A microchip-based multianalyte assay system for the assessment of cardiac risk

The development of a novel chip-based multianalyte detection system with a cardiac theme is reported. This work follows the initial reports of "electronic taste chips" whereby multiple solution-phase analytes such as acids, bases, metal cations, and biological cofactors were detected and quantitated. The newly fashioned "cardiac chip" exploits a geometry that allows for isolation and entrapment of single polymeric spheres in micromachined pits while providing to each bead the rapid introduction of a series of reagents/washes through microfluidic structures. The combination of these miniaturized components fosters the completion of complex assays with short analysis times using small sample volumes. Optical signals derived from single beads are used to complete immunological tests that yield outstanding assay characteristics. The power and utility of this new methodology is demonstrated here for the simultaneous detection of the cardiac risk factors, C-reactive protein and interleukin-6, in human serum samples. This demonstration represents the first important step toward the development of a useful cardiac chip that targets numerous risk factors concurrently and one that can be customized readily for specific clinical settings.     

Reformulated radial basis function neural networks with adjustable weighted norms

This article presents a new family of reformulated radial basis function (RBF) neural networks that employ adjustable weighted norms to measure the distance between the training vectors and the centers of the radial basis functions. The reformulated RBF model introduced in this article incorporates norm weights that can be updated during learning to facilitate the implementation of the desired input‐output mapping. Experiments involving classification and function approximation tasks verify that the proposed RBF neural networks outperform conventional RBF neural networks and reformulated RBF neural networks employing fixed Euclidean norms. Reformulated RBF neural networks with adjustable weighted norms are also strong competitors to conventional feedforward neural networks in terms of performance, implementation simplicity, and training speed. © 2003 Wiley Periodicals, Inc.     

The use of multicomponent statistical analysis in hydrogeological environmental research

The present article examines the possibilities of investigating NO(3)(-) spread in aquifers by applying multicomponent statistical methods (factor, cluster and discriminant analysis) on hydrogeological, hydrochemical, and environmental parameters. A 4-R-Mode factor model determined from the analysis showed its useful role in investigating hydrogeological parameters affecting NO(3)(-) concentration, such as its dilution by upcoming groundwater of the recharge areas. The relationship between NO(3)(-) concentration and agricultural activities can be determined sufficiently by the first factor which relies on NO(3)(-) and SO(4)(2-) of the same origin-that of agricultural fertilizers. The other three factors of R-Mode analysis are not connected directly to the NO(3)(-) problem. They do however, by extracting the role of the unsaturated zone, show an interesting relationship between organic matter content, thickness and saturated hydraulic conductivity. The application of Hirerarchical Cluster Analysis, based on all possible combinations of classification method, showed two main groups of samples. The first group comprises samples from the edges and the second from the central part of the study area. By the application of Discriminant Analysis it was shown that NO(3)(-) and SO(4)(2-) ions are the most significant variables in the discriminant function. Therefore, the first group is considered to comprise all samples from areas not influenced by fertilizers lying on the edges of contaminating activities such as crop cultivation, while the second comprises all the other samples.     

Clustering algorithm for the topological design of hierarchical,multidrop data networks

Imulec, a clustering algorithm for the interactive design of hierarchical centralized data networks is presented. The algorithm locates potential concentrator sites of various levels using a clustering procedure. It is capable of handling different types of concentrators and provides a multidrop line layout of the network considering various constraints, such as line capacities, maximum traffic per concentrator, maximum number of input ports to a concentrator etc. The designs obtained are compared with previous published results.     

Static plastic behavior of a strand

The static plastic collapse of a single strand which is idealised as m bars with circular cross-sections and helical axes has been examined using the limit theorems of plasticity. An exact theoretical solution which retains the influence of contact forces was obtained for a strand subjected to an axial load accompanied by a torsional moment.     

Extractable waxes from Greek lignites

An investigation on the solvent-extraction yields of Greek lignites has shown that the yields are generally low compared with the yields from certain American and German lignites, and similar to the yields from Czechoslovakian lignites. The highest yields were obtained from lignites of the Psachna deposit. The only extract which resembled rather closely in its nature the Riebeck crude montan wax was obtained by benzene extraction from Ptolemais lignite. The most significant differences between benzene extracts from Greek lignites and Riebeck crude montan wax were the differences in melting points and the greater resin content of the Greek waxes. Extraction with benzene/methanol mixture instead of benzene gave higher yields and extracts characterized by higher melting points, and higher acid and ester values. The compatibility of the extracts with paraffin wax was low; only benzene extract from Ptolemais lignite was completely miscible. No relation was found between the wax yield and the ratio volatile matter/fixed carbon of the coal. We also conclude that extraction of waxes from Greek lignites is not commercially attractive.     

