Scaling relations of branching pulsatile flow

Apparently complex flow structures obey to scaling relations that enable to make it viable the study of their configuration and flow dynamics. This is the case of flow structures that exhibit several branching levels and are thought to perform optimally. Here we present scaling relations of diameters and lengths of branching cylindrical channels with pulsatile flows, and compare them with other relations published in the literature. It is shown that, under constant global volume of the flow tree, and for zero pulse frequency these scaling relations reduce to Murrays's law of consecutive diameters. Optimal scaling depends on pulse frequency, distensibility of the channel walls, and asymmetry of the daughter vessels. In case that in addition to global volume of the flow tree, the pressure head is also kept constant, a similar scaling law of channel lengths emerges that holds together with the law of diameter scaling. The effect of channel distensibility is shown to be somehow important, such that for achieving optimal performance (lowest impedance) channels with lower relative distensibility must have their diameter increased. Results are compared with those of other models for the case of some arteries

Heart rate, arterial distensibility, and optimal performance of the arterial tree

In this study we explore the ability of a previously developed model of pulsatile flow for explaining the observed reduction of arterial distensibility with heart rate. The parameters relevant for the analysis are arterial wall distensibility together with permeability and reflection coefficients of the end capillaries. A non-specific artery and the ensemble of tissues supplied by that artery were considered in the model. The blood current within that artery was equalized to the sum of all micro currents in the tissues supplied by that artery. A formula emerged that relates changes in arterial distensibility with heart rate, and also with some particular aspects of microcirculation. Then, that formula was tested with data of distensibilities of the radial and carotid arteries observed at the heart rates of 63, 90, and 110 b.p.m. The formula correctly predicted the trend of decreased distensibility with heart rate for both arteries. Moreover, due to the fact that the carotid artery supplies the brain, and because the Blood–Brain barrier is highly restrictive to colloids in the blood, for the carotid artery the formula predicted a less marked decrease in distensibility than in the case of the radial artery feeding muscle tissue, which has a greater permeability to colloids, a trend that was confirmed by data. It was found that reduction of arterial distensibility with heart rate was greater in arteries that supply end capillaries with high permeability and low reflection coefficients

Statistical modeling in the analysis of river water quality monitoring sites

Surface water quality monitoring has as its main objective the characterization of water resources as well as the monitoring of its space-time evolution in order to achieve an appropriate administration. Dissolved oxygen (DO) is an important indicator for the estimation of the water quality index, and the lack of this quality variable may cause significant environmental issues. The aim of this contribution is to propose a geostatistical model that can used to characterize and assess water quality behaviour/evolution based on a rather extended data relative to the River Douro Basin (in Portugal) that consists mainly of monthly measurements of dissolved oxygen concentration in a network of water quality along this basin. The monthly data set reports to the period between March 2002 and February 2013

Coffee industrial waste as a natural source of bioactive compounds with antibacterial and antifungal activities

Coffee is one of the most popular and consumed beverages in the world, which leads to a high contents of solid residue known as spent coffee grounds (SCG). As is known, coffee beans contain several classes of health related chemicals, including phenolic compounds, melanoidins, diterpenes, xanthines and carotenoids which are associated with therapeutic and pharmaceutical effects, due to antimicrobial, antioxidant, anti-infectious and antitumour activities. Considering that this coffee industrial waste has no commercial value and are currently disposed as a solid waste or employed as fertilizers, we intend to highlight the use of SCG as a raw material with potential interest to the food and pharmaceutical industries. Moreover, this work seems to be valuable to promote the use of SCG as natural and an inexpensive food supplements or pharmaceutical additive. The phytochemical compounds content among the crude aqueous extracts of SCG followed this order: phenolics > flavonoids > carotenoids (mg/ g dry waste), respectively. Caffeine content found in SCG was ~ 0.82 g/100 g dry waste, 70 % lower than coffee roasting beans. Coffee ground extracts showed inhibition to S. aureus and E. coli growth for concentrations of 1.0 mg/ mL and a stronger inhibition was also observed against C. albicans, C. krusei and C. parapsilosis growth using lower concentration (0.5 mg/ mL).info:eu-repo/semantics/publishedVersio

Coffee industrial waste as a natural source of bioactive compounds with antibacterial and antifungal activities

Coffee is one of the most popular and consumed beverages in the world, which leads to a high contents of solid residue known as spent coffee grounds (SCG). As is known, coffee beans contain several classes of health related chemicals, including phenolic compounds, melanoidins, diterpenes, xanthines and carotenoids which are associated with therapeutic and pharmaceutical effects, due to antimicrobial, antioxidant, anti-infectious and antitumour activities. Considering that this coffee industrial waste has no commercial value and are currently disposed as a solid waste or employed as fertilizers, we intend to highlight the use of SCG as a raw material with potential interest to the food and pharmaceutical industries. Moreover, this work seems to be valuable to promote the use of SCG as natural and an inexpensive food supplements or pharmaceutical additive. The phytochemical compounds content among the crude aqueous extracts of SCG followed this order: phenolics > flavonoids > carotenoids (mg/ g dry waste), respectively. Caffeine content found in SCG was ~ 0.82 g/100 g dry waste, 70 % lower than coffee roasting beans. Coffee ground extracts showed inhibition to S. aureus and E. coli growth for concentrations of 1.0 mg/ mL and a stronger inhibition was also observed against C. albicans, C. krusei and C. parapsilosis growth using lower concentration (0.5 mg/ mL).info:eu-repo/semantics/publishedVersio

