Evidence for a meteoritic origin of the September 15, 2007, Carancas crater

On September 15th, 2007, around 11:45 local time in Peru, near the Bolivian border, the atmospheric entry of a meteoroid produced bright lights in the sky and intense detonations. Soon after, a crater was discovered south of Lake Titicaca. These events have been detected by the Bolivian seismic network and two infrasound arrays operating for the Comprehensive Nuclear-Test-Ban Treaty Organization, situated at about 80 and 1620 km from the crater. The localization and origin time computed with the seismic records are consistent with the reported impact. The entry elevation and azimuthal angles of the trajectory are estimated from the observed signal time sequences and backazimuths. From the crater diameter and the airwave amplitudes, the kinetic energy, mass and explosive energy are calculated. Using the estimated velocity of the meteoroid and similarity criteria between orbital elements, an association with possible parent asteroids is attempted. The favorable setting of this event provides a unique opportunity to evaluate physical and kinematic parameters of the object that generated the first actual terrestrial meteorite impact seismically recorded

Onderzoek naar de ammoniak- en geuremissie van stallen LVII : natuurlijk geventileerde potstal voor melkgeiten = Naturally ventilated, deep litter housing for dairy goats

Door de IMAG-meetploeg werd onderzoek verricht naar de ammoniak- en geuremissie van een natuurlijk geventileerde potstal voor melkgeiten. Zowel in de zomer als in de winter werd een periode gemeten. Het loopgedeelte van de melkgeiten was voorzien van een strolaag (pot). De geiten kregen gedoseerd krachtvoer en konden onbeperkt gerstestro opnemen. Dagelijks werd een hoeveelheid niet opgegeten stro in de pot geveegd, zodat de strolaag geleidelijk dikker werd

Breakdown of the few-level approximation in collective systems

The validity of the few-level approximation in dipole-dipole interacting collective systems is discussed. As example system, we study the archetype case of two dipole-dipole interacting atoms, each modelled by two complete sets of angular momentum multiplets. We establish the breakdown of the few-level approximation by first proving the intuitive result that the dipole-dipole induced energy shifts between collective two-atom states depend on the length of the vector connecting the atoms, but not on its orientation, if complete and degenerate multiplets are considered. A careful analysis of our findings reveals that the simplification of the atomic level scheme by artificially omitting Zeeman sublevels in a few-level approximation generally leads to incorrect predictions. We find that this breakdown can be traced back to the dipole-dipole coupling of transitions with orthogonal dipole moments. Our interpretation enables us to identify special geometries in which partial few-level approximations to two- or three-level systems are valid

ESPON SUPER – Sustainable Urbanisation and land-use Practices in European Regions. A GUIDE TO SUSTAINABLE URBANISATION AND LAND-USE

Guides help you do things. You turn to them when you need to find out how to solve a problem. They are a form of knowledge transfer, written by experts in a way that is accessible and helpful to a wide audience. This guide was written by the researchers engaged in the ESPON 2020 applied research project on Sustainable Urbanisation and Land-Use Practices in European Regions (SUPER). It aims to help people and institutions engaged with land-use management at various levels across Europe to promote sustainable urbanisation in their territories. Overall, the guide offers information, ideas and perspectives to help decision-makers and policymakers to proactively contribute to more equal, balanced, and sustainable territorial development. The decision to convert land to a different use influences our quality of life and that of future generations, and, as this Guide shows, a large toolbox of interventions exists that can help alter prevailing land-use practices. Choosing among them is a tough decision, and implementation may require strong political commitment and bold leadership. We hope that this Guide provides the inspiration to accept this challenge

Quasiclassical negative magnetoresistance of a 2D electron gas: interplay of strong scatterers and smooth disorder

We study the quasiclassical magnetotransport of non-interacting fermions in two dimensions moving in a random array of strong scatterers (antidots, impurities or defects) on the background of a smooth random potential. We demonstrate that the combination of the two types of disorder induces a novel mechanism leading to a strong negative magnetoresistance, followed by the saturation of the magnetoresistivity $\rho_{xx}(B)$ at a value determined solely by the smooth disorder. Experimental relevance to the transport in semiconductor heterostructures is discussed.Comment: 4 pages, 2 figure

Enhanced structural correlations accelerate diffusion in charge-stabilized colloidal suspensions

Theoretical calculations for colloidal charge-stabilized and hard sphere suspensions show that hydrodynamic interactions yield a qualitatively different particle concentration dependence of the short-time self-diffusion coefficient. The effect, however, is numerically small and hardly accessible by conventional light scattering experiments. Applying multiple-scattering decorrelation equipment and a careful data analysis we show that the theoretical prediction for charged particles is in agreement with our experimental results from aqueous polystyrene latex suspensions.Comment: 1 ps-file (MS-Word), 14 page

Investigations on Tetragonally Distorted Sodium Thallide NaTl‐tI8

In-depth investigations of the long-time known Zintl phase NaTl revealed a phase transition of tetragonal NaTl-tI8 [I4(1)/amd; a = 5.2268(9) angstrom, c = 7.539(1) angstrom, V = 205.97(9) angstrom(3)] to Zintl's cubic NaTl-cF16 [Fd3m; a = 7.4697(6) angstrom, V = 416.79(5) angstrom(3)] between 351 and 355 K. This phase transformation was observed for NaTl prepared by two different synthetic routes including Zintl's original procedure. An excess of sodium applied during the synthesis in liquid ammonia also resulted in the formation of NaTl-tI8. DSC measurements suggest a first order phase transition. In addition to in-situ temperature dependent powder X-ray diffraction experiments, DSC measurements and solid-state NMR investigations, we also performed theoretical DOS and band structure calculations for the cubic and tetragonal phase, respectively. The results suggest Na-Tl interactions in the second coordination sphere being responsible for the observed tetragonal distortion of Zintl's cubic NaTl

Adsorption of Multi-block and Random Copolymer on a Solid Surface: Critical Behavior and Phase Diagram

The adsorption of a single multi-block $AB$-copolymer on a solid planar substrate is investigated by means of computer simulations and scaling analysis. It is shown that the problem can be mapped onto an effective homopolymer adsorption problem. In particular we discuss how the critical adsorption energy and the fraction of adsorbed monomers depend on the block length $M$ of sticking monomers $A$, and on the total length $N$ of the polymer chains. Also the adsorption of the random copolymers is considered and found to be well described within the framework of the annealed approximation. For a better test of our theoretical prediction, two different Monte Carlo (MC) simulation methods were employed: a) off-lattice dynamic bead-spring model, based on the standard Metropolis algorithm (MA), and b) coarse-grained lattice model using the Pruned-enriched Rosenbluth method (PERM) which enables tests for very long chains. The findings of both methods are fully consistent and in good agreement with theoretical predictions.Comment: 27 pages, 12 figure

Group velocity control in the ultraviolet domain via interacting dark-state resonances

The propagation of a weak probe field in a laser-driven four-level atomic system is investigated. We choose mercury as our model system, where the probe transition is in the ultraviolet region. A high-resolution peak appears in the optical spectra due to the presence of interacting dark resonances. We show that this narrow peak leads to superluminal light propagation with strong absorption, and thus by itself is only of limited interest. But if in addition a weak incoherent pump field is applied to the probe transition, then the peak structure can be changed such that both sub- and superluminal light propagation or a negative group velocity can be achieved without absorption, controlled by the incoherent pumping strength