A highly stable UV clock laser

Optical clocks are the most precise frequency measurement devices, with a systematic fractional frequency uncertainty as low as 10−18. While these clocks are typically operated in stationary laboratories, there is a growing interest in implementing transportable optical clocks. As part of this thesis, a transportable 40Ca+/27Al+ quantum logic clock is being developed. For spectroscopy of the 27Al+ clock transition from 1S0 to 3P0, a highly stable UV laser system is required. This thesis focuses on the evaluation of a transportable and highly frequency stable UV laser system built for the 40Ca+/27Al+ clock. The laser system includes a highly frequency stable cavity designed for stabilizing the seed laser frequency and a system for quadrupling the laser frequency without introducing phase disturbances. The cavity consists of a Fabry-P´erot resonator, consisting of a 20 cm long spacer made from ultra-low expansion glass (ULE) with Al0.92Ga0.08As/GaAs mirror coatings on fused silica substrates, optically bonded to the spacer. The calculated thermal noise floor limit is approximately 7-8 × 10−16. The laser is locked to the resonance frequency of the cavity using the Pound Drever- Hall locking technique. A residual amplitude modulation (RAM) stabilization scheme is employed, and the fractional frequency instability limit due to RAM is evaluated. Optical properties such as finesse, linewidth, and birefringence line splitting of the cavity are measured. Additionally, the main sources of relative length change in the cavity are assessed, including vibration noise, photo-thermal noise, and photo-birefringence noise. These noise sources, including RAM, are found to be at or below the thermal noise limit. The cavity is temperature-stabilized using two passive and one active heat shield and is further isolated against temperature fluctuations. The remaining length changes of the cavity due to thermal expansion of the cavity spacer and thermal stress inside the heat shields is evaluated to be dominant over longer timescales. The frequency stability of the cavity is measured by phase comparison with a more stable reference cavity using an optical frequency comb. A fractional frequency instability, represented by the modified Allen deviation, of 2 × 10−16 is achieved. The seed laser frequency is quadrupled using a transportable and compact setup consisting of two single-pass second harmonic generation stages. The single-pass configuration enables phase stabilization of the seed light and UV light throughout the entire setup. The performance of the system is evaluated, demonstrating negligible phase distribution and sufficient UV output power for operating an optical 27Al+ clock. Furthermore, the current status of transportable 40Ca+/27Al+ ion clock is presented, including the physics package with the ion trap in a vacuum chamber, magnets and coils for magnetic field generation, optical paths for ion integration, and the imaging system all mounted on a breadboard

The Opportunities and Threats of Turning Airports into Hubs

This paper examines the opportunities and threats which arise when turning origin/destination airports into hubs. The analysis focuses on market development trends, competitive structures, especially in the light of airline network strategies and the growing rivalry between airports, and finally the potential financial impacts for the airport, including both investment efforts and the financial results from hub operations. We argue that in most cases a decision against converting a traditional origin/destination airport into a major transfer point is preferable to the transformation into a hub

Eine digital unterstützte Methodik zur sensorischen Nutzung von Konstruktionselementen

