Decomposition kinetics and recycle of binary hydrogen‐tetrahydrofuran clathrate hydrate

Decomposition kinetics and recycle of hydrogen–tetrahydrofuran (H₂–THF) clathrate hydrates were investigated with a pressure decay method at temperatures from 265.1 to 273.2 K, at initial pressures from 3.1 to 8.0 MPa, and at stoichiometric THF hydrate concentrations for particle sizes between 250 and 1000 μm. The decomposition was modeled as a two‐step process consisting of H₂ diffusion in the hydrate phase and desorption from the hydrate cage. The adsorption process occurred at roughly two to three times faster than the desorption process, whereas the diffusion process during formation was slightly higher (ca. 20%) than that during decomposition. Successive formation and decomposition cycles showed that occupancy seemed to decrease only slightly with cycling and that there were no large changes in hydrate structure due to cycling. Results provide evidence that the formation and decomposition of H₂ clathrate hydrates occur reversibly and that H₂ clathrate hydrates can be recycled with pressure. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Terahertz dielectric properties of plasma-sprayed thermal-barrier coatings

We investigated the electromagnetic wave transmittance and dielectric properties of yttria partially stabilised zirconia thermal-barrier coatings by terahertz time-domain spectroscopy in which the samples were irradiated by a pulsed THz wave in the frequency range of 0.1-6.3 THz. The coating microstructure was varied by changing the spray conditions and the THz transmittance and dielectric constants were examined as functions of frequency. The coatings exhibited a high transmittance of 20%-80% at frequencies below 0.5 THz and almost zero transmittance above 1.5 THz. The refractive index n for different coatings ranges from 4 to 6, depending on the coating microstructure. For any given coating, n increases to some extent with increasing frequency. Unlike the imaginary part of the dielectric constant, the real part of the dielectric constant is strongly correlated with the porosity of the coatings, which suggests that terahertz spectroscopy may potentially be used to non-destructively evaluate the porosity of ceramic coatings.     

A Novel Method of Measuring Moisture Content Distribution in Timber During Drying Using CT Scanning and Image Processing Techniques

A new method for the nondestructive measurement of moisture content (MC) distribution in timber during drying was developed using X-ray computed tomography (CT) scanning and image processing techniques. The deformed cross section in the CT images due to shrinkage was corrected with the image registration, and the shrinkage was measured by digital image correlation analysis. The pixel-wise MC distributions during drying were measured and visualized successfully. The total timber MC estimated from the MC values of each pixel were strongly correlated with those measured by calculation without geometrical transformation of CT images. The coefficient of determination (R ²) and the standard error of prediction (SEP) were 0.99 and 0.18%, respectively, within the MC range of 19.2–47.3%. In addition, the measured shrinkage distribution during drying was in accordance with the diamonding deformation observed. The results suggest that CT scanning combined with image processing techniques is an effective tool for nondestructive assessment of MC distribution during drying.     

Prenatal Exposure to Polycyclic Aromatic Hydrocarbons and Birth Outcomes

The effect of prenatal exposure to polycyclic aromatic hydrocarbons (PAHs) at the environmental level on birth size was examined. The concentration of 1-hydroxypyrene (1-OHP) in spot urine samples collected from 50 pregnant women in Tokyo was measured and was related to birth weight, length, and head circumference of the newborns the subjects delivered. Analysis of inter- and intra-individual variation in 1-OHP concentration in spot urine samples from non-smoking subjects revealed that single spot urine can represent the subject's exposure to PAHs over several weeks and utility of spot urine for assessing PAHs exposure level of non-smokers was indicated. Geometric mean urinary concentration of 1-OHP of the subjects was 0.056 μmol/mol creatinine, and smoking mothers (n = 7) excreted more 1-OHP (0.200 μmol/mol-cre) than non-smoking mothers (0.046 μmol/mol-cre). Multiple regression analysis using birth outcomes as the dependent variable and urinary 1-OHP and other covariates as independent variables revealed that urinary 1-OHP was not a significant variable to explain birth outcomes among non-smoking mothers.     

