The millimeter-wave properties of superconducting microstrip lines

We have developed a novel technique for making high quality measurements of the millimeter-wave properties of superconducting thin-film microstrip transmission lines. Our experimental technique currently covers the 75-100 GHz band. The method is based on standing wave resonances in an open ended transmission line. We obtain information on the phase velocity and loss of the microstrip. Our data for Nb/SiO/Nb lines, taken at 4.2 K and 1.6 K, can be explained by a single set of physical parameters. Our preliminary conclusion is that the loss is dominated by the SiO dielectric, with a temperature-independent loss tangent of 5.3 ± 0.5 x 10^(-3) for our samples

Sub micron area Nb/AlO(x)/Nb tunnel junctions for submillimeter mixer applications

In this paper, we report on a fabrication process developed for submicron area tunnel junctions. We have fabricated Nb/AlO(x)/Nb tunnel junctions with areas down to 0.1 sq micron using these techniques. The devices have shown excellent performance in receiver systems up to 500 GHz and are currently in use in radio astronomy observatories at 115, 230, and 500 GHz

Human fur gene encodes a yeast KEX2-like endoprotease that cleaves pro-beta-NGF in vivo.

Extracts from BSC-40 cells infected with vaccinia recombinants expressing either the yeast KEX2 prohormone endoprotease or a human structural homologue (fur gene product) contained an elevated level of a membrane-associated endoproteolytic activity that could cleave at pairs of basic amino acids (-LysArg- and -ArgArg-). The fur-directed activity (furin) shared many properties with Kex2p including activity at pH 7.3 and a requirement for calcium. By using antifurin antibodies, immunoblot analysis detected two furin translation products (90 and 96 kD), while immunofluorescence indicated localization to the Golgi apparatus. Coexpression of either Kex2p or furin with the mouse beta-nerve growth factor precursor (pro-beta-NGF) resulted in greatly enhanced conversion of the precursor to mature nerve growth factor. Thus, the sequence homology shared by furin and the yeast KEX2 prohormone processing enzyme is reflected by significant functional homology both in vitro and in vivo

Position and energy-resolved particle detection using phonon-mediated microwave kinetic inductance detectors

We demonstrate position and energy-resolved phonon-mediated detection of particle interactions in a silicon substrate instrumented with an array of microwave kinetic inductance detectors (MKIDs). The relative magnitude and delay of the signal received in each sensor allow the location of the interaction to be determined with ≲ 1mm resolution at 30 keV. Using this position information, variations in the detector response with position can be removed, and an energy resolution of σ_E = 0.55 keV at 30 keV was measured. Since MKIDs can be fabricated from a single deposited film and are naturally multiplexed in the frequency domain, this technology can be extended to provide highly pixelized athermal phonon sensors for ∼1 kg scale detector elements. Such high-resolution, massive particle detectors would be applicable to rare-event searches such as the direct detection of dark matter, neutrinoless double-beta decay, or coherent neutrino-nucleus scattering

Evolution de la ressource en eau dans la vallée du Merguellil (Tunisie centrale)

International audienceLa plaine de Kairouan (Tunisie centrale) se trouve au débouché des trois grandes vallées du Zéroud, du Merguellil et du Nebhana. Dans ce contexte semi-aride (pluies moyennes entre 200 et 400 mm.an−1), l'intensification de l'irrigation au cours des dernières décennies a suscité une forte croissance de la demande en eau. En même temps, différents aménagements affectent l'ensemble du fonctionnement hydrologique : multiples ouvrages de conservation des eaux et des sols, petits et moyens, d'une part, grands barrages de protection contre les crues sur les trois oueds majeurs d'autre part. La distribution de l'eau B la surface du bassin-versant et dans le sous-sol a donc considérablement évolué et change encore. Dans la plaine du Merguellil, à l'aval du barrage el Haouareb, la nappe alluviale quaternaire est devenue la seule ressource en eau disponible. Elle est actuellement exploitée sans réel contrôle, ce qui conduit à une baisse sensible de son niveau (de 0,25 à 1 m par an). Elle n'est plus alimentée comme en régime naturel par les crues de l'oued, désormais entièrement bloquées par le barrage. Elle ne reçoit plus que les apports des nappes latérales et le flux souterrain passant sous le barrage. L'avenir du développement agricole régional dépend de manière évidente de la maîtrise de la ressource souterraine et donc de sa bonne connaissance. Malgré de multiples mesures de terrain et études entreprises depuis plusieurs décennies, il reste encore de nombreuses incertitudes qui rendent le bilan actuel de la nappe très incertain, à la fois sur les flux entrants et sortants. La surexploitation est nette et générale et aucune solution alternative simple n'apparaît. Le risque d'augmentation à long terme de la minéralisation existe mais ce problème est moins grave et moins immédiat que la baisse piézométrique

