Probabilistic cell modelling of cleavage fracture

Various aspects on probabilistic modelling of cleavage fracture are discussed. The investigation involves consideration of a unit cell with an explicitly modelled void. The results from this model are compared with results for the case when the void content is accounted for in the sense of a Gurson-Tvergaard law. It is found that explicit modelling of the void can give substantially different results for the fracture probability. The effect depends on the exponent in the assumed Weibull distribution, the threshold stress, the constraint conditions and the hardening of the material. This revised version was published online in August 2006 with corrections to the Cover Date.     

Influence of HIV-related immunodeficiency on the histopathology of chronic hepatitis C

OBJECTIVE: There is substantial evidence demonstrating the aggravating effect of human immunodeficiency virus (HIV) infection on the progression of chronic hepatitis C virus (HCV) infection. There is however, little data on the affect of certain factors which could affect liver pathology findings in patients with concomitant HIV infection such as the duration of HIV infection or T-cell subpopulation counts. We examined pathology findings in patients with concomitant HIV and HCV infections to determine the impact of immunodepression. PATIENTS AND METHODS: We reviewed liver pathology data collected in patients with concomitant HIV and HCV infections grouping patients according to severity of the liver pathology: group 1 = cirrhosis or active hepatitis; group 2 = minimally active hepatitis or histologically normal liver. Transparietal liver biopsies were obtained for the work-up of viral hepatitis or because of long-term unexplained fever or suspected lymphoma. Epidemiological and biological data were obtained from medical files. The duration of the liver disease was estimated from the date of exposure to risk of immunodepression as determined by the peripheral CD4+ and CD8+ counts. All pathology specimens were read by two pathologists who established the Knodell score for each patient. RESULTS: Fifty patients were included: 23 were classed in group 1 and 28 in group 2. The Knodell score was significantly different between the two groups, 11 +/- 4 and 4 +/- 3 respectively (p < 0.0001). Disease duration was similar for the two groups: mean 8 years. Mean CD4+ count was significantly higher in group 1: 312/mm3 versus 110/mm3 for group 2 (p = 0.0057); as was the mean CD8+ count (758/mm3 versus 360/mm3, p = 0.0013). For the entire study population, there was a significantly negative correlation (p < 0.05) between the Knodell score and the CD4+ count (r = 0.31) and for the CD8+ count (r = 0.41). CONCLUSION: HCV-related liver pathology in patients co-infected with HIV depends on the level of immunodepression. CD8+ counts are better correlated with pathology findings than with CD4+ counts.     

The effects of insulin, transferrin and androgens on rat prostate explants in serum-free organ culture

A model previously developed in our laboratory to culture rat prostate explants in serum-free chemically-defined medium was used to evaluate the direct influence of potential regulators. The aim of the present work was to verify the effects of insulin (I) and transferrin (Tr), two hormones considered as essential in other serum-free culture systems, and three androgenic hormones, since the prostate is known to be androgen-dependent. Explants of rat prostate were cultured for five days in serum-free Leibovitz's L-15 medium (37 degrees C, 95% air-5% CO2). The addition of Tr (50 micrograms/ml) had no effect, but I (5 micrograms/ml) significantly increased DNA synthesis. This influence was amplified by combination of the two hormones. However, protein synthesis was only slightly stimulated. Testosterone (T) or androstanediol significantly increased DNA synthesis when compared to corresponding control values at five days. In combination with I plus Tr, each hormone showed potentiated effects, particularly T with a twofold increase over day 0 values. When dihydrotestosterone was added singly, the incorporation of 3H-thymidine was stimulated by 300% over control values at five days, and by 100% over values in uncultured explants. This influence was maximal since it was not improved by I plus Tr. Protein synthesis was increased significantly by the triple combination. In addition, each androgen as well as the combination of I plus Tr had a positive influence on explant morphology. The above conditions optimize the present culture system and establish its usefulness as a valuable tool to study the direct influence of different effectors in prostate metabolism and to eventually identify putative cancer markers.     

A novel mutation of presenilin 1 in familial Alzheimer's disease in Israel detected by denaturing gradient gel electrophoresis

Germline mutations in the presenilin 1 (PS1) gene apparently account for the majority of early-onset, familial Alzheimer's disease (AD). Using a mutation-screening strategy (denaturing gradient gel electrophoresis; DGGE), we analyzed a large family with early onset AD and seizures. The patients in this family showed a novel missense mutation in exon 5 of the PS1 gene (A to T change in codon 120, altering glutamine to aspartic acid). This novel mutation is located within the second hydrophilic domain of the molecule, a region not particularly involved in previously described germline mutations, and is of unknown biological significance. These results also demonstrate that DGGE can be used effectively to screen for mutations within this gene.     

