Modified NASA-Lewis chemical equilibrium code for MHD applications

A substantially modified version of the NASA-Lewis Chemical Equilibrium Code was recently developed. The modifications were designed to extend the power and convenience of the Code as a tool for performing combustor analysis for MHD systems studies. The effect of the programming details is described from a user point of view

Ultrametric probe of the spin-glass state in a field

We study the ultrametric structure of phase space of one-dimensional Ising spin glasses with random power-law interaction in an external random field. Although in zero field the model in both the mean-field and non-mean-field universality classes shows an ultrametric signature [Phys. Rev. Lett. 102, 037207 (2009)], when a field is applied ultrametricity seems only present in the mean-field regime. The results for the non-mean field case in an external field agree with data for spin glasses studied within the Migdal-Kadanoff approximation. Our results therefore suggest that the spin-glass state might be fragile to external fields below the upper critical dimension.Comment: 5 pages, 4 figures, 1 tabl

"Baustelle Boden" in der Klimakommune Vrees

Vrees, das Dorf der 1000 Eichen am Rande des Hümmling, setzt seit mehr als 25 Jahren auf regenerative Energien und nachwachsende (Energie-)Rohstoffe. Die Vorgaben der Agenda 21 als Folge des Brundtland-Berichtes 1987 sowie der Klimaschutz-Konvention nach dem Weltgipfel von Rio 1992 leiteten einen Prozess der Umorientierung bezüglich der kommunalen Energieversorgung ein. Seit 1997 versorg ein Holzhackschnitzelheizwerk 75 Haushalte, Fotovoltaik- und Windkraftanlagen folgten. Energieautark wurde die Gemeinde Vrees durch zwei Biogasanlagen, Satteliten-Blockheizkraftanlage und ein Fernwärmenetz, das ständig erweitert wird. Vrees ist Bioenergiedorf und wurde 2016 mit einem der drei Hauptpreise im Wettbewerb „Klima kommunal“ ausgezeichnet. Dieser Beitrag zum Klimaschutz hat einen hohen Preis. Umgerechnet ein Drittel der landwirtschaftlichen Nutzfläche der Gemeinde wird für die Erzeugung der notwendigen Biomasse benötigt. Fruchtfolgen mit hohen Anteilen an Mais und Grünroggen sowie hohe Düngergaben belasten den Landschaftshaushalt, die Nitratwerte in den Beobachtungbrunnen haben bereits bedenklich hohe Werte erreicht. Diese Problematik ist allen Beteiligten durchaus bewusst und wird im Rahmen eines konstruktiven Dialogprozesses regelmäßig diskutiert. Um diesen Dialog zu unterstützen, wurde 2015 auf dem Gelände der größeren Biogasanlage eine begehbare Bodengrube geöffnet, die einen Eschboden erschließt. Eschböden und ihre Entstehung stehen gemeinhin für historische Landnutzung und erklären die Entwicklung der Kulturlandschaft. Hier und insbesondere im Zusammenhang mit der Biogasanlage steht der Eschboden für einen Paradigmenwechsel. Informations- und Unterrichtsmaterialien ermöglichen der Öffentlichkeit, Schulklassen, Studierenden und nicht zuletzt auch allen Beteiligten, die aktuelle Situation zu begreifen und sich am Entwurf von Modellen für eine Nachhaltige Entwicklung ländlicher Räume zu beteiligen

Functional characterization of the human Cdk10/Cyclin Q complex

Cyclin-dependent kinases (CDKs) are key players in cell cycle regulation and transcription. The CDK-family member Cdk10 is important for neural development and can act as a tumour suppressor, but the underlying molecular mechanisms are largely unknown. Here, we provide an in-depth analysis of Cdk10 substrate specificity and function. Using recombinant Cdk10/CycQ protein complexes, we characterize RNA pol II CTD, c-MYC and RB1 as in vitro protein substrates. Using an analogue-sensitive mutant kinase, we identify 89 different Cdk10 phosphosites in HEK cells originating from 66 different proteins. Among these, proteins involved in cell cycle, translation, stress response, growth signalling, as well as rRNA, and mRNA transcriptional regulation, are found. Of a set of pan-selective CDK- and Cdk9-specific inhibitors tested, all inhibited Cdk10/CycQ at least five times weaker than their proposed target kinases. We also identify Cdk10 as an in vitro substrate of Cdk1 and Cdk5 at multiple sites, allowing for a potential cross-talk between these CDKs. With this functional characterization, Cdk10 adopts a hybrid position in both cell cycle and transcriptional regulation

