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We present a vision system design for landing an unmanned aerial vehicle on a ship’s flight deck autonomously. The edge information from the international landing target is used to perform line segment detection, feature point mapping and clustering. Then a cascade filtering scheme is applied for target recognition. Meanwhile, the 4 DoF pose of the vehicle with respect to the target is estimated. The vision system has been implemented on the Asctec Pelican quadrotor in conjunction with a state estimator to perform real-time target recognition and tracking. An onboard controller is designed to close the control loop. Experiments show that the vision system is accurate, robust, and capable of dealing with an incomplete landing target, whilst the overall implementation shows the practicability of real-time onboard target tracking and closed-loop control.

Galactic conformity is the phenomenon whereby a galaxy of a certain physical property is correlated with its neighbors of the same property, implying a possible causal relationship. The observed auto correlations of emission-line galaxies (ELGs) from the highly complete DESI One-Percent Survey exhibit a strong clustering signal on small scales, providing clear evidence for the conformity effect of ELGs. Building upon the original subhalo abundance-matching (SHAM) method developed by Gao et al., we propose a concise conformity model to improve the ELG–halo connection. In this model, the number of satellite ELGs is boosted by a factor of ∼5 in the halos whose central galaxies are ELGs. We show that the mean ELG satellite number in such central halos is still smaller than 1 and that the model does not significantly increase the overall satellite fraction. With this model, we can well recover the ELG auto correlations to the smallest scales explored with the current data (i.e., r p > 0.03 Mpc h −1 in real space and at s > 0.3 Mpc h −1 in redshift space), while the cross correlations between luminous red galaxies and ELGs are nearly unchanged. Although our SHAM model has only eight parameters, we further verify that it can accurately describe the ELG clustering in the entire redshift range from z = 0.8 to 1.6. We therefore expect that this method can be used to generate high-quality ELG lightcone mocks for DESI.

Previous works of low-redshift quasar host galaxies have focused on compact quasars and found that their host galaxies are mainly star-forming galaxies. Here, we present a study of host galaxies for quasars with extended morphologies in ground-based optical images. We select a sample of more than 1000 type 1 quasars at redshift 0.1 < z < 1 that are classified as extended objects by the Dark Energy Spectroscopic Instrument (DESI). Combining high-resolution spectra from DESI and high-quality images from Subaru Hyper Suprime-Cam, we develop a spectrophotometric decomposition technique to iteratively decompose each quasar into an active galactic nucleus (AGN) component and its host galaxy. The technique can effectively break the degeneracy between the AGN and host components and capture the host spectral features. Our results show that the host galaxies of most quasars have low star formation rates (SFRs) and low specific SFRs, indicating that they are quiescent galaxies. Many of them exhibit prominent post-starburst features with the existence of significant old stellar populations. These properties are quite different from the nature of compact quasars with star-forming host galaxies. In addition, the relation between the black hole mass and stellar mass for our sample is broadly consistent with the canonical local relations. This work is complementary to the previous studies and suggests that the host galaxies of low-redshift quasars are more diverse than was thought.

The deposition of dust on snow accelerates melt by perturbing snow albedo, directly by darkening the snow surface and indirectly by enhancing snow grain growth. The snow darkening process impacts hydrology by shifting runoff timing and magnitude. Dust on snow deposition has been documented in the Wasatch Mountains, snowmelt from which accounts for up to 80% of surface water supply for Salt Lake City, UT, but the impact on snow melt has not yet been investigated. Here, we present a case study of a dust event observed in the Wasatch (13-14th April, 2017), sampled coincidentally in the air and at the snow surface at an instrumented high elevation site (Atwater Study Plot, Alta, UT). Atmospheric backtrajectory modeling, the results of which were supported by measurements, showed that dust originated predominantly from the west: the Great Salt Lake Desert and the Great Salt Lake (GSL) dry lake bed. The deposited dust mass accounted for ∼50% of the season total dust loading in snow, and daily mean radiative forcing of 20-50 W m−2 accelerated snow melt by approximately 25%. This has important implications for The Greatest Snow on Earth , and snow water resources; the water level of the GSL has been declining, exposing dry lake beds, and there are no legal water rights or protections to maintain lake levels or mitigate dust emission.

We present a fast and reconfigurable architecture for Shack–Hartmann wavefront sensing implemented on FPGA devices using a stream-based center of gravity to measure the spot displacements. By calculating the center of gravity around each incoming pixel with an optimal window matching the spot size, the common trade-off between noise and bias errors and dynamic range due to window size existing in conventional center of gravity methods is avoided. In addition, the accuracy of centroid estimation is not compromised when the spot moves to or even crosses the sub-aperture boundary, leading to an increased dynamic range. The calculation of the centroid begins while the pixel values are read from an image sensor and further computation such as slope and partial wavefront reconstruction follows immediately as the sub-aperture centroids are ready. The result is a real-time wavefront sensing system with very low latency and high measurement accuracy feasible for targeting on low-cost FPGA devices. This architecture provides a promising solution which can cope with multiple target objects and work in moderate scintillation.

