Collision of two counterflowing gravity currents of equal densities and heights was investigated by means of three-dimensional high-resolution simulations with the goal of understanding the flow structures and energetics in the collision region in more detail. The lifetime of collision is approximately $3 \tilde {H}/\tilde {u}_f$, where $\tilde {H}$ is the depth of heavy and ambient fluids, and $\tilde {u}_f$ is the front velocity of the approaching gravity currents, and the lifetime of collision can be divided into three phases. During Phase I, $-0.2 \leqslant (\tilde {t}-\tilde {t}_c) \tilde {u}_f/\tilde {H} \leqslant 0.5$, where $\tilde {t}$ is the time, and $\tilde {t}_c$ is the time instance at which the two colliding gravity currents have fully osculated, geometric distortions of the gravity current fronts result in stretching of pre-existing vorticity in the wall-normal direction inside the fronts, and an array of vertical vortices extending throughout the updraught fluid column develop along the interface separating the two colliding gravity currents. The array of vertical vortices is responsible for the mixing between the heavy fluids of the two colliding gravity currents and for the production of turbulent kinetic energy in the collision region. The presence of the top boundary deflects the updraughts into the horizontal direction, and a number of horizontal streamwise vortices are generated close to the top boundary. During Phase II, $0.5 \leqslant (\tilde {t}-\tilde {t}_c) \tilde {u}_f/\tilde {H} \leqslant 1.2$, the horizontal streamwise vortices close to the top boundary induce turbulent buoyancy flux and break up into smaller structures. While the production of turbulent kinetic energy weakens, the rate of transfer of energy to turbulent flow due to turbulent buoyancy flux reaches its maximum and becomes the primary supply in the turbulent kinetic energy in Phase II. During Phase III, $1.2 \leqslant (\tilde {t}-\tilde {t}_c) \tilde {u}_f/\tilde {H} \leqslant 2.8$, the collided fluid slumps away from the collision region, while the production of turbulent kinetic energy, turbulent buoyancy flux and dissipation of energy attenuate. From the point of view of energetics, the production of turbulent kinetic energy and turbulent buoyancy flux transfers energy away from the mean flow to the turbulent flow during the collision. Our study complements previous experimental investigations on the collision of gravity currents in that the flow structures, spatial distribution and temporal evolution of the mean flow and turbulent flow characteristics in the collision region are presented clearly. It is our understanding that such complete information on the energy budgets in the collision region can be difficult to attain in laboratory experiments.

It is usually believed that wall slip contributes small effects to macroscopic flow characteristics. Here we demonstrate that this is not the case for the thermocapillary migration of a long bubble in a slippery tube. We show that a fraction of the wall slip, with the slip length $\lambda $ much smaller than the tube radius $R$, can make the bubble migrate much faster than without wall slip. This speedup effect occurs in the strong-slip regime where the film thickness $b$ is smaller than $\lambda $ when the Marangoni number $S= \tau _{T} R/\sigma _{0}~ (\ll 1)$ is below the critical value $S^* \sim (\lambda /R)^{1/2}$, where $\tau _{T}$ is the driving thermal stress and $\sigma _{0}$ is the surface tension. The resulting bubble migration speed is found to be $U_{b} \sim (\sigma _{0}/\mu )S^{3}(\lambda /R)$, which can be more than a hundred times faster than the no-slip result $U_{b} \sim (\sigma _{0}/\mu )S^{5}$ (Wilson, J. Eng. Math., vol. 29, 1995, pp. 205–217; Mazouchi & Homsy, Phys. Fluids, vol. 12, 2000, pp. 542–549), with $\mu $ being the fluid viscosity. The change from the fifth power law to the cubic one also indicates a transition from the no-slip state to the strong-slip state, albeit the film thickness always scales as $b\sim RS^{2}$. The formal lubrication analysis and numerical results confirm the above findings. Our results in different slip regimes are shown to be equivalent to those for the Bretherton problem (Liao, Li & Wei, Phys. Rev. Lett., vol. 111, 2013, 136001). Extension to polygonal tubes and connection to experiments are also made. It is found that the slight discrepancy between experiment (Lajeunesse & Homsy, Phys. Fluids, vol. 15, 2003, pp. 308–314) and theory (Mazouchi & Homsy, Phys. Fluids, vol. 13, 2001, pp. 1594–1600) can be interpreted by including wall slip effects.

