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Purpose: We examined changes in stride temporal parameters and spring-mass model characteristics during repeated sprints following a 3-week period of "live high–train low and high" (LHTLH) altitude training in team-sport players. Methods: While residing under normobaric hypoxia (≥14 h/d; inspired oxygen fraction [FiO2] 14.5%–14.2%) for 14 days, elite field hockey players performed, in addition to their regular field hockey practice in normoxia, 6 sessions (4 × 5 × 5-s maximal sprints; 25-s passive recovery; 5-min rest) under either normobaric hypoxia (LHTLH; FiO2 ∼14.5%, n = 11) or normoxia (live high–train low; FiO2 20.9%, n = 12). A control group (live low–train low; FiO2 ∼20.9%, n = 9) residing in normoxia without additional repeated-sprint training was included. Before (Pre) and a few days (Post-1) and 3 weeks (Post-2) after the intervention, stride mechanics were assessed during an overground repeated-sprint test (8 × 20 m, 20-s recovery). Two-way repeated-measures analysis of variance (time [Pre, Post-1, and Post-2] × condition [LHTLH, live high–train low, and live low–train low]) were conducted. Results: Peak sprinting speed increased in LHTLH from Pre to Post-1 (+2.2% [2.0%]; P =.002) and Post-2 (+2.0% [2.4%]; P =.025), with no significant changes in live high–train low and live low–train low. There was no main effect of time (all P ≥.062), condition (all P ≥.771), or a significant time × condition interaction (all P ≥.230) for any stride temporal variable (contact time, flight time, stride frequency, and stride length) or spring-mass model characteristics (vertical and leg stiffness). Conclusions: Peak sprinting speed improved in elite field hockey players following LHTLH altitude training, while stride mechanical adjustments to repeated overground sprints remained unchanged for at least 3 weeks postintervention. [ABSTRACT FROM AUTHOR]

Background: Repeated exposure to heat (ie, plasma volume expansion) or altitude (ie, increase in total hemoglobin mass), in conjunction with exercise, induces hematological adaptations that enhance endurance performance in each respective environment. Recently, combining heat and altitude training has become increasingly common for athletes preparing to compete in temperate, sea-level conditions. Purpose: To review the physiological adaptations to training interventions combining thermal and hypoxic stimuli and summarize the implications for temperate, sea-level performance. Current Evidence: To date, research on combining heat and hypoxia has employed 2 main approaches: simultaneously combining the stressors during training or concurrently training in the heat and sleeping at altitude, sometimes with additional training in hypoxia. When environmental stimuli are combined in a training session, improvements in aerobic fitness and time-trial performance in temperate, sea-level conditions are generally similar in magnitude to those observed with heat, or altitude, training alone. Similarly, training in the heat and sleeping at altitude does not appear to provide any additional hematological or nonhematological benefits for temperate; sea-level performance relative to training in hot, hypoxic, or control conditions. Conclusions: Current research regarding combined heat and altitude interventions does not seem to indicate that it enhances temperate, sea-level performance to a greater extent than "traditional" (heat or hypoxia alone) training approaches. A major challenge in implementing combined-stressor approaches lies in the uncertainty surrounding the prescription of dosing regimens (ie, exercise and environmental stress). The potential benefits of conducting heat and altitude exposure sequentially (ie, one after the other) warrants further investigation. [ABSTRACT FROM AUTHOR]

Purpose: To compare the effects of graded hypoxia during exhaustive intermittent cycling on subsequent rapid and maximal torque-production capacity. Methods: Fifteen well-trained cyclists repeated intermittent cycling bouts (15 s at 30% of anaerobic power reserve; rest = 45 s) until exhaustion at sea level (FiO2 ∼0.21/end-exercise arterial oxygen saturation ∼96%), moderate hypoxia (FiO2 ∼0.16/∼90%), and severe hypoxia (FiO2 ∼0.12/∼79%). Rapid (rate of torque development [RTD]) and maximal isometric torque-production capacities of the knee extensors were assessed at baseline (visit 1) and exhaustion (visits 2–4). Results: Exercise capacity decreased with hypoxia severity (39 [30], 22 [13], and 13 [6] cycle efforts in sea level, moderate hypoxia, and severe hypoxia, respectively; P =.002). Changes in maximal-voluntary-contraction torque between baseline and postexercise in all conditions were not statistically significant (pooled values: −2.6% [5.7%]; P =.162). Peak RTD measured postexercise was reduced below baseline in all conditions (–21.5% [5.1%]; P ≤.015). Compared with baseline, absolute RTD values were lower at 0- to 30-millisecond (–35.1% [5.3%], P ≤.020), 0- to 50-millisecond (–40.0% [3.9%], P ≤.002), 0- to 100-millisecond (–30.7% [3.7%], P ≤.001), and 0- to 200-millisecond (–18.1% [2.4%], P ≤.004) time intervals in all conditions. Conclusions: Exhaustive intermittent cycling induces substantial yet comparable impairments in RTD of knee extensors between normoxia and moderate to severe hypoxia. [ABSTRACT FROM AUTHOR]

Purpose: Total hemoglobin mass (tHbmass) and blood volume (BV) are important determinants of maximal oxygen uptake and endurance capacity. Higher-caliber endurance athletes usually possess higher tHbmass and BV values. This study aimed to compare tHbmass and BV among swimmers of diverse competitive calibers and distances. Methods: Thirty swimmers (16 female and 14 male) participated in the study: 3 were tier 5, world class (869 [59] FINA points); 15 were tier 4, elite/international (853 [38] points); and 12 were tier 3, highly trained/national (808 [35] points). They specialized in competition distances ranging from 200 m to open-water 10 km. Between February 2019 and February 2020, all swimmers had their tHbmass and BV measured by carbon monoxide rebreathing 1 to 6 times and participated in multiple competitions and race events. Results: Relative tHbmass and BV were not different (P >.05) between tiers among women or among men (pooled tHbmass values 14.5 [0.5], 12.5 [1.5], 12.6 [2.3] g/kg for tier 5, tier 4, and tier 3, respectively). No differences were observed in relative tHbmass (P =.215) and BV (P =.458) between pool and open-water swimmers or between 200-, 400-, and 1500-m specialists (P >.05). No significant correlations were found between the highest measured absolute or relative tHbmass and BV and the highest FINA points scored over the follow-up period (R = −.42–.17, P =.256–.833), irrespective of competition distance. Conclusion: tHbmass and BV values did not differ between swimmers of different calibers or among competition distances. Furthermore, these values did not correlate with FINA points, either in males or in females. The present results indicate that hematological characteristics may have a lesser impact on swimming performance than on land-based endurance sports. [ABSTRACT FROM AUTHOR]

Objectives: Repeated-sprint training in hypoxia (RSH) is an effective way of improving physical performance compared with similar training in normoxia. RSH efficiency relies on hypoxia severity, but also on the oxidative–glycolytic balance determined by both sprint duration and exercise-to-rest ratio. This study investigated the effect of 2 types of RSH sessions during a classic altitude camp in world-class female rugby sevens players. Methods: Sixteen players performed 5 RSH sessions on a cycle ergometer (simulated altitude: 3000 m above sea level [asl]) during a 3-week natural altitude camp (1850 m asl). Players were assigned to 2 different protocols with either a high (RSH1:3, sprint duration: 8–10 s; exercise-to-rest ratios: 1:2–1:3; n = 7) or a low exercise-to-rest ratio (RSH1:5, sprint duration: 5–15 s; exercise-to-rest ratios: 1:2–1:5; n = 9). Repeated-sprint performances (maximal and mean power outputs [PPOmax, and PPOmean]) were measured before and after the intervention, along with physiological responses. Results: PPOmax (962 [100] to 1020 [143] W, P =.008, Cohen d = 0.47) and PPOmean (733 [71] to 773 [91] W, P =.008, d = 0.50) increased from before to after. A significant interaction effect (P =.048, d = 0.50) was observed for PPOmean, with a larger increase observed in RSH1:3 (P =.003). No interaction effects were observed (P >.05) for the other variables. Conclusion: A classic altitude camp with 5 RSH sessions superimposed on rugby-sevens-specific training led to an improved repeated-sprint performance, suggesting that RSH effects are not blunted by prolonged hypoxic exposure. Interestingly, using a higher exercise-to-rest ratio during RSH appears to be more effective than when applying a lower exercise-to-rest ratio. [ABSTRACT FROM AUTHOR]

Summary: This paper addresses the adaptive saturation prescribed performance control problem for air‐breathing hypersonic vehicles with parameter uncertainties and unknown external disturbances. First of all, different from the traditional performance function, a novel class of performance functions is presented without the initial state information, which does not require to reset parameters even if the initial velocity and altitude change. To ensure the successful design of the velocity controller and altitude controller, the constrained errors are transformed into the unconstrained errors by the projection technique. Secondly, the adaptive neural network and the sliding mode control techniques are combined to design the adaptive neural network sliding mode controllers, which guarantee that the velocity and altitude tracking errors can respectively approach the predetermined regions within the identical preset finite time. Finally, the effectiveness of the designed controllers is verified by an example with comparisons. [ABSTRACT FROM AUTHOR]

