Abstract
Estimating global and multi-level Thermosphere Neutral Density (TND) is important for studying coupling processes within the upper atmosphere, and for applications like orbit prediction. ...Models are applied for predicting TND changes, however, their performance can be improved by accounting for the simplicity of model structure and the sampling limitations of model inputs. In this study, a simultaneous Calibration and Data Assimilation (C/DA) algorithm is applied to integrate freely available CHAMP, GRACE, and Swarm derived TND measurements into the NRLMSISE-00 model. The improved model, called ‘C/DA-NRLMSISE-00’, and its outputs fit to these measured TNDs, are used to produce global TND fields at arbitrary altitudes (with the same vertical coverage as the NRLMSISE-00). Seven periods, between 2003-2020 that are associated with relatively high geomagnetic activity selected to investigate these fields, within which available models represent difficulties to provide reasonable TND estimates. Independent validations are performed with along-track TNDs that were not used within the C/DA framework, as well as with the outputs of other models such as the Jacchia-Bowman 2008 and the High Accuracy Satellite Drag Model. The numerical results indicate an average 52%, 50%, 56%, 25%, 47%, 54%, and 63% improvement in the Root Mean Squared Errors of the short term TND forecasts of C/DA-NRLMSISE00 compared to the along-track TND estimates of GRACE (2003, altitude 490 km), GRACE (2004, altitude 486 km), CHAMP (2008, altitude 343 km), GOCE (2010, altitude 270 km), Swarm-B (2015, altitude 520 km), Swarm-B (2017, altitude 514 km), and Swarm-B (2020, altitude 512 km), respectively.
High altitude ecosystems are often home to endemic species that have evolved in isolation from their low elevation counterparts. In many cases, especially in insects, such mountain endemics are often ...apterous (due to their reduced ability to fly and disperse). In most cases, so far, these mountain endemics are genetically differentiated from lowland sister species or populations. During an excursion in Central Spain, we encountered two such strikingly different morphotypes of the rove beetle
Lobrathium multipunctum
(Gravenhorst, 1802) (Coleoptera, Staphylinidae, Paederinae). The morphotype from high elevation was smaller and paler than those at low elevation, which were slightly larger, darker and regularly coloured. The high altitude morphotype was earlier considered a separate species (
Lobrathium hispanicum
Dodero, 1916) from its widespread lower-land counterpart (
Lobrathium multipunctum
(Gravenhorst, 1802)) before their relatively recent synonymy. Using the cytochrome c oxidase subunit I (COI) barcode region, we tested whether these distinct morphotypes are distinct species. We found that their synonymy is supported, based on multiple species delimitation methods. We suggest that this phenomenon may be more widespread amongst insects and other organismal groups. We note that the presence of high altitude morphotypes which are phylogenetically nested within, or genetically identical to, widespread lowland species (regular morphotype) is rarely reported in the literature on beetles (and other insects). These findings thus highlight the need for caution when describing mountain endemics and further highlight DNA barcoding as a helpful tool for their study.
Travel to high altitude is increasing. The authors discuss physiological changes at high altitude, pretravel evaluation for common medical conditions, and the risks of high-altitude headache, acute ...mountain sickness, high-altitude pulmonary edema, and high-altitude cerebral edema.
An increasing number of persons, exposed to high altitude for leisure, sport, or work, may suffer from severe high-altitude illness.
To assess, in a large cohort of subjects, the association between ...physiological parameters and the risk of altitude illness and their discrimination ability in a risk prediction model.
A total of 1,326 persons went through a hypoxic exercise test before a sojourn above 4,000 m. They were then monitored up at high altitude and classified as suffering from severe high-altitude illness (SHAI) or not. Analysis was stratified according to acetazolamide use.
Severe acute mountain sickness occurred in 314 (23.7%), high-altitude pulmonary edema in 22 (1.7%), and high-altitude cerebral edema in 13 (0.98%) patients. Among nonacetazolamide users (n = 917), main factors independently associated with SHAI were previous history of SHAI (adjusted odds ratios aOR, 12.82; 95% confidence interval CI, 6.95-23.66; P < 0.001), ascent greater than 400 m/day (aOR, 5.89; 95% CI, 3.78-9.16; P < 0.001), history of migraine (aOR, 2.28; 95% CI, 1.28-4.07; P = 0.005), ventilatory response to hypoxia at exercise less than 0.78 L/minute/kg (aOR, 6.68; 95% CI, 3.83-11.63; P < 0.001), and desaturation at exercise in hypoxia equal to or greater than 22% (aOR, 2.50; 95% CI, 1.52-4.11; P < 0.001). The last two parameters improved substantially the discrimination ability of the multivariate prediction model (C-statistic rose from 0.81 to 0.88; P < 0.001). Preventive use of acetazolamide reduced the relative risk of SHAI by 44%.
