Differential correction and preliminary orbit determination for lunar satellite orbits

Differential correction and preliminary orbit calculation for lunar satellite orbit

Conditions du développement de la tourbière de Farnham, Québec

Les analyses polliniques et macrofossiles d'une carotte de sédiments provenant de la marge de la tourbière de Farnham ont permis de retracer cinq étapes dans le développement de la tourbière. L'accumulation des sédiments a débuté au sein d'un marais situé au centre de la dépression à la suite du retrait de la Mer de Champlain vers 8500 ans BP. L'entourbement centrifuge subséquent a atteint le point d'échantillonnage vers 8100 ans BP. À cette époque, un mélèzin (1) a laissé place en quelques décennies à un fen arboré (2) jusque vers 6900 ans BP. Par la suite, un fen au couvert arborescent très ouvert (3) s'est mis en place et des mares se sont constituées à la surface de la tourbière jusque vers 5800 ans BP. L'accumulation de la tourbe a provoqué (4) l'ombrotrophication de la tourbière, ce changement trophique ayant persisté jusqu'à nos jours. L'action des feux et l'activité anthropique ont entraîné récemment (5) l'implantation d'espèces arborescentes de milieux perturbés. L'entourbement et les différentes étapes du développement de la marge de la tourbière ont été déterminés par l'accumulation de la tourbe, l'hydrologie locale, le climat et les feux. La formation des mares à la surface de la tourbière vers 6900 ans BP, à la charnière entre les régimes de fen et de bog, ainsi que l'expansion synchrone de Tsuga canadensis au sein des forêts environnantes, témoignent de conditions climatiques plus humides associées à une hausse des précipitations ou à une baisse de l'évapotranspiration.Pollen and plant macrofossil sequence of a core at the margin of the Farnham bog provide a local developmental record that can be subdivided into five main stages for this part of the peatland. Organic sedimentation began around 8500 year BP in a shallow pound at the centre of the depression following the retreat of the Champlain Sea. Subsequent centrifugal paludification caused the onset of peat accumulation at the sampling point about 8100 year BP. An initial forested fen dominated by larch (1) has been rapidly followed by a treed fen (2) until 6900 year BP. This stage was succeeded by a fen characterized by sparse trees and the development of open-water pools (3) until 5800 year BP. At that time, the vegetation changed to oligotrophic bog (4) until the present. Recently, the influence of external factors such as fire and anthropogenic activity resulted (5) in the establishment of tree species typical of disturbed environments. Paludification and local developmental trends are closely controlled primarily by continuous peat accumulation, local hydrology, climate and fire. The formation of pools around 6900 year BP and the synchronous spread of Tsuga canadensis populations in the surrounding forests suggest an increasing trend towards moister conditions with higher precipitation and/or reduced summer évapotranspiration.Die Analyse von Pollen und Makrofossilen eines Sedimentbohrkerns vom Rand des Torfmoors von Farnham fuhrten zur Aufdeckung von funf Etappen bei der Entwicklung des Torfmoors. Die Ansammlung der Sedimente hat um 8500 v.u.Z mitten in einem Sumpf im Zentrum der Niederung begonnen, nachdem das Meer von Champlain sich zuruckgezogen hatte. Die darauffolgende zentrifugale Vertorfung hat den Ort der Probenahme gegen 8100 Jahre v.u.Z. erreicht. Zu dieser Zeit ist ein von Làrchen beherrschtes Torfmoor (1) in einigen Jahrzehnten einem Baum-Torfmoor (2) gewichen bis gegen 6900 v.u.Z. Danach hat sich ein Torfmoor mit sehr offener baumartiger Bewachsung (3) angesiedelt und bis gegen 5800 v.u.Z. haben sich Tumpel an der Oberflâche des Torfmoores gebildet. Die Anhâufung des Torfs fùhrte zur Nàhrstoffverarmung (4) des Torfmoors, welche bis heute angehalten hat. Die Einwirkung von Brânden und menschlicher Aktivitât haben in heutiger Zeit (5) zur Ansiedlung von Baumarten gefuhrt, die fur gestôrte Milieus typisch sind. Die Vertorfung und die verschiedenen Entwicklungsetappen des Torfmoorrands waren durch die Torfanhàufung, den lokalen Wasserhaushalt, das Klima und die Brànde bestimmt. Die Bildung der Tùmpel an der Oberflâche des Torfmoors gegen 6900 v.u.Z., an der Umbiegung zwischen dem Torfmoor- und dem Sumpf-System, sowie die gleichzeitige Ausdehnung von Tsuga canadiensis in den umliegenden Wâldern bezeugen feuchtere klimatische Bedingungen in Verbindung mit einer Zunahme der Niederschlàge oder einer Abnahme der Verdunstung

