Altitude Levels Research Articles

Prevalence of metabolic syndrome and its components according to altitude levels: a systematic review and meta-analysis

Prevalence of metabolic syndrome and its components according to altitude levels: a systematic review and meta-analysis

Effects of short-term exposure to high altitude on cardiac function

Abstract Background What effect does short-term high altitude exposure have on heart function? Can people exercise in the highlands? what changes occur in heart function during exercise in highland areas? This study will explore these topics. Objectives To investigate the difference of heart function between people at sea level and at high altitude, and to study the changes of short time exercise on heart function at high altitude. Methods 36 healthy subjects were recruited to go to high altitude area after underwent exercise echocardiography on a supine bicycle at sea level. They ascended to 3600m within 24 hours by bus.Another exercise echocardiography was performed on the day of arrival.Heart rate (HR), blood pressure (BP) and blood oxygen saturation (SaO2) were monitored in real time during both examinations. Parameters such as left ventricular ejection fraction, E/ E 'and mean pulmonary artery pressure (mPAP) after rest and exercise were calculated.ΔmPAP /CO was calculated by (mean mPAP at peak -mean mPAP at rest )/(mean CO at peak-mean CO at rest). Results At peak exercise,SaO2,TRV,RVD2,SPAP,mPAP,PVR, ePLAR,RVAS,ΔMpap/CO were much higher at high altitude levels. (P < 0.001); E,A,FAC,ΔS were significantly lower than that of the sea leval; at rest, HR,TRV,sPAP,mPAP ,PVR were much higher at high altitude levels than at sea leval(P < 0.001)，SaO2,RVOT ACT, were significantly lower than that of the sea leval(P < 0.001). Conclusions When healthy people are in high altitude environment, the heart function changes obviously. Supine bicycle exercise stress echocardiography can well monitor the heart function changes and provide quantitative data, providing new technical methods for future related research.

Hematological and performance adaptations to altitude training (2,320m) in elite middle-distance and distance swimmers.

Elite swimmers often schedule altitude training camps ahead of major events in an attempt to maximize performance. However, the relationships between altitude-induced hematological changes, markers of training adaptation, and performance changes in such context are unclear. This study assessed hematological status, markers of daily adaptation, and swimming performance in elite middle-distance and distance swimmers during a 22-day altitude training camp at 2,320m, 2weeks prior to World Championship qualification competition. Venous blood was obtained and total hemoglobin mass (tHbmass) measured (CO rebreathing) in 7 elite swimmers (4 females, 3 males) 8days before and on day 22 of the altitude camp. Resting heart rate, peripheral oxygen saturation, urinary specific gravity, body mass, fatigue and self-reported sleep duration and quality were monitored daily during the altitude camp. Swimming performance was assessed through a standardized set (6 sets of 4 maximal repetitions of 100m front crawl) on days 3, 10 and 17 of the camp, and at sea level competitions (200m-1,500m) immediately after the camp, and 2weeks later. tHbmass (+5.6 ± 3.3%; range: 2.1%-11.0%; p < 0.05), red blood cell count, hemoglobin concentration, hematocrit increased at the end of the training camp (p < 0.05). Performance at altitude improved throughout the camp (+1.4 ± 0.4%; range: 0.7%-2.5%; p < 0.05). No significant relationship was noted between hematological changes, the change in altitude performance and any of the monitored daily markers of adaptation during the camp. Compared to the swimmers' previous personal best, competition performances did not improve immediately (2.5% ± 1.9% slower times) and 2weeks after altitude (1.2% ± 1.4% slower times). The 22-day altitude training camp at 2,320m was beneficial for elite swimmers' tHbmass, hematological status and performance at altitude, but these benefits did not clearly translate into enhanced sea level performance immediately after or 2weeks later. The present study confirms the large inter-individual variability in hematological responses to altitude training, and that the improvement in performance at altitude and sea level may depend on factors other than the increase in tHbmass alone.

