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Search Results: 1 - 10 of 58598 matches for " Marco Antonio Cavalcanti Garcia "
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Efeitos de dois parametros antropométricos no comportamento do sinal mecanomiográfico em testes de for?a muscular
Polato, Danielle;Carvalho, Maílson Correa de;Garcia, Marco Antonio Cavalcanti;
Revista Brasileira de Medicina do Esporte , 2008, DOI: 10.1590/S1517-86922008000300012
Abstract: in spite of being a useful method on muscle contraction analysis, few studies have been dedicated to understand how some anthropometrical parameters can interfere in the mechanomyographic (mmg) signal properties. therefore, the aim of this study was to evaluate the effects of skinfold thickness and arm circumference in the mmg signal behavior in the temporal and frequency domains at different levels of isometric contraction. twenty-one males (24.9 ± 7.8 years) and 21 females (20.7 ± 2.5 years), all right-handed, participated in this study. prior to the mmg signals collection, a maximum voluntary contraction test (mvc) was performed to further determine the five levels (20%, 40%, 60%, 80% and 100% of cvm) used during the tests. the two groups performed isometric contractions in the five different levels while mmg signal was collected from the right biceps brachii muscle by a biaxial accelerometer. the root mean square value (rms), and the median frequency (mf) calculated from the mmg power spectrum were extracted from the mmg signals in x direction, which meant perpendicular to the muscle fibres direction. the bicipital skinfold thickness (bd_dc_b), and the circumference of the right arm, with and without contraction of elbow muscles flexors, have also been measured. the mf presented a decreasing behaviour with the increasing level of contraction; the rms value followed an increasing pattern, though. there were significant statistical differences (p < 0.05) for the anthropometric variables between groups. it is suggested that the rms value, differently from the mf, which can be disrupted by the tissues between the muscle and the transducer, should be better correlated with muscle force level.
Influência da distancia intereletrodos e da cadência de movimento no domínio da frequência do sinal de EMG de superfície
Tank, Flávia Fernandes;Silva, Gustavo Telles da;Oliveira, Carlos Gomes de;Garcia, Marco Antonio Cavalcanti;
Revista Brasileira de Medicina do Esporte , 2009, DOI: 10.1590/S1517-86922009000500008
Abstract: surface electromyography (semg), despite being widely used in biomechanical investigations, still presents massive questioning about the influence of the distance of the inter-electrodes (die) in the signal morphology, especially in isotonic contractions. thus, much of the research developed is still limited to the laboratory, where it is possible to establish better control over the recording and analysis protocols, which is not commonly observed in the clinical-sportive practice. therefore, the aim of this study was to examine the effects of two electrodes placement protocols and the performance of isotonic contractions in the semg sign frequency domain. fifteen right-handed male subjects (aged 22.8 ± 3.5 years) performed dynamic contractions of the right brachial biceps with load estimated in 20% of the maximum voluntary contraction in three different cadences (30, 45 and 60 bpm). the semg signals were registered by two channels with dies of 4.2 and 13 cm, respectively. the semg signals assessment was based on the median frequency of the potential spectrum of the signal, calculated via fast fourier transform. die and cadence were defined as factors (two-way anova; α = 0.05). no statistical differences or any interaction between both factors were observed in the three cadences (p> 0.05). regardless of the distance used between electrodes, an investigation in the semg signal frequency domain in dynamic tasks should be avoided, even from reduced dies, as suggested in the literature, since variations in the torque and muscular length may disrupt the signal and hence its interpretation.
Comportamento temporal da velocidade de condu??o de potenciais de a??o de unidades motoras sob condi??es de fadiga muscular
Garcia, Marco Antonio Cavalcanti;Magalh?es, José;Imbiriba, Luís Aureliano;
Revista Brasileira de Medicina do Esporte , 2004, DOI: 10.1590/S1517-86922004000400007
Abstract: muscle fatigue, which is defined as the failure to maintain a required or expected force, has been investigated in both clinical and sports applications. on the investigation of muscle fatigue effects related to muscular control, surface electromyography (semg) has been the most common electrodiagnostic method, because some different parameters can be extracted from the emg signal. among the parameters, motor units action potential conduction velocity (muapcv) has been one of the most important, in spite of being usually detected through indwelling electrodes. thus, the aim of this work was to estimate muapcv through semg, detecting its temporal behavior during isometric contractions until exhaustion. eighteen students from eefd/ufrj (9 men and 9 women mean age 25.6 ± 6.8 years), right handed, consented to participate on this study. the emg signals were collected from the right biceps braquii muscle through surface electrodes on 3 different levels of isometric contractions (25%, 50 e 75% of maximum load (ml)), which were divided into 3 periods that would define the beginning (p1), the middle (p2), and the end (p3) of the contraction. muapcv presented a temporal reduction with fatigue installation, showing a statistical difference among periods (p < 0.0001), comparing all the 3 loads. however, it was observed an abrupt decrease of muapcv at p3, mainly for 50 and 75% of ml. the results point out that muapcv must be quite sensible to ph reduction and changes on ionic concentrations, defined by blood supply decreases. furthermore, the adaptations introduced on semg to muapcv estimation were considered satisfactory, reinforcing this method on electrodiagnostic evaluations.
