland rotation on methanogenic archaeal community structure in paddy field soil.

    PubMed

    Liu, Dongyan; Ishikawa, Hiroki; Nishida, Mizuhiko; Tsuchiya, Kazunari; Takahashi, Tomoki; Kimura, Makoto; Asakawa, Susumu

    2015-01-01

    Methanogenic archaea are strict anaerobes and demand highly reduced conditions to produce methane in paddy field soil. However, methanogenic archaea survive well under upland and aerated conditions in paddy fields and exhibit stable community. In the present study, methanogenic archaeal community was investigated in fields where paddy rice (Oryza sativa L.) under flooded conditions was rotated with soybean (Glycine max [L.] Merr.) under upland conditions at different rotation histories, by polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE) and real-time quantitative PCR methods targeting 16S rRNA and mcrA genes, respectively. Soil samples collected from the fields before flooding or seeding, during crop cultivation and after harvest of crops were analyzed. The abundance of the methanogenic archaeal populations decreased to about one-tenth in the rotational plots than in the consecutive paddy (control) plots. The composition of the methanogenic archaeal community also changed. Most members of the methanogenic archaea consisting of the orders Methanosarcinales, Methanocellales, Methanomicrobiales, and Methanobacteriales existed autochthonously in both the control and rotational plots, while some were strongly affected in the rotational plots, with fatal effect to some members belonging to the Methanosarcinales. This study revealed that the upland conversion for one or longer than 1 year in the rotational system affected the methanogenic archaeal community structure and was fatal to some members of methanogenic archaea in paddy field soil. PMID:25113614

  10. Three-dimensional vortex structures in a rotating dipolar Bose–Einstein condensate

    NASA Astrophysics Data System (ADS)

    Kishor Kumar, Ramavarmaraja; Sriraman, Thangarasu; Fabrelli, Henrique; Muruganandam, Paulsamy; Gammal, Arnaldo

    2016-08-01

    We study three-dimensional vortex lattice structures in purely dipolar Bose–Einstein condensate (BEC). By using the mean-field approximation, we obtain a stability diagram for the vortex states in purely dipolar BECs as a function of harmonic trap aspect ratio (λ) and dipole–dipole interaction strength (D) under rotation. Rotating the condensate within the unstable region leads to collapse while in the stable region furnishes stable vortex lattices of dipolar BECs. We analyse stable vortex lattice structures by solving the three-dimensional time-dependent Gross–Pitaevskii equation in imaginary time. Further, the stability of vortex states is examined by evolution in real-time. We also investigate the distribution of vortices in a fully anisotropic trap by increasing eccentricity of the external trapping potential. We observe the breaking up of the condensate in two parts with an equal number of vortices on each when the trap is sufficiently weak, and the rotation frequency is high.

  11. Solar Cycle Fine Structure and Surface Rotation from Ca II K-Line Time Series Data

    NASA Technical Reports Server (NTRS)

    Scargle, Jeff; Keil, Steve; Worden, Pete

    2011-01-01

    Analysis of three and a half decades of data from the NSO/AFRL/Sac Peak K-line monitoring program yields evidence for four components to the variation: (a) the solar cycle, with considerable fine structure and a quasi-periodicity of 122.4 days; (b) a stochastic process, faster than (a) and largely independent of it, (c) a quasi-periodic signal due to rotational modulation, and of course (d) observational errors (shown to be quite small). Correlation and power spectrum analyses elucidate periodic and aperiodic variation of these chromospheric parameters. Time-frequency analysis is especially useful for extracting information about differential rotation, and in particular elucidates the connection between its behavior and fine structure of the solar cycle on approximately one-year time scales. These results further suggest that similar analyses will be useful at detecting and characterizing differential rotation in stars from stellar light-curves such as those being produced at NASA's Kepler observatory.

  12. Supramolecular structures and photoelectronic properties of the inclusion complex of a cyclic free-base porphyrin dimer and C60.

    PubMed

    Nobukuni, Hirofumi; Shimazaki, Yuichi; Uno, Hidemitsu; Naruta, Yoshinori; Ohkubo, Kei; Kojima, Takahiko; Fukuzumi, Shunichi; Seki, Shu; Sakai, Hayato; Hasobe, Taku; Tani, Fumito

    2010-10-11

    A cyclic free-base porphyrin dimer H4-CPD(Py) (CPD = cyclic porphyrin dimer) linked by butadiyne moieties bearing 4-pyridyl groups self-assembles to form a novel porphyrin nanotube in the crystalline state. The cyclic molecules link together through nonclassical C-H⋅⋅⋅N hydrogen bonds and π–π interactions of the pyridyl groups along the crystallographic a axis. H4-CPD(Py) includes a C60 molecule in its cavity in solution. In the crystal structure of the inclusion complex (C60⊂H4-CPD(Py)), the dimer “bites” a C60 molecule by tilting the porphyrin rings with respect to each other, and there are strong π–π interactions between the porphyrin rings and C60. The included C60 molecules form a zigzag chain along the crystallographic b axis through van der Waals contacts with each other. Femtosecond laser flash photolysis of C60⊂H4-CPD(Py) in the solid state with photoexcitation at 420 nm shows the formation of a completely charge-separated state {H4-CPD(Py)·+ + C60·−}, which decays with a lifetime of 470 ps to the ground state. The charge-carrier mobility of the single crystal of C60⊂H4-CPD(Py) was determined by flash photolysis time-resolved microwave conductivity (FP-TRMC) measurements. C60⊂H4-CPD(Py) has an anisotropic charge mobility (Σμ = 0.16 and 0.13 cm2 V(−1)  s(−1)) along the zigzag chain of C60 (which runs at 45° and parallel to the crystallographic b axis). To construct a photoelectrochemical cell, C60⊂H4-CPD(Py) was deposited onto nanostructured SnO2 films on a transparent electrode. The solar cell exhibited photovoltaic activity with an incident photon to current conversion efficiency of 17%.

  13. Cyclic Voltammetry.

    ERIC Educational Resources Information Center

    Evans, Dennis H.; And Others

    1983-01-01

    Cyclic voltammetry is a simple experiment that has become popular in chemical research because it can provide useful information about redox reactions in a form which is easily obtained and interpreted. Discusses principles of the method and illustrates its use in the study of four electrode reactions. (Author/JN)

  14. Molecular structure of the 2:2 complex of cyclic oxaalkyl diamide of o-phthalic acid with sodium perchlorate

    NASA Astrophysics Data System (ADS)

    Huczyński, Adam; Ratajczak-Sitarz, Małgorzata; Katrusiak, Andrzej; Brzezinski, Bogumil

    2010-04-01

    Structure of the 2:2 complex of cyclic oxaalkyl diamide of o-phthalic acid (CPhDA) with sodium perchlorate is studied by X-ray diffraction, ESI-MS, FT-IR, 1H and 13C NMR as well as PM5 semiempirical methods. The crystal space group is P21/n with a = 8.599(1) Å, b = 14.802(2) Å, c = 13.988(2) Å, β = 93.37(1)° and Z = 4. In the dimeric crystal structure each sodium cation is coordinated by oxygen atoms of two CPhDA molecules. The ESI-MS measurements have proved that in the gas phase the 2:2 (or 1:1) as well as 2:1 complexes are formed. In the acetonitrile solution the equilibrium between the 2:2 and 1:1 complexes is found. The structures of the 2:2, 1:1 and 2:1 complexes of CPhDA with sodium cation are visualized using the PM5 method and discussed in detail.

  15. Three-dimensional flow structure along simultaneously pitching and rotating wings: effect of pitch rate

    NASA Astrophysics Data System (ADS)

    Bross, M.; Rockwell, D.

    2015-04-01

    The flow structure along a simultaneously pitching and rotating wing is investigated using quantitative flow visualization. Imaging is performed for a range of pitch rates, with emphasis on the three-dimensional structure during start-up and relaxation. Surfaces of transparent iso- Q and helicity are employed to interpret the flow physics. The onset and development of the components of the vortex system, i.e., the leading-edge, tip, and trailing-edge vortices, are strongly influenced by the value of pitch rate relative to the rotation rate. Comparisons at the same angle of attack indicate that the formation of vortical structures is delayed with increasing pitch rate. However, comparisons at the same rotation angle for different values of pitch rate reveal similar flow structures, thereby indicating predominance of rotation effects. Extreme values of pitch rate can lead to radically different sequences of development of the components of the three-dimensional vortex system. Nevertheless, consistently positive vorticity flux is maintained through these components and the coherence of the vortex system is maintained.

  16. Parallel processing for nonlinear dynamics simulations of structures including rotating bladed-disk assemblies

    NASA Technical Reports Server (NTRS)

    Hsieh, Shang-Hsien

    1993-01-01

    The principal objective of this research is to develop, test, and implement coarse-grained, parallel-processing strategies for nonlinear dynamic simulations of practical structural problems. There are contributions to four main areas: finite element modeling and analysis of rotational dynamics, numerical algorithms for parallel nonlinear solutions, automatic partitioning techniques to effect load-balancing among processors, and an integrated parallel analysis system.

  17. A search for rotationally-modulated wind-structure in Wolf-Rayet star WR 137

    NASA Astrophysics Data System (ADS)

    Harries, Tim J.

    1999-08-01

    We wish to obtain high signal-to-noise, moderate dispersion time- series spectroscopy of the dust-producting Wolf-Rayet star WR 137. These data will be used to examine the frequency, life-times, and velocity distributions of density inhomogeneities within the wind, and to search for periodic modulation of the line-profile morphology indicative of large-scale azimuthal structure. Evidence for rotational modulation will provide strong support for the hypothesis that WR 137 has an equatorially-compressed wind as a result of rapid rotation, and that it is a carbon-sequence analogue of WRs 6 and 134.

  18. The structure and molecular mechanics calculations of the cyclic (1 → 2)-β- D-glucan secreted by Rhizobium tropici CIAT 899

    NASA Astrophysics Data System (ADS)

    Gil Serrano, Antonio M.; Franco-Rodríguez, Guillermo; González-Jiménez, Isabel; Tejero-Mateo, Pilar; Molina, José Molina; Dobado, J. A.; Megías, Manuel; Romero, Maria Jesús

    1993-12-01

    The structure of the extracellular cyclic (1 → 2)-β- D-glucan secreted by Rhizobium tropici CIAT 899 has been studied by methylation analysis, 1D and 2D NMR experiments, HPLC and FAB-MS. Molecular mechanics (MM2) and theoretical 3JHH coupling constants calculations were performed.

  19. From polymer to monomer: cleavage and rearrangement of Si-O-Si bonds after oxidation yielded an ordered cyclic crystallized structure.

    PubMed

    Zuo, Yujing; Gou, Zhiming; Cao, Jinfeng; Yang, Zhou; Lu, Haifeng; Feng, Shengyu

    2015-07-27

    Polymerization reactions are very common in the chemical industry, however, the reaction in which monomers are obtained from polymers is rarely invesitgated. This work reveals for the first time that oxone can break the Si-O-Si bond and induce further rearrangement to yield an ordered cyclic structure. The oxidation of P1, which is obtained by reaction of 2,2'-1,2-ethanediylbis(oxy)bis(ethanethiol) (DBOET) with 1,3-divinyl-1,1,3,3-tetramethyldisiloxane (MM(Vi)), with oxone yielded cyclic crystallized sulfone-siloxane dimer (P1-ox) after unexpected cleavage and rearrangement of the Si-O-Si bond.

  20. Gas turbine rotor/case structural response to rotating stall: Experimental documentation and analytical approach

    NASA Technical Reports Server (NTRS)

    Haley, P. J.

    1982-01-01

    The forcing functions and structural responses characterizing gas turbine rotor/case system vibration due to rotating stall in an axial flow compressor are described. Two data sets with fundamentally different response characteristics are presented; one is supersynchronous and the other subsynchronous. Conventional beam element rotor dynamics analysis is shown to be severely limited in its ability to predict these responses. A new analytical approach, which significantly increases structural response predictive capability for these phenomena, is briefly discussed.

  1. Plastic-Strain-Amplitude Dependence of Dislocation Structures in Cyclically Deformed <112>-Oriented Cu-7 at. pct Al Alloy Single Crystals

    NASA Astrophysics Data System (ADS)

    Li, X. W.; Peng, N.; Wu, X. M.; Wang, Z. G.

    2014-08-01

    Dislocation structures in Cu-7 at. pct Al alloy single crystals cyclically deformed at different plastic strain amplitudes were investigated by transmission electron microscope (TEM) and compared with the results of Cu single crystals. It is found that the plastic strain amplitude γ pl has an obvious effect on the slip deformation mode, and consequently on the cyclic hardening behavior of Cu-7 at. pct Al alloy single crystals with an intermediate stacking fault energy. For instance, a high slip planarity ( i.e., only formation of planar-slip bands) contributes to the occurrence of a gentle cyclic hardening with a much lower saturation stress at a low γ pl of 4.5 × 10-4. A mixed planar/wavy-slip mode ( e.g., persistent Lüder's bands/wall-like microstructures) at an intermediate γ pl of 2.2 × 10-3 causes an obvious cyclic hardening up to a comparable saturation stress to that for the Cu single crystal. In contrast, the deformation mode is dominated by wavy slip ( e.g., ill-defined dislocation cells and walls) at the highest γ pl of 7.2 × 10-3, causing that its cyclic hardening curve is quite similar to that for the Cu single crystal; in this case, a slightly higher saturation stress level than that for the Cu single crystal is reached due to the additional solid solution strengthening.

  2. In-flight investigation of a rotating cylinder-based structural excitation system for flutter testing

    NASA Technical Reports Server (NTRS)

    Vernon, Lura

    1993-01-01

    A research excitation system was test flown at the NASA Dryden Flight Research Facility on the two-seat F-16XL aircraft. The excitation system is a wingtip-mounted vane with a rotating slotted cylinder at the trailing edge. As the cylinder rotates during flight, the flow is alternately deflected upward and downward through the slot, resulting in a periodic lift force at twice the cylinder's rotational frequency. Flight testing was conducted to determine the excitation system's effectiveness in the subsonic, transonic, and supersonic flight regimes. Primary research objectives were to determine the system's ability to develop adequate force levels to excite the aircraft's structure and to determine the frequency range over which the system could excite structural modes of the aircraft. In addition, studies were conducted to determine optimal excitation parameters, such as sweep duration, sweep type, and energy levels. The results from the exciter were compared with results from atmospheric turbulence excitation at the same flight conditions. The comparison indicated that the vane with a rotating slotted cylinder provides superior results. The results from the forced excitation were of higher quality and had less variation than the results from atmospheric turbulence. The forced excitation data also invariably yielded higher structural damping values than those from the atmospheric turbulence data.

  3. Story Structure in a Sample of African-American Children: Evidence for a Cyclical Story Schema.

    ERIC Educational Resources Information Center

    Bidell, Thomas R.; Hubbard, Lady June; Weaver, Monica

    A study examined the scripts or schemata--cognitive structures that represent story prototypes--used by African-American children and how they differ from story telling patterns of White middle-class children using a Western, linear "problem solving" story schemata. Samples of oral narratives were collected from 50 African-American children, ages…

  4. Vortex structures of rotating spin-orbit-coupled Bose-Einstein condensates

    SciTech Connect

    Zhou Xiangfa; Zhou Jing; Wu Congjun

    2011-12-15

    We consider the quasi-two-dimensional two-component Bose-Einstein condensates with Rashba spin-orbit (SO) coupling in a rotating trap. The rotation angular velocity couples to the mechanical angular momentum, which contains a noncanonical part arising from SO coupling. The effects of an external Zeeman term favoring spin polarization along the radial direction is also considered, which has the same form as the noncanonical part of the mechanical angular momentum. The rotating condensate exhibits a variety of rich structures by varying the strengths of the trapping potential and interaction. With a strong trapping potential, the condensate exhibits a half-quantum vortex-lattice configuration. Such a configuration is driven to the normal one by introducing the external radial Zeeman field. In the case of a weak trap potential, the condensate exhibits a multidomain pattern of plane-wave states under the external radial Zeeman field.

  5. Instantaneous mode contamination and parametric combination instability of spinning cyclically symmetric ring structures with expanding application to planetary gear ring

    NASA Astrophysics Data System (ADS)

    Wang, Shiyu; Sun, Wenjia; Wang, Yaoyao

    2016-08-01

    This work addresses the free and parametric elastic vibrations of the spinning cyclically symmetric ring structures. The focus is on the instantaneous mode contamination, parametric combination instability and their connections. An analytical model is developed by using the Hamilton's principle for the in-plane bending deflection, the distinction of which is in the arbitrary distributions of the attached mass and stiffness. A special case with equally-spaced discrete mass particles and spinning springs is detailed. The uneven tangential force and the time-invariant deflection caused by the mass particles are formulated. The results imply that the order of such deflection is equal to the number of the mass particles. The instantaneous mode contamination and parametric combination instability are captured by the perturbation and superposition mode shapes of the stationary smooth ring by introducing complex coefficients. The contamination rule is similar to that of the stationary structure but the contamination strength is time-variant due to the spinning springs. New analytical results and quantitative explanations on the contamination and instability especially their connections are presented. As an application of the proposed method, the free and parametric vibrations of the planetary gear ring are formulated. Main results are demonstrated by means of the numerical simulations and compared with the existing studies.

  6. Rotating columns: Relating structure-from-motion, accretion/deletion, and figure/ground

    PubMed Central

    Froyen, Vicky; Feldman, Jacob; Singh, Manish

    2013-01-01

    We present a novel phenomenon involving an interaction between accretion deletion, figure-ground interpretation, and structure-from-motion. Our displays contain alternating light and dark vertical regions in which random-dot textures moved horizontally at constant speed but in opposite directions in alternating regions. This motion is consistent with all the light regions in front, with the dark regions completing amodally into a single large surface moving in the background, or vice versa. Surprisingly, the regions that are perceived as figural are also perceived as 3-D volumes rotating in depth (like rotating columns)—despite the fact that dot motion is not consistent with 3-D rotation. In a series of experiments, we found we could manipulate which set of regions is perceived as rotating volumes simply by varying known geometric cues to figure ground, including convexity, parallelism, symmetry, and relative area. Subjects indicated which colored regions they perceived as rotating. For our displays we found convexity to be a stronger cue than either symmetry or parallelism. We furthermore found a smooth monotonic decay of the proportion by which subjects perceive symmetric regions as figural, as a function of their relative area. Our results reveal an intriguing new interaction between accretion-deletion, figure-ground, and 3-D motion that is not captured by existing models. They also provide an effective tool for measuring figure-ground perception. PMID:23946432

  7. Rotating columns: relating structure-from-motion, accretion/deletion, and figure/ground.

    PubMed

    Froyen, Vicky; Feldman, Jacob; Singh, Manish

    2013-08-14

    We present a novel phenomenon involving an interaction between accretion deletion, figure-ground interpretation, and structure-from-motion. Our displays contain alternating light and dark vertical regions in which random-dot textures moved horizontally at constant speed but in opposite directions in alternating regions. This motion is consistent with all the light regions in front, with the dark regions completing amodally into a single large surface moving in the background, or vice versa. Surprisingly, the regions that are perceived as figural are also perceived as 3-D volumes rotating in depth (like rotating columns)-despite the fact that dot motion is not consistent with 3-D rotation. In a series of experiments, we found we could manipulate which set of regions is perceived as rotating volumes simply by varying known geometric cues to figure ground, including convexity, parallelism, symmetry, and relative area. Subjects indicated which colored regions they perceived as rotating. For our displays we found convexity to be a stronger cue than either symmetry or parallelism. We furthermore found a smooth monotonic decay of the proportion by which subjects perceive symmetric regions as figural, as a function of their relative area. Our results reveal an intriguing new interaction between accretion-deletion, figure-ground, and 3-D motion that is not captured by existing models. They also provide an effective tool for measuring figure-ground perception.

  8. Probing the three-dimensional structure of a rotating turbulent flow

    NASA Astrophysics Data System (ADS)

    Ruppert-Felsot, Jori E.; Zhang, Hepeng

    2005-11-01

    We study laboratory produced fluid turbulence under the influence of rapid rotation. Three-dimensional turbulence was generated by strong pumping through sources and sinks at the bottom of a deep rotating tank (48.4 cm high, 39.4 cm diameter) filled with water. The resulting flow evolved toward quasi-two-dimensional (quasi-2D) turbulence with increasing height in the tank. The quasi-2D flow near the top of the tank contained many long-lived coherent vortices and jetsootnotetextJ. E. Ruppert- Felsot, O. Praud, E. Sharon, and H. L. Swinney, Phys. Rev. E 72, 016311 (2005). Digital particle image velocimetry measurements of the flow field were made using tracer particles illuminated by laser light-sheets. Measurements using two synchronized cameras and vertically separated horizontal light-sheets revealed that the coherent vortices were columnar and vertically extended throughout the tank. We found the simultaneously measured vertically separated horizontal projections of the velocity field to be well correlated even at moderate rotation. Further, a gradual spatial decay was observed in the correlation for increasing vertical separation, rather than a sharp transition. The findings were consistent with the effect of rotation to cause a quasi-2D column-like flow structure aligned along the axis of rotation.

  9. Turbulent statistics and flow structures in spanwise-rotating turbulent plane Couette flows

    NASA Astrophysics Data System (ADS)

    Gai, Jie; Xia, Zhenhua; Cai, Qingdong; Chen, Shiyi

    2016-09-01

    A series of direct numerical simulations of spanwise-rotating turbulent plane Couette flows at a Reynolds number of 1300 with rotation numbers Ro between 0 and 0.9 is carried out to investigate the effects of anticyclonic rotation on turbulent statistics and flow structures. Several typical turbulent statistics are presented, including the mean shear rate at the centerline, the wall-friction Reynolds number, and volume-averaged kinetic energies with respect to the secondary flow field, turbulent field, and total fluctuation field. Our results show that the rotation changes these quantities in different manners. Volume-averaged balance equations for kinetic energy are analyzed and it turns out that the interaction term acts as a kinetic energy bridge that transfers energy from the secondary flow to the turbulent fluctuations. Several typical flow regimes are identified based on the correlation functions across the whole channel and flow visualizations. The two-dimensional roll cells are observed at weak rotation Ro=0.01 , where alternant clustering of vortices appears. Three-dimensional roll cells emerge around Ro≈0.02 , where the clustering of vortices shows the meandering and bifurcating behavior. For moderate rotation 0.07 ≲Ro≲0.36 , well-organized structures are observed, where the herringbonelike vortices are clustered between streaks from the top view of three-dimensional flow visualization and form annuluses. More importantly, the vortices are rather confined to one side of the walls when Ro≤0.02 and are inclined from the bottom to upper walls when Ro≥0.07 .

  10. Near-infrared Structure of Fast and Slow-rotating Disk Galaxies

    NASA Astrophysics Data System (ADS)

    Schechtman-Rook, Andrew; Bershady, Matthew A.

    2014-11-01

    We investigate the stellar disk structure of six nearby edge-on spiral galaxies using high-resolution JHK s-band images and three-dimensional radiative transfer models. To explore how mass and environment shape spiral disks, we selected galaxies with rotational velocities between 69 km s-1 structure. Of the fast-rotating (V rot > 150 km s-1) galaxies, only NGC 4013 has the super-thin+thin+thick nested disk structure seen in NGC 891 and the Milky Way, albeit with decreased oblateness, while NGC 1055, a disturbed massive spiral galaxy, contains disks with hz <~ 200 pc. NGC 4565, another fast-rotator, contains a prominent ring at a radius ~5 kpc but no super-thin disk. Despite these differences, all fast-rotating galaxies in our sample have inner truncations in at least one of their disks. These truncations lead to Freeman Type II profiles when projected face-on. Slow-rotating galaxies are less complex, lacking inner disk truncations and requiring fewer disk components to reproduce their light distributions. Super-thin disk components in undisturbed disks contribute ~25% of the total K s-band light, up to that of the thin-disk contribution. The presence of super-thin disks correlates with infrared flux ratios; galaxies with super-thin disks have f{K_s}/f60 μ m ≤ 0.12 for integrated light, consistent with super-thin disks being regions of ongoing star-formation. Attenuation-corrected vertical color gradients in (J - K s) correlate with the observed disk structure and are consistent with population gradients with young-to-intermediate ages closer to the mid-plane, indicating that disk heating—or cooling—is a ubiquitous phenomenon.

  11. Exact solution to the problem of N bodies forming a multi-layer rotating structure.

    PubMed

    Smulsky, Joseph J

    2015-01-01

    Exact solutions to the problem of the Newtonian gravitational interaction of N material points moving around N 2 concentric circular orbits are considered. Each circular orbit contains N 3 axisymmetrically located bodies having identical masses. The structure as a whole rotates around its symmetry axis. Such structures are identical to the homographic-dynamics configurations, or planar central configurations, known from literature. Conceptually, those structures can be considered as structures formed by mutually embedded polygons with point bodies placed at polygon vortices. For structures involving less than 20 bodies, solutions were obtained using Hamiltonian-mechanics methods. In the study, the forces acting on each body in the rotating structure from the side of all other bodies were found. The differential motion equations of the bodies were reduced to a system of linear algebraic equations for the body masses. Solutions in various forms were obtained. For specifying the initial parameters and for calculating all other characteristics of the structures, a computer program RtCrcSt2.for has been developed. Structures comprising up to one million bodies have been calculated. Graphical images of obtained structures are presented, and their properties are described. Stability problems for examined structures are considered, and possible application of obtained results to celestial- and space-mechanics problems is discussed. PMID:26203407

  12. Exact solution to the problem of N bodies forming a multi-layer rotating structure.

    PubMed

    Smulsky, Joseph J

    2015-01-01

    Exact solutions to the problem of the Newtonian gravitational interaction of N material points moving around N 2 concentric circular orbits are considered. Each circular orbit contains N 3 axisymmetrically located bodies having identical masses. The structure as a whole rotates around its symmetry axis. Such structures are identical to the homographic-dynamics configurations, or planar central configurations, known from literature. Conceptually, those structures can be considered as structures formed by mutually embedded polygons with point bodies placed at polygon vortices. For structures involving less than 20 bodies, solutions were obtained using Hamiltonian-mechanics methods. In the study, the forces acting on each body in the rotating structure from the side of all other bodies were found. The differential motion equations of the bodies were reduced to a system of linear algebraic equations for the body masses. Solutions in various forms were obtained. For specifying the initial parameters and for calculating all other characteristics of the structures, a computer program RtCrcSt2.for has been developed. Structures comprising up to one million bodies have been calculated. Graphical images of obtained structures are presented, and their properties are described. Stability problems for examined structures are considered, and possible application of obtained results to celestial- and space-mechanics problems is discussed.

  13. Similarity recognition of molecular structures by optimal atomic matching and rotational superposition.

    PubMed

    Helmich, Benjamin; Sierka, Marek

    2012-01-15

    An algorithm for similarity recognition of molecules and molecular clusters is presented which also establishes the optimum matching among atoms of different structures. In the first step of the algorithm, a set of molecules are coarsely superimposed by transforming them into a common reference coordinate system. The optimum atomic matching among structures is then found with the help of the Hungarian algorithm. For this, pairs of structures are represented as complete bipartite graphs with a weight function that uses intermolecular atomic distances. In the final step, a rotational superposition method is applied using the optimum atomic matching found. This yields the minimum root mean square deviation of intermolecular atomic distances with respect to arbitrary rotation and translation of the molecules. Combined with an effective similarity prescreening method, our algorithm shows robustness and an effective quadratic scaling of computational time with the number of atoms.

  14. The rotational order–disorder structure of the reversibly photoswitchable red fluorescent protein rsTagRFP

    SciTech Connect

    Pletnev, Sergei; Subach, Fedor V.; Verkhusha, Vladislav V.; Dauter, Zbigniew

    2014-01-01

    An analysis of the rotational order–disorder structure of the reversibly photoswitchable red fluorescent protein rsTagRFP is presented. The rotational order–disorder (OD) structure of the reversibly photoswitchable fluorescent protein rsTagRFP is discussed in detail. The structure is composed of tetramers of 222 symmetry incorporated into the lattice in two different orientations rotated 90° with respect to each other around the crystal c axis and with tetramer axes coinciding with the crystallographic twofold axes. The random distribution of alternatively oriented tetramers in the crystal creates the rotational OD structure with statistically averaged I422 symmetry. Despite order–disorder pathology, the structure of rsTagRFP has electron-density maps of good quality for both non-overlapping and overlapping parts of the model. The crystal contacts, crystal internal architecture and a possible mechanism of rotational OD crystal formation are discussed.

  15. Diversity among microbial cyclic lipopeptides: iturins and surfactins. Activity-structure relationships to design new bioactive agents.

    PubMed

    Bonmatin, Jean-Marc; Laprévote, Olivier; Peypoux, Françoise

    2003-09-01

    A prominent group of bioactive lipopeptides produced by Bacillus species is constituted by iturins, surfactins and lichenysins. Interest in such substances results in their exceptional surfactant power, and their valuable antifungal, antibacterial, antitumoral and anti-Mycoplasma properties. As is typical for peptidic secondary-metabolites synthesized by the polyenzymic pathway, they are produced as mixtures of components varying in the peptidic and/or in the lipidic structure. In the context of structure-activity relationships, it is possible to take advantage of the adaptability of the biosynthesis system by systematically adding selected amino acids in the culture medium of the producing bacterium. When an amino acid is used as the sole nitrogen source, it is inserted directly into selected positions of the peptide sequence, thus amplifying the original structural microheterogeneity via a production of variants. This method revealed very efficient for increasing the amounts of preexisting variants and for building new variants of surfactins and lichenysins but totally inefficient with iturins. In this group, the peptidic diversity strictly depends on the selected strain. So far the screening remained the only method to discover new iturins. Another interesting peculiarity is the common occurrence in a single strain of two lipopeptides with different core structures such as surfactins and iturins. Taken together, these features led to an extensive metabolite pattern. Besides, engineered variants and chemical derivatives enlarged the array of available molecules. Despite the high degree of chemical similarity, the separation of variants and/or homologues was successfully achieved by reversed-phase HPLC leading to well-separated compounds ideally suited to investigation of structure-activity relationships. Improved physical techniques such as 2D-NMR and mass spectrometry allowed to describe efficiently and rapidly the composition of cyclic lipopeptides even in

  16. Distinct molecular structures and hydrogen bond patterns of α,α-diethyl-substituted cyclic imide, lactam, and acetamide derivatives in the crystalline phase

    NASA Astrophysics Data System (ADS)

    Krivoshein, Arcadius V.; Ordonez, Carlos; Khrustalev, Victor N.; Timofeeva, Tatiana V.

    2016-10-01

    α,α-Dialkyl- and α-alkyl-α-aryl-substituted cyclic imides, lactams, and acetamides show promising anticonvulsant, anxiolytic, and anesthetic activities. While a number of crystal structures of various α-substituted cyclic imides, lactams, and acetamides were reported, no in-depth comparison of crystal structures and solid-state properties of structurally matched compounds have been carried out so far. In this paper, we report molecular structure and intermolecular interactions of three α,α-diethyl-substituted compounds - 3,3-diethylpyrrolidine-2,5-dione, 3,3-diethylpyrrolidin-2-one, and 2,2-diethylacetamide - in the crystalline phase, as studied using single-crystal X-ray diffraction and IR spectroscopy. We found considerable differences in the patterns of H-bonding and packing of the molecules in crystals. These differences correlate with the compounds' melting points and are of significance to physical pharmacy and formulation development of neuroactive drugs.

  17. Structure and mode of action of cyclic lipopeptide pseudofactin II with divalent metal ions.

    PubMed

    Janek, Tomasz; Rodrigues, Lígia R; Gudiña, Eduardo J; Czyżnikowska, Żaneta

    2016-10-01

    The interaction of natural lipopeptide pseudofactin II with a series of doubly charged metal cations was examined by matrix-assisted laser-desorption ionization-time of flight (MALDI-TOF) mass spectrometry and molecular modelling. The molecular modelling for metal-pseudofactin II provides information on the metal-peptide binding sites. Overall, Mg(2+), Ca(2+) and Zn(2+) favor the association with oxygen atoms spanning the peptide backbone, whereas Cu(2+) is coordinated by three nitrogens. Circular dichroism (CD) results confirmed that Zn(2+) and Cu(2+) can disrupt the secondary structure of pseudofactin II at high concentrations, while Ca(2+) and Mg(2+) did not essentially affect the structure of the lipopeptide. Interestingly, our results showed that the addition of Zn(2+) and Cu(2+) helped smaller micelles to form larger micellar aggregates. Since pseudofactin II binds metals, we tested whether this phenomena was somehow related to its antimicrobial activity against Staphylococcus epidermidis and Proteus mirabilis. We found that the antimicrobial effect of pseudofactin II was increased by supplementation of culture media with all tested divalent metal ions. Finally, by using Gram-positive and Gram-negative bacteria we showed that the higher antimicrobial activity of metal complexes of pseudofactin II is attributed to the disruption of the cytoplasmic membrane. PMID:27416562

  18. Structural Characterisation of Fenchone and its Complexes with Ethanol by Broadband Rotational Spectroscopy

    NASA Astrophysics Data System (ADS)

    Loru, Donatella; Sanz, M. Eugenia

    2016-06-01

    Although significant advances in understanding the human olfactory system have taken place over the last two decades, detailed information on how the interactions between odorants and olfactory receptors occur at the molecular level is still lacking. To achieve a better understanding on the molecular mechanisms involved in olfaction, we are investigating several odorants and their interactions with mimics of amino acid residues in olfactory receptors. We present here the structural characterisation of fenchone (C10H16O) and its complexes with ethanol (to mimic the side chain of serine) using a 2-8 GHz chirped-pulse Fourier transform microwave spectrometer built at King's College London. The rotational spectrum of the parent species and all the 13C and 18O isotopologues of fenchone was observed, and from the experimental rotational constants the substitution (r0) and effective (rs) structures of fenchone were determined. The rotational spectrum of fenchone-ethanol was observed by adding ethanol to the carrier gas and passing the mixture through a receptacle with fenchone. Several 1:1 complexes of fenchone-ethanol have been identified in the rotational spectrum. In all the complexes the ethanol molecule binds to the carbonyl group through an O-H· · · O hydrogen bond.

  19. Cyclic tetraureas with variable flexibility--synthesis, crystal structures and properties.

    PubMed

    Meshcheryakov, Denys; Arnaud-Neu, Françoise; Böhmer, Volker; Bolte, Michael; Cavaleri, Julien; Hubscher-Bruder, Véronique; Thondorf, Iris; Werner, Sabine

    2008-09-21

    Macrocyclic molecules containing several amide or urea functions may serve as anion receptors. We describe the synthesis of 32-membered macrocycles, in which four rigid xanthene units (X) and/or diphenyl ether units (D) as flexible analogues are linked via urea groups. All six possible combinations of these units (XXXX, XXXD, XXDD, XDXD, XDDD and DDDD) were synthesized and two examples were characterised by single-crystal X-ray analyses (DDDD and two structures for XXXD). Both macrocycles showed distinct differences in their overall conformation and consequently in their hydrogen-bonding pattern. Hydrogen-bonded solvent molecules are found for both compounds and intramolecular hydrogen bonds for the two structures of XXXD, but surprisingly no direct intermolecular hydrogen bonds between the macrocyclic tetraurea molecules. The interaction with various anions was studied by (1)H NMR spectroscopy. Stability constants for all tetramers were determined by UV spectroscopy for complexes with chloride, bromide, acetate and dihydrogenphosphate in acetonitrile-THF (3:1). The strongest binding was found for XXXD and acetate (log beta = 7.4 +/- 0.2), the weakest for XXXX and acetate (log beta = 5.1 +/- 0.5). MD simulations in chloroform and acetonitrile boxes show that all molecules except DDDD adopt very similar conformations characterized by an up-down-up-down arrangement of the spacer groups. Clustered solvation shells of acetonitrile molecules around XXXX and DDDD suggest their preorganization for spherical/planar and tetrahedral/bidentate anions, respectively, which in turn was corroborated by simulation of the corresponding complexes with chloride and dihydrogenphosphate.

  20. Nucleoprotein structure influences the response of the mouse mammary tumor virus promoter to activation of the cyclic AMP signalling pathway.

    PubMed Central

    Pennie, W D; Hager, G L; Smith, C L

    1995-01-01

    Recent studies have provided evidence of crosstalk between steroid receptors and cyclic AMP (cAMP) signalling pathways in the regulation of gene expression. A synergism between intracellular phosphorylation inducers and either glucocorticoids or progestins has been shown to occur during activation of the mouse mammary tumor virus (MMTV) promoter. We have investigated the effect of 8-Br-cAMP and okadaic acid, modulators of cellular kinases and phosphatases, on the hormone-induced activation of the MMTV promoter in two forms: a transiently transfected template with a disorganized, accessible nucleoprotein structure and a stably replicating template with an ordered, inaccessible nucleoprotein structure. Both okadaic acid and 8-Br-cAMP synergize significantly with either glucocorticoids or progestins in activating the transiently transfected MMTV template. In contrast, 8-Br-cAMP, but not okadaic acid, is antagonistic to hormone-induced activation of the stably replicating MMTV template. Nuclear run-on experiments demonstrate that this inhibition is a transcriptional effect on both hormone-induced transcription and basal transcription. Surprisingly, 8-Br-cAMP does not inhibit glucocorticoid-induced changes in restriction enzyme access and nuclear factor 1 binding. However, association of a complex with the TATA box region is inhibited in the presence of 8-Br-cAMP. Thus, cAMP treatment interferes with the initiation process but does not inhibit interaction of the receptor with the template. Since the replicated, ordered MMTV templates and the transfected, disorganized templates show opposite responses to 8-Br-cAMP treatment, we conclude that chromatin structure can influence the response of a promoter to activation of the cAMP signalling pathway. PMID:7891707

  1. Structural analysis of the STING adaptor protein reveals a hydrophobic dimer interface and mode of cyclic di-GMP binding.

    PubMed

    Ouyang, Songying; Song, Xianqiang; Wang, Yaya; Ru, Heng; Shaw, Neil; Jiang, Yan; Niu, Fengfeng; Zhu, Yanping; Qiu, Weicheng; Parvatiyar, Kislay; Li, Yang; Zhang, Rongguang; Cheng, Genhong; Liu, Zhi-Jie

    2012-06-29

    STING is an essential signaling molecule for DNA and cyclic di-GMP (c-di-GMP)-mediated type I interferon (IFN) production via TANK-binding kinase 1 (TBK1) and interferon regulatory factor 3 (IRF3) pathway. It contains an N-terminal transmembrane region and a cytosolic C-terminal domain (CTD). Here, we describe crystal structures of STING CTD alone and complexed with c-di-GMP in a unique binding mode. The strictly conserved aa 153-173 region was shown to be cytosolic and participated in dimerization via hydrophobic interactions. The STING CTD functions as a dimer and the dimerization was independent of posttranslational modifications. Binding of c-di-GMP enhanced interaction of a shorter construct of STING CTD (residues 139-344) with TBK1. This suggests an extra TBK1 binding site, other than serine 358. This study provides a glimpse into the unique architecture of STING and sheds light on the mechanism of c-di-GMP-mediated TBK1 signaling.

  2. Rotational Structure of the Ir/fir Bands of Small Pahs

    NASA Astrophysics Data System (ADS)

    Pirali, O.; Gruet, S.; Vervloet, M.; Goubet, M.; Huet, T. R.; Georges, R.; Soulard, P.; Asselin, P.

    2013-06-01

    Accurate spectroscopic measurements in the laboratory of PAH molecules are required to better understand their excitation/relaxation processes which could be responsible for the Unidentified Infrared Bands observed in various objects in space. In particular very few is known concerning the rotational structure of the IR/FIR bands of PAHs. We used the high resolution Fourier Transform interferometer of the AILES beamline of synchrotron SOLEIL to record the rotationally resolved spectra of several IR/FIR vibrational modes of naphthalene (C_{10}H_{8}) and its derivatives: quinoline (C_9H_7N), isoquinoline (C_9H_7N), azulene (C_{10}H_{8}), quinoxaline (C_8H_6N_2), quinazoline (C_8H_6N_2). Firstly, the intense band associated with the ν_{46} CH bending out of plane mode of naphthalene recorded under jet conditions (Jet-AILES experiment developed on the AILES beamline by the IPR-LADIR-PhLAM consortium) revealed transitions involving low J and Ka rotational quantum numbers. These new data permitted to accurately fit the ground state rotational constants and to improve the ν_{46} band constants. As a second step, we performed the rotational analysis of the low frequency ν_{47} and ν_{48} bands of naphthalene recorded at room-temperature in the long absorption pathlength cell from ISMO. As a last step, the high resolution spectra of several bands of azulene, quinoline, isoquinoline and quinoxaline were recorded at room temperature and analyzed using the same procedure. All the rotational constants fitted in the present work were compared to the results of anharmonic DFT calculations realized at various levels of accuracy. S. Albert, et al.; Faraday Discussions, 150, 51 (2011)

  3. Paleomagnetic and structural constraints on rotations in the North Chilean coast ranges

    NASA Astrophysics Data System (ADS)

    Forsythe, R.; Chisholm, L.

    1994-10-01

    Paleomagnetic analysis of seventy-six samples from six sites in the Jurassic to Cretaceous plutons (radiometric ages from 157 to 128 Ma) of the Coastal Cordillera of northern Chile yielded stable remanent magnetization directions. The plutons record both a normal and a reversed characteristics direction. The mean normal direction has a declination of 3.4° an inclination of -38.5°, and an alpha 95 of 10.5°. The mean reversed direction has a declination of 207.8°, an inclination of 33.8°, and an alpha 95 of 10.8°. Paleopoles calculated from these mean and latitude=63.5° S, longitude=191.9° E respectively. In comparison to an APW path, the reversed pole indicates a clockwise rotation of approximately 28°, similar to other regional results, whereas the normal pole is concordant with the present day magnetic field. These results, in and of themselves, could support oroclinal bending or local block rotations. However arrays of secondary faults to the Atacama fault system in the sampling area show characteristic spacings, orientations, and displacements. Restoration of displacements results in a 31° clockwise rotation of fault blocks; essentially removing the observed paleomagnetic discordance. Thus, structural data confirms the local block rotation model. The existence of clockwise discordant paleomagnetic data within the sinistral (counterclockwise) Atacama Fault zone (AFZ) underscores the ambiguity of using the sense of rotation to infer the sense of motion on the larger shear zone. Age constraints for motions along the AFZ suggest that these rotations were completed in the Early Cretaceous; essentially coeval with magmatic activity within the Coast Ranges, and underscores the magmatic arc, rather than forearc, setting for this tectonic event.

  4. Structure-structure coupling by liquids: Vibration measurements on a rotating disk with self-tracking LDV

    NASA Astrophysics Data System (ADS)

    Weder, Mario; Horisberger, Beat; Monette, Christine; Dual, Jürg

    2016-06-01

    We present an experimental setup to investigate the structure-structure coupling of a stationary and a rotating disk coupled by an intermediate liquid. This coupling mechanism is particularly important in the mechanical design of Francis turbines, where the vibration of the turbine runner is coupled with the adjacent non-rotating structure. The vibration of the disks is measured using laser Doppler velocimetry (LDV). Whereas we could use a standard scanning LDV system to measure the stationary disk, we had to design and implement a polar scan unit based on the self-tracking LDV method. Here we show the design concept of the setup with a closer look on the self-tracking LDV system as well as selected results of the coupled vibration.

  5. Volcanics and structure of the famous narrowgate rift: Evidence for cyclic evolution: AMAR 1

    SciTech Connect

    Crane, K.; Ballard, R.D.

    1981-06-10

    A near-bottom photographic survey on the Mid-Atlantic Ridge from the FAMOUS region south to Transform B reveals structural and volcanologic evidence for an alternating widening and narrowing rift valley. Extension wedges appear to be propagating south from Transform A and north from Transform B. These merge at Mt. Mars, where the rift valley is narrowest and shallowest (Narrowgate), giving the valley a symmetrical hourglass shape. Three major volcanic en echelon lineaments trend N10 /sup 0/E, 10/sup 0/ oblique to the strike of the inner walls. Faulting and fissuring are antisymmetrical across the rift valley in contrast to the major extension. This contrasting antisymmetry reflects the surficial distribution of stress across crust of varying strengths, whereas the large-scale wedge phenomenon determines the periodicity of transition from a narrow valley to a wide valley. Using vector analysis, the extension wedges are propagating at about 9 cm/yr toward each other. At this rate a narrow rift valley will be fully transformed into wide rift in 0.64 m.y.

  6. Annual reversible plasticity of feeding structures: cyclical changes of jaw allometry in a sea urchin

    PubMed Central

    Ebert, Thomas A.; Hernández, José Carlos; Clemente, Sabrina

    2014-01-01

    A wide variety of organisms show morphologically plastic responses to environmental stressors but in general these changes are not reversible. Though less common, reversible morphological structures are shown by a range of species in response to changes in predators, competitors or food. Theoretical analysis indicates that reversible plasticity increases fitness if organisms are long-lived relative to the frequency of changes in the stressor and morphological changes are rapid. Many sea urchin species show differences in the sizes of jaws (demi-pyramids) of the feeding apparatus, Aristotle's lantern, relative to overall body size, and these differences have been correlated with available food. The question addressed here is whether reversible changes of relative jaw size occur in the field as available food changes with season. Monthly samples of the North American Pacific coast sea urchin Strongylocentrotus purpuratus were collected from Gregory Point on the Oregon (USA) coast and showed an annual cycle of relative jaw size together with a linear trend from 2007 to 2009. Strongylocentrotus purpuratus is a long-lived species and under field conditions individuals experience multiple episodes of changes in food resources both seasonally and from year to year. Their rapid and reversible jaw plasticity fits well with theoretical expectations. PMID:24500161

  7. Effect of cyclic freeze-thawing process on the structure and properties of collagen.

    PubMed

    Ding, Cuicui; Zhang, Min; Li, Guoying

    2015-09-01

    The influence of freeze-thawing cycles (named 'N') on the rheological and thermal properties of bovine skin collagen solution was investigated using a rheometer and differential scanning calorimetry (DSC). The results of dynamic frequency sweep tests showed that the elasticity of collagen increased as N increased to 3, 5 and 7. Especially, after the freeze-thawing cycles of N=7, the recovery capacity of collagen remarkably increased (from 17.76% to 74.98%) and the hysteresis loop areas of collagen also became larger (from 95.53 to 218.24 Pa/s). Moreover, DSC and non-isothermal kinetic analysis revealed that although the freeze-thawing process had little impact on the thermal denaturation temperature, the endothermic enthalpy was increased by 73% when N=7, as estimated from the area under the endothermic peak and from the Friedman isoconversional method. In addition, as observed by atomic force microscopy (AFM), the fibers of collagen became thicker after the process of freeze-thawing cycles, indicating that the aggregation of collagen molecules was enhanced in the process of freeze-thawing. Meanwhile, the morphology of freeze-thawed collagen sponge examined by scanning electron microscopy (SEM) exhibited a porous network structure, and the pores became more regular with increasing N.

  8. Vortex structures of rotating Bose-Einstein condensates in an anisotropic harmonic potential

    SciTech Connect

    Matveenko, S. I.

    2010-09-15

    We found an analytical solution for the vortex structure in a rapidly rotating trapped Bose-Einstein condensate in the lowest Landau level approximation. This solution is exact in the limit of a large number of vortices and is obtained for the case of a condensate in a anisotropic harmonic potential. The solution describes as limiting cases both a triangle vortex lattice in the symmetric potential trap and a quasi-one-dimensional structure of vortex rows in an asymmetric case, when the rotation frequency is very close to the lower trapping potential frequency. The shape of the density profile is found to be close to the Thomas-Fermi inverted paraboloid form, except in the vicinity of edges of a condensate cloud.

  9. Influence of the organized structure of 1-alkyl-3-methylimidazolium tetrafluoroborates on the rotational diffusion of structurally similar nondipolar solutes.

    PubMed

    Gangamallaiah, V; Dutt, G B

    2014-11-26

    To understand how the organized structure of the ionic liquids influences the location and mobility of nondipolar solutes, rotational diffusion of 2,5-dimethyl-1,4-dioxo-3,6-diphenylpyrrolo[3,4-c]pyrrole (DMDPP) and 1,4-dioxo-3,6-diphenylpyrrolo[3,4-c]pyrrole (DPP) has been examined in 1-alkyl-3-methylimidazolium (alkyl = ethyl, butyl, hexyl, and octyl) tetrafluoroborates. Both the solutes are structurally similar-the sole difference being the two NCH3 groups of DMDPP are replaced by two NH groups in DPP. The rotational diffusion of DPP is found to be significantly slower than DMDPP due to specific interactions between the NH groups of the solute and the anion of the ionic liquid. It has been observed that for a given viscosity and temperature, the rotational diffusion of DMDPP becomes progressively faster with an increase in the length of the alkyl chain on the imidazolium cation. DMDPP resides in the nonpolar domains of these ionic liquids whose sizes increase with an increase in the length of the alkyl chain, and as a result it experiences microviscosity that is lower than the bulk viscosity. However, an increase in the length of the alkyl chain has no apparent effect on the rotational diffusion of DPP because specific interactions with tetrafluoroborate necessitate the solute to be located in the vicinity of the anion. The results of this work exemplify that despite having similar size and shape, the rotational diffusion of DMDPP and DPP is quite contrasting as their sites of solubilization and the nature of interactions with the surroundings are vastly different owing to subtle variations in their chemical structures.

  10. HD 18078: A very slowly rotating Ap star with an unusual magnetic field structure

    NASA Astrophysics Data System (ADS)

    Mathys, G.; Romanyuk, I. I.; Kudryavtsev, D. O.; Landstreet, J. D.; Pyper, D. M.; Adelman, S. J.

    2016-02-01

    Context. The existence of a significant population of Ap stars with very long rotation periods (up to several hundred years) has progressively emerged over the past two decades. However, only lower limits of the periods are known for most of them because their variations have not yet been observed over a sufficient timebase. Aims: We determine the rotation period of the slowly rotating Ap star HD 18078 and we derive constraints on the geometrical structure of its magnetic field. Methods: We combine measurements of the mean magnetic field modulus obtained from 1990 to 1997 with determinations of the mean longitudinal magnetic field spanning the 1999-2007 time interval to derive an unambiguous value of the rotation period. We show that this value is consistent with photometric variations recorded in the Strömgren uvby photometric system between 1995 and 2004. We fit the variations of the two above-mentioned field moments with a simple model to constrain the magnetic structure. Results: The rotation period of HD 18078 is (1358 ± 12) d. The geometrical structure of its magnetic field is consistent to first order with a colinear multipole model whose axis is offset from the centre of the star. Conclusions: HD 18078 is only the fifth Ap star with a rotation period longer than 1000 d for which the exact value of that period (as opposed to a lower limit) could be determined. The strong anharmonicity of the variations of its mean longitudinal magnetic field and the shift between their extrema and those of the mean magnetic field modulus are exceptional and indicative of a very unusual magnetic structure. Based in part on observations made at Observatoire de Haute Provence (CNRS), France; at Kitt Peak National Observatory, National Optical Astronomy Observatory (NOAO Prop. ID: KP2442; PI: T. Lanz), which is operated by the Association of Universities for Research in Astronomy (AURA) under cooperative agreement with the National Science Foundation; at the Canada

  11. Effect of Isomeric Structures of Branched Cyclic Hydrocarbons on Densities and Equation of State Predictions at Elevated Temperatures and Pressures

    SciTech Connect

    Wu, Yue; Bamgbade, Babatunde A; Burgess, Ward A; Tapriyal, Deepak; Baled, Hseen O; Enick, Robert M; McHugh, Mark

    2013-07-25

    The cis and trans conformation of a branched cyclic hydrocarbon affects the packing and, hence, the density, exhibited by that compound. Reported here are density data for branched cyclohexane (C6) compounds including methylcyclohexane, ethylcyclohexane (ethylcC6), cis-1,2-dimethylcyclohexane (cis-1,2), cis-1,4-dimethylcyclohexane (cis-1,4), and trans-1,4-dimethylcyclohexane (trans-1,4) determined at temperatures up to 525 K and pressures up to 275 MPa. Of the four branched C6 isomers, cis-1,2 exhibits the largest densities and the smallest densities are exhibited by trans-1,4. The densities are modeled with the Peng–Robinson (PR) equation of state (EoS), the high-temperature, high-pressure, volume-translated (HTHP VT) PREoS, and the perturbed chain, statistical associating fluid theory (PC-SAFT) EoS. Model calculations highlight the capability of these equations to account for the different densities observed for the four isomers investigated in this study. The HTHP VT-PREoS provides modest improvements over the PREoS, but neither cubic EoS is capable of accounting for the effect of isomer structural differences on the observed densities. The PC-SAFT EoS, with pure component parameters from the literature or from a group contribution method, provides improved density predictions relative to those obtained with the PREoS or HTHP VT-PREoS. However, the PC-SAFT EoS, with either set of parameters, also cannot fully account for the effect of the C6 isomer structure on the resultant density.

