Bipolar Tribocharging Signal During Friction Force Fluctuations At Metal-insulator Interfaces.

Friction and triboelectrification of materials show a strong correlation during sliding contacts. Friction force fluctuations are always accompanied by two tribocharging events at metal-insulator [e.g., polytetrafluoroethylene (PTFE)] interfaces: injection of charged species from the metal into PTFE followed by the flow of charges from PTFE to the metal surface. Adhesion maps that were obtained by atomic force microscopy (AFM) show that the region of contact increases the pull-off force from 10 to 150 nN, reflecting on a resilient electrostatic adhesion between PTFE and the metallic surface. The reported results suggest that friction and triboelectrification have a common origin that must be associated with the occurrence of strong electrostatic interactions at the interface.

[access To Basic Health Services And Associated Factors: A Population-based Study].

This study sought to identify factors involved in access to the services of a basic health unit. It is a cross-sectional, population-based study involving 101 randomly-selected families residing in the area covered by the health unit. An adult resident of each household was interviewed. The response variable was whether or not the resident frequented the health unit if he/she or anyone in the family required assistance to resolve a health issue. The independent variables investigated were service provision aspects, demographic and socio-economic characteristics, individual habits, morbidities and use of the health unit. In addition to descriptive and univariate analysis, logistic regression was applied in the multivariate analysis. The results show that access to the basic health unit is associated with the treatment received previously (OR = 3,224) with accessibility (OR = 0,146) and micro-area of residence (OR = 10,918). These findings suggest that access is related to the impressions created by the care received at the health unit and is based on experiences with the service, but can also be strongly modulated by individual aspects and factors related to the territory.

Effect Of Atorvastatin On Wound Healing In Rats.

Skin-wound healing is a complex and dynamic biological process involving inflammation, proliferation, and remodeling. Recent studies have shown that statins are new therapeutical options because of their actions, such as anti-inflammatory and antioxidant activity, on vasodilation, endothelial dysfunction and neoangiogenesis, which are independent of their lipid-lowering action. Our aim was to investigate the effect of atorvastatin on tissue repair after acute injury in healthy animals. Rats were divided into four groups: placebo-treated (P), topical atorvastatin-treated (AT), oral atorvastatin-treated (AO), topical and oral atorvastatin-treated (ATO). Under anesthesia, rats were wounded with an 8-mm punch in the dorsal region. Lesions were photographed on Days 0, 1, 3, 7, 10, 12, and 14 post-injury and samples taken on Days 1, 3, 7, and 14 for protein-expression analysis of insulin receptor substrate (IRS)-1, phosphatidylinositol 3-kinase (PI3K), protein kinase B (Akt), glycogen synthase kinase (GSK)-3, endothelial nitric oxide synthase (eNOS), vascular endothelial growth factor (VEGF), extracellular signal-regulated kinase (ERK), interleukin (IL)-10, IL-1β, IL-6, and tumor necrosis factor (TNF)-α. Upon macroscopic examination, we observed significant reductions of lesion areas in groups AT, AO, and ATO compared to the P group. Additionally, AT and AO groups showed increased expression of IRS-1, PI3K, Akt, GSK-3, and IL-10 on Days 1 and 3 when compared with the P group. All atorvastatin-treated groups showed higher expression of IRS-1, PI3K, Akt, GSK-3, IL-10, eNOS, VEGF, and ERK on Day 7. On Days 1, 3, and 7, all atorvastatin-treated groups showed lower expression of IL-6 and TNF-α when compared with the P group. We conclude that atorvastatin accelerated tissue repair of acute lesions in rats and modulated expressions of proteins and cytokines associated with cell-growth pathways.

Muscle Hyperalgesia Induced By Peripheral P2x3 Receptors Is Modulated By Inflammatory Mediators.

