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International audience; Abradable coatings are part of dynamic seals used in aircraft engines to reduce inter-stage leakages. However, during running, severe interactions may occur between the rotating blades and the coating of the casing leading to these parts getting damaged. Numerical approaches simulating these interactions could be a way to prevent these contact risks but they require both a characterization of the thermomechanical behavior of the abradable material and of the blade. This paper presents a quasi-static compression behavior study of a heterogeneous and porous AlSi-PE abradable used in the low-pressure compressor of aircraft engines. Combined with the results obtained for tests conducted at high compression strain-rates and extreme temperatures recently published in a previous paper (Skiba et al., in Dyn Behav Mater 6:213–223, 2020. 10.1007/s40870-020-00242-y), a thermoelastoviscoplastic bilinear constitutive law is proposed. This formulation allows the prediction of the macroscopic behavior of a heterogeneous and porous AlSi-PE abradable material from room temperature to 360 °C and with strain-rates ranging from 10–3 to 103 s−1.

The solubility was studied for compounds in the system Zr(SO4)2–K2SO4–H2SO4–H2O in the section at 10 wt % H2SO4 under isothermal conditions at 25°C in the cuts at a constant solvent content of 60 wt % (H2O + H2SO4). Equilibrium in the system was reached for 16 h while continuously stirring. In the section at 10 wt % H2SO4, equilibrium solid phases are the compounds K2Zr(SO4)3 ⋅ 2H2O, K3Zr(OH)(SO4)3 ⋅ 2H2O, K6Zr(SO4)5 ⋅ 3H2O, and β-K2SO4. The recovered compounds were investigated by X-ray powder diffraction, crystal optical, thermal analyses and IR spectroscopy. It was found that the solubilities of the potassium zirconium sulfates are much lower than those of the sodium zirconium compounds. The results are of practical importance for sulfuric acid treatment of eudialyte, a zirconium-containing mineral, huge reserves of which occur in the Kola Peninsula.

Cardiovascular disease (CVD) is the leading cause of death worldwide. The most dangerous life-threatening symptoms of CVD are myocardial infarction and stroke. The causes of CVD are not entirely clear, and new therapeutic targets are still being sought. One of the factors involved in CVD development among vascular damage and oxidative stress is chronic inflammation. It is known that hyaluronic acid plays an important role in inflammation and is regulated by numerous stimuli, including proinflammatory cytokines. The main receptors for hyaluronic acid are CD44 and RHAMM. These receptors are membrane proteins that differ in structure, but it seems that they can perform similar or synergistic functions in many diseases. Both RHAMM and CD44 are involved in cell migration and wound healing. However, their close association with CVD is not fully understood. In this review, we describe the role of both receptors in CVD.

It has been a year since the coronavirus disease 2019 (COVID-19) was declared pandemic and wreak havoc worldwide. Despite meticulous research has been done in this period, there are still much to be learn from this novel coronavirus. Globally, observational studies have seen that majority of the patients with COVID-19 have preexisting hypertension. This raises the question about the possible relationship between COVID-19 and hypertension. This review summarizes the current understanding of the link between hypertension and COVID-19 and its underlying mechanisms.

The opioid system is well-known for its role in modulating nociception and addiction development. However, there are premises that the endogenous opioid system may also affect blood pressure. The main goal of the present study was to determine the impact of different endogenous opioid system activity and its pharmacological blockade on blood pressure. Moreover, we examined the vascular function in hyper- and hypoactive states of the opioid system and its pharmacological modification. In our study, we used two mouse lines which are divergently bred for high (HA) and low (LA) swim stress-induced analgesia. The obtained results indicated that individuals with low endogenous opioid system activity have higher basal blood pressure compared to those with a hyperactive opioid system. Additionally, naloxone administration only resulted in the elevation of blood pressure in HA mice. We also showed that the hypoactive opioid system contributes to impaired vascular relaxation independent of endothelium, which corresponded with decreased guanylyl cyclase levels in the aorta. Together, these data suggest that higher basal blood pressure in LA mice is a result of disturbed mechanisms in vascular relaxation in smooth muscle cells. We believe that a novel mechanism which involves endogenous opioid system activity in the regulation of blood pressure will be a promising target for further studies in hypertension development.