  12. eCG concentrations, luteal structures, return to cyclicity, and postabortion fertility in embryo transfer recipient mares.

    PubMed

    Cuervo-Arango, J; Aguilar, J J; Vettorazzi, M L; Martínez-Boví, R

    2015-10-01

    The present study characterizes the relationship between the levels of eCG, ovarian morphology, resumption of cyclicity, and fertility in postaborted embryo transfer recipient mares. A total of 32 pregnant recipient mares carrying a male fetus were aborted at approximately 65 days of gestation by single transcervical administration of cloprostenol. In addition, 25 gestation age-matched mares were used as nonaborted controls. The concentration of progesterone, but not of eCG, differed significantly between controls and aborted mares 48 hours after abortion. Of treated mares, 84.4% (27 of 32) expelled the fetus within 48 hours of treatment. The eCG concentration and the number of supplementary luteal structures were lower in mares aborted in November (equivalent to May in Northern Hemisphere) than in January. A total of 6.2%, 37.5%, and 56.2% of the mares entered anestrus, ovulated normally, and had 1 to 2 consecutive anovulatory cycles, respectively. The mean interval from abortion to the first ovulation was 28.5 ± 3.3 days (range, 5-65 days). The correlation between the levels of eCG at abortion and the interval to the first ovulation was poor (r = 0.38; P = 0.03). Of aborted mares, 90% (18 of 20) were reused and became pregnant after embryo transfer at a mean of 57.6 ± 4.4 days after abortion (range, 19-103 days) and eCG concentration of 0.9 ± 0.3 IU/mL (range, 0.1-3.6 IU/mL). In conclusion, the levels of eCG at the time of abortion were extremely variable and did not correlate well with the number of luteal structures or the interval from abortion to the first ovulation.

  13. Tectonic rotations and internal structure of Eocene plutons in Chuquicamata, northern Chile

    NASA Astrophysics Data System (ADS)

    Somoza, R.; Tomlinson, A. J.; Zaffarana, C. B.; Singer, S. E.; Puigdomenech Negre, C. G.; Raposo, M. I. B.; Dilles, J. H.

    2015-07-01

    A paleomagnetic and AMS study on Eocene plutonic complexes in the Calama area, northern Chile, reveals high-temperature, high-coercivity magnetizations of dominantly thermoremanent origin and magnetic fabrics controlled by magnetite. The paleomagnetic results indicate that ~ 43 Ma plutons underwent clockwise tectonic rotation, whereas adjacent ~ 39 Ma plutons did not undergo discernible rotation. This points to a middle Eocene age for the younger tectonic rotations associated with the Central Andean Rotation Pattern in the Chuquicamata-Calama area. The petrofabric in these rocks formed under conditions ranging from purely magmatic (i.e. before full crystallization) to low-temperature solid-state deformation. AMS and paleomagnetism suggest that the plutonic bodies were formed by progressive amalgamation of subvertical magma sheets spanning multiple magnetic polarity chrons. The parallelism between magmatic and tectonic foliations suggests that regional tectonic stress controlled ascent, emplacement and rock deformation during cooling. In this context, we suggest that magma ascent and emplacement in the upper crust likely exploited Mesozoic structures which were locally reactivated in the Eocene.

  14. A link between structure, diffusion and rotations of hydrogen bonding tracers in ionic liquids

    NASA Astrophysics Data System (ADS)

    Araque, Juan C.; Daly, Ryan P.; Margulis, Claudio J.

    2016-05-01

    When solutes are small compared to the size of the ions in an ionic liquid, energetic heterogeneities associated with charge enhanced (stiff) and charge depleted (soft) nanoenvironments are sampled. In a recent article [J. C. Araque et al., J. Phys. Chem. B 119(23), 7015-7029 (2015)], we explored large deviations from Stokes-Einstein translational diffusion caused by such a heterogeneity. The current article is set to explore the effect of soft and stiff solvent environments (i.e., structure) on OH-bond rotations in the case of water and small alcohols in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([" separators="Im1,2 + ][" separators="NTf2- ]). Is solute rotational dynamics heterogeneous? If so, are solute rotations and translations coupled in the sense that stiff and soft solvent environments hinder or speed up both types of dynamics? For the systems studied here, there appears to be a clear connection between translations, rotations, and stiff/soft solvent environments. We also discuss interesting asymmetries of the correlation between solutes with anions and cations.

  15. Clues for a Tortonian reconstruction of the Gibraltar Arc: Structural pattern, deformation diachronism and block rotations

    NASA Astrophysics Data System (ADS)

    Crespo-Blanc, Ana; Comas, Menchu; Balanyá, Juan Carlos

    2016-06-01

    We proposed a reconstruction of one of the tightest orogenic arcs on Earth: the Gibraltar Arc System. This reconstruction, which includes onshore and offshore data, is completed for approximately 9 Ma. The clues that lead us to draw it are based on a review in terms of structures and age of the superposed deformational events that took place during Miocene, with special attention to the external zones. This review and new structural data presented in this paper permit us to constrain the timing of vertical axis-rotations evidenced by previously published paleomagnetic data, and to identify homogeneous domains in terms of relationships between timing of deformation events, (re)magnetization and rotations. In particular, remagnetization in the Betics took place after the main shortening which produced the external fold-and-thrust belts (pre-upper Miocene), but was mostly previous to a contractive reorganization that affected the whole area; it should have occurred during lower Tortonian (between 9.9 and 11 Ma). From Tortonian to Present, block-rotations as high as 53° took place. Together with plate convergence, they accommodated a tightening and lengthening of the Gibraltar Arc System and drastically altered its geometry. As the orientation and position of any pre-9 Ma kinematic indicator or structural element is also modified, our reconstruction should be used as starting point for any pre-Tortonian model of the westernmost orogenic segment of the Alpine-Mediterranean system.

  16. Structure of the torque ring of the flagellar motor and the molecular basis for rotational switching.

    PubMed

    Lee, Lawrence K; Ginsburg, Michael A; Crovace, Claudia; Donohoe, Mhairi; Stock, Daniela

    2010-08-19

    The flagellar motor drives the rotation of flagellar filaments at hundreds of revolutions per second, efficiently propelling bacteria through viscous media. The motor uses the potential energy from an electrochemical gradient of cations across the cytoplasmic membrane to generate torque. A rapid switch from anticlockwise to clockwise rotation determines whether a bacterium runs smoothly forward or tumbles to change its trajectory. A protein called FliG forms a ring in the rotor of the flagellar motor that is involved in the generation of torque through an interaction with the cation-channel-forming stator subunit MotA. FliG has been suggested to adopt distinct conformations that induce switching but these structural changes and the molecular mechanism of switching are unknown. Here we report the molecular structure of the full-length FliG protein, identify conformational changes that are involved in rotational switching and uncover the structural basis for the formation of the FliG torque ring. This allows us to propose a model of the complete ring and switching mechanism in which conformational changes in FliG reverse the electrostatic charges involved in torque generation. PMID:20676082

  17. Structure of the torque ring of the flagellar motor and the molecular basis for rotational switching

    SciTech Connect

    Lee, Lawrence K.; Ginsburg, Michael A.; Crovace, Claudia; Donohoe, Mhairi; Stock, Daniela

    2010-09-13

    The flagellar motor drives the rotation of flagellar filaments at hundreds of revolutions per second, efficiently propelling bacteria through viscous media. The motor uses the potential energy from an electrochemical gradient of cations across the cytoplasmic membrane to generate torque. A rapid switch from anticlockwise to clockwise rotation determines whether a bacterium runs smoothly forward or tumbles to change its trajectory. A protein called FliG forms a ring in the rotor of the flagellar motor that is involved in the generation of torque through an interaction with the cation-channel-forming stator subunit MotA. FliG has been suggested to adopt distinct conformations that induce switching but these structural changes and the molecular mechanism of switching are unknown. Here we report the molecular structure of the full-length FliG protein, identify conformational changes that are involved in rotational switching and uncover the structural basis for the formation of the FliG torque ring. This allows us to propose a model of the complete ring and switching mechanism in which conformational changes in FliG reverse the electrostatic charges involved in torque generation.

  18. Principles of teaching in a structured training programme, the rotations, and the surgical training plan.

    PubMed

    Steiger, H J

    2004-01-01

    The present paper is divided into two parts. In the first part it summarises the essentials of transfer of knowledge and personality from trainer to trainee. The training capacity of a programme should be identified first since the number of residents in training has implications on the structure of the programme. The capacity is limited by the number of surgical "resident cases", which should at least amount to 70 per year and resident. For the future, more emphasis should be laid on the acquirement of methods of self-teaching and continuous self-education, in order to provide the trainees with the ability to cope with changes during their later career more easily. In part two the organisation of rotations as well as the structured surgical training plan are discussed. Teaching can be organised either as a gradual exposure to more and more complex procedures or as a sequence of speciality rotations. Structured teaching of theoretical contents should accompany practical teaching and in academic programmes a scientific rotation should be integrated. The ongoing subspecialisation is currently exceeding the limits of complete coverage during a six-year-programme.

  19. Isolation and structural analysis of the cyclic fatty acid monomers formed from eicosapentaenoic and docosahexaenoic acids during fish oil deodorization.

    PubMed

    Berdeaux, Olivier; Fournier, Véronique; Lambelet, Pierre; Dionisi, Fabiola; Sébédio, Jean Louis; Destaillats, Frédéric

    2007-01-01

    Long-chain polyunsaturated fatty acids (LC-PUFAs) present in fish oils are thermolabile molecules. Among the degradation reactions encountered, thermal cyclization occurs during refining or other heat treatments. Numerous studies have been carried out in the past to quantify and determine the structures of cyclic fatty acid monomers (CFAMs) formed from oleic, linoleic and linolenic acids in heated vegetable oils. Recently, much attention have been given to LC-PUFAs due to their potential health benefits. However, data on quantification of CFAMs formed from these fatty acids, such as eicosapentaenoic acid (EPA, cis-5, cis-8, cis-11, cis-14, cis-17 20:5) and docosahexaenoic acid (DHA, cis-4, cis-7, cis-10, cis-13, cis-16, cis-19 22:6), the two main LC-PUFAs in fish oils, are scarce. In the present study, structural analyses of CFAMs formed from EPA and DHA during the deodorization of fish oil are presented. Fish oil sample was deodorized at 250 degrees C for 3 h under a pressure of 1.5 mbar in a laboratory deodorizer. The CFAMs formed during heat treatment of fish oil were isolated by a combination of saponification, esterification, urea fractionations and column chromatography. Structural analyses of C20- and C22-CFAMs were achieved by gas-chromatography electronic-ionization mass-spectrometry (GC-EI-MS) of their 4,4-dimethyloxazoline (DMOX) derivatives. We identified seven out of 13 possible structures of hydrogenated CFAMs formed from EPA, and nine out of 16 possible structures of CFAM formed from DHA. Major CFAMs from both EPA and DHA were cyclohexyl isomers. All possible cyclohexyl isomers were found but only nine out of 18 of the cyclopentyl isomers were present in concentration sufficient for identification. Chemical mechanisms involved in the formation of polyunsaturated LC-PUFAs have been investigated. The results have shown that general principle involved in the cyclization of LC-PUFAs is same as that for the thermal cyclization of oleic, linoleic and alpha

  20. Heme Distortions in Sperm-Whale Carbonmonoxy Myoglobin: Correlations between Rotational Strengths and Heme Distortions in MD-Generated Structures

    SciTech Connect

    KIEFL,CHRISTOPH; SCREERAMA,NARASIMHA; LU,YI; QIU,YAN; SHELNUTT,JOHN A.; WOODY,ROBERT W.

    2000-07-13

    The authors have investigated the effects of heme rotational isomerism in sperm-whale carbonmonoxy myoglobin using computational techniques. Several molecular dynamics simulations have been performed for the two rotational isomers A and B, which are related by a 180{degree} rotation around the {alpha}-{gamma} axis of the heme, of sperm-whale carbonmonoxy myoglobin in water. Both neutron diffraction and NMR structures were used as starting structures. In the absence of an experimental structure, the structure of isomer B was generated by rotating the heme in the structure of isomer A. Distortions of the heme from planarity were characterized by normal coordinate structural decomposition and by the angle of twist of the pyrrole rings from the heme plane. The heme distortions of the neutron diffraction structure were conserved in the MD trajectories, but in the NMR-based trajectories, where the heme distortions are less well defined, they differ from the original heme deformations. The protein matrix induced similar distortions on the heroes in orientations A and B. The results suggest that the binding site prefers a particular macrocycle conformation, and a 180{degree} rotation of the heme does not significantly alter the protein's preference for this conformation. The intrinsic rotational strengths of the two Soret transitions, separated according to their polarization in the heme plane, show strong correlations with the ruf-deformation and the average twist angle of the pyrrole rings. The total rotational strength, which includes contributions from the chromophores in the protein, shows a weaker correlation with heme distortions.

  1. Cyclic multiverses

    NASA Astrophysics Data System (ADS)

    Marosek, Konrad; Dąbrowski, Mariusz P.; Balcerzak, Adam

    2016-09-01

    Using the idea of regularization of singularities due to the variability of the fundamental constants in cosmology we study the cyclic universe models. We find two models of oscillating and non-singular mass density and pressure (`non-singular' bounce) regularized by varying gravitational constant G despite the scale factor evolution is oscillating and having sharp turning points (`singular' bounce). Both violating (big-bang) and non-violating (phantom) null energy condition models appear. Then, we extend this idea on to the multiverse containing cyclic individual universes with either growing or decreasing entropy though leaving the net entropy constant. In order to get an insight into the key idea, we consider the doubleverse with the same geometrical evolution of the two `parallel' universes with their physical evolution [physical coupling constants c(t) and G(t)] being different. An interesting point is that there is a possibility to exchange the universes at the point of maximum expansion - the fact which was already noticed in quantum cosmology. Similar scenario is also possible within the framework of Brans-Dicke theory where varying G(t) is replaced by the dynamical Brans-Dicke field φ(t) though these theories are slightly different.

  2. Prediction and verification of creep behavior in metallic materials and components for the space shuttle thermal protection system. Volume 2: Phase 2 subsize panel cyclic creep predictions

    NASA Technical Reports Server (NTRS)

    Cramer, B. A.; Davis, J. W.

    1975-01-01

    A method for predicting permanent cyclic creep deflections in stiffened panel structures was developed. The resulting computer program may be applied to either the time-hardening or strain-hardening theories of creep accumulation. Iterative techniques were used to determine structural rotations, creep strains, and stresses as a function of time. Deflections were determined by numerical integration of structural rotations along the panel length. The analytical approach was developed for analyzing thin-gage entry vehicle metallic-thermal-protection system panels subjected to cyclic bending loads at high temperatures, but may be applied to any panel subjected to bending loads. Predicted panel creep deflections were compared with results from cyclic tests of subsize corrugation and rib-stiffened panels. Empirical equations were developed for each material based on correlation with tensile cyclic creep data and both the subsize panels and tensile specimens were fabricated from the same sheet material. For Vol. 1, see N75-21431.

  3. Effects of bimetallic doping on small cyclic and tubular boron clusters: B7M2 and B14M2 structures with M = Fe, Co.

    PubMed

    Pham, Hung Tan; Nguyen, Minh Tho

    2015-07-14

    Using density functional theory with the TPSSh functional and the 6-311+G(d) basis set, we extensively searched for the global minima of two metallic atoms doped boron clusters B6M2, B7M2, B12M2 and B14M2 with transition metal element M being Co and Fe. Structural identifications reveal that B7Co2, B7Fe2 and B7CoFe clusters have global minima in a B-cyclic motif, in which a perfectly planar B7 is coordinated with two metallic atoms placed along the C7 axis. The B6 cluster is too small to form a cycle with the presence of two metals. Similarly, the B12 cluster is not large enough to stabilize the metallic dimer within a double ring 2 × B6 tube. The doped B14M2 clusters including B14Co2, B14Fe2 and B14CoFe have a double ring 2 × B7 tubular shape in which one metal atom is encapsulated by the B14 tube and the other is located at an exposed position. Dissociation energies demonstrate that while bimetallic cyclic cluster B7M2 prefers a fragmentation channel that generates the B7 global minimum plus metallic dimer, the tubular structure B14M2 tends to dissociate giving a bimetallic cyclic structure B7M2 and a B@B6 cluster. The enhanced stability of the bimetallic doped boron clusters considered can be understood from the stabilizing interactions between the anti-bonding MOs of metal-metal dimers and the levels of a disk aromatic configuration (for bimetallic cyclic structures), or the eigenstates of the B14 tubular form (in case of bimetallic tubular structure).

  4. On the molecular/solid-state boundary. A cyclic iron-sulfur cluster of nuclearity eighteen: Synthesis, structure, and properties

    SciTech Connect

    You, Jing-Feng; Snyder, B.S.; Holm, R.H. ); Papaefthymiou, G.C. )

    1990-01-31

    The reaction system FeCl{sub 3}:3.15Na(PhNC(O)Me): 1.78Li{sub 2}S in ethanol/methanol (2:1 (V/v)) affords, after the addition of Pr{sub 4}NBr and a 5-day period of reaction and crystallization, the black compound (Pr{sub 4}N){sub 6}Na{sub 4}Fe{sub 18}S{sub 30} in 60-75% yield. When this material is very slowly crystallized from acetontrile/ether, the solvated compound (Pr{sub 4}N){sub 6}Na{sub 4}Fe{sub 18}S{sub 30} {times} 14MeCN is obtained. This compound crystallizes in triclinic space group P{anti 1} with a = 16.286 (8) {angstrom}, b = 16.718 (8) {angstrom}, c = 17.902 (9) {angstrom}, {alpha} = 115.28 (3){degree}, {beta} = 91.07 (4){degree}, {gamma} = 101.64 (4){degree}, and Z = 1. The structure was refined to R = 6.5%. The crystal structure consists of discrete Pr{sub 4}N{sup +} ions and two Na{sup +} ions weakly associated with the cluster (Na{sub 2}Fe{sub 18}S{sub 30}){sup 8{minus}}, which has a remarkable and unprecedented structure. It is constructed by the fusion of 24 nonplanar Fe{sub 2}s{sub 2} rhombs in edge- and corner-sharing modes such that there are 20 {mu}{sub 2}-S, 8 {mu}{sub 3}-S, and 2 {mu}{sub 4}-S, every FeS{sub 4} unit is tetrahedral, and the 18 Fe atoms are essentially planar. The result is a cyclic or toroidal structure, of lateral dimensions 13.3 {times} 16.0 {angstrom} and a maximum thickness of ca. 3.3 {angstrom}, in which there are no terminal ligands. Two Na{sup +} ions are bound to interior sulfur atoms of the cluster, whose framework can be considered to arise from the sequential connection of known Fe{sub 3}S{sub 4} and Fe{sub 6}S{sub 9} cluster cores. Alternative conceptions of cluster buildup in terms of shared Fe{sub 2}S{sub 2} rhombs and FeS{sub 4} tetrahedra are presented and illustrated.

  5. INTERNAL STRUCTURE OF ASTEROIDS HAVING SURFACE SHEDDING DUE TO ROTATIONAL INSTABILITY

    SciTech Connect

    Hirabayashi, Masatoshi; Sánchez, Diego Paul; Scheeres, Daniel J.

    2015-07-20

    Surface shedding of an asteroid is a failure mode where surface materials fly off due to strong centrifugal forces beyond the critical spin period, while the internal structure does not deform significantly. This paper proposes a possible structure of an asteroid interior that leads to surface shedding due to rapid rotation rates. A rubble pile asteroid is modeled as a spheroid composed of a surface shell and a concentric internal core, the entire assembly called the test body. The test body is assumed to be uniformly rotating around a constant rotation axis. We also assume that while the bulk density and the friction angle are constant, the cohesion of the surface shell is different from that of the internal core. First, developing an analytical model based on limit analysis, we provide the upper and lower bounds for the actual surface shedding condition. Second, we use a Soft-sphere Discrete Element Method (SSDEM) to study dynamical deformation of the test body due to a quasi-static spin-up. In this paper we show the consistency of both approaches. Additionally, the SSDEM simulations show that the initial failure always occurs locally and not globally. In addition, as the core becomes larger, the size of lofted components becomes smaller. These results imply that if there is a strong core in a progenitor body, surface shedding is the most likely failure mode.

  6. Synthesis of a Bent 2-Silaallene with a Perturbed Electronic Structure from a Cyclic Alkyl(amino) Carbene-Diiodosilylene.

    PubMed

    Li, Yan; Chan, Yuk-Chi; Li, Yongxin; Purushothaman, Indu; De, Susmita; Parameswaran, Pattiyil; So, Cheuk-Wai

    2016-09-01

    The cyclic alkyl(amino) carbene (cAAC) 1 reacted with SiI4 in toluene, affording the cAAC-silicon tetraiodide complex [(cAACMe)SiI4] (2, cAACMe = :C(CH2)(CMe2)2NAr, Ar = 2,6-iPr2C6H3). It further reacted with two equivalents of KC8 in toluene at room temperature to afford the first cAAC-diiodosilylene [(cAACMe)SiI2] (3). DFT calculations show that the Ccarbene-Si bond in 3 is formed by the donation of the lone pair of electrons on the Ccarbene atom to the SiI2 moiety, while the π-back-bonding of the lone pair of electrons on the Si atom to the Ccarbene atom is negligible. The presence of the lone pair of electrons on the silicon atom in 3 is also evidenced by its reaction with N3SiMe3 to form the cAAC-silaimine complex [(cAACMe)Si(NSiMe3)I2] (4). Compound 3 reacted with IiPrMe (:C{N(iPr)CMe}2) in n-hexane to form the NHC-cAAC-silyliumylidene iodide [cAACMe(SiI)IiPrMe]I (5), which was then reacted with two equivalents of KC8 in toluene to furnish [cAACMeSi(IiPrMe)] (6). The experimental and theoretical studies suggest that 6 can be described as a bent silaallene with a perturbed electronic structure, which can be attributed to the different donor-acceptor properties of cAACMe and IiPrMe. Compounds 3-6 were elucidated by NMR spectroscopy, X-ray crystallography, and theoretical studies. PMID:27560615

  7. Molecular and Electronic Structure of Cyclic Trinuclear Gold(I) Carbeniate Complexes: Insights for Structure/Luminescence/Conductivity Relationships

    SciTech Connect

    McDougaldJr, Roy N; Chilukuri, Bhaskar; Jia, Huiping; Perez, Michael R; Rabaa, Hassan; Wang, Xiaoping; Nesterov, Vladimir; Cundari, Thomas R.; Gnade, Bruce E; Omary, Mohammad A

    2014-01-01

    An experimental and computational study of correlations between solid-state structure and optical/electronic properties of cyclotrimeric gold(I) carbeniates, [Au-3(RN=COR')(3)] (R, R' = H, Me, Bu-n, or (c)Pe), is reported. Synthesis and structural and photophysical characterization of novel complexes [Au-3(MeN=(COBu)-Bu-n)(3)], [Au-3((BuN)-Bu-n=COMe)(3)], [Au-3((BuN)-Bu-n=(COBu)-Bu-n)(3)], and [Au-3((c)PeN=COMe)(3)] are presented. Changes in R and R' lead to distinctive variations in solid-state stacking, luminescence spectra, and conductive properties. Solid-state emission and excitation spectra for each complex display a remarkable dependence on the solid-state packing of the cyclotrimers. The electronic structure of [Au-3(RN=COR')(3)] was investigated via molecular and solid-state simulations. Calculations on [Au-3(HN=COH)(3)] models indicate that the infinitely extended chain of eclipsed structures with equidistant Au-Au intertrimer aurophilic bonding can have lower band gaps, smaller Stokes shifts, and reduced reorganization energies (lambda). The action of one cyclotrimer as a molecular nanowire is demonstrated via fabrication of an organic field effect transistor and shown to produce a p-type field effect. Hole transport for the same cyclotrimer-doped within a poly(9-vinylcarbazole) host-produced a colossal increase in current density from similar to 1 to similar to 1000 mA/cm(2). Computations and experiments thus delineate the complex relationships between solid-state morphologies, electronic structures, and optoelectronic properties of gold(I) carbeniates.

  8. Near-infrared structure of fast and slow-rotating disk galaxies

    SciTech Connect

    Schechtman-Rook, Andrew; Bershady, Matthew A.

    2014-11-10

    We investigate the stellar disk structure of six nearby edge-on spiral galaxies using high-resolution JHK {sub s}-band images and three-dimensional radiative transfer models. To explore how mass and environment shape spiral disks, we selected galaxies with rotational velocities between 69 km s{sup –1} structure. Of the fast-rotating (V {sub rot} > 150 km s{sup –1}) galaxies, only NGC 4013 has the super-thin+thin+thick nested disk structure seen in NGC 891 and the Milky Way, albeit with decreased oblateness, while NGC 1055, a disturbed massive spiral galaxy, contains disks with h{sub z} ≲ 200 pc. NGC 4565, another fast-rotator, contains a prominent ring at a radius ∼5 kpc but no super-thin disk. Despite these differences, all fast-rotating galaxies in our sample have inner truncations in at least one of their disks. These truncations lead to Freeman Type II profiles when projected face-on. Slow-rotating galaxies are less complex, lacking inner disk truncations and requiring fewer disk components to reproduce their light distributions. Super-thin disk components in undisturbed disks contribute ∼25% of the total K {sub s}-band light, up to that of the thin-disk contribution. The presence of super-thin disks correlates with infrared flux ratios; galaxies with super-thin disks have f{sub K{sub s}}/f{sub 60} {sub μm}≤0.12 for integrated light, consistent with super-thin disks being regions of ongoing star-formation. Attenuation-corrected vertical color gradients in (J – K {sub s}) correlate with the observed disk structure and are consistent with population gradients with young-to-intermediate ages closer to the mid-plane, indicating that disk heating—or cooling—is a ubiquitous phenomenon.

  9. A numerical method for generating rapidly rotating bipolytropic structures in equilibrium

    NASA Astrophysics Data System (ADS)

    Kadam, Kundan; Motl, Patrick M.; Frank, Juhan; Clayton, Geoffrey C.; Marcello, Dominic C.

    2016-10-01

    We demonstrate that rapidly rotating bipolytropic (composite polytropic) stars and toroidal discs can be obtained using Hachisu's self-consistent field technique. The core and the envelope in such a structure can have different polytropic indices and also different average molecular weights. The models converge for high T/|W| cases, where T is the kinetic energy and W is the gravitational energy of the system. The agreement between our numerical solutions with known analytical as well as previously calculated numerical results is excellent. We show that the uniform rotation lowers the maximum core mass fraction or the Schönberg-Chandrasekhar limit for a bipolytropic sequence. We also discuss the applications of this method to magnetic braking in low-mass stars with convective envelopes.

  10. Asymmetric modes and the transition to vortex structures in rotating Rayleigh-Benard convection

    SciTech Connect

    Zhong, F.; Ecke, R.; Steinberg, V. )

    1991-10-28

    We report heat transport measurements and optical shadowgraph visualization of rotating Rayleigh-Benard convection. For dimensionless rotation rates 140{lt}{Omega}{lt}4300, the initial transition to convection, occurring at a Rayleigh number {ital R} much less than the linear-stability value for roll or vortex states, is a forward Hopf bifurcation to an azimuthally asymmetric state with mode number {ital n}. States with {ital n}=3, 4, 5, 6, and 7 exist at low to moderate {ital R} and precess with frequencies that depend on {ital R} and {Omega}. At higher {ital R} there is a continuous transition to a state with noisy, time-dependent heat transport, a distinct array of vortices in the central region, and a modulation of the precession speed of the outer structures.

  11. Forced vibration analysis of rotating structures with application to vertical axis wind turbines

    NASA Astrophysics Data System (ADS)

    Lobitz, D. W.

    Predictive methods for the dynamic analysis of wind turbine systems are important for assessing overall structural integrity and fatigue life. For the former, the identification of resonance points (spectral analysis) is of primary concern. For the latter forced vibration analysis is necessary. These analyses are complicated by the fact that, for a spinning turbine, the stress-producing deformations take place in both fixed and rotating reference systems simultaneously. As an example, the tower of a horizontal axis wind turbine (HAWT) must be analyzed in a fixed frame, and the rotor in a rotating one. Forced vibration analysis is further complicated in that accurate models need to be developed for aeroload prediction. Methods which are available for forced vibration analysis of both horizontal and vertical axis machines are identified and the method which was developed for vertical axis wind turbines is emphasized, with some comparisons of the predictions to experimental data.

  12. Rotational spectra of rare isotopic species of fluoroiodomethane: determination of the equilibrium structure from rotational spectroscopy and quantum-chemical calculations.

    PubMed

    Puzzarini, Cristina; Cazzoli, Gabriele; López, Juan Carlos; Alonso, José Luis; Baldacci, Agostino; Baldan, Alessandro; Stopkowicz, Stella; Cheng, Lan; Gauss, Jürgen

    2012-07-14

    Supported by accurate quantum-chemical calculations, the rotational spectra of the mono- and bi-deuterated species of fluoroiodomethane, CHDFI and CD(2)FI, as well as of the (13)C-containing species, (13)CH(2)FI, were recorded for the first time. Three different spectrometers were employed, a Fourier-transform microwave spectrometer, a millimeter/submillimter-wave spectrometer, and a THz spectrometer, thus allowing to record a huge portion of the rotational spectrum, from 5 GHz up to 1.05 THz, and to accurately determine the ground-state rotational and centrifugal-distortion constants. Sub-Doppler measurements allowed to resolve the hyperfine structure of the rotational spectrum and to determine the complete iodine quadrupole-coupling tensor as well as the diagonal elements of the iodine spin-rotation tensor. The present investigation of rare isotopic species of CH(2)FI together with the results previously obtained for the main isotopologue [C. Puzzarini, G. Cazzoli, J. C. López, J. L. Alonso, A. Baldacci, A. Baldan, S. Stopkowicz, L. Cheng, and J. Gauss, J. Chem. Phys. 134, 174312 (2011); G. Cazzoli, A. Baldacci, A. Baldan, and C. Puzzarini, Mol. Phys. 109, 2245 (2011)] enabled us to derive a semi-experimental equilibrium structure for fluoroiodomethane by means of a least-squares fit procedure using the available experimental ground-state rotational constants together with computed vibrational corrections. Problems related to the missing isotopic substitution of fluorine and iodine were overcome thanks to the availability of an accurate theoretical equilibrium geometry (computed at the coupled-cluster singles and doubles level augmented by a perturbative treatment of triple excitations).

  13. Rotational spectra of rare isotopic species of fluoroiodomethane: Determination of the equilibrium structure from rotational spectroscopy and quantum-chemical calculations

    NASA Astrophysics Data System (ADS)

    Puzzarini, Cristina; Cazzoli, Gabriele; López, Juan Carlos; Alonso, José Luis; Baldacci, Agostino; Baldan, Alessandro; Stopkowicz, Stella; Cheng, Lan; Gauss, Jürgen

    2012-07-01

    Supported by accurate quantum-chemical calculations, the rotational spectra of the mono- and bi-deuterated species of fluoroiodomethane, CHDFI and CD2FI, as well as of the 13C-containing species, 13CH2FI, were recorded for the first time. Three different spectrometers were employed, a Fourier-transform microwave spectrometer, a millimeter/submillimter-wave spectrometer, and a THz spectrometer, thus allowing to record a huge portion of the rotational spectrum, from 5 GHz up to 1.05 THz, and to accurately determine the ground-state rotational and centrifugal-distortion constants. Sub-Doppler measurements allowed to resolve the hyperfine structure of the rotational spectrum and to determine the complete iodine quadrupole-coupling tensor as well as the diagonal elements of the iodine spin-rotation tensor. The present investigation of rare isotopic species of CH2FI together with the results previously obtained for the main isotopologue [C. Puzzarini, G. Cazzoli, J. C. López, J. L. Alonso, A. Baldacci, A. Baldan, S. Stopkowicz, L. Cheng, and J. Gauss, J. Chem. Phys. 134, 174312 (2011);, 10.1063/1.3583498 G. Cazzoli, A. Baldacci, A. Baldan, and C. Puzzarini, Mol. Phys. 109, 2245 (2011)], 10.1080/00268976.2011.609142 enabled us to derive a semi-experimental equilibrium structure for fluoroiodomethane by means of a least-squares fit procedure using the available experimental ground-state rotational constants together with computed vibrational corrections. Problems related to the missing isotopic substitution of fluorine and iodine were overcome thanks to the availability of an accurate theoretical equilibrium geometry (computed at the coupled-cluster singles and doubles level augmented by a perturbative treatment of triple excitations).

  14. Structural parameters modulating the cellular uptake of disulfide-rich cyclic cell-penetrating peptides: MCoTI-II and SFTI-1.

    PubMed

    D'Souza, Charlotte; Henriques, Sónia Troeira; Wang, Conan K; Craik, David J

    2014-12-17

    Peptides are emerging as a new class of therapeutics due to their high potency and specificity for a range of targets, including the inhibition of protein-protein interactions. Disulfide-rich cyclic peptides, in particular, have attracted much attention in drug design due to their ultra-stable structure. Moreover, some of them have been shown to internalize into cells, which makes them potential scaffolds to deliver pharmaceutically bioactive sequences to intracellular targets. Here we examined the effects of structural modifications on the cell-penetrating properties of two disulfide-rich cyclic cell-penetrating peptides, Momordica cochinchinensis trypsin inhibitor II (MCoTI-II) and sunflower trypsin inhibitor-1 (SFTI-1). We found that the cellular uptake of MCoTI-II can be improved by increasing the overall positive charge of the native sequence. On the other hand, mutations to SFTI-1 did not significantly influence its cellular uptake, suggesting a non-specific endocytosis-dependent mechanism of cellular uptake. This study provides an understanding of the structural features affecting the internalization of MCoTI-II and SFTI-1, and hence provides a guide for the development of these disulfide-rich cyclic scaffolds into potential drug leads. PMID:24985034

  15. Structural parameters modulating the cellular uptake of disulfide-rich cyclic cell-penetrating peptides: MCoTI-II and SFTI-1.

    PubMed

    D'Souza, Charlotte; Henriques, Sónia Troeira; Wang, Conan K; Craik, David J

    2014-12-17

    Peptides are emerging as a new class of therapeutics due to their high potency and specificity for a range of targets, including the inhibition of protein-protein interactions. Disulfide-rich cyclic peptides, in particular, have attracted much attention in drug design due to their ultra-stable structure. Moreover, some of them have been shown to internalize into cells, which makes them potential scaffolds to deliver pharmaceutically bioactive sequences to intracellular targets. Here we examined the effects of structural modifications on the cell-penetrating properties of two disulfide-rich cyclic cell-penetrating peptides, Momordica cochinchinensis trypsin inhibitor II (MCoTI-II) and sunflower trypsin inhibitor-1 (SFTI-1). We found that the cellular uptake of MCoTI-II can be improved by increasing the overall positive charge of the native sequence. On the other hand, mutations to SFTI-1 did not significantly influence its cellular uptake, suggesting a non-specific endocytosis-dependent mechanism of cellular uptake. This study provides an understanding of the structural features affecting the internalization of MCoTI-II and SFTI-1, and hence provides a guide for the development of these disulfide-rich cyclic scaffolds into potential drug leads.

  16. Effect of ion-beam treatment on structure and fracture resistance of 12Cr1MoV steel under static, cyclic and dynamic loading

    SciTech Connect

    Panin, S. V. Vlasov, I. V. Sergeev, V. P.; Maruschak, P. O.

    2015-10-27

    Features of the structure and properties modification of 12Cr1MoV steel subjected to irradiation by zirconium ion beam have been investigated with the use of optical and electron microscopy as well as microhardness measurement. It has been shown that upon treatment the structure modification occurred across the entire cross-section of specimens with the thickness of 1 mm. Changes in the mechanical properties of these specimens under static, cyclic and impact loading are interpreted in terms of identified structure changes.

  17. The rotational order–disorder structure of the reversibly photoswitchable red fluorescent protein rsTagRFP

    PubMed Central

    Pletnev, Sergei; Subach, Fedor V.; Verkhusha, Vladislav V.; Dauter, Zbigniew

    2014-01-01

    The rotational order–disorder (OD) structure of the reversibly photoswitchable fluorescent protein rsTagRFP is discussed in detail. The structure is composed of tetramers of 222 symmetry incorporated into the lattice in two different orientations rotated 90° with respect to each other around the crystal c axis and with tetramer axes coinciding with the crystallographic twofold axes. The random distribution of alternatively oriented tetramers in the crystal creates the rotational OD structure with statistically averaged I422 symmetry. Despite order–disorder pathology, the structure of rsTagRFP has electron-density maps of good quality for both non-overlapping and overlapping parts of the model. The crystal contacts, crystal internal architecture and a possible mechanism of rotational OD crystal formation are discussed. PMID:24419376

  18. Horizon structure and shadow of rotating Einstein-Born-Infeld black holes

    NASA Astrophysics Data System (ADS)

    Atamurotov, Farruh

    2016-07-01

    We investigate the horizon structure of the rotating Einstein-Born-Infeld solution which goes over to the Einstein-Maxwell's Kerr-Newman solution as the Born-Infeld parameter goes to innity ( ! 1). We nd that for a given , mass M and charge Q, there exist critical spinning parameter aE and rEH, which corresponds to an extremal Einstein-Born-Infeld black hole with degenerate horizons, and aE decreases and rEH increases with increase in the Born-Infeld parameter . While a < aE describe a non-extremal Einstein-Born- Infeld black hole with outer and inner horizons. Similarly, the effect of on innite redshift surface and in turn on ergoregion is also included. It is well known that a black hole can cast a shadow as an optical appearance due to its strong gravitational eld. We also investigate the shadow cast by the rotating Einstein- Born-Infeld black hole and demonstrate that the null geodesic equations can be integrated that allows us to investigate the shadow cast by a black hole which is found to be a dark zone covered by a circle. Interestingly, the shadows of Einstein-Born-Infeld black hole is slightly smaller than for the Reissner-Nordstrom black hole which are concentric circles, for different values of the Born-Infeld parameter , whose radius decreases with increase in the value of parameter . The shadows for the rotating Einstein-Born-Infeld solution are also included.

  19. Theoretical investigation of rotational rainbow structures in X-Na2 collisions using CI potential surfaces. II. Combined rotational-vibrational excitation for X = He scattering

    NASA Astrophysics Data System (ADS)

    Müller, Wolfgang; Schinke, Reinhard

    1981-08-01

    Combined rotational-vibrational excitaton cross sections for He-Na2 scattering are reported for collision energies of 0.05?E?0.15 eV. The infinite-order-sudden (IOS) approximation is used to decouple the rotational and the orbital angular momenta, whereas the vibrational degree of freedom is treated exactly by solving vibrationally coupled radial equations. An analytical potential energy surface obtained from 160 ab initio CI energies is used in these scattering calculations. The cross sections for vibrational excitation or de-excitation are extremely small compared to the vibrationally elastic cross sections but increase rapidly with the collision energy. The influence of the target vibration on pure rotational excitation processes is negligibly small for energies considered in this study, such that the rigid-rotor approximation applied previously for the same system is confirmed to be reasonable. Furthermore, the rotational rainbow structures which are characteristic for the He-Na2 system depend only very slightly on whether the molecule is initially in the ground n = 0 or the first vibrationally excited state n = 1. This was in contradiction to the experimental finding of Bergmann et al. [J. Chem. Phys. 72, 4777 (1980)], who reported a dramatic enhancement of the rotational energy transfer for scattering within the n = 1 vibrational state. The rotational rainbow maxima occur at almost equal positions independent of whether the transition is vibrationally elastic or inelastic. A small shift to wider scattering angles in the case of Δn = 1 is observed at lower energies.

  20. Plexus structure imaging with thin slab MR neurography: rotating frames, fly-throughs, and composite projections

    NASA Astrophysics Data System (ADS)

    Raphael, David T.; McIntee, Diane; Tsuruda, Jay S.; Colletti, Patrick; Tatevossian, Raymond; Frazier, James

    2006-03-01

    We explored multiple image processing approaches by which to display the segmented adult brachial plexus in a three-dimensional manner. Magnetic resonance neurography (MRN) 1.5-Tesla scans with STIR sequences, which preferentially highlight nerves, were performed in adult volunteers to generate high-resolution raw images. Using multiple software programs, the raw MRN images were then manipulated so as to achieve segmentation of plexus neurovascular structures, which were incorporated into three different visualization schemes: rotating upper thoracic girdle skeletal frames, dynamic fly-throughs parallel to the clavicle, and thin slab volume-rendered composite projections.

  1. Rotating Pip Detection and Stall Warning in High-Speed Compressors Using Structure Function

    NASA Technical Reports Server (NTRS)

    Bright, Michelle M.; Qammar, Helen; Vhora, Hanif; Schaffer, Michael

    1999-01-01

    A statistic for both rotating pip and incipient stall detection, called Structure Function is introduced for use in high speed research compressor environments. Experimental studies on stall inception processes have long observed two types of pre-stall compressor activity. Presently there exist methods for indicating modal stall precursive events in the compressor. This is a first application of a new method to detect rotating pip activity prior to stall in research compressors. The algorithm requires a very short sample of data to distinguish pip activity prior to stall, and thus may be used in a real time application. Additionally, this Structure Function algorithm is also used as a single sensor stall warning method under a variety of operating conditions, including clean inlet conditions, radially and circumferentially distorted inlet conditions, and in examples of steady air injection along the casing, and controlled air injection conditions. Structure Function provides a potential advantage over linear spectral techniques and wavelet algorithms for stall detection due to the simplicity of the algorithm and because it does not rely on a priori knowledge of frequency content.

  2. Structure and stability of a round jet exiting a rotating pipe at moderate Reynolds numbers

    NASA Astrophysics Data System (ADS)

    del Pino, C.; Sanmiguel-Rojas, E.

    2005-11-01

    The three-dimensional (3D) structure of a jet of water coming out of a rotating circular pipe into a quiescent tank of water is analyzed both experimentally (through LDA and PIV techniques), and numerically, for several values of the Reynolds number (Re) of the order of a few hundreds, and for several values of the swirl parameter (L). The observed 3D structure are discussed in the light of a spatial stability analysis of the corresponding axisymmetric jet for the same values of Re and L. Good agreement between the experimental measurements and the 3D numerical simulations, and between these and the structures predicted by the stability analysis for the most unstable waves, is found. Helical travelling waves with azimuthal wave number |n|=1 are the first to be detected in the swirless jet as Re is increased, and in the swirling jet for a given Re as L is increased.

  3. Preparation and structural characterization of cDHAP-cyclic form of dihydroxyacetone phosphate-revealing chair and skew conformations of 1,3,2-dioxaphosphorinane ring.

    PubMed

    Slepokura, Katarzyna

    2013-03-01

    A cyclic form of dihydroxyacetone phosphate, cDHAP, was obtained by the acidic hydrolysis of its dimethyl acetal (MeO)(2)cDHAP, and was crystallized in the hydrate, cDHAP-H (gem-diol; 1,3,2-dioxaphosphinane-2,5,5-triol 2-oxide) and the ketone, cDHAP-K (2-hydroxy-1,3,2-dioxaphosphinan-5-one 2-oxide) forms. The synthesis, MS and NMR analyses, crystallization and solid state structures determined by X-ray crystallography are described. The equilibrium state between the hydrate and ketone was established, revealing ∼86% of cDHAP-H in aqueous solution at room temperature. The striking structural feature of the ketone and hydrate forms of the same cyclic phosphate diester in the crystalline state is different conformations of the six-membered P/O/C/C/C/O 1,3,2-dioxaphosphorinane ring, namely chair (C) in cDHAP-H·H2O (9a-H) and skew (S) in cDHAP-K (9a-K). Apart from one previous report on the non-chair-puckered, disordered [(MeO)2cDHAP]- anion in the crystal of its ammonium salt (Ślepokura, K. Carbohydr. Res. 2008, 343, 113-131), this is the unique example of the cyclic phosphate diester in skew conformation. Both 9a-H and 9a-K crystallize with the phosphate group protonated, which has been so far rarely observed in the cyclic phosphates. Deformation of the phosphate group and flattening of the chair-puckered ring in 9a-H is typical of protonated P/O/C/C/C/O rings. However, the skew-puckered 9a-K shows different values of O-P-O angles versus the same lengths of P-O(endo) and P-O(exo) bonds. PMID:23353635

  4. Vibrational and Rotational Structure and Excited-State Dynamics of Pyrene

    NASA Astrophysics Data System (ADS)

    Kowaka, Yasuyuki; Ashizawa, Nolitaka; Baba, Masaaki

    2010-06-01

    Pyrene is one of the prototypical compact polycyclic aromatic hydrocarbons (PAHs), and It is important to investigate its molecular structure precisely, because it does not conform to Hückel's 4n+2 rule. We analyzed high-resolution and ultrahigh-resolution spectra of jet-cooled pyrene and elucidated the vibrational and rotational structures in the S_0 ^1A_g and S_1 ^1B3u states. We conclude that the molecule is planar with D2h symmetry. The rotational constants and vibrational normal energies are very similar for the S_0 and S_1 states, indicating that its geometrical structure and potential energy curves are not changed much upon electronic excitation. This small change is common to large PAH molecules because the changes of bond orders by one electron excitation is diluted with a large number of π electrons. The rates of Radiationless transitions in the S_1 state are closely related with the molecular structure and the potential energy curves. Intersystem crossing (ISC) to the triplet state is expected to be very slow in planar PAHs. Internal conversion (IC) to the S_0 state does not occur, if the molecular structure and potential energy curves are identical for the S_0 and S_1 states. In perylene, the fluorescence lifetime is 1400 ns, and the fluorescence quantum yield is considerably high. These properties are attributed to its small changes in molecular structure and potential energy curves upon S_1 ← S_0 excitation. M. Baba, Y. Kowaka et al., J. Chem. Phys., 131, 224318 (2009)

  5. Rotational and Fine Structure of Pseudo-Jahn Molecules with C_1 Symmetry

    NASA Astrophysics Data System (ADS)

    Liu, Jinjun

    2016-06-01

    It has been found in our previous works that rotational and fine-structure analysis of spectra involving nearly degenerate electronic states may aid in interpretation and analysis of the vibronic structure, specifically in the case of pseudo-Jahn-Teller (pJT) molecules with C_s symmetry. The spectral analysis of pJT derivatives (isopropoxy and cyclohexoxy of a prototypical JT molecule (the methoxy radical) allowed for quantitative determination of various contributions to the energy separation between the nearly degenerate electronic states, including the relativistic spin-orbit (SO) effect, the electrostatic interaction, and their zero-point energy difference. These states are coupled by SO and Coriolis interactions, which can also be determined accurately in rotational and fine structure analysis. Most recently, the spectroscopic model for rotational analysis of pJT molecules has been extended for analysis of molecules with C_1 symmetry, i.e., no symmetry. This model includes the six independently determinable components of the spin-rotation (SR) tensor and the three components of the SO and Coriolis interactions. It has been employed to simulate and fit high-resolution laser-induced fluorescence (LIF) spectra of jet-cooled alkoxy radicals with C_1 symmetry, including the 2-hexoxy and the 2-pentoxy radicals, as well as previously recorded LIF spectrum of the trans-conformer (defined by its OCCC dihedral angle) of the 2-butoxy radical. Although the LIF spectra can be reproduced by using either the SR constants or SO and Coriolis constants, the latter simulation offers results that are physically more meaningful whereas the SR constants have to be regarded as effective constants. Furthermore, we will review the SO and Coriolis constants of alkoxy radicals that have been investigated, starting from the well-studied methoxy radical (CH_3O). J. Liu, D. Melnik, and T. A. Miller, J. Chem. Phys. 139, 094308 (2013) J. Liu and T. A. Miller, J. Phys. Chem. A 118, 11871

  6. Roles of Shape and Internal Structure in Rotational Disruption of Asteroids

    NASA Astrophysics Data System (ADS)

    Hirabayashi, Masatoshi; Scheeres, Daniel Jay

    2015-08-01

    An active research area over the last decade has been to explore configuration changes of rubble pile asteroids due to rotationally induced disruption, initially driven by the remarkable fact that there is a spin period threshold of 2 hr for asteroids larger than a few hundred meters in size. Several different disruption modes due to rapid rotation can be identified, as surface shedding, fission and failure of the internal structure. Relevant to these discussions are many observations of asteroid shapes that have revealed a diversity of forms such as oblate spheroids with equatorial ridges, strongly elongated shapes and contact binaries, to say nothing of multi-body systems. With consideration that rotationally induced deformation is one of the primary drivers of asteroid evolution, we have been developing two techniques for investigating the structure of asteroids, while accounting for their internal mechanical properties through plastic theory. The first technique developed is an analytical model based on limit analysis, which provides rigorous bounds on the asteroid mechanical properties for their shapes to remain stable. The second technique applies finite element model analysis that accounts for plastic deformation. Combining these models, we have explored the correlation between unique shape features and failure modes. First, we have been able to show that contact binary asteroids preferentially fail at their narrow necks at a relatively slow spin period, due to stress concentration. Second, applying these techniques to the breakup event of active asteroid P/2013 R3, we have been able to develop explicit constraints on the cohesion within rubble pile asteroids. Third, by probing the effect of inhomogeneous material properties, we have been able to develop conditions for whether an oblate body will fail internally or through surface shedding. These different failure modes can be tested by measuring the density distribution within a rubble pile body through

  7. Rotational structure and outflow in the infrared dark cloud 18223-3

    NASA Astrophysics Data System (ADS)

    Fallscheer, C.; Beuther, H.; Zhang, Q.; Keto, E.; Sridharan, T. K.

