MOTS-c attenuates cardiac dysfunction following high altitude exposure by promoting mitophagy.

This study examined how sex influences blood flow during exercise at altitude and relative contributions of adrenergic mechanisms. Thirteen participants (8 M/5F) were tested at low and high altitude (days 3–11). Participants performed rhythmic handgrip for 3 min at 25% maximal voluntary contraction during local infusions of saline, propranolol (β‐adrenergic blockade), and phentolamine with propranolol (α‐β‐adrenergic blockade). Doppler ultrasound was used to examine brachial artery blood flow (FBF) and calculate forearm vascular conductance (FVC). Resting FBF and FVC were higher in males compared to females across all conditions (p = 0.024; p = 0.025, respectively). Blockade condition significantly altered FBF and FVC (p < 0.001 for both) but there was no effect of altitude (p = 0.330; p = 0.718, respectively). During exercise, ΔFBF was influenced by condition (p < 0.001), but not by sex (p = 0.696) or altitude (p = 0.813). Similarly, ΔFVC was different across conditions (control: 9.4 ± 2.3 mL/min/mmHg/FAV; β‐blockade: 11.4 ± 12.8 mL/min/mmHg/FAV; α‐β‐blockade: 3.9 ± 1.1 mL/min/mmHg/FAV; p < 0.001), with no effect of sex (p = 0.646) or altitude (p = 0.889). These results suggest males and females do not respond differently to exercise at altitude, and light‐intensity exercise hyperemia may be preserved during early acclimatization. α‐adrenergic receptors appear important for exercising blood flow, but β‐adrenergic receptors may not be critical in this response.

The low-altitude airspace plays a vital role in supporting economic development; however, the downwash airflow generated by low-altitude aircraft can entrain ground particles into the engine, posing significant risks to flight safety and operational costs. To mitigate this issue, an inertial particle separator (IPS) is typically installed at the engine inlet to clean incoming airflow, yet the influence of rotor downwash on IPS performance remains poorly understood. In this study, a combined experimental and computational approach was employed to investigate the aerodynamic characteristics and separation efficiency of the IPS under low-altitude conditions. Computational fluid dynamics (CFD) simulations were used to assess the impact of downwash airflow on the IPS inlet. The results indicate that downwash significantly alters the inlet flow conditions and reduces separation efficiency. Specifically, the high curvature of streamlines near the lip leads to flow separation and elevated energy losses. Moreover, as the intake flow rate at the upper end of the IPS increases, pressure drops at the hub are observed. In contrast to previous studies, the measured separation efficiency was less than 50%, highlighting that IPS optimization must account for rotor downwash effects at low altitudes. Additionally, separation efficiency was found to be inversely proportional to rotor speed and particle diameter, yet positively correlated with the ratio of scavenge flow to core flow (SCR). These findings provide reliable guidance for the design and optimization of IPS systems for low-altitude operations.

Impact of the menstrual cycle on oxidative stress, inflammation and iron status at high altitude.

Whether the lower cabin pressure altitude used by modern long-haul aircraft shortens recovery after barotraumatic otitis (BO) remains uncertain. We assessed the association between cabin altitude [6000 ft (≈1829 m) vs. 8000 ft (≈2438 m)] and BO-related sick-leave duration in airline crew. We conducted a retrospective study of 4271 BO episodes among Air France pilots and cabin crew (2015-2024). Analyses were restricted to long-haul operations. Exposure was cabin altitude class inferred from aircraft type; the outcome was workdays lost per episode. We fitted linear models and count models that account for overdispersion and excess zeros, adjusting for sex, crew role, season, and calendar year. Across episodes, 8010 workdays were lost, with a right-skewed distribution (median 1-2 d; mean ≈ 5.5 d). No association was observed between cabin altitude and sick-leave duration; in count models the estimated ratio was 1.02 with a 95% confidence interval of 0.91-1.14, and results were consistent across specifications. Male sex was associated with shorter absences (about -2.5 d; 95% confidence interval -4.6 to -0.5), and pilots with longer absences than cabin crew (about +9.4 d; 95% confidence interval +0.5 to +18.2). Findings for BO were stable over time. This study suggests that cabin altitude, while relevant to in-flight comfort, is unlikely to be a major determinant of BO recovery in operational practice. Individual factors (e.g., sex and crew function) appeared more influential. Limitations include the fact that exposure was only defined by aircraft type and lack of unmeasured operational factors; future prospective studies integrating technical flight data are required. Scaramuzzo P, Comesse M-A, Klerlein M. Cabin altitude and barotraumatic otitis in commercial aircrew. Aerosp Med Hum Perform. 2026; 97(2):100-105.

