New Simple Procedure for the Computation of the Multimode Admittance or Impedance Matrix of Planar Waveguide Junctions

Much effort has been devoted in the past to the development of electromagnetic simulation algorithms for wave- guide junctions that could at the same time include higher-order mode interactions and lead to computationally efficient codes. Even though this is indeed a classical subject, there is still a strong interest in this area as waveguide systems become increas- ingly complex, and ever shorter development and manufacturing times are required. In this paper a simple method is described for the evaluation of the multimode network representation of planar waveguide junctions in terms of admittance or impedance parameters. The key feature of the method is that it starts from the wanted final results, the equivalent network representation, in order to obtain an analytic expression for the evaluation of the relevant matrix elements. The procedure is based on general network theory and is equivalent to ideally measuring directly the value of the admittance or impedance elements. In this paper the evaluation procedure is fully described. Measured results of actual hardware are then compared with simulations indicating that the codes developed are indeed very accurate as well as computationally very efficient.Agencia Espacial Europe

Consolidation mechanisms and interfacial phenomena in thermoplastic powder impregnated composites

Thermoplastic powder impregnation of continuous reinforcement filaments is studied in this work, focusing on impregnation mechanisms and interfacial phenomena. Various existing techniques to mingle powdered resins to continuous filaments are reviewed; a powder impregnation line designed at the Laboratoire de Technologie des Composites et Polymères (LTC) is presented. Two important types of powder coated towpregs are addressed: FIT bundles (Fibres Imprégnées de Thermoplastique) of powder loaded fibres enclosed in a thin resin sheath, and molten powder towpregs in which the particles are fixed to the fibres in an oven by melting the resin. The impregnation mechanisms of powder coated towpregs are examined. The formation of resin bridges between adjacent fibres is first investigated using a hot stage placed on a microscope. In the absence of externally applied pressure, impregnation is driven by surface energy effects. The driving forces leading to the spreading of the bridge along the fibres are analysed at two levels: at a macroscopic scale, characterising the capillary pressure governing the flow of a liquid into a porous solid, and at a micro-mechanical level analysing the capillary forces in a system defined by a liquid drop in contact with two solid particles. To achieve impregnation at a satisfactory rate, however, it is essential to apply external pressure to most thermoplastic systems during consolidation. An analytical model for the consolidation stage of unidirectional-powder coated towpregs is presented, placing in context effects due to surface energy, viscous flow, externally applied pressure and fibre bed elasticity. The initial conditions for the computation depend on the impregnation technique used. FIT bundles, and molten powder towpregs are examined. The model is compared at each stage to experimental data obtained by compression moulding powder impregnated towpregs in an instrumented hydraulic press using a closed matched-die mould. This model optimises the processing conditions of a given fibre-resin system to achieve a void free laminate with improved mechanical properties. Mechanical properties can further be improved by optimising interfacial adhesion between resin and fibres. Surface energy effects on composite mechanical properties are studied, relating thermodynamic quantities to adhesive strength. A criterion for optimum adhesion is proposed. The influence of the thermodynamic adhesion between fibres and matrix on the mechanical properties of a continuous fibre reinforced composite is studied for two systems: carbon fibre reinforced poly(ether-ether-ketone) and glass fibre reinforced poly(ether-imide). The fibre surface is modified chemically and characterised by optical contact angle measurements of molten resin droplets on the fibres. Unidirectional fibre reinforced laminates are manufactured. Transverse flexural strength is reported as a function of thermodynamic wetting parameters. Adhesion at the fibre-resin interface is found to correlate with both composite strength and void morphology within the laminate after consolidation. Full potential of powder coated towpregs as a precursor for compression moulded composite parts can be reached by the fabrication of drapeable textile preforms. Corrugated sheets are processed usign FIT woven fabrics. Mechanical property measurements show that complex high quality parts can be processed at high rates using powder coated towpregs