    2009-09-01

    Aims: We examine an Infrared Dark Cloud (IRDC) at high spatial resolution as a means to study rotation, outflow, and infall at the onset of massive star formation. Methods: The IRDC 18223-3 was observed at 1.1 mm and 1.3 mm with the Submillimeter Array (SMA) and follow-up short spacing information was obtained with the IRAM 30 m telescope. Additional data were taken at 3 mm with the IRAM Plateau de Bure interferometer (PdBI). Results: Submillimeter Array observations combined with IRAM 30 m data in 12CO(2-1) reveal the outflow orientation in the IRDC 18223-3 region, and PdBI 3 mm observations confirm this orientation in other molecular species. The implication of the outflow's presence is that an accretion disk is feeding it, so using line data for high density tracers such as C18O, N2H^+, and CH3OH, we looked for indications of a velocity gradient perpendicular to the outflow direction. Surprisingly, this gradient turns out to be most apparent in CH3OH. The large size (28 000 AU) of the flattened rotating object detected indicates that this velocity gradient cannot be due solely to a disk, but rather from inward spiraling gas within which a Keplerian disk likely exists. The rotational signatures can be modeled via rotationally infalling gas. From the outflow parameters, we derive properties of the source such as an outflow dynamical age of ~37 000 years, outflow mass of ~13 M⊙, and outflow energy of ˜1.7 × 1046 erg. While the outflow mass and energy are clearly consistent with a high-mass star forming region, the outflow dynamical age indicates a slightly more evolved evolutionary stage than previous spectral energy distribution (SED) modeling indicates. Conclusions: The orientation of the molecular outflow associated with IRDC 18223-3 is in the northwest-southeast direction and velocity gradients orthogonal to the outflow reveal a large rotating structure likely harboring an accretion disk within. We also present a model of the observed methanol velocity

  8. Connecting [NiFe]- and [FeFe]-hydrogenases: mixed-valence nickel-iron dithiolates with rotated structures.

    PubMed

    Schilter, David; Rauchfuss, Thomas B; Stein, Matthias

    2012-08-20

    New mixed-valence iron-nickel dithiolates are described that exhibit structures similar to those of mixed-valence diiron dithiolates. The interaction of tricarbonyl salt [(dppe)Ni(pdt)Fe(CO)(3)]BF(4) ([1]BF(4), where dppe = Ph(2)PCH(2)CH(2)PPh(2) and pdt(2-) = -SCH(2)CH(2)CH(2)S-) with P-donor ligands (L) afforded the substituted derivatives [(dppe)Ni(pdt)Fe(CO)(2)L]BF(4) incorporating L = PHCy(2) ([1a]BF(4)), PPh(NEt(2))(2) ([1b]BF(4)), P(NMe(2))(3) ([1c]BF(4)), P(i-Pr)(3) ([1d]BF(4)), and PCy(3) ([1e]BF(4)). The related precursor [(dcpe)Ni(pdt)Fe(CO)(3)]BF(4) ([2]BF(4), where dcpe = Cy(2)PCH(2)CH(2)PCy(2)) gave the more electron-rich family of compounds [(dcpe)Ni(pdt)Fe(CO)(2)L]BF(4) for L = PPh(2)(2-pyridyl) ([2a]BF(4)), PPh(3) ([2b]BF(4)), and PCy(3) ([2c]BF(4)). For bulky and strongly basic monophosphorus ligands, the salts feature distorted coordination geometries at iron: crystallographic analyses of [1e]BF(4) and [2c]BF(4) showed that they adopt "rotated" Fe(I) centers, in which PCy(3) occupies a basal site and one CO ligand partially bridges the Ni and Fe centers. Like the undistorted mixed-valence derivatives, members of the new class of complexes are described as Ni(II)Fe(I) (S = ½) systems according to electron paramagnetic resonance spectroscopy, although with attenuated (31)P hyperfine interactions. Density functional theory calculations using the BP86, B3LYP, and PBE0 exchange-correlation functionals agree with the structural and spectroscopic data, suggesting that the spin for [1e](+) is mostly localized in a Fe(I)-centered d(z(2)) orbital, orthogonal to the Fe-P bond. The PCy(3) complexes, rare examples of species featuring "rotated" Fe centers, both structurally and spectroscopically incorporate features from homobimetallic mixed-valence diiron dithiolates. Also, when the NiS(2)Fe core of the [NiFe]-hydrogenase active site is reproduced, the "hybrid models" incorporate key features of the two major classes of hydrogenase. Furthermore, cyclic

  9. Connecting [NiFe]- and [FeFe]-hydrogenases: mixed-valence nickel-iron dithiolates with rotated structures.

    PubMed

    Schilter, David; Rauchfuss, Thomas B; Stein, Matthias

    2012-08-20

    New mixed-valence iron-nickel dithiolates are described that exhibit structures similar to those of mixed-valence diiron dithiolates. The interaction of tricarbonyl salt [(dppe)Ni(pdt)Fe(CO)(3)]BF(4) ([1]BF(4), where dppe = Ph(2)PCH(2)CH(2)PPh(2) and pdt(2-) = -SCH(2)CH(2)CH(2)S-) with P-donor ligands (L) afforded the substituted derivatives [(dppe)Ni(pdt)Fe(CO)(2)L]BF(4) incorporating L = PHCy(2) ([1a]BF(4)), PPh(NEt(2))(2) ([1b]BF(4)), P(NMe(2))(3) ([1c]BF(4)), P(i-Pr)(3) ([1d]BF(4)), and PCy(3) ([1e]BF(4)). The related precursor [(dcpe)Ni(pdt)Fe(CO)(3)]BF(4) ([2]BF(4), where dcpe = Cy(2)PCH(2)CH(2)PCy(2)) gave the more electron-rich family of compounds [(dcpe)Ni(pdt)Fe(CO)(2)L]BF(4) for L = PPh(2)(2-pyridyl) ([2a]BF(4)), PPh(3) ([2b]BF(4)), and PCy(3) ([2c]BF(4)). For bulky and strongly basic monophosphorus ligands, the salts feature distorted coordination geometries at iron: crystallographic analyses of [1e]BF(4) and [2c]BF(4) showed that they adopt "rotated" Fe(I) centers, in which PCy(3) occupies a basal site and one CO ligand partially bridges the Ni and Fe centers. Like the undistorted mixed-valence derivatives, members of the new class of complexes are described as Ni(II)Fe(I) (S = ½) systems according to electron paramagnetic resonance spectroscopy, although with attenuated (31)P hyperfine interactions. Density functional theory calculations using the BP86, B3LYP, and PBE0 exchange-correlation functionals agree with the structural and spectroscopic data, suggesting that the spin for [1e](+) is mostly localized in a Fe(I)-centered d(z(2)) orbital, orthogonal to the Fe-P bond. The PCy(3) complexes, rare examples of species featuring "rotated" Fe centers, both structurally and spectroscopically incorporate features from homobimetallic mixed-valence diiron dithiolates. Also, when the NiS(2)Fe core of the [NiFe]-hydrogenase active site is reproduced, the "hybrid models" incorporate key features of the two major classes of hydrogenase. Furthermore, cyclic

  10. Structural basis of metallo-β-lactamase, serine-β-lactamase and penicillin-binding protein inhibition by cyclic boronates.

    PubMed

    Brem, Jürgen; Cain, Ricky; Cahill, Samuel; McDonough, Michael A; Clifton, Ian J; Jiménez-Castellanos, Juan-Carlos; Avison, Matthew B; Spencer, James; Fishwick, Colin W G; Schofield, Christopher J

    2016-01-01

    β-Lactamases enable resistance to almost all β-lactam antibiotics. Pioneering work revealed that acyclic boronic acids can act as 'transition state analogue' inhibitors of nucleophilic serine enzymes, including serine-β-lactamases. Here we report biochemical and biophysical analyses revealing that cyclic boronates potently inhibit both nucleophilic serine and zinc-dependent β-lactamases by a mechanism involving mimicking of the common tetrahedral intermediate. Cyclic boronates also potently inhibit the non-essential penicillin-binding protein PBP 5 by the same mechanism of action. The results open the way for development of dual action inhibitors effective against both serine- and metallo-β-lactamases, and which could also have antimicrobial activity through inhibition of PBPs. PMID:27499424

  11. Structural basis of metallo-β-lactamase, serine-β-lactamase and penicillin-binding protein inhibition by cyclic boronates

    PubMed Central

    Brem, Jürgen; Cain, Ricky; Cahill, Samuel; McDonough, Michael A.; Clifton, Ian J.; Jiménez-Castellanos, Juan-Carlos; Avison, Matthew B.; Spencer, James; Fishwick, Colin W. G.; Schofield, Christopher J.

    2016-01-01

    β-Lactamases enable resistance to almost all β-lactam antibiotics. Pioneering work revealed that acyclic boronic acids can act as ‘transition state analogue' inhibitors of nucleophilic serine enzymes, including serine-β-lactamases. Here we report biochemical and biophysical analyses revealing that cyclic boronates potently inhibit both nucleophilic serine and zinc-dependent β-lactamases by a mechanism involving mimicking of the common tetrahedral intermediate. Cyclic boronates also potently inhibit the non-essential penicillin-binding protein PBP 5 by the same mechanism of action. The results open the way for development of dual action inhibitors effective against both serine- and metallo-β-lactamases, and which could also have antimicrobial activity through inhibition of PBPs. PMID:27499424

  12. Structural basis of metallo-β-lactamase, serine-β-lactamase and penicillin-binding protein inhibition by cyclic boronates

    NASA Astrophysics Data System (ADS)

    Brem, Jürgen; Cain, Ricky; Cahill, Samuel; McDonough, Michael A.; Clifton, Ian J.; Jiménez-Castellanos, Juan-Carlos; Avison, Matthew B.; Spencer, James; Fishwick, Colin W. G.; Schofield, Christopher J.

    2016-08-01

    β-Lactamases enable resistance to almost all β-lactam antibiotics. Pioneering work revealed that acyclic boronic acids can act as `transition state analogue' inhibitors of nucleophilic serine enzymes, including serine-β-lactamases. Here we report biochemical and biophysical analyses revealing that cyclic boronates potently inhibit both nucleophilic serine and zinc-dependent β-lactamases by a mechanism involving mimicking of the common tetrahedral intermediate. Cyclic boronates also potently inhibit the non-essential penicillin-binding protein PBP 5 by the same mechanism of action. The results open the way for development of dual action inhibitors effective against both serine- and metallo-β-lactamases, and which could also have antimicrobial activity through inhibition of PBPs.

  13. Optimization and Validation of Rotating Current Excitation with GMR Array Sensors for Riveted Structures Inspection.

    PubMed

    Ye, Chaofeng; Udpa, Lalita; Udpa, Satish

    2016-09-16

    In eddy current non-destructive testing of a multi-layered riveted structure, rotating current excitation, generated by orthogonal coils, is advantageous in providing sensitivity to defects of all orientations. However, when used with linear array sensors, the exciting magnetic flux density ( B x ) of the orthogonal coils is not uniform over the sensor region, resulting in an output signal magnitude that depends on the relative location of the defect to the sensor array. In this paper, the rotating excitation coil is optimized to achieve a uniform B x field in the sensor array area and minimize the probe size. The current density distribution of the coil is optimized using the polynomial approximation method. A non-uniform coil design is derived from the optimized current density distribution. Simulation results, using both an optimized coil and a conventional coil, are generated using the finite element method (FEM) model. The signal magnitude for an optimized coil is seen to be more robust with respect to offset of defects from the coil center. A novel multilayer coil structure, fabricated on a multi-layer printed circuit board, is used to build the optimized coil. A prototype probe with the optimized coil and 32 giant magnetoresistive (GMR) sensors is built and tested on a two-layer riveted aluminum sample. Experimental results show that the optimized probe has better defect detection capability compared with a conventional non-optimized coil.

  14. Optimization and Validation of Rotating Current Excitation with GMR Array Sensors for Riveted Structures Inspection

    PubMed Central

    Ye, Chaofeng; Udpa, Lalita; Udpa, Satish

    2016-01-01

    In eddy current non-destructive testing of a multi-layered riveted structure, rotating current excitation, generated by orthogonal coils, is advantageous in providing sensitivity to defects of all orientations. However, when used with linear array sensors, the exciting magnetic flux density (Bx) of the orthogonal coils is not uniform over the sensor region, resulting in an output signal magnitude that depends on the relative location of the defect to the sensor array. In this paper, the rotating excitation coil is optimized to achieve a uniform Bx field in the sensor array area and minimize the probe size. The current density distribution of the coil is optimized using the polynomial approximation method. A non-uniform coil design is derived from the optimized current density distribution. Simulation results, using both an optimized coil and a conventional coil, are generated using the finite element method (FEM) model. The signal magnitude for an optimized coil is seen to be more robust with respect to offset of defects from the coil center. A novel multilayer coil structure, fabricated on a multi-layer printed circuit board, is used to build the optimized coil. A prototype probe with the optimized coil and 32 giant magnetoresistive (GMR) sensors is built and tested on a two-layer riveted aluminum sample. Experimental results show that the optimized probe has better defect detection capability compared with a conventional non-optimized coil. PMID:27649202

  15. Internal rapid rotation and its implications for stellar structure and pulsations

    NASA Astrophysics Data System (ADS)

    Reese, Daniel R.

    2015-09-01

    Massive and intermediate mass stars play a crucial role in astrophysics. Indeed, massive stars are the main producers of heavy elements, explode in supernovae at the end of their short lifetimes, and may be the progenitors of gamma ray bursts. Intermediate mass stars, although not destined to explode in supernovae, display similar phenomena, are much more numerous, and have some of the richest pulsation spectra. A key to understanding these stars is understanding the effects of rapid rotation on their structure and evolution. These effects include centrifugal deformation and gravity darkening which can be observed immediately, and long terms effects such as rotational mixing due to shear turbulence, which prolong stellar lifetime, modify chemical yields, and impact the stellar remnant at the end of their lifetime. In order to understand these effects, a number of models have been and are being developed over the past few years. These models lead to increasingly sophisticated predictions which need to be tested through observations. A particularly promising source of constraints is seismic observations as these may potentially lead to detailed information on their internal structure. However, before extracting such information, a number of theoretical and observational hurdles need to be overcome, not least of which is mode identification. The present proceedings describe recent progress in modelling these stars and show how an improved understanding of their pulsations, namely frequency patterns, mode visibilities, line profile variations, and mode excitation, may help with deciphering seismic observations.

  16. Optimization and Validation of Rotating Current Excitation with GMR Array Sensors for Riveted Structures Inspection.

    PubMed

    Ye, Chaofeng; Udpa, Lalita; Udpa, Satish

    2016-01-01

    In eddy current non-destructive testing of a multi-layered riveted structure, rotating current excitation, generated by orthogonal coils, is advantageous in providing sensitivity to defects of all orientations. However, when used with linear array sensors, the exciting magnetic flux density ( B x ) of the orthogonal coils is not uniform over the sensor region, resulting in an output signal magnitude that depends on the relative location of the defect to the sensor array. In this paper, the rotating excitation coil is optimized to achieve a uniform B x field in the sensor array area and minimize the probe size. The current density distribution of the coil is optimized using the polynomial approximation method. A non-uniform coil design is derived from the optimized current density distribution. Simulation results, using both an optimized coil and a conventional coil, are generated using the finite element method (FEM) model. The signal magnitude for an optimized coil is seen to be more robust with respect to offset of defects from the coil center. A novel multilayer coil structure, fabricated on a multi-layer printed circuit board, is used to build the optimized coil. A prototype probe with the optimized coil and 32 giant magnetoresistive (GMR) sensors is built and tested on a two-layer riveted aluminum sample. Experimental results show that the optimized probe has better defect detection capability compared with a conventional non-optimized coil. PMID:27649202

  17. Probing the Structure of Ionic Liquid Surfaces by Rotationally and Electronically Inelastic Scattering of no

    NASA Astrophysics Data System (ADS)

    Ziemkiewicz, M. P.; Zutz, A.; Nesbitt, D. J.

    2012-06-01

    Room temperature ionic liquids (RTIL’s) are a highly diverse class of materials with many potential technological applications. They are candidates for use in advanced electrolytes, green solvents, and supported liquid membranes for CO_2 sequestration. We present studies where inelastic scattering of high or low velocity nitric oxide provides insight into the microscopic structure of these complex surfaces. As an open shell diatomic, jet-cooled NO [^2π1/2(J = 0.5)] features both molecular and electronic collision dynamics as seen by probing scattered rotational and spin-orbit distributions respectively. These studies show substantial variation in degree of rotational and electronic excitation as ionic liquid identity is varied. Also, surface heating is found to have a strong effect on scattered spin-orbit branching, possibly due to the dependence of surface structure on temperature. This is discussed in terms of a picture where the electronic degree of freedom may serve as a sensitive measure of the cationic versus anionic nature of the top few layers of this material.

  18. Rotation and the internal structures of the major planets and their inner satellites

    NASA Technical Reports Server (NTRS)

    Dermott, S. F.

    1984-01-01

    Measurements of the rotational periods coupled with those of the masses, the mean radii, and the shapes or the gravitational moments (J2 and J4) enable important constraints to be placed on the internal structures of some remote bodies. Values of J2 for Uranus and Neptune have been calculated from the observed precession rates of the narrow eccentric and inclined Uranian rings and of the orbit of Triton, Neptune's massive satellite. Recent observations of the motions of spots have yielded reliable rotational periods for these planets. These observations are used to show that Uranus and Neptune may have quite different internal structures. The shapes of satellites that are close to their primaries may yield information on the degree of internal differentiation of these bodies. Io, Mimas, Enceladus, and Miranda are of interest in this respect. Residuals in the observed precession rates of the Uranian rings, about 0.005 deg/day, that cannot be accounted for by the best-fit model of J2 and J4 may be related directly to observed irregular variations in ring width of magnitude over 2 km and may indicate the existence of shepherding satellites with mass ratios of over 10 to the -10th. If this is the case, then the effects of these satellites on the precession rates of the rings will result in an appreciable uncertainty in the value of J4 for Uranus.

  19. Structure Elucidation at the Nanomole-Scale. 1. Trisoxazole Macrolides and Thiazole-containing Cyclic Peptides from the Nudibranch Hexabranchus sanguineus

    PubMed Central

    Dalisay, Doralyn S.; Rogers, Evan W.; Edison, Arthur S.; Molinski, Tadeusz F.

    2009-01-01

    A single specimen of Hexabranchus sanguineus, a nudibranch from the Indo-Pacific that is known to sequester kabiramides B, C and other trisoxazole macrolides, yielded new kabiramide analogs – 9-desmethylkabiramide B and 33-methyltetrahydrohalichondramide – and two new unexpected thiazole-containing cyclic peptides in sub-micromole amounts. The structures of these cyclic peptides were determined by analyses of 1D and 2D NMR spectra recorded with a state-of-the-art 1-mm 1H NMR high-temperature superconducting micro-cryoprobe, together with mass spectra. In addition to two proline residues, each peptide contains a thiazole- or oxazole-modified amino acid residue, together with conventional amino acid residues. All of the amino acid residues were L- as determined by Marfey’s analysis of the acid hydrolysates of the peptides. This is the first report of cyclic thiazole peptides from H. sanguineus. Since thiazole-oxazole modified peptides are typically associated with cyanobacteria and tunicates, the finding may imply a dietary component of the H. sanguineus that was previously overlooked. PMID:19254038

  20. Conformation of cyclic octapeptides. VI. Structure of cyclo-bis-(-L-alanyl-glycyl-L-prolyl-L-phenylalanyl-) tetrahydrate.

    PubMed

    Bhandary, K K; Kopple, K D

    1991-07-15

    C38H48N8O8.4H2O, Mr = 816.9, monoclinic, P21, a = 10.381 (1), b = 13.273 (1), c = 15.742 (1) A. beta = 101.83 (1) degree, V = 2123.1 A3, Z = 2, Dx = 1.278 g cm-3, lambda (Cu K alpha) = 1.5418 A, mu = 7.6 cm-1, F(000) = 872, R = 0.035, wR = 0.045 for 3497 reflections [I greater than 2 sigma (I)], 4552 unique reflections measured. The synthetic cyclic octapeptide crystallizes from water/methanol solution as a tetrahydrate and the crystals are isomorphous to those of the disulfide-bridged cystine analog cyclo-bis(-L-Cys-Gly-L-Pro-L-Phe-) [Kopple, Wang, Cheng & Bhandary (1988). J. Am. Chem. Soc. 110, 4168-4176]. The coordinates of the Cys analog were taken as the starting coordinates for full-matrix least-squares refinement. The cyclic octapeptide ring has two beta turns encompassing the residues Pro-L-Phe, one type I and the other type II, with all peptide links trans. The conformation of the cyclic octapeptide backbone is similar to the Cys analog; all backbone dihedral angles in the two molecules agree to within 6 degrees. This suggests that the disulfide bridge of the Cys analog does not impose any conformational constraint on the octapeptide ring backbone.

  1. N-Methyl inversion and structure of six-membered heterocyclic rings: rotational spectrum of 1-methyl-4-piperidone.

    PubMed

    Evangelisti, Luca; Lesarri, Alberto; Jahn, Michaela K; Cocinero, Emilio J; Caminati, Walther; Grabow, Jens-Uwe

    2011-09-01

    The conformational and structural properties of the six-membered heterocyclic ring of 1-methyl-4-piperidone have been observed in a jet-cooled supersonic expansion using Fourier transform microwave spectroscopy (FT-MW). The rotational spectrum evidenced two different conformations originated by nitrogen inversion, with the N-methyl group in either equatorial (most stable) or axial position. Additional observation of the rotational spectra for all possible carbon, nitrogen, and oxygen monosubstituted species (4 × (13)C, (15)N, (18)O) in natural abundance allowed us to determine substitution (r(s)) and effective structures (r(0)) for the equatorial conformer. Additional ab initio and DFT calculations provided comparative rotational parameters, structural data, conformational energies, and the axial-equatorial interconversion barrier. The structural data were compared with the related azabicycle of tropinone, revealing the molecular changes and structural relaxation associated with the presence of the two-carbon bridge in the latter molecule.

  2. Shuttle Endeavour is revealed after rollback of the Rotating Service Structure

    NASA Technical Reports Server (NTRS)

    1998-01-01

    The Service Structure driver (inside the cab near bottom of photo) begins rolling back the Rotating Service Structure on Launch Pad 39A to reveal the Space Shuttle Endeavour with its external tank and two solid rocket boosters on top of the Mobile Launcher Platform. Endeavour is ready for launch of mission STS- 88 targeted for 3:56 a.m. on Dec. 3. The first U.S. launch for the International Space Station, STS-88 is expected to last 11 days, 19 hours and 49 minutes, and land at 10:17 p.m. EST on Dec. 14. Endeavour carries the Unity connecting module which the crew will be mating with the Russian-built Zarya control module already in orbit. In addition to Unity, two small replacement electronics boxes are on board for possible repairs to Zarya batteries.

  3. Fine structure of alpha decay to rotational states of heavy nuclei

    SciTech Connect

    Wang, Y. Z.; Dong, J. M.; Peng, B. B.; Zhang, H. F.

    2010-06-15

    To gain a better insight into alpha-decay fine structure, we calculate the relative intensities of alpha decay to 2{sup +} and 4{sup +} rotational states in the framework of the generalized liquid drop model (GLDM) and improved Royer's formula. The calculated relative intensities of alpha decay to 2{sup +} states are in good agreement with the experimental data. For the relative intensities of alpha decay to 4{sup +} states, a good agreement with experimental data is achieved for Th and U isotopes. The formula we obtain is useful for the analysis of experimental data of alpha-decay fine structure. In addition, some predicted relative intensities which are still not measured are provided for future experiments.

  4. Rotation sensing with Er3+-doped active ring resonator slow light structure

    NASA Astrophysics Data System (ADS)

    Gu, Hong; Liu, Xiaoqin

    2016-10-01

    An optical gyroscope, which is constituted by Er3+-doped active ring resonator (EDARR) slow light structure, is presented for the first time. The principle of improving the sensitivity of the detection of angular velocity is analysed in detail. The expression of the rotation phase difference of EDARR between the counter-propagating waves is derived and discussed. At the resonant frequency, the phase shift difference has the maximum value when the light power in the cavity is far greater than the input light power. We designed an experimental scheme of Er3+-doped active ring resonator slow light system. Two additional bias phases ϕb = ±π/2 were introduced in the optical path, by recording the light intensity difference ? and I0 at the resonant frequency ?, the input angular velocity can be obtained. The slow light structure based on EDARR can enhance the sensitivity of the detection of the angular velocity by three orders of magnitude.

  5. Paleomagnetic and structural evidence for middle Tertiary counterclockwise block rotation in the Dixie Valley region, west-central Nevada

    SciTech Connect

    Hudson, M.R.; Geissman, J.W.

    1987-07-01

    Paleomagnetic data from late Oligocene to early Miocene ash-flow tuffs at four localities in the northern Dixie Valley region, west-central Nevada, indicate that parts of the crust have rotated counterclockwise by at least 25/sup 0/ and perhaps significantly more in late Cenozoic time. Field relations in White Rock Canyon, Stillwater Range, suggest that rotation (1) was accommodated by right-lateral slip on northwest-trending faults, (2) spanned ash-flow tuff emplacement, and (3) probably ceased before eruption of overlying middle Miocene basalts. Accurate estimates of Cenozoic extension, as well as evaluation of earlier Mesozoic structures, must include the strain partitioned into rotation in the area.

  6. Self-similar hot accretion flow onto a rotating neutron star: Structure and stability

    NASA Astrophysics Data System (ADS)

    Medvedev, Mikhail V.; Narayan, Ramesh

    2001-10-01

    We present analytical and numerical solutions which describe a hot, viscous, two-temperature accretion flow onto a rotating neutron star or any other rotating compact star with a surface. We assume Coulomb coupling between the protons and electrons, and free-free cooling from the electrons. Outside a thin boundary layer, where the accretion flow meets the star, we show that there is an extended settling region which is well-described by two self-similar solutions: (i) a two-temperature solution which is valid in an inner zone r<=102.5 (r is in Schwarzchild units), and (ii) a one-temperature solution at larger radii. In both zones, ρ~r-2, Ω~r-3/2, v~r0, Tp~r-1 in the two-temperature zone, Te~r-1/2. The luminosity of the settling zone arises from the rotational energy of the star as the star is braked by viscosity. Hence the luminosity and the flow parameters (density, temperature, angular velocity) are independent of M. The settling solution described here is not advection-dominated, and is thus different from the self-similar ADAF found around black holes. When the spin of the star is small enough, however, the present solution transforms smoothly to a (settling) ADAF. We carried out a stability analysis of the settling flow. The flow is convectively and viscously stable and is unlikely to have strong winds or outflows. Unlike another cooling-dominated system-the SLE disk,-the settling flow is thermally stable provided that thermal conduction is taken into account. This strong saturated-like thermoconduction does not change the structure of the flow. .

  7. Horizon structure of rotating Einstein-Born-Infeld black holes and shadow

    NASA Astrophysics Data System (ADS)

    Atamurotov, Farruh; Ghosh, Sushant G.; Ahmedov, Bobomurat

    2016-05-01

    We investigate the horizon structure of the rotating Einstein-Born-Infeld solution which goes over to the Einstein-Maxwell's Kerr-Newman solution as the Born-Infeld parameter goes to infinity (β → ∞). We find that for a given β , mass M, and charge Q, there exist a critical spinning parameter aE and rHE, which corresponds to an extremal Einstein-Born-Infeld black hole with degenerate horizons, and aE decreases and rHE increases with increase of the Born-Infeld parameter β , while arotating Einstein-Born-Infeld black hole and demonstrate that the null geodesic equations can be integrated, which allows us to investigate the shadow cast by a black hole which is found to be a dark zone covered by a circle. Interestingly, the shadow of an Einstein-Born-Infeld black hole is slightly smaller than for the Reissner-Nordstrom black hole, which consists of concentric circles, for different values of the Born-Infeld parameter β , whose radius decreases with increase of the value of the parameter β . Finally, we have studied observable distortion parameter for shadow of the rotating Einstein-Born-Infeld black hole.

  8. Engineering cyclic peptide toxins.

    PubMed

    Clark, Richard J; Craik, David J

    2012-01-01

    Peptide-based toxins have attracted much attention in recent years for their exciting potential applications in drug design and development. This interest has arisen because toxins are highly potent and selectively target a range of physiologically important receptors. However, peptides suffer from a number of disadvantages, including poor in vivo stability and poor bioavailability. A number of naturally occurring cyclic peptides have been discovered in plants, animals, and bacteria that have exceptional stability and potentially ameliorate these disadvantages. The lessons learned from studies of the structures, stabilities, and biological activities of these cyclic peptides can be applied to the reengineering of toxins that are not naturally cyclic but are amenable to cyclization. In this chapter, we describe solid-phase chemical synthetic methods for the reengineering of peptide toxins to improve their suitability as therapeutic, diagnostic, or imaging agents. The focus is on small disulfide-rich peptides from the venoms of cone snails and scorpions, but the technology is potentially widely applicable to a number of other peptide-based toxins. PMID:22230565

  9. Nonlinear stability theorem for rotating coherent structures in a non-neutral plasma column

    NASA Astrophysics Data System (ADS)

    Davidson, Ronald C.; Lund, Steven M.

    1991-09-01

    A nonlinear stability theorem is developed for arbitrary-amplitude, two-dimensional coherent structures, nR(θ - ωr t) and φR(θ - ωr t), in a strongly magnetized, low-density (ω2pe/ω2ce ≪ 1) non-neutral plasma column confined radially by a uniform axial magnetic field B0êz. Here, a grounded, perfectly conducting, cylindrical wall is located at radius r = rw, and ωr = const is the angular rotation velocity of the coherent structures about the cylinder axis (r=0). A cold-fluid guiding-center model based on the continuity-Poisson equations is used to describe the nonlinear evolution of the electron density ne(r,θ,t) = nR + δne and electrostatic potential φ(r,θ,t) = φR + δφ. Making use of global (spatially averaged) nonlinear conservation constraints, it is shown that ∂nR(ψR)/∂ψR ≤ 0 is a sufficient condition for nonlinear stability of the rotating equilibrium state (φR,nR) to arbitrary-amplitude perturbations δne and δφ. Here, ψR(r,θ - ωr t) = -eφR(r,θ - ωr t) + ωr(eB0/2c)r 2 is an effective streamfunction, and the stability theorem is valid no matter how complex the radial and azimuthal structure of φR(r,θ - ωr t) and nR(r,θ - ωr t).

  10. Potent μ-Opioid Receptor Agonists from Cyclic Peptides Tyr-c[D-Lys-Xxx-Tyr-Gly]: Synthesis, Biological, and Structural Evaluation.

    PubMed

    Li, Yangmei; Cazares, Margret; Wu, Jinhua; Houghten, Richard A; Toll, Laurence; Dooley, Colette

    2016-02-11

    To optimize the structure of a μ-opioid receptor ligand, analogs H-Tyr-c[D-Lys-Xxx-Tyr-Gly] were synthesized and their biological activity was tested. The analog containing a Phe(3) was identified as not only exhibiting binding affinity 14-fold higher than the original hit but also producing agonist activity 3-fold more potent than morphine. NMR study suggested that a trans conformation at D-Lys(2)-Xxx(3) is crucial for these cyclic peptides to maintain high affinity, selectivity, and functional activity toward the μ-opioid receptor. PMID:26789491

  11. Potent μ-Opioid Receptor Agonists from Cyclic Peptides Tyr-c[D-Lys-Xxx-Tyr-Gly]: Synthesis, Biological, and Structural Evaluation.

    PubMed

    Li, Yangmei; Cazares, Margret; Wu, Jinhua; Houghten, Richard A; Toll, Laurence; Dooley, Colette

    2016-02-11

    To optimize the structure of a μ-opioid receptor ligand, analogs H-Tyr-c[D-Lys-Xxx-Tyr-Gly] were synthesized and their biological activity was tested. The analog containing a Phe(3) was identified as not only exhibiting binding affinity 14-fold higher than the original hit but also producing agonist activity 3-fold more potent than morphine. NMR study suggested that a trans conformation at D-Lys(2)-Xxx(3) is crucial for these cyclic peptides to maintain high affinity, selectivity, and functional activity toward the μ-opioid receptor.

  12. Infrared spectra, methyl group structure and internal rotation in some methy - metal compounds

    NASA Astrophysics Data System (ADS)

    McKean, D. C.; McQuillan, G. P.; Torto, I.; Morrisson, A. R.

    1986-03-01

    Recent and current work on spectra in the CH and CD stretching regions of methyl-metal compounds is reviewed. Free internal rotation with CH force constant variation is found in MMe 3 (M  Ga, Tl) and MMe(CO) 5 (M  Mn, Re) compounds, studied in the gas phase. From solution measurements, no such rotation occurs in CpMMe(CO) 3 (M  Cr,Mo,W) and Cp 2MMe 2 (M  Ti,Zr,Hf), in most of which each methyl group contains two types of CH bond. In each d-subgroup, ν isCH decreases with increasing atomic number, while δ sCH 3 increases. The reverse occurs from Ga to Tl. r oCH values are predicted. There is evidence for the breakdown of the ν isCH/∠HCH correlation, especially in MeTiCl 3 where several features point to an unusual structure of the methyl group.

  13. Deriving the Global Structure of the Galactic Magnetic Field from Faraday Rotation Measures of Extragalactic Sources

    NASA Astrophysics Data System (ADS)

    Pshirkov, M. S.; Tinyakov, P. G.; Kronberg, P. P.; Newton-McGee, K. J.

    2011-09-01

    We made use of the two latest sets of rotation measures (RMs) of extragalactic radio sources, namely the NRAO VLA Sky Survey rotation measures catalog and a compilation by Kronberg and Newton-McGee, to infer the global structure of the Galactic magnetic field (GMF). We have checked that these two data sets are mutually consistent. Given the existence of clear patterns in the all-sky RM distributions we considered GMF models consisting of two components: disk (spiral or ring) and halo. The parameters of these components were determined by fitting different model field geometries to the observed RMs. We found that the model consisting of a symmetric (with respect to the Galactic plane) spiral disk and antisymmetric halo fits the data best and reproduces the observed distribution of RMs over the sky very well. We confirm that ring disk models are disfavored. Our results favor small pitch angles around ~ - 5° and an increased vertical scale of electron distribution, in agreement with some recent studies. Based on our fits, we select two benchmark models suitable for studies of cosmic ray propagation, including cosmic rays at ultrahigh energies.

  14. Output-only cyclo-stationary linear-parameter time-varying stochastic subspace identification method for rotating machinery and spinning structures

    NASA Astrophysics Data System (ADS)

    Velazquez, Antonio; Swartz, R. Andrew

    2015-02-01

    Economical maintenance and operation are critical issues for rotating machinery and spinning structures containing blade elements, especially large slender dynamic beams (e.g., wind turbines). Structural health monitoring systems represent promising instruments to assure reliability and good performance from the dynamics of the mechanical systems. However, such devices have not been completely perfected for spinning structures. These sensing technologies are typically informed by both mechanistic models coupled with data-driven identification techniques in the time and/or frequency domain. Frequency response functions are popular but are difficult to realize autonomously for structures of higher order, especially when overlapping frequency content is present. Instead, time-domain techniques have shown to possess powerful advantages from a practical point of view (i.e. low-order computational effort suitable for real-time or embedded algorithms) and also are more suitable to differentiate closely-related modes. Customarily, time-varying effects are often neglected or dismissed to simplify this analysis, but such cannot be the case for sinusoidally loaded structures containing spinning multi-bodies. A more complex scenario is constituted when dealing with both periodic mechanisms responsible for the vibration shaft of the rotor-blade system and the interaction of the supporting substructure. Transformations of the cyclic effects on the vibrational data can be applied to isolate inertial quantities that are different from rotation-generated forces that are typically non-stationary in nature. After applying these transformations, structural identification can be carried out by stationary techniques via data-correlated eigensystem realizations. In this paper, an exploration of a periodic stationary or cyclo-stationary subspace identification technique is presented here for spinning multi-blade systems by means of a modified Eigensystem Realization Algorithm (ERA) via

  15. Stress Relaxation for Granular Materials near Jamming under Cyclic Compression

    NASA Astrophysics Data System (ADS)

    Farhadi, Somayeh; Zhu, Alex Z.; Behringer, Robert P.

    2015-10-01

    We have explored isotropically jammed states of semi-2D granular materials through cyclic compression. In each compression cycle, systems of either identical ellipses or bidisperse disks transition between jammed and unjammed states. We determine the evolution of the average pressure P and structure through consecutive jammed states. We observe a transition point ϕm above which P persists over many cycles; below ϕm, P relaxes slowly. The relaxation time scale associated with P increases with packing fraction, while the relaxation time scale for collective particle motion remains constant. The collective motion of the ellipses is hindered compared to disks because of the rotational constraints on elliptical particles.

  16. Stress Relaxation for Granular Materials near Jamming under Cyclic Compression.

    PubMed

    Farhadi, Somayeh; Zhu, Alex Z; Behringer, Robert P

    2015-10-30

    We have explored isotropically jammed states of semi-2D granular materials through cyclic compression. In each compression cycle, systems of either identical ellipses or bidisperse disks transition between jammed and unjammed states. We determine the evolution of the average pressure P and structure through consecutive jammed states. We observe a transition point ϕ_{m} above which P persists over many cycles; below ϕ_{m}, P relaxes slowly. The relaxation time scale associated with P increases with packing fraction, while the relaxation time scale for collective particle motion remains constant. The collective motion of the ellipses is hindered compared to disks because of the rotational constraints on elliptical particles. PMID:26565498

  17. Identification, Characterization, and Structure Analysis of the Cyclic di-AMP-binding PII-like Signal Transduction Protein DarA*

    PubMed Central

    Gundlach, Jan; Dickmanns, Achim; Schröder-Tittmann, Kathrin; Neumann, Piotr; Kaesler, Jan; Kampf, Jan; Herzberg, Christina; Hammer, Elke; Schwede, Frank; Kaever, Volkhard; Tittmann, Kai; Stülke, Jörg; Ficner, Ralf

    2015-01-01

    The cyclic dimeric AMP nucleotide c-di-AMP is an essential second messenger in Bacillus subtilis. We have identified the protein DarA as one of the prominent c-di-AMP receptors in B. subtilis. Crystal structure analysis shows that DarA is highly homologous to PII signal transducer proteins. In contrast to PII proteins, the functionally important B- and T-loops are swapped with respect to their size. DarA is a homotrimer that binds three molecules of c-di-AMP, each in a pocket located between two subunits. We demonstrate that DarA is capable to bind c-di-AMP and with lower affinity cyclic GMP-AMP (3′3′-cGAMP) but not c-di-GMP or 2′3′-cGAMP. Consistently the crystal structure shows that within the ligand-binding pocket only one adenine is highly specifically recognized, whereas the pocket for the other adenine appears to be promiscuous. Comparison with a homologous ligand-free DarA structure reveals that c-di-AMP binding is accompanied by conformational changes of both the fold and the position of the B-loop in DarA. PMID:25433025

  18. Identification, characterization, and structure analysis of the cyclic di-AMP-binding PII-like signal transduction protein DarA.

    PubMed

    Gundlach, Jan; Dickmanns, Achim; Schröder-Tittmann, Kathrin; Neumann, Piotr; Kaesler, Jan; Kampf, Jan; Herzberg, Christina; Hammer, Elke; Schwede, Frank; Kaever, Volkhard; Tittmann, Kai; Stülke, Jörg; Ficner, Ralf

    2015-01-30

    The cyclic dimeric AMP nucleotide c-di-AMP is an essential second messenger in Bacillus subtilis. We have identified the protein DarA as one of the prominent c-di-AMP receptors in B. subtilis. Crystal structure analysis shows that DarA is highly homologous to PII signal transducer proteins. In contrast to PII proteins, the functionally important B- and T-loops are swapped with respect to their size. DarA is a homotrimer that binds three molecules of c-di-AMP, each in a pocket located between two subunits. We demonstrate that DarA is capable to bind c-di-AMP and with lower affinity cyclic GMP-AMP (3'3'-cGAMP) but not c-di-GMP or 2'3'-cGAMP. Consistently the crystal structure shows that within the ligand-binding pocket only one adenine is highly specifically recognized, whereas the pocket for the other adenine appears to be promiscuous. Comparison with a homologous ligand-free DarA structure reveals that c-di-AMP binding is accompanied by conformational changes of both the fold and the position of the B-loop in DarA. PMID:25433025

  19. Complex Structure in Class 0 Protostellar Envelopes. III. Velocity Gradients in Non-axisymmetric Envelopes, Infall, or Rotation?

    NASA Astrophysics Data System (ADS)

    Tobin, John J.; Hartmann, Lee; Bergin, Edwin; Chiang, Hsin-Fang; Looney, Leslie W.; Chandler, Claire J.; Maret, Sébastien; Heitsch, Fabian

    2012-03-01

    We present an interferometric kinematic study of morphologically complex protostellar envelopes based on observations of the dense gas tracers N2H+ and NH3. The strong asymmetric nature of most envelopes in our sample leads us to question the common interpretation of velocity gradients as rotation, given the possibility of projection effects in the observed velocities. Several "idealized" sources with well-ordered velocity fields and envelope structures are now analyzed in more detail. We compare the interferometric data to position-velocity (PV) diagrams of kinematic models for spherical rotating collapse and filamentary rotating collapse. For this purpose, we developed a filamentary parameterization of the rotating collapse model to explore the effects of geometric projection on the observed velocity structures. We find that most envelopes in our sample have PV structures that can be reproduced by an infalling filamentary envelope projected at different angles within the plane of the sky. The infalling filament produces velocity shifts across the envelope that can mimic rotation, especially when viewed at single-dish resolutions and the axisymmetric rotating collapse model does not uniquely describe any data set. Furthermore, if the velocities are assumed to reflect rotation, then the inferred centrifugal radii are quite large in most cases, indicating significant fragmentation potential or more likely another component to the line-center velocity. We conclude that ordered velocity gradients cannot be interpreted as rotation alone when envelopes are non-axisymmetric and that projected infall velocities likely dominate the velocity field on scales larger than 1000 AU. Based on observations carried out with the IRAM Plateau de Bure Interferometer, Combined Array for Research in Millimeter-wave Astronomy (CARMA), and the NRAO Very Large Array.

  20. Kinematic morphology of large-scale structure: evolution from potential to rotational flow

    SciTech Connect

    Wang, Xin; Szalay, Alex; Aragón-Calvo, Miguel A.; Neyrinck, Mark C.; Eyink, Gregory L.

    2014-09-20

    As an alternative way to describe the cosmological velocity field, we discuss the evolution of rotational invariants constructed from the velocity gradient tensor. Compared with the traditional divergence-vorticity decomposition, these invariants, defined as coefficients of the characteristic equation of the velocity gradient tensor, enable a complete classification of all possible flow patterns in the dark-matter comoving frame, including both potential and vortical flows. We show that this tool, first introduced in turbulence two decades ago, is very useful for understanding the evolution of the cosmic web structure, and in classifying its morphology. Before shell crossing, different categories of potential flow are highly associated with the cosmic web structure because of the coherent evolution of density and velocity. This correspondence is even preserved at some level when vorticity is generated after shell crossing. The evolution from the potential to vortical flow can be traced continuously by these invariants. With the help of this tool, we show that the vorticity is generated in a particular way that is highly correlated with the large-scale structure. This includes a distinct spatial distribution and different types of alignment between the cosmic web and vorticity direction for various vortical flows. Incorporating shell crossing into closed dynamical systems is highly non-trivial, but we propose a possible statistical explanation for some of the phenomena relating to the internal structure of the three-dimensional invariant space.

  1. Single mask, simple structure micro rotational motor driven by electrostatic comb-drive actuators

    NASA Astrophysics Data System (ADS)

    Pham, Phuc Hong; Viet Dao, Dzung; Dang, Lam Bao; Sugiyama, Susumu

    2012-01-01

    We report a design and fabrication of a new micro rotational motor (MRM) using silicon micromachining technology with the overall diameter of 2.4 mm. This motor utilizes four silicon electrostatic comb-drive actuators to drive the outer ring (or rotor) through ratchet teeth. The novel design of the anti-reverse structure helps us to overcome the gap problem after deep reactive ion etching of silicon. The MRM was fabricated by using silicon on insulator wafer with the thickness of the device layer being 30 µm and one mask only. The motor was successfully tested for performance. It was driven by periodic voltage with different frequencies ranging from 1 to 50 Hz. The angular velocity of the outer ratchet ring was proportional to the frequency. Moreover, when the driving frequency is lower than 30 Hz, the experiment results perfectly match the theoretical calculation.

  2. Shuttle Endeavour is revealed after rollback of the Rotating Service Structure

    NASA Technical Reports Server (NTRS)

    1998-01-01

    With the Rotating Service Structure on Launch Pad 39A rolled back, the Space Shuttle Endeavour on top of the Mobile Launcher Platform is poised for launch on mission STS-88. Lift-off is targeted for 3:56 a.m. on Dec. 3. The first U.S. launch for the International Space Station, STS-88 is expected to last 11 days, 19 hours and 49 minutes, and land at 10:17 p.m. EST on Dec. 14. Endeavour carries the Unity connecting module which the crew will be mating with the Russian-built Zarya control module already in orbit. In addition to Unity, two small replacement electronics boxes are on board for possible repairs to Zarya batteries.

  3. Investigation of Pendulum Structures for Rotational Energy Harvesting from Human Motion

    NASA Astrophysics Data System (ADS)

    Ylli, K.; Hoffmann, D.; Willmann, A.; Folkmer, B.; Manoli, Y.

    2015-12-01

    Energy Harvesting from human motion as a means of powering body-worn devices has been in the focus of research groups for several years now. This work presents a rotational inductive energy harvester that can generate a sufficient amount of energy during normal walking to power small electronic systems. Three pendulum structures and their geometrical parameters are investigated in detail through a system model and system simulations. Based on these results a prototype device is fabricated. The masses and angles between pendulum arms can be changed for the experiments. The device is tested under real-world conditions and generates an average power of up to 23.39 mW across a resistance equal to the coil resistance of the optimal pendulum configuration. A regulated power output of the total system including power management of 3.3 mW is achieved.

  4. Rotational spectroscopy and molecular structure of the 1-chloro-1-fluoroethylene-acetylene complex.

    PubMed

    Leung, Helen O; Marshall, Mark D; Grimes, David D

    2011-01-21

    Guided by ab initio calculations, Fourier transform microwave spectra in the 6-21 GHz region are obtained for seven isotopomers of the complex formed between 1-chloro-1-fluoroethylene and acetylene. These include the four possible combinations of (35)Cl- and (37)Cl-containing CH(2)CClF with the most abundant acetylene isotopic modification, HCCH, and its H(13)C(13)CH analogue, as well as three singly substituted deuterated isotopomers. Analysis of the spectra determines the rotational constants and additionally, the complete chlorine quadrupole hyperfine coupling tensors in both the inertial and principal electric field gradient axis systems, and where appropriate, the diagonal components of the deuterium quadrupole coupling tensors. The inertial information contained in the rotational constants provides the structure for CH(2)CClF-HCCH: a primary, hydrogen bonding interaction existing between the HCCH donor and the F atom acceptor on the 1-chloro-1-fluoroethylene moiety, while a secondary interaction occurs between the acetylenic bond on the HCCH molecule and the H atom cis to the hydrogen-bonded F atom on the substituted ethylene, which causes the hydrogen bond to deviate from linearity. This is similar to the structure obtained for 1,1-difluoroethylene-HCCH [H. O. Leung and M. D. Marshall, J. Chem. Phys. 126, 154301 (2006)], and indeed, to within experimental uncertainty, the intermolecular interactions in CH(2)CClF-HCCH and its 1,1-difluoroethylene counterpart are practically indistinguishable, even though ab initio calculations at the MP2∕6-311G++(2d, 2p) level suggest that the former complex is more strongly bound. PMID:21261349

  5. Hints of a rotating spiral structure in the innermost regions around IRC +10216

    PubMed Central

    Quintana-Lacaci, G.; Cernicharo, J.; Agúndez, M.; Prieto, L. Velilla; Castro-Carrizo, A.; Marcelino, N.; Cabezas, C.; Peña, I.; Alonso, J.L.; Zúñiga, J.; Requena, A.; Bastida, A.; Kalugina, Y.; Lique, F.; Guélin, M.

    2016-01-01

    The Atacama Large Millimeter/submillimeter Array (ALMA) is allowing us to study the innermost regions of the circumstellar envelopes of evolved stars with un-precedented precision and sensitivity. Key processes in the ejection of matter and dust from these objects occur in their inner zones. In this work, we present sub-arcsecond interferometric maps of transitions of metal-bearing molecules towards the prototypical C-rich evolved star IRC +10216. While Al-bearing molecules seem to be present as a roughly spherical shell, the molecular emission from the salts NaCl and KCl presents an elongation in the inner regions, with a central minimum. In order to accurately analyze the emission from the NaCl rotational lines, we present new calculations of the collisional rates for this molecule based on new spectroscopic constants. The most plausible interpretation for the spatial distribution of the salts is a spiral with a NaCl mass of 0.08M☉. Alternatively, a torus of gas and dust would result in similar structures as those observed. From the torus scenario we derive a mass of ~ 1.1 × 10−4M☉. In both cases, the spiral and the torus, the NaCl structure presents an inner minimum of 27 AU. In the case of the torus, the outer radius is 73 AU. The kinematics of both the spiral and the torus suggests that they are slowly expanding and rotating. Alternative explanations for the presence of the elongation are explored. The presence of these features only in KCl and NaCl might be a result of their comparatively high dipole moment with respect to the Al-bearing species. PMID:26997665

  6. Impact of patient rotational errors on target and critical structure dose in IMRT: A 3D simulation study

    NASA Astrophysics Data System (ADS)

    Arumugam, S.; Xing, A.; Vial, P.; Scotti, A.; Stirton, R.; Goozee, G.; Holloway, Lois

    2013-06-01

    The impact of 3D rotational errors in patient positioning on dose delivered target volumes and critical structures in IMRT was studied. Patient rotational errors ranging from -30 to +30 was introduced to IMRT treatment plans of pelvis, head and neck and brain treatment sites and the impact of rotational error on DVH metrics was assessed. The magnitude of impact of rotational error on the error in dose delivered to the target volume and critical structures depends on the location of the structures from plan isocentre. In studied plans, a maximum percentage difference of up to -9.8(1s=13.4) % in D95 to PTV was observed for head and neck treatments. Similarly, in Brain treatments a maximum difference of up to 24.0(1s=33.0) % in maximum dose of Optic chiasm was observed. The results suggest that failure to correct patient's rotational error results in under-dosage to target volumes and over-dosage to the critical structures in some specific treatment scenarios.

  7. Tuning the photoluminescence of condensed-phase cyclic trinuclear Au(I) complexes through control of their aggregated structures by external stimuli

    NASA Astrophysics Data System (ADS)

    Fujisawa, Kaori; Yamada, Shigeyuki; Yanagi, Yukihiro; Yoshioka, Yasunori; Kiyohara, Ayumi; Tsutsumi, Osamu

    2015-03-01

    A series of new cyclic trinuclear Au(I) complexes with alkoxy side chains of various lengths were synthesized as photoluminescence materials. None of the complexes emitted luminescence in solution; however, some showed photoluminescence in the crystalline phase. Single crystal X-ray structural analyses revealed that an intermolecular interaction between two Au atoms (aurophilic interaction) existed only in the emissive complexes, which formed molecular aggregates in the crystal. Because isolated molecules show no luminescence in the present system, we conclude that only molecules aggregated via aurophilic interactions can luminesce. We demonstrated that luminescence properties, such as colour and intensity, were very sensitive to the aggregated structure of the molecules. We also found that such luminescence properties can be controlled by a change in the aggregated structure induced by external stimuli, such as heat, solvent, and mechanical stress.

  8. Application of HAADF STEM image analysis to structure determination in rotationally disordered and amorphous multilayered films

    NASA Astrophysics Data System (ADS)

    Mitchson, Gavin; Ditto, Jeffrey; Woods, Keenan N.; Westover, Richard; Page, Catherine J.; Johnson, David C.

    2016-08-01

    We report results from high angle annular dark field scanning transmission electron microscopy (HAADF STEM) image analysis of complex semi-crystalline and amorphous materials, and apply the insights gained from local structure information towards global structure determination. Variations in HAADF STEM intensities for a rotationally disordered heterostructure and an amorphous oxide film are statistically analyzed to extract information regarding the inhomogeneity of the films perpendicular to the substrate. By assuming chemical homogeneity in the film axis parallel to the substrate, the signal intensity variation parallel to the substrate is used to estimate the signal noise level, allowing evaluation of the significance of intensity differences in the substrate normal direction. The positions of HAADF STEM intensity peaks in the perpendicular direction, averaged from multiple images, provide a valuable initial model for a Rietveld refinement of the global c-axis structure of the heterostructure. For an amorphous multi-coat solution-cast oxide sample, the analysis reveals statistically significant variations in the HAADF STEM intensity profile perpendicular to the substrate. These variations indicate an inhomogeneous density profile, presumably related to the spin-casting of individual layers and have implications for understanding the chemical interactions that occur between layers when preparing multilayer amorphous oxide films from solution.

