Mechanical behaviour in compression loading of 2D-composite materials made of carbon fabrics and a ceramic matrix

2D-carbon-carbon/ceramic composites, made from a 2D-carbon-carbon (2D-C-C) porous preform infiltrated with BN, SiC, TiC or B₄C, are mechanically characterized under compression loading in directions parallel or orthogonal to the carbon fabric layers. Three types of behaviour are observed: non-linear and time dependent behaviour, a quasi-linear domain and a pseudo-plastic behaviour related to damaging mechanisms. Underp-compression, the variations of the Young modulus as a function of compacity obey a parabolic or linear law depending on whether the material is weakly or highly densified. Undero-compression, an exponential law is observed whatever the densification degree. The variations of failure strength compacity follow similar laws. Phenomenological models are given which depict quite well the mechanical behaviours of the composites. Undero-compression, failure occurs as the result of damaging mechanisms taking place within the inter-layer ceramic bridges binding the fabric layers together. Underp-compression, a transition is observed, from interlayer delamination to intralayer failure, for a critical compacity of about 0.85 provided the infiltrated ceramic is strong enough (i.e. for SiC and TiC). Such a transition is assumed to also occur for 2D-C-C/B ₄ ^– C composites. On the contrary, for weak ceramic matrices (e.g. BN), failure inp-compression always occurs by delamination. The results suggest that the composite toughness could be increased by an optimization of the composite microstructure.     

Share with strangers: Privacy bubbles as user-centered privacy control for mobile content sharing applications

A continually increasing number of pictures and videos is shared in online social networks. Current sharing platforms, however, only offer limited options to define who has access to the content. Users may either share it with individuals or groups from their social graph, or make it available to the general public. Sharing content with users to which no social ties exist, even if they were physically close to the places where content was created and witnessed the same event, is however not supported by most existing platforms. We thus propose a novel approach to share content with such users based on so-called privacy bubbles. Privacy bubbles metaphorically represent the private sphere of the users and automatically confine the access to the content generated by the bubble creator to people within the bubble. Bubbles extend in both time and space, centered around the collection time and place, and their size can be adapted to the user's preferences. We confirm the user acceptance of our concept through a questionnaire-based study with 175 participants, and a prototype implementation shows the technical feasibility of our scheme.     

A new framework for evaluating potential risk of back disorders due to whole body vibration and repeated mechanical shock

A number of studies have examined the potential relationship between exposure to occupational vibration and low back pain associated with operation of vehicles. Only a handful of studies, however, have attempted to differentiate between the relative contributions of the steady state and transient mechanical shock components (the latter also being known as 'jarring and jolting', 'high acceleration event', 'multiple shocks' and 'impact') of the vibration exposure. The primary objective of this paper is to present a review of current studies that examine mechanical shock, present a case for the importance of evaluating both steady state and mechanical shock components and propose a new framework for evaluating the health effects due to occupational vibration exposure. A computerized bibliographical search of several databases was performed with special reference to the health effects of mechanical shock in relation to lower back disorders. Based on the analysis, eight experimental studies and nine epidemiological studies with relevance to exposure to 'mechanical shock' were identified. These studies suggested that rough vehicle rides are prevalent and that repeated exposure to mechanical shock may increase the risk of lower back pain. There is an urgent need for assessing the health effects of mechanical shocks in epidemiological studies. In particular, the new ISO 2631-5: International Organization for Standardization 2004 standard for shock exposure assessment should be evaluated with regard to musculoskeletal health effects.     

Marking algorithms for service differentiation of TCP traffic

Class-based service architectures for quality-of-service (QoS) differentiation typically provide loss, throughput, and delay differentiation. However, proposals for class-based service differentiation generally do not account for the needs of TCP traffic, which are characterized by a coupling of packet losses and achievable throughput. Ignoring this coupling may result in poor service differentiation at the microflow level. This paper shows how Explicit Congestion Notification (ECN) can be used to achieve service differentiation for TCP traffic classes at the microflow level. We present a traffic-marking algorithm for routers, which, if used in conjunction with ECN, regulates the transmission rate of TCP sources in such a way that packet drops due to buffer overflows are avoided. We demonstrate how the algorithm can be integrated in a service architecture with absolute and proportional QoS guarantees. Simulation results illustrate the effectiveness of the presented algorithms at avoiding packet losses and regulating traffic for meeting service guarantees, and provide a comparison with other algorithms proposed in the literature.     

