In this prospective cohort of 1,012 Swiss hospital employees, 3 different assays were used to screen serum for SARS-CoV-2 antibodies. Seropositivity was 1%; the positive predictive values of the lateral-flow immunoassay were 64% (IgG) and 13% (IgM). History of fever and myalgia most effectively differentiated seropositive and seronegative participants.

Endmember modelling on the terrigenous silt fraction of nine marine sediment cores spanning up to 180,000 years reveals the influx of North African dust into the Eastern Mediterranean Sea. The dust grain size modes decrease with transport distance, from >50 µm off the African coast to ca. 30 µm in the Aegean Sea. The dust signal is strongly influenced by hydrological changes in northern Africa. Changes from arid to humid periods are documented in the grain size data of all cores. The climatic signal gets weaker with growing distance from the source and close to large fluvial sediment sources such as the Nile. Frequency and wavelet analyses show a strong orbital precession signal that is known to trigger the migration of the monsoonal rain belt in northern Africa. The influence of climate changes on suborbital time scales on dust influx is less distinct, but Dansgaard-Oeschger interstadials and Heinrich-like events are documented in some cores. In the sediment core closest to the source, three endmembers represent one or more dust sources in northern Africa. With growing distance from the source, the three modes cannot be separated anymore and appear as one multimodal dust endmember.

This paper presents a comparison of chip connections using aerosol jet (AJ) and bond technology on low-cost printed circuit board (PCB) substrates. First, the behavior of the used gap filler material and the used silver ink for AJ technology on PCBs are characterized. In addition to comparing the radio frequency (RF) performance (DC to 67 GHz) of the two technologies, the mechanical stability is also compared. While the AJ technology transitions score above all for their RF performance and the lower requirements (surface finish, pad size, and adhesion) on the PCB, the bonding technology has clear advantages, especially with a different coefficient of thermal expansion values of the substrates to be connected. Finally, the measurement results of a complete package are shown, whereby the chip connection is realized once by means of AJ and once by bonding wires.

The Azerbaijani, Azerbaijanian or Azeri language belongs to the western group of the southwestern, or Oghuz, branch of the Turkic language family and is mainly spoken in Azerbaijan and Iran. Azerbaijani is the official language of the Republic of Azerbaijan and over 80% of its population use it as their first language (Johanson 2010). Among non-Persian languages in Iran, Azerbaijani, with approximately 15–20 million native speakers, has the largest number of speakers (Crystal 2010). In total, more than 50 million people speak Azerbaijani (Khalilzadeh 2013).

Plant invasions in tropical agricultural landscapes have been poorly studied so far. Here, we use plot data collected in 2015 in the La Gamba valley in southern Costa Rica to analyse the spread of two invasive alien species (Hydrilla verticillata, Hedychium coronarium) on the landscape level. In total, we recorded the aquatic H. verticillata, which was locally introduced into the La Gamba valley in 2005, in 26% of all plots (size: 15 m2), while H. coronarium, which occurs along water courses, was recorded in 80% of all plots (size: 25 m2). Generalized Linear Models (GLMs) showed that the habitat type invaded and shading had no significant effect on H. verticillata presence and abundance. However, proximity to the point of local introduction and habitat diversity in the adjacent landscape did positively affect its presence. For H. coronarium, GLMs showed a significant correlation with the invaded habitat type. The probability of H. coronarium presence was highest in herbaceous vegetation and cover was higher compared with other habitats. There was no effect on native plant species richness and cover by H. verticillata, while H. coronarium exerted a negative impact on herbaceous plant species number and, in particular, cover. Hydrilla verticillata is a rather recent addition to the local alien flora, and thus dispersal limitation still restricts its local range. Compared with observed rates of spread in other regions, spread velocity within the first decade of its local presence was low. In contrast, H. coronarium has been locally present for a substantially longer time period. This species encounters suitable habitat conditions in herbaceous vegetation along water courses, where it builds up dense clonal stands which negatively affect herbaceous vegetation. Our results show that while both study species are invasive in Central American lowlands, their local abundance and impacts on native vegetation may differ profoundly.

We present the realization of a cooperative radar system for ranging applications with integrated data-transmission capability. The simultaneous transmission is performed by the radar-hardware without the necessity of additional components or an auxiliary data-link. Therefore, the data are directly embedded in the transmitted chirp of a frequency-modulated continuous-wave radar sensor. A second station, acting as receiver, uses an identical, but unmodulated chirp for down-conversion. The resulting signal then is processed by a non-coherent demodulator setup, extracting the communication data. Measurement results from transmission of messages with different bit-rates are shown. By utilizing existing radar-hardware a transmission rate of up to 256 kbps is possible, without the need of a dedicated transceiver. Additionally, a method to optimize the ranging results by variable distribution of the available signal power between distance-measurement and communication system is presented.

