Interference-Aware RZF Precoding for Multi Cell Downlink Systems

Recently, a structure of an optimal linear precoder for multi cell downlink systems has been described in [1, Eq (3.33)]. Other references (e.g., [2,3]) have used simplified versions of the precoder to obtain promising performance gains. These gains have been hypothesized to stem from the additional degrees of freedom that allow for interference mitigation through interference relegation to orthogonal subspaces. However, no conclusive or rigorous understanding has yet been developed. In this paper, we build on an intuitive interference induction trade-off and the aforementioned precoding structure to propose an interference aware RZF (iaRZF) precoding scheme for multi cell downlink systems and we analyze its rate performance. Special emphasis is placed on the induced interference mitigation mechanism of iaRZF. For example, we will verify the intuitive expectation that the precoder structure can either completely remove induced inter-cell or intra-cell interference. We state new results from large-scale random matrix theory that make it possible to give more intuitive and insightful explanations of the precoder behavior, also for cases involving imperfect channel state information (CSI). We remark especially that the interference-aware precoder makes use of all available information about interfering channels to improve performance. Even very poor CSI allows for significant sum-rate gains. Our obtained insights are then used to propose heuristic precoder parameters for arbitrary systems, whose effectiveness are shown in more involved system scenarios. Furthermore, calculation and implementation of these parameters does not require explicit inter base station cooperation.Comment: Accepted for publication in IEEE Transactions on Signal Processing, 201

Differential Effects of Bone Structural and Material Properties on Bone Competence in C57BL/6 and C3H/He Inbred Strains of Mice

The femoral neck is a relevant and sensitive site for studying the degree of osteopenia. Engineering principles predict that bone structural parameters, like cross-sectional geometry, are important determinants of bone mechanical parameters. Mechanical parameters are also directly affected by the material properties of the bone tissue. However, the relative importance of structural and material properties is still unknown. The aim of this study was to compare bone competence and structural parameters between a murine strain showing a low bone mass phenotype, C57BL/6 (B6), and another one showing a high bone mass phenotype, C3H/He (C3H), in order to better determine the role of bone structure and geometry in bone failure behavior. Murine femora of 12- and 16-week-old B6 and 12- and 16-week-old C3H inbred strains were mechanically tested under axial loading of the femoral head. In order to assess the structural properties, we performed three-dimensional morphometric analyses in five different compartments of the mouse femur using micro-computed tomography. The mechanical tests revealed that B6 femora became stiffer, stronger, and tougher at 12-16weeks, while bone brittleness stayed constant. C3H bone stiffness increased, but strength remained constant, work to failure decreased, and bone became more brittle. These age effects indicated that B6 did not reach peak bone properties at 16weeks of age and C3H did reach maximal skeletal biomechanical properties before 16weeks of age. Our investigations showed that 83% of the strength of the femoral neck in the B6 strain was explained by cortical thickness at this location; in contrast, in C3H none of the mechanical properties of the femoral neck was explained by bone structural parameters. The relative contributions of bone structural and material properties on bone strength are different in B6 and C3H. We hypothesize that these different contributions are related to differences at the ultrastructural level of bone that affect bone failur

Virtual learning environment for interactive engagement with advanced quantum mechanics

A virtual learning environment can engage university students in the learning process in ways that the traditional lectures and lab formats can not. We present our virtual learning environment \emph{StudentResearcher} which incorporates simulations, multiple-choice quizzes, video lectures and gamification into a learning path for quantum mechanics at the advanced university level. \emph{StudentResearcher} is built upon the experiences gathered from workshops with the citizen science game Quantum Moves at the high-school and university level, where the games were used extensively to illustrate the basic concepts of quantum mechanics. The first test of this new virtual learning environment was a 2014 course in advanced quantum mechanics at Aarhus University with 47 enrolled students. We found increased learning for the students who were more active on the platform independent of their previous performances.Comment: 8 pages, 6 figure

