Força muscular respiratória, qualidade de vida e modulação autonômica da frequência cardíaca na distrofia miotônica

Background: The myotonic dystrophy (MD) is a multisystem neuromuscular disease that can affect the respiratory muscles and heart function, and cause impairment in quality of life. Objectives: Investigate the changes in respiratory muscle strength, health-related quality of life (HRQoL) and autonomic modulation heart rate (HR) in patients with MD. Methods: Twenty-three patients performed assessment of pulmonary function, sniff nasal inspiratory pressure (SNIP), the maximal inspiratory (MIP) and expiratory (MEP) pressure, and of HRQoL (SF-36 questionnaire). Of these patients, 17 underwent assessment of heart rate variability (HRV) at rest, in the supine and seated positions. Results: The values of respiratory muscle strength were 64, 70 and 80% of predicted for MEP, MIP, and SNIP, respectively. Significant differences were found in the SF-36 domains of physical functioning (58.7 ± 31,4 vs. 84.5 ± 23, p<0.01) and physical problems (43.4 ± 35.2 vs. 81.2 ± 34, p<0.001) when patients were compared with the reference values. Single linear regression analysis demonstrated that MIP explains 29% of the variance in physical functioning, 18% of physical problems and 20% of vitality. The HRV showed that from supine position to seated, HF decreased (0.43 x 0.30), and LF (0.57 x 0.70) and the LF/HF ratio (1.28 x 2.22) increased (p< 0.05). Compared to healthy persons, LF was lower in both male patients (2.68 x 2.99) and women (2.31 x 2.79) (p< 0.05). LF / HF ratio and LF were higher in men (5.52 x 1.5 and 0.8 x 0.6, p <0.05) and AF in women (0.43 x 0.21) (p< 0.05). There was positive correlation between the time of diagnosis and LF / HF ratio (r = 0.7, p <0.01). Conclusions: The expiratory muscle strength was reduced. The HRQoL was more impaired on the physical aspects and partly influenced by changes in inspiratory muscle strength. The HRV showed that may be sympathetic dysfunction in autonomic modulation of HR, although with normal adjustment of autonomic modulation during the change of posture. The parasympathetic modulation is higher in female patients and sympathetic tends to increase in patients with longer diagnosis

Valores de referência para pressão inspiratória nasal SNIFF na população brasileira

The strength of respiratory muscle are frequently assessed by maximal inspiratory and expiratory pressure, however, the maneuvers to assess PImax and PEmax are difficult for many patients. The sniff nasal inspiratory pressure (SNIP) is a simple and noninvasive technique use to assess inspiratory muscles strength. Reference values have been previous established for SNIP in adults but no previous studies have provided reference values for SNIP in adult Brazilian population. The main objective of this study were propose reference values of SNIP for Brazilian population through establishment of relationship between anthropometric measurements, physical activity profile and SNIP and at the same time compare the values obtained with reference values previously published. We studied 117 subjects (59 male and 58 female) distributed in different age grouped 20-80 years old. The results showed on significant positive relationship between SNIP and height and negative correlation with age (p<0.05). In the multiple linear regression analysis only age continued to have an independent predictive role for the two dependent variables that correlated with SNIP. The values of SNIP found in Brazilian population were higher when compared with predict values of previous studies. The results of this study provide reference equations of SNIP for health Brazilian population from 20 to 80 years old

Avaliação das variáveis cardiovasculares, capacidade de caminhar e nível de atividade física de obesos mórbidos antes e depois da cirurgia bariátrica

