Synthesizing higher nitride of molybdenum (Mo) and iron (Fe) in ammonia (NH3) gas stream under irradiation of concentrated solar beam in a solar furnace

Flowing gaseous ammonia NH₃ with suppressed extent of dissociation (un‐cracked NH₃) is acknowledged to function as a powerful nitriding medium to realize formation of metal nitride MN_x with considerably high N/M ratio x that cannot be achieved through reaction of M with N₂ gas. For example, mono‐nitride δ‐MoN of Mo and ε‐FeN_x phase of Fe with x = 0.33 ? 0.50 (i. e. hypo‐stoichiometric sub‐nitride ε‐Fe₂N) were reported to be difficult to prepare in N₂ gas environment even at elevated pressure but might be synthesized in flowing NH₃ gas at normal pressure when reaction temperature and NH₃ gas flow rate were set adequately. In the present work, nitriding experiments for Mo and Fe were carried out in flowing NH₃ gas under irradiation with concentrated solar beam. The acquired experimental evidences demonstrated that temperature range for formation of δ‐MoN was somewhat extended in flowing NH₃ gas under heating with concentrated solar beam compared with that under heating in conventional laboratory or industrial electric furnace. On the other hand, no such merit of extending temperature range for formation of ε‐Fe₂N in flowing NH₃ gas was detected in the present work under heating with concentrated solar beam.     

On the automorphism group of a binary self-dual [120, 60, 24] code

We prove that an automorphism of order 3 of a putative binary self-dual $[120, 60, 24]$ [ 120 , 60 , 24 ] code $C$ C has no fixed points. Moreover, the order of the automorphism group of $C$ C divides $2^a\cdot 3 \cdot 5\cdot 7\cdot 19\cdot 23\cdot 29$ 2 a · 3 · 5 · 7 · 19 · 23 · 29 with $a\in \mathbb N _0$ a ∈ N 0 . Automorphisms of odd composite order $r$ r may occur only for $r=15, 57$ r = 15 , 57 or $r=115$ r = 115 with corresponding cycle structures $3 \cdot 5$ 3 · 5 - $(0,0,8;0), 3\cdot 19$ ( 0 , 0 , 8 ; 0 ) , 3 · 19 - $(2,0,2;0)$ ( 2 , 0 , 2 ; 0 ) or $5 \cdot 23$ 5 · 23 - $(1,0,1;0)$ ( 1 , 0 , 1 ; 0 ) respectively. In case that all involutions act fixed point freely we have $|\mathrm{Aut}(C)| \le 920$ | Aut ( C ) | ≤ 920 , and $\mathrm{Aut}(C)$ Aut ( C ) is solvable if it contains an element of prime order $p \ge 7$ p ≥ 7 . Moreover, the alternating group $\mathrm{A}_5$ A 5 is the only non-abelian composition factor which may occur in $\mathrm{Aut}(C)$ Aut ( C ) .     

Preparation, characterization, and in vitro evaluation of nanostructured chitosan/apatite and chitosan/Si-doped apatite composites

Chitosan/apatite (CHI/Ap) composites are attracting great attention as biomaterials for bone repair and regeneration procedures. The reason is their unique set of properties: bioactivity and osteoconductivity provided by Ap and resorbability supplied by CHI among others. Thus, in this study, CHI/Ap and CHI/Si-doped Ap composites were prepared and characterized. Particle size, surface area, in vitro physiological stability, enzymatic biodegradation, and bioactivity were evaluated. Unimodal particle size distribution was obtained for composites with high CHI/Ap ratios while bimodal distribution was present in composites with low CHI/Ap ratio. Physiological stability decreased with Si doping and with the CHI content. Acetylation degree and molecular weight of CHI did not affect in vitro stability. Rate of enzymatic degradation increased with the CHI content in composites. Si-doped Ap composites also showed increased degradation with respect to non-doped ones. The bioactivity of the composites was evidenced by the deposition on their surface of a calcium phosphate layer with Ap morphology after immersion in simulated body fluid. Both, biodegradation and bioactivity were dependent on the molecular weight of the polymeric CHI matrix. These results suggest that the CHI/Ap composites obtained are promising materials for bone regeneration applications.     

Hybrid organic–inorganic materials based on polypyrrole and 1,3-dithiole-2-thione-4,5-dithiolate (DMIT) containing dianions

The synthesis of hybrid materials by electropolymerization of pyrrole and inorganic complexes based on the DMIT ligand (1,3-dithiole-2-thione-4,5-dithiolate), e.g. [NEt₄]₂[M(DMIT) _n ] (M = Ni, Pd or Pd, n = 2; M = Sn, n = 3], in acetonitrile solution is reported. Spectroscopic data showed that DMIT-containing anions, [M(DMIT) _n ]²⁻, were inserted into the polypyrrole framework without chemical modification during the electropolymerization process. Cyclic voltammetry showed that materials obtained were electroactive, undergoing redox processes related to both the conducting polymer and the counteranions. The electrochemical results also suggest that, in the case of the transition metal containing films, the counteranions are not trapped in the PPy matrix but undergo anion exchange during the redox cycle of PPy. However, an opposite behaviour was observed with the film with [M(DMIT) _n ]²⁻. The films exhibit good thermal stabilities and have conductivity values expected for semiconductors. This study of these hybrid materials highlights the importance of targeting specific materials for specific applications.