Phase formation and thermal stability of ultrathin nickel-silicides on Si(100)

The solid-state reaction and agglomeration of thin nickel-silicide films was investigated from sputter deposited nickel films (1-10 nm) on silicon-on-insulator (100) substrates. For typical anneals at a ramp rate of 3 degrees C/s, 5-10 nm Ni films react with silicon and form NiSi, which agglomerates at 550-650 degrees C, whereas films with a thickness of 3.7 nm of less were found to form an epitaxylike nickel-silicide layer. The resulting films show an increased thermal stability with a low electrical resistivity up to 800 degrees C

Fluorescence-detected Fourier transform electronic spectroscopy by phase-tagged photon counting

Fluorescence-detected Fourier transform (FT) spectroscopy is a technique in which the relative paths of an optical interferometer are controlled to excite a material sample, and the ensuing fluorescence is detected as a function of the interferometer path delay and relative phase. A common approach to enhance the signal-to-noise ratio in these experiments is to apply a continuous phase sweep to the relative optical path, and to detect the resulting modulated fluorescence using a phase-sensitive lock-in amplifier. In many important situations, the fluorescence signal is too weak to be measured using a lock-in amplifier, so that photon counting techniques are preferred. Here we introduce an approach to low-signal fluorescence-detected FT spectroscopy, in which individual photon counts are assigned to a modulated interferometer phase ('phase-tagged photon counting,' or PTPC), and the resulting data are processed to construct optical spectra. We studied the fluorescence signals of a molecular sample excited resonantly by a pulsed coherent laser over a range of photon flux and visibility levels. We compare the performance of PTPC to standard lock-in detection methods and establish the range of signal parameters over which meaningful measurements can be carried out. We find that PTPC generally outperforms the lock-in detection method, with the dominant source of measurement uncertainty being associated with the statistics of the finite number of samples of the photon detection rate.Comment: 32 pages, 8 figure

Broadband quadrature-squeezed vacuum and nonclassical photon number correlations from a nanophotonic device

We report the first demonstrations of both quadrature squeezed vacuum and photon number difference squeezing generated in an integrated nanophotonic device. Squeezed light is generated via strongly driven spontaneous four-wave mixing below threshold in silicon nitride microring resonators. The generated light is characterized with both homodyne detection and direct measurements of photon statistics using photon number-resolving transition edge sensors. We measure $1.0(1)$~dB of broadband quadrature squeezing (${\sim}4$~dB inferred on-chip) and $1.5(3)$~dB of photon number difference squeezing (${\sim}7$~dB inferred on-chip). Nearly-single temporal mode operation is achieved, with raw unheralded second-order correlations $g^{(2)}$ as high as $1.87(1)$ measured (${\sim}1.9$~when corrected for noise). Multi-photon events of over 10 photons are directly detected with rates exceeding any previous quantum optical demonstration using integrated nanophotonics. These results will have an enabling impact on scaling continuous variable quantum technology.Comment: Significant improvements and updates to photon number squeezing results and discussions, including results on single temporal mode operatio

Separation between coherent and turbulent fluctuations. What can we learn from the Empirical Mode Decomposition?

The performances of a new data processing technique, namely the Empirical Mode Decomposition, are evaluated on a fully developed turbulent velocity signal perturbed by a numerical forcing which mimics a long-period flapping. First, we introduce a "resemblance" criterion to discriminate between the polluted and the unpolluted modes extracted from the perturbed velocity signal by means of the Empirical Mode Decomposition algorithm. A rejection procedure, playing, somehow, the role of a high-pass filter, is then designed in order to infer the original velocity signal from the perturbed one. The quality of this recovering procedure is extensively evaluated in the case of a "mono-component" perturbation (sine wave) by varying both the amplitude and the frequency of the perturbation. An excellent agreement between the recovered and the reference velocity signals is found, even though some discrepancies are observed when the perturbation frequency overlaps the frequency range corresponding to the energy-containing eddies as emphasized by both the energy spectrum and the structure functions. Finally, our recovering procedure is successfully performed on a time-dependent perturbation (linear chirp) covering a broad range of frequencies.Comment: 23 pages, 13 figures, submitted to Experiments in Fluid