Vertebrate Herbivory on Eucalyptus—Identification of Specific Feeding Deterrents for Common Ringtail Possums (Pseudocheirus peregrinus) by Bioassay-Guided Fractionation of Eucalyptus ovata Foliage

Factors determining the acceptance of Eucalyptus ovata foliage by common ringtail possums (Pseudocheirus peregrinus) were studied. Bioassay-guided fractionation was used with foliage from both browser-susceptible and browser-resistant trees to identify the chemical components underlying the resistance. In foliage from browser-resistant trees, the deterrent principles were contained in the base-soluble fraction of the chloroform extract. Further fractionation of this material yielded polar and nonpolar fractions that contained acylphloroglucinol derivatives, and from the polar fraction we isolated macrocarpal G. Addition of this compound to an artificial diet at a concentration of 2.1% of dry matter resulted in a 90% reduction of voluntary food intake compared with solvent-treated controls. This is the first time that a specific compound in Eucalyptus has been shown to inhibit feeding of any marsupial folivore.     

Ozone Degrades Common Herbivore-Induced Plant Volatiles: Does This Affect Herbivore Prey Location by Predators and Parasitoids?

Inducible terpenes and lipoxygenase pathway products, e.g., green-leaf volatiles (GLVs), are emitted by plants in response to herbivory. They are used by carnivorous arthropods to locate prey. These compounds are highly reactive with atmospheric pollutants. We hypothesized that elevated ozone (O₃) may affect chemical communication between plants and natural enemies of herbivores by degrading signal compounds. In this study, we have used two tritrophic systems (Brassica oleracea–Plutella xylostella–Cotesia plutellae and Phaseolus lunatus–Tetranychus urticae–Phytoseiulus persimilis) to show that exposure of plants to moderately enhanced atmospheric O₃ levels (60 and 120 nl l⁻¹) results in complete degradation of most herbivore-induced terpenes and GLVs, which is congruent with our hypothesis. However, orientation behavior of natural enemies was not disrupted by O₃ exposure in either tritrophic system. Other herbivore-induced volatiles, such as benzyl cyanide, a nitrile in cabbage, and methyl salicylate in lima bean, were not significantly reduced in reactions with O₃. We suggest that more atmospherically stable herbivore-induced volatile compounds can provide important long-distance plant-carnivore signals and may be used by natural enemies of herbivores to orientate in O₃-polluted environments.     

Roles of Flavor and Reward Intensities in Acquisition and Generalization of Food Preferences: Do Strong Plant Signals Always Deter Herbivory?

Plants possess a variety of flavor intensities and nutritional qualities that influence diet selection by herbivores. Some studies suggest that herbivores prefer less intense flavors, either in nutritious or toxic foods. However, if flavor preferences are learned, and if they are influenced by flavor-postingestive feedback interactions, then herbivores should form preferences for either weak or strong flavors when they are followed by greater nutrient rewards. We conditioned two groups of lambs with intraruminal infusions of 30 g of starch while they consumed onion-flavored straw at concentrations of 0.5% (group 1) or 4% (group 2). On alternate days, lambs received infusions of 150 g of starch while they consumed onion-flavored straw at concentrations of either 4% (group 1) or 0.5% (group 2). When offered a choice of straw in both flavor concentrations, lambs preferred the concentration—high or low—associated with the higher dose of starch during conditioning (P < 0.05). When offered a choice of onion-flavored straw in four concentrations (0.25, 1, 2, and 5%), lambs in group 1 preferred the highest onion concentration (5%), whereas lambs in group 2 preferred lower onion concentrations (0.25, 1, and 2%) (P < 0.001). the same pattern of preference was maintained when lambs had no food (day 1; no preload), or an energy(day 2; barley preload) or a protein-rich (day 3; alfalfa–soybean preload) meal before testing (P > 0.05). Lambs with no experience of onion or starch (inexperienced lambs) preferred 0.5% onion-flavored straw to 4% onion-flavored straw (P < 0.001), and 1 and 2% onion-flavored straw to 0.5% and 5% onion-flavored straw (P < 0.05). Thus, strong flavors were initially avoided (inexperienced lambs), but they came to be preferred after their association with higher doses of starch (group 1). Collectively, our results suggest that herbivores acquire and generalize preferences for flavor intensities as a function of their previous experience with the quantitative relationship between flavor intensity and nutrient reward. This ability is critical for survival because flavors, nutrients, and toxins all vary in concentrations in different plant species and parts, as well as temporally within a species.     

