Characterization of hybrid organic and inorganic functionalised membranes for proton conduction

Titanium zirconium phosphate and organic polymer hybrid (poly-vinyl alcohol, (3-glycidoxypropyl)-trimethoxysilane and ethylene glycol) based membranes were investigated for their potential application as proton conductors. The hybrid materials were characterized by XRD, FTIR, SEM, TGA and impedance spectroscopy analysis. It was found that embedding of functionalised inorganic particles (TiZrP) into composite polymer matrix allowed for some crystallinity formation, and cross-linking of hydroxyl groups during annealing or reactions within the organic and inorganic phases during synthesis. A complex structure was formed, as many FTIR peaks were masked by more defined peaks assigned to P–O–R bonds. The high concentration of phosphorus in the TiZrP (1:1:9 molar ratio) samples resulted in more hydrophilic particles. This was further reflected in the hybrid membranes as the water losses increased from 13 to 25 wt.% as a function of the TiZrP content changing from 10 to 50 wt.% in the final hybrid membrane, respectively. As a result, proton conductivity increased by two to three orders of magnitude from blank (organic phase only) membranes (2.61 × 10^− 5 S cm^− 1) to TiZrP hybrid membrane (2.41 × 10^− 2 S cm^− 1) at 20 °C. Proton conduction changed as a function of temperature and the Ti1Zr1P9 particles content, mainly attributed to the membrane ability to retain water, thus complying with the Grotthus mechanism.     

Surface passivation of InGaP/GaAs HBT using silicon-nitride film deposited by ECR-CVD plasma

In this paper we have developed a passivation technique with silicon-nitride (SiN_X) film that requires no surface pre-treatment, and is fully compatible to monolithic microwave integrated circuits (MMICs). The nitride depositions were carried out by ECR-CVD (electron cyclotron resonance-chemical vapor deposition) directly over InGaP/GaAs heterojunction structures, which are used for heterojunction bipolar transistors (HBTs). Optical emission spectrometry (OES) was used for plasma characterization, and low formation of H and NH molecules in the gas phase was detected at pressure of 2.5 mTorr. These molecules can degrade III-V semiconductor surfaces due to the preferential loss of As or P and hydrogen incorporation at the substrate. The substrates were cleaned with organic solvents using a Sox-let distillate. The ECR depositions were carried out at a fixed substrate temperature of 20 °C, SiH₄/N₂ flow ratio of 1, Ar flow of 5 sccm pressure of 2.5 mTorr and microwave (2.45 GHz) power of 250 W and RF (13.56 MHz) power of 4 W. We have applied this film for InGaP/GaAs HBT fabrication process with excellent results, where two major contribuiton is related to this passivation technique, the enhancement in the transistor dc gain β and the improvement in the signal-to-noise ratio when compared unpassivated and passivated devices.     

Theoretical and X-Ray Evidence of Electrostatic Phosphonium anti and gauche Effects

Sulphur, not phosphorus, is the only known third-row element capable of experiencing an electrostatic gauche effect with fluorine. Some six-membered rings containing an endocyclic phosphorus atom and a β-fluorine substituent that can interconvert to axial (gauche relative to phosphorus) and equatorial positions were then analysed. While phosphines do not establish an electrostatic attraction between fluorine and phosphorus, some oxidised forms exhibit surprising stability for the sterically disfavoured axial orientation. Because the nature of this behaviour was not obvious, since an intramolecular hydrogen bond can appear, a phosphonium derivative was further studied and its axial conformation was found to be highly stable. A preference for the gauche arrangement appears even for the acyclic and sterically hindered (2-fluoroethyl)triphenylphosphonium cation. On the other hand, (ethane-1,2-diyl)bis(phosphonium) cations are exclusively in anti conformation due to an (+/+)-electrostatic repulsion between the positively charged phosphonium groups.     