Nonlinear black-box modeling in system identification: a unified overview

A nonlinear black-box structure for a dynamical system is a model structure that is prepared to describe virtually any nonlinear dynamics. There has been considerable recent interest in this area, with structures based on neural networks, radial basis networks, wavelet networks and hinging hyperplanes, as well as wavelet-transform-based methods and models based on fuzzy sets and fuzzy rules. This paper describes all these approaches in a common framework, from a user's perspective. It focuses on what are the common features in the different approaches, the choices that have to be made and what considerations are relevant for a successful system-identification application of these techniques. It is pointed out that the nonlinear structures can be seen as a concatenation of a mapping form observed data to a regression vector and a nonlinear mapping from the regressor space to the output space. These mappings are discussed separately. The latter mapping is usually formed as a basis function expansion. The basis functions are typically formed from one simple scalar function, which is modified in terms of scale and location. The expansion from the scalar argument to the regressor space is achieved by a radial- or a ridge-type approach. Basic techniques for estimating the parameters in the structures are criterion minimization, as well as two-step procedures, where first the relevant basis functions are determined, using data, and then a linear least-squares step to determine the coordinates of the function approximation. A particular problem is to deal with the large number of potentially necessary parameters. This is handled by making the number of ‘used’ parameters considerably less than the number of ‘offered’ parameters, by regularization, shrinking, pruning or regressor selection.     

Concealed weapon detection and visualization in a synthesized image

Images acquired by heterogeneous image sensors may provide complementary information about the scene, for instance, the visual image can provide personal identification information like the facial pattern while the infrared (IR) or millimeter wave image can detect the suspicious regions of concealed weapons. Usually, a technique, namely multiresolution pixel-level image fusion is applied to integrate the information from multi-sensor images. However, when the images are significantly different, the performance of the multiresolution fusion algorithms is not always satisfactory. In this study, a new strategy consisting of two steps is proposed. The first step is to use an unsupervised fuzzy k-means clustering to detect the concealed weapon from the IR image. The detected region is embedded in the visual image in the second step and this process is implemented with a multiresolution mosaic technique. Therefore, the synthesized image retains the quality comparable to the visual image while the region of the concealed weapon is highlighted and enhanced. The experimental results indicate the efficiency of the proposed approach.This material is based on part of the work carried out at the SPCR laboratory of Lehigh University and the work is partially supported by the U. S. Army Research Office under grant number DAAD19-00-1-0431. The content of the information does not necessarily reflect the position or the policy of the federal government, and no official endorsement should be inferred.     

Self-awareness and other-awareness. II: Mirror self-recognition, social contingency awareness, and synchronic imitation.

Eighteen-month-old children were tested for mirror self-recognition using the classic rouge test or an alternative procedure, for social contingency awareness by being closely imitated for a long time, and for the capacity for communication by synchronic imitation. The classic mirror rouge test was shown to produce false negatives. Most recognizers and nonrecognizers became aware of being imitated and imitated the activity of a model, but only recognizers engaged in sustained synchronic imitation of the model. The results support our hypothesis that self-recognition and spontaneous perspective-taking develop in close synchrony because both require a capacity for secondary representation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inhibition of tumour cell invasion by protease inhibitors: correlation with the protease profile

The invasive potential of eight established human tumour cell lines of different origin has been studied in the Matrigel assay. Between 25% and 70% of the cells migrated through the Matrigel layer within 24 h, indicating that invasiveness varies with the cell type. Semiquantitative measurements of the proteases MMP-2 and MMP-9, and cathepsins B and L were performed in these cell lines and the cell culture media. High invasive potential was found in those cell lines expressing high levels of cathepsins B and L or matrix metal proteases (MMP), either alone or in combination. Overexpression of one of these enzymes is enough to explain a high invasive potential of a cell line. Selective protease inhibitors at 10 nM concentration in the culture medium were used to inhibit the migration of tumour cells in the Matrigel assay. The MMP inhibitor Batimastat reduced the invasive potential of all cell lines studied independently of the MMP expression. The effect of cysteine protease inhibitors was strongly correlated with the protease profile of the tumour cell line. Our findings support the hypothesis of a very complex activation cascade of matrix-degrading proteolytic enzymes and they underline the need to analyse the protease profile of any tumour before beginning an antiproteolytic tumour treatment.