Ablation of Caterpillar Labial Salivary Glands: Technique for Determining the Role of Saliva in Insect–Plant Interactions

There has been an ardent interest in herbivore saliva due to its roles in inducing plant defenses and its impact on herbivore fitness. Two techniques are described that inhibit the secretion of labial saliva from the caterpillar, Helicoverpa zea, during feeding. The methods rely on cauterizing the caterpillar's spinneret, the principal secretory structure of the labial glands, or surgically removing the labial salivary gland. Both methods successfully inhibit secretion of saliva and the principal salivary enzyme glucose oxidase. Caterpillars with inhibited saliva production feed at similar rates as the untreated caterpillars, pupate, and emerge as adults. Glucose oxidase has been suggested to increase the caterpillar's survival through the suppression of inducible anti-herbivore defenses in plants. Tobacco (Nicotiana tabacum) leaves fed on by caterpillars with ablated salivary glands had significantly higher levels of nicotine, an inducible anti-herbivore defense compound of tobacco, than leaves fed upon by caterpillars with intact labial salivary glands. Tomato (Lycopersicon esculentum) leaves fed upon by caterpillars with suppressed salivary secretions showed greatly reduced evidence of hydrogen peroxide formation compared to leaves fed upon by intact caterpillars. These two methods are useful techniques for determining the role that saliva plays in manipulating plant anti-herbivore defenses.     

Effect of synthesis methods and aging on synthesis of uvarovite garnet by ceramic and sol–gel processes

Abstract

The uvarovite garnet (CaO)₃ (Cr₂O₃ )(SiO₂ )₃ has been synthesised (mineralised with borax to facilitate diffusion of precursors) by several sol–gel methods. Two routes for uvarovite formation have been observed: where CaCrO₄ forms as an intermediate phase; and where metastable pseudowollastonite (α-CaSiO₃ ) forms as an intermediate phase. Synthesis via CaCrO₄ appears to be more reactive in unaged samples. The reactivity of samples can be directly related to the chemical homogeneity of raw powders, and two methods of synthesis, Pechini and alkoxide, were found to stand out for their reactivity. Aging of raw powders for 6 months inhibits nucleation. Consequently, samples without nucleating agents (i.e. chlorides), such as gels from alkoxides, lead to the stabilisation of amorphous material or metastable phases (α-CaSiO₃ ) and, as a result, hinder uvarovite formation. In contrast, aged samples involving heterogeneous nucleation agents, as in the Pechini method with CaCl₂ as precursor, enhance reactivity.     

Effect of solvent and temperature on the preparation of potassium niobate by hydrothermal-assisted sol–gel processing

In this study the preparation of potassium niobate powder, a material with high electro-optic and nonlinear optical coefficients, by hydrothermal-assisted sol–gel processing from potassium-niobium ethoxide [KNb(OC₂H₅)₆] have been performed. The development of potassium niobate phases by hydrothermal hydrolysis of potassium niobium ethoxide at 100 and 200 °C in ethanol, toluene, and a mixture of benzene and ethanol was pursued by X-ray diffraction. Selected powders obtained from hydrothermal-assisted sol–gel processing were characterized by X-ray powder diffraction, thermal analysis (TGA/DSC), and scanning electron microscopy (SEM). X-ray diffraction results showed that the hydrothermal hydrolysis of potassium-niobium ethoxide in ethanol at 100 and 200 °C results in the formation of cubic phase KNbO₃. Hydrolysis in a mixture of benzene/ethanol and toluene at 200 °C produces an orthorhombic phase KNbO₃, which is a mixture of the potassium deficient phase, K₄Nb₆O₁₇, and cubic and orthorhombic KNbO₃ phases. The potassium niobate powder prepared by the hydrothermal method had the advantage of low weight loss during calcination. SEM micrographs showed that the shape of particles prepared by hydrothermal-assisted sol–gel processing is more uniform when compared with the sample prepared by conventional sol–gel processing.     

