Direct Metal-Free Transformation of Alkynes to Nitriles: Computational Evidence for the Precise Reaction Mechanism

Density functional theory calculations elucidated the precise reaction mechanism for the conversion of diphenylacetylenes into benzonitriles involving the cleavage of the triple C≡C bond, with N-iodosuccinimide (NIS) as an oxidant and trimethylsilyl azide (TMSN₃) as a nitrogen donor. The reaction requires six steps with the activation barrier ΔG^‡ = 33.5 kcal mol⁻¹ and a highly exergonic reaction free-energy ΔG_R = −191.9 kcal mol⁻¹ in MeCN. Reaction profiles agree with several experimental observations, offering evidence for the formation of molecular I₂, interpreting the necessity to increase the temperature to finalize the reaction, and revealing thermodynamic aspects allowing higher yields for alkynes with para-electron-donating groups. In addition, the proposed mechanism indicates usefulness of this concept for both internal and terminal alkynes, eliminates the option to replace NIS by its Cl- or Br-analogues, and strongly promotes NaN₃ as an alternative to TMSN₃. Lastly, our results advise increasing the solvent polarity as another route to advance this metal-free strategy towards more efficient processes.     

Comparison of different plant layouts and fuel storage solutions for fuel cells utilization on a small ferry

In the path towards the decarbonization of the maritime sector, Low Temperature Polymer Electrolyte Membrane Fuel Cells (LT-PEMFC) fed by hydrogen are gaining attention as they could guarantee zero local emissions propulsion. In this study, a process simulation model is implemented to analyze the influence of peak shaving in a hybrid LT-PEMFC/lithium-ion battery power plant for the propulsion of a small size RoRo car and passenger ferry in different operative conditions. Results show that battery peak shaving could allow a reduction of FC installed power of up to 72%. As for compressed H₂ storage, the results show that for sailing time in the range of 5–10 min, Type I cylinders at 250 bar are a viable option. For longer routes, Type III cylinders at 350 bar or Type IV cylinders at 700 bar should be considered in order to avoid excessive reduction in the pay-load.     

Extraordinary Adaptive Plasticity of Colorado Potato Beetle: “Ten-Striped Spearman” in the Era of Biotechnological Warfare

Expanding from remote areas of Mexico to a worldwide scale, the ten-striped insect, the Colorado potato beetle (CPB, Leptinotarsa decemlineata Say), has risen from being an innocuous beetle to a prominent global pest. A diverse life cycle, phenotypic plasticity, adaptation to adverse conditions, and capability to detoxify or tolerate toxins make this insect appear to be virtually “indestructible”. With increasing advances in molecular biology, tools of biotechnological warfare were deployed to combat CPB. In the last three decades, genetically modified potato has created a new challenge for the beetle. After reviewing hundreds of scientific papers dealing with CPB control, it became clear that even biotechnological means of control, if used alone, would not defeat the Colorado potato beetle. This control measure once again appears to be provoking the potato beetle to exhibit its remarkable adaptability. Nonetheless, the potential for adaptation to these techniques has increased our knowledge of this pest and thus opened possibilities for devising more sustainable CPB management programs.     

Boiling of R134a inside a glass minichannel. A new statistical approach of flow pattern characterization based on flow visualization

A test rig to study R134a flow boiling inside mini and micro-channels has been constructed. The test section is made up of a glass tube and several ITO conductive layers as heaters. A novel image processing technique has been developed for the study of R134a flow boiling regimes. The software routine extracts the bubble contours, measures geometrical features of each frame and collects the data analytically and statistically. The results refer to mass flux between 20 and 122 kg/m² s and the heat flux between 200 and 45,000 W/m², at the saturation temperatures of 20–25 °C. The tube inner diameter is 4 mm and the heated length was globally of 320 mm, distributed in eight shorter heaters of 40 mm each. The main goals are the development of a method that, starting from the analysis of several parameters, is able to identify the flow pattern inside the tube, as well as the study of the effects of coalescence on the flow pattern development along the tube.The flow patterns have been identified from a statistical point of view and the “transition zone” has been quantitatively characterized. Part of the analysis is then devoted to the flow pattern variation along the test section. The experiments demonstrated that coalescence is a phenomenon that can be analyzed also in terms of a statistical approach and that the flow pattern variations are not only a function of the mass flux and the quality, but along the tube bubble coalescence and gravity effects have a role in the flow patterns appearance.     