ANALYSIS OF FLAVONOID COMPOUNDS OF GANDARIA FRUIT (Bouea macrophylla GRIFF) AT VARIOUS Elevations IN AMBON ISLAND

Introduction: Gandaria (Bouea macrophylla Griff) is a tropical fruit plant which in the Maluku region is only found in several areas, namely Ambon Island as the largest production center. Gandaria contains secondary metabolites, one of which is flavonoids, which are generally found in various plants and are very potential to be researched and developed by Indonesian researchers because they have many good benefits for living things. Methods: This study used qualitative and quantitative research methods to test the color of the gandaria fruit samples to identify the presence of flavonoid compounds and then to find out how much flavonoids were in the gandaria fruit research samples taken from various altitudes on Ambon island. Results: The results of this study indicate that the Suli area as the area with the lowest altitude where the sample was taken contains the highest levels of flavonoids with an average of 21.498 mgQE/g, then the area of medium altitude where the sample is taken, namely Kusu-kusu has a flavonoid content with an average of 9.692 mgQE/g then in the area with the highest altitude level in sampling, namely Soya with the lowest flavonoid content with an average flavonoid content of 9.084 mgQE/g.

Exploring the role of canopy cover and environmental factors in shaping carbon storage in Desa’a forest, Ethiopia

BackgroundDry Afromontane forests play a vital role in mitigating climate change by sequestering and storing carbon, as well as reducing greenhouse gas emissions. Despite previous research highlighting the importance of carbon stocks in these ecosystems, the influence of canopy cover and environmental factors on carbon storage in dry Afromontane forests has been barely assessed. This study addresses this knowledge gap by investigating the effects of environmental factors and vegetation cover on carbon stocks in Desa’a forest, a unique and threatened Afromontane dry forest ecosystem in northern Ethiopia. Data on woody vegetation, dead litter, grass biomass, and soil samples were collected from 57 plots. A one-way analysis of variance (ANOVA) was performed at a 95% confidence level (α = 0.05) to examine the influence of canopy cover and environmental factors on the carbon stocks of various pools.ResultsAmong the 35 woody species identified, Juniperus procera was the most dominant, while Carissa edulis Vahl and Eucalyptus globulus were the least dominant. The average total carbon stock was 92.89 Mg ha−1, with contributions from aboveground carbon, below-ground carbon, litter carbon, grass carbon, and soil organic carbon. Among the carbon pools, soil organic carbon had the highest carbon stock, accounting for 76.8% of the total, followed by above-ground biomass carbon at 17.7%. Significant variations in carbon stocks were found across altitude class and canopy level but not slope and aspect factors.ConclusionsIn summary, altitude and canopy level were found to significantly influence carbon stocks in Desa’a forest, providing valuable insights for conservation and climate change mitigation efforts in dry Afromontane forests. Forest intervention planning and management strategies should consider the influence of different environmental variables and tree canopy levels.

The atmospheric composition of the ultra-hot Jupiter WASP-178 b observed with ESPRESSO

Context. Ultra-hot Jupiters (UHJ) have emerged as ideal testbeds for new techniques for studying exoplanet atmospheres. Only a limited number of them are currently well studied, however. Aims. We search for atmospheric constituents for the UHJ WASP-178 b with two ESPRESSO transits. Additionally, we show parallel photometry that we used to obtain updated and precise stellar, planetary, and orbital parameters. Methods. The two transits we obtained were analysed with narrow-band transmission spectroscopy and with the cross-correlation technique to provide detections at different altitude levels. We focused on searching for Na I, Hα, Hβ, Hγ, Mg I, and Li I lines in narrow-band data, as well as Fe I and Fe II, and attempted to confirm Mg I with the cross-correlation technique. We corrected for the Rossiter-McLaughlin effect and regions with a low signal-to-noise ratio due to Na I absorption in the interstellar medium. We then verified our results via bootstrapping. Results. We report the resolved line detections of Na I (5.5σ and 5.4σ), Hα (13σ), Hβ (7.1σ), and tentatively Mg I (4.6σ). With a cross-correlation, we confirm the Mg I detection (7.8 σ and 5.8 σ), and we additionally report the detections of Fe I (12σ and 10σ) and Fe II (11σ and 8.4σ) on both nights separately. The detection of Mg I remains tentative, however, because the results on the two nights differ. The results also differ compared with the properties derived from the narrow-band data. Conclusions. None of our resolved spectral lines probing the middle to upper atmosphere shows significant shifts relative to the planetary rest frame. Hα and Hβ exhibit a respective line broadening of 39.6 ± 2.1 km s−1 and 27.6 ± 4.6 km s−1, however, indicating the onset of possible escape. WASP-178 b differs from similar UHJ by its lack of strong atmospheric dynamics in the upper atmosphere. The broadening seen for Fe I (15.66 ± 0.58 km s−1) and Fe II (11.32 ± 0.52 km s−1) might indicate the presence of winds in the mid-atmosphere, however. Future studies of the impact of the flux variability caused by the host star activity might shed more light on the subject. Previous work indicated the presence of SiO cloud-precursors in the atmosphere of WASP-178 b and a lack of Mg I and Fe II. However, our results suggest that a scenario in which the planetary atmosphere is dominated by Mg I and Fe II is more likely. In light of our results, we encourage future observations to further elucidate these atmospheric properties.