Femoral stiffness and strength critically depend on loading angle: a parametric study in a mouse-inbred strain

Biomechanical tests of human femora have shown that small variations of the loading direction result in significant changes in measured bone mechanical properties. However, the heterogeneity in geometrical and bone tissue properties does not make human bones well suited to reproducibly assess the effects of loading direction on stiffness and strength. To precisely quantify the influence of loading direction on stiffness and strength of femora loaded at the femoral head, we tested femora from C57BL/6 inbred mice. We developed an image-based alignment protocol and investigated the loading direction influence on proximal femur stiffness and strength. An aluminum femoral phantom and C57BL/6 femora were tested under compression with different loading directions. Both tests, with the aluminum phantom and the murine bones, showed and quantified the linear dependence of stiffness on loading direction: a 5° change in loading direction resulted in almost 30% change in stiffness. Murine bone testing also revealed and quantified the variation in strength due to loading direction: 5° change in loading direction resulted in 8.5% change in strength. In conclusion, this study quantified, for the first time, the influence of misalignment on bone stiffness and strength for femoral head loading. We showed the extreme sensitivity of this site regarding loading directio

Optimal 3D Cell Planning: A Random Matrix Approach

International audienceThis article proposes a large system approximation of the ergodic sum-rate (SR) for cellular multi-user multiple-input multiple-output uplink systems. The considered system has various degrees of freedom, such as clusters of base stations (BSs) performing cooperative multi-point processing, randomly distributed user terminals (UTs), and supports arbitrarily configurable antenna gain patterns at the BSs. The approximation is provably tight in the limiting case of a large number of single antenna UTs and antennas at the BSs. Simulation results suggest that the asymptotic analysis is accurate for small system dimensions. Our deterministic SR approximation result is applied to numerically study and optimize the effects of antenna tilting in an exemplary sectorized 3D small cell network topology. Significant SR gains are observed with optimal tilt angles and we provide new insights on the optimal parameterization of cellular networks, along with a discussion of several non-trivial effects

Post-processing technique for improved assessment of hard tissues in the submicrometer domain using local synchrotron radiation-based computed tomography

During the last two decades micro-computed tomography has become the method of choice for the non-destructive assessment and quantitative morphometry of hard tissues in three dimensions. With the advent of third-generation synchrotron radiation sources, micro-computed tomography in the micrometer range has become feasible and has been employed to analyze local bone tissue properties. However, owing to limitations regarding the tradeoff between object size and spatial resolution, non-destructive conventional global computed tomography of hard tissues, such as bone, remains unachievable in the submicrometer domain so far. Here, we report on a post-processing technique for the assessment of hard tissues using local synchrotron radiation-based computed tomography, which overcomes this experimental limitatio

Influence of chain topology (cyclic versus linear) on the nucleation and isothermal crystallization of poly(L-lactide) and poly(D-lactide)