Background & objectives Living at high altitudes causes chronic exposure to hypoxia, which triggers various physiological and autonomic adaptations, and many residents show successful acclimatization. Long-term exposure leads to time-dependent alterations in autonomic nervous system function, even in healthy individuals. Heart rate (HR) variability has long been a valuable tool for assessing autonomic activity, yet only a few studies have examined its association with altitude in healthy populations. This study assessed the impact of altitude on cardiac autonomic activity through HR variability analysis in healthy Sikkimese natives. Methods A cross-sectional study was conducted among the Sikkimese population residing at high, intermediate and low altitudes of Sikkim. Two areas from each altitude category were selected. Based on the population of the selected areas, the sample size was distributed using probability proportional to size, sampling. Systematic random sampling was then used to select participants. For each participant, a 5-min ECG was recorded using lead II of a Power Lab system. HR variability analysis was performed to derive time and frequency-domain indices from spectral analysis of successive R-R intervals. Results We found significantly higher values of time domain HR variability indices including standard deviation of all normal-to-normal intervals (SDNN) and root mean square of successive differences between normal heartbeats (RMSSD) among the people residing at higher altitudes in Sikkim (P<0.001). Interpretation & conclusions Residents living at high altitudes exhibit enhanced parasympathetic cardiac activity compared to those residing at lower and intermediate elevations, reflecting a possible adaptive response to chronic hypobaric hypoxia.

Flavonoids, as vital secondary metabolites, improve grape (Vitis vinifera L.) berry quality and shape wine flavor. Characterized by intense ultraviolet radiation and large diurnal temperature shifts, the high-altitude regions of Southwest China are well-suited for growing late-ripening grapes like Cabernet Sauvignon. However, how altitude influences flavonoid composition and the molecular mechanisms governing these changes remains poorly understood. In this study, we combined transcriptomic analysis with flavonoid profiling to monitor grape berry skins at four key developmental stages (from green berry to harvest) under two typical altitude gradients. Of the genes related to flavonoids, VvbHLH88 was identified as a candidate transcription factor related to the biosynthesis of anthocyanins (a class of flavonoids) by comparing skins from grapes grown at high and low altitudes. Determination of the anthocyanin content in wounded tissues of VvbHLH88-overexpressing and -silenced grape revealed that VvbHLH88 was a positive regulator of anthocyanin biosynthesis. Transcriptome analysis of VvbHLH88-overexpressing healing tissues showed that the expression of anthocyanin synthesis branching enzyme genes was upregulated. In addition, VvbHLH88 directly bound to the promoter of the UDP-glucoflavone-3-O-glucosyltransferase (VvUFGT) gene and activated its transcriptional regulation of anthocyanin synthesis. Consequently, these results uncover specific molecular pathways and transcriptional networks through which high-altitude ecological factors modulate flavonoid metabolism in grape berries, advancing our theoretical understanding of how environmental cues influence metabolic regulation and fruit quality.

Abstract The South Andes mountain range is a global hot spot for stratospheric gravity waves. Here, we identify two selected case study flows over the South Andes, using data from the ERA5 reanalysis, one featuring extensive vertical and downstream wave propagation with a characteristic cellular pattern, and the other with little to no wave propagation. Core features of these two flow fields are identified and shown to correspond to different analytical solutions to the linear Taylor-Goldstein equation: one with vertical wave propagation (with and without rotation), and one with trapped waves propagating downstream. The importance of rotation is emphasised for its ability to suppress mountain waves at low altitudes, and wave trapping is identified as potentially contributing to the downstream propagation of waves in the stratosphere for one of the flow snapshots. The dimensionless number γ , the ratio of the height-scale of the Scorer parameter and the mountain’s horizontal length-scale, is highlighted as playing a critical role in the behaviour of trapped waves in multiple analytical models.

National parks are a key institutional tool for coordinating ecological conservation and sustainable development. This paper takes the pilot national park program in Yunnan Province, China, as a case study. Using panel data from 127 counties between 2001 and 2023, we empirically examine the economic impact of the national park pilot program using a Time-varying difference-in-differences (DID) approach and a Spatial Durbin Model (SDM). The study finds that (1) the pilot policy significantly increased per capita GDP in the counties by approximately 5057 RMB, with a 4- to 5-year lag effect and a long-term marginally increasing trend; (2) the policy drives economic growth through three main channels: increased fiscal transfers from higher levels of government, induced industrial upgrading, and the stimulation of fixed-asset investment; (3) the policy’s impact is more significant in areas with low economic levels, high altitudes, and high ecological quality; (4) national parks not only stimulate local economic growth but also promote coordinated development in surrounding regions through significant spatial spillover effects. This paper confirms the feasibility of transforming ecological advantages into economic advantages and provides empirical evidence for optimizing spatial governance in “Global South” countries.

