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Cantilever sensors have attracted considerable attention over the last decade because of their potential as a highly sensitive sensor platform for high throughput and multiplexed detection of proteins and nucleic acids. A micromachined cantilever platform integrates nanoscale science and microfabrication technology for the label-free detection of biological molecules, allowing miniaturization. Molecular adsorption, when restricted to a single side of a deformable cantilever beam, results in measurable bending of the cantilever. This nanoscale deflection is caused by a variation in the cantilever surface stress due to biomolecular interactions and can be measured by optical or electrical means, thereby reporting on the presence of biomolecules. Biological specificity in detection is typically achieved by immobilizing selective receptors or probe molecules on one side of the cantilever using surface functionalization processes. When target molecules are injected into the fluid bathing the cantilever, the cantilever bends as a function of the number of molecules bound to the probe molecules on its surface. Mass-produced, miniature silicon and silicon nitride microcantilever arrays offer a clear path to the development of miniature sensors with unprecedented sensitivity for biodetection applications, such as toxin detection, DNA hybridization, and selective detection of pathogens through immunological techniques. This article discusses applications of cantilever sensors in cancer diagnosis.
A set of Bragg peaks consistent with a hexagonal Bravais lattice was observed in the x-ray powder diffraction pattern of cubic pyrochlore rubidium tungstoniobate (RbNbWO6) subjected to high-energy ball milling. The calculated lattice parameters for this hexagonal phase are similar to those of compounds with tungsten bronze structure. In fact, the powder pattern of the hexagonal phase could be refined with a structural model based on the tungsten bronze structure. The hexagonal phase produced by high-energy ball milling of RbNbWO6 transforms back to the pyrochlore structure upon heating to 773 K in air. A similar phase was obtained by ball milling the mixture RbNbWO6 + WO3, but, in this case, the stoichiometric hexagonal tungsten bronze compound thus obtained remained stable up to 1273 K.
This investigation analyzed the effect of reactant particle size on the stress development characteristics of NiAl synthesized through self-propagating high temperature synthesis. Four sample combinations of NiAl were synthesized based on initial particle diameters of the reactants: (i) 10 μm Al and 10 μm Ni (S1), (ii) 10 μm Al and 100 nm Ni (S2), (iii) 50 nm Al and 10 μm Ni (S3), and (iv) 50 nm Al and 100 nm Ni (S4). Characterization of NiAl was performed by parallel comparison of the distribution of residual stresses of the samples prior to and after the reaction. Residual stresses were quantified using x-ray diffraction. Upon characterization it was found that combinations S1, S2, and S3 exhibited tensile residual stresses, while combination S4 exhibited compressive residual stresses. Statistical analysis confirmed that self-propagating high temperature synthesis products derived from nanoparticle reactant sizes exhibited compressive residual stresses offering improved fatigue resistance in composite production.
Spherical particles of ferrite (intermediate between Fe3O4 and γ-Fe2O3) were grown on seed crystals (∼9 nm) via the green rust route in an aqueous solution added with sucrose, which promotes spherical growth. By highly dispersing the seed crystals in an HNO3 solution, we could control the diameter of the particles over a wide range of 20–200 nm (geometric standard deviation: 1.1–1.4) by changing the amount of the seed crystals. At the beginning of the seed growth, clusters of the seed crystals were resolved into smaller clusters, each composed of a few seed crystals.
A high-conductivity and super-high-strength alloy, Cu-8.0Ni-1.8Si-0.6Sn-0.15Mg, has been developed. The processing conditions of the alloy have been investigated. The evolution of microstructure of the alloy on aging has been examined by transmission electron microscopy. The processing condition giving the highest hardness and good electrical conductivity is as follows: solution treatment at 970 °C for 4 h, cold rolling to 60% reduction, and aging at 500 °C for 30 min. The processed alloy has an average tensile strength of 1180 MPa, 0.2% proof strength of 795 MPa, elongation of 2.75%, and average electrical conductivity of 26.5% IACS. Orthorhombic Ni2Si precipitates are responsible for the age-hardening effect. The orientation relationship between the precipitates and the matrix is (110)m(211)p and. DO22 ordering together with spinodal decomposition also contributed to the hardening.