  9. A benchmark study of molecular structure by experimental and theoretical methods: Equilibrium structure of thymine from microwave rotational constants and coupled-cluster computations

    NASA Astrophysics Data System (ADS)

    Vogt, Natalja; Demaison, Jean; Ksenafontov, Denis N.; Rudolph, Heinz Dieter

    2014-11-01

    Accurate equilibrium, re, structures of thymine have been determined using two different, and to some extent complementary techniques. The composite ab initio Born-Oppenheimer, re(best ab initio), structural parameters are obtained from the all-electron CCSD(T) and MP2 geometry optimizations using Gaussian basis sets up to quadruple-zeta quality. The semi-experimental mixed estimation method, where internal coordinates are fitted concurrently to equilibrium rotational constants and geometry parameters obtained from a high level of electronic structure theory. The equilibrium rotational constants are derived from experimental effective ground-state rotational constants and rovibrational corrections based on a quantum-chemical cubic force field. Equilibrium molecular structures accurate to 0.002 Å and 0.2° have been determined. This work is one of a few accurate equilibrium structure determinations for large molecules. The poor behavior of Kraitchman's equations is discussed.

  10. Nonlinear Langmuir structures: Soliton and shock in a rotating weakly relativistic electron-positron magnetoplasma with stationary positive ions

    SciTech Connect

    El-Labany, S. K.; Moslem, W. M.; El-Awady, E. I.

    2010-06-15

    Theoretical and numerical studies are performed for nonlinear Langmuir structures (soliton and shock) in a rotating weakly relativistic electron-positron magnetoplasma with background stationary positive ions. For this purpose, the reductive perturbation technique is employed to the weakly relativistic hydrodynamical electrons/positrons fluid equations and Poisson equation, obtaining extended Zakharov-Kuznetsov equation. The latter has been solved analytically. The features of the nonlinear excitations and their propagation conditions are investigated numerically. Our finding could elucidate the nonlinear electrostatic structures that propagate in astrophysical plasma situations where rotating, magnetized plasma can exist; such as polar cups region of pulsars, around active galactic nuclei, neutron stars, and white dwarfs.

  11. Structure and development of old-growth, unmanaged second-growth, and extended rotation Pinus resinosa forests in Minnesota, USA

    USGS Publications Warehouse

    Silver, Emily J.; D'Amato, Anthony W.; Fraver, Shawn; Palik, Brian J.; Bradford, John B.

    2013-01-01

    The structure and developmental dynamics of old-growth forests often serve as important baselines for restoration prescriptions aimed at promoting more complex structural conditions in managed forest landscapes. Nonetheless, long-term information on natural patterns of development is rare for many commercially important and ecologically widespread forest types. Moreover, the effectiveness of approaches recommended for restoring old-growth structural conditions to managed forests, such as the application of extended rotation forestry, has been little studied. This study uses several long-term datasets from old growth, extended rotation, and unmanaged second growth Pinus resinosa (red pine) forests in northern Minnesota, USA, to quantify the range of variation in structural conditions for this forest type and to evaluate the effectiveness of extended rotation forestry at promoting the development of late-successional structural conditions. Long-term tree population data from permanent plots for one of the old-growth stands and the extended rotation stands (87 and 61 years, respectively) also allowed for an examination of the long-term structural dynamics of these systems. Old-growth forests were more structurally complex than unmanaged second-growth and extended rotation red pine stands, due in large part to the significantly higher volumes of coarse woody debris (70.7 vs. 11.5 and 4.7 m3/ha, respectively) and higher snag basal area (6.9 vs. 2.9 and 0.5 m2/ha, respectively). In addition, old-growth forests, although red pine-dominated, contained a greater abundance of other species, including Pinus strobus, Abies balsamea, and Picea glauca relative to the other stand types examined. These differences between stand types largely reflect historic gap-scale disturbances within the old-growth systems and their corresponding structural and compositional legacies. Nonetheless, extended rotation thinning treatments, by accelerating advancement to larger tree diameter

  12. Matrix formulation and singular-value decomposition algorithm for structured varimax rotation in multivariate singular spectrum analysis

    NASA Astrophysics Data System (ADS)

    Portes, Leonardo L.; Aguirre, Luis A.

    2016-05-01

    Groth and Ghil [Phys. Rev. E 84, 036206 (2011), 10.1103/PhysRevE.84.036206] developed a modified varimax rotation aimed at enhancing the ability of the multivariate singular spectrum analysis (M-SSA) to characterize phase synchronization in systems of coupled chaotic oscillators. Due to the special structure of the M-SSA eigenvectors, the modification proposed by Groth and Ghil imposes a constraint in the rotation of blocks of components associated with the different subsystems. Accordingly, here we call it a structured varimax rotation (SVR). The SVR was presented as successive pairwise rotations of the eigenvectors. The aim of this paper is threefold. First, we develop a closed matrix formulation for the entire family of structured orthomax rotation criteria, for which the SVR is a special case. Second, this matrix approach is used to enable the use of known singular value algorithms for fast computation, allowing a simultaneous rotation of the M-SSA eigenvectors (a Python code is provided in the Appendix). This could be critical in the characterization of phase synchronization phenomena in large real systems of coupled oscillators. Furthermore, the closed algebraic matrix formulation could be used in theoretical studies of the (modified) M-SSA approach. Third, we illustrate the use of the proposed singular value algorithm for the SVR in the context of the two benchmark examples of Groth and Ghil: the Rössler system in the chaotic (i) phase-coherent and (ii) funnel regimes. Comparison with the results obtained with Kaiser's original (unstructured) varimax rotation (UVR) reveals that both SVR and UVR give the same result for the phase-coherent scenario, but for the more complex behavior (ii) only the SVR improves on the M-SSA.

  13. Matrix formulation and singular-value decomposition algorithm for structured varimax rotation in multivariate singular spectrum analysis.

    PubMed

    Portes, Leonardo L; Aguirre, Luis A

    2016-05-01

    Groth and Ghil [Phys. Rev. E 84, 036206 (2011)PLEEE81539-375510.1103/PhysRevE.84.036206] developed a modified varimax rotation aimed at enhancing the ability of the multivariate singular spectrum analysis (M-SSA) to characterize phase synchronization in systems of coupled chaotic oscillators. Due to the special structure of the M-SSA eigenvectors, the modification proposed by Groth and Ghil imposes a constraint in the rotation of blocks of components associated with the different subsystems. Accordingly, here we call it a structured varimax rotation (SVR). The SVR was presented as successive pairwise rotations of the eigenvectors. The aim of this paper is threefold. First, we develop a closed matrix formulation for the entire family of structured orthomax rotation criteria, for which the SVR is a special case. Second, this matrix approach is used to enable the use of known singular value algorithms for fast computation, allowing a simultaneous rotation of the M-SSA eigenvectors (a Python code is provided in the Appendix). This could be critical in the characterization of phase synchronization phenomena in large real systems of coupled oscillators. Furthermore, the closed algebraic matrix formulation could be used in theoretical studies of the (modified) M-SSA approach. Third, we illustrate the use of the proposed singular value algorithm for the SVR in the context of the two benchmark examples of Groth and Ghil: the Rössler system in the chaotic (i) phase-coherent and (ii) funnel regimes. Comparison with the results obtained with Kaiser's original (unstructured) varimax rotation (UVR) reveals that both SVR and UVR give the same result for the phase-coherent scenario, but for the more complex behavior (ii) only the SVR improves on the M-SSA. PMID:27300889

  14. Matrix formulation and singular-value decomposition algorithm for structured varimax rotation in multivariate singular spectrum analysis.

    PubMed

    Portes, Leonardo L; Aguirre, Luis A

    2016-05-01

    Groth and Ghil [Phys. Rev. E 84, 036206 (2011)PLEEE81539-375510.1103/PhysRevE.84.036206] developed a modified varimax rotation aimed at enhancing the ability of the multivariate singular spectrum analysis (M-SSA) to characterize phase synchronization in systems of coupled chaotic oscillators. Due to the special structure of the M-SSA eigenvectors, the modification proposed by Groth and Ghil imposes a constraint in the rotation of blocks of components associated with the different subsystems. Accordingly, here we call it a structured varimax rotation (SVR). The SVR was presented as successive pairwise rotations of the eigenvectors. The aim of this paper is threefold. First, we develop a closed matrix formulation for the entire family of structured orthomax rotation criteria, for which the SVR is a special case. Second, this matrix approach is used to enable the use of known singular value algorithms for fast computation, allowing a simultaneous rotation of the M-SSA eigenvectors (a Python code is provided in the Appendix). This could be critical in the characterization of phase synchronization phenomena in large real systems of coupled oscillators. Furthermore, the closed algebraic matrix formulation could be used in theoretical studies of the (modified) M-SSA approach. Third, we illustrate the use of the proposed singular value algorithm for the SVR in the context of the two benchmark examples of Groth and Ghil: the Rössler system in the chaotic (i) phase-coherent and (ii) funnel regimes. Comparison with the results obtained with Kaiser's original (unstructured) varimax rotation (UVR) reveals that both SVR and UVR give the same result for the phase-coherent scenario, but for the more complex behavior (ii) only the SVR improves on the M-SSA.

  15. Dislocation model of nucleation and development of slip bands and their effect on service life of structural materials subject to cyclic loading

    SciTech Connect

    Shetulov, D. I.; Andreev, V. V. Myasnikov, A. M.

    2015-12-15

    Most of the destructions of machine parts are of fatigue character. Under cyclic loading, the surface layer, in which hardening–softening processes rapidly occur, is formed almost at once after its beginning. The interaction of plastic-deformation traces with each other and with other structural elements, such as grains, results in the formation of a characteristic microstructure of the machine-part surface subject to cyclic loadings. The character of accumulation of slip bands and their shape (narrow, wide, twisting, and broken) depends on the conditions under which (under what factors) the cyclic loading occurs. The fatigue-resistance index expressed in terms of the slope of left portion of the fatigue curve linearized in logarithmic coordinates also depends on the set of relevant factors. The dependence of the surface damageability on the fatigue resistance index makes it possible to implement the method of predicting the fatigue curve by the description of the factors acting on a detail or construction. The position of the inflection point on the curve in the highcycle fatigue region (the endurance limit and the number of loading cycles, the ordinate and abscissa of the inflection point on the fatigue curve, respectively) also depends on the set of relevant factors. In combination with the previously obtained value of the slope of the left portion of the curve in the high-cycle fatigue region, this makes it possible to construct an a priori fatigue curve, thus reducing the scope of required fatigue tests and, hence, high expenses because of their long duration and high cost. The scope of tests upon using the developed method of prediction may be reduced to a minimum of one or two samples at the predicted level of the endurance limit.

  16. Dislocation model of nucleation and development of slip bands and their effect on service life of structural materials subject to cyclic loading

    NASA Astrophysics Data System (ADS)

    Shetulov, D. I.; Andreev, V. V.; Myasnikov, A. M.

    2015-12-01

    Most of the destructions of machine parts are of fatigue character. Under cyclic loading, the surface layer, in which hardening-softening processes rapidly occur, is formed almost at once after its beginning. The interaction of plastic-deformation traces with each other and with other structural elements, such as grains, results in the formation of a characteristic microstructure of the machine-part surface subject to cyclic loadings. The character of accumulation of slip bands and their shape (narrow, wide, twisting, and broken) depends on the conditions under which (under what factors) the cyclic loading occurs. The fatigue-resistance index expressed in terms of the slope of left portion of the fatigue curve linearized in logarithmic coordinates also depends on the set of relevant factors. The dependence of the surface damageability on the fatigue resistance index makes it possible to implement the method of predicting the fatigue curve by the description of the factors acting on a detail or construction. The position of the inflection point on the curve in the highcycle fatigue region (the endurance limit and the number of loading cycles, the ordinate and abscissa of the inflection point on the fatigue curve, respectively) also depends on the set of relevant factors. In combination with the previously obtained value of the slope of the left portion of the curve in the high-cycle fatigue region, this makes it possible to construct an a priori fatigue curve, thus reducing the scope of required fatigue tests and, hence, high expenses because of their long duration and high cost. The scope of tests upon using the developed method of prediction may be reduced to a minimum of one or two samples at the predicted level of the endurance limit.

  17. Structure-Based Design and Synthesis of Potent Cyclic Peptides Inhibiting the YAP-TEAD Protein-Protein Interaction.

    PubMed

    Zhang, Zhisen; Lin, Zhaohu; Zhou, Zheng; Shen, Hong C; Yan, S Frank; Mayweg, Alexander V; Xu, Zhiheng; Qin, Ning; Wong, Jason C; Zhang, Zhenshan; Rong, Yiping; Fry, David C; Hu, Taishan

    2014-09-11

    The YAP-TEAD protein-protein interaction (PPI) mediates the oncogenic function of YAP, and inhibitors of this PPI have potential usage in treatment of YAP-involved cancers. Here we report the design and synthesis of potent cyclic peptide inhibitors of the YAP-TEAD interaction. A truncation study of YAP interface 3 peptide identified YAP(84-100) as a weak peptide inhibitor (IC50 = 37 μM), and an alanine scan revealed a beneficial mutation, D94A. Subsequent replacement of a native cation-π interaction with an optimized disulfide bridge for conformational constraint and synergistic effect between macrocyclization and modification at positions 91 and 93 greatly boosted inhibitory activity. Peptide 17 was identified with an IC50 of 25 nM, and the binding affinity (K d = 15 nM) of this 17mer peptide to TEAD1 proved to be stronger than YAP(50-171) (K d = 40 nM).

  18. The structure and dynamics of coherent vortex tubes in rotating shear turbulence of zero-mean-absolute vorticity.

    NASA Astrophysics Data System (ADS)

    Tanaka, Mitsuru; Yanase, Shinichiro

    2010-05-01

    The effect of the system rotation on shear flow turbulence is one of the central issues of fluid mechanics in relation to geophysical and astrophysical phenomena as well as engineering applications such as turbo machinery, so is still being vigorously investigated. If a turbulent shear flow is rotated as a whole about the axis parallel to the mean-shear vorticity, the flow structure is significantly influenced by the magnitude and direction of vorticity associated with the mean shear relative to those of the system rotation. The flow field is called either cyclonic or anti-cyclonic accordingly as vorticities associated with the mean shear and the system rotation are parallel or anti-parallel. Turbulence has a tendency to keep its two-dimensional structure along the system rotation both for cyclonic and for an anti-cyclonic regions for rapid system rotation, whereas the two-dimensional structure is unstable and easily broken down to three-dimensional in an anti-cyclonic region if the system rotation is relatively slow to the mean-shear vorticity. If the flow field is anti-cyclonic and the mean-shear vorticity cancels out that of the system rotation, the mean absolute vorticity is zero in the flow field, and then it is called the zero-mean-absolute-vorticity state (ZAVS). ZAVS, which is neutral to the above-mentioned instability, is observed in many rotating shear flow turbulence. One of the most remarkable features of ZAVS turbulence is the generation of very coherent quasi-streamwise vortex tubes which are not observed in other cases of rotating or nonrotating turbulence. Though the importance of the role of vortex tubes in shear flow turbulence is generally recognized, it is not easy to study their dynamics due to the interactions between vortex tubes and vortex-shear layers which are generated from the background mean-shear vorticity. In ZAVS, on the other hand, it is rather easy to investigate vortex tubes in turbulence because they are stable and long

  19. Nonexponential decay of internal rotational correlation functions of native proteins and self-similar structural fluctuations.

    PubMed

    Cote, Yoann; Senet, Patrick; Delarue, Patrice; Maisuradze, Gia G; Scheraga, Harold A

    2010-11-16

    Structural fluctuations of a protein are essential for the function of native proteins and for protein folding. To understand how the main chain in the native state of a protein fluctuates on different time scales, we examined the rotational correlation functions (RCFs), C(t), of the backbone N-H bonds and of the dihedral angles γ built on four consecutive C(α) atoms. Using molecular dynamics simulations of a model α/β protein (VA3) in its native state, we demonstrate that these RCFs decay as stretched exponentials, ln[C(t)] ≈ D(α)t(α) with a constant D(α) and an exponent α (0 < α < 0.35) varying with the free-energy profiles (FEPs) along the amino acid sequence. The probability distributions of the fluctuations of the main chain computed at short time scale (1 ps) were identical to those computed at large time scale (1 ns) if the time is rescaled by a factor depending on α < 1. This self-similar property and the nonexponential decays (α ≠ 1) of the RCFs are described by a rotational diffusion equation with a time-dependent diffusion coefficient D(t) = αD(α)t(α-1). The present findings agree with observations of subdiffusion (α < 1) of fluorescent probes within a protein molecule. The subdiffusion of (15)N-H bonds did not affect the value of the order parameter S(2) extracted from the NMR relaxation data by assuming normal diffusion (α = 1) of (15)N-H bonds on a nanosecond time scale. However, we found that the RCF does not converge to S(2) on the nanosecond time scale for residues with multiple-minima FEPs.

  20. Structure and Rotation of the Solar Interior: Initial Results from the MDI Medium-L Program

    NASA Technical Reports Server (NTRS)

    Kosovichev, A. G.; Schou, J.; Scherrer, P. H.; Bogart, R. S.; Bush, R. I.; Hoeksema, J. T.; Aloise, J.; Bacon, L.; Burnette, A.; DeForest, C.; Giles, P. M.; Leibrand, K.; Nigam, R.; Rubin, M.; Scott, K.; Williams, S. D.; Basu, Sarbani; Christensen-Dalsgaard J.; Daeppen W.; Duvall, T. L., Jr.

    1997-01-01

    The medium-l program of the Michelson Doppler Imager instrument on board SOHO provides continuous observations of oscillation modes of angular degree, l, from 0 to approximately 300. The data for the program are partly processed on board because only about 3% of MDI observations can be transmitted continuously to the ground. The on-board data processing, the main component of which is Gaussian-weighted binning, has been optimized to reduce the negative influence of spatial aliasing of the high-degree oscillation modes. The data processing is completed in a data analysis pipeline at the SOI Stanford Support Center to determine the mean multiplet frequencies and splitting coefficients. The initial results show that the noise in the medium-l oscillation power spectrum is substantially lower than in ground-based measurements. This enables us to detect lower amplitude modes and, thus, to extend the range of measured mode frequencies. This is important for inferring the Sun's internal structure and rotation. The MDI observations also reveal the asymmetry of oscillation spectral lines. The line asymmetries agree with the theory of mode excitation by acoustic sources localized in the upper convective boundary layer. The sound-speed profile inferred from the mean frequencies gives evidence for a sharp variation at the edge of the energy-generating core. The results also confirm the previous finding by the GONG (Gough et al., 1996) that, in a thin layer just beneath the convection zone, helium appears to be less abundant than predicted by theory. Inverting the multiplet frequency splittings from MDI, we detect significant rotational shear in this thin layer. This layer is likely to be the place where the solar dynamo operates. In order to understand how the Sun works, it is extremely important to observe the evolution of this transition layer throughout the 11-year activity cycle.

  1. Structure elucidation of cyclic pyoverdins and examination of rearrangement reactions in MS/MS experiments by determination of exact product ion masses.

    PubMed

    Schäfer, Mathias; Fuchs, Regine; Budzikiewicz, Herbert; Springer, Andreas; Meyer, Jean-Marie; Linscheid, Michael

    2006-09-01

    Structure elucidation of naturally occurring linear and cyclic peptidic compounds can be complicated by rearrangement reactions induced upon collision activation (CA) when parts of the molecule migrate, suggesting incorrect substitution patterns. Such complex rearrangements are examined and discussed for two iron complexing compounds produced by the bacterial genus Pseudomonas (so-called pyoverdins). Various MS2- and MS3-product ion experiments were performed using a quadrupole-ion trap (QIT) at low resolution and a FT-ICR at high resolution allowing accurate mass determinations. The results of the multidimensional study confirm the proposed processes. On the basis of the series of tandem-MS experiments the structure of a new pyoverdin from a P. fluorescens strain [PVD(D47)] is deduced. PMID:16888716

  2. The rotational and fine-structure spectrum of FeH, studied by far-infrared laser magnetic resonance.

    PubMed

    Brown, John M; Körsgen, Helga; Beaton, Stuart P; Evenson, Kenneth M

    2006-06-21

    Transitions between the spin-rotational levels of the FeH radical in the upsilon=0 level of the X (4)Delta ground state have been detected by the technique of laser magnetic resonance at far-infrared wavelengths. Both pure rotational and fine-structure transitions have been observed; lambda-type doubling is resolved on all the observed transitions. The energy levels of FeH are strongly affected by the breakdown of the Born-Oppenheimer approximation and cannot be modeled accurately by an effective Hamiltonian. The data are therefore fitted to an empirical formula to yield term values and g factors for the various spin-rotational levels involved. Many of the resonances show a doubling that arises from the proton hyperfine structure. These splittings are analyzed in a similar manner.

  3. Ion drag as a mechanism of plasma dust structure rotation in a strata in a magnetic field

    NASA Astrophysics Data System (ADS)

    Dzlieva, E. S.; Karasev, V. Yu.; Mashek, I. Ch.; Pavlov, S. I.

    2016-06-01

    In experiments on complex plasmas, afixed strata region in which the levitation of dust structures is observed is investigated using the method of probing by calibrated dust particles of different sizes in an applied magnetic field under elevated pressures. The measured azimuthal velocity of the probing particles corresponds to the action of the ion drag force for 4 μm-size particles and to the entrainment by the rotating gas owing to the electron vortex flow inside the strata for 1 μm-size particles. Extrapolation to pressures and magnetic fields in which the rotation inversion of dust structures is observed in experiments shows that the ion drag is the dominating force causing rotation with a negative projection of the angular velocity onto the magnetic induction.

  4. The effect of cyclic feathering motions on dynamic rotor loads. [for helicopters

    NASA Technical Reports Server (NTRS)

    Harvey, K. W.

    1974-01-01

    The dynamic loads of a helicopter rotor in forward flight are influenced significantly by the geometric pitch angles between the structural axes of the hub and blade sections and the plane of rotation. The analytical study presented includes elastic coupling between inplane and out-of-plane deflections as a function of geometric pitch between the plane of rotation and the principal axes of inertia of each blade. The numerical evaluation is based on a transient analysis using lumped masses and elastic substructure techniques. A comparison of cases with and without cyclic feathering motion shows the effect on computed dynamic rotor loads.

  5. Silicon Oxysulfide, OSiS: Rotational Spectrum, Quantum-Chemical Calculations, and Equilibrium Structure.

    PubMed

    Thorwirth, Sven; Mück, Leonie Anna; Gauss, Jürgen; Tamassia, Filippo; Lattanzi, Valerio; McCarthy, Michael C

    2011-06-01

    Silicon oxysulfide, OSiS, and seven of its minor isotopic species have been characterized for the first time in the gas phase at high spectral resolution by means of Fourier transform microwave spectroscopy. The equilibrium structure of OSiS has been determined from the experimental data using calculated vibration-rotation interaction constants. The structural parameters (rO-Si = 1.5064 Å and rSi-S = 1.9133 Å) are in very good agreement with values from high-level quantum chemical calculations using coupled-cluster techniques together with sophisticated additivity and extrapolation schemes. The bond distances in OSiS are very short in comparison with those in SiO and SiS. This unexpected finding is explained by the partial charges calculated for OSiS via a natural population analysis. The results suggest that electrostatic effects rather than multiple bonding are the key factors in determining bonding in this triatomic molecule. The data presented provide the spectroscopic information needed for radio astronomical searches for OSiS.

  6. Interpretation of the Structure Function of Rotation Measure in the Interstellar Medium

    NASA Astrophysics Data System (ADS)

    Xu, Siyao; Zhang, Bing

    2016-06-01

    The observed structure function (SF) of rotation measure (RM) varies as a broken power-law function of angular scales. The systematic shallowness of its spectral slope is inconsistent with the standard Kolmogorov scaling. This motivates us to examine the statistical analysis on RM fluctuations. The correlations of RM constructed by Lazarian & Pogosyan are demonstrated to be adequate in explaining the observed features of RM SFs through a direct comparison between the theoretically obtained and observationally measured SF results. By segregating the density and magnetic field fluctuations and adopting arbitrary indices for their respective power spectra, we find that when the SFs of RM and emission measure have a similar form over the same range of angular scales, the statistics of the RM fluctuations reflect the properties of density fluctuations. RM SFs can be used to evaluate the mean magnetic field along the line of sight, but cannot serve as an informative source on the properties of turbulent magnetic field in the interstellar medium. We identify the spectral break of RM SFs as the inner scale of a shallow spectrum of electron density fluctuations, which characterizes the typical size of discrete electron density structures in the observed region.

  7. Structured Overlapping Grid Simulations of Contra-rotating Open Rotor Noise

    NASA Technical Reports Server (NTRS)

    Housman, Jeffrey A.; Kiris, Cetin C.

    2015-01-01

    Computational simulations using structured overlapping grids with the Launch Ascent and Vehicle Aerodynamics (LAVA) solver framework are presented for predicting tonal noise generated by a contra-rotating open rotor (CROR) propulsion system. A coupled Computational Fluid Dynamics (CFD) and Computational AeroAcoustics (CAA) numerical approach is applied. Three-dimensional time-accurate hybrid Reynolds Averaged Navier-Stokes/Large Eddy Simulation (RANS/LES) CFD simulations are performed in the inertial frame, including dynamic moving grids, using a higher-order accurate finite difference discretization on structured overlapping grids. A higher-order accurate free-stream preserving metric discretization with discrete enforcement of the Geometric Conservation Law (GCL) on moving curvilinear grids is used to create an accurate, efficient, and stable numerical scheme. The aeroacoustic analysis is based on a permeable surface Ffowcs Williams-Hawkings (FW-H) approach, evaluated in the frequency domain. A time-step sensitivity study was performed using only the forward row of blades to determine an adequate time-step. The numerical approach is validated against existing wind tunnel measurements.

  8. Structured caustic vector vortex optical field: manipulating optical angular momentum flux and polarization rotation.

    PubMed

    Chen, Rui-Pin; Chen, Zhaozhong; Chew, Khian-Hooi; Li, Pei-Gang; Yu, Zhongliang; Ding, Jianping; He, Sailing

    2015-05-29

    A caustic vector vortex optical field is experimentally generated and demonstrated by a caustic-based approach. The desired caustic with arbitrary acceleration trajectories, as well as the structured states of polarization (SoP) and vortex orders located in different positions in the field cross-section, is generated by imposing the corresponding spatial phase function in a vector vortex optical field. Our study reveals that different spin and orbital angular momentum flux distributions (including opposite directions) in different positions in the cross-section of a caustic vector vortex optical field can be dynamically managed during propagation by intentionally choosing the initial polarization and vortex topological charges, as a result of the modulation of the caustic phase. We find that the SoP in the field cross-section rotates during propagation due to the existence of the vortex. The unique structured feature of the caustic vector vortex optical field opens the possibility of multi-manipulation of optical angular momentum fluxes and SoP, leading to more complex manipulation of the optical field scenarios. Thus this approach further expands the functionality of an optical system.

  9. Structured caustic vector vortex optical field: manipulating optical angular momentum flux and polarization rotation

    PubMed Central

    Chen, Rui-Pin; Chen, Zhaozhong; Chew, Khian-Hooi; Li, Pei-Gang; Yu, Zhongliang; Ding, Jianping; He, Sailing

    2015-01-01

    A caustic vector vortex optical field is experimentally generated and demonstrated by a caustic-based approach. The desired caustic with arbitrary acceleration trajectories, as well as the structured states of polarization (SoP) and vortex orders located in different positions in the field cross-section, is generated by imposing the corresponding spatial phase function in a vector vortex optical field. Our study reveals that different spin and orbital angular momentum flux distributions (including opposite directions) in different positions in the cross-section of a caustic vector vortex optical field can be dynamically managed during propagation by intentionally choosing the initial polarization and vortex topological charges, as a result of the modulation of the caustic phase. We find that the SoP in the field cross-section rotates during propagation due to the existence of the vortex. The unique structured feature of the caustic vector vortex optical field opens the possibility of multi-manipulation of optical angular momentum fluxes and SoP, leading to more complex manipulation of the optical field scenarios. Thus this approach further expands the functionality of an optical system. PMID:26024434

  10. Structure-from-motion: dissociating perception, neural persistence, and sensory memory of illusory depth and illusory rotation.

    PubMed

    Pastukhov, Alexander; Braun, Jochen

    2013-02-01

    In the structure-from-motion paradigm, physical motion on a screen produces the vivid illusion of an object rotating in depth. Here, we show how to dissociate illusory depth and illusory rotation in a structure-from-motion stimulus using a rotationally asymmetric shape and reversals of physical motion. Reversals of physical motion create a conflict between the original illusory states and the new physical motion: Either illusory depth remains constant and illusory rotation reverses, or illusory rotation stays the same and illusory depth reverses. When physical motion reverses after the interruption in presentation, we find that illusory rotation tends to remain constant for long blank durations (T (blank) ≥ 0.5 s), but illusory depth is stabilized if interruptions are short (T (blank) ≤ 0.1 s). The stability of illusory depth over brief interruptions is consistent with the effect of neural persistence. When this is curtailed using a mask, stability of ambiguous vision (for either illusory depth or illusory rotation) is disrupted. We also examined the selectivity of the neural persistence of illusory depth. We found that it relies on a static representation of an interpolated illusory object, since changes to low-level display properties had little detrimental effect. We discuss our findings with respect to other types of history dependence in multistable displays (sensory stabilization memory, neural fatigue, etc.). Our results suggest that when brief interruptions are used during the presentation of multistable displays, switches in perception are likely to rely on the same neural mechanisms as spontaneous switches, rather than switches due to the initial percept choice at the stimulus onset.

  11. Solar rotation.

    NASA Astrophysics Data System (ADS)

    Dziembowski, W.

    Sunspot observations made by Johannes Hevelius in 1642 - 1644 are the first ones providing significant information about the solar differential rotation. In modern astronomy the determination of the rotation rate is done in a routine way by measuring positions of various structures on the solar surface as well as by studying the Doppler shifts of spectral lines. In recent years a progress in helioseismology enabled determination of the rotation rate in the layers inaccessible for direct observations. There are still uncertainties concerning, especially, the temporal variations of the rotation rate and its behaviour in the radiative interior. We are far from understanding the observations. Theoretical works have not yet resulted in a satisfactory model for the angular momentum transport in the convective zone.

  12. Internal rotation potential and relaxation of structure in nitrobenzene studied by microwave spectroscopy supported by quantum chemistry

    NASA Astrophysics Data System (ADS)

    Larsen, Niels Wessel

    2010-01-01

    Rotational constants for the vibrational ground state and three torsionally excited states of nine nitrobenzene isotopologues were used to investigate the internal rotation potential and the structure of nitrobenzene. Relaxation parameters were calculated by the B3LYP and MP2(full) methods with the aug-cc-pVDZ and aug-cc-pVTZ basis sets. The four sets of relaxation parameters all led to a clear improvement in the fit to rotational constants as compared with fits without relaxation of structure. The improvement was different from set to set, with B3LYP/aug-cc-PVDZ as a surprising winner. However, letting three of the relaxation parameters vary freely, gave virtually identical results for the molecular structure and potential function in all cases. Assuming higher order potential coefficient to vanish, the resultant potential parameters were, with 1 σ uncertainties, V2 = 1678 ± 19 cm -1 and V4 = -207 ± 6 cm -1. The barrier to internal rotation was estimated to 1575 ± 150 cm -1. A small change in structure upon ortho deuteration was found.

  13. Advances in targeting cyclic nucleotide phosphodiesterases.

    PubMed

    Maurice, Donald H; Ke, Hengming; Ahmad, Faiyaz; Wang, Yousheng; Chung, Jay; Manganiello, Vincent C

    2014-04-01

    Cyclic nucleotide phosphodiesterases (PDEs) catalyse the hydrolysis of cyclic AMP and cyclic GMP, thereby regulating the intracellular concentrations of these cyclic nucleotides, their signalling pathways and, consequently, myriad biological responses in health and disease. Currently, a small number of PDE inhibitors are used clinically for treating the pathophysiological dysregulation of cyclic nucleotide signalling in several disorders, including erectile dysfunction, pulmonary hypertension, acute refractory cardiac failure, intermittent claudication and chronic obstructive pulmonary disease. However, pharmaceutical interest in PDEs has been reignited by the increasing understanding of the roles of individual PDEs in regulating the subcellular compartmentalization of specific cyclic nucleotide signalling pathways, by the structure-based design of novel specific inhibitors and by the development of more sophisticated strategies to target individual PDE variants.

  14. Tharsis Binucleus-Type Vortex Structure (TBVS) on Mars: Implications for Differential Rotation of Mars

    NASA Astrophysics Data System (ADS)

    Zeng, Z.; Birnbaum, S.; Zhu, M.; Xie, H.; Liu, L.; Yang, W.

    2006-12-01

    Large, arcuate faults in the Tharsis region of Mars are here interpreted to be a Giant Binucleus-Type Vortex Structure. Centered in Tharsis Montes (247.4°E, 0.9°N) with a radius of ~3500 km, and here named the Tharsis Binucleus-Type Vortex Structure (TBVS), it extends into both the southern and northern hemispheres of Mars. The pattern of the major extensional faults related to the TBVS includes a northern portion and a southern portion and is characterized by a sigmoid structure. In the northern portion adjacent to the Alba Patera summit cone (Tantalus Fossae), extensional faults trend northeast or north-east-north while faults found south of Alba Patera (Ceraunius Fossae) trend north-south. The extensional faults sited south to southwest of Tharsis Montes mainly trend to the southwest. As a typical feature the faults located south-east-south of Tharsis Montes (Claritas Fossae) show an obvious curved shape: the northern part trends northwest and north- west-north while the southern part trends north-east-north and northeast. Turbine-like extensional faults around Tharsis Montes are distinguished. Five examples of binucleus-type vortex structures on Earth were found and researched by Zuoxun Zeng and Lilin Liu (1990, 1992 and 1993). The TBVS is similar to the Yegezikala binucleus-type vortex structure (Zuoxun Zeng, 1990) in terms of the nuclear column: two cores linking together as one magma body. Physical modeling and numerical modeling using finite-element analysis indicate that the formation of the TBVS is related to torsional shear around the center of Tharsis Montes. The torsional shear is possibly a result of the twist of the Martian crust about its axis due to differential rotation between the two hemispheres. The earlier twist of the Martian crust controlled the northeast-trending fractures, magma bodies and volcano chains. The cooled and fixed northeast-trending magma bodies in the Tharsis area played the role of nuclear columns during the formation of

  15. Structure and modelling of the three-dimensional boundary layer on a rotating disk: Progress report

    SciTech Connect

    Eaton, J.K.

    1993-12-31

    The objectives of this research are to develop an improved understanding of the effects of mean flow three dimensionality on boundary layer flow and heat transfer. The specific problem of interest, the flow on a large rotating disk in an otherwise quiescent environment was selected for its geometric simplicity and for its relevance to rotating machinery design.

  16. Validation of a Fluid–Structure Interaction Model of Solute Transport in Pores of Cyclically Deformed Tissue Scaffolds

    PubMed Central

    Op Den Buijs, Jorn; Ritman, Erik L.

    2010-01-01

    Convection induced by repetitive compression of porous tissue scaffolds enhances solute transport inside the scaffold. Our previous experiments have shown that pore size, shape, and orientation with respect to strain direction greatly influence loading-induced solute transport. The objective of this study was to develop a computational model of deformation-induced solute transport in porous tissue scaffolds, which included the pore geometry of the scaffold. This geometry consisted of a cubic scaffold with single channel in the middle of the scaffold, immersed in a fluid reservoir. Cylindrical pores with circular or elliptic cross section, and spheroid pores were modeled. The scaffold was cyclically compressed from one side, causing fluid motion and dispersion of solute inside the scaffold pore. Scaffold deformation was solved using the finite element method, and fluid flow and solute transport were solved using the finite volume method. The distortion of the scaffold–fluid interface was transferred as a boundary condition to the fluid flow solver. Both convection and diffusion were included in the computations. The solute transport rates in the different scaffold pore geometries agreed well with our previous experimental results obtained with X-ray microimaging. This model will be used to explore transport properties of a spectrum of novel scaffold designs. PMID:20136371

  17. Rotational spectroscopy of pyridazine and its isotopologs from 235-360 GHz: equilibrium structure and vibrational satellites.

    PubMed

    Esselman, Brian J; Amberger, Brent K; Shutter, Joshua D; Daane, Mitchell A; Stanton, John F; Woods, R Claude; McMahon, Robert J

    2013-12-14

    The rotational spectrum of pyridazine (o-C4H4N2), the ortho disubstituted nitrogen analog of benzene, has been measured and analyzed in the gas phase. For the ground vibrational state of the normal isotopolog, over 2000 individual rotational transitions have been identified between 238 and 360 GHz and have been fit to 13 parameters of a 6th-order centrifugal distortion Hamiltonian. All transitions in this frequency region can now be predicted from this model to near experimental accuracy, i.e., well enough for the purpose of any future radio-astronomical search for this species. Three isotopologs, [3-(13)C]-C4H4N2, [4-(13)C]-C4H4N2, and [1-(15)N]-C4H4N2, have been detected in natural abundance, and several hundred lines have been measured for each of these species and fit to 6th-order Hamiltonians. Ten additional isotopologs were synthesized with enhanced deuterium substitution and analyzed to allow for a complete structure determination. The equilibrium structure (Re) of pyridazine was obtained by correcting the experimental rotational constants for the effects of vibration-rotation coupling using interaction constants predicted from CCSD(T) calculations with an ANO0 basis set and further correcting for the effect of electron mass. The final Re structural parameters are determined with excellent accuracy, as evidenced by their ability to predict 28 independent moments of inertia (Ia and Ib for 14 isotopologs) very well from 9 structural parameters. The rotational spectra of the six lowest-energy fundamental vibrational satellites of the main isotopolog have been detected. The rotational spectra of the five lowest-energy vibrational satellites have been assigned and fit to yield accurate rotational and distortion constants, while the fit and assignment for the sixth is less complete. The resultant vibration-rotation interaction (α) constants are found to be in excellent agreement with ones predicted from coupled-cluster calculations, which proved to be the key

  18. Rotational spectroscopy of pyridazine and its isotopologs from 235–360 GHz: Equilibrium structure and vibrational satellites

    SciTech Connect

    Esselman, Brian J.; Amberger, Brent K.; Shutter, Joshua D.; Daane, Mitchell A.; Woods, R. Claude; McMahon, Robert J.; Stanton, John F.

    2013-12-14

    The rotational spectrum of pyridazine (o-C{sub 4}H{sub 4}N{sub 2}), the ortho disubstituted nitrogen analog of benzene, has been measured and analyzed in the gas phase. For the ground vibrational state of the normal isotopolog, over 2000 individual rotational transitions have been identified between 238 and 360 GHz and have been fit to 13 parameters of a 6th-order centrifugal distortion Hamiltonian. All transitions in this frequency region can now be predicted from this model to near experimental accuracy, i.e., well enough for the purpose of any future radio-astronomical search for this species. Three isotopologs, [3-{sup 13}C]-C{sub 4}H{sub 4}N{sub 2}, [4-{sup 13}C]-C{sub 4}H{sub 4}N{sub 2}, and [1-{sup 15}N]-C{sub 4}H{sub 4}N{sub 2}, have been detected in natural abundance, and several hundred lines have been measured for each of these species and fit to 6th-order Hamiltonians. Ten additional isotopologs were synthesized with enhanced deuterium substitution and analyzed to allow for a complete structure determination. The equilibrium structure (R{sub e}) of pyridazine was obtained by correcting the experimental rotational constants for the effects of vibration-rotation coupling using interaction constants predicted from CCSD(T) calculations with an ANO0 basis set and further correcting for the effect of electron mass. The final R{sub e} structural parameters are determined with excellent accuracy, as evidenced by their ability to predict 28 independent moments of inertia (I{sub a} and I{sub b} for 14 isotopologs) very well from 9 structural parameters. The rotational spectra of the six lowest-energy fundamental vibrational satellites of the main isotopolog have been detected. The rotational spectra of the five lowest-energy vibrational satellites have been assigned and fit to yield accurate rotational and distortion constants, while the fit and assignment for the sixth is less complete. The resultant vibration-rotation interaction (α) constants are found to

  19. The Iodine Hvperfine Structure in the Microwave Spectrum of Ethyl Iodide: Nuclear Quadrupole and Spin Rotation Coupling

    NASA Astrophysics Data System (ADS)

    Lee, W. W.; Scherr, Lawrence M.; Barsh, Max K.

    1988-11-01

    Some rotational transitions of ethyl iodide, CH3CH2I, have been reinvestigated by microwave Fourier transform (MWFT) spectroscopy. The iodine hyperfine structure splittings were first ana lyzed using a direct diagonalization procedure of the complete quadrupole Hamiltonian matrix. The results of this analysis showed deviations from our measurements up to 60 kHz. A new analysis using additional spin rotation coupling matrix elements reproduces our measurements within the experi­mental error limit and decreases the standard deviation of the least squares fit from 28 kHz to only 4 kHz.

  20. Dynamic characterization, monitoring and control of rotating flexible beam-mass structures via piezo-embedded techniques

    NASA Technical Reports Server (NTRS)

    Lai, Steven H.-Y.

    1992-01-01

    A variational principle and a finite element discretization technique were used to derive the dynamic equations for a high speed rotating flexible beam-mass system embedded with piezo-electric materials. The dynamic equation thus obtained allows the development of finite element models which accommodate both the original structural element and the piezoelectric element. The solutions of finite element models provide system dynamics needed to design a sensing system. The characterization of gyroscopic effect and damping capacity of smart rotating devices are addressed. Several simulation examples are presented to validate the analytical solution.

  1. Rotating spin and giant splitting: unoccupied surface electronic structure of Tl/Si(111).

    PubMed

    Stolwijk, Sebastian D; Schmidt, Anke B; Donath, Markus; Sakamoto, Kazuyuki; Krüger, Peter

    2013-10-25

    We present a combined experimental and theoretical study on the unoccupied surface electronic structure of the Tl/Si(111) surface. Spin- and angle-resolved inverse-photoemission measurements with sensitivity to both the in-plane and the out-of-plane polarization direction detect a spin-orbit-split surface state, which is well described by theoretical calculations. We demonstrate that the spin polarization vector rotates from the classical in-plane Rashba polarization direction around Γ[over ¯] to the direction perpendicular to the surface at the K[over ¯](K[over ¯]') points-a direct consequence of the symmetry of the 2D hexagonal system. A giant splitting in energy of about 0.6 eV is observed and attributed to the strong localization of the unoccupied surface state close to the heavy Tl atoms. This leads to completely out-of-plane spin-polarized valleys in the vicinity of the Fermi level. As the valley polarization is oppositely oriented at the K[over ¯] and K[over ¯]' points, backscattering should be strongly suppressed in this system.

  2. Structure and Rotational Dynamics of Isoamyl Acetate and Methyl Propionate Studied by Microwave Spectroscopy

    NASA Astrophysics Data System (ADS)

    Stahl, W.; Nguyen, H. V. L.; Sutikdja, L. W.; Jelisavac, D.; Mouhib, H.; Kleiner, I.

    2012-06-01

    The microwave spectra of a number of organic aliphatic esters have been recorded for the first time in the 3-26.5 GHz frequency range, using the molecular beam Fourier-transform microwave (MB-FTMW) spectrometer in Aachen, with an instrumental uncertainty of a few kHz for unblended lines. The combined use of ab initio quantum chemical calculations and spectral analysis allowed us to determine the spectroscopic parameters and potential barriers to internal rotation of the methyl groups for the lowest energy conformers. We will compare here the results from ab initio calculations and from two different hamiltonian methods (the XIAM and BELGI codes) for isoamyl acetate H3C-COO-(CH2)2-CH(CH3)2, an one-top internal rotor molecule with a C1 symmetry and for methyl propionate CH3CH2COOCH3 containing two inequivalent methyl tops (C3v), with different barrier heights. This study is part of a larger project which aims at determining the structures of the lowest energy conformers for a serie of organic esters and ketones which are of interest for flavour or perfume applications.

  3. Electronic Structure of Hydrogen Donors in Semiconductors and Insulators Probed by Muon Spin Rotation

    NASA Astrophysics Data System (ADS)

    Shimomura, Koichiro; Ito, Takashi U.

    2016-09-01

    Hydrogen in semiconductors and insulators plays a crucial role in their electric conductivity. Substantial experimental and theoretical efforts have been made to establish this hypothesis in the last decade, and the muon spin rotation technique has played a pioneering role. Positive muons implanted into such low-carrier systems often form a muonium (an analogue of hydrogen, the bound state of a positive muon and an electron). Although its dynamical aspect may be different from the heavier hydrogen, the electronic structure of the muonium is expected to be identical to that of hydrogen after a small correction of the reduced mass (˜0.4%). Since the discovery of a shallow muonium in CdS, its properties have been intensively studied in many semiconductors and insulators, and then it was interpreted as a possible origin of n-type conductivity under the context of a classical shallow donor model. In this article, we will describe the principle of muonium experiments and survey recent achievements in this field.

  4. CMOS-compatible polarization rotator design based on asymmetrical periodic loaded waveguide structure

    NASA Astrophysics Data System (ADS)

    Sun, Yao; Ye, Winnie N.

    2016-03-01

    Silicon-on-insulator (SOI) technology has been a promising platform for photonic applications. However, the high index-contrast between silicon and the top cladding (SiO2 or air) of the SOI waveguides makes the modal birefringence hard to control. Consequently, SOI based photonics integrated circuits (PICs) are in general highly polarization-sensitive, making polarization management important. In this paper, a polarization rotator (PR) design on the 220 nm SOI platform is demonstrated through numerical simulations and experiments. The demonstrated PR design is based on asymmetrical periodic loaded waveguide structures. The demonstrated design features compact device footprint and can be fabricated by CMOS compatible process. In addition, no special cladding is required to break the vertical symmetry of the waveguide. The design has shown promising performance over the C-band wavelengths (1530 nm-1565 nm) by simulations. However, the fabrication requirements are stringent for the design, thus the performance of the fabricated devices are limited by the current fabrication technology.

  5. Comparison of Algorithms for Determination of Rotation Measure and Faraday Structure. I. 1100-1400 MHz

    NASA Astrophysics Data System (ADS)

    Sun, X. H.; Rudnick, L.; Akahori, Takuya; Anderson, C. S.; Bell, M. R.; Bray, J. D.; Farnes, J. S.; Ideguchi, S.; Kumazaki, K.; O'Brien, T.; O'Sullivan, S. P.; Scaife, A. M. M.; Stepanov, R.; Stil, J.; Takahashi, K.; van Weeren, R. J.; Wolleben, M.

    2015-02-01

    Faraday rotation measures (RMs) and more general Faraday structures are key parameters for studying cosmic magnetism and are also sensitive probes of faint ionized thermal gas. A definition of which derived quantities are required for various scientific studies is needed, as well as addressing the challenges in determining Faraday structures. A wide variety of algorithms has been proposed to reconstruct these structures. In preparation for the Polarization Sky Survey of the Universe's Magnetism (POSSUM) to be conducted with the Australian Square Kilometre Array Pathfinder and the ongoing Galactic Arecibo L-band Feeds Array Continuum Transit Survey (GALFACTS), we run a Faraday structure determination data challenge to benchmark the currently available algorithms, including Faraday synthesis (previously called RM synthesis in the literature), wavelet, compressive sampling, and QU-fitting. The input models include sources with one Faraday thin component, two Faraday thin components, and one Faraday thick component. The frequency set is similar to POSSUM/GALFACTS with a 300 MHz bandwidth from 1.1 to 1.4 GHz. We define three figures of merit motivated by the underlying science: (1) an average RM weighted by polarized intensity, R{{M}wtd}, (2) the separation Δφ of two Faraday components, and (3) the reduced chi-squared χ r2. Based on the current test data with a signal-to-noise ratio of about 32, we find the following. (1) When only one Faraday thin component is present, most methods perform as expected, with occasional failures where two components are incorrectly found. (2) For two Faraday thin components, QU-fitting routines perform the best, with errors close to the theoretical ones for R{{M}wtd} but with significantly higher errors for Δφ . All other methods, including standard Faraday synthesis, frequently identify only one component when Δφ is below or near the width of the Faraday point-spread function. (3) No methods as currently implemented work well for

  6. Comparison of algorithms for determination of rotation measure and Faraday structure. I. 1100–1400 MHz

    SciTech Connect

    Sun, X. H.; Akahori, Takuya; Anderson, C. S.; Farnes, J. S.; O’Sullivan, S. P.; Rudnick, L.; O’Brien, T.; Bell, M. R.; Bray, J. D.; Scaife, A. M. M.; Ideguchi, S.; Kumazaki, K.; Stepanov, R.; Stil, J.; Wolleben, M.; Takahashi, K.; Weeren, R. J. van E-mail: larry@umn.edu

    2015-02-01

    Faraday rotation measures (RMs) and more general Faraday structures are key parameters for studying cosmic magnetism and are also sensitive probes of faint ionized thermal gas. A definition of which derived quantities are required for various scientific studies is needed, as well as addressing the challenges in determining Faraday structures. A wide variety of algorithms has been proposed to reconstruct these structures. In preparation for the Polarization Sky Survey of the Universe's Magnetism (POSSUM) to be conducted with the Australian Square Kilometre Array Pathfinder and the ongoing Galactic Arecibo L-band Feeds Array Continuum Transit Survey (GALFACTS), we run a Faraday structure determination data challenge to benchmark the currently available algorithms, including Faraday synthesis (previously called RM synthesis in the literature), wavelet, compressive sampling, and QU-fitting. The input models include sources with one Faraday thin component, two Faraday thin components, and one Faraday thick component. The frequency set is similar to POSSUM/GALFACTS with a 300 MHz bandwidth from 1.1 to 1.4 GHz. We define three figures of merit motivated by the underlying science: (1) an average RM weighted by polarized intensity, RM{sub wtd}, (2) the separation Δϕ of two Faraday components, and (3) the reduced chi-squared χ{sub r}{sup 2}. Based on the current test data with a signal-to-noise ratio of about 32, we find the following. (1) When only one Faraday thin component is present, most methods perform as expected, with occasional failures where two components are incorrectly found. (2) For two Faraday thin components, QU-fitting routines perform the best, with errors close to the theoretical ones for RM{sub wtd} but with significantly higher errors for Δϕ. All other methods, including standard Faraday synthesis, frequently identify only one component when Δϕ is below or near the width of the Faraday point-spread function. (3) No methods as currently implemented

  7. Analysis of the forearm rotational efficiency in extant hominoids: new insights into the functional implications of upper limb skeletal structure.

