Efficient Emulation of Radiative Transfer Codes Using Gaussian Processes and Application to Land Surface Parameter Inferences

There is an increasing need to consistently combine observations from different sensors to monitor the state of the land surface. In order to achieve this, robust methods based on the inversion of radiative transfer (RT) models can be used to interpret the satellite observations. This typically results in an inverse problem, but a major drawback of these methods is the computational complexity. We introduce the concept of Gaussian Process (GP) emulators: surrogate functions that accurately approximate RT models using a small set of input (e.g., leaf area index, leaf chlorophyll, etc.) and output (e.g., top-of-canopy reflectances or at sensor radiances) pairs. The emulators quantify the uncertainty of their approximation, and provide a fast and easy route to estimating the Jacobian of the original model, enabling the use of e.g., efficient gradient descent methods. We demonstrate the emulation of widely used RT models (PROSAIL and SEMIDISCRETE) and the coupling of vegetation and atmospheric (6S) RT models targetting particular sensor bands. A comparison with the full original model outputs shows that the emulators are a viable option to replace the original model, with negligible bias and discrepancies which are much smaller than the typical uncertainty in the observations. We also extend the theory of GP to cope with models with multivariate outputs (e.g., over the full solar reflective domain), and apply this to the emulation of PROSAIL, coupled 6S and PROSAIL and to the emulation of individual spectral components of 6S. In all cases, emulators successfully predict the full model output as well as accurately predict the gradient of the model calculated by finite differences, and produce speed ups between 10,000 and 50,000 times that of the original model. Finally, we use emulators to invert leaf area index ( L A I ), leaf chlorophyll content ( C a b ) and equivalent leaf water thickness ( C w ) from a time series of observations from Sentinel-2/MSI, Sentinel-3/SLSTR and Proba-V observations. We use sophisticated Hamiltonian Markov Chain Monte Carlo (MCMC) methods that exploit the speed of the emulators as well as the gradient estimation, a variational data assimilation (DA) method that extends the problem with temporal regularisation, and a particle filter using a regularisation model. The variational and particle filter approach appear more successful (meaning parameters closer to the truth, and smaller uncertainties) than the MCMC approach as a result of using the temporal regularisation mode. These work therefore suggests that GP emulators are a practical way to implement sophisticated parameter retrieval schemes in an era of increasing data volumes

Ethics of a partially effective dengue vaccine: Lessons from the Philippines

Dengvaxia, a chimeric yellow fever tetravalent dengue vaccine developed by SanofiPasteur is widely licensed in dengue-endemic countries. In a large cohort study Dengvaxia was found to partially protect children who had prior dengue virus (DENV) infections but sensitized seronegative children to breakthrough DENV disease of enhanced severity. In 2019, the European Medicines Agency and the US FDA issued licenses that reconciled safety issues by restricting vaccine to individuals with prior dengue infections. Using revised Dengvaxia efficacy and safety data we sought to estimate hospitalized and severe dengue cases among the more than 800,000 9 year-old children vaccinated in the Philippines. Despite an overall vaccine efficacy of 69% during 4 years post-vaccination we project there will be more than one thousand vaccinated seronegative and seropositive children hospitalized for severe dengue. Assisting these children through a program of enhanced surveillance leading to improved care deserves widespread support. Clinical responses observed during breakthrough dengue infections in vaccinated individuals counsel prudence in design of vaccine policies. Recommendations concerning continued use of this dengue vaccine are: (1) obtain a better definition of vaccine efficacy and safety through enhanced phase 4 surveillance, (2) obtain a valid, accessible, sensitive, specific and affordable serological test that identifies past wild-type dengue virus infection and (3) clarify safety and efficacy of Dengvaxia in flavivirus immunes. In the absence of an acceptable serological screening test these unresolved ethical issues suggest Dengvaxia be given only to those signing informed consent.Marie Skłodowska-Curie grant agreement No 79249

Fuentes de conocimiento externo en el sector arqueológico español: Mapeo de la fase emergente en una actividad empresarial

[EN] Recent studies of innovation highlight the importance of external knowledge sourcing. Existing empirical works are based on national surveys and specific industries. The present study contributes to the analysis of strategies for sourcing external knowledge, based on a specific case study and moment in time: the Spanish archaeological sector and its emergence as a new business activity. Our results show that external knowledge sourcing involves diverse mechanisms, agents and two main strategies: cooperation and knowledge acquisition. In an expanding knowledge-based sector emerging in an uncertain context and whose sources of knowledge are scattered, innovation strategy should focus on the search for external knowledge ¿cooperation and acquisition strategies-, rather than on internal sources.[ES] Estudios recientes señalan la importancia de las fuentes externas de conocimiento como estrategia para innovar. La evidencia empírica se fundamenta en encuestas nacionales y en industrias específicas. El presente estudio contribuye al análisis de las estrategias de incorporación de conocimiento externo mediante un caso de estudio y en un momento concreto: el sector arqueológico español y su emergencia como nueva actividad económica. Los resultados muestran que las fuentes de conocimiento externo implican diversos mecanismos, agentes y dos estrategias principalmente: cooperar y adquirir conocimiento. En un sector en expansión, basado en el conocimiento, que surge en un contexto incierto y cuyas fuentes de conocimiento están dispersas, el foco de la innovación puede encontrarse en las estrategias de búsqueda de conocimiento externo -cooperación y adquisición-, más que en fuentes internas.This work was supported by the ACE (Archaeology in Contemporary Europe) Project, funded by the European Commission Cultural Programme between 2008 and 2012. The authors are grateful to the archaeologists and archaeological firms that participated in the study. Special thanks go to the Institute of Heritage Sciences (Incipit-CSIC) and INGENIO (CSIC-UPV) for the support and help. We also thank the anonymous reviewers for their helpful comments. Finally, we appreciate the English text editing by Cynthia Little, a specialist in our area, which always helps us in this activity.Parga-Dans, E.; Castro-Martínez, E.; Sánchez-Barrioluengo, M. (2017). External knowledge sourcing in the Spanish archaeological sector: Mapping the emergent stage of a business activity. Revista española de Documentación Científica. 40(1):1-14. doi:10.3989/redc.2017.1.1380S114401Langvall, O. (2011). Impact of climate change, seedling type and provenance on the risk of damage to Norway spruce (Picea abies (L.) Karst.) seedlings in Sweden due to early summer frosts. Scandinavian Journal of Forest Research, 26(S11), 56-63. doi:10.1080/02827581.2011.564399Nielsen, U. B., Madsen, P., Hansen, J. K., Nord-Larsen, T., & Nielsen, A. T. (2014). Production potential of 36 poplar clones grown at medium length rotation in Denmark. Biomass and Bioenergy, 64, 99-109. doi:10.1016/j.biombioe.2014.03.03

