Photosynthesis, stomatal conductance and leaf water potential in crabwood (Carapa guianensis)

Leaf water potential is one of the most important factors affecting stomatal functioning. The aim of this study was to assess the effect of variation in diurnal irradiance and vapour pressure deficit on photosynthesis (A), stomatal conductance (g s) and leaf water potential (psi) in Carapa guianensis (Aubl.). Data were collected from 07:00 to 17:00 h. Photosynthetic rates reached a maximum (2.5 µmol m-2 s-1) at 10:00 h, thereafter declined to a minimum of 1 µmol m-2 s-1 at 16:00 h. Stomatal conductance oscillated during the day, from 0.04 mol m-2 s-1 (at midday) to 0.02.mol.m-2.s-1 at the end of the afternoon. Leaf water potential was higher early in the morning (-0.3 MPa) and lower (-0.75 MPa) at mid-afternoon (14:30 -15:00 h). After reaching a minimum, psi increased up to -0.64 MPa at sunset. Photosynthetic rates increased linearly as a function of g s (P < 0.01). Also there was a positive relationship between psi and g s (P< 0.01). Photosynthetic rates declined during the day after reaching a peak early in the morning, which makes clear that environmental factors that influence psi greatly affect carbon assimilation of C. guianensis.O potencial hídrico da folha é um dos fatores mais importantes que afetam o funcionamento dos estômatos. O objetivo deste trabalho foi avaliar o efeito da variação diurna na irradiância e déficit de pressão de vapor (DPV) na fotossíntese (A), condutância estomática (g s) e potencial hídrico da folha (psi) em Carapa guianensis (Aubl.). Os dados foram coletados de 07:00 às 17:00 h. A taxa fotossintética atingiu um valor máximo (2,5 µmol m-2 s-1) às 10:00 h, depois declinou até atingir um mínimo de 1 µmolm-2 s-1 às 16:00 h. A condutância estomática oscilou durante o dia, de 0,04 molm-2s-1 (ao meio dia) para 0,02 molm-2s- 1 no final da tarde. O potencial hídrico da folha foi máximo nas primeiras horas do dia (-0,3 MPa) e mínimo (-0,75 MPa) no meio da tarde (14:30 a 15:00 h). Após ter alcançado um mínimo, o psi aumentou até -0,64 MPa no fim da tarde. A taxa fotossintética aumentou linearmente em função do g s (P < 0,01). Também houve uma relação positiva entre psi e g s (P < 0,01). A taxa fotossintética declinou durante o dia após ter alcançado um pico no início da manhã, demonstrando que os fatores ambientais que afetam o psi têm efeito significativo na assimilação do carbono de C. guianensis

The small foreigner: new laws will promote the introduction of non-native zooplankton in Brazilian aquatic environments

Abstract Non-native species of zooplankton have been introduced in Brazilian continental aquatic environments for a variety of reasons (e.g., non-native fish stocking, aquaculture), but many pathways of zooplankton introductions remain unknown. Recently, the governor of the State of Amazonas passed Law No. 79/2016, which allows for aquaculture operations using non-native fish in that state. This change in policy will likely result in the species introduction or propagule pressure of non-native zooplankton such as: Mesocyclops ogunnus Onabamiro, 1957; Kellicottia bostoniensis (Rousselet, 1908); Daphnia lumholtzi Sars, 1885; Lernaea cyprinacea (Linnaeus, 1758); Lamproglena monodi Capart, 1944. Of further concern is federal law No. 5989/09, which proposes the use of non-native fish in Brazilian aquaculture nationwide. We believe that both laws will intensify the introduction of non-native zooplankton. Once established in aquatic environments, non-native species of zooplankton could result in negative impacts (e.g., a loss of ecosystem services, food web alterations). Therefore, Brazilian authorities should incentivize the use of local native species rather than pass laws that threaten the environment

Measurement of the total cross section and ρ -parameter from elastic scattering in pp collisions at √s=13 TeV with the ATLAS detector

In a special run of the LHC with β⋆=2.5 km, proton–proton elastic-scattering events were recorded at s√=13 TeV with an integrated luminosity of 340 μb−1 using the ALFA subdetector of ATLAS in 2016. The elastic cross section was measured differentially in the Mandelstam t variable in the range from −t=2.5⋅10−4 GeV2 to −t=0.46 GeV2 using 6.9 million elastic-scattering candidates. This paper presents measurements of the total cross section σtot, parameters of the nuclear slope, and the ρ-parameter defined as the ratio of the real part to the imaginary part of the elastic-scattering amplitude in the limit t→0. These parameters are determined from a fit to the differential elastic cross section using the optical theorem and different parameterizations of the t-dependence. The results for σtot and ρ are σtot(pp→X)=104.7±1.1 mb ,ρ=0.098±0.011. The uncertainty in σtot is dominated by the luminosity measurement, and in ρ by imperfect knowledge of the detector alignment and by modelling of the nuclear amplitude.publishedVersio

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time, and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space. While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes, vast areas of the tropics remain understudied. In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity, but it remains among the least known forests in America and is often underrepresented in biodiversity databases. To worsen this situation, human-induced modifications may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge, it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost