Experimental research activity on additive manufacturing of microwave passive waveguide components

All metal passive waveguide components are key building-blocks of several RF systems used for telecommunications, navigation, imaging, radio-astronomy, and cosmology. The accurate manufacture of these devices in Additive Manufacturing (AM) technologies can open the way to a high integration level of microwave functionalities with a significant cost and mass reduction. In the paper, after an introduction on the most common AM technologies with particular detail on selective laser melting (SLM) and stereo-lithography apparatus (SLA) processes, the results on the on-going research activity are discussed. Measured performances are reported for AM prototypes of Ku/K/Ka-band rectangular and circular waveguide lines, microwave filters and a smooth wall horn

Characteristic Mode Analysis of Multi-Octave Asymmetric Dipoles

This paper discusses the impedance and front-to-back ratio performance of asymmetric dipoles. These parameters are very important when the antennas are placed over a conductive ground plane and should operate over multi-octave frequency bands. The operation of these antennas is usually described relying on analogies with more classical structures such as symmetric dipoles and tapered slot antennas. To provide a solid theoretical background to this intuition, this work presents the application of characteristic mode analysis to multi-octave dipole antennas. Firstly, a brief review of the main characteristic mode content is presented. Then, characteristic mode analysis is applied to three antenna concepts to emphasize how their geometry impacts on the relevant figures of merit. This allows to draw some conclusions on the achievable performance by different designs

Rescue leadless pacemaker implantation in a pacemaker-dependent patient with congenital heart disease and no alternative routes for pacing

Congenital heart disease patients are considered a unique group of patients regarding their high risk of conduction abnormalities, whether de novo or surgically induced, and the challenges in both implantation and management of device related complications. We present a case of a pacemaker-dependent patient with congenital heart disease who experienced complications of both previous epicardial and transvenous pacing which rendered her a non-suitable candidate of both routes

Maternal Risk of Breeding Failure Remained Low throughout the Demographic Transitions in Fertility and Age at First Reproduction in Finland

Radical declines in fertility and postponement of first reproduction during the recent human demographic transitions have posed a challenge to interpreting human behaviour in evolutionary terms. This challenge has stemmed from insufficient evolutionary insight into individual reproductive decision-making and the rarity of datasets recording individual long-term reproductive success throughout the transitions. We use such data from about 2,000 Finnish mothers (first births: 1880s to 1970s) to show that changes in the maternal risk of breeding failure (no offspring raised to adulthood) underlay shifts in both fertility and first reproduction. With steady improvements in offspring survival, the expected fertility required to satisfy a low risk of breeding failure became lower and observed maternal fertility subsequently declined through an earlier age at last reproduction. Postponement of the age at first reproduction began when this risk approximated zero–even for mothers starting reproduction late. Interestingly, despite vastly differing fertility rates at different stages of the transitions, the number of offspring successfully raised to breeding per mother remained relatively constant over the period. Our results stress the importance of assessing the long-term success of reproductive strategies by including measures of offspring quality and suggest that avoidance of breeding failure may explain several key features of recent life-history shifts in industrialized societies

Cork : properties, capabilities and applications

Cork is a natural, renewable, sustainable raw material that has been used for many centuries. As a result of this very long term interest, the scientific literature on cork is extensive. The present review focuses on the chemical composition, physical and mechanical properties of cork and on its products and sub-products. The substantial efforts to fully characterise cork, as well as new developments and evolving research, are reviewed, beginning with its histology, growth and morphology (at macro- and microscales). The chemical structure is analysed in detail, covering both the materials that form the wall structure and the low molecular weight, extractable components. The unique properties of cork are discussed and correlated with current knowledge on morphology and chemical structure. Finally, the important industrial applications of cork are reviewed, in the context of research to provide cork with novel, high added-value applications

The large scale polarization explorer (LSPE) for CMB measurements: performance forecast

The measurement of the polarization of the Cosmic Microwave Background (CMB) radiation is one of the current frontiers in cosmology. In particular, the detection of the primordial divergence-free component of the polarization field, the B-mode, could reveal the presence of gravitational waves in the early Universe. The detection of such a component is at the moment the most promising technique to probe the inflationary theory describing the very early evolution of the Universe. We present the updated performance forecast of the Large Scale Polarization Explorer (LSPE), a program dedicated to the measurement of the CMB polarization. LSPE is composed of two instruments: LSPE-Strip, a radiometer-based telescope on the ground in Tenerife-Teide observatory, and LSPE-SWIPE (Short-Wavelength Instrument for the Polarization Explorer) a bolometer-based instrument designed to fly on a winter arctic stratospheric long-duration balloon. The program is among the few dedicated to observation of the Northern Hemisphere, while most of the international effort is focused into ground-based observation in the Southern Hemisphere. Measurements are currently scheduled in Winter 2022/23 for LSPE-SWIPE, with a flight duration up to 15 days, and in Summer 2022 with two years observations for LSPE-Strip. We describe the main features of the two instruments, identifying the most critical aspects of the design, in terms of impact on the performance forecast. We estimate the expected sensitivity of each instrument and propagate their combined observing power to the sensitivity to cosmological parameters, including the effect of scanning strategy, component separation, residual foregrounds and partial sky coverage. We also set requirements on the control of the most critical systematic effects and describe techniques to mitigate their impact. LSPE will reach a sensitivity in tensor-to-scalar ratio of σr < 0.01, set an upper limit r < 0.015 at 95% confidence level, and improve constraints on other cosmological parameters

Fast-growing bio-based materials as an opportunity for storing carbon in exterior walls

Storing carbon in construction products and building components seems a particularly attractive strategy for compensating the initial greenhouse gas (GHG) emissions from production and construction. Typically, in LCA methods, when a sustainable forestry management is assumed, biogenic carbon is not included in the calculation since forest products are considered as carbon neutral due to the full regeneration of biomass in forest at the end of a rotation period. The purpose of this article is to investigate the effect of storing carbon in biogenic materials and lime-based products when they are used as construction materials and left long in a building. Five different alternative exterior walls with different construction technologies are compared. In the first two alternatives (STR and HEM), a significant amount of fast-growing biogenic material is used as thermal insulation, while the third (TIM) represents a typical timber frame structure with mineral insulation. The last two are traditional wall alternatives based on bricks (BRI) and cast concrete (CON) with an additional external thermal insulation composite system (ETICS) in EPS. A model based on a dynamic LCA is adopted to include timing in the calculation. The results, expressed in terms of radiative forcing in the atmosphere, show that storing carbon in fast-growing biogenic materials is much more efficient than in timber elements. The carbon stored in fast-growing biogenic materials is fully captured by crop regrowth only one year after construction, while a longer time is expected for forest products due to the long rotation period required for forest regrowth

Towards a model for circular renovation of the existing building stock: A preliminary study on the potential for CO2 reduction of bio-based insulation materials

In the context of strategies for mitigating the impacts of climate change within European cities, increasing attention is being paid worldwide to the use of urban green infrastructure which, in addition to the potential for improving the quality of the urban environment, allow significant amounts of CO2 to be removed from the air. However, considering the peculiarities of the dense European cities, most of the available surfaces in urban areas are the perimeter walls of buildings of considerable age that are in urgent need of measures to upgrade their energy performance. Based on this premise, this paper investigates the potential for CO2 storage resulting from the application of energy retrofit solutions using biogenic insulating materials. Starting from the analysis of the demand for insulation materials necessary for the energy requalification of the residential existing building stock in 28 European countries, following the renovation target fixed by EU, the research analyses, through the adoption of a dynamic LCA approach, the environmental benefits of bio-based materials compared to traditional solutions. The use of these materials, especially if they are fast-growing - as the study shows - offers several advantages in terms of climate change mitigation by reducing the energy needs and CO2 emissions of the existing building stock and increasing carbon storage capacity within cities. The results of this study are intended to provide a robust database on which to build a model of circular building renovation that takes into account the environmental long-term effects of measures for increasing energy efficiency of buildings