Broadband ac conductivity of conductor-polymer composites

The electrical conductivity of a composite model system formed by highly structured carbon black (CB) filled, within an amorphous polymer, poly(ethylene terephtalate) composite is studied. The dc conductivity as a function of CB content follows a scaling law of the type σ∝(p−pc)t yielding for the percolation concentration, pc=0.011 and for the exponent, t=2.17. The analysis of the temperature dependence of the conductivity suggests that for temperatures larger than 45 K, conduction can be ascribed to thermal fluctuation induced tunneling of the charge carriers through the insulating layer of polymer separating two CB aggregates. At lower temperatures, conductivity becomes temperature independent, which is typical of conventional tunneling. The frequency dependence of the conductivity is also studied between dc and 109 Hz. By the introduction of a shift factor ap, a procedure for the construction of a master curve based on a “time-length equivalence principle” is proposed. Finally, a model is introduced to describe the frequency dependence of the conductivity of CB-filled composites based on the behavior of charge carriers placed in a fractal object

Determination of the largest clast sizes of tephra deposits for the characterization of explosive eruptions: a study of the IAVCEI commission on tephra hazard modelling

The distribution of clasts deposited around a volcano during an explosive eruption typically contoured by isopleth maps provides important insights into the associated plume height, wind speed and eruptive style. Nonetheless, a wide range of strategies exists to determine the largest clasts, which can lead to very different results with obvious implications for the characterization of eruptive behaviour of active volcanoes. The IAVCEI Commission on Tephra Hazard Modelling has carried out a dedicated exercise to assess the influence of various strategies on the determination of the largest clasts. Suggestions on the selection of sampling area, collection strategy, choice of clast typologies and clast characterization (i.e. axis measurement and averaging technique) are given, mostly based on a thorough investigation of two outcrops of a Plinian tephra deposit from Cotopaxi volcano (Ecuador) located at different distances from the vent. These include: (1) sampling on a flat paleotopography far from significant slopes to minimize remobilization effects; (2) sampling on specified-horizontal-area sections (with the statistically representative sampling area depending on the outcrop grain size and lithic content); (3) clast characterization based on the geometric mean of its three orthogonal axes with the approximation of the minimum ellipsoid (lithic fragments are better than pumice clasts when present); and (4) use of the method of the 50th percentile of a sample of 20 clasts as the best way to assess the largest clasts. It is also suggested that all data collected for the construction of isopleth maps be made available to the community through the use of a standardized data collection template, to assess the applicability of the new proposed strategy on a large number of deposits and to build a large dataset for the future development and refinement of dispersal model

MatD^3^: A Database and Online Presentation Package for Research Data Supporting Materials Discovery, Design, and Dissemination

The discovery of new materials as well as the determination of a vast set of materials properties for science and technology is a fast growing field of research, with contributions from many groups worldwide. Materials data from individual research groups is traditionally disseminated by means of loosely interconnected, peer-reviewed publications. MatD3 is an open-source, dedicated database and web application framework designed to store, curate and disseminate experimental and theoretical materials data generated by individual research groups or research consortia. A research group can set up its own instance of MatD3 and publish scientific results or simply use an existing online MatD3 instance. Disseminating research data in this form enables broader access, reproducibility, and repurposing of scientific products. MatD3 is a general purpose database that does not focus on any specific level of theory or experimental method. Instead, the focus is on storing and making accessible the data and making it straightforward to curate them

Multi-strain probiotic improves subjective sleep quality with no impact on body composition, hemodynamics, and physical activity

The objective of the study was to examine the impact of a multi-strain probiotic (MSP) on sleep, physical activity, and body composition changes. We used a randomised, double-blind, placebo-controlled approach with 70 healthy men and women (31.0 ± 9.5 years, 173.0 ± 10.4 cm, 73.9 ± 13.8 kg, 24.6 ± 3.5 kg/m2) supplemented daily with MSP (4 × 109 live cells Limosilactobacillus fermentum LF16, Lacticaseibacillus rhamnosus LR06, Lactiplantibacillus plantarum LP01, and Bifidobacterium longum 04; Probiotical S.p.A., Novara, Italy) or placebo (PLA). In response to supplementation (after 0, 2, 4, and 6 weeks of supplementation) and 3 weeks after stopping supplementation, participants had subjective (Pittsburgh Sleep Quality Index, PSQI) and objective sleep indicators, body composition, daily physical activity and resting hemodynamics assessed. Subjective sleep quality indicators using the PSQI (sleep latency, sleep disturbance, and global PSQI score) improved (P \u3c 0.05) at various time points with MSP supplementation. Systolic blood pressure in PLA increased (P \u3c 0.05) after 6 weeks of supplementation with no change in MSP. No changes (P \u3e 0.05) in sleep (hours asleep, minutes awake, number of times awake) or physical activity (step count, minutes of sedentary activity, total active minutes) metrics assessed by the wearable device were observed. Additionally, no changes in resting heart rate, diastolic blood pressure, and body composition were discerned. In conclusion, MSP supplementation improved the subjective ability to fall asleep faster and disturbances experienced during sleep, which resulted in improved overall sleep quality as assessed by the PSQI. No differences in other sleep indicators, physical activity, hemodynamics, and body composition were observed during or following MSP supplementatio

