Facetting of the self-assembled droplet epitaxial GaAs quantum dot

In this work, droplet epitaxially grown GaAs quantum dots on AlGaAs surface are studied. The quantum dots are investigated in situ with RHEED and ex situ with TEM method. The TEM picture shows that the quantum dot is perfectly crystalline and fits very well to the crystal structure of the substrate. Furthermore, the side of the quantum dot shows stepped facet shape. Here, we show, how the stepped side shape forms from the droplet during crystallization. The RHEED picture shows broadened chevron-tail, which can be explained by the shape of the quantum dot.     

Dialysate saving by automated control of flow rates: comparison between individualized online hemodiafiltration and standard hemodialysis

Cost reduction and quality improvement seem to be conflicting issues. However, online hemodiafiltration (oHDF) with new automatic functions offers a cost‐efficient therapy compared to hemodialysis (HD). Seven dialysis centers conducted a randomized clinical trial with cross‐over design: high‐flux HD vs. postdilutional oHDF with functions coupling both dialysate and substitution flow rates to blood flow rates. During the 6 weeks of the study, all treatment parameters remained unchanged for HD and oHDF, apart from dialysate and substitution flow rate. Treatment data were recorded during each treatment, and predialytic and postdialytic concentrations of urea were recorded at the end of each study phase. The analysis involved 956 treatments of 54 patients. The mean dialysate consumption was 123.2 ± 6.4 l for HD and 113.4 ± 14.9 l for oHDF (p < 0.0001), the mean dialysis dose was 1.42 ± 0.23 for HD and 1.47 ± 0.26 for oHDF (p < 0.0001); oHDF resulted in a lower dialysate consumption (8.0% less) and a slightly increased dialysis dose (Kt/V 3.5% higher) compared to HD. oHDF with the investigated automatic functions offers substantial savings in dialysate consumption without decreasing dialysis dose.     

Combinatorial Design of Al2O3 Supported Au Catalysts For Preferential CO Oxidation

Multi-component Au/Al₂O₃ catalysts were designed and tested for PROX reaction using holographic research strategy. On the bases of our previous study Pb has been selected as the main modifier of the Au. In addition to Au and Pb the catalysts library contained V, Ba, Ce, Sm, Ag and Cu resulting in multi component catalysts tailored for PROX reaction. After preparation and testing of 173 catalysts within five generations new catalyst compositions with excellent performance have been obtained. Upon using the best catalyst CO could be removed almost completely and the selectivity of oxygen towards the CO oxidation was around 75%. In the course of catalyst library design it has been revealed that the selection of the objective function (OF) has high impact both on the rate of optimization and the performance of catalysts designed. The complex OF was created from two single desirability functions related to CO conversion and oxygen selectivity towards CO oxidation. In order to maintain high optimization rate there was a need to change the weights of single desirability functions in the course of catalyst library design. The results show that Pb, Sm, Cu and Ag are the key modifiers for PROX reaction under experimental conditions applied.     

Finding maximal orders in semisimple algebras over Q

We consider the algorithmic problem of constructing a maximal order in a semisimple algebra over an algebraic number field. A polynomial time ff-algorithm is presented to solve the problem. (An ffalgorithm is a deterministic method which is allowed to call oracles for factoring integers and for factoring polynomials over finite fields. The cost of a call is the size of the input given to the oracle.) As an application, we give a method to compute the degrees of the irreducible representations over an algebraic number fieldK of a finite groupG, in time polynomial in the discriminant of the defining polynomial ofK and the size of a multiplication table ofG.     

Phosphoric acid doped membranes based on Nafion, PBI and their blends - Membrane preparation, characterization and steam electrolysis testing

Proton exchange membrane steam electrolysis at temperatures above 100 °C has several advantages from thermodynamic, kinetic and engineering points of view. A key material for this technology is the high temperature proton exchange membrane. In this work a novel procedure for preparation of Nafion^® and polybenzimidazole blend membranes was developed. Homogeneous binary membranes covering the whole composition range were prepared and characterized with respect to chemical and physiochemical properties such as water uptake, phosphoric acid doping, oxidative stability, mechanical strength and proton conductivity. An MEA based on phosphoric acid doped Nafion^® was operated at 130 °C at ambient pressure with a current density of 300 mA cm⁻² at 1.75 V, with no membrane degradation observed during a test of 90 h. The PBI based MEAs showed better polarization curves (500 mA cm⁻² at 1.75 V) but poor durability.     

Heterologous functionality and roles of conserved cysteine motifs of the [NiFe]-hydrogenase accessory protein,HupK/HoxV

Numerous auxiliary proteins participate in the complex posttranslational modification process of [NiFe]-hydrogenases. In Thiocapsa roseopersicina, the HupK protein is important for the formation of active membrane-bound hydrogenases. The HupK proteins of various origins have moderate similarity to each other and to the large subunits of [NiFe]-hydrogenases. Site directed mutagenesis experiments were performed to disclose the role of the highly conserved cysteines in HupK. Cys54 was shown to be indispensable for the proper function of HupK and recreation of a large subunit like cysteine profile had negative effect on the activity of HupSL hydrogenase. Although, the results of the mutagenesis study slightly differed from that obtained for Ralstonia eutropha HoxV, it was clearly demonstrated that HupK from T. roseopersicina and HoxV from R. eutropha can substitute each other. It was also demonstrated that HoxV could be involved in the maturation of both Hup and Hyn hydrogenases in T. roseopersicina.