In the past several years researchers have focused on the study of the antioxidant properties of barley and barley malt as well as their influence on beer quality. Some malt constituents have been ...reported as potent antioxidants due to their radical‐scavenging and reducing properties, with a positive effect on beer oxidative stability. However, barley and malt can suffer some serious modifications during malting and roasting, namely on the levels of phenolic compounds and the development of Maillard reaction products, which may have a great impact on the overall antioxidant properties of malt. Although some studies have reported an increase of the antioxidant capacity during malting, others have mentioned an opposite effect. Recently, researchers have shown that compounds developed in malt during heat treatment at high temperature and long periods of time, as result of the Maillard reaction, can also exhibit pro‐oxidant properties involving the metal‐catalyzed Fenton reaction due to its reductive properties. This paper reviews important information and recent data regarding the chemical changes malting and roasting undergo along with their influence on the different anti‐ and pro‐oxidant properties described for barley and malt. The contribution of individual components to the overall antioxidant capacity of malt is also discussed.
Understanding the oxidation of the purines adenine and guanine is primary to improving electrochemical methods of DNA detection and analysis. Adenine in the solution phase is reported to undergo a ...complex electrochemical oxidation mechanism that is overall a −6H+, −6e− process, involving irreversible chemical steps. The observed voltammetry associated with the oxidation of adenine is strongly dependent upon the electrode used; this is a reflection of both the kinetics of oxidation and strength of bonding to the electrode surface, both of which are surface specific. Two main cases are presented within the article, one in which the adsorption of adenine to the electrode surface is strong, as is the case with gold and one in which the bonding is weaker, as found with graphitic surfaces. In the case of gold, adsorption is strong enough to prevent the adenine oxidation to be observed within the electrochemical window and further to this the formed monolayer prevents oxidation of the gold surface. With graphitic surfaces adsorption is weaker and as such oxidation of adenine is observed, this oxidative signal is demonstrated to be due to the oxidation of both surface bound and solution phase species. A generic method for analyzing the peak currents for reversible electron transfers coupled with an irreversible chemical process is presented. The analysis is dependent upon knowledge of the number of electrons transferred prior to the first chemically irreversible process and the total number of electrons transferred during the redox process. In addition to this, the analysis provides a description for the peak height of voltammetric waves that have contributions from both adsorbed and solution phase species, with these two processes being resolved through their differing dependencies with scan rate. The methodology is then used for the analysis of the oxidation of adenine on an edge-plane pyrolytic graphite electrode, where the influences on peak current from adsorption and diffusion are demonstrated. The diffusion coefficient for adenine is found to be (1.25 ± 0.2) × 105 cm s−1, which is in close agreement to that found by independent measurements reported in the literature. The adsorption of adenine at low concentrations to the electrode surface, is shown to exhibit a linear dependence of coverage with the solution phase concentration, where the surface coverage is given by Γ = KC* with a measured K value of (1.7 ± 0.1) × 10−3 cm and C* is the solution phase concentration.
The effects of mineral fertilizers on the physicochemical properties of olives and oil under rainfed conditions is scarce. In this three-year study, the results of a nitrogen (N), phosphorus (P), ...potassium (K) and boron (B) fertilization trial carried out in a young rainfed olive grove and arranged as a nutrient omission trial are reported. The control consisted of the application of N, P, K and B (NPKB) and four other treatments corresponded to the removal of one of them (N0, P0, K0 and B0). Olive yield and several variables associated with the physicochemical properties of olives and oil were evaluated. The NPKB treatment increased olive yield compared to the treatment that did not receive N (N0). Although dependent on the climate conditions of the crop season, the NPKB treatment increased fruit weight and the pulp/pit ratio and its fruits tended to accumulate more oil than K0. However, the phenolics concentrations on fruits and oil tended to be lower. All olive oil samples were classified in the "extra virgin" category and all showed a decrease in its stability between 3 and 15 months of storage, regardless of treatment, especially in N0, P0 and B0 treatments. The results of the sensorial analysis indicate that all the oils fell into the medium fruitiness and greenly-fruity category. Only in P0 and B0 were defects detected, namely muddy sediment. Thus, this study seems to indicate the importance of N application, but also a balanced nutrient application and that further studies are needed, given the difficulty in finding clear trends in the response of measured variables to fertilizer treatments.
This study reports the synthesis of polyurethane-lignin copolymer blended with carbon multilayer nanotubes to be used in all-solid-state potentiometric chemical sensors. Known applicability of ...lignin-based polyurethanes doped with carbon nanotubes for chemical sensing was extended to eucalyptus LignoBoost
kraft lignin containing increased amounts of polyphenolic groups from concomitant tannins that were expected to impart specificity and sensitivity to the sensing material. Synthesized polymers were characterized using FT-MIR spectroscopy, electrical impedance spectroscopy, scanning electron microscopy, thermogravimetric analysis, and differential scanning calorimetry and are used for manufacturing of all solid-state potentiometric sensors. Potentiometric sensor with LignoBoost
kraft lignin-based polyurethane membrane displayed theoretical response and high selectivity to Cu (II) ions, as well as long-term stability.