Morbidly obese patients present an increase in heart rate, blood pressure and perceived exertion besides lower walking ability compared to normal weight people. However, little is known about how these variables are presented after bariatric surgery. Moreover, despite the distance walked during the six-minute walk (6MWT) improve after surgery is not well established if the level of physical activity influences this improvement. Objective: To evaluate cardiovascular performance, perceived effort, ability of walking and physical activity level of patients with morbid obesity before and after bariatric surgery. Methods: The cardiovascular performance, perception of effort, the ability to walk and level of physical activity were assessed in 22 patients before (BMI = 50.4 kg/m2) and after (BMI = 34.8 kg/m2) bariatric surgery through the 6MWT. The heart rate, blood pressure and perceived exertion were assessed at rest, at the end of the 6MWT and in the second minute post-test (HR recovery). The ability to walk was measured by total distance walked at the end of the test while the level of physical activity was estimated by applying the Baecke questionnaire, analyzing domains occupation, leisure and locomotion and leisure and physical activity. Results: The HR at rest and recovery decreased significantly (91.2 ± 15.8 bpm vs. 71.9 ± 9.8 bpm, 99.5 ± 15.3 bpm vs 82.5 ± 11.1 bpm, respectively), as well as all the arterial pressure and perceived exertion after surgery. The distance achieved by the patients increased by 58.4 m (p = 0.001) postoperatively. Time postoperatively had correlation with the percentage of excess weight lost (r = 0.48, p = 0.02), BMI (r =- 0.68, p = 0.001) and the Baecke (r = 0.52, p = 0.01) which did not happen with the distance walked (r = 0.37, p = 0.09). Despite weight loss, patients showed no difference in the level of physical activity in any of the areas before and after surgery. Conclusion: The cardiovascular performance, the perception of effort and ability to walk seem to improve after bariatric surgery. However, despite improvement in the ability to walk by the distance achieved in the 6MWT after weight loss, this is not reflected in an increase in physical activity level of obese patients after surgery

Tradução, adaptação cultural e avaliação psicométrica da prova cognitiva de leganés em uma população idosa brasileira com baixo nível de escolaridade

Introdução: The scales of cognitive screening are important tools for early detection of dementia, creating the possibility of developing measures to slow this process and assist in the management of the disease. Objective: To validate the Leganés Cognitive Test (Prueba Cognitive de Leganés) (PCL) for cognitive screening in low educated elderly Brazilians. Methods: The study sample was composed of 59 elderly residents from the city of Santa Cruz, Brazil with low schooling levels. Reliability was analyzed with a 2-day interval between assessments, and concurrent validity was assessed using the Mini Mental State Examination (MMSE). Results: According to the PCL, the prevalence of dementia was 11.8%. The scale items showed a moderate to strong correlation between domains (p <0.01), and inter-rater reliability exhibited ICC = 0.81, 95% CI (0.72-0.88). Factor analysis resulted in two factors: memory and orientation. Interscale agreement was considered poor (k = - 0.02), supporting the hypothesis of an educational impact on final MMSE scores. Conclusion: The results suggest that PCL has acceptable levels of reliability for use in low educated elderly Brazilians

Efeitos da adição de carga no treino de marcha na esteira em indivíduos com Doença de Parkinson: ensaio clínico controlado randomizado