Development and evaluation of a hypermedia system that integrates basic concepts of mechanics, biomechanics and human anatomy
Flavia Rezende,Marco Antonio Cavalcanti Garcia,Cláudio dos Santos Dias Cola
Investiga??es em Ensino de Ciências , 2006,
Abstract: This work describes the modeling of a hypermedia learning system (called “Biomec”) that integrates physical, biomechanical and anatomical concepts involved in the human motion and a study carried out with undergraduate students who interacted with the system. The instructional design of the “Biomec” hypermedia system was developed on the basis of a theoretical framework which articulates the Cognitive Flexibility Theory and the interdisciplinary approach to knowledge. The system was evaluated based on its use by students of Biomechanics I and Kinesiology in a Pre Service Teachers Training Course of Physical Education aiming to discuss the following questions: (i) what is its impact on the students’ attitude related to Physics? (ii) in what extent does the hypertextual approach to the content favor the interdisciplinary conception of human motion? (iii) in what extent do the students’ navigation profiles adapt to conceptual needs of the different disciplines of the course? The students answered instruments that assessed affective and cognitive aspects before and after the interaction with the system, and had their navigation registered and analyzed. The set of data obtained allowed to conclude that the “Biomec” system is a relevant instructional material, capable of positively influence the students’ attitude related to Physics, to favor the interdisciplinary approach of human motion and to attend the students enrolled in Biomechanics I better than the students enrolled in Kinesiology.
Evaluation of simulated bone lesion in the head of the mandible by using multislice computed tomography
Utumi, Estevam Rubens;Perrella, Andréia;Albuquerque, Marco Antonio Portela;Adde, Carlos Alberto;Rocha, Rodney Garcia;Cavalcanti, Marcelo Gusm?o Paraíso;
Journal of Applied Oral Science , 2009, DOI: 10.1590/S1678-77572009000500030
Abstract: conventional radiography has shown limitation in acquiring image of the atm region, thus, computed tomography (ct) scanning has been the best option to the present date for diagnosis, surgical planning and treatment of bone lesions, owing to its specific properties. objective: the aim of the study was to evaluate images of simulated bone lesions at the head of the mandible by multislice ct. material and methods: spherical lesions were made with dental spherical drills (sizes 1, 3, and 6) and were evaluated by using multislice ct (64 rows), by two observers in two different occasions, deploying two protocols: axial, coronal, and sagittal images, and parasagittal images for pole visualization (anterior, lateral, posterior, medial and superior). acquired images were then compared with those lesions in the dry mandible (gold standard) to evaluate the specificity and sensibility of both protocols. statistical methods included: kappa statistics, validity test and chi-square test. results demonstrated the advantage of associating axial, coronal, and sagittal slices with parasagittal slices for lesion detection at the head of the mandible. results: there was no statistically significant difference between the types of protocols regarding a particular localization of lesions at the poles. conclusions: protocols for the assessment of the head of the mandible were established to improve the visualization of alterations of each of the poles of the mandible's head. the anterior and posterior poles were better visualized in lateral-medial planes while lateral, medial and superior poles were better visualized in the anterior-posterior plane.
Interpreta??o dos mecanismos de grada??o da for?a muscular através da acelerometria
Matta, Thiago Torres da;Perini, Talita Ad?o;Oliveira, Glauber Lameira de;Ornellas, Juliana dos Santos;Louzada, Angelina Adriana;Magalh?es, José;Imbiriba, Luís Aureliano;Garcia, Marco Antonio Cavalcanti;
Revista Brasileira de Medicina do Esporte , 2005, DOI: 10.1590/S1517-86922005000500012
Abstract: the aim of this study was to characterize the temporal and spectral components of the muscle contractions in different contraction levels through the accelerometry. fifteen male and twelve female right-handed individuals participated in this study. the trial was constituted by a maximal workload (mw) test that allowed to determine five different workloads (20%, 40%, 60%, 80% and 100% of mw) which, by its turn, allowed to determine five percentage workloads during the strength test (20%, 40%, 60%, 80%, and 100% of the mw) in isometry during eight seconds each of them. a biaxial accelerometer was put on the muscular abdomen of the right brachii biceps muscle. the mean square root (rms value), a temporal parameter, and the mean frequency (mfe), a spectral parameter were extracted from the accelerometry signals (mmg signals). such parameters were analyzed towards the x (perpendicular to the fibers) and y (parallel to the fibers) directions. both groups presented a descent behavior pattern of the loaded mfe (y), and the most accentuated was the female group. the mfe variable (x) in the female group presented similar behavior before the mfe (y), and it was observed a statistically significant difference only between 20% of the mw and every other workload (p = 0.0022 for 40% and p < 0.0001 for the remaining). the male group did not present any statistically significant difference between workloads. the rms value (y) presented an ascent behavior with the workload in both genders, presenting differences between the 20% and 40% workloads of the mw (p = 0.000), and 80% and 100% of the mw (p = 0.01) in the male group. but it was observed no statistically significant difference between workloads in the female group. it is argued that during the muscular contraction, there is non-uniform variations on the fiber's diameter, besides the low frequency lateral oscillations. such information seems to have strong correlation between the type of the fibers, and this could contribute for
Area laws and entanglement distillability of thermal states
Daniel Cavalcanti,Alessandro Ferraro,Artur Garcia-Saez,Antonio Acin
Physics , 2008,
Abstract: We study the entanglement distillability properties of thermal states of many-body systems. Following the ideas presented in [D.Cavalcanti et al., arxiv:0705.3762], we first discuss the appearance of bound entanglement in those systems satisfying an entanglement area law. Then, we extend these results to other topologies, not necessarily satisfying an entanglement area law. We also study whether bound entanglement survives in the macroscopic limit of an infinite number of particles.
