R. R. T. Marinho

The electronic structure of free water clusters probed by Auger electron spectroscopy

(H2O)(N) clusters generated in a supersonic expansion source with N approximately 1000 were core ionized by synchrotron radiation, giving rise to core-level photoelectron and Auger electron spectra (AES), free from charging effects. The AES is interpreted as being intermediate between the molecular and solid water spectra showing broadened bands as well as a significant shoulder at high kinetic energy. Qualitative considerations as well as ab initio calculations explain this shoulder to be due to delocalized final states in which the two valence holes are mostly located at different water molecules. The ab initio calculations show that valence hole configurations with both valence holes at the core-ionized water molecule are admixed to these final states and give rise to their intensity in the AES. Density-functional investigations of model systems for the doubly ionized final states--the water dimer and a 20-molecule water cluster--were performed to analyze the localization of the two valence holes in the electronic ground states. Whereas these holes are preferentially located at the same water molecule in the dimer, they are delocalized in the cluster showing a preference of the holes for surface molecules. The calculated double-ionization potential of the cluster (22.1 eV) is in reasonable agreement with the low-energy limit of the delocalized hole shoulder in the AES.

Predicting energy consumption with StreamMine3G

In this paper, we present our approach on solving the DEBS Grand Challenge using StreamMine3G, a distributed, highly scalable, elastic and fault tolerant ESP system. We will provide an overview about the system architecture of Stream-Mine3G and implementation details of an application aimed at consumption prediction and outlier detection. Using our elastic approach, we can provide an accurate prediction as we can keep a practically unbounded history able to deal with high volume, highly fluctuating workloads. Our system also provides techniques for dealing with incomplete data in the source stream, which is a common problem when processing data from a large number of sources. Finally, we provide performance measurements showing that we are able to process the dataset given as part of the 2014 DEBS Challenge (135 GB) at a throughput of up to 40 kEvents/s.

Polarization dependent effects in photo-fragmentation dynamics of free molecules

We present multicoincidence spectra of nitrogen, formic acid and methyl methacrylate. We demonstrate how to probe the local symmetry of molecular orbitals from molecules core excited with linearly polarized synchrotron radiation. The intensity distribution of the photoelectron photo-ion photo-ion coincidence (PEPIPICO) spectrum reflects the selectivity and localization of core excitation by polarized light. By simulating the spectra the angular dependence of the fragmentation is determined.

Auger decay of core-excited higher Rydberg states of carbon monoxide

The de-excitation of higher core-excited Rydberg states of carbon monoxide has been studied. It is found that already with a main quantum number of 4 or higher, Rydberg states of p-symmetry can be successfully treated within the single-particle hydrogenic model for both the core-excited and the final states. From a study of the binding energy of the Rydberg electron in the final state versus the core-excited state, the importance of relaxation in the core-excited intermediate state is shown. Also, for core-excited Rydberg states with main quantum number of 5 or higher, an almost total quenching of strict spectator lines in the de-excitation spectra is observed.

Security and privacy aware data aggregation on cloud computing

The use of cloud computing has become common due to advantages such as low cost and sizing of computing resources according to demand. However, it also raises security and privacy concerns, because critical data – for example, in IoT applications – are stored and processed in the cloud. This paper proposes a software architecture that supports multiple approaches to secure data aggregation. For validation purposes, this software architecture was used in the development of applications for smart grids, computing instantaneous consumption of a region and the monthly bill of an individual consumer. The consumption data can be collected by smart meters, enabling consumers to reduce electricity costs through close monitoring. However, such data may reveal sensitive information if no privacy techniques are applied. Therefore, the proposed software architecture proved to be viable from experiments with techniques such as homomorphic encryption and hardware security extensions (Intel SGX).