Search Results (434)

Psittacine beak and feather disease virus (PBFDV), a member of the family Circoviridae, is a major pathogen affecting psittacine birds worldwide; however, its potential for airborne dissemination in veterinary environments remains poorly understood. This study aimed to investigate PBFDV contamination in air conditioning systems within a veterinary hospital and to compare the distribution and levels of viral load across different functional areas. Environmental swab samples were collected from 17 air conditioning units located in examination rooms, surgical suites, wards, and laboratory areas. Viral nucleic acids were extracted and analyzed using quantitative polymerase chain reaction (qPCR) on the Genesig q16 (Version 4) platform. PBFDV DNA was detected in multiple units, with viral loads ranging from <10 to >25,000 PBFDV genome copies per qPCR reaction. The highest levels were observed in an examination room (26,172 copies) and a surgical room (25,730 copies), whereas several locations showed low or negligible contamination (<100 copies). These findings indicate that air conditioning systems may act as a possible environmental contamination pathway and potential sources of viral dissemination within clinical settings. The results underscore the importance of routine environmental monitoring and targeted disinfection strategies. As a preliminary model, this study provides baseline data to support the development of effective biosecurity measures to reduce the risk of airborne transmission of PBFDV in veterinary facilities. Full article

Coxiella burnetii is an intracellular bacterium responsible for an anthropozoonosis that can be asymptomatic or manifest as acute or chronic Q fever. This extensive series of 588 patients represents one of the largest single-center studies on sporadic acute Q fever, highlighting the Canary Islands as a high-incidence region in Spain. Epidemiologically, the domestic cycle is the primary driver of infection, with caprine livestock serving as the main reservoir, showing a local prevalence of 60.4%. Transmission is predominantly airborne via aerosols; the environmental resilience of C. burnetii facilitates its transport into urban areas, where the majority of patients reside despite lacking direct animal contact. While fever, headache, and diaphoresis are hallmark symptoms, over 90% of patients exhibit transient urinalysis abnormalities, a finding that often leads to misdiagnosis and inappropriate antimicrobial use. Clinically, the non-specific (45.7%) and hepatic (44.1%) forms are most prevalent, whereas the pulmonary form (7.8%) is strongly associated with smoking and alcohol consumption. Although localized forms affecting the nervous system or skin (such as panniculitis) were observed, the overall prognosis remains excellent with no progression to chronic Q fever in this series. In summary, the extensive series described characterizes acute Q fever patients in the Autonomous Community of the Canary Islands, with features that are similar in some cases but also show notable differences compared to other national and international series. Furthermore, depending on the patients’ age, the time elapsed between the onset of clinical manifestations and hospital evaluation, and the clinical form, acute Q fever displays significant differences. Full article

Synthetic Aperture Radar (SAR) is one of mainstream remote sensing techniques, offering all-weather, day-and-night operational capabilities. However, throughout the processes of signal transmission, propagation, and reception, it is difficult to ensure that the amplitude and phase of the SAR signal strictly follow a linear frequency modulation (LFM) characteristic. The resulting signal distortion often leads to main lobe broadening and sidelobe elevation, degrading the focusing performance of SAR images. Traditionally, this issue has been addressed primarily through SAR system internal calibration and pre-distortion compensation, which makes it challenging to maintain the signal in an ideal state over the long term. At the same time, many simplified SAR systems also lack an internal calibration design, such as low-cost UAV-borne SAR payloads. In this paper, we propose a novel signal distortion compensation method based on SAR image data. Without relying on SAR system calibration signals, this method estimates and compensates for signal distortion directly using SAR image data, thereby improving SAR image focusing performance, achieving a resolution closer to the theoretical bandwidth and lower sidelobe. The processing and analysis of both manned and unmanned airborne SAR image data and calibration signals demonstrate that the proposed method effectively compensates for signal distortion phases, achieving performance comparable to that of real-time calibration-signal-based methods. Full article

