Constraints on mantle evolution from Ce-Nd-Hf isotope systematics

Mantle evolution is governed by continuous depletion by partial melting and replenishment by recycling oceanic and continental crust. Several important unknowns remain, however, such as the extent of compositional variability of the residual depleted mantle, the timescale, mass flux and composition of recycled oceanic and continental crust. Here, we investigate the Ce-Nd-Hf isotope systematics in a globally representative spectrum of mid ocean ridge and ocean island basalts. Using a Monte Carlo approach for reproducing the observed Ce-Nd-Hf isotope variation shows that the type and age of depleted mantle and recycled crust have the dominant influence on the slope, scatter, and extent of the modeled Ce-Nd-Hf isotope array. The model results suggest a relatively young (Peer reviewe

Frequency response of an atomic force microscope in liquids and air: Magnetic versus acoustic excitation

We discuss the dynamics of an amplitude modulation atomic force microscope in different environments such as water and air. Experiments, analytical expressions, and numerical simulations show that the resonance curves depend on the excitation method used to drive the cantilever, either mechanical or magnetic. This dependence is magnified for small force constants and quality factors, i.e., below 1 N/m and 10, respectively. We show that the equation for the observable, the cantilever deflection, depends on the excitation method. Under mechanical excitation, the deflection involves the base and tip displacements, while in magnetic excitation, the cantilever deflection and tip displacement coincideThis work was financially supported by the European Commission (FORCETOOL) and the Ministerio de Educación y Ciencia (MAT2006-03833). We do thank stimulating discussions with J.R. Lozano, S. Patil and N.F. Martinez.Peer reviewe

The Arteriovenous Loop: Engineering of Axially Vascularized Tissue

Background: Most of the current treatment options for large-scale tissue defects represent a serious burden for the patients, are often not satisfying, and can be associated with significant side effects. Although major achievements have already been made in the field of tissue engineering, the clinical translation in case of extensive tissue defects is only in its early stages. The main challenge and reason for the failure of most tissue engineering approaches is the missing vascularization within large-scale transplants. Summary: The arteriovenous (AV) loop model is an in vivo tissue engineering strategy for generating axially vascularized tissues using the own body as a bioreactor. A superficial artery and vein are anastomosed to create an AV loop. This AV loop is placed into an implantation chamber for prevascularization of the chamber inside, e.g., a scaffold, cells, and growth factors. Subsequently, the generated tissue can be transplanted with its vascular axis into the defect site and anastomosed to the local vasculature. Since the blood supply of the growing tissue is based on the AV loop, it will be immediately perfused with blood in the recipient site leading to optimal healing conditions even in the case of poorly vascularized defects. Using this tissue engineering approach, a multitude of different axially vascularized tissues could be generated, such as bone, skeletal or heart muscle, or lymphatic tissues. Upscaling from the small animal AV loop model into a preclinical large animal model could pave the way for the first successful attempt in clinical application. Key Messages: The AV loop model is a powerful tool for the generation of different axially vascularized replacement tissues. Due to minimal donor site morbidity and the possibility to generate patient-specific tissues variable in type and size, this in vivo tissue engineering approach can be considered as a promising alternative therapy to current treatment options of large-scale defects

Design of an imaging spectrometer for Earth observation using freeform mirrors

Design of an imaging spectrometer for earth observation using freeform mirrors Thomas Peschel1, Christoph Damm1, Matthias Beier1, Andreas Gebhard1, Stefan Risse1, Ingo Walter2, Ilse Sebastian2, David Krutz2 1 Fraunhofer Institut für Angewandte Optik und Feinwerktechnik, Jena 2 DLR, Institut für Optische Sensorsysteme, Berlin In 2017 the new hyperspectral DLR Earth Sensing Imaging Spectrometer (DESIS) will be integrated in the Multi-User-System for Earth Sensing (MUSES) platform /1/ installed on the International Space Station (ISS). The DESIS instrument is developed under the responsibility of the DLR. It will deliver images of the earth with a spatial resolution of 30 m on ground in 235 spectral channels in the wavelength range from 400 nm to 1 µm. As partner of the development team Fraunhofer IOF is responsible for the optical system of the imaging spectrometer.The optical system is made of two primary components: A compact Three-Mirror-Anastigmat (TMA) telescope images the ground strip under observation onto a slit. The following spectrometer reimages the slit onto the detector and performs the spectral separation using a reflective grating. The whole optical system is realized using metal-based mirrors the surfaces of which are made by Single-Point-Diamond Turning (SPDT). Since the spectral range is in the visible, a post-processing of the surfaces by Nickel plating is necessary. The final surface shape and roughness are realized by a second SPDT step and subsequent Magneto-Rheological Finishing. The TMA provides a focal length of 320 mm and an aperture of F/2.8. Its mechanical design relies on the Duolith-technology of IOF as well as optical and mechanical reference structures on the mirrors /2/ manufactured in the same SPDT run. This strategy allows for a significantly simplified adjustment of the optical system /3/. The spectrometer was designed on the basis of the so-called Offner scheme. Because of the high aperture of the system a freeform mirror had to be introduced in order to provide a good imaging quality over the whole spectral range. The above optical design requires a grating on a curved surface. Technologies are developed in order to fabricate the grating either by SPDT or, alternatively, by laser lithography. The mechanical design uses light-weight housing elements which wrap the optical path to suppress stray light. An athermal design is provided by using the same metal for mirrors and housing. To provide high adjustment precision, the housing elements carry reference and mounting features made by SPDT as well. This approach allows for a stiff mechanical set-up of the system, which is compatible with the harsh requirements of a space flight. References: 1 N. Humphrey, “A View From Above: Imaging from the ISS”, Teledyne DALSA 2014, http://possibility.teledynedalsa.com/a-view-from-above/ 2 S. Scheiding, e.a., “Ultra-precisely manufactured mirror assemblies with well-defined reference structures“, Proc. SPIE 7739, 2010. 3 T. Peschel, e.a., “Anamorphotic telescope for earth observation in the mid-infrared range”, ICSO 201

Application of fuzzy sets in reliability calculation of the oil and gas equipment

Oil and gas equipment, and electric motors in particular, often operate in different duty cycles under changing environmental conditions. The exact effect of these factors on the equipment reliability is rather uncertain. Defining the reliability parameters as fuzzy numbers allows managing such uncertainty. The paper provides an example of fuzzy-valued reliability function estimation. Four-parameter additive Weibull distribution is considered as a reliability model with bathtubshaped failure rate function