Summary: Unraveling the mechanisms of home‐field advantage (HFA) is essential to gain a complete understanding of litter decomposition processes. However, knowledge of the relationships between HFA effects and microbial communities is lacking.To examine HFA effects on litter decomposition, we identified the microbial communities and conducted a reciprocal transplant experiment, including all possible combinations of soil and litter, between sites at two elevations in cool‐temperate forests.Soil origin, rather than HFA, was an important factor in controlling litter decomposition processes. Microbiome‐wide association analyses identified litter fungi and bacteria specific to the source soil, which completely differed at a low taxonomic level between litter types. The relative abundance of these microbes specific to source soil was positively correlated with litter mass loss.The results indicated that the unique relationships between plant litter and soil microbes through plant–soil linkages drive litter decomposition processes. In the short term, soil disturbances resulting from land‐use changes have the potential to disrupt the effect of soil origin and hinder the advancement of litter decomposition. These findings contribute to an understanding of HFA mechanisms and the impacts of land‐use change on decomposition processes in forest ecosystems. See also the Commentary on this article by Keiser, 243: 2048–2049. [ABSTRACT FROM AUTHOR]

Luks AM, Grissom CK. Evaluation and Management of the Individual with Recurrent HAPE. High Alt Med Biol. 25:238–246, 2024. Individuals with a history of acute altitude illness often seek recommendations from medical providers on how to prevent such problems on future ascents to high elevation. Although many of these cases can be managed with pharmacologic prophylaxis and counseling about the appropriate rate of ascent alone, there are some situations in which further diagnostic evaluation may also be warranted. One such situation is the individual with recurrent episodes of high altitude pulmonary edema (HAPE), as one of several predisposing factors may be present that warrants additional interventions beyond pharmacologic prophylaxis and slow ascent and may even preclude future travel to high altitude. This review considers this situation in greater detail. Structured around the case of an otherwise healthy 27-year-old individual with recurrent episodes of HAPE who would like to climb Denali (6,190 m), the review examines the known risk factors for disease and then provides guidance regarding when and how to evaluate such individuals and appropriate steps to prevent HAPE on further ascents to high elevation. Except in rare circumstances, a history of recurrent HAPE does not preclude further ascent to high elevation, as a multipronged approach including pharmacologic prophylaxis, careful planning about the rate of ascent, and the degree of physical effort and other strategies, such as preacclimatization, staged ascent, and use of hypoxic tents, can be employed to reduce the risk of recurrence with future travel. [ABSTRACT FROM AUTHOR]

Fossati, Alexandre, and Aleid C. J. Ruijs. Changes in fingertip cold-induced vasodilatation (hunting reaction) on acute exposure to altitude. High Alt Med Biol. 25:212–217, 2024. Objective: Cold-induced vasodilation (CIVD) of the extremities is an interesting part of human physiology. Although the physiology of the CIVD reaction remains unknown, there are indications that hypoxia influences our CIVD reaction. The objective of this study is to measure the influence of acute hypoxia on the CIVD reaction of the fingertips. Methods: The CIVD reaction was measured using immersion of one hand in a water bath of 0°C in 12 healthy volunteers at low (1,235 m) and high (3,800 m) altitude during 35 minutes. High altitude was reached by a 20-minute cable car ride. Testing was performed indoors (room temperature, 22–25°C) at both altitudes. Data analysis was performed measuring the parameters of the CIVD reaction. Differences were found using the paired Student's t-test. Results: There was no significant difference in baseline finger temperature, onset time, peak time, and frequency of the CIVD reaction. However, at high altitude, maximum temperature and amplitude were significantly higher, slope was steeper, and minimum temperature was lower. Conclusion: We did not find evidence for a diminished CIVD reaction at high altitude due to hypoxia. [ABSTRACT FROM AUTHOR]

Hermand, Eric, Léo Lesaint, Laura Denis, Jean-Paul Richalet, and François J. Lhuissier. A step test to evaluate the susceptibility to severe high-altitude illness in field conditions. High Alt Med Biol. 25:158–163, 2024.—A laboratory-based hypoxic exercise test, performed on a cycle ergometer, can be used to predict susceptibility to severe high-altitude illness (SHAI) through the calculation of a clinicophysiological SHAI score. Our objective was to design a field-condition test and compare its derived SHAI score and various physiological parameters, such as peripheral oxygen saturation (SpO2), and cardiac and ventilatory responses to hypoxia during exercise (HCRe and HVRe, respectively), to the laboratory test. A group of 43 healthy subjects (15 females and 28 males), with no prior experience at high altitude, performed a hypoxic cycle ergometer test (simulated altitude of 4,800 m) and step tests (20 cm high step) at 3,000, 4,000, and 4,800 m simulated altitudes. According to tested altitudes, differences were observed in O2 desaturation, heart rate, and minute ventilation (p < 0.001), whereas the computed HCRe and HVRe were not different (p = 0.075 and p = 0.203, respectively). From the linear relationships between the step test and SHAI scores, we defined a risk zone, allowing us to evaluate the risk of developing SHAI and take adequate preventive measures in field conditions, from the calculated step test score for the given altitude. The predictive value of this new field test remains to be validated in real high-altitude conditions. [ABSTRACT FROM AUTHOR]

Introduction: Endurance exercise at altitude can increase cardiac output and pulmonary vascular pressure to levels that may exceed the stress tolerability of the alveolar--capillary unit. This study examined the effect of ultramarathon trail racing at different altitudes (ranging from <1000 m to between 1500 and 2700 m) on alveolar--capillary recruitment and lung diffusion. Methods: Cardiac and lung function were examined before and after an ultramarathon in 67 runners (age: 41 ± 9 yr, bodymass index: 23 ± 2 kg⋅m-2, 10 females), and following 12-24 h of recovery in a subset (n = 27). Cardiac biomarkers (cTnI and BNP) were assessed from whole blood, whereas lung fluid accumulation (comet tails), stroke volume (SV), and cardiac output (Q)were quantified via echocardiography. Lung diffusing capacity for carbonmonoxide (DLco) and its components, alveolar membrane conductance (Dm) and capillary blood volume (Vc), were determined via a single-breath method at rest and during three stages of submaximal semirecumbent cycling (20, 30, and 40W). Results:Average race time was 25 ± 12 h. From pre- to post-race, there was an increase in cardiac biomarkers (cTnI: 0.04 ± 0.02 vs 0.13 ± 0.03 ng⋅mL-1,BNP: 20 ± 2 vs 112 ± 21 pg⋅mL-1; P < 0.01) and lung comet tails (2 ± 1 vs 7 ± 6, P < 0.01), a decrease in resting and exercise SV (76 ± 2 vs 69 ± 2 mL, 40 W: 93 ± 2 vs 88 ± 2 mL; P < 0.01), and an elevation in Q at rest (4.1 ± 0.1 vs 4.6 ± 0.2 L⋅min-1, P < 0.01; 40 W: 7.3 ± 0.2 vs 7.4 ± 0.3 L⋅min-1, P = 0.899). Resting DLco and Vc decreased after the race ( P < 0.01), whereas Dm was unchanged ( P = 0.465); however, during the three stages of exercise, DLco, Vc, and Dm were all reduced from pre- to post-race (40 W: 36.3 ± 0.9 vs 33.0 ± 0.8 mL⋅min-1⋅mm Hg-1, 83 ± 3 vs 73 ± 2 mL, 186 ± 6 vs 170 ± 7 mL⋅min-1⋅mm Hg-1, respectively; P < 0.01). When corrected for alveolar volume and Q, DLco decreased from pre- to post-race ( P < 0.01), and changes in DLco were similar for all ultramarathon events ( P > 0.05). Conclusions: Competing in an ultramarathon leads to a transient increase in cardiac injury biomarkers, mild lung-fluid accumulation, and impairments in lung diffusion. Reductions in DLco are predominantly caused by a reduced Vc and possible pulmonary capillary de-recruitment at rest. However, impairments in alveolar--capillary recruitment and Dm both contribute to a fall in exertional DLco following an ultramarathon. Perturbations in lung diffusion were evident across a range of event distances and varying environmental exposures. [ABSTRACT FROM AUTHOR]

