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The combustion-related primary and secondary carbon particles have gained more importance in the recent past due to their radiative and chemical properties. The present paper deals with the results obtained from observations on Organic Carbon (OC) and Elemental Carbon (EC) during 2019–20 over a high-altitude location, Mahabaleshwar in the Western Ghats in peninsular India. The data is classified into summer (March to May 2019) and winter (December 2019 to February 2020). Mean OC mass was more during summer (13.6 ± 4.4 μg / m3) than winter (11.1 ± 3.2 μg / m3). However, mean EC mass was more in winter (3.6 ± 1.1 μg / m3) than in summer (2.2 ± 1.1 μg / m3). The mean annual OC/EC ratio was 7.4 ± 4.4 in summer and 3.1 ± 0.7 in winter, suggesting more presence of secondary organic carbon (SOC) during summer. Estimated SOC formed about 62% of OC in summer whereas in winter both SOC and primary organic carbon (POC) formed 50% each of OC. Together both POC and EC contributed to 46% of the total carbon (TC) in summer and 62% in winter indicating more primary fraction during winter. The effective carbon ratio (ECR) was 1.6 and 0.7 during summer and winter respectively, indicating the dominance of scattering-type secondary carbonaceous aerosols in summer. Cluster and concentrated weighted trajectory (CWT) analysis indicated high concentrations of OC and EC in continental originated trajectories. However, a high OC/EC ratio was observed for air masses arriving from long-distance sources.

The chemical composition of nonrefractory submicron aerosol particles was measured at the Puy‐de‐Dôme (PUY) station (1,465 m a.s.l) during 2015 using a Time‐of‐Flight Aerosol Chemical Speciation Monitor (ToF‐ACSM). These aerosol chemistry measurements are combined with online black carbon (BC) measurements to provide an overview of the submicron aerosol composition. Averaged over the entire year, and normalized to standard temperature and pressure, organic aerosol (OA) dominates the PM1 concentration during all seasons and within all air mass types (2.12 ± 1.73 µgm−3), and is responsible for summertime increases in aerosol concentration. Highest mass concentrations were measured during the summer, when air masses were arriving over mainland Europe and lowest in the winter months (when most air masses were of Atlantic origin). OA source apportionment was performed separately during each season, using the Source Finder (SoFi) interface for the multilinear engine. The PUY site, situated at 1,465 m a.s.l, although mainly sampling in the atmospheric boundary layer, it is sometimes sampling in the lower free troposphere (FT), providing the opportunity to identify the characteristics of FT aerosol. In order to accurately identify these sampling periods, the methodology described in Farah et al. (2018), during the same time period (2015/2016), was applied to the data. During this period, FT air masses are sampled approximately 20% of the time. This work provides, on one hand, a description of long‐term aerosol chemical properties at a remote regional site in central Europe and, on the other hand a characteristic chemical signature of FT aerosols over this region. This data can be used to improve our understanding of the transport and aging properties of aerosols at regional observation sites. Key Points Statistical analysis of one year of aerosol chemical data at the Puy‐de‐Dome research station Evidence of biomass burning injections into free troposphere (FT) during spring seasons Chemical signature of FT aerosol particles identified

Aerosol particles are important due to their direct and indirect impacts on climate. Within the planetary boundary layer (BL), these particles have a relatively short lifetime due to their frequent removal process by wet deposition. When aerosols are transported into the free troposphere (FT), their atmospheric lifetime increases significantly, making them representative of large spatial areas. In this work, we use a combination of in situ measurements performed at the high altitude PUY (Puy de Dôme, 45°46′ N, 2°57′ E, 1465 m a.s.l) station, together with LIDAR profiles at Clermont-Ferrand for characterizing FT conditions, and further characterize the physical properties of aerosol in this poorly documented area of the atmosphere. First, a combination of four criteria was used to identify whether the PUY station lies within the FT or within the BL. Results show that the PUY station is located in BL with frequencies ranging from 50% during the winter, up to 97% during the summer. Then, the classification is applied to a year-long dataset (2015) of particle size distribution data to study the differences in particle physical characteristics (size distribution) and black carbon (BC) concentrations between the FT and the BL. Although BC, Aitken, and the accumulation mode particles concentrations were higher in the BL than in the FT in winter and autumn, they were measured to be higher in the FT compared to BL in spring. No significant difference between the BL and the FT concentrations was observed for the nucleation mode particles for all seasons, suggesting a continuous additional source of nucleation mode particles in the FT during winter and autumn. Coarse mode particle concentrations were found higher in the FT than in the BL for all seasons and especially during summer. This indicates an efficient long-range transport of large particles in the FT from distant sources (marine and desert) due to higher wind speeds in the FT compared to BL. For FT air masses, we used 204-h air mass back-trajectories combined with boundary layer height estimations from ECMWF ERA-Interim to assess the time they spent in the FT since their last contact with the BL and to evaluate the impact of this parameter on the aerosol properties. We observed that even after 75 h without any contact with the BL, FT aerosols preserve specific properties of their air mass type.

