Beauty is in the Eye of the Smartphone Holder - A Data Driven Analysis of YouTube Mobile QoE

International audienceMeasuring the Quality of Experience (QoE) undergone by cellular network users has become paramount for cellular ISPs. Given its overwhelming dominance and ever-growing popularity, this paper focuses on the analysis of QoE for YouTube in mobile networks. Using a large-scale dataset of crowdsourced YouTube QoE measurements collected in smartphones with YoMoApp, we analyze the evolution of multiple relevant QoE-related metrics over time for YouTube mobile users. The dataset includes measurements from more than 360 users worldwide, spanning over the last five years. Our data-driven analysis shows a systematic performance and QoE improvement of YouTube in mobile devices over time, accompanied by an improvement of cellular network performance and by an optimization of the YouTube streaming behavior for smartphones

Towards Probing Conformational States of Y2 Receptor Using Hyperpolarized 129Xe NMR

G protein-coupled receptors can adopt many different conformational states, each of them exhibiting different restraints towards downstream signaling pathways. One promising strategy to identify and quantify this conformational landscape is to introduce a cysteine at a receptor site sensitive to different states and label this cysteine with a probe for detection. Here, the application of NMR of hyperpolarized 129Xe for the detection of the conformational states of human neuropeptide Y2 receptor is introduced. The xenon trapping cage molecule cryptophane-A attached to a cysteine in extracellular loop 2 of the receptor facilitates chemical exchange saturation transfer experiments without and in the presence of native ligand neuropeptide Y. High-quality spectra indicative of structural states of the receptor–cage conjugate were obtained. Specifically, five signals could be assigned to the conjugate in the apo form. After the addition of NPY, one additional signal and subtle modifications in the persisting signals could be detected. The correlation of the spectroscopic signals and structural states was achieved with molecular dynamics simulations, suggesting frequent contact between the xenon trapping cage and the receptor surface but a preferred interaction with the bound ligand

Supramolecular spangling, crocheting, and knitting of functionalized pyrene molecules on a silver surface

Pyrenes, as photoactive polycyclic aromatic hydrocarbons (PAHs), represent promising modules for the bottom-up assembly of functional nanostructures. Here, we introduce the synthesis of a family of pyrene derivatives peripherally functionalized with pyridin-4-ylethynyl termini and comprehensively characterize their self-assembly abilities on a smooth Ag(111) support by scanning tunneling microscopy. By deliberate selection of number and geometric positioning of the pyridyl-terminated substituents, two-dimensional arrays, one-dimensional coordination chains, and chiral, porous kagomé-type networks can be tailored. A comparison to phenyl-functionalized reference pyrenes, not supporting the self-assembly of ordered structures at low coverage, highlights the role of the pyridyl moieties for supramolecular crocheting and knitting. Furthermore, we demonstrate the selective spangling of pores in the two-dimensional pyrene assemblies by a distinct number of iodine atoms as guests by atomically resolved imaging and complementary X-ray photoelectron spectroscopy

Molecular spintronics: Coherent spin transfer in coupled quantum dots

Time-resolved Faraday rotation has recently demonstrated coherent transfer of electron spin between quantum dots coupled by conjugated molecules. Using a transfer Hamiltonian ansatz for the coupled quantum dots, we calculate the Faraday rotation signal as a function of the probe frequency in a pump-probe setup using neutral quantum dots. Additionally, we study the signal of one spin-polarized excess electron in the coupled dots. We show that, in both cases, the Faraday rotation angle is determined by the spin transfer probabilities and the Heisenberg spin exchange energy. By comparison of our results with experimental data, we find that the transfer matrix element for electrons in the conduction band is of order 0.08 eV and the spin transfer probabilities are of order 10%.Comment: 13 pages, 6 figures; minor change

Potential of indicators to unveil the hidden side of cropping system classification: Differences and similarities in cropping practices between conventional, no-till and organic systems

To compare different cropping systems, it is crucial to describe explicitly the associated cropping practices. A set of 31 indicators and six composite indexes addressing farm structure, crop diversification, soil disturbance, organic matter inputs, nitrogen fertilisation, crop protection, and yield was used to describe 59 winter wheat fields belonging to conventional, no-till and organic systems, in Switzerland. The aim of this study was to investigate the complementarity and redundancy of the indicators and their potential to characterise these cropping systems. In general, weak correlations were observed between the studied indicators, showing the importance of using a set of indicators to fully characterise cropping practices. The complex indicators were often correlated with simpler ones, but it cannot be excluded that they can prove to be more useful in different contexts. Retaining a combination of simple and complex indicators to obtain a broad picture of cropping practices is thus recommended. The indicators highlighted differences but also similarities between the three systems. For example, the input of organic matter and crop rotation diversification were similar between the three systems. In contrast, total nitrogen fertilisation (lower for organic systems) and soil disturbance (lower for no-till systems) were different. A high within-system variability was observed for some indicators, suggesting that using quantitative indicators rather than simple classifications based on a general description of the systems allows a better characterisation of these systems. Overall, the use of indicators has the potential to improve our understanding of the influence of cropping practices on the soil and environment