Near-ground flight is an important state of microducted fan aircraft. To explore the ground effects on the aerodynamic performance of microducted fan systems in near-ground hovering, a full three-dimensional (3D) numerical simulation methodology, which was validated by current experiments, is established in this paper. First, the hovering performance of ducted fan systems without ground effects was studied. Taking the system without ground effects as the reference, the ground effects due to altitude and slope were calculated and analyzed. The simulation results revealed that compared with the results of the current experiments, the maximum prediction error of 6% is reached when the induced power is 30 W. This indicates that the simulation methodology can work effectively. Moreover, a comparison of the performance of the system without ground effects revealed that ground effects can be ignored when the system altitude is greater than the duct length. In contrast, when the system altitude is within the duct length, the mass flow rate can greatly decrease with decreasing system altitude. This is because the blocking effect from the ground becomes significant. Additionally, the ground slope makes the flow field of the ducted fan system asymmetric. Globally, the system is not as sensitive to ground slopes within 18° because the ground effects for both sides of the ducted system are balanced to a certain extent. A side away from the ground can enhance the aerodynamic performance of the system. However, the other side close to the ground weakens the system performance. The mass flow and thrust performance can increase slightly when the slope is less than 12°, and the system behavior tends to stabilize when the slope is greater than 12°. Practical Applications: When microducted aircrafts are used to perform tasks, such as taking photos and ground detection, they are usually flown close to the ground, and alternate hovering with and without ground effects is frequently conducted. Thus, problems related to the aerodynamic interference between the terrain and the fuselage and between the fuselage and the rotor can occur. As shown in this study, the aerodynamic performance of ducted fan systems is affected by ground effects when ducted systems operate at an altitude of one times the duct length. In addition, at an altitude of 0.5 times the duct length, the thrust of the duct system increases with increasing slope within 18°. When the slope is greater than 12°, the influence of the slope from the left and right sides at the duct outlet is almost balanced. In general, the system altitude, ground slope and their effects on system performance need to be considered during the design process. The results can provide a design benchmark and optimization directions for designers, thereby reducing environmental constraints on ducted aircrafts and cost and improving the reliability. [ABSTRACT FROM AUTHOR]

The middle and lower reaches of the Yangtze River, a primary region for freshwater lakes in China, have undergone significant transformations throughout the Holocene. These changes, driven by factors such as sea-level rise, climate change, and human activities, have led to the progressive elevation of water levels in this area. As a result, a floodplain has emerged, characterized by the formation of numerous shallow lakes along the river course. However, the pattern of water-level changes in the main channel of the Yangtze River during the Holocene remains unclear. This gap in knowledge poses challenges for understanding sediment transport dynamics, the interactions between the river and its adjacent lakes, and the prevention and control of flood disasters in the Yangtze River basin. To shed light on these issues, our study compiled data on the surface elevation and water depth of 81 lakes in the mid-lower reaches of the Yangtze River basin. Additionally, we analyzed historical water-level records from the 1900s to the 1970s at eight gauging stations from Shashi to Jiangyin along the river's main stream. Our findings reveal that, particularly along the Jingjiang section, the basal elevation of most lakes is lower than the Yangtze River's water level during the dry season. Conversely, the water level of the main stream exceeds that of both the floodplain and the lakes enclosed by the Jingjiang embankment. In the tidal reach, especially within the Taihu Lake basin, the basal elevation of lakes typically falls below sea level. Meanwhile, lakes located along the section from Chenglingji to Wuhu exhibit basal elevations that correspond with the Yangtze River's annual average and dry season water levels. Given the widespread presence of lakes along the middle and lower reaches of the Yangtze River, our study introduces a new proxy for reconstructing the mean water level of the mid-lower Yangtze River in the Holocene. By analyzing sediments from Nanyi Lake and Chenyao Lake in the lower Yangtze River, we attempted to reconstruct the water level of the Yangtze River's main channel since 8 ka BP. [ABSTRACT FROM AUTHOR]

This study investigated the annual and seasonal mean temperature trends of North-East Indian region and surrounding territories over the period 1901–2020 with special emphasis on the trends from the recent past (1979–2020) utilising Climatic Research Unit (CRU) and ECMWF Reanalysis version-5 (ERA5) data. Spatio-temporal distribution of surface temperature across different seasons and associated biases between 1901 and 2020 were examined. The long-term trend of temperature was evaluated by linear regression for each month from the entire 120-yr period over the whole study domain. Further, Mann–Kendall and Sen's slope test was employed to assess the magnitude of the trend at 11 selected locations of varying altitudes. Areas around Bangladesh, which are notably polluted, as well as Myanmar and the Indian states of West Bengal, Jharkhand, Bihar and Chhattisgarh exhibited notable mean temperatures than the rest of the region. Both near-surface and 2m-temperature displayed positive trends for the period 1901–1950, 1979–2020, and during the whole duration 1901–2020, despite negative trends during 1951–1978. It has been observed that the regions with relatively higher elevations have experienced a larger warming rate than the low-elevation zones. Highlights: Annual and seasonal temperature trends for North-East India and surrounding territories were studied. Mann-Kendall and Sen's slope test was carried out for 11 selected locations. Post-monsoon season experienced greatest rise in mean temperatures between 1901 and 2020. Temperature data revealed increasing trends for periods 1901–1950, 1979–2020, but decreasing trends for 1951-1978. Warming rates were higher for higher elevation zones, particularly during the postmonsoon and winter months. [ABSTRACT FROM AUTHOR]

Mountainous zones are often characterized by complex orography and contacts between different aquifers that usually complicate the use of isotope hydrology techniques. The Apennine chain (Italy) and 10 mountain and mid‐mountain areas belonging to it are the objective of this study. An original isotopic data treatment, able to identify the most probable recharge area for several springs/springs' groups/wells, has been developed. The method consists of a two‐step approach: (1) the determination of the spring/wells computed isotope recharge elevation; (2) an advanced δ18O precipitation distribution model over the study area supported by statistical and GIS‐based procedures implemented by two processes: first, the clipping of precipitation δ18O values (depicted from the δ18O–elevation relationships obtained for each study area) over a most probable recharge area for each analyzed spring or well and, second, the calculation of the overlapping distribution between the spring/well mean δ18O values ± σ and the precipitation δ18O content for each outcropping aquifer. A new regional δ18O gradient covering 150 km latitudinal length of central Italy has been defined. Seven LMWL and δ18O–elevation relationships able to represent the local precipitation isotopic composition have been obtained. The mean elevation of the springs and wells recharge areas have been assessed by a comparison between the obtained gradient with nine δ18O gradients available in the literature and those obtained at a local scale. The new isotopic modeling approach can stress whether the mere isotope modeling based on the stable isotope of oxygen agrees with the hydrogeological setting of the study areas. [ABSTRACT FROM AUTHOR]

The increasing availability of unoccupied aircraft systems (UAS, also referred to as drones) has led to their use in taking vertical aerial photographs at relatively small spatial scales. These photographs can be used to measure the distances between objects appearing in the photographs. However, relief displacement can cause an object above or below ground level to appear at a point in a vertical aerial photograph that is not directly in-line with the object's actual location, causing a measurement error. A UAS was used in this study as a photographed airborne object because its location and altitude could be controlled. We were interested in predicting the horizontal distance of the UAS's appearance from the centre of a vertical aerial photograph. Predictions of the location of the photographed UAS's appearance in vertical aerial photographs over both level and sloped surfaces matched measured appearance distances within 0.06–0.48 m. This study shows that the relief displacement formulas typically used to compute the height of a vertical structure appearing in a vertical aerial photograph can additionally be used to compute the actual location of an airborne object (e.g., a flying UAS, bird, bat) if the object's altitude is known or can be estimated. [ABSTRACT FROM AUTHOR]

The shipborne High-Frequency Hybrid Sky-Surface Wave Radar integrates a sky-wave transmitting channel and a ground-wave receiving channel on a shipborne platform. This hybrid radar system combines a skywave source with the added flexibility of a far-away shipborne radar. Ionospheric stratification and height uncertainty introduce uncertainties in the sky-wave channel, resulting in multiple measurements of one target. Additionally, the shipborne platform position is affected by sea state, causing errors in azimuth accuracy setting and subsequently reducing target tracking precision. In this paper, we propose for the first time a target tracking method that combines ionospheric variations with the motion of a shipborne platform. It introduces the variational Bayesian method into the multiple detection mode, which solves the effects of ionospheric altitude error and orientation error of shipborne platforms due to different sea states on target tracking. Simulation experiments validate the effectiveness of the proposed method. Therefore, the proposed method promises advancements in shipborne radar systems for maritime surveillance applications. [ABSTRACT FROM AUTHOR]

Driving in an off‐road environment is challenging for autonomous vehicles due to the complex and varied terrain. To ensure stable and efficient travel, the vehicle requires consideration and balancing of environmental factors, such as undulations, roughness, and obstacles, to generate optimal trajectories that can adapt to changing scenarios. However, traditional motion planners often utilize a fixed cost function for trajectory optimization, making it difficult to adapt to different driving strategies in challenging irregular terrains and uncommon scenarios. To address these issues, we propose an adaptive motion planner based on human‐like cognition and cost evaluation for off‐road driving. First, we construct a multilayer map describing different features of off‐road terrains, including terrain elevation, roughness, obstacle, and artificial potential field map. Subsequently, we employ a convolutional neural network‐long short‐term memory network to learn the trajectories planned by human drivers in various off‐road scenarios. Then, based on human‐like generated trajectories in different environments, we design a primitive‐based trajectory planner that aims to mimic human trajectories and cost weight selection, generating trajectories that are consistent with the dynamics of off‐road vehicles. Finally, we compute optimal cost weights and select and extend behavioral primitives to generate highly adaptive, stable, and efficient trajectories. We validate the effectiveness of the proposed method through experiments in a desert off‐road environment with complex terrain and varying road conditions. The experimental results show that the proposed human‐like motion planner has excellent adaptability to different off‐road conditions. It shows real‐time operation, greater stability, and more human‐like planning ability in diverse and challenging scenarios. [ABSTRACT FROM AUTHOR]