Introduction: The intrinsic gait disorders in individuals with Parkinson's disease (PD) are one of the most disabling motor symptoms. Among the therapeutic approaches used in attempts to improve the motor function, especially the gait pattern of individuals, stands out the treadmill gait training associated with the addition of load. However, there are few findings that elucidate the benefits arising from such practice. Objective: To assess the effects of adding load on the treadmill gait training in individuals with PD. Material and Methods: A controlled, randomized and blinded clinical trial, was performed with a sample of 27 individuals (18 men and 9 women) with PD, randomly assigned to three experimental conditions, namely: treadmill gait training (n=9), treadmill gait training associated with addition of 5% load (n=9) and treadmill gait training associated with addition of 10% load (n=9). All volunteers were assessed, during phase on of Parkinson's medication, regarding to demographic, clinical and anthropometric (identification form) data, level of disability (Hoehn and Yahr Modified Scale), cognitive function (Mini Mental State Examination), clinical functional - in those areas activity of daily living and motor examination (Unified Parkinson's Disease Rating Scale - UPDRS) and gait cinematic analysis was performed through Qualisys Motion Capture System®. The intervention protocol consisted of gait training in a period of 4 consecutive weeks, with three weekly sessions, lasting 30 minutes each. The post-intervention assessment occurred the next day after the last training session, which was performed cinematic analysis of gait and the UPDRS. Data analysis was performed using the software Statistical Package for Social Sciences® (SPSS) 17.0. Results: The age of volunteers ranged from 41 to 75 years old (62,26 ± 9,07) and the time of clinical diagnosis of PD between 2 to 9 years (4,56 ± 2,42). There was a reduction regarding the score from motor exam domain (p=0,005), only when training with the addition of a 5% load. As for the space-time variables there was no significant difference between groups (p>0,120); however, the training with addition of 5% load presented the following changes: increase in stride length (p=0,028), in step length (p=0,006), in time balance of the most affected member (p=0,006) and reduction in support time of the referred member (p=0,007). Regarding angular variables significant differences between groups submitted to treadmill gait training without addition load and with 5% of load were observed in angle of the ankle at initial contact (p=0,019), in plantar flexion at toe-off (p=0,003) and in the maximum dorsiflexion in swing (p=0,005). While within groups, there was a reduction in amplitude of motion of the ankle (p=0,048), the only workout on the treadmill. Conclusion: The treadmill gait training with addition of 5% load proved to be a better experimental condition than the others because it provided greater gains in a number of variables (space-time and angular gait) and in the motion function, becoming a therapy capable of effectively improving the progress of individuals with PD

A capitania de São José do Piauhy na racionalidade espacial Pombalina (1750-1777)

Em meio às intervenções políticas, econômicas e administrativas realizadas no Brasil a partir de 1750, é possível observar como se deram as tentativas de organização da capitania de São José do Piauhy e até mesmo o seu reconhecimento como importante área pecuarista da colônia. Neste trabalho, realizou-se um recorte espacial priorizando a região em que a apropriação territorial teria se dado de forma mais diversa em tal capitania, pois além dos procedimentos de aquisição de sesmarias, existiram ainda os processos de herança e confisco. Sobre estes últimos, os mesmos incidiram sobre as fazendas que pertenceram ao sertanista baiano Domingos Afonso Mafrense, e que após serem deixadas de herança para os religiosos da Companhia de Jesus (1711), foram confiscadas pela Coroa Portuguesa (1759). Isso aconteceu em meio ao planejamento e execução de medidas governamentais que atingiram todos os domínios portugueses durante esse período, a chamada Política Pombalina. Tais intervenções administrativas, por sua vez, puderam ser analisadas tomando-se como referência a confecção da primeira representação cartográfica destinada a tal capitania, o Mappa Geográfico da Capitania do Piauhy, produzido pelo engenheiro italiano Henrique Antônio Galúcio. Deste modo, considerando-se as particularidades da política portuguesa destinada ao interior do Brasil, em meados do séc. XVIII, com destaque para as medidas incidentes sobre os modos de vida indígena e rural, observou-se a tentativa de implantar-se uma nova forma de organização espacial, a partir de modos e instalações urbanas. Neste contexto, São José do Piauhy passa a ser alvo de intensas investidas enquanto área oficialmente pertencente ao Estado do Grão-Pará e Maranhão

Avaliação do padrão do ciclo sono-vigília e a cognição em estudantes de medicina com diferentes esquemas de horários de aulas