ATP, via activation of P2X3 receptors, has been highlighted as a key target in inflammatory hyperalgesia. Therefore, the aim of this study was to confirm whether the activation of P2X3 receptors in the gastrocnemius muscle of rats induces mechanical muscle hyperalgesia and, if so, to analyze the involvement of the classical inflammatory mediators (bradykinin, prostaglandins, sympathetic amines, pro-inflammatory cytokines and neutrophil migration) in this response. Intramuscular administration of the non-selective P2X3 receptor agonist α,β-meATP in the gastrocnemius muscle of rats induced mechanical muscle hyperalgesia, which, in turn, was prevented by the selective P2X3 and P2X2/3 receptors antagonist A-317491, the selective bradykinin B1-receptor antagonist Des-Arg9-[Leu8]-BK (DALBK), the cyclooxygenase inhibitor indomethacin, the β1- or β2-adrenoceptor antagonist atenolol and ICI 118,551, respectively. Also, the nonspecific selectin inhibitor fucoidan. α,β-meATP induced increases in the local concentration of the pro-inflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin 1β (IL-1β), which were reduced by bradykinin antagonist. Finally, α,β-meATP also induced neutrophil migration. Together, these findings suggest that α,β-meATP induced mechanical hyperalgesia in the gastrocnemius muscle of rats via activation of peripheral P2X3 receptors, which involves bradykinin, prostaglandins, sympathetic amines, pro-inflammatory cytokines release and neutrophil migration. It is also indicated that bradykinin is the key modulator of the mechanical muscle hyperalgesia induced by P2X3 receptors. Therefore, we suggest that P2X3 receptors are important targets to control muscle inflammatory pain.

Influence of Laser Photobiomodulation on Collagen IV During Skeletal Muscle Tissue Remodeling After Injury in Rats

Objective: The aim of the present study was to determine the effect of GaAlAs low-level laser therapy (LLLT) on collagen IV remodeling of the tibialis anterior (TA) muscle in rats after cryolesion. Background: Considerable interest exists in skeletal muscle regeneration in situations such as repair after exercise-induced muscle injury, after muscle transplantation, in muscular dystrophy, exercise-induced muscle injury, and the recovery of strength after atrophy due to disuse. A number of studies have demonstrated the potential of LLLT in facilitating the muscle-healing process; however, no consensus is found in the literature regarding the best laser-irradiation parameters. Methods: Adult male Wistar rats (n = 45) were used and randomly divided into three groups: control (n = 5); nontreated cryolesioned group (n = 20), and LLLT-cryolesioned group (n = 20). The cryolesioned groups were analyzed at 1, 7, 14, and 21 days after the injury procedure. Laser irradiation was performed 3 times per week on the injured region by using the GaAlAs laser (660 nm; beam spot of 0.04 cm(2), output power of 20 mW, power density of 500 mW/cm(2), and energy density of 5 J/cm(2), for 10 sec). The muscles were removed, frozen, cryosectioned, and then stained with hematoxylin-eosin for the visualization of general morphology or used for immunohistochemical analysis of collagen IV. Results: It was demonstrated that LLLT promotes an increase in collagen IV immunolabeling in skeletal muscle in the first 7 days after acute trauma caused by cryoinjury, but does not modify the duration of the tissue-repair process. Even with LLLT, the injured muscle tissue needs similar to 21 days to achieve the same state of organization as that in the noninjured muscle. Conclusion: The collagen IV content is modulated in regenerating skeletal muscle under LLLT, which might be associated with better tissue outcome, although the histologic analysis did not detect tissue improvement in the LLLT group.

Theory of small-signal ac response of a dielectric liquid containing two groups of ions

The analysis of Macdonald for electrolytes is generalized to the case in which two groups of ions are present. We assume that the electrolyte can be considered as a dispersion of ions in a dielectric liquid, and that the ionic recombination can be neglected. We present the differential equations governing the ionic redistribution when the liquid is subjected to an external electric field, describing the simultaneous diffusion of the two groups of ions in the presence of their own space charge fields. We investigate the influence of the ions on the impedance spectroscopy of an electrolytic cell. In the analysis, we assume that each group of ions have equal mobility, the electrodes perfectly block and that the adsorption phenomena can be neglected. In this framework, it is shown that the real part of the electrical impedance of the cell has a frequency dependence presenting two plateaux, related to a type of ambipolar and free diffusion coefficients. The importance of the considered problem on the ionic characterization performed by means of the impedance spectroscopy technique was discussed. (c) 2008 American Institute of Physics.

