Biogenic volatile organic compounds (BVOCs) are important components of the atmosphere due to their contribution to atmospheric chemistry and biogeochemical cycles. Tropical forests are the largest ...source of the dominant BVOC emissions (e.g. isoprene and monoterpenes). In this study, we report isoprene and total monoterpene flux measurements with a proton transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS) using the eddy covariance (EC) method at the Tapajós National Forest (2.857∘ S, 54.959∘ W), a primary rainforest in eastern Amazonia. Measurements were carried out from 1 to 16 June 2014, during the wet-to-dry transition season. During the measurement period, the measured daytime (06:00–18:00 LT) average isoprene mixing ratios and fluxes were 1.15±0.60 ppb and 0.55±0.71 mg C m−2 h−1, respectively, whereas the measured daytime average total monoterpene mixing ratios and fluxes were 0.14±0.10 ppb and 0.20±0.25 mg C m−2 h−1, respectively. Midday (10:00–14:00 LT) average isoprene and total monoterpene mixing ratios were 1.70±0.49 and 0.24±0.05 ppb, respectively, whereas midday average isoprene and monoterpene fluxes were 1.24±0.68 and 0.46±0.22 mg C m−2 h−1, respectively. Isoprene and total monoterpene emissions in Tapajós were correlated with ambient temperature and solar radiation. Significant correlation with sensible heat flux, SHF (r2=0.77), was also observed. Measured isoprene and monoterpene fluxes were strongly correlated with each other (r2=0.93). The MEGAN2.1 (Model of Emissions of Gases and Aerosols from Nature version 2.1) model could simulate most of the observed diurnal variations (r2=0.7 to 0.8) but declined a little later in the evening for both isoprene and total monoterpene fluxes. The results also demonstrate the importance of site-specific vegetation emission factors (EFs) for accurately simulating BVOC fluxes in regional and global BVOC emission models.
To evaluate the efficacy of a carrageenan-based lubricant gel in reducing the risk of genital human papillomavirus (HPV) infections in women.
We conducted a planned interim analysis of a randomized, ...double-blind, placebo-controlled, phase 2B trial. Women aged 18 years and older were randomly assigned (1:1) to a carrageenan-based gel or a placebo gel to be self-applied every other day for the first month and before and after each intercourse during follow-up. Assessments were performed at 0.5, 1, 3, 6, 9 and 12 months. The primary outcome was incidence of a new infection by an HPV type that was not present at baseline. Intention-to-treat analyses were performed.
Between January 2013 and June 2017, a total of 280 participants were randomly assigned to the carrageenan (n = 141) or the placebo (n = 139) arm. All participants were included in safety analyses, but three (1%) were excluded from efficacy analyses (HPV results unavailable for two participants in the carrageenan and one participant in the placebo arm). The median follow-up time was 9.2 months (interquartile range, 1.9–13.2 months). A total of 59 (42%) of 139 participants in the carrageenan arm and 78 (57%) of 138 participants in the placebo arm became infected by at least one new HPV type (hazard ratio = 0.64, 95% confidence interval = 0.45–0.89, p 0.009). A total of 62 (44%) of 141 participants in the carrageenan arm versus 43 (31%) of 139 participants in the placebo arm reported an adverse event (p 0.02), none of which was deemed related to the gels.
Our trial's interim analysis suggests that using a carrageenan-based lubricant gel can reduce the risk of genital HPV infections in women.