A frame quality control mechanism for H.264/AVC is proposed in this research. The research objective is to ensure that a suitable quantization parameter (QP) can be assigned to each frame so that the target quality of each frame will be achieved. One of the potential application is consistently maintaining  frame quality during the encoding process to facilitate video archiving and/or video surveillance. A single-parameter distortion to quantization (D–Q) model is derived by training a large number of frame blocks. The model parameter can be determined from the frame content before the exact encoding process. Given the target quality for a video frame, we can then select an appropriate QP according to the proposed D–Q model. Model refinement and QP adjustment of subsequent frames can be applied by examining the coding results of previous data. Such quality measurements as peak signal to noise ratio (PSNR) and structural similarity (SSIM) can be employed. The experimental results verify the feasibility of the proposed constant quality video coding framework.

In this study, we investigated whether landscape-scale variation of soil P accounts for 13C and 15N composition of detrital invertebrates in a lowland tropical rain forest in Costa Rica. The top 10-cm soil, leaf-litter samples and plant foliage were collected among 18 plots representing a three-fold soil P gradient during 2007–2009. Body tissue of litter invertebrates (extracted from leaf-litter samples) along with soil, leaf litter and green foliage were analysed for total C, total N, δ13C and δ15N values. Differences in δ13C and δ15N signatures across plots and relative trophic distances of detrital food webs (Δ δ15N), and their variation with soil P gradient were evaluated. We found soil P gradient had a significantly positive correlation with δ15N of Asterogyne martiana foliage, leaf litter, collembolans and oribatid mites. The δ15N of the collembolans and pseudoscorpions positively correlated to leaf-litter δ15N. Δ δ15N between the trophic levels remained consistent across the soil P gradient. Higher δ15N in the collembolans and oribatid mites might be derived from their consumption on 15N-enriched decayed debris or fungal hyphae growing on it. It suggests that fine-scale soil P variation can affect trophic dynamics of detrital arthropods via regulation of microbial community and nutrient dynamics.

Episodic memory tasks are one of the most sensitive tools to discriminate Alzheimer’s disease (AD). This study aimed to validate a shorter version verbal memory test that will efficiently assess Chinese elderly with memory complaints. One hundred and eighty-five elderly with normal cognition (NC) and 217 AD patients were evaluated. Each participant received the Chinese Version Verbal Learning Test (CVVLT) consisting of 9 two-character nouns with 4 learning trials, 2 delayed recalls in 30 seconds and 10 minutes, and a word recognition test. In the NC elderly, age and sex had significant effects on recall scores in CVVLT, while education level showed an inverse correlation with 3 different patterns of errors made during the learning, recall, and recognition trials. AD patients had lower scores across all recall tests. In those with lower educational level, NC elderly had higher perseveration errors than AD patients. The cutoff value between the AD and NC groups in the 10-minute recall was 4/5 for those aged >75 years and 5/6 for those aged <75 years. This study has good validity in discriminating AD participants and the data here can help in diagnosing AD and mild cognitive impairment using the CVVLT. (JINS, 2010, 16, 244–251.)

We have fabricated La0.6Ca0.4MnO3 periodic arrays exhibiting tunable optical properties and magnetic properties using nontoxic and environmentally friendly electron beam resist made from La0.6Ca0.4MnO3 sol-gel precursor. We studied their unique optical properties by using the spectral microreflectometer and their magnetic properties using the superconducting quantum interference device and magnetic force microscopy. Additionally, the resist has the ability to demonstrate both positive and negative resist behaviors depending on the electron beam dosage. With these special characteristics, we can fabricate periodic structure on a thin film possessing controlled optical reflectance properties with one fixed design electron beam pattern without changing the structural parameters but changing the electron beam dosage only. Our approach provides an uncomplicated route for the fabrication of nanometer scale magnetic patterns, which serve as the building blocks in the search for novel properties of periodic magnetic arrays.

In this paper, we report that the experimental procedures for the preparation of conductive color powders that were aggregated from color pigment and conductive materials. We first modified the pigment and make the particles surface to have charges (ex: positive) and modified another conductive materials like ITO、Au、Ag particles or conductive polymer to be opposite charges (ex: negative). Then these two kinds of charge particles will aggregate in appropriate processing by static electricity and form a powder. After annealing treatment, the conductive color powder with ITO particles reveals good thermal stability and lower surface resistivity.

