Readout and Control of a Power-recycled Interferometric Gravitational-wave Antenna

Interferometric gravitational wave antennas are based on Michelson interferometers whose sensitivity to small differential length changes has been enhanced by adding multiple coupled optical resonators. The use of optical cavities is essential for reaching the required sensitivity, but sets challenges for the control system which must maintain the cavities near resonance. The goal for the strain sensitivity of the Laser Interferometer Gravitational-wave Observatory (LIGO) is 10^-21 rms, integrated over a 100 Hz bandwidth centered at 150 Hz. We present the major design features of the LIGO length and frequency sensing and control system which will hold the differential length to within 5 10^-14 m of the operating point. We also highlight the restrictions imposed by couplings of noise into the gravitational wave readout signal and the required immunity against them.Comment: Presentation at ICALEPCS 2001, San Jose, November 2001, (WECT003), 3 page

Magnetocardiography with a modular spin-exchange relaxation free atomic magnetometer array

We present a portable four-channel atomic magnetometer array operating in the spin exchange relaxation-free regime. The magnetometer array has several design features intended to maximize its suitability for biomagnetic measurement, specifically foetal magnetocardiography, such as a compact modular design, and fibre coupled lasers. The modular design allows the independent positioning and orientation of each magnetometer, in principle allowing for non-planar array geometries. Using this array in a magnetically shielded room, we acquire adult magnetocadiograms. These measurements were taken with a 6-11 fT Hz^(-1/2) single-channel baseline sensitivity that is consistent with the independently measured noise level of the magnetically shielded room.Comment: 15 pages, 5 figure

Klassifizierung von Siedlungsschichten an Sedimenten aus Bohrungen in archäologischen Denkmälern am Beispiel der wikingerzeitlichen Siedlung Haithabu

Ablagerungen in ehemaligen Siedlungen sind ein wichtiges Archiv zur Rekonstruktion von Mensch-Landschafts-Interaktionen. Bedeutende archäologische Befunde sind oft Denkmäler, die vor starken Eingriffen rechtlich geschützt sind. Haithabu, als ein wikingerzeitliches Handelszentrum und eine der ersten urbanen Siedlungen Nordeuropas, steht unter archäologischem Denkmalschutz. Daher werden Felduntersuchungen hier auf minimal-invasive Methoden, wie Bohrungen, eingeschränkt. Aus Bohrungen resultieren jedoch nur Punktinformationen, die eine Klassifizierung von Siedlungsschichten und das Verständnis ihrer räumlichen Zusammenhänge erschweren. Um die lokale Landschaftsentwicklung Haithabus zu untersuchen, wurden mehrere Hundert Bohrungen durchgeführt. Die Bohrkerne enthielten häufig Schichten, die morphologisch nicht eindeutig zu anthropogenen oder natürlichen Sedimenten zugeordnet werden konnten. Um solche Sedimente zu klassifizieren, wurde das Material von 8 Bohrkernen geochemisch untersucht. Die Parameter magnetische Suszeptibilität, Gehalt an organischer Substanz, Anteil an Steinen, Knochen, Artefakten und Holzresten wurden für statistische Analysen ausgewählt und dienten als Basis für die Klassifikation. Zur Bestimmung der Faktoren der Datenvarianz wurde eine Hauptkomponentenanalyse verwendet. Drei Hauptkomponenten, die 75,6 % der Varianz erklärten und ein Eigenwert > 1 hatten, wurden für die hierarchische Clusteranalyse benutzt. Die Clusteranalyse hat 15 Cluster ergeben, die signifikante Unterschiede in mindestens einem Parameter haben. Auf Basis dieser Ergebnisse wurden drei Sedimenttypen ermittelt, die insgesamt 12 Sedimentklassen aufweisen. Der erste Sedimenttyp enthält begrabene Bodenhorizonte und natürliche Ablagerungen, unter denen sich feines und grobes mineralisches Material sowie Torf befinden. Der zweite Sedimenttyp besitzt Übergangseigenschaften mit geringen Mengen an Holzresten und Knochen. Der dritte Typ besteht aus Schichten verschiedener Textur und variierenden Inhalts an organischem Material, die durch hohe Werte anthropogener Indikatoren (Artefakte und magnetische Suszeptibilität) gekennzeichnet sind. Sedimenttypen 2 und 3 enthalten sowohl Kolluvien als auch in situ Siedlungsschichten. Dieser Ansatz hat es ermöglicht, heterogene Ablagerungen Haithabus basierend auf objektiven und einfach messbaren Parametern zu klassifizieren. Er kann für geoarchäologische Forschungen in Siedlungen mit begrenztem Zugang durch Ausgrabungen angewandt werden

