Modelling the kinetics of thermal inactivation of apple polyphenoloxidase

The enzymatic browning of fruits and vegetables caused by mechanical injury during postharvest storage or processing is initiated by the catalytic action of polyphenoloxidase (PPO). A bleaching treatment prior to processing is still considered mostly effective in inhibiting the catalytic activity of PPO, and thus controlling undesirable enzymatic browning. In this work, different mathematical routines were assessed in terms of their adequacy to describe the thermal inactivation of PPO from Golden apples over a range of temperatures from 62.5 to 72.5 ºC. The classical approach to kinetic modelling of the decay activity of apple PPO, commonly reported to follow a first-order model, employs a two-step procedure, in which the model parameters are individually obtained, by each temperature studied, using non-linear or linear regressions. Thereafter, the estimated parameters are further used to calculate their temperature dependence. Alternatively, a one-step method provides a regression fit to all experimental data sets, with the temperature dependence equation being directly built in the kinetic model. This fitting technique thus, (a) avoids the estimation of intermediate parameters and, (b) substantially increases the degrees of freedom and hence the precision of parameters’ estimates. Within this issue was further explored the logarithmic transformation of the mathematical equations used on the adequacy of the model to describe experimental data. In all cases non-weighted least-squares regression procedures were used. Both the examination and criticism of the current modelling strategies were done by assessing statistical data obtained, such as the confidence intervals of the estimates, correlation coefficients, sum of squares, and residuals normality

Microwave-Assisted Extraction of Brewers' Spent Grain Arabinoxylans

Brewers´ spent grain (BSG) is a by-product from beer industry that can be exploited as a source of arabinoxylo-oligosaccharides (AXOS) with prebiotic activity. In this study, microwave-assisted extractions were performed during 2 min at 140-210°Cin order to evaluate the feasibility of this extraction technology for quantitative extraction of the arabinoxylans (AX) or AXOS from BSG. The AX yield increasedwith the increase of the temperature in the range used. The best condition of extraction of the AXwas 210 ºC during 2 min, allowing the extraction of 43% of total AX. These AX showed structural variability which allow to define specific types of compounds for different applications and uses depending on the extraction conditions used

Impact of the valley degree of freedom on the control of donor electrons near a Si/SiO_2 interface

We analyze the valley composition of one electron bound to a shallow donor close to a Si/barrier interface as a function of an applied electric field. A full six-valley effective mass model Hamiltonian is adopted. For low fields, the electron ground state is essentially confined at the donor. At high fields the ground state is such that the electron is drawn to the interface, leaving the donor practically ionized. Valley splitting at the interface occurs due to the valley-orbit coupling, V_vo^I = |V_vo^I| e^{i theta}. At intermediate electric fields, close to a characteristic shuttling field, the electron states may constitute hybridized states with valley compositions different from the donor and the interface ground states. The full spectrum of energy levels shows crossings and anti-crossings as the field varies. The degree of level repulsion, thus the width of the anti-crossing gap, depends on the relative valley compositions, which vary with |V_vo^I|, theta and the interface-donor distance. We focus on the valley configurations of the states involved in the donor-interface tunneling process, given by the anti-crossing of the three lowest eigenstates. A sequence of two anti-crossings takes place and the complex phase theta affects the symmetries of the eigenstates and level anti-crossing gaps. We discuss the implications of our results on the practical manipulation of donor electrons in Si nanostructures.Comment: 8 pages, including 5 figures. v2: Minor clarifying changes in the text and figures. Change of title. As published in PR

Theory of one and two donors in Silicon

We provide here a roadmap for modeling silicon nano-devices with one or two group V donors (D). We discuss systems containing one or two electrons, that is, D^0, D^-, D_2^+ and D_2^0 centers. The impact of different levels of approximation is discussed. The most accurate instances -- for which we provide quantitative results -- are within multivalley effective mass including the central cell correction and a configuration interaction account of the electron-electron correlations. We also derive insightful, yet less accurate, analytical approximations and discuss their validity and limitations -- in particular, for a donor pair, we discuss the single orbital LCAO method, the Huckel approximation and the Hubbard model. Finally we discuss the connection between these results and recent experiments on few dopant devices.Comment: 13 pages, 6 figure

The Expression of Chemokines Is Downregulated in a Pre-Clinical Model of TTR V30M Amyloidosis

