Partial Shell Research Articles

Partial shell-filled core-shell tecto(dendrimers): a strategy to surface differentiated nano-clefts and cusps.

Poly(amidoamine) (PAMAM) dendrimer shell reagents possessing either nucleophilic (i.e., primary amines) or electrophilic (i.e., carboxymethyl esters) functional groups have been covalently assembled around appropriate electrophilic or nucleophilic dendrimer core reagents to produce partial shell filled/core-shell tecto(dendrimers). Partial shell-filled products with saturation levels ranging from 28% to 66% were obtained. These metastable, remarkably monodispersed assemblies possess functionally differentiated nano-cusps and clefts that exhibit "autoreactive" behavior. Pacification of these autoreactive products with appropriate alkanolamine reagents produced robust, nonreactive, "hydroxy-amine-differentiated" surfaces that exhibit very active self-assembly properties. Based on the monodispersity, dimensional scaling, and electrophoretic similarities of PAMAM dendrimers to globular proteins, these assemblies may be viewed as crude biomimetics of classical core shell-type protein aggregates. These dimensionally larger, but analogous PAMAM core-shell tecto(dendrimer) architectures extend and complete a similar pattern of autoreactivity and pacification that was observed earlier for traditional mono PAMAM dendrimer core-shell modules possessing unsaturated shell levels.

Animated molecular dynamics simulations of hydrated caesium-smectite interlayers

Computer animation of center of mass coordinates obtained from 800 ps molecular dynamics simulations of Cs-smectite hydrates (1/3 and 2/3 water monolayers) provided information concerning the structure and dynamics of the interlayer region that could not be obtained through traditional simulation analysis methods. Cs+ formed inner sphere complexes with the mineral surface, and could be seen to jump from one attracting location near a layer charge site to the next, while water molecules were observed to migrate from the hydration shell of one ion to that of another. Neighboring ions maintained a partial hydration shell by sharing water molecules, such that a single water molecule hydrated two ions simultaneously for hundreds of picoseconds. Cs-montmorillonite hydrates featured the largest extent of this sharing interaction, because interlayer ions were able to inhabit positions near surface cavities as well as at their edges, close to oxygen triads. The greater positional freedom of Cs+ within the montmorillonite interlayer, a result of structural hydroxyl orientation and low tetrahedral charge, promoted the optimization of distances between cations and water molecules required for water sharing. Preference of Cs+ for locations near oxygen triads was observed within interlayer beidellite and hectorite. Water molecules also could be seen to interact directly with the mineral surface, entering its surface cavities to approach attracting charge sites and structural hydroxyls. With increasing water content, water molecules exhibited increased frequency and duration of both cavity habitation and water sharing interactions. Competition between Cs+ and water molecules for surface sites was evident. These important cooperative and competitive features of interlayer molecular behavior were uniquely revealed by animation of an otherwise highly complex simulation output.

ISO observations of symbiotic stars

We present ISO SWS and LWS observations of the symbiotic star HM Sge. The infrared emission longward of ~5μ m is dominated by a silicate dust shell. There is a number of high ionization emission lines superimposed on the dust continuum. The ISO continuum spectra can be fitted with a single, optically thick silicate dust shell but such a model does not fit other known properties of this system, such as the observed colours, the optical visibility of the red giant and the occurrence of a dust obscuration event. We favour a two component model in which in addition to a partial Mira dust shell, a second dust component is associated with the hot source. This second shell is located at the interface between the Mira dust shell and the dust free region carved out by the hot component. This picture corresponds closely to that deduced independently from radio observations. The two dust components are very different. The dust envelope associated with the Mira is very extended and optically thin, whereas the second dust component is geometrically rather thin but dust rich. The model not only fits the ISO data reasonably well, but is also compatible with other IR properties of HM Sge. The thin dust shell contributes strongly to the dust emission over most of the ISO range. It may be the combination of the two shells that makes a symbiotic a D type. The general agreement of the present models with ISO observations indicate that radiation (rather than collisions) as the main dust heating mechanism is sufficient.

