Migraine with aura is one of the causes of stroke mimics. We retrospectively reviewed the 10-year medical records of patients who were treated with acute stroke management protocol. We analyzed the frequency and characteristics of patients with a final diagnosis of migraine with aura. Among the 1355 patients with stroke mimics, migraine with aura was the final diagnosis in 36 patients (2.7%). The most common auras included sensory and brainstem auras followed by motor, visual, and speech/language auras. One patient manifested transient atrial fibrillation during the migraine attack, which can be a link with acute stroke.

Cultivated soybeans [Glycinemax (L.) Merr.] have various flower colours such as dark purple, purple, light purple, pink, magenta, near white and white. About one-third of the soybean accessions in the United States Department of Agriculture – Germplasm Resource Information Network (USDA-GRIN) Soybean Germplasm Collections have white flowers and are the second dominant accessions after the purple-flowered accessions. Earlier studies have shown that the w1 recessive allele of the W1 gene encoding flavonoid 3′,5′-hydroxylase produces white flowers. In the present study, we aimed to understand why the white-flowered accessions have become abundant among the cultivated soybeans and what their genetic and regional origin is. For this purpose, 99 landraces with white flowers and 39 landraces with purple flowers from eight Asian countries and Russia were analysed with regard to the nucleotide sequences of the W1 locus. We not only found that the w1 alleles of the 99 white-flowered landraces were identical to those of the white-flowered Williams 82, but also found that these w1 alleles displayed no polymorphism at all. By carrying out a phylogenetic analysis, we were able to identify a group with W1 alleles from which the w1 allele might have diverged.

Despite numerous previous studies, relationships between watershed land use and adjacent streams and rivers at various scales in Korea remain unclear. This study investigated the relationships between land uses and the physical, chemical, and biological characteristics of 720 sites of streams and rivers across the country. The land uses at two spatial scales, including a 1-km buffer and the base watershed management region (BWMR), were computed in a geographical information system (GIS) with a digital land use/land cover map. Characteristics of land uses at two spatial scales were then correlated with the monitored multidimensional characteristics of the streams and rivers. The results of this study indicate that land use types have significant effects on stream and river characteristics. Specifically, most characteristics were negatively correlated with the proportions of urban, rice paddy, agricultural, and bare soil areas and positively correlated with the amount of forest. The site-scale and BWMR-scale analyses suggest that BWMR land use patterns were more strongly related to ecological integrity than they were to site land use patterns. Improving our understanding of land use effects will largely depend on relating the results of site-specific studies that use similar response techniques and measures to evaluate ecological integrity. In addition, our results clearly indicate that the characteristics of streams and rivers are closely linked and that land use types differentially affect those characteristics. Thus, effective restoration and management for ecological integrity of lotic system should consider the physical, chemical, and biological factors in combination.

Electron tomography and high-resolution transmission electron microscopy were used to characterize the unique 3-dimensional (3D) structures of twinned Zn3P2 (tetragonal) and InAs (zinc blende) nanowires synthesized by the vapor transport method. The Zn3P2 nanowires adopt a unique superlattice structure that consists of twinned octahedral slice segments having alternating orientations along the axial [111] direction of a pseudocubic unit cell. The apices of the octahedral slice segment are indexed as six equivalent <112> directions at the [111] zone axis. At each 30 degrees turn, the straight and zigzagged morphologies appear repeatedly at the <112> and <011> zone axes, respectively. The 3D structure of the twinned Zn3P2 nanowires is virtually the same as that of the twinned InAs nanowires. In addition, we analyzed the 3D structure of zigzagged CdO (rock salt) nanowires and found that they include hexahedral segments, whose six apices are matched to the <011> directions, linked along the [111] axial direction. We also analyzed the unique 3D structure of rutile TiO2 (tetragonal) nanobelts; at each 90 degree turn, the straight morphology appears repeatedly, while the in-between twisted form appears at the [011] zone axis. We suggest that the TiO2 nanobelts consist of twinned octahedral slices whose six apices are indexed by the <011>/<001> directions with the axial [010] direction.

