Effects of different external carbon sources and electron acceptors on interactions between denitrification and phosphorus removal in biological nutrient removal processes

The effects of two different external carbon sources (acetate and ethanol) and electron acceptors (dissolved oxygen, nitrate, and nitrite) were investigated under aerobic and anoxic conditions with non-acclimated process biomass from a full-scale biological nutrient removal-activated sludge system. When acetate was added as an external carbon source, phosphate release was observed even in the presence of electron acceptors. The release rates were 1.7, 7.8, and 3.5 mg P/(g MLVSS·h) (MLVSS: mixed liquor volatile suspended solids), respectively, for dissolved oxygen, nitrate, and nitrite. In the case of ethanol, no phosphate release was observed in the presence of electron acceptors. Results of the experiments with nitrite showed that approximately 25 mg NO₂-N/L of nitrite inhibited anoxic phosphorus uptake regardless of the concentration of the tested external carbon sources. Furthermore, higher denitrification rates were obtained with acetate (1.4 and 0.8 mg N/(g MLVSS·h)) compared to ethanol (1.1 and 0.7 mg N/(g MLVSS·h)) for both anoxic electron acceptors (nitrate and nitrite).     

New realities for Polish primary school informatics education affected by COVID-19

Education and Information Technologies - In the paper, the authors discuss the first research effort to explore the transition from traditional teaching into distance teaching in Polish primary...     

Teaching history,teaching nationalism: a qualitative study of history teachers in a Polish post-industrial town

This paper aims to analyse Polish history teachers’ perceptions of the role of historical education in the context of nationalism, class and locality. Drawing on the results of qualitative research conducted in the post-industrial and post-German city of Wa?brzych in Poland, we argue that teachers are not fully aware of the role of nationalist politics in representations of the past. Teachers regard these nationalist representations as natural and taken for granted. They are not only unable to assume responsibility for promoting nationalism among students but also reproduce a dominant nationalist discourse by using history to nurture their students’ attachment to the idea of a homogeneous and solidary nation that transcends class divisions and erases local specificity. They see their role primarily in terms of reinforcing the dominant structures of collective memory in their pupils.     

Book reviews

International Review of Education -     

CHANGES IN THE ORGANIZATION AND THE FINANCING OF SCIENTIFIC RESEARCH IN POLAND: DIRECTION AND DILEMMAS

The year 1990 marked a transitional period in the development of science and technology in Poland. A package of bills passed by the Polish Parliament in December 1989 has laid down the basis for the elaboration of a new funding system taking into account the opening and the liberalization of Polish society and the ending of the overcentralized system of control in the areas concerned. The four aims of the proposed reform are the replacement of administrative control over science by co‐operation between the government and the scientific community in the determination of science policy; the diversification of funding methods for basic and applied research; the introduction of the competitive principle with regard to research funding, including peer review for project proposals; and the ending of the separation of science into ‘sections’ of different state organizations. From now on, researchers and research organizations will have to elaborate funding packages for themselves, drawing upon numerous sources, and to adapt themselves to current perceived and expressed national needs. The author cautions, however, that an overemphasis of the market principle could have detrimental effects on academic freedom and on the productivity of theoretical research.

     

A model of ice friction for a speed skate blade

The FAST 2.0i numerical model of ice friction was developed for an inclined speed skate blade. It describes ice friction at sliding velocities sufficiently high to produce a lubricating layer of meltwater, which completely separates the ice and slider surfaces (known as the hydrodynamic friction regime). Friction arises from ploughing a groove in the ice and from the shear stress in the lubricating Couette flow. The model takes into account frictional melting, heat conduction into the ice and the lateral squeeze flow of the lubricating liquid. We use the numerical model to calculate the ice–blade contacts, the parameters of the lubricating liquid layer, and the relative importance of the various contributions to the overall friction coefficient. We also use it to perform sensitivity studies and to predict the variation of ice friction during a typical skating stroke. The model results compare favorably with measurements of the ice friction coefficient during speed skating, made by others.     

A preliminary evaluation of VEGF-A,VEGFR1 and VEGFR2 in patients with well-controlled type 2 diabetes mellitus

Objective

Decompensated chronic hyperglycemia often leads to late microvascular complications such as retinopathy, diabetic foot syndrome, and diabetic kidney disease. The aim of this study was to determine the concentration of vascular endothelial growth factor A (VEGF-A) and its receptors in patients with well-controlled diabetes.

Methods

The study was conducted on 31 patients with well-controlled type 2 diabetes without micro-or macroangiopathy. Thirty healthy volunteers were enrolled in a control group. Serum concentrations of VEGF-A, VEGF receptors 1 and 2 (VEGFR1 and VEGFR2), fasting glucose, and lipid profiles were measured, and the plasma concentration of glycated hemoglobin (HbA1c) was determined.

Results

No significant differences were observed between the concentration of VEGF-A, VEGFR1 or VEGFR2 in the subject group and that in the control group. Positive correlations were noted between the levels of VEGF-A, VEGFR2, and triglyceride, and there was a negative correlation between the levels of VEGFR2 and high-density lipoprotein (HDL)-cholesterol in the study group.

Conclusions

The concentrations of VEGF-A and its receptors 1 and 2 in patients with well-controlled diabetes are comparable to those of healthy individuals, which may indicate that appropriate control of glucose levels delays the occurrence of vascular complications. A negative correlation between VEGFR2 and HDL-cholesterol levels, and positive correlations between VEGF-A, VEGFR2, and triglyceride levels, suggest that lipid abnormalities occurring in diabetes may be involved in the modulation of angiogenesis.     

Finite frequency range robust iterative learning control of linear discrete system with multiple time-delays

This paper uses repetitive process stability theory to design robust iterative learning control law for linear discrete systems with multiple time-delays and polytopic uncertainty. Both dynamic and static forms of the control law are considered and used when designing robust iterative learning control schemes. Also, based on the generalized Kalman-Yakubovich-Popov Lemma, the proposed design procedures a required frequency attenuation over a finite frequency range and the monotonic trial-to-trial error convergence. Moreover, linear matrix inequality techniques are applied to formulate the convergence conditions and to obtain formulas for the control law designs. Finally, an illustrative numerical simulation example is given and concludes the paper.