Simple model of the optical characteristics of bubbles and sediments in seawater of the surf zone

The development of a simple model of the seawater inherent optical properties (IOPs) associated with bubbles and sediments would represent a great advance in surf zone optics. We present one solution for this problem using a combination of geometrical optics and Fraunhofer diffraction. An analytic model of the IOPs of bubbles and sediments (the extinction and absorption coefficients, and phase function) is developed in terms of the moments of the particle size distribution and the complex refractive index of particles.     

Alcohol and tobacco cessation in alcohol-dependent smokers: Analysis of real-time reports.

Alcohol-tobacco interactions and relapse precipitants were examined among alcohol-dependent smokers in a trial of concurrent alcohol and tobacco treatment. After discharge from treatment, participants completed 14 days of electronic diary (ED) assessments of mood, self-efficacy, urges to drink or smoke, and drinking and smoking behavior. ED data revealed an increase in frequency of alcohol urges after smoking episodes. Drinking relapse episodes were predicted by prior ED ratings of low self-efficacy to resist drinking and high urge to smoke. Smoking relapse episodes were predicted by high urge to smoke and high negative, high arousal mood. Results support a cross-substance cue reactivity model of multiple substance use and a limited-strength model, but not a cross-substance coping model. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Determination of the effective diffusion coefficient in porous media including Knudsen effects

A 3-D bond pore network model is presented and used to evaluate the effect of pore size and connectivity on the effective diffusion coefficient in random porous media. The control equations of the system are set up and the simulation method is discussed. The simulation results show that when the average pore size d _m < 1 μm, the effective diffusion coefficient is strongly dependent on pore size. The analysis shows that Knudsen and bulk diffusion effects can be decoupled, and for any given diffusion conditions, the effect coefficient accounting for Knudsen diffusion can be obtained. Thus, the effect of pore size can been readily accounted for by correcting the bulk effective diffusivity with the Knudsen effect coefficient. The simulations also show that the percolation threshold in random porous materials decreases with increased pore network connectivity.     

Two-dimensional diffusion processes as models in lifetime studies

Let X(t) denote the remaining useful lifetime of a machine, and Y(t) be a standard Brownian motion. Assume that the derivative ρ[X(t),?Y(t)] of X(t) is a deterministic function of (at least) Y(t). We consider the two-dimensional degenerate diffusion process (X(t),?Y(t)). We obtain explicit expressions for the expected value of the random variable T(x,?y) denoting the first time the machine must be replaced, or repaired, for various functions ρ[X(t),?Y(t)].     

Activity-based probes linked with laser-cleavable mass tags for signal amplification in imaging mass spectrometry: analysis of serine hydrolase enzymes in mammalian tissue

A novel functional imaging mass spectrometry technology is described that utilizes activity-based probes for imaging enzyme active sites in tissue sections. We demonstrate this technology using an activity-based probe (fluorophosphate) that is specific for serine hydrolases. A dendrimer containing multiple mass tags that is attached to the activity-based probe is used to analyze the binding sites of the probe through release and measurement of the mass tags on laser irradiation. A generation 8 poly(amido amine) dendrimer with 1024 amino groups was labeled with an azide group, and then, more than 900 mass tags were attached in order to achieve signal amplification of nearly 3 orders of magnitude. The experimental protocol first involves binding of the activity-based probe containing an alkyne group to serine hydrolases in the tissue section followed by attachment of the dendrimer labeled with mass tags to the bound probe by Click chemistry. On irradiation of the labeled tissue by the laser beam in a raster pattern, the mass tags are liberated and recorded by the mass analyzer; consequently, the ion image of the mass tag reveals the distribution of serine hydrolases in the tissue. This process was shown using rat brain and mouse embryo sections. Targeted imaging has the advantage of providing high spatial resolution and high sensitivity through the use of signal amplification chemistry with high target specificity through the use of an enzyme activity probe.     

