Improving Tribological Properties of Cast Al-Si Alloys through Application of Wear-Resistant Thermal Spray Coatings

Flame Spray Thermal Spray coatings are low-cost, high-wear surface-treatment technologies. However, little has been reported on their potential effects on cast automotive aluminum alloys. The aim of this research was to investigate the tribological properties of as-sprayed NiCrBSi and WC/12Co Flame Spray coatings applied to two cast aluminum alloys: high-copper LM24 (AlSi8Cu3Fe), and low-copper LM25 (AlSi7Mg). Potential interactions between the mechanical properties of the substrate and the deposited coatings were deemed to be significant. Microstructural, microhardness, friction, and wear (pin-on-disk, microabrasion, Taber abrasion, etc.) results are reported, and the performance differences between coatings on the different substrates were noted. The coefficient of friction was reduced from 0.69-0.72 to 0.12-0.35. Wear (pin-on-disk) was reduced by a factor of 10³-10⁴, which was related to the high surface roughness of the coatings. Microabrasion wear was dependent on coating hardness and applied load. Taber abrasion results showed a strong dependency on the substrate, coating morphology, and homogeneity.     

Changes in kinetic parameters of decomposition of MgH2 destabilized by irradiation with C ions

In attempt to improve desorption behaviour of MgH₂, the influence of well-defined structural changes induced within a thin surface layer of MgH₂ have been investigated. The defects were induced by 30 keV C²⁺ ions irradiation using different fluencies ranging from 10¹²–10¹⁶ ions/cm². The hydrogen desorption properties were investigated by thermal desorption spectroscopy analysis (TDS), while kinetics parameters were deduced using non-isothermal kinetic approach. The existence of multiple TDS peaks and different curve shapes indicate difference in desorption mechanism. To understand changes in the rate limiting step, shapes of all desorption peaks have been analyzed using different kinetic models. Regarding the irradiated sample, the function based on Avrami–Erofeev model with n=4$n=4$ gives the best fit over θ   range from 0.3 to 0.8 while for untreated sample the best fit is obtained for Avrami–Erofeev model with n=3$n=3$. The change in mechanism can be attributed to the different way of nuclei growth.     

Improving conversion efficiency of solar energy to electricity in cyanobacterial PEMFC by high levels of photo-H2 production

In this study, we described an efficient electrical power generating system containing cyanobacterial photo-H₂ production and custom-built proton exchange membrane fuel cell (PEMFC). The filamentous N₂-fixing cyanobacterium Anabaena cylindrica was used as the photo-H₂ producer. A photosynthesis inhibitor-diuron (DCMU) was used for the enhancement of photo-H₂ production in the culture under argon gas. For the first time, a total of 1.0 μM DCMU was found to be the most effective treatment, as this produced 3.6 fold higher levels of H₂ in microalgae. By measuring polarization curve, the gas mixture collected from the culture was proven to be an effective fuel for electrical generation through a custom-built PEMFC. When the PEMFC was directly combined with the culture tube, the cells generated as much as 843 mV during a 5-day incubation due to the efficient conversion of solar energy to H₂ by A. cylindrica. Light energy conversion efficiency (LCE) for both solar energy to H₂ and solar energy to electricity were also determined. The LCE for the cyanobacterial conversion of solar energy to H₂ reached a peak at four days with a maximal value of 2.05% and an average value of 1.70% ± 0.17. The corresponding LCE for the conversion of solar energy to electricity in this system was 1.13% at peak and 0.94% ± 0.09 on average.     

NUMERICAL INVESTIGATION OF HEAT TRANSFER IN INTENSIVE COOLING TUBES WITH TURBULENCE BUSHES

The heat transfer in intensive cooling tubes with turbulence bushes is studied numerically. Based on experimental data, a two-dimensional, two-phase heat transfer model was developed, which describes the coupled temperature fields in the wire and the annulus. Due to the very high wall temperature of the wire and the special flow conditions, convection-controlled film boiling occurs, in which the heat transfer depends mainly on the parameters of single-phase convection. The asymmetric turbulent flow is described by an appropriate one-dimensional model. In order to investigate shape variations of the bushes, additional experiments or two-dimensional flow simulations are required. Therefore, further modeling is focused on the single-phase heat transfer considering the two-dimensional flow. This numerical model is also validated by experimental results. The numerical experiments show the mechanism of the shape influence of the turbulence bushes on the pressure drop and the heat transfer coefficient. They permit optimization of newly designed turbulence bushes and deliver the characteristic bush parameters for the two-phase model.     

