High resolution microscopy study in Cr3C2-doped WC-Co

Microstructure in Cr₃C₂-doped WC-Co was examined by high-resolution electron microscopy (HRTEM) and X-ray energy dispersive spectroscopy (EDS) with a special interest in the segregation of Cr at WC/Co interfaces and WC/WC grain boundaries. The macroscopic morphology of carbide grains in Cr₃C₂-doped WC-Co was almost the same as that of non-doped one, however, doping of a small amount of Cr₃C₂ on WC-Co was found to be effective to reduce the grain size of carbide grains. HRTEM study revealed that both WC/Co and WC/WC interfaces were free from secondary phases or amorphous films. Nano-probe EDS analysis revealed that Cr segregated at both WC/Co and WC/WC interfaces in the Cr₃C₂ doped WC-Co. The grain growth retardation of carbide grains observed in the Cr₃C₂-doped WC-Co must be closely related to the segregation of Cr. On the other hand, an asymmetric tilt 2 grain boundary of WC/WC was observed in the grain orientationof (0001)//(11 0), [1 10]//[ 101]. The formation of this coherent boundary results from a small misfit of about 2% in a/c-axis of WC hexagonal lattice structure. The segregation of Cr and Co was detected also at this boundary in spite of high coherent boundary. This would be due to a small distortion of the grain boundary from an ideal 2 boundary.     

Method to determine temperature distribution and intrinsic emissivity of a cavity

A method is presented to determine simultaneously the temperature distribution and the intrinsic emissivities of a cavity surface when radiance distributions along the cavity wall for two wavelengths are given. The intrinsic emissivity and reflection characteristics are assumed not to depend on position on the cavity wall. The intrinsic emissivity and reflection characteristics giving the smallest difference between calculated temperature distributions for the two wavelengths are found. The values found and thus the temperature distributions are verified to be close to the true ones. The method is examined on a cylindrocone by a simulation and applied to radiance temperature distributions measured on a commercially available double cone.     

Method for determination of aflatoxin M₁ in cheese and butter by HPLC using an immunoaffinity column

A rapid, sensitive convenient method for determination of aflatoxin M? (AFM?) in cheese and butter by HPLC was developed and validated. The method employs a safe extraction solution (mixture of acetonitrile, methanol and water) and an immunoaffinity column (IAC) for clean-up. Compared with the widely used method employing chloroform and a Florisil column, the IAC method has a short analytical time and there are no interference peaks. The limits of quantification (LOQ) of the IAC method were 0.12 and 0.14 μg/kg, while those of the Florisil column method were 0.47 and 0.23 μg/kg in cheese and buffer, respectively. The recovery and relative standard deviation (RSD) for cheese (spiked at 0.5 μg/kg) in the IAC method were 92% and 7%, respectively, while for the Florisil column method the corresponding values were 76% and 10%. The recovery and RSD for butter (spiked at 0.5 μg/kg) in the IAC method were 97% and 9%, and those in the Florisil method were 74% and 9%, respectively. In the IAC method, the values of in-house precision (n=2, day=5) of cheese and butter (spiked at 0.5 μg/kg) were 9% and 13%, respectively. The IAC method is superior to the Florisil column method in terms of safety, ease of handling, sensitivity and reliability. A survey of AFM? contamination in imported cheese and butter in Japan was conducted by the IAC method. AFM? was not detected in 60 samples of cheese and 30 samples of butter.     

Effects of Limbic stimulation and the microinontophoresis of aminergic drugs on the single unit activity of hypothalamic neurosecretory cells (author''s transl)

1. The Na, K, Ca and Mg content and the 45Ca uptake and loss were determined in rat aortae incubated in physiological solution or in solution containing LaCl3 instead of CaCl2. 2. Aortae washed in La-solution contained less Ca and Na than controls in physiological solution, the K content was not modified and the Mg content was slightly decreased. 3. In 50 mM-La solution the 45Ca diffusion space was intermediate between the values found for the [14C]sorbitol space and the [14C]inulin space, indicating that there was no Ca entry within the cell nor Ca binding at superficial sites. 45Ca loss from the tissue was directly related to the La concentration. 4. Noradrenaline increased the rate of uptake of 45Ca into the Ca fraction resistant to displacement by La. This increase was dose dependent, a response of 50% of the maximum being produced by 2 x 10(-8) noradrenaline as for the contraction. In the presence of phentolamine, the dose-effect curves for the action of noradrenaline on 45Ca uptake were displaced in a manner characteristic of competitive antagonism. The rhoA2 for phentolamine was 7-8. 5. In physiological solution, the rate of loss of 45Ca, from the Ca fraction resistant to displacement by La, was increased by noradrenaline the ED50 was 2 x 10(-8) M, and the effect was abolished by phentolamine. 6. In view of the similarity of phentolamine rhoA2 estimated by measuring noradrenaline sensitive 45Ca uptake or noradrenaline evoked contraction, it is likely that the activation of alpha-adrenergic receptors is responsible for both effects.     