Diese Arbeit dreht sich um die Entwicklung einer Methodik zur sensorischen Nutzung von Konstruktionselementen sowie um die Digitalisierung der Werkzeuge, welche in der Methodik zum Einsatz kommen. Die Arbeit bewegt sich somit in den Themenfeldern der Sensorik, der methodischen Produktentwicklung, der Digitalisierung von Methoden und der damit verbundenen Softwareentwicklung. Zur Umsetzung des Ziels, die sensorische Nutzung von Konstruktionselementen methodisch sowohl effektiv als auch effizient zu unterstützen, kommt nach der Vorstellung des Stands der Forschung die Forschungsmethode Action Research zum Einsatz. Deren iterativer Aufbau führt zu den drei großen Handlungsblöcken dieser Arbeit. Im ersten Teil wird eine Methodik zur sensorischen Nutzung von Konstruktionselementen induktiv entwickelt. Hierzu wird die Konzeptphase des allgemeinen Entwicklungsmodells der Produktentwicklung gezielt auf die Nutzung für sensorisch nutzbare Komponenten angepasst, indem die Analyse und Konzeptentwicklung gezielt durch dafür geeignete Werkzeuge unterstützt wird. Die Beurteilung der Konzepte erfolgt durch eine Auswahl und Bewertung der Konzepte. Die Bewertung wird dabei gezielt durch ein allgemeines Zielsystem, welches Kriterien zur Berechnung der technischen Wertigkeit umfasst, unterstützt. Die Analyse der Methodik führt zum zweiten und größten Handlungsblock, der Entwicklung einer graphenbasierten Datenbank physikalischer Effekte. Dieser Effektgraph wird durch eine zugehörige Software unterstützt, welche es ermöglicht, aus der Datenbank Effektketten zu bilden und mit Hilfe dieser die methodische Entwicklung sensorisch nutzbarer Konstruktionselemente zu unterstützen. Die Kombination aus Datenbank und Software ermöglicht es, die für die Methodik wichtigen Kriterien zügig auszugeben. Für das Kriterium des Störgrößeneinflusses wird eigens ein Algorithmus aufgebaut, welcher die bisherige methodische Bewertung des Störgrößeneinflusses komplett automatisiert. Im dritten Handlungsblock wird dazu passend eine digitale Beschreibungsform für technische Systeme entwickelt, welche es ermöglicht, mit dieser Effektketten gezielt zu filtern. Hierzu erlaubt die Beschreibungsform die Darstellung sowohl von Komponenten als auch von Interaktionen in technischen Systemen. Am Ende jedes Handlungsblocks erfolgt eine Reflexion des Vorgehens und die Evaluation der Ergebnisse. Aus dieser lässt sich der weitere Handlungsbedarf für den nächsten Block ableiten. Als finale Evaluation aller Arbeitsergebnisse wird eine Studie mit ProbandInnen aus dem industriellen Umfeld durchgeführt. In dieser zeigt sich, dass der Einsatz der Methodik signifikant stark zur Verbesserung der Konzeptentwicklung für sensorisch nutzbare Komponenten beiträgt. Die Arbeit schließt mit einem Fazit zum Erfüllungsgrad der gesetzten Ziele und Forschungsfragen sowie einem Ausblick auf künftige Forschungspotentiale

Vaccination directed against the human endogenous retrovirus-K envelope protein inhibits tumor growth in a murine model system

Human endogenous retrovirus (HERV) genomes are chromosomally integrated in all cells of an individual. They are normally transcriptionally silenced and transmitted only vertically. Enhanced expression of HERV-K accompanied by the emergence of anti-HERV-K-directed immune responses has been observed in tumor patients and HIV-infected individuals. As HERV-K is usually not expressed and immunological tolerance development is unlikely, it is an appropriate target for the development of immunotherapies. We generated a recombinant vaccinia virus (MVA-HKenv) expressing the HERV-K envelope glycoprotein (ENV), based on the modified vaccinia virus Ankara (MVA), and established an animal model to test its vaccination efficacy. Murine renal carcinoma cells (Renca) were genetically altered to express E. coli beta-galactosidase (RLZ cells) or the HERV-K ENV gene (RLZ-HKenv cells). Intravenous injection of RLZ-HKenv cells into syngenic BALB/c mice led to the formation of pulmonary metastases, which were detectable by X-gal staining. A single vaccination of tumor-bearing mice with MVA-HKenv drastically reduced the number of pulmonary RLZ-HKenv tumor nodules compared to vaccination with wild-type MVA. Prophylactic vaccination of mice with MVA-HKenv precluded the formation of RLZ-HKenv tumor nodules, whereas wild-type MVA-vaccinated animals succumbed to metastasis. Protection from tumor formation correlated with enhanced HERV-K ENV-specific killing activity of splenocytes. These data demonstrate for the first time that HERV-K ENV is a useful target for vaccine development and might offer new treatment opportunities for diverse types of cancer

Multistatic SAR Imaging: First Results of a Four Phase Center Experiment with TerraSAR-X and TanDEM-X

Multichannel synthetic aperture radar (SAR) imaging offers the possibility to overcome the pulse repetition frequency (PRF) constraints inherent to single-channel SAR systems. The multichannel approach enables the acquisition of wide swathes with high azimuth resolution. Using a constellation or swarm of small satellites, a cost efficient, faulttolerant system can be envisaged. This paper describes the first results of a multistatic four phase center experiment conducted with TerraSAR-X and TanDEM-X. The experiment is intended to increase the know-how and demonstrate the capabilities for the design of future SAR systems. Key challenges are addressed, the experimental acquisition is described and an evaluation approach is presented. Finally, first results focusing on the azimuth ambiguity performance are shown

Robust A*-Search Image Segmentation Algorithm for Mine-like Objects Segmentation in SONAR Images