The sleep patterns of students entering the university, is accompanied by many factors that can lead to changes in sleep habits, such as academic demands, new social opportunities, reduced parental care and irregular teaching schedules. The irregular pattern of sleep-wake cycle is usually accompanied by several daytime consequences, for example, reduced levels of motivation, performance, concentration, alertness and mood as well as increased fatigue and sleepiness.Thus, there are numerous reasons to support the fact that these students may suffer damage in their academic performance. The aim of this study was to evaluate the sleep-wake cycle (SWC) and cognition in medical students with different schemes teaching schedules. One group started classes at 08am, while the other started at 07am. We analyzed the data from 88 volunteers, 39 from each group. However, only those who participated in both stages of the study (n = 78) underwent cognitive testing. For subjective evaluation of the SWC was used questionnaires to check the quality of sleep, chronotype, daytime sleepiness and sleep habits. For objective evaluation was used actigraphy. For cognitive assessment was used the test MoCA (Montreal Cognitive Assessment). The results indicate that the group has class earlier had a greater irregularity of the SWC and a worse performance in cognitive testing. There was a difference between the schedules the week and weekend in the subjective variables, bedtime, wake up and sleep duration in both groups. The objective variables, time in bed showed difference between the schedules the week and weekend to the group started class at 08am and the variables bedtime, get up time, actual sleep time, time in bed and wake bouts in the class at 07am. In the cognitive test, there were differences between the groups in overall score and in the areas of executive function and memory recall. Thus, it is suggested that the class starting time may cause irregularity of the SWC and the irregularity may cause mild cognitive impairment. Moreover, cognitive testing MoCA was sensitive to detect differences among students, although the difference between the schedules is small

Disfunção sexual feminina e níveis dos hormônios esteroidais em mulheres obesas atendidas no ambulatório de cirurgia bariátrica do hospital universitário Onofre Lopes em Natal/RN

A disfunção sexual corresponde a alterações em uma ou mais fases da resposta sexual humana e apresenta maior prevalência na população feminina. Ademais, a participação de alguns fatores como obesidade e níveis dos hormônios esteroidais na disfunção sexual feminina (DSF) permanece incerta. O presente estudo deteve-se na análise da ocorrência de DSF numa população de mulheres portadoras de obesidade, cadastradas no Ambulatório de Cirurgia Bariátrica do Hospital Universitário Onofre Lopes, da Universidade Federal do Rio Grande do Norte, no município de Natal, RN. O estudo foi realizado em uma amostra composta por trinta e uma mulheres, com idade entre 20 e 50 anos, com índice de massa corpórea (IMC) > 30 Kg/m2. A todas as pacientes foi aplicado um questionário composto por uma seção com dados socio-econômicos, e outra abordando a saúde sexual feminina, sendo esta última correspondente ao Female Sexual Function Index (FSFI), para diagnóstico de DSF. A partir dessa caracterização, as pacientes foram reunidas nos grupos CD (pacientes com disfunção, n= 9) e SD (sem disfunção, n= 22). Para a análise do efeito da obesidade na DSF, as pacientes foram reunidas nos grupos 1 (6 pacientes com IMC grau I e II: entre 30 e 40 Kg/m2) e 2 (25 com IMC grau III: acima de 40). Para o estudo da participação dos hormônios esteroidais foram determinadas as concentrações séricas de cortisol, estradiol e dehidroepiandrosterona (DHEA) pelo método de quimiluminescência. A análise estatística dos dados foi realizada usando os testes ANOVA, MANOVA (Pillai), além de análise de Cluster. Para identificar as diferenças entre os domínios do FSFI, foi usado o teste T de Student. A significância considerada para todos os testes foi para p< 0,01. Das pacientes estudadas, 25,8% apresentaram DSF de acordo com o escore total do FSFI. A análise estatística posterior evidenciou que as diferenças ocorreram para os domínios desejo, excitação e orgasmo. Não foi encontrada relação da presença de DSF com os diferentes graus de obesidade ou com os níveis hormonais dos esteróides cortisol, estradiol ou DHEA. Contudo, foi encontrado aumento significativo nos níveis séricos de estradiol para o grupo 1, que corresponde ao de menor índice de IMC. Estes resultados mostram que a prevalência de DSF não diferiu entre os graus I,II e III de obesidade das pacientes deste estudo mas, quando presente, a disfunção ocorre nos domínios desejo, excitação e orgasmo. A maior concentração de estradiol encontrada nas pacientes de menor índice de IMC sugere uma possível relação entre as duas variáveis que precisa ser investigada em estudos futuros.