In this paper, ring closure click chemistry methods have been used to produce cyclic c-PLLA and c-PDLA of a number average molecular weight close to 10 kg/mol. The effects of stereochemistry of the polymer chains and their topology on their structure, nucleation and crystallization were studied in detail employing Wide Angle X-ray Scattering (WAXS), Small Angle X-ray Scattering (SAXS), Polarized Light Optical Microscopy (PLOM) and standard and advanced Differential Scanning Calorimetry (DSC). The crystal structures of linear and cyclic PLAs are identical to each other and no differences in superstructural morphology could be detected. Cyclic PLA chains are able to nucleate much faster and to produce a higher number of nuclei in comparison to linear analogues, either upon cooling from the melt or upon heating from the glassy state. In the samples prepared in this work, a small fraction of linear or higher molecular weight cycles was detected (according to SEC analyses). The presence of such “impurities” retards spherulitic growth rates of c-PLAs making them nearly the same as those of l-PLAs. On the other hand, the overall crystallization rate determined by DSC was much larger for c-PLAs, as a consequence of the enhanced nucleation that occurs in cyclic chains. The equilibrium melting temperatures of cyclic chains were determined and found to be 5 ºC higher in comparison with values for l-PLAs. This result is a consequence of the lower entropy of cyclic chains in the melt. Self-nucleation studies demonstrated that c-PLAs have a shorter crystalline memory than linear analogues, as a result of their lower entanglement density. Successive self-nucleation and annealing (SSA) experiments reveal the remarkable ability of cyclic molecules to thicken, even to the point of crystallization with extended collapsed ring conformations. In general terms, stereochemistry had less influence on the results obtained in comparison with the dominating effect of chain topology.“UPV/EHU Infrastructure: INF 14/38”; “Mineco/FEDER: SINF 130I001726XV1/Ref: UNPV13–4E–1726” and “Mineco MAT2014-53437-C2-P”, 'Ministerio de Economia y Competitividad (MINECO), code: MAT2015-63704-P (MINECO/FEDER, UE) and by the Eusko Jaurlaritza (Basque Government), code: IT-654-13. O.C acknowledges financial support from the European Commission and Région Wallonne FEDER program (Materia Nova) and OPTI²MAT program of excellence, by the Interuniversity Attraction Pole Program (P7/05) initiated by the Belgian Science Policy office and by the FNRS-FRFC. OC is Research Associate of the F.R.S.-FNRS. Organic Synthesis and Mass Spectrometry Laboratory thanks F.R.S.-FNRS for the financial support for the acquisition of the Waters QToF Premier and Synapt-G2Si mass spectrometers and for continuing support. Finally, all authors would like to acknowledge Research and Innovation Staff Exchange (RISE) H2020-MSCA-RISE-2017-778092, project BIODEST for promoting cooperation between the Mons team and the UPV/EHU team

Differential effects of bone structural and material properties on bone competence in C57BL/6 and C3H/He inbred strains of mice

The femoral neck is a relevant and sensitive site for studying the degree of osteopenia. Engineering principles predict that bone structural parameters, like cross-sectional geometry, are important determinants of bone mechanical parameters. Mechanical parameters are also directly affected by the material properties of the bone tissue. However, the relative importance of structural and material properties is still unknown. The aim of this study was to compare bone competence and structural parameters between a murine strain showing a low bone mass phenotype, C57BL/6 (B6), and another one showing a high bone mass phenotype, C3H/He (C3H), in order to better determine the role of bone structure and geometry in bone failure behavior. Murine femora of 12- and 16-week-old B6 and 12- and 16-week-old C3H inbred strains were mechanically tested under axial loading of the femoral head. In order to assess the structural properties, we performed three-dimensional morphometric analyses in five different compartments of the mouse femur using micro-computed tomography. The mechanical tests revealed that B6 femora became stiffer, stronger, and tougher at 12-16weeks, while bone brittleness stayed constant. C3H bone stiffness increased, but strength remained constant, work to failure decreased, and bone became more brittle. These age effects indicated that B6 did not reach peak bone properties at 16weeks of age and C3H did reach maximal skeletal biomechanical properties before 16weeks of age. Our investigations showed that 83% of the strength of the femoral neck in the B6 strain was explained by cortical thickness at this location; in contrast, in C3H none of the mechanical properties of the femoral neck was explained by bone structural parameters. The relative contributions of bone structural and material properties on bone strength are different in B6 and C3H. We hypothesize that these different contributions are related to differences at the ultrastructural level of bone that affect bone failur

Vergleichende ökonomisch-ökologische Analyse von biologisch und konventionell wirtschaftenden Betrieben in Luxemburg („öko-öko“)