In this work, we report a new Mg-based glass-forming system of Mg–Ni–(Gd,Nd), which can be produced into glassy rods with maximum diameters of 2–5 mm by copper mold casting. The Mg75Ni15Gd10–xNdx(x = 0–10) BMGs simultaneously possess a high level of glass transition temperatures, high specific strength up to 2.75 × 105 Nm/kg, and enhanced malleability with plastic strains over 1%. In particular, the Mg75Ni15Gd5Nd5 BMG with the glass-forming ability (GFA) up to 5 mm, exhibited compressive yield strength over 900 MPa and plastic strain up to 50% without failure for the specimen with an aspect ratio of 0.5. The improved GFA and malleability for the Mg75Ni15Gd10–x Ndx(x = 0–10) BMGs were discussed, which exhibited their promising potentials for the application as lightweight engineering materials.
The growth of SrTiO3 (STO) thin films is examined using classical molecular dynamics simulations. First, a beam of alternating SrO and TiO2 molecules is deposited on the (001) surface of STO with incident kinetic energies of 0.1, 0.5, or 1.0 eV/atom. Second, deposition of alternating SrO and TiO2 monolayers, where both have incident energies of 1.0 eV/atom, is examined. The resulting thin film morphologies predicted by the simulations are compared to available experimental data. The simulations indicate the way in which the incident energy, surface termination, and beam composition influence the morphology of the thin films. On the whole, some layer-by-layer growth is predicted to occur on both SrO- and TiO2-terminated STO for both types of deposition processes, with the alternating monolayer approach yielding thin films with compositions that are much closer to that of bulk STO.
Phase transformations in (111) Si after spherical indentation have been investigated by cross-sectional transmission electron microscopy. Even at an indentation load of 20 mN, a phase transformation zone including the high-pressure crystalline Si phases was observed within the residual imprints. The volume of the transformation zone, as well as that of the crystalline phases increased with the indentation load. Below the transformation zone, slip was found to occur on {311} planes rather than on {111} planes, usually observed on indentation of (100) Si. The distribution of defects was asymmetric, and for indentation loads up to 80 mN, their density was significantly lower than that reported for (100) Si. The experimental observations correlated well with modeling of the applied stress through ELASTICA.
Nanostructured bulk NiAl materials were prepared at high pressure and temperature (0–5.0 GPa and 600–1500 °C, respectively). The sintered samples were characterized by x-ray diffraction, scanning electron microscope, density, and indentation hardness measurements. The results show that NiAl nanoparticles may have a compressed surface shell, which may be the reason why NiAl nanomaterials were difficult to densify sintering using conventional methods and why high-pressure sintering was an effective approach. We also observed that B2-structured NiAl could undergo a temperature-dependent phase transition and could be transformed into Al0.9Ni4.22 below 1000 °C for the first time. It is interesting to note that Vickers hardness decreased as grain size decreased below ∼30 nm, indicating that the inverse Hall-Petch effect may be observed in nano-polycrystalline NiAl (n-NiAl) samples. Moreover, a tentative interpretation was developed for high-pressure nanosintering, based on the shell-core model of nanoparticles.
In this article, the chemical and structural changes inside soda-lime glasses induced by femtosecond (fs) laser pulsing have been reported, based on transmission electron microscopy and electron energy loss spectroscopy studies. Under fs-laser interaction, Na-rich phases are formed, and Na nanoparticles are also precipitated around the Na-rich phases. These findings demonstrate how powerful and efficient the fs-laser pulsing and interaction can be in making novel microstructures in soda-lime silicate glass, and they bridge the gap between the macroscale property changes and nanometer-scale structures.
This article provides a brief overview of recent progress in the synthesis and functionalization of magnetic nanoparticles and their applications in the early detection of malignant tumors by magnetic resonance imaging (MRI). The intrinsic low sensitivity of MRI necessitates the use of large quantities of exogenous contrast agents in many imaging studies. Magnetic nanoparticles have recently emerged as highly efficient MRI contrast agents because these nanometer-scale materials can carry high payloads while maintaining the ability to move through physiological systems. Superparamagnetic ferrite nanoparticles (such as iron oxide) provide excellent negative contrast enhancement. Recent refinement of synthetic methodologies has led to ferrite nanoparticles with narrow size distributions and high crystallinity. Target-specific tumor imaging becomes possible through functionalization of ferrite nanoparticles with targeting agents to allow for site-specific accumulation. Nanoparticulate contrast agents capable of positive contrast enhancement have recently been developed in order to overcome the drawbacks of negative contrast enhancement afforded by ferrite nanoparticles. These newly developed magnetic nanoparticles have the potential to enable physicians to diagnose cancer at the earliest stage possible and thus can have an enormous impact on more effective cancer treatment.