An investigation of cutting edge failure due to chip crush in carbide dry hobbing using the finite element method

The aim of this research is to investigate a type of failure of dry carbide hobbing that occurs when the generated chips are pinched and crushed between the hob cutting edge and the work gear tooth flank by utilizing the finite element method. This problem is of great importance because gear hobbing is extensively used in the manufacturing industry. Many machine tool manufacturers have so far developed dry hobbing techniques using carbide hobs as there is a growing acknowledgment that it is necessary to employ carbide hobbing for higher productivity and pollution free gear cutting. To meet the increasing needs of cost reduction and environmentally friendly methods, dry hobbing being employed for gear mass production has completely eliminated the need of tool cooling. However, carbide hobbing has not come into wide use due to the high cost of carbide hobs, and mainly due to the unexpected chipping of the brittle carbide material, making it difficult to control the tool service life. Dry hobbing often causes problems such as chipping of the carbide hob tooth and/or damage of the surface finishing when the generated chips are pinched and crushed between the hob cutting edge and the work gear tooth flank. A manufacturing case of helical gears is taken as a case study, and it was simulated using a coupled thermomechanical rigid viscoplastic FEM analysis. Simulations have successfully identified a chip crush between four adjacent generating positions and thus, a definite mechanism that cause chip crush is revealed. Furthermore, valuable insights during chip formation, i.e., stress, strain, strain rate, temperature gradients, etc., are also provided.     

Location of biomarkers and reagents within agarose beads of a programmable bio-nano-chip

The slow development of cost-effective medical microdevices with strong analytical performance characteristics is due to a lack of selective and efficient analyte capture and signaling. The recently developed programmable bio-nano-chip (PBNC) is a flexible detection device with analytical behavior rivaling established macroscopic methods. The PBNC system employs ≈300 μm-diameter bead sensors composed of agarose "nanonets" that populate a microelectromechanical support structure with integrated microfluidic elements. The beads are an efficient and selective protein-capture medium suitable for the analysis of complex fluid samples. Microscopy and computational studies probe the 3D interior of the beads. The relative contributions that the capture and detection of moieties, analyte size, and bead porosity make to signal distribution and intensity are reported. Agarose pore sizes ranging from 45 to 620 nm are examined and those near 140 nm provide optimal transport characteristics for rapid (<15 min) tests. The system exhibits efficient (99.5%) detection of bead-bound analyte along with low (≈2%) nonspecific immobilization of the detection probe for carcinoembryonic antigen assay. Furthermore, the role analyte dimensions play in signal distribution is explored, and enhanced methods for assay building that consider the unique features of biomarker size are offered.     

Analytical calculation of the quantum-mechanical transmission coefficient for a triangular,planar-doped potential barrier

The thermionic emission limit for current transport in planar-doped triangular barrier devices is determined by the quantum-mechanical reflection of the charge carriers at the barrier. In this paper we present an analytical calculation for the quantum-mechanical transmission and reflection coefficients for such a barrier.     

Optical characteristics of multitransverse-mode two-dimensionalvertical-cavity top surface-emitting laser arrays

We observe for the first time up to nine transverse modes lasing in the individual elements of a two-dimensional vertical-cavity top surface-emitting laser array under pulsed operation. These modes consist of the TEM_0,0, TEM_0,1, TEM_1,0, TEM_1,1, TEM_0,2, TEM_2,0, TEM_1,2 , TEM_2,1, and TEM_2,2 modes, Each of these modes couples coherently across the array to form very distinct supermodes. The transverse modes as well as the resulting supermodes are identified by examining the near-field and far-field profiles as well as the corresponding spectra. We also obtain a record 1.4 W (pulsed) of coherent output power from the array during multitransverse-mode operation. In addition, the polarization properties of the array are investigated, It is found that the TEM_0,1 mode is horizontally polarized along the [011] crystalline axis while all the other modes are dominantly vertically polarized along the [011¯] axis