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Fatigue failure cracking under fluctuating stressing has been a major concern of engineering for many years. Fatigue failures have become more common and thereby significantly influencing engineering design as sources of vibration and dynamic loading of components have increased. The repairs of damaged metallic structures using bonded composite patch have been proved as an economical method to increase the fatigue life of damaged structures. This paper deals with an experimental study on the fatigue life of AA7075-T6 aluminium alloy plates reinforced with single-sided boron/epoxy patches. The study focuses on the effect of different curing cycles on the fatigue life of reinforced/repaired structure. Bonds were tested with four different curing cycles. Distortion behaviour of bonded repair is studied. The influence of the curing cycle conditions on fatigue life is presented. Also, the repair patch effectiveness on the stress state at the crack tip in increasing the fatigue life of the unrepaired structure is shown. The obtained results show that repair of the cracked plate can be done effectively by using bonded composite patches. It is shown to decrease the crack growth rate to enhance the fatigue life of the structure by 70%. Elevated curing temperatures enhance the adhesion between the metal surface and the composite patch and overall durability. However, elevated cure temperature may result in distortion with bending curvature. The optimum combination of temperature and duration for the curing cycle is of importance to reduce the distortion.

Background: The essential oils of aromatic plants are increasingly used as new biocontrol alternative agents against microbial strains and insect pests of fruits and vegetables, because of their specificity of biodegradable nature. Objective: This work, treats for the first time the chemical composition, antioxidant, antifungal and insecticidal activities of the essential oils obtained from Echinops spinosus and Carlina vulgaris from Algeria. Methods: The chemical compositions of oils were investigated using GC-FID and GC/MS. Antioxidant activity was assessed using three methods (2,2-diphenyl-1-picrylhydrazyl, Ferric-Reducing Antioxidant Power (FRAP) and β-carotene assay). Fumigation toxicity of E. spinosus and C. vulgaris essential oils was tested against Bactrocera oleae pests of olives. Results: Eighteen and thirteen components representing 95.4 and 97.9% were identified in root essential oils from Echinops spinosus and Carlina vulgaris, respectively. Polyacetylenes were the majority compounds of essential oils. 5 (But-1-yn-3-enyl).2,2'bithiophene and α-terthienyle were highly dominants in the E. spinosus essential oil from the roots (54.4 and 26.3%, respectively). Roots of C. vulgaris produce an essential oil dominated by carlina oxide (33.7%) and 13-methoxy carlina oxide (11.5%). Comparison of the antioxidant activity of E. spinosus essential oil showed more important antioxidant effect than C. vulgaris essential oil and the synthetic antioxidant (BHT). Evaluation of the antifungal activity showed an interesting efficiency of both essential oils against P. expansum and A. niger with EC50s varied from 5 to 14.5 mg/L. C. arvensis essential oil exhibited good larvicidal properties. At the concentration of 325 μL/L air, the oil caused mortality of 100% for Bactrocera Oleae adults after 24 h of exposure. Conclusion: Both essential oils rich to polyacetylenes and polythiophenes.components have shown interesting biological activities, which suggests that plants have the potential to be used as biopesticides and provide an alternative to chemical pesticides.

In this paper, the effect of corrosion on the performance of the bonded composite patch repair in aluminum alloy A5083 marine structure was investigated using three dimensional finite element methods. To this end, two patches made in carbon/epoxy and boron/epoxy, bonded on corroded plates with and without crack, were tested under different applied loads. The effect of both corrosion and cracked materials on the damage of the adhesive FM73, was also highlighted. The obtained results show that, the corrosion has a significant effect on the quality repair performance. Indeed, it is proved that, the rate of damage increases with the increase of the applied load, and is more significant in the case of plates cracked and repaired by carbon/epoxy patch. Hence, the best performances were obtained using boron/epoxy patches

We report the unique electrochemical properties of nitrogen-containing carbon nanostructures (N-CP) grown on commercial carbon paper (CP), used as electrocatalysts in all-vanadium redox flow batteries (VRFBs). The focus is on the anode, where mitigation of the hydrogen evolution reaction and loss in redox kinetics due to cycling is considered as a challenge. The growth of bamboo-like carbon nanostructures is achieved through a catalytic chemical vapor deposition (CVD) process with a very small geometric loading of Fe (from FeCl3) as the catalyst. Anhydrous acetonitrile, used as a nitrogen/carbon precursor, is fed to the electrode sample at 900 °C for 3 hours in a stream of H2–Ar (carrier gas). The three-electrode-cell study shows enhanced kinetics and durability of the electrode for V3+/V2+ redox reactions; N-CP shows a significant suppression of the peak potential separation (ΔE ∼ 80 mV), indicating faster kinetics compared to conventional CP (ΔE ∼ 160 mV). In addition, the subscale cell performance shows good durability (about 5% and 15% loss in energy efficiency in N-CP and CP, respectively) after 50 charge–discharge cycles. The improved durability of the N-CP electrode is attributed to the presence of nitrogen–carbon nanostructures, increased active area, and improved sp2 carbon content. Such findings can contribute to the development of large scale high performance VRFB systems.

Background: The emergence of carbapenemase-producing Enterobacterales (CPE) is a public health problem, requiring rapid and reliable diagnostic methods. The aim is to compare the new rapid immunochromatographic (IC) test: RESIST-5 O.O.K.N.V with PCR and the predictive model of EUCAST algorithm for the detection of CPE. Methods: A longitudinal cross-sectional study was carried out in the bacteriology-virology laboratory of the Ibn Rochd-Casablanca University Hospital, from 1 February 2019 to 28 February 2020, concerning strains with reduced sensitivity to Ertapenem. The identification of bacterial species was carried out according to the standard criteria of microbiology and antibiogram according to CASFM-EUCAST 2019 recommendations. The sensitivity and specificity of the rapid IC test were calculated. Results: The results of the new IC test showed a sensitivity and specificity of 100% for the detection of OXA-48 and NDM. These carbapenemases were detected simultaneously with a sensitivity and specificity of 100%. OXA-48 was the most common carbapenemas found (36%), followed by NDM (24%) and (13.4%) cases of OXA-48 and NDM coexistence. Conclusion: The rapid IC test could be a rapid and effective diagnostic tool for detecting the most common carbapenemases in our context, and to accelerate the implementation of adequate antibiotic therapy and infection control measures in patients with CPE infections

