Drop of Activity of the Oxygen Electrode on the Base of Ag Catalyst (Polytetrafluorethylene)

The article describes the determination of the effect of »impurities«, o,riginating from dissolution of the cell components, upon the activity of the oxygen electrode Ag-catalyst .in 7 N KOH. It was confirmed that the silver surface plays a more serious part in electrochemical processes than it had been assumed previously. It refers, above all, to the formation and solubility of silver oxides and further to eventual adsorption of ions [Ag(OH) 2]- on the active surface of the oxygen electrode silver catalyst, especially with positive potentials in unloaded conditions. For the determination of the total effect of events upon the activity of the oxygen electrode, methods comparing the changes of current density, in dependence on time, were applied. Current density was measured with electrode potential of -300 mV vs. Hg/HgO. The experiments proved that the activity of the oxygen electrode on the base of Ag catalyst ~ PTFE in unloaded conditions and without oxygen pressure in 7 N KOH at the approximate temperature of 63° C, drops expressively with time. More we observed the influence of the collector material construction, effect of Zn, Ni, Cd and Fe, effect of amalgamation of the oxygen electrode and effect of CO i- upon its activity. It was proved, on the basis of experimental results, that the oxygen electrode on the basis of Ag/PTFE is practically inapplicable. »Selfpoisoning « occurs here probably due to the effect of ions [Ag(OH) 2]-. On the other hand, the formation of [Ag(OH)2]- can be utilized in the production technology of electron conductive skeleton of the electrode by the application of a mixture of silver and electronegative metal, e. g. Zn

Managing Dynamic User Communities in a Grid of Autonomous Resources

One of the fundamental concepts in Grid computing is the creation of Virtual Organizations (VO's): a set of resource consumers and providers that join forces to solve a common problem. Typical examples of Virtual Organizations include collaborations formed around the Large Hadron Collider (LHC) experiments. To date, Grid computing has been applied on a relatively small scale, linking dozens of users to a dozen resources, and management of these VO's was a largely manual operation. With the advance of large collaboration, linking more than 10000 users with a 1000 sites in 150 counties, a comprehensive, automated management system is required. It should be simple enough not to deter users, while at the same time ensuring local site autonomy. The VO Management Service (VOMS), developed by the EU DataGrid and DataTAG projects[1, 2], is a secured system for managing authorization for users and resources in virtual organizations. It extends the existing Grid Security Infrastructure[3] architecture with embedded VO affiliation assertions that can be independently verified by all VO members and resource providers. Within the EU DataGrid project, Grid services for job submission, file- and database access are being equipped with fine- grained authorization systems that take VO membership into account. These also give resource owners the ability to ensure site security and enforce local access policies. This paper will describe the EU DataGrid security architecture, the VO membership service and the local site enforcement mechanisms Local Centre Authorization Service (LCAS), Local Credential Mapping Service(LCMAPS) and the Java Trust and Authorization Manager.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics (CHEP03), La Jolla, Ca, USA, March 2003, 7 pages, LaTeX, 5 eps figures. PSN TUBT00

N-Myc-induced metabolic rewiring creates novel therapeutic vulnerabilities in neuroblastoma

N-Myc is a transcription factor that is aberrantly expressed in many tumor types and is often correlated with poor patient prognosis. Recently, several lines of evidence pointed to the fact that oncogenic activation of Myc family proteins is concomitant with reprogramming of tumor cells to cope with an enhanced need for metabolites during cell growth. These adaptions are driven by the ability of Myc proteins to act as transcriptional amplifiers in a tissue-of-origin specific manner. Here, we describe the effects of N-Myc overexpression on metabolic reprogramming in neuroblastoma cells. Ectopic expression of N-Myc induced a glycolytic switch that was concomitant with enhanced sensitivity towards 2-deoxyglucose, an inhibitor of glycolysis. Moreover, global metabolic profiling revealed extensive alterations in the cellular metabolome resulting from overexpression of N-Myc. Limited supply with either of the two main carbon sources, glucose or glutamine, resulted in distinct shifts in steady-state metabolite levels and significant changes in glutathione metabolism. Interestingly, interference with glutamine-glutamate conversion preferentially blocked proliferation of N-Myc overexpressing cells, when glutamine levels were reduced. Thus, our study uncovered N-Myc induction and nutrient levels as important metabolic master switches in neuroblastoma cells and identified critical nodes that restrict tumor cell proliferation