    PubMed

    Ibáñez-Gimeno, Pere; Galtés, Ignasi; Manyosa, Joan; Malgosa, Assumpció; Jordana, Xavier

    2014-11-01

    The greatly diversified locomotor behaviors in the Hominoidea impose different mechanical requirements in the upper limb of each species. As forearm rotation has a major role in locomotion, the skeletal structures involved in this movement may display differences among taxa that reflect functional adaptations. To test this, we use a biomechanical model that quantifies the rotatory capacity of pronator teres (rotational efficiency) from skeletal measurements. Using a large sample of hominoids, we aim to identify the morphological adaptations that confer differences in the mechanics of forearm motion and to assess the functional advantage of these adaptations. Forearm positions along the pronation-supination range where rotational efficiency is maximal depend on the orientation of the humeral medial epicondyle and differ among taxa. Our results indicate that these are related to locomotor mode. Knuckle-walkers exhibit a medial epicondyle more posteriorly directed, which, in elbow angles close to extension, causes rotational efficiency to be maximal in pronated positions of the forearm. Species with a significant amount of arboreal locomotion, such as vertical climbing, i.e., Pongo spp., Pan troglodytes and Gorilla gorilla, display more proximally oriented epicondyles, which, in elbow flexion, leads to maximum rotational efficiencies in supinated positions of the forearm. Hylobatidae, with the less posteriorly and proximally oriented epicondyle, show their maximum rotational efficiencies closer to the forearm neutral position throughout most of the flexion-extension range, which may be linked to brachiation in this taxon. In humans, the epicondylar orientation and thus the positions of the maximum rotational efficiencies fall between arboreal and terrestrial hominoids. This may be related to the enhanced manipulative skills of the upper limb. In conclusion, the current analysis indicates that the orientation of the humeral medial epicondyle is linked to the locomotor

  8. Analysis of the forearm rotational efficiency in extant hominoids: new insights into the functional implications of upper limb skeletal structure.

    PubMed

    Ibáñez-Gimeno, Pere; Galtés, Ignasi; Manyosa, Joan; Malgosa, Assumpció; Jordana, Xavier

    2014-11-01

    The greatly diversified locomotor behaviors in the Hominoidea impose different mechanical requirements in the upper limb of each species. As forearm rotation has a major role in locomotion, the skeletal structures involved in this movement may display differences among taxa that reflect functional adaptations. To test this, we use a biomechanical model that quantifies the rotatory capacity of pronator teres (rotational efficiency) from skeletal measurements. Using a large sample of hominoids, we aim to identify the morphological adaptations that confer differences in the mechanics of forearm motion and to assess the functional advantage of these adaptations. Forearm positions along the pronation-supination range where rotational efficiency is maximal depend on the orientation of the humeral medial epicondyle and differ among taxa. Our results indicate that these are related to locomotor mode. Knuckle-walkers exhibit a medial epicondyle more posteriorly directed, which, in elbow angles close to extension, causes rotational efficiency to be maximal in pronated positions of the forearm. Species with a significant amount of arboreal locomotion, such as vertical climbing, i.e., Pongo spp., Pan troglodytes and Gorilla gorilla, display more proximally oriented epicondyles, which, in elbow flexion, leads to maximum rotational efficiencies in supinated positions of the forearm. Hylobatidae, with the less posteriorly and proximally oriented epicondyle, show their maximum rotational efficiencies closer to the forearm neutral position throughout most of the flexion-extension range, which may be linked to brachiation in this taxon. In humans, the epicondylar orientation and thus the positions of the maximum rotational efficiencies fall between arboreal and terrestrial hominoids. This may be related to the enhanced manipulative skills of the upper limb. In conclusion, the current analysis indicates that the orientation of the humeral medial epicondyle is linked to the locomotor

  9. Integrating Structured Learning and Scholarly Activities into Clerkship Rotations: A Win–Win for Students and Preceptors

    PubMed Central

    Miller, Stephannie; Fulton, Judith; Mostow, Eliot

    2014-01-01

    Objective: To merge scholarly activity into the curriculum developed for medical students electing a rotation in wound care and/or dermatology. Approach: The authors adapted the unique wound care curriculum developed for medical student rotators and residents to incorporate structured scholarly projects, opportunities for mentorship, and feedback for continued improvement. Results: Benefits have been observed to both students and to the clinic, as reflected by online survey results, increased productivity in the form of posters and manuscripts, and opportunities for professional networking. Discussion: Rotations and clerkships can be transformed from haphazard, bystander observational experiences to active participation that enhances comprehension and retention, while also providing benefits to preceptors. Innovation: Integration between research, education, and clinical activities in a structured way can provide opportunity for enhanced learning experiences and promote the concept of evidence-based practice. Conclusion: With observed benefits to students, researchers, and staff in this clinical setting, other clerkship rotation settings should consider an integrated and structured approach to learning, which includes scholarly activities. Further rigorous program evaluation is necessary to further quantify preliminary positive feedback regarding this approach. PMID:24804160

  10. Method and structure for skewed block-cyclic distribution of lower-dimensional data arrays in higher-dimensional processor grids

    DOEpatents

    Chatterjee, Siddhartha; Gunnels, John A.

    2011-11-08

    A method and structure of distributing elements of an array of data in a computer memory to a specific processor of a multi-dimensional mesh of parallel processors includes designating a distribution of elements of at least a portion of the array to be executed by specific processors in the multi-dimensional mesh of parallel processors. The pattern of the designating includes a cyclical repetitive pattern of the parallel processor mesh, as modified to have a skew in at least one dimension so that both a row of data in the array and a column of data in the array map to respective contiguous groupings of the processors such that a dimension of the contiguous groupings is greater than one.

  11. Structural and cyclic volta metric investigations on BIPBVOX solid electrolyte synthesized by ethylene glycol-citric acid sol-gel route

    NASA Astrophysics Data System (ADS)

    Naqvi, Faria K.; Beg, Saba; Al-Areqi, Niyazi A. S.

    2016-05-01

    Samples of BIPBVOX.x (Bi2V1-xPbxO5.5-x/2) in the composition range 0.05 ≤ x ≤ 0.20 were prepared by ethylene glycol- citric acid sol-gel synthesis route. Structural investigations were carried out by X-ray diffraction, DTA. The highly conducting γ'- phase was effectively stabilized at room temperature for compositions with x ≥ 0.17. Cyclic voltammetric measurements showed reversible redox reactions of vanadium and irreversible redox reaction of Bi3+ in the BIPBVOX system during the first cathodic and anodic sweep. However, a higher stability against the reduction of Bi3+ to metallic bismuth was seen for x=0.20.

  12. Ionization Structure and Mass-Loss for Rapidly-Rotating Near Main-Sequence B Stars

    NASA Astrophysics Data System (ADS)

    Bjorkman, J. E.; Abbott, B. P.

    1999-05-01

    Ultraviolet resonance line profiles of rapidly-rotating near main-sequence B stars indicate that the two-dimensional ionization structure of the circumstellar envelope can be crucial to our understanding of the mass-loss rate. We investigate these two-dimensional effects through the use of a radiation transfer model to construct piece-wise spherical ionization fractions for the wind-compressed disk model of a rotating stellar wind. Using these ionization fractions, we generate theoretical line profiles using a two-dimensional Monte Carlo simulation of the radiation transport for the UV resonance lines of Si iii, Si iv, C iii, C iv, and N v. For the B2.5 IV star chosen for this study, we find the mass-loss rate to be on the order of a few times 10(-9) Msuntextrm { yr}(-1) and the X-ray emission measure log EM_X ~ 52.5 cm(-3) . This result is consistent with observed X-ray luminosities as well as UV resonance line profiles. Our mass-loss rate is higher by a factor of 5--10 over those predicted theoretically (via spherically symmetric radiation-driven wind theory) and observationally (due to uncertainties in the ionization fractions). In addition, we also examine the effects of a latitudinal density gradient on the line profiles. We find that the line profiles are sensitive to two-dimensional effects, showing disproportionate amounts of emission versus absorption as the viewing location changes from pole to equator. Specifically, N v, which is abundant in the polar regions and depleted in the equator, shows enhanced emission for an observer looking edge-on to the equatorial wind-compressed disk. We show that spherically symmetric models cannot account for the anomalously strong emission or absorption resulting from a latitudinal ionization gradient in the wind. This work has been supported under NASA grants NAG5-3447 (BPA) and NAG5-3248 (JEB) to the University of Toledo.

  13. [Development of the craniofacial structures and mandibular growth rotation: a longitudinal study with Enlow analysis (counterpart analysis)].

    PubMed

    Işeri, H

    1989-04-01

    The aim of the present study was to evaluate the development of craniofacial structures in individuals with different actual mandibular growth rotation pattern. Enlow's counterpart analysis was used for this evaluation. The material was consisted 166 cephalometric films of 83 male and female subjects. A total of fourteen variables were employed and the data was analysed by various statistical methods. The vertical growth of middle cranial fossa and mandibular ramus as the equivalent of nasomaxillary complex was found to be the key sites in the determination of mandibular growth rotation pattern. Besides this, the sagittal location of maxilla and mandible related to the cranial base was different in backward and forward mandibular rotation patterns.

  14. Recognizing magnetic structures by present and future radio telescopes with Faraday rotation measure synthesis

    NASA Astrophysics Data System (ADS)

    Beck, R.; Frick, P.; Stepanov, R.; Sokoloff, D.

    2012-07-01

    Context. Modern radio telescopes allow us to record a large number of spectral channels. The application of a Fourier transform to spectropolarimetric data in radio continuum, Faraday rotation measure (RM) synthesis, yields the “Faraday spectrum”, which hosts valuable information about the magneto-ionic medium along the line of sight. Aims: We investigate whether the method of wavelet-based RM synthesis can help us to identify structures of regular and turbulent magnetic fields in extended magnetized objects, such as galaxies and galaxy clusters. Methods: The analysis of spectropolarimetric radio observations of multi-scale targets calls for a corresponding mathematical technique. Wavelets allow us to reformulate the RM synthesis method in a scale-dependent way and to visualize the data as a function of Faraday depth and scale. Results: We present observational tests to recognize magnetic field structures. A region with a regular magnetic field generates a broad “disk” in Faraday space, with two “horns” when the distribution of cosmic-ray electrons is broader than that of the thermal electrons. Each field reversal generates one asymmetric “horn” on top of the “disk”. A region with a turbulent field can be recognized as a “Faraday forest” of many components. These tests are applied to the spectral ranges of various synthesis radio telescopes. We argue that the ratio of maximum to minimum wavelengths determines the range of scales that can be identified in Faraday space. Conclusions: A reliable recognition of magnetic field structures in spiral galaxies or galaxy clusters requires the analysis of data cubes in position-position-Faraday depth space (“PPF cubes”), observed over a wide and continuous frequency range, allowing the recognition of a wide range of scales as well as high resolution in Faraday space. The planned Square Kilometre Array (SKA) will fulfill this condition and will be close to representing a perfect

  15. Cyclic ductile and brittle deformation related to coseismic thrust fault propagation: Structural record at the base of a basement nappe (Preveli, Crete)

    NASA Astrophysics Data System (ADS)

    Nüchter, Jens-Alexander; Wassmann, Sara; Stöckhert, Bernhard

    2013-09-01

    structural record at the base of a basement nappe (Preveli nappe, Crete, Greece) thrust upon sedimentary rocks is investigated, aimed on understanding mechanisms which result in decoupling of the thrust sheet from its original substratum. We identify several superimposed deformation stages, each with characteristic structural style and indications of episodic deformation at initially high differential stress. The final stage involves formation of a matrix supported breccia transected by pseudotachylytes, comprising the lowermost 30 m of the nappe. Brecciation and pseudotachylyte formation occurred in a single event, and structures were not modified afterward. Complete induration of breccia and composition of phengite crystallized during devitrification of pseudotachylytes place the sequence of events into the middle crust. We propose a model relating episodic deformation and cyclic stress history to propagation of a thrust fault in a limited number of seismic events. Terminal brecciation and frictional fusion record passage of the fault front beneath the site of observation and decoupling of the thrust sheet. Absence of discernible further deformation is consistent with negligible basal friction during transport as a nappe. Brecciation and pseudotachylyte formation mark the switch from a history of repeated coseismic loading and postseismic stress relaxation in the plastosphere, driven by seismic events on the approaching thrust fault, to passive transport with deformation localized in a weak thrust plane. For a sequence of superimposed ductile to brittle structures, our model provides an alternative to progressive cooling and exhumation concomitant with deformation over millions of years.

  16. Crystal structure of release factor RF3 trapped in the GTP state on a rotated conformation of the ribosome

    SciTech Connect

    Zhou, Jie; Lancaster, Laura; Trakhanov, Sergei; Noller, Harry F.

    2012-03-26

    The class II release factor RF3 is a GTPase related to elongation factor EF-G, which catalyzes release of class I release factors RF1 and RF2 from the ribosome after termination of protein synthesis. The 3.3 {angstrom} crystal structure of the RF3 {center_dot} GDPNP {center_dot} ribosome complex provides a high-resolution description of interactions and structural rearrangements that occur when binding of this translational GTPase induces large-scale rotational movements in the ribosome. RF3 induces a 7{sup o} rotation of the body and 14{sup o} rotation of the head of the 30S ribosomal subunit, and itself undergoes inter- and intradomain conformational rearrangements. We suggest that ordering of critical elements of switch loop I and the P loop, which help to form the GTPase catalytic site, are caused by interactions between the G domain of RF3 and the sarcin-ricin loop of 23S rRNA. The rotational movements in the ribosome induced by RF3, and its distinctly different binding orientation to the sarcin-ricin loop of 23S rRNA, raise interesting implications for the mechanism of action of EF-G in translocation.

  17. Ramps, Relays, and Rotation: Interbasin Accommodation Structures in the Northern Rio Grande Rift, New Mexico

    NASA Astrophysics Data System (ADS)

    Benage, M. C.; Baldridge, W. S.; Ferguson, J. F.; Braile, L. W.; Young, G. R.; Godfrey, K. E.; Polgar, C.; Barber, R.

    2008-12-01

    Structural connections (accommodation zones) between basins in continental rifts control distribution and facies of syntectonic sediments and magmatic rocks, and therefore resources such as groundwater, hydrocarbons, and minerals. These zones are commonly buried beneath rift-filling sediments, thus geophysical methods are of paramount importance in understanding them. In the Summer of Applied Geophysical Experience (SAGE) program we focus on the small Hagan basin, located in an accommodation zone between the right-stepping Albuquerque and Española basins (respectively AB and EB) near the eastern margin of the Rio Grande rift in northern New Mexico. We integrate existing geological mapping and borehole information with geophysical (mainly seismic) data acquired by industry surveys and by SAGE. The broad accommodation zone comprises several north-trending (basin-parallel), right-stepping faults (E to W: La Bajada, San Francisco, and Rincon) downthrown toward the rift axis. Faults partially overlap with each other, serving to "relay" extension between the main AB and EB. Individual basin-parallel faults are dominantly dip slip with an unknown but small amount of lateral slip. Decreasing offset toward fault tips results in plunging hanging-wall ramps. Thus, ramps underwent horizontal-axis rotation and extension, creating normal faults perpendicular to the major relay faults. Extension from the main EB is transferred to the LB fault along an intrabasin northward plunging ramp. Minor footwall uplift ("Cerrillos uplift") along the LB fault created a shallow synform at the southern end of the EB. Major footwall uplift occurring ~10 Ma on the SF and RC faults (master faults of the northern AB) created a narrow basin (Hagan) within the accommodation zone. From the fact that lower Tertiary sediments in the Hagan basin are deformed parallel to underlying Paleozoic and Mesozoic rocks and that uplift of the Sandia Mountains occurred ~10 Ma, we infer that structures in the

  18. Dual specificity and novel structural folding of yeast phosphodiesterase-1 for hydrolysis of second messengers cyclic adenosine and guanosine 3',5'-Monophosphate

    DOE PAGESBeta

    Tian, Yuanyuan; Cui, Wenjun; Huang, Manna; Robinson, Howard; Wan, Yiqian; Wang, Yousheng; Ke, Hengming

    2014-08-05

    Cyclic nucleotide phosphodiesterases (PDEs) decompose second messengers cAMP and cGMP that play critical roles in many physiological processes. PDE1 of Saccharomyces cerevisiae has been subcloned and expressed in Escherichia coli. Recombinant yPDE1 has a KM of 110 μM and a kcat of 16.9 s⁻¹ for cAMP and a KM of 105 μM and a kcat of 11.8 s₅⁻¹ for cGMP. Thus, the specificity constant (kcat/KMcAMP)/(kcat/KMcGMP) of 1.4 indicates a dual specificity of yPDE1 for hydrolysis of both cAMP and cGMP. The crystal structures of unliganded yPDE1 and its complex with GMP at 1.31 Å resolution reveal a new structural foldingmore » that is different from those of human PDEs but is partially similar to that of some other metalloenzymes such as metallo-β-lactamase. In spite of their different structures and divalent metals, yPDE1 and human PDEs may share a common mechanism for hydrolysis of cAMP and cGMP.« less

  19. The B3 Subunit of the Cone Cyclic Nucleotide-gated Channel Regulates the Light Responses of Cones and Contributes to the Channel Structural Flexibility.

    PubMed

    Ding, Xi-Qin; Thapa, Arjun; Ma, Hongwei; Xu, Jianhua; Elliott, Michael H; Rodgers, Karla K; Smith, Marci L; Wang, Jin-Shan; Pittler, Steven J; Kefalov, Vladimir J

    2016-04-15

    Cone photoreceptor cyclic nucleotide-gated (CNG) channels play a pivotal role in cone phototransduction, which is a process essential for daylight vision, color vision, and visual acuity. Mutations in the cone channel subunits CNGA3 and CNGB3 are associated with human cone diseases, including achromatopsia, cone dystrophies, and early onset macular degeneration. Mutations in CNGB3 alone account for 50% of reported cases of achromatopsia. This work investigated the role of CNGB3 in cone light response and cone channel structural stability. As cones comprise only 2-3% of the total photoreceptor population in the wild-type mouse retina, we used Cngb3(-/-)/Nrl(-/-) mice with CNGB3 deficiency on a cone-dominant background in our study. We found that, in the absence of CNGB3, CNGA3 was able to travel to the outer segments, co-localize with cone opsin, and form tetrameric complexes. Electroretinogram analyses revealed reduced cone light response amplitude/sensitivity and slower response recovery in Cngb3(-/-)/Nrl(-/-) mice compared with Nrl(-/-) mice. Absence of CNGB3 expression altered the adaptation capacity of cones and severely compromised function in bright light. Biochemical analysis demonstrated that CNGA3 channels lacking CNGB3 were more resilient to proteolysis than CNGA3/CNGB3 channels, suggesting a hindered structural flexibility. Thus, CNGB3 regulates cone light response kinetics and the channel structural flexibility. This work advances our understanding of the biochemical and functional role of CNGB3 in cone photoreceptors.

  20. The B3 Subunit of the Cone Cyclic Nucleotide-gated Channel Regulates the Light Responses of Cones and Contributes to the Channel Structural Flexibility.

    PubMed

    Ding, Xi-Qin; Thapa, Arjun; Ma, Hongwei; Xu, Jianhua; Elliott, Michael H; Rodgers, Karla K; Smith, Marci L; Wang, Jin-Shan; Pittler, Steven J; Kefalov, Vladimir J

    2016-04-15

    Cone photoreceptor cyclic nucleotide-gated (CNG) channels play a pivotal role in cone phototransduction, which is a process essential for daylight vision, color vision, and visual acuity. Mutations in the cone channel subunits CNGA3 and CNGB3 are associated with human cone diseases, including achromatopsia, cone dystrophies, and early onset macular degeneration. Mutations in CNGB3 alone account for 50% of reported cases of achromatopsia. This work investigated the role of CNGB3 in cone light response and cone channel structural stability. As cones comprise only 2-3% of the total photoreceptor population in the wild-type mouse retina, we used Cngb3(-/-)/Nrl(-/-) mice with CNGB3 deficiency on a cone-dominant background in our study. We found that, in the absence of CNGB3, CNGA3 was able to travel to the outer segments, co-localize with cone opsin, and form tetrameric complexes. Electroretinogram analyses revealed reduced cone light response amplitude/sensitivity and slower response recovery in Cngb3(-/-)/Nrl(-/-) mice compared with Nrl(-/-) mice. Absence of CNGB3 expression altered the adaptation capacity of cones and severely compromised function in bright light. Biochemical analysis demonstrated that CNGA3 channels lacking CNGB3 were more resilient to proteolysis than CNGA3/CNGB3 channels, suggesting a hindered structural flexibility. Thus, CNGB3 regulates cone light response kinetics and the channel structural flexibility. This work advances our understanding of the biochemical and functional role of CNGB3 in cone photoreceptors. PMID:26893377

  1. [Cyclic structural changes in endoplasmic reticulum and Golgi apparatus in the hippocampal neurons of ground squirrels during hibernation].

    PubMed

    Bocharova, L S; Gordon, R Ia; Rogachevskiĭ, V V; Ignat'ev, D A; Khutsian, S S

    2011-01-01

    Repetitive remodeling and renewal of the cytoplasmic structures realizing synthesis of proteins accompanies the cycling of ground squirrels between torpor and arousal states during hibernation season. Earlier we have shown partial loss of ribosomes and nucleolus inactivation in CA3 hippocampal pyramidal neurons in each bout of torpor with rapid and full recovery after warming up. Here we describe reversible structural changes in endoplasmic reticulum (ER) and Golgi complex (G) in these neurons. Transformation of ER from mainly cysternal to tubular form and from mainly granular to smooth type occurs at every entrance in torpor, while the opposite change occurs at arousal. Torpor state is also associated with G fragmentation and loss of its flattened cisternae. Appearance in torpor of the autophagosomal vacuoles containing fragments of membrane structures and ribosomes is a sign of their partial destruction. Granular ER restoration, perhaps through assembly from the multilamellar membrane structures, whorls or bags, begins as early as in the middle of the torpor bout, while G flattened cisternae reappear only at warming. ER and G completely restore their structure 2-3 hours after the provoked arousal. Thus, hibernation represents and example of nerve cell structural adaptation to alterations in functional and metabolic activity through both active destruction and renewal of ribosomes, ER, and G. Perhaps, it is the incomplete ER autophagosomal degradation at torpor provides its rapid renewal at arousal by reassembly from the preserved fragments. PMID:21598689

  2. Cyclic phosphonium ionic liquids

    PubMed Central

    Mukhlall, Joshua A; Romeo, Alicia R; Gohdo, Masao; Ramati, Sharon; Berman, Marc; Suarez, Sophia N

    2014-01-01

    Summary Ionic liquids (ILs) incorporating cyclic phosphonium cations are a novel category of materials. We report here on the synthesis and characterization of four new cyclic phosphonium bis(trifluoromethylsulfonyl)amide ILs with aliphatic and aromatic pendant groups. In addition to the syntheses of these novel materials, we report on a comparison of their properties with their ammonium congeners. These exemplars are slightly less conductive and have slightly smaller self-diffusion coefficients than their cyclic ammonium congeners. PMID:24605146

  3. Structural dynamics of a methionine γ-lyase for calicheamicin biosynthesis: Rotation of the conserved tyrosine stacking with pyridoxal phosphate.

    PubMed

    Cao, Hongnan; Tan, Kemin; Wang, Fengbin; Bigelow, Lance; Yennamalli, Ragothaman M; Jedrzejczak, Robert; Babnigg, Gyorgy; Bingman, Craig A; Joachimiak, Andrzej; Kharel, Madan K; Singh, Shanteri; Thorson, Jon S; Phillips, George N

    2016-05-01

    CalE6 from Micromonospora echinospora is a (pyridoxal 5' phosphate) PLP-dependent methionine γ-lyase involved in the biosynthesis of calicheamicins. We report the crystal structure of a CalE6 2-(N-morpholino)ethanesulfonic acid complex showing ligand-induced rotation of Tyr100, which stacks with PLP, resembling the corresponding tyrosine rotation of true catalytic intermediates of CalE6 homologs. Elastic network modeling and crystallographic ensemble refinement reveal mobility of the N-terminal loop, which involves both tetrameric assembly and PLP binding. Modeling and comparative structural analysis of PLP-dependent enzymes involved in Cys/Met metabolism shine light on the functional implications of the intrinsic dynamic properties of CalE6 in catalysis and holoenzyme maturation. PMID:27191010

  4. Rotational Spectrum and Structure of the 1,1-Difluoroethylene···Carbon Dioxide Complex.

    PubMed

    Anderton, Ashley M; Peebles, Rebecca A; Peebles, Sean A

    2016-01-21

    Rotational spectra for five isotopologues of the 1:1 weak complex between 1,1-difluoroethylene (H2C═CF2) and carbon dioxide (CO2) have been measured using 480 MHz bandwidth chirped-pulse and resonant cavity Fourier-transform microwave spectroscopy between 5.5 and 18.5 GHz. The observed structure of the complex is planar, with the CO2 aligned roughly parallel to the C═C bond, and experimental structural parameters derived from rotational constants are consistent with the most stable geometry predicted by basis set superposition error and zero point energy corrected ab initio geometry optimizations at the MP2/6-311++G(2d,2p) level. Comparisons with the recently characterized vinyl fluoride···carbon dioxide complex reveal slightly longer intermolecular distances in the present complex, but very similar binding energies.

  5. Structural Analysis and Direct Imaging of Rotational Stacking Faults in Few-Layer Graphene Synthesized from Solid Botanical Precursor

    NASA Astrophysics Data System (ADS)

    Kalita, Golap; Wakita, Koichi; Umeno, Masayoshi

    2011-07-01

    Here, we report the structural analysis and rotational stacking faults of few-layer graphene sheets derived by the controlled pyrolysis of the solid botanical derivative camphor (C10H16O). The second-order Raman spectra of the sheets show that the graphene layers are more than one single layer, and the numbers of layers can be controlled by adjusting the amount of camphor pyrolyzed. Transmission electron microscopy images show a minimum of 3 layers for thinner graphene sheets and a maximum of 12 layers for thicker graphene sheets. Low-voltage aberration-corrected high-resolution transmission electron microscopy is also carried out to gain insight into the hexagonal structure and stacking of graphene layers. The transmission electron microscopy study showed the presence of moiré patterns with a relative rotation between graphene layers.

  6. Structural dynamics of a methionine γ-lyase for calicheamicin biosynthesis: Rotation of the conserved tyrosine stacking with pyridoxal phosphate

    PubMed Central

    Cao, Hongnan; Tan, Kemin; Wang, Fengbin; Bigelow, Lance; Yennamalli, Ragothaman M.; Jedrzejczak, Robert; Babnigg, Gyorgy; Bingman, Craig A.; Joachimiak, Andrzej; Kharel, Madan K.; Singh, Shanteri; Thorson, Jon S.; Phillips, George N.

    2016-01-01

    CalE6 from Micromonospora echinospora is a (pyridoxal 5′ phosphate) PLP-dependent methionine γ-lyase involved in the biosynthesis of calicheamicins. We report the crystal structure of a CalE6 2-(N-morpholino)ethanesulfonic acid complex showing ligand-induced rotation of Tyr100, which stacks with PLP, resembling the corresponding tyrosine rotation of true catalytic intermediates of CalE6 homologs. Elastic network modeling and crystallographic ensemble refinement reveal mobility of the N-terminal loop, which involves both tetrameric assembly and PLP binding. Modeling and comparative structural analysis of PLP-dependent enzymes involved in Cys/Met metabolism shine light on the functional implications of the intrinsic dynamic properties of CalE6 in catalysis and holoenzyme maturation. PMID:27191010

  7. The Effects of Differential Rotation on the Magnetic Structure of the Solar Corona: MHD Simulations

    NASA Technical Reports Server (NTRS)

    Lionello, Roberto; Riley, Pete; Linker, Jon A.; Mikic, Zoran

    2004-01-01

    Coronal holes are magnetically open regions from which the solar wind streams. Magnetic reconnection has been invoked to reconcile the apparently rigid rotation of coronal holes with the differential rotation of magnetic flux in the photosphere. This mechanism might also be relevant to the formation of the slow solar wind, the properties of which seem to indicate an origin from the opening of closed magnetic field lines. We have developed a global MHD model to study the effect of differential rotation on the coronal magnetic field. Starting from a magnetic flux distribution similar to that of Wang et al., which consists of a bipolar magnetic region added to a background dipole field, we applied differential rotation over a period of 5 solar rotations. The evolution of the magnetic field and of the boundaries of coronal holes are in substantial agreement with the findings of Wang et al.. We identified examples of interchange reconnection and other changes of topology of the magnetic field. Possible consequences for the origin of the slow solar wind are also discussed.

  8. An Analytic Mathematical Model to Explain the Spiral Structure and Rotation Curve of NGC 3198

    NASA Astrophysics Data System (ADS)

    Rout, Bruce; Rout, Cameron

    2016-06-01

    An analytical model of galactic morphology is presented. This model presents resolutions to two inter-related parameters of spiral galaxies: one being the flat velocity rotation profile and the other being the spiral morphology of such galaxies. This model is a mathematical transformation dictated by the general theory of relativity applied to rotating polar coordinate systems that conserve the metric. The model shows that the flat velocity rotation profile and spiral shape of certain galaxies are both products of the general theory. Validation of the model is presented by application to 878 rotation curves provided by Salucci, and by comparing the results of a derived distance modulus to those using Cepheid variables, water masers and Tully-Fisher calculations. The model suggests means of determining galactic linear density, mass and angular momentum. We also show that the morphology of NGC 3198 is congruent to the geodesic as observed within a rotating reference frame and that galaxies are gravitationally viscous and self bound.

  9. A cyclic GMP-dependent signalling pathway regulates bacterial phytopathogenesis.

    PubMed

    An, Shi-Qi; Chin, Ko-Hsin; Febrer, Melanie; McCarthy, Yvonne; Yang, Jauo-Guey; Liu, Chung-Liang; Swarbreck, David; Rogers, Jane; Maxwell Dow, J; Chou, Shan-Ho; Ryan, Robert P

    2013-09-11

    Cyclic guanosine 3',5'-monophosphate (cyclic GMP) is a second messenger whose role in bacterial signalling is poorly understood. A genetic screen in the plant pathogen Xanthomonas campestris (Xcc) identified that XC_0250, which encodes a protein with a class III nucleotidyl cyclase domain, is required for cyclic GMP synthesis. Purified XC_0250 was active in cyclic GMP synthesis in vitro. The linked gene XC_0249 encodes a protein with a cyclic mononucleotide-binding (cNMP) domain and a GGDEF diguanylate cyclase domain. The activity of XC_0249 in cyclic di-GMP synthesis was enhanced by addition of cyclic GMP. The isolated cNMP domain of XC_0249 bound cyclic GMP and a structure-function analysis, directed by determination of the crystal structure of the holo-complex, demonstrated the site of cyclic GMP binding that modulates cyclic di-GMP synthesis. Mutation of either XC_0250 or XC_0249 led to a reduced virulence to plants and reduced biofilm formation in vitro. These findings describe a regulatory pathway in which cyclic GMP regulates virulence and biofilm formation through interaction with a novel effector that directly links cyclic GMP and cyclic di-GMP signalling.

  10. Rotational band structures in sup 127 Cs: Shape changes induced by h sub 11/2 neutron alignment

    SciTech Connect

    Liang, Y.; Ma, R.; Paul, E.S.; Xu, N.; Fossan, D.B. ); Wyss, R.A. )

    1990-09-01

    Several rotational bands have been populated to high spin in {sup 127}Cs following the {sup 120}Sn({sup 11}B,4{ital n}) reaction. Rotational bands built on low-lying proton {ital g}{sub 7/2}, {ital d}{sub 5/2}, and {ital g}{sub 9/2} (hole) orbitals, and the unique-parity {ital h}{sub 11/2} orbital were observed and identified. For the {pi}{ital g}{sub 9/2} (hole) case, both signatures were seen in a strongly coupled {Delta}{ital I}=1 band, while for the other cases, decoupled {Delta}{ital I}=2 bands were observed with strong in-band quadrupole transitions. Through comparisons with cranked-shell-model calculations, these band structures are understood to be associated with a prolate ({gamma}{approximately}0{degree}) deformed nuclear shape. At frequencies above {h bar}{omega}=0.3 MeV, the rotational alignment of a pair of {ital h}{sub 11/2} neutrons was observed for each of the {ital h}{sub 11/2}, {ital g}{sub 7/2}, and {ital d}{sub 5/2} bands. This neutron alignment is predicted to drive the nuclear core away from a prolate shape towards the collectively rotating oblate ({gamma}={minus}60{degree}) shape. Changes in the measured signature splittings for the bands below and above the alignment are consistent with the shape changes.

  11. Phase behaviors of cyclic diblock copolymers.

    PubMed

    Zhang, Guojie; Fan, Zhongyong; Yang, Yuliang; Qiu, Feng

    2011-11-01

    A spectral method of self-consistent field theory has been applied to AB cyclic block copolymers. Phase behaviors of cyclic diblock copolymers, such as order-disorder transition, order-order transition, and domain spacing size, have been studied, showing good consistency with previous experimental and theoretical results. Compared to linear diblocks, cyclic diblocks are harder to phase separate due to the topological constraint of the ring structure. A direct disorder-to-cylinder transition window is observed in the phase diagram, which is significantly different from the mean field phase diagram of linear diblock copolymers. The domain spacing size ratio between cyclic and linear diblock copolymers is typically close to 0.707, indicating in segregation that the cyclic polymer can be considered to be made up of linear diblocks with half of the original chain length. PMID:22070321

  12. Structural Basis of Differential Ligand Recognition by Two Classes of bis-(3-5)-cyclic Dimeric Guanosine Monophosphate-binding Riboswitches

    SciTech Connect

    K Smith; C Shanahan; E Moore; A Simon; S Strobel

    2011-12-31

    The bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP) signaling pathway regulates biofilm formation, virulence, and other processes in many bacterial species and is critical for their survival. Two classes of c-di-GMP-binding riboswitches have been discovered that bind this second messenger with high affinity and regulate diverse downstream genes, underscoring the importance of RNA receptors in this pathway. We have solved the structure of a c-di-GMP-II riboswitch, which reveals that the ligand is bound as part of a triplex formed with a pseudoknot. The structure also shows that the guanine bases of c-di-GMP are recognized through noncanonical pairings and that the phosphodiester backbone is not contacted by the RNA. Recognition is quite different from that observed in the c-di-GMP-I riboswitch, demonstrating that at least two independent solutions for RNA second messenger binding have evolved. We exploited these differences to design a c-di-GMP analog that selectively binds the c-di-GMP-II aptamer over the c-di-GMP-I RNA. There are several bacterial species that contain both types of riboswitches, and this approach holds promise as an important tool for targeting one riboswitch, and thus one gene, over another in a selective fashion.

  13. Structure of the Cyclic Nucleotide-Binding Homology Domain of the hERG Channel and Its Insight into Type 2 Long QT Syndrome

    PubMed Central

    Li, Yan; Ng, Hui Qi; Li, Qingxin; Kang, CongBao

    2016-01-01

    The human ether-à-go-go related gene (hERG) channel is crucial for the cardiac action potential by contributing to the fast delayed-rectifier potassium current. Mutations in the hERG channel result in type 2 long QT syndrome (LQT2). The hERG channel contains a cyclic nucleotide-binding homology domain (CNBHD) and this domain is required for the channel gating though molecular interactions with the eag domain. Here we present solution structure of the CNBHD of the hERG channel. The structural study reveals that the CNBHD adopts a similar fold to other KCNH channels. It is self-liganded and it contains a short β-strand that blocks the nucleotide-binding pocket in the β-roll. Folding of LQT2-related mutations in this domain was shown to be affected by point mutation. Mutations in this domain can cause protein aggregation in E. coli cells or induce conformational changes. One mutant-R752W showed obvious chemical shift perturbation compared with the wild-type, but it still binds to the eag domain. The helix region from the N-terminal cap domain of the hERG channel showed unspecific interactions with the CNBHD. PMID:27025590

  14. Microwave spectrum, r(0) structure, dipole moment, barrier to internal rotation, and Ab initio calculations for fluoromethylsilane.

    PubMed

    Durig, James R; Panikar, Savitha S; Groner, Peter; Nanaie, Hossein; Bürger, Hans; Moritz, Peter

    2010-04-01

    The microwave spectra of seven isotopomers of fluoromethylsilane, CH(2)FSiH(3), in the ground vibrational state were measured and analyzed in the frequency range 18-40 GHz. The rotational and centrifugal distortion constants were evaluated by the least-squares treatment of the observed frequencies of a- and b-type R- and b-type Q-transitions. The values for the components of the dipole moment were obtained from the measurements of Stark effects from both a- and b-type transitions and the determined values are: |mu(a)| = 1.041(5), |mu(b)| = 1.311(6), and |mu(t)| = 1.674(4) D. Structural parameters have been determined and the heavy atom distances (r(0)) in Angstroms are: Si-C = 1.8942(57) and C-F = 1.4035(55) and the angle in degree, angleSiCF = 109.58(14). A semi-experimental r(e) structure was also determined from experimental ground state rotational constants and vibration-rotation constants derived from ab initio force fields. The internal torsional fundamental, SiH(3), was observed at 149.2 cm(-1) with two accompanying hot bands at 138.8 and 127.5 cm(-1). The barrier to internal rotation was obtained as 717.3(16) cm(-1) (2.051(46) kcal mol(-1)) by combining the analysis of the microwave A and E splittings and the torsional fundamental and hot band frequencies. Ab initio calculations have been carried out with full electron correlation by the second-order perturbation method with several different basis sets up to MP2/6-311+G(d,p) to obtain geometrical parameters, barriers to internal rotation, and centrifugal distortion constants. Adjusted r(0) structural parameters have been obtained by combining the ab initio MP2/6-311+G(d,p) predicted values with the determined rotational constants for the fluoride as well as with the previously reported microwave data for the chloro- and bromo- compounds. These experimental results are compared to the corresponding parameters for the carbon analogues.

  15. Earle K. Plyler Prize for Molecular Spectroscopy & Dynamics Lecture: Broadband Rotational Spectroscopy for Chemical Kinetics, Molecular Structure, and Analytical Chemistry

    NASA Astrophysics Data System (ADS)

    Pate, Brooks

    2013-03-01

    Advances in high-speed digital electronics have enabled a new generation of molecular rotational spectroscopy techniques that provide instantaneous broadband spectral coverage. These techniques use a chirped excitation pulse to coherently excite the molecular sample over a spectral bandwidth of 10 GHz or larger through rapid passage. The subsequent time-domain emission is recorded using high-speed digitizers (up to 100 Gigasample/s) and the frequency domain spectrum is produced by fast Fourier transformation. The chirped-pulse Fourier transform (CP-FT) method has been implemented in the microwave frequency range (2-40 GHz) for studies of cold samples in pulsed jet sources and in the mm-wave/terahertz (THz) frequency range for studies of samples at room-temperature. The method has opened new applications for molecular rotational spectroscopy in the area of chemical kinetics where dynamic rotational spectroscopy is used to measure the rates of unimolecular isomerization reactions in highly excited molecules prepared by pulsed infrared laser excitation. In these applications, the isomerization rate is obtained from an analysis of the overall line shapes which are modified by chemical exchange leading to coalescence behavior similar to the effect in NMR spectroscopy. The sensitivity of the method and the ability to extend it to low frequency (2-8 GHz) have significantly increased the size range of molecules and molecular clusters for structure determination using isotopic substitution to build up the 3D molecular structures atom-by-atom. Application to the structure of water clusters with up to 15 water molecules will be presented. When coupled with advances in solid-state mm-wave/THz devices, this method provides a direct digital technique for analytical chemistry of room-temperature gases based on molecular rotational spectroscopy. These high-throughput methods can analyze complex sample mixtures with unmatched chemical selectivity and short analysis times. Work

  16. A method for finding candidate conformations for molecular replacement using relative rotation between domains of a known structure.

    PubMed

    Jeong, Jay I; Lattman, Eaton E; Chirikjian, Gregory S

    2006-04-01

    This paper presents a methodology to obtain candidate conformations of multidomain proteins for use in molecular replacement. For each separate domain, the orientational relationship between the template and the target structure is obtained using standard molecular replacement. The orientational relationships of the domains are then used to calculate the relative rotation between the domains in the target conformation by using pose-estimation techniques from the field of robotics and computer vision. With the angle of relative rotation between the domains as a cost function, iterative normal-mode analysis is used to drive the template structure to a candidate conformation that matches the X-ray crystallographic data obtained for the target conformation. The selection of the correct intra-protein domain orientations from among the many spurious maxima in the rotation function (including orientations obtained from domains in symmetry mates rather than within the same copy of the protein) presents a challenge. This problem is resolved by checking R factors of each domain, measuring the absolute value of relative rotation between domains, and evaluating the cost value after each candidate conformation is driven to convergence with iterative NMA. As a validation, the proposed method is applied to three test proteins: ribose-binding protein, lactoferrin and calcium ATPase. In each test case, the orientation and translation of the final candidate conformation in the unit cell are generated correctly from the suggested procedure. The results show that the proposed method can yield viable candidate conformations for use in molecular replacement and can reveal the structural details and pose of the target conformation in the crystallographic unit cell. PMID:16552141

  17. Changes in the Structure and Properties of Welded Joints of Low-Alloy Steels, Subjected to Cyclic Loads

    NASA Astrophysics Data System (ADS)

    Kuskov, V. N.; Kovenskiy, I. M.; Kuskov, K. V.

    2016-04-01

    Time-varying loads negatively affect the properties and structure of materials. Structural failures typically occur at loads below the yield point. In this work, fatigue tests of welded joints of low-alloy steels were carried out in an asymmetric cycle at loads of 60 and 80% of the yield strength. The stress ratio was 0.8-0.9. On the basis of the results of the tests, equations linking the number of cycles to failure with test parameters were obtained. Such equations can be used for estimating the residual life of elements both under construction and in operation. It has been found that the failure is not instantaneous. Specimens of steels continue to resist variable loads for 4000 - 26000 cycles to failure, depending on steel grade and the parameters of the test. Under operating conditions, it gives an opportunity to discover the onset of failure and dispose of the defective part or to replace the entire structure. A standard technique was used to measure the microhardness on the fractured specimens. The distance between the nearest indentations was 0.2 mm. The results of the measurements were plotted in graphs of ahardness change characteristic for all steels under study. A microhardness “step” has been discovered in areas with high dislocation density, as evidenced by x-ray diffraction and transmission electron microscopy. An intermediate stage of the investigation is the development of recommendations for determining the moment of failure of welded constructions with a probability of 95%.

  18. The evolution of the structural, vibrational and electronic properties of the cyclic ethers - on ring size. An ab initio study

    NASA Astrophysics Data System (ADS)

    Ford, Thomas A.

    2014-09-01

    The molecular structures, vibrational spectra and atomic charges of the alicyclic ethers containing from two to five carbon atoms have been determined by means of ab initio calculations, at the level of second order Møller-Plesset perturbation theory and using Dunning's augmented correlation-consistent polarized valence triple-zeta basis set. Two isomers of the oxetane, tetrahydrofuran and tetrahydropyran molecules have been identified and their relative energies determined. Structural properties, such as the COC bond angles and the CH bond lengths, are found to increase steadily with increasing ring size and with decreasing ionization energy. The mean CH2 stretching and bending wavenumbers exhibit the reverse behaviour, while the mean wavenumbers of the CH2 wagging and twisting modes follow the same trend as the structural features. The ring mode wavenumbers vary in a less regular way. The charges of the oxygen, α-carbon and axial and equatorial α- and β-hydrogen atoms also do not show systematic dependences on ring size or ionization energy. The trends in the values of these properties have been rationalized.

  19. Normal mode determination of perovskite crystal structures with octahedral rotations: theory and applications.

    PubMed

    Islam, Mohammad A; Rondinelli, James M; Spanier, Jonathan E

    2013-05-01

    Nuclear site analysis methods are used to enumerate the normal modes of ABX3 perovskite polymorphs with octahedral rotations. We provide the modes of the 14 subgroups of the cubic aristotype describing the Glazer octahedral tilt patterns, which are obtained from rotations of the BX6 octahedra with different sense and amplitude about high-symmetry axes. We tabulate all normal modes of each tilt system and specify the contribution of each atomic species to the mode displacement pattern, elucidating the physical meaning of the symmetry unique modes. We have systematically generated 705 schematic atomic displacement patterns for the normal modes of all 15 (14 rotated + 1 unrotated) Glazer tilt systems. We show through some illustrative examples how to use these tables to identify the octahedral rotations, symmetric breathing, and first-order Jahn-Teller anti-symmetric breathing distortions of the BX6 octahedra, and the associated Raman selection rules. We anticipate that these tables and schematics will be useful in understanding the lattice dynamics of bulk perovskites and could serve as a reference point in elucidating the atomic origins of a wide range of physical properties of synthetic perovskite thin films and superlattices. PMID:23567868

  20. Are Math Grades Cyclical?

    ERIC Educational Resources Information Center

    Adams, Gerald J.; Dial, Micah

    1998-01-01

    The cyclical nature of mathematics grades was studied for a cohort of elementary school students from a large metropolitan school district in Texas over six years (average cohort size of 8495). The study used an autoregressive integrated moving average (ARIMA) model. Results indicate that grades do exhibit a significant cyclical pattern. (SLD)

  1. Affordable Cyclic Voltammetry

    ERIC Educational Resources Information Center

    Stewart, Greg; Kuntzleman, Thomas S.; Amend, John R.; Collins, Michael J.

    2009-01-01

    Cyclic voltammetry is an important component of the undergraduate chemical curriculum. Unfortunately, undergraduate students rarely have the opportunity to conduct experiments in cyclic voltammetry owing to the high cost of potentiostats, which are required to control these experiments. By using MicroLab data acquisition interfaces in conjunction…

  2. Structure and Evolution of Interstellar Gas in Flattened, Rotating Elliptical Galaxies

    NASA Astrophysics Data System (ADS)

    Brighenti, Fabrizio; Mathews, William G.

    1996-10-01

    We study the time-dependent evolution of interstellar gas in a family of elliptical galaxies having identical masses and central densities but various ellipticities and total angular momenta. Dark halos are assumed to be flattened in the same manner as the stars. Normal mass loss from evolving galactic stars is sufficient to account for the amount of hot interstellar gas observed. Gas ejected from stars shares the random motions of the stars and the bulk stellar velocity relative to the local interstellar medium; the ejected gas thermalizes to a temperature similar to the virial temperature of the stellar system. The random stellar motions and galactic rotation are found by solving Jeans's equations in cylindrical geometry. For a sequence of galaxies differing only in degree of flattening-E0, E2, and E4-we find that the X-ray images and luminosities are not very different. As the hot interstellar gas loses energy by radiation, it cools to the very center of these nonrotating galaxies regardless of flattening. The X-ray surface brightness is generally slightly steeper than the optical surface brightness of starlight. However, when a small but typical galactic rotation is introduced, the evolution of the interstellar medium is radically altered. The average X- ray surface brightness {SIGMA}_X_ is lower in the galactic center compared to nonrotating galaxies. This lower {SIGMA}_X_ can be achieved without invoking an ad hoc mass dropout from the hot gas. As the gas cools in rotating galaxies, it is deposited in a large disk comparable in size to the effective radius. Alter evolving for several gigayears, most of the new gas in the cooling flow is constrained by angular momentum conservation to arrive at the outer edge of the disk, Causing a local enhancement in the X-ray surface brightness. This results in flattened inner X-ray surface brightness contours that have peanut shapes when viewed nearly perpendicular to the axis of galactic rotation. As gas approaches the

  3. Ultrasound Dimensions of the Rotator Cuff and Other Associated Structures in Korean Healthy Adults.

    PubMed

    Kim, Kyeongwon; Kim, Hong Geum; Song, Daeheon; Yoon, Jung Yoon; Chung, Myung Eun

    2016-09-01

    In evaluating patients complaining of shoulder pain, ultrasonography is an emerging imaging tool due to convenience, low cost, high sensitivity and specificity. However, normative values of ultrasound dimensions of the shoulder to be compared with pathologic findings in Korean adults are not provided yet. We evaluated the ultrasound dimensions of the rotator cuff, long head of biceps tendon, deltoid muscle and acromioclavicular joint in Korean healthy adults. Shoulder ultrasonography was performed on 200 shoulders from 100 healthy adults. The dimensions of the thickness of rotator cuff (supraspinatus, infraspinatus, subscapularis tendon), deltoid muscle, long head of biceps tendon, subacromial subdeltoid bursa, and acromioclavicular joint interval were measured in a standardized manner. Differences in measurements among sex, age, and dominant arms were compared. The thickness of rotator cuff tendons (supraspinatus, infraspinatus, subscapularis) and deltoid muscle were significantly different between men and women. The thickness of subacromial subdeltoid bursa was significantly different between men and women for non-dominant side. In rotator cuff tendon measurements, the differences between dominant and non-dominant shoulders were not significant, which means the asymptomatic contralateral shoulder can be used to estimate the normal reference values. When stratified by age divided by 10 years, the measurements of supraspinatus, subscapularis and deltoid thickness showed tendency of increase with the age. The acromioclavicular joint interval, on the other hand, revealed decreasing tendency. This report suggests normative values of ultrasound dimensions of healthy Korean population with varying age, and can be useful as reference values in evaluating shoulder pathology, especially in rotator cuff tendon pathology. PMID:27510393

  4. Ultrasound Dimensions of the Rotator Cuff and Other Associated Structures in Korean Healthy Adults

    PubMed Central

    2016-01-01

    In evaluating patients complaining of shoulder pain, ultrasonography is an emerging imaging tool due to convenience, low cost, high sensitivity and specificity. However, normative values of ultrasound dimensions of the shoulder to be compared with pathologic findings in Korean adults are not provided yet. We evaluated the ultrasound dimensions of the rotator cuff, long head of biceps tendon, deltoid muscle and acromioclavicular joint in Korean healthy adults. Shoulder ultrasonography was performed on 200 shoulders from 100 healthy adults. The dimensions of the thickness of rotator cuff (supraspinatus, infraspinatus, subscapularis tendon), deltoid muscle, long head of biceps tendon, subacromial subdeltoid bursa, and acromioclavicular joint interval were measured in a standardized manner. Differences in measurements among sex, age, and dominant arms were compared. The thickness of rotator cuff tendons (supraspinatus, infraspinatus, subscapularis) and deltoid muscle were significantly different between men and women. The thickness of subacromial subdeltoid bursa was significantly different between men and women for non-dominant side. In rotator cuff tendon measurements, the differences between dominant and non-dominant shoulders were not significant, which means the asymptomatic contralateral shoulder can be used to estimate the normal reference values. When stratified by age divided by 10 years, the measurements of supraspinatus, subscapularis and deltoid thickness showed tendency of increase with the age. The acromioclavicular joint interval, on the other hand, revealed decreasing tendency. This report suggests normative values of ultrasound dimensions of healthy Korean population with varying age, and can be useful as reference values in evaluating shoulder pathology, especially in rotator cuff tendon pathology. PMID:27510393

  5. Rotational spectra, conformational structures, and dipole moments of thiodiglycol by jet-cooled FTMW and ab initio calculations

    NASA Astrophysics Data System (ADS)

    Xu, Li-Hong; Liu, Qiang; Suenram, R. D.; Lovas, F. J.; Hight Walker, A. R.; Jensen, J. O.; Samuels, A. C.

    2004-12-01

    The rotational spectra of three low-energy conformers of thiodiglycol (TDG) (HOCH 2CH 2SCH 2CH 2OH) have been measured in a molecular beam using a pulsed-nozzle Fourier-transform microwave spectrometer. To determine the likely conformational structures with ab initio approach, conformational structures of 2-(ethylthio)ethanol (HOEES) (CH 3CH 2SCH 2CH 2OH) were used as starting points together with the consideration of possible intramolecular hydrogen bonding in TDG. Three lower-energy conformers have been found for TDG at the MP2=Full/6311G** level and ab initio results agree nicely with experimentally determined rotational constants. In addition, Stark measurements were performed for two of the three conformers for dipole moment determinations, adding to our confidence of the conformational structure matches between experimental observations and ab initio calculations. Of the three lower-energy conformers, one displays a compact folded-like structure with strong hydrogen bonding between the two hydroxyl groups and the central sulfide atom. Two other conformers have relatively open chain-like structures with hydrogen bonding between each of the hydroxyl groups to the central sulfur atom, of which one has pure b-type dipole moment according to the ab initio results.

  6. Genetics Home Reference: cyclic neutropenia

    MedlinePlus

    ... Understand Genetics Home Health Conditions cyclic neutropenia cyclic neutropenia Enable Javascript to view the expand/collapse boxes. Download PDF Open All Close All Description Cyclic neutropenia is a disorder that causes frequent infections and ...

