Chemical Stability of ZnO–Na2O–SO3–P2O5 Glasses

We report on chemical stability and corrosion behavior of highly depolymerized sulfophosphate glasses from the system ZnO–Na₂O–SO₃–P₂O₅ in aqueous solution, providing data on weight loss, ion release rates, and modifications of surface topology as a function of time, temperature and pH value. Observations seem consistent with the previously developed structural model of chemical heterogeneity, where cations Na⁺ and Zn²⁺ cluster selectively in the vicinity of sulfate and phosphate anions, respectively.     

Goal-oriented a posteriori error estimates for transport problems

Some aspects of goal-oriented a posteriori error estimation are addressed in the context of steady convection–diffusion equations. The difference between the exact and approximate values of a linear target functional is expressed in terms of integrals that depend on the solutions to the primal and dual problems. Gradient averaging techniques are employed to separate the element residual and diffusive flux errors without introducing jump terms. The dual solution is computed numerically and interpolated using higher-order basis functions. A node-based approach to localization of global errors in the quantities of interest is pursued. A possible violation of Galerkin orthogonality is taken into account. Numerical experiments are performed for centered and upwind-biased approximations of a 1D boundary value problem.     

A parameterized model of heat storage by lake sediments

A model of seasonal heat storage by lake sediments is proposed oriented at applications in climate modeling and at lake parameterization in numerical weather prediction. The computational efficiency is achieved by reformulating of the heat transfer problem as a set of ordinary differential equations for evolution of the temperature wave inside the upper sediment layer. Arising temperature and depth scales completely replace the conductivity of the sediment in the heat transfer equation and can be easily achieved from the lake water temperature observations without any data on the sediment thermal properties. The method is proposed for the scales estimation from the inverse solution of the model equations in special case of the constant water-sediment heat flux in ice-covered lakes. The method is tested on data from sediments of Lake Krasnoye, North-Western Russia. The long-term (1961–2002) modeling of temperature in German lakes Müggelsee and Heiligensee with a coupled one-dimensional model of lake water column and sediments has demonstrated an appreciable effect of the sediment heat storage on near-bottom temperatures in both lakes. Thus, incorporation of the sediment layer into lake temperature models can essentially improve, at low computational costs, the model performance, especially for shallow lakes. In addition, a better forecast of near-bottom temperature evolution on climatic scales can provide a better understanding of the response of lake benthic communities to global warming.     

Large-area organic photovoltaic module—Fabrication and performance

Here we describe the fabrication of the largest (233 cm² total area) organic photovoltaic (OPV) module (polymer:fullerene) to be certified by the National Renewable Energy Laboratory (NREL). OPV solar cells were fabricated at Plextronics by spin coating a blend of poly 3-hexylthiophene-2,5 diyl (P3HT) and [6,6] phenyl C₆₁ butyric acid methyl ester (PCBM) on top of our hole transport layer (HTL), Plexcore^® OC. In laboratory-scale devices (0.09 cm²), this system routinely exhibits power conversion efficiencies exceeding 3.7%. This P3HT:PCBM active layer and HTL ink system was used to scale up to the larger area module (15.2 cm×15.2 cm module size, i.e. 233 cm² total area; 108 cm² active area), which was certified by NREL as having 1.1% total area efficiency (3.4% active area efficiency).     

Fast variation method for elastic strip calculation

A new, fast, variation method (FVM) for determining an elastic strip response to stresses arbitrarily distributed on the flat side of the strip is proposed. The remaining surface of the strip may have an arbitrary form, and it is free of stresses. The FVM, as well as the wellknown finite element method, starts with the variational principle. However, it does not use the meshing of the strip. A comparison of FVM results with the exact analytical solution in the special case of shear stresses and a rectangular strip demonstrates an excellent agreement     

Application of natural receptors in sensors and assays

Biosensors are analytical devices that use a biological or biologically derived material immobilized at a physicochemical transducer to measure one or more analytes. Although there are a large number of reviews on biosensors in general, there has been little systematic information presented on the application of natural receptors in sensor technology. This perspective discusses broadly the fundamental properties of natural receptors, which make them an attractive option for use as biorecognition elements in sensor technology. It analyses the current situation by reference to typical examples, such as the application of nicotinic acetylcholine receptor and G protein-linked receptors in affinity sensors and analyses the problems that need to be resolved prior to any commercialization of such devices.     

Atmospheric optical turbulence over land in middle east coastal environments: prediction modeling and measurements

Beam intensity scintillations, characterized by a refractive-index structure parameter and caused by variations of macrometeorological features of the coastal atmosphere such as air temperature, wind speed and direction, and relative humidity, are examined theoretically and experimentally. In our theoretical analysis we present two well-known models considered separately for over-water and over-land atmospheric optical communication or imaging channels. By means of comparison with our experiments carried out in midland coastal environments in southern and northern Israel, we show the limitations of the models to predict the refractive-index structure Cn2 parameter for both daytime and nighttime turbulent atmospheres in different coastal zone meteorological conditions. We also present an extension of an existing model with two different practical applications that, as is shown experimentally, can be a good predictor of Cn2 for optical atmospheric paths over midland coastal zones.     

Wide-aperture,line-focused ultrasonic material characterization system based on lateral scanning

We present a new wide-aperture, line-focused ultrasonic material characterization system. The foci of the transmitting and receiving transducers are located in the specimen-immersion liquid interface; and the output voltage V(x, t) of the system is recorded as a function of the lateral position of the receiving transducer. The two-dimensional spectrum of V(x, t) can be expressed as a product of the transfer function of the system and the reflectance function of the interface. In comparison with a system based on scanning in the z direction, the angular resolution of the proposed technique increases with decreasing angle of incidence. There are no geometrical restrictions on the length of the recorded spatial data and the angle of incidence in the case of lateral scanning. The temperature coefficient of the measurement error is low because of the constancy of the propagation distance of ultrasound in the immersion fluid during data acquisition.