Separation of atomic and molecular ions by ion mobility with an RF carpet

Gas-filled stopping cells are used at accelerator laboratories for the thermalization of high-energy radioactive ion beams. Common challenges of many stopping cells are a high molecular background of extracted ions and limitations of extraction efficiency due to space-charge effects. At the FRS Ion Catcher at GSI, a new technique for removal of ionized molecules prior to their extraction out of the stopping cell has been developed. This technique utilizes the RF carpet for the separation of atomic ions from molecular contaminant ions through their difference in ion mobility. Results from the successful implementation and test during an experiment with a 600~MeV/u $^{124}$Xe primary beam are presented. Suppression of molecular contaminants by three orders of magnitude has been demonstrated. Essentially background-free measurement conditions with less than $1~\%$ of background events within a mass-to-charge range of 25 u/e have been achieved. The technique can also be used to reduce the space-charge effects at the extraction nozzle and in the downstream beamline, thus ensuring high efficiency of ion transport and highly-accurate measurements under space-charge-free conditions.Comment: 8 pages, 4 figure

When simulated environments make the difference: the effectiveness of different types of training of car service procedures

An empirical analysis was performed to compare the effectiveness of different approaches to training a set of procedural skills to a sample of novice trainees. Sixty-five participants were randomly assigned to one of the following three training groups: (1) learning-by-doing in a 3D desktop virtual environment, (2) learning-by-observing a video (show-and-tell) explanation of the procedures, and (3) trial-and-error. In each group, participants were trained on two car service procedures. Participants were recalled to perform a procedure either 2 or 4 weeks after the training. The results showed that: (1) participants trained through the virtual approach of learning-by-doing performed both procedures significantly better (i.e. p < .05 in terms of errors and time) than people of non-virtual groups, (2) the virtual training group, after a period of non-use, were more effective than non-virtual training (i.e. p < .05) in their ability to recover their skills, (3) after a (simulated) long period from the training—i.e. up to 12 weeks—people who experienced 3D environments consistently performed better than people who received other kinds of training. The results also suggested that independently from the training group, trainees’ visuospatial abilities were a predictor of performance, at least for the complex service procedure, adj R2 = .460, and that post-training performances of people trained through virtual learning-by-doing are not affected by learning styles. Finally, a strong relationship (p < .001, R2 = .441) was identified between usability and trust in the use of the virtual training tool—i.e. the more the system was perceived as usable, the more it was perceived as trustable to acquire the competences

Further Development and Application of a Mobile Multiple-Reflection Time-of-Flight Mass Spectrometer for Analytical High-Resolution Tandem Mass Spectrometry