Quantitative studies on the enzymatic hydrolysis of milk proteins brought about by cardosins precipitated by ammonium sulfate

Hydrolysis of whey proteins may produce peptide mixtures with better functional properties than the original protein mixture, viz. higher solubilites and lower allergenic effects. Cynara cardunculus is a wild plant that possesses (aspartic) proteases in its flower cells; those enzymes exhibit general proteolytic and specific milk clotting activities, which are rather useful in traditional cheesemaking. This study was thus aimed at characterizing the enzymatic action of crude extracts of said plant after preliminary purification by salting out with ammonium sulfate at two different concentration levels, viz. 30% and 70% saturation. The coagulant activity on milk, and the proteolytic activity using casein and azocasein as substrates, of the crude extract and of each precipitated fraction were measured at 37°C and pH 5.2. The profile of hydrolysis of the major whey proteins, i.e. α-lactalbumin (α-La), β-lactoglobulin (β-Lg) and bovine serum albumin (BSA) was characterized by gel permeation chromatography and polyacrylamide gel electrophoresis (PAGE) in the presence of sodium dodecyl sulfate. The 30% and 70% saturation fractions exhibited lower coagulant and proteolytic specific activities than the crude extract. However, the relative ratio of coagulant to proteolytic activity, which is a useful indicator of appropriateness for cheesemaking, was higher for the partially purified fractions. The extents of hydrolysis of whey proteins brought about by the partially purified extracts were above those by their crude counterpart, but qualitative hydrolysis patterns were essentially identical to each other; by 24 h, α-La was substantially depleted, whereas β-Lg was very poorly hydrolyzed and BSA was only slightly hydrolyzed. The native proteins were converted to lower and lower molecular weight peptides

Phenolic acids and derivatives: studies on the relationship among structure, radical scavenging activity, and physicochemical parameters

The antiradical activity of caffeic acid (1), dihydrocaffeic acid (5), and their corresponding n-alkyl esters was evaluated by using the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH(*)) method. Dihydrocaffeic acid (5) was the most potent compound, having an antiradical effect higher than that of (+/-)-alpha-tocopherol, whereas caffeic acid (1) was less efficient. Esterification of the carboxyl group of dihydrocaffeic acid (5) had a dramatic effect on its antiradical potency, but similar effects were not observed for caffeic acid (1) derivatives. The n-alkyl esters of both phenolic series had similar potencies, and their antiradical activities were independent of the alkyl chain length. Dose-dependent scavenger effects were found in both series. Acid-base properties of the compounds, evaluated by using potentiometry and spectrophotometry, showed that the catechol moiety had pK(a2) and pK(a3) values of 9. 24-9.02 and 11.38-10.99 in the dihydrocaffeic series and 8.48-8.24 and 11.38-11.07 in the caffeic series, respectively. Antiradical activity and pK(a) values of the compounds were not related.info:eu-repo/semantics/publishedVersio

Comparing the effects of glazing and chitosan-based coating applied on frozen salmon on its organoleptic and physicochemical characteristics over six-months storage

The perishable nature of fish, with an increase in fish consumption in recent years, led to the improvement of fish preservation techniques. Chitosan coatings adds to the traditional water glazing. The effect of a chitosan solution of 1.5% on the sensory properties of Atlantic salmon (Salmo salar) was studied over six months of storage. The sensory properties of the salmon were assessed through the use of a texturometer and a trained panel of judges. Microbiological parameters were studied in the form of Total Volatile Base Nitrogen (TVB-N) and Total Viable Count (TVC) tests. Microbiological analysis showed that chitosan had an anti-microbiological effect on the salmon samples, reducing the number of microorganisms present, while TVB-N values were maitained stable during experiment. Textural Profile Analysis (TPA) was performed and the results showed no significant differences between different coatings regarding texture. Sensory analysis by a trained panel showed that chitosan was a better choice in frozen samples, while in thawed and cooked samples no significant differences existed between chitosan-coated and glazed samples. Flavor diffusion from the chitosan coating was assessed, and analysis of the results showed no correlation between coating type and sample flavor, indicating that no flavor diffusion had occurred.The contribution of VANIBRU, Lda. regarding the PhD scholarship of Nuno Soares and the use of industrial facilities are gratefully acknowledged

Interfacial stabilization of enzymes in microemulsions

One of the major constrains to the use of enzymes in industrial processes is their insufficient stability under processing conditions, namely high temperatures, presence of ultrasounds, among others. Herein, we investigated the use of oil-in-water proteinaceous (BSA) microemulsions as a novel methodology for the stabilization of laccase from ascomycete Micelliophthora thermophila. The immobilization of laccase onto the produced microemulsions benefitiated its stability under ultrasonic conditions. The half life time of immobilized laccase was 2.4-fold higher (from 23 to 56 minutes) than laccase in the free form. This technique show promising potentialities for the stabilization of enzymes used onto a variety of processes, namely textile bleaching, surface hydrolysis, among others