Pathophysiological In Vitro Profile of Neuronal Differentiated Cells Derived from Niemann-Pick Disease Type C2 Patient-Specific iPSCs Carrying the NPC2 Mutations c.58G>T/c.140G>T

Niemann-Pick type C2 (NP-C2) disease is a rare hereditary disease caused by mutations in the NPC2 gene. NPC2 is a small, soluble protein consisting of 151 amino acids, primarily expressed in late endosomes and lysosomes (LE/LY). Together with NPC1, a transmembrane protein found in these organelles, NPC2 accomplishes the exclusion of cholesterol; thus, both proteins are essential to maintain cellular cholesterol homeostasis. Consequently, mutations in the NPC2 or NPC1 gene result in pathophysiological accumulation of cholesterol and sphingolipids in LE/LY. The vast majority of Niemann-Pick type C disease patients, 95%, suffer from a mutation of NPC1, and only 5% display a mutation of NPC2. The biochemical phenotype of NP-C1 and NP-C2 appears to be indistinguishable, and both diseases share several commonalities in the clinical manifestation. Studies of the pathological mechanisms underlying NP-C2 are mostly based on NP-C2 animal models and NP-C2 patient-derived fibroblasts. Recently, we established induced pluripotent stem cells (iPSCs), derived from a donor carrying the NPC2 mutations c.58G>T/c.140G>T. Here, we present a profile of pathophysiological in vitro features, shared by NP-C1 and NP-C2, of neural differentiated cells obtained from the patient specific iPSCs. Profiling comprised a determination of the NPC2 protein level, detection of cholesterol accumulation by filipin staining, analysis of oxidative stress, and determination of autophagy. As expected, the NPC2-deficient cells displayed a significantly reduced amount of NPC2 protein, and, accordingly, we observed a significantly increased amount of cholesterol. Most notably, NPC2-deficient cells displayed only a slight increase of reactive oxygen species (ROS), suggesting that they do not suffer from oxidative stress and express catalase at a high level. As a site note, comparable NPC1-deficient cells suffer from a lack of catalase and display an increased level of ROS. In summary, this cell line provides a valuable tool to gain deeper understanding, not only of the pathogenic mechanism of NP-C2, but also of NP-C1.     

Time domain simulation of skin- and proximity-effect in multiconductor transmission lines

Contents A new method of modeling the skin- and proximity-effect within transmission lines is presented. This technique is used in connection with an algorithm for a fast time domain simulation of the signal propagation in lossy interconnect systems. The frequencydependence of the line parameters is taken automatically into consideration by the chosen approach and does not need to be known in advance. In addition the simulation of line systems in a nonlinear circuit environment (such as digital circuits) is possible, since the algorithm operates in the time domain. The validity of the computed results in the time domain has been proven by a comparison with results gained from frequency domain simulations. Simulation results are given for different planar transmission line systems.

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Simulation des Skin- und Proximity-Effekts in Leitungssystemen im Zeitbereich

Übersicht Eine neue Methode der Modellierung des Skin- und Proximity-Effekts in Leitungssystemen wird vorgestellt. Diese Technik wird in Verbindung mit einem Algorithmus, zur schnellen Zeitbereichs-Simulation der Signalausbreitung auf verlustbehafteten Leitungssystemen verwendet. Die Frequenzabhängigkeit der Leitungsparameter wird bei dem verwendeten Ansatz automatisch berücksichtigt und muß nicht von vornherein bekannt sein. DarÜber hinaus ist die Simulation von Leitungssystemen in einer nichtlinearen Schaltungsumgebung (wie z. B. in digitalen Schaltungen) möglich, da der Algorithmus vollständig im Zeitbereich arbeitet. Die Gültigkeit der errechneten Ergebnisse wurde durch einen Vergleich mit entsprechenden Frequenzbereichssimulationen überprüft. Simulationsergebnisse werden für verschiedene Leitungssysteme vorgestellt und diskutiert.

     

Sumixam maximus gen.and sp.nov.,a New Pennsylvanian Species of Archaeorthoptera(Neoptera;Indiana,USA)

A new Mazon-Creek-type fossil specimen is described as Sumixam maximus gen. and sp. nov.,fossil relatives): it exhibits one of the diagnostic character states of this taxon, which is the fusion of CuA (emerging from M + CuA) with CuP, or a branch of it. A more precise taxonomic assignment is out of reach. The new taxon exhibits a fusion of the anterior branch of MA with RP, and a point of divergence of MA and MP located near the point of divergence of CuA (from M + CuA), but lack a branching of CuPa. This unique combination of character states is probably derived with respect to a number of contemporaneous species. Sumixam maximus gen. and sp. nov. is most likely the closest known relative of the panorthopterans, which include all the recent Archaeorthoptera.     