Characterisation of Xerogels Derived from Sucrose Templated Sol-Gel Synthesis

This work presents the results of the nanostructural characterisation of the effect of sucrose as a template added to a sol derived from a tetraethoxysilane acid catalysed process. By increasing the sucrose template ratio, N₂ adsorption isotherms showed that the xerogel samples changed from a micropore to a mesopore nanostructure as evidenced by the formation of hysteresis at 0.5 partial pressure. In turn, this led to a direct increase in surface areas, pore volumes and average pore sizes. Sucrose has two molecular components of the same molecular weight: D-fructose and D-glucose. D-fructose resulted in the formation of higher pore volumes and pore sizes, while D-glucose formed higher surface area xerogels. Depending of the template ratio employed in the xerogel synthesis, average pore radius ranged from 8.8 to 26 Å, while surface areas increased by over two fold up to 750 m²·g^?1. However, pore volumes increased by as much as six fold, from 0.15 to almost 1 cm³·g^?1.     

Unidirectional switching between two flavylium reaction networks by the action of alternate stimuli of acid and base

The introduction of an ester group in the flavylium core allowed the reversible conversion between two different flavylium compounds each one exhibiting its own reaction network. An unidirectional switching cycle between 7-diethylamino-2-(4-(methoxycarbonyl)phenyl)-1-benzopyrylium and 2-(4-carboxyphenyl)-7-diethylamino-1-benzopyrylium was achieved by means of alternate acid and base stimuli. Addition of base to a methanolic solution of the ester derivative gives rise to the trans-chalcone of the parent carboxylic acid, which upon acidification of the solution forms the respective flavylium cation. This species esterifies under very acidic conditions to restore the original methyl ester derivative. The chemical reaction networks of both compounds were fully characterized from their thermodynamic and kinetic aspects, by a series of pH jumps followed by UV-vis absorption and emission spectroscopy, stopped flow and (1)H NMR. The crystal structure of the trans-chalcone of the ester derivative was unveiled showing a supramolecular structure involving hydrogen bonding.     

Anti-inflammatory activity of alkaloids: an update from 2000 to 2010

Many natural substances with proven anti-inflammatory activity have been isolated throughout the years. The aim of this review is to review naturally sourced alkaloids with anti-inflammatory effects reported from 2000 to 2010. The assays were conducted mostly in vivo, and carrageenan-induced pedal edema was the most used experimental model. Of the 49 alkaloids evaluated, 40 demonstrated anti-inflammatory activity. Of these the most studied type were the isoquinolines. This review was based on NAPRALERT data bank, Web of Science and Chemical Abstracts. In this review, 95 references are cited.     

Spaceability in Banach and quasi-Banach sequence spaces

Let X be a Banach space. We prove that, for a large class of Banach or quasi-Banach spaces E of X-valued sequences, the sets E-?_q∈Γ?_q(X), where Γ is any subset of (0,∞], and E-c₀(X) contain closed infinite-dimensional subspaces of E (if non-empty, of course). This result is applied in several particular cases and it is also shown that the same technique can be used to improve a result on the existence of spaces formed by norm-attaining linear operators.     

Terpenoids from Croton regelianus

Two new terpenoids, the bisnorditerpene rel‐(5β,8α,10α)‐8‐hydroxy‐13‐methylpodocarpa‐9(11),13‐diene‐3,12‐dione ( 1 ) and the guaiane sesquiterpene rel‐(1R,4S,6R,7S,8aR)‐decahydro‐1‐(hydroxymethyl)‐4,9,9‐trimethyl‐4,7‐(epoxymethano)azulen‐6‐ol ( 2 ), together with seven known compounds, were isolated from Croton regelianus var. matosii. The structures of the isolated compounds were determined by HR‐ESI‐TOF and a combination of 1D‐ and 2D‐NMR experiments.     

Compatibility study of hydroxychloroquine sulfate with pharmaceutical excipients using thermal and nonthermal techniques for the development of hard capsules

Journal of Thermal Analysis and Calorimetry - Hydroxychloroquine is effectively used in the treatment for malaria, lupus erythematosus and rheumatoid arthritis. The study of drug–excipient...     

Comment on “Random Quantum Circuits are Approximate 2-designs” by A.W. Harrow and R.A. Low (Commun. Math. Phys. 291, 257–302 (2009))

In [A.W. Harrow and R.A. Low, Commun. Math. Phys. 291(1):257–302 (2009)], it was shown that a quantum circuit composed of random 2-qubit gates converges to an approximate quantum 2-design in polynomial time. We point out and correct a flaw in one of the paper’s main arguments. Our alternative argument highlights the role played by transpositions induced by the random gates in achieving convergence.