Optimal non-circular fiber geometries for image scrambling in high-resolution spectrographs

Optical fibers are a key component for high-resolution spectrographs to attain high precision in radial velocity measurements. We present a custom fiber with a novel core geometry - a 'D'-shape. From a theoretical standpoint, such a fiber should provide superior scrambling and modal noise mitigation, since unlike the commonly used circular and polygonal fiber cross sections, it shows chaotic scrambling. We report on the fabrication process of a test fiber and compare the optical properties, scrambling performance, and modal noise behavior of the D-fiber with those of common polygonal fibers.Comment: 7 pages, 6 figures, submitted to SPIE Astronomical Telescopes & Instrumentation 2016 (9912-192

Influence of Protein Type on the Antimicrobial Activity of LAE Alone or in Combination with Methylparaben

The cationic surfactant Lauric arginate (LAE) has gained approval for utilization in meat products (limit: 200 mg/kg). However, as for other antimicrobials, its activity is reduced when applied to complex food matrices. The current study therefore aims to better understand protein-antimicrobial agent-interactions and their influence on the antimicrobial activity of (i) LAE and (ii) methylparaben against Listeria innocua and Pseudomonas fluorescens in defined model systems (pH 6). Antimicrobials were utilized alone or in combination with nutrient broth containing either no protein or 2% bovine serum albumin, whey protein isolate, or soy protein hydrolysate. LAE was found to form complexes with all proteins due to electrostatic attraction, determined using microelectrophoretic and turbidity measurements. Minimal lethal concentrations of LAE were remarkably increased (4–13 fold) in the presence of proteins, with globular proteins having the strongest impact. Combinations of LAE (0–200 µg/mL) with the less structure-sensitive component methylparaben (approved concentration 0.1%) remarkably decreased the concentrations of LAE needed to strongly inhibit or even kill both, L. innocua and P. fluorescens in the presence of proteins. The study highlights the importance of ingredient interactions impacting microbial activity that are often not taken into account when examining antimicrobial components having different structure sensitivitie

3 kW Thermoelectric Generator for Natural Gas-Powered Heavy-Duty Vehicles – Holistic Development, Optimization and Validation

Emissions from heavy-duty vehicles need to be reduced to decrease their impact on the climate and to meet future regulatory requirements. The use of a cost-optimized thermoelectric genera-tor based on total cost of ownership is proposed for this vehicle class with natural gas engines. A holistic model environment is presented that includes all vehicle interactions. Simultaneous op-timization of the heat exchanger and thermoelectric modules is required to enable high system efficiency. A generator design combining high electrical power (peak power of about 3,000 W) with low negative effects was selected as a result. Numerical CFD and segmented high-temperature thermoelectric modules are used. For the first time, the possibility of an eco-nomical use of the system in the amortization period of less than << 2 years is available, with a fuel reduction in a conventional vehicle topology of already up to 2.8%. A significant improve-ment in technology maturity was achieved and the power density of the system was significant-ly improved to 298 W/kg and 568 W/dm3 compared to the state of the art. A functional model successfully validated the simulation results with an average deviation of less than 6%. An elec-trical output power of up to 2,700 W was measured

HD-TEG: Effizienzsteigerungspotential bei Nutzfahrzeugen durch den Einsatz eines neuartigen Abwärmenutzungssystems (Thermoelektrik)