Balancing conservation and development: a review of navigating Malaysian forest policies and initiatives

Although Malaysia is renowned for its tropical rainforest and biodiversity, deforestation for economic development remains contentious. This review analyses Malaysian forest policies, afforestation, and forest carbon payment mechanisms, and makes policy recommendations. It categorises forests by altitude and protection level, highlighting diverse ecosystems. Policies, including the National Forestry Act of 1978 (Amendment 1993), Sabah Forest Policy (2018), and Sarawak Forest Policy (2019), prioritise sustainable management. Agencies shift towards conservation, moving beyond timber‐centric approaches, while revenue streams such as carbon offsetting, payment for ecosystem services, and non‐timber forest products gain traction. Forest connectivity programs protect state‐owned lands from logging, and have increased protected forests since 2005. Government incentives for afforestation and reforestation include tax exemptions. Malaysia commits to REDD+ with forest carbon offset and conservation certificate schemes. A structured implementation approach is proposed, emphasizing the need to understand and communicate market demand for forest carbon offset initiatives.

Performance assessment of ammonia as a turbofan engine fuel during various altitude levels

This research is focused on analysing the thermodynamic performance outcomes of the ammonia-fueled turbofan engine. The assessment contains exergy sustainability, economic aspects, environmental impact, and energy and exergy analysis at take-off, climb-out, climb and cruise levels. The required mathematical modelling for thermodynamic analysis of the turbofan engine was performed with Engineering Equation Solver (EES) software. Then it was calculated how much improvement could be achieved in the amount of emissions that occur in the case of using ammonia and kerosene. It was determined that the combustion chamber (CC) has the greatest improvement potential of the turbofan. The maximum productivity lack rate (83.87 %) was determined in the CC at the cruise level, minimum productivity lack rate (0.72 %) was found to be the LPC at the same level. During the take-off level, the turbofan engine had the highest energetic and exergetic fuel costs, reaching 37138.38 $/h and 34195.78 $/h, respectively. The highest specific fuel consumption (85.602 kg/kN.h), thermal efficiency (53.78 %) and thrust efficiency (40.29 %) of the turbofan engine using ammonia as fuel carried out at the take-off level. Eventually, the maximum carbon dioxide emission reduction was calculated as 43.84 tonCO2/h when compared to kerosene fuel.

Characterization of lipid composition and physicochemical properties of clarified yak milk fat

In the present study, the samples of clarified milk fat (CMF) of yak species (Arunachali yak and yak-cow hybrid) were collected and analysed for physicochemical parameters, colour values, fatty acid composition and triglyceride profile, and FT-IR characteristics. The obtained results showed that CMF contains a variable amount of moisture (0.25 %–20.28 %), free fatty acid (0.12–2.03 % oleic acid), peroxide values (0.30–1.20 meq.O2/kg fat), Reichert Meissl value (19.06–23.54) and Butyro-Refractrometer reading (43.03–44.47). The colour value (L*, a*, b*) varied with altitude level and region significantly (p < 0.05). The regional variations in triglycerides and fatty acid profile of CMF were also found significantly (p < 0.05). The preliminary data of FT-IR spectra of all samples showed almost similar functional groups but slight difference in the absorbance as well as peaks in the finger print region.

Flying to high-altitude destinations.