EarlyChandraX‐Ray Observations of η Carinae

Subarcsecond-resolution Chandra observations of η Carinae reveal a 40'' × 70'' ring or partial shell of X-ray emission surrounding an unresolved bright central source. The spectrum of the central source is strongly absorbed and can be fitted with a high-temperature thermal continuum and emission lines. The surrounding shell is well outside the optical/infrared bipolar nebula and is coincident with the outer shell of η Car. The X-ray spectrum of the shell is much softer than that of the central source. The X-ray shell is irregular and only correlates well with optical features in which a bright X-ray knot coincides with a bright feature of the outer shell. Implications for the binary model of the central source are discussed.

ITAL]Hubble Space Telescope[/ITAL] Proper-Motion Measurements of the η Carinae Nebula

We present proper-motion measurements of the bipolar lobes and equatorial disk features ejected from η Carinae during the last century and deduce their relative ages in order to determine the likelihood of multiple ejection events. Hubble Space Telescope Wide Field Planetary Camera 2 images taken in 1994, 1995, and 1999 were compared, and the motions of small (~1'') patches throughout the nebula were measured. Assuming that the material has not been accelerated or decelerated, the projected expansion velocities of both lobes and two equatorial features (the Paddle and regions in the NN Jet) indicate that the bipolar lobes and fast equatorial ejecta have the same origin date, some 150 years ago during the Great Eruption. We also conclude that the ejection of the partial shell of outer debris preceded the Great Eruption by at least several decades or possibly a century, confirming that the nebula surrounding η Car represents at least two outburst events and maybe more.

The galactic plane region near $\mathsf{\ell=93^\circ}$

We present new Canadian Galactic Plane Survey radio continuum and 21 cm HI line observations of NRAO 655 (G93.4+1.8), plus radio recombination line observations, and optical H -line observations. The radio spectrum of NRAO 655 conrms its emission as thermal. From the 21 cm HI data we nd an atomic hydrogen cavity associated with this object atv' 71: 5k m s 1 . The cavity corresponds in position and size to the brightest radio continuum emission from NRAO 655. The corresponding kinematic distance is 8.8 kpc, placing NRAO 655 in the Perseus Arm. NRAO 655's linear size is therefore 70 pc 130 pc. To conrm the21 cm HI velocity we present the rst recombination line detection of NRAO 655 (H158 line, v' 71 km s 1 ), and the rst observations of a molecular cloud coinciding with NRAO 655 (at v' 72 km s 1 ). The rst optical detection of 656 nm H emission line features in NRAO 655 is also presented, and the H emission line brightness is determined. We suggest that the eastward extension of this strongly asymmetric object originates in a champagne outflow, and we estimate its age. We show that a single early-type star cannot be responsible for the outflow, whereas a group of later-type stars would suce. A partial HI shell is seen adjacent to the brightest part of NRAO 655; we suggest that it has been formed by dissociation of H2 in the molecular cloud.

WSRT and VLA Observations of the 6 Centimeter and 2 Centimeter Lines of H[TINF]2[/TINF]CO in the Direction of W58C1 (ON 3) and W58C2

