Remotely piloted LTA vehicle for surveillance

Various aspects of a remotely piloted mini-LTA vehicle for surveillance, monitoring and measurement for civilian and military applications are considered. Applications, operations and economics are discussed

The normal parameterization and its application to collision detection

Collision detection is a central task in the simulation of multibody systems. Depending on the description of the geometry, there are many efficient algorithms to address this need. A widespread approach is the common normal concept: potential contact points on opposing surfaces have antiparallel normal vectors. However, this approach leads to implicit equations that require iterative solutions when the geometries are described by implicit functions or the common parameterizations. We introduce the normal parameterization to describe the boundary of a strictly convex object as a function of the orientation of its normal vector. This parameterization depends on a scalar function, the so-called generating potential from which all properties are derived: points on the boundary, continuity/differentiability of the boundary, curvature, offset curves or surfaces. An explicit solution for collisions with a planar counterpart is derived and four iterative algorithms for collision detection between two arbitrary objects with the normal parametrization are compared. The application of this approach for collision detection in multibody models is illustrated in a case study with two ellipsoids and several planes

Explicit analytical solutions for two-dimensional contact detection problems between almost arbitrary geometries and straight or circular counterparts

Contact between complex bodies and simple counterparts like straight lines or circles occur in many two-dimensional mechanical models. The corresponding contact detection problems are complicated and thus far, no explicit formulas have been available. In this paper, we address the contact detection problem between two planar bodies: one being either a straight line or a circle and the other an almost arbitrary geometry—the only requirement is a unique contact point for all possible contact situations. To solve this general problem, a novel procedure is applied which provides necessary conditions for the description of the geometry based on the special case of a rolling contact. This results in a parameterization of the geometry which gives the potential contact point depending on the relative orientation between the two bodies. Although the derivation is based on a rolling contact, the result is valid in general and can also be used for efficient contact detection when the bodies are separated. The derived equations are simple and easy to implement, which is demonstrated for two examples: a foot-ground contact model and a cam-follower mechanism

Approaching ‘kit-type’ labelling with 68Ga: the DATA chelators

The DATA chelators are a novel class of tri-anionic ligands based on 6-amino-1,4-diazepine-triacetic acid, which have been introduced recently for the chelation of 68Ga. Compared with macrocyclic chelators based on the cyclen scaffold (i.e., DOTA, DO3A, and DO2A derivatives), DATA chelators undergo quantitative radiolabelling more rapidly and under milder conditions. In this study, a systematic evaluation of the labelling of four DATA chelators—DATAM, DATAP, DATAPh, and DATAPPh—with 68Ga is presented. The results highlight the extraordinary potential of this new class of chelators for application in molecular imaging using 68Ga positron emission tomography (PET)

Broad-band transmission spectrum and K-band thermal emission of WASP-43b as observed from the ground

(Abridged) We observed one transit and one occultation of the hot Jupiter WASP-43b simultaneously in the g'r'i'z'JHK bands using the GROND instrument on the MPG/ESO 2.2-meter telescope. From the transit event, we have independently derived WASP-43's system parameters with high precision, and improved the period to be 0.81347437(13) days. No significant variation in transit depths is detected, with the largest deviations coming from the i', H, and K bands. Given the observational uncertainties, the broad-band transmission spectrum can be explained by either a flat featureless straight line that indicates thick clouds, synthetic spectra with absorption signatures of atomic Na/K or molecular TiO/VO that indicate cloud-free atmosphere, or a Rayleigh scattering profile that indicates high-altitude hazes. From the occultation event, we have detected planetary dayside thermal emission in the K-band with a flux ratio of 0.197 +/- 0.042%, which confirms previous detections obtained in the 2.09 micron narrow band and Ks-band. The K-band brightness temperature 1878 +108/-116 K favors an atmosphere with poor day- to night-side heat redistribution. We also have a marginal detection in the i'-band (0.037 +0.023/-0.021%), which is either a false positive, a signature of non-blackbody radiation at this wavelength, or an indication of reflective hazes at high altitude.Comment: 14 pages, 9 figures, accepted for publication in A&

Band structure of helimagnons in MnSi resolved by inelastic neutron scattering

A magnetic helix realizes a one-dimensional magnetic crystal with a period given by the pitch length $\lambda_h$. Its spin-wave excitations -- the helimagnons -- experience Bragg scattering off this periodicity leading to gaps in the spectrum that inhibit their propagation along the pitch direction. Using high-resolution inelastic neutron scattering the resulting band structure of helimagnons was resolved by preparing a single crystal of MnSi in a single magnetic-helix domain. At least five helimagnon bands could be identified that cover the crossover from flat bands at low energies with helimagnons basically localized along the pitch direction to dispersing bands at higher energies. In the low-energy limit, we find the helimagnon spectrum to be determined by a universal, parameter-free theory. Taking into account corrections to this low-energy theory, quantitative agreement is obtained in the entire energy range studied with the help of a single fitting parameter.Comment: 5 pages, 3 figures; (v2) slight modifications, published versio

Thickness-dependent spontaneous dewetting morphology of ultrathin Ag films

We show here that the morphological pathway of spontaneous dewetting of ultrathin Ag films on SiO2 under nanosecond laser melting is found to be film thickness dependent. For films with thickness h between 2 <= h <= 9.5 nm, the morphology during the intermediate stages of dewetting consisted of bicontinuous structures. For films 11.5 <= h <= 20 nm, the intermediate stages consisted of regularly-sized holes. Measurement of the characteristic length scales for different stages of dewetting as a function of film thickness showed a systematic increase, which is consistent with the spinodal dewetting instability over the entire thickness range investigated. This change in morphology with thickness is consistent with observations made previously for polymer films [A. Sharma et al, Phys. Rev. Lett., v81, pp3463 (1998); R. Seemann et al, J. Phys. Cond. Matt., v13, pp4925, (2001)]. Based on the behavior of free energy curvature that incorporates intermolecular forces, we have estimated the morphological transition thickness for the intermolecular forces for Ag on SiO2 . The theory predictions agree well with observations for Ag. These results show that it is possible to form a variety of complex Ag nanomorphologies in a consistent manner, which could be useful in optical applications of Ag surfaces, such as in surface enhanced Raman sensing.Comment: 20 pages, 5 figure

The PETfold and PETcofold web servers for intra- and intermolecular structures of multiple RNA sequences

The function of non-coding RNA genes largely depends on their secondary structure and the interaction with other molecules. Thus, an accurate prediction of secondary structure and RNA–RNA interaction is essential for the understanding of biological roles and pathways associated with a specific RNA gene. We present web servers to analyze multiple RNA sequences for common RNA structure and for RNA interaction sites. The web servers are based on the recent PET (Probabilistic Evolutionary and Thermodynamic) models PETfold and PETcofold, but add user friendly features ranging from a graphical layer to interactive usage of the predictors. Additionally, the web servers provide direct access to annotated RNA alignments, such as the Rfam 10.0 database and multiple alignments of 16 vertebrate genomes with human. The web servers are freely available at: http://rth.dk/resources/petfold