The effects of polymer substrates on the interfacial structure and the thermal stability of Ga-doped ZnO (GZO) thin films were investigated. The GZO thin films were deposited on polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) substrates by rf-magnetron sputtering at room temperature, and thermal stability tests of the GZO thin films on the polymer substrates were performed at 150°C up to 8 h in air. Electrical and structural characterizations of the GZO thin films on the PET and the PEN substrates were carried out, and the origins of the stable interfacial structure and the improved thermal stability of the GZO thin film on the PEN substrate were discussed.

Intra-uterine growth retardation has been linked to the development of type 2 diabetes in later life. Mitochondrial changes have been suggested as a link between fetal malnutrition and adult insulin resistance. Taurine has been implicated in this process. We investigated whether protein malnutrition in early life alters mitochondria of the pancreatic islets in adulthood, and whether taurine supplementation restores these changes. Male offspring of rats fed a control diet, a low-protein diet or a low-protein diet supplemented with taurine during pregnancy and lactation were weaned onto the control diet. In each group, at 20 weeks of age, intravenous glucose tolerance tests, euglycaemic–hyperinsulinaemic clamp studies, morphometric analysis of the pancreatic islets and ultra-structural analysis of the mitochondria of the β-cells were performed. The expressions of cytochrome c oxidase (COX) I and mitochondrial respiratory chain complex II were also measured. Fetal protein-malnourished rats showed decreased pancreatic islet mass and reduced insulin-secretory responses to a glucose load. These rats also showed reduced mitochondrial DNA-encoded COX I gene expression in the islets. Electron microscopic examination showed abnormal mitochondrial shapes in the β-cells of fetal protein-malnourished rats. Taurine supplementation to the low-protein diet restored all these changes. Our findings indicate that a maternal protein-restriction diet causes long-lasting mitochondrial changes that may contribute to the development of type 2 diabetes later in life. The lack of taurine may be a key causative factor for these dysfunctional mitochondrial changes.

The diatoms are an ecologically important group of algae that have been extensively studied by ecologists and taxonomists. However, the large-scale patterns of diatom distribution and the factors underlying this distribution are largely unknown. The aims of this study were to identify the large-scale spatial patterns of benthic diatom assemblages in Korean streams and rivers, and to assess the importance of numerous environmental factors on diatom distribution. We classified 720 study sites based on diatom flora. Benthic diatoms, water chemistry, altitude, and riparian land cover and use were characterized by multivariate analyses, Monte Carlo permutation tests, and indicator species analysis. In total, we identified 531 diatom taxa. Diatom assemblages were mostly dominated by species of the genera Achnanthes, Navicula, Nitzschia, Cocconeis, Fragilaria (Synedra included), Cymbella, Gomphonema, and Melosira. Cluster analysis partitioned all 720 sites into eight groups based on diatom species composition. Canonical correspondence analysis indicated that altitude, land cover and use, current velocity, electrical conductivity, and nutrient levels explained a significant amount of the variation in the composition of assemblages of benthic diatoms. At the national scale, a downstream ecological gradient was apparent, from fast-flowing, mostly oligotrophic highland streams to slow-flowing, mostly eutrophic lowland rivers. Our data suggest that spatial factors explain some of the variation in diatom distribution. The present investigation of the spatial patterns of benthic diatoms, the ecological determinants of diatom occurrence, and the identification of diatom indicator species contributes to development of a program for assessing the biological integrity of lotic ecosystems in Korea.

The anisotropy in the fatigue behavior of rolled Mg–3Al–1Zn alloy between the rolling direction and normal direction to the rolling plane was investigated. The {10-12} twinning–detwinning characteristics were found to play key roles in the anisotropic fatigue deformation behavior by inducing a change in the predominant plastic deformation mechanism, which controlled the flow stress and finally influenced the fatigue resistance by generating mean stress. Energy-based approach was successfully used to describe anisotropic fatigue life behavior.

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.

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 in-situ SEM observation of real-time hillock evolution in pure Al thin films on glass substrate during isothermal annealing at 194°C was analyzed quantitatively to understand the compressive stress relaxation mechanism by focusing on the effect of Mo interlayer between Al film and glass substrate. There is a good correlation between the hillock-induced stress relaxation and the measured stress relaxation by wafer curvature method. It is also clearly shown that the existence of Mo interlayer plays an important role in hillock formation probably due to the large difference in interfacial diffusivity of Al films.

