Direction Of Rotation Axis Research Articles

Molecular Dynamics Simulation of [Gd(egta)(H2O)]− in Aqueous Solution: Internal Motions of the Poly(amino carboxylate) and Water Ligands, and Rotational Correlation Times

Molecular dynamics simulations of [Gd(egta)(H(2)O)](-) (egta(4-)=3,12-bis(carboxymethyl)-6,9-dioxa-3,12-diazatetradecanedioate(4-)) have been performed without any artificial constraint on the first coordination sphere, such as covalent bonds between the Gd(3+) and the coordination sites. Two new crystallographic structures were determined for this gadolinium chelate and used to start two molecular dynamics simulations. [Gd(egta)(H(2)O)](-) and [Gd(egta)](-) were both observed during the simulations, with a mean volume for the reaction of dissociation [Gd(egta)(H(2)O)](-)-->[Gd(egta)](-)+H(2)O of +7.2 cm(3)mol(-1), which corroborates the previously published experimental value of +10.5 cm(3)mol(-1). Changes in the conformation of the complex with the inversion of several dihedral angles are observed in the simulations independently from the water dissociation. Very fast changes of the third-order rotation axis direction of the Gd(3+) coordination polyhedron (of symmetry D(3h)) are observed during the simulations and are related to the mechanism of electronic relaxation of the complex. Different rotational correlation times (tau(R)) were calculated from the simulations on various observables of the complex. Protons of the inner sphere have different tau(R). The mean tau(R) of the two Gd-HW(HW=hydrogen of water molecule) vectors is 72% lower than tau(R) of the complex, and 75% lower than tau(R) of the vector Gd-OW (OW=oxygen of water molecule). This discrimination of the tumbling rates should be taken into account in future global (17)O NMR, EPR and NMRD (nuclear magnetic relaxation dispersion) data analysis.

The Confinement and Breakout of Protostellar Winds: Quasi‐Steady Solution

The driving sources of optical jets and molecular outflows may be accreting protostars. Accordingly, we consider the interaction of a spherical, protostellar wind with the time-dependent infall from a rotating parent cloud. The two flows collide in a shocked shell, whose evolution we follow numerically. Both wind and infall material enter the shell and flow down toward an equatorial disk. We assume that the shell is axisymmetric and evolves quasi-steadily, i.e., over a period long compared to the crossing time of the transverse flow. At early times, no shell exists, as infall crushes the wind against the protostellar surface. When a steady state shell does first appear, it is roughly spherical, with radius r ~ 1013 cm. Gradually, the surface both swells and elongates in the direction of the cloud's rotational axis. This elongation is a response to the increasing centrifugal distortion of the infall. On the other hand, the main force confining the shell is not the infall ram pressure but stellar gravity. Elongation continues until the polar radius extends to about 1016 cm, at which point our quasi-steady assumption breaks down. This event, which typically occurs some 105 yr after the start of infall, marks the breakout of the wind. Comparing our theoretical results to observed outflow sources, we find that both the initial appearance and disruption of our shell occur too late after formation of the central protostar. We speculate that a fully time-dependent calculation will yield a phase of periodic advance and retreat of the shell, leading eventually to breakout.

The effect of the magnetopause shapes of Jupiter and Saturn on magnetosheath parameters

The solar wind flow past nonaxisymmetric magnetospheres exhibits features which are absent in the case of axisymmetric magnetospheres such as that of Earth. We discuss results obtained by a numerical integration of the dissipationless MHD equations, under simplifying assumptions, and apply them to the two outer planets Jupiter and Saturn, both of whose magnetospheres depart substantially from axisymmetry. We model these magnetospheres as paraboloids with two different radii of curvature at the subsolar point, L 0 and L 1, where L 0 and L 1 refer to a magnetopause cut comtaining the rotational axis, and to the rotational equator, respectively ( L 0 < L 1). The degree of flattening is expressed by a parameter q:= L 0 L 1 , and, following earlier modelling and data analysis work, we set q = 0.35 for Jupiter and q = 0.64 for Saturn. We find here that the structure and behaviour of physical parameters in the magnetosheath of Saturn is intermediate to that at Earth and at Jupiter. For both planets, the thickness of the magnetosheath and the width and structure of the plasma depletion layer are found to be strong functions of the orientation of the interplanetary magnetic field (IMF). The effect of the IMF on the magnetosheath is strongest (weakest) when the IMF is directed perpendicular (parallel) to the rotational equator. For any intermediate orientation, a smooth rotation of the magnetosheath magnetic field towards the direction of the planet's rotational axis is superimposed on the field strength enhancement (and the density reduction) as the respective magnetopauses are approached. For Saturn, we study the dependence of magnetosheath parameters for various IMF orientations at two Alfvén Mach numbers. Throughout, we compare our results to similar calculations of solar wind flow past Earth.