International gibt es zahlreiche vergleichende Untersuchungen von ökonomischen oder ökologischen Leistungen von biologisch und konventionell wirtschaftenden Betrieben (Baumgartner et al., 2010; Offermann and Nieberg, 2000; Olesen et al., 2006). Dabei werden meist aber entweder ökonomische oder ökologische Wirkungen untersucht. Studien, die beide Aspekte zu einer übergreifenden Sichtweise vereinen, sind rar (Schader, 2009). Dabei sind gerade solche integrierte Studien aus agrarpolitscher Sicht höchst relevant. Denn bei der Gestaltung der Gemeinsamen Agrarpolitik (GAP) auf Mitgliedsstaatenebene spielt die Frage der Ausrichtung der Maßnahmen eine zentrale Rolle. Die Pläne zur ländlichen Entwicklung und die darin beinhalteten Agrarumweltprogramme bilden die 2. Säule der GAP, die während der letzten Jahre im Vergleich zur ersten Säule finanziell an Bedeutung gewann. Eine dieser Maßnahmen ist die Flächen- und Umstellungsförderung des biologischen Landbaus, welche in allen Mitgliedsstaaten implementiert wird. Während die Effektivität der Maßnahme in der Erbringung von Umweltleistungen wenig umstritten ist, streiten sich Ökonomen, ob der biologische Landbau diese Umweltleistungen auch kostengünstig erbringen kann (Dabbert, 2002). Kürzlich zeigte Schader (2009), dass hier keine grundsätzlichen Vorbehalte vorgebracht werden müssen, die Effizienz aber regions- und länderspezifisch evaluiert werden sollte. In der Politikevaluation spricht man hier von sogenannten „targeting and tailoring“ (OECD, 2007) der Maßnahmen. Auch in Luxemburg, einem Land in dem die Entwicklung des biologischen Landbaus bisher vergleichsweise schleppend voranging, ist diese Frage von agrarpolitischer Relevanz. Gerade im Zusammenhang des 2009 ins Leben gerufenen „Aktionsplan für biologische Landwirtschaft Luxemburg“ stellt sich die Frage, zu welchen Kosten die biologisch wirtschaftenden Betriebe Umweltleistungen erfüllen und ob diese Zahlungen angemessen sind. Eine derartige Evaluationsstudie ist bisher in Luxemburg nicht durchgeführt worden. Die vorliegende Studie versucht diese Wissenslücke zu schließen. Dabei wird das Ziel verfolgt, die ökologischen Leistungen und monetären Kosten der biologisch wirtschaftenden Betriebe in Luxemburg vergleichbaren konventionellen Betrieben gegenüberzustellen. Daraus sollen Aussagen über die ökologische Effektivität und die ökonomische Effizienz der biologischen Wirtschaftsweise in Luxemburg abgeleitet werden. In dem Projekt „öko-öko“ werden ökologische Wirkungen von Biobetrieben und konventionellen Betrieben in Luxemburg verglichen. Zusätzlich wird die betriebswirtschaftliche Situation und die Förderung der verschiedenen Betriebe beleuchtet. Daraufhin werden die ökonomischen und ökologischen Größen miteinander in Beziehung gesetzt, um Erkenntnisse für eine Optimierung der Effektivität und Effizienz der Förderung der Biobetriebe in Luxemburg zu gewinnen. Dazu wird zunächst eine Übersicht über die vorhandene Literatur gegeben (Kapitel 2). In Kapitel 3 wird der methodische Zugang erläutert, der für diese Studie gewählt wurde und die Datengrundlage wird kurz beschrieben. Dies beinhaltet auch eine kurze Analyse der Betriebsstruktur der Stichprobe der analysierten Betriebe. Danach werden die ökologischen (Kapitel 4) und ökonomischen (Kapitel 5) Parameter analysiert und diskutiert. Kapitel 6 analysiert die Kosteneffizienz der Zahlungen an biologisch wirtschaftende Betriebe. In Kapitel 7 werden Schlussfolgerungen aus den Ergebnissen der Studie für die Wissenschaft und Agrarpolitik abgeleitet