Effect of applied voltage on wetting and corrosion of corundum refractory by CaO–SiO2–MgO molten slag

The wetting and corrosion behavior of the corundum substrate anode by CaO–SiO₂–MgO molten slag was investigated via the joint application of the sessile drop method with applied voltage and SEM-EDS technique. The slag drop exhibited a good wettability on the corundum substrate. The apparent contact angle at zero voltage slightly exceeded that at a 1 V applied voltage but was lower than those at 1.5 V and 2 V ones. Low applied voltage of 1 V had little effect on the corundum substrate's direct dissolution corrosion processes; high ones of not less than 1.5 V caused the electrode reaction to occur. The stirring effect of O₂ bubbles from the anode reaction aggravated the substrate's direct dissolution and physical stripping. It was found that the applied voltage could inhibit the slag penetration, and the apparent contact angle had no obvious relation with the direct dissolution thickness and penetration depth. A thin but almost continuous MgO?Al₂O₃ (MA) layer could form at the slag/substrate interface at the applied voltage of 1.5 V. These results indicate the positive effect of applied voltage on the distribution of interfacial products and the molten slag penetration in reducing the corrosion of corundum anode under certain conditions. However, when the applied voltage was too high, the vigorous electrode reaction could aggravate the direct dissolution and physical stripping of the corundum anode, and damage the continuation of the formed interface product layer with a high melting point.     

Effect of yttria on crystallization and microstructure of an alumina–YAG fiber prepared by aqueous sol–gel process

Continuous fiber development is needed for high performance and high temperature composites. Various methods have been used to make ceramic fibers. In this research, composite fibers (yttrium aluminum garnet (YAG)/Al₂O₃) were prepared by a sol–gel method using aqueous solution. They were synthesized from aluminum salt, aluminum metal, yttrium oxide and water used as solvent. Transparent gel fibers were obtained by immersing a thin wire into the viscous sol, then pulling it out by hand. The obtained fibers contained very fine grains with diameter ranging from 10 to 80 μm after heat treatment. When yttria content was increased, the crystallization of YAG shifted to a lower temperature, whereas the transformation temperature to α-Al₂O₃ shifted to a higher temperature. Nevertheless, the fibers with different amounts of yttria contained alumina and YAG after heat treatment at 1400 °C. The composite fibers had vermicular structure and were denser than alumina fibers. The yttria percent concerning the limits of this study (≤10 wt%) effected on fiber diameter. As the yttria content was increased, the fiber diameter increased, whereas grain size and densification of the composite fibers decreased.     

Heat Treatment Effect on Lignin and Carbohydrates in Corsican Pine Earlywood and Latewood Studied by PY–GC–MS Technique

Lignin-derived degradation products from non-treated (NT) and heat-treated (T) Corsican pine (Pinus nigra subsp. laricio) obtained by pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS) were investigated, whereby the earlywood (EW) and latewood (LW) parts of the annual ring were considered separately. The data evaluation was done by principal component analysis (PCA) and the Kruskal–Wallis test. There are no differences in the pyrolysis products composition between EW and LW, but NT and T samples were discernible by PCA applied to Py–GC–MS data. Less phenols with longer chains (4-vinylguaiacol, and trans-isoeugenol) than those with shorter chains (guaiacol, 4-methylguaiacol) and an increase of anhydrosugar (AHS) were found among the pyrolysis products after heat treatment. These signs for autocondensation and side chain cleavages in the lignin during heat treatment were more evident in the EW than in the LW and for the crystallization of cellulose. A slight decrease of the carbohydrate/lignin ratio (C/L) after heat treatment indicates a greater degradation of carbohydrates compared to lignin. The relation of pyrolysis products of lignin and mechanical properties of wood was evaluated by regression analysis. An inverse correlation between short-chain phenols and MOE and a direct correlation between long-chain phenols and compression strength was found in case of NT wood, while a weak positive correlation could be observed between short-chain phenols and the density in T wood.     

