Energy dissipation in depth-sensing indentation as a characteristic of the nanoscratch behavior of coatings

Wear behavior of coatings has usually been described in terms of mechanical properties such as hardness (H) and effective elastic modulus (E*). Alternatively, an energy approach appears as a promising analysis taking into account the influence of those properties. In a nanoindentation test, the dissipated energy depends not only on the hardness and elastic modulus, but also on the elastic recovery (W(e)). This work aims to establish a relation between plastic deformation energy (E(p)) during depth-sensing indentation method and the grooving resistance of coatings in nanoscratch tests. An energy dissipation coefficient (K(d)) was defined, calculated as the ratio of the plastic to the total deformation energy (E(p)/E(t)), which represents the energy dissipation of materials. Reactive depositions using titanium as the target and nitrogen and methane as reactive gases were obtained by triode magnetron sputtering, in order to assess wear and nanoindentation data. A topographical, chemical and microstructural characterization has been conducted using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), wave dispersion spectroscopy (WDS), scanning electron (SEM) and atomic force microscopy (AFM) techniques. Nanoscratch results showed that the groove depth was well correlated to the energy dissipation coefficient of the coatings. On the other hand, a reduction in the coefficient was found when the elastic recovery was increased. (C) 2009 Elsevier B.V. All rights reserved.

Galerkin finite element method for incompressible thermofluid flows framed within the bond graph theory

In this paper a bond graph methodology is used to model incompressible fluid flows with viscous and thermal effects. The distinctive characteristic of these flows is the role of pressure, which does not behave as a state variable but as a function that must act in such a way that the resulting velocity field has divergence zero. Velocity and entropy per unit volume are used as independent variables for a single-phase, single-component flow. Time-dependent nodal values and interpolation functions are introduced to represent the flow field, from which nodal vectors of velocity and entropy are defined as state variables. The system for momentum and continuity equations is coincident with the one obtained by using the Galerkin method for the weak formulation of the problem in finite elements. The integral incompressibility constraint is derived based on the integral conservation of mechanical energy. The weak formulation for thermal energy equation is modeled with true bond graph elements in terms of nodal vectors of temperature and entropy rates, resulting a Petrov-Galerkin method. The resulting bond graph shows the coupling between mechanical and thermal energy domains through the viscous dissipation term. All kind of boundary conditions are handled consistently and can be represented as generalized effort or flow sources. A procedure for causality assignment is derived for the resulting graph, satisfying the Second principle of Thermodynamics. (C) 2007 Elsevier B.V. All rights reserved.

On the solubility of proteins as a function of pH: Mathematical development and application

Thermodynamic relations between the solubility of a protein and the solution pH are presented in this work. The hypotheses behind the development are that the protein chemical potential in liquid phase can be described by Henry`s law and that the solid-liquid equilibrium is established only between neutral molecules. The mathematical development results in an analytical expression of the solubility curve, as a function of the ionization equilibrium constants, the pH and the solubility at the isoelectric point. It is shown that the same equation can be obtained either by directly calculating the fraction of neutral protein molecules or by integrating the curve of the protein average charge. The methodology was successfully applied to the description of the solubility of porcine insulin as a function of pH at three different temperatures and of bovine beta-lactoglobulin at four different ionic strengths. (C) 2011 Elsevier B.V. All rights reserved.

Ovarian function in cows submitted to acute stress during proestrus

Studies in which ACTH was administrated in heifers after the occurrence of luteolysis showed a delay in the onset of estrus and the estrus duration was shortened. This study evaluated the effect of acute stress by road transportation on estrous behavior and ovulation, monitored by serum progesterone and cortisol concentrations in cows at the periovulatory period, using a crossover design. Eleven crossbred cows, divided into Control and Transport groups had their estrus cycle synchronized with GnRH, an intravaginal progesterone device, and cloprostenol. Thirty hours after withdrawal of the device, the animals of the Transport group were transported for 60 min by truck and those from the Control group remained at pasture. Ovarian ultrasound examination was performed every 12 h from device withdrawal until ovulation in every cow. From the day after removal of the device until ovulation estrous behavior was monitored 24 h a day. Blood samples for serum cortisol and progesterone concentrations were taken at -90, -60, 0, 30, 60 and 180 min in relation to the end of transportation. Transportation during the estrous period induced stress in cows as reflected by changes in serum concentrations of progesterone and cortisol. However, we did not detect impairment in estrus expression, estrus duration or ovulation (P>0.05). (C) 2010 Elsevier B.V. All rights reserved.