Every year millions of people fly to high-altitude destinations. They thereby expose themselves to specific high-altitude conditions. The hypoxic environment (low ambient oxygen availability) constitutes a major factor affecting health and well-being at high altitude. While the oxygen availability is already moderately reduced inside the aircraft cabin, this reduction becomes aggravated when leaving the plane at high-altitude destinations. Especially if not pre-acclimatized, the risk of suffering from high-altitude illnesses, e.g., acute mountain sickness, high-altitude cerebral or pulmonary edema, increases with the level of altitude. In addition, diminished oxygen availability impairs exercise tolerance, which not only limits physical activity at high altitude but may also provoke symptomatic exacerbation of pre-existing diseases. Moreover, the cold and dry ambient air and increased levels of solar radiation may contribute to adverse health effects at higher altitude. Thus, medical pre-examination and pre-flight advice, and proper preparation (pre-acclimatization, exercise training, and potentially adaptation of pharmacological regimes) are of utmost importance to reduce negative health impacts and frustrating travel experiences.

High-level performances following low altitude training and tapering in warm environments in elite racewalkers.

Current guidelines for prolonged altitude exposure suggest altitude levels ranging from 2000 to 2500m to optimize an increase in total hemoglobin mass (Hbmass). However, natural low altitude locations (<2000m) 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 1720m (PIO2=121mmHg; 20.1°C; 67% relative humidity [RH]), followed by a 3-week tapering phase (20m; PIO2=150mmHg; 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 2weeks 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.

Prevalence and Risk Factors of Ocular Demodex at Ultra-High Altitude and Sea Level: A Cross-Sectional Study of Shigatse and Shanghai.

Purpose: Demodex infestation is a risk factor for several ocular surface diseases. However, the prevalence of ocular Demodex infection in the ultra-high altitude population is not clear. This study aimed to compare the prevalence and factors associated with Demodex in populations residing in ultra-high altitude region and sea level areas. Methods: Consecutive patients who visited Shigatse People's Hospital (> 4,000 m) and Shanghai Tongren Hospital (sea level) for eye complaints between January 2023 and January 2024 were included. Subjects were divided into ultra-high altitude and sea level groups. All subjects underwent eyelash epilation for ocular Demodex identification and counting. Demographic and lifestyle information was also collected. Results: A total of 517 subjects were eligible, including 255 subjects in the ultra-high-altitude group and 262 subjects in the sea level group. In the overall analysis, the prevalence of ocular Demodex infection was significantly different between the ultra-high-altitude and sea level groups (15.7% vs. 33.2%, P < 0.001). Multiple logistic regression showed that age, time spent outdoors, and makeup were associated with ocular Demodex infection in both groups. In addition, in the ultra-high-altitude group, people who wear sun hats outdoors were more likely to be infected with Demodex. Conclusion: The infection rate of ocular Demodex in the residents of ultra-high altitude area was significantly lower than that in the residents of sea level area, which may be related to lower ambient temperature, lower humidity, and higher solar radiation. Additionally, age, time spent outdoors, and makeup may be associated with ocular Demodex infection.