Effect of SiC nanoparticles on in-situ synthesis of SiC whiskers in corundum–mullite–SiC composites obtained by carbothermal reduction

Corundum–mullite–SiC composites were synthesised using a carbothermal reduction method. The effects of SiC nanoparticles and sintering temperatures on the phase transformation of the composites and the synthesis of SiC whiskers were studied by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Results indicated that corundum, mullite, and SiC whiskers were produced as final products at 1600–1650 °C. SiC whiskers were formed through the vapor–solid mechanism. The added SiC nanoparticles worked as nucleating agents to facilitate the carbothermal reduction of aluminosilicates and formation of SiC whiskers. The sample with the added SiC nanoparticles exhibited a high yield of β-SiC of 17.1%. Furthermore, the SiC nanoparticles decreased the formation temperature of SiC whiskers from the original 1600 °C to 1500 °C, and the porosity of the composites was increased from 56.7% to 64.7% by increasing the partial pressure of SiO gas. This study provides an insight into the more efficient synthesis of composites with SiC whiskers through the carbothermal reduction of aluminosilicates.     

Effect of ethanol addition in gasoline and gasoline–surrogate on soot formation in turbulent spray flames

The effect of ethanol on soot formation has been studied in turbulent spray flames of gasoline/ethanol and gasoline–surrogate/ethanol mixtures containing 10%, 20% and 30% of alcohol in volume. A hybrid burner specially designed to stabilize different liquid fuels flames with identical hydrodynamic conditions has been used. Spatially resolved measurements of soot volume fraction and of soot precursors concentration have been carried out by coupling Laser-Induced Incandescence (LII) at 1064 nm and Laser-Induced Fluorescence (LIF) at 532 nm. Significant reductions of the concentrations of soot and soot precursors have been observed when adding ethanol to gasoline. A similar behaviour has been obtained with a gasoline–surrogate which has been found to reproduce well the sooting propensity of the unleaded gasoline used in this work. The analysis of the correlation existing between the peak soot volume fraction measured in flames and the Threshold Soot Index (TSI) of the different mixtures tested in this work revealed that the effect of ethanol was not only a dilution one but that the oxygen contained in the alcohol also influence the soot formation. Finally, the comparison of the LII fluence curves and time decays obtained in gasoline/ethanol mixtures showed that soot particles oxidized faster when ethanol is added to the base fuel.     

Effect of particle size on microstructural and mechanical properties of UHMWPE–TiO2 composites produced by gelation and crystallization method

In this study, Ultra-high-molecular-weight polyethylene (UHMWPE) in 0.5 wt % concentration—0.5, 1, and 2 wt % nanosized and micron-sized TiO₂ composites were produced via gelation/crystallization method in decalin + antioxidant solution at 150 °C for 45 min by using magnetic stirrer. The gel composites were cooled in an aluminum tray embedded in iced water under ambient conditions and dried in an oven at 130 °C for 90 min to remove any residual trace of decalin and to strengthen the UHWMPE matrix. Scanning electron microscopy–EDS images indicate that TiO₂ particles were integrated well with the polymer matrix. differential scanning calorimetry studies revealed that the crystallinity of pure UHMWPE was calculated as 56% and an increase of 13.32% for micron sized and 19.25% for nano sized TiO₂. Crystalline and amorphous phases of UHMWPE–TiO₂ composites confirmed by Raman are in good agreement with the literature. The elastic modulus of test materials ranged from 610 to 791 MPa for micron sized and raised from 675 to 1085 for nano sized reinforcing agents. Ultimate tensile stress increased about 35% for micron sized and 60% for nano sized weight 1% TiO₂ reinforced composites. Biomineralization tests (performed in stimulated body fluid, at 37 °C and 6.5 pH during 1 month) have shown that produced composites are compatible as acetabular liner replacement for hipjoints due to no accumulation (Ca, P, Na, etc.) on UHMWPE–TiO₂ composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47402.     

