Henryk Maciejewski

Estimation of repairable system availability within fixed time horizon

The paper presents an efficient approach to estimating the availability of a repairable system observed within a fixed time horizon, which is regarded as a random variable over range [0,1]. A Beta distribution based approximation of this characteristic is proposed. The presented results are derived from Monte Carlo simulation and statistical analysis of the simulation results. Numerical examples are also provided to illustrate the practical impact of this approach.

A comprehensive study of outage rates of air blast breakers

This paper presents results of an extensive study launched by Hydro One Networks aimed at determining air blast circuit breaker reliability measures from a statistical analysis of outage data. The study examines how the breaker failure rate depends on such factors as equipment age, voltage level, manufacturer, and number of repairs. Planned outage rates due to equipment maintenance were also investigated. Results presented in this paper are based on outage records involving 318 breakers and covering a period of 12 years. The results can form input information for probabilistic risk analysis studies.

The gene expression profiles of canine mammary cancer cells grown with carcinoma-associated fibroblasts (CAFs) as a co-culture in vitro.

BackgroundIt is supposed that fibroblasts present in tumour microenvironment increase cancer invasiveness and its ability to metastasize but the mechanisms have not been clearly defined yet. Thus, the current study was designed to assess changes in gene expression in five various cancer cell lines grown as a co-culture with the carcinoma-associated fibroblasts (CAFs) in vitro.ResultsA carcinoma-associated fibroblast cell line was isolated from a canine mammary cancer. Then, a co-culture of cancer cells with the CAFs was established and maintained for 72 hrs. Having sorted the cells, a global gene expression in cancer cells using DNA microarrays was examined. The analysis revealed an up-regulation of 100 genes and a down-regulation of 106 genes in the cancer cells grown as a co-culture with the CAFs in comparison to control conditions. The PANTHER binomial statistics tool was applied to determine statistically over-manifested pathways (p < 0.05). Bulk of the up-regulated genes are involved in the adhesion, the angiogenesis, the epithelial-mesenchymal transition (EMT) and generally take part in the developmental processes. These results were further confirmed using real-time qPCR. Moreover, a wound-healing assay and growth characteristics on Matrigel matrix showed that CAFs increase cancer cell migration and matrix invasion.ConclusionThe results of the current study showed that the co-culturing of cancer cells and the CAFs caused significant changes to the cancer gene expression. The presence of the CAFs in a microenvironment of cancer cells promotes adhesion, angiogenesis and EMT.

Gene expression profiling in peripheral blood nuclear cells in patients with refractory ischaemic end-stage heart failure

Functional analysis of up- and down-regulated genes might reveal whether peripheral blood cells may be considered as a material of diagnostic or prognostic value in patients with end-stage heart failure (HF). The aim of the present study was to compare the transcriptomic profile of peripheral blood nuclear cells from 6 male patients with ischaemic end-stage HF with those of 6 male patients with asymptomatic cardiac dysfunction. The expression of genes in peripheral blood nuclear cells in both groups of patients was measured using whole-genome oligonucleotide microarrays utilizing 35 035 oligonucleotide probes. Microarray analyses revealed 130 down-regulated genes and 15 up-regulated genes in the patients with end-stage HF. Some of the down-regulated genes belonged to the pathways that other studies have shown to be down-regulated in cardiomyopathy. We also identified up-regulated genes that have been correlated with HF severity (CXCL16) and genes involved in the regulation of expression of platelet activation factor receptor (PTAFR, RBPSUH, MCC, andPSMA7). In conclusion, the identification of genes that are differentially expressed in peripheral blood nuclear cells of patients with HF supports the suggestion that this diagnostic approach may be useful in searching for the molecular predisposition for development of severe refractory HF in patients with post-infarction asymptomatic abnormalities and remodelling of the left ventricle. These results need further investigation and validation.

Gene expression profiles in canine mammary carcinomas of various grades of malignancy.

BackgroundThe frequency of mammary malignancies in canine patients is even three times over than in human. In various types of cancer different intracellular signalling pathways are perturbed, thus the patients with pathologically the same type of cancer often have dissimilar genetic defects in their tumours and respond in a heterogeneous manner to anticancer treatment. That is why the objective of the hereby study was to assess the gene expression profiles in canine mammary carcinomas (in unsupervised manner) classified by pathologists as grade 1 (well differentiated), grade 2 (moderately differentiated) and grade 3 (poorly differentiated) and compare their molecular and pathological classifications.ResultsOur unsupervised analysis classified the examined tissues into three groups. The first one significantly differed from the others and consisted of four carcinomas of grade 3 and one carcinoma of grade 2. The second group consisted of four grade 1 carcinomas. The very heterogeneous (based on their pathological parameters) group was the last one which consisted of two grade 1 carcinomas, two grade 3 carcinomas and five grade 2 carcinomas. Hierarchical dendrogram showed that the most malignant tumour group had significantly distinct gene expression.ConclusionsMolecular classification of canine mammary tumours is not identical with pathological classification. In our opinion molecular and pathological characterization of canine mammary malignancy can complement one another. However, furthers studies in this field are required.

