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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.
Whether an association exists between cerebral microbleeds (CMBs) and functional recovery after ischemic stroke is unclear. We aimed to evaluate the association between CMBs and functional outcome after acute ischemic stroke.
Consecutive patients with acute stroke were enrolled, and all patients were stratified into good and poor functional outcome groups at discharge and 6 months after ischemic stroke by using a modified Rankin Scale score. Cardiovascular risk factors, CMBs, and white matter hyperintensities were compared between these two outcome groups. Logistic regression analysis was used to estimate the risk of poor functional outcomes.
A total of 225 patients were enrolled, 121 of whom were classified as having a good functional outcome at discharge and 142 as having a good 6-month functional outcome. The presence of CMBs was associated with a poor functional outcome at discharge [CMBs (+) patients in poor vs. good functional group; 48.1% vs. 30.6%; p=0.007] and 6 months [53.0% vs. 30.3%; p=0.001]. After adjustment for confounding factors, only the presence of infratentorial CMBs was associated with a poor functional outcome at discharge and 6 months. The poor functional outcome group had more CMBs than the good outcome group at 6 months.
Infratentorial cerebral microbleeds were significantly associated with worse functional outcomes not only in the early phase of ischemic stroke but also in the chronic phase. These findings suggest that the presence of infratentorial CMBs can predict poor functional outcome after acute ischemic stroke.
The purpose of this study was to investigate whether there is any association between preeclampsia and eNOS, DDAH, and VEGF gene polymorphisms, and also to search for a possible association between haplotypes in eNOS, DDHA, and VEGF genes and the risk for preeclampsia. DNA was extracted from whole blood of 223 preeclampsia patients and 237 healthy pregnant women. The genotypes were analyzed by a single base primer extension assay using a SNaPShot assay kit. Results were analyzed with the Student's t-test, Chi-square test, and Logistic regression analysis. Haplotype analyses were performed using Haploview 3.2 version. There were no significant differences in genotype or allele frequencies of eNOS, DDAH, and VEGF gene polymorphisms between preeclampsia patients and controls. No increase in the risk of preeclampsia for those genes was observed under any model of inheritance and there were no statistically significant associations between any haplotypes and preeclampsia risk. Polymorphisms in eNOS, DDAH, and VEGF gene do not seem to be risk factors for preeclampsia.
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.
There has been a significant effort to create spiral sensors by changing either the periodic d-spacing of the structure or the dielectric constants of the materials by combining the multi-faceted environmental responsiveness of polymer hydrogels with dielectrical structures.1 Reversible spiral switches with dimensional functionalities that respond to chemical environment were constructed. When the spiral photonic actuator was swollen in hydrophilic acetic acid, right-handed spiral structures are formed, while the spiral photonic actuator was swollen in hydrophobic hexane, left-handed spiral structures are formed. All actuators returned back to the transparent planar state after deswelling processes. These reversible spiral photonic actuators can be applied in the application of mechanical actuators, electrical devices, and optical components.
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 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
We have fabricated two metal/double insulator/metal diodes using a sputtering system and atomic layer deposition. Here, we show metal/double insulator/metal diode applied as a switch element. The diode exhibits good rectifying characteristics at room temperature. We used the electrode material with Pt and insulators were HfO2/ZrO2 and NiO/ZnO each. The devices were fabricated using the lithographic system and top electrode sizes were 30 µm x 30 µ;m. The double insulator diode produces an enhanced nonlinearity by incorporating two adjacent oxides instead of the single oxide layer of the MIM diode. In the double insulator diode the mode of tunneling under positive applied biases can be made different from that under negative applied biases resulting in improved asymmetry.
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.