Effect of Nano–Magnesium Hydroxide on Mechanical and Flame-Retarding Properties of SBR and PBR: A Comparative Study

Magnesium hydroxide [Mg(OH)₂] is one of the potential inorganic fillers. In this work, nanoparticles (37±5 nm) of the magnesium hydroxide were prepared using matrix-mediated growth and control technique, and their size was confirmed by X-ray diffraction technique. Nano-Mg(OH)₂-SBR and nano-Mg(OH)₂-PBR composites with 2–10% (w/w) filler loading were prepared by compounding on laboratory-scale two-roll mill and a compression molding machine. These composites were tested for tensile and physical properties, and the properties were compared with the composites of commercial Mg(OH)₂. The incorporation of nanofiller improved the properties of nanocomposites.     

Effect of bias voltage on microstructure and phase evolution of Cr–Mo–N coatings by an arc bonded sputter system

Cr–Mo–N hard coatings were deposited on SKD11 and silicon wafer substrates at various substrate bias voltages by hybrid PVD consisting of arc ion plating and unbalanced magnetron sputtering. The results showed that the microstructure, phase evolution, and mechanical properties of the coatings were significantly altered at the different substrate bias voltage ranging from 0 to −400 V. The X-ray diffraction analysis results revealed that most of the diffraction peaks originated from the Cr–N phase. These peaks were observed at lower positions with no substrate bias and were shifted to higher positions with increasing substrate bias power. The preferred orientation of the (200) plane became dominant accompanying the (220) plane as the bias voltage was increased. Maximum hardness of approximately 30 GPa was obtained at a bias voltage of −200 V. Additionally, wear test results reveal that the lowest coefficient of friction, between 0.4 and 0.5, was obtained from the Cr–Mo–N film formed at a bias voltage of −200 V.     

Effect of fiber architecture and density on the ablation behavior of carbon/carbon composites modified by Zr–Ti–C

Three carbon/carbon (C/C) composites modified by Zr–Ti–C, with different fiber architecture in preforms and the same density, were prepared using chemical vapor infiltration and reactive melt infiltration methods. Two other samples with the same architecture in preforms and different density were also fabricated by the same methods. Their ablation behaviors were examined by oxy-acetylene flame. The results showed that the samples with chopped web needled perform had better ablation resistance than that of the samples with needle-integrated and fine-weave pierced perform. In the models of ablation behaviors, the sealing time of pores and gaps on the ablated surfaces has been defined to indirectly estimate the ablation property. The analysis of models also indicated that high density of the composites and appropriate small diameter of bundles of carbon fibers led to the short sealing time and good ablation resistance of the C/C–carbide composites.     

Effect of Si content on the microstructure and properties of Ti–Si–C composite coatings prepared by reactive plasma spraying

