Modeling and identification of freeplay nonlinearity

A nonlinear analysis is performed for the purpose of identification of the pitch freeplay nonlinearity and its effect on the type of bifurcation of a two degree-of-freedom aeroelastic system. The databases for the identification are generated from experimental investigations of a pitch-plunge rigid airfoil supported by a nonlinear torsional spring. Experimental data and linear analysis are performed to validate the parameters of the linearized equations. Based on the periodic responses of the experimental data which included the flutter frequency and its third harmonics, the freeplay nonlinearity is approximated by a polynomial expansion up to the third order. This representation allows us to use the normal form of the Hopf bifurcation to characterize the type of instability. Based on numerical integrations, the coefficients of the polynomial expansion representing the freeplay nonlinearity are identified. Published by Elsevier Ltd.

Evaluation of inadequate anti-retroviral treatment in patients with HIV/AIDS

Introduction: Since the emergence of antiretroviral therapy, the survival of patients infected with human immunodeficiency virus has increased. Non-adherence to this therapy is directly related to treatment failure, which allows the emergence of resistant viral strains. Methods: A retrospective descriptive study of the antiretroviral dispensing records of 229 patients from the Center for Health Care, University Hospital, Federal University of Juiz de Fora, Brazil, was conducted between January and December 2009. Results: The study aimed to evaluate patient compliance and determine if there was an association between non-adherence and the therapy. Among these patients, 63.8% were men with an average age of 44.0 +/- 9.9 years. The most used treatment was a combination of 2 nucleoside reverse transcriptase inhibitors with 1 non-nucleoside reverse transcriptase inhibitor (55.5%) or with 2 protease inhibitors (28.8%). It was found that patients taking lopinavir/ritonavir with zidovudine and lamivudine had a greater frequency of inadequate treatment than those taking atazanavir with zidovudine and lamivudine (85% and 83.3%, respectively). Moreover, when the combination of zidovudine/lamivudine was used, the patients were less compliant (chi(2) = 4.468, 1 degree of freedom, p = 0.035). Conclusions: The majority of patients failed to correctly adhere to their treatment; therefore, it is necessary to implement strategies that lead to improved compliance, thus ensuring therapeutic efficacy and increased patient survival.

Experimental Comparison of Two Degrees-of-Freedom Vortex-Induced Vibration on High and Low Aspect Ratio Cylinders with Small Mass Ratio

Vortex-induced motion (VIM) is a specific way for naming the vortex-induced vibration (VIV) acting on floating units. The VIM phenomenon can occur in monocolumn production, storage and offloading system (MPSO) and spar platforms, structures presenting aspect ratio lower than 4 and unity mass ratio, i.e., structural mass equal to the displaced fluid mass. These platforms can experience motion amplitudes of approximately their characteristic diameters, and therefore, the fatigue life of mooring lines and risers can be greatly affected. Two degrees-of-freedom VIV model tests based on cylinders with low aspect ratio and small mass ratio have been carried out at the recirculating water channel facility available at NDF-EPUSP in order to better understand this hydro-elastic phenomenon. The tests have considered three circular cylinders of mass ratio equal to one and different aspect ratios, respectively L/D = 1.0, 1.7, and 2.0, as well as a fourth cylinder of mass ratio equal to 2.62 and aspect ratio of 2.0. The Reynolds number covered the range from 10 000 to 50 000, corresponding to reduced velocities from 1 to approximately 12. The results of amplitude and frequency in the transverse and in-line directions were analyzed by means of the Hilbert-Huang transform method (HHT) and then compared to those obtained from works found in the literature. The comparisons have shown similar maxima amplitudes for all aspect ratios and small mass ratio, featuring a decrease as the aspect ratio decreases. Moreover, some changes in the Strouhal number have been indirectly observed as a consequence of the decrease in the aspect ratio. In conclusion, it is shown that comparing results of small-scale platforms with those from bare cylinders, all of them presenting low aspect ratio and small mass ratio, the laboratory experiments may well be used in practical investigation, including those concerning the VIM phenomenon acting on platforms. [DOI: 10.1115/1.4006755]