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Plasma enhanced chemical vapor deposition of titanium (IV) ethoxide–oxygen–helium mixtures

Thin films were deposited by plasma enhanced chemical vapor deposition from titanium (IV) ethoxide (TEOT)–oxygen–helium mixtures. Actinometric optical emission spectroscopy was used to obtain the relative plasma concentrations of the species H, CH, O and CO as a function of the percentage of oxygen in the feed, R_ox. The concentrations of these species rise with increasing R_ox and tend to fall for R_ox greater than about 45%. As revealed by a strong decline in the emission intensity of the actinometer Ar as R_ox was increased, the electron mean energy or density (or both) decreased as greater proportions of oxygen were fed to the chamber. This must tend to reduce gas-phase fragmentation of the monomer by plasma electrons. As the TEOT flow rate was fixed, however, and since the species H and CH do not contain oxygen, the rise in their plasma concentrations with increasing R_ox is explained only by intermediate reactions involving oxygen or oxygen-containing species. Transmission infrared (IRS) and X-ray photoelectron (XPS) spectroscopies were employed to investigate film structure and composition. The presence of CH₂, CH₃, CC, C–O and CO groups was revealed by IRS. In addition, the presence of C–O and CO groups was confirmed by XPS, which also revealed titanium in the + 4 valence state. The Ti content of the films, however, was found to be much less than that of the monomer material itself.     

Amperometric urea biosensors based on the entrapment of urease in polypyrrole films

Urease (Urs) was immobilized in electrochemically prepared polypyrrole (PPy) and the resulting films were characterized by cyclic voltammetry, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and ultraviolet visible spectroscopy (UV-VIS). The enzymatic activity of Urs entrapped in the PPy matrix was confirmed by the catalytic conversion of urea into carbon dioxide and ammonia, when urea was detected amperometrically at different concentrations in standard samples and commercial fertilizers. The PPy/Urs biosensors exhibited selectivity, a relatively high efficiency at urea concentrations below 3.0 mmol L⁻¹, and a sensitivity to urea of 2.41 μA cm⁻² mmol⁻¹ L.     

Using Probabilistic Methods to Estimate the Public Sector Comparator

Abstract: The use of the public sector comparator (PSC) is gaining momentum as a tool to ensure value for money in public–private partnership (PPP) projects. Several countries have been engaging in the calculation of the PSC, but the methodologies are excessively dependent on deterministic models, as referred to by the existing literature. Alternatives to accommodate uncertainty and forecast bias are required to improve the robustness of the calculations. This article proposes new developments in existing methodologies able to accommodate dynamic analysis to cope with uncertainty in the assumptions. A simulation model was used to compute the variability in the PSC, but the research went a step further in developing a Bayesian network approach. The output of both models is a probability distribution for the PSC, instead of just a single value, therefore, the authors have developed a methodology for comparing the PSC distribution with the PPP value.     

Degradation of 32 emergent contaminants by UV and neutral photo-fenton in domestic wastewater effluent previously treated by activated sludge

This study focuses on the removal of 32 selected micropollutants (pharmaceuticals, corrosion inhibitors and biocides/pesticides) found in an effluent coming from a municipal wastewater treatment plant (MWTP) based on activated sludge. Dissolved organic matter was present, with an initial total organic carbon of 15.9 mg L⁻¹, and a real global quantity of micropollutants of 29.5 μg L⁻¹. The treatments tested on the micropollutants removal were: UV-light emitting at 254 nm (UV₂₅₄) alone, dark Fenton (Fe^2+,3+/H₂O₂) and photo-Fenton (Fe^2+,3+/H₂O₂/light). Different irradiation sources were used for the photo-Fenton experiences: UV₂₅₄ and simulated sunlight. Iron and H₂O₂ concentrations were also changed in photo-Fenton experiences in order to evaluate its influence on the degradation. All the experiments were developed at natural pH, near neutral. Photo-Fenton treatments employing UV₂₅₄, 50 mg L⁻¹ of H₂O₂, with and without adding iron (5 mg L⁻¹ of Fe²⁺ added or 1.48 mg L⁻¹ of total iron already present) gave the best results. Global percentages of micropollutants removal achieved were 98 and a 97% respectively, after 30 min of treatments. As the H₂O₂ concentration increased (10, 25 and 50 mg L⁻¹), best degradations were observed. UV₂₅₄, Fenton, and photo-Fenton under simulated sunlight gave less promising results with lower percentages of removal.The highlight of this paper is to point out the possibility of the micropollutants degradation in spite the presence of DOM in much higher concentrations.