In a large population of altitude visitors, chemosensitivity parameters (high desaturation and low ventilatory response to hypoxia at exercise) were independent predictors of severe high-altitude illness. They improved the discrimination ability of a risk prediction model.
A estimativa de dados meteorológicos é imprescindível quando não se dispõe de dados observacionais. No entanto, a confiabilidade no uso destes, está condicionada a existência de concordância entre os ...dados preditos e os observados. Particularmente para a variável temperatura do ar, sendo uma das mais importantes para o planejamento das atividades agrícolas. Diante disso, objetivou-se com este trabalho, estimar os valores máximos, mínimos e médios da tempetura do ar, na escala decendial, a partir de coordenadas geográficas e altitude para o estado de Goiás. Para tanto, foram consideradas séries históricas de dados (1987-2017) oriundas de 27 municípios goianos. Para as estimativas consideradas neste estudo utilizou-se técnicas de análise de regressão múltipla, onde foi verificada a significância dos modelos preditores. Os coeficientes de determinação ajustados resultantes do modelo encontrado variaram de 0,66 a 0,82 para Tmax, de 0,56 a 0,72 para Tmin e de 0,66 a 0,74 para Tmed. Com este resultado, as médias das temperaturas máximas e médias decendiais, podem ser estimadas satisfatoriamente nos municípios goianos por meio da altitude, latitude e longitude.
In response to hypobaric hypoxia (HH), which occurs at high altitude, the brain undergoes deleterious changes at the structural and metabolite level. In vivo T sub(2) weighted imaging (T2WI) and ...super(1)H-MRS was performed to understand the structural and metabolic changes in the hippocampus region of rat brain. Data were acquired pre-exposure (baseline controls), immediately after exposure and subsequently at the first, fourth, seventh and 14th days post exposure at normoxia. T sub(2) weighted images of rat brain showed hyperintensity in the CA2/CA3 region of the hippocampus 7 d after acute HH, which persisted till 14 d, probably indicating structural changes in the hippocampus. super(1)H-MRS results showed no change in metabolite level immediately after acute HH exposure, but on the first day of normoxia the myo-inositol level was significantly decreased, possibly due to altered astrocyte metabolism. Metabolic alterations showing an increase in choline and decrease in glutamate on the fourth day of normoxia may be seen as a process of demyelination and loss of glutamate pool respectively. On the seventh and 14th days of normoxia, decreases in N-acetylaspartate, creatine and glutamine+glutamate were observed, which might be due to decreased viability of glutamatergic neurons. In vivo super(1)H-MRS demonstrated early neurometabolic changes prior to probable structural changes post acute HH exposure. The extension of these studies will help in early risk assessment, developing intervention and strategies for combating HH related changes. Copyright copyright 2014 John Wiley & Sons, Ltd. In vivo T2WI and super(1)H-MRS reveal the structural and metabolic changes in the hippocampus region of rat brain post acute hypobaric hypoxic (HH) exposure of 48h. The up- and down-regulation of various metabolites such as myo-inositol, N-acetyl aspartate, creatine and glutamine+glutamate indicates altered astrocyte cellular metabolism, demyelination, neuronal loss and degenerative changes in the brain. These studies will be helpful in early prediction of pathology, which will help in the development of new neuroprotective drugs for combating HH induced changes.
After ascent to high altitude (≥2500 m), the inability of the human body to adapt to the hypobaric and hypoxia environment can induce tissue hypoxia, then a series of high altitude illnesses ...including acute mountain sickness (AMS), high altitude pulmonary edema (HAPE), and high altitude cerebral edema (HACE) would develop. Symptoms of AMS include headache, dizziness, nausea, and vomiting; HAPE is characterized by orthopnea, breathlessness at rest, cough, pink frothy sputum, and results in obvious pulmonary edema that poses significant harm to people; HACE is characterized by ataxia and decreased consciousness, leading to coma and brain herniation which would be fatal if not treated promptly. This review article provides a current understanding of the pathophysiology of these three forms of high altitude illness and elaborates the current prevention and treatment measures of these diseases.
•AHAI refers to a series of syndromes including AMS, HAPE and HACE.•HAPE is related with hypoxic pulmonary hypertension and alveolar fluid clearance.•AMS and HACE is related with cerebral hemodynamics and cytokines variation.•Current chemical drugs used to prevent AHAI have obvious toxic side effects.•Foodborne natural substances should be developed to prevent against AHAI.
