Altitude Levels Research Articles

Identification and Mapping of Areas Indicated Violating Spatial Use in The North Bandung Region

North Bandung Region (KBU) is a conservation area, water catchment and investment magnet attracting high due to its strategic location at an altitude level above 750 meters above sea level. Developments at KBU have a disastrous impact on the below highland. This research was conducted to identify mismatches in spatial use and indications of violations of spatial use with the superimpose method of spatial plan maps with existing land cover maps. Continued spatial analysis, object/point filtering, field observations, focus group discussions, spatial performance analysis and impact calculations. The results stated that there were 4,414 polygons and 42 typologies of spatial mismatch and 108 points of indication of violation. Found four typologies of violations of spatial use; spatial use that is not in accordance with the spatial plan, is not in accordance with the spatial use permit granted by the authorized official, is not in accordance with the permit requirements, and issues a permit that is not in accordance with the spatial plan. Recommendations for law enforcement measures in the form of administrative and/or criminal sanctions are given to points of activity that are indicated to have experienced violations of spatial use.

Hypoxia is not the primary mechanism contributing to exercise-induced proteinuria

IntroductionProteinuria increases at altitude and with exercise, potentially as a result of hypoxia. Using urinary alpha-1 acid glycoprotein (α1-AGP) levels as a sensitive marker of proteinuria, we examined the impact...

Potential impacts of mining of super-thick coal seam on the local environment in arid Eastern Junggar coalfield, Xinjiang region, China

Coal mining has serious impacts on local environment, including damage to the land and soil by subsidence, damage to ground-water systems through the fracturing and subsiding of overlying rocks, contamination of surface waters with acid mine drainage, and pollution of the atmosphere by release of toxic gases. The damage to ground water and its consequent impacts on the regional environment is the core of research of the coal mining from the perspective of environment protection. The present paper focuses on the changes of surface vegetation coverage, the pollutants released from pit coal power plants, and the damages to the ground aquifers induced by mining activities in arid Eastern Junggar coalfield of China. At first, the authors investigated the changes of surface vegetation coverage, since mining began in the 2000s using Landsat data. Results show that the low surface vegetation coverage (grade 1 plus grade 2) in the southern part of the region decreased from 11.62 × 108 m2 in 2003 to 9.57 × 108 m2 in 2017 (−17.6%), while it increased from 11.58 × 108 m2 in 2003 to 12.70 × 108 m2 in 2017 (+ 9.7%) in the eastern part. The high surface vegetation coverage (grade 3 plus grade 4) in the southern part increased from 1.94 × 108 m2 in 2003 to 4.00 × 108 m2 in 2017 (+ 106.2%), while it decreased from 4.39 × 108 m2 in 2003 to 3.26 × 108 m2 in 2017 (−25.74%) in the eastern part. The data of annual precipitation during the same period in this area show that the changes of surface vegetation coverage have less relationship with the annual precipitation, which indicates that the mining activities is probably the major factor for that. Second, a statistic of air pollutants generated from pit coal power plants was made based on data of references. Results show that the estimated gaseous pollutant emissions increased as 865.23 tons of smoke particles, 5940.73 tons of SO2, and 7584.48 tons of NO2 in 2013, which increased rapidly with 9.73 times the smoke particle, 21.69 times the SO2, and 9.24 times the NO2 than that of 2007. And then, the physical and numerical simulation of the damage of mining activities to aquifers was made to show the permeability of the reference points of overlying aquifers varies associated with mining activities. Results show that the porous rock matrix permeability has a negative relationship with fluctuation during mining, while the fracture permeability shows a positive one. Finally, a case investigation in southern area surrounding this coalfield was illustrated. Result shows that the local ground-water level decreased by 16 m difference from the altitude level of + 774 m in 2003 to + 758 m in 2013. Data and results from this study presented the already and the potential pollutions and damages to local environment induced by the mining activities in this region.

Age and altitude of residence determine anemia prevalence in Peruvian 6 to 35 months old children.

