Quantum interference in radial heterostructure nanowires

Core/shell heterostructure nanowires are one of the most interesting mesoscopic systems potentially suitable for the study of quantum interference phenomena. Here, we report on experimental observations of both the Aharonov-Bohm (h/e) and the Altshuler-Aronov-Spivak (h/2e) oscillations in radial core/shell (In2O3/InOx) heterostructure nanowires. For a long channel device with a length-to-width ratio of about 33, the magnetoresistance curves at low temperatures exhibited a crossover from low-field h/2e oscillation to high-field h/ e oscillation. The relationship between the oscillation period and the core width was investigated for freestanding or substrate-supported devices and indicated that the current flows dominantly through the core/shell interface.     

The application of the pseudospectral method to the analysis of helical springs of arbitrary shape

The pseudospectral method is applied to the static analysis of helical springs of arbitrary shape. The displacements and the rotations are approximated by series expansions of Chebyshev polynomials. The entire domain is considered as a single element and the governing equations are collocated to yield the system of algebraic equations. The boundary conditions are considered as the constraints, and the set of equations is condensed so that the number of degrees of freedom of the problem matches the total number of the expansion coefficients. Displacements and rotations are computed for noncylindrical helical springs as well as cylindrical helical springs, and parameters that affect the convergence of the solution are discussed. This paper was recommended for publication in revised form by Associate Editor Jeong Sam Han Jinhee Lee received B. S. and M. S. degrees from Seoul National Uni-versity and KAIST in 1982 and 1984, respectively. He received his Ph.D. degree from University of Michigan in 1992 and joined Dept. of Mechano-Informatics of Hongik University in Choongnam, Korea. His research interests include inverse problems, pseudospectral method, vibration and dynamic systems.     

Chemiluminescence‐Generating Nanoreactor Formulation for Near‐Infrared Imaging of Hydrogen Peroxide and Glucose Level in vivo

Water‐dispersed all‐in‐one nanoprobes composed of densely integrated peroxyoxalate fuel and a cyanine dye are formulated to optimize the nanoscopic chemiluminescence reaction. It is demonstrated that the chemiluminescent nanoformulation can generate bright near‐infrared signal in response to external hydrogen peroxide that is biologically implicated with cell signaling and diseases. Successful imaging of endogenously overproduces hydrogen peroxide and indirect determination of glucose level in vivo with the chemiluminescent nanoprobes offers an opportunity for early diagnosis of diseases.     

Effects of Waxy Wheat Flour and Water on Frozen Dough and Bread Properties

ABSTRACT:  The quality of bread made from frozen dough is diminished by changes that occur during freezing. New cultivars of waxy wheat flour (WWF), containing less than 2% amylose, offer unique properties for the production of baked products. In this study, dough properties and bread quality were investigated at various levels of WWF (0% to 45% flour weight) and water (55% to 65%). Dough stickiness increased with higher levels of WWF and water. During frozen storage, dough with greater WWF and lower water had less change in stickiness. Maximum resistance to extension (MRE) decreased with higher WWF and water. Dough with greater WWF and less water had less change in extensibility after frozen storage. Dough with greater WWF and water was more extensible. Nuclear magnetic resonance (NMR) studies showed that frozen dough with higher WWF content had lower transverse relaxation ( T ₂) time of 9 to 11ms. After frozen storage, dough with higher WWF still showed lower T ₂. Dough with 15% WWF had higher yeast activity. Bread made from 15% and 30% WWF had higher volume in bread made from unfrozen and frozen dough. Bread firmness decreased with higher amounts of WWF and water. This research demonstrated that specific combinations of WWF and water produced a better quality of frozen dough and bread.     