Anion exchange membranes (AEMs) are becoming increasingly common in electrochemical energy conversion and storage systems around the world (EES). Proton-/cation-exchange membranes (which conduct positive charged ions such as H+ or Na+) have historically been used in many devices such as fuel cells, electrolysers, and redox flow batteries. High capital costs and the use of noble metal catalysts are two of the current major disadvantages of polymer electrolyte membrane (PEM)-based systems. AEMs may be able to overcome the limitations of conventional PEMs. As a result, polymers with anion exchange properties have recently attracted a lot of attention due to their significant benefits in terms of transitioning from a highly acidic to an alkaline environment, high kinetics for oxygen reduction and fuel oxidation in an alkaline environment, and lower cost due to the use of non-precious metals. The aim of this research was to learn more about the development of a new AEM based on poly tetraarylphosphonium ionomers (pTAP), which has high ionic conductivity, alkaline stability, thermal stability, and good mechanical properties, making it a more cost-effective and stable alternative to conventional and commercial AEMs. A simple solution casting method was used to build novel anion exchange composite membranes with controlled thicknesses using the synthesized pTAP with polysulfone (PS). To ensure their suitability for use as an electrolyte in alkaline electrochemical systems, the composite membranes were characterized using FTIR, XRD, water uptake, ionic conductivity, and alkaline stability. At 40 °C, the PS/pTAP 40/60 percent membrane had a maximum ionic conductivity of 4.2 mS/cm. The thermal and mechanical stability of the composite membranes were also examined, with no substantial weight loss observed up to 150 °C. These findings pave the way for these membranes to be used in a wide variety of electrochemical applications.

Introducing redox-active moieties into an ionic liquid (IL) structure is an exciting and attractive approach that has received increasing interest over recent years for a various range of energy applications. The so-called redox-active ionic liquids (RAILs) provide a highly versatile platform to potentially create multifunctional electroactive materials. Ionic liquids are molten salts consisting of ionic species, often having a melting point lower than 100 °C. Such liquids are obtained by combining a bulky asymmetric organic cation and a small anion. Here, we report on the synthesis of a novel RAIL, namely 1-butyl-3-methylimidazolium hydroquinone sulfonate ((BMIM)(HQS)). (BMIM)(HQS) was synthesized in a two-step procedure, starting by the quaternization of methylimidazole using butylchloride to produce 1-butyl-3-methylimidazolium chloride ((BMIM)(Cl)), and followed by the anion exchange reaction, where the chloride anion is exchanged with hydroquinone sulfonate. The resulting product was characterized by 1H NMR, 13C NMR, FT-IR spectroscopy, themogravimetric analysis, and differential scanning calorimetry, and shows a high stability up to 340 °C. Its electrochemical behavior was investigated using cyclic voltammetry at different temperatures and its viscosity analysis was also performed at variable temperatures. The electrochemical response of the presented RAIL was found to be temperature dependent and diffusion controlled. Overall, our results demonstrated that (BMIM)(mix of HQS and HSQ) is redox active and possesses high stability and low volatility, leading to the employment of this RAIL without any additional supporting electrolyte or additives.

Column leaching tests become methodology important for assessing the risk of release of pollutants from soil into groundwater. In this present study column leaching test were applied on soil samples taken directly in the vicinity of Kenadsa coking plant (Algeria) in order to evaluate the mobility of copper and their potential environmental risks. These samples have been lixiviated in laboratory column in water-saturated condition at room temperature. All leachates have been collected by fraction and analyzed from copper and dissolved organic carbon. The percentages leached in column with water are very low (< 1%). The concentrations of copper in the resulting leachates do not present a toxicological hazard. The effect of dissolved organic carbon on copper leaching was also investigated in this study; the results of column leaching showed that the mobility of copper in these contaminated soil samples is associated with the mobility of dissolved organic carbon.

Layered transition metal dichalcogenides (TMDs) materials have shown high potential in many optoelectronic and photovoltaic applications due to their intriguing semiconducting properties. Most noticeably, the layered molybdenum disulfide (MoS2) has drawn much attention because of its unique layer-dependent band gap tunability and high electron mobility. A facile non-vacuum electrodeposition approach is used to deposit bulk MoS2 films onto FTO substrate immersed in an aqueous precursor solution of molybdenum and sulfur. The as-deposited and post-treated films are studied using X-ray diffraction, electron microscopy equipped with energy-dispersive x-ray spectroscopy, light absorption measurement, and X-ray photoelectron spectroscopy. Although the obtained gap energy values, 1.3–1.4 eV, of bulk MoS2 are indirect, the measured light absorption characteristic is high, especially above 1.7 eV. Also, electrochemical impedance spectroscopy studies of the films show that carrier concentration in higher than 1015 cm−3.

The synthesis of complex spiro{pyrrolidine-3,1'-pyrrolo[3,4-c]pyrrole} skeleton employing mild conditions is presented. The order of addition of a primary amine, two equivalents of the corresponding maleimide and finally, the aldehyde is of a paramount importance to obtain these final compounds in very high yields. The mechanism is studied performing very simple tests, the Michael type addition of the amine onto the maleimide being the key step. Interestingly, the hybrid scaffold is prepared by sequential addition of two different maleimides. In addition, a more interesting architecture is prepared through a metathesis reaction between allylic residues bonded in the molecule precursor. We gratefully acknowledge financial support from the Spanish Ministerio de Ciencia, Innovación y Universidades (projects CTQ2016-81893REDT, and RED2018-102387-T) the Spanish Ministerio de Economía, Industria y Competitividad, Agencia Estatal de Investigación (AEI) and Fondo Europeo de Desarrollo Regional (FEDER, EU) (projects CTQ2016-76782-P, CTQ2016-80375-P, CTQ2017-82935-P and PID2019-107268GB-I00), Generalitat Valenciana (CIDEGENT/2020/058) and the University of Alicante.