In this work, a mobile multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS) for analytical mass spectrometry was enhanced in many important aspects. Technical as well as software-based improvements have been added to the instrument, thus greatly increasing its performance and applicability. Changes have been applied to the whole beam preparation system of the MR-TOF-MS. In this context, the electronic setup was completely overhauled and a quadrupole mass filter was commissioned. Collision-induced dissociation and a new trigger system have been implemented, enabling the possibility to perform sophisticated tandem mass measurements. Additional modifications have been done to the ion-optics and detector system of the time-of-flight analyzer to improve the instrument´s resolving power and sensitivity. An average mass accuracy of 0.3 ppm was achieved in measurements with several isotopes of the molecules hexamethoxyphosphazene and caffeine. With a flight time of about 6 ms, mass resolving powers of 200,000 could be obtained. The amino acid arginine was utilized to probe the instrument´s linear dynamic range, which was found to cover 5 orders of magnitude in analyte concentration. Space charge effects in the analyzer were extensively investigated. Corresponding simulations and measurements are in excellent agreement with each other. Several approaches such as the change of the position of intermediate time-focus and the use of high extraction field strengths seem to be very promising solutions and will be able to reduce space charge effects in future measurements. It was shown that the method of mass-selective re-trapping is ideally suited to perform tandem mass measurements with high-resolution mass separation in every stage of the measurement. Resolving powers as well as efficiencies of re-trapping were studied in detail and separation powers of up to 70,000 have been obtained. Measurements with the two amino acids glutamine and lysine (mass difference of 36.4 mu) were conducted to illustrate the MS/MS and MSn capabilities of the instrument. Additionally, a crude oil sample has been analyzed in a first proof-of-principle application. There, a specific compound could be successfully isolated from its isobaric contaminants and the corresponding fragment spectrum has been recorded.Im Rahmen dieser Arbeit wurde ein mobiles Multireflexions-Flugzeitmassenspektrometer (MR-TOF-MS) für analytische Massenspektrometrie in vielen wichtigen Aspekten weiterentwickelt. Es wurden technische als auch software-basierte Verbesserungen vorgenommen, welche die Leistungsfähigkeit und den Anwendungsbereich des Massenspektrometers stark erweitern. Es wurden Änderungen am gesamten Strahlvorbereitungs-System des MR-TOF-MS durchgeführt. Der elektronische Aufbau wurde in diesem Zusammenhang komplett überarbeitet und ein Quadrupol-Massenfilter in Betrieb genommen. Sowohl stoßinduzierte Dissoziation als auch ein neues Zeitablauf-System wurden implementiert, wodurch anspruchsvolle Messungen im Bereich der Tandem-Massenspektrometrie ermöglicht werden. Weiterhin wurden Modifikationen am ionenoptischen System und am Detektor des Analysators durchgeführt, um das Auflösungsvermögen und die Empfindlichkeit des Instruments zu erhöhen. In Messungen mit verschiedenen Isotopen von Coffein und Hexamethoxyphosphazen wurde eine durchschnittliche Massengenauigkeit von 0,3 ppm erzielt. Mit einer Flugzeit von etwa 6 ms konnte ein Massenauflösungsvermögen von 200.000 erreicht werden. Die Aminosäure Arginin wurde zur Bestimmung des Dynamikbereichs des Instruments verwendet, welcher insgesamt 5 Größenordnungen an Analyt-Konzentration umfasst. Ferner wurden umfangreiche Untersuchungen zu Raumladungseffekten im Analysator durchgeführt. Entsprechende Simulationen und Messungen stimmen in hervorragender Weise überein. Verschiedene Lösungsansätze, wie das Ändern der Position des intermediären Zeit-Fokus oder das Verwenden höherer Extraktions-Feldstärken, sind sehr vielversprechend und können Raumladungseffekte in zukünftigen Messungen reduzieren. Es wurde gezeigt, dass sich der massenselektive Wiedereinfang ("Re-Trapping") ideal zur Durchführung hochauflösender Massenmessungen in jeder Stufe der Massenseparation eignet. Auflösungsvermögen und Effizienzen dieser Methode wurden im Detail untersucht und Separationsvermögen von bis zu 70.000 gemessen. Um das MS/MS und MSn Potential des Instruments zu illustrieren, wurden Messungen mit den Aminosäuren Glutamin und Lysin (Massendifferenz von 36.4 mu) durchgeführt. Desweiteren wurde eine Rohöl-Probe in einer ersten Machbarkeitsmessung analysiert. In dieser wurde eine spezielle Verbindung von ihren isobaren Kontaminanten isoliert und das dazugehörige Fragmentspektrum aufgezeichnet

An analysis of the ships parts control center inventory model and a possible alternative model.

All original copies missing. Best digital copy available.The inventory model implemented is a sophisticated, stationary, continuous-review, constrained reorder-level, reorder-quantity model. In accordance with DOD Instruction 4140.39, the goal of this model is to minimize the total of variable inventory order and holding costs subject to a constraint on time-weighted, essentiality-weighted requisitions short. SPCC attempts to accomplish this goal by using various probability distributions to estimate demand during leadtime. The purpose of this thesis is to examine this existing model, to discuss the validity of its underlying assumptions when applied to a military supply system, to offer a possible alternative model using distribution free assumptions, and finally to evaluate the models.http://archive.org/details/annalysisofships1094541050U.S. Navy (USN) authorApproved for public release; distribution is unlimited