Absorption in the J = 211–212 transition of formaldehyde at 2 cm toward the ultracompact H II regions C1 and C2 of W58 has been observed with the Very Large Array with an angular resolution of ~02 and a velocity resolution of ~1 km s-1. The high-resolution continuum image of C1 (also known as ON) shows a partial shell that opens to the northeast. Strong H2CO absorption is observed against W58C1. The highest optical depth (τ > 2) occurs in the southwest portion of C1 near the edge of the shell, close to the continuum peak. The absorption is weaker toward the nearby, more diffuse compact H II region C2, τ ≤ 0.3. The H2CO velocity (-21.2 km s-1) toward C1 is constant and agrees with the velocity of CO emission, main-line OH masers, and the H76α recombination line, but differs from the velocity of the 1720 MHz OH maser emission (~-13 km s-1). Observations of the absorption in the J = 110–111 transition of formaldehyde at 6 cm toward W58C1 and C2 carried out earlier with the Westerbork Aperture Synthesis Telescope at lower resolution (~4'' × 7'') show comparable optical depths and velocities to those observed at 2 cm. Based on the mean optical depth profiles at 6 and 2 cm, the volume density of molecular hydrogen n(H2) and the formaldehyde column density N(H2CO) were determined. The n(H2) is ~6 × 104 cm-3 toward C1. N(H2CO) for C1 is ~8 × 1014 cm-2, while that toward C2 is ~8 × 1013 cm-2.

Deep X-Ray Observations of Supernova Remnants G359.1–0.5 and G359.0–0.9 with ASCA

We present the results of deep ASCA observations of two shell-like radio supernova remnants (SNRs) located in the direction to the galactic center (GC) region. Unlike the radio morphology, G359.1-0.5 shows center-filled X-rays with prominent Kα lines of He-like silicon and H-like sulfur. The plasma requires at least two temperature components: a silicon-dominated cool plasma of 0.6 keV temperature and a sulfur-dominated higher temperature plasma of 4.4 keV. Because the absorption column is ∼ 6× 1022 H cm-2, this SNR would be near to the GC. The spherical plasma is attributable to supernova ejecta with the total mass of Si and S being about 0.1 M⊙ and 0.3 M⊙, respectively. X-rays from G359.0-0.9 trace the partial shell structure of the radio emission. The spectrum is well fitted to a single-temperature plasma of 0.4 keV with a non-solar abundance of magnesium or iron. Because the absorption column is not very large, ∼ 1.8× 1022 H cm-2, G359.0-0.9 would be in front of the GC region. The total supernova energy, interstellar density near to the X-ray emitting shell, and age of the SNR are estimated to be 1.2× 1051 erg, 0.5 cm-3, and 1.8× 104 yr, respectively. We also discuss possible implications on the origin of the large-scale hot plasma surrounding the GC.

113 反転形安全破裂板の飛移り座屈現象に残留応力が及ぼす影響に関する研究(O.S.1-3 適応構造/安全構造)(オーガナイズドセッション1 知的材料・構造システム)

In safety valve of pressure vessel, reverse safety rupture discs have been in use. They make use of snap-through buckling of partial spherical shell. Especially, bulging method has the advantage of simple forming in production. The buckling pressure of a partial spherical shell with a flange formed by this method is much lower than one of partial spherical shell without a flange obtained by buckling. Therefore, it is very difficult to predict it in safety rupture discs. In this study, static experiments and finite element analyses were carried out and results concluded that the residual stresses locally developed in plastic forming much the buckling pressure much lower.

Analysis of Forced Vibration of Rotating Thick Shells of Revolution Subjected to Prestresses.

Numerical analysis method of transient forced vibration responses of thick rotating shells of revolution is developed. The method can consider the anisotropic laminated layers and the effects of prestresses such as the in-plane compression stress, internal pressure and torsional shear stress. Finite element method is applied using truncated conical shell element based on the first-order shear deformation theory, and the finite strain is considered to execute the non-linear analysis of the quasi-static displacements due to the rotation and prestresses except for the case of internal pressure. Transient responses of a laminated truncated conical shell and a partial spherical shell subjected to concentrated step and half-wave sinusoidal shock forces are calculated and compared with the previous results based on the classical shell theory. Finally, the effects of three kinds of prestresses are systematically examined by using a truncated conical shell model with the both ends clamped.

