Annealing-induced enhancement of ferromagnetism in SnO2-core/Cu-shell coaxial nanowires

In this study, we have coated tin oxide (SnO₂) nanowires with a Cu shell layer via the sputtering method and subsequently investigated the effects of thermal annealing. The annealing-induced changes in morphologies, microstructures, and compositions of the resulting core-shell nanowires were characterized by using scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and energydispersive X-ray spectroscopy (EDX). The Cu shell layers were agglomerated to form clusters, which were mainly comprised of the Cu₂O phase. For the first time, a hysteresis loop indicating weak ferromagnetism was observed from the pure SnO₂ nanowires. Both the coercivity and the retentivity in the hysteresis loop were slightly increased by Cu-sputtering, indicating a very slight enhancement of ferromagnetism. Also, the ferromagnetic behavior was significantly enhanced by thermal annealing. We discuss the possible mechanisms of annealing-induced enhancement of ferromagnetism in the SiO₂/Cu core-shell nanowires, which include the generation of Cu₂O phase, Cu-doping into the SnO₂ lattice, and the generation of oxygen vacancies in SnO₂ core nanowires.     

A high-frequency annular-array transducer using an interdigital bonded 1-3 composite

This paper reports the design, fabrication, and characterization of a 1-3 composite annular-array transducer. An interdigital bonded (IB) 1-3 composite was prepared using two IB operations on a fine-grain piezoelectric ceramic. The final composite had 19-μm-wide posts separated by 6-μm-wide polymer kerfs. A novel method to remove metal electrodes from polymer portions of the 1-3 composite was established to eliminate the need for patterning and aligning the electrode on the composite to the electrodes on a flexible circuit. Unloaded epoxy was used for both the matching and backing layers and a flexible circuit was used for interconnect. A prototype array was successfully fabricated and tested. The results were in reasonable agreement with those predicted by a circuit-analogous model. The average center frequency estimated from the measured pulse-echo responses of array elements was 33.5 MHz and the -6-dB fractional bandwidth was 57%. The average insertion loss recorded was 14.3 dB, and the maximum crosstalk between the nearest-neighbor elements was less than -37 dB. Images of a wire phantom and excised porcine eye were obtained to show the capabilities of the array for high-frequency ultrasound imaging.     

Directed self-assembly of organic semiconductors via confined evaporative capillary flows for use in organic field-effect transistors

We fabricated well-defined 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-PEN) crystal arrays for use in electronic applications via a simple but effective method, the confined evaporative capillary flow (CEC) method. This has been accomplished by systematically controlling the contact line pinning at the edge of glass stylus and the outward hydrodynamic flow within the drying droplet with various processing solvents and surface properties of the substrate during solidification. We found that after CEC coating of TIPS-PEN solution dissolved into toluene onto SiO₂ surface, ribbon-shaped TIPS-PEN crystals were well developed with a width of 20–100 μm and length of 300 μm – 2 mm, which is presumably owing to optimized capillary evaporation. Specifically, TIPS-PEN crystals present highly preferred crystal orientation along the (l 0 0) axis, which can lead to efficient charge transport in a lateral direction. Thus, TIPS-PEN field-effect transistors (FETs) exhibited a good hole mobility of 0.72 cm²/Vs.     

Feasibility of estimating glomerular filtration rate in children using single-sample adult technique

