254 research outputs found

    Project Dawdler: a Proposal in Response to a Low Reynolds Number Station Keeping Mission

    Get PDF
    In direct response to Request for Proposals: Flight at very low Reynolds numbers - a station keeping mission, the members of Design Squad E present Project Dawdler: a remotely-piloted airplane supported by an independently controlled take-off cart. A brief introduction to Project Dawdler's overall mission and design, is given. The Dawdler is a remotely-piloted airplane designed to fly in an environmentally-controlled closed course at a Reynolds number of 10(exp 5) and at a cruise velocity of 25 ft/s. The two primary goals were to minimize the flight Reynolds number and to maximize the loiter time. With this in mind, the general design of the airplane was guided by the belief that a relatively light aircraft producing a fairly large amount of lift would be the best approach. For this reason the Dawdler utilizes a canard rather than a conventional tail for longitudinal control, primarily because the canard contributes a positive lift component. The Dawdler also has a single vertical tail mounted behind the wing for lateral stability, half of which is used as a rudder for yaw control. Due to the fact that the power required to take-off and climb to altitude is much greater than that required for cruise flight and simple turning maneuvers, it was decided that a take-off cart be used. Based on the current design, there are two unknowns which could possibly threaten the success of Project Dawdler. First, the effect of the fully-movable canard with its large appropriation of total lift on the performance of the plane, and secondly, the ability of the take-off procedure to go as planned are examined. These are questions which can only be answered by a prototype

    Strongly driven quantum pendulum of the OCS molecule

    Full text link
    We demonstrate and analyze a strongly driven quantum pendulum in the angular motion of stateselected and laser aligned OCS molecules. Raman-couplings during the rising edge of a 50-picosecond laser pulse create a wave packet of pendular states, which propagates in the confining potential formed by the polarizability interaction between the molecule and the laser field. This wave-packet dynamics manifests itself as pronounced oscillations in the degree of alignment with a laser-intensity dependent period.Comment: 6 pages, 4 figure

    Standardizing a component metadata infrastructure

    No full text
    This paper describes the status of the standardization efforts of a Component Metadata approach for describing Language Resources with metadata. Different linguistic and Language & Technology communities as CLARIN, META-SHARE and NaLiDa use this component approach and see its standardization of as a matter for cooperation that has the possibility to create a large interoperable domain of joint metadata. Starting with an overview of the component metadata approach together with the related semantic interoperability tools and services as the ISOcat data category registry and the relation registry we explain the standardization plan and efforts for component metadata within ISO TC37/SC4. Finally, we present information about uptake and plans of the use of component metadata within the three mentioned linguistic and L&T communities

    Gene therapy for articular cartilage repair

    Get PDF
    Articular cartilage serves as the gliding surface of joints. It is susceptible to damage from trauma and from degenerative diseases. Restoration of damaged articular cartilage may be achievable through the use of cell-regulatory molecules that augment the reparative activities of the cells, inhibit the cells\u27; degradative activities, or both. A variety of such molecules have been identified. These include insulin-like growth factor I, fibroblast growth factor 2, bone morphogenetic proteins 2, 4, and 7, and interleukin-1 receptor antagonist. It is now possible to transfer the genes encoding such molecules into articular cartilage and synovial lining cells. Although preliminary, data from in-vitro and in-vivo studies suggest that gene therapy can deliver such potentially therapeutic agents to protect existing cartilage and to build new cartilage. Keywords: gene therapy, vectors, articular cartilage, arthritis, animal model

    Towards automatic quality assessment of component metadata

    No full text
    Measuring the quality of metadata is only possible by assessing the quality of the underlying schema and the metadata instance. We propose some factors that are measurable automatically for metadata according to the CMD framework, taking into account the variability of schemas that can be defined in this framework. The factors include among others the number of elements, the (re-)use of reusable components, the number of filled in elements. The resulting score can serve as an indicator of the overall quality of the CMD instance, used for feedback to metadata providers or to provide an overview of the overall quality of metadata within a reposi-tory. The score is independent of specific schemas and generalizable. An overall assessment of harvested metadata is provided in form of statistical summaries and the distribution, based on a corpus of harvested metadata. The score is implemented in XQuery and can be used in tools, editors and repositorie