Thanks to their uniqueness, nanowires allow the realization of novel semiconductor crystal structures with yet unexplored properties, which can be key to overcome current technological limits. Here we develop the growth of wurtzite GaP/In(x)G(x)G(1-x) core shell nanowires with tunable indium concentration and optical emission in the visible region from 590 nm (2.1 eV) to 760 nm (1.6 eV). We demonstrate pseudodirect (Gamma(8c)-Gamma(9v)) to direct ((Gamma 7c-Gamma 9v)) transition crossover through experimental and theoretical approach. Time resolved and temperature dependent photoluminescence measurements were used, which led to the observation of a steep change in carrier lifetime and temperature dependence by respectively one and 3 orders of magnitude in the range 0.28 +/- 0.04

Transition-metal phosphides are deemed as potential alternative to platinum for large-scale and sustainable electrocatalytic hydrogen production from water. In this study, facile preparation of interconnected hollow cobalt monophosphide (CoP) supported on carbon nanotubes is demonstrated and evaluated as a low-cost electrocatalyst for hydrogen evolution reaction. Hexamethylenetetramine is used as a structure-directing agent to guide the formation of interconnected cobalt oxide, which further grows into interconnected hollow CoP. Interconnected and hollow microstructural artifacts impart benign attributes, such as enhanced specific and electrochemically active surface area, low intrinsic charge transfer resistance, high interfacial charge transfer kinetics, and improved mass transport, to the electrocatalyst. As a result, the as-prepared electrode exhibits remarkable electrocatalytic performance, low onset (18 mV) and overpotential (η10 = 73 mV); small Tafel slope (54.6 mV dec-1); and high turnover frequency (0.58 s-1 at η = 73 mV). In addition, the electrode shows excellent electrochemical stability.

Although a photoelectrochemical approach offers one of the most promising processes for solar energy conversion, it still suffers from the unavailability of photocatalysts that can absorb the photons across the ultraviolet–visible region and efficiently generate electron–hole pairs with longer lifetimes. Here, we report the fabrication of heterostructure comprising reduced TiO2 (TiOx) and reduced graphene oxide (RGO) through a facile nonhydrolytic route using benzyl alcohol as a solvent, shape-directing, and a strong reducing agent. Reduction of Ti4+ and graphene oxide was observed in the absence of any additional reducing agent. Nearly monoshaped square nanoplates of TiOx with size in the range of 10–20 nm were formed. Nanoplates consisted of Ti3+ and were capable of absorbing a broad solar spectrum (ultraviolet–visible region). Formation of Ti3+ was confirmed by electron paramagnetic resonance spectroscopy, while a Mott–Schottky plot corroborated the band shift in TiOx. Findings suggest that defects wer...

A series of nanostructured catalysts based on cobalt-modified molybdenum carbides, intended as alternative replacement for platinum has been developed for the hydrogen evolution reaction (HER) from brine. The catalysts were synthesized by simple impregnation of the metal salts on carbon support and followed by pyrolysis in CH4 atmosphere. The obtained catalysts show impressive HER activities in both brine and alkaline media. At current density of −7.0 mA cm−2, the overpotential for Co modified Mo/C catalysts was greater than that obtained with a commercial Pt/C catalyst by 63–89 mV and 15–148 mV for brine and alkaline solution, respectively. Our findings for HER in both media are consistent with electrochemical desorption of hydrogen gas following the Volmer-Heyrovsky mechanism as the rate-determining step. The HER activities of the catalysts were correlated to their high mesopore surface areas with active pores, nanocrystallites, and low charge transfer resistances as confirmed by electrochemical impedance spectroscopy.

In Morocco, the 13-valent pneumococcal conjugate vaccine (PCV-13) was introduced in the national immunization program (NIP) in October 2010 and replaced by the PCV-10 in July 2012. The present study aimed to determine the prevalence of erythromycin-resistant Streptococcus pneumoniae (ERSP) and to analyze the phenotypic and genotypic characteristics of these isolates in Casablanca, Morocco from January 2007 to December 2014. Isolates were obtained from the Microbiology Laboratory of Ibn Rochd University Hospital Centre of Casablanca. Serogrouping was done using Pneumotest Kit and serotyping by the Quellung capsular swelling. Antibiotic susceptibility pattern was determined by disk diffusion and Etest methods. A total of 655S. pneumoniae isolates were collected from 2007 to 2014 from pediatric and adult patients. Fifty-five percent of these isolates were from invasive pneumococcal diseases. Of the 655 isolates, 92 (14%) were ERSP. Globally, the proportion of ERSP from 2007 to 2010 (before vaccination) and from 2011 to 2014 (after vaccination) were 11.6% and 17.2% (p=0.04), respectively. Of the 92 ERSP, 89%, 4% and 7% displayed constitutive MLSB (resistance to macrolide, lincosamide and streptogramin B), inducible MLSB, and M phenotype (resistance to macrolide only), respectively. ERSP genotypic analysis showed that 90.2% carried the ermB gene, 6.5% the mefE gene, and 3.3% both the genes (ermB+mefE). The most prevalent ERSP serotypes were 6B, 19F and 23F before vaccination and 19F, 6B, 6A and 23F after vaccination. Erythromycin resistance among S. pneumoniae is relatively high in Casablanca. The contribution of PCVs to the reduction in antibiotic use is encouraging but this should be accompanied by a rational use of antibiotic.

We have serendipitously facile developed a dual-performing electrocatalyst for oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) by co-doped cobalt and nitrogen on tungsten carbide matrix. Its improved ORR and HER activities in 0.1 M KOH were confirmed using a thin-film rotating ring-disk electrode (TF-RRDE) and electrochemical impedance spectroscopy (EIS). The exchange current density and Tafel slope obtained from EIS data for HER are 1.6 × 10 −2 mA cm −2 . and ∼43 mV dec −1 respectively, suggesting Volmer-Heyrovsky mechanism for HER. In addition to its good durability for both cathodic processes, catalyst shows a 4-electron transfer process for ORR, excellent tolerance towards methanol oxidation, and low H 2 O 2 formation (∼3.0%). At half-wave potential of ∼0.8 V, no significant degradation was observed after 10,000 (0.65 - 1.0 V) potential cycles in oxygen saturated medium. A catalyst of such benign properties is highly indispensable for energy conversion systems.

