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The chemical composition of PM 10 and non-overlapping PM 2.5 was studied at the summit of Mt. Chacaltaya (5380 m a.s.l., lat. - 16.346950°, long. - 68.128250°) providing a unique long-term record spanning from December 2011 to March 2020. The chemical composition of aerosol at the Chacaltaya Global Atmosphere Watch (GAW) site is representative of the regional background, seasonally affected by biomass burning practices and by nearby anthropogenic emissions from the metropolitan area of La Paz–El Alto. Concentration levels are clearly influenced by seasons with minima occurring during the wet season (December to March) and maxima occurring during the dry and transition seasons (April to November). Ions, total carbon (EC + OC), and saccharide interquartile ranges for concentrations are 558–1785, 384–1120, and 4.3–25.5 ng m -3 for bulk PM 10 and 917–2308, 519–1175, and 3.9–24.1 ng m -3 for PM 2.5 , respectively, with most of the aerosol seemingly present in the PM 2.5 fraction. Such concentrations are overall lower compared to other high-altitude stations around the globe but higher than Amazonian remote sites (except for OC). For PM 10 , there is dominance of insoluble mineral matter (33 %–56 % of the mass), organic matter (7 %–34 %), and secondary inorganic aerosol (15 %–26 %). Chemical composition profiles were identified for different origins: EC, NO 3- , NH 4+ , glucose, and C 2 O 42- for the nearby urban and rural areas; OC, EC, NO 3- , K + , acetate, formate, levoglucosan, and some F - and Br - for biomass burning; MeSO 3- , Na + , Mg 2+ , K + , and Ca 2+ for aged marine emissions from the Pacific Ocean; arabitol, mannitol, and glucose for biogenic emissions; Na + , Ca 2+ , Mg 2+ , and K + for soil dust; and SO 42- , F - , and some Cl - for volcanism. Regional biomass burning practices influence the soluble fraction of the aerosol between June and November. The organic fraction is present all year round and has both anthropogenic (biomass burning and other combustion sources) and natural (primary and secondary biogenic emissions) origins, with the OC/EC mass ratio being practically constant all year round (10.5 ± 5.7, IQR 8.1–13.3). Peruvian volcanism has dominated the SO 42- concentration since 2014, though it presents strong temporal variability due to the intermittence of the sources and seasonal changes in the transport patterns. These measurements represent some of the first long-term observations of aerosol chemical composition at a continental high-altitude site in the tropical Southern Hemisphere. [ABSTRACT FROM AUTHOR]

The chemical composition of PM10 and PM2.5 was studied at the summit of Mt. Chacaltaya (5380 masl, lat.-16.346950º, lon. -68.128250º) providing a unique long-term record spanning from December 2011 to March 2020. The chemical composition of aerosol at the Chacaltaya GAW site is representative of the regional background, seasonally affected by biomass burning practices and by nearby anthropogenic emissions from the metropolitan area of La Paz – El Alto. Concentration levels are clearly influenced by seasons with minimum occurring during the wet season (December to March) and maxima occurring during the dry and transition seasons (April to November). Ions, total carbon (EC+OC) and saccharide concentrations range between 558–1785, 384–1120 and 4.3–25.5 ng m-3 for bulk PM10 and 917–2308, 519–1175 and 3.9–24.1 ng m-3 for PM2.5, respectively. Such concentrations are overall lower compared to other high-altitude stations around the globe, but higher than Amazonian remote sites (except for OC). For PM10, there is dominance of insoluble mineral matter (33–56 % of the mass), organic matter (7–34 %) and secondary inorganic aerosol (15–26 %). Chemical composition profiles were identified for different origins: EC, NO3-, NH4+, glucose, C2O4-2 for the nearby urban and rural areas; OC, EC, NO3-, K+, acetate, formiate, levoglucosan, some F- and Br- for biomass burning; MeSO3-, Na+, Mg2+, Br- for aged marine emissions from the Pacific Ocean; arabitol, mannitol, K+ for biogenic emissions; Na+, Ca2+, Mg2+ for soil dust, and SO42-, F-, and some Cl- for volcanism. Regional biomass-burning practices influence the soluble fraction of the aerosol particularly between July and September. The organic fraction is present all year round and has both anthropogenic (biomass burning and other combustion sources) and natural (primary and secondary biogenic emissions) origins, with the OC/EC mass ratio being practically constant all year round (10.5±38.9). Peruvian volcanism dominates the SO42- concentration since 2014, though it presents a strong temporal variability due to the intermittence of the sources and seasonal changes on the transport patterns. These measurements represent some of the first long-term observations of aerosol chemical composition at a continental high-altitude site in the tropical Southern hemisphere. [ABSTRACT FROM AUTHOR]

