Showing papers on "Shell (structure) published in 2010"

Surgical instrument with curvilinear tissue-contacting surfaces

Abstract: A surgical stapling instrument including a handle assembly, an elongated body portion, a shell assembly and an anvil assembly. The elongated body portion extends distally from the handle assembly and defines a longitudinal axis. The shell assembly is disposed adjacent a distal end of the elongated body portion and includes a non-planar, tissue-contacting surface oriented obliquely with respect to the longitudinal axis. The anvil assembly includes a non-planar, tissue-contacting surface oriented obliquely with respect to the longitudinal axis. The tissue-contacting surface of the anvil assembly is configured to align with the tissue-contacting surface of the shell assembly when the anvil assembly and shell assembly are in the approximated position.

Fe3O4/TiO2 Core/Shell Nanotubes: Synthesis and Magnetic and Electromagnetic Wave Absorption Characteristics

Abstract: Fe3O4/TiO2 core/shell nanotubes are fabricated via a three-step process. α-Fe2O3 nanotubes are first obtained, and α-Fe2O3/TiO2 core/shell nanotubes are subsequently fabricated using Ti(SO4)2 as a Ti source by a wet chemical process. The thickness of the amorphous TiO2 shell is about 21 nm. After a H2 deoxidation process, the amorphous TiO2 layer changes into crystalline structures composed of TiO2 nanoparticles with an average diameter of 2.5 nm, and its thickness is decreased to about 18 nm. At the same time, α-Fe2O3 transforms into cubic Fe3O4. Consequently, crystalline Fe3O4/TiO2 core/shell nanotubes can be fabricated through the process above. The measurements of the magnetic properties demonstrate that the Fe3O4/TiO2 core/shell nanotubes exhibit ferromagnetic behavior at room temperature, and the Verwey temperature is about 120 K. The eddy current effect is largely reduced and the anisotropy energy is improved significantly for the core/shell nanotubes due to the presence of the TiO2 shells. The max...

Synthesis, Multi-Nonlinear Dielectric Resonance, and Excellent Electromagnetic Absorption Characteristics of Fe3O4/ZnO Core/Shell Nanorods

Abstract: Fe3O4/ZnO core/shell nanorods are successfully fabricated by combing an inorganic-phase reaction with a hydrogen annealing process. The transmission electron microscopy analysis indicates that the diameter and the length of the core/shell nanorods are 25−80 and 0.35−1.2 μm, respectively. Electromagnetic properties of the core/shell nanorod−wax composites are investigated. The permittivity of the composites shows four dielectric resonant peaks in 2−18 GHz, which can be explained by the transmission line theory. The resonant behavior mainly results from interface polarization induced by the special core/shell structures, dipole polarization of both Fe3O4 and ZnO, and electron transfer between Fe2+ and Fe3+ ions in Fe3O4. The maximum reflection loss is about −30 dB at 10.4 GHz for the composites with a thickness of 1.5 mm, and the absorption bandwidth with the reflection loss below −20 dB is up to 11 GHz for an absorber with the thickness in 2−4 mm. Thus, our results demonstrate that the Fe3O4/ZnO core/shell...

Nanowire-in-microtube structured core/shell fibers via multifluidic coaxial electrospinning

Abstract: A multifluidic coaxial electrospinning approach is reported here to fabricate core/shell ultrathin fibers with a novel nanowire-in-microtube structure from more optional fluid pairs than routine coaxial electrospinning. The advantage of this approach lies in the fact that it introduces an extra middle fluid between the core and shell fluids of traditional coaxial electrospinning, which can work as an effective spacer to decrease the interaction of the other two fluids. Under the protection of a proper middle fluid, more fluid pairs, even mutually miscible fluids, can be operated to generate "sandwich"-structured ultrathin fibers with a sharp boundary between the core and shell materials. It thereby largely extends the scope of optional materials. Selectively removing the middle layer of the as-prepared fibers results in an interesting nanowire-in-microtube structure. Either homogeneous or heterogeneous fibers with well-tailored sandwich structures have been successfully fabricated. This method is an important extension of traditional co-electrospinning that affords a more universal avenue to preparing core/shell fibers; moreover, the special hollow cavity structure may introduce some extra properties into the conventional core/shell structure, which may find potential applications such as optical applications, microelectronics, and others.

