High energy extraction of electron beam pumped KrF lasers at multi atmospheres

The construction is described of a simple and compact KrF laser with electron beam excitation. The electron beam is generated in a coaxial vacuum diode, driven directly by a ten-stage coaxial Marx generator. A flat MgF2 outcoupler and a suprasil roof prism, protected by an MgF2 window, proved to be resistant against optically and chemically induced damage. A gas mixture of 4.5 bar Ar, 150 mbar Kr and 10 mbar F2 gives an energy output of 0.46 J from a 16 cm3 volume in 40 ns pulses or 0.72 MW/cm3

Application of an adaptive model hierarchy to parametrized optimal control problems

In this contribution we apply an adaptive model hierarchy, consisting of a full-order model, a reduced basis reduced order model, and a machine learning surrogate, to parametrized linear-quadratic optimal control problems. The involved reduced order models are constructed adaptively and are called in such a way that the model hierarchy returns an approximate solution of given accuracy for every parameter value. At the same time, the fastest model of the hierarchy is evaluated whenever possible and slower models are only queried if the faster ones are not sufficiently accurate. The performance of the model hierarchy is studied for a parametrized heat equation example with boundary value control

Be greedy and learn: efficient and certified algorithms for parametrized optimal control problems

We consider parametrized linear-quadratic optimal control problems and provide their online-efficient solutions by combining greedy reduced basis methods and machine learning algorithms. To this end, we first extend the greedy control algorithm, which builds a reduced basis for the manifold of optimal final time adjoint states, to the setting where the objective functional consists of a penalty term measuring the deviation from a desired state and a term describing the control energy. Afterwards, we apply machine learning surrogates to accelerate the online evaluation of the reduced model. The error estimates proven for the greedy procedure are further transferred to the machine learning models and thus allow for efficient a posteriori error certification. We discuss the computational costs of all considered methods in detail and show by means of two numerical examples the tremendous potential of the proposed methodology

An investigation of the role of Ne, Ar, and Kr as buffer gas in a coaxial e-beam pumped KrF laser

The role of Ne, Ar, and Kr as a buffer gas was investigated in a KrF laser pumped by a coaxiale-beam. The coaxial diode has a length of 20 cm and the anode tube diameter is 1 cm. The tube can be pressurized with the laser gas mixture up to 12 bar while a current density of 250 A/cm2can be achieved. It is found that both the maximum energy extraction and the optimized gas pressure with each buffer gas increase in the sequence Kr-Ar-Ne. From the experimental results, the quenching parameters of Kr, Ar, and Ne are deduced

A Parallel Implementation of Stickel\u27s AC Unification Algorithm in a Message-Passing Environment

Unification algorithms are an essential component of automated reasoning and term rewriting systems. Unification finds a set of substitutions or unifiers that, when applied to variables in two or more terms, make those terms identical or equivalent. Most systems use Robinson\u27s unification algorithm or some variant of it. However, terms containing functions exhibiting properties such as associativity and commutativity may be made equivalent without appearing identical. Systems employing Robinson\u27s unification algorithm must use some mechanism separate from the unification algorithm to reason with such functions. Often this is done by incorporating the properties into a rule base and generating equivalent terms which can be unified by Robinson\u27s algorithm. However, rewriting the terms in this manner can generate large numbers of useless terms in the problem space of the system. If the properties of the functions are incorporated into the unification algorithm itself, there is no need to rewrite the terms such that they appear identical. Stickel developed an algorithm to unify two terms containing associative and commutative functions. The unifiers (there may be more than one) are found by creating a homogeneous linear Diophantine equation with integer coefficients from the terms being unified. The unifiers can be constructed from solutions to this equation. The unifiers generated from one solution of the Diophantine equation are independent of any other solution to the equation. Therefore, once the Diophantine equation has been solved, the unifiers can be calculated from the solutions in parallel. We have implemented Stickel\u27s AC unification algorithm to run in parallel on a local area network of Sun 4/110 workstations in an effort to improve the speed of AC unification

Effekte einer Schulung in Wiederbelebung für Schüler*innen der Jahrgangsstufe 6 durch das Berliner Jugendrotkreuz