In diesem Projekt wurde die Effizienzsteigerung von modernen schweren Nutzfahrzeugen durch den Einsatz eines neuartigen Abwärmenutzungssystems demonstriert. Dabei wurde erstmalig ein nutzfahrzeugspezifisches System basierend auf der Thermoelektrik mit Hilfe eines gesamtheitlichen Entwicklungsansatzes entwickelt und das Potential dieser Technologie für heutige und zukünftige Nutzfahrzeuge dargestellt. Als Referenzfahrzeug diente ein innovatives Serien-Nutzfahrzeug mit Erdgasmotor, welches als eine Schlüsseltechnologie für den zukünftigen emissionsärmeren Straßengüterverkehr im Nah- sowie im Fernbereich gilt. Projektschwerpunkte waren gleichermaßen die Effizienzsteigerung des thermoelektrischen Systems und des Fahrzeuges sowie die Kostensenkung des Systems durch Verwendung von seriennahen Aufbautechnologien und Fertigungsverfahren. Die Systemkosten von Abwärmenutzungssystemen im Nutzfahrzeug müssen sich anwendungsspezifisch in möglichst kurzer Nutzungszeit im Realbetrieb amortisieren. Dazu wurde eine Bauweise des TEG gewählt, die eine hohe Energieausbeute bei gleichzeitig geringem Gewicht verspricht und somit Vorteile sowohl unter Realfahrbedingungen als auch in relevanten Fahrzyklen bietet. Eine neuartige ganzheitliche Auslegungsmethode bietet das Potential, thermoelektrische Systeme in Zukunft deutlich effizienter auslegen zu können. Hierbei wurden neben der Systemauslegung erstmals auch alle Wechselwirkungen mit dem Nutzfahrzeug betrachtet und quantifiziert. Die Umsetzung dieser Ansätze wurden in mehreren Funktionsmustern dargestellt. Durch die enge Zusammenarbeit der Projektpartner, konnte das Wissen und die umfangreiche Erfahrung beider in das Projekt einfließen, um der Technologie im Nutzfahrzeug zum Durchbruch zu verhelfen. Als Ergebnis konnte erstmalig ein Abwärmenutzungssystem in Form eines Thermoelektrischen Generators für ein innovatives Erdgasnutzfahrzeug wirtschaftlich ausgelegt werden. Die berechnete Amortisation wurde zumeist in einer Zeit von kleiner als zwei Jahren, unter Annahme der Serienentwicklung des Systems, erzielt. Die Kraftstoffreduktion liegt bei bis zu 2,5 %, das entspricht rund 1 kg/100 km Kraftstoff. Zukünftiges Potential liegt bei weiteren 1,2 Prozentpunkten. Bei einer Hardwarerealisierung wurde am Funktionsmuster über 2,5 kW elektrische Leistung gemessen

Thermoelectric Generators with High Potential for Waste Heat Recovery in Heavy-Duty Vehicle Applications: Validation by a Functional Prototype with up to 2.7 kW

This research study demonstrates the engineering and measurement of a TEG prototype for heavyduty vehicles applications. The thermoelectric module area corresponds to approximately 1370 cm2 and consists of 144 segmented thermoelectric high-power modules based on bismuth telluride and skutterudite. The experimental setup enables the validation of the technology thermoelectric up to technology readiness level 5, which is rare in scientific publications on a 1:1 scale. The measured performance data of a functional prototype will be presented, as well as the electrical output power and compared with the simulated values. As a result, the simulative holistic design method of thermoelectric generators developed at the DLR Institute of Vehicle Concepts is successfully verified. In the measurement points performed, the accuracy of the simulated temperatures reaches in average more than 98%. The accuracy of the simulated output power is in average more than 94% and the minimum deviation is only -0.5%. The maximum electrical output power of 2,700 W could be measured at hot gas inlet temperature of 745 °C, mass flow of 0.25 kg/s, coolant inlet temperature of 20 °C and volume flow of 0.5 dm3/s. A significant improvement in the system level of thermoelectric generators for heavy-duty vehicles could be reached and the power density of the system could be increased to 174 W/kg and 326 W/dm3 compared to the state of the art based on the experimental measured values

Rhythm monitoring, success definition, recurrence, and anticoagulation after atrial fibrillation ablation: results from an EHRA survey

Atrial fibrillation (AF) is a major challenge for the healthcare field. Pulmonary vein isolation is the most effective treatment for the maintenance of sinus rhythm. However, clinical endpoints for the procedure vary significantly among studies. There is no consensus on the definition of recurrence and no clear roadmap on how to deal with recurrences after a failed ablation. The purpose of this study was to perform a survey in order to show how clinicians currently approach this knowledge gap. An online survey, supported by the European Heart Rhythm Association (EHRA) Scientific Initiatives Committee, was conducted between 1 April 2022 and 8 May 2022. An anonymous questionnaire was disseminated via social media and EHRA newsletters, for clinicians to complete. This consisted of 18 multiple-choice questions regarding rhythm monitoring, definitions of a successful ablation, clinical practices after a failed AF ablation, and the continuance of anticoagulation. A total of 107 replies were collected across Europe. Most respondents (82%) perform routine monitoring for AF recurrences after ablation, with 51% of them preferring a long-term monitoring strategy. Cost was reported to have an impact on the choice of monitoring strategy. Self-screening was recommended by most (71%) of the respondents. The combination of absence of symptoms and recorded AF was the definition of success for most (83%) of the respondents. Cessation of anticoagulation after ablation was an option mostly for patients with paroxysmal AF and a low CHA2DS2-VASc score. The majority of physicians perform routine monitoring after AF ablation. For most physicians, the combination of the absence of symptoms and electrocardiographic endpoints defines a successful result after AF ablation