Homeless shelter residents and staff may be at higher risk of SARS-CoV-2 infection. However, SARS-CoV-2 infection estimates in this population have been reliant on cross-sectional or outbreak investigation data. We conducted routine surveillance and outbreak testing in 23 homeless shelters in King County, Washington, to estimate the occurrence of laboratory-confirmed SARS-CoV-2 infection and risk factors during 1 January 2020–31 May 2021. Symptom surveys and nasal swabs were collected for SARS-CoV-2 testing by RT-PCR for residents aged ≥3 months and staff. We collected 12,915 specimens from 2,930 unique participants. We identified 4.74 (95% CI 4.00–5.58) SARS-CoV-2 infections per 100 individuals (residents: 4.96, 95% CI 4.12–5.91; staff: 3.86, 95% CI 2.43–5.79). Most infections were asymptomatic at the time of detection (74%) and detected during routine surveillance (73%). Outbreak testing yielded higher test positivity than routine surveillance (2.7% versus 0.9%). Among those infected, residents were less likely to report symptoms than staff. Participants who were vaccinated against seasonal influenza and were current smokers had lower odds of having an infection detected. Active surveillance that includes SARS-CoV-2 testing of all persons is essential in ascertaining the true burden of SARS-CoV-2 infections among residents and staff of congregate settings.

This paper investigates the aerodynamics of a wing under figure-of-eight flapping motion based on Fluid–Structure Interaction (FSI) Computational Fluid Dynamics (CFD) simulations. The kinematic of a wing under figure-of-eight motion creates a condition with a variable angle-of-attack. The effect of using different angles of attack at an initial condition, namely initial pitch angles, for the wing and the spatial size of the figure-of-eight pattern, namely the input link angle, is investigated. The initial pitch angles input is varied from 0° to 330° in steps of 30°, and the input link angles used are 30°, 45°, and 60°. The Young’s modulus of the wing is 3.4 GPa spanwise, which is the elastic modulus of balsa wood material. In comparison with an initial pitch angle of 0°, the 90° initial pitch angle shows much better flight performance in terms of lift generated and stability. The results show that the maximum average lift coefficient of 0.393 occurs at the 90° initial pitch angle. The maximum lift-induced moment for the 90° initial pitch angle is only 5.55% of the maximum lift induced moment for the 0° initial pitch angle. A higher input link angle generates a greater lift force. The pressure distribution in the vicinity of the wing area and the von Mises stress of the wing are also presented.

Gravitational waves from coalescing neutron stars encode information about nuclear matter at extreme densities, inaccessible by laboratory experiments. The late inspiral is influenced by the presence of tides, which depend on the neutron star equation of state. Neutron star mergers are expected to often produce rapidly rotating remnant neutron stars that emit gravitational waves. These will provide clues to the extremely hot post-merger environment. This signature of nuclear matter in gravitational waves contains most information in the 2–4 kHz frequency band, which is outside of the most sensitive band of current detectors. We present the design concept and science case for a Neutron Star Extreme Matter Observatory (NEMO): a gravitational-wave interferometer optimised to study nuclear physics with merging neutron stars. The concept uses high-circulating laser power, quantum squeezing, and a detector topology specifically designed to achieve the high-frequency sensitivity necessary to probe nuclear matter using gravitational waves. Above 1 kHz, the proposed strain sensitivity is comparable to full third-generation detectors at a fraction of the cost. Such sensitivity changes expected event rates for detection of post-merger remnants from approximately one per few decades with two A+ detectors to a few per year and potentially allow for the first gravitational-wave observations of supernovae, isolated neutron stars, and other exotica.

Here we present the synthesis of porous platinum–palladium macrobeams templated from high aspect ratio Magnus’ salt needle derivatives. The combination of [PtCl4]2− and/or [PdCl4]2− with [Pt(NH3)4]2+ ions results in salt needles ranging from 15 to 300 µm in length. Electrochemical reduction of the salt templates results in porous macrobeams with a square cross-section. Porous side wall texture and elemental composition was controlled with initial platinum to palladium salt ratio. Macrobeam free-standing films exhibited a specific capacitance up to 11.73 F/g and a solvent accessible surface area of 26.6 m2/g. These salt-templated porous platinum–palladium macrobeams offer a promising material for fuel cell catalysis.

