Initial ionization rates in shock-heated Argon, Krypton, and Xenon

The rate of ionization behind strong shock waves in argon, krypton, and xenon, is observed by a transverse microwave probe, over a range of electron densities low enough that atom-atom inelastic collisions are the rate-determining mechanism. Shocks of Mach number 7.0 to 10.0 propagate down a 2-in. sq. aluminum shock tube into ambient gases at pressures of 3.0 to 17.0 mm. Hg., heating them abruptly to atomic temperatures of 5500°K to 9600°K. The subsequent relaxation toward ionization equilibrium is examined in its early stages by the reflection, transmission, and phase shifts of a 24.0 Gc/sec (1.25 cm) transverse microwave beam propagating between two rectangular horns abreast a glass test section. The data yield effective activation energies of 11.9 ± 0.5 eV for argon, 10.4 ± 0.5 eV for krypton, and 8.6 ± 0.5 eV for xenon. These coincide, within experimental error, with the first excitation potentials, rather than the ionization potentials of the gases, indicating that in this range ionization proceeds via a two-step process involving the first excited electronic states of which the excitation step is rate controlling

Response of electrostatic probes to ionized gas flows in a shock tube

In his excellent analysis of electrical measurements in shock tube flows, Hollyer(1) has demonstrated certain pitfalls in the application of conventional Langmuir probe techniques to the evaluation of charge densities in the moving stream of hot gas confined within the tube walls. The purpose of this note is to describe somewhat similar experiments which illustrate other eccentricities in probe behavior under these conditions

Minkowski decompositions for generalized associahedra of acyclic type

We give an explicit subword complex description of the generators of the type cone of the g-vector fan of a finite type cluster algebra with acyclic initial seed. This yields in particular a description of the Newton polytopes of the F-polynomials in terms of subword complexes as conjectured by S. Brodsky and the third author. We then show that the cluster complex is combinatorially isomorphic to the totally positive part of the tropicalization of the cluster variety as conjectured by D. Speyer and L. Williams.Comment: 17 pages. v2: updated and extended examples, added footnote that Theorem 1.4 also follows from [AHL20, Theorems 4.1 & 4.2

Recent advances in MPD thruster research at Princeton

A summary of last years anode, plasma, and cathode findings is presented. A summary of this years activities and findings is also presented. A brief discussion of previous and current understanding is given and covers the following topics: existence of microinstabilities; the scaling of Va with the Hall parameter; the scaling of anomalous resistivity with the Hall parameter; the relation between anomalous resistivity and the anode drop; the presence of turbulence in the anode region; numerical simulation with anomalous transport; the use of magnets to decrease dissipation; performance testing with the new anode; the mechanisms behind the ionization sink; and lithiated cathode research

Microwave Probing of Ionized-Gas Flows

The measurement of free-electron densities and collision frequencies in ionized-gas flows by a probing transverse microwave beam is described. Interpretation of the observed reflection and transmission coefficients and their phases is developed on the basis of an idealized plane wave-plane slab model, for which typical results are displayed. Application of the device and technique to a specific experiment—the buildup of ionization behind a strong shock in argon—is outlined. Effects of various departures of the microwave radiation patterns and flow configurations from the slab assumptions are discussed and examples evaluated

Einsatz eines Niederspannungslängsreglers zur Behebung von Spannungsunsymmetrien hervorgerufen durch Elektromobilität und dezentrale Energieerzeugung

Mit dem steigenden Anteil einphasiger dezentraler Energieerzeuger (Photovoltaiksysteme) und moderner einphasiger Lasten (Elektrofahrzeuge) wächst die Herausforderung für den Netzbetrieb im Niederspannungsnetz. Dabei ist die Spannungsqualität von ländlichen Regionen mit langen Leitungen besonders gefährdet. Spannungsregler wie regelbare Ortsnetztransformatoren oder Spannungslängsregler bieten hier eine praktische Alternative zum Netzausbau. Im Fokus dieser Arbeit stehen die durch einphasige Photovoltaiksysteme und einphasige Elektrofahrzeuge entstehenden Spannungsunsymmetrien im Niederspannungsnetz. Dafür wird zunächst ein realitätsnahes Niederspannungsmodell erstellt, welches die Analyse von Spannungsunsymmetrien ermöglicht. Zudem werden ein regelbarer Ortsnetztransformator, die Ansteuerungslogik eines Spannungslängsreglers und ein Zick-Zack Lastregler modelliert. Anschließend werden mit statischen und dynamischen Worst Case Szenarien die Regler mit geeigneten Kriterien hinsichtlich ihres Regelverhaltens untersucht. Abschließend wird ermittelt, inwiefern die Regler das Integrationspotential weiterer unsymmetrischer Leistungen steigern können