Plasma Kallikrein and Angiotensin I-converting enzyme N- and C-terminal domain activities are modulated by the insertion/deletion polymorphism

Angiotensin I-converting enzyme (ACE) is recognized as one of the main effector molecules involved in blood pressure regulation. In the last few years some polymorphisms of ACE such as the insertion/deletion (I/D) polymorphism have been described, but their physiologic relevance is poorly understood. In addition, few studies investigated if the specific activity of ACE domain is related to the I/D polymorphism and if it can affect other systems. The aim of this study was to establish a biochemical and functional characterization of the I/D polymorphism and correlate this with the corresponding ACE activity. For this purpose, 119 male brazilian army recruits were genotyped and their ACE plasma activities evaluated from the C- and N-terminal catalytic domains using fluorescence resonance energy transfer (FRET) peptides, specific for the C-domain (Abz-LFK(Dnp)OH), N-domain (Abz-SDK(Dnp)P-OH) and both C- and N-domains (Abz-FRK(Dnp)P-OH). Plasma kallikrein activity was measured using Z-Phe-Arg-AMC as substrate and inhibited by selective plasma kallikrein inhibitor (PKSI). Some physiological parameters previously described related to the I/D polymorphism such as handgrip strength, blood pressure, heart rate and BMI were also evaluated. The genotype distribution was II n = 27, ID n = 64 and DD n = 28. Total plasma ACE activity of both domains in II individuals was significantly lower in comparison to ID and DD. This pattern was also observed for C- and N-domain activities. Difference between ID and DD subjects was observed only with the N-domain specific substrate. Blood pressure, heart rate, handgrip strength and BMI were similar among the genotypes. This polymorphism also affected the plasma kallikrein activity and DD group presents high activity level. Thus, our data demonstrate that the I/D ACE polymorphism affects differently both ACE domains without effects on handgrip strength. Moreover, this polymorphism influences the kallikrein-kinin system of normotensive individuals. (C) 2009 Elsevier Ltd. All rights reserved.

Kernel machines for epilepsy diagnosis via EEG signal classification: A comparative study

Objective: We carry out a systematic assessment on a suite of kernel-based learning machines while coping with the task of epilepsy diagnosis through automatic electroencephalogram (EEG) signal classification. Methods and materials: The kernel machines investigated include the standard support vector machine (SVM), the least squares SVM, the Lagrangian SVM, the smooth SVM, the proximal SVM, and the relevance vector machine. An extensive series of experiments was conducted on publicly available data, whose clinical EEG recordings were obtained from five normal subjects and five epileptic patients. The performance levels delivered by the different kernel machines are contrasted in terms of the criteria of predictive accuracy, sensitivity to the kernel function/parameter value, and sensitivity to the type of features extracted from the signal. For this purpose, 26 values for the kernel parameter (radius) of two well-known kernel functions (namely. Gaussian and exponential radial basis functions) were considered as well as 21 types of features extracted from the EEG signal, including statistical values derived from the discrete wavelet transform, Lyapunov exponents, and combinations thereof. Results: We first quantitatively assess the impact of the choice of the wavelet basis on the quality of the features extracted. Four wavelet basis functions were considered in this study. Then, we provide the average accuracy (i.e., cross-validation error) values delivered by 252 kernel machine configurations; in particular, 40%/35% of the best-calibrated models of the standard and least squares SVMs reached 100% accuracy rate for the two kernel functions considered. Moreover, we show the sensitivity profiles exhibited by a large sample of the configurations whereby one can visually inspect their levels of sensitiveness to the type of feature and to the kernel function/parameter value. Conclusions: Overall, the results evidence that all kernel machines are competitive in terms of accuracy, with the standard and least squares SVMs prevailing more consistently. Moreover, the choice of the kernel function and parameter value as well as the choice of the feature extractor are critical decisions to be taken, albeit the choice of the wavelet family seems not to be so relevant. Also, the statistical values calculated over the Lyapunov exponents were good sources of signal representation, but not as informative as their wavelet counterparts. Finally, a typical sensitivity profile has emerged among all types of machines, involving some regions of stability separated by zones of sharp variation, with some kernel parameter values clearly associated with better accuracy rates (zones of optimality). (C) 2011 Elsevier B.V. All rights reserved.

