Influence of sintering temperature on the microstructure and thermoelectric properties of polycrystalline Fe1.9925P0.0075O3.

The solution combustion process is used to synthesize Fe1.9925P0.0075O3 nano-powders. The sintered Fe1.9925P0.0075O3 bodies are alpha-Fe2O3-based single phase with the rhombohedral structure. The electrical conductivity increases with an increase in sintering temperature because of an increase in grain size and density. The absolute value of the Seebeck coefficient escalates with an increase in sintering temperature up to 1000 degrees C, and then decreases with a further rise in its sintering temperature. The Fe1.9925P0.0075O3 sintered at 1000 degrees C shows the highest power factor, i.e., 1.39 x 10(-5) W m(-1) K(-2) at 700 degrees C.

Thermoelectric properties of nanocrystalline Ca(3-x)Cu(x)Co4O9 (0 < or = x < or = 0.32) for power generation.

We successfully synthesized nano-sized Ca(3-x)Cu(x)Co4O9 (0 < or = x < or = 0.32) powders by solution combustion process. Plate-like grains and porous structure were observed in the sintered Ca(3-x)Cu(x)Co4O9 ceramics. The sintered Ca(3-x)Cu(x)Co4O9 showed a monoclinic symmetry. The electrical conductivity of the Ca(3-x)Cu(x)Co4O9 increased with increasing temperature, indicative of a semiconducting behavior. The added Cu led to a significant increase in the electrical conductivity. The Seebeck coefficient of the Cu-added Ca(3-x)Cu(x)Co4O9 was much higher than that of the Cu-free Ca3Co4O9. The highest power factor (9.99 x 10(-4) Wm(-1)K-2) was obtained for Ca2.76Cu0.24Co4O9 at 800 degrees C.

Thermoelectric properties of Ca(1-x-y)Dy(x)CeyMnO3 for power generation.

The sintered Ca(1-x-y)Dy(x)CeyMnO3 bodies were a single phase with a perovskite structure without any impurity phases. The calculated crystallite sizes of the Ca(1-x-y)Dy(x)CeyMnO3 were in the range of 43.3 to 63.3 nm. The composition significantly affected their microstructural and thermoelectric characteristics. The doped Dy led to both an increase in the electrical conductivity as well as the absolute value of the Seebeck coefficient, resulting in an enhanced power factor. The highest power factor (5.1 x 10(-4) Wm(-1) K(-2)) was obtained for Ca(0.8)Dy(0.2)MnO3 at 800 degrees C. In this study, we systematically discussed the thermoelectric properties of the Ca(1-x-y)Dy(x)CeyMnO3, with respect to the substitution of Dy and/or Ce for Ca.

Pretreatment of polyethylene terephthalate substrate for the growth of Ga-doped ZnO thin film.

The effect of the pretreatment of polyethylene terephthalate (PET) substrate on the growth of transparent conducting Ga-doped ZnO (GZO) thin film was investigated. Because of its high gas and moisture absorption and easy gas permeation, PET substrate was annealed at 100 degrees C in a vacuum chamber prior to the sputtering growth of GZO thin film for the outgassing of impurity gases. GZO thin film was deposited on the pretreated PET substrate by rf-magnetron sputtering and significantly improved electrical properties of GZO thin film was achieved. Electrical and structural characterizations of the GZO thin films were carried out by 4-point probe, Hall measurement, and scanning electron microscopy, and the effects of the pretreatment on the improved properties of GZO thin films were discussed. This result is not only useful to PET substrate, but also could be applicable to other plastic substrates which inevitably containing the moisture and impurity gases.

Highly Dispersible Buckled Nanospring Carbon Nanotubes for Polymer Nano Composites.

We propose the unique structure of highly dispersible single-walled carbon nanotubes (SWCNTs) in various solvents and polymers using the ZnO nano particle template. Buckled nanospring-shaped carbon nanotubes (NS-CNTs) were synthesized by a chemical reaction of ZnO nanoparticles with acid-treated SWCNTs and then dissolving ZnO through chemical etching. The unique structure of distorted hexagonal NS-CNTs encircled around ZnO nanoparticles was formed by the bending of SWCNTs caused by the agglomeration of chemically adsorbed Zn(OH)2, which is further crystallized as the polycrystalline ZnO inner core. The highly dispersible NS-CNTs could be incorporated in the poly[(vinylidenefluoride-co-trifluoroethylene] [P(VDF-TrFE)] copolymer, one of widely studied ferro- and piezo-electric polymer, up to the value of 15 wt% as nanofillers. The relative dielectric constant (K) of polymer nanocomposite, at 1 kHz, was greatly enhanced from 12.7 to the value of 62.5 at 11 wt% of NS-CNTs, corresponding to a 492% increase compared to that of pristine P(VDF-TrFE) with only a small dielectric loss tangent (D) of 0.1.