Zusammenfassung Hintergrund Der out-of-hospital cardiac arrest (OHCA) stellt eine der häufigsten Todesursachen dar. Ersthelfer haben entscheidend Einfluss auf Überleben und Überlebensqualität. Der Fokus liegt auf frühzeitiger, qualitativ hochwertiger Cardiopulmonaler Reanimation (CPR). Ersthelfer-Reanimationsrate und -qualität sind weiter verbesserbar. Ein Lösungsansatz beinhaltet systematische Ausbildung bereits in Schulen. Das Berliner Jugendrotkreuz (JRK) führt seit den 1990er Jahren Schulungen in der Jahrgangsstufe 3-6 durch - bisher ohne Belege für die Wirksamkeit dieser Schulungen. Diese Studie analysiert den kurz- und längerfristigen Effekt einer einmaligen Schulung in Jahrgangsstufe 6 durch das JRK. Die Studie prüft außerdem, ob Schülergruppen mit Teilnahme an Schulungen bereits in Jahrgangsstufe 3-5 besseres Wissen bzw. Fertigkeiten entwickeln. Methodik Wir untersuchten alle Schulungen, die das JRK in Berlin für Schüler*innen der Jahrgangsstufe 6 in einem Zeitraum von 4 Monaten durchführte. Die Schulungen dauerten jeweils 180 Minuten (Notruf/Wundversorgung 90 Minuten, Bewusstlosigkeit/Stabile Seitenlage (SSL) 70 Minuten, Kreislaufstillstand/CPR 20 Minuten). Die Überprüfung erfolgte anhand von Multiple Choice und Freitext-Fragen ebenso wie Praktischen Prüfungsszenarien. Die Überprüfung fand zu drei Zeitpunkten statt: direkt vor (t0), direkt nach (t1) und 10 Wochen nach (t2) der Schulung. Die Schüler*innen waren aufgefordert, frühere Schulungsteilnahmen zu dokumentieren. Ergebnisse Insgesamt 232 Schüler*innen aus 10 Schulklassen nahmen teil. Fragen: Die Ergebnisse variierten abhängig vom Zeitpunkt: t0 30,4% korrekte Antworten, t151,9%, t2 48,1% (p jeweils < 0,05). Gut ein Viertel der Schüler*innen hatte in Jahrgangsstufe 4 bereits an einer Schulung teilgenommen (ohne CPR). Statistische Unterschiede gegenüber der Schülergruppe ohne frühere Schulung zeigten sich nicht (t0 ohne 29,7% vs. t0 mit 35,7%, p=0,53; t1 ohne 63,1% vs. t1 mit 57,1%, p=0,57). Ergebnisse zum Thema Notruf waren jederzeit sehr gut (t0 91,4%, t1 98,9%). Fehler passierten häufig bei Diagnostik und Therapie des Kreislaufstillstands: Auf Diagnostik wurde zugunsten der sofortigen SSL verzichtet (Atemkontrolle t1 18,4%, SSL t1: 80,5%) und SSL anstatt CPR als Therapie benannt (Thoraxkompressionen t1 17,4%, SSL t1 10,4%). Prüfungsszenarien: Die Schüler*innen führten nach der Schulung suffizient Thoraxkompressionen durch (t1 91,7%), die Schüler*innen wendeten die SSL teilweise korrekt an (t1 65%). Diskussion Die Schulung zeigt auch längerfristig einen positiven Effekt. Eine vorausgegangene Schulung in früheren Jahrgangsstufen hatte keinen Einfluss. Die Studie bestätigt, dass Kinder der Jahrgangsstufe 6 suffizient Thoraxkompressionen durchführen können. Konklusion Das JRK vermittelt die Maßnahmen der Basisreanimation erfolgreich an Schüler*innen der Jahrgangsstufe 6. Defizite fanden sich bei der Vermittlung des Erkennens eines Kreislaufstillstands. Schwierigkeiten traten nachfolgend bei der Entscheidungsfindung hinsichtlich der Maßnahmen zur Behandlung eines Kreislaufstillstands auf. Die Schulung der SSL sollte überdacht werden.Abstract Introduction Out of hospital cardiac arrest (OHCA) is one of the most common causes of death worldwide. The rapid and effective application of cardiopulmonary resuscitation (CPR) by bystanders plays a decisive role to improve OHCA outcome. Therefore, it is crucial to implement systematic CPR trainings for lay bystanders, specifically amongst schoolchildren. The Berlin youth red-cross has been conducting CPR trainings amongst 3rd-6th graders since the 1990s. The effectiveness of these trainings has yet to be formally evaluated. This study set out to assess the short- and long-term effects of a one-time CPR training amongst 6th graders. Furthermore, this study examined whether schoolchildren with prior training developed better skills and knowledge than children without prior training. Methods All courses for 6th graders within a 4-month period were analyzed. The trainings lasted 180 minutes each and covered: emergency call/wound care (90 minutes), unconsciousness/recovery position (70), and cardiac arrest/CPR (20). Knowledge was tested via multiple choice and open-ended questions, skills were assessed by standardized scenario tests. Assessments were performed immediately before (t0), immediately after (t1), and 10 weeks post training (t2). Schoolchildren were asked to provide information about further trainings. Results Overall, 232 schoolchildren from 10 classes participated in the study. Written test: The percentage of correct answers in the written test significantly differed depending upon the time point: t0 30.4%, t1 51.9%, and t2 48.1% (p<0.05). For the 25% of all schoolchildren had partaken in prior training sessions (w/o CPR) no statistical difference could be shown as compared to schoolchildren without prior trainings (t0 35.7% vs 29.7%, t1 57.1% vs 63.1% p=0.57). Results concerning emergency call were very good (t0 91.4%, t1 98.9%). Errors occurred frequently regarding diagnosis of (recovery position t1 80,5% vs respiratory check t1 18.4%) and interventions for cardiac arrest (recovery position t1 10.4%; CPR t1 17.4%). Scenario test: In the practical test post training the children performed adequate chest compressions (t1 91.7%); about one third of the children did not apply a correct recovery position (t1 65.0%) Discussion The training showed an overall long-term positive effect of CPR training amongst participating schoolchildren. Prior training did not show any influence. This study thereby confirms that 6th graders can successfully apply adequate chest compressions. Conclusion The training was effective in teaching 6th graders correct chest compressions. Deficits were seen concerning the identification of cardiac arrest and the appropriate actions required. Teaching the recovery position should be re-evaluated

