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We report here on two extensive data sets across the tree line in the Sierra Nevada de Mérida in the Venezuelan Andes. First, we describe the tree distribution with elevation at this site. Second, we report on several years of temperature data beginning in 2001 for the soil surface, 10, 20, and 40 cm depth from 2,000 to 4,978 m elevation. The tree line at this site is dominated by Polylepis and is located near 4,100 m. At the tree line, the annual mean temperature at 10 cm depth was 6.66°C with an annual maximum temperature of 13°C and an annual minimum temperature of 1.4°C; the lowest maximum temperature for any day of the year was 6°C, so though there is not continuous growth, every day of the year the temperature gets high enough that some growth is possible. The mean annual air temperature was 6.4°C. The topographic lapse rate across the tree line is 5.7°C/km for all depths. Below 3,500 to 2,500 m elevation in the cloud forest zone the topographic rate decreases to 0.9°C/km. Our results are consistent with the emerging model of temperature correlation with the elevation of tree line. Temperature archive data set identifier: . [ABSTRACT FROM AUTHOR]

Awareness of best safety practices in the industrial sector will allow students in chemistry and chemical engineering programs to apply these approaches to their own safety assessments. Process safety is a critical function within the pharmaceutical industry to ensure safety when performing reactions. An introduction to process safety and a series of case studies illustrating how safety is routinely considered within the pharmaceutical industry is presented. The concepts presented herein are applicable to multiple industries, academic research, and chemical reactions conducted on all scales. The case studies include examples where a synthesis was redesigned to afford a triazole intermediate without forming potentially explosive byproducts, an exothermic reaction was controlled by understanding the heat output with time and developing a portion-wise addition procedure, and a reaction that displayed extremely fast gas evolution was managed by using an alternative solvent and controlling the rate of reagent addition.

Traces of life are nearly ubiquitous on Earth. However, a central unresolved question is whether these traces always indicate an active microbial community or whether, in extreme environments, such as hyperarid deserts, they instead reflect just dormant or dead cells. Although microbial biomass and diversity decrease with increasing aridity in the Atacama Desert, we provide multiple lines of evidence for the presence of an at times metabolically active, microbial community in one of the driest places on Earth. We base this observation on four major lines of evidence: (i) a physico-chemical characterization of the soil habitability after an exceptional rain event, (ii) identified biomolecules indicative of potentially active cells [e.g., presence of ATP, phospholipid fatty acids (PLFAs), metabolites, and enzymatic activity], (iii) measurements of in situ replication rates of genomes of uncultivated bacteria reconstructed from selected samples, and (iv) microbial community patterns specific to soil parameters and depths. We infer that the microbial populations have undergone selection and adaptation in response to their specific soil microenvironment and in particular to the degree of aridity. Collectively, our results highlight that even the hyperarid Atacama Desert can provide a habitable environment for microorganisms that allows them to become metabolically active following an episodic increase in moisture and that once it decreases, so does the activity of the microbiota. These results have implications for the prospect of life on other planets such as Mars, which has transitioned from an earlier wetter environment to today's extreme hyperaridity.

We installed a meteorological recording system at Badwater (elev. −75 m), the lowest point in Death Valley, California and recorded data over the period 1998–2019. A second station (the Outhouse Station) was established nearby from 2014 to 2019. Here, we report on and publicly archive the data from these two stations. Of interest was the comparison between two air temperature measurements at the Badwater Station, the first with an aspirated platinum resistance temperature device and the second with a thermistor probe in a passive sun shield. During the hottest periods of the summer when temperatures were typically between 30°C at night and 50°C daily peak, the passively shielded sensor indicated up to 0.5°C warmer than the aspirated temperature sensor due to radiative effects. The data suggest a correction for radiative heating of (T–35)/30, for T > 35°C, where, T, is the uncorrected temperature reading of a passively shielded sensor subtracted after any calibration at lower temperatures. Our station was the first precision temperature measurements at Badwater. A longer record exists for the reporting station near the visitor's centre at the Furnace Creek. The summer temperature maxima at the Badwater site correlate well with the values the same day from the Furnace Creek site. The daily maximum temperatures in winter at the Badwater site appear to be about 1°C lower than at the Furnace Creek site. The largest differences are in the minimum temperatures for which the Badwater site averages about 2–3°C warmer than the Furnace Creek site. [ABSTRACT FROM AUTHOR]