Morphology-controlled therapeutic activity of cerium oxide nanoparticles for mild traumatic brain injury

The design and optimization of nanostructures with unique morphologies and properties are at the forefront of biomedical nanotechnology. Cerium oxides are widely used to investigate the effect of morphology on performance. However, elucidating the morphology–activity relationship of cerium oxide nanocrystals in biomedical applications remains challenging. Herein, the therapeutic effects of cerium oxide nanoparticles with different morphologies: cerium oxide nanorods with two different aspect ratios (CeO_x NRs_A and CeO_x NRs_B), cerium oxide nanopolyhedra (CeO_x NPs), and cerium oxide nanocubes (CeO_x NCs) are investigated in in vivo and in vitro mild traumatic brain injury (TBI) models. Cerium oxide nanoparticles inhibit oxidative stress and inflammation after mild TBI, alleviating cognitive impairment; furthermore, the therapeutic effect is significantly affected by their morphology. Owing to the higher Ce³⁺/Ce⁴⁺ ratio, exposure of more active crystal surfaces, and greater number of exposed oxygen vacancies, CeO_x NRs show better activity than CeO_x NPs and CeO_x NCs for mild TBI. Among the two investigated types of cerium oxide nanorods, CeO_x NRs_A, with a higher Ce³⁺/Ce⁴⁺ ratio on the surface, appear to spread better than CeO_x NRs_B in the injured lesions. The factors causing morphology-controlled biomedical performance, such as Ce³⁺/Ce⁴⁺ molar ratio, surface area, and aspect ratio, are discussed.     

Structure-dependent growth control in nanowire synthesis via on-film formation of nanowires

On-film formation of nanowires, termed OFF-ON, is a novel synthetic approach that produces high-quality, single-crystalline nanowires of interest. This versatile method utilizes stress-induced atomic mass flow along grain boundaries in the polycrystalline film to form nanowires. Consequently, controlling the magnitude of the stress induced in the films and the microstructure of the films is important in OFF-ON. In this study, we investigated various experimental growth parameters such as deposition rate, deposition area, and substrate structure which modulate the microstructure and the magnitude of stress in the films, and thus significantly affect the nanowire density. We found that Bi nanowire growth is favored in thermodynamically unstable films that facilitate atomic mass flow during annealing. A large film area and a large thermal expansion coefficient mismatch between the film and the substrate were found to be critical for inducing large compressive stress in a film, which promotes Bi nanowire growth. The OFF-ON method can be routinely used to grow nanowires from a variety of materials by tuning the material-dependent growth parameters.     

A Field Effect Transistor Fabricated with Metallic Single-Walled Carbon Nanotubes

We report novel transport properties of the individual single-walled carbon nanotube (SWNT) field effect transistors (FETs) decorated with the protein (streptavidin)-coated nanoparticles. Upon adsorption of the protein-coated nanoparticles at the metal-nanotube contact, the metallic SWNT devices abruptly exhibit a p-type semiconducting behavior. In the case of semiconducting SWNT devices, the adsorptions of protein-coated nanoparticles make the gating more effective, resulting in a far suppressed off-state leakage current as well as an enhanced on-state p-channel current. Through the ab initio electronic structure calculations, it is suggested that such an apparent metal-semiconductor transition may be due to the intervening charged species in the contact area, originated from the surface of the proteins. Noting the separation of the semiconducting nanotubes from metallic ones would be a formidable task; we suggest that the device concept here could be another breakthrough for the nanotube-based electronic devices, in which the nanotubes are not necessarily semi-conducting.     

Theoretical study on evaporation of sessile water droplets on a glass panel with infrared radiation

An evaporation model of a water droplet on a glass substrate is developed to estimate the process time needed to manufacture a liquid crystal display panel (LCD). By using an infrared (IR) lamp as a radiation source to evaporate the droplet, the changes in droplet size and evaporation time are calculated. The peak wavelength of the lamp and initial droplet size are used to estimate the process time. A change in the distribution of droplets is calculated to practically apply the model used in the drying process. By analyzing the contributions of radiation and conduction, we found that the evaporation process is driven by different heat transfer mechanisms according to the peak wavelength of the lamp.