The respiratory tract acts as a crucial barrier influenced by environmental factors, particularly affecting the homeostasis of its mucous membranes. Environmental conditions, including climate and atmospheric composition, play a significant role in the development and progression of respiratory diseases such as bronchial asthma and allergic rhinitis. Various risk factors, including genetic predisposition, viral infections, allergen exposure, and pollutants, along with changes in the microbiome, are key determinants in the manifestation and progression of these diseases. Certain pollutants like ozone (O3), nitrogen dioxide (NO2), and particulate matter (PM2.5) contribute to airway inflammation and hyperresponsiveness, potentially leading to increased oxidative stress and respiratory distress. This study aims to comparatively analyze the clinical characteristics and processes of free radical oxidation in the tissues of the respiratory tract of children with respiratory diseases living at different altitudes in Kyrgyzstan. A total of 209 children, including 104 with chronic respiratory diseases and 105 healthy controls, were examined. The study included clinical examinations, endoscopic evaluations, and biopsies when necessary. Biological samples such as exhaled air condensate and nasal lavages were collected to measure various biochemical indicators including total lipids, hydroperoxides, diene conjugates, and oxidative index. Preliminary results indicate that children residing at higher altitudes exhibit more pronounced changes in respiratory tissues, likely due to climatic and environmental factors specific to high-altitude regions. These children showed significantly higher levels of free radical oxidation products and altered surface tension in biological samples compared to those living at lower altitudes. Complaints such as shortness of breath, difficulty breathing, cough, and nasal congestion were also more frequent among children at higher altitudes. The study highlights the need for further research to better understand the impact of altitude on respiratory health and to develop effective strategies for the treatment and prevention of respiratory diseases in children. Future research should focus on the longitudinal tracking of respiratory health, detailed environmental assessments, and the development of targeted public health strategies to address the unique challenges faced by high-altitude populations. Ultimately, this research aims to improve respiratory health outcomes for children living in diverse geographic settings. [ABSTRACT FROM AUTHOR]

Summary: Background: The composition of the root microbiome affects the host's growth, with variation in the host genome associated with microbiome variation. However, it is not known whether this intra-specific variation of root microbiomes is a consequence of plants performing targeted manipulations of them to adapt to their local environment or varying passively with other traits. To explore the relationship between the genome, environment and microbiome, we sampled seeds from teosinte populations across its native range in Mexico. We then grew teosinte accessions alongside two modern maize lines in a common garden experiment. Metabarcoding was performed using universal bacterial and fungal primers to profile their root microbiomes. Results: The root microbiome varied between the two modern maize lines and the teosinte accessions. We further found that variation of the teosinte genome, the ancestral environment (temperature/elevation) and root microbiome were all correlated. Multiple microbial groups significantly varied in relative abundance with temperature/elevation, with an increased abundance of bacteria associated with cold tolerance found in teosinte accessions taken from high elevations. Conclusions: Our results suggest that variation in the root microbiome is pre-conditioned by the genome for the local environment (i.e. non-random). Ultimately, these claims would be strengthened by confirming that these differences in the root microbiome impact host phenotype, for example, by confirming that the root microbiomes of high-elevation teosinte populations enhance cold tolerance. [ABSTRACT FROM AUTHOR]

Different meteor radars at low latitudes observed abnormally strong westward mesospheric winds around the March Equinox of 2023, that is, during the first phase of the Mesospheric Semiannual Oscillation. This event was the strongest of at least the last decade (2014–2023). The westward winds reached −80 m/s at 82 km of altitude in late March, and decreased with increasing altitude and latitude. A considerable increase in the diurnal tide amplitude was also observed. The Whole Atmosphere Community Climate Model with thermosphere‐ionosphere eXtension constrained to meteorological reanalysis up to ∼50 km does not capture the observed low‐latitude behavior. Additionally, these strong mesospheric winds developed during the westerly phase of the Quasi‐Biennial Oscillation, in accordance with the filtering mechanism of gravity waves in the stratosphere proposed in previous works. Finally, analysis of SABER temperatures strongly suggests that the breaking of the migrating diurnal tide may be the main driver of these strong winds. Plain Language Summary: Around the March Equinox of 2023, abnormally strong westward winds were observed in the low latitude region at altitudes between 80 and 100 km. This event was the strongest in at least the last decade. The westward winds reached a maximum amplitude of 80 m/s at 82 km of altitude during late March, and decreased with increasing altitude and latitude. A considerable increase in the amplitude of the diurnal tide was also observed. Simulations based on a whole atmosphere global circulation model constrained to meteorological reanalysis up to ∼50 km do not capture the observed behavior. Results based on specular meteor radar and satellite measurements suggest that the strong westward winds were driven by two main factors: the filtering mechanism of eastward‐propagating gravity waves in the stratosphere and the breaking of the diurnal tide at about 85 km of altitude. Key Points: Strong mesospheric westward winds during March equinox 2023 are observed globally at low latitudesThe westward winds reached a peak of −80 m/s at 82 km, the largest in the last ten years, accompanied by an enhancement of the diurnal tideThe breaking of the DW1 plays a role in generating these strong winds, in addition to the filtering of gravity waves in the stratosphere [ABSTRACT FROM AUTHOR]

Leaf-cutting ants are among the most prominent herbivores in neotropical forests and savannas, and Argentina represents the southern limit of their distribution. Despite their importance, few systematic studies analyze the presence and distribution of leaf-cutting ants in Argentina. Our aim was to describe, through an intensive field sampling, the leaf-cutting ant species present in the central Argentine mountains and analyze their distribution along the elevation gradient. We collected ants from 69 nests in 56 out of the 250 plots visited along the study elevation gradient (400–2700 m above sea level) in seven different habitats, from forests to rocky areas. We found six species. The most frequent were Acromyrmex lobicornis and Acromyrmex crassispinus, while Acromyrmex heyeri, Amoimyrmex silvestrii, Amoimyrmex striatus, and Amoimyrmex bruchi were far less frequent. The species distributed at the highest elevation was A. lobicornis (1223 to 2163 m a.s.l.), showing significant differences with the other species. We found leaf-cutting ants in all habitats, with a higher presence in grazing lawns, shrublands, and exotic forests. Our results indicate that leaf-cutting ants are present in most of the mountain range, as the area above their upper limit of distribution represents less than 5% of the total mountain area. [ABSTRACT FROM AUTHOR]

Field surveys on large centipedes of Nui Chua National Park, south-central part of Vietnam, were conducted in September 2023 and February 2024. As a result, a total of 12 species/subspecies belonging to five genera and two families of the order Scolopendromorpha were recorded. Of two families, Scolopendridae has nine species in four genera, while Cryptopidae has only two species in one genus. In addition, the distribution pattern of the large centipedes is discussed based on the season (rainy versus dry), altitudes, and different habitats. [ABSTRACT FROM AUTHOR]

Background: Periodontitis is the sixth-most common disease worldwide. The oral microbiome composition and its association with Periodontal disease (PD) have been largely explored; however, limited studies have explored the microbial profiles of both oral and toothbrushes in patients with PD. Thus, this study aimed to ascertain the oral and toothbrushes microbial composition in high-altitude populations, hypothesizing that their correlation with periodontal health would differ from those at lower altitudes, potentially indicating links between environmental factors, microbial colonization patterns, and periodontal health in distinct geographic contexts. Methods: In the present study, we enrolled 35 individuals including 21 healthy and 14 diagnosed with PD from the Lhasa region of Tibet, China. Saliva and toothbrush samples were collected from each participant to assess the association between toothbrush usage and oral microbiome with PD using 16 S rRNA gene-specific V3-V4 regions sequencing. To assess the oral and toothbrush microbiome composition and diversity and its possible link to PD. Results: Significantly higher Alpha diversity (Shannon index) was observed between the PD group and PD toothbrushes (p = 0.00021) and between the PD group and Healthy toothbrushes (p = 0.00041). The predominant species were Proteobacteria, Bacteroidota, Firmicutes, Actinobacteria, and Fusobacteria, with genera Pseudomonas, Veillonella, Neisseria, Acinetobacter, and Haemophilus. In addition, PICRUST2 analysis unveiled 44 significant pathways differentiating the disease and healthy groups, along with 29 pathways showing significant differences between their respective toothbrush microbial profiles. The distinct oral and toothbrush microbial composition among high-altitude populations suggests potential adaptations to the challenges of high-altitude environments. Conclusion: This study emphasizes the importance of tailored dental care strategies, accounting for altitude and racial factors, to effectively manage periodontal health in these communities. Further research is warranted to investigate the specific microbial mechanisms and develop targeted interventions for optimizing oral health in populations across varying altitudes. [ABSTRACT FROM AUTHOR]

