A biomimetic piezoelectric pump: Computational and experimental characterization

Flow pumps have been developed for classical applications in Engineering, and are important instruments in areas such as Biology and Medicine. Among applications for this kind of device we notice blood pump and chemical reagents dosage in Bioengineering. Furthermore, they have recently emerged as a viable thermal management solution for cooling applications in small-scale electronic devices. This work presents the performance study of a novel principle of a piezoelectric flow pump which is based oil the use of a bimorph piezoelectric actuator inserted in fluid (water). Piezoelectric actuators have some advantages over classical devices, such as lower noise generation and ease of miniaturization. The main objective is the characterization of this piezoelectric pump principle through computational simulations (using finite element software), and experimental tests through a manufactured prototype. Computational data, Such as flow rate and pressure curves, have also been compared with experimental results for validation purposes. (C) 2009 Elsevier B.V. All rights reserved.

Topology Optimized Design, Microfabrication and Characterization of Electro-Thermally Driven Microgripper

This article presents a systematic and logical study of the topology optimized design, microfabrication, and static/dynamic performance characterization of an electro-thermo-mechanical microgripper. The microgripper is designed using a topology optimization algorithm based on a spatial filtering technique and considering different penalization coefficients for different material properties during the optimization cycle. The microgripper design has a symmetric monolithic 2D structure which consists of a complex combination of rigid links integrating both the actuating and gripping mechanisms. The numerical simulation is performed by studying the effects of convective heat transfer, thermal boundary conditions at the fixed anchors, and microgripper performance considering temperature-dependent and independent material properties. The microgripper is fabricated from a 25 mm thick nickel foil using laser microfabrication technology and its static/dynamic performance is experimentally evaluated. The static and dynamic electro-mechanical characteristics are analyzed as step response functions with respect to tweezing/actuating displacements, applied current/power, and actual electric resistance. A microgripper prototype having overall dimensions of 1mm (L) X 2.5mm (W) is able to deliver the maximum tweezing and actuating displacements of 25.5 mm and 33.2 mm along X and Y axes, respectively, under an applied power of 2.32 W. Experimental performance is compared with finite element modeling simulation results.

Applying semantics to grid middleware

Scheduling parallel and distributed applications efficiently onto grid environments is a difficult task and a great variety of scheduling heuristics has been developed aiming to address this issue. A successful grid resource allocation depends, among other things, on the quality of the available information about software artifacts and grid resources. In this article, we propose a semantic approach to integrate selection of equivalent resources and selection of equivalent software artifacts to improve the scheduling of resources suitable for a given set of application execution requirements. We also describe a prototype implementation of our approach based on the Integrade grid middleware and experimental results that illustrate its benefits. Copyright (C) 2009 John Wiley & Sons, Ltd.

Single Axis Controlled Hybrid Magnetic Bearing for Left Ventricular Assist Device: Hybrid Core and Closed Magnetic Circuit

In previous studies, we presented main strategies for suspending the rotor of a mixed-flow type (centrifugal and axial) ventricular assist device (VAD), originally presented by the Institute Dante Pazzanese of Cardiology (IDPC), Brazil. Magnetic suspension is achieved by the use of a magnetic bearing architecture in which the active control is executed in only one degree of freedom, in the axial direction of the rotor. Remaining degrees of freedom, excepting the rotation, are restricted only by the attraction force between pairs of permanent magnets. This study is part of a joint project in development by IDPC and Escola Politecnica of Sao Paulo University, Brazil. This article shows advances in that project, presenting two promising solutions for magnetic bearings. One solution uses hybrid cores as electromagnetic actuators, that is, cores that combine iron and permanent magnets. The other solution uses actuators, also of hybrid type, but with the magnetic circuit closed by an iron core. After preliminary analysis, a pump prototype has been developed for each solution and has been tested. For each prototype, a brushless DC motor has been developed as the rotor driver. Each solution was evaluated by in vitro experiments and guidelines are extracted for future improvements. Tests have shown good results and demonstrated that one solution is not isolated from the other. One complements the other for the development of a single-axis-controlled, hybrid-type magnetic bearing for a mixed-flow type VAD.