A systematic theoretical study of the structural and electronic properties of new half-Heusler compounds is performed to find the appropriate target key physical parameters for photovoltaic application. As a result, five ternary half-Heusler compounds ScAgC, YCuC, CaZnC, NaAgO, and LiCuS are studied by density functional theory for potential applications in multi-junction solar cells. The calculated formation enthalpies indicate that these materials are thermodynamically stable. Using state-of-the-art modified Becke–Johnson exchange potential approximation, we find a direct band gap close to 1 eV (1.88 eV) for ScAgC, YCuC, CaZnC, NaAgO (LiCuS) being quasi-lattice matched to GaAs (Si). In addition, the band offsets between half-Heusler compounds and GaAs (Si) and their consequences for heterostructures are derived using the modified Tersoff method for the branch-point energy. Furthermore, the elastic constants and phonon dispersion curves are calculated. They indicate the respective mechanical and dynamical stability of these half-Heusler compounds.

Nitrogen functionalities such as pyridinic-nitrogen, pyrrolic-nitrogen and graphitic-nitrogen based active sites are commonly produced when nitrogen precursors are pyrolyzed on carbon matrix. In this study, we demonstrate two catalysts prepared via pyrolysis of Polyaniline and Vinazene with carbon. Their excellent Oxygen reduction reaction (ORR) activities and potential cycling stability were confirmed using thin film rotating ring-disk electrode (RRDE) in 0.1 M KOH and 0.1 M HClO 4 . Structural-performance correlation analysis confirms that not only graphitic nitrogen is responsible for high ORR, but also other nitrogen functions including pyrrolic one. However, catalyst that is rich in graphitic-N shows more stability especially in acidic medium.

Large-scale production of H2 by electrochemical water splitting is discerned as one of the most economical and viable approaches and designing Pt-less electrocatalysts remains at the forefront of this technology development. Herein, in situ transformation of metal–organic frameworks (MOF), impregnated with a molybdenum precursor, into a porous and rigid carbon support and molybdenum carbide (Mo2C) was demonstrated to fabricate highly active and stable β-Mo2C/C heterostructure for electrocatalytic H2 evolution. The two-step synthesis approach involved the impregnation of molybdenum source into frameworks of MOF (namely MIL-53(Al)) followed by nucleation and growth of Mo2C nanocrystals into confined porous texture through carburization. Characterization revealed the formation of mesoporous carbon embodied with crystalline nanoparticles of β-Mo2C (between 5 and 10 nm). A probable mechanism for the formation of Mo2C/C nanocomposite is proposed. The propensity of the catalyst was tested towards the electrocatalytic H2 evolution reaction (HER) under alkaline aqueous media (1 M KOH). The electrocatalyst showed a remarkable HER activity as compared to the benchmark electrocatalyst Pt/C and Mo2C/XC72 black catalysts at 10 mA cm−2 and stability for 20 h at the same current density. Electrochemical impedance spectroscopy results of Mo2C/C were construed by two time constants, porosity and charge transfer, and the HER reaction followed the Volmer–Heyrovsky mechanism.

Novel indium oxide (In 2 O 3 ) nanobricks have been prepared by template-less and surfactant-free hydrothermal synthesis method and were characterized by X-ray diffraction (XRD), Raman spectroscopy, photoluminescence (PL) spectroscopy and field emission scanning electronic microscopy (FESEM). The synthesized In 2 O 3 nanobricks were successfully immobilized on the surface of glassy carbon electrode for the detection of Parabens (butylparaben). Owing to the unique structure and intriguing properties of these In 2 O 3 nanobricks, the nanostructured thin-film electrode has shown an obvious electrocatalytic activity for the detection of butylparaben (BP). The detection limit (LOD) was estimated as 3 s/m and the sensitivity (LOQ) was calculated as 10 s/m and were found to be 0.08 μM and 0.26 μA μM −1 cm −2 respectively. This sensor showed high sensitivity compared with the reported electrochemical sensors for the detection of BP. The fabricated sensor was successfully applied for the detection of butyl paraben in real cosmetic samples with good recovery ranging from 96.0 to 100.3%.

The co-doping effect of a rare earth (RE) metal and a transition metal (TM) on ceria oxidation catalysis through the evaluation of samarium-copper co-doped catalysts with Ce-Sm-xCu-O (x: 0–20 at.%, Ce/Sm = 1) nominal compositions, is discussed. The CO oxidation reaction was used as a prototype reaction due to its pivotal role in the fuel cell technology. Ce-Sm-20Cu-O catalyst presented a 64% increase in the CO oxidation activity compared to that of pristine ceria. Diffraction and Raman studies proved that the Cu, Sm co-doping induces many defects related to the dopants (Sm, Cu) and the oxygen vacant sites, while the presence of hybrid CuO/Ce-Sm(Cu)-O fluorite/SmO8 (cubic metastable) phases is the most representative scenario of this oxide microstructure. A size polydispersity of CuO phases was achieved by introducing air cooling during the microwave heating. Cu, Sm atoms were uniformly doped in CeO2 structure according to the HAADF-STEM studies. These results are in agreement with EDS analysis, where Cu, Sm and Ce are located in all the analyzed areas without any preferential distribution. The XPS studies demonstrated the co-presence of Cu2+/Cu1+ and Ce4+/Ce3+ redox couples in agreement with the Bader charge analysis from the ab initio calculations, the latter influencing greatly the oxidation activity of the catalysts. Density functional theory (DFT) calculations shed light on the oxide surface and the underlying mechanism governing the oxidation catalysis taking place. In particular, Cu2+ and Sm3+ dopants were found to be located in the nearest neighbor (NN) sites of oxygen vacancies. Different oxygen vacancies configurations were studied (single vs. double, surface vs. subsurface), where the single vacancies are more stable on the surface, whereas the double vacancies configurations are more stable on the subsurface. Regarding the Ce3+ location, in the presence of single and double oxygen vacancy, the Ce3+ ions prefer to be located in the 1st NN/2nd NN and 2nd NN of the first Ce layer, relative to the oxygen vacancy, respectively. The total Density of States (DOS) analysis of the co-doped systems revealed that the dopants induced new surface states inside the ceria band gap, which can accommodate the unpaired electrons of the vacant oxygen sites. These electronic modifications justify the much lower energy of oxygen vacancy formation (Evf) in both cases, the Sm-doped, and Cu, Sm -doped CeO2 (1 1 1) geometries. Specifically, the Evf lowering upon doping was found to be almost two times larger for the Cu adjacent oxygen vacancies (Cu2+-□) compared to the Sm ones (Sm3+-□), consistent with the CO adsorption trend as the Cu-Sm-CeO2 (1 1 1) system is energetically more favorable than the Sm-CeO2 (1 1 1) and pure CeO2 (1 1 1) surfaces.