Inflammation is a hallmark of several neurodegenerative disorders including hereditary amyloidogenic transthyretin amyloidosis (ATTRv). ATTRv is an autosomal dominant neurodegenerative disorder with extracellular deposition of mutant transthyretin (TTR) aggregates and fibrils, particularly in nerves and ganglia of the peripheral nervous system. Nerve biopsies from ATTRv patients show increased cytokine production, but interestingly no immune inflammatory cellular infiltrate is observed around TTR aggregates. Here we show that as compared to Wild Type (WT) animals, the expression of several chemokines is highly downregulated in the peripheral nervous system of a mouse model of the disease. Interestingly, we found that stimulation of mouse Schwann cells (SCs) with WT TTR results in the secretion of several chemokines, a process that is mediated by toll-like receptor 4 (TLR4). In contrast, the secretion of all tested chemokines is compromised upon stimulation of SCs with mutant TTR (V30M), suggesting that V30M TTR fails to activate TLR4 signaling. Altogether, our data shed light into a previously unappreciated mechanism linking TTR activation of SCs and possibly underlying the lack of inflammatory response observed in the peripheral nervous system of ATTRv patients.The work was funded by the project Norte-01-0145-FEDER-000008 - Porto Neurosciences and Neurologic Disease Research Initiative at I3S, supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (FEDER). JM was supported by FCT with a PhD fellowship SFRH/BD/129345/2017. MS is funded by FCT through Estı́mulo Individual ao Emprego Cientı́fico

Thermal inactivation kinetics of suspensions of bacillus amyloliquefaciens a-amylase in hydrophobic organic solvents

The thermal inactivation of suspensions of á-amylase from Bacillus amyloliquefaciens equilibrated at three low moisture contents and with added hydrophobic organic solvents of different hydrophobicity (dodecane, octane and 1-octanol) was systematically studied at temperatures between 135 to 150°C. The inactivation kinetics showed a first order decay in all cases. The enzyme is much more thermostable and less temperature sensitive than in aqueous solution. The behaviour was compared to inactivation in dry atmospheres, at similar water contents, without solvents. The organic solvents caused a larger influence of the water content and some environments caused significant changes in the rate constants, but the activation energy was not significantly affected. The solvent showing a higher impact on the kinetic parameters was 1-octanol

Measurement of a superficial texture by applying the alpha parameter on the profile P, for measuring a manual transmission gear

The objective of this work is to demonstrate the P Profile application in the measurement of superficial texture of the cone seat of the synchronization ring gear of a Mechanical Transmission. It is known that this superficial texture is an essential factor for the good performance and durability of a Mechanical Transmission, since the variation of this texture is directly linked to the synchronization failure, premature wear of the synchronization ring coupling guides, gear and sleeve

Recreational Use of Protected Areas: Spatiotemporal Insights from the Wikiloc Mobile App

Managing the rising number of visitors to protected areas (PAs) without compromising their environmental goals is a critical challenge that requires a complete understanding of how and when visitors use these spaces. Georeferenced data from fitness-tracking apps can provide detailed information about the visitor’s spatiotemporal behaviour inside PAs, but its potential is still underexplored. This study uses georeferenced data, from Wikiloc, to analyse the visitors’ spatiotemporal behaviour in Alvão Natural Park, Portugal. Our findings show that: 52% of the visitors’ use is concentrated around the Fisgas de Ermelo Waterfall; photos’ hotspots coincide with the waterfalls and viewpoints facing them; 2% of the routes crossed a zone where recreational use is illegal; Spring (26%) and April (11%) receive the most visitors; 52% of routes are done on the weekends; 66% of visitors are inside the park during noon; start/end places are located near parking spaces; the most frequent times to start a route are between 08:00-13:00 hrs, ending between 13-18:00 hrs. A new method was developed to calculate daily visitor numbers without photo concentration bias. These results offer valuable insights that can aid in PAs' environmental and recreational use management by quickly providing detailed and low-cost visitor monitoring data

High Efficacy of Two Artemisinin-Based Combinations (Artesunate + Amodiaquine and Artemether + Lumefantrine) in Caala, Central Angola.

In April 2004, 137 children 6-59 months of age with uncomplicated Plasmodium falciparum (Pf) malaria (Caala, Central Angola) were randomized to receive either artemether-lumefantrine (Coartem) or artesunate + amodiaquine (ASAQ). After 28 days of follow-up, there were 2/61 (3.2%) recurrent parasitemias in the Coartem group and 4/64 (6.2%) in the ASAQ group (P = 0.72), all classified as re-infections after PCR genotyping (cure rate = 100% [95%CI: 94-100] in both groups). Only one patient (ASAQ group) had gametocytes on day 28 versus five (Coartem) and three (ASAQ) at baseline. Compared with baseline, anemia was significantly improved after 28 days of follow-up in both groups (Coartem: from 54.1% to 13.4%; ASAQ: from 53.1% to 15.9%). Our findings are in favor of a high efficacy of both combinations in Caala. Now that Coartem has been chosen as the new first-line anti-malarial, the challenge is to insure that this drug is available and adequately used