Kardar-Parisi-Zhang asymptotics for the two-dimensional noisy Kuramoto-Sivashinsky equation

We study numerically the Kuramoto-Sivashinsky (KS) equation forced by external white noise in two space dimensions, that is a generic model for e.g. surface kinetic roughening in the presence of morphological instabilities. Large scale simulations using a pseudospectral numerical scheme allow us to retrieve Kardar-Parisi-Zhang (KPZ) scaling as the asymptotic state of the system, as in the 1D case. However, this is only the case for sufficiently large values of the coupling and/or system size, so that previous conclusions on non-KPZ asymptotics are demonstrated as finite size effects. Crossover effects are comparatively stronger for the 2D case than for the 1D system.Comment: 5 pages, 3 figures; supplemental material available at journal web page and/or on reques

Dynamical Renormalization Group Study for a Class of Non-local Interface Equations

We provide a detailed Dynamic Renormalization Group study for a class of stochastic equations that describe non-conserved interface growth mediated by non-local interactions. We consider explicitly both the morphologically stable case, and the less studied case in which pattern formation occurs, for which flat surfaces are linearly unstable to periodic perturbations. We show that the latter leads to non-trivial scaling behavior in an appropriate parameter range when combined with the Kardar-Parisi-Zhang (KPZ) non-linearity, that nevertheless does not correspond to the KPZ universality class. This novel asymptotic behavior is characterized by two scaling laws that fix the critical exponents to dimension-independent values, that agree with previous reports from numerical simulations and experimental systems. We show that the precise form of the linear stabilizing terms does not modify the hydrodynamic behavior of these equations. One of the scaling laws, usually associated with Galilean invariance, is shown to derive from a vertex cancellation that occurs (at least to one loop order) for any choice of linear terms in the equation of motion and is independent on the morphological stability of the surface, hence generalizing this well-known property of the KPZ equation. Moreover, the argument carries over to other systems like the Lai-Das Sarma-Villain equation, in which vertex cancellation is known {\em not to} imply an associated symmetry of the equation.Comment: 34 pages, 9 figures. Journal of Statistical Mechanics: Theory and Experiments (in press

Effect of Hyperbaric Storage at Room Temperature on the Activity of Polyphenoloxidase in Model Systems and Fresh Apple Juice

The effect of hyperbaric storage (HS) on polyphenoloxidase activity (PPO) was studied in model solutions and apple juice. Model solutions containing increasing amounts of mushroom (Agaricus bisporus) PPO (up to 26 U) were stored at room temperature at pressure up to 200 MPa. During HS, samples were assessed for residual PPO activity. The enzyme was completely inactivated according to a first-order kinetic model that was used to calculate PPO decimal reduction time (Dp) and pressure sensitivity (zp = 140.8 MPa) in diluted model solutions (2 U PPO). The increase in enzyme concentration (6–26 U) nullified the effect of HS, probably due to protein structure stabilization by self-crowding. The application of HS at 100 and 200 MPa to apple juice promoted a decrease in total bacteria, lactic acid bacteria, yeasts, and molds. These changes occurred in concomitance with the inactivation of PPO (zp = 227.3 MPa). At 200 MPa, PPO inactivation followed a biphasic first-order kinetic, suggesting the presence of PPO isozymes with different pressure sensitivity. The inactivation of PPO was observed to occur more rapidly with increasing storage pressure and led to the maintenance of the original bright juice color. This study proves the capability of HS to control enzyme-related quality decay in fruit juices and, potentially, in many other food matrices suffering enzymatic alteration

Evaluation of an in-capillary approach for performing quantitative cytochrome P450 activity studies

An automated in-capillary assay requiring very small quantities of reagents was developed for performing in vitro cytochrome P450 (CYP450) drug metabolism studies. The approach is based on the following: (i) hydrodynamic introduction of nanoliter volumes of substrate and enzyme solutions in the sandwich mode, within a capillary; (ii) mixing the reagents by diffusion across the interfaces between the injected solutions; (iii) collection of the capillary content at the end of the in-capillary assay; and (iv) off-line analysis of the incubation mixture by ultrahigh pressure liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). After optimizing the injection sequence of the reagents, the in-capillary approach was applied to the quantitative determination of the kinetics of drug metabolism reactions catalyzed by three CYP450 isozymes involved in human drug metabolism: CYP1A2, CYP2D6, and CYP3A4. It was demonstrated that this in-capillary method was able to provide similar kinetic parameters for CYP450 activity (e.g., Michaelis constants and turnover values) as the classical in vitro method, with a drastic reduction of reagent consumption. Injection setups used for in-capillary CYP450 assay

Modeling the effect of the oxidation status of the ingredient oil on stability and shelf life of low-moisture bakery products: The case study of crackers

In packed low-moisture foods such as crackers, oxidation is generally the main cause of quality depletion during storage. It is commonly believed, but scarcely investigated, that product shelf life depends on the oxidative status of the lipid ingredients. In this study, the influence of oxidation degree of the ingredient sunflower oil on cracker oxidative stability and hence shelf life was investigated. To this aim, oil with increasing peroxide values (PVs) (5, 11, and 25 mEqO2/kgoil) was used to prepare crackers. Just after production, crackers presented similar peroxide and rancid odor intensity, probably due to the interactive pathways of oxidative and Maillard reactions. Crackers were packed and analyzed for PV and rancid odor during storage at 20, 40, and 60 \u25e6C. Rancid odor well discriminated cracker oxidative status. Relevant oxidation rates were used to develop a shelf life predictive model based on the peroxide value of the ingredient oil. It was estimated that an oil PV from 5 to 15 mEqO2/kgoil shortens cracker Shelf Life (SL) by 50%, independently of storage temperature. These results demonstrate the critical impact of ingredient quality on product performance on the market