Trans-Planckian problem in the healthy extension of Horava-Lifshitz gravity

Planck scale physics may influence the evolution of cosmological fluctuations in the early stages of cosmological evolution. Because of the quasiexponential redshifting, which occurs during an inflationary period, the physical wavelengths of comoving scales that correspond to the present large-scale structure of the Universe were smaller than the Planck length in the early stages of the inflationary period. This trans-Planckian effect was studied before using toy models. The Horava-Lifshitz (HL) theory offers the chance to study this problem in a candidate UV complete theory of gravity. In this paper we study the evolution of cosmological perturbations according to HL gravity assuming that matter gives rise to an inflationary background. As is usually done in inflationary cosmology, we assume that the fluctuations originate in their minimum energy state. In the trans-Planckian region the fluctuations obey a nonlinear dispersion relation of Corley-Jacobson type. In the "healthy extension" of HL gravity there is an extra degree of freedom which plays an important role in the UV region but decouples in the IR, and which influences the cosmological perturbations. We find that in spite of these important changes compared to the usual description, the overall scale invariance of the power spectrum of cosmological perturbations is recovered. However, we obtain oscillations in the spectrum as a function of wave number with a relative amplitude of order unity and with an effective frequency which scales nonlinearly with wave number. Taking the usual inflationary parameters we find that the frequency of the oscillations is so large as to render the effect difficult to observe.

The effect of curing light and chemical catalyst on the degree of conversion of two dual cured resin luting cements

The aim of this study was to evaluate the influence of different curing lights and chemical catalysts on the degree of conversion of resin luting cements. A total of 60 disk-shaped specimens of RelyX ARC or Panavia F of diameter 5 mm and thickness 0.5 mm were prepared and the respective chemical catalyst (Scotchbond Multi-Purpose Plus or ED Primer) was added. The specimens were light-cured using different curing units (an argon ion laser, an LED or a quartz-tungsten-halogen light) through shade A2 composite disks of diameter 10 mm and thickness 2 mm. After 24 h of dry storage at 37A degrees C, the degree of conversion of the resin luting cements was measured by Fourier-transformed infrared spectroscopy. For statistical analysis, ANOVA and the Tukey test were used, with p a parts per thousand currency signaEuro parts per thousand 0.05. Panavia F when used without catalyst and cured using the LED or the argon ion laser showed degree of conversion values significantly lower than RelyX ARC, with and without catalyst, and cured with any of the light sources. Therefore, the degree of conversion of Panavia F with ED Primer cured with the quartz-tungsten-halogen light was significantly different from that of RelyX ARC regardless of the use of the chemical catalyst and light curing source. In conclusion, RelyX ARC can be cured satisfactorily with the argon ion laser, LED or quartz-tungsten-halogen light with or without a chemical catalyst. To obtain a satisfactory degree of conversion, Panavia F luting cement should be used with ED Primer and cured with halogen light.

Bifurcation analysis of an aeroelastic system with concentrated nonlinearities

Analytical and numerical analyses of the nonlinear response of a three-degree-of-freedom nonlinear aeroelastic system are performed. Particularly, the effects of concentrated structural nonlinearities on the different motions are determined. The concentrated nonlinearities are introduced in the pitch, plunge, and flap springs by adding cubic stiffness in each of them. Quasi-steady approximation and the Duhamel formulation are used to model the aerodynamic loads. Using the quasi-steady approach, we derive the normal form of the Hopf bifurcation associated with the system's instability. Using the nonlinear form, three configurations including supercritical and subcritical aeroelastic systems are defined and analyzed numerically. The characteristics of these different configurations in terms of stability and motions are evaluated. The usefulness of the two aerodynamic formulations in the prediction of the different motions beyond the bifurcation is discussed.

The relationship between the speech perception and the degree of satisfaction among adult users of cochlear implants

Introduction: In recent years, the benefits associated with the use of cochlear implants (CIs), especially with regard to speech perception, have proven to surpass those produced by the use of hearing aids, making CIs a highly efficient resource for patients with severe/profound hearing loss. However, few studies so far have assessed the satisfaction of adult users of CIs. Objective: To analyze the relationship between the level of speech perception and degree of satisfaction of adult users of CI. Method: This was a prospective cross-sectional study conducted in the Audiological Research Center (CPA) of the Hospital of Craniofacial Anomalies, University of São Paulo (HRAC/USP), in Bauru, São Paulo, Brazil. A total of 12 users of CIs with pre-lingual or post-lingual hearing loss participated in this study. The following tools were used in the assessment: a questionnaire, "Satisfaction with Amplification in Daily Life" (SADL), culturally adapted to Brazilian Portuguese, as well as its relationship with the speech perception results; a speech perception test under quiet conditions; and the Hearing in Noise Test (HINT)Brazil under free field conditions. Results: The participants in the study were on the whole satisfied with their devices, and the degree of satisfaction correlated positively with the ability to perceive monosyllabic words under quiet conditions. The satisfaction did not correlate with the level of speech perception in noisy environments. Conclusion: Assessments of satisfaction may help professionals to predict what other factors, in addition to speech perception, may contribute to the satisfaction of CI users in order to reorganize the intervention process to improve the users' quality of life.