Barramundi (Lates calcarifer) are a highly valued aquaculture species, and, as obligate carnivores, they have a demonstrated preference for dietary protein over lipid or starch to fuel energetic growth demands. In order to investigate how carnivorous fish regulate nutritional cues, we examined the metabolic effects of feeding two isoenergetic diets that contained different proportions of digestible protein or starch energy. Fish fed a high proportion of dietary starch energy had a higher proportion of liver SFA, but showed no change in plasma glucose levels, and few changes in the expression of genes regulating key hepatic metabolic pathways. Decreased activation of the mammalian target of rapamycin growth signalling cascade was consistent with decreased growth performance values. The fractional synthetic rate (lipogenesis), measured by TAG 2H-enrichment using 2H NMR, was significantly higher in barramundi fed with the starch diet compared with the protein diet (0·6 (se 0·1) v. 0·4 (se 0·1) % per d, respectively). Hepatic TAG-bound glycerol synthetic rates were much higher than other closely related fish such as sea bass, but were not significantly different (starch, 2·8 (se 0·3) v. protein, 3·4 (se 0·3) % per d), highlighting the role of glycerol as a metabolic intermediary and high TAG-FA cycling in barramundi. Overall, dietary starch significantly increased hepatic TAG through increased lipogenesis. Compared with other fish, barramundi possess a unique mechanism to metabolise dietary carbohydrates and this knowledge may define ways to improve performance of advanced formulated feeds.

To date, there are no reliable and simple calculation models that simulate the kinetics of dissociation at negative temperatures. One of the important problems is to reduce the cost of storage and transportation of natural gas hydrates. The paper presents experimental data on the effect of layer thickness and temperature on the dissociation kinetics, as well as the effect of the external air velocity. The model enables effective modeling of the dissociation kinetics both outside the self-preservation region and in the annealing temperature window. The experiments were carried out in the presence of non-stationary and non-isothermal dissociation. The thickness of the gas hydrate layer significantly affects the dissociation rate. The effect of thickness persists over a wide range of air velocities. The inhomogeneity of the temperature field inside the powder layer increases with increasing layer thickness, resulting in the appearance of two self-preservation sites on the dissociation curve.

The solubility was studied in the system NaCl–AlCl3−SrCl2–HCl–H2O of the eutonic type at 25°C in the section 28 wt % HCl. It was determined that it is possible to derive equations of the solubility surface of crystallizing salts and to calculate the composition of the eutonic solution.

The development of alcohol dependence and depression is determined by various genetic and environmental factors. In the presented study, we used high analgesia (HA) and low analgesia (LA) mouse lines, characterized by different endogenous opioid system activity and divergent blood–brain barrier permeability, to determine the influence of cross-fostering of these lines raised by surrogate mothers on ethanol consumption and development of depressive-like behaviors. We also investigated ethanol drinking by biological parents or surrogate mothers. Furthermore, we investigated whether these parental changes would alter the effect of naloxone on ethanol intake and depressive-like behaviors in offspring. Our results reveal that cross-fostering of HA and LA raised by surrogate mothers has a greater impact on depressive-like behaviors than ethanol consumption. Ethanol intake by biological parents substantially affected depressive-like behaviors and ethanol consumption in offspring. Moreover, ethanol intake by biological parents or an adoptive mother modified the effect of naloxone on ethanol consumption and preference and depressive-like behaviors in the HA offspring only. Together, these results indicate that cross-fostering differentially affects the effect of naloxone on alcohol consumption and the development of depression.

Solubility was studied in the system NaCl–AlCl3–HCl–H2O at 25°C in the section 28 wt % HCl. The system is of the eutonic type and has an extensive sodium chloride crystallization region. The composition of the eutonic solution is the following, wt %: NaCl, 0.47; AlCl3 • 6H2O, 8.88; HCl, 25.38; and H2O, 65.27. The lines of saturated solutions were approximated by polynomial equations.

The solubility in the quaternary water–salt system Zr(SO4)2 · 4Н2О–Na2SO4–H2SO4–H2O at 25°C was studied. It was found that, in the system, there is crystallization of not only Na2SO4 and Zr(SO4)4 · 4H2O, but also sodium sulfate zirconates Na2Zr(SO4)2(OH)2 · 0.3H2O, Na4Zr(SO4)4 · 3H2O, and Na2Zr(SO4)2 · 3H2O and two new compounds, S1 and S2, which are presumably Na2ZrO(SO4)2 · 2H2O and Na2Zr2O2(SO4)3 · 6H2O.

