A 2 MV Van de Graaff accelerator as a tool for planetary and impact physics research

Investigating the dynamical and physical properties of cosmic dust can reveal a great deal of information about both the dust and its many sources. Over recent years, several spacecraft (e.g., Cassini, Stardust, Galileo, and Ulysses) have successfully characterised interstellar, interplanetary, and circumplanetary dust using a variety of techniques, including in situ analyses and sample return. Charge, mass, and velocity measurements of the dust are performed either directly (induced charge signals) or indirectly (mass and velocity from impact ionisation signals or crater morphology) and constrain the dynamical parameters of the dust grains. Dust compositional information may be obtained via either time-of-flight mass spectrometry of the impact plasma or direct sample return. The accurate and reliable interpretation of collected spacecraft data requires a comprehensive programme of terrestrial instrument calibration. This process involves accelerating suitable solar system analogue dust particles to hypervelocity speeds in the laboratory, an activity performed at the Max Planck Institut fu?r Kernphysik in Heidelberg, Germany. Here, a 2 MV Van de Graaff accelerator electrostatically accelerates charged micron and submicron-sized dust particles to speeds up to 80 km s(-1). Recent advances in dust production and processing have allowed solar system analogue dust particles (silicates and other minerals) to be coated with a thin conductive shell, enabling them to be charged and accelerated. Refinements and upgrades to the beam line instrumentation and electronics now allow for the reliable selection of particles at velocities of 1-80 km s(-1) and with diameters of between 0.05 μm and 5 μm. This ability to select particles for subsequent impact studies based on their charges, masses, or velocities is provided by a particle selection unit (PSU). The PSU contains a field programmable gate array, capable of monitoring in real time the particles' speeds and charges, and is controlled remotely by a custom, platform independent, software package. The new control instrumentation and electronics, together with the wide range of accelerable particle types, allow the controlled investigation of hypervelocity impact phenomena across a hitherto unobtainable range of impact parameters.     

Evaluation of a new computer-assisted surgical planning and navigation system based on two-dimensional fluoroscopy for insertion of a proximal femoral nail: an experimental study

Pertrochanteric femoral fractures are common and intramedullary nailing is an accepted method for their surgical treatment. Accurate placement of the implant is essential to ensure fixation. The conventional technique can require multiple guide wire passes, and relies heavily on fluoroscopy. A computer-assisted planning and navigation system based on two-dimensional fluoroscopy for guide wire placement in the femoral neck has been developed, in order to perform intramedullary pertrochanteric fracture fixation using the proximal femoral nail (PFNA). The planning process was supported by a 'zero-dose C-arm navigation' system. The PFNA was inserted into 12, intact, femoral sawbones guided by the computer-based navigation, and into 12, intact, femoral sawbones using a conventional fluoroscopic-assisted technique. Guide wire and subsequent blade placement in the femoral neck was evaluated. The computer-assisted technique achieved a significant decrease in the number of required fluoroscopic images and in the number of guide wire passes. The obtained average blade placement accuracy in the femoral neck was equivalent to the conventional technique. The operation time was significantly longer in the navigation-assisted group. The addition of computer-assisted planning and surgical guidance to the intramedullary nailing of pertrochanteric femoral fractures offers a number of clinical benefits based on the results of this sawbone study. Further studies including fractured sawbones and cadaver models with extension of the navigation process to all steps of PFNA introduction and with the goal of reducing operation time are indispensable before integration of this navigation system into clinical practice.     

Print your atomic force microscope

Progress in scanning probe microscopy profited from a flourishing multitude of new instrument designs, which lead to novel imaging modes and as a consequence to innovative microscopes. Often these designs were hampered by the restrictions, which conventional milling techniques impose. Modern rapid prototyping techniques, where layer by layer is added to the growing piece either by light driven polymerization or by three-dimensional printing techniques, overcome this constraint, allowing highly concave or even embedded and entangled structures. We have employed such a technique to manufacture an atomic force microscopy (AFM) head, and we compared its performance with a copy milled from aluminum. We tested both AFM heads for single molecule force spectroscopy applications and found little to no difference in the signal-to-noise ratio as well as in the thermal drift. The lower E modulus seems to be compensated by higher damping making this material well suited for low noise and low drift applications. Printing an AFM thus offers unparalleled freedom in the design and the rapid production of application-tailored custom instruments.     