For clades originating in warm climates, the tropical niche conservatism hypothesis predicts that current biological assemblages in colder or drier climates are expected to have lower phylogenetic diversity, and species in colder or drier climates are expected to be more closely related to each other (i.e., higher phylogenetic clustering). Liverworts are one of the oldest clades of extant land plants. They originated about 500 Ma during a warm (“greenhouse”) period and experienced multiple major cycles of warm and cold periods. Here, I test the tropical niche conservatism hypothesis using liverwort assemblages distributed along an elevational gradient crossing about 5000 m of elevation in the central Himalaya. I found that, in general, phylogenetic diversity and dispersion decrease with increasing elevation and thus with decreasing temperature, which is consistent with the tropical niche conservatism hypothesis. Phylogenetic diversity decreases with elevation monotonically, but phylogenetic dispersion decreases with elevation in a triphasic (zig‐zag) pattern, which is generally consistent with the triphasic pattern found in angiosperms and polypod ferns along the same elevational gradient. Temperature‐related variables explained approximately the same amount of the variation in phylogenetic diversity and dispersion as did precipitation‐related variables, although mean annual temperature explained 9%−15% more variation than did annual precipitation. Climate extreme variables explained approximately the same amount of variation in phylogenetic diversity and dispersion as did climate seasonality variables. [ABSTRACT FROM AUTHOR]

Based on the hourly precipitation data from the observation stations, the accuracy of hourly QPEs from Fengyun geostationary satellites FY-4A, FY-2 H and multi-satellite joint IMERG-Early precipitation products over the southeastern Tibetan Plateau were compared and assessed. And the relationship between the accuracy of various satellites and terrain were discussed. The results show that: (1) The QPEs of FY-4A, FY-2 H and IMERG-Early can reflect the temporal and spatial distribution characteristics of real precipitation; (2) The QPEs of FY-4A and FY-2 H overestimate the precipitation in the researched region, and the overestimation of FY-4A was more obvious, while IMERG-Early QPE underestimates the precipitation. IMERG-Early QPE showed the best overall accuracy performance. (3) All three satellite QPEs were less accurate in July and August. (4) The accuracy of the QPEs of FY-4A and FY −2 H were better than that of IMERG-Early QPE in heavy rainfall. (5) The accuracy of three satellite QPEs increase with the increase of altitude. The results can provide reference for selecting satellite QPEs for operational applications in the southeastern Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Navigation system performance degrades significantly in complex environments. It is important to analyze satellite visibility through 3D terrain modelling and separate the satellite signals propagated by NLOS to suppress the NLOS error. However, the traditional 3D terrain modelling visibility analysis method based on the pure terrain cover angle is only suitable for determining the visibility of GNSS satellites and may incorrectly separate LOS propagate measurement signals from members with low relative ranges and elevation angles under air–ground swarm conditions. To this end, this paper proposes a belief-propagating cooperative navigation method based on air–ground visibility analysis, which avoids mistakenly separating close-range LOS cooperative navigation signals by simultaneously considering the distances, elevation angles, and azimuths of the signal sources relative to the air–ground swarm members. The simulation shows that the cooperative navigation NLOS identification method based on air–ground visibility analysis proposed in this paper can more accurately realize the separation of NLOS signals under cooperative conditions than the traditional pure angular 3D terrain modelling visibility analysis method can, and the localization error of the members to be assisted is significantly reduced. [ABSTRACT FROM AUTHOR]

This research investigates precision enhancement in regional quasi-geoid refinement through ADS80 tri-linear array scanning stereoscopic imagery for aerial triangulation coupled with GNSS gravity-potential modeling. By acquiring stereoscopic imagery and analyzing triangulation accuracy using an ADS80 camera, we performed this study over the Qinghai–Tibet Plateau's elevated, desolate terrain, collecting 593 GNSS points following high-precision stereoscopic imagery modeling. By utilizing 12 gravity satellite models, we computed geoid heights and China's 1985 Yellow Sea elevations for 28 benchmarks and GNSS points, thereby refining the Qinghai Province Quasi-Geoid Model (QPQM) using geometric techniques. The findings reveal that POS-assisted ADS80 stereoscopic imagery yields high-precision triangulation with maximal horizontal and elevation accuracies of 0.083/0.116 cm and 0.053/0.09 cm, respectively, across five control point arrangements. The RMSE of normal heights for 1985, processed via these GNSS points, achieved decimeter precision. By applying error corrections from benchmarks to the 1985 elevation data from gravity satellites and performing weighted averaging, the precision of EGM2008, SGG-UGM-2, and SGG-UGM-1 models improved to 8.61 cm, 9.09 cm, and 9.38 cm, respectively, surpassing the QPQM by 9.22 cm to 9.99 cm. This research demonstrates that the proposed methods can significantly enhance the precision of regional quasi-geoid surfaces. Additionally, these methods offer a novel approach for rapidly establishing regional quasi-geoid models in the uninhabited areas of the Qinghai–Tibet Plateau. [ABSTRACT FROM AUTHOR]

Doppler positioning, as an early form of positioning, has regained significant research interest in the context of Low Earth Orbit (LEO) satellites.Given the LEO mega-constellation scenario, the objective function of Doppler positioning manifests significant nonlinearity, leading to ill-conditioning challenges for prevalent algorithms like iterative least squares (LS) estimation, especially in cases where inappropriate initial values are selected. In this study, we investigate the causes of ill-posed problems from two perspectives. Firstly, we analyze the linearization errors of the Doppler observation equations in relation to satellite orbital altitude and initial value errors, revealing instances where traditional algorithms may fail to converge. Secondly, from an optimization theory perspective, we demonstrate the occurrence of convergence to locally non-unique solutions for Doppler positioning. Subsequently, to address these ill-conditioning issues, we introduce Tikhonov regularization terms in the objective function to constrain algorithm divergence, with a fitted model for the regularization coefficient. Finally, we conduct comprehensive simulation experiments in both dynamic and static scenarios to validate the performance of the proposed algorithm. On the one hand, when the initial values are set to 0, our algorithm achieves high-precision positioning, whereas the iterative LS fails to converge. On the other hand, in certain simulation scenarios, the iterative LS converges to locally non-unique solutions, resulting in positioning errors exceeding 50 km in the north and east directions, several hundred kilometers in the vertical direction, and velocity errors surpassing 120 m/s. In contrast, our algorithm demonstrates typical errors of a position error of 6.8462 m, velocity error of 0.0137 m/s, and clock drift error of 8.3746 × 10 − 6 s/s. This work provides an effective solution to the sensitivity issue of initial points in Doppler positioning and can serve as a reference for the algorithm design of Doppler positioning receivers with LEO mega-constellations. [ABSTRACT FROM AUTHOR]

Simple Summary: Male anurans attract conspecific females for reproduction by giving advertisement calls. As calling implies high energetic costs, theory predicts that in mixed-species assemblages call features differ among species to reduce acoustic interference. Each species occupies a distinct acoustic niche in the soundscape. In equatorial wetlands water bodies for reproduction are available all over the year, therefore, we expect that diel and seasonal partitioning of acoustic space should be less important than differences in call structure to reduce competition and niche overlap. Additionally, acoustic communities should be species-saturated. We tested these predictions in four communities at 2546–3188 m a.s.l. in the Volcanoes National Park, Rwanda. Using automated recording devices from September 2019 to March 2020, we obtained an extensive dataset on call activity. The communities included 4–6 species, depending on the wetland structure, with a common stock of three species (Hyperolius castaneus, H. glandicolor, Leptopelis kivuensis). Independent of elevation, niche breadth for call features was similar and overlap reduced by partitioning the frequency range used. The diel and seasonal niche breadth of specific call activity varied according to the local temperature regime at different altitudes. We conclude that stochastic niche theory describes accurately the processes shaping equatorial highland communities. The soundscape is a complex arrangement of sounds originating from animals and the environment. It is considered a reliable proxy for ecosystem niche structure at the community level. Acoustic communities of anuran species include advertising males, which compete in acoustic space for conspecific females. Stochastic niche theory predicts that all local niches are occupied, and the acoustic community is species-saturated. Acoustic niches, which include the spectral and temporal call structure and diel and seasonal patterns of call activity, are of similar breadth with small overlap. We tested these predictions in four communities inhabiting pristine wetlands at 2546–3188 m a.s.l. in the Volcanoes National Park, Rwanda. We sampled 74 days of hourly 5 min recordings of the local soundscape (September 2019–March 2020) using passive automated monitoring devices (Songmeter SM4). We identified species based on the advertisement call features and measured call activity as calls per minute. The communities included 4–6, species depending on wetland structure, with a shared stock of three species (Hyperolius castaneus, H. glandicolor, Leptopelis kivuensis). Independent of elevation, niche breadth for call features was similar among species and overlap reduced by partitioning the frequency range used. The diel and seasonal niche breadth of specific call activity varied according to the local temperature regime at different altitudes representing the variable part of the acoustic niche. We conclude that communities are indeed species-saturated and acoustic niches differ primarily by the fixed call features remaining locally adaptable by the modulation of the call activity pattern, corroborating the predictions of the stochastic niche theory. [ABSTRACT FROM AUTHOR]