The combustion and dissociation of the double hydrate of propane-methane have been studied in terms of several key parameters: the velocity of the forced air flow U0, heat flux, temperature difference, and geometry of the work area. Simple expressions relating the dissociation rate with the specified key parameters have been obtained. The ratio of dissociation rates J1/J2 was determined, where the dissociation rates J1 and J2 correspond to the experiment with and without combustion, respectively. At U0 = 0 m/s, the ratio J1/J2 equals 8–9, and in the presence of forced gas flow J1/J2 = 11–12. Forced convection increases this ratio. Approximate correlations have been obtained for assessing the time of combustion beginning and the duration of the gas hydrate burning. The dissociation rate is nonlinearly related to the velocity U0. Two characteristic modes of gas hydrate dissociation are distinguished. Measurements of velocity fields obtained using the Particle Tracking Velocimetry (PTV) method show that the interaction of forced and free convection flows leads to a decrease in the maximum resultant velocity. Due to fuel excess over the oxidizer (violation of stoichiometric ratio), there are periodic emissions of gas bubbles, leading to incomplete combustion of the fuel. To improve the efficiency of combustion, it is advisable to use velocities U0 = 1.2–3 m/s. A further increase in U0 leads to the extinguishing of the flame.

Selective sorption and/or fixation of cations with low hydration energies (e.g. K+, NH 4 + , Rb+, Cs+) by vermiculites is a well known phenomenon in soil science and it has been described by many investigators since the 1950s. Because most of the available studies deal with trioctahedral vermiculites, cation fixation in dioctahedral vermiculites is not as well understood as fixation by trioctahedral structures. The objective of the present study was to investigate the influence of NH 4 + saturation on the structure of a natural dioctahedral vermiculite. Because no dioctahedral vermiculite standard reference material was available, two natural dioctahedral vermiculite-rich soil clay samples were used in the study. The clays were saturated with NH 4 + using different protocols to simulate natural processes that likely take place in soils. The degree of NH 4 + fixation by the dioctahedral vermiculite was evaluated using X-ray diffraction, elemental N analysis, and infrared spectroscopy. All the treatments that involved NH 4 + saturation caused NH 4 + fixation and irreversible collapse (i.e. contraction to ~10 A) of at least a portion of the previously hydrated (vermiculitic) interlayers. Air drying of the NH 4 + -saturated samples greatly enhanced the degree of the collapse. The results indicated that the collapse of dioctahedral vermiculite leads to the formation of a NH4-illite-like phase that is likely to occur in some soils and sediments that are rich in organic matter. The formation of a NH4-illite-like phase by NHNH 4 + fixation in vermiculitic interlayers needs to be taken into consideration in studies that deal with the clay mineralogy of sedimentary basins.

Background and aim: Perivascular adipose tissue (PVAT) positively regulates vascular function through production of factors such as adiponectin but this effect is attenuated in obesity. The enzyme AMP-activated protein kinase (AMPK) is present in PVAT and is implicated in mediating the vascular effects of adiponectin. In this study, we investigated the effect of an obesogenic high fat diet (HFD) on aortic PVAT and whether any changes involved AMPK. Methods: Wild type Sv129 (WT) and AMPKα1 knockout (KO) mice aged 8 weeks were fed normal diet (ND) or HFD (42% kcal fat) for 12 weeks. Adiponectin production by PVAT was assessed by ELISA and AMPK expression studied using immunoblotting. Macrophages in PVAT were identified using immunohistochemistry and markers of M1 and M2 macrophage subtypes evaluated using real time-qPCR. Vascular responses were measured in endothelium-denuded aortic rings with or without attached PVAT. Carotid wire injury was performed and PVAT inflammation studied 7 days later. Key results: Aortic PVAT from KO and WT mice was morphologically indistinct but KO PVAT had more infiltrating macrophages. HFD caused an increased infiltration of macrophages in WT mice with increased expression of the M1 macrophage markers Nos2 and Il1b and the M2 marker Chil3. In WT mice, HFD reduced the anticontractile effect of PVAT as well as reducing adiponectin secretion and AMPK phosphorylation. PVAT from KO mice on ND had significantly reduced adiponectin secretion and no anticontractile effect and feeding HFD did not alter this. Wire injury induced macrophage infiltration of PVAT but did not cause further infiltration in KO mice. Conclusions: High-fat diet causes an inflammatory infiltrate, reduced AMPK phosphorylation and attenuates the anticontractile effect of murine aortic PVAT. Mice lacking AMPKα1 phenocopy many of the changes in wild-type aortic PVAT after HFD, suggesting that AMPK may protect the vessel against deleterious changes in response to HFD.