In early 2020, a respiratory virus swept across the world. The World Health Organization (WHO) confirmed pandemic status and the virus was identified as a coronavirus with superlative transmission properties. Using work from the 1950s, the WHO declared that the virus was transmitted through respiratory ‘droplets’, which were expelled by infected persons through coughing/sneezing. These would fall to the ground within 1–2 m. Scientists investigating viral transmission questioned this premise because recent work had shown that viruses populate the smallest respiratory particles, remaining airborne for much longer than larger ‘droplets’ and capable of spreading throughout the indoor environment. Advice such as handwashing, surface disinfection and social distancing was not as important as face masks and adequate indoor ventilation. People needed to know that poor ventilation constituted the highest risk for contracting the virus. Instead, homes and surfaces were disinfected and social distancing was maintained in community settings. The scientists formed a consortium named Group 36 in order to contest the WHO over airborne transmission but they could not present definitive evidence in the short term to reverse initial guidance. This account details the evolution of understanding of COVID-19 transmission and the role of Group 36 and others in challenging WHO-based policies based on dated physical science. Full article

To address the critical issues of geometric ill-conditioning and non-line-of-sight (NLOS) interference faced by broadcast radio positioning systems in long-distance transmission (≥200 km) and low-altitude flight scenarios (1000 m to 3000 m), this paper proposes a Differential and Robust Positioning method for Airborne Platforms (DPAP). Integrating radio differential positioning, the proposed method enhances the single-point positioning algorithm through a grid search and iteratively reweighted least squares to mitigate geometric ill-conditioning and numerical instability in low-altitude environments. Furthermore, a passive differential positioning approach is introduced to eliminate common errors using neighboring reference stations. Finally, a scenario-aware safe fusion strategy ensures that the fused solution is never inferior to the optimal sub-solution under any circumstances. Simulation results demonstrate that, under conditions involving six ground stations, user-to-station distances of no less than 200 km, and 15% of links experiencing NLOS propagation, the differential and robust positioning method achieves a positioning accuracy of 0.588 m RMS. This represents an improvement of approximately one order of magnitude compared to RSPP (12.304 m), and outperforms traditional Huber M-estimation (0.678 m) and elevation-weighted least squares methods (1.462 m). All results are based on Monte Carlo simulations; real-world validation with SDR hardware and flight tests is left for future work. This work provides a scalable, infrastructure-light backup for safe UAV operations in GNSS-hostile environments, directly supporting the emerging low-altitude economy. Full article

Integrating existing tree-level information into harvester operator decision-making can significantly enhance precision forest management, particularly with respect to biodiversity preservation and climate-smart adaptation. During harvester operations, a primary challenge lies in positioning the machine with sufficient accuracy in real time to relate a priori individual-tree-level reference information to the operator. We propose a lightweight procedure using tree-to-tree matching to continuously register a real-time tree map collected from a harvester (or another mobile laser scanning system) to a precomputed reference map derived from an airborne laser scanner (ALS). We assess the robustness of the method using simulated tree maps and validate its real-world performance in experiments using a LiDAR-equipped harvester performing a thinning operation in a boreal forest. In simulations, registration was found to be robust up to a moderate tree density of approximately 1700 ha⁻¹, even when using a reference map with a lower positional accuracy and higher error rates than in our harvester experiments. Using real-world data from the thinning operation, the registration method was demonstrated to successfully mitigate meter-scale positioning drifts remaining in the LiDAR-inertial trajectory. After the continuous registration procedure, the positioning error was reduced to the level of 0.5 m, constrained by the accuracy of the prior map derived from sparse ALS data with ∼5 transmissions/m². Importantly, the registration procedure was shown to update in real time (at most 20 ms update time for stands with densities of at most 2000 ha⁻¹, after an initial computational phase. Notable features of the registration procedure are its low memory consumption, fast runtime and capacity to accurately position the harvester despite LiDAR-inertial positioning drift. While these results demonstrate the potential for real-time operation, full implementation requires the development of real-time tree detection and estimation of tree attributes. Full article