Effects of Na+-Ca2+ exchanger activity on the alpha-amino-3-hydroxy-5-methyl-4-isoxazolone-propionate-induced Ca2+ influx in cerebellar Purkinje neurons.

Variations in intracellular calcium activity ([Ca2+]i) play crucial roles in information processing in Purkinje neurons such as synaptic plasticity. Although Na+-Ca2+ exchanger (NCX) has been shown to participate in the regulation of homeostasis and secretion in neuronal cells, the physiological role of NCX in Purkinje neurons, such as a role in cerebellar synaptic plasticity, is not well understood. NCX in acutely dissociated rat Purkinje neurons was identified by double staining with anti-calbindin D-28k antibody and anti-NCX antibody. The physiological activity of NCX was examined by measuring transient intracellular Ca2+ changes resulting from the Ca2+ influx via reverse mode of NCX (with 0 mM Na+/2.5 mM Ca2+ solutions) and the efflux via the forward mode of NCX (with 140 mM Na+/0 mM Ca2+ solutions). This transient increase in Ca2+ concentration was not elicited in the cells pretreated with NCX antisense oligodeoxynucleotides. And the Ca2+ influx resulting from the reverse mode of NCX was significantly reduced by 2-[2-[4-(4-nitrobenyloxy) phenyl] ethyl] isothiourea methanesulfonate, while the Ca2+ efflux via forward mode was inhibited by bepridil. The physiological role of NCX in synaptic function was studied by measuring Ca2+ transients induced by alpha-amino-3-hydroxy-5-methyl-4-isoxazolone-propionate (AMPA) receptor activation. This AMPA-evoked response was decreased with the inhibition of NCX forward mode and also, to less degree, with the inhibition of reverse mode. In antisense oligodeoxynucleotides pretreated cells, the AMPA-evoked response was also reduced, as was the case in NCX-inhibitor treated cells. The inhibition of NCX activity had depressant effects on Ca2+ transients induced by AMPA receptor activation. These results suggest that NCX plays a physiological role in modulating the activity of cerebellar Purkinje neurons, such as synaptic plasticity, via interaction with AMPA receptors in Purkinje neurons.

Inter-relationships between arteriosclerotic risk factors: a meta-analysis.

This study was performed to clarify the overall inter-relationships between the arteriosclerotic risk factors, including smoking, alcoholic consumption, obesity, serum cholesterol and triglyceride levels, high density lipoprotein, and systolic and diastolic blood pressure using a meta analysis method. The subjects of this study were included in 24 primary studies reported in Korea since 1980, which concerned arteriosclerotic risk factors. The results show that smoking is significantly associated with total cholesterol (R = .04), triglyceride (R = .10) and HDL-cholesterol (R = -.06). Alcohol consumption is also significantly and positively associated with all three serum lipid parameters: cholesterol (R = .04), triglyceride (R = .08) and HDL-cholesterol (R = .10). The effect of smoking and alcohol consumption on cholesterol levels were found to be almost equal. However, smoking has a predominant effect on triglyceride, whereas, alcohol consumption exerts an influence primarily on the HDL-cholesterol level. Obesity was positively correlated with cholesterol (R = .25) and triglyceride (R = .21), however, it was negatively correlated with HDL-cholesterol (R = -.14). It appears that the serum lipid parameter, which shows strongest correlation with obesity, is the total cholesterol level. Obesity also showed a significant correlation with systolic (R = .19) and diastolic blood pressure (R = .13). Blood pressure was also positively correlated with cholesterol (R = .18) and triglyceride (R = .26), however, it correlated negatively with HDL-cholesterol (R = -.23). In conclusion, the overall inter-relationships between the arteriosclerotic risk factors; smoking, alcohol consumption, obesity, serum lipid level and blood pressure were all found to be significant.

The compound relationship of smoking and alcohol consumption with obesity.

