Microwave conductivity of thin YBCO film in magnetic field

The microwave response of a thin film of high temperature superconductor YBa_2Cu_3O_7 - δ was measured for a wide region of temperatures and magnetic fields. From the measured complex frequency shift, the complex conductivity was calculated. The model for effective conductivity in the mixed state was fitted to the complex conductivity data and the values of upper critical fields B_c2(T) and depinning frequencies ω_0 (T) have been obtained as fitted parameters

Špilja u kamenolomu Debeljača

Špilja u kamenolomu Debeljača otkrivena je 2004. godine kada se tijekom miniranja u kamenolomu u blizini Lovinca u južnom dijelu Like otvorila 25-metarska jama. Špilja je istražena tijekom 2004. godine do 723 m duljine i 63 m dubine. Špilju karakteriziraju strujnice velikih dimenzija, te brojni koraloidi pri njenom kraju. Mjestimični eliptični oblici kanala posljedica su ranijih faza speleogeneze. Špilja je u postupku zaštite od strane Državnog zavoda za zaštitu prirode

Northern Velebit (Croatia) karst hydrological system: results of a preliminary 2H and 18O stable isotope study

Researching the hydrogeological properties of karst systems is very challenging due to their extreme heterogeneity. A grey-box approach in karst research combines the results from classical hydrogeological methods with direct observations within the karstic underground, i.e. in the caves. Isotope research has become a widely used method in the investigation of karst systems. The results presented are of a preliminary 2H and 18O stable isotope study of the Northern Velebit karst system (Croatia) employing the grey-box approach. Groundwater samples were collected during two summer expeditions in deep caves within the karst massif. Monthly precipitation samples were also collected (at three locations between approx. 900 m and 1600 m altitude), as well as water samples at some of the most significant springs, i.e. discharge outlets of the system. For a single expedition, the stable isotope composition is almost constant, i.e. the stable isotope measurements are within the measurement error across the complete cave profile. Similar characteristics across different caves during the same year were also noted. Samples of water from the springs were taken during base-flow conditions and they have similar isotopic contents to the cave water. The results obtained indicate that homogenization of the water already occurs within the subsurface epikarst zone above the sampling locations in the caves, but a future extended sampling campaign during variable hydrologic conditions is needed to confirm this. The final research goal is to establish a conceptual grey-box model for the functioning of this complex hydrogeological system.</p