Drugs have been released from an array of reservoirs in a biodegradable, polymeric microdevice. The reservoirs are formed in a polylactic acid (PLA) substrate and covered with a thin polymer membrane of a faster degra...
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Spinel tin nitride (Sn 3 N 4 ) was prepared by high-pressure solid-state metathesis reactions. Tin tetraiodide was reacted with lithium nitride and ammonium chloride in a piston–cylinder apparatus at 623 K and 2.5 GP...
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Spinel tin nitride (Sn 3 N 4 ) was prepared by high-pressure solid-state metathesis reactions. Tin tetraiodide was reacted with lithium nitride and ammonium chloride in a piston–cylinder apparatus at 623 K and 2.5 GPa. Powder X-ray diffraction combined with Rietveld refinement confirmed the spinel structure, with a lattice constant of a = 9.0144(1) Å. Raman spectroscopy revealed five active vibrational modes at 160, 252, 416, 524, and 622 cm −1 , which are consistent with the spinel structure. Mid-infrared spectroscopy exhibited only a Sn–N stretching mode at 547 cm −1 . Transmission electron microscopy was used to reveal particle size and morphology. Electron probe microanalysis was used to verify the elemental composition.
High energy synchrotron x-rays (124.63 keV) are used to investigate the initial stages of the devitrification for the Zr70Pd20Cu10 metallic glass prepared by melt-spinning (MS). Due to the excellent signal:noise, we a...
High energy synchrotron x-rays (124.63 keV) are used to investigate the initial stages of the devitrification for the Zr70Pd20Cu10 metallic glass prepared by melt-spinning (MS). Due to the excellent signal:noise, we are able to determine the initial nucleating phase by analyzing the differences in the total scattering function S(Q) as a function of time at a temperature ~ 50 K below the crystallization temperature. The alloy undergoes a structural relaxation prior to nucleation and growth. Devitrification proceeds from nucleation of the icosahedral phase. The differential pair distribution function (dPDF) indicates that the as-quenched alloy may have icosahedral-like order which undergoes local rearrangement to true icosahedral order at an annealing temperature 50 K below the crystallization temperature. More importantly, time-resolved high-energy synchrotron is shown to have excellent sensitivity to the initial atomic rearrangements preceding nucleation in metallic glasses.
We develop the delta-P1 approximation for frequency-domain radiative transport predictions. Comparison with Monte Carlo simulations establishes superior accuracy of the delta-P1 approximation relative to the standard ...
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A modified Mach Zehnder interferometer system has been developed to measure surface motion with 4 ns temporal resolution and 0.2 nm displacement sensitivity. We discuss its use to measure the optical properties of hom...
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MEMS devices are manufactured using similar microfabrication techniques as those used to create integrated circuits. They often, however, have moving components that allow physical or analytical functions to be perfor...
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Colloid formation and subsequent laser-induced bleaching in fluorite has been studied by transmission election microscopy and electron diffraction. At high incident electron-beam (e-beam) energies, Ca colloids with di...
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The stability of gold nanoparticles modified with heterobifunctional poly (ethylene glycol) (PEG) were investigated. An effective method for preparing hetero-bifunctional PEG by anionic ring-opening polymerization was...
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ISBN:
(纸本)1877040193
The stability of gold nanoparticles modified with heterobifunctional poly (ethylene glycol) (PEG) were investigated. An effective method for preparing hetero-bifunctional PEG by anionic ring-opening polymerization was also developed. Streptavidin-PEG gold nanoparticle showed extremely high response with biotinylated surface plasmon resonance (SPR) sensors. PEG-modified gold nanoparticles showed remarkable stability in physiological conditions, such as the solution of high ionic strength.
We have performed a detailed study of the magnetic and structural properties of the compound Nd5(Si0.6Ge0.4)4 by means of neutron powder diffraction, magnetization, linear thermal expansion, and magnetostriction exper...
We have performed a detailed study of the magnetic and structural properties of the compound Nd5(Si0.6Ge0.4)4 by means of neutron powder diffraction, magnetization, linear thermal expansion, and magnetostriction experiments. A coupled magnetic and crystallographic first-order transformation from a room-temperature monoclinic Gd5Si2Ge2-type paramagnetic state to a low-temperature orthorhombic Gd5Si4-type ferromagnetic structure takes place on cooling at ∼68K. This magnetostructural transition shifts towards higher temperatures by the application of an external magnetic field at a rate of 0.11(1)K∕kOe, which is lower than the ∼0.6to∼0.3K∕kOe observed in the Gd5(SixGe1−x)4 and Tb5(SixGe1−x)4 compounds. The magnetostructural transformation cannot be completed in the isothermal regime by a 120kOe magnetic field. It is suggested that the single-ion anisotropy of the Nd ions hinders the completion of the field-induced transformation. The existence of a simultaneous magnetic and crystallographic transformation in this alloy, which is in sharp contrast with other previously studied Nd5(SixGe1−x)4 alloys, is discussed in terms of the role of interstitial impurities in triggering and coupling/decoupling the crystallographic transition.
The room temperature crystal structures of Er5SixGe4−x alloys change systematically with the concentration of Ge from the orthorhombic Gd5Si4-type when x=4, to the monoclinic Gd5Si2Ge2 type when 3.5⩽x⩽3.9 and to the o...
The room temperature crystal structures of Er5SixGe4−x alloys change systematically with the concentration of Ge from the orthorhombic Gd5Si4-type when x=4, to the monoclinic Gd5Si2Ge2 type when 3.5⩽x⩽3.9 and to the orthorhombic Sm5Ge4 type for x⩽3. The Curie-Weiss behavior of Er5SixGe4−x materials is consistent with the Er3+ state. The compounds order magnetically below 30K, apparently adopting complex noncollinear magnetic structures with magnetization not reaching saturation in 50kOe magnetic fields. In Er5Si4, the structural-only transformation from the monoclinic Gd5Si2Ge2-type to the orthorhombic Gd5Si4-type phase occurs around 218K on heating. Intriguingly, the temperature of this polymorphic transformation is weakly dependent on magnetic fields as low as 40kOe (dT∕dH=−0.058K∕kOe) when the material is in the paramagnetic state nearly 200K above its spontaneous magnetic ordering temperature. It appears that a magnetostructural transition may be induced in the 5:4 erbium silicide at ∼18K and above by 75kOe and higher magnetic fields. Only Er5Si4 but none of the other studied Er5SixGe4−x alloys exhibit magnetic field induced transformations, which are quite common in the closely related Gd5SixGe4−x system. The magnetocaloric effects of the Er5SixGe4−x alloys are moderate.
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