The purpose of this study was to examine 1) whether the relationship between smoking and obesity was linear or non-linear (specifically U-shaped), and 2) if this relationship was proved to U-shaped, whether it was due to the interaction of the effects of smoking and alcohol consumption on obesity. The present study was performed using cross sectional data taken from the medical records of 400 male patients. Data was analyzed using linear and curvilinear estimation, Fisher's exact test, and two-way ANCOVA. The relationship between smoking intensity and BMI was able to be explained significantly by a quadratic model, rather than by linear model. As has been shown in other studies, this relationship was parabolic (or U-shaped), though it was not particularly remarkable. This U-shaped relationship appeared to be due to the interaction of the effects of smoking intensity and alcohol consumption on BMI. On the other hand, the relationship between smoking intensity and the percentage of body fat was able to be explained significantly by a linear as well as a quadratic model. Additionally, the interaction effect between smoking intensity and alcohol consumption did not influence the percentage of body fat significantly. In conclusion, there is no doubt that smoking and obesity are both serious health hazards. Based on the results of this and other studies, it can be confirmed that heavy smoking has a positive relationship with obesity. Therefore, the health benefits of smoking cessation, as well as the correction of unhealthy habits such as alcohol consumption should be clearly emphasized.

Acute effect of ethanol on firing patterns of Purkinje cells in the rat cerebellar slice preparation.

This study examined the acute effects of ethanol (EtOH) on the firing patterns of Purkinje cells (PCs) using an intracellular recording in slice preparation of rat cerebellum. The experiments were performed in sagittal cerebellar slices (400 micrometer) of adult Sprague-Dawley rats (80-100g). Ethanol was applied by a bath superfusion with a known concentration expressed as the percentage of solution by volume (v/v) at 0.1, 0.5, 1, 2, and 4%. The result of the Chi-square test illustrated that the firing patterns were altered significantly after EtOH (p=0.007). However, the firing patterns that were altered by EtOH application were not affected by EtOH concentration (p= 0.1296). Among the 54 PCs tested, 30 PCs did not display any spontaneous firing activity and 24 PCs displayed spontaneous spike activity, either spiking in the simple manner (n=14) or cyclicly oscillating (n=10). In the presence of EtOH, 31 PCs were quiet, 22 PCs exhibited simple spiking activity and 1 PC continued to oscillate. Most PCs that displayed spontaneous activity before EtOH application progressively slowed their spike activity after EtOH superfusion. Especially, it was evident that 9 out of 10 oscillating PCs stopped their regular cyclic activity. In addition, 9 out of 14 PCs that displayed simple spike activity ceased to fire after EtOH application. Eleven out of 30 quiet PCs began to fire irregularly after EtOH application and this phenomenon usually occurred with membrane depolarization. EtOH induced spontaneous activity in 36.7% (11/30) of the quiescent PCs. In conclusion, there was differential EtOH sensitivity in the vitro slice preparation. EtOH depressed the endogenously generated spontaneous activity, especially the oscillatory firing activity. In contrast, the silent PCs were excited after EtOH application. Since this differential sensitivity persists in the presence of tetrodotoxin (TTX), it is suggested that this differential sensitivity is peculiar to the PCs.

4-Aminopyridine (4-AP) augments Ca(2+)-dependent action potential and changes oscillatory firing patterns in rat cerebellar Purkinje cells.

Intracellular recordings in cerebellar slice preparation showed that applications of 4-AP altered the pattern of oscillatory firing activity in Purkinje cells (PCs), especially yielding pronounced changes in action potential shape. 4-AP increased the amplitude and duration of action potential significantly and decreased the spike frequency. After 4-AP application, the duration of bursting was prolonged and the duration of after-burst hyperpolarization was progressively shortened. In all PCs tested, the rhythmicity of oscillatory firing activity was abolished completely at the steady state. These results suggest that 4-AP-sensitive currents determine the shape and frequency of individual Ca(2+)-dependent action potentials as well as maintaining oscillatory firing activity in PCs.

Tendon transfer or tendon graft for ruptured finger extensor tendons in rheumatoid hands.

We evaluated the clinical outcome of tendon reconstruction using tendon graft or tendon transfer and the parameters related to clinical outcome in 51 wrists of 46 patients with rheumatoid arthritis with finger extensor tendon ruptures. At a mean follow-up of 5.6 years, the mean metacarpophalangeal (MP) joint extension lag was 8 degrees (range, 0-45) and the mean visual analogue satisfaction scale was 74 (range, 10-100). Clinical outcome did not differ significantly between tendon grafting and tendon transfer. The MP joint extension lag correlated with the patient's satisfaction score, but the pulp-to-palm distance did not correlate with patient satisfaction. We conclude that both tendon grafting and tendon transfer are reliable reconstruction methods for ruptured finger extensor tendons in rheumatoid hands.

