Influence of pattern gradation on the design of piezocomposite energy harvesting devices using topology optimization

Piezoelectric materials can be used to convert oscillatory mechanical energy into electrical energy. Energy harvesting devices are designed to capture the ambient energy surrounding the electronics and convert it into usable electrical energy. The design of energy harvesting devices is not obvious, requiring optimization procedures. This paper investigates the influence of pattern gradation using topology optimization on the design of piezocomposite energy harvesting devices based on bending behavior. The objective function consists of maximizing the electric power generated in a load resistor. A projection scheme is employed to compute the element densities from design variables and control the length scale of the material density. Examples of two-dimensional piezocomposite energy harvesting devices are presented and discussed using the proposed method. The numerical results illustrate that pattern gradation constraints help to increase the electric power generated in a load resistor and guides the problem toward a more stable solution. (C) 2012 Elsevier Ltd. All rights reserved.

Immunophenotyping and extracellular matrix remodeling in pulmonary and extrapulmonary sarcoidosis

Objective: To investigate the significance of cellular immune markers, as well as that of collagen and elastic components of the extracellular matrix, within granulomatous structures in biopsies of patients with pulmonary or extrapulmonary sarcoidosis. Methods: We carried out qualitative and quantitative evaluations of inflammatory cells, collagen fibers, and elastic fibers in granulomatous structures in surgical biopsies of 40 patients with pulmonary and extrapulmonary sarcoidosis using histomorphometry, immunohistochemistry, picrosirius red staining, and Weigert's resorcin-fuchsin staining. Results: The extrapulmonary tissue biopsies presented significantly higher densities of lymphocytes, macrophages, and neutrophils than did the lung tissue biopsies. Pulmonary granulomas showed a significantly higher number of collagen fibers and a lower density of elastic fibers than did extrapulmonary granulomas. The amount of macrophages in the lung samples correlated with FVC (p < 0.05), whereas the amount of CD3+, CD4+, and CD8+ lymphocytes correlated with the FEV1/FVC ratio and VC. There were inverse correlations between TLC and the CD1a+ cell count (p < 0.05), as well as between DLCO and collagen/elastic fiber density (r = -0.90; p = 0.04). Conclusions: Immunophenotyping and remodeling both showed differences between pulmonary and extrapulmonary sarcoidosis in terms of the characteristics of the biopsy samples. These differences correlated with the clinical and spirometric data obtained for the patients, suggesting that two different pathways are involved in the mechanism of antigen clearance, which was more effective in the lungs and lymph nodes.

Algebraic-graph method for identification of islanding in power system grids

In this paper, a new algebraic-graph method for identification of islanding in power system grids is proposed. The proposed method identifies all the possible cases of islanding, due to the loss of a equipment, by means of a factorization of the bus-branch incidence matrix. The main features of this new method include: (i) simple implementation, (ii) high speed, (iii) real-time adaptability, (iv) identification of all islanding cases and (v) identification of the buses that compose each island in case of island formation. The method was successfully tested on large-scale systems such as the reduced south Brazilian system (45 buses/72 branches) and the south-southeast Brazilian system (810 buses/1340 branches). (C) 2011 Elsevier Ltd. All rights reserved.

Endogenous nitric oxide formation correlates negatively with circulating matrix metalloproteinase (MMP)-2 and MMP-9 levels in black subjects

Deficient formation of endogenous nitric oxide (NO) contributes to cardiovascular diseases, and this may be associated with increased circulating levels of matrix metalloproteinase-9 (MMP-9), as previously shown in white subjects. Because interethnic differences exist with respect to risk factors, prevalence, and severity of cardiovascular diseases, we designed this study to examine whether the circulating levels of nitrites (a marker of endogenous NO formation) are associated with the plasma levels of MMP-9 and MMP-2 in healthy black subjects. We studied 198 healthy subjects self-reported as blacks not taking any medications. Venous blood samples were collected and plasma and whole blood nitrite levels were measured using an ozone-based chemiluminescence assay. Plasma MMP-2 and MMP-9 levels were determined by gelatin zymography. We found a positive correlation between plasma MMP-9 and MMP-2 levels (P < 0.0001, rs = 0.556). Interestingly, we found a negative relationship between the plasma MMP-9 levels and the plasma or whole blood nitrites levels (P = 0.04, rs = -0.149; and P < 0.0001, rs = -0.349, respectively). In parallel, we found similar negative relationships between plasma MMP-2 levels and plasma or whole blood nitrites levels (P = 0.02, rs = -0.172; and P < 0.0001, rs = -0.454, respectively). This is the first study to show that endogenous nitric oxide formation correlates negatively with the circulating levels of both MMP-2 and MMP-9 in black subjects. Our findings suggest a mechanistic link between deficient NO formation and increased MMPs levels, which may promote cardiovascular diseases.