The genus Cyathea is the most widely distributed tree fern in the Sierra Nororiental Poblana of Mexico. However, wild populations have been affected due to excessive logging and continuous extraction ...of rhizomes. The reproduction of these plants under controlled conditions is unsuccessful due to the low germination and survival rates. While there is little information on the mycorrhization in these plants in the wild, it is known that they establish partnerships with arbuscular mycorrhizal fungi (AMF) that facilitate assimilation of nutrients, spore germination, establishment and development. In this paper the characteristics of mycorrhizal colonization are described in Cyathea spp. populations at different altitudes on the Apulco river basin, Puebla, Mexico. The study was conducted in three locations during spring and summer, evaluating morphospecies composition, total number of spores, mycorrhizal colonization and the amount of extra-radicular mycelium by wet sieving technique and microscopy. It was found that changes in mycorrhizal colonization and total number of spores in the tree fern are due to differences in phosphorus concentration, vegetation and altitude. Eleven morphospecies were described whose presence in the form of spores changes depending on the season; only one morphospecies was found in all location in both seasons, while two other morphospecies were only observed associated with Cyathea spp. in a pine-oak forest. These results allow to propose some morphospecies as inoculants to facilitate reforestation programs.
Remote ischemic preconditioning (RIPC) has been shown to protect remote organs, such as the brain and the lung, from damage induced by subsequent hypoxia or ischemia. Acute mountain sickness (AMS) is ...a syndrome of nonspecific neurologic symptoms and in high-altitude pulmonary edema excessive hypoxic pulmonary vasoconstriction (HPV) plays a pivotal role. We hypothesized that RIPC protects the brain from AMS and attenuates the magnitude of HPV after rapid ascent to 3,450 m. Forty nonacclimatized volunteers were randomized into two groups. At low altitude (750 m) the RIPC group (
= 20) underwent 4 × 5 min of lower-limb ischemia (induced by inflation of bilateral thigh cuffs to 200 mmHg) followed by 5 min of reperfusion. The control group (
= 20) underwent a sham protocol (4 × 5 min of bilateral thigh cuff inflation to 20 mmHg). Thereafter, participants ascended to 3,450 m by train over 2 h and stayed there for 48 h. AMS was evaluated by the Lake Louise score (LLS) and the AMS-C score. Systolic pulmonary artery pressure (SPAP) was assessed by transthoracic Doppler echocardiography. RIPC had no effect on the overall incidence (RIPC: 35%, control: 35%,
= 1.0) and severity (RIPC vs.
= 0.496 for LLS;
= 0.320 for AMS-C score) of AMS. RIPC also had no significant effect on SPAP maximum after 10 h at high altitude; RIPC: 33 (SD 8) mmHg; controls: 37 (SD 7) mmHg;
= 0.19. This study indicates that RIPC, performed immediately before passive ascent to 3,450 m, does not attenuate AMS and the magnitude of high-altitude pulmonary hypertension.
Remote ischemic preconditioning (RIPC) has been reported to improve neurologic and pulmonary outcome following an acute ischemic or hypoxic insult, yet the effect of RIPC for protecting from high-altitude diseases remains to be determined. The present study shows that RIPC, performed immediately before passive ascent to 3,450 m, does not attenuate acute mountain sickness and the degree of high-altitude pulmonary hypertension. Therefore, RIPC cannot be recommended for prevention of high-altitude diseases.
The key elements in acclimatization aim at securing the oxygen supply to tissues and organs of the body with an optimal oxygen tension of the arterial blood. In acute exposure, ventilation and heart ...rate are elevated with a minimum reduction in stroke volume. In addition, plasma volume is reduced over 24–48 h to improve the oxygen‐carrying capacity of the blood, and is further improved during a prolonged sojourn at altitude through an enhanced erythropoiesis and larger Hb mass, allowing for a partial or full restoration of the blood volume and arterial oxygen content. Most of these adaptations are observed from quite low altitudes ∼1000 m above sea level (m a.s.l.) and become prominent from 2000 m a.s.l. At these higher altitudes additional adaptations occur, one being a reduction in the maximal heart rate response and consequently a lower peak cardiac output. Thus, in spite of a normalization of the arterial oxygen content after 4 or more weeks at altitude, the peak oxygen uptake reached after a long acclimatization period is essentially unaltered compared with acute exposure. What is gained is a more complete oxygenation of the blood in the lungs, i.e. SaO2 is increased. The alteration at the muscle level at altitude is minor and so is the effect on the metabolism, although it is debated whether a possible reduction in blood lactate accumulation occurs during exercise at altitude. Transient acute mountain sickness (headache, anorexia, and nausea) is present in 10–30% of subjects at altitudes between 2500 and 3000 m a.s.l. Pulmonary edema is rarely seen below 3000 m a.s.l. and brain edema is not seen below 4000 m a.s.l. It is possible to travel to altitudes of 2500–3000 m a.s.l., wait for 2 days, and then gradually start to train. At higher altitudes, one should consider a staged ascent (average ascent rate 300 m/day above 2000 m a.s.l.), primarily in order to sleep and feel well, and minimize the risk of mountain sickness. A new classification of altitude levels based on the effects on performance and well‐being is proposed and an overview given over the various modalities using hypoxia and altitude for improvement of performance.
PDF