Estimation of Impact of Maintenance Policies on Equipment Risk of Failure

This work shows an approach to solve a problem of estimation of hazard rate of equipment under different maintenance policies. This approach is based on a model of equipment deterioration over time. The main incentive when building the model was to make it feasible to directly feed into the model real failure data obtained from historical maintenance records. Using this approach it is possible to estimate remaining life and hazard rate of a piece of equipment under a fixed maintenance policy. To illustrate the method discussed, a numerical example is given based on real life data. This example suggests that in some cases it is possible to express the relationship between some parameters of the maintenance policy and the equipment hazard function in the form of Cox proportional hazards model

Lymphocytic, cytokine and transcriptomic profiles in peripheral blood of dogs with atopic dermatitis

BackgroundCanine atopic dermatitis (cAD) is a common chronic and pruritic skin disease in dogs. The development of cAD involves complex interactions between environmental antigens, genetic predisposition and a number of disparate cell types. The aim of the present study was to perform comprehensive analyses of peripheral blood of AD dogs in relation to healthy subjects in order to determine the changes which would be characteristic for cAD.ResultsThe number of cells in specific subpopulations of lymphocytes was analyzed by flow cytometry, concentration of chosen pro- and anti-inflammatory cytokines (IL-4, IL-10, IL-13, TNF-α, TGF-β1) was determined by ELISA; and microarray analysis was performed on RNA samples isolated from peripheral blood nuclear cells of AD and healthy dogs. The number of Th cells (CD3+CD4+) in AD and healthy dogs was similar, whereas the percentage of Tc (CD3+CD8+) and Treg (CD4+CD25+ Foxp3+) cells increased significantly in AD dogs. Increased concentrations of IL-13 and TNF-α, and decreased levels of IL-10 and TGF-β1 was observed in AD dogs. The level of IL-4 was similar in both groups of animals. Results of the microarray experiment revealed differentially expressed genes involved in transcriptional regulation (e.g., transcription factors: SMAD2, RORA) or signal transduction pathways (e.g., VEGF, SHB21, PROC) taking part in T lymphocytes lineages differentiation and cytokines synthesis.ConclusionsResults obtained indicate that CD8+ T cells, beside CD4+ T lymphocytes, contribute to the development of the allergic response. Increased IL-13 concentration in AD dogs suggests that this cytokine may play more important role than IL-4 in mediating changes induced by allergic inflammation. Furthermore, observed increase in Treg cells in parallel with high concentrations of TNF-α and low levels of IL-10 and TGF-β1 in the peripheral blood of AD dogs point at the functional insufficiency of Treg cells in patients with AD.

Hierarchical control of a distributed solar collector field

This article presents a hierarchical control structure aimed at optimizing the electricity production process in solar power plants with distributed collectors. In these systems, a fluid is heated using the energy provided by the solar irradiation until a desired outlet temperature range is achieved, despite of the effect of disturbances (mainly radiation and inlet temperature),using as manipulated variable the fluid flow. The heated fluid is then used for feeding a heat exchanger where steam is produced for electricity generation using a turbine. Nonlinear models are used in the design of the different layers of the control architecture.

Accelerated life test data analysis with generalised life distribution function and with no aging model assumption

Abstract The purpose of this paper is to present a method of statistical analysis of Accelerated Life Test (ALT) data which allows to drop assumptions usually made on the type of life distribution function at each stress level and the life-stress relationship. The method proposed can be used to derive life distribution function for nominal stress level based on a number of accelerated non-censored tests. The method can be especially useful in a variety of areas where the assumptions on life distribution function and/or life-stress relationship is not well justified by empirical or theoretical model.

Five markers useful for the distinction of canine mammary malignancy

BackgroundSpontaneous canine mammary tumors constitute a serious clinical problem. There are significant differences in survival between cases with different tumor grades. Unfortunately, the distinction between various grades is not clear. A major problem in evaluating canine mammary cancer is identifying those, that are “truly” malignant. That is why the aim of our study was to find the new markers of canine malignancy, which could help to diagnose the most malignant tumors.ResultsAnalysis of gene expression profiles of canine mammary carcinoma of various grade of malignancy followed by the boosted tree analysis distinguished a `gene set`. The expression of this gene set (sehrl, zfp37, mipep, relaxin, and magi3) differs significantly in the most malignant tumors at mRNA level as well as at protein level. Despite this `gene set` is very interesting as an additional tool to estimate canine mammary malignancy, it should be validated using higher number of samples.ConclusionsThe proposed gene set can constitute a `malignancy marker` that could help to distinguish the most malignant canine mammary carcinomas. These genes are also interesting as targets for further investigations and therapy. So far, only two of them were linked with the cancer development.