The solubility at 25°C in the NdCl3-SmCl3-HCl-H2O and NdCl3-GdCl3-HCl-H2O quaternary water-salt systems has been studied in 40% hydrochloric acid sections. The NdCl3-SmCl3-HCl-H2O system represents a continuous series of solid solutions (type I solid solutions). The NdCl3-GdCl3-HCl-H2O system is a system with peritonic discontinuity (type V solid solutions). The discontinuity point of the peritonic solution has the following composition (wt %): NdCl3 · 6H2O, 1.13; GdCl3 · 6H2O, 0.11; HCl, 39.5; H2O, 59.26.

This paper presents distribution and properties of soils within the Fuglebekken catchment in neighbourhood of the Polish Polar Station in Hornsund, SW Spitsbergen (Svalbard Archipelago). The present study describes 8 representative soil profiles out of 34 profiles studied for the whole catchment. Soils of the Fuglebekken catchment show initial stage of their formation because of very slow rate of chemical and biological weathering in Arctic climate conditions. Upliftedmarine terraces of the Fuglebekken catchment are characterized by domination of Haplic Cryosolswhich are related to stony and gravelly parent material (reworked marine sediments). Such soils constitute of 17% of the studied area. Turbic Cryosols forming characteristic micro−relief occur on flat surfaces and gentle slopes. Such soils (covering 7% of the catchment) are formed from loamy parent material. Along streams Hyperskeletic Cryosols (Reductaquic) and Turbic Histic Cryosols occur. The last two soil units (constituting 11% of the catchment) are mantled by continuous and dense vegetation cover (especially mosses) due to high content of water rich in nutrients flowing from colonies of sea birds located on slopes of Ariekammen and Fugleberget. The studied soils are generally characterized by shallowoccurrence of permafrost (i.e. at 30-50 cm), high content of pebbles, sandy or sandy loam texture, and neutral or slightly alkaline reaction. Soils occurring along streams and near colonies of sea birds show higher content of nutrients (N and P) in comparison with other soils and are covered by more dense vegetation. This indicates important impact of bird guano on chemical composition of soil solution and fertility of such soils.

The technique of receiving of nano-silica nanopowders, consisting of nanoparticles with the known size, form, internal and surface structure and physicochemical properties was developed. The degree of hydrophilicity of those powders was determined. The method of the surface modification (hydrophobization) of the received nanoparticles was carried out and was optimized. Replacement of surface OH-groups on the CH3-group was produced by blowing SiCl2(CH3)2 vapor over the modified powders surface. The carbon content of the modified powders reached 3.2 %. The comparison of the hydrophobization process for the nanopowders received by two different origins was carried out. It was shown that the surface modification of Aerosil powders is faster than Tarkosil ones at similar hydrophilicity degree. Also hydrophobiс Aerosil contains more amount of carbon was cleared (up to 5,9 %). The complete replacement of OH-groups on the organic groups on the surface of powders was showed by IR spectroscopy. The representation of the organic groups by several combinations of fragments, rather than just the CH3 was showed