The Amazon Basin provides an excellent environment for studying the sources, transformations, and properties of natural aerosol particles and the resulting links between biological processes and ...climate. With this framework in mind, the Amazonian Aerosol Characterization Experiment (AMAZE-08), carried out from 7 February to 14 March 2008 during the wet season in the central Amazon Basin, sought to understand the formation, transformations, and cloud-forming properties of fine- and coarse-mode biogenic aerosol particles, especially as related to their effects on cloud activation and regional climate. Special foci included (1) the production mechanisms of secondary organic components at a pristine continental site, including the factors regulating their temporal variability, and (2) predicting and understanding the cloud-forming properties of biogenic particles at such a site. In this overview paper, the field site and the instrumentation employed during the campaign are introduced. Observations and findings are reported, including the large-scale context for the campaign, especially as provided by satellite observations. New findings presented include: (i) a particle number-diameter distribution from 10 nm to 10 μm that is representative of the pristine tropical rain forest and recommended for model use; (ii) the absence of substantial quantities of primary biological particles in the submicron mode as evidenced by mass spectral characterization; (iii) the large-scale production of secondary organic material; (iv) insights into the chemical and physical properties of the particles as revealed by thermodenuder-induced changes in the particle number-diameter distributions and mass spectra; and (v) comparisons of ground-based predictions and satellite-based observations of hydrometeor phase in clouds. A main finding of AMAZE-08 is the dominance of secondary organic material as particle components. The results presented here provide mechanistic insight and quantitative parameters that can serve to increase the accuracy of models of the formation, transformations, and cloud-forming properties of biogenic natural aerosol particles, especially as related to their effects on cloud activation and regional climate.
Currently, 2 vaccines exist that prevent infection by the genotypes of human papillomavirus (HPV) responsible for approximately 70% of cervical cancer cases worldwide. Although vaccination is ...expected to reduce the prevalence of these HPV types, there is concern about the effect this could have on the distribution of other oncogenic types. According to basic ecological principles, if competition exists between ≥2 different HPV types for niche occupation during natural infection, elimination of 1 type may lead to an increase in other type(s). Here, we discuss this issue of "type replacement" and present different epidemiologic approaches for evaluation of HPV type competition. Briefly, these approaches involve: 1) calculation of the expected frequency of coinfection under independence between HPV types for comparison with observed frequency; 2) construction of hierarchical logistic regression models for each vaccine-targeted type; and 3) construction of Kaplan-Meier curves and Cox models to evaluate sequential acquisition and clearance of HPV types according to baseline HPV status. We also discuss a related issue concerning diagnostic artifacts arising when multiple HPV types are present in specific samples (due to the inability of broad-spectrum assays to detect certain types present in lower concentrations). This may result in an apparent increase in previously undetected types postvaccination.
Isoprene fluxes vary seasonally with changes in environmental factors (e.g.,
solar radiation and temperature) and biological factors (e.g., leaf
phenology). However, our understanding of the seasonal ...patterns of isoprene
fluxes and the associated mechanistic controls is still limited, especially in
Amazonian evergreen forests. In this paper, we aim to connect intensive,
field-based measurements of canopy isoprene flux over a central Amazonian
evergreen forest site with meteorological observations and with tower-mounted camera leaf phenology to improve our understanding of patterns and causes
of isoprene flux seasonality. Our results demonstrate that the highest
isoprene emissions are observed during the dry and dry-to-wet transition
seasons, whereas the lowest emissions were found during the wet-to-dry
transition season. Our results also indicate that light and temperature cannot totally explain isoprene flux seasonality. Instead, the camera-derived
leaf area index (LAI) of recently mature leaf age class (e.g., leaf ages of
3–5 months) exhibits the highest correlation with observed isoprene flux
seasonality (R2=0.59, p<0.05). Attempting to better represent
leaf phenology in the Model of Emissions of Gases and Aerosols from Nature
(MEGAN 2.1), we improved the leaf age algorithm by utilizing results from the
camera-derived leaf phenology that provided LAI categorized into three
different leaf ages. The model results show that the observations of
age-dependent isoprene emission capacity, in conjunction with camera-derived
leaf age demography, significantly improved simulations in terms of seasonal
variations in isoprene fluxes (R2=0.52, p<0.05). This study
highlights the importance of accounting for differences in isoprene emission
capacity across canopy leaf age classes and identifying forest adaptive
mechanisms that underlie seasonal variation in isoprene emissions in
Amazonia.
