Der Fürst Karl Lieven und die Kaiserliche Universität Dorpat unter seiner Oberleitung / aus der Erinnerung und nach seinen Briefen und amtlichen Erlassen geschildert von Dr. Friedrich Busch, ... ord. Prof. d. Kirchengeschichte u. theologischen Literatur an d. Dorpatischen Univ.

http://tartu.ester.ee/record=b1710664~S1*es

Kiri Karl Morgensternile

http://tartu.ester.ee/record=b1783567~S1*es

Ueber die Glaubwürdigkeit des alten Testaments : an die Gebildeten unter seinen verächtern

https://www.ester.ee/record=b4542556*es

Substantial Genetic Progress in the International Apis mellifera carnica Population Since the Implementation of Genetic Evaluation

The Apis mellifera carnica subspecies of the honeybee has long been praised for its gentleness and good honey yield before systematic breeding efforts began in the early 20th century. However, before the introduction of modern techniques of genetic evaluation (best linear unbiased prediction, BLUP) and a computerized data management in the mid 1990s, genetic progress was slow. Here, the results of the official breeding value estimation in BeeBreed.eu are analyzed to characterize breeding progress and inbreeding. From about the year 2000 onward, the genetic progression accelerated and resulted in a considerable gain in honey yield and desirable properties without increased inbreeding coefficients. The prognostic quality of breeding values is demonstrated by a retrospective analysis. The success of A. m. carnica breeding shows the potential of BLUP-based breeding values and serves as an example for a large-scale breeding program.Peer Reviewe

Local Impact of Humidification on Degradation in Polymer Electrolyte Fuel Cells

Water management represents one of the main challenges in the design and operation of Polymer Electrolyte Fuel Cells (PEFCs). Besides performance, the water level also affects the durability of the cell. Understanding the degradation processes is of vital importance for extending durability of PEFCs by suitable mitigation strategies. In this work, the degradation processes related to operation with fully- and non-humidified gas streams were locally studied. The differences were analyzed using in-situ diagnostic tools, such as segmented cell for local current density measurements, during a 300 h test operating under constant conditions, in combination with local post-test analysis, i.e. SEM/EDX and XPS. The results showed the deep impact of the RH on homogeneity during the degradation process due to the fact that different water distribution influences the chemical environment. Under non-humidified gas streams, the cathode inlet region exhibited increased degradation, whereas with fully humidified gases the bottom of the cell had the higher performance losses. The degradation and the degree of reversibility produced by Pt dissolution, PTFE defluorination, and contaminants such as silicon (Si) and nickel (Ni) were locally evaluate

Experimental and numerical study on catalyst layer of polymer electrolyte membrane fuel cell prepared with diverse drying methods

High manufacturing cost is a major challenge to commercialization of the polymer electrolyte membrane fuel cell (PEMFC) technology in high volume market. Catalyst layer (CL) of PEMFC should incorporate high effective porosity, electrochemically active surface-area, gas permeability, and favorable ionomer distribution. Drying of the CL is a very significant step of electrode fabrication, and determines most of the properties mentioned above, but is rarely a subject of investigation. From various possible drying processes of CL, freeze-drying shows some beneficial properties, such as higher porosity, better ionomer distribution, and reduces the mass transport resistance significantly by allowing more reactant gas into reactive interface. In this work, the influence of diverse drying techniques on the microstructure and performance is investigated. Complementarily, a transient 2D physical continuum-model is used to investigate the effect of the structural properties on cell performance of electrodes prepared with different drying methods. A sensitivity analysis has been also performed to determine the influence of individual parameters applied in the model. Both of the experimental and simulation results stress on the fact that the freeze-drying technique not only significantly enhances the oxygen transport properties through ionomer but also improves the porosity along with the tortuosity of the CL microstructure

Wetting Behavior of Aprotic Li–Air Battery Electrolytes

The open architecture of cathodes in Li–air batteries implies the need for open porosity with adequate pore size distribution and surface energy optimization with regard to the electrolyte. The interaction of liquid and cathode material, especially the wetting properties, which depend on cathode material, roughness and porosity, and electrolyte properties, needs to be understood properly to avoid flooding and assure high active areas. In this work, contact angle goniometry, capillary rise method, and pressure saturation curves are used to investigate the wetting properties of dimethyl sulfoxide (DMSO), tetraethylene glycol dimethyl ether (Tetraglyme), a 1:1 mixture of ethylene carbonate and dimethyl carbonate (EC:DMC) and water on a gas diffusion layer (GDL) Sigracet 39BC, and a pure flat polytetrafluorethylene (PTFE) foil. Contact angle measurement shows that all three organic solvents wet the GDL hydrophobic agent PTFE. Capillary rise measurements show that all sample liquids slowly imbibe into the porous network. While for Tetraglyme an efficient penetration is limited by the high viscosity, water flow rate is slowed down by the hydrophobic pore network of the GDL. Pressure saturation curves for DMSO, Tetraglyme, and EC:DMC can be obtained for the first time and are compared with the water pressure saturation curve