Comparative Study of Micro- and Nano-structured Coatings for High-Temperature Oxidation in Steam Atmospheres

For many high-temperature applications, coatings are applied in order to protect structural materials against a wide range of different environments: oxidation, metal dusting, sulphidation, molten salts, steam, etc. The resistance achieved by the use of different kind of coatings, such as functionally graded material coatings, has been optimized with the latest designs. In the case of supercritical steam turbines, many attempts have been made in terms of micro-structural coatings design, mainly based on aluminides, and other diffusion coating systems in order to consider alternatives, nano-structured coatings based on Cr and Al compositions and deposited by a physical vapor deposition technique, were assessed to high-temperature oxidation resistance in steam environments. The oxidation kinetics where analyzed for up to 2,000 h at 650 °C by means of gravimetric measurements. The evaporation behavior was also analyzed by thermogravimetric-mass spectrometry. Excellent results where observed for some of the nano-structured coatings tested. Those results where compared to results obtained for micro-structured coatings. Based on that comparison, it was deduced that the nano-structured coatings have a potential application as protective systems in high-temperature steam environments.     

Induction of Vesicle Formation by Exposing Apple Tissue to Vacuum Impregnation

This paper demonstrates that vacuum impregnation of mature apple tissue in the presence of different sugars results in the formation of membrane vesicles inside the cells. Vesiculation is regarded to be a metabolic consequence of the impregnation process. Vesiculation is shown when the endocytic marker FM4-64 was impregnated into the apple tissue together with the sugar solutions. Vesicles were formed at the plasma membrane already 30 min after impregnation and remained inside the cells for at least 24 h, a metabolic process that was inhibited in the presence of chloroquine, a specific endosomic inhibitor. This phenomenon was not dependent on the osmotic strength when sucrose was used for impregnation. However, the vesiculation drastically dropped when a hypertonic trehalose solution was impregnated. We suggest that the impregnated sugars may not totally remain in the extracellular space between the cells, as normally believed, but at least a fraction might be incorporated into the cells.     

Processing influence on dielectric,mechanical, and electrical properties of reduced graphene oxide–TPU nanocomposites

Two different reduced graphene oxides (rGOs) with similar concentration of oxygen and defects and differences in exfoliation were prepared to produce the rGO/thermoplastic polyurethane nanocomposites by solution blending (SB) and melt compounding (MC). Morphology, electrical, and dielectric properties were studied. Large agglomerates have been observed for the composites produced by SB and discrete and low agglomerated rGO particles in the case on the composites produced by MC. These morphological differences justify the observations in hardness, electrical conductivity, and even in the dielectric properties. The composites do not follow Jonscher's universal power law (UPL) and a linear trend between UPL factors (Log A vs n) has been observed for composites produced by SB, however, no trend is observed in the composites produced by MC, being the first time observed. Differences in the tunneling effect and breakage of H-bonds within the polymer can be suggested from the dielectric relaxation characterization. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47220.     

Fujisaki–Okamoto hybrid encryption revisited

At Crypto’99, Fujisaki and Okamoto [11] presented a generic transformation from weak secure asymmetric and symmetric schemes into an IND-CCA hybrid encryption scheme in the Random Oracle Model, which has been extensively used in several cryptographic scenarios. The work we present here forms part of the careful revision of the provable security techniques initiated by Shoup in [25] insofar as we find some ambiguities in the proof of this generic conversion, which can lead to false claims. Consequently, the original conversion is modified and the class of asymmetric primitives that can be used is shortened. Furthermore, the concept of easily verifiable primitive is formalized, showing its connection with the gap problems introduced in [18]. Using these ideas, a completely new security proof for the modified transformation is given, which is phrased using currently widely accepted techniques. The reduction thereby obtained turns out to be tight, enhancing the concrete security claimed in the original work for the easily verifiable primitives. For the remaining primitives, the concrete security is improved at the cost of stronger assumptions. Finally, the resistance of the new conversion against reject timing attacks is addressed.     

Input/Output Decoupling of Square Linear Systems by Dynamic Two‐Parameter Stabilizing Control

Analytical expressions of the free parameters of a two‐parameter stabilizing control (TPSC), solving an input/output (I/O) decoupling problem, are presented, and stability conditions are given. Multi‐input‐multi‐output (MIMO), proper, lumped and linear time invariant (LTI) systems are considered. These systems have stabilizable and detectable realizations. The separation principle is applied to design a dynamic output control in a controller‐observer feedback configuration. The I/O relation of the overall system is equivalent to a subsystem, in which the I/O decoupling problem has a solution. Also, if the state dimension of the plant is even, and is double the input dimension of the plant, then coprime factorizations of the plant used for the stabilizing controllers are proposed. The results are illustrated through an example.     

Mechanical properties of natural hydraulic lime-based mortars

One hundred eighty different mortars made with a natural hydraulic lime (NHL) and different kinds of aggregates were prepared to be used in restoration works. The factors affecting the mechanical behavior have been studied at long-term test. Compressive and flexural strengths of the specimens were discussed according to curing time, binder/aggregate ratios, attributes of the aggregates and porosity.

Three phases of hardening have been established as a function of the chemical composition: C₃S contributes to the strength at early ages. C₂S and the carbonation process give their strengths at long term. Specimens with larger binder amounts have shown higher porosity and strength. The characteristics of the aggregates have been correlated with the strength and porosity. Limestone aggregates contribute to the strength. Rounded-shaped aggregates increasing large pores cause a strength reduction, hence their use is not advisable. Aggregates with small grain size show a good cohesion at the interface improving the strength.     

Bioactive Steroids and Triterpenes from Melilotus messanensis and Their Allelopathic Potential

The aerial parts of Melilotus messanensis (sweet clover) afforded, from moderately and polar bioactive fractions, 11 triterpenes and five steroids. A series of aqueous solutions at 10^–4–10^–9 M of five steroids and nine triterpenes was monitored to test their effects on germination and growth of the monocots Hordeum vulgare and Allium cepa, and the dicots Lactuca sativa (var. nigra and var. romana) and Lycopersicon esculentum. An important stimulatory effect on H. vulgare germination (between 40% and 80% for almost all tested compounds) was observed. Some considerations about the ecological role of triterpenes on M. messanensis are made. In addition to known lupane triterpenes (platanic acid and 3,28,30-lup-20(29)-enetriol), oleanane triterpenes (soyasapogenol B, soyasapogenol G, and messagenolide), a gammacerane triterpene (gammacer-16-en-3-one), five new lupane triterpenes (messagenic acids A–E: (27-cis-4-hydroxycinnamoyloxy)-betulinic acid; 27-(trans-4-hydroxycinnamoyloxy)betulinic acid; 20(S)-3-hydroxy-29-oxolupan-28-oic acid; 3,30-dihydroxylup-20(29)-en-28-oic acid; and 3,20-dihydroxylup-18(19)-en-28-oic acid, respectively), and sterols (-sitosterol, ergosterol peroxide, 7-hydroxysitosterol, 7-hydroxysitosterol, and 7-oxositosterol) were isolated and chemically characterized. Their structures and stereochemistry were elucidated by spectroscopic methods (one- and two-dimensional ¹H and ¹³C NMR, IR, MS).