Relationship Between Cortisol Levels and Memory Performance may be Modulated by the Presence or Absence of Cognitive Impairment: Evidence from Healthy Elderly, Mild Cognitive Impairment and Alzheimer`s Disease Subjects

An inverted U-shape function between cortisol levels and memory performance has been reported in studies on both young animals and humans. Yet little is known about this relationship in normal aging or in older subjects with cognitive impairment. This issue is particularly significant since increased levels of cortisol have been reported in Alzheimer`s disease (AD). The present study examined the association between cortisol levels and visual memory performance in healthy subjects as well as in individuals presenting mild cognitive impairment (MCI) or AD. Salivary cortisol was measured in 40 healthy elderly subjects, 31 individuals with amnestic MCI, and 40 subjects with mild probable AD. Memory performance was evaluated using the Brief Cognitive Screening Battery. Higher cortisol levels were associated with better memory performance in healthy elderly (p = 0.005), while higher cortisol levels were correlated with poorer memory performance in MCI subjects (p = 0.011). No correlation between cortisol and memory was found in the AD group (p > 0.05). These results suggest that the relationship between cortisol levels and memory performance in the aging process could vary according to the presence or absence of cognitive impairment.

Low-intensity Ultrasound Increases FAK, ERK-1/2, and IRS-1 Expression of Intact Rat Bones in a Noncumulative Manner

Background Low-intensity pulsed ultrasound stimulation (LIPUS) reportedly increases osteogenesis in fracture models but fails in intact bone, suggesting LIPUS does not act on mechanotransduction and growth factor pathways of intact bone. Questions/Purposes We asked whether daily 20-minute LIPUS applied to intact tibias would act on bone proteins involved in mechanotransduction (focal adhesion kinase [FAK], and extracellular signal-regulated kinase-1/2 [ERK-1/2]), and growth factor signaling (insulin receptor substrate-1 [IRS-1]) pathways at 7, 14, and 21 days of treatment. Methods Immunoblotting was performed to detect FAK, ERK-1/2, and IRS-1 expression and activation from the stimulated intact tibias at 7, 14, and 21 days of daily 20-minute LIPUS. Results LIPUS increased FAK expression (at 7 days), ERK-1/2 (at 14 days), and IRS-1 (at 7 days), but expression decreased 7 days later, indicating a noncumulative effect of LIPUS. As only FAK expression was detected at 21 days, these observations suggest LIPUS influences nuclear reactions that may be modulated by a major cellular mechanism preferentially inhibiting IRS-1 expression and not FAK expression. Increased ERK-1/2 expression at 14 days suggests the differing mechanisms for promoting ERK-1/2, FAK, and IRS-1 syntheses. IRS-1 expression behaved similarly to FAK expression; therefore, LIPUS may modulate growth factor pathways. LIPUS increased sustained FAK and ERK-1/2 activation, but not IRS-1, suggesting sustained ERK-1/2 activation is not the result of mechanically induced growth factor activation. Conclusions LIPUS acts on mechanotransduction and growth factor pathways in intact bone in a noncumulative manner. Clinical relevance These data suggest LIPUS applied to intact bone acts on proteins involved in osteogenesis.

Noise reduction in biomedical speech signal processing based on time and frequency Kalman filtering combined with spectral subtraction

The goal of this paper is to study and propose a new technique for noise reduction used during the reconstruction of speech signals, particularly for biomedical applications. The proposed method is based on Kalman filtering in the time domain combined with spectral subtraction. Comparison with discrete Kalman filter in the frequency domain shows better performance of the proposed technique. The performance is evaluated by using the segmental signal-to-noise ratio and the Itakura-Saito`s distance. Results have shown that Kalman`s filter in time combined with spectral subtraction is more robust and efficient, improving the Itakura-Saito`s distance by up to four times. (C) 2007 Elsevier Ltd. All rights reserved.