Since the early 1950s, Papanicolaou ("Pap") cytology screening has dramatically reduced cervical cancer mortality in most high-income settings. Currently, human papillomavirus (hpv) vaccination has ...the greatest potential to reduce the global burden of cervical cancer and precancerous lesions. However, as the prevalence of precancerous lesions declines, maintaining cytology as the primary screening test in settings with established programs might become less efficient. A reduction in test performance (sensitivity, specificity, and positive predictive value) would lead to an increase in unnecessary colposcopy referrals. Fortunately, hpv dna testing has emerged as a suitable candidate to replace cytology. Compared with the Pap test, hpv testing is less specific but much more sensitive in detecting high-grade precancerous lesions, less prone to human error, and more reproducible across settings. Linkage of hpv vaccination and screening registries could serve the added role of monitoring vaccine efficacy. As a triage test, cytology is expected to perform with sufficient accuracy because most hpv-positive smears would contain relevant abnormalities. This approach and others-for example, hpv testing followed by genotyping-are being evaluated in large population studies and have already been recommended in some settings. Other specific biomarkers that might perform well for screening and triage include hpv E6/E7 messenger rna testing, methylation of host or viral genes, and p16(INK4a) staining. Considering the rapid pace of major discoveries and the anticipated arrival of a nonavalent hpv vaccine (currently in phase iii trials), the evidence base in this field has become an elusive target and will continue to be an obstacle for policymakers.
The coupling between different types of surface (tropical forest or grass) and the Convective Boundary Layer (CBL) has been investigated using observational (rawinsoundings) data collected over ...Rondonia in southwest Amazonia. The data reported here support the notion that deforestation may modify the dynamics of the boundary layer, in particular during the dry season. In this period the sensible heat fluxes are very high over pasture, creating a CBL around 550 m deeper compared to that over the forest. The measurements showed the height of the fully developed CBL for pasture to be 1650 m, compared to around 1100 m for forest. During the wet season the height of the CBL is lower than during the dry season and has the same height (around 1000 m) for forest and pasture sites. The CBL over pasture is hotter and drier than over forest during the dry season, but during the wet season the air temperatures and humidities are similar. Comparing the CBL growth during the dry and wet season, there is evidence that the CBL properties over the forest are not dependent on the surface characteristics, but over the pasture they are. PUBLICATION ABSTRACT
Contributing to improve the terrestrial surface parameterizations of numerical weather forecasting models (e.g. Kaimal and Finnigan 1994; Belcher and Hunt 1998; Belcher et al. 2012; Xu et al. 2017) ...and the development of different models of turbulence based on empirical relations or involving solutions of the momentum equation using closing techniques that investigate the structure of air flow over forests (Shaw 1977; Wilson & Shaw, 1977; Katul et al., 2004;Yi et al. 2005; Yi 2008; Xu et al. 2013, 2015; Sousa et al.2016; Santana et al. 2017). ...knowledge of this structure is necessary for a better understanding of the impact that vegetation elements such as leaves, branches and trunks cause in the field of wind and in the transport of mass, energy and momentum. According to some studies (see Wilson e Shaw 1977; Raupach et al. 1996; Finnigan 2000) vegetation interacts with and influences the wind flow of the lowest atmospheric layers as follows: 1) In extracting momentum from the flow due to the aerodynamic drag of the plant parts; 2) In converting kinetic energy of the mean flow into turbulent kinetic energy in the wakes formed behind obstructions to the flow; 3) in breaking down largescale turbulent motions into smaller scale motions, again in the wake flow. The profiles were measured by two triaxial sonic anemometers: one operated above the forest canopy while the other was roving at different heights at the spruce site were 12.1, 9.2, 6.2, 4.2, and 1.8 m; at the jack pine site 17, 13.1, 8.7, 5.8 and 1.9 m; and at the aspen site 13.1, 8.7, 5.8, 3.4 and 1.4 m. Amiro 1990, estimated the height of the canopy top (h) to be about 15 m for the pine canopy, and 10 m for the spruce and aspen canopies and your best estimates of total leaf area index (LAI) are about 10 for the spruce canopy, 4 for the aspen canopy, and 2 for the pine canopy. (3) Where -u'w' is the average shear stress. 2.2.2 Alternative method to the estimate of the drag coefficient If the normalization profiles of wind speed and cumulative leaf area are the same between two systems, the relative distribution of the drag coefficient differs only by LAI. ...an alternative method to the estimate of the drag coefficient is proposed considering a dependence on the LAI profile, thus, ...
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