Thickness Of Outer Shell Research Articles

Electrospun Core−Shell Structure Nanofibers from Homogeneous Solution of Poly(ethylene oxide)/Chitosan

The core−shell structure nanofibers of poly(ethylene oxide)/chitosan have been electrospun from the homogeneous solution of chitosan (CS, as shell) and poly(ethylene oxide) (PEO, as core). The preparation process of core−shell structure was quite simple and efficient without any complex electrospinning setup or post-treatment. The core−shell structure and major component of each layer had been characterized by TEM and further supported by SEM, XRD, DSC, and EDS studies. The blending ratio of PEO and CS, molecular weight of chitosan, and temperature of electrospinning were thought to be the key influence factors on the formation of core−shell structure. Because of the chitosan outer layer and shell thickness being controllable, the core−shell structure nanofiber would show a potential application for the biomedical fields involving wound care and tissue engineering.

Frequency dependence of switching field in the soft nucleus of FeSiB–CoNi microwires

AbstractThe dynamic (AC) switching field in the soft FeSiB bistable nucleus of the Fe77.5Si7.5B15–Co90Ni10 bi‐phase microwires family has been measured over the frequency range 20 Hz to 2 kHz. Microwires with a CoNi thickness ranging between 0.5 μm and 8 μm were studied. Results are well fitted by a power law dependence of the switching field H * on magnetic field frequency f. As the thickness of the harder CoNi outer shell is increased, the parameters which characterise the best fit experience noticeable changes. The origin of such behaviour is interpreted in terms of modifications in the soft FeSiB nucleus domain structure, accordingly to previous established models. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Spontaneous Vesicle Formation of Poly(ethylene oxide)−Poly(propylene oxide)−Poly(ethylene oxide) Triblock Copolymer

A novel method has been developed to prepare vesicles from aqueous solutions of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer, by adding anionic surfactant sodium dodecyl sulfate (SDS) and inorganic salt NaF. As determined by TEM and dynamic light scattering (DLS) measurements, the average diameter of vesicles is about 800 nm having 50 nm outer shell thickness. Identifying hydrophobic interactions between the block copolymers and the microenvironments around the vesicles using FTIR, 1H NMR, and fluorescence spectroscopy techniques revealed the vesicle formation mechanism. The spontaneously formed vesicles were further cross-linked by converting the terminal hydroxyl groups of block copolymers into aldehydes, and then chemically bridging the polymer chains by the reaction between aldehydes and diamine compounds. The cross-linked vesicles are proved much more stable than free vesicles even at higher dilutions. The obtained vesicles with good stability and biocompatibility are promising candidates for widespread applications.

Tunable near-infrared optical properties of three-layered metal nanoshells

The extinction spectra of a three-layered metal nanoshell, which consists of a particle with a dielectric core, a middle Ag (Au) layer, and an outer Au (Ag) shell, have been investigated by means of the Mie theory. With a decrease in the outer shell thickness or the middle layer thickness, the wavelengths of the localized surface plasmon resonance (LSPR) for SiO(2)-Ag-Au (SiO(2)-Au-Ag) nanoshells show distinct redshifts and the full widths at half maximum (FWHMs) for the dipole peaks in the extinction spectra decrease first and then increase. We have further investigated the influence of the embedding medium on the LSPRs for SiO(2)-Ag-Au and SiO(2)-Au-Ag nanoshells and found that the resonance wavelengths of the particles show redshift and the FWHM of the dipole peak increases with increasing the dielectric constant of the embedding medium. The calculated results indicate that the LSPR of the three-layered gold-silver nanoshells can be controlled to the near-infrared region by changing the geometry, which has practical biomedical application.

