A Comparative Analysis of SARS-CoV-2 Viral Load Across Different Altitudes

Background: SARS-CoV-2 has spread throughout the world, including areas located at high or very high altitudes. There is a debate about the role of high altitude hypoxia on viral transmission, incidence, and COVID-19 related mortality. This is the first comparison of SARS-CoV-2 viral load across elevations ranging from 0 to 4,300 m.Objective: To describe the SARS-CoV-2 viral load across samples coming from 62 cities located at low, moderate, high, and very high altitudes in Ecuador.Methodology: An observational analysis of viral loads among nasopharyngeal swap samples coming from a cohort of 4,929 patients with a RT-qPCR test positive for SARS-CoV-2.Results: The relationship between high and low altitude only considering our sample of 4,929 persons is equal in both cases and not significative (p-value 0.19). In the case of low altitude, adding the gender variable to the analysis, it was possible to find a significative difference between female and male gender (p-value 0.068). Considering initially gender and then altitude, it was possible to find a significative difference between high and low altitude for male gender (p-value 0.065). There is not enough evidence to state that viral load is affected directly by altitude range but adding a new variable as sex in the analysis shows that the presence of new variables influences the relationship of altitude range and viral load.Conclusions: There is no evidence that viral load differs at altitude level when we consider only one measure. Using as reference the variable gender is possible to note that at low altitude there is a difference between female and male gender. There is not difference between gender at high altitude level. In the case of considering gender as reference variable, it was possible to find that high and low altitude are different for male gender an equal for female gender. Viral load not only depends on altitude range; it also is affected by other variables like sex.

Prediction of the Cavitation over a Twisted Hydrofoil Considering the Nuclei Fraction Sensitivity at 4000 m Altitude Level

Cavitation phenomenon is important in hydraulic turbomachineries. With the construction of pumping stations and hydro power stations on plateau, the influence of nuclei fraction on cavitation becomes important. As a simplified model, a twisted hydrofoil was used in this study to understand the cavitation behaviors on pump impeller blade and turbine runner blade at different altitude levels. The altitudes of 0 m, 1000 m, 2000 m, 3000 m and 4000 m were comparatively studied for simulating the plateau situation. Results show that the cavitation volume proportion fcav increases with the decreasing of cavitation coefficient Cσ. At a specific Cσ, high altitude and few nuclei will cause smaller size of cavitation. The smaller Cσ is, the higher the sensitivity Δfcav is. The larger Cσ is, the higher the relative sensitivity Δfcav* is. On the twisted foil, flow incidence angle increases from the sidewall to mid-span with the decreasing of the local minimum pressure. When Cσ is continually decreasing, the size of cavitation extends in spanwise, streamwise and thickness directions. The cavity is broken by the backward-jet flow when Cσ becomes small. A tail generates and the cavity becomes relatively unstable. This study will provide reference for evaluating the cavitation status of the water pumps and hydroturbines installed on a plateau with high altitude level.

INFORMATION AND KINETIC APPROACH TO THE EVALUATION OF STRESS STATE OF VESSELS OPERATING UNDER PRESSURE IN HYDROGEN ENVIRONMENTS

Separation of the influence of various factors on the strength of the material and control parameters is the basis for increasing the diagnostic efficiency. The article describes methods for assessing the state of pressure vessels, features of their damage under conditions of hydrogen absorption, presents data from acoustic emission and ultrasonic testing, compares them, sets out an approach to non-destructive assessment of the strength state of technical objects, based on a multilevel model of time dependences of acoustic emission parameters (AE), the kinetic concept of strength, micromechanics of fracture of discrete media, their relationship with the resource, parameters of fatigue curves and characteristics of the material structure, the problems of the influence of strength and metrological heterogeneity on the information content of control, the sequence of assessing the indicators of the strength state and resource of vessels, the model of strength and metrological heterogeneity of the AE are presented control, explaining the maximum activity of AE during tests in the first periods of operation, a methodology for assessing the strength state of pressure vessels is presented. Demonstration of the effectiveness of the technique is shown as an example of AE testing of an absorber for purifying hydrogen sulfide with a monoethanolamine solution by predicting the resource of its components and comparing the prediction results with the coordinate-altitude level of the adsorber belt, which correlates with the average internal hydrostatic stresses. Approbation of the approach has shown its versatility on the example of effective application for objects with defects of both fatigue and chemical origin under conditions of hydrogenation. Using the example of assessing the state of the most damaged lower belt, it is shown that an increase in the AE activity during hydrogenation of the material occurs mainly due to the growth of the acoustically active volume of the controlled zone, which is not unambiguously associated with the resource, and therefore the activity and energy intensity of the AE should not be considered sufficient a sign of the danger of a defect formed under the influence of hydrogen-containing media.

