ESTUDO DA INTERAÇÃO ENTRE O TRANSPORTE DE COMPOSTOS ORGÂNICOS VOLÁTEIS BIOGÊNICOS E QUÍMICA DENTRO DE UM DOSSEL DA FLORESTA TROPICAL UTILIZANDO LARGE EDDY SIMULATION

A multitude of biogenic volatile organic compounds (BVOCs) are emitted within the canopy air-space of tropical forests. These compounds undergo reactions with atmospheric oxidants (eg. Ozone O3, the nitrate NO3 or the hydroxyl OH radicals), which mainly originate above the canopy, and reaction products can subsequently condense to form secondary organic aerosols. Canopy resolving Large Eddy Simulation (LES) combined with a representation of atmospheric chemistry presents a valuable tool for a better understanding of the interaction between chemistry and transport processes. This requires the adequate resolution of concentration fields of reactants (BVOCs and oxidants) as well as the flow field inside the canopy. We present the results of an LES study with 17 layers inside the forest (2 m vertical resolution), which includes a simplified BVOC chemistry in order to estimate the export of BVOCs and their principal reaction products such as methyl vinyl ketone (MVK) and methacrolein (MACR) from a tropical canopy. These results are compared to field measurements of ozone, nitrogen oxides, isoprene, monoterpenes as well as MVK and MACR observed during a field campaign at the Cuieiras Biological Reserve K34 (2°36’32” S, 60° 12’33” W) tower from April 2014 to January 2015.Florestas tropicais emitem um grande número de compostos orgânicos voláteis biogênicos (COVB), que podem reagir com oxidantes atmosféricos (como por exemplo radicais Ozônio O3, nitrato NO3 ou hidroxila OH, normalmente originados acima do dossel) e os produtos da reação podem condensar formando aerossóis orgânicos secundários. Simulações de Grandes Vórtices (LES, da sigla em inglês) que resolvem o dossel, combinadas com uma representação da química da atmosfera, são uma poderosa ferramenta para um melhor entendimento da interação entre os processos químicos e de transporte. Para tanto, uma resolução adequada do campo de concentração dos reagentes (COVB e oxidantes), assim como do escoamento dentro do dossel são necessários. Nesse trabalho são apresentados os resultados de um estudo utilizando LES com 17 camadas dentro da floresta (resolução vertical de 2 m), incluindo uma química simplificada de COVB, para estimar o transporte através do topo da floresta de COVBs e de seus principais produtos, como o metil vinil cetona (MVC) e a Metacroleína (MACR). Os resultados são comparados com medições de campo de ozônio, óxidos de nitrogênio, isopreno, monoterpenos, assim como MVC e MACR observados durante uma campanha na torre K34 da Reserva Biológica Cuieiras (2°36’32” S, 60° 12’33” W) de Abril/2014 a Janeiro/2015

Robust observations of land-to-atmosphere feedbacks using the information flows of FLUXNET

Feedbacks between atmospheric processes like precipitation and land surface fluxes including evapotranspiration are difficult to observe, but critical for understanding the role of the land surface in the Earth System. To quantify global surface-atmosphere feedbacks we use results of a process network (PN) applied to 251 eddy covariance sites from the LaThuile database to train a neural network across the global terrestrial surface. There is a strong land–atmosphere coupling between latent (LE) and sensible heat flux (H) and precipitation (P) during summer months in temperate regions, and between H and P during winter, whereas tropical rainforests show little coupling seasonality. Savanna, shrubland, and other semi-arid ecosystems exhibit strong responses in their coupling behavior based on water availability. Feedback couplings from surface fluxes to P peaks at aridity (P/potential evapotranspiration ETp) values near unity, whereas coupling with respect to clouds, inferred from reduced global radiation, increases as P/ETp approaches zero. Spatial patterns in feedback coupling strength are related to climatic zone and biome type. Information flow statistics highlight hotspots of (1) persistent land–atmosphere coupling in sub-Saharan Africa, (2) boreal summer coupling in the central and southwestern US, Brazil, and the Congo basin and (3) in the southern Andes, South Africa and Australia during austral summer. Our data-driven approach to quantifying land atmosphere coupling strength that leverages the global FLUXNET database and information flow statistics provides a basis for verification of feedback interactions in general circulation models and for predicting locations where land cover change will feedback to climate or weather

Quantum spin helices more stable than the ground state: onset of helical protection

Topological magnetic structures are promising candidates for resilient information storage. An elementary example are spin helices in one-dimensional easy-plane quantum magnets. To quantify their stability, we numerically implement the stochastic Schr\"odinger equation and time-dependent perturbation theory for spin chains with fluctuating local magnetic fields. We find two classes of quantum spin helices that can reach and even exceed ground-state stability: Spin-current-maximizing helices and, for fine-tuned boundary conditions, the recently discovered "phantom helices". Beyond that, we show that the helicity itself (left- or right-rotating) is even more stable. We explain these findings by separated helical sectors and connect them to topological sectors in continuous spin systems. The resulting helical protection mechanism is a promising phenomenon towards stabilizing helical quantum structures, e.g., in ultracold atoms and solid state systems. We also identify an - up to our knowledge - previously unknown new type of phantom helices.Comment: 6+4 pages, 3 figures; version 2: minor updates, additional reference