The Feature Analysis and Modeling of Upper Atmospheric Midnight Density Maximum

The features of upper atmospheric midnight density maximum (MDM) around low geographic latitudes are studied based on neutral mass densities data at altitudes 360–480 km, derived from the accelerometer measurements aboard on the three polar orbiting satellites CHAMP (CHAllenging Minisatellite Payload), GRACE-A (Gravity Recovery and Climate Experiment-A), and SWARM-C (The Earth's Magnetic Field and Environment Explorers-C). The MDM appears during the local times from 23:00 to 02:00 LT (Local Time), whose peak locates at the low latitudes within 15∘ and two valleys locate at the middle latitudes between 35∘ and 45∘ on both hemispheres separately. The structure of MDM drifts toward the southern hemisphere overall. The MDM's amplitude decreases with increases in altitude and solar radiation level. The seasonal effect weakens the MDM's amplitudes around the summer and winter solstices, while the amplitudes around the spring and autumn equinoxes are extremely significant due to the slight seasonal difference between both hemispheres. Three atmospheric density models DTM2000 (Drag Temperature Model 2000), NRLMSISE00 (US Naval Research Laboratory Mass Spectrometer and Incoherent Scatter Radar Extended atmosphere model), and JB2008 (Jacchia-Bowman 2008 model) are used to simulate the MDM along these three satellites' orbits, and compared with the observations. It is found that the JB2008 model is failed to describe the MDM, and the other two models underestimate the MDM's amplitudes at altitudes 360 km and 480 km: the simulated amplitudes by the DTM2000 model are 46% and 53% of the observed amplitudes, respectively, and only 33% and 26% for the NRLMSISE00 model. These three models are also failed to depict the MDM's variation with altitude, solar radiation level, and seasonal effects. In order to correct the model prediction, a 6th-order Legendre polynomial of geographic latitude, coupled with arguments of local time and altitude, is designed to fit the MDM signals from the three satellites' observations. In terms of amplitude and phase of the MDM, the fitting results agree with the observations very well, and the correlation coefficient is 0.923. It indicates that this empirical polynomial could be helpful to the density model correction and high accuracy prediction of spacecrafts in low Earth orbits.

Effects of Altitude training on Ethiopian endurance athletes recovery heart rate and hematological variables

Background and Study Aim. A recent study indicates that Ethiopian middle- and long-distance athletes originate from diverse geographical regions, including areas of varying elevation. This study aimed to analyze the impact of altitude training on hematological parameters and recovery heart rates among young male endurance trainees training at sites located at different altitude levels. Material and Methods. The study employed a quasi-experimental, counterbalanced approach involving 15 male trainees. Five individuals from each training center experienced the standard training program across three distinct geographical locations and elevations. Pre- and post-test data were collected on red blood cells, hemoglobin, hematocrit, platelet count, and recovery heart rate before and after six months, from 6:00–8:00 AM. ANCOVA was utilized to analyze the data. Results. Following the intervention, the mean Red Blood Cell (RBC) count was observed to be higher in trainees from low altitude (5.18±0.33) compared to those from moderate altitude (4.48±0.14 and 5.21±0.22), with a significance level of p&lt;0.05. The mean Hemoglobin (HGB) count was found to be higher in moderate altitude trainees (17.00±0.70 and 16.31±0.65) than in low altitude trainees (15.82±1.37), although this difference was not statistically significant (p&gt;0.05). Similarly, the mean Hematocrit (HCT) count was low for both low altitude (46.04±3.49) and moderate altitude trainees (46.46±3.9 and 45.42±1.54), with no significant difference noted (p&gt;0.05). The mean Platelet (PLT) count was 226.8±75.88 for low altitude trainees and 265.8±23.18, 276±53.96 for moderate altitude trainees, with no significant difference between the groups (p&gt;0.05). As for the recovery heart rate, mean values showed no significant difference between the pre-and post-test groups. In the pretest, the mean recovery heart rate was 30.00±14.70 for low-altitude trainees and 43.20±8.90, 43.20±13.68 for moderate-altitude trainees (p&gt;0.05). In the post-test, the mean recovery heart rate was 25.20±7.82 for low-altitude trainees and 32.40±10.04, 36.00±7.35 for moderate-altitude trainees (p&gt;0.05). Conclusions. The findings indicate that training at different altitudes impacts the hematological and cardiovascular systems of endurance athletes in varied ways. This underscores the importance of developing tailored training programs to optimize performance and recovery. These results are particularly relevant for coaches and athletes seeking to enhance endurance training outcomes through altitude training strategies.

Path Planning of Unmanned Aerial Vehicles Based on an Improved Bio-Inspired Tuna Swarm Optimization Algorithm.

The Sine-Levy tuna swarm optimization (SLTSO) algorithm is a novel method based on the sine strategy and Levy flight guidance. It is presented as a solution to the shortcomings of the tuna swarm optimization (TSO) algorithm, which include its tendency to reach local optima and limited capacity to search worldwide. This algorithm updates locations using the Levy flight technique and greedy approach and generates initial solutions using an elite reverse learning process. Additionally, it offers an individual location optimization method called golden sine, which enhances the algorithm's capacity to explore widely and steer clear of local optima. To plan UAV flight paths safely and effectively in complex obstacle environments, the SLTSO algorithm considers constraints such as geographic and airspace obstacles, along with performance metrics like flight environment, flight space, flight distance, angle, altitude, and threat levels. The effectiveness of the algorithm is verified by simulation and the creation of a path planning model. Experimental results show that the SLTSO algorithm displays faster convergence rates, better optimization precision, shorter and smoother paths, and concomitant reduction in energy usage. A drone can now map its route far more effectively thanks to these improvements. Consequently, the proposed SLTSO algorithm demonstrates both efficacy and superiority in UAV route planning applications.