A modified Primal-Dual Logarithmic-Barrier Method for solving the Optimal Power Flow problem with discrete and continuous control variables

The aim of solving the Optimal Power Flow problem is to determine the optimal state of an electric power transmission system, that is, the voltage magnitude and phase angles and the tap ratios of the transformers that optimize the performance of a given system, while satisfying its physical and operating constraints. The Optimal Power Flow problem is modeled as a large-scale mixed-discrete nonlinear programming problem. This paper proposes a method for handling the discrete variables of the Optimal Power Flow problem. A penalty function is presented. Due to the inclusion of the penalty function into the objective function, a sequence of nonlinear programming problems with only continuous variables is obtained and the solutions of these problems converge to a solution of the mixed problem. The obtained nonlinear programming problems are solved by a Primal-Dual Logarithmic-Barrier Method. Numerical tests using the IEEE 14, 30, 118 and 300-Bus test systems indicate that the method is efficient. (C) 2012 Elsevier B.V. All rights reserved.

Dynamical changes from harmonic vibrations of a limited power supply driving a Duffing oscillator

The harmonic oscillations of a Duffing oscillator driven by a limited power supply are investigated as a function of the alternative strength of the rotor. The semi-trivial and non-trivial solutions are derived. We examine the stability of these solutions and then explore the complex behaviors associated with the bifurcations sequences. Interestingly, a 3D diagram provides a global view of the effects of alternate strength on the appearance of chaos and hyperchaos on the system.

Is the History of Falls an Indicative of Greater Decline in Quadriceps Muscle Function and Postural Sway?

To evaluate whether a history of falls is directly related to the quadriceps muscular function and body sway, 26 elderly women were divided on the basis of the presence or absence of a history of falls. Evaluation of muscular power and anteroposterior and mediolateral displacements of center of pressure during consecutive stand and sit 5 times were performed. Fallers exhibited higher mediolateral displacement than nonfallers. No differences were observed for quadriceps power and for sit-to-stand time between groups (P<.05). The fall history was not related to the quadriceps muscular function or to the anteroposterior displacement during sit to stand.

Extracellular matrix composition in COPD

Extracellular matrix (ECM) composition has an important role in determining airway structure. We postulated that ECM lung composition of chronic obstructive pulmonary disease (COPD) patients differs from that observed in smoking and nonsmoking subjects without airflow obstruction. We determined the fractional areas of elastic fibres, type-I, -III and -IV collagen, versican, decorin, biglycan, lumican, fibronectin and tenascin in different compartments of the large and small airways and lung parenchyma in 26 COPD patients, 26 smokers without COPD and 16 nonsmoking control subjects. The fractional area of elastic fibres was higher in non-obstructed smokers than in COPD and nonsmoking controls, in all lung compartments. Type-I collagen fractional area was lower in the large and small airways of COPD patients and in the small airways of non-obstructed smokers than in nonsmokers. Compared with nonsmokers, COPD patients had lower versican fractional area in the parenchyma, higher fibronectin fractional area in small airways and higher tenascin fractional area in large and small airways compartments. In COPD patients, significant correlations were found between elastic fibres and fibronectin and lung function parameters. Alterations of the major ECM components are widespread in all lung compartments of patients with COPD and may contribute to persistent airflow obstruction.

Source of slow lithium atoms from Ne or H-2 matrix isolation sublimation

We have studied, via laser absorption spectroscopy, the velocity distribution of Li-7 atoms released from cryogenic matrices of solid neon or molecular hydrogen. The Li atoms are implanted into the Ne or H-2 matrices - grown onto a sapphire substrate - by laser ablation of a solid Li or LiH precursor. A heat pulse is then applied to the sapphire substrate sublimating the matrix together with the isolated atoms. With a NiCr film resistor deposited directly onto the sapphire substrate we are able to transfer high instantaneous power to the matrix, thus reaching a fast sublimation regime. In this regime the Li atoms can get entrained in the released matrix gas, and we were also able to achieve matrix sublimation times down to 10 mu s for both H-2 or Ne matrix, enabling us to proceed with the trapping of the species of our interest such as atomic hydrogen, lithium, and molecules. The sublimation of the H-2 matrix, with its large center-of-mass velocity, provides evidence for a new regime of one-dimensional thermalization. The laser ablated Li seems to penetrate the H-2 matrix deeper than it does in Ne. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4704125]

Calculation of parameter ranges for robust gain tuning of power system controllers

