Surface modification of FePO4 particles with conductive layer of polypyrrole

Polypyrrole–FePO₄ powder was synthesized by an oxidative polymerization of pyrrole monomer on the surface of FePO₄ powder. The polymerization reaction was initiated using hydrogen peroxide in an acidified solution and catalysed with Fe³⁺. The samples were investigated by light microscopy (LM), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). These methods confirmed the presence of polypyrrole on FePO₄ particles and its homogeneous distribution in the composite material. To determine the PPy content in the PPy–FePO₄ composites a thermogravimetric analysis was used. Cyclic voltammetry curves (CV) were measured and compared in a non-aqueous lithium salt solution for electrodes consisting of pellets made from pure FePO4 and FePO₄/PPy. Electrochemical impedance spectroscopy (EIS) showed that coating of PPy significantly decreases the charge transfer resistance of PPy–FePO₄ electrodes.     

Surface treatment of LiFePO4 cathode material with PPy/PEG conductive layer

In this work, we studied LiFePO₄ particles coated with thin films of highly conductive polypyrrole (PPy) and their electrochemical performance in cathode layers of lithium cells. Carbon-free LiFePO₄ particles were synthesized by a solvothermal method. Besides this, a part of the experiments were carried out on commercial carbon-coated LiFePO₄ for comparison. Polypyrrole coated LiFePO₄ particles (PPy-LiFePO₄) were obtained by a straightforward oxidative polymerization of dissolved pyrrole on LiFePO₄ particles dispersed in water. The use of polyethylene glycol (PEG) as an additive during the polymerization was decisive to achieve high electronic conductivities in the final cathode layers. The carbon-free and carbon-coated LiFePO₄ particles were prepared with PPy and with PPy/PEG coating. The obtained PPy-LiFePO₄ and PPy/PEG-LiFePO₄ powders were characterized by SEM, EIS, cyclic voltammetry, and galvanostatic charge/discharge measurements in lithium-ion cells with lithium metal as counter and reference electrode. Carbon-free LiFePO₄ coated with PPy/PEG hybrid films exhibited very good electrode kinetics and a stable discharge capacity of 156 mAh/g at a rate of C/10. Impedance measurements showed that the PPy/PEG coating decreases the charge-transfer resistance of the corresponding LiFePO₄ cathode material very effectively, which was attributed to a favorable mixed ionic and electronic conductivity of the PPy/PEG coatings.     

Small molecule correctors of F508del-CFTR discovered by structure-based virtual screening

Folding correctors of F508del-CFTR were discovered by in silico structure-based screening utilizing homology models of CFTR. The intracellular segment of CFTR was modeled and three cavities were identified at inter-domain interfaces: (1) Interface between the two Nucleotide Binding Domains (NBDs); (2) Interface between NBD1 and Intracellular Loop (ICL) 4, in the region of the F508 deletion; (3) multi-domain interface between NBD1:2:ICL1:2:4. We hypothesized that compounds binding at these interfaces may improve the stability of the protein, potentially affecting the folding yield or surface stability. In silico structure-based screening was performed at the putative binding-sites and a total of 496 candidate compounds from all three sites were tested in functional assays. A total of 15 compounds, representing diverse chemotypes, were identified as F508del folding correctors. This corresponds to a 3% hit rate, ~tenfold higher than hit rates obtained in corresponding high-throughput screening campaigns. The same binding sites also yielded potentiators and, most notably, compounds with a dual corrector-potentiator activity (dual-acting). Compounds harboring both activity types may prove to be better leads for the development of CF therapeutics than either pure correctors or pure potentiators. To the best of our knowledge this is the first report of structure-based discovery of CFTR modulators.     

Functionality of novel black silicon based nanostructured surfaces studied by TOF SIMS

A functionality of the novel black silicon based nanostructured surfaces (BS 2) with different metal surface modifications was tested by time-of-flight secondary ion mass spectrometry (TOF SIMS). Mainly two surface functions were studied: analytical signal enhancement and analyte pre-ionization effect in SIMS due to nanostructure type and the assistance of the noble metal surface coating (Ag or Au) for secondary ion formation. As a testing analyte a Rhodamine 6G was applied. Bi⁺ has been used as SIMS primary ions. It was found out that SIMS signal enhancement of the analyte significantly depends on Ag layer thickness and measured ion mode (negative, positive). The best SIMS signal enhancement was obtained at BS2 surface coated with 400 nm of Ag layer. SIMS fragmentation schemes were developed for a model analyte deposited onto a silver and gold surface. Significant differences in pre-ionization effects can play an important role in the SIMS analysis due to identification and spectra interpretation.     

Properties of intersecting families of ordered sets

The first part of this paper deals with families of ordered k-tuples having a common element in different position. A quite general theorem is given and special cases are considered. The second part deals with t families of sets with some intersection properties, and generalizes results by Bollobás, Frankl, Lovász and Füredi to this case.     

Chiroptical Detection of Nonchromophoric,Achiral Guests by Enantiopure Alleno‐Acetylenic Helicages

Enantiopure alleno‐acetylenic ligands assemble diastereoselectively upon the addition of a zinc(II) salt to form triple‐stranded helicates, which provide a sufficiently large helical cage (“helicage”) for the encapsulation of guests. The inclusion complexation of heteroalicycles is confirmed by ROESY and DOSY NMR spectroscopy and quantified in ¹H NMR binding titrations. The ECD spectra of the helicates, which showed strong Cotton effects and exciton coupling, were found to be extremely sensitive to the nature of the guest molecules. Consequently, a series of nonchromophoric, achiral guests of different sizes as well as regioisomers (1,3‐ and 1,4‐dioxane) became distinguishable on the basis of their induced CD (ICD) spectra. Molecular dynamics (MD) simulations show the adaptability of the cavity size to individual guest molecules and support the selective ICD output. Particularly high affinity towards 1,4‐dioxane allowed its selective detection at parts‐per‐million (ppm) levels in aqueous solutions.     

Pursuit–Evasion Games with incomplete information in discrete time

Pursuit–Evasion Games (in discrete time) are stochastic games with nonnegative daily payoffs, with the final payoff being the cumulative sum of payoffs during the game. We show that such games admit a value even in the presence of incomplete information and that this value is uniform, i.e. there are e{\epsilon}-optimal strategies for both players that are e{\epsilon}-optimal in any long enough prefix of the game. We give an example to demonstrate that nonnegativity is essential and expand the results to Leavable Games.     

Frequency dynamics of semiconductor lasers with atomic absorbers: theory and experiments

In this paper we discuss the spectral behavior of monomode semiconductor laser systems whose output amplitude is constant, but whose frequency may be bistable, multistable, locked or present instabilities. The explored configurations are: (i) a laser diode (Fabry-Pérot) under orthogonal filtered optical feedback; and (ii) an extended-cavity diode laser with an intracavity strongly-saturated resonant vapor. Starting from rate equations for the carrier density and for the radiation field oscillating in the cavity of these systems we describe spectral features which are in very good quantitative agreement with experimental observations.     

Gravitational self-force on a particle orbiting a Kerr black hole

We present a practical method for calculating the gravitational self-force, as well as the electromagnetic and scalar self-forces, for a particle in a generic orbit around a Kerr black hole. In particular, we provide the values of all the regularization parameters needed for implementing the (previously introduced) mode-sum regularization method. We also address the gauge-regularization problem, as well as a few other issues involved in the calculation of gravitational radiation reaction in Kerr spacetime.