An autonomous distributed control method based on tie‐set graph theory in future grid

In future power grids where electricity flows bidirectionally, the essential problem is to maximize the total efficiency of distributed energy resources. In complicated and large‐scale systems such as modern power distribution networks, maximizing the efficiency of the entire system as a whole is extremely difficult. To solve the global optimization problem of such a complex network, this paper proposes an efficient distributed control method for future grid on the basis of tie‐set graph theory, where a tie‐set is a set of all the edges in a loop of a graph. On the basis of tie‐set graph theory, global optimization of an entire network can be realized as a result of local optimization in μ‐dimensional liner vector space, where μ is the nullity of the underlying graph of a power network. Although each tie‐set has its limited local information, an entire network is gradually optimized in an orderly manner because of the theoretical basis of a tie‐set graph. Simulation results of several thousand‐node networks demonstrate balanced allocation of dispersed energy resources and thus effectiveness of the proposed method. Copyright © 2012 John Wiley & Sons, Ltd.     

Space charge capacitance of ferroelectric memory cells in the nonlinear regime

Abstract

Recently ferroelectric thin-film capacitors have been modelled using the sub-surface space charge region. The model is similar to the well known abrupt p-n junction theory or semiconductors. This paper describes the sub-surface space charge using the landau free energy within a polarized medium. The capacitance of the ferroelectric storage cell is described from these first principles. The model predicts that the result of the abrupt p-n junction depletion capacitance (linear medium model) is the limit of the ferroelectric p-n junction model (non-linear medium) when the polarization approaches zero. The results of the model are applied successfully to 60/40 PZT capacitors where the intrinsic heterogeneity (high electron concentration in the near surface region) is always present due to high oxygen vacancy concentration. Both the linear and the nonlinear models are reasonable at high voltages but only the non-linear model is accurate at lower voltages. The results are also useful to characterize device parasitics and elucidate the effect of the microstructure on device behavior.     

Morphometric,quantitative, and three‐dimensional analysis of the heart muscle fibers of old rats: Transmission electron microscopy and high‐resolution scanning electron microscopy methods

This research investigated the morphological, morphometric, and ultrastructural cardiomyocyte characteristics of male Wistar rats at 18 months of age. The animals were euthanized using an overdose of anesthesia (ketamine and xylazine, 150/10 mg/kg) and perfused transcardially, after which samples were collected for light microscopy, transmission electron microscopy, and high‐resolution scanning electron microscopy. The results showed that cardiomyocyte arrangement was disposed parallel between the mitochondria and the A‐, I‐, and H‐bands and their M‐ and Z‐lines from the sarcomere. The sarcomere junction areas had intercalated disks, a specific structure of heart muscle. The ultrastructural analysis revealed several mitochondria of various sizes and shapes intermingled between the blood capillaries and their endothelial cells; some red cells inside vessels are noted. The muscle cell sarcolemma could be observed associated with the described structures. The cardiomyocytes of old rats presented an average sarcomere length of 2.071 ± 0.09 μm, a mitochondrial volume density (Vv) of 0.3383, a mitochondrial average area of 0.537 ± 0.278 μm², a mitochondrial average length of 1.024 ± 0.352 μm, an average mitochondrial cristae thickness of 0.038 ± 0.09 μm and a ratio of mitochondrial greater length/lesser length of 1.929 ± 0.965. Of the observed mitochondrial shapes, 23.4% were rounded, 45.3% were elongated, and 31.1% had irregular profiles. In this study, we analyzed the morphology and morphometry of cardiomyocytes in old rats, focusing on mitochondria. These data are important for researchers who focus the changes in cardiac tissue, especially changes owing to pathologies and drug administration that may or may not be correlated with aging. Microsc. Res. Tech., 2013. © 2012 Wiley Periodicals, Inc.