We report the catalyst-free synthesis of ZnO nanobranches on Si nanowires using metalorganic chemical vapor deposition. The formation of single-crystalline ZnO nanobranches on Si nanowire backbones has been confirmed by lattice resolved transmission electron microscopy. Depending on the growth parameters, especially the growth temperature, the morphology and size of the ZnO nanobranches evolved from nanothorn-shaped (at 350 °C) to nanoneedle-shaped structures (at 500 °C). When the growth temperature was further increased to 800 °C, thin ZnO nanowire branches grew out of the Si nanowire backbones coated with thin ZnO shells, whereas no ZnO branch was formed on bare Si nanowires due to limited nucleation. The growth behavior was further exploited to fabricate ZnO/Si nanowire networks by growing the ZnO nanowires selectively on laterally aligned Si–ZnO core-shell nanowire arrays. In addition, cathodoluminescent properties of ZnO nanobranches on Si nanowire backbones are discussed with respect to position and size.

The effects of the Zr/Ti ratio on the electrical properties of lead zirconate titanate (PZT) thick films prepared by the aerosol deposition (AD) process were investigated to optimize the electrical properties of the thick film. The Zr/Ti ratio was varied among 45/55, 52/48, and 60/40, and the post-annealing temperature was varied from 500 to 900 °C. Microscopic examination of the as-deposited films revealed crack-free and dense microstructures with a thickness of 10 μm. The annealed films showed markedly improved electrical properties in comparison with the as-deposited films with increasing post-annealing temperature. With increasing Zr/Ti ratio, the remnant polarization and coercive field decreased. The dielectric constant and piezoelectric coefficient, d33, were highest for the PZT 52/48 film. This film annealed at 900 °C exhibited the best overall combination of electrical properties, with a dielectric constant, remnant polarization, and piezoelectric coefficient of 1320, 31.1 μC/cm2, and 150 pC/N, respectively.

The low frequency noise of individual ZnO nanowire (NW) field effect transistors (FETs) exposed to air is systematically characterized. The measured noise power spectrum shows a classical 1/f type. The noise amplitude is independent of source-drain current and inversely proportional to gate voltage. The extracted Hooge's constant of ZnO NW is found to be 6.52×10−3. In addition, the low frequency noise of ZnO NW according to NW resistance and contact property are investigated. The noise amplitude is proportional to the square of ZnO NW resistance. If a sample shows a nonlinear current-voltage (I-V) characteristic due to a poor electrical contact, the noise power spectrum is proportional to the third power of current instead of the square of current.

