Mo complexes are currently the most active catalysts for nitrogen fixation under ambient conditions. In comparison, tungsten platforms are scarcely examined. For active catalysts, the control of N
...proton reduction selectivities remains a difficult task. We here present N
splitting using a tungsten pincer platform, which has been proposed as the key reaction for catalytic nitrogen fixation. Starting from WCl
(PNP) (PNP = N(CH
CH
P
Bu
)
), the activation of N
enabled the isolation of the dinitrogen bridged redox series (N
){WCl(PNP)}
. Protonation of the neutral complex results either in the formation of a nitride W(N)Cl(
PNP)
or H
evolution and oxidation of the W
N
core, respectively, depending on the acid and reaction conditions. Examination of the nitrogen splitting
proton reduction selectivity emphasizes the role of hydrogen bonding of the conjugate base with the protonated intermediates and provides guidelines for nitrogen fixation.
Aflatoxin, a naturally occurring toxin produced by the fungus
is the most economically important mycotoxin in the world, with harmful effects on human and animal health. Preventive measures such as ...irrigation and planting dates can minimize aflatoxin contamination most years. However, no control strategy is completely effective when environmental conditions are extremely favorable for growth of the fungus. The most effective control method is growing maize hybrids with genetic resistance to aflatoxin contamination. The aim of this research was to evaluate the sensitivity of different maize hybrids to
infection and aflatoxin accumulation. Twenty commercial maize hybrids were evaluated in field trials with artificial inoculations using the colonized toothpicks method. The mycotoxin production potential of
isolates was confirmed by cluster amplification patterns (CAPs) analysis. The results of this research indicated the existence of significant differences in maize hybrids susceptibility to Aspergillus ear rot and aflatoxin B
accumulation. No hybrid included in this research showed complete resistance in all conditions, but some hybrids showed partial resistance. Different hybrids also responded differently depending on the sowing date. This research showed that infection intensity is not always consistent with aflatoxin levels, and therefore visual evaluation is not enough to assess maize safety.
Anionic metal oxide clusters, so‐called polyoxometalates, can be developed as molecular model compounds to mimic the chemical and photochemical reactivity of solid‐state metal oxides on the molecular ...level. Inspired by the well‐known visible‐light photocatalyst BiVO4, the first molecular bismuth vanadium oxide has been synthesized to investigate the chemical and photochemical similarities between the solid‐state and molecular compounds. The cluster H3(Bi(dmso)3)4V13O40⋅ca. 4 DMSO was obtained from simple precursors in almost quantitative yield. Structural analysis showed that the cluster shell is based on the unusual all‐vanadium ε‐Keggin framework ε‐V12O4015−, which is stabilized by coordination of four BiIII centers. The acidic character of the three cluster protons was demonstrated by titration studies. The cluster shows promising photocatalytic properties in visible‐light photooxidation reactions and has high activity (turnover number >1200), high quantum yield (Φ=7.6 %), and good recyclability, which make it a promising first example of a new class of heterometallic polyoxometalates.
An all‐vanadium ε‐Keggin anion ε‐(VO4)V12O3615− is surrounded by a tetrahedral arrangement of four Bi centers in polyoxometalate 1 a, which is the first structurally characterized bismuth vanadium oxide cluster (central V blue, V green, Bi orange). The cluster is acidic and photoactive under visible‐light irradiation, and shows high turnover numbers and good quantum yields in the photooxidation of model pollutant patent blue V (PBV).
The aim of the study was to evaluate the bio-efficacy of two different acaricides against mobile stages of hard ticks
Ixodes ricinus
,
Dermacentor marginatus
, and
Haemaphysalis punctata
in their ...natural habitats. The study was conducted during 2020 and 2021 at localities populated by
I. ricinus
as the predominant species, at which the presence of
Borrelia afzelii
,
Borrelia garinii
, and
Borrelia lusitaniae
was confirmed. During the first investigation year, a combination of two pyrethroids, permethrin, and tetramethrin, with an insecticide synergist piperonyl butoxide (trade name: Perme Plus®) was tested. At the first evaluation, 24 h after the treatment with Perme Plus®, the efficacy expressed as a reduction rate of the population density was within the interval of satisfying performance (70–90%) at all localities, while the highest efficacy (97.8%) was recorded on the 14th post-treatment day. In the second investigation year, the formulation based on lambda-cyhalothrin (trade name: Icon® 10CS) was used. On the first post-treatment evaluation day, satisfying effects were also demonstrated. The highest recorded efficacy rate of lambda-cyhalothrin (94.7%) was recorded on the 14th post-treatment day. Both tested acaricides manifested satisfying initial acaricidal effects against mobile stages of ticks and provided long-term effects. Comparison of the regression trend lines of population reduction revealed that satisfying effects of treatment with Perme Plus® lasted until the 17th post-treatment day, while in the case of Icon® 10CS, the residual effects were significantly prolonged (30 days).