Nutrition in bean plants and anthracnose intensity in function of silicon and copper application.

Nutrition in bean plants and anthracnose intensity in function of silicon and copper application. The objective of this work was to evaluate the effect of calcium silicate and copper sulfate on anthracnose intensity and nutrition of bean plants. The experiment was conducted using an experimental design in randomized blocks following a 4 x 4 factorial arrangement , (four levels of calcium silicate and four levels of copper sulfate) and two additional treatments (plants without inoculation and plants sprinkled with Benomyl). Four evaluations of the incidence and severity of anthracnose were done, in addition to measuring, total leaf area. At the end of the evaluations, incidence: and data were integrated over time, obtaining the area under disease progress curve (AUDPC). Contents of N, P, K, Ca, Mg, B, Cu, Fe, Mn, Zn, Si and lignin were determined in the aerial Part. A linear decrease of the intensity AUDPC was observed with the increase of the doses of calcium silicate. The severity AUDPC was influenced by the doses of copper, obtaining a reduction of 35% on the higher dosage. The supply of silicon and copper altered the content of the K, mg, S, Zn, Ca and Si in the aerial part of the bean plants.

Brazil nut ingestion increased plasma selenium but had minimal effects on lipids, apolipoproteins, and high-density lipoprotein function in human subjects

The Brazil nut (Bertholletia excelsa) of the Amazon region is consumed worldwide. It is rich in both monounsaturated fatty acids and polyunsaturated fatty acids and is known for its high selenium content. This study tested the hypothesis whether the consumption of this nut could affect the plasma lipids and apolipoproteins and some functional properties of the antiatherogenic high-density lipoprotein (HDL). Fifteen normolipidemic subjects aged 27.3 +/- 3.9 years and with body mass index of 23.8 +/- 2.8 kg/m(2) consumed 45 g of Brazil nuts per day during a 15-day period. On days 0 and 15, blood was collected for biochemical analysis, determination of HDL particle size, paraoxonase 1 activity, and lipid transfer from a lipoprotein-like nanoparticle to the HDL fraction. Brazil nut ingestion did not alter HDL, low-density lipoprotein cholesterol, triacylglycerols, apolipoprotein A-1, or apolipoprotein B concentrations. HDL particle diameter and the activity of antioxidative paraoxonase 1, mostly found in the HDL fraction, Were also unaffected. Supplementation increased the reception of cholesteryl esters (P <.05) by the HDL yet did not alter the reception of phospholipids, free cholesterol, or triacylglycerols. As expected, plasma selenium was significantly increased. However, the consumption of Brazil nuts for short duration by normolipidemic subjects in comparable amounts to those tested for other nuts did not alter serum lipid profile. The only alteration in HDL function was the increase in cholesteryl ester transfer. This latter finding may be beneficial because it would improve the nonatherogenic reverse cholesterol transport pathway. (c) 2008 Elsevier Inc. All rights reserved.

Dietary glutamine supplementation affects macrophage function, hematopoiesis and nutritional status in early weaned mice

Background Et aims: To investigate the effect that early weaning associated with the ingestion of either a glutamine-free or supplemented diet has on the functioning of peritoneal. macrophages, hematopoiesis and nutritional status of mice. Methods: Swiss Webster mice were early weaned on their 14th day of life and distributed to two groups, being fed either a glutamine-free diet (-GLN) or a glutamine-supplemented diet (+GLN). Animals belonging to a control group (CON) were weaned on their 21st day of life. Results: The -GLN and +GLN groups had a lower lean body mass, carcass protein and ash content, plasma glutamine concentration and lymphocyte counts both in the peripheral blood and bone marrow when compared to the CON group (P < 0.05). Dietary supplementation with glutamine reversed both the lower concentrations of protein and DNA in the muscle and liver, as well. as the reduced capacity of spreading and synthesizing nitric oxide, hydrogen peroxide, TNF-alpha, IL-1 beta and IL-6 in cultures of peritoneal. macrophages obtained from the -GLN group (P < 0.05). Conclusion: These data indicate that the ingestion of glutamine modulates the function of peritoneal macrophages in early weaned mice. However, a glutamine-supplemented diet cannot substitute maternal milk in respect to immunological and metabolic parameters. (C) 2008 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.