Can in vitro studies aid in the development and use of antiseizure therapies? A report of the ILAE/AES Joint Translational Task Force

In vitro preparations (defined here as cultured cells, brain slices, and isolated whole brains) offer a variety of approaches to modeling various aspects of seizures and epilepsy. Such models are particularly amenable to the application of anti-seizure compounds, and consequently are a valuable tool to screen the mechanisms of epileptiform activity, mode of action of known anti-seizure medications (ASMs), and the potential efficacy of putative new anti-seizure compounds. Despite these applications, all disease models are a simplification of reality and are therefore subject to limitations. In this review, we summarize the main types of in vitro models that can be used in epilepsy research, describing key methodologies as well as notable advantages and disadvantages of each. We argue that a well-designed battery of in vitro models can form an effective and potentially high-throughput screening platform to predict the clinical usefulness of ASMs, and that in vitro models are particularly useful for interrogating mechanisms of ASMs. To conclude, we offer several key recommendations that maximize the potential value of in vitro models in ASM screening. This includes the use of multiple in vitro tests that can complement each other, carefully combined with in vivo studies, the use of tissues from chronically epileptic (rather than naïve wild-type) animals, and the integration of human cell/tissue-derived preparations

A randomized controlled trial to examine the impact of a multi-strain probiotic on self-reported indicators of depression, anxiety, mood, and associated biomarkers

Objective: To examine the efficacy of supplementing with a multi-strain probiotic (MSP) on changes associated with mood, anxiety, and neurotransmitter levels. Method: In a randomized, double-blind, placebo-controlled fashion, 70 healthy men and women (31.0  ±  9.5  years, 173.0  ±  10.4  cm, 73.9  ±  13.8  kg, 24.6  ±  3.5  kg/m2 ) supplemented with a single capsule of MSP (a total daily dose of 4 × 109 colony forming units [CFU] comprised of a 1 × 109   CFU dose from each of the following strains: Limosilactobacillus fermentum LF16, Lacticaseibacillus rhamnosus LR06, Lactiplantibacillus plantarum LP01, and Bifidobacterium longum 04, Probiotical S.p.A., Novara, Italy) or a maltodextrin placebo (PLA). After 0, 2, 4, and 6  weeks of supplementation and 3  weeks after ceasing supplementation, study participants completed the Beck Depression Inventory (BDI-II), State-Trait Anxiety Inventory (STAI), and Leiden Index of Depression Sensitivity (LEIDS-R) questionnaires and had plasma concentrations of cortisol, dopamine, serotonin, and C-reactive protein determined. Results: BDI, STAI, and total LEIDS-R scores were reduced from baseline (p  \u3c  0.05) with MSP supplementation after 4 and 6  weeks of supplementation and 3  weeks after supplementation while no changes (p  \u3e  0.05) were reported in PLA. When compared to PLA, MSP scores for state anxiety, trait anxiety, and LEIDS-R (hopeless, aggression, rumination, and total score) were significantly lower (p  \u3c  0.05) after supplementation. Plasma serotonin concentrations in MSP were increased from baseline after 6  weeks of supplementation and 3  weeks after ceasing supplementation. No changes (p  \u3e  0.05) in plasma dopamine, C-reactive protein, or cortisol concentrations were observed between groups. Conclusion: MSP supplementation resulted in widespread improvements in several questionnaires evaluating mood, anxiety, and depression in young, healthy men and women. MSP supplementation increased serotonin increased after 6  weeks of MSP supplementation with no change in dopamine, C-reactive protein, or cortiso