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The crystal structure of 1H-pyrazol-2-ium hydrogen oxalate has been studied at 100 K. It consists of two-dimensional layers built with one-dimensional chains that contain pyrazolium and oxalate acids bonded by N–H…O and O–H…O hydrogen bonds. According to the X-ray data and the Quantum Theory of Atoms in Molecules, it was shown that weak and moderate hydrogen bonds are present in the crystal at room temperature. The thermal stability was studied with the DSC, TGA, and DTG methods: three endothermic peaks are observed at 384, 420, and 469 K. Conductivity measurements have been performed in the temperature range from 300 to 433 K. At 383 K the pyrazole–oxalic acid framework loses its rigidity and the crystal undergoes an ordered–disordered phase transition. At this temperature, the value of the activation energy of proton conductivity changes from 1.14 to 2.31 eV. The proton conduction pathways and the transport mechanism have been studied with theoretical methods. [ABSTRACT FROM AUTHOR]

For the first time polysaccharidic ulvans have been isolated from freshwater green macroalgae Ulva flexuosa and Cladophora glomerata . One of the main components of ulvan is 3-sulfated rhamnoglucuronan showing a wide range of interesting properties and being a source of rare sugars. The production of mono- and oligo-saccharides from this polysaccharide can potentially be applied in cosmetic, pharmaceutical and food industry. In this paper a new and effective method for the isolation of ulvans from freshwater algae is described. The substance has been characterized after enzymatic hydrolysis by Fourier Transform Infrared (FT-IR) spectroscopy and elemental analysis. FT-IR spectroscopy permits identification of the band characteristic of the sulfonic acid groups, specific for this kind of polysaccharides. With increasing size of the thalli, the amount of ulvans in the algae cells increases. Hence, freshwater green macroalgae U. flexuosa and C. glomerata were found as a new source of polysaccharidic ulvans that can be considered to be potentially used in medicine, pharmacy, food and cosmetic industry. [ABSTRACT FROM AUTHOR]

The process of magnetic relaxation was studied in bismuth ferrite BiFeO3multiferroic micro-cubes obtained by means of microwave assisted Pechini process. Two different mechanisms of relaxation were found. The first one is a rapid magnetic relaxation driven by the domain reorientations and/or pinning and motion of domain walls. This mechanism is also responsible for the irreversible properties at low temperatures. The power-law decay of the magnetic moment confirms that this relaxation takes place in the system of weakly interacting ferromagnetic or superferromagnetic domains. The second mechanism is a long-term weak magnetic relaxation due to spin glass-phase. [ABSTRACT FROM AUTHOR]