Thick transparent rutile TiO2 films crystallized in solution.

We report a novel process for the preparation of dense, transparent TiO2 films of 2.5 mum thickness on a F-doped SnO2-covered glass substrate. The starting solution contained peroxotitanate complex ions, which are relatively stable under the experimental conditions, permitting the deposition of highly textured rutile nanocrystalline films. The nanocrystals exhibit specific orientations along the (101) and (002) crystalline planes. Kinetic studies suggest that the precipitation started from the formation of amorphous solids, followed by crystallization through a dissolution-recrystallization process. Although a minor phase of anatase was detected only for powders collected from solutions after film preparation, not for films, the transformation from amorphous to anatase was believed to occur before further transformation of anatase to rutile. The present method enables film synthesis on a surface with a large area, and therefore could be integrated into the processing of electroluminescent devices.

Surface precipitation of highly porous hydrotalcite-like film on Al from a zinc aqueous solution.

A hydrotalcite-like film has been successfully deposited on an Al-bearing glass substrate based on an interface reaction between an Al layer and a zinc aqueous solution. The film selectively grew on the Al surface but not on the glass surface. The film on Al was composed of layered nanosheets of a hydrotalcite-like compound containing Al and Zn. Comparably, deposits on the plastic surface and precipitates in solution were wurzite-type ZnO with various morphologies depending upon the preparation conditions. At low supersaturation degrees, single crystals and superstructures of Zn-Al hydrotalcite were also obtained. This porous hydrotalcite film has a potential application as catalyst supports, environmental materials, or matrixes for hydrotalcite-based nanocomposite films. Using Al as a reaction interface makes it easy to coat porous hydrotalcites on a series of matrix materials varying in shapes and properties, which is important for achieving practical applications. In addition, the method developed should be widely applicable to other systems for the preparation of porous or oriented hydrotalcite-like thin films by an appropriate combination of divalent/trivalent solution-substrate systems.

Development of a structural equation model for causal relationships among arteriosclerosis risk factors.

The purpose of this study was to clarify the dynamic causal relationships among arteriosclerotic risk factors, including age, smoking, alcoholic consumption, exercise, hypercholesterolemia, hypertriglyceridemia, and hypertension. Data were collected from the medical records of 400 male clients who visited a university hospital located in Inchon, Korea, from May 1996 to December 1996 for physical examinations. The Lineal Structural Relationships 8 program was used to verify the fitness of the hypothetical model to data. All of the fit statistics, except the Chi-square value, showed that the hypothetical model was well fitted to the data. Seven percent of obesity was explained by the variables of age, smoking, alcohol consumption, and exercise. Sixty percent of hyperlipidemia could be explained by the variables of age, smoking, exercise, and obesity. And 22% of hypertension was explained by the variables of age, smoking, alcohol consumption, exercise, and hyperlipidemia. Our results showed that these risk factors were directly and indirectly interrelated, and lifestyle variables (smoking, alcohol consumption, and exercise) influence almost all of arteriosclerotic risk factors.

Nucleation and growth of hydroxyapatite on an amino organosilane overlayer.

An amino organosilane overlayer (NH(2)-overlayer) was successfully processed on Si/SiO(2) substrates. Remarkable nucleation and growth of hydroxyapatite were found to take place on an NH(2)-overlayer after Si/SiO(2) substrates covered with the NH(2)-overlayer were soaked in supersaturated solutions with respect to Ca(2+) and PO(4)(3-) ions [1.0SBF (simulated body fluid), which contains similar compositions to that in a living body and 1.5SBF in which only Ca(2+) and PO(4)(3-) concentrations are 1.5 times than that in 1.0SBF]. The experimental results demonstrated that HAp nucleation on an NH(2)-overlayer is related to the electrostatic attractive force between positive NH(2)-overlayer surface and negative incipient HAp microparticles homogeneously nucleated in 1.5SBF solution at 50 degrees C. On the contrary, fewer HAp particles were observed on negatively charged "OH" terminated self-assembled monolayer (SAM) because of the repulsive interaction. The Ca/P molar ratios of HAp particles increased from 0.92 at the beginning of nucleation in 1.5SBF to 1.63 in 14 days after growth in 1.0SBF at 37 degrees C. After 14 days of soaking in 1.0SBF, a dense HAp film with the thickness up to 8.6 microm was formed on the NH(2)-overlayer.