Integrating the Roles for Cytokinin and Auxin in De Novo Shoot Organogenesis: From Hormone Uptake to Signaling Outputs

De novo shoot organogenesis (DNSO) is a procedure commonly used for the in vitro regeneration of shoots from a variety of plant tissues. Shoot regeneration occurs on nutrient media supplemented with the plant hormones cytokinin (CK) and auxin, which play essential roles in this process, and genes involved in their signaling cascades act as master regulators of the different phases of shoot regeneration. In the last 20 years, the genetic regulation of DNSO has been characterized in detail. However, as of today, the CK and auxin signaling events associated with shoot regeneration are often interpreted as a consequence of these hormones simply being present in the regeneration media, whereas the roles for their prior uptake and transport into the cultivated plant tissues are generally overlooked. Additionally, sucrose, commonly added to the regeneration media as a carbon source, plays a signaling role and has been recently shown to interact with CK and auxin and to affect the efficiency of shoot regeneration. In this review, we provide an integrative interpretation of the roles for CK and auxin in the process of DNSO, adding emphasis on their uptake from the regeneration media and their interaction with sucrose present in the media to their complex signaling outputs that mediate shoot regeneration.     

Influence of Particle Shape on Filtration Processes

The influence of particle shape on filtration processes was investigated. Two types of particles, including spherical polystyrene latex (PSL) and iron oxide, and perfect cubes of magnesium oxide, were examined. It was found that the removal efficiency of spherical particles on fibrous filters is very similar for corresponding sizes within the range of 50–300 nm, regardless of the fact that the densities of PSL and iron oxide differ by a factor of five. On the other hand, the removal efficiency of magnesium oxide cubic particles was measured, and found to be much lower than the removal efficiency for the aerodynamically similar spheres. Such disparity was ascribed to the different nature of the motion of the spherical and cubic particles along the fiber surface, following the initial collision. After touching the fiber surface and before coming to rest, the spherical particles could either slide or roll compared to the cubic ones, which could either slide or tumble. During tumbling, the area of contact between the particle and the fiber changes significantly, thus affecting the bounce probability, whilst for the spheres, the area of contact remains the same for any point of the particle trajectory. The extra probability of particle bounce by the cubes was derived from the experimental data. The particle kinetic energy was proposed to be responsible for the difference in removal efficiency of particles with alternative shapes, if all other process parameters remain the same. The increase in kinetic energy is shown to favor the increase of the bounce probability.     

A neutron balance approach in flux shape control

Among the procedures built to verify the reactor power capability there is the determination of the value of parameters constrained to the control of the neutron flux shape. The most common of this kind of problem is the search of the axial position of a control bank leading the axial offset of the power distribution to a target value. The most used procedures to solve this kind of problem are based on the iterative Newton–Raphson method. We present here another way to solve these problems where an equation, derived from the neutron balance, is set and the parameter controlling the shape is the unknown. This method has the advantage to reduce considerably the computation time in situations where changes on the control parameter induce a high distortion on the flux distribution, as is the case of the control rods. CPU time gains of a factor 3 are attained. As an example the case of control of the axial offset of the power distribution is presented, showing its performance and the gain in stability.     

Occurrence of deoxynivalenol and its 3-β-D-glucoside in wheat and maize

Deoxynivalenol-3-β-D-glucoside (D3G), a phase II plant metabolite of the mycotoxin deoxynivalenol (DON), occurs in naturally Fusarium-contaminated cereals. In order to investigate the frequency of occurrence as well as the relative and absolute concentrations of D3G in naturally infected cereals, 23 wheat samples originating from fields in Austria, Germany and Slovakia as well as 54 maize samples from Austrian fields were analysed for DON and D3G by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Both analytes were detected in all the 77 field samples. DON was found at levels from 42 to 4130 ng g^?1 (977 ± 1000 ng g^?1 on average). The D3G concentrations in all cereal samples were in the range 10–1070 ng g^?1 (216 ± 253 ng g^?1 on average), corresponding to about 5–46 mol% of their DON concentrations (15 ± 8 mol% on average).     

AN UPDATE OF ZINC ION AS AN EFFECTOR OF FLOCCULATION IN BREWER'S YEAST STRAINS

Zn⁺⁺ ion was observed to be a strong effector of the flocculation—deflocculation process in an in vitro system for strains of Saccharomyces cerevisiae at ion concentration ranges that are normal in conventional substrates, such as wort. All strains of Saccharomyces uvarum (carlsbergensis) examined in this study did not exhibit any flocculation response to Zn⁺⁺ ion. This test could be employed to distinguish between ale and lager flocculating yeast strains.