Heating, ventilation, and air conditioning (HVAC) systems are essential for indoor air quality and thermal comfort but can simultaneously act as vectors for microbial contamination, particularly bacteria and fungi. While the COVID-19 pandemic intensified focus on airborne viral transmission, bacterial and fungal contamination in indoor environments remains a persistent and significant health risk. This study presents a detailed case study of a restaurant HVAC system, analysing the impact of different ventilation strategies on bacterial contamination, infection transmission risk, energy consumption, and thermal comfort. By focusing on a real-world application, the research evaluates practical challenges and trade-offs associated with HVAC operation modifications aimed at mitigating microbial risks while maintaining acceptable energy and comfort levels. The research compares three operational scenarios: normal operation with air recirculation, 24 h operation with 100% outdoor air, and extended operation periods. Results demonstrate that while strategies emphasizing outdoor air intake and extended operation reduce infection probability by up to 60–65%, they simultaneously increase energy consumption by over 1700% and compromise thermal comfort parameters. In the h24 case, the pre-heat coil rises from 2421.7 to 43,923.7 kWh and the post-heat coil from 24,812.8 to 152,970.4 kWh, while the Plus 2 h strategy reduces the energy penalty by roughly 42–51% with respect to the h24 case. The findings are contextualized within current research on bacterial and fungal risks in HVAC systems, highlighting the critical need for balanced ventilation strategies that integrate health protection, energy efficiency, and comfort considerations. Full article

Adolescent vaping has become a persistent health and behavioural challenge in schools, yet many institutions lack reliable tools to detect and respond to concealed e-cigarette use. This study addresses this problem by evaluating the real-world performance of a low-cost “Internet of Things” (IoT) vape detection system deployed across 37 high-risk restroom and change-room locations at a large Australian Independent school. The aim was to determine whether an IoT-based environmental monitoring platform could accurately identify vaping events, support timely staff intervention, and provide actionable insights into student behaviour patterns. A longitudinal case study design was used, collecting continuous particulate matter (PM_2.5 and PM₁₀) data at one-minute intervals over an 18-month period, where PM_2.5 and PM₁₀ refer to particulate matter with aerodynamic diameters ≤ 2.5 µm and ≤10 µm, respectively, reported in micrograms per cubic metre (µg/m³. Threshold-based alerting, cloud-based data processing, and school-led Closed-circuit television (CCTV) verification were combined to assess detection accuracy, temporal trends, and operational responses. The system recorded more than 300 vaping-related incidents, with clusters aligned to predictable times of day and higher prevalence among senior students. Operational detection performance was high, with alert events characterised by rapid, concurrent PM_2.5 and PM₁₀ excursions consistent with vaping-related aerosol profiles, although staff responsiveness declined over time due to alert fatigue and competing priorities. A major environmental smoke event demonstrated the need for context-aware logic to reduce false positives. The findings demonstrate that real-time aerosol monitoring is not only technically reliable but also highly effective in detecting vaping within school environments. These perspectives help explain why user engagement, alert fatigue, and institutional follow-through are as critical as sensor accuracy itself. Ultimately, the effectiveness of vape detection relies on strong organisational commitment, well-defined response workflows, and alignment with broader wellbeing and policy strategies. When these elements are in place, such systems can evolve from simple detection tools into intelligent, integrated components of school health governance. Full article

Antibiotic resistance genes (ARGs) are prevalent in livestock environments due to antimicrobial use, yet their airborne dispersal into human-occupied indoor spaces remains poorly characterized. We investigated whether airborne ARGs disperse from livestock stables into farmers’ homes and surrounding outdoor environments. Electrostatic dust collectors were deployed in paired pig and cow stables and their associated homes in Jutland, Denmark, to collect settled airborne dust. Pooled samples were analyzed using shotgun metagenomic sequencing. ARG dispersal patterns were assessed using FEAST source tracking and ecological similarity metrics, including shared ARG ratios and Jaccard indices. Pig production systems exhibited higher antibiotic use and stronger resistome continuity with farmers’ homes than cow systems, reflected by greater FEAST contributions (P = 0.029) and Jaccard similarity (P = 0.029). Beta-diversity analysis supported higher compositional similarity between pig stables and homes (PERMANOVA R² = 0.23, p = 0.052), whereas cow environments showed greater divergence (R² = 0.41, P = 0.035). Across environments, tetracycline, macrolide–lincosamide–streptogramin B, and aminoglycoside resistance genes dominated, consistent with livestock-specific antibiotic use patterns. Supplementary indoor–outdoor comparisons across cow, pig, and chicken stables (from an independent 2024 sampling campaign not directly comparable to the 2008 EDC-based survey) revealed contrasting dispersal dynamics, with higher bacterial species spillover from cow stables but stronger ARG overlap from pig stables. Collectively, these findings are consistent with airborne ARG connectivity across occupational and environmental interfaces and support consideration of air as a potential pathway in One Health AMR surveillance. Full article