Objectives This study aimed to investigate the nature of the amino acid motifs found in PBPs of Streptococcus pneumoniae isolates in invasive diseases from pediatric patients at Casablanca, Morocco. Five penicillin-susceptible (PSSP), ten penicillin-intermediate (PISP), and fifteen penicillin-resistant S. pneumoniae (PRSP) were studied by PCR–RFLP and DNA sequencing of the pbp1a, − 2b, and − 2x genes. Results There were no changes in the conserved motifs of PBP1a, PBP2b and PBP2x for PSSP strains. Substitution close to PBP1a conserved motifs were found in all PRSP isolates and six/five PISP. Analysis of PBP2b showed that all but one of the 10 PISP strains and all PRSP had substitutions. Substitution close to PBP2x motifs showed that all but three of the 10 PISP strains and all PRSP had substitutions in tow conserved motifs. A total of 6, 11 and 10 genotypes were found after analysis of pbp1a, pbp2b, and pbp2x, respectively. The penicillin-nonsusceptible S. pneumoniae isolated in Casablanca share most amino acid substitutions of those reported worldwide, but they occurred among pneumococci with low level resistance to b-lactams.

Direct methanol fuel cells (DMFCs) proved to be an auspicious choice in the applications of portable power electronics and energy transportation, apart from their high cost catalysts materials. To this end, we have developed precious metal free low-cost active anode materials for DMFCs. Three metals composite (Ni, Cu, and Mo) based electrocatalyst on a multi-walled carbon nanotubes (MWCNTs) support were prepared. The sequential wetness impregnation at different temperatures method combined with a freeze-drying procedure was used to dope the metals nanoparticles on the carbon nanotube. Their compositions and textures were characterized using powder X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray (EDX) detector, elemental mapping, transmission electron microscopy (TEM), high resolution TEM and inductively coupled plasma-mass spectroscopy (ICP-MS). The electrochemical behavior of the prepared electrocatalysts for methanol oxidation was investigated in alkaline media. Cyclic voltammetry (CV) measurements indicate that the catalyst containing 80% of Ni, 10% of Cu and 10% of Mo shows a better electrocatalytic activity than those of other composites in present work. Also the incorporated co-catalysts (Mo and Cu) contribute significantly to the electrocatalytic activity along with Ni via Ni?Cu and Ni?Mo interfaces. The effect of scan rate and methanol concentration was also studied to evaluate the adsorption and oxidation of methanol molecules on the surface of catalyst. The chronoamperometry (CA) was used to evaluate the stability and durability of the as-synthesized Ni/Cu/Mo@MWCNTs catalyst. ? 2018 Elsevier B.V. This work has been financially supported by King Abdulaziz City for Science and Technology (KACST) through the Science Technology Unit at King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia through Project No. 10-ENE-1374 as part of the National Science, Technology and Innovation Plan (NSTIP). Appendix A Scopus

Monoclinic WO 3 nanocuboids with preferred texturing in the plane were synthesized hydrothermally using oxalic acid as the structure-directing agent. The faceted WO 3 showed excellent photoelectrochemical oxidation of H 2 O and photocatalytic removal of methyl-tertiary-butyl ether, better than that of its non-faceted counterpart. Improved catalytic activity of nanocuboids is attributed to its surface structure and wettability.

Due to exciting catalytic activity and selectivity, tailoring of nanocatalysts consisting of preferred crystal facets and desired structural properties remains at the forefront of materials engineering. A facile one-step nonhydrolytic solvothermal synthesis of a nanocomposite of reduced graphene oxide and one-dimensional nitrogen-doped Nb2O5 (N-NbOx) with exposed ⟨001⟩ facet is described. Triethylamine performed the dual role as nitrogen source and capping agent to control the size and unidirectional growth of Nb2O5 nanocrystallites. The nanocomposite showed efficient visible-light-mediated (λ > 420 nm) water splitting in a photoelectrochemical cell. A plausible mechanism for the formation of N-NbOx nanorods and improved photoelectrochemical efficacy in terms of their oriented growth is proposed.

The 2-vinyl-4, 5-dicyanoimidazole (Vinazene) was used as a nitrogen precursor to synthesize a promising non-precious metal (NPM) catalyst for oxygen reduction reaction (ORR). Vinazene together with an iron source was impregnated into a carbon matrix and pyrolyzed at 900 °C in N 2 atmosphere. The structure of the resulting Fe–N–C nanocomposite was analyzed by X-ray photoelectron spectroscopy, Raman spectroscopy and X-ray diffraction. Both rotating disk electrode (RDE) and rotating ring-disk electrode (RRDE) experiments showed excellent ORR activity for the obtained catalyst with low H 2 O 2 formation (∼3.0%) in 0.1 M KOH. The catalyst was found to be rich in mesoporous structure along with high percentage of pyrrolic-N function with surface area of about 673 m 2 g −1 and pore size of 4.2 nm. In addition to its excellent ORR activity, the catalyst showed remarkable tolerance towards methanol oxidation and demonstrates good stability over 10,000 potential cycles (0.6–1.0 V Vs RHE). We believe that this N-rich Vinazene molecule will be beneficial to further development of nitrogen doped carbon electrocatalysts.

Non-precious metal (NPM) catalysts are synthesized by polymerizing aniline salt using an aqueous Fe 3+ /H 2 O 2 coupled catalytic system on a carbon matrix with a porous creating agent. The sulfur containing compunds such as ammonium peroxydisulfate, are eliminated in this method resulting in a much simpler process. The catalysts’ porous structures are enhanced with ammonium carbonate as a sacrificial material that yields voids when decomposed during the heat treatment at 900 °C in N 2 atmosphere. Two catalysts Fe-N-C/Vu and Fe-N-C/KB (Vu = Vulcan and KB = Ketjen black) were synthesized and characterized. Their oxygen reduction reaction (ORR) activities were investigated using a rotating ring-disk electrode (RRDE) in both 0.1 M KOH and 0.1 M HClO 4 . The catalysts show improved ORR activities close to that of Pt-based catalysts, low H 2 O 2 formation and also demonstrated a remarkable tolerance towards methanol oxidation.