Influence of miniscrew dental root proximity on its degree of late stability

Purpose of this study was to evaluate the influence of miniscrew dental root proximity on its late stability degree. 40 miniscrews were inserted between maxillary second premolars and first molars for anterior retraction. Post-surgical radiographs were used to measure the septum width in the insertion site, insertion height, distal and mesial distance from miniscrew to dental root, and the smallest distance between miniscrew and dental root. The miniscrews were divided in two groups according to septum width: ?3 mm (20 miniscrews) and >3 mm (20 miniscrews). The soft tissue in the insertion site, sensitivity during load, plaque around the miniscrew, and evaluation period were also considered. The results showed no significant difference in miniscrew mobility degree and success rate between groups. Miniscrew dental root proximity did not influence the stability and success rate when the distance between the miniscrew and dental root indicated no periodontal ligament invasion. The overall success rate was 90% and no variable was associated with miniscrew failure. Nevertheless, patient sensitivity was frequently associated with some degree of mini-implant mobility. The septum width did not influence the stability and success rate of this anchorage system, but the extreme root proximity did.

Degree of satisfaction among hearing aid users

Introduction: Hearing loss (HL) is defined as the complete or partial loss of hearing ability. Aims: To characterize (1) the degree of satisfaction among adult and elderly hearing aid (HA) users who were treated by a public hearing health service and (2) the relationship between satisfaction and the variables of gender, age, degree of HL, and type of HA. Method: The clinical and experimental study included the administration of the Satisfaction with Amplification in Daily Life (SADL) questionnaire to 110 patients who had used HAs for more than 3 months and were 18 years of age or older. Results: Test patients were sex-balanced (48% were women) and had a mean age of 67 years. A relatively high incidence of sensorineural moderate HL was detected in the study patients (66%) and device B was the most commonly used HA type (48%). No significant differences were evident between HA satisfaction and sex. The importance placed on services/costs and personal image varied between age groups. Correlation was evident at all levels between user satisfaction and amplification. Decreased satisfaction was observed in individuals with severe and/or profound HL. The type of HA used yielded statistically significant differences in the positive effects referring. Conclusion: No correlations were evident between the different factors proposed. HA users exhibited high levels of satisfaction in all SADL areas

Degree of multicollinearity and variables involved in linear dependence in additive-dominant models

The objective of this work was to assess the degree of multicollinearity and to identify the variables involved in linear dependence relations in additive-dominant models. Data of birth weight (n=141,567), yearling weight (n=58,124), and scrotal circumference (n=20,371) of Montana Tropical composite cattle were used. Diagnosis of multicollinearity was based on the variance inflation factor (VIF) and on the evaluation of the condition indexes and eigenvalues from the correlation matrix among explanatory variables. The first model studied (RM) included the fixed effect of dam age class at calving and the covariates associated to the direct and maternal additive and non-additive effects. The second model (R) included all the effects of the RM model except the maternal additive effects. Multicollinearity was detected in both models for all traits considered, with VIF values of 1.03 - 70.20 for RM and 1.03 - 60.70 for R. Collinearity increased with the increase of variables in the model and the decrease in the number of observations, and it was classified as weak, with condition index values between 10.00 and 26.77. In general, the variables associated with additive and non-additive effects were involved in multicollinearity, partially due to the natural connection between these covariables as fractions of the biological types in breed composition.

Application of H∞ theory to a 6 DOF flight simulator motion base

The purpose of this study is to apply inverse dynamics control for a six degree of freedom flight simulator motion system. Imperfect compensation of the inverse dynamic control is intentionally introduced in order to simplify the implementation of this approach. The control strategy is applied in the outer loop of the inverse dynamic control to counteract the effects of imperfect compensation. The control strategy is designed using H∞ theory. Forward and inverse kinematics and full dynamic model of a six degrees of freedom motion base driven by electromechanical actuators are briefly presented. Describing function, acceleration step response and some maneuvers computed from the washout filter were used to evaluate the performance of the controllers.

Metabolism of plasma cholesterol and lipoprotein parameters are related to a higher degree of insulin sensitivity in high HDL-C healthy normal weight subjects

Abstract Background We have searched if plasma high density lipoprotein-cholesterol (HDL-C) concentration interferes simultaneously with whole-body cholesterol metabolism and insulin sensitivity in normal weight healthy adult subjects. Methods We have measured the activities of several plasma components that are critically influenced by insulin and that control lipoprotein metabolism in subjects with low and high HDL-C concentrations. These parameters included cholesteryl ester transfer protein (CETP), phospholipid transfer protein (PLTP), lecithin cholesterol acyl transferase (LCAT), post-heparin lipoprotein lipase (LPL), hepatic lipase (HL), pre-beta-1HDL, and plasma sterol markers of cholesterol synthesis and intestinal absorption. Results In the high-HDL-C group, we found lower plasma concentrations of triglycerides, alanine aminotransferase, insulin, HOMA-IR index, activities of LCAT and HL compared with the low HDL-C group; additionally, we found higher activity of LPL and pre-beta-1HDL concentration in the high-HDL-C group. There were no differences in the plasma CETP and PLTP activities. Conclusions These findings indicate that in healthy hyperalphalipoproteinemia subjects, several parameters that control the metabolism of plasma cholesterol and lipoproteins are related to a higher degree of insulin sensitivity.