Spouted Bed Drying of Milk–Blackberry Pulp: Analysis of Powder Production Efficiency and Powder Characterization

Spouted bed drying of milk–blackberry pulp mixture at different ratios (V/V) was analyzed in this work. The effects of addition of adjuvant (maltodextrin, casein, and palm oil) in the milk–blackberry mixture and maltodextrin in the pure blackberry pulp were analyzed focusing on enhancing powder production efficiency. The best results were obtained for the paste composition of 25% concentrated milk–75% blackberry pulp (V/V) without addition of adjuvant, yielding stable fluid dynamic behavior, powder production efficiency greater than 60%, linear powder production kinetics, high anthocyanin content, and low final moisture content of the powder (3.08% wb).     

Volatile Organic Compounds Induced by Herbivory of the Soybean Looper <Emphasis Type="Italic">Chrysodeixis includens</Emphasis> in Transgenic Glyphosate-Resistant Soybean and the Behavioral Effect on the Parasitoid, <Emphasis Type="Italic">Meteorus rubens</Emphasis>

Transgenic soybean plants (RR) engineered to express resistance to glyphosate harbor a variant of the enzyme EPSPS (5-enolpyruvylshikimate-3-phosphate synthase) involved in the shikimic acid pathway, the biosynthetic route of three aromatic amino acids: phenylalanine, tyrosine, and tryptophan. The insertion of the variant enzyme CP4 EPSPS confers resistance to glyphosate. During the process of genetic engineering, unintended secondary effects are likely to occur. In the present study, we quantified volatile organic compounds (VOCs) emitted constitutively or induced in response to herbivory by the soybean looper Chrysodeixis includens in transgenic soybean and its isogenic (untransformed) line. Since herbivore-induced plant volatiles (HIPVs) are known to play a role in the recruitment of natural enemies, we assessed whether changes in VOC profiles alter the foraging behavior of the generalist endoparasitic larval parasitoid, Meteorus rubens in the transgenic line. Additionally, we assessed whether there was a difference in plant quality by measuring the weight gain of the soybean looper. In response to herbivory, several VOCs were induced in both the conventional and the transgenic line; however, larger quantities of a few compounds were emitted by transgenic plants. Meteorus rubens females were able to discriminate between the odors of undamaged and C. includens-damaged plants in both lines, but preferred the odors emitted by herbivore-damaged transgenic plants over those emitted by herbivore-damaged conventional soybean plants. No differences were observed in the weight gain of the soybean looper. Our results suggest that VOC-mediated tritrophic interactions in this model system are not negatively affected. However, as the preference of the wasps shifted towards damaged transgenic plants, the results also suggest that genetic modification affects that tritrophic interactions in multiple ways in this model system.     

Semirational Protein Engineering of CYP153AM.aq.‐CPRBM3 for Efficient Terminal Hydroxylation of Short‐ to Long‐Chain Fatty Acids

The regioselective terminal hydroxylation of alkanes and fatty acids is of great interest in a variety of industrial applications, such as in cosmetics, in fine chemicals, and in the fragrance industry. The chemically challenging activation and oxidation of non‐activated C?H bonds can be achieved with cytochrome P450 enzymes. CYP153A_M.aq.‐CPR_BM3 is an artificial fusion construct consisting of the heme domain from Marinobacter aquaeolei and the reductase domain of CYP102A1 from Bacillus megaterium. It has the ability to hydroxylate medium‐ and long‐chain fatty acids selectively at their terminal positions. However, the activity of this interesting P450 construct needs to be improved for applications in industrial processes. For this purpose, the design of mutant libraries including two consecutive steps of mutagenesis is demonstrated. Targeted positions and residues chosen for substitution were based on semi‐rational protein design after creation of a homology model of the heme domain of CYP153A_M.aq., sequence alignments, and docking studies. Site‐directed mutagenesis was the preferred method employed to address positions within the binding pocket, whereas diversity was created with the aid of a degenerate codon for amino acids located at the substrate entrance channel. Combining the successful variants led to the identification of a double variant—G307A/S233G—that showed alterations of one position within the binding pocket and one position located in the substrate access channel. This double variant showed twofold increased activity relative to the wild type for the terminal hydroxylation of medium‐chain‐length fatty acids. This variant furthermore showed improved activity towards short‐ and long‐chain fatty acids and enhanced stability in the presence of higher concentrations of fatty acids.