The effect of synthesis parameters on morphology of ZSM-12 (MTW) zeolite with tetra ethyl ammonium bromide (TEABr) as an organic-structure directing agent was investigated systematically. Aluminum sulfate octahydrate (Al 2 (SO 4 ) 3 ·18H 2 O) was used as an aluminum (Al) source. The Si/Al ratio was varied from 40 to 180 and alkalinity ratio (NaOH/Si) was set between 0.132 and 0.160. Effects of crystallization temperature and time were studied. The contribution of the aging period on the final morphology of ZSM-12 was investigated in the range of 1.5–6 h. Phase identification of as-synthesized ZSM-12 was confirmed by X-ray diffraction and morphology of crystals was studied by electron microscopy. The alkalinity was one of the most substantial factors that induced the formation of ZSM-5 (MFI) nuclei as a competing phase. Pure ZSM-12 was obtained with Si/Al of 80 at 145 °C. Different agglomeration shapes of ZSM-12 were observed by changing Si/Al ratio. Prolonged aging time up to 6 h induced the formation of ZSM-5 nuclei.

Synthesis of mesoporous nanocrystalline iron-doped titania following the sol–gel method is presented in this work. Samples with various molar ratios (0.1, 0.25, 0.5, 1.0, 2.5, 5.0, 10 and 20%) of Fe to Ti were prepared. The particle size was found to be in the range of ∼12 nm while mesopores were approximately near to ∼5.5 nm. The effect of Fe as doping element on titania properties, such as crystallite size, surface area, pore size, pore volume and d-spacing was investigated. Moreover, distribution of Fe in TiO2 matrix was determined by elemental mapping whereas change in absorption properties was evaluated by diffuse reflectance spectroscopy. It was observed that as the Fe content was increased, a partial phase transformation from anatase to rutile and pseudorutile took place. Effect of ultraviolet, ultraviolet-visible and visible radiations on the photocatalytic activity of these catalysts was studied by removal of Methyl Orange as model pollutant. As results, it was found that the photocatalytic activity of such catalysts depends strongly on Fe amount and type of radiation.

The chemical composition of the essential oils and hydrosol extract from aerial parts of Calendula arvensis L. was investigated using GC-FID and GC/MS. Intra-species variations of the chemical compositions of essential oils from 18 Algerian sample locations were investigated using statistical analysis. Chemical analysis allowed the identification of 53 compounds amounting to 92.3 - 98.5% with yields varied of 0.09 - 0.36% and the main compounds were zingiberenol 1 (8.7 - 29.8%), eremoligenol (4.2 - 12.5%), β-curcumene (2.1 - 12.5%), zingiberenol 2 (4.6 - 19.8%) and (E,Z)-farnesol (3.5 - 23.4%). The study of the chemical variability of essential oils allowed the discrimination of two main clusters confirming that there is a relation between the essential oil compositions and the harvest locations. Different concentrations of essential oil and hydrosol extract were prepared and their antioxidant activity were assessed using three methods (2,2-diphenyl-1-picrylhydrazyl, Ferric-Reducing Antioxidant Power Assay and β-carotene). The results showed that hydrosol extract presented an interesting antioxidant activity. The in vitro antifungal activity of hydrosol extract produced the best antifungal inhibition against Penicillium expansum and Aspergillus niger, while, essential oil was inhibitory at relatively higher concentrations. Results showed that the treatments of pear fruits with essential oil and hydrosol extract presented a very interesting protective activity on disease severity of pears caused by P. expansum.

An iron-based non-precious metal (NPM) catalyst was synthesized by chemically coating a polymer containing nitrogen, such as polyaniline (PANI), on multiwalled carbon nanotubes (MWCNTs), followed by iron complexation and heat treatment in a decomposable source of nitrogen (ammonia) at high temperature. Its excellent activities for oxygen reduction reaction (ORR) in both acidic and alkaline media were confirmed by thin film rotating disk electrode technique. Also, durability test was performed in both media. After 20,000 (0.65–1.0 V) potential cycles, the half-wave potential decayed by only 40 mV in 0.1 M HClO 4 , while in 0.1 M KOH it gained 25 mV. In addition, no activity decay was observed by adding methanol in the acidic solution indicating its excellent tolerance to methanol oxidation.

The surge in the field of renewable energy aiming to develop clean energy technology is continuing to rise. Quest for a H2-based economy derived from non-fossil resources remains at the forefront of future fuels. During the past few decades there has been intense research on the utilization of electrical energy to produce H2 in an energy efficient and environmentally benign way. Electrocatalytic hydrogen generation via water electrolysis provides an important alternative to that extracted from hydrocarbon resources. One of the most crucial components which could revolutionize H2 production is that the design and development of a novel electrocatalyst that can efficiently split water to generate H2. Currently, platinum (Pt) is known as the state-of-the art electrocatalyst for hydrogen evolution reaction (HER). However, due to cost and scarcity of Pt, research focus shifted to precious-metal-free based materials for efficient HER reaction. As results, a wide variety of transition-metal-based electrocatalysts have been developed and investigated. To this end and due to unique d-band electronic structure, Mo-based electrocatalyst such as, Mo2C and MoS2 has been the subject of intense investigation for HER reaction. Yet, functional and robust catalysts operating with reasonable current densities (J) at low overpotential in brine water are still scarce.Herein, we demonstrate a facile synthesis of β-Mo2C embedded on mesoporous carbon support; Metal Organic Framework (MIL 53(Al)) was utilized as a novel source for mesoporous carbon support. Microscopic studies revealed the formation of monodisperse Mo2C with

We report first-principles calculations of the structural, lattice-dynamical and dielectric properties for zinc-blend beryllium chalcogenides: BeS, BeSe, and BeTe. The ground state properties, such as the lattice structure and bulk modulus, are calculated using a plane wave pseudopotential method within the density functional theory. A linear response approach is employed in order to derive the high-frequency dielectric constants, Born effective charges and phonon frequencies. Furthermore, the pressure dependence of phonon modes is also detailed.