BackgroundA Demographic and Family Health Survey (ENDES, for Encuesta Demográfica y de Salud Familiar in Spanish) is carried out annually in Peru. Based on it, the anemia prevalence was 43.6% in 2016 and 43.8% in 2017 using the WHO cutoff value of 11 g/dL and the altitude-correction equation.ObjectiveTo assess factors contributing to anemia and to determine its prevalence in Peruvian children 6 to 35 months old.MethodsWe used the MEASURE DHS-based ENDES survey to obtain representative data for11364 children from 6 to 35 months old on hemoglobin and health determinants. To evaluate normal hemoglobin levels, we used the original WHO criterion of the 5th percentile in children without chronic malnutrition and then applied it to the overall population. Relationships between hemoglobin and altitude levels, usage of cleaning methods to sanitize water safe to drink, usage of solid fuels and poverty status were tested using methodology for complex survey data. Percentile curves were made for altitude intervals by plotting hemoglobin compared to age. The new anemia rates are presented in graphs by Peruvian political regions according to the degree of public health significance.ResultsHemoglobin increased as age and altitude of residence increased. Using the 5th percentile, anemia prevalence was 7.3% in 2016 and 2017. Children from low altitudes had higher anemia prevalence (8.5%) than those from high altitudes (1.2%, p<0.0001). In the rainforest area of Peru, anemia prevalence was highest (13.5%), while in the highlands it was lowest (3.3%, p<0.0001). With access to safe drinking water and without chronic malnutrition, anemia rates could be reduced in the rainforest by 45% and 33%, respectively.ConclusionAnemia prevalence in Peruvian children from 6 to 35 months old was 7.3% in 2016 and 2017.

Estimation of the vegetation diversity of the Western Tannu-Ola Range

This paper discusses the main indicators diversity of vegetation in key areas of the northern macro slope of the Western Tannu-Ola Range. The degree of forest cover and vegetation fragmentation were estimated using Landsat-TM/ ETM+/OLI images for June 25, 1992, June 18, 1998 and June 24, 2015 in QGIS using the plugin Landscape Ecology. The Simpson index shows of increasing biodiversity in different altitudes. The results showed that with increasing climate warming in the region and maintaining this trend, the proportion of dark coniferous forest at all altitude levels (foothill, mid-elevation and high-elevation zones) will increase. And this led to a decrease in the fragmentation of the forest cover of northern macro slope of this range.

Influence of annual atmospheric tide asymmetry on annual anomalies of the ionospheric mean state

Through respectively adding June tide and December tide at the low boundary of the GCITEM-IGGCAS model (Global Coupled Ionosphere–Thermosphere–Electrodynamics Model, Institute of Geology and Geophysics, Chinese Academy of Sciences), we simulate the influence of atmospheric tide on the annual anomalies of the zonal mean state of the ionospheric electron density, and report that the tidal influence varies with latitude, altitude, and solar activity level. Compared with the density driven by the December tide, the June tide mainly increases lower ionospheric electron densities (below roughly the height of 200 km), and decreases electron densities in the higher ionosphere (above the height of 200 km). In the low-latitude ionosphere, tides affect the equatorial ionization anomaly structure (EIA) in the relative difference of electron density, which suggests that tides affect the equatorial vertical E×B plasma drifts. Although the tide-driven annual anomalies do not vary significantly with the solar flux level in the lower ionosphere, in the higher ionosphere the annual anomalies generally decrease with solar activity.

Comparisons of spectrally resolved nightglow emission locally simulated with space and ground level observations

A mesospheric model of the airglow emission is developed to recover the night variations observed at ground level. The model is based on a 1D vertical photochemical model, including the photodissociation and heating processes. The spectral radiation is calculated at high altitude and propagated through the atmosphere to the ground. We also include short scale vertical dynamic such as turbulences and the molecular diffusion. Simulations reveal realistic emissions when compared with space observations. In addition, we estimate the impact of changes associated with parameterized atmospheric tides. The comparison with observations is performed over high altitude and ground level. We confront the model outputs at high altitude with satellite observations (SABER and GOMOS) and the simulations propagated at ground level are compared to local measurements campaigns performed in France and India. Biases between observed and simulated radiances and volume emission rates are suspected to be due to the impact of gravity waves or the large scale dynamic.