Computational fluid dynamics investigation of a centrifugal blood pump

In the development of a ventricular assist device, computational fluid dynamics (CFD) analysis is an efficient tool to obtain the best design before making the final prototype. In this study, different designs of a centrifugal blood pump were developed to investigate flow characteristics and performance. This study assumed the blood flow as being an incompressible homogeneous Newtonian fluid. A constant velocity was applied at the inlet; no slip boundary conditions were applied at device wall; and pressure boundary conditions were applied at the outlet. The CFD code used in this work was based on the finite volume method. In the future, the results of CFD analysis can be compared with flow visualization and hemolysis tests.

Particle-Image Velocimetry Study of a Pediatric Ventricular Assist Device

Particle-image velocimetry (PIV) was used to visualize the flow within an optically transparent pediatric ventricular assist device (PVAD) under development in our laboratory The device studied is a diaphragm type pulsatile pump with an ejection volume of 30 ml per beating cycle intended for temporary cardiac assistance as a bridge to transplantation or recovery in children. Of particular interest was the identification of flow patterns, including regions of stagnation and/or strong turbulence that often promote thrombus formation and hemolysis, which can degrade the usefulness of such devices. For this purpose, phase-locked PIV measurements were performed in planes parallel to the diaphram that drives the flow in the device. The test fluid was seeded with 10 Am polystyrene spheres, and the motion of these particles was used to determine the instantaneous flow velocity distribution in the illumination plane. These measurements revealed that flow velocities up to 1.0 m/s can occur within the PVAD. Phase-averaged velocity fields revealed the fixed vortices that drive the bulk flow within the device, though significant cycle-to-cycle variability was also quite apparent in the instantaneous velocity distributions, most notably during the filling phase. This cycle-to-cycle variability can generate strong turbulence that may contribute to greater hemolysis. Stagnation regions have also been observed between the input and output branches of the prototype, which can increase the likelihood of thrombus formation. [DOI: 10.1115/1.4001252]

Evaluation of two round baling systems for harvesting understory biomass

The objective of this study was to evaluate the performance and to estimate costs of two round baling systems for harvesting understory biomass. One system was a cutter-shredderbaler prototype (Bio-baler). The other system required two successive operations. The first operation was cutting and shredding with a Supertrak tractor equipped with a Fecon mulcher head. The second operation was baling with a Claas baler. The machines were evaluated in three different pine stands on the Osceola National Forest in Florida, United States. Data collection included time study, fuel consumption and bale measurements. Material was collected from a sample of bales for heat and moisture content determination. On the most representative site (Site 2), the Bio-baler recovered 8.05 green t ha(-1) while the mulcher and the Claas baler recovered 9.75 green t ha(-1) (43 and 52 percent of original understory biomass, respectively). Productivity was 0.30 ha h(-1) for the Bio-baler and 0.51 ha h(-1) for the Claas baler. Density of the bales was 321 green kg m(-3) for the Bio-baler and 373 green kg m(-3) for the Claas baler. Average net heat content was 6263 MJ bale(-1) for the Bio-baler and 6695 MJ bale(-1) for the Claas baler with biomass containing 38 percent of moisture content on a wet basis. cost per unit area was less with the Bio-baler (US$320.91 ha(-1)) than with the mulcher-baler system (US$336.62-US$596.77 ha(-1)). Published by Elsevier Ltd.

Effectiveness of two systems for the spraying of pesticides in citrus trees

Citriculture normally uses high application volumes in pesticide solutions (of 2.000 to 5.000 L ha(-1)) to control pests and diseases that affect the crop, which generates an increase in operational costs. For this reason, diverse systems of application are being developed to reduce application volumes and improve the uniformity of pesticide deposition. The goal of this work was to evaluate the efficiency of two application systems of pesticides in citrus trees. One system used a prototype for terrestrial application with rotary disc atomizers that are widely used in agricultural aviation, and the other system used hollow cone tip hydraulics. For the treatment of the trees the insecticide Metidation was used at the dose of 180 gr per hectare. To study the droplet spectrum, water-sensitive papers were installed at different positions in the trees canopy, and for the study of insecticide deposition leaves of the treated plants were collected. The water-sensitive papers were collected and analyzed using a computerized image analysis system (e-Sprinkle, EMBRAPA, Sao Paulo, Brazil), and the leaves analyzed by the technique of gas chromatography. Pesticide deposition was similar in both application system, although the solution volume used by the application system equipped with rotary disc atomizers was one quarter of the volume used by the application system equipped with hydraulic tips, reducing considerably the cost of the phytosanitary treatments.