Numerical modelling of solar wind flow about nonaxisymmetric magnetospheres: Planets Jupiter and Saturn

We discuss results on the solar wind flow past the non-axisymmetric magnetospheres of planets Jupiter and Saturn obtained by integrating numerically the dissipationless MHD equations under simplifying assumptions. We model these equatorially broadened magnetospheres as paraboloids with two different radii of curvature at the subsolar point. The thickness of the magnetosheath and the width and structure of the plasma depletion layer are found to be strong functions of the orientation of the interplanetary magnetic field (IMF). The effect of the IMF on the magnetosheath is strongest (weakest) when the IMF is directed perpendicular (parallel) to the rotational equator. For any intermediate IMF orientation, a smooth rotation of the magnetosheath magnetic field towards the direction of the planet's rotational axis is superimposed on the field strength enhancement (and the density reduction) as the respective magnetopauses are approached. These effects are more pronounced at Jupiter than at Saturn.

Lightcurves, pole direction and shape of asteroids 121 Hermione, 150 Nuwa, 236 Honoria, 287 Nephthys and 377 Campania

Rotational periods, V lightcurves, B-V color indexes, rotation axis direction and shape of five asteroids are presented. The B and V photoelectric observations were carried out at Serra la Nave stellar station of Catania Astrophysical Observatory during March and August 1992 and May, July and September 1993. The synodic rotational periods determined are: 121 Hermione ( P = 9 h.238±0 h.010), 150 Nuwa ( P = 8 h.140±0 h.005), 236 Honoria ( P = 12 h.333±0 h.006), 287 Nephthys ( P = 7 h.580±0 h.004), 377 Campania ( P = 8 h.48±0 h.01). No variation of the (B-V) color with the rotation appears for the asteroids observed. The determination of the pole direction and shape is performed by applying the Amplitude-Magnitude method (Zappalà et al., Asteroids, Comets, Meteors, pp. 73–76. Uppsala Universitet, Reprocentralen, HSC, Uppsala, 1983) to the data collected by us and to those reported in the literature.

Planetary-Induced Nutation of the Earth: Direct Terms

Small torques by the planets can alter the direction of the Earth's rotation axis in space. These direct planetary-induced nutations have been computed using a numerical technique. 62 nutation terms with periods between 0.2 and 883 yr are presented. The maximum,nutation is 0.5 marcsec. Also given are planetary-induced rates and accelerations of precession and obliquity.

Measurement of diurnal and semidiurnal rotational variations and tidal parameters of Earth

We discuss the determination of diurnal and semidiurnal variations in the rotation rate and the direction of rotation axis of Earth from the analysis of 8 years of very long baseline interferometry (VLBI) data. This analysis clearly show that these variations are largely periodic and tidally driven; that is, the periods of the variations correspond to the periods of the largest lunar and solar tides. For rotation rate variations, expressed in terms of changes in universal time (UT), the tidal lines with the largest observed signals are O1 (amplitude 23.5 microseconds in time (μs), period 25.82 solar hours); K1 (18.9 μs, 23.93 hours); M2 (17.9 μs, 12.54 hours); and S2 (8.6 μs, 12.00 hours). For variations in the direction of the rotation axis (polar motion), significant signals exist in the retrograde semidiurnal band at the M2 and S2 tides (amplitudes 265 and 119 microarc seconds (μas), respectively); the prograde diurnal band at the O1, K1, and P1 tides (amplitudes 199,152, and 60 μas, respectively); and the prograde semidiurnal band at the M2 and K2 tides (amplitudes 58 and 39 μas, respectively). Variations in the retrograde diurnal band are represented by corrections to the nutations of Earth's body axes, and our estimates here are consistent with previous estimates except that a previously noted discrepancy in the 13.66‐day nutation (corresponding to the O1 tide) is largely removed in this new analysis. We estimate that the standard deviations of these estimates are 1.0 μs for the UTl variations and 14–16 μas for the polar motion terms. These uncertainties correspond to surface displacements of ∼0.5 mm. From the analysis of atmospheric angular momentum data we conclude that variations in UTl excited by the atmosphere with subdaily periods are small (∼1 μs). We find that the average radial tidal displacements of the VLBI sites in the diurnal band are largely consistent with known deficiencies in current tidal models, i.e., deficiencies of up to 0.9 mm in the treatment of the free core nutation resonance. In the semidiurnal band, our analysis yields estimates of the second‐degree harmonic radial Love number h2 at the M2 tide of 0.604+i0.005±0.002. The most likely explanation for the rotational variations are the effects of ocean tides, but there may also be some contributions from atmospheric tides, the effects of triaxiality of Earth, and the equatorial second‐degree‐harmonic components of the core‐mantle boundary.