Social media has an important role in diffusion of information, during COVID-19 pandemic it could help to promote preventive behaviors, however its role and the pathway is still unclear. Objective: To investigate the association among social media exposure, risk perception, preventive behaviors, and attitudes toward the COVID-19 epidemic in Bolivia. Methods: We launched an online survey in La Paz and El Alto, Bolivia, during April and May 2020. The questionnaire examined: Socio-demographic factors, Social media use, Risk Perception, Preventive behaviors, attitudes and the willingness to use a vaccine if it were available in the context of the COVID-19 epidemic. A logistic regression was used to evaluate factors associated with risk perception and a structural equation model (SEM) was performed to explore the pathway of the relationship among social media exposure, risk perception and preventive behaviors and attitudes. Results: Among 886 participants, the most were young adults, between 18–25 years old (73.4%) and 577 (65.1%) were female. During the the week before the survey 387 (43.7%) reported be exposure to social media Covid-19 information almost always or always. Moreover 304 (34.3%) were categorized as with a high risk perception. The multivariable analyses show that being female (aOR = 1.5, CI 95% 1.1–2.1) and having high exposure to Covid-19 information on social media (aOR = 2.5, CI 95% 1.3–5.3) were associated with a higher risk perception for Covid-19. Furthermore, SEM results indicated that risk perception is associated with the adoption of preventive behaviors and attitudes (β = 0.605, p < 0.001) including the acceptance of a vaccine if one were available (β = 0.388, p < 0.001). Conclusion: Social media exposure to COVID-19 information influences the adoption of preventive attitudes and behaviors through shaping risk perception. Understanding the role of social media during the pandemic could help policymakers and communicators to develop better communication strategies that enable the population to adopt appropriate attitudes and behaviors. [ABSTRACT FROM AUTHOR]

The quantification of archaeological artefacts with X‐ray Fluorescence is quite complex because it demands some calibration procedure. It is also rather more challenging when the customization of the portable equipment for in situ measurements is required. The objective of this study was to introduce a quantitative method by performing a calibration curve for a ternary gold alloy (Au, Ag and Cu). Fast Monte Carlo simulation combined with in situ portable XRF (pXRF) measurements in order to circumvent the calibration requirement using standard reference materials was used. Measurements with a laboratory‐made equipment were taken from a set of 16 pre‐hispanic gold alloy artefacts of a collection from the Museo Nacional de Etnografia y Folklore, La Paz, Bolivia. The spectra simulation was conducted with the XMI‐MSIM software.The results demonstrated that the combined use of pXRF measurements and spectra simulation via Monte Carlo is a feasible method for gold alloy quantification. In the examined samples, the Cu content was below 5% and for Au it ranged from 13 to 100%. Moreover, some peculiarities of the artefacts archaeological context were discussed. [ABSTRACT FROM AUTHOR]

Two unknown 1,2,4-oxadiazoles (3-(pyridin-3-yl)-5-(thiophen-3-yl)-1,2,4-oxadiazole and 5-(3-hydroxyphenyl)-3-(pyridin-3-yl)-1,2,4-oxadiazole) and one known 1,2,4-oxadiazole (5-(3-methoxyphenyl)-3-(pyridin-3-yl)-1,2,4-oxadiazole) were isolated from tubers of Neowerdermannia vorwerkii , collected from the San Juan Huancollo, Ingavi province, La Paz, Bolivia. The chemical structures of these compounds were elucidated through NMR and HRMS spectroscopic analyses. All compounds showed apoptotic capacity against the SK-HEP-1 and Caco-2 tumour cells. 5-(3-methoxyphenyl)-3-(pyridin-3-yl)-1,2,4-oxadiazole and 5-(3-hydroxyphenyl)-3-(pyridin-3-yl)-1,2, 4-oxadiazole showed slight apoptotic capacities, with an IC 50 between 17.46 ± 0.75 to 15.91 ± 0.62 μ M and 39.29 ± 0.98 to 34.81 ± 0.70 μ M, respectively. 3-(pyridin-3-yl)-5-(thiophen-3-yl)-1,2,4-oxadiazole showed a higher apoptotic capacity with an IC 50 in the range of 0.98 ± 0.11 to 0.76 ± 0.03 μ M, similar to that of the positive control (Dimethylenastron). [Display omitted] • Two unknown 1,2,4-oxadiazoles and one known 1,2,4-oxadiazole were first isolated from N. vorwerkii. • Compounds showed apoptotic capacity against different tumour cell lines. [ABSTRACT FROM AUTHOR]

Two alkaloids were isolated and identified for the first time in the black tubers of Tropaeolum tuberosum, collected from the Titicani-Taca, Ingavi province in La Paz, Bolivia. Their structures were elucidated by extensive NMR and MS spectroscopic analyses. The isolated compounds were evaluated for their cytotoxicity and apoptotic capacity against four human cancer cell lines. 2-Benzyl-3-thioxohexahydropyrrolo[1,2-c]imidazole-1-one (1) showed slight cytotoxic activity against all the cancer cell lines which were tested, with IC 50 values ranging from 27.45 ± 0.80 to 31.07 ± 0.87 μ M. Moreover, N -(4-acetyl-5-methyl-5-phenyl-4,5-dihydro-1,3,4-thiadiazol-2-yl) acetamide (2) showed significant anti-cancer potential, with IC 50 values between 1.26 ± 0.57 μ M and 1.37 ± 0.09 μ M against all human cancer cell lines which were tested. Treatment of tumour cell lines with the compounds caused an increase in the apoptotic rate of these cells, observing that compound 2 presented an apoptotic effect which was double with respect to the control (Dimethylenastron). Isolated T. tuberosum compounds interact on the DNA chain. Image 1 • Isolation of compounds from T. tuberosum with apoptotic capacity in tumour cells. [ABSTRACT FROM AUTHOR]