Hybrid simulation of magnetotail reconnection

Magnetic reconnection is studied by using a large-scale two-dimensional hybrid simulation code that treats the ions fully kinetically and the electrons as a massless fluid. Reconnection is realised by localising an anomalous resistivity in a kinetic tail equilibrium. Within a distance of about 80 lobe ion inertia lengths tailward from the neutral line the fast reconnection jet is characterised over most of the region by partial shell type ion distributions; i.e., the distribution in the central current sheet is not thermalised. Inward drifting cold lobe ions perform in the centre of the reconnection wedge due to the small magnetic field curvature Speiser-type orbits and are subsequently ejected again onto lobe field lines. This situation is similar to the collisionless reconnection scenario described by Hill (1975). The cross-tail current of the thin current sheet is supported by the drifting ions. This current sheet warps and an instability develops further away from the neutral line, resulting in a filamentation of the cross tail current. The simulation demonstrates that ion kinetic effects are of importance for the large-scale structure of the magne-totail during near-Earth reconnection.

Generalized ion ring instability driven by ions with a partial shell distribution

A generalized ion ring instability driven by energetic ions with a shell velocity distribution, which has a central pitch angle at 90°, is studied. We consider waves propagating in both parallel and oblique direction as well as different pitch angle spreads of a partial shell. These unperturbed distributions represent different stages during the time evolution of an ion distribution, that is a ring initially. The evolution is attributed to pitch angle scattering due to wave‐particle interactions. Numerical results obtained by us show that the instability diminishes rapidly, especially for oblique propagation, while the pitch angle spread increase.

Controlled Adsorption of Carbon Nanotubes on Chemically Modified Electrode Arrays

For applications of carbon nanotubes in electronic components site-specific assembly of nanotubes onto patterned substrates is required. The Figure shows, as an example, a surface modification that favors attachment of nanotubes to an electrode (Au/Pd). The adsorbed nanotube (gray) has a partial surfactant shell and there is an alkanethiol monolayer between the nanotube and electrode. The Si/SiO2 wafer is unaffected.

Controlled Adsorption of Carbon Nanotubes on Chemically Modified Electrode Arrays

For applications of carbon nanotubes in electronic components site-specific assembly of nanotubes onto patterned substrates is required. The Figure shows, as an example, a surface modification that favors attachment of nanotubes to an electrode (Au/Pd). The adsorbed nanotube (gray) has a partial surfactant shell and there is an alkanethiol monolayer between the nanotube and electrode. The Si/SiO2 wafer is unaffected.

Five Mature Supernova Remnants in the Large Magellanic Cloud

Radio observations of the extended supernova remnants (SNRs) N23:SNR, N120:SNR, 0525-660, N49, and N44:shell 3 in the Large Magellanic Cloud show a variety of structures and little difference from shell SNRs in the Milky Way. N23:SNR and N120:SNR have very regular outlines, but the shells are much brighter on the sides toward the most prominent parts of their associated H II region complexes, probably reflecting density gradients in the surroundings. N23:SNR has a mixed magnetic field orientation and a mean magnetic field strength of 15 μG. Its magnetic energy is about 4 times less than the relativistic electron energy. SNR 0525-660 appears to be isolated in the northern region of the LMC; it has a partial shell of thin filaments and some bright, patchy emission across the face of the remnant. N49, one of the brightest SNRs in the LMC, shows the strongest polarized emission in the west, where the total intensity is very weak, probably as a result of high magnetic field organization. N44:shell 3, on the northeastern edge of a very large H II region complex, is definitely confirmed as an SNR but has a different central position and outline at radio wavelengths than it does at X-ray wavelengths.