Determinants of Acute Respiratory Infection Among Children in Ethiopia: A Multilevel Analysis from Ethiopian Demographic and Health Survey.

BackgroundAcute respiratory infection (ARI) is one of the leading public health challenges among children in low- and middle-income countries. Child mortality due to ARI is disproportionately higher in African regions. In Ethiopia, an encouraging progress in the reduction of ARI was observed until 2010, however, since then the national prevalence is unchanged. There is limited information for the persistently higher prevalence of the infection. Therefore, the aim of this study was to determine regional variations and identify factors associated with the infection.MethodsThis study used data from the Ethiopian Demographic and Health Survey (EDHS) conducted in 2016. The analysis used information from 10,006 children. A two-level logistic regression analysis was used to consider the cluster random effect.ResultsOut of 10,006 children included, 15.9%, 8.9%, and 8.8% reported cough, short rapid breaths, and chest complaint respectively two weeks before the survey, making the overall prevalence of ARI 8.8%. Children aged six to 11 years (adjusted odds ratio (AOR)=1.466, 95%CI: 1.143–1.881), and 12 to 23 (AOR=1.390, 95%CI: 1.109–1.742), small birth size (AOR=1.387, 95%CI), and animal dung as cooking fuel (AOR=1.904, 95%CI: 1.152–3.146) are significantly associated with higher odds of ARI in the final multilevel modeling. The AOR (95%CI) for ARI for differing levels of altitude were: 1000 to 2000, 1.805 (1.403–2.483); 2000 to 3000, 1.882 (1.427–2.483); above 3000, 2.24 (1.023–4.907).ConclusionARI is still a significant public health problem in Ethiopia among children underfive, with a huge variation in the burden across the regional states. Age of children, birth size, household cooking fuel, and altitude above sea level were important variables. Therefore, regional governments, health-care workers and concerned organizations should give emphasis to minimize ARI and the consequences associated with the disease.

Dynamics of the growth processes of Prunus armeniaca L. seedlings in the conditions of Inner Mountain Dagestan

The paper presents the results of assessing the dynamics of growth processes 364 seedlings of 16 apricot samples under conditions of a critical altitude level for them in Dagestan (1900 m). A comparative study of apricot samples showed that during the growing season, annual seedlings form a small height of the main shoot (18.7–28.7 cm), subramose (0.4–2.7) and leafiness (14.7–23.6). Analysis of the relative dynamics of shoot growth showed that the maximum growth was observed in May-June (62.8–95.7%) and low in July-September (1.0–24.5%). A reliable correlation was established between the relative growth of the studied samples and their winter hardiness, namely, the higher the relative increase in July-September, the lower the winter hardiness. The correlation in MayJune was -0.77**, and in July and September 0.62* and 0.64 **, respectively. The experiment showed the information content of studying the growth of shoot length as a diagnostic feature in assessing the winter hardiness of apricot seedlings in the mountainous conditions of Dagestan.

Characteristics and meteorological mechanisms of transboundary air pollution in a persistent heavy PM2.5 pollution episode in Central-East China

