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  • Author: Zbigniew Wiśniewski x
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Robert Duchnowski and Zbigniew Wiśniewski

Shift-Msplit estimation

The method that is proposed in the present paper is a special case of squared Msplit estimation. It concerns a direct estimation of the shift between the parameters of the functional models of geodetic observations. The shift in question may result from, for example, deformation of a geodetic network or other non-random disturbances that may influence coordinates of the network points. The paper also presents the example where such shift is identified with a phase displacement of a wave. The shift is estimated on the basis of wave observations and without any knowledge where such displacement took place. The estimates of the shift that are proposed in the paper are named Shift-Msplit estimators.

Open access

Zbigniew Wiśniewski

Abstract

MP estimation is a method which concerns estimating of the location parameters when the probabilistic models of observations differ from the normal distributions in the kurtosis or asymmetry. The system of Pearson’s distributions is the probabilistic basis for the method. So far, such a method was applied and analyzed mostly for leptokurtic or mesokurtic distributions (Pearson’s distributions of types IV or VII), which predominate practical cases. The analyses of geodetic or astronomical observations show that we may also deal with sets which have moderate asymmetry or small negative excess kurtosis. Asymmetry might result from the influence of many small systematic errors, which were not eliminated during preprocessing of data. The excess kurtosis can be related with bigger or smaller (in relations to the Hagen hypothesis) frequency of occurrence of the elementary errors which are close to zero. Considering that fact, this paper focuses on the estimation with application of the Pearson platykurtic distributions of types I or II. The paper presents the solution of the corresponding optimization problem and its basic properties.

Although platykurtic distributions are rare in practice, it was an interesting issue to find out what results can be provided by MP estimation in the case of such observation distributions. The numerical tests which are presented in the paper are rather limited; however, they allow us to draw some general conclusions.

Open access

Anna Kalinowska, Zbigniew Szkop and Rafał Wiśniewski

Abstract

The present investigation has been conducted to compare the level of environmental awareness among the University of Warsaw Bachelor students of selected fields of study, which are: economics, geography and environmental protection. Diagnostic survey method was used to collect data from 180 students. The research interviewees included 60 economics students (equivalent to 33.3% of all respondents), 56 geography students (31.1% of respondents) and 64 environmental science students (35.6% of respondents). The gender division was as follows: 119 females (66.1% of all respondents) and 61 males (33.9%) took part in the research. The survey consisted of two parts. The main part - “The study of environmental awareness” - referred to the dependent variable. Respondents were asked to provide answers to 21 questions. Twenty of them were closed-ended questions, while one was open-ended. The second part was demographics, which referred to independent variable – selected socio-demographic characteristics of respondents. The data were subjected to descriptive and chi-square analyses. Statistical analysis software STATA for Windows was used for statistical analysis. The significance level was set at 5%. The study showed that the field of study significantly affects the answers declared by students in 6 of 21 questions (number: 6, 8, 11, 12, 16 and 20). Gender significantly affects the answers declared by students in 2 questions (number: 2 and 10). It can therefore be assumed that field of study had much stronger influence on student’s level of environmental awareness than their gender.

Open access

Zbigniew Heleniak, Zbigniew Zdrojewski, Piotr Wisniewski, Leszek Bieniaszewski, Boleslaw Rutkowski and Alicja Debska-Slizien

Abstract

Endothelial dysfunction could be related to the limited availability of nitric oxide (NO). NO is synthesized with the participation of an NO synthase whose activity is inhibited by asymmetric dimethylarginine (ADMA). The synthesis of ADMA is exacerbated by oxidative stress, and several studies have shown the efficacy of drugs acting on the renin-angiotensin-aldosterone system (RAAS) (converting enzyme inhibitors and angiotensin II receptor antagonists) in reducing the level of ADMA. The probable mechanism of drug action is a reduction of oxidative stress through a decrease of angiotensin II formation. The aim of this study was to assess the influence of RAAS blockers on the plasma concentration of ADMA in patients with chronic glomerulonephritis (ChGN). The study included 37 patients, placed into group A and group B, depending on the treatment. Both groups were treated with RAAS blockers. In group B, immunosuppressive drugs were additionally administered. The control visits were at the 0, 6 and 12 months of observation. In both the studied groups (A+B), a significant reduction of ADMA (0.77 vs 0.4 μmol/l; p<0.05) was noticed. In patients suffering from ChGN, the use of RAAS blockers resulted in a significant decrease of plasma ADMA concentration, independently of immunosupressive treatment.