Cell-edge users (CEUs) in cellular networks typically suffer from poor channel conditions due to long distances from serving base stations and physical obstructions, resulting in much lower data rates compared to cell-center users (CCUs). This paper proposes an Unmanned Aerial Vehicles (UAV)-assisted cellular network with intelligent power control to address the performance gap between CEUs and CCUs. Unlike conventional approaches that either deploy UAVs for all users or use no UAV assistance, our model uses a distance-based criterion where only users beyond a reference distance receive UAV relay assistance. Each UAV operates as an amplify-and-forward relay, enabling assisted users to receive signals from both the base station and the UAV simultaneously, thereby achieving diversity gain. To optimize transmission power allocation across base stations, we employ a Deep Q-Network (DQN) learning framework that learns power control policies without requiring accurate channel models. Simulation results show that the proposed approach achieves a peak average rate of 2.28 bps/Hz at the optimal reference distance of 400m, which represents a 3.6% improvement compared to networks without UAV assistance and 0.9% improvement compared to networks where all users receive UAV support. The results also reveal that UAV altitude and reference distance are critical factors affecting system performance, with lower altitudes providing better performance.

Differential ecotoxicological responses of high- and low-altitude amphibians to acute UVB exposure: An integrated analysis of skin, oxidative, and DNA repair mechanisms.

Respiratory support use in neonatal intensive care units (NICUs) varies worldwide, influenced by clinical practices, resources, and patient populations. Whether high-altitude independently affects the duration of respiratory support in preterm infants remains unclear. This study aimed to determine whether altitude is independently associated with the duration of respiratory support in preterm infants ≤32 weeks' gestational age (GA) admitted to Latin American NICUs.We performed a multicenter, observational cohort study by secondary analysis of prospectively collected data from the EpicLatino Network, a registry of NICUs across Latin America (2015-2022). Infants ≤32 weeks who received invasive or non-invasive respiratory support were included; supplemental oxygen delivered via low-flow nasal cannula or oxygen hood was not considered respiratory support, and those with missing outcome data were excluded. The primary outcome was total duration of respiratory support, measured as total days of support until discontinuation, discharge, transfer, or truncation by death. Altitude was classified as high (≥2,000 m) or low (<2,000 m). Multivariable analyses were adjusted for neonatal, maternal, and unit characteristics.A total of 4,428 infants were included; 2,723 (61.5%) in low-altitude NICUs and 1,705 (38.5%) in high-altitude NICUs. Overall, 81.4% discontinued respiratory support and 18.6% died. Mortality was 19.1% in low-altitude and 17.9% in high-altitude NICUs. Median duration of support was 8 days (interquartile range [IQR]: 5-14) overall, with 9 days (IQR: 4-27) in low-altitude and 7 days (IQR: 3-17) in high-altitude NICUs. High-altitude centers showed shorter respiratory support in unadjusted analyses. After adjustment for neonatal, maternal, and unit factors, altitude was not independently associated with support duration.After adjustment for neonatal, maternal, and unit factors, altitude was not independently associated with the duration of respiratory support. Importantly, high altitude was never associated with worse outcomes. · High-altitude NICUs showed shorter respiratory support use, likely reflecting environmental hypoxemia, but this association disappeared after adjusting for clinical and unit factors.. · Mortality was similar at high and low altitudes, indicating that shorter duration at altitude was not explained by earlier deaths.. · Altitude may influence initial decisions on invasive support, but patient and institutional characteristics appear more relevant in determining total duration..

Abstract. Atmospheric concentration of methane (CH4), a potent greenhouse gas, increased significantly since pre-industrial times, with anthropogenic emissions originating primarily from agriculture, fossil fuel sector and waste management. However, considerable uncertainties persist in the detection and quantification of anthropogenic CH4 emissions. In this study, we present first CH4 observations, plume detections and emission estimates from the new state-of-the-art Airborne Visible InfraRed Imaging Spectrometer 4 (AVIRIS-4), which participated in a blind controlled release experiment in September 2024 in southern France. We used an albedo-corrected matched filter to retrieve CH4 maps from the spectral images and estimated CH4 emission with the Integrated Mass Enhancement (IME) and Cross-Sectional Flux (CSF) methods. Our results demonstrate that AVIRIS-4 can reliably detect emissions as low as 5.5 kg CH4 h−1 under good weather conditions at low flight altitudes (&lt; 1500 m) and 1.45 kg CH4 h−1 under ideal conditions. These low-altitude detection limits are substantially lower than published detection limits for the predecessor instrument AVIRIS-NG, which were in the order of 10–16 kg CH4 h−1 under comparable conditions. While AVIRIS-4 provides highly accurate CH4 maps at &lt; 0.5 m resolution, emission estimation is limited by the accuracy of the effective wind speed, whose uncertainty and natural variability contribute substantially to the overall uncertainty. Using wind speed at source height performs well for small releases (below 20 kg CH4 h−1) (rRMSE =1.065; rMBE =0.361) and overall (rRMSE =0.702; rMBE =−0.204). Using literature-derived effective wind speeds improves the apparent fit between estimated and reported CH4 emissions, but degrades performance both in overall agreement (rRMSE =2.098; rMBE =0.964) and for low-emission events (rRMSE =2.367; rMBE =1.711). Interestingly, the high spatial resolution makes it possible to retrieve the cast shadow of the CH4 plume, which can be used to estimate source and plume height, and could provide an approach for better constraining the height-dependency of the effective wind speed. On the bottom line, the controlled release experiment provides critical insights into the sensor's capabilities and guides further improvements to detect and quantify low intensity sources in the fossil fuel and waste management sectors, with implications for more accurate global greenhouse gas monitoring.