Void fraction measurement and signal analysis from multiple-electrode impedance sensors

Void fraction sensors are important instruments not only for monitoring two-phase flow, but for furnishing an important parameter for obtaining flow map pattern and two-phase flow heat transfer coefficient as well. This work presents the experimental results obtained with the analysis of two axially spaced multiple-electrode impedance sensors tested in an upward air-water two-phase flow in a vertical tube for void fraction measurements. An electronic circuit was developed for signal generation and post-treatment of each sensor signal. By phase shifting the electrodes supplying the signal, it was possible to establish a rotating electric field sweeping across the test section. The fundamental principle of using a multiple-electrode configuration is based on reducing signal sensitivity to the non-uniform cross-section void fraction distribution problem. Static calibration curves were obtained for both sensors, and dynamic signal analyses for bubbly, slug, and turbulent churn flows were carried out. Flow parameters such as Taylor bubble velocity and length were obtained by using cross-correlation techniques. As an application of the void fraction tested, vertical flow pattern identification could be established by using the probability density function technique for void fractions ranging from 0% to nearly 70%.

Ultrasonic Viscosity Measurement Using the Shear-Wave Reflection Coefficient with a Novel Signal Processing Technique

Real-time viscosity measurement remains a necessity for highly automated industry. To resolve this problem, many studies have been carried out using an ultrasonic shear wave reflectance method. This method is based on the determination of the complex reflection coefficient`s magnitude and phase at the solid-liquid interface. Although magnitude is a stable quantity and its measurement is relatively simple and precise, phase measurement is a difficult task because of strong temperature dependence. A simplified method that uses only the magnitude of the reflection coefficient and that is valid under the Newtonian regimen has been proposed by some authors, but the obtained viscosity values do not match conventional viscometry measurements. In this work, a mode conversion measurement cell was used to measure glycerin viscosity as a function of temperature (15 to 25 degrees C) and corn syrup-water mixtures as a function of concentration (70 to 100 wt% of corn syrup). Tests were carried out at 1 MHz. A novel signal processing technique that calculates the reflection coefficient magnitude in a frequency band, instead of a single frequency, was studied. The effects of the bandwidth on magnitude and viscosity were analyzed and the results were compared with the values predicted by the Newtonian liquid model. The frequency band technique improved the magnitude results. The obtained viscosity values came close to those measured by the rotational viscometer with percentage errors up to 14%, whereas errors up to 96% were found for the single frequency method.

An In-Depth Study of the Barkhausen Emission Signal Properties of the Plastically Deformed Fe-2%Si Alloy

This paper presents the results of the in-depth study of the Barkhausen effect signal properties for the plastically deformed Fe-2%Si samples. The investigated samples have been deformed by cold rolling up to plastic strain epsilon(p) = 8%. The first approach consisted of time-domain-resolved pulse and frequency analysis of the Barkhausen noise signals whereas the complementary study consisted of the time-resolved pulse count analysis as well as a total pulse count. The latter included determination of time distribution of pulses for different threshold voltage levels as well as the total pulse count as a function of both the amplitude and the duration time of the pulses. The obtained results suggest that the observed increase in the Barkhausen noise signal intensity as a function of deformation level is mainly due to the increase in the number of bigger pulses.

Phase-Locked Loop design applied to frequency-modulated atomic force microscope

The atomic force microscope (AFM) introduced the surface investigation with true atomic resolution. In the frequency modulation technique (FM-AFM) both the amplitude and the frequency of oscillation of the micro-cantilever must be kept constant even in the presence of tip-surface interaction forces. For that reason, the proper design of the Phase-Locked Loop (PLL) used in FM-AFM is vital to system performance. Here, the mathematical model of the FM-AFM control system is derived considering high order PLL In addition a method to design stable third-order Phase-Locked Loops is presented. (C) 2010 Elsevier B.V. All rights reserved.