Previous research has shown the significant transboundary air pollution (TAP) in China. Despite its adverse environmental and human health impacts, the characteristics and mechanisms of TAP have yet to be fully understood. This study comprehensively analyzed intensive ground and upper levels measurements along with the atmospheric modeling approach to determine the driving meteorological conditions responsible for the formation and evolution of a persistent severe PM2.5 pollution episode in Central-East China (CEC, 112°E −118°E, 30°N −34°N) starting from 18:00 on Dec. 3 to 18:00 on Dec. 5, 2017, which had obvious characteristics of TAP and explosive increases in PM2.5 concentration. We assessed and quantified contributions of local and nonlocal emissions to PM2.5 in the region and different cities during the episode and determined the altitude level at which TAP occurred. Results show that PM2.5 concentration in most cities in CEC region experienced two major increases: the first increase was due to the change in wind direction from south to north, transporting pollutants from north China to CEC; the second increase was driven by several important meteorological factors, including warm/cold advection at different altitudes, large-scale subsidence, and radiative cooling, jointly resulting in a deep (reaching around 800 m) and strong elevated temperature inversion with a significant reduction in mixing layer thickness and thus causing a rapid increase in PM2.5 concentration in CEC region. On average, TAP accounted for 42% of total PM2.5 concentration in the region during the event, in which the TAP impact varied by cities, ranging from ~26% to ~70%. Our findings demonstrate the synergetic effect of TAP and large-scale subsidence, providing a critical reference for air pollution forecast and assessment in the eastern China.

Geobotanic and phytoindication characteristics of Amorpha fruticosa L. population in the serious coenosis conditions of the floodplain in the lower level Kaniv hydro power plant

On the basis of geobotanical descriptions of phytocenoses with Amorpha fruticosa L., representing primary succession separate stages of different floodplain altitude levels made on the islands territory below the Kaniv hydro power plant, the general characteristic of the vegetation dynamics with this species participation is presented. Using the method of phytoindication, the main characteristics of ecological factors indicators and their change directions during xero-, meso- and hydroseries are determined. The ecological factors indicators were obtained by the method of syphitoindication: soil moisture (Hd), variability of soil moisture (fH), soil aeration (Ae), general soil salt regime (trophic) (SL), soil acidity (Rc), mineral nitrogen content (Nt ) and carbonate content (Ca) in the soil, thermal regime (Tm), continental (Kn), frost (cryo) (Cr), climate humidity (humidity) (Om), luminosity (Lc). To compare ecological amplitude and elucidate the relationship between coenoses, the cluster analysis method and the shifted ratio analysis (DCA) method were used. A. fruticosa, characterized by a wide phytocenotic range, is included in phytocenoses at all stages of succession of Middle Dnieper floodplain three levels, representing xero-, meso- and hydroseries. During the succession, the qualitative and quantitative changes of such phytocenoses geobotanical characteristics as the species number and their composition, the A. fruticosa role as a coenotic agent, the age structure of its co-populations are natural. Also, based on the phytoindication method, the differences of phytocenoses representing xero-, meso- and hydroseries are monitored, a relatively wide range of ecotopes differing in humidity and soil aeration factors, favorable for the growth of A. fruticosa regular trend of most ecological factors during xeroseries and hydroseries towards the indices of mesoseries phytocenoses

VERTICAL PROFILE OF DENSITY IN A VAN DER WAALS ATMOSPHERE IN NATAL CITY

The van der Waals state equation for atmosphere is determined from the critical temperature and critical pressure of the air gases. The meteorological radiosonde measures atmospheric pressure, temperature, and other meteorological variables, at several altitude levels. Therefore, the diurnal and nocturnal vertical profiles of the monthly average density of the atmosphere were constructed, considering the atmospheric system as an ideal gas and also as a van der Waals gas. For this purpose, the radiosonde data of the atmosphere of the metropolitan region of Natal-RN, Brazil, from 2010 to 2017, with altitude ranging from 50m to 10km.