TAOS II is a next-generation occultation survey with the goal of measuring the size distribution of the small end of the Kuiper Belt (objects with diameters 0.5–30 km). Such objects have magnitudes r > 30, and are thus undetectable by direct imaging. The project will operate three telescopes at San Pedro Mártir Observatory in Baja California, México. Each telescope will be equipped with a custom-built camera comprised of a focal-plane array of CMOS imagers. The cameras will be capable of reading out image data from 10,000 stars at a cadence of 20 Hz. The telescopes will monitor the same set of stars simultaneously to search for coincident occultation detections, thus minimising the false-positive rate. This talk described the project, and reported on the progress of the development of the survey infrastructure.

The phytotoxicity of soil-applied terbutryn [2-(tert-butylamino)-4-(ethylamino)-6-(methylthio)-s-triazine] to wheat (Triticum aestivum Vill.) was significantly affected by soil moisture and soil temperature. Distribution coefficients (Kd) provided a better indication of the phytotoxicity of terbutryn to wheat than any single measured parameter contributing to herbicide adsorption by the soil. Soil temperatures and soil moisture levels suitable for good plant growth tended to enhance the phytotoxicity of terbutryn. No phytotoxic levels of terbutryn to wheat were detected in Teller sandy loam after 20 weeks of incubation at above 10C and 14% soil moisture by weight. However, phytotoxicity to wheat was observed in air-dry terbutryntreated soil after an incubation period of 20 weeks, regardless of incubation temperature. Significant quantities of terbutryn may remain in the field under dry soil conditions.

Soil columns and soil thin-layer chromatography were used to evaluate the mobility of napropamide [2-(α-naphthoxy)-N,N,-diethylpropionamide] in various soils. The surface-applied herbicide did not move deeper than approximately 6 cm in a Teller sandy loam soil after a water application of 10.2 cm. The Rf values for napropamide and two reference herbicides were in the order of fluometuron [1,1-dimethyl-3-(α,α,α-trifluoro-m-tolyl)urea] > napropamide > terbutryn [2-(tert-butylamino)-4-(ethylamino)-6-(methylthio)-s-triazine]. The mobility of each herbicide was reduced with an increase in clay and organic matter content. Carbon-14 ring labeled napropamide was used to determine the adsorption and desorption characteristics of the herbicide in various soils. The Rf values obtained with napropamide and each soil agreed with the adsorptive characteristics. Small applications of a muck soil to a sand (2%, w/w) significantly increased herbicide adsorption and decreased herbicide desorption.

In this work, we present a reliability and stability study of doped hydrogenated amorphous silicon (n+-a-Si:H) thin-film silicon MEMS resonators. The n+-a-Si:H structural material was deposited using radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) and processed using surface micromachining at a maximum deposition temperature of 110 ºC. n+-a-Si:H resonant bridges can withstand the industry standard of 1011 cycles at high load with no structural damage. Tests performed up to 3x1011 cycles showed a negligible level of degradation in Q during the entire cycling period which in addition shows the high stability of the resonator. In measurements both in vacuum and in air a resonance frequency shift which is proportional to the number of cycles is established. This shift is between 0.1 and 0.4%/1x1011 cycles depending on the applied VDC. When following the resonance frequency in vacuum during cyclic loading, desorption of air molecules from the resonator surface is responsible for an initial higher resonance frequency shift before the linear dependence is established.

The fabrication and characterization of thin-film silicon bulk resonators processed on glass substrates is described. The microelectromechanical (MEMS) structures consist of surface micromachined disk resonators of phosphorous-doped hydrogenated amorphous silicon (n+-a-Si:H) deposited by radiofrequency plasma enhanced chemical vapour deposition (RF-PECVD). The devices are driven into resonance by electrostatic actuation and the vibrational displacement is detected optically. Resonance frequencies up to 30 MHz and quality factors in the 103-104 range in vacuum were measured. A high density of modes that increases with resonator diameter was observed. Membrane-like vibrational modes show good agreement with finite element simulations. The effect of geometrical dimensions of the disks on the resonance frequency was also studied. When operated in air higher harmonic modes show increasing quality factors.