One piece co-formed exterior hard shell case with an elastomeric liner for mobile electronic devices

Abstract: A one-piece co-formed exterior hard shell case with an elastomeric liner formed on the interior of the exterior hard shell for mobile electronic devices. This hard protective exterior shell allows the device maximum protection from impacts with sharp objects while the interior elastomeric portion that provides shock protection for the device from impacts. The exterior hard shell part is formed to fit the device closely with a small offset from the devices surface. The exterior hard shell raps around the edges of the device. To allow the shell to be able to be mounted on the device the corners of the hard shell are cut open. This allows each sidewall to flex away when a device is inserted and snap back once it is in place. The elastomeric material fills in the gaps created at the corners of the exterior hard shell to allow flex for mounting.

Double-detonation sub-Chandrasekhar supernovae: synthetic observables for minimum helium shell mass models

Abstract: Abridged. In the double detonation scenario for Type Ia supernovae (SNe Ia) a detonation initiates in a shell of He-rich material accreted from a companion star by a sub-Chandrasekhar-mass White Dwarf (WD). This shell detonation drives a shock front into the carbon-oxygen (C/O) WD that triggers a secondary detonation in the core. The core detonation results in a complete disruption of the WD. Earlier studies concluded that this scenario has difficulties in accounting for the observed properties of SNe Ia since the explosion ejecta are surrounded by the products of explosive He burning in the shell. Recently, it was proposed that detonations might be possible for much less massive He shells than previously assumed. Moreover, it was shown that even detonations of these minimum He shell masses robustly trigger detonations of the C/O core. Here we present time-dependent multi-wavelength radiative transfer calculations for models with minimum He shell mass and derive synthetic observables for both the optical and {\gamma}-ray spectral regions. These differ strongly from those found in earlier simulations of sub-Chandrasekhar-mass explosions in which more massive He shells were considered. Our models predict light curves which cover both the range of brightnesses and the rise and decline times of observed SNe Ia. However, their colours and spectra do not match the observations. In particular, their B-V colours are generally too red. We show that this discrepancy is mainly due to the composition of the burning products of the He shell of our models which contain significant amounts of Ti and Cr. Using a toy model, we also show that the burning products of the He shell depend crucially on its initial composition. This leads us to conclude that good agreement between sub-Chandrasekhar-mass explosions and observed SNe Ia may still be feasible but further study of the shell properties is required.

Heat dissipation device

Abstract: The utility model discloses a heat dissipation device for the chip dispels the heat on giving the circuit board, including radiator body, screw, spring, last lock nut, lower lock nut, it has the through -hole to open on the radiator body, and the through -hole has also been opened to the relevant position on the circuit board, passing in the through -hole on the through -hole of screw from the radiator body and the circuit board, going up lock nut and be located between radiator body and the circuit board, lower lock nut is located circuit board below for the circuit board is fixed with the screw, the screw includes spiral shell nail -head part, and the spring is located between the through -hole of spiral shell nail -head part and radiator body, the spiral diameter of spring is less thanspiral shell nail -head part's diameter. The utility model discloses make radiator and the chip can effective laminating, damage the chip when preventing fixed radiator, in case of necessity can automatically regulated radiator position, guarantee the radiating effect.

Soft template synthesis of yolk/silica shell particles.

Abstract: Yolk/shell particles possess a unique structure that is composed of hollow shells that encapsulate other particles but with an interstitial space between them. These structures are different from core/shell particles in that the core particles are freely movable in the shell. Yolk/shell particles combine the properties of each component, and can find potential applications in catalysis, lithium ion batteries, and biosensors. In this Research News article, a soft-template-assisted method for the preparation of yolk/silica shell particles is presented. The demonstrated method is simple and general, and can produce hollow silica spheres incorporated with different particles independent of their diameters, geometry, and composition. Furthermore, yolk/mesoporous silica shell particles and multishelled particles are also prepared through optimization of the experimental conditions. Finally, potential applications of these particles are discussed.

A new non-linear higher-order shear deformation theory for large-amplitude vibrations of laminated doubly curved shells

Abstract: A consistent higher-order shear deformation non-linear theory is developed for shells of generic shape, taking geometric imperfections into account. The geometrically non-linear strain–displacement relationships are derived retaining full non-linear terms in the in-plane displacements; they are presented in curvilinear coordinates in a formulation ready to be implemented. Then, large-amplitude forced vibrations of a simply supported, laminated circular cylindrical shell are studied (i) by using the developed theory, and (ii) keeping only non-linear terms of the von Karman type. Results show that inaccurate results are obtained by keeping only non-linear terms of the von Karman type for vibration amplitudes of about two times the shell thickness for the studied case.