Aerosols are a major transmission route for seasonal influenza infections. Titanium dioxide (TiO₂) photocatalyst has broad-spectrum antiviral activity, including in vitro influenza virus inactivation; however, whether the TiO₂ photocatalyst can effectively inactivate airborne influenza A viruses in vivo under conditions that mimic natural aerosol transmission remains unclear. Here, we evaluated in vivo inactivation of airborne H1N1 seasonal influenza virus by a photocatalyst-equipped air purifier using a mouse model. Influenza virus WSN strain aerosols were sprayed in a 60 L acrylic box with a nebulizer, circulated through a photocatalyst-equipped air purifier, exposed to BALB/c mice for 40 min after circulation, and subsequently collected with an air sampler. Thirty minutes of TiO₂ photocatalyst treatment reduced influenza virus infectivity by 99.97%, and significantly lowered lung viral titer in mice on day 3 post-infection. Over 14 days post-infection, mice showed no >10% weight loss, 100% survival, and disease progression to the PBS (−) aerosol group. This suggests that the photocatalyst-equipped air purifier may reduce H1N1 seasonal influenza onset, preventing viral spread. Full article

Based on monolithic microwave integrated circuit (MMIC) technology, this paper presents the design and implementation of a low-cost, highly integrated Ka-band sixteen-channel transmit/receive (T/R) module, specifically tailored to meet the application requirements of phased array antennas in airborne and spaceborne radar systems, satellite communications, and 5G/6G millimeter-wave networks. The proposed module employs an MMIC-based single-channel dual-chip discrete architecture, optimally integrating amplitude-phase multifunction chips and transmit-receive multifunction chips in terms of both fabrication process and performance characteristics, achieving a favorable balance between high performance and high-integration density. Using low-cost, low-temperature co-fired ceramic (LTCC) substrates, full-silver conductive paste, and a nickel–palladium–gold plating process, a novel “back-to-back” thin-slice packaging technique is presented to improve integration, lower manufacturing costs, and boost long-term reliability. Furthermore, the design incorporates glass insulators and a direct array interconnection scheme, which significantly minimizes transmission losses and reduces interface dimensions. The final module measures 70.3 mm × 26.2 mm × 10.9 mm and weighs only 34 g. Experimental results demonstrate a transmit output power of at least 23 dBm, a receive gain exceeding 26 dB, and a noise figure below 3.5 dB, achieving a 22.5–58% reduction in volume per channel while maintaining competitive RF performance. To improve testing effectiveness and guarantee data consistency, an automated radio frequency (RF) test system based on Python 3.11.5 was also developed. This work provides a practical technical approach for the engineering realization of Ka-band phased array systems. Full article

The increasing use of mechanical ventilation systems in energy efficient buildings introduces a significant pathway for acoustic crosstalk between rooms via air ducts. Air ducts connecting rooms can reduce airborne sound insulation, and therefore such systems can affect acoustic comfort not only through the noise they generate. This article focuses on a common situation where air ductwork located outside of ventilated rooms has branches leading into rooms (e.g., ventilation system in ceiling plenum in corridor connected to habitable rooms in apartment). The study provides new experimental data on sound transmission through ventilation ducts. Various materials (steel and glass wool pre-insulated ducts) and duct configurations were investigated. The results are presented by means of normalized level differences specific to the ventilation system, D_n,s, to facilitate their further use, e.g., for predictions of total airborne sound insulation between rooms according to ISO 12354-1:2017, which contains a prediction model enabling the combination of D_n,s,w of the system with R_w of the wall. The results show a significant variation in sound insulation (D_n,s,w) from 37 dB (for sheet metal system) to 73 dB (for glass wool system), which implies that sound-absorbing ductwork provides considerably higher acoustic comfort. The acoustic performance of traditional sheet metal ductwork was highly dependent on terminal elements and was often insufficient to meet common sound insulation requirements, whereas ductwork made of sound-absorbing materials provided consistently high insulation. Full article