Fragipan horizon is a natural, subsurface soil layer exhibiting higher bulk density and lower porosity in comparison with the overlying horizons significantly restricting infiltration of water and root penetration. In contrast to hard and cemented horizons (e.g. duripan), clods of the fragipan horizon (Btx) slake or fracture immediately when placed in water. The most interesting issue concerning genesis and properties of the fragipan horizon is its reversible cementation, i.e. very hard consistence in dry state and brittle consistence in moist state. The main objective of the present study was to explain and improve the understanding of the specific consistence of the fragipan horizon in moderately humid climate on the example of Albeluvisols of the Carpathian Foothills in Poland basing on mineral and chemical composition of bridges linking coarse soil material. Quantitative X-ray diffraction shows that the studied fragipan horizon contains high concentration of swelling clay minerals. Soil material from the fragipan horizon exhibits numerous clay and iron–clay coatings and clay infillings indicating translocation of colloidal clay and iron oxides from overlying horizons. In addition, bridges between coarse grains of the soil material occur. The fragipan cementing material is composed mainly of SiO2, Al2O3, and Fe2O3 with lower concentration of K2O, MgO, CaO, and Na2O. The chemical composition of bridges within the pan is similar to that of clay coatings and clay infillings suggesting that clay minerals are major bonding agents and are responsible for brittleness and more friable consistence of the pan in the moist state. Additionally, free iron, aluminium, and silica may play some role in specific cementation of the investigated fragipan horizon but these elements are not main bonding agents.

The solubility in the quaternary water-salt systems LaCl3-NdCl3-HCl-H2O (1) and LaCl3-PrCl3-HCl-H2O (2) at 25°C was studied in the section of 40 wt % hydrochloric acid, a system with a eutonic discontinuity. The composition at the point of discontinuity for the eutonic solution is the following. In system 1: 4.67 wt % LaCl3 · 7H2O, 0.37 wt % PrCl3 · 7H2O, 37.98 wt % HCl, and 56.98 wt % H2O; in system 2: 4.37 wt % LaCl3 · 7H2O, 0.93 wt % NdCl3 · 6H2O, 37.88 wt % HCl, and 56.82 wt % H2O.

Interlayered clays are common constituents of several soil orders. The presence of interlayering is indicated by modified thermal stability of soil vermiculites and smectites. In most studies the clays have been reported as Al-hydroxy-interlayered minerals. Despite the abundance of organic compounds in many soils, the potential existence of soil organo-clay intercalations has rarely been considered. In the present study three clay subfractions separated from the eluvial (E) horizon of one podzol from the Tatra Mts., Poland, were studied using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and elemental CHNS analysis, in the natural state and after being subjected to organic matter removal, free iron oxides removal, saturation with different cations, and heating at 330 °C and 550 °C. All fractions contain a “~14 A clay”. In the natural state the “~14 A clay” shows high thermal resistance, manifested by only a partial shift to 10 A after heating at 330 °C. This behavior strongly suggests the presence of interlayering. Saturation with K + shifted the ~ 14 A reflection to ~ 13–11 A, which suggests displacement of a charged species from the interlayer. Clay sample treatment with H 2 O 2 and NaOCl reduced the stability of the interlayered phase because 330 ° C heat treatment shifted the ~ 14 A phase to ~ 10 A, which suggests that the interlayered phase might be organic. Furthermore, the 13–18% organic carbon content of the clays and near disappearance of infrared peaks at 2855 cm − 1 , 2926 cm − 1 , 1738 cm − 1 , ~ 1600 cm − 1 , and ~ 1400 cm − 1 after H 2 O 2 or NaOCl treatment suggests that the clay interlayer phase is mostly organic. Both Al-hydroxy and organic interlayers can be evaluated using a combination of X-ray diffraction, elemental analysis, and infrared spectroscopy and should be considered as possible interlayer phases during the study of interlayered clays.

Solubilities were studied in the NaCl-ZrOCl2-HCl-H2O water-salt system along the 28 wt % HCl section at 25, 50, and 75°C. This is a eutonic system. The compositions of the eutonic solution are as follows (wt % NaCl, ZrOCl2 · 8H2O, HCl, and H2O, respectively): at 25°C, 0.26, 1.88, 27.4, and 70.46; at 50°C, 2.82, 2.68, 26.46, and 68.04; and at 75°C, 1.9, 16.1, 22.96, and 59.04.

Decomposition curves of gas hydrates formed in the ethane–hydrogen–water system were studied in the pressure interval 2–250 MPa. Gas hydrates synthesized at low (up to 5 MPa) pressures were also studied with use of X-ray powder diffraction and Raman spectroscopy. It was shown that ethane–hydrogen mixtures with hydrogen contents 0–30 mol.% form cubic structure I gas hydrates. Higher hydrogen concentration most probably results in appearance of another hydrate phase. We speculate that the gas mixtures with the hydrogen content above 60 mol.% form cubic structure II double hydrate of hydrogen and ethane at temperatures below ≈280 K and pressures above 25 MPa.