  7. Secular rotational motions and the mechanical structure of a dynamical viscoelastic earth

    NASA Technical Reports Server (NTRS)

    Yuen, D. A.; Sabadini, R.

    1984-01-01

    A survey is presented of analytical methods for computing the linear responses of the rotational axis of a layered viscoelastic earth to surface loading. Theoretical research in this area is first summarized, and the differences between the mechanical boundary conditions to be applied at the interface separating the upper and lower mantles for an adiabatically and chemically stratified mantle are discussed. Some examples of polar wander and secular variation of the spin rate from glacial excitation are presented for various types of chemical and viscosity stratifications. The effects of an artificial density jump at the base of the lithosphere in models are examined, and certain issues concerning the fluid tidal Love number for different types of density stratification are addressed. The meaning of effective plate thickness over geological time scales for rotational dynamics is discussed.

  8. Ultrasound vs. MRI in the assessment of rotator cuff structure prior to shoulder arthroplasty

    PubMed Central

    Fischer, Christian Alexander; Weber, Marc-André; Neubecker, Clément; Bruckner, Thomas; Tanner, Michael; Zeifang, Felix

    2015-01-01

    Background/Aims We compared the accuracy of US to 3 T Tesla MRI for the detection of rotator cuff and long biceps tendon pathologies before joint replacement. Methods 45 patients were prospectively included. Results For the supraspinatus tendon, the accuracy of US when using MRI as reference was 91.1%. For the infraspinatus tendon, the accuracy with MRI as reference was 84.4%. The subscapularis tendon was consistently assessed by US and MRI in 35/45 patients (accuracy 77.8%). For the long biceps tendon the accuracy was 86.7%. Conclusion US detection of rotator cuff and biceps tendon integrity is comparable to MRI and should be preferred in revision cases. PMID:25829757

  9. Exocyclic push-pull conjugated compounds. Part 3. An experimental NMR and theoretical MO ab initio study of the structure, the electronic properties and barriers to rotation about the exocyclic partial double bond in 2- exo-methylene- and 2-cyanoimino-quinazolines and -benzodiazepines

    NASA Astrophysics Data System (ADS)

    Benassi, R.; Bertarini, C.; Hilfert, L.; Kempter, G.; Kleinpeter, E.; Spindler, J.; Taddei, F.; Thomas, S.

    2000-03-01

    The structure of a number of 2- exo-methylene substituted quinazolines and benzodiazepines, respectively, 1, 3a, b, 4( X=-CN, -COOEt ) and their 2-cyanoimino substituted analogues 2, 3c, d( X=-CN, -SO 2C 6H 4-Me (p) was completely assigned by the whole arsenal of 1D and 2D NMR spectroscopic methods. The E/ Z isomerism at the exo-cyclic double bond was determined by both NMR spectroscopy and confirmed by ab initio quantum chemical calculations; the Z isomer is the preferred one, its amount proved dependent on steric hindrance. Due to the push-pull effect in this part of the molecules the restricted rotation about the partial C 2,C 11 and C 2,N 11 double bonds, could also be studied and the barrier to rotation measured by dynamic NMR spectroscopy. The free energies of activation of this dynamic process proved very similar along the compounds studied but being dependent on the polarity of the solvent. Quantum chemical calculations at the ab initio level were employed to prove the stereochemistry at the exo-cyclic partial double bonds of 1- 4, to calculate the barriers to rotation but also to discuss in detail both the ground and the transition state of the latter dynamic process in order to better understand electronic, inter- and intramolecular effects on the barrier to rotation which could be determined experimentally. In the cyanoimino substituted compounds 2, 3c, d, the MO ab initio calculations evidence the isomer interconversion to be better described by the internal rotation process than by the lateral shift mechanism.

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

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

    Evidence is presented 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. Gaps such as these can be produced in a ring of large bodies or small uncharged particles by a nonaxisymmetric gravitational field (both of the above can be associated with the l = m = 3 harmonic), a fact that is relevant to models of planetary interiors.

  11. Structural changes of block copolymers with bi-modal orientation under fast cyclical stretching as observed by synchrotron SAXS

    PubMed Central

    Brubert, J.; Serrani, M.; Talhat, A.; De Gaetano, F.; Costantino, M. L.; Moggridge, G. D.

    2015-01-01

    Load-bearing tissues are composite materials that depend strongly on anisotropic fibre arrangement to maximise performance. One such tissue is the heart valve, with orthogonally arranged fibrosa and ventricularis layers. Their function is to maintain mechanical stress while being resilient. It is postulated that while one layer bears the applied stress, the orthogonal layer helps to regenerate the microstructure when the load is released. The present paper describes changes in the microstructure of a block copolymer with cylindrical morphology, having a bio-inspired microstructure of anisotropic orthogonally oriented layers, under uniaxial strain. To allow structural observations during fast deformation, equivalent to the real heart valve operation, we used a synchrotron X-ray source and recorded 2D SAXS patterns in only 1 ms per frame. The deformation behaviour of the composite microstructure has been reported for two arrangements of the cylinders in skin and core layers. The behaviour is very different to that observed either for uniaxially oriented or isotropic samples. Deformation is far from being affine. Cylinders aligned in the direction of stretch show fragmentation, but complete recovery of the spacing between cylinders on removal of the load. Those oriented perpendicular to the direction of stretch incline at an angle of approximately 25° to their original direction during load. PMID:25781560

  12. ROTATION OF WHITE-LIGHT CORONAL MASS EJECTION STRUCTURES AS INFERRED FROM LASCO CORONAGRAPH

    SciTech Connect

    Yurchyshyn, Vasyl; Abramenko, Valentyna; Tripathi, Durgesh

    2009-11-01

    Understanding the connection between the magnetic configurations of a coronal mass ejection (CME) and their counterpart in the interplanetary medium is very important in terms of space weather predictions. Our previous findings indicate that the orientation of a halo CME elongation may correspond to the orientation of the underlying flux rope. Here we further explore these preliminary results by comparing orientation angles of elongated LASCO CMEs, both full and partial halos, to the EUV Imaging Telescope post-eruption arcades (PEAs). By analyzing a sample of 100 events, we found that the overwhelming majority of CMEs are elongated in the direction of the axial field of PEAs. During their evolution, CMEs appear to rotate by about 10 deg. for most of the events (70%) with about 30 deg. - 50 deg. for some events, and the corresponding time profiles display regular and gradual changes. It seems that there is a slight preference for the CMEs to rotate toward the solar equator and heliospheric current sheet (59% of the cases). We suggest that the rotation of the ejecta may be due to the presence of a heliospheric magnetic field, and it could shed light on the problems related to connecting solar surface phenomena to their interplanetary counterparts.

  13. O-Toluic Acid Monomer and Monohydrate: Rotational Spectra, Structures, and Atmospheric Implications

    NASA Astrophysics Data System (ADS)

    Schnitzler, Elijah G.; Zenchyzen, Brandi L. M.; Jäger, Wolfgang

    2015-06-01

    Clusters of carboxylic acids with water, sulfuric acid, and other atmospheric species potentially increase the rate of new particle formation in the troposphere. Here, we present high-resolution pure rotational spectra of o-toluic acid and its complex with water in the range of 5-14 GHz, measured with a cavity-based molecular beam Fourier-transform microwave spectrometer. In both the monomer and the complex, the carboxylic acid functional group adopts a syn- conformation, with the acidic proton oriented away from the aromatic ring. In the complex, water participates in two hydrogen bonds, forming a six-membered intermolecular ring. Despite its large calculated c-dipole moment, no c-type transitions were observed for the complex, because of a large amplitude "wagging" motion of the unbound hydrogen of water, similar to the case of the benzoic acid-water complex. No methyl internal rotation splittings were observed, consistent with a high barrier (7 kJ mol-1) calculated for the monomer at the B3LYP/6-311++G(d,p) level of theory. Using statistical thermodynamics, experimental rotational constants were combined with a theoretical frequency analysis and binding energy to give an estimate of the percentage of hydrated acid in the atmosphere under various conditions. F. Riccobono, et al., Science, 344, 717 (2014). R. Zhang, et al., Science, 304, 1487 (2004). E. G. Schnitzler and W. Jäger, Phys. Chem. Chem. Phys., 16, 2305 (2014).

  14. Vibration suppression control of smart piezoelectric rotating truss structure by parallel neuro-fuzzy control with genetic algorithm tuning

    NASA Astrophysics Data System (ADS)

    Lin, J.; Zheng, Y. B.

    2012-07-01

    The main goal of this paper is to develop a novel approach for vibration control on a piezoelectric rotating truss structure. This study will analyze the dynamics and control of a flexible structure system with multiple degrees of freedom, represented in this research as a clamped-free-free-free truss type plate rotated by motors. The controller has two separate feedback loops for tracking and damping, and the vibration suppression controller is independent of position tracking control. In addition to stabilizing the actual system, the proposed proportional-derivative (PD) control, based on genetic algorithm (GA) to seek the primary optimal control gain, must supplement a fuzzy control law to ensure a stable nonlinear system. This is done by using an intelligent fuzzy controller based on adaptive neuro-fuzzy inference system (ANFIS) with GA tuning to increase the efficiency of fuzzy control. The PD controller, in its assisting role, easily stabilized the linear system. The fuzzy controller rule base was then constructed based on PD performance-related knowledge. Experimental validation for such a structure demonstrates the effectiveness of the proposed controller. The broad range of problems discussed in this research will be found useful in civil, mechanical, and aerospace engineering, for flexible structures with multiple degree-of-freedom motion.

  15. Rotational Preference in Gymnastics

    PubMed Central

    Heinen, Thomas; Jeraj, Damian; Vinken, Pia M.; Velentzas, Konstantinos

    2012-01-01

    In gymnastics, most skills incorporate rotations about one or more body axes. At present, the question remains open if factors such as lateral preference and/or vestibulo-spinal asymmetry are related to gymnast’s rotational preference. Therefore, we sought to explore relationships in gymnast’s rotation direction between different gymnastic skills. Furthermore, we sought to explore relationships between rotational preference, lateral preference, and vestibulo-spinal asymmetry. In the experiment n = 30 non-experts, n = 30 near-experts and n = 30 experts completed a rotational preference questionnaire, a lateral preference inventory, and the Unterberger-Fukuda Stepping Test. The results revealed, that near-experts and experts more often rotate rightward in the straight jump with a full turn when rotating leftward in the round-off and vice versa. The same relationship was found for experts when relating the rotation preference in the handstand with a full turn to the rotation preference in the straight jump with a full turn. Lateral preference was positively related to rotational preference in non-expert gymnasts, and vestibulo-spinal asymmetry was positively related to rotational preference in experts. We suggest, that gymnasts should explore their individual rotational preference by systematically practicing different skills with a different rotation direction, bearing in mind that a clearly developed structure in rotational preference between different skills may be appropriate to develop more complex skills in gymnastics. PMID:23486362

  16. Rotational preference in gymnastics.

    PubMed

    Heinen, Thomas; Jeraj, Damian; Vinken, Pia M; Velentzas, Konstantinos

    2012-06-01

    In gymnastics, most skills incorporate rotations about one or more body axes. At present, the question remains open if factors such as lateral preference and/or vestibulo-spinal asymmetry are related to gymnast's rotational preference. Therefore, we sought to explore relationships in gymnast's rotation direction between different gymnastic skills. Furthermore, we sought to explore relationships between rotational preference, lateral preference, and vestibulo-spinal asymmetry. In the experiment n = 30 non-experts, n = 30 near-experts and n = 30 experts completed a rotational preference questionnaire, a lateral preference inventory, and the Unterberger-Fukuda Stepping Test. The results revealed, that near-experts and experts more often rotate rightward in the straight jump with a full turn when rotating leftward in the round-off and vice versa. The same relationship was found for experts when relating the rotation preference in the handstand with a full turn to the rotation preference in the straight jump with a full turn. Lateral preference was positively related to rotational preference in non-expert gymnasts, and vestibulo-spinal asymmetry was positively related to rotational preference in experts. We suggest, that gymnasts should explore their individual rotational preference by systematically practicing different skills with a different rotation direction, bearing in mind that a clearly developed structure in rotational preference between different skills may be appropriate to develop more complex skills in gymnastics. PMID:23486362

  17. Aircraft control by propeller cyclic blades

    NASA Technical Reports Server (NTRS)

    Deyoung, J.

    1979-01-01

    A theory is developed for aircraft control obtained from the propeller forces and moments generated by blade angle variation during a blade revolution. The propeller blade is pitched harmonically one cycle per propeller revolution which results in vehicle control forces and moments, termed cyclic-control. Using a power series respresentation of an arbitrary function of cyclic-blade angle, cyclic-control theory is developed which leads to exact solutions in terms of derivatives of steady-state thrust and power with respect to blade angle. An alternative solution, when the cyclic-blade angle function is limited to a sinusoidal cycle, is in terms of Bessel functions. An estimate of non-steady azimuth angle change or lag is presented. Cyclic-control analysis applied to the counter-rotating propeller shows that control forces or moments can be uniquely isolated from each other. Thus the dual rotor, in hovering mode, has propulsion without rotor tilt or moments, or, when in propeller mode at the tail of an air ship or submarine, vehicle control with no vehicle movement. Control isolation is also attainable from three or more propellers in-line.

  18. Finite vortex numbers and symmetric vortex structures in a rotating trapped Fermi gas in the BCS-BEC crossover

    NASA Astrophysics Data System (ADS)

    Song, T. L.; Ma, Y. L.

    2011-08-01

    The ground state of a three-dimensional (3D) rotating trapped superfluid Fermi gas in the BCS-BEC crossover is mapped to finite N v -body vortex states by a simple ansatz. The total vortex energy is measured from the ground-state energy of the system in the absence of the vortices. The vortex state is stable since the vortex potential and rotation energies are attractive while the vortex kinetic energy and interaction between vortices are repulsive. By combining the analytical and numerical works for the minimal vortex energy, the 2D configurations of N v vortices are studied by taking into account of the finite size effects both on xy-plane and on z-direction. The calculated vortex numbers as a function of the interaction strength are appropriate to the renew experimental results by Zwierlein in [ High-temperature superfluidity in a ultracold Fermi gas, Ph.D. thesis, Massachusetts Institute of Technology, 2006]. The numerical results show that there exist two types of vortex structures: the trap center is occupied and unoccupied by a vortex, even in the case of N v < 10 with regular polygon and in the case of N v ≥ 10 with finite triangle lattice. The rotation frequency dependent vortex numbers with different interaction strengths are also discussed.

  19. Solution structure of the PilZ domain protein PA4608 complex with cyclic di-GMP identifies charge clustering as molecular readout.

    PubMed

    Habazettl, Judith; Allan, Martin G; Jenal, Urs; Grzesiek, Stephan

    2011-04-22

    Cyclic diguanosine monophosphate (c-di-GMP) is a ubiquitous bacterial second messenger that controls the switch from a single-cell lifestyle to surface-attached, multicellular communities called biofilms. PilZ domain proteins are a family of bacterial c-di-GMP receptors, which control various cellular processes. We have solved the solution structure of the Pseudomonas aeruginosa single-domain PilZ protein PA4608 in complex with c-di-GMP by NMR spectroscopy. Isotope labeling by (13)C and (15)N of both the ligand and the protein made it possible to define the structure of c-di-GMP in the complex at high precision by a large number of intermolecular and intraligand NOEs and by two intermolecular hydrogen bond scalar couplings. Complex formation induces significant rearrangements of the C- and N-terminal parts of PA4608. c-di-GMP binds as an intercalated, symmetric dimer to one side of the β-barrel, thereby displacing the C-terminal helix of the apo state. The N-terminal RXXXR PilZ domain motif, which is flexible in the apo state, wraps around the ligand and in turn ties the displaced C terminus in a loose manner by a number of hydrophobic contacts. The recognition of the dimeric ligand is achieved by numerous H-bonds and stacking interactions involving residues Arg(8), Arg(9), Arg(10), and Arg(13) of the PilZ motif, as well as β-barrel residues Asp(35) and Trp(77). As a result of the rearrangement of the N and C termini, a highly negative surface is created on one side of the protein complex. We propose that the movement of the termini and the resulting negative surface form the basis for downstream signaling. PMID:21310957

  20. Solution-phase parallel synthesis of a pharmacophore library of HUN-7293 analogues: a general chemical mutagenesis approach to defining structure-function properties of naturally occurring cyclic (depsi)peptides.

    PubMed

    Chen, Yan; Bilban, Melitta; Foster, Carolyn A; Boger, Dale L

    2002-05-15

    HUN-7293 (1), a naturally occurring cyclic heptadepsipeptide, is a potent inhibitor of cell adhesion molecule expression (VCAM-1, ICAM-1, E-selectin), the overexpression of which is characteristic of chronic inflammatory diseases. Representative of a general approach to defining structure-function relationships of such cyclic (depsi)peptides, the parallel synthesis and evaluation of a complete library of key HUN-7293 analogues are detailed enlisting solution-phase techniques and simple acid-base liquid-liquid extractions for isolation and purification of intermediates and final products. Significant to the design of the studies and unique to solution-phase techniques, the library was assembled superimposing a divergent synthetic strategy onto a convergent total synthesis. An alanine scan and N-methyl deletion of each residue of the cyclic heptadepsipeptide identified key sites responsible for or contributing to the biological properties. The simultaneous preparation of a complete set of individual residue analogues further simplifying the structure allowed an assessment of each structural feature of 1, providing a detailed account of the structure-function relationships in a single study. Within this pharmacophore library prepared by systematic chemical mutagenesis of the natural product structure, simplified analogues possessing comparable potency and, in some instances, improved selectivity were identified. One potent member of this library proved to be an additional natural product in its own right, which we have come to refer to as HUN-7293B (8), being isolated from the microbial strain F/94-499709.

  1. On Cyclically Symmetrical Spacetimes

    NASA Astrophysics Data System (ADS)

    Barnes, A.

    2001-07-01

    In a recent paper Carot et al. considered the definition of cylindrical symmetry as a specialisation of the case of axial symmetry. One of their propositions states that if there is a second Killing vector, which together with the one generating the axial symmetry, forms the basis of a two-dimensional Lie algebra, then the two Killing vectors must commute, thus generating an Abelian group. In this paper a similar result, valid under considerably weaker assumptions, is derived: any two-dimensional Lie transformation group which contains a one-dimensional subgroup whose orbits are circles, must be Abelian. The method used to prove this result is extended to apply to three-dimensional Lie transformation groups. It is shown that the existence of a one-dimensional subgroup with closed orbits restricts the Bianchi type of the associated Lie algebra to be I, II, III, VIIq = 0, VIII or IX. Some results on n-dimensional Lie groups are also derived and applied to show there are severe restrictions on the structure of the allowed four-dimensional Lie transformation groups compatible with cyclic symmetry.

  2. Cyclic control stick

    DOEpatents

    Whitaker, Charles N.; Zimmermann, Richard E.

    1989-01-01

    A cyclic control stick of the type used in helicopters for reducing the safety hazards associated with such a mechanism in the event of a crewman being thrown violently into contact with the cyclic control stick resulting from a crash or the like. The cyclic control stick is configured to break away upon the exertion of an impact force which exceeds a predetermined value and/or is exerted for more than a momentary time duration. The cyclic control stick is also configured to be adjustable so as to locate the grip thereof as far away from the crewman as possible for safety reasons without comprising the comfort of the crewman or the use of the control stick, and a crushable pad is provided on the top of the grip for impact energy absorbing purposes.

  3. Small-scale variations in the galactic magnetic field - The rotation measure structure function and birefringence in interstellar scintillations

    NASA Technical Reports Server (NTRS)

    Simonetti, J. H.; Cordes, J. M.; Spangler, S. R.

    1984-01-01

    The structure function of rotation measures of extragalactic sources and birefringence in interstellar scintillations are used to investigate variations in the interstellar magnetic field on length scales of about 0.01-100 pc and 10 to the 11th cm, respectively. Model structure functions are derived for the case of a power-law power spectrum of irregularities in the quantity (n(e)B), and an estimate for the structure function is computed for several regions of the sky using data on extragalactic sources. The results indicate an outer angular scale for rotation measure (RM) variations of not less than about 5 deg (a linear scale of about 9-90 pc at a distance of 0.1-1 kpc). There is also evidence for RM variations on angular scales as small as 1 arcmin, but it cannot be determined whether these are intrinsic to the source or caused by the interstellar medium. The effect of a random, Faraday-active medium on the diffraction of radio waves is derived, and an upper limit to the variations in n(e)B on a length scale of 10 to the 11th cm is obtained from available observations.

  4. EVIDENCE ON THE SIMPLE STRUCTURE AND FACTOR INVARIANCE ACHIEVED BY FIVE ROTATIONAL METHODS ON FOUR TYPES OF DATA.

    PubMed

    Dielman, T E; Cattell, R B; Wagner, A

    1972-01-01

    Five methods of factor rotation-Maxplane, Oblimax, Promax, Harris- Kaiser, and Varimax-were applied to four types of data-questionnaire, objeckive test, a physical problem, and a plasmode. In addition, the Maxplane procedure was followed in each case by Rotoplot-assisted visual robations. The results were compared with respect to simple structure (hyperplane percentages) and factor invaniance (congruence coefficient). It was concluded that, in general, the oblique methods were superior to Varimax in terms of simple structure although not consistently in terms of factor invariance. Among the oblique methods, the Rotoplot-assisted Maxplane usually resulted in the maximum simple structure at the f .10 hyperplane width but not consistently at either of the other two arbitrarily chosen widths. The unassisted Maxplane was generally excelled by the less expensive oblique methods both wiith respect to hyperplane count and factor invariance. The Harris-Kaiser method was generally more satisfadory in terms of the two criteria combined.

  5. Rotational structure and signature inversion in odd-odd [sup 84]Y

    SciTech Connect

    Chattopadhyay, S.; Jain, H.C.; Sheikh, J.A.; Agarwal, Y.K.; Jhingan, M.L. )

    1993-01-01

    High spin states with angular momentum up to 21[h bar] in [sup 84]Y have been established for the first time through the discrete-line [gamma]-ray spectroscopy using the [sup 59]Co([sup 28]Si,2[ital pn])[sup 84]Y reaction at 98 MeV. The experimental level scheme exhibits rotational characteristics with a large signature splitting and also signature inversion at [ital I]=11[h bar]. Theoretical calculations using the particle-rotor model with axial symmetry provide a good description of the observed phenomena.

  6. Electronic structure with vibration-rotation study of the NaYb molecule

    NASA Astrophysics Data System (ADS)

    Tohme, Samir N.; Korek, Mahmoud

    2015-10-01

    The potential energy curves have been investigated for the 15 lowest doublet and quartet electronic states in the 2s+1Λ± representation of the molecule NaYb via CASSCF/MRCI (single and double excitations with Davidson correction) calculations. The spectroscopic constants (Te, De, ωe, Be, re, …) have been calculated in addition to the permanent dipole moments μ. By using the canonical functions approach, the eigenvalues Ev, the rotational constants Bv, the centrifugal distortion constant Dv, and the abscissas of the turning points rmin and rmax have been calculated for different electronic states. Fourteen molecular states have been studied theoretically for the first time.

  7. Cyclic steps on ice

    NASA Astrophysics Data System (ADS)

    Yokokawa, M.; Izumi, N.; Naito, K.; Parker, G.; Yamada, T.; Greve, R.

    2016-05-01

    Boundary waves often form at the interface between ice and fluid flowing adjacent to it, such as ripples under river ice covers, and steps on the bed of supraglacial meltwater channels. They may also be formed by wind, such as the megadunes on the Antarctic ice sheet. Spiral troughs on the polar ice caps of Mars have been interpreted to be cyclic steps formed by katabatic wind blowing over ice. Cyclic steps are relatives of upstream-migrating antidunes. Cyclic step formation on ice is not only a mechanical but also a thermodynamic process. There have been very few studies on the formation of either cyclic steps or upstream-migrating antidunes on ice. In this study, we performed flume experiments to reproduce cyclic steps on ice by flowing water, and found that trains of steps form when the Froude number is larger than unity. The features of those steps allow them to be identified as ice-bed analogs of cyclic steps in alluvial and bedrock rivers. We performed a linear stability analysis and obtained a physical explanation of the formation of upstream-migrating antidunes, i.e., precursors of cyclic steps. We compared the results of experiments with the predictions of the analysis and found the observed steps fall in the range where the analysis predicts interfacial instability. We also found that short antidune-like undulations formed as a precursor to the appearance of well-defined steps. This fact suggests that such antidune-like undulations correspond to the instability predicted by the analysis and are precursors of cyclic steps.

  8. Cyclic polymers from alkynes

    NASA Astrophysics Data System (ADS)

    Roland, Christopher D.; Li, Hong; Abboud, Khalil A.; Wagener, Kenneth B.; Veige, Adam S.

    2016-08-01

    Cyclic polymers have dramatically different physical properties compared with those of their equivalent linear counterparts. However, the exploration of cyclic polymers is limited because of the inherent challenges associated with their synthesis. Conjugated linear polyacetylenes are important materials for electrical conductivity, paramagnetic susceptibility, optical nonlinearity, photoconductivity, gas permeability, liquid crystallinity and chain helicity. However, their cyclic analogues are unknown, and therefore the ability to examine how a cyclic topology influences their properties is currently not possible. We have solved this challenge and now report a tungsten catalyst supported by a tetraanionic pincer ligand that can rapidly polymerize alkynes to form conjugated macrocycles in high yield. The catalyst works by tethering the ends of the polymer to the metal centre to overcome the inherent entropic penalty of cyclization. Gel-permeation chromatography, dynamic and static light scattering, viscometry and chemical tests are all consistent with theoretical predictions and provide unambiguous confirmation of a cyclic topology. Access to a wide variety of new cyclic polymers is now possible by simply choosing the appropriate alkyne monomer.

  9. Cyclic polymers from alkynes.

    PubMed

    Roland, Christopher D; Li, Hong; Abboud, Khalil A; Wagener, Kenneth B; Veige, Adam S

    2016-08-01

    Cyclic polymers have dramatically different physical properties compared with those of their equivalent linear counterparts. However, the exploration of cyclic polymers is limited because of the inherent challenges associated with their synthesis. Conjugated linear polyacetylenes are important materials for electrical conductivity, paramagnetic susceptibility, optical nonlinearity, photoconductivity, gas permeability, liquid crystallinity and chain helicity. However, their cyclic analogues are unknown, and therefore the ability to examine how a cyclic topology influences their properties is currently not possible. We have solved this challenge and now report a tungsten catalyst supported by a tetraanionic pincer ligand that can rapidly polymerize alkynes to form conjugated macrocycles in high yield. The catalyst works by tethering the ends of the polymer to the metal centre to overcome the inherent entropic penalty of cyclization. Gel-permeation chromatography, dynamic and static light scattering, viscometry and chemical tests are all consistent with theoretical predictions and provide unambiguous confirmation of a cyclic topology. Access to a wide variety of new cyclic polymers is now possible by simply choosing the appropriate alkyne monomer. PMID:27442285

  10. Indentification of a Rotator Phase of Octamethyl Ferrocene and Correlations Between its Structural and Dynamical Properties

    SciTech Connect

    Asthalter,T.; Sergueev, I.; Van Burck, U.; Dinnebier, R.

    2006-01-01

    The low- and high-temperature phases of octamethyl ferrocene were studied in detail, using high-resolution X-ray powder diffraction, differential scanning calorimetry and nuclear resonant scattering, in particular the novel technique of synchrotron radiation perturbed angular correlations (SRPAC). Much as in the case of an analogous but more unsymmetrical molecule, octamethyl ethinyl ferrocene, the high-temperature phase possesses the space group R{bar 3}m source with lattice parameters a = b = 12.5568(1) Angstroms, c = 9.6045(1) Angstroms, which in the rhombohedral setting correspond to a = 7.9251(1) Angstroms, {alpha}=104.79 degrees. An increase of the volume per formula unit of about 12% across the phase transition is observed. The rotation of the electric field gradient, which can be identified with the rotation of the entire molecule within the lattice, follows Arrhenius behavior with a high activation energy of (40.3 {+-} 3.3)kJ mol{sup -1}. Whereas precursor effects and a change in activation energy were observed for octamethyl ethinyl ferrocene, no such effects are observed for octamethyl ferrocene. We relate this difference to the absence of the ethinyl substituent in octamethyl ferrocene.

  11. Multiconnected rotating helical structures in the volume of a wave front inverting mirror

    NASA Astrophysics Data System (ADS)

    Okulov, A. Yu.; Zakharyan, R. A.

    2009-09-01

    Phase conjugating mirrors based on stimulated Brillouin scattering (SBS) are analyzed from the point of view of conservation of the angular momentum of light. The three-wave system of equations for the pump field, the Stokes wave, and the acoustic field is used to demonstrate that the interference of the optical vortex (phase singularity) of the pump wave with the counterpropagating phase conjugated vortex of the Stokes wave forms a helical interference pattern rotating with the angular frequency equal to the frequency of the hypersonic wave. The rotating interference pattern produces a helical acoustic wave via electrostriction and transfers the orbital angular momentum. The standard quantum mechanical interpretation of SBS based upon the laws of conservation of energy and momentum for interacting optical photons and acoustic phonons is supplemented with the description of the transfer of the orbital angular momentum from the pump photon to the counterpropagating Stokes photon and the helical acoustic phonon, which corresponds the circular motion of the medium around the phase singularity.

  12. A rotating spiral structure in the innermost regions around IRC+10216

    NASA Astrophysics Data System (ADS)

    Quintana-Lacaci, G.; Cernicharo, J.; Agúndez, M.; Velilla Prieto, L.; Castro-Carrizo, A.; Marcelino, N.; Cabezas, C.; Peña, I.; Alonso, J. L.; Zuñiga, J.; Requena, A.; Bastida, A.; Kalugina, Y.; Lique, F.; Guélin, M.

    2016-07-01

    ALMA interferometer is providing us molecular maps with unprecedent precision and sensitivity, Key processes in the ejection of matter and dust from these objects occur in their inner zones. We have obtained sub-arcsecond interferometric maps of rotational transitions of metal-bearing molecules towards the prototypical C-rich evolved star IRC+ 10216. While Al- bearing molecular emission presents a roughly spherical shell, the molecular emission from NaCl and KCl presents an elongation in the inner regions, with a central minimum. The presence of the observed features only in KCl and NaCl might be a direct result of their comparatively high dipole moment with respect to the Al-bearing species. The most plausible interpretation for the spatial distribution of the salts is a spiral with a NaCl mass of 0.08 M ⊙ with an inner radius of 27 AU. The gas kinematics suggests that it is slowly expanding and rotating. Alternative gas distributions which could result in the presence of the elongation are also explored.

  13. The block structure and Quaternary strike-slip block rotation of central Japan

    NASA Astrophysics Data System (ADS)

    Kanaori, Yuji; Kawakami, Shin-Ichi; Yairi, Kenji

    1992-02-01

    Central Japan is situated on the inflection point of the bow-shaped Japanese islands. Numerous NW-SE trending active faults, arranged in parallel at intervals of 20 to 80 km are found in this area. These active faults are more than 30 km long with shattered zones from 30 to 300 m wide. Several active faults constitute a given block boundary, which serves as the dividing line for one of the four blocks that make up central Japan. The block boundaries require careful study since numerous historical earth-quakes have occurred along these lines. Offset measurements of basement rocks, created during the Quaternary period due to left-lateral faulting, amount to 1 to 7 km. Gravity lineaments, which link points of sudden change and saddles of Bouguer anomalies, are clearly found along the block boundaries. The NW-SE trending active faults appearing on the ground surface are associated with motions of the block boundaries. Block rotational movement, caused by left-lateral faulting, plays an important role in the crustal deformation of central Japan. Rotational angles of the blocks calculated from the amount of displacement of basement rocks, initiated during the Quaternary period, are estimated to be 3° to 7° in a clockwise manner.

  14. Structural similarities in tetraaryltins described by virtual non-crystallographic rotations or translations: Kitaigorodskii's morphotropism is revisited.

    PubMed

    Kálmán, Alajos; Fábián, László

    2007-06-01

    Recently Kálmán [(2005), Acta Cryst. B61, 536-547] revealed that semirigid molecules or their patterns held together e.g. by hydrogen bonds may perform non-crystallographic rotations (through 180, 90 degrees etc.) around themselves whenever a substitution, ring enlargement or isomerization destroys the existing close packing, i.e. the novel substituent or the enlarged ring can no longer fit in the hollows formed between the molecules. In other words, the old and new arrangements of such chemically similar molecules can be converted into each other by virtual rotations. However, when a semirigid molecule without substitution, but under the influence of solvents, temperature etc., is fully or partly rearranged in the solid state, the corresponding non-crystallographic rotation (hereinafter ncr) is real and gives rise to polymorphism. Such polymorphs are hallmarked by full or partial isostructurality and show that ncrs always occur together with isostructurality. First Kitaigorodskii [(1961), Organic Chemical Crystallography, New York: Consultants Bureau] reported on the structural similarity of three tetraaryltins, (p-RC(6)H(4))(4)Sn, R = H, CH(3), CH(3)O, which is terminated by the larger C(2)H(5)O group. A revisit to these structures revealed that the tetragonal --> monoclinic conversion termed by Kitaigorodskii as a ;morphotropic step' is also performed by an ncr. Similarly, other tetraaryltins in the literature are related by ncrs or the nc translation of the semirigid tetrahedra, or they remain isostructural. Since one of the definitions of morphotropism, a word of Greek origin, is 'turn of form', the ncrs of semirigid molecules can be denoted--following Kitaigorodskii--by this word, whereas its alternative definition in the morphological crystallography of ;unidirectional changes' [applied by Groth (1870). Ber. Chem. Ges. 3, 449-457] covers the non-crystallographic translations described first in this work.

  15. Gas-phase doubly charged complexes of cyclic peptides with copper in +1, +2 and +3 formal oxidation states: formation, structures and electron capture dissociation.

    PubMed

    Afonso, Carlos; Tabet, Jean-Claude; Giorgi, Gianluca; Tureček, František

    2012-02-01

    Copper complexes with a cyclic D-His-β-Ala-L-His-L-Lys and all-L-His-β-Ala-His-Lys peptides were generated by electrospray which were doubly charged ions that had different formal oxidation states of Cu(I), Cu(II) and Cu(III) and different protonation states of the peptide ligands. Electron capture dissociation showed no substantial differences between the D-His and L-His complexes. All complexes underwent peptide cross-ring cleavages upon electron capture. The modes of ring cleavage depended on the formal oxidation state of the Cu ion and peptide protonation. Density functional theory (DFT) calculations, using the B3LYP with an effective core potential at Cu and M06-2X functionals, identified several precursor ion structures in which the Cu ion was threecoordinated to pentacoordinated by the His and Lys side-chain groups and the peptide amide or enolimine groups. The electronic structure of the formally Cu(III) complexes pointed to an effective Cu(I) oxidation state with the other charge residing in the peptide ligand. The relative energies of isomeric complexes of the [Cu(c-HAHK + H)](2+) and [Cu(c-HAHK - H)](2+) type with closed electronic shells followed similar orders when treated by the B3LYP and M06-2X functionals. Large differences between relative energies calculated by these methods were obtained for open-shell complexes of the [Cu(c-HAHK)](2+) type. Charge reduction resulted in lowering the coordination numbers for some Cu complexes that depended on the singlet or triplet spin state being formed. For [Cu(c-HAHK - H)](2+) complexes, solution H/D exchange involved only the N-H protons, resulting in the exchange of up to seven protons, as established by ultra-high mass resolution measurements. Contrasting the experiments, DFT calculations found the lowest energy structures for the gas-phase ions that were deprotonated at the peptide C(α) positions.

  16. Synthesis of cyclic N 1-pentylinosine phosphate, a new structurally reduced cADPR analogue with calcium-mobilizing activity on PC12 cells

    PubMed Central

    Borbone, Nicola; Pinto, Brunella; Secondo, Agnese; Costantino, Valeria; Tedeschi, Valentina; Piccialli, Vincenzo; Piccialli, Gennaro

    2015-01-01

    Summary Cyclic N 1-pentylinosine monophosphate (cpIMP), a novel simplified inosine derivative of cyclic ADP-ribose (cADPR) in which the N 1-pentyl chain and the monophosphate group replace the northern ribose and the pyrophosphate moieties, respectively, was synthesized. The role played by the position of the phosphate group in the key cyclization step, which consists in the formation of a phosphodiester bond, was thoroughly investigated. We have also examined the influence of the phosphate bridge on the ability of cpIMP to mobilize Ca2+ in PC12 neuronal cells in comparison with the pyrophosphate bridge present in the cyclic N 1-pentylinosine diphosphate analogue (cpIDP) previously synthesized in our laboratories. The preliminary biological tests indicated that cpIMP and cpIDP induce a rapid increase of intracellular Ca2+ concentration in PC12 neuronal cells. PMID:26877790

  17. Probe measurements of the three-dimensional magnetic field structure in a rotating magnetic field sustained field-reversed configuration

    SciTech Connect

    Velas, K. M.; Milroy, R. D.

    2014-01-15

    A translatable three-axis probe was constructed and installed on the translation, confinement, and sustainment upgrade (TCSU) experiment. With ninety windings, the probe can simultaneously measure B{sub r}, B{sub θ}, and B{sub z} at 30 radial positions, and can be placed at any desired axial position within the field reversed configuration (FRC) confinement chamber. Positioning the probe at multiple axial positions and taking multiple repeatable shots allows for a full r-z map of the magnetic field. Measurements were made for odd-parity rotating magnetic field (RMF) antennas and even-parity RMF. The steady state data from applying a 10 kHz low pass filter used in conjunction with data at the RMF frequency yields a map of the full 3D rotating field structure. Comparisons will be made to the 3D magnetic structure predicted by NIMROD simulations, with parameters adjusted to match that of the TCSU experiments. The probe provides sufficient data to utilize a Maxwell stress tensor approach to directly measure the torque applied to the FRC's electrons, which combined with a resistive torque model, yields an estimate of the average FRC resistivity.

  18. Regular rotating electrically charged structures in nonlinear electrodynamics minimally coupled to gravity

    NASA Astrophysics Data System (ADS)

    Dymnikova, Irina; Galaktionov, Evgeny

    2016-03-01

    In nonlinear electrodynamics minimally coupled to gravity, regular spherically symmetric electrically charged solutions satisfy the weak energy condition and have obligatory de Sitter center. By the Gürses-Gürsey algorithm they are transformed to regular axially symmetric solutions asymptotically Kerr-Newman for a distant observer. Rotation transforms de Sitter center into de Sitter equatorial disk embedded as a bridge into a de Sitter vacuum surface. The de Sitter surfaces satisfy p = -ρ and have properties of a perfect conductor and ideal diamagnetic. The Kerr ring singularity is replaced with the superconducting current which serves as a non-dissipative electromagnetic source of the asymptotically Kerr-Newman geometry. Violation of the weak energy condition is prevented by the basic requirement of electrodynamics of continued media.

  19. An algorithm for computing the 2D structure of fast rotating stars

    NASA Astrophysics Data System (ADS)

    Rieutord, Michel; Espinosa Lara, Francisco; Putigny, Bertrand

    2016-08-01

    Stars may be understood as self-gravitating masses of a compressible fluid whose radiative cooling is compensated by nuclear reactions or gravitational contraction. The understanding of their time evolution requires the use of detailed models that account for a complex microphysics including that of opacities, equation of state and nuclear reactions. The present stellar models are essentially one-dimensional, namely spherically symmetric. However, the interpretation of recent data like the surface abundances of elements or the distribution of internal rotation have reached the limits of validity of one-dimensional models because of their very simplified representation of large-scale fluid flows. In this article, we describe the ESTER code, which is the first code able to compute in a consistent way a two-dimensional model of a fast rotating star including its large-scale flows. Compared to classical 1D stellar evolution codes, many numerical innovations have been introduced to deal with this complex problem. First, the spectral discretization based on spherical harmonics and Chebyshev polynomials is used to represent the 2D axisymmetric fields. A nonlinear mapping maps the spheroidal star and allows a smooth spectral representation of the fields. The properties of Picard and Newton iterations for solving the nonlinear partial differential equations of the problem are discussed. It turns out that the Picard scheme is efficient on the computation of the simple polytropic stars, but Newton algorithm is unsurpassed when stellar models include complex microphysics. Finally, we discuss the numerical efficiency of our solver of Newton iterations. This linear solver combines the iterative Conjugate Gradient Squared algorithm together with an LU-factorization serving as a preconditioner of the Jacobian matrix.

  20. Angular analysis of the cyclic impacting oscillations in a robotic grinding process

    NASA Astrophysics Data System (ADS)

    Rafieian, Farzad; Girardin, François; Liu, Zhaoheng; Thomas, Marc; Hazel, Bruce

    2014-02-01

    In a robotic machining process, a light-weight cutter or grinder is usually held by an articulated robot arm. Material removal is achieved by the rotating cutting tool while the robot end effector ensures that the tool follows a programmed trajectory in order to work on complex curved surfaces or to access hard-to-reach areas. One typical application of such process is maintenance and repair work on hydropower equipment. This paper presents an experimental study of the dynamic characteristics of material removal in robotic grinding, which is unlike conventional grinding due to the lower structural stiffness of the tool-holder robot. The objective of the study is to explore the cyclic nature of this mechanical operation to provide the basis for future development of better process control strategies. Grinding tasks that minimize the number of iterations to converge to the target surface can be better planned based on a good understanding and modeling of the cyclic material removal mechanism. A single degree of freedom dynamic analysis of the process suggests that material removal is performed through high-frequency impacts that mainly last for only a small fraction of the grinding disk rotation period. To detect these discrete cutting events in practice, a grinder is equipped with a rotary encoder. The encoder's signal is acquired through the angular sampling technique. A running cyclic synchronous average is applied to the speed signal to remove its non-cyclic events. The measured instantaneous rotational frequency clearly indicates the impacting nature of the process and captures the transient response excited by these cyclic impacts. The technique also locates the angular positions of cutting impacts in revolution cycles. It is thus possible to draw conclusions about the cyclic nature of dynamic changes in impact-cutting behavior when grinding with a flexible robot. The dynamics of the impacting regime and transient responses to impact-cutting excitations

  1. Rotating plug bearing and seal

    DOEpatents

    Wade, Elman E.

    1977-01-01

    A bearing and seal structure for nuclear reactors utilizing rotating plugs above the nuclear reactor vessel. The structure permits lubrication of bearings and seals of the rotating plugs without risk of the lubricant draining into the reactor vessel below. The structure permits lubrication by utilizing a rotating outer race bearing.

  2. Random cyclic matrices.

    PubMed

    Jain, Sudhir R; Srivastava, Shashi C L

    2008-09-01

    We present a Gaussian ensemble of random cyclic matrices on the real field and study their spectral fluctuations. These cyclic matrices are shown to be pseudosymmetric with respect to generalized parity. We calculate the joint probability distribution function of eigenvalues and the spacing distributions analytically and numerically. For small spacings, the level spacing distribution exhibits either a Gaussian or a linear form. Furthermore, for the general case of two arbitrary complex eigenvalues, leaving out the spacings among real eigenvalues, and, among complex conjugate pairs, we find that the spacing distribution agrees completely with the Wigner distribution for a Poisson process on a plane. The cyclic matrices occur in a wide variety of physical situations, including disordered linear atomic chains and the Ising model in two dimensions. These exact results are also relevant to two-dimensional statistical mechanics and nu -parametrized quantum chromodynamics. PMID:18851127

  3. Block Copolymer Modified Epoxy Amine System for Reactive Rotational Molding: Structures, Properties and Processability

    NASA Astrophysics Data System (ADS)

    Lecocq, Eva; Nony, Fabien; Tcharkhtchi, Abbas; Gérard, Jean-François

    2011-05-01

    Poly(styrene-butadiene-methylmethacrylate) (SBM) and poly(methylmethacrylate-butyle-acrylate-methylmethacrylate) (MAM) triblock copolymers have been dissolved in liquid DGEBA epoxy resin which is subsequently polymerized by meta-xylene diamine (MXDA) or Jeffamine EDR-148. A chemorheology study of these formulations by plate-plate rheology and by thermal analysis has allowed to conclude that the addition of these copolymer blocks improve the reactive rotational moulding processability without affecting the processing time. Indeed, it prevents the pooling of the formulation at the bottom of the mould and a too rapid build up of resin viscosity of these thermosetting systems. The morphology of the cured blends examined by scanning electron microscopy (SEM) shows an increase of fracture surface area and thereby a potential increase of the toughness with the modification of epoxy system. Dynamic mechanical spectroscopy (DMA) and opalescence of final material show that the block PMMA, initially miscible, is likely to induce phase separation from the epoxy-amine matrix. Thereby, the poor compatibilisation between the toughener and the matrix has a detrimental effect on the tensile mechanical properties. The compatibilisation has to be increased to improve in synergy the processability and the final properties of these block copolymer modified formulations. First attempts could be by adapting the length and ratio of each block.

  4. Flow in cyclic cosmology

    SciTech Connect

    Kinney, William H.; Dizgah, Azadeh Moradinezhad

    2010-10-15

    In this paper, we use a known duality between expanding and contracting cosmologies to construct a dual of the inflationary flow hierarchy applicable to contracting cosmologies such as ekpyrotic and cyclic models. We show that the inflationary flow equations are invariant under the duality and therefore apply equally well to inflation or to cyclic cosmology. We construct a self-consistent small-parameter approximation dual to the slow-roll approximation in inflation, and calculate the power spectrum of perturbations in this limit. We also recover the matter-dominated contracting solution of Wands, and the recently proposed adiabatic ekpyrosis solution.

  5. Cyclic membrane separation process

    DOEpatents

    Nemser, Stuart M.

    2005-05-03

    A cyclic process for controlling environmental emissions of volatile organic compounds (VOC) from vapor recovery in storage and dispensing operations of liquids maintains a vacuum in the storage tank ullage. In the first part of a two-part cyclic process ullage vapor is discharged through a vapor recovery system in which VOC are stripped from vented gas with a selectively gas permeable membrane. In the second part, the membrane is inoperative while gas pressure rises in the ullage. In one aspect of this invention, a vacuum is drawn in the membrane separation unit thus reducing overall VOC emissions.

  6. Realistic Cyclic Magnetic Universe

    NASA Astrophysics Data System (ADS)

    Medeiros, L. G.

    2012-09-01

    This work presents a complete cyclic cosmological scenario based on nonlinear magnetic field. It is constructed from a model composed of five fluids, namely baryonic matter, dark matter, radiation, neutrinos and a cosmological magnetic field. The first four fluids are treated in the standard way and the fifth fluid, the magnetic field, is described by a nonlinear electrodynamics. The free parameters are fitted by observational data (SNIa, CMB, extragalactic magnetic fields, etc.) and by simple theoretical considerations. As a result arises a cyclic cosmological model that preserves the main successes of the standard Big Bang model and solves some other problems such as the initial singularity, the present acceleration and the Big Rip.

  7. Antimicrobial cyclic peptides for plant disease control.

    PubMed

    Lee, Dong Wan; Kim, Beom Seok

    2015-03-01

    Antimicrobial cyclic peptides derived from microbes bind stably with target sites, have a tolerance to hydrolysis by proteases, and a favorable degradability under field conditions, which make them an attractive proposition for use as agricultural fungicides. Antimicrobial cyclic peptides are classified according to the types of bonds within the ring structure; homodetic, heterodetic, and complex cyclic peptides, which in turn reflect diverse physicochemical features. Most antimicrobial cyclic peptides affect the integrity of the cell envelope. This is achieved through direct interaction with the cell membrane or disturbance of the cell wall and membrane component biosynthesis such as chitin, glucan, and sphingolipid. These are specific and selective targets providing reliable activity and safety for non-target organisms. Synthetic cyclic peptides produced through combinatorial chemistry offer an alternative approach to develop antimicrobials for agricultural uses. Those synthesized so far have been studied for antibacterial activity, however, the recent advancements in powerful technologies now promise to provide novel antimicrobial cyclic peptides that are yet to be discovered from natural resources.

  8. Antimicrobial Cyclic Peptides for Plant Disease Control

    PubMed Central

    Lee, Dong Wan; Kim, Beom Seok

    2015-01-01

    Antimicrobial cyclic peptides derived from microbes bind stably with target sites, have a tolerance to hydrolysis by proteases, and a favorable degradability under field conditions, which make them an attractive proposition for use as agricultural fungicides. Antimicrobial cyclic peptides are classified according to the types of bonds within the ring structure; homodetic, heterodetic, and complex cyclic peptides, which in turn reflect diverse physicochemical features. Most antimicrobial cyclic peptides affect the integrity of the cell envelope. This is achieved through direct interaction with the cell membrane or disturbance of the cell wall and membrane component biosynthesis such as chitin, glucan, and sphingolipid. These are specific and selective targets providing reliable activity and safety for non-target organisms. Synthetic cyclic peptides produced through combinatorial chemistry offer an alternative approach to develop antimicrobials for agricultural uses. Those synthesized so far have been studied for antibacterial activity, however, the recent advancements in powerful technologies now promise to provide novel antimicrobial cyclic peptides that are yet to be discovered from natural resources. PMID:25774105

  9. Structure and modeling of the three dimensional boundary layer on a rotating disk. Final report

    SciTech Connect

    Eaton, J.K.

    1996-12-01

    Almost all practical turbulent flows include three dimensional boundary layers (3DTBL`s), and in many cases, the 3DTBL is the dominant feature of the flow. A boundary layer is defined as a thin layer adjacent to the surface in which the velocity drops rapidly from the freestream value to zero at the wall. A 3D boundary layer is one in which the flow direction also changes rapidly approaching the wall. This change in the flow direction called skewing is caused by transverse pressure gradients, centrifugal forces, or motion of the surface. Most research on turbulent boundary layers has been done in simple two dimensional flows in carefully controlled wind tunnels. Such boundary layers are now well understood, and excellent models are available describing both the fluid mechanics and heat transfer behavior. Recent fluid mechanics studies have shown that skewing can have a pronounced effect on the boundary layer turbulence. Models based on eddy-viscosity concepts fail, and more complex stress transport models cannot capture the reduction of turbulent mixing that usually accompanies skewing. It was unknown prior to the present study what effect the skewing might have on turbulent heat transfer. It was suspected that turbulent heat transport would be reduced in analogy to the reductions of turbulent shear stress. It was also unknown how the skewing would effect the turbulent Prandtl number, a quantity which is embedded in most turbulent heat transfer prediction schemes. The objectives of the present study were then to study the surface heat transfer rate and the turbulent heat flux in a simple three dimensional boundary layer. In particular, the research addressed the heat transfer from a heated disk rotating in an otherwise quiescent environment.

  10. Predictors of human rotation.

    PubMed

    Stochl, Jan; Croudace, Tim

    2013-01-01

    Why some humans prefer to rotate clockwise rather than anticlockwise is not well understood. This study aims to identify the predictors of the preferred rotation direction in humans. The variables hypothesised to influence rotation preference include handedness, footedness, sex, brain hemisphere lateralisation, and the Coriolis effect (which results from geospatial location on the Earth). An online questionnaire allowed us to analyse data from 1526 respondents in 97 countries. Factor analysis showed that the direction of rotation should be studied separately for local and global movements. Handedness, footedness, and the item hypothesised to measure brain hemisphere lateralisation are predictors of rotation direction for both global and local movements. Sex is a predictor of the direction of global rotation movements but not local ones, and both sexes tend to rotate clockwise. Geospatial location does not predict the preferred direction of rotation. Our study confirms previous findings concerning the influence of handedness, footedness, and sex on human rotation; our study also provides new insight into the underlying structure of human rotation movements and excludes the Coriolis effect as a predictor of rotation.