The ZnO TFTs have attracted much attention as key component for flexible displays because they can be fabricated on plastic substrates at low temperature and exhibit good electrical performance. However, the ZnO films are polycrystalline with grain boundaries even if formed at room temperature, which deteriorate the uniformity of TFT characteristics. A few research groups have reported high performance amorphous indium-gallium-zinc oxide TFTs to solve the native problem of nonuniformity of ZnO TFTs. However, there are few researches on the process parameter effects on the variation of a-IGZO TFT characteristics. In this study, we focus on the effect of the source/drain overlap length on threshold voltage(VT) of a-IZO TFTs with differentiating channel deposition method. The experimental structures for this work are bottom-gated TFTs with a-IGZO channel that were deposited by RF and DC magnetron sputtering on glass. RF and DC sputtering were carried out by magnetron power density of (1.4 W/cm2)/ (2.0 W/cm2) in Ar/O2 gas ratio of (65/35)/(72/28), and the entire gas pressure were 5.0 mTorr and 3.4 mTorr. The width/length(um/um) of device was split to 10/7,10/10,10/30,10/50. Each of the patterns has seven source/drain overlap length: -3um,-2um,-1um,0um,1um,2um,3um. We extracted VT of RF and DC through the VG-ID curve. There are significant VT difference in both RF and DC according to the overlap length: VT of DC(RF) is 1.31(0.74)V at W/L=10/50 and 10.21(5.74)V at W/L=10/30. VT increases definitely where less than 1um overlap length and short channel TFT is more influenced by overlap length, which is more severe in RF group. We calculated total channel resistance (RT) from VD-ID curve. RT of devices with the positive overlap can be expressed by RT, Postive=Rch+Rc. Here, Rch is net channel resistance which becomes smaller when channel length decreases and Rc is contact resistance. RT with negative overlap, is RT, Negative=Rch+Rc+Roffset. Roffset is offset resistance formed by negative overlap and can be extracted by subtracting RT, Postive from total RT, Negative. The RT of DC(RF) at offset channel length of-1um,-2um,and-3um is 4.43105(2.7 106)cm, 1.17 106(3.48 106)cm, and 1.46 106(4.73 106)cm, respectively(W/L=10/10um) RF group which shows inferior electrical characteristics such as lower mobility and larger subthreshold slope to DC, have larger Roffset than the DC. This implies that the devices require a bit of positive source/drain overlap length for uniform VT especially when the channel resistance is high. But Overlap region causes difficulties in the device area to be miniaturized. In summary, as the source/drain overlap length decreases to negative value, the threshold voltage of a-IGZO TFTs increases sharply and these tendency strongly depends on a-IZO film quality, which means the overlap length is very important control parameter of a-IGZO TFTs for the uniform threshold voltage especially when the channel resistance is high

a-IGZO TFT is a promising candidate device for an alternative to poly-Si TFTs or a-Si TFTs, because they provide better uniformity in terms of their important device parameters, including the threshold voltage and mobility due to their amorphous phase, and a high mobility (>10 cm2/Vs) is attainable with these devices even in the amorphous phase. Recently, a-IGZO TFTs have been extensively studied by various groups. However, there is little report on interface and bulk effect on device performances and reliability as separately. For investigating the interface and bulk effect, we fabricated two a-IGZO thin film transistors with different channel deposition conditions, RF and DC magnetron sputtering. Specific conditions of RF and DC sputtering are described as follows; magnetron power density of 1.4 W/cm2/2.0 W/cm2 in Ar/O2 gas ratio of (65/35)/(72/28), and the entire gas pressure was 5.0 mTorr and 3.4 mTorr, respectively.In order to characterize the channel quality, C-V curve was measured with various frequencies of (10KHz˜1MHz). RF sputtered channel has higher frequency dependency compared to DC sputtered channel. It means that RF sputtered channel has higher bulk traps in channel compared to DC sputtered channel.

Device performance was characterized through the ID-VG measurement. Electrical parameters of RF and DC sputtered devices are VT=3.5/2.7V, on-off ratio=105/08, SS=2/0.4 V/decade, and uFE= 5/11 cm2/V-s, respectively. It is thus clear that the device performance of DC sputtered device is more superior to RF sputtered device. Therefore, it can be said that the poor device performance of RF device is ascribed to insufficient channel quality, as mentioned in C-V curve.

For reliability study, we measured PBTI and ID-VG hysteresis with normalized gate stress bias and high temperature hot chuck system. Through the unchanged field effect mobility during the stress and relaxation time, and nearly recovered VT and subthreshold slope (SS) after long relaxation time, we were able to know that pre-existed trap was main factor of reliability degradation. Moreover, SS degradation during stress time is more severe in RF device than DC device. It is also proving that RF channel characteristic is worse than DC channel. In high temperature, leakage current increments of RF device were more severe than DC device. This also indicates that bulk traps of RF device in channel region are larger than that of DC device. VT shift of DC sputtered device for PBT stress and hysteresis was higher than that of RF sputtered device. As well known, PBTI is closely related to insulator bulk traps, which shows that channel deposition conditions affect insulator trap characteristics. In summary, device performance of a-IGZO deposited by DC sputtering is better than RF sputtering, which is because DC sputtering improves channel quality of a-IGZO. However, VT shift of DC sputtered device are worse than RF sputtering, which may be related with high magnetron power density.

