Connections matter: On the importance of pore percolation for nanoporous supercapacitors

Nanoporous supercapacitors play a key role in energy storage and thereby attract growing interest from the research community. Development of porous electrodes for supercapacitors is of the paramount importance, but their characterization still remains a challenge. Herein, we analyze two examples of the popular carbide-derived and activated carbon electrodes from the point of view of interpore connectivity and ion permeation. Due to limited percolation, the effective porosity, as seen by an ion, decreases with an increase in the ion size, which can reduce the stored energy density substantially. Our results highlight the importance of high quality well-percolated porous electrodes for supercapacitors and suggest that the interpore connectivity is an important characteristic to consider when optimizing the existing and developing new electrode materials

Virus Identification in Unknown Tropical Febrile Illness Cases Using Deep Sequencing

Dengue virus is an emerging infectious agent that infects an estimated 50–100 million people annually worldwide, yet current diagnostic practices cannot detect an etiologic pathogen in ∼40% of dengue-like illnesses. Metagenomic approaches to pathogen detection, such as viral microarrays and deep sequencing, are promising tools to address emerging and non-diagnosable disease challenges. In this study, we used the Virochip microarray and deep sequencing to characterize the spectrum of viruses present in human sera from 123 Nicaraguan patients presenting with dengue-like symptoms but testing negative for dengue virus. We utilized a barcoding strategy to simultaneously deep sequence multiple serum specimens, generating on average over 1 million reads per sample. We then implemented a stepwise bioinformatic filtering pipeline to remove the majority of human and low-quality sequences to improve the speed and accuracy of subsequent unbiased database searches. By deep sequencing, we were able to detect virus sequence in 37% (45/123) of previously negative cases. These included 13 cases with Human Herpesvirus 6 sequences. Other samples contained sequences with similarity to sequences from viruses in the Herpesviridae, Flaviviridae, Circoviridae, Anelloviridae, Asfarviridae, and Parvoviridae families. In some cases, the putative viral sequences were virtually identical to known viruses, and in others they diverged, suggesting that they may derive from novel viruses. These results demonstrate the utility of unbiased metagenomic approaches in the detection of known and divergent viruses in the study of tropical febrile illness

The formation of human populations in South and Central Asia

By sequencing 523 ancient humans, we show that the primary source of ancestry in modern South Asians is a prehistoric genetic gradient between people related to early hunter-gatherers of Iran and Southeast Asia. After the Indus Valley Civilization’s decline, its people mixed with individuals in the southeast to form one of the two main ancestral populations of South Asia, whose direct descendants live in southern India. Simultaneously, they mixed with descendants of Steppe pastoralists who, starting around 4000 years ago, spread via Central Asia to form the other main ancestral population. The Steppe ancestry in South Asia has the same profile as that in Bronze Age Eastern Europe, tracking a movement of people that affected both regions and that likely spread the distinctive features shared between Indo-Iranian and Balto-Slavic languages

Investigation of the correlation patterns and the Compton dominance variability of Mrk 421 in 2017

Aims. We present a detailed characterisation and theoretical interpretation of the broadband emission of the paradigmatic TeV blazar Mrk 421, with a special focus on the multi-band flux correlations.Methods. The dataset has been collected through an extensive multi-wavelength campaign organised between 2016 December and 2017 June. The instruments involved are MAGIC, FACT, Fermi-LAT, Swift, GASP-WEBT, OVRO, Medicina, and Metsahovi. Additionally, four deep exposures (several hours long) with simultaneous MAGIC and NuSTAR observations allowed a precise measurement of the falling segments of the two spectral components.Results. The very-high-energy (VHE; E > 100 GeV) gamma rays and X-rays are positively correlated at zero time lag, but the strength and characteristics of the correlation change substantially across the various energy bands probed. The VHE versus X-ray fluxes follow different patterns, partly due to substantial changes in the Compton dominance for a few days without a simultaneous increase in the X-ray flux (i.e., orphan gamma-ray activity). Studying the broadband spectral energy distribution (SED) during the days including NuSTAR observations, we show that these changes can be explained within a one-zone leptonic model with a blob that increases its size over time. The peak frequency of the synchrotron bump varies by two orders of magnitude throughout the campaign. Our multi-band correlation study also hints at an anti-correlation between UV-optical and X-ray at a significance higher than 3 sigma. A VHE flare observed on MJD 57788 (2017 February 4) shows gamma-ray variability on multi-hour timescales, with a factor ten increase in the TeV flux but only a moderate increase in the keV flux. The related broadband SED is better described by a two-zone leptonic scenario rather than by a one-zone scenario. We find that the flare can be produced by the appearance of a compact second blob populated by high energetic electrons spanning a narrow range of Lorentz factors, from gamma(min)' = 2 x 10(4) to gamma(max)' = 6 x 10(5).</p

Feeling your neighbors across the walls: How interpore ionic interactions affect capacitive energy storage.

Progress in low-dimensional carbon materials has intensified research on supercapacitors with nanostructured/nanoporous electrodes. The theoretical and simulation work so far has focused on charging single nanopores or nanoporous networks and the effects due to ionic interactions inside the pores, while the effect of interpore ion-ion correlations has received less attention. Herein, we study how the interactions between the ions in the neighboring pores across the pore walls affect capacitive energy storage. We develop a simple lattice model for the ions in a stack of parallel-aligned nanotubes, solve it by using the perturbation and "semi-mean-field" theories, and test the results by Monte Carlo simulations. We demonstrate that the interpore ionic interactions can have a profound effect on charge storage; in particular, such interactions can enhance or diminish the stored energy density, depending on the sign of like-charge interactions. We also find that charging can proceed either continuously or via a phase transition. Our results call for more detailed investigations of the properties of carbon pore walls and suggest that tuning their electrostatic response may be promising for the rational design of an optimal supercapacitor