Comparing representative selection strategies for dissimilarity representations

Many of the computational intelligence techniques currently used do not scale well in data type or computational performance, so selecting the right dimensionality reduction technique for the data is essential. By employing a dimensionality reduction technique called representative dissimilarity to create an embedded space, large spaces of complex patterns can be simplified to a fixed‐dimensional Euclidean space of points. The only current suggestions as to how the representatives should be selected are principal component analysis, projection pursuit, and factor analysis. Several alternative representative strategies are proposed and empirically evaluated on a set of term vectors constructed from HTML documents. The results indicate that using a representative dissimilarity representation with at least 50 representatives can achieve a significant increase in classification speed, with a minimal sacrifice in accuracy, and when the representatives are selected randomly, the time required to create the embedded space is significantly reduced, also with a small penalty in accuracy. © 2006 Wiley Periodicals, Inc. Int J Int Syst 21: 1093–1109, 2006.     

Budesonide affects allergic mucociliary dysfunction

Airway inflammation characterized by neutrophils and free elastase contributes to allergic mucociliary dysfunction. Glucocorticosteroids are the most important anti-inflammatory agents used in the treatment of asthma, but their effect on allergic mucociliary dysfunction is not known. Therefore, we assessed both the prophylactic and therapeutic effects of the glucocorticosteroid budesonide on antigen-induced mucociliary dysfunction in sheep. Tracheal mucus velocity (TMV), a marker of mucociliary clearance, was measured by using a roentgenographic technique. When budesonide was administered either 30 min before or 1 h after airway challenge with Ascaris suum, the antigen-induced fall in TMV at 6 h was prevented. The effects on TMV at 8 and 24 h after challenge were also determined when budesonide and, for comparative purposes, alpha1-protease inhibitor were given 6 h after antigen challenge. Budesonide treatment improved TMV at 8 h, but TMV was not significantly different from antigen alone at 24 h. Treatment with alpha1-protease inhibitor, however, caused only a significant reversal of the antigen-induced fall in TMV at 24 h after challenge; this indicates a more prolonged effect than budesonide. Our results suggest that antiproteases may have a potential role as a therapeutic approach to mucociliary dysfunction in asthma and provide evidence for another means by which glucocorticosteroids contribute to the control of the disease.     

Modeling the combined impact of moisture and char shrinkage on the pyrolysis of a biomass particle

A detailed computational model of pyrolysis of a moist, shrinking biomass particle is presented. This model is used to examine the effect of varying the moisture content for a single shrinking biomass particle subjected to a constant external temperature. Particle half-thicknesses ranging from 5 μm to 2 cm, temperatures from 800 to 2000 K, moisture contents from 0 to 30% (dry basis), and shrinkage factors from 1.0 to 0.4 are examined. The impact of moisture content and shrinkage was found to be a function of pyrolysis regime. In general, coupling between moisture content and shrinkage was found to result in longer pyrolysis times than if they were considered separately. Additionally, coupling between moisture content and shrinkage increased tar yield and decreased light hydrocarbon yield compared to considering moisture and shrinkage separately.     

Equilibrium swelling and solvation studies on crosslinked polyacrylamides

Polyacrylamide (PA) crosslinked with four different crosslinking agents, triethyleneglycol dimethacrylate (TEGDMA), N,N′‐methylene bisacrylamide (NNMBA), hexanediol dimethacrylate (HDDMA) and divinylbenzene (DVB), with mole percents ranging from 5 to 20, was prepared by solution polymerization and subjected to swelling and solvation studies. Solubility parameters and cohesive energy density were determined from swelling studies. Molecular weight between crosslinks for these systems were determined by Flory–Rehner analysis. There is a discontinuous volume change for 10% NNMBA and HDDMA crosslinked PA, 15% TEGDMA crosslinked PA and 10 and 15% DVB crosslinked PA in solvent mixtures of acetic acid and water due to phase change occurring at this stage. The hydrogels exhibit inhomogeneous crosslink distribution due to multiple crosslinking, cyclization and network irregularity owing from arising from entanglements. As the percentage of crosslinking increases, crosslinks become more homogeneous due to a decrease in entanglements. Copyright © 2004 Society of Chemical Industry     

Development and analysis of a neural network approach toPisarenko's harmonic retrieval method