Comparison of Carotid Atherosclerosis between Patients at High Altitude and Sea Level: A Chinese Atherosclerosis Risk Evaluation Study

Objectives: To investigate the differences in characteristics of carotid plaques between patients Xining at high altitude and Jinan at sea level using magnetic resonance (MR) imaging. Methods: Subjects were recruited from a cross-sectional, observational, multicenter imaging study of CARE-II study. Forty-nine (mean age 63.3 ± 12.0 years, 33 males) and 51 (mean age 64.5 ± 12.0 years, 34 males) patients were recruited from a site located in a high altitude region and a site located near sea level, respectively. All patients underwent multicontrast MR vessel wall imaging for carotid arteries on 3.0 T MR scanner. The carotid plaques features were compared between 2 patient groups. Results: Compared with patients at sea level, those at high altitude had significantly greater lumen area (58.5 ± 17.8 mm2 versus 50.0 ± 19.6 mm2, P = .008), smaller maximum normalized wall index (48.6% ± 14.2% versus 57.8% ± 16.3%, P = .002), and smaller percentage volume of calcium (0.9% versus 5.6%, P < .001) in the symptomatic carotid artery. After adjustment for clinical risk factors including age, sex, systolic blood pressure, LDL-C, and statin use, these differences in plaque morphology and composition remained statistically significant. After further adjustment for normalized wall index as a measure of plaque burden, percentage volume of calcification was still significantly smaller in patients at high altitude area than that in patients at sea level area (P = .047). Conclusion: Symptomatic subjects from a high altitude area have lower plaque burden and less calcification in the carotid artery compared to those from an area near sea level.

Altitude and human disturbance are associated with helminth diversity in an endangered primate, Procolobus gordonorum.

Gastrointestinal parasites colonizing the mammalian gut influence the host immune system and health. Parasite infections, mainly helminths, have been studied intensively in both humans and non-human animals, but relatively rarely within a conservation framework. The Udzungwa red colobus monkey (Procolobus gordonorum) is an endangered endemic primate species living in the Udzungwa Mountains of Tanzania, a global biodiversity hotspot. Since this endemic primate species is highly sensitive to human disturbance, here we investigate whether habitat type (driven by natural and human-induced factors) is associated with helminth diversity. Using standard flotation and sedimentation techniques, we analyzed 251 fecal samples belonging to 25 social groups from four different forest blocks within the Udzungwa Mountains. Five parasitic helminth taxa were recovered from Udzungwa red colobus, including Trichuris sp., Strongyloides fulleborni, S. stercoralis, a strongylid nematode and Colobenterobius sp. We used Generalized Linear Mixed Models to explore the contribution of habitat type, altitude and fecal glucocorticoid levels (as biomarkers of stress) in predicting gut parasite variation. Although some parasites (e.g., Trichuris sp.) infected more than 50% of individuals, compared to others (e.g., Colobenterobius sp.) that infected less than 3%, both parasite richness and prevalence did not differ significantly across forests, even when controlling for seasonality. Stress hormone levels also did not predict variation in parasite richness, while altitude could explain it resulting in lower richness at lower altitudes. Because human activities causing disturbance are concentrated mainly at lower altitudes, we suggest that protection of primate forest habitat preserves natural diversity at both macro- and microscales, and that the importance of the latter should not be underestimated.

Transport of black carbon from planetary boundary layer to free troposphere during the summer monsoon over South Asia

Abstract This study uses Weather Research and Forecasting model, coupled with Chemistry (WRF-Chem), to understand black carbon (BC) vertical transport over South Asia during the active convection period. We analyze the climatology (1995–2014) of convective weather using TRMM lightning data. The results show both temporal and spatial variability within South Asia. The WRF-Chem model simulation for BC transport was conducted for an ENSO (El-Nino Southern Oscillation) moderate year - 2013. The model simulates the observed concentrations trend for most of the region except the central Himalayan cities. Our analysis indicates the dominant role of synoptic atmospheric dynamics and upper boundary conditions for the inverted seasonal trend of BC during the pre-monsoon season over these cities. The study presents time series and seasonal scale analysis of BC concentration over South Asia at various altitude levels. Our model simulations suggest that free troposphere (FT) BC concentration is higher in the monsoon season compared to the winter season at the same elevation. In addition, our results show the presence of a persistent BC plume from 500 hPa and above over central India with implications for the summer monsoon. The presence of an anti-cyclonic region during the monsoon season at the higher troposphere (500–300 hPa) contributes to this stable BC layer. Although individual high convection days (high helicity/CAPE) can easily transport a significant amount of BC from the surface to the FT, simulations do not show significant BC transported to the upper troposphere-lower stratosphere during these days. While satellite derived products provide some insights into model predictions, there is a need for in-situ measurements of BC concentration aloft over South Asia to further constrain model performance and improve understanding of BC transport to FT.