Impact of high-pressure carbon dioxide on polyphenoloxidase activity and stability of fresh apple juice

Freshly-extracted apple juice was exposed to high pressure carbon dioxide (HP-CO2) treatment at 20, 35 and 45 °C at different pressure conditions (6.0, 12.0 and 18.0 MPa) for up to 30 min. Samples were analysed for residual enzymatic activity. The time needed for 90% enzyme inactivation (Dp) decreased when CO2 pressure increased, while the CO2 pressure sensitivity of the enzyme (zp) showed no variation with temperature. The HP-CO2 treatment at 12 MPa and 35 °C allowed the minimum residual enzyme activity (20%) to be reached in 10 min. Samples treated under these conditions showed lower polyphenoloxidase activity and higher microbial stability than untreated apple juice while presenting a sensory fresh-likelihood higher than thermally pasteurized apple juice. © 2016 Elsevier Lt

Probing protein sequences as sources for encrypted antimicrobial peptides

Starting from the premise that a wealth of potentially biologically active peptides may lurk within proteins, we describe here a methodology to identify putative antimicrobial peptides encrypted in protein sequences. Candidate peptides were identified using a new screening procedure based on physicochemical criteria to reveal matching peptides within protein databases. Fifteen such peptides, along with a range of natural antimicrobial peptides, were examined using DSC and CD to characterize their interaction with phospholipid membranes. Principal component analysis of DSC data shows that the investigated peptides group according to their effects on the main phase transition of phospholipid vesicles, and that these effects correlate both to antimicrobial activity and to the changes in peptide secondary structure. Consequently, we have been able to identify novel antimicrobial peptides from larger proteins not hitherto associated with such activity, mimicking endogenous and/or exogenous microorganism enzymatic processing of parent proteins to smaller bioactive molecules. A biotechnological application for this methodology is explored. Soybean (Glycine max) plants, transformed to include a putative antimicrobial protein fragment encoded in its own genome were tested for tolerance against Phakopsora pachyrhizi, the causative agent of the Asian soybean rust. This procedure may represent an inventive alternative to the transgenic technology, since the genetic material to be used belongs to the host organism and not to exogenous sources

A kinetic study on the effect of hyperbaric storage on the development of Maillard reaction in glucose-glycine model systems

The effect of pressure (0.1, 15, 50 and 100 MPa) and temperature (43, 53, 63 °C) on the formation rate (k) of Maillard α-dicarbonyls (absorbance at 294) and melanoidins (absorbance at 420 nm), was studied during hyperbaric storage (HS) of glucose-glycine model solutions (pH 6). While increasing storage temperature increased k values according to the Arrhenius equation (Ea ~ 85 kJ mol−1), increasing pressure decreased reaction rates as predicted by the Eyring model (Va ~ 11 mL mol−1). Pressure did not affect reaction temperature sensitivity, indicating no significant mechanism changes under hyperbaric conditions. A combined model predicting the effect of concomitant changes of temperature and pressure on Maillard reaction rate was implemented and validated within and outside (20–25 °C, 20–200 MPa) its building range. Results indicate HS to limit Maillard browning in food, with possible practical applications, and the potential to develop predictive models based on temperature-accelerated HS trials. Industrial relevance: The capability of hyperbaric storage to impair Maillard reaction rate extends the scope of this multi-tasking technology to the prevention of color alterations due to non-enzymatic browning. The latter is expected to be of industrial relevance in the case of perishable foods affected by this phenomenon, such as thermally-treated milk. In these matrices, the technology could concomitantly guarantee microbiological safety, protein functionalization, and Maillard browning impairment

Integration of crops, livestock, and forestry: a system of production for the Brazilian Cerrados.

Some of the most promising and at the same time some of the most challenging areas of future food production are found in the savannas of South America. Integrating cropping, livestock, and forestry in these regions can increase the eco-efficiency of agricultural production. This chapter presents a case study of an integrated crop, livestock, and forestry system in Brazil. The study area is in Goiás State in the Cerrado region, a vast savanna covering almost one quarter of Brazil's land area. About half of the area suited to agriculture in the Cerrado is under cultivated pasture, but much of this is degraded as a result of overgrazing. The systems studied in this report include different arrangements to test productivity, profitability and sustainability of eucalyptus, crops, and pastures. Findings demonstrated that integrated crop, livestock, and forestry systems are economically and technically feasible in the Cerrados. In addition to producing food of high biological value (meat and milk), cultivated pasture provides other important environmental benefits, including long-term ground cover, carbon fixation, increases in soil organic matter content; and reduction in the emission of greenhouse gases

Exploring the effects of hyperbaric storage on the optical, structural, mechanical and diffusional properties of food packaging materials

The effect of hyperbaric storage (HS) on food packaging materials was evaluated. PA/PE, PP/EVOH/PE, PET and PLA pouches filled with hydroethanolic simulant (D1) were stored at 0.1 and 200 MPa for up to 35 days and analyzed for optical, structural, mechanical and diffusional properties. HS weakened PLA seals, which easily failed after 7 days releasing the simulant. Both PET and PLA films swelled during HS, reducing PET physical ageing and PLA crystallinity. These structural effects caused PET and PLA mechanical properties to vary during HS, and a slight WVTR increase in PLA. Optical, structural and mechanical properties of multi-material films did not change upon HS. Nevertheless, both PA/PE and PP/EVOH/PE released critical amounts of adhesives after 7 and 35 days under pressure, respectively. Results indicate the critical role of the packaging material of foods intended for HS, and the need for its careful selection in future studies on the topic