Gravitational-wave Detection With Matter-wave Interferometers Based On Standing Light Waves

We study the possibility of detecting gravitational-waves with matter-wave interferometers, where atom beams are split, deflected and recombined totally by standing light waves. Our calculation shows that the phase shift is dominated by terms proportional to the time derivative of the gravitational wave amplitude. Taking into account future improvements on current technologies, it is promising to build a matter-wave interferometer detector with desired sensitivity.Comment: 7 pages, 3 figures. To be published in General Relativity and Gravitatio

Global maps of soil temperature.

Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2 m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we provide global maps of soil temperature and bioclimatic variables at a 1-km <sup>2</sup> resolution for 0-5 and 5-15 cm soil depth. These maps were created by calculating the difference (i.e. offset) between in situ soil temperature measurements, based on time series from over 1200 1-km <sup>2</sup> pixels (summarized from 8519 unique temperature sensors) across all the world's major terrestrial biomes, and coarse-grained air temperature estimates from ERA5-Land (an atmospheric reanalysis by the European Centre for Medium-Range Weather Forecasts). We show that mean annual soil temperature differs markedly from the corresponding gridded air temperature, by up to 10°C (mean = 3.0 ± 2.1°C), with substantial variation across biomes and seasons. Over the year, soils in cold and/or dry biomes are substantially warmer (+3.6 ± 2.3°C) than gridded air temperature, whereas soils in warm and humid environments are on average slightly cooler (-0.7 ± 2.3°C). The observed substantial and biome-specific offsets emphasize that the projected impacts of climate and climate change on near-surface biodiversity and ecosystem functioning are inaccurately assessed when air rather than soil temperature is used, especially in cold environments. The global soil-related bioclimatic variables provided here are an important step forward for any application in ecology and related disciplines. Nevertheless, we highlight the need to fill remaining geographic gaps by collecting more in situ measurements of microclimate conditions to further enhance the spatiotemporal resolution of global soil temperature products for ecological applications

LADUMA: looking at the distant universe with the MeerKAT array

The cosmic evolution of galaxies’ neutral atomic gas content is a major science driver for the Square Kilometre Array (SKA), as well as for its South African (MeerKAT) and Australian (ASKAP) precursors. Among the H I large survey programs (LSPs) planned for ASKAP and MeerKAT, the deepest and narrowest tier of the “wedding cake” will be defined by the combined L-band+UHF-band Looking At the Distant Universe with the MeerKAT Array (LADUMA) survey, which will probe H I in emission within a single “cosmic vuvuzela” that extends to z = 1.4, when the universe was only a third of its present age. Through a combination of individual and stacked detections (the latter relying on extensive multi-wavelength studies of the survey’s target field), LADUMA will study the redshift evolution of the baryonic Tully–Fisher relation and the cosmic H I density, the variation of the H I mass function with redshift and environment, and the connection between H I content and galaxies’ stellar properties (mass, age, etc.). The survey will also build a sample of OH megamaser detections that can be used to trace the cosmic merger history. This proceedings contribution provides a brief introduction to the survey, its scientific aims, and its technical implementation, deferring a more complete discussion for a future article after the implications of a recent review of MeerKAT LSP project plans are fully worked out

State selected total Penning ionization cross sections for the systems neon [Ne*(3P0,3P2)] + argon, krypton, xenon and molecular nitrogen in the energy range 0.06 <E0(eV) <8.0

The velocity dependence and absolute values of the total ionisation cross sections of Ar, Kr, Xe and N2 by metastable Ne*(3P0) and Ne*(3P2) atoms have been measured in a crossed beam scattering experiment. State selection of the beam of metastable atoms has been performed by optical pumping with a cw dye laser. Our technique, which uses the UV photons released in the radiative decay following the laser excitation to measure the density of metastable atoms in the scattering centre, is very insensitive to details of the process of optical pumping. Systematic errors in detection efficiencies of the metastable atoms are largely eliminated in this approach. We have analysed our experimental data in terms of an optical potential, using a least-squares method to determine the potential parameters. For the real part we use an ion—atom Morse—Morse—spline—van der Waals potential (V0(r) as proposed by Siska. The well area for V0(r) 0.1 eV is left unmodified. The energy dependence of the cross sections for the Ne*-rare gas systems points unambiguously to a pronounced "kink" in the repulsive branch at 0.1–0.2 eV. For the imaginary part, with the usual exponential behaviour, we have to introduce a saturation to a constant value at small internuclear distances r <rIm with rIm in the range 2.1 <rIm(Å) <2.6 which is only probed for energies 0.15 eV. These modifications result in a satisfactory description of the data for the Ne*(3P2)—Ar, Kr, Xe systems. For the Ne*(3P0 systems additional modifications of the well area are necessary. By calibrating the density—length product of the secondary beam and using the available detection efficiencies for ions and UV photons of the spiraltron detector we have also determined absolute values of the total ionisation cross section. In the thermal energy range (0.06–0.16 eV) they are in fair agreement with the rate constants for the quenching of metastable atoms as measured by Brom in flowing afterglows

Accurate (0.25 mrad) perpendicular alignment of a continuous-wave single-mode dye laser beam and an atomic beam

Two simple methods are described for an accurate perpendicular alignment of a laser beam and an atomic beam, which is required for a velocity independent, i.e., Doppler-free interaction, of the laser beam with the atomic beam. With the first method a free running single-mode cw dye laser beam and an atomic beam are aligned perpendicular with an accuracy of 0.25 mrad. This alignment takes typically 2 h. The second method needs a laser beam that is absolutely stabilized to the investigated atomic transition. With this method a 0.2-mrad accurate perpendicular alignment is obtained within only 5 min

The plasminogen activation system plays a role in the migration of human smooth muscle cells in vitro (abstract)

The plasminogen activation system is known to be involved in several cell migration processes. A role for plasminogen activators in smooth muscle cell migration after vascular injury has been suggested from several animal studies. However, not much is known about their involvement in human vascular remodelling. In this study, the role of the plasminogen activation system in human smooth muscle cells was investigated in more detail using an in vitro wound assay. Confluent cultures were wounded by stripping the cells away from their extracellular matrix with the use of Millipore strips. After wounding, cells start to migrate from the wounded edge into the denuded area. Migration was followed during 24 hours and quantified by counting the number of cells that migrated into the denuded area. Migration was inhibited to 61.9 + 7.1 % of control by the addition of the plasmin inhibitor aprotinin (100 KIU/mL) to the culture medium. Blocking the activity of u-PA or t-PA using specific polyclonal antibodies reduced migration to 57.8 ±6.1% with anti-uPA and had no significant effect on migration with anti-tPA. Interference in the uPA/uPAR interaction by addition of soluble uPAR had a similar effect as for anti-uPA. A possible involvement of LRP or the VLDL receptor was shown by adding the receptor antagonist RAP to the culture medium, which inhibited migration to 61.0 ± 7.9 % of control. These results suggest an involvement of the plasminogen activation system and particularly surface bound u-PA in human smooth muscle cell migration