Field effect transistors(FETs) made of ZnO nanowires are very sensitive to the gas environment, so that the passivation can be a good way to get reliable nanowire FETs with longer lifetime and the better mobility. The studies on the passivation effects with the positive electron-beam resist was investigated by selectively covering the part of nanowire devices between the electrodes. Reproducible electrical characteristics were recorded, reflecting the stable electrical properties by the passivation which deters the degradation of a device. Considering the defect states of oxide nanowires dominate the charge states, the pre-state just before the passivation process will be crucial to understand the reproducible and controllable device characteristics of nanowire devices.

Highly (100) oriented Pb(Zr,Ti)O3 [PZT] films were fabricated using lanthanum nitrate/nickel acetate double layers as a buffer layer, regardless of the other deposition conditions, such as the pyrolysis temperature, pyrolysis time, annealing temperature, and heating rate. The buffer layer was also acted as a very effective barrier against Pb-Si interdiffusion, thus allowing for the direct deposition of PZT films on Si, SiO2/Si, and glass substrates. The strong orientation was attributed to the formation of a crystalline intermediate phase between the PZT and lanthanum nitrate during annealing. The lanthanum nitrate/nickel acetate double layers became a lanthanum nickel oxide (LaNiO3), which shows good electrical conductivity, after an annealing process at 650°C. The nature and the role of lanthanum nitrate buffer as a layer for the growth of highly (100) oriented PZT films have been studied. The dielectric, ferroelectric, piezoelectric and electrooptic properties of the highly (100) oriented PZT films with a lanthanum nitrate/nickel acetate buffer layer were measured and compared with the values measured from the (111) and (100) oriented PZT films deposited without buffer layer.

Bilayer structures consisting of ZrO2-3mol% Y2O3(TZ-3Y) and zirconia-alumina composites as inner (substrate) and outer (coating) layers, respectively, are fabricated using gel-casting for the inner layer and dip-coating for the outer layer in aqueous system. The relatively tough TZ-3Y is used as the inner layer for damage absorption due to its mechanical properties. The mixture ratio of alumina/zirconia slips for dip-coating is 1:9, 2:8, and 3:7 as mole ratio. The processing additives for gel casting, such as dispersant, monomer, dimer, and initiator, are adjusted and optimized by measuring viscosity. From which the solid loading of starting material (TZ-3Y) is determined. The optimum amount of dispersant (D-3019; anionic dispersant agent) for TZ-3Y is 0.7 wt%. The slip pH affects the electric double layer in sols, which causes the different rheological behaviors and solid loadings. The castable solid loading of TZ-3Y is 37 vol%, showing a pseudoplastic rheological behavior. The effect of slip type (different mixture ratio) on sintered body is investigated through hardness (Vickers indentation), microstructure (SEM), and strength (4-point bending tests). Strength of sintered bodies after dip-coating into the slips is higher than that before dip-coating, but hardness is not much different among cases. The effects of thickness in the outer layer on damage resistance and mechanical properties of the bilayer structures are discussed extensively.

Porcelain (veneer layer)/alumina (core layer) is a typical dental crown structure. Due to its high incidence of failure, a new porcelain/mullite (buffer layer)/alumina trilayer structure is designed, fabricated, and evaluated. Alumina green bodies were prepared by gel-casting process, and then calcined at 900 and 1100°C to infiltrate mullite precursor slurry of silica-rich (Al2O3·2SiO2) composition into the bodies. Porosity in the bodies is not dependent on calcination temperature, resulting in a similar infiltration depth. Porcelain was coated on the alumina sintered at 1600°C with and without mullite buffer layer. There are no delamination or cracks observed after firing the layered materials. Rod type microstructure and continuous composition are indicated at the interface in the case of the layered structure with mullite buffer layer. To investigate the cracking resistance behavior for this new structure, Vickers indentation and Hertzian contact fatigue tests were conducted. Cracks do not penetrate the interface with mullite buffer layer into the porcelain, showing a reversal case for the layered structure without mullite buffer layer. The layered structure with mullite buffer layer shows higher critical load for fracture than that without mullite buffer layer. Fracture mode of the layered structures in cyclic fatigue shows a top layer (porcelain) fracture at relatively low load (P = 250 N) and higher cycles (n = 106), and a bottom layer (alumina) fracture at higher load (P = 300 N) and relatively low cycles (n = 105).