The quality and flavour effects of robusta coffee cultivated at various altitudes in Aceh Tengah District - Gayo Highlands were investigated

Abstract Gayo Highland (GH) is known for its arabica GH also planted robusta in lower altitude areas, but its quality is rarely reported. In Indonesia, robusta is mostly planted in Lampung and Java and thus is well-examined and reported. This study explores the quality of the Gayo-robusta-picked coffee cherries and its green bean and the effect of post-harvest practices farmers apply towards the quality of Gayo robusta. This research used RBF Design with two factors and four repetitions. Factor A is altitude levels, which are 600-800 m.a.s.l, 801-1.000 m.a.s.l and 1.001-1.200 m.a.s.l. Factor B is post-harvest practices, which have two levels with and without post-harvest practices. The result shows that 800-1.000 m.a.s.l altitude showed better quality of red cherries (75.25% ± 3.30) as the black and green cherries percentages are lower than other levels. As the altitude increases, green beans tend to have higher moisture, defect value, and bigger size. The average moisture of the green bean was 12.44%, the defect value was 12.51%, and the green bean size that passed the 6.5 mm sieve was 86.84%. For the cupping test, the average score was 67.33. The best treatment was robusta was planted on 600-800 m.a.s.l and, with post-harvest practices, had a cup test value of 80.25 and was considered a quality of fine Robusta.

Examining the Effects of Altitude on Workload Demands in Professional Basketball Players during the Preseason Phase.

Basketball involves frequent high-intensity movements requiring optimal aerobic power. Altitude training can enhance physiological adaptations, but research examining its effects in basketball is limited. This study aimed to characterize the internal/external workload of professional basketball players during preseason and evaluate the effects of altitude and playing position. Twelve top-tier professional male basketball players (Liga Endesa, ACB; guards: n = 3, forwards: n = 5, and centers: n = 4) participated in a crossover study design composed of two training camps with nine sessions over 6 days under two different conditions: high altitude (2320 m) and sea level (10 m). Internal loads (heart rate, %HRMAX) and external loads (total distances covered across speed thresholds, accelerations/decelerations, impacts, and jumps) were quantified via wearable tracking and heart rate telemetry. Repeated-measures MANOVA tested the altitude x playing position effects. Altitude increased the total distance (+10%), lower-speed running distances (+10-39%), accelerations/decelerations (+25-30%), average heart rate (+6%), time in higher-intensity HR zones (+23-63%), and jumps (+13%) across all positions (p < 0.05). Positional differences existed, with guards accruing more high-speed running and centers exhibiting greater cardiovascular demands (p < 0.05). In conclusion, a 6-day altitude block effectively overloads training, providing a stimulus to enhance fitness capacities when structured appropriately. Monitoring workloads and individualizing training by playing position are important when implementing altitude training, given the varied responses.

Investigation of Diesel Spray Characteristics in Low-temperature and Low-pressure Conditions

This study investigates the influence of altitude and injection pressure on diesel fuel spray characteristics, aiming to optimize diesel usage in high-altitude conditions. Experiments were conducted at three altitude levels (plains, 1670 m, and 2400 m) with corresponding atmospheric pressures and temperatures, alongside six injection pressures ranging from 50 MPa to 100 MPa. The investigation focused on key spray parameters: equivalence ratio, spray penetration velocity, turbulence kinetic energy, evaporation rate, spray penetration distance, and Sauter Mean Diameter (SMD). Findings indicate that increased injection pressure enhances spray penetration velocity, evaporation rate, and turbulence kinetic energy, while reducing SMD, irrespective of altitude. Conversely, higher altitudes were associated with increased spray penetration speed, larger SMD, decreased evaporation rate, increased turbulence, and a higher equivalence ratio. The study concludes that both altitude and injection pressure significantly impact diesel spray characteristics, providing essential theoretical support for the application and optimization of diesel fuels in varied altitude conditions.