We describe two new species of the microhylid frog genus Choerophryne Van Kampen, 1914 from the mountains of Papua New Guinea. The first is a scansorial species known only from foothill forest at altitudes of 440-950 m a.s.l. on the northern slopes of Papua New Guinea's Central Cordillera. It is a moderately large member of the genus (males 16.8-20.6 mm snout-urostyle length) that utters long series of short whistling calls each lasting 77-125 ms. The second species is arboreal and known only from a small area of montane forest at altitudes of 2060-2300 m a.s.l. on the southern edge of the Central Cordillera. It is also moderately large for the genus (three males with snout-urostyle lengths of 19.3-20.6 mm) and produces long series of short buzzing calls, each lasting 124-173 ms. Descriptions of these two species bring the number of recognised Choerophryne to 39, and at least 18 additional species in the genus await formal description. [ABSTRACT FROM AUTHOR]

We use community phylogenetics to elucidate the community assembly mechanisms for Geometridae moths (Lepidoptera) collected along a complete rainforest elevational gradient (200–3700 m a.s.l) on Mount Wilhelm in Papua New Guinea. A constrained phylogeny based on COI barcodes for 604 species was used to analyse 1390 species x elevation occurrences at eight elevational sites separated by 500 m elevation increments. We obtained Nearest Relatedness Index (NRI), Nearest Taxon Index (NTI) and Standardised Effect Size of Faith's Phylogenetic Diversity (SES.PD) and regressed these on temperature, plant species richness and predator abundance as key abiotic and biotic predictors. We also quantified beta diversity in the moth communities between elevations using the Phylogenetic Sorensen index. Overall, geometrid communities exhibited phylogenetic clustering, suggesting environmental filters, particularly at higher elevations at and above 2200 m a.s.l and no evidence of overdispersion. NRI, NTI and SES.PD showed no consistent trends with elevation or the studied biotic and abiotic variables. Change in community structure was driven by turnover of phylogenetic beta-diversity, except for the highest 2700–3200 m elevations, which were characterised by nested subsets of lower elevation communities. Overall, the elevational signal of geometrid phylogeny was weak-moderate. Additional insect community phylogeny studies are needed to understand this pattern. [ABSTRACT FROM AUTHOR]

Background: Exposure to a high-altitude environment is a risk factor for cerebral venous thrombosis (CVT) probably due to hypercoagulability. The study aims to explore the unique characteristics of CVT patients in high-altitude areas of China by comparing them with those in plain areas. Methods: We retrospectively included consecutive patients with CVT admitted to Tibet Autonomous Region People's Hospital (altitude 3650 m) and Peking Union Medical College Hospital (altitude 43.5 m) between January 2015 and December 2023. Patients from the plateau and the plain were considered two independent groups in this study. The risk factors, clinical and radiological presentations, treatment, and outcomes were analyzed and compared between the two groups. Results: A total of 169 patients with CVT were included in the study, 48 patients from plateau and 121 patients from plain. The median age was 27 and 34 years old, and women accounted for 66.7% and 54.5% respectively. Headache (91.7% vs. 71.1%, P = 0.004), altered consciousness (31.3% vs. 16.5%, P = 0.033), hemorrhage (41.7% vs. 19.0%, P = 0.002), and venous infarction (50.0% vs. 25.6%, P = 0.002) on imaging were more common in patients from plateau than those from plain. Pregnancy or puerperium was significantly more common in highland patients (25% vs. 5.8%, P < 0.001). The levels of D-Dimer (1.7 vs. 0.8 mg/L FEU, P = 0.01), fibrinogen (3.7 vs. 3.0 g/L, P < 0.001), hemoglobin (157 vs. 129 g/L, P = 0.01), white blood cells (9.6 vs. 7.5*1012/L, P < 0.001) and highly sensitive C-reactive protein (20.2 vs. 3.2 mg/L, P = 0.005) were remarkably higher in highland patients. The percentage of receiving anticoagulant therapy was lower in high-altitude patients (70.8% vs. 93.4%, P < 0.001). Favorable outcome at follow-up was observed in 81.4% of highland patients and 90.7% of lowland patients, with a median follow-up time of 330 days and 703 days respectively. Conclusions: The more severe clinical and imaging manifestations along with prominent inflammatory and hypercoagulable states were observed in plateau CVT patients, probably due to exposure to the hypoxic environment at high altitude. Pregnancy or puerperium were more common in highland patients. The overall prognosis of CVT patients from both groups were favorable. [ABSTRACT FROM AUTHOR]

The route to chaos and the phase dynamics of the large scales in a rotating shallow-water model have been rigorously examined through the construction of an autonomous five-mode Galerkin truncated system employing complex variables, useful in investigating how large/meso-scales are destabilized and how their dynamics evolves and transits to chaos. This investigation revealed two distinct transitions into chaotic behaviour as the level of energy introduced into the system was incrementally increased. The initial transition manifests through a succession of bifurcations that adhere to the established Feigenbaum sequence. Conversely, the subsequent transition, which emerges at elevated levels of injected energy, is marked by a pronounced shift from quasi-periodic states to chaotic regimes. The genesis of the first chaotic state is predominantly attributed to the preeminence of inertial forces in governing nonlinear interactions. The second chaotic state, however, arises from the augmented significance of free surface elevation in the dynamical process. A novel reformulation of the system, employing phase and amplitude representations for each truncated variable, elucidated that the phase components present a temporal piece-wise locking behaviour by maintaining a constant value for a protracted interval, preceding an abrupt transition characterised by a simple rotation of ±π, even as the amplitudes display chaotic behaviour. It was observed that the duration of phase stability diminishes with an increase in injected energy, culminating in the onset of chaos within the phase components at high energy levels. This phenomenon is attributed to the nonlinear term of the equations, wherein the phase components are introduced through linear combinations of triads encompassing disparate modes. When the locking durations vary across modes, the resultant dynamics is a stochastic interplay of multiple π phase shifts, generating a stochastic dynamic within the coupled phase triads, observable even at minimal energy injections. [ABSTRACT FROM AUTHOR]

Coastal wetlands play an important role in the global water and biogeochemical cycles. Climate change makes it more difficult for these ecosystems to adapt to the fluctuation in sea levels and other environmental changes. Given the importance of eco-geomorphological processes for coastal wetland resilience, many eco-geomorphology models differing in complexity and numerical schemes have been developed in recent decades. However, their divergent estimates of the response of coastal wetlands to climate change indicate that substantial structural uncertainties exist in these models. To investigate the structural uncertainty of coastal wetland eco-geomorphology models, we developed a multi-algorithm model framework of eco-geomorphological processes, such as mineral accretion and organic matter accretion, within a single hydrodynamics model. The framework is designed to explore possible ways to represent coastal wetland eco-geomorphology in Earth system models and reduce the related uncertainties in global applications. We tested this model framework at three representative coastal wetland sites: two saltmarsh wetlands (Venice Lagoon and Plum Island Estuary) and a mangrove wetland (Hunter Estuary). Through the model-data comparison, we showed the importance of using a multi-algorithm ensemble approach for more robust predictions of the evolution of coastal wetlands. We also found that more observations of mineral and organic matter accretion at different elevations of coastal wetlands and evaluation of the coastal wetland models at different sites in diverse environments can help reduce the model uncertainty. [ABSTRACT FROM AUTHOR]

In order to solve the problems of loss of moving targets due to the flight status of the unmanned aerial vehicle (UAV) itself, the interference of the environment the randomness of the target and other reasons in the process of collecting moving target image information by the UAV platform, a deep deterministic policy gradient (DDPG) algorithm UAV following method based on moving target recognition was proposed. Facing the vehicle target on the highway, the relationship among the height, posture and high-speed vehicle motion of the UAV was analyzed. the velocity adaptive model of the target detection frame rate of the mobile platform was estab lished, and the flight attitude and speed of the UAV were corrected in real time according to the motion state of the target, so that the UAV could maintain the relative position and angle with the target. Then, based on the value network of DDPG algorithm, the value of UAV taking spe- cific actions in different states was estimated; the strategy network generates the strategy of UAV taking actions in a given state, and gives UAV flight altitude and speed control parameters for target tracking, so that the UAV could automatically adjust the flight state according to the movement change of the target, and realize the adaptive tracking of the moving target. Simulation experiments show that the DDPG algorithm can provide stable flight attitude data and a reliable control basis for the UAV following task, and the UAV can track the ground moving target in a circular area with a speed range of 0~33 m/s and a radius of 120 m in real time, and can achieve continuous and stable tracking within the endurance range. [ABSTRACT FROM AUTHOR]