    Setting the photoelectron clock through molecular alignment

    Get PDF
    The interaction of strong laser fields with matter intrinsically provides a powerful tool for imaging transient dynamics with an extremely high spatiotemporal resolution. Here, we study strong-field ionisation of laser-aligned molecules, and show a full real-time picture of the photoelectron dynamics in the combined action of the laser field and the molecular interaction. We demonstrate that the molecule has a dramatic impact on the overall strong-field dynamics: it sets the clock for the emission of electrons with a given rescattering kinetic energy. This result represents a benchmark for the seminal statements of molecular-frame strong-field physics and has strong impact on the interpretation of self-diffraction experiments. Furthermore, the resulting encoding of the time-energy relation in molecular-frame photoelectron momentum distributions shows the way of probing the molecular potential in real-time, and accessing a deeper understanding of electron transport during strong-field interactions

    A new body mass estimation of <i>Brachiosaurus brancai</i> Janensch, 1914 mounted and exhibited at the Museum of Natural History (Berlin, Germany)

    Get PDF
    Body mass and surface areas are important in several aspects for an organism living today. Therefore, mass and surface determinations for extinct dinosaurs could be important for paleo-biological aspects as well. Based on photogrammetrical measurement the body mass and body surface area of the Late Jurassic Brachiosaurus brancai Janensch, 1914 from Tendaguru (East Africa), a skeleton mounted and exhibited at the Museum of Natural History in Berlin (Germany), has been re-evaluated. We determined for a slim type of 3D reconstruction of Brachiosaurus brancai a total volume of 47.9 m3 which represents, assuming a mean tissue density of 0.8 kg per 1,000 cm3, a total body mass of 38,000 kg. The volume distributions from the head to the tail were as follows: 0.2 m3 for the head, neck 7.3 m3, fore limbs 2.9 m3, hind limbs 2.6 m3, thoracic-abdominal cavity 32.4 m3, tail 2.2 m3. The total body surface area was calculated to be 119.1 m2, specifically 1.5 m2 for the head, 26 m2 neck, fore limbs 18.8 m2, hind limbs 16.4 m2, 44.2 m2 thoracic-abdominal cavity, and finally the tail 12.2 m2. Finally, allometric equations were used to estimate presumable organ sizes of this extinct dinosaur and to test whether their dimensions really fit into the thoracic and abdominal cavity of Brachiosaurus brancai if a slim body shape of this sauropod is assumed. doi:10.1002/mmng.200700011</a

    Atomic-resolution imaging of carbonyl sulfide by laser-induced electron diffraction

    Get PDF
    Measurements on the strong-field ionization of carbonyl sulfide molecules by short, intense, 2 µm wavelength laser pulses are presented from experiments where angle-resolved photoelectron distributions were recorded with a high-energy velocity map imaging spectrometer, designed to reach a maximum kinetic energy of 500 eV. The laser-field-free elastic-scattering cross section of carbonyl sulfide was extracted from the measurements and is found in good agreement with previous experiments, performed using conventional electron diffraction. By comparing our measurements to the results of calculations, based on the quantitative rescattering theory, the bond lengths and molecular geometry were extracted from the experimental differential cross sections to a precision better than ±5 pm and in agreement with the known values

    Charge transfer in dissociating iodomethane and fluoromethane molecules ionized by intense femtosecond X-ray pulses

    Get PDF
    Citation: Boll, R., Erk, B., Coffee, R., Trippel, S., Kierspel, T., Bomme, C., . . . Rudenko, A. (2016). Charge transfer in dissociating iodomethane and fluoromethane molecules ionized by intense femtosecond X-ray pulses. Structural Dynamics, 3(4). doi:10.1063/1.4944344Additional Authors: Marchenko, T.;Miron, C.;Patanen, M.;Osipov, T.;Schorb, S.;Simon, M.;Swiggers, M.;Techert, S.;Ueda, K.;Bostedt, C.;Rolles, D.;Rudenko, A.Ultrafast electron transfer in dissociating iodomethane and fluoromethane molecules was studied at the Linac Coherent Light Source free-electron laser using an ultraviolet-pump, X-ray-probe scheme. The results for both molecules are discussed with respect to the nature of their UV excitation and different chemical properties. Signatures of long-distance intramolecular charge transfer are observed for both species, and a quantitative analysis of its distance dependence in iodomethane is carried out for charge states up to I21+. The reconstructed critical distances for electron transfer are in good agreement with a classical over-the-barrier model and with an earlier experiment employing a near-infrared pump pulse. © 2016 Author(s)
    corecore