We report on the pore size distribution and water retention of Beacon sandstone from Antarctica that harbours a cryptoendolithic community, predominantly lichens, just below the surface. We measured the pore size distribution, drying time and equilibrium relative humidity of sandstone samples that were colonized by lichens. The incremental pore volume distribution peaks at ~10 μm radius, but ~20% of the pore volume occurs for a radius < 0.02 μm. Water from snowmelt fills ~20% of the total pore volume. It takes ~4–5 days of evaporation to lose 90% of the water. As the rock loses water, the equilibrium relative humidity remains at 99% until an appreciable amount (80–90%) of the pore water is lost, after which the equilibrium relative humidity starts to decrease. The relative humidity remains at > 80% (68 h) long after the water content falls to < 98% (19 h) - the point at which liquid water is estimated no longer to be present. Lichens can remain active in air with high relative humidity (> 80%). Thus, the pore size distribution of the sandstone may play a role in explaining why lichens dominate these sandstones. [ABSTRACT FROM AUTHOR]

Issue Addressed Methods Results Conclusions So What? Little is currently known about the relationships between body composition and the social determinants of health among Aboriginal and Torres Strait Islander youth in Australia, which could help inform policy responses to address health inequities.This study aimed to explore the relationship between various social factors and healthy body mass index (BMI) and waist/height ratio (WHtR) among Aboriginal and Torres Strait Islander youth aged 16–24 years. Baseline survey data from 531 participants of the ‘Next Generation: Youth Well‐being study’ were used. Robust Poisson regression quantified associations between healthy body composition and self‐reported individual social factors (education, employment and income, government income support, food insecurity, home environment, relationship status, racism), family factors (caregiver education and employment) and area‐level factors (remoteness, socioeconomic status).Healthy body composition was less common among those living in a crowded home (healthy WHtR aPR 0.67 [0.47–0.96]) and those receiving government income support (healthy BMI aPR 0.74 [0.57–0.95]). It was more common among those with tertiary educated caregivers (healthy BMI aPR 1.84 [1.30–2.61]; healthy WHtR aPR 1.41 [1.05–1.91]) and those in a serious relationship (healthy BMI aPR 1.33 [1.02–1.75]).Social factors at the individual and family level are associated with healthy body composition among Aboriginal and Torres Strait Islander youth.The findings of this study highlight the potential for health benefits for youth from policies and programs that address social inequities experienced by Aboriginal and Torres Strait Islander people in Australia. [ABSTRACT FROM AUTHOR]

The Sample Analysis at Mars (SAM) investigation on the Mars Science Laboratory (MSL) Curiosity rover has detected oxidized nitrogen-bearing compounds during pyrolysis of scooped aeolian sediments and drilled sedimentary deposits within Gale crater. Total N concentrations ranged from 20 to 250 nmol N per sample. After subtraction of known N sources in SAM, our results support the equivalent of 110-300 ppm of nitrate in the Rocknest (RN) aeolian samples, and 70-260 and 330-1,100 ppm nitrate in John Klein (JK) and Cumberland (CB) mudstone deposits, respectively. Discovery of indigenous martian nitrogen in Mars surface materials has important implications for habitability and, specifically, for the potential evolution of a nitrogen cycle at some point in martian history. The detection of nitrate in both wind-drifted fines (RN) and in mudstone (JK, CB) is likely a result of N2 fixation to nitrate generated by thermal shock from impact or volcanic plume lightning on ancient Mars. Fixed nitrogen could have facilitated the development of a primitive nitrogen cycle on the surface of ancient Mars, potentially providing a biochemically accessible source of nitrogen.