Pisarenko's harmonic retrieval (PHR) method is perhaps the first eigenstructure based spectral estimation technique. The basic step in this method is the computation of eigenvector corresponding to the minimum eigenvalue of the autocorrelation matrix of the underlying data. The authors recast a known constrained minimization formulation for obtaining this eigenvector into the neural network (NN) framework. Using the penalty function approach, they develop an appropriate energy function for the NN. This NN is of feedback type with the neurons having sigmoidal activation function. Analysis of the proposed approach shows that the required eigenvector is a minimizer (with a given norm) of this energy function. Further, all its minimizers are global minimizers. Bounds on the integration time step that is required to numerically solve the system of nonlinear differential equations, which define the network dynamics, have been derived. Results of computer simulations are presented to support their analysis     

Enhanced endothelin-mediated coronary vasoconstriction and attenuated basal nitric oxide activity in experimental hypercholesterolemia

Matrix metalloproteinases (MPs) constitute a family of proteolytic enzymes (proteases) that degrade extracellular matrix (ECM) and promote the local or metastatic potential of carcinoma cells, and whose action is restrained by special inhibitors (metalloproteinase inhibitors; MIs). We assessed the role of the MPs stromelysin-3 (STR-3), putative metalloproteinase-1 (PUMP-I), and the gelatinases of molecular weights 72 kDa and 92 kDa, as well as the role of their inhibitors tissue inhibitor of metalloproteinase-1 (TIMP-1) and TIMP-2, as markers of metastatic potential in 25 fresh biopsies of squamous-cell lung carcinomas (SCLCs). We examined levels of messenger ribonucleic acid (mRNA) expression for these MPs and inhibitors through Northern blot analysis in 10 carcinomas of high-to-moderate differentiation without lymph-node involvement, and in 15 infiltrative carcinomas of moderate-to-low differentiation with lymph-node involvement. Five cases with significant epithelial atypia and five samples with normal mucosa were used as controls. Expression of STR-3 and TIMP-2 was also assessed immunohistochemically with the avidin-biotin-complex (ABC) technique. We noticed a progressive increase in the expression levels of MPs, especially of STR-3, and of TIMP-2, from the stage of epithelial atypia to the detection of carcinoma, finding the highest values of these substances among carcinomas of low differentiation with nodal metastases. These findings were also confirmed with immunohistochemical analysis. Our results suggest that there is a significant association of the expression of MPs and MIs with both the local and metastatic potential and the degree of cellular differentiation of SCLC, and that this association is clinically important because of its prognostic and therapeutic implications.     

Induction of low-affinity GABAA receptors by the GABA-agonist THIP (4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol) in cultured rat cerebellar granule cells is prevented by inhibition of polyamine biosynthesis

GABAA agonist-induced formation of low-affinity GABAA receptors in cultured cerebellar granule cells was studied in the presence or absence of alpha-difluoromethylornithine (DFMO), a blocker of polyamine formation. High- and low-affinity GABAA receptors were monitored by Scatchard analysis of [3H]GABA binding to membranes from cells cultured for either 4 or 10 days in the presence or absence of the GABA agonist 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP). Cultures grown for 4 days were exposed to THIP and DFMO for an additional period of 6 hr (acute exposure), whereas cultures grown for 10 days were exposed to the same agents during the entire culture period (chronic exposure). Regardless of the culture period or drug exposure protocol, control cells expressed only a high-affinity (KD 7 nM) binding site for GABA, whereas the cultures treated with THIP for either 6 hr or 10 days exhibited an additional low-affinity binding site (KD approximately 500 nM). Chronic exposure to DFMO prevented the THIP induction of low-affinity GABAA receptors, whereas acute exposure to DFMO had no effect on the ability of THIP to induce low-affinity GABAA receptors. Measurements of the intracellular polyamine concentration demonstrated a slight decrease in the putrescine level in the granule cells exposed to DFMO or THIP + DFMO for 6 hr. In contrast, granule cells chronically (10 days) exposed to DFMO or THIP + DFMO were depleted of putrescine and spermidine. Hence, the ability of THIP to induce low-affinity GABAA receptors was prevented by the simultaneous depletion of the cellular content of putrescine and spermidine, whereas inhibition of ornithine decarboxylase and of putrescine formation was not sufficient to prevent THIP-induced receptor formation.     

Impinging jet absorbers

This article reviews the authors' achievements in the field of impinging jet absorbers with and without chemical reaction. The major conclusions of the investigations indicated that such absorbers exhibit the highest values for the mass transfer coefficients, and that such devices equipped with Caldyn CSL nozzles are a more attractive option than conventional absorbers.