Silicon nitride–Si2N2O in situ composites were prepared by hot pressing powder mixtures of α–Si3N4, 6 wt% Y2O3, 1 wt% Al2O3, and 0–12 wt% SiO2. X-ray diffraction (XRD) analysis indicated that the volume percents of Si2N2O were 0, 13, 31, and 54 for the composites prepared with 0, 4, 8, and 12 wt% SiO2, respectively. XRD results also indicated that both silicon nitride grains and Si2N2O grains were laid down perpendicular to hot pressing direction. As the volume percent of Si2N2O increased, the width and the amount of elongated silicon nitride grains decreased, but the fracture toughness increased. Young's modulus of the in situ composites decreased as the Si2N2O content was increased. The erosion rate decreased as the Si2N2O content was increased, in part, due to both the increased fracture toughness and the reduced grain size. Erosion of the composites occurred primarily due to the grain dislodgment. The sample without Si2N2O experienced micro-chipping due to transgranular fracture.

The effects of IrO2/Pt layered hybrid bottom and/or top electrode structures on the leakage current density versus voltage (J–V), polarization versus voltage (P–V), ferroelectric imprint, and fatigue properties of chemical-solution-derived Pb(ZrxTi1−x)O3 (PZT, Zr/Ti = 35/65) thin films were investigated. The best P–V and J–V performances were obtained from a capacitor with nonhybrid electrodes (Pt/PZT/Pt capacitor). However, the poor fatigue performance of the capacitor required the adoption of hybrid electrode structures. A thin IrO2 layer, as thin as 6 nm, which was inserted between top Pt electrode and PZT layer was sufficient for improving the fatigue performance without any degradation of the other ferroelectric properties. However, the same layer adopted on the bottom Pt electrode was not effective in improving the fatigue performance with degradation in P–V and J–V properties. This was ascribed to IrO2 layer dissolution into the PZT layer during the crystallization annealing of the PZT thin film. A thicker IrO2 layer resulted in more serious degradation.

Carbon nanotubes (CNTs) have been significantly used for the field emitters for display applications. It is necessary to investigate the process variables affecting the screen printing of carbon nanotubes for the fabrication of good-quality field emitter devices with uniformity. Screen printing techniques have some advantages such as the short processing time and lower processing cost. The carbon nanotube pastes for screen printing are normally composed of organic binders, carbon nanotubes, and some additive materials. In this study, the carbon nanotube emitters for field emission displays were fabricated with different processing variables such as paste viscosity, paste composition, screen mesh, etc. The CNT pastes were printed on Cr-coated/Ag-printed soda-lime glass substrates. As a result, the processing variables were optimized for the good screen printing. From the I-V characteristics, the turn-on field of single-walled nanotubes was lower than that of multi-walled nanotubes. The decrease in the mesh number of screen masks resulted in decreasing the turn-on field and increasing the electron emission current due to the higher density and vertical alignment of printed-CNTs.

Silicon nitride with the aligned reinforcing grains was prepared by tape casting with addition of the silicon nitride whiskers and gas-pressure sintering at 2148 K. The microstructure and the mechanical properties of the sintered sample, including the fracture toughness and the three-point flexural strength, were highly anisotropic. Both the fracture toughness and the flexural strength were the highest when the crack-propagation direction was normal to the alignment direction. This result was interpreted from the laminate composite materials’ point of view. Although the large elongated grains were as long as 44.4 ± 12 μm and as wide as 5.1 ± 0.67 μm, they were not the fracture origins.