We present first-principles results obtained within the framework of density functional theory referring to Mg adsorption and its incorporation in two distinct InN surfaces ((0 0 0 1), ( 0 0 0 1 ¯ ) ) under various adsorption coverage conditions. In all deposition cases we deducted the bonding characteristics and the electronic character of the structures. It is found that in In rich conditions N-polarity facilitates the diffusion of In and Mg adatoms while In-polarity facilitated the Mg-induced weakening of adatom (In, Mg)–surface interactions for small doses of Mg. This implies that the Mg dopant decreases In and Mg diffusion barrier leading to smoother surfaces. Interestingly, we found significant differences of Mg incorporation in In- and N-polar surfaces: Mg incorporation is easier in bare N-polar than in the In-polar surface, except when an In contracted bilayer is formed on top of the InN. In the case of In-polarity, Mg impurities start to penetrate in the subsurface region as the Mg coverage increases. In the contracted In bilayer case, Mg incorporation in the InN is significantly enhanced. Furthermore, we found that the presence of Mg close to the ( 0 0 0 1 ¯ ) InN surface does not alter significantly the local structure, contrary to the In-polarity case in which a flattening of the bilayers is observed at the highest Mg coverage that may lead to the formation of basal inversion domain boundaries.

Adhesively bonded composite patch repair has been widely used to restore or extend the service life of cracked structural components due to its effectiveness to mechanical repair technique. In this work, the finite element method is applied to analyse the performance of the bonded composite patch for repairing cracks emanating from semicircular notch root in pure mode II. The stress intensity factor was computed at the crack tip repaired using a boron/epoxy patch for different orientation of fibers, taking into account the disbond. In this case, the increase of a patch thickness reduces the negative effects of disbond. When this effect is significant between the patch and the plate, it reduces the repair effectiveness. The maximum reduction obtained by using a boron/epoxy of fibers in the x-direction is of the order of 20% more important compared to a patch having its fibers in the y-direction. The stress intensity factor exhibits an asymptotic behaviour as the disbond size increases.

A significant problem hindering large-scale implementation of proton exchange membrane (PEM) fuel cell technology is the loss of performance during extended operation and automotive cycling. Recent investigations of the deterioration of cell performance have revealed that a considerable part of the performance loss is due to the degradation of the electrocatalyst. In this study, an attempt is made to experimentally simulate the degradation processes such as carbon corrosion and platinum (Pt) surface area loss using an accelerated thermal sintering protocol. Two types of Tanaka fuel cell catalyst samples were heat-treated at 250 °C in humidified helium (He) gas streams and several oxygen (O2) concentrations. The catalysts were then cycled electrochemically in pellet electrodes to determine the hydrogen adsorption (HAD) area and its evolution in subsequent electrochemical cycling. Samples that had undergone different degrees of carbon corrosion and Pt sintering were characterized for changes in carbon mass, active Pt surface area, BET (Brunauer, Emmett and Teller) surface area, and Pt crystallite size. Studies of the effect of oxygen and water concentration on two Tanaka catalysts, dispersed on carbon supports with varying BET areas, revealed that carbon oxidation in the presence of Pt follows two pathways: an oxygen pathway that leads to mass loss due to formation of gaseous products, and a water pathway that results in mass gains, especially for high BET area supports. These processes may be assisted by the formation of highly reactive OH and OOH type radicals. Platinum surface area loss, measured at varying oxygen concentrations and as a function of sintering time using X-ray diffraction (XRD), CO chemisorption, and electrochemical hydrogen adsorption, reveal an important role for carbon corrosion rather than an increase in Pt particle size for the surface area loss. Platinum surface area loss during 10 h of thermal degradation was equivalent to electrochemical degradation observed over 500 cycles for a Tanaka Pt/Vulcan electrode cycled between 0 and 1.2 V (normal hydrogen electrode-NHE). Carbon mass loss observed for 5 h of thermal degradation was comparable to that obtained during a potential hold for 86 h at 1.2 V (NHE) and 95 °C for the same catalysts.

In a wiped film apparatus, the hydrodynamic conditions of the flow have a direct effect on the film thickness and on the residence time of the molecules and thus on the effectiveness of mass and heat transfer. Measurements of the residence time distribution (RTD), for different stirring velocities, allowed to propose a model for the flow as a series of perfectly mixed cells in parallel with a series of perfectly mixed cells exchanging mass with a dead zone.

A sample of an Algerian diatomite is characterized and treated in order to use it as gas chromatographic solid column support. This sample has been characterized by various analytical methods such as X-ray diffraction, scanning electron microscopy (SEM), atomic absorption and emission spectrometries and mercury porosimetry. Tests of separation of various hydrocarbon and alcohol mixtures have been performed. Results show that the prepared supports have similar performances than those of commercial products. On the other hand, enrichment process does not show any significant increase in the support quality.

Rosemary oil may be isolated by three different processes, including steam distillation, water distillation and controlled instantaneous decompression. The concrete resulting from extraction by volatile organic solvents was also made using hexane, dichloromethane and ethanol. The oils and extracts obtained were analyzed by gas chromatography (GC) and gas chromatography coupled to mass spectroscopy (GC/MS) in order to determine their chemical composition. A scanning electron microscope was used to observe the impact of different processes on the structure of leaves and essential oil bearing trichomes.

Coriander seeds oil may be extracted by various processes such as hydrodistillation and solvent extraction. The concrete was obtained by extraction using hexane and ethanol as solvents. The oil and extracts were analysed by gas chromatography and gas chromatog-raphy coupled to mass spectroscopy in order to determine their chemical composition. The impact of different processes on the structure of seeds has been observed by the use of a microscope.

Rosemary oil was extracted by both steam and hydrodistillations then analysed by gas chromato- graphy and gas chromatography-mass spectrometry. The effect of time of extraction enabled us to follow the evolu- tion of the yield and oil composition obtained by both processes. Copyright © 2003 John Wiley & Sons, Ltd.

We present first-principles pseudopotential plane-wave calculations to explore the effects of alloying of non conventional III–V compound GaN with bismuth. We found a highly nonlinear reduction of the energy gap of GaN for small Bi composition. Consequently the optical band gap bowing is found extremely important and composition dependent. The stronger contribution is due principally to structural and, to less extent, to charge transfer effects. Moreover, because of strong relativistic effects caused by bismuth, we found a giant bowing for the spin–orbit splitting energy of valence band, by far the largest of any III–V ternary alloys.

Bonded composite patch play an important role for repairing and restoring damage materials. In this study we compare the efficiency between two patches: boron epoxy and carbon epoxy repair in marine structure. The results obtained by finite element show that the two bonded composite patches behave almost the same and reduce the damage zone area, but the boron epoxy patch have a good performance for repairing a long cracks as shown by the obtained results.