Gravidez tardia: bem-estar subjetivo e percepção da gestação

The subjective well- being (SWB) is formed by global judgments of satisfaction with life, or with peculiar domains the positive and the negative emotional experiences. The perception in turn, is the process of interpretive process of sensory data with cognitive or informative sense, absorbed in function of a context. From this perspective, the research aimed to evaluate SWB and the perception of advanced age pregnant women. Participated in the survey 80 pregnant with 35 years old or older (Group A or older) and 80 pregnant aged between 20 and 34 years old (Group B or young adults). The instruments used were: the scale of subjective well-being and a questionnaire, that included sociodemographic informations, items about pregnancy and a statement based on the Free Association of Words Technique (FAWT) to approach the perception of pregnancy. The data from the questionnaire and scale, in order to compare the data between groups suffered descriptive and inferential statistical analyzes. The analyzes performed with chi-square test among groups, which had values that were statistically significant, with the sociodemographic variables the type of contraceptive and health problems. The indicators of the SWB had further more by means in groups. The results of the Wilcoxon's test that there were no differences between the groups referred above. In the relation indicators of well being with variables age, education and income, some associations were significant. In addition, the words derived from the (FAWT) were analyzed using the software Programmer s Permenttant l´Analyse des Evocation (EVOC2000) and categorized according to content analysis of Bardin in three thematic categories (positive and negative affects, perception of gestation and implications of pregnancy) discussed as a group, since most of words were common. The study highlights shown how similar were the presented data by pregnant women surveyed. It is supposed about this fact the similarity is related to the social context. The relevance of this study for the health care network is to help with proposals aimed at specific improvements to the public and the sector, beside demonstrate that advanced age pregnant women and young adulst in the researched context showed no differences in the most of the studied characteristics

Doadores de sangue: qualidade de vida e atendimento em hemocentro de Natal / RN

The context of blood donation in Brazil faces problems since the start of its operations in the 1940, in the beginning the biggest obstacle was obtain safe and qualified blood, and then, established criteria for donations, the barrier is the low number of suitable candidates for donation. This suitability is associated with the good health of those who goes to the services of blood banks and the return of the donor is often conditioned by the way care is given and perceived by the user. The quality of life, defined as a perception that a person has of her/his position in the world, can influence the health and emerges as a way to focus on the subjectivity in a context dominated by objective and practical exams; listen to the views about the received services increases the focus on the user and provides feedback to the institution, guiding and planning its future actions. The purpose of this study was to verify the quality of life in blood donors and their perceptions of care in a blood center in Natal/RN. This is a descriptive cross sectional study conducted with blood donors from Dalton Cunha Barbosa blood center. The used protocols were: a structures questionnaire with questions on sociodemographic and services perception data, and SF-36 quality of life instrument. The sociodemographic and SF-36 data ware analyzed using descriptive and inferential statistics, using the statistical package PASW 18.0; those related to treatment were submitted to thematic content analysis. The results revealed a sample mainly composed by men, married people, who attended high school and had already made previous donations, with the first two groups returning more often for donations. The scores of the SF-36 confirm the certificated of good health of the screens, beind high in all areas and featuring a healthy population; statistically significant differences were denoted between sexes, levels of education and marital status. The speeches about the service were mostly positive and had as main focus acess, agility, technical aspects and subjective feelings. The data regarding the Rio Grande do Norte blood donors profile confirmed some characteristics of the Brazilian ones, those data of the SF-36 were similar to those found in studies with healthy groups and the impressions about the care received show similarities with national and international studies about the attendance at blood banks

Evidências de validade do Millon Behavioral Medicine Diagnostic (MBMD) na avaliação psicológica de candidatos à cirurgia bariátrica