Efectos agudos y crónicos del uso de máscaras de entrenamiento en altura durante el ejercicio: revisión

The so-called Elevation Training Mask (ETM) is marketed for the purpose of emulating the hypoxic conditions that prevail at different altitude levels. The present work reviews the studies that analyze the acute and chronic effects of using ETM on variables associated with physical performance. Although there is some controversy, most studies report an acute hypoxic effect and improvements in cardiorespiratory parameters derived from using ETM, in addition to being, in general terms, well tolerated. For strength training, the use of ETM could be detrimental. More studies with different populations and studies with longer interventions are needed.

Groundwater dynamics, land cover and salinization in the dry Chaco in Paraguay

A two-year experimental study on saline groundwater dynamics in the Paraguayan dry Chaco is reported. This study was designed to better understand dryland salinity as a natural phenomenon and a potential consequence of land use changes, in order to avoid adverse economic and environmental impacts. A total of 28 wells at two study sites located nearby Loma Plata were monitored approximately every two weeks for groundwater conductivity and water table level, following transects from sown pasture to native forest and topographic gradients from bush or pasture to a nearby temporarily flooded lagoon. Results show a relation among topography, land cover, precipitation, groundwater salinity and surface salinization. Under pasture, groundwater was less saline in the average and the water table was slightly higher than under adjacent forest. Under forest, infiltrating rainwater never reached groundwater level, whereas under pasture, rainwater diluted the groundwater at several occasions during the observation period. Along the topographic gradients, there was a fringe prone to surface salinization along the borderline of the lagoon. At higher topographic levels, the saline ground water was low enough to not reach the surface by capillary ascension. On the other hand, high water table in the center of the lagoon fed by inflowing rainwaters (which had a slightly higher altitude level than the water table under adjacent land covers), displaced the saline groundwater vertically and horizontally. These findings provide information for land use planning in the region, which is prone to dryland salinity due to a generally high saline water table.

Changes in gene expression and metabolic profile of drupes of Olea europaea L. cv Carolea in relation to maturation stage and cultivation area

BackgroundOlive (Olea europaea L.) is an emblematic oil tree crop in the Mediterranean basin. Currently, despite olive features as a moderately thermophilic species, its cultivation is worldwide spreading due to the health-related impact of olive products on human nutrition. A point of concern for the expanding olive cultivation is related to the influence that, in addition to genotype, environmental factors exerts on drupe development and metabolism with consequent impact on fruit key traits. In this context, the aim of the present work was to gain further information on the genetic networks controlling drupe maturation phase and, mainly, on their modulation in response to environmental cues.ResultsTo achieve this goal, a comparative transcriptome-wide investigation was carried out on drupes of Olea europaea cultivar Carolea, collected from plants growing in areas at different altitude level and therefore experiencing different climatic conditions. Two maturation stages of drupe were analysed: green mature and turning-purple. Metabolic characterization of drupe was also performed. At both transcriptomic and metabolic level differences were detected in the pathway of fatty acids (FAs) and phenol compounds, in relation to both drupe maturation stage and cultivation area. Among the most relevant differences detected during the transition from GM to TP stages there were: the upregulation of FADs genes in the drupes of population growing at 700 masl, the upregulation of phenol biosynthesis-related genes in drupes growing at 10 and 200 masl and very interestingly the downregulation of specific genes involved in secoiridoids production in drupes growing at 700 masl. Globally, these results suggested that stability of FAs and phenols, mainly of secoiridoids group, is promoted at high altitude, while at lower altitude phenol biosynthesis is prolonged.ConclusionThe obtained results showed a differential modulation of genetic pathways related to olive compound quality in relation to the cultivation area, likely imposed by the different temperature impending at each altitude. The derived molecular information appears of interest for both breeding and biotechnological programs of olive species, especially with respect to the modulation of antioxidant secoiridoid compounds which play a key role in conferring both sensorial and healthy characteristic to olive products.

