ISO 17025 quality system in a university environment

The experience of working under an ISO 17025 compliant quality system in a university environment is described in the example of the Testing Centre of University of Tartu. University-specific features of the quality system include that the Testing Centre acts as the “quality system server” for other units of the university and graduate students participate in the work carried out under the quality system. The benefits for the university and the graduate students are discussed. It is concluded that implementation of an ISO 17025 compatible quality system in a university is fully accomplishable and gives significant added value to the university by helping to destroy the ivory tower perception about universities and by introducing real-world flavour into the studies and broaden the minds (quality awareness) of the students.     

Oxygen reduction on electrodeposited silver catalysts in alkaline solution

In this study, silver was electrochemically deposited onto glassy carbon (GC) substrate using constant potential regime and tested for oxygen reduction reaction (ORR) in alkaline media. The surface morphology of Ag/GC electrodes was studied by scanning electron microscopy (SEM). It was established that after 10 s of deposition, a number of Ag nanoparticles with the size of 15 nm are produced that grow to about 45 nm after 300 s of electrodeposition. The ORR studies were conducted in 0.1 M KOH solution employing the rotating disk electrode (RDE) method. The Tafel slope at low current densities for electrodeposited silver is in the range from ?70 to ?80 mV. The RDE measurements showed that the electron transfer number (n) is 3.5 for smaller amounts of electrodeposited Ag, and it increases with increasing the loading of Ag on the GC surface. These n values suggest that the electroreduction of oxygen on Ag/GC electrodes proceeds mainly to water.     

Separation and analysis of peptides and proteins from Vipera lebetina snake venom

Our studies of Levantine viper venom have demonstrated that the venom is a rich source of biomedically important proteins and peptides. The venom contains metalloproteases: thrombolytic, fibrin-degrading lebetase, an endothelial cell apoptosis inducing metalloprotease (VLAIP), factor X activator (VLFXA); serine proteases: factor V activator, bradykinin-releasing serine proteases, β-fibrinogenase, α-fibrinogenase and chymotrypsin-like protease and different other enzymes such as phosphodiesterase, 5`-nucleotidase, ribonuclease, phospholipase A2s and L-amino acid oxidase. Among nonenzymatic components venom contains: nerve growth factor, vascular endothelial growth factor, disintegrins, C-type lectins.Here we report the isolation and characterization of proteins and peptides from Vipera lebetina venom using size exclusion, ion exchange, hydrophobic interaction and affinity chromatography, HPLC, UPLC and MALDI-TOF MS methods. N-terminal sequences and internal sequences of tryptic peptides of different proteins were determined using Edman sequencing and LC-ESI-MS/MS techniques. On the basis of fragmental sequences of proteins the oligonucleotides were designed and used as primers for cDNA cloning. Using cDNA library of the venom gland of a single snake the cDNAs coding proteins were cloned and sequenced. Protein sequences were deduced from cDNA sequences.The substrate specificity of venom proteases against insulin B-chain, bradykinin, substance P, and 6-10 amino acid residues containing peptides synthesized according to potential cleavage regions of fibrinogen, factor X, factor IX, factor V, α₂-macroglobulin bait region and pregnancy zone protein were studied using MALDI-TOF mass spectrometry technique.     

Experimental investigations of sound reflection from hot and subsonic flow duct termination

The knowledge of the reflection properties of open end jet ducts is important for different applications, where the flow and high temperature conditions are involved and add complexity to the problem. In this paper, the magnitude of the reflection coefficients together with the respective end-corrections is experimentally determined for hot flow duct openings. A Mach number range up to 0.3 for cold jets and up to 0.12 for a jet temperature of 200 °C is treated. The experimental results are compared with the numerical model proposed by Munt (Acoustic transmission properties of a jet duct with subsonic jet flow: 1. The cold jet reflection coefficient, Journal of Sound and Vibration 142 (1990) 413–436) and a good correlation in plane-wave region is demonstrated. To reduce experimental uncertainty, the sound reflection properties at the duct opening are obtained by using an overdetermined two-microphone technique with the implementation of a three pressure transducer array. By introducing a modified multistep version of the stepped sine excitation, the accuracy of data acquisition process is improved without compromising the measurement time.     

Finite element modelling of ion transport in the electrolyte of a 3D-microbattery

A mathematical model describing ionic transport in a 3D-microbattery (3D-MB) electrolyte is developed here using finite element methodology. The model is then exploited to study a 3D-MB based on an interdigitated plate (“trench”) architecture for a 10 μm-thick electrolyte layer separating 10 μm-thick graphite anode and LiCoO₂ cathode plates. The effect of varying plate length, end-shape and electronic conductivity is also modelled. It is shown that the 3D-MB architecture gives rise to qualitatively non-uniform current densities, leading to sub-optimal surface utilization. This can, in turn, be optimized by varying electrode geometries and/or material properties.