In this study, Ti–Si–C composite coatings were synthesized via plasma spraying of agglomerated powders prepared by a spray drying/precursor pyrolysis technology using Ti, Si, and sucrose powders. The influence of Si content, ranging from 0 wt% to 24 wt%, on the microstructure, mechanical properties, and oxidation resistance of the composite coatings was investigated. Results show that the phase composition of the Ti–Si–C composite coatings changes with the increasing Si content. The coatings without Si addition consist of TiC and Ti₃O; the coatings with 6–18 wt% Si are composed of TiC, Ti₅Si₃, and Ti₃O; the coatings with Si content of 24 wt% form only TiC and Ti₅Si₃ phases. As the Si content increases, the hardness of the Ti–Si–C composite coatings increases first and then decreases, depending on the intrinsic hardness of the ceramic phases, the brittleness of Ti₅Si₃, and the defects such as pores and cracks. The Ti–Si–C composite coatings have high wear resistance due to the in-situ synthesized high-hardness TiC and Ti₅Si₃. Owing to the high brittleness of Ti₅Si₃, the increasing Si content leads to higher wear volume loss at room temperature, which can be partially improved in high-temperature wear tests. The oxidation resistance of Ti–Si–C composite coatings increases with the increase of Si content, and the higher the oxidation temperature, the more obvious the influence of the Si addition on oxidation resistance.     

Understanding Trends in Catalytic Activity: The Effect of Adsorbate–Adsorbate Interactions for CO Oxidation Over Transition Metals

Using high temperature CO oxidation as the example, trends in the reactivity of transition metals are discussed on the basis of density functional theory (DFT) calculations. Volcano type relations between the catalytic rate and adsorption energies of important intermediates are introduced and the effect of adsorbate–adsorbate interaction on the trends is discussed. We find that adsorbate–adsorbate interactions significantly increase the activity of strong binding metals (left side of the volcano) but the interactions do not change the relative activity of different metals and have a very small influence on the position of the top of the volcano, that is, on which metal is the best catalyst.     

mPEG–NHS carbonates: Effect of alkyl spacers on the reactivity: Kinetic and mechanistic insights

Nowadays, the chemical conjugation to mPEG, also known as PEGylation, is a well-recognized technology used to improve the pharmaceutical properties of the therapeutic proteins. Over the last 20 years, more than 10 PEGylated macromolecules reached the market with tremendous success, whereas various other bioconjugates are under advanced clinical trials. mPEG–N-hydroxysuccinimidyl carbonate is an important reagent of widespread application for the PEGylation of biomacromolecules. One of the most important challenges in this technology is the development of more selective PEGylation reagents aimed to provide more consistent polymer–protein conjugates. One approach followed to improve the selectivity of PEGylation reagents is the design of less reactive derivatives, for example, by incorporation of alkyl spacers between the polymer chain and the terminal reactive group. In this work, we prepared a family of mPEG–N-hydroxysuccinimidyl carbonates bearing spacers of up to 6 carbon atoms. The kinetics of hydrolysis of the carbonates was studied under different experimental conditions, as a straight measure of the influence of the length of the spacer on the reactivity. By DFT calculations, we propose a detailed mechanism for the hydrolysis reaction. The influence of the length of alkyl spacer on the reactivity of the carbonates and related esters is studied and discussed in detail. Finally, to further evaluate the reactivity, selected N-hydroxysuccinimidyl carbonates were studied in the conjugation reaction of bovine lactoferrin. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47028.     

Deactivation of a Pt/Silica–Alumina Catalyst and Effect on Selectivity in the Hydrocracking of n-Hexadecane

The deactivation behavior of a bifunctional catalyst consisting of platinum on amorphous silica–alumina was studied in the hydrocracking of n-hexadecane. The initial decline in activity and the change in selectivity were monitored at the following reaction conditions: pressure = 30 bar; temperature = 310 °C; hydrogen-to-hexadecane feed molar ratio = 10. Initially, hexadecane conversion and selectivity to cracking products decreased rapidly with time-on-stream, and stabilized after 40 h on stream. This could be related to an initial loss of metal surface area, which decreased the activity of monofunctional hydrogenolysis generating cracking products. The acidic function seemed to be unaffected under these reaction conditions. The stable catalyst was exposed to a lower hydrogen-to-hexadecane ratio to accelerate deactivation by coking. A decline in the activity of both functions was observed. The activity of the acidic function could be almost completely recovered by oxidative regeneration, while the metal activity was only partially recovered.