Effluent content from albedo degradation and kinetics at different temperatures in the enzymatic peeling of grapefruits

This work studies the variation in the effluent content from the reactor in enzymatic peeling of grapefruits, to determine the loss of soluble solids, reducing sugars and galacturonic acid, the main component from the albedo of the skin to model the solid–liquid transfer in this process. Experiments to study the efficiency of the enzymatic reaction include the effect of the temperature on the kinetics of albedo degradation to find an equation relating both variables and also the activation energy of this process, its value being 36.9 kJ/mol.     

cis-Diaminedichloroplatinum(II) complexes reversibly bound to water-soluble polyaspartamide carriers for chemotherapeutic applications. II: Platinum coordination to ethylenediamine ligands attached to poly(ethylene oxide)-grafted carrier polymers

In continuation of previous investigations aiming at the development of macromolecular metal complexes for biomedical use, this communication describes poly(alkylene oxide)-grafted polymeric platinum complexes. The platinum-containing macromolecules are obtained from presynthesized polyaspartamide carriers bearing poly(ethylene/propylene oxide) side chains and hydroxyethyl side groups as hydrosolubilizing units in addition to ethylenediamine side group terminals for metal coordination. Platination is brought about by treatment of the carriers with tetrachloroplatinate(II) ion in aqueous solution at 25–60°C. pH 4–6. The polymeric products, purified by dialysis in aqueous solution, are isolated by freeze-drying in yields of 60–80%. Platinum contents are in the range of 4–15%. The metal is bound to the carrier through chelation with the ethylenediamine ligands, forming square-planarcis-dichloroethylenediamine-platinum(II) complex species as side-chain terminals. Initially, the product polymers dissolve smoothly in water. Although on room-temperature storage in the solid state they gradually turn insoluble as a consequence of intermolecular solid-state interaction, solubility is retained on low-temperature storage and in frozen aqueous solutions.     

Synthesis of tadpole-shaped POSS-containing hybrid polymers via “click chemistry”

Copper-catalyzed alkyne-azide “click chemistry” is applied in the preparation of tadpole-shaped (“monochelic”) POSS-end functional hybrid polymers by combining with ATRP and RAFT polymerization. Alkyne-functionalized ATRP initiator and RAFT agent were respectively synthesized and applied in the preparation of alkyne-terminal poly(methyl methacrylate) and polystyrene. The tadpole-shaped POSS-containing hybrid polymers are easily obtained by the click reaction with an azido-functional POSS molecule. This presents a novel and effective method to prepare POSS-containing hybrid polymers.     

Nitrogen balances in farmers fields under alternative uses of a cover crop legume: a case study from Nicaragua

Canavalia brasiliensis (canavalia), a drought tolerant legume, was introduced into the smallholder traditional crop-livestock production system of the Nicaraguan hillsides as green manure to improve soil fertility or as forage during the dry season for improving milk production. Since nitrogen (N) is considered the most limiting nutrient for agricultural production in the target area, the objective of this study was to quantify the soil surface N budgets at plot level in farmers fields over two cropping years for the traditional maize/bean rotation and the alternative maize/canavalia rotation. Mineral fertilizer N, seed N and symbiotically fixed N were summed up as N input to the system. Symbiotic N₂ fixation was assessed using the ¹⁵N natural abundance method. Nitrogen output was quantified as N export via harvested products. Canavalia derived in average 69% of its N from the atmosphere. The amount of N fixed per hectare varied highly according to the biomass production, which ranged from 0 to 5,700 kg ha^?1. When used as green manure, canavalia increased the N balance of the maize/canavalia rotation but had no effect on the N uptake of the following maize crop. When used as forage, it bears the risk of a soil N depletion up to 41 kg N ha^?1 unless N would be recycled to the plot by animal manure. Without N mineral fertilizer application, the N budget remains negative even if canavalia was used as green manure. Therefore, the replenishment of soil N stocks by using canavalia may need a few years, during which the application of mineral N fertilizer needs to be maintained to sustain agricultural production.     

Interpolyelectrolyte complexes of diblock copolymers via interaction of complementary polyelectrolyte-surfactant complexes in chloroform

We have studied the interpolyelectrolyte complexation in chloroform between polystyrene-block-poly(cetyltrimethylammonium acrylate), (PA⁻ CTA⁺), and poly(2-(methacryloyloxy)ethyldimethylethyl-ammonium dodecyl sulfate) (quaternized poly(2-(dimethylamino)ethyl methacrylate) complexed with sodium dodecyl sulfate), (PDMAEMAQ⁺ DS⁻). Turbidimetry, dynamic/static light scattering, and transmission electron microscopy show the formation of large aggregated interpolyelectrolyte complex species, which are colloidally stable in chloroform or even chloroform-soluble if the certain conditions are met. We suggest such co-assemblies to be micellar species with a core assembled from electrostatically coupled fragments of the polymeric components. The corona is built up either from a mixture of polystyrene blocks and excessive fragments of (PDMAEMAQ⁺ DS⁻) chains or from a mixture of polystyrene blocks and excessive fragments of (PA⁻ CTA⁺) blocks, depending on which polymeric component was taken in excess for the interpolyelectrolyte complexation. However, their real structures may deviate from such idealized consideration because of the non-equilibrium character of interpolyelectrolyte complexation in organic media of low polarity.     

Manufacturer-independent mechatronic information model for control systems

Modular system-based engineering is the key to a quick, customized machine and plant configuration. This approach is seen as the best method to implement different functional requirements with a minimum amount of resources. The interdisciplinary configuration of control systems to automate machines has previously not been supported by engineering tools. This is partially due to the lack of standardized mechatronic information models. The machine manufacturer is required to create the necessary mechatronic information models uniquely for each control system independently. Thus, he does not comply with any modeling specifications. As a result, the mechatronic information models are not applicable for other control system architectures. The conventionally used mechatronic information models as well as the manufacturer-specific engineering tools define the control hardware components and their configurations. An abstraction of the logical and functional layers does not take place. Consequently, a mechatronic control architecture model is required. This architecture can serve as a modeling basis in modular system-based interdisciplinary engineering tools. Therefore, an approach to a manufacturer independent, mechatronic information model for control systems is the subject of this article.     

The Chemical Evolution of the La<Subscript>0.6</Subscript>Sr<Subscript>0.4</Subscript>CoO<Subscript>3−δ</Subscript> Surface Under SOFC Operating Conditions and Its Implications for Electrochemical Oxygen Exchange Activity

Owing to its extraordinary high activity for catalysing the oxygen exchange reaction, strontium doped LaCoO₃ (LSC) is one of the most promising materials for solid oxide fuel cell (SOFC) cathodes. However, under SOFC operating conditions this material suffers from performance degradation. This loss of electrochemical activity has been extensively studied in the past and an accumulation of strontium at the LSC surface has been shown to be responsible for most of the degradation effects. The present study sheds further light onto LSC surface changes also occurring under SOFC operating conditions. In-situ near ambient pressure X-ray photoelectron spectroscopy measurements were conducted at temperatures between 400 and 790 °C. Simultaneously, electrochemical impedance measurements were performed to characterise the catalytic activity of the LSC electrode surface for O₂ reduction. This combination allowed a correlation of the loss in electro-catalytic activity with the appearance of an additional La-containing Sr-oxide species at the LSC surface. This additional Sr-oxide species preferentially covers electrochemically active Co sites at the surface, and thus very effectively decreases the oxygen exchange performance of LSC. Formation of precipitates, in contrast, was found to play a less important role for the electrochemical degradation of LSC.