One and two degrees-of-freedom Vortex-Induced Vibration experiments with yawed cylinders

Vortex-Induced Vibration (VIV) experiments were carried out with yawed cylinders. The purpose was to investigate the validity of the Independence Principle (IP) for properly describing the flow characteristics and the dynamics of structures subjected to oblique flow. Five yaw angles in relation to the direction perpendicular to the free stream velocity were tested, namely View the MathML sourceθ=0°,10°,20°,30° and 45°. Both the upstream and downstream orientations were tested. The models were mounted on a leaf spring apparatus that allows experiments with one or two degrees of freedom. The Reynolds numbers based on the component normal to the cylinder axis fell in the interval 3×103of displacement and hydrodynamic forces were acquired. Considering only the component of the free stream which is normal to the cylinder axis, the results of amplitude and force coefficients agreed reasonably well with the non-yawed ones for yaw angles up to 20° for both one and two degrees-of-freedom experiments. This indicates the validity of the IP for this yaw angle range. For yaw angles larger than 20°, a decrease in the maximum amplitude was observed. The decrease in the oscillation amplitudes was related to a larger modulation in the phase shift between force and displacement. Differences in the results for upstream and downstream were observed and were more evident for the larger yaw angle. These differences can be associated to the asymmetric cylinder end conditions.

Determination of degree of ionization of poly(allylamine hydrochloride) (PAH) and poly[1-[4-(3-carboxy‑4 hydroxyphenylazo)benzene sulfonamido]-1,2-ethanediyl, sodium salt] (PAZO) in layer-by-layer films using vacuum photoabsorption spectroscopy

Electrostatic and hydrophobic interactions govern most of the properties of supramolecular systems, which is the reason determining the degree of ionization of macromolecules has become crucial for many applications. In this paper, we show that highresolution ultraviolet spectroscopy (VUV) can be used to determine the degree of ionization and its effect on the electronic excitation energies of layer-by-layer (LbL) films of poly(allylamine hydrochloride) (PAH) and poly[1-[4-(3-carboxy-4 hydroxyphenylazo)- benzene sulfonamido]-1,2-ethanediyl, sodium salt] (PAZO). A full assignment of the VUV peaks of these polyelectrolytes in solution and in cast or LbL films could be made, with their pH dependence allowing us to determine the p'K IND. a' using the Henderson-Hasselbach equation. The p'K IND. a' for PAZO increased from ca. 6 in solution to ca. 7.3 in LbL films owing to the charge transfer from PAH. Significantly, even using solutions at a fixed pH for PAH, the amount adsorbed on the LbL films still varied with the pH of the PAZO solutions due to these molecular-level interactions. Therefore, the procedure based on a comparison of VUV spectra from solutions and films obtained under distinct conditions is useful to determine the degree of dissociation of macromolecules, in addition to permitting interrogation of interface effects in multilayer films.

Evaluation of degree of conversion and hardness of dental composites photo-activated with different light guide tips

Objective: The aim of this study was to evaluate the degree of conversion and hardness of different composite resins, photo-activated for 40 s with two different light guide tips, fiber optic and polymer. Methods: Five specimens were made for each group evaluated. The percentage of unreacted carbon double bonds (% C=C) was determined from the ratio of absorbance intensities of aliphatic C=C (peak at 1637 cm-1) against internal standard before and after curing of the specimen: aromatic C-C (peak at 1610 cm-1). The Vickers hardness measurements were performed in a universal testing machine. A 50 gf load was used and the indenter with a dwell time of 30 seconds. The degree of conversion and hardness mean values were analyzed separately by ANOVA and Tukey's test, with a significance level set at 5%. Results: The mean values of degree of conversion for the polymer and fiber optic light guide tip were statistically different (P<.001). The hardness mean values were statistically different among the light guide tips (P<.001), but also there was difference between top and bottom surfaces (P<.001). Conclusions: The results showed that the resins photo-activated with the fiber optic light guide tip promoted higher values for degree of conversion and hardness.