To clarify the texture evolution mechanism of Fe-Mn-Si-based shape memory alloys, the rolling texture of an Fe-14Mn-5Si-9Cr-5Ni shape memory alloy is investigated during rolling to a final reduction of 82% at 873 K. A new rolling texture caused by single slip plane slipping is observed from such alloy, which is different from the conventional copper-type and brass-type textures. By means of the {111} pole figure scattering analysis of the local deformation structure, we conclude that such single slip plane slipping results in the weakness of brass orientation in the α fiber and the great enhancement of β fiber connecting S′ {331}<213> and B′ orientations {110}<114>.
A new powder metallurgy technique for creating porous NiTi is demonstrated, combining liquid phase sintering of prealloyed NiTi powders by Nb additions and pore creation by NaCl space-holders. The resulting foams exhibit well-densified NiTi–Nb walls surrounding interconnected pores created by the space-holder, with controlled fraction, size, and shape. Only small amounts of Nb (3 at.%) are needed to produce a eutectic liquid that considerably improves the otherwise poor densification of NiTi powders. NiTi–Nb foams with 34–44% porosity exhibit high compressive failure stress (>1,500 MPa), ductile behavior (>50% compressive strain), low stiffness (10–20 GPa), and large shape-memory recovery strains. These thermomechanical properties, together with the known biocompatibility of the alloy, make these open-cell foams attractive for bone implant applications.
Calcium phosphate crystals were synthesized by diffusing calcium ions into silica hydrogels containing phosphate ions. Hydroxyapatite [HAp, Ca10(PO4)6(OH)2] and octacalcium phosphate [OCP, Ca8(HPO4)2(PO4)4.5H2O] with different types of crystal morphology were formed in the gel. The HAp had an irregular or rod shape, a few micrometers in length, while the OCP had an irregular, spherulite, rod- or ribbonlike shape, ranging in size from a few micrometers to several tens of micrometers, depending on the amount of phosphoric acid added and the reaction temperature. The morphology of the OCP changed from an irregular shape to a ribbonlike or rod shape, via a spherulite shape, depending on the amount of phosphoric acid added and the reaction temperature. The degree of supersaturation of the reaction environment and the rate-determining step in the HAp and OCP crystal growth mechanism have been ascribed to the changes in crystal morphology of the HAp and OCP.
Commercial-grade dense Ti-6Al-4V alloy substrate was mechanically roughened, cleaned, and treated with a globular protein [bovine serum albumin (BSA)] for 4 h. Biomimetic calcium phosphate (Ca-P) coating was applied onto the above-treated substrate by immersion into simulated body fluid (SBF) at 25 °C for a period of 4 days, with periodic replacement by freshly prepared SBF at 48-h intervals. After 4 days, branched micron-sized fibers of hydroxyapatite (HAp), resembling the structure of bone, were obtained, connecting the clusters of HAp crystal plates in the coating (thickness ∼200 μm) on the substrate surface. Structural and compositional characterization of the coating was carried out using field emission scanning electron microscopy (FE-SEM) with energy-dispersive x-ray analysis unit (EDX) facility, x-ray diffraction (XRD), and Fourier transform infrared (FTIR) data. In vitro cytotoxicity (ISO 10993-5, 1999), cell adhesion assays, and phase contrast microscopy were performed using NIH 3T3 fibroblast cell lines to ascertain the bioactivity of the coated substrates, with and without protein treatment. Based on our study, we propose a correlation between a specific physical structure of the HAp coating and its biological properties.
The aim of this chapter is to describe a range of industrial processing technologies for reactive polymer systems, and specifically to
characterise the process and highlight important processing-quality-control tests, process variables and typical systems used,
highlight applications of chemorheology in the process and
examine the use of chemorheology in modelling of the production process.
In this way we will be bringing the concepts and understanding from all subsequent chapters into practical processing applications in order to aid acquisition of deeper understanding of these processes.
Casting
Process diagram and description
Casting is a relatively simple process (Figure 6.1) involving the pouring of a thermosetting liquid into a mould, where the liquid hardens into a solid, dimensionally-stable shape.
Examples of products include rod stocks, spheres, gears, bushings and complex moulded items. In casting applications structural properties such as hardness, toughness, dimensional stability and machinability are of most interest.
Quality-control tests and important process variables
Important process variables include
cost
viscosity
reaction exotherm
shrinkage
pot life
Cost is typically reduced by minimizing the amount of resin used (either via incorporation of fillers or modifiers, or by foaming). Viscosity is critical for casting operations, in which requirements concerning ease of processibility and large loadings of fillers need to be optimized. Exotherms typically pose processing problems for large casting masses since the cure reaction evolves >100 kJ/mol (Section 3.2.2), which may be reduced by incorporation of fillers, modifiers and the correct curing agent at an optimum concentration.