Simulating arbitrary hyperspectral bandsets from multispectral observations via a generic Earth Observation-Land Data Assimilation System (EO-LDAS)

This paper presents results of using multi-sensor and multi-angular constraints in the generic Earth Observation-Land Data Assimilation System (EO-LDAS) for reproducing arbitrary bandsets of hyperspectral reflectance at the top-of-canopy (TOC) level by merging observations from multispectral sensors with different spectral characteristics. This is demonstrated by combining Multi-angle Imaging Spectroradiometer (MISR) and Landsat Enhanced Thematic Mapper Plus (ETM+) data to simulate the Compact High Resolution Imaging Spectrometer CHRIS/PROBA hyperspectral signal over an agricultural test site, in Barrax, Spain. However, the method can be more generally applied to any combination of spectral data, providing a tool for merging EO data to any arbitrary hyperspectral bandset. Comparisons are presented using both synthetic and observed MISR and Landsat data, and retrieving surface biophysical properties. We find that when using simulated MISR and Landsat data, the CHRIS/PROBA hyperspectral signal is reproduced with RMSE 0.0001– 0.04. LAI is retrieved with r2 from 0.97 to 0.99 and RMSE of from 0.21 to 0.38. The results based on observed MISR and Landsat data have lower performances, with RMSE for the reproduced CHRIS/PROBA hyperspectral signal varying from 0.007 to 0.2. LAI is retrievedwith r2 from 0.7 to 0.9 and RMSE from 0.7 to 1.4. We found that for the data considered here the main spectral variations in the visible and near infrared regions can be described by a limited number of parameters (3–4) that can be estimated from multispectral information. Results show that the method can be used to simulate arbitrary bandsets, which will be of importance to any application which requires combining new and existing streams of new EO data in the optical domain, particularly intercalibration of EO satellites in order to get continuous time series of surface reflectance, across programmes and sensors of different designs

Analysing the PMIP4-CMIP6 collection: a workflow and tool (pmip_p2fvar_analyzer v1)

Experiment outputs are now available from the Coupled Model Intercomparison Project's sixth phase (CMIP6) and the past climate experiments defined in the Palaeoclimate Modelling Intercomparison Project's fourth phase (PMIP4). All of this output is freely available from the Earth System Grid Federation (ESGF). Yet there is overhead in analysing this resource that may prove complicated or prohibitive. Here we document the steps taken by ourselves to produce ensemble analyses covering past and future simulations. We outline the strategy used to curate, adjust the monthly calendar aggregation and process the information downloaded from the ESGF. The results of these steps were used to perform analysis for several of the initial publications arising from PMIP4. We provide post-processed fields for each simulation, such as climatologies and common measures of variability. Example scripts used to visualise and analyse these fields are provided for several important case studies

Organizational perceptions of e-commerce: Re-assessing the benefits

This paper reports on preliminary findings from a wider and more in-depth study of six traditional organizations from different sectors that have successfully introduced e-commerce initiatives. The research adopted a case study approach, within which a questionnaire, identifying 16 generic benefits synthesized from the literature, was administered. The organizations were also asked to characterize whether e-commerce was strategic for them or not. The findings suggest that those organizations that perceived e-commerce to be strategic tended to consider intangible benefits as more important than tangible benefits, indicating perhaps a move away from the traditional view of e-commerce as a marketing driver to increase or create sales. Those organizations perceiving e-commerce as non-strategic rated the tangible benefits in much the same way as the strategic organizations, but rated the intangibles lower. Also it was found that e-commerce was important as a communication tool, not only with customers, as might be expected, but also with staff within the organization. The value of intra-organizational e-commerce was also found to be important, perhaps more than previously thought, as was its use in communicating and disseminating knowledge. The findings also reflect the importance of the sector and environment of the organization in determining their perceptions of e-commerce

Full superconducting gap in the candidate topological superconductor In1−x_{1-x}Pbx_xTe for x = 0.2

High-pressure synthesis techniques have allowed for the growth of samples on the indium-rich side of (Pb,In)Te, which have increased superconducting transition temperatures compared to lead-rich compounds. In this study we present measurements of the temperature dependence of the London penetration depth $\Delta \lambda(T)$ in the compound In$_{0.8}$Pb$_{0.2}$Te, which shows a bulk $T_{c,onset}$ of $\sim4.75$ K. The results indicate fully gapped BCS-like behavior, ruling out odd-parity, topologically nontrivial $A_{2u}$ pairing; however, odd-parity $A_{1u}$ pairing is still possible. Critical field values measured below 1 K and other superconducting parameters are also presented.Comment: 8 pages, 9 figure