Effects of altitude on density and biometric properties of hornbeam wood (Carpinus betulus)

Aim of the study: This study aimed to investigate the effect of altitude difference on the wood dry density, fiber dimensions, and morphological properties of hornbeam wood (Carpinus betulus L.).Area of study: The study area was located in the province of Mazandaran, north of Iran.Material and method: 18 mature trees were randomly selected and harvested at six altitude levels (300, 500, 700, 900, 1100, and 1300 m) in the north of Iran. The clear test samples‎ were prepared‎ at diameter at breast height (DBH) to measure the wood dry density, fiber length, fiber diameter, cell wall thickness, Runkel coefficients, flexibility coefficients, and slenderness coefficients. Further ‎analyses included the relationships between the wood properties and site conditions (temperature, ‎precipitation, crown canopy, ‎and understory herb layer) as well as tree’s main dimensions ‎(tree height and the DBH).Main results: The results indicated significant effects of altitude variations on the studied ‎properties. The pattern variations of wood properties were very regular at different levels of height. The average fiber length and fiber diameter decreased while the wood dry density and cell wall thickness increased with increasing the altitude levels. The average values of wood dry density, fiber length, fiber diameter, cell wall thickness, slenderness coefficients, flexibility coefficients, and Runkel coefficients of hornbeam wood were 698 kg/m3, 1.42mm, 25.58 µm, 5.72µm, 55.55, 54.04%, and 0.93, respectively, in the above six altitudes. Pearson matrix correlation showed that there were significant relationships between temperature, crown canopy, tree height and DBH ‎with the studied wood properties (except the slenderness coefficients)‎.Research highlights: The hornbeams grown at altitudes above 900-1300 m were not suitable for pulp and ‎paper production‎ due to relatively higher Runkel coefficients, the lower flexibility coefficients, as well as smaller fiber length than other altitude levels.Additional Keywords: Carpinus betulus; altitude variation; density; fiber dimensions; morphological properties.Abbreviations used: WDD (wood dry density); FL (fiber length); FD (fiber diameter), CWT (cell wall thickness); FC (flexibility coefficient); RC (Runkel coefficients); SC (slenderness coefficient).

Performance and health effects of mild hypoxic hypoxia in simulated 6-hour exposures between 2,438 and 3,048 metres

Introduction: The Royal Canadian Air Force (RCAF) imposes a daily 4-hour (h)limit for operating unpressurized aircrafts, including helicopters, between 2,438 and 3,048 m (8,000 [8K] and 10,000 [10K] ft) if supplemental oxygen (O2) is unavailable. This regulation may negatively impact RCAF operations because weight and space restrictions limit sufficient O2 to achieve mission success. The effects of exposure durations beyond the 4-h limit are currently unknown, but extensions have the potential to improve operational effectiveness. This study examined the effects of hypoxic exposures on symptoms, mood and performance as a function of altitude and exposure duration. Methods: Seventeen military helicopter pilots were randomly exposed to two 6-h altitude levels (8K and 9.9K) on 2 separate days in a hypobaric chamber. Daily, participants periodically performed a simulated rotary wing flight task, and completed a cognitive test battery. Cerebral regional and finger pulse oxyheamoglobin saturation levels and heart rate were continuously monitored. Participants indicated their subjective hypoxia signs and symptoms, mood and fatigue. Results: Exposure to altitude significantly decreased cerebral and pulse O2 saturations, but values remained steady during the 6-h exposure. No negative decrements were observed on cognition or simulation performance. Self-reported symptoms of fatigue and headache were reported at altitude with a slight increase with time. Discussion: No clear evidence of significant deficits on performance was observed in participants when exposed to mild levels of hypoxia for up to 6 h without supplemental O2.