This paper presents a position gauging system of welding joints. While the principle measurement concept was already introduced by Schrattenecker et al. in 2014, here it is focused on different types of practically used welding materials. The sensor used is based on the frequency-modulated continuous-wave principle operating in the W-band. Position estimation (PoE) of different welding geometries is carried out with polarimetric scattering effects introduced by geometrical discontinuities. For the real-time calculation of the signal models a field simulation tool we developed is used. Aside from a variety of geometries, we introduce a geometrical optimization approach that increases the achievable accuracy of the measurement concept. The optimization and PoE of the different welding materials were examined in various simulations and the results were verified by measurements in the laboratory and in an industrial environment. Simulation and measurement were in good agreement.

We present the implementation of a cooperative radar system on a gantry rail crane for distance measurements in an industrial environment. The measurement approach is based on the dual-ramp frequency-modulated continuous-wave principle, using identical sensor-nodes at the endpoints of the range of interest. Pseudo-range information is exchanged via a dedicated data-link between these stations. At the sensor-node a flexible high-performance signal processing and remote management engine is implemented. The system setup is controlled by a single host-PC, which is used as a man–machine interface for configuration of the remotely controlled measurement stations, system surveillance, and visualization of the measurement data. Indoor characterization of the developed hardware is sufficient for an efficient calibration of the system, minimizing distance offsets. On-site measurements at distances up to 1000 m with an accuracy better than 2 cm confirm the performance of the ranging system. Furthermore, the results are verified by simulation.

Revisiting the classical acoustics problem of rectangular side-branch cavities in a two-dimensional duct of infinite length, we use the finite-element method to numerically compute the acoustic resonances as well as the sound transmission and reflection for an incoming fundamental duct mode. To satisfy the requirement of outgoing waves in the far field, we use two different forms of absorbing boundary conditions, namely the complex scaling method and the Hardy space method. In general, the resonances are damped due to radiation losses, but there also exist various types of localized trapped modes with nominally zero radiation loss. The most common type of trapped mode is antisymmetric about the duct axis and becomes quasi-trapped with very low damping if the symmetry about the duct axis is broken. In this case a Fano resonance results, with resonance and antiresonance features and drastic changes in the sound transmission and reflection coefficients. Two other types of trapped modes, termed embedded trapped modes, result from the interaction of neighbouring modes or Fabry–Pérot interference in multi-cavity systems. These embedded trapped modes occur only for very particular geometry parameters and frequencies and become highly localized quasi-trapped modes as soon as the geometry is perturbed. We show that all three types of trapped modes are possible in duct–cavity systems and that embedded trapped modes continue to exist when a cavity is moved off centre. If several cavities interact, the single-cavity trapped mode splits into several trapped supermodes, which might be useful for the design of low-frequency acoustic filters.

In contrast to completely open systems, laterally confined domains can sustain localized, truly trapped modes with nominally zero radiation loss. These discrete resonant modes cannot be excited linearly by the continuous propagating duct modes due to symmetry constraints. If the symmetry of the geometry is broken the trapped modes become highly localized quasi-trapped modes which can interfere with the propagating duct modes. The resulting narrowband Fano resonances with resonance and antiresonance features are a generic phenomenon in all scattering problems with multiple resonant pathways. This paper deals with the classical scattering of acoustic waves by various obstacles such as hard-walled single and multiple circular cylinders or rectangular and wedge-like screens in a two-dimensional duct without mean flow. The transmission and reflection coefficients as well as the (complex) resonances are computed numerically by means of the finite-element method in conjunction with two different absorbing boundary conditions, namely the complex scaling method and the Hardy space method. The results exhibit the typical asymmetric Fano line shapes near the trapped-mode resonances if the symmetry of the geometry is broken.

Two photon photopolymerization (2PP) is a new and modern method in solid freeform fabrication. 2PP allows the fabrication of sub-micron structures from a photopolymerizable resin. By the use of near-infrared (NIR) lasers it is possible to produce 3D structures with a spatial feature resolution as good as 200 nm. This technique can be used in polymer-based photonic and micro-electromechanical systems (MEMS), for 3D optical data storage or for the inscription of optical waveguides based on a local refractive index change upon laser exposure. Since the 2PP only takes place inside the focus of the laser beam, complex 3D-structures can be in-scri-bed into a suitable matrix material.

In the presented work, 2PP is used to write optical waveguides into a prefabricated mechanically flexible polydimethylsiloxane matrix. The waveguides were structured by selectively irradiating a polymer network, which was swollen by a monomer mixture. The monomer was polymerized by two photon photopolymerization and the uncured monomer was removed by evaporation at elevated temperatures. This treatment led to a local change in refractive index in the order of Δn = 0.02, which was significantly above the industrial requirement of Δn = 0.003. The measured optical losses were around 2.3dB/cm. Since all unreacted monomers were removed by eva-po-ration, the final waveguide was stable up to temperatures of more than 200°C.

In a second approach highly porous sol-gel materials (based on tetramethoxysilane (TMOS) as precursor and the surfactant cetylpyridinium chloride monohydrate as structural temp-late) were utilized as matrix materials. The precursor was organically modified with poly(ethylene glycol) spacers in order to increase the toughness and thus facilitate the fabrication of transparent porous monoliths and flexible films. The pores of the sol-gel-derived matrix were filled with acrylate-based monomers of high refractive index and after selective irradiation using 2PP waveguides (Δn = 0.015) could be written into the material.