Near infrared (NIR) remote sensing has applications in vegetation analysis as well as geological investigations. For extra-terrestrial applications, this is particularly relevant to Moon, Mars and asteroid exploration, where minerals exhibiting spectral phenomenology between 600 and 800 nm have been identified. Recent progress in the availability of processors and sensors has created the possibility of development of low-cost instruments able to return useful scientific results. In this work, two Raspberry Pi camera types and a panchromatic astronomy camera were trialed within a pushbroom sensor to determine their utility in measuring and processing the spectrum in reflectance. Algorithmic classification of all 15 test materials exhibiting spectral phenomenology between 600 and 800 nm was easily performed. Calibration against a spectrometer considers the effects of the sensor, inherent image processing pipeline and compression. It was found that even the color Raspberry Pi cameras that are popular with STEM applications were able to record and distinguish between most minerals and, contrary to expectations, exploited the infra-red secondary transmissions in the Bayer filter to gain a wider spectral range. Such a camera without a Bayer filter can markedly improve spectral sensitivity but may not be necessary.

An inventory of 761 confirmed pyrocumulonimbus (pyroCb) events observed worldwide during 2013-2023 answers many open questions on the inter-annual, seasonal, sub-daily, and regional variability of this hazardous fire weather phenomenon, along with potential controlling factors. It reveals that the 2023 fire season set new records for total pyroCb activity regionally (142 events in Canada alone) and worldwide (169 events). Smoke injection altitudes range from the mid-troposphere to the lower stratosphere (8–18 km), with 414 pyroCb events (55%) linked to smoke injection within 1 km of the tropopause or higher. Estimated aerosol mass in these plumes spans four orders of magnitude, which has significant implications for climate-scale radiative effects and ozone chemistry. The cumulative aerosol particle mass injected near the tropopause over an active fire season can rival that of recent extreme pyroCb events and significant volcanic eruptions. This pyroCb inventory is critical for advancing fire weather prediction capabilities to aid firefighting efforts and improving smoke transport forecasts. It sets a foundation for an Earth System Data Record that can be used to identify longer-term trends in pyroCb activity and consequent impacts.

Background Female sex workers (FSW) have a greater HIV burden compared to other reproductive-aged women and experience high incidence of pregnancies. However, there are limited data on mother-to-child transmission of HIV in the context of sex work. This study assessed the uptake of prevention of mother-to-child transmission (PMTCT) services to understand the vertical HIV transmission risks among FSW in South Africa. Methods FSW ≥18 years were recruited into a cross-sectional study using respondent-driven sampling (RDS) between October 2014–April 2015 in Port Elizabeth, South Africa. An interviewer-administered questionnaire captured information on demographics, reproductive health histories, and HIV care, including engagement in PMTCT care and ART. HIV and pregnancy testing were biologically assessed. This analysis characterizes FSW engagement in HIV prevention and treatment cascades of the four prongs of PMTCT. Results Overall, 410 FSW were enrolled. The RDS-weighted HIV prevalence was 61.5% (95% bootstrapped confidence interval 54.1–68.0). A comprehensive assessment of the four PMTCT prongs showed gaps in cascades for each of the prongs. In Prongs 1 and 2, gaps of 42% in consistent condom use with clients among HIV-negative FSW and 43% in long-term high efficacy contraceptive method use among HIV-positive FSW were observed. The analyses for prongs three and four pertained to 192 women with children < 5 years; 101/192 knew their HIV diagnosis prior to the study, of whom 85% (86/101) had their children tested for HIV after birth, but only 36% (31/86) of those who breastfed retested their children post-breastfeeding. A substantial proportion (35%, 42/120) of all HIV-positive women with children < 5 years of age were HIV-negative at their last delivery and seroconverted after delivery. Less than half (45%) of mothers with children < 5 years (45/101) were on ART and 12% (12/101) reported at least one child under five living with HIV. Conclusion These findings show significant gaps in engagement in the PMTCT cascades for FSW, evidenced by sub-optimal uptake of HIV prevention and treatment in the peri/post-natal periods and insufficient prevention of unintended pregnancies among FSW living with HIV. These gaps result in elevated risks for vertical transmission among FSW and the need for PMTCT services within FSW programs.

Background Stigma, criminalisation and a lack of data on drug use contribute to the “invisibility” of people who inject drugs (PWID) and make HIV prevention and treatment service delivery challenging. We aimed to confirm locations where PWID congregate in Cape Town, eThekwini and Tshwane (South Africa) and to estimate PWID population sizes within selected electoral wards in these areas to inform South Africa’s first multi-site HIV prevention project for PWID. Methods Field workers (including PWID peers) interviewed community informants to identify suspected injecting locations in selected electoral wards in each city and then visited these locations and interviewed PWID. Interviews were used to gather information about the accessibility of sterile injecting equipment, location coordinates and movement patterns. We used the Delphi method to obtain final population size estimates for the mapped wards based on estimates from wisdom of the crowd methods, the literature and programmatic data. Results Between January and April 2015, we mapped 45 wards. Tshwane teams interviewed 39 PWID in 12 wards, resulting in an estimated number of accessible PWID ranging from 568 to 1431. In eThekwini, teams interviewed 40 PWID in 15 wards with an estimated number of accessible PWID ranging from 184 to 350. The Cape Town team interviewed 61 PWID in 18 wards with an estimated number of accessible PWID ranging between 398 and 503. Sterile needles were only available at one location. Almost all needles were bought from pharmacies. Between 80 and 86% of PWID frequented more than one location per day. PWID who reported movement visited a median of three locations a day. Conclusions Programmatic mapping led by PWID peers can be used effectively to identify and reach PWID and build relationships where access to HIV prevention commodities for PWID is limited. PWID reported limited access to sterile injecting equipment, highlighting an important HIV prevention need. Programmatic mapping data show that outreach programmes should be flexible and account for the mobile nature of PWID populations. The PWID population size estimates can be used to develop service delivery targets and as baseline measures.