UAV-Assisted Mobile Ad Hoc Networks (UAMANETs) provide flexible communication support in dynamic and infrastructure-limited environments. This paper studies a representative UAMANET architecture in which a subset of UAVs forms stable task clusters with ground nodes while simultaneously acting as relays in an airborne backbone network. To characterize the network capacity under contention-based medium access and multi-hop routing, we introduce Aggregate Multi-hop Information Efficiency (AMIE), a capacity-oriented metric that jointly accounts for MAC-layer contention, multi-hop routing, and end-to-end transmission reliability. Based on an IEEE 802.11p access model, we extend Bianchi’s CSMA/CA analytical framework to UAMANETs, enabling a quantitative characterization of how spectrum resource allocation affects AMIE through link activation probability, transmission interruption, and end-to-end hop count. Building on the derived analytical insights, we further develop a soft centralized resource management framework, in which an existing MSF-PSO algorithm is employed as a numerical solver to optimize resource allocation under implicit MAC-layer coupling constraints. Numerical results demonstrate that, compared with conventional IEEE 802.11p spectrum resource settings, the proposed framework can achieve substantial AMIE improvements under representative network configurations. Full article

The highly pathogenic avian influenza virus (HPAIV) is widely distributed worldwide and causes significant economic losses. Transmission of HPAIV occurs through direct contact between infected and susceptible birds or indirectly via contaminated materials. In recent years, airborne transmission of HPAIV has also been reported, underscoring the need for novel approaches to effectively inactivate airborne HPAIV. Photocatalysts have attracted significant attention as potential antiviral agents. In this study, we demonstrated that a TiO₂-mediated photocatalytic reaction inactivated HPAIV and H1N1 seasonal influenza viruses in liquid, reducing their infectivity by 90.7% and 94.4%, respectively, after 60 min. Mechanistic analyses revealed decreased virion size and surface structure disruption, as determined by transmission electron microscopy. Additional evidence of viral protein and genome damage was obtained using Western blotting and RT-qPCR, respectively. Given the broad antiviral activity of photocatalysts, these findings suggest that they can inactivate influenza viruses regardless of strain or subtype. Notably, photocatalysts inactivated 80% of aerosolized H1N1 seasonal influenza viruses within 5 min. These results provide strong evidence that photocatalysts are capable of inactivating airborne influenza viruses. This study represents the first demonstration that photocatalysts can inactivate HPAIV and aerosolized influenza viruses. These findings provide strong evidence that photocatalysts represent a promising countermeasure against HPAIV, with potential applicability across different strains and subtypes. Full article

Household airborne transmission can be promoted when infectious and susceptible occupants share indoor air for long periods, yet practical infection-risk models often require pathogen-specific parameters that are uncertain. This study proposes a measurement-informed multizone/HVAC-network workflow that identifies inter-room airflow rates (q) from CO₂ tracer time series and estimates an effective first-order non-ventilation aerosol loss rate (λ) by fitting PM_2.5 concentration decay dynamics; the identified parameters are then reused within the same whole-house recirculating network model (vtsim) to compute a steady-state exhaled-air tracer concentration index for scenario comparison. The workflow is demonstrated in a high-insulation, airtight detached house equipped with a duct-type whole-house air-conditioning system with return-air recirculation. The results indicate measurable cross-room dispersion under baseline operation and show that a return-side filtration scenario reduces the steady-state index in non-source rooms relative to baseline under the tested operating assumptions. These findings illustrate how measurement-informed identification can support rapid, threshold-free relative comparison of ventilation/HVAC operation or mitigation scenarios within a specific house, rather than estimating absolute infection probability. Limitations include potential non-uniqueness in inverse identification, simplified treatment of leakage and pressure-drop-induced airflow changes, and the use of a steady-state index for inherently transient residential exposures; further validation across additional houses and HVAC topologies is warranted. Full article