The ac pollution flashover performance and flashover process of LXHY3-I6O insulators was investigated at a high altitude site (altitude of 1400m) in this paper. The solid layer method was used, and even-rising voltage method was adopted. According to the test results, the average pollution flashover voltage (Uav) decreased with the increase of pollution, and there was no obvious relationship between the exponent characterising the influence of pollution and the length of the insulator strings. The relationship between Uav and the length of the insulator strings was nearly linear. Subsequently, the effect of the pollution and the length of insulator strings on the critical flashover arc trajectory were analysed. It concluded that the critical flashover distance (lc) decreased with the increase of pollution, and it was shorter than the leakage distance (L0), whereas there was no significant relationship between lc/L0 and the length of insulator strings. The arc appearance at the high altitude site was very irregular with obvious bending and rocking; the local arcs deviated from the surface of the polluted insulators even more seriously and the diameter was thicker than those obtained in the normal environment. Moreover, the brightness and diameter of local arcs was related to pollution.

In order to solve the problem of ineffective pre-splitting blasting and reduce the damage caused to preserved rock bodies in the Niukutou open-pit quarry in the alpine region of Qinghai Province, China, this study investigated the influence of different delay times on the damage caused to the rock mass, combining numerical calculations with field tests. Using the finite element software ANSYS/LS-DYNA 19.0 and based on the constitutive model of saturated skarn, numerical models of pre-splitting blasting with four different delay times (0 ms, 12 ms, 18 ms, and 24 ms) were established. These models systematically analyze the damage evolution of rock and the effective stress distribution in specific elements under different delay times. The results indicate that a maximum damage depth of 32.56 cm occurs when the inter-hole delay is 0 ms, while a minimum damage depth of 30.61 cm is observed when the inter-hole delay is 18 ms. Further analysis reveals that the peak effective stress is highest when the inter-hole delay is 0 ms, and that the peak effective stress at 18 ms is higher than that at 12 ms and 24 ms. Considering the need to control the damage caused to the surrounding rock and the blasting effectiveness, the best pre-splitting blasting effect is achieved with an inter-hole delay of 18 ms. Field tests show that the damage depth of the retained rock mass is 1.62 m when the inter-hole delay is 0 ms; however, it decreases to 0.90 m when the delay is 18 ms, representing a 44% reduction in rock mass damage depth. This study provides theoretical support and practical guidance for the optimization of pre-splitting blasting in saturated skarn in alpine regions.

Human colonization of the high-altitude Tibetan Plateau has generally been thought to have been confined to the past few thousand years of the Holocene. Zhang et al. report an investigation of the Nwya Devu archaeological site in central Tibet, 4600 meters above sea level, with Paleolithic occupation dates of ∼40 thousand to 30 thousand years ago (see the Perspective by Zhang and Dennell). The site has yielded a range of stone tools, indicating the adaptive ability of early modern humans to the harsh environment of the “roof of the world.” The findings also suggest that people from Tibet and Siberia may have interacted at this time. Science , this issue p. 1049 ; see also p. 992 The Nwya Devu Paleolithic site in Tibet, 4600 meters above sea level, preserves evidence of early human high-altitude adaptation. The Tibetan Plateau is the highest and one of the most demanding environments ever inhabited by humans. We investigated the timing and mechanisms of its initial colonization at the Nwya Devu site, located nearly 4600 meters above sea level. This site, dating from 40,000 to 30,000 years ago, is the highest Paleolithic archaeological site yet identified globally. Nwya Devu has yielded an abundant blade tool assemblage, indicating hitherto-unknown capacities for the survival of modern humans who camped in this environment. This site deepens the history of the peopling of the “roof of the world” and the antiquity of human high-altitude occupations more generally.

