POSITIONING DURING RESISTANCE ELBOW FLEXOR EXERCISE AFFECTS ELECTROMYOGRAPHIC ACTIVITY, HEART RATE, and PERCEIVED EXERTION

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Efeito da velocidade de corrida em variáveis eletromiográficas e metabólicas

The aim of this study was to analyze the electromyographic signal of the rectus femuris (RF), vastus lateralis (VL), biceps femuris (BF), tibialis anterior (TA), and gastrocnemius lateralis (GL) muscles of seven male volunteers, during different running velocities; and determine and compare the EMG(FT) (electromyographic fatigue threshold), LT (lactate threshold) and AT (anaerobic threshold). The running protocol started with a velocity of 10 km.h(-1) and each three minutes elapsed occurred an increments of 1 km.h(-1) until the exhaustion, with an 30 second interval between each velocity increment to collect 25 mu l of blood. The increase of RMS values was verified in the RF in the velocities of 12 km.h(-1) to 14 km.h(-1). The EMG(FT) showed similarity between the muscles and in the indexes were found the following significant differences: AT > LT; EMG(FT) RF and EMG(FT) VL < AT and EMG(FT) VL and EMG(FT) BF > LT. These data confirmed the viability of using the EMGFT as a possible indicator to analyze the muscle fatigue.

Electromyographic activity of trunk muscles during exercises with flexible and non-flexible poles

Objective: Hand-held flexible poles which are brought into oscillation to cause alternating forces on trunk, are advocated as training devices that are supposed to solicit increased levels of stabilizing trunk muscle activity. The aim of this study was to verify this claim by comparing electromyographic (EMG) activity of trunk muscles during exercises performed with a flexible pole and a rigid pole.Methods: Twelve healthy females performed three different exercises with flexible and rigid poles. EMG activity of iliocostalis lumborum (IL), multifidus (MU), rectus abdominis (RA), external oblique (EO) and internal oblique (IO), and was continuously measured. The EMG signals were analyzed in time domain by calculation of the Root Mean Square (RMS) amplitudes over 250 ms windows. The mean RMS-values over time were normalized by the maximum RMS obtained for each muscle.Results: The IO showed a 72% greater EMG activity during the exercises performed with the flexible pole than with the rigid pole (p = 0.035). In exercises performed in standing, the IO was significantly more active than when sitting (p = 0.006).Conclusion: As intended, the cyclic forces induced by the oscillating pole did increase trunk muscle activation. However, the effect was limited and significant for the IO muscle only.

Lumbar muscles recruitment during resistance exercise for upper limbs

The aim of this study was to evaluate the EMG activity of lumbar multifidus (MU), longissimus thoracis (LT) and iliocostalis (IC) muscles during an upper limb resistance exercise (biceps curl). Ten healthy males performed maximal voluntary isometric contraction (MVC) of the trunk extensors, after this, the biceps curl exercise was executed at 25%, 30%, 35% and 40% one repetition maximum during 1 min, with 10 min rest between them. EMG root mean square (RMS) and median frequency (MFreq) were calculated for each lifting and lowering of the bar during the exercise bouts, to calculate slopes and intercepts. The results showed increases in the RMS and decreases in the MFreq slopes. RMS slopes were no different between muscles, indicating similar fatigue process along the exercise irrespective of the load level. MU and LT presented higher RMS irrespective of the load level, which can be related to the specific function during the standing position. on the other hand, IC and MU presented higher MFreq intercepts compared to LT, demonstrating possible differences in the muscle fiber conduction velocity of these muscles. These findings suggest that trunk muscles are differently activate during upper limb exercises, and the fatigue process affects the lumbar muscles similarly. (C) 2008 Elsevier Ltd. All rights reserved.