O papel do comprador no processo de compras em institui es públicas de ciência e tecnologia em saúde (C&T/S) The role of the public purchaser in public institutions of science and technology in health
Marco Antonio Cavalcanti Batista,José Manuel Santos de Varge Maldonado
Revista de Administra??o Pública , 2008, DOI: 10.1590/s0034-76122008000400003
Abstract: Este artigo aborda o papel do comprador público nas aquisi es de bens e servi os para as institui es públicas de ciência e tecnologia em saúde (C&T/S), tendo como referência o CPqAM/Fiocruz. O estudo contempla características e causas que potencializam os contextos da gest o das compras institucionais, os aspectos da administra o pública brasileira, a fun o administrativa de compra, o papel do comprador público no processo, o seu perfil, o seu comportamento ético, bem como a possibilidade de redu o de custos na aquisi o de materiais para a pesquisa científica. This article addresses the role of the public purchaser in the acquisitions of goods and services for public institutions of science and technology in health (S&T/H), using as a reference the CPqAM/Fiocruz. The study examines characteristics and causes of the development of the management of institutional purchases, the aspects of Brazilian public administration, the administrative function of purchasing, the position of the public purchaser in the process, his or her profile and ethical behavior, as well as the possibility of cost reduction in the acquisition of materials for scientific research.
Harmoniza??o e classifica??o toxicológica de agrotóxicos em 1992 no Brasil e a necessidade de prever os impactos da futura implanta??o do GHS
Garcia,Eduardo Garcia; Bussacos,Marco Antonio; Fischer,Frida Marina;
Ciência & Saúde Coletiva , 2008, DOI: 10.1590/S1413-81232008000900032
Abstract: in 1992, brazil modified its toxicological classification criteria for pesticides. this modification aimed to follow the guidelines of the world health organization (who) hazard classification of pesticides. in 2002, the united nations adopted the "globally harmonized system for the classification and labelling of chemicals" (ghs). as a result, the who is reviewing its classification and brazil will probably follow the example. therefore it seems timely to estimate the impact of the changes in the criteria adopted in 1992 in the toxicological reclassification and labelling of the commercially available products registered at that time. it is estimated that 58.6% of the total of registered pesticides (74.9% liquid and 31.0% solid formulations) might have been reclassified to less hazardous classes. the hazard warnings on the labels may have caused negative consequences due to misinterpretations by farmers or rural workers. for countries already having a hazard classification system, it is therefore recommendable to estimate the possible impact of the changes before implanting the ghs.
Impacto da legisla??o no registro de agrotóxicos de maior toxicidade no Brasil
Garcia Garcia,Eduardo; Bussacos,Marco Antonio; Fischer,Frida Marina;
Revista de Saúde Pública , 2005, DOI: 10.1590/S0034-89102005000500020
Abstract: objective: to evaluate the impact of the application of the "pesticides law" (law no. 7,802/89) on the toxicological classification profile of registered pesticides in brazil, from 1990 to 2000. methods: data on registered commercial products in the years 1990 and 2000 were analyzed according to toxicological class, date of registration of the active ingredient (before or after the law) and usage class (insecticides, fungicides, herbicides and others). relative identified distribution analysis was utilized for verifying statistical differences between distributions according to toxicological classes. results: among the 863 registered commercial products in 2000, 46.6% were already registered before the pesticide law. among the 461 commercial products registered after the law, 59.2% were derivatives of active ingredients registered before the law, and 41.4% were classified as highly hazardous (classes i and ii of the brazilian toxicological classification). no significant differences in toxicological classification profile were identified between the group of pesticides derived from active ingredients registered before the law and the group derived from active ingredients registered after the law (p<0.0859). conclusions: ten years after the pesticide law came into effect, no significant improvement had been observed in the toxicological classification profile of registered pesticides. this was due especially to the continuing presence of products registered before the law and the registration of new commercial products derived from "old" active ingredients. there was still a high proportion of registrations in the most hazardous classes. it is recommended that compulsory periodic reevaluation of all registered pesticides should be reestablished.
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