EXAFS as a tool to interrogate the size and shape of mono and bimetallic catalyst nanoparticles.

Abstract: The influence of atom packing and the geometric arrangement of atoms on the coordination number(s) and resultant simulated EXAFS spectra for face centrered cubic (fcc), hexagonal close packed (hcp) and body centered cubic (bcc) monometallic structures and fcc bimetallic structures, has been examined for metal clusters with an isotropic diameter up to 3 nm. We observe clear differences as a function of size and shape for all types of packing; in particular the surface aspect ratios (surface-to-bulk) of the shapes strongly influences the ‘growth curves’ as a function of the number of atoms for all packing types examined. Discrimination between the different types of structure based on the coordination shell occupancy appears possible, although is dependent on the type of packing. For fcc and hcp packing, structures comprising less than 200 atoms, and particularly less than 100 atoms, exhibit strong variation in the first shell coordination number as a function of shape. For bcc structures this dependency of the coordination shell number for small clusters is much less pronounced and in some cases (for higher shell (>N4) coordination numbers) an opposite trend is observed in that the difference in coordination number as a function of shape becomes more marked with an increasing number of atoms. For the fcc bimetallic systems, model structures possessing distinct bimetal distributions, including both non-random and random alloy types, were simulated and examined. Clear variations in both the 1st shell coordination number and in the simulated spectra were observed as a function of the bimetal structure. A dual edge analysis of the data and subsequent examination of the coordination shell numbers as a function of the bimetal distribution enables for the size, composition and distribution of the each species, to be determined.

Optimization of a composite cylinder under bending by tailoring stiffness properties in circumferential direction

Abstract: A fiber-reinforced cylindrical shell with given geometry and material properties is optimized for maximum load-carrying capability under bending. The shell is assumed to be built using an advanced fiber-placement machine, which allows in-plane steering and overlapping of fibers, resulting in a so-called variable-stiffness shell. The design methodology for strength and stiffness variation in circumferential direction by means of fiber placement is explained and restrictions on the manufacturability are specified. Implementation in the commercially available finite element package ABAQUS ® for structural analysis is described. Subsequently, the cylinder is optimized to carry a maximum buckling load under bending, while applying a strength constraint. Constraints on the global stiffness are imposed by means of comparison with a baseline quasi-isotropic shell, while a matrix dominated lay up is avoided at all locations in the laminate in order to ensure that the laminate is strong enough in all directions in case a hole is present. Optimization is done using a surrogate model in order to minimize the amount of finite element analyses. Improvements of up to 17% are obtained by changing the load path. The tension side is made stiffer and the compression side softer in longitudinal direction by changing the fiber orientation from near zero at the upper (tension) side to higher fiber angles at the lower (compression) side, such that load is relieved from the compression side. This results in a higher load-carrying capability of the cylinder.

Composition-Tuned ZnO−CdSSe Core−Shell Nanowire Arrays

Abstract: Vertically aligned ZnO−CdSSe core−shell nanocable arrays were synthesized with a controlled composition and shell thickness (10−50 nm) by the chemical vapor deposition on the pregrown ZnO nanowire arrays. They consisted of a composition-tuned single-crystalline wurtzite structure CdS1-xSex (x = 0, 0.5, and 1) shell whose [0001] direction was aligned along the [0001] wire axis of the wurtzite ZnO core. The analysis of structural and optical properties shows the formation of Zn containing alloy in the interface region between the ZnO core and shell, which can facilitate the growth of single-crystalline shell layers by reducing both the lattice mismatch and the number of defect sites. In contrast, the TiO2 (rutile) nanowire array can form the polycrystalline shell under the same condition. The photoelectrochemical cell using the ZnO−CdS photoelectrode exhibits a higher photocurrent and hydrogen generation rate than that using the TiO2−CdS one. We suggest that the formation of the CdZnSSe intermediate layers ...

Synthesis, characterization, defect chemistry, and FET properties of microwave-derived nanoscaled zinc oxide

Abstract: The formation of nanoscale zinc oxide particles with an almost-monomodal size distribution synthesized by microwave heating of solutions of mononuclear zinc oximato or zinc acetylacetonato complexes in various alkoxyethanols is investigated. Transparent stable suspensions that contain these particles can be obtained from the zinc oximato precursor. Based on electron paramagnetic resonance (EPR) studies, a core/shell model with a finite surface shell thickness of 1.000 ± 0.025 nm is proposed for the ZnO nanoparticles. Field-effect transistor (FET) devices with these ZnO particles as the active semiconducting layer exhibited a charge carrier mobility of 0.045 cm2/(V s) and Ion/off current ratios of ∼460.000, with a threshold voltage of 8.78 V.