the Millon Behavioral Medicine Diagnostic is an instrument, developed from a consensus among health professionals, to identify psychological factors that may compromise the conducting of medical treatment in order to allow a better adhesion. As it has been one of the most used tools to assess bariatric surgery, the objective of this research is to verify the evidence validity of Millon Behavioral Medicine Diagnostic (MBMD) for psychological assessment of candidates for bariatric surgery. Method: males and females volunteers, aged 18 to 70, grouped in 150 patients admitted for surgical procedures or suffering from chronic diseases (control group) and 426 patients candidates for bariatric surgery, contacted in person or by the internet. For the study in the face group were also administered Millon Index of Personality Styles (MIPS), the Millon Clinical Multiaxial Inventory-III (MCMI-III) and the General Health Questionnaire of Goldberg, just in bariatric surgery patients. Results: there are indicators of semantic adaptation of the instrument, with 27 factors in five areas of the instrument, all with satisfactory levels of validity. The reliabitity indicators were satisfactory in 18 of the 32 scales that comprise the MBMD, while relations with the other three instruments showed significant variations compared to the original indicators. The MBMD was sensitive to differences between groups about gender, age, education, marital status, body mass index, comorbidities and chronic disease patients and with or without obesity. The use of this instrument in the assessment of candidates for bariatric surgery presents indicators of validity in view the limitations as to the realiability of certain scales

A presença da produção científica em psicologia na formação de psicólogos do Rio Grande do Norte

The present research aimed to analyze the presence of national scientific production in undergraduate studies in Psychology of Rio Grande do Norte. Therefore, the bibliographical references contained in education plan of subjects linked to the common center of the courses, which were taught in 2011 in three Psychology courses of the state, were focused. The analysis of the material was based on bibliographical and contextual aspects of the production, such as year, nationality, type of material, authorship (including the link of authors to PPGs), structuring axis of the subject in which it was mentioned, among others. The results showed that the national production is predominant in all courses, and they are, mostly, originated from PPGs of Psychology. Among these, the publications resulted from programs in Southwest, with emphasis to PUC-SP, are recent (mostly from 2000s) and they are predominantly composed by books (organizations and full texts). Regarding the distribution of Psychology PPGs production by the structuring axes, it is observed that it surpasses the foreign production only in axis C (procedures of scientific investigation and professional practice) and axis F (professional practices). Accordingly, it is concluded that Psychology production is found in graduation, sharing space with foreign publications and from other areas of knowledge. On the one hand, this is positive, by taking into account the importance of several foreign works and from other fields to build the knowledge in Psychology; on the other hand, it shows that the production from this area is inserted in graduation in a less significant way than its growth, which points out the existence of gaps in the development of some investigative domains from national Psychology

Síntese, sinterização e caracterização de ferritas à base de Ni-Zn

Were synthesized different ferrites NixZn1-xFe2O4 (0,4 ≤ x ≤ 0,6) compositions by using citrate precursor method. Initially, the precursors citrates of iron, nickel and zinc were mixed and homogenized. The stoichiometric compositions were calcined at 350°C without atmosphere control and the calcined powders were pressed in pellets and toroids. The pressed material was sintered from 1100º up to 1200ºC in argon atmosphere. The calcined powders were characterized by XRD, TGA/DTG, FTIR, SEM and vibrating sample magnetometer (VSM). All sintered samples were characterized using XRD, SEM, VSM and measurements of magnetic permeability and loss factor were obtained. It was formed pure ferromagnetic phase at all used temperatures. The Rietveld analyses allowed to calculate the cations level occupation and the crystallite size. The analyses obtained nanometric crystals (12-20 nm) to the calcined powder. By SEM, the sintered samples shows grains sizes from 1 to 10 μm. Sintered densities (ρ) were measured by the Archimedes method and with increasing Zn content, the bulk density decrease. The better magnetization results (105-110 emu/g) were obtained for x=0,6 at all sintering temperatures. The hysteresis shows characteristics of soft magnetic material. Two magnetization processes were considered, superparamagnetism at low temperature and the magnetic domains formation at high temperatures. The sintered toroids presents relative magnetic permeability (μr) from 7 to 32 and loss factor (tanδ) of about 1. The frequency response of toroids range from 0,3 kHz to 0,2 GHz. The composition x=0,5 presents both greater μr and tanδ values and x=0,6 the most broad range of frequency response. Various microstructural factors show influence on the behavior of μr and tanδ, such as: grain size, porosity across grain boundary and inside the grain, grain boundary content and domain walls movement during the process of magnetization at high frequency studies (0,3kKz 0,2 GHz)