An Experimental Reef Program to Test Designs of an Artificial Reef for Kelp Mitigation

An artificial reef is being planned to mitigate alleged losses of giant kelp and the invertebrate and fish communities associated with a kelp bed. The project\u27s first step was to initiate comprehensive siting and design studies. A 25-yr time series of kelp surface canopy maps for a 100 km reach of coastline was entered into a GIS database and analyzed in conjunction with geotechnical and human-use information to define ecologically favorable and acceptable sites in the general area. A site was chosen near an area that appeared most promising in the primary study area. This study\u27s field work determined that the design of the mitigation reef will not be straightforward and that an experimental phase to test various designs needs to be performed. We recommend that a low relief (0.5-1.5 m) reef with relatively high exposure to sand scour and occasional, partial burial be constructed in order to promote the establishment of kelp. Scattered rock and broken concrete at three different density spreads (17, 34, and 67%) on the bottom will be tested. This study has revealed that existing artificial reefs have not typically sustained a persistent kelp bed. This fact, therefore, makes the Phase I experiment even more critical than originally thought

Stützlehrerinnen und Stützlehrer in der beruflichen Integrationsförderung: Erarbeitung eines Aufgabenprofils auf Basis berufsanalytischer Verfahren

"Im Zentrum des Beitrages stehen die Aufgaben von Lehrkräften für den Stütz- und Förderunterricht (Stützlehrer / -innen), die wesentlich an der Berufsausbildung Benachteiligter beteiligt sind. Die Gruppe der Stützlehrer wurde in wissenschaftlichen Diskursen zum Übergangssystem bislang allenfalls randständig thematisiert, sodass kaum empirische Befunde vorliegen. Insbesondere die Aufgaben der Stützlehrer / -innen – als wichtige Grundlage weiterer Untersuchungen – sind bislang kaum systematisch erfasst und dargestellt. Im Rahmen berufsanalytischer Verfahren wurden die wesentlichen Aufgaben aus der Perspektive der Wissenschaft, der Auftraggeber (Bundesagentur für Arbeit), der Arbeitgeber (Bildungsträger) und der Beschäftigten (Stützlehrer) mittels Dokumentenanalysen und Interviews erfasst. Auf dieser Grundlage wurde ein Aufgabenprofil als Basis weiterer berufsanalytischer Forschungsarbeiten abgeleitet." [Autorenreferat

Prognostic Relevance of the Eighth Edition of TNM Classification for Resected Perihilar Cholangiocarcinoma

Objectives: In our study, we evaluated and compared the prognostic value and performance of the 6th, 7th, and 8th editions of the American Joint Committee on Cancer (AJCC) staging system in patients undergoing surgery for perihilar cholangiocarcinoma (PHC). Methods: Patients undergoing liver surgery with curative intention for PHC between 2002 and 2019 were identified from a prospective database. Histopathological parameters and stage of the PHC were assessed according to the 6th, 7th, and 8th editions of the tumor node metastasis (TNM) classification. The prognostic accuracy between staging systems was compared using the area under the receiver operating characteristic curve (AUC) model. Results: Data for a total of 95 patients undergoing liver resection for PHC were analyzed. The median overall survival time was 21 months (95% CI 8.1–33.9), and the three- and five-year survival rates were 46.1% and 36.2%, respectively. Staging according to the 8th edition vs. the 7th edition resulted in the reclassification of 25 patients (26.3%). The log-rank p-values for the 7th and 8th editions were highly statistically significant (p ≤ 0.01) compared to the 6th edition (p = 0.035). The AJCC 8th edition staging system showed a trend to better discrimination, with an AUC of 0.69 (95% CI: 0.52–0.84) compared to 0.61 (95% CI: 0.51–0.73) for the 7th edition. Multivariate survival analysis revealed male gender, age >65 years, positive resection margins, presence of distant metastases, poorly tumor differentiation, and lymph node involvement, such as no caudate lobe resection, as independent predictors of poor survival (p < 0.05). Conclusions: In the current study, the newly released 8th edition of AJCC staging system showed no significant benefit compared to the previous 7th edition in predicting the prognosis of patients undergoing liver resection for perihilar cholangiocarcinoma. Further research may help to improve the prognostic value of the AJCC staging system for PHC—for instance, by identifying new prognostic markers or staging criteria, which may improve that individual patient’s outcome