Advances in Polar Materials for Lithium-Sulfur Batteries

Lithium-sulfur batteries are regarded as promising candidates for energy storage devices due to their high theoretical energy density. Various approaches are proposed to break through the obstacles that are preventing Li-S batteries from realizing practical application. Recently, the importance of the strong chemical interaction between polar materials and polysulfides is recognized by researchers to improve the performance of Li-S batteries, especially with respect to the shuttle effect. Polar materials, unlike nonpolar materials, exhibit strong interactions with polysulfides without any modification or doping because of their intrinsic polarity, absorbing the polar polysulfides and thus suppressing the notorious shuttle effect. The recent advances on polar materials for Li-S batteries are reviewed here, especially the chemical polar-polar interaction effects toward immobilizing dissolved polysulfides, and the relationship between the intrinsic properties of the polar materials and the electrochemical performance of the Li-S batteries are discussed. Polar materials, including polar inorganics in the cathode and polar organics as binder for the Li-S batteries are respectively described. Finally, future directions and prospects for the polar materials used in Li-S batteries are also proposed

Impulsive rotational Raman scattering of N2 by a remote "air laser" in femtosecond laser filament

We report on experimental realization of impulsive rotational Raman scattering from neutral nitrogen molecules in a femtosecond laser filament using an intense self-induced white-light seeding "air laser" generated during the filamentation of an 800 nm Ti: Sapphire laser in nitrogen gas. The impulsive rotational Raman fingerprint signals are observed with a maximum conversion efficiency of ~0.8%. Our observation provides a promising way of remote identification and location of chemical species in atmosphere by rotational Raman scattering of molecules.Comment: 4 pages, 4 figure

Remote creation of strong and coherent emissions in air with two-color ultrafast laser pulses

We experimentally demonstrate generation of strong narrow-bandwidth emissions with excellent coherent properties at ~391 nm and ~428 nm from molecular ions of nitrogen inside a femtosecond filament in air by an orthogonally polarized two-color driver field (i. e., 800 nm laser pulse and its second harmonic). The durations of the coherent emissions at 391 nm and 428 nm are measured to be ~2.4 ps and ~7.8 ps respectively, both of which are much longer than the duration of the pump and its second harmonic pulses. Furthermore, the measured temporal decay characteristics of the excited molecular systems suggest an "instantaneous" population inversion mechanism that may be achieved in molecular nitrogen ions at an ultrafast time scale comparable to the 800 nm pump pulse.Comment: 19 pages, 4 figure

Functionalized silicon nanoparticles from reactive cavitation erosion of silicon wafers

Sonochemical reactor used for reactive cavitation erosion formation of functionalized silicon nanoparticles.</p

Self-induced white-light seeding laser in a femtosecond laser filament

We report, for what we believe to be the first time, on the generation of remote self-seeding laser amplification by using only one 800 nm Ti:Sapphire femtosecond laser pulse. The laser pulse (~ 40 fs) is first used to generate a filament either in pure nitrogen or in ambient air in which population inversion between ground and excited states of nitrogen molecular ions is realized. Self-induced white light inside the filament is then serving as the seed to be amplified. The self-induced narrow-band laser at 428 nm has a pulse duration of ~2.6 ps with perfect linear polarization property. This finding opens new possibilities for remote detection in the atmosphere.Comment: 18 pages, 5 figure

Second harmonic generation in a centrosymmetric gas medium with spatiotemporally focused intense femtosecond laser pulses

We demonstrate unexpectedly strong second harmonic generation (SHG) in Argon gas by use of spatiotemporally focused (SF) femtosecond laser pulses. The resulting SHG by the SF scheme at a 75 cm distance shows a significantly enhanced efficiency than that achieved with conventional focusing scheme, which offers a new promising possibility for standoff applications. Our theoretical calculations reasonably reproduce the experimental observations, which indicate that the observed SHG mainly originates from the gradient of nonuniform plasma dynamically controlled by the SF laser field.Comment: 14 pages, 4 figure

Gain dynamics of a free-space nitrogen laser pumped by circularly polarized femtosecond laser pulses

We experimentally demonstrate ultrafast dynamic of generation of a strong 337-nm nitrogen laser by injecting an external seed pulse into a femtosecond laser filament pumped by a circularly polarized laser pulse. In the pump-probe scheme, it is revealed that the population inversion between the excited and ground states of N2 for the free-space 337-nm laser is firstly built up on the timescale of several picoseconds, followed by a relatively slow decay on the timescale of tens of picoseconds, depending on the nitrogen gas pressure. By measuring the intensities of 337-nm signal from nitrogen gas mixed with different concentrations of oxygen gas, it is also found that oxygen molecules have a significant quenching effect on the nitrogen laser signal. Our experimental observations agree with the picture of electron-impact excitation.Comment: 9 pages, 5 figure

miRBaseConverter: an R/Bioconductor package for converting and retrieving miRNA name, accession, sequence and family information in different versions of miRBase

Abstract Background miRBase is the primary repository for published miRNA sequence and annotation data, and serves as the “go-to” place for miRNA research. However, the definition and annotation of miRNAs have been changed significantly across different versions of miRBase. The changes cause inconsistency in miRNA related data between different databases and articles published at different times. Several tools have been developed for different purposes of querying and converting the information of miRNAs between different miRBase versions, but none of them individually can provide the comprehensive information about miRNAs in miRBase and users will need to use a number of different tools in their analyses. Results We introduce miRBaseConverter, an R package integrating the latest miRBase version 22 available in Bioconductor to provide a suite of functions for converting and retrieving miRNA name (ID), accession, sequence, species, version and family information in different versions of miRBase. The package is implemented in R and available under the GPL-2 license from the Bioconductor website ( http://bioconductor.org/packages/miRBaseConverter/ ). A Shiny-based GUI suitable for non-R users is also available as a standalone application from the package and also as a web application at http://nugget.unisa.edu.au:3838/miRBaseConverter . miRBaseConverter has a built-in database for querying miRNA information in all species and for both pre-mature and mature miRNAs defined by miRBase. In addition, it is the first tool for batch querying the miRNA family information. The package aims to provide a comprehensive and easy-to-use tool for miRNA research community where researchers often utilize published miRNA data from different sources. Conclusions The Bioconductor package miRBaseConverter and the Shiny-based web application are presented to provide a suite of functions for converting and retrieving miRNA name, accession, sequence, species, version and family information in different versions of miRBase. The package will serve a wide range of applications in miRNA research and could provide a full view of the miRNAs of interest.https://deepblue.lib.umich.edu/bitstream/2027.42/146768/1/12859_2018_Article_2531.pd