Adaptive machine learning-based surrogate modeling to accelerate PDE-constrained optimization in enhanced oil recovery

In this contribution, we develop an efficient surrogate modeling framework for simulation-based optimization of enhanced oil recovery, where we particularly focus on polymer flooding. The computational approach is based on an adaptive training procedure of a neural network that directly approximates an input-output map of the underlying PDE-constrained optimization problem. The training process thereby focuses on the construction of an accurate surrogate model solely related to the optimization path of an outer iterative optimization loop. True evaluations of the objective function are used to finally obtain certified results. Numerical experiments are given to evaluate the accuracy and efficiency of the approach for a heterogeneous five-spot benchmark problem.publishedVersio

Recruitment of Eph receptors into signaling clusters does not require ephrin contact

Eph receptors and their cell membrane–bound ephrin ligands regulate cell positioning and thereby establish or stabilize patterns of cellular organization. Although it is recognized that ephrin clustering is essential for Eph function, mechanisms that relay information of ephrin density into cell biological responses are poorly understood. We demonstrate by confocal time-lapse and fluorescence resonance energy transfer microscopy that within minutes of binding ephrin-A5–coated beads, EphA3 receptors assemble into large clusters. While remaining positioned around the site of ephrin contact, Eph clusters exceed the size of the interacting ephrin surface severalfold. EphA3 mutants with compromised ephrin-binding capacity, which alone are incapable of cluster formation or phosphorylation, are recruited effectively and become phosphorylated when coexpressed with a functional receptor. Our findings reveal consecutive initiation of ephrin-facilitated Eph clustering and cluster propagation, the latter of which is independent of ephrin contacts and cytosolic Eph signaling functions but involves direct Eph–Eph interactions

Quinone-mediated extracellular electron transfer processes in ex situ biomethanation reactors

Redox mediators are used in a wide diversity of systems including biological ones. We investigated the effect of adding an artificial quinone (2,7-AQDS) as external redox molecule to an anaerobic digester system dominated by hydrogenotrophic methanogens. When oxidized AQDS was present, the methanogens diverted electrons from H2 to reduce AQDS instead of CO2. The AQDS reduction process was accompanied by a temporary CH4 inhibition, which was re-established several days after the full reduction of AQDS to AH2QDS. The presence of AQDS furthermore resulted in a community shift from Methanobacterium as the dominant methanogen to a more diverse community of methanogens. Protein expression profiles showed a shift in cofactor preference of the adapted community, as a potential response mechanism to AQDS inhibition. AH2QDS was only used as electron donor to a limited extent. Stable isotope incorporation experiments here indicated that the acetogen Acetoanaerobium used AH2QDS to reduce CO2 into acetate.</p