Fermion-Boson Interactions and Quantum Algebras

Quantum Algebras (q-algebras) are used to describe interactions between fermions and bosons. Particularly, the concept of a su_q(2) dynamical symmetry is invoked in order to reproduce the ground state properties of systems of fermions and bosons interacting via schematic forces. The structure of the proposed su_q(2) Hamiltonians, and the meaning of the corresponding deformation parameters, are discussed.Comment: 20 pages, 10 figures. Physical Review C (in press

Parton distribution functions from nonlocal light-cone operators with definite twist

We introduce the chiral-even and chiral-odd quark distributions as forward matrix elements of related bilocal quark operators with well-defined (geometric) twist. Thereby, we achieve a Lorentz invariant classification of these distributions which differ from the conventional ones by explicitly taking into account the necessary trace terms. The relations between both kinds of distribution functions are given and the mismatch between their different definition of twist is discussed. Wandzura-Wilczek--like relations between the conventional distributions (based on dynamical twist) are derived by means of geometric twist distribution functions.Comment: 17 pages, REVTEX, Extended version, The Introduction has been rewritten, Setion V "Wandzura-Wilczek--like relations" and App. B are added; Sign errors are correcte

Effects of fringing magnetic fields on MHD seawater thruster performance

There are several loss mechanisms that influence the flow and electrical field characteristics of an MHD seawater thruster and hence its performance. Among those losses are the jet losses, ohmic losses, three-dimensional effects, and electrical end losses. Some of those loss mechanisms have been discussed before, together with the parameters affecting the thruster performance. Thruster electrical end losses are caused by the fringing of the magnetic field near the ends of the electrodes, and by the nonuniformity of the current and electric fields across the thruster, particularly near the ends of the electrodes. Therefore, the current density cannot be calculated from a simple one-dimensional relationship. Rather, a multi-dimensional solution of the electric fields should be performed. No simple expression can be written for the electrical end losses, because end effects depend on several parameters that include the thruster aspect ratio, load factor and the profile of the magnetic field in the fringe region away from the electrodes

Bosonization in d=2 from finite chiral determinants with a Gauss decomposition

We show how to bosonize two-dimensional non-abelian models using finite chiral determinants calculated from a Gauss decomposition. The calculation is quite straightforward and hardly more involved than for the abelian case. In particular, the counterterm $A\bar A$, which is normally motivated from gauge invariance and then added by hand, appears naturally in this approach.Comment: 4 pages, Revte

Dynamic response of steam-reformed, methanol-fueled, polymer electrolyte fuel cell systems

Analytical models were developed for the dynamic response of steam-reformed, methanol-fueled, polymer electrolyte fuel cell (PEFC) systems for transportation applications. Focus is on heat transfer effects likely to limit rapid response of PEFC systems. Depending on the thermal mass, the heat exchangers and steam reformer can have time constants on the order of several seconds to many minutes. On the other hand, the characteristic time constants associated with pressure/density disturbances arising from flow rate fluctuations are on the order of milliseconds. In vehicular applications, the response time of the turbomachinery, which is determined by rotational inertia, can be on the order of seconds or less. Dynamic reformer model was used to examine methanol conversion efficiency and thermal performance during a cold start. Response times are determined to achieve 50-100% of the steady-state methanol conversion for two catalyst tube diameters. Thermal performance is considered in terms of the approach to steady-state temperature, possibility of catalyst overheating, and penalty in system efficiency incurred during startup time. For the complete reference PEFC system, various turn-down scenarios were simulated by varying the relative rates of change of fuel cell loading and system flows. Depending on relative rates of cell loading changes to flow rate changes, overheating of the catalyst can occur due to excess heat transfer in the reformer preheater; this can be controlled by an additional water quench between catalyst bed and preheater, but only if the flow rate change is sufficiently fast relative to load changes