Dispersal is a complex series of movements before an individual establishes a home range. Animals must travel and forage in unfamiliar landscapes that include anthropogenic risks such as road crossings, harvest, and urban landscapes. We compare dispersal behavior of juvenile mountain lions (Puma concolor) from two geographically distinct populations in California and Nevada, USA. These two sites are ecologically similar but have different management practices; hunting is permitted in Nevada, whereas mountain lions are protected in California. We used GPS‐collar data and net‐squared displacement analysis to identify three dispersal states: exploratory, departure, and transient home range. We then compared each dispersal state of the two mountain lion populations using an integrated step selection analysis (iSSA). The model included explanatory variables hypothesized to influence one or more dispersal states, including distance to forest, shrub, water, hay and crop, developed lands, and four‐wheel drive roads, as well as elevation and terrain ruggedness. Results revealed consistent habitat selection between sites across most landscape variables, with one notable exception: anthropogenic covariates, including distance to developed land, distance to hay and crop, and distance to four‐wheeled drive roads, were only statistically significant on modeled habitat selection during dispersal in the population subject to hunting (i.e., Nevada). Results suggest that hunting (pursuit with hounds resulting in harvest) and non‐lethal pursuit (pursuit with hounds but no harvest allowed) increase avoidance of anthropogenic landscapes during dispersal for juvenile mountain lions. By comparing populations, we provided valuable insights into the role of management in shaping dispersal behavior. [ABSTRACT FROM AUTHOR]

We consider a complex control problem: making a monopod accurately reach a target with a single jump. The monopod can jump in any direction at different elevations of the terrain. This is a paradigm for a much larger class of problems, which are extremely challenging and computationally expensive to solve using standard optimization-based techniques. Reinforcement learning (RL) is an interesting alternative, but an end-to-end approach in which the controller must learn everything from scratch can be non-trivial with a sparse-reward task like jumping. Our solution is to guide the learning process within an RL framework leveraging nature-inspired heuristic knowledge. This expedient brings widespread benefits, such as a drastic reduction of learning time, and the ability to learn and compensate for possible errors in the low-level execution of the motion. Our simulation results reveal a clear advantage of our solution against both optimization-based and end-to-end RL approaches. [ABSTRACT FROM AUTHOR]

Considering that the existing path planning algorithms for mobile robots under rugged terrain do not consider the ground flatness and the lack of optimality, which leads to the instability of the center of mass of the mobile robot, this paper proposes an improved A* algorithm for mobile robots under rugged terrain based on the ground accessibility model and the ground ruggedness model. Firstly, the ground accessibility and ruggedness models are established based on the elevation map, expressing the ground flatness. Secondly, the elevation cost function that can obtain the optimal path is designed based on the two types of models combined with the characteristics of the A* algorithm, and the continuous cost function is established by connecting with the original distance cost function, which avoids the center-of-mass instability caused by the non-optimal path. Finally, the effectiveness of the improved algorithm is verified by simulation and experiment. The results show that compared with the existing commonly used path planning algorithms under rugged terrain, the enhanced algorithm improves the smoothness of paths and the optimization degree of paths in the path planning process under rough terrain. [ABSTRACT FROM AUTHOR]

Clouds are crucial in regulating the Earth's energy budget. Global cloud top heights have been easily retrieved from satellite measurements, but there are few methods for determining cloud base height (CBH) from satellite measurements. The Cloud Base Altitude Spatial Extrapolator (CBASE) algorithm was proposed to derive the height of the lower-troposphere liquid cloud base by using the Cloud-Aerosol Lidar with Orthogonal polarization cloud aerosol LiDAR (CALIOP) profiles and weather observations at airports from aviation routine and special weather report (METARs and SPECIs, called METAR) observation data in the United States. A modification to the CBASE algorithm over China (CNMETAR-CBASE) is presented in this paper. In this paper, the ability of the CBASE algorithm to calculate CBH in China is evaluated, and METAR observations over China (CNMETAR) were then used to modify the CBASE algorithm. The results including CNMETAR observation data in China can better retrieve CBH over China compared with the results using the original CBASE algorithm, and the accuracy of the global CBH results has been improved. Overestimations of CBH with the original algorithm range from 500 to 800 m in China, which have been reduced to about 300 m with an improved algorithm. The deviations calculated by the algorithm also have a significant reduction, from 480 m (CBASE) to 420 m (CNMETAR-CBASE). In conclusion, the modified CBASE algorithm not only calculates the CBH more accurately in China but also improves the results of the global CBH retrieved from satellites. [ABSTRACT FROM AUTHOR]

Aim: Greater quantification and characterisation of training load (TL) throughout Live-high, train-high (LHTH) altitude (ALT) training is required to identify periodisation strategies that may lead to physiological and performance improvements in swimmers. Purpose: This study aimed to examine the physiological responses and performance outcomes of 14 high-performance swimmers (FINA points: 836.0 ± 35.1) following 3 weeks of LHTH at 2320 m, while characterising the training load periodisation strategy adopted during the intervention. Methods: Haemoglobin (Hb) mass was measured pre-, 7 and 14 days post-ALT via CO rebreathing. Performance in each athlete's primary event at national standard meets were converted to FINA points and compared from pre-to-post-ALT. TL was quantified at sea level (SL) and ALT through session rating of perceived exertion (RPE), where duration of each session was multiplied by its RPE for each athlete, with all sessions totalled to give a weekly TL. Pre-to-post-ALT changes were evaluated using repeated-measures ANOVA. Results: Hb mass increased significantly from 798 ± 182 g pre-ALT to 828 ± 187 g at 7 days post (p = 0.013) and 833 ± 205 g 14 days post-ALT (p = 0.026). Weekly TL increased from SL (3179 ± 638 au) during week one (4797 ± 1349 au, p < 0.001) and week two (4373 ± 967 au, p < 0.001), but not week three (3511 ± 730 au, p = 0.149). No evidence of improved SL swimming performance was identified. Conclusion: A periodisation strategy characterised by a sharp spike in TL followed by a slight de-load towards the end of a LHTH intervention led to improved physiological characteristics but no change in the competitive performance of high-performance swimmers. [ABSTRACT FROM AUTHOR]

Climatic suitability rationalization indicators based on meteorological data were collected from 20 national meteorological observation stations in and around the Ili River Valley from 1991 to 2020 to optimize agricultural planting structures, improve the utilization of climate resources, and effectively regionalize suitable planting areas for Shushanggan apricot in the Ili river valley. Additionally, the biological characteristics of the Shushanggan apricot and the key meteorological factors were influencd its growth and development. Subsequently, to develope a spatial distribution model for these climatic suitability indicators. By reclassifying and overlaying the four regionalization indicators, a comprehensive climate-appropriate regionalization for Shushanggan apricot was obtained cultivation in the Ili river valley. The analysis revealed that the cultivation of Shushanggan apricots in the Ili River Valley can be categorized into four distinct areas: most suitable, suitable, sub-suitable, and unsuitable. The most suitable planting areas are predominantly situated in the river valley plains and low mountainous regions, with altitudes ranging between 700 and 1200 m, particularly in the northern part of the Ili River Valley, the north segment of Wusun mountain, and the east segment of Xinyuan county. Sub-optimal planting areas are found in river valley plains and low mountainous regions, with altitudes below 700 m and between 1200 and 1500 m. Conversely, unsuitable planting areas are in mid-low mountainous regions above 1,500 m. These findings provide valuable insights for governmental bodies seeking to optimize agricultural cultivation structures in the Ili River Valley. [ABSTRACT FROM AUTHOR]

Current guidelines for prolonged altitude exposure suggest altitude levels ranging from 2000 to 2500 m to optimize an increase in total hemoglobin mass (Hbmass). However, natural low altitude locations (<2000 m) remain popular, highlighting the interest to investigate any possible benefit of low altitude camps for endurance athletes. Ten elite racewalkers (4 women and 6 men) underwent a 4‐week "live high‐train high" (LHTH) camp at an altitude of 1720 m (PIO2 = 121 mmHg; 20.1°C; 67% relative humidity [RH]), followed by a 3‐week tapering phase (20 m; PIO2 = 150 mmHg; 28.3°C; 53% RH) in preparation for the World Athletics Championships (WC). Venous blood samples were withdrawn weekly during the entire observation period. In addition, blood volumes were determined weekly by carbon monoxide rebreathing during altitude exposure and 2 weeks after return to sea level. High‐level performances were achieved at the WC (five placings among the Top 10 WC races and three all‐time career personal bests). A slight but significant increase in absolute (+1.7%, p = 0.03) and relative Hbmass (+2.3%, p = 0.02) was observed after 4‐week LHTH. In addition, as usually observed during LHTH protocols, weekly training distance (+28%, p = 0.02) and duration (+30%, p = 0.04) significantly increased during altitude compared to the pre‐LHTH period. Therefore, although direct causation cannot be inferred, these results suggest that the combination of increased training load at low altitudes with a subsequent tapering period in a warm environment is a suitable competition‐preparation strategy for elite endurance athletes. Highlights: Despite current guidelines for prolonged altitude exposure, natural low altitude locations (<2000 m) remain popular among elite endurance athletes, highlighting the interest to investigate any possible benefit of low altitude camps.This study reports that elite racewalkers achieved a modest but significant increase in Hbmass after a 4‐week LHTH camp at an altitude of 1720 m. Furthermore, this intervention led to performance success at the subsequent World Athletics Championships.The combination of an increased training load while exposed to low altitude is suggested as a valuable competition preparation strategy for elite endurance athletes. [ABSTRACT FROM AUTHOR]