Ion kinetic effects in magnetic reconnection: Hybrid simulations

Magnetic reconnection in a low beta plasma is studied by using a large‐scale two‐dimensional hybrid simulation code that treats the ions fully kinetically and the electrons as a massless fluid. Reconnection is realized by localizing an anomalous resistivity in the the center of a Harris‐type current sheet. The results are applicable to reconnection in the geomagnetic tail. Within a distance of about 200 ion inertial lengths from the neutral line the fast reconnection jet is characterized over most of the region by partial shell type ion distributions; i.e., the distribution in the central current sheet is not thermalized. Inward drifting cold lobe ions perform in the center of the reconnection wedge due to the small magnetic field curvature Speiser‐type orbits and are subsequently ejected again onto lobe field lines. This stadium is similar to the collisionless reconnection scenario described by Hill [1975]. The cross‐tail current of the thin current sheet is supported by the drifting ions. This current sheet warps and an instability develops, which leads further away from the neutral line to a filament ation of the cross tail current. These simulations suggested that after near‐Earth reconnection proceeds to lobe magnetic field lines a postplasmoid plasma sheet with a thin current sheet builds up, which is of a boundary layer type. The thin current sheet is instable. At about 200 ion inertial lengths away from the neutral line the instability has reached a nonlinear state and the cross‐tail current becomes patchy; the incoming and ejected cold lobe ions are isotropized in the ensuing magnetic field and thus constitute a hot plasma sheet distribution. This can then support the occurrence of slow mode shocks at the boundary of the reconnection layer with backstreaming ions upstream of the shocks.

The effect of a partial resistive shell on the magnetohydrodynamical stability of tokamak plasmas

A comprehensive theory is developed to determine the effect of a partial resistive shell on the growth rate of the external kink mode in a low-β, large aspect-ratio, circular flux-surface tokamak. In most cases, it is possible to replace a partial shell by a complete “effective shell” of somewhat larger radius. In fact, the radius of the effective shell can be used to parametrize the ability of a partial shell to moderate the growth of the external kink mode. It is necessary to draw a distinction between “resonant shells,” for which the eddy currents excited in the shell are able to flow in unidirectional continuous loops around the plasma, and “nonresonant shells,” for which this is not possible. As a general rule, resonant shells perform better than similar nonresonant shells. The theory is used to derive some general rules regarding the design of incomplete passive stabilizing shells. The theory is also employed to determine the effectiveness of two realistic feedback stabilization schemes for the resistive shell mode, both of which only require a relatively small number of independent feedback controlled conductors external to the plasma.

ROSATObservations of the Supernova Remnant CTB 1

We present ROSAT PSPC observations of the supernova remnant CTB 1 (G116.9 +0.2). The remnant is detected for the first time in the X-ray region. The X-ray morphology places the remnant into the class of center-filled remnants with a centrally peaked X-ray emission profile and accompanying optical and radio shells. The emission is consistent with a thermal plasma with T = 3 × 106 K and absorption NH = 7 × 1021 cm-2. A "breakout" along the northeast rim of the remnant is coincident with the position of an X-ray pulsar. A much larger feature appears to be a partial shell which may be associated with a previous supernova remnant that swept the area around CTB 1 clean. The appearance of the remnant is most easily explained by evaporating clouds. Projection effects caused by an asymmetric remnant are discussed as another, less plausible, explanation.

Supplemental partial height concert shell incorporating quadratic diffusor panels

A recently completed project to modify the acoustical performance of Boettcher Concert Hall included the addition of several modifications to improve cross‐stage hearing of the musicians. Boettcher Concert Hall utilizes an in‐the‐round seating arrangement, therefore, the enclosure design was restricted to partial height. Custom designed quadratic diffusors were incorporated into the concert shell design. Tests were conducted both on an individual panel section in an anechoic chamber and in situ. The results of the tests are presented.

Ab initio approach to the development of interatomic potentials for the shell model of silica polymorphs

We have developed a new method for deriving parameters for the shell model of silica polymorphs. All parameters for the shell model are derived in a self-consistent way from ab initio energy surfaces, polarizabilities and dipole moments of small clusters. This yields an ab initio partial charge shell model potential. The predictive power of our potential is demonstrated by presenting predictions for the structure of α-quartz, α-cristobalite, coesite, stishovite and the IR spectrum of α-quartz which are compared with experiment and predictions of the widely used potentials of Jackson and Catlow, and Kramer, Farragher, van Beest and van Santen.