EMG amplitude and frequency parameters of muscular activity: Effect of resistance training based on electromyographic fatigue threshold

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Microeletrodos: I. Construção e caracterização

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Avaliação de forrageiras de inverno irrigadas sob pastejo

O experimento foi conduzido na UNESP - Jaboticabal com o objetivo de obter informações sobre o rendimento de matéria seca (RMS) e composição química das forrageiras de inverno, aveia preta (Avena strigosa Schreb) e triticale (X Triticosecale Wittmack), em plantio direto sob palhada de área com milheto (Pennisetum americanum (L.) K. Schum.) ou híbrido sorgo sudão (Sorghum bicolor (L.) Moench x Sorghum sudanense (Piper) Stapf) submetidas a pastejo. A forragem foi rebaixada por vacas da raça Holandês. O delineamento experimental utilizado foi em blocos casualizados, em arranjo de parcelas subdivididas, sendo analisado nas parcelas as espécies forrageiras e nas sub-parcelas as épocas de pastejo, com quatro repetições. Os tratamentos testados foram: AS: Aveia Preta sobre palhada de sorgo; AM: Aveia preta sobre palhada de milheto; TS: Triticale sobre palhada de sorgo; e, TM: Triticale sobre palhada de milheto. As pastagens apresentaram RMS semelhantes e, em relação às épocas de avaliação observou-se menor rendimento no segundo corte. Foram observados maiores teores de PB e de FDA na forragem colhida no primeiro corte e de hemicelulose no segundo corte, enquanto os valores de FDN não foram diferentes. A forragem de triticale apresentou menor conteúdo de PB e maiores teores de constituintes da parede celular.

Non-linear growth models for bullfrog tadpoles

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Reflux esophagitis in chagasic megaesophagus

The esophagitis associated with chagasic megaesophagus is commonly attributed to food and secretion stasis, thereby its name of stasis esophagitis. The present work suggests instead that in some chagasic patients the clinical, endoscopic and histological findings are more compatible with a true reflux esophagitis.

Spectroscopic studies of the Eu3+ and Er3+ ions in the fluorozirconate LaZr2F11 matrix

An investigation by optical spectroscopy of the Eu3 + and Er3 + active ions in the crystallized fluorozirconate matrix LaZr2F11 is presented. The D-5(1) --> F-7(0-5) emission lines of Eu3 + are used to extract the F-7(0-5) energy scheme and the observed extinctions permit the deduction of irreducible representations (IRREPS) associated with corresponding sub-levels in the D-2 symmetry. The crystal field analysis was carried out on a 387 x 387 basis set, comprising the F-7, D-5(1,2,3) F-5(1,2), (5)G(1,2,3) and P-3(1,2,3,4,5,6) terms of the Eu-3 (+) 4f(6) configuration. The deviation and rms are 6.8 and 7.9 cm (-1), respectively for 38 levels and ten parameters. The experimental crystal field parameters are in good agreement with the ab-initio ones. Moreover, the relative intensities of the D-5(0) --> F-7(2,3,4) emissions are well reproduced by an 'ab-initio' calculation, except for three lines. The Er3 + ions introduced in LaZr2F11, microcrystals also lie in an unique crystallographic site. A total of 31 energy levels were recorded and the crystal field analysis led to 6.6 and 7.8 cm (-1) for the deviation and rms, respectively, for nine variable parameters taken into account. The experimental CF parameters for Er3 + and Eu3 + are very similar, which seems to show that the host lattice contracts around the smaller Er3 + ion. The informations given by both Eu3 + and Eu3 + optical probes in LaZr2F11 are very consistent with the structure previously determined for the isotypic PrZr2F11 fluoride. (C) 2000 Elsevier B.V. B.V. All rights reserved.

Effect of tillage on fractal indices describing soil surface microrelief of a Brazilian Alfisol

Soil surface roughness is known to influence water infiltration, runoff and erosion. Soil surface roughness changes with management and weather and its mathematical description still remains an important issue. The main objective of this study was to investigate the effect of tillage on the two fractal indices, fractal dimension, D, and crossover length, 1, currently used in characterizing soil surface microrelief. The statistical index random roughness, RR, was also assessed. Field experiments were done on an Alfisol located at Rio Grande do Sul State (Brazil). Two tillage treatments (conventional versus direct drilling) were tested. The soil surface microrelief was assessed by point elevation measurements in 16 plots for each treatment. The sampling scheme was a square grid with 20 x 20 mm between point spacing and the plot size was 280 x 280 mm, so that each data set consisted of 225 individual elevation points. All indices were calculated after trend removal, both by slope correction, i.e., oriented microrelief, and by slope plus tillage marks correction, i.e., random microrelief. The implemented algorithm for estimating D and 1 consisted in evaluating the roughness around the local root mean square deviation (RMS) of the point elevation values. Irrespective of tillage treatment and detrending procedure, fractal behavior extended only over a bounded range of scales, from 40 to 100 mm, due to the experimental setup. In these conditions, assessing fractal indices was not always straightforward. The statistical index RR and the fractal index I were significantly different between tillage treatments for oriented and random surface conditions. D values of random soil surfaces were not affected by tillage treatment, whereas D values of oriented microrelief were significantly lower in the direct drilled plots. Removal of tillage marks trend resulted in a significant increase in D values. Within each tillage treatment, 1 and D were significantly correlated. (c) 2006 Elsevier B.V. All rights reserved.