Management of upper airway edema caused by hereditary angioedema

Hereditary angioedema is a rare disorder with a genetic background involving mutations in the genes encoding C1-INH and of factor XII. Its etiology is unknown in a proportion of cases. Recurrent edema formation may involve the subcutis and the submucosa - the latter can produce obstruction in the upper airways and thereby lead to life-threatening asphyxia. This is the reason for the high, 30-to 50-per-cent mortality of undiagnosed or improperly managed cases. Airway obstruction can be prevented through early diagnosis, meaningful patient information, timely recognition of initial symptoms, state-of-the-art emergency therapy, and close monitoring of the patient. Prophylaxis can substantially mitigate the risk of upper airway edema and also improve the patients' quality of life. Notwithstanding the foregoing, any form of upper airway edema should be regarded as a potentially life-threatening condition. None of the currently available prophylactic modalities is capable of preventing UAE with absolute certainty

Seismic isolation and suspension systems for Advanced LIGO

To meet the overall isolation and alignment requirements for the optics in Advanced LIGO, the planned upgrade to LIGO, the US laser interferometric gravitational wave observatory, we are developing three sub-systems: a hydraulic external pre-isolator for low frequency alignment and control, a two-stage active isolation platform designed to give a factor of ~1000 attenuation at 10 Hz, and a multiple pendulum suspension system that provides passive isolation above a few hertz. The hydraulic stage uses laminar-flow quiet hydraulic actuators with millimeter range, and provides isolation and alignment for the optics payload below 10 Hz, including correction for measured Earth tides and the microseism. This stage supports the in-vacuum two-stage active isolation platform, which reduces vibration using force feedback from inertial sensor signals in six degrees of freedom. The platform provides a quiet, controlled structure to mount the suspension system. This latter system has been developed from the triple pendulum suspension used in GEO 600, the German/UK gravitational wave detector. To meet the more stringent noise levels required in Advanced LIGO, the baseline design for the most sensitive optics calls for a quadruple pendulum, whose final stage consists of a 40 kg sapphire mirror suspended on fused silica ribbons to reduce suspension thermal noise

Proton capture cross section of Sr isotopes and their importance for nucleosynthesis of proton-rich nuclides

The (p,$\gamma$) cross sections of three stable Sr isotopes have been measured in the astrophysically relevant energy range. These reactions are important for the $p$-process in stellar nucleosynthesis and, in addition, the reaction cross sections in the mass region up to 100 are also of importance concerning the $rp$-process associated with explosive hydrogen and helium burning. It is speculated that this $rp$-process could be responsible for a certain amount of $p$-nuclei in this mass region. The (p,$\gamma$) cross sections of $^{84,86,87}$Sr isotopes were determined using an activation technique. The measurements were carried out at the 5 MV Van de Graaff accelerator of the ATOMKI, Debrecen. The resulting cross sections are compared with the predictions of statistical model calculations. The predictions are in good agreement with the experimental results for $^{84}$Sr(p,$\gamma$)$^{85}$Y whereas the other two reactions exhibit differences that increase with mass number. The corresponding astrophysical reaction rates have also been computed.Comment: Phys. Rev. C in pres