Investigation of blind tip estimation

In this work we study functions for maximum likelihood estimation in blind tip estimation. We will implement the expectation maximization (EM), the stochastic EM, and stochastic approximation EM algortithms to estimate the unknown tip geometry. To demonstrate the functionality of the algorithms we applied it to dilated artificial input signal.     

Threshold photoionization in time-of-flight mass spectrometry

Multi-photon excitation in a time-of-flight mass spectrometer (TOF-MS) is shown to lead to threshold ions with defined internal energy. A powerful technique for the production of threshold ions is based on the excitation of high long-lived Rydberg states embedded in the ionization continuum. The Rydberg molecules are separated with suitable separation techniques from ions produced by a direct multi-photon ionization process. Finally, the ionization of the Rydberg molecules in a delayed pulsed electric field leads to threshold ions. This work reviews several separation techniques, and reports on applications of threshold ionization for investigation of the structure, energetics, and dynamics of neutral molecules, molecular cations, and cluster cations.     

An overview of recommender systems in the healthy food domain

Recently, food recommender systems have received increasing attention due to their relevance for healthy living. Most existing studies on the food domain focus on recommendations that suggest proper food items for individual users on the basis of considering their preferences or health problems. These systems also provide functionalities to keep track of nutritional consumption as well as to persuade users to change their eating behavior in positive ways. Also, group recommendation functionalities are very useful in the food domain, especially when a group of users wants to have a dinner together at home or have a birthday party in a restaurant. Such scenarios create many challenges for food recommender systems since the preferences of all group members have to be taken into account in an adequate fashion. In this paper, we present an overview of recommendation techniques for individuals and groups in the healthy food domain. In addition, we analyze the existing state-of-the-art in food recommender systems and discuss research challenges related to the development of future food recommendation technologies.     

Enantioseparations in Achiral Environments and Chromatographic Systems

Since the very first resolution of racemic tartaric acid by Pasteur, the importance of resolution and methodology has been on a path of continuous understanding and expansion. The science and chemistry of achieving such targets has changed a lot. The advent of chromatography changed the direction by involving synthetic, semisynthetic, or naturally occurring chiral materials for a direct approach to resolution, where rapid and reversible association occurs to form diastereomers with different stabilities and partition coefficients responsible for overall enantioseparation. It has now reached a stage where the separation of excess enantiomers from nonracemic mixtures has been achieved in a totally achiral environment, which does not appear to be in line with the prevalent concepts of basic stereochemistry. Caution should be exercised when enantiomerically enriched mixtures – obtained by enantioselective synthesis – are chromatographed for purification in preparative organic synthesis.     

Taxonomy for the Network and Service Management Research Field

Network and service management has established itself as a research field in the general area of computer networks. However, up to now, no appropriate organization of the field has been carried out in terms of a comprehensive list of terms and topics. In this paper, we introduce a taxonomy for network and service management. With such a taxonomy, it is possible to better understand the landscape of research as well as to reason about possible future challenges and opportunities. As such, in addition to the taxonomy itself, we also present an initial analysis of the field’s past, present, and future, based on the records of papers submitted and accepted in major conferences in the area, as well as a site survey performed through a questionnaire answered by experts from both industry and academia.     

VPI-FP: an integrative information system for factory planning

Nowadays, one of the main challenges in factory planning is the consistent and coherent information modelling along planning processes. Despite the current efforts in the fields of virtual production as well as digital and virtual factory, planning and simulation applications mostly support only the analysis and the optimisation of single planning aspects. However, to match nowadays challenges, planners require solutions that provide an integrated view to evaluate planning scenarios in advance and to achieve increasing production quality and efficiency. The concept of virtual production intelligence (VPI) provides a basic concept for such an integrative information system that enables planners to integrate, to aggregate and to analyse data gathered during one planning project as well as to compare different projects. In this study, we present such an information system for factory planning using the concept of the VPI. The focus lies in particular on the information modelling as well as the information integration and evaluation. Therefore, the study presents theoretical basics and implementations of the VPI platform within a precise application scenario in factory planning. This is to process and provide a consolidated information base along the whole planning process to support factory planning projects.