This work was undertaken to verify whether a single-sample adult technique, when applied using body surface-corrected plasma concentration, can be used in place of specific pediatric method to estimate 51Cr-EDTA renal clearance in children. METHODS: In a series of 90 children (aged 0.1 to 15 yr). 51Cr-EDTA renal clearance was calculated using for different approaches. The first approach used specific pediatric single-sample methods; three techniques were chosen and they all used 120-min plasma concentration. The second approach used the same three specific pediatric methods, but they were applied using 120-min plasma concentration prescaled for 1.73 m2 body surface area. The third approach used single-sample methods designed for adults; three methods were again chosen. They all used 240-min plasma concentration. The fourth approach used the same adults algorithms, but they were applied using 240-min plasma concentration prescaled for 1.73 m2 body surface area. RESULTS: Clearances calculated using the three specific pediatric methods were all closely cross-correlated regardless of whether or not the plasma concentration was prescaled. The use of classical adult methods produced in some cases obviously erroneous clearance values. Improvements were observed when the same adult methods were applied using prescaled plasma concentration. Nonetheless, the clearance values obtained only fairly correlated with those obtained using specific pediatric methods. CONCLUSION: The single-sample adult technique using plasma concentration prescaled for 1.73 m2 body surface area cannot be used in place of a specific pediatric single-sample method to estimate 51Cr-EDTA renal clearance in children.     

Protection of Digital TV from Cognitive Radio Interference

Analytic modeling and computational simulation for the protection of DTV from cognitive radio interference are performed. Protection is achieved by using the protection ratio, which is derived through system modeling and its analysis. On the frequency coordination between digital TV and cognitive radio, an analysis in a co‐channel environment, in a rural area in Korea, is performed.     

IC/microfluidic hybrid system for magnetic manipulation of biological cells

This paper introduces an integrated circuit (IC)/microfluidic hybrid system for magnetic manipulation of biological cells. The hybrid system consists of an IC and a microfluidic system fabricated on top. Biological cells attached to magnetic beads are suspended inside the microfluidic system that maintains biocompatibility. The IC contains a microcoil array circuit that produces spatially-patterned microscopic magnetic fields. Programmable, rapid reconfiguration of the field pattern made possible by the IC allows an efficient simultaneous manipulation of multiple individual bead-bound cells with precise position control. Two prototypes, SiGe/microfluidic and CMOS/microfluidic hybrid systems, validate the proposed approach.     

Influencing factors on the pyroelectric properties of Pb(Zr,Ti)O3 thin film for uncooled infrared detector

Zr-rich PZT thin films were synthesized by metallorganic decomposition and their dielectric and pyroelectric properties were investigated with different ratios of zirconium/titanium and poling condition. All the films became effectively (1 1 1) textured and well crystallized at the annealing temperature of 700 °C. With increasing Zr content, coercive field increased and voltage dependent capacitance curve appeared asymmetrical, indicating the presence of antiferroelectric phase, PbZrO₃, in film composition. The pyroelectric coefficient in the practically applicable temperature ranges of 20–60 °C was found to be maximum for the thin film with 0.85 mol of zirconium in PZT. Further increase in zirconium content led to severe deterioration in pyroelectric properties. The values of pyroelectric coefficient and figures of merit were greatly influenced by poling direction and temperature. The result was explained in terms of electric phase and state of polarization in film.     

Measurement of Power Frequency Fluctuations Using the FFT

A new method for detecting fluctuations in the fundamental frequency component of a power system, by relating it to a leakage coefficient in the FFT, is presented. The phenomenon of leakage in the FFT is used advantageously to increase spectral resolution. The leakage coefficient is a quantitative measure of the deviation from the fundamental frequency component with respect to the sampling frequency. Theoretical aspects are considered along with a method for on-line implementation.     

Scanning electron microscopy of central nervous system cerebrospinal-fluid-contacting surfaces: a bibliography (1963-1995)

This bibliography is compiled to assist in locating papers related to the application of scanning electron microscopy (SEM) to cerebrospinal-fluid-contacting surfaces in vertebrates. The use of SEM by neuroscientists has continued apace since the publication of the first bibliography in 1980. SEM studies now include more than 50 species of vertebrates and range from cyclostomes to humans; they encompass development from embryo to senescence and concern both normal and pathologic morphology. Although remarkable strides have been made toward a greater understanding of many aspects of the structure and function of cerebrospinal-fluid-contacting surfaces, many significant problems await the judicious application of scanning electron microscopy.