Cropland Carbon Uptake Delayed and Reduced by 2019 Midwest Floods

While large‐scale floods directly impact human lives and infrastructures, they also profoundly impact agricultural productivity. New satellite observations of vegetation activity and atmospheric CO₂ offer the opportunity to quantify the effects of such extreme events on cropland carbon sequestration. Widespread flooding during spring and early summer 2019 induced conditions that delayed crop planting across the U.S. Midwest. As a result, satellite observations of solar‐induced chlorophyll fluorescence from TROPOspheric Monitoring Instrument and Orbiting Carbon Observatory reveal a 16‐day shift in the seasonal cycle of photosynthesis relative to 2018, along with a 15% lower peak value. We estimate a reduction of 0.21 PgC in cropland gross primary productivity in June and July, partially compensated in August and September (+0.14 PgC). The extension of the 2019 growing season into late September is likely to have benefited from increased water availability and late‐season temperature. Ultimately, this change is predicted to reduce the crop productivity in the Midwest Corn/Soy belt by ~15% compared to 2018. Using an atmospheric transport model, we show that a decline of ~0.1 PgC in the net carbon uptake during June and July is consistent with observed CO₂ enhancements of up to 10 ppm in the midday boundary layer from Atmospheric Carbon and Transport‐America aircraft and over 3 ppm in column‐averaged dry‐air mole fractions from Orbiting Carbon Observatory. This study quantifies the impact of floods on cropland productivity and demonstrates the potential of combining solar‐induced chlorophyll fluorescence with atmospheric CO₂ observations to monitor regional carbon flux anomalies

Fechamento do Balanço de Energia em uma Floresta Tropical: Contribuições da troca Turbulenta e Armazenamento de Calor Ecossistema

The surface energy balance is rarely closed using the common half-hourly averaging period for turbulent fluxes as eddies of greater characteristic time scales often provide a non-trivial contribution to energy exchange. Here, we briefly discuss previous efforts to improve surfasse energy balance closure of a tropical rainforest ecosystem – the K34 site - and describe how measurements from the GoAmazon campaign can be used to improve our understanding of energy flux and storage in tropical canopies.O balanço de energia da superfície raramente é fechado usando o período médio a cada meia hora comum para fluxos turbulentos como turbilhões de maior tempo característico escalas costumam oferecer uma contribuição não-trivial para troca de energia. Aqui, discutimos brevemente os esforços anteriores para melhorar o fechamento do balanço de energia da superfície de uma floresta tropical ecossistema tropical - o site K34 - e descrever como mediçõesda campanha GoAmazon pode ser usado para melhorar a nossa compreensão do fluxo de energia e armazenamento em copas tropicais

Loss of MMP-27 Predicts Mandibular Bone Invasion in Oral Squamous Cell Carcinoma

Invasion of the mandibular bone is frequent in oral squamous cell carcinoma (OSCC), which often results in extensive ablative and reconstructive procedures for the patient. The purpose of this single-center, retrospective study was to identify and evaluate potential biomarkers and risk factors for bone invasion in OSCC. Initially, in silico gene expression analysis was performed for different HNSCC tumor T-stages to find factors associated with invasive (T4a) tumor growth. Afterwards, the protein expression of bone-metabolizing MMP-27, TNFRSF11B (Osteoprotegerin, OPG), and TNFSF11 (RANKL) was investigated via Tissue Microarrays (TMAs) for their impact on mandibular bone invasion. TMAs were assembled from the bone–tumor interface of primary OSCCs of the floor of the mouth and gingiva from 119 patients. Sixty-four carcinomas with patho-histological jaw invasion (pT4a) were compared to 55 carcinomas growing along the mandible without invasion (pT2, pT3). Tissue samples were additionally evaluated for patterns of invasion using the WPOI grading system. Statistical analysis of in silico data revealed decreased MMP-27 mRNA expression to be strongly associated with the pT4a-stage in OSCC, indicating invasive tumor growth with infiltration of adjacent anatomical structures. Our own clinico-pathological data on OSCCs presented a significant decrease of MMP-27 in tumors invading the nearby mandible (pT4a), compared to pT2 and pT3 tumors without bone invasion. Loss of MMP27 evolved as the strongest predictor of mandibular bone invasion in binary logistic regression analysis. To our knowledge, this is the first study investigating the role of MMP-27 expression in OSCC and demonstrating the importance of the loss of MMP-27 in mandibular bone invasion