Flow rate sprinkler development for site-specific irrigation

Due to the rapid depletion of water resources, water must be used more efficiently in agriculture to maintain current levels of yield in irrigated areas. The efficiency of irrigation systems can be increased by adjusting the amount of water applied to specific conditions of soil and crop, which may vary in a field. Taking into account spatial and temporal variability, it is evident that an equipment capable of providing different irrigation levels is necessary to meet the water requirement of the soil. This work aims to develop and evaluate a flow rate sprinkler to be used in center pivots or linear moving irrigation systems, with potential for utilization in irrigation scheduling. A prototype was developed by duplicating its calibrations, and discharge coefficient adjustment was carried out in the laboratory. To predict the flow rate, a successful model that represented the operation of the flow rate sprinkler was established. The calibration of the flow rate sprinkler prototype showed satisfactory statistical and technical results. Automation of the prototype was achieved by driving a step motor using communication from the parallel port of a microcomputer, which was controlled by a software developed for this purpose. The results were satisfactory and technically feasible.

Test procedure for variable rate fertilizer on coffee

The objective was to develop and test a procedure for applying variable rates of fertilizers and evaluate yield response in coffee (Coffea arabica L.) with regard to the application of phosphorus and potassium. The work was conducted during the 2004 season in a 6.4 ha field located in central Sao Paulo state. Two treatments were applied with alternating strips of fixed and variable rates during the whole season: one following the fertilizing procedures recommended locally, and the other based on a grid soil sampling. A prototype pneumatic fertilizer applicator was used, carrying two conveyor belts, one for each row. Harvesting was done with a commercial harvester equipped with a customized volumetric yield monitor, separating the two treatments. Data were analyzed based on geostatistics, correlations and regressions. The procedure showed to be feasible and effective. The area that received fertilizer applications at a variable rate showed a 34% yield increase compared to the area that received a fixed rate. The variable rate fertilizer resulted in a savings of 23% in phosphate fertilizer and a 13% increase in potassium fertilizer, when compared to fixed rate fertilizer. Yield in 2005, the year after the variable rate treatments, still presented residual effect from treatments carried out during the previous cycle.

Emulsified systems based on glyceryl monostearate and potassium cetyl phosphate: Scale-up and characterization of physical properties

introducing a pharmaceutical product on the market involves several stages of research. The scale-up stage comprises the integration of previous phases of development and their integration. This phase is extremely important since many process limitations which do not appear on the small scale become significant on the transposition to a large one. Since scientific literature presents only a few reports about the characterization of emulsified systems involving their scaling-up, this research work aimed at evaluating physical properties of non-ionic and anionic emulsions during their manufacturing phases: laboratory stage and scale-up. Prototype non-ionic (glyceryl monostearate) and anionic (potassium cetyl phosphate) emulsified systems had the physical properties by the determination of the droplet size (D[4,3 1, mu m) and rheology profile. Transposition occurred from a batch of 500-50,000 g. Semi-industrial manufacturing involved distinct conditions: intensity of agitation and homogenization. Comparing the non-ionic and anionic systems, it was observed that anionic emulsifiers generated systems with smaller droplet size and higher viscosity in laboratory scale. Besides that, for the concentrations tested, augmentation of the glyceryl monostearate emulsifier content provided formulations with better physical characteristics. For systems with potassium cetyl phosphate, droplet size increased with the elevation of the emulsifier concentration, suggesting inadequate stability. The scale-up provoked more significant alterations on the rheological profile and droplet size on the anionic systems than the non-ionic. (C) 2008 Elsevier B.V. All rights reserved.

Evaluation of ent-Kaurenoic Acid Derivatives for their Anticariogenic Activity

Ent-kaur-16(17)-en-19-oic acid (kaurenoic acid, KA) is a tetracyclic diterpene prototype for natural anticaries agents. Six KA derivatives were prepared and their antimicrobial activity against the main microorganisms involved in the caries process evaluated. The sodium salt of KA (KA-Na) was the most active, displaying very promising MIC values for most pathogens. Time-kill assays against the primary causative agent of caries (Streptococcus mutans) indicated that KA and KA-Na only inhibited growth in the first 12 h, suggesting a bacteriostatic effect. After this period (12-24 h), their bactericidal effect was clearly noted. KA and KA-Na showed no synergy when combined with the gold standard anticariogenic (chlorhexidine dihydrochloride, CHD) in the checkerboard assays against S. mutans.

