Charmed hadron signals of partonic medium

We present a short review of our results on the collectivity and the suppression pattern of charmed mesons in heavy-ion collisions based on the microscopic Hadron-String Dynamics (HSD) transport approach for different scenarios of charm interactions with the surrounding matter - the 'comover' dissociation by mesons with further recreation by D+Dbar channels and 'pre-hadronic' interaction scenarios. While at SPS energies the hadronic 'comover' absorption scenario is found to be compatible with the experimental data, the dynamics of c and cbar quarks at RHIC are dominated by partonic or 'pre-hadronic' interactions in the strongly coupled quark-gluon plasma stage and cannot be modeled by pure hadronic interactions. We find that the collective flow of charm in the purely hadronic scenario appears compatible with the data at SPS energies but underestimates the data at top RHIC energies. Thus, the large elliptic flow v2 of D mesons and the low R_AA(pT) of J/Psi seen experimentally at RHIC have to be attributed to early interactions of non-hadronic degrees of freedom. Simultaneously, we observe that non-hadronic interactions are mandatory in order to describe the narrowing of the J/Psi rapidity distribution from p+p to central Au+Au collisions at the top RHIC energy. We demonstrate additionally that the strong quenching of high-pT J/Psi's in central Au+Au collisions indicates that a fraction of final J/Psi mesons is created by a coalescence mechanism close to the phase boundary.Comment: Talk given at International Conference on Strangeness in Quark Matter (SQM 2008), Beijing, China, 6-10 Oct 200

Contribution of biomass fires to black carbon supply in a tropical river basin assessed using a Lagrangian atmospheric transport model and MODIS burned area product

Black carbon (BC) is known to be a potential sink of carbon for the global carbon cycle, particularly if long-term ocean stores are reached. Fluvial transport to the oceans can occur through the dissolution of BC in river water. Evidence from the Paraiba do Sul river basin, Brazil suggests that river DBC concentration is related to charcoal formed during the deforestation of the Brazilian Atlantic Forest. However, we highlight several key potential sources of BC to the basin that are yet to be considered. We hypothesize that external biomass fires are a source of BC to the basin on the basis that BC released from them can be transported over large distances before being deposited. This hypothesis is tested by quantifying the number of biomass fires intercepted by trajectories en route to the basin using the HYSPLIT model and a MODIS burned area dataset. We then create a Black Carbon Fallout Index (BCFI) which is rationalized by our assumption that atmospheric BC delivery to the basin is proportional to the number of interceptions of air masses en route to the basin. Our results suggest that the BC fallout from air masses reaching the basin in the dry season can explain 50% of the variance in DBC measured in the PSR channel during a subsequent collection campaign (p<.001). Spatial and temporal variations in the supply of BC to the basin throughout the dry season may in part be linked to the fires associated with the cultivation of sugarcane in southeast Brazil

Space-time calibration of wind speed forecasts from regional climate models

Numerical weather predictions (NWP) are systematically subject to errors due to the deterministic solutions used by numerical models to simulate the atmosphere. Statistical postprocessing techniques are widely used nowadays for NWP calibration. However, time-varying bias is usually not accommodated by such models. Its calibration performance is also sensitive to the temporal window used for training. This paper proposes space-time models that extend the main statistical postprocessing approaches to calibrate NWP model outputs. Trans-Gaussian random fields are considered to account for meteorological variables with asymmetric behavior. Data augmentation is used to account for censuring in the response variable. The benefits of the proposed extensions are illustrated through the calibration of hourly 10 m wind speed forecasts in Southeastern Brazil coming from the Eta model.Comment: 43 pages, 13 figure

Revisiting the S-matrix approach to the open superstring low energy effective lagrangian

The conventional S-matrix approach to the (tree level) open string low energy effective lagrangian assumes that, in order to obtain all its bosonic ${\alpha'}^N$ order terms, it is necessary to know the open string (tree level) $(N+2)$-point amplitude of massless bosons, at least expanded at that order in $\alpha'$. In this work we clarify that the previous claim is indeed valid for the bosonic open string, but for the supersymmetric one the situation is much more better than that: there are constraints in the kinematical bosonic terms of the amplitude (probably due to Spacetime Supersymmetry) such that a much lower open superstring $n$-point amplitude is needed to find all the ${\alpha'}^N$ order terms. In this `revisited' S-matrix approach we have checked that, at least up to ${\alpha'}^4$ order, using these kinematical constraints and only the known open superstring 4-point amplitude, it is possible to determine all the bosonic terms of the low energy effective lagrangian. The sort of results that we obtain seem to agree completely with the ones achieved by the method of BPS configurations, proposed about ten years ago. By means of the KLT relations, our results can be mapped to the NS-NS sector of the low energy effective lagrangian of the type II string theories implying that there one can also find kinematical constraints in the $N$-point amplitudes and that important informations can be inferred, at least up to ${\alpha'}^4$ order, by only using the (tree level) 4-point amplitude.Comment: 34 pages, 3 figure, Submitted on Aug 4, 2012, Published on Oct 15, 201

Large-scale commodity agriculture exacerbates the climatic impacts of Amazonian deforestation

In the Amazon rainforest, land use following deforestation is diverse and dynamic. Mounting evidence indicates that the climatic impacts of forest loss can also vary considerably, depending on specific features of the affected areas. The size of the deforested patches, for instance, was shown to modulate the characteristics of local climatic impacts. Nonetheless, the influence of different types of land use and management strategies on the magnitude of local climatic changes remains uncertain. Here, we evaluated the impacts of large-scale commodity farming and rural settlements on surface temperature, rainfall patterns, and energy fluxes. Our results reveal that changes in land-atmosphere coupling are induced not only by deforestation size but also, by land use type and management patterns inside the deforested areas. We provide evidence that, in comparison with rural settlements, deforestation caused by large-scale commodity agriculture is more likely to reduce convective rainfall and increase land surface temperature. We demonstrate that these differences are mainly caused by a more intensive management of the land, resulting in significantly lower vegetation cover throughout the year, which reduces latent heat flux. Our findings indicate an urgent need for alternative agricultural practices, as well as forest restoration, for maintaining ecosystem processes and mitigating change in the local climates across the Amazon basin.Peer reviewe

Use of MODIS Sensor Images Combined with Reanalysis Products to Retrieve Net Radiation in Amazonia

In the Amazon region, the estimation of radiation fluxes through remote sensing techniques is hindered by the lack of ground measurements required as input in the models, as well as the difficulty to obtain cloud-free images. Here, we assess an approach to estimate net radiation (Rn) and its components under all-sky conditions for the Amazon region through the Surface Energy Balance Algorithm for Land (SEBAL) model utilizing only remote sensing and reanalysis data. The study period comprised six years, between January 2001–December 2006, and images from MODIS sensor aboard the Terra satellite and GLDAS reanalysis products were utilized. The estimates were evaluated with flux tower measurements within the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA) project. Comparison between estimates obtained by the proposed method and observations from LBA towers showed errors between 12.5% and 16.4% and 11.3% and 15.9% for instantaneous and daily Rn, respectively. Our approach was adequate to minimize the problem related to strong cloudiness over the region and allowed to map consistently the spatial distribution of net radiation components in Amazonia. We conclude that the integration of reanalysis products and satellite data, eliminating the need for surface measurements as input model, was a useful proposition for the spatialization of the radiation fluxes in the Amazon region, which may serve as input information needed by algorithms that aim to determine evapotranspiration, the most important component of the Amazon hydrological balance