Calcium in Red Blood Cells—A Perilous Balance

Ca²⁺ is a universal signalling molecule involved in regulating cell cycle and fate, metabolism and structural integrity, motility and volume. Like other cells, red blood cells (RBCs) rely on Ca²⁺ dependent signalling during differentiation from precursor cells. Intracellular Ca²⁺ levels in the circulating human RBCs take part not only in controlling biophysical properties such as membrane composition, volume and rheological properties, but also physiological parameters such as metabolic activity, redox state and cell clearance. Extremely low basal permeability of the human RBC membrane to Ca²⁺ and a powerful Ca²⁺ pump maintains intracellular free Ca²⁺ levels between 30 and 60 nM, whereas blood plasma Ca²⁺ is approximately 1.8 mM. Thus, activation of Ca²⁺ uptake has an impressive impact on multiple processes in the cells rendering Ca²⁺ a master regulator in RBCs. Malfunction of Ca²⁺ transporters in human RBCs leads to excessive accumulation of Ca²⁺ within the cells. This is associated with a number of pathological states including sickle cell disease, thalassemia, phosphofructokinase deficiency and other forms of hereditary anaemia. Continuous progress in unravelling the molecular nature of Ca²⁺ transport pathways allows harnessing Ca²⁺ uptake, avoiding premature RBC clearance and thrombotic complications. This review summarizes our current knowledge of Ca²⁺ signalling in RBCs emphasizing the importance of this inorganic cation in RBC function and survival.     

Corrosion Resistance of MgZn Alloy Covered by Chitosan-Based Coatings

Chitosan coatings are deposited on the surface of Mg20Zn magnesium alloy by means of the spin coating technique. Their structure was investigated using Fourier Transform Infrared Spectroscopy (FTIR) an X-ray photoelectron spectroscopy (XPS). The surface morphology of the magnesium alloy substrate and chitosan coatings was determined using Scanning Electron Microscope (FE-SEM) analysis. Corrosion tests (linear sweep voltamperometry and chronoamperometry) were performed on uncoated and coated magnesium alloy in the Hank’s solution. In both cases, the hydrogen evolution method was used to calculate the corrosion rate after 7-days immersion in the Hank’s solution at 37 °C. It was found that the corrosion rate is 3.2 mm/year and 1.2 mm/year for uncoated and coated substrates, respectively. High corrosion resistance of Mg20Zn alloy covered by multilayer coating (CaP coating + chitosan water glass) is caused by formation of CaSiO₃ and Ca₃(PO₄)₂ compounds on its surface.     

Discrete Optimization Problems with Interval Data: Pareto Set of Solutions or Set of Weak Solutions?

For optimization problems with interval uncertainty, traditionally researchers have considered definitions based on element-wise optimality: a feasible solution is a strong solution if it optimizes the objective function f(x, c) for all possible values of the parameters c within the given intervals c, and it is a weak solution if it optimizes the objective function f(x, c) for some values cc. In our previous papers, we introduced the alternative approach based on the idea of Pareto optimality.In this paper, we analyze the relation between these two concepts of optimality, and provide arguments in favor of the Pareto approach.     

Inversion voltammetric determination of microconcentrations of Cd (II) and Zn (II) when they are jointly present in waters

The method of inversion voltamperometry was used to investigate electrochemical behavior of microconcentrations of Cd (II) and Zn (II) in waters on a mercury film electrode. We studied the impact of cadmium and zinc during their joint determination. We established optimal conditions for obtaining analytical signals of cadmium and zinc.     

Analysis of data and recommendations on heat transfer by liquid metals in rod bundles

Translated from Atomnaya Énergiya, Vol. 65, No. 6, pp. 423–426, December, 1988.