Core Sizes and Internal Structure of Earth's and Jupiter's Satellites

Models of the internal structure of the Moon and Galilean satellites of Jupiter—Io, Europa, and Ganymede—based on the geophysical (the mass and moment of inertia from recent Lunar Prospector and Galileo gravity measurements, and seismic velocities for the Moon), geochemical (the chemical composition of meteorites), and thermodynamic (modeling of phase relations and physical properties in the Na 2O–TiO 2–CaO–FeO–MgO–Al 2O 3–SiO 2–Fe–FeS system) constraints are constructed. Bulk composition of the Moon (enrichment in SiO 2, FeO, and refractories, and depletion in MgO) resembles neither the terrestrial matter nor the material of chondrites and achondrites. The radii of a lunar core are estimated to be 310–320 km for the Fe core, and 430–440 km for the eutectic Fe–FeS core. The Moon has the lowest Fe tot/Si weight ratio, 0.40–0.47, among the terrestrial planets, chondrites, and satellites of the outer Solar System. The correspondence between the density and moment of inertia values for bulk Io and rock–iron cores of Europa and Ganymede shows that their bulk compositions are, in general, similar and may be described by the composition close to L and LL chondrites. For such composition and density models, radii of the Fe core and eutectic Fe–FeS core are estimated to be R(Fe core)=590–630 km and R(Fe–FeS core)=830–875 km for Io, R(Fe core)=420–510 km and R(Fe–FeS core)=610–710 km for Europa, and R(Fe core)=580–650 km and R(Fe–FeS core)=820–900 km for Ganymede with an outer shell composed of the ice solid phases. The results of modeling support the hypothesis that Io, Europa, and Ganymede have a massive metallic core in which a magnetic field may be produced. Thickness of an ice–liquid outer shell in Europa is estimated to be 120–140 km (7–8% of total mass); thickness of a solid ice outer shell in Ganymede is expected to be 890–920 km (46–48% of total mass). Models showing the outer shell of Ganymede to consist of a mixture of water and ice are considered, and the thickness of an outer water-ice shell (780–850 km) and Fe–FeS core radii are estimated. The possibility of an inner liquid–water layer beneath the icy surface of Ganymede cannot be ruled out if the bulk composition of its rock–iron core were close to the composition of LL (rather than L) chondrites.

Europa's differentiated internal structure: inferences from four Galileo encounters.

Radio Doppler data from four encounters of the Galileo spacecraft with the jovian moon Europa have been used to refine models of Europa's interior. Europa is most likely differentiated into a metallic core surrounded by a rock mantle and a water ice-liquid outer shell, but the data cannot eliminate the possibility of a uniform mixture of dense silicate and metal beneath the water ice-liquid shell. The size of a metallic core is uncertain because of its unknown composition, but it could be as large as about 50 percent of Europa's radius. The thickness of Europa's outer shell of water ice-liquid must lie in the range of about 80 to 170 kilometers.

Analysis of an orthotropic cylindrical shell having a transversely isotropic core subjected to axisymmetric load

A long two-layered circular cylinder having a thin orthotropic outer shell and a thick transversely isotropic core subjected to an axisymmetric radialv line load has been analysed. For analysis of the outer shell the classical thin shell theory was adopted and for analysis of the inner core the elasticity theory was used. The continuity of stresses and deformations at the interface has been satisfied by assumming perfect adhesion between the layers. Numerical results have been presented for two different ratios of outer shell thickness to inner radius and for three different ratios of modulus of elasticity in the radial direction of outer shell to inner core. The results have been compared with the elasticity solution of the same problem to bring out the reliability of this hybrid method.

Theoretical conversion efficiency of relativistic electron beams into ion beams in the vicinity of a target

In order to reach the power density and total energy required for inertial confinement fusion targets using electron beams, a modular approach employing multiple diodes, plasma channel transport, and relativistic electron beam (REB) overlap is being pursued. This paper reports on an analytic study of the conversion efficiency of REB’s to ions by a combination of magnetic reflection and electrostatic reflexing of the electrons in the overlap region. The initial power density (but not total power) of the incident electron beam in this scheme is reduced by the ratio of electron beam overlap radius to final pellet radius squared, and the required power density gain in the overlap region is relaxed to unity. We find for a uniform REB energy distribution (the most probable distribution function at the overlap radius): (1) the ions cannot reach the full potential of the generator; (2) ion beam conversion efficiency remains low (∼5% in energy) and increases slowly with outer shell thickness; and (3) ion voltage remains almost constant for a wide range of generator voltages.