Light-emitting diode lamp

Abstract: A light-emitting diode lamp includes a top shell, a bottom shell fixed to the top shell, a printed circuit board carrying light-emitting diodes, a lens, and a latch fixed on the bottom shell movably. The bottom shell defines two grooves. One end of the grooves is open and adjacent to the open end of the other groove. The printed circuit board is between the top shell and the bottom shell. The lens is slidingly retained by the grooves. The latch is located at the open ends of the grooves and preventing the lens from disengaging from the grooves.

Effect of shell thickness and composition on blinking suppression and the blinking mechanism in 'giant' CdSe/CdS nanocrystal quantum dots.

Abstract: We recently developed an inorganic shell approach for suppressing blinking in nanocrystal quantum dots (NQDs) that has the potential to dramatically improve the utility of these fluorophores for single-NQD tracking of individual molecules in cell biology. Here, we consider in detail the effect of shell thickness and composition on blinking suppression, focusing on the CdSe/CdS core/shell system. We also discuss the blinking mechanism as understood through profoundly altered blinking statistics. We clarify the dependence of blinking behavior and photostability on shell thickness, as well as on interrogation times. We show that, while the thickest-shell systems afford the greatest advantages in terms of enhanced optical properties, thinner-shell NQDs may be adequate for certain applications requiring relatively shorter interrogation times. Shell thickness also determines the sensitivity of the NQD optical properties to aqueous-phase transfer, a critical step in rendering NQDs compatible with bioimaging applications. Lastly, we provide a proof-of-concept demonstration of the utility of these unique NQDs for fluorescent particle tracking. High-resolution image of an ultra-thick-shell ‘giant’ nanocrystal quantum dot (left). Suppressed blinking behaviour afforded by this class of semiconductor nanocrystal yields new statistical relationships in the probability densities of fluorescence on- and off-time distributions (right).

Strain-Induced Band Gap Modification in Coherent Core/Shell Nanostructures

Abstract: Using first-principles calculations within density functional theory, we study the relative impacts of quantum confinement and strain on the electronic structure of two II−VI semiconductor compounds with a large lattice-mismatch, CdSe and CdTe, in core/shell nanowire geometries with different core radii and shell thicknesses. For fixed CdSe core radius, we find that the electronic band gap in the core is significantly reduced with increasing CdTe shell thickness, by an amount comparable to that expected from quantum confinement, due to the development of a large and highly anisotropic strain throughout the heterostructure. A straightforward analysis allows us to separate quantitatively changes in band gap due to quantum confinement and strain. Our studies elucidate and quantify the importance of strain in determining the electronic and optical properties of core/shell nanostructures.

Electronic structures of the CdSe/CdS core-shell nanorods.

Abstract: The electronic structures of the CdSe/CdS core−shell nanorods are systemically investigated by large-scale first-principles quality calculations. The effects of band alignment, quantum confinement, piezoelectric field, and dipole moments are analyzed and delineated by comparing the results of systems with or without some of these attributes. We found complicated interplays between these effects in determining the nanorod band gap and electron hole wave function localizations. The hole wave function is found to be localized inside the CdSe core, while the electron wave function is localized in the CdS shell, with its distance to the CdSe core depending on the surface passivation. The permanent dipole moment induced by different surface passivations can change the electron hole separation, while the piezoelectric effect plays a relatively minor role. Finally, we demonstrate that it is straightforward to manipulate the nanorod electronic structure by changing its CdSe core position.

Internal Structure of InP/ZnS Nanocrystals Unraveled by High-Resolution Soft X-ray Photoelectron Spectroscopy

Abstract: High-energy resolution photoelectron spectroscopy (ΔE < 200 meV) is used to investigate the internal structure of semiconductor quantum dots containing low Z-contrast elements. In InP/ZnS core/shell nanocrystals synthesized using a single-step procedure (core and shell precursors added at the same time), a homogeneously alloyed InPZnS core structure is evidenced by quantitative analysis of their In3d5/2 spectra recorded at variable excitation energy. When using a two-step method (core InP nanocrystal synthesis followed by subsequent ZnS shell growth), XPS analysis reveals a graded core/shell interface. We demonstrate the existence of In−S and Sx−In−P1−x bonding states in both types of InP/ZnS nanocrystals, which allows a refined view on the underlying reaction mechanisms.