Venus Atmospheric Dynamics at Two Altitudes: Akatsuki and Venus Express Cloud Tracking, Ground-Based Doppler Observations and Comparison with Modelling

We present new results of our studies of zonal and meridional winds in both hemispheres of Venus, using ground- and space-based coordinated observations. The results obtained from telescope observations were retrieved with a Doppler velocimetry method. The wind velocities retrieved from space used an improved cloud-tracked technique based on the phase correlation between images. We present evidence that the altitude level sensed by our Doppler velocimetry method is approximately four kilometres higher (~4 km) than that using ground-tracked winds (using 380 or 365 nm). Since we often take advantage of coordinated space and ground observations simultaneously, this altitude difference will be very relevant in order to estimate the vertical wind shear at the related heights in future observation campaigns. We also explored a previous coordinated campaign using Akatsuki observations and its Ultraviolet Imager (UVI) at 283 and 365 nm filters, which showed that cloud-tracked winds showed a difference of about 10–15 ms−1, as in the case of the comparison between the Doppler velocimetry winds and the 365 nm cloudtracked winds. The results’ comparison also strongly suggested that the cloud-tracked winds based on the 283 nm filter’s images were sensing at about the same atmospheric altitude level as the Doppler winds. The observational results were compared with the ground-to-thermosphere 3D model developed at the Laboratoire de Meteorologie Dynamique (IPSL-Venus General Circulation Model (VGCM)) and AFES-Venus General Circulation Model (GCM), at several pressure levels (and related heights). The analysis and results showed the following: (1) additional confirmation of the coherence and complementarity in the results provided by these techniques on both the spatial and temporal time scales of the two methods; (2) we noticed in the following that the results from the two different Akatsuki/UVI filters (283 and 365 nm) showed an average difference of about 10–15 ± 5 ms−1, and we suggest this may be related to SO2 atmospheric fluctuations and the particular conditions in the coordinated observing time window; (3) we present evidence indicating that, in the context of our observations, visible Doppler methods (highly self-consistent) seem to sense wind speeds at a vertical level closer to or within the range sensed by the UVI 283 nm filter images (again, in the context of our observations); (4) modelling predicted wind profiles suggests that the layers of the atmosphere of Venus sensed by the methods referred to in Point 3 differ by approximately four km in altitude (~4 ± 2 km) regarding the cloud-tracked winds retrieved using 365 or 380 nm images.

Effect of site conditions on the properties of hawthorn (Crataegus azarolus L.) wood

This study investigated the influence of site conditions on the physical and morphological properties of hawthorn (Crataegus azarolus L.) wood grown in Zagros forests of Iran. Hawthorn is a valuable woody species in Iran’s Zagros forests with data deficiency in its wood properties. To our best knowledge, there is no study on the properties of hawthorn wood. Twenty-seven mature trees were randomly chosen and sampled at three altitude levels (1 800–2 000, 2 000–2 200, and 2 200–2 400 m) in the Bazoft region of Chaharmahal Va Bakhtiari, Iran. Dry wood density, volumetric shrinkage, fibre length, fibre diameter, cell wall thickness were then determined. Multivariate analysis of variance (MANOVA) was conducted to evaluate significant differences between the mean values of studied wood properties at different altitude levels and slope classes. Moreover, the relationships between the above-mentioned properties and some site conditions (temperature, precipitation, altitude, and slope) as well as growth parameters of trees (tree height, DBH, age, crown dimensions, volume, etc.) were studied by principal component analysis (PCA). The results indicated that trees growing at the second altitude level had the highest oven-dry density values, and those at the third altitude level had the lowest ones. Results also indicated a significant effect of altitude levels on fibre length, fibre diameter, and cell wall thickness. In contrast, a significant difference was found between the mean values of fibre diameter at different slope classes. PCA indicated that altitude, precipitation, and temperature are the most important environmental site variables affecting the wood characteristics.