This work proposes a computational tool to assist power system engineers in the field tuning of power system stabilizers (PSSs) and Automatic Voltage Regulators (AVRs). The outcome of this tool is a range of gain values for theses controllers within which there is a theoretical guarantee of stability for the closed-loop system. This range is given as a set of limit values for the static gains of the controllers of interest, in such a way that the engineer responsible for the field tuning of PSSs and/or AVRs can be confident with respect to system stability when adjusting the corresponding static gains within this range. This feature of the proposed tool is highly desirable from a practical viewpoint, since the PSS and AVR commissioning stage always involve some readjustment of the controller gains to account for the differences between the nominal model and the actual behavior of the system. By capturing these differences as uncertainties in the model, this computational tool is able to guarantee stability for the whole uncertain model using an approach based on linear matrix inequalities. It is also important to remark that the tool proposed in this paper can also be applied to other types of parameters of either PSSs or Power Oscillation Dampers, as well as other types of controllers (such as speed governors, for example). To show its effectiveness, applications of the proposed tool to two benchmarks for small signal stability studies are presented at the end of this paper.

The β to α phase transition of tantalum coatings deposited by modulated pulsed power magnetron sputtering

Tantalum coatings are of particular interest today as promising candidates to replace potentially hazardous electrodeposited chromium coatings for tribological and corrosion resistant applications, such as the internal lining on large-caliber gun barrels. Tantalum coatings have two crystalline phases, α-Ta (body-centered-cubic) and β-Ta (metastable tetragonal) that exhibit relatively different properties. Alpha-Ta is typically preferred for wear and corrosion resistant applications and unfortunately, is very difficult to deposit without the assistance of substrate heating or post-annealing treatments. Furthermore, there is no general consensus on the mechanism which causes α or β to form or if there is a phase transition or transformation from β → α during coating deposition. In this study, modulated pulsed power (MPP) magnetron sputtering was used to deposit tantalum coatings with thicknesses between 2 and 20 μm without external substrate heating. The MPP Ta coatings showed good adhesion and low residual stress. This study shows there is an abrupt β → α phase transition when the coating is 5–7 μm thick and not a total phase transformation. Thermocouple measurements reveal substrate temperature increases as a function of deposition time until reaching a saturation temperature of ~ 388 °C. The importance of substrate temperature evolution on the β → α phase transition is also explained.

Surface modification by metal ion implantation forming metallic nanoparticles in insulating matrix.

There is special interest in the incorporation of metallic nanoparticles in a surrounding dielectric matrix for obtaining composites with desirable characteristics such as for surface plasmon resonance, which can be used in photonics and sensing, and controlled surface electrical conductivity. We investigated nanocomposites produced through metallic ion implantation in insulating substrate, where the implanted metal self-assembles into nanoparticles. During the implantation, the excess of metal atom concentration above the solubility limit leads to nucleation and growth of metal nanoparticles, driven by the temperature and temperature gradients within the implanted sample including the beam-induced thermal characteristics. The nanoparticles nucleate near the maximum of the implantation depth profile (projected range), that can be estimated by computer simulation using the TRIDYN. This is a Monte Carlo simulation program based on the TRIM (Transport and Range of Ions in Matter) code that takes into account compositional changes in the substrate due to two factors: previously implanted dopant atoms, and sputtering of the substrate surface. Our study suggests that the nanoparticles form a bidimentional array buried few nanometers below the substrate surface. More specifically we have studied Au/PMMA (polymethylmethacrylate), Pt/PMMA, Ti/alumina and Au/alumina systems. Transmission electron microscopy of the implanted samples showed the metallic nanoparticles formed in the insulating matrix. The nanocomposites were characterized by measuring the resistivity of the composite layer as function of the dose implanted. These experimental results were compared with a model based on percolation theory, in which electron transport through the composite is explained by conduction through a random resistor network formed by the metallic nanoparticles. Excellent agreement was found between the experimental results and the predictions of the theory. It was possible to conclude, in all cases, that the conductivity process is due only to percolation (when the conducting elements are in geometric contact) and that the contribution from tunneling conduction is negligible.

Stopping power and depth dose profile of H+ and He+ ion beams in hydroxyapatite thin films.

Hadron therapy is a promising technique to treat deep-seated tumors. For an accurate treatment planning, the energy deposition in the soft and hard human tissue must be well known. Water has been usually employed as a phantom of soft tissues, but other biomaterials, such as hydroxyapatite (HAp), used as bone substitute, are also relevant as a phantom for hard tissues. The stopping power of HAp for H+ and He+ beams has been studied experimentally and theoretically. The measurements have been done using the Rutherford backscattering technique in an energy range of 450-2000 keV for H+ and of 400-5000 keV for He+ projectiles. The theoretical calculations are based in the dielectric formulation together with the MELF-GOS (Mermin Energy-Loss Function – Generalized Oscillator Strengths) method [1] to describe the target excitation spectrum. A quite good agreement between the experimental data and the theoretical results has been found. The depth dose profile of H+ and He+ ion beams in HAp has been simulated by the SEICS (Simulation of Energetic Ions and Clusters through Solids) code [2], which incorporates the electronic stopping force due to the energy loss by collisions with the target electrons, including fluctuations due to the energy-loss straggling, the multiple elastic scattering with the target nuclei, with their corresponding nuclear energy loss, and the dynamical charge-exchange processes in the projectile charge state. The energy deposition by H+ and He+ as a function of the depth are compared, at several projectile energies, for HAp and liquid water, showing important differences.

