Rebound surface hardness of concrete: Introduction of an empirical constitutive model

Surface hardness testing of concrete is a long established NDT method for in situ strength estimation. Nowadays, the rebound hammer is the surface hardness testing device for concrete of the most widespread use. Based on a comprehensive literature review it was realized that no general theory was developed in the last more than 50 years that could describe the relationship between surface hardness and compressive strength of concrete. The diversity of the numerous empirical proposals that can be found in the technical literature needs to be explained. It can be even found in some publications that the method is suitable only for assessing the uniformity of concrete. There is long a time need for a model that can clarify the rebound surface hardness of concrete. Present paper introduces a phenomenological constitutive model (SBZ-model) that can be formulated for the surface hardness of concrete as a time dependent material property. The generating functions of the model are based on the time dependent development of the capillary pore system of the hardened cement paste in concretes that is characterised by the water–cement ratio as a practical simplification. The modelling assumptions and the use of the model would add to the fundamental understanding of the rebound surface hardness of concrete. An extensive experimental verification study clearly demonstrated the reasonable application possibilities of the SBZ-model.     

Production and Application of Novel Sterol Esterases from <Emphasis Type="Italic">Aspergillus</Emphasis> Strains by Solid State Fermentation

Among numerous mesophilic fungi screened for sterol esterase activity followed by the esterification reaction between plant β-sitosterol and lauric acid in organic solvent, six Aspergillus strains were selected as the most active producers. These fungi had not been studied previously for sterol esterase production. The fungi were cultivated under solid state fermentation (SSF) conditions. The gently dried SSF cultures as such were tested in the esterification reactions, without any special enzyme isolation and purification (downstream) processes. All the six Aspergillus SSF preparations were able to synthesize sterol esters. Sterol esterase activity of these GRAS cleared Aspergillus strains was inducible by sterol ester supplementation to the SSF medium and showed remarkably different moisture optimum during growth as compared to the production of lipase (determined by pNP-palmitate). Genome analysis revealed that sterol esterase production might be a common feature of many Aspergillus species. The synthetic usefulness of the best SSF preparations of A. oryzae NRRL 6270 and A. sojae NRRL 6271 was demonstrated by synthesis of esters of plant sterols with lauric acid resulting in 45–63% conversions (GC) and 27–38% isolated yields of steryl laurates. The isomer preference of A. oryzae NRRL 6270 towards the 10E,12Z isomer of conjugated linoleic acid (CLA) in the esterification reaction with plant sterols was also determined.     

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FROM DISCRETE-TIME MODELS TO CONTINUOUS-TIME, ASYNCHRONOUS MODELING OF FINANCIAL MARKETS

Most agent-based simulation models of financial markets are discrete-time in nature. In this paper, we investigate to what degree such models are extensible to continuous-time, asynchronous modeling of financial markets. We study the behavior of a learning market maker in a market with information asymmetry, and investigate the difference caused in the market dynamics between the discrete-time simulation and continuous-time, asynchronous simulation. We show that the characteristics of the market prices are different in the two cases, and observe that additional information is being revealed in the continuous-time, asynchronous models, which can be acted upon by the agents in such models. Because most financial markets are continuous and asynchronous in nature, our results indicate that explicit consideration of this fundamental characteristic of financial markets cannot be ignored in their agent-based modeling.     

Pea Aphids, Acyrthosiphon Pisum, Suppress Induced Plant Volatiles in Broad Bean, Vicia Faba

Plants defend themselves against herbivory through several means, including the production of airborne volatile organic compounds (VOCs). These VOCs benefit plants by attracting natural enemies of their herbivores. The pea aphid, Acyrthosiphon pisum, is able to feed on its host plant, Vicia faba, without inducing detectable changes in plant VOC emission. Levels of VOCs emission are not significantly different between control plants and those fed upon by aphids for up to 5 days. Using a second herbivore, the beet armyworm caterpillar, Spodoptera exigua, we demonstrate that several expected caterpillar-induced VOCs are reduced when co-infested with pea aphids, thus demonstrating that pea aphids have the ability to inhibit the release of certain VOCs. This study shows, for the first time, that aphids not only avoid triggering plant volatile emission, but also can actively inhibit herbivore-induced volatiles.     

Heterogeneous Asymmetric Reactions 20. Effect of Ultrasonic Variables on the Enantiodifferentiation in Cinchona-Modified Platinum-Catalyzed Sonochemical Hydrogenations

The effect of sonochemical variables on a cinchona alkaloid modified Pt/Al₂O₃ catalyst system and its application in -ketoester hydrogenation are described. The sonochemical pretreatment of these commercial Pt/Al₂O₃-cinchonidine catalysts resulted in excellent ee values (up to 92-98% ee) under mild experimental conditions. To gain more insight into the nature of the ultrasonic effect the reactions were screened under widely varied conditions (ultrasound source, frequency, insonation time). Besides investigating the reactions, the catalyst-modifier system was also studied. The changes in metal particle size were determined by transmission electron microscopy, while the alteration of modifier concentration in the solvent upon sonication was followed by UV-vis spectroscopy. The transformation of the modifier during the pretreatment was detected by GC-MS and verified by NMR. Summarizing the results, the major effects of the sonochemical activation on the cinchona-modified supported Pt catalyst system can be described. The ultrasonic pretreatment increased the quantity of adsorbed cinchona and blocked its hydrogenation to provide more and highly stable chiral active sites for enantioselection.     