Síntese análise das propriedades magnéticas da ferrita de NiMg e características de absorção de radiação

It was synthesized different Ni1-xMgxFe2O4 (0,2 ≤ x ≤ 0,7) compositions by use of citrate precursor method. Initially, the precursory citrates of iron, nickel and magnesium were mixed and homogenized. The stoichiometric compositions were calcined from 350°C to 1200°C at ambient atmosphere or in argon atmosphere. The calcined powders were characterized by XRD, TGA/DTG, FTIR, magnetic measures and reflectivity using the wave guide method. I was observed pure magnetic phase formation between 350°C and 500°C, with formation of ferrite and hematite after 600°C at ambient atmosphere. The calcined powder at argon atmosphere formed pure ferromagnetic phase at 1100°C and 1200°C. The Rietveld analyses calculated the cations level occupation and the crystallite size. The analyses obtained nanometric crystals (11-66 nm), that at 900°C/3h presents micrometric sizes (0,45 - 0,70 Om). The better magnetization results were 54 Am2/Kg for x= 0,2 composition, calcined at 350°C/3h and 30 min, and 55,6 Am2/Kg for x= 0,2 1200°C, calcined in argon. The hysteresis shows characteristics of soft magnetic material. Two magnetization processes were considered, superparamagnetism at low temperature and the magnetic domains formation at high temperatures. The materials presented absorption less or equal the 50 % in ranges specific frequency. As for the 2,0 and 3,0 thickness (in 11,0 - 11,8 GHz), the reflectivity of the x= 0,3, 0,5 and 0,4 compositions, all calcined at 900°C/3h showed agreement with MS and O. Various factors contribute for the final radiation absortion effect, such as, the particle size, the magnetization and the polymer characteristics in the MARE composition. The samples that presented better magnetization does not obtaining high radiation absorption. It is not clear the interrelaction between the magnetization and the radiation absorption in the strip of frequencies studied (8,2 - 12,4 GHz)

Otimização da síntese de nanoferritas de nizn dopada com cobre e cobalto

Different compositions of Ni0,5-xCuxZn0,5Fe2O4 and Ni0,5-xCoxZn0,5Fe2O4 0 ≤ x ≤ 0.3 were synthesized ferrite y the citrate precursor method. The stoichiometric compositions were calcined in air at 350°C and then pressed into pellets and toroids. The pressed samples were sintered at temperatures of 1000, 1050 and 1100°C/3h in air control at the speed of heating and cooling. The calcined powders were characterized by XRD, TGA / DTG, FTIR, SEM and vibrating sample magnetometry (VSM) and the sintered samples by XRD, SEM, MAV, density and measurements of permeability and magnetic losses. There was pure phase formation ferrimagnetism applied at all temperatures except for A-I composition at all sintering temperatures and A-II only at a temperature of 1100°C. Crystallite sizes were obtained by Rietveld analysis, nanometer size from 11 to 20 nm for the calcined powders. For SEM, the sintered samples showed grain size between 1 and 10 micrometers. Bulk density (ρ) of sintered material presented to the Families almost linear behavior with increasing temperature and a tendency to decrease with increasing concentration of copper, different behavior of the B Family, where the increase in temperature decreased the density. The magnetic measurements revealed the powder characteristics of a soft ferrimagnetic material. Two processes of magnetization were considered, the superparamagnetism at low temperatures (350°C) and the formation of magnetic domains at higher temperatures. Obtaining the best parameters for P and B-II magnetic ferrites at high temperatures. The sintered material at 1000°C showed a relative permeability (μ) from 50 to 800 for the A Family and from 10 to 600 for the B Family. The samples sintered at 1100°C, B Family showed a variation from 10 to 1000 and the magnetic loss (tan δ) of A and B Families, around of 1. The frequency response of the toroidal core is in the range of 0.3 kHz. Several factors contribute to the behavior of microstructure considering the quantities μ and tan δ, such as the grain size, inter-and intragranular porosity, amount of grain boundary and the aspects of the dynamics of domain walls at high frequencies.