A key question in evolutionary biology concerns the relative importance of different sources of adaptive genetic variation, such as de novo mutations, standing variation, and introgressive hybridization. A corollary question concerns how allelic variants derived from these different sources may influence the molecular basis of phenotypic adaptation. Here, we use a protein-engineering approach to examine the phenotypic effect of putatively adaptive hemoglobin (Hb) mutations in the high-altitude Tibetan wolf that were selectively introgressed into the Tibetan mastiff, a high-altitude dog breed that is renowned for its hypoxia tolerance. Experiments revealed that the introgressed coding variants confer an increased Hb–O2 affinity in conjunction with an enhanced Bohr effect. We also document that affinity-enhancing mutations in the β-globin gene of Tibetan wolf were originally derived via interparalog gene conversion from a tandemly linked β-globin pseudogene. Thus, affinity-enhancing mutations were introduced into the β-globin gene of Tibetan wolf via one form of intragenomic lateral transfer (ectopic gene conversion) and were subsequently introduced into the Tibetan mastiff genome via a second form of lateral transfer (introgression). Site-directed mutagenesis experiments revealed that the increased Hb–O2 affinity requires a specific two-site combination of amino acid replacements, suggesting that the molecular underpinnings of Hb adaptation in Tibetan mastiff (involving mutations that arose in a nonexpressed gene and which originally fixed in Tibetan wolf) may be qualitatively distinct from functionally similar changes in protein function that could have evolved via sequential fixation of de novo mutations during the breed’s relatively short duration of residency at high altitude.

High-altitude environments present a range of biochemical and physiological challenges for organisms through decreases in oxygen, pressure, and temperature relative to lowland habitats. Protein-level adaptations to hypoxic high-altitude conditions have been identified in multiple terrestrial endotherms; however, comparable adaptations in aquatic ectotherms, such as fishes, have not been as extensively characterized. In enzyme proteins, cold adaptation is attained through functional trade-offs between stability and activity, often mediated by substitutions outside the active site. Little is known whether signaling proteins [e.g., G protein-coupled receptors (GPCRs)] exhibit natural variation in response to cold temperatures. Rhodopsin (RH1), the temperature-sensitive visual pigment mediating dim-light vision, offers an opportunity to enhance our understanding of thermal adaptation in a model GPCR. Here, we investigate the evolution of rhodopsin function in an Andean mountain catfish system spanning a range of elevations. Using molecular evolutionary analyses and site-directed mutagenesis experiments, we provide evidence for cold adaptation in RH1. We find that unique amino acid substitutions occur at sites under positive selection in high-altitude catfishes, located at opposite ends of the RH1 intramolecular hydrogen-bonding network. Natural high-altitude variants introduced into these sites via mutagenesis have limited effects on spectral tuning, yet decrease the stability of dark-state and light-activated rhodopsin, accelerating the decay of ligand-bound forms. As found in cold-adapted enzymes, this phenotype likely compensates for a cold-induced decrease in kinetic rates—properties of rhodopsin that mediate rod sensitivity and visual performance. Our results support a role for natural variation in enhancing the performance of GPCRs in response to cold temperatures.

Study of human adaptation to extreme environments is important for understanding our cultural and genetic capacity for survival. The Pucuncho Basin in the southern Peruvian Andes contains the highest-altitude Pleistocene archaeological sites yet identified in the world, about 900 meters above confidently dated contemporary sites. The Pucuncho workshop site [4355 meters above sea level (masl)] includes two fishtail projectile points, which date to about 12.8 to 11.5 thousand years ago (ka). Cuncaicha rock shelter (4480 masl) has a robust, well-preserved, and well-dated occupation sequence spanning the past 12.4 thousand years (ky), with 21 dates older than 11.5 ka. Our results demonstrate that despite cold temperatures and low-oxygen conditions, hunter-gatherers colonized extremehigh-altitudeAndean environments in the Terminal Pleistocene, within about 2 ky of the initial entry of humans to South America.

High-altitude environments characterized by low air pressure, hypoxia, and strong solar radiation have a significant impact on human thermal comfort; however, existing thermal comfort theories and evaluation models are primarily developed under low-altitude climatic conditions, and their applicability in plateau regions remains limited. With the acceleration of urbanization and the increase in residential, tourism, and occupational activities in high-altitude areas, systematically reviewing the research progress on thermal comfort in such environments is of great practical significance. This study combines systematic literature retrieval and bibliometric analysis, based on the Web of Science Core Collection and China National Knowledge Infrastructure (CNKI) databases, to analyze relevant studies published since 2001. Using CiteSpace, research hotspots, collaboration networks, and evolutionary trends are visualized. The results indicate that current research hotspots mainly focus on physiological responses and thermal adaptation mechanisms under low-pressure and hypoxic conditions, thermal comfort regulation strategies for high-altitude buildings and environments, and the applicability and modification of conventional thermal comfort models. Emerging trends include multi-environmental factor coupling analysis, adaptive model development, region-specific building design approaches, and health-oriented comprehensive evaluation frameworks. The findings provide valuable references for building thermal environment design, regional revision of thermal comfort evaluation standards, and policy-making in high-altitude regions.