Effects of the interaction between cold spells and fine particulate matter on mortality risk in Xining: a case-crossover study at high altitude.

With global climate change, the health impacts of cold spells and air pollution caused by PM2.5 are increasingly aggravated, especially in high-altitude areas, which are particularly sensitive. Exploring their interactions is crucial for public health. We collected time-series data on meteorology, air pollution, and various causes of death in Xining. This study employed a time-stratified case-crossover design and conditional logistic regression models to explore the association between cold spells, PM2.5 exposure, and various causes of death, and to assess their interaction. We quantitatively analyzed the interaction using the relative excess odds due to interaction (REOI), attributable proportion due to interaction (AP), and synergy index (S). Moreover, we conducted stratified analyses by average altitude, sex, age, and educational level to identify potential vulnerable groups. We found significant associations between cold spells, PM2.5, and various causes of death, with noticeable effects on respiratory disease mortality and COPD mortality. We identified significant synergistic effects (REOI>0, AP > 0, S > 1) between cold spells and PM2.5 on various causes of death, which generally weakened with a stricter definition of cold spells and longer duration. It was estimated that up to 9.56% of non-accidental deaths could be attributed to concurrent exposure to cold spells and high-level PM2.5. High-altitude areas, males, the older adults, and individuals with lower educational levels were more sensitive. The interaction mainly varied among age groups, indicating significant impacts and a synergistic action that increased mortality risk. Our study found that in high-altitude areas, exposure to cold spells and PM2.5 significantly increased the mortality risk from specific diseases among the older adults, males, and those with lower educational levels, and there was an interaction between cold spells and PM2.5. The results underscore the importance of reducing these exposures to protect public health.

Tibetans exhibit lower hemoglobin concentration and decreased heart response to hypoxia during poikilocapnia at intermediate altitude relative to Han Chinese.

High-altitude populations exhibit distinct cellular, respiratory, and cardiovascular phenotypes, some of which provide adaptive advantages to hypoxic conditions compared to populations with sea-level ancestry. Studies performed in populations with a history of high-altitude residence, such as Tibetans, support the idea that many of these phenotypes may be shaped by genomic features that have been positively selected for throughout generations. We hypothesize that such traits observed in Tibetans at high altitude also occur in Tibetans living at intermediate altitude, even in the absence of severe sustained hypoxia. We studied individuals of high-altitude ancestry (Tibetans, n = 17 females; n = 12 males) and sea-level ancestry (Han Chinese, n = 6 females; n = 10 males), both who had been living at ∼1300m (∼4327ft) for at least 18 months. We measured hemoglobin concentration ([Hb]), hypoxic ventilatory response (HVR), and hypoxic heart rate response (HHRR) with end-tidal CO2 (PetCO2) held constant (isocapnia) or allowed to decrease with hypoxic hyperventilation (poikilocapnia). We also quantified the contribution of CO2 on ventilation and heart rate by calculating the differences of isocapnic versus poikilocapnic hypoxic conditions (Δ /ΔPetCO2 and ΔHR/ΔPetCO2, respectively). Male Tibetans had lower [Hb] compared to Han Chinese males (p < 0.05), consistent with reports for individuals from these populations living at high altitude and sea level. Measurements of ventilation (resting ventilation, HVR, and PetCO2) were similar for both groups. Heart rate responses to hypoxia were similar in both groups during isocapnia; however, HHRR in poikilocapnia was reduced in the Tibetan group (p < 0.03), and the heart rate response to CO2 in hypoxia was lower in Tibetans relative to Han Chinese (p < 0.01). These results suggest that Tibetans living at intermediate altitude have blunted cardiac responses in the context of hypoxia. Hence, only some of the phenotypes observed in Tibetans living at high altitude are observed in Tibetans living at intermediate altitude. Whereas blunted cardiac responses to hypoxia is revealed at intermediate altitudes, manifestation of other physiological adaptations to high altitude may require exposure to more severe levels of hypoxia.