One-pot facile synthesis and electrochemical evaluation of selenium enriched cobalt selenide nanotube for supercapacitor application

The present study emulates a one-pot facile synthesis of selenium-enriched CoSe nanotube using a chemical bath deposition (CBD) procedure. Schematic incorporation of 3D Ni foam current collectors as substrates for the growth of CoSe–Se nanotubes helped us achieve a binder-less thin film coating. The controlled synthesis of CoSe–Se nanotube was carried out by optimizing the temperature and time of the deposition. CoSe–Se nanotubes were grown on a porous Ni foam substrate using lithium chloride as a shape directing agent. The study found that the one dimensional structure of the nanotubes with porous nature results in an uninterrupted network of electroactive sites. Due to the superior conductivity, the as-fabricated material exhibited excellent rate capability and a higher degree of electrolyte ion diffusion across the CoSe–Se crystal structure. The CoSe–Se@Ni foam electrodes exhibited a specific capacitance of 1750.81 F g^?1 at 1 A g^?1. The electrode exhibited excellent cycling stability and showed a capacitance retention of 95% after 4000 charge-discharge cycles. Finally, an asymmetric supercapacitor (ASC) device was fabricated with the as-synthesized CoSe–Se@Ni foam electrode as the cathode, activated carbon@Ni foam electrode as the anode, and a thin filter paper separator soaked in 1 M aqueous KOH electrolyte solution. The ASC device showed a specific capacitance value of 106.73 F g^?1 at 0.5 A g^?1, and achieved an energy density of 37.94 Wh kg^?1 at a power density of 475.30 W kg^?1. The ASC device was utilized in an extended potential window of 1.6 V. The fabricated device displayed exceptional cycling stability with a capacitance retention of 93% after 5000 charge-discharge cycles.     

Solubility of polymers in supercritical fluids

The phase separation of solutions of monodisperse polystyrene samples of molecular weight 9000 in pure and also binary mixtures ofn-butane andn-pentane has been examined under both subcritical and supercritical conditions over the whole concentration range using a variable-volume view cell capable of operating at up to 100 MPa and 500 K. The phase behavior of these solutions is discussed in terms of the coexistence curves and the theoretical predictions based on the mean-field lattice-gas theory.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

Thermally stimulated discharge currents from pyrene-doped polystyrene films

Pyrene was mixed with polystyrene (PS) in different molar concentrations in the range 0.2–12 mol.% and thermally stimulated discharge (TSD) current spectra of the doped PS films were studied for various dopant concentrations, polarizing fields and forming temperatures. Unpolarized films were observed to give a peak at 95°C. The TSD current peak in the main relaxation region of PS shifts to the lower temperature side of the spectrum with increasing concentration of the dopant. The strong dependence of space charge polarization on the dopant concentration and the forming temperature is assigned to an increase in the conductivity of the polymer.     

Parallel adaptive simulations of dynamic fracture events

Finite element simulations of dynamic fracture problems usually require very fine discretizations in the vicinity of the propagating stress waves and advancing crack fronts, while coarser meshes can be used in the remainder of the domain. This need for a constantly evolving discretization poses several challenges, especially when the simulation is performed on a parallel computing platform. To address this issue, we present a parallel computational framework developed specifically for unstructured meshes. This framework allows dynamic adaptive refinement and coarsening of finite element meshes and also performs load balancing between processors. We demonstrate the capability of this framework, called ParFUM, using two-dimensional structural dynamic problems involving the propagation of elastodynamic waves and the spontaneous initiation and propagation of cracks through a domain discretized with triangular finite elements.     

Equivalence of Polynomial Identity Testing and Polynomial Factorization

In this paper, we show that the problem of deterministically factoring multivariate polynomials reduces to the problem of deterministic polynomial identity testing. Specifically, we show that given an arithmetic circuit (either explicitly or via black-box access) that computes a multivariate polynomial f, the task of computing arithmetic circuits for the factors of f can be solved deterministically, given a deterministic algorithm for the polynomial identity testing problem (we require either a white-box or a black-box algorithm, depending on the representation of f).Together with the easy observation that deterministic factoring implies a deterministic algorithm for polynomial identity testing, this establishes an equivalence between these two central derandomization problems of arithmetic complexity.Previously, such an equivalence was known only for multilinear circuits (Shpilka & Volkovich, 2010).     