AlGaN/GaN high electron mobility transistors (HEMTs) with a polarized Polyvinylidene difluoride (PVDF) film coated on the gate area exhibited significant changes in channel conductance upon exposure to different ambient pressures. The PVDF thin film was deposited on the gate region with an inkjet plotter. Next, the PDVF film was polarized with an electrode located 2 mm above the PVDF film at a bias voltage of 10 kV and 70 °C. Variations in ambient pressure induced changes in the charge in the polarized PVDF, leading to a change of surface charges on the gate region of the HEMT. Changes in the gate charge were amplified through the modulation of the drain current in the HEMT. By reversing the polarity of the polarized PVDF film, the drain current dependence on the pressure could be reversed. Our results indicate that HEMTs have potential for use as pressure sensors.

Chloride ion concentration can be used as a biomarker for the level of pollen exposure in allergic asthma, chronic cough and airway acidification related to respiratory disease. AlGaN/GaN high electron mobility transistor (HEMT) with an InN thin film in the gate region was used for real time detection of chloride ion detection. The InN thin film provided surface sites for reversible anion coordination. The sensor exhibited significant changes in channel conductance upon exposure to various concentrations of NaCl solutions. The sensor was tested over the range of 100 nM to 100 μM NaCl solutions. The effect of cations on the chloride ion detection was also studied.

Antibody-functionalized, Au-gated AlGaN/GaN high electron mobility transistors (HEMTs) were used to detect Perkinsus marinus. The antibody was anchored to the gate area through immobilized thioglycolic acid. The AlGaN/GaN HEMT were grown by a molecular beam epitaxy system (MBE) on sapphire substrates. Infected sea waters were taken from the tanks in which Tridacna crocea infected with P. marinus were living and dead. The AlGaN/GaN HEMT showed a rapid response of drain-source current in less than 5 seconds when the infected sea waters were added to the antibody-immobilized surface. The recyclability of the sensors with wash buffers between measurements was also explored. These results clearly demonstrate the promise of field-deployable electronic biological sensors based on AlGaN/GaN HEMTs for Perkinsus marinus detection.

This paper presents the fluorescence detection of DNA hybridization with a surface immobilized probe using an hydrogenated amorphous silicon photosensor. This sensor integrates a SiO2 layer for DNA probe immobilization, a p-i-n amorphous silicon (a-Si:H) photodiode for fluorescence detection and a fluorescence filter of amorphous silicon carbon (a-SiC:H) to cut the excitation light. With this integrated photosensor system, a five order of magnitude difference was obtained in the signal measured at the emission wavelength and that measured at the excitation wavelength for the same incident photon flux. The fluorophore Alexa Fluor 430 was used to label the DNA target molecules and a laser at 405 nm and a photon flux of 5.7×1016 cm−2.s−1 was used as the excitation light source. The detection limit achieved for fluorophores in solution in contact with the device and for fluorophores immobilized on the device surface is 5×10−9 M and 0.4 pmol/cm2, respectively. The fluorescence detection of the DNA target hybridization with a covalently or electrostatically immobilized probe was successfully detected at a surface density of ∼3 pmol/cm2.

The on-chip application of single, sub-ms voltage pulses promotes the immobilization of single stranded DNA (ssDNA) probes from a solution to a chemically functionalized SiO2 surface and as well as the hybridization between ssDNA targets from a solution to covalently immobilized ssDNA probes (E-assisted DNA reactions). Compared to diffusion-based surface reactions (in the absence of the applied electric field), an improvement of several orders of magnitude in the kinetics of the immobilization and hybridization reactions is observed with low amplitude (below 2 V) and short duration (100 ns to 1 ms) voltage pulses. E-assisted DNA reactions are demonstrated using mm-size macroelectrodes and then optimized using μm-size microelectrodes.

We present the design of two biointerfaces on a SiO2 substrate for single stranded DNA (ssDNA) immobilization using either covalent grafting or electrostatic adsorption. The influence of the type of biointerface on the rate of diffusion-limited hybridization reaction with complementary ssDNA from a solution is studied. Patterning of the biointerfacefunctionalization layers and the scaling down of the reaction volumes to µL range is demonstrated. The use of externally applied electric field pulses is shown to accelerate the hybridization reaction kinetics to the sub-ms time scale.