Liquid core structure and PKP station anomalies derived from PKP(BC) propagation times

PKP(BC) travel time residuals in the distance range 148.5–155.5° have been extracted from the catalogues of the International Seismological Centre and inverted to retrieve possible heterogeneities or anisotropy at the base of the liquid core, and PKP(BC) station anomalies. A binning has first been applied to the data to minimize the biases that result from the uneven sampling of the Earth by the PKP(BC) rays and from the heterogeneities in the source regions. For the liquid core structure, the data reveal weak heterogeneities, with travel time delays slightly higher near the South Pole and lower beneath southeast Asia, but most of these variations stay below the error bar level. The search for anisotropy at the base of the liquid core also leads to inconclusive results, with a weak tendency for lower velocities in the direction of the Earth's rotation axis. Station anomalies appear to be by far the major contribution to the PKP(BC) residuals. Their values are compared with the P station corrections, and with the values predicted by lower-mantle tomographic models. They show that the lower mantle makes an important contribution to the PKP residuals at medium wavelengths; these delays are generally underpredicted by tomographic models.

Large deformation analysis of shells with finite element method based on the S-R decomposition theorem

A finite element formulation based on the S-R decomposition theorem of strain and rotation is presented for the analysis of finite strain and finite rotation of shells. The element adopted is a modified curved shell element.The displacement fixed is expressed as nonlinear functions of translations, direction of rotation axis and rotation angle of nodes on the midsurface. The displacement model is very general and is suitable for arbitrary rotation of shells. The computer program based on the formulation is simple and efficient. Numerical examples are given.

Rotation axes of asteroids: Results for 14 objects

In this paper results of determinations of the rotation axis direction (as given by ecliptic coordinates of its intersection with geocentric celestial sphere) for 14 asteroids are presented for which a sufficient number of good observations are available. The calculation is performed by using the improved amplitude-magnitude method developed by V. Zappalà, M. Di Martino, P. Farinella, and P. Paolicchi (1983, In Asteroids, Comets, Meteors, pp. 73–76). Additionally, an improvement of the method is described regarding a weighting procedure. Whenever possible, the results are compared with already existing data, coming from other methods (mainly from photometric astrometry). In general, very good agreement was found, which can be considered as strongly encouraging for further application of the adopted procedure. Some preliminary approaches for a statistical investigation are given.

Modulation of galactic cosmic ray anisotropy in heliomagnetosphere: Average sidereal daily variation

We formulate the modulation of galactic anisotropy of cosmic rays caused by their orbital deflection in the heliomagnetosphere. According to the formulation, the average sidereal i-th harmonic daily variation ( i = 1,2,…) produced from the anisotropy from an arbitrary direction can be expressed by a linear combination of three basic vectors for uni-directional anisotropy and five basic vectors for bi-directional anisotropy. These vectors are obtained by calculating trajectories of cosmic rays (20−10 4GV) in a model magnetosphere having Parker's Archimedian spiral structure with a flat or a wavy neutral sheet in either of two polarity states, one is called “Positive” state (away field in the northern space of the neutral sheet and toward field in the southern space) and the other is called “Negative” state (reversed state of the above). Among general characteristics of the sidereal daily variations, the most remarkable features are: (1) The observable variations in low rigidity (≲ 2000 GV) can be produced even from an uni-directional anisotropy in the direction of the Earth's rotation axis. These variations are strongly dependent on the polarity state, i.e., they are greater in the Positive state than in the Negative. (2) Those produced from the anisotropy in the Equatorial plane also show the polarity dependence but contrary to the previous case they are greater in the Negative state than in the Positive. Their magnitude in the former state is not so small even in the extremely low rigidity (∼ 100 GV) as compared with that in high rigidity region. (3) These general characteristics are not altered by the introduction of the wavy neutral sheet or the magnetic irregularities, but the variations are affected more or less, depending on the heliolatitudinal extent of the wavy sheet or the degree of cosmic ray scattering with the irregularities, (4) Sidereal daily variation for the wavy sheet shows a toward-away field dependence similar to that of Swinson-type of solar origin, but the dependence is predominant in intermediate rigidity region (∼ 500 GV), in marked contrast to that of solar origin. (5) Finally, whichever its direction may be, the uni-directional anisotropy produces the sidereal diurnal variation common to two conjugate stations in the Northern and Southern hemisphere. If there is any difference between the observed variations at the stations, it should be interpreted as being due to higher order anisotropy such as the bi-directional anisotropy.