Sleep Patterns and Blood Pressure Among Chinese Adults in Different Ethnic Groups Across Varied Altitudes.

Abstract Geologists working at high altitude (&amp;gt;2,500 m, or 8,200 ft) are susceptible to altitude sickness or acute mountain sickness (AMS; mal de altura, mal de montaña, soroche, or puna in Spanish), a condition resulting from inadequate time for physiological acclimatization to lower ambient oxygen availability at reduced barometric pressure, which is driven by hypobaric hypoxia. This article outlines the symptoms, causes, prevention, and treatment of AMS, a condition triggered by exposure to high altitude without adequate acclimatization. There are three degrees of AMS—mild, moderate, and severe. Many people feel mild AMS when reaching high altitude but most acclimatize rapidly. Those with moderate AMS feel debilitated and usually require descending to low altitude to feel better. Severe AMS includes life-threatening complications involving high-altitude pulmonary edema (HAPE), an accumulation of fluid in the lungs causing shortness of breath, cough, and hypoxia, and/or high-altitude cerebral edema (HACE), the swelling of the brain leading to ataxia, confusion, and altered consciousness. Both HAPE and HACE are medical emergencies that require immediate descent and, if available, oxygen therapy and pharmacologic support. The primary cause of AMS is hypobaric hypoxia—a partial reduction in the pressure of oxygen due to decreased atmospheric pressure at altitude. The risk increases with rapid ascent, which does not allow sufficient time for the body to initiate acclimatization mechanisms such as increased ventilation and red blood cell production.

Machine learning techniques for detecting anomalies in ADS-B data in the context of low altitude aviation

Data Freshness Performance Analysis and Optimization in Timely and Secure Low Altitude Economics

A Lightweight PUF-Based Secure Group Communication Scheme for Low Altitude Network With Dynamic Group Membership

Rambutan (Nephelium lappaceum L.) is a widely distributed plant in various regions and is known to contain flavonoid compounds. In pharmaceutical development, the geographical location of plant growth can influence the levels of secondary metabolites. This study aims to determine the total flavonoid content in rambutan leaves based on differences in altitude using UV-Visible spectrophotometry at a wavelength of 435 nm. The leaves were extracted via maceration using ethanol p.a. as the solvent. The total flavonoid content was determined using AlCl₃ reagent with quercetin as the standard. The results showed that rambutan leaves collected from lowland areas (Komo Luar Subdistrict, Wenang District, Manado City) had a higher total flavonoid content (42.7 ppm) compared to those of highland regions (Kampung Jawa Subdistrict, Tomohon City), which contained 30.4 ppm. These findings indicate that plants grown at lower altitudes produce higher levels of flavonoids, possibly due to increased light intensity and climatic conditions, which promote the synthesis of secondary metabolites such as flavonoids.

The European mudminnow ( Umbra krameri ) is an endemic species of the Danube and Dniester River basins and is classified as a vulnerable species on the IUCN Red List. Due to the drainage of marshes and swamps, as well as the significant reduction of floodplains, its populations in the Carpathian Basin have drastically declined in recent decades. In Romania, its distribution is restricted to wetland habitats at lower altitudes outside the Carpathians. During our surveys over the past 10 years, the species has not been found in many of its previously known locations. However, we have discovered several new, previously unknown populationsSuppl. material 1 (e.g., Homorodul Vechi River, Upper Ier Watershed etc.). These populations do not indicate the species' expansion but rather highlight the under-researched nature of its potential habitats. Restoring the species' former habitats, along with the proper protection of its current habitats, could significantly improve the species' situation. At the same time, reassessing its current status and reclassify the species from the vulnerable category to the endangered category is necessary.