Magnetic field detection for current evaluation by magnetic force microscopy

A current measurement method through magnetic field detection by magnetic force microscopy was proposed and demonstrated. We observed the magnetic field induced by an AC below 2.2 μA around a GaAs/AlGaAs mesa stripe. To achieve high sensitivity in magnetic field detection, we tuned the AC bias frequency to the torsional resonant frequency of the cantilever. As a result, the sensitivity of the magnetic field detection was much improved and specific features of the magnetic field around the mesa stripe were clearly observed at a current in sub-μA range.     

Thermal and electrical properties of perovskite-type strontium molybdate

Polycrystalline samples of perovskite-type strontium molybdate, SrMoO₃, have been prepared and the thermal and electrical properties have been measured from room temperature to about 1000 K. The electrical resistivity is of an order of magnitude of 10⁻⁵ to 10⁻⁶ (Ω m) in the whole temperature range. The Seebeck coefficient is around 4–9 μV K⁻¹. At room temperature, the thermal conductivity is about 30 W m⁻¹ K⁻¹, and it decreases with increasing temperature.     

Preparation of highly mesoporous carbon membranes via a sol-gel process using resorcinol and formaldehyde

This paper reports the preparation of highly mesoporous carbon membranes, which are obtained by the pyrolysis of sol-gel derived mesoporous polymer membranes using resorcinol and formaldehyde (RF). Two series of RF carbon membranes were prepared by changing the resorcinol to catalyst molar ratio. The nitrogen adsorption-desorption measurement shows that the RF carbon membranes possess a well-developed mesoporous structure with controlled pore diameters of 5.48 nm and 13.9 nm. The helium and nitrogen permeances of both RF carbon membranes were independent of the feed pressure, indicating that there was no contribution of viscous flow and the membranes are initially crack-free. The gas permeation result showed that the dominant mechanism of gas transport through both the RF carbon membranes is Knudsen diffusion. With regard to the permeation of condensable gases such as CH₄ and CO₂, it was observed that the surface flow also contributes to the total permeation.     

Synthesis of ordered mesoporous carbon thin films at various temperatures in vapor infiltration method

Mesoporous carbon thin films with ordered structures were prepared by using resorcinol-surfactant self-assembly. A mixture of resorcinol, surfactant, and ethanol coated on silicon substrates was exposed to formaldehyde vapor as a cross-linking agent to form structured resorcinol/formaldehyde resin films. The films were then carbonized at 800 °C in an inert atmosphere to remove the surfactant and to obtain structured carbon materials. With this vapor infiltration method, thin films with several structures were obtained from the same precursor solution by employing different vapor infiltration temperatures. The results were interpreted from the transformation of the self-assembly during the vapor infiltration process.     

Biomarkers for colorectal cancer

Colorectal cancer (CRC) is the third most common epithelial malignancy in the world. Since CRC develops slowly from removable precancerous lesions, detection of the lesion at an early stage by regular health examinations can reduce the incidence and mortality of this malignancy. Colonoscopy significantly improves the detection rate of CRC, but the examination is expensive and inconvenient. Therefore, we need novel biomarkers that are non-invasive to enable us to detect CRC quite early. A number of validation studies have been conducted to evaluate genetic, epigenetic or protein markers for identification in the stool and/or serum. Currently, the fecal occult blood test is the most widely used method of screening for CRC. However, advances in genomics and proteomics will lead to the discovery of novel non-invasive biomarkers.     

Solid polymerization and supramolecular chirality formation of azobenzene substituted diacetylene Langmuir–Blodgett films

An azobenzene mesogen-substituted diacetylene (NADA) monolayer has been transferred onto the solid substrate by the traditional Langmuir–Blodgett (LB) method. Solid-state polymerization of NADA LB films can be sensitized in visible light region. In situ UV–vis absorption measurement enables us to study polymerization kinetics of NADA LB films. The polymerization process can be described as a first order rate equation and polymerization rate constants are characterized in detail. Furthermore, achiral NADA molecules can form chiral LB films through overcrowded packing of the azobenzene moiety.     

Vacancy site occupation by Co and Ir in half-Heusler ZrNiSn and conversion of the thermoelectric properties from n-type to p-type

The n-type thermoelectric properties of the half-Heusler compound ZrNiSn can be converted to p-type by the addition of Co and Ir. We found that Co and Ir atoms preferably occupy the vacancy sites instead of substituting at Ni sites. This implies that the phase stability of the compound gradually changes towards that of the Heusler compound Zr(Ni,M)₂Sn, where M is Co and/or Ir. The occupation of vacancy sites by Co and Ir atoms leads to a drastic reduction in lattice thermal conductivity owing to the enhancement of phonon scattering by the solid solution effect.     

Strength and ductility evaluation of steel bridge piers with linearly tapered plates

Important issues on the application of linearly tapered steel plates to highway bridge piers are discussed in this paper based on extensive experimental work. The factors that affect the seismic resisting performance of tapered plate steel columns were examined. The main factors considered are: (1) types of tapering mold line (outer, central, and inside tapering); (2) tapering ratio (or the slope of thickness change); (3) stiffeners’ rigidity; and (4) tapered stiffeners. To this end, four groups of specimens were tested under cyclic lateral loads and constant axial load. The columns with the outside taper plates were found to have the best strength and ductility characteristics among the three types of mold lines. In the case of different tapering ratios, the largest ductility was observed in the specimens with the tapering ratio slightly less than or equal to unity. The stiffeners’ rigidity ratio of around 3.0 was found to give the best ductility performance in columns with both constant thickness and varying thickness stiffeners. The test results were compared with a recently proposed design equation for limit strain of box columns with tapered plates. Finally, finite element analyses were performed and comparisons between the test and the analyses’ results of several test specimens are presented.     

Self‐Powered Trace Memorization by Conjunction of Contact‐Electrification and Ferroelectricity

Triboelectric nanogenerator (TENG) is a newly invented technology that can effectively harvest ambient mechanical energy from various motions with promising applications in portable electronics, self‐powered sensor networks, etc. Here, by coupling TENG and a thin film of ferroelectric polymer, a new application is designed for TENG as a self‐powered memory system for recording a mechanical displacement/trace. The output voltage produced by the TENG during motion can polarize the dipole moments in the ferroelectric thin film. Later, by applying a displacement current measurement to detect the polarization density in the ferroelectric film, the motion information of the TENG can be directly read. The sliding TENG and the single‐electrode TENG matrix are both utilized for realizing the memorization of the motion trace in one‐dimensional and two‐dimensional space, respectively. Currently, the ferroelectric thin film with a size of 3.1 mm² can record a minimum area changing of 30 mm² and such resolution can still be possibly improved. These results prove that the ferroelectric polymer is an effective memory material to work together with TENG and thereby the fabricated memory system can potentially be used as a self‐powered displacement monitor.