Plasma surface modification and characterization of collagen‐based artificial cornea for enhanced epithelialization

Argon plasma treatment enhanced the attachment of epithelial cells to a collagen‐based artificial cornea crosslinked using glutaraldehyde (GA) and glutaraldehyde‐polyethylene oxide dialdehyde (GA‐PEODA) systems. The epithelialization of untreated and treated surfaces was evaluated by the seeding and growth of human corneal epithelial cells. Characterization of polymer surface properties such as surface hydrophilicity and roughness was also made by contact angle measurement and atomic force microscopy, respectively. Contact angle analysis revealed that the surface hydrophilicity significantly increased after the treatment. In addition, AFM characterization showed an increase in surface roughness through argon plasma treatment. Based on the biological and surface analysis, argon plasma treatment displays promising potential for biocompatibility enhancement of collagen‐based artificial corneas. It was also found that the cell attachment to artificial cornea surfaces was influenced by the combined effects of surface chemistry (i.e., surface energy), polymer surface morphology (i.e., surface roughness), and polar interactions between functional groups at the polymer surface and cell membrane proteins. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Design tradeoff analysis of floating-point adders in FPGAs

With gate counts of ten million, field-programmable gate arrays (FPGAs) are becoming suitable for floating-point computations. Addition is the most complex operation in a floating-point unit and can cause major delay while requiring a significant area. Over the years, the VLSI community has developed many floating-point adder algorithms aimed primarily at reducing the overall latency. An efficient design of the floating-point adder offers major area and performance improvements for FPGAs. Given recent advances in FPGA architecture and area density, latency has become the main focus in attempts to improve performance. This paper studies the implementation of standard; leading-one predictor (LOP); and far and close datapath (2-path) floating-point addition algorithms in FPGAs. Each algorithm has complex sub-operations which contribute significantly to the overall latency of the design. Each of the sub-operations is researched for different implementations and is then synthesized onto a Xilinx Virtex-II Pro FPGA device. Standard and LOP algorithms are also pipelined into five stages and compared with the Xilinx IP. According to the results, the standard algorithm is the best implementation with respect to area, but has a large overall latency of 27.059 ns while occupying 541 slices. The LOP algorithm reduces latency by 6.5% at the cost of a 38% increase in area compared to the standard algorithm. The 2-path implementation shows a 19% reduction in latency with an added expense of 88% in area compared to the standard algorithm. The five-stage standard pipeline implementation shows a 6.4% improvement in clock speed compared to the Xilinx IP with a 23% smaller area requirement. The five-stage pipelined LOP implementation shows a 22% improvement in clock speed compared to the Xilinx IP at a cost of 15% more area.     

An adaptive power system stabilizer based on recurrent neuralnetworks

Application of recurrent, neural networks in the design of an adaptive power system stabilizer (PSS) is presented in this paper. The architecture of the proposed adaptive PSS has two recurrent neural networks. One functions as a tracker to learn the dynamic characteristics of the power plant and the second one functions as a controller to damp the oscillations caused by the disturbances. In the proposed approach, the weights of the neural networks are updated on-line. Therefore, any new information available during actual control of the plant is considered. Simulation studies show that the artificial neural network (ANN) based PSS can provide very good damping over a wide range of operating conditions     

An application of frequency and duration approach in generationplanning

The available analytical tools for planning not only inadequately model pumped storage (PS) power plant units but also underestimate their load-levelling benefits. Therefore, if a PS power plant is among the candidate plants, its selection in the final “optimal plan” is highly unlikely. This research deals to assess the complete load-levelling benefits of PS units. The technique used is the frequency and duration approach coupled with the equivalent load duration curve (ELDC) method, used for generation planning. The proposed method is applied to IEEE RTS data and it is shown that almost 50% of PS benefits are not quantified in ELDC method     

Structured carbon haemoadsorbents for the removal of middle molecular weight toxins

There is continued interest in the development of novel haemoadsorbents for the removal of middle molecular weight molecules from blood in patients suffering with chronic renal failure. Conventional activated carbons have shown poor biocompatibility whereas polymer coated carbons have been applied with limited success. The external biocompatible coating significantly reduces the adsorption capacity for middle molecules due to size exclusion and slows down the adsorption kinetics due to mass transport limitations. In this work, we show that polymer derived mesoporous activated carbons (pore size in the range 2-50 nm) and surface area of between 400 and 800 m²/g are efficient adsorbents for middle molecular weight species such as interleukin IL-1beta.     

Integrated Urban Lei River (North Pakistan) Water Resources Management

The urban Lei river consists of a catchment area of about 211 km 2 . About 55% lies in Islamabad (population about 3 million) and the rest in Rawalpindi (population about 3 million). The city of Islamabad is growing without considering its hydrogeological set-up, which is creating further flood problems in Rawalpindi. Even after the drought of 1994, groundwater is being privately exploited without any central legal control. Measures for increasing the amount of available groundwater would improve drinking water both qualitatively and quantitatively, reduce loss through uncontrolled runoff, reduce aquifer depletion and lead also to improved monitoring. The chessboard regional city planning of Islamabad, as laid down in the Master Plan (1960), has to be replanned inter-disciplinary according to topographical, geological, meteorological, hydrological and hydrogeological investigations. Sustainable ecological solutions ought not be sacrificed to political short-sighted expedience.     

Possible Impact of Global Warming on Water Resources and Objects of Power Engineering

The main directions in global warming and its possible impact on the hydrological system are determined. __________ Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 5, May 2005, pp. 2 – 14.     

Exact memory size estimation for array computations

This paper presents a new algorithm for exact estimation of the minimum memory size required by programs dealing with array computations. Based on parametric partitioning of the iteration space and formalized live variable analysis, our algorithm transforms the minimum memory size estimation into an equivalent problem: integer point counting for intersection/union of mappings of parameterized polytopes. A heuristics was then proposed to solve the counting problem. Experimental results show that the algorithm achieves the exactness traditionally associated with totally unrolling loops while exploiting reduced computation complexity by preserving the original loop structure     

A synchronous generator fuzzy excitation controller optimallydesigned with a genetic algorithm

Design of a fuzzy logic power system controller with satisfactory performance is not an easy task. The difficulties come from two aspects. First, design of a fuzzy logic controller mainly uses the experience of the human experts. To acquire enough heuristic knowledge from the domain experts and to represent this kind of knowledge appropriately with a set of fuzzy rules present difficulties. Second, it is difficult to appropriately tune the parameters used in the fuzzy logic controller. These parameters are commonly determined by a “trial and error” method which is rather time consuming. In this paper, genetic algorithm is introduced to design an optimal fuzzy logic controller. The proposed method has been used to design an optimal fuzzy logic excitation controller for a generating unit. Test results with the fuzzy logic controller show very satisfactory results