Bulk-quantity single crystalline wurtzite gallium nitride nanowires with a mean diameter of 25 nm were synthesized on silicon substrate using a catalyst-assisted reaction of gallium and gallium nitride mixture with ammonia. They exhibit a strong and broad photoluminescence in the energy range of 2.9-3.6 eV with no yellow band. X-ray diffraction and Raman scattering data suggest that the nanowires would experience biaxial compressive stresses in the inward radial direction and the induced tensile uniaxial stresses in the wire axis. The blue photoluminescence would originate from the recombination of the bound excitons under the compressive and tensile stresses.
Tin oxide has been proposed as a promising alternative anode material for microbatteries. It has been reported that its theoretical volumetric capacity is four times larger than that of carbon-based materials, while its gravimetric capacity is twice as large. In this experiment, optimal Si and Bi doped SnO2 films were prepared with e-beam evaporation to improve both the cycle performance and the reversible capacity. The films with addition of Si only exhibited reductions in aggregation of tin particles and formation of micro-cracks. However, there still remained cracks, which induce capacity loss during cycling. To improve capacity retention, Bi was added with Si to SnO2 films, which exhibited the highest reversible capacity of 200µAh/cm2-µm at 200th cycle. The films doped with Bi and Si were found to be ill-defined and featureless without noticeable particle aggregation and cracks. However, the films that underwent cycling tests showed again aggregated tin particles and formation of cracks, which would induce cell failure during cycling. We believe that some types of Li-Bi phases as mixed-conductor matrices have improved the cycle life.
The Far-ultraviolet IMaging Spectrograph (FIMS) is a small spectrograph optimized for the observations of diffuse hot interstellar medium in far-ultraviolet wavebands (900–1150Å and 1335–1750Å). The instrument is expected to be sensitive to emission line fluxes an order of magnitude fainter than any previous missions. FIMS is currently under development and is scheduled for launch in 2002.
There have been increasing interests in lithium rechargeable batteries, especially microbatteries, with rapid development of portable electronic equipments and MEMS(Micro electromechanical systems) technology. In this work, lithium manganese oxide, as a strong candidate for the battery materials, which is more abundant, stable in ambient state and less toxic than the other oxides such as lithium nickel oxides and lithium cobalt oxides, was deposited by rf magnetron sputter. The effect of thermal treatment on the microstructure and electrode characteristics of lithium manganese oxide cathode was investigated. In electrochemical experiment using liquid electrolyte, half-cell failure would be caused by manganese dissolution, degradation of electrolyte materials during charging/discharging process and so on. In this research we focus on interface reaction problem that would affect the cyclability and lifetime of microbattery. In order to reduce the interface reaction during operation, we introduce DLC(Diamond-like-Carbon) film that has high electrical resistivity, mechanical hardness and chemical stability. DLC film was deposited on sputtered lithium manganese oxide electrode by ECRCVD(Electron Cyclotron Resonance Chemical Vapor Deposition). DLC-top-layer LiMn2O4 film was more stable during charging/discharging reaction and higher discharge capacity in wide voltage windows than LiMn2O4 film.
The microstructural variation and the interdiffusion of Pt (80 nm)/Ti (70 nm)/SiO2/Si during annealing in O2 were investigated using Auger electron spectroscopy, x-ray diffraction, transmission electron microscopy, and scanning electron microscopy. While the as-deposited and 400 °C annealed samples showed well-defined layer structures without any significant interfacial reaction, the degree of oxidation remarkably increased with increasing temperature above 500 °C. The PtTi alloy phase with Pmma structure (AuCd type) was observed from the 500 °C annealed sample. Drastic interdiffusion occurring above 600 °C changed the Pt/Ti bilayer into a very entangled structure. Some TiO2 phases were exposed to the ambient between Pt hillocks. In addition, a small amount of Pt-silicide was found near the TiOx/SiO2 interface.
We prepared CdS thin films from a solution containing cadmium acetate, thiourea, ammonia, and ammonium acetate. We varied fabrication conditions such as the concentrations of reactants, reaction temperature, and heat treatment, to investigate the changes in structural and optical properties of the film. Effects of substrate on the properties were also investigated.
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