Glutamine in vitro supplementation partly reverses impaired macrophage function resulting from early weaning in mice

Objective: Glutamine is one of the most abundant amino acids found in maternal milk, and its concentration increases throughout lactation. Because glutamine is essential for macrophage functionality, it is hereby suggested that early weaning in conjunction with the absence of glutamine consumption impairs the functioning of macrophages, which could in turn be reversed with an in vitro supplementation with glutamine. Methods: Swiss Webster mice were early weaned at 14 d of age (EW group) or at 21 d of age (control group, n = 8 per group). The EW group was fed a glutamine-free diet from days 14 to 21 of life. Results: Mice in the EW group presented a significant decrease in plasma and muscle concentrations of glutamine and an increase in the activity of glutamine synthetase in the muscle. Peritoneal macrophages obtained from animals in the EW group presented a significant increase in the production of interleukin (IL)-10 and a significant decrease in the synthesis of IL-1 beta, IL-6, tumor necrosis factor-a, nitric oxide, and hydrogen peroxide and in their ability to adhere, spread, phagocytize, and kill fungi. Glutamine in vitro supplementation reversed the decrease in IL-6, nitric oxide, and hydrogen peroxide synthesis and the decrease in the capacity to adhere, spread, and phagocytize in animals of the EW group. Conclusion: These new. data may imply that a lack of glutamine intake in early weaned mice hampers the functioning of peritoneal macrophages. (C) 2008 Elsevier Inc. All rights reserved.

Sterilization of Medical Devices by Ethylene Oxide, Determination of the Dissipation of Residues, and Use of Green Fluorescent Protein as an Indicator of Process Control

Ethylene oxide (EO) is used to sterilize Oxygenator and Tubing applied to heart surgery. Residual levels of EO and its derivatives, ethylene chlorohydrin (ECH) and ethylene glycol (EG), may be hazardous to the patients. Therefore, it must be removed by the aeration process. This study aimed to estimate the minimum aeration time for these devices to attain safe limits for use (avoiding excessive aeration time) and to evaluate the Green Fluorescent Protein (GFP) as a biosensor capable of best indicating the distribution and penetration of EO gas throughout the sterilization chamber. Sterilization cycles of 2, 4, and 8 h were monitored by Bacillus atrophaeus ATCC 9372 as a biological indicator (131) and by the GFP. Residual levels of EO, ECH, and EG were determined by gas chromatography (GC), and the residual dissipation was studied. Safe limits were reached right after the sterilization process for Oxygenator and after 204 h of aeration for Tubing. In the 2 h cycle, the GFP concentration decreased from 4.8 (+/- 3.2)% to 7.5 (+/- 2.5)%. For the 4 h cycle, the GFP concentration decreased from 17.4 (+/- 3.0)% to 21.5 (+/- 6.8)%, and in the 8 h cycle, it decreased from 22.5 (+/- 3.2)% to 23.9 (+/- 3.9)%. This finding showed the potentiality for GFP applications as an EO biosensor. (C) 2009 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 9113: 626-630, 2009

Impact of cholesterol on ABC and SLC transporters expression and function and its role in disposition variability to lipid-lowering drugs

This report focuses on the effects of cholesterol on the expression and function of the ATP-binding cassette (ABCB1, ABCG2 and ABCC2) and solute-linked carrier (SLCO1B1 and SLCO2B1) drug transporters with a particular focus on the potential impact of cholesterol on lipid-lowering drug disposition. Statins are the most active agents in the treatment of hypercholesterolemia. However, considerable interindividual variation exists in the response to statin therapy. Therefore, it would be huge progress if factors were identified that reliably differentiate between responders and nonresponders. Many studies have suggested that plasma lipid concentrations can affect drug disposition of compounds, such as ciclosporin and amphotericin B. Both compounds are able to affect the expression and function of ABC transporters. Although still speculative, these effects might be owing to the regulation of drug transporters by plasma cholesterol levels. Studies with normo- and hyper-cholesterolemic individuals, before and after atorvastatin treatment, have demonstrated that plasma cholesterol levels are correlated with drug transporter expression, as well as being related to atorvastatin`s cholesterol-lowering effect. The mechanism influencing the correlation between cholesterol levels and the expression and function of drug transporters remains unclear. Some studies provide strong evidence that nuclear receptors, such as the pregnane X receptor and the constitutive androstane receptor, mediate this effect. In the near future, pharmacogenomic studies with individuals in a pathological state should be performed in order to identify whether high plasma cholesterol levels might be a factor contributing to interindividual oral drug bioavailability.