  11. Cyclic Voltammetry Experiment.

    ERIC Educational Resources Information Center

    Van Benschoten, James J.; And Others

    1983-01-01

    Describes a three-part experiment designed to introduce cyclic voltammetry to graduate/undergraduate students. Part 1 demonstrates formal reduction potential, redox electron transfer, diffusion coefficient, and electrochemical reversibility. Part 2 investigates electrochemical behavior of acetaminophen. Part 3 examines such experimental variables…

  12. Radioimmunoassay for cyclic nucleotides

    SciTech Connect

    Chiang, C.S.

    1984-02-21

    An improved radioimmunoassay for the determination of cyclic nucleotides in body fluids which comprises adding a source of divalent cation prior to assay minimizes the effects of both endogenous calcium ion and EDTA used as an anticoagulant in blood plasma samples.

  13. Detection and correction of underassigned rotational symmetry prior to structure deposition

    SciTech Connect

    Poon, Billy K.; Grosse-Kunstleve, Ralf W.; Zwart, Peter H.; Sauter, Nicholas K.

    2010-05-01

    An X-ray structural model can be reassigned to a higher symmetry space group using the presented framework if its noncrystallographic symmetry operators are close to being exact crystallographic relationships. About 2% of structures in the Protein Data Bank can be reclassified in this way. Up to 2% of X-ray structures in the Protein Data Bank (PDB) potentially fit into a higher symmetry space group. Redundant protein chains in these structures can be made compatible with exact crystallographic symmetry with minimal atomic movements that are smaller than the expected range of coordinate uncertainty. The incidence of problem cases is somewhat difficult to define precisely, as there is no clear line between underassigned symmetry, in which the subunit differences are unsupported by the data, and pseudosymmetry, in which the subunit differences rest on small but significant intensity differences in the diffraction pattern. To help catch symmetry-assignment problems in the future, it is useful to add a validation step that operates on the refined coordinates just prior to structure deposition. If redundant symmetry-related chains can be removed at this stage, the resulting model (in a higher symmetry space group) can readily serve as an isomorphous replacement starting point for re-refinement using re-indexed and re-integrated raw data. These ideas are implemented in new software tools available at http://cci.lbl.gov/labelit.

  14. Semiclassical shell-structure moment of inertia for equilibrium rotation of a simple Fermi system

    SciTech Connect

    Magner, A. G.; Sitdikov, A. S. Khamzin, A. A.; Bartel, J.

    2010-08-15

    Semiclassical shell-structure components of the collectivemoment of inertia are derived within the mean-field cranking model in the adiabatic approximation in terms of the free-energy shell corrections through those of a rigid body for the statistically equilibriumrotation of a Fermi system at finite temperature by using the nonperturbative extended Gutzwiller periodic-orbit theory. Their analytical structure in terms of the equatorial and 3-dimensional periodic orbits for the axially symmetric harmonic oscillator potential is in perfect agreement with the quantum results for different critical bifurcation deformations and different temperatures.

  15. Cooperative-Motion-Induced Structural Evolution in Dusty-Plasma Liquids with Microheterogeneity: Rupture, Rotation, Healing, and Growth of Ordered Domains

    NASA Astrophysics Data System (ADS)

    Yang, Chi; Io, Chong-Wai; I, Lin

    2012-11-01

    The cooperative motion induced structural evolution of the liquid with microheterogeneity is investigated in quasi-2D dusty plasma liquids, through direct optical visualization. A novel bond-dynamics analysis is used to further classify the robust cooperative 2D clusters into static, rotating, and drifting patches, beyond the earlier findings of the cooperative hopping strings and bands. The relative motion between two adjacent clusters causes the formation of a fractal network with narrow shear strips along the cluster interface. The rotation of the large ordered patch through rupturing into multiple rotating patches followed by the healing process, and the growth to a larger ordered patch by aligning the different lattice orientations of the adjacent ordered domains through patch rupturing, rotation, drifting, and merging are the key processes for the microstructural evolution.

  16. Titan’s internal structure inferred from its gravity field, shape, and rotation state

    NASA Astrophysics Data System (ADS)

    Baland, Rose-Marie; Tobie, Gabriel; Lefèvre, Axel; Van Hoolst, Tim

    2014-07-01

    Several quantities measured by the Cassini-Huygens mission provide insight into the interior of Titan: the second-degree gravity field coefficients, the shape, the tidal Love number, the electric field, and the orientation of its rotation axis. The measured obliquity and tides, as well as the electric field, are evidence for the presence of an internal global ocean beneath the icy shell of Titan. Here we use these different observations together to constrain the density profile assuming a four-layer interior model (ice I shell, liquid water ocean, high pressure ice mantle, and rock core). Even though the observed second degree gravity field is consistent with the hydrostatic relation J2=10C22/3, which is a necessary but not sufficient condition for a synchronous satellite to be in hydrostatic equilibrium, the observed shape of the surface as well as the non-zero degree-three gravity signal indicate some departure from hydrostaticity. Therefore, we do not restrain our range of assumed density profiles to those corresponding to the hydrostatic value of the moment of inertia (0.34). From a range of density profiles consistent with the radius and mass of the satellite, we compute the obliquity of the Cassini state and the tidal Love number k2. The obliquity is computed from a Cassini state model for a satellite with an internal liquid layer, each layer having an ellipsoidal shape consistent with the measured surface shape and gravity field. The observed (nearly hydrostatic) gravity field is obtained by an additional deflection of the ocean-ice I shell interface, assuming that the layers have uniform densities. We show that the measured obliquity can be reproduced only for internal models with a dense ocean (between 1275 and 1350 kg m-3) above a differentiated interior with a full separation of rock and ice. We obtain normalized moments of inertia between 0.31 and 0.33, significantly lower than the expected hydrostatic value (0.34). Evolutionary mechanisms leading to a

  17. Salen complexes of zirconium and hafnium: synthesis, structural characterization, controlled hydrolysis, and solvent-free ring-opening polymerization of cyclic esters and lactides.

    PubMed

    Saha, Tanmoy Kumar; Ramkumar, Venkatachalam; Chakraborty, Debashis

    2011-04-01

    Dinuclear salen compounds of zirconium and hafnium are efficient initiators for the solvent-free ring-opening polymerization of cyclic ester monomers and lactides. There is a correlation between the theoretical and experimental number-average molecular weights (M(n)'s) in these polymerizations. Polymerization of β-butyrolactone gives poly(3-hydroxybutyrate) with a good M(n) and molecular weight distribution.

  18. One common structural peculiarity of the Solar system bodies including the star, planets, satellites and resulting from their globes rotation

    NASA Astrophysics Data System (ADS)

    Kochemasov, , G. G.

    2008-09-01

    Often observed a sensible difference in appearance and structure between tropical and extra-tropical zones of various heavenly bodies including rocky and gas planets, satellites and Sun compels to look for a common reason of such phenomenon. All bodies rotate and their spherical shape makes zones at different latitudes to have differing angular momenta as a distance to the rotation axis diminishes gradually from the equator to the poles (this is felt particularly when one launches rockets into space -preferable more cheap launches are from the equatorial regions - Kourou is better than Baikonur). One of remarkable changes occurs at tropics. As a single rotating planetary body tends to have angular momenta of its tectonic blocks equilibrated it starts mechanisms leveling this basic physical property. At tropical zones (bulged also due to the rotation ellipsoid) the outer shell - crust as a consequence tends to be destroyed, sunk, subsided and shrunk; a density of crust material changes; the atmosphere reacts changing chemistry and structure; in terrestrial anthroposphere man looses its mass and stature. But according to the Le Chatelier rule mechanisms with an opposing tendency also begin to act. At Earth the wide planetary long tropical zone is marked by destruction of the crust. It is demonstrated by development of numerous islands of the Malay Archipelago (the Sunda Isls., Maluku Isls, Philippines) between the Southeastern Asia and Australia. In Africa and South America huge depressions of the Congo and Amazon Rivers develops where the Archean crust is subsided to depths of more than 2 km. In the Pacific along the equator numerous islands of Micronesia occur. Subsidence of the basaltic oceanic crust is followed by an intensive folding and faulting of basalt and sedimentary layers (Fig. 1) as a larger mass must be held by a smaller space (a planetary radius is diminished). The central Atlantic is very demonstrative in this sense suffering huge transform fault

  19. Response of soil microbial biomass and community structures to conventional and organic farming systems under identical crop rotations.

    PubMed

    Esperschütz, Jürgen; Gattinger, Andreas; Mäder, Paul; Schloter, Michael; Fliessbach, Andreas

    2007-07-01

    In this study the influence of different farming systems on microbial community structure was analyzed using soil samples from the DOK long-term field experiment in Switzerland, which comprises organic (BIODYN and BIOORG) and conventional (CONFYM and CONMIN) farming systems as well as an unfertilized control (NOFERT). We examined microbial communities in winter wheat plots at two different points in the crop rotation (after potatoes and after maize). Employing extended polar lipid analysis up to 244 different phospholipid fatty acids (PLFA) and phospholipid ether lipids (PLEL) were detected. Higher concentrations of PLFA and PLEL in BIODYN and BIOORG indicated a significant influence of organic agriculture on microbial biomass. Farmyard manure (FYM) application consistently revealed the strongest, and the preceding crop the weakest, influence on domain-specific biomass, diversity indices and microbial community structures. Esterlinked PLFA from slowly growing bacteria (k-strategists) showed the strongest responses to long-term organic fertilization. Although the highest fungal biomass was found in the two organic systems of the DOK field trial, their contribution to the differentiation of community structures according to the management regime was relatively low. Prokaryotic communities responded most strongly to either conventional or organic farming management.

  20. [THE MODEL OF NUCLEOSOME STRUCTURE BASED ON THE LOCAL ROTATION OF THE NUCLEOHISTONE CHAIN, WHICH INDUCES ITS FOLDING].

    PubMed

    Priyatkina, T N

    2015-01-01

    An alternative model to the "double turn of DNA on the histone core" approach is forwarded based on the biochemical, cytological, and crystallographic data on the structural organization of the chromatin units--nucleosomes. The model assumes that the initial structure is a linear nucleohistone cord with a repeating symmetrical histone sequence. The compact (core) particle (a minimal nucleosome) is forming upon a stepwise rotation of DNA (kinks) at the centre and at two symmetrical sites into each repeating fragment stemming from the electrostatic binding of the lysine ε-NH2-groups with the followed one by one phosphates of the sugar-phosphate chain. As a result, we have a rhomboid structure composed of two counter-symmetrical DNA folds stabilized by histone-histone interactions. Based on disposable data, the histone sequence along nucleosome DNA is deduced. The following characteristics of the sequence are considered: continuity, non-overlapping, versatility, and dyadic symmetry in dispose of two every kind histone molecules and the sequence on the whole. The model is in agreement with a topology of nucleosome DNA, as well as the pattern of DNA-histone and histone-histone interactions in chromatin.

  1. [THE MODEL OF NUCLEOSOME STRUCTURE BASED ON THE LOCAL ROTATION OF THE NUCLEOHISTONE CHAIN, WHICH INDUCES ITS FOLDING].

    PubMed

    Priyatkina, T N

    2015-01-01

    An alternative model to the "double turn of DNA on the histone core" approach is forwarded based on the biochemical, cytological, and crystallographic data on the structural organization of the chromatin units--nucleosomes. The model assumes that the initial structure is a linear nucleohistone cord with a repeating symmetrical histone sequence. The compact (core) particle (a minimal nucleosome) is forming upon a stepwise rotation of DNA (kinks) at the centre and at two symmetrical sites into each repeating fragment stemming from the electrostatic binding of the lysine ε-NH2-groups with the followed one by one phosphates of the sugar-phosphate chain. As a result, we have a rhomboid structure composed of two counter-symmetrical DNA folds stabilized by histone-histone interactions. Based on disposable data, the histone sequence along nucleosome DNA is deduced. The following characteristics of the sequence are considered: continuity, non-overlapping, versatility, and dyadic symmetry in dispose of two every kind histone molecules and the sequence on the whole. The model is in agreement with a topology of nucleosome DNA, as well as the pattern of DNA-histone and histone-histone interactions in chromatin. PMID:26495705

  2. A structural basis for the regulation of an H-NOX-associated cyclic-di-GMP synthase/phosphodiesterase enzyme by nitric oxide-bound H-NOX.

    PubMed

    Lahiri, Tanaya; Luan, Bowu; Raleigh, Daniel P; Boon, Elizabeth M

    2014-04-01

    Biofilms are surface-attached communities of bacteria enclosed in a polysaccharide matrix. Bacteria in a biofilm are extremely resistant to antibiotics. Several recent reports have linked the signaling molecule nitric oxide (NO) with biofilm dispersal. We have previously reported that an H-NOX (heme-nitric oxide/oxygen binding) protein in the biofilm-dwelling bacterium Shewanella woodyi mediates NO-induced biofilm dispersal. In S. woodyi, H-NOX (SwH-NOX) is cocistronic with a gene encoding a dual-functioning diguanylate cyclase/phosphodiesterase enzyme, designated here as HaCE (H-NOX-associated cyclic-di-GMP processing enzyme). Enzymes such as these are responsible for regulating the intracellular concentrations of cyclic-di-GMP, a secondary signaling molecule essential to biofilm formation in bacteria. We have demonstrated that NO-bound SwH-NOX regulates both enzymatic activities of SwHaCE, resulting in decreased cellular cyclic-di-GMP levels and disruption of biofilm formation. Thus, H-NOX/HaCE represents a potential drug target for regulating biofilm formation. In this work, the SwH-NOX surface residues critical for the formation of a protein complex with SwHaCE are identified using nuclear magnetic resonance, fluorescence quenching, and cosedimentation. Enzyme assays confirm this protein-protein interface and its importance for H-NOX/HaCE function.

  3. Effect of cyclic tensile load on the regulation of the expression of matrix metalloproteases (MMPs -1, -3) and structural components in synovial cells.

    PubMed

    Raïf, El Mostafa

    2008-12-01

    Synovial cells are reported to colonize synthetic ligament scaffolds following anterior cruciate ligament (ACL) reconstruction but the process leading to ligamentization is poorly understood. The present study investigated the effect of cyclic tensile strain on the expression of genes involved in matrix remodelling in bovine synovial cells seeded onto an artificial ligament scaffold. Synovial cells were seeded and cultured on polyester scaffolds for 3 weeks and subsequently subjected to cyclic tensile strain of 4.5% for 1 hr at frequency of 1 Hz. Changes in the levels of expression of genes for major ligament components (type I and type III collagen) and also metalloproteinases (MMP-1 and MMP-3), and TIMP-1 were examined using RT-PCR. Additionally, metalloproteinase activity was measured using both zymography and collagenase assays. The gene expression of MMP-3 transcripts in the loaded group was almost 3-fold that observed in control group but no differences were observed in other transcripts. Consistent with these findings, MMP-3 activity increased by 85% under mechanical stimulus, and MMP-1 activity showed no changes. Over expression of MMP-3 under cyclic tensile load may mediate the proteolysis of certain substrates surrounding the ligament scaffold. This will play a critical role in facilitating cell migration, proliferation and tissue remodelling by breaking down the provisional tissue formed by the synovium, and by generating factors that induce angiogenesis and chemotactic cell migration.

  4. Modeling rapidly rotating stars

    NASA Astrophysics Data System (ADS)

    Rieutord, M.

    2006-06-01

    We review the quest of modeling rapidly rotating stars during the past 40 years and detail the challenges to be taken up by models facing new data from interferometry, seismology, spectroscopy... We then present the progress of the ESTER project aimed at giving a physically self-consistent model for the structure and evolution of rapidly rotating stars.

  5. The role of peel stresses in cyclic debonding

    NASA Technical Reports Server (NTRS)

    Everett, R. A., Jr.

    1982-01-01

    When an adhesively bonded joint is undergoing cyclic loading, one of the possible damage modes that occurs is called cyclic debonding - progressive separation of the adherends by failure of the adhesive bond under cyclic loading. In most practical structures, both peel and shear stresses exist in the adhesive bonding during cyclic loading. The results of an experimental and analytical study to determine the role of peel stresses on cyclic debonding in a mixed mode specimen are presented. Experimentally, this was done by controlling the forces that create the peel stresses by applying a clamping force to oppose the peel stresses. Cracked lap shear joints were chosen for this study. A finite element analysis was developed to assess the effect of the clamping force on the strain energy release rates due to shear and peel stresses. The results imply that the peel stress is the principal stress causing cyclic debonding.

  6. Rotating Vesta

    NASA Video Gallery

    Astronomers combined 146 exposures taken by NASA's Hubble SpaceTelescope to make this 73-frame movie of the asteroid Vesta's rotation.Vesta completes a rotation every 5.34 hours.› Asteroid and...

  7. Rotational moulding.

    PubMed

    Crawford, R J; Kearns, M P

    2003-10-01

    Rotational moulding promises designers attractive economics and a low-pressure process. The benefits of rotational moulding are compared here with other manufacturing methods such as injection and blow moulding. PMID:14603714

  8. Multi-source energy harvester to power sensing hardware on rotating structures

    SciTech Connect

    Schlichting, Alezander D; Ouellette, Scott; Carlson, Clinton P; Farinholt, Kevin M; Park, Gyuhae; Farrar, Charles

    2010-01-01

    The U.S. Department of Energy (DOE) proposes to meet 20% of the nation's energy needs through wind power by the year 2030. To accomplish this goal, the industry will need to produce larger (> 100m diameter) turbines to increase efficiency and maximize energy production. It will be imperative to instrument the large composite structures with onboard sensing to provide structural health monitoring capabilities to understand the global response and integrity of these systems as they age. A critical component in the deployment of such a system will be a robust power source that can operate for the lifespan of the wind turbine. In this paper we consider the use of discrete, localized power sources that derive energy from the ambient (solar, thermal) or operational (kinetic) environment. This approach will rely on a multi-source configuration that scavenges energy from photovoltaic and piezoelectric transducers. Each harvester is first characterized individually in the laboratory and then they are combined through a multi-source power conditioner that is designed to combine the output of each harvester in series to power a small wireless sensor node that has active-sensing capabilities. The advantages/disadvantages of each approach are discussed, along with the proposed design for a field ready energy harvester that will be deployed on a small-scale 19.8m diameter wind turbine.

  9. Spectroscopic study on deuterated benzenes. II. High-resolution laser spectroscopy and rotational structure in the S{sub 1} state

    SciTech Connect

    Kunishige, Sachi; Katori, Toshiharu; Baba, Masaaki; Hayashi, Masato; Hasegawa, Hirokazu; Ohshima, Yasuhiro

    2015-12-28

    High-resolution spectra of the S{sub 1}←S{sub 0} transition in jet-cooled deuterated benzenes were observed using pulse dye amplification of single-mode laser light and mass-selective resonance enhanced multiphoton ionization (REMPI) detection. The vibrational and rotational structures were accurately analyzed for the vibronic levels in the S{sub 1} state. The degenerate 6{sup 1} levels of C{sub 6}H{sub 6} or C{sub 6}D{sub 6} are split into 6a{sup 1} and 6b{sup 1} in many of deuterated benzenes. The rigid-rotor rotational constants were assessed and found to be slightly different between 6a and 6b because of different mean molecular structures. Their rotational levels are significantly shifted by Coriolis interactions. It was found that the Coriolis parameter proportionally changed with the number of substituted D atoms.

  10. Interpretation of tandem mass spectra obtained from cyclic nonribosomal peptides.

    PubMed

    Liu, Wei-Ting; Ng, Julio; Meluzzi, Dario; Bandeira, Nuno; Gutierrez, Marcelino; Simmons, Thomas L; Schultz, Andrew W; Linington, Roger G; Moore, Bradley S; Gerwick, William H; Pevzner, Pavel A; Dorrestein, Pieter C

    2009-06-01

    Natural and non-natural cyclic peptides are a crucial component in drug discovery programs because of their considerable pharmaceutical properties. Cyclosporin, microcystins, and nodularins are all notable pharmacologically important cyclic peptides. Because these biologically active peptides are often biosynthesized nonribosomally, they often contain nonstandard amino acids, thus increasing the complexity of the resulting tandem mass spectrometry data. In addition, because of the cyclic nature, the fragmentation patterns of many of these peptides showed much higher complexity when compared to related counterparts. Therefore, at the present time it is still difficult to annotate cyclic peptides MS/MS spectra. In this current work, an annotation program was developed for the annotation and characterization of tandem mass spectra obtained from cyclic peptides. This program, which we call MS-CPA is available as a web tool (http://lol.ucsd.edu/ms-cpa_v1/Input.py). Using this program, we have successfully annotated the sequence of representative cyclic peptides, such as seglitide, tyrothricin, desmethoxymajusculamide C, dudawalamide A, and cyclomarins, in a rapid manner and also were able to provide the first-pass structure evidence of a newly discovered natural product based on predicted sequence. This compound is not available in sufficient quantities for structural elucidation by other means such as NMR. In addition to the development of this cyclic annotation program, it was observed that some cyclic peptides fragmented in unexpected ways resulting in the scrambling of sequences. In summary, MS-CPA not only provides a platform for rapid confirmation and annotation of tandem mass spectrometry data obtained with cyclic peptides but also enables quantitative analysis of the ion intensities. This program facilitates cyclic peptide analysis, sequencing, and also acts as a useful tool to investigate the uncommon fragmentation phenomena of cyclic peptides and aids the

  11. Investigation of the gas-phase structure and rotational barrier of trimethylsilyl trifluoromethanesulfonate and comparison with covalent sulfonates

    NASA Astrophysics Data System (ADS)

    Defonsi Lestard, María E.; Tuttolomondo, María E.; Varetti, Eduardo L.; Wann, Derek A.; Robertson, Heather E.; Rankin, David W. H.; Altabef, Aida Ben

    2010-12-01

    The molecular structure of trimethylsilyl trifluoromethanesulfonate, CF 3SO 2OSi(CH 3) 3, has been determined in the gas phase from electron-diffraction data supplemented by ab initio (MP2) and DFT calculations using 6-31G(d), 6-311++G(d,p) and 6-311G++(3df,3pd) basis sets. Both experimental and theoretical data indicate that only one gauche conformer is possible by rotating about the O-S bond. The anomeric effect is a fundamental stereoelectronic interaction and presents a profound influence on the electronic geometry. We have investigated the origin of the anomeric effect by means of NBO and AIM analysis. A natural bond orbital analysis showed that the lpπ[O bonded to Si)] → σ *[C-S] hyperconjugative interaction favors the gauche conformation. In addition, comparison of the structural and stereoelectronic properties of the title molecule with those of silyl trifluoromethanesulfonate and methyl trifluoromethanesulfonate has been carried out.

  12. Scale invariant density perturbations from cyclic cosmology

    NASA Astrophysics Data System (ADS)

    Frampton, Paul Howard

    2016-04-01

    It is shown how quantum fluctuations of the radiation during the contraction era of a comes back empty (CBE) cyclic cosmology can provide density fluctuations which re-enter the horizon during the subsequent expansion era and at lowest order are scale invariant, in a Harrison-Zel’dovich-Peebles sense. It is necessary to be consistent with observations of large scale structure.

  13. Simulation of self-organization processes in crystal-forming systems: Supramolecular cyclic R6 cluster precursors and self-assembly of TeO2- TEL ( Tellurite) and TeO2- PAR ( Paratellurite) structures

    NASA Astrophysics Data System (ADS)

    Ilyushin, G. D.

    2014-11-01

    The supramolecular chemistry of oxides of sp elements (SO2, SeO2, and TeO2) is considered. The self-assembly of TeO2- TEL ( Tellurite) and TeO2- PAR ( Paratellurite) crystal structures is simulated. Methods of combinatorial and topological analysis (TOPOS program package) are applied which are based on constructing a basis 3D network of the structure in the form of a graph, the sites of which correspond to the positions of centroids of TeO2 molecules and the edges characterize bonds between them. The topological type of the basis 2D network in the TeO2- TEL structure corresponds to graphite (C- GRA), while in the TeO2- PAR structure the basis network corresponds to the 3D diamond network (C- DIA). A nanocluster precursor of cyclic type ( R6) composed of six covalently bound TeO2 molecules (chair conformation) is established for both structures. The desymmetrization of the cyclic structure of the R6 cluster in TeO2- PAR is related to the formation of Te-Te bonds with lengths of 3.824 and 4.062 Å. The symmetry and topology code of the processes of self-assembly of 3D structures from nanocluster precursors is completely reconstructed into the form "primary chain → microlayer → microframework." In both structures R6 clusters form 2D packings with a coordination number of 6. The cluster self-assembly model explains the specific features of the morphogenesis of TeO2- TEL and TeO2- PAR (phases with low and high crystallization temperatures, respectively): platelike shape, perfect cleavage in the (110) plane, and preferred growth in the primar-chain direction [100] in the former case and growth in the direction of the primary [001] axis with the preferred formation of tetragonal prism faces (110) in the latter case.

  14. Future Mars geophysical observatories for understanding its internal structure, rotation, and evolution

    NASA Astrophysics Data System (ADS)

    Dehant, Veronique; Banerdt, Bruce; Lognonné, Philippe; Grott, Matthias; Asmar, Sami; Biele, Jens; Breuer, Doris; Forget, François; Jaumann, Ralf; Johnson, Catherine; Knapmeyer, Martin; Langlais, Benoit; Le Feuvre, Mathieu; Mimoun, David; Mocquet, Antoine; Read, Peter; Rivoldini, Attilio; Romberg, Oliver; Schubert, Gerald; Smrekar, Sue; Spohn, Tilman; Tortora, Paolo; Ulamec, Stephan; Vennerstrøm, Susanne

    2012-08-01

    Our fundamental understanding of the interior of the Earth comes from seismology, geodesy, geochemistry, geomagnetism, geothermal studies, and petrology. For the Earth, measurements in those disciplines of geophysics have revealed the basic internal layering of the Earth, its dynamical regime, its thermal structure, its gross compositional stratification, as well as significant lateral variations in these quantities. Planetary interiors not only record evidence of conditions of planetary accretion and differentiation, they exert significant control on surface environments. We present recent advances in possible in-situ investigations of the interior of Mars, experiments and strategies that can provide unique and critical information about the fundamental processes of terrestrial planet formation and evolution. Such investigations applied on Mars have been ranked as a high priority in virtually every set of European, US and international high-level planetary science recommendations for the past 30 years. New seismological methods and approaches based on the cross-correlation of seismic noise by two seismic stations/landers on the surface of Mars and on joint seismic/orbiter detection of meteorite impacts, as well as the improvement of the performance of Very Broad-Band (VBB) seismometers have made it possible to secure a rich scientific return with only two simultaneously recording stations. In parallel, use of interferometric methods based on two Earth-Mars radio links simultaneously from landers tracked from Earth has increased the precision of radio science experiments by one order of magnitude. Magnetometer and heat flow measurements will complement seismic and geodetic data in order to obtain the best information on the interior of Mars. In addition to studying the present structure and dynamics of Mars, these measurements will provide important constraints for the astrobiology of Mars by helping to understand why Mars failed to sustain a magnetic field, by

  15. Hall effects on the steady structure of the rotational layer at the dayside magnetopause

    SciTech Connect

    Westerberg, Lars G.; Aakerstedt, Hans O.

    2007-10-15

    The influence of the Hall term in the generalized Ohm's law on the large-scale plasma flow during conditions of ongoing magnetic reconnection at the dayside magnetopause (MP) is investigated. Of special interest is the plasma flow behavior during the transition of the MP transition layer as the Hall effect grows in proportion to the viscous-resistive effects. The governing equations are solved approximately by an ordinary perturbation expansion in orders of large Reynolds and Lundqvist numbers. It is shown that the flow pattern is strongly dependent on the magnitude of the Hall parameter; as it approaches zero, the viscous-resistive solution is obtained, while for an ordering of the same magnitude as the resistivity/viscosity, the Hall effect begins to affect the flow structure severely. For an increasing value on the Hall parameter, oscillations are brought into the system, an effect that is enhanced with the magnitude of the Hall parameter. Furthermore, it is shown that as the Hall effect begins to dominate, the transition layer thickens.

  16. A Three-dimensional Non-spherical Calculation Of The Rotationally Distorted Shape And Internal Structure Of A Model Of Jupiter With A Polytropic Index Of Unity

    NASA Astrophysics Data System (ADS)

    Zhang, Keke; Kong, D.; Schubert, G.; Anderson, J.

    2012-10-01

    An accurate calculation of the rotationally distorted shape and internal structure of Jupiter is required to understand the high-precision gravitational field that will be measured by the Juno spacecraft now on its way to Jupiter. We present a three-dimensional non-spherical numerical calculation of the shape and internal structure of a model of Jupiter with a polytropic index of unity. The calculation is based on a finite element method and accounts for the full effects of rotation. After validating the numerical approach against the asymptotic solution of Chandrasekhar (1933) that is valid only for a slowly rotating gaseous planet, we apply it to a model of Jupiter whose rapid rotation causes a significant departure from spherical geometry. The two-dimensional distribution of the density and the pressure within Jupiter is then determined via a hybrid inverse approach by matching the a priori unknown coefficient in the equation of state to the observed shape of Jupiter. After obtaining the two-dimensional distribution of Jupiter's density, we then compute the zonal gravity coefficients and the total mass from the non-spherical Jupiter model that takes full account of rotation-induced shape changes. Our non-spherical model with a polytrope of unit index is able to produce the known mass and zonal gravitational coefficients of Jupiter. Chandrasekhar, S. 1933, The equilibrium of distorted polytropes, MNRAS 93, 390

  17. Analysis of the Rotational Structure in the High-Resolution Infrared Spectrum of trans-Hexatriene-1-13C1; a Semiexperimental Equilibrium Structure for the C6 Backbone for trans-Hexatriene

    SciTech Connect

    Craig, Norman C.; Tian, Hengfeng; Blake, Thomas A.

    2012-03-29

    trans-Hexatriene-1-13C1 (tHTE-1-13C1) has been synthesized, and its high-resolution (0.0015 cm-1) infrared spectrum has been recorded. The rotational structure in the C-type bands for v26 at 1011 cm-1 and v30 at 894 cm-1 has been analyzed. To the 1458 ground state combination differences from these bands, ground state rotational constants were fitted to a Watson-type Hamiltonian to give A0 = 0.8728202(9), B0 = 0.0435868(4), and C0 = 0.0415314(2) cm-1. Upper state rotational constants for the v30 band were also fitted. Predictions of the ground state rotational constants for t-HTE-1-13C1 from a B3LYP/cc-pVTZ model with scale factors based on the normal species were in excellent agreement with observations. Similar good agreement was found between predicted and observed ground state rotational constants for the three 13C1 isotopologues of cis-hexatriene (cHTE), as determined from microwave spectroscopy. Equilibrium rotational constants for tHTE and its three 13C1 isotopologues, of which two were predicted, were used to find a semiexperimental equilibrium structure for the C6 backbone of tHTE. This structure shows increased structural effects of pi-electron delocalization in comparison with butadiene.

  18. Genetic and Environmental Influences on the Verbal-Perceptual-Image Rotation (VPR) Model of the Structure of Mental Abilities in the Minnesota Study of Twins Reared Apart

    ERIC Educational Resources Information Center

    Johnson, Wendy; Bouchard, Thomas J.; McGue, Matt; Segal, Nancy L.; Tellegen, Auke; Keyes, Margaret; Gottesman, Irving I.

    2007-01-01

    In previous papers [Johnson, W., & Bouchard Jr., T. J. (2005a). Constructive Replication of the Visual-Perceptual-Image Rotation (VPR) Model in Thurstone's (1941) Battery of 60 Tests of Mental Ability. Intelligence, 33, 417-430.] [Johnson, W., & Bouchard Jr., T. J. (2005b). The Structure of Human Intelligence: It's Verbal, perceptual, and image…

  19. Rotating mobile launcher

    NASA Technical Reports Server (NTRS)

    Gregory, T. J.

    1977-01-01

    Apparatus holds remotely piloted arm that accelerates until launching speed is reached. Then vehicle and counterweight at other end of arm are released simultaneously to avoid structural damage from unbalanced rotating forces.

  20. Rotational Spectroscopy of CF_2ClCCl_3 and Analysis of Hyperfine Structure from Four Quadrupolar Nuclei

    NASA Astrophysics Data System (ADS)

    Kisiel, Zbigniew; Bialkowska-Jaworska, Ewa; Uriarte, Iciar; Basterretxea, Francisco J.; Cocinero, Emilio J.

    2016-06-01

    CF_2ClCCl_3 has recently been identified among several new ozone- depleting substances in the atmosphere. There are no literature reports concerning rotational spectroscopy of this molecule, although we were recently able to report its first chirped pulse, supersonic expansion spectrum. CF_2ClCCl_3 has a rather small dipole moment so that the spectrum is weak and each transition displays very complex nuclear quadrupole hyperfine structure resulting from the presence of four chlorine nuclei. We have presently been able to carry out a complete analysis of the hyperfine structure by combining the information from chirped pulse spectra with dedicated higher resolution measurements made with a cavity supersonic expansion instrument. The hyperfine analysis was carried out with Pickett's SPFIT/SPCAT package and the sizes of Hamiltonian matrices are sufficiently large to require the use of 64-bit compilation of these programs (made available for both Windows and Linux systems on the PROSPE website). The resulting fit is to within experimental accuracy and is supported by ab initio calculations. The precise values of off-diagonal hyperfine constants for all nuclei lead to useful angular information that is complementary to direct structural information from moments of inertia. J.C.Laube, M.J.Newland, C.Hogan, et al., Nature Geoscience 7, 266 (2014). Z.Kisiel, E.Białkowska-Jaworska, L.Pszczółkowski, I.Uriarte, P.Ejica, F.J.Basterretxea, E.J.Cocinero, 70th ISMS, Champaign-Urbana, Illinois, RF-11 (2015). Z.Kisiel, E.Białkowska-Jaworska, L.Pszczółkowski, J.Chem.Phys. 109, 10263 (1998).

  1. Rotational testing.

    PubMed

    Furman, J M

    2016-01-01

    The natural stimulus for the semicircular canals is rotation of the head, which also might stimulate the otolith organs. Vestibular stimulation usually induces eye movements via the vestibulo-ocular reflex (VOR). The orientation of the subject with respect to the axis of rotation and the orientation of the axis of rotation with respect to gravity together determine which labyrinthine receptors are stimulated for particular motion trajectories. Rotational testing usually includes the measurement of eye movements via a video system but might use a subject's perception of motion. The most common types of rotational testing are whole-body computer-controlled sinusoidal or trapezoidal stimuli during earth-vertical axis rotation (EVAR), which stimulates primarily the horizontal semicircular canals bilaterally. Recently, manual impulsive rotations, known as head impulse testing (HIT), have been developed to assess individual horizontal semicircular canals. Most types of rotational stimuli are not used routinely in the clinical setting but may be used in selected research environments. This chapter will discuss clinically relevant rotational stimuli and several types of rotational testing that are used primarily in research settings. PMID:27638070

  2. [Correlation of fine structures of distributions of amplitudes of a photomultiplier dark current fluctuations with the Earth rotations about its axis].

    PubMed

    Fedorov, M V; Belousov, L V; Voeĭkov, V L; Zenchenko, K I; Zenchenko, T A; Konradov, A A; Shnol', S E

    2001-01-01

    The fine structures of distributions of photomultiplier dark current fluctuations measured in two laboratories 2000 km distant from other: in the international Institute of Biophysics (Neuss, Germany) and in the Moscow State University (Moscow, Russia) were compared. It is shown that similar forms of appropriate histograms are apparently more often realized at both locations at the same local time. This confirms the previous conclusion that the fine structure of distributions correlates with rotation of the Earth about its axis.

  3. A novel and robust rotation and scale invariant structuring elements based descriptor for pedestrian classification in infrared images

    NASA Astrophysics Data System (ADS)

    Soundrapandiyan, Rajkumar; Chandra Mouli, P. V. S. S. R.

    2016-09-01

    In this paper, a novel and robust rotation and scale invariant structuring elements based descriptor (RSSED) for pedestrian classification in infrared (IR) images is proposed. In addition, a segmentation method using difference of Gaussian (DoG) and horizontal intensity projection is proposed. The three major steps are moving object segmentation, feature extraction and classification of objects as pedestrian or non-pedestrian. The segmentation result is used to extract the RSSED feature descriptor. To extract features, the segmentation result is encoded using local directional pattern (LDP). This helps in the identification of local textural patterns. The LDP encoded image is further quantized adaptively to four levels. Finally the proposed RSSED is used to formalize the descriptor from the quantized image. Support vector machine is employed for classification of the moving objects in a given IR image into pedestrian and non-pedestrian classes. The segmentation results shows the robustness in extracting the moving objects. The classification results obtained from SVM classifier shows the efficacy of the proposed method.

  4. [Symmetry types, systems and multiplicity of the structure of adenovirus capsid. II. Rotational facet-groups of five-, three- and two-fold symmetry axes].

    PubMed

    Nász, István; Adám, Eva

    2006-01-01

    horizontally in the middle along the 6 geodetic ribbon like motifs a regular decagonal intersection forms and the capsid can be cut into two equal parts, in which the polypeptides show a 72 degree rotation from each other, but with a proper rotation the polypeptides get into a congruent position, which means 300 or 600 specific facet combinations. The capsid similar to the icosahedron has also 15 virtual mirror planes which divide the capsid into two, identically arranged halves, forming six right angle triangles on each facet, altogether 120 smaller rectangular so-called Mobius-triangles on the surface. In the three-fold symmetry axis of the facets, these triangles in two separate groups of three can be rotated symmetrically with 120 degrees according to the orientation of the polypeptide subunits in a way that the hexon and other polypeptides too nearly cover each other. Consequently, the adenovirus capsid is a symmetrically arranged body in which several various symmetry types and symmetry systems can be found and their structural symmetry elements exist simultaneously and covering each other. The icosahedral symmetry types and systems are valid and functional simultaneously and in parallel with great multiplicity, but the existence of more than 1500 elements in several depth levels, their order of location and distribution make the symmetry of the capsid richer and more complex.

  5. On the Product of Rotations

    ERIC Educational Resources Information Center

    Trenkler, G.; Trenkler, D.

    2008-01-01

    Using the elementary tools of matrix theory, we show that the product of two rotations in the three-dimensional Euclidean space is a rotation again. For this purpose, three types of rotation matrices are identified which are of simple structure. One of them is the identity matrix, and each of the other two types can be uniquely characterized by…

  6. Doppler observations of solar rotation

    NASA Technical Reports Server (NTRS)

    Scherrer, P. H.; Wilcox, J. M.

    1980-01-01

    Daily observations of the photospheric equatorial rotation rate using the Doppler effect are made at the Stanford Solar Observatory. These observations show no variations in the rotation rate that exceed the observational error of about 1%. The average rotation rate is indistinguishable from that of sunspots and large-scale magnetic field structures.

  7. Doppler observations of solar rotation

    NASA Technical Reports Server (NTRS)

    Scherrer, P. H.

    1980-01-01

    Daily observations of the photospheric equatorial rotation rate using the Doppler effect mode at the Sanford Solar Observatory are presented. These observations show no variations in the rotation rate that exceed the observational error of about one percent. The average rotation rate is indistinguishable from that of sunspots and large scale magnetic field structures.

  8. Cell reorientation under cyclic stretching

    PubMed Central

    Livne, Ariel; Bouchbinder, Eran; Geiger, Benjamin

    2014-01-01

    Mechanical cues from the extracellular microenvironment play a central role in regulating the structure, function and fate of living cells. Nevertheless, the precise nature of the mechanisms and processes underlying this crucial cellular mechanosensitivity remains a fundamental open problem. Here we provide a novel framework for addressing cellular sensitivity and response to external forces by experimentally and theoretically studying one of its most striking manifestations – cell reorientation to a uniform angle in response to cyclic stretching of the underlying substrate. We first show that existing approaches are incompatible with our extensive measurements of cell reorientation. We then propose a fundamentally new theory that shows that dissipative relaxation of the cell’s passively-stored, two-dimensional, elastic energy to its minimum actively drives the reorientation process. Our theory is in excellent quantitative agreement with the complete temporal reorientation dynamics of individual cells, measured over a wide range of experimental conditions, thus elucidating a basic aspect of mechanosensitivity. PMID:24875391

  9. Isotopic studies of trans- and cis-HOCO using rotational spectroscopy: Formation, chemical bonding, and molecular structures.

    PubMed

    McCarthy, Michael C; Martinez, Oscar; McGuire, Brett A; Crabtree, Kyle N; Martin-Drumel, Marie-Aline; Stanton, John F

    2016-03-28

    HOCO is an important intermediate in combustion and atmospheric processes because the OH + CO → H + CO2 reaction represents the final step for the production of CO2 in hydrocarbon oxidation, and theoretical studies predict that this reaction proceeds via various intermediates, the most important being this radical. Isotopic investigations of trans- and cis-HOCO have been undertaken using Fourier transform microwave spectroscopy and millimeter-wave double resonance techniques in combination with a supersonic molecular beam discharge source to better understand the formation, chemical bonding, and molecular structures of this radical pair. We find that trans-HOCO can be produced almost equally well from either OH + CO or H + CO2 in our discharge source, but cis-HOCO appears to be roughly two times more abundant when starting from H + CO2. Using isotopically labelled precursors, the OH + C(18)O reaction predominately yields HOC(18)O for both isomers, but H(18)OCO is observed as well, typically at the level of 10%-20% that of HOC(18)O; the opposite propensity is found for the (18)OH + CO reaction. DO + C(18)O yields similar ratios between DOC(18)O and D(18)OCO as those found for OH + C(18)O, suggesting that some fraction of HOCO (or DOCO) may be formed from the back-reaction H + CO2, which, at the high pressure of our gas expansion, can readily occur. The large (13)C Fermi-contact term (aF) for trans- and cis-HO(13)CO implicates significant unpaired electronic density in a σ-type orbital at the carbon atom, in good agreement with theoretical predictions. By correcting the experimental rotational constants for zero-point vibration motion calculated theoretically using second-order vibrational perturbation theory, precise geometrical structures have been derived for both isomers.

  10. Isotopic studies of trans- and cis-HOCO using rotational spectroscopy: Formation, chemical bonding, and molecular structures

    NASA Astrophysics Data System (ADS)

    McCarthy, Michael C.; Martinez, Oscar; McGuire, Brett A.; Crabtree, Kyle N.; Martin-Drumel, Marie-Aline; Stanton, John F.

    2016-03-01

    HOCO is an important intermediate in combustion and atmospheric processes because the OH + CO → H + CO2 reaction represents the final step for the production of CO2 in hydrocarbon oxidation, and theoretical studies predict that this reaction proceeds via various intermediates, the most important being this radical. Isotopic investigations of trans- and cis-HOCO have been undertaken using Fourier transform microwave spectroscopy and millimeter-wave double resonance techniques in combination with a supersonic molecular beam discharge source to better understand the formation, chemical bonding, and molecular structures of this radical pair. We find that trans-HOCO can be produced almost equally well from either OH + CO or H + CO2 in our discharge source, but cis-HOCO appears to be roughly two times more abundant when starting from H + CO2. Using isotopically labelled precursors, the OH + C18O reaction predominately yields HOC18O for both isomers, but H18OCO is observed as well, typically at the level of 10%-20% that of HOC18O; the opposite propensity is found for the 18OH + CO reaction. DO + C18O yields similar ratios between DOC18O and D18OCO as those found for OH + C18O, suggesting that some fraction of HOCO (or DOCO) may be formed from the back-reaction H + CO2, which, at the high pressure of our gas expansion, can readily occur. The large 13C Fermi-contact term (aF) for trans- and cis-HO13CO implicates significant unpaired electronic density in a σ-type orbital at the carbon atom, in good agreement with theoretical predictions. By correcting the experimental rotational constants for zero-point vibration motion calculated theoretically using second-order vibrational perturbation theory, precise geometrical structures have been derived for both isomers.

  11. Interactions of cyclic and non-cyclic naphthalene diimide derivatives with different nucleic acids.

    PubMed

    Czerwinska, Izabella; Sato, Shinobu; Juskowiak, Bernard; Takenaka, Shigeori

    2014-05-01

    Recently, strategy based on stabilization of G-quadruplex telomeric DNA by small organic molecule has been realized by naphthalene diimide derivatives (NDIs). At the same time NDIs bind to DNA duplex as threading intercalators. Here we present cyclic derivative of naphthalene diimide (ligand 1) as DNA-binding ligand with ability to recognition of different structures of telomeric G-quadruplexes and ability to bis-intercalate to double-stranded helixes. The results have been compared to non-cyclic derivative (ligand 2) and revealed that preferential binding of ligands to nucleic acids strongly depends on their topology and structural features of ligands. PMID:24726302

  12. Structure of sheared and rotating turbulence: Multiscale statistics of Lagrangian and Eulerian accelerations and passive scalar dynamics.

    PubMed

    Jacobitz, Frank G; Schneider, Kai; Bos, Wouter J T; Farge, Marie

    2016-01-01

    The acceleration statistics of sheared and rotating homogeneous turbulence are studied using direct numerical simulation results. The statistical properties of Lagrangian and Eulerian accelerations are considered together with the influence of the rotation to shear ratio, as well as the scale dependence of their statistics. The probability density functions (pdfs) of both Lagrangian and Eulerian accelerations show a strong and similar dependence on the rotation to shear ratio. The variance and flatness of both accelerations are analyzed and the extreme values of the Eulerian acceleration are observed to be above those of the Lagrangian acceleration. For strong rotation it is observed that flatness yields values close to three, corresponding to Gaussian-like behavior, and for moderate and vanishing rotation the flatness increases. Furthermore, the Lagrangian and Eulerian accelerations are shown to be strongly correlated for strong rotation due to a reduced nonlinear term in this case. A wavelet-based scale-dependent analysis shows that the flatness of both Eulerian and Lagrangian accelerations increases as scale decreases, which provides evidence for intermittent behavior. For strong rotation the Eulerian acceleration is even more intermittent than the Lagrangian acceleration, while the opposite result is obtained for moderate rotation. Moreover, the dynamics of a passive scalar with gradient production in the direction of the mean velocity gradient is analyzed and the influence of the rotation to shear ratio is studied. Concerning the concentration of a passive scalar spread by the flow, the pdf of its Eulerian time rate of change presents higher extreme values than those of its Lagrangian time rate of change. This suggests that the Eulerian time rate of change of scalar concentration is mainly due to advection, while its Lagrangian counterpart is only due to gradient production and viscous dissipation. PMID:26871161

  13. Structure of sheared and rotating turbulence: Multiscale statistics of Lagrangian and Eulerian accelerations and passive scalar dynamics

    NASA Astrophysics Data System (ADS)

    Jacobitz, Frank G.; Schneider, Kai; Bos, Wouter J. T.; Farge, Marie

    2016-01-01

    The acceleration statistics of sheared and rotating homogeneous turbulence are studied using direct numerical simulation results. The statistical properties of Lagrangian and Eulerian accelerations are considered together with the influence of the rotation to shear ratio, as well as the scale dependence of their statistics. The probability density functions (pdfs) of both Lagrangian and Eulerian accelerations show a strong and similar dependence on the rotation to shear ratio. The variance and flatness of both accelerations are analyzed and the extreme values of the Eulerian acceleration are observed to be above those of the Lagrangian acceleration. For strong rotation it is observed that flatness yields values close to three, corresponding to Gaussian-like behavior, and for moderate and vanishing rotation the flatness increases. Furthermore, the Lagrangian and Eulerian accelerations are shown to be strongly correlated for strong rotation due to a reduced nonlinear term in this case. A wavelet-based scale-dependent analysis shows that the flatness of both Eulerian and Lagrangian accelerations increases as scale decreases, which provides evidence for intermittent behavior. For strong rotation the Eulerian acceleration is even more intermittent than the Lagrangian acceleration, while the opposite result is obtained for moderate rotation. Moreover, the dynamics of a passive scalar with gradient production in the direction of the mean velocity gradient is analyzed and the influence of the rotation to shear ratio is studied. Concerning the concentration of a passive scalar spread by the flow, the pdf of its Eulerian time rate of change presents higher extreme values than those of its Lagrangian time rate of change. This suggests that the Eulerian time rate of change of scalar concentration is mainly due to advection, while its Lagrangian counterpart is only due to gradient production and viscous dissipation.

  14. A non-contacting approach for full field dynamic strain monitoring of rotating structures using the photogrammetry, finite element, and modal expansion techniques

    NASA Astrophysics Data System (ADS)

    Baqersad, Javad

    Health monitoring of rotating structures such as wind turbines and helicopter rotors is generally performed using conventional sensors that provide a limited set of data at discrete locations near or on the hub. These sensors usually provide no data on the blades or interior locations where failures may occur. Within this work, an unique expansion algorithm was extended and combined with finite element (FE) modeling and an optical measurement technique to identify the dynamic strain in rotating structures. The merit of the approach is shown by using the approach to predict the dynamic strain on a small non-rotating and rotating wind turbine. A three-bladed wind turbine having 2.3-meter long blades was placed in a semi-built-in boundary condition using a hub, a machining chuck, and a steel block. A finite element model of the three wind turbine blades assembled to the hub was created and used to extract resonant frequencies and mode shapes. The FE model was validated and updated using experimental modal tests. For the non-rotating optical test, the turbine was excited using a sinusoidal excitation, a pluck test, arbitrary impacts on three blades, and random force excitations with a mechanical shaker. The response of the structure to the excitations was measured using three-dimensional point tracking. A pair of high-speed cameras was used to measure the displacement of optical targets on the structure when the blades were vibrating. The measured displacements at discrete locations were expanded and applied to the finite element model of the structure to extract the full-field dynamic strain. The results of the work show an excellent correlation between the strain predicted using the proposed approach and the strain measured with strain-gages for all of the three loading conditions. Similar to the non-rotating case, optical measurements were also preformed on a rotating wind turbine. The point tracking technique measured both rigid body displacement and flexible

  15. Efficient Synthesis of Cyclic Block Copolymers by Rotaxane Protocol by Linear/Cyclic Topology Transformation.

    PubMed

    Valentina, Stephanie; Ogawa, Takahiro; Nakazono, Kazuko; Aoki, Daisuke; Takata, Toshikazu

    2016-06-20

    High-yielding synthesis of cyclic block copolymer (CBC) using the rotaxane protocol by linear-cyclic polymer topology transformation was first demonstrated. Initial complexation of OH-terminated sec-ammonium salt and a crown ether was followed by the successive living ring-opening polymerizations of two lactones to a linear block copolymer having a rotaxane structure by the final capping of the propagation end. CBC was obtained in a high yield by an exploitation of the mechanical linkage through the translational movement of the rotaxane component to transform polymer structure from linear to cyclic. Furthermore, the change of the polymer topology was translated into a macroscopic change in crystallinity of the block copolymer. PMID:27037975

  16. Efficient Synthesis of Cyclic Block Copolymers by Rotaxane Protocol by Linear/Cyclic Topology Transformation.

    PubMed

    Valentina, Stephanie; Ogawa, Takahiro; Nakazono, Kazuko; Aoki, Daisuke; Takata, Toshikazu

    2016-06-20

    High-yielding synthesis of cyclic block copolymer (CBC) using the rotaxane protocol by linear-cyclic polymer topology transformation was first demonstrated. Initial complexation of OH-terminated sec-ammonium salt and a crown ether was followed by the successive living ring-opening polymerizations of two lactones to a linear block copolymer having a rotaxane structure by the final capping of the propagation end. CBC was obtained in a high yield by an exploitation of the mechanical linkage through the translational movement of the rotaxane component to transform polymer structure from linear to cyclic. Furthermore, the change of the polymer topology was translated into a macroscopic change in crystallinity of the block copolymer.

  17. Comparative study of dynamic structure of pig and chicken aspartate aminotransferases by measuring the rotational correlation time.