The advances in wireless communications are still very limited when intended to be used on Underwater Communication Systems mainly due to the adverse proprieties of the submarine channel to the ...acoustic and radio frequency (RF) waves propagation. This work describes the development and characterization of a polyvinylidene difluoride ultrasound transducer to be used as an emitter in underwater wireless communications. The transducer has a beam up to 10° × 70° degrees and a usable frequency band up to 1 MHz. The transducer was designed using Finite Elements Methods and compared with real measurements. Pool trials show a transmitting voltage response (TVR) of approximately 150 dB re µPa/V@1 m from 750 kHz to 1 MHz. Sea trials were carried in Ria Formosa, Faro (Portugal) over a 15 m source—receiver communication link. All the signals were successfully detected by cross-correlation using 10 chirp signals between 10 to 900 kHz.
A linear electromagnetic energy harvesting device for underwater applications, fabricated with a simple manufacturing process, was developed to operate with movement frequencies from 0.1 to 0.4 Hz. ...The generator has two coils, and the effect of the combination of the two coils was investigated. The experimental study has shown that the energy capture system was able to supply energy to several ocean sensors, producing 7.77 mJ per second with wave movements at 0.4 Hz. This study shows that this energy is enough to restore the energy used by the battery or the capacitor and continue supplying energy to the sensors used in the experimental work. For an ocean wave frequency of 0.4 Hz, the generator can supply power to 8 sensors or 48 sensors, depending on the energy consumed and its optimization.
It has increasingly been recognized that electrical currents play a pivotal role in cell migration and tissue repair, in a process named "galvanotaxis". In this review, we summarize the current ...evidence supporting the potential benefits of electric stimulation (ES) in the physiology of peripheral nerve repair (PNR). Moreover, we discuss the potential of piezoelectric materials in this context. The use of these materials has deserved great attention, as the movement of the body or of the external environment can be used to power internally the electrical properties of devices used for providing ES or acting as sensory receptors in artificial skin (e-skin). The fact that organic materials sustain spontaneous degradation inside the body means their piezoelectric effect is limited in duration. In the case of PNR, this is not necessarily problematic, as ES is only required during the regeneration period. Arguably, piezoelectric materials have the potential to revolutionize PNR with new biomedical devices that range from scaffolds and nerve-guiding conduits to sensory or efferent components of e-skin. However, much remains to be learned regarding piezoelectric materials, their use in manufacturing of biomedical devices, and their sterilization process, to fine-tune their safe, effective, and predictable in vivo application.
Because of the close relation between oxidative stress and a plethora of inflammatory diseases, antioxidants have received an increased attention for incorporation into dermatological products. Their ...use and absorption are, however, limited by their low solubility in water-rich formulations. Herein, a set of novel cholinium-based salts, namely dicholinium ellagate and cholinium caffeate, syringate, vanillate, gallate, and salicylate, were synthesized and characterized. Their melting and decomposition temperatures, water solubility, and toxicological, antioxidant, cytotoxicity and pro-/anti-inflammatory activities were addressed. These new salts, exclusively composed of ions derived from natural sources, display a high thermal stability–up to 150 °C. The synthesized compounds are significantly more soluble in water (on average, 3 orders of magnitude higher) than the corresponding phenolic acids. Furthermore, they present not only similar but even higher antioxidant and anti-inflammatory activities, as well as comparable cytotoxicity and lower ecotoxicity profiles than their acidic precursors. Among all the investigated salts, dicholinium ellagate is the most promising synthesized salt when considering the respective antioxidant and anti-inflammatory activities. Because all the synthesized salts are based on the cholinium cation, they can further be envisaged as essential nutrients to be used in oral drugs.
The selection of natural and chemical compounds for potential applications in new pharmaceutical formulations constitutes a time-consuming procedure in drug screening. To overcome this issue, new ...devices called biosensors, have already demonstrated their versatility and capacity for routine clinical diagnosis. Designed to perform analytical analysis for the detection of a particular analyte, biosensors based on the coupling of proteins to amperometric and optical devices have shown the appropriate selectivity, sensibility and accuracy. During the last years, the exponential demand for pharmacokinetic studies in the early phases of drug development, along with the need of lower molecular weight detection, have led to new biosensor structure materials with innovative immobilization strategies. The result has been the development of smaller, more reproducible biosensors with lower detection limits, and with a drastic reduction in the required sample volumes. Therefore in order to describe the main achievements in biosensor fields, the present review has the main aim of summarizing the essential strategies used to generate these specific devices, that can provide, under physiological conditions, a credible molecule profile and assess specific pharmacokinetic parameters.
Glutathione (GSH) is a small peptide of great relevance in many biological processes. Its determination is a valuable aid to understand the cellular health status. Important information is obtained ...not only from the quantification of its free reduced form (GSH) but also of its oxidized form (GSSG) and both the ratio and absolute amounts of these two species. We report an electro-analytical methodology for determining the reduced and total GSH using square wave voltammetry and a screen-printed electrode modified with carbon nanotubes (CNT–SPE). For the total glutathione determination, sodium borohydride was chosen as a reducing agent for its effectiveness and inert electrochemical activity. Human saliva samples were successfully analysed by the developed methodology as a proof-of-concept and validated independently with a commercially available enzyme assay kit.
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