Three‐dimensional modelling of catalyst layers in PEM fuel cells: Effects of non‐uniform catalyst loading

Improving the performance of polymer‐electrolyte membrane (PEM) fuel cells depends on the optimization of catalyst layer composition and structure for large active surfaces. Modelling studies provide a valuable tool for investigating the effects of catalyst layer composition and structure on the electrochemical and physical phenomena occurring in PEM fuel cells. Previous modelling studies have shown that the distribution of electrochemical reactions in catalyst layers is highly dependent on the complex interaction of activation and ohmic effects as well as contributions from transport limitations and variations in local and overall current densities. In this paper, three‐dimensional, multicomponent and multiphase transport computations are performed using a computational fluid dynamics (CFD) code (FLUENT^TM) with a new PEM fuel cell module, which has been further improved by taking into account the detailed composition and structure of the catalyst layers using the multiple thin‐film agglomerate model. The detailed modelling of reactions in the catalyst layers is used to determine methods of improving the effectiveness of catalyst layers for a given platinum loading. First, available data on catalyst layer composition and structure are used in CFD computations to predict reaction rate distributions. Based on these results, spatial variations in catalyst loading are then implemented in CFD computations for the same overall catalyst loading to investigate possible performance gains. It is found that grading catalyst loading towards the membrane in the anode and the gas channel inlet in the cathode provides the most beneficial effects on the fuel cell performance. Thus the results suggest that significant savings in cost can be attained by reducing the platinum loading in underutilized regions of the catalyst layers, while at the same time improving the performance. Copyright © 2009 John Wiley & Sons, Ltd.     

在极端物理环境下实现正常测试

极端探测可能会是任何一种探测情况.在这些情况下,若不做适当的考虑,就有可能损坏探头和附件,或者导致测量结果不可靠或效果不佳.本文几项策略有助于在这些情况中尽可能地延长探头的使用寿命.     

Preliminary characterization of food tablets from date (Phoenix dactylifera L.) and spirulina (Spirulina sp.) powders

In this work, some physical properties (hardness, friability, disintegration time and erosion) of food tablets containing various food powders obtained from dates (Phoenix dactylifera L.), spirulina (Spirulina sp.) and oranges (juice and zest) were investigated. Also, experimental data related to the release kinetic of phycocyanin (antioxidant substance of spirulina) into different liquid mediums correctly fit the Korsmeyer-Peppas model since the coefficient of determination R² ranged from 0.84 (HCl 0.1 N solution) to 0.98 (distilled water). So, the date and spirulina powder-based food tablets could be of various uses: 1) consumption as such by all categories of consumers, 2) feeding of patients for whom it is difficult to chew or swallow food, knowing that these tablets can be either sucked or swallowed, and 3) as natural and cheap drug delivery carriers.     

Maturity effects on concrete strength

Strength-matruity relationships for concrete subjected to curing at various combinations of 30°F (?1°C), 70°F (21°C), and 110°F (43°C) temperatures are compared. Maturity is calculated using a popular maturity equation that integrates temperature with respect to time. The maturity equation is shown to be inaccurate. The equation does not properly account for the effects of temperatures occurring within about seven hours after placement on later strengths.     

The low‐temperature method for study of coniferous tissues in the environmental scanning electron microscope

The use of non‐standard low‐temperature conditions in environmental scanning electron microscopy might be promising for the observation of coniferous tissues in their native state. This study is aimed to analyse and evaluate the method based on the principle of low‐temperature sample stabilization. We demonstrate that the upper mucous layer is sublimed and a microstructure of the sample surface can be observed with higher resolution at lower gas pressure conditions, thanks to a low‐temperature method. An influence of the low‐temperature method on sample stability was also studied. The results indicate that high‐moisture conditions are not suitable for this method and often cause the collapse of samples. The potential improvement of stability to beam damage has been demonstrated by long‐time observation at different operation parameters. We finally show high applicability of the low‐temperature method on different types of conifers and Oxalis acetosella. Microsc. Res. Tech., 78:13–21, 2015. © 2014 Wiley Periodicals, Inc.