Fluorine‐18 Radiolabeling and Radiopharmacological Characterization of a Benzodioxolylpyrimidine‐based Radiotracer Targeting the Receptor Tyrosine Kinase EphB4

Members of the Eph receptor tyrosine kinase family play essential roles in the pathogenesis of cancer and are therefore promising candidates for molecular imaging by positron emission tomography (PET), for example. In this regard, radiochemical access to novel PET radiotracers derived from potent inhibitors that target the EphB4 kinase domain and which bear a benzodioxolylpyrimidine structural motif was developed. A synthetic route was established for a new fluorine‐18‐containing radiotracer and for the desired precursor based on a high‐affinity benzodioxolylpyrimidine receptor tyrosine kinase inhibitor lead structure. The radiotracer [¹⁸F] 15 was obtained in 16 % radiochemical yield with a specific activity of ～7 GBq μmol^?1 and >95 % radiochemical purity. Due to the implication of EphB4, particularly in the progression, angiogenesis, and metastasis of melanoma, EphB4‐overexpressing human melanoma cells were generated and used as a novel in vitro model for radiopharmacological evaluation of the radiotracer. We demonstrate that the corresponding non‐radioactive reference compound regained its functionality as an inhibitor for both EphB4 receptor tyrosine kinase and Src kinase. EphB4 was significantly inhibited at compound concentrations >1 μM . Cellular uptake studies with [¹⁸F] 15 revealed substantial uptake in both EphB4‐overexpressing and control cells. Moreover, NMRI nu/nu mice bearing both EphB4‐overexpressing tumors and control tumors were used for radiopharmacological characterization by biodistribution studies ex vivo and by dynamic small‐animal PET experiments in vivo. Despite the high metabolic stability of the novel radiotracer observed in vivo, no substantial binding or accumulation in EphB4‐overexpressing and control tumors was observed. Nevertheless, we point out that the approach presented herein gives convenient access to novel ¹⁸F‐labeled benzodioxolylpyrimidines and is a promising strategy for the further development of novel radiotracers for imaging Eph receptor tyrosine kinases in cancer.     

Optimized time alignment algorithm for LC-MS data: correlation optimized warping using component detection algorithm-selected mass chromatograms

Correlation optimized warping (COW) based on the total ion current (TIC) is a widely used time alignment algorithm (COW-TIC). This approach works successfully on chromatograms containing few compounds and having a well-defined TIC. In this paper, we have combined COW with a component detection algorithm (CODA) to align LC-MS chromatograms containing thousands of biological compounds with overlapping chromatographic peaks, a situation where COW-TIC often fails. CODA is a variable selection procedure that selects mass chromatograms with low noise and low background (so-called "high-quality" mass chromatograms). High-quality mass chromatograms selected in each COW segment ensure that the same compounds (based on their mass and their retention time) are used in the two-dimensional benefit function of COW to obtain correct and optimal alignments (COW-CODA). The performance of the COW-CODA algorithm was evaluated on three types of complex data sets obtained from the LC-MS analysis of samples commonly used for biomarker discovery and compared to COW-TIC using a new global comparison method based on overlapping peak area: trypsin-digested serum obtained from cervical cancer patients, trypsin-digested serum from a single patient that was treated with varying preanalytical parameters (factorial design study), and urine from pregnant and nonpregnant women. While COW-CODA did result in minor misalignments in rare cases, it was clearly superior to the COW-TIC algorithm, especially when applied to highly variable chromatograms (factorial design, urine). The presented algorithm thus enables automatic time alignment and accurate peak matching of multiple LC-MS data sets obtained from complex body fluids that are often used for biomarker discovery.     

Systematic review comparing penetrating keratoplasty and deep anterior lamellar keratoplasty for management of keratoconus

Aim

Perception of reduced incidence of graft rejection after deep anterior lamellar keratoplasty (DALK) has attracted many surgeons towards this technique in keratoconus. This review aims to compare the visual, refractive and graft outcomes after penetrating keratoplasty (PK) and DALK for keratoconus.