Antimicrobial activity of kaurane diterpenes against oral pathogens

Two kaurane diterpenes, ent-kaur-16(17)-en-19-oic acid (KA) and 15-beta-isovaleryloxy-ent-kaur-16(17)-en-19-oic acid (KA-Ival), isolated from Aspilia foliacea, and the methyl ester derivative of KA (KA-Me) were evaluated against oral pathogens. KA was the most active compound, with MIC values of 10 mu g mL(-1) against the following microorganisms: Streptococcus sobrinus, Streptococcus mutans, Streptococcus mitis, Streptococcus sanguinis, and Lactobacillus casei. However, KA did not show significant activity against Streptococcus salivarius and Enterococcus faecalis, with MIC values equal to 100 and 200 mu g mL(-1), respectively. Our results show that KA has potential to be used as a prototype for the discovery of new effective anti-infection agents against microorganisms responsible for caries and periodontal diseases. Moreover, these results allow to conclude that minor structural differences among these diterpenes significantly influence their antimicrobial activity, bringing new perspectives to studies on the structure-activity relationship of this type of metabolites with respect to caries and periodontal diseases.

Smart Alerts: Development of Software to Optimize Data Monitoring

Dherte PM, Negrao MPG, Mori Neto S, Holzhacker R, Shimada V, Taberner P, Carmona MJC - Smart Alerts: Development of a Software to Optimize Data Monitoring. Background and objectives: Monitoring is useful for vital follow-ups and prevention, diagnosis, and treatment of several events in anesthesia. Although alarms can be useful in monitoring they can cause dangerous user`s desensitization. The objective of this study was to describe the development of specific software to integrate intraoperative monitoring parameters generating ""smart alerts"" that can help decision making, besides indicating possible diagnosis and treatment. Methods: A system that allowed flexibility in the definition of alerts, combining individual alarms of the parameters monitored to generate a more elaborated alert system was designed. After investigating a set of smart alerts, considered relevant in the surgical environment, a prototype was designed and evaluated, and additional suggestions were implemented in the final product. To verify the occurrence of smart alerts, the system underwent testing with data previously obtained during intraoperative monitoring of 64 patients. The system allows continuous analysis of monitored parameters, verifying the occurrence of smart alerts defined in the user interface. Results: With this system a potential 92% reduction in alarms was observed. We observed that in most situations that did not generate alerts individual alarms did not represent risk to the patient. Conclusions: Implementation of software can allow integration of the data monitored and generate information, such as possible diagnosis or interventions. An expressive potential reduction in the amount of alarms during surgery was observed. Information displayed by the system can be oftentimes more useful than analysis of isolated parameters.

Magnetic purification of biotinylated cDNA removes false priming and ensures strand-specificity of RT-PCR for enteroviral RNAs

The detection of replicative intermediate RNAs as markers of active replication of RNA viruses is an essential tool to investigate pathogenesis in acute viral infections, as well as in their long-term sequelae. In this regard, strand-specific PCR has been used widely to distinguish (-) and (+) enteroviral RNAs in pathogenesis studies of diseases such as dilated cardiomyopathy. It has been generally assumed that oligonucleotide-primed reverse transcription of a given RNA generates only the corresponding specific cDNA, thus assuring the specificity of a PCR product amplified from it. Nevertheless, such assumed strand-specificity is a fallacy, because falsely primed cDNAs can be produced by RNA reverse transcription in the absence of exogenously added primers, (cDNA(primer)(-)), and such falsely primed cDNAs are amplifiable by PCR in the same way as the correctly primed cDNAs. Using as a prototype the coxsackievirus B5 (CVB5), a (+) strand RNA virus, it was shown that cDNA(primer)(-) renders the differential detection of viral (-) and (+) RNAs by conventional PCR virtually impossible, due to gross non-specificity. Using in vitro transcribed CVB5 RNAs (+) and (-), it was shown that cDNA(primer)(-) could be removed effectively by magnetic physical separation of correctly primed biotinylated cDNA. Such strategy enabled truly strand-specific detection of RNA (-) and (+), not only for CVB5, but also for other non-polio enteroviruses. These findings indicate that previous conclusions supporting a role for the persistence of actively replicating enterovirus in the pathogenesis of chronic myocarditis should be regarded with strong skepticism and purification of correctly primed cDNA should be used for strand-specific PCR of viral RNA in order to obtain reliable information on this important subject. (C) 2009 Elsevier B.V. All rights reserved.