GaN film grown on Si substrate with AlN/AlxGa1−xN buffer is studied by low pressure metal organic chemical vapor deposition (MOCVD) method. The AlxGa1−xN film with Al composition varying from 0∼ 0.66 was used. The correlation of the Al composition in the AlxGa1−xN film with the stress of the GaN film grown was studied using high resolution X-ray diffraction including symmetrical and asymmetrical ω/2θscans and reciprocal space maps. It is found that with proper design of the Al composition in the AlxGa1−xN buffer layer, crack-free GaN films can be successfully grown on Si (111) substrates using AlN and AlxGa1−xN buffer layers.

Little is known about the biological effect of folate in the protection against mitochondrial (mt) oxidative decay. The objective of the present study was to examine the consequence of folate deprivation on mt oxidative degeneration, and the mechanistic link underlying the relationship. Male Wistar rats were fed with an amino acid-defined diet containing either 8 (control) or 0 (folate-deficient, FD) mg folic acid/kg diet. After a 4-week FD feeding period, significant elevation in oxidative stress was observed inside the liver mitochondria with a 77 % decrease in mt folate level (P < 0·001), a 28 % reduction in glutathione peroxidase activity (P = 0·0333), a 1·2-fold increase of mt protein carbonyls (P = 0·0278) and an accumulated 4834 bp large-scale deletion in mtDNA. The elicited oxidative injuries in FD liver mitochondria were associated with 30 % reduction of cytochrome c oxidase (CcOX) activity (P = 0·0264). The defective CcOX activity in FD hepatocytes coincided with mt membrane potential dissipation and intracellular superoxide elevation. Exposure of FD hepatocytes to pro-oxidant challenge (32 μm-copper sulphate for 48 h) led to a further loss in CcOX activity and mt membrane potential with a simultaneous increase in superoxide production. Preincubation of pro-oxidant-treated FD hepatocytes with supplemental folic acid (10–1000 μm) reversed the mt oxidative defects described earlier and diminished superoxide overproduction. Increased supplemented levels of folic acid strongly correlated with decreased lipid peroxidation (γ − 0·824, P = 0·0001) and protein oxidative injuries (γ − 0·865, P = 0·0001) in pro-oxidant-challenged FD liver mitochondria. Taken together, the results demonstrated that folate deprivation induces oxidative stress in liver mitochondria, which is associated with CcOX dysfunction, membrane depolarization and superoxide overproduction. The antioxidant activity of supplemental folic acid may partially, if not fully, contribute to the amelioration of pro-oxidant-elicited mt oxidative decay.

Few studies have been conducted to investigate ecological roles of litter amphibians in forest ecosystems. In this study, ten field enclosures (3 m × 2 m × 0.4 m) were used to evaluate effects of the toad Bufo bankorensis on the abundance of litter invertebrates (microbivores, fragmenters and predatory arthropods) and litter decomposition rates in a subtropical forest of southern Taiwan. Litterbags collected from toad and control (toad-excluded) enclosures were analysed for the communities and abundances of litter invertebrates and decay loss during this decomposition study from September to December 2001. The presence of B. bankorensis significantly changed phosphorus concentrations in the litter, but not the densities of litter invertebrates (microbivores, fragmenters and predatory arthropods) or rates of litter decomposition. These results were not consistent with previous studies, which have shown that Plethodon cenereus in a temperate forest of north-east USA and Eleutherodactylus coqui in a tropical rain forest of Puerto Rico significantly changed decomposition rates. We suggest that ecological roles of ground-dwelling amphibians may be species-specific and vary with different terrestrial ecosystems.

For embedded DRAM (E-DRAM) devices with feature sizes of 0.25 µm and beyond, contact processes with low contact resistance and low junction leakage current are required. The contact etch process needs to etch through multi-layer structures with SiO2, SiON/SiN layers and stop on Ti-polycide gate and Ti-salicide active regions at the same time. The key issues include high selectivity to TiSix, vertical profile, complete removal of SiON/SiN cap layer and no polymer residues. In this paper, multi-layer contact etching without attacking TiSix is reported. Using new process chemistry, the new contact etch process has been demonstrated for the manufacturing of 0.25 µm E-DRAM and beyond.