We sought to determine the effects of acute simulated altitude on the maximal lactate steady state (MLSS) and physiological responses to cycling at and 10 W above the MLSS-associated power output (PO) (MLSSp and MLSSp+10, respectively). Eleven (4 females) participants (means [SD]; 28 [4] yr; V̇ o 2max: 54.3 [6.9] mL·kg−1·min−1) acclimatized to ∼1,100 m performed 30-min constant PO trials in simulated altitudes of 0 m sea level (SL), 1,111 m mild altitude (MILD), and 2,222 m moderate altitude (MOD). MLSSp, defined as the highest PO with stable (<1 mM change) blood lactate concentration ([BLa]) between 10 and 30 min, was significantly lower in MOD (209 [54] W) compared with SL (230 [56] W; P < 0.001) and MILD (225 [58] W; P = 0.001), but MILD and SL were not different (P = 0.12). V̇ o 2 and V̇ co 2 decreased at higher simulated altitudes due to lower POs (P < 0.05), but other end-exercise physiological responses (e.g., [BLa], ventilation [V̇ e ], heart rate [HR]) were not different between conditions at MLSSp or MLSSp + 10 (P > 0.05). At the same absolute intensity (MLSSp for MILD), [BLa], HR, and V̇E and all perceptual variables were exacerbated in MOD compared with SL and MILD (P < 0.05). Maximum voluntary contraction, voluntary activation, and potentiated twitch forces were exacerbated at MLSSp + 10 relative to MLSSp within conditions (P < 0.05); however, condition did not affect performance fatiguability at the same relative or absolute intensity (P > 0.05). As MLSSp decreased in hypoxia, adjustments in PO are needed to ensure the same relative intensity across altitudes, but common indices of exercise intensity may facilitate exercise prescription and monitoring in hypoxia. NEW & NOTEWORTHY: This study demonstrates the power output and metabolic rate associated with the maximal lactate steady-state (MLSS) decline in response to simulated altitude; however, common indices of exercise intensity remained unchanged when cycling was performed at the work rate associated with MLSS at each simulated altitude. These results support previous studies that investigated the effects of hypoxia on alternative measures of the critical intensity of exercise and will inform exercise prescription/monitoring across altitudes. [ABSTRACT FROM AUTHOR]

The fusion of multiple precipitation products can effectively improve precipitation accuracy. In order to reduce the uncertainty of traditional precipitation members and improve the applicability of Bayesian model averaging (BMA), this study proposes a dynamic ensemble calibration framework with seasonality and real‐time capability, namely dynamic K‐nearest neighbour BMA (DKBMA), for the integration calibration and comparison of ERA5 reanalysis products and three satellite precipitation products (CMORPH, 3B42RT and 3B42V7). The application results of the DKBMA in the Yujiang River basin, Southern China, during the period of 2011–2016 show that (1) the DKBMA can overcome the problem of ERA5 error interference on the seasonal scale, reduce the systematic bias of ensemble precipitation members at coastal sites and demonstrate strong robustness at different altitudes. (2) Compared with the traditional BMA, the DKBMA has significantly improved accuracy, especially in capturing extreme precipitation events. The correlation coefficient has increased from 0.793 (traditional BMA) to 0.841 (DKBMA), the root‐mean‐square error has decreased from 35.61 (traditional BMA) to 30.95 (DKBMA), and the absolute value of relative bias has decreased from 62.80% (traditional BMA) to 49.94% (DKBMA). The proposed DKBMA in this study can provide a new solution for the fusion of multi‐source precipitation products in data‐scarce regions. [ABSTRACT FROM AUTHOR]

(1) Background: The aim of this work was to characterize climatic evolution and change based on multicriteria classification through the dynamics of bioclimatic indices in viticulture across Italy and its regional administrative boundaries, focusing on latitudes and elevations. (2) Methods: This study analyzes climate change influences on Italian viticulture with reference to historical information (1991–2021) and future scenarios (until 2080) primarily based on the SSP2-4.5 and SSP5-8.5 scenarios, taking into account 13 GCMs. (3) Results: The bioclimatic indices have all shown a significant trend in the historical period, with an increase in temperature and a decrease in precipitation, reflecting their effects on the entire Italian territory with respect to the HI, up to 44° N for the CI, and up to 46° N for the DI, regardless of altitude. The future scenarios highlighted a shift towards the warmer classes of the two temperature-based indices (HI and CI) for both SSPs, especially for altitudes up to 900 m a.s.l. The DI-based classification based on the DI remained relatively stable in Italy over time, although DI values will become increasingly negative in the near future. (4) Conclusions: The climate in Italy is warming, especially in the south and in the coastal regions. By 2080, more areas will be "very hot" with "warm nights". Drought will also increase and have a negative impact on viticulture. These findings spotlight the need for adaptive strategies in viticulture to hold satisfactory productivity under changing climatic conditions. [ABSTRACT FROM AUTHOR]

In order to improve the intelligent perception and adaptability of the 6G network, drones joined this challenge. For large-scale long-range Unmanned Aerial Vehicle (UAV), most of the time during normal flight belongs to fixed altitude flight. It is required to sail along the planned optimal path. Whether it can fly along the optimal path is mainly attributed to the tracking problem of horizontal flight trajectory. In order to minimize the UAV horizontal plane tracking error, it is necessary to consider the influence of many factors (such as strong winds, heavy rain, obstacles, etc.). Due to the complexity of High-Altitude environment, these disturbances are uncertain. In addition, there are some dynamic errors in the model of UAV control system, and these errors also have uncertainties. And, due to the change of global planning path coordinates, the control system needs to adjust the set value in real time during AUV horizontal trajectory tracking, and the conventional control algorithm is difficult to meet the requirements. Therefore, firstly, the influence of prediction uncertainty of grey prediction on AUV horizontal track tracking control is used; Then the grey prediction is improved according to the practical application; Ultimately, the control law is designed by combining the grey prediction with the control method. Finally, the grey prediction fuzzy adaptive PID method of UAV flight control is applied to the planned path simulation, and good control results are obtained. [ABSTRACT FROM AUTHOR]

High altitude platforms (HAPs) have been considered a promising paradigm to assist mobile edge computing (MEC) in wide-area internet of things (IoT) scenarios due to their wide coverage, large payload capacity, and excellent channel quality. In this paper, a HAP-assisted MEC system is investigated, where the HAP is deployed as an edge server to provide computation offloading services for IoT terminal devices (TDs) with limited local computing capability. Offloading is enabled by uplink and downlink communications between TDs and HAP in a clustered non-orthogonal multiple access (C-NOMA) manner. Considering potential economic benefits and expected environmental impact, we aim to minimize system energy consumption, subject to the constraints on maximum tolerable delay, transmit power budget, and uplink and downlink decoding power. To this end, an iterative algorithm based on relaxation and successive convex approximation methods is proposed, which efficiently solves this challenging non-convex problem by alternately optimizing power allocation and HAP deployment. Numerical results show that the proposed scheme significantly reduces the system energy consumption compared to the other benchmark scheme. It is also shown that the system energy consumption is indirectly effected by the decoding order in the uplink and downlink C-NOMA. [ABSTRACT FROM AUTHOR]

Drought is an extreme phenomenon which occurs due to a prolonged duration of peculiarly low precipitation in a region. This can affect various sectors like agriculture, livestock, and human health among others. Countries like Pakistan which have agriculture-based economy can have severe consequences due to drought. In this study, Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI) are applied to examine drought features at different time scales over Punjab Province which is the food basket for Pakistan. The drought occurrence was examined through drought frequency, concentrating on spatial and temporal scales and considering different geomorphologies. A modified Mann-Kendall test and multiple linear regression are used to examine monthly data from 12 weather stations collected between 1980 and 2020. Stations at high elevations have very variable precipitation, which can lead to periodic droughts. Surprisingly, SPEI shows more drought sensitivity than SPI. The severity of the drought has decreased recently, especially after the 1998–2002 peak period. Correlation analysis demonstrates a substantial link between SPI and SPEI at high elevation stations, with Murree displaying the strongest correlation (0.9334) on a one-month time frame, and Bahawalpur exhibiting a comparably lower correlation (0.6824). Positive trends in SPI and SPEI values are revealed by Mann-Kendall trend tests, which are most prominent at higher elevations and on the northern Punjab. On a one-month time scale, the Mianwali station has the strongest trend in SPEI (0.1497), whereas Bahawalnagar has negligible trends in both SPI (0.0214) and SPEI (0.0459). At high elevation sites, the frequency of drought is constantly high, and SPEI routinely detects greater drought at low elevations. Similar drought frequencies are shown by both indices for the northern region of Punjab. The results of a multiple linear regression model demonstrate the significant impact of meteorological variables on monthly mean precipitation, which advances our knowledge of Punjab's spatiotemporal drought dynamics and provides important information for planning for resilience and water resource management. [ABSTRACT FROM AUTHOR]