Strongly quadrature-dependent noise in superconducting micro-resonators measured at the vacuum-noise limit

We measure frequency- and dissipation-quadrature noise in superconducting lithographed microwave resonators with sensitivity near the vacuum noise level using a Josephson parametric amplifier. At an excitation power of 100~nW, these resonators show significant frequency noise caused by two-level systems. No excess dissipation-quadrature noise (above the vacuum noise) is observed to our measurement sensitivity. These measurements demonstrate that the excess dissipation-quadrature noise is negligible compared to vacuum fluctuations, at typical readout powers used in micro-resonator applications. Our results have important implications for resonant readout of various devices such as detectors, qubits and nano-mechanical oscillators.Comment: 13 pages, 4 figure

Frequency shifts of photoassociative spectra of ultracold metastable Helium atoms : a new measurement of the s-wave scattering length

We observe light-induced frequency shifts in one-color photoassociative spectra of magnetically trapped $^4$He$^*$ atoms in the metastable $2^3S_1$ state. A pair of ultracold spin-polarized $2^3S_1$ helium atoms is excited into a molecular bound state in the purely long range $0_u^+$ potential connected to the $2^3S_1 - 2^3P_0$ asymptote. The shift arises from the optical coupling of the molecular excited bound state with the scattering states and the bound states of two colliding $2^3S_1$ atoms. We measure the frequency-shifts for several ro-vibrational levels in the $0^+_u$ potential and find a linear dependence on the photoassociation laser intensity. Comparison with a theoretical analysis provides a good indication for the s-wave scattering length $a$ of the quintet ($^5\Sigma_g^+$) potential, $a=7.2\pm 0.6$ nm, which is significantly lower than most previous results obtained by non-spectroscopic methods.Comment: 7 pages, 4 figure

Towards a typology of spatial relations and properties for urban applications

Relations that occur between features located in space–like the fact that a street is surrounded by very high buildings, that an airport is close to a city- as well as spatial properties of features–like the height and width of a door- play an important role for many urban applications. Digital models of cities can assist in the evaluation of these relations and properties either through visualisation or through computation, mainly based on geometrical information. Hence, considering the objective of explaining to potential users of these city models what useful information they can derive from these data and how, a possible way to address this objective lies in the usage of a pivot model composed of relevant spatial properties and relations, connected to information meaningful to the user and connected to the possible computation of them on available data. This paper firstly sets the ground for a typology of such relevant relations and properties that are shared by different applications and that can be derived/approximated from existing data. It then proposes a model to describe these properties and relations and connect them to their possible computation based on data (2D or 3D). An important aspect of this model is to distinguish between a conceptual layer where relations occur between “real world” features and an implementation layer where they are calculated based on database features and geometries

A Titanium Nitride Absorber for Controlling Optical Crosstalk in Horn-Coupled Aluminum LEKID Arrays for Millimeter Wavelengths

We discuss the design and measured performance of a titanium nitride (TiN) mesh absorber we are developing for controlling optical crosstalk in horn-coupled lumped-element kinetic inductance detector arrays for millimeter-wavelengths. This absorber was added to the fused silica anti-reflection coating attached to previously-characterized, 20-element prototype arrays of LEKIDs fabricated from thin-film aluminum on silicon substrates. To test the TiN crosstalk absorber, we compared the measured response and noise properties of LEKID arrays with and without the TiN mesh. For this test, the LEKIDs were illuminated with an adjustable, incoherent electronic millimeter-wave source. Our measurements show that the optical crosstalk in the LEKID array with the TiN absorber is reduced by 66\% on average, so the approach is effective and a viable candidate for future kilo-pixel arrays.Comment: 7 pages, 5 figures, accepted for publication in the Journal of Low Temperature Physic

Onset of dispersion in Nb microstrip transmission lines at submillimeter wave frequencies

We have measured the dispersion in phase velocity of a Nb-SiO(x)-Nb microstrip transmission line resonator over a frequency range from 50 GHz to 800 GHz. A submicron Nb/Al-AlO(x)/Nb Josephson junction was used as a voltage-controlled oscillator to excite the high order modes in the resonator. The same junction is used as a direct detector resulting in a series of step-like structures in the DC current-voltage characteristic at the position of each mode frequency. The transmission line is dispersionless up to about 500 GHz where the phase velocity begins to decrease. This is well below the gap frequency f(sub g) approx. equals 700 GHz. Results agree qualitatively with the expected theoretical behavior near f(sub g). This onset of dispersion and loss in Nb transmission lines will have a significant impact on the design of submillimeter wave RF circuits