The structure of clathrate hydrates with tetraisoamylammonium polyacrylate salt incorporated as guest has been studied in this work. Also, quantitative studies on the stability changes of the clathrate hydrates with different degrees of cross-linking of the guest polymer (varied from 0 to 3%) have been conducted. A single crystal X-ray diffraction study of a crystal of the hydrate with linear (uncross-linked) tetraisoamylammonium polyacrylate as guest reveals a hexagonal structure (space group P6m2, a = 12.15 A, c =12.58 A at 100 K) with 39 host framework water molecules per one guest monomeric unit. Powder X-ray diffraction analyses confirm the identity of the above crystal structure of the hydrate with linear guest polymer and the crystal structure of the hydrates with cross-linked guest (hexagonal, a = 12.25 A, c =12.72 A at 276 K). In order to quantitatively determine the stability differences of the hydrates with the included guests having various degrees of cross-linking of the anionic chain, a series of differential scanning calorimetry measurements of the fusion enthalpy of the hydrate samples has been carried out. On the basis of the results obtained, a structural model describing the decrease in the stability of the clathrate hydrates with tetraisoamylammonium polyacrylate guest as a function of the degree of cross-linking of the guest polymer has been suggested.

Formation of the only cubic structure II double hydrate of propane and hydrogen occurs in the propane–hydrogen–water system. The decomposition curves of the double hydrate at low pressures are situated at 3–4° above the decomposition curve of propane hydrate; at pressures 2000–2500 bar double hydrate decompose at 20° above propane hydrate.

The solubility in the PrCl3-SmCl3-HCl-H2O quaternary water-salt system was studied at 25°C along the 40% hydrochloric acid section (a system with solid solutions and discontinuity). The composition of the discontinuity point was as follows: PrCl3 · 7H2O, 2.33; SmCl3 · 6H2O, 0.11; HCl, 40.05; and H2O, 57.51 wt %.

Solubility in quaternary water-salt systems AlCl3-SrCl2-HCl-H2O (I) and NaCl-SrCl2-HCl-H2O (II) at 25°C along the 28% HCl section of the eutonic-type systems has been investigated. The compositions of eutonic solutions are the following (wt %): in system I, 3.11 AlCl3 ·6 H2O, 7.57 SrCl2 · 6H2O, 22.21 HCl, and 57.11 H2O; and in system II, 2.3 SrCl2 · 6H2O, 1.7 NaCl, 26.88 HCl, and 69.12 H2O.

Phase equilibria in the system H2-CH4-H2O are investigated by means of differential thermal analysis within hydrogen concentration range 0-70 mol % and at a pressure up to 250 MPa. All the experiments were carried out under the conditions of gas excess. With an increase in hydrogen concentration in the initial gas mixture, decomposition temperature of the formed hydrates decreased. X-ray diffraction patterns and Raman spectra of the quenched hydrate samples obtained at a pressure of 20 MPA from a gas mixture containing 40 mol % hydrogen were recorded. It turned out that the hydrate has cubic structure I under these conditions. The Raman spectra showed that hydrogen molecules are not detected in the hydrate within the sensitivity of the method, that is, almost pure methane hydrate is formed. The general view of the phase diagram of the investigated system is proposed. A thermodynamic model was proposed to explain a decrease in hydrate decomposition temperature in the system with an increase in the concentration of hydrogen in the initial mixture.

A technique and an example of solving the problem of PRC correction of minimum-phase recursive digital low-pass filters (RDF) have been considered using the minimax (Chebyshev) proximity criterion of approximable and approximating functions.

The review considers current works on clathrate hydrogen compounds, aimed at creating hydrogen accumulators suitable for practical application. Analysis of published data showed that clathrate hydrates formed by pure hydrogen are unsuitable for this purpose in view of their fairly low limiting hydrogen content and the necessity for their synthesis of extremely high pressures (>100 MPa) that are still industrially unfeasible. The possibilities for hydrogen storage in double (including auxiliary guest molecules along with hydrogen) clathrate hydrates are considered. It is concluded from published data that sorbents on the basis of the so-called “metal-organic frameworks” (MOFs) with a pore size of 1–2 nm hold a greater promise for hydrogen storage at temperatures of about 100 and moderately (up to 10 MPa) high pressures, but the development of all the considered methods of hydrogen storage has not yet grown out of laboratory experiments.