Effect of blood haemoglobin concentration on V(O2,max) and cardiovascular function in lowlanders acclimatised to 5260 m

[EN] The principal aim of this investigation was to determine the influence of blood haemoglobin concentration ([Hb]) on maximal exercise capacity and maximal O(2) consumption (V(O(2),max)) in healthy subjects acclimatised to high altitude. Secondarily, we examined the effects of [Hb] on the regulation of cardiac output (CO), blood pressure and muscular blood flow (LBF) during exercise. Eight Danish lowlanders (three females and five males; 24 +/- 0.6 years, mean +/- S.E.M.) performed submaximal and maximal exercise on a cycle ergometer after 9 weeks at an altitude of 5260 m (Mt Chacaltaya, Bolivia). This was done first with the high [Hb] resulting from acclimatisation and again 2-4 days later, 1 h after isovolaemic haemodilution with Dextran 70 to near sea level [Hb]. After measurements at maximal exercise while breathing air at each [Hb], subjects were switched to hyperoxia (55 % O(2) in N(2)) and the measurements were repeated, increasing the work rate as tolerated. Hyperoxia increased maximal power output and leg V(O(2),max), showing that breathing ambient air at 5260 m, V(O(2),max) is limited by the availability of O(2) rather than by muscular oxidative capacity. Altitude increased [Hb] by 36 % from 136 +/- 5 to 185 +/- 5 g l(-1) (P < 0.001), while haemodilution (replacing 1 l of blood with 1 l of 6 % Dextran) lowered [Hb] by 24 % to 142 +/- 6 g l(-1) (P < 0.001). Haemodilution had no effect on maximal pulmonary or leg V(O(2),max), or power output. Despite higher LBF, leg O(2) delivery was reduced and maximal V(O(2)) was thus maintained by higher O(2) extraction. While CO increased linearly with work rate irrespective of [Hb] or inspired oxygen fraction (F(I,O(2))), both LBF and leg vascular conductance were systematically higher when [Hb] was low. Close and significant relationships were seen between LBF (and CO) and both plasma noradrenaline and K(+) concentrations, independently of [Hb] and F(I,O(2)). In summary, under conditions where O(2) supply limits maximal exercise, the increase in [Hb] with altitude acclimatisation does not improve maximal exercise capacity or V(O(2),max), and does not alter peak CO. However, LBF and vascular conductance are higher at altitude when [Hb] is lowered to sea level values, with both relating closely to catecholamine and potassium concentrations. This suggests that the lack of effect of [Hb] on V(O(2),max) may involve reciprocal changes in LBF via local metabolic control of the muscle vasculature.

Proteolysis of the receptor for advanced glycation end products by matrix metalloproteinases

RAGE mediates diverse physiological and pathological effects by binding a variety of ligands. Despite incomplete understanding of RAGE-mediated disorders soluble RAGE (sRAGE) has been identified as a potential biomarker for RAGE-related diseases and possibly represents a hopeful pharmaceutical against RAGE-mediated disorders. Nevertheless, the source of sRAGE remains poorly investigated. Currently sRAGE is thought to be derived exclusively from alternative splicing of mRNA. In this thesis it was investigated whether sRAGE can also be released as a result of ectodomain shedding of full-length RAGE. Using cells overexpressing RAGE as a model system, it was demonstrated clearly that RAGE undergoes ectodomain shedding in both constitutive and regulated manner. Several stimuli including PMA, AMPA, calcium and chelerythrine stimulated the release of sRAGE into cell culture medium. Moreover, possible mechanisms that regulate ectodomain shedding of RAGE were investigated and it was found that shedding of RAGE is likely independent from PKC and MAPK pathways. By using gain of function and loss of function approaches MMP9 but not ADAM10, ADAM17 or MT1-MMP was characterized as the metalloproteinase that mediates shedding of RAGE. Furthermore, it was shown that cytoplasmic domain of RAGE is not essential for shedding of RAGE. In addition, the potential cleavage site of RAGE by MMP9 was investigated and a lack of sequence specificity for the RAGE processing proteinase was demonstrated by mutation analysis. Finally the physiopathological significance of shedding of RAGE is discussed. In conclusion, for the first time ectodomain shedding of human RAGE and the underlying regulatory mechanisms were investigated. The data open a new field for modulation of RAGE shedding as a novel intervention approach against RAGE-mediated diseases.