Chemical and Colloidal Stability of Carboxylated Core-Shell Magnetite Nanoparticles Designed for Biomedical Applications

Despite the large efforts to prepare super paramagnetic iron oxide nanoparticles (MNPs) for biomedical applications, the number of FDA or EMA approved formulations is few. It is not known commonly that the approved formulations in many instances have already been withdrawn or discontinued by the producers; at present, hardly any approved formulations are produced and marketed. Literature survey reveals that there is a lack for a commonly accepted physicochemical practice in designing and qualifying formulations before they enter in vitro and in vivo biological testing. Such a standard procedure would exclude inadequate formulations from clinical trials thus improving their outcome. Here we present a straightforward route to assess eligibility of carboxylated MNPs for biomedical tests applied for a series of our core-shell products, i.e., citric acid, gallic acid, poly(acrylic acid) and poly(acrylic acid-co-maleic acid) coated MNPs. The discussion is based on physicochemical studies (carboxylate adsorption/desorption, FTIR-ATR, iron dissolution, zeta potential, particle size, coagulation kinetics and magnetization measurements) and involves in vitro and in vivo tests. Our procedure can serve as an example to construct adequate physico-chemical selection strategies for preparation of other types of core-shell nanoparticles as well.     

Heterogeneous Asymmetric Reactions 34. New Data in the Enantioselective Hydrogenation of Ethyl Pyruvate Catalyzed by Cinchona Alkaloid-Modified Pt/Al2O3 in Toluene

The enantioselective hydrogenation of ethyl pyruvate (EtPy) on Pt-alumina (E 4759) catalyst modified by dihydrocinchonidine (DHCD) at a hydrogen pressure of 1 bar in toluene was studied. The effects of the modifier concentration (0.001-1 mmol l^-1) and temperature (-10, 0, 24 °C) on the reaction rate and the enantioselectivity have been studied. Under mild experimental conditions (hydrogen pressure: 1 bar, temperature: -10 °C, DHCD concentration: 0.1 mmol l^-1) an optical yield of 88% can be achieved. When EtPy hydrogenation was studied in AcOH under identical conditions, it was established that the DHCD/Pt_surf ratio necessary for achieving maximum enantioselectivity is highly solvent dependent: this ratio is 0.007 in AcOH and 0.12 in toluene. This large difference in DHCD/Pt_surf may be a reflection of a difference in reaction mechanism.     

Identification of the Female-Produced Sex Pheromone of an Invasive Greenhouse Pest,the European Pepper Moth (<Emphasis Type="Italic">Duponchelia fovealis</Emphasis>)

The European pepper moth (Duponchelia fovealis, Lepidoptera, Crambidae, Spilomelinae) is an invasive pest of greenhouses in many countries, causing serious damages to horticultural plants. Coupled gas chromatographic-electroantennographic detection analysis of the female gland extract revealed two antennally active peaks. Using coupled gas chromatography–mass spectrometry (GC-MS), one was identified as (Z)-11-hexadecenal (Z11–16:Ald); however, further analysis on different types of capillary columns indicated that the second active compound has two different isomers, (E)-13-octadecenal (E13–18:Ald) and (Z)-13-octadecenal (Z13–18:Ald). The approximate ratio of E13–18:Ald, Z13–18:Ald and Z11–16:Ald in the crude pheromone gland extract was 10:1:0.1, respectively. Single sensillum recordings showed that there was one sensory neuron that responded with a high amplitude spike to both E13–18:Ald and Z13–18:Ald, while another neuron housed in the same sensillum responded to Z11–16:Ald. Field evaluation of the identified compounds indicated that the E13–18:Ald was necessary to evoke the attraction of males; although the presence of Z13–18:Ald and Z11–16:Ald increased the catches in traps. The highest number of caught males was achieved when E13–18:Ald, Z13–18:Ald and Z11–16:Ald were present in baits in the same ratio as in the female gland extract. This pheromone can be used in a monitoring strategy and could potentially lead to the development of mating disruption.     

Enhanced separation of highly non-ideal mixtures with extractive heterogeneous-azeotropic distillation

The distillation based separation can be extremely complex if highly non-ideal mixtures are to be separated. In spite of different successfully applied unit operations there is still a possible way to improve the distillation technique and widen its toolbar. A new improvement in this area is the development of the extractive heterogeneous-azeotropic distillation (EHAD). This unit operation includes the merits of extractive- and heterogeneous-azeotropic distillations in one unit without extra material addition. Our work supports EHAD features with successful experiments compared with modelling and comparison with other separation structures proving that the application of EHAD makes the separation of extremely non-ideal mixtures possible on an easy, powerful, energy saving, and cost efficient way.