    PubMed

    Timofeev, V P; Dudich, I V; Volkenstein, M V

    1980-01-01

    The rotational correlation time of two homologous cytoplasmic aspartate aminotransferase molecules isolated from pig and chicken hearts was obtained by spin-labeling technique. The maleimide and iodoacetamide spin-labels modifying external SH-groups of a protein were used. In the interpretation of ESR spectra a rotational motion of nitroxide group relative to the protein molecule was taken into account. To determine the macromolecule rotational correlation time two methods of the immobilization of a protein molecule were used: 1) by means of increasing protein solution viscosity and 2) by fixation of the protein molecule on adsorbent. From comparison of experimental and theoretical values of rotational correlation time it was conclude that the both enzymes exhibits an intramolecular flexibility.

  18. Cyclic Material Properties Test to Determine Hardening/Softening Characteristics of HY-80 Steel

    SciTech Connect

    S.C. Hodge; J.M. Minicucci; T.F. Trimble

    2003-04-30

    The Cyclic Material Properties Test was structured to obtain and provide experimental data for determining cyclic hardening/softening characteristics of HY-80 steel. The inelastic strain history data generated by this test program and the resulting cyclic stress-strain curve will be used to enhance material models in the finite element codes used to perform nonlinear elastic-plastic analysis.

  19. Comparative study on a core-offset fiber temperature sensor between the faraday rotation mirror structure and the double coupling structure

    NASA Astrophysics Data System (ADS)

    Wang, Fang; Zhu, Han; Li, Yunpeng; Zhao, Huihui; Wang, Xu; Liu, Yufang

    2016-05-01

    A temperature sensor based on core-offset single mode fiber (SMF) and a Faraday rotation mirror (FRM) has been proposed and experimentally demonstrated in this paper. This sensor was fabricated by splicing in a section of SMF between two SMFs with a core-offset at two splicing joints. The end of the joint is connected to the FRM, which can double the sensitivity and improve the polarization state stabilization at the sensor output. The variation of the transmission spectrum of the sensor with respect to the surrounding temperature has been experimentally studied. A comparison is made between this design and a laser temperature sensor made of the same core-offset fiber utilizing a double coupling (DC) structure. The results show that, within the range of 1539.42-1553.90 nm, the sensitivity of the proposed sensor is 0.89039 nm/°C and in the range of 47-63 °C. Additionally, the power attenuation is 2.257 dB/°C. The temperature sensitivity in the SMF and FRM sensor is increased by an order of magnitude in comparison with the DC sensor. The instability and low sensitivity characteristics of a laser temperature sensor constructed with DC structure can be solved through the use of core-offset SMF and FRM.

  20. Cone-beam computed tomography based evaluation of rotational patterns of dentofacial structures in skeletal Class III deformity with mandibular asymmetry

    PubMed Central

    Ryu, Hyeong-Seok; An, Ki-Yong

    2015-01-01

    Objective The purpose of this study was to assess rotational patterns of dentofacial structures according to different vertical skeletal patterns by cone-beam computed tomography (CBCT) and analyze their influence on menton deviation in skeletal Class III deformity with mandibular asymmetry. Methods The control group consisted of 30 young adults (15 men, 15 women) without any severe skeletal deformity. The asymmetry group included 55 adults (28 men, 27 women) with skeletal Class III deformity and at least 3-mm menton deviation from the midsagittal plane; it was divided into the hyperdivergent and hypodivergent subgroups using a mandibular plane angle cutoff of 35°. Fourteen rotational variables of the dental arches and mandible were measured and compared among the groups. Correlations between menton deviation and the other variables were evaluated. Results The asymmetry group showed significantly larger measurements of roll and yaw in the mandible than the control group. The hypodivergent subgroup showed significant differences in maxillary posterior measurements of yaw (p < 0.01) and maxillary anterior shift (p < 0.05) compared with the hyperdivergent subgroup. All the mandibular measurements had significant correlations with menton deviation (p < 0.01). Most measurements of roll were positively correlated with one another (p < 0.01). Measurements of yaw and roll in the posterior regions were also positively correlated (p < 0.05). Conclusions Menton deviation in skeletal Class III deformity with mandibular asymmetry is influenced by rotation of mandibular posterior dentofacial structures. The rotational patterns vary slightly according to the vertical skeletal pattern. PMID:26258061

  1. The hyperfine structure in the rotational spectra of D2(17)O and HD(17)O: Confirmation of the absolute nuclear magnetic shielding scale for oxygen.

    PubMed

    Puzzarini, Cristina; Cazzoli, Gabriele; Harding, Michael E; Vázquez, Juana; Gauss, Jürgen

    2015-03-28

    Guided by theoretical predictions, the hyperfine structures of the rotational spectra of mono- and bideuterated-water containing (17)O have been experimentally investigated. To reach sub-Doppler resolution, required to resolve the hyperfine structure due to deuterium quadrupole coupling as well as to spin-rotation (SR) and dipolar spin-spin couplings, the Lamb-dip technique has been employed. The experimental investigation and in particular, the spectral analysis have been supported by high-level quantum-chemical computations employing coupled-cluster techniques and, for the first time, a complete experimental determination of the hyperfine parameters involved was possible. The experimentally determined (17)O spin-rotation constants of D2 (17)O and HD(17)O were used to derive the paramagnetic part of the corresponding nuclear magnetic shielding constants. Together with the computed diamagnetic contributions as well as the vibrational and temperature corrections, the latter constants have been employed to confirm the oxygen nuclear magnetic shielding scale, recently established on the basis of spin-rotation data for H2 (17)O [Puzzarini et al., J. Chem. Phys. 131, 234304 (2009)].

  2. Rotating Wavepackets

    ERIC Educational Resources Information Center

    Lekner, John

    2008-01-01

    Any free-particle wavepacket solution of Schrodinger's equation can be converted by differentiations to wavepackets rotating about the original direction of motion. The angular momentum component along the motion associated with this rotation is an integral multiple of [h-bar]. It is an "intrinsic" angular momentum: independent of origin and…

  3. Modelling rotational and cyclical spectral solar irradiance variations

    NASA Astrophysics Data System (ADS)

    Unruh, Yvonne

    Solar irradiance changes are highly wavelength dependent: solar-cycle variations in the UV can be on the order of tens of percent, while changes in the visible are typically only of the order of one or two permille. With the launch of a number of instruments to measure spectral solar irradiance, we are now for a first time in a good position to explore the changing solar irradiance over a large range of wavelengths and to test our irradiance models as well as some of their underlying assumptions. I will introduce some of the current modelling approaches and present model-data comparisons, using the SATIRE irradiance model and SORCE/SIM measurements as an example. I will conclude by highlighting a number of outstanding questions regarding the modelling of spectral irradiance and current approaches to address these.

  4. Rotational spectra and structure of the Ar2-H2S complex: pulsed nozzle Fourier transform microwave spectroscopic and ab initio studies.

    PubMed

    Mandal, Pankaj K; Ramdass, Dharmender J; Arunan, E

    2005-07-21

    This paper reports the rotational spectrum and structure of the Ar2-H2S complex and its HDS and D2S isotopomers. The ground state structure has heavy-atom C2v symmetry with the two Ar atoms indistinguishable and H2S freely rotating as evinced by the fact that asymmetric top energy levels with Kp=odd levels are missing. The rotational constants for the parent isotopomer are: A=1733.115(1) MHz, B=1617.6160(5) MHz and C=830.2951(2) MHz. Unlike the Ar-H2S complex, the Ar2-H2S does not show an anomalous isotopic shift in rotational constants on deuterium substitution. However, the intermolecular potential is still quite floppy, leading to very different centrifugal distortion constants for the three isotopomers. The Ar-Ar and Ar-c.m.(H2S) distances are determined to be 3.820 A and 4.105 A, respectively. The A rotational constants for Ar2-H2S/HDS/D2S isotopomers are very close to each other and to the B constant of free Ar2, indicating that H2S does not contribute to the moment of inertia about the a-axis. Ab initio calculations at MP2 level with aug-cc-pVQZ basis set lead to an equilibrium C2v minimum structure with the Ar-Ar line perpendicular to the H-H line and the S away from Ar2. The centrifugal distortion constants, calculated using the ab initio force field, are in reasonable agreement with the experimental values. However, they do not show the variation observed for different isotopmers. The binding energy of Ar2-H2S has been determined to be 507 cm-1(6.0 kJ mol-1) by CBS extrapolation after correcting for basis set superposition error. Potential energy scans point out that the barrier for internal rotation of H2S about its b axis is only 10 cm-1 and it is below the zero point energy (13.5 cm-1) in this torsional degree of freedom. Internal rotation of H2S about its a- and c-axes also have small barriers of about 50 cm-1 only, suggesting that H2S is extremely floppy within the complex.

  5. Advanced Developments in Cyclic Polymers: Synthesis, Applications, and Perspectives

    PubMed Central

    Zhu, Yinghuai; Hosmane, Narayan S

    2015-01-01

    Due to the topological effect, cyclic polymers demonstrate different and unique physical and biological properties in comparison with linear counterparts having the same molecular-weight range. With advanced synthetic and analytic technologies, cyclic polymers with different topologies, e.g. multicyclic polymers, have been reported and well characterized. For example, various cyclic DNA and related structures, such as cyclic duplexes, have been prepared conveniently by click chemistry. These types of DNA have increased resistance to enzymatic degradation and have high thermodynamic stability, and thus, have potential therapeutic applications. In addition, cyclic polymers have also been used to prepare organic–inorganic hybrids for applications in catalysis, e.g. catalyst supports. Due to developments in synthetic technology, highly pure cyclic polymers could now be produced in large scale. Therefore, we anticipate discovering more applications in the near future. Despite their promise, cyclic polymers are still less explored than linear polymers like polyolefins and polycarbonates, which are widely used in daily life. Some critical issues, including controlling the molecular weight and finding suitable applications, remain big challenges in the cyclic-polymer field. This review briefly summarizes the commonly used synthetic methodologies and focuses more on the attractive functional materials and their biological properties and potential applications. PMID:26478835

  6. Rotating arc spark plug

    DOEpatents

    Whealton, John H.; Tsai, Chin-Chi

    2003-05-27

    A spark plug device includes a structure for modification of an arc, the modification including arc rotation. The spark plug can be used in a combustion engine to reduce emissions and/or improve fuel economy. A method for operating a spark plug and a combustion engine having the spark plug device includes the step of modifying an arc, the modifying including rotating the arc.

  7. Solid state {sup 1}H spin-lattice relaxation and isolated-molecule and cluster electronic structure calculations in organic molecular solids: The relationship between structure and methyl group and t-butyl group rotation

    SciTech Connect

    Wang, Xianlong E-mail: pbeckman@brynmawr.edu; Mallory, Frank B.; Mallory, Clelia W.; Odhner, Hosanna R.; Beckmann, Peter A. E-mail: pbeckman@brynmawr.edu

    2014-05-21

    We report ab initio density functional theory electronic structure calculations of rotational barriers for t-butyl groups and their constituent methyl groups both in the isolated molecules and in central molecules in clusters built from the X-ray structure in four t-butyl aromatic compounds. The X-ray structures have been reported previously. We also report and interpret the temperature dependence of the solid state {sup 1}H nuclear magnetic resonance spin-lattice relaxation rate at 8.50, 22.5, and 53.0 MHz in one of the four compounds. Such experiments for the other three have been reported previously. We compare the computed barriers for methyl group and t-butyl group rotation in a central target molecule in the cluster with the activation energies determined from fitting the {sup 1}H NMR spin-lattice relaxation data. We formulate a dynamical model for the superposition of t-butyl group rotation and the rotation of the t-butyl group's constituent methyl groups. The four compounds are 2,7-di-t-butylpyrene, 1,4-di-t-butylbenzene, 2,6-di-t-butylnaphthalene, and 3-t-butylchrysene. We comment on the unusual ground state orientation of the t-butyl groups in the crystal of the pyrene and we comment on the unusually high rotational barrier of these t-butyl groups.

  8. A novel approach to gravitation from fluid theory: Titius-Bode structures, flat rotation rate of galaxies and other predictions

    NASA Astrophysics Data System (ADS)

    Munera, Hector A.

    2015-08-01

    The formal analogy between electromagnetism (EM) and gravitation was noted by Maxwell and Faraday, and later on by Heaviside in the 1890s; the analogy was extensively used in the gravito-magnetism of the 20th century. The connection between EM and fluid theory is explicit in Maxwell’s work, and the equivalence of Maxwell equations (ME) to various wave equations is explained in electrodynamics textbooks (say, Jackson’s) additionally, a little-known paper presented by Henri Malet to the Paris Academy of Sciences (1926), demonstrated that the validity of ME concurrently requires the validity of the vector and the scalar homogeneous wave equations.In the 1990s the present author reported in Foundations of Physics Letters the existence of novel solutions for the homogeneous wave equation in spherical coordinates; it turns out that one class of our solutions (the nonharmonic functions of the first-kind, NHFFK) is equivalent to the unified force of nature proposed around 1760 by Boscovich from philosophical considerations, but without a formal mathematical basis. Our finding is significant because it lends a mathematical foundation to Boscovich’s force, which has extremely interesting properties, as quantization in energy and distance —noted by J. J. Thomson before Bohr’s quantum theory.Associated with spherical surfaces in gravitational equilibrium, the family of even NHFFKs described here predict Titius-Body structures at different scales, as the solar system and the moons of Mars, Jupiter, Uranus, Saturn, and Neptune. Each calculated radius is compared to an average distance of moons/planets: the correlation and the R2 coefficients are quite high. The same NHFFK also predict the existence of ring structures, as those observed in Saturn, and in asteroids belts in our solar system. Newtonian gravity appears as the limit at very large distances from the center of force. The family of odd NHFFK exhibits a non-zero limit as distance tends to infinity, feature that

  9. Cosmic perturbations through the cyclic ages

    SciTech Connect

    Erickson, Joel K.; Gratton, Steven; Steinhardt, Paul J.; Turok, Neil

    2007-06-15

    We analyze the evolution of cosmological perturbations in the cyclic model, paying particular attention to their behavior and interplay over multiple cycles. Our key results are: (1) galaxies and large scale structure present in one cycle are generated by the quantum fluctuations in the preceding cycle without interference from perturbations or structure generated in earlier cycles and without interfering with structure generated in later cycles; (2) the ekpyrotic phase, an epoch of gentle contraction with equation of state w>>1 preceding the hot big bang, makes the universe homogeneous, isotropic and flat within any given observer's horizon; and (3) although the universe is uniform within each observer's horizon, the structure of the cyclic universe on very large scales is more complex, owing to the effects of superhorizon length perturbations, and cannot be described globally as a Friedmann-Robertson-Walker cosmology. In particular, we show that the ekpyrotic contraction phase is so effective in smoothing, flattening and isotropizing the universe within the horizon that this phase alone suffices to solve the horizon and flatness problems even without an extended period of dark energy domination (a kind of low energy inflation). Instead, the cyclic model rests on a genuinely novel, noninflationary mechanism (ekpyrotic contraction) for resolving the classic cosmological conundrums.

  10. Analysis of the rotational structure in the high-resolution infrared spectrum of trans-hexatriene-1-13C1: a semiexperimental equilibrium structure for the C6 backbone of trans-hexatriene.

    PubMed

    Craig, Norman C; Tian, Hengfeng; Blake, Thomas A

    2012-03-29

    trans-Hexatriene-1-(13)C(1) (tHTE-1-(13)C(1)) has been synthesized, and its high-resolution (0.0015 cm(-1)) infrared spectrum has been recorded. The rotational structure in the C-type bands for ν(26) at 1011 cm(-1) and ν(30) at 894 cm(-1) has been analyzed. To the 1458 ground state combination differences from these bands, ground state rotational constants were fitted to a Watson-type Hamiltonian to give A(0) = 0.8728202(9), B(0) = 0.0435868(4), and C(0) = 0.0415314(2) cm(-1). Upper state rotational constants for the ν(30) band were also fitted. Predictions of the ground state rotational constants for tHTE-1-(13)C(1) from a B3LYP/cc-pVTZ model with scale factors based on the normal species were in excellent agreement with observations. Similar good agreement was found between predicted and observed ground state rotational constants for the three (13)C(1) isotopologues of cis-hexatriene, as determined from microwave spectroscopy. Equilibrium rotational constants for tHTE and its three (13)C(1) isotopologues, of which two were predicted, were used to find a semiexperimental equilibrium structure for the C(6) backbone of tHTE. This structure shows increased structural effects of π-electron delocalization in comparison with butadiene and some differences from the cis isomer of HTE. Structures predicted with the MP2/cc-pVTZ model are also compared.

  11. Structural characteristics and spectral behaviours of the preferred conformation of a cyclic pentapeptide, cycloaspeptide G from Cordyceps-colonising fungus Isoria farinose

    NASA Astrophysics Data System (ADS)

    Mang, Chao-Yong; Zhao, Yu; Li, Hai-Feng; Lan, Hai; Yan, Ya; Yang, Ming-Hui

    2015-01-01

    The density functional theory (DFT) is exploited to search the stable conformations of a cyclic pentapeptide called cycloaspeptide G from Cordyceps-colonising fungus Isoria farinose. Its time-dependent version is employed to describe the profiles of electronic circular dichroism (ECD) of the preferred conformation, where the solvent effect in methanol is taken into account on the basis of the polarisable continuum model computation. Four stable conformers are optimised, and the results of the harmonically vibrational frequency calculations illustrate that they are the true minima. In the vibrational CD spectrum at the B3LYP/6-31G* level, the negative peak at 3334 cm-1 has its origin of the NH stretches of the peptide ring. In the ECD spectrum at the B3LYP/6-31G* level, three strong bands are negative, positive, and negative. Since the ECD spectrum at the B3LYP/6-31G* level is remarkably different from that at the B3LYP/6-31G level, it is necessary for the expended functions to be added to the 6-31G basis set.

  12. Investigation of the Rotational Spectrum of Pyrimidine from 3 to 337 GHz: Molecular Structure, Nuclear Quadrupole Coupling, and Vibrational Satellites.

    PubMed

    Kisiel; Pszczólkowski; López; Alonso; Maris; Caminati

    1999-06-01

    A comprehensive reinvestigation of the rotational spectrum of pyrimidine was carried out by using several different spectrometers. All singly substituted 13C- and 15N-isotopic species of pyrimidine have been measured in natural abundance with millimeter-wave free jet and waveguide Fourier transform microwave techniques, and complete rs and r0 heavy atom geometries have been determined. The ground state rotational spectrum in the centimeter-wave region was measured at sub-Doppler resolution of the cavity Fourier transform spectrometer and all elements in the inertial and principal nuclear quadrupole-coupling tensors of the nitrogen nuclei in pyrimidine have been determined. The room-temperature spectrum was measured up to 337 GHz and J = 66 with BWO-based spectrometers and sextic level centrifugal distortion constants in the rotational Hamiltonian have been determined for the ground state and three lowest vibrational fundamentals of pyrimidine. Copyright 1999 Academic Press.

  13. A model of rotationally-sampled wind turbulence for predicting fatigue loads in wind turbines

    NASA Technical Reports Server (NTRS)

    Spera, David A.

    1995-01-01

    Empirical equations are presented with which to model rotationally-sampled (R-S) turbulence for input to structural-dynamic computer codes and the calculation of wind turbine fatigue loads. These equations are derived from R-S turbulence data which were measured at the vertical-plane array in Clayton, New Mexico. For validation, the equations are applied to the calculation of cyclic flapwise blade loads for the NASA/DOE Mod-2 2.5-MW experimental HAWT's (horizontal-axis wind turbines), and the results compared to measured cyclic loads. Good correlation is achieved, indicating that the R-S turbulence model developed in this study contains the characteristics of the wind which produce many of the fatigue loads sustained by wind turbines. Empirical factors are included which permit the prediction of load levels at specified percentiles of occurrence, which is required for the generation of fatigue load spectra and the prediction of the fatigue lifetime of structures.

  14. A model of rotationally-sampled wind turbulence for predicting fatigue loads in wind turbines

    NASA Astrophysics Data System (ADS)

    Spera, David A.

    1995-05-01

    Empirical equations are presented with which to model rotationally-sampled (R-S) turbulence for input to structural-dynamic computer codes and the calculation of wind turbine fatigue loads. These equations are derived from R-S turbulence data which were measured at the vertical-plane array in Clayton, New Mexico. For validation, the equations are applied to the calculation of cyclic flapwise blade loads for the NASA/DOE Mod-2 2.5-MW experimental HAWT's (horizontal-axis wind turbines), and the results compared to measured cyclic loads. Good correlation is achieved, indicating that the R-S turbulence model developed in this study contains the characteristics of the wind which produce many of the fatigue loads sustained by wind turbines. Empirical factors are included which permit the prediction of load levels at specified percentiles of occurrence, which is required for the generation of fatigue load spectra and the prediction of the fatigue lifetime of structures.

  15. Fiber-optic rotation of micro-scale structures enabled microfluidic actuation and self-scanning two-photon excitation

    NASA Astrophysics Data System (ADS)

    Black, Bryan J.; Luo, Dijun; Mohanty, Samarendra K.

    2012-11-01

    Here, we report non-restricted, controlled fiber optic rotation of micro-motor, in counter-propagating fiber-optic beams having transverse-offset, for actuation of microfluidic flow. Ray-optics based simulations of the torque (and angular velocity) were conducted for different fiber transverse-offsets in order to determine optimal geometry for effective actuation. Further, self-scanning two-photon excitation of the fiber-optically rotated microscopic object is achieved by use of an ultrafast laser beam in one of the fiber arm.

  16. Rotating Responsibility Reaps Rewards.

    ERIC Educational Resources Information Center

    Wilson, Barbara; Schullery, Nancy

    2000-01-01

    Describes a process used for group assignments in a business communication course which holds all group members accountable by using a structure of rotating responsibility. Discusses selecting assignments and implementing the process, noting how this structure requires equivalent advance preparation from all members and provides opportunities for…

  17. Rotational Energy.

    ERIC Educational Resources Information Center

    Lockett, Keith

    1988-01-01

    Demonstrates several objects rolling down a slope to explain the energy transition among potential energy, translational kinetic energy, and rotational kinetic energy. Contains a problem from Galileo's rolling ball experiment. (YP)

  18. Viscosity structure of Earth's mantle inferred from rotational variations due to GIA process and recent melting events

    NASA Astrophysics Data System (ADS)

    Nakada, Masao; Okuno, Jun'ichi; Lambeck, Kurt; Purcell, Anthony

    2015-08-01

    We examine the geodetically derived rotational variations for the rate of change of degree-two harmonics of Earth's geopotential, skew5dot J_2, and true polar wander, combining a recent melting model of glaciers and the Greenland and Antarctic ice sheets taken from the IPCC 2013 Report (AR5) with two representative GIA ice models describing the last deglaciation, ICE5G and the ANU model developed at the Australian National University. Geodetically derived observations of skew4dot J_2 are characterized by temporal changes of -(3.7 ± 0.1) × 10-11 yr-1 for the period 1976-1990 and -(0.3 ± 0.1) × 10-11 yr-1 after ˜2000. The AR5 results make it possible to evaluate the recent melting of the major ice sheets and glaciers for three periods, 1900-1990, 1991-2001 and after 2002. The observed skew4dot J_2 and the component of skew4dot J_2 due to recent melting for different periods indicate a long-term change in skew4dot J_2-attributed to the Earth's response to the last glacial cycle-of -(6.0-6.5) × 10-11 yr-1, significantly different from the values adopted to infer the viscosity structure of the mantle in most previous studies. This is a main conclusion of this study. We next compare this estimate with the values of skew4dot J_2 predicted by GIA ice models to infer the viscosity structure of the mantle, and consequently obtain two permissible solutions for the lower mantle viscosity (ηlm), ˜1022 and (5-10) × 1022 Pa s, for both adopted ice models. These two solutions are largely insensitive to the lithospheric thickness and upper mantle viscosity as indicated by previous studies and relatively insensitive to the viscosity structure of the D″ layer. The ESL contributions from the Antarctic ice sheet since the last glacial maximum (LGM) for ICE5G and ANU are about 20 and 30 m, respectively, but glaciological reconstructions of the Antarctic LGM ice sheet have suggested that its ESL contribution may have been less than ˜10 m. The GIA-induced skew4dot J_2 for GIA

  19. Understanding Lipid Recognition by Protein-Mimicking Cyclic Peptides.

    PubMed

    Hosseini, Azade S; Zheng, Hong; Gao, Jianmin

    2014-10-21

    This paper describes our investigation of the structural determinants of a designed cyclic peptide (cLac, cyclic peptide mimicking lactadherin)(1) for phosphatidylserine (PS) recognition. A highly efficient strategy that takes advantage of the native chemical ligation (NCL) chemistry has been developed for the synthesis and labeling of cyclic peptides in general. Ala scanning of the cLac peptide revealed a sophisticated model for PS binding, in which the peptide scaffold assembles multiple polar residues to balance the desolvation and electrostatic interactions (salt bridge and hydrogen bonding) to achieve lipid selectivity. The results suggest that cLac effectively mimics the membrane binding mechanism of the parent protein lactadherin.

  20. Turbulent fluid-structure interaction of water-entry/exit of a rotating circular cylinder using SPH method

    NASA Astrophysics Data System (ADS)

    Ghazanfarian, Jafar; Saghatchi, Roozbeh; Gorji-Bandpy, Mofid

    2015-12-01

    This paper studies the two-dimensional (2D) water-entry and exit of a rotating circular cylinder using the Sub-Particle Scale (SPS) turbulence model of a Lagrangian particle-based Smoothed-Particle Hydrodynamics (SPH) method. The full Navier-Stokes (NS) equations along with the continuity have been solved as the governing equations of the problem. The accuracy of the numerical code is verified using the case of water-entry and exit of a nonrotating circular cylinder. The numerical simulations of water-entry and exit of the rotating circular cylinder are performed at Froude numbers of 2, 5, 8, and specific gravities of 0.25, 0.5, 0.75, 1, 1.75, rotating at the dimensionless rates of 0, 0.25, 0.5, 0.75. The effect of governing parameters and vortex shedding behind the cylinder on the trajectory curves, velocity components in the flow field, and the deformation of free surface for both cases have been investigated in detail. It is seen that the rotation has a great effect on the curvature of the trajectory path and velocity components in water-entry and exit cases due to the interaction of imposed lift and drag forces with the inertia force.

  1. Rotational spectrum and structure of cyclohexene oxide and the argon-cyclohexene oxide van der Waals complex.

    PubMed

    Frohman, Daniel J; Novick, Stewart E; Pringle, Wallace C

    2013-12-19

    The rotational spectra of cyclohexene oxide and its van der Waals complex with argon have been observed with a Balle-Flygare type pulsed jet Fourier transform microwave spectrometer in the 6 to 20 GHz region. This work improves the existing rotational and quartic centrifugal distortion constants of cyclohexene oxide, its six singly substituted (13)C, and the (18)O isotopologue. In addition, the (17)O isotopologue was observed in natural abundance. The quadrupole coupling constants for the (17)O isotopologue are χ(aa) = 8.855(5), χ(bb) = -4.560(4), and χ(cc) = -4.296(4) MHz. The argon-(12)C6H10(16)O complex has rotational constants of A = 2146.4825(2), B = 908.64292(8), and C = 859.00320(8) MHz. Additionally, the six unique singly substituted (13)C isotopologues of the argon complex are reported here. The position of the argon that is consistent with the parent and six (13)C complex rotational constants is above the ring on the side opposite the epoxide.

  2. Cyclic AMP in prokaryotes.

    PubMed Central

    Botsford, J L; Harman, J G

    1992-01-01

    Cyclic AMP (cAMP) is found in a variety of prokaryotes including both eubacteria and archaebacteria. cAMP plays a role in regulating gene expression, not only for the classic inducible catabolic operons, but also for other categories. In the enteric coliforms, the effects of cAMP on gene expression are mediated through its interaction with and allosteric modification of a cAMP-binding protein (CRP). The CRP-cAMP complex subsequently binds specific DNA sequences and either activates or inhibits transcription depending upon the positioning of the complex relative to the promoter. Enteric coliforms have provided a model to explore the mechanisms involved in controlling adenylate cyclase activity, in regulating adenylate cyclase synthesis, and in performing detailed examinations of CRP-cAMP complex-regulated gene expression. This review summarizes recent work focused on elucidating the molecular mechanisms of CRP-cAMP complex-mediated processes. For other bacteria, less detail is known. cAMP has been implicated in regulating antibiotic production, phototrophic growth, and pathogenesis. A role for cAMP has been suggested in nitrogen fixation. Often the only data that support cAMP involvement in these processes includes cAMP measurement, detection of the enzymes involved in cAMP metabolism, or observed effects of high concentrations of the nucleotide on cell growth. PMID:1315922

  3. Cyclic Vomiting Syndrome

    PubMed Central

    2009-01-01

    Initially described in children, cyclic vomiting syndrome (CVS) is an idiopathic disorder that affects patients of all ages and is characterized by recurrent episodes of vomiting separated by symptom-free intervals or baseline health. Frequent misdiagnoses and delays in diagnosis often lead to years of recurrent vomiting. Similarities in the clinical features and symptoms of children and adults with CVS are often linked to migraines. Association with mitochondrial disorders and neuroendocrine dysfunction have been described in the pediatric CVS literature, whereas migraines, anxiety, and panic are common in adults with CVS. Various psychological, infectious, and physical stressors commonly precipitate episodes of CVS. Treatment is mostly empiric, with few controlled therapeutic studies conducted thus far. Associations with migraines have aided in developing pharmacologic treatment strategies for prophylaxis as well as abortive therapy during episodes, including the use of trip-tans. Most children outgrow CVS with time, though some children transition to migraine headaches or continue to have CVS as adults. Improved recognition of CVS in adults, along with the emergence of data in the use of anticonvulsants and antiemetics, may help further delineate pathophysiologic connections and therapeutic options for this debilitating disorder.

  4. Ada and cyclic runtime scheduling

    NASA Technical Reports Server (NTRS)

    Hood, Philip E.

    1986-01-01

    An important issue that must be faced while introducing Ada into the real time world is efficient and prodictable runtime behavior. One of the most effective methods employed during the traditional design of a real time system is the cyclic executive. The role cyclic scheduling might play in an Ada application in terms of currently available implementations and in terms of implementations that might be developed especially to support real time system development is examined. The cyclic executive solves many of the problems faced by real time designers, resulting in a system for which it is relatively easy to achieve approporiate timing behavior. Unfortunately a cyclic executive carries with it a very high maintenance penalty over the lifetime of the software that is schedules. Additionally, these cyclic systems tend to be quite fragil when any aspect of the system changes. The findings are presented of an ongoing SofTech investigation into Ada methods for real time system development. The topics covered include a description of the costs involved in using cyclic schedulers, the sources of these costs, and measures for future systems to avoid these costs without giving up the runtime performance of a cyclic system.

  5. Generation and Characterization of Monoclonal Antibodies against a Cyclic Variant of Hepatitis C Virus E2 Epitope 412-422

    PubMed Central

    Sandomenico, Annamaria; Leonardi, Antonio; Berisio, Rita; Sanguigno, Luca; Focà, Giuseppina; Focà, Annalia; Ruggiero, Alessia; Doti, Nunzianna; Muscariello, Livio; Barone, Daniela; Farina, Claudio; Owsianka, Ania; Vitagliano, Luigi

    2016-01-01

    ABSTRACT The hepatitis C virus (HCV) E2 envelope glycoprotein is crucial for virus entry into hepatocytes. A conserved region of E2 encompassing amino acids 412 to 423 (epitope I) and containing Trp420, a residue critical for virus entry, is recognized by several broadly neutralizing antibodies. Peptides embodying this epitope I sequence adopt a β-hairpin conformation when bound to neutralizing monoclonal antibodies (MAbs) AP33 and HCV1. We therefore generated new mouse MAbs that were able to bind to a cyclic peptide containing E2 residues 412 to 422 (C-epitope I) but not to the linear counterpart. These MAbs bound to purified E2 with affinities of about 50 nM, but they were unable to neutralize virus infection. Structural analysis of the complex between C-epitope I and one of our MAbs (C2) showed that the Trp420 side chain is largely buried in the combining site and that the Asn417 side chain, which is glycosylated in E2 and solvent exposed in other complexes, is slightly buried upon C2 binding. Also, the orientation of the cyclic peptide in the antibody-combining site is rotated by 180° compared to the orientations of the other complexes. All these structural features, however, do not explain the lack of neutralization activity. This is instead ascribed to the high degree of selectivity of the new MAbs for the cyclic epitope and to their inability to interact with the epitope in more flexible and extended conformations, which recent data suggest play a role in the mechanisms of neutralization escape. IMPORTANCE Hepatitis C virus (HCV) remains a major health care burden, affecting almost 3% of the global population. The conserved epitope comprising residues 412 to 423 of the viral E2 glycoprotein is a valid vaccine candidate because antibodies recognizing this region exhibit potent neutralizing activity. This epitope adopts a β-hairpin conformation when bound to neutralizing MAbs. We explored the potential of cyclic peptides mimicking this structure to elicit

  6. LOOKING DEEP INTO THE CAT'S EYE: STRUCTURE AND ROTATION IN THE FAST WIND OF THE PN CENTRAL STAR OF NGC 6543

    SciTech Connect

    Prinja, R. K.; Massa, D. L.; Cantiello, M.

    2012-11-10

    We present HST/STIS time-series spectroscopy of the central star of the 'Cat's Eye' planetary nebula NGC 6543. Intensive monitoring of the UV lines over a 5.8 hr period reveals well-defined details of large-scale structure in the fast wind, which are exploited to provide new constraints on the rotation rate of the central star. We derive characteristics of the line profile variability that support a physical origin due to corotating interaction regions (CIRs) that are rooted at the stellar surface. The recurrence time of the observed spectral signatures of the CIRs is used to estimate the rotation period of the central star and, adopting a radius between 0.3 and 0.6 R{sub Sun} constrains the rotational velocity to the range 54 km s{sup -1} {<=} v{sub rot} {<=} 108 km s{sup -1}. The implications of these results for single star evolution are discussed based on models calculated here for low-mass stars. Our models predict a subsurface convective layer in NGC 6543 which we argue to be causally connected to the occurrence of structure in the fast wind.

  7. Static and dynamic finite rotation FE-analysis of thin-walled structures with piezoelectric sensor and actuator patches or layers

    NASA Astrophysics Data System (ADS)

    Rao, M. N.; Schmidt, R.

    2014-09-01

    This paper deals with static and dynamic analysis of thin-walled structures with integrated piezoelectric layers as sensors and actuators in the geometrically nonlinear range of deformations. A variational formulation is derived by using the Reissner-Mindlin first-order shear deformation (FOSD) hypothesis and full geometrically nonlinear strain-displacement relations accounting for finite rotations. The finite rotations are treated by Rodriguez parameterization. In order to enhance the accuracy of a four-node shell element, a combination of an assumed natural strain (ANS) method for the shear strains, an enhanced assumed strain (EAS) method for the membrane strains and an enhanced assumed gradient (EAG) method for the electric field are employed. The present shell element has five mechanical degrees of freedom (DOFs) and three electrical DOFs per node. The Newton-Raphson method for static analysis and the Newmark method for dynamic analysis are used to perform linear and nonlinear simulations. In comparison to the results obtained by simplified nonlinear models reported in the existing literature, the finite-element simulations performed in this paper show the importance of the present model, precisely for structures undergoing finite deformations and rotations.

  8. Spin--rotation and hyperfine structure in the X sup 2. Sigma. sup + state of yttrium monosulfide by molecular-beam laser-radio-frequency double resonance

    SciTech Connect

    Azuma, Y.; Childs, W.J. )

    1990-12-15

    The molecular-beam laser-radio-frequency double-resonance method has been used to measure the spin--rotation and magnetic hyperfine structure of yttrium monosulfide (YS) in its {ital X} {sup 2}{Sigma}{sup +} electronic ground state. The spin--rotation constant {gamma} is found to be positive, unlike that of YO. The Fermi contact and dipolar hyperfine interactions (due to the spin {ital I}=1/2 of {sup 89}Y) are found to be rather close to the corresponding quantities in YO. The contact hfs constant {ital b} in the excited {ital B} {sup 2}{Sigma}{sup +} state of YS was determined by combining the directly measured {ital X} {sup 2}{Sigma}{sup +} splitting information with {ital B}--{ital X} optical hfs observations.

  9. New cytotoxic cyclic peroxide acids from Plakortis sp. marine sponge

    PubMed Central

    Hoye, Thomas R.; Alarif, Walied M.; Basaif, Salim S.; Abo-Elkarm, Mohamed; Hamann, Mark T.; Wahba, Amir E.; Ayyad, Seif-Eldin N.

    2016-01-01

    Bioassay-guided fractionation of the extract of Jamaican marine sponge Plakortis sp. followed by preparative TLC and HPLC yielded several known methyl ester cyclic peroxides (1a, 2a, 3a, 4, 5), known plakortides (6,7), known bicyclic lactone (8) and new cyclic peroxide acids (1b, 2b, 3b). The chemical structures were elucidated by extensive interpretation of their spectroscopic data. These natural products showed remarkable in vitro cytotoxicity against several cancer cell lines. PMID:26835518

  10. Similarity analysis, synthesis, and bioassay of antibacterial cyclic peptidomimetics

    PubMed Central

    Berhanu, Workalemahu M; Ibrahim, Mohamed A; Pillai, Girinath G; Oliferenko, Alexander A; Khelashvili, Levan; Jabeen, Farukh; Mirza, Bushra; Ansari, Farzana Latif; ul-Haq, Ihsan; El-Feky, Said A

    2012-01-01

    Summary The chemical similarity of antibacterial cyclic peptides and peptidomimetics was studied in order to identify new promising cyclic scaffolds. A large descriptor space coupled with cluster analysis was employed to digitize known antibacterial structures and to gauge the potential of new peptidomimetic macrocycles, which were conveniently synthesized by acylbenzotriazole methodology. Some of the synthesized compounds were tested against an array of microorganisms and showed antibacterial activity against Bordetella bronchistepica, Micrococcus luteus, and Salmonella typhimurium. PMID:23019443

  11. High-affinity Cyclic Peptide Matriptase Inhibitors*

    PubMed Central

    Quimbar, Pedro; Malik, Uru; Sommerhoff, Christian P.; Kaas, Quentin; Chan, Lai Y.; Huang, Yen-Hua; Grundhuber, Maresa; Dunse, Kerry; Craik, David J.; Anderson, Marilyn A.; Daly, Norelle L.

    2013-01-01

    The type II transmembrane serine protease matriptase is a key activator of multiple signaling pathways associated with cell proliferation and modification of the extracellular matrix. Deregulated matriptase activity correlates with a number of diseases, including cancer and hence highly selective matriptase inhibitors may have therapeutic potential. The plant-derived cyclic peptide, sunflower trypsin inhibitor-1 (SFTI-1), is a promising drug scaffold with potent matriptase inhibitory activity. In the current study we have analyzed the structure-activity relationships of SFTI-1 and Momordica cochinchinensis trypsin inhibitor-II (MCoTI-II), a structurally divergent trypsin inhibitor from Momordica cochinchinensis that also contains a cyclic backbone. We show that MCoTI-II is a significantly more potent matriptase inhibitor than SFTI-1 and that all alanine mutants of both peptides, generated using positional scanning mutagenesis, have decreased trypsin affinity, whereas several mutations either maintain or result in enhanced matriptase inhibitory activity. These intriguing results were used to design one of the most potent matriptase inhibitors known to date with a 290 pm equilibrium dissociation constant, and provide the first indication on how to modulate affinity for matriptase over trypsin in cyclic peptides. This information might be useful for the design of more selective and therapeutically relevant inhibitors of matriptase. PMID:23548907

  12. Reanalysis and extension of the MnH A7Π- X7Σ + (0, 0) band: Fine structure and hyperfine-induced rotational branches

    NASA Astrophysics Data System (ADS)

    Varberg, Thomas D.; Gray, Jeffrey A.; Field, Robert W.; Merer, Anthony J.

    1992-12-01

    The A7Π- X7Σ + (0, 0) band of MnH at 568 nm has been recorded by laser fluorescence excitation spectroscopy. The original rotational analysis of Nevin [ Proc. R. Irish Acad.48A, 1-45 (1942); 50A, 123-137 (1945)] has been extended with some corrections at low J. Systematic internal hyperfine perturbations in the X7Σ + state, caused by the Δ N = 0, Δ J = ±1 matrix elements of the 55Mn hyperfine term in the Hamiltonian, have been observed in all seven electron spin components over the entire range of N″ studied. These perturbations destroy the "goodness" of J″ as a quantum number, giving rise to hyperfine-induced Δ J = ±2 rotational branches and to observable energy shifts of the most severely affected levels. The A7Π state, with A = 40.5 cm -1 and B = 6.35 cm -1, evolves rapidly from Hund's case ( a) to case ( b) coupling, which produces anomalous branch patterns at low J. A total of 156 rotational branches have been identified and fitted by least squares to an effective Hamiltonian, providing precise values for the rotational and fine structure constants. Values of the principal constants determined in the fit are (1σ errors in units of the last digit are listed in parentheses): The fine structures of the A7Π and X7Σ + states confirm the assignment of the A ← X transition as Mn 4 pπ ← 4 sσ in the presence of a spectator, nonbonding Mn 3 d5 ( 6S) open core.

  13. Self-consistent internal structure of a rotating gaseous planet and its comparison with an approximation by oblate spheroidal equidensity surfaces

    NASA Astrophysics Data System (ADS)

    Kong, Dali; Zhang, Keke; Schubert, Gerald

    2015-12-01

    In an important paper, Roberts (1963b) studied the hydrostatic equilibrium of an isolated, self-gravitating, rapidly rotating polytropic gaseous body based on a controversial assumption/approximation that all (outer and internal) equidensity surfaces are in the shape of oblate spheroids whose eccentricities are a function of the equatorial radius and whose axes of symmetry are parallel to the rotation axis. We compute the three-dimensional, finite-element, fully self-consistent, continuous solution for a rapidly rotating polytropic gaseous body with Jupiter-like parameters without making any prior assumptions about its outer shape and internal structure. Upon partially relaxing the Roberts' approximation by assuming that only the outer equidensity surface is in the shape of an oblate spheroid, we also compute a finite-element solution with the same parameters without making any prior assumptions about its internal structure. It is found that all equidensity surfaces of the fully self-consistent solution differ only slightly from the oblate spheroidal shape. It is also found that the characteristic difference between the fully self-consistent solution and the outer-spheroidal-shape solution is insignificantly small. Our results suggest that the Roberts' assumption of spheroidal equidensity surfaces represents a reasonably accurate approximation for rotating polytropic gaseous bodies with Jupiter-like parameters. The numerical accuracy of our finite-element solution is checked by an exact analytic solution based on the Green's function using the spheroidal wave function. The three different solutions in non-spherical geometries - the fully self-consistent numerical solution, the numerical solution with the outer spheroidal shape and the exact analytical solution - can also serve as a useful benchmark for other solutions based on different numerical methods.

  14. Cyclic Vomiting Syndrome: An Update Illustrated by a Case Report

    PubMed Central

    Hermus, Ingeborg P. M.; Willems, Stacey J. B.; Bogman, Aimée C. C. F.; Janssen, Paddy K. C.; Brabers, Leonie; Schieveld, Jan N. M.

    2016-01-01

    Objective: This article presents an update on cyclic vomiting syndrome, a potentially exhausting disorder that can occur in children, adolescents, and adults and and has a huge impact on the quality of life. A structured literature search was conducted to explore the current knowledge about antipsychotics in the treatment of cyclic vomiting syndrome. A case report is presented of a 15-year-old boy with refractory cyclic vomiting syndrome (ICD-10 criteria), who finally responded to a unique combination of risperidone and amitriptyline. Data Sources: A literature search of English articles was performed in November 2015 using PubMed and the Cochrane Library with cyclic vomiting syndrome, cyclic vomiting, risperidone, and antipsychotics as key words. All types of publications were included. The publication period covered a span from 1976 to 2014. Study Selection and Data Extraction: In total, 13 articles were found. After screening the title and abstract, only 2 were selected. Results: In the current literature, only the use of chlorpromazine in the treatment of cyclic vomiting syndrome is mentioned. The possible underlying working mechanism of chlorpromazine is not clarified. Conclusions: Antipsychotics are hardly mentioned in the literature with regard to their antiemetic properties. Antipsychotics like risperidone, and its unique combination with amitriptyline, might be an important alternative to achieve a satisfactory treatment result in refractory cases of cyclic vomiting syndrome. PMID:27733950

  15. Algebraic curves of maximal cyclicity

    NASA Astrophysics Data System (ADS)

    Caubergh, Magdalena; Dumortier, Freddy

    2006-01-01

    The paper deals with analytic families of planar vector fields, studying methods to detect the cyclicity of a non-isolated closed orbit, i.e. the maximum number of limit cycles that can locally bifurcate from it. It is known that this multi-parameter problem can be reduced to a single-parameter one, in the sense that there exist analytic curves in parameter space along which the maximal cyclicity can be attained. In that case one speaks about a maximal cyclicity curve (mcc) in case only the number is considered and of a maximal multiplicity curve (mmc) in case the multiplicity is also taken into account. In view of obtaining efficient algorithms for detecting the cyclicity, we investigate whether such mcc or mmc can be algebraic or even linear depending on certain general properties of the families or of their associated Bautin ideal. In any case by well chosen examples we show that prudence is appropriate.

  16. Structural investigation of the β-cyclodextrin complexes with linalool and isopinocampheol - Influence of monoterpenes cyclicity on the host-guest stoichiometry

    NASA Astrophysics Data System (ADS)

    Ceborska, Magdalena

    2016-05-01

    The crystal structures of the complexes of β-cyclodextrin with two chiral terpene alcohols are presented. (-)-Linalool forms the complex of a 2:2 host-guest stoichiometry, while the complex with (-)-isopinocampheol exhibits a 2:3 stoichiometry. The comparison of the crystal structures with the data for other complexes of β-cyclodextrin with chiral monoterpene alcohols obtained from Cambridge Structural Database (CSD) highlights the tendency of linear and monocyclic alcohols to form complexes of 2:2 stoichiometry whereas bicyclic alcohols prefer to form 2:3 host-guest inclusion complexes.

  17. Nonsurgical treatment of cyclic esotropia.

    PubMed

    Voide, Nathalie; Presset, Claudine; Klainguti, Georges; Kaeser, Pierre-François

    2015-04-01

    Cyclic esotropia is characterized by a 24-hour period of straight eye position followed by 24 hours of large-angle esotropia. Possible mechanisms include notably progressive loss of compensation of a latent strabismus. The classic treatment is surgical correction of the angle measured on the days with manifest deviation. We report the first case of cyclic esotropia successfully treated by prismatic correction of the latent strabismus present on "straight" days. PMID:25828819

  18. Rotational spectrum and carbon-13 hyperfine structure of the C3H, C5H, C6H, and C7H radicals.

    PubMed

    McCarthy, M C; Thaddeus, P

    2005-05-01

    By means of Fourier transform microwave spectroscopy of a supersonic molecular beam, we have detected the singly substituted carbon-13 isotopic species of C(5)H, C(6)H, and C(7)H. Hyperfine structure in the rotational transitions of the lowest-energy fine structure component ((2)Pi(12) for C(5)H and C(7)H, and (2)Pi(32) for C(6)H) of each species was measured between 6 and 22 GHz, and precise rotational, centrifugal distortion, Lambda-doubling, and (13)C hyperfine coupling constants were determined. In addition, resolved hyperfine structure in the lowest rotational transition (J = 32-->12) of the three (13)C isotopic species of C(3)H was measured by the same technique. By combining the centimeter-wave measurements here with previous millimeter-wave data, a complete set of (13)C hyperfine coupling constants were derived to high precision for each isotopic species. Experimental structures (r(0)) have been determined for C(5)H and the two longer carbon-chain radicals, and these are found to be in good agreement with the predictions of high-level coupled-cluster calculations. C(3)H, C(5)H, and C(7)H exhibit a clear alternation in the magnitude and sign of the (13)C hyperfine coupling constants along the carbon-chain backbone. Because the electron spin density is nominally zero at the central carbon atom of C(3)H, C(5)H, and C(7)H, and at alternating sets of carbon atoms of C(5)H and C(7)H, owing to spin polarization, almost all of the (13)C coupling constants at these atoms are small in magnitude and negative in sign. Spin-polarization effects are known to be important for the Fermi-contact (b(F)) term, but prior to the work here they have generally been neglected for the hyperfine terms a, c, and d.

  19. Boscovich force in spherical coordinates: some gravitational implications for deflection of light, Trojan orbits, Titius-Bode structures, ring structures and flat rotation rate of galaxies

    NASA Astrophysics Data System (ADS)

    Munera, Hector A.

    2015-08-01

    From philosophical considerations, Boscovich proposed around 1760 a unified force of nature. Boscovich’s force turns out to be a particular case of the novel solutions for the homogeneous wave equation in spherical coordinates found by the present author in the 1990s [Found. Phys. Lett. 10, 31-41 (1997)]. As noted by J. J. Thomson before Bohr’s quantum theory, Boscovich’s force exhibits quantization in energy and distance.For each quantum number, our non-harmonic functions of the first kind (NHF-1k) predict the existence of a discrete number of spherical surfaces in dynamical equilibrium (SSDE), leading to both Titius-Bode and ring structures. Predictions agree with observed Titius-Bode patterns in our planetary system, and in the moons of Mars, Jupiter, Uranus, Saturn, and Neptune. At distances beyond the quantum structure associated with SSDEs, for even NHF-1ks the force becomes Newton’s inverse-square law; however, odd NHF-1ks exhibit a non-zero limit as distance tends to infinity, which immediately explains the flat rotation rate of spiral galaxies without additional asumptions as dark matter or MOND models. The SSDEs provide the physical counterpart to the mathematical spheres that appear in the recent solution of the three-body problem and the orbits of Trojan moons [Suvakov & Dmitrasinovic, Phys. Rev. Lett. 110, 114301 (2013)]. The inner-most SSDE is a photon-sphere, but inside it there is a monotonously increasing repulsion, thus acting as a “white” hole; this could be relevant in the context of the contradictory appearance of a black and a white hole in the creation of black holes in the laboratory [Leonhard & Philbin ArXiv:0803.0669 5 March 2008]. Deflection of light does not occur at the SSDEs but at intermediate locations where gravitational attraction reaches a maximum. Calculation of deflection involves three non-Newtonian aspects: the force is not exactly Newton’s, the distance is larger than the radius of the physical surface, and

  20. Earth Rotation

    NASA Technical Reports Server (NTRS)

    Dickey, Jean O.

    1995-01-01

    The study of the Earth's rotation in space (encompassing Universal Time (UT1), length of day, polar motion, and the phenomena of precession and nutation) addresses the complex nature of Earth orientation changes, the mechanisms of excitation of these changes and their geophysical implications in a broad variety of areas. In the absence of internal sources of energy or interactions with astronomical objects, the Earth would move as a rigid body with its various parts (the crust, mantle, inner and outer cores, atmosphere and oceans) rotating together at a constant fixed rate. In reality, the world is considerably more complicated, as is schematically illustrated. The rotation rate of the Earth's crust is not constant, but exhibits complicated fluctuations in speed amounting to several parts in 10(exp 8) [corresponding to a variation of several milliseconds (ms) in the Length Of the Day (LOD) and about one part in 10(exp 6) in the orientation of the rotation axis relative to the solid Earth's axis of figure (polar motion). These changes occur over a broad spectrum of time scales, ranging from hours to centuries and longer, reflecting the fact that they are produced by a wide variety of geophysical and astronomical processes. Geodetic observations of Earth rotation changes thus provide insights into the geophysical processes illustrated, which are often difficult to obtain by other means. In addition, these measurements are required for engineering purposes. Theoretical studies of Earth rotation variations are based on the application of Euler's dynamical equations to the problem of finding the response of slightly deformable solid Earth to variety of surface and internal stresses.