The paper considers methods of treatment and examples to the problem of approximation of AFR of digital recursive low-pass filters with any ratio between the powers of the numerator and denominator of the transfer function polynomials and for a prescribed cutoff function of AFR in the transitional domain of frequencies.

The amount and dislocation of the gamma-radionuclides (artificial cesium and natural potassium) in the Haplic podsol profiles of the Tatra Mountains have been described. These soils belong to the group of penetrable formations what is a result of their texture. They provide a good example of percolation and sorption possibilities of the radionuclides within the soil profile. The highest concentration of radionuclides has been detected in raw humus and spodic (illuvial humus-iron) layers, at the surface.

An international cooperative project on distribution of ozone in the Carpathian Mountains, Central Europe was conducted from 1997 to 1999. Results of that project indicated that in large parts of the Carpathian Mountains, concentrations of ozone were elevated and potentially phytotoxic to forest vegetation. That study led to the establishment of new long-term studies on ecological changes in forests and other ecosystems caused by air pollution in the Retezat Mountains, Southern Carpathians, Romania and in the Tatra Mountains, Western Carpathians on the Polish–Slovak border. Both of these important mountain ranges have the status of national parks and are Man & the Biosphere Reserves. In the Retezat Mountains, the primary research objective was to evaluate how air pollution may affect forest health and biodiversity. The main research objective in the Tatra Mountains was to evaluate responses of natural and managed Norway spruce forests to air pollution and other stresses. Ambient concentrations of ozone (O3), sulfur dioxide (SO2), nitrogen oxides (NOx) as well as forest health and biodiversity changes were monitored on densely distributed research sites. Initial monitoring of pollutants indicated low levels of O3, SO2, and NOx in the Retezat Mountains, while elevated levels of O3 and high deposition of atmospheric sulfur (S) and nitrogen (N) have characterized the Tatra Mountains. In the Retezat Mountains, air pollution seems to have little effect on forest health; however, there was concern that over a long time, even low levels of pollution may affect biodiversity of this important ecosystem. In contrast, severe decline of Norway spruce has been observed in the Tatra Mountains. Although bark beetle seems to be the immediate cause of that decline, long-term elevated levels of atmospheric N and S depositions and elevated O3 could predispose trees to insect attacks and other stresses. European and US scientists studied pollution deposition, soil and plant chemistry, O3-sensitive plant species, forest insects, and genetic changes in the Retezat and Tatra Mountains. Results of these investigations are presented in a GIS format to allow for a better understanding of the changes and the recommendations for effective management in these two areas. Keywords: Air quality, Ozone, Biodiversity, Ecology, Forests, Carpathian Mountains, Poland, Slovakia, Romania

The aim of the study is to present the results of determination of radioactivity of artificial ^{137}Cs and natural ^{40}K and certain heavy metals in soil samples collected from the eastern part of the Main Ridge of Carpathians, including the Beskid Niski Mts and the Bieszczady Mts. The evaluation of level of radionuclides was based on the bulk density analysis of the soil. A valuable finding of the study was a good linear correlation between the level of ^{137}Cs concentration and bulk density of the soil as well as an inverse correlation between radioactivity of natural ^{40}K and tested soil density. This might indicate though a high competitiveness of these elements between each other. Moreover, a good correlation between the concentrations of artificial element ^{137}Cs and Pb has been also observed in soil samples collected from the Beskid Niski Mts. In most cases, the level of artificial ^{137}Cs was lower comparing to an average ^{137}Cs concentration established for soils in Poland.

The solubility in the PrCl3-SmCl3-HCl-H2O quaternary water-salt system was studied at 25°C along the 40% hydrochloric acid section (a system with solid solutions and discontinuity). The composition of the discontinuity point was as follows: PrCl3 · 7H2O, 2.33; SmCl3 · 6H2O, 0.11; HCl, 40.05; and H2O, 57.51 wt %.