This paper addresses a sonar image segmentation method employing a Robust A*-Search Image Segmentation (RASIS) algorithm. RASIS is applied on Mine-Like Objects (MLO) in sonar images, where an object is defined by highlight and shadow regions, i.e. regions of high and low pixel intensities in a side-scan sonar image. RASIS uses a modified A*-Search method, which is usually used in mobile robotics for finding the shortest path where the environment map is predefined, and the start/goal locations are known. RASIS algorithm represents the image segmentation problem as a path-finding problem. Main modification concerning the original A*-Search is in the cost function that takes pixel intensities and contour curvature in order to navigate the 2D segmentation contour. The proposed method is implemented in Matlab and tested on real MLO images. MLO image dataset consist of 70 MLO images with manta mine present, and 70 MLO images with cylinder mine present. Segmentation success rate is obtained by comparing the ground truth data given by the human technician who is detecting MLOs. Measured overall success rate (highlight and shadow regions) is 91% for manta mines and 81% for cylinder mines

Characterization of the human endogenous retrovirus K Gag protein: identification of protease cleavage sites

<p>Abstract</p> <p>Background</p> <p>Viral genomes of the human endogenous retrovirus K (HERV-K) family are integrated into the human chromosome and are transmitted vertically as Mendelian genes. Although viral particles are released by some transformed cells, they have never been shown to be infectious. In general, gammaretroviruses are produced as immature viral particles by accumulation of the Gag polyproteins at the plasma membrane, which subsequently bud from the cell surface. After release from the cell, Gag is further processed by proteolytic cleavage by the viral protease (PR), which results in morphologically mature particles with condensed cores. The HERV-K Gag polyprotein processing and function has not yet been precisely determined.</p> <p>Results</p> <p>We generated a recombinant poxvirus, encoding the human endogenous retrovirus K consensus gag-pro-pol genes (MVA-HERV-K_con) and obtained high levels of HERV-K Gag expression. The resulting retroviral particle assembled at the plasma membrane, as is typical for gammaretroviruses; and immature as well as mature retrovirus-like particles (VLPs) were observed around the infected cells. VLPs were purified, concentrated and separated by two-dimensional gel electrophoresis. The HERV-K Gag fragments were identified by mass spectroscopy and N-terminal sequencing which revealed that HERV-K Gag is processed into MA, a short spacer peptide, p15, CA and NC.</p> <p>Conclusion</p> <p>The cleavage sites of HERV-K Gag were mapped and found to be highly conserved among HERV-K genomes. The consensus HERV-K gag gene used in this study is known to support viral, infectivity <abbrgrp><abbr bid="B1">1</abbr></abbrgrp>, and thus the cleavage sites that were mapped in this study for all the Gag components are relevant for HERV-K infectivity.</p

Orbital Parameter Determination for Wide Stellar Binary Systems in the Age of Gaia

The orbits of binary stars and planets, particularly eccentricities and inclinations, encode the angular momentum within these systems. Within stellar multiple systems, the magnitude and (mis)alignment of angular momentum vectors among stars, disks, and planets probes the complex dynamical processes guiding their formation and evolution. The accuracy of the \textit{Gaia} catalog can be exploited to enable comparison of binary orbits with known planet or disk inclinations without costly long-term astrometric campaigns. We show that \textit{Gaia} astrometry can place meaningful limits on orbital elements in cases with reliable astrometry, and discuss metrics for assessing the reliability of \textit{Gaia} DR2 solutions for orbit fitting. We demonstrate our method by determining orbital elements for three systems (DS Tuc AB, GK/GI Tau, and Kepler-25/KOI-1803) using \textit{Gaia} astrometry alone. We show that DS Tuc AB's orbit is nearly aligned with the orbit of DS Tuc Ab, GK/GI Tau's orbit might be misaligned with their respective protoplanetary disks, and the Kepler-25/KOI-1803 orbit is not aligned with either component's transiting planetary system. We also demonstrate cases where \textit{Gaia} astrometry alone fails to provide useful constraints on orbital elements. To enable broader application of this technique, we introduce the python tool \texttt{lofti\_gaiaDR2} to allow users to easily determine orbital element posteriors.Comment: 18 pages, 10 figures, accepted for publication in Ap

Quantum data processing and error correction

This paper investigates properties of noisy quantum information channels. We define a new quantity called {\em coherent information} which measures the amount of quantum information conveyed in the noisy channel. This quantity can never be increased by quantum information processing, and it yields a simple necessary and sufficient condition for the existence of perfect quantum error correction.Comment: LaTeX, 20 page