Indium tin oxide films prepared via wet chemical route

In this work, indium tin oxide (ITO) films were prepared using a wet chemical route, the Pechini method. This consists of a polyesterification reaction between an alpha-hydroxicarboxylate complex (indium citrate and tin citrate) with a polyalcohol (ethylene glycol) followed by a post annealing at 500 degrees C. A 10 at.% of doping of Sn4+ ions into an In2O3 matrix was successfully achieved through this method. In order to characterize the structure, the morphology as well as the optical and electrical properties of the produced ITO films, they were analyzed using different experimental techniques. The obtained films are highly transparent, exhibiting transmittance of about 85% at 550 nm. They are crystalline with a preferred orientation of [222]. Microscopy discloses that the films are composed of grains of 30 nm average size and 0.63 nm RMS roughness. The films' measured resistivity, mobility and charge carrier concentration were 5.8 x 10(-3) Omega cm, 2.9 cm(2)/V s and -3.5 x 10(20)/cm(3), respectively. While the low mobility value can be related to the small grain size, the charge carrier concentration value can be explained in terms of the high oxygen concentration level resulting from the thermal treatment process performed in air. The experimental conditions are being refined to improve the electrical characteristics of the films while good optical, chemical, structural and morphological qualities already achieved are maintained. (C) 2007 Elsevier B.V. All rights reserved.

A multi-cell variable frequency interleaved ZCS boost rectifier digitally controlled by FPGA

This paper presents a multi-cell single-phase high power factor boost rectifier in interleave connection, operating in critical conduction mode, employing a soft-switching technique, and controlled by Field Programmable Gate Array (FPGA). The soft-switching technique is based on zero-current-switching (ZCS) cells, providing ZC (zero-current) turn-on and ZCZV (zero-current-zero-voltage) turn-off for the active switches, and ZV (zero-vohage) turn-on and ZC (zero-current) turn-off for the boost diodes. The disadvantages related to reverse recovery effects of boost diodes operated in continuous conduction mode (additional losses, and electromagnetic interference (EMI) problems) are minimized, due to the operation in critical conduction mode. In addition, due to the interleaving technique, the rectifier's features include the reduction in the input current ripple, the reduction in the output voltage ripple, the use of low stress devices, low volume for the EMI input filter, high input power factor (PF), and low total harmonic distortion (THD) in the input current, in compliance with the IEC61000-3-2 standards. The digital controller has been developed using a hardware description language (VHDL) and implemented using a XC2S200E-SpartanII-E/Xilinx FPGA device, performing a true critical conduction operation mode for all interleaved cells, and a closed-loop to provide the output voltage regulation, like as a preregulator rectifier. Experimental results are presented for a implemented prototype with two and with four interleaved cells, 400V nominal output voltage and 220V(rms) nominal input voltage, in order to verify the feasibility and performance of the proposed digital control through the use of a FPGA device.

Dielectric properties of Na1-xLixNbO3 ceramics from powders obtained by chemical synthesis

Ultra-fine powders of Na1-xLixNbO3 (x=0; 0.06; 0.09; 0.12) were synthesized by the Polymeric Precursors Method. Such powders had their orthorhombic structures determined by X-ray diffraction and their surface area determined by BET isotherms (less than 10 m(2) g(-1)). Densification was followed by dilatometric study. The powders, calcined at 700 degrees C for 5 h, were sintered at 1290 degrees C during 2 h under ambient atmosphere with no application of extra pressure. The samples with relative densities higher than 95% were analyzed by impedance spectroscopy at room temperature, under a signal amplitude of 1 V-rms. Dielectric constants of about 180 and dielectric loss factor of about 0.03 were measured showing small dependence with frequency. The electrical properties were similar to those obtained for samples sintered by hot pressing. (C) 1999 Elsevier B.V. Limited and Techna S.r.l. All rights reserved.