A versatile target manipulator for use in ultra-high vacuum

A target manipulator for use in ultra-high vacuum is described. With this manipulator a target can be translated 20 mm in three mutually perpendicular directions and rotated around three mutually perpendicular rotation axes. The directions of the rotation axes are independent of each other. A special feature of this design is that the third rotation (the tilt) does not change the direction of the azimuthal rotation axis. The azimuthal and polar rotation have a range of 360°. The target temperature and beam currents can be measured at the back of the target. The target can be heated by electron bombardment on the front or by an electrical heater at the back. The whole manipulator can be mounted on a 4″ flange of the target chamber. To perform the rotation the manipulator head requires a volume with diameter of 50 mm at the centre of the target chamber. Targets with a maximum diameter of 13 cm can be inserted. Only materials suited for ultra-high vacuum are used in the construction.

New problems in nutation calculation

The effects of Oppolzer terms on the determination of latitude variation, polar motion and declination are discussed. We suggest that the celestial pole may be defined as the intersection of the rotation axis, corrected for the lunisolar polar motion with the celestial sphere. Or approximately, it may be defined as the intersection of the diurnal mean direction of rotation axis with the celestial sphere.

Anisotopy of migration and faceting of large-angle grain boundaries in ice bicrystals

Abstract Migration of large-angle grain boundaries in ice bicrystals has been investigated by the method of capillary force developed by Sun and Bauer (1970 a, b). Strong anisotropy of the migration rate was observed between two cases when the boundaries moved parallel and perpendicular to the direction of rotation axis ω. X-ray diffraction topographic observations of grain boundaries (〈1010>/34〉) during migration by the capillary force revealed that they had a strong tendency to be parallel to low-energy facets and that the boundaries that were not parallel to any low-energy facets moved faster than those that were parallel. From observations in three specific directions of the normals of these facets, it was concluded that the facets were the high-density planes of the coincidence site lattice composed of two adjacent crystals. The anisotropy of the migration rate was interpreted in terms of the difference in the density of steps among facets: the non-faceted boundary with many steps moves faster than t...

Mariner 9 Celestial Mechanics Experiment: Gravity Field and Pole Direction of Mars

Analysis of the Mariner 9 radio-tracking data shows that the Martian gravity field is rougher than that of Earth or the moon, and that the accepted direction of Mars's rotation axis is in error by about 0.5 degrees . The new value for the pole direction for the epoch 1971.9, referred to the mean equatorial system of 1950.0, is right ascension alpha= 317.3 degrees +/- 0.3 degrees , declination delta = 52.6 degrees +/- 0.2 degrees . The values found for the coefficients of the low-order harmonics of Mars's gravity field are as follows: J(2)=(1.96+/-0.01)x10(-3), referred to an equatorial radius of 3394 kilometers; C(22) = -(5 +/- 1) x 10(-5); and S(22) = (3 +/- 1) x 10(-5). The value for J(2) is in excellent agreement with the result from, Wilkins' analysis of the observations of Phobos. The other two coefficients imply a value of (2.5 +/- 0.5) x 10(-4) for the fractional difference in the principal equatorial moments of inertia; the axis of the minimum moment passes near 105 degrees W.

Variable-speed single-phase induction motor

A present invention provides an inexpensive variable speed single phase induction motor capable of obtaining high efficiency performance and variable speed characteristic such as the BLDC motor also not include the additional expensive inverter drive. The present invention according to the variable speed single phase induction motor includes a motor casing, a rotary shaft rotatably coupled to the motor casing, the rotor core and the said rotor core rotates integrally coupled to the said rotary shaft an induction rotor provided with a the inserted conductor bars, the stator the induction rotor plurality arranged to be separated from each other in the rotation axis direction comprises a hollow to be inserted, of which the part or the whole forming a rotating magnetic field When, inserted between the induction rotor and the stator, wherein a freely rotatably coupled to the rotating shaft, characterized in that it comprises a plurality of synchronous rotor respectively corresponding to the stator. .Field

Isotropic Rotational Brownian Motion

The Brownian motion of the orientation of any rigid body (sphere, set of rectangular axes, etc.) is calculated for the case of individual random infinitesimal rotations whose probabilities are independent of the direction of the axis of rotation (isotropic case). The calculations are carried out by means of quaternions; the more important formulas are also given in terms of the rotation angle and axis direction. The unit solution, or distribution of orientations arising from a specified initial orientation, is found as a series converging rapidly for not-too-small times. It turns out to be expressible in terms of a theta function, and thus there is also available a series converging rapidly for small times. The use of the unit solution as a propagation function is discussed briefly, and is illustrated by verification of the iteration property of the unit solution.