Signe Žvagiņa, Zaiga Petriņa, Vizma Nikolajeva and Anita Lielpētere
Rhizobium leguminosarum biovar viciae is a bacterium, which can establish nodules on roots of legumes. Rhizobial inoculants are used in agriculture as bio-fertilizers. Peat, clay powder and three kinds of expanded clay were tested for the immobilization of bacteria. The results showed that carrier material influences the success of immobilization and that storage temperature influences the survival. The best results were achieved with maintenance of bacteria in a suspension and immobilization on peat. We recommend storage of rhizobial products at a temperature of −18 °C or 4 °C.
Daiga Pipira, Juris Kostjukovs and Ģirts Stinkulis
Siliciclastic deposits of the Burtnieki Formation and the Amata Formation in Latvia contain carbonate inclusions in places. Morphological peculiarities and mineral composition indicate that these carbonates represent dolocretes formed during subaerial exposure events in Devonian Burtnieki and Amata times. Dolocretes show nodular and veiny structure, circumgranular cracks, and other features of brecciation, but massive dolocretes also have been found in the Amata Formation. These features indicate that the dolocretes formed under the influence of both groundwater activity and pedogenic processes. These dolocretes were formed during episodes of subaerial exposure in repeated processes of drying and wetting either due to fluctuations of the groundwater table or climate change from semi-arid to semi-humid.
Dlouhodobým cílem programu řízení životnosti tlakových částí kotlů je eliminace poruchových odstávek a bezpečné provozování těchto zařízení. K detekci kritických blokací ohybů trubek odloupnutými částicemi epitaktické vrstvy byla ve spolupráci s EPRI vybrána metoda LFET (Low Frequency Electromagnetic Testing) a pro měření celkové tloušťky oxidické vrstvy metoda UT (Ultrasonic Testing), které nacházejí uplatnění zejména v USA. Ultrazvukový tloušťkoměr je použitelný pouze pro feritické materiály. Upravená metoda vířivých proudů (ET) bude sloužit ke stanovení tloušťky epitaktické vrstvy na austenitických ocelích.
K. Kreislová, H. Geiplová, I. Skořepová, J. Skořepa and D. Majtás
Atmosférická koroze a klasifi kace agresivity atmosfér je dlouhodobým předmětem studia SVUOM. Ve spolupráci s CGS byly v roce 2001 vytvořeny mapy korozních rychlostí a korozních tříd pro uhlíkovou ocel, patinující ocel, zinek, měď, bronz a hliník. Tento článek uvádí aktuální přístup k modelování atmosférické koroze v České republice, který je založen na modifi kovaných funkcích zahrnujících klimatická data, znečištění ovzduší a nově i vliv rozmrazujících solí v okolí dálnic.
In this literature review we identify and quantify the parameters influencing the low-cycle fatigue life of materials commonly used in nuclear power plants. The parameters are divided into several groups and individually described. The main groups are material properties, mode of cycling and environment parameters. The groups are further divided by the material type - some parameters influence only certain kind of material, e.g. sulfur content may decreases fatigue life of carbon steel, but is not relevant for austenitic stainless steel; austenitic stainless steel is more sensitive to concentration of dissolved oxygen in the environment compared to the carbon steel. The combination of parameters i.e. conjoint action of several detrimental parameters is discussed. It is also noted that for certain parameters to decrease fatigue life, it is necessary for other parameter to reach certain threshold value. Two different approaches have been suggested in literature to describe this complex problem - the Fen factor and development of new design fatigue curves. The threshold values and examples of commonly used relationships for calculation of fatigue lives are included. This work is valuable because it provides the reader with long-term literature review with focus on real effect of environmental parameters on fatigue life of nuclear power plant materials.
Silvija Strikauska, Andrejs Berzins, Lauris Arbidans, Agnese Kukela, Olga Muter and Maris Klavins
Contaminated microfibre cloths (80 % polyester and 20 % polyamide) which were previously used in waterless car cleaning process were treated in ultrasonic bath. Efficiency of water, ethanol, 2-propanol and ethylene glycol as liquid phase for ultrasonic treatment was compared. Chemical oxygen demand (COD), concentration of surfactants and total nitrogen in the extract were tested after 0 min, 10 min, 30 min and 60 min ultrasonic (US) exposure (42 kHz). In all cases the COD values gradually increased in a time dependent manner from 6 % to 35 % with ethanol, from 17 % to 37 % with ethyleneglycol and from 17 % to 33 % with 2-propanol at 10 to 60 min US mode, respectively.
In this report the obtaining and properties of hightemperature porous ceramic materials using local carbonate clays and quartz sand resources was studied. Materials with two different porosities were obtained by using different synthesis temperatures. The test results show that these materials contain cordierite as their main crystalline phase. The porosity directly influences the compressive strength and it is greatly reduced when overall porosity increases. The CTE of obtained materials is low − about 3-10−6 1/°C.
Juris Burlakovs, Rūta Ozola, Juris Kostjukovs, Ivars Kļaviņš, Oskars Purmalis and Māris Kļaviņš
Jurassic clay rich in organic matter from western Latvia is known already from early 19th century. Jurassic clays provide an interest because of high potential for innovative use due to its clay mineral composition jointly with organic material. Properties of the Jurassic clayey deposits were studied by using various physical and chemical methods. Material gained from field was tested by modern techniques such as UV-Vis, 3D fluorescence and FTIR - spectra, which show patterns of organic compounds in the clay material. AAS analyses characterized inorganic content. PXRD studies raised discussions about the origin of kaolin, illite and smectite and interactions among these clay minerals. Obtained results show that Jurassic clays with organic matter have future potential for possible use in cosmetic industry and as a sorbent material.
A simple, fast and reproducible analytical method for fractionation of freely available bryophyte lipids was developed. Lipid fractionation was achieved by solid phase extraction using porous silica and silica derivatized with -NH2 groups and the compounds were quantified as their trimethylsilyl derivatives by gas chromatography-mass spectrometry. The suggested fractionation method allows to identify several groups of substances prospective in respect of search of new biologically active compounds in bryophytes as well as in respect of understanding of their metabolism.
Dagnija Vecstaudza, Maris Klavins, Olga Muter and Reinis Rutkis
Surface cleaning preparations pose a serious threat to the environment. Toxicity of a pre-manufactured preparation SCP-1 was tested on bacteria, algae and higher plants and was expressed as a minimal inhibitory concentration (MIC). Obtained results showed that among unicellular and more complex testorganisms MIC values differed 10-100 fold suggesting that an application of complex test-organism battery is necessary to evaluate the toxicity of SCP-1 thoroughly. MIC values were different from the critical micelle concentration; this indicates that the SCP1 mechanism of action might not involve membrane disruption and/or destabilization.