In this research the 3-D transient non-linear thermal analysis of the hard-facing process was performed by using the experimental testing and finite element method. Testing was done at three ...different carbon steels and the obtained results were compared to one obtained by empirical formulas and welding recommendations. Experimental testing was done on hard faced specimens (plates) with different thickness. Temperatures and temperature cycles was measured by using thermocouples in order to determine maximal temperature and cooling time between 800?C and 500?C. After experimental testing the finite element method analysis was done. The simulations were executed on the open source platform Salome using the open source finite element solver Code Aster. The Gaussian double ellipsoid was selected in order to enable greater possibilities for the calculation of the moving heat source. The numerical results were compared with available experimental and mathematical results.
Antibiotics are among the most commonly prescribed drugs in children. Adherence to the treatment with these drugs is of the utmost importance to prevent the emergence of resistant bacteria, a global ...health threat. In children, medicine acceptability is likely to have a significant impact on compliance. Herein we used a multivariate approach, considering simultaneously the many aspects of acceptability to explore the drivers of oral antibiotic acceptability in children under twelve, especially in toddlers and in preschoolers. Based on 628 real-life observer reports of the intake of 133 distinct medicines, the acceptability reference framework highlighted the influence of many factors such as age and sex of patients, previous exposure to treatment, place of administration, administration device, flavor agent in excipients and active pharmaceutical ingredient. These findings from an international observational study emphasize the multidimensional nature of acceptability. Therefore, it is crucial to consider all these different aspects for assessing this multi-faceted concept and designing or prescribing a medicine in order to reach adequate acceptability in the target population.
Various factors of thermo-chemical erosion process in gun steel were analysed. The factors are mainly related to the thermal load of gun barrel inside surface, characteristics of barrel surface and ...chemical interactions between propellant combustion products and barrel surface. The experimental simulation of conditions in gun barrel was carried out by vented vessel firings in the device based on modification of 37 mm M39 gun. The nozzle mass loss during firing was the measure of gun steel erosion. The main thermal factor of erosion is maximum nozzle inner surface temperature. This temperature was determined experimentally by micro thermocouples measurements at specified distance away from the inner surface and by numerical analysis of the inverse heat conduction problem. Modelling of two-phase flow of propellant combustion products and unburned propellant grains in the vented vessel and heat transfer to the nozzle were conducted using developed one-dimensional interior ballistic code and computational fluid dynamics simulation in FLUENT. Influence of different propellants, titanium-dioxide/wax wear reducing liner and tungsten-disulfide nanoparticles layer on nozzle erosion was analysed. Good agreement between experimental and computational results was achieved.
Temperature distribution in the metallic plate influenced by high frequency electromagnetic wave depends on thermal and electrical properties of the plate material. The goal of the paper is to ...present the significance of the temperature dependence of the electrical resistivity and its influence on the plate heating. A mathematical model of the problem was established and an analytical closed-form solution the problem was presented. The active power of the electromagnetic wave was calculated by Poynting vector. Temperature field was obtained by integral-transform technique. Numerical examples were presented for three different materials (copper, aluminum, and steel). Calculated results show the large influence of temperature dependent electrical resistance on heating of the metallic plate.
A theoretical film rupture model was used for computational procedure to predict the crack growth rate within the Stress Corrosion Cracking (SCC) conditions. Chemical, electrochemical and mechanical ...aspects of the SCC were analyzed and set into the computer program to calculate crack growth rate. Extended Finite Element Model (XFEM) was applied to calculate Stress Intensity Factor (SIF) in two loading modes - tensile test specimen and compact tension (CT) specimen. Elastic-plastic fracture mechanics (EPFM) was used for CT specimen. The computational model was verified with experimental results published in literature. Results have shown good agreement in two cases analysed here, stainless and common structural steel, indicating great potential of the XFEM to simulate the crack growth rate within the SCC conditions.
•The damaged jet engine exhaust nozzle’s inner sleeve was analyzed.•Analyzed structure was subjected to thermo-mechanical cyclic loading.•Crack propagation in repaired inner sleeves were simulated ...and analyzed.•It was determined which type of repair gives longer fatigue life for damaged part.
The exhaust nozzle, made of titanium, is the part of a jet engine where the final expansion of the hot gas from the turbine occurs and where the speed of the exhaust gas is further increased to create thrust. During the work, it is exposed to elevated temperatures and compressive and hoop stresses, which makes the cracks’ occurrence in the exhaust nozzle’s inner sleeve unavoidable, making repairs during maintenance necessary. In this study, crack growth in the repaired inner sleeve was analyzed. The aim of the study was to evaluate the fatigue life of the damaged inner sleeve when a new method of repair is applied and to compare obtained number of cycles with the number observed in the maintenance workshop after the old method of repair was used. Developing the numerical model and conducting simulations using the extended finite element method (XFEM) and finite element method (FEM), it was concluded that a new type of repair should be used to provide longer fatigue life of the damaged exhaust nozzle.
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