Shock wave propagation through air: a reactive molecular dynamics study

Shock compression of air is observed in numerous situations ranging from explosions to hypersonic vehicle entry into atmosphere. In an effort to develop continuum-based equation of state for air subjected to shock compression, it is necessary to understand the dynamics of the shock compression process with regards to formation of new chemical species in air at the molecular level. With this in perspective, three different models of air (consisting a mixture of O 2 , N 2 and CO 2 gas, with or without H 2 O based on presence of humidity) are subjected to shock compression ranging from 0.5 km s −1 to 5.0 km s −1 particle velocities. Thermodynamic quantities are evaluated to plot Rankine Hugoniot planes for the three different air models: dry air at mean sea level (MSL), humid air at MSL and dry air at high altitude level of 36 000 ft above MSL. It is observed that high shock velocities eventually results in dissociation of gaseous molecules and formation of new gaseous species which has been quantified in the manuscript.

Cognitive Impairment During Combined Normobaric vs. Hypobaric and Normoxic vs. Hypoxic Acute Exposure

INTRODUCTION: Exposure to hypoxia has a deleterious effect on cognitive function; however, the putative effect of hypobaria remains unclear. The present study aimed to evaluate cognitive performance in pilot trainees who were exposed to acute normobaric (NH) and hypobaric hypoxia (HH). Of relevance for military pilots, we also aimed to assess cognitive performance in hypobaric normoxia (HN).METHODS: A total of 16 healthy pilot trainees were exposed to 4 randomized conditions (i.e., normobaric normoxia, NN, altitude level of 440 m; HH at 5500 m; NH, altitude simulation of 5500 m; and HN). Subjects performed a cognitive assessment (KLT-R test). Cerebral oxygen delivery (cDO2) was estimated based middle cerebral artery blood flow velocity (MCAv) and pulse oxygen saturation (Spo2) monitored during cognitive assessment.RESULTS: Percentage of errors increased in NH (14.3 9.1%) and HH (12.9 6.4%) when compared to NN (6.5 4.1%) and HN (6.0 4.0%). Number of calculations accomplished was lower only in HH than in NN and HN. When compared to NN, cDO2 decreased in NH and HH.DISCUSSION: Cognitive performance was decreased similarly in acute NH and HH. The cDO2 reduction in NH and HH implies insufficient MCAv increase to ensure cognitive performance maintenance. The present study suggests negligible hypobaric influence on cognitive performance in hypoxia and normoxia.Aebi MR, Bourdillon N, Noser P, Millet GP, Bron D. Cognitive impairment during combined normobaric vs. hypobaric and normoxic vs. hypoxic acute exposure. Aerosp Med Hum Perform. 2020; 91(11):845851.

Composition of soil bacterial and fungal communities in relation to vegetation composition and soil characteristics along an altitudinal gradient

ABSTRACT The objective of the present study was to evaluate how altitudinal gradients shape the composition of soil bacterial and fungal communities, humus forms and soil properties across six altitude levels in Hyrcanian forests. Soil microbiomes were characterized by sequencing amplicons of selected molecular markers. Soil chemistry and plant mycorrhizal type were the two dominant factors explaining variations in bacterial and fungal diversity, respectively. The lowest altitude level had more favorable conditions for the formation of mull humus and exhibited higher N and Ca contents. These conditions were also associated with a higher proportion of Betaproteobacteria, Acidimicrobia, Acidobacteria and Nitrospirae. Low soil and forest floor quality as well as lower bacterial and fungal diversity characterized higher altitude levels, along with a high proportion of shared bacterial (Thermoleophilia, Actinobacteria and Bacilli) and fungal (Eurotiomycetes and Mortierellomycota) taxa. Beech-dominated sites showed moderate soil quality and high bacterial (Alphaproteobacteria, Acidobacteria, Planctomycetes and Bacteroidetes) and fungal (Basidiomycota) diversity. Particularly, the Basidiomycota were well represented in pure beech forests at an altitude of 1500 m. In fertile and nitrogen rich soils with neutral pH, soil quality decreased along the altitudinal gradient, indicating that microbial diversity and forest floor decomposition were likely constrained by climatic conditions.