Low-pressure structural properties of simple cubic polonium are explored through first-principles density-functional theory based relativistic total energy calculations using pseudopotentials and plane-wave basis set, as well as linear-response theory. We have found that Po undergoes structural phase transition at low pressure near 2 GPa, where the element transforms from simple cubic to a mixture of two trigonal phases namely, hR1 ( α = 86 ° ) and hR2 ( α = 97.9 ° ) structures. The lattice dynamics calculations provide strong support for the observed phase transition, and show the dynamical stability (instability) of the hR2 (hR1) phase.

Germanium powder reacts slowly with 3,5-di-tert-butyl-1,2-benzoquinone (dbbq) in refluxing toluene to give products whose composition depends on the initial mole ratio of the reactants. When Ge ∶ dbbsq = 1 ∶ 2, the solid product is a monoradical + diradical species, but in non-aqueous solvents this converts to a diamagnetic oligomer. Treatment with 2,2′-bipyridine, or monodentate nitrogen donors (= L) gives diamagnetic germanium(IV) derivatives Ge(dbc)2L2 (dbc2− = 3,5-di-tert-butylcatecholate dianion). When the initial Ge ∶ dbbq mole ratio = 1 ∶ 3, the product is the diradical Ge(dbbsq˙)2(dbc). The reaction of Ge and 4 dbbq, or the treatment of GeX4 (X = Cl, Br) with 4 moles of Na(dbbsq˙), gives a product identified as Ge(dbbsq˙)2(dbc)(dbbq), but the structure of this compound is unclear. The solid state and solution properties of these unusual compounds are discussed in the light of 1H NMR and electron spin resonance (ESR) spectroscopy.

The electrochemical oxidation of tris (2,4,6-tri-methyl-phenyl) phosphine (TMP) in acetonitrile was investigated on a platinum electrode. A fast mono-electronic transfer ( E p = 0.71 V vs sce ) gives rise to the corresponding long-lived phosphoniumyl cation radical. This electrochemically generated radical undergoes a slow reaction with residual water, generating the corresponding phosphine oxide (TMPO) and hydro phosphonium (TMPH + ). The kinetics of the decay of the cation radical has been studied, and a reaction mechanism is proposed. When TMP is oxidized on a platinum electrode at potentials higher than 1.5 V vs sce , a fast surface reaction involving residual water takes place. This process was studied by voltammetry at a rotating ring-disk electrode; the same products, TMPO and TMPH + were formed.

Recently several hexagonal polytypes such as 2H, 4H, and 6H have been discovered for conventional III–V semiconductor compounds in addition to the cubic 3C zinc-blende polytype by investigating nanorods grown in the [111] direction in different temperature regimes. Also III-mononitrides crystallizing in the hexagonal 2H wurtzite structure under ambient conditions can be deposited in zinc-blende geometry using various growth techniques. The polytypic crystal structures influence the local electronic properties and the internal electric fields due to the spontaneous polarization in non-cubic crystals.In this paper we give a comprehensive review on the thermodynamic, structural, and electronic properties of twelve Al, Ga, and In antimonides, arsenides, phosphides, and nitrides as derived from ab initio calculations. Their lattice parameters, energetic stability, and characteristic band structure energies are carefully discussed and related to the atomic geometries of the polytypes. Chemical trends are investigated. Band offsets between polytypes and their consequences for heterocrystalline structures are derived. The described properties are discussed in the light of available experimental data and previous computations. Despite several contradictory results in the literature, a unified picture of the III–V polytypes and their heterocrystalline structures is developed.

Moderate-temperature fuel cells are clean power generators for both stationary and mobile applications. In particular, polymer electrolyte membrane fuel cells (PEMCs) have attracted much attention due to their high gravimetric and volumetric power densities. However, due to their acidic environment, platinum-based nanocatalysts are the only feasible electrocatalyts for such systems. High cost and limited resources of this precious metal hinder the commercialization of PEMFCs. As a result, tremendous efforts are being exerted to either reduce Pt loading or substitute Pt metal with other non-noble metals. In this context, metal carbides have been extensively investigated due to their bifunctional mechanism as a catalyst as well as a catalyst support. Hence, the aim of using metal carbides is to replace carbon support since carbon suffers from corrosion problem and at the same time to reduce a substantial amount of Pt in fuel cell cathode. In this chapter, we have given an overview on metal carbides and their benefits as catalyst support for fuel cell cathode reactions.

Highly crystalline and high aspect-ratio ZnO nanotetrapods were grown by a novel and swift microwave synthesis. FESEM analysis revealed that each tetrapod has four thin arms and are derived from the midst of the crystal. The diameter of each arm is larger at the base and smaller at the tip. Structural analysis revealed that these nanotetrapods are single crystalline and have a wurtzite hexagonal crystal structure. These ZnO nanotetrapods were used for the detection of BPA. The electrochemical sensor based on the ZnO nanotetrapods modified electrode showed electrocatalytic activity in terms of significant improvement of the anodic current of BPA and lowering of the detection limit. Under optimized conditions, the squarewave oxidation peak current of BPA was linear over the concentration range of 12.4 nM to 1.2 μM with the detection limit of 1.7 nM and sensitivity of 5.0 μA nM−1 cm−2. This sensor showed high sensitivity and response compared with other electrochemical sensors reported for the detection of BPA.

The Raman and infrared spectra of some polycrystalline substituted pyridine/oxalic acid complexes have been investigated and assignments in terms of group frequencies are given. Various hydrogen bonds (NH⋯O, OH⋯O, OH⋯N) are distinguished and crystal structures are proposed. For the stronger bases (methyl- or aminopyridines with pka ≈ 6) proton transfer occurs. The 1/1 complex contains infinite chains of hydrogen oxalate ions linked by strong OH⋯O hydrogen bonds with vOH between 2000 and 800 cm−1. ROH⋯O distances are 2.47–2.62 A). The substituted pyridinium cations are linked to the chain backbone by medium NH⋯O hydrogen bonds with NH⋯O lengths of 2.71–2.81 A. The 3,5-dichloropyridine forms a 2/1 adduct without proton transfer, in accordance with its pka (0.6), and strong OH⋯N hydrogen bonds occur (vOH about 2000 cm−1 and R OH⋯N = 2.65 A ). Finally, the 2,6-dihalogenopyridine derivatives do not form complex with oxalic acid, presumably because of steric hindrance.