Two types of glass plates coated with uniformly aligned polyurethane films were produced by repeating the cycles of the alternative exposures of the glass plates to 1,4-phenylene diisocyanate (PDI) and 2-butyne-1,4-diol (BDO) and to PDI and terephthalic acid bis-(2-hydroxy ethyl) ester (TBE) for 500 times at elevated temperatures. The glass plates coated with uniformly aligned poly-(PDI-BDO)500 (500 represents the number of the cycle) produced monolayers of closely packed 2D arrays of silicalite-1 crystals with the average size of 370 × 200 × 500 nm on the glass plates upon immersion of the glass plates into a dense gel consisting of tetraethylorthosilicate (TEOS), tetrapropylammonium hydroxide (TPA+OH-), and water (mole ratio = 7:1.5:330) followed by the hydrothermal reaction at 180°C for 2 h. The silicalite-1 crystals were aligned with the c-axes perpendicular to the substrate plane. Upon switching the polymer from poly-(PDI-BDO)500 to poly-(PDI-TBE)500 the orientations of the silicalite-1 crystals in the 2D arrays changed from c to a axes perpendicular to the substrate. This report therefore demonstrates that the uniformly aligned polyurethane films serve as the templates for the growth of closely packed multi-crystal arrays of silicalite-1 in uniform orientations and the nature of the polyurethane film affects the resulting orientations of the crystals. We propose that the supramolecularly organized organic-inorganic composites consisting of the hydrolyzed organic products and the seed crystals responsible for the above phenomena.

Because otoacoustic emissions (OAEs) are transmitted from the cochlea to the ear canal via the middle ear, the transmission properties of the middle ear directly influence OAEs’ characteristics. In general, middle-ear effusion (MEE) reduces measured emission amplitudes and sometimes eliminates the response entirely. The purpose of this study was to establish the relationship between the conduction of the middle ear and OAEs’ properties and to elucidate the effect of middle-ear effusion on detecting OAEs’. Spontaneous otoacoustic emissions (SOAEs), transiently evoked otoacoustic emissions (TEOAEs) and distortion product otoacoustic emissions (DPOAEs) were recorded from 44 normal ears and 32 ears with middle-ear effusion. DPOAEs were collected in two basic forms consisting of distortion product audiograms (DP grams) and input-output (I-O) functions, elicited by two primary tones F1 and F2 and varying geometric mean frequencies between 1–6 kHz. The results of air and bone conduction hearing levels in pure tone audiogram were also analysed. In 21 ears out of 32 otitis media with effusion (OME) ears, SOAEs were absent. In the 28 ears with middle-ear effusion, the response and wave reproducibility were diminished, and in the 17 ears with middle-ear effusion, the DP gram was diminished or eliminated. In particular, I-O function curves at 3 kH and 4 kHz were diminished by the primary tones of 45 and 55 dB under the condition of MEE. The SOAEs, TEOAEs and DPOAEs (DP gram and I-O function curve) are highly reliable and useful tests for monitoring changes in middle-ear condition in children with OME and in predicting the course of OME.

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.

A systematic study of photoluminescence (PL) and time-resolved PL spectra from In0.15Ga0.85N/In0.015Ga0.985N quantum wells (QWs) with different Si doping concentration in the barriers has been carried out. As the Si doping concentration increases, the PL emission intensity was increased and the PL peak energy was blueshifted. The energy separation between the spontaneous emission (SPE) and stimulated emission (SE) peaks decrease with increasing Si doping concentration. We also observed that the slow decay time τ2 in the QWs decreases with increasing Si doping concentration, from ∼ 130 ns for [Si] = 2 × 1018 cm−3 to ∼ 30 ns for [Si] = 1 × 1019 cm−3. The PL emission peak shifts to lower energies with delay time after a pulsed excitation and this shift decreases with increasing Si doping concentration. The increased recombination rate, the decrease of peak shift with delay time, and the reduced separation between the SPE and SE peaks with increasing Si doping concentration are attributed to the screening of piezoelectric field by carriers originated from Si doped barriers.