Plasma catecholamine levels in the coronary sinus, aorta and femoral vein of subjects undergoing cardiac catheterization at rest and during exercise

Plasma catecholamine (CA) levels in the coronary sinus (CS), aorta (Ao) and femoral vein (fv) were simultaneously measured in 22 patients with various heart diseases at rest and during handgrip exercise (IHG). The mean resting levels of plasma norepinephine (NE) in CS, Ao and FV were 359 +/- 49 (SEM) pg/ml, 290 +/- 27 and 234 +/- 24, respectively. The corresponding values of epinephrine (E) were 127 +/- 18 pg/ml, 186+/- 30 and 97 +/- 11, respectively. The E values in Ao were significantly greater than those in CS and in FV (p less than 0.05). IHG exercise induced an obvious elevation of plasma CA levels in every portion of the circulation studied. The mean increments of NE concentration were 81%, 54% and 67% of the resting levels at CS, Ao and FV, respectively, while IHG induced elevation of E were 70% of the resting values at each portion studied. Significant correlations were observed between individual CA concentrations in CS and in Ao, and also between those in Ao and in FV at rest. Under raised sympathoadrenal conditions, however, individual values of NE in CS failed to correlate signficantly to those in Ao and in FV, respectively. The NE output from CS was limited to only 3% and 5% of those in Ao at rest and during IHG, respectively. An actual mean increment of NE on its passing through the coronary circulation was only 2% or less of NE output in ao at both stages. It appears, thus, to be untenable that the cardiac tissue is one of the major source of circulating CA at physiological condition. From these reasons, the direct measurement of NE levels in CS may be mandatory, when plasma CA assay is designed for the purpose of studying the role of the sympathetic nerve activity in the regulation of cardiac function.     

Diffusionless Cubic-to-Tetragonal Phase Transition and Microstructural Evolution in Sintered Zirconia–Yttria Ceramics

Microstructural changes associated with the diffusionless cubic-to-tetragonal phase transition ( c–t ') in sintered ZrO₂–Y₂O₃ ceramics with 4 to 20 mol% Y₂O₃ are investigated. Ceramics containing 4 to 7 mol% Y₂O₃ that are quickly cooled from high temperatures experience cubic-to-tetragonal transformation by a diffusionless mechanism. The TEM diffraction pattern of the transformation product, t '-ZrO₂, reveals (112) reflections that are suppressed in the c -ZrO₂ phase. The microstructural features of the t '-ZrO₂ phase include antiphase boundaries and a twinned substructure in the (112) dark-field images. The (112) reflections result from the displacement of oxygen atoms in the lattice during phase transformation. With increasing Y₂O₃ content, the antiphase domain size, the tetragonality of the lattice, and the intensity of the (112) reflections decrease. When the Y₂O₃ content reaches 8 mol% or more, the (112) reflections appear, but the dark-field image shows no antiphase boundary, and the tetragonality decreases to 1. In ceramics with 14 to 20 mol% Y₂O₃, no suppressed reflection appears because the c–t transformation is fully suppressed. A model of the lattice structure is calculated and the intensity of diffraction determined experimentally; on this basis, the mechanism of diffusionless c–t 'transformation is discussed.     

Diffusional cubic-to-tetragonal phase transformation and microstructural evolution in ZrO2-Y2O3 ceramics

The diffusional cubic-to-tetragonal (c-t) phase transformation and microstructural evolution were studied on ZrO₂-Y₂O₃ ceramics with 4 to 6 mol% Y₂O₃ annealed in the two phase (c + t) region for longer periods of time. It was shown that in early stages of annealing a tweed structure of t-ZrO₂ was developed. With increasing annealing time this tweed structure becomes coarser and changes into internally twinned colony structure. The colonies can grow to large sizes but their twin-spacing remains almost constant. The effect of increasing annealing temperature was shown to be more obvious than prolonging annealing time in the transition from tweed to colony structure. The mechanism of the diffusional c-t transformation was discussed.     

Modeling and resonance suppression control for electro-hydrostatic actuator as a two-mass resonant system

Electro-hydrostatic actuators (EHAs) possess excellent power/weight ratio and space-saving properties. However, uncertainty exists with respect to the presence of non-linear behaviors and dynamic characteristics. Servo pumps, hydraulic motors, and oil-filled pipes can be regarded as motors, loads, and springs, respectively. Hence, EHAs can be modeled as two-mass resonant systems. In this paper, we show a parameter identification method for modeling EHAs as two-mass resonant systems. Then, in order to suppress the effect of resonance, self-resonance cancellation technique is implemented. As a result, phase delay is significantly improved in the position tracking.