Low percolation threshold and high electrical conductivity in melt‐blended polycarbonate/multiwall carbon nanotube nanocomposites in the presence of poly(ε‐caprolactone)

This study focuses on the electrical properties of polycarbonate (PC)/poly(ε‐caprolactone) (PCL)‐multiwall carbon nanotube (MWCNT) nanocomposites. MWCNTs were incorporated into thermoplastic PC matrix by simple melt blending using biodegradable PCL based concentrates with MWCNT loadings (3.5 wt%). Because of the lower interfacial energy between MWCNT and PCL, the nanotubes remain in their excellent dispersion state into matrix polymer. Thus, electrical percolation in PC/PCL‐MWCNT nanocomposites was obtained at lower MWCNT loading rather than direct incorporation of MWCNT into PC matrix. AC and DC electrical conductivity of miscible PC/PCL‐MWCNT nanocomposites were studied in a broad frequency range, 10¹?10⁶ Hz and resulted in low percolation threshold (p_c) of 0.14 wt%, and the critical exponent (t) of 2.09 from the scaling law equation. The plot of logσ_DC versus p^?1/3 showed linear variation and indicated the existence of tunneling conduction among MWCNTs. At low MWCNT loading, the influence of large polymeric gaps between conducting clusters is the reason for the frequency dependent electrical conductivity. Transmission electron microscopy and field emission scanning electron microscopy showed that MWCNTs were homogeneously dispersed and developed a continuous interconnected network path throughout the matrix phase and miscibility behavior of the polymer blend. POLYM. ENG. SCI., 54:646–659, 2014. © 2013 Society of Plastics Engineers     

Novel LOX Variants in Five Families with Aortic/Arterial Aneurysm and Dissection with Variable Connective Tissue Findings

Thoracic aortic aneurysm and dissection (TAAD) is a major cause of cardiovascular morbidity and mortality. Loss-of-function variants in LOX, encoding the extracellular matrix crosslinking enzyme lysyl oxidase, have been reported to cause familial TAAD. Using a next-generation TAAD gene panel, we identified five additional probands carrying LOX variants, including two missense variants affecting highly conserved amino acids in the LOX catalytic domain and three truncating variants. Connective tissue manifestations are apparent in a substantial fraction of the variant carriers. Some LOX variant carriers presented with TAAD early in life, while others had normal aortic diameters at an advanced age. Finally, we identified the first patient with spontaneous coronary artery dissection carrying a LOX variant. In conclusion, our data demonstrate that loss-of-function LOX variants cause a spectrum of aortic and arterial aneurysmal disease, often combined with connective tissue findings.     

Impact of shape (nanofiller vs. nanorod) of TiO2 nanoparticle on free-standing solid polymeric separator for energy storage/conversion devices

We report the investigation on examining the impact of nanofiller (NF)- versus nanorod (NR)-shaped titanium oxide (TiO₂) nanoparticle on the structural, electrochemical, transport, thermal, and dielectric properties of the solid polymer electrolyte (SPE). Thin SPE films comprising of poly(ethylene oxide), sodium hexafluorophosphate, and dispersed with TiO₂ NF, TiO₂ NR (synthesized by hydrothermal route) has been prepared via solution cast technique. The shape of nanoparticle influences the morphological and structural properties as observed in field emission scanning electron microscope and X-ray diffraction analysis. The highest ionic conductivity was exhibited by the NR dispersed system and is higher than NF dispersed system for all recorded concentration consistently. It is attributed to the formation of the long-range conductive path with NR when compared with NF. In addition, the electrochemical stability window is much higher (~5 V) than the NF-doped system. Furthermore, the dielectric properties of SPE were investigated and fitted in the complete frequency window (1 Hz–1 MHz; T = 40–100 °C @ 10 °C). It is observed that the NR dispersed system shows higher dielectric strength and low relaxation time with respect to NF dispersed system. The results suggest that the NR dispersed SPE possess enhanced properties and is more appropriate for an application in high energy density solid-state Na ion batteries. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47361.     

Low percolation threshold in polycarbonate/multiwalled carbon nanotubes nanocomposites through melt blending with poly(butylene terephthalate)

Here, we demonstrate an easy method for the preparation of highly electrically conductive polycarbonate (PC)/multiwalled carbon nanotubes (MWCNTs) nanocomposites in the presence of poly(butylene terephthalate) (PBT). In the presence of MWCNTs, PC and PBT formed a miscible blend, and the MWCNTs in the PC matrix were uniformly and homogeneously dispersed after the melt mixing of the PC and PBT–MWCNT mixture. Finally, when the proportion of the PC and PBT–MWCNT mixture in the blend/MWCNT nanocomposites was changed, an electrical conductivity of 6.87 × 10^?7 S/cm was obtained in the PC/PBT–MWCNT nanocomposites at an MWCNT loading as low as about 0.35 wt %. Transmission electron microscopy revealed a regular and homogeneous dispersion and distribution of the MWCNTs and formed a continuous conductive network pathway of MWCNTs throughout the matrix phase. The storage modulus and thermal stability of the PC were also enhanced by the presence of a small amount of MWCNTs in the nanocomposites. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013