Mitochondrial function in the yeast form of the pathogenic fungus Paracoccidioides brasiliensis

Differences between the respiratory chain of the fungus Paracoccidioides brasiliensis and its mammalian host are reported. Respiration, membrane potential, and oxidative phosphorylation in mitochondria from P. brasiliensis spheroplasts were evaluated in situ, and the presence of a complete (Complex I-V) functional respiratory chain was demonstrated. In succinate-energized mitochondria, ADP induced a transition from resting to phosphorylating respiration. The presence of an alternative NADH-ubiquinone oxidoreductase was indicated by: (i) the ability to oxidize exogenous NADH and (ii) the lack of sensitivity to rotenone and presence of sensitivity to flavone. Malate/NAD(+)-supported respiration suggested the presence of either a mitochondrial pyridine transporter or a glyoxylate pathway contributing to NADH and/or succinate production. Partial sensitivity of NADH/succinate-supported respiration to antimycin A and cyanide, as well as sensitivity to benzohydroxamic acids, suggested the presence of an alternative oxidase in the yeast form of the fungus. An increase in activity and gene expression of the alternative NADH dehydrogenase throughout the yeast`s exponential growth phase was observed. This increase was coupled with a decrease in Complex I activity and gene expression of its subunit 6. These results support the existence of alternative respiratory chain pathways in addition to Complex I, as well as the utilization of NADH-linked substrates by P. brasiliensis. These specific components of the respiratory chain could be useful for further research and development of pharmacological agents against the fungus.

Chronic hyperhomocysteinemia impairs vascular function in ovariectomized rat carotid arteries

Homocysteine is an independent risk factor for coronary heart disease, as well as for cerebrovascular and peripheral vascular diseases. The purpose of this study was to investigate the effects of hyperhomocysteinemia (HHcy) on vascular reactivity within carotid artery segments isolated from ovariectomized female rats. Treatment with dl-Hcy thiolactone (1 g/kg body weight per day) reduced the phenylephrine-induced contraction of denuded rings. However, the treatment did not alter KCl-induced contractions, or relaxations induced by sodium nitroprusside or acetylcholine. We report elevated expressions of iNOS, eNOS, and nitrotyrosine in homocysteine-treated rat artery sections. Moreover, the inhibition of NOS by l-NAME, 1,400 W, or l-NNA restored phenylephrine-induced vasoconstriction in carotid artery segments from Hcy-treated rats. In conclusion, our findings show that severe HHCy can promote an acute decrease in the endothelium-independent contractile responses of carotid arteries to adrenergic agonists. This effect was restored by nitric oxide synthase inhibitors, which further supports the involvement of nitric oxide in HHcy-derived vascular dysfunction.

Central Cardiovascular Anatomy and Function in Crocodilia

Abstract: Among the vertebrates, crocodilians have the most complex anatomy of the heart and outflow channels. Their cardiovascular anatomy may also be the most func­tionally sophisticated, combining as it does the best features of both reptilian and mammalian (and avian) systems. The puzzlingly complex "plumbing" of crocodilians has fascinated ana­tomists and physiologists for a very long time, the first paper being that by Panizza (1833). Gradually, with the application of successive techniques of investigation as they became available, its functional significance has become reasonably clear, and the complexity is now revealed as a cardiovascular system of considerable elegance. In this paper I will review the main anatomical features of the heart and outflow channels, discuss what is known about the way they work, and speculate about the probable functional significance.

Heat transfer and entropy generation optimization of forced convection in a porous-saturated duct of rectangular cross-section

We investigate analytically the first and the second law characteristics of fully developed forced convection inside a porous-saturated duct of rectangular cross-section. The Darcy-Brinkman flow model is employed. Three different types of thermal boundary conditions are examined. Expressions for the Nusselt number, the Bejan number, and the dimensionless entropy generation rate are presented in terms of the system parameters. The conclusions of this analytical study will make it